JP3362969B2 - Charging device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device such as an image forming device using a semiconductive polymer member used in an electrophotographic process. 2. Description of the Related Art In recent years, with the advance of electronic technology, a demand for a semiconductive member used in an electrophotographic process has been increased, and in particular, an elastic roller used in a charging process has attracted attention. It is necessary that the semiconductive member used in such applications not only has a predetermined electric resistance value and hardness, but also has sufficient mechanical strength against stress such as rotating while continuously applying pressure. It is. Conventionally, semiconductive members used in such applications include polymer oxides such as polymer elastomers and polymer foams, metal oxide powder, carbon black, lithium perchlorate and sodium perchlorate. Inorganic ionic substances such as inorganic ionic substances, cationic surfactants such as modified aliphatic dimethylethylammonium ethosulfate, organic ionic substances such as quaternary ammonium salts such as tetrabutylammonium borofluoride, and charge transfer complexes can be formed. A polymer member adjusted to a predetermined resistance value by mixing a conductive agent such as an electron accepting substance is used. [0004] Such members need to have low hardness in order to obtain high quality images. In order to reduce the hardness of the polymer member, a method of mixing foam into a foam body, a method of reducing the blending amount of carbon black or the like used as a reinforcing material, a method of changing to a grade having a low degree of reinforcement, oil, etc. Is used. However, simply changing the method of forming a foam body, reducing the amount of reinforcing material, or changing the type of reinforcing material will result in the breaking strength of the member.
Degree is lowered, this kind of members to be used by rotating in a state of normally applying a load of more than 500 g, the breaking strength of the member is broken during long-term use if the lower 2.2 kgf / cm ² In particular, when the pressure is 2 kgf / cm ² or less, the frequency of breakage of the member increases. Also,
The method of adding a plasticizer has a problem that the plasticizer bleeds during use for a long period of time and contaminates the photoreceptor. Accordingly, an object of the present invention is to solve the drawbacks of the conventional semiconductive polymer member and to provide a charging device for an image forming apparatus using a semiconductive polymer member having the above-mentioned various characteristics. . The inventors of the present invention have made intensive studies to achieve the above object, and as a result, have made a special method for producing a polyurethane foam, and added a conductive agent thereto. by imparting conductivity, fracture strength degree 2kg
f / cm ² or more, Asker C hardness of 50 ° or less, and electrical resistance of 1 × 10 ⁴ to 1 × 10 ¹² Ωcm. Invented the invention. Hereinafter, the present invention will be described in detail. The semiconductive polymer member according to the present invention is obtained by adding and mixing a conductivity imparting agent to a polyurethane foam, and has an electric resistance of 22 V and a relative humidity of 55% at a measurement voltage of 1000 V and a volume resistance of 1%. × 10 ⁴ to 1 × 10 ¹² Ωc
m, preferably 2 × 10 ^{7 to} 5 × 10 ¹¹ Ωcm,
Breaking strength degree 2 kgf / cm ² or more, preferably 2.2k
gf / cm ² or more and Asker C hardness of 50 ° or less, preferably 42 ° or less. Here, polyurethane foams include polyether polyols, polyester polyols, polybutadiene polyols, polyisoprene polyols, polyols obtained by addition-polymerizing polyethylene oxide or polypropylene oxide to glycerin, ethylene glycol,
Polyol components such as propanediol and butanediol are converted to liquid M such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), crude diphenylmethane diisocyanate (crude MDI) and uretonimine-modified diphenylmethane diisocyanate.
