JPH05188757A - Developing device - Google Patents

Abstract

PURPOSE:To form a toner layer having less noncharged toner and a desired electrostatic charge quantity on a developer carrier and to supply the toner to a latent image carrier. CONSTITUTION:As a developing roller 4, one constituted so that a dielectric part 41 and an electric conductor part 42 are mixed and exposed in a very small area, on a surface is used. A toner supplying roller 5 press-contacting to the developing roller 4, is composed of a sponge-like roller, and a roller on which a large number of fur brushes are planted, and rotated so that the surface of the roller 5 is moved in the same direction as the surface of the developing roller 4 on a contact part with the developing roller 4. Further, in the structure of the contact area of a developer layer forming member 8 press-contacting to the developing roller 4, at pressure lower than that in the conventional manner, with the developing roller 4, the dielectric part 41 and the electric conductor part 42 are mixed and exposed in the very small area, like the developing roller 4.

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 in an image forming apparatus such as a copying machine, a facsimile and a printer, and more particularly to a developing device using a one-component developer.

[0002]

2. Description of the Related Art In an image forming apparatus in which an electrostatic latent image is formed on a latent image carrier and visualized by a developer, one component is used in view of downsizing, cost reduction and high reliability of the developing apparatus. A developing device using a system developer (hereinafter referred to as toner) is advantageous. In addition, it is advantageous to use a non-magnetic toner because it has high transparency for colorization. And
A developer carrier that is driven so that the surface of the toner moves toward the surface facing the latent image carrier so as to supply a predetermined charge to the toner and supply the toner to the developing area that faces the latent image carrier. There is known a developing device having a developer supplying member for supplying toner to the surface of the developer carrying member. For example, JP-A-61
No. 42672 discloses that a medium resistance (10 ⁹ to 10 ¹¹ Ωcm) developing roller having a float electrode as a developer carrying member and a sponge roller made of, for example, polyurethane as a developer supplying member are brought into pressure contact with each other. It is disclosed that they are arranged and rotated so that the surfaces of each of them are moved in opposite directions at the pressure contact portions of both. This developing device is also provided with a blade as a developer layer forming member that presses against the developing roller with a predetermined contact force in order to regulate the toner adhesion amount on the developing roller to a predetermined amount. In this developing device, the toner conveyed to the pressure contact portion of both by the rotation of the sponge roller is frictionally charged at the pressure contact portion and adhered to the surface of the developing roller. Then, the layer thickness of the toner layer made of toner adhered to the surface is regulated by the blade to form a predetermined amount of toner layer on the developing roller. Then, by rotating the developing roller, the toner layer is conveyed to a contact portion with the photoconductor as a latent image carrier to develop the electrostatic latent image on the photoconductor.

[0003]

The optimum toner charge amount and toner adhesion amount in the one-component developing system, for example, the non-magnetic one-component developing system will be described below. The toner charge amount is preferably 5 to 10 μc / g as an average charge amount, and the toner charge amount distribution is desired to be a stable distribution in which there are few relatively low-charged toners that cause sharpness and deterioration of resolution and scumming. .. On the other hand, the amount of toner deposited on the developing roller, image bearing member at 0.6~1.0mg / cm ² about the toner adhesion amount, 0.5~0.7mg / cm ² of about toner adhesion on paper transfer It is desirable that the amount can be obtained. The toner adhesion amount on the latent image carrier and the transfer sheet depends not only on the toner adhesion amount on the developing roller but also on the relative speed between the latent image carrier and the developing roller in the developing area.

However, according to the conventional developing device, since the toner layer on the developing roller is one layer and the adhesion amount is small, the charge amount of the toner conveyed to the developing area is 5 to 5 on average.
Although it is about 15 μc / g, the toner adhesion amount on the developing roller is 0.2 to 0.8 mg / cm ² , and in order to obtain the desired toner adhesion amount on the latent image carrier, etc. It is necessary to set the speed of the developing roller to 2 to 4 times the speed of the latent image carrier. In this way, when the rotation of the developing roller is set high in order to cover the insufficient toner adhesion amount on the developing roller, not only it is difficult to increase the image forming speed, but also when the solid portion is developed. There is also a phenomenon of "beyond the trailing edge of the toner" in which the density of the trailing edge of the image becomes high. This phenomenon is not a big problem in a black and white image, but in a color image there is a problem that the color is transmitted through the toner and the color is visualized, so that the density is high at the rear end portion, and in the case of a superimposed image, a color difference occurs. .. Further, since the developing roller is rotated at a relatively high speed, toner sticking is likely to occur on the pressure contact surface with the blade that is in pressure contact with the developing roller. When the toner adheres, streak-like unevenness occurs in the toner layer, resulting in uneven density in the developed image.

