JPH04337768A - Developing device - Google Patents

Abstract

PURPOSE:To provide a developing device which stably executes soft and uniform press-contact development and to form a high-resolution image with little density fluctuation over a long term. CONSTITUTION:A foam part 41 is provided on the outer periphery of a base substance 40, and a 1st solid surface layer part 42 which is made of the same material as the foam part 41 and continues thereto is provided on the outer periphery of the foam part 41. Then, a 2nd solid surface layer part 43 is provided on the end face of the foam part 41, and further a 1st magnetic field generating layer 44 and a 2nd magnetic field generating layer 45 are formed on the 1st solid surface layer part 42 and the 2nd solid surface layer part 43, respectively. At or near the press-contact part of a toner carrier with a latent image carrier, an image is developed with magnetic toner in accordance with developing electric field. The hardness and the electric resistance of the toner carrier are prevented from being changed. Furthermore, stable developing voltage is impressed from a shaft. Then, the contamination of the inside and the outside of an image forming device by the toner is prevented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for forming an image using an electrophotographic process, and more particularly to a developing apparatus that performs development by pressing a toner carrier against a latent image carrier.

0002

[Prior Art] A conventional developing device is USP-37311
As disclosed in No. 46, toner is conveyed and developed using a toner carrier having a foamed member as a backing and a flexible conductive layer provided on the surface of the foamed member.

0003

[Problem to be solved by the invention] However, the above-mentioned USP
In the prior art disclosed in No. 3731146, in order to form a uniform conductive layer on the surface of a foamed member, the conductive layer must be formed to have a thickness equal to or larger than the cell size of the foamed member. However, it has been difficult to achieve the flexibility of the foam member on the surface of the toner carrier. Therefore, the developing pressure and developing nip width (contact width) change due to environmental changes, etc., resulting in density fluctuations and a decrease in resolution. In addition, when manufacturing a toner carrier, a series of steps such as forming a foam member, machining the foam member, and forming a conductive layer is required at a minimum, and since the foam member is flexible, the time required for machining is particularly high. This has resulted in an increase in the cost of the toner carrier.

[0004] In order to solve this problem, the present applicant developed a developing device in which the toner carrier is made of a foamed member having a continuous foam portion and a solid surface layer made of the same material, and a conductive layer formed on the solid. We are proposing a device. The purpose is to propose a developing device that can stably perform soft pressure development using a flexible foam member. Still another object is to propose a developing device with high resolution and little variation in density. Still another object is to propose a toner carrier that is easy to manufacture and inexpensive.

The present invention is to further improve the above-mentioned developing device proposed by the present applicant, and its purpose is to perform soft and uniform pressure development over a long period of time using a flexible foam member. An object of the present invention is to provide a developing device that can perform development stably. Still another object is to provide a developing device that is less contaminated by toner inside and outside the image forming apparatus.

[0006]

[Means for Solving the Problems] The developing device of the present invention brings the toner carrier into pressure contact with the latent image carrier through the toner, so that the latent image on the latent image carrier is formed by the toner on the toner carrier. In a developing device in which the toner carrier has a foam part and a continuous first solid surface layer part made of the same material as the foam part on the outer periphery, a first substantially solid surface layer on the outer periphery is provided on an end surface of the toner carrier. It is characterized by having a second solid surface layer made of a different material from the surface layer, or having a different thickness, a different hardness, or a different external shape.

Further, the developing device of the present invention is characterized in that a conductive layer is formed on the solid surface layer portion of the toner carrier.

Furthermore, the developing device of the present invention is characterized in that a magnetic field generating layer is formed on the solid surface layer portion of the toner carrier.

[0009]

[Operation] According to the above structure of the present invention, by forming a solid surface layer also on the end face of the toner carrier, it is possible to prevent toner from being mixed into the foam part, and to prevent changes in the hardness of the foam part, Changes in resistance can be prevented.

