JPH10333423A - Developing roller, developing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the developing quality of an electrostatic latent image by preventing the electric resistance value of a developing roller from being varied. SOLUTION: An electrical conductive elastic roller part 11 formed at the outside circumferential part of the core bar 7 of the developing roller 1 is constituted of an inner layer 8, a surface layer 9 and an intermediate adhesive layer 10 making the layers 8 and 9 adhere. Since the uniform electric resistance value in the layer 10 is regulated to be smaller than the electric resistance value of the layer 8, the electric resistance value varied in the layer 8 is uniformized to the fixed electric resistance value in the layer 10 even when the electric resistance value of the layer 8 is varied. Therefore, since the electric resistance value of the roller part 11 of the roller 1 is prevented from being varied, the electric resistance value of the roller 1 is uniformized as the result. Thus, the developing quality of the electrostatic latent image is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic developing device for developing an electrostatic latent image formed on a latent image carrier such as a photoreceptor with one-component toner, and a developing roller used in the electrophotographic developing device. And an image forming apparatus using the developing device.

[0002]

2. Description of the Related Art In electrophotographic image formation, the surface of a photoreceptor as a latent image carrier is uniformly charged, exposed to form an electrostatic latent image, and toner is adhered to the electrostatic latent image. This is performed using an electrophotographic process of developing and developing and transferring and fixing the toner image to a recording medium. As one of the systems in which toner is attached to an electrostatic latent image on the surface of a photoreceptor to develop and visualize, a one-component contact development system using one-component toner is generally used. Next, an example of this method will be described. First, a one-component toner frictionally charged at a contact portion between a developing roller and a replenishing roller that rotates in the same direction while being pressed against the developing roller with a predetermined bite amount is applied to the developing roller by a potential difference between the developing roller and the replenishing roller. Adhere to. Further, the one-component toner attached to the developing roller is
The contact portion between the developing roller and a developing blade provided in contact with the surface of the developing roller with a predetermined bite amount is further frictionally charged, the thickness of the toner layer is regulated, and the potential difference between the developing roller and the developing blade is adjusted. Is supplied to the photoconductor while being attracted to the developing roller. Thereafter, at the contact portion between the developing roller and the photoconductor, the one-component toner supplied from the developing roller is developed and attracted to the electrostatic latent image on the photoconductor surface due to a potential difference between the developing roller and the photoconductor. Imaged.

[0003]

As shown in FIG. 5, a developing roller 2 generally used in a one-component contact developing system is used.
Reference numeral 0 denotes a metal core 21 made of metal such as stainless steel and the metal core 2.
A roller portion 24 has a two-layer structure having an inner layer 22 as an elastic layer and a coated surface layer 23 as a dielectric layer on the first layer 1. The inner layer 22 is formed of a soft material having an elasticity of about 40 ° in terms of rubber equivalent hardness (JIS-A hardness), and a specific forming material is silicon rubber or the like. Also, the surface layer 23
Is formed of a material having a rubber equivalent hardness (JIS-A hardness) of about 60 °, which has relatively low elasticity as compared with the inner layer 22, and a specific forming material is urethane resin or the like. . In addition, since the inner layer 22 and the surface layer 23 are each formed of an insulating material, the conductivity is improved by appropriately mixing carbon black, a surfactant, or the like in order to enhance the charging performance of the one-component toner. It is provided to adjust the electric resistance value.

Here, for example, consider the case where silicon rubber is used for the inner layer 22 and urethane resin is used for the surface layer 23. The inner layer 22 is made to have a medium resistance (here, an electric resistance value of 10 ⁸ Ω · cm) by dispersing and mixing conductive carbon black into silicon rubber forming the inner layer 22. However, the layer thickness of the inner layer 22 is as thick as about 4 mm, and when viewed microscopically on a scale of one-component toner particles, fine conductive carbon black is scattered in a wide insulating region of the silicon rubber. The electric resistance in the vicinity of the parting line at the time of molding of No. 22 varies. Also, if a large amount of carbon black is mixed into silicon rubber to reduce the electric resistance and improve conductivity, the silicon rubber is hardened, and it becomes impossible to obtain an ideal elasticity, so that it cannot function as an elastic layer.

