JP2003202731A - Electrostatic charging member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic charging member capable of largely assuring a nip width in the entire area of a roll, preventing an image defect, controlling a resistance value to an aimed range and achieving the stability of image quality. <P>SOLUTION: The electrostatic charging member is furnished with a first conductive elastic layer 12 disposed on an arbor 11 and a second conductive elastic layer 13 disposed on this first conductive elastic layer 12, in which the first conductive elastic layer 12 consists of a polyurethane foam of open cells having hardness below 500 N and the second conductive elastic layer 13 consists of a conductive rubber-like elastic body blended with epichlorohydrin rubber and the surface of the conductive rubber-like elastic body 13 is provided with a surface treatment layer 14 subjected to surface treatment by a surface treating liquid containing isocyanate. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member used for uniformly charging a photoconductor of an image forming apparatus such as an electrophotographic copying machine and a printer.

[0002]

2. Description of the Related Art Charging rolls and the like of image forming apparatuses such as electrophotographic copying machines and printers are required not only to be non-staining to photoconductors, but also to have predetermined conductivity and friction coefficient. Therefore, conventionally, polyurethane and silicone rubber have been used, but various coating layers and coatings have been used on the surface of various elastic layers instead of polyurethane and silicone rubber due to reasons such as contamination to photoreceptors and electrostatic properties. A tube is proposed.

For example, Japanese Patent Application Laid-Open No. 5-204234 proposes a developing roll having a conductive outermost layer made of a polyamide resin tube on a conductive sponge layer. Further, JP-A-7-134467 discloses a charging member having a surface layer containing a lubricant such as wax. Further, JP-A-8-160701 discloses a charging member having a coating layer made of a conductive polymer containing fluorocarbon or a surface layer made of a seamless tube.

[0004]

In the conventional charging member described above, since the hardness of the inner sponge layer is relatively high, the nip width with respect to a constant displacement and a constant load cannot be obtained, and the central portion and the end portion of the roll cannot be obtained. There is a problem that the nip width tends to be different.

On the other hand, when a resin tube made of polyamide or the like is used as the outer layer, the rigidity of the resin tube itself is relatively high, which makes it difficult to follow the roll deformation.

Further, when the rubber-like elastic tube is used, the resistance value of the rubber-like elastic body is likely to vary, and it is difficult to control the resistance value within a target range.

In view of such circumstances, the present invention can secure a large nip width over the entire roll, prevent image defects, control the resistance value within a target range, and stabilize image quality. An object of the present invention is to provide a charging member capable of performing the above.

[0008]

According to a first aspect of the present invention for solving the above-mentioned problems, a first conductive elastic layer provided on a cored bar and a first conductive elastic layer provided on the first conductive elastic layer are provided. And a second conductive elastic layer, wherein the first conductive elastic layer is made of an open-cell polyurethane foam having a hardness of 500 N or less, and the second conductive elastic layer is made of epichlorohydrin phosphorus. It is composed of a conductive rubber-like elastic body obtained by blending chloroprene with a system rubber, and the surface of the conductive rubber-like elastic body is provided with a surface treatment layer surface-treated with a surface treatment liquid containing isocyanate. There is a charging member.

A second aspect of the present invention is the same as the first aspect, wherein the surface treatment liquid is at least one polymer selected from an acrylic fluoropolymer and an acrylic silicone polymer, and a conductivity-imparting agent. The charging member is characterized by containing an isocyanate component.

A third aspect of the present invention is the charging member according to the first or second aspect, characterized in that the conductive rubber-like elastic body contains 5 to 20 parts by weight of chloroprene rubber.

A fourth aspect of the present invention is the charging member according to any one of the first to third aspects, wherein the chloroprene rubber has a melt viscosity at 50 ° C. of 500,000 to 1.3 million cps. It is in.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the second conductive elastic layer has a rubber hardness of 80 ° or less in JIS A type. It is on the charging member.

