JPH0429268A - Developing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention supplies toner to a rotationally driven toner carrier, carries the toner on the surface of the carrier, and transports the toner to form a latent image carrier. The present invention relates to a developing device that visualizes an electrostatic latent image formed on a latent image carrier in a development area where the toner carriers face each other using toner carried on the 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.

However, in conventional developing devices that use -component developers, it is difficult to transport a sufficient amount of toner to the developing area to form a high-quality visible image with a predetermined density. .

Therefore, a developing device has been proposed in which an uneven surface is formed on the surface of a toner carrier, and toner is filled and carried on the uneven surface to increase the amount of toner conveyed to a developing area. However, according to this configuration.

Although the amount of toner that can be conveyed increases, the toner being conveyed contains a large amount of toner that is insufficiently charged.
This may reduce the quality of the visible image formed.

[Problem to be solved by the invention]

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

[Means to solve the problem]

In order to achieve the above object, the present invention uses, as a toner carrier, a carrier whose surface has charge retention properties in the developing device described at the beginning, and selectively charges the surface of the toner carrier. The charge applying means is arranged close to the surface of the toner carrier and at a minute interval from each other, and is arranged at a predetermined distance. It is characterized by comprising a plurality of electrodes to which voltage is applied to cause discharge to the toner carrier.

〔Example〕

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

FIG. 1 is a schematic diagram showing an example of a developing device according to the present invention, and first the overall structure and operation thereof will be explained.

In FIG. 1, a drum-shaped photoreceptor 1, which is an example of a latent image carrier, is driven in the direction of arrow A, 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, 10' to 1012Ω・■
That's about it. 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, and the roller 5 is rotated clockwise in FIG. 1 facing the photoreceptor 1. Ru. 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. Further, a toner supply roller 6, which is an example of a toner supply member, is supported on the front and rear side plates of the toner container 3, and the roller 6 is actively rotated, for example, in a counterclockwise direction while contacting the developing roller 5.

The toner 4 in the toner container 3 is conveyed to a toner supply roller 6 while being stirred by an agitator rotating clockwise, and then supplied to a developing roller 5 by this roller 6. During this supply, the toner is frictionally charged to a predetermined polarity (in this example, a positive polarity opposite to the electrostatic latent image on the photoreceptor 1), electrostatically adheres to the circumferential surface of the developing roller 5, and is carried on the developing roller 5. (See Figure 2). The configuration and operation related to this will be explained in detail later.

The toner supplied and supported on the circumferential surface of the developing roller 5 as described above is conveyed by the rotation of the roller 5, and is leveled by the doctor blade 8, which is an example of a layer thickness regulating member.
Thickness is regulated. Next, this toner is conveyed to a developing area 9 where the photoreceptor 1 and the developing roller 5 face each other, where it is electrostatically transferred to the electrostatic latent image formed on the photoreceptor 1, making the latent image visible. Visualize. The visible image formed on the photoreceptor 1 is transferred to a transfer paper (not shown), and fixed onto the transfer paper by a fixing device. In FIG. 1, reference numeral 70 denotes a charger that charges the photoreceptor 1, 71 a light image that exposes the surface of the photoreceptor after charging, and 72 a transfer sheet for transferring the visible image formed on the surface of the photoreceptor. This is a transfer charger that transfers images to

A bias voltage is applied to the developing roller 5 and the toner supply roller 6 by a power source 50, and the conductive support supporting the photosensitive layer of the photoreceptor 1 is grounded.

The above-mentioned configuration itself is the same as that of a conventional developing device, and in such a conventional developing device, a predetermined amount of sufficiently charged toner necessary for forming a high-quality visible image is transported to a developing area. was difficult. In order to eliminate such drawbacks, the illustrated developing device is constructed as follows.

First, as shown in an enlarged view in FIG. 2, the developing roller 5 has an electrically conductive base made of a conductive roller 10 made of metal such as aluminum, and a dielectric material 32 laminated over its entire surface. On the other hand, on the upstream side of the toner supply roller 6 in the rotational direction of the developing roller 5 and on the downstream side of the developing area 9,
A conductive charge eliminating roller 33, which is an example of a charge eliminating means, and a charge applying means 34 are arranged in sequence in the rotational direction of the developing roller 5.

The static eliminating roller 33 rotates while contacting the developing roller 5,
AC voltage is applied by the AC power supply 35, and the developing area 9
The surface of the developing roller 5 that has passed through the toner is neutralized and residual toner is scraped off. The static eliminating roller 33 is made of, for example, conductive foam, conductive rubber, or metal.

Instead of the roller 33, a static eliminator consisting of a blade or the like may be used, and an alternating current voltage may be applied to this to bring the blade into contact with the surface of the developing roller 5.

