JPH0223864B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention visualizes an electrostatic latent image formed on a latent image carrier using a developer carried on a developer carrier. The present invention relates to a developing device, and particularly to a developer carrier thereof.

[Conventional technology]

Developing devices of the above type have been widely used in various recording devices such as electronic copying machines. The electrostatic latent images visualized by such a developing device can be roughly divided into high and low spatial frequencies: so-called line images (linear electrostatic latent images) consisting of high spatial frequency components, and low and low spatial frequency components. It can be divided into a so-called solid image (planar electrostatic latent image) consisting of spatial frequency components.
When visualizing these images, different requirements are imposed. In other words, for a solid image, it is necessary to obtain a visible image with a density that roughly corresponds to the level of the surface potential, but for a line image, the surface potential should be obtained not only when the surface potential is high but also when it is quite low. It is required to obtain a visible image with relatively high density. These requirements can be met relatively easily by using a two-component developer that contains a carrier in addition to toner, but conventional development using a one-component developer that does not contain a carrier Depending on the device, it is not easy to satisfy the above requirements.

From the above-mentioned viewpoint, the present applicant has proposed a developing device, especially a developer-carrying member thereof, that can satisfy the above-mentioned requirements to a high degree while suppressing a decrease in development efficiency even when a one-component developer is used. proposed a new structure (Patent Application No. 185726/1983). The developer carrier according to this proposal includes a conductive support and a large number of microelectrodes having a size of, for example, about 10μ to 500μ, which are electrically insulated from the support and from each other. This microelectrode acts in the same way as a carrier in a two-component developer, and can substantially satisfy the requirements described above.

By the way, when the developer carrier according to the above proposal is used, if the part of the microelectrode provided therein facing the latent image carrier is located parallel to the surface of the latent image carrier. , a sharp visible image without blur can be obtained. To obtain such a developer carrier, for example, a flat plate-like microelectrode is used, and the electrode is electrically conductive through a dielectric material so that its flat surface is oriented parallel to the surface of the latent image carrier. Although it may be fixed to a support, it is not easy to manufacture such a developer carrier, leading to an increase in cost.

Therefore, the particles obtained by coating the conductive particles constituting the microelectrode with a dielectric resin are fixed on a conductive support via a dielectric, and the surface is ground to remove at least some of the conductive particles. When exposed on the surface of the developer carrier, it is possible to easily manufacture a developer carrier in which the microelectrode portion facing the latent image carrier is located parallel to the surface of the latent image carrier. Since the conductive particles constituting the microelectrode are coated with a dielectric resin in advance, it is possible to prevent the particles from coming into contact with each other, and it is possible to eliminate the risk of impairing the function of the microelectrode.

However, in the above-described manufacturing method, when the surface of the developer carrier is ground, burrs are generated at the ends of the conductive particles, and there is a risk that the burrs may come into contact with adjacent conductive particles. When such contact occurs, each conductive particle becomes electrically conductive, forming a large-sized electrode that cannot be called a microelectrode, and the function of the microelectrode is lost.

〔the purpose〕

The present invention has been made based on the above-mentioned novel recognition, and it is an object of the present invention to provide a developing device of the type described at the beginning, which solves the above-mentioned problems with a simple configuration.

〔composition〕

In order to achieve the above-mentioned object, the present invention includes a developer carrier as a conductive support and microelectrodes that are substantially electrically insulated from the support and substantially insulated from each other. It has a large number of conductive particles, and the conductive particles have a specific volume resistivity.
10 ¹² Ω・cm or more and a thickness of 0.5 μ to 0.5 mm is coated in advance with a resin, the surface of the developer carrier is ground, and at least a portion of the conductive particles are on the surface of the developer carrier. We propose a configuration that is exposed to

The thickness of the resin coated on the conductive particles is from 0.5μ to
A setting of 0.1 mm is particularly advantageous.

