JP4144701B2 - Charging roll - Google Patents

Description

【００７９】
【表２】

【００８０】
【発明の効果】
以上説明したように、本発明によると、導電性、汚染性及び帯電特性に優れ放電音が小さく且つ少ない工程で精度よく製造できる帯電ロールを提供することができる。
【図面の簡単な説明】
【図１】本発明の帯電ロールの概略断面図である。
【図２】本発明の帯電ロールの製造方法の一例を示す断面図である。
【図３】本発明の帯電ロールの製造方法の一例を示す断面図である。
【図４】試験例１の電気抵抗値の測定方法を示す図である。
【符号の説明】
１０ 帯電ロール
１１ 芯金
１２ 第１の導電性弾性層
１３ 第２の導電性弾性層
１２ａ 発泡前の第1の導電性弾性層
２０ クロスヘッドダイス
２１ 芯金ガイド
３０ 金型
３１ 円筒型
３２ コマ
３３ 押さえ金型[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a charging roll used for uniformly charging a photosensitive member of an image forming apparatus such as an electrophotographic copying machine and printer or a toner jet copying machine and printer.
[0002]
[Prior art]
A charging roll of an image forming apparatus such as an electrophotographic copying machine or a printer is required to have predetermined conductivity in addition to non-contamination to a photoreceptor. Conventionally, polyurethane and silicone rubber were used, but various coating layers, surface treatment layers or coated tubes were provided on the surface of various elastic layers for reasons such as contamination of the photoreceptor and chargeability. Have been proposed (see Patent Documents 1 to 4). Conventionally, in order to maintain charging characteristics, the charging member is required to have high dimensional accuracy of the outer diameter, and after polishing the elastic layer, as described above, the coating layer, the surface treatment layer, or the covering tube is provided. It was general.
[0003]
[Patent Document 1]
JP-A-6-175470 (claims)
[Patent Document 2]
Japanese Patent Application Laid-Open No. 5-281831 (claims)
[Patent Document 3]
JP 2002-040760 A (Claims etc.)
[Patent Document 4]
JP-A-4-214579 (Claim 2, [0022), etc.)
[Patent Document 5]
JP-A-2002-244457 (Claims, [0018], etc.)
[0004]
[Problems to be solved by the invention]
In recent years, however, charging rolls are required to have more stable charging characteristics, and there are also demands for reducing discharge noise and reducing costs.
[0005]
Therefore, in order to maintain high charging characteristics at low cost, it is necessary to realize a charging roll that can secure a sufficient nip width with very low hardness, even at the expense of dimensional accuracy. By providing a tube-shaped surface layer on a low-hardness elastic layer, a charging roll satisfying all these characteristics was realized.
[0006]
Here, the present applicant has previously developed a conductive elastic foam layer provided on a support and a release layer provided on the conductive elastic foam layer. The release layer is conductive. Attention was paid to a transfer member (see Patent Document 5) which is a sleeve member pre-molded with resin. However, the resin tube disclosed here cannot achieve the target hardness, and if the elastic layer is made to have a low hardness, the resin tube cannot be coated after polishing, so that the resin tube will foam. However, it was difficult to achieve a low hardness foam molding in this tube.
[0007]
In view of such circumstances, it is an object of the present invention to provide a charging roll that is excellent in conductivity, contamination, and charging characteristics and has a small discharge sound.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventors have repeatedly studied, and as a result, the first conductive elastic layer is a nitrile rubber (NBR) foam, and the second conductive elastic layer is an isocyanate surface treatment layer. In order to complete the present invention, it is found that by using an epichlorohydrin rubber (ECO) having a charge roll that is excellent in conductivity, contamination and charging characteristics, has low discharge noise, and can be manufactured accurately with few steps. It came.
[0009]
A first aspect of the present invention that solves the above-described problems includes a first conductive elastic layer provided on a cored bar, and a second conductive elastic layer provided on the first conductive elastic layer. And the first conductive elastic layer contains nitrile rubber, conductive carbon black, and 28 parts by weight or more of a plasticizer with respect to 100 parts by weight of nitrile rubber and DC-100V. The electric resistance value when applied is 1.0 × 10 ⁵ It is made of a nitrile rubber foam having an Ω or less and rubber hardness of 40 ° or less in Asker C, and the second conductive elastic layer is made of epichlorohydrin rubber and surface-treated with a surface treatment liquid containing isocyanate on the surface. The charging roll has a surface treatment layer, and the first conductive elastic layer and the second conductive elastic layer are bonded without an adhesive.
[0010]
A second aspect of the present invention is the charging roll according to the first aspect, wherein the second conductive elastic layer has a rubber hardness of 35 to 75 degrees according to JIS A.
