JPS60102670A - Method and apparatus for developing toner image - 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 Field of Industrial Application The present invention has a multipolar magnetic core and a rotating sleeve surrounding it,
A homogeneous layer of insulating magnetic single-component toner circulates around the circumferential surface of the sleeve, the rotating sleeve faces a moving base with a development gap in between, and a magnetic brush adjacent to an alternating current voltage with respect to the base. The present invention relates to a method and apparatus for developing a toner image onto a photoconductive support bearing an electrostatic latent image using a substrate provided with an electrostatic latent image.

PRIOR ART AND PROBLEM TO BE SOLVED BY THE INVENTION In the known method (US Pat. No. 4,299,900), the multipolar magnetic core remains stationary.

Only the sleeve rotates. By placing a doctor made of magnetizable material opposite one pole of the magnetic core, it is possible to apply the toner to the sleeve in a very thin layer. The development gap is set so that a distance is maintained between the toner layer and the base bearing the charge image in the gap. The frequency is approximately 200 Hz between the base and the magnetic brush.
A low frequency AC voltage with a % voltage value of approximately 800V is applied. It is preferable to employ the above-mentioned thin toner layer. One reason for this is that the amount of toner provided for development is relatively small. Another reason is that the thinner toner layer requires that the spacing between the base and toner layer in the developer gap be maintained very precisely, and as a result, the mounting of the magnetic brush and base is subject to very tight tolerance requirements. Because it will be.

In practice, achieving such tight tolerances often comes at a cost. Moreover, after a long period of use, play adjustment takes place, with the result that it is no longer possible to maintain tolerances and there is a risk that poor development results will appear.

In another known method (US Pat. No. 4,121,931), an insulating magnetic monocomponent toner is circulated on a rotating sleeve surrounding a multipolar magnetic core in such a layer thickness that it is in contact with the base.

By applying a DC voltage between the sleeve and the support carrying the charge image, the monocomponent toner becomes charged with a polarity opposite to that of the zone of the support to be developed, which causes υ Toner transfer occurs. Developing thin lines and sharp edges is difficult with this method. Furthermore, since it is impossible to completely discharge the photoconductive support material, especially when copying a large number of sheets, residual charges remain even in non-imaged areas. Due to the applied direct current voltage, toner transfer occurs even in some of these non-image areas, and a detrimental background is formed in these areas as well, which has an adverse effect on the quality of the copy.

It is an object of the present invention to provide a method and apparatus for the development of toner images which allows the development of fine lines and sharp edges without imaging M' and which does not impose stringent requirements on maintaining small tolerances in the development gap. It is about providing.

Means and operation for solving the problem The purpose is to rotate the magnetic core, set the frequency of the alternating current voltage to 15) kHz or more, and maintain the thickness of the single-component toner layer at least as thick as the development gap. achieved by. Since no space is provided between the toner layer and the base, rather they are brought into contact with each other, the toner layer may be relatively thick, and therefore a large amount of toner can contribute to development. By bringing the toner into direct contact with the charge image, fine line imaging is improved because image line disturbances of the charge image are avoided. By rotating the magnetic core and applying a high frequency voltage, an alternating electromagnetic field is obtained which vibrates particularly fine toner particles at high speed. As a result, the small toner particles are able to move through the toner material in response to the charge difference without being significantly hindered by the larger toner particles. The availability of fine toner particles to the charge image is therefore increased, which is particularly advantageous for the precise formation of sharp edges and thin lines. By increasing the mobility of particularly fine toner particles within a single component toner, the quality of reproduction is significantly improved.

An alternating voltage is applied, preferably with a frequency of 18 to 20 kl (z). This frequency is so high that it is possible to loosen the toner layer as a whole, rather than the toner particles themselves being subjected to a translational movement by the toner field. .The peak-to-peak amplitude of the AC voltage is 1400VPP or more, preferably 1
Preferably, it is 600 vpp or more.

According to another embodiment of the invention, the alternating current voltage is superimposed with a direct voltage of 30 to 60 V of the same polarity as the charge image of the base.

This method avoids the occurrence of toner transfer in non-image areas which may carry residual charges, especially during multi-copying. That is, this is because the generation of potential difference in non-image areas is prevented.

According to another embodiment of the invention, the magnetic single-component toner comprises a multipolar magnetic core surrounded by a driving sleeve, which faces the passing support material across a development gap, and the peripheral surface of said sleeve is insulating. A toner image is developed on the photoconductive base bearing an electrostatic latent image by a magnetic brush which protrudes into each replenishment container and has a doctor at the outlet of the replenishment container and is spaced from the sleeve. In the device for which the sleeve and doctor are
A rotary drive means is incorporated in the magnetic core, and the frequency of the alternating current voltage is at least 15 kHz. With this device, an alternating electromagnetic field is obtained in the development gap where the toner material is in contact with the support material, which alternating electromagnetic field contributes to loosening the toner material and increasing the mobility of especially small toner particles. Therefore, it is easy to transfer the small toner particles, and this transfer occurs mainly under the action of the electrostatic field of the support material'+[charged image.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Other characteristics and advantages of the invention will become apparent from the following description of the embodiment shown in FIG. 1 and from the appended claims.

A drum 1 serving as a base is coated on its sides with a layer 2 of a photoconductive material, for example selenium, said layer 2 being grounded,
That is, it is connected to zero potential.

An electrostatic latent image is generated on the No. 2 in a known manner, and the latent image is developed by the transfer of the insulating magnetic single-component toner 6.

Particle size of 5 μm to 30 μm, preferably 5 μm
A magnetic single-component toner with a resistance of 1 to 25 μm and a resistance of 10 ohms is used.