The surface layer 23 is made to have a medium resistance (an electric resistance of 10 ⁸ Ω · cm in this case) by mixing a conductive surfactant into a urethane resin forming the surface layer 23. The surface layer 23 is formed as a thin layer having a thickness of about 10 μm by coating, and is less likely to cause non-uniform charging due to the incorporation of a surfactant having a more uniform electric resistance than carbon black. However, when a surfactant is mixed, it is easily affected by the environment such as temperature and humidity. As a result, the electric resistance sometimes fluctuates by two to three orders of magnitude, and in particular, at high temperature and high humidity or at low temperature and low humidity, problems such as background contamination occur in the development of the electrostatic latent image. In this case, since the electric resistance value of the inner layer 22 and the electric resistance value of the surface layer 23 are set to the same numerical value, the variation of the electric resistance value of the inner layer 22 becomes the variation of the electric resistance value of the entire developing roller 20. As a result, the charged state given to the one-component toner in units of microns becomes non-uniform, and when an electrostatic latent image is developed in this state, problems such as uneven density occur in the image.

Further, in order to make the variation of the electric resistance value in the inner layer 22 uniform at a constant electric resistance value, the surface layer 23 is formed.
Is smaller than the electric resistance value of the inner layer 22 (here, the electric resistance value is 10 ⁷ Ω · cm), a large amount of surfactant must be mixed into the urethane resin. The triboelectric charging of the layer 23 is deteriorated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a developing roller capable of preventing variation in electric resistance and improving the development quality of an electrostatic latent image, a developing device using the developing roller, and a developing device using the developing roller. To obtain an image forming apparatus.

An object of the present invention is to provide a developing roller capable of improving the development quality of an electrostatic latent image by improving the triboelectric charging performance, a developing device using the developing roller, and an image forming apparatus using the developing device. Is to get the equipment.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a developing roller having an ideal elasticity to improve the development quality of an electrostatic latent image, a developing device using the developing roller, and a developing device using the developing device. That is, to obtain an image forming apparatus.

[0010]

According to a first aspect of the present invention, there is provided a developing roller provided with a conductive elastically deformable roller portion on an outer peripheral portion of a metal core, wherein the roller portion is formed of a dielectric layer. A surface layer as an inner layer as an elastic layer,
The surface layer and the inner layer are formed of an intermediate layer that adheres to the inner layer.

Therefore, the roller portion of the developing roller has a three-layer structure of a surface layer, an inner layer, and an intermediate layer for bonding both of them, and the electric resistance of the intermediate layer is regulated to be smaller than the electric resistance of the inner layer. Even if the electric resistance of the inner layer varies, the electric resistance varied in the inner layer is made uniform in the intermediate layer in the intermediate layer having an electric resistance smaller than the electric resistance of the inner layer. Thereby, the electric resistance value of the developing roller is made uniform.

According to a second aspect of the present invention, in the developing roller according to the first aspect, the electric resistance of the intermediate layer is regulated to be at least 10 ¹ Ω · cm smaller than the electric resistance of the inner layer.

Therefore, the difference between the electric resistance of the intermediate layer and the electric resistance of the inner layer is restricted to at least 10 ¹ Ω · cm or more, and each electric resistance makes the electric resistance of the developing roller uniform. Is maintained at a value suitable for

According to a third aspect of the present invention, there is provided a developing roller provided with a conductive elastically deformable roller portion on an outer peripheral portion of a metal core, wherein the roller portion is a surface layer as a dielectric layer; An inner layer as an elastic layer, and an intermediate layer that adheres the surface layer and the inner layer, the electric resistance of the intermediate layer is regulated to be smaller than both the electric resistance of the surface layer and the electric resistance of the inner layer. .

