JP3080426B2 - Developing device - 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 device in which an electrostatic latent image carrier for carrying an electrostatic latent image is opposed to a developer carrier for carrying a developer, and a bias is applied to the developing unit. The present invention relates to a developing device used for an image forming apparatus such as an electronic copying machine, a printer, and a facsimile that performs development.

[0002]

2. Description of the Related Art In the above-described developing apparatus using a one-component developer, in order to obtain a visible image excellent in image reproducibility and gradation, an electrostatic latent image carrier and a developer carrier are connected. It has already been proposed to provide, as a bias, an alternating electric field in which a first alternating electric field and a second alternating electric field having a higher frequency than the first alternating electric field are superimposed on the developing gap therebetween (Japanese Patent Publication No. 63-2118).
No. 7). An outline of the first proposal will be described with reference to FIGS.

The casing of the developing device 2 shown in FIG.
An opening for development is provided in a portion facing the photosensitive drum 3 as an electrostatic latent image carrier, and a developing roller 1 as a developer carrier is provided with a predetermined gap through the opening to the photosensitive drum 3. And rotatably provided in the casing. Around the developing roller 1, a blade member 4 for regulating the thickness of the toner layer carried and conveyed by the roller 1 is provided so as to resiliently press the roller 1 above the roller 1. The thickness of the toner 7 supplied from the toner tank 5 formed in accordance with the rotation of the agitator 6 and the toner supply roller 8 is regulated. Instead of the blade member 4, a regulating roller or a regulating belt may be used. The agitator 6 rotates clockwise as indicated by the arrow, and agitates the toner 7 by the resistance of the tip thereof and moves the toner 7 to the left in the drawing.

The toner supply roller 8 supplies the toner 7 conveyed by the agitator 6 to the surface of the developing roller 1 by rubbing the surface of the developing roller 1 in the forward or reverse direction. And has the function of scraping off the toner 7 that has returned and returned.

[0005] The toner 7 supplied to the surface of the developing roller 1 by the toner supply roller 8 is also charged by the frictional charging effect generated by mutual friction with the toner supply roller 8 or the developing roller 1, and the toner 7 itself is also charged. 1 is electrostatically carried on the surface. Thus, the thickness of the toner 7 carried and transported by the developing roller 1 is regulated by the blade member 4 which resiliently presses above the developing roller 1, and is transported to the developing section where the photosensitive drum 3 and the developing roller 1 are opposed to each other. Is done. The blade member 4 may be manufactured by attaching a material having a toner charging property such as urethane rubber to an elastic leaf spring, or may use an elastic member as it is. The blade member 4 may be provided in the trailing direction as shown in the drawing with respect to the rotation direction of the developing roller 1,
It may be provided in the reverse reading direction.

Reference numeral 9 denotes a power supply for applying a low frequency alternating voltage, and reference numeral 10 denotes a power supply for applying a high frequency voltage, which is supplied to a gap between the developing roller 1 and the toner supply roller 8 in a superimposed manner. FIG. 2 shows the waveform of the alternating voltage applied thereby. In the figure,
The potential of the electrostatic latent image is such that the image portion potential (V _D ) is 700 V, the non-image portion potential (V _L ) is 200 V, and the low frequency voltage that gives the first alternating electric field has a maximum value of 800 V and a minimum value of −10.
It is a rectangular wave of 0 V, which has a frequency of 5 kHz and an amplitude of 600.
A high frequency sine wave giving a second alternating electric field of V is superimposed.

As described above, the first and second signals having different frequencies are used.
By applying the alternating electric field in a superimposed manner, the toner is surely transferred from the developing roller 1 to the photosensitive drum 4 and reversely transferred, and the toner positively adhered to the non-image portion of the photosensitive drum 4 is reliably obtained. It can be collected from the non-image portion.

When no external electrode is applied to the developing device shown in FIG. 1, the slope γ value of the VD curve (characteristic curve of the image density D with respect to the electrostatic latent image potential V) is very large. By applying an electric field, the γ value is reduced, the gradation is improved, and a high-density image can be obtained.

