JP2001160318A - Conductive film and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a useful conductive film having flexibility, better and stable performances, and to provide its manufacturing method. SOLUTION: This porous polyamide film with a porous structure with fine nonlinear through-holes, porosity of 35 to 85%, hole diameter of 0.01 to 5 μm and film thickness of 5 to 50 μm, and has a overlapping structure of a fine porous layer and a layer with relatively large voids or openings in the cross-section of the film. On this porous polyamide film, in which the above two layers have mutually been connected via fine through-holes, an electroconductive polymer is made to retain.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a flexible polymer film for a conductor.

[0002]

2. Description of the Related Art In recent years, an electric vehicle which does not emit exhaust gas and noise has been attracting attention as global environmental problems increase. However, current batteries have low energy density and low output density, and therefore have problems such as short running distance, poor acceleration, small space in the vehicle, and poor vehicle stability.

In addition, notebook personal computers, pocket personal computers, mobile phones, pagers, handy terminals, electronic notebooks, calculators, liquid crystal televisions, electric shavers, electric tools, memory cards, backup power supplies, portable power supplies
D. Development of high-capacity and good reversible electrodes and secondary batteries for use as power supplies for equipment such as navigation systems and automobiles, electric vehicles, and power storage systems. It is thriving.

[0004] Conductive polymers have been developed from the viewpoint that the electrode of a secondary battery, particularly the cathode material, affects the performance of the battery, or because it is light and easily formed into a film.
For example, Japanese Patent Application Laid-Open No. H11-126610 discloses a polymer battery capable of rapid charging and discharging and having excellent cycle characteristics. It is disclosed that a π-conjugated polymer such as polypyrrole, polypyridine, polypyrimidine or a derivative thereof is used in a film form for those electrodes.

Heretofore, with respect to conductive polymers having such characteristics, for example, polyaniline, studies for improving the conductivity have been made mainly in connection with dopants. That is, although various dopants incorporated into polyaniline, iodine, perhydrochloride, alkyl sulfate, and tetracyanoethylene have been tried, satisfactory results have not been obtained in terms of improving solubility and conductivity.
As a physical conductivity improving means, the conductivity in the stretching direction is improved by controlling the orientation by stretching.

[0006] Also, a development focusing on the aggregation structure of a conductive polymer has been disclosed. For example, JP-A-11-135
No. 379 discloses a porous electrode characterized in that conductive fine particles are dispersed in porous rubber, and a mixture containing conductive fine particles and a rubber solution in which rubber is dissolved in a solvent, Next, a method for producing a porous electrode, which comprises forming a film made of the mixture on a conductive substrate and drying the film, is disclosed.

In addition, in Acc. Chem. Res. 28, 61, 1995, aniline was polymerized by using pores of polycarbonate or alumina as a template to produce fibrous polyaniline, which had high conductivity. Report polyaniline.

However, in the previous studies,
Neither the method by adding a dopant nor the method by physical orientation control can significantly improve the conductivity to a practical level. Further, even though these conductive polymers are in the form of a film, their mechanical strength is inferior, and they may be broken when wound or bent. In addition, as a battery function, the discharge power is small,
The discharge capacity tended to decrease with cycling.

Therefore, it was considered that the structure of the template (matrix) was important in order to improve the conductive performance.
That is, it was considered that a structure in which the conductive polymer densely penetrates into the pores of the matrix and further penetrates the pores so that the conductive polymer adheres and forms a network is preferable. In addition, a conductive polymer that can be used as a conductor while supporting the conductive polymer, has flexibility, and has excellent conductive performance has been expected.

Furthermore, if the supported polymer used has excellent mechanical properties and has a conductive function in combination with the supported polymer, it is expected that materials useful as electric functional materials, including electrode materials, can be provided. Was.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a conductive film which is flexible, has good performance, has stable performance and is useful. is there.

More specifically, the present invention provides a conductive film having excellent mechanical strength, in which a conductive polymer is supported on a flexible porous plastic, which has high conductivity and stable performance. It is to be. Also,
An object of the present invention is to provide a porous film having a simple manufacturing process as a carrier film for a conductive film.

[0013] The present invention is a flexible conductive film having controlled pores and capable of a simple manufacturing method, and more stable and superior performance. Battery electrodes, enzyme electrodes, other artificial muscles,
It can be provided for sensors, electrochromic materials, solid capacitors, and the like.

