JP2001005294A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent toner in developer from being splashed, to prevent carrier in the developer from being stuck to an image carrier and to obtain a smooth and excellent image when developing is executed by feeding the developer including the toner and the carrier to a developing area opposed to the image carrier in a magnetic brush state by a developer carrier. SOLUTION: In this developing device, the developing is executed by holding the developer 2 including the toner(t) and the carrier by the magnetic force of a magnet member 11a arranged inside the developer carrier 11, feeding it to the developing area opposed to the image carrier in the magnetic brush state by the carrier 11 and applying alternating voltage to the carrier 11. Then, the carrier 11 is moved in a reverse direction to the image carrier in the developing area and the coating ratio of the magnetic brush of the developer 2 that the surface of the carrier 11 is coated is set to be within 10 to 60% in the developing area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used for developing an electrostatic latent image formed on an image carrier in an image forming apparatus such as a copying machine or a printer, and more particularly, to a toner and a carrier. Is held on the surface of the developer carrying member by the magnetic force of a magnet member provided inside the developer carrying member, and the developer carries the developer with the image carrier in a state of a magnetic brush. In a developing device that transports the developer to the opposing developing area, applies an AC voltage to the developer carrier, and supplies the toner in the developer from the developer carrier to the image carrier to perform development. It is characterized in that it is prevented from scattering to the outside, that the carrier is prevented from adhering to the image carrier, and that an image with good texture can be obtained.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer, various developing devices have been used to develop an electrostatic latent image formed on an image carrier.

As one of such developing devices, as shown in FIG. 1, a cylindrical developer carrying member provided with a magnet member 11a on the inner peripheral side so as to face the image carrying member 1 is provided. The body 11 is disposed on the apparatus main body 10, and the developer 2 contained in the apparatus main body 10 is supplied to the surface of the developer carrier 11 by a developer supply member 12 such as a bucket roller, and the developer 2 is magnetized. The developer is held on the surface of the developer carrier 11 by the magnetic force of the member 11a, and in this state, the developer 2 is rotated to transport the developer 2 in a state of a magnetic brush. After regulating the amount of the developer 2 conveyed to the developing area facing the body 1 by the regulating member 13, the developer 2 is guided to the developing area to develop the electrostatic latent image formed on the image carrier 1. There is something that I tried to do .

Here, in such a developing device,
The image carrier 1 and the developer carrier 11 move in the same direction in the development area.
In order to guide a sufficient amount of developer to the image carrier 1, the moving speed of the developer carrier 11 is higher than the moving speed of the image carrier 1.

However, when the moving speed of the developer carrier 11 is made faster than the moving speed of the image carrier 1, the toner image formed on the image carrier 1 is transported by the developer carrier 11. There is a problem in that the trailing end of the toner image formed on the image carrier 1 by being scraped off by the magnetic brush 2 is blurred, and the toner image is disturbed, so that a good image cannot be obtained.

For this reason, in recent years, as shown in FIG. 1, a bias voltage in which an AC voltage is superimposed on a DC voltage is applied from a bias power supply 14 to a developer carrier 11 so that the developer carrier 11 is A development has been developed in which development is performed by applying an electric field in which an AC electric field is superimposed on a DC electric field to a development area where the body 1 faces.

Here, when the developing is performed by applying an electric field in which a DC electric field and an AC electric field are superposed on each other in the developing region where the developer carrier 11 and the image carrier 1 are opposed to each other, the developer 2 The toner inside is in a powder cloud state and development is performed, and the developer 2 transported to the image carrier 1 by the developer carrier 11 is reduced so that efficient development can be performed. Of the developer 2 conveyed by the developer carrier 11 is less likely to be scraped off by the magnetic brush.

However, when the development is performed in this way, the toner in the powder cloud state is easily scattered from the apparatus main body 10 to the outside due to the flow of air due to the movement of the developer carrier 11 and the image carrier 1. In particular, when the amount of the developer 2 conveyed to the image carrier 1 by the developer carrier 11 increases, the amount of scattered toner increases, and the inside of an image forming apparatus such as a copying machine becomes dirty with toner. was there.

Further, as described above, the carrier in the developer 2 easily adheres to the image carrier 1 due to the AC electric field applied between the developer carrier 11 and the image carrier 1. If the amount of the developer 2 conveyed to the image carrier 1 by the carrier 11 is small, the carrier easily adheres to the image carrier 1 due to the action of the sneaking electric field at the edge portion of the electrostatic latent image formed on the image carrier 1. There was also the problem of becoming.

