JP2006178100A - Developing roll - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing roll capable of preventing an image from occurring horizontal stripes and fogging phenomenon. <P>SOLUTION: The developing roll is provided with a shaft 1, an intermediate layer 3 formed along an outer periphery surface of the shaft 1 and a surface layer 4 formed along an outer periphery surface of the intermediate layer 3. Particles G for formation of a rough surface are dispersed in the intermediate layer 3 and the surface of the surface layer 4 is formed rough by the distribution of the dispersed particles G. Average thickness of both end parts A in the axial direction in the surface layer 4 is made thinner than the average thickness of a central part B in the axial direction which is in between the end parts A in the axial direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a developing roll used in electrophotographic equipment such as a copying machine and a printer.

  In an electrophotographic apparatus such as a copying machine or a printer, a developing roll is provided against the photosensitive drum. In this developing roll, generally, a base rubber layer and a surface layer are sequentially formed on the outer peripheral portion of the shaft body, and an intermediate layer is formed between the base rubber layer and the surface layer as necessary.

  In addition, uniform and reliable toner conveyance on the outer peripheral surface of the developing roll is an important role in obtaining a high-quality image. For this reason, in general, the surface of the surface layer of the developing roll is roughened to improve toner transportability. There are various methods for roughening the surface. For example, the outer peripheral surface of the base rubber layer is roughened by subjecting the outer peripheral surface of the base rubber layer of the developing roll to blasting such as sandblasting or polishing using a grinding wheel. And roughening the rough surface by surface processing (see Patent Document 1) or the inner peripheral surface of the mold for forming the base rubber layer of the developing roll by electric discharge machining. There is known a method of transferring the rough surface to the surface of the surface layer via an intermediate layer (see Patent Document 2) and the like.

On the other hand, as shown in FIG. 3, the developing roll is usually arranged near the opening of the toner box T, and the side wall of the toner box T has both end portions in the axial direction of the surface of the surface of the developing roll 10. A seal member (made of felt or the like) S that is in sliding contact with the toner box T is disposed to prevent toner leakage from the toner box T. The portion in sliding contact with the seal member S is a non-development region (a portion corresponding to the electrostatic latent image non-formation region on the surface of the photosensitive drum 20), and the portions sandwiched between the non-development regions at both ends are development regions (photosensitive drums). 20 corresponding to the electrostatic latent image forming area on the surface).
Japanese Patent Laid-Open No. 7-319287 (paragraph [0020]) Japanese Patent Laid-Open No. 11-65267 (page 3, FIG. 3)

  However, the developing roller 10 and the seal member S are in strong pressure contact with each other in order to ensure prevention of toner leakage from the toner box T. For this reason, the frictional force between the developing roll 10 and the seal member S is large, and depending on the magnitude of the frictional force, the developing roll 10 cannot be smoothly slid and rotated, and the rotational speed is not stable. When the changes, horizontal stripes appear in the image. Further, in the contact development method in which the developing roll 10 repeatedly slides without being rotated with the photosensitive drum 20, if the frictional force between the developing roll 10 and the photosensitive drum 20 is large, a stick-slip phenomenon occurs, and the image is laterally displayed. Streaks occur.

  As a method for preventing the occurrence of these horizontal streaks, a method of reducing the frictional force by reducing the contact area with the seal member S or the photosensitive drum 20 by further increasing the surface roughness of the surface layer of the developing roll 10 can be considered. However, when the surface roughness is further increased in this way, the amount of toner transport increases, and a fogging phenomenon (a phenomenon in which unnecessary toner adheres to the white background portion of the paper and causes black spots or the like) occurs in the image after copying.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a developing roll capable of preventing a horizontal stripe and a fog phenomenon from occurring in an image.

  In order to achieve the above object, the developing roll of the present invention comprises a shaft body, an intermediate layer formed along the outer peripheral surface of the shaft body, and a surface layer formed along the outer peripheral surface of the intermediate layer. The developing roll has particles for forming a rough surface dispersed in the intermediate layer, and the surface of the surface layer is formed into a rough surface by the distribution of the dispersed particles. In the surface layer, the average thickness of both end portions in the axial direction is The configuration is such that it is thinner than the average thickness of the axially central portion sandwiched between the axially opposite ends.

