JPH1177710A - Conductive roller having stepped axis - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive roller which is used as a roller for charging in which the difference in a photosensitive material abrasion quantities between a part to which both ends of the roller are pressed and a middle part is reduced remarkably to reduce the difference in properties between both end of the roller and the middle part is improved, a roller for development, a roller for transfer, and others in contact with a photosensitive material. SOLUTION: In a conductive roller, the outside shape of both end bearing parts of a rotary axis 2 is an axis with a step part 6 which is smaller than the outside diameter is a middle conductive elastic layer 3 forming part, a space part is formed from both ends of the layer 3 of a non-expanded rubber elastomer to the inside, a space inside both ends forms a taper in which the diameter decreases toward the peripheral surface of the rotary axis 2 and is formed in the shape of a circular truncated cone viewed from both end sides. The conductivity of the roller is a level of so-called semi-conductivity 10<3> -10<9> Ω-cm electric resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive roller used in an electrophotographic apparatus as a charging roller, a developing roller, a transfer roller and the like in contact with a photosensitive member.

[0002]

2. Description of the Related Art In an electrophotographic apparatus, devices such as charging, development, transfer and cleaning are arranged around a photoreceptor, and these devices have an electric resistance of 10 ³ to 10 ¹⁰ Ω ·. c
control in a specific range of a so-called semiconductor region of about m
Rolled and elongated rollers (hereinafter referred to as “conductive rollers”) are often used. These conductive rollers usually have a structure in which a conductive elastic layer is formed on the outer periphery of a metal rotating shaft or a structure in which a surface layer is provided on the outer periphery of the conductive elastic layer. It is preferably used because it is easy to obtain and a constant contact width (nip) is easily obtained. To manufacture these conductive rollers, a molded article made of an elastomer such as rubber or a foam thereof containing a conductivity-imparting agent is provided on the outer periphery of the rotating shaft, and the outer diameter and length of the molded article are adjusted. A conductive elastic layer (single-layer roller) is formed by finishing to a predetermined size, or after finishing the outer diameter of the molded body to a predetermined size, a surface layer is formed by applying a conductive resin solution to the outer periphery thereof. It is common to cut into a predetermined length to form a two-layer roller. In the above manufacturing process, both ends of the molded article tend to swell due to reaction and thermal shrinkage in the case of an elastomer such as rubber, and to foaming and the like in the case of a foam in the case of release. In the case where the diameter of the rotating shaft does not change in the length direction and the conductive elastic layer is a foam, this swelling tendency is slight, but the two-layer roll is used.
In the case where the rotating shaft is a stepped shaft (the diameter of both ends is smaller than the central portion), the shrinkage is stopped at the stepped portion when forming the first layer as shown in FIG. The surface is polished to a diameter, and a stress due to dripping and drying shrinkage when a second layer is applied and formed thereon is applied. When cut to a predetermined length in this state, the concentrated stress at the step portion is released. Therefore, the outer diameter swelling at both ends is large, and if the obtained conductive roller is used in contact with the photoreceptor as a charging roller or a developing roller, the swelling at both ends of the roller may occur. There has been a problem that the abrasion of the photoreceptor in the pressed portion is accelerated, and the charging characteristics and the developing characteristics vary widely at both ends and the center.

[0003]

SUMMARY OF THE INVENTION The present invention solves the problem in the case of a two-layer roller using the stepped shaft described above. Provided is a conductive roller having less variation in charging characteristics and developing characteristics due to body wear.

[0004]

According to the present invention, a conductive elastic layer is provided concentrically on the outer periphery of a rotating shaft, and a conductive elastic layer is provided on a conductive roller used in contact with a photosensitive member. A frusto-conical hollow centered on the rotation axis is formed inside both ends of the. That is, the conductive roller of the present invention has a taper having an angle of about 30 to 60 degrees with respect to the outer peripheral surface of the rotating shaft so that the space gradually decreases in diameter from each end to the center. By forming the truncated cone-shaped space, the contact pressure of the end portion to the photoconductor is soft and preferable. The “conductive” of the conductive roller of the present invention means a material having a level of semiconductivity with an electric resistance of about 10 ³ to 10 ⁹ Ω-cm.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The rotating shaft is made of a metal pipe or rod having high electrical conductivity and high rigidity, and has both ends for supporting bearings and mounting driving parts (gears, pulleys). What is precision machined to a smaller diameter than the part is used. In terms of rust prevention, stainless steel and surface treatment (plating, phosphoric acid treatment, etc.)
Steel is preferably used. These are positioned and arranged in a conductive elastic layer forming mold after degreasing and washing and applying an adhesive.
The conductive elastic layer is a non-foamed rubber elastic material such as polyurethane, silicon rubber, EPDM, NBR, etc., having a low hardness (JIS A20 to 40 degrees) containing a conductivity imparting agent (carbon black, metal powder, etc.). As a method of forming the conductive elastic layer, for example, holding the rotating shaft in a mold, filling a rubber elastic material forming material in a preheated mold, and vulcanizing or curing and simultaneously adhering to the rotating shaft, The outer diameter may be polished. In order to form a surface layer on the outer periphery of the obtained conductive elastic layer, a resin material such as polyurethane or polyamide was dissolved in a solvent, a conductive agent was dispersed to prepare a dipping coating solution, and a conductive elastic layer was formed. What is necessary is just to immerse a roller, apply | coat and dry.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The formation of a conductive roller according to the present invention will be described with reference to the process chart of FIG. Polyester polyol [molecular weight = 2000, number of OH groups = 2.3] 1 part by weight of carbon black is added to 100 parts by weight, and the mixture is kneaded with a roll and uniformly dispersed. Do. Next, add 7.5 parts by weight of tosolein diisocyanate,
After stirring with an agitator, the mixed reaction solution was pre-adhesive treated. A rotating shaft having a step 6 (both ends outer diameter 6 mm, central part 8 mm) was positioned and arranged, and a mold adjusted to 150 ° C (from product dimensions) (Having a cavity for forming a conductive elastic layer with a long and large outer diameter), cured at 150 ° C. for 30 minutes, demolded, post-crosslinked at 150 ° C. × 2 hr, and covered the conductive elastic layer 3 by covering the step. The formed roll material was obtained (step (a).

