JPH0133823B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a developing method for visualizing an electrostatic latent image formed on the surface of a material layer such as a photoconductive layer or a dielectric layer using a magnetic toner. This invention relates to a developing method in which the surface of a material layer is rubbed with a magnetic brush.

[Prior art]

In the magnetic brush development method, a magnetic material is supplied from a developing tank containing a magnetic substance onto a magnet roll and conveyed to a developing area by the magnet roll. The electrostatic latent image carrier that forms the development area between the magnet roll and the magnet roll may be a substantially insulating polyester sheet, Se, CdS mylar, PVC, or ZnO.
etc. are well known.

The developer conveyed to the developing area by the magnet roll forms a magnetic brush at least in that area, and this magnetic brush rubs the surface of the carrier to visualize the electrostatic latent image. The above magnet roll and magnetic brush developing device using the same are disclosed in, for example, U.S. Pat. No. 3,455,276 and U.S. Pat.
It is described in the specification of No. 4081571, etc.

As the above developer, a so-called two-component developer, which is a mixture of a magnetic carrier and a toner, has been used. However, this two-component developer requires a means to keep the toner concentration in the developer constant and a stirring means to frictionally charge the toner and carrier well, so the structure of the developing device is There are problems such as the structure becoming more complex and larger.

Therefore, a one-component magnetic toner consisting of toner particles whose main components are resin and magnetic powder is being used as a developer. As this magnetic toner, so-called conductive magnetic toners described in US Pat. No. 3,639,245, US Pat. No. 3,925,219, etc. are known. This conductive magnetic toner is
Although it has been put into practical use in the CPC method due to its low electrical resistance, it cannot be practically used in the PPC method due to problems with transfer. Examples of magnetic toner suitable for the PPC method that includes a transfer process include U.S. Patent No.
High-resistance magnetic toners are used as described in US Pat. No. 4,265,993 and US Pat. No. 4,121,931.

As a method for developing an electrostatic latent image using a one-component magnetic toner, for example, the above-mentioned US Pat.
No. 4,081,571 and US Pat. No. 4,267,248. First, in US Pat. No. 4,081,571, toner conveyed on a sleeve accumulates on the upstream side of the position where the sleeve and photoreceptor face each other, thereby forming a toner reservoir. The toner in this toner reservoir is agitated, for example, by rotating the magnet in the opposite direction to the sleeve. Next, U.S. Patent No.
In No. 4,267,248, the sleeve and magnet rotate in the same direction, so the sleeve tends to transport toner in the opposite direction from the magnet. Therefore, 2
Two toner flows are formed, one from the toner container to the photoreceptor due to the rotation of the magnet, close to the toner layer on the sleeve, and the other from the photoreceptor to the toner container at the bottom of the toner layer due to the rotation of the sleeve. The flows are close together. When this second flow reaches the doctor blade, the toner supplied from the toner container onto the sleeve is pulled back and this downstream is weakened, thus keeping the toner supply constant.

By the way, one-component magnetic toner, especially the above-mentioned
The magnetic toner used in the PPC method tends to have a high resistance from the viewpoint of transferability, and in order to obtain clear images with high resolution, the particle size is reduced (for example, the particle size distribution is 10
~30 μm), the fluidity is poor and blocking tends to occur in the toner container or on the magnet roll.

〔the purpose〕

An object of the present invention is to provide a developing method that can always form a stable toner flow without causing blocking even when using magnetic toner that has low fluidity and tends to aggregate.

Another object of the present invention is to provide a developing method that provides high quality images.

