JPH0427983A - Developer carrying member - Google Patents

Abstract

PURPOSE:To assure the sufficient electrostatic charge quantity of toners stably over a long period of time by making conductor parts and dielectric parts in microareas on the surface of the developer carrying member to constitute this member and specifying the coefft. of friction of the dielectrics. CONSTITUTION:This developer carrying member is so constituted that the conductor parts and the dielectric parts coexist in the microareas on the surface thereof. The coefft. of friction of the surface of the dielectric parts is specified within a 0.05 to 0.3 range. The friction with the toners is not sufficiently executed and the electrostatic charge quantity decreases if the coefft. of friction of the dielectrics is below 0.05. The toners are adsorbed on the dielectrics and generate filming during the long-term use and the electrostatic charge quantity changes with lapse of time if the coefft. of friction exceeds 0.3. The sufficient electrostatic charge quantity is imparted to the toners over a long period of time in this way and the high-quality images having the high density are stably obtd. over a long period of time.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention supplies a non-magnetic one-component developer to which an auxiliary agent has been externally added as necessary to a developer carrier that is driven once. 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]

An electronic copying machine that forms an electrostatic latent image on a latent image carrier and visualizes this using a developer to obtain a recorded image.

2. Description of the Related Art In image forming apparatuses such as printers and facsimiles, dry-type developing devices that use powdered developer are 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 -component developer, which 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, if a color image including full color or multicolor is formed using magnetic toner, the developed visible image will be unclear and a vivid color image cannot be obtained. Particularly 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 have been proposed in the past. For example, Japanese Patent Application Laid-Open No. 61-42672 discloses that a dielectric (insulator) layer is laminated on the surface of a developer carrier (developing roller), and in contrast, for example, a developing device consisting of a sponge roller is used. The agent supplying member is brought into pressure contact with the other to triboelectrically charge them to opposite polarities, and a non-magnetic l-ner charged to the opposite polarity to the dielectric is electrostatically attached to the dielectric to produce the -component developer. A method has been proposed in which the image is transported to a developing area. 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.

Note that the toner supply member has a resistance of 102 to 10 r''Ω・
Use C■ conductive foam (Japanese Patent Application Laid-open No. 60-229057), elastic body with skin layer (Japanese Patent Application Laid-Open No. 60-229060), fur brush (Japanese Patent Application Laid-open No. 61-42672), etc. It has been proposed that the developing roller be made of a metal body with an uneven surface (Japanese Patent Laid-Open No. 60-5
No. 3976), integrated insulation coated roller (Japanese Unexamined Patent Application Publication No. 1987-
46768) Medium and low antibody coated roller (Japanese Patent Application Laid-open No. 1983-
13278) 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 are explained as follows.

For black and white, emphasis is placed on the amount of charge, which is generally 10~
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.
1-0.3mg/am2, but 0.4mg/am2 on the transfer paper
-0.510 g/cm" 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 photoreceptor. There is a problem with the rotation of , that is, the phenomenon of "toner from the rear edge" occurs, that is, when developing a solid area, the density at the rear edge of the 9th image becomes higher.To prevent this phenomenon, The speed of the developing roller must be brought close to the speed of the photoreceptor. In other words, the amount of toner deposited on the developing roller must be increased and the number of rotations must be decreased.

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 degree of coloring is even higher than that of black toner, which is 0.8 to 1, 2.
The adhesion amount on the developing roller is required to be 5-20 μC/g (preferably 10-15 μC/g) in order to obtain a stable image.
) is desired.

As a method to solve these problems, the present inventors
First, ``To the developer carrier that is rotationally driven.

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, even in the image forming method in which a large number of microfields are formed near the surface of the developer carrier as described above, it is difficult to carry a sufficient and stable amount of toner by the microfields. Although the toner can be supported on the body, the amount of charge on the toner largely depends on the properties of the dielectric material, especially the surface properties.Due to these properties, charging of the toner may be insufficient, and filming may result in a stable charge over a long period of time. There was a problem that it was difficult to secure the quantity.

Therefore, an object of the present invention is to provide a developer carrier capable of stably securing a sufficient amount of toner charge over a long period of time in the above-described image forming method.

