JPH077876B2 - Conductive resin film and method for manufacturing the same - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a conductive resin film and a method for producing the same, and more particularly, to an antistatic material or electrostatic coating used in the form of a sheet, film, paste, paint or the like. The present invention relates to conductive resin films in a wide range of fields such as conductive paints, circuit wiring, electrode extraction, electrical contacts, conductive films, surface heating elements, electromagnetic shield materials, and corona discharge prevention materials.

2. Description of the Related Art Conventionally, as a conductive resin film, there has been a conductive filler added type.

Materials that are added to the resin film to impart conductivity, that is, fillers include metals such as silver, copper, aluminum, nickel, palladium, iron, silicon oxide, tin oxide, indium oxide,
It is a metallic compound such as lead oxide or the like, and a non-metal crystalline or non-crystalline material such as carbon, which is used in the form of flakes, powder, spheres, or fibers. Also, on the surface of these fillers,
It is also well known to coat and use a conductive material such as metal or metal oxide.

However, in order to increase the conductivity by using these fillers, it is indispensable to completely disperse the filler by making the dimensions of the filler sufficiently small and to add it in a large amount. It was

However, the addition of a large amount of conductive material deteriorates the mechanical properties of the coating film, and the conductivity of copper, aluminum, iron, etc. decreases due to the formation of a surface oxide layer, and the coating film deteriorates due to copper and iron oxides. There was a drawback. Therefore, inexpensive and highly stable carbon black has been used, but it has a drawback that the hue is limited.

The present invention provides a conductive resin film having a proper flexibility, a hue that is not limited, and a flexible flexible conductive film that is free from oxidative deterioration and a method for manufacturing the same, by only blending the resin component in a low ratio. For the purpose of provision.

Means for Solving the Problems In view of the above-mentioned object, the present inventors have invented that, as a result of earnest research, the object can be achieved by the following means.

That is, the present invention is a conductive resin film containing a zinc oxide whisker comprising a core and needle-shaped crystal parts extending in different four-axis directions from the core.

The present invention further comprises a zinc oxide whisker comprising a core portion and needle-shaped crystal portions extending from the core portion in different four-axis directions, and at least a part of the needle-shaped crystal portion is coated with a conductive material. It is a conductive resin film.

Furthermore, in the present invention, the diameter of the base of the needle-shaped crystal part is 0.1 to 14 μm.
And a conductive resin film containing a tetrapot-shaped zinc oxide whisker having a length from the base to the tip of 3 to 200 μm.

Next, the present invention provides a first step of blending a tetrapot-shaped zinc oxide whisker or a tetrapot-shaped zinc oxide whisker at least a part of which is coated with a conductive material in a binder solution, and further forming a film and heating or Second to dry
It is a method for producing a conductive resin film, which comprises steps.

The present invention also provides a first step of surface-treating a tetrapot-shaped zinc oxide whisker or a tetrapot-shaped zinc oxide whisker, at least a part of which is coated with a conductive material, with a binder solution. And a third step of further forming a film and heating or drying the same, and a method for producing a conductive resin film.

Action The zinc oxide whiskers used in the present invention have a three-dimensional structure and a tetrapod-like three-dimensional peculiar structure. Therefore, when incorporated in the coating film, the whisker needle-shaped crystal parts are different from other ones. Since it brings about an extremely efficient contact with the needle-shaped crystal part of the whisker, it becomes possible to form the conductive path efficiently with an extremely small amount. This has a very high contact probability as compared with a simple linear fiber body or flake filler which has been conventionally considered to be advantageous for electrical contact.
In this way, in the present invention, a conductive path is easily formed in the resin with a low compounding ratio, so that a conductive resin film having a high degree of flexibility can be formed.

In particular, when a solvent-type binder solution is used, a large film shrinkage occurs in the three-dimensional direction during film formation.
At this time, the contact between the whiskers in the film becomes strong in the three-dimensional direction, so that the contact resistance between the whiskers becomes small and the conductivity of the film becomes high. This process is an extremely strong effect unique to the 3D whiskers.