[Structure] The developing method of the present invention uses a cylindrical cylinder which is rotatably arranged opposite to a carrier having an electrostatic latent image on its surface and which has a rotatable permanent magnet roll having a plurality of magnetic poles therein. A magnetic brush is formed on the non-magnetic sleeve by supplying magnetic toner onto a shaped non-magnetic sleeve and rotating the permanent magnet roll and the non-magnetic sleeve in the same direction, and the magnetic brush covers the carrier surface. In the developing method using rubbing, a toner pool is formed near the tip by installing a shielding plate on the non-magnetic sleeve, the tip of which comes in contact with the non-magnetic sleeve, and the non-magnetic By setting the number of rotations of the sleeve to 1/20 or less, the sleeve has a length of 0.3 to 0.5 mm that can follow the rotating magnetic field of the permanent magnet roll and is substantially the same as the moving speed of the surface of the non-magnetic sleeve. The present invention is characterized in that a magnetic brush is formed that moves at a speed in a direction opposite to that of the non-magnetic sleeve.

〔Example〕

The details of the present invention will be explained below with reference to the drawings.

In FIG. 1, a drum-shaped photoreceptor 1 is rotating in the direction of arrow Z in the figure, and a cylindrical non-magnetic sleeve 2 is rotatably disposed opposite the photoreceptor 1. A permanent magnet roll 3 having a plurality of magnetic poles on its surface is rotatably arranged inside. Photoreceptor 1 and non-magnetic sleeve 2
The gap between the two is designated as D, and is hereinafter referred to as the development gap.

In FIG. 1, an amount of magnetic toner 5 is provided on a non-magnetic sleeve 2 and a permanent magnet roll 3 is provided.
When rotated in the direction of the arrow X shown in the figure, the magnetic toner 5
is conveyed in the direction of the arrow y in the figure while rotating due to the rotating magnetic field of the permanent magnet roll 3. Next, when a shielding plate 6 is placed on the non-magnetic sleeve, the tip of which comes into contact with the shielding plate 6, a toner reservoir 51 having a constant thickness t is formed near the tip of the shielding plate 6. At this time, the non-magnetic sleeve 2 is moved in the same direction as the permanent magnet roll 3, that is,
The number of rotations of the non-magnetic sleeve is approximately 1/20 or less of that of the permanent magnet roll.
For example, if the rotation speed of the permanent magnet roll is set to about 50 r.pm or less when the rotation speed is 1000 r.pm, the following flow of toner will occur. That is, by the rotation of the permanent magnet roll 3, the magnetic toner 5 is transported in the direction of the arrow y shown in the figure, and tries to accumulate one after another near the tip of the shielding plate 6. In other words, the toner reservoir 51 tries to grow, but it does not Due to the rotation of the magnetic sleeve 2, the toner reservoir 5
Since the toner on the lower layer side of 1 is pulled back in the direction of the arrow X in the figure, the thickness t of the toner reservoir 51 is kept almost constant. In this manner, toner flows within the toner reservoir 51 as indicated by the arrows in the figure. The inventor of the present invention found that when the rotation speed of the permanent magnet roll was kept constant and the rotation speed of the sleeve was varied, the following situation occurred.

First, when the number of rotations of the sleeve is low, the speed at which the toner brush moves along the sleeve due to rotation (hereinafter referred to as "toner brush rotation speed") is faster than the circumferential speed of the sleeve. No magnetic brush 52 is formed.

Next, the rotational speed of the sleeve increases, specifically
When the circumferential speed of the sleeve approaches the rotational speed of the toner brush at 20 to 30 rpm or more, the toner pool 5
A part of the toner in the sleeve 1 near the sleeve is carried out in the direction of the arrow X to form the magnetic brush 52. Here, since the amount of toner carried out from the toner reservoir 51 is small, the thickness of the magnetic brush 52
t' is thin enough to follow the rotating magnetic field caused by the rotation of the permanent magnet roll 3. Of the toner on this thin magnetic brush, the toner near the surface of the sleeve 2 moves in the direction of arrow X, but most of the toner moves in the direction of arrow Y due to the rotating magnetic field.
Therefore, the magnetic brush 52 as a whole appears to move in the opposite direction to the sleeve 2. Further, the moving speed of the magnetic brush 52 is approximately equal to the circumferential speed of the sleeve 2.

