JP3834176B2 - Method for producing conductive roll and conductive roll - Google Patents

Description

【００３７】
画出し試験は上記５段階評価で行った。比較例６の場合、加硫時にマイクロスフェアーが膨張しすぎて崩壊した。
表１から、本発明の導電性ゴムロールは比較例１，２の導電性ゴムロールに比べて明らかに優れた品質を有していることが確認できる。また、未膨張微小球を用いる比較例３〜６ではセル径のバラツキが大きくなっているが、本発明の実施例１〜３では３０〜４０μｍと略バラツキが少なく均一化しており、かつ、低硬度であり、さらに、画出し試験の評価においても極めて優れていることが確認できた。
【００３８】
【発明の効果】
以上の説明より明らかなように、本発明によれば、硬い外殻を持たない設計通りの大きさの気泡が均一に分布した低硬度のスポンジ体形状精度の高い導電性ロールを得ることができる。よって、該導電性ロールを現像装置の導電性機構に用いると、質的に優れた画像を提供することができる。また、本発明は、ロールに含まれる気泡（セル）の空孔率及びロール表面の粗度を目的に応じて設計することが容易であるという効果も有する。
【図面の簡単な説明】
【図１】 本発明の一実施形態にかかる導電性ゴムロールが示された断面図である。
【図２】 被膜層を研磨する前のロールの横断面図である。
【図３】 被膜層を研磨した後のロールの横断面図である。
【符号の説明】
１ 導電性ゴムロール
２ 芯軸
３ 気泡
３ａ 凹部
４ 弾性体
５ 加硫成形体
６ 被膜層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a conductive roll used in a conductive mechanism of a developing device in a laser beam printer, a copying machine, a facsimile machine, an ATM, or the like, and a method for manufacturing the conductive roll.
[0002]
[Prior art]
In order to improve the image quality of an image formed by an image forming apparatus using an electrophotographic process, the developer conveyed to the developing area for visualizing the electrostatic latent image is charged to a desired charge amount. It is necessary to supply the developer uniformly to the development area. In such an image forming apparatus, conductive rolls having various required characteristics are used. Such rolls include a charging roll (charging the photoreceptor uniformly), a toner supply roll (moving the toner from the toner box to the developing roll), a developing roll (moving the toner to the exposed photoreceptor), and There is a transfer roll (the toner transferred to the photosensitive member is moved to paper or the like).
[0003]
Usually, image formation by the image forming apparatus is performed in the following steps. First, the charging roll uniformly charges the electrostatic latent image holding member such as a photosensitive drum (charging), and then irradiates a light image to form an electrostatic latent image on the electrostatic latent image carrier by image exposure (exposure). ). Next, the developer (toner) charged by the developing device is supplied from the toner supply roll to the developing roll, and further supplied from the developing roll onto the latent image carrier on which the electrostatic latent image is formed, and visualized, A toner image is formed (development). The developed image thus obtained is transferred onto a printing medium such as paper via a transfer roll and fixed (transfer, fixing).
[0004]
The required properties common to the above conductive rolls are (1) low hardness, (2) low compressive strain, (3) appropriate electrical resistance, and (4) appropriate surface roughness. Is achieved evenly, that is, uniformity is also an important characteristic.
[0005]
[Problems to be solved by the invention]
Conventionally, since these conductive rolls are often brought into contact with a rigid photoreceptor, there is a risk that defects will occur on the image if the roll surface is hard, and a reduction in hardness is an essential required characteristic. Also, roll shape accuracy and hardness uniformity were important.
[0006]
As a means for achieving low hardness, the entire roll is generally formed of a foamable elastic body from the viewpoint of easy hardness control. This foamable elastic body can be obtained by blending a conductive agent and a foaming agent with a rubber component as a main component and forming by heating and foaming. The most common blowing agent is an organic blowing agent, that is, a substance that chemically decomposes and releases a gas under the influence of heat. In this method, since gas is rapidly released in a certain temperature range, relatively large bubbles are formed, and a conductive roll having low hardness and excellent elasticity can be obtained.
[0007]
However, since organic foaming agents explode gas due to a chemical reaction, the foaming state and bubble shape are significantly affected by temperature conditions. For example, when the foamed elastic body is formed into a roll shape, the distribution of receptive heat differs in the axial direction and the radial direction, resulting in positional variations in the foamed state and the bubble shape. However, since the conductive roll is required to have shape accuracy and hardness uniformity, when such a variation occurs, there is a problem that the required performance is not satisfied.
