JPH01119689A - Electrolytic oxide film and production thereof - Google Patents

Abstract

PURPOSE:To form conductive high-polymer films by forming the film of an arom. compd. monomer on the surface of a substrate which is an insulating material and forming a pair of conductors which do not conduct each other thereon, then immersing the substrate into an electrolytic soln. and impressing a DC voltage to the conductors. CONSTITUTION:The film 5 which consists of the monomer 2 of the arom. compd. such as biphenyl or is formed by mixing an electrolyte such as the salts of alkali metals with this monomer is formed by a vacuum deposition method, etc., on the substrate 1 made of the insulating material such as glass or plastic as an electrode substrate. >=1 Pairs of the conductors 3, 4 which consist of Au, Pt, Ni, Cr, etc., and do not conduct each other are formed to a pattern shape thereon. Electrolytic oxidation is effected by impressing a DC voltage between the conductors 3 and 4 after immersing the substrate 1 having only the monomer film 2 into an electrolytic soln. dissolved with the electrolyte of the alkali metal, etc., and without immersing the substrate having the mixed film 5 composed of the monomer and the electrolyte into the electrolytic soln. The electrolytic oxidide film having the patterned conductivity is thus formed on the monomer film 2 or the mixed film 5 composed of the monomer and the electrolyte.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improved electrolytic oxide film and a method for producing the same.

[Conventional technology]

A conductive polymer film can be formed on an electrode substrate by dissolving a certain type of aromatic compound in a solvent containing an electrolyte and electrolytically oxidizing the compound. As such aromatic compounds, heterocyclic compounds such as pyrroles and thiophenes, and polycyclic aromatic compounds such as azulene, pyrene, and triphenylene are known [for example, J, Bargon, S, Mormant (B,
Mohmand), R, T, Walt W 7 (R,
J. Waltman), IBM Journal of Research and Development (M. Jo
urnalof Re5earch & Develo
p-ment) Volume 27, Issue 4, Page 550 (191
35)].

However, the method of forming a polymer film by direct electrolytic oxidation on an electrode substrate has various drawbacks as described below.

First of all, there is the problem of limitations on the aromatic monomers that can be used. In other words, a conductive polymer film is usually formed by placing an electrode substrate together with a counter electrode in a solution in which an aromatic compound as a monomer and an electrolyte for conducting electricity are dissolved in an organic solvent such as acetonitrile. It is formed by passing current between them. Therefore, the aromatic compound monomer needs to satisfy the condition that it is soluble in the solution for electrolytic oxidation. In addition, if the solubility of the aromatic polymer formed on the electrode substrate surface is similar to the solubility of the monomer, the cough polymer will dissolve in the solution and form a stable polymer film on the electrode substrate. Difficult to form. in this way,
The conventional solution-based production method has the drawback that there is a limit to the amount of aromatic compound monomers that can stably form a film on the electrode substrate.

Second, films produced by conventional electrolytic oxidation deposition from a solution are generally aggregates of bulk polymers grown from multiple parts of the substrate, so they have pinholes and large irregularities. Therefore, high surface smoothness cannot be expected. In addition, because it is strongly affected by the electrode surface properties, there are many cases where island-like precipitation occurs, and therefore, in order to obtain a homogeneous film, a great deal of effort is required to control the electrode surface treatment, cleaning, electrolytic oxidation conditions, etc. There were problems such as.

Fifth, the aromatic compound monomer consumed by the electrolytic reaction is only a small part of what is present in the electrolytic solution, and furthermore, even when polymerized, the proportion of polymers that are not fixed to the substrate and elutes into the solution. is large, resulting in large contamination of the solution. Therefore, it is necessary to frequently replace the electrolytic solution, which poses a problem in terms of economical use of raw materials and solvents.

Fourth, in the conventional film formation using electrolytic oxidation deposition from a solution, both the polymerization reaction and the oxidation reaction of the aromatic compound monomer compete with each other during deposition on the electrode. The flowing current can be observed as the sum of the number of electrons required for both reactions. Therefore, even if the current flowing during film formation is monitored, it is not possible to accurately estimate the amount of aromatic polymer deposited on the electrode substrate.

Therefore, there has been a problem in that it is difficult to directly manage the film formation process.

