JPS5948389B2 - magnetic brush developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic brush developing device that uses a so-called one-component magnetic developer that does not contain a granular carrier.

As such a device, the inventions described in Japanese Patent Laid-Open No. 49-4532 and Japanese Patent Laid-Open No. 50-31827 are already known.

The drawbacks of the prior art including these inventions are listed below. (i) The exposure latitude is narrow.

Poor midtone reproduction. (゛) Copy reproducibility of low contrast originals is poor.

When a magnetic developer with high electrical resistance is used, ghost-like background stains occur around the image area.
゜Good When a non-magnetic material with high electrical resistance is used as the developing roller, a unique ghost-like background stain occurs around the image area.

(φ Approximately uniform gray background stain occurs over the entire surface to be developed.

In particular, when the average particle size of the magnetic developer is small, or when a magnetic developer containing a magnetic developer with a small particle size and a wide particle size distribution is used, this kind of background staining may occur. The above-mentioned unique ghost-like background stains around the image area occur significantly. (R0 Development unevenness occurs.

In particular, when copying low-contrast originals and multicolor originals, the exposure amount must be slightly insufficient.
Uneven shading occurs in the image in a direction parallel to the scanning direction of the surface to be developed. (Vll) Poor resolution and sharpness.

Although these shortcomings in the prior art can be solved individually, the overall solution is insufficient.

In particular, solutions to one problem may give rise to other new drawbacks. For example, in order to lower the electrical resistance of a magnetic developer, a method has been proposed in which the content of a conductive pigment such as carbon black is increased in the magnetic developer. Although this method improves the above-mentioned drawback Oi0 to a considerable extent, the content of the conductive pigment required for this method is extremely high, and as a result, a new drawback arises in that the fixing performance becomes extremely poor. In addition, as another method for lowering the electrical resistance of the magnetic developer, a method has been proposed in which a conductive pigment is attached to the surface of the magnetic developer to lower the electrical resistance of the surface of the magnetic developer. .

According to this method, it is possible to lower the electrical resistance of the developer by using a small amount of conductive pigment, and the above-mentioned drawback 011 can be avoided.
) is improved to a considerable extent. However, at the same time, a new drawback arises in that the fixing performance is significantly deteriorated.
Furthermore, a method is known in which a one-component magnetic developer is used to perform magnetic brush development and then the developer image is transferred onto plain paper.

In this method, since transfer is usually performed electrically, a magnetic developer with high electrical resistance must be used. Therefore, the above-mentioned disadvantage of lowering the electrical resistance of the developer is eliminated.
The improved method 1i) cannot be an effective method for this system. An object of the present invention is to provide a magnetic brush developing device using a one-component magnetic developer, which eliminates the various drawbacks of the prior art described above.

According to the present invention, magnetic developers with high electric resistance, those with a wide particle size distribution, those with a small average particle size, and even those with a low content of powdered magnetic material therein can be used as magnetic developers. The restrictions on magnetic developers are significantly relaxed compared to the prior art.

In addition, as the non-magnetic material, it is possible to use plastic molded bodies, plastic tubes, etc., which have a low-energy surface to which the developer is difficult to adhere and therefore are hard to stain, and which have high electrical resistance. Furthermore, since it is possible to widen the distance between the doctor and the non-magnetic material as the doctor member, restrictions on the manufacturing method and material are relaxed in terms of accuracy and wear resistance. Furthermore, since it is possible to widen the distance between the doctor and the non-magnetic material and to reduce the torque during doctoring, restrictions on the magnetic developer from the viewpoint of wear resistance are relaxed.

That is, this makes it possible to use a magnetic developer that contains a low melting point substance or a low softening point substance and is easy to fix. As described above, according to the present invention, not only can the various drawbacks of the prior art be improved to a sufficient degree, but also other items such as accuracy, cost, freedom of material selection, and fixability of copied images can be improved. , also regarding reliability issues such as durability, etc.
Many benefits can be obtained.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing an embodiment of the present invention.
Inside the rotatable non-magnetic material 1, there is a magnetic pole S1 for development.
and N,, S,, N2, S, as a magnetic pole for developer transport.
, and N3 are arranged stationary. A one-component magnetic developer 4 is housed in the hopper 3, and the developer 4 is supplied to the surface of the sleeve 1 from its lower opening. The developer supplied onto the sleeve is raised like a brush by the magnetic force of the magnet 2, and its layer thickness is regulated by the tip of the doctor 5. The developer brush on the sleeve comes into contact with the surface to be developed 6 moving in the direction of the arrow at a developing position between the developing magnetic poles S and N.
Visualizes the electrostatic latent image on the surface to be developed. The surface to be developed is a sheet-like, band-like, or drum-like photoreceptor or recording medium. In the apparatus shown in FIG. 1, the number of magnetic poles of the magnet 2 is six, and the angles between the magnetic poles are made equal to each other. However, this is not necessarily necessary, and the point is that the developing positions are It is to be located between adjacent magnetic poles.

