JPH07160113A - Toner carrier and its production - Google Patents

Abstract

PURPOSE:To obtain a toner carrier capable of generating a minute closed- electric-field at the time of development which is produced at a low cost by providing a closed-electric field generation layer on the surface of a roller-like conductive substrate, and making the closed-electric-field generation layer in such a way that dielectric parts, made of fine lumps of polar rubber, are dispersed into a conductive part made of conductively-processed resin. CONSTITUTION:The toner carrier 5 is composed of the closed-electric-field generation layer 20, and the conductive substrate 10 on the surface of which the generation layer 20 is layer-built. The conductive substrate 10 is in the form of a roller and made of a conductor such as aluminum. The closed-electric- field generation layer 20 generates a minute closed-electric-field in the vicinity of the surface of the toner carrier 5 and is made by dispersing the dielectric parts 11, made of the fine lumps of polar rubber, into the conductive part 12 made of the conductively-processed resin. In the surface of the toner carrier 5, the dielectric parts 11, electrified to the polarity opposite to the polarity of the electrification of the toner, and the conductive part 12 mixedly exist, therefore a large potential-difference is made between the surfaces of both the parts 11 and 12 and the minute closed-electric field is generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner carrier used in a developing device of an image forming apparatus and a manufacturing method thereof.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electronic copying machine, a laser printer or a plain paper facsimile, a powdery toner in which an auxiliary agent is externally added to a toner carrier which is driven to rotate, that is, one component. An electrostatic latent image formed on the latent image carrier in the developing area where the latent image carrier and the toner carrier face each other by supplying a system developer and carrying the toner carried on the surface of the toner carrier. It is well known in the art to use a developing device that visualizes a toner image with the toner carried and carried by the toner carrier.

This type of developing device has the advantages that the maintenance of the device can be simplified and the structure of the device can be made smaller than the developing device using a two-component developer having toner and carrier. .

In a developing device using a one-component type developer, for example, the toner is predetermined by friction between the toner supply member for supplying the toner to the toner carrier and the toner, friction between the toner and the toner carrier, and the like. Triboelectrically charged in polarity,
Such toner is used to visualize an electrostatic latent image. At this time, in order to form a high-quality visible image with a predetermined density, it is necessary to convey a sufficiently charged toner to a necessary extent to a developing area.

There are two types of toner: magnetic toner in which magnetic powder is kneaded into each toner particle itself, and non-magnetic toner containing no magnetic substance. In a developing device using magnetic toner, the toner carrier is used. Since the toner can be carried on the carrier by utilizing the magnetic force of the magnet provided therein, a large amount of toner can be transported to the developing area, and the above-mentioned requirements can be satisfied. However, since it is necessary to internally install a magnet on the toner carrier, there is an unavoidable drawback that the structure is complicated. on the other hand,
When a non-magnetic toner is used, it cannot be carried on the toner carrier by magnetic force, so that it is difficult to convey a large amount of toner to the developing area, and it is particularly difficult to satisfy the above requirements.

Therefore, the applicant of the present invention has proposed a developing device which can carry a large amount of toner on a toner carrier by utilizing a minute closed electric field and can convey a required amount of toner to a developing area. In this developing device, as disclosed in, for example, JP-A-3-274581 and JP-A-3-288873, a dielectric portion and a conductive portion are mixedly exposed on the surface of a toner carrier to expose the dielectric portion. By charging to a specified polarity,
A minute closed electric field is formed near the surface of the toner carrier, and a sufficient amount of toner is carried and carried to the developing area by the action of the electric field.

By using such a toner carrier, a required amount of toner, whether magnetic toner or non-magnetic toner, can be conveyed to the developing area, and a high quality visible image can be obtained. Moreover, it is not necessary to provide a magnet inside the toner carrier, and the structure of the developing device can be simplified.

The present applicant has also proposed a number of such toner carriers and methods for manufacturing the same. As an example of the manufacturing method, a lattice-shaped concave portion is formed on the surface of a roller-shaped conductive substrate by square groove knurling, and a resin material as a dielectric is applied around the conductive substrate so that the concave portion is filled. After the resin is coated and dried and solidified, the resin coating layer is cut or polished to expose a part of the conductive substrate, and the exposed conductive portion of the conductive substrate and the dielectric of the coating resin are exposed. This is a method of mixing parts on the surface.