[0014]

SUMMARY OF THE INVENTION The present invention provides a porous structure having fine non-linear through-holes and a porosity of 35 to 85.
%, A porous polyamide film having a pore size of 0.01 to 5 μm and a film thickness of 5 to 50 μm, and having a relatively large void or opening in the cross-sectional direction of the film and a layer made of microporous material And a conductive film carried on a porous polyamide film in which the two layers are connected to each other by through-holes. Furthermore, the present invention relates to a conductive film, characterized in that a granular structure is formed on the surface of the layer having relatively large voids, and the positions of the voids are not biased on the grain boundaries.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The conductor film of the present invention will be described below. The conductor film of the present invention has a porous structure having fine non-linear through holes, a porosity of 35 to 85%, a pore diameter of 0.01 to 5 μm, and a film thickness of 5 to 50 μ.
m. With this structure, when polymerizing the conductive polymer, the conductive polymer is supported on the nonlinear through-hole,
A flexible conductive film in which the conductive polymer has formed a network-like structure can be obtained.

The conductor film of the present invention has a porosity of 35 to 85%, preferably 40 to 80%. If the porosity is lower than 35%, the amount of the conductive polymer carried is not sufficient, and if the porosity is higher than 85%, the mechanical strength of the porous film decreases, and uniform support cannot be achieved.

The conductor film of the present invention has a pore size of 0.01 to 5 μm, preferably 0.05 to 5 μm,
More preferably, it is 0.1 to 3 μm. The pore size is 0.
If it is smaller than 01 μm, the size of the hole cannot be controlled. On the other hand, when the pore diameter exceeds 5 μm, the mechanical strength of the porous film is undesirably reduced. It is unsuitable as a conductive polymer pore.

The conductor film of the present invention has a thickness of 5
５０50 μm, preferably the film thickness is 5-35 μm. 5
If the thickness is smaller than μm, the mechanical strength will be low and the performance of the conductor will be inferior. If the film thickness is larger than 50 μm,
This range is appropriate because the conductor-carrying film becomes thick and has poor performance.

The conductor film of the present invention has a structure in which a layer made of microporous and a layer having relatively large voids or openings are stacked in the cross-sectional direction of the porous polymer film, and A conductive film, wherein the two layers are connected to each other by through-holes. With such a structure, the conductive polymer grows in a network by sewing through the gap.

Further, a grain structure is formed on the surface of the layer having relatively large voids, and the location of the voids is not biased on the grain boundaries. It can be said that the granular structure of this surface is excellent in mechanical strength and dimensional stability because the position of the void is not biased on the grain boundary.

The polyamide used in the present invention includes:
Various known ones can be mentioned. For example, oxalic acid, adipic acid, sebacic acid, terephthalic acid, isophthalic acid, dicarboxylic acids such as 1,4-cyclohexyldicarboxylic acid and ethylenediamine, hexamethylenediamine, 1,4-cyclohexyldiamine, m-xylylenediamine, pentamethylene Diamine, crystalline polyamide obtained by polycondensation of a diamine such as decamethylene diamine, ε-caprolactam, ε-aminocaproic acid, ω
-Crystalline polyamide obtained by polymerizing laurolactam, ω-aminododecanoic acid, ω-aminoundecanoic acid,
And crystalline polyamides composed of these copolymers. Specifically, polyamide 6, polyamide 6
6, polyamide 610, polyamide 12, polyamide 6
6 / 6T (T represents a terephthalic acid component) and the like.
It may be a mixture of the above polyamides.

The molecular weight of the polyamide resin is not particularly limited, as long as it can form a homogeneous solution with an alcohol solvent having a boiling point of 80 ° C. or lower. Preferably,
The polyamide resin has a number average molecular weight of 9,000 to 100,0.
00. If the number average molecular weight is less than 9,000, the mechanical strength is insufficient, and the number average molecular weight becomes 10
If it is larger than 000, the solution viscosity becomes too high, so that it is difficult to form a uniform porous film.

Next, a method for producing a conductive film of the present invention will be described below. The conductor film of the present invention is prepared by preparing a homogeneous solution comprising a polyamide and an alcohol solvent having a boiling point of 80 ° C. or less, casting the solution in a film on a substrate, and coating the resulting film with a film surface. It is manufactured by drying while causing a fluctuation in the polyamide concentration in the film in the inward direction.