Furthermore, by forming a solid surface layer made of a material different from that of the foam portion on the end face of the toner carrier, the solid surface layer can be formed on the cut surface of the foam portion, which is advantageous for mass production and reduces costs. .

Furthermore, by forming a solid surface layer portion also on the end face of the toner carrier, a conductive layer having sufficient flexibility can be formed on the end face of the toner carrier. Further, by forming a conductive layer on the solid surface layer portion of the end face of the toner carrier, conduction can be easily and reliably established from a base such as a shaft to the conductive layer on the outer peripheral portion of the image carrier. Furthermore, a developing voltage that is not affected by changes in electrical resistance due to changes in the amount of deformation of the foam portion can be applied from a base such as a shaft.

Furthermore, by forming a solid surface layer portion also on the end face of the toner carrier, a magnetic field generating layer having sufficient flexibility can be formed on the end face of the toner carrier. In addition, by forming a magnetic field generating layer on the solid surface layer of the end surface of the toner carrier, the toner leaking from the seal formed at the approximate end of the outer periphery of the toner carrier is transferred to the end surface of the toner carrier by magnetic force. This can prevent contamination by toner inside and outside the image forming apparatus.

[0013]

Embodiment FIG. 1 is a cross-sectional schematic view of an image forming apparatus using a developing device according to a specific embodiment of the present invention. A photosensitive layer 3 made of a photoconductive material is formed. After charging the photosensitive layer 3 using a charger 4 such as a corona charger or a charging roller, light emitted from a light source 5 such as a laser or LED is passed through an imaging optical system 6 to form an image on the photosensitive layer 3. A desired electrostatic latent image pattern is formed by selectively irradiating light according to the voltage to obtain a potential contrast. On the other hand, the developing device 7
1 conveys and develops the toner 8, which is an image forming body, and the toner carrier 9 that conveys the toner 8 is connected to the shaft 1.
A foam part 11 and a continuous first solid surface layer part 12 made of the same material as the foam part 11 are sequentially formed on the outer periphery of the foam part 0, and the end surface is also made of a material or has a thickness different from that of the first solid surface layer part on the outer periphery. A second solid surface layer 14 having different hardness, different hardness, or different outer diameter is formed. However, the corner between the outer periphery and the end face is chamfered,
Alternatively, it may be formed with a monotonous curved surface from the outer circumferential portion to the end surface, or the first solid surface layer portion 12 and the second solid surface layer portion 14 may be formed substantially continuously. Further, the first solid surface layer portion 12 or the second solid surface layer portion may be a foamed member in which the diameter of the foamed cells is smaller than the particle size of the toner. By forming a solid surface layer also on the end face of the toner carrier, it is possible to prevent toner from getting mixed into the foam part, and it is possible to prevent changes in the hardness and electrical resistance of the foam part. Furthermore, by making the solid surface layer 12 on the outer periphery of the toner carrier 9 a continuous solid surface layer made of the same material as the foam portion 11, the solid surface layer 12 can be formed during molding of the foam portion 11, thereby reducing the number of steps. Costs are reduced. Furthermore, a blade 15 made of non-magnetic or magnetic metal or resin is pressed against the toner carrier 9 to charge the toner 8 to a predetermined polarity and thin the toner layer to an appropriate amount. 8 directly and rotate the toner carrier 9 to release a thin layer of toner 8.
It is used to transport. The toner carrier 9 is the latent image carrier 1
The potential contrast of the latent image carrier 1 and the potential contrast between the latent image carrier 1 and the toner carrier 9 or between the latent image carrier 1 and the blade 15 are in contact with each other at a predetermined pressure at or near this pressure contact portion. A developing electric field is formed by the developing bias voltage applied between the two, and the charged toner 8 is developed according to the developing electric field. In this way, the electrostatic latent image pattern on the latent image carrier 1 is visualized by the charged toner 8. Further, the toner image is transferred onto the recording paper 17 using a transfer device 16 such as a corona transfer device or a transfer roller,
A desired image can be obtained on the recording paper 17 by fixing the toner 8 on the recording paper 17 using heat or pressure.