[Means to solve the problem]

As a result of extensive studies, the present inventors found that a developer carrier in which the friction coefficient of the dielectric material constituting the surface of the developer carrier is within the range of 0.05 to 0.3 is suitable for the above purpose. However, the present invention was completed.

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. A developer characterized in that a conductive part and a dielectric part are mixed in a small area on the surface thereof, and the friction coefficient of the dielectric is within the range of 0.05 to 0.3. A carrier is provided.

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. By setting the friction coefficient of the dielectric material constituting the surface of the agent carrier within the range of 0.05 to 0.3, a sufficient amount of triboelectric charge can be imparted to the toner, and as a result, the toner can be stably charged for a long period of time. A large amount of sufficiently charged non-magnetic toner can be carried on the developer carrier and transported to the development area.

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.
Forced to 0.

Toner 60 is supplied to toner supply member 40 . On the other hand, the developer carrier (GL image roller) 2 of the present invention has completed development.
0 is rotation in the direction of the arrow (for example, 400 rpm) L/
, and reaches a 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, 30
0 rpm) L, the developer carrier 20 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.

The size of the area is assuming that the shape is circular.

Minute areas with diameters of lθ to 5001 Js are distributed randomly or according to a certain rule. As for the area ratio, it is preferable that the area of the conductor portion is in the range of 20 to 50%.

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:
First, the toner carried by the supply member 4o, which is stabilized and initialized by friction, 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 of the photoreceptor, and the dielectric portion of the developer carrier 2o is of the same polarity.

At this time, the electric field on the developer carrier 2o becomes a micro field (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 toner layer thickness is further controlled by a toner layer thickness regulating member 3o, and the toner layer reaches the IR image area 8o.

The developer carrier 2o and the electrostatic latent image carrier (
The electric field between the photoreceptors 10 has a large electrode effect, and the toner on the developer carrier 2o easily adheres to the electrostatic latent image carrier 1o, thereby performing development.

As described above, the toner carried by the supply member 4o is triboelectrically charged with the dielectric material and is electrically attached to the dielectric material portion. By setting the value in the range of 0.05 to 0.3, it becomes possible to impart a sufficient amount of friction bands to the toner.

If the friction coefficient of the dielectric is less than 0.05, sufficient friction with the toner will not occur, and the amount of charge will be small. On the other hand, if it exceeds 0.3, the toner will be adsorbed onto the dielectric material, causing filming during long-term use, and the amount of charge will change over time. The friction coefficient of the dielectric part surface is 0.05
Only within the range of ~0.3 can a sufficient amount of charge be obtained and be stable over a long period of time.

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, polystyrene,
polyurethane, polyvinyl chloride, polyvinylidene chloride,
Examples include resins such as silicone resin, and rubbers such as butadiene rubber, styrene-butadiene rubber, ethylene propylene rubber, chloroprene rubber, chlorinated polyethylene, epichlorohydrin rubber, nitrile rubber, acrylic rubber, silicone rubber, and fluorine rubber, but they are heat resistant. From the viewpoint of moisture resistance, it is preferable to use silicone resins and fluororesins.

In the present invention, among these, the friction coefficient is 0.0.
Select one within the range of 5 to 0.3. It is also possible to mix a filler such as a solid lubricant and adjust the coefficient of friction to a desired value.

On the other hand, as conductor materials, conventionally known AQ, SUS
In addition to metals such as , Fe, and Ni, and ceramics, materials made by adding conductive particles such as carbon and metal particles to the resins and rubbers mentioned above as dielectric materials to make them conductive are used. be able to.

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.

In order to produce the developer carrier of the present invention, for example, (i)
First, a metal roller with a V-groove processing such as a fleur-de-lis knurling process is made on the surface. In this case, v'a is 0.1.
Processed at a pitch of ~0.5 mm and at an angle of approximately 45° with respect to the longitudinal direction of the roller) [see Figure 3 (a)], (
iii. Next, the V-grooved metal surface is coated with a dielectric material by a method such as spraying or dipping, cured and dried under predetermined conditions, and the coating thickness is such that the V-groove is completely filled) [Reference: Figure 3(b)], (i
ii) Next, the surface of the roller is cut or polished so that the conductive surface and the dielectric surface are mixed in a small area, and the conductive part area is 20 to 60 mm [see; Fig. 3 (
C)] method is adopted.

