JP4771843B2 - Conductive roll - Google Patents

Description

  The present invention relates to a conductive roll used in an electrophotographic apparatus such as a copying machine, a printer, and a facsimile machine.

  In general, image formation in a contact charging type electrophotographic copying machine is performed as follows. That is, first, a charging roll is pressed against the photosensitive drum to uniformly charge the surface of the photosensitive drum, and an original image is projected onto the charged photosensitive drum surface via an optical system. An electrostatic latent image is formed by canceling the charging. Next, after a toner is attached to the electrostatic latent image to form a toner image, the toner image is transferred to a copy sheet. In this way, a copy image can be obtained.

  For such image formation, in addition to the charging roll, a developing roll for applying toner to the electrostatic latent image on the surface of the photosensitive drum for development, a toner supply roll for supplying toner to the developing roll, and a toner image for copying paper Various conductive rolls (including a semiconductive roll) such as a transfer roll for transferring to the surface are used.

  These conductive rolls generally have a configuration in which a conductive elastic layer having desired electrical characteristics is formed on the outer periphery of the shaft body directly or via another layer. It is important that the electrical resistance in the layer is uniform and stable without variation, and that the surface roughness is small and that the dimensional accuracy is excellent.

Therefore, in order to suppress variation in electrical resistance in the conductive elastic layer, for example, a semiconductive roll is obtained by adding carbon black and conductive metal oxide having conductivity to the conductive elastic layer ( Patent Document 1) and similarly, it has been proposed to obtain semiconductive rolls by adding conductive organic particles and insulating particles such as silica particles to the conductive elastic layer (see Patent Document 2). Further, in order to reduce the surface roughness during extrusion or cutting in the conductive elastic layer, for example, it is proposed to obtain a conductive member by adding calcium carbonate to conductive rubber (see Patent Document 3). Has been.
Japanese Patent Laid-Open No. 9-302151 JP-A-9-143310 JP 2002-194203 A

  However, as described above, when inorganic particles such as carbon black, silica particles, calcium carbonate, or conductive organic particles are added to the conductive elastic layer, these particles become the “ground” part of the conductive elastic layer. Since it is harder than the elastic material, the hardness of the entire conductive elastic layer is increased, the stress on the toner and the contact member (regulating member) is increased, toner fusing occurs, and uniform with the photosensitive drum. Contact is not obtained, charging becomes non-uniform, and troubles such as image defects are likely to occur. At the same time, since the compression set is also deteriorated, there is a problem that the roll life is shortened.

  Therefore, there is a strong desire to establish a technology that keeps the hardness of the conductive elastic layer low, suppresses variations in electrical resistance, reduces surface roughness, and exhibits excellent dimensional accuracy without deteriorating compression set. Although it is rare, no such technology has been established yet.

  The present invention has been made in view of such circumstances, has low hardness, has good compression set characteristics, suppresses variations in electrical resistance, and has a small surface roughness and good dimensional accuracy. An object of the present invention is to provide an excellent conductive roll having

In order to achieve the above object, the present invention provides a conductive roll in which a conductive elastic layer is formed on the outer periphery of a shaft body directly or via another layer, and the conductive elastic layer has the following properties: Conductivity in which (A) to (D) are essential components and the blending ratio of the non-conductive inorganic particles (C) is set to 55 to 80 parts by weight with respect to 100 parts by weight of the rubber base material (A) . formed from the composition, and [measured in accordance with JIS B0601 (1994)] the surface roughness Rz of the first aspect of the der Ru conductive roll less than 10 [mu] m.
(A) Rubber base material.
(B) Conductive agent.
(C) Non-conductive inorganic particles.
(D) Non-conductive crosslinked rubber particles.

  In addition, the present invention has, in particular, a conductive roll in which an ionic conductive agent is used as the conductive agent that is the component (B), and a nonconductive material that is the component (D). A conductive roll in which the average primary particle size of the crosslinked rubber particles is 5 μm or less is set as a third gist.

That is, as a result of intensive studies to solve the above-mentioned problems, the present inventors have conducted a conductive material mainly composed of a rubber base material (component A) and a conductive agent (component B) as a conductive elastic layer forming material. When non-conductive inorganic particles (C component , hereinafter abbreviated as “inorganic particles” ) and non-conductive crosslinked rubber particles (D component) are further blended with the conductive rubber composition, the non-conductive crosslinked rubber particles are electrically conductive. Because it has lower hardness and lower compression set than the elastic material containing the conductive agent, which is the “ground” part of the elastic elastic layer, it contains a lot of inorganic particles that have excellent electrical resistance variation suppression effect and surface roughness reduction effect However, as a whole, it has been found that a conductive roll having a low hardness and a low compression set can be obtained, and the present invention has been achieved.

