JP2005274769A - Elastic roll - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an elastic roll which will cause degradation of image quality even without grinding. <P>SOLUTION: An elastic rubber layer 2 is formed on the outer surface of a shaft 1, and the outer surface of the elastic rubber layer 2 has spiral stripes 3 formed projecting as the flow lines, when molding the elastic rubber layer 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an elastic roll such as a developing roll, a charging roll, and a transfer roll used in electrophotographic equipment such as a copying machine and a printer.

  In electrophotographic devices such as copying machines and printers, an elastic roll such as a developing roll, a charging roll, and a transfer roll is provided together with a photosensitive drum. As shown in FIG. 4, these elastic rolls have a rubber elastic layer 52 formed on the outer peripheral surface of a shaft body 51. If necessary, a thin coating layer such as a resistance adjusting layer or a protective layer is formed on the outer peripheral surface of the rubber elastic layer 52.

  The elastic roll is usually formed using a cylindrical mold. That is, first, an adhesive or the like is applied to the outer peripheral surface of the shaft body 51, this is coaxially installed in the hollow portion of the cylindrical mold, and both ends are sealed with lids, and then the rubber elastic layer 52 is formed. Inject material. Next, the rubber elastic layer 52 is formed by vulcanization by oven vulcanization or the like. Thereafter, the mold is removed, and if necessary, a liquid material for forming a coating layer is applied to the surface of the rubber elastic layer 52 by a roll coating method, a spray coating method, a dipping method, etc., and then drying, heat treatment, etc. To form a coating layer such as a resistance adjusting layer or a protective layer.

In forming the rubber elastic layer 52, the outer peripheral surface of the rubber elastic layer 52 is usually polished after demolding in order to increase accuracy (see Patent Document 1). On the other hand, recently, in order to reduce costs, it has also been proposed to ensure high accuracy without polishing (without polishing) (see Patent Document 2).
JP 7-295331 A JP-A-8-276512

  However, when the rubber elastic layer 52 is formed, a bulge portion is formed on the surface of the rubber elastic layer 52 as a convex line in the axial direction as shown in FIG. Therefore, this is an obstacle to polishing.

  That is, for example, when the forming material (rubber material) of the rubber elastic layer 52 is injected into the cylindrical mold from a pair of material injection ports provided at the left and right positions of the lid, In the fusion portion of the rubber flow, the pressure is increased by the pressure from each rubber flow to be fused. For this reason, after demolding, the fusion part of the rubber flow rises like a mountain range and appears as a ridge 53. More specifically, as described in FIGS. 7 and 8 of JP-A-8-142229, when two material inlets are formed at one end of a cylindrical mold, the forming material There can be two fusion parts (usually there are as many fusion parts as the number of material injection ports), and they extend in parallel to the axial direction. Then, after demolding, these fused portions appear as two ridges 53 on the outer peripheral surface of the rubber elastic layer 52 (FIG. 4 also shows the two ridges 53). The ridge 53 appears on the surface even when the coating layer is formed. For this reason, when an elastic roll is used with the ridges 53 being present, between the elastic roll and a contact member such as a photosensitive drum, a blade, or another roll body in contact with the elastic roll, the elastic roll rotates. The convex 53 and other portions are alternately in contact with each other, resulting in uneven contact, and streaky density unevenness occurs in the image. And the said protruding item | line 53 of the outer peripheral surface of the rubber elastic layer 52 cannot be eliminated unless it grind | polishes, and becomes an obstacle of grinding | polishing-less.

  In addition, the demand for higher image quality is becoming stricter. Therefore, by increasing the number of material injection ports, the protrusions 53 are made smaller by, for example, reducing unevenness in flow of forming material, unevenness in fusion, etc., or improving material reactivity. However, it has its limitations and needs to be improved.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an elastic roll that is polishing-free and does not cause deterioration in image quality.

  In order to achieve the above object, the elastic roll of the present invention appears on the outer peripheral surface of the shaft body, the rubber elastic layer formed on the outer peripheral portion of the shaft body, and when the rubber elastic layer is cast. It is an elastic roll which has the protruding item | line which consists of a fusion part of a rubber flow, Comprising: The said protruding item | line takes the structure that it is formed helically with respect to the axial direction of a roll.

