JPH0336574A - Developing device - Google Patents

Abstract

PURPOSE:To stably form a high-quality image for a long time by specifying the surface roughness of a magnetic roller. CONSTITUTION:In a developing device 7, toner 8 being the component element of developer is electrostatically charged and conveyed by the rotating cylindrical magnetic roller 9. In such case, the surface roughness of the magnetic roller 9 is set <=40% volume mean grain diameter of the toner 8 in terms of mean roughness with ten marks in JIS standard, that is, in the specification by JIS-B0601. Therefore, pressure and frictional force applied to the contact part of the toner 8 with the magnetic roller 9 are reduced when the toner 8 passes between the magnetic roller 9 and a developer conveying quantity regulating member 10, so that the filming of the toner 8 on the magnetic roller 9 and the deterioration of the toner 8 are suppressed. Thus, the high-quality image is stably formed.

Description

[Detailed description of the invention] 1. Industrial application field] The present invention relates to a magnetic brush developing device.

[Prior Art] A conventional developing device, known as a magnetic brush developing device, has a plurality of magnetic poles attached to the inside of a rotatable non-magnetic and conductive cylindrical developer conveying member, also called a developing sleeve. It has a magnetized cylindrical magnetic roller, holds the developer on the developer transport member by a magnetic field generated by the magnetic roller, and develops by rotating at least one of the magnetic roller and the developer transport member. It was used to transport the developer on the agent transport member. As is well known, examples of the developer include a one-component developer made up of only toner and a two-component developer made up of toner and carrier.

In such a developing device, it is necessary to polish the outer diameter of the magnetic roller, to process the outer diameter of the developer conveying member, and to precisely arrange the magnetic roller with a small gap between the magnetic roller and the developer conveying member. This caused an increase in man-hours and costs. Furthermore, the developing device has many components such as a magnetic roller, a developer conveying member, and parts for supporting each component, making it impossible to reduce the size and weight of the developing device. Furthermore, if the number of magnetized poles of the magnetic roller is increased in order to reduce the unevenness of development temperature caused by the magnetic pole pitch of the magnetic roller that occurs in the image when the magnetic roller is rotated, sufficient leakage magnetic flux will be generated on the developer transport member. Therefore, it was not possible to secure a sufficient amount of developer to be transported.

[The problem that the invention tries to solve! ! ! ] Therefore, the applicant devised a developing device that conveys developer directly on the surface of a magnetic roller as a developing device that solves these problems. This makes it difficult to stably form a uniform toner layer that is evenly charged, and it is difficult to stably form high-quality images over a long period of time. Ta.

SUMMARY OF THE INVENTION The present invention is intended to solve these problems, and its purpose is to provide a developing device that can stably form high-quality images over a long period of time.

[Means for Solving the Problems] A developing device of the present invention includes a cylindrical magnetic roller magnetized with a plurality of magnetic poles, and a magnetic field generated by the magnetic roller causes the developer to be transferred to the magnetic roller. In a developing device that transports the developer by rotating the magnetic roller, the surface roughness of the magnetic roller is expressed in accordance with the JIS standard 10-point average roughness (J-K5-BO801). It is characterized by having a volume average particle size of 40% or less.

[Function] According to the above configuration of the present invention, when the toner passes between the magnetic roller and the developer transport tray regulating member, the pressure and frictional force applied to the contact portion between the toner and the magnetic roller are reduced. This reduces toner filming on the magnetic roller and toner deterioration, making it possible to stably form high-quality images.

Hereinafter, the present invention will be explained in detail with reference to Examples.

[Example] 1st I! 1 is a cross-sectional schematic diagram of an image forming apparatus including a developing device according to an embodiment of the present invention.

A latent image carrier 1 rotating in the direction indicated by A in the figure has a photoconductive layer 3 coated on a conductive support 2. After being charged to a potential of form an image.

Developing device! ! 7 is the developer composition li [toner 8
The toner 8 is conveyed by a cylindrical magnetic roller 9 rotating in the direction indicated by B in the figure. The toner 8 held on the magnetic roller 9 by the magnetic force is regulated to an appropriate amount by the developer conveyance amount regulating member 10, and then conveyed to the development gap where the latent image carrier 1 and the magnetic roller 9 are close to each other. The electric potential of the electrostatic latent image on the image carrier 1 and the electric potential 1 [1
1, the toner 8 is applied to the latent image carrier 1 according to the bias voltage applied to the latent image carrier 1.
By adhering to the electrostatic latent image, the electrostatic latent image on the latent image carrier 1 is visualized.

The toner 8 (on which the electrostatic latent image has been developed) on the latent image carrier 1 is transferred onto the recording paper 13 by the transfer FIIr 12, and further fixed on the recording paper 13 by means such as pressure or heating, thereby forming a desired image. can be obtained.

In this embodiment, as shown in FIG. 1, the rotation directions of the latent image carrier 1 and the magnetic roller 9 are indicated by A in the figure.
and B, but this does not limit the present invention.Furthermore, although toner 8, which is a one-component developer, is shown as the developer in FIG. 1, the present invention is not limited to this. Any developer known as a one-component magnetic brush developer or a two-component magnetic brush developer can be used. Furthermore, as the magnetic material of the magnetic roller used in the present invention, known magnetic materials such as ferrite, alnico, manganese aluminum, and rare earth magnets can be used (particularly atomic numbers 58 to 71 (element symbols Ce to 14 kinds of rare earth elements ranging from Lu), among which at least one of the rare earth elements represented by Nd, Pr and Sm, and at least one of the 3D transfer metals represented by Fe, Ni and Co are added. It is desirable to use magnets.