In the present invention, “non-conductive crosslinked rubber particles” means crosslinked rubber particles having a volume resistivity greater than 1 × 10 ³ Ω · cm.

Since the conductive elastic layer of the conductive roll of the present invention is formed by using a conductive rubber composition having a special composition as described above, the conductive roll is inorganic for suppressing variation in electric resistance and reducing surface roughness. Although the particles are contained in a large proportion of 55 to 80 parts by weight with respect to 100 parts by weight of the rubber base material , as a whole, the hardness is low and the compression set is low. Therefore, according to the conductive roll of the present invention, the stress with the toner and the contact member is suppressed, the contact with the photosensitive drum becomes uniform, and troubles such as a defect in the image do not occur. And it has a long roll life and can be used well over a long period of time.

  Among the conductive rolls of the present invention, in particular, those using an ionic conductive agent as the conductive agent as the component (B) can eliminate the addition amount of conductive inorganic particles (electronic conductive agent). Therefore, it is further preferred to have low hardness and low compression set.

  Further, among the conductive rolls of the present invention, in particular, the non-conductive crosslinked rubber particles (D) having an average particle size of 5 μm or less are included in the conductive elastic layer. Since it is more densely dispersed, it has a low hardness and a low compression set, which is preferable.

  Next, an embodiment of the present invention will be described. However, the present invention is not limited to this embodiment.

  For example, as shown in FIG. 1, the conductive roll of the present invention has a conductive elastic layer 2 formed along the outer peripheral surface of the shaft body 1, and a resin coating film on the outer peripheral surface of the conductive elastic layer 2. The protective layer 3 made of is formed.

  The shaft body 1 of the charging roll is not particularly limited, and may be a solid body or a hollow cylindrical body. The forming material is not particularly limited, and examples thereof include metal materials such as aluminum and stainless steel. In addition, you may apply | coat an adhesive agent, a primer, etc. to the surface of the shaft 1 as needed. In addition, the adhesive, primer, etc. may be made conductive as necessary.

  And as a forming material of the electroconductive elastic layer 2 formed in the outer peripheral surface of the said shaft body 1, a rubber base material (A component), a electrically conductive agent (B component), an inorganic particle (C component), non- A conductive rubber composition containing conductive cross-linked rubber particles (component D) as an essential component is used.

  The rubber substrate (component A) is not particularly limited, and examples thereof include hydrin rubbers such as polyurethane elastomers, epichlorohydrin homopolymers, epichlorohydrin-ethylene oxide copolymers, epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymers, and the like. ECO, etc.), styrene-butadiene rubber (SBR), polynorbornene rubber, ethylene-propylene-diene rubber (EPDM), acrylonitrile-butadiene rubber (NBR), hydrogenated acrylonitrile-butadiene rubber (H-NBR), butadiene rubber (BR) , Isoprene rubber (IR), natural rubber (NR), silicone rubber, acrylic acid-modified rubber and the like. These may be used alone or in combination of two or more.

In addition, as the conductive agent (component B), there are two types of electronic conductive agent and ionic conductive agent. As the electronic conductive agent, acetylene black, special conductive black (Ketjen black), conductive furnace black ( Conductive metal oxides such as conductive carbon black, graphite, potassium titanate, iron oxide, c-TiO ₂ , c-ZnO, c-SnO _2, etc. And metal powders such as nickel and copper. Examples of the ionic conductive agent include structural charge-specific anions such as quaternary ammonium salts, borates, lithium perchlorate, and potassium perchlorate, and ionic conductive agents such as a surfactant. These conductive agents may be used alone or in combination of two or more.

  Among these conductive agents, it is particularly preferable to use only an ionic conductive agent in order to lower the hardness and the compression set of the conductive elastic layer 2.

  The blending ratio of the conductive agent is appropriately set according to the intended use of the conductive roll. Usually, when the electronic conductive agent is used alone, the electronic conductive agent is used as the rubber base material 100. It is suitable to mix 5 to 50 parts by weight (hereinafter abbreviated as “parts”), more preferably 15 to 40 parts. Moreover, when using an ionic conductive agent independently, it is suitable to mix | blend 0.1-10 parts of ionic conductive agents with respect to 100 parts of said rubber base materials, More preferably, it is 0.5-4 parts. .

Examples of inorganic particles (component C) used in the present invention include calcium carbonate, silica, talc, clay, carbon black other than conductive carbon black, metals other than conductive metal oxides such as TiO ₂ , ZnO, and SnO _2. Examples thereof include oxides, pumice powder, mica powder, barium sulfate, calcium sulfate, magnesium carbonate, magnesium silicate and the like. These inorganic particles may be used alone or in combination of two or more.

