JP2007231089A - Electroconductive composition and its molded body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electroconductive composition excellent in voltage stability and environmental stability and provide its molded body. <P>SOLUTION: The electroconductive composition contains carbon nanofibers and electroconductive powders in a matrix and has the relationship of following equation (1) between the volume resistance R100 under applied voltage 100 V and the volume resistance value R1000 under applied voltage 1,000 V. Preferably, the composition contains the carbon nanofibers with a particle size of ≤0.1 μm, an aspect ratio of ≥5 and a powder resistance of ≤1.0 Ω cm and the electroconductive powders whose powder compact has a resistance value of 10<SP>0</SP>-10<SP>8</SP>Ω cm under the pressure of 100 kg/cm<SP>2</SP>, and the content of the carbon nanofibers is ≥0.1 wt.%, that of the electroconductive powders is ≥10 wt.%, and the total content of these is one to give a volume resistance of 10<SP>3</SP>-10<SP>12</SP>Ωcm under the voltage 100 V applied for the composition. The equation (1) is shown by log<SB>10</SB>R100-log<SB>10</SB>R1000≤1.0 (1). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a conductive composition excellent in voltage stability and environmental stability and a molded product thereof. In general, various parts used in electrophotographic image forming apparatuses such as copying machines, facsimiles, and printers, and electrostatic recording apparatuses, for example, for charging, developing, transferring, fixing, discharging, cleaning, paper feeding, transporting, etc. Conductive resin compositions, conductive elastomer compositions, conductive paints, and the like are used for blades, rollers, belts, brushes, and the like. The present invention is suitable as these materials, and has stable conductivity particularly in a semiconductive region (10 ³ to 10 ¹² Ω · cm, also referred to as a medium resistance region), and can be used under a medium voltage (100 V to 1000 V). The present invention relates to a conductive composition excellent in voltage stability and environmental stability and a molded product thereof.

Conductive resin compositions, conductive elastomer compositions, and conductive compositions such as conductive paints are often used in electrophotographic image forming apparatuses such as copying machines, facsimiles, and printers, and electrostatic recording apparatuses. ing. Conventional conductive compositions include, for example, insulating elastomers such as silicone, polyurethane, epichlorohydrin, NBR, EPDM, polycarbonate (PC), polyvinylidene fluoride (PVdF), polyimide (PI), polyamideimide (PAI), ethylenetetra An insulating resin such as a fluoroethylene copolymer (ETFE) is used as a base and a conductive material such as an ion conductive material, a conductive polymer, carbon black, or a metal oxide is added thereto.

Many of the conventional conductive compositions have imparted functional conductivity by adjusting the amount of conductive material added. However, in recent years, with the improvement in performance of these OA equipments, Strict control is required. However, powdered conductive materials such as carbon and metal oxides have a slight difference in addition amount, slight changes in conditions such as material temperature, molding temperature and molding time, and differences in molding methods. There is a problem that the conductivity is greatly fluctuated because the form is easily changed. In particular, in the semiconductive region, it is often difficult to impart stable conductivity over the entire molded product even if the shape and molding conditions of the molded product are carefully managed.

In addition, many of the conventional conductive compositions have a high so-called voltage dependency in which the electrical resistance value changes depending on the applied voltage in the semiconductive region. For example, a conductive composition is known in which voltage dependency is eased by using spherical carbon black alone (Patent Documents 1 and 2). Even in this conductive composition, the volume resistivity is 10 ⁵ Ω · cm. In the above, the volume resistance value may deviate by 10 Ω · cm or more due to a difference in carbon amount by about ± 0.5 mass% and a difference in molding conditions (molding speed, temperature, humidity).

On the other hand, those using ion conductive materials tend to suppress changes in resistance due to voltage and current (ie. Voltage dependence), but changes in resistance due to temperature and humidity (ie. (Environment dependency) tends to increase. Furthermore, there are problems that the resistance is easily changed by energization and that ions tend to bleed and become a contamination source.

In addition, Patent Document 3 describes a conductive polymer including white conductive powder and hollow microfibers. This is to suppress blackening by mixing both, to obtain a white conductive composition, can be further colored in any color, like the present invention, medium resistance range ~ There is no recognition of the stability of electrical resistance in the high resistance region.
JP-A-11-106657 JP-A-11-190328 JP H09-111135A

The present invention solves the above-mentioned problems in conventional conductive compositions, and has stable conductivity particularly in a medium resistance region (10 ³ to 10 ¹² Ω · cm), and under a medium voltage (100 V to A conductive composition excellent in voltage stability and environmental stability at 1000 V) and a molded product thereof are provided.

