JP2000306435A - Conductive high-polymer thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive high-polymer thin film having power of spatial resolution added to functions, such as electric conduction, possessed by a conductive high polymer, or a conductive high-polymer thin film capable of combining functions, such as electric conduction and electromagnetic shielding, of a conductive high polymer with functions, such as reflection prevention, deriving from a phase separation structure. SOLUTION: This conductive high-polymer thin film with a phase separation structure is obtained by dissolving at least one kind of conductive high polymer and at least one kind of non-conductive high polymer in a common solvent, and coating a solid substrate with thus obtained high-polymer solution. The phases of the conductive high polymer include substantially columnar shapes, and the phases of the conductive high polymer are in contact with the solid substrate, or connected with continuity to the phases of the conductive high polymer in contact with the solid substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a conductive polymer thin film having a structure in which a conductive polymer and a non-conductive polymer are formed by phase separation. To be more specific, a conductive polymer thin film that can be used by adding spatial resolution to the functions such as electric conductivity of a conductive polymer or a function such as electric conduction and electromagnetic shielding of a conductive polymer and a phase separation structure The present invention relates to a conductive polymer thin film capable of combining functions such as antireflection and the like.

[0002]

2. Description of the Related Art A one-dimensional π-conjugated polymer is a so-called conductive polymer in which electronic and optical properties such as electric conductivity are changed over a wide range by doping, and vigorous research is being conducted. . Hereinafter, the one-dimensional π-conjugated polymer is referred to as a conductive polymer regardless of the doping level. For example, by dispersing doped high-conductivity conductive polymer fine particles in a non-conductive polymer film rich in flexibility and mechanical strength as a filler,
A conductive polymer film can be obtained (for example,
Banerjee and BM Mandal, Macromolecules 28, 394
0 (1995)). In such a study, a conductive polymer that has been doped in advance is generally used as a filler.
In addition, a thin film is obtained by dissolving both a soluble conductive polymer and a non-conductive polymer having a similar chemical structure in a common solvent that dissolves both, and casting a mixed solution to obtain a thin film. (S. Hotta, SDDV Rughooputh and AJ Hee
ger, Synth. Met. 22, 79 (1987)). In this case, it is shown that the conductive polymer and the non-conductive polymer contained in the thin film are relatively uniformly mixed on the order of several nm.

In addition, a conductive polymer is also used as a light emitting layer of a polymer electroluminescent device. In this case, a thin film is formed by applying a solution of a conductive polymer soluble in a solvent (for example, W. Rie, in "Organic Electroluminescent
Materials and Devices ", S. Miyata and HS Nalwa
ed., Gordon and Breach, 1997, p. 73). In research on polymer electroluminescent devices, a luminescent conductive polymer and a non-luminescent non-conductive polymer (polystyrene, polymethyl methacrylate, polycarbonate, etc.) are dissolved in a common solvent, and the polymer solution is applied. The use of a phase separation structure formed by the conductive polymer and the non-conductive polymer has been reported (O. Inganas, in "Or"
ganic Electroluminescent Materials and Devices ",
S. Miyataand HS Nalwa ed., Gordon and Breach, 1
997, p.147). In this case, it is known that the domain of the conductive polymer formed by the phase separation emits light.
When a conductive polymer is used as a light emitting layer of an electroluminescent element, doping may not be performed, or electrochemical doping may be performed for the purpose of improving luminous efficiency. As described above, studies on thin films using a mixture of a conductive polymer and a non-conductive polymer and utilizing the electronic and optical properties of the conductive polymer have been actively conducted. However, there is no study utilizing a structure formed by phase separation in applications other than electroluminescence.

[0004]

As described above, research on thin films using a mixture of a conductive polymer and a non-conductive polymer has been conducted energetically, but the prior art is based on electroluminescence. Excluding applications, the focus is on the electronic and optical properties of the entire thin film containing the conductive polymer (so-called physical properties as a bulk), such as the spatial resolution of such physical properties and the phase separation structure with such physical properties. There is no example in which functions derived from are combined and used. On the other hand, in electroluminescence applications, a phase separation structure formed by a mixture of a conductive polymer and a non-conductive polymer is used, and fine conductive polymer domains dispersed in a thin film emit light. Although electroluminescence with a high resolution has been realized, the conductivity of such a light-emitting domain is essentially extremely low when utilizing the light-emitting function of a conductive polymer.