However, each of the conventionally proposed methods for manufacturing a toner carrier requires a number of complicated steps, which inevitably increases the manufacturing cost of the toner carrier.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a low-cost toner carrier capable of forming a minute closed electric field and a method for producing the same.

[0011]

In order to achieve the above-mentioned object, the present invention provides a closed electric field forming layer in which minute clusters of polar rubber are dispersed in a resin which has been subjected to conductive treatment, and a closed electric field forming layer. A toner carrier having a conductive substrate laminated on the surface is proposed.

[0012] Similarly, in order to achieve the above-mentioned object, the present invention obtains a solution of a polar rubber, and mixes and conducts a conductive-treated resin in the solution to obtain a coating solution. Is applied to the surface of a conductive base material to form a closed electric field forming layer in which fine particles of polar rubber are dispersed in a resin that has been subjected to a conductive treatment. suggest.

At this time, it is advantageous to conduct a conductive treatment on the resin by dispersing carbon in the resin.

[0014]

Embodiments of the present invention will now be described in detail with reference to the drawings.

First, in order to understand the present invention, a schematic configuration of a developing device using the toner carrier according to the present invention and an example of its action will be clarified.

In FIG. 1, a drum-shaped photoconductor 1 which is an example of a latent image carrier is rotationally driven in the direction of arrow A, and a developing device 2 is provided opposite to this. An auxiliary agent is mixed into the toner container 3 of the developing device 2 if necessary (external addition).
The powdered toner 4 thus prepared, that is, the one-component developer is stored. In the example of FIG. 1, a non-magnetic toner is used as the toner, and its volume resistivity is, for example, 10 ⁷ to 1
It is assumed to be about 0 ¹² Ωcm. A belt-shaped latent image carrier may be used.

On the front and rear side plates of the toner container 3, a developing roller 5 is supported with a part thereof exposed from the opening of the container, and the roller 5 faces the photoconductor 1 in a counterclockwise direction (in the figure). It is driven to rotate in the Y direction). Developing roller 5
Represents one configuration example of the toner carrier, and an endless belt-shaped toner carrier can be used instead of the roller 5.

A toner supply roller 6, which is an example of a toner supply member, is supported on the front and rear side plates of the toner container 3, and the roller 6 is driven to rotate counterclockwise, for example, while being in contact with the developing roller 5.

The toner 4 in the toner container 3 is carried to a toner supply roller 6 while being agitated by an agitator 7 which rotates clockwise, and then supplied to a developing roller 5 by this roller 6. During this supply, the toner is triboelectrically charged to a predetermined polarity, electrostatically adheres to the peripheral surface of the developing roller 5, and is carried on the developing roller 5. The situation at this time will be described in detail later.

The toner supplied and carried on the peripheral surface of the developing roller 5 as described above is conveyed by the rotation of the roller 5 and is leveled by the doctor blade 8 which is an example of a toner layer thickness regulating member to regulate the thickness. To be done. Instead of the blade 8, a toner layer thickness regulating member including, for example, a roller or a belt can be used.

Next, the toner is conveyed to the developing area 9 where the photoconductor 1 and the developing roller 5 face each other, and the toner on the developing roller 5 is electrostatically applied to the electrostatic latent image formed on the photoconductor 1. Then, the latent image is visualized as a toner image. As described above, the developing roller 5 is rotatably driven to carry and convey the toner for visualizing the electrostatic latent image.

The toner that has passed through the developing area 9 without being used for development is returned to the toner supply roller 6 while being carried by the developing roller 5. Further, the visible image formed on the photoconductor 1 is transferred to a transfer paper (not shown) and fixed on the transfer paper by a fixing device.