Furthermore, it has been confirmed that the above magnetic brush 52 has a property of being able to immediately return to its original state even if it is temporarily disturbed by, for example, paper or a portion thereof is removed. Since the magnetic brush 52 repeats rotation by following the rotating magnetic field of the permanent magnet roll 3 without any delay, when the magnetic brush 52 rubs the photosensitive member 1, the magnetic brush 52 and the photosensitive member Since the body 1 comes into soft contact with the toner, extremely good developability can be obtained. Moreover, even if the toner in the magnetic brush 52 is consumed during development, the magnetic brush 52
Since the toner can immediately return to its original state, there will be no shortage of toner. In addition, the toner reservoir 51
The flow of toner as shown in FIG. 1 occurs inside the sleeve, but some of the toner near the sleeve is carried out in the direction of the arrow X in the figure due to the rotation of the sleeve, so as long as the toner pool 51 exists, the toner pool will continue to flow. 5
Toner is fed into the magnetic brush 52 from the magnetic brush 1 .
Therefore, when the toner in the magnetic brush 52 is consumed by development, the toner reservoir 51 becomes smaller (however, its thickness remains the same), but the toner in the magnetic brush 52 is consumed.
Condition 2 remains unchanged.

Further, in order to always form the magnetic brush 52 as described above, the tip of the shielding plate 6 must be kept in contact with the sleeve. This is because, for example, if there is a gap between the tip of the shielding plate 6 and the sleeve 2, the magnetic toner 5 in the toner reservoir 51 will be transported in the direction of the arrow y in the figure through this gap. A magnetic brush is formed. As a result, the magnetic brush 52 cannot sufficiently follow the permanent magnet roll 3. However, if this gap is approximately 0.1 mm or less, it is possible to form a magnetic brush that can sufficiently follow the rotating magnetic field of the permanent magnet roll. It is extremely difficult to form it uniformly and is not practical. Since the tip of the shielding plate 6 comes into contact with the sleeve 2, it is preferable that the tip has some flexure in order to obtain uniform contact, and is therefore made of an elastic member such as a spring material or hard rubber. It is preferable to do so. Further, the shielding plate 6 may not have elasticity itself, but a porous elastic body may be fixed only to its tip.
In addition, in FIG. 1, the permanent magnet roll 3 and the sleeve 2 are rotated in the same direction, and the number of rotations of the sleeve is set low, so that pressure is applied to the toner at the contact area between the shielding plate 6 and the sleeve 2. There will be no agglomeration.

Next, the length of the magnetic brush formed in FIG. 1 can be adjusted as follows. In other words, the length of the magnetic brush is determined by the number of magnetic poles that pass through a certain point when the permanent magnet roll rotates (hereinafter referred to as the number of moving magnetic poles), regardless of the magnetic force of the permanent magnet roll or the magnetic properties of the magnetic toner (IHC, 4πIs). ) and the circumferential speed of the sleeve, and is determined by calculation. The calculation results are shown in FIG. In Figure 2, f is the number of moving magnetic poles mentioned above (pieces/sec)
For example, the number of magnetic poles of a permanent magnet roll is
If it is 12 poles, the rotation speed of the permanent magnet roll should be 1000 r.p.
m., the value is f=200. Therefore, the length of the magnetic brush is determined by the number of magnetic poles of the permanent magnet roll,
It can be adjusted by varying the rotation speed and the circumferential speed of the sleeve. In this case, the higher the magnetic properties of the magnetic toner, the wider the range in which a good magnetic brush can be formed. For example, if a permanent magnet roll with 12 magnetic poles is rotated at 1500 rpm, that is, f = 300, and a magnetic toner with a magnetic powder content of 50 wt% is used, the circumferential speed of the sleeve will be 50 to 90 mm. /sec, a good magnetic brush (thickness: 0.2 to 0.3 mm) can be obtained, whereas when using a magnetic toner with a magnetic powder content of 70 wt%, the circumferential speed of the sleeve is 50 to 110 mm.
A good magnetic brush can be obtained even at mm/sec.

