JPH0481784A - Development device - Google Patents

Abstract

PURPOSE:To convey toner which is charged electrostatically to a sufficient quantity to a development area by a sufficient amount and to form a visible image of high quality by using a material which is charged electrostatically for the surface of a toner carrier, making an electrostatic charging member which is applied with a voltage abut on the surface of the toner carrier, and charging the surface electrostatically to the opposite polarity from the electrostatic charging polarity of the toner. CONSTITUTION:The toner carrier 5 having the surface which is charged electrostatically is used and the electrostatic charging member 60 which abuts on the surface of the toner carrier 5 and is applied with the voltage having the opposite polarity from the electrostatic charging polarity of the toner 4 to charge the surface of the toner carrier 5 to the opposite polarity from the toner 4 is provided, so that the toner 4 is carried on the toner carrier 5 and conveyed to the development area with electrostatic charges on the surface of the toner carrier 5 which is charged electrostatically by the electrostatic charging member 60. Consequently, the quantity of electrostatic charging is increased with the simple configuration and much toner can be carried on the toner carrier 5 and conveyed to the development area.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is directed to carrying toner charged to a predetermined polarity on the surface of a toner carrier and transporting the toner, so that the latent image carrier and the toner carrier are mutually connected to each other. The present invention relates to a developing device that visualizes an electrostatic latent image formed on a latent image carrier in opposing development areas using toner carried on a toner carrier.

[Conventional technology]

In an image forming apparatus such as an electronic copying machine, a laser printer, or a facsimile machine that obtains a recorded image by visualizing an electrostatic latent image formed on a latent image carrier, a toner to which an adjuvant is externally added as necessary, i.e. - It has been well known to employ a developing device of the above type using a component-based developer.

This type of developing device has the advantage that maintenance and management of the device can be simplified and the structure of the device can be made smaller, compared to a developing device using a two-component developer containing a carrier. - In a developing device that uses a component-based developer, in order to form a high-quality visible image with a predetermined density, a large amount of sufficiently charged toner is transported to the development area, and the latent image is made visible by the toner. There is a need to.

In a conventional developing device using a one-component developer, an insulating layer is provided on the surface of a toner carrier, a toner supply member made of, for example, a sponge roller is brought into pressure contact with the toner carrier, and both are triboelectrically charged to different polarities. In addition, a developing device is generally used in which toner that is triboelectrically charged to a polarity opposite to that of the insulating layer on the surface of the toner carrier is electrostatically attached to the surface of the toner carrier and is transported to a developing area (for example, (Japanese Patent Application Laid-Open No. 61-43767).

However, with this configuration, the surface of the toner carrier is configured to be charged by friction with the toner supply member, so it is difficult to increase the amount of charge, and it is difficult to carry a large amount of toner on the toner carrier. It is difficult to transport the film to the developing area.

In addition, after scraping off the toner on the surface of the toner carrier after passing through the development area, the surface of this carrier is charged to a predetermined polarity by corona discharge with a corona discharger, and the toner is electrostatically attached to the surface. A developing device has also been proposed that transports this to a developing area. However, with this configuration, toner adheres to the charge wire of the corona discharger, causing
There is a risk that its function will deteriorate early.

[Problem to be solved by the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a developing device which eliminates the above-mentioned conventional drawbacks by a simple structure.

[Means to solve the problem]

In order to achieve the above object, the present invention uses a toner carrier having a chargeable surface as a toner carrier in a developing device of the type described at the beginning. A charging member is provided that charges the surface of the toner carrier to a polarity opposite to that of the toner by applying a voltage with a polarity opposite to that of the toner, and the toner is charged by the charge on the surface of the toner carrier charged by the charging member. We propose a configuration in which the toner is carried on a toner carrier and transported to a developing area.

〔Example〕

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

In FIG. 1, a drum-shaped photoreceptor 1, which is an example of a latent image carrier, is driven in six directions of arrows, and a developing device 2 is provided opposite to it. In the toner container 3 of the developing device 2, there is a non-magnetic toner 4 mixed with an auxiliary agent as needed.
That is, a non-magnetic one-component developer is accommodated therein. The specific volume resistivity of the toner is, for example, about 10 7 to 10 12 Ω■.