Furthermore, the first conductive layer 18 may be formed on the first solid surface layer portion 12 and the second conductive layer 19 may be formed on the second solid surface layer portion 14. However, the first conductive layer 18 and the second conductive layer 19 may be formed continuously. The toner carrier 9 is pressed against the latent image carrier 1 at a predetermined pressure, and the potential contrast of the latent image carrier 1 and the conductivity between the latent image carrier 1 and the toner carrier 9 are reduced at or near the pressure contact portion. A developing electric field is formed by a developing bias voltage applied between the layer 18 and the developing electric field, and the non-magnetic toner 8 charged according to the developing electric field is developed. In this way, the electrostatic latent image pattern on the latent image carrier 1 is visualized by the charged non-magnetic toner 8. By forming the solid surface layer portion 14 also on the end face of the toner carrier 9, a conductive layer 19 having sufficient flexibility can be formed on the end face of the toner carrier 9. Further, by forming the conductive layer 19 on the solid surface layer portion 14 of the end face, conduction can be easily and reliably established from the shaft 10 to the conductive layer 18 on the outer peripheral portion of the toner carrier 9. Furthermore, it is possible to apply a developing voltage from the shaft 10 that is not affected by changes in electrical resistance due to changes in the amount of deformation of the foam portion 11.

Furthermore, a first magnetic field generating layer 20 is formed on the first solid surface layer 12 on the outer periphery of the foamed member 13, and a second magnetic field generating layer 20 is formed on the second solid surface layer 14 on the end surface of the foamed member 13. A layer 21 may also be formed. However, the first magnetic field generating layer 20 and the second magnetic field generating layer 21 may be formed continuously. By configuring the toner carrier 9 to have the magnetic field generation layer 20, the magnetic toner 8 can be directly held and transported on the outer periphery of the toner carrier 9 by magnetic force due to leakage magnetic flux on the surface of the magnetic field generation layer 20. By forming the solid surface layer portion 14 also on the end face of the toner carrier 9, a magnetic field generating layer 21 having sufficient flexibility can be formed on the end face of the toner carrier 9. Further, by having the magnetic field generating layer 21 on the solid surface layer 14 of the end face of the foam member 13, leakage magnetic flux on the surface of the magnetic field generating layer 21 can prevent the seal formed at the approximate end of the outer periphery of the toner carrier 9. The leaked magnetic toner 8 is held on the end surface of the toner carrier 9 by magnetic force, and scattering of the magnetic toner 8 can be prevented, thereby preventing contamination of the inside and outside of the image forming apparatus.

Specific examples of the layer structure of the toner carrier will be shown below.

FIG. 2 is a schematic cross-sectional view showing a specific example in which a conductive layer is formed on the surface of a toner carrier. The toner carrier shown in FIG. 2 includes a foam part 31 on a base 30 such as a shaft, a continuous first solid surface layer part 32 made of the same material as the foam part on the outer periphery, and a material different from the first solid surface layer part on the outer periphery. A second solid surface layer 33 of different thickness, hardness, or outer diameter is formed on the end face, and a first conductive layer 34 is formed on the outer solid surface layer 32. In addition, the solid surface layer 3 of the end face
3, a second conductive layer 35 is formed on top of the second conductive layer 35. however,
The first conductive layer 34 and the second conductive layer 35 may be formed continuously. However, the order in which the foam portion, first solid surface layer portion, and second solid are formed may be rearranged. By forming the solid surface layer portion 33 also on the end surface of the toner carrier 9 in this way, the conductive layer 35 having sufficient flexibility can be formed on the end surface of the toner carrier 9. Further, a conductive layer 34 is formed on the outer periphery of the toner carrier 9,
In addition, by forming the conductive layer 35 on the solid surface layer 33 of the end face, a developing bias voltage is applied to the conductive layer 34 on the outer periphery through the conductive layer 35 of the end face during press-contact development, and the developing electrode can carry a latent image. A sufficient developing electrode effect can be obtained by placing the electrode closest to the body, and images with high resolution and excellent area gradation with little edge effect (a condition in which a strong electric field is generated at the edge of the image and excessive toner is developed) can be formed. Further, a conductive layer 35 is provided on the solid surface layer portion 33 of the end surface of the toner carrier.
By forming the conductive layer 34 on the outer periphery of the image carrier
Conductivity can be easily and reliably established from the base 30. Furthermore, a developing voltage that is not affected by changes in electrical resistance due to changes in the amount of deformation of the foam portion 31 can be applied from a base such as the shaft 10. Regarding the electrical resistance of the conductive layer 34 and the conductive layer 35, the conductive layer 3
A stable developing current can be obtained by setting the electrical resistance between the surface of 4 and the developing bias voltage application part to be 100 MΩ or less, and the thickness of the conductive layer 34 and the conductive layer 35 should have sufficient flexibility. In order to ensure this, the thickness is preferably 100 μm or less.

