JPH021882A - Electrophotographic developing method - Google Patents

Abstract

PURPOSE:To obtain an object image superior in visibility and gradient by employing developer consisting of the mixture of a high resistance magnetic toner and high resistance magnetic carrier, employing a developing sleeve which contains a magnetic roll in it, and then developing under an alternating electric field or alternating magnetic field. CONSTITUTION:The developer consists of the mixture of the high resistance toner and high resistance carrier. The developer is stored in a developing container 5 and is carried by means of an agitator 6 to the sleeve 3 on which it is magnetism-attracted to form a magnetic brush. The magnetic brush is pushed out by means of a doctor blade; it forms a soft brush, coupled with the rotation of the sleeve 3; and it rubs an electrostatic image carrier 1. AC power 7 is connected between the image carrier 1 and magnetic roll 2, and the alternating electric field is impressed between the image carrier 1 and sleeve 3. Under the action of the alternating electric field, the magnetic brush on the sleeve 3 rubs the electrostatic image carrier 1, thereby developing an electrostatic image.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to an electrophotographic developing method, and in particular, it uses a developer made of a mixture of a high-resistance magnetic toner and a high-resistance magnetic carrier to develop a clear texture image. The present invention relates to a magnetic brush developing method that can obtain a copy image free of blemishes.

[Prior Art] Conventionally, as a magnetic brush developing method, a one-component method using a -component developer and a two-component method using a two-component developer are known. - The component-based method uses either conductive toner or high-resistance magnetic toner, and has the advantage that the structure of the developing device is simple and maintenance is easy. For example, with conductive toner, it is difficult to reproduce low-contrast originals, and the transfer efficiency is poor, causing B10 off phenomenon and transfer blur.Also, with high-resistance toner, low-resistance toner Although it has the advantage of better transfer and high-speed development, it still solves several problems such as thicker and thinner reproduced lines, uneven development of solid black areas, and blurring. On the other hand, the two-component method uses a developer that combines magnetic toner and magnetic carrier, which improves the reproducibility of low-contrast originals and fine lines, but the transfer material There are problems with controlling the age of the carrier and the concentration of toner in the developer.

As a solution to the problems of these two conventional developing methods, a developing method using a developer made by mixing minute magnetic carriers and non-magnetic toner is known (for example,
9-24416).

In the method disclosed in this publication, a magnetic brush is formed using a magnetic developer made of a mixture of an insulating magnetic carrier and an insulating non-magnetic toner having a particle size of substantially 5 to 3 um. Development is carried out by rubbing the surface of the electrostatic image carrier under the action of an alternating magnetic field.

[Problems to be Solved by the Invention] Although the method using the above-mentioned microcarriers provides a very high-quality developed image with no background blur and can solve some of the above-mentioned problems, it is still difficult to use toner particles. Concerning one-time control of toner, the mixing ratio of which must be controlled within the range of 6 to 35 wt%! ! The issue remains.

The present invention has been made in view of the above-mentioned problems, and is an electronic device that substantially eliminates the need to control toner density, and can obtain copied images with no ground blur, excellent image clarity, and rich gradation. The purpose is to provide the foundation for photographic development methods.

[! ! Means for Solving the Problem] For this reason, whereas the conventional method described above uses a mixture of a non-magnetic toner and a carrier, the electrophotographic method according to the present invention
The JL image method uses a developer made of a mixture of high-resistance magnetic toner and high-resistance magnetic carrier, and magnetically attracts the developer around the circumference of a developing sleeve having a magnetic roll inside to form a magnetic brush. Is the magnetic brush silent under the action of alternating tffi field and alternating 8iW? If [! l! It is characterized by developing an electrostatic image on the body.

That is, the present invention uses a relatively small amount of high-resistance magnetic toner in order to maintain the advantages of the magnetic brush development method using high-resistance magnetic toner while eliminating its disadvantages of thick lines and curling. A high-resistance magnetic carrier is mixed, and an electrostatic image is created by a magnetic brush made of this mixture under the action of an alternating electric field and alternating magnetic field W.

