JPH0850397A - Electrostatic charge device - Google Patents

Abstract

PURPOSE:To increase the changing rate of electric resistance between conditions of low temp. and low humidity and high temp. and high humidity by adding an electron accepting material which can produce charge-transfer complexes to a polymer material such as polymer elastomers and polymer foams of polyurethane or the like. CONSTITUTION:As the electron accepting material to produce charge-transfer complexes, tetracyanoethylene or the like is used, and further, its derivatives are preferably used to improve compatibility with a polymer material as the matrix. One of these in a single state or combination of two or more kinds can be used. The amt. of the electron accepting material to form charge-transfer complexes to be added is 0.001 to 20 pts.wt., preferably 0.01 to 1 pts.wt. based on 100 pts.wt. of the polymer material. The semiconductive polymer member is stable for changes in the electric resistance with respect to applied voltage. As for the dependency of the electric resistance on the measured voltage, the electric resistance at 10V measured voltage is twice or less as high as the electric resistance at 5000V measured voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device for an image forming apparatus.

[0002]

2. Description of the Related Art With the progress of electrophotographic technology, there is an increasing demand for a semiconductive member used in an electrophotographic process, and in particular, an elastic roller used in a charging process has attracted attention. ing. The semi-conductive member used for such an application has not only a predetermined electric resistance value but also a small variation in the electric resistance position, little dependence on the applied voltage of the electric resistance, and low temperature low humidity and high temperature high humidity. It is necessary that the fluctuation range of the electric resistance is small and the fluctuation range of the electric resistance when continuously energized is small.

Conventionally, as a semiconductive member used for such an application, a powder of metal or metal oxide or whiskers is mixed in a polymer substance such as a polymer elastomer or polymer foam, or carbon black or the like. A polymer member adjusted to a predetermined resistance value by mixing a filler is used, but this type of polymer member has a large variation in the position of the electric resistance and a large dependence of the electric resistance on the measured voltage. There was a problem.

Further, inorganic ionic substances such as lithium perchlorate, sodium perchlorate and calcium perchlorate, and / or
Or cations such as lauryl trimethyl ammonium chloride, stearyl trimethyl ammonium chloride, octadecyl trimethyl ammonium chloride, dodecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride, modified aliphatic dimethyl dimethyl ethyl ammonium ethosulfate Surfactants, zwitterionic surfactants such as lauryl betaine, stearyl betaine and dimethyl alkyllauryl betaine, quaternary ammonium salts such as tetraethylammonium perchlorate, tetrabutylammonium perchlorate and tetrabutylammonium bromide. Conductive agents consisting of organic ionic substances such as and / or antistatic agents such as hydrophilic polyethers and polyesters are used as polymeric elastomers. Polymeric materials such as polymer foams and polymer foams that have been adjusted to a prescribed resistance value are also known, but this type of polymeric material has a low electrical resistance at low temperature and low humidity and high temperature and high humidity. There was a problem that the fluctuation range was large.

Therefore, the present invention solves the drawbacks of the conventional semiconductive polymer member, and provides a charging member having the above-mentioned various characteristics and a charging device equipped with a power source suitable for the member. To aim.

[0006]

Means and Action for Solving the Problems The present inventors have
As a result of intensive studies to achieve the above object, as a result of adding an electron-accepting substance capable of forming a charge transfer complex to a polymer substance such as a polymer elastomer representative of polyurethane or a polymer foam, electric resistance Has a temperature of 15 ~
Measured voltage 1 at 32.5 ° C and 10-85% relative humidity
Volume resistance in the range of 0 to 5000 V is 1 × 10 ⁵ Ω · cm or more and 1 × 10 ¹⁰ Ω · cm or less, and there is little variation in the position of the electrical resistance, and the variation of the electrical resistance during low temperature and low humidity and high temperature and high humidity. It was discovered that a semi-conductive polymer member with a small width can be obtained for the first time, and that this semi-conductive polymer member is effective as a charging member such as a charging roll, and as a power source for driving this member, environmental conditions and The present invention has been accomplished by finding that a constant current power supply and a device capable of controlling a power supply condition by detecting a load resistance are effective.