Next, depending on the kind of the binder solution, it is possible to selectively use zinc oxide whiskers whose surface is treated or not. This is selected in consideration of the dispersibility of the whiskers in the binder solution.

Zinc oxide whiskers are white and conductive (about 10Ω-c
It is a stable substance with m), and the resistance can be reduced by coating a better conductive substance on this surface.

Next, regarding the size of the whiskers, if the whiskers are too large, the whiskers are likely to be broken or settle, so that the dispersion is insufficient and the conductivity is lowered.

On the other hand, a whisker that is too small is not preferable because the efficiency of forming a conductive path decreases and the conductivity decreases. However, as a general tendency, the larger the number of contact points, the more the conductive path is formed, which promotes the formation of an effective conductive path.

Examples The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

In the present invention, a zinc oxide whisker having a completely new shape is used as the filler or the conductive filler.

This zinc oxide whisker has a tetrapot structure, and its electron micrograph is shown in FIG.

This tetrapot zinc oxide whisker is
Metal zinc powder having an oxide film on its surface can be produced by heat treatment in an atmosphere containing oxygen. The obtained zinc oxide whiskers have an apparent bulk specific gravity of 0.02 to 0.1, and have a high yield of 70 wt% or more, and are extremely mass-producible.

The X-ray diffraction pattern of this whisker showed all zinc oxide peaks, while the electron diffraction results also showed single crystallinity with few transitions and lattice defects. In addition, the content of impurities was also small, and the result of atomic absorption analysis was 99.98% zinc oxide.

By the way, the needle-shaped crystal part of zinc oxide whiskers may be mixed with triaxial, biaxial, or even uniaxial ones in addition to the quadriaxial ones. Is. It was also observed that zinc oxide in plate form was mixed.

Next, a large whisker (length greater than 200 μm, diameter 1
A system in which a large proportion (more than 4 μm) occupies a large proportion (for example, 60 wt% or more), or a small whisker (a length smaller than 3 μm and a diameter smaller than 0.1 μm) is large (for example 80 wt%).
% Or more), the conductivity decreases, which is not preferable.

In particular, when using zinc oxide whiskers surface-treated with a coupling agent, it is preferable that the length from the base to the tip of the needle-shaped crystal part is 3 to 80 μm and the diameter of the base is 0.7 to 8 μm. A resin film is easily obtained.

Next, a conductive resin film using zinc oxide whiskers coated with a conductive material will be described.

As a metal coating method for the surface of zinc oxide whiskers having a tetrapot structure, there are various chemical vapor deposition methods such as electroless plating and electrolytic plating, various CVD methods, vacuum deposition, ion plating, sputtering, PVD method and coating coating. ，
Immersion coating, spray coating, etc. are used.

The conductive material to be coated is Ag, Cu, Au, Cr, Al, Mo,
W, Zn, Ni, Cd, Co, Fe, Pt, Sn, Ta, Nb, Pb, As, Sb, Zr, Ti, La, Bi,
Mg, Hg, Ir, Th, V, Tc, Ru, Hf, Re, Os, Tl, In, Ga, U, Si, B, K, Na,
Sr, Be, Ca, Ba, Ra, Li, Sc, Y, Ac, O, C, N, etc. Single or multiple kinds of alloys, compounds, and mixtures, with conductivity suitable for the purpose under the intended use conditions A material exhibiting the following is selected, and a material that is less likely to deteriorate in conductivity due to photoreactive oxidation, reduction, chemical reaction, aging, etc. is particularly preferable. In that respect, Ag, Au, Cu, Cr, Ni, A
Metals such as l and metal oxide-based conductive materials such as antimony tin oxide and indium oxide are particularly effective.

