JP2921586B2 - Developer carrier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention supplies a non-magnetic one-component developer externally supplemented with an auxiliary agent as necessary to a rotatable developer carrier,
Carrying and transporting the developer on the surface of the developer carrier,
In a developing region where the latent image carrier and the developer carrier are opposed to each other, the electrostatic latent image formed on the latent image carrier is visualized by the developer carried on the developer carrier. The present invention relates to a developer carrier used in an image forming method.

[Conventional technology]

An image forming apparatus such as an electronic copier, a printer or a facsimile that forms a latent image on a latent image carrier and visualizes the latent image with a developer to obtain a recorded image is a dry type using a powdery developer. Is widely used.

As such a powdery developer, a two-component developer having a toner and a carrier and a one-component developer without a carrier are known, and two-component development using the former two-component developer is known. In the method, although a relatively stable and good recorded image is obtained, deterioration of the carrier and fluctuation of the mixing ratio of the toner and the carrier are apt to occur, maintenance of the apparatus is complicated, and the structure of the entire apparatus is easily enlarged. Has disadvantages.

From such a viewpoint, a one-component developing method using a one-component developer which does not have the above-mentioned disadvantages has attracted attention. The one-component developer includes a toner composed of only a toner and a toner obtained by externally adding an auxiliary agent as needed and mixing the toner and the auxiliary agent. As the toner, there are a magnetic toner in which magnetic powder is kneaded into each toner particle itself, and a non-magnetic toner containing no magnetic material.

Here, since the magnetic material is generally opaque, if a color image including full-color or multi-color is formed with a magnetic toner, the developed visible image becomes unclear and a vivid color image cannot be obtained. Therefore, it is desirable to adopt a one-component developing method using a non-magnetic toner especially for color development.

By the way, in a developing device employing a one-component developing method, a one-component developer is carried on a developer carrier and transported. In a developing region where the developer carrier and the latent image carrier are opposed to each other, The electrostatic latent image formed on the latent image carrier is visualized with a developer, but in order to form a high quality visible image of a predetermined density, a large amount of sufficiently charged toner must be applied to the developing area. The latent image needs to be conveyed and visualized with the toner.

When the magnetic toner is used, the above-described requirement can be satisfied relatively easily because the one-component developer can be carried on the developer carrier by using the magnetic force of a magnet provided in the developer carrier. Is possible.

However, when a non-magnetic one-component developer is used,
Since this cannot be carried on the developer carrying member by magnetic force, it is difficult to satisfy the above requirements. Various countermeasures against this have been proposed in the past. For example, JP-A-61-42672 discloses a developer carrier (developing roller).
A layer of a dielectric (insulator) is formed on the surface of the substrate, and a developer supply member such as a sponge roller is pressed against the layer to frictionally charge the two with different polarities. A method has been proposed in which a non-magnetic toner charged to a polarity is electrostatically attached to a dielectric and such a one-component developer is transported to a development area. However, even with this method, the strength of the electric field formed in the vicinity of the dielectric surface cannot be sufficiently increased, so that it is difficult to carry a large amount of toner on the surface of the developing roller, and the developing roller can be transported to the developing area. Insufficient amounts of the agent make it difficult to form a high-density visible image.

A configuration in which a non-magnetic toner is applied between the developing roller and the developer supply member in a direction in which the non-magnetic toner is electrostatically transferred to the developing roller is also known, but even if such a configuration is added, It is difficult to attach a sufficient amount of toner to the developing roller.

As the toner supply member, 10 ² -10 ⁶ Ω · cm conductive foam (JP 60-229057 JP), integral skin elastic body (JP 60-229060 JP) and fur brush (Japanese Patent Application Laid-Open No. 61-42672) and the like, and as a developing roller, a metal body having an uneven surface (Japanese Patent Application Laid-Open No. 60-53976), an insulating coated roller body ( Japanese Unexamined Patent Publication No. Sho 55-46768 discloses a medium resistance coated roller (Japanese Unexamined Patent Publication No. 58-13278) and an electrode roller having an insulator and a conductive surface (Japanese Unexamined Patent Publication No. Sho 53-36245). .