FIG. 3(a) is a schematic cross-sectional view showing a specific example in which a magnetic field generating layer is formed on the surface of a toner carrier, in which a foam portion 41 is formed on a base body 40 such as a shaft, and a first continuous layer made of the same material is formed. A second solid surface layer 43 made of a different material, different in thickness, different in hardness, or different in outer diameter from the first solid surface layer on the outer periphery is formed on the end face, Solid surface layer 4
A first magnetic field generating layer 44 is formed on the solid surface layer 43, and a second magnetic field generating layer 45 is formed on the solid surface layer 43. However, the foam part 41, the first solid surface layer part 42, the second solid surface layer part 47, the first conductive layer 46, the second conductive layer 47, the first magnetic field generation layer 44, and the second magnetic field generation layer 4
5 may be formed in a different order. Further, the first magnetic field generating layer 44 and the second magnetic field generating layer 45 may be formed continuously. In this way, by forming the solid surface layer portion 14 also on the end surface of the toner carrier 9, the toner carrier 9
A magnetic field generating layer 21 having sufficient flexibility can be formed on the end face of the magnetic field generating layer 21 . Further, by having the magnetic field generating layer 45 on the solid surface layer 43 of the end face, leakage magnetic flux on the surface of the magnetic field generating layer 45 leaks from the seal formed at the approximate end of the outer periphery of the toner carrier 9. The magnetic toner 8 is held on the end surface of the toner carrier 9 by magnetic force, and scattering of the magnetic toner 8 can be prevented, thereby preventing contamination of the inside and outside of the image forming apparatus. Furthermore, the magnetic field generating layer 44 can be made conductive to obtain a developing electrode effect. Note that the thickness of the first magnetic field generating layer 44 and the second magnetic field generating layer 45 is preferably 100 μm or less in order to ensure sufficient flexibility.

FIG. 3(b) is a cross-sectional schematic view showing still another specific example in which a magnetic field generating layer is formed on the surface of a toner carrier. A continuous first solid surface layer 42 is formed of the same material as 41, and a second solid is made of a different material from the first solid surface layer on the outer periphery, has a different thickness, has a different hardness, or has a different outer diameter. A surface layer 43 is formed on the end surface, a first conductive layer 46 is formed on the solid surface layer 42 on the outer periphery, a second conductive layer 47 is formed on the solid surface layer 43 on the end surface, and a conductive layer 46 is formed on the solid surface layer 42 on the outer periphery. A first magnetic field generating layer 44 is formed on the layer 46, and a second magnetic field generating layer 45 is formed on the conductive layer 47 on the end face. However, the foam part 41, the first solid surface layer part 42, the second solid surface layer part 47, the first conductive layer 46, the second conductive layer 47, the first magnetic field generation layer 44, and the second magnetic field generation layer 45 may be formed in a different order. Furthermore, by forming the solid surface layer portion 43 on the end surface of the toner carrier, a conductive layer 47 having sufficient flexibility is formed on the end surface of the toner carrier.
and a magnetic field generating layer 45 can be formed. Furthermore, by forming the conductive layer 46 and the magnetic field generation layer 44 on the solid surface layer 42 on the outer periphery, a sufficient developing electrode effect can be obtained, and an image with high resolution and excellent area gradation can be formed. , it is possible to obtain sufficient toner retention power, and to form images with little background fog and high contrast. In addition, by forming the magnetic field generation layer 45 on the end face, the magnetic toner 8 leaked from the seal formed at the approximate end of the outer periphery of the toner carrier 9 due to leakage magnetic flux on the surface of the magnetic field generation layer 45 is transferred to the toner carrier 9. It is possible to prevent the magnetic toner 8 from scattering by magnetically holding the toner 8 on the end surface of the toner 9, thereby preventing contamination of the inside and outside of the image forming apparatus. In addition, by forming a conductive layer 47 on the solid surface layer 43 on the end face, a developing bias voltage that is not affected by changes in the amount of deformation of the foam portion 41 is applied to the conductive layer 46 on the outer periphery via the base 40 such as a shaft. It is possible to form an image with high resolution and excellent area gradation.

