JPH0475076A - Toner carrier and its magnetizing method - Google Patents

Abstract

PURPOSE:To obtain a toner carrier which can be used in a developing device in which a high-resolution and high-quality image having small irregularity in density is formed by providing a layer for generating the magnetic field of specified coercive force on the toner carrier. CONSTITUTION:The toner carrier 9 is obtained by respectively concentrically disposing an elastic layer 11 and the magnetic field generating layer 12 on the outer periphery of a shaft 10, and it carried magnetic toner on the surface of its outer periphery by leakage magnetic flux on the outer periphery of the layer 12. By setting the coercive force of the magnetic field generating layer of the carrier 9 at <=2000[Oe], the magnetizing pattern of a magnetizing master is copied on the magnetic field generating layer of the toner carrier, and the magnetizing pattern having fine pitches is excellently formed in mass-production. Thus, the high-resolution and high-quality image having small irregularity in density is stable formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a toner carrier used in a developing device for developing magnetic toner and a method for manufacturing the same.

[Prior Art] As disclosed in USP-4851874, a conventional toner carrier is made by forming a mixed material in which a permanent magnetic material is dispersed in a medium such as a resin on a conductive hollow cylinder, and then applying the mixture to the surface of a magnetic roller. It was used to transport toner.

In addition, conventional methods of magnetizing a toner carrier include a method of using a magnetizing yoke as known as a method of magnetizing a permanent magnet,
As a known method of magnetizing a magnetic drum, a method using a floating magnetic head has been used.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, although a developing device with a simple structure is obtained by conveying toner on the surface of a magnetic roller,
The magnetization pitch of the toner carrier causes uneven toner conveyance, resulting in density unevenness in the output image.

Additionally, since toner carriers are generally small in diameter (diameter 40 mm or less) and long (length 200 mm or less), it is difficult to generate a sufficient magnetic field with the magnetizing yoke even if magnetization is attempted at minute pitches. If this is not possible and the toner carrier is formed by magnetizing the magnetic field generation layer after manufacturing, the minimum magnetization reversal pitch should be set to 0.
．． It was difficult to reduce the thickness to 5 [mm] or less. moreover,
As a means to magnetize the magnetic field generation layer at a minute pitch,
It is easy to imagine using a floating magnetic head like that used in magnetic printers, but in reality it is difficult to maintain a constant gap between the magnetic head and the magnetic field generation layer, and the magnetic head There is a problem in that it is difficult to produce a toner carrier that generates a magnetic field sufficient to hold toner at a minute pitch due to crashes.

SUMMARY OF THE INVENTION The present invention is intended to solve these problems, and an object of the present invention is to provide a toner carrier suitable for developing magnetic toner. Still another object is to provide a toner carrier that can be used in a high-quality developing device with high resolution and little temperature unevenness. Still another object is to provide a magnetization method capable of magnetizing the magnetic field generating layer of a toner carrier at a minute pitch. Still another object is to provide a simple and inexpensive method for magnetizing a toner carrier.

[Means for Solving the Problems] The toner carrier of the present invention is a toner carrier that conveys magnetic toner and is elastically deformable, and the toner carrier has a magnetic field generating layer having a coercive force of 2000 [Oe] or less. It is characterized by having at least.

Further, a method for magnetizing a toner carrier of the present invention is a method for magnetizing a magnetic field generating layer of a toner carrier, in which the magnetic field generating layer is magnetized by magnetic copying by a magnetization master having a predetermined magnetization pattern. It is characterized by

[Function] According to the above configuration of the present invention, since the magnetic field generation layer is elastically deformable, the magnetic field generation layer can be magnetized by bringing the magnetization master into close contact with the surface of the toner carrier, and the toner carrier can be magnetized. Uniform magnetization can be achieved at minute pitches according to the magnetization pattern of the magnetization master. Furthermore, by forming the magnetic field generating layer of the toner carrier from a magnetic material having a predetermined coercive force, even leakage magnetic flux from the surface of the magnetization master can sufficiently magnetize the magnetic field generating layer.