[0008]
In order to make the foamed state and bubble shape more uniform, a polymer material containing a resin sphere encapsulating low-boiling hydrocarbons is used, and foaming properties in which bubbles called foamable cells are formed in the polymer material substrate A method of manufacturing an elastic body has been proposed (Japanese Patent Laid-Open No. 10-123825). However, since the resin spheres used here are thermally expandable microcapsules and are in an unexpanded state at the blending stage, the particle size changes due to the influence of heat and pressure at the vulcanization molding stage. Therefore, it is very difficult to control them to achieve low hardness and uniformity.
[0009]
Further, in this method, it is possible to form small bubbles as compared with the foam formation method using the organic foaming agent, but since the distribution of receptive heat differs in the axial direction and the radial direction, the foamed state and Positional variation occurs in the bubble shape, so-called cell diameter (hole size) is not constant, and it is difficult to obtain a roll having uniform hardness and surface roughness. In addition, the expanded resin sphere remains spherical after vulcanization, and its outer shell is a high-hardness resin, so that the effect of reducing the hardness of the roll surface is insufficient.
[0010]
Thus, the conventional method of expanding the resin sphere simultaneously with vulcanization cannot obtain a uniform foam, and therefore the cell diameter size and distribution are not uniform, and the porosity and surface roughness are not uniform. The degree of design has become difficult. Further, since the hardness of the outer shell of the expanded resin sphere is high, there is a problem that the hardness of the entire roll is high and it is difficult to achieve low hardness.
[0011]
The present invention has been made in view of the above problems, and the pore size (cell diameter), porosity, hardness, and surface roughness can be made as designed, and the pore size and positional variations can be achieved. It is an object of the present invention to provide a method for producing a conductive roll and a conductive roll that have no hardness, have a sufficiently low hardness characteristic, and have a uniform hardness and surface roughness.
[0012]
[Means for Solving the Problems]
To solve the above problems, the present invention is a thermoplastic resin when the outer shell made both blended pressure-hollow microspheres and conductive agent unvulcanized rubber composition, the melting of the thermoplastic resin A method for producing a conductive roll having a bubble corresponding to the hollow microsphere is obtained by vulcanizing and molding at a temperature or lower and then heating at or above the melting temperature of the thermoplastic resin to melt the outer shell. Yes.
[0013]
In the present invention, the conductive rubber roll has “bubbles corresponding to hollow microspheres” means that the vulcanized conductive rubber roll corresponds to the volume and shape of the hollow microspheres in the unvulcanized rubber composition. It means that it is comprised with the elastic body containing the bubble (cell) of a volume and a shape.
[0014]
The conductive rubber roll of the present invention described above has the following characteristics.
(1) Since it contains bubbles corresponding to the hollow microspheres contained in the unvulcanized rubber composition, it is possible to obtain a conductive rubber roll having a cell diameter according to the pre-blended particle size, and uniform Low hardness is achieved.
(2) Since the bubble diameter is unchanged before and after the vulcanization molding, when the surface layer of the molded product is polished, the desired uniform surface roughness depends on the particle size of the blended thermoplastic hollow microspheres. The surface layer is obtained.
(3) Since the surface roughness is uniform, a high-quality roll can be obtained when further coating is applied if desired.
[0015]
The conductive rubber roller, the thermoplastic resin when the outer shell made both blended pressure-hollow microspheres and conductive agent unvulcanized rubber composition, vulcanized at below the melting temperature of the thermoplastic resin After molding, the outer shell is melted by heating above the melting temperature of the thermoplastic resin.
[0016]
In the present invention, the unvulcanized rubber composition contains expanded microspheres so that the particle size (volume) of the hollow microspheres mixed with the unvulcanized composition does not change before and after the vulcanization treatment. It is characterized by that. Since this unvulcanized rubber composition is vulcanized and molded below the melting temperature of the thermoplastic resin, the volume and shape can be maintained without breaking the outer shell of the hollow microsphere. Next, when the thermoplastic resin is heated at the melting temperature of the thermoplastic resin, the thermoplastic resin that is the outer shell of the microsphere is melted and integrated with the surrounding crosslinked rubber, and the bubbles are surrounded by the surrounding elastic body (not the hard outer shell). As a result, a reduction in hardness can be achieved, and a conductive rubber roll having a uniformly low hardness can be obtained.