On the other hand, in recent years, there has been a rapid increase in demand for digital display devices such as liquid crystal displays, touch pen type handwriting input devices, facsimile devices, and the like. Arbitrary patterns can be used for display parts and connectors of input/output parts of these home devices, such as display parts of liquid crystal display devices and electrochromic display devices, connection of electrode extraction parts, input of touch pens, output extraction of image sensors in facsimile machines, etc. There is a need for an inexpensive film with high conductivity. In addition, sensor elements are becoming smaller and more solid-state year by year, and for example, for ion sensors, it is required to create a homogeneous film with electrical conductivity and redox properties in an arbitrary pattern on minute electrode parts. ing.

Conventionally, conductive polymer films have been produced by mixing various thermoplastic resins with conductive optical fibers and molding them into films, and by vapor-depositing conductive materials on the surface of polymer films. Spray coating or plating have been used. Although it is easy to obtain a uniformly conductive film with any of these films, in order to obtain a film that is imparted with conductivity only in a desired pattern, it is necessary to subject the film to some kind of pattern forming process.

On the other hand, unlike such composite systems of metals or carbon and various resins, the aforementioned conductive polymer materials, in which the polymer material itself is electrically conductive, are attracting attention because of their high electrical conductivity. In addition to exhibiting electrical conductivity, these polymers have reversible redox properties and electrochromism, and are attracting attention as materials for batteries, displays, and sensors. However, in the method of forming a polymer film by electrolytic oxidation on an electrode substrate, the monomers that can be used are limited due to the solubility of the formed polymer, the homogeneity of the formed film is low, and the formation As already mentioned, there are various problems such as the amount of monomer used is large compared to the amount of membrane, and the electrolytic solvent is significantly contaminated. Furthermore, the resulting conductive polymer film is generally fragile and difficult to mold, so no technology has been established for patterning it. Furthermore, in such electrolytic polymerization from a monomer solution, the monomer in the solution diffuses onto the electrode surface and polymerizes.
On the electrode surface, the diffusion state of monomers differs between the center and the periphery, resulting in different polymerization rates, making it difficult to obtain a homogeneous polymer film at each position on the electrode.

When using patterned electrodes, 1. Because the diffusion state of the monomer becomes complicated depending on the size of the pattern and the pattern density, a uniform film cannot be obtained and it is difficult to control polymerization. Recently, a method has been discovered in which a general-purpose polymer such as polyvinyl chloride is coated on a patterned substrate having nine conductive sites, and this is used as an electrode for electrolytic oxidation in a 7-mer solution.

[Problem that the invention seeks to solve]

However, in the patterned conductive polymer film obtained by this method, the conductive polymer is dispersed in a general-purpose polymer, and the conductivity is extremely low, the redox rate is also low, and the electroconductive polymer is dispersed in a general-purpose polymer. Chromism and sensitivity as a sensor also decrease. Moreover, the polymerization itself also depends on the diffusion of monomers in general-purpose polymers, and the problem of nonuniformity of polymerization associated with this has not been solved at all.

The present invention has been made to eliminate these drawbacks, and its purpose is to provide a highly homogeneous polymer film or patterned polymer film, and an efficient method for producing the same.

[Means for solving problems]

To summarize the present invention, the first invention of the present invention is an invention of a method for producing an electrolytic oxide film, which includes a step of producing a film on an aromatic compound on a substrate, and a step of producing a film on an aromatic compound monomer. The method is characterized in that it includes the following steps: forming one or more pairs of conductors having conductivity that are not electrically conductive to each other on the film, and electrolytically oxidizing the aromatic compound monomer.

Further, a second invention of the present invention is an invention of another method for producing a patterned electrolytic oxide film, which includes a step of producing a mixed film of an aromatic compound monomer and an electrolyte on a substrate; It is characterized by including the following steps: forming one or more pairs of electrically conductive materials that are not electrically conductive to each other on a mixed film of monomer and electrolyte, and electrolytically oxidizing the aromatic compound monomer.

A fifth invention of the present invention is an invention of an electrolytic oxide film, and is characterized by having an electrolytic oxide film formed on a substrate by electrolytic oxidation of an aromatic compound monomer on the substrate.

Furthermore, a fourth invention of the present invention is another invention of an electrolytic oxide film, in which an electrolytic oxide film is formed on a substrate by electrolytic oxidation of a mixture of an aromatic compound monomer and an electrolyte. It is characterized by having.