On the other hand, the electric conductivity of the conductive polymer can be adjusted in the range of semiconductor to metal by doping. An object of the present invention is to utilize a phase-separated structure of a mixture of a conductive polymer and a non-conductive polymer, so that a phase of a conductive polymer having a semiconductor to metal electric conductivity can be used in applications other than electroluminescence. Are spatially distributed thin films, that is,
Thin films that can use the electronic and optical properties of conductive polymers with spatial resolution, optical functions based on phase-separated structures (such as anti-reflection functions), and the conductivity and electromagnetic shielding of conductive polymers An object of the present invention is to provide a thin film capable of combining functions such as properties.

[0006]

Means for Solving the Problems The inventors of the present invention have made intensive studies to overcome the above-mentioned problems, and as a result, have found that one or more soluble insoluble polymers and one or more non-conductive polymers are incompatible. By applying a polymer mixture solution in which a soluble polymer is dissolved in a common solvent for both, and controlling the formation of a phase-separated structure by coating conditions, etc., it is possible to add spatial resolution to the function of the conductive polymer. Alternatively, the present inventors have found that a conductive polymer thin film capable of combining the function of the conductive polymer and the function based on the phase separation structure can be produced, and reached the present invention.

That is, the gist of the present invention is to provide a phase obtained by dissolving at least one kind of conductive polymer and at least one kind of non-conductive polymer in a common solvent and applying the polymer solution on a solid substrate. A conductive polymer thin film having a separation structure, wherein the phase of the conductive polymer includes a substantially columnar form, and the phase of the conductive polymer is in contact with the solid substrate or in contact with the solid substrate. A conductive polymer thin film characterized by being continuous with a conductive polymer phase.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The conductive polymer to be used in the present invention is a one-dimensional π-conjugated polymer soluble in a solvent, and the solubility thereof is usually 0.1 mg / mL or more, preferably 0.5 mg / mL.
/ ML or more, more preferably 1 mg / mL or more.
The type of the conductive polymer is not particularly limited,
Examples thereof include a polyparaphenylene polymer, a polyparaphenylenevinylene polymer, a polythiophene polymer, a polyaniline polymer, and a copolymer containing them. The non-conductive polymer is soluble in a common solvent with the conductive polymer, and its solubility is usually 0.1 mg / m 2.
L or more, preferably 0.5 mg / mL or more, more preferably 1 mg / mL or more.

The type of the non-conductive polymer is not particularly limited, and examples thereof include a polystyrene polymer, a polymethacrylate polymer, a polycarbonate polymer, and a polyphenylene oxide polymer. However,
The combination of highly compatible conductive and non-conductive polymers may not form a clear phase separation structure,
Not desirable. The amount ratio of the conductive polymer and the non-conductive polymer, as the weight of the conductive polymer in the total amount of both,
Usually, it is 10 to 90%, preferably 20 to 80%, more preferably 30 to 70%.

The common solvent to be used in the present invention varies depending on the combination of the conductive polymer and the non-conductive polymer used. Examples thereof include chloroform, carbon tetrachloride, dichloromethane, toluene, xylene, benzene, dichlorobenzene, and the like. Examples include tetrahydrofuran, methyl ethyl ketone, dioxane, N-methylpyrrolidone, and the like. These may be used alone, or may be a mixed solvent of two or more types, but it is necessary to select at least one in which the mixed solution of the conductive polymer and the non-conductive polymer before coating does not undergo phase separation. is there. The conductive polymer and the non-conductive polymer may each be a composition as long as the mixed solution does not undergo phase separation. Various additives may be added as long as the effects of the present invention are not impaired.

[0011] The thin film of the present invention is prepared by applying the mixed solution on a solid substrate. Examples of the solid substrate material used in the present invention include metals, metal oxides, polymers, and the like, but are not particularly limited as long as they are insoluble in the solvent in the mixed solution. Specific examples include SiO2, indium tin oxide (hereinafter referred to as "ITO"), Au, Ag, and polyaniline. In addition, metals, metal oxides, organic compounds, etc. are deposited on a solid substrate by vapor deposition, sputtering, Lambmuir-Blodgett (LB) method, self-assembly (self-assembly) method, or organic, inorganic multilayer film or organic / An inorganic composite multilayer film may be used as a substrate. Further, on such a solid substrate, a solid substrate in which a pattern is formed using an inorganic compound or an organic compound having an affinity for either the conductive polymer or the non-conductive polymer in the mixed solution may be used. .