The object of the present invention is effectively achieved by including, as a constituent material, a material prepolymerized with an isocyanate such as DI or isophorone diisocyanate. As the chain extender, known polyols such as ethylene glycol, propanediol, and butanediol can be used, but polyols having a molecular weight of 500 or less, preferably 200 or less are particularly preferably used. The object of the present invention can be effectively achieved by using a mechanical floss method (a method of mixing bubbles by mechanical stirring) as a foaming method. The semiconductive polymer member of the present invention comprises the above-mentioned polymer substance as a base material and a conductivity-imparting agent added thereto. There are no restrictions on the conductive agent for imparting conductivity, but powders of metals and metal oxides, whiskers, fillers such as carbon black, and inorganic ionic substances such as lithium perchlorate, sodium perchlorate, and calcium perchlorate And / or lauryl trimethyl ammonium chloride,
Of cationic surfactants such as stearyltrimethylammonium chloride, octadecyltrimethylammonium chloride, dodecylammonium chloride, hexadecyltrimethylammonium chloride, modified aliphatic dimethylethylammonium ethosulfate, lauryl betaine, stearyl betaine, dimethylalkyl lauryl betaine Zwitterionic surfactants such as quaternary ammonium salts such as tetraethylammonium perchlorate, tetrabutylammonium perchlorate and tetrabutylammonium fluoride; and / or antistatic such as hydrophilic polyols and polyesters. Agent, tetracyanoethylene, tetracyanoquinodimethane, benzoquinone, chloranil, anthraquinone,
Electron accepting substances capable of forming a charge transfer complex such as anthracene, dichlorodicyanobenzoquinone, ferrocene, and phthalocyanine can be used, and these compounds are used for the purpose of improving the compatibility with the urethane foam as the base material. An electron-accepting substance capable of forming a derivative or a charge-transfer complex may be used in the form of a complex with an electron-donating substance such as tetrathiafulvalene or lithium. In addition, as long as the effect of the present invention is not impaired, a polymer polyol that is not prepolymerized may be used in combination, or a foaming agent such as water or chlorofluorocarbon may be used in combination. The above-mentioned member is not limited to a shape used for a charging device, but is usually used in the form of a roller having a metal core disposed at the center. Although there is no limitation on the method of forming the roller, a method of polishing with a grindstone or a method of obtaining a self-skinned foam or an elastomer by using a mold adapted to the shape of the roller is generally used. From the viewpoints of environmental safety, noise, image improvement, etc., it is also possible to provide one or more conductive, semiconductive or insulating various coating layers on the charging member of the present invention. . As these various coating layers, for example, nylon or the like is preferably used, and in particular, by forming a copolymer nylon containing 15% by weight or more of nylon 12,
It is possible to improve the charging environment safety. The melting point of this copolymerized nylon is preferably 120 ° C. or less, particularly 70 ° C.
To 120 ° C, particularly preferably 90 to 110 ° C. In this case, the volume specific resistivity of the coating is not limited, but is usually preferably 10 ⁶ to 10 ¹³ Ωcm. For the purpose of adjusting the volume resistivity, one or more metal oxide particles such as carbon black, tin oxide and titanium oxide can be blended. It is also preferable to form the coating layer with a resin layer containing a urethane-modified acrylic resin containing 5 to 70% by weight of an acrylic resin component, and the acrylic resin component having a glass transition temperature in the range of room temperature to 120 ° C. is preferably used. Can be In this case, the volume resistivity of the coating is not limited, but is preferably 10 ⁶ to 10 ¹³ Ωcm. For the purpose of adjusting the volume resistivity, one or more kinds of metal oxide particles such as carbon black, tin oxide and titanium oxide can be blended, and the urethane-modified acrylic resin contains 1 to 50% by weight of a silicone component. % Is also preferred. In addition, a particle size of 3 near the surface of the member to be charged.
Noise can be reduced by arranging particles of 5 to 100 μm. In this case, there is no limitation on the particles, and any of insulating or conductive particles is preferably used, and the insulating particles may be coated with a conductive coating or an elastic material. There is no limitation on the amount of the particles, but 3 parts per 100 parts by weight of the polymer capable of forming a coating film or an elastic material
~ 50 parts by weight are preferred. Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. The humidity is relative humidity and the hardness is Asker C
Hardness. [Example 1] 100 parts by weight of a polyether-based prepolymer prepared by prepolymerizing polyether polyol having a molecular weight of 5,000 by adding propylene oxide and ethylene oxide to glycerin with tolylene diisocyanate, 1,4-butanediol 6.55 parts by weight, silicone surfactant 2 parts by weight, dibutyltin dilaurate 0.5 part by weight.
01 parts by weight, and 0.015 parts by weight of a modified aliphatic dimethylethylammonium ethosulfate were mixed with a mixer.
The mixture was mechanically foamed, and a mixture thereof was used to prepare a self-skinned urethane foam charging roller having a diameter of 16.5 mm and a length of 215 mm, which was disposed around a metal shaft having a diameter of 6 mm. The hardness of the charging roller was 38 °. Next, the charging roller is incorporated in the image forming apparatus shown in FIG.
% Was measured in an environment of 1% at 1000V.
0 ⁸ Ω. When a grayscale, solid black, and solid white image was printed using a constant voltage power supply of -1700 V as a charging power supply, a good image was obtained. Further, by removing the metal shaft of the charging roller to create a ring-shaped test piece having a thickness of 4 mm, breaking strength of was a tensile test was 2.9kgf / cm ^2. Comparative Example 1 Glycerin was added with propylene oxide and ethylene oxide to have a molecular weight of 5000.
100 parts by weight of polyether polyol, 6.03 parts by weight of tolylene diisocyanate, 2 parts by weight of a silicone surfactant, 0.03 parts by weight of dibutyltin dilaurate, 0.015 parts by weight of modified aliphatic dimethylethylammonium ethosulfate Was mixed and mechanically foamed with a mixer, and a urethane foam charging roller with a self-skin having a diameter of 16.5 mm and a length of 215 mm, which was disposed around a metal shaft having a diameter of 6 mm, was prepared from the mixture. The hardness of the charging roller was 35 °. Next, the charging roller is incorporated in the image forming apparatus shown in FIG.
