JPH04337767A - 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 made of a different material from the foam part 41 is provided on the outer periphery of the foam part 41. Then, a 2nd solid surface layer part 43 which is made of the same material as the foam part 41 and continues thereto 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 portion and a first solid surface layer portion made of a material different from the foam portion on the outer periphery of the foam portion, an end surface of the toner carrier is provided with a material same as the foam portion. It is characterized by having a continuous second solid surface layer portion.

Further, the developing device of the present invention is characterized in that the first or second solid surface layer portion has foam cells, and the size of the foam cells is smaller than the particle size of the toner.

Furthermore, 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.

0010

[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 making the solid surface layer on the end face of the toner carrier a continuous solid surface layer made of the same material as the foam portion, the solid surface layer can be formed during molding of the foam portion, reducing the number of steps and cost. Decrease.

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 onto the end surface of the toner carrier by magnetic force. It is possible to prevent contamination by toner inside and outside the image forming apparatus.

[0014]

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 first solid surface layer 12 made of a material different from that of the foam part 11 are sequentially formed on the outer periphery of the foam part 0, and a continuous second solid surface part 14 made of the same material as the foam part is also formed on the end surface. This is what I did. However, the corner between the outer periphery and the end face may be chamfered or formed with a monotonous curved surface from the outer periphery to the end face, and the first solid surface layer 12 and the second solid surface layer 14 are approximately They may be formed continuously. In addition, the second solid surface layer 1
In step 4, the entire or surface of the foam portion 11 may be heated to crush the foam cells or make the diameter of the foam cells smaller than that of the toner. Further, the first solid surface layer portion 12 or the second solid surface layer portion 14 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. Further, the solid surface layer 12 of the end face of the toner carrier 9 is attached to the foam portion 11.
By making the solid surface layer part continuous from the same material as the foam part 11, the solid surface layer part 12 can be formed during molding of the foam part 11, thereby reducing the number of steps and cost. 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. A thin layer of toner 8 is conveyed by directly holding the toner 8 and rotating a toner carrier 9. The toner carrier 9 is pressed against the latent image carrier 1 at a predetermined pressure, and at or near the pressure contact portion, the potential contrast of the latent image carrier 1 and the difference between the latent image carrier 1 and the toner carrier 9 are reduced. A developing electric field is formed by a developing bias voltage applied between the latent image carrier 1 and the blade 15, 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. Furthermore, 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, and the toner 8 is fixed onto the recording paper 17 using heat or pressure to transfer the desired image onto the recording paper 17. You can get on top.

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 the developing bias voltage applied between the layer 12 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 generation layer 20 is formed on the second solid surface layer 14 on the end surface of the foamed member 13. A generation 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 generation layer 21 on the solid surface layer 14 on the end face of the foamed member 13, a seal is formed at approximately the edge of the outer periphery of the toner carrier 9 due to leakage magnetic flux on the surface of the magnetic field generation layer 21. The magnetic toner 8 leaked from the toner carrier 9 is held on the end surface of the toner carrier 9 by magnetic force, thereby preventing the magnetic toner 8 from scattering and contaminating 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 has a foam portion 31 on a base 30 such as a shaft, a first solid surface layer 32 on the outer periphery, and a second solid surface layer 33 on the end surface, and a foam portion 31 on the outer periphery of the solid surface layer 32. A first conductive layer 34 is formed thereon. In addition, a second conductive layer 35 is formed on the solid surface layer portion 33 on the end face. 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 peripheral portion of the toner carrier 9, and in addition, a solid surface layer 34 is formed on the end surface.
By forming the conductive layer 35 on the latent image carrier 3, a development bias voltage is applied to the conductive layer 34 on the outer periphery through the conductive layer 35 on the end face during pressure contact development, and the development electrode is brought closest to the latent image carrier. A developing electrode effect can be obtained, and an image with high resolution and excellent area gradation can be formed with less edge effect (a state in which a strong electric field is generated at the edge portion of the image and excessive toner is developed). Further, by forming the conductive layer 35 on the solid surface layer 33 on the end face of the toner carrier, conduction can be easily and reliably established from the base 30 to the conductive layer 34 on the outer peripheral part of the image carrier. Furthermore, the foam part 3
A developing voltage that is not affected by changes in electrical resistance due to changes in the amount of deformation of the shaft 10 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, if the electrical resistance between the surface of the conductive layer 34 and the development bias voltage application part is 100 MΩ or less, a stable developing current can be obtained, and the conductive layer 34 and conductive layer 3
Regarding the wall thickness of No. 5, in order to ensure sufficient flexibility,
The thickness is preferably 100 μm or less.

