JP2662677B2 - Developer carrier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method of supplying a developer to which a auxiliar is externally added to a rotationally driven developer carrier, if necessary. The electrostatic latent image formed on the latent image carrier is transferred to the developer carrier in a development area where the latent image carrier and the developer carrier are opposed to each other while the developer is carried on the surface and transported. The present invention relates to a developer carrying member used in an image forming method for visualizing an image with the carried developer.

[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 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.

Examples of the toner supply member include a conductive foam of 10 ² to 10 ⁶ Ω · cm (JP-A-60-229057), an elastic body with a skin layer (JP-A-60-229060), and a 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.

For black and white, the charge amount is important, and it is generally 10 to
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, there is a problem that when the solid portion is developed, a 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, in the color toner, the color characteristics are small in degree of coloring in comparison with black toner, and when you try to improve the "from toner rear", further more 0.8~1.2mg / cm ² compared to the black toner
Is required on the developing roller. Also, regarding the charge amount, in order to obtain a stable image, 5 to 20 μm
A value of C / g (preferably 10-15 μC / g) is desired.

As a method of solving these problems, the present inventors have previously described "supplying a developer to which a supplement is externally added to a rotationally driven developer carrier, if necessary, The electrostatic latent image formed on the latent image carrier is carried on the developer carrier in a developing region where the latent image carrier and the developer carrier are opposed to each other. In the developing method of forming a visible image using the developer, a plurality of minute closed electric fields are formed near the surface of the developer carrier by selectively holding electric charges on the surface of the developer carrier. An image forming method of sucking charged toner by an electric field, adhering and carrying a developer on the surface of a developer carrying member, and visualizing an electrostatic latent image with the carried developer was proposed.

According to this invention, since a large number of minute closed electric fields (microfields) are formed in the vicinity of the surface of the developer carrying member, the intensity of the electric field can be significantly increased as compared with the related art,
This has many advantages such that a large amount of a sufficiently charged developer can be carried on a developer carrier and transported 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 in the vicinity of the surface of the developer carrier as described above, the developer carrier has a triboelectric charge property due to a change in environment such as temperature and humidity. Therefore, there is a problem that the electric field intensity fluctuates and adversely affects the electric field strength of the microfield, and the amount of toner attached and the amount of charge become unstable.

In particular, since the dielectric portion constituting the developer carrier holds electric charge by frictional charging with other members, the selection of a material forming the dielectric portion is extremely important,
There has been a demand for the development of a material that does not affect the microfield effect, the amount of toner attached, and the amount of charge of the toner even when environmental fluctuations occur.

The present invention has been made in view of such circumstances, and in the above-described image forming method, even if an environment such as temperature or humidity changes, a stable microfield effect is exhibited and the toner adhesion amount is insufficient. An object of the present invention is to provide a developer carrying member that solves the problem of insufficient charge.

[Means for solving the problem]

The present inventors have conducted intensive studies and as a result, have found that a developer carrying member provided with a dielectric portion made of an insulating material having a specific volume resistance is suitable for the above object, and have completed the present invention. Reached.

That is, according to the present invention, at least the surface of the developer carrying member is configured such that the dielectric portion and the conductor portion are mixed in a small area, and the dielectric portion is charged,
Form a large number of minute electric fields near the surface of the developer carrier,
An image forming method of supplying a developer onto the developer carrying member, causing the developer to be carried on the surface of the developer carrying member by the minute closed electric field, and visualizing an electrostatic latent image by the carried developer. A developer carrier to be used, in which a dielectric portion and a conductor portion are distributed on the surface, and a material constituting the dielectric portion has a volume electric resistance at a temperature of 30 ° C. and a humidity of 90%.
Provided is a developer carrier characterized in that it has a resistivity of 10 ¹³ Ω · cm or more, and has a fluctuation difference from the volume electric resistance at a temperature of 10 ° C. and a humidity of 20% within 15 times.

The image forming method using the developer carrying member of the present invention has a configuration in which at least the surface of the developer carrying member is configured such that the dielectric portion and the conductor portion are mixed in a small area, and the dielectric portion is charged. As a result, a large number of small closed electric fields are formed near the surface of the developer carrying member, so that the electric field strength can be significantly increased as compared with the conventional case, and the electric field strength varies even when the environment changes. In addition, since the amount of toner attached and the amount of charge do not change due to changes in the environment, a large amount of sufficiently charged developer can be uniformly carried on the developer carrier and conveyed to the development area.