Therefore, the roller portion of the developing roller has a three-layer structure of a surface layer, an inner layer, and an intermediate layer for bonding both of them, and the electric resistance of the intermediate layer is regulated to be smaller than the electric resistance of the inner layer. Even if the electric resistance of the inner layer varies, the electric resistance varied in the inner layer is made uniform in the intermediate layer in the intermediate layer having an electric resistance smaller than the electric resistance of the inner layer. Thereby, the electric resistance value of the developing roller is made uniform. Furthermore, since the electric resistance of the surface layer is uniformed as the developing roller in the intermediate layer, it is not necessary to further uniform the surface layer, and the electric resistance of the intermediate layer is not set smaller than the electric resistance of the intermediate layer. In this case, the electric resistance may be set to a predetermined value in consideration of only the frictional charging performance. Therefore, the electric resistance can be set to a value larger than the electric resistance of the intermediate layer. Thereby, the frictional charging performance of the developing roller is improved.

According to a fourth aspect of the present invention, in the developing roller according to the third aspect, the electric resistance of the intermediate layer is at least 10 ¹ Ω · cm, which is higher than both the electric resistance of the surface layer and the electric resistance of the inner layer. Regulated small.

Accordingly, the difference between the electric resistance of the intermediate layer and the electric resistance of the inner layer is restricted to at least 10 ¹ Ω · cm, and each electric resistance equalizes the electric resistance of the developing roller. Is maintained at a value suitable for Further, since the difference between the electric resistance of the intermediate layer and the electric resistance of the surface layer is regulated to at least 10 ¹ Ω · cm or more, each electric resistance is a value suitable for enhancing the triboelectric charging performance of the developing roller. Is maintained.

The invention described in claim 5 provides the invention according to claims 1 to 4
In the developing roller according to any one of the above, the intermediate layer is provided in contact with the metal core.

Therefore, since the intermediate layer and the core metal are provided in contact with each other, the electric resistance of the developing roller is made uniform in the intermediate layer having a uniform electric resistance regardless of the electric resistance of the inner layer. Thereby, the inner layer does not have to have conductivity, and ideal elasticity can be obtained.

According to a sixth aspect of the present invention, there is provided a developing device according to any one of the first to fifth aspects, wherein the developing roller is disposed at a position in contact with a latent image carrier for forming an electrostatic latent image. A developing blade that elastically abuts on the surface of the developing roller at a position upstream of the pressure contact portion between the roller and the latent image bearing member in the rotation direction to regulate the toner layer thickness while frictionally charging the one-component toner;

Accordingly, the thickness of the toner layer is regulated by the developing blade elastically in contact with the surface of the developing roller, and the one-component toner is supplied to the pressure contact portion between the developing roller and the latent image carrier while being frictionally charged. You. In this case, the roller portion of the developing roller is composed of three layers, a surface layer, an inner layer, and an intermediate adhesive layer that adheres both of them, and the uniform electric resistance value of the intermediate layer is regulated to be at least smaller than the electric resistance value of the inner layer. In addition, the electric resistance value of the developing roller is made uniform, and density unevenness during development is prevented, whereby the development quality of the electrostatic latent image can be improved.

According to a seventh aspect of the present invention, there is provided an image forming apparatus, comprising: a latent image carrier; a charging device for uniformly charging the surface of the latent image carrier; 7. An image exposure device for forming an electrostatic latent image by developing the electrostatic latent image formed on the latent image carrier, and a developing device for transferring a developed image from the latent image carrier to a recording medium. The image forming apparatus includes a transfer device and a fixing device that fixes the developed image transferred to the recording medium.

Therefore, the electrostatic latent image formed by the exposure of the image exposure device after the charging device uniformly charges the surface of the latent image carrier is developed by the developing device using one-component toner. In this case, the roller portion of the developing roller provided in the developing device is composed of three layers, a surface layer, an inner layer, and an intermediate adhesive layer that adheres both of them, and a uniform electric resistance value of the intermediate layer is set to at least the electric resistance of the inner layer. Since the value is regulated to be smaller than the value, the electric resistance value of the developing roller is made uniform, and density unevenness during development is prevented. Thereby, the development quality of the electrostatic latent image can be improved.