The coating method is not particularly limited, and examples thereof include a spin coating method, a dip coating method, a casting method, and an ink jet method. After the mixed solution is applied, the conductive polymer and the non-conductive polymer are selected so that the conductive polymer and the non-conductive polymer in the mixed solution undergo phase separation with the evaporation of the solvent. . In general, when drying is performed slowly, or when phase separation proceeds immediately with evaporation of the solvent after coating, the structure formed by phase separation tends to become coarse. Further, depending on the affinity and surface energy of the conductive polymer and the non-conductive polymer with respect to the solid substrate, the specific polymer separated in phase may be selectively segregated on the solid substrate. In the most extreme case, the phase-separated specific polymer forms a layer on the substrate side or on the opposite surface, and may have a sandwich-like structure.
It is not preferable to add a spatial resolution to the function of the conductive polymer or to combine the function of the conductive polymer with the function derived from the phase separation structure. In other words, the phase separation structure in the thin film formed by such coating depends on the drying speed during coating, the surface energy of the polymer, the affinity of the polymer for the solid substrate, and the conductivity in the mixed solution used for coating. Depends on the type and composition of the conductive polymer and the non-conductive polymer.

Therefore, a phase separation structure which is preferable for adding a spatial resolution to the function of the conductive polymer or for combining and using the function of the conductive polymer and the function derived from the phase separation structure is provided. In order to obtain a conductive polymer thin film, besides selecting a solid substrate / conductive polymer / non-conductive polymer / solvent properly, the rotation speed and rotation time of the spin coating method, or the dip coating method or the casting method The drying method after application is adjusted, and the phase separation structure that is coarsened and / or segregated with time is fixed by solidifying the applied film after application. From the viewpoint of controlling the phase separation structure by application and drying conditions, spin coating is a preferred method.

In order to add a spatial resolution to the function of the conductive polymer or to combine the function of the conductive polymer with the function derived from the phase separation structure, the above-described sandwich structure is used. In addition, it is necessary to avoid a structure in which a phase made of a conductive polymer is extremely segregated on the thin film surface facing the solid substrate. That is, when the area of the conductive polymer phase on the surface of the thin film is Sc and the area of the non-conductive polymer phase is Si, the weight of the conductive polymer in the polymer solution used for coating is φc, Let φi be the weight of the conductive polymer,
It is preferable that Sc / Si <10φc / φi. From such a viewpoint, it is more preferable that Sc / Si <5φc.
/ Φi, more preferably Sc / Si <2φc / φi, and most preferably Sc / Si <1φc / φi. Such Sc and Si are evaluated by observing the thin film surface facing the solid substrate with an optical microscope or an atomic force microscope according to the size of the phase separation structure and performing general image processing. When the field of view for such surface observation is narrow, measurement is performed for several fields of view, and statistically significant values are obtained as typical Sc and Si of the thin film surface. When the domain mainly composed of a conductive polymer contains minute domains of a non-conductive polymer in, for example, a salami shape, such a domain of the non-conductive polymer is regarded as a conductive polymer, and Sc is regarded as a conductive polymer. evaluate.
Similarly, when the domain mainly composed of a non-conductive polymer contains minute domains of the conductive polymer, for example, in a salami shape, the domain of the conductive polymer is regarded as a non-conductive polymer, and To evaluate. Also, on the film surface,
When it is difficult to discriminate between the phase of the conductive polymer and the phase of the non-conductive polymer, the phase may be determined by performing selective elution using a solvent that selectively dissolves either phase.