Further, according to the above structure of the present invention, it is possible to form a uniform toner thin layer on the toner carrier by magnetizing the magnetic field generating layer of the toner carrier at a minute pitch, and toner carriers can carry magnetic toner. It can be stably held on the body, reduce density unevenness and toner scattering due to variations in magnetic field and toner layer thickness, and can perform high-resolution development.

Further, according to the above configuration of the present invention, since the toner carrier has elasticity, stable pressure development is possible and a high resolution image can be obtained due to the development electrode effect.

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

[Example M] FIG. 1 is a cross-sectional schematic diagram of a toner carrier according to an embodiment of the present invention, in which an elastic layer 11 and a magnetic field generating layer 12 are arranged concentrically around the outer periphery of a shaft 1o. Magnetic toner (not shown) is supported on the outer peripheral surface of the toner carrier by leakage magnetic flux around the outer periphery of the magnetic field generating layer 12. Therefore, since the magnetic field generation layer 12 is elastically deformable, after forming the toner carrier, the magnetization master can be stably brought into close contact with the surface of the toner carrier to magnetize the magnetic field generation layer 12. Fine-pitch magnetization can be performed according to the pattern.

In FIG. 1, a shaft 10 is made of a highly rigid metal such as stainless steel or aluminum, or a relatively rigid resin such as a fiber-mixed resin. The elastic layer 11 is made of natural rubber, silicone rubber, urethane rubber, butadiene rubber, chloroprene rubber, neoprene rubber, NBR, etc., and the form of the elastic layer is rubber, foam, sponge, etc. By setting the layer thickness of the layer 11 to 500 [μm] or more, a toner carrier capable of stable elastic deformation can be obtained.

Furthermore, for the magnetic field generation layer 12, a known magnetic recording material or magnet material can be used.
Magnetic material containing at least one element among e, Ni, Co, and Mn, for example, γ-Fe
2O3, Ba-Fe, Ni-Co, Co-Cr, M
n-A1 etc. can be used, and by dispersing it in resin to form a magnetic field generation layer, flexibility can be improved, and the film thickness is 100 mm.
[μm] or less, preferably around 10 [μm1],
By setting the minimum magnetization reversal pitch to 100 [μm] or less, the toner can be made into a uniformly thin layer, and at the same time, fluctuations in the amount of toner conveyance can be suppressed to a minute pitch, thereby reducing density unevenness.

Here, the minimum magnetization reversal pitch refers to the minimum value of the distance between the respective magnetization centers where the magnetization direction is reversed in any direction. Note that the layer structure of the toner carrier as shown in FIG. can be effective. Further, the structure of the toner carrier is not limited to a roller shape, but may be a thin cylindrical shape or a belt shape.

FIG. 2 is a schematic diagram showing a method of magnetizing a toner carrier according to another embodiment of the present invention. A magnetized master 21 whose surface portion has been magnetized in advance in a predetermined magnetization pattern is pressed onto the carrier 9, and the toner carrier 9 and the magnetized master 21 are rotated at a circumferential speed while in close contact to generate a magnetic field at the close contact portion. It magnetizes layer 12. Therefore, the leakage magnetic flux on the surface of the magnetization master 21 can be effectively passed through the magnetic field generation layer, and uniform magnetization can be performed under a sufficient magnetic field. It can be formed on the generation layer 12 in a short time and with high precision. In addition, magnetization master 21
As for the structure, any structure may be used as long as it generates leakage magnetic flux on the surface, and various forms such as a cylindrical shape, a belt shape, a flat plate shape, etc. are possible.
Examples of cylindrical objects include those in which a magnetic layer is formed on the surface of a non-magnetic metal cylinder such as aluminum or stainless steel by coating or plating, and the magnetic layer is magnetized in the horizontal direction, and magnetic metal cylinders such as iron. Preferably, a magnetic layer is similarly formed on the surface and magnetized in the perpendicular direction (thickness direction). Further, as the material of the magnetic layer of the magnetization master 21, the magnetic material of the magnetic field generation layer of the toner carrier described above can be used, but Co-N1-P, NiP, Co-Ni-Cr, etc., which have a high residual magnetic flux density, can be used. When a rare earth magnetic material is used, a high magnetic flux density can be obtained on the surface, and the magnetic field generating layer of the toner carrier can be magnetized in a state close to saturation magnetization. Furthermore, the magnetization master is magnetized by forming a fine pitch magnetization pattern on the magnetization master 21 using a magnetic head, a special magnetization yoke, etc., but the toner carrier is magnetized by the magnetization pattern of the magnetization master 21. Since this is carried out by copying it onto the magnetic field generation layer 12 of the toner carrier 9, the magnetization state is lattice magnetization,
Magnetization in which the lattice is tilted, magnetization in a portion of the lattice, magnetization in which N and S poles appear alternately in the circumferential or axial direction, N and S poles alternate in a spiral pattern. Various types of magnetization such as magnetization are possible, and the magnetization reversal pitch can not only be repeated at a constant pitch but also change the pitch freely, and the magnetization direction can be horizontal or vertical magnetization. Either is fine.

