JP2007232760A - Developing roll - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing roll designed so as to prevent the effect of an insulation layer formed on the external circumferential part of a base rubber layer. <P>SOLUTION: The base rubber layer 2 is formed along the external circumferential surface of a shaft body 1 by die molding. A large number of recesses A are formed in the external circumferential surface of the base rubber layer 2, which corresponds to the transfer surface of the die, by laser etching such that the edges of the openings of the recesses overlap and at least part of the external circumferential surface is removed. The proportion of the removed part is set to 80% or more of the area of the original external circumferential surface. The outermost layer 3 is formed along the external circumference of the base rubber layer 3. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

As shown in FIG. 7, a developing roll used in an electrophotographic apparatus such as a copying machine or a printer usually has a base rubber layer 2 formed on the outer peripheral surface of the shaft body 1, and directly or directly on the outer periphery of the base rubber layer 2. The outermost layer 3 is formed through another layer (directly in FIG. 7) (see, for example, Patent Document 1). Then, by adjusting the resistance of the base rubber layer 2 and the outermost layer 3, etc., the occurrence of ghost (a phenomenon in which an image that was previously printed remains in an image that should be printed) is suppressed.
JP-A-10-239985

  However, even if the ghost is generated as described above, it may still occur. Therefore, the present inventors have repeatedly studied the cause of the ghost. As a result, it was found that the insulating layer 21 was formed on the outer peripheral surface of the base rubber layer 2, which caused charges to easily remain on the surface of the developing roll. The insulating layer 21 is formed because, when the base rubber layer 2 is molded, the portion having a predetermined thickness from the outer peripheral surface in contact with the mold surface of the mold is vulcanized by the heat of vulcanization. I also found out that there was.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a developing roll that prevents the influence of an insulating layer formed on the outer peripheral portion of the base rubber layer.

  In order to achieve the above object, the developing roll of the present invention comprises a shaft body, a base rubber layer formed by molding on the outer peripheral surface of the shaft body, and a direct or other layer on the outer periphery of the base rubber layer. A developing roll having an outermost layer formed through the outer peripheral surface of the base rubber layer serving as a transfer surface of the mold surface of the mold, and a large number of recesses formed by laser etching, with the opening edges overlapping each other. The distribution is formed in a state where at least a part of the outer peripheral surface is deleted, and the deleted part is set to 80% or more of the surface area of the original outer peripheral surface.

  The present invention has been made by further research based on the above findings of the present inventors. That is, in the present invention, after the base rubber layer is formed by molding, the insulating layer formed to have a predetermined thickness below the transfer surface of the mold surface is subjected to laser etching, and the laser etching is performed. By forming a large number of concave portions so that the opening edge portions overlap each other, most of the insulating layer is eliminated and ghosting is prevented. This laser etching is performed so that 80% or more of the surface area of the transfer surface (original outer peripheral surface) of the mold surface of the mold is removed, thereby preventing the occurrence of ghost.

  In the developing roll of the present invention, a large number of recesses by laser etching are distributed and formed on the outer peripheral surface of the base rubber layer serving as a transfer surface of the mold surface of the mold in a state where the opening edges overlap with each other. Part of the insulating layer formed on the outer periphery of the base rubber layer is deleted by the above laser etching because a part of it is set to 80% or more of the surface area of the original outer peripheral surface. Has been. For this reason, almost no electric charge remains on the surface of the developing roll, and as a result, ghost can be prevented and a high-quality image can be obtained.

  Next, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to this.

  FIG. 1 shows an embodiment of the developing roll of the present invention. The developing roll of this embodiment includes a cylindrical shaft body 1, a base rubber layer 2 formed on the outer peripheral surface of the shaft body 1, and an outermost layer 3 formed on the outer peripheral surface of the base rubber layer 2. It is composed of The base rubber layer 2 is formed by molding, and in this embodiment, the entire original outer peripheral surface (the original outer peripheral surface) of the base rubber layer 2 serving as a transfer surface of the mold surface of the mold. 100% of the surface area), a large number of recesses A formed by laser etching are formed in a state where the opening edge portions overlap each other. By forming the recess A, the base rubber layer 2 has the entire insulating layer formed on the outer periphery thereof removed. In particular, as in this embodiment, when laser etching is performed on the entire original outer peripheral surface (transfer surface of the mold surface of the mold) of the base rubber layer 2, the outer peripheral surface of the base rubber layer 2 is arithmetically averaged. It is formed on a rough surface with a roughness (Ra) of about 0.3 to 0.5 μm. The outermost layer 3 is formed on the laser-etched surface, and the arithmetic average roughness (Ra) of the outermost layer 3 is formed on a rough surface of about 0.09 to 0.30 μm, which is suitable as a developing roll. It is formed with a rough surface.