In the developing device 2 shown here, the developing roller 5 has a closed electric field forming layer 20 as shown in FIG.
And the conductive substrate 10 having the forming layer 20 laminated on the surface. In this example, the conductive substrate 10 is
It is formed in a roller shape and is made of a conductor such as aluminum, iron or iron alloy. Closed electric field forming layer 20
Is for forming a minute closed electric field field in the vicinity of the surface of the developing roller 5, as will be described later, and is schematically shown in FIG. 2 in the conductive portion 12 made of a conductive-treated resin. It is formed by dispersing the dielectric portion 11 made of a minute lump of polar rubber. In this example, hydrin rubber is used as the polar rubber that constitutes the dielectric portion 11, but polar rubber such as NBR (acrylic nitrile budadien rubber) or chloroprene can also be used. Further, the resin forming the conductive portion 12 is subjected to conductive treatment by a conductor such as carbon dispersed in the resin. In this way, the dielectric part 11 and the conductive part 1 composed of the minute spherical lumps of polar rubber.
2 and 2 are mixedly exposed on the surface of the developing roller 5 in an irregular state as shown in FIG.

Incidentally, FIG. 3 shows a state when the surface of the developing roller is observed by using a microscope as described later, and the size of each dielectric portion 11 is roughly from the scale shown by 50 μm in this figure. I can understand that. Further, in FIG. 3, the dielectric portion 11 is shaded so that the dielectric portion 11 and the conductive portion 12 can be easily distinguished from each other.

On the other hand, as shown in FIGS. 1 and 2, the toner supply roller 6 in contact with the developing roller 5 comes into contact with the toner 4 and frictionally charges the toner 4 to a predetermined polarity, in this example, a negative polarity, Further, it is made of a material that comes into contact with the dielectric portion 11 on the surface of the developing roller 5 and frictionally charges the dielectric portion 11 with a polarity opposite to the charging polarity of the toner (plus in this example). Figure 1
The toner supply roller 6 illustrated in FIG. 2 includes a conductor core member 14 and a cylindrical foam body 15 laminated around the core member 14, and the foam body 15 presses against the developing roller 5 while elastically deforming. Instead of the foam 15, a fur brush or the like known per se may be used.

As described above with reference to FIG. 1, the portion of the developing roller that has passed through the developing area 9 is the toner supply roller 6.
The toner supply roller 6 moves to a position where it comes into contact with the roller 6, and the toner not carried by the development carried on the developing roller 5 is mechanically and electrically scraped off by the toner supply roller 6.

At the same time, the dielectric portion 11 on the surface of the developing roller is
The toner is brought into contact with the toner supply roller 6, and the friction thereof charges the toner to a positive polarity opposite to the charging polarity of the toner, and the electric charge is accumulated and held in the dielectric portion 11. At that time, the development area 9
Even if an electrostatic afterimage due to the influence of the electrostatic latent image on the photoconductor 1 remains on the dielectric part 11 on the peripheral surface of the developing roller that has passed through the dielectric part 11 due to friction with the toner supply roller 6. It is possible to initialize the developing roller 5 by charging up to the state, making the amount of charge uniform, eliminating residual images.

On the other hand, the toner 4 carried to the developing roller 5 while being in contact with the peripheral surface of the toner supply roller 6 is schematically shown in an enlarged scale in FIG. The toner is triboelectrically charged to a negative polarity and supplied to the developing roller 5. At this time, the toner 4 can be further triboelectrically charged by friction with the dielectric portion 11 on the surface of the developing roller.

On the surface of the developing roller, a dielectric portion 11 having a polarity opposite to the charging polarity of the toner and a conductive portion 12 are mixed,
Moreover, since the conductive portion 12 is grounded via the conductive substrate 10 electrically connected to the conductive portion 12, or is connected to the bias power source (not shown) and is applied with the bias voltage, the developing roller is formed. On the surface of No. 5, a charge pattern corresponding to the surface shape of the dielectric part 11 is formed.

For this reason, as shown in FIG.
A large potential difference is created between the surface of the dielectric part 11 and the surface of the dielectric part 11, and a closed electric field is formed between them. That is, in the vicinity of the surface of the developing roller 5, a minute closed electric field (microfield) is formed by the above charge pattern. More specifically, when the lines of electric force representing the state of the electric field are considered, lines of electric force E are formed in the space near the surface of the developing roller 5 as shown by a large number of arc-shaped lines in FIG. ,
The line of electric force exits from the developing roller 5 and returns to the same developing roller 5. In this way, the closed electric field forming layer 20 forms an electric field having a large electric field gradient in the vicinity of the surface of the developing roller.

