JPH04181971A - Developing device - Google Patents

Abstract

PURPOSE:To obtain a developing device capable of press-contact developing without damaging a latent image carrier at a low cost by constituting a magnetic field generating layer of a thermal contraction sleeve which is obtained by dispersing magnetic powder. CONSTITUTION:A developing roller 9 carrying toner 8 is constituted by concentrically disposing an elastic layer 11 and the electric conductive magnetic field generating layer 12 made of the thermal contraction sleeve which is obtained by dispersing the magnetic powder on the outer periphery of a shaft 10. The magnetic field generating layer 12 is a thermal contraction tube which is obtained by dispersing the magnetic powder 21 in the binder 22, and a material having the thermal contraction such as polyvinyl chloride, polyethylene, or polypropylene is used as the binder 22, and the magnetic powder known as a magnetic recording material or a magnet material is used as the magnetic powder 21. Thus, the damage of the magnetic field generating layer at the time of assembling is reduced and the man-hour of assembling is reduced, then the developing roller is obtained at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developing device that develops magnetic toner, and more particularly to a developing device that is characterized by a toner carrier that conveys the magnetic toner.

[Prior Art] A conventional developing device using magnetic toner is disclosed in Japanese Patent Application Laid-Open No. 1986-
42738, the toner carrier is formed of a conductive rubber magnet to ensure a sufficient amount of toner conveyance for development and to reduce the contact pressure between the toner carrier and the latent image carrier. The development was carried out under pressure.

In addition, as a method for performing pressure development by relaxing the contact pressure between the toner and the latent image carrier, as disclosed in Japanese Patent Laid-Open No. 63-226676, a cylindrical thin film having an excess circumference with respect to the drive roller is used. A toner carrier is configured by the member sleeve,
Some have made it possible to convey and develop non-magnetic toner by elastically bringing the surplus portion into close contact with the latent image carrier.

[Problems to be Solved by the Invention] However, in the prior art described above, carbon or the like is mixed into the rubber in order to impart conductivity to the rubber magnet.
If you want to obtain a conductivity below [Ωcn], the rubber hardness should be 4
It is difficult to reduce the angle to less than 5 degrees, and if a hard rubber magnet is pressed against the latent image carrier, the toner will solidify at the pressure contact area between the toner carrier and the latent image carrier, and not only will a good image not be obtained, but the latent image carrier will not be able to obtain a good image. There is a problem in that the image carrier is worn out.

In addition, in the above-mentioned conventional technology, since the thin film member and the drive roller are not fixed, it is necessary to handle the thin film member alone during assembly, and the end face must be deformed when inserting the drive roller, and the toner carrier may be incorporated into the developing device. However, there were problems such as deformation of the thin film member and loss of cylindricity, causing uneven toner conveyance.

Therefore, the present invention aims to solve these problems.
The purpose is to provide a developing device that can perform pressure development without damaging the latent image carrier at a low cost.

Still another object is to provide a developing device whose toner carrier is easy to handle during assembly and which is easy to assemble.

Still another object is to provide a developing device suitable for performing high-resolution development using magnetic toner.

[Means for Solving the Problems] A developing device of the present invention is a developing device that conveys magnetic toner by a toner carrier and develops the magnetic toner on a latent image carrier, wherein the toner carrier carries a magnetic field generating layer. The magnetic field generating layer is formed from a heat-shrinkable sleeve in which magnetic powder is dispersed.

Further, the developing device of the present invention is characterized in that the toner carrier has at least an elastic or flexible member and a magnetic field generating layer, and the magnetic field generating layer is formed of a heat-shrinkable sleeve.

Furthermore, the minimum magnetization reversal pitch of the magnetic field generation layer is 100 cμ.
It is characterized by being less than m.

[Function] According to the above configuration of the present invention, by configuring the magnetic field generating layer with a heat shrinkable sleeve in which magnetic powder is dispersed, damage to the magnetic field generating layer during assembly can be reduced, and heat shrinkage can be used. Since the magnetic field generating layer can be attached to the elastic layer without an adhesive layer, the number of assembly steps can be reduced and the developing roller can be provided at low cost.In addition, the magnetic field generating layer can also be placed on elastic layers that do not have good foaming or hydrophilic properties. It becomes possible to do so.

