JP3147922B2 - Developing method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing method and an apparatus used in an image forming apparatus such as an electrophotographic copying machine, a printer or a facsimile, and more particularly to a developing method in which a developer is carried on a developer carrier. The present invention relates to a developing method and an apparatus for performing development by transporting the developer to a developing unit facing an electrostatic latent image carrier.

[0002]

2. Description of the Related Art In this type of developing method, a developer carrying member having a thin layer of developer formed on its surface and an electrostatic latent image carrying member are opposed to each other in a developing section. 2. Description of the Related Art There is known an image forming apparatus which forms an electric field capable of transferring a developer on a body to an electrostatic latent image carrier and develops the electrostatic latent image on the electrostatic latent image carrier. In this developing method, there is a threshold for transferring the developer from the developer carrier to the electrostatic latent image carrier, and the developer may adhere to an image portion having a surface potential exceeding this threshold. On the other hand, since the developer hardly adheres to an image portion having a surface potential equal to or lower than the threshold value, there is a problem that an image having a so-called γ and poor gradation is formed. However, it is known that this problem can be solved by forming an alternating electric field having a relatively low frequency in the developing section (for example, see Japanese Patent Publication No. 64-1013).

However, simply applying a low-frequency alternating electric field to the developing section lowers the image density if the condition of the alternating electric field is such that the gradation property can be improved. However, there is a problem that the line portion of the image becomes thicker when the value is increased. Further, in this type of developing method, particularly when a non-magnetic toner is used as a developer, when the reciprocating motion of the non-magnetic toner is caused, the toner is turned into a powder cloud and the image density is significantly reduced. and (for example, see Japanese Patent Tokuoyake flat 2-14706). In recent years, along with diversification of output information of an image created by an image forming apparatus, higher image quality than ever has been desired. Accordingly, the present applicant has previously described, in a developing device that carries a developer on a developer carrier and performs development in a developing unit where the developer carrier and the electrostatic latent image carrier are opposed to each other, A developer carrier having a large number of electric field arrangements formed on its surface as an agent carrier, and a voltage applying means for forming an electric field in the developing section, and a potential on the electrostatic latent image carrier, A developing device characterized in that the movement of the developer is controlled by an electric field determined by the correlation between the electric potential on the developer carrier and the electric field formed by the voltage applying means. Such a developing device forms a large number of electric fields on the surface of the developer carrier, and forms the electric potential on the electrostatic latent image carrier, the potential on the developer carrier, and the voltage applying means. is to control the movement of the developer by the electric field is determined by the electric field is, thus, the deposit an appropriate amount of the developer to the electrostatic latent image on the electrostatic latent image bearing member, the image density is high and the line There is an advantage that a developed image excellent in the reproducibility and gradation of the figure can be obtained.

[0004]

SUMMARY OF THE INVENTION The present invention is an improvement of the above-mentioned developing apparatus, and aims at achieving high image density and excellent line diagram reproducibility and gradation. And a developing apparatus using a developing bias suitable for obtaining a developed image.

[0005]