In other words, the conventional method of producing polymer membranes is electrolytic polymerization from a solution of aromatic compound monomers, which requires a complicated pattern formation process on the produced film.
It is accompanied by many problems such as limitations on usable monomers due to solubility and contamination of electrolytic solvents. In contrast, in the present invention, a smooth film of an aromatic compound monomer is prepared in advance on a substrate by a coating method, a vacuum evaporation method, or the like. Next, one or more pairs of electrical conductors having electrical conductivity are formed on the film of the aromatic compound monomer, for example, produced using a method such as vacuum evaporation, sputtering, or CVD, or a conductive material that has been produced in advance. one or more pairs of conductors having Note that this step is not necessary if a conductor is formed on the substrate in advance. An electrolytic oxide film is obtained by immersing a substrate having this film in an electrolytic solution and applying an appropriate DC voltage to a part of the conductor as a positive electrode and the rest as a negative electrode. Alternatively, instead of producing a film on an aromatic compound, a film of a mixture of an aromatic compound monomer and an electrolyte may be produced, and one or more pairs of conductors may be deposited on the film or on the substrate by vacuum evaporation, sputtering, A conductive material having electrical conductivity is brought into contact with a pattern formed using a method such as a CtVD method or prepared in advance. Next, by applying an appropriate DC voltage to a part of the conductor as a positive electrode and the remaining part as a negative electrode, a patterned electrolytic oxide film is obtained without using a solvent.

According to the method of the present invention, the electrolytic oxidation reaction proceeds even on a substrate on which a composite film of an aromatic compound monomer or an aromatic compound monomer and an electrolyte and one or more pairs of electrically conductive materials are attached, Even when using monomers that are difficult to produce polymer films from conventional homogeneous solution systems, stable electrolytic oxide films can be created on substrates, and the current flow during the polymerization reaction can be adjusted and the shape of the conductor can be controlled. A patterned electrolytic oxide film can be obtained by forming an arbitrary pattern. Note that the term "polymer" as used in the present invention refers to a state in which two or more of the monomers are bonded together.

Hereinafter, the electrolytic oxide film of the present invention and its manufacturing method will be explained in more detail.

The aromatic compound monomer necessary for producing the electrolytic oxide film of the present invention is not particularly limited as long as it can be electrolytically oxidized, but examples include biphenyl, p-terphenyl, 0-
Monomers used in ordinary electrolytic oxidation polymerization such as terphenyl, p-quarterphenyl, 2-hydroxybiphenyl, N-vinylcarbazole, N-ethynylcarbazole, terthiophene, N-phenylvirol, etc. Derivatives and quantified oligomers can be used. Normally liquid monomers can be used as long as they can be made into a solid film in the form of derivatives or oligomers.

It is sufficient that the aromatic compound monomer film on the substrate is adhered to the substrate with sufficient adhesion to not peel off during electrolytic oxidation.
For example, the aromatic compound monomer is vacuum-deposited onto the substrate, or a solution containing the aromatic compound monomer is spin-coded onto the substrate and then dried;
It can be produced by immersing a substrate in the solution and then drying it. A similar method can be used when producing a film made of a mixture of an aromatic compound monomer and an electrolyte instead of producing a film of an aromatic compound monomer on a substrate. That is, in the present invention, the method for producing the aromatic compound monomer film is not limited.

The substrate is not particularly limited as long as it is insulative and not corroded by the electrolytic reaction solution. For example, glass, plastic/film, ceramics, paper,
Minerals or a combination of these materials can be used.

The electrolyte to be mixed with the aromatic compound monomer of the present invention is not particularly limited as long as it can be diffused into the aromatic compound monomer film. , Br-10
2-1 engineering (mu 2,0.)-1--1P! 8q −,0
71803-1O10,-,8011-1BF,-1N
O3-1c horse coo'''', etc.], tetraalkylammonyl fluoroborate, barchlorate, sulfate, sulfonate, or derivatives thereof, 1'
bBrl, Ag(80i0I's)t, Zn(day 0
．． Various salts such as OF', ), ZnO1, and Ag0104 can be used. In addition, a low-molecular or high-molecular matrix material that aids electrolyte diffusion can also be included. Such matrix materials include, for example, low molecular weight ion carriers such as crown ether, polyethylene oxide, polyethylene oxide, polytetrahydrofuran, poly[(alkoxy)
Phosphazene], poly(N-acetylethyleneimine)
Examples include polymers such as polyvinyl acetate, polyethyleneimine, and polymers supporting ion carriers.