Therefore, the present invention comprises (1) a semiconductive polymer member which can be applied with a bias voltage, which is obtained by adding an electron accepting substance capable of forming a charge transfer complex to a polymer substance as a base material. Charging member included as an element, and environmental conditions and / or
Or a charging device characterized by comprising a power supply for a charging device for detecting a load resistance and controlling power supply conditions, (2) an electron accepting substance capable of forming a charge transfer complex on a polymer material as a base material There is provided a charging device comprising: a charging member including, as a constituent element, a semiconductive polymer member capable of applying a bias voltage obtained by adding the above-mentioned compound, and a power source for a constant current charging device.

The present invention will be described in more detail below.
The semiconductive polymer member according to the present invention is obtained by adding and mixing a conductivity-imparting agent to a polymer substance, and its electric resistance is at a temperature of 15 to 32.5 ° C. and a relative humidity of 10 to 85%. Volume resistance 1 × 1 in the range of measurement voltage 10-5000V
0 ⁵ to 1 × 10 ¹⁰ Ω · cm, preferably 2 × 10 ^{7 to} 5 ×
10 ⁹ Ω · cm, the positional variation of the electric resistance is ± 20% or less, preferably ± 10% or less, and the electric resistance at low temperature and low humidity (15 ° C., 10%) is high temperature and high humidity (32 It is within 50 times, preferably within 40 times, the electrical resistance of 0.5 ° C., 85%).

Examples of the polymer substance include resins such as polyethylene, polypropylene and polyurethane, natural rubber, butadiene rubber, styrene butadiene rubber, isoprene rubber, synthetic rubber such as EPDM and NBR, and foams thereof. Polymer foams and elastomers are preferably used in the present invention, and urethane foams and urethane elastomers are particularly preferable in the present invention.

The foaming method for obtaining the polymer foam is not limited, but a method of foaming a rubber member with a foaming agent, a method of a urethane member with a foaming agent or a method of mixing air bubbles by mechanical stirring. Is preferably used. The method for producing the rubber-based member is not limited, but after mixing the rubber material with a conductivity-imparting agent, a crosslinking agent such as sulfur or peroxide, a reinforcing agent such as carbon black, an antioxidant, a crosslinking reaction accelerator, etc. The method of heat curing is preferably used. The method for producing the urethane-based member is not limited, but polyether polyol, polyester polyol, polybutadiene polyol, polyisoprene polyol, polyol obtained by addition-polymerizing polyethylene oxide or polypropylene oxide to glycerin, ethylene glycol, propanediol, butanediol, etc. Chain extender and liquid MD such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), crude diphenylmethane diisocyanate (crude MDI) and uretonimine modified diphenylmethane diisocyanate
A method in which a curing agent such as I or isophorone diisocyanate is mixed with the above-mentioned conductivity-imparting agent, a reinforcing agent such as carbon black, a crosslinking reaction catalyst, and the like and then heat curing is preferably used.

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. In the present invention, the charge transfer complex is used as the conductivity-imparting agent. An electron-accepting substance capable of forming a charge transfer complex is suitable, and the addition of the electron-accepting substance capable of forming a charge transfer complex effectively achieves the object of the present invention.

Here, examples of the electron accepting substance capable of forming a charge transfer complex include tetracyanoethylene, tetracyanoquinodimethane, benzoquinone, chloranil, anthraquinone, anthracene, dichlorodicyanobenzoquinone, ferrocene and phthalocyanine. Derivatives of these compounds are also preferably used for the purpose of improving the compatibility with the base polymer material, and the like.
The seeds may be used alone or in combination of two or more. Of these, tetracyanoquinodimethane and tetracyanoethylene are preferable. Further, the electron-accepting substance capable of forming the charge transfer complex may be used in the form of a complex with an electron-donating substance such as tetrathiafulvalene or lithium.