Further, in the developing device shown in FIG. 1, a first step in which the toner reciprocates between the photosensitive drum 3 and the developing roller 1 is performed. A second step of transferring toner from the non-image area to the developing roller 1, wherein the first step includes a first alternating electric field, and the second step includes an alternating electric field smaller than the intensity of the first alternating electric field. It has already been proposed to apply a superimposed alternating electric field of a second alternating electric field higher in frequency than the first alternating electric field to perform development (Japanese Patent Publication No. 63-21188).

In the first step of the second proposal, the toner particles are positively reciprocated (transition-reverse transition) between the developing roller 1 and the non-image portion of the photosensitive drum 3. In this process, toner is positively attached to the non-image portion. This causes ground fog, which is removed in the next second step. On the other hand, in the first step in which the toner can be adhered to the non-image area, the adhesion is further enhanced in the image area having a potential as an electrostatic image. Therefore, the so-called half
Even in a portion having a density close to a bright portion of a halftone image portion including a tone, toner adheres according to the potential.

The high-frequency electric field applied in the second step is as follows:
In the developing process, the toner is always kept in a swinging state, and has an effect of releasing the toner from strong restraint on the developing roller or the latent image forming surface. As a result, the toner transferred to the non-image portion in the phenomenon promoting stage of the first step of the phenomenon described above easily returns to the developing roller side in the second step.

[0012]

When no external electric field is applied to the developing gap between the electrostatic latent image carrier and the developer carrier, the slope of the VD curve, the so-called γ value, is very large. It can be seen that by applying a low-frequency alternating electric field according to the first and second proposals, the γ value is reduced and the gradation is improved. When the frequency of the external electric field is increased, the γ value gradually increases, and the effect of increasing the gradation becomes weaker. When the gap is 100 μ, the effect becomes extremely weak when the frequency exceeds 1 KHz, and the gap becomes 300 μ. In the case of, the effect decreases when the frequency is about 800 Hz, and 1
If it exceeds KHz, the effect becomes extremely weak. Further, there is a disadvantage that ground fog occurs as a side effect. SUMMARY OF THE INVENTION It is an object of the present invention to provide a developing device having a high gradation with no background fog.

[0013]

SUMMARY OF THE INVENTION According to the present invention, there is provided a developer carrier for forming a plurality of minute closed electric fields on a surface thereof, a first alternating electric field, and a second alternating electric field having a higher frequency than the first alternating electric field. Means for applying a bias to form an alternating electric field in which the electric field is superimposed on the electrostatic latent image carrier, an electric field due to the bias, and a minute closed electric field on the developer carrier in the developing unit. The transfer of the developer held on the developer carrier to the electrostatic latent image carrier and the reverse transfer of the developer by the electric field determined by the formula (1) and development are performed.

Further, according to the present invention, there is provided a developer carrier for forming a large number of micro-closed electric fields on a surface thereof, means for applying a bias for forming a first alternating electric field as a first step, and a second step. Means for applying a bias for forming an alternating electric field in which an alternating electric field smaller than the first alternating electric field and a second alternating electric field having a higher frequency than the first alternating electric field are superimposed. The electrostatic latent image carrier of the developer held on the developer carrier by an electric field determined by the electric potential on the image carrier, the electric field due to the bias, and the minute closed electric field on the developer carrier The problem can be solved by performing the transfer to the reverse transfer and the reverse transfer and developing.

[0015]

The developer carrier having a large number of minute closed electric fields on its surface can provide a desired amount of toner adhesion and toner charge. On the other hand, since the toner is held by the electric charge of the dielectric portion, the toner is peeled off. As a result, the toner transfer rate from the developer carrier to the electrostatic latent image carrier is reduced. On the other hand, by applying the low frequency voltage of the first alternating electric field,
An image having good γ characteristics can be obtained, and the toner is kept in a oscillating state by the high frequency second alternating electric field, and the toner is released from the strong restraint on the developer carrier or the latent image forming surface, thereby reducing the toner transfer rate. To prevent.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a developing device 2 shown in FIG. 1, between a developing roller 1 and a photosensitive drum 3, a first alternating electric field and a high frequency voltage are supplied from a power supply 9 for applying a low frequency alternating voltage as described above. A second power source having a frequency higher than that of the first alternating electric field from a power source for application
An electric field is provided superimposed. Further, according to the present invention, the phenomenon roller is configured as follows.

