JPH0450878A - Developer carrier - Google Patents

Abstract

PURPOSE:To prevent filming occurring and to stably secure the attached quantity of toner and the electrostatic charged quantity of the toner for a long time by constituting a part having the holding function of electric charge of a material having more elasticity than a material constituting the other part on the surface of a developer carrier. CONSTITUTION:The part which has the holding function of the electric charge and a part which does not have the function coexist on the surface of the developer carrier 20 with a fine area. Besides, the part which has the function is constituted of the material having more elasticity than the material constituting the part which does not have the function. That means, many fine closed electric fields are formed near the surface of the carrier 20 by selectively holding the electric charge on the surface of the carrier 20. Then, developer 60 is carried on the surface of the carrier 20 by the fine closed electric fields and an electrostatic latent image is made a visible image by the carried developer. Thus, the filming of the toner is prevented from occurring and the attached quantity and the electrostatic charged quantity of the toner are stably obtained for a long time.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention supplies a non-magnetic one-component developer to which an adjuvant is externally added as necessary to a rotationally driven developer carrier. The developer is carried on the surface of a developer carrier, and the electrostatic latent image formed on the latent image carrier is transferred to a development area where the latent image carrier and the developer carrier face each other. The present invention relates to a developer carrier used in an image forming method in which an image is visualized by the developer carried on the developer carrier.

[Conventional technology]

Image forming devices such as electronic copying machines, printers, and facsimile machines that form an electrostatic latent image on a latent image carrier and visualize it with a developer to obtain a recorded image use a dry type that uses a powdered developer. This developing device is widely used.

As such powder-like developers, two-component developers containing toner and carrier and one-component developers that do not contain carrier are known, and two-component developers using the former two-component developer are known. Although this method allows relatively stable and good recorded images to be obtained, carrier deterioration and toner-to-carrier mixing ratio fluctuations are likely to occur, the maintenance and management of the device is complicated, and the overall structure of the device tends to increase in size. It has its drawbacks.

From this point of view, a one-component development system using a one-component developer that does not have the above-mentioned drawbacks is attracting attention. - Component type developers include those consisting only of toner and those consisting of a mixture of toner and an auxiliary agent, to which an auxiliary agent is externally added as required. Furthermore, toners include magnetic toners in which magnetic powder is kneaded into each toner particle itself, and non-magnetic toners that do not contain magnetic material.

Here, since magnetic materials are generally opaque, when a full-color or multi-color image is formed using magnetic toner, the developed visible image becomes unclear, making it impossible to obtain a vivid color image. Therefore, especially for color development, it is desirable to adopt a one-component development method using non-magnetic toner.

By the way, in a developing device that employs a -component development method, a -component developer is carried on a developer carrier and transported, and in a development area where the developer carrier and the latent image carrier face each other, The electrostatic latent image formed on the latent image carrier is made into a visible image using a developer, but in order to form a high-quality visible image with a predetermined density, a large amount of sufficiently charged toner must be applied to the development area. It is necessary to convey the latent image and visualize the latent image using the toner.

When magnetic toner is used, the one-component developer can be carried on the developer carrier by using the magnetic force of a magnet installed inside the developer carrier, so the above requirements can be met relatively easily. Is possible.

However, when a non-magnetic one-component developer is used, it is difficult to satisfy the above requirements because it cannot be supported on a developer carrier by magnetic force. Various countermeasures against this problem have been proposed in the past. For example, in Japanese Patent Laid-Open No. 61-42672, a layer of dielectric material (insulator) is laminated on the surface of the developer carrier (developing roller). A developer supply member made of, for example, a sponge roller is brought into pressure contact with the dielectric material, and the two are frictionally charged to opposite polarities, and non-magnetic toner charged to the opposite polarity to the dielectric material is electrostatically attached to the dielectric material. A method of transporting such a -component developer to a development area has been proposed. However, even with this method, it is not possible to sufficiently increase the strength of the electric field formed near the dielectric surface, so it is difficult to carry a large amount of toner on the surface of the developing roller. Due to the insufficient amount of agent, it is difficult to form a high-density visible image.