In a sixth aspect of the present invention, in any one of the first to fifth aspects, the surface resistance value of the first conductive elastic layer is 5 × 10 ⁵ Ω or less, and the entire charging member is The charging member is characterized by having a surface resistance value of 1 × 10 ⁶ to 1 × 10 ⁸ Ω.

In a seventh aspect of the present invention, in any one of the first to sixth aspects, the ratio of the maximum value and the minimum value (maximum value / minimum value) of the electric resistance value of the charging member over the entire surface. But,
The charging member is 10 or less.

An eighth aspect of the present invention is any one of the first to seventh aspects, wherein the charging member has a surface roughness Rz of 20.
The charging member is characterized by having a thickness of less than μm.

In a ninth aspect of the present invention, in any one of the first to eighth aspects, the axial length of the second conductive elastic layer is larger than the length of the first conductive elastic layer. The charging member is characterized by being long.

A tenth aspect of the present invention is the method according to any one of the first to ninth aspects, wherein the second conductive layer has a thickness corresponding to the thickness of the first conductive elastic layer and the second conductive elastic layer. The charging member is characterized in that the thickness ratio of the elastic layer is in the range of 5 to 50%.

According to the present invention, the first conductive elastic layer is a continuous foamed polyurethane foam having a hardness of 500 N or less, and the second conductive elastic layer is a conductive rubber-like elastic body. When a load / constant displacement is applied, the nip width can be made large evenly over the entire roll, and since the second conductive elastic layer is flexible, it can pinch the adhered substances on the surface of the photoconductor. It is possible to reduce the image defect due to.

Here, the first conductive elastic layer has a hardness of 50.
It is a polyurethane foam having open cells of 0 N or less. The hardness of 500 N or less means that the hardness according to the measuring method of JIS K6400 is 500 N or less.
It has a low hardness that cannot be measured with ker C.

The material is not particularly limited as long as it is an open-cell polyurethane, but it is necessary to impart conductivity with a conductive agent. The conductivity may be imparted by electronic conductivity by conductive carbon, ionic conductivity by lithium perchlorate or the like, or hybrid conductivity by combining these. The electric resistance value of the first conductive elastic layer is preferably about 5 × 10 ⁵ Ω or less.

The thickness of the first conductive elastic layer is not particularly limited, but is, for example, about 0.8 to 5 mm.

On the other hand, the second conductive elastic layer is made of a conductive rubber-like elastic body obtained by blending epichlorohydrin phosphorus rubber with chloroprene. Here, conductivity is added as necessary, and the volume resistance value is 1 × 10 ¹⁰ Ω or less. In the case of imparting conductivity, electronic conductivity by conductive carbon, ionic conductivity by lithium perchlorate or the like, or hybrid conductivity combining them may be used. The rubber hardness is JIS A 80 ° or less, preferably 60 ° or less.

In the present invention, since the second conductive elastic layer is composed of a conductive rubber-like elastic body obtained by blending epichlorohydrin-based rubber with chloroprene, the second conductive elastic layer is formed. As compared with the case of using epichlorohydrin rubber, variations in electric resistance value can be suppressed to be small, and the electric resistance value can be controlled within a target range.

The thickness of the second conductive elastic layer is not particularly limited as long as a predetermined nip width can be obtained in cooperation with the first conductive elastic layer, but is, for example, 0.1 to 3 mm. The degree is preferably about 0.3 to 1 mm.

The mixing ratio of chloroprene to the epichlorohydrin type rubber is preferably 5 to 20% by weight of chloroprene. When the amount of chloroprene is less than this, it is difficult to obtain the effect of stabilizing the electric resistance value, and when the amount of chloroprene is more than this, the electric resistance value increases and it becomes difficult to control.

The epichlorohydrin type rubber used in the present invention refers to epichlorohydrin rubber alone, epichlorohydrin-ethylene oxide copolymer and the like.