  That is, in the developing roll of the present invention, the particles for forming the rough surface are dispersed in the intermediate layer below the surface layer. For this reason, on the outer peripheral surface of the intermediate layer, the particle part is a convex part, and the other part is a concave part, and is formed in an uneven rough surface. The surface is also rough. Further, in the surface layer, the average thickness of both end portions in the axial direction is thinner than the average thickness of the central portion in the axial direction sandwiched between both end portions in the axial direction. For this reason, the influence of the rough surface of the outer peripheral surface of the intermediate layer on the surface roughness of the surface layer is such that the axial end portions where the average thickness of the surface layer is thin are stronger than the axial central portion where the average thickness of the surface layer is thick. . That is, the surface roughness of the surface layer is greater at both axial end portions than in the axial central portion. For this reason, the contact area between the seal member in the toner box and the photosensitive drum in the contact development method is smaller at both axial end portions than at the axial central portion. Furthermore, the outer diameter of the surface layer is smaller at both axial end portions because the average thickness of the surface layer is thinner than at the axial center portion. For this reason, the contact pressure with the seal member and the photosensitive drum is smaller at both axial end portions than at the axial central portion. As described above, the contact area and the contact pressure with the seal member and the photosensitive drum are smaller at both axial end portions than the axial center portion, so that the frictional force with the seal member and the photosensitive drum can be reduced. . In addition, in the central portion in the axial direction, the surface roughness of the surface layer can be made appropriate for toner transportability by adjusting the thickness of the surface layer forming material applied. Therefore, the developing roll of the present invention can reduce the frictional force with the seal member and the photosensitive drum at both axial end portions while maintaining the toner transportability appropriately at the axial central portion.

  In the present invention, “both end portions in the axial direction” are within the range of the non-development region (the portion corresponding to the electrostatic latent image non-formation region outside the electrostatic latent image formation region on the photosensitive drum surface). positioned.

  In the developing roll of the present invention, particles for forming a rough surface are dispersed in the intermediate layer, and the surface of the surface layer is formed into a rough surface by the distribution of the dispersed particles. Furthermore, in the said surface layer, the average thickness of the axial direction both ends is thinner than the average thickness of the axial center part pinched | interposed into the axial both ends. For this reason, the surface roughness of the surface layer can be set such that both axial end portions are larger than the axial central portion, and the outer diameter of the surface layer is smaller than the axial central portion. Can be. Accordingly, while the toner transportability is properly maintained at the central portion in the axial direction, the frictional force between the seal member in the toner box and the photosensitive drum in the contact development method can be reduced at both end portions in the axial direction. As a result, the occurrence of fogging phenomenon is prevented, smooth sliding rotation is possible between the seal member and the photosensitive drum, and the occurrence of horizontal stripes on the image is prevented.

  In particular, when the average thickness of both end portions in the axial direction of the surface layer is in the range of 0 to 80% of the average thickness of the central portion in the axial direction, the occurrence of fogging phenomenon and horizontal stripes can be suitably prevented. .

  Further, the arithmetic average roughness (Ra) of the central portion in the axial direction of the surface layer is set within a range of 0.1 to 1.0 μm, and the arithmetic average roughness (Ra) of both end portions in the axial direction is set to the central portion in the axial direction. Even when the arithmetic average roughness (Ra) of the portion is in the range of 1.1 to 7.5 times, the occurrence of fogging phenomenon and horizontal stripes can be suitably prevented.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  1 and 2 show an embodiment of the developing roll of the present invention. The developing roll according to this embodiment includes a shaft body 1, a base rubber layer 2 formed on the outer peripheral surface of the shaft body 1, an intermediate layer 3 formed on the outer peripheral surface of the base rubber layer 2, and an intermediate The surface layer 4 is formed on the outer peripheral surface of the layer 3. In the intermediate layer 3, the rough surface forming particles G are dispersed. Due to the distribution of the dispersed particles G, on the outer peripheral surface of the intermediate layer 3, the part of the particles G is a convex part, and the other part is a concave part, and is formed in an uneven rough surface. Further, the surface of the outer surface layer 4 is also roughened by the influence of the rough surface of the intermediate layer 3. Further, the surface layer 4 is formed such that the average thickness of the axial end portions A is thinner than the average thickness of the axial central portion B sandwiched between the axial end portions A. For this reason, as for the outer diameter of the surface layer 4, the axial direction both-ends part A is smaller than the axial direction center part B. FIG. In FIG. 2, S is a felt seal member.