The average particle size of the inorganic particles is not particularly limited, but from the viewpoint of easy mixing with other materials and uniform dispersibility, the average primary particle size (average particle size of primary particles). Is preferably 0.005 to 5 μm. The mixing ratio of the inorganic particles, with respect to the base rubber 100 parts, be set 55 to 80 ° parts, it is necessary in the electrical resistance variation suppressing effect and the surface roughness reduction effect. That is, when the blending ratio of the inorganic particles is too small, electric resistance variation suppressing effect and roughness reduction effect may become insufficient, on the contrary, when the mixing ratio of the inorganic particles is too large, the resulting This is because the hardness of the conductive roll may increase.

  Non-conductive crosslinked rubber particles (component D) used in the present invention include particles made of vulcanized (cross-linked) rubber and non-conductive. The rubber is not particularly limited, and any suitable rubber can be used as in the rubber base material. Of these, silicone rubber, NBR, carboxy-modified NBR, and the like are preferably used. These non-conductive crosslinked rubber particles may be used alone or in combination of two or more.

  Such non-conductive crosslinked rubber particles are usually obtained by pulverizing a crosslinked rubber material formed into a lump or sheet using a freeze pulverization method, a grinding pulverization method, etc., or an emulsion containing a rubber particle composition. It can be obtained by a method of cross-linking rubber particles by spray drying in a hot air stream, a method of dynamically cross-linking a rubber particle composition dispersed in a rubber base material, or the like. In addition, a commercially available product with a material and particle size that suits the purpose may be used.

  The average particle size of the non-conductive crosslinked rubber particles is not particularly limited, but is preferably as small as possible from the viewpoint of easy mixing with other materials and uniform dispersibility. When the thickness of the conductive elastic layer 2 is 5 μm or less, the hardness and compression set of the obtained conductive elastic layer 2 become smaller, which is preferable. In addition, the blending ratio of the non-conductive crosslinked rubber particles is set to 5 to 80 parts, particularly 10 to 50 parts with respect to 100 parts of the rubber base material. It is suitable for distortion. That is, when the amount is less than 5 parts, these effects may be insufficient. Conversely, when the amount exceeds 80 parts, non-conductive inorganic particles are exposed on the surface of the conductive elastic layer 2, and the electric resistance uniformity of the surface is increased. This is because there is a risk of damage.

  In addition to the above essential components (A) to (D), the conductive rubber composition used in the present invention, if necessary, a foaming agent, a crosslinking agent, a crosslinking accelerator, a processing aid, a colorant, Plasticizers, oils and the like can be added as appropriate.

  On the other hand, the material for forming the protective layer 3 formed on the outer peripheral surface of the conductive elastic layer 2 is not particularly limited, and is an amide resin, a urethane resin, an acrylic resin, an olefin resin, an epoxy resin. Any kind of resin, polyester resin, acrylic fluorine resin, silicone-modified acrylic resin, fluorinated olefin resin, etc., as long as it is conventionally used as the outermost layer (protective layer) of the conductive roll It doesn't matter. And these may be used independently or may use 2 or more types together. In order to impart conductivity, a conductive agent such as carbon black, metal oxide, quaternary ammonium salt, borate or lithium perchlorate is appropriately added to the material. In addition, fillers, stabilizers, rough surface forming particles, ultraviolet absorbers, antistatic agents, reinforcing agents, lubricants, mold release agents, dyes, pigments, flame retardants, oils and the like are appropriately blended as necessary. be able to.

  The material for forming the protective layer 3 is dissolved or dispersed in an organic solvent and prepared as a coating liquid. Examples of the organic solvent include methyl ethyl ketone (MEK), methanol, toluene, isopropyl alcohol, methyl cellosolve, dimethylformamide and the like. These may be used alone or in combination of two or more.

  The electroconductive roll of this invention can be produced as follows using these materials, for example.

  First, the shaft body 1 serving as a core metal is prepared, an adhesive is applied to the outer peripheral surface thereof, and the shaft body 1 is mounted in a mold for forming the conductive elastic layer 2. And after pouring the conductive rubber composition for conductive elastic layer 2 formation knead | mixed with kneaders, such as a kneader, in a metal mold | die, the metal mold | die is closed and heat processing (130-200 degreeC * 20-) 90 minutes) to cure. And the roll by which the electroconductive elastic layer 2 was formed in the outer peripheral surface of the shaft body 1 is taken out by removing the cured molded product from the mold.