  The present inventors obtained the following knowledge as a result of repeated research to reduce the adverse effects of the ridges appearing on the outer peripheral surface when the rubber elastic layer of the elastic roll is formed by casting. That is, the cause of the uneven stripe density of the image due to the ridge is that the ridge is in contact with the photosensitive drum or the like in the contact between the elastic roll and the photosensitive drum or the like because the ridge is parallel to the axial direction. It is in linear contact with the member. Therefore, when the elastic roll rotates during development, streaky density unevenness occurs in the image due to the protrusions. Therefore, as a result of further research based on this knowledge, when the ridge is formed in a spiral shape, the ridge and the contact member such as the photosensitive drum come into point contact instead of line contact, and the streak-like shape The inventors found that there was almost no density unevenness and reached the present invention.

  In the elastic roll of the present invention, since the protrusions on the outer peripheral surface of the rubber elastic layer are formed in a spiral shape, the protrusions come into point contact with a contact member such as a photosensitive drum. Almost no effect on the image. As a result, even if the outer peripheral surface of the rubber elastic layer is not polished, the image quality is not deteriorated.

  In particular, when the angle between the ridge and the roll axis is set in the range of 2 ° to 80 °, a higher quality image can be obtained.

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

  FIG. 1 shows an embodiment of the elastic roll of the present invention. In this elastic roll, a rubber elastic layer 2 is formed on the outer peripheral surface of the shaft body 1, and the rubber flow is fused to the outer peripheral surface of the rubber elastic layer 2 when the rubber elastic layer 2 is cast-molded. Are formed in a spiral shape.

  Such an elastic roll is produced by using a bottomed cylindrical mold 10 while coaxially rotating the bottomed cylindrical mold 10 using a molding mold (see FIGS. 2 and 3) described later. It is performed by injecting the rubber material of the rubber elastic layer 2. Then, the elastic roll shown in FIG. 1 is obtained by performing heat molding and then removing the mold in the same manner as in the prior art. In the molding die in this embodiment, since the material discharge ports 21 are formed on the left and right (see FIG. 3), the two protrusions (fused portions) 3 appear and are spiral. It has become.

  That is, as described above, when the rubber material is injected while the bottomed cylindrical mold 10 is rotated coaxially, the rubber flows from the left and right material discharge ports 21 are also fused while rotating coaxially. The part is spiral with respect to the rotation axis. Then, on the outer peripheral surface of the rubber elastic layer 2 of the elastic roll obtained by demolding, the spiral fused portion rises like a mountain range and appears as a ridge 3.

  With such a spiral ridge 3, contact with the ridge 3 becomes a point contact with respect to a contact member such as a photosensitive drum in contact with the elastic roll. As a result, streaky density unevenness is almost eliminated.

  As long as the ridge 3 is formed in a spiral shape, the angle θ formed with the axis of the roll is not particularly limited, but is preferably 2 ° to 80 ° from the viewpoint of obtaining a higher quality image. It is set in the range, more preferably in the range of 5 ° to 70 °. This angle θ depends on the rotational speed of the bottomed cylindrical mold 10 and the discharge amount of the rubber material per unit time. For example, if the discharge amount of the rubber material per unit time is the same, the bottomed cylindrical shape The angle θ increases as the rotational speed of the mold 10 increases. If the rotational speed of the bottomed cylindrical mold 10 is the same, the greater the amount of rubber material discharged per unit time, the greater the angle θ is. Get smaller. Further, the height of the ridges 3 is not particularly limited, but is preferably as low as possible from the viewpoint of realizing a high-quality image. The height of the ridges 3 is higher as the discharge pressure of the rubber material is higher (the higher the discharge amount of the rubber material per unit time), but is usually in the range of 5 to 10 μm.

  Here, a molding die that enables the rubber material injection will be described. As shown in FIGS. 2 and 3, the molding die includes a bottomed cylindrical die 10 and a rubber material for the rubber elastic layer 2 (see FIG. 1), one end portion of the bottomed cylindrical die 10 ( An injection machine 20 for injection from the upper end portion in FIG. 2 and a rotary drive device 30 for rotating the bottomed cylindrical mold 10 coaxially are provided.