The present invention relates to a conductive composition and a molded body thereof that have solved the above problems by the following constitution.
(1) The carbon nanofiber and the conductive powder are contained in the matrix, and the volume resistance R100 under an applied voltage of 100V and the volume resistance value R1000 under an applied voltage of 1000V are in the relationship of the following formula (1): Conductive composition.
Log ₁₀ R100−log ₁₀ R1000 ≦ 1.0 (1)
[Where R100 is the volume resistivity (Ω · cm) under an applied voltage of 100V, and R1000 is the volume resistivity (Ω · cm) under an applied voltage of 1000V]
(2) particle size 0.1μm or less and an aspect ratio of 5 or more, and powder resistance and 1.0 [Omega] · cm or less of the carbon nanofiber, 100 kg / cm compact resistance under pressure of ² 10 ⁰ 10 ⁸ The conductive composition as described in (1) or (2) above, comprising a conductive powder of Ω · cm.
(3) The carbon nanofiber content is 0.1 parts by weight or more and the conductive powder content is 10 parts by weight or more with respect to 100 parts by weight of the matrix material in the composition, The conductive composition as described in any one of (1) to (3) above, wherein the total content is such that the volume resistance of the composition under an applied voltage of 100 V is from 10 ³ to 10 ¹² Ω · cm.
(4) A transfer sheet, a conductive sheet, a conductive blade, a conductive gear, a conductive roller, a conductive brush, a conductive yarn, a conductive tube formed from the conductive composition described in any one of (1) to (4) above. Or conductive roll.

In the conductive composition of the present invention, since a good conductive path is formed by containing carbon nanofibers and conductive powder in the matrix, the voltage dependency is low and the stability against voltage change is good. . Specifically, in the conductive composition of the present invention, the difference between the volume resistance R100 under an applied voltage of 100 V and the volume resistance value R1000 under an applied voltage of 1000 V is log ₁₀ R100−log ₁₀ R1000 ≦ 1.0 [Formula R100 is in the range of volume resistivity (Ω · cm) under an applied voltage of 100 V, and R1000 is in the range of volume resistivity (Ω · cm) under an applied voltage of 1000 V, and has good stability against voltage change.

According to the present invention, for example, carbon nanofibers having a particle diameter of 0.1 μm or less, an aspect ratio of 5 or more and a powder resistance of 1.0 Ω · cm or less, and a green compact resistance value under a pressure of 100 kg / cm ^2. By using a conductive powder of 1 Ω · cm or more, and the total amount of these carbon nanofibers and conductive powder is contained so that the volume resistance of the composition is 10 ³ to 10 ¹² Ω · cm. It is possible to obtain a conductive composition having a stable conductivity and excellent in voltage stability and environmental stability under a medium voltage.

The conductive composition of the present invention has low voltage dependency and low environmental dependency. Therefore, when this conductive composition is used, it is electrically very stable in the image forming process of charging / developing / transfer / fixing. Therefore, mechanical control for overcoming the electrical instability can be facilitated. Furthermore, the transfer voltage can be easily controlled, and the mechanism of the image forming apparatus can be simplified. As a result, it is possible to achieve high speed, high image quality, and cost reduction in the image forming apparatus. In addition, when controlling the applied voltage or applied current according to the printing conditions, paper type, and environmental conditions, it is possible to control with high accuracy, resulting in an improvement in printing quality and a reduction in size and size. This is advantageous for cost reduction.