The type of chloroprene used in the present invention may be any one as long as it has good compatibility with epichlorohydrin rubber, but it is preferable to use one having a melt viscosity of 500,000 to 1.3 million cps at 50 ° C. Is preferred. This is because when chloroprene having a melt viscosity deviating from this is used, the effect of stabilizing the electric resistance value is not remarkably exhibited.

The charging member of the present invention preferably has an electric resistance value of 1 × 10 ⁶ to 1 × 10 ⁸ Ω as a whole. This is because it is suitable for use as a charging member and the like.

Further, the ratio of the maximum value and the minimum value of the electric resistance value of the charging member over the entire surface (maximum value / minimum value).
Is preferably 10 or less. This is because the second conductive elastic layer is made of a conductive rubber-like elastic body in which epichlorohydrin-line rubber is blended with chloroprene, so that the variation in the electric resistance value is reduced, and the surface is spread in the surface direction as a whole. This is achieved by reducing the variation. By reducing the variation in the electric resistance value in the plane direction as described above, it is possible to improve the image quality when it is used as a charging member.

The surface of the second conductive elastic body is preferably surface-treated by an isocyanate treatment in which an isocyanate compound is impregnated and cured. The surface treatment liquid may be one in which an isocyanate compound is dissolved in an organic solvent, or one in which carbon black is added, and at least one selected from acrylic fluoropolymers and acrylic silicone polymers. It is preferable to use a surface treatment liquid containing the polymer, the conductivity imparting agent, and the isocyanate component, and it is preferable to have a surface treatment layer formed by impregnating such a surface treatment liquid.

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 (T
ODI) and the above-described multimers and modified products.

The acrylic fluoropolymer and acrylic silicone polymer are soluble in a predetermined solvent and can react chemically with an isocyanate compound to be chemically bonded. Acrylic fluoropolymers include, for example, hydroxyl groups,
It is a solvent-soluble fluorine-containing polymer having an alkyl group or a carboxyl group, and examples thereof include block copolymers of acrylic acid ester and fluorinated alkyl acrylate and derivatives thereof. The acrylic silicone-based polymer is a solvent-soluble silicone-based polymer, and examples thereof include block copolymers of acrylic acid ester and acrylic acid siloxane ester and derivatives thereof.

In the present invention, one kind or a mixture of two or more kinds of these polymers is used. The polymer in the surface treatment liquid is
It is preferably 2 to 30% by weight based on the isocyanate component. If the amount is too small, the effect of holding the carbon black in the surface treatment layer becomes small, and if the amount is too large, the isocyanate component becomes relatively small and an effective surface treatment layer cannot be formed.

Further, carbon black is used as a conductive agent in the surface treatment liquid. The type of carbon black is not particularly limited, and examples thereof include Ketjen Black (manufactured by Lion Corp.) and Toka Black # 5500 (manufactured by Tokai Carbon Corp.). Carbon black in the surface treatment liquid is preferably 10 to 40% by weight based on the isocyanate component. This is because if it is less than this range, effective charging characteristics cannot be exhibited, and if it is too large, problems such as falling off occur and it is not preferable.

Further, the surface treatment liquid contains a solvent which dissolves these acrylic fluoropolymer or acrylic silicone polymer and the isocyanate compound. The solvent is not particularly limited, but an organic solvent such as ethyl acetate, methyl ethyl ketone (MEK), toluene may be used.

The surface roughness R of the charging member of the present invention as described above.
It is preferable that z is 20 μm or less. This is intended to improve the image when used as a charging member or the like.

Further, in the charging member of the present invention, it is preferable that the axial length of the second conductive elastic layer is longer than the length of the first conductive elastic layer. This is to prevent leakage due to the first conductive elastic layer coming into direct contact with the photoconductor.