〔Example〕

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

Example 1 200 parts of fluororesin
Product name: Lumiflon LF200 (manufactured by Asahi Glass Co., Ltd.) Coronate EH 20 parts Toluene 100 parts Xylene 100 parts No. 4
The coefficient of friction of the dielectric material sheet was measured to be 0.23 in accordance with JIS K7125 using the apparatus shown in the figure.

Using the materials of the above formulation, the developer carrier (
A developing roller) was manufactured.

(i) A V-groove was provided on the surface of the metal roller by machining the fleur-de-lis 1. The V-grooves had a pitch of 0.2 mm and were machined at approximately 45 degrees with respect to the longitudinal direction of the roller.

(ii) The V-grooved roller surface was coated with the above dielectric material, and cured and dried at 100° C. for 71 hours. The coating thickness was such that the grooves were completely filled.

(iii) 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%.

Example 2 A developing roller was produced in the same manner as in Example 1, except that a dielectric material having the following formulation was used.

Agent A 50 parts Solvent ^
consists of the following formulation.

melt In addition.

and U toluene ethyl acetate butyl ethyl acetate cellosolve acetate methyl isobutyl ketone xylene cyclohexane 39.0 parts 17.5 parts 17.5 parts 17.5 parts 3.9 parts 2.6 parts 2 The friction coefficient of .0 parts was measured in the same manner as in Example 1 and found to be 0.25.

Comparative Example A developing roller was produced in the same manner as in Example 2, except that the solid lubricant in the dielectric material was not used. The friction coefficient of the dielectric material in this case was determined in Example 1.
When measured in the same manner as above, it was 0.40.

〔evaluation〕

Each of the above developing rollers was evaluated as follows.

Attach the toner flushing developing roller to the developing device shown in FIG.
Check the state of toner on the surface of the developing roller after running idly for a while.
Evaluation was made 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=Toner in a molten state 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.

Toner Adhesion Amount/Charge Amount Each developing roller was attached to the developing device shown in FIG. 1, and the toner adhesion amount and toner charge amount on the roller were measured after the developing roller rotated 10 times. 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 can be prevented and a sufficient amount of toner charge can be obtained.

〔Effect of the invention〕

The developer carrier of the present invention has a conductor portion and a dielectric portion mixed on the surface thereof in a small area, and the friction coefficient of the dielectric material is 0.
．． 05 to 0.3, a large number of minute closed electric fields are formed near the surface of the developer carrier by selectively holding charges on the surface of the developer carrier, A non-magnetic one-component developer made of toner to which an adjuvant is externally added as necessary is supplied onto this developer carrier,
When the developer carrier of the present invention is used in an image forming method in which the developer is supported on the surface of the developer carrier by the minute closed electric field and an electrostatic latent image is visualized by the carried developer,
A sufficient amount of charge can be applied to the toner for a long period of time without toner filming. Therefore, a large amount of sufficiently charged non-magnetic one-component developer is supported on the developer carrier and transported to the development area. I can do it. As a result, high-density, high-quality images can be stably obtained over a long period of time.

[Brief explanation of the drawing]

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, FIGS. 3(a) to 3(c) are schematic cross-sectional views showing the surface state during the manufacturing process of the developer carrier of the present invention. Further, FIG. 4 is an explanatory diagram of an apparatus used to measure the coefficient of friction of a dielectric material forming the surface of a developer carrier in Examples and Comparative Examples. 10... Electrostatic latent image carrier, 20... Developer carrier,
30... Toner layer thickness regulating member, 40... Toner supply member, 50... Stirring blade, 60... Toner, 70...
...Toner tank, 80...Development area.

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 conductive part and a dielectric part are mixed in a small area on the surface thereof, and the friction coefficient of the dielectric is 0.05 to 0.3. A developer carrier characterized by being within the range of.