[0011]
A third aspect of the present invention is the charging roll according to the first or second aspect, wherein the second conductive elastic layer has a surface roughness Rz of 8 μm or less.
[0012]
A fourth aspect of the present invention is the charging roll according to any one of the first to third aspects, wherein the thickness of the second conductive elastic layer is 0.3 to 1.2 mm. .
[0013]
According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the electrical resistance value when DC-100V is applied is 1.0 × 10 6. ⁴ ~ 1.0 × 10 ⁷ The charging roll is characterized by being Ω.
[0014]
According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the surface treatment liquid is at least one polymer selected from an acrylic fluorine-based polymer and an acrylic silicone-based polymer, a conductivity imparting agent, The charging roll further contains at least one of the above.
[0015]
According to a seventh aspect of the present invention, in any one of the first to sixth aspects, the second conductive elastic layer is a sleeve member formed in advance, and the first conductive elastic layer is the cored bar. The charging roll is formed by foaming the first conductive elastic layer before foaming between the sleeve member and the previously formed sleeve member.
[0016]
In order to satisfy the predetermined conductivity (electric resistance value), it is necessary to add a sufficient amount of conductive carbon black to the first conductive elastic layer, but adding conductive carbon black increases the hardness and is sufficient. A nip cannot be obtained. On the other hand, if the addition amount of the plasticizer is increased in order to reduce the hardness, the plasticizer moves to the outer surface of the charging roll, contaminates the abutted photoreceptor, and foaming to reduce the hardness. Make it difficult. However, when a nitrile rubber foam, particularly a medium-high nitrile or a high nitrile rubber is used as the first conductive elastic layer, it can be made highly foamed due to the low gas permeability of the nitrile rubber. It has been found that a low-fouling and low-hardness foam can be realized. Further, when the second conductive elastic layer is a sleeve member made of a pre-formed epichlorohydrin rubber and the first conductive elastic layer is foam-molded therein, the second conductive elastic layer is not polished and does not involve an adhesive. Since the layers can be bonded with sufficient strength, an accurate charging roll can be obtained with fewer steps.
[0017]
FIG. 1 shows a cross section of the charging roll of the present invention. As shown in FIG. 1, the charging roll 10 is provided with a first conductive elastic layer 12 and a second conductive elastic layer 13 in this order on a core metal 11, and the second conductive elastic layer 13. Has a surface treatment layer on the surface.
[0018]
The first conductive elastic layer provided on the core of the charging roll of the present invention contains nitrile rubber, conductive carbon black, and 28 parts by weight or more plasticizer with respect to 100 parts by weight of nitrile rubber. In addition, the electric resistance value when DC-100V is applied is 1.0 × 10 ⁵ It consists of a nitrile rubber foam having an Ω or less and a rubber hardness of 40 ° or less in Asker C. The nitrile rubber is not particularly limited, but is preferably a medium-high nitrile, a high nitrile, or an extremely high nitrile rubber having a nitrile amount of 31% or more from the viewpoint of gas permeability described later. Also, from the viewpoint of easy foaming, those with low Mooney viscosity, for example, Mooney viscosity is ML _{1 + 4} It is preferable to use one of 45 or less at (100 ° C.). Hydrogenated NBR may also be used, but the hydrogenation rate is preferably 95% or less because it becomes easy to settle due to peroxide crosslinking.
[0019]
The electric resistance value of the first conductive elastic layer for satisfying the characteristics as the charging roll is 1.0 × 10 ⁵ Since it is Ω or less, conductive carbon black is used as the conductivity-imparting agent, and the electric resistance value is 1.0 × 10. ⁵ Add so that Ω or less. For example, 25 parts by weight or more may be added with respect to 100 parts by weight of nitrile rubber. The kind of conductive carbon black is not particularly limited, and examples thereof include ketjen black (manufactured by Lion Corporation) and talker black # 5500 (manufactured by Tokai Carbon Corporation).
[0020]
Further, in order to secure a sufficient nip as a charging roll, the first conductive elastic layer needs to have a rubber hardness of 40 ° or less in Asker C. In this way, when the hardness is low, the nip width can be set large, and therefore, charging can be suitably performed without unevenness. The rubber hardness of Asker C was measured at a constant load of 1000 gf using a test piece having a thickness of 12 mm or more, and was prepared under the same conditions as the first conductive elastic layer. Here, when the second conductive elastic layer of the manufactured charging roll is peeled off and the first conductive elastic layer is measured so as to have a thickness of 12 mm or more, almost the same hardness is exhibited.