In addition, by disposing the magnetic field generating layer on the elastic layer, the conductivity and magnetic properties of the magnetic field generating layer can be set appropriately for development, and the toner carrier can be developed in pressure contact with the highly rigid latent image carrier. Development can also be carried out without damaging the latent image carrier.

Furthermore, since pressure-contact development can be performed, there is no need to manage the development gap between the toner carrier and the latent image carrier, and high-speed printing is possible because the contact width (width of the lubricant) is expanded.

Furthermore, by providing the magnetic field generation layer on the surface of the toner carrier, leakage magnetic flux from the magnetic material can be effectively used for toner retention, and sufficient toner retention force and conveyance amount can be obtained by making the magnetic field generation layer thinner. Can be layered.

Furthermore, the minimum magnetization reversal pitch of the magnetic field generation layer was set to 100 [μ
m] or less, a uniform and thin toner layer (or a thin magnetic brush layer with a fine pitch) can be formed on the toner carrier, and temperature unevenness due to fluctuations in the magnetic field or toner layer thickness can be prevented. can be reduced.

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

[Example] FIG. 1 is a cross-sectional schematic diagram of an image forming apparatus using a developing device of the present invention. The latent image carrier 1 has an organic or inorganic photoconductive photosensitive layer 3 coated on a conductive support 2, and the photosensitive layer 3 is charged with a corona charger, a charging roller, etc. After charging using device 4, a laser or LED
The light emitted from the light source 5 is passed through the imaging optical system 6 to the photosensitive layer 3.
A latent electrostatic image is formed by selectively irradiating light according to the image to obtain potential contrast. On the other hand, the developing device 7 conveys and develops the magnetic toner 8, and the developing roller 9 conveying the toner 8 has an elastic layer 1 formed on the outer periphery of the shaft 10.
1 and a conductive magnetic field generating layer 12 made of a heat-shrinkable sleeve in which magnetic powder is dispersed are arranged concentrically, and magnetic toner 8 is generated by leakage magnetic flux around the outer periphery of the magnetic field generating layer 12.
The toner 8 is held on the developing roller 9, and the toner 8 is made into a thin layer by rotating the developing roller 9 while forming an appropriate amount of toner into a thin layer with an elastic blade 13 in the shape of an N leaf spring made of non-magnetic or magnetic metal or resin. It is used to transport. The developing roller 9 is pressed against the latent image carrier 1 with a predetermined pressure, but the toner 8
In order to prevent the phenomenon of solidification at the press-contact portion, the press-contact force is relaxed by an elastic layer 11 formed of an elastic member. When the toner 8 on the developing roller 9 is conveyed to the pressure contact portion, it adheres to the latent image carrier 1 according to the potential contrast of the latent image carrier 1 and the developing electric field formed by the developing bias applying means 14, forming an electrostatic latent image. is visualized. moreover,
A toner image is transferred onto a 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. .

FIG. 2 is a more detailed sectional view of a toner carrier in an embodiment of the present invention, in which a magnetic field generating layer 12 disposed on an elastic layer 11 has magnetic powder 21 dispersed in a binder 22. It is a heat-shrinkable tube, and the binder 22 includes polyvinyl chloride, polyethylene, polypropylene, linear polyester, polyamide resin, crystalline polyolefin, crosslinked polyolefin, non-crosslinked polyolefin, crystalline polyolefin copolymer, fluororesin, and silicone rubber. , E
Heat-shrinkable materials such as PDM can be used, and magnetic powder 2
As 1, a magnetic powder known as a magnetic recording material or a magnet material can be used, and more specifically, Fe, Ni
, Co, Mn, Cr, a magnetic material containing at least one kind of element, for example, 7'-F
e 203, Ba-Fe, Ni-Co, Co
-Cr, Mn-A1, etc. can be used, and the elastic layer 11 can be made of natural rubber, silicone rubber, isoprene rubber, urethane rubber, butadiene rubber, chloroprene rubber, neoprene rubber, NBR, etc., or rubber, foam, sponge, etc. It is possible to use all resins that can be used in the form of foams and can be formed into elastic foams including elastomers, such as styrene resins, vinyl chloride resins, polyurethane resins, polyethylene resins, methacrylic resins, etc.