In the related art, although not shown, in the developing region where the image carrier and the developer carrier are opposed to each other, development is performed by moving the image carrier and the developer carrier in opposite directions. Such a developing device is also used, and when such a developing device is used, the toner image formed on the image carrier is less likely to be scraped off by the developer conveyed by the developer carrier. At the same time, since the moving directions of the developer carrier and the image carrier in the developing area are opposite, scattering of the toner from the apparatus main body to the outside is reduced.

However, even when the development is performed by moving the image carrier and the developer carrier in the developing region in opposite directions, the developing region opposed to the image carrier by the developer carrier is also used. Depending on the state of the developer conveyed, the carrier in the developer adheres to the image carrier, and the texture of the formed image is deteriorated.

[0012]

SUMMARY OF THE INVENTION According to the present invention, a developer containing a toner and a carrier is held on the surface of a developer carrier by the magnetic force of a magnet member provided inside the developer carrier. The developer is transported by the developer carrier to the developing area facing the image carrier in a state of a magnetic brush, and an AC voltage is applied to the developer carrier, so that the developer is transferred from the developer carrier to the image carrier. An object of the present invention is to solve the above-described various problems in a developing device configured to perform development by supplying toner therein.

In the present invention, the developer carrier is moved in the opposite direction to the image carrier in the development area as described above, and the development is carried out by suppressing the toner from scattering from the apparatus main body to the outside. It is another object of the present invention to prevent the carrier in the developer from adhering to the image carrier and to obtain a good image with good texture.

[0014]

In the developing device according to the present invention, in order to solve the above-mentioned problems, a developer including a toner and a carrier is supplied to a magnet member provided inside a developer carrier. The developer is held on the surface of the developer carrier by force, and the developer is transported by the developer carrier to a development area facing the image carrier in the state of a magnetic brush, and an AC voltage is applied to the developer carrier. hand,
In a developing device that supplies toner in a developer from the developer carrier to the image carrier to perform development, the developer carrier is moved in a direction opposite to the image carrier in the development area, and is moved in the development area. The coverage of the magnetic brush of the developer covering the surface of the developer carrying member was set in the range of 10 to 60%.

Here, as in the developing device according to the present invention, the developer carrier is moved in the developing area in the direction opposite to the image carrier, and the magnetic brush of the developer is moved in the developing area by the developer carrier. Coverage rate for surface coating is 1
When the content is in the range of 0 to 60%, the toner is prevented from scattering from the apparatus main body to the outside during the development, and the magnetic brush of the developer is formed on the surface of the developer carrier at an appropriate density in the development area. The magnetic brush of the developer becomes coarse and the texture of the formed image decreases.On the contrary, the magnetic brush of the developer becomes too dense, and the carrier becomes magnetic due to collision of the magnetic brushes. It is prevented from coming off the brush and adhering to the image carrier, so that there is no carrier adhesion and a good image with good texture can be obtained.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a developing device according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings.

In the developing device of this embodiment, FIG.
As shown in FIG. 1, a developer 2 containing a toner t and a carrier is accommodated in the apparatus main body 10 and a cylindrical developer carrier is opposed to the image carrier 1 with a required distance Ds therebetween. And a magnet member 11a having a plurality of magnetic poles N ₁ , S ₁ , N ₂ , S ₂ , and S ₃ on the inner peripheral side of the developer carrier 11.
The developer 2 is held on the surface of the developer carrier 11 by the magnetic force 1a.

The developer 2 is supplied to the developer carrier 11 by the developer supply member 12 provided in the apparatus main body 10, and the developer 2 is supplied by the magnetic force of the magnet member 11a. 11, the developer carrier 11 is rotated in the same direction as the image carrier 1, and the developer 2 is conveyed to a development area facing the image carrier 1 in the state of a magnetic brush. As well as
The amount of the developer 2 conveyed by the developer carrier 11 is regulated by the regulating member 13, and in the developing region where the developer carrier 11 and the image carrier 1 face each other, the image carrier 1 is This developer carrier 1 which rotates in the same direction as
1 moves the magnetic brush of the developer 2 in the direction opposite to that of the image carrier 1.

Here, in the developing device of this embodiment, when the magnetic brush of the developer 2 conveyed to the developing region by the developer carrier 11 is regulated by the regulating member 13 as described above, The coverage of the magnetic brush of the developer 2 covering the surface of the developer carrier 11 is 1
The range is from 0 to 60%.