For the purpose of adding spatial decomposition to the function of the conductive polymer, the thin film includes a phase of the conductive polymer having a substantially columnar shape, and such a phase is formed on the solid substrate. It must be in contact with or be continuous with the conductive polymer phase in contact with the solid substrate. As such a desirable structure, sectional views are shown in FIGS.
(J) illustrates an observation view from the surface. Although FIG. 1 shows an example in which the conductive polymer phase is exposed on the thin film surface facing the solid substrate and the thin film surface is flat, the present invention is not limited thereto. The cross-sectional shape of the substantially columnar shape is not particularly limited, and examples thereof include a circle, an ellipse, a distorted circle, a distorted ellipse, and a shape in which a plurality of circles and ellipses are fused. The spatial morphology of the phase made of such a conductive polymer is determined by using a solvent that selectively dissolves the non-conductive polymer contained in the coating film, eluting the non-conductive polymer, and then using an optical microscope. And by observing with an atomic force microscope. Note that a structure in which a phase made of a conductive polymer is simultaneously desorbed when a non-conductive polymer is selectively eluted is not preferable because the phase made of a conductive polymer is not in contact with a solid substrate. Also,
When the thickness of the thin film is large, a desired phase separation structure cannot be obtained, and thus the thickness is usually 10 to 50,000 nm, preferably 10 to 5000 nm, more preferably 10 to 50 nm.
0 nm.

The electric charge of the conductive polymer contained in the coating film
Electronic and optical properties such as air conductivity are affected by doping.
Controlled. Specifically, acceptors or donors, etc.
Chemical doping of a dopant in the gas or liquid phase
Ping or electrochemical doping method (electrical
Conductive polymer by chemical doping)
What is necessary is to dope. The dopant is particularly limited
However, for example, as an acceptor, generally, a salt
Halogen such as elemental, bromine and iodine, PF_Five, AsF_Five,
SbF_Five, BF_ThreeLewis acids such as HF, HCl, H_Two
SO_Four, CF_ThreeSO_ThreeH, ClSO_ThreeProtons such as H
Acid, FeCl_Three, TiCl_Four, ZrCl_FourSuch as transition gold
Genus compound, Cl^-, Br^-, I^-, ClO_Four ^-, PF₆
^-, BF_Four ^-, AsF₆ ^-, SbF₆ ^-Electrolyte
Nyons are known. On the other hand, donors
Examples include rukari metal, alkaline earth metal, and lanthanoid
Is shown. Such chemical doping or electrochemical doping
The doping method of the conductive polymer and the doping method
And general ones may be used.
Not (for example, Naoya Ogata, conductive polymer, Kodansha
Scientific, 1990). Doping is highly conductive
Where molecules become insoluble in solvents due to doping

In the case of doping, doping may be performed after forming a coating film, and when the doped conductive polymer is soluble in a solvent, doping may be performed at the stage of preparing a solution used for coating, or Alternatively, doping may be performed after forming the coating film. The level of such doping is in the electronic transition absorption spectrum of the thin film at a wavelength of 400 nm to 80 nm.
When the maximum absorbance at less than 0 nm (referred to as wavelength region 1) is A1, and the maximum absorbance at a wavelength of 800 nm or more and 1200 nm or less (referred to as wavelength region 2) is A2, A2 / A1> 0.01. Do. For the measurement of the absorbance, a general ultraviolet-visible absorption spectrum measuring device may be used. Here, in the wavelength region 2, since electron transition absorption based on polaron and / or bipolaron generated by doping is observed, the absorbance of the undoped conductive polymer is zero or extremely small, but the doping is not performed. The absorbance in the wavelength region increases as the level of the compound increases (for example, edited by Katsumi Yoshino, electro-optical functional polymer, Kodansha Scientific, 1989).
On the other hand, an electron transition absorption spectrum of the undoped conductive polymer is observed in the wavelength region 1, and the absorbance in such a wavelength region decreases as the doping level increases (for example, edited by Katsumi Yoshino, Electro-optical function). Polymer, Kodansha Scientific, 1989). Therefore, A2 / A1 defined by the maximum value A1 of the absorbance in the wavelength region 1 and the maximum value A2 of the absorbance in the wavelength region A2.
Can be used as a measure of the level of doping, is zero or very small in the undoped state, and the electrical conductivity and A2 / A1 increase with increasing doping level. From the viewpoint of utilizing the electric conductivity of the conductive polymer, A2 / A1> 0.01, preferably A2 / A1> 0.1, and more preferably A2 / A1.
It is preferable that 1> 0.5.