[0021]
As described above, the electric resistance value is 1.0 × 10 ⁵ Addition of conductive carbon black in an amount of Ω or less increases the hardness. Therefore, it is necessary to add a plasticizer to reduce the hardness. Here, the electric resistance value is 1.0 × 10 ⁵ When an amount of carbon black of Ω or less is added, it is usually necessary to add about 70 to 80 parts by weight of the plasticizer with respect to 100 parts by weight of the base rubber. However, since the nitrile rubber used in the present invention has low gas permeability and can be reduced in hardness by high foaming, the amount of plasticizer added is, for example, 28 to 40 parts by weight with respect to 100 parts by weight of nitrile rubber. It can be low. Thus, since the addition amount of the plasticizer is low, the plasticizer does not move to the outer surface of the charging roll and does not contaminate the contacted photoreceptor. Moreover, although it will become difficult to knead | mix when the addition amount of a plasticizer is large, in this invention, since a plasticizer content is low, it can mix suitably. The plasticizer is not particularly limited, but di- (2- ethyl Mention may be made of polar oils such as hexyl) phthalate (DOP). When DOP is used as a plasticizer, it becomes difficult to move to the second conductive elastic layer made of epichlorohydrin rubber, or it becomes a charging roll with excellent contamination.
[0022]
The expansion ratio of the nitrile rubber foam is preferably 2.0 to 4.0 times. When the first conductive elastic layer is formed by foaming between a core metal and a previously formed sleeve member, the expansion ratio is determined by the space between the first conductive elastic layer and the sleeve member before foaming. The ratio is determined by the ratio of the amount of the first conductive elastic layer before foaming. Here, the first conductive elastic layer before foaming needs to be foamed from 2.0 to 4.0 times when foamed in an unconstrained state. By doing so, the two layers can be pressure-bonded and molded and firmly bonded. However, too much foaming is not preferable because the sleeve member will burst. This foaming condition defines the foaming ratio under unconstrained conditions depending on the type and amount of the foaming agent, and controls the thickness at which the first conductive elastic layer before foaming is provided on the core metal with high accuracy. The heating conditions are set appropriately. The foam may be a closed cell or open cell. Here, since the nitrile rubber used in the present invention has a low gas permeability, the conductive elastic layer having a high expansion ratio as described above can be obtained without adding a gas permeation preventive agent or the like. Therefore, the characteristics of the charging roll do not deteriorate due to the addition of a gas permeation preventive agent or the like. Moreover, it is preferable that the average cell diameter of a nitrile rubber foam is 100-300 micrometers.
[0023]
The charging roll of the present invention comprises a second conductive elastic layer on the first conductive elastic layer. The second conductive elastic layer is made of epichlorohydrin-based rubber and has a surface-treated layer surface-treated with a surface treatment liquid containing isocyanate on the surface.
[0024]
Examples of the epichlorohydrin rubber include an epichlorohydrin homopolymer, an epichlorohydrin-ethylene oxide copolymer, an epichlorohydrin-allyl glycidyl ether copolymer, and an epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer.
[0025]
The surface treatment layer is formed by impregnating a surface treatment solution containing isocyanate. As this surface treatment liquid, an isocyanate compound dissolved in an organic solvent, or a carbon black added thereto can be used. At least one selected from an acrylic fluorine-based polymer and an acrylic silicone-based polymer can be used. It is preferable to use a surface treatment liquid containing at least one of a seed polymer and a conductivity imparting agent together with an isocyanate component.
[0026]
Here, as the isocyanate compound, 2,6-tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), paraphenylene diisocyanate (PPDI), 1,5-naphthalene diisocyanate (NDI) and 3,3 -Dimethyldiphenyl-4,4'-diisocyanate (TODI) and the above-mentioned multimers and modified products.
[0027]
The acrylic fluorine-based polymer and the acrylic silicone-based polymer are soluble in a predetermined solvent and can be chemically bonded by reacting with an isocyanate compound. The acrylic fluorine-based polymer is, for example, a solvent-soluble fluorine-based polymer having a hydroxyl group, an alkyl group, or a carboxyl group, and examples thereof include block copolymers of acrylic acid esters and fluorinated alkyl acrylates and derivatives thereof. . The acrylic silicone polymer is a solvent-soluble silicone polymer, and examples thereof include block copolymers of acrylic acid esters and acrylic acid siloxane esters, and derivatives thereof. These polymers can be used alone or in combination. The polymer in the surface treatment liquid is preferably 2 to 30% by weight based on the isocyanate component. If the amount is too small, the effect of retaining the carbon black in the surface treatment layer becomes small. If the amount is too large, the isocyanate component becomes relatively small and an effective surface treatment layer cannot be formed.
