JPH0434473A - Developer carrier - Google Patents

Abstract

PURPOSE:To prevent a toner filming and the unevenness of development by providing dielectric regions and conductive regions in a mixed state in fine areas on a surface and forming also a surface of the dielectric body region at a lower position than the surface of the conductive body region. CONSTITUTION:The surface of the developer carrier 20 is constituted of the fine dielectric region and the fine conductive region electrically connected with the conductive base, and the surface of the fine dielectric region is lower than the surface of the fine conductive region. In this case, in the vicinity of the surface of the developer carrier 20, a number of fine closed electric fields are formed, so that the electric field strength can be increased and the contact rotation of the dielectric body part with a toner supplying member 40 is properly adjusted, since the surface of the fine dielectric region is lower than the surface of the fine conductive region. Thus the toner filming on the surface of the dielectric body part is prevented and the unevenness of rotation due to the reduction of a driving torque to the developer carrier 20 is prevented.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention supplies a non-magnetic one-component developer to which an auxiliary agent is externally added as necessary to a developer carrier that is rotated and opened. 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.The former two-component developer using two-component thread developer 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-based developers include those consisting only of toner and those consisting of a mixture of toner and auxiliary agent, with external addition of an auxiliary agent as required. There are two types of toner: magnetic toner, which has magnetic powder kneaded into each toner particle itself, and non-magnetic toner, which does not contain magnetic material.Since magnetic material is generally opaque, full color or multicolor toner can be used. If a color image including color images is formed using magnetic toner, the developed visible image becomes unclear and a vivid color image cannot be obtained.Therefore, especially for color development, one-component development using non-magnetic toner is recommended. It is desirable to adopt this method.

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 transport 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 dielectric layer (M edge body) is laminated on the surface of a developer carrier (developing roller). 1. A developer supplying member made of a sponge roller, for example, is brought into pressure contact with the material, and both 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 in which the -component developer is conveyed to the 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, 102~1O6Ω・a
- 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 Patent Application Laid-open No. 5336245).

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, the amount of charge is important, and it is - IO 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.
1-0.3mg/cm”, but 0.4mg/cm” on the transfer paper.
-0.5 tag/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.
The problem with rotating the developing roller twice as much is that it causes the phenomenon of ``toner from the rear edge'', that is, when developing a solid area, the density at the rear edge of one image becomes higher. To prevent this, the speed of the developing roller must be made close 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 decreased.

On the other hand, with color toner, the degree of coloring is lower than that of black toner, and if you try to improve "from the rear end of the toner", the degree of coloring will be even higher than that of black toner, from 0.8 to 1,2
The amount of adhesion on the developing roller is required to be 5 to 20 μC/g (preferably 10 to 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 holding charges on the surface, a large number of minute electric fields are formed near the surface of the carrier, and the charged toner is attracted by this 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 invention, since a large number of microfields are formed near the surface of the developer carrier, 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 above-mentioned image forming method in which a large number of microfields are formed near the surface of the developer carrier, in order to obtain a stable toner adhesion amount and charge amount over time, it is necessary to To prevent so-called toner filming, in which toner adheres to the toner, and to eliminate uneven rotation when a developer carrying member and a toner supply member (such as a sponge roller or fur brush) contact and rotate. In order to prevent unevenness, it is required to reduce the driving torque of the developer carrier.

Therefore, an object of the present invention is to provide a developer carrier that solves the problems of filming and development unevenness in the image forming method described above.

[Means to solve the problem]

As a result of extensive studies, the present inventors found that a developer carrier in which the surface of the micro dielectric region is lower than the surface of the micro conductive region 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 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 surface of which has microdielectric properties. and a micro-conductive region electrically connected to a conductive substrate, the surface of the micro-dielectric region being lower than the surface of the micro-conductive region. 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. On the surface of the developer carrier, the surface of the micro dielectric region is lower than the surface of the micro conductive region, which prevents toner filming and reduces the driving torque of the developer carrier. As a result, uneven development can be prevented.

