JPH0437879A - developer carrier - Google Patents

Abstract

PURPOSE:To secure the sufficient quantity of toner adhesion and the sufficient quantity of toner electrostatic charge and to make it possible to carry much charged non-magnetic toner by embedding insulating particles on the surface of a conductive layer formed an a conductive base of a developer carrier and smoothing the surface. CONSTITUTION:The developer carrier 20 is constituted so as to mix insulating particles and a conductive material on its surface as a fine area part. The carrier 20 completing development is rotated in an arrow direction and comes into contact with a toner feeding member 40. Residual toner in a non-image part which has not been developed is mechanically and electrically scraped and an insulating part is frictionally charged with electricity. The charge of the carrier 20 and that of toner due to the preceding development are frictionally uniformed and initialized. Toner carried by the member 40 is frictionally charged and electrostatically stuck to the insulating part of the carrier 20. Since closed electric fields are formed on the surface of the carrier 20, their field inclination is increased and multilayer of toner can be stuck to the carrier 20.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention supplies a non-magnetic one-component developer to which an adjuvant is externally added as necessary to a rotatably active 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-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. 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. 61-52653 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.
20, C/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.
1J, 3mg/cm2, but 0.4-
0.5 mg/cm2 is required, and by increasing the speed of the developing roller to 3 to 4 times the speed of the photoreceptor,
Covers the amount of toner adhesion. However, due to the rotation of the developing roller 3 to 4 times, there is a phenomenon of "toner from the rear end"
That is, when a solid area is developed, there is a problem in that the density at the rear end of the image becomes high. 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, its color properties are lower than that of black toner, and when trying to improve the 1' from the rear edge of the toner, the color characteristic is 0.8 to 1.2, which is even higher than that of black toner.
The adhesion amount 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, 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 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.
This device has many advantages, such as being able to carry a large amount of charged non-magnetic 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 possible to carry a sufficient and stable amount of toner on the developer carrier by the microfields. ,
The amount of charge on the toner may be insufficient, and in terms of ensuring a stable amount of charge over a long period of time,
Still not satisfied.

Therefore, an object of the present invention is to provide a developer carrier capable of stably securing a sufficient amount of toner adhesion and a sufficient amount of 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 have found that a developer carrier in which insulating fine particles are embedded in a conductive surface is suitable for the above purpose, and has 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 electric fields are formed near the surface of the developer carrier, and a non-magnetic toner 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 one-component developer is supplied, the developer is carried on the surface of a developer carrier by the minute electric field, and an electrostatic latent image is visualized by the carried developer. A conductive layer is provided on a conductive substrate, and insulating fine particles are embedded in the surface of the conductive layer,
Further, there is provided a developer carrier characterized in that the surface of the conductive layer has been subjected to a smoothing treatment.

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 the conventional method. The developer carrier has a structure in which insulating fine particles are embedded in the surface of a conductive layer provided on a conductive substrate, and the surface of the conductive layer is smoothed, so that a sufficient amount of toner is adhered to the toner. The amount of charge can be ensured, and as a result, a large amount of sufficiently charged non-magnetic toner can be carried on the developer carrier and transported to the development area stably for 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, 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, the developer carrier 2
o and the toner 60, and the toner 60 is attached 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, 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. It is composed of Regarding the size of the area, if the shape is circular, minute areas with a diameter of 10 to 500 pieces are distributed randomly or according to a certain rule. The area ratio is preferably in the range of 20 to 60% of the area of the conductor portion.

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 insulator 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 insulator portion of the developer carrier 20 . At this time, the polarity of the toner is opposite to the charge of the photoreceptor, and the insulating portion of the developer carrier 20 is of the same polarity.

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 conductor portion and an insulator portion are mixed in a small area on the surface thereof, but the conductive material used for the conductor portion is ,
A material having a resistance of 10 12 Ω·am or less, preferably 10 8 Ω·cm or less can be used. Specifically, examples include organic polymers to which a conductivity imparting agent 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, fluorine comb, silicone-modified ethylene-propylene rubber, etc.