In order to achieve the above object, the present invention is directed to an electrostatic latent image carrier for carrying an electrostatic latent image and a developer carrier for carrying a developer. In a developing method in which development is performed by applying an alternating electric field in the developing unit while maintaining a gap in the developing unit and performing development by using an alternating electric field, the developer carrier may be formed on a conductive substrate by 10 ³ Ωcm to 10 ⁸ Ω.
a first substance having a resistance of 2 cm and a second substance having a higher resistance than the first substance are provided regularly or irregularly, so that both substances are mixedly exposed on the surface, and at least the surface of the second substance is exposed. expose portion using a developer bearing member is charged to a polarity opposite polarity or the same polarity of the developer to form a large number of fine closed field on the surface of, as the alternating electric field, the waveform forming the alternating electric field Is the difference between the maximum potential and the minimum potential of the gap d.
Using an alternating electric field that is equal to or more than (3 × d) volts and equal to or less than (3 × d + 1000) volts (unit is microns), the potential on the electrostatic latent image carrier, the alternating electric field,
Is characterized in that to control the movement of the developer by the electric field is determined by the electric field on the developer carrying member. According to a second aspect of the present invention, an electrostatic latent image carrier for carrying an electrostatic latent image is brought into contact with a developer carrier for carrying a developer in a developing section, and an alternating electric field is applied in the developing section to perform development. In the developing method, a first substance having a resistance of 10 ³ Ωcm to 10 ⁸ Ωcm and a second substance having a higher resistance than the first substance are regularly or irregularly formed on the conductive substrate as the developer carrier. Regularly, both substances are mixedly exposed on the surface, and at least the exposed portion of the second substance on the surface is charged to the opposite polarity or the same polarity as the developer, so that a large number of micro- closed portions are formed on the surface. Using a developer carrying member that forms an electric field, using, as the alternating electric field, an alternating electric field in which a potential difference between a maximum potential and a minimum potential of a waveform that forms the alternating electric field is 100 volts or more and 1150 volts or less, A potential on the electrostatic latent image carrier, And 互電 field, an electric field on the developer carrying member
Is characterized in that to control the movement of the developer by the electric field is determined by the. According to a third aspect of the present invention, in the developing method of the first or second aspect, the developer carrier is replaced with the developer carrier.
10 ³ Ωcm to 1 in which insulating particles are dispersed on a conductive substrate
0 provided with a surface layer of electrically conductive material having a resistance of ⁶ Omega cm, a number of the surface insulating particles section exposed at least on the surface is charged to a polarity opposite polarity or the same polarity of the developer fine and it is characterized in the use of the developer carrying member to form a closed electric field. The inventions of claims 4, 5 and 6 provide a developing device for performing the developing method of claims 1, 2 and 3.

[0006]

According to the present invention, a large number of electric fields are formed on the surface of a developer carrier, and a potential on the electrostatic latent image carrier, a potential on the developer carrier, and an alternating voltage applied to the developing section are changed. The movement of the developer is controlled by the electric field determined by the electric field, and accordingly, an appropriate amount of the developer is attached according to the electrostatic latent image on the electrostatic latent image carrier. Then, the electrostatic latent image carrier that carries the electrostatic latent image and the developer carrier that carries the developer are opposed to each other while maintaining a gap in the developing unit, and an alternating electric field is applied in the developing unit to perform development. In this case, as an alternating electric field applied to the developing unit, a potential difference between a maximum potential and a minimum potential of a waveform forming the alternating electric field is defined by the gap d (unit: microns).
An alternating electric field of not less than (3 × d) volts and not more than (3 × d + 1000) volts is used, so that the developer on the developing carrier is caused to fly toward the electrostatic latent image carrier with high efficiency. Further, when an electrostatic latent image carrier for carrying an electrostatic latent image and a developer carrier for carrying a developer are brought into contact with each other in a developing section, and an alternating electric field is applied in the developing section to perform development, As the alternating electric field, an alternating electric field in which the potential difference between the maximum potential and the minimum potential of the waveform forming the alternating electric field is 100 volts or more and 1150 volts or less is used. Flying toward the electrostatic latent image carrier with efficiency. The upper limit of each of the above potential differences is for preventing leakage of the applied voltage in the developing section.

[0007]