[0028]
Moreover, it is preferable to use carbon black as a conductivity imparting agent in the surface treatment liquid. The type of carbon black is not particularly limited and is the same as described above. The carbon black in the surface treatment liquid is preferably 10 to 40% by weight with respect to the isocyanate component. If it is less than this, effective charging characteristics cannot be exhibited, and if it is too much, problems such as dropping off are caused, which is not preferable.
[0029]
Furthermore, the surface treatment liquid contains a solvent that dissolves these acrylic fluorine-based polymer or acrylic silicone-based polymer and an isocyanate compound. Although it does not specifically limit as a solvent, What is necessary is just to use organic solvents, such as ethyl acetate, methyl ethyl ketone (MEK), and toluene.
[0030]
By providing a surface treatment layer as a surface layer on the charging roll, bleeding of the plasticizer added to the first conductive elastic layer to the surface of the charging roll can be prevented. It becomes a charging roll.
[0031]
The rubber hardness of the second conductive elastic layer is preferably 35 to 75 ° according to JIS A, and more preferably 45 to 70 °. This is because if it is lower than the above range, the durability as a charging roll is not satisfied, and if it is higher than the above range, the product hardness becomes high.
[0032]
The surface roughness of the second conductive elastic layer is preferably 8 μm or less, more preferably 6 μm or less, and most preferably 2.5 μm or less. When the surface roughness is 8 μm or less, it is possible to obtain a charging roll to which the toner component hardly adheres. However, if it is larger than 8 μm and 12 μm or less, it can be used depending on the toner.
[0033]
The thickness of the second conductive elastic layer is preferably 0.3 to 1.2 mm. Here, the entire charging roll and the diameter of the core metal are not particularly limited. However, since the charging roll is about φ14 to 18 mm and the core metal is about φ6 to 8 mm, the thickness of the first conductive elastic layer is usually used. A preferable range of the thickness is determined. Also, the length of the charging roll is not particularly limited, but can be, for example, about 210 mm to 320 mm.
[0034]
The charging roll of the present invention has an electrical resistance value of 10 at a low temperature and low humidity environment (10 ° C, 30% RH) to a high temperature and high humidity environment (40 ° C, 80% RH) when DC-100V is applied. ⁴ -10 ⁷ Can be Ω.
[0035]
In the charging roll of the present invention, the first conductive elastic layer is made of such a highly foamed and low hardness nitrile rubber foam, and the second conductive elastic layer is made of epichlorohydrin rubber. Discharge noise can be reduced.
[0036]
The second conductive elastic layer is preferably made of a sleeve member molded in advance. When the second conductive elastic layer is a pre-formed sleeve member, the charging roll of the present invention foams the first conductive elastic layer before foaming between the pre-formed sleeve member and the cored bar. The first conductive elastic layer becomes a foam having a size regulated by the inner surface of the second conductive elastic layer. Therefore, as a result, the polishing step of the first conductive elastic layer becomes unnecessary. Moreover, since they are epichlorohydrin rubber and nitrile rubber, even if the two layers are joined without using an adhesive, they can be bonded with no problem when using a charging roll.
[0037]
The method for producing the charging roll of the present invention is not particularly limited. For example, a step of forming a sleeve member to be the second conductive elastic layer, a step of providing a surface treatment layer on the outer surface of the sleeve member, a cored bar, The step of forming the first conductive elastic layer before foaming thereon and the core metal provided with the first conductive elastic layer before foaming are disposed in a sleeve member disposed in the mold and foamed. It can be manufactured by a process. An example of a manufacturing method is shown below.
[0038]
First, the sleeve member to be the second conductive elastic layer is formed by transfer, injection, or extrusion. When molding by transfer or injection molding, the sleeve member will be more accurate and smooth than a separately polished outer surface if a mirror-polished die is used, so the outer surface will not be polished for dimension adjustment. May be. The sleeve member is coated on a core metal having the same diameter as that of the sleeve member, and immersed in a surface treatment liquid. The surface treatment liquid is applied to the surface, and then heated, whereby the surface treatment layer is formed on the outer surface of the sleeve member. Form.
[0039]
Next, the first conductive elastic layer 12a before foaming is extruded on the core metal 11 using the crosshead die 20 shown in the cross-sectional view of FIG. As shown in FIG. 2, the cored bar 11 is positioned and held by the cored bar guide 21 in the crosshead die 20 for molding the first conductive elastic layer 12 a before foaming. The core metal 11 is advanced from the injection hole (not shown) to the crosshead die 20 while injecting unfoamed unvulcanized rubber to be the first conductive elastic layer 12a before foaming, and foamed on the core metal 11 The previous first conductive elastic layer 12a is extruded. Thereafter, the core metal 11 and the first conductive elastic layer 12a before foaming are cut to a desired length. The first conductive elastic layer 12a before foaming may be formed by injection molding using a mold.