 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
Is rotated, and the toner adhered on the developer carrying member 20 is stabilized in charge while being controlled in thickness by the toner layer thickness regulating member (elastic blade) 30, and reaches the developing region 80. 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 insulating 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 toner layer thickness of the toner layer is further controlled by the toner layer thickness regulating member 30, so that the toner in the developing area 80 becomes an electric field that easily adheres to the photoreceptor, and development is performed.

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

As described above, at least the surface of the developer carrying member of the present invention is such that the dielectric portion and the conductive portion are mixed in a small area, and a large number of particles are provided near the surface by charging the dielectric portion. A small closed electric field is formed, and the material constituting the dielectric part has a volume resistance of 0 ^{13 at a} temperature of 30 ° C and a humidity of 90%.
It is Ω · cm or more, and the fluctuation difference from the volume resistance at a temperature of 10 ° C. and a humidity of 20% is within 15 times.

The first characteristic of the dielectric part forming material used in the present invention is temperature.
The volume resistance at 30 ° C. and 90% humidity is 10 ¹³ Ω · cm or more, preferably 10 ¹⁴ Ω · cm or more. If the volume resistance under the above conditions is less than 10 ¹³ Ω · cm, the triboelectric charging property is largely changed by the environmental change, which is not desirable.

The second characteristic of the dielectric part forming material used in the present invention is that the volume resistance at a temperature of 30 ° C. and a humidity of 90% and the temperature of 10 ° C.
The difference between the volume resistivity at 20% and that at 20% is within 15 times.

In the present invention, by selecting a material having a small variation range of the volume resistance value as a constituent material of the dielectric part even by the environmental change, the microfield effect is sufficiently exhibited even when the environment changes, Further, a developer carrying member capable of sufficiently carrying a toner having an appropriate charge amount can be obtained.

If a material having a differential volume resistance value exceeding the above range is used, the microfield effect changes due to environmental fluctuations, so that not only the electric field intensity becomes unstable, but also the charge amount and adhesion amount of the toner. As a result, the function and effect of the present invention cannot be obtained.

Specific examples of the dielectric portion forming material used in the present invention include organic polymers such as silicone-based resin (rubber) and fluorine-based resin (rubber) or modified products thereof.

As the silicone resin (rubber), dimethylsiloxane, methylvinylsiloxane, phenyl-modified siloxane, fluorine-modified siloxane, epoxy-modified siloxane,
Acrylic modified siloxane, carboxyl modified siloxane, alcohol modified siloxane, polyester modified siloxane, and the like.

Examples of the fluorine resin (rubber) include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoropropylvinyl ether copolymer (PFA), and polychlorotrifluoro. Ethylene (PCTFE),
Ethylene-tetrafluoroethylene copolymer (ETFE),
Ethylene-chlorotrifluoroethylene copolymer (ECTF
E), polyvinylidene fluoride (PVdF), polyvinyl fluoride (PVF), vinylidene fluoride-based fluororubber, copolymer of a fluorine-containing monomer and a crosslinking group-containing hydrocarbon-based monomer, or epoxy of these fluorine-based polymer particles Examples thereof include those dispersed in a binder such as a resin and a silicone polymer.

As a conductive material forming the conductor portion, 10 ¹² Ωcm
Or less, preferably 10 ⁸ Ω · cm or less.
Specific examples thereof include those obtained by adding a conductive filler to organic polymers in addition to metals such as Al, SUS, Fe, and Ni, and ceramics. In this case, the following are mentioned as organic polymers.

Vinyl resins such as polyvinyl chloride, polyvinyl butyral, polyvinyl alcohol, polyvinylidene chloride, polyvinyl acetate, and polyvinyl formal; polystyrene resins such as polystyrene, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer; polyethylene , Polyethylene resins such as ethylene-vinyl acetate copolymer; acrylic resins such as polymethyl methacrylate, polymethyl methacrylate-styrene copolymer; polyacetal, polyamide, cellulose, polycarbonate, phenoxy resin, polyester, fluororesin, polyurethane, Phenolic resin,
Resin materials such as urea resin, melamine resin, epoxy resin, unsaturated polyester resin, silicone resin; natural rubber,
Rubber such as 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, polysulfide rubber, silicone rubber, fluorine rubber, etc. Materials and so on.

Examples of the conductive filler 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. And electroless plating products obtained by plating on titanium oxide, mica and the like; graphite, metal fibers, carbon fibers, and the like.