At the development position, the distance d between the surface to be developed 6 and the surface of the sleeve 1 is set to be smaller than or equal to the thickness t of the developer brush layer at this position, so that the surface to be developed 6 is sufficient to cover the developer brush layer. It is designed to make contact with And the doctor
The tip of 5 is arranged so as to face one of the adjacent magnetic poles or any other magnetic pole at the development position. The thickness of the developer brush varies greatly depending on its relative position with the magnetic pole, and exhibits an overall wavy cross section.

That is, as shown in FIG. 2, the magnetic developer particles in the magnetic developer brush form a chain bond, and the chain is erected against the non-magnetic material surface at the magnetic pole position, corresponding to the magnetic field line distribution. The length of each chain is significantly non-uniform. Further, between the magnetic poles of only one polarity, the valley chains twist along the non-magnetic material surface, and the thickness of the developer brush is extremely uniform. The developer particle packing density in the developer brush has a minimum value at the magnetic pole position,
It shows the maximum value between magnetic poles of different polarity. These characteristics of the developer brush have a great effect on the copied image.
In the conventional magnetic brush development method, the development position is set at the magnetic pole position, and development is carried out by bringing the raised developer brush portion, which has a low developer density, into contact with the surface to be developed.

Low developer density has negative consequences for copy reproducibility, especially for low contrast originals, and the use of a raised developer brush section has good results in exposure latitude and halftone reproduction. In the latter case, the contact area with the surface to be developed is large, which is thought to be the reason for the good results. Therefore, if the position between the magnetic poles where the developer density is high is set as the development position, and the developer passes through the brush layer at that part by submerging the surface to be developed, the contact area with the surface to be developed can be reduced. can be expanded, so that good results can be produced for each of the above characteristics. Therefore, in the present invention, as shown in FIG. 1, the development position is set between the magnetic poles S and N1, and the distance d between the surface of the sleeve 1 and the surface of the surface to be developed 6 is determined by the developer brush layer at that position. less than or equal to the origin t, preferably t-d=or! It is set to be m~0.3wn. As a result, an image quality that can be determined to be good in all other characteristics is obtained, except for the occurrence of uneven development. Furthermore, by setting the doctor 5 at the magnetic pole position, uneven development was also eliminated. This is because by setting the doctor at this position, the precision required of the doctor is reduced. That is, when the thickness of the developer brush is adjusted to be small and uniform, the doctor efficiency is high at that position, and as a result, the distance between the doctor and the non-magnetic material can be set relatively wide at that position. It becomes possible. At the same time, the settings at this position of the doctor do not have any negative effect on other characteristics of image quality.
Therefore, it can be an effective method for improving uneven development. Further, as a drawback of the prior art, when a developer containing a low melting point substance or a low softening point substance that is easy to fix is used for a long period of time, the developer adheres to the doctor member and the non-magnetic member. A secondary effect was obtained in that the defect of white streaks (a phenomenon in which undeveloped areas appear in a linear manner) due to clogging was eliminated. It can be understood that this is achieved because the developer particle packing density of the developer brush at this position is small, and the friction between the doctor and the developer is reduced accordingly. In addition, the angle between the magnetic poles θ1 + θ2 (however, θ1 = θ2) from the center of the single-polarity sleeve is 90 degrees to
After changing the angle up to 20 degrees and examining the effect of this angle on the copied image, we found that the appropriate angle is 75 degrees to 35 degrees.
The results showed that the more preferable conditions were 60 degrees to 45 degrees.

That is, when the angle between the magnetic poles of the Tatsumi polarity is smaller than 35 degrees, the obtained copy image is almost the same as the image obtained in the prior art, and therefore, the preferred conditions in the present invention are Not considered.

Also, is the angle 75? When larger than this, significantly lower quality copy images were obtained. There was significant unevenness in development, and the magnetic developer was scattered on the copy paper, resulting in extremely uneven background stains. Furthermore, the line drawings are discontinuous and the sharpness is extremely poor. These can be interpreted by considering the magnetic field line distribution and magnetic field strength. The reasons why the development position according to the present invention provides good image quality can be summarized as follows.

(1) The packing density of developer particles in the developer brush is high.

(2) The thickness of the developer brush is uniform, and a uniform equipotential surface is formed over the entire width of the surface to be developed.

(3) Proper contact between the developer brush and the surface to be developed.

It is not appropriate whether the contact between the two is in an insufficient state or in an excessive state. (4) The width of the contact area between the developer brush and the surface to be developed is large.

When the electrical resistance between the developer and the non-magnetic material is high, assuming an equivalent cycle during development, the time constant of the circuit is large, and therefore a long time, or a large contact area width, is required for development. Ru. Specifications of some examples are shown below.