[0040]
Here, FIG. 3 shows a mold for forming the charging roll of the present invention using the core metal 11 covered with the first conductive elastic layer 12a before foaming.
[0041]
The metal mold 30 includes a cylindrical mold 31 made of a metal pipe member whose inner diameter is defined with high accuracy, and a top 32 that holds both ends of the core metal 11. The cylindrical mold 31 and the top 32 are concentric. It is held by a presser mold 33 that is a split mold provided at both ends so as to be in a state. Here, a recess 32b is provided around the fitting hole 32a of the core bar 11 of the top 32, and a gas vent hole 32c is provided so as to communicate with the recess 32b. Further, both end portions of the cylindrical mold 31 and the top 32 are simply brought into contact with each other, and the concave portion 32 b communicates with a gap 34 between the both ends of the cylindrical mold 31 and the top 32. Yes. Accordingly, after molding, a space portion remains in the recess 32b between the first conductive elastic layer 12 and the top 32, and the space portion communicates with the gas vent hole 32c and the gap 34. ing.
[0042]
In order to foam the first conductive elastic layer 12a before foaming using such a mold 30 to form a charging roll, first, both end portions of the core metal 11 are inserted into the fitting holes 32a of the top 32. On the other hand, the sleeve member 13a is disposed in the cylindrical mold 31, and the top 32 and the cylindrical mold 31 are held by the pressing mold 33 (see FIG. 3A). Thereafter, by heating the mold 30, the first conductive elastic layer 12a before foaming is foamed and vulcanized (see FIG. 3B) to obtain the target charging roll 10 (see FIG. 1). ).
[0043]
By such foam molding, the first conductive elastic layer 12 is firmly bonded to the core metal 11 and is also firmly bonded to the second conductive elastic layer 13. Furthermore, particularly in a high temperature and high humidity environment, there may be a problem that rust is usually generated between the elastic layer of the charging roll and the cored bar. Occurrence can be reduced. In addition, since the thickness of the first conductive elastic layer 12a before foaming is defined with high accuracy and the dimension after foaming is also defined by the sleeve member 13a held by the cylindrical mold 31 having a high-precision inner diameter, The foaming conditions are defined with high precision, and the foaming ratio, foaming state, and the like can be controlled with high precision. Of course, the reason why such foam molding can be realized is that a nitrile rubber material is used.
[0044]
Further, since a pipe member having a high-precision inner diameter is used as the cylindrical mold 31, the dimensional accuracy after foam molding can be maintained at a high quality, and the second conductive elastic body 13 without a parting line is obtained. Can do.
[0045]
Furthermore, since the second conductive elastic layer 13 having the surface treatment layer formed by foam molding is heat-treated while being pressed against the inner peripheral surface of the cylindrical mold 31, the surface roughness of the surface becomes gentle. Further, toner filming is more difficult to occur.
[0046]
In the mold 30 described above, a metal pipe member is used as the cylindrical mold 31. Instead, an elastic sleeve such as a fluorine-based resin or a silicone-based resin is used, and the outer peripheral surface of the elastic sleeve is divided by a mold or the like. You may make it hold | maintain. In this case as well, similar foam molding can be performed, but there is an effect that it is easier to remove from the pipe member.
[0047]
DETAILED DESCRIPTION OF THE INVENTION
EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to this.
[0048]
(Example 1)
100 parts by weight of epichlorohydrin rubber (ECO), 20 parts by weight of Toka Black # 4500 as a conductive material, 0.5 parts by weight of sodium trifluoride acetate, 5 parts by weight of zinc white, 2 parts by weight of stearic acid, and a vulcanizing agent 1.5 parts by weight of each was added and kneaded with a roll mixer, and after injection molding, steam vulcanization was performed at 150 ° C. × 1 h to form a rubber sleeve having a thickness of 0.75 mm. Next, 100 parts by weight of ethyl acetate, 20 parts by weight of an isocyanate compound (MDI), 4 parts by weight of acetylene black (manufactured by Denki Kagaku), and 2 parts by weight of an acrylic silicone polymer (Modiper FS700; manufactured by NOF Corporation) A surface treatment was performed using a surface treatment liquid obtained by dispersing and mixing with a ball mill for 3 hours to form a surface treatment layer to obtain a second conductive elastic layer. That is, the surface treatment layer was formed by immersing the rubber sleeve for 60 seconds while maintaining the surface treatment liquid at 23 ° C., and then heating in an oven maintained at 120 ° C. for 1 hour.