The conductive polymer thin film thus obtained may be used, depending on its use, by removing the non-conductive polymer contained in the thin film,
It may be eluted before or after doping with a solvent that selectively dissolves the non-conductive polymer. In this case, a conductive polymer thin film having an uneven structure reflecting the phase separation structure in the thin film is obtained. The conductive polymer thin film obtained in the present invention can control the electronic and optical properties of the conductive polymer contained in the thin film by the doping level. In addition to being able to provide thin films distributed with high resolution, functions such as electric conduction of conductive polymers and electromagnetic shielding,
It is possible to provide a functional thin film capable of combining functions such as anti-reflection properties utilizing unevenness of the phase separation structure.

[0019]

The present invention will be described in more detail with reference to the following Examples, which, however, are not intended to limit the scope of the present invention unless it exceeds the gist thereof. Example 1 7.5 mg of poly (3-
Hexylthiophene) and a chloroform solution obtained by dissolving 7.5 mg of polystyrene in 1 ml of chloroform were dropped, and a thin film was formed by a spin coating method under the conditions of a rotation speed of 500 rpm and a rotation time of 60 s. The weight average molecular weights of the used poly (3-hexylthiophene) and polystyrene are as follows:
About 1 × 10 ⁵ (GPC measurement value / polystyrene standard) and 2
× 10 ⁵ . After spin coating, the resultant was degassed and dried at about 60 ° C. for about 1 hour (hereinafter, the thin film obtained in this step is referred to as a spin-coated thin film). The thickness of the obtained spin-coated thin film was 220 nm.

For morphological observation, an optical microscope and an atomic force microscope (hereinafter referred to as "AFM") were used. A
The measurement conditions for the FM measurement were a dynamic mode, a scanning speed of 0.2 Hz, and SEIKO Electronics SPI-3800.
This was performed using FIG. 2 shows the result of observation of the spin-coated thin film with an optical microscope. Since poly (3-hexylthiophene) is colored, the assignment of the domain observed in FIG. 2 is easy, and in this figure, the blackish portion is mainly composed of poly (3-hexylthiophene). Phase. By performing image processing on the observation result of the optical microscope, Sc /
Si = 0.27 ± 0.05 <φc / φi = 1 was obtained. In order to evaluate the phase separation structure in the spin-coated thin film, poly (3-hexylthiophene) was not dissolved, and only polystyrene was spin-coated using ethyl acetate, which is a solvent for selectively dissolving only polystyrene. Eluted from the thin film. Specifically, a part of the spin-coated thin film was immersed in an ethyl acetate solution for about 10 hours. After the immersed film was taken out and dried, AFM observation was performed. The AFM measurement results shown in FIG. 3 indicate that the phase mainly composed of poly (3-hexylthiophene) has a substantially columnar structure and is in contact with the ITO substrate. That is, the phase separation structure in the spin-coated thin film is schematically shown in FIG.

Next, the spin-coated thin film from which polystyrene was not eluted was subjected to iodine doping in a gas phase according to a conventional method. FIG. 4 shows UV / Vis and near-infrared absorption spectra of the spin-coated thin film after the gas phase doping.
It was shown to. The measurement was performed using HITACHI U-4000. FIG. 4 shows that the wavelength is 400 nm or more and 800 nm.
Ratio A2 between the maximum value A1 of the absorbance at less than and the maximum value A2 of the absorbance at a wavelength of 800 nm or more and 1200 nm or less.
/ A1, A2 / A1 = 0.35 / 0.42 = 0.
83 were obtained. Before doping, A2 / A1
Was almost zero. In the absorption spectrum after gas phase doping, electron transition absorption due to doping was confirmed in a wide wavelength range of 1000 nm or less. It is well known that the electronic transition absorption is characteristic of a conductive polymer doped at a high level, and a polythiophene-based polymer has a few to several tens of Ω when it has the electronic transition absorption. -1 cm-1 (G. Tourillon and F. Garnier, J. Ph.
ys. Chem. 87, 2289 (1983)). That is, it was shown that, of the structure schematically shown in FIG. 1B, the phase formed of the conductive polymer had high electric conductivity.

