JPS6079367A - Developer carrier and its manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field 1 The present invention relates to a magnetic developer carrier and a method for manufacturing the same, and more particularly, to a developer carrier suitable for a developing device using -component high resistance magnetic toner and its manufacturing method. This relates to a manufacturing method.

BACKGROUND OF THE INVENTION In electrostatic recording devices such as electrophotographic copying machines, facsimile machines, printers, etc., the development characteristics required for development are different depending on whether the document is a line image or a solid image. FIG. 1 is a graph showing the preferred development characteristics, with the horizontal axis representing original image density and the vertical axis representing copy image density.

In the figure, the solid line A is the development characteristic required for a solid image, and the broken line B
indicates the development characteristics required for line images. According to this, the rising gradient is steeper in the case of a line image (broken 11IB) than in the case of a solid image (solid line A). The reason for this is that when the original is a line image, if the original image density is low, the brightness of the image will be inferior, so it is necessary to increase the copy image density to compensate for this, but if the original is a solid image, the original image density will be lower. This is because if a corresponding copy image density is obtained, the image will be sufficiently clear.

For this reason, so-called edge hardening has been used conventionally.

That is, the strength of the electric field at the edges of the electrostatic latent image is stronger than the strength of the electric field at the center of the image, resulting in a larger amount of toner adhering to the edges of the image, resulting in an edge effect. Therefore, in the case of a line image with a small image area, most of the latent image forming area corresponds to the edge and is subject to the edge effect, resulting in a high value of the density of the copied image.

However, this edge effect is sufficiently effective when a two-component developer containing a toner and a carrier is used, but when a one-component toner that does not contain a carrier is used. had the disadvantage that an effective edge effect could not be obtained.

Therefore, the applicant of the present application has proposed a developing device equipped with a developer carrier having a unique configuration that makes it possible to obtain the above-mentioned suitable development characteristics even when using a -component type developer (
(Japanese Patent Application No. 185726/1982). As shown in FIG. 2, the developer carrier according to this proposal has minute electrode particles 2a made of a conductive material on the outer peripheral surface of a cylindrical conductive support 1 in the circumferential direction and The electrode layer 2 is formed so as to be uniformly scattered in the width direction, and the individual electrode particles 2a are insulated from each other and held in an electrically floating state. When a magnetic developer is used, a magnet roll 3 that supplies magnetic force to support the magnetic developer inside the support 1 has its shaft 3a.
is rotatably supported and arranged. In the developer carrier configured in this way, not only is the magnet roll 3 enlarged in order to obtain the necessary magnetic force on the surface of the electrode layer 2, but also the gap G between this and the inner peripheral surface of the support must be properly managed. This is difficult, and as a result, assembly workability deteriorates, leading to a significant increase in costs. Another drawback is that it is difficult to properly control the electrode thickness t2A of each electrode particle 2a in order to obtain the desired edge effect. Furthermore, when the latent image carrier to be developed is a rigid body such as a photosensitive drum, there is also the problem that the developing effect is deteriorated.

Purpose The present invention has been made in view of the above points, and promotes weight reduction, improves assembly workability, contributes to cost reduction, and also provides desired rigid latent image carriers. An object of the present invention is to provide a developer carrier capable of exhibiting the edge effect and obtaining high image quality, and a method for manufacturing the same.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Below, the structure of the present invention will be explained in detail based on specific examples. First, the structure of a developer carrier as an embodiment of the present invention will be explained based on the schematic cross-sectional view of FIG. In FIG. 3, a cylindrical core metal 4 as a conductive support made of a conductive material such as aluminum or stainless steel is fixed to a rotating shaft 4a. A composite rubber layer made of a mixture of a rubber material such as acrylonitrile butadiene rubber (NBR) and a magnetic material such as ferrite is formed on the outer circumferential surface of the core bar 4, and then this is bonded by a known method. A magnetized rubber magnet layer 5 is formed. In this case, the N and S poles may be magnetized alternately along the circumferential direction of the rubber magnet Ii5, and the magnetization conditions such as the distribution density of the magnetic poles may be determined by the rotational speed of the developer carrier and above. It is desirable to set this by considering the balance between the thickness of the laminated layers and the moving speed of the latent image carrier that conveys the latent image to be developed. Note that the conductive support is not limited to the cylindrical core metal 4, and may be formed in the shape of an endless belt.

