JP3359058B2 - 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 used for an image forming apparatus such as a copying machine, a facsimile, a printer, and the like. It is about.

[0002]

2. Description of the Related Art In an image forming apparatus for forming an electrostatic latent image on a latent image carrier and visualizing the latent image with a developer, one component is required in view of miniaturization, cost reduction, high reliability, etc. of the developing device. A developing device using a system developer is advantageous. In particular, it is advantageous to use a non-magnetic toner because of its high transparency for colorization. As a developing device using a one-component developer, a developer carrier that carries the one-component developer on the surface and transports the developer along a predetermined circulation path including a development area, and stores the one-component developer. There is known a storage device having a storage unit and a developer supply unit that supplies the one-component developer stored in the developer storage unit to the development developer carrier in contact with the developer carrier. (See, for example,
-42672, JP-A-61-238072).

[0003]

Here, for example, in a non-magnetic one-component developing system, the optimum amount of adhesion and charge of a one-component developer (hereinafter referred to as toner) on a developer carrier will be described. The toner adhesion amount on the developer carrier is
Toner adhesion amount of about 0.6~1.0mg / cm ² on the image bearing member, it is desirable toner adhesion amount of about 0.5~0.7mg / cm ² on paper transfer is obtained. The amount of toner adhered on the latent image carrier and the transfer paper depends not only on the amount of toner adhered on the developer carrier, but also on the relative speed between the latent image carrier and the developer carrier in the development area.

However, according to this type of developing device which has been put to practical use, the amount of toner transported to the developing area is average because the toner layer on the developer carrier has only one layer and the amount of adhesion is small. Although the charge amount is about 5 to 15 μc / g, the toner adhesion amount on the developer carrier is 0.2 to 0.8 mg / cm ² , and the desired toner on the latent image carrier or the like In order to obtain the adhesion amount, it is necessary to set the speed of the developer carrier to two to four times the speed of the latent image carrier. When the rotation of the developer carrier is set to be high in order to cover the insufficient amount of toner adhered on the developer carrier, not only is it difficult to increase the image forming speed, but also the solid portion is There is also a phenomenon that the density at the rear end of the image becomes higher when the image is developed. This phenomenon does not cause a big problem in a black and white image, but in a color image, the color is transmitted through the toner and the color is visually perceived. .

In order to prevent the phenomenon of "from the rear end of the toner" and to obtain a desired amount of toner adhered on the latent image carrier, the speed of the developer carrier must be reduced. It is necessary to approach the speed of the body, that is, to approach the constant speed development, and to increase the amount of toner adhered on the developer carrying member as compared with the related art. Specifically, in order to secure a sufficient amount of toner adhered on the latent image carrier or transfer paper by substantially constant speed development, the amount of toner adhered on the developer carrier is determined by a contact developing method with high developing efficiency. At least 0.8mg
/ cm ² , at least 1.0 in non-contact developing method with poor development efficiency
mg / cm ² . In order to obtain such a toner adhesion amount on the developer carrying member, the toner layer thickness must be two or more.

In addition, if the toner layer on the developer carrier conveyed to the developing area contains uncharged toner or oppositely charged toner, it causes deterioration of development transfer, background contamination, resolution degradation, and the like. Therefore, the toner charge amount is 5 to 1 in average charge amount.
0 μc / g is desirable. Further, it is desirable that the toner charge amount distribution is a stable distribution with a relatively small amount of relatively low-charged toner causing deterioration in sharpness and resolution and background fouling.

[0007] As described above, two or more multi-layered toner layers having an average charge amount of 5 to 10 µc / g and having a stable charge distribution without containing an uncharged toner or a reversely charged toner are provided on the developer carrying member. Forming on the body is the biggest problem in increasing the image forming speed and enabling constant speed development to prevent "from the rear end of the toner".

[0008] The applicant of the present invention has previously used a developer carrier as a developer carrier from a dielectric portion whose surface is regularly or irregularly distributed over a small area and a grounded conductive portion.
At a contact portion between the developer carrier and a developer supply member rotating at a position in contact with the surface of the developer carrier, the one-component developer is frictionally charged, and the dielectric portion is charged with the developer supply member and the one-component developer. A plurality of minute electric fields are formed near the surface of the developer by frictional charging with the developer, whereby the triboelectrically charged one-component developer is carried in multiple layers on the developer carrier by the minute electric field. An application was filed for the device (Japanese Patent Application No. 2-15110). According to the developing device of the invention of the prior application, it is possible to form a multi-layered toner layer having a stable charge amount on the developer carrier. The present invention has been made by further research on the developing device of the prior invention.

It is an object of the present invention to provide a one-component system capable of forming a toner layer having a desired amount of charge with a small amount of reversely charged toner or uncharged toner on a developer carrier and supplying the toner layer to the latent image carrier. It is to provide.

[0010]

In order to solve the above-mentioned problems, a first aspect of the present invention is directed to a developer carrying member which carries and transports a one-component developer on a surface thereof, and stores the one-component developer. And a developer supply means for frictionally charging the one-component developer from the developer storage means and causing the developer to be carried on the developer carrier, and the developer conveyed by the developer carrier. in the developing device for visualizing the electrostatic latent image by using a component developer, what number of infinitesimal closed field holds selectively charge on the surface as a developer carrying member can be formed used, the degree of developing agent supply means, a charge providing means for providing a selectively charge to the surface in order to form the fine small closed electric field, which and fine small closed electric field by a predetermined potential is maintained gaps While facing the surface, the triboelectrically charged one-component developer faces the surface while facing the surface. Developing for conveying the electrode means for forming an electric field on the electric force around the fine small closed electric field, the one-component developer is frictionally charged on the surface of the electric field and fine small closed electric field is formed And the developer carrying member, wherein the dielectric portion and the grounded conductor portion are regularly and irregularly mixed and distributed on the surface, and the transporting portion is The charge applying means is constituted by a rotating body which is rotated at a position in contact with the surface of the developer carrying member, and the charge applying means is formed by a surface of the rotating body formed of a material capable of frictionally charging the dielectric portion to a predetermined polarity. Wherein the electrode means is formed of a conductive material, and is set to a predetermined potential at which a potential difference from the conductor portion forming the electric field exerting the electrostatic force in a state facing the conductor portion can occur. The rotating surface is constituted by an inner surface of a large number of minute recesses formed on the rotating surface, The opening diameter is characterized in that it has formed to be more than twice the size of the maximum pitch of the dielectric unit distribution.

[0011]

[0012]

[0013]

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

In the developing device according to any one of the first to eighth aspects, charge is selectively applied to the surface of the developer carrier by the charge applying means,
By charge is held in the developer carrying member surface, numerous fine small closed electric field on the surface is formed. The predetermined potential is an electrode means facing the surface while maintaining a gap to the extent that the fine small closed electric field is maintained, the electrostatic force toward the surface friction charged one-component developer an electric field on, formed around the fine small closed electric field, thereby, the electric field and the fine small closed electric field is in a state of coexist on said surface. FIG. 1 schematically shows such a state. In the illustrated example, the dielectric portion 52 and the conductor portion 51 are configured to coexist on the surface so as to selectively hold the electric charge on the surface of the developer carrying member. A positive charge is provided. Due to the positive charges, a minute closed electric field is formed on the adjacent portion between the conductor portion 51 and the dielectric portion, which is expressed by the line of electric force as if it were coming out of the conductor portion 51 to the surface and entering the dielectric portion 52. ing. Then, an electrode means set to a predetermined potential opposes the surface of the developing carrier with a gap, and applies an electrostatic force toward the surface to the one-component developer 4 triboelectrically charged around the minute closed electric field. Are formed. Then, with a developer conveying unit, for conveying the one-component developer is frictionally charged on the surface of the electric field and fine small closed electric field is formed. Some of the one-component developer conveyed by the developer conveying means are carried on the developer carrying member in the fine small closed electric field,
The other part is carried on the developer carrier by the electric field, so that a sufficiently charged one-component developer is stacked on the developer carrier in an amount sufficient to perform good development. It is carried. Then, the one-component developer transported to the developer carrier is used for developing the latent image on the latent image carrier. In addition, since the developer carrying member is configured such that a dielectric portion and a grounded conductor portion are regularly and irregularly mixed and distributed on the surface, electric charges are held by the dielectric portion. Are getting to get. When the electric charge is retained in the dielectric portion, a charge having a polarity opposite to that of the electric charge is induced in the conductor portion close to the dielectric portion, whereby the dielectric portion and the conductor portion fine small closed electric field on the adjacent portion can be formed. In addition, a rotating body whose surface is formed of a material capable of frictionally charging the dielectric portion to a predetermined polarity rotates while being in contact with the developer carrying member, whereby a charge is applied to the dielectric portion by frictional charging. imparting to form a fine small closed electric field on an adjacent portion of the dielectric portion and the conductor material portion of to the developer carrying member surface as described above. Further, the rotating surface in a number formed fine recesses, the inner surface portion which is at a predetermined potential of conductive material, said developing agent holding a gap to the extent that the fine small closed electric field is maintained opposite to the surface of the carrier, by which, together with the fine small closed electric field is maintained,
An electric field is generated between the conductor portion and the electrode, which applies an electrostatic force toward the conductor portion to the triboelectrically charged one-component developer. Further, by the rotation of the rotary member, the friction charged one-component developer, the recess and being supported on the rotating surface of the other recess electric field and a development bearing member fine small closed electric field is formed Conveyed over the surface. Some of the one-component developer conveyed herein is carried near the adjacent portion of the dielectric portion and the conductor material portion in the fine small closed electric field, also some other conductor conductor with electric field Carried on the part. In particular, since the one-component developer possessed by the triboelectric charge also exerts a mirror image force on the conductor portion, a large amount of the one-component developer is carried by this mirror image force. As a result, a sufficiently charged one-component developer is carried on the development carrier in an amount sufficient to perform good development. Since the recess opening diameter is formed to be more than twice the size of the maximum pitch of the dielectric unit distribution, while favorably maintaining the infinitesimal closed field, said developer carrying member A predetermined electric field can be formed between the conductive portion of the rotating member and the inner surface of the concave portion of the rotating body.