Then, a developing bias power supply 14 is connected to the developer carrier 11 and the developing bias power supply 14
The developing bias voltage in which the AC voltage is superimposed on the DC voltage is applied to the developer carrier 11 to cause an oscillating electric field to act on the developing area. The developing is performed by supplying the toner t in the developer 2 from the moving developer carrier 11 to the electrostatic latent image formed on the image carrier 1.

Here, when the development is performed in this manner, the scattering of the toner t in the developer 2 to the outside is suppressed, and the carrier in the developer 2 adheres to the image carrier 1. The toner t is appropriately supplied from each magnetic brush of the developer 2 in the developing area in the developing area, and a good image with good texture can be obtained.

Further, in the developing device of the present invention, a toner accommodating portion 15 for accommodating the toner t is provided at an upper portion of the main assembly 10 of the device.
Is supplied to the image carrier 1 and development is performed.
In the case where the toner concentration in the developer 2 within the toner container 0 is reduced, the toner supply roller 16 provided below the toner container 15 is rotated to remove the toner t stored in the toner container 15 The developer 2 in the main body 10 is supplied.

[0023]

Next, an experiment was carried out using the developing device shown in FIG. 2 described above, and when the developing was carried out using the developing device of the embodiment satisfying the conditions of the present invention, the carrier in the developer became an image. It is clarified that the adhesion to the carrier is suppressed, and that the toner is appropriately supplied from each magnetic brush of the developer in the developing area, so that a good-quality image can be obtained.

(Experimental Example 1) In Experimental Example 1, a binder type carrier containing 500 parts by weight of a magnetic powder with respect to 100 parts by weight of a binder resin was used as a carrier for the developer 2. As shown in Table 1 below, the average particle size was 10 μm, 12 μm, 20 μm,
Eight types of carriers having 5 μm, 60 μm, 70 μm, 90 μm, and 100 μm are used, while negatively charged toner is used as the toner, and eight types of developing agents each having a toner concentration of 13% by weight in the developer. Agent was used.

In the developing device shown in FIG. 2, the peripheral speed v1 of the developer carrier 11 moving in the opposite direction to the image carrier 1 in the development area as described above and the image carrier 1
, The ratio θ (= v1 / v2) to the peripheral speed v2 is set to 1.8, the initial surface potential Vo of the image carrier 1 is
The surface potential Vir of the exposed portion of the image carrier 1
To −100 V, and a DC voltage Vb of −350 V from the developing bias power supply 14 to the developer carrier 11.
And the peak-to-peak value Vpp is 1.4 kV and the frequency f is 3
An alternating voltage consisting of a rectangular wave having a kHz and a duty ratio of 1: 1 was superimposed and applied.

In Experimental Example 1, the distance Ds between the image carrier 1 and the developer carrier 11 is set to 0.3 m.
m, and the amount of the developer transported to the developing area by the developer carrier 11 per unit area is set to 5.0 mg / cm ² , respectively, under the above conditions. An image was formed by performing reversal development. When the image was formed in this manner, the toner was hardly scattered outside.

Here, in the case of forming an image as described above, the coverage (%) of the magnetic brush of each developer covering the surface of the developer carrier 11 in the development area is determined, and the formation rate is determined. The texture of the formed image and the carrier adhesion in the formed image were evaluated, and the results are shown in Table 1 below.

Here, regarding the evaluation of the texture, ◎ indicates that the obtained image is very smooth, を indicates that the image is slightly smooth, Δ indicates that there is no practical problem, and 場合 indicates that the texture is very bad. As indicated by x.

As for the evaluation of carrier adhesion, ○ indicates that there was no carrier adhesion, Δ indicates that carrier adhesion occurred but there was no practical problem, and X indicates that carrier adhesion increased and became a problem. I did it.

[0030]

[Table 1]

As is apparent from the results, when the amount of the developer transported to the developing area per unit area is the same, as the particle diameter of the carrier becomes smaller, the magnetic brush of the developer becomes larger in the developing area. In the case of the embodiment satisfying the conditions of the present invention in which the coverage of coating the surface of the developer carrier 11 is increased and the texture of the formed image is improved and the coverage is 10% or more, At a level having no practical problem. When the coverage was 15% or more, the texture was further improved. In particular, when the coverage was 45% or more, a very smooth textured image was obtained.

On the other hand, when the particle size of the carrier was 12 μm or less and the coverage was 45% or more, carrier adhesion occurred at a level that would not cause any practical problem.