In a developing apparatus using a non-magnetic one-component developer, a sponge roller is disclosed in JP-A-60-229057, an elastic roller is disclosed in JP-A-62-222960, and a developing roller is disclosed in JP-A-61-52663.
In the publication, a fur brush or the like is used to apply electric charge to the toner by frictional charging between the toner and the replenishing member, and further, by friction in contact with the developing roller, electrostatically attaches the toner to the developing roller. The latent image on the photosensitive member is developed by controlling the toner layer using a layer thickness regulating member such as a blade. As the material of the developing roller, various materials such as an insulating material, a medium-resistance material, and a laminated material are used.

According to the methods described in these references, toner is adhered to the developing roller by frictional charging between the toner replenishing member and the developing roller. And toner adhesion is insufficient. The following describes the optimal amount of adhesion and the amount of charge in the non-magnetic one-component developing system.

In the case of black and white, the amount of charge is important, which is generally 10-
20 μC / g. If the value is smaller than this value, the image quality such as background smear and sharpness is inferior. Regarding the coating weight, although the adhesion amount on the developing roller is 0.1 to 0.3 mg / cm ^2, the transfer paper is required 0.4~0.5mg / cm ^2, the speed of the developing roller of the photosensitive body speed 3 to 4 times, the amount of adhered toner is covered. However,
For the rotation of the developing roller 3 to 4 times, "from the rear end of the toner"
That is, when the solid portion is developed, the phenomenon that the density at the rear end of the image becomes high occurs. In order to prevent this phenomenon, the speed of the developing roller should be close to the speed of the photoconductor. That is, the number of rotations must be reduced by increasing the amount of adhesion on the developing roller.

On the other hand, the color characteristics of the color toner are lower than that of the black toner, and the color characteristics are smaller than that of the black toner.
An adhesion amount of m ^{2 on} the developing roller is required. Regarding the charge amount, in order to obtain a stable image, 5 to 20
A value of μC / g (preferably 10-15 μC / g) is desired.

As a method for solving these problems, the present inventors have previously described "a one-component developer composed of a non-magnetic toner externally supplemented with an auxiliary agent as needed on a rotatable developer carrier." The latent image carrier is supplied and carried on the surface of the carrier, and the latent image carrier and the developer carrier are opposed to each other. In a developing method of visualizing an image with the developer carried on a developer carrier, a plurality of minute particles are formed in the vicinity of the surface of the carrier by selectively holding electric charges on the surface of the developer carrier. An image forming method in which a closed electric field is formed, the charged toner is sucked by the closed electric field, the developer is adhered to and supported on the surface of the developer carrier, and the electrostatic latent image is visualized by the carried developer. Suggested.

According to such a method, a large number of minute closed electric fields (microfields) are formed in the vicinity of the surface of the developer carrying member, so that the electric field intensity can be significantly increased as compared with the related art.
This has many advantages such that a large amount of a sufficiently charged non-magnetic toner can be carried on a developer carrier and conveyed to a development area.

[Problems 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 carrying member, the developer carrying member has many members, for example, a toner supply member, a toner layer thickness regulating member, A photosensitive member or the like is in contact (during contact development), and the developer carrier rubs against the above members when the developing device is driven. Therefore, when the friction coefficient of the surface of the developer carrying member is large, the driving torque increases,
The burden on the developer carrier also increases. Therefore, there arises a problem that the durability such as abrasion resistance of the developer carrier is also reduced.

Accordingly, it is an object of the present invention to provide a developer carrying member capable of reducing frictional force with another contact member and having improved durability such as abrasion resistance in the above-described image forming method.

[Means for solving the problem]

As a result of intensive studies, the present inventors have found that a developer carrier having a friction coefficient of 0.3 or less on the surface of the developer carrier is suitable for the above object, and have completed the present invention.