  In the production of such a developing roll, a mixture of particles G is used as a forming material for the intermediate layer 3, and the thickness at which the forming material for the surface layer 4 is applied is determined by the axial end portions A and the axial central portion B. Except for making it thinner, it can be performed in the same manner as in the prior art. For example, first, an adhesive is applied to the outer peripheral surface of the shaft body 1, this is coaxially installed in the hollow portion of the cylindrical mold, and both end openings are sealed with lids, and then the base rubber layer 2 is formed. The base rubber layer 2 is formed by injecting and molding the material, followed by vulcanization by oven vulcanization or the like. Then, by applying the forming material of the intermediate layer 3 mixed with the particles G to the outer peripheral surface of the base rubber layer 2 by roll coating method, spray coating method, dipping method or the like, the particles are dried (cured), and then the particles The intermediate layer 3 in which G is dispersed is formed. Next, the material for forming the surface layer 4 is applied to the outer peripheral surface of the intermediate layer 3 by a roll coating method or the like. At this time, the coating is made thinner at both axial end portions A than at the axial central portion B. For example, when coating is performed by the roll coating method, the discharge amount of the forming material of the surface layer 4 is reduced in the axial end portions A than in the axial central portion B, or the axial movement speed of the roll or the forming material discharge nozzle Speed up or do both. Thereafter, drying (curing) is performed to form a surface layer 4 having an average thickness that is thinner at both axial end portions A than at the axial central portion B. In this way, the developing roll is obtained.

  Here, the surface layer 4 will be described in more detail. The material for forming the surface layer 4 is usually in a liquid state, and flows from the convex portion to the concave portion on the rough surface of the intermediate layer 3 after it is applied to the outer peripheral surface of the intermediate layer 3 and dried (cured). . And the thickness of the surface layer 4 is thin at the convex part of the uneven rough surface, and thick at the concave part. And the amount which flows from the said convex part to a recessed part increases so that the formation material of the surface layer 4 is apply | coated thickly. For this reason, the influence which the rough surface of the outer peripheral surface of the intermediate | middle layer 3 has on the surface roughness of the surface layer 4 becomes small, so that the thickness which apply | coats the formation material of the surface layer 4 is thick. Accordingly, since the surface layer 4 is formed with a thinner material in the axial end portions A than in the axial center portion B, the surface roughness of the surface layer 4 is larger in the axial end portions A than in the axial center portion B. Become. For this reason, the contact area with the photosensitive drum 20 (see FIG. 3) in the contact development method is smaller in the axial end portions A than in the axial central portion B. Further, as described above, since the outer diameter of the surface layer 4 is smaller in the axial end portions A than in the axial central portion B, the contact pressure with the photosensitive drum 20 (see FIG. 3) in the contact development method is The axial end portions A are smaller than the axial central portion B.

  In general, the developing roll 10 (see FIG. 3) is in sliding contact with the seal member S at the side wall portion of the toner box T. However, in the developing roll of this embodiment, the average thickness of the surface layer 4 is different in the axial direction. The boundary position R between the both end portions A and the axial center portion B is set within a range in which the seal member S is in sliding contact (see FIG. 2). As a result, both end portions of the central portion B in the axial direction of the surface layer 4 having a relatively small surface roughness are also in sliding contact with the seal member S, so that the gap between the surface layer 4 and the seal member S is small and toner leakage is prevented. . In addition, since the axially opposite end portions A of the surface layer 4 have a relatively large surface roughness and a relatively small outer diameter, they are in sliding contact with the seal member S, so that the contact area with the seal member S is reduced. The frictional force decreases. The boundary position R [width at each end portion of the axially opposite end portions A with a small average thickness (length in the axial direction)] depends on the type in which the developing roll is incorporated, but usually both ends of the surface layer 4 It is set to 2 to 7 mm inward in the axial direction from the edge.