  Next, a coating liquid for forming the protective layer 3 is applied to the outer peripheral surface of the conductive elastic layer 2. The coating method is not particularly limited, and conventional methods such as a dipping method, a spray method, and a roll coating method can be applied. Then, after coating, the protective layer 3 is formed by drying and heat treatment (vulcanization treatment, 100 to 200 ° C. × 20 to 90 minutes). In this manner, a conductive roll having a two-layer structure as shown in FIG. 1 can be produced.

  In addition, although the thickness of the said conductive elastic layer 2 and the protective layer 3 is not specifically limited, Usually, the thickness of the conductive elastic layer 2 is set to about 0.5-5 mm, and the thickness of the said protective layer 3 is It is set to about 1 to 50 μm.

The conductive roll thus obtained has a conductive elastic layer 2 using a conductive rubber composition having a special composition containing inorganic particles (component C) and non-conductive crosslinked rubber particles (component D). As a whole, it has low hardness and low compression set despite the fact that it contains a large amount of inorganic particles in order to suppress variations in electrical resistance and reduce surface roughness. ing. Therefore, according to the conductive roll, stress with the toner and the contact member is suppressed, and troubles such as a defect in the image do not occur. Moreover, the roll life is long and it can be used satisfactorily for a long time.

  In the above example, the conductive elastic layer 2 is integrally formed on the outer periphery of the shaft body 1 by mold molding. However, the conductive elastic layer 2 is electrically conductive on the outer peripheral surface of the shaft body 1 by extrusion molding without using a mold. The elastic layer 2 may be integrally formed.

  Further, the conductive roll of the present invention is not limited to the two-layer structure as shown in FIG. 1. For example, a softener transition prevention layer is provided between the shaft body 1 and the conductive elastic layer 2, or the conductive roll By providing a resistance adjustment layer between the elastic layer 2 and the protective layer 3, an appropriate multilayer structure can be obtained.

  Next, examples will be described together with comparative examples.

[Preparation of conductive composition for forming conductive elastic layer]
The conductive elastic layer forming materials shown in Tables 1 and 2 below were prepared at the following ratios. Of these, after mixing rubber base material, stearic acid, inorganic particles, non-conductive crosslinked rubber particles or conductive rubber particles for 5 minutes with a Banbury mixer, two sulfur, morpholine disulfide, tetramethyl thiuram disulfide are mixed. By kneading with a roll, conductive rubber compositions a to j for forming a conductive elastic layer were prepared.

  However, in Table 1 and Table 2, details of each material marked with * 1 to * 11 are as follows.

* 1: Epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer Product name Hydrin T3106 (manufactured by Zeon Corporation)
* 2: Quaternary ammonium salt represented by the following chemical formula (1)

* 3: Conductive carbon black Product name Ketjen Black EC300J (Ketjen Black International)
* 4: Product name Silver W (Shiraishi Kogyo Co., Ltd.)
* 5: Product name Aerosil 200 (manufactured by Nippon Aerosil Co., Ltd.)
* 6: Carbon black Product name Thermax N990 (manufactured by Cancarb)
* 7: Non-conductive crosslinked silicone rubber particles, average primary particle size: 5 μm, volume resistivity: 3 × 10 ¹³ Ω · cm
Product name KMP597 (manufactured by Shin-Etsu Chemical Co., Ltd.)
* 8: Non-conductive crosslinked NBR particles, average primary particle size: 0.1 μm, volume resistivity: 3 × 10 ¹¹ Ω · cm
Product name Narpow VP-402 (manufactured by China Petrochemical)
* 9: Non-conductive crosslinked carboxyl-modified NBR particles, average primary particle size: 0.1 μm, volume resistivity: 7 × 10 ¹¹ Ω · cm
Product name Narpow VP-502 (manufactured by China Petrochemical)
* 10: Non-conductive crosslinked silicone rubber particles, average primary particle size: 0.2 μm, volume resistivity: 1 × 10 ¹³ Ω · cm
Product name Narpow VP-601A (manufactured by China Petrochemical)
* 11: According to the conductive crosslinked rubber particles (a) used in the examples of Japanese Patent No. 3593402. Average primary particle size 0.2 μm, volume resistivity: 1 × 10 ³ Ω · cm or less.
The manufacturing method is as follows.

To 100 parts of silicone rubber (TSE3452HCR, manufactured by GE Toshiba Silicone), 1.5 parts of dicumyl peroxide was added and kneaded with two rolls, then vulcanized at 160 ° C for 20 minutes, and then at 4 ° C at 200 ° C. The rubber sheet (volume resistivity 3 × 10 ^{2 to} 6 × 10 ² Ω · cm) of 120 mm × 120 mm × 2 mm was obtained by vulcanization for a time. The rubber sheet was cooled and pulverized using liquid nitrogen and classified to obtain conductive rubber particles having a particle size of 25 to 100 μm (average particle size of 75 μm).