[0049]
Medium-high nitrile rubber with 33% nitrile (Mooney viscosity: ML _{1 + 4} (100 ° C.) 30) 100 parts by weight, 5 parts by weight of zinc white, 1 part by weight of stearic acid, 25 parts by weight of Toka Black # 5500, 30 parts by weight of DOP, 1 part by weight of vulcanizing agent (sulfur), vulcanizing aid 3.5 parts by weight, foaming agent ADCA 5 parts by weight, foaming aid 3 parts by weight, inorganic foaming agent 3 parts by weight and kneaded with a roll mixer (first conductive elastic layer before foaming) Is formed on a core metal of φ8 mm in a thickness of 1 mm, and then the second conductive elastic layer is coated, heated at 150 ° C. for 1 hour to foam the first conductive elastic layer before foaming, The first conductive elastic layer and the second conductive elastic layer were integrally formed to produce a charging roll of φ14 × 320 mm.
[0050]
(Example 2)
A charging roll was produced in the same manner as in Example 1 except that 0.5 part by weight of sodium trifluoride acetate was used as the conductive material added to the rubber sleeve.
[0051]
(Example 3)
A charging roll was produced in the same manner as in Example 1 except that 60 parts by weight of Asahi Thermal (manufactured by Asahi Carbon Co., Ltd.) was used as the conductive material added to the rubber sleeve.
[0052]
Example 4
Medium-high nitrile rubber with 33% nitrile (Mooney viscosity: ML _{1 + 4} (100 ° C.) 30) Instead of 100 parts by weight, high nitrile rubber with 40% nitrile (Mooney viscosity: ML _{1 + 4} (100 ° C.) 45) A charging roll was produced in the same manner as in Example 1 except that 100 parts by weight were used.
[0053]
(Example 5)
A charging roll was produced in the same manner as in Example 1 except that a rubber sleeve was formed by extrusion molding, the outer surface of the rubber sleeve was polished, and then a surface treatment layer was formed to form a second conductive elastic layer.
[0054]
(Comparative Example 1)
100 parts by weight of epichlorohydrin rubber, 0.2 parts by weight of sodium trifluoride acetate as a conductive material, 5 parts by weight of zinc white, 2 parts by weight of stearic acid, 1.5 parts by weight of vulcanizing agent, and 30 parts by weight of calcium carbonate, respectively The mixture was added and kneaded by a roll mixer, and this was press vulcanized and polished at 160 ° C. for 30 minutes by transfer molding to form a rubber roll having a rubber thickness of 3 mm. Next, with the same surface treatment liquid as in the example kept at 23 ° C., the rubber roll was immersed for 60 seconds, and then heated in an oven kept at 120 ° C. for 1 hour to form a surface treatment layer on the rubber roll. A charging roll of φ14 × 320 mm was manufactured.
[0055]
(Comparative Example 2)
The first conductive elastic layer is made by impregnating a carbon black dispersion with Asker F 30 ° urethane foam previously foamed, and is bonded to the second conductive elastic layer with a urethane adhesive. A charging roll was produced in the same manner as in Example 1 except that.
[0056]
(Comparative Example 3)
100 parts by weight of epichlorohydrin rubber, 20 parts by weight of Toka Black # 5500 as a conductive material, 25 parts by weight of adipate plasticizer di- (2-ethylhexyl) adipate (DOA), 30 parts by weight of calcium carbonate, 5 parts by weight of zinc oxide, 2 parts by weight of stearic acid, 1.5 parts by weight of vulcanizing agent, 5 parts by weight of foaming agent ADCA, 3 parts by weight of foaming aid and 3 parts by weight of inorganic foaming agent were added and kneaded with a roll mixer (before foaming) A charging roll was produced in the same manner as in Example 1 except that the first conductive elastic layer was formed on a φ8 mm cored bar with a thickness of 1.5 mm.
[0057]
(Comparative Example 4)
A charging roll was produced in the same manner as in Comparative Example 3 except that the first conductive elastic layer before foaming was formed on a core metal of φ8 mm with a thickness of 1 mm.
[0058]
(Comparative Example 5)
100 parts by weight of EPDM, 50 parts by weight of Toka Black # 5500, 75 parts by weight of naphthenic oil, 5 parts by weight of zinc oxide, 1 part by weight of stearic acid, 2 parts by weight of sulfur, 3.5 parts by weight of vulcanization aid, and foaming agent ADCA5 A rubber (first electrically conductive elastic layer before foaming) kneaded with a roll mixer after adding parts by weight, 3 parts by weight of a foaming aid and 3 parts by weight of an inorganic foaming agent, is thickened on a core metal of φ8 mm. A charging roll was produced in the same manner as in Example 1 except that the thickness was 1.5 mm.