FIG. 3(a) is a cross-sectional schematic 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 and a first solid surface layer portion 42 are formed on a base body 40 such as a shaft. A second solid surface layer 43 was formed on the end face, a first magnetic field generation layer 44 was formed on the solid surface layer 42, and a second magnetic field generation layer 45 was formed on the solid surface layer 43. It is something. However, the foam part 41
, the first solid surface layer 42 and the second solid surface layer 4
7, the first conductive layer 46, the second conductive layer 47, the first magnetic field generating layer 44, and the second magnetic field generating layer 45 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. By forming the solid surface layer portion 14 also on the end face of the toner carrier 9 in this way, the magnetic field generating layer 21 having sufficient flexibility can be formed on the end face of the toner carrier 9. Also,
By having the magnetic field generating layer 45 on the solid surface layer 43 on the end face, magnetic flux leaked from the surface of the magnetic field generating layer 45 leaks from the seal formed at approximately the edge of the outer periphery of the toner carrier 9. The 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, in which a foam portion 41 is formed on a base body 40 such as a shaft, and a first layer is formed on the outer periphery. A solid surface layer 42 is formed in order, a second solid surface layer 43 is formed on the end surface, and a solid surface layer 4 on the outer periphery is formed.
2, a second conductive layer 47 is formed on the solid surface layer 43 of the end face, and a first magnetic field generating layer 44 is formed on the conductive layer 46 on the outer periphery. , a second magnetic field generating layer 45 is formed on a conductive layer 47 on the end face. However, the foam portion 41 and the first solid surface layer portion 4
2, the second solid surface layer portion 47, the first conductive layer 46, the second conductive layer 47, the first magnetic field generating layer 44, and the second magnetic field generating layer 45 may be formed in a different order. Further, by forming the solid surface layer portion 43 also on the end face of the toner carrier in this manner, it is possible to form the conductive layer 47 and the magnetic field generating layer 45 with sufficient flexibility on the end face of the toner carrier. Further, a conductive layer 4 is provided on the solid surface layer portion 42 on the outer periphery.
6 and the magnetic field generation layer 44, a sufficient developing electrode effect can be obtained, and images with high resolution and excellent area gradation can be formed, as well as sufficient toner holding power can be obtained, and background fog can be prevented. It is possible to form an image with low contrast 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 holding it on the end surface of the image forming apparatus 9 by magnetic force, 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 of the end face,
A developing bias voltage that is not affected by changes in the amount of deformation of the foam portion 41 can be applied to the conductive layer 46 on the outer periphery via the base 40 such as a shaft, and an image with high resolution and excellent area gradation can be formed. Can be done.

More detailed examples will be shown below.