[0024]

FIG. 1 shows a first embodiment of the present invention.
A description will be given based on FIG. This embodiment is an example in which the present invention is applied to a copying machine A as an image forming apparatus. FIG.
1 is a schematic diagram illustrating an internal configuration of a copying machine A according to the present embodiment. As shown in FIG. 1, the copying machine A is provided with a paper passing path b for connecting a paper feeding device a for storing a transfer paper P as a recording medium and a discharge unit (not shown). An image processing unit d including a fixing device c is provided therein.

The image processing section d mainly comprises a drum-shaped photosensitive member e as a latent image carrier which is driven to rotate clockwise. Around the photosensitive member e, a charging device f of a roller charging type for uniformly charging the photosensitive member e to −750 V, irradiating a light beam to the exposure position EX to set the charging potential of −750 V to about −50 V and statically. An image exposure apparatus g for forming an electrostatic latent image, a non-magnetic one-component toner T (hereinafter referred to as toner T)
), A developing device h, a transfer device i, and a cleaning device j of a one-component developing system using the following method.

Here, the developing device h will be described. FIG. 2 is a schematic diagram mainly showing the vicinity of the developing device h of the copying machine A. As shown in FIG. 2, the developing device h is disposed at a position where the developing device h is pressed against the surface of the photoconductor e with a predetermined bite amount, and is driven to rotate counterclockwise in the opposite direction to the photoconductor e. A replenishing roller 2 that is disposed at a position where it is pressed against the developing roller 1 and is driven to rotate counterclockwise in the same direction as the developing roller 1 to replenish the toner T onto the surface of the developing roller 1; A developing blade 3 provided at a position elastically in contact with the surface of the developing roller 1 with a predetermined bite amount is disposed in a developing container 4. In this case, the linear velocity ratio between the developing roller 1 and the supply roller 2 is set to 1: 1.5, and the supply roller 2 is set to have a higher linear velocity.

A bias potential is appropriately applied to the developing roller 1 by a developing bias power source 5, and a bias potential is appropriately applied to the replenishing roller 2 and the developing blade 3 by a replenishing developing bias power source 6. in this case,
The charging potential by the developing bias power supply 5 is -400 V
The charging potential of the replenishment developing bias power source 6 is -6.
It is set to 50V.

Next, the developing roller 1 will be described.
Here, FIG. 3 is a vertical sectional side view showing the structure of the developing roller 1. As shown in FIG. 3, the developing roller 1 has a metal core 7 made of metal such as stainless steel, and an inner layer 8, a surface layer 9, and an intermediate layer 10 provided on an outer peripheral portion of the metal core 7. And a roller section 11 having a three-layer structure. Hereinafter, the inner layer 8, the surface layer 9, and the intermediate layer 10 constituting the three layers will be described.

First, the inner layer 8 plays a role as an elastic layer for securing elasticity necessary for preventing an excessive increase in torque at the time of contact with the photosensitive member e. For this reason, the inner layer 8
Is made of a soft material having an elasticity of about 40 ° in terms of rubber equivalent hardness (JIS-A hardness). Specific examples of the forming material include silicone rubber and urethane rubber. In this embodiment, silicon rubber is used as a forming material. The thickness of the inner layer 8 is about 4 mm. Also,
The inner layer 8 appropriately contains carbon black for imparting conductivity, and is set to have, for example, an electric resistance value of 10 ⁸ Ω · cm.

The surface layer 9 is formed of a material which is excellent in charge of the toner T and releasability since it functions as a dielectric layer for carrying the toner T to the photosensitive member e while performing triboelectric charging. I have. Further, the forming material is required to be a material that does not contaminate the photoconductor e with oil or the like and that has little variation in electrical characteristics such as resistance. Therefore, the surface layer 9
Is formed of a hard material having a rubber equivalent hardness (JIS-A hardness) of about 60 ° which is relatively lower in elasticity than the inner layer 8. Specific examples of the forming material include a urethane resin, a silicon resin, and a fluorine resin. In this embodiment,
Urethane resin is used as a forming material. The surface layer 9
Has a layer thickness of about 10 μm and is a thin layer formed by coating. Also, carbon black is appropriately mixed into the surface layer 9 to impart conductivity, and is set so that, for example, the electric resistance value is 10 ⁸ Ω · cm.