Furthermore, a configuration is also known in which an electric field is applied between the developing roller and the developer supply member in a direction in which the non-magnetic toner electrostatically moves toward the developing roller, but even if such a configuration is added, It is difficult to make a sufficient amount of toner adhere to the developing roller.

In addition, as a toner supply member, 102 to 106 Ω・c
m conductive foam (Japanese Unexamined Patent Publication No. 60-229057)
, elastic body with skin layer (Japanese Unexamined Patent Publication No. 60-229060) and fur brush (Japanese Unexamined Patent Publication No. 61-42672)
It has been proposed to use a metal body with an uneven surface (Japanese Patent Laid-Open No. 60-53
No. 976), integrated insulation coated roller (Japanese Patent Application Laid-Open No. 55-4
No. 6768) Medium and low antibody coated roller (Japanese Patent Application Laid-open No. 58-1
3278) and an electrode roller having an insulator and a conductive surface (Japanese Unexamined Patent Publication No. 53-36245).

Furthermore, in a developing device using a non-magnetic component developer,
In Japanese Patent Application Laid-Open No. 60-229057, a sponge roller,
JP-A No. 62-229060 uses an elastic roller, and JP-A No. 61-52663 uses a fur brush or the like to apply an electric charge to the toner through frictional charging between the toner and a replenishing member, and furthermore, by contact with a developing roller. Friction causes the toner to electrostatically adhere to the developing roller, and a layer thickness regulating member such as a blade is used to control the toner layer to develop the latent image on the photoreceptor. Various materials are used for the developing roller, such as insulating materials, medium resistance materials, and laminated materials.

According to the methods shown in these references, toner adhesion to the developing roller is achieved by frictional electrification between the toner replenishing member and the developing roller, but sufficient electrification cannot be achieved due to friction between the toner-attached member. This results in insufficient toner adhesion. The optimum adhesion amount and charge amount in the non-magnetic component development method will be explained as follows.

For black and white, emphasis is placed on the amount of charge, which is -10~ for boat fishing.
It is 20μC/g. If the value is smaller than this value, the image quality will be poor in terms of background stains, sharpness, etc.

Regarding the amount of adhesion, the amount of adhesion on the developing roller is 0.
1 to 0.3 ng/cm", but 0.4 ng/cm" on the transfer paper
-0.5 mg/am" is required, and the amount of toner adhesion is covered by increasing the speed of the developing roller to 3 to 4 times the speed of the photoconductor. This rotation has a problem in that it causes a phenomenon of ``toner from the trailing edge'', that is, when a solid area is developed, the density of the trailing edge of the image becomes higher.

To prevent this phenomenon, the speed of the developing roller should be made close to the speed of the photoreceptor. In other words, it is necessary to increase the amount of toner deposited on the developing roller and reduce the number of rotations.

On the other hand, with color toner, the degree of coloring is smaller than that of black toner, and if you try to improve the "from the trailing edge of the toner", the color characteristic will be 0.8 to 1.2 m, which is even more than that of black toner.
An amount of adhesion on the developing roller of g/cm2 is required.

Regarding the amount of charge, in order to obtain a stable image, the amount of charge should be 5 to 20 μC/g (preferably 10 to 15 μC/g).
) is desired.

As a method to solve these problems, the present inventors
First, "to the developer carrier that is active in rotation.

A one-component developer consisting of a non-magnetic toner to which an auxiliary agent is externally added as necessary is supplied, the developer is carried on the surface of the carrier, and the developer is conveyed to the latent image carrier and the developer carrier. In the developing method, an electrostatic latent image formed on the latent image carrier is visualized by the developer carried on the developer carrier in a development area where the developer carrier is opposite to each other. By selectively retaining charges on the surface, a large number of minute closed electric fields are formed near the surface of the carrier, and the charged toner is attracted by the closed electric field, and the developer is attached to the surface of the developer carrier and carried. and proposed an image-forming method in which an electrostatic latent image is visualized using the developer carried thereon.