A developing roller 5 is supported on the front and rear side plates of the toner container 3 with a portion exposed from the opening of the container.
is opposed to the photoreceptor 1 and rotated clockwise in FIG. Although the developing roller 5 constitutes an example of a configuration of a toner carrier, a belt-shaped toner carrier may be used instead of the roller 5.

The developing roller 5 is composed of a conductive base body 52 made of, for example, an aluminum tube, and a film-like insulating layer 53 laminated on the surface thereof.

Its surface has chargeability, that is, charge retention.

The toner 4 is frictionally charged and carried on the surface of the developing roller as will be described later, but the I! Marginal layer 5
3 is made of a material that is charged to a polarity opposite to that of the toner. Examples of the material for this insulating layer include:
Polyethylene terephthalate, polycarbonate, epoxy, styrene-acrylic copolymer, polyester, silicone polymer, fluoropolymer, etc. can be used, and such materials are applied by spraying or the like to the surface of the base 52 having a cylindrical surface, and then cured. Let me M
The edge M53 can be used. These substances are often used as constituent materials for film materials of organic photoreceptors, and exhibit excellent properties not only in charging properties but also in abrasion resistance, and are suitable for the insulating layer 53 of the developing roller 5. It is a good material.

Although the thickness of the insulating layer 53 varies slightly depending on the charging performance of the material, it is preferably approximately 1 to 100 μm, preferably 5 to 50 μm, so as to obtain good charge retention.

When the toner carrier is a belt, an endless sheet-like conductive substrate with an insulating layer laminated on the surface is used, similarly to the above-mentioned developing roller.

A bias voltage as described later is applied to the base body 52 of the developing roller 5 by a power source 51.

Above the above-mentioned developing roller 5, there is a conductive charging roller 6o rotatably supported on the front and rear side plates of the toner container 3.
The charging roller 60 constitutes an example of a charging member that charges the insulating layer 53 on the surface of the developing roller to a polarity opposite to that of the toner.

The charging roller 60 contacts the surface of the developing roller 5, that is, the surface of the insulating layer 53, while rotating counterclockwise in FIG. Further, a DC voltage having a polarity opposite to the charging polarity of the toner is applied to the charging roller 60 by a power source 55. In this way, by applying a higher voltage to the charging roller 60 than to the developing roller 5, the insulating layer 53 on the surface of the developing roller 5 is charged by charge injection or discharging.
An electric charge is applied, and the surface of the developing roller 5 is charged to a polarity opposite to that of the toner. The surface potential of the developing roller S is, for example, 50 to 500V in absolute value, preferably 100 to 300V.
It operates with a voltage of 0OV and applies an electric charge to the surface of the developing roller 5.

The charging roller 60 can be made of any suitable material as long as it can impart an electric charge to the developing roller 5 as described above.For example, it can be made of a conductive sponge material made of foamed urethane rubber, polyester, Teflon (trade name), etc. It is possible to use fibers in which a conductive substance is dispersed and made into a brush shape. Alternatively, a charging member other than a roller-shaped charging member, for example, block-shaped or blade-shaped, may be used and brought into contact with the developing roller 5 in a stationary state to charge the surface of the roller.

On the other hand, when viewed from the direction of rotation of the developing roller 5, the charging roller 60
A toner supply roller 6 rotatably supported by the front and rear side plates of the toner container 3 is disposed downstream of the toner container 3.
is actively rotated, for example, in a counterclockwise direction while contacting the developing roller 5. The toner supply roller 6 constitutes an example of a toner supply member that supplies toner to the developing roller 5.

The toner 4 in the toner container 3 is agitated by the clockwise rotating agitator, and is moved in the rotational direction by the resistance of the tip of the agitator 7 to the toner supply roller 6.
Then, this roller 6 transfers the developing roller 5 to the developing roller 5.
It is supplied so that it can be rubbed on. At this time, the toner is triboelectrically charged to a stable predetermined positive or negative polarity due to strong friction between the toner supply roller 6 and the developing roller 5.