  More specifically, the bottomed cylindrical mold 10 has one end portion (upper end portion in FIG. 2) opened and the other end portion (lower end portion in FIG. 2) is the bottom portion 11. And the opening surface of one end part closely_contact | adheres to the following material discharge port 21 formation surface of the injection machine 20 (fixed state), and slides. Further, on the inner surface of the bottom portion 11 at the other end, a shaft body support hole portion 12 for fitting the end portion of the shaft body 1 is formed in order to support the shaft body 1 coaxially.

  The injection machine 20 can be the same as the conventional one. In this embodiment, the following is used. That is, in the injection machine 20, two material discharge ports 21 (see FIG. 3) are formed on the surface (the lower end in FIG. 2) to which the opening surface of one end of the bottomed cylindrical mold 10 is in close contact. Yes. Moreover, in order to support the shaft body 1 coaxially with the position of the two material discharge ports 21, a shaft body support hole into which the end of the shaft body 1 is fitted is formed in the material discharge port 21 formation surface. A portion 22 is formed. Further, the injector 20 is provided with a supply part (not shown) for extruding the rubber material of the rubber elastic layer 2 (see FIG. 1) with a screw (not shown). It communicates with the material discharge port 21 through 23. Thus, in the present invention, cast molding means a molding method in which a rubber material is injected into the bottomed cylindrical mold 10, and the injection can be performed by extruding the solid material as described above, A liquid material may be poured, and the injection method is not limited.

  The rotary drive device 30 is not particularly limited as long as the bottomed cylindrical mold 10 can be rotated coaxially, but in this embodiment, a device using belt drive is used. Yes. That is, the rotary drive device 30 travels the pulley 31 fixed coaxially to the outer surface of the bottom of the bottomed cylindrical mold 10, the endless belt 32 wound around the pulley 31, and the endless belt 32. And a drive unit (not shown) such as a motor.

  In the above-described embodiment, the one having two material discharge ports 21 is used. However, the present invention is not limited to this, and one having one material discharge port 21 or three or more formed. You may use what was done. When rotating the bottomed cylindrical mold 10, the shaft body 1 is usually rotated together with the bottomed cylindrical mold 10.

  Moreover, you may form a coating layer in the outer peripheral surface of the rubber elastic layer 2 as needed to the said elastic roll. Even when this coating layer is formed, the ridges 3 appear on the surface of the coating layer and exhibit the same actions and effects as the elastic roll. The coating layer is usually formed by coating the liquid material of the coating layer by a roll coating method, a spray coating method, a dipping method, or the like.

  Next, the material for forming the elastic roll of the present invention will be described.

  As the shaft body 1, the rubber elastic layer 2, and the covering layer, those usually used are used and are not particularly limited.

  That is, the shaft body 1 may be solid or hollow, and examples of the forming material include iron, iron plated, stainless steel, aluminum, and the like. And you may apply | coat an adhesive agent, a primer, etc. to the outer peripheral surface of the said shaft body 1 as needed. Further, the adhesive, primer, etc. may be made conductive as necessary.

  As the material for forming the rubber elastic layer 2, the following main materials are 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), Examples thereof include hydrogenated acrylonitrile-butadiene rubber (H-NBR) and chloroprene rubber (CR). These may be used alone or in combination of two or more. Among these, it is preferable to use silicone rubber from the viewpoint of low hardness and less sag. If necessary, a conductive agent such as carbon black, silicone oil, a vulcanizing agent, a vulcanization accelerator, a lubricant, an auxiliary agent, and the like may be appropriately added. The thickness of the rubber elastic layer 2 is not particularly limited, but is usually set to about 0.5 to 5 mm.

  As the liquid material for the coating layer, the following main materials are used in the form of a solution using a solvent such as methyl ethyl ketone (MEK). 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 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. Among these, H-NBR is particularly preferable from the viewpoint of adhesiveness and coating solution stability. Moreover, you may add suitably conductive agents, such as carbon black, as needed. The coating layer may be a single layer or may be composed of a plurality of layers with different materials. The thickness of each layer is not particularly limited, but is usually set to about 3 to 50 μm.

  Next, examples will be described together with conventional examples.