  Thus, in the axial end portions A, the contact area and the contact pressure with the seal member S and the photosensitive drum 20 (see FIG. 3) are smaller than the axial center portion B. The frictional force with the photosensitive drum 20 can be reduced. Moreover, in the central portion B in the axial direction, the surface roughness of the surface layer 4 can be made appropriate and the toner transportability can be improved by adjusting the thickness at which the material for forming the surface layer 4 is applied.

  The surface roughness of the surface layer 4 can be set to an arithmetic average roughness (Ra) in the range of 0.1 to 1.0 μm in the axial central portion B from the viewpoint of improving toner transportability. More preferably, it is in the range of 0.4 to 0.9 μm. Further, at the axial end portions A, from the viewpoint of reducing the frictional force with the sealing member S and the photosensitive drum 20 (see FIG. 3), the arithmetic average roughness (Ra) of the axial central portion B is 1.1 to 1.1. It is preferable to set within the range of 7.5 times (1.0 ≦ Ra ≦ 3.0 μm), and more preferably within the range of 1.1 to 3.0 times. The arithmetic average roughness (Ra) is a value measured in accordance with the method described in JIS B 0601.

  Therefore, in the developing roll of the present invention, the toner transportability is good at the axial central portion B (excluding the portion that is in sliding contact with the seal member S). Then, since the frictional force with the sealing member S and the photosensitive drum 20 (see FIG. 3) is reduced, smooth sliding rotation is possible, and the occurrence of horizontal stripes on the image is prevented.

  Further, as described above, the material for forming the surface layer 4 flows from the convex portion of the rough surface of the intermediate layer 3 to the concave portion, and the thickness of the surface layer 4 is thin at the convex portion of the rough surface and thick at the concave portion. It depends on the position. Therefore, in the present invention, as the “average thickness of the surface layer”, the thickness of the surface layer 4 at a plurality of positions is measured, and the average value is taken. The thickness of the surface layer 4 can be measured, for example, by cutting the developing roll and viewing the cross section of the surface layer 4 with an electron microscope. Although a measurement location is not specifically limited, For example, measuring 5 each of a convex part and a recessed part is mention | raise | lifted.

  And the average thickness of the axial direction center part B of the surface layer 4 is based on the surface roughness of the outer peripheral surface of the intermediate | middle layer 3, However, it is a viewpoint made into the said preferable arithmetic mean roughness (0.1 <= Ra <= 1.0micrometer). Therefore, it is preferable to set within a range of 5 to 15 μm, and more preferably within a range of 6 to 12 μm. Moreover, the average thickness of the axial direction both-ends part A of the surface layer 4 is a viewpoint made into the said preferable arithmetic mean roughness [1.1-7.5 times of arithmetic mean roughness (Ra) of the axial direction center part B], It is preferable to set within the range of 0 to 80% of the average thickness of the central portion B in the axial direction, and more preferably within the range of 0 to 50%.

  Next, materials for forming the shaft body 1, the base rubber layer 2, the intermediate layer 3, and the surface layer 4 constituting the developing roll of the present invention will be described.

  The shaft body 1 is not particularly limited, and may be solid or hollow. The material of the shaft body 1 is not particularly limited, and examples thereof include iron, iron plated, stainless steel, and aluminum. Then, an adhesive, a primer or the like is usually applied to the surface of the shaft body 1. Further, the adhesive, primer, etc. may be made conductive as necessary.

  As a material for forming the base rubber layer 2, the following main material containing a conductive agent is used. That is, the main material is not particularly limited. For example, polyurethane elastomer, ethylene-propylene-diene rubber (EPDM), styrene-butadiene rubber (SBR), silicone rubber, acrylonitrile-butadiene rubber (NBR). , Hydrogenated acrylonitrile-butadiene rubber (H-NBR), chloroprene rubber (CR), and the like. Among these, it is preferable to use conductive silicone rubber from the viewpoint of low hardness and less sag. If necessary, a conductive agent, silicone oil, vulcanizing agent, vulcanization accelerator, lubricant, auxiliary agent, and the like may be added as appropriate. And the thickness of the said base rubber layer 2 is although it does not specifically limit, Usually, it sets to about 0.5-5 mm.

