JPH07118578A - Electroconductive coating and electroconductive member produced using the same - Google Patents

Abstract

PURPOSE:To provide an electroconductive coating which is little in moisture absorption and dependence of electric resistance on surroundings, and is improved in dielectric strength and dimensional stability, by containing an electroconductive material and a specific binder. CONSTITUTION:A polyol component mainly comprising polytetramethylene oxide is reacted with an isocyanate component to obtain a binder comprising a polyurethane having a no.-average mol.wt. of 5,000 to 200,000 and a wt.- average mol.wt. of 5,000 to 200,000. 100 pts.wt. binder is blended with 0.1-60 pts.wt. electroconductive material, and, if necessary, a leveling agent, a dispersing assistant, a defoaming agent, etc., to obtain an electroconductive coating. A base material such as an electroconductive rubber is coated with the electroconductive coating to obtain an electroconductive member having a thickness of 1 to 1,000mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for coating electronic components, particularly for coating electronic components used at high voltage, and a conductive coating which gives a conductive film having high withstand voltage, and The present invention relates to a conductive member on which such a conductive film is formed.

[0002]

2. Description of the Related Art Conventionally, in an electronic device such as a copying machine or a printer, an elastic body such as rubber or resin containing a conductive substance is used in the process of charging, developing, transferring, fixing and the like. Conductive members such as rollers and blades are used. These conductive members are often used in the state where a high voltage of several kV is applied, and are used in a so-called medium resistance region of about 10 ⁵ to 10 ¹² Ω · cm. It is extremely difficult to accurately and reproducibly control the electric resistance of the rubber or the like in a region.

Therefore, as the base material for forming the conductive member, a rubber having a low electric resistance and easy control of the electric resistance is used, and a conductive paint prepared by blending polyurethane or the like on the surface of the rubber is used. The electrical resistance is often adjusted by forming a coating film having a high electrical resistance on the surface of rubber. In this case, because the electric resistance of the coating film formed of the conductive paint is high,
Most of the high voltage applied to the conductive member will be applied to the thin coating film, and if the withstand voltage of the coating film is not sufficient, the coating film will be destroyed, so the coating film must be thickened. Therefore, it is necessary to repeat coating and drying several times, which causes a rise in the processing cost of the conductive member. In addition, since the obtained conductive member has a thick polyurethane film, the hardness of the conductive member becomes high, which causes a problem that sufficient elasticity cannot be obtained.

The present invention has been made to solve the above problems, and it is an object of the present invention to provide a conductive coating material which gives a conductive film having a high withstand voltage and a conductive member having such a conductive film formed thereon. And

[0005]

Means and Actions for Solving the Problems As a result of intensive studies for achieving the above-mentioned object, the present inventor has found that a conductive material prepared by blending polyurethane as a binder with a polyol component mainly composed of polytetramethylene oxide as a binder. Film capable of forming a conductive film having a high withstand voltage, and, when a conductive film using this binder is formed on a substrate, a film having a sufficient withstand voltage even if the film is thin Therefore, it was found that a conductive member having sufficient elasticity can be obtained.

That is, there are polyester-based and polyether-based polyurethanes. In the case of polyester-based polyurethanes, the environmental dependence is small but the water resistance is poor,
Moreover, in a conductive coating material in which these are used as a binder in a conductive material, the formed film has a low withstand voltage. On the other hand, in the case of a conductive coating material in which polytetramethylene oxide-based polyurethane is mixed with a conductive material, in order to obtain a conductive film having a particularly high withstand voltage, the thickness of the conductive film as an electric resistance adjusting film is Since it can be made thin, a conductive member having a low hardness can be obtained, and its hygroscopicity is smaller than that of a general polyether polyurethane, so that the environmental dependence of the electric resistance is small and the electric conductivity is small. The present inventors have found that it is also preferable from the viewpoint of dimensional stability of the elastic film, and have completed the present invention.

Therefore, the present invention provides a conductive coating material prepared by blending a conductive material with polyurethane having a polyol component mainly composed of polytetramethylene oxide as a binder, and a conductive film having the polyurethane as a binder as a base material. A conductive member formed is provided.

The present invention will be described in more detail below. The conductive coating material of the present invention comprises a conductive material containing polyurethane as a binder whose polyol component is mainly composed of polytetramethylene oxide.