Hereinafter, the present invention will be specifically described based on examples.
The conductive composition of the present invention contains carbon nanofibers and conductive powder in the matrix, and the volume resistance R100 under an applied voltage of 100V and the volume resistance value R1000 under an applied voltage of 1000V are in the relationship of the following formula (1). It is a conductive composition characterized by being.
Log ₁₀ R100−log ₁₀ R1000 ≦ 1.0 (1)
[Where R100 is the volume resistivity (Ω · cm) under an applied voltage of 100V, and R1000 is the volume resistivity (Ω · cm) under an applied voltage of 1000V]

The following compounds can be used as the matrix material used in the conductive composition of the present invention. For example, a resin composition can be used as the matrix material. This includes thermoplastic resins, thermosetting resins, UV curable resins, and the like. Specific resins used include polyester resins, acrylic resins, urethane resins, acrylic urethane resins, nylon resins, epoxy resins, polyvinyl acetal resins, vinylidene chloride resins, fluorine resins, silicone resins, Polycarbonate resin, polyphenylene sulfide resin, polyimide resin, polyamideimide resin, vinylidene fluoride resin (PVDF), polyetherimide resin, silicone imide resin, urethane imide resin, polyurethane resin, polyurea resin, epoxy resin, melanin resin, etc. Examples thereof include unsaturated polyester resins and vinyl ester resins. Of these, polyimide resins, polyamideimide resins, and vinylidene fluoride resins with high elastic modulus are preferably used. In particular, a relatively inexpensive polyamide-imide resin is preferable.

When the matrix material is an elastomer, for example, silicone, acrylonitrile butadiene, urethane rubber, epichlorohydrin rubber, chloroprene rubber, acrylic rubber, styrene butadiene rubber, butadiene rubber, isoprene rubber, natural rubber, acrylic rubber, chloroprene rubber, Butyl rubber, epichlorohydrin rubber, or thermoplastic elastomer is used. In particular, from the viewpoints of altitude, viscosity, durability, etc., silicone type and urethane type are preferable. These may be used alone or in combination of two or more.

The elastic material of the matrix material may be a foam. In this case, a material having a density of about 0.05 to 0.9 g / cm ³ is suitable. Furthermore, the matrix material may be a paint, and as the paint, a water-based fluororubber paint, a urethane paint, an acrylic paint, a silicone paint, or the like can be used.

The conductive powder preferably has a green compact resistance value of 1 Ω · cm or more under a pressure of 100 kg / cm ² . Examples of the conductive powder material include conductive metal oxides, nitrides, carbides, oxynitrides, and silicon compounds. Examples of conductive metal oxides include tin oxide (SnO ₂ ), antimony tin oxide (ATO), indium tin oxide (ITO), antimony oxide (Sb ₂ O ₅ ), zinc oxide, and aluminum zinc oxide (AZO). , Titanium oxide, antimony-doped titanium oxide, potassium titanate and the like. Examples of the conductive oxynitride include titanium oxynitride.

A conductive powder in which the surface of the nonconductive powder is coated with a conductive metal oxide or the like can also be used. Specifically, the surface of non-conductive powder such as silica, aluminum oxide, magnesium oxide, zirconium oxide, alkali metal titanate (potassium titanate, etc.), aluminum borate, barium sulfate, synthetic fluorine mica, etc. is applied to ATO, AZO, ITO. Those coated with a transparent or white conductive metal oxide such as can be used. In addition, a powder whose surface is made of titanium oxide, zinc oxide, or the like is covered with ATO, AZO, ITO, or the like to increase conductivity may be used.

The particle size of the conductive powder is generally in substantially spherical powder is suitably those having a BET specific surface area of 0.5~50m ² / g, preferably from 3~30m ² / g. In high aspect ratio powder is suitably those having a BET specific surface area of 0.1 to 10 m ² / g, preferably from 1 to 10 m ² / g.

The conductive composition of the present invention contains carbon nanofibers together with conductive powder. The carbon nanofibers preferably have an aspect ratio of 5 or more, a diameter of 0.1 μm or less, and a bulk resistivity (measured at a pressure of 100 kg / cm ² ) of 1 Ω · cm or less.

Since it is difficult to disperse the carbon nanofibers as they are in the matrix, it is preferable to perform a treatment for improving the dispersibility. For example, surface treatment such as oxidation treatment using ozone gas or the like can be performed to improve compatibility with the matrix and disperse. Further, since it is difficult to disperse in the paint, in addition to the surface treatment, it can be dispersed in a solvent constituting the paint in advance and mixed with the paint. In order to satisfactorily disperse in this dispersion, it is possible to use a surface-treated powder such as an oxidation treatment with ozone gas or the like, or to add and disperse various additives.

When the conductive powder is used alone, the conductivity can be increased by using a large amount, but the voltage dependency becomes very high. On the other hand, when carbon nanofibers are used alone, the resistance value of the fiber itself is low, so it is difficult to stably obtain a resistance value of about 10 ² Ω · cm, but the contact resistance is reduced because it is not powdery. Therefore, there is little voltage dependency.

