Developing roll and developing device

Abstract

The present invention provides a developing roll used in an image forming device employing xerography, the developing roll comprising a cylindrical metal core, an annular rubber elastic layer disposed around the core, and an annular surface layer disposed around the elastic layer. The surface layer comprises a central portion in the longitudinal center of the developing roll and end portions on either longitudinal end of the developing roll. The outer peripheral surface of the end portions of the surface layer has a coefficient of kinetic friction equal to or less than 0.1 and a ten-point mean roughness Rz equal to or less than 1.8 μm.

Description

[Technical Field]

[0001] The present invention relates to a developing roll and a developing device in an image forming apparatus that utilizes an electrophotographic system. [Background technology]

[0002] An image forming apparatus that uses electrophotography is provided with a developing device that supplies developer, i.e., toner, to a photosensitive drum. The developing device has a toner container and a developing roll. The toner adhering to the outer surface of the developing roll is supplied to the photosensitive drum as the developing roll rotates. An electrostatic latent image is formed on the photosensitive drum, and a visible toner image is generated when toner particles are transferred from the developing roll to the electrostatic latent image by Coulomb force.

[0003] Of the toner adhering to the entire outer peripheral surface of the developing roll, the toner that does not transfer to the photosensitive drum (i.e., is not used in image formation) is collected in a cartridge in the developing device. It is preferable to collect all toner that is not used in image formation in the cartridge. Furthermore, to prevent toner from leaking from the cartridge, the cartridge is provided with a seal member that surrounds the end of the developing roll.

[0004] Measures to reduce toner leakage have also been implemented for developing rolls that come into contact with sealing members. Patent Document 1 discloses a developing roll in which resin particles are contained in the coating layer of the developing roll, and the ends of the coating layer contain fluororesin. Patent Document 2 discloses that the coefficient of friction at both ends of the outer circumferential surface of the roll that comes into contact with the sealing member is set to 0.15 or less. Patent Document 3 discloses a developing roll in which the surface roughness Ra at the roll ends is smaller than that at the center of the roll. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-46467 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-083728 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-248673 Summary of the Invention

[0006] The present invention provides a developing roll and a developing device that can reduce toner leakage over a long period of time.

[0007] A developing roll according to one embodiment of the present invention is used in an image forming apparatus that utilizes an electrophotographic system. The developing roll comprises a cylindrical metal core, a rubber annular elastic layer disposed around the core, and an annular surface layer disposed around the elastic layer. The surface layer comprises a central portion located at the center of the developing roll in the longitudinal direction and end portions located at both ends of the developing roll in the longitudinal direction. The dynamic friction coefficient of the outer peripheral surface of the end portions of the surface layer is 0.1 or less, and the ten-point average roughness R of the outer peripheral surface of the end portions of the surface layer is 0.1 or less. z is 1.8 μm or less.

[0008] The outer peripheral surface of the end of the surface layer of the developing roll is in slidable contact with a seal member that reduces leakage of toner particles from a toner container. In this embodiment, the dynamic friction coefficient of the end of the surface layer is small and the ten-point average roughness R z The small size of the seal member reduces damage to the seal member, and therefore it is possible to reduce toner leakage over a long period of time. [Brief explanation of the drawings]

[0009] [Figure 1] 1A and 1B are diagrams illustrating a state in which a developing roll according to an embodiment of the present invention is in use. [Figure 2] FIG. 2 is a cross-sectional view of a developing roll according to the embodiment. [Figure 3] FIG. 2 is a front view of a sample developing roll according to an embodiment. [Figure 4] FIG. 10 is a front view of a developing roll of another sample according to the embodiment. [Figure 5] FIG. 10 is a front view of a developing roll of another sample according to the embodiment. [Figure 6] 10 is a table showing the parameters of each sample and the experimental results of toner leakage. DETAILED DESCRIPTION OF THE INVENTION

[0010] Various embodiments of the present invention will now be described with reference to the accompanying drawings, in which the drawings are not necessarily to scale and some features may be exaggerated or omitted.