In this method, many small closed electric fields (microfields) are formed near the surface of the developer carrier, so the electric field strength can be significantly increased compared to the conventional method, and a large amount of sufficiently charged non-magnetic This has many advantages, such as being able to carry toner on a developer carrier and transport it to a developing area.

[Problem to be solved by the invention]

However, in the image forming method in which a large number of microfields are formed near the surface of the developer carrier as described above, in order to form a uniform thin layer, it is necessary to bring the toner layer thickness regulating member into contact with the developer carrier. However, due to the sliding force with this toner layer thickness regulating member, the toner films on the developer carrier, affecting the aforementioned micro field, making it difficult to ensure a uniform and stable toner adhesion amount and charge amount. making it difficult.

Therefore, an object of the present invention is to provide a developer carrier that can prevent filming from occurring and stably ensure a sufficient amount of toner adhesion and toner charge over a long period of time in the above-described image forming method. be.

[Means to solve the problem]

As a result of extensive studies, the present inventors found that a developer carrier in which a portion having a charge retention function on the surface of the developer carrier is made of a material having more elasticity than other portions is suitable for the above purpose. Based on this knowledge, we have completed the present invention.

That is, according to the present invention, on the surface of the developer carrier,
By selectively retaining electric charge, a large number of minute closed electric fields are formed near the surface of the developer carrier, and a non-magnetic film made of toner to which an auxiliary agent is externally added as necessary is placed on the developer carrier. A developer carrier used in an image forming method in which a component-based developer is supplied, the developer is carried on the surface of the developer carrier by the minute closed electric field, and an electrostatic latent image is visualized by the carried developer. , the surface of which has a mixture of portions that have a charge retention function and portions that do not have this function in a minute area, and in addition, the portion that has this function has more elasticity than the portion that does not have this function. A developer carrier is provided, characterized in that it is made of a material.

In the image forming method using the developer carrier of the present invention, since a large number of minute closed electric fields are formed near the surface of the developer carrier, the electric field strength can be significantly increased compared to the conventional method. On the surface of the agent carrier, a portion having a charge retention function (e.g. dielectric portion) is made of a material having more elasticity than a portion not having this function (e.g. conductor portion), thereby reducing toner filming. The occurrence of such toner particles is sufficiently prevented, and a sufficient amount of toner adhesion and toner charge can be ensured stably over a long period of time.

This image forming method will be explained below.

FIG. 1 shows an outline of a typical developing device useful for carrying out this image forming method, centering on the developer carrier section. In FIG. 1, toner 6 contained in a toner tank 70 is shown.
0 is a toner supply member (sponge roller, fur brush, etc.) 4 by a stirring blade (toner supply auxiliary member) 50.
0, the toner 60 is forcibly brought to the toner supply member 4
0. On the other hand, the developer carrier (developing roller) 20 of the present invention, which has completed the development, rotates in the direction of the arrow (for example, 40 rpm) and reaches the contact portion with the toner supply member 40 . The toner supply member 40 rotates in the opposite direction to the developer carrier 20 (for example, at 300 rpm) L, the developer carrier 2
0 and the toner 60 are charged, and the toner 60 is deposited on the developer carrier 20.

Further, the developer carrier 20 rotates, and the toner adhering to the developer carrier 20 is removed by the toner layer thickness regulating member (elastic blade) 3.
0, the charging is stabilized while the thickness is controlled, and the developing area 80 is reached. In the development area 80, the latent image is developed by contact or non-contact development. Here, if necessary, direct current may be applied to the developer carrier 20 and the toner supply member 40.
The optimal image can be controlled by applying bias such as alternating current, direct current superimposed alternating current, and pulses.

