JPH0431880A - Developer carrier - Google Patents

Abstract

PURPOSE:To maintain the electrostatically charged amount or the adhesive amount of toner at an appropriate value by forming the dielectric part of a developer carrier of a material having a specified volume resistivity. CONSTITUTION:The dielectric part and a conductive part coexist on the surface of the developer carrier 20 in a state having minute areas. As for the material constituting the dielectric part, the volume resistivity is >=10<13>OMEGA.cm under a condition that temperature is 30 deg.c and humidity is 90%, and variation difference between the volume resistivity under the above condition and that under a condition that temperature is 10 deg.C and humidity is 20% is <=1.5 times. Thus, a microfield effect is excellently found even when environment is changed and the toner having the appropriate electrostatically charged amount is sufficiently carried and a high-density and high-quality image is obtained.

Description

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

[Conventional technology]

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

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

From this point of view, a one-component development system using a one-component developer that does not have the above-mentioned drawbacks is attracting attention. - Component type developers include those consisting only of toner and those consisting of a mixture of toner and an auxiliary agent, with an auxiliary agent externally added thereto 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 color image including full color or multicolor is formed using magnetic toner, the developed visible image becomes unclear and a vivid color image cannot be obtained. 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 utilizing the magnetic force of the magnet 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). 1. A developer supplying member made of, for example, a sponge roller is brought into pressure contact with the dielectric 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 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.

Note that the toner supply member has a resistance of 102 to 1011Ω.
Use Cm conductive foam (Japanese Unexamined Patent Publication No. 60-229057), elastic body with skin layer (Unexamined Japanese Patent Application No. 60-229060), fur brush (Unexamined Japanese Patent Application 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-
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. 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 charging between the toner replenishing member and the developing roller, but sufficient charging cannot be achieved because the toner-attached member rubs. As a result, Tona
- Adhesion is insufficient. The optimum adhesion amount and charge amount in the non-magnetic component development method will be explained as follows.

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

Regarding the amount of adhesion, the amount of adhesion on the developing roller is 0.
1-0.3a+g/cm", but 0.3a+g/cm" on the transfer paper.
4-0.5B/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 rotation of the roller has a problem in that it causes a phenomenon of "toner from the trailing edge", that is, when a solid area is developed, the density at the trailing edge of the image becomes higher.

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

On the other hand, with color toner, the degree of coloring is lower than that of black toner, and when trying to improve the "from the rear end of the toner", the color characteristic is 0.8 to 1.2 m, which is even more than that of black toner.
An amount of adhesion on the developing roller of g/cm2 is required.

In addition, regarding the amount of charge, in order to obtain a stable image, 5 to 20 μC/g (preferably 10 to 15 μC/g)
A value of 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 transferred by the developer carried by the developer carrier. In the visual development method, 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 broom electric toner is attracted by this closed electric field. and deposit and carry the developer 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, 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, the triboelectric charging properties of the developer carrier may change due to changes in the environment such as temperature and humidity. There is a problem in that the amount of toner adhesion and the amount of charge become unstable due to fluctuations, which adversely affects the electric field strength of the microfield.

In particular, since the dielectric portion that constitutes the developer carrier retains electric charge due to frictional electrification with other members, the selection of the material that forms the dielectric portion is extremely important, and environmental changes may occur. There has also been a demand for the development of materials that do not affect the microfield effect, the amount of toner adhesion, and the amount of charge on the toner.

The present invention has been made in view of such circumstances, and
To provide a developer carrier that exhibits a stable microfield effect even when the environment such as temperature and humidity changes, and solves the problems of insufficient toner adhesion and insufficient charge in the image forming method. There is a particular thing.

[Means to solve the problem]

As a result of intensive studies, the present inventors discovered that a developer carrier provided with a dielectric portion made of an insulating material having a specific volume resistance is suitable for the above purpose, and thus completed the present invention. It's arrived.

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 at least a dielectric material on the surface thereof. The material of the dielectric part has a volume resistivity of 1011Ω・CII or more at a temperature of 30'C and a humidity of 9 inches, and
0℃.

Provided is a developer carrier characterized in that the difference in variation from the volume resistivity at 20% humidity is within 1.5 times.