[Operation] According to such a means, the magnetic toner on the sleeve is vibrated due to the action of the alternating electric field and the alternating magnetic field, and the magnetic toner on the sleeve is vibrated, and the magnetic toner is vibrated at the fji-ki brush in contact with the electrostatic image carrier from the sleeve surface.
! l! Reciprocating movement between the TS body and the sleeve surface (lti movement)
repeat. At this time, since there is a latent image potential on the surface of the electrostatic image carrier, the magnetic toner adheres only to the portion of the carrier corresponding to the electrostatic image due to the Crohn's force. In this way, compared to the conventional developing method using a constant magnetic field or constant potential, the magnetic toner is attracted to the latent image potential area due to the synergistic effect of the alternating electric field and alternating magnetic field, and the magnetic toner is attracted to the latent image potential area, producing a clear, fog-free copy image. Form. Further, by mixing with a high-resistance magnetic carrier, a triboelectric charge is imparted to the high-resistance magnetic toner, which improves its adhesion to an electrostatic image and improves the fluidity of the developer.

[Example code] Embodiments of the present invention will be described below with reference to the drawings.

In the figure, l is an electrostatic image carrier formed by forming a suitable photoreceptor on the circumferential surface of a cylindrical drum, and is designed to rotate in the direction of arrow A at a predetermined circumferential speed. An electrostatic potential difference image is formed on the surface of the photoreceptor by a suitable electrostatic image forming means therein. The photoreceptor and electrostatic image forming means may be of a known construction, such as those used in xerography.

A magnet roll 2 is provided close to and parallel to the electrostatic image carrier 1 so as to be rotatable in the direction opposite to the electrostatic image carrier 1 (in the direction of arrow B). The cylindrical sleeve (developing sleeve) 3 moves at approximately 1 of the peripheral speed of the electrostatic image carrier l.
．． It is provided so as to rotate in the same direction (direction of arrow C) at a circumferential speed that is 5 to 2.5 times higher. The setting value of the circumferential speed of the tube relative to the circumferential speed of the electrostatic image carrier is important; if it is less than 1.5 times, the copy density of the formed copy image will be too low; If it exceeds this, the copy density will become too high. The surface of the sleeve is processed to have a surface roughness of, for example, 1 to 3 um, increasing the developer conveying power.

The magnet roll 2 is magnetized with NS poles alternately, and it is particularly preferable to have a magnetic force with a surface gauss of about 450 to 600 gauss on the TQ image sleeve, and its rotation moves the magnetic poles to form an electrostatic image facing the magnet roll. An alternating magnetic field is created on the carrier surface. Regarding the frequency of the alternating magnetic field,
It is desirable to set the number of poles and rotational speed of the magnet roll so that the magnetic pole passes through the image portion passing through the developing section at least 8 times. For example, if the circumferential speed of the electrostatic image bearing pair is 60 m / 5eC1 magnet roll has a magnetization width of 6-12
In the case of a roll that is polarized, the rotational speed of the magnet roll is desirably set to about 500 r,p,+11 or more. If the frequency is lower than this alternating magnetic field frequency, there is a tendency for a thin copied image with toner scattered around the characters.

A doctor blade 4 located close to the sleeve 3 is made of non-magnetic material and forms a uniform layer of developer of a suitable thickness on the sleeve.

For example, the gap between the sleeve 3 and the electrostatic image carrier l is set to 0.65.
0.75 mm, a suitable soft brush can be formed by setting the gap from the tip of the doctor blade 4 to the sleeve at 0.35 to 0.45.

The developer used in the present invention is a mixture of a high-resistance magnetic toner and a high-resistance magnetic carrier, and the mixing ratio of the high-resistance magnetic toner in the developer is 50 wt% or more, more preferably around 70 wt%. . The high-resistance magnetic toner is made of an insulating resin such as acrylic resin containing 40 to 60 itz% of magnetic fine powder such as ferrite based on the total toner.
Average particle size 12c with electrical resistance value of 0I5Ω・1 or more
+ m, preferably 7 to 15 urR. On the other hand, a high resistance magnetic carrier has a resistance of 108Ω・1 under the same conditions.
or more, preferably 40 to 1100u
It consists of a spherical carrier. In addition, the two-gas resistance value in the present invention is determined by putting toner into a cylinder having a circular electrode of 0.073 cm2 on the bottom, applying a pressure of about 2.7 kg/cm2 to this toner with a piston, and increasing the thickness. Approximately 1
．． 5ml11, and change the voltage applied between the piston and the electrode from 50V to 100OV to flow between them? ii flow was measured and the value was calculated from this.