On the rubber magnet layer 5, an elastic dielectric layer 6 made of an elastic dielectric material such as rubber is formed. Examples of elastic electrical materials include (chloroprene or silicone)
Synthetic rubbers such as, etc. are preferred, but natural rubbers are also applicable. The layer thickness t6 of the elastic dielectric layer 6 needs to be set in consideration of the decrease in magnetic force on the surface of the electrode layer 7.

On the elastic dielectric layer 6, an electrode is formed by holding a large number of hemispherical conductive particles 7a as microelectrodes in a dielectric adhesive 7b in an electrically insulated state B()0-t state). Layer 7 is formed. The electrode N7 of this example is formed by holding a large number of copper particles in an epoxy resin as a room-temperature curing adhesive, with some of the copper particles exposed on the surface as microelectrodes, and insulated from each other. In this case, the surface of the electrode layer 7 is finished smoothly without any unevenness, and each conductive particle 7a is held aligned with its bottom surface in contact with the surface of the elastic dielectric layer 6. Therefore, the electrode thickness t7A and the electrode layer thickness ta become equal.

Therefore, the electrode layer thickness t7 is, for example, 52 when the particle size of the particles 7a used is 74 to 104 Jllll.
It is required to keep it within the allowable range of 62JIffl to 62JIffl. The reason is as follows.

FIG. 4 is a graph showing the relationship between the electrode thickness t7A of the particle 7a and the ratio of the area exposed on the surface to the total surface area (expressed as area ratio AR). In Figure 4,
Curve α1 curve β and curve γ each have a particle size of 104 μm.
The relationships among the largest particles, particles with an average particle size, and smallest particles with a particle size of 74 μm are shown. According to this,
An area ratio AR of 45% or more is required in order to exhibit the desired edge effect and obtain suitable development characteristics as shown in Figure 1.
In order to ensure this, the electrode thickness [maximum value of 7A to 62
Just set it to JII11. In addition, in order to maintain the anchor effect and prevent particle detachment, the maximum particle (curve α
) It is necessary to ensure an electrode thickness t7A of 52JII+1 or more, which is half of 52JII+1. Therefore, the allowable range of the electrode thickness t7A is 52 to 62JII+1. By the way, in the developer carrier of the present invention, as described above, the electrode thickness is j77.
Since 1 and the electrode layer thickness t7 are equal, the process may be controlled so that the electrode layer thickness t7 falls within the above-mentioned allowable range.

In the developer carrier constructed as described above, the magnet as a magnetic field generating means is formed in a light layer using rubber as a medium material, and is integrally coated on the same support as the electrode layer etc. Since it is formed, troublesome work such as gap management is omitted, improving assembly work efficiency and promoting cost reduction. Further, since the elastic layer is interposed in the middle, it is possible to flexibly contact a rigid latent image carrier such as a photoreceptor drum and exhibit a suitable developing effect.

Next, one implementation of a manufacturing method capable of manufacturing the developer carrier configured as described above while appropriately controlling the electrode layer thickness will be described. First, a core 4 of a magnet roll made of a conductive material and having a rotating shaft 4a as shown in FIG. 5 is formed.

After the core metal 4 is formed, its outer circumferential surface is cleaned and then a rubber magnet layer is deposited thereon. A preferred embodiment of this process is
This is shown in FIGS. 6(a) to 6(0). According to this method, as shown in FIG. 6(a), first, a rubber material such as chlorinated polyethylene or NBR which has been masticated is coated with a vulcanizing agent or the like according to the purpose along with ferrite as a magnetic material. Various ingredients are added and kneaded using a two-roll machine 8 or the like. Then, the composite rubber material 5-, which has been kneaded and has a uniform composition, is formed into a sheet shape and wound around the circumferential surface of the core bar 4 as shown in FIG. 7(b). Next, a rubber sheet 5 is placed on the core metal 4 in the cavity 9a in the mold 9 of the pressure press.
A workpiece (hereinafter referred to as work W) wrapped with ' is housed, and heated and vulcanized while applying pressure. As a result, the seventh
(b) As shown in the figure, a composite rubber layer 5- having a substantially uniform layer thickness ts' is formed on the same surface of the core bar 4. Thereafter, magnetization is carried out in a conventional manner to form a rubber magnet layer 5' in which, for example, N and S poles are alternately provided along the circumferential direction, as shown in FIG. 7(a).