As the conductive material, tin oxide, aluminum, indium oxide, titanium oxide, zinc oxide, carbon black, or conductive particles such as a conductive polymer, NaClO ₄ , LiClO ₄ , Ca (ClO ₄ ) ₂ And ionic substances such as perchlorates such as NaSCN, KSCN, etc., ammonium salts such as NH ₄ , NR _{4 and the} like. Among them, carbon black is particularly preferable, and carbon black is particularly preferable. Specific examples thereof include acetylene black, Ketchen black, channel black, furnace black, and modified carbon such as oxidized carbon. Of these, HCF carbon for color is particularly preferably used.

The binder to be blended with the conductive material is polyurethane whose polyol component is mainly composed of polytetramethylene oxide, but a binder obtained by copolymerizing some other polyalkylene oxide-based polyol can also be used. In this case, specific examples of the alkylene oxide include ethylene oxide and propylene oxide, and the copolymerization amount of these is preferably 40% by weight or less, and particularly preferably 30% by weight or less based on the entire polyol component. preferable.

As the polyol component, a polyester-based or general polyether-based polyol may be mixed and used. In this case, it is preferable that the content of these polyols is 40% by weight or less based on the entire polyol component.
It is particularly preferably 30% by weight or less.

As the isocyanate component for forming the polyurethane, a usual isocyanate component can be used. For example, MD
I, TDI, IPDI, etc. can be used. Also,
Known catalysts and the like can be used.

The form of the above polyurethane is not particularly limited, and any of soluble polyurethane, thermoplastic polyurethane, one-component or two-component solution polyurethane, one-shot method or premer method polyurethane can be used. From the viewpoint of preparation of paint, solution polyurethane is preferable.

The molecular weight of this polyurethane is such that the number average molecular weight (Mn) in terms of polystyrene is 5,000 to 20,000.
The thing of 0 is preferable, and it is more preferable to use the thing of 10,000-100,000 especially. Similarly, the weight average molecular weight (Mw) is preferably from 5,000 to 200,000, and particularly preferably from 10,000 to 150,000.

The blending ratio of the polyurethane and the conductive material can be adjusted by the electric resistance of the conductive film to be obtained. The blending amount of the conductive material is about 0.1 to 60 parts by weight with respect to 100 parts by weight of polyurethane. It is preferable that

As the other components, additives such as a leveling agent, a dispersion aid and an antifoaming agent can be added to the conductive coating material of the present invention to the extent that the effects of the present invention are not impaired.

The method for preparing the electrically conductive coating material of the present invention is not particularly limited, and examples of the dispersion method include a sand mill, a ball mill, a roller mill and a red devil.
The order of addition may be either batch or premix, but it is preferable to adopt a method of premixing.

The method for producing the electroconductive member of the present invention is not particularly limited, but a method of applying the electroconductive coating material to a substrate such as electroconductive rubber or a polyurethane composed of polytetramethylene oxide. There is a method of integrally forming a conductive film on a base material such as a conductive rubber by melt-coating or extruding a thermoplastic resin composition containing the base material on a base material such as an electrically conductive rubber with an extruder or a doctor blade. in this case,
The thickness of the film is not particularly limited, but usually 1 to
It can be 1000 μm.

When the conductive coating material of the present invention is applied to a substrate, it is preferably dissolved in a solvent and used as the solvent. As the solvent, alcohols, ethers, esters, ketones, amides, hydrocarbons are used. It is also possible to use water, organic solvents such as halogenated hydrocarbons and the like, and specific examples of the organic solvent include toluene, xylene, methyl ethyl ketone and isopropyl alcohol. These may be used alone or in combination of two or more.

When the above polyurethane is used as a binder together with a conductive material in the form of a thermoplastic composition by melt coating or extrusion molding, the method for preparing this composition is not particularly limited, but the polyurethane and the conductive material are Can be prepared by kneading with a roll mill, kneader, extruder or the like, and if necessary,
Plasticizers, stabilizers, dispersion aids and other resins can be added.

The base material on which the conductive film is formed is not particularly limited, and a conductive base material such as conductive rubber can be used. Specific examples of the conductive rubber include natural rubber, butyl rubber, polyisoprene rubber, polybutadiene rubber, silicone rubber, styrene butadiene rubber, ethylene propylene rubber, polyurethane type, polyester type, polyamide type, polystyrene-diene type,
Conductive material such as thermoplastic rubber such as polyolefin
For example, a mixture of carbon black can be used.

The conductive member may have various shapes such as a roll shape, a plate shape, a block shape, a spherical shape, and a brush shape.