FIG. 1 is a schematic view showing an example of a developing device according to the present invention. First, the overall structure and operation will be clarified.
In FIG. 1, a belt-shaped photoconductor 1, which is an example of a latent image carrier, is driven in the direction of arrow A, and a developing device 2 is provided to face the photoconductor. In the toner container 3 of the developing device 2, a non-magnetic toner 4 from which an auxiliary agent is removed as necessary, that is, a non-magnetic one-component developer is stored. The specific volume resistivity of the toner is, for example, about 10 ⁷ to 10 ¹² Ωcm. In the present invention, a substantially spherical toner having a uniform small particle diameter is used as the toner 4 as described later. On the front and rear side plates of the toner container 3, a developing roller 5 is supported in a state where a part thereof is exposed from the opening of the container. It is rotationally driven at the number of rotations. The developing roller 5 is an example of a toner carrier, but a belt-shaped toner carrier may be used instead of the roller 5. A toner supply roller 6 as an example of a toner supply member is supported on the front and rear side plates of the toner container 3. The roller 6 contacts the developing roller 5 at a rotation speed of, for example, 300 rpm in a counterclockwise direction (or in a clockwise direction). Good). The toner 4 in the toner container 3 is conveyed to the toner supply roller 6 while being stirred by the agitator 7 rotating clockwise, and then supplied to the developing roller 5 by the roller 6. At the time of this supply, the toner is frictionally charged to a predetermined polarity, in this example, a positive polarity having a polarity opposite to that of the electrostatic latent image on the photosensitive member 1, electrostatically adheres to the peripheral surface of the developing roller 5, and is carried on the developing roller 5. Is done. The configuration and operation related to this will be described later in detail. The toner supplied and carried on the peripheral surface of the developing roller 5 as described above is
It is conveyed by the rotation of the roller 5 and is leveled by a doctor blade 8 which is an example of a layer thickness regulating member, and is regulated to a uniform thickness. Next, the toner is conveyed to a developing area 9 where the photoconductor 1 and the developing roller 5 are opposed to each other, where the toner is electrostatically transferred to an electrostatic latent image formed on the photoconductor 1 and the latent image is converted into a visible image. Become The doctor blade 8 is the elastic support member 3
0 supported. The toner that has not passed through the development area 9 without being used for development is returned to the toner supply roller 6 while being carried on the development roller 5. Further, the visible image formed on the photoreceptor 1 is transferred to a transfer sheet (not shown) and fixed on the transfer sheet by a fixing device.

The above-described structure itself is the same as that of a conventional developing device. In such a conventional developing device, it is difficult to transport a large amount of non-magnetic toner that is sufficiently charged to a developing area. In some cases, the density of the visible image formed by this may decrease. Therefore, in the illustrated developing device, as schematically shown in FIG.
For example, a conductive roller 10 made of metal such as Al, Fe, Cu, etc.
And a medium resistor 1 fixed to the peripheral surface thereof
2 and a high-resistance body 11 are used. The resistivity of the medium resistor 12 is higher than the resistivity of the conductive substrate surface (the conductive roller 10 in this example), for example, 1
0 ³ to 10 ⁸ Ωcm, and the resistivity of the high-resistance body 11 is higher than that of the medium-resistance body 12.
It is set to 0 ^{9-10 15} about Ωcm. Both resistors 1
Reference numerals 1 and 12 are made of a dielectric material having such a resistivity. FIG. 3 showing an enlarged view of the developing roller surface.
As can be seen from FIG. 3 (b) and FIG. 3 (c) showing a partial cross-sectional view near the same surface, the high resistance elements 11 and the medium resistance elements 12 are arranged regularly (or in an irregular state). These are exposed on the surface of the developing roller 5. Each medium resistor 12
And the shape of the high-resistance body 11 can be set as appropriate, but when the surface shape is rectangular as illustrated in FIG. 3, the lengths D1 and D2 of the sides are set to appropriate values of, for example, about 10 to 500 μm. be able to. Such a resistor 11,
12 and the resistivity thereof are set so that the strength of a closed electric field described later can be increased so that an optimal amount of toner can be carried on the developing roller 5, and that the toner on the surface has a medium resistance. The selection is appropriately made so as not to inject undesired charges into the toner on the body 12 or to leak the developing bias. In this example, the high resistance element 11 and the medium resistance element 12
A material having a polarity opposite to the charging polarity of the toner, that is, a material that is frictionally charged to a negative polarity is selected. Further, if necessary, a bias voltage such as direct current, alternating current, direct current superimposed alternating current, or pulse can be applied to the conductive roller 10 of the developing roller 5 to improve the image quality of a visible image, and the roller 10 is grounded. Such a configuration is also possible. The same applies to the toner supply roller 6. When the toner carrier comprises a belt, a medium resistor and a high resistor are laminated and fixed on the surface of the conductive base of the belt in the above-described state. On the other hand, the toner supply roller 6 that is in contact with the developing roller 5 contacts the high resistance element 11 and the medium resistance element 12 of the development roller 5 and frictionally charges them to a polarity (negative polarity) opposite to the charging polarity of the toner. It is composed of In the example shown in FIGS. 1 and 3, the toner supply roller 6 includes a conductor core member 14 and a cylindrical foam (for example, polyurethane foam) 15 laminated around the conductor core member 14, and the foam 15 is elastic. When the toner supply roller 6 is used while being pressed against the developing roller 5 while being deformed, the foam 15 may be made of a material that frictionally charges the resistors 11 and 12 to the negative polarity as described above. Good. Foam 15
Instead, a known brush, such as a fur brush, may be used.