Since the surface of the adhered rubber magnet layer 5' usually has many irregularities, a first surface treatment is performed using a grinding method such as a cylindrical grinder to smooth the surface and reduce the layer thickness ts. ' to a desired value, for example, 5 to 3 mm. In this example, as shown in FIG. 8, the outer diameter of the workpiece W is machined by cylindrical grinding with the center of the workpiece W as a reference. In this case, by gripping the rotating shaft 4a of the core metal 4 with a support 10 of a cylindrical grinder and performing the grinding process, a rubber magnet layer 5 having an accurately uniform layer thickness t5 is formed without eccentricity.

After forming the rubber magnet layer 5, the surface of the rubber magnet layer 5 is cleaned, and then an elastic dielectric layer is formed using a rubber material containing no magnetic material in the same manner as when the composite rubber layer 5- is deposited. Form the adhesion. That is, as shown in FIGS. 6(a) to 6(C), a rubber material such as a cone is mixed with a compounding material such as a vulcanizing agent, kneaded, and wound on the rubber magnet layer 5. As a result, as shown in Fig. 9, the layer thickness [
A substantially uniform elastic dielectric layer 6' (before surface finishing) is formed.

Similarly, the surface of the formed elastic dielectric layer 6- has a large number of unevenness, which is disadvantageous in controlling the electrode layer thickness later. Therefore, the surface of the elastic dielectric layer 6' is subjected to a second surface treatment using the same grinding method as the first surface treatment applied to the rubber magnet layer 5. As a result, as shown in FIG. 10, the elastic dielectric layer 6 is finished with a smooth surface and a uniform layer thickness t6.

After forming the elastic dielectric 116, its surface is cleaned and then, as shown in FIG.
1, a dielectric first adhesive 7b such as a cold-setting epoxy resin is uniformly sprayed onto the surface of the elastic dielectric layer 6. As a result, the first adhesive film 7b as shown in FIG. 12 is deposited, and its thickness i7e is determined by the conductive particles 7a having a particle size of, for example, 74 to 104 pm, which are dispersed in the next step. Approximately 3 to 15 scales are suitable because they can be easily held in contact with the surface of the elastic dielectric layer 6 (see FIG. 14). In this case, the rotating shaft 4a of the core bar 4 is horizontally and rotatably supported, and the workpiece W is rotated at an appropriate speed while the air spray 11 is reciprocated at a predetermined speed to apply the first adhesive. By repeating spraying, the first adhesive film 7b having a uniform thickness can be easily deposited.

After the first adhesive film 7b is applied, a large number of conductive particles are applied approximately uniformly to the surface of the elastic dielectric 116 before it is cured. For example, as shown in FIG. 13, this attachment method involves storing a large amount of copper particles having a particle size of 74 to 1104p as conductive particles 7a in 1 to 12 equipped with a dispersing port 12a, and horizontally The tray 12 is reciprocated at an appropriate speed and tilted appropriately along the workpiece W which is supported and rotated, and the particles 7a are dropped layer by layer from the spraying port 12a and uniformly sprinkled onto the first adhesive 117b. Good.

In this case, each conductive particle 7a used here is preliminarily coated with, for example, acrylic lacquer or methyl methacrylate-1-(M
If the particles 7a are coated with a dielectric material such as MA), even if the particles 7a are scattered randomly under a natural painting, each particle 7a can be more reliably electrically insulated from the surroundings ()〇-T. situation)
can be held in the first adhesive film 7b. By the way, each particle 7a sprinkled on the first adhesive film 7b naturally sinks to the surface of the elastic dielectric layer 6 because the film thickness of the first adhesive lB17b is as thin as 3 to 15 μm. Therefore, the fourteenth
As shown in the figure, the bottom surface of each particle 7a can be easily and reliably aligned with the surface of the elastic dielectric layer 6 simply by allowing the individual particles 7a to fall naturally. In this example, copper particles are used as the conductive particles 7a, but the present invention is not limited to this, and other conductive particles such as brass, phosphorous copper, stainless steel, etc. can also be used. However, in this case as well, these particles do not float and are reliably deposited on the dielectric layer 2.
It is necessary to appropriately set the film thickness of the first adhesive 117b according to the size and specific gravity of the particles so that the first adhesive 117b sinks on the surface.