In the image forming method using the developer carrier of the present invention, since a large number of minute closed chamber fields are formed near the surface of the developer carrier, the electric field strength can be significantly increased compared to the conventional method. The strength does not change even if the environment changes,
Furthermore, since the amount of toner adhesion and the amount of charge do not change due to changes in the environment, a large amount of sufficiently charged non-magnetic toner can be uniformly 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.
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 that has completed the development rotates in the direction of the arrow (for example, withstands 400 rρ, and reaches the contact portion with the toner supply member 40. The toner supply member 40 carries the developer The developer carrier 20 and the toner 60 are rotated in the opposite direction to the developer carrier 20 (for example, 300 rpm) L, and the developer carrier 20 and the toner 60 are charged, so that 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, bias such as direct current, alternating current, direct current superimposed alternating current, pulse, etc. can be applied to the developer carrier 20 and the toner supply member 40 to control an optimal image.

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, if the shape is circular, the diameter is 1
Minute areas with a size of 0 to 500 μs are distributed randomly or according to a certain rule. As for the area ratio, the area of the insulating portion is preferably in the range of 20 to 60%.

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

At this time, the electric field on the developer carrier 20 becomes a microfield (closed electric field) as shown in FIG. 2, and becomes an electric field with a large electric field gradient, making it possible to adhere the toner in multiple layers. Further, since the adhered toner is in a closed electric field, it is strongly attracted to the developer carrier 20 side and becomes difficult to separate. The thickness of this toner layer is further controlled by a toner layer thickness regulating member 30, and the toner in the development area 80 becomes an electric field that easily adheres to the photoreceptor, 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 dielectric portion and a conductive portion mixed in a small area on at least its surface, and the material constituting the dielectric portion has a volume resistance at a temperature of 30° C. and a humidity of 90%. is 1013Ω·Cl11 or more, and the variation difference from the volume resistivity at a temperature of 10°C and a humidity of 2 parts is 1.
It is within 5 times.

The first characteristic of the dielectric part forming material used in the present invention is the temperature 3
Volume resistance at 0℃ and 90% humidity is 1013Ω・CI
! 1 or more, preferably 1014Ω·0m or more. Volume resistance under the above conditions is 1013Ω・01
If it is less than 1, the triboelectric charging properties will change greatly depending on environmental changes, which is not desirable.

The second characteristic of the dielectric part forming material used in the present invention is the volume resistance value at a temperature of 30°C and a humidity of 90%, the temperature of io°C,
The difference in variation from the volume resistivity value at 20% humidity is within 1.5 times.

In the present invention, by selecting a material for the dielectric portion that exhibits small changes in volume resistivity even when the environment changes, the microfield effect can be sufficiently expressed even when the environment changes. Further, a developer carrier that can sufficiently support toner having an appropriate amount of charge can be obtained.

If a material with a differential difference in volume resistivity that exceeds the above range is used, the microfield effect will change due to environmental changes, which will not only make the electric field unstable but also affect the amount of charge and adhesion of the toner. This results in non-uniformity, making it impossible to obtain the effects of the present invention.

Specific examples of the dielectric part forming material used in the present invention include organic polymers such as silicone resin (rubber) and fluororesin (rubber), or modified products thereof.

Silicone resins (rubbers) include dimethylsiloxane, methylvinylsiloxane, phenyl-modified siloxane, fluorine-modified siloxane, epoxy-modified siloxane, acrylic-modified siloxane, carboxyl-modified siloxane,
Examples include alcohol-modified siloxane and polyester-modified siloxane.

Examples of fluororesin (rubber) include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoropropyl vinyl ether copolymer (PFA), and polychlorotrifluoroethylene. Fluoroethylene (P
CTFE), ethylene-tetrafluoroethylene copolymer (ETFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride (p
vdF), polyvinyl fluoride (PVF), vinylidene fluoride-based fluororubber, copolymers of fluorine-containing monomers and crosslinking group-containing hydrocarbon monomers.

Alternatively, these fluoropolymer particles can be mixed with epoxy resin,
Examples include those dispersed in a binder such as a silicone polymer.

The conductive material forming the conductor part is 1012Ω・
cm or less, preferably 1011 Ω·crIQ or less, can be used. Specific examples include AM, S[IS,
In addition to metals such as Fe and Ni, ceramics, etc., examples of organic polymers include those in which a conductive filler is added.