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 ground blurring at the edges of the image, and it is possible to stably form solid images with a high temperature layer with an OD value of 1.4 or more. did it.

In addition, magnetic powder and conductive particles are dispersed in the magnetic field generating layer to provide sufficient toner holding power and conductivity for development, so even though the hardness of the magnetic field generating layer has increased, the magnetic field generating layer is retained. The elastic layer can effectively disperse and relieve the contact pressure between the magnetic field generating layer and the latent image carrier, and the nip width can be widened, making it possible to perform high-speed printing.

Furthermore, by constructing the magnetic field generating layer with a heat-shrinkable sleeve, it is possible to easily arrange the magnetic field generating layer even when the elastic layer is composed of foamed resin, etc., and the surface is full of pores. Ta.

Furthermore, the minimum magnetization reversal pitch of the magnetic field generation layer was set to 100 [μ
m] or less, the leakage magnetic flux that attracts the magnetic toner is limited to approximately several + [μm] from the surface of the magnetic field generation layer, and at the same time, the toner is uniformly thinned and the amount of toner conveyed on the developing roller by magnetic brush formation is reduced. It is possible to suppress fluctuations in pitch to a minute pitch and reduce irregularities.

FIG. 3 is a cross-sectional schematic view of an image forming apparatus using a developing device according to another embodiment of the present invention, in which members having the same functions and names as those in FIG. 1 are given the same numbers and explained. omitted. The developing device 31 conveys and develops the magnetic toner 8, and the developing roller 32 that conveys the toner 8 includes a driving roller 33 that is rotationally driven and has a friction portion on the outer periphery, and an extra length on the outer periphery of the driving roller 33. It is composed of a cylindrical conductive thin film member 34 which is externally wrapped with a cylindrical conductive thin film member 34, and a conductive magnetic field generating layer 35 formed from a heat shrinkable sleeve in which magnetic powder is dispersed. The toner 8 is held on the developing roller 32 and conveyed. The developing roller 32 is pressed against the latent image carrier 1 at a predetermined pressure, and when the toner 8 on the developing roller 32 is conveyed to the pressing portion, it is developed according to the developing electric field.

The developing roller 32 is pressed against the latent image carrier 1 with a predetermined pressure, but in order to prevent the toner 8 from solidifying at the pressed portion, a thin film member 34 made of a flexible member is used. It reduces the pressure welding force.

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
The [DPI] line image is stably formed without line thickening, and there is no tailing or blurring at the edge of the image, and the oD
It was possible to stably form a high-temperature solid image with a value of 1.4 or higher.

In addition, the flexibility of the thin film member effectively disperses the pressure applied to the magnetic field generation layer, making it possible to have a wide developing nip. The magnetic field generating layer could be easily constructed by using a heat-shrinkable sleeve in which the magnetic field was dispersed.

In FIG. 3, the thin film member 34 is made of Ni, Cu, Zn, A
In addition to first grade metals or alloys containing them, it is possible to use film-like resins, rubber, etc. formed into a thin cylindrical shape.

FIG. 4 shows a developing roller 9 in another embodiment of the present invention.
FIG. 1 is an explanatory diagram of the manufacturing method, with the same function as in FIG. 1.
Named members are given the same numbers and explanations are omitted. Fourth
In the figure, the elastic layer is made of silicone rubber with an outer diameter of 20 [mm], and the magnetic field generating layer 12 is made of a heat-shrinkable sleeve with magnetic powder dispersed in polyvinyl chloride with an inner diameter of 20 [mm].
5 [mm], and after inserting the elastic layer into the magnetic field generation layer, it is fixed to the elastic layer while being sequentially contracted from one end of the magnetic field generation layer by heating means 41, so that the elastic layer is not In the case of foam, heating the entire heat-shrinkable sleeve in a furnace at once can avoid the problem of air bubbles remaining between the heat-shrinkable sleeve and the elastic layer, creating unevenness on the surface of the magnetic field generating layer, and also In addition to being able to reduce the occurrence of defective products due to the handling of the magnetic field generation layer during the manufacturing process, the developing roller can be constructed extremely easily since it does not require high-precision parts such as shaft fitting or assembly work. .