(Experimental Example 2) In Experimental Example 2, as a carrier used for the developer 2, magnetic powder was added to 100 parts by weight of a binder resin in the same manner as in Experimental Example 1 described above.
It is a binder type carrier containing at a ratio of 00 parts by weight, and has an average particle size of 10 μm as shown in Table 4 below.
m, 25 μm, and 100 μm, while the amount of developer transported per unit area by the developer carrier 11 to the development area is 7.0 mg.
/ Cm ^{2 to} 12.0 mg / cm ² , except that the image was formed by reversal development in the same manner as in Experimental Example 1 above. It should be noted that even when an image was formed in this way, the toner was hardly scattered outside.

Also, in Experimental Example 2, in the same manner as in Experimental Example 1, the coverage (%) at which the magnetic brush of each developer covers the surface of the developer carrier 11 in the development area. And the evaluation of the texture of the formed image and the evaluation of carrier adhesion in the formed image were performed. The results are shown in Table 2 below.

[0035]

[Table 2]

As is apparent from the results, as the amount of developer transported to the developing area per unit area increases and as the particle size of the carrier decreases, the magnetic brush of the developer moves in the developing area. Developer carrier 11
The coating rate of coating on the surface of the resulting image was increased, and the texture in the formed image was improved, while the formed image was liable to cause carrier adhesion.

When the above-mentioned coverage exceeds 60%, a large amount of carrier adhesion occurs, which is a problem. On the other hand, in the embodiments satisfying the conditions of the present invention where the coverage is 60% or less. In the case where the carrier adhesion is not a problem in practical use, particularly when the coverage is less than 45%,
Carrier adhesion hardly occurred.

(Experimental Example 3) In Experimental Example 3, only the carrier used for the developer 2 was changed in Experimental Example 1, and in Experimental Example 3, as shown in Table 3 below, Binder type carriers having diameters of 25 μm and 100 μm, each containing 100 parts by weight of a binder resin and magnetic powder at a ratio shown in the same table, were used. In the same manner as described above, an image was formed by performing reversal development. It should be noted that even when an image was formed in this way, the toner was hardly scattered outside.

Also, in Experimental Example 3, in the same manner as in Experimental Example 1, the magnetic brush of each developer covers the surface of the developer carrier 11 in the developing area (%). Was determined, and the texture of the formed image was evaluated. The results are shown in Table 3 below.

[0040]

[Table 3]

As is apparent from these results, when the amount of the developer transported per unit area transported to the developing area is the same, as the particle size of the carrier becomes smaller, the magnetic powder contained in the carrier becomes smaller. As the percentage decreases,
When the developer magnetic brush is used in the developer area,
1, the texture of the formed image is improved and the texture of the formed image is increased to 10% or more, and the texture is practically no problem. When the coverage was 27% or more, the texture was further improved. In particular, when the coverage was 42% or more, a very smooth textured image was obtained.

(Experimental Example 4) In Experimental Example 4, only the carrier used for the developer 2 was changed in Experimental Example 1, and in Experimental Example 4, as shown in Table 4 below, A binder type carrier in which the ratio of the magnetic powder is 200 parts by weight and 500 parts by weight with respect to 100 parts by weight of the resin, and a carrier whose particle diameter is changed as shown in the table is used. In the same manner as in the above-described Experimental Example 1, reversal development was performed to form an image. It should be noted that even when an image was formed in this way, the toner was hardly scattered outside.

In this experimental example 4, as in the case of the above-mentioned experimental example 1, the coverage (%) at which the magnetic brush of each developer covers the surface of the developer carrier 11 in the development area. ) And evaluation of carrier adhesion in the formed image, and the results are shown in Table 4 below.
Indicated according to

[0044]

[Table 4]

As is clear from the results, as in the case of Experimental Example 3, as the ratio of the magnetic powder contained in the carrier decreases and as the particle size of the carrier decreases, the magnetic properties of the developer decrease. The coverage with which the brush covers the surface of the developer carrying member 11 in the developing area has increased.

When the coverage exceeds 60%,
Although the carrier adhesion was large, the coverage was 60%.
% Or less in the examples satisfying the conditions of the present invention, carrier adhesion did not pose a practical problem. Particularly when the coverage was 44% or less, carrier adhesion hardly occurred.

(Experimental Example 5) In Experimental Example 5, a fired ferrite powder having a predetermined particle size (manufactured by Powder Tech Co., Ltd.) was used as a carrier for the developer 2 and the core material was used. Coated with acrylic resin,
A ferrite-based resin-coated carrier having a magnetic force of 2300 G. As shown in Table 5 below, three types of carriers having an average particle diameter of 25 μm, 60 μm, and 120 μm are used, while a negative toner is used. Using a chargeable toner, the toner concentration in each developer is 10% by weight.
Were used.