[0027]

[0028]

According to the present invention, the ratio of the total area of the dielectric part to the total area of the total area of the dielectric part and the total area of the conductor part in the developer bearing member is as follows. 6. The method according to claim 5, wherein the distance is in the range of 30 to 70%.
As described in the invention, the electric resistance of the developer carrier is 1 × 10 ¹² Ωcm or more in the dielectric portion and 1 in the conductor portion in all environments.
× 10 ⁹ Ωcm or less, wherein the developer carrier is used as a part of a grounded conductive base as the conductive part and as the dielectric part, as in the invention of claim 6. Of the dielectric part has a width or size of 50
To be in the range of from 500 to 500 μm, so as to be mixedly exposed on the surface, or as in claim 7,
The developer carrier may be a part of a conductive substrate serving as the conductor portion, and a minute dielectric having a depth perpendicular to the surface of the developer carrier serving as the dielectric portion in a range of 50 to 200 μm. and part of the body is, when it is configured to mix exposed on the surface it can be satisfactorily formed fine small closed electric field on said developer carrying member.

Further, as in the invention of 請 Motomeko 8, the developer carrying member, when the surface roughness (Rz) is configured to be less than 50% of the size of the one-component developer, The surface of the developer carrying member becomes substantially smooth, which can effectively prevent the one-component developer from sticking to the developer carrying member due to rubbing between the developer carrying member and the rotating body. it can.

[0031]

[0032]

[0033]

[0034]

[0035]

[0036]

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a developing device of an electrophotographic copying machine will be described below. FIG. 2A is a front view illustrating a schematic configuration of the developing device according to the present embodiment. The photosensitive drum 1 as a latent image carrier has a peripheral speed of 120 mm, for example.
/ Sec, and is driven to rotate clockwise by the arrow. A developing device 2 is disposed on the right side of the photosensitive drum 1. Around the photosensitive drum 1, a well-known charging device, an exposure optical system, a transfer separation device, a cleaning device, and a static elimination device (all not shown) are provided for performing an electrophotographic process. The developing device 2 according to the present embodiment includes a casing 3 having an opening facing the surface of the photosensitive drum 1, and a developer partially exposed from the opening and rotationally driven in a counterclockwise direction at a predetermined peripheral speed by an arrow. A developing roller 5 serving as a carrier, a toner supply roller 6 serving as a developer supply unit which is driven to rotate clockwise by an arrow while being pressed against the right side of the development roller 5, and a right side inside the casing 3. An agitator 7 for supplying a non-magnetic one-component developer (hereinafter referred to as toner) 4 contained in a hopper portion as a configured developer storage means to the surface of the supply roller 5 and stirring the toner in the hopper portion; A partition plate 10 for restricting the toner in the hopper from directly entering the vicinity of the surface of the developing roller 5, and a rotation of the developing roller 5 conveys the toner to a developing area which is a portion facing the photosensitive drum 1. And a layer thickness leveling plate 8 uniformly level the thickness of the toner layer on the developing roller 5 to be.

As shown in FIG. 2A, the developing roller 5 may be arranged so as to face the surface of the photosensitive drum 1 with a predetermined gap in the developing area 9 to perform non-contact development. As shown in FIG. 6 or FIG. 7, contact development may be performed by arranging the toner layer on the developing roller 5 so as to contact the surface of the photoconductor 1. In FIG. 7, the belt-shaped photoconductor 1 is used. In each case,
In order to prevent the above-mentioned phenomenon that the toner is shifted to the rear end, the rotation of the developing roller 5 is controlled by changing the surface moving direction in the developing area in the same direction as the photosensitive drum 1 and the peripheral speed of the photosensitive drum 1. Speed almost equal to the speed, that is, about 12 in this example.
0 mm / sec. However, in the contact development, if the development is absolutely constant speed, there is no speed difference between the surface of the photosensitive drum 1 and the surface of the developing roller 5, and therefore, regardless of the potential on the surface of the photosensitive drum 1, There is a risk of toner adhesion. To prevent this, the peripheral speed of the developing roller 5 is set to be slightly higher. For example, peripheral speed ratio (peripheral speed of photosensitive drum: peripheral speed of developing roller 5)
Is preferably from 1.05 to 1.1. With this speed ratio, the trailing edge of the toner is not noticeable. Also,
An appropriate developing bias is applied to the developing roller 5 by a power supply 20. For example, in the case of non-contact development, a developing bias with good flight conditions is applied.

As the developing roller 5 of the present embodiment, a roller capable of selectively holding electric charges on the surface is used. For example, as shown in FIGS. 3A and 3B, a developing roller 5 configured such that a dielectric portion 52 capable of holding a charge on its surface and a grounded conductive portion 51 are mixedly exposed in a small area. Is used. FIG. 3A is a plan view of the surface of the developing roller 5, and FIG. 3B is a cross-sectional view taken along a cutting line aa in FIG. 3A. This dielectric portion 52 has, for example, 10
^It is made of a dielectric material having a resistance of ¹³ Ωcm or more, and the size of the exposed surface is about 50 to 200 μm in diameter.
The size in the direction perpendicular to the surface, that is, the size in the depth direction is 5
The thickness should be about 0 to 150 μm. Such dielectric portions 52 are dispersed randomly or according to a certain rule. If the total area of the dielectric portion 52 is in the range of 30 to 70%, preferably 40 to 60% of the total area of both portions, the shape of the dielectric portion 52 is Optional.

As described above, the developing roller 5 in which the conductive portion 51 and the dielectric portion 52 are mixedly exposed on the surface is formed, for example, by forming predetermined grooves into a iris shape by knurling on the surface of the metal roller. The surface of the roller is coated with a predetermined dielectric material to form a dielectric layer coat, and the surface of this roller is cut to expose the core portion as a conductor portion 51 to the surface, and to form a knurled groove. It can be manufactured by exposing the filled resin portion as the dielectric portion 41 on the surface.

Further, the surface layer is made of a conductive resin material in which dielectric particles having a particle size of, for example, 50 to 500 μm are dispersed,
A developing roller 5 having the particles exposed on the surface can also be used. This can be manufactured by, for example, forming a surface layer made of a conductive resin material in which dielectric particles are dispersed on a metal roller by coating or the like, and polishing the surface thereof. FIG. 8A is a cross-sectional view near the surface layer of the developing roller 5 manufactured in this manner, and FIG. 8B is a plan view showing a part of the surface of the developing roller 5. When the toner is used by friction charging to a negative polarity, acrylic particles, polyamide particles, and the like can be used as the dielectric particles, and an acrylic resin, a urethane resin, or the like in which carbon black is dispersed as a conductive resin. Can be used. Many other resins can be used depending on the triboelectric charging polarity of the toner. FIG. 9 shows the relationship between the size of the dielectric particles and the intensity of the electric field formed on the surface of the developing roller 1 as described later. As can be seen from the drawing, if the particle size is 50 μm or more, a sufficient electric field of 0.7 V / μm for supporting the toner can be obtained. The upper limit of the particle size is limited by problems on the image and the roller method, and the size of the exposed surface is limited to about 500 μm in diameter. The problem on the image is that since the toner adhesion on the developing roller 5 varies depending on the electric field, if the particles are large, the toner becomes sparse and the image becomes uneven. The size of the exposed particles in the depth direction (the direction perpendicular to the surface of the developing roller) is limited mainly by the roller method, and is limited to about 200 μm.

As shown in FIG. 7, for contact development corresponding to a hard photosensitive drum, the developing roller 5 is a soft roller having a JIS hardness of 30 to 70 degrees as measured from the surface. It is desirable. As such a developing roller 5, a roller in which an elastic surface layer on a substrate is formed of an elastic conductive material in which dielectric particles are dispersed can be used. For example, a conductive elastomer in which dielectric particles are dispersed and whose particles are exposed on the surface can be used. As the elastic conductive material, for example, a material obtained by adding a conductivity imparting agent to a rubber material can be used. Representative examples include diene rubber, olefin rubber, and ether rubber. Epoxy, acrylic, polyamide, polystyrene resin or the like having a resistance of 10 ¹³ Ωcm or more can be used as the dielectric particles. When the elastic developing roller 5 is brought into contact with the hard photosensitive drum as in this example, the maintenance of the developing cap is easy and the accuracy of the developing roller is advantageous.

It is desirable that the conductive portion 51 of the developing roller 5 has a volume resistance of 10 ⁶ Ωcm or less so that a minute electric field described later can be efficiently formed. Further, carbon or the like may be internally added to the same material as that of the dielectric portion 52, for example, a material having a resistance of 10 ¹³ Ωcm or more to make the resistance of 10 ⁸ Ωcm or less.

The toner supply roller 6 functions as a developer conveying means for conveying the toner to the surface of the developing roller 5 as conventionally known. The electric charge applying means for applying electric charge to the dielectric portion 52 and the electrode means facing the roller 5 at a predetermined potential while maintaining a predetermined interval on the surface of the roller 5 are also provided. Specifically, the dielectric portion 52 of the developing roller 5 is frictionally charged on the surface of the toner supply roller 6 to apply a charge having a polarity opposite to the charged polarity of the toner, thereby functioning as the charge applying unit. For this,
At least the surface is made of a material capable of frictionally charging the dielectric portion 52 to a predetermined polarity. In the case where the toner supply roller 6 is also provided with a function of frictionally charging the toner from the hopper at a contact portion with the surface of the developing roller 5, for example, the frictional charging series toner material and the dielectric material 52 Adopt the one located in Note that, in relation to the frictional charging characteristics of the material of the conductor portion 51 of the developing roller 5, the material may be frictionally charged to the same polarity as the dielectric portion 52. Further, a large number of minute concave portions are formed on the surface of the toner supply roller 6, and the inner peripheral surface portion of the concave portion functions as an electrode. For this reason, the concave portion is formed so as to have a depth such that a minute electric field formed by the triboelectric charge of the dielectric portion 52 described later is maintained (does not collapse), and at least one of the concave portions is formed therein. The peripheral surface is formed of a conductive material. Then, the inner peripheral surface portion is a potential for forming an electric field in the gap with the conductor portion 51 that applies an electrostatic force to the frictionally charged toner from the inner peripheral surface portion side toward the conductor portion 51, that is, It is set to a potential that causes a potential difference from the conductor portion 51 in which an electric field in any direction is formed. The above-described toner supply roller 6 can be constituted by, for example, a roller (hereinafter, referred to as a sponge roller) in which a foamed elastic material layer having conductivity and predetermined frictional charging characteristics is formed on a cored bar at a predetermined potential. . In addition, it is desirable that the resistance value of such a sponge roller is semiconductive or less. Further, in order to give the above-mentioned electrode function to the inner peripheral surface of the many minute concave portions on the surface of the sponge roller, for example, a predetermined voltage is applied to the sponge roller by the power supply 21 as shown in FIG. .
The rotation of the toner supply roller 6 is a forward rotation in which the surface moves in the same direction as the surface of the developing roller 5 at the contact portion A with the developing roller 5. The peripheral speed is set to, for example, about 0.6 to 1.5 times the peripheral speed of the developing roller 5.