In order to obtain a desired toner adhesion amount on the latent image bearing member without causing such a phenomenon "from the rear end of the toner", the speed of the developing roller is set to that of the latent image bearing member. It is necessary to approach the speed, that is, to approach the constant-velocity development, and increase the toner adhesion amount on the developing roller as compared with the conventional one. Specifically, in order to secure a sufficient toner adhesion amount on the latent image carrier or the transfer paper at almost constant speed development, the toner adhesion amount on the developing roller is at least determined by a contact developing method with high development efficiency. 0.8 mg
/ cm ² , at least 1.0 by non-contact development method with poor development efficiency
Must be mg / cm ² . In order to obtain such toner adhesion amount on the developing roller, the toner layer thickness must be two or more layers.

Here, the contact pressure of the blade may be set to be weak only for the purpose of making the toner layer thickness of two or more layers. However, in the developing device according to the above conventional example,
Since the surface of the developing roller and the sponge roller move in opposite directions at the pressure contact portions of the developing roller and the sponge roller, the surface of the developing roller passing through the pressure contact portions also contains uncharged toner from the toner accommodating portion. Supplied with a sponge roller. Therefore, a large amount of uncharged toner is contained in the upper layer portion of the toner layer on the developing roller that enters the blade contact portion. Therefore, the distribution of the charge amount of the toner on the developing roller that has passed through the blade contact portion is in the range of 10 μc / g or less, and includes uncharged toner and reversely charged toner. This non-charged toner or the like has a poor development transfer, and causes background stains and resolution deterioration.

As described above, all the toner in the upper layer of the toner layer on the developing roller is fully charged, and there is no uncharged toner. Forming on the developing roller is the most important issue in increasing the image forming speed and enabling constant speed development for preventing "from the trailing edge of the toner".

The present invention has been made in view of the above problems, and an object of the present invention is to carry a developer layer on a toner layer having a small amount of uncharged toner, a desired charge amount, and a uniform level. To provide a one-component developing device and a developing method which can be formed on a body and supplied to a latent image carrier.

[0009]

[Means for Solving the Problems] To solve the above problems
According to the invention of claim 1, the surface is driven so as to move.
And the surface of the developer carrier
A developer supplying member that is driven to move, and the developer.
Contact the surface of the developer carrier to which the developer was supplied by the supply member.
And a developer layer forming member to be touched.
The current state of being supplied and thinned by the developer layer forming member.
The latent image on the latent image carrier is visible with the developer on the image carrier
In a developing device for imaging, the surface of the developer supply member is transferred.
The moving directions are the same at the contact part with the surface of the developer carrier.
Set to move and develop as the developer layer forming member.
Conductive parts and dielectric parts are regularly or regularly formed on the surface in contact with the agent carrier.
Is characterized by using irregularly distributed small areas
It is what

According to a second aspect of the present invention, in the developing device according to the first aspect, the conductive portion and the dielectric portion, which are grounded on the surface as the developer carrier, are regularly or irregularly distributed in a small area. A plurality of minute electric fields are formed in the vicinity of the surface of the developer carrying member by rubbing the surface of the developer carrying member with a developer supplying member, and the developer frictionally charged at the contact portion is developed by the minute electric field. It is characterized in that it is carried in a laminated state on a carrier.