Next, the mechanism of toner adhesion to this type (electrode type) developer carrier 20 will be explained.

As an example of the developer carrier 20, as shown in FIG. 2, the developer carrier 20 is configured such that a dielectric portion and a conductive portion coexist in a small area on its surface. Assuming that the area is circular, minute areas with diameters of 10 to 500 μs are distributed randomly or according to a certain rule. As for the area ratio, the area of the conductor part is 20
A range of 60% is preferred.

Toner adhesion is as follows. First, the developer carrier 20 that has completed development rotates in the direction of the arrow and comes into contact with the toner supply member 40 . The remaining toner in the non-image area that has not been developed is mechanically and electrically scraped off by the toner supply member 40, and the dielectric portion is charged by friction. At this time, the charges on the developer carrier 20 and toner due to the previous development are as follows:
It is stabilized and initialized by friction. Next, the toner carried by the supply member 40 is charged by friction and electrostatically adheres to the dielectric portion of the developer carrier 20 . At this time, the polarity of the toner is opposite to the charge on the photoreceptor, and the dielectric portion of the developer carrier 20 is of the same polarity.

At this time, the electric field on the developer carrier 20 becomes a microfield (closed electric field) as shown in FIG. 2, and becomes an electric field with a large electric field gradient, making it possible to adhere the toner in multiple layers. Further, since the adhered toner is in a closed electric field, it is strongly attracted to the developer carrier 20 side and becomes difficult to separate.

The thickness of this toner layer is further controlled by a toner layer thickness regulating member 30, and the toner layer reaches the development area 80.

The developer carrier 20 and the electrostatic latent image carrier (
The electric field between the photoconductors 10 has a large electrode effect, and the toner on the developer carrier 20 easily adheres to the electrostatic latent image carrier 10, thereby performing development.

In the above development process, the thin toner layer is controlled and made uniform by the toner layer thickness regulating member 30;
At this time, a large sliding force is applied to the toner in the narrow gap between the developer carrier 20 and the toner layer thickness regulating member 30. On the other hand, the toner adheres to the dielectric portion constituting the surface of the developer carrier. Therefore, the toner subjected to a large sliding force with the toner layer thickness regulating member 30 causes filming on the dielectric portion of the developer carrier 20 .

When the toner films on the dielectric portion, the frictional charging property with the toner decreases, and the amount of toner charge decreases. At the same time, since the charging potential of the dielectric portion on the surface of the developer carrier also decreases, the electric field strength of the microfield also weakens, making it impossible to obtain a sufficient amount of toner adhesion.

However, the developer carrier of the present invention is characterized in that the dielectric portion constituting the surface thereof is made of a material having more elasticity than the conductive portion, and since such a structure is adopted, the present invention According to the developer carrier, the occurrence of filming is sufficiently prevented, and a stable toner adhesion amount and toner charge amount can be obtained over a long period of time.

Specifically, in the developer carrier having such a configuration, as shown in FIG.
Due to the pressure contact force of the regulating member 30 when sliding against the
The surface of the dielectric portion of the developer carrier 20 is depressed. Therefore, the force applied to the toner is relaxed and filming does not occur. In addition, since wear is alleviated, it is possible to use materials with slightly poor wear resistance, expanding the range of material selection.

Here, the dielectric portion quickly restores its original state after passing through the toner layer thickness regulating member, and the surface of the developer carrier becomes smooth again. If the dielectric surface remains depressed, image dropouts, image unevenness, etc. will occur.