As shown in FIG. 3, the developing roller 1 has a dielectric portion 11 (elastic insulating particles) and a conductive portion 12 on its surface.
(Elastic conductive material) in a small area.

The toner adhesion is as follows. First, the developing roller 1 that has completed the development rotates in the direction of the arrow and comes into contact with the toner supply roller 8. Here, the remaining toner in the non-image area which has not been developed is mechanically and
It is scraped off electrically and the dielectric part is charged by friction. At this time, the charge of the developing roller 1 and the toner by the previous development is fixed by friction and initialized. next,
The toner conveyed by the toner supply roller 8 is charged by friction, and electrostatically adheres to the dielectric portion of the developing roller 1. At this time, the polarity of the toner is opposite to the charge of the photoconductor, and the dielectric portion of the developing roller 1 has the same polarity.
At this time, the electric field on the developing roller 1 becomes a microfield (closed electric field) 13 as shown in FIG. 3, and becomes an electric field having a large electric field gradient, so that the toner can be adhered in multiple layers. Further, since the adhered toner has a closed electric field, it is strongly pulled toward the developing roller 1 and hardly separated. The thickness of the toner layer is further controlled by a blade member 4 that regulates the thickness of the toner layer, so that the toner in the development area becomes an electric field that easily adheres to the photoreceptor, and development is performed.

Next, the developing roller 1 will be described.

As described above, the developing roller 1 has at least the surface on which the conductor portion 12 and the dielectric portion 11 are mixed, and these forming materials are elastic conductive materials containing elastic insulating particles. .

The elastic insulating particles constituting the dielectric portion 11 have a volume resistance of 10 ¹³ Ω · cm or more, preferably 10 ¹³ Ω · cm or more.
¹⁴ Ω · cm or more and an effective rubber hardness (a value obtained by measuring the shape of the developer carrying member using a spring-type hardness tester A type defined in JIS K6301) of 50 degrees or less, preferably 40 degrees or less Is used.

Examples of such materials include silicone-modified ethylene propylene rubber, epichlorohydrin rubber, butyl rubber, silicone rubber, and ethylene propylene rubber. The average particle size is 5 μm or more, preferably 10 μm or more. If it is less than 5 μm, it is difficult to form a microfield, and stable toner adhesion and charging cannot be obtained. Further, the particle shape may be either a regular shape or an irregular shape.

The elastic conductive material preferably has a volume resistivity of 10 ¹² Ω · cm or less, preferably 10 ⁸ Ω · cm or less, and has an effective rubber hardness of 50 degrees or more, preferably 40 degrees or less. Hereinafter, those obtained by adding a conductive filler to rubbers are used.

The rubbers include silicone-modified ethylene-propylene rubber, styrene-butadiene rubber, epichlorohydrin rubber, ethylene-propylene rubber, urethane rubber, fluorine rubber, silicone rubber, nitrile rubber,
Acrylic rubber, butyl rubber, isoprene rubber and the like can be mentioned.

Further, as the conductive filler, Ni, C
metal powders such as u; carbon blacks such as furnace black, lamp black, thermal black, acetylene black, and channel black; conductive oxides such as tin oxide, zinc oxide, molybdenum oxide, antimony oxide, and potassium titanate; An electroless plating product plated on mica or the like; graphite, metal fiber, carbon fiber, and the like.

The developing roller 1 shown in FIG. 4 has a surface layer made of a conductive material base 16 in which insulating particles 15 are dispersed and fixed on a conductive metal roller 14. As the conductive material, like the developing roller shown in FIG. 3, 10 ¹² Omega
Cm or less, preferably 10 ⁸ Ωcm or less. 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).