The intermediate layer 10 has an adhesive property to both the inner layer 8 and the surface layer 9 and increases the adhesive strength between the inner layer 8 and the surface layer 9. And are physically mixed. In the present embodiment, a mixture of silicon rubber and urethane resin is used as a forming material. The intermediate layer 10 is a thin layer having a thickness of about 10 μm. Also, carbon black is appropriately mixed into the intermediate layer 10 in order to impart conductivity, and is set so that, for example, the electric resistance value is 10 ⁷ Ω · cm.

The replenishing roller 2 is formed by disposing a sponge-like inner layer made of urethane, silicon or the like on the outer peripheral portion of a metal core, and covering the soft surface of the inner layer with a resin.

The process of forming an image on the transfer paper P in such a configuration will be described. First, the photoreceptor e is uniformly charged to -750 V by the charging of the roller charging system by the charging device f. Subsequently, at the exposure position EX of the uniformly charged photoconductor e, a light beam corresponding to image information is emitted from the image exposure device g to form an electrostatic latent image.
That is, the charged potential of the portion irradiated with the light beam is about -50 V, and a potential difference is generated between the portion not irradiated with the light beam and the irradiated portion, whereby an electrostatic latent image is formed.
Next, the electrostatic latent image formed on the photoreceptor e moves toward a contact portion with the developing device h.

In the developing device h, the toner T is pumped up in the developing container 4 by the supply roller 2 and supplied to the surface of the developing roller 1. Specifically, supply roller 2
Rotates in the same direction as the developing roller 1 while being pressed against the developing roller 1 and biting. At this time, the developing roller 1 and the replenishing roller 2 rub against each other with a linear velocity difference, so that the toner T is triboelectrically charged to the negative electrode. Further, the toner T has a bias potential difference (250 V) between the developing roller 1 and the replenishing roller 2.
V), the toner is supplied while being rubbed while being attracted to the surface of the developing roller 1 having a low potential.

When the toner T supplied to the developing roller 1 passes through the developing blade 2 as the developing roller 1 rotates, the toner T is directed to a contact portion with the photosensitive member e while the thickness of the toner layer is regulated into a thin film state. Transported. In this case, since the toner T is triboelectrically charged to the negative electrode by the contact between the developing roller 1 and the developing blade 3, the charge amount of the toner T further increases.
In addition, due to the bias potential difference (250 V) between the developing roller 1 and the developing blade 3, the toner T is conveyed while being attracted to the surface of the developing roller 1 having a lower potential.

Next, at the contact portion between the photosensitive member e and the developing roller 1, the toner T is transferred from the developing roller 1 by the bias potential difference (350 V) between the electrostatic latent image formed on the surface of the photosensitive member e and the developing roller 1. Since the electrostatic latent image is attracted onto the electrostatic latent image having a low potential, the electrostatic latent image is developed and visualized.

Here, in the present embodiment, the roller portion 11 of the developing roller 1 has a three-layer structure including an inner layer 8, a surface layer 9, and an intermediate layer 10. In this case, the inner layer 8
Has a layer thickness of about 4 mm, and fine conductive carbon black is scattered in a wide insulating area of silicon rubber, and the electric resistance varies particularly near the parting line at the time of molding. I have. For this reason, in the inner layer 8, even if the electric resistance value is set to be 10 ⁸ Ω · cm, the electric resistance value is partially 10 ⁹ Ω · cm.
・ There are some places of about cm. Further, since the intermediate layer 10 is a thin layer having a thickness of about 10 μm, even if carbon black is mixed, the electric resistance is uniform without variation. In this case, since the set electric resistance of the intermediate layer 10 is set to be smaller than the set electric resistance of the inner layer 8 by 10 ¹ Ω · cm, even if the electric resistance of the inner layer 8 varies, In the middle layer 10 having a small value, the inner layer 8
The electric resistance value which has been dispersed is uniformized to a level of 10 ⁷ Ω · cm. As a result, the development quality of the electrostatic latent image is improved.