The agitator 7 supplies the toner contained in the hopper to the surface of the toner supply roller 6 and agitates the toner contained therein. When supply to the surface of the supply roller 6 is possible,
It may be omitted.

The partition plate 10 is provided so as to restrict the toner contained in the hopper from directly entering the vicinity of the surface of the developing roller 5 and to allow the toner contained to be supplied to the surface of the toner supply roller 6. However, if there is no possibility that the toner contained in the hopper directly enters the vicinity of the surface of the developing roller 5 due to the shape of the hopper or the like, it may be omitted.

The layer thickness equalizing plate 8 has a light contact pressure of about 10 to 20 g / cm in the case of non-contact development, and a contact pressure of about 30 g / cm in the case of contact development. 5 so as to abut. The reason why the contact pressure is set to be relatively high in the case of contact development is that, in the case of contact development, the transfer ratio of development to the photosensitive drum 1 is relatively high, so that the appropriate amount of toner adhering to the developing roller 5 is reduced. , For example, 0.8 to 1.0
This is because the amount is relatively small at about mg / cm ³ . As the material of the layer thickness equalizing plate 8, it is desirable to employ a material located between the toner material and the dielectric material 52 in the charging sequence, similarly to the surface material of the toner supply roller 6. .

In the above configuration, the agitator 6 is used to store the toner in the hopper by the agitator 6 on the surface of the toner supply roller 6 which is exposed to the hopper at the supply portion between the lower edge of the partition plate 10 and the inner surface of the lower wall of the casing 3. A toner is supplied. The toner supplied to the toner supply roller 6 adheres to the gap and the surface of the sponge or the brush, and is conveyed toward the contact portion A between the toner supply roller 6 and the developing roller 5 by rotating the toner supply roller 6 clockwise. . On the other hand, the surface portion of the developing roller 5 that has passed the developing area 9 due to the rotation of the developing roller 5 in the counterclockwise direction of the arrow also enters the contact portion A with the toner supply roller 6.

At the contact portion A, the surface of the toner supply roller 6 and the surface of the development roller 5 move with a relative speed difference, and the friction between the development roller 5, the toner 4 and the toner supply roller 6 causes the dielectric portion of the development roller 5 to move. 52
Is charged in the opposite polarity to the desired toner charging polarity (regular development (P
/ P), the charge is of the same polarity as the photoreceptor charge, and in reversal development (N / P), the charge is of the opposite polarity to the photoreceptor charge). Since the conductor portion 51 adjacent to the dielectric portion 52 in which the electric charge is stored is grounded, electric charges of opposite polarities are induced, and the electric charges are induced on adjacent portions of both portions, as shown in FIGS.
As shown in (a), a minute electric field having a large component parallel and perpendicular to the surface of the developing roller 5 is formed. On the other hand, since the toner supply roller is rotating in the forward direction with respect to the developing roller 5, the toner attached to the toner supply roller 6 is rubbed at the contact portion A between the developing roller 5 and the supply roller, and most of the toner has a desired polarity ( In normal development, it has the opposite polarity to the photoconductor charge, and in reverse development, it has the same polarity as the photoconductor charge).

At the contact portion A, since a predetermined potential difference is formed between the toner supply roller 6 and the developing roller 5, an electric field (hereinafter, referred to as a bias electric field) substantially perpendicular to the surface of the developing roller 5 is generated. This electric field is formed in the conductor part 51 more than the dielectric part 52 of the developing roller 5. This is because the conductor part 51 is the toner supply roller 6
This is because the electrode is slightly separated in the dielectric portion 52. Further, since the inside of the minute concave portion on the surface of the toner supply roller 6 is a gap that does not break the minute electric field even at this contact portion,
As shown in FIG. 4B, a small electric field is maintained here. Therefore, the micro electric field due to the triboelectric charging of the dielectric part 52 and the bias electric field coexist on the surface of the developing roller 5 in the contact part A.

Then, the toner supplied into the concave portion and frictionally charged in contact with the surface of the toner supply roller 6 or the surface of the developing roller 5 is transferred to the conductor portion 51 by a minute closed electric field.
And a force toward the vicinity of the dielectric portion 52 and a force mainly toward the conductor portion 51 due to the bias electric field. On the surface of the developing roller 5 near the portion adjacent to the conductor portion 51 and the dielectric portion 52, the toner captured by the minute electric field is carried more strongly than usual. The small closed electric field is reduced by carrying the toner (FIG. 5A). An external force (scavenging force) such that the charged toner is laminated on the conductor portion 51 and rubbed on the surface of the toner supply roller 6 around the concave portion
Is applied, the multi-layer toner layer continues to be carried without collapse. In this manner, a stable multilayer toner layer can be formed by combining the minute electric field and the bias electric field on the developing roller 5. By passing the toner, the toner is recovered to the initial amount. (FIG. 5 (b)) In this way, a multilayer toner layer is formed that is maintained to some extent even when an external force pressed by a toner layer regulating blade or the like is applied. Here, in the roller having such a configuration, toner adhesion is observed also in the dielectric portion, but in the dielectric portion, the toner amount corresponding to the triboelectric charge on the surface adheres, whereas in the conductive portion 51, Since the image force of the charged toner acts, a larger amount of toner can be attached. As described above, the developing roller 5 holds the contact portion A in a state where a sufficiently charged toner is carried in multiple layers.
Go out. In the present embodiment, since the toner supply roller 6 and the developing roller 5 are rotated in the forward direction, the rotation of the toner supply roller 6 causes the non-charged portion from the hopper on the developing roller 5 passing through the contact portion A. Does not supply toner.

The toner layer on the developing roller 5 that has passed through the contact portion A is evenly controlled in thickness by the layer thickness equalizing member 8 that is lightly in contact with the developing roller 5, and is then conveyed to the developing area 9. You. In the developing region 9, development is performed while the surface of the developing roller 5 and the surface of the photosensitive drum 1 to which the optimal developing bias is applied by the contact or non-contact developing method are moved at substantially constant speed. In the developing region 9, an electric field is also formed in which the conductive portion 51 of the developing roller 5 exerts an electrode effect and toner on the developing roller 5 easily adheres to the photosensitive drum 1.

As described above, according to this embodiment, the developing roller 5
The conductor part 51 grounded to the dielectric part 52 on the surface
And the toner supply roller 6 is used to frictionally charge the dielectric portion 52, whereby the toner is finely closed by the triboelectric charge of the dielectric portion 52. Since an electric field is formed and a large amount of toner can be easily sucked to the surface of the developing roller 5, a multilayer toner layer can be easily formed on the developing roller 5.

Also, a large number of predetermined minute concave portions are formed on the surface of the toner supply roller 6 which rotates in contact with the developing roller 5, and a predetermined potential difference is provided between the rollers 5, 6. Since the minute closed electric field and the electric field substantially perpendicular to the surface of the developing roller 5 due to this potential difference coexist at the contact portions of the rollers 5 and 6, the charged toner is carried, so that a multilayer toner layer can be reliably formed. Moreover, the conductor portion 51
The upper carried toner exits the contact portion in such a state that the component parallel to the surface of the developing roller 5 is surrounded by the toner strongly supported by the minute electric field having a large component, and thereafter the toner layer exerts an external force. Even when the toner layer is received, the toner layer is continuously carried without being disintegrated, and a sufficient amount of the toner layer can be supplied to the developing area 9.

Further, the toner supply roller 6 and the developing roller 5 are rotated in the forward direction, whereby the rotation of the toner supply roller 6 does not supply the uncharged toner from the hopper onto the developing roller 5 that has passed through the contact portion A. With this configuration, the amount of toner adhered to the developing roller 5 is hardly affected by environmental fluctuations, and a charge amount distribution of the toner with less uncharged toner can be obtained, so that development characteristics can be stabilized. Accordingly, a multilayer toner layer having a desired charge amount can be stably formed on the developing roller 5 with a small amount of uncharged toner, so that constant speed development is also possible. There is no need to provide a blade or the like for removing the uncharged toner, and the configuration of the developing device can be simplified accordingly. And
Since the developing roller 5 is rotated so as to move at substantially the same speed as the photosensitive drum 1 in the developing area 9, “from the rear end of the toner” does not occur, and a color image has excessive density or overlap at the rear end. It is possible to obtain a good image without any trouble such as a color difference between images. Further, since the non-charged toner is not contained in the toner layer on the developing roller 5, it is possible to obtain good image quality without background stain and resolution degradation.

The toner used in the developing device is preferably less than 10 ¹³ Ωcm, since the lower the resistance, the quicker the charge and the more easily the toner layer can be formed. However, in the case of a developing device of an image forming apparatus to be transferred to the transfer paper by applying a transfer electric field to the toner image formed on the photoreceptor, since the transfer defect to be less resistance, 10 ⁶ to 10 ¹² Those within the range of Ωcm are suitable.

Hereinafter, more specific embodiments of the present embodiment will be described as specific examples. [Specific Example 1] (1) Developing roller 5-A groove having a depth of 0.1 mm and a groove width of 0.2 mm was formed on the surface of a cored roller having a diameter of 25 mm by knurling to a pitch of 0.3
It was formed in an iris shape at an angle of 45 degrees in mm. An epoxy-modified silicone resin (Toray SR2115: trademark) is coated on the surface of this cored roller,
After drying at 0 ° C. for about 30 minutes, a dielectric layer coat was applied. -The surface of this roller was cut to expose the core metal portion as a conductor portion 51 on the surface, and the resin portion remaining filled in the knurled groove was used as the dielectric portion 41. At this time, the total area of the conductor portion 51 was set to be 50% of the whole (accordingly, the total area of the dielectric portion 41 was 50% of the whole). The surface roughness is R3 to 20 μm, preferably 5 to 20 μm.
About 10 μm. (2) Toner supply roller 6 A diameter 1 having a conductive foamed elastic layer 15 made of foamed polyurethane mixed with carbon and having a volume resistance of about 1 × 10 ⁶ Ωcm.
It is composed of a 4mm sponge roller, and the bite amount is 1
It was arranged in contact with the developing roller 5 in mm.・ The average pore opening diameter on the surface of this sponge roller is 0.2
To 0.3 mm. (3) Toner Supply Roller Bias A bias having the same polarity as the DC component of the developing roller 5 and an absolute value larger by 100 V, specifically -600 V, was applied to the core 14 of the sponge roller. (4) Layer thickness equalizing plate 8 An elastic plate made of urethane rubber having a thickness of 2 mm was placed in contact with the developing roller 5 at a contact pressure of 10 to 20 g / cm. (5) Developing bias, developing gap
A two-peak AC bias of 1000 V and 1000 Hz was applied (instead of this, a DC bias of -800 V may be applied). The developing gap was set to 150 μm. (6) Photoreceptor-OPC-Uniform charging was performed so that the negative latent image became -850 V in the background portion and -150 V in the writing portion (image portion). (7) Toner A negatively charged toner using a non-magnetic styrene acrylic resin and a polyester resin was used. · A SiO ₂ fine powder 0.5 wt% was externally added as an external additive. (8) Evaluation The adhesion amount and the like of the toner layer adhered and carried on the developing roller 5 were measured under the above conditions.
A toner layer having a charge amount distribution of 2.0 mg / cm ² , an average charge amount of 8 to 15 μc / g, and a small amount of uncharged toner could be formed. The obtained image was a solid image with no background stain and a good line image. The hole opening diameter (opening diameter of the concave portion) at this time was almost twice the formation pitch of the dielectric portions 52.