The method for producing the charging member of the present invention is not particularly limited, but generally, the first conductive elastic layer is formed on the cored bar, and if necessary, after polishing for size adjustment,
A second conductive elastic layer is formed. The second conductive elastic layer may be formed directly on the first conductive elastic layer,
It may be manufactured separately in a tubular shape, and then covered with an adhesive layer if necessary.

[0039]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on Examples, but the present invention is not limited thereto.

(Example) FIG. 1 shows a cross section of a charging roll according to an example. As shown in FIG. 1, the charging roll 10 is
The first conductive elastic layer 12, the second conductive elastic layer 13, and the surface-treated layer 14 are sequentially provided on the cored bar 11.

The first conductive elastic layer 12 has a rubber hardness of J.
69 N (Asker F
30 °) continuous foamed polyurethane with a surface resistance of 1
0 was ⁴ or less.

The second conductive elastic layer 13 is made of epichlorohydrin rubber (Daiso Epichromer CG102) 95.
Chloroprene rubber (manufactured by DuPont; Neoprene FB: melt viscosity at 50 ° C: 500,000 to 1.3 million cp) based on parts by weight
s) Polymer 100 pre-blended with 5 parts by weight
5 parts by weight of zinc oxide, 5 parts by weight of Ketjen Black EC as a conductive material, and 2 parts by weight of 2-mercaptoimidazoline (Axel 22) as a vulcanizing agent are added to each part by weight and kneaded with a roll mixer. Then, after extrusion molding, steam vulcanization was performed at 150 ° C. for 1 hour, and after cooling, a rubber tube having a thickness of 0.5 mm was formed by polishing.

Surface-treated layer 14 of second conductive elastic layer 13
Is 100 parts by weight of ethyl acetate, an isocyanate compound (M
DI) 20 parts by weight, acetylene black (manufactured by Denki Kagaku Co., Ltd.) 4 parts by weight, and acrylic silicone polymer (Modiper FS700; manufactured by NOF CORPORATION) 2 parts by weight were mixed and dispersed in a ball mill for 3 hours. 23
The roll was immersed for 60 seconds while maintaining the temperature at 0 ° C, and then heated for 1 hour in an oven maintained at 120 ° C.

(Comparative Example) A charging roll was formed in the same manner as in Example except that the polymer of the conductive elastic layer in Example was 100 parts by weight of epichlorohydrin rubber.

(Test Example 1): Electrical resistance value Low temperature and low humidity environment (10 ° C. × 20) in the above Examples and Comparative Examples.
%), A roll resistance value when kept in a normal temperature and normal humidity environment (20 ° C. × 50%) and a high temperature and high humidity environment (30 ° C. × 85%). The electric resistance is measured by charging the charging roll with S
Place on the electrode member made of US304 plate
With a load of 0 g, the electric resistance value between the core metal and the electrode member was measured by ULTRA HIGH RESISTANCE.
It measured using E METER R8340A (made by Advantest Corporation). The results are shown in Table 1 below.

[0046]

[Table 1]

As a result, the environmental dependency of the electric resistance value of the charging roll of the example tended to be smaller than that of the comparative example.

(Test Example 2): Image Evaluation The charging roll of the example and the charging roll of the comparative example were assembled in a commercially available laser printer, and a low temperature and low humidity environment (10 ° C.)
When the image was output at (× 20%), the image of the example was good, but the image of the comparative example had an image defect due to insufficient charging. In addition, under high temperature and high humidity conditions, image defects due to leaks occurred.

(Test Example 3) The variation in the electric resistance value in the roll was measured when the roll was kept in the normal temperature and normal humidity environment (23 ° C. × 55% RH) of the above-mentioned Examples and Comparative Examples. The electric resistance value is measured by pressing a bearing electrode with a width of 5 mm against the surface of the charging roll with a load of 100 g and rotating the electric resistance value between the core metal and the bearing electrode while rotating at 10 rpm.
TRA HIGH RESISTANCE METER
It measured using R8340A (made by Advantest Corporation). The measurement points were measured in the longitudinal direction at three points, 10 mm apart from both ends and in the center, respectively, and were measured at 10 points in the rotational direction. The results are shown in Table 2 below.