The addition amount of the electron accepting substance capable of forming the charge transfer complex is 0.001 to 20 parts by weight, preferably 0.01 to 1 part by weight, based on 100 parts by weight of the polymer substance. Is preferable from the viewpoint of achieving the object of the present invention.

In addition to the electron-accepting substance capable of forming the above charge-transfer complex, a known conductive filler such as carbon black, metal powder or metal oxide may be used in combination so long as the effect of the present invention is not impaired. Well, ionic conductive agents consisting of inorganic ionic substances such as lithium perchlorate and organic ionic substances such as quaternary ammonium salts, cationic surfactants, anionic surfactants, amphoteric ionic surfactants such as various betaines. You may use together an agent and a nonionic antistatic agent, such as hydrophilic polyether and polyester. Further, in the urethane-based member, it is also preferable that the polyol component is prepolymerized with isocyanate in advance.

Further, the semiconductive polymer member of the present invention has a stable electric resistance variation with respect to an applied voltage, preferably 2 times or less, more preferably 1.2 times or less. To be That is, the electrical resistance of the polymer member to which the conductivity is imparted by the filler such as carbon black, metal powder, and metal oxide varies with the applied voltage. For example, when the applied voltage is 10V, the applied resistance is 5000V.
The value of the electric resistance of the semiconductive polymer member of the present invention depends on the measured voltage when the electric resistance at a measured voltage of 10 V is less than twice the electric resistance at a measured voltage of 5000 V. is there.

The charging member used in the charging device of the present invention is formed by using the above-mentioned semi-conductive polymer member, and the shape used for this charging member is not limited, but it is usually in the form of a roller with a cored bar disposed in the center. Used. There is no limitation on the method of forming the roller shape, but a method of polishing with a grindstone or a method of obtaining a foam with self-skin or an elastomer by using a mold adapted to the shape of the roller is usually used.

Further, from the viewpoint of environmental stability, noise, image improvement, etc., it is possible to provide one or more various conductive, semi-conductive or insulating various coating layers on the charging member of the present invention. . For these various coating layers, for example, nylon or the like is preferably used, and particularly, nylon 12 is 15% by weight.
By forming the copolymerized nylon contained above, it is possible to improve the stability of the charging environment. The melting point of this copolymer nylon is preferably 120 ° C. or lower, and particularly 70 to
It is preferably 120 ° C, particularly 90 to 110 ° C. In this case, the volume resistivity of the coating film is not limited, but it is usually preferably 10 ⁶ to 10 ¹³ Ω · cm. For the purpose of adjusting this volume resistivity, one or more kinds of metal oxide particles such as carbon black, tin oxide and titanium oxide can be blended.

The acrylic resin component is 5 to 70% by weight.
It is also preferable to form the coating layer with a resin layer containing the urethane-modified acrylic resin contained therein, and one having a glass transition temperature of the acrylic resin component in the range of room temperature to 80 ° C. is preferably used. Although the volume resistivity of the coating in this case is not limited,
Usually, it is preferable to set 10 ⁶ to 10 ¹³ Ω · cm. 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 silicone component is added to the urethane-modified acrylic resin in an amount of 1 to 50% by weight. Is also preferable.

Further, the particle size of 35 to 35 is provided in the vicinity of the surface to be charged.
Noise can be reduced by disposing particles of 100 μm. There is no limitation on the particles in this case, any of the particles having an insulating property or conductivity is preferably used,
The insulating particles may be coated with a conductive coating film or an elastic material. There is no limitation on the amount of the particles to be blended, but it is 3 to 50 relative to 100 parts by weight of the polymer capable of forming a coating film or elastic material.
Parts by weight are preferred.