[Action and effect]

According to the above configuration, each conductive particle can be separated by 1 μ or more through the resin coated thereon,
Therefore, even if burrs are formed on the conductive particles when the surface of the developer carrier is ground, the burrs can be prevented from coming into contact with adjacent particles. Furthermore, the conductive particles are not too far apart from each other and do not lose their function as microelectrodes.

Furthermore, burrs on each conductive particle may be caused by external force applied to the completed developer carrier when it is used, but in this case as well, the structure of the present invention can prevent conduction between the particles. .

〔Example〕

Hereinafter, the structure of the developer carrier according to the present invention will be explained by explaining an example of its manufacturing method.

Example 1 Aluminum particles sieved to a size of 70 to 80 μm were used as conductive particles, mixed into a solvent containing an epoxy resin with a volume resistivity of 10 ¹⁴ Ω・cm, and then milled using a ball mill. Approximately 1
The mixture was stirred for a period of time to fully disperse the conductive particles. Next, this was sprayed and dried using a spray dryer to obtain conductive particles of aluminum coated with epoxy resin. At this time, the thickness of the epoxy resin coating layer was approximately 3 μm.

Next, as shown in FIG. 1a, for example, a hollow cylindrical conductive support 1 is prepared. When the developing device using the completed developer carrier uses a magnetic developer, a conductive support 1 made of a non-magnetic material (aluminum, stainless steel, etc.) is prepared.

Degrease the outer peripheral surface of the support 1 as necessary,
Thereafter, dielectric powder 2 is applied to the entire outer peripheral surface using an electrostatic coating machine 3. Although an appropriate resin such as an epoxy resin can be used as the powder 2, polyester resin powder was used in this example. After the powder is applied, it is cured to form a dielectric layer 2a on the entire outer peripheral surface of the conductive support 1 as shown in FIG. 2a, and the surface is polished if necessary. In this example, the thickness of the dielectric layer 2a after polishing was about 0.5 mm. Then, as shown in Figure 2b,
An epoxy adhesive, which is an example of a dielectric adhesive 5, is applied to the surface of the dielectric layer 2a by a pressure-feeding air spray 4.
(Fig. 1b).

Next, before the adhesive layer 5 is cured, the particles 6 described above are coated with an epoxy resin from above the adhesive layer 5.
a to form a particle layer 6 (FIG. 2c).
In order to scatter the particles 6a, the particles 6a are stored in the hopper 8 as shown in FIG. Ta. Each particle is coated with dielectric epoxy resin, so
After being dispersed, the conductive particles are electrically insulated from each other and also from the conductive support 1.

Next, before curing the adhesive layer 5, a heat-shrinkable tube 20 is placed over the particle layer 6 as shown in FIG. The particles 6a are pressed down to align the particles 6a and form a substantially single layer (FIG. 2d).
Here, we use a 50μ thick polyester tube 2.
0 was used.

Next, after removing the tube 20, a dielectric adhesive is further applied over the particle layer 6 to form a second dielectric adhesive layer 9 as shown in FIG. 2e. Second
As the adhesive layer 9, the same epoxy resin as the first adhesive layer 5 was used.

Then, after the second adhesive layer 9 is completely cured, its surface is ground to make the surface smooth and at least some of the aluminum particles are exposed on the surface as shown in FIG. 2 f and g. . This grinding is carried out by a first grinding wheel 10 rotating clockwise and a second grinding wheel 1 rotating counterclockwise, as shown in FIG.
The conductive support 1 having the layers 2a, 5, 6, and 9 formed thereon is fixed between the conductive support 1 and the second adhesive layer 9, and the surface of the second adhesive layer 9 is ground with these grindstones 10 and 11. Next, the abrasive material on the surface is cleaned and the outer diameter dimension is inspected to complete the final developer carrier 12. If necessary, this surface may be further coated with a very thin dielectric film.