The developing roller 1 is prepared by adding insulating particles to a conductive material based on a normal dispersion method such as ball milling or kneading, and then subjecting the mixed material to a method such as injection molding, extrusion molding, spray coating, dipping, or the like. By
It can be manufactured by molding on a conductive metal roller typified by a metal roller of SUS, iron, Al, or the like, and then performing polishing so that the surface becomes smooth.

Next, in the developing roller 1 shown in FIG. 5, a dielectric portion 17 and a conductor portion 18 are mixed in a very small area on the surface thereof.
In addition, the derivative portion 17 is formed in the foam cell 19 near the surface of the conductive foam layer.

Dielectric part 17 formed in foam cell 19
Any material can be used as long as it has insulating properties, but its volume resistivity is 10 ¹² Ω · cm or more, especially 1
Those having a value of 0 ¹⁴ Ω · cm or more are preferable.

Examples of such insulating materials include organic polymers such as vinyl resins and polystyrene resins.

The conductor portion 18 is formed of a conductive foam layer. As a resin material forming the foam, organic polymers such as natural rubber and silicone rubber can be used.

In order to prepare the developing roller shown in FIG. 5, for example, (i) a conductive foam composition composed of rubbers, a conductivity-imparting agent, a foaming agent and other additives is extrusion-molded on the outer periphery of a cored bar. Then, the elastic foam layer is provided, and the surface thereof is ground to expose the foam cells, a concave portion for embedding the dielectric portion is formed, and then the dielectric material 20 is sprayed and dipped in the concave portion. And cured (fired) under predetermined conditions (temperature and time) (the thickness of the coating film is set so that the concave portion is completely buried) (FIG. 6 (a)), (ii) the surface is subsequently cut or A method is employed in which the conductive surface and the dielectric surface are polished so as to be mixed in a very small area by polishing, and the conductive portion is polished so as to have an area of 20 to 60% (FIG. 6B).

The developing roller shown in FIGS. 7 to 9 will be described below. The developing roller 1 shown in these figures includes a base made of a conductive roller 21 made of a metal such as Al, Fe, Cu, etc., and a medium resistor 22 and a high resistor 23 fixed to the peripheral surface thereof. Rollers are used. The resistivity of the medium resistor 22 is higher than the resistivity of the conductive substrate surface (the conductive roller 21 in this example) and is set to, for example, about 10 ^{3 to} 10 ⁸ Ω · cm.
The resistivity of No. 3 is even higher than the resistivity of the medium resistor 22, and is set to, for example, about 10 ^{9 to} 10 ¹⁵ Ω · cm. Both resistors 22 and 23 are made of a dielectric material having such a resistivity.

In FIG. 8, a horizontal line is shown with respect to the high-resistance element 23 to make it easy to distinguish between the two resistance elements 22 and 23. As can be seen from FIG. 8 and FIGS. The high resistance element 23 and the medium resistance element 22 are arranged regularly (or in an irregular state), and they are exposed on the surface of the developing roller 1.

The shape of each of the middle resistor 22 and the high resistor 23 can be appropriately set. When the surface shape is rectangular as illustrated in FIG. 8, the lengths D1 and D2 of one side are, for example, 1
It can be set to an appropriate value of about 0 to 500 μm. The values relating to the sizes of the resistors 22 and 23 and the resistivity thereof are appropriately selected so as to increase the intensity of a closed electric field described later and to carry an optimal amount of toner on the developing roller 1. .

In this embodiment, the high resistance element 23 and the medium resistance element 2
As 2, 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.

The toner 7 conveyed to the developing roller 1 while being in contact with the peripheral surface of the toner supply roller 8 is frictionally charged to a positive polarity by friction with the toner supply roller 8 as schematically shown in FIG. The toner is supplied to the roller 1, and is frictionally charged to a more positive polarity due to the friction with the developing roller 1 at this time, and electrostatically adheres to the peripheral surface of the developing roller 1.

At this time, the high-resistance element 23 and the medium-resistance element 22 of the developing roller 1 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 23 is larger than the amount of charge of the middle resistor 22, and a difference occurs between the surface potentials of the two. For this reason, a closed electric field is formed between the two resistors 22 and 23.