Example 1 (1) Magnetic developer: average particle size (diameter) 6
．． 4μ standard deviation 4.3μ specific resistance 6.9
×1013Ω゜m (Measurement conditions: electric field strength 200 V/cmD6C) Specific gravity 2.2 (2) Developed object: Photosensitive paper for electronic recopy (manufactured by Ricoh) (
3) Magnetic force of magnet: 1400 Gauss (4) Non-magnetic sleeve: Teflon (5) Angle between Tatsumi polar magnetic poles: 60° (6) Distance between doctor blade and non-magnetic material 0.4~
Changes to 1.2 fights.

The doctor blade is set at the magnetic pole position.

(7) When the thickness of the developer brush is t and the distance between the nonmagnetic material and the surface to be developed is d, it changes from t-d-0.3 to +0.5.

Result: A state was created in which the developer brush and the surface to be developed came into contact between the magnetic poles of Tatsumi polarity, and t-d=O to +O. 3wr!
When n, a copy image improved to a sufficient extent was obtained.

Example 2 (1) Magnetic developer: Average particle size 8.0μ Standard deviation 4.4μ Specific resistance 1.61×109
Ω． (-m (Electric field strength during measurement 200 V/cmDC) (2) Developed object: Photosensitive paper for electronic recopy (manufactured by Ricoh) (
3) Magnetic force of magnet: 1000 Gauss (4) Non-magnetic material: Bakelite (5) Angle between Tatsumi polar magnetic poles: 45° (6) Distance between doctor blade and non-magnetic material 0.4~
Changed to 1.2rMn.

The doctor blade is set at the magnetic pole position.

(7) Thickness of the developer brush t If the distance between the non-magnetic material and the surface to be developed is d, then t-d=0~
+0.3rfm (8) Bring the developer brush into contact with the surface to be developed between magnetic poles of different polarity.

Result: A copy image improved to a sufficient extent was obtained.

Example 3 (1) Magnetic developer: Average particle size 7.7μ Standard deviation 3.9μ Specific resistance 5.4×107Ω
・m (Electric field strength during measurement 200 VrD0C.) 5.0×5. (2) Object to be developed: Electrostatic recording paper for Rifux (manufactured by Ricoh)
(3) Magnetic force: 1000 Gauss (4) Non-magnetic sleeve: Aluminum surface with a thickness of 500 mm
coated with a Teflon tube.

(5)? Angle between polar magnetic poles: 35° (6) Distance between doctor blade and non-magnetic material 0.4W
Two types of rln and 1.2rfffL (7) t-d=
O~+o. 3wn (8) Bring the developer brush into contact with the surface to be developed between the magnetic poles of Tatsumi polarity.

Result: A copy image improved to a sufficient extent was obtained.

Example 4 (1) Magnetic developer: Average particle size: 10.6μ Standard deviation:
5.2μ specific resistance 4.8X103Ω・m (Electric field strength at the time of measurement 30V/cm D.C.) (2) Developed object: Electronic Ricopy photosensitive paper (manufactured by Ricoh) (3
) Magnetic force: 750 Gauss (4) Non-magnetic sleeve:
Aluminum (5) Angle between magnetic poles of polarity: 400 (6) Distance between doctor blade and non-magnetic material 2 types: 0.4 wL and 1.2 wL (7) t-d=O~+0.3
(8) Bring the developer brush and the surface to be developed into contact between the magnetic poles of Tatsumi polarity.

Result: A copy image improved to a sufficient extent was obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of a magnetic brush developing device according to the present invention, and FIG. 2 is an explanatory diagram showing the behavior of developer on a non-magnetic sleeve. 1: Non-magnetic sleeve, 2: Magnet, 3: Hopper, 4:
One-component magnetic developer, 5: doctor, 6: surface to be developed.

Claims (1)

[Claims] 1. The one-component magnetic developer supplied from the hopper to the surface of the rotating non-magnetic sleeve is attracted to the surface of the sleeve by the magnetic force of a magnet having a plurality of magnetic poles that is statically provided within the sleeve. The thickness of the developer layer on the sleeve is adjusted by the tip of the doctor provided at a certain gap on the sleeve surface, and the developer layer is brought into contact with the surface to be developed at a predetermined development position. In a magnetic brush developing device that visualizes the electrostatic latent image on the surface to be developed, the development position is set at the center between different adjacent magnetic poles of the magnet, and the opening between the magnetic poles at that position from the center of the sleeve is determined. The angle is between 35 degrees and 75 degrees,
The thickness of the developer layer at the development position is set to be greater than or equal to the gap between the surface to be developed and the sleeve surface at that position, and the tip of the doctor is set to one of the magnetic poles other than the one adjacent to the development position. A magnetic brush developing device characterized by being arranged facing each other.