[0011] As shown in FIG. 1, an image forming apparatus that uses an electrophotographic method has a photosensitive drum 10 and a developing device 11. The photosensitive drum 10 rotates in the direction of the arrow. The developing device 11 supplies toner particles 12, which serve as a developer, to the photosensitive drum 10. An electrostatic latent image is formed on the surface of the photosensitive drum 10 by a latent image forming device (not shown), and as the toner particles 12 are transferred from the developing device 11 to the electrostatic latent image, a visible toner image made of the toner particles 12 is formed on the outer peripheral surface of the photosensitive drum 10.

[0012] The developing device 11 includes a toner container (cartridge) 14 that stores a collection of toner particles 13, an elastic roll 15 that is entirely disposed within the toner container 14, a developing roll 20 that is partially disposed within the toner container 14, and a doctor blade 16 (regulating blade) that is supported by the toner container 14. The elastic roll 15 is pressed against the developing roll 20, and the developing roll 20 is pressed against the photosensitive drum 10. The elastic roll 15 and the developing roll 20 are each rotated in the directions indicated by the arrows, and a substantially constant amount of toner particles in the toner container 14 adheres to the developing roll 20. As the developing roll 20 rotates, the toner particles adhered to the developing roll 20 are transported toward the photosensitive drum 10.

[0013] A doctor blade 16 disposed at the toner particle outlet of the toner container 14 is supported by a support plate 17 fixed to the toner container 14. The doctor blade 16 is pressed against the outer peripheral surface of the developing roll 20, and regulates the amount of toner particles adhering to the developing roll 20 and transported from the toner container 14. In this way, the developing roll 20 is brought into contact with each of the photosensitive drum 10, the elastic roll 15, and the doctor blade 16 with a certain degree of force.

[0014] Although not shown, the developing device 11 may be provided with a member for stirring the toner particle mass 13 in the toner container 14, a screw for transporting the toner particles in the toner container 14, and the like.

[0015] 2, the developing roll 20 includes a cylindrical metal core material 21, a rubber elastic layer 22 of uniform thickness that is disposed around the core material 21, and a rubber surface layer 23 of uniform thickness that is disposed around the elastic layer 22. The core material 21 has a diameter of several mm, the elastic layer 22 has a thickness of 1 to 3 mm, and the surface layer 23 has a thickness of several μm to several tens of μm.

[0016] The elastic layer 22 is made of silicone rubber and is provided to ensure the elasticity of the developing roll 20.

[0017] The surface layer 23 is provided to improve the wear resistance of the surface of the developing roll 20. Therefore, the material composition of the surface layer 23 is different from the material composition of the elastic layer 22.

[0018] Figure 3 shows one end of the developing roll 20 and its vicinity. Although not shown, the other end of the developing roll 20 is configured symmetrically to that in Figure 3. The core material 21 extends further outward in the axial direction of the developing roll 20 than the elastic layer 22 and the surface layer 23. In other words, the core material 21 protrudes from the edge 23E of the surface layer 23 (which is also the edge of the elastic layer 22). An end 21a of the core material 21 is supported by a bearing (not shown), allowing the developing roll 20 to rotate around the axis Ax.

[0019] Both ends of the developing roll 20 are surrounded by seal members 30. The seal members 30 are formed of nonwoven fabric, for example, felt. The seal members 30 are supported and fixed to the toner container 14 (not shown in FIG. 3 ) to prevent or reduce leakage of toner particles from the toner container 14. As shown in the figure, the outer peripheral surfaces of the ends of the surface layer 23 and the outer peripheral surface of the core material 21 are in slidable contact with the seal members 30. The contact length C between the ends of the surface layer 23 of the developing roll 20 and the seal members 30 is, for example, 5 mm.

