JPH0610267B2 - Polymer thin film and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improved aromatic polymer thin film and a method for producing the same.

[Conventional technology]

A certain kind of aromatic compound is dissolved in a solvent to which an electrolyte is added and electrolytically oxidized to form a conductive polymer thin film on an electrode substrate.

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. J. Bargon, S.M. S. Mohmand, RJ Waltman,
IBM Journal of Research & Developm
ent) 27, No. 4, page 330 (1983)].

[Problems to be solved by the invention]

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

First of all, there is the problem of limiting the aromatic monomers that can be used. That is, the conductive polymer thin film is usually put together with a counter electrode in a solution prepared by dissolving an electrode substrate in an organic solvent such as acetonitrile and an electrolyte for energizing an aromatic compound serving as a monomer, and between the two electrodes. Is formed by energizing. Therefore, the aromatic compound monomer needs to satisfy the condition that it is soluble in the solution for electrolytic oxidation. Further, when the solubility of the aromatic polymer formed on the surface of the electrolytic substrate is similar to that of the monomer, the polymer is dissolved in the solution to form a stable polymer thin film on the electrode substrate. Is difficult. As described above, the conventional method of producing from a solution has a drawback that the aromatic compound monomer capable of stably forming a thin film on the electrode substrate is limited.

Secondly, a thin film prepared by deposition by electrolytic oxidation from a conventional solution generally has an aggregate of macromolecules grown from a plurality of parts on a substrate, and therefore has pinholes, and further has large irregularities. Therefore, high smoothness of the surface cannot be expected. In addition, since it is strongly affected by the surface properties of the electrode, it is often deposited in an island shape. Therefore, in order to obtain a uniform film, a great deal of labor is required to manage the surface of the electrode, cleaning, electrolytic oxidation conditions, etc. There was a problem such as doing.

Thirdly, the aromatic compound monomer consumed by the electrolytic reaction is a very small part of what is present in the electrolytic solution, and further, even if the aromatic compound monomer is polymerized, it is not fixed to the substrate but is eluted in the solution. The solution is highly contaminated due to the large size. Therefore, it is necessary to frequently replace the electrolytic solution, which causes a problem in economical use of raw materials and solvents.

Fourthly, in the formation of a thin film utilizing deposition by electrolytic oxidation from a conventional solution, both the polymerization reaction and the oxidation reaction of the aromatic compound monomer take place competitively during deposition on the electrode. The flowing current is observed as the sum of the number of electrons required for both reactions. Therefore, it is impossible to estimate the exact amount of the aromatic compound deposited on the electrode substrate by monitoring the current flowing when the thin film is formed. Therefore, it is difficult to directly control the film forming process.

The present invention has been made to eliminate these drawbacks, and an object thereof is to provide a polymer thin film having no pinhole and having high smoothness, and an efficient production method thereof.

[Means for solving problems]

Briefly describing the present invention, the first invention of the present invention is an invention of a polymer thin film, which is characterized in that a laminate of an aromatic compound thin film and an electrolyte membrane formed on an electrode substrate is electrolytically oxidized. To do.

And a second invention of the present invention is an invention of a method for producing a polymer thin film, which comprises a step of producing a thin film of an aromatic compound on an electrode substrate, a step of producing an electrolyte membrane on the thin film, and Each step of electrolytically oxidizing the thin film is included.

That is, in the present invention, the conventional method for producing a polymer film by electrolytic oxidation has been to dissolve an aromatic compound monomer in a solution, polymerize it by electrolytic oxidation, and at the same time deposit it on an electrode. On the other hand, a smooth thin film of an aromatic compound monomer is prepared on the electrode substrate in advance by a coating method, a vacuum deposition method, or the like. Then, an electrolyte membrane is formed on the monomer thin film. After further adhering the upper electrode thereon, a voltage is applied between the two electrodes to obtain a polymer thin film of the monomer by electrolytic oxidation. The inventors of the present invention, even when using a monomer in which electrolytic oxidation reaction proceeds even on such a substrate on which an aromatic monomer thin film is formed, and it is difficult to prepare a polymer thin film from a conventional homogeneous solution system,
It was found that a stable polymer thin film can be prepared on the electrode substrate. The “polymer” of the polymer thin film referred to in the present invention indicates a state in which two or more of the monomers are bound.

Hereinafter, the polymer thin film of the present invention and the method for producing the same will be described in more detail.

The aromatic compound monomer necessary for preparing the polymer thin film of the present invention is not particularly limited as long as it can be electrolytically oxidized, and examples thereof include biphenyl, p-terphenyl, o-terphenyl, p-quaterphenyl, and 2. -Hydroxybiphenyl, N-vinylcarbazole, N-ethylcarbazole, and other monomers used in ordinary polymerization by electrolytic oxidation, derivatives thereof, and oligomers in a quantitative form can be used.

The aromatic compound monomer thin film on the electrode substrate may be adhered to the electrode with an adhesive force that does not peel off during electrolytic oxidation. For example, the monomer is vacuum-deposited on the electrode substrate, or an aromatic compound monomer thin film is used. It can be produced by spin-coating a solution containing a compound monomer on an electrode substrate and then drying it, or by immersing the electrode substrate in a solution containing an aromatic compound monomer and then drying it. That is, the method for producing the aromatic monomer thin film is not limited in the present invention. The aromatic monomer thin film formed on the electrode substrate may have a single composition or a mixture of a plurality of monomers. Also, a laminate of a plurality of monomers may be used.

The electrode substrate is not particularly limited as long as it has a conductive portion and is not corroded by an electrode reaction.
For example, glass or plastic film coated with metal or metal oxide, or the metal itself,
And so on. Further, the conductive portion may be processed into a pattern, and in this case, a polymer film obtained by electrolytically oxidizing the aromatic compound monomer thin film in a pattern can be formed.