[0059]
(Comparative Example 6)
A charging roll was produced in the same manner as in Comparative Example 5, except that the first conductive elastic layer before foaming was formed on a core metal of φ8 mm with a thickness of 1 mm.
[0060]
(Test Example 1)
For the charging rolls of the above examples and comparative examples, the thickness, hardness (Asker C), average cell diameter (average value of 100 cells) and electric resistance value of the first conductive elastic layer, second conductivity Elastic layer thickness, hardness (JIS A) and surface roughness Rz, low temperature and low humidity environment of charging roll (L / L: 10 ° C x 20%), normal temperature and normal humidity environment (N / N: 20 ° C x 50%) -The electrical resistance value was measured when each environment was maintained under a high temperature and high humidity environment (H / H: 30 ° C x 85%). In addition, about the 1st electroconductive elastic layer, it peeled and measured the 2nd electroconductive elastic layer of the manufactured charging roll. Tables 1 and 2 show the measurement results and the outline of each charging roll.
[0061]
As shown in FIG. 4, the electrical resistance value of the charging roll is determined by placing the charging roll 10 on the electrode member 40 made of a SUS304 plate and applying a 100 g load to both ends of the core metal 11. The electrical resistance value between the gold | metal | money 11 and the electrode member 40 was measured using ULTRA HIGH RESISTANCE METER R8340A (made by Advantest Corporation). The applied voltage at this time was DC-100V. The resistance value of the first conductive elastic layer was measured in the same manner for the one obtained by peeling off the second conductive elastic layer of the charging roll.
[0062]
(Test Example 2): Adhesive evaluation
The first conductive elastic layer and the second conductive elastic layer of the charging rolls of Examples and Comparative Examples were peeled off by hand, and the adhesive strength of the two layers was: ○: sufficiently bonded, Δ: manually It was evaluated that it was peeled off immediately, x: not joined. The results are shown in Tables 1 and 2.
[0063]
As a result, in Examples 1 to 5 and Comparative Example 3, the adhesive force was good, but Comparative Example 2 and Comparative Example 5 were not firmly bonded.
[0064]
(Test Example 3): Environmental characteristic (image) evaluation
The charging rolls of the above examples and comparative examples were attached to the charging portion of a commercially available laser printer (LP-8600FX manufactured by EPSON). This printer was started, and an image was output under each of the L / L, N / N, and H / H environments in Test Example 1. ○: No unevenness was observed in the image. Δ: Some unevenness was observed in the image. Was evaluated as. The results are shown in Tables 1 and 2.
[0065]
As a result, Examples 1 to 5 and Comparative Examples 1 to 3 were good in all environments and did not show unevenness and deterioration, but Comparative Example 5 showed image unevenness and deterioration in an L / L environment. It was.
[0066]
(Test Example 4): Storage test
The toner roll of a commercially available laser printer (EPSON LP-8600FX) is assembled with the charging rolls of the above examples and comparative examples and brought into contact with the photoreceptor, and the cartridge is kept in an environment of 50 ° C. and 90% RH for 14 days. After that, the cartridge and the charging roll were assembled to the printer and an image was output. At this time, the image was compared and the surface of the charging roll was observed with a microscope. ○: Bleeding of the roll surface and deterioration of the image were not observed. X: Evaluation was made on the assumption that bleeding on the roll surface and deterioration of the image were observed. The results are shown in Tables 1 and 2.
[0067]
As a result, in the charging roll of Comparative Example 3, bleeding was observed on the roll surface, and the image was also deteriorated.
[0068]
(Test Example 5): Pinhole leak test
A commercially available laser printer (LP-8600FX manufactured by EPSON) is mounted with the photoconductor having a 0.1 mm pinhole and the charging rolls of the above examples and comparative examples, and the environment is 30 ° C. and 85% RH. After holding for a day, images were output and the images at this time were compared. ◎: Image black spot spread was not seen with respect to the pinhole diameter, ○: Image black spot spread was slightly seen with respect to the pinhole diameter, As evaluated. The results are shown in Tables 1 and 2.
[0069]
As a result, in the charging rolls of Examples 1, 2, 4 and 5, no image black spot spread was observed with respect to the pinhole diameter.
[0070]
(Test Example 6): Evaluation of adhesion of printing durability toner component
The charging rolls of the above examples and comparative examples are attached to a commercially available laser printer (LP-8600FX manufactured by EPSON). Microscopic observation and image comparison of the roll surface after continuous printing of 5000 sheets are performed. It was evaluated that no unevenness was observed in the image, Δ: the roll surface was filmed or unevenness was observed in the image. The results are shown in Tables 1 and 2.
