JPH034268A - Developing device - Google Patents

Abstract

PURPOSE:To prevent the carrier sticking to an image carrying member and the roughening of images by specifying the magnetic flux density of a developing magnetic pole to a specific value or above and specifying the position of a developing magnetic flux and the ratio of the circumferential speed of a developing sleeve to the image carrying member. CONSTITUTION:A magnet 13 is fixed in the developing sleeve 3 and the develop ing magnetic pole S1 forming a magnetic brush in the position of the magnet 13 is provided to this magnet. The magnetic flux of the magnetic pole S1 is set at >=800 gauss and the angle theta of the magnetic pole S1 and an alternate long and short dash line L (the line connecting the center of the sleeve 3 and the center of the image carrying member 1) with the center of the sleeve 3 is set at 3 to 10 deg.. The ratio A of the circumferential speed of the sleeve 3 to the image carrying member 1 (the moving speed of the sleeve 3/the moving speed of the carrying member 1 X 100%) is so specified as to be within the range expressed by equation. In the equation, D is the weight average grain size (mum) of the magnetic particles. The carrier sticking, the roughening of the image and the splashing of the developer are prevented in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a developing device, particularly an electrophotographic copying machine, an electrostatic recording machine,
The present invention relates to a developing device applied to an image forming apparatus such as a magnetic recording machine.

[Conventional technology]

2. Description of the Related Art Magnetic brush developing devices that use a two-component developer containing non-magnetic toner and magnetic particles (carrier) are widely used as image forming devices such as electrophotographic copying machines, electrostatic recording machines, and magnetic recording machines.

One of the magnetic brush developing devices includes a non-magnetic cylinder (hereinafter referred to as a sleeve) as a developer support means rotatably attached to a developer container, and a plurality of magnetic poles fixed within this sleeve. It is known that the image forming apparatus includes a magnetic roller and conveys the developer by rotating the sleeve, and a magnet (hereinafter referred to as a developing magnetic pole) is disposed at a developing position substantially facing the image carrier. Further, for the purpose of improving image quality, by forming an alternating electric field at the developing position where the sleeve and the image carrier face each other,
There are known devices that prevent images from being swept together and improve the reproducibility of halftone images. Furthermore, as the demand for high-quality images has increased in recent years, some attempts have been made to obtain high-resolution and high-definition images by reducing the particle size of toner; Since the toner supply capacity decreases if the carrier is used alone, carriers with smaller particle diameters are known.

[Problem that the invention is trying to solve]

However, in the conventional example described above, since the particle size of the carrier is reduced, the carrier may adhere to the image bearing member, thereby causing image defects.

In addition, the density of the image was insufficient, especially in halftones, resulting in a poor image with "ruggedness".

[Means to solve the problem]

According to the present invention, a two-component developer having magnetic particles with a weight average particle size of 30 to 80 μm and a non-magnetic toner with a volume average particle size of 10 μm or less is used, and the developer is moved relative to the image carrier, and A developing device that includes a developer carrier that supports and transports a developer to a developing position, and a plurality of magnetic poles fixed inside the developer carrier, and that forms an alternating electric field at the developing position. The magnetic pole is 800 gauss or more (preferably 1000 gauss or more), and the developing magnetic pole is located 3 degrees to 10 degrees (more preferably 3 degrees to 5 degrees) away from the closest position to the image carrier, and , when the weight average particle diameter of the magnetic particles is D [μm], and the circumferential speed ratio of the developer carrier to the image carrier is A, then "carrier adhesion", "image roughness" and " This prevents the developer from scattering.

〔Example〕

An embodiment of the present invention will be described below based on the accompanying drawings.

FIG. 1 is a sectional view of a first embodiment in which the present invention is applied to a copying machine using a drum-type electrophotographic photoreceptor.

Although not shown in the figure, well-known electrophotographic process means such as a charging mechanism, an image exposure mechanism, a transfer mechanism, a cleaning mechanism, and a static elimination mechanism are arranged around the photosensitive drum 6.

