JPS6259632A - Production of electroconductive polysilane - Google Patents

Abstract

PURPOSE:To facilitate the formation of an electroconductive polysilane suitable as a transparent electric conductor for solar batteries, etc., by dissolving a specified polysilane in sulfuric acid and evaporating the sulfuric acid from the obtained sulfuric acid solution by heating. CONSTITUTION:A polysilane of the formula (wherein R<1> and R<2> are each H, methyl, ethyl, propyl, phenyl, toluyl, vinyl or the like, provided that the case in which the both are H at the same time is excluded), e.g., polydimethylsilane or polymethylphenylsilane, is dissolved in sulfuric acid. Concentrated sulfuric acid is desirable as said sulfuric acid, but diluted sulfuric acid of a concentration >=50vol% may be used. An electroconductive polysilane is obtained by evaporating the sulfuric acid from the obtained sulfuric acid solution of the polysilane by heating it in such a manner that it is dropped onto a heated substrate. By utilizing this method, the surface of a glass or ceramic substrate can be easily coated with the electroconductive polysilane to render it electroconductive.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for easily producing conductive polysilane.

[Conventional technology]

Solar cells, liquid crystal panels, electrochromic (fIC)
) materials, transparent conductors for use in glass heating elements, etc. are desired. Conventionally, ITO (
Indium, tin, oxide) films were widely used. ITO films are produced by sputtering, vapor deposition, chloride hydrolysis, or the like. However, either method requires a large-scale device, takes a long time to manufacture, and increases the cost.

, polyacetylene as a conductor to replace this ITO film,
The use of conductive polymers such as polypyrrole and polythenylene has been proposed. However, most of these conductive polymers absorb visible light and have poor light transmittance, which has a significant effect when applied to solar cells and the like. Among these, recently, a polysilane compound in which silicon (Si) is bonded in a linear chain in one dimension has been polymerized with a high molecular weight. This polysilane compound has a high transmittance of visible light in a film-like body, and is attracting attention.

Polysilane compounds are usually insulators when they are synthesized, but the following methods can be used to impart conductivity.

That is, in the presence of arsenic pentafluoride (AsFs), polymethylphenylsilane, which is a type of polysilane compound, is irradiated with light in the ultraviolet region (254 nm).

By this method, polymethylphenylsilane is three-dimensionally crosslinked to incorporate the dopant, and 0.5S/(Jl
It has been reported that a material with an electrical conductivity of
103°7352 (1981)).

However, this method uses highly toxic AsF5;
It is difficult to operate because it requires light irradiation, and it is not possible to increase the area, which is an advantage of polymers.

[Problem that the invention seeks to solve]

The present invention aims to solve the above-mentioned problems and provide a method for producing a highly conductive polysilane.

[Means for solving the problem] The method for producing conductive polysilane of the present invention is performed using the following formula [A]
Dissolve the polysilane represented by in sulfuric acid.

The method is characterized in that the sulfuric acid solution is then heated.

(However, in the above formula, RI and RZ are each hydrogen, an alkyl group such as a methyl group, an ethyl group, or a propyl group, an aryl group such as a phenyl group, a tolyl group, or an allyl group such as a vinyl group, and may be the same or different. Moyoiga 9
Both cannot be hydrogen at the same time. ) In the present invention, polysilane is a starting material for obtaining conductive polysilane, and is represented by the above formula [A]. For example, the polysilane includes polydimethylsilane, polymethylphenylsilane, polyhexylmethylsilane, polymethylpropylsilane, polycyclohexylmethylsilane, polydiphenylsilane,
Examples include polyphenethylmethylsilane. These polysilanes may be used alone or in combination of two or more. In the case of two or more types, a mixture or a copolymer may be used.

Although any method may be used to synthesize polysilane, one typical method is to react dihalosilane with a raw alkali metal in an organic solvent and synthesize it by condensation polymerization.

As for the shape of polysilane.

It may be in the form of a film, powder, or fibrous ring.

When this polysilane is dissolved using sulfuric acid as a solvent, the polysilane is slowly dissolved. It is thought that the secondary phenomenon occurs when this polysilane is dissolved in sulfuric acid. A part of the 5i-Si bonds in polysilane are broken by reacting with sulfuric acid, and are recombined via sulfur and oxygen in sulfuric acid, and sulfate ions are taken in and coordinated with the main chain. This incorporated sulfate ion gives polysilane electrical conductivity. and.

