JPH0445466A - Developer carrier - Google Patents

Abstract

PURPOSE:To obtain a stable image without having irregularities over a long period by forming a large number of fine closed electric fields in the vicinity of the surface of this developer carrier, and using materials having the almost abrasion property for a conductor and a dielectric constituting the surface of the developer carrier. CONSTITUTION:This developer carrier 20 finished to carry out development is rotated in the direction of the arrow, and reaches a part which comes into contact with a toner supplying member 40. The toner supplying part 40 is rotated in the direction reverse to the carrier 20, and imparts electrification to the carrier 20 and toner 60, to stick the toner 60 on the carrier 20. Further, the carrier 20 is rotated, and the stuck toner on the carrier 20 reaches a developing region 80 while its thickness is controlled by a toner layer thickness regulating member 30. In an electric field between the carrier 20 and an electrostatic latent image carrier 10 on the developing region 80, its electrode effect is large, the toner on the carrier 20 is easily stuck to the electrostatic latent image carrier 10, and the development is carried out. Then, in the developer carrier, the materials having the almost same abrasion test property are used for the conductor and dielectric constituting the surface, so that even if it is used for the long period and the surface is worn, a stable image can be obtained without loosing the smoothness of the surface.

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]

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 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, 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.6 Therefore, 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 supported on the developer carrier by utilizing the magnetic force of a magnet inside the developer carrier, so the above requirements can be met relatively easily. It 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 has been proposed for transporting a darning-component developer to a development 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.

In addition, as a toner supply member, 102~10@Ω・c
Use of Il conductive foam (Japanese Patent Laid-Open No. 60-229057), elastic body with skin layer (Japanese Patent Laid-Open No. 60-229060), fur brush (Japanese Patent Laid-Open No. 61-42672), etc. has been proposed, and as a developing roller, 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-
No. 46758) Medium and low antibody coated roller
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-62-229060 discloses an elastic roller.

In JP-A No. 61-52663, a fur brush or the like is used to apply an electric charge to the toner by frictional charging between the toner and a replenishing member, and further electrostatically charge the toner to the developing roller by friction in contact with the developing roller. and then use a layer thickness regulating member such as a blade.

The toner layer is controlled to develop the latent image on the photoreceptor. Various materials are used for the developing roller, such as N magnetic 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. <<, resulting 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 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.6. Regarding the amount of adhesion, the amount of adhesion on the developing roller is 0.1-0.3m.
g/cm2, but 0.4-0.5mg on the transfer paper
/c+s2 is required, and the amount of toner adhesion is covered by making the speed of the developing roller 3 to 4 times the speed of the photoreceptor. However, when the developing roller rotates 3 to 4 times, there is a problem that a 'toner from the rear edge' phenomenon occurs, that is, when a solid area is developed, the density at the rear edge of one image becomes higher. To prevent this phenomenon, it is necessary to bring the speed of the developing roller closer to the speed of the photoreceptor.In other words, the amount of adhesion on the developing roller must be increased and the number of rotations must be reduced.

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.
An amount of adhesion on the developing roller of 11 Ig/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).
c/g) is desired.

As a method to solve these problems, the present inventors
First, a one-component developer consisting of a non-magnetic toner to which an adjuvant is externally added as necessary is supplied to a rotationally driven developer carrier, and the developer is carried on the surface of the carrier. In a developing area where the latent image carrier and the developer carrier face each other, the electrostatic latent image formed on the latent image carrier is made visible by the developer carried on the developer carrier. In the developing method for image formation, a large number of minute electric fields are formed near the surface of the developer carrier by selectively holding charges on the surface of the developer carrier, and the charged toner is attracted by the closed electric field, The developer is attached and supported on the surface of the developer carrier,
We proposed an image forming method in which an electrostatic latent image is visualized using the developer carried thereon.

In this method, many minute 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, the surface of the developer carrier is abraded due to rubbing against toner and various contact members. In particular, since the developer carrier has two different materials on its surface, a conductive part and a dielectric part, if the two materials wear to different degrees, the surface will lose its smoothness and the image will become uneven. There was a problem in that this occurred.

Therefore, an object of the present invention is to provide a developer carrier that can provide stable images over a long period of time in the above-mentioned image forming method.

[Means to solve the problem]

As a result of extensive studies, the present inventors found that a developer carrier using materials having approximately the same wear characteristics for the conductor and dielectric material constituting the surface of the developer carrier 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 charge.

A large number of minute electric fields are formed near the surface of the developer carrier, and a non-magnetic one-component developer consisting of toner to which an auxiliary agent is externally added as necessary is supplied onto the developer carrier. A developer carrier used in an image forming method in which the developer is supported on the surface of the developer carrier by an electric field and an electrostatic latent image is visualized by the carried developer, the developer carrier having a conductive portion on the surface. and a dielectric part coexist in a small area, and the conductor and dielectric have almost the same wear test characteristics (JIS K
6902) is provided.

In the image forming method using the developer carrier of the present invention, since a large number of minute electric fields are formed near the surface of the developer carrier, the electric field strength can be significantly increased compared to conventional methods. By using materials with almost the same abrasion characteristics for the conductor and dielectric that make up the surface of the agent carrier, the surface smoothness will not be impaired even after long-term use.
This makes it possible to obtain stable images.