  As the material for forming the intermediate layer 3, the following main material containing a conductive agent and rough surface forming particles G is used. That is, the main material is not particularly limited. For example, hydrogenated acrylonitrile-butadiene rubber (hydrogenated nitrile rubber: H-NBR), acrylonitrile-butadiene rubber (nitrile rubber: NBR), polyurethane-based elastomer, Chloroprene rubber (CR), natural rubber, butadiene rubber (BR), acrylic rubber (ACM), isoprene rubber (IR), styrene-butadiene rubber (SBR), hydrin rubber (ECO, CO), urethane rubber, fluorine rubber, etc. It is done. These may be used alone or in combination of two or more. Of these, H-NBR and polyurethane-based elastomers are particularly preferred from the viewpoints of adhesiveness and coating solution stability. And although the thickness of the said intermediate | middle layer 3 is not specifically limited, It sets to about 5-15 micrometers including the diameter of the particle | grains G, The arithmetic mean roughness (Ra) of the outer peripheral surface is 0.9-2.5 micrometers. Set to degree.

  The rough surface-forming particles G are not particularly limited, and examples thereof include urethane resin particles, silica particles, polyamide resin particles, fluororesin particles, acrylic resin particles, and urea resin particles. These may be used alone or in combination of two or more. Especially, a silica particle is used suitably from a viewpoint which can improve abrasion resistance.

  The average particle size of the particles G is not particularly limited, but is preferably set in the range of 5 to 30 μm, more preferably in the range of 7 to 15 μm. In such a range, in the developing roll, the arithmetic average roughness (Ra) of the rough surface portion of the central portion B in the axial direction of the outer peripheral surface of the surface layer 4 is 0.1 to 1.0 μm which is the preferable range. It becomes easy to set to the range of 0.4-0.9 micrometer which is a range and a more preferable range. The average particle diameter of the particles G is a value derived using a sample arbitrarily extracted from the population, and the shape of the particles G is not a true sphere but an oval (a sphere having an elliptical cross section) or the like. When the particle diameter is not uniformly determined as in the above, the simple average value of the longest diameter and the shortest diameter is set as the particle diameter of the particle G.

  As a material for forming the surface layer 4, the following main material containing a conductive agent is used. That is, the main material is not particularly limited. For example, urethane resin, polyamide resin, acrylic resin, acrylic silicone resin, butyral resin (PVB), alkyd resin, polyester resin, fluorine rubber, fluorine resin, fluorine Examples thereof include a mixture of rubber and fluororesin, silicone resin, silicone graft acrylic polymer, acrylic graft silicone polymer, nitrile rubber, urethane rubber and the like. These may be used alone or in combination of two or more. Among these, urethane resin is preferable in terms of wear resistance.

  In the above embodiment, one base rubber layer 2 is formed between the shaft body 1 and the intermediate layer 3, but the intermediate layer 3 may be formed directly on the outer peripheral surface of the shaft body 1, Two or more layers may be formed between the shaft body 1 and the intermediate layer 3. If the rough surface of the outer peripheral surface of the intermediate layer 3 can appear on the surface of the surface layer 4, one or more layers may be formed between the intermediate layer 3 and the surface layer 4. In these cases, the thickness of each layer is appropriately set.

  Moreover, in the said embodiment, although the sealing member S was slidably contacted not only to the axial direction both ends A but also the both ends of the axial center part B, it was made to slidably contact only the axial both ends A. Also good. Even in this case, toner leakage is prevented by the elastic contact of the seal member S. In addition to the felt, the seal member S can be made of sponge, rubber, resin, or the like.

  Next, examples will be described together with comparative examples.

[Example 1]
As described below, a shaft 1, a material for forming each layer, and the like were prepared, and a developing roll was produced in the same manner as in the above embodiment.

[Shaft 1]
A solid solid cylindrical shaft body 1 having an outer diameter of 8 mm and a length of 350 mm was prepared.

[Material for forming base rubber layer 2]
Conductive silicone rubber (X34-270A / B, manufactured by Shin-Etsu Chemical Co., Ltd.) was kneaded with a kneader to prepare a base rubber layer 2 forming material.