Since a large number of high-resistance elements 23 and medium-resistance elements 22 are alternately arranged on the surface of the conductive roller 21 so as to be countless, the surface of the developing roller 1 has an infinite number of minute closed electric fields (micro-fields). ) Are 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, electric lines of electric force E are formed in the space near the surface of the developing roller 1 as represented by a large number of arc-shaped lines in FIG. The force lines exit the developing roller 1 and return to the same developing roller 1, and a number of closed electric fields are formed near the surface of the roller 1. Thus, an electric field having a large electric field gradient is formed near the surface of the developing roller.

Since the surface sizes of the high-resistance element 23 and the medium-resistance element 22 are very small as described above, each closed electric field is also very small, so that each closed electric field has a so-called edge effect or fringing effect ( Due to the peripheral electric field effect), the intensity becomes very strong. With such a high intensity closed electric field,
The positively charged toner, as schematically shown in FIG.
It is strongly pulled by the surface of the high resistance element 23 and is held on the developing roller 1 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 is held on the developing roller 1 along the line of electric force E.

At this time, the toner is strongly triboelectrically charged due to the friction between the toner supply roller 8 and the developing roller 1 and is held on the surface of the developing roller 1 by the action of a strong minute electric field. Carries a large amount of toner having a high charge. In addition, when the layer thickness of the toner carried on the developing roller 1 is regulated by a doctor blade 4 made of, for example, urethane, a sufficiently charged toner is strongly held on the surface of the developing roller 1 by a minute closed electric field. Even when a small amount of toner is mixed with the toner, such toner is removed by the contact pressure with the doctor blade 4, and as a result, only the toner having a large charge amount is conveyed to the developing area in a larger amount than before, and The electrostatic latent image is visualized as described above. The electric field between the developing roller 1 and the photoconductor 1 in the developing area has a large electrode effect, so that the toner on the developing roller 1 easily adheres to the photoconductor drum 3. In this manner, the image density of the visible image can be increased and the background can be prevented from being stained.

In FIGS. 11 and 12, the developing roller 1 is made of a plurality of materials having different resistances or dielectric constants. That is, the developing roller is formed by applying a mesh-like knurling process to the surface of a roller made of a conductive material, for example, a metal material such as aluminum, or a conductive rubber or a conductive plastic, and applying a polycarbonate, acryl, polyester, or tetrafluoride to the streaks. A dielectric resin such as ethylene is rubbed and filled to form a fine mesh-shaped insulating region surface 25, and a fine conductive region surface 24 is formed in contact therewith.

Fine conductive region surface 24 and insulating region surface 2
The method of forming 5 is not limited to the above example,
Various methods can be adopted.

The size of the insulating region is 30 as an average diameter.
２０００2000 μm, preferably 50-1000 μm. When the shape of the insulating region surface 25 is, for example, a circle, as shown in FIG.
The distance is set to 0 μm, preferably about 100 to 400 μm, and the center-to-center distance P1 is appropriately set in a well-balanced manner. When the shape of the insulating region surface 25 is rectangular, the length of the shortest side is about 30 to 2000 μm. Similarly, when the shape of the insulating region surface 25 is an ellipse or an ellipse, the width on the minor axis side is 30 to 2000.
It is about μm. When the shape of the insulating region surface 25 is another shape, the width is set to 30 to 2000 μm according to these.
m. The occupied area ratio is 50 to 80%, preferably 65 to 75% of the surface area of the developing roller 1.
It is good. By making the structure of the developing roller 1 in this manner, the toner 7 is charged by the frictional charging effect generated when the toner 7 is rubbed against the developing roller 1 by the toner supply roller 8, and a sufficient amount of the toner 7 is applied to the surface of the developing roller 1. It can carry toner.

[0045]

As described above, by improving the toner adhesion amount and the toner charge amount of the developing roller, and further increasing the development transfer rate by weakening the toner adhesion force, it is possible to obtain an image with good gradation and high density.