A developing device for carrying out the developing method of the present invention will be explained with reference to FIG. This developing device includes a cylindrical non-magnetic sleeve 2 rotatably disposed opposite a photoconductor 1, a permanent magnet roll 3 rotatably disposed inside the sleeve 2 and having a plurality of magnetic poles on its surface, and a lower part of the developing device. It has a toner supply port 71 and a toner tank 7 in which the magnetic toner 5 is stored. Further, a supporting portion 72 is formed on the side of the toner tank 7 facing the sleeve 2, and the supporting portion 72 has a non-magnetic and elastic shielding plate 6 such that its tip lightly contacts the surface of the sleeve 2. installed. The toner tank 7 also has a toner supply port 71.
A rocking plate 8 made of a non-magnetic material and having elasticity is attached opposite to the sleeve 2 , and a minute gap d is formed between the tip of the rocking plate 8 and the surface of the sleeve 2 .

In the above developing device, with an outer diameter of 29.3 mmφ, 12
It has a magnetic pole, and the magnetic velocity density on the sleeve 2 is
Using 550G permanent magnet roll 3 and outer diameter 32mm
Using a non-magnetic sleeve 2 of φ, a permanent magnet roll 3
at 1000r.pm and non-magnetic sleeve 2 at 30~
Both were rotated in the direction of arrow x in the figure within a range of 50 rpm. A Se drum having an outer diameter of 120 mm was used as the photoreceptor 1, and was rotated in the direction of the arrow z in the figure.
The development gap was set in the range of 0.3 to 0.5 mm. The magnetic toner contains 60wt% magnetic powder.
The particles used had a particle size of 10 to 20 μm and a specific resistance of 10 ¹⁴ Ω·cm at D.C4000V/cm. The results under this condition are as follows.

When the magnetic toner 5 is supplied onto the sleeve 2 from the toner supply port 71, a toner reservoir 51 is formed on the sleeve 2 from the tip of the shielding plate 6 in the direction of arrow x in the figure, and a thin layer of magnetic brush 5 is formed on the sleeve 2.
2 is formed. Here, if the gap d between the tip of the rocking plate 8 and the sleeve 2 is set slightly wider than the thickness of the magnetic brush 52, the magnetic toner of the magnetic brush 52 is conveyed in the direction of the arrow y in the figure, so the toner reservoir 51
The toner gradually grows and reaches the tip of the swing plate 8, and then wraps around the top surface 8a of the swing plate 8 from this tip to form a toner reservoir 53. At this time, the magnetic toner in the toner reservoir 53 is attracted toward the sleeve 2 by the magnetic attraction force of the permanent magnet roll, so the oscillating plate 8 moves in the direction of the arrow U in the figure and moves to the position shown by the broken line in the figure, that is, its tip. reaches a position where it contacts the surface of the sleeve 2. Therefore, the vicinity of the toner replenishing port 71 of the toner tank 7 is substantially closed by the swing plate 8, so that replenishment of toner onto the sleeve 2 is interrupted. When development is performed and the magnetic toner 5 on the magnetic brush 52 is consumed, the consumed magnetic toner 5 is replenished from the toner reservoir 53 in the following manner. The toner in the toner reservoir 53 near the tip of the swinging plate 8 is subjected to an upward force in the figure due to the force due to the rotation (the toner reservoir 53 is pushed up). On the other hand, since the toner reservoir 53 also receives downward force due to gravity, it maintains a balanced state within a certain range. When the toner is consumed, the magnetic brush 52 is removed from the toner reservoir 53 while maintaining this state.
Toner is replenished. When the toner reservoir 53 gradually disappears in this way, the elastic force of the rocking plate 8 overcomes the magnetic attraction force, causing the rocking plate 8 to move in the direction of the arrow U in the figure, and when the toner reservoir 53 completely disappears, The moving plate 8 returns to its original position. In this state, the magnetic toner 5 in the toner tank 7 is again supplied onto the sleeve 2, and the above steps are repeated.
As mentioned above, the swing plate 8 functions like an automatic valve for supplying the magnetic toner 5 in the toner tank 6 onto the sleeve 2, and when its tip comes into contact with the sleeve surface, it acts like a shield plate. It fulfills the following functions.