The conductive composition of the present invention contains carbon nanofibers together with the conductive powder, so that they are uniformly mixed inside the composition, and the carbon nanofibers are responsible for the formation of the conductive path, rather than the contact between the conductive powders. Since a good conductive path is formed, voltage dependency is reduced and stable conductivity is obtained.

Furthermore, since the conductive composition of the present invention forms a conductive path better than the contact between the conductive powders by using the carbon nanofibers and the conductive powder in combination, the conductive composition is also excellent in stability against environmental fluctuations. Specifically, the volume resistivity RLL under the low temperature and low humidity environment and the volume resistivity RHH under the high temperature and high humidity environment can be controlled within the range represented by the following equation (2).
Log ₁₀ RLL-log ₁₀ RHH ≦ 1.5 (2)
[In the formula, RLL is a volume resistivity (Ω · cm) in a low temperature and low humidity environment (10 ° C., relative humidity 20%), and RHH is a volume resistivity (40 ° C., relative humidity 80%) in a high temperature and humidity environment (40% relative humidity). (Ωcm))

The amount of the conductive filler (conductive powder and carbon nanofiber) is such that the volume resistance of the composition under an applied voltage of 100 V is 10 ³ to 10 ¹² Ω · cm, preferably 10 ⁴ to 10 ¹⁰ Ω · cm. It is. By using the carbon nanofiber together with the conductive powder, good conductivity can be obtained in a smaller amount than when the conductive powder is used alone or when the carbon nanofiber is used alone.

Specifically, it is appropriate that the conductive filler is added in an amount of less than 0.1 to 5 parts by weight with respect to 100 parts by weight of the matrix material, and 0.2 to 3.0 parts by weight. Is preferable, and 0.5 to 2.0 parts by weight is more preferable. The conductive powder is suitably added in an amount of 10 to 150 parts by weight, preferably 10 to 50 parts by weight, and more preferably 15 to 30 parts by weight. If the content of the carbon nanofiber is small, it is difficult to reduce the voltage dependency. On the other hand, if the content is large, the resistance value decreases more than intended. If the content of the conductive powder is small, it is difficult to obtain the desired conductivity. On the other hand, if the amount is large, the voltage dependency becomes high.

An ionic conductive material may be added to stabilize the conductivity. Examples of ionic conductive materials include traethylammonium, tetrabutylammonium, dodecyltrimethylammonium (such as lauryltrimethylammonium), octadecyltrimethylammonium (such as stearyltrimethylammonium), hexadecyltrimethylammonium, benzyltrimethylammonium, and modified aliphatic dimethylethylammonium. Perchlorates, chlorates, hydrochlorides, bromates, iodates, borofluorides, sulfates, alkyl sulfates, carboxylates, sulfonates and other ammonium salts; lithium, sodium, Alkali metal or alkaline earth metal perchlorate such as calcium and magnesium, chloric acid, hydrochloride, bromate, iodate, borofluoride, trifluoromethyl sulfate, sulfonate, etc. It can be used. These may be used alone or in combination of two or more.

In addition to the above conductive filler, the conductive composition of the present invention includes a dispersant, leveling agent, anti-aging agent, lubricant, antioxidant, plasticizer, colorant or non-reinforcing silica, diatomaceous earth, calcium carbonate, carbonate You may mix | blend fillers, such as magnesium, spherical particle silica, a calcium carbonate, and a glass bead, suitably. There is no particular limitation on the type and amount thereof.

The method for mixing and dispersing the conductive filler in the matrix material is not limited. Existing methods can be used. For example, for thermoplastic resins and elastomers, use a kneader, pressure mixer, intensive mixer, Henschel mixer, mixing roll, three rolls, heated roll mill, extrusion mixer, melt blender, etc. to melt or soften The conductive filler may be mixed and dispersed in the polymer in a state. The produced electrically conductive composition may be formed into pellets, granules, or the like, or may be directly formed into a desired shape as it is.

Regarding the conductive composition of the present invention, the molding method and the shape of the molded product are not limited. As the molding method, various methods including melt spinning, extrusion molding, injection molding, and press molding can be used, and the shape of the molded product may be appropriately selected according to the type of resin. Specifically, for example, a melt molding method or a solution molding method can be used. The shape of the molded product can be finished into necessary members such as fibers (including filaments), films, sheets, seamless tubes, rods, tubes, rolls, and three-dimensional molded products.