According to a third aspect of the present invention, there is provided a developing method, wherein a developer carrying member supplies a developer to the electrostatic latent image carrying member to develop the electrostatic latent image on the electrostatic latent image carrying member. At the contact portion between the developer supply member and the developer carrying member that move the surfaces in the same direction, the developer is triboelectrically charged and carried on the developer carrying member, and the developer carrying frictionally charged developer is carried. The body surface is rubbed with a developer layer forming member having a developer held on the surface by a minute closed electric field to form a uniform developer layer, and the developer layer is formed on the electrostatic latent image carrier. It is characterized in that it is conveyed to the facing portion.

[0012]

In the developing device of the first and second aspects, the developer is conveyed to the contact portion with the surface of the developer carrying member by the movement of the surface of the developer supply member, and the developer is frictionally charged at the contact portion. At this time, the moving direction of the surface of the developer supply member and the surface of the developer carrier is such that both surfaces move in the same direction at the contact portions of both, so that the surface of the developer carrier passing through the contact portions The developer supplying member does not directly supply the uncharged developer from the toner containing portion. Therefore, on the surface of the developer carrying member which has passed through the contact portion, only the developer sufficiently charged by the triboelectric charging at the contact portion is carried in a laminated state on the surface by the minute electric field near the surface of the developer carrying member. .. on the other hand,
The surface of the developer layer forming member, which is in contact with the developer carrier in which the conductive portion and the dielectric portion are regularly or irregularly distributed in a minute area, is triboelectrically charged by the developer carrier, whereby many near the surface. A small electric field is formed. This minute electric field holds the triboelectrically charged developer on the surface of the developer layer forming member. Then, when the developer layer carried on the developer carrying member passes through the contact portion with the developer layer forming member, it is slid by the developer layer forming member held on the surface of the developer layer forming member. Rubbing, which smoothes the layer thickness.

Further, in the developing device of the second aspect, the surface of the developer carrying member on which the conductive portion and the dielectric portion are regularly or irregularly distributed in a minute area is triboelectrically charged by the developer supplying member. A large number of minute electric fields are formed near the surface of the developer carrier. Then, on the surface of the developer carrying member that has passed through the contact portion, the developer sufficiently charged by frictional charging at the contact portion is carried in a laminated state on the surface by a minute electric field near the surface of the developer carrying member.

Further, in the developing method of claim 3, the developer is triboelectrically charged at the contact portion between the developer supply member and the developer carrying member, which surfaces move in the same direction, and is carried on the developer carrying member. The surface of the developer carrier carrying the frictionally charged developer is rubbed by a developer layer forming member having the developer held on the surface by a minute electric field to form a uniform developer layer, The developer layer is conveyed to the portion facing the electrostatic latent image carrier by the developer carrier.

[0015]

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. 2 is a front view showing a schematic configuration of the developing device according to this embodiment. The photosensitive drum 1 as a latent image carrier has a peripheral speed of 120 mm / sec.
Then, it is driven to rotate clockwise by the arrow. The photosensitive drum 1
The developing device 2 is disposed on the right side of the. Around the photosensitive drum 1, a known charging device, an exposure optical system, a transfer / separation device, a cleaning device, and a destaticizing device (none of which are shown) are arranged to carry out an electrophotographic process. The developing device 2 of this embodiment includes a casing 3 having an opening facing the surface of the photoconductor drum 1, and a developing roller which is partially exposed from the opening and is rotationally driven counterclockwise in the arrow direction at a predetermined peripheral speed. 4, a toner supply roller 5 as a developer supply member which is rotationally driven in the clockwise direction of the arrow in a state of being pressed against the right side portion of the developing roller 4, and a hopper portion formed on the right side portion in the casing 3. An agitator 6 that supplies non-magnetic toner (hereinafter referred to as toner) contained in the toner to the surface of the supply roller 5 and agitates the toner in the hopper, and a portion that opposes the photosensitive drum 1 by rotation of the developing roller 4. Developer layer forming member 8 for making the thickness of the toner layer on the developing roller 4 conveyed to the developing area uniform.
And have.

The casing 3 has a shape such that an inner surface portion below the toner supply roller 5 maintains a predetermined gap with the surface of the toner supply roller 5.