Originally, zinc oxide whiskey itself is semi-conductive and is a material that conducts electricity to some extent, so it is not always necessary to coat the entire surface of one whisker, and partial coating is sufficient depending on the purpose. Demonstrate. If the conductive material to be coated has a thickness of 25 Å or more, the conductivity of zinc oxide-
The effect of weakening the light dependence begins to appear, and 100 Å or more is effectively sufficient, and the conductive properties of the composite system stabilize.

Next, the present invention is applied to solvent type and solventless type resin films. In particular, by using a solvent type binder solution, an extremely effective conductive resin film can be obtained.

Next, a binder solution is a low-viscosity solution (for example, 1 to 50 wt% solution) in which a resin is dispersed or dissolved in a solvent.
Therefore, the resins used are polycarbonate, polystyrene, polyphenylene oxide, acrylic resin,
Resins that are easily soluble in organic solvents such as alkyd resins, acetyl cellulose, cyanoethylated cellulose, and cyanoethylated pullulan are particularly preferable, but polyvinyl chloride, polypropylene, polyethylene, chlorinated polyethylene, polyethylene terephthalate, polybutylene terephthalate, polyamide, polysulfone, Polyetherimide,
Polyether sulfone, polyphenylene sulfide,
Polyetherketone, polyetheretherketone, ABS
Resin, polybutadiene, methyl methacrylate, polyacrylonitrile, polyacetal, polycarbonate, ethylene-vinyl acetate copolymer, polyvinyl acetate, ethylene-tetrafluoroethylene copolymer, aromatic polyester, polyvinyl fluoride, polyvinylidene fluoride In the case of a single resin such as polyvinylidene chloride or Teflon, or a thermoplastic resin of a copolymer of a plurality of resins, it can be used by dispersing or dissolving it in a solvent.

In addition, thermosetting resins such as epoxy resin, unsaturated polyester resin, urethane resin, silicone resin, melamine-urea resin, and phenol resin can be similarly used.

The solvent used is dichloromethane, dichloroethane, chloroform, acetone, methyl ethyl ketone, nitromethane, acetonitrile, acrylonitrile, dimethylformamide, dimethyl sulfoxide, pyridine, dioxane, methylene chloride, tetrahydrofuran,
Toluene, xylene, cyclohexanone, methyl acetate,
Organic solvents such as butyl acetate, methanol, ethanol, butyl alcohol carbon tetrachloride, and water can be used alone or in combination.

Next, the compounding ratio of zinc oxide whisker and resin depends on the size of the whisker, the type of surface treatment, the type of resin, the type of solvent used, and the desired high conductivity, so it is not limited. Although not present, it is effective at 2 Vol.% Or more, and particularly 4 to 50 Vol.%, More preferably 4 to 20 Vol.%, A stable conductive resin film can be obtained.

The mixed solution is thoroughly stirred with a magnetic stirrer, etc., paying attention to breakage of the tetrapot whiskers.

After that, a film is formed by an appropriate method such as doctor blade, spraying, casting, brush coating, bar coating, spinner and the like.

Next, the conductive resin film is completed by heating or drying, but particularly in the case of particles using a thermoplastic resin (the particle size must be less than the average length of whiskers) dispersion system, the temperature above the softening point of the resin The film formation may be completed after the resin is melted by.

Then, a zinc oxide whisker surface-treated with a coupling agent is used to obtain a highly conductive resin film.

As the coupling agent, a silane-based coupling agent, a chromium-based coupling agent, a titanium-based coupling agent, a silyl peroxide-based coupling agent, and an organic phosphoric acid-based coupling agent can be used, and the silane coupling agent is particularly effective.

As the silane coupling agent, γ-glycidoxypropyltrimethoxysilane (A-187), γ-methacryloxypropyltrimethoxysilane (A-174), vinyl-tris (bettermethoxyethoxy) silane (A-17
2), γ-aminopropyltriethoxysilane (A-110
0), vinyltriethoxysilane, beta, 3,4 epoxycyclohexylethyltrimethoxysilane, gammamercaptopropyltrimethoxysilane and the like are used, and the A-187 system is particularly effective. As a chromium-based coupling agent, methacrylate chromic chloride (MCC:
Volan; DuPot product name), Valchrome 5015 (Valchem product name) and the like are used.

