JP3444391B2 - Conductive roll - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic copying machine,
The present invention relates to a conductive roll that can be used in electrophotographic image forming apparatuses such as electrophotographic printers and electrophotographic facsimiles, and is particularly suitable as a charging roll.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine, an electrophotographic facsimile or an electrophotographic printer, an electrostatic latent image is formed on a surface of a photoconductor and toner is attached to the electrostatic latent image to form a toner image. An image is formed by transferring this toner image to a copying machine. In such an electrophotographic process, in order to form an electrostatic latent image on the surface of the photoconductor, it is necessary to charge the surface of the photoconductor in advance. A corona discharge method or a triboelectric charging method has been conventionally known as a method for charging the surface of the photoconductor in this way. Here, since the corona discharge method requires a high-voltage power source, which makes the apparatus complicated and expensive, a frictional charging method, which is simple in terms of the apparatus and does not require a high-voltage power source, has been receiving attention. The frictional charging method is, for example, a method in which a conductive roll to which a bias voltage is applied is brought into sliding contact with the surface of the photoconductor to charge the surface of the photoconductor.

FIG. 1 shows an example of the construction of an electrophotographic copying machine which adopts such a friction charging system. As shown in the figure, around the electrophotographic photoreceptor 11, a charging roll 12,
Document light image exposure device 13, developing device 14, transfer roll 15,
The cleaning device 16 and the eraser lamp 17 are arranged in order. Here, the charging roll 12 pressed against the surface of the photoconductor 11 is connected to a power source 18, and a bias voltage is applied to the shaft of the charging roll 12 to charge the surface of the photoconductor 11 to a predetermined voltage. Has become. Then, the photoconductor 1 charged in this way
An electrostatic latent image is formed on the surface 1 by the original light image exposure device 13, and then a toner image corresponding to the electrostatic latent image is formed by the developing device 14. It is transferred to the transfer material 19. After the transfer, the surface of the photoconductor 11 is cleaned by the cleaning device 16 and then irradiated with light from the eraser lamp 17 in preparation for the next charging.

As described above, the electrophotographic image forming apparatus uses a conductive roll such as a charging roll, a developing roll, a transfer roll, and a cleaning roll. Among them, the charging roll is 10 ⁵ to 10 ⁷ It is required to have semiconductivity of about Ω · cm, and various structures have been proposed.

Conventionally, as a conductive roll used for a charging roll or the like, a conductive core metal is provided with a conductive elastic layer,
There is known a structure in which a resistance adjusting layer is further provided on the conductive elastic layer (Japanese Patent Laid-Open Nos. 1-142569, 4-311972, and 7-140).
760, Japanese Patent Publication No. 7-58403, etc.). That is, the conductive roll having such a structure generally has a resistance adjusting layer on the surface of a conductive elastic layer made of synthetic rubber such as silicone rubber, ethylene propylene rubber, nitrile rubber, urethane rubber mixed with conductive particles. By providing a thin layer for the
It is intended to satisfy the electric resistance of 0 ⁵ to 10 ⁷ Ω · cm. However, when a conductive roll having such a structure is used as a charging roll, there is a problem that an intermediate layer and an outermost layer must be provided in order to prevent image defects due to poor charging and contamination of the photoreceptor. As a result, a multilayer structure is formed, which is economically disadvantageous.
Further, since the electric characteristics of the conductive elastic layer are obtained by the contact between the mixed conductive powders, there is a problem that uneven charging easily occurs due to the nonuniformity of the electric characteristics.

On the other hand, as a conductive roll which solves such a problem, an elastic layer made of an electrically medium resistance material in which conductive particles are not dispersed is provided on the surface of a conductive cored bar. There are known structures having a surface layer made of a non-adhesive substance having higher non-adhesiveness than the above substances (JP-A-6-266206 and JP-A-7-1601).
55 publication). Here, as the electric medium resistance substance, epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer, or epichlorohydrin-ethylene oxide binary copolymer alone or a mixture thereof epichlorohydrin rubber (10 ⁷ to 1) is used.
0 ¹⁰ Ω · cm), and the non-adhesive substance is a fluorine-containing cross-linked copolymer obtained by cross-linking a fluorine-containing copolymer having fluoro olefin and vinyl ether having a hydroxyl group as a constituent with isocyanate. Listed.

[0007]

However, when a surface layer such as a fluorine-containing cross-linked copolymer is provided on the elastic body mainly composed of epichlorohydrin rubber as described above, electric characteristics are improved as compared with the case where the surface layer is not provided. There is a problem that the environment dependency of is significantly increased. On the other hand, when the surface layer is not provided, problems such as organic photoreceptor (OPC) contamination occur.

Therefore, the present invention has been made in view of such circumstances.
An object of the present invention is to provide a conductive roll having an elastic layer mainly composed of epichlorohydrin rubber, which is free from OPC contamination and has a small environmental dependence of electric characteristics.