Example 2 Iron particles with a size of 40 to 50μ were used as conductive particles, and the specific volume resistivity was 10 ¹⁵
A solvent in which acrylic resin of Ω·cm was dissolved was sprayed, and this was dried to obtain particles having an acrylic resin coat layer of approximately 1 μm thickness. A developer carrier was manufactured using these particles in the same manner as in Example 1.

Example 3 Conductive particles made of aluminum coated with resin as in Example 1 were dispersed in silicone rubber, and were formed into a sheet shape (or cylindrical shape) with a thickness of 100μ to 500μ. This was wound and fixed on the dielectric layer 2a formed on the conductive support 1 in the same manner as in Example 1, and its surface was ground to expose at least a portion of the conductive particles, forming a developer carrier. I got it.

As in Examples 1 and 2, by using resins that are compatible with each other as the resin that coats each conductive particle and the resin of the first and second adhesive layers, each particle is firmly fixed. This prevents the inconvenience of easy detachment.

In the above embodiment, the dielectric layer 2a was formed on the conductive support 1, but this was determined by the thickness t of the layer excluding the conductive support 1 in the completed developer carrier 12 (Fig. 2). f) to a desired thickness. Therefore, when a sufficient thickness t can be obtained with only the adhesive layers 5 and 9, the dielectric layer 2a may be omitted.

Next, the basic functions of the developer carrier manufactured as described above will be explained with reference to the drawings.

FIGS. 3a and 3b show a latent image carrier constituted as a photoreceptor 13 and a developer carrier 12 positioned with a slight gap between the latent image carrier 13 and the developer carrier 12 located at a developing area D (FIG. 5, FIG. 6 is an explanatory diagram showing a state in which they are facing each other in FIG. 6). The photoreceptor 13 shown here as an example consists of a conductive substrate 14 and a photosensitive layer 15 provided on its surface, and as the developer carrier 12, the one shown in FIG. 2f is used. . However, in FIG. 3, the dielectric layer 2a, the first adhesive layer 5, and the second adhesive layer 9 are shown as one layer. Between the photoreceptor 13 and the developer carrier 12, there is a toner particle containing only toner particles charged to a predetermined polarity (negative in FIG. 3) or a component other than the carrier mixed therein. A component-based developer, that is, toner (not shown) is carried on the carrier 12.
It is located in a state where it is supported by. For example, electrostatic latent images L ₁ and L ₂ are formed on the photosensitive layer 15 of the photoreceptor 13 by charges having a polarity opposite to that of the toner particles, and the latent image L ₁ shown in FIG. The latent image _L2 shown in FIG. 3b is a picture-like solid image.

The toner carried on the developer carrier 12 electrostatically adheres to the latent images L ₁ , L ₂ on _the photosensitive layer 15 to make the latent images visible.
The stronger the electric field near the surface of the photosensitive layer 15, the greater the amount attached to _L2 , and the higher the density of the developed visible image. Therefore, when considering the strength of the electric field generated based on the charge of each latent image L ₁ and L ₂ , first of all, if the electrostatic latent image is the line image shown in Figure 3a, then from this latent image L ₁ Even though some of the emitted electric lines of force are directed toward the conductive support 1, most of them are directed toward the background portion of the photosensitive layer 15 (the portion where the latent image _L1 is not formed) as shown in FIG. 3a. Head towards. This is because although there is a conductive support 1 that acts as a counter electrode to the photoreceptor 13, they are electrically insulated from each other and also from the conductive support 1. A large number of microelectrodes 6
This is because b is located near the photosensitive layer 15. When the microelectrode 6b is present, the number of electric lines of force coming out from the latent image _L1 toward the background increases compared to when the microelectrode 6b is not present. In this way the latent image L ₁
The edge effect is the development in which an electric field is generated between the surface and the background, and the edge effect can be increased by providing the microelectrode 6b. In this way, the strength of _the electric field in the vicinity of the surface of latent image L ₂ shown in FIG. The density of the visible image increases.