[Specific Example 2] A point that a belt-shaped photosensitive member as shown in FIG. 6 is used as a photosensitive member, that a contact gap is developed at a developing gap of 0 mm, and that a contact pressure of the layer thickness equalizing plate 8 is 30 g / cm. Developing under the same conditions as in Example 1 except that -600 V was used as the developing bias,
When the amount of the toner layer attached was 0.8 to 1.0 mg / cm ² , a good toner layer could be formed, and a good image could be obtained.

[Specific Example 3] A hard photosensitive drum as shown in FIG. 7 is used as a photosensitive member, and dielectric particles having a resistance of 10 ¹³ Ωcm or more are dispersed as a developing roller 5 on an elastic surface layer elastic conductive substrate. The point of using a soft roller with a JIS hardness in the range of 30 to 70 degrees measured from the surface, the point of contact development with a development gap of 0 mm, and the contact pressure of the layer thickness equalizing plate 8 to 30 g / cm. The development was carried out under the same conditions as in Example 1 except for the point that the toner layer was used and -600 V as the developing bias. The amount of the toner layer adhered was 0.8 to 1.0 mg / cm ² . Similarly, a good toner layer could be formed, and a good image could be obtained.

[Specific Example 4] A hard photosensitive drum as shown in FIG. 7 is used as the photosensitive member, and the following surface layer hardness of the developing roller 5 is 70 to 100 degrees, preferably 90 to 100 degrees. Example 1 except that a roller within the range of (1), contact development with a development gap of 0 mm, and use of -600 V as a development bias were used.
When the development was performed under the same conditions as described above, the amount of the toner layer attached was 1.0 to 1.2 mg / cm ² , and a similarly good toner layer could be formed, and a similarly good image could be obtained. did it. According to this example, contact development is performed with a minute nip width between the photosensitive member and the hard type photosensitive member. For this reason, a good image was obtained even if there was a slight difference in the linear velocity between the photosensitive member and the developing roller due to the narrow nip width, and an image with a good balance between background contamination and the rear end was obtained. Further, even if the linear velocity ratio during development is increased, it is hard to come out from the rear end. Further, since the roller for contact development is relatively firm, it is superior in the accuracy of the roller. Developing roller 5: The surface layer is made of a conductive resin in which dielectric particles are dispersed.・ The conductive resin is made of acrylic resin, urethane resin, elastomer, etc. with carbon black dispersed, and has a thickness of 5
mm surface layer. -Dielectric particles are resins with strong negative charge, such as acrylic resin and polyamide resin.-The resistance of the developing roller is 1 × 10 ⁸ Ωcm or less.

[Specific Example 5] The above-described specific example 4 was used except that a belt-like photosensitive member as shown in FIG. 6 was used as the photosensitive member and that the contact pressure of the layer thickness equalizing plate 8 was 30 g / cm. When the development was performed under the same conditions, the amount of the toner layer attached was 0.8 to 1.0 mg / cm ² , and a similarly good toner layer could be formed, and a similarly good image could be obtained. Was.

[Specific Example 6] The developing roller 5 has a particle size of 5
Dielectric particles (acrylic resin,
The same conditions as in Example 1 above, except that a 20 mm diameter roller having a surface layer made of a conductive resin (such as an acrylic resin or a urethane resin in which carbon black is dispersed) in which a polyamide resin or the like is dispersed is used. When the development was carried out, the toner layer adhesion amount was 1.5 to 2.0.
Similarly, a good toner layer could be formed at a charge amount of 8 to 15 μC / g at mg / cm ² , and a similarly good image could be obtained. The toner of this example had a resistance of 7 × 10 ¹⁰ Ωcm.

[Specific Example 7] The point that a belt-shaped photosensitive member as shown in FIG. 6 was used as the photosensitive member, that the contact development was performed with a development gap of 0 mm, and that the contact pressure of the layer thickness equalizing plate 8 was 30 g / cm. Developing was performed under the same conditions as in Example 6 except that −600 V was used as the developing bias.
When the amount of the toner layer attached was 0.8 to 1.0 mg / cm ² , a good toner layer could be formed, and a good image could be obtained.

Next, the electrical characteristics of the toner supply roller 6 and the applied bias will be described in detail. As described above,
Since the toner supply roller 6 forms a predetermined electric field at the contact portion A with the developing roller 5 due to the potential difference from the developing roller 5, it is desirable to reduce the leakage between the rollers 6 and 5. For this purpose, it is advantageous to make the toner supply roller 6 semiconductive. The toner supply roller 6 used in each of the above embodiments satisfies this requirement because the volume resistance of the foamed conductive layer is about 1 × 10 ⁶ Ωcm. Hereinafter, various conditions that have been found to be suitable for making the toner supply roller 6 semiconductive as a result of examination will be described. First, the voltage applied by the power supply 21 to the core 14 of the toner supply roller 6 having such a semiconductive layer formed on the core was examined in more detail. Between the toner supply roller 6 and the developing roller 5 to form an optimal toner layer on the developing roller 5 by setting the magnitude of the potential difference formed between the toner supply rollers to within the range of 50 V to 300 V. I can do it. That is, when the voltage is less than 50 V, the effect of increasing the amount of adhesion is not observed. When the voltage exceeds 300 V, the amount of adhesion is saturated at 1.5 to 2.0 mg / cm. There was a leak with the roller 6, and it was difficult to form a stable potential difference.

When such a potential difference is formed, it is desirable that the volume resistivity between the developing roller 5 and the sponge roller 6 is in the range of 10 ^{6 to} 10 ¹⁰ Ωcm. According to this, by setting the current I to 500 μA or less, wasteful power consumption of the power pack is reduced, and a desired electric field can be obtained without reducing the applied voltage, and a predetermined toner supply amount can be obtained. A roller provided with an elastic layer made of a foamed polyurethane of a conductive material dispersion type is used as the toner supply roller 6, and the contact state of the toner supply roller 6 with the developing roller 5 is 30.
cm, the contact nip width was 0.587 cm, and the thickness of the sponge layer at the time of contact was 0.4 cm. When a supply bias of 150 [V] was applied, the observed current was 2 μA, that is, the resistance was 7. In the case of 5 × 10 ⁷ Ω, the volume resistivity is 3 × 10 ⁹ Ωcm, which satisfies the above-mentioned appropriate condition. FIGS. 14A and 14B show an example in which the above-mentioned volume resistivity is 3 × 10 ⁹ Ωcm and satisfies the above condition (hereinafter referred to as this example), and the above-mentioned volume resistivity is smaller than the lower limit of the above condition. Another example (hereinafter referred to as conventional example)
, The logarithmic value of the supply potential difference and the current value (FIG. 14)
(A)) and the relationship between the supply potential difference and the logarithmic value of the volume resistivity (FIG. 14 (b)). Of the symbols indicating sample points, diamonds indicate sample points in this example when toner is not present in the hopper, triangles indicate sample points in this example when toner is present in the hopper, and squares indicate sample points when toner is not present in the hopper. The sample points and the crosses of the conventional example indicate the sample points of the conventional example when there is toner in the hopper, respectively. These figures do not show sample points when a bias of 150 V is applied to the conventional example, but the observed current greatly exceeds log ₁₀ I> -3, that is, 1 mA, and exceeds the power supply capacity of the power pack of the machine body. As a result of the voltage leaking out of tracking, a voltage drop occurred. In addition, the resistance at this time is lower than 10 ⁶ Ωcm, which indicates that it is not suitable as a condition. However, in this example, an electric field for appropriately supplying without obtaining a voltage drop as described above was obtained, and a proper supply amount was obtained. Note that, under the apparatus conditions according to this measurement example, as can be seen from each figure, there was no significant difference depending on the presence or absence of the toner in the hopper.

The toner supply roller 6 has a depth of 0.3 to 1.8 mm when pressed against the developing roller 5.
It was also found that when the speed ratio was in the range of 0.5 to 2.5 times, an appropriate rubbing force (scavenging force) on the developing roller was generated, and an optimal amount of toner charge and adhesion were obtained. . If the bite amount is less than 0.3 mm, sufficient friction is not performed, and the toner charge amount decreases. If the bite amount exceeds 1.8 mm, the rotational torque increases and the load on the motor increases. If the speed ratio is less than 0.5, the supply amount is low with respect to the consumption of the toner, and the recovery to the initial adhesion state cannot be performed by one supply. If it exceeds 2.5 times, the rotational torque increases and the load on the motor increases.

It was also found that a favorable toner layer could be formed even when a bias alternating with the potential of the developing roller 5 was applied to the toner supply roller 6. This is because the charged toner moves not in one direction but in both directions at the contact portion A of the rollers 5 and 6, so that the charged toner trapped inside the surface portion of the toner supply roller 6 can be satisfactorily developed. It is considered that the transfer to the 5 surfaces increases the supply efficiency. For example, DC-8
When 00V is used, Vp-p50 is applied to the sponge roller 6.
A superimposed AC bias of 0 V, a frequency of 300 Hz and a DC of -800 V is applied. Vp-
When a superimposed AC bias of p600 V, a frequency of 1 KHz, and a DC of -500 V is used, a DC of -500 V is applied to the sponge roller 6. Also, as the developing bias, V
When a superimposed AC bias having a peak-to-peak voltage of 1200 V, a frequency of 750 Hz, and a direct current of -600 V is used, a bias as shown in FIG.
In these cases, the developing roller 5 and the sponge roller 6 may be connected via a zener or a capacitor, and a bias having the same phase, the same waveform, and shifted by the direct current may be applied. According to this, even when a periodic developing bias such as an alternating current or a pulse is applied to the developing roller 5, the sponge roller 6 and the developing roller 5 are connected via a capacitor or a Zener diode.
A single bias generator can apply to the sponge roller a periodic bias in which a DC component having the same phase and the same polarity as the toner is superimposed on the potential of the developing roller 5.