[Formation material of intermediate layer 3]
Urethane resin particles [Art Pearl U600T (average particle size: 10 μm), manufactured by Negami Kogyo Co., Ltd.] were prepared as the rough surface-forming particles G, and a material for forming the intermediate layer 3 was prepared as follows. That is, with respect to 100 parts by weight of H-NBR (Nipol 0020, manufactured by Nippon Zeon Co., Ltd.), 20 parts by weight of the urethane resin particles, 0.05 parts by weight of stearic acid (Lunac S30, manufactured by Kao Corporation), zinc white (ZnO) 5 parts by weight, 40 parts by weight of carbon black (Denka Black HS-100, manufactured by Denki Kagaku Kogyo), 1 part by weight of vulcanization accelerator (BZ), 2 parts by weight of vulcanization accelerator (CZ), 1 part by weight of sulfur After being used at a ratio and kneaded by a kneader, 400 parts by weight of MEK was added, mixed and stirred to prepare a material for forming the intermediate layer 3.

[Material for forming surface layer 4]
After 100 parts by weight of polycarbonate diol-based urethane resin (Nipporan 5196, manufactured by Nippon Polyurethane Co., Ltd.) at a ratio of 40 parts by weight of carbon black (Denka Black HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.), A material for forming the surface layer 4 was prepared by adding 400 parts by weight of MEK, mixing and stirring.

[Preparation of developing roll]
The base rubber layer 2 (thickness 4 mm, length 240 mm) was formed on the outer peripheral surface of the shaft body 1 by molding (190 ° C. × 30 minutes) using a cylindrical mold in the same manner as in the above embodiment. . And after forming the formation material of the intermediate | middle layer 3 on the outer peripheral surface of the base rubber layer 2 with a roll coating method, it is made to dry (harden | cure), thickness 10 micrometers (including the diameter of particle | grain G), and the arithmetic mean of an outer peripheral surface The intermediate layer 3 having a roughness (Ra) of 1.5 μm was formed. Thereafter, the material for forming the surface layer 4 is applied to the outer peripheral surface of the intermediate layer 3 by a roll coating method, and then dried (cured) to obtain an average thickness of 8.0 μm at both ends A in the axial direction, and an arithmetic average roughness of the surface. A surface layer 4 having a thickness (Ra) of 1.0 μm, an average thickness of the central portion B in the axial direction of 15.0 μm, and an arithmetic average roughness (Ra) of 0.1 μm on the surface thereof was formed. At this time, the discharge amount of the forming material was decreased at both axial end portions A than when the surface layer 4 forming material was applied to the axial central portion B. In addition, the width (length in the axial direction) of the axially opposite end portions A having a small average thickness was 4 mm at each end. Thereby, a developing roll was obtained. The arithmetic average roughness (Ra) was measured using a surface roughness meter (manufactured by Tokyo Seimitsu Co., Ltd., Surfcom 1400D).

[Example 2]
In Example 1 above, the average thickness of the axial end portions A of the surface layer 4 is 3.0 μm, the arithmetic average roughness (Ra) of the surface is 1.2 μm, the average thickness of the axial central portion B is 10.0 μm, The arithmetic average roughness (Ra) of the surface was set to 0.75 μm. Other than that, it was the same as in Example 1 above.

Example 3
In Example 1, the average thickness of the axial end portions A of the surface layer 4 is 0.0 μm, the arithmetic average roughness (Ra) of the surface is 1.5 μm, the average thickness of the axial central portion B is 5.0 μm, The arithmetic average roughness (Ra) of the surface was 1.0 μm. Other than that, it was the same as in Example 1 above.

Example 4
In Example 1 above, the average thickness of the axial end portions A of the surface layer 4 is 3.0 μm, the arithmetic average roughness (Ra) of the surface is 1.2 μm, the average thickness of the axial central portion B is 7.5 μm, The arithmetic average roughness (Ra) of the surface was 0.4 μm. Other than that, it was the same as in Example 1 above.

Example 5
In Example 1 above, the average thickness of both end portions A in the axial direction of the surface layer 4 is 1.0 μm, the arithmetic average roughness (Ra) of the surface thereof is 1.4 μm, the average thickness of the central portion B in the axial direction is 9.0 μm, The arithmetic average roughness (Ra) of the surface was 0.9 μm. Other than that, it was the same as in Example 1 above.