[0048] Then, to change the conveyance amount per unit area of each developer conveyed to the developing region by the developer carrying member 11 to ^{7.0mg / cm 2 ~20.0mg / cm 2} , otherwise In the same manner as in the above-described Experimental Example 1, reversal development was performed to form an image. It should be noted that even when an image was formed in this way, the toner was hardly scattered outside.

Also, in Experimental Example 5, in the same manner as in Experimental Example 1, the coverage (%) at which the magnetic brush of each developer covers the surface of the developer carrier 11 in the development area. And the evaluation of the texture of the formed image and the evaluation of carrier adhesion in the formed image were performed. The results are shown in Table 5 below.

[0050]

[Table 5]

As is clear from the results, even when the ferrite-based resin-coated carrier is used, the developer is transported to the development area per unit area in the same manner as when the binder-type carrier is used. As the amount increases, and as the particle size of the carrier decreases,
When the developer magnetic brush is used in the developer area,
The coverage of the surface of No. 1 was increased, and the texture of the formed image was improved, while the formed image was liable to cause carrier adhesion.

Even when a ferrite-based resin-coated carrier is used, as in the case where a binder-type carrier is used, if the above-mentioned coverage exceeds 60%, a large amount of carrier adhesion occurs, causing a problem. On the other hand, in the case of the embodiment satisfying the conditions of the present invention in which the coverage is 60% or less, the carrier adhesion does not become a practical problem, especially when the coverage is less than 45%. In
Carrier adhesion hardly occurred.

(Experimental Example 6) In Experimental Example 6, a binder-type carrier having an average particle diameter of 30 μm and a ratio of magnetic powder of 500 parts by weight to 100 parts by weight of a binder resin was used. A developer having a toner concentration of 10% by weight in the developer was used, and a developer carrier 11 having a modified surface roughness was used.

In the experimental example 6, the ratio θ between the peripheral speed v1 of the developer carrier 11 and the peripheral speed v2 of the image carrier 1 moving in the opposite direction to the image carrier 1 in the developing area.
(= V1 / v2) as shown in Table 6 below,
The reversal development was performed in the same manner as in Experimental Example 1 except that the coverage of the magnetic brush of the developer covering the surface of the developer carrier 11 in the development area was 31%. An image was formed. It should be noted that even when an image was formed in this way, the toner was hardly scattered outside.

Here, in this experimental example 6, the number N (pieces / mm ² ) of magnetic brushes per unit area on the surface of the developer carrier 11 in the developing area was measured, and N × θ And the above experimental example 1
In the same manner as in the above case, the texture of the formed image was evaluated, and the results are shown in Table 6 below.

[0056]

[Table 6]

As a result, even when the magnetic brush of the developer covers the surface of the developer carrier 11 in the developing area at the same coverage of 31%, the value of N × θ is 9%.
By doing so, the texture of the formed image was further improved.

[0058]

As described above in detail, in the developing device according to the present invention, the developer containing the toner and the carrier is supplied to the developer carrier by the magnetic force of the magnet member provided inside the developer carrier. The developer is held on the surface, and the developer is transported by the developer carrier to the developing area facing the image carrier in a state of a magnetic brush. And the magnetic brush of the developer covers the surface of the developer carrier in the developing area in the range of 10 to 60%, so that the toner is suppressed from scattering from the apparatus main body during development. At the same time, the density of the magnetic brush of the developer in the developing area is appropriately maintained, and a good image with good texture can be obtained. Also it has decreased from adhering to the body.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a conventional developing device.

FIG. 2 is a schematic explanatory view of a developing device according to the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 image carrier 2 developer 11 developer carrier 11a magnet member 13 regulating member 14 developing bias power source t toner

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Noboru 2-13-13 Azuchicho, Chuo-ku, Osaka-shi Inside Osaka International Building Minolta Co., Ltd. No. 13 Osaka International Building Minolta Co., Ltd. F-term (reference) 2H031 AC15 AC19 AD09 BA04 CA11

Claims (1)

[Claims] A developer containing a toner and a carrier is held on the surface of a developer carrier by a magnetic force of a magnet member provided inside the developer carrier, and the developer is magnetically applied by the developer carrier. The developer is transported in the state of a brush to a developing area facing the image carrier, and an AC voltage is applied to the developer carrier to supply the toner in the developer from the developer carrier to the image carrier to perform development. In the developing device, the developer carrier is moved in a direction opposite to the image carrier in the developing area, and the coverage of the magnetic brush of the developer covering the surface of the developer carrier in the developing area is increased. A developing device characterized by being in the range of 10 to 60%.