Further, it has been found that in order to form a semiconductive conductive foamed elastic layer (conductive sponge), it is desirable to disperse the conductive material in the material before foaming. Unlike a conventional general method of forming a conductive sponge, a conductive impregnating material is attached to an insulating foamed polyurethane to obtain conductivity. It is kneaded and dispersed to have conductivity as a material, and is molded through a foaming process. According to the conventional forming method, the current mainly flows through the conductive impregnated material on the surface layer of the foamed polyurethane, and according to this forming method, the current flows in the bulk direction because the material has a uniform resistance over the entire volume. Will flow evenly. Therefore, when the surface deterioration with time, that is, the peeling of the conductive impregnated material occurs, the resistance is increased, and consequently the toner supply property is reduced. Even if surface deterioration occurs, there is no change in resistance and the toner supply amount can be maintained well.

Further, as shown in FIG. 13A, the shape of the foamed elastic body constituting the toner supply roller 6 is determined from the relationship between the apparent density and the hardness × the cell size. The relationship between the apparent density (X) and the hardness × the number of cells (Y) is such that Y is a straight line (40X−3) in the range of X ≧ 40.
(Y + 500 = 0) was found to be desirable. It is considered that the apparent density, the hardness and the number of cells greatly contribute to the charging efficiency when the toner is frictionally charged. That is, the developer is sandwiched between the developing roller 5 and the supply member and pressed to increase the contact probability, thereby increasing the charging efficiency. However, it can be said that this factor also has a role of transporting the developer from the hopper, and the gap of the supply member represents the possible transport amount. This is an effect opposite to the charging efficiency described above. Therefore, an appropriate relationship between the apparent density and (hardness × number of cells), which can obtain an appropriate charge amount and supply amount, was obtained by an experiment, and the above conditions were obtained.
For example, type A in FIG.
5, the hardness was 20, and the number of cells was 40. From X = 55, Y = 800 was obtained, and the condition was satisfied. A toner supply amount of 1.5 mg / cm ² was obtained. Type B: apparent density; hardness for 30; 12, cell number;
= 30 with respect to Y = 504, which did not satisfy this condition, and the toner supply amount was relatively small at 1.0 mg / cm ² .

The case where the toner supply roller 6 is made semiconductive has been described above. However, instead of the toner supply roller 6, the developing roller 5 is made semiconductive so that a potential difference is formed between the two rollers 5 and 6. You can also. That is,
Either one of the rollers 5 and 6 may be made semiconductive, and the other may be made conductive. In this case, the potential difference between the rollers 5 and 6 is maintained by the resistance of the toner 4 at the contact portion between the rollers 5 and 6 as schematically shown in FIG. 6, a toner having a volume specific resistance that does not cause dielectric breakdown due to a difference in applied voltage to 6 is used. For example, the electric potential difference is set to 200 V or less, and the electric resistivity of one of the conductive portion 51 of the developing roller 5 and the toner supply roller 6 is 1 × 10 ^6.
Above and less than 1 × 10 ⁹ Ωcm, the other having an electrical resistivity of 1 ×
10 ⁶ Ωcm or less, the electrical resistivity of the toner is 1 × 10 ¹³ Ωcm
Good toner supply is possible by the above combination.

In the specific examples so far, a minute electric field is formed by applying a charge having a polarity opposite to the charged polarity of the toner to the dielectric portion 52 of the developing roller 5. In addition, a minute electric field can be similarly formed by applying a charge having the same polarity as the charge polarity of the toner to the dielectric portion 52, or the amount of toner adhesion can be increased by the coexistence of the minute electric field and the bias electric field. 10 (a) and (b) and FIGS. 11 (a) and 11 (b) show the state of the electric field of each part on the surface of the developing roller 5 in this case, and set the dielectric part 52 to the opposite polarity to the charging polarity of the toner. FIGS. 4A and 4B and FIGS. 5A and 5B when charged.
It corresponds to. For example, as shown in FIG. 10A, the frictional charge of the same polarity as that of the toner 4 is accumulated on the surface of the dielectric portion 52 by rubbing the developing roller 5 with the toner toner supply roller 6. Due to the minute electric field, the toner adheres on the adjacent portion between the dielectric portion 52 and the conductor portion 51. In this case, the positions of the materials used for the developing roller 5, the toner supply roller 6, the toner 4, and the layer thickness equalizing member 8 in the charging series are described as follows when the toner 4 is used with negative charging. become. (+) Toner supply roller 6, layer thickness equalizing member 8> developing roller 5, toner 4 (−) The material of the dielectric portion 52 of the developing roller 6 is Teflon resin, polyethylene resin, toner supply roller 6, Polyurethane, polycarbonate and the like can be used as the material of the fixing member 8, and polystyrene, polyester and the like can be used as the material of the toner 4.

Although the specific examples so far are of the reversal development type, they can also be applied to the regular development type. In this case, the positions of the materials used for the developing roller 5, the toner supply roller 6, the toner 4, and the layer thickness leveling member 8 on the charging series in the case where the toner 4 is positively charged and used are as follows. (-) Developing roller 5 (dielectric part, conductive part) <toner supply roller 6, layer thickness equalizing member 8 <toner 4 (+) The material of developing roller dielectric part 52 is Teflon resin,
Polyurethane resin, polycarbonate resin can be used as the material of the polyethylene resin, the supply roller 6, and the layer thickness regulating member 8, and polystyrene resin, acrylic resin, and the like can be used as the material of the toner 4. For example, -200 V is used as an appropriate developing bias 20. Specific examples of such a developing device of the regular developing system are as follows.

[Specific Example 8] (1) Developing roller 5-Dielectric layer coating is made of fluororesin (Asahi Glass Lumiflon 200)
C) is the same as the above-mentioned specific example except that C) is coated and dried at 100 ° C. for about 30 minutes. (4) Layer thickness leveling member 8-Contact pressure with developing roller: 20 to 30 g / cm (5) Development bias, development gap contact development-DC voltage of -200 V is applied to development roller 6 (3) Toner supply roller bias・ Same potential as developing roller (6) Photoreceptor ・ OPC ・ Surface potential: image portion -700V, exposed portion -100V (7) Toner 4 ・ Positively charged toner using non-magnetic styrene acrylic resin ・ External additive: SiO ₂ Fine powder 0.5 wt% (positive chargeability) Other conditions are the same as in Example 1. (Hereinafter, margin)

Next, another embodiment of the present invention will be described in which a toner layer having a desired amount of charge with a small amount of reversely charged toner or uncharged toner can be formed on a developer carrying member and supplied to the latent image carrying member. . In the embodiment shown in FIGS. 2, 6, and 7, the toner supply roller 6 functions as a developer conveying unit that conveys the toner to the surface of the developing roller 5 as conventionally known. In the present embodiment, the function as a charge applying means for applying an electric charge to the dielectric portion 52 of the developing roller 5 and an electrode means facing the surface of the roller 5 at a predetermined potential while maintaining a predetermined interval are provided. In the example, of the three functions, a function as a charge applying means is provided in another member. FIG. 15 is a schematic configuration diagram of the developing device according to the present embodiment. In FIG. 15, a charging roller 60 as charging means is provided so as to come into contact with the surface portion of the developing roller 5 which has returned to the inside of the casing 3 after passing through the developing area 9. The contact portion is driven to rotate so that the surface moves in a direction opposite to the surface. The charging roller 60 frictionally charges the dielectric portion 52 of the developing roller 5 on the surface to apply a charge having a polarity opposite to the charging polarity of the toner, so that at least the surface has the dielectric portion 52 at a predetermined polarity. It is made of a material that can be charged by friction. Further, in order to also have a function of removing residual toner on the surface of the developing roller 5, at least the surface layer is sponge-shaped. Further, in order to enhance the ability to remove the residual toner from the surface of the developing roller 5, a voltage may be applied between the developing roller 5 and the developing roller 5 to generate a potential difference that generates an electrostatic force for attracting the residual toner. In this embodiment, the toner supply roller 6 is spaced from the developing roller 5 by a predetermined distance in order to reduce the restriction on the surface shape when the toner supply roller 6 functions as an electrode means. And face each other. At least the surface of the toner supply roller 6 is in the form of a sponge so that the toner conveying function can be favorably exhibited. Further, in order to reduce or restrict the surface material by sharing or separating the function of charging the toner, a scraping member as a developer scraping member is used to reliably transfer the conveyed toner to the surface of the developing roller 5. The blade 61 is disposed in contact with the surface of the toner supply roller 6 near the facing portion. The material of at least the surface of the scraping blade 61 is set to frictionally charge the toner to a predetermined polarity. Preferably, the conductor is good and a voltage can be applied as needed. The other points are the same as those of the above embodiment, and the corresponding members are denoted by the same reference numerals and description thereof will be omitted.

In the above configuration, the developing roller 5 having completed the development rotates in the direction shown by the arrow (about 120 mm / sec, which is almost the same speed as the photosensitive drum 1), and comes into contact with the charging roller 60. Here, while being rubbed by the charging roller 60, the toner in the undeveloped portion is scraped off, and the triboelectric charge having a polarity opposite to that of the toner is accumulated in the dielectric portion 52. The conductor portion 51 near the dielectric portion 52 includes:
Since the conductor portion 51 is grounded, a charge having a polarity opposite to that of the dielectric portion 52 is induced, and a large vertical and horizontal closed electric field (microfield) is formed near the edges of the conductive surface and the dielectric surface ( (See FIG. 4). The surface in this state moves to a portion facing the toner supply roller 6.

At the opposite portion between the developing roller 5 and the toner supply roller 6, a potential having the same polarity as the toner charge is applied to the toner supply roller 6 so that the developing roller 5
An electric field is formed in the direction perpendicular to the conductor portion 51 on the surface. Here, a state in which the minute closed electric field by the dielectric part 52 on the surface of the developing roller 5 and the electric field between the toner supply roller 6 and the conductor part 51 on the surface of the developing roller 5 are compatible is established (see FIG. 1).