Further, the set electric resistance value (1
0 ⁷ Ω · cm) is the set electric resistance value of the surface layer 9 (10 ⁸ Ω · cm).
Ω · cm) is set smaller than 10 ¹ Ω · cm.
This is because the electric resistance varied in the inner layer 8 has already been made uniform to the level of 10 ⁷ Ω · cm in the intermediate layer 10, so that the surface layer 9 is not mixed with carbon black as a conductive agent more than necessary. This is because it is possible to set the electric resistance value considering only the frictional charging of the toner T. That is, since the frictional charging performance to the toner T is enhanced, the development quality of the electrostatic latent image can be improved also in this case.

Thereafter, in the transfer device i, the visualized toner image on the surface of the photoreceptor e is sucked by the potential difference, and the toner image is transferred to the transfer paper P. In the cleaning device j, the toner T remaining on the photoconductor e after the transfer process is scraped off and cleaned. After transfer,
The unfixed toner adhering to the transfer paper P is fixed by the heating / pressing action in the fixing device c arranged on the downstream side in the paper passage path b. Thereby, an image is formed on the transfer paper P.

Next, a second embodiment of the present invention will be described with reference to FIG.
It will be described based on. The same parts as those described in the first embodiment of the present invention are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 4 is a vertical sectional front view showing the structure of the developing roller 12 according to the second embodiment of the present invention. This embodiment differs from the first embodiment in that a developing roller 12 shown in FIG. 4 is provided instead of the developing roller 1 shown in FIG.

As shown in FIG. 4, the developing roller 12 includes a metal core 13 made of metal such as stainless steel, and an inner layer 14, a surface layer 15, and an intermediate layer 16 provided on an outer peripheral portion of the metal core 13. And a roller portion 17 having a three-layer structure. Hereinafter, the inner layer 14, the surface layer 15, and the intermediate layer 16 constituting the three layers will be described.

First, the inner layer 14 plays a role as an elastic layer for securing elasticity necessary for preventing an excessive increase in torque upon contact with the photosensitive member e. Therefore, the inner layer 1
No. 4 is formed of a soft material having an elasticity of about 40 ° in terms of rubber equivalent hardness (JIS-A hardness). Specific examples of the forming material include silicone rubber and urethane rubber. In this embodiment, silicon rubber is used as a forming material. The thickness of the inner layer 14 is about 4 mm. Here, the inner layer 14 does not have conductivity and has insulating properties.

The surface layer 15 is formed of a material which is excellent in charge and releasability of the toner T, because it functions as a dielectric layer for carrying the toner T to the photosensitive member e while performing triboelectric charging. I have. Further, the forming material is required to be a material that does not contaminate the photoconductor e with oil or the like and that has little variation in electrical characteristics such as resistance. For this reason, the surface layer 15 is formed of a hard material having a rubber equivalent hardness (JIS-A hardness) of about 60 °, which is relatively low in elasticity as compared with the inner layer 14. Specific examples of the forming material include a urethane resin, a silicon resin, and a fluorine resin. In this embodiment, a urethane resin is used as a forming material. The surface layer 15 has a thickness of about 10 μm and is a thin layer formed by coating. The surface layer 15 is appropriately mixed with carbon black for imparting conductivity, and is set to have an electrical resistance of, for example, 10 ⁸ Ω · cm.