Aromatic compound motsumer membrane obtained by the above method,
Alternatively, the materials for the conductor fabricated on the mixed film of aromatic compound monomer and electrolyte include noble metals such as gold, platinum, and palladium, base metals such as nickel, chromium, and stainless steel, tin oxide, indium oxide, and tin-indium oxide. Conductive metal oxides such as oxides (TO) can be used. Furthermore, a combination of these materials can also be used.

To form one or more pairs of conductors made of these materials on the aromatic compound monomer film, a combination of methods such as vacuum evaporation, sputtering, and AVN methods and a mask having a fine pattern may be used. Can be done. Further, one or more pairs of conductors having electrical conductivity prepared in advance may be attached and brought into contact with the aromatic compound monomer film. That is, in the present invention, the method for forming a conductive material having electrical conductivity in a pattern is not limited.

FIGS. 1 and 2 are schematic diagrams of the structure of an example of an aromatic compound monomer film or a mixed film of an aromatic compound monomer and an electrolyte, and a patterned conductor according to the present invention.

Figures 1-1 and 1-2 illustrate the case where the aromatic compound monomer membrane is used alone;
The figure is a plan view, and Figures 1-2 are side views. In each figure, numeral 1 is an insulating substrate, 2 is an aromatic compound monomer film,
S and 4 are conductors that have conductivity in a pattern, 3 is a portion that becomes a positive electrode of the conductor that has conductivity in a pattern, and 4 is a portion that becomes a negative electrode of the conductor that has conductivity in a pattern. means. In addition, Figures 2-1 and 2-2 illustrate the case where a membrane containing a mixture of aromatic compound monomer and electrolyte is used; Figure 2-1 is a plan view, and Figure 2-2 is a plan view. The figure is a side view. Code 1.3 in each figure
．． 4 has the same meaning as in FIG. 1, and 5 means a mixed membrane of an aromatic compound and an electrolyte.

A substrate made of an aromatic compound monomer film prepared by the above method and a conductor having conductivity in a pattern,
A pattern-shaped electrolytic oxide film is created only in the vicinity of the negative conductor by immersing it in an electrolytic solution together with the counter electrode, and applying an appropriate DC voltage to one of the conductors as a positive electrode and the other as a negative electrode. Can be done.

Examples of electrolytes necessary for energizing the electrolytic solution include alkali metal and tetraalkylammonium halides, fluoroborates, barchlorates, sulfates,
Sulfonates and the like can be used.

In addition, when using a substrate consisting of a mixed film of aromatic compound monomer and electrolyte and one or more pairs of conductors, one conductor can be used as a positive electrode and the other as a negative electrode without using an electrolytic solution. By applying a direct current voltage, a patterned electrolytic oxide film can be formed only in the vicinity of one conductor.

The electrolytically oxidized film obtained in this way is a seven-layer film without pinholes or irregularities produced on a substrate, or a monomer-electrolyte mixture film that is electrolytically oxidized as it is, and is different from the original seven-layer film. It maintains the same high quality construction.

The conductor may be removed if necessary. In addition, when the electrolytic oxide film is made using a mixed film of monomer and electrolyte,
Although it is possible to use the electrolytic oxide membrane in a composite state with an electrolyte, it is also possible to take out only the electrolytic oxide membrane and use it alone by immersing it in a solvent that dissolves the electrolyte and removing the electrolyte. It is possible. In addition, as raw material monomers necessary for electrolytic reactions, only those present on the substrate surface are required, and furthermore, unlike in conventional homogeneous solution systems, this reaction does not occur. Therefore, it is also possible to set the amount, film thickness, etc. of the electrolytic oxide film to be formed on the electrode substrate in advance.

Further, it is also possible to obtain a patterned electrolytic oxide film by adjusting the current flowing during the polymerization reaction and forming the conductor into an arbitrary pattern.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited thereto.