Then, the toner is conveyed to the opposing portion by the rotation of the toner supply roller 6, and the toner separated from the toner supply roller 6 by the scraping blade 61 is supplied. The toner is supplied to the toner supply roller 6
The toner is charged by friction with the sponge held in the foam cells on the surface and with the surface, and is arranged so as to be inserted into the toner supply roller 6. The contact with the scraping blade 61 further increases the charge amount. Then, the toner trapped in the microfield near the edge of the dielectric portion 52 is strongly held on the roller, and the charged toner is further deposited on the conductive surface. In this manner, a stable multilayer toner layer can be formed by combining the electric field due to the potential difference between the micro-closed electric field (microfield) on the roller and the sponge roller, and a part of the toner on the roller is developed by development. Is consumed, the amount of toner is recovered to the initial amount in one toner supply process.

In the roller having such a configuration, the dielectric portion 5
2, the amount of toner corresponding to the triboelectric charge on the surface adheres to the dielectric part 52, whereas the conductive part 51 generates a mirror charge of the charged toner. Becomes possible. The developing roller 5 further rotates, and the layer thickness equalizing member 8 forms a uniform toner layer. Since the toner captured in the microfield near the edge of the dielectric surface is strongly held on the roller 5, even when an external force (scavenging force) such as a blade is applied, the multilayer toner layer is maintained without being collapsed. Is done. The toner supply roller 6 is a developing roller 5
The developing roller 5 is rotated in the same direction (forward rotation) at about 0.6 to 1.5 times the speed of the developing roller 5 in the contact portion with the toner, thereby electrostatically adhering the toner. As a result, 1.
A toner adhesion amount of 5 to 2.0 mg / cm ² and a charge amount of 8 to 15 μc / g were obtained, and a thin layer having sufficient characteristics for development was obtained.

Then, the developing area 9 is reached. In the development area, development was performed by a non-contact development method. The speed of the photoconductor and the speed of the developing roller 5 are set to be constant, and a developing bias with good flight conditions is applied. Here, N / P development was used. The obtained image was free of background stains, and good solid and line images were obtained.

Next, a more specific embodiment of the present embodiment will be described below as a specific example. [Specific Example 9 (1) charging roller 60 Material: foam kneading carbon polyurethane sponge roller diameter 10mm · Sponge volume resistivity: about 1 × 10 ⁸ [Omega] cm & Sponge Apparent Density: 55~70Kg / m ³ · bite: 0. 5 mm Bias voltage (depending on power supply 22): peak-to-peak 1000 with DC-200V to -300V superimposed
AC bias of V, 1000 Hz is applied (instead of this, a DC bias of -500 V to -600 V may be applied) (2) Toner supply roller 6-Material: Foamed polyurethane sponge roller with carbon kneading 14 mm in diameter-Development Gap with roller 5: 1 mm Sponge volume resistance: about 1 × 10 ⁶ Ωcm Sponge apparent density: 45-60 Kg / m ³ Aperture diameter: 0.2-0.3 mm on average Bias (by power supply 21): sponge A peak-to-peak 1000 V, 1000 Hz AC bias in which DC -1500 V is superimposed on the roller core 14 is applied (instead of this, a DC bias of -1800 V may be applied). (3) Scraping blade 61 -Material: SUS-Biting: 1mm-Bias: The same potential as the toner supply roller 6 It was the same as the body Example 1.

Next, a description will be given of another embodiment of the present invention in which a toner layer having a desired charge amount with a small amount of reversely charged toner or uncharged toner can be formed on a developer carrying member and supplied to a latent image carrying member. . In FIG. 16, this embodiment is provided with a charging roller 60 as a charging means as in the above embodiment. The toner supply roller 6 is constituted by a fur brush roller in which a fiber brush 15a is provided on a cored bar 14. The lower the resistance of the fur brush, the better the chargeability of the toner. The toner supply roller 6 is arranged at a distance from the surface of the developing roller 5 and is driven in a predetermined direction. Further, a conductive screen 62 is arranged on the side of the developing roller 5 opposite to the toner supply roller 6 such that the brush 15a bites a predetermined amount. A predetermined voltage is applied to the conductive screen 62. The other points are the same as those of the above embodiment, and the corresponding members are denoted by the same reference numerals and description thereof will be omitted.

In the above configuration, the developing roller 5 that has completed the development rotates in the direction shown by the arrow (about 120 mm / sec, which is almost the same speed as the photosensitive drum 1), and comes into contact with the charging roller 60. Here, while being rubbed by the charging roller 60, the toner in the undeveloped portion is scraped off,
A triboelectric charge having a polarity opposite to that of the toner is accumulated in the dielectric portion 52. Since the conductor portion 51 is grounded, a charge having a polarity opposite to that of the dielectric portion 52 is induced in the conductor portion 51 in the vicinity of the dielectric portion 52. A closed electric field (microfield) having a large direction is formed (see FIG. 4). The surface in this state moves to a portion facing the toner supply roller 6.

At the opposite portion of the developing roller 5 and the toner supply roller 6, a potential having the same polarity as that of the toner charge is applied to the conductive screen 62, so that the conductive screen 62 is perpendicular to the conductive portion 51 on the surface of the developing roller 5. Is formed. Here, a state in which the minute closed electric field by the dielectric part 52 on the surface of the developing roller 5 and the electric field between the toner supply roller 6 and the conductor part 51 on the surface of the developing roller 5 are compatible is established (see FIG. 1).

Then, the toner is conveyed to the facing portion by the rotation of the toner supply roller 6, and the toner separated from the brush 15 a of the toner supply roller 6 by the conductive screen 62 is supplied. This toner is charged by friction with the fur brush, and furthermore, the conductive screen 6
2 further increases the charge amount. Then, the toner trapped in the microfield near the edge of the dielectric surface is strongly held on the roller, and the charged toner is further deposited on the conductive surface. In this manner, a stable multilayer toner layer can be formed by synthesizing the electric field due to the potential difference between the micro-closed electric field (micro-field) on the roller and the screen. Even when the toner is consumed, the toner is recovered to the initial amount by the single toner supply process.

In the roller having such a configuration, the dielectric portion 5
2, the amount of toner corresponding to the triboelectric charge on the surface adheres to the dielectric part 52, whereas the conductive part 51 generates a mirror charge of the charged toner. Becomes possible. The developing roller 5 further rotates, and the layer thickness equalizing member 8 forms a uniform toner layer. Since the toner trapped in the microfield near the edge of the dielectric surface is strongly held on the roller, even when an external force (scavenging force) such as a blade is applied, the multilayer toner layer is held without collapse. You. The toner supply roller 6 rotates at about 1 to 2 times the speed of the developing roller 5 in the same direction (forward rotation) at the contact portion with the developing roller 5 to electrostatically adhere the toner. As a result, 1.5 to 2.0 mg
/ Cm ² and a charge amount of 8 to 15 μc / g, and a thin layer having sufficient properties for development was obtained.

Then, the developing area 9 is reached. In the development area, development was performed by a non-contact development method. The speed of the photoconductor and the speed of the developing roller 5 are set to be constant, and a developing bias with good flight conditions is applied. Here, N / P development was used. The obtained image was free of background stains, and good solid and line images were obtained.

Next, a more specific embodiment of the present embodiment will be described below as a specific example. [Specific Example 10] (1) Conductive screen 62-Material: SUS, diameter 0.5 mm-Gap with developing roller 5: 1 mm-Interval and number of pieces: 1.5 mm 4-Bias (by power supply 21): DC- AC bias of peak-to-peak 1000 V, 1000 Hz superimposed with 1500 V applied (alternatively, DC bias of -1800 V may be applied) (2) Toner supply roller 6-Material: kneading acrylic polymer carbon black Inclusive fibers (Toray SA -7: trademark) biting the roller diameter 14 mm · conductive screen 62: 1 mm · brush fiber volume resistivity: about 10 ³ ~10 ⁵ Ωcm · density: 3-70000 present / inch · bias (power 21): The same potential as the conductive screen The other aspects were the same as in the above specific example 9.

In the embodiment of FIGS. 15 and 16, the charging roller 60 is used as a member for charging the dielectric portion 52 on the surface of the developing roller 5 and removing the undeveloped toner to initialize the surface. Instead, as shown in FIG. 17, a charging blade 60a as a charging / initializing member may be used. In particular, as shown in the figure, it is desirable that the surface of the developing roller 5 is brought into contact with the counter. Efficiently charging the dielectric portion 52 on the developing roller 5 may be a low resistance of the charging blade, the resistor 10 ⁶
Ωcm or less is good. As the blade material, for example, a material obtained by adding 30 parts of carbur black to 100 parts of polyester urethane rubber can be used.

Although the embodiments shown in FIGS. 15 to 17 have been described with reference to N / P development using a negatively charged photosensitive member, it goes without saying that general conditions such as polarity and P / P development can be developed. It is.

Next, a description will be given of another embodiment of the present invention in which a toner layer having a desired amount of charge with a small amount of reversely charged toner or non-charged toner can be formed on a developer carrying member and supplied to the latent image carrying member. FIG. 18A is a schematic configuration diagram of a developing device according to the present embodiment, and FIG. 18B is a partially enlarged view thereof. FIG.
8A, the developing device of the present embodiment includes a casing 3 having an opening facing the surface of a photosensitive member (not shown) serving as a latent image carrier, and a predetermined peripheral speed that is partially exposed from the opening. A developing roller 5 as a developer carrying member that is rotationally driven clockwise by an arrow; and a developer supply member that is rotationally driven counterclockwise by an arrow in a state of being rightward of the developing roller 5 and close to the surface of the developing roller 5. Toner supply roller 6 as
And a non-magnetic toner (hereinafter, referred to as toner) contained in a hopper configured on the right side of the casing 3.
An agitator 7 for supplying toner to the surface of the supply roller 5 and agitating the toner in the hopper portion; And a charging roller 60 serving as a friction charging member that is driven to rotate clockwise.