[0020] The doctor blade 16 described above applies pressure to the outer peripheral surface of the developing roll 20, charging the toner particles by frictional force and causing the toner particles to adhere to the developing roll 20. As described above, the toner particles that have been charged and adhered to the developing roll 20 are transferred to the electrostatic latent image on the photoreceptor drum 10. Therefore, the doctor blade 16 contacts the center of the developing roll 20, which contributes to image formation, but does not contact either end of the developing roll 20. In this embodiment, notches 18 are formed in the doctor blade 16 near either end of the developing roll 20. The length N of the notch 18 is, for example, 5 mm.

[0021] In order to reduce leakage of toner particles through the gap between the seal member 30 and the developing roll 20, the end portions 23B at both ends of the developing roll 20 in the longitudinal direction of the surface layer 23 of the developing roll 20 are formed from a material different from the material of the central portion 23A at the center of the developing roll 20 in the longitudinal direction. Specifically, the central portion 23A of the surface layer 23 is made of urethane resin, and the end portions 23B of the surface layer 23 are made of silicone resin. The end portions 23B are flush with the central portion 23A.

[0022] In this embodiment, the central portion 23A of the surface layer 23 was produced as follows. First, in the first step, the following materials were mixed: 16.5 wt.% of urethane-modified hexamethylene diisocyanate (Duranate (trade name) grade E402-80B, manufactured by Asahi Kasei Corporation, Tokyo, Japan) with a solid content of 80 wt.% 36.7% by weight of reactive silicone oil ("X-22-160AS" (trade name) manufactured by Shin-Etsu Chemical Co., Ltd., Tokyo, Japan); butyl acetate as diluting solvent, 46.8 wt.%;

[0023] The mixture was then left at 120°C for 3 hours to promote the reaction of the components and produce a prepolymer.

[0024] Next, in the second step, the following materials were mixed: The prepolymer produced in the first stage was 31.0 wt.% As a binder, 4.8% by weight of isocyanate with a solid content of 75% by weight ("Desmodur L75" (trade name) manufactured by Sumika Covestro Urethane Co., Ltd. (Hyogo, Japan)) A carbon dispersion liquid having a solid content of 20 to 30% by weight ("MHI-BK" (trade name) manufactured by Mikuni Color Co., Ltd. (Hyogo, Japan)) was added to the 17.9% by weight, butyl acetate as diluting solvent, 43.7 wt.%;

[0025] In the third step, 2.6 wt% of silicone rubber particles were added to the mixture obtained in the second step to obtain a coating solution. The silicone rubber particles were "EP-2720" (product name) manufactured by DuPont Toray Specialty Materials Co., Ltd. (Tokyo, Japan). The hardness of the silicone rubber particles measured using a durometer ("Type A" according to "JIS K 6253" and "ISO 7619") was 70 degrees. The average particle size of the silicone rubber particles was 2 μm.

[0026] In the fourth step, the coating liquid was applied to the periphery of the central portion in the axial direction of the elastic layer 22 and dried to form the central portion 23A of the surface layer 23.

[0027] In this embodiment, the end portion 23B of the surface layer 23 was produced as follows. The method for producing the first stage prepolymer is the same as that for the central portion 23A.

[0028] Next, in the second step, the following materials were mixed: The prepolymer produced in the first stage was 31.5 wt. % As a binder, 4.9% by weight of isocyanate ("Desmodur L75" (trade name)) Carbon dispersion ("MHI-BK" (trade name)) 18.2 wt.%, 1.0 wt. % of silicone resin ("Modiper FS700" (trade name) manufactured by NOF Corporation, Tokyo, Japan) with a solid content of 100 wt. % butyl acetate as diluting solvent, 44.4 wt.%;

[0029] In the third step, the coating liquid obtained in the second step was coated around both ends of the elastic layer 22 in the axial direction, and dried to form the ends 23B of the surface layer 23. The above components were mixed to prepare a dispersion of the binder and dilution solvent.

[0030] The applicant prepared several samples made of silicone resin with different lengths of the end 23B, and conducted experiments on each sample to determine whether leakage of toner particles through the gap between the sealing member 30 and the developing roll 20 could be suppressed.