Since the surface of the dielectric portion 11 is adjacent to the surface of the conductive portion 12 in a minute area, the strength of each minute closed electric field becomes very strong due to the so-called edge effect or fringing effect. Due to the closed electric field, the toner charged to the opposite polarity to the dielectric portion 11 is strongly attracted to the surface of the dielectric portion 11 by the Coulomb force, and is held on the developing roller 5 in a state in which it is difficult to separate a large amount. At this time, the toner is strongly triboelectrically charged due to the friction between the toner supply roller 6 and the developing roller 5, and is held on the surface of the developing roller 5 by the action of a strong minute closed electric field. A large amount of toner having a toner is carried.

In addition, when the toner carried on the developing roller 5 is elastically pressed by the doctor blade 8 and the layer thickness is regulated, the sufficiently charged toner is strongly held on the surface of the developing roller 5 by the minute closed electric field. However, even if toner having a small charge amount is mixed with such toner, it is removed by the contact pressure with the doctor blade 8, and eventually, only the toner having a large charge amount enters the developing area 9 in a large amount. The electrostatic latent image is conveyed and visualized as described above. It is also possible to apply a voltage to the doctor blade 8 to inject an electric charge into the toner.

In this way, even if a non-magnetic toner is used as the toner 4, it can be sufficiently charged and conveyed to the developing area 9 in a large amount, so that the density of the visible image can be prevented from being insufficient and a high quality image can be obtained. A visual image can be formed.

It is also possible to charge the dielectric portion 11 of the developing roller to the same polarity as the toner 4 and to electrostatically attach a large amount of the toner to the surface of the conductive portion 12.

When a developing roller that does not utilize a minute closed electric field is used, the amount of toner that can be conveyed to the developing area is insufficient. To compensate for this, the linear velocity of the developing roller surface is set to 3 times the linear velocity of the photosensitive member surface. It has been conventionally performed to increase the rotation speed of the developing roller to about four times. However, if the rotation speed of the developing roller is increased in this way, a jitter is caused due to an increase in the torque load of the developing roller, and a linear velocity difference between the photoconductor and the developing roller is caused. Due to the phenomenon, a phenomenon that the toner trails toward the trailing edge occurs in the visible image, and the image quality thereof deteriorates. By using the developing roller 5 shown in FIGS. 1 to 3, even if the surface linear velocity of the developing roller 5 is set to be the same as the surface linear velocity of the photoconductor 1, it is possible to prevent a decrease in image density of a visible image, and It is also possible to prevent the occurrence of the phenomenon of toner and the trailing edge of the toner. However,
Naturally, the developing operation may be executed by setting the surface linear velocity of the developing roller 5 shown in FIGS. 1 to 3 higher than the surface linear velocity of the photoconductor 1.

Next, an example of a method of manufacturing the developing roller 5 as described above will be described. The manufacturing method illustrated here is an example of the result of an experiment conducted by the present inventor.

First, hydrin rubber, which is an example of polar rubber, is plasticized by using two roll kneaders, and the obtained rubber pound is cut into chips of about 2 × 2 mm by using a pelletizer. The chip is put into a solvent and stirred with a stirrer for about 4 hours to obtain a polar rubber solution.

The roll kneader used in this experiment was an 8-inch roll manufactured by Nishimura Machinery Co., Ltd. The rotation speed of the front roll was 18 rpm and the rotation speed of the rear roll was 20 rpm. U-210 manufactured by Horai Co., Ltd. was used as a pelletizer. As the hydrin rubber, 30 g of trade name Epichromer H manufactured by Daiso Co. was used, and as the solvent thereof, 300 g of butyl acetate was used.

A polar rubber solution is obtained as described above, and a predetermined amount of conductive liquid resin is mixed and stirred in the solution to obtain a coating liquid. In this experiment, 10 g of carbon made of Printex (trade name, Furnace Black manufactured by Degussa, Germany) was dispersed in a dielectric resin containing 100 g of Lumiflon LF-601C (trade name) as the main agent (fluorine resin paint) and 20 g of the same curing agent to make conductive A treated liquid resin was produced and used. In this way, by dispersing carbon in the resin, the resin can be easily subjected to conductive treatment.