On the other hand, as shown in FIGS. 1 and 3, the charge applying means 34 are arranged at a predetermined distance from each other in the axial direction of the developing roller 5, and their tips are attached to the surface of the developing roller 5 by about 200 μm, for example. It has a large number of needle-like electrodes 51 that are close to each other with an interval d1 of
2 and is fixed in a comb-like shape. The support member 52 is fixed to the toner container 3 via a bracket. The electrode 51 is made of a conductive material such as styrene-free or other metal, and has a diameter d2 at its tip;
The spacing d3 between each electrode is set to, for example, about 200 μ-. The base ends of each electrode 51 are electrically connected to each other via a conductor 53, and are connected to another power source 37 connected to the aforementioned power source 50.
It is configured such that a voltage is applied by. The power supply 37 constitutes an example of voltage application means for applying a predetermined voltage to the electrode 51, and in this case, in this example, the fourth
A pulsed alternating voltage as shown in FIG. 3(a) is applied to each electrode 51 by a power source 37, and its polarity is negative, which is opposite to the charging polarity of the toner.

With such a configuration, when the developing roller portion that has been subjected to the static eliminating action by the static eliminating roller 33 and has had residual toner removed faces the electrodes 51, corona discharge is generated due to the aforementioned high voltage applied to these electrodes 51. The corona ion flow heads towards the developing roller 5 and the dielectric material 32 on its surface.
the given polarity.

In this example, it is charged to negative polarity. At this time, the developing roller 5
1 is rotating, and each electrode 51 has a
Since the alternating voltage as shown in FIG. 5 is applied and the electrodes 51 are separated from each other by d3, the surface of the developing roller 5 that has passed through the electrodes 51 has numerous dot-shaped spots as shown by broken lines in FIG. A large number of charges are applied. In this manner, the electrode 51 selectively applies electric charge to the portion of the surface of the developing roller 5 where the discharge has occurred. Here, if the surface portion of the developing roller 5 that is charged is represented by Xl, and the portion that is substantially uncharged is represented by X2, the surface potentials of the two sections are greatly different. Innumerable minute charge patterns X1 are formed. Therefore, near the surface of the developing roller, there are many small closed electric fields (
microfield). That is, as schematically shown in FIG. 6, in the space near the surface of the developing roller 5, there is a space between the charged developing roller portion X1 and the substantially uncharged portion X2. Electric force represented by many arc-shaped lines, i! E is formed. At this time, since the charged portion X1 and the uncharged portion X2 are adjacent to each other in a small area, the strength of each small closed electric field becomes very strong due to the edge effect or peripheral electric field effect. In this way, an electric field with a large electric field gradient is formed near the surface of the developing roller 5.

On the other hand, as described above, the toner 4 supplied to the developing roller 5 by the toner supply roller 6 has a predetermined polarity, in this example, a positive polarity, due to friction with both rollers 5 and 6, as schematically shown in FIG. is strongly triboelectrically charged. The illustrated toner supply roller 6 is made up of a core member 14 to which a voltage is applied by the power source 50 as described above, and a foam 15 of, for example, urethane resin laminated around the core member 14. A brush or the like can also be used.

As described above, the positively charged toner 4 is transferred to the developing roller 5.
At this time, as described above, a large number of minute charge patterns are formed on the surface of the developing roller 5, and as a result, countless minute/JN closed electric fields are formed, so that the toner is developed by this electric field. It is attracted and carried on the roller 5. As described above, the strength of this electric field is strong and the toner is also strongly charged, so a large amount of highly charged toner is carried on the developing roller 5.

The toner supported in this way passes through a doctor blade 8 made of, for example, urethane resin, and its layer thickness is regulated, but in this process, even if toner with a small amount of charge is mixed in the supported toner, , such toner is removed by the contact pressure with the doctor blade 8, and in the end, only the toner with a large amount of charge is strongly held by the small/h closed electric field and is conveyed in large quantities to the developing area 9, where it is statically charged as described above. Visualize the latent image. For example, 8 to 15μc prevents background smearing of the visible image and increases its sharpness.
It is possible to transport a large amount of toner charged to about 0.6 to 2.0 mg/cd, preferably 0.8 to 1.2 μg/d, to the development area 9. Therefore, even if the toner is black or another chromatic color, the quality of the visible image can be improved. In the developing area 9, the electric lines of force from the developing roller 5 head towards the electrostatic latent image on the photoreceptor 1, the force of holding the toner on the developing roller weakens, and the latent image is effectively visualized. can do.

The surface of the developing roller 5 that has passed through the developing area 9 is again neutralized by the neutralizing roller 33, and then charged again by the charge applying means 34 as described above, and conveys the toner to the developing area 9 while carrying the toner.

If each electrode 51 is configured to always apply a charge to the same portion of the developing roller, it is also possible to omit the charge eliminating means such as the charge eliminating roller 33.

The charged portion X1 of the developing roller 5, that is, the size, shape, and pitch of the charge pattern can be set as appropriate in consideration of the amount of toner to be conveyed to the developing area and other conditions, as shown in FIG. Its diameter and pitch p,
pi is 1, for example, about 1°0 μm to 500 μm. Such values are determined by the diameter d2 of each electrode 51, the interval d3 . The distance d1 between the electrode tip and the developing roller 5, the voltage application time T of the pulsed alternating voltage applied to the electrode 51 (Fig. 4(a)
), the surface linear velocity (peripheral velocity) of the developing roller 5, etc. can be determined as appropriate.