[Examples 1 to 8, Comparative Examples 1 and 2]
(1) Preparation of a sample, and using the conductive rubber compositions a to j, press vulcanization at 160 ° C. for 30 minutes to obtain a sample of a predetermined shape (samples according to Examples 1 to 8 and Comparative Examples 1 and 2) ).

  And using the said sample, the hardness was measured based on JISK6253, and the compression set was measured based on JISK6262. These results are also shown in Tables 3 and 4 below.

(2) Preparation of charging roll After preparing a core metal having a diameter of 6 mm and applying an adhesive to the outer peripheral surface thereof, the conductive rubber compositions a to j are extruded onto this surface using an extruder. Then, heat crosslinking was performed under conditions of 160 ° C. × 30 minutes, and a roll in which a conductive elastic layer (thickness 3 mm) was formed on the outer peripheral surface of the cored bar was produced. In addition, 50 parts of fluorine-modified acrylate resin (Dainippon Ink Co., Ltd., Defensa TR230K), 50 parts of fluorinated olefin resin (Atfina Japan Co., Ltd., Kyner SL), and conductive titanium oxide (Ishihara Techno Co., Ltd., Thailand Bake) 100 parts of (ET-300W) was dissolved in 200 parts of MEK, and this was dispersed and prepared using a sand mill to prepare a coating solution for forming a protective layer. And the coating liquid for the said protective layer formation is apply | coated to the outer peripheral surface of the conductive elastic layer of the said roll by a dipping method, and after drying, it heats on 150 degreeC x 60 minute conditions, and a protective layer (thickness 6 micrometers) ) To obtain charging rolls (charging rolls according to Examples 1 to 8 and Comparative Examples 1 and 2).

  The charging rolls thus obtained were evaluated for the following items, and the results are shown in Tables 3 and 4 below.

[Extruded skin]
In the process of producing the charging roll, the surface roughness of the roll in which the conductive elastic layer is formed on the core metal was measured according to JIS B0601 (1994) and evaluated according to the following evaluation criteria.
A: Rz is less than 5 μm B: Rz is 5 μm or more and less than 10 μm Δ: Rz is 10 μm or more and less than 15 μm X: Rz is 15 μm or more

[Image output evaluation]
The charging roll was incorporated into a commercially available laser printer (manufactured by Hewlett-Packard Japan, Ltd., Laser Jet 4240), and the image was imaged in a 15 ° C. × 10% RH environment to evaluate the image quality. The evaluation was performed by visual inspection, and “O” indicates that no image defects such as image unevenness, spots, etc. are observed, and “X” indicates that the image defects are recognized.

[Set evaluation]
The charging roll was pressed against the photosensitive drum and left for 1 week in an environment of 40 ° C. × 95% RH. Then, this charging roll was incorporated in a commercially available laser printer (Laser Jet 4240, manufactured by Hewlett-Packard Japan, Inc.), and the image was imaged in a 15 ° C. × 10% RH environment to evaluate the image quality. The evaluation was performed by visual inspection, and “O” indicates that no image defects such as image unevenness, spots, etc. are observed, and “X” indicates that the image defects are recognized.

  From the above results, it can be seen that the example product of the present invention has low hardness and low compression set, and the image evaluation is high. On the other hand, it can be seen that both the comparative example products have high hardness and compression set, and the image evaluation is poor.

It is sectional drawing which shows one Example of the electroconductive roll of this invention.

Explanation of symbols

1 shaft body 2 conductive elastic layer

Claims (3)

The outer periphery of the shaft member, a conductive roll conductive elastic layer formed directly or via another layer, the conductive elastic layer, the following the (A) ~ (D) as essential components The non-conductive inorganic particles (C) are formed using a conductive composition having a blending ratio of 55 to 80 parts by weight with respect to 100 parts by weight of the rubber base (A) , and the surface roughness thereof is is conductive roll Rz [JIS measured according to B0601 (1994)] is characterized in der Rukoto less than 10 [mu] m.
(A) Rubber base material.
(B) Conductive agent.
(C) Non-conductive inorganic particles.
(D) Non-conductive crosslinked rubber particles.   The conductive roll according to claim 1, wherein an ionic conductive agent is used as the conductive agent which is the component (B).   The conductive roll according to claim 1 or 2, wherein the non-conductive crosslinked rubber particles as the component (D) have an average primary particle size of 5 µm or less.

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