As the carbon, in addition to those exemplified above, for example, channel black, acetylene black,
Even lamp black can be used by adjusting the amount of addition.

Further, as the dielectric resin, in addition to the above-mentioned ones, alkyd, melamine, silicone, urethane, unsaturated polyester, acrylic, vinyl acetate, and other generally insulative resins which can be made into paints can be used.
This can be used after being subjected to a conductive treatment.

Further, as a solvent, ethyl acetate, xylene, toluene, ethylene glycol monoethyl ether acetate, tetrahydrofuran, cyclohexane,
Any one can be used as long as it is a good solvent for hydrin rubber such as methyl ethyl ketone, methyl isobutyl ketone, dipentene, and acetone.

In addition to obtaining the coating solution prepared as described above, a conductive substrate 10 as a base of the developing roller is prepared as shown in FIG. 5, and the above coating is applied to the surface of the substrate 10 as follows. The liquid is applied and dried to obtain the developing roller 5.

In this experiment, a conductive substrate 10 made of aluminum was used, and the surface thereof was coated with the coating liquid by a spray gun. The spray gun used is ST-6R (nozzle caliber φ0.5 mm) manufactured by Fuwa Seiki Co., Ltd., and the spray gun is placed 73 mm away from the base 10 while rotating the conductive base 10 at a rotation speed of 400 rpm. The nozzle is arranged and the spray gun is swung at a speed of 40 mm per second, and the coating liquid atomized from the nozzle is applied to the surface of the conductive substrate 10. The atomization air flow rate at this time is 2
The discharge rate was 0 liter / minute, the discharge rate was 4 cc / minute, and the coating liquid was applied by reciprocating the spray gun 25 times in the axial direction of the conductive substrate 10.

Next, the coating liquid applied on the surface of the conductive substrate 10 was dried in an atmosphere of 100 ° C. for 60 minutes to cure the above-mentioned curing agent. In this way, as shown in FIGS. 1 to 3, the conductive portion 1 made of the conductive-treated resin is used.
The developing roller 5 is formed by forming on the conductive substrate 10 a closed electric field forming layer 20 in which a dielectric portion 11 made of a minute mass of polar rubber (hydrin rubber) is dispersed.

Although the surface of the closed electric field forming layer 20 after curing can be smoothed by polishing or the like, the above-described method can provide a developing roller having a smooth surface without polishing.

As described above, FIG. 3 shows a state in which the surface of the completed developing roller 5 is observed by using a phase contrast microscope. From this figure, in the conductive portion 12 of conductive fluororesin. It can be well understood that the dielectric part 11 in the form of a microsphere made of hydrin rubber is mixed in. By dispersing the minute lump-shaped dielectric portion 11 in the conductive portion 12 in this way, a minute closed electric field can be formed in the vicinity of the surface of the developing roller during the developing operation, and a required amount of toner can be conveyed to the developing area.

By producing the developing roller 5 by using the hydrin rubber solution as described above, it is possible to disperse the minute lumps of hydrin rubber in the resin which has been subjected to the conductive treatment. The reason is considered as follows.

Since hydrin rubber has polar groups such as Cl group and ethylene oxide group in the molecule, it is known that it has a strong cohesive force and has rubber properties comparable to natural rubber and rich in elasticity. There is. Such a hydrin rubber is dissolved in a solvent to obtain a rubber solution, but when the hydrin rubber is dissolved in the solvent, the rubber is stably dispersed and neither aggregation nor precipitation occurs. However, depending on the dilution ratio of the solvent, or depending on the solvent used, the solution is stirred with a stirrer or the like, mixed, and then allowed to stand,
In the solvent, the rubber separates into microspheres and begins to aggregate. This tendency is more remarkable as the solvent dilution rate is lower, and xylene, toluene, hydrin rubber such as methyl isobutyl ketone is more prone than when a solvent having high solubility of hydrin rubber such as cyclohexanone, ethyl acetate, cellosolve acetate and tetrahydrofuran is used. It appears more markedly when a solvent having low solubility of is used.