The charging device of the present invention is different from the charging device manufactured by using a member having semiconductivity imparted by a conventionally used inorganic ionic conductive agent, in comparison with the charging device at high temperature and high humidity and at low temperature and low humidity. Although the variation of the resistance is small, the variation of the electrical resistance is not suppressed as much as that of the charging device manufactured by using the member to which the semiconductivity is imparted by the carbon black or the metal oxide. And / or a charging device power supply for detecting load resistance and controlling power supply conditions is used. Specifically, when the load resistance is large and / or the load resistance is large, the power supply voltage is controlled to be high under environmental conditions such as low temperature and low humidity, and when the load resistance is small and / or the high temperature when the load resistance is small. Under environmental conditions such as high humidity, it is preferable to control the power supply voltage to be low. As an example of the voltage control range in this case, the power supply voltage at low temperature and low humidity and / or when the load resistance is large is 2 to 100 times, preferably 5 times the power supply voltage at high temperature and high humidity and / or when the load resistance is small. It can be up to 30 times.

A constant current power supply device is used as another power supply device suitable for the charging device of the present invention. According to the research conducted by the present inventors, the charging device of the present invention can obtain a good image when a constant current is applied regardless of load resistance and environmental conditions. It is considered that this is because the charge amount is determined by the current.

The power source of the charging device is presumed to be a DC power source, but it is also preferable to superimpose an alternating current such as a sine wave, a sawtooth wave, or a rectangular wave on this power source. It is also preferable to use a DC power supply.

A preferred range of the power supply capacity of the charging device of the present invention is a voltage of 10 kV or less, preferably 4 kV or less, and a current of 5 mA or less, preferably 1 mA or less.

[0024]

The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. The humidity is relative humidity.

Example 1 A molecular weight of 5,000 was obtained by adding propylene oxide and ethylene oxide to glycerin.
100 parts by weight of polyether polyol, 1,4-
6.56 parts by weight of butanediol, 22 parts by weight of tolylene diisocyanate, 2 parts by weight of silicone-based surfactant, 0.01 part by weight of dibutyltin dilaurate, 0.03 part by weight of tetracyanoquinodimethane are mixed in a mixer, and A self-skinning urethane foam charging roller having a diameter of 16.5 mm and a length of 215 mm was prepared by coating a metal shaft having a diameter of 6 mm with the mixture.

Next, the charging roller was placed on a copper plate having a thickness of 2 mm, and the electrical resistance between the core metal and the copper plate was measured four times while rotating the roller while pressing both ends of the roller with a force of 500 g. did. The temperature and humidity at the time of measurement are 15 each
C was 10%. The electrical resistance was 4.1 × 10 ⁸ Ω when the applied voltage was 1000 V, and 3.9 × 10 ⁸ Ω when the applied voltage was 4000 V, as an average value of four times. The position variation of the electric resistance was within ± 5% of the average value. When the temperature and humidity at measurement are 32.5 ° C and 85% respectively, the applied voltage is 1
Electric resistance at 000V is an average of 4 times 3.2 × 10 ⁷ Ω
Met.

Further, the charging roller was incorporated in the image forming apparatus shown in FIG. Here, in FIG. 1, 1 is a photoconductor, 2 is a charging roller, 3 is a developing roller, 4 is a transfer roller, 5 is a transfer material (plain paper), and the photoconductor 1 is subjected to laser beam exposure 6. In this case, the power source connected to the transfer roller 2 is -1700 V in an environment where the temperature and humidity are 15 ° C and 10%, and -14 in the environment where 32.5 ° C and 85% are used.
It was set to be 0V. Temperature and humidity are 15 ℃,
When a grayscale image, a black solid image, and a white solid image were printed in an environment of 10%, a good image was obtained. Further temperature,
When a grayscale image, a black solid image, and a solid white image were printed in an environment where the humidity was 32.5 ° C. and the humidity was 85%, good images were obtained.