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, at 400 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/, charges the developer carrier 20 and the toner 60, and causes the toner 60 to adhere to 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, for example, the developer carrier 20 is constructed so that a dielectric portion and a conductive portion coexist in a small area on its surface. Assuming that the size of the area is circular, the area of the conductor part is 6 as an area ratio in which minute areas with a diameter of 10 to 500 ps are distributed randomly or according to a certain rule. 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 micro field (closed field) as shown in the second part, and becomes an electric field with a large electric field gradient, making it possible to adhere the toner in multiple layers. . Furthermore, since the adhered toner forms a closed 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 particular, the developer carrier of the present invention has almost the same abrasion test characteristics (JIS K
6902), even if the surface is worn out by friction with toner and various contact members during long-term use, the smoothness of the surface will not be impaired and stable images can be obtained. .

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 resins, and rubbers such as butadiene rubber, styrene-butadiene rubber, ethylene propylene rubber, gloloprene rubber, chlorinated polyethylene, epichlorohydrin rubber, nitrile rubber, acrylic rubber, silicone rubber, and fluorine rubber. From the viewpoint of moisture resistance, it is preferable to use silicone resins and fluororesins.

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 fine particles to the resins and rubbers mentioned above as dielectric materials to make them conductive are used. be able to.

In the present invention, as a conductive material and a dielectric material,
Among the above-mentioned materials, those having substantially the same wear characteristics are selected and used. In addition, molybdenum disulfide (M
oS2), boron nitride (BN), silicon nitride (sx3N
It is also possible to adjust the wear characteristics by blending a solid lubricant such as 4).

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, the following method is adopted.

(i) First, the conductive material is coated on a metal roller by a method such as spraying or dipping, and is cured and dried under predetermined conditions to form a film.

(n) Next, the obtained film is subjected to blasting treatment to make the surface uneven. [See FIG. 3(a)] (■) Subsequently, the roller surface is coated with the dielectric material until it becomes smooth, cured, and dried to form a film. [
See Figure 3(b)] (iv) Furthermore, the obtained surface is cut or polished so that the conductive surface and dielectric surface are mixed in a small area, so that the conductive part area becomes 20 to 60%. Sharpen to. [See; 3rd
Figure (C)] [Examples] The present invention will be described in more detail below with reference to Examples. Note that parts represent parts by weight.

Example A developing roller was produced in the following manner.

(i) The following conductor-forming components were spray-coated on a metal roller and cured at 100° C. for 71 hours to form a 50-tone film.

(Aishinseki UA) 3; 3rd year chemical engineering Kurisha split: Solid content 75 Misaki S
N-type catalyst (trade name Cat, 55; manufactured by Sanyo Chemical Industries, Ltd.)
5 parts methyl ethyl ketone
300 parts (ii) Next, this film was subjected to blasting treatment to make the surface uneven.

(iii) Subsequently, the following dielectric forming component was applied until the roller surface became smooth, and cured at 100° C./1 hour to form a film.

Coronate EH 20 parts Toluene 50
Part xylene 50
Part (■) This surface was further polished so that the conductor part and the dielectric part coexisted, and at this time, the area occupied by the conductor part was 50%.

Comparative Example A developing roller was produced in the same manner as in the example except that the solid lubricant in the dielectric forming components was not used.

〔evaluation〕

Regarding each of the above-mentioned developing rollers, abrasion tests were conducted on the conductive and dielectric materials, and then one image and the surface condition of the developing roller were observed and evaluated.

Wear tests were conducted on each of the conductor and dielectric materials in accordance with a method strictly compliant with JIS K 6902.

As a result, the amount of wear of the conductor-forming material and the dielectric-forming material in the developing roller of the example was the same, but in the developing roller of the comparative example, the amount of wear of the dielectric-forming material was the same as that of the conductor-forming material. The amount of wear was approximately twice that of the material.

Roller surface When each developing roller was installed in the developing device shown in Fig. 1 and 100,000 solid black images were copied, the initial state was almost maintained when the developing roller of the example was used. When the developing roller of the comparative example was used, density unevenness occurred in the form of spots.

Further, when both of the developing rollers were taken out and the surfaces were observed, the surface of the developing roller of the example was almost smooth, whereas the surface of the developing roller of the comparative example was uneven.

〔Effect of the invention〕

The developer carrier of the present invention has a structure in which a conductive part and a dielectric part coexist in a small area on the surface thereof, and the conductive part and the dielectric part are made of a material having almost the same wear test characteristics. By selectively retaining electric charge on the surface of the developer carrier, a large number of minute closed fields are formed near the surface of the developer carrier, and on this developer carrier, 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 micro closed field, and an electrostatic latent image is formed by the supported developer. When the developer carrier of the present invention is used in a visualizing image forming method, stable images without unevenness can be 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 chamber 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. 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 conductive part and the dielectric part have almost the same wear test characteristics ( 1. A developer carrier, characterized in that it is made of a material having the following characteristics (according to JIS K6902).