FIG. 3 is a diagram showing the relationship between the coercive force of the magnetic field generating layer of the toner carrier and the magnetic susceptibility of the magnetic field generating layer by the magnetization master in still another embodiment of the present invention, in which the coercive force of the magnetic field generating layer is 2000. Sufficient magnetization can be obtained for a toner carrier having a magnetic field generating layer with a coercive force of 2000 [Oe] or less, whereas a toner carrier having a magnetic field generating layer with a coercive force of 2000 [Oe] or more has a magnetic field due to leakage magnetic flux on the surface of the magnetization master. It was found that the generation layer could not be sufficiently magnetized.

Therefore, the coercive force of the magnetic field generation layer of the toner carrier is 2000
[Oe] or less, it is possible to copy the magnetization pattern of the magnetization master onto the magnetic field generation layer of the toner carrier and form a magnetization pattern with a fine pitch with good mass productivity.
It is possible to maintain stable development for a long time without density unevenness, and to obtain a highly reliable toner carrier. As for the magnetization of the magnetization master, as is known, it is possible to use a method using a magnetization yoke or a method using a magnetic head. Regarding the magnetic properties of the magnetization master, both the coercive force and the residual magnetic flux density are determined by the toner support. It is desirable that the magnetic field generation layer be higher than the magnetic field generation layer of the body, and depending on the magnetization pattern of the magnetization master, a magnetization pattern with a magnetization reversal pitch of several [μm] to several hundred [μm] can be magnetically copied onto any magnetic recording medium. .

FIG. 4 is a schematic cross-sectional view of an image forming apparatus using a toner carrier according to still another embodiment of the present invention. It is a film in which a photosensitive layer 3 having photoconductivity is coated, and after the photosensitive layer 3 is charged using a charger 4 such as a corona charger or a charging roller, light emitted from a light source 5 such as a laser or an LED is charged. is selectively irradiated onto the photosensitive layer 3 according to the image through the imaging optical system 6 to obtain a potential contrast and form an electrostatic latent image. On the other hand, the developing device 7 conveys and develops the magnetic toner 8, and has a toner carrier 9 that conveys the toner 8.
has an elastic layer 11 and a magnetic field generation layer 1 on the outer periphery of the shaft 10.
2 are arranged concentrically, and the magnetic field generating layer 1
The magnetic toner 8 is held directly on the toner carrier 9 by the leakage magnetic flux on the outer periphery of the toner 2, and the toner carrier 9 is regulated in an appropriate amount by a plate-shaped blade 13 made of non-magnetic or magnetic metal or resin. The thin layer of toner 8 is conveyed by rotating the toner. The toner carrier 9 is pressed against the latent image carrier 1 at a predetermined pressure, and when the toner 8 on the toner carrier 9 is conveyed to the pressure contact portion, the potential contrast of the latent image carrier 1 and the developing bias applying means are The toner 8 charged according to the developing electric field generated by the toner 14 adheres to the latent image carrier 1, and the electrostatic latent image is visualized. Further, a toner image is transferred onto the recording paper 16 using a transfer device 15 such as a corona transfer device or a transfer roller, and the toner is fixed on the recording paper using heat or pressure to obtain a desired image on the recording paper. It is.