The more detailed operation of the above configuration will be described below. As described above with reference to FIG.
The developing roller portion that has passed the developing area 9 moves to the toner supply roller 6 and contacts the roller 6. Here, the toner carried on the developing roller 5 and not supplied to the development is mechanically and electrically scraped off by the toner supply roller 6. At the same time, the high resistance body 11 of the developing roller 5
And the medium resistor 12 comes into contact with the toner supply roller 6 and is charged to the negative polarity opposite to the charging polarity of the toner by the friction. At this time, even if an electrostatic residual image due to the influence of the electrostatic latent image of the photoconductor 1 remains on the resistors 11 and 12 on the peripheral surface of the developing roller passing through the developing area 9, the friction with the toner supply roller 6 is maintained. As a result, the resistors 11 and 12 are charged to a substantially saturated state, the residual image is eliminated, and the developing roller 5 is initialized. 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 frictionally charged to a positive polarity by friction with the toner supply roller 6 as schematically shown in FIG. Is supplied to the developing roller 5. At this time, the toner is further frictionally charged to the positive polarity by friction with the developing roller 5, and electrostatically adheres to the peripheral surface of the developing roller 5. At this time, the high-resistance element 11 and the medium-resistance element 12 of the developing roller 5 are triboelectrically charged to the negative polarity. However, since their resistances are different from each other, as shown schematically in FIG. The amount of charge of the resistor 11 is larger than the amount of charge of the middle resistor 11, and a difference occurs between the surface potentials of the two. Therefore, a closed electric field is formed between the two resistors 11 and 12. On the surface of the conductive roller 10, a large number of high-resistance
Since the 1 and the medium resistor 12 are alternately located, countless minute closed electric fields (microfields) are formed on the surface of the developing roller 5 in a state of being uniformly distributed on the surface of the developing roller. That is, when considering the lines of electric force representing the state of the electric field, the lines of electric force E are formed in the space near the surface of the developing roller 5 as represented by a large number of arc-shaped lines in FIG. The lines of electric force exit from the developing roller 5 and return to the same developing roller 5, and a number of closed electric fields are formed near the surface of the roller 5. Thus, an electric field having a large electric field gradient is formed near the surface of the developing roller. High resistance 11
Since the surface size of the intermediate resistor 12 is very small as described above, each closed electric field is also very small. As a result, the intensity of each closed electric field is reduced by the so-called edge effect or fringing effect (peripheral electric field effect). Very strong. The toner positively charged by such a high-intensity closed electric field is not charged as shown in FIG.
As shown schematically in FIG. 7A, the high resistance body 11 is strongly pulled on the surface of the high resistance body 11 and is held on the developing roller 5 in a state where it is difficult to separate a large amount. That is, the charged toner is given a strong binding force inside the closed electric field, and the developing roller 5 is moved along the line of electric force.
It is kept above. At this time, the toner is strongly triboelectrically charged by 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 micro-closed electric field. When the layer thickness of the toner is regulated by a doctor blade 8 made of, for example, urethane, a sufficiently charged toner is strongly held on the surface of the developing roller 5 by a minute closed electric field, but a toner having a small charge amount is mixed with the toner. However, the toner is removed by the contact pressure with the doctor blade 8, so that only the toner having a large charge amount is conveyed to the developing area 9 in a larger amount than before, and the electrostatic latent image is formed as described above. Visualize. Developing roller 5 and photoconductor 1 in developing area 9
Between the developing roller 5 and the developing roller 5
The upper toner is likely to adhere to the photoconductor 1. In this manner, the image density of the visible image can be increased and the background can be prevented from being stained. In the vicinity of the surface of the developing roller 5, only a small closed electric field is formed over the entire surface as schematically shown in FIG. In any case, since a closed electric field exists, its intensity is increased,
A large amount of toner can be carried.