As described above, the toner 4 is strongly charged to a predetermined polarity in a stable state and is rubbed against the surface of the developing roller. At this time, the surface of the developing roller 5 is charged with a polarity opposite to that of the toner by the charging roller 60 as described above. Since the toner is electrically charged and the electrical charge is held in the insulating layer 53, the toner supplied to the developing roller 5 strongly adheres to the surface of the developing roller 5 due to the adsorption force due to the electrical charge on the surface of the roller 5. At this time, since the charge on the toner is also stable, a large amount of highly charged toner adheres to the surface of the developing roller. Moreover, the state of adhesion becomes stable.

The toner supply roller 6 is made of an appropriate material that provides a toner frictional charging function and does not erase the charge on the surface of the developing roller. It is made of sponge material made from foamed urethane rubber, and brush-shaped fibers made from polyester, Teflon (trade name), etc.

The toner supplied and supported on the circumferential surface of the developing roller 5 as described above is conveyed by the rotation of the developing roller 5, and the doctor member, which is an example of a layer thickness regulating member, is elastically pressed against the surface of the developing roller 5. 8 to regulate the thickness to be uniform. The blade member 8 is made of an elastic cylindrical leaf spring laminated with a material having toner charging performance, such as urethane rubber, or an elastic member itself.

Next, the toner on the developing roller is conveyed to a developing area 9 where the photoreceptor 1 and the developing roller 5 face each other.
The electrostatic latent image is transferred electrostatically to the electrostatic latent image formed on the image, and the latent image is made into a visible image. In the developing area 9, a voltage is applied to the developing roller 5 by a power source 51 connected to the developing roller 5 and the toner supply roller 6, and an amount of toner corresponding to the potential of the electrostatic latent image is applied to the photoreceptor. Development is performed by shifting to the 1 side.

The developing roller portion that has passed through the developing area 9 reaches the charging roller 60 again, but at this time, the toner remaining on the developing roller 5 is removed by the charging roller 60, and at the same time, the toner remaining on the developing roller 5 is removed by the voltage application from the power source 55 as described above. The surface of the developing roller is charged. In this way, the charging roller 60 shown in FIG. 1 functions to charge the surface of the developing roller and to remove toner from the surface of the roller. The removed toner is collected by the scraper 125 on the developing roller 5 and the scraper 25 pressed against the charging roller 6o, and is reused.

In FIG. 1, reference numeral 70 indicates a charger that charges the photoreceptor 1, 71 indicates a light image irradiated onto the photoreceptor after charging, and 72 indicates a visible light image formed on the photoreceptor. This is a transfer charger that transfers an image onto a transfer paper (not shown).

According to the above-described configuration, the charging roller 60 applies an electric charge to the surface of the developing roller 5, and the toner is attracted and held by the electric charge, so that the surface of the developing roller is frictionally charged by the toner supply member as in the conventional case. than the configuration,
The potential on the surface of the developing roller can be increased. Therefore, a large amount of highly charged toner can be stably carried on the surface of the developing roller and transported to the developing area 9. Therefore, insufficient image density of the developed visible image can be prevented, and a high-quality visible image with less background smudge can be formed.

Further, unlike the case where the surface of the developing roller is charged by a corona discharger, it is possible to prevent the problem of early deterioration of the charging performance of the developing roller.

Further, the insulating layer 53 on the surface of the developing roller may contain any electrical resistance adjusting agent such as carbon black, titanium oxide, silicon oxide, etc. depending on the purpose. It becomes possible to freely control the amount of toner that adheres to the roller.

As the surface layer of the developing roller 5, instead of using the above-mentioned insulating layer 53 that always shows insulation, a photoconductive and chargeable material that shows insulation in the dark can also be used.

The voltage applied to the charging roller 60 may be a combination of direct current and alternating current.