The intermediate layer 16 has an adhesive property to both the inner layer 14 and the surface layer 15 and increases the adhesive strength between the inner layer 14 and the surface layer 15. Are physically mixed with each other.
In the present embodiment, a mixture of silicon rubber and urethane resin is used as a forming material. The intermediate layer 16 has a layer thickness of 10
μm, and is adhered not only to the outer peripheral portion of the inner layer 14 but also to the side surface 14a side of the inner layer 14 at both ends of the roller portion 17 of the developing roller 12 so as to cover the entire inner layer 14. ing. Thus, the intermediate layer 16 is in direct contact with the metal core 13 at both ends of the roller portion 17 of the developing roller 12. The intermediate layer 16 is also appropriately mixed with carbon black for imparting conductivity, and is set to have an electric resistance of, for example, 10 ⁷ Ω · cm.

In this case, since the intermediate layer 16 is in direct contact with the metal core 13, the electric resistance of the intermediate layer 16 is made uniform (10 ⁷ Ω · cm) regardless of the electric resistance of the inner layer 14. Therefore, as a result, the development quality of the electrostatic latent image is improved. Further, since the inner layer 14 does not need to be conductive and does not contain carbon black or the like, ideal elasticity can be obtained, and the development quality of the electrostatic latent image can be improved.

In the second embodiment of the present invention, the intermediate layer 16 and the metal core 13 are brought into contact at both ends of the roller portion 17 of the developing roller 12, but the present invention is not limited to this. There is no problem even if the intermediate layer 16 and the metal core 13 are brought into contact only at one end of the roller portion 17 of the roller 12.

In each of the embodiments, a non-magnetic one-component toner is used. However, the present invention is not limited to this, and there is no problem even if a magnetic one-component toner is used.

In each of the embodiments, the drum-shaped photosensitive member is used as the latent image carrier. However, the present invention is not limited to this. There is no.

Furthermore, in each of the embodiments, the intermediate layer is formed of a material obtained by physically mixing the material for forming the inner layer and the material for forming the surface layer. However, the present invention is not limited to this. The intermediate layer may be formed by containing only one of the materials.

[0051]

According to the first aspect of the present invention, the roller portion of the developing roller is composed of a surface layer, an inner layer, and an intermediate layer that adheres both of them to each other. Is regulated to be smaller than the electric resistance of the inner layer,
Even if the electrical resistance value of the inner layer varies, the intermediate layer makes the electrical resistance value of the entire developing roller uniform, thereby preventing the occurrence of density unevenness during development due to the variation of the electrical resistance value. The development quality of the electrostatic latent image can be improved.

According to the second aspect of the present invention, in the developing roller according to the first aspect, the difference between the electric resistance of the intermediate layer and the electric resistance of the inner layer is regulated to at least 10 ¹ Ω · cm or more. The respective electric resistances can be maintained at values suitable for making the electric resistance of the developing roller uniform.

According to the third aspect of the present invention, the roller portion of the developing roller is composed of three layers: a surface layer, an inner layer, and an intermediate layer that adheres both of them, and the electric resistance value of the intermediate layer is reduced by the inner layer. And the electric resistance of the surface layer is regulated to be smaller than the electric resistance of the inner layer. In addition to preventing the occurrence of density unevenness during development due to the variation in resistance value, the frictional charge amount of the toner is increased by enhancing the frictional charge performance of the surface layer, thereby improving the development quality of the electrostatic latent image. Can be achieved.

According to the fourth aspect of the invention, in the developing roller according to the third aspect, the difference between the electric resistance of the intermediate layer and the electric resistance of the inner layer is regulated to at least 10 ¹ Ω · cm or more. The respective electric resistances can be maintained at values suitable for making the electric resistance of the developing roller uniform. Further, since the difference between the electric resistance of the intermediate layer and the electric resistance of the surface layer is regulated to at least 10 ¹ Ω · cm or more, each electric resistance is set to a value suitable for enhancing the triboelectric charging performance of the surface layer. Can be maintained.

According to the fifth aspect of the present invention, in the developing roller according to any one of the first to fourth aspects, since the intermediate layer and the cored bar are provided in contact with each other, regardless of the electric resistance value of the inner layer. By making the electric resistance value of the entire developing roller uniform by the intermediate layer, the inner layer does not need to have conductivity, and ideal elasticity can be obtained.