Also, instead of supporting the workpiece W horizontally as described above, the first
As shown in FIG. 5, the workpiece W may be supported and rotated in an appropriately inclined state, and the particles 7a may be uniformly scattered by gravity in the same way. As a result, particle 7a
It becomes possible to further improve the adhesion density. Thereafter, the first adhesive 7b is naturally dried without heating and is almost completely cured.

After the first adhesive film 6b is almost completely dried and cured, a dielectric second adhesive 7b' is again thickly coated on the conductive particles 7a and the first adhesive film 7b in the same manner as before. overcall h). In this case, if an adhesive made of the same substance as the previous one is used, the two will be firmly adhered to each other and the particles 7a can be fixed more firmly in contact with the surface of the elastic dielectric layer 6, which is advantageous in terms of durability. be. However, particles 7 adhere to each other.
As long as a can be reliably fixed, combinations of dielectric adhesives made of different materials are also possible. As shown in FIG. 16, by applying the adhesive twice in between the drying process, the previously applied first adhesive film 7b is not redissolved, and therefore each The particles 7a can be firmly fixed in a settled state on the surface of the elastic dielectric 116 without being suspended, and as described above, the electrode thickness of each particle can be replaced by an easily controllable electrode layer thickness.

After applying a thick coat of adhesive, let it dry and harden. In this case, as in the previous adhesive drying process, the work W
It is sufficient to dry it by rotating it and supporting it horizontally. As a result, as shown in FIG. 16, the first adhesive film 7b, the conductive particles 7a, and the second adhesive are laminated on the elastic dielectric layer 6 without the thickly applied second adhesive 7b' dripping. 7
The layer thickness Ty- of the electrode layer 7- (a state before some of the particles 7a are exposed on the surface) including the electrode layers b- becomes uniform. In this way, an electrode layer 7' having a diameter of about 150 cm, for example, is formed.

After forming the electrode layer 7', as shown in FIG. 17, the surface of the electrode layer 7 is subjected to a third surface treatment by a grinding method to smooth the surface and to remove a portion of each conductive particle 7a from the surface. The electrode layer 7- is finished as the electrode layer 7 by exposing the electrode layer 7- to the electrode layer 7-. Here, it is required that the layer thickness t7 of the electrode layer 7 is within the allowable range of 52 to 62μ, but in this example, the rotation axis of the core metal 4
Since the machining axis is always constant by using a as the machining axis, the layer thickness t7 can be easily kept within the above-mentioned patent range. That is, when the third surface processing is carried out using, for example, a cylindrical grinder, the second surface processing for the elastic dielectric layer 6- is performed as shown in the figure.
By gripping the rotary shaft 4a, which was used as the processing axis during surface processing, with a support 10- such as a chuck in this process as well, the processing axes in both processes coincide, and therefore the layer thickness t7 is made uniform with high precision. be done. In this example, the second adhesive 7b''
In the drying process after thick coating, the second adhesive 7b" is prevented from sagging before it hardens by the method described above, and the voltage applied before finishing is
Since the process is controlled so that the layer thickness t7- is approximately average,
The desired electrode layer 7 can also be obtained by a superfinishing method or a centerless grinding method based on the outer peripheral surface, which does not require aligning the machining axes.

In addition, if a rotating shaft is not formed on the core metal, or if the workpiece
If it is not cylindrical but has an endless belt shape or a planar shape,
The workpiece W may be stretched between an appropriate number of rollers and rotated, and a rotating grindstone may be pressed against the workpiece W in the same manner as in cylindrical grinding to perform various surface treatments.

As described above, the third surface treatment is carried out over the entire circumferential surface of the electrode layer 7-, and as shown in FIG. form 7. After this, the developer carrier 12 as a final product is completed by cleaning the dirt such as cutting oil.

In the above example, the step of magnetizing the rubber layer was carried out after forming the composite rubber layer 5', but this magnetization step could be carried out in other cases, for example, when the composite rubber M5- was subjected to the first surface treatment. It is also possible to carry out after applying the second surface treatment to the elastic dielectric layer 6-, after drying the second adhesive 7b, or after applying the third surface treatment to the electrode layer 7'. be. however,@
Taking into account the adhesion of dust after magnetization and the occurrence of scratches on the outer peripheral surface of the workpiece due to handling during magnetization, it is desirable that the second adhesive 7b be used after drying. Further, although the adhesive application step is divided into two steps, it may be divided into one step or three or more steps as necessary. Furthermore, it is also possible to omit the first surface treatment.