[0017]
In the conductive rubber roll of the present invention, the required characteristics including the above-mentioned (1) to (4) can be appropriately adjusted by adjusting the spherical diameter of the hollow microsphere, the blending amount (porosity), and the blending amount of the conductivity imparting agent. Can be satisfied.
[0018]
The hollow microspheres are formed by encapsulating an encapsulant in a thermoplastic resin outer shell. Examples of the thermoplastic resin used in the present invention include copolymers such as vinylidene chloride and acrylonitrile, phenolic resins, and the like, but polyacrylonitrile-based resins are preferable in that their melting points are high. As the encapsulating agent, a compound having a relatively low boiling point is used, and examples include isobutane and isopentane, and isopentane is preferable.
[0019]
In order to achieve uniform hardness and elasticity, the hollow microspheres have a particle size in the range of 10 to 200 μm, preferably 20 to 100 μm, more preferably 30 to 60 μm. Such hollow microspheres can be produced according to a conventional method, but commercially available inflated balloons may be used.
[0020]
The blending ratio of the hollow microspheres in the rubber composition for vulcanization also varies depending on the type of conductive roll and other compounding agents, but usually the proportion volume of hollow microspheres in the rubber composition (% ) Is 10 to 80% by volume, preferably 30 to 70% by volume, more preferably 50 to 60% by volume. Therefore, the proportion volume of the bubbles in the roll to be molded is preferably 30 to 70% by volume, and the Shore E hardness of the roll to be molded is 20 to 40. As described above, the Shore hardness is set to 20 to 40 when the hardness is less than 20, the compression strain becomes too large and the compression strain becomes too large. Moreover, it is because defects on the image are likely to occur.
[0021]
Examples of the rubber component (polymer component) to be contained in the unvulcanized crosslinked rubber composition include acrylonitrile-butadiene rubber (NBR), ethylene-propylene-diene copolymer rubber (EPDM), acrylic rubber, epichlorohydrin rubber, Urethane rubber, SBR, CR and the like can be mentioned, and one or more selected from these can be used. Among these, NBR and epichlorohydrin rubber are high in polarity per se, and thus are preferable as raw materials for the conductive rubber roll of the present invention.
[0022]
Examples of the conductivity-imparting agent include carbon black such as channel black, first black, and acetylene black, an electronic conductive agent such as carbon fiber, or an ionic conductive agent such as lithium salt and zinc white. These are used alone or in combination of two or more. Carbon black is preferable because the conductivity is not easily affected by temperature and humidity and an excellent reinforcing effect is exhibited. The compounding amount of the conductivity imparting agent may be within a range known in the art, but in the case of carbon black, it is 3 to 50 parts by weight, preferably 5 to 40 parts by weight with respect to 100 parts by weight of the rubber component.
[0023]
Moreover, a vulcanizing agent, a vulcanization accelerator, a vulcanization aid, a vulcanization retarder, a filler and the like are appropriately blended in the crosslinked rubber composition. As the vulcanizing agent, for example, sulfur, organic sulfur-containing compounds such as N, N-dithiobismorpholine, and organic peroxides such as benzoyl peroxide can be used. As the vulcanization accelerator, for example, inorganic accelerators such as slaked lime, magnesia (MgO), and resurge (PbO), and organic accelerators described below can be used. Examples of the organic accelerator include thiazole vulcanization accelerators such as 2-mercaptobenzothiazole and N-cyclohexyl-2-benzothiazolesulfene, and aliphatic first compounds such as N-butylamine, tert-butylamine and propylamine. Oxidation condensate of amine and 2-mercaptobenzothiazole, oxidation condensate of aliphatic secondary amine such as dicyclohexylamine, pyrrolidine, piperidine and 2-mercaptobenzothiazole, alicyclic primary amine and 2-mercaptobenzothiazole Sulfenamide-based vulcanization accelerators such as oxidative condensate with morpholine compound and 2-mercaptobenzothiazole, tetramethylthiuram monosulfide (TMTM), tetramethylthiuram disulfide (TMTD), tetraethyl Chiuramjimonos Thiuram vulcanization accelerators such as fido (TETD), tetrabutyl thiuram dimonosulfide (TBTD), dipentamethylene thiuram tetrasulfide (DPTT), zinc dimethyldithiocarbamate (ZnMDC), zinc diethyldithiocarbamate (ZnEDC), A dithiocarbamate vulcanization accelerator such as zinc di-N-butylcarbamate (ZnBDC) can be used. These vulcanization accelerators can be used alone or in combination of two or more substances. Examples of the vulcanization acceleration aid include metal oxides such as zinc oxide and magnesium oxide, and fatty acid vulcanization acceleration aids such as stearic acid, oleic acid, palmitic acid, and behenic acid. 1 type (s) or 2 or more types can be used.