[Example 1] A shaft and a polyurethane foam member are integrally molded by reaction injection molding using polyurethane as the main raw material, cut in a plane perpendicular to the longitudinal direction, and the end face is heated and pressurized to determine the diameter of the foam cell. was made smaller than the toner to form a second solid surface layer. Furthermore, a first solid surface layer portion was formed on the outer periphery to form 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. This toner carrier has an outer diameter of 60 m.
When pressed at 2 g/mm onto a latent image carrier of
A uniform developing nip width (contact width) of m was obtained, and a developing device capable of maintaining a soft, uniform, and stable pressure contact state 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 is formed with excellent area gradation,
A high-density solid image with an OD value of 1.4 or more could be stably formed uniformly 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. Also,
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 are integrally molded by reaction injection molding using polyurethane as the main raw material, cut at a plane perpendicular to the longitudinal direction, and the end face is heated and pressurized to adjust the diameter of the foam cell. was made smaller than the toner to form a second solid surface layer. Furthermore, a first solid surface layer portion was formed on the outer periphery. Furthermore, the first solid surface layer on the outer periphery and the second solid surface layer on the end surface were spray-coated with a conductive paint containing polyurethane as a binder and carbon black dispersed therein to a film thickness of about 50 μm to form a conductive material with an outer diameter of 20 mm. A toner carrier was formed. 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. Moreover, this toner carrier has an outer diameter of 30 mm.
Sufficient flexibility and compression set characteristics were obtained even when pressed against a latent image carrier of 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. When this toner carrier was pressed against a latent image carrier with an outer diameter of 30 mm at 3 g/mm, a developing nip width (contact width) of approximately 2 mm was obtained, and a soft, uniform, and stable pressure contact state could be maintained. A developing device was obtained. When such a developing device was used in the image forming apparatus shown in FIG. 1 to continuously form 600DPI line images, character images, and solid images on 15,000 sheets, there were few edge effects and the 600DPI line images became line thick. It is possible to form high-resolution images stably without any distortion, has good dot recording reproducibility, has excellent area gradation, and can stably produce high-density solid images with an OD value of 1.4 or more. It was possible to form the entire surface uniformly. Also,
No adhesion or fusion of toner 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 are integrally molded by reaction injection molding using polyurethane as the main raw material, a second solid surface layer is formed on the end surface, and a first solid surface layer is formed on the end surface. formed on the outer periphery. 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. Approximately 10μ of magnetic conductive paint with γ-Fe2O3 and carbon black dispersed as a binder
A toner carrier having a conductive magnetic field generating layer with an outer diameter of 20 mm was formed by dip coating with a film thickness of m. 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. The toner carrier having this magnetic field generation layer is line-magnetized at a minute pitch with a magnetization reversal pitch of 50 μm, and a thin toner layer (toner layer thickness of about 20 μm) of magnetic toner is held on the surface of the toner carrier by magnetic force. was completed. In addition, this toner carrier has an outer diameter of 30 mm.
Sufficient flexibility and compression set characteristics were obtained even when pressed against a latent image carrier. 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.
When pressed at g/mm, the developing nip width was approximately 2 mm (
A developing device capable of maintaining a soft, uniform, and stable pressure contact state was obtained. When such a developing device was used in the image forming apparatus shown in FIG. 1 to continuously form 600DPI line images, character images, and solid images on 15,000 sheets, there were few edge effects and the 600DPI line images became line thick. It is possible to form high-resolution images, such as being able to form images stably over the entire surface without causing any damage, and there is no trailing or background fog at the edges of the image, with good dot recording reproducibility, excellent area gradation, and OD.
It was possible to stably and uniformly form a solid image with a high density of 1.4 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 change in 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.

[0027]

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 entering the foam portion.
Changes in the hardness and electrical resistance of the foam part can be prevented.

Furthermore, by making the solid surface layer on the end face of the toner carrier a continuous solid surface layer made of the same material as the foam portion, the solid surface layer can be formed during molding of the foam portion, reducing the number of steps and costs. Decrease. Furthermore, if the foamed cells on the end surface after molding of the foam part are crushed or the diameter of the foamed cells is made smaller than that of the toner, and a substantially solid layer is formed on the end surface of the toner end holder to form a toner carrier,
A substantially solid layer can be formed on the cut surface of the foam part, making it suitable for mass production and reducing 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 of the end face, conduction can be easily and reliably established from the axis to the conductive layer on the outer peripheral portion 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 on the end surface of the toner carrier by magnetic force, and the toner can be imaged. Contamination by toner inside and outside the forming device can be prevented.

[Brief explanation of the drawing]

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 (4)

[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. A developing device having a first solid surface layer made of a material different from that of the foam portion on the outer periphery of the foam portion, and a second solid surface portion made of the same material as the foam portion and continuous with the end surface of the toner carrier. A developing device characterized by: 2. The developer according to claim 1, wherein the first or second solid surface layer portion has foam cells, and the size of the foam cells is smaller than the particle size of the toner. Device. 3. The developing device according to claim 1, wherein a conductive layer is formed on the solid surface layer portion of the toner carrier. 4. 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.