Effects As detailed above, according to the present invention, by interposing an elastic dielectric layer made of a rubber material as an intermediate layer, it can flexibly come into contact with a rigid latent image carrier and provide a suitable developing effect. It becomes possible to easily manufacture a developer carrier that can exhibit the following characteristics. or,
By forming a rubber magnet layer with rubber as a medium integrally on the conductive support and forming the electrode layer so that the electrode thickness and the electrode layer thickness are equal, the trouble of adjusting the magnetic force is saved and assembly work efficiency is improved. In addition, the electrode thickness can be easily and reliably managed by substituting the electrode layer thickness. Therefore, it is possible to efficiently manufacture a high-quality developer carrier at a low cost, which ensures sufficient magnetic force, promotes weight reduction, and exhibits a desired edge effect even on a rigid latent image carrier.

It should be noted that the present invention should not be limited to the specific embodiments described above, and it goes without saying that various modifications can be made within the technical scope of the present invention. For example, when applying an adhesive, other immersion molding methods (dip molding method), etc.4, Brief explanation of the drawings 9''' Figure 1 is a graph showing suitable development characteristics, Figure 2 is a graph showing suitable development characteristics. FIG. 3 is a schematic sectional view showing a conventional developer carrier 12. FIG. 4 is a schematic sectional view showing a developer carrier 12 as an embodiment of the present invention. A graph showing the relationship, FIG. 5 is a perspective view showing the core bar 4 in one embodiment of the method of the present invention, and FIGS. 6(a) to 6(C) respectively show the composite rubber layer 5 Each explanatory diagram showing the formation process of ′,
7(a) and 7(b) are a schematic side view, a schematic front sectional view, and a schematic front sectional view showing the rubber magnet layer 5-, respectively.
9 and 10 are schematic sectional views showing the state of the elastic dielectric layer 6' before and after the second surface processing, respectively. 12 and 12 are schematic cross-sectional views showing the first adhesive adhesion process and the amount of the adhesive formed, and FIGS. 13 and 14 are the same steps of adhering the conductive particles and the amount of the formation. FIG. 15 is an explanatory diagram showing another example of the particle adhesion process, and FIG. 16 is a schematic cross-sectional diagram showing the amount of the second adhesive formed after thick coating. 17 are schematic cross-sectional views similarly showing the third surface processing step.

(Explanation of symbols) 2.7: Electrode! 4: Core metal 5': Composite rubber layer, rubber magnet layer (before surface treatment) 5: Composite rubber layer, rubber magnet layer (After surface processing) 6: Elastic M conductive layer Patent applicant Rico Co., Ltd. Figure 1 Figure 2 Figure 5 6th (C) Figure 7(0) Figure 7(b) 1 Figure 5 Figure 9 Figure 11 Figure 12 Figure 13 Figure 14 a n

Claims (1)

[Claims] 1. A rubber magnet layer made of a magnetized composite made of a mixed material of rubber and a magnetic material, an elastic dielectric layer made of a rubber material, and a microelectrode on a conductive support. 1. A developer carrier comprising a laminated electrode layer in which a large number of conductive particles are held in a dielectric adhesive in an electrically insulated state. 2. The developer carrier according to the above item 1, wherein the dielectric adhesive is a room temperature curable adhesive made of an epoxy resin. 3. forming a support made of a conductive material; forming a composite rubber layer made of a rubber material and a magnetic material on the support; magnetizing the composite rubber layer; A step of forming an elastic dielectric NH made of a rubber material on the surface of a rubber layer, applying a dielectric adhesive to the surface of the elastic dielectric layer, and adhering a large number of conductive particles as microelectrodes on the elastic dielectric layer. A method for producing a developer carrier, comprising the steps of: forming an electrode layer; and surface-processing the electrode layer to expose a portion of each of the conductive particles on the surface. 4. In the above item 3, the step of forming the dielectric #1 layer includes the step of applying a dielectric first adhesive to the surface of the elastic dielectric layer, and the step of applying a dielectric first adhesive to the surface of the elastic dielectric layer. attaching the conductive particles onto the elastic dielectric layer; drying the first adhesive; and overcoating the first adhesive and the conductive particles with a second dielectric adhesive. A method for producing a developer carrier, comprising the steps of: 5. In the above item 4, the first adhesive and the second adhesive
A method for manufacturing a developer carrier, characterized in that the adhesive is a room-temperature curing adhesive made of epoxy resin.