As the titanium-based coupling agent, tetraisopropyl titanate, tetrabutyl titanate, tetrastearyl titanate, isopropoxy titanium stearate, titanium lactate or the like can be used.

Next, as a silyl peroxide type coupling agent, (CH ₃ ) _4-n Si (OO t-butyl) _n Etc. can be used.

Further, as the organic phosphoric acid-based coupling agent, Etc. can be used.

Further, as the method of surface treatment with the coupling agent, a general powder surface treatment method can be applied.

Taking a silane coupling agent as an example, 1) The silane coupling agent is dissolved in water (containing a small amount of HCl) or a solvent (containing a small amount of acetic acid).

2) Heat to 100 ° C or below (hydrolysis of coupling agent molecules).

3) Put zinc oxide whiskers to be treated in this solution to make a well-dispersed slurry (a reaction layer of coupling agent molecules is formed on the powder surface).

4) Separate the zinc oxide whiskers from the treatment liquid and dry it to 150
Heat it to below ℃.

The surface treatment is completed by the above steps.

Next, the coupling agent was added to the zinc oxide whiskers at 0.
It was found that the effect was exhibited by the treatment of 005 wt% to 10 wt%, but the effect was particularly large in the range of 0.01 to 5 wt%.

In the present invention, zinc oxide whiskers or zinc oxide whiskers coated with a conductive material can be added to the resin film to impart sufficient conductivity, but depending on the purpose of conductivity, other fillers such as , Silver, copper,
Gold, aluminum, nickel, palladium, iron, stainless steel, tin oxide, indium oxide, lead oxide, silicon carbide,
Powders, flakes, beads, fibers of zirconium carbide, titanium carbide, highly conductive carbon, graphite, acetylene black, etc., or various powders coated with the above materials, flakes, beads, fibers, and raw materials not coated with a conductive material. It is also possible to use and mix tetrapot zinc oxide whiskers together.

Example 1 First, a tetrapot-shaped zinc oxide whisker was prepared. The length from the base to the tip of the needle-shaped crystal part of this whisker is 3
The diameter of the base portion was distributed to 0.7 to 3 μm at ˜30 μm.

Next, silane treatment was performed using an A-187 silane coupling agent. That is, first, A-187 was dissolved in a hydrochloric acid aqueous solution (PH-5). At this time, the amount of A-187 was 1 wt% with respect to the amount of whiskers to be treated. Next, this solution was heated at 80 ° C. for 1 hour, and thereafter, a sufficiently dried zinc oxide whisker was added and sufficiently stirred to obtain a well-dispersed slurry. Next, this slurry was filtered under reduced pressure, dried at 80 ° C. for 3 hours, sufficiently loosened, and heated at 150 ° C. for 8 hours to complete the surface treatment.

Next, prepare 30 cc of dichloromethane in a beaker and add 1 g of polycarbonate powder (Panlite K-13, Teijin Chemicals Ltd.).
00) was charged with stirring with a magnetic stirrer to obtain a polycarbonate resin varnish.

Further, 1 g of a tetrapot-shaped zinc oxide whisker treated with silane was put into this varnish, sufficiently stirred and dispersed, and then cast on a glass plate to form a film with a doctor blade. Next, it was dried with a drying device at 60 ° C. for 1 hour, cooled, peeled from the glass plate, and subjected to evaluation measurement. The average thickness of the formed film was 200 μm. The whisker content is about 17V.
It was ol.% (50 wt%).

The prepared film was cut into a 6 mm × 30 mm square, and both ends were clipped to measure the resistance value in the longitudinal direction. The volume resistivity (Ω-cm) was calculated in consideration of the reading of the resistance value and the film thickness. The results are shown in Table 1.