[0024]
As other additives, reinforcing agents are usually used, but when carbon black is blended as a conductivity-imparting agent, it also acts as a reinforcing agent. Furthermore, an anti-aging agent, a wax, etc. can be mix | blended as needed. Examples of the antioxidant include imidazoles such as 2-mercaptobenzimidazole, phenyl-α-naphthylamine, N, N′-di-6-naphthyl-p-phenylenediamine, and N-phenyl-N′-isopropyl-p. -Amines such as phenylenediamine, phenols such as di-tert-butyl-p-cresol, styrenated phenol and the like.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the conductive rubber roll of the present invention will be described in detail with reference to the drawings.
[0026]
FIG. 1 is a cross-sectional view of a conductive rubber roll 1 according to an embodiment of the present invention. The roll 1 has a configuration in which an outer periphery of a core shaft 2 is covered with an elastic body 4 including a large number of bubbles 3. The elastic body 4 is manufactured from an unvulcanized rubber composition containing hollow microspheres, and the vulcanized molded body 5 contains bubbles 3 having a size and shape corresponding to the hollow microspheres.
[0027]
The hollow microspheres are inflated balloons having an average particle diameter of 50 μm in which isopentane is encapsulated in the outer shell of a thermoplastic polyacrylic resin. During heating, the outer shell melts and the hollow remains as it is to form bubbles (cells), so the generated bubbles 3 have the same size and shape as the middle sphere microspheres. Therefore, if hollow microspheres of uniform size are uniformly distributed in the unvulcanized rubber composition, bubbles of uniform size are uniformly distributed in the rubber roll, and the elastic body 4 is uniform. Have excellent elasticity and shape accuracy.
[0028]
The molded conductive rubber roll 1 has a coating layer 6 on its surface as shown in FIG. When this coating layer 6 is removed by cutting or polishing, for example, as shown in FIG. 3, the bubbles 3 near the surface layer of the elastic body 4 of the roll are cut to form a large number of recesses 3a on the roll surface. . As described above, the bubbles 3 are in a state where the thermoplastic resin constituting the outer shell of the hollow microspheres is melted and the peripheral walls of the bubbles 3 are integrated with the vulcanized molded body 5. Therefore, the hardness is low and the quality is constant as compared with a roll having many bubbles in which the outer shell expanded in the conventional vulcanization process remains. Moreover, the size of the bubbles 3 and the recesses 3a in the elastic body 4 can be designed in advance by selecting the particle size of the microspheres contained in the unvulcanized composition. Accordingly, there is no variation in the size and distribution of the recesses on the surface, and a uniform surface roughness can be obtained.
[0029]
(Example)
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, these do not limit this invention. Unless otherwise stated, each component ratio is expressed in parts by weight.
The vulcanized rubber composition and reaction conditions are summarized in Table 1 below.
[0030]
The conductive rubber roll of Example 1 will be described as an example. 70 parts of acrylonitrile-butadiene copolymer (trade name “NIPPOL 401LL” of Nippon Zeon Co., Ltd.), ethylene-propylene-diene copolymer (commercial product of Mitsui Chemicals, Inc.) Name "EPT4021") 30 parts, carbon black (trade name "Seast 3" of Tokai Carbon Co., Ltd.) 40 parts, sulfur (Tsurumi Chemical Co., Ltd. trade name "powder sulfur") 1 part, vulcanization accelerator 1 part each of the product names “Noxeller M” and “Noxeller BZ” supplied by Shinsei Chemical Industry Co., Ltd. 5 parts of zinc oxide (Mitsui Metal Mining) and 1 part of stearic acid (Japanese fats and oils) as vulcanization accelerators To make a full compound, and then hollow microspheres (expancel trade name “EXPANCEL091DE”) were added to the rubber composition in an amount of 60% by volume. In addition, the mixture was kneaded with two more stages. The hollow microspheres have an average particle size of 30 to 40 μm, the outer shell is an acrylonitrile-based resin (melting temperature 160 ° C.), and is an encapsulant inpentane.