Example 1 A thin pyrene film (thickness: 5 μm) was prepared on a quartz glass substrate by vacuum evaporation, and a metal mask was placed on the film and platinum was sputtered to form a 1-pitch comb shape. An electrode was prepared.This pyrene and a comb-shaped electrode were vapor-deposited, the nine substrates were immersed in an electrolytic solution, and pyrene was electrolytically oxidized at a constant voltage of 2.5 V using one of the comb-shaped electrodes as a positive electrode and the other as a negative electrode. The electrolyte was an electrolytic salt (tetraethylammonium perchlorate) α in a water/ethanol mixed solvent.
It was assumed that 1M was dissolved. By applying voltage for about 3 minutes, polymerization gradually occurred from the periphery of the comb-shaped positive electrode. After thoroughly washing this film with water and drying it overnight, microscopic observation revealed that an electrolytically oxidized pyrene film was formed in a pattern with much better homogeneity than that obtained using the conventional solution method. It was confirmed that

Example 2 A carbazole thin film (thickness Q, 4 μm) was prepared on a quartz glass substrate by a solution coating method, and a pair of comb-shaped stainless steel electrodes with a 5-pitch pitch were fixed in close contact with each other on the film. did. The substrate having this carbazole film and patterned electrodes was immersed in the same electrolyte solution as in Example 1, and one of the patterned electrodes was used as a positive electrode and the other as a negative electrode, and carbazole was electrolytically oxidized at a constant voltage of 2.57. Ta. After about 5 minutes of voltage application, the periphery of the positive patterned electrode gradually turned dark green. After thoroughly washing the film with water and drying it overnight, microscopic observation revealed that a patterned electrolytically oxidized carbazole film was formed that was much more homogeneous than that produced by the conventional solution method. It was confirmed that

Examples 5 to 10 Inchanaphthene (Example 5) and azulene (Example 4) were deposited on a quartz glass substrate by a solution coating method or a vacuum evaporation method.
), methyl azulene (Example 5), N-phenylpyrrole (Example 6), naphthalene (Example 7), triphenyl/(Example 8), biphenyl (Example 8), m-vinylcarbazole ( A thin film of Example 10) was produced. Next, a platinum comb-shaped electrode similar to that in Example 1 is made on these films, or a pair of stainless steel electrodes similar to that in Example 2 are brought into close contact with each other, with one of the patterned electrodes being a positive electrode and the other being a negative electrode. Electrolytic oxidation of aromatic compound monomers was carried out at a constant voltage of 2.5V. After applying voltage for about 5 minutes,
These membranes were thoroughly washed with water and dried overnight before microscopic observation. As a result, it was confirmed that an electrolytic oxide film with extremely superior homogeneity was formed compared to that obtained using the conventional solution method. The implementation conditions are shown in Table 1.

Example 11 A thin film of a mixture of pyrene, lithium trifluoromethanesulfonate, and polyoxyethylene was prepared on a quartz glass evaporation plate by vacuum evaporation, and then a metal mask was closely attached to the film in the same manner as in Example 1. An 11 fil pitch comb-shaped electrode was prepared by sputtering platinum.Next, pyrene was electrolytically oxidized at a constant voltage of 2.5V using one of the comb-shaped electrodes as a positive electrode and the other as a negative electrode.

By applying voltage for about 2 minutes, polymerization gradually occurred from the periphery of the comb-shaped positive electrode. When we observed this film using a microscope, we found that
It was confirmed that an electrolytically oxidized pyrene mixed film was formed in a pattern with much better homogeneity than that produced by the conventional solution method.

Example 12 A film of a mixture of carbazole, lithium trifluoromethanesulfonate, and polyoxyethylene was prepared on a quartz glass substrate by a solution coating method, and a stainless steel film having the same shape as that used in Example 2 was further applied on the film. The electrode pair was tightly fixed.

Next, one of the electrodes was set as a positive electrode and the other as a negative electrode, and 2.5
Electrolytic oxidation of carbazole was performed at a constant voltage of v. After about 5 minutes of voltage application, the periphery of the positive patterned electrode gradually turned dark green.

When this film was observed under a microscope, it was confirmed that an electrolytically oxidized carbazole mixed film was formed in a pattern with much better homogeneity than that produced by the conventional solution method.