[0071]
As a result, in Examples 1 to 5 and Comparative Examples 2, 3 and 5, there was little filming on the roll surface and image degradation was not observed, but in Comparative Example 1, the roll surface was filmed and the image was uneven. It was seen.
[0072]
(Test Example 7): Discharge sound evaluation
The charging roller of each of the above examples and comparative examples is attached to a commercially available laser printer (LP-8600FX manufactured by EPSON) replaced with a photosensitive member that does not incorporate a sponge member or the like as a silencer, and the original photosensitive member with a built-in silencer and Compared with the discharge sound when the charging roll was used, the discharge sound was evaluated as ◯: the same level, Δ: slightly increased discharge sound, ×: considerably increased discharge sound. The results are shown in Tables 1 and 2.
[0073]
As a result, in Example and Comparative Example 3, it was found that the discharge sound was reduced.
[0074]
As shown in Tables 1 and 2, the charging roll of the example was a charging roll excellent in all characteristics such as conductivity, contamination, and charging characteristics.
[0075]
On the other hand, a comparative example manufactured by molding the first conductive elastic layer before foaming using ECO or EPDM with the same thickness on the core metal and foaming in the same rubber sleeve as in Example 1. In No. 4 or Comparative Example 6, the charging roll could not be manufactured due to insufficient foaming.
[0076]
Further, in Comparative Example 5 manufactured by foaming EPDM in the same rubber sleeve as in Example 1, the two layers are not joined with sufficient strength, and in order to obtain a predetermined electric resistance, conductivity is obtained. Since a large amount of carbon was added, the hardness of the first conductive elastic layer was high.
[0077]
Furthermore, in Comparative Example 3 manufactured by foaming ECO in the same rubber sleeve as in Example 1, the hardness of the first conductive elastic layer was high because high foaming could not be achieved as in Example, From the results of the storage test, it was found that the contamination was poor. Therefore, it was found that increasing the amount of the plasticizer added to the charging roll of Comparative Example 3 in order to reduce the hardness is not preferable because the contamination is further deteriorated.
[0078]
[Table 1]

[0079]
[Table 2]

[0080]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a charging roll that is excellent in conductivity, contamination, and charging characteristics, has low discharge noise, and can be manufactured with high accuracy in a small number of steps.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a charging roll of the present invention.
FIG. 2 is a cross-sectional view illustrating an example of a method for producing a charging roll according to the present invention.
FIG. 3 is a cross-sectional view showing an example of a method for producing a charging roll according to the present invention.
4 is a diagram illustrating a method for measuring an electrical resistance value in Test Example 1. FIG.
[Explanation of symbols]
10 Charging roll
11 Core
12 First conductive elastic layer
13 Second conductive elastic layer
12a First conductive elastic layer before foaming
20 Crosshead dies
21 Core guide
30 mold
31 Cylindrical type
32 frames
33 Presser mold

Claims (7)

In a charging roll comprising a first conductive elastic layer provided on a mandrel and a second conductive elastic layer provided on the first conductive elastic layer, the first conductive The elastic layer contains nitrile rubber, conductive carbon black, and 28 parts by weight or more of a plasticizer with respect to 100 parts by weight of nitrile rubber, and has an electric resistance value of 1.0 × 10 ⁵ Ω when DC-100V is applied. The second conductive elastic layer is made of epichlorohydrin rubber and surface-treated with a surface treatment liquid containing isocyanate on the surface, the rubber hardness being 40 degrees or less in Asker C. A charging roll having a surface treatment layer, wherein the first conductive elastic layer and the second conductive elastic layer are bonded without an adhesive. 2. The charging roll according to claim 1, wherein the second conductive elastic layer has a rubber hardness of 35 to 75 ° according to JIS A. 3. 3. The charging roll according to claim 1, wherein the second conductive elastic layer has a surface roughness Rz of 8 μm or less. 4. The charging roll according to claim 1, wherein a thickness of the second conductive elastic layer is 0.3 to 1.2 mm. 5. 5. The charging roll according to claim 1, wherein an electric resistance value when DC-100 V is applied is 1.0 × 10 ^{4 to} 1.0 × 10 ⁷ Ω. 6. The surface treatment solution according to claim 1, further comprising at least one of at least one polymer selected from an acrylic fluorine-based polymer and an acrylic silicone-based polymer, and a conductivity imparting agent. A charging roll. 7. The sleeve according to claim 1, wherein the second conductive elastic layer is a sleeve member formed in advance, and the first conductive elastic layer is formed of the core metal and the pre-formed sleeve member. A charging roll characterized by being formed by foaming the first conductive elastic layer before foaming.

Images