[Comparative Example 1]
In the first embodiment, the average thickness of the surface layer 4 is 10.0 μm in both the axial end portions A and the axial central portion B, and the arithmetic average roughness (Ra) of the surface is set in the axial end portions A in the axial direction. The central part B was also 0.75 μm. Other than that, it was the same as in Example 1 above.

[Comparative Example 2]
In the first embodiment, the average thickness of the surface layer 4 is set to 3.0 μm at both the axial end portion A and the axial central portion B, and the arithmetic average roughness (Ra) of the surface is set to the axial end portion A in the axial direction. The central part B was also 1.20 μm. Other than that, it was the same as in Example 1 above.

[Sliding start torque]
The developing rolls of Examples 1 to 5 and Comparative Examples 1 and 2 thus obtained were brought into contact with the photosensitive drum. At this time, the abutting portions of the developing rolls were abutted so as to be recessed by 1 mm in the radial direction. Then, with the photosensitive drum fixed, a rotational driving force was applied to the developing roll, and the torque at which the developing roll began to rotate was measured with a torque gauge (5DPSK, manufactured by KANON). The measured torque is also shown in Table 1 below.

[Presence or absence of horizontal lines]
The developing rolls of Examples 1 to 5 and Comparative Examples 1 and 2 were incorporated into a laser printer (LASEJET 4600, manufactured by Hewlett Packard) using a contact developing method, and were blackened in an environment of 20 ° C. and 50% RH. The image was put out. And the presence or absence of a horizontal streak was visually confirmed about the image. As a result, an image having no horizontal streak was evaluated as “◯”, and an image in which a horizontal streak could be clearly confirmed was evaluated as “x”, and the results were also shown in Table 1 below.

[Presence of fogging phenomenon]
Further, the ratio of the printing area to the sheet area was set to 5%, and the image was printed until the toner ran out, and then the white solid image was printed. The image was visually checked for fogging (unnecessary toner adhesion). As a result, it was evaluated that no fogging phenomenon occurred when there was no unwanted toner adhered to the image, and x when the fogging phenomenon occurred when the unwanted toner adhesion could be clearly confirmed on the image. This is also shown in Table 1.

[Toner leakage]
As described above, after image formation was performed until the toner was exhausted, the contamination inside the actual machine due to the toner was visually evaluated. As a result, the case where there was no toner leakage was evaluated as “O” if there was no toner leakage, and the case where there was contamination was evaluated as “X” because there was toner leakage.

  From the results in Table 1 above, it can be seen that the developing rolls of Examples 1 to 5 have a relatively small sliding start torque and have no horizontal streaking or fogging phenomenon in the image, and are good products as the developing roll.

It is the front view which a part fractured | ruptured typically showing one Embodiment of the image development roll of this invention. It is an expanded sectional view showing typically the one end part of the above-mentioned development roll. It is explanatory drawing which shows the arrangement | positioning state of the said developing roll.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shaft body 3 Intermediate layer 4 Surface layer A Axial direction both end part B Axial direction center part G Particle

Claims (3)

  A developing roll having a shaft body, an intermediate layer formed along the outer peripheral surface of the shaft body, and a surface layer formed along the outer peripheral surface of the intermediate layer. The surface of the surface layer is formed into a rough surface due to the distribution of the dispersed particles, and the average thickness of both end portions in the axial direction of the surface layer is that of the central portion in the axial direction sandwiched between the both end portions in the axial direction. A developing roll characterized by being thinner than an average thickness.   The developing roll according to claim 1, wherein the average thickness of both end portions in the axial direction of the surface layer is in the range of 0 to 80% of the average thickness of the central portion in the axial direction.   The arithmetic average roughness (Ra) of the axial center portion of the surface layer is set within a range of 0.1 to 1.0 μm, and the arithmetic average roughness (Ra) of both axial end portions is the axial central portion of the surface layer. The developing roll according to claim 1 or 2, wherein the developing roll is in the range of 1.1 to 7.5 times the arithmetic average roughness (Ra).

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