That is, according to the present invention, a plurality of minute closed electric fields are formed in the vicinity of the surface of the developer carrier by selectively holding electric charges on the surface of the developer carrier. Supplying a non-magnetic one-component developer composed of a toner to which an auxiliary agent is externally added, if necessary, causing the developer to be carried on the surface of the developer carrier by the minute closed electric field; A developer carrier used in an image forming method for visualizing a latent image, in which a conductive portion and a dielectric portion are mixed in a small area on the surface, and the friction coefficient of the surface is 0.3 or less. A developer carrier is provided.

Further, according to the present invention, the developer carrying member has a dielectric part and a conductive part distributed on a surface, and charges the dielectric part to hold a charge. The developer is charged in an amount corresponding to the charge with a polarity opposite to that of the charge by electrostatic induction generated in accordance with the charge of the portion, and a charge arrangement is formed on the surface of the developer carrying member. There is provided the developer carrying member, wherein an electric field is formed.

According to the image forming method using the developer carrying member of the present invention, a large number of minute closed electric fields are formed near the surface of the developer carrying member. When the friction coefficient of the surface of the developer carrier is 0.3 or less, the driving torque can be reduced, and as a result, a large amount of non-magnetic toner, which is stable for a long period of time and is sufficiently charged, is carried on the developer carrier and is transferred to the developing area. It can be transported.

 Hereinafter, such an image forming method will be described.

FIG. 1 shows an outline of a typical developing device useful for carrying out this image forming method, focusing on a developer carrying portion. First
In the figure, the toner 60 contained in the toner tank 70 is
Is forcibly brought to a toner supply member (such as a sponge roller or a fur brush) 40 by a stirring blade (toner supply auxiliary member) 50, and the toner 60 is supplied to the toner supply member 40. On the other hand, the developer carrier (developing roller) 20 of the present invention after development is rotated in the direction of the arrow (for example, 400 rpm).
Then, it reaches a contact portion with the toner supply member 40. The toner supply member 40 rotates in the opposite direction to the developer carrier 20 (for example, 300 rpm)
Then, the developer carrier 20 and the toner 60 are charged, and the toner 60 adheres to the developer carrier 20. Further, the developer carrier 20
The toner adheres on the developer carrier 20 is rotated by the toner layer thickness regulating member (elastic blade) 30 to stabilize the charge while controlling the thickness, and reaches the developing region 80. In the development area 80, the latent image is developed by contact or non-contact development. Here, if necessary, a bias such as direct current, alternating current, direct current superimposed alternating current, or pulse 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 the developer carrier 20 of this type (electrode type) will be described. As an example of the developer carrier 20, as shown in FIG. 2, for example, a dielectric portion and a conductor portion are mixed on a surface thereof with a small area. As for the size of the area, assuming that the shape is circular, minute areas having a diameter of 10 to 500 μm are dispersed randomly or according to a certain rule. As the area ratio, the area of the conductive portion is preferably in the range of 20 to 60%.

The toner adhesion is as follows. First, the developer carrier 20 that has completed the development rotates in the direction of the arrow and comes into contact with the toner supply member 40. Here, the remaining toner in the non-image portion 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 of the developer carrier 20 and the toner by the previous development are fixed and initialized by friction. Next, the toner carried by the supply member 40 is charged by friction and adheres to the dielectric portion of the developer carrier 20 electrostatically. At this time, the polarity of the toner is opposite to the charge of the photosensitive member, and the dielectric portion of the developer carrier 20 has 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 having a large electric field gradient, so that the toner can be attached to multiple layers. In addition, since the attached toner has a closed electric field, it is strongly pulled toward the developer carrier 20 and is hardly separated.

The thickness of the toner layer is further controlled by the toner layer thickness regulating member 30, and reaches the developing region 80. Development area 80
The electric field between the developer carrier 20 and the electrostatic latent image carrier (photoreceptor) 10 causes the electrode effect to increase, and the toner on the developer carrier 20 tends to adhere to the electrostatic latent image carrier 10 An electric field is generated, and development is performed.