Example 2 The application conditions by the spin coating method were as follows:
A spin-coated thin film was formed in the same manner as in Example 1 except that m was used. The thickness of the spin-coated thin film was 120 nm. FIG. 5 shows the result of observing the spin-coated thin film with an optical microscope. As can be seen from the comparison with FIG. 2 of Example 1, the size of the phase made of poly (3-hexylthiophene) on the film surface is small. As in Example 1, Sc / Si = 0.69 ± 0.07 <φc / φ
i = 1 was obtained. That is, the phase-separated structure can be controlled by the conditions of application by spin coating. The morphology after elution of polystyrene was determined by AFM in the same manner as in Example 1.
As a result, it was confirmed that it had the phase separation structure schematically shown in FIG. 1B as in Example 1, except that the size of the phase separation structure was small. As a result of doping the spin-coated thin film with iodine in the same manner as in Example 1, the same absorption spectrum as in Example 1 was obtained, and the poly (3) in the doped spin-coated thin film was used.
-Hexylthiophene) was shown to have high electrical conductivity.

[0023]

According to the present invention, the functions of the conductive polymer thin film and the conductive polymer which can be used by adding spatial resolution to the functions such as the electric conduction of the conductive polymer and the functions derived from phase separation can be obtained. It is possible to provide a conductive polymer thin film that can be composited.

[Brief description of the drawings]

FIG. 1 is a schematic view of a cross section of a preferred phase separation structure of a conductive polymer thin film (a)-(d). (E)-(g) It is a schematic diagram of the cross section of an unfavorable phase separation structure. (H)-(j) is a schematic view of a preferred phase-separated structure of the conductive polymer thin film when observed from the surface of the thin film facing the solid substrate.

FIG. 2 is a photograph of the conductive polymer thin film obtained in Example 1 observed with an optical microscope.

FIG. 3 is a photograph obtained by AFM observation of a phase composed of poly (3-hexylthiophene) after polystyrene is selectively eluted from the conductive polymer thin film obtained in Example 1.

FIG. 4 is a graph showing a UV / Vis near-infrared absorption spectrum of the conductive polymer thin film obtained in Example 1 after doping with iodine.

FIG. 5 is a photograph of the conductive polymer thin film obtained in Example 2 observed with an optical microscope.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiro Kobashi 1000 Kamoshitacho, Aoba-ku, Yokohama-shi, Kanagawa Prefecture Mitsubishi Chemical Corporation Yokohama Research Laboratory F-term (reference) 4F006 AB16 AB32 AB72 BA07 CA05 4J038 DK001 DN011 HA106 KA06 NA20 PB09 PC02 PC08 5G307 HA01 HB06 HC01

Claims (7)

[Claims] 1. dissolving at least one conductive polymer and at least one non-conductive polymer in a common solvent,
A conductive polymer thin film having a phase separation structure obtained by applying such a polymer solution on a solid substrate, wherein the conductive polymer phase has a substantially columnar form, and the conductive polymer phase Wherein the conductive polymer thin film is in contact with the solid substrate or is continuous with the conductive polymer phase in contact with the solid substrate. 2. When the area of the conductive polymer phase on the surface of the thin film is Sc and the area of the nonconductive polymer phase is Si, the weight of the conductive polymer in the polymer solution used for coating is 2. Is φc, the weight of the non-conductive polymer is φi, and Sc / Si
The conductive polymer thin film according to claim 1, wherein the ratio is <10φc / φi. 3. The conductive polymer thin film according to claim 1, wherein the conductive polymer in the thin film is doped with at least one dopant. 4. In the electronic transition absorption spectrum of a thin film, when the maximum absorbance at a wavelength of 400 nm to less than 800 nm is A1, and the maximum absorbance at a wavelength of 800 nm to 1200 nm is A2, A2 / A1>
The conductive polymer thin film according to claim 1, wherein the value is 0.01. 5. The conductive polymer thin film according to claim 1, wherein the thin film has a thickness of 10 to 50,000 nm. 6. The conductive polymer thin film according to claim 1, wherein the conductive polymer is a polythiophene-based polymer. 7. dissolving at least one conductive polymer and at least one non-conductive polymer in a common solvent,
A method for producing a conductive polymer thin film, comprising a step of applying the polymer solution on a solid substrate.