In the case of a thermoplastic resin, the conductive powder and the carbon nanofiber may be mixed in a molten state before being cured in advance, and then subjected to cross-linking and curing to obtain a desired shape. The conductive powder and the carbon nanofibers may be mixed in a powder state, but each may be previously dispersed in a solvent, and this may be mixed with a resin before curing.

Even when the matrix material is a coating material, the conductive filler may be mixed with the coating material in a powder state and dispersed with a disper or the like. The conductive filler may be dispersed in each solvent and mixed with the paint.

In any of the above cases, the conductive filler mixed in the matrix is uniformly dispersed. If the conductive filler is not uniformly dispersed in the matrix, the conductivity is biased, and good conductivity cannot be obtained for the entire composition.

According to the conductive composition of the present invention, high-quality conductive parts having low voltage dependency and excellent environmental stability, such as transfer sheets, conductive brushes, conductive yarns, conductive tubes, conductive rolls, and the like are obtained. be able to.

Examples of the present invention are shown below together with comparative examples.

[Examples and Comparative Examples]
Using the materials shown in Table 1, conductive resin pellets were produced in which the conductive filler was uniformly dispersed by adding the conductive filler to the resin and kneading with an extrusion kneader according to the indicated blending amount. This was melt extruded to form a resin film having a thickness of 100 μm. The volume resistivity of this resin film was measured. The results are shown in Table 1.

(Measurement of volume resistivity)
The volume resistivity at applied voltages of 100 V and 1000 V was measured as follows. The sample was cut into a width of 1 cm and a length of 12 cm, and a copper conductive tape was applied to both sides at 1 cm to form electrodes. The electrical resistance value between the electrodes was measured using a superinsulator (SM-8210, manufactured by Toa Denpa Inc.), and based on the following equation from the width (w), thickness (t) and distance (l) between the samples. The volume resistance value was determined.
R (v) [Ωcm] = R [Ω] · (w [cm] · t [cm] / l [cm])

The following materials were used.
Resin: Polycarbonate resin (H-4000 manufactured by Mitsubishi Engineering Plastics)
Paint: Acrylic paint (Kansai paint)
Carbon nanofiber (CNF): Diameter 20 nm, aspect ratio 100 or more, dust volume resistance 5.0 × 10 ^-2 Ωcm
Conductive powder: Tin oxide (SnO ₂ ) powder (S-1S manufactured by Mitsubishi Materials Corp.) Compact powder volume resistance value 5.0 × 10 ⁵ Ωcm, specific surface area BET 15 m ² / g
White conductive powder W-1 (W-1 manufactured by Mitsubishi Materials Co., Ltd.) Compact volume resistance 5 Ωcm, specific surface area BET 5 m ² / g

Claims (4)

A conductive composition comprising carbon nanofibers and conductive powder in a matrix, wherein the volume resistance R100 under an applied voltage of 100V and the volume resistance value R1000 under an applied voltage of 1000V are in the relationship of the following formula (1): object.
Log ₁₀ R100−log ₁₀ R1000 ≦ 1.0 (1)
[Where R100 is the volume resistivity (Ω · cm) under an applied voltage of 100V, and R1000 is the volume resistivity (Ω · cm) under an applied voltage of 1000V]
Carbon nanofibers having a particle diameter of 0.1 μm or less, an aspect ratio of 5 or more, and a powder resistance of 1.0 Ω · cm or less, and a green compact resistance value of 100 ⁰ to 10 ⁸ Ω · cm under a pressure of 100 kg / cm ² The electrically conductive composition of Claim 1 or 2 containing these conductive powders.
The carbon nanofiber content is 0.1 parts by weight or more and the conductive powder content is 10 parts by weight or more with respect to 100 parts by weight of the matrix material in the composition, and the total content of the carbon nanofibers and the conductive powder The conductive composition according to any one of claims 1 to 3, wherein the volume resistance of the composition under an applied voltage of 100 V is 10 ³ to 10 ¹² Ω · cm.
A transfer sheet, a conductive sheet, a conductive blade, a conductive gear, a conductive roller, a conductive brush, a conductive yarn, a conductive tube, or a conductive roll formed from the conductive composition according to claim 1.