The fluorinated alcohol solvent having a boiling point of 80 ° C. or lower used in the present invention is specifically a fluorinated alcohol such as hexafluoroisopropanol (HFIP) or trifluoroethanol, or the above fluorinated alcohol 40
It is a solvent in which at least mol% and at most 60 mol% of aliphatic alcohol are mixed. The aliphatic alcohol is, specifically,
These are methanol, ethanol and 1-butanol. Preferred are methanol and ethanol. When the proportion of the aliphatic alcohol mixed with the fluorinated alcohol is 60
If it exceeds mol%, the solubility of the polyamide resin in the solvent is greatly reduced, so the above ratio is preferable.

In the present invention, the polyamide and the alcohol solvent are 0.5 to 7% by weight, preferably 2 to 5% by weight of the polyamide and 99.5 to 9% by weight of the alcohol solvent.
The polyamide solution is prepared by dissolving at a ratio of 3% by weight, preferably 98 to 95% by weight. When the proportion of the polyamide is more than 7% by weight, the air permeability of the obtained porous membrane decreases, which is not appropriate. The above-mentioned ratio is preferable because the film is uniformly peeled and easily broken.

In the present invention, the polyamide solution is cast on a substrate in the form of a film, and the obtained film is dried while fluctuating the polyamide concentration in the film in the in-plane direction of the film. Thus, a polyamide porous membrane can be produced. The polyamide solution may be cast into a liquid film, such as on an electrode, any metal or conductive polymer, and then dried.

The substrate used in the present invention is a substrate which does not repel the above polyamide solution when the solution is dropped on the substrate. For example, a plate shape such as a glass plate, a mica plate, and a quartz plate or a cloth is suitable. The substrate is not limited to a flat plate, but may be a cylinder or a substrate having a complicated shape as necessary.

The thickness of the film of the polyamide solution formed on the substrate is adjusted in the range of 5 to 50 μm, preferably 5 to 35 μm, as the average thickness of the film including voids after drying. This depends on the concentration of the polyamide solution and the thickness of the liquid film. When the average thickness is smaller than 5 μm, the film tends to be densified or damaged in the drying step, and when the average thickness is larger than 50 μm, the air permeability of the obtained film is reduced.

The drying of the film of the polyamide solution formed on the substrate is performed under such conditions that the polyamide concentration fluctuates in the in-plane direction of the film during the drying step. The fluctuation of the polyamide concentration is about 1 mm between a part where the solution film during drying is slightly clouded and a transparent part.
It can be known by dividing at the following intervals. Conditions in which the fluctuation of the polyamide concentration occurs include conditions in which the drying is performed at a temperature of 40 ° C. or less for 1 minute or more, and preferably for a drying time of 2 minutes or more. For example, a crystalline polyamide having a number average molecular weight of about 10,000 When polyamide 6 is used, it is preferable to dry the solution film in an air atmosphere at about 30 ° C. or lower. It is not preferable that the film is dried under conditions that do not cause the concentration fluctuation, since the resulting film becomes dense.

Then, the dried film is peeled from the substrate to obtain a polyamide porous film. Further, when a polyamide solution is applied on an electrode, an element, or a conductor, the conductive polymer may be carried as it is without peeling. By doing so, for example, the conductor-carrying film is easily formed in the process of manufacturing the electrode.

In the obtained porous polyamide film, a layer made of microporous material and a layer having relatively large voids or openings are stacked in the cross-sectional direction of the film.
The layers have a structure in which the layers are connected to each other by through-holes. Furthermore, a granular structure is generated on the layer side surface having relatively large voids, and the positions of the voids are not biased on the grain boundaries. Therefore, it is superior in mechanical strength and dimensional stability as compared with a polyamide porous membrane obtained by a conventional production method.

The conductive polymer of the present invention is any one of polypyrrole, polyaniline, polythiophene and derivatives thereof. Particularly preferred are polypyrrole, polyaniline and derivatives thereof.

The method of polymerizing a conductive polymer in the presence of a polyamide porous membrane can be carried out by oxidative polymerization or electrolytic polymerization, and polymerized and deposited on the surface of the porous membrane and in the pores of the porous membrane. . For example, when a polyamide film is immersed between a pyrrole monomer aqueous solution and an oxidizing agent solution such as iron trichloride and polymerized, polypyrrole precipitates in a network.

In the presence of a porous film, gas-phase oxidative polymerization can also be performed. For example, in the case of polypyrrole, it is treated with a solution of iron trichloride, suspended in a container filled with pyrrole vapor, washed with alcohol after a certain period of time, and dried. A polypyrrole-carrying film is obtained.