Example 1 In this example, carbon black, Fe30 a
A one-component developer using a magnetic toner having a volume average particle diameter of 10 μmφ and containing polyester resin as a main component was used.

In the image forming apparatus using the developing device having the above configuration, JI
Using magnetic rollers 9, each having a different surface roughness according to S standard 10 point average roughness (, 7IS-B0601) (in the range of 1 to 10 μm), 50 sheets of A4 size plain paper were
When images equivalent to 000 sheets were continuously formed, the images obtained when the surface roughness based on the JIS standard 10-point average roughness of the magnetic roller 9 was made larger than 4 μm had brush marks and ground covering. Although toner filming was clearly observed on the body roller 9, JI of the magnetic roller 9
Images obtained when the surface roughness according to the 10-point average roughness of the S standard is 4 μm or less are good images with no brush marks or ground covering, and no filming due to toner is observed on the magnetic roller 9. There wasn't.

The volume average particle diameter of the toner used in this example was 10
Since it is μmφ, JIS standard 10 of the magnetic roller 9
A good image can be obtained when the surface roughness based on the point average roughness is 4 μm or less, that is, when the surface roughness based on the JI 310 point average roughness of the magnetic roller 9 is 40% or less of the volume average particle diameter of the toner.

Example 2 In this example, carbon black and polyester resin were used as main constituents with a volume average particle diameter of 12 μmφ.
A two-component developer was used in which a toner was mixed with soft magnetic particles having a particle diameter of 100 μm as a carrier.

In an image forming apparatus using a developing device having the above configuration, magnetic rollers 9 each having a different surface roughness according to JIS-S standard 10-point average roughness (JIS-B0601) are used to form images equivalent to 500 sheets of A4 size plain paper. When formed continuously, JIS standard 1 of magnetic roller 9 was obtained.
Brush marks and ground covering were clearly observed in the images obtained when the surface roughness based on the 0-point average roughness was greater than 4.8 μm, and toner filming was clearly observed on the magnetic roller 9. The image obtained when the surface roughness of the body roller 9 according to the JIS standard 10-point average roughness is 4.8 μm or less is a good image with no brush marks or ground covering. No filming was allowed.

The volume average particle diameter of the toner used in this example was 12
Since it is μmφ, JIS standard 10 of the magnetic roller 9
A good image can be obtained when the surface roughness according to the point average roughness is 4°8 μm or less, that is, when the surface roughness according to the JISIO point average roughness of the magnetic roller 9 is 40% or less of the volume average particle diameter of the toner. .

Example 3 In this example, carbon black, wax, F
A one-component developer consisting of a magnetic toner having a volume average particle diameter of 9 μmφ, in which particles containing e5Oa as a main component and coated with a styrene/acrylic resin, was used.

In the image forming apparatus using the developing device having the above configuration, JI
When images equivalent to 500 sheets of A4 size plain paper were continuously formed using magnetic rollers 9 each having a different surface roughness according to the S standard 10-point average roughness (JIS-B0601), the results showed that the magnetic rollers 9 JIS standard 1
Brush marks and ground covering were clearly observed in the images obtained when the surface roughness based on the 0-point average roughness was greater than 3.6 μm, and toner filming was clearly observed on the magnetic roller 9. The image obtained when the surface roughness of the body roller 9 according to the JIS standard 10-point average roughness is 3.6 μm or less is a good image with no brush marks or ground covering. No filming was allowed.

The volume average particle diameter of the toner used in this example was 9μ
mφ, when the surface roughness according to the JIs standard 10 point average roughness of the magnetic roller 9 is 3.6 μm or less, that is, the surface roughness according to the JI 810 point average roughness of the magnetic roller 9 is the volume average particle of the toner. Good images can be obtained when the diameter is 40% or less.

Although the embodiments have been described above, the present invention is particularly effective when applied not only to the above embodiments but also to a wide range of image forming apparatuses such as electrophotographic recording apparatuses, such as page printers, facsimile machines, and copying machines.

[Effects of the Invention] As described above, the present invention includes a cylindrical magnetic roller magnetized with a plurality of magnetic poles, and uses a magnetic field generated by the magnetic roller to move the developer to the magnetic roller. In a developing device that transports the developer by rotating the magnetic roller, the surface roughness of the magnetic roller is determined according to the JIS standard 10-point average roughness (JIS-B0
By setting the particle size to 40% or less of the volume average particle size of the toner, which is a component of the developer, as indicated by 601), toner filming on the magnetic roller can be prevented, and toner particles that are easily plastically deformed or self-agglomerating can be prevented. Even when using strong toner, there is an image forming device that can stably form a toner layer of uniform thickness on a magnetic roller with a simple structure, and can stably form high-resolution, high-quality images. This has the effect of making it possible.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional schematic diagram of an image forming apparatus including a developing device according to an embodiment of the present invention. Latent image carrier Toner Magnetic roller Developer conveyance amount regulating member Power supply or higher

Claims (1)

[Claims] It has a cylindrical magnetic roller magnetized with a plurality of magnetic poles, the developer is held on the magnetic roller by a magnetic field generated by the magnetic roller, and the developer is rotated to hold the developer on the magnetic roller. In the developing device that conveys the
A developing device characterized in that the surface roughness of the magnetic roller is 40% or less of the volume average particle diameter of toner, which is a component of the developer, as expressed by JIS standard 10-point average roughness (JIS-B0601). .