As shown in FIG. 2, the developing roller 4 may be arranged with a predetermined gap from the surface of the photosensitive drum 1 to perform non-contact development, or the toner layer on the developing roller 4 is exposed. You may make it arrange | position so that it may contact the surface of the body drum 1 and may perform contact development. In any case, in order to prevent the above-mentioned phenomenon that the trailing edge of the toner is deviated, the developing roller 4 is rotated such that the surface moving direction in the developing area is the same direction as the photosensitive drum 1 and the peripheral speed thereof is the same. The peripheral speed of the photosensitive drum 1 is approximately equal to the peripheral speed, that is, about 120 mm / sec in this example. However, in the contact development, if the development is completely constant speed, there is no difference in speed between the surface of the photosensitive drum 1 and the surface of the developing roller 4, so that the physical development is performed regardless of the potential of the surface of the photosensitive drum 1. Toner may adhere. To prevent this,
The peripheral speed of the developing roller 4 is set to be slightly higher. For example, the peripheral speed ratio (1 peripheral speed of the photosensitive drum: 4 peripheral speed of the developing roller) is preferably 1: 1.05 to 1.1. With such a speed ratio, the above-mentioned trailing edge toner deviation is not noticeable. Further, an appropriate developing bias voltage, for example, direct current, alternating current, alternating current of direct current superposition, pulse voltage or the like is applied to the developing roller 4. In particular, in the case of non-contact development, it is desirable to apply a voltage having an alternating component with good flight conditions (AC, AC with superimposed DC, or pulse voltage).

The developing roller 4 of this example has a structure shown in FIG. 3A for the purpose of increasing the amount of adhered toner.
As shown in (c) to (c), the dielectric portion 41 and the conductor portion 42 are configured to be exposed in a mixed manner in a minute area on the surface. FIG. 3A is an explanatory diagram showing the surface of the developing roller 4, FIG. 3B is its cross section, and FIG. The size of the dielectric portion 41 is, for example, about 50 to 200 μm in diameter. It is arranged that such dielectric portions 41 are dispersed randomly or according to a certain rule. The area ratio of both parts is the dielectric part 41.
The area is preferably in the range of 40 to 70%. As the material of the dielectric portion 41, a material having a resistance value such that electric charges are not accumulated by frictional charging by the toner supply roller 5 is used. To form the surface layer portion shown in the figure, for example, knurling the surface of the cored bar roller to form a predetermined groove, coating an insulating resin, for example, and then cutting the surface to form a cored bar. And the resin in the groove is the dielectric part 4
1 can be formed by exposing each surface. The surface structure shown in FIGS. 4 (a) and 4 (b) may be replaced with the surface structure shown in FIGS. 3 (a) to 3 (c). FIG. 3A is the surface of the developing roller, and FIG.
FIG. 3 is an explanatory diagram showing a toner layer formation state on the surface thereof. In the surface portion of this example, after a surface layer made of a conductive material in which dielectric particles having a particle size of, for example, 50 to 100 μm are dispersed is formed on a cored roller, the surface layer is slightly cut if necessary. Can be formed by

The toner supply roller 5 preferably has a structure such as a roller provided with a sponge layer and a roller having a large number of fur brushes planted therein so that the toner can be retained inside the vicinity of the surface. Further, at least the surface material is in the middle of the toner material and the developing roller 4 material in the triboelectrification series so that the toner and the developing roller 4 can be contacted with the developing roller 4 and desired triboelectrification can be given. To adopt. In addition, a resistance value such that the toner or the counter charge in the triboelectric charging of the minute dielectric portion 41 of the developing roller 4 is not accumulated, for example, 10 ⁶
Those having a resistance value of Ωcm or less are preferable. The toner supply roller 5 is rotated in the forward direction in which the surface moves in the same direction as the surface of the developing roller 4 at the contact portion with the developing roller 4. The peripheral speed is preferably set to about 1.2 to 1.5 times the peripheral speed of the developing roller 4, for example.
Further, the same voltage as that applied to the developing roller 4 may be applied to the core metal of the toner supply roller 5.

The agitator 6 supplies the toner contained in the hopper portion to the surface of the toner supply roller 5 and agitates the toner. The agitator 6 uses the weight of the toner due to the shape of the hopper portion and the fluidity of the toner. When it is possible to supply to the surface of the supply roller 5,
You may omit it.