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, 400 rpm) L, 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, withstands 300 rpm), charges the developer carrier 20 and the toner 60, and causes the toner 60 to adhere onto 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, the developer carrier 20. direct current to 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 has a structure in which a dielectric region (dielectric portion) and a conductive region (conductor portion) are mixed in a small area on its surface. has been done. Assuming that the size of the area is circular, the area of the conductor part is the area ratio of 0 where minute areas with diameters of 10 to 500 mm are distributed randomly or according to a certain rule. is preferably in the range of 20 to 60%. Also, the surface of the dielectric part is lower than the surface of the conductor part (that is, it is concave), and the difference (ff) is about 3 to 6 times the average particle diameter of the toner. 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 of the photoreceptor, and the dielectric portion of the developer carrier 20 is of the same polarity.

During the toner supply and initialization process due to contact rotation between the developer carrier 20 and the toner supply member 40, the dielectric part surface is lowered (concave), so that the dielectric part and the toner supply The contact rotation with the member 40 is optimized, and as a result, toner filming on the surface of the dielectric portion is prevented, and rotation unevenness is prevented by reducing the driving torque of the developer carrier 20.

Further, the electric field on the developer carrier 20 at this time 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. Become. 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.

Next, the developer carrier of the present invention will be explained.

As described above, the developer carrier of the present invention has a structure in which a conductive region (conductor part) and a dielectric region (dielectric part) coexist in a small area on its surface. As the conductive material used for the conductor part, the following can be used: 1012Ω・ell or less, preferably 10”Ω・cm. Specific examples include metals such as AQ, SUS, Fe, and N1, and ceramics. In addition to the above, examples include organic polymers to which a conductive filler is added. In this case, the organic polymers include the following.

Vinyl resins such as polyvinyl chloride, polyvinyl butyral, polyvinyl alcohol, polyvinylidene chloride, polyvinyl acetate, and polyvinyl formal; polystyrene,
Polystyrene resins such as styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer; polyethylene resins such as polyethylene, ethylene-vinyl acetate copolymer; polymethyl methacrylate, polymethyl methacrylate-styrene copolymer, etc. Acrylic resin; resin materials such as polyacetal, polyamide, cellulose, polycarbonate, phenoxy resin, polyester, fluororesin, polyurethane, phenol resin, urea resin, melamine resin, epoxy resin, unsaturated polyester resin, silicone resin; natural rubber, isoprene Rubber, butadiene rubber, styrene-butadiene rubber, butyl rubber, ethylene-propylene rubber, chloroprene rubber, chlorinated polyethylene rubber, epichlorohydrin rubber, nitrile rubber, acrylic rubber, urethane rubber,
Rubber materials such as polysulfide rubber, silicone rubber, fluororubber, silicone-modified ethylene-propylene rubber, etc.

Examples of conductive fillers include metal powders such as Ni and Cu; carbon blacks such as furnace black, lamp black, thermal black, acetylene black, and channel black; and tin oxide.

Conductive oxides such as zinc oxide, molybdenum oxide, antimony oxide, and potassium titanate; electroless plated products plated on titanium oxide and mica; graphite, metal fibers, carbon fibers, and the like.

Note that an organic ion conductor in which metal ions are coordinated to a polymer matrix such as polyethylene oxide or polysiloxane can also be used.

On the other hand, the material used for the dielectric part costs $1! If it is related,
Can be used, but 1013Ω・C1 or more, especially 101Ω
It is preferable that the resistance is 4Ω·cffi or more. Specifically, those mainly composed of aliphatic fluorine-containing compounds or silicone resins are used.

Examples of aliphatic fluorine-containing compounds include polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and tetrafluoroethylene-ethylene copolymer. , a fluorine-containing polymer such as polychlorotrifluoroethylene, or an aliphatic fluorocarbon or aliphatic fluorochlorocarbon compound having a polar group such as an ether group, a carboxyl group, or a hydroxyl group at the end or in the molecular chain. Examples of the silicone resin include condensation reaction type, addition reaction type, and peroxide curing reaction type silicone resins, and modified resins obtained by copolymerizing organic resins.

To prepare the developer carrier of the present invention, 1 For example, (i)
In this case, first, a metal roller with a V-groove formed by fleur-de-lis knurling or the like on one surface is prepared.