According to the developing device of the sixth aspect,
While frictionally charging the one-component toner, the thickness of the toner layer is regulated by a developing blade elastically in contact with the surface of the developing roller,
In the case of supplying the developing roller to the pressure contact portion between the developing roller and the latent image carrier, the roller portion of the developing roller is composed of a surface layer, an inner layer, and an intermediate adhesive layer that adheres both of them, and the electric power of the intermediate layer is formed. Since the resistance value is regulated to be at least smaller than the electric resistance value of the inner layer, even if the electric resistance value of the inner layer varies, the electric resistance value of the entire developing roller is made uniform by the intermediate layer, so that the development time is reduced. Is prevented from occurring, and the development quality of the electrostatic latent image can be improved.

According to the image forming apparatus of the present invention, the electrostatic latent image formed by the exposure of the image exposure device after the charging device uniformly charges the surface of the latent image carrier is subjected to the one-component toner by the developing device. When developing using
The roller portion of the developing roller provided in the developing device is composed of three layers, a surface layer, an inner layer, and an intermediate adhesive layer that adheres both of them, and the electric resistance of the intermediate layer is regulated to be at least smaller than the electric resistance of the inner layer. Therefore, even if the electric resistance of the inner layer varies, the electric resistance of the developing roller as a whole is made uniform by the intermediate layer, thereby preventing the occurrence of density unevenness during development, and Can be improved in development quality.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an internal configuration of a copying machine according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram mainly showing the vicinity of a developing device of a copying machine.

FIG. 3 is a vertical sectional side view showing a structure of a developing roller.

FIG. 4 is a vertical sectional front view showing a structure of a developing roller according to a second embodiment of the present invention.

FIG. 5 is a vertical sectional side view showing a structure of a conventional developing roller.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1,12 Developing roller 3 Developing blade 7,13 Core metal 8,14 Inner layer 9,15 Surface layer 10,16 Intermediate adhesive layer 11,17 Roller part P Recording medium T One-component toner c Fixing device e Latent image carrier f Charging Device g Image exposure device h Developing device i Transfer device

Claims (7)

[Claims] 1. A developing roller provided with a conductive elastically deformable roller on the outer periphery of a cored bar, wherein the roller is a surface layer as a dielectric layer, an inner layer as an elastic layer, and A developing roller comprising an intermediate layer for bonding a surface layer and an inner layer, wherein an electric resistance value of the intermediate layer is regulated to be smaller than an electric resistance value of the inner layer. 2. The developing roller according to claim 1, wherein the electric resistance of the intermediate layer is regulated to be at least 10 ¹ Ω · cm smaller than the electric resistance of the inner layer. 3. A developing roller provided with a conductive elastically deformable roller on the outer periphery of a cored bar, wherein the roller is a surface layer as a dielectric layer, an inner layer as an elastic layer, and It is constituted by an intermediate layer that bonds the surface layer and the inner layer, and the electric resistance of the intermediate layer is regulated to be smaller than both the electric resistance of the surface layer and the electric resistance of the inner layer. Developing roller. 4. The electric resistance of the intermediate layer is at least one of the electric resistance of the surface layer and the electric resistance of the inner layer.
4. The developing roller according to claim 3, wherein the developing roller is regulated to be smaller than 0 ¹ Ω · cm. 5. The developing roller according to claim 1, wherein the intermediate layer is provided in contact with the metal core. 6. The developing roller according to claim 1, wherein said developing roller is disposed at a position in contact with a latent image carrier for forming an electrostatic latent image. Elastically contacting the developing roller surface at a position in the rotation direction upstream from the pressing portion,
A developing blade for regulating the thickness of the toner layer while frictionally charging the one-component toner. 7. A latent image carrier, a charging device for uniformly charging the surface of the latent image carrier, and an image for forming an electrostatic latent image by exposing the uniformly charged latent image carrier. An exposure device; a developing device for developing the electrostatic latent image formed on the latent image carrier; a transfer device for transferring a developed image from the latent image carrier to a recording medium; and the recording medium. A fixing device for fixing the developed image transferred to the image forming apparatus.