On the other hand, the electrostatic latent image L ₂ of the solid image shown in FIG.
In this case, the electric lines of force emanating from the central region excluding the edges of the latent image L ₂ are directed toward the conductive support 1 as the counter electrode. This is because the dielectric thickness from this central region to the support 1 is smaller than the dielectric thickness from the central region of the latent image L ₂ to the background portion of the photosensitive layer 15 . This development occurs in the same way even if the microelectrode 6b is not present. In other words, for a solid image, the strength of the electric field near the surface of the central region of the latent image _L2 is not greatly affected by the presence or absence of the microelectrode 6b.

As mentioned above, by providing the microelectrode 6a, it is possible to particularly increase the development efficiency of line images. It is expressed as shown in Fig. 4. A broken line A in FIG. 4 shows the density relationship of a visible image obtained from a line image, and a solid line B shows a density relationship of a visible image obtained from a solid image. Broken line A
As can be seen by comparing the solid line B and the solid line B, the rising slope of the dashed line A is steeper than that of the solid line B. This is because line images are visualized with higher development efficiency than solid images. It is. A typical operator would like to clearly reproduce the thin line image (line image) of a document even if it is thin, and would like to obtain a high-density copy image. It is normal to want to obtain a copy image with a density that approximately corresponds to the density of the original image, and this requirement can be met by the developer carrier shown in FIGS. 3a and 3b. .

Furthermore, as shown in FIGS. 3a and 3b, the portion of each microelectrode 6b facing the photoreceptor 13 is located parallel to the surface of the photoreceptor 13 due to the above-mentioned grinding. The electric lines of force formed between the electrostatic latent image and the microelectrode can be made almost straight except for the edge region of the latent image, and this allows toner to be applied to the surface of the photoreceptor away from the latent image. It is possible to prevent the adhesion of particles and obtain a sharp visible image without blur.

Next, FIG. 5 shows a developing device 21 having a developer carrier 12, and for understanding the present invention, this will also be briefly explained. In this developing device 21, a one-component developer (toner) 22 with highly resistive magnetic toner particles is used, and its specific volume resistivity is 10 ¹⁰
It is Ω·cm or more, and in the actual experiment, toner with a resistance of 10 ¹⁵ Ω·cm or more was used. Roller-shaped magnets 24 having alternately opposite polarities are installed inside the developer carrier 12, and the magnets 24 are driven to rotate counterclockwise in the developer carrier 12, and the magnets 24 are driven clockwise. Therefore, the toner 22 in the tank 23 is conveyed counterclockwise while being carried by the carrier 12 by magnetic force, and is regulated to be extremely thin by the developer layer thickness regulating member formed by the blade 25. The blade 25 is made of a magnetic elastic plate, and is pressed against the surface of the carrier 12 by the magnetic force of the magnet 24, thereby regulating the layer thickness of the toner 22. When the blade 25 is pressed against the carrier 12 through the toner in this way, this pressing force may cause burrs on the particles constituting the microelectrode 6b.
Since it is relatively large at 1μ or more, the particles do not conduct with each other due to burrs.

The toner with a regulated layer thickness is transferred to a belt-shaped photoreceptor 1.
The toner is transported to a developing area D where the latent image carrier formed as 3 and the developer carrier 12 face each other, and during this transportation, the toner is charged to a predetermined polarity due to friction with the surface of the carrier 12, etc. . On the other hand, the roller 26,
The photoreceptor 13 wrapped around the photoreceptors 27 and 28 is driven in the direction of the arrow, and an electrostatic latent image is formed on its surface by a latent image forming means (not shown). The toner on the carrier 12 that has reached the development area D adheres to the latent image on the photoreceptor 13, as described above with reference to FIG. 3, and makes the latent image visible. The photoreceptor 13 is pressed against the developer carrier 12 through the toner, but according to such a contact development method, the carrier 12
Although a large external force is applied from the photoreceptor 13 to the surface of the microelectrode 6b on the carrier 12, the microelectrode 6b on the carrier 12
Since it is firmly fixed to the holder, it can be prevented from falling off.