The developing device develops a latent image formed on a latent image carrier l such as a photoreceptor or dielectric by electrophotography, electrostatic recording, etc. It is configured to include a developing sleeve 3 as a developer carrier, a blade 4 as a developer layer regulating member, and the like. That is, an opening is formed in the developing container 2 at a position close to the latent image carrier l, and the developing sleeve 3 is rotatably provided in this opening. The blade 4 is attached with a predetermined gap.

The developing sleeve 3 is made of a non-magnetic material and rotates in the direction of the arrow in the figure during the developing operation, and has a magnet 13 fixed therein as a magnetic field generating means. A developing magnetic pole S that forms a magnetic field at a developing position to which a developer is applied and forms a magnetic brush at this position, and a magnetic pole N I * that conveys a developer 8, which will be described later.
31 having N 2+ S 2+ N 3 is a developing roller, and the device L composed of the developing sleeve 3 and the magnet 13 is indicated by a chain line connecting the center of the developing sleeve 3 and the center of the image carrier l. , which indicates the center of the opposing relationship between the developing sleeve 3 and the image carrier 1, where the developing sleeve 3 and the image carrier 1 are closest to each other, and is also the central position of the developing area (developing position).

θ is the angle between the developing magnetic pole and the dashed-dotted line with respect to the center of the developing sleeve 3; when the developing magnetic pole is upstream of the dashed-dotted line with respect to the moving direction of the developing sleeve, it is 0, and when it is downstream, it is −. do.

That is, the pole position of the developing magnetic pole can be indicated by θ. Further, the blade 4 is made of aluminum (AI!).

5US316), etc., and as mentioned above, it is attached with a predetermined gap between it and the surface of the developing sleeve 3, and the developing sleeve 3 is transported over this gap to the developing section. The amount of developer 8, specifically, the thickness of developer 8 on developing sleeve 3 is regulated. Therefore, in this embodiment, both non-magnetic toner and magnetic particles pass between the tip of the blade 4 and the surface of the developing sleeve 3 and are sent to the developing section.

The developer 8 includes a non-magnetic toner 81 and magnetic particles (carrier).
It is a two-component developer consisting of 82.

The non-magnetic toner 81 used had a volume average particle diameter of 10 μm or less. The volume average particle size was measured using a Coulter Counter TA-II using a 100 μm aperture.

That is, a Coulter counter TAn type (
CX-1 and an interface (manufactured by Nikkaki) that outputs the number average distribution and volume average distribution using
A personal computer (manufactured by Canon) is connected, and the electrolyte is 1% NaCj using primary sodium chloride! Prepare an aqueous solution.

The measurement method is 100 to 150 m of the electrolytic aqueous solution! ! 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, as a dispersant is added therein, and 0.5 to 50 mg of a measurement sample is added thereto.

The electrolytic solution in which the sample was suspended was dispersed for about 1 to 3 minutes using an ultrasonic disperser, and the particle size distribution of particles of 2 to 40 μm was measured using a 100 μm aperture using the Coulter counter TA-If type. to find the volume average distribution.

The volume average particle diameter is obtained from the volume average distribution thus determined.

82 is a magnetic particle with a weight average particle size of 30 to 80 μm1
Ferrite particles (maximum magnetization 60 emu/g) coated with a resin preferably have a resistance value of 10'Ω or more, preferably 10''ΩCm or more with a diameter of 40 to 70 μm.

The resistance value of the magnetic particles is measured using a measuring electrode area of 4 crr.
f. Using a side-Germany type cell with an electrode gap of 0.4 cm, the voltage E (V/Cm) between both electrodes was applied under a pressure of 1 kg to one electrode, and the current flowing through the circuit was measured. The method used is to obtain the resistance value of the magnetic particles from

This developer 8 is transported to the developing section, and is transported to the transport magnetic pole N while being held by the sleeve 3.