In the developing section, the alternating electric field applied by the developing bias applying means causes the minute electric field between the medium resistor 12 and the high resistor 11 existing on the surface of the developing roller 5 and the charged toner 4 To provide mechanical energy suitable for developing the electrostatic latent image. That is, the developing roller 5
The surface potential of the high-resistance body 11 is as described above.
Since the charge amount of 1 is larger than the charge amount of the middle resistor 11, the charge amount differs in each region. In particular,
The surface potential of the high-resistance body 11 becomes a potential that is relatively largely deviated by the charge held by the applied voltage. Therefore, the electric field between the surface of the developing roller 5 and the photosensitive drum 3 not only corresponds to the image portion or the non-image portion of the photosensitive drum 3 but also the electric field between the high-resistance body 11 on the surface of the developing roller 5 and the non-image portion. It differs depending on which of the middle resistor 12 is used. As described above, since minute portions having different potentials are mixed on the surface of the developing roller 5 to form different electric fields between the photosensitive member 1 and the photosensitive member 1, an image having a high density and a gradation property is not impaired. Can be obtained.

As a result of an experiment using the above-described apparatus, the potential difference (hereinafter referred to as amplitude) between the maximum potential and the minimum potential of the waveform forming the alternating electric field is 100 volts as the alternating electric field applied to the current region 9. If an alternating electric field of not less than 1150 volts is used, the toner on the developing roller from the developing roller 5 to the photoreceptor 1 can fly with high efficiency and good gradation. There was found. Here, the flying efficiency of the toner (hereinafter referred to as a flying rate) is the amount of the toner transferred to the photoconductor 1 by the development with respect to the amount of the toner adhered to the developing roller 5 before the development in the case of performing the saturated development (for example, (Determined by measuring the amount of toner on the developing roller 5 after development). By using the above-mentioned alternating electric field, a flight rate of 90% or more could be obtained. The cycle of the alternating electric field is 25
A frequency of 0 Hz to 2000 Hz is preferable. For example, when the developing device of FIG. 1 is applied with an alternating electric field in which a DC component having a period of 500 Hz and an amplitude of 800 volts and a DC component of −500 volts is applied, development is performed. An image without weight gain was obtained.

In the example of FIG. 1, contact development is performed in the development area 9, but a latent image may be visualized by a non-contact development method. In this case, the alternating electric field applied to the developing unit 9 has an amplitude corresponding to the gap d (unit: microns) between the photosensitive member 1 and the developing roller 5 in the developing area.
If an alternating electric field that is equal to or more than (3 × d) volts and equal to or less than (3 × d + 1000) volts is used, it is possible to fly the toner on the developing roller from the developing roller 5 to the photosensitive member 1 with high efficiency. It was also found that the gradation was good. Again, 1150 volts is the upper limit for preventing bias leakage. Again, the frequency is 250Hz
To 2000 Hz is preferred. As a result, the toner on the developing roller 5 was able to fly toward the photoreceptor 1 with high efficiency (flying rate of 70% or more) as in the above-described embodiment. FIG. 4 shows the amplitude of the alternating electric field that satisfies the above condition with the developing gap as the horizontal axis, and the region between two straight lines underground is the range of the amplitude that satisfies the above condition. It is. For example, in the developing device of FIG. 1 described above, when the gap between the photoreceptor 1 and the current roller 5 is set to 100 μm and an AC voltage having an amplitude of 1000 volts and a frequency of 500 Hz is applied to perform non-contact development, It was possible to obtain an image which was excellent in gradation in density and did not cause thickening of the diagram.

In the apparatus of the above embodiment, the high-resistance element 11 and the medium-resistance element 12 are charged in the opposite polarity to the toner, but the two resistors 11 and 12 are charged to the same polarity as the charging polarity of the toner. In particular, a large amount of toner can be deposited on the surface of the medium resistor 12. Further, it is also possible to adopt a configuration in which the medium resistor 12 is not substantially charged, and only the high resistor 11 is charged to a predetermined polarity, and a closed electric field is formed between these members to carry the toner. It is sufficient to charge at least the high-resistance element of the high-resistance element and the medium-resistance element, and form a closed electric field based on the difference in surface potential to carry the toner. Further, as a substrate for laminating and fixing the high-resistance element and the medium-resistance element, only a surface on which these resistance elements are laminated is made conductive, and this conductive layer is grounded or a predetermined bias voltage is applied thereto. You may make it. Further, at least the high-resistance element of the high-resistance element and the medium-resistance element is charged to a predetermined polarity, and a small electric field is formed near the surface of the toner carrier due to a difference in the surface potential to visualize the latent image. Although the toner supply roller 6 is used as a charging unit for adhering the non-magnetic toner to the toner carrier by the closed electric field, other independent charging units may be used as appropriate.