In the embodiment shown in FIG. 1, the charging roller 60 and the developing roller 5 occupy a position that closes the opening of the toner container 3, effectively blocking the toner 4 in the toner container 3 from the outside. Therefore, it is possible to prevent toner from scattering outside the developing device.

Further, in the example shown in FIG. 1, the developing roller 5 and the photoreceptor 1
is, for example, 30 to 500 μm, preferably 50 to 25 μm.
Although they face each other with an interval of about 0 μm, they may be brought into contact with each other with the toner interposed therebetween. It is also possible to use a flexible belt as the photoreceptor, and to contact the developing roller 5 with a distance corresponding to the thickness of the toner. When the photoreceptor 1 and the developing roller 5 are separated from each other as shown in FIG. 1, the rotational load on the developing roller 5 is reduced compared to when they are in contact with each other.
This makes it possible to use a small motor for driving the photoreceptor 1. By setting the circumferential speeds of the photoreceptor 1 and the developing roller to be approximately equal, it is possible to further reduce the driving torque, and furthermore, the load acting on the toner can be reduced, and the life of the toner can be extended.

As a method of development performed in the development area 9.

There are regular development and reverse development, and it goes without saying that the potential level of the bias voltage (development bias) applied to the development roller 5 should be changed depending on the development method employed. Further, as the developing bias, only a direct current voltage or one in which alternating current is added can be used. When a square wave pulse voltage is used as the alternating current voltage, the frequency should be changed from 300 to 20
00 hertz, preferably in the range of 500 to 1500 hertz, and the time of the high potential part and the time of the low potential part in one cycle are made different, and the time ratio (duty ratio) of these is set to a value other than 1. When set, photoreceptor 1
It is possible to improve the sharpness of the upper low-potential portion and increase the image density of the high-potential portion, thereby obtaining a visible image with less background smudge.

The optimum value of the above duty ratio differs depending on the polarity of the electrostatic latent image and the charging polarity of the toner.
It is preferable to set the ratio of the time of -100 V or more) to the time of the low potential part (-soov or less) to 5 to 18:2 to 8.

In the case of regular development, if this ratio is generally reversed, an excellent developed image can be obtained which similarly increases sharpness in low potential areas, increases image density in high potential areas, and suppresses background smearing.

As mentioned above, by employing a rectangular wave pulse voltage as the developing bias, the rectangular wave pulse electric field formed in the developing area 9 acts on a sufficient amount of toner with a stable charge amount, and the latent image is developed. Since suitable mechanical energy is applied to the photoreceptor, it is possible to improve the sharpness of low potential areas on the photoreceptor, increase the image density of high potential areas, and more reliably achieve the effect of suppressing background smearing.

As described above, a developing device using a one-component developer of non-magnetic toner which is particularly suitable for color development has been described. It can also be applied to a developing device using a.

〔Effect of the invention〕

According to the present invention, the surface of the toner carrier is made of a chargeable material, and a charging member to which a voltage is applied is brought into contact with the surface of the toner carrier, so that the surface of the toner carrier has a polarity opposite to that of the toner. Since the toner is electrically charged, a sufficient amount of toner with a stable electrical charge can be transported to the development area, and a high-quality visible image can be formed. Moreover, the structure of the toner carrier is simple, and an increase in cost can be suppressed.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an example of a developing device according to the present invention. 2...Developing device 4...Toner 9...Developing area agent Norio Hoshino, patent attorney Figure 1←

Claims (1)

[Scope of Claims] Toner charged to a predetermined polarity is carried on the surface of a toner carrier, and the toner is conveyed to the latent image carrier in a development area where the latent image carrier and the toner carrier face each other. In a developing device that visualizes a formed electrostatic latent image with toner carried on a toner carrier, a toner carrier having a chargeable surface is used as the toner carrier, and the toner carrier has a chargeable surface. in contact with the surface,
In addition, a charging member is provided which charges the surface of the toner carrier to a polarity opposite to that of the toner by applying a voltage having a polarity opposite to that of the toner. . A developing device characterized by carrying toner on a toner carrier and transporting the toner to a developing area.