The electrolyte membrane material is not particularly limited as long as it contains diffusible electrolyte ions in the aromatic compound monomer thin film, and for example, alkali metal or tetraalkylammonium fluoroborate, perchlorate, sulfate, sulfonate, or those. It is possible to use a derivative obtained by dispersing the derivative in a low-molecular or high-molecular matrix. The matrix material is not particularly limited, but an ether-based polymer, a polymer supporting an ionic carrier such as a crown ether, or the like has provided good results. The electrolyte membrane is formed by vacuum-depositing the electrolyte membrane material on the aromatic compound thin film, or by dissolving a solution of the aromatic compound in a solvent that does not dissolve the monomer of the aromatic compound in the aromatic compound monomer thin film. It can be prepared by spin-coating on and then drying, or by dipping an electrode substrate on which an aromatic compound monomer thin film is directed in the solution and then drying. That is, in the present invention, the method for producing the electrolyte membrane is not limited.

The upper electrode is not particularly limited as long as it has a conductive portion and is not corroded by an electrolytic reaction.
Gold, chromium, aluminum, tin oxide, other metals, metal oxides, etc. can be used. A method such as vacuum deposition or sputtering can be used to manufacture electrodes of these substances. Further, it is also possible to use a conductive surface such as glass or plastic film coated with a metal or a metal oxide, or the metal itself in contact with the surface of the electrolyte membrane.

An aromatic-based polymer thin film is obtained by energizing the aromatic-based compound monomer thin film produced by the above method through two electrodes.

The polymer thin film obtained in this way is a monomer thin film without pinholes or irregularities produced on the electrode substrate, which is polymerized as it is, and retains the same good structure as the original monomer thin film. ing. These polymer thin films can be used in a state where they are combined with an electrolyte membrane and electrodes, but by removing the electrolyte membrane and the upper electrode by immersing it in a solvent that dissolves the electrolyte membrane, It is also possible to take out only the molecular thin film and use it alone. Further, the raw material monomers necessary for the electrolysis reaction only need to be those present on the surface of the electrode substrate, and furthermore, the aromatic compound monomer does not disappear during the electrolysis reaction as in the solution system. Therefore, it is possible to preset the amount, thickness, etc. of the polymer thin film formed on the electrode.

The reason why such a smooth and high-quality polymer thin film is obtained is
The electrolyte component in the electrolyte membrane diffuses into the monomer thin film formed on the electrode substrate and reaches the electrode surface, whereby a conductive part is formed, an electrolytic reaction occurs, and an electrolytic oxidation reaction proceeds on the electrode surface. It is estimated that the polymer thin film is formed from the electrode substrate side. Therefore, a uniform polymer thin film can be obtained by selecting the monomer thin film in which the electrolyte can diffuse and the composition of the electrolyte film.

〔Example〕

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

Example 1 A pyrene thin film was formed on a Nesa glass substrate by a vacuum evaporation method, and then a mixture of lithium trifluoromethanesulfonate and polyoxyethylene was evaporated, and then platinum was further evaporated as an upper electrode. A constant voltage of 2.5 V was applied with the substrate on which the pyrene was deposited as a positive electrode and the platinum upper electrode as a negative electrode. During the voltage application for about 5 minutes, the pyrene thin film observed through the Nesa glass substrate gradually changed from colorless to yellow. After the reaction, this composite thin film of pyrene and electrode was immersed in water to dissolve the electrolyte membrane, and the resulting pyrene thin film was dried under reduced pressure for one day and then observed under a microscope. It was confirmed that a very smooth thin film was formed.

Examples 2 to 10 Carbazole (Example 2), isothianaphthene (Example 3), azulene (Example 4), methylazulene (Example 5), N on a conductive electrode substrate in the same manner as in Example 1. A thin film of phenylpyrrole (Example 6), naphthalene (Example 7), triphenylene (Example 8), biphenyl (Example 9), N-vinylcarbazole (Example 10), then an electrolyte membrane. It was prepared by a coating method or a vacuum evaporation method, and an upper electrode was further laminated. Using these composite thin films, electrolytic polymerization was performed in the same manner as in Example 1 to obtain an aromatic polymer thin film. The manufacturing conditions are summarized in Table 1. When these composite thin films were immersed in a solvent that dissolves the electrolyte membrane, and the resulting polymer thin films were dried under reduced pressure for one day and then observed under a microscope. It was confirmed that a thin film with high smoothness was formed on the surface.

[Effects of the Invention] As described above, by producing an aromatic monomer thin film on an electrode substrate according to the present invention, and laminating an electrolyte membrane and an upper electrode, and then performing electrolytic polymerization, there is no pinhole and smoothing. It is possible to produce a highly aromatic aromatic polymer thin film easily and without the need for an electrolyte solution, which is a remarkable effect. The polymer thin film obtained is
Like a film obtained by ordinary electrolytic polymerization, it has conductivity, redox property, and electrochromism. Therefore, it is useful as a secondary battery, especially a thin film battery or a display material. Further, in these applications, the system for forming the electrolytically polymerized thin film of the present invention can be used as it is as a battery cell or a display cell.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01M 4/02 B 4/60

Claims (2)

[Claims] 1. A polymer thin film of an aromatic compound, which is formed by electrolytically oxidizing a laminate of an aromatic compound thin film and an electrolyte membrane formed on an electrode substrate. 2. A step of forming an aromatic compound thin film on an electrode substrate, a step of forming an electrolyte membrane on the thin film, and a step of electrolytically oxidizing the aromatic compound thin film. A method for producing a polymer thin film characterized by the above.