[Brief description of the drawings]

FIG. 1 is a sectional view of a developing device to which the present invention is applied.

FIG. 2 is a diagram showing a superimposed applied voltage waveform.

FIG. 3 is an explanatory diagram of generation of a closed electric field in a developing roller.

FIG. 4 is a partial cross-sectional view of a developing roller having another configuration.

FIG. 5 is an explanatory diagram of a developing roller in which a dielectric portion is formed in a foam cell.

FIG. 6 is a schematic cross-sectional view showing a process of producing the developing roller shown in FIG.

FIG. 7 is an explanatory view showing a developing roller having still another configuration.

FIG. 8 is an enlarged plan view of a part of the surface of a developing roller schematically showing each resistor.

FIG. 9 is a sectional view taken along line IV-IV in FIG.

FIG. 10 is an explanatory diagram showing electric lines of force of a minute closed electric field formed on the surface of the developing roller shown in FIGS. 8 and 9;

FIG. 11 is a perspective view of a developing roller having still another configuration.

FIG. 12 is a sectional view of a part of the developing roller shown in FIG. 11;

FIG. 13 is an explanatory diagram showing electric lines of force of a minute closed electric field formed on the surface of the developing roller shown in FIG. 11;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Developing roller 2 Developing device 3 Photoreceptor drum 7 Toner 9 Power supply for low frequency alternating voltage application 10 Power supply for high frequency alternating voltage application 11, 17 Dielectric part 12, 18 Conductor part 13 Closed electric field 19 Foaming cell 22 Medium resistor 23 High resistance body 24 Conductive area surface 25 Insulating area surface

──────────────────────────────────────────────────続 き 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. (56) References JP-A-61-273563 (JP, A) JP-A-2-61652 (JP, A) JP-A-1-267566 (JP, A) JP-A-60-61774 (JP, A) Japanese Utility Model Showa 60-54150 (JP, U) Japanese Utility Model Showa 62-79257 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/06 G03G 15 / 08

Claims (14)