  More specifically, the shape of each recess before overlapping formed by laser etching is preferably formed in a circular shape from the viewpoint of easy formation, and the concave shape of each recess is preferably It is formed into a curved surface (for example, a hemispherical shape) consisting of a part of a spherical shape. And the said insulating layer is deleted substantially uniformly by forming so that the opening edge part of such each recessed part may overlap. Further, the opening shape of each recess before overlapping is not limited to the circular shape described above, and may be an elliptical shape, a rectangular shape, or the like.

  From the viewpoint of deleting the insulating layer (thickness of about 1 to 3 μm), the shape of each recess before overlapping is a circular shape having a diameter in the range of 110 to 140 μm, and the concave shape is 2 to 10 μm in depth. A part of the spherical surface within the range is preferable. And it is preferable to make it the overlapping degree of the opening edge part of each recessed part within the range of 0-12% of a recessed part diameter. Here, “overlap at 0% of the diameter of the recess” means a state in which the opening edges of adjacent recesses are in contact. In addition, the shape dimensions of the opening shape and the concave surface shape of each recess before overlapping each other adjust the laser beam output, the degree of convergence of the laser beam by the lens, the irradiation time, etc. in the laser marker used for forming each recess. It is set by doing.

  The dimensions of the concave portions A after being overlapped are preferably 110 μm or more in diameter and 2 μm or more in depth, more preferably in the range of 110 to 125 μm in diameter and in the range of 2 to 8.5 μm in depth. . Further, the distribution of the recesses A may be regularly formed in the axial direction and the circumferential direction, or may be randomly performed. Here, the above-mentioned diameter is obtained by measuring the outer peripheral surface of the base rubber layer 2 with an electron microscope, taking an average value of the maximum diameter and the minimum diameter of each recess A, and measuring them with any of the 10 recesses A. It is expressed by the average value of. The depth is expressed by an average value obtained by cutting the base rubber layer 2 in the thickness direction, measuring the depth of the concave portion A with any of the ten concave portions A with an electron microscope, and measuring the depth of the concave portion A. Is done.

  For producing such a developing roll, as described below, after forming the base rubber layer 2 on the outer peripheral surface of the shaft body 1, the recess A is formed by laser etching, and then the outermost layer 3 is formed. Is done.

  More specifically, first, an adhesive or the like is applied to the outer peripheral surface of the shaft body 1 as necessary, and this is coaxially installed in the hollow portion of the molding die and sealed, and then the base rubber layer 2 is sealed. The forming material is injected and molded. Next, vulcanization is performed by oven vulcanization or the like to form the base rubber layer 2 (usually about 0.5 to 5 mm in thickness), and then demolding.

  Then, laser etching is performed on the entire outer peripheral surface (transfer surface of the mold surface of the mold) of the base rubber layer 2. In this laser etching, the laser beam is converged into minute dots by a lens system, and a point-like portion having a high laser beam density is formed on the outer peripheral surface of the base rubber layer 2. Absorbs the laser beam to cause ablation (melting), and the minute concave portion A can be formed in the dot-like portion. For example, by arranging a plurality of the lens systems in a straight line along the axial direction of the roll body, a point-like portion where the laser light is converged in a point shape is formed on the outer peripheral surface of the base rubber layer 2 in the axial direction. If a large number of lines are scattered in a straight line from one end edge to the other end edge, the dotted portions can be formed in the recess A at a time. Further, when the roll body is intermittently rotated around the axis, and laser light is intermittently irradiated in synchronization with the rotation, a large number of recesses A can be distributed and formed on the outer peripheral surface of the base rubber layer 2. . As an apparatus capable of such laser etching, for example, there is Fine Marker ML-7110B manufactured by Miyachi Technos.