More detailed examples will be shown below.

[Example 1] A shaft and a polyurethane foam member were integrally molded by reaction injection molding using polyurethane as a main raw material, and a continuous first solid surface layer portion made of the same material as the foam portion was formed on the outer periphery. Furthermore, a second solid surface layer portion was formed on the end face using a plate-shaped rubber material different from that of the foam portion, thereby forming a toner carrier having an outer diameter of 20 mm. The surface of the toner carrier after molding can have any surface roughness depending on the surface condition of the mold, and by polishing the mold, a sufficiently smooth surface with a surface roughness of 5 μm or less can be obtained, and the toner carrier can be Post-processing such as polishing the outer diameter of the body was not necessary. Furthermore, the weight of this toner carrier excluding the shaft was 26 g for a 230 mm long toner carrier. When this toner carrier was pressed against a latent image carrier having an outer diameter of 60 mm at 2 g/mm, a uniform developing nip width (contact width) of approximately 2 mm was obtained, and a soft, uniform, and stable pressure contact state was maintained. A developing device capable of this was obtained. When such a developing device was used in the image forming apparatus shown in Fig. 1 to continuously form 300DPI line images, character images, and solid images on 15,000 sheets, the 300DPI line images were stable without line thickening. It was possible to uniformly and stably form a high-density solid image with excellent area gradation properties and an OD value of 1.4 or more over the entire surface. Furthermore, no toner adhesion or fusion was observed on the latent image carrier or toner carrier, and no damage to the toner was observed. Further, no change in the hardness of the toner carrier was observed. However, image formation was performed with a configuration in which a developing bias voltage was applied to the blade and the charge on the toner carrier was removed after development.

[Example 2] A shaft and a polyurethane foam member were integrally molded by reaction injection molding using polyurethane as the main raw material, and a continuous first solid surface layer portion made of the same material as the foam portion was formed on the outer periphery. Furthermore, a second solid surface layer portion was formed on the end face using a plate-shaped rubber material different from that of the foam portion, thereby forming a toner carrier having an outer diameter of 20 mm. In addition, about 50% of the conductive paint in which carbon black is dispersed using polyurethane as a binder is applied to the first solid surface layer on the outer periphery and the second solid surface layer on the end surface.
A conductive toner carrier having an outer diameter of 20 mm was formed by spray coating with a film thickness of μm. The surface of the toner carrier after being coated with the conductive layer had a sufficiently smooth surface, and post-processing such as polishing the outer diameter of the toner carrier was unnecessary. Furthermore, sufficient flexibility and compression set characteristics were obtained even when this toner carrier was pressed against a latent image carrier having an outer diameter of 30 mm. Further, the electrical resistance between the outer circumferential surface of the toner carrier and the shaft was 1 MΩ or less, indicating appropriate conductivity, and development could be performed by applying a developing bias voltage to the shaft. This toner carrier was applied to a latent image carrier with an outer diameter of 30 mm at a rate of 3 g/m
When pressed at a pressure of m, a developing nip width (contact width) of about 2 mm was obtained, and a developing device capable of maintaining a soft, uniform, and stable pressure contact state was obtained. When such a developing device is used in an image forming apparatus as shown in FIG.
When 0DPI line images, character images, and solid images were continuously formed on 15,000 sheets, 600DPI line images were stably formed without line thickening with little edge effect, and high-resolution images could be formed. The recording reproducibility of dots was good, the area gradation was excellent, and a high-density solid image with an OD value of 1.4 or more could be stably and uniformly formed over the entire surface. Furthermore, no toner adhesion or fusion was observed on the latent image carrier or toner carrier, and no damage to the toner was observed. Furthermore, no change in hardness or change in electrical resistance of the toner carrier was observed.