Comparative Example 1 0.03 parts by weight of a 33% solution of sodium perchlorate (NaClO ₄ , molecular weight 122.5) in diethylene glycol monomethyl ester was used instead of 0.03 parts by weight of tetracyanoquinodimethane as a conductive agent. An experiment was conducted in the same manner as in Example 1 except that the parts were used. When the temperature and humidity at the time of measurement are 15 ° C. and 10%, respectively, and the electric resistance is an average value of four times and the applied voltage is 1000 V, 9.5 × 10
It was 9.5 × 10 ⁸ Ω at ⁸ Ω and 4000V. The position variation of the electric resistance was within ± 5% of the average value. Also, the temperature and humidity at the time of measurement are 32.5 ° C and 8 respectively.
At 5%, the applied voltage was 1000 V and the electrical resistance was 2.5 × 10 ⁶ Ω as an average of four times. Compared to the examples, the urethane foam of this comparative example has a large variation in electric resistance at low temperature and low humidity and at high temperature and high humidity.

Grayscale, black solid, and white solid images were printed in the same manner as in Example 1. Even in the environments of temperature and humidity of 32.5 ° C. and 85%, respectively, the temperature and humidity were 1 respectively.
Good images were not obtained even in an environment of 5 ° C and 10%.

[Second Embodiment] In place of the power source of the first embodiment,
An experiment was conducted in the same manner as in Example 1 except that a constant current power source of 4.5 μA (voltage capacity 2 kV) was used. Temperature and humidity are 3 each
Even in an environment of 2.5 ° C and 85%, temperature and humidity are 15 each
Good images were obtained even in the environment of 10 ° C.

Comparative Example 2 An experiment was conducted in the same manner as in Example 1 except that the conductive agent blended was changed to 0.03 part by weight of tetracyanoquinodimethane and 1.5 parts by weight of acetylene black was used. The temperature and humidity at the time of measurement are 15 ℃ and 10%,
The electrical resistance was 1.3 × 10 ⁸ Ω when the applied voltage was 1000 V and 3.5 × 10 ⁷ Ω when the applied voltage was 4000 V, as an average value of four times. The position variation of the electric resistance is ± 50 with respect to the average value.
% Or more. Also, the temperature and humidity during measurement are 3 each
At 2.5 ° C. and 85%, the electric resistance was 4.5 × 10 ⁸ Ω at an applied voltage of 1000 V in an average of four times.

When a grayscale image, a black solid image and a white solid image were printed in an environment where the temperature and humidity were 15 ° C. and 10%, respectively, good images could not be obtained with the gray scale.
It is considered that this is because the variation in the resistance position is large.

[Comparative Example 3] Instead of the power source of Comparative Example 1-
An experiment was conducted in the same manner as in Comparative Example 1 except that a constant current power source of 4.5 μA (voltage capacity 2 kV) was used. 1 for temperature and 1 for humidity
Good images were not obtained in an environment of 5 ° C. and 10%. It is considered that this is because the power supply voltage was insufficient to generate a current of −4.5 μA.

[0034]

By using the charging device of the present invention in an image forming apparatus, a suitable image can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of an image forming apparatus incorporating a charging roller of Examples and Comparative Examples.

[Explanation of symbols]

 1 photoconductor 2 charging roller 3 developing roller 4 transfer roller 5 transfer material 6 laser beam

Claims (2)

[Claims] 1. A charging member comprising, as a constituent, a semiconductive polymer member capable of applying a bias voltage formed by using a polymer substance as a base material and adding an electron accepting substance capable of forming a charge transfer complex thereto. A charging device, comprising: a power supply for a charging device that detects environmental conditions and / or load resistance to control power supply conditions. 2. A charging member comprising, as a constituent, a semiconductive polymer member capable of applying a bias voltage, which is formed by adding an electron accepting substance capable of forming a charge transfer complex to a polymer as a base material. A charging device comprising: a power supply for a constant current charging device.