  In the formation of the recess A, the degree of overlap of the opening edge is set by adjusting the lens system so that the opening edges of the adjacent recess A and the recess A overlap each other. While adjusting so that it may become a pitch, it is performed by adjusting so that intermittent rotation of a roll body may become a predetermined angle. Further, as described above, the size of each concave portion before overlapping is performed by adjusting the output of the laser light, the degree of convergence of the laser light by the lens, the irradiation time, and the like. In this way, the developing roll can be produced. As the laser beam, an Nd-YAG laser or an excimer laser is usually used. The concave portion A may be formed by scanning one laser beam in the axial direction of the roll body and intermittently irradiating the laser beam during the scanning process.

  Next, the outermost layer 3 (usually, the outermost layer 3 (usually, the outer layer 3) is applied to the outer peripheral surface of the base rubber layer 2 by the laser etching using a roll coating method, a spray coating method, a dipping method, and the like. A thickness of about 3 to 30 μm).

  In such a developing roll, since the insulating layer formed on the outer peripheral portion of the base rubber layer 2 is entirely removed by the formation of the recess A by the laser etching, the developing roll of the developing roll can be used in actual use. As a result, almost no charge remains on the surface, and as a result, ghosting can be prevented and a high-quality image can be obtained.

  In particular, as in this embodiment, when laser etching is performed on the entire outer peripheral surface of the base rubber layer 2, the surface roughness of the outer peripheral surface of the base rubber layer 2 is relatively small [the arithmetic average roughness (Ra Therefore, the surface roughness of the outer peripheral surface of the outermost layer 3 is also relatively small [the arithmetic average roughness (Ra) is about 0.09 to 0.30]. Toner deterioration is suppressed.

  Here, materials for forming the shaft body 1, the base rubber layer 2, and the outermost layer 3 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, a material containing a conductive agent in the following main material is usually 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. Of these, silicone rubber is preferably used from the viewpoint of low hardness and less sag. Moreover, silicone oil, a vulcanizing agent, a vulcanization accelerator, a lubricant, an auxiliary agent and the like may be appropriately added as necessary.

  As a material for forming the outermost layer 3, 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. Of these, urethane resins are preferred from the viewpoint of wear resistance.

  FIG. 2 shows another embodiment of the developing roll of the present invention. In the developing roll of this embodiment, the portion where the recess A is formed by laser etching is 80% or more and less than 100% of the surface area of the transfer surface (original outer peripheral surface of the base rubber layer 2) 2a of the mold surface. The remaining portion remains the transfer surface 2a of the mold surface. When laser etching is performed in this manner, the surface roughness becomes larger than that of the above embodiment, and the outer peripheral surface of the base rubber layer 2 has a roughness with an arithmetic average roughness (Ra) of about 0.5 to 2.0 μm. The outer peripheral surface of the outermost layer 3 is formed into a rough surface having an arithmetic average roughness (Ra) of about 0.3 to 1.0 μm.

  As described above, even if the transfer surface 2a of the mold surface remains on the outer peripheral surface of the base rubber layer 2, if the transfer surface 2a is small (less than 20% of the surface area of the transfer surface 2a), the developing roll shown in FIG. Similarly, ghosting can be prevented and a good quality image can be obtained.

  The ratio of laser etching on the transfer surface (outer peripheral surface of the base rubber layer 2) 2a of the mold surface is determined by the outer diameter of the recess formed by laser etching and the degree of overlap of the opening edge of each recess. From the set value, it can be calculated by calculation. Moreover, the confirmation of the ratio can be performed by observing with an electron microscope.

  In each of the above embodiments, an intermediate layer may be formed between the base rubber layer 2 and the outermost layer 3 in some cases. As a material for forming the intermediate layer, a material containing a conductive agent in the following main material is usually 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 elastomers are particularly preferred from the viewpoints of adhesiveness and coating liquid stability.

  Next, examples will be described together with comparative examples.

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

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

[Material for forming outermost layer]
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.), The outermost layer forming material was prepared by adding 400 parts by weight of MEK, mixing and stirring.