After leaving at room temperature for 2 hours, the surface is polished with a grindstone 8 (step (b)), and a dipping tank (coating liquid, polyester-based thermoplastic polyurethane, 100 parts of E185PM00 manufactured by Nippon Milactran Co., Ltd.) is provided with a coating liquid 10. Is dissolved in a tetrahydrofuran part, and a coating solution 4 is provided on the surface with a resin solution (solid content: 20%) in which 100 parts of carbon black is dispersed (step (c)), and dried to obtain a coating film having a thickness of 20 μm. Was provided.
Thereafter, both ends were cut in accordance with the length L (240 mm) of the elastic layer (step (d)), and unnecessary portions 9 were removed (step (e)). The hardness (JIS A) of this roller is 35 °,
The electrical resistance was 5 × 10 ⁶ ohm-cm. Further, a sharp edged cutting tool 5 was inserted at both ends of the urethane portion of the inner layer of the roller at an angle of 40 ° with respect to the rotation axis, and the inner urethane portion was cut out to form a truncated cone-shaped hollow portion 11 (step). (F)). Using the obtained conductive roller as a developing roller of a printer using a ─ component non-magnetic system, a continuous running test of 2,000 sheets was performed, and 0, 0 from the one end in the length direction of the photoconductor to the other end. 20, 60, 100
FIG. 4 shows the results of measuring the amount of shaving at eight locations, namely, 140, 180, 220, and 240 mm. In addition, the conductivity control row of Comparative Example
As the la, those having no hollow portions formed at both ends until the step (e) were used. As is apparent from FIG. 4, when the conductive roller of the embodiment is used, the difference between the photoreceptor shaved amount at the end and the center is 2 μm, whereas that of the comparative example is the conductive roller. In the case where a laser is used, it is as large as 7 μm.

[0008]

According to the present invention, a hollow frustoconical shape is formed at both ends of the inner layer of a two-layer roller comprising a rotating shaft having both ends stepped, a non-foamed conductive rubber elastic layer and a surface coating layer. ,
The difference in the amount of wear of the photoreceptor between the portion where the both ends of the roller were pressed and the center was significantly reduced, and the characteristic difference between the ends of the roller and the center was improved. Also, current leakage due to damage to the photoreceptor surface
And other problems were resolved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a conductive roller of the present invention.

FIG. 2 is a cross-sectional view of a conventional conductive roller.

FIG. 3 shows (a) a step of coating an inner layer in the production process of the present invention;
(B) polishing step (c) dipping step (d)
Is an end cutting step, (e) is an unnecessary part removing step,
(F) is an explanatory view showing an end hollow forming step.

FIG. 4 is a diagram showing the amount of wear of the photoconductor for each roller position;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1; Roller of this invention 2; Rotating shaft 3; Inner layer (conductive elastic layer) 4: Outer layer (surface coating layer) 5; Blade 6; Step 7; Internal stress 8; Grinding stone 9; Coating liquid 11; cut removal part L; product length

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[Procedure amendment]

[Submission date] November 13, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

[Title of the Invention] A conductive roller having a stepped shaft

Claims (2)

[Claims] 1. A conductive roller which is formed by concentrically laminating a conductive elastic layer and a surface layer on the outer periphery of a rotating shaft and which is used in contact with a photoreceptor, wherein the outer ends of both ends of the rotating shaft have conductive elasticity in the center. A conductive roller having a stepped shaft smaller than an outer diameter of a layer forming portion, wherein a space is formed from both ends of a conductive elastic layer made of a non-foamed rubber elastic body to inside. 2. The taper according to claim 2, wherein the space inside both ends has a taper whose diameter gradually decreases as approaching the outer peripheral surface of the rotating shaft, and is formed in a truncated cone shape as viewed from both ends. The conductive roller according to claim 1, wherein