Reference numeral 12 denotes a tidying member for preventing the developer from scattering and being pulled back to the upstream side.One end of the tidying member is a free end, and the other end is fixed to the developer container 2. The department is
It is in contact with the developer at or upstream of the transport magnetic pole N.

The developer 8 sent to the developing section is transported to the transport magnetic pole N while being held in the sleeve 3.
This prevents the particles from scattering when they stand up, and prevents them from being pulled back toward the developing magnetic pole S1.

The transport magnetic pole N and the magnetic pole N2 have the same polarity, and a repulsive magnetic field is generated between them. Therefore, the developer held in the sleeve 3 and transported to the transport magnetic pole N is removed from the sleeve 3 by the action of this repulsive magnetic field, and is stirred and mixed by the first transport means 9, which will be described later, to the vicinity of the magnetic pole N2. in,
New developer is supplied.

That is, the developer that has undergone the development history on the sleeve 3 is peeled off and new developer that has been sufficiently mixed is constantly supplied to the sleeve 3, so that stable and good images can be obtained.

By the way, the inside of the developing container 2 is divided into a developing chamber (first chamber) S-+ and a stirring chamber (second chamber) S-2 by a partition wall 5 extending perpendicularly to the plane of the paper in FIG. A toner storage chamber S=a is formed above the chamber S-2 with a partition wall 6 in between, and replenishment toner (non-magnetic toner) 81 is stored in the toner storage chamber S-3. In addition, there is a supply port 6 in the bulkhead 6.
A is open, and an amount of replenishing toner 81 commensurate with the amount of consumed toner is dropped and replenished into the stirring chamber S-2 through the replenishing port 6a. Moreover, the above-mentioned developing chamber S-+ and stirring chamber S
-2 contains developer 8. In addition, developer container 2
The partition wall 5 is not formed at the front and back ends of FIG. (not shown) is formed.

The developing chamber S-+ is located at the inner bottom of the developing container 2 near the developing sleeve 3, and rotates in the direction of the arrow shown (counterclockwise) to move the developer 8 from the back side to the front side in FIG. A first conveyance means 9 is provided above the first conveyance means 9 and rotates in the direction of the arrow shown (counterclockwise) to convey the developer 8 from the front side to the back side in FIG. A second conveying means 10 is provided. Further, the first conveying means 9 is provided in the stirring chamber S-Z.
A third conveyance means 11 is provided at approximately the same horizontal position and rotates in the direction of the arrow shown (clockwise) to convey the developer 8 from the front side to the rear side in FIG. In addition, the above 11th
Second and third conveyance means9. 10. Specifically, the reference numeral 11 is constituted by a screw having a spiral shape.

Next, a method for measuring magnetic flux density in the present invention will be explained.

FIG. 2 is a diagram for explaining a method for measuring the magnetic flux density Bγ in the vertical direction on the sleeve 3, and the measurement was performed using a Gauss meter model 640 manufactured by Bell. In the figure, the sleeve 3 is fixed horizontally, and the magnet roller 13 inside the sleeve 3 is rotatably attached.

Reference numeral 17 denotes an axial probe, which is fixed with a slight distance from the sleeve 3 so that the center of the sleeve 3 and the center of the probe 17 are approximately in the same horizontal plane.
The sleeve 3 and the magnet roller 13, which are connected to the sleeve 6 and measure the magnetic flux density in the vertical direction on the sleeve, are substantially concentric circles, and the spacing between the sleeve 3 and the magnet roller 13 can be considered to be equal everywhere.

Therefore, by rotating the magnet roller 13, the vertical magnetic flux density Bγ on the sleeve 3 can be measured with respect to the circumferential surplus.