[Preparation of developing roll]
A base rubber layer (thickness 4 mm, length 240 mm) was formed on the outer circumferential surface of the shaft body by molding (190 ° C. × 30 minutes) using a molding die. Then, using Nd-YAG laser, 80% of the outer peripheral surface of the base rubber layer (transfer surface of the mold surface of the mold) is subjected to laser etching, so that a large number of recesses are distributed so that the opening edges overlap. did. Next, after forming the outermost layer forming material on the outer peripheral surface of the roll body thus obtained by a roll coating method, the outermost layer (thickness 30 μm) was formed by drying (curing). In the laser etching, Fine Marker ML-7110B manufactured by Miyachi Technos was used as a laser etching apparatus. The laser etching conditions are: output: 26 A, frequency: 17.6 kHz, speed: 2050 mm / second, distance between the outer peripheral surface of the base rubber layer (the mold surface of the mold surface) and the laser beam focusing lens: 360 mm (the original focal length of the laser beam focusing lens is 350 mm).

  In Example 1 described above, the portion subjected to laser etching was the entire outer peripheral surface (transfer surface of the mold surface of the mold) (100%) of the base rubber layer. Further, among the laser etching conditions, the distance between the outer peripheral surface of the base rubber layer (the transfer surface of the mold surface of the mold) and the laser beam focusing lens was 370 mm. Other than that, it was the same as in Example 1 above.

  In Example 2 described above, the distance between the outer peripheral surface of the base rubber layer (the transfer surface of the mold surface of the mold) and the laser beam focusing lens among the laser etching conditions was 375 mm. Other than that, it was the same as in Example 1 above.

  In Example 2 described above, the distance between the outer peripheral surface of the base rubber layer (transfer surface of the mold surface of the mold) and the laser beam focusing lens among the laser etching conditions was 380 mm. Other than that, it was the same as in Example 1 above.

[Comparative Example 1]
In Example 1 described above, the portion subjected to laser etching was 70% of the outer peripheral surface (transfer surface of the mold surface of the mold) of the base rubber layer. Further, among the laser etching conditions, the distance between the outer peripheral surface of the base rubber layer (the transfer surface of the mold surface of the mold) and the laser beam focusing lens was set to 350 mm. Other than that, it was the same as in Example 1 above.

[Comparative Example 2]
In Example 1 described above, the outermost layer was formed without performing laser etching. Other than that, it was the same as in Example 1 above.

[Surface resistance and volume resistance of base rubber layer]
In Examples 1 to 4 and Comparative Examples 1 and 2, the surface resistance and volume resistance of the base rubber layer were measured prior to the formation of the outermost layer.

Of these, the surface resistance was measured as follows. That is, as shown in FIG. 3, the roll body 10 to be measured is placed on two metal rollers (outer diameter 12 mm) 21 and 22 that are installed in parallel with a gap, and at 60 rpm. While rotating, a load W of 9.8 N in total (4.9 N at each end) was applied to both ends of the shaft body 1 in the downward direction. In this state, a DC voltage of −10V is applied from one metal roller 21 to the surface of the roll body 10 to detect a potential difference V ₂ applied to the reference resistance R ₂ from the other metal roller 22, and the roll body 10. A current value I ₂ (= V ₂ / R ₂ ) flowing in the circumferential direction of the surface of the (base rubber layer ₂ ) was calculated. Then, to calculate the current value I ₂ and the voltage applied (-10 V) above the roll body 10 from the surface resistance R ₁ (= 10 / I ₂₎ (base rubber layer 2). The surface resistance R ₁ is also shown in Table 1 below. The reference resistance R ₂ is very low compared to the roll body 10 and does not affect the measurement result.

In addition, as shown in FIG. 4, the volume resistance is measured by placing the roll body 10 to be measured on one metal roller (outer diameter 30 mm) 23 and rotating the roll body 10 at 60 rpm. A total load of 9.8 N (4.9 N at each end) was applied to both ends of each. In this state, a DC voltage of −10 V is applied from the shaft body 1 of the roll body 10 to detect a potential difference V ₄ applied from the metal roller 23 to the reference resistance R ₄ , and the roll body 10 (base rubber layer 2). The current value I ₄ (= V ₄ / R ₄ ) flowing in the thickness direction was calculated. Then, to calculate the current value I ₄ and the applied voltage (-10 V) above the roll body 10 from the volume resistance R ₃ of (the base rubber layer _{2) (= 10 / I 4} ).