The developer layer forming member 8 is arranged so as to come into contact with the developing roller 4 with a light linear pressure of about 7 g / cm, which is lower than that of the conventional member. Then, in this embodiment, the contact surface of the developer layer forming member 8 with the developing roller 4 is the same as the developing roller 4 described above.
2 and the dielectric part 41 are configured to be exposed in a mixed manner in a very small area. FIG. 1 schematically shows the cross section.
In the illustrated example, the surface portion structure is the same as that of the developing roller 4 shown in FIGS. 4A and 4B.

In the above structure, the toner contained in the hopper is supplied to the surface of the toner supply roller 5 by the agitator 6. The toner supplied to the toner supply roller 5 adheres to the voids and the surface of the sponge or brush and is conveyed toward the contact portion between the toner supply roller 5 and the developing roller 4 by the clockwise rotation of the toner supply roller 5. On the other hand, at the contact portion with the toner supply roller 5,
The surface portion of the developing roller 4 that has passed through the developing area also enters due to the counterclockwise rotation of the developing roller 4 in the arrow direction.

At this contact portion, the surface of the toner supply roller 5 and the surface of the developing roller 4 move with a relative speed difference, so that they do not adhere to the surface of the photosensitive drum 1 when passing through the developing area and remain on the surface of the developing roller 4. The toner remaining in the non-image portion is mechanically and electrically scraped off by the toner supply roller 5 (for example, a sponge roller), and the electric charge on the developing roller 4 is also made constant by frictional charging by the toner supply roller 5. As a result, the developing roller 4
The surface is initialized. Then, due to the friction between the developing roller 4 and the toner and the toner supplying roller 5, the dielectric portion 41 of the developing roller 4 is charged with a polarity opposite to the desired toner charging polarity (in normal development (P / P), the same polarity as the photoconductor charge). Is applied, and in the reverse development (N / P), the charge is of the opposite polarity to the photoconductor charge. For example, as shown by electric force line E in FIG. Create (closed electric field). On the other hand, since the toner supply roller is rotating in the forward direction with respect to the developing roller 4, the toner attached to the toner supply roller 5 is slid between the developing roller 4 and the toner supply roller 5, and most of the toner has a desired polarity (regular). In development, it has a polarity opposite to that of the photoreceptor charge, and in reversal development, it has the same polarity as the photoreceptor charge. Then, the charged toner on the toner supply roller 5 is electrostatically attracted by the electric field of the microfield on the developing roller 4 and adheres to the surface of the developing roller 4 in multiple layers. As a result, the developing roller 4 exits the contact portion while carrying a sufficiently charged toner in multiple layers. In this embodiment, since the toner supply roller 5 and the developing roller 4 are rotated in the forward direction, unlike the developing device according to the above-described conventional example, the development which has passed through the contact portion by the rotation of the toner supply roller 5 is performed. The uncharged toner from the hopper is not supplied onto the roller 4. This point will be described in detail later.

The toner layer on the developing roller 4 that has passed through the contact portion is rubbed with a uniform thickness by the developer layer forming member 8 that is in light contact with the developing roller 4. Here, on the contact surface of the developer layer forming member 8 with the developing roller 4, the conductor portion 42 and the dielectric portion 41 are mixed as described above, and
The development roller 4 or the toner on the development roller 4 is frictionally charged to form a microfield like the surface portion of the development roller 4. A part of the charged toner on the developing roller 4 is sucked by the microfield, whereby the toner layer is held on the surface of the developer layer forming member 8. Therefore, when the toner layer on the developing roller 4 passes through the contact portion with the developer layer forming member 8, the toner layer is rubbed by the developer layer forming member 8 holding toner, and the toner layer at the contact portion with the toner supply roller 5 is rubbed. Eliminates unevenness during rubbing. Then, the developing roller 4 rotates to convey the developing roller 4 to the developing area. In the developing area, the development is performed while the surface of the developing roller 4 to which the optimum developing bias is applied by the contact or non-contact developing method and the surface of the photosensitive drum 1 move at substantially the same speed. In this developing area, the electric conductor portion 42 of the developing roller 4 exerts an electrode effect to form an electric field in which the toner on the developing roller 4 easily adheres to the photosensitive drum 1.