In this example, the dark potential is -650V and the bright potential is -200V, and the developing sleeve 3 is provided with an alternating voltage (a DC voltage of -350V is superimposed on an AC voltage with a frequency of 2000Hz and a peak-to-peak voltage of 2000V). was applied to form an alternating electric field at the development position, and the developer was vibrated to develop the latent image. The outer diameter of the photosensitive drum 1 as an image carrier is φ80 mm, and the outer diameter of the developing sleeve 3 is φ32 mm.
, the distance between the developing sleeve 3 and the regulating blade 4 is set to 500 mm.
μ, the distance between the developing sleeve 3 and the photosensitive drum 1 is 800μ
, the circumferential speed of the photosensitive drum l was 160 mm/s. The thickness of the developer layer is greater than the minimum gap between the sleeve and the drum at the development position, and the developer layer contacts the drum for development.

Furthermore, the particle size of the non-magnetic toner 81 is 10 as described above.
A size smaller than μm was used.

By changing the circumferential speed of the developing sleeve, the circumferential speed ratio A of the developing sleeve to the photosensitive drum was investigated under various conditions. Furthermore, the magnetic flux density of the developing magnetic pole, the position of the developing magnetic pole, the particle size of the magnetic particles, etc. were also investigated under various conditions.

(Example 1) Specifically, under the conditions described above, the magnetic flux density of the developing magnetic pole was 1000 Gauss, and the angle θ between the developing magnetic pole and the dashed line was
was fixed at +5°, and experiments were conducted under various conditions with the particle diameter D [μm] and circumferential speed ratio A [%] of the magnetic particles 82.

FIG. 3 is a diagram for explaining these results, in which the horizontal axis is the circumferential speed ratio A [%], and the vertical axis is the particle diameter D [μm] of the magnetic particles.

When the weight average particle size of the magnetic particles exceeded 80 μm, ie, edge blurring occurred on the image above the straight line in FIG. As the particle size of the magnetic particles increases, the surface area of the magnetic particles becomes relatively smaller, that is, the effective surface area for frictional charging with the non-magnetic toner 81 becomes smaller, resulting in toner with sufficient triboelectric charging, which causes fogging. It is thought that it will become an image.

At this time, if the toner density was reduced in order to prevent fogging, the image density would decrease, which was not desirable.

Conversely, if the weight average particle diameter of the magnetic particles is smaller than 30 μm, that is, in the lower part of the straight line L2, the magnetic particles 8
2 itself is developed on the photosensitive drum 1, causing so-called "carrier adhesion."

As a result, it has the disadvantage of causing spots in the solid image. Furthermore, when cleaning the photosensitive drum 1, the surface of the photosensitive drum is rubbed with magnetic particles, which tends to easily damage the surface of the photosensitive drum.

The volume average particle size of the non-magnetic toner 81 in the developer 8 is 10μ.
It was possible to obtain a high-resolution, high-definition image by reducing the particle size to less than m. However, in order to obtain a high-quality image, the weight average particle size of the magnetic particles is important, and a range of 30 μm to 80 μm is good. Ta.

Next, the circumferential speed ratio A will be explained. If the circumferential speed ratio A is small, the image will be rough, and conversely, if the circumferential speed ratio A is increased, it will cause "toner scattering."

This is related not only to the peripheral speed ratio A but also to the particle size of the magnetic particles.

When the weight average particle size of the magnetic particles was in the range of 30 μm to 80 μm, the circumferential speed ratio A was varied and studied, and it was found that there was a relationship as shown below.

A "rugged" image occurs on the left side of the line L3, and "toner scattering" occurs on the right side of the straight line L4.

That is, the weight average particle diameter of the magnetic particles is 30 μm to 80 μm.

(Example 2) With the same configuration as Example 1, the developing magnetic pole was set at 5° from the straight line.
Upstream (θ = +5°), the weight average particle size of the magnetic particles is 55
Table 1 shows the results obtained regarding the magnetic flux density of the developing magnetic pole and carrier adhesion using various developing rollers, with the circumferential speed ratio A fixed at 1.75.