Immediately after obtaining such a hydrin gum solution by stirring and mixing with a stirrer, or immediately after allowing it to stand, the resin which has been subjected to the electroconductivity treatment as described above is put into this solution and mixed. The coating liquid is stirred to obtain a coating liquid, which is sprayed onto the surface of the conductive substrate 10 to be applied. When the coating liquid adheres to the conductive substrate 10, most of the solvent has already evaporated. . Also, after the adhesion, drying and evaporation occur, and in the process from application to drying, the hydrin rubber aggregates,
Separation proceeds.

As described above, the self-aggregation of hydrin rubber causes the dielectric part 11 made of hydrin rubber in the form of microspheres to appear in an island shape in the conductive part 12 of conductive fluororesin. It is inferred that.

This is a polar rubber other than hydrin rubber,
This phenomenon also occurs when NBR, chloroprene, or the like is used, and even if a developing roller is manufactured in the same manner as described above using such a polar rubber, the developing roller 5 shown in FIGS. Similarly to, it is possible to obtain a developing roller having a closed electric field forming layer in which fine particles of NBR or chloroprene are dispersed in a conductive-treated resin.

In the above-mentioned experimental example, the coating liquid was applied to the surface of the conductive substrate 10 by spraying. However, in this way, when the coating liquid becomes a mist, the solvent thereof flies, and at that time. Aggregation of hydrin rubber occurs at. Therefore, the dielectric portion 11 on the surface of the completed developing roller is replaced with the conductive portion 12.
It can be finely dispersed inside, and the minute closed electric field can be increased during the developing operation. On the other hand, even if the coating liquid is applied to the surface of the conductive substrate 10 by dipping the conductive substrate 10 in the coating liquid or coating the surface of the substrate 10 with the coating liquid, The developing roller 5 having the predetermined function can be obtained.

As described above, the developing roller can be easily manufactured with a small number of steps, and the manufacturing cost of the developing roller can be significantly reduced as compared with the conventional case.

The present invention can also be applied to a belt-shaped toner carrier and a manufacturing method thereof. The difference between the toner carrier and the above-mentioned developing roller in structure is that the conductive substrate is a conductor. It's just a belt or a seat. Using such a conductive substrate, a belt-shaped toner carrier can be manufactured in the same manner as described above.

Further, when the toner carrier manufactured according to the present invention is adopted in the developing device using the non-magnetic toner as illustrated in FIG. 1, it is possible to form a vivid color image such as full-color or multi-color. It will be possible,
It can be advantageously used in a developing device using a one-component developer composed of a magnetic toner to which an auxiliary agent is externally added if necessary. At this time, since it is not necessary to provide a magnet inside the toner carrier, there is an advantage that the structure of the apparatus can be simplified.

[0057]

According to the structure of the first aspect, it is possible to provide a low-cost toner carrier capable of forming a minute closed electric field during the developing operation.

According to the second aspect of the invention, it is possible to easily manufacture the toner carrier capable of forming the minute closed electric field during the developing operation with a small number of steps.

According to the third aspect of the invention, the resin can be electrically conductively processed at low cost.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a developing device.

FIG. 2 is an explanatory diagram schematically showing a dielectric portion of a developing roller and toner particles in an enlarged manner compared to other portions.

FIG. 3 is an enlarged plan view of the surface of the developing roller.

FIG. 4 is an explanatory diagram showing electric lines of force of a minute closed electric field formed near the surface of the developing roller.

FIG. 5 is a perspective view showing a roller-shaped conductive substrate.

[Explanation of symbols]

 10 Conductive Substrate 20 Closed Electric Field Forming Layer

Claims (3)

[Claims] 1. A closed electric field forming layer in which minute lumps of polar rubber are dispersed in a conductive-treated resin, and a conductive substrate having the closed electric field forming layer laminated on the surface thereof. And a toner carrier. 2. A polar rubber solution is obtained, and a conductively treated resin is mixed and stirred in the solution to obtain a coating solution.
By applying the coating liquid to the surface of the conductive substrate, a closed electric field forming layer in which minute lumps of polar rubber are dispersed in the conductive-treated resin is formed on the surface of the conductive substrate. And a method for manufacturing a toner carrier. 3. The method for producing a toner carrier according to claim 2, wherein the resin is subjected to a conductive treatment by dispersing carbon in the resin.