Here, the stabilization of the toner charge distribution of the toner layer carried by the developing roller 4 by the forward rotation of the toner supply roller 5 and the developing roller 4 will be described in detail. FIG. 5A and FIG. 6A show that the toner supply roller 5 (sponge roller in the illustrated example) and the developing roller 4 are respectively rotated to the developing roller 4 in the forward rotation and the reverse rotation. It is a schematic representation of toner adhesion and charging status. In the figure, ◯ indicates toner, and only those that are charged are marked with a + in the circle to indicate whether or not they are charged. As shown in FIG. 5A, when the toner supply roller 5 and the developing roller 4 rotate in the forward direction, the charged toner that has already adhered to the toner supply roller 5 and the toner newly supplied from the hopper unit. Both of the charged toners are conveyed by the toner supply roller 5 to a contact portion with the developing roller 4, and at this contact portion, all the toners are charged by the friction between the rollers 4 and 5 and adhere to the developing roller 4. Since the toner supply roller 5 and the developing roller 4 are rotated in the forward direction, the rotation of the toner supply roller 5 does not supply uncharged toner from the hopper to the developing roller 4 that has passed through this contact portion. .. Therefore, the amount of toner adhering to the developing roller 4 that has passed through the contact portion is relatively stable because it is determined by the electric field of the developing roller 4, the porosity of the sponge roller as the toner supply roller 5, and the like. On the other hand, as shown in FIG. 6A, even when the toner supply roller 5 and the developing roller 4 rotate in the opposite direction, the charged toner already attached to the toner supply roller 5 and the new supply from the hopper unit are supplied. Both of the uncharged toners are conveyed by the toner supply roller 5 to the contact portion with the developing roller 4. In particular, as in the illustrated example, new toner (a blank arrow indicates a supply path to the surface of the toner supply roller 5) supplied from the hopper portion remains on the toner supply roller 5 and the developing roller 4 In the case where the toner is conveyed to the contact portion with, the relatively large amount of uncharged toner is conveyed to the entrance of the contact portion. Then, the toner that has entered the contact portion and is sufficiently charged by the friction between the rollers 4 and 5 positively adheres to the surface of the developing roller 4 and is discharged from the contact portion. In addition, the insufficiently charged toner carried on the toner supply roller 5 to the entrance of the contact portion is also contacted by electrostatic force (gradient force) due to the electric field on the developing roller 4 or toner cohesive force. Adheres on the developing roller 4 after passing through the part. The amount of toner physically attached due to the toner cohesive force and the like greatly changes depending on the environment. In particular, when a micro-field electric field is formed on the surface to form a multi-layered toner like the developing roller 4 of the present embodiment, the amount of the uncharged toner attached also becomes large and is carried on the developing roller 4. The toner charge amount distribution becomes unstable.

FIGS. 5B and 6B show the charging of the toner in the toner layer carried by the developing roller 4 when the toner supply roller 5 and the developing roller 4 rotate in the forward direction and in the reverse direction, respectively. From these graphs showing the amount distribution, when there is a reverse rotation (FIG. 6 (b)), there is a large amount of uncharged toner, whereas there is a case of forward rotation (FIG.
It can be seen that the amount of uncharged toner is drastically reduced in (b).

As described above, when the toner supply roller 5 and the developing roller 4 rotate in the forward direction, the developing roller 4
The amount of toner adhered to the toner is unlikely to be affected by environmental fluctuations, and a charge amount distribution of toner containing less uncharged toner can be obtained, which is extremely advantageous for stability of developing characteristics.
In the above embodiment, the toner supply roller 5 is rotated clockwise and the developing roller 4 is rotated counterclockwise, as shown in FIG. By rotating the supply roller 5 counterclockwise and the developing roller 4 clockwise, both may be rotated forward. In this case, in order to carry out constant speed development, the photosensitive drum 1 is rotationally driven counterclockwise.