The developing roller 5 may be arranged at a predetermined distance from the surface of the photosensitive member to perform non-contact development, or may be arranged so that the toner layer on the developing roller 5 contacts the surface of the photosensitive member. Alternatively, contact development may be performed.
In any case, in order to prevent the above-described phenomenon of the toner near the trailing end, the rotation of the developing roller 5 should be adjusted so that the surface moving direction in the developing area is the same as that of the photoconductor and the peripheral speed is the photoconductor. To be almost equal to the peripheral speed of. However, in the contact development, if the development is completely constant speed, there is no speed difference between the surface of the photoconductor and the surface of the developing roller 5, so that physical toner adhesion occurs regardless of the potential of the surface of the photoconductor. There is fear. To prevent this, the peripheral speed of the developing roller 5 is set to be slightly higher. For example, peripheral speed ratio (photoconductor peripheral speed: developing roller 5 peripheral speed)
Is preferably from 1.05 to 1.1. With this speed ratio, the trailing edge of the toner is not noticeable. Also,
An appropriate developing bias voltage, for example, DC, AC, AC superimposed with DC, pulse voltage, or the like is applied to the developing roller 5. In particular, in the case of non-contact development, it is desirable to apply a voltage (alternating current, alternating current of direct current superimposition, or pulse voltage) having an alternating component with good flight conditions.

As the developing roller 5 in this example, one having a structure as shown in FIG. 3 or FIG. 8 can be used.

The toner supply roller 6 is a roller provided with a sponge layer, such as a polyurethane sponge roller kneaded with carbon having a volume resistance of about 1 × 10 ⁶ Ωcm, so that the toner can be held inside the vicinity of the surface. Consists of rollers. Instead of this, a structure such as a fur brush roller on which a large number of fur brushes are planted may be employed. Since the distance between the toner supply roller 6 and the developing roller 5 and the linear velocity ratio between the two rollers 6 and 5 affect the amount of toner supplied to the developing roller 5, the desired amount of toner adhering on the developing roller 5 is determined. Set to obtain. For example, in general, the amount of toner adhered to the developing roller 5 required for development is 0.8 to 1.0 mg / cm ² in contact development, and 1.2 in non-contact (flying) development because of the transfer ratio of development. １．５1.5 mg / cm ² is optimal. In order to obtain such a toner adhesion amount, the distance between the toner supply roller 6 and the developing roller 5 is set to 100.
When set to μm, the linear velocity ratio between the toner supply roller 6 and the development roller 5 (the linear velocity of the toner supply roller 6 / the linear velocity of the development roller 5) is 1.0 to 1.2 in contact development.
In the case of performing non-contact development, it is desirable to set it to 1.5 to 2.0. The distance between the rollers 5 and 6 is set to 1 due to the transferability from the toner supply roller 6 to the developing roller 5 and the like.
It is desirable to set within the range of 00 to 150 μm. A charging blade 31 as a charging unit is provided so as to be in pressure contact with the toner supply roller 6. Further, a counter blade 71 is provided so that the leading end contacts the surface of the toner supply roller 6 at a portion facing the developing roller 5. The counter blade 71 scrapes off the toner carried on the toner supply roller 6 and scatters the toner on the portion facing the developing roller 5. When the toner supply roller 6 is configured by a fur brush roller as described above, a flicker member is provided instead of the counter blade 71. Note that a predetermined voltage may be applied to the toner supply roller 6 in order to form an electric field between the toner supply roller 6 and the development roller 5 that promotes transfer of the toner to the development roller 5. 1
It may be grounded as shown in FIG.

The agitator 7 supplies the toner contained in the hopper to the surface of the toner supply roller 6 and agitates the toner contained in the hopper. When the supply to the supply roller 6 surface is possible,
It may be omitted.

The charging roller 60 rubs the surface of the developing roller 5 that has returned to the casing 3 after passing through the portion facing the photoreceptor to remove residual toner and initialize the developing roller 5. This is for forming a large number of minute closed electric fields as indicated by a symbol E in FIG. 3A by frictionally charging the surface. At least the surface of the charging roller 60 is made of a material capable of exhibiting such a cleaning function and a triboelectric charging function. For example,
The same volume resistance as the toner supply roller 6, about 1 × 10 ⁶ Ωc
It can be composed of m foamed polyurethane sponge rollers. Such a charging roller 6
The linear velocity of 0 is set, for example, to the same linear velocity as that of the developing roller 5 (the moving direction at the contact portion is reversed). Further, as shown in FIG. 18A, the same voltage may be applied to the developing roller 5. In order to remove the toner from the surface of the charging roller 60, a counter blade 72 whose leading end is pressed against the surface of the charging roller 60 is provided.

In the above configuration, the toner contained in the hopper is removed by the agitator 7 from the toner supply roller 6.
Supplied to the surface. The toner supplied to the toner supply roller 6 adheres to the gap and the surface of the sponge or the brush,
The toner is supplied to the contact portion with the charging blade 31 by the counterclockwise rotation of the toner supply roller 6, and is frictionally charged to a predetermined polarity by the friction with the charging blade 31 at the contact portion. To form This toner thin layer is electrostatically bound by a counter charge generated on the toner supply roller 6 at the time of friction, and is conveyed to a portion facing the developing roller 3 by rotation of the toner supply roller 6.

On the other hand, at the opposing portion between the toner supply roller 6 and the developing roller 5, the developing roller 5 passes through the developing area by rotating the developing roller 5 in a counterclockwise direction, and the charging roller 6
The surface portion of the developing roller 5 that has passed through the contact portion with the zero also enters. When the surface portion of the developing roller 5 passes through a contact portion with the charging roller 60, the charging roller 60
The toner remaining on the surface of the developing roller 5 without adhering to the surface of the photoreceptor when passing through the developing area is mechanically,
A large number of minute electric fields are formed by being electrically scraped and triboelectrically charged. The toner removed from the developing roller 5 and adhered on the charging roller 3 is scraped off by the counter blade 72 and reused.

Here, in the illustrated example, the residual toner on the developing roller 5 that has passed through the developing area as described above is removed by the charging roller 60 and the counter blade 72
To return to the agitator 7 side. Further, depending on the rotation of the toner supply roller 6, only the toner held on the toner supply roller 70 through the contact portion of the charging blade 70 is carried into the opposite portion of the developing roller 5. Therefore, at the opposed portion between the toner supply roller 6 and the developing roller 5, the toner on the toner supply roller 70 faces the surface of the developing roller 5 with a gap. At the opposing portion between the developing roller 5 and the toner supply roller 6, the toner layer on the toner supply roller 6
Mechanically peels off from the toner supply roller 6 by
The charged toner escapes from the binding due to the counter charge on the surface of the toner supply roller 6 and flies to a minute closed electric field on the developing roller 5, and is electrostatically attracted by the electric field of the microfield on the developing roller to form a multilayer on the surface of the developing roller 5. To form a thin toner layer. At this time, the flying toner has a charge amount of 5 to 7 μc / g, and the lowly charged toner and the oppositely charged toner do not fly. This effect can be sufficiently obtained with the charging roller grounded. Then, the developing roller 5 exits the facing portion in a state where a sufficiently charged toner is carried in multiple layers, and conveys the toner layer to a developing area which is a facing portion with the photoconductor.

In the developing area, the development is performed while the surface of the developing roller 5 to which the optimal developing bias is applied and the surface of the photoreceptor are moved at almost constant speed by the contact or non-contact developing method. In this developing area, an electric field is also formed in which the conductive portion 51 of the developing roller 5 exerts an electrode effect and the toner on the developing roller 5 easily adheres to the photoconductor. Then, the surface portion of the developing roller 5 after developing the electrostatic latent image in this developing region reaches a contact portion with the charging roller 60 by rotation of the developing roller 5, where cleaning is performed and initialization is performed. Together with the toner to prepare for the next step.

As described above, according to this embodiment, the developing roller 5
In the opposed portion between the toner supply roller 6 and the toner supply roller 6, the charged toner forming the toner layer on the toner supply roller 6 flies to the minute closed electric field on the developing roller 5, and
The developing roller 5 is attracted by a large number of
A multilayer toner thin layer is formed thereon. Therefore, a sufficient amount of toner can be carried on the developing roller 5 and transported to the developing area. Further, at the opposing portion between the developing roller 5 and the toner supply roller 6, the toner flies to the minute closed electric field on the developing roller 5, is attracted by the many minute electric fields on the developing roller 5, and adheres to the developing roller 5. Has a charge amount of 5 to 7 μc / g, and low-charge toner and reverse-charge toner do not adhere to the developing roller 5.
Therefore, the toner layer conveyed to the developing area does not contain the low-charged toner or the oppositely-charged toner, and can prevent problems such as background contamination due to the oppositely-charged toner. Further, since the toner layer on the developing roller 5 is a thin layer formed by flying, the surface is relatively uniform. For this reason, the thinning blade conventionally disposed so as to be in contact with the developing roller 5 can be omitted. As described above, since a good thin toner layer can be formed on the developing roller 5, the system can be stabilized and the image quality can be improved.

Hereinafter, more specific aspects of the present embodiment will be described as specific examples. [Example 11] OPC as a photosensitive member using negatively charged toner
Non-contact reversal development was performed using a drum. A developing roller 5 having a knurled dielectric portion (Toray: silicon resin SR2115 (trade name)) on the above-described conductive roller is used. The area ratio of the dielectric portion to the conductive portion in the entire developing roller 5 is 1: 1 was used. The toner supply roller 6 and the charging roller 60 have a volume resistance of about 1
A × 10 ⁶ Ωcm foamed polyurethane sponge roller kneaded with carbon was used. By setting the linear velocity ratio between the developing roller 5 and the toner supply roller 6 to 1: 2 for non-contact development, a toner thin layer of 1.4 mg / cm ² and 7 μc / g was formed on the developing roller. Otherwise, follow the above conditions,
As a bias, a voltage obtained by superimposing AC500HZ1000V on DC700V was applied to perform constant-speed development. As a result, an image having excellent sharpness and a uniform solid portion could be obtained.

[Specific Example 12] Contact development was performed using a positively charged toner and an OPC drum as a photosensitive member. The developing roller 5 has a volume resistance of 1 × 10 ⁴ Ωcm as a surface layer.
A fluororesin having a particle size of 50 to 100 .mu.m was uniformly dispersed in the conductive rubber described above, and the area ratio between the dielectric part and the conductive part on the surface was set to 1: 1. Toner supply roller 6
And the charging roller 60 has a volume resistance of about 1 × 10 ⁶
A foamed polyurethane sponge roller kneaded with carbon of Ωcm was used. For contact development, the linear velocity ratio between the developing roller 5 and the toner supply roller 6 is set to 1: 1 so that the toner adheres to the developing roller 5 at 0.8 mg / cm ^2. When a DC bias was applied as a bias and development was performed at a constant speed by contact, an image having excellent sharpness and a uniform solid portion could be obtained.