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; polyacetal, polyamide, cellulose, polycarbonate, phenoxy resin, polyester, fluororesin, polyurethane.

Resin materials such as phenolic resin, urea resin, melamine resin, epoxy resin, unsaturated polyester resin, silicone resin; natural rubber, imprene rubber, butadiene rubber, styrene-butadiene rubber, butyl rubber, ethylene-propylene rubber, chloroprene rubber, chlorinated polyethylene rubber , epichlorohydrin rubber, nitrile rubber, acrylic rubber, urethane rubber, polysulfide rubber, silicone rubber, fluororubber, and other rubber materials.

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

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.

For producing the developer carrier of the present invention, for example.

First, a metal roller whose surface is grooved by fleur-de-lis knurling or the like is prepared.In this case, the grooves are 0.1 to 0.
5ma+pitch, about 45mm in the longitudinal direction of the roller
[Reference: Fig. 4 (a)]. Then, the grooved metal surface is coated with, for example, a fluororesin (Lumiflon L).
Coated with F200 (manufactured by Asahi Glass Co., Ltd.) and heated to 100℃
The roller is cured and dried for about 30 minutes (the coating thickness should be such that the grooves are completely filled) (see Figure 4 (b)), and then the surface of the roller is cut or polished so that a conductive surface is mixed in a small area. , a method is adopted in which the surface of the conductive part is removed by 20-60% [see FIG. 4(C)].

〔Example〕 Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 A developer carrier (
A developing roller) was manufactured.

(i) Grooves were formed on the surface of the SLiS roller by fleur-de-lis knurling. (2) The grooves were 0.3 ml and 11 pitches, and were machined at approximately 45 degrees with respect to the longitudinal direction of the roller.

(ii) Apply the above dielectric material to the V-grooved roller surface,
Coated. 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 were mixed in a small area, so that the conductive part area was 502.

Example 2 A developer carrier was produced in the same manner as in Example 1 except that the dielectric material was replaced with the following material.

Example 3 A developer carrier was produced in the same manner as in Example 1 except that the dielectric material was replaced with the following material.

Comparative Example 1 A developer carrier was produced in the same manner as in Example 1, except that the dielectric material was replaced with the following material.

Comparative Example 2 of Dielectric Portion Material A developer carrier was produced in the same manner as in Example 1 except that the dielectric portion material was replaced with the following material.

The developer carriers of Examples 1 and 2 were mounted on an imager as shown in FIG. 1, and the toner charge amount and toner adhesion amount at 30° C./90% and 10° C. 720% were measured. The results are shown in Table-1.

In the developing device shown in FIG. 1, urethane rubber was used as the toner layer thickness regulating member, a conductive urethane sponge was used as the toner supply member, and decapolar toner was used as the toner.

Table 1 also shows the dielectric material at 30°C, 790% and 1
The volume resistivity value at 0°C and 720% is also shown.

The volume resistance value was determined by spray coating the dielectric material on AQ-deposited PET to a film thickness of 20 mm, curing it, and then applying 4329A HIGHRESISTACE.
Measured using METER (manufactured by YHP) under DClooV environmental conditions: 30°C 790%, 10°C/
This is the value after being left at 20% for 24 hours.

Examples 1 to 3 obtained as described above and comparison [Effects of the invention] The developer carrier of the present invention has a dielectric portion formed of a material having a specific volume resistance as described above. With this configuration, even if the environment such as temperature and humidity changes, the microfield effect can be sufficiently expressed, and the amount of charge and adhesion of toner can be maintained at appropriate values.

Therefore, 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 on this developer carrier, auxiliary electric fields are applied as needed. A non-magnetic one-component developer made of toner externally added is supplied, the developer is carried on the surface of the developer carrier by the fine tJs closed electric field, and the electrostatic latent image is made visible by the carried developer. When the developer carrier of the present invention is used in an image 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. As a result, toner filming does not occur, and high-quality images with high density can be 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 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. No. 7/// Figure 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, in which a dielectric portion and a conductive portion are mixed in a small area on at least the surface thereof, and the material constituting the dielectric portion is heated at a temperature of 30° C. and a humidity of 90%. A developer carrier having a volume resistivity of 10^1^3 Ω·cm or more, and a variation difference from the volume resistivity at a temperature of 10° C. and a humidity of 20% within 1.5 times. .