In addition, in FIGS. 1 to 4, the present invention is not limited only to the configurations shown in the figures. In particular, the structure of the heat-shrinkable sleeve that is the magnetic field generation layer is not limited to that shown in FIGS.
It is also possible to add additives such as a dispersant to a binder in which magnetic powder is dispersed, or to disperse 81-capable powder other than magnetic powder, such as conductive particles, to form a floating electrode and improve the developing electrode effect. There are also configurations in which a functional layer, such as a conductive layer, is provided on the outer or inner circumferential surface of the generation layer to improve the developing electrode effect or abrasion resistance, and configurations in which the magnetic field generation layer is made with fine holes or a mesh shape. It is possible.

Further, although the arrows indicate the rotation direction of each member, this does not limit the present invention.

Furthermore, the developing method can be used regardless of whether it is regular development or reversal development.

Further, as the toner used in the present invention, all toners known as magnetic toners can be used, and either resin-based toners or wax-based toners may be used. As is well known, the composition of the developer is a mixture of resin, magnetic powder, colorant, external additives, and other additives, and is produced by a pulverization method, a polymerization method, or the like.

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 developing devices such as electrophotography.
It is especially effective when applied to printers, copiers, facsimiles, and displays.

[Effects of the Invention] As described above, according to the present invention, by forming the magnetic field generating layer with a heat-shrinkable sleeve in which magnetic powder is dispersed, problems caused by handling of the magnetic field generating layer during the manufacturing process of the toner carrier can be avoided. This has the effect that the occurrence of non-defective products can be reduced, and the magnetic field generating layer can be extremely easily provided even on an elastic layer or the like that does not have good foamability or hydrophilicity.

In addition, since development can be performed with the toner carrier in pressure contact with the latent image carrier, the development electrode can be brought closest to the latent image carrier and a high-resolution image can be formed by the development electrode effect. has.

Furthermore, the minimum magnetization reversal pitch of the magnetic field generation layer was set to 100 [μ
m] or less, a uniform and thin toner layer (or a thin magnetic brush layer with a fine pitch) can be formed on the toner carrier, and temperature unevenness due to fluctuations in the magnetic field or toner layer thickness can be prevented. It is possible to perform high-resolution development.

Therefore, the developing device of the present invention has the excellent effect of being able to provide a developing device at a low cost that can produce high-resolution images with few image defects such as ground blur and trailing in magnetic development.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional schematic view of an image forming apparatus using a developing device of the present invention, FIG. 2 is a cross-sectional view of a toner carrier in an embodiment of the present invention, and FIG. FIG. 4 is a cross-sectional schematic view of an image forming apparatus in an embodiment, and FIG. 4 is an explanatory diagram of a method for manufacturing a developing roller in another embodiment of the present invention. 1 ・・・・・・・・・・・・・・・Latent image carrier 7
．． 31......Developing device 8...
・・・・・・・・・・・・ Toner 9.32 ・・・・・・
・・・・・・Developing roller 11 ・・・・・・・・・
...... Elastic layer 12.35 ......
・・・Magnetic field generation layer 21 ・・・・・・・・・・・・・・・
・・・Magnetic powder 22 ・・・・・・・・・・・・・・・
・Binder 34・・・・・・・・・・・・・・・・・・
Thin film members and above Figure 3 A4

Claims (3)

[Claims] (1) A developing device that conveys magnetic toner by a toner carrier and develops the magnetic toner onto a latent image carrier, wherein the toner carrier has a magnetic field generating layer, and the magnetic field generating layer is made of magnetic powder. A developing device characterized in that it is formed of a heat-shrinkable sleeve in which is dispersed a heat-shrinkable sleeve. (2) The developing device according to claim 1, wherein the toner carrier has at least an elastic or flexible member and a magnetic field generating layer, and the magnetic field generating layer is formed by the heat shrinkable sleeve. Device. (3) The minimum magnetization reversal pitch of the magnetic field generation layer is 100[
3. The developing device according to claim 1 or 2, wherein the developing device has a particle size of 1.0 μm or less.