Such mixed developer is stored in the developer container 5,
It is carried by the agitator 6 to the sleeve 3 and magnetically attracted thereon to form a magnetic brush. The magnetic brush is adjusted by a doctor blade 4, and in combination with the rotation of the sleeve forms a soft brush that rubs the electrostatic image carrier.

On the other hand, between the electrostatic image carrier 1 and the magnet roll 2, an AC type R
6 are connected. The AC power supply 7 is a DC bias (for example, about 100cm) with an AC bias applied to it.
An alternating voltage with a frequency of 800 to 2 KHz is generated, thereby applying an alternating electric field between the electrostatic image bearing belt l and the sleeve 3. The peak voltage of the AC power supply varies depending on the gap between the electrostatic image carrier 1 and the sleeve 3, but when this gap is 0.7 mm, the peak voltage is preferably about 1500 V or more.

In this way, the magnetic brush formed on the sleeve 3 rubs against the electrostatic image carrier under the action of an alternating electric field, thereby developing the electrostatic image.

During development, only the magnetic toner is consumed and needs to be replenished, but unlike the conventional two-component method, it is not necessary to replenish the toner in fixed quantities while taking into account the toner concentration. It is only necessary to replenish the developer appropriately when the remaining amount of developer becomes low.

[Effects of the Invention] As described above, the developing method according to the present invention maintains the advantages of the one-component method using a high-resistance magnetic toner, and also solves the problems thereof, and there is no background blurring. , a copy image with excellent image line brightness and rich gradation can be obtained without the trouble of controlling toner density.

[Brief explanation of the drawing]

The figure is a schematic side view of essential parts of an example of an apparatus for carrying out the developing method according to the present invention. l... Electrostatic image carrier 2... Magnet roll 3...
fil image Suri Sleeve 4...Doctor Blade 7...
·AC source.

Claims (9)

[Claims] (1) Using a developer made of a mixture of high-resistance magnetic toner and a high-resistance magnetic carrier, the developer is magnetically attracted to the circumferential surface of a developing sleeve having a magnetic roll inside to form a magnetic brush. An electrophotographic developing method comprising: developing an electrostatic image by rubbing it on an electrostatic image carrier under the action of an alternating electric field and an alternating magnetic field. (2) The electrophotographic developing method according to claim 1, wherein the mixing ratio of the high-resistance magnetic toner in the developer is 50 wt% or more. (3) The frequency of the alternating electric field is 800 to 2 kHz, and the frequency of the alternating magnetic field is such that the magnetic pole passes eight times or more with respect to the image portion passing through the developing section. The electrophotographic developing method according to item 1 or 2. (4) The electrophotographic developing method according to any one of claims 1 to 3, wherein the alternating electric field is formed by multiplying a DC bias by an AC bias. (5) The electrical resistance of the high resistance magnetic toner is 10^1^5
An electrophotographic developing method according to any one of claims 1 to 4, characterized in that the resistance is Ω·cm or more. (6) The high-resistance magnetic toner is applied to an insulating resin with a molecular weight of 40 to 60%.
3. The electrophotographic developing method according to claim 1, wherein the electrophotographic developing method contains wt% of magnetic fine powder. (7) The electrophotographic developing method according to claim 1 or 2, wherein the high-resistance magnetic carrier is a spherical carrier with a thickness of 40 to 100 um. (8) A developer made by mixing a high-resistance magnetic toner and a high-resistance magnetic carrier at a toner mixing ratio of 50 wt% or more is magnetically attracted to the circumferential surface of a developing sleeve having a magnetic roll inside, and a magnetic brush is applied. The developing sleeve is moved in approximately the same direction as the moving direction of the electrostatic image carrier at a speed of 1.5 to 2.5 times, and the magnetic brush is moved under the action of an alternating electric field and an alternating magnetic field to form an electrostatic image. An electrophotographic developing method characterized by developing an electrostatic image by rubbing it on a carrier. (9) A magnetic brush is formed by magnetically adsorbing the developer to the circumferential surface of a developing sleeve having a magnetic roll inside, using a developer made of a mixture of a high-resistance magnetic toner and a high-resistance magnetic carrier. An electrophotographic developing method characterized by developing an electrostatic image by rubbing it on an electrostatic image carrier.