[0009]

The present invention for solving the above-mentioned problems provides a conductive roll having, on the surface of a core metal, an elastic layer made of rubber mainly containing a copolymer of epichlorohydrin and ethylene oxide, The electrically conductive roll is characterized in that the elastic layer contains an ionic conductive agent and the surface of the elastic layer is subjected to a curing treatment.

In the conductive roll of the present invention, an elastic layer made of rubber mainly containing a copolymer of epichlorohydrin and ethylene oxide is directly provided on the core bar without using an elastic rubber layer containing conductive powder. Since it is a structure, the electrical characteristics are uniform, and since the elastic layer made of rubber mainly composed of a copolymer of epichlorohydrin and ethylene oxide contains an ionic conductor and is subjected to a surface hardening treatment, The environmental characteristics of electrical characteristics are low, and there is no risk of contaminating the photoconductor.

In the present invention, the epichlorohydrin and ethylene oxide copolymer generally means that the epichlorohydrin / ethylene oxide molar ratio is 65/3.
Electric resistance of 10 ⁷ to 10 ¹⁰ Ω at about 5 to 40/60
The term "cm" means that it is mainly used, or that it can be used alone or in the range in which an accessory component is added within a range not impairing the effects of the present invention.

In the present invention, an ionic conductive agent is added to the rubber component containing such a copolymer as a main component. In the present invention, an ionic conductive agent is added to an elastic layer made of a rubber mainly composed of a copolymer of epichlorohydrin and ethylene oxide to prevent an increase in environmental dependency of electric properties due to surface hardening treatment. Is.

Here, as the ionic conductive agent, for example,
Examples thereof include alkali metal salts such as Li, Na and K, acetates, sulfates and the like. Further, the addition amount of the ion conductive agent may be set within a range in which the effect of the present invention is exhibited, and for example, 0.001 to 3 parts by weight per 100 parts by weight of the rubber component.
Use about 0 parts by weight.

In the elastic body of the present invention, other than the ionic conductive agent, a vulcanizing agent and other fillers may be appropriately used as long as the effects of the present invention are not impaired.

The hardness of the elastic layer of the present invention is JIS
It is about 35 to 45 ° on the A scale.

The electric resistance value of the elastic layer thus formed is, for example, 10 ⁵ to 10 ⁸ Ω · cm. The surface of this elastic body is hardened.

Here, the curing treatment in the present invention is carried out, for example, by immersing the elastic layer in a treatment solution containing an isocyanate-containing compound and heating it, and a curing treatment layer having the effect of the present invention is obtained. Anything will do. The hardening layer thus obtained preferably has a high hardness. For example, when the hardness is about 70 ° or more on the JIS A scale, the OPC contamination prevention effect becomes more remarkable.

The treatment solution containing an isocyanate-containing compound used in the present invention is a solution obtained by dissolving an isocyanate-containing compound in an organic solvent, a solution obtained by dissolving an isocyanate-containing compound and a polyol in an organic solvent, and a solution generally used for those solutions. Examples include a solution to which an auxiliary agent or the like commonly used in the urethane forming reaction is added.

In the present invention, the isocyanate-containing compound is
An isocyanate compound, a silane compound having an isocyanate group, and a dimethylsiloxane compound having an isocyanate group. Examples of the isocyanate compound include diphenylmethane diisocyanate, tolylene diisocyanate, naphthalene diisocyanate, tolidine diisocyanate, paraphenylene diisocyanate, isophorone diisocyanate, and prepolymers or modified products thereof. Examples of the polyol include polyester polyol, polyether polyol, polyester polycarbonate polyol and the like. Also,
As these isocyanate compounds or polyols, those having a siloxane bond can be used. Examples of the auxiliary agent used in the urethane forming reaction include chain extenders or cross-linking agents such as glycols, hexanetriol, trimethylolpropane, amines and the like.

As the organic solvent for dissolving these compounds, it is preferable to use an aprotic polar solvent, and it is particularly preferable to use ethyl acetate, dimethylformamide or a mixture thereof. The amount of these organic solvents is such that the viscosity of the treatment solution for carrying out the curing treatment of the present invention is 1
0-500c. p. Is adjusted so that

The hardening treatment layer of the present invention is formed with a thickness of several μm to several tens μm from the surface of the elastic layer. Further, the formation of such a cured layer is not limited to that described above. Further, the conductive roll of the present invention having such a cured layer is useful for a charging roll and a roll closely related to OPC such as a transfer roll.

[0022]

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 1 0.3 part by weight of lithium perchlorate chlorate, 5 parts by weight of lead oxide (PbO), and 100% by weight of epichlorohydrin rubber (Epichromer CG-102; manufactured by Daiso Co., Ltd.) were used as a vulcanizing agent. 2 parts by weight of 2-mercaptoimidazoline (Axel-22) was mixed with a roll mixer, press-formed on the surface of a metal shaft having a diameter of 6 mm, and polished to a diameter of 12 mm to form an elastic layer.