Next, a developing apparatus according to another embodiment of the present invention will be described. This developing device is different from the above-described embodiment in the configuration of the developing roller 5, and the other configuration is basically the same as the above-described embodiment. As schematically shown in FIG. 2 as a schematic enlarged view, the developing roller 5 of the present embodiment uses a conductive substrate on which a surface layer made of a conductive material in which insulating particles are dispersed is formed. The surface has a conductor portion made of a conductive material mixed with an insulator portion in which insulating particles are exposed. The toner adhesion is as follows. First, the surface portion of the developing roller 5 that has completed the development comes into contact with the toner supply roller 6 by the rotation of the developing roller 5 in the direction of the arrow.
Here, the remaining toner in the non-image portion that has not been developed is mechanically and electrically scraped off by the toner supply roller 6, and the insulator portion is frictionally charged to a polarity opposite to the polarity of the toner. At this time, the charges of the developing roller 5 and the toner by the previous development are fixed by friction and initialized. Next, the toner supply roller 6
The toner carried by the developing roller is charged by friction and adheres mainly to the insulator portion of the developing roller 5. At this time, the electric field on the developing roller 5 becomes a microfield (small closed electric field) as shown in FIG. 2, and becomes an electric field with a large electric field gradient, so that the toner can be adhered to multiple layers. Further, since the adhered toner has a closed electric field, it is strongly pulled toward the developing roller 5 and is hardly separated. Also in this developing roller 5, since the amount of frictional charge by the toner supply roller 6 is different between the insulator portion and the conductor portion, like the developing roller according to the above-described embodiment, the developing portion applies the developing bias. The alternating electric field applied by the means acts on the minute electric field between the medium resistance body 12 and the high resistance body 11 existing on the surface of the developing roller 5 and the charged toner 4 to develop the electrostatic latent image. By giving suitable mechanical energy, it is possible to obtain an image which has high density and does not impair gradation. In this embodiment,
The insulator part is charged to the polarity opposite to the polarity of the toner,
The surface material of the toner supply roller 40 may be appropriately selected so as to be frictionally charged to the same polarity as the charge polarity of the toner. Also in this case, a microfield can be similarly formed by the potential difference between the insulator and the conductor, and in this case, the toner mainly adheres to the conductor.

The developing roller 5 of this embodiment will be described in more detail. As described above, the developing roller 5 of this embodiment has a surface layer made of a conductive material in which insulating particles are dispersed on a conductive substrate, and the conductive material has a surface layer of 10 ¹² Ωcm.
Below, preferably 10 ⁸ Ωcm or less can be used.
To be specific, there may be mentioned those obtained by adding a conductivity-imparting agent to organic polymers. In this case, the organic polymers include a resin material (plastomer) and a rubber material (elastomer). Examples of the conductivity-imparting agent include metal powder, carbon black, conductive oxide, electroless plating, graphite, metal fiber, and carbon fiber. still,
When an elastomer is used in the organic polymers as the conductive material, the surface layer of the developing roller becomes elastic, and the contact with the rigid drum-shaped photoreceptor becomes easy, so that the contact development becomes very The use of conductive elastomers is particularly preferred, as this makes it easier. On the other hand, as the insulating particle material, a material having a resistivity of 10 ¹³ Ωcm or more, preferably 10 ¹⁴ Ωcm or more is used. The average particle size is preferably 5 μm or more. If it is less than 5 μm, it is difficult to form a minute electric field,
Stable toner application and electrification cannot be obtained. In addition, fixed form,
Irrespective of irregular shape. Specifically, inorganic particles such as alumina and organic particles such as epoxy resin can be used. When the conductive elastomer is used as the conductive material, it is desirable to use the elastomer as the insulating particles in order to further promote the low hardness. In order to produce the insulating elastomer particles, known methods such as a method of freezing the elastomer with dry ice or the like, pulverizing and pulverizing, forming an aqueous emulsion using a surfactant or the like, and then curing the emulsion are used. Adopted. The amount of the insulating particles to be added to the conductive material is appropriately selected in the range of 10 to 200 parts by weight based on 100 parts by weight of the conductive material. The area of the surface insulating portion of the developer carrier is 20 to 60
% Is preferable, and the amount of the insulating particles to be added is appropriately adjusted so as to be within this range after the preparation of the carrier.