(57) [Claims] An image forming apparatus includes an electrostatic latent image carrier that carries an electrostatic latent image and a developer carrier that carries a developer in a developing unit, and a bias is applied to the developing unit to perform development. The conductive portion of the substrate and the dielectric portion fixed to the substrate are regularly or irregularly mixed and exposed on the surface of the conductive substrate, and at least the dielectric portion is made of a developer.
A developer carrying member that forms a large number of minute closed electric fields on the surface by being charged to the opposite polarity or the same polarity as the polarity, and an alternating electric field obtained by superimposing a first alternating electric field and a second alternating electric field having a higher frequency than the first alternating electric field. Means for applying a bias to be formed, wherein in the developing section, the potential on the electrostatic latent image carrier, the electric field due to the bias, and the minute closing on the developer carrier
The developer carrier by the electric field determined by the
Transfer of the held developer to the electrostatic latent image carrier,
A developing device characterized by performing reverse transfer and developing. 2. A developing device, comprising: an electrostatic latent image carrier for carrying an electrostatic latent image and a developer carrier for carrying a developer facing each other in a developing section; , together with the different material is mixed exposed regularly or irregularly resistivity or dielectric constant, low
Develop at least several materials with different resistance or dielectric constant
A developer carrier that forms a large number of minute closed electric fields on the surface by being charged to a polarity opposite to or the same as the polarity of the developer;
And means for applying a bias to form an alternating electric field and alternating electric field superimposing the second alternating field of high frequency than the first alternating electric field at the developing unit, the potential on the latent electrostatic image bearing member Electric field due to bias and micro-close on the developer carrier
An electric field determined by the electric field and the developer carrier
Transfer of the developer held on the electrostatic latent image carrier to the developer
A developing device for performing development by performing transfer and reverse transfer . 3. A developing device in which an electrostatic latent image carrier carrying an electrostatic latent image and a developer carrier carrying a developer are opposed in a developing section, and a bias is applied in the developing section to perform development. Along with molding a conductive material containing insulating particles, at least the insulating particles
A developer carrying member that forms a large number of minute closed electric fields on the surface by being charged to the opposite polarity or the same polarity as the polarity, and an alternating electric field obtained by superimposing a first alternating electric field and a second alternating electric field having a higher frequency than the first alternating electric field. Means for applying a bias to be formed, wherein in the developing section, the potential on the electrostatic latent image carrier, the electric field due to the bias, and the minute closing on the developer carrier
The developer carrier by the electric field determined by the
Transfer of the held developer to the electrostatic latent image carrier,
A developing device characterized by performing reverse transfer and developing. 4. A developing device in which an electrostatic latent image carrier carrying an electrostatic latent image and a developer carrier carrying a developer are opposed to each other in a developing section, and a bias is applied in the developing section to perform development. A conductive part and a dielectric part are mixed in a minute area on the surface, and the dielectric part is formed in a foam cell near the surface of the conductive foam layer. A developer carrier that forms a large number of micro-closed electric fields on the surface when the portion is charged to a polarity opposite or the same as the polarity of the developer; and a first alternating electric field and a second alternating electric field having a higher frequency than the first alternating electric field. Means for applying a bias for forming a superimposed alternating electric field ,
Determined by the potential on the electrostatic latent image carrier, the electric field due to the bias, and the minute closed electric field on the developer carrier
The developer held on the developer carrier by an electric field
Transfer to the electrostatic latent image carrier, reverse transfer and development
Developing apparatus is characterized in that that. 5. A developing device in which an electrostatic latent image carrier for carrying an electrostatic latent image and a developer carrier for carrying a developer are opposed in a developing section, and a bias is applied in the developing section to perform development. In addition, a conductive part and a dielectric part are mixed in a minute area on the surface and made of an elastic conductive material containing insulating particles, and at least the dielectric part has a polarity opposite to that of the developer. A developer carrier that forms a large number of minute closed electric fields on the surface by being charged to a polarity or the same polarity, and a bias that forms an alternating electric field in which a first alternating electric field and a second alternating electric field higher in frequency than the first alternating electric field are superimposed; and means for applying said at developing unit, by an electric field determined by a micro閉電field on field and said developer carrying member by electric potential and the bias on the electrostatic latent image bearing member, before
The electrostatic latent image of the developer held on the developer carrier
A developing device for performing development by performing transfer to a carrier and reverse transfer . 6. A developer carrier comprising a conductive part and a dielectric part mixed on a surface thereof in a very small area, each of which is made of an elastic conductive material containing elastic insulating particles. , At least the dielectric part is charged to the opposite polarity or the same polarity as the polarity of the developer, so that many minute
The developing device according to claim 5, which forms a closed electric field . 7. Before Symbol developing device according to any one claims 1 to 6, characterized in that it is held to the developer carrying member developer by the micro閉電field. 8. A developing device for developing an electrostatic latent image bearing member carrying an electrostatic latent image and a developer carrying member carrying a developer in a developing portion by applying a bias in the developing portion. The conductive portion of the substrate and the dielectric portion fixed to the substrate are regularly or irregularly mixed and exposed on the surface of the conductive substrate, and at least the dielectric portion is made of a developer.