Next, the constituent materials of the developer carrier of the present invention will be explained. Materials used as the dielectric constituting the developer carrier of the present invention include alkyd resin, chlorinated polyether, chlorinated polyethylene, epoxy resin, fluororesin, phenol resin, polyamide, polycarbonate, polyethylene, methacrylic resin, polypropylene, Resins such as polystyrene, polyurethane, polyvinyl chloride, polyvinylidene chloride, silicone resin, butadiene rubber, styrene butadiene rubber, ethylene propylene rubber, chloroprene rubber, chlorinated polyethylene, epichlorohydrin rubber, nitrile rubber, acrylic rubber, silicone rubber,
Rubbers such as fluororubber may be used, but silicone resins and fluororesins are preferably used from the viewpoint of heat resistance and moisture resistance.

On the other hand, as conductor materials, conventionally known AQ, 5LI
In addition to metals such as S, Fe, and Ni and ceramics, conductive particles such as carbon and metal particles are added to the resins and rubbers exemplified as the dielectric materials,
A conductive material can be used.

In the present invention, both of the above materials are selected so that the dielectric material has more elasticity than the conductive material.

These materials are layer-molded on rollers by selecting an appropriate method from among spray coating, dipping coating, injection molding, extrusion molding, press molding, and the like.

Next, a method for manufacturing the developer carrier of the present invention will be explained. As a representative example of the method for manufacturing a developer carrier, the case of the V-groove roller shown in FIG. 2 will be explained as follows.

(i) First, a metal roller whose surface is machined with V grooves is manufactured. The method for machining the lattice-shaped grooves is a method such as fleur-de-lis knurling. (2) The grooves have a pitch of 0.1 to 0.5 mm and are formed at an angle of about 45 degrees with respect to the longitudinal direction of the roller. [See FIG. 4(a)] (n) Next, (1) a dielectric material is coated on the grooved metal surface by a method such as spraying or dipping, and is cured and dried under predetermined conditions.

(The coating thickness should be such that the V-groove is completely filled.) [See Figure 4 (b)] (ni) Next, the surface of the roller is cut or polished so that the conductive surface and dielectric surface are mixed in a small area. The area of the conductive part is reduced to 20 to 60%.

[See FIG. 4(C)] After kneading the conductive material, the mixed material is injection molded or extruded onto the surface of a metal roller.

Layer molding is performed by a normal molding method such as press molding, spray coating, dipping, etc., and then the above (i) to
It is also possible to adopt the method of performing the process (■).

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples. Note that parts represent parts by weight.

Example 1 A developer carrier (developing roller) was produced in the following manner.

(i) With fleur-de-lis knurling on the metal roller surface,
■Grooves were provided. The V-grooves had a pitch of 0.2@m and were machined at approximately 45 degrees with respect to the longitudinal direction of the roller.

(if) A dielectric forming component having the following formulation was spray coated on the V-grooved roller surface, and cured and dried at 150° C. for 1 hour. The coating thickness was such that the grooves were completely filled.

Methyl vinyl polysiloxane 100 parts Quartz 20 parts Toluene 500 parts (■)
The surface of the roller was polished so that a conductive surface and a dielectric surface coexisted in a small area, so that the area of the conductive part was 50%.

Example 2 A developing roller was produced in the following manner.

(i) Conductive primer (product name DY39-011;
A conductor-forming component having the following formulation was applied onto the core bar coated with Toray Silicone Co., Ltd.), followed by subsequent vulcanization at 170°C.
10 minutes, 120kgf/cm”, secondary vulcanization: 200℃7
Press molding was carried out under conditions of 4 hours. The hardness of this conductive rubber was 28 degrees (JIS A).

Yi! Growth is shameful - one minute The above mixture was kneaded using two rolls.

(ii) Grooves were provided on the press-molded surface by fleur-de-lis knurling.

(iii) Next, dielectric forming components having the following formulation were wound around a grooved roller and vulcanized and molded by steam vulcanization. The hardness of this dielectric elastic body is 20 degrees (JIS
A).

11'' 9 Shiryaku Methylvinylpolysiloxane 100 parts quartz
20 parts of the above mixture
Kneaded with this roll.

(iv) The surface of the roller was polished so that a conductive surface and a dielectric surface coexisted in a small area, so that the conductive part area was 50%.