Examples 15 to 15 Isothia naphthi y (Example 15) and asrene (actual mf) were deposited on a quartz glass substrate by solution coating or vacuum deposition.
lJ14), a mixed membrane of N-phenylpyrrole (Example 15) and an electrolyte was prepared.

Next, a platinum comb-shaped electrode similar to that in Example 1 was fabricated on these films, or a stainless steel electrode pair similar to that in Example 2 was brought into close contact with the membrane, with one of the electrodes being the positive electrode and the other being the negative electrode. Electrolytic oxidation of aromatic compound monomers was performed at a constant voltage of 2-5V. After about 5 minutes of voltage application, these films were observed under a microscope, and it was found that a patterned electrolytic oxidation mixed film was formed that was much more homogeneous than that made using the conventional solution method. This was confirmed. The implementation conditions are shown in Table 2.

Example 16 A carbazole thin film (film thickness cL 4 μm groove) was prepared on a quartz glass substrate by a solution coating method, and a pair of comb-shaped stainless steel electrodes having a pitch of 5 cm were closely fixed on the film, facing each other. The substrate having this carbazole film and patterned electrodes was immersed in the same electrolytic solution as in Example 1, and one of the patterned electrodes was used as a positive electrode and the other as a negative electrode, and carbazole was electrolytically oxidized at a constant voltage of 2.5V. Ta. By applying voltage for about 1 minute, the area around the patterned positive electrode gradually changed from colorless to dark green. After thoroughly washing this film with water and drying it overnight, microscopic observation revealed that a patterned electrolytically oxidized carbazole film was formed that was much more homogeneous than that made using the conventional solution method. It was confirmed that there is.

Example 17 A film of a mixture of carbazole, lithium trifluoromethanesulfonate, and polyoxyethylene was prepared on a quartz glass substrate by a solution coating method, and a stainless steel film having the same shape as that used in Example 2 was further applied on the film. The electrode pair was tightly fixed.

Next, one of the electrodes was set as a positive electrode and the other as a negative electrode, and 2.5
Electrolytic oxidation of carbazole was performed at a constant voltage of v. By applying voltage for about 1 minute, the area around the patterned positive electrode gradually changed from colorless to dark green. When this film was observed under a microscope, it was confirmed that a patterned electrolytically oxidized carbazole mixed film had been formed which was much more homogeneous than that produced by the conventional solution method.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to easily produce an electrolytic oxide film with excellent homogeneity, which is a particularly remarkable effect.

The resulting electrolytic oxide film has improved conductivity, redox properties, and electrochromism, similar to films obtained by ordinary electrolytic polymerization. Therefore, it is useful as a secondary battery, a thin film battery, a sensor, and a display material.

[Brief explanation of the drawing]

Figures 1-1 and 1-2 are schematic diagrams illustrating the case where the aromatic compound monomer membrane of the present invention is used alone, and Figures 2-1 and 2-2 are 1-1 and 2-1 are plan views, and FIGS. 1-2 and 2-2 are schematic diagrams illustrating a case where a membrane containing a mixture of an aromatic compound monomer and an electrolyte is used. FIG. 1: Insulating substrate, 2: Aromatic compound monomer film, 3 and 4: Conductor having conductivity in a pattern, 5: Mixed film of aromatic compound monomer and electrolyte Patent applicant Nippon Telegraph and Telephone Corporation

Claims (1)

[Claims] 1. A step of producing a film of an aromatic compound monomer on a substrate, a step of forming one or more pairs of conductors having conductivity that are not electrically conductive to each other on the film of an aromatic compound monomer. ,
A method for producing an electrolytically oxidized film, comprising the steps of electrolytically oxidizing the aromatic compound monomer. 2. A step of producing a mixed film of an aromatic compound monomer and an electrolyte on a substrate, a step of forming one or more pairs of conductors having conductivity that are not electrically conductive to each other on the mixed film of an aromatic compound monomer and an electrolyte. A method for producing an electrolytically oxidized film, comprising the steps of: , electrolytically oxidizing the aromatic compound monomer. 3. An electrolytic oxide film comprising, on a substrate, an electrolytic oxide film formed by electrolytic oxidation of an aromatic compound monomer on the substrate. 4. An electrolytic oxide film comprising, on a substrate, an electrolytic oxide film formed by electrolytic oxidation of a mixture of an aromatic compound monomer and an electrolyte on the substrate.