The film had a smooth surface and was highly flexible. According to this measuring method, a film of 10 ⁵ Ω-cm or less can be used as a conductive film for electrostatic coating, and its application is extremely wide.

Comparative Example 1 By using a tetrapot-shaped zinc oxide whisker having the same size as in Example 1 without silane treatment, Example 1 was used.
Table 1 shows the evaluation results obtained by forming a film in exactly the same manner as in. In this film, whiskers were strongly aggregated, and the surface was messy, resulting in extremely poor film quality.

Comparative Example 2 A tetrapod-shaped zinc oxide whisker having a large shape was prepared, a film was formed in the same manner as in Example 1, and the evaluation results are shown in Table 1. The surface of this film was slightly uneven.

Comparative Example 3 A tetrapod-shaped zinc oxide whisker having a small shape was prepared, a film was prepared in the same manner as in Example 1, and the evaluation results are shown in Table 1.

Comparative Example 4 A commercially available zinc white (No. 1: French method) was prepared, and a film was prepared and evaluated in exactly the same manner as in Example 1 from silane treatment to film formation and measurement. The results are shown in Table 1. .

Comparative Example 5 The silane-treated tetrapot-shaped zinc oxide whiskers prepared in Example 1 were prepared.

Next, in a Brabender heated to 300 ° C, a polycarbonate resin beret (Tanjin Kasei Co., Ltd., Panlite K-13) was used.
00) and the above whiskers were kneaded (mixing ratio was 50 wt%) and pressed at 300 ° C. to form a film having a thickness of 200 μm.

Next, this film was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 2 Tetrapot-shaped zinc oxide whiskers were treated with silane in the same manner as in Example 1, thoroughly mixed with the composition of Composition 1, spray-coated on a glass plate, dried at room temperature for 30 minutes, and then evaluated. The results are shown in Table 1.

The film thickness was 200 μm.

Example 3 A tetrapot-shaped zinc oxide whisker was treated with silane in the same manner as in Example 1, sufficiently mixed with the composition of Composition 2, cast on a glass plate, and formed into a film having a thickness of 200 μm with a doctor blade, and then at room temperature. After air-drying for time, it was evaluated. The results are shown in Table 1.

Example 4 First, the silanized zinc oxide whiskers of Example 1 were prepared. Next, fine polypropylene powder pulverized to a diameter of 0.5 μm was prepared, and both were sufficiently stirred and dispersed in dichloromethane to obtain a uniform slurry. The whisker content was 35 wt%. This slurry was applied on a glass plate, formed into a film with a doctor blade, and dried in an atmosphere at 60 ° C. for 1 hour. Next, it was placed in a constant temperature bath at 260 ° C. for 10 minutes to dissolve polypropylene and form a film. This film (thickness 200
(μm) was peeled from the glass plate and the evaluation results are shown in Table 1.

Example 5 As-produced zinc oxide whiskers were thoroughly mixed in the composition 3 and then It was cast on a glass plate, dried at room temperature for 1 hour, and then dried at 80 ° C. for 4 hours, and then evaluated. The average film thickness was 200 μm. The results are shown in Table 2.

Example 6 Using another size of as-produced zinc oxide whiskers, evaluation was performed in exactly the same manner as in Example 5, and the results are shown in Table 2. At this time, the film was formed so that the film thickness was also 200 μm.

Example 7 The surface of a zinc oxide whisker was silver-plated by a method of electroless plating. 1 on this mountain of whiskers that has naturally accumulated
Paired tester (Kaise, Digital Multimeter SK-65
When the needle of 11) was inserted, it showed 0.2Ω.

Using this silver-plated whisker, a polycarbonate film was formed in the same manner as in Example 1. At this time, the average film thickness is 160
was μm. The evaluation results of this film are shown in Table 2.

Examples 8 to 13 A conductive sheet was formed into a film using various binders and various zinc oxide whiskers, and the evaluation results are shown in Table 2. The film thicknesses were all set to an average of 200 μm, and the content of zinc oxide whiskers was 10 vol.% Based on the entire solid content.