[0050]

[Table 2]

From the results shown in Table 2, it was found that the variation in the electric resistance value in the roll of the example was very small as compared with the comparative example.

[0052]

As described above, according to the present invention,
It is possible to provide a charging member that can secure a large nip width over the entire roll, can prevent image defects, can control the electric resistance value within a target range, and can stabilize image quality. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a charging roll according to an exemplary embodiment of the present invention.

[Explanation of symbols]

10 charging roll 11 core 12 First conductive elastic layer 13 Second conductive elastic layer 14 Surface treatment layer

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 15/16 103 G03G 15/16 103 // (C08L 71/03 C08L 11:00 11:00) (72) ) Inventor Shinobu Hasegawa 2-3-6, Shirute, Tsurumi-ku, Yokohama-shi, Kanagawa Kitatsun Industry Co., Ltd. (72) Kenji Kuwamura 2-3-6, Shirute, Tsurumi-ku, Yokohama-shi, Kanagawa F-Term, Hokushin Kogyo Co., Ltd. (Reference) 2H200 FA16 HA03 HA28 HB12 HB22 HB45 HB46 HB47 MA03 MA04 MA08 MA20 MB01 MC01 MC02 MC06 3J103 AA02 AA14 AA32 AA51 AA85 BA41 EA02 EA03 EA11 FA18 GA02 GA57 GA58 HA03 HA12 HA20 HA48 HA53 HA04 A72A07 A04 A72A07 A04 A72A07A04 A72A07 A04 A72A07 A04 A72A07A04 A72A07A04 CH041 DA016 DE196 FD116 GM00 GQ00

Claims (10)

[Claims] 1. A first conductive elastic layer provided on a core metal, and a second conductive elastic layer provided on the first conductive elastic layer. Hardness of conductive elastic layer is 5
The conductive rubber-like elastic body is composed of an open-cell polyurethane foam of 00N or less, and the second conductive elastic layer is a conductive rubber-like elastic body in which epichlorohydrin-line rubber is blended with chloroprene. The charging member is characterized in that a surface treatment layer whose surface is treated with a surface treatment liquid containing isocyanate is provided. 2. The surface treatment liquid according to claim 1,
A charging member comprising at least one polymer selected from acrylic fluoropolymers and acrylic silicone polymers, a conductivity-imparting agent, and an isocyanate component. 3. The charging member according to claim 1, wherein the conductive rubber-like elastic body contains 5 to 20 parts by weight of chloroprene rubber. 4. The chloroprene rubber according to claim 1, which has a melt viscosity of 500,000 to 13 at 50 ° C.
A charging member characterized in that it has a charge rate of 0,000 cps. 5. The rubber according to claim 1, wherein the second conductive elastic layer has a rubber hardness of JIS A type 8 or less.
A charging member which is 0 ° or less. 6. The electric resistance value of the first conductive elastic layer is 5 × 10 ⁵ Ω or less and the surface resistance value of the entire charging member is 1 × 10 ⁶ according to claim 1. ~ 1x
A charging member having a resistance of 10 ⁸ Ω. 7. The ratio (maximum value / minimum value) of the maximum value and the minimum value over the entire surface of the electric resistance value of the charging member according to claim 1, which is 10 or less. Characteristic charging member. 8. The charging member according to claim 1, wherein the surface roughness Rz of the charging member is 20 μm or less. 9. The charging member according to claim 1, wherein an axial length of the second conductive elastic layer is longer than a length of the first conductive elastic layer. . 10. The ratio of the thickness of the second conductive elastic layer to the thickness of the first conductive elastic layer and the thickness of the second conductive elastic layer according to claim 1. , 5
A charging member characterized by being in a range of 50%.