[0023]

EXAMPLES The present invention will be specifically described below by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Example 1 A solution polyurethane having a polytetramethylene oxide-based polyol component and isophorone diisocyanate as the isocyanate (molecular weight converted to polystyrene: Mn = 25600, Mw = 466).
00) is used as a binder, and methyl ethyl ketone, isopropyl alcohol, and toluene are used in a weight ratio of 2:
It was diluted with a mixed solvent of 1: 7 to prepare a solution having a resin concentration of 20% by weight. Next, HCF carbon for color (specific surface area: 260 m ² / g, oil absorption: 40 ml /
100 g) was dispersed in 8 parts and 12 parts of the above polyurethane by the red devil method and mixed to prepare a conductive paint.

By dipping this paint on a base material (thickness 3.0 mm) having a volume resistance of 10 ³ Ωcm by blending carbon with polybutadiene rubber, 100
A conductive member having a coating film having a thickness of μm was prepared, and the volume resistance and the withstand voltage were measured. The results are shown in Table 1.

[0026]

[Table 1]

Example 2 A solution type polyurethane in which the polyol component was composed of 75% of polytetramethylene oxide type and 25% of polyethylene oxide type and the isocyanate was methylenebisphenyl diisocyanate (the molecular weight was Mn = 60,000 in terms of polystyrene, Mw = 1
05000) was used as a binder, and this was diluted with a solvent in which toluene, N, N-dimethylformamide and methyl ethyl ketone were mixed at a weight ratio of 5: 2: 3 to prepare a solution having a resin concentration of 15.5% by weight. Next, HCF carbon for color (specific surface area: 260 m ² / g,
Oil absorption: 40 ml / 100 g) above polyurethane 10
10 parts and 18 parts with respect to 0 part were dispersed and mixed by a red devil method to prepare a conductive paint.

By dipping this coating material on a base material (thickness 3.0 mm) having a volume resistance of 10 ³ Ωcm by blending carbon with polybutadiene rubber, 100
A conductive member having a coating film of μm formed was prepared, and the volume resistance and the withstand voltage were measured by the following measuring methods. The results are shown in Table 2.
Shown in.

[0029]

[Table 2]

[Comparative Example 1] The polyol component is a polyester system (condensation system of adipic acid and 1,4-butanediol).
Then, polyurethane having an isocyanate of methylenebisphenyl diisocyanate (Mn = 80,000 in terms of polystyrene conversion, Mw = 140,000) was used as a binder, which was diluted with a mixed solvent of methyl ethyl ketone and dioxane to obtain a solution having a resin concentration of 20% by weight. Was produced. Next, HCF carbon for color (specific surface area: 260 m ² / g, oil absorption: 40 ml / 10 was added to this solution.
0 g) to 13 parts and 1 part to 100 parts of the above polyurethane
Seven parts were dispersed by the red devil method and mixed to prepare a conductive paint.

This coating material was dipped on the same substrate as in Example 1 to prepare a conductive member having a 100 μm coating film, and the volume resistance and withstand voltage were measured. The results are shown in Table 3.

[0032]

[Table 3]

[Comparative Example 2] Polyurethane oxide-based polyol component and solution-type polyurethane in which the isocyanate is tolylene diisocyanate (Molecular weight in terms of polystyrene: Mn = 32000, Mw = 48000)
Was used as a binder and diluted with a mixed solvent of methyl ethyl ketone and toluene to prepare a solution having a resin concentration of 20% by weight. Next, HCF carbon for color (specific surface area: 260 m ² / g, oil absorption: 40 ml / 10 was added to this solution.
0 g) to 7 parts and 10 parts of 100 parts of the above polyurethane.
As a part, they were dispersed by the red devil method and mixed to prepare a conductive paint.

This coating material was dipped on the same substrate as in Example 1 to prepare a conductive member having a 100 μm coating film, and the volume resistance and the withstand voltage were measured. The results are shown in Table 4.

[0035]

[Table 4]

[0036]

The conductive film formed of the conductive coating material of the present invention has a withstand voltage even when the film thickness is thin, by using polyurethane having a polyol component mainly composed of polytetramethylene oxide as a binder. Since it is expensive, it is possible to reduce the film thickness when forming the conductive film on the conductive base material, which can simplify the work and reduce the cost. Further, this polyurethane is used as a binder. When the conductive film is formed as an electric resistance adjusting film, the conductive member is particularly useful for applications such as a conductive roller.

Claims (2)

[Claims] 1. A conductive coating material comprising a conductive material and polyurethane as a binder whose polyol component is mainly composed of polytetramethylene oxide. 2. A conductive member having a conductive film formed of polyurethane as a binder whose polyol component is mainly composed of polytetramethylene oxide.