The visible image formed on the photoreceptor is transferred to a transfer paper by a transfer device (not shown), and then transferred to the photoreceptor 13.
The toner that has passed through the development area D without adhering to the toner is returned to the tank 23 again.

In FIG. 6, the photoreceptor 13 is formed in the shape of a drum that rotates in the direction of the arrow, and the developer layer thickness regulating member is formed as a doctor blade 125 made of a rigid body, and the layer thickness is controlled by the doctor blade 125. The toner is smoothed to a uniform thickness by the magnetic leveling plate 225, and
The returned toner is scraped off by a scraping plate 29. Other configurations are 5th
The configuration is substantially the same as that shown in the figure.

The gap _g1 between the photoreceptor 13 and the developer carrier 12 is relatively large, about 100μ, and the thickness d of the toner layer on the carrier 12 is about 20 to 30μ, and in this state, so-called non-contact development is performed. will be held.

Although the advantageous embodiments of the present invention have been described above, the following various modifications are possible.

Although it is possible to form minute recesses approximately 1/2 to 3 times the diameter of the toner particles on the surface of the developer carrier to maintain a constant amount of developer conveyance, it is difficult to manufacture such a developer carrier. For example, after grinding the second adhesive layer to expose at least a portion of the conductive particles as previously described in Examples 1 to 3, the surface may be sandblasted or Fine recesses may be formed on the surface by etching. After grinding the surface of the second adhesive layer, the conductive particles are etched using a predetermined etching solution, and a part of the upper part of the conductive particles is removed as shown in FIG.
It is also possible to form a structure in which the microelectrode 6b is located at the bottom of the recess 30.

As the conductive particles constituting the microelectrode, in addition to aluminum and iron, suitable magnetic and non-magnetic conductive materials such as metals such as copper, bronze, nickel, ferrite, and stainless steel can be used.
The shape thereof can also be made into an appropriate shape such as a sphere, a rectangular parallelepiped, or a cube.

Further, an elastic material can also be used as the dielectric layer shown in Examples 1 to 3.

The developer carrier according to the present invention is shown in FIGS.
It is obvious that the present invention can be applied to various developing devices other than the one illustrated in the figure, and the developer carrier can also be formed into a sheet or belt shape.

[Brief explanation of drawings]

FIGS. 1a to 1e are explanatory diagrams showing the steps of the method for manufacturing a developer carrier according to the present invention, and FIGS. 2a to g
3A and 3B are longitudinal cross-sectional views and front views schematically showing the form of the developer carrier in the order of manufacturing steps, and FIGS. 3A and 3B are
An explanatory diagram showing an example of the function of a developer carrier, FIG. 4 is a graph showing an example of the relationship between the density of an original image and the density of a visible image, and FIGS. Cross-sectional view of a developing device having a agent carrier, No. 7
The figure is a sectional view illustrating a method of forming recesses on the surface of the developer carrier. 1... Conductive support, 6b... Microelectrode, 12
...Developer carrier, 21...Developing device, 22...
developer.

Claims (1)

[Scope of Claims] 1. A developing device that visualizes an electrostatic latent image formed on a latent image carrier using a one-component developer carried on a developer carrier, comprising the steps of: the body has an electrically conductive support and a number of electrically conductive particles as microelectrodes that are substantially electrically insulated from the support and from each other; The particles have a specific volume resistivity of 10 ¹² Ω・cm or more and a thickness of
The developer carrier is coated with a resin having a thickness of 0.5 μ to 0.5 mm in advance, and the surface of the developer carrier is ground, and at least a portion of the conductive particles are exposed on the surface of the developer carrier. Developing device. 2. The developing device according to claim 1, wherein the resin has a thickness of 0.5 μ to 0.1 mm.