■The grooves are machined at a pitch of 0.1 to 0.5 mm, and at an angle of about 45° to the longitudinal direction of the roller) [see Figure 3 (a)], (...) Next, V grooves are machined. The dielectric material is coated on the metal surface by a method such as spraying or dipping, and then cured (baked) under predetermined conditions (temperature, time) (the thickness of the coating film is 20 to 70 pa recessed from the edge of the V-groove). (see Figure 3(b)), (iii
) 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 surface of the roller is polished so that the area of the conductive part is 20 to 6 parts [see Fig. 3 (C)].
This method is adopted.

(tv) After kneading the conductive material, the mixed material is layer-molded on the surface of a metal roller by a usual molding method such as injection molding, extrusion molding, press molding, spray coating, dipping, etc., and then The above (i) to (
It is also possible to adopt the method of performing the process (ii).

〔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) A V-groove was provided on the surface of a metal roller (φ25) by fleur-de-lis knurling. (2) The grooves had a pitch of 0.2 mm and were machined at approximately 45 degrees to the longitudinal direction of the roller.

(ii) Polytetrafluoroethylene (trade name Polyflon TEF M-5;
After electrostatic coating (manufactured by Daikin Industries, Ltd.), 350℃, approx. 1
Baked for an hour. The thickness of the coating film was set to be SO and recessed from the edge of the groove.

(in) 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 about 50%.

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

(i) After kneading the following conductive materials using a two-roller machine,
Layers were formed on a stainless steel core using an extrusion method.

The crosslinking conditions were precure: 170°C/10 minutes.

50 kgf/cm'', secondary curing: 150° C./2 hours.

The surface of the conductive roller (φ25) thus obtained was grooved by fleur-de-lis knurling. (2) The grooves had a pitch of 0.51 and were machined at an angle of about 45 degrees with respect to the longitudinal direction of the roller.

(…) ■ After coating the dielectric material below with air spray on a grooved conductive roller, heat at 150°C.
It was cured in 2 hours.

10 parts of xylene The thickness of the coating film was 50 IJa recessed from the edge of the groove.

(■) 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 approximately 50 mm.

Comparative example A developing roller was produced in the following manner.

(i) A metal roller (φ2
5) was electrostatically coated with polytetrafluoroethylene (trade name: Polyflon TFE M-5; manufactured by Daikin Industries, Ltd.), and then baked at 350°C for about 1 hour. The coating film was thick enough to completely fill the grooves.

(if) 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 approximately 50%.

(2) Each developing roller was attached to the developing device shown in FIG. 1, and the toner charge amount, toner adhesion amount, toner filming property, and roller rotation torque were measured.

The results are shown in Table 1.

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.

The toner filming property was evaluated based on the following criteria based on the state of toner adhesion on the surface of the developing roller after 72 hours using the above-mentioned developing device.

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

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

Rank ■: Cannot be completely wiped off and a thin layer of toner remains.

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

From the results shown in Table 1, it can be seen that with the developing roller of the present invention, toner filming is prevented, rotational torque is reduced, and a sufficient amount of toner charge and adhesion can be obtained.

〔Effect of the invention〕

The developer carrier of the present invention has a structure in which a dielectric region and a conductive region coexist in a small area on the surface thereof, and the surface of the dielectric region is lower than the surface of the conductive region. Therefore, by selectively retaining electric charges on the surface of the developer carrier, a large number of minute electric fields are formed near the surface of the developer carrier, and on this developer carrier, electric charges are applied as needed. A non-magnetic one-component developer made of toner externally added with an auxiliary agent is supplied, the developer is carried on the surface of the developer carrier by the minute electric field, and an electrostatic latent image is formed by the carried developer. When the developer carrier of the present invention is used in a visualizing image forming method, toner filming can be prevented,
Moreover, by reducing the rotational torque, uneven development is prevented, and a large amount of sufficiently charged non-magnetic one-component developer can be carried on the developer carrier and transported to the development area, resulting in high concentration and high quality. Images can be stably obtained.

[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 electric 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, 2o... 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 Patent applicant Rico Co., Ltd.

Claims (2)

[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, the surface of which is composed of a microscopic dielectric region and a microscopic conductive region electrically connected to a conductive substrate, and furthermore, the surface of the microscopic dielectric region is is lower than the surface of the minute conductive region. (2) The developer carrier according to claim 1, wherein the surface of the minute dielectric region is 3 to 6 times lower than the surface of the conductive minute region by an average particle diameter of the toner.