[Example 1]
An elastic roll comprising a shaft body, a rubber elastic layer, and a coating layer was produced using the molding die shown in FIGS. That is, a solid iron column having a diameter of 12 mm was prepared as a shaft. The rubber elastic layer was formed to a thickness of 4 mm, and the following materials were prepared as the forming material. The coating layer was formed to a thickness of 10 μm, and the following liquid materials were prepared.

[Rubber elastic layer forming material]
Liquid silicone rubber compounded with a conductive agent (X-34-264A / B, manufactured by Shin-Etsu Chemical Co., Ltd.) was used as a material for forming the rubber elastic layer.

[Liquid material for coating layer]
Stearic acid 0.5 parts by weight, zinc white (ZnO) 5 parts by weight, carbon black (Denka Black HS-100, Denki Kagaku Kogyo Co., Ltd.) with respect to 100 parts by weight of H-NBR (Zetpol 0020, manufactured by Nippon Zeon) 15 parts by weight, 1 part by weight of vulcanization accelerator (BZ), 2 parts by weight of vulcanization accelerator (CZ) and 1 part by weight of sulfur were kneaded using a ball mill, and then 400 parts by weight of MEK was added and mixed and stirred. By doing so, the liquid material of the coating layer was prepared.

(Production of elastic roll)
In the same manner as in the above embodiment, a rubber elastic layer was formed on the outer peripheral surface of the shaft body by molding using the molding die. At this time, the rotational speed of the bottomed cylindrical mold was 10 revolutions / minute, and the discharge amount of the rubber material was 5.0 g / second. Molding was performed at 190 ° C. for 30 minutes. On the outer peripheral surface of the rubber elastic layer formed in this manner, a protrusion having a height of 5 μm was spirally formed. And the liquid material of the coating layer was applied to the outer peripheral surface of the rubber elastic layer by a roll coating method, and then dried to form a coating layer. Thereby, an elastic roll was obtained. On the outer peripheral surface of the coating layer, the ridges were covered with the coating layer, and the height was 5 μm.

[Example 2]
In Example 1 above, the discharge rate of the rubber material was 10.0 g / second. Other than that, it was the same as in Example 1 above. As a result, protrusions having a height of 10 μm were spirally formed on the outer peripheral surfaces of the rubber elastic layer and the coating layer.

[Conventional example 1]
In Example 1 above, the rubber material was poured into the bottomed cylindrical mold without rotating the bottomed cylindrical mold. Other than that, it was the same as in Example 1 above. As a result, on the outer peripheral surfaces of the rubber elastic layer and the coating layer, protrusions having a height of 5 μm were linearly formed in parallel to the roll axis.

[Conventional example 2]
In Example 2 above, the rubber material was injected into the bottomed cylindrical mold without rotating the bottomed cylindrical mold. Other than that was carried out similarly to the said Example 2. As a result, protrusions having a height of 10 μm were formed linearly in parallel with the roll axis on the outer peripheral surfaces of the rubber elastic layer and the coating layer.

〔image〕
The elastic rolls of Examples 1 and 2 and Conventional Examples 1 and 2 thus obtained were incorporated into a laser beam printer (MICROLINE 7300, manufactured by Oki Data Co., Ltd.) as a developing roll, and images were actually output. The density unevenness of the image after 10,000 images was visually determined.

  As a result, when the elastic rolls of Examples 1 and 2 were used, there was no density unevenness in the image, and when the elastic rolls of Conventional Examples 1 and 2 were used, density unevenness was observed.

It is sectional drawing which shows one Embodiment of the elastic roll of this invention. It is explanatory drawing which shows the molding die for producing the said elastic roll. It is sectional drawing which shows the AA cross section of FIG. It is explanatory drawing which a part which showed the conventional elastic roll fractured | ruptured.

Explanation of symbols

1 shaft body 2 rubber elastic layer 3 ridge

Claims (2)

  An elastic roll having a shaft body, a rubber elastic layer formed on the outer peripheral portion of the shaft body, and a ridge formed by a fusion portion of rubber flows appearing on the outer peripheral surface when the rubber elastic layer is cast. The elastic roll is characterized in that the ridge is formed in a spiral shape with respect to the axial direction of the roll.   The elastic roll according to claim 1, wherein an angle formed by the ridge and the axis of the roll is set in a range of 2 ° to 80 °.