[Example 3] A shaft and a polyurethane foam member were integrally molded by reaction injection molding using polyurethane as the main raw material, and a continuous first solid surface layer portion made of the same material as the foam portion was formed on the outer periphery. Further, a second solid surface layer portion was formed on the end face using a plate-shaped rubber material different from that of the foam portion, thereby forming a toner carrier. Furthermore, the first solid surface layer on the outer periphery is roller coated with a magnetic conductive paint containing polyurethane as a binder and γ-Fe2O3 and carbon black dispersed therein, to a thickness of about 10 μm, and the second solid surface layer on the end surface is coated with polyurethane. A magnetic conductive paint containing γ-Fe2O3 and carbon black as a binder dispersed therein was dip coated to a thickness of about 10 μm to form a toner carrier having a conductive magnetic field generating layer with an outer diameter of 20 mm. The surface of the toner carrier after being coated with the magnetic field generation layer had a sufficiently smooth surface, and post-processing such as polishing the outer diameter of the toner carrier was not necessary. 5 toner carriers having this magnetic field generating layer
Line magnetization is performed at a minute pitch with a magnetization reversal pitch of 0 μm,
A thin toner layer (toner layer thickness of about 20 μm) of magnetic toner could be held on the surface of the toner carrier by magnetic force. Furthermore, sufficient flexibility and compression set characteristics were obtained even when this toner carrier was pressed against a latent image carrier having an outer diameter of 30 mm. Further, the electrical resistance between the outer circumferential surface of the toner carrier and the shaft was 1 MΩ or less, indicating appropriate conductivity, and development could be performed by applying a developing bias voltage to the shaft. A toner carrier having a magnetic field generating layer magnetized at a minute pitch is placed on a latent image carrier having an outer diameter of 60 mm at a rate of 2 g/m.
When pressed at a pressure of m, a developing nip width (contact width) of about 2 mm was obtained, and a developing device capable of maintaining a soft, uniform, and stable pressure contact state was obtained. When such a developing device is used in an image forming apparatus as shown in FIG.
When 0DPI line images, character images, and solid images were continuously formed over 15,000 sheets, high-resolution images were formed with little edge effect and 600DPI line images could be stably formed over the entire surface without line thickening. There is no trailing or background fog at the edges of the image, good dot recording reproducibility, excellent area gradation, and an OD value of 1.
It was possible to stably and uniformly form a solid image with a high density of 4 or more over the entire surface. In addition, there was no background fog on the recording paper, and there was no background fog on the latent image carrier, making it possible to significantly reduce the amount of waste toner, confirming the reduction in background fog due to the magnetic binding force. Further, no toner adhesion or fusion was observed on the latent image carrier or toner carrier, and no damage to the toner was observed. Further, no change in hardness or electrical resistance of the toner carrier was observed. Furthermore, no toner contamination inside or outside the image forming apparatus was observed.