In addition, conductivity imparting agents include metal powders such as Ni and Cu; carbon blacks such as furnace black, lamp black, thermal black, acetylene black, and channel black; tin oxide, zinc oxide, molybdenum oxide, antimony oxide, and titanic acid. Conductive oxides such as potash; electroless plated materials such as titanium oxide and mica; inorganic fillers such as graphite, metal fibers, and carbon fibers; surfactants; 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, as the insulating fine particle material used for the insulator part, 1
013 Ω·01 or more, preferably 10 14 Ω·01 or more is used. In addition, the average particle size is 1
It is better to have a voice above 10, preferably above 10. Less than one voice,
It is difficult to form microfields, and stable toner adhesion and charging cannot be obtained. In addition, it does not matter whether it is a fixed form or an amorphous form.

These specific materials include alumina, beryllia,
Inorganic particles such as magnesia, silicon nitride, boron nitride, mullite, steatite, forsterite, zircon, cordierite, epoxy resin, fluororesin, silicone resin, acrylic resin, nylon resin, polymethyl methacrylate resin, polystyrene Examples include organic particles such as resin.

The developer carrier of the present invention can be manufactured, for example, by the following method.

(i) First, a conductive material is laminated on a metal roller by a method such as extrusion molding, spray coating, or dipping.

(ii) Insulating particles are buried in the surface before curing if the conductive material is a curable material, or before volatilizing the solvent in the case of a solvent-soluble material. It does not matter whether the insulating particles are exposed on the surface or not.

(iii) Curing or drying the conductive material.

(La) The surface of the roller is made smooth by polishing or cutting, so that conductive parts and insulating parts coexist on the surface.

〔Example〕

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

Example A developing roller was produced in the following manner.

(i) After kneading the following conductive materials using a two-roller machine,
A layer was formed on a SUS metal roll by a pressing method. (Layer thickness approximately 6 mm) (ii) Silicone powder as insulating fine particles (trade name TORAYFIL E-850; manufactured by Toray Silicone Co., Ltd.)
was embedded in the surface of the conductive layer, and then attached to a Ni pipe (20+++a+φ).

(Stone) After being cured at 170° C. for 30 minutes, it was allowed to cool, the Ni pipe was removed, and secondary vulcanization was performed at 200° C. for 74 hours.

(iv) Thereafter, the surface was polished smooth so that the area ratio of the conductive part to the insulating part was about 171.

Each developing roller was attached to the developing device shown in FIG. 1, and the amount of toner charge and toner adhesion was measured. As a result, the toner charge amount was 10.2 μC/g, the toner adhesion amount was 1,
06 mg/am'', desired toner charging and toner adhesion were obtained.

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.

〔Effect of the invention〕

The developer carrier of the present invention has a structure in which insulating fine particles are embedded in the surface of a conductive layer provided on a conductive substrate, and the surface of the conductive layer is smoothed. By selectively retaining 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 the auxiliary agent is removed from the developer carrier as necessary. An image in which a non-magnetic one-component developer consisting of an attached toner is supplied, the developer is carried on the surface of a developer carrier by the minute closed electric field, and the electrostatic latent image is visualized by the carried developer. When the developer carrier of the present invention is used in the forming method, a large amount of sufficiently charged non-magnetic one-component developer can be carried on the developer carrier and transported to the development area stably for a long period of time. It is possible to stably obtain high-density, high-quality images.

[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 due to a microfield is generated on the developer carrier of the present invention in the apparatus shown in FIG. lO...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. Patent applicant Rico Co., Ltd.

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, comprising a conductive layer provided on a conductive substrate, insulating fine particles embedded in the surface of the conductive layer, and the surface of the conductive layer subjected to a smoothing treatment. A developer carrier characterized by being subjected to.