In order to manufacture the developing roller 20 of this embodiment, for example, the above-mentioned insulating particles are added to the above-mentioned conductive material by a usual dispersion method such as ball milling or kneading, and then the mixed material is added. Injection molding, extrusion molding, spray coating, dipping, etc.
It is manufactured by molding on a conductive substrate typified by a metal roller of S, iron, Al or the like, and then polishing the surface so as to be smooth. Note that a plastomer can be used in order to improve the adhesion between the conductive material and the conductive substrate. In this case, the plastomer is preferably conductive.

Hereinafter, specific examples will be described. Parts are by weight. Conductive paint 100 parts [Product name: Electrodag 440 (manufactured by Acheson Japan) (solid content 70%; acrylic resin containing Ni particles)] Acrylic resin 50 parts (average particle size 80 μm) Diluent 200 parts [(trade name SB- 1 (manufactured by Acheson Japan Co., Ltd.)] The coating solution having the above formulation is applied to a SUS metal roller by spray coating, dried at 80 ° C. for 1 hour, polished, and developed with a surface layer having a thickness of 100 μm. A roller was made.

Using the developing roller 5 of this embodiment in the developing device of FIG. 1, contact development and non-contact development were performed. As in the case of using the developing roller 5 in the above embodiment, the case of contact development was Has an amplitude greater than 100 volts and 11
In the case of an alternating electric field of not more than 50 volts and non-contact development, not less than (3 × d) volts and (3 × d + 100)
0) By using an alternating electric field of less than or equal to volt, the toner on the developing roller from the developing roller 5 to the photosensitive member 1 could be efficiently scattered, and the gradation was good.

[0019]

According to the present invention, the movement of the developer and the potential on the electrostatic latent image bearing member, and the potential on the developer carrying member, by an electric field which is determined by the alternating electric field applied to the developing unit , Which allows an appropriate amount of developer to adhere to the electrostatic latent image on the electrostatic latent image carrier, thereby providing a high image density and excellent image reproducibility and gradation. Can be obtained. Then, by using a predetermined applied voltage as an alternating electric field applied to the developing unit, the developer on the developing carrier is caused to fly toward the electrostatic latent image carrier with high efficiency, and the gradation is not impaired. And the density of the image can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view illustrating an example of a developing device.

FIG. 2 is a partially enlarged view of the vicinity of a surface of a developing roller that can be used in the developing device of the present invention.

3A and 3B show another developing roller that can be used in the developing device of the present invention, wherein FIG. 3A is a partial cross section at a contact portion with the toner supply roller, FIG. 3B is an enlarged view of the surface thereof, (C) is a partially enlarged view near the surface, and (d) is an explanatory diagram showing lines of electric force of a minute closed electric field formed near the surface.

FIG. 4 is a graph showing a relationship between a preferable amplitude of an alternating electric field and a developing gap in non-contact development.

[Explanation of symbols]

Reference Signs List 2 developing device 4 non-magnetic toner 6 toner supply roller 9 developing area 11 high resistance element 12 medium resistance element

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Shigekazu Enoki 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Junko Tomita 1-3-6 Nakamagome, Ota-ku, Tokyo No. Ricoh Co., Ltd. (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/06 101 G03G 15/08

Claims (6)