[0103]

Effects of the Invention] According to the developing apparatus of claims 1 to 8, to form a large number of fine small closed electric field by selectively applies charge to the surface of the developer carrying member in the charging unit, the electrode means , an electric field exerts an electrostatic force toward the surface in one-component developer is frictionally charged without disturbing the fine small closed electric field, formed around the <br/> infinitesimal closed field, thereby, the and the electric field and the fine small closed electric field is in a state in which coexist on the surface. And
In the developer conveying unit to convey the one-component developer is frictionally charged on the surface of the electric field and fine small closed electric fields are formed, excellent in both electric field, the one-component developer is charged The developer is carried on the development carrier in a stacked state in an amount sufficient for performing a proper development. Then, the one-component developer transported to the developer carrier is provided as an electrostatic latent image on the latent image carrier. Therefore, a one-component developer such as a non-charged developer is not transported to the development area,
It is possible to obtain a good developed image free from background contamination, resolution degradation, and the like. In addition, since almost no uncharged developer, the amount of which is easily attached to the developer carrier depending on the environment, is carried on the developer carrier, and a sufficiently charged one-component developer is carried in a sufficient amount, A good developed image can be obtained. Also, on the surface of the rotating body made of a predetermined material,
A dielectric portion and a grounded conductor portion are regularly or irregularly mixed and distributed, and the dielectric portion of the developer carrying member is triboelectrically charged and the dielectric portion and the conductor on the developer carrying surface are frictionally charged. on the adjacent section to form a fine small closed electric field between the parts, the rotary member of a number formed fine recesses in the surface of, the inner surface portion which is at a predetermined potential of a conductive material, fine small closed electric field While maintaining the electric field, an electric field is formed between the electric conductor part and the inner surface part, which applies an electrostatic force toward the electric conductor part to the one-component developer triboelectrically charged, thereby forming the electric field on the surface. and a fine small closed electric field is in a state in which coexist. By rotation of the rotary member, it is conveyed on the developer carrying member surface to the electric field and fine small closed electric field while being carried on the rotating surface of the other recess and the recess is formed, and is frictionally charged and the part of the one-component developer, carried on adjacent vicinity of the fine small closed electric field dielectric portion and the conductor material portion, also on the conductor material portion a part of the other in the electric field Carry. In particular, since the one-component developer possessed by the triboelectric charge also exerts a mirror image force on the conductor portion, a large amount of the one-component developer is carried by this mirror image force. In this way, a sufficiently charged one-component type developer is carried on the development carrier in a stacked state in an amount sufficient for good development. Then, the one-component developer transported by the developer carrier is used for developing the electrostatic latent image on the latent image carrier. Therefore, since a one-component developer such as a non-charged developer is not conveyed to the developing area, a good developed image free from background stain, resolution degradation, and the like can be obtained. In addition, since almost no uncharged developer, the amount of which is easily attached to the developer carrier depending on the environment, is carried on the developer carrier, and a sufficiently charged one-component developer is carried in a sufficient amount, A good developed image can be obtained. Further, it is possible to form a predetermined electric field between the infinitesimal while the closed field satisfactorily maintained, conductive portions of the developer carrying member and the recess inner surface portion of the rotating body.

[0104]

[0105]

[0106] Further, according to the developing apparatus of claim 4 to 7, it is possible to satisfactorily form a fine small closed electric field on said developer carrying member.

[0107] Further, according to the developing apparatus of claim 8, the developer carrying member surface is substantially smooth, thereby, the one-component developer by rubbing between the developer carrying member and the rotating member Sticking to the carrier can be effectively prevented.

[0108]

[0109]

[0110]

[0111]

[0112]

[0113]

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an electric field on a surface of a developer carrying member in a developing device of the present invention.

2A is a schematic configuration diagram of a developing device according to an embodiment of the present invention, and FIG. 2B is an enlarged view of a part of the developing device.

FIG. 3A is a cross-sectional view of the developing roller of the developing device taken along line aa in FIG. 3B, and FIG. 3B is a plan view of a part of the surface of the developing roller.

4A is an explanatory diagram of an electric field in the vicinity of a dielectric portion of the developing roller, and FIG. 4B is an explanatory diagram of an electric field in an opposing portion between the developing roller and a concave portion of the toner supply roller.

5A is an explanatory diagram of a toner carrying state by an electric field in the vicinity of the dielectric portion, and FIG. 5B is an explanatory diagram of a toner carrying state by an electric field in the opposite portion. FIG.

FIG. 6 is a schematic configuration diagram showing an example of an arrangement when the developing device of the present invention is used for contact development on a belt-shaped photosensitive member.

FIG. 7 is a schematic configuration diagram showing an example of an arrangement when the developing device of the present invention is used for contact development on a drum-shaped photosensitive member.

FIG. 8A is a schematic diagram of a cross-sectional structure of a developing roller according to a modification, and FIG. 8B is a plan view of a part of the surface of the developing roller.

FIG. 9 is a characteristic diagram of the developing roller.

FIG. 10 is an explanatory view of an electric field near a dielectric portion of a developing roller in a developing device according to another embodiment of the present invention, and FIG.
FIG. 4 is an explanatory diagram of an electric field at an opposing portion between the developing roller and a concave portion of the toner supply roller.

FIG. 11A is an explanatory diagram of a toner carrying state by an electric field in the vicinity of the dielectric portion, and FIG. 11B is an explanatory diagram of a toner carrying state by an electric field in the opposite portion.

FIG. 12 is an explanatory diagram of a potential difference between a developing roller and a toner supply roller in the developing device.

13A is a characteristic diagram when a sponge roller is used as a toner supply roller, and FIG. 13B is a waveform diagram illustrating an example of a bias applied to the supply roller.

14A is a characteristic diagram illustrating a relationship between a potential difference between a developing roller and a toner supply roller and a current flowing between the two rollers, and FIG. 14B is a diagram illustrating a relationship between the same potential difference and a volume specific resistance of the toner supply roller. FIG.

FIG. 15 is a schematic configuration diagram of a developing device according to another embodiment of the present invention.

FIG. 16 is a schematic configuration diagram of a developing device according to still another embodiment of the present invention.

FIG. 17 is a schematic configuration diagram of a developing device according to still another embodiment of the present invention.

18A is a schematic configuration diagram of a developing device according to still another embodiment of the present invention, and FIG. 18B is a partially enlarged view of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Developing device 3 Casing 4 Toner 5 Developing roller 6 Toner supply roller 7 Agitator 8 Layer thickness equalizing member 9 Developing area 10 Separator 20 Power supply for developing roller 21 Power supply for toner supply roller 31 Charging blade 51 Conductor part 52 Dielectric part 60 Charging roller 61 Scraping blade 62 Charging blade 71 Counter blade 72 Counter blade A Contact part

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuichi Ueno 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Akira Sawada 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Utsugi 1-3-6 Nakamagome, Ota-ku, Tokyo, Japan Ricoh Co., Ltd. (56) References JP-A-1-93773 (JP, A) JP-A-55 -62469 (JP, a) JP Akira 56-40864 (JP, a) JitsuHiraku flat 3-122451 (JP, U) (58 ) investigated the field (Int.Cl. ^7, DB name) G03G 15/08

Claims (8)

(57) [Claims] A developer carrying member for carrying and transporting the one-component developer on the surface; a storage means for storing the one-component developer; A developer supply means for charging the developer to be carried on the developer carrier, and developing the electrostatic latent image into a visible image using the one-component developer transported by the developer carrier. in, used as a large number of fine small closed electric field holds selectively charge on the surface as a developer carrying member can be formed, the developing agent supply means, in order to form the fine small closed electric field a charge applying means for applying a selectively charge on the surface, opposite to the surface while maintaining a gap to the extent that and fine small closed electric field by a predetermined potential is maintained, frictional charged one-component developer An electrode hand for forming an electric field that exerts an electrostatic force on the agent toward the surface around the micro-closed electric field A developer carrying means for carrying a one-component developer triboelectrically charged on the surface on which the electric field and the micro-closed electric field are formed, wherein the developer carrier Are arranged so that the dielectric portion and the grounded conductor portion are regularly and irregularly mixed and distributed on the surface, and the transporting means is rotated at a position where it contacts the surface of the developer carrier. The electric charge applying means is constituted by a surface of the rotating body formed of a material capable of frictionally charging the dielectric portion to a predetermined polarity; and the electrode means is formed of a conductive material. And, a predetermined potential that can cause a potential difference with the conductor portion that forms the electric field that exerts the electrostatic force in a state facing the conductor portion,
The rotating surface is constituted by an inner surface of a large number of minute concave portions formed on the rotating surface, and the concave portion has an opening diameter of 2 which is the maximum pitch of the dielectric portion distribution.
A developing device characterized in that the developing device is formed so as to be at least twice as large. 2. The method according to claim 1, wherein the dielectric portion is formed by distributing dielectric particles irregularly on the surface of the developer carrier, and the concave portion has an opening diameter twice or more as large as the dielectric particle diameter. 2. The device according to claim 1, wherein the first and second portions are formed to have a size.
Developing device. 3. The dielectric part is constituted by distributing dielectric particles irregularly on the surface part of the developer carrier, and the concave part has an opening diameter of 2 which is the average distance between the dielectric part particles.
2. The developing device according to claim 1, wherein the developing device is formed so as to be at least twice as large. 4. A ratio of the total area of the dielectric part to the total area of the dielectric part and the total area of the conductor part in the developer carrier is in the range of 30 to 70%. 2. The developing device according to claim 1, wherein the developing device is configured to have the following configuration. 5. The electric resistance of the developer carrying member is 1 × 10 12 Ωcm or more in the dielectric portion and 1 × 1 Ωcm in the conductor portion in all environments.
2. The developing device according to claim 1, wherein the developing device is configured to be less than 09 Ωcm. 6. A method according to claim 6, wherein said developer carrier is formed such that a part of a grounded conductive base as said conductor part and a part of a dielectric as said dielectric part are formed by the width or width of said dielectric part. Size 5
2. The developing device according to claim 1, wherein the developing device is configured to be mixedly exposed on the surface so as to be within a range of 0 to 500 [mu] m. 7. A method according to claim 7, wherein said developer carrying member is provided with a part of a conductive base as said conductor part and a depth of 50 to 200 μm in a direction perpendicular to a surface of said developer carrying member as said dielectric part. 2. The developing device according to claim 1, wherein a part of the minute dielectric in the range is mixedly exposed on the surface. 8. The developing device according to claim 1, wherein said developer carrying member has a surface roughness (Rz) of 50% or less of the size of the one-component developer.