[Comparative Example 1] A shaft and silicone rubber were integrally molded by injection molding using silicone rubber to which a conductive agent was added as a main raw material to form a conductive toner carrier having an outer diameter of 20 mm. The surface of the toner carrier after molding required post-processing to polish the outer diameter of the toner carrier in order to remove unnecessary parts such as parting lines and achieve outer diameter accuracy. Moreover, the weight of this toner carrier excluding the shaft was 75 g for a 230 mm long toner carrier, which could not be reduced in weight. Even if this toner carrier is pressed against a latent image carrier with an outer diameter of 60 mm at 2 g/mm, almost no developing nip width (contact width) is obtained, and the developing nip width (contact width) is about 1 mm.
In order to obtain this, it is necessary to press the toner carrier against the latent image carrier with a pressing force of 20 g/mm or more, which increases the size of the pressing mechanism parts and the like. Damage caused by pressure occurred. When such a developing device is used in an image forming apparatus as shown in FIG.
When 00DPI line images, character images, and solid images were continuously formed on 10,000 sheets, 600D
The PI line image became thick and only an image with a lot of background fog could be formed. In addition, damage occurs on the latent image carrier after forming images on several dozen sheets, and toner sticks or fuses on the latent image carrier or toner carrier, making it difficult to perform normal image formation. It was difficult.

Although the embodiments have been described above, the present invention can be applied not only to the above embodiments but also to a wide range of developing devices such as electrophotography, and especially when applied to printers, copying machines, facsimile machines, and displays. It is valid.

[0026]

Effects of the Invention As described above, according to the present invention, by forming a solid surface layer also at the end of the toner carrier, it is possible to prevent toner from being mixed into the foam portion. Changes in hardness and electrical resistance can be prevented.

Furthermore, by forming a solid surface layer portion made of a material different from that of the foam portion on the end face of the toner carrier, the solid surface layer portion can be formed during molding of the foam portion, thereby reducing the number of steps and costs.

Furthermore, by forming the solid surface layer on the end face of the toner carrier, the solid surface layer can be formed on the cut surface of the foam portion, which is advantageous for mass production and reduces costs.

Furthermore, by forming a conductive layer on the solid surface layer portion of the end face, conduction can be easily and reliably established from the axis to the conductive layer on the outer periphery of the image carrier. Furthermore, a stable developing voltage that is not affected by changes in the amount of deformation of the foam portion can be applied from a base such as a shaft.

Furthermore, by forming a solid surface layer portion also on the end face of the toner carrier, a magnetic field generating layer having sufficient flexibility can be formed on the end face of the toner carrier. In addition, by forming a magnetic field generating layer on the solid surface layer of the end surface, toner leaking from the seal formed at the approximate end of the outer periphery of the toner carrier is restrained by magnetic force to the end surface of the toner carrier, thereby forming an image. Contamination by toner inside and outside the device can be prevented.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional schematic diagram of an image forming apparatus using a developing device in a specific embodiment of the present invention.

FIG. 2 is a cross-sectional schematic view showing a specific example in which a conductive layer is formed on the surface of a toner carrier in the developing device of the present invention.

FIG. 3 is a schematic cross-sectional view showing a specific example in which a magnetic field generating layer is formed on the surface of a toner carrier in the developing device of the present invention.

[Explanation of symbols]

1 Latent image carrier 7 Developing device 8 Toner 9 Toner carrier 10 Shaft 11 31 41 Foam portion 12 32 42 First solid surface layer portion 14
33 43 Second solid surface layer portion 13 Foamed member 30 40 Base

Claims (3)

[Claims] 1. The toner carrier is pressed against the latent image carrier through the toner, and the latent image on the latent image carrier is developed by the toner on the toner carrier, and the toner carrier is attached to the foam portion and the toner carrier. In a developing device having a continuous first solid surface layer made of the same material as the foam portion on the outer periphery of the foam portion, an end surface of the toner carrier is made of a material different from the foam portion or the same material as the foam portion. A developing device comprising a second solid surface layer portion having a different size or hardness. 2. The developing device according to claim 1, wherein a conductive layer is formed on the solid surface layer portion of the toner carrier. 3. The developing device according to claim 1, wherein a magnetic field generating layer is formed on the solid surface layer portion of the toner carrier.