Using an image forming apparatus as shown in FIG.
When line images, character images, and solid images of [DPI] were continuously formed over 10,000 sheets, the result was 600
[DPI] line images are stably formed without line thickening, there is no trailing or blurring at the edges of the image, and the OD
It is possible to stably form a high-temperature solid image with a value of 1.4 or higher without any unevenness of soaking, and there is no ground force blur on the recording paper as well as on the latent image carrier, reducing the amount of waste toner. We were able to reduce it significantly.

In FIG. 4, arrows indicate the rotation directions of the respective members. Also, as toner suitable for the toner carrier of the present invention, all known magnetic toners can be used, including resin-based toners. Toner: Any wax-based toner may be used.The composition of the developer is, as is well known, a mixture of resin, magnetic powder, colorant, external additives, and other additives, and is created by a pulverization method, a polymerization method, etc. be done. Furthermore, as is well known in the art with two-component developers, a chargeability improver or a fluidity improver may be added to the toner to form a multi-component developer.

Although the embodiments have been described above, the present invention can be applied not only to the above embodiments but also to a wide range of toner carriers in developing devices such as electrophotography, and in particular to printers, copiers, facsimile machines, and displays. It is effective if the magnetization method is applied not only to the magnetization of a toner carrier but also to the magnetization of a magnetic encoder.

[Effects of the Invention] As described above, according to the present invention, by performing development with a toner carrier having at least an elastic layer and a magnetic field generating layer, pressure development using magnetic toner becomes possible, and high resolution can be achieved. This has the effect of stably forming high-quality images with little unevenness in hot water temperature. Furthermore, by configuring the toner carrier to have at least a magnetic field generating layer with a coercive force of 2000 [Oe] or less, it is possible to not only generate leakage magnetic flux sufficient to hold the toner on the surface of the toner carrier;
The magnetic field generating layer of the toner carrier can be efficiently magnetized by a simple operation of copying the magnetization pattern of the magnetization master.

In addition, by magnetizing the magnetic field generation layer while the toner carrier is in close contact with the magnetization master, it is possible to magnetize the magnetic field generation layer of the toner carrier at a minute pitch according to the magnetization pattern of the magnetization master, and in addition, it is possible to magnetize the magnetic field generation layer of the toner carrier in close contact with the magnetization master. This is a method of magnetizing a toner carrier that can be magnetized by stably applying a sufficient magnetic field to a magnetic field generation layer due to the state of the magnetic field, and can provide a very simple and inexpensive magnetization method. Therefore, it is possible to provide an inexpensive toner carrier that can stably form a thin layer of magnetic toner.

Therefore, the present invention has the excellent effect that fine pitch magnetization of the toner carrier is easily possible, and images with high resolution and less temperature unevenness can be stably formed using the toner carrier of the present invention. It has the following.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a toner carrier according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing a method of magnetizing a toner carrier according to another embodiment of the present invention, and FIG. A diagram showing the relationship between the coercive force of the magnetic field generating layer of the toner carrier and the magnetic susceptibility of the magnetic field generating layer by the magnetization master in other examples,
FIG. 4 is a schematic cross-sectional view of an image forming apparatus using a toner carrier according to still another embodiment of the present invention. Toner Toner carrier shaft elastic layer Magnetic field generating layer Magnetization master Applicant Seiko Epson Co., Ltd. Agent Patent attorney Kizobe Suzuki (1st name) Figure 3

Claims (2)

[Claims] (1) A toner carrier that conveys magnetic toner and is elastically deformable, the toner carrier having a coercive force of 2000 [O
e] A toner carrier characterized by having at least the following magnetic field generating layer: (2) A method for magnetizing a magnetic field generating layer of a toner carrier according to claim 1, wherein the magnetic field generating layer is magnetized by magnetic copying by a magnetization master having a predetermined magnetization pattern. A method of magnetizing a toner carrier.