A method of electrolytic polymerization in the presence of a porous film is to form a porous film on a platinum electrode, use a platinum electrode sealed with glass as a second electrode, and use the second electrode as a pyrrole derivative monomer and boron ammonium fluoride. Into an acetonitrile solution containing and polymerized. A conductive polymer having a shape similar to that of the oxidative polymerization is formed on the porous film.

The conductor is, for example, polypyrrole,
Pyrrole is oxidatively polymerized in the presence of the carrier film to form polypyrrole on the carrier film.
A network-like polypyrrole penetrating not only on the surface but also into the through-holes is carried on the porous film of the carrier film, and a flexible conductor having excellent performance can be obtained. Adhesion between the carrier and the conductor cannot be expected to have a special effect, but the fine discontinuous through-holes in the carrier film are considered to have sufficient physical adhesion to the conductor.

An oxide serving as a dopant may be added during or after polymerization. As the dopant, chlorine, hydrochloric acid, bromine, manganese peroxide salt, arsenic fluoride, 2,
Preferred are 5-dimechaptolyl-1,3,4-thiazole, tetracyanotetraazanaphthalene, tetracyanoethylene and the like.

[0038]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples. Test / evaluation methods or criteria in Reference Examples, Examples and Comparative Examples are as follows.

(Evaluation of Polyamide Porous Film) The thickness, porosity, tensile strength, piercing strength, heat shrinkage, and electric conductivity of the conductive film were measured as follows.

(1) Porosity The thickness and weight of the porous film cut to a predetermined size were measured, and the porosity was determined from the basis weight by the following equation (1). In the formula (1), S represents the area of the porous film, d represents the film thickness, W represents the measured weight, and D represents the density of the polyamide. Porosity (%) = 100−100 × (W / D) / (S × d) (1)

(2) Tensile strength Measured according to JIS K 7127. Test speed 1 using Toyo Baldwin Tensilon universal testing machine
The tensile strength was measured at 0 mm / min. (3) Puncture strength A sample was fixed to a circular holder having a diameter of 11.28 mm and an area of 1 cm ² , and a needle having a tip shape of 0.5R and a diameter of 1 mmφ was lowered at a speed of 2 mm / sec and pierced to measure a penetration load. did.

(4) Dry Heat Shrinkage Temperature 23 ° C., relative humidity 5 according to JIS K 7100
After marking the sample conditioned at 0% for a predetermined length, the sample was placed in an oven set at 160 ° C. in an unconstrained state.
After leaving still for a minute, the dimensions after removal were measured. The dry heat shrinkage ratio follows the following equation (2). L1 in the equation (2) means the film size after being removed from the oven, and L0 means the initial film size. Dry heat shrinkage (%) = [1− (L1 / L0)] × 100 (2)

(5) Conductivity The dimensions of the sample were measured, and the voltage was measured at a constant current by the four-terminal method, and the resistance was calculated. σ: conductivity (Scm ⁻¹ ), i: current, l: distance between electrodes, ΔV: voltage, S: sample cross-section σ = il / (ΔV · S) (3)

Example 1 (Preparation of Polyamide Porous Film) Polyamide 6 having a number average molecular weight of 13,000 was used as a polyamide, and HFIP was used as an alcohol solvent having a boiling point of 80 ° C. or lower. H so that the polyamide has a concentration of 2% by weight.
The polyamide solution was obtained by dissolving in FIP at room temperature.

The obtained polyamide solution was cast on a glass plate so that the thickness of the solution was 300 μm. When the film of the polyamide solution was naturally dried at normal temperature and atmospheric pressure, the film fluctuated in the in-plane direction of the film, and then a dried film was obtained. Subsequently, the film was peeled from the glass plate to obtain a polyamide porous film. The thickness of the obtained porous film was 15 μm. When a liquid such as water, methanol, or acetone was dropped on the film surface, the liquid permeated. Further, when observed with a scanning electron microscope, the obtained porous film was obtained by laminating a layer having pores of 3 μm or less and a layer having relatively large pores of 8 μm or more in the cross-sectional direction of the film. It had a structure in which the two layers were connected to each other by through micropores having a diameter of 1 μm or less.

The density of polyamide 6 is 1.13 g / c
The porosity of the porous film obtained using m ³ was 51%, the tensile strength was 1.9 kgf / mm ² , the piercing strength was 76 gf, and the dry heat shrinkage was 1.0%. This film is designated as PPA1.