When the resistance was measured in a 5% environment,
× 10 ⁸ Ω. When a grayscale, solid black, and solid white image was printed using a constant voltage power supply of -1700 V as a charging power supply, a good image was obtained. Further, by removing the metal shaft of the charging roller to create a ring-shaped test piece having a thickness of 4 mm, breaking strength of <br/> was subjected to tensile test was 0.6 kgf / cm ^2. Comparative Example 2 Propylene oxide and ethylene oxide were added to glycerin to give a molecular weight of 5,000.
100 parts by weight of polyether polyol, 9.15 parts by weight of crude diphenylmethane diisocyanate, 2 parts by weight of a silicone surfactant, 0.003 parts by weight of dibutyltin dilaurate, 0.015 parts by weight of modified aliphatic dimethylethylammonium ethosulfate Was mixed and mechanically foamed with a mixer, and the mixture was used to place a metal shaft having a diameter of 6 mm at the center and a diameter of 16.5 mm and a length of 215 mm.
A self-skinning urethane foam charging roller having a thickness of mm was prepared. The hardness of the charging roller was 38 °. Next, the charging roller is incorporated in the image forming apparatus shown in FIG.
When the resistance was measured in a 5% environment,
× 10 ⁸ Ω. When a grayscale, solid black, and solid white image was printed using a constant voltage power supply of -1700 V as a charging power supply, a good image was obtained. Further, by removing the metal shaft of the charging roller to create a ring-shaped test piece having a thickness of 4 mm, breaking strength of <br/> was subjected to tensile test was 0.2 kgf / cm ^2. Comparative Example 3 Propylene oxide and ethylene oxide were added to glycerin to give a molecular weight of 5,000.
100 parts by weight of a polyether prepolymer obtained by prepolymerizing the polyether polyol prepared with tolylene diisocyanate, 6.1 parts by weight of 1,4-butanediol, 0.5 part by weight of distilled water, 0.01 part of dibutyltin dilaurate
13. parts by weight, 0.03 parts by weight of triethylenediamine, and 0.015 parts by weight of a modified aliphatic dimethylethylammonium ethosulfate mixed with a mixer, and the resulting mixture is disposed around a metal shaft having a diameter of 6 mm.
A self-skinning urethane foam charging roller having a length of 5 mm and a length of 215 mm was prepared. Charging roller hardness is 37 °
Met. Next, the charging roller is incorporated in the image forming apparatus shown in FIG.
% Was measured in an environment of 1% at 1000V.
0 ⁸ Ω. When a grayscale, solid black, and solid white image was printed using a constant voltage power supply of -1700 V as a charging power supply, a good image was obtained. Further, by removing the metal shaft of the charging roller to create a ring-shaped test piece having a thickness of 4 mm, breaking strength of was a tensile test was 0.9 kgf / cm ^2. [Comparative Example 4] Propylene oxide and ethylene oxide were added to glycerin to give a molecular weight of 5,000.
100 parts by weight of polyether polyol, 15.5 parts by weight of tolylene diisocyanate, 6.55 parts by weight of 1,4-butanediol, 2 parts by weight of a silicone surfactant, 0.01 part by weight of dibutyltin dilaurate, modified fat Mixing and mechanical foaming of 0.015 parts by weight of trimethyl dimethylethylammonium ethosulfate with a mixer, and using the mixture, a urethane foam charging roller having a diameter of 16.5 mm and a length of 215 mm, which is disposed around a metal shaft having a diameter of 6 mm. Created. The hardness of the charging roller was 42 °. Next, the charging roller is incorporated in the image forming apparatus shown in FIG.
When the resistance was measured in a 5% environment,
× 10 ⁸ Ω. Using a constant voltage power supply of -1700 V as a charging power supply, when a gray scale, black solid, or white solid image was printed, a good image was obtained. Further, by removing the metal shaft of the charging roller to create a ring-shaped test piece having a thickness of 4 mm, breaking strength of <br/> was subjected to tensile test was 1.8 kgf / cm ^2. The semiconductive polymer member of the present invention has a low hardness, a high breaking strength and a predetermined resistance value, and is used for a charging roller in an electrophotographic process. Then, a suitable image can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of an example showing a structure of an image forming apparatus.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-200921 (JP, A) JP-A-6-16301 (JP, A) JP-A-5-318497 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G03G 15/02 G03G 15/16 103

Claims (1)

(57) [Claims] 1. The breaking strength is 2 kgf / cm ² or more, the Asker-C hardness is 50 ° or less, and the electric resistance is 1 × 10 ⁴ to 1 × 10 ¹² Ωcm. a charging device of an image forming apparatus using the including semiconductive polymer members of polyurethane foam as the material is, the polyurethane-off
From a polyol component prepolymerized
Included and foamed by mechanical floss method
A charging device of an image forming apparatus using a semi-conductive polymer member, wherein.