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

In order to produce the developer carrying member of the present invention, for example, first, a metal roller having a groove formed on the surface thereof by iris knurling or the like is produced (in this case, the groove has a pitch of 0.1 to 0.5 mm, and the groove is formed in the longitudinal direction of the roller). (Refer to FIG. 4 (a)). Then, the grooved metal surface is coated with, for example, a fluororesin (Lumiflon LF200; manufactured by Asahi Glass Co., Ltd.), and heated at 100 ° C. For about 30 minutes (see FIG. 4 (b)). Then, the conductive surface is mixed with a small area by cutting or polishing the roller surface. , Conductive part surface is 20 ~ 60%
(See FIG. 4 (c)).

〔Example〕

 Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1 Dielectric Part Material Deoxime Condensation Reaction Type Silicone Resin (trade name: SR2411: Toray Silicone Co., Ltd.) A developer carrying member (developing roller) was produced using the above-mentioned formulation material in the following manner.

(I) A V-groove was provided on the surface of the SUS roller by iris knurling. The V-groove was formed at a pitch of 0.3 mm, and was machined at about 45 degrees with respect to the longitudinal direction of the roller.

(Ii) The surface of the roller subjected to the V-groove processing was coated with the above dielectric material. 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 very small area, and the area of the conductive portion was set to 50%.

Example 2 A developer carrying member was prepared in the same manner as in Example 1 except that the dielectric portion material was changed to the following.

Derivative part material Epoxy-modified silicone resin (trade name: SR2115: Toray Silicone Co., Ltd.) Comparative Example 1 A developer carrier was prepared in the same manner as in Example 1, except that the dielectric part material was changed to the following. .

Derivative part material Acrylic urethane resin (trade name # 8500: Asia Industries Co., Ltd.) Comparative Example 2 A developer carrying member was prepared in the same manner as in Example 1 except that the dielectric part material was changed to the following. .

Derivative part material Epoxy resin (trade name: Sumicon EME-210F: Sumitomo Bakelite Co., Ltd.) Examples 1 to 3 and Comparative Example 1 obtained as described above
The developer carrying members of Nos. 1 to 2 were mounted on a developing device as shown in FIG. 1, and the charge amount of the toner and the amount of toner adhesion at 30 ° C./90% and 10 ° C./20% were measured. Table 1 shows the results.

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

Table 1 shows that 30 ° C / 90% and 10 ° C / 90%
The volume resistance at 20% is also shown.

The volume resistance value was measured by spray coating on a PET on which a dielectric material was deposited to a thickness of 20 μm so as to have a film thickness of 20 μm, and then using a 4329A HIGH RESISTACE METER (manufactured by YHP). Environmental conditions 30 ° C / 9 at DC100V
This is the value after standing at 0%, 10 ° C / 20% for 24 hours.

[Effect of the Invention] The developer carrying member of the present invention has a configuration in which the dielectric portion is formed of the material having the specific volume resistance as described above, so that even if the environment such as temperature or humidity changes, The microfield effect can be sufficiently exhibited, and the charge amount and the adhesion amount of the toner can be maintained at appropriate values.

Therefore, at least the surface of the developer carrying member is configured such that the dielectric portion and the conductive portion are mixed in a very small area, and by charging the dielectric portion, a large number of minute particles are formed near the surface of the developer carrying member. A closed electric field is formed, a developer to which an auxiliary agent is externally added as necessary is supplied onto the developer carrying member, and the developer is carried on the surface of the developer carrying member by the minute closed electric field. When the developer carrying member of the present invention is used in an image forming method for visualizing an electrostatic latent image by a developer, a large amount of a non-magnetic one-component developer sufficiently charged is carried on the developer carrying member. As a result, toner filming does not occur, and a high-density high-quality image can be obtained.

[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. 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.

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-2-61652 (JP, A) JP-A-1-102485 (JP, A) JP-A-2-18580 (JP, A) JP-A-2-162 33166 (JP, A) Actually open 1-149657 (JP, U)

Claims (1)

(57) [Claims] At least the surface of a developer carrier is constituted so that a dielectric part and a conductor part are mixed in a small area,
By charging the dielectric portion, a number of minute closed electric fields are formed in the vicinity of the surface of the developer carrier, and a non-magnetic layer made of a toner to which an auxiliary agent is externally added as necessary is provided on the developer carrier. A developer carrier used in an image forming method for supplying a component developer, causing the developer to be carried on the surface of the developer carrier by the minute closed electric field, and visualizing an electrostatic latent image with the carried developer; The dielectric part and the conductor part are mixed in a small area at least on the surface thereof, and the material constituting the dielectric part has a volume resistance of 10 ¹³ Ω · cm at a temperature of 30 ° C. and a humidity of 90%.
A developer carrying member having a volume difference at a temperature of 10 ° C. and a humidity of 20% within 15 times.