For example, the frequency of the alternating electric field applied to the electrode 51 is f (
Hz), its cycle is T (sec), and the developing roller 5
If the peripheral speed of is V* (m/5ee), then these and the pitch P of the charge pattern X1 in the developing roller moving direction
The relationship with (a) is T (see) = P (an) / V (mm/5
ee) or P (m+n) = V (m/5ee) / f
(1/5ee), so for example, V = 1
00 (mm/5ee), Pm2O3 (μm
), then f=100/(400X10-')=250(Hz
) may be applied to the electrode 51.

Furthermore, in order to set P in the range of 0.1 mn to 0.5 mn, it is sufficient to set 2(am)XV≦f≦100(on)XV.

In this way, the shape, pitch, and size of the charge pattern X1 can be set to desired values that meet the requirements of each developing device.

In addition to the voltage applied to the electrode 51 as shown in FIG. 4(a), a voltage obtained by superimposing a direct current on an alternating voltage may be applied, for example, as shown in FIG. 4(b). A charge pattern with a difference in surface potential corresponding to a high potential portion (TH) and a low potential portion (T, ) is formed on the surface of the roller 5, and a large number of minute closed electric fields can be generated.

Furthermore, instead of the alternating voltage as shown in FIGS. 4(a) and 4(b), direct current, alternating current, or a voltage with a superimposed direct current may be constantly applied to the electrode 51. A charge pattern X1 extending in the circumferential direction of the developing roller 5 is formed on the dielectric material 32, as shown by the broken line in FIG.

In each of the embodiments described above, if the resistance value of the surface of the developing roller 5 is low, the electric charge tends to leak, and the electric charge cannot be retained, the electric field strength of the minute closed electric field weakens, and the toner retention force decreases. Therefore, the dielectric material 3 on the surface of the developing roller
Volume resistivity of 2 is less likely to cause charge leakage than 10
It is desirable to set it to Ω・1 or more.

Moreover, instead of the dielectric material 32 on the surface of the conductive roller 10,
A photosensitive layer (photoconductive layer) that exhibits insulation in the dark and exhibits conductivity when exposed to light may be laminated. Even when such a developing roller is used, charges can be selectively applied by the charge applying means 34. Further, as the static eliminating means for the developing roller, a lamp for irradiating light onto the photosensitive layer, a corona discharger, etc. can also be used.

In short, it is sufficient to use a developing roller whose surface has charge retention properties, and the same applies when the toner carrier is a belt.

Further, in each of the above-mentioned embodiments, a developing device using a single-component non-magnetic toner developer particularly suitable for color development has been exemplified, but the present invention is constructed using a magnetic toner to which an auxiliary agent is externally added as necessary. It can also be applied to a developing device using a one-component developer.

Further, it is also possible to selectively apply a charge having the same polarity as the toner to the surface of the toner carrier by the charge applying means, and to support the toner by a minute closed electric field formed thereby.

〔Effect of the invention〕

According to the present invention, a required amount of highly charged toner can be conveyed to the development area to form a visible image with a desired density. In addition, the charge applying means can form a desired charge pattern on the toner carrier, and since the electrode is not in contact with the toner carrier, there is a risk of damaging the toner carrier or the electrode. FIG. 2 is a schematic cross-sectional view showing an example of a developing device, FIG. 2 is an explanatory diagram schematically showing toner particles in an enlarged manner, FIG. 3 is an enlarged view of the charge applying means seen from the left side of FIG. Figures (a) and (b) are diagrams illustrating the voltage applied to the electrodes, Figure 5 is an explanatory diagram showing the charge pattern formed on the developing roller, and Figure 6 is a diagram showing the charge pattern formed near the surface of the developing roller. Explanatory diagram showing lines of electric force of a minute closed electric field, No. 7
The figure is an explanatory diagram similar to FIG. 5, showing another example of the charge pattern.

2...Developing device 4...Toner 9...Developing area 34...Charge applying means 51...Electrode representative Patent attorney Norio Hoshino Figure 2

Claims (1)

[Scope of Claims] Toner is supplied to a rotationally driven toner carrier, the toner is carried on the surface of the carrier, and the toner is conveyed in a developing area where the latent image carrier and the toner carrier face each other. , a developing device that visualizes an electrostatic latent image formed on a latent image carrier with toner carried on a toner carrier, using a carrier whose surface has charge retention properties as the toner carrier; , a charge applying means for selectively applying a charge to the surface of the toner carrier and forming a large number of minute closed electric fields near the surface; What is claimed is: 1. A developing device comprising a plurality of electrodes which are arranged at a minute interval from each other and which are applied with a predetermined voltage to generate discharge on a toner carrier.