Next, a 10% ethyl acetate solution of isocyanate (MDI; Dainippon Ink and Chemicals, Inc.) was prepared as a curing treatment liquid. After soaking the elastic layer in this treatment solution for 10 seconds, the ethyl acetate was dried at room temperature, and then 120
The conductive roll of Example 1 was obtained by heating for 1 hour at 0 ° C. to complete the curing reaction of the isocyanate impregnated on the surface of the elastic layer.

Example 2 As a curing treatment liquid, a silane compound ((CH ₃ ) ₃ SiNC having an isocyanate group was used.
O; manufactured by Toray Dow Corning Co., Ltd.) was prepared, and the elastic layer formed on the metal shaft was immersed for 10 seconds in the same manner as in Example 1. Then 1 at 120 ℃
The conductive roll of Example 2 was heated for a period of time.

Comparative Example 1 A lithium perchlorate-containing epichlorohydrin rubber roll (rubber roll of Comparative Example 1) was molded in the same manner as in Example 1 except that the surface hardening treatment was not performed.

Comparative Example 2 Polytetramethylene glycol having a molecular weight of 3000 (GP-3000; manufactured by Sanyo Kasei Co., Ltd.)
0.3 parts by weight of lithium perchlorate was added to 100 parts by weight, and the mixture was heated and stirred at 100 ° C. to be completely dissolved. Then, the liquid polymer is added to an isocyanate (Coronate H).
(X; made by Nippon Polyurethane Co., Ltd.) 15 parts by weight was added, and this was cast-formed so as to form an elastic layer on the surface of a metal shaft having a diameter of 6 mm. This elastic layer was subjected to polishing molding to obtain a rubber roll of Comparative Example 2.

Comparative Example 3 A rubber roll of Comparative Example 3 was prepared by forming a coating layer on the surface of the elastic layer of the rubber roll of Comparative Example 1 using a urethane coating (Neoretz R-940; manufactured by Kusumoto Kasei Co., Ltd.).

(Comparative Example 4) Epichlorohydrin rubber 10
Using 0 parts by weight, 5 parts by weight of zinc oxide, and 2 parts by weight of 2-mercaptoimidazoline, press molding was performed in the same manner as in Example 1 to obtain a rubber roll of Comparative Example 4.

Comparative Example 5 The surface of the rubber roll of Comparative Example 4 was subjected to a surface hardening treatment in the same manner as in Example 1 to obtain a rubber roll of Comparative Example 5.

(Test Example 1): Electric resistance value resistance meter Advantest R-8340 was used and the rubber rolls of the above-mentioned respective Examples and Comparative Examples were subjected to LL: 10 ° C.
30% RH; NN: 25 ° C., 55% RH; HH: 40
The electric resistance value of the roll was measured when the roll was held in each environment of ° C and 80% RH. The results are shown in Table 1.

(Test Example 2): OPC damage The rubber roller of each of the above Examples and Comparative Examples was pressure-bonded to the organic photoreceptor (OPC) with a pressing force of 500 g, and the temperature was 50 ° C.
The OPC surface after being kept in an environment of 90% RH for 10 days was observed under a microscope. The results are also shown in Table 1.

(Test Example 3): Image evaluation The rubber rolls of each of the above Examples and Comparative Examples were attached to the charged portion of a commercially available laser printer, and each roll was used as a charging roll. This printer was started, and an image was output under each of the LL and HH environments of Test Example 1. The results are also shown in Table 1.

[0034]

[Table 1]

As is clear from the results shown in Table 1, Example 1
The conductive rolls of Nos. 2 and 2 have small environmental dependence of electric resistance value, have good image evaluation in LL and NN environments, and have no OPC contamination.

[0036]

As described above, the conductive roll of the present invention is a conductive roll having an elastic layer mainly composed of epichlorohydrin rubber, which is free from OPC contamination and has a small environmental dependence of electrical characteristics. Is.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a schematic configuration of an electrophotographic copying machine to which a conductive roll of the present invention can be applied.

[Explanation of symbols]

11 photoconductor 12 charging roll 13 Original image exposure device 14 Developer 15 Transfer roll 16 Cleaning device 17 Eraser lamp

Claims (2)

(57) [Claims] 1. A conductive roll having, on a surface of a core metal, an elastic layer made of a rubber mainly containing a copolymer of epichlorohydrin and ethylene oxide, wherein the elastic layer contains an ionic conductive agent and A conductive roll having a layer surface that has been cured. 2. The conductive roll according to claim 1, wherein the curing treatment is performed by immersing the elastic layer in a treatment solution containing an isocyanate-containing compound and heating the same.