As described above, according to this embodiment, the developing roller 4
As the surface of the dielectric part 41 and the conductor part 42 are mixed in a very small area, and
Since the dielectric portion 41 is triboelectrically charged by the toner supply roller 5 to form a large number of fine electrodes, it is possible to easily attract a large amount of sufficiently charged toner to the surface of the developing roller 4. A sufficiently charged multi-layered toner layer can be easily formed on the developing roller 4. Further, the toner supply roller 5 and the developing roller 4 are rotated in the forward direction so that uncharged toner from the hopper portion is not supplied onto the developing roller 4 that has passed through the contact portion due to the rotation of the toner supply roller 5. Therefore, the amount of toner adhered to the developing roller 4 is unlikely to be affected by environmental changes, and the distribution of the amount of charge of the toner with a small amount of uncharged toner can be obtained and the developing characteristics can be stabilized.
Therefore, since a multi-layered toner layer having a small amount of uncharged toner and a desired charge amount can be stably formed on the developing roller 4, constant speed development is also possible.

Further, the conductor portion 42 and the dielectric portion 41 are mixed on the contact surface of the developer layer forming member 8 with the developing roller 4, and the developing roller 4 and the like are frictionally charged to generate a microfield. Since the toner layer is formed on the developing roller 4, the toner layer on the developing roller 4 is made uniform while the toner is held on the contact surface. Therefore, the toner layer on the developing roller 4 can be made stable and uniform over a long period of time. Further, by rotating the toner supply roller 5 in the forward direction as described above, only the sufficiently charged toner can be supplied to the developing roller 4, so that the toner supply roller 5 moves in the reverse direction at the contact portion with the developing roller 4. Unlike the moving one, it is possible to set the pressure contact force of the developer layer forming member 8 to the developing roller 4 to a relatively low pressure contact force in order to remove uncharged toner in the upper layer portion of the toner layer on the developing roller 4. Also, it is advantageous to prevent the toner adhesion to the developer layer forming member 8. Further, as the developing roller 4, the dielectric portion 41 is provided on the surface.
Since the grounding conductor portion 42 and the grounded conductor portion 42 are mixed together in a small area, there is a possibility that the developing roller 4 may have a slight unevenness in the amount of adhesion. Developing roller 4 which has passed the contact part of
The thickness of the toner layer on the roller is controlled to be uniform by the developer layer forming member 8 that comes into light contact with the surface portion, and the thickness of the toner layer conveyed to the developing area is made uniform, so that the density uniformity of the developed image is improved. , You can get a good quality solid image.

Further, since the developing roller 4 is rotated so as to move at substantially the same speed as the photosensitive drum 1 in the developing area, "from the trailing edge of the toner" does not occur, and even in the color image at the trailing edge portion. It is possible to obtain a good image without problems such as excessive density and different colors of superimposed images.

Further, since the toner layer on the developing roller 4 contains no uncharged toner, it is possible to obtain a good image quality without background stains and resolution deterioration.

Although the example of the non-magnetic one-component developing device has been described above, the present invention can be similarly applied to a one-component developing device using magnetic toner.

[0033]

According to the present invention, the surface of the developer supplying member and the surface of the developer carrying member are moved in the same direction at the contact portion between the two, so that the developer on the developer supplying member is removed. By adhering to the surface of the developer carrying member, the uncharged developer from the toner accommodating portion is directly supplied to the surface of the developer carrying member that has passed through the contact portion by moving the surface of the developer supplying member,
As a result, only the developer that is sufficiently charged by the triboelectric charging at the contact portion is carried on the surface of the developer carrier in a laminated state, so that there is little uncharged toner and a multilayer toner layer having a desired charge amount is developed. It can be formed on the agent carrier and supplied to the latent image carrier. Therefore, by performing the constant-speed development, it is possible to prevent "from the trailing edge of the toner" and obtain a good developed image even in the case of a color image without excessive density at the trailing edge and color difference of the superimposed image. Further, since the uncharged toner and the like are not conveyed to the developing area, it is possible to obtain a good developed image without causing background stains and resolution deterioration. In addition, since the uncharged developer whose amount of adhesion to the developer carrier easily fluctuates depending on the environment is not carried on the developer carrier, it is possible to form a stable developer layer on the developer carrier. As a result, it is not necessary to dispose a blade or the like on the surface of the developer bearing member so as not to convey such an uncharged developer as it is to the developing area. Therefore, it is possible to omit such a blade and simplify the structure of the developing device accordingly. In addition, a large number of minute electric fields formed on the surface of the developer layer forming member in which the conductive portion and the dielectric portion that are in contact with the developer carrier are regularly or irregularly distributed in a fine area, The developer layer carried on the developer carrier is made uniform while the surface of the developer is frictionally charged, so that the developer is less likely to stick to the developer layer forming member and the developer is uniform over a long period of time. Layers can be formed. Therefore, it is possible to obtain a stable developed image over time and in the environment.