Table 1 (Example 3) With the same configuration as Example 1, the magnetic flux density of the developing magnetic pole was set to 100.
0 Gauss, and the weight average particle diameter of the magnetic particles was 55 μm (D=5
5) The peripheral speed ratio A was fixed at 1.75, the position of the developing magnetic pole was varied from θ=-15 to +15°, and experimental data obtained regarding "carrier adhesion" is shown in Table 2.

Table-2 ×: Too much carrier adhesion Poor △: Little carrier adhesion Good (acceptable) ○: Very little carrier adhesion Good ◎: Very little carrier adhesion Very good When the magnetic flux density of the developing magnetic pole is 80 Gauss or more, "carrier adhesion" is not a problem. In particular, at 1000 gauss or higher, it was extremely good, but at 750 gauss, spots appeared on the solid image and were not acceptable.

When the pole position of the developing magnetic pole was θ=±3° to 10°, carrier adhesion was good, especially when θ=±3° to 5°, it was very good, but when θ=0° and θ=±15 It was bad at ゜. In addition, the pole position of the developing magnetic pole is set to the upstream side by θ = +3°~
When it was set to 10', there was a slight tendency for the peta image to become dense.

Also, change the pole position of the developing magnetic pole to the downstream side θ=-3a to 10'
In this case, the image tended to be slightly clearer.

(Example 4) The weight average particle diameter of the magnetic particles was 5 in the same configuration as in Example 1.
5 μm (D=55), circumferential speed ratio A of 1.75, magnetic flux density of the developing magnetic pole is fixed at 100OG, pole position is fixed at θ=+5°, and the half value of the magnetic flux density of the developing magnetic pole is 35° to 45°. The image quality was evaluated and the experimental results obtained are shown in the table.
Shown in 3.

Table 3 When the half-width of the developing magnetic pole was within 40°, the image was clear and the image quality was good, especially when the half-width was 35°, it was extremely good, but when the half-width was 45° was defective.

〔Effect of the invention〕

As described above, the present invention has the effect of preventing carrier adhesion to an image bearing member, image blurring, and developer scattering.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the present invention applied to a copying apparatus using a drum-type photoreceptor, FIG. 2 is a diagram for explaining a method for measuring the magnetic flux density Bγ in the vertical direction, and FIG. FIG. 1 is a diagram for explaining an embodiment of the present invention. l... Image carrier 2... Developer container 3... Developing sleeve 13... Magnet 8... Developer 81... Non-magnetic toner 82... Sl... L... θ ... A... Magnetic particle development magnetic pole The linear angle between the development sleeve center and the image carrier center and the image carrier opposing center (straight line L) (upstream side is positive with respect to the sleeve movement direction, downstream side is (negative side) The peripheral speed ratio of the developing sleeve to the image carrier is 2 factors M″IL.

Claims (4)

[Claims] (1) A two-component developer having magnetic particles with a weight average particle size of 30 to 80 μm and a non-magnetic toner with a volume average particle size of 10 μm or less is used, and the developer is supported by moving relative to the image carrier. In a developing device, the developing device includes a developer carrier that is conveyed to a developing position, and a plurality of magnetic poles fixed inside the developer carrier, and that forms an alternating electric field at the developing position. Gauss or higher, and the position of the developing magnetic pole is 3 points from the closest position between the image carrier and the developer carrier.
The weight average particle diameter of the magnetic particles is D [μm], and the circumferential speed ratio of the developer carrier to the image carrier (moving speed of the developer carrier/image carrier When A is the moving speed of
A developing device characterized by: (2) In the developing device according to claim 1, the position of the developing magnetic pole is 3 degrees to 10 degrees upstream in the direction of movement of the developer carrier from the closest position between the developer carrier and the image carrier. A developing device characterized by being located at a remote location. (3) In the developing device according to claim 1, the position of the developing magnetic pole is 3 degrees to 10 degrees downstream in the direction of movement of the developer carrier from the closest position between the developer carrier and the image carrier. A developing device characterized by being located at a remote location. (4) The developing device according to claim 1, 2, or 3, wherein the half width of the developing magnetic pole is 40 degrees or less.