Comparative Example A developing roller was produced in the same manner as in Example 2, except that the following formulation was used as the dielectric forming component. The hardness of this dielectric part is 50 degrees (JI
SA).

Coronate EH (50% xylene solution) 20 parts toluene 200 parts xylene
200 copies [Evaluation] Each of the above developing rollers was evaluated as follows.

Toner filming Attach each developing roller to the developing device shown in Figure 1.
The state of toner adhesion on the surface of the developing roller after 10,000 copies was evaluated according to the following criteria. The results are shown in Table 1.

Rank A: Toner on the roller surface can be easily wiped off with a cloth.

Rank B: A slight amount of toner remains after wiping.

Rank C: The toner cannot be completely wiped off and a thin film of toner remains.

Rank D: Melted toner is strongly adhered to the roller surface.

In the above developing device, the toner thinning blade is made of urethane rubber, the toner supply roller is made of conductive urethane sponge, and the toner is positively charged toner.
Loaded.

Amount of Toner/Amount of Charge Each developing roller was attached to the developing device shown in FIG. 1, and the amount of toner adhering to the roller and the amount of toner charge after the initial 10 rotations of the developing roller were measured. In addition, the amount of toner adhesion on the developing roller and the amount of toner charge after copying 10,000 sheets were measured. The results are shown in Table 1.

From the results shown in Table 1, it can be seen that by using the developing roller of the present invention, toner filming on the surface of the developing roller can be prevented, and a stable toner adhesion amount and toner charge amount can be obtained over a long period of time.

[Effects of the Invention] The developer carrier of the present invention has a portion having a charge retention function and a portion not having the charge retention function coexisting in a small area on its surface, and the portion having the function has the same function. Since the structure is made of a material that is more elastic than the non-containing parts, by selectively retaining electric charge on the surface of the developer carrier, a large number of minute particles are generated near the surface of the developer carrier. A closed electric field is formed, a non-magnetic one-component developer made of toner with external addition of an auxiliary agent as required is supplied onto this developer carrier, and the developer is supported by the minute closed electric field. When the developer carrier of the present invention is used in an image forming method in which an electrostatic latent image is visualized by the developer carried on the body surface, toner filming can be prevented and the toner is stable for a long time. The amount of toner adhesion and the amount of toner charge can be obtained. As a result, high-density, high-quality images can be stably obtained over a long period of time.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view centered on a developer carrier portion showing an example of a developing device in which a microfield electric field is formed on a developer carrier useful for carrying out the present invention. Also,
FIG. 2 is a schematic cross-sectional view for explaining a state in which a closed field is generated by a microfield on a developer carrier in the apparatus shown in FIG. Further, FIG. 3 is a schematic cross-sectional view for explaining the behavior of toner when the surface of the developer carrier of the present invention rubs against the toner layer thickness regulating member. Also, Figures 4(a) to (c)
FIG. 2 is a schematic cross-sectional view showing the surface state during the manufacturing process of the developer carrier of the present invention. 10... Electrostatic latent image carrier, 20... Developer carrier,
30... Toner layer thickness regulating member, 4o... Toner supply member, 50... Stirring blade, 60... Toner, 7o...
...Toner tank, 80...Development area. Figure 1

Claims (1)

[Claims] (1) By selectively retaining electric charges on the surface of the developer carrier, a large number of minute closed electric fields are formed near the surface of the developer carrier, and as needed, A non-magnetic one-component developer made of toner externally added with an adjuvant is supplied, the developer is supported on the surface of the developer carrier by the minute closed electric field, and the electrostatic latent image is made visible by the supported developer. A developer carrier used in an image forming method, in which a portion having a charge retention function and a portion not having this function coexist on its surface in a minute area, and furthermore, the portion having the function is A developer carrier characterized in that it is made of a material that has more elasticity than a portion that does not have this function.