Next, the developer carrier of the present invention will be described. As a material used as a dielectric constituting the developer carrier,
Resins such as alkyd resin, chlorinated polyether, chlorinated polyethylene, epoxy resin, fluororesin, phenolic resin, polyamide, polycarbonate, polyethylene, methacrylic resin, polypropylene, polystyrene, polyurethane, polyvinyl chloride, polyvinylidene chloride, and silicone resin , Butadiene rubber, styrene-butadiene rubber, ethylene propylene rubber, chloroprene rubber, chlorinated polyethylene, epichlorohydrin rubber, nitrile rubber, acrylic rubber, silicone rubber, rubber such as fluorine rubber, and the like, from the viewpoint of heat resistance and moisture resistance. Thus, the use of a silicone resin or a fluorine resin is preferred.

On the other hand, as the conductor material, conventionally known Al, SUS, F
e, In addition to metals and ceramics such as Ni, and the like, conductive materials such as carbon and metal fine particles are added to the resins and rubbers exemplified as the dielectric material described above, and conductive materials are used. Can be.

In the present invention, among these, the coefficient of friction is 0.3
Materials are appropriately selected as described below. Further, the coefficient of friction can be adjusted by a filler such as a solid lubricant.

To produce the developer carrier of the present invention, for example,
(I) First, a metal roller whose surface is grooved by iris knurling or the like is manufactured (in this case, the V groove is 0.1 mm).
~ 0.5mm pitch, about 45 ° to roller longitudinal direction
(See FIG. 3 (a)], (ii) Next, spray a dielectric material on the metal surface processed by V-groove.
Coating by a method such as dipping, curing and drying under predetermined conditions (the applied thickness is such that the V-groove is completely buried) (see FIG. 3 (b)), (iii) Then, the roller surface is The conductive surface and the dielectric surface are cut with a small area by cutting or polishing, and the conductive area is 20 to
A method of cutting to 60% [see; FIG. 3 (c)] is employed.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to examples. Parts represent parts by weight.

Example 1 Dielectric material Fluorine resin 200 parts (trade name: Lumiflon LF200; manufactured by Asahi Glass Co., Ltd.) Coronate EH 20 parts Toluene 100 parts Xylene 100 parts Using a material having the above formulation, a developer carrier (developing roller) was formed in the following manner. Produced.

(I) Iris knurling on the metal roller surface
A V-groove was provided. The V-groove was formed at a pitch of 0.2 mm, and was machined at about 45 degrees with respect to the longitudinal direction of the roller.

(Ii) The above-mentioned dielectric material was coated on the roller surface subjected to V-groove processing, and cured and dried at 100 ° C. for 1 hour.
The coating thickness was such that the grooves were completely filled.

(Iii) The surface of the roller was polished so that the conductive surface and the dielectric surface were mixed in a small area, and the area of the conductive portion was set to 50%.

The coefficient of friction of the surface of the obtained developing roller was measured using the apparatus shown in FIG. 4, and was 0.20. In the above measurement, the developing roller was driven by a motor at a linear velocity of 10
It was rotated at a constant speed of 0 mm / min.

Example 2 A developing roller was manufactured in the same manner as in Example 1, except that the following formulation was used as the dielectric material. Dielectric material 100 parts urethane resin (trade name C-230U; Hirono Chemical Co., Ltd.) Hardener 30 parts (trade name PU-614; Hirono Chemical Co., Ltd.) Solid lubricant 30 parts (boron nitride BN) Solvent A 50 Part Solvent A has the following composition. Solvent A Toluene 39.0 parts Ethyl acetate 17.5 parts Butyl acetate 17.5 parts Ethyl cellosolve acetate 17.5 parts Methyl isobutyl ketone 3.9 parts Xylene 2.6 parts Cyclohexane 2.0 parts The friction coefficient of the obtained developing roller surface is measured by the same method as in Example 1. As a result, it was 0.21.