(57) [Claims] An electrostatic latent image carrier carrying an electrostatic latent image and a developer carrier carrying a developer are opposed to each other with a gap kept in a developing section, and an alternating electric field is applied in the developing section. In a developing method for performing development, a first substance having a resistance of 10 ³ Ωcm to 10 ⁸ Ωcm and a second substance having a higher resistance than the first substance are regularly formed on a conductive substrate as the developer carrier. The two materials are mixed or exposed on the surface by being provided regularly or irregularly, and at least the exposed portion of the second material on the surface is charged to a polarity opposite to or the same as the polarity of the developer, so that a large number of the materials are exposed on the surface. And a potential difference between the maximum potential and the minimum potential of the waveform forming the alternating electric field is (3 units) with respect to the gap d (unit: microns). × d) bolts or more and (3 × d + 10)
00) The developer is moved by an electric field determined by the electric potential on the electrostatic latent image carrier, the alternating electric field, and the electric field on the developer carrier using an alternating electric field of not more than 00 volts. A developing method characterized by controlling the following. 2. A developing method in which an electrostatic latent image carrier carrying an electrostatic latent image is brought into contact with a developer carrier carrying a developer in a developing section, and an alternating electric field is applied in the developing section to perform development. Wherein, as the developer carrier, a first substance having a resistance of 10 ³ Ωcm to 10 ⁸ Ωcm and a second substance having a higher resistance than the first substance are regularly or irregularly formed on a conductive substrate. The developer is provided so that both substances are mixedly exposed on the surface, and at least the exposed portion of the second substance on the surface is charged to a polarity opposite to or the same as the polarity of the developer, so that a number of minute closed electric fields are formed on the surface. A developer carrying member to be formed, wherein the potential difference between the maximum potential and the minimum potential of the waveform forming the alternating electric field is 100 volts or more and 11
Using an alternating electric field of 50 volts or less, the movement of the developer is determined by an electric field determined by the potential on the electrostatic latent image carrier, the alternating electric field, and the electric field on the developer carrier. A developing method characterized by controlling. Wherein instead of the developer carrying member provided with a surface layer of electrically conductive material having a resistivity of 10 ³ [Omega] cm to 10 ⁶ [Omega] cm by dispersing the insulating particles in the conductive substrate, exposed at least on the surface 3. The developing device according to claim 1, wherein said insulating particles are charged with a polarity opposite to or the same as the polarity of said developer to form a plurality of minute closed electric fields on said surface. Method. 4. An electrostatic latent image carrier carrying an electrostatic latent image and a developer carrier carrying a developer are opposed to each other with a gap kept in a developing section, and an alternating electric field is applied by a voltage applying means in the developing section. And a second material having a resistance of 10 ³ Ωcm to 10 ⁸ Ωcm on the conductive substrate, and a second material having a higher resistance than the first material. Substances are provided regularly or irregularly, and both substances are mixedly exposed on the surface, and at least the exposed portion of the second substance on the surface is charged to the opposite polarity or the same polarity as the polarity of the developer. A developer carrying member that forms a large number of micro-closed electric fields on the surface is used. As the voltage applying means, the potential difference between the maximum potential and the minimum potential of the waveform forming the alternating electric field is the gap d (unit: microns). To (3 × d) volts or more and (3 × d + 1)
000) volts or less, and the electric field determined by the electric potential on the electrostatic latent image carrier, the electric field by the voltage applying unit, and the electric field on the developer carrier is used. A developing device for controlling movement of a developer. 5. An electrostatic latent image carrier carrying an electrostatic latent image and a developer carrier carrying a developer are brought into contact in a developing section, and an alternating electric field is applied by a voltage applying means in the developing section to perform development. A first substance having a resistance of 10 ³ Ωcm to 10 ⁸ Ωcm and a second substance having a higher resistance than the first substance are regularly arranged on the conductive substrate as the developer carrier. Alternatively, both the substances are irregularly provided so that both substances are mixedly exposed on the surface, and at least the exposed portion of the second substance on the surface is charged to the polarity opposite to or the same as the polarity of the developer, so that a large number of A voltage is applied such that the potential difference between the maximum potential and the minimum potential of the waveform forming the alternating electric field is not less than 100 volts and not more than 1150 volts, using a developer carrying member forming a minute closed electric field. Means for carrying the electrostatic latent image And the potential on the body, a developing device, wherein the electric field generated by said voltage applying means, to control the movement of the developer by the electric field is determined by the electric field on the developer carrying member. 6. A method according to claim 6, further comprising a surface layer made of a conductive material having a resistance of 10 ³ Ωcm to 10 ⁶ Ωcm in which insulating particles are dispersed on a conductive substrate, wherein said surface layer is exposed at least on the surface. 6. The developing device according to claim 4, wherein said insulating particles are charged with a polarity opposite to or the same as the polarity of said developer to form a large number of minute electric fields on said surface. apparatus.