[0031] In each sample, the diameter of the core material 21 was 6 mm, the thickness of the elastic layer 22 was 1.5 mm, and the thickness of the surface layer 23 was 10 μm±2 μm. The contact length C between the end of the surface layer 23 of the developing roll 20 and the seal member 30 was 5 mm. The length N of the notch 18 of the doctor blade 16 was 5 mm.

[0032] Sample 1 is shown in Fig. 3. The length T from the edge 23E of the surface layer 23 to the end 23B made of silicone resin was 10 mm.

[0033] Sample 2 is shown in Fig. 4. The length T from the edge 23E of the surface layer 23 to the end 23B made of silicone resin was 5 mm.

[0034] Sample 3 is shown in Figure 5. The length T from the edge 23E of the surface layer 23 of Sample 3 to the end portion 23B made of silicone resin was 0 mm. In other words, the entire surface layer 23 was made of urethane resin. In other words, the entire surface layer 23 was the central portion 23A.

[0035] FIG. 5 is a table showing the parameters of each sample and the experimental results of toner leakage.

[0036] The surface roughness (ten-point average roughness R z ) was measured using a contact-type surface roughness measuring instrument. The measuring instrument was a Surfcorder "SE500" manufactured by Kosaka Laboratory Co., Ltd. (Tokyo, Japan). The radius of the SE500 stylus was 2 μm, the tip angle of the stylus was 60 degrees, and the contact force was 0.75 mN. The measurement cutoff value λc was 0.8 mm, the roughness measurement length (reference length) was 4 mm, and the stylus feed speed was 0.5 mm / sec. The measurement location was the center of the sample in the longitudinal direction.

[0037] The dynamic friction coefficient of the outer peripheral surface of the surface layer 23 of each sample was measured using a friction coefficient measuring device (a surface property measuring device ("TYPE:14" (trade name) manufactured by Shinto Scientific Co., Ltd., Tokyo, Japan)) under the measurement conditions shown below in accordance with ASTM D 1894. A load of 50 g was applied to the surface layer 23 using an iron ball indenter. The measurement width was 1 cm. The measurement speed was 50 mm / sec.

[0038] Samples 1 and 2 differ only in the length T of the end 23B. In sample 3, the entire surface layer 23 is made of urethane resin, so the roughness R z and the coefficient of kinetic friction are the same.

[0039] In the toner leakage experiment, each sample was installed in a toner cartridge, i.e., toner container 14, for a color printer "HL-L8360CDW" (product name) manufactured by Brother Industries, Ltd. (Aichi, Japan). The toner cartridge was TN-493M manufactured by Brother Industries, Ltd.

[0040] In the experiment, the developing roll 20 of the cartridge was rotated at 100 rpm without the cartridge installed in the printer. The printer was visually inspected for leakage of toner particles for 30 minutes or more, which corresponds to the time required for printing 500 sheets of A4 paper.

[0041] As is clear from Figure 6, there was no leakage of toner particles for 30 minutes or more in Sample 1. However, in Samples 2 and 3, leakage of toner particles occurred within 30 minutes.

[0042] Therefore, it is preferable that the dynamic friction coefficient of the outer peripheral surface of the end portion 23B of the surface layer 23 is lower than that of the central portion 23A of the surface layer 23, and the ten-point average roughness R of the outer peripheral surface of the end portion 23B of the surface layer 23 is z is preferably lower than that of the central portion 23A of the surface layer 23. More specifically, the dynamic friction coefficient of the outer peripheral surface of the end portion 23B of the surface layer 23 is 0.1 or less, and the ten-point average roughness R z It is preferable that the coefficient of dynamic friction of the outer peripheral surface of the end 23B is 1.8 μm or less. In the experiment, when the coefficient of dynamic friction of the outer peripheral surface of the end 23B is 0.1, there was no leakage of toner. When the coefficient of dynamic friction of the end 23B of the surface layer 23 is small, it is thought that there is little damage to the seal member 30 and it is possible to reduce toner leakage over a long period of time. Therefore, when the coefficient of dynamic friction of the outer peripheral surface of the end 23B is smaller than 0.1, it is predicted that there will also be no leakage of toner. Furthermore, in the experiment, when the ten-point mean roughness R of the outer peripheral surface of the end 23B is z When the surface roughness R of the edge 23B of the surface layer 23 was 1.8 μm, there was no toner leakage. z When the ten-point mean roughness R of the outer peripheral surface of the end 23B is small, it is considered that damage to the seal member 30 is small and toner leakage can be reduced for a long period of time. z If the gap is smaller than 1.8 μm, it is also predicted that there will be no toner leakage.