(Preparation of Conductive Polymer-Supported Polyamide)
The porous polyamide film PPA1 obtained above is immersed with a 0.3 mol / L aqueous solution of pyrrole monomer and a 2 mol / L aqueous solution of iron trichloride in a glass apparatus with the porous film PPA1 interposed therebetween with the polyamide film interposed therebetween. Polymerized for 1 hour. Upon polymerization, the polymer was deposited inside and outside the porous film. This was immersed in 4 mol / L hydrochloric acid for 24 hours to perform doping. This was washed with ethanol and dried. Observation with a scanning electron microscope showed that polypyrrole was formed in a fine fiber network in the pores of the porous polyamide film. This conductive polymer supporting film is referred to as PPS1.

The resulting polypyrrole was 140% by weight based on PPA1. Assuming that the volume ratio to the solid content of the porous film is 109% by volume and the density of polypyrrole is 1.47 g / cm ³ , it is calculated that almost all voids are filled with polypyrrole. The conductivity of the conductive polymer-supported polyamide film PPS1 thus obtained was measured and found to be 4.5 Scm ^-1 . The mechanical properties of the PPS1 obtained here were flexible, the tensile strength was 1.8 kg / mm ² , the piercing strength was 85 g, and it was a sufficient strength. The mechanical properties of the conductor film were sufficient.

Example 2 The porous film (PPA1) used in Example 1 was treated with an aqueous solution of iron trichloride and oxidatively polymerized in the presence of dried PPA1 in a pyrrole vapor atmosphere for 7 days. This was washed with ethanol and dried. 24M with 4M hydrochloric acid
It was immersed for a time to perform doping. Assuming that the volume ratio of the porous film to the solid volume is 160% by volume and the density of polypyrrole is 1.47 g / cm ³ , it is calculated that almost all voids are filled with polypyrrole. The conductive polymer-supported polyamide film P thus obtained
The measured conductivity of PS2 was 24.0 Scm ^-1 . The mechanical properties of the PPS2 obtained here were flexible, the tensile strength was 2.0 kg / mm ² and the piercing strength was 90 g, which was sufficient. The mechanical properties of the conductor film PPS2 were sufficient.

Comparative Example 1 The conductive polymer polypyrrole was polymerized in the same manner as in Example 1 without using the porous polyamide as the supported polymer. The resulting polypyrrole is doped with hydrochloric acid and has a thickness of 9 μm.
Met. When measuring the conductivity 3.3Scm ^{- 1.} When the mechanical properties were measured, the tensile strength was 0.2 kg /
In mm ² , the piercing strength was 8 g. The conductive performance and mechanical strength were insufficient.

[0051]

The conductor film of the present invention is a conductor film in which a conductive polymer is carried on a porous film having a structure having non-linear through holes in the cross-sectional direction of the film. It can provide useful materials for battery electrodes and other electric and electronic materials.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01M 4/02 A61F 2/08 5G307 // A61F 2/08 A61L 27/00 Z 5H050 A61L 27/00 H01G 4 / 18 321 H01G 4/18 321 G01N 27/30 353Z 9/016 H01G 9/00 301F F-term (reference) 4C081 AB18 BB03 DA02 DB04 DB05 DB06 DB07 DC01 DC05 EA05 4C097 AA20 CC01 DD02 EE11 FF04 FF05 FF4 MM044 CB47 CE35 CE43 CE94 DA02 DA03 DA13 DA20 DA23 DA47 4F100 AK35C AK46A AK46B AK80C AR00C BA03 BA07 BA10A BA10C BA31 DC11B DJ00A DJ00B EH112 EH312 EJ012 JA20A JG01 JG01C JK17 5E08 FG05 EG05 FG05 BA08 CA20 EA23 EA30 FA02 FA10 FA13 FA18 GA15

Claims (4)

[Claims] 1. A porous structure having fine nonlinear through-holes, a porosity of 35 to 85%, and a pore size of 0.01 to 5 μm.
m, a porous polyamide film having a film thickness of 5 to 50 μm, and having a structure in which a layer made of microporous material and a layer having relatively large voids or openings are stacked in the cross-sectional direction of the film. A conductive film, wherein a conductive polymer is carried on a porous polyamide film in which the two layers are connected to each other by through-holes. 2. The conductive film according to claim 1, wherein a granular structure is formed on the surface of the layer having relatively large voids, and the positions of the voids are not biased on the grain boundaries. 3. The conductive film according to claim 1, wherein the conductive polymer is one of polypyrrole, polythiophene, polyaniline, and derivatives of these polymers. 4. In the presence of a porous polyamide film,
The polymer of a conductive polymer is polymerized.
4. The method for producing a conductor film according to item 3.