Single-component toner 6 is stored in a replenishment container 5 having an opening at the bottom, and a magnetic brush is placed in the area of this opening. The magnetic brush includes at least eight multi-pole magnetic cores alternating circumferentially and each having magnetic poles extending in the axial direction. The magnetic core 3 is surrounded by an alloy steel sleeve 4. The magnetic core 3 and the sleeve 4 are rotated in opposite directions as shown by arrows. The rotation speed of the sleeve 4 is about 200 to 270 mIn, and the rotation speed of the magnetic core 3 is about 1000 to 1350 mIn.
It is driven at a rotational speed of in''. Sleeve 4 and magnetic core 3
It is preferred to maintain a rotational speed ratio of about 1:5. Single-component toner 6, independent of the rotation of sleeve 4 and magnetic core 3, is supplied onto sleeve 4 in the circumferential direction, precisely in the direction of movement opposite to the direction of rotation of magnetic core 3. The thickness of the layer 8 of single-component toner 6 circulating on the sleeve 4 is limited by a doctor blade 7 attached to the supply container 5 with a radial edge relative to the strip IJ-f 4.

Since the doctor blade 7 is made of a magnetizable material, for example a steel plate, the thickness of the layer 8 between the magnetic core 3 and the blade of the doctor blade 7 is set to be slightly thinner than the gap @a2.

The magnetic core 3 and the stones of the drum 1 are parallel to each other.

The magnetic brush is placed between the sleeve 4 and the drum 10 layer 2 at approximately 0.
, 25 to 0.4wn. The distance a2 between the doctor 7 and the circumferential surface of the sleeve 4 is such that the thickness of the layer 8 of the monocomponent toner 6 is at least equal to the development gap 7' a 1 , preferably slightly more than this, i.e. from about 5 to 15 Set it so that only Chi sounds like a dog.

The sleeve 4, which is preferably electrically conductive and may optionally be provided with a thin electrically insulating covering, is applied by a generator 9 with a high frequency alternating current voltage superimposed on a weak direct current voltage. 3
The DC voltage of 0 to 60V1, preferably 40V, has a polarity that corresponds to the polarity of the charge image area of layer 2. Preferably, the sinusoidal alternating voltage has a frequency of 15 kHz or more, preferably 18 to 20 kHz. The peak-to-peak amplitude of the AC voltage is 1600 vpp. In a preferred embodiment, the ambient velocity of the conductive layer is approximately 10 to 15 t.
Set so that yn/see.

Due to the high frequency alternating field 1d which cooperates with the alternating magnetic field generated as the magnetic core 3 rotates and also cooperates with the single component toner layer 8, the mobility of especially small toner particles increases, resulting in thin lines. The relatively large amount of fine toner particles provided at the edges and sharp edges provides excellent development results. By bringing the layer 8 of monocomponent toner 6 into contact with the photoconductive layer 2, scattering of the image lines of the charge image is avoided, so that, in synergy with other measures, extremely sharp images are obtained. Furthermore, by superimposing the DC voltages, the generation of background images can be prevented even in the case of multiple +Ii copies.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a toner image developing device of the present invention. DESCRIPTION OF SYMBOLS 1... Drum, 2... Photoconductive layer, 3... Magnetic core, 4
... Sleeve, 5... Supply container, 6... Toner,
7...Doctor, 8...Tona layer, 9...Generator, ill...Development gap・Continued from white page 1 0 Inventor Klaus Taureen Federal Republic of Germany. Torase 42

Claims (1)

[Scope of Claims] 1. A multipolar magnetic core and a rotating sleeve surrounding the core, a homogeneous layer of insulating magnetic single-component toner circulates on the surface of the sleeve, and the rotating sleeve moves while sandwiching a developing layer. A toner image is formed on said photoconducting support bearing an electrostatic m-image using an arrangement in which a magnetic brush is provided opposite to a base and adjacent to an alternating current voltage with respect to the base. The developing method is characterized in that the magnetic core is driven to rotate, the frequency of the alternating current voltage is 15 kHz or more, and the thickness of the single-component toner layer is maintained at least as thick as the development gap. A method of representing a toner image. 2. The method according to claim 1, characterized in that an alternating voltage with a frequency of 18 to 20 kHz is applied. 3. The peak-to-peak amplitude of the AC voltage is 1400 vpP or more,
The method according to claim 1 or 2, characterized in that it is preferably 1600 vpI) or higher. 4. A method as set forth in any one of claims 1 to 3, characterized in that one layer of toner circulates four times in the direction of movement of the base in the development gap f. 5. The AC voltage has a polarity that matches the latent image of the base.
5. The method according to claim 1, wherein a DC voltage of 0 to 60 V is superimposed. 6. The method according to any one of claims 1 to 5, characterized in that a monocomponent toner having a resistance value of about 10 ohms and a particle size of about SP to 30 μm is used. 7. Consisting of a multipolar magnetic core surrounded by a driven sleeve facing a passing base with a development gap in between, the peripheral surface of the sleeve protrudes into an insulating magnetic single-component toner supply container, and the supply container In an apparatus for developing a toner image on the photoconducting base bearing an electrostatic latent image by a magnetic brush having a doctor provided at a discharge opening of the sleeve (4) to maintain a predetermined distance from the sleeve (4). and the doctor (7) is larger than the developing gear, the magnetic core (3) contains rotational drive means, and the frequency of the alternating current voltage is at least 15 kHz. Characteristic toner image developing device. 8. Device according to claim 7, characterized in that the doctor (7) is made of a magnetizable material. 9. The sleeve (4) is rotationally driven so that it moves in the same direction as the base (2) in the developing gap (a) and the magnetic core (3) is driven in the opposite direction to the sleeve (4). An apparatus according to claim 7 or 8.