Comparative Example 6 A polycarbonate sheet was prepared (thickness: 200 μm) and evaluated, and the results shown in Table 2 were obtained.

Comparative Example 7 A commercially available zinc white (No. 1: French method) was prepared and blended in polycarbonate (33 wt%; 10 Vol.%) Sheet (about 2
The evaluation results for the thickness of 00 μm) are shown in Table 2.

Comparative Example 8 When fine zinc oxide whiskers were prepared and evaluated in the same manner as in Example 5, the results shown in Table 2 were obtained. The film thickness was about 200 μm.

Comparative Example 9 A tetrapot-shaped zinc oxide whisker having a length of 200 to 300 μm and a diameter of the base portion of 14 to 16 μm was prepared and formed into a film in exactly the same manner as in Example 5, which resulted in a bad film quality with many surface irregularities and a volume. The resistance value was about 7 × 10 ⁵ Ω-cm. At this time, the film thickness was 150 to 400 μm, which was a rough surface.

Example 14 In a field of view of 1500 times with an electron microscope, the diameter of the base of the needle-shaped crystal part is 0.1 to 3 μm, and the length from the base to the tip is 3 to 30.
A zinc oxide whisker having a μm-tetrapod shape was prepared.

Next, the composition 4 was mixed and mixed, and zinc oxide whiskers 9 g polyvinyl chloride-acrylic copolymer resin 12 g composition 4 methyl ethyl ketone 50 g toluene 15 g methyl isobutyl ketone 25 g were well stirred in a container for 3 minutes with a glass rod.

This coating material was thinly cast on a glass plate, naturally dried for 3 hours, and further dried at 80 ° C. for 15 hours.

The coating film obtained was white and had a smooth surface condition. A metal (silver plating) was applied between two points on this coating film (distance: 5 cm at the center).
It was found that when it was pressed down with a needle and a voltage of 100 V DC was applied, 20 μA flowed, indicating good conductivity. This coating has an average of 100 μm
Was the thickness of.

EFFECTS OF THE INVENTION As described above, according to the conductive resin film of the present invention and the method for producing the conductive resin film, a conductive resin film rich in flexibility can be obtained because suitable conductivity can be obtained only by adding a small amount of whiskers. The obtained film is stable and the hue is not limited.

As described above, the application range of the present invention is extremely wide, and its industrial applicability is extremely great.

[Brief description of drawings]

FIG. 1 is an electron micrograph showing the crystal structure of zinc oxide whiskers used in the conductive resin film of the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location H01B 1/20 B 7244-5G (72) Inventor Moto Kitano 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Sangyo Co., Ltd. (72) Inventor ▲ Yoshi ▼ Hideyuki Ta, 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-3-48500 (JP, A)

Claims (5)

[Claims] 1. A conductive resin film containing a zinc oxide whisker comprising a core and needle-shaped crystal parts extending in four different axial directions from the core. 2. A zinc oxide whisker comprising a core portion and needle-shaped crystal portions extending from the core portion in different four-axis directions, and at least a part of the needle-shaped crystal portion is coated with a conductive material. Blended conductive resin film. 3. The conductive resin film according to claim 1, wherein the base of the needle-shaped crystal portion has a diameter of 0.1 to 14 μm, and the length from the base to the tip is 3 to 200 μm. 4. A tetrapot-shaped zinc oxide whisker, or
A method for producing a conductive resin film comprising a first step of blending a tetrapot-shaped zinc oxide whisker at least a part of which is coated with a conductive material in a binder solution, and a second step of further forming a film and heating or drying. 5. A tetrapot-shaped zinc oxide whisker, or
A first step in which a tetrapot-shaped zinc oxide whisker at least a part of which is coated with a conductive material is surface-treated with a coupling agent, a second step in which the whisker is mixed with a binder solution, and a film is formed and heated or Third to dry
A method for producing a conductive resin film, which comprises steps.