A developer carrying member that forms a large number of minute closed electric fields on the surface by being charged to the opposite polarity or the same polarity as the polarity ; a means for applying a bias for forming a first alternating electric field as a first step; and means for applying a bias for forming an alternating electric field by superimposing a second alternating electric field of high frequency smaller alternating electric field and a first alternating electric field from the first alternating electric field, the
In the developing unit, the potential on the electrostatic latent image carrier, the electric field due to the bias, and the minute closed electric field on the developer carrier are used .
Is held by the developer carrier by the electric field determined
Transfer of the developer to the electrostatic latent image carrier,
Developing apparatus characterized by development performed. 9. A developing device in which an electrostatic latent image carrier for carrying an electrostatic latent image and a developer carrier for carrying a developer are opposed in a developing section, and a bias is applied in the developing section to perform development. , together with the different material is mixed exposed regularly or irregularly resistivity or dielectric constant, low
Develop at least several materials with different resistance or dielectric constant
A developer carrier that forms a large number of minute closed electric fields on the surface by being charged to a polarity opposite to or the same as the polarity of the developer;
A means for applying a bias for forming a first alternating electric field as a step, and a bias for forming an alternating electric field in which an alternating electric field smaller than the first alternating electric field and a second alternating electric field higher in frequency than the first alternating electric field are superimposed as a second step. Means for applying,
In the developing unit, an electric field due to the potential and the bias on the electrostatic latent image carrier and a minute closed electric field on the developer carrier
Held on the developer carrier by the electric field determined by
Transfer, reversal of the developed developer to the electrostatic latent image carrier
A developing device for performing transfer and developing. 10. A developing device in which an electrostatic latent image carrier for carrying an electrostatic latent image and a developer carrier for carrying a developer are opposed in a developing section, and a bias is applied in the developing section to perform development. Along with molding a conductive material containing insulating particles, at least the insulating particles
A developer carrying member that forms a large number of minute closed electric fields on the surface by being charged to the opposite polarity or the same polarity as the polarity ; a means for applying a bias for forming a first alternating electric field as a first step; and means for applying a bias for forming an alternating electric field by superimposing a second alternating electric field of high frequency smaller alternating electric field and a first alternating electric field from the first alternating electric field, the
In the developing unit, the potential on the electrostatic latent image carrier, the electric field due to the bias, and the minute closed electric field on the developer carrier are used .
Is held by the developer carrier by the electric field determined
Transfer of the developer to the electrostatic latent image carrier,
Developing apparatus characterized by development performed. 11. A developing device in which an electrostatic latent image carrier for carrying an electrostatic latent image and a developer carrier for carrying a developer are opposed in a developing section, and a bias is applied in the developing section to perform development. A conductive part and a dielectric part are mixed in a minute area on the surface, and the dielectric part is formed in a foam cell near the surface of the conductive foam layer. A developer carrying member that forms a large number of micro-closed electric fields on the surface by charging the part with a polarity opposite to or the same as the polarity of the developer; and a unit that applies a bias that forms a first alternating electric field as a first step. , and means for applying a bias for forming a smaller alternating electric field than the first alternating electric field as a second step alternating electric field superimposing the second alternating field of high frequency than the first alternating electric field at the developing unit, the The charge on the electrostatic latent image carrier The electric field is determined by the electric field and the micro閉電field on the developer carrying member by the bias and
From the above, the developer of the developer held by the developer carrier
A developing device for performing development by performing transfer to an electrostatic latent image carrier and reverse transfer . 12. A developing device in which an electrostatic latent image carrier for carrying an electrostatic latent image and a developer carrier for carrying a developer are opposed in a developing section, and a bias is applied in the developing section to perform development. In addition, a conductive part and a dielectric part are mixed in a minute area on the surface and made of an elastic conductive material containing insulating particles, and at least the dielectric part has a polarity opposite to that of the developer. A developer carrier that forms a large number of minute closed electric fields on the surface by being charged to the same polarity or the same polarity; a unit that applies a bias that forms a first alternating electric field as a first step; and means for applying a bias for forming an alternating electric field superimposed with smaller alternating electric field and a second alternating electric field of high frequency than the first alternating electric field electric field at the developing section, on the latent electrostatic image bearing member Potential and said bi The electric field is determined by the by scan the field and the minute閉電field on the developer carrying member, said developing
Electrostatic latent image carrier of the developer held by developer carrier
A developing device, which performs development by performing transfer to a reverse transfer and reverse transfer . 13. A developer carrier comprising a conductive part and a dielectric part mixed on a surface with a very small area on the surface and made of an elastic conductive material containing elastic insulating particles. At least the dielectric portion is charged to a polarity opposite to or the same as the polarity of the developer, so that a large number of fine particles are formed on the surface.
The developing device according to claim 12, wherein the developing device forms a small closed electric field . 14. The developing device according to claim 8, wherein the developer is held on the developer carrier by the minute closed electric field .