Particularly, according to the developing device of the second aspect, the developer supplying member has a surface on which the grounded conductive portion and the dielectric portion of the developer carrier are regularly or irregularly distributed in a minute area. By triboelectrification, a large number of minute electric fields are formed in the vicinity of the surface of the developer carrier, whereby only the developer sufficiently charged by the triboelectrification at the contact portion is formed on the surface by the minute electric field in the vicinity of the surface of the developer carrier. Since the toner is carried in a laminated state, it is possible to reliably form a multi-layered toner layer having a small amount of uncharged toner and a desired charge amount.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating a main part of a developing device according to an embodiment.

FIG. 2 is a front view of the developing device.

3A is a plan view showing a part of the surface of the developing roller 4 of the developing device, FIG. 3B is a sectional view of the surface portion, and FIG.
Is an explanatory view of a toner layer formation state on the surface.

FIG. 4A is a plan view showing a part of the surface of a developing roller 4 according to a modified example, and FIG. 4B is an explanatory view of a toner layer forming state on the surface.

5A is an explanatory view illustrating a toner supply action of the toner supply roller 5 to the developing roller 4 in the developing device, and FIG. 5B is a charge amount distribution of toner of a toner layer on the developing roller 4. Graph.

FIG. 6A illustrates a toner supply operation of the toner supply roller 5 to the developing roller 4 when the relationship between the rotation directions of the toner supply roller 5 and the developing roller 4 is different from that of the developing device. Explanatory drawing, (b) is a graph showing the charge amount distribution of the toner of the toner layer on the developing roller 4 in that case.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photoconductor drum, 2 Development device 3 Casing, 4 Development roller 5 Toner supply roller, 6 Agitator 8 Developer layer forming member, 41 Dielectric part 42 Conductor part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoki Iwata 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Umitsu Fujishiro 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Inventor Akira Sawada 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (3)

[Claims] 1. A developer carrying member whose surface is driven to move, a developer supplying member which is driven so that the surface comes into contact with the surface of the developer carrying member, and a developer supplying member. A developer layer forming member that comes into contact with the surface of the developer carrier to which the developer is supplied, and is supplied by the developer supplying member,
In a developing device for visualizing a latent image on a latent image bearing member by a developer on the developer bearing member thinned by the developer layer forming member, the moving direction of the surface of the developer feeding member Are set so as to move in the same direction at the contact portion with the surface of the developer bearing member, and the conductive portion and the dielectric portion are regular or irregular on the surface contacting the developer bearing member as the developer layer forming member. A developing device characterized by using a material distributed in a minute area. 2. A surface of the developer carrier, which is grounded on the surface thereof, is regularly or irregularly distributed in a minute area as the developer carrier, and the surface of the developer carrier is slid by a developer supplying member. A large number of minute electric fields are formed in the vicinity of the surface of the developer carrier by rubbing, and the developer frictionally charged at the contact portion is carried in a laminated state on the developer carrier by the minute electric field. Item 1 developing device. 3. A developing method in which a developer carrying member supplies a developer to an electrostatic latent image carrying member to develop an electrostatic latent image on the electrostatic latent image carrying member, and the surfaces move in the same direction. At the contact portion between the developer supply member and the developer carrier, the developer is triboelectrically charged to be carried on the developer carrier, and the surface of the developer carrier carrying the triboelectrified developer is generated by a minute electric field. A uniform developer layer is formed by rubbing with a developer layer forming member that holds the developer on the surface, and the developer layer is conveyed by the developer carrier to a portion facing the electrostatic latent image carrier. And a developing method.