[Surface roughness of base rubber layer]
Further, the arithmetic average roughness (Ra) at any three points on the outer periphery of each position at three positions in the axially inner 5 mm from the both ends of the base rubber layer and in the axially central position is measured by a surface roughness meter. (Measured by Tokyo Seimitsu Co., Ltd., Surfcom 1400D). And the average value of arithmetic average roughness (Ra) in the total of 9 points | pieces (3 points x 3 positions) was computed, and the result was combined with the following Table 1, and was described.

[Development roll surface resistance and volume resistance]
After the formation of the outermost layer, the surface resistance and volume resistance of the developing roll were measured in the same manner as in the case of the base rubber layer. That is, in FIG. 3 and FIG. The results are also shown in Table 1 below.

[Surface roughness of developing roll]
In addition, the arithmetic average roughness (Ra) at any three points on the outer periphery of each position at three positions on the axially inner side 5 mm and the axially central position from both ends of the outermost layer is measured with a surface roughness meter ( Measurement was performed using a surfcom 1400D manufactured by Tokyo Seimitsu Co., Ltd. And the average value of arithmetic average roughness (Ra) in the total of 9 points | pieces (3 points x 3 positions) was computed, and the result was combined with the following Table 1, and was described.

[Residual charge decay rate]
As shown in FIG. 5A, the developing roll is rotated, a constant current of 100 μA is passed from the corotron T to the surface, and the electric charge on the developing roll surface at a position rotated 90 ° from the position where the current is passed is potential. As measured. This measurement was performed at a central position in the axial direction using a probe (potential detector) P. Then, in FIG. 5B showing the measurement result, the attenuation rate is calculated by the following equation (1) from the ratio between the residual charge value when the constant current is stopped and the residual charge value after 0.5 seconds. The results are shown in Table 1 below. Here, it can be said that the higher the attenuation rate, the higher the attenuation rate, and the more effective the prevention of ghost.

[Ghost concentration ratio]
As shown in FIG. 6, an image was printed such that the first color of the developing roll was a dark color and the second and subsequent colors were a light color. Then, the ratio of the density of the image B in the second round to the density of the image C after the second round of the developing roll (the density of the image C to be originally printed) is expressed by the following formula (2 ). The ghost concentration ratio is preferably as close to 100%. For concentration measurement, Macbeth PROCESS MEASUREMENTS was used as a densitometer.

  From the results in Table 1 above, it can be seen that the developing rolls of Examples 1 to 4 have a high residual charge decay rate, which prevents ghosting. On the other hand, in the developing rolls of Comparative Examples 1 and 2, the residual charge decay rate is low, and it can be seen that ghosts are generated.

It is explanatory drawing which showed typically one Embodiment of the image development roll of this invention. It is explanatory drawing which showed typically other embodiment of the image development roll of this invention. It is explanatory drawing which showed the measuring method of surface resistance typically. It is explanatory drawing which showed the measuring method of volume resistance typically. (A) is explanatory drawing which showed the measuring method of a residual charge typically, (b) is a graph which shows the measurement result. It is explanatory drawing which showed the measuring method of ghost density | concentration. It is explanatory drawing which shows the conventional image development roll.

Explanation of symbols

1 shaft body 2 base rubber layer 3 outermost layer A recess

Claims (2)

  A developing roll having a shaft body, a base rubber layer formed by molding on the outer peripheral surface of the shaft body, and an outermost layer formed on the outer periphery of the base rubber layer directly or via another layer. Thus, a large number of recesses formed by laser etching are distributed and formed on the outer peripheral surface of the base rubber layer, which serves as a transfer surface of the mold surface of the mold, with the opening edges overlapping each other, and at least a part of the outer peripheral surface is deleted. The developing roll is characterized in that the deleted portion is set to 80% or more of the surface area of the original outer peripheral surface.   The developing roll according to claim 1, wherein the concave portion has a diameter of 110 μm or more and a depth of 2 μm or more.