[0043] Furthermore, a comparison of Samples 1 and 2 indicates that the length T from the edge 23E of the surface layer 23 to the end 23B of the surface layer 23 is preferably 10 mm or more. Experiments have shown that when the length T is 10 mm, there is no toner leakage. The central portion 23A of the surface layer 23 is made of a material to which toner easily adheres, while the end 23B of the surface layer 23 is made of a material to which toner does not easily adhere. It is believed that when the length T of the end 23B is large, fewer toner particles reach the seal member 30. Therefore, it is predicted that there will be no toner leakage when the length T is greater than 10 mm.

[0044] From another perspective, it is preferable that the central portion 23A, to which toner is likely to adhere, is far from the seal member 30. From the results of Figs. 3 and 4, it is preferable that the length T of the end portion 23B is longer than the contact length C between the end portion 23B of the surface layer 23 of the developing roll 20 and the seal member 30, and it is preferable that T C is 5 mm or more. In other words, the urethane resin surface of the surface layer 23 has a high dynamic friction coefficient and a ten-point average roughness R z The center part is made of 23A and silicone resin (the dynamic friction coefficient of the outer surface is low, and the ten-point average roughness R z It is preferable that the distance between the boundary of end 23B (where the distance is small) and the part of end 23B that comes into contact with sealing member 30 that surrounds end 23B is 5 mm or more.

[0045] Other variations Although the present invention has been shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that changes may be made in form and detail without departing from the scope of the invention as set forth in the appended claims. Such changes, modifications and alterations are intended to be included within the scope of the invention. [Explanation of symbols]

[0046] 20 Developing roll 21 Core material 22 Elastic layer 23 Surface layer 23A Central part 23B End 23E Edge

Claims

1. A developing roll used in an image forming apparatus that uses an electrophotographic system, A cylindrical metal core material, a rubber annular elastic layer disposed around the core material; a ring-shaped surface layer disposed around the elastic layer, the surface layer has a central portion located at the center of the developing roll in the longitudinal direction and end portions located at both ends of the developing roll in the longitudinal direction, the material forming the edge of the surface layer is different from the material forming the central portion of the surface layer; the dynamic friction coefficient of the outer peripheral surface of the central portion of the surface layer is higher than the dynamic friction coefficient of the outer peripheral surfaces of the end portions of the surface layer, and the ten-point mean roughness Rz of the outer peripheral surface of the central portion of the surface layer is larger than the ten-point mean roughness Rz of the outer peripheral surfaces of the end portions of the surface layer; the coefficient of dynamic friction of the outer peripheral surface of the end of the surface layer is 0.1 or less, and the ten-point average roughness Rz of the outer peripheral surface of the end of the surface layer is 1.8 μm or less; The end is surrounded by a sealing member, a boundary between the central portion and the end portion is located closer to the center in the longitudinal direction than a portion of the end portion that contacts the seal member; The distance in the longitudinal direction between the boundary between the central portion and the end portion and the portion of the end portion that comes into contact with the sealing member is 5 mm or more. A developing roll characterized by:

2. The central portion of the surface layer is made of urethane resin, and the end portion of the surface layer is made of silicone resin.

2. The developing roll according to claim 1.

3. The developing roll according to claim 1 ; a toner container in which a portion of the developing roll is disposed and which stores toner particles; a seal member supported and fixed to the toner container, the seal member reducing leakage of toner particles from the toner container.

4. The sealing member is made of nonwoven fabric.

4. The developing device according to claim 3.

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