[0031]
In the vulcanization molding, a preform was obtained by extruding into a cylindrical shape with an extruder and preliminarily molding, and then cutting into a predetermined size. This preform is put into a vulcanizing can, and the thermoplastic resin, which is the outer shell of the hollow microsphere, is not melted and vulcanized under a temperature condition where the rubber component is crosslinked, and then the thermoplastic resin melts. Heating was performed at temperature. The vulcanization treatment was performed at about 140 ° C. for about 30 minutes or at about 130 ° C. for about 30 minutes. The melt heating was performed at 180 ° C. for 10 minutes. The conditions for these vulcanization treatments vary depending on the type of hollow microsphere thermoplastic resin, the type of rubber component, the additive such as a crosslinking agent, and the blending ratio, and are adjusted as appropriate.
[0032]
Next, a metal shaft (φ6) was inserted into the molded body, and was cut by polishing to finish a conductive rubber roll (outer diameter φ15 mm, length 220 mm).
[0033]
In order to measure the distribution state of the bubbles contained in the conductive rubber roll, an image of 500 times was taken with a video micro, and the variation range in the obtained data (n = 30) was examined. The hardness was measured by Shore E, and the average value at 5 points in the plane was taken. The drawing test was performed using LAZERSHOT4000 (manufactured by Hewlett Packard). Samples were imaged as halftone images using a transfer roll, and evaluated in five stages (good 5 to bad 1).
[0034]
In Example 2, the composition and blending amount of the rubber composition and the expanded hollow microspheres were the same as in Example 1, and the vulcanization temperatures were different. The conductive rubber roll of Example 2 was obtained in the same manner as in Example 1.
[0035]
In addition, as comparative examples, when hollow microspheres are not used (Comparative Examples 1 and 2) and when unexpanded hollow microspheres (trade name “Microsphere F-50” of Matsumoto Yushi Seiyaku Co., Ltd.) are respectively blended with 10 phr ( The characteristics of the conductive rubber rolls of Comparative Examples 3 to 6) were examined. Detailed conditions and results are shown in Table 1.
[0036]
[Table 1]

[0037]
The image output test was performed by the above five-level evaluation. In the case of Comparative Example 6, the microspheres expanded too much and collapsed during vulcanization.
From Table 1, it can be confirmed that the conductive rubber roll of the present invention has clearly superior quality compared to the conductive rubber rolls of Comparative Examples 1 and 2. Further, in Comparative Examples 3 to 6 using unexpanded microspheres, the variation in cell diameter is large, but in Examples 1 to 3 of the present invention, 30 to 40 μm is substantially uniform with little variation and low It was confirmed that the hardness was extremely excellent in the evaluation of the image drawing test.
[0038]
【The invention's effect】
As is clear from the above description, according to the present invention, it is possible to obtain a conductive roll having a low hardness sponge body shape accuracy in which bubbles of a size as designed without a hard outer shell are uniformly distributed. . Therefore, when the conductive roll is used for the conductive mechanism of the developing device, an image with excellent quality can be provided. Moreover, this invention also has the effect that it is easy to design the porosity of the bubble (cell) contained in a roll, and the roughness of the roll surface according to the objective.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a conductive rubber roll according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a roll before polishing a coating layer.
FIG. 3 is a cross-sectional view of a roll after polishing a coating layer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Conductive rubber roll 2 Core shaft 3 Bubble 3a Recessed part 4 Elastic body 5 Vulcanized molded body 6 Film layer

Claims (3)

  An unvulcanized rubber composition comprising a thermoplastic resin as an outer shell and an expanded hollow microsphere and a conductivity-imparting agent is vulcanized and molded at a temperature below the melting temperature of the thermoplastic resin, and then thermoplastic. A method for producing a conductive roll, wherein the outer shell is melted by heating at a temperature equal to or higher than the melting temperature of the resin, and has bubbles corresponding to the hollow microspheres.   The electroconductive roll manufactured by the manufacturing method of Claim 1.   The bubble is 30 to 70% by volume, each bubble diameter (cell diameter) is 10 to 200 μm, Shore E hardness is 20 to 40, and a conductivity imparting agent is blended in the rubber composition. Conductive roll.

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