As described above, in the developing device shown in FIG. 3, since the magnetic brush 52 is formed in a thin layer that can follow the rotating magnetic field of the permanent magnet roll 3, stable and good development can be performed. In addition, since the amount of magnetic toner supplied onto the sleeve is automatically controlled according to the amount of consumed magnetic toner 5,
The thickness of the magnetic brush 52 can be maintained constant without using a doctor plate as in conventional developing devices.

In the present invention, more preferable results can be obtained by performing development under the following conditions. If the length of the magnetic brush is too long, it will not be able to sufficiently follow the rotation of the permanent magnet roll, and if it is too short, it will not be able to make sufficient contact with the surface of the photoreceptor, so set it within a range of about 0.3 to 0.5 mm. is preferred. Further, the developing gap is preferably set to be equal to or less than the length of the magnetic brush in order to ensure contact between the magnetic brush and the surface of the photoreceptor. However, when the development gap is set to 0.3 to 0.4 mm, good development can be performed even if the magnetic brush does not necessarily contact the surface of the photoreceptor. Next, the moving speed of the sleeve surface is preferably set to about 1 to 3 times the developing speed. This is because if the speed of the sleeve is within this range, good development can be carried out even if triboelectric charging occurs when the magnetic brush contacts the surface of the photoreceptor and background fog is likely to occur.

[Effects] According to the developing method of the present invention, the following effects can be obtained.

(1) Since a thin layer of magnetic brush that can be added to the rotation of the permanent magnet roll is formed in the development area, good development can be performed.

(2) Since the toner in the toner reservoir formed on the sleeve is constantly stirred, and the toner in the magnetic brush is always conveyed while rotating, blocking can be prevented even with toner with low fluidity. .

(3) Since the thickness of the magnetic brush can be maintained constant without using a doctor plate, the structure of the developing device can be simplified and adjustments can be made easily.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a developing section for explaining the principle of the present invention, FIG. 2 is a diagram showing calculation results of the length of the magnetic brush, and FIG. 3 is an example of a developing device implementing the present invention. FIG. 1: Photoreceptor, 2: Non-magnetic sleeve, 3: Permanent magnet roll, 5: Magnetic toner, 6: Shielding plate.

Claims (1)

[Scope of Claims] 1. A cylindrical non-magnetic roller, which is rotatably arranged opposite to a carrier having an electrostatic latent image on its surface, and which has a rotatable permanent magnet roll having a plurality of magnetic poles therein. Supplying magnetic toner onto the magnetic sleeve, forming a magnetic brush on the non-magnetic sleeve that rotates the permanent magnet roll and the non-magnetic sleeve in the same direction, and rubbing the surface of the carrier with the magnetic brush. In the developing method, a shielding plate whose tip is in contact with the surface of the non-magnetic sleeve is installed, so that a shielding plate whose tip is in contact with the surface of the non-magnetic sleeve is placed on the downstream side of the shielding plate when viewed from the rotational direction of the non-magnetic sleeve, and the length of the shielding plate is longer than the ear length of the magnetic brush. Forms a toner reservoir with a large thickness,
By setting the rotational speed of the non-magnetic sleeve to about 1/20 or less of the rotational speed of the permanent magnet roll, the sleeve has a panicle length of 0.3 to 0.5 mm that can follow the rotating magnetic field of the permanent magnet roll. A developing method comprising forming a magnetic brush that moves in a direction opposite to the non-magnetic sleeve at substantially the same speed as the surface of the non-magnetic sleeve. 2. The developing method according to claim 1, wherein the rotational speed of the non-magnetic sleeve is set in a range of 30 to 50 rpm.