JPS5855378Y2 - Magnetic brush roll for electrophotography - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a magnetic brush roll having appropriate irregularities on the surface of the magnetic brush cylinder to prevent deterioration of the developer.

A cylinder containing a rectangular or cylindrical fixed magnet, which constitutes the magnetic brush roll, magnetically attracts and adheres a developer consisting of a magnetic carrier and toner to its surface, and as the cylinder rotates, the attached developer is removed. is being transported.

Conventionally, in order to improve the transportability of the developer, an uneven layer with a size equal to or larger than the particle size of the carrier particles was provided on the surface of the cylinder. Figure 1 is a cross-sectional view of a part of the cylinder. It is expressed.

However, in this roll, the carrier particles collide violently with the irregularities on the cylinder surface, and toner mainly composed of polymers adheres to the carrier surface during the collision, resulting in a thin film of toner being formed on the carrier surface.

As a result, the original triboelectric charging of toner and carrier is impaired,
This caused an early decline in developing ability.

This invention forms uneven parts on the surface of the magnetic brush roll cylinder that are smaller than the diameter of the carrier and larger than the toner, and the carrier comes into contact with the uneven parts so that the protrusions support the load of the carrier, thereby preventing the toner from being damaged. This reduces the impact of the carrier on the carrier, and greatly reduces the adhesion of toner to the carrier.

Therefore, the present invention has significantly improved the triboelectric charging performance of the developer.

FIG. 2 is a cross-sectional view of a portion of the cylinder of the present invention.

The irregularities provided on the surface of the roll cylinder of the present invention include (1) polyurethane, for example, provided on the cylinder surface;
Fibers (e.g., carbon fibers, steel fibers, stainless steel fibers, boron fibers, ceramic fibers, etc.) cut into appropriate lengths with a diameter smaller than the carrier diameter and larger than the toner diameter in a single layer of polymer such as polyester or polyethylene.
A single layer of polymer containing 10% or more of

(2) On the cylinder surface, 10% of powder (for example, powder of carbon, boron, glass, ceramic, etc.) with a diameter smaller than the carrier diameter and larger than 1 Henner diameter is added to the polymer as described in (1) above. A single layer of the above mixed polymer is provided to form uneven parts.

(3) The surface of the cylinder is formed with an uneven portion having a diameter smaller than the canoa diameter and larger than the gattner diameter by sandblasting.

(4) The cylinder surface is covered with a mesh [a mesh made of fibers as described in (1) above] having a diameter smaller than the carrier diameter and larger than the toner diameter.

(5) Other methods, such as those created by exposing a photosensitive resin to a dot, line, or mesh image and processing it using a known method.

etc. are valid.

In the present invention, the pressure applied to the toner cannot be sufficiently reduced by providing grooves or holes larger than the carrier.

Further, in order to sufficiently create grooves or holes, it is desirable to use fibers or particles cut to an appropriate length, which is slightly smaller than the diameter of the carrier.

With fibers or particles larger than this, the toner tends to be compressed by the carrier and cylinder.

Note that the length of the fibers may be arbitrary, but shorter lengths are preferable in terms of fabricating the uneven layer.

Further, in order to support the load of the carrier and to avoid strong pressure between the carrier and the toner by retracting the toner into the groove or hole, it is necessary to make the groove or hole larger than the diameter of the toner.

Furthermore, in this invention, by making the cylinder non-magnetic, the lines of magnetic force can effectively reach the magnetic carrier, and the attraction force of the carrier to the cylinder does not weaken, so the frictional force between the carrier and the cylinder is reduced. The carrier is sufficiently transported without deterioration.

Therefore, the cylinders, fibers, and particles used in the present invention are preferably non-magnetic, and preferable results can be obtained by using fibers and particles made of stainless steel, carbon, boron, glass, ceramic, etc.

Note that the fibers and particles may be used alone or together.

The present invention will be described below with reference to Examples.

Example 1 A layer of polyester was provided on the cylinder surface of a magnetic brush roll.

This polyester layer was dispersed with 15% carbon fibers having a diameter of about 20 μm.

Due to the inclusion of carbon fibers, uneven portions were formed on the cylinder surface layer.

In the magnetic roll manufactured in this way, the load of the carrier is supported by the uneven portions of the fibers, and the pressure and impact between the toner mainly composed of polymer and the carrier are greatly reduced.
Almost no pressure-induced fusion of the toner under the carrier was observed.

Similarly, polyurethane and polyethylene are layered on the cylinder surface, and this layer is filled with steel fibers, steel fibers,
When magnetic brush rolls containing 15% boron fiber and 15% ceramic fiber were prepared and tested, both showed good results.

In the present invention, in order to improve the developer conveyance ability, as shown in FIG. 3, unevenness may be provided on the cylinder surface, which is several times to several tens of times the carrier particle diameter, in addition to the above-mentioned unevenness. can.

An example of this will be explained next.

Example 2 First, irregularities approximately 20 times the carrier particle size were provided on the smooth cylinder surface.

Next, polyethylene in which boron powder having a size twice the toner particle size was dispersed was sprayed onto the cylinder surface to a thickness of 50 μm.

On the surface of the cylinder, an uneven portion having a size approximately 20 times the carrier particle size and an uneven portion having a size approximately twice the toner particle size were formed.

A magnetic brush roll using this cylinder has excellent developer transportability, and the life of the developer is several times longer than that of a magnetic brush roll without small irregularities.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view of a conventionally used magnetic brush roll. 2 and 3 are partial sectional views showing an embodiment of the magnetic brush roll according to the present invention. Symbols in the figure: 1...Support, 2, 3...Irregular layer, 4...
...Fiber, 5...Powder.

Claims (1)

[Scope of utility model registration request] A magnetic roll for electrophotography, characterized in that a nonmagnetic cylinder that rotates around a fixed magnet is provided with nonmagnetic irregularities smaller than the carrier and larger than the toner on the surface thereof.