Comparative Example A developing roller was manufactured in the same manner as in Example 2, except that the solid lubricant in the dielectric material was not used. The coefficient of friction of the surface of the obtained developing roller was measured by the same method as in Example 1, and was found to be 0.35.

[Evaluation]

Amount of Toner Adhesion / Charge Amount Each developing roller is mounted on the developing device shown in FIG.
After 10 rotations of the developing roller, the toner adhesion amount and the toner charge amount on the roller were measured. Table 1 shows the results.

In the developing device, the toner thinning blade was made of urethane rubber, the toner supply roller was made of conductive urethane sponge, and the toner was charged with positively charged toner.

Abrasion of Developing Roller Using the same developing device and toner as described above, the amount of abrasion of each developing roller after idling for 200 hours was measured by measuring the diameter of the developing roller. The diameter of the roller was measured by a laser micro gauge (DT-4002A; manufactured by Iwatsu Electronics Co., Ltd.). Table 1 shows the results.

From the results shown in Table 1, it can be seen that by using the developing roller of the present invention, a sufficient amount of adhered toner and a sufficient amount of charged toner are obtained, and the abrasion of the developing roller is reduced, that is, the durability is improved.

〔The invention's effect〕

The developer carrying member of the present invention has a structure in which a conductive portion and a dielectric portion are mixed in a very small area on the surface thereof, and the surface has a friction coefficient of 0.3 or less. In addition, by selectively holding electric charges, a large number of minute closed electric fields are formed in the vicinity of the surface of the developer carrying member, and a non-consumer made of a toner externally supplemented with an auxiliary agent as necessary is formed on the developer carrying member. The present invention relates to an image forming method for supplying a magnetic one-component developer, causing the developer to be carried on the surface of a developer carrier by the minute closed electric field, and visualizing an electrostatic latent image with the carried developer. When the developer carrier is used, a large amount of a sufficiently charged non-magnetic one-component developer can be carried on the developer carrier and transported to the development area, and the frictional force with other contact members can be increased. Can be alleviated, and wear resistance, that is, durability is improved. As a result, high-density high-quality images can be stably obtained over a long period of time.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view centering on a developer carrying portion showing an example of a developing device in which a microfield electric field is formed on a developer carrying member useful for carrying out the present invention. Also,
FIG. 2 is a schematic cross-sectional view for explaining a state where a closed electric field is generated by a microfield on a developer carrier in the apparatus shown in FIG. 3 (a) to 3 (c) are schematic cross-sectional views showing surface states in the process of manufacturing the developer carrier of the present invention.
FIG. 4 is an explanatory view of an apparatus used for measuring a friction coefficient of a surface of a developer carrying member in Examples and Comparative Examples. 10 electrostatic latent image carrier, 20 developer carrier, 30 toner layer thickness regulating member, 40 toner supply member, 50 stirring blade, 60 toner, 70 toner tank , 80 ... Development area.

Continuation of the front page (56) References JP-A-55-62469 (JP, A) JP-A-60-54150 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 15 / 08

Claims (2)

(57) [Claims] An electric charge is selectively retained on the surface of a developer carrier to form a large number of micro-closed electric fields near the surface of the developer carrier. Accordingly, a non-magnetic-component developer composed of a toner externally added with an auxiliary agent is supplied, and the developer is carried on the surface of the developer carrying member by the minute closed electric field, and an electrostatic latent image is formed by the carried developer. A developer carrying member used for an image forming method for visualizing an image, in which a conductive portion and a dielectric portion are mixed in a very small area on the surface, and the friction coefficient of the surface is 0.3 or less. A developer carrier characterized by the following. 2. The developing device according to claim 1, wherein the developer carrying member has a dielectric portion and a conductive portion distributed on a surface thereof, and charges the dielectric portion to hold a charge. The charge is charged to an amount corresponding to the charge with a polarity opposite to that of the charge by electrostatic induction generated in response to the electric charge to form a charge arrangement on the surface of the developer carrying member, and a number of minute closed electric fields are formed between the charges. The developer carrier according to claim 1, wherein