When a sulfuric acid solution in which this polysilane is dissolved is heated to remove the sulfuric acid by evaporation, the polysilane has a structure in which the main chain is three-dimensionally crosslinked. Therefore, the polysilane finally produced has electrical conductivity and is insoluble in most solvents.

Even if sulfuric acid is applied to a conductive polymer 1 other than polysilane, such as polyacetylene, a reaction similar to that described above is thought to occur, but in polyacetylene and the like, the main chain is oxidized and becomes brittle.

In addition, when an acid other than sulfuric acid (for example, nitric acid) is used as a solvent, the nitric acid decomposes and ignites when dissolving polysilane.
The polysilane will be burned out. Furthermore, when using hydrochloric acid, acetic acid, phosphoric acid, etc., polysolane does not dissolve.

The sulfuric acid used is preferably concentrated sulfuric acid, but dilute sulfuric acid diluted with water, alcohol, etc. and having a concentration of 50 νo1% or more may be used. It is difficult to dissolve polysilane with dilute sulfuric acid whose concentration is less than 50 vol%.

The dissolution rate of polysilane in sulfuric acid is r'ag acid 10 c
It is preferable to dissolve 5 g or less of polysilane per c.

Even if an attempt is made to dissolve more than 5 g of polysilane, an insoluble portion will result. In addition, when trying to obtain a film-like conductive polysilane, the above dissolution rate is 10c of concentrated sulfuric acid.
It is preferable to dissolve 0.1 g or more per c. If it is less than 0.1 g, it is difficult to obtain a stable film.

The dissolution of polysilane in sulfuric acid is very slow;
By leaving it for 0 hours or more, a sulfuric acid solution in which polysilane is uniformly dissolved can be obtained. but.

If left for more than one week, the sulfuric acid solution will be affected by oxidation, etc., which is not preferable.

By heating the sulfuric acid solution, sulfuric acid is evaporated off and conductive polysilane is formed. In the heating step, the sulfuric acid solution contained in a container or the like may be heated as it is, or the sulfuric acid solution may be uniformly dropped onto the substrate and then heated. When heating as is, powdered conductive polysilane is obtained. Also.

When it is dropped onto a substrate and heated, a film-like product can be obtained and the substrate can also be coated with conductive polysilane. Therefore, an insulating substrate made of glass or ceramics can be coated with the polysilane to impart electrical conductivity. Also.

The fibrous material is molded from the film-like material described above.

Alternatively, it can be obtained by spraying the sulfuric acid solution in a high temperature atmosphere.

The heating temperature is preferably within the range of 300 to 350°C.

At temperatures below 300°C, sulfuric acid evaporates <<, 350°C.
If the temperature exceeds ℃, the polysilane will decompose. The heating time is preferably within a range in which most of the sulfuric acid is evaporated and removed.

Further, the heating step is preferably performed in an inert gas atmosphere such as nitrogen gas to avoid the influence of oxidation.

The conductivity of the manufactured conductive polysilane varies depending on the type of polysilane, the amount of sulfuric acid used, etc., but is generally 10.
-' to 10S/e11. Furthermore, when conductive polysilane is made into a film, it has very good visible light transmittance and becomes transparent. The acid film.

The electrode of the light incident part of the solar cell and the liquid crystal panel part.

It can be used as a one-sided heating element made of electrochromic material.

〔Effect of the invention〕

According to the present invention, conductive polysilane can be produced by very simple operations. Also.

By using the method of the present invention, the surface of a glass or ceramic substrate can be easily coated with conductive polysilane, thereby imparting conductivity to the substrate.

Furthermore, according to the present invention, conductive polysilane can be produced with good processability into any shape, such as powder, film, or fiber, regardless of the shape of polysilane as a starting material.

〔Example〕

Hereinafter, five aspects of the present invention will be explained in detail.

Example 1 First, polydimethylsilane was synthesized as follows. n
- 11.5 g of sodium flakes in 110 cc of octane
was added, heated to 120°C, and stirred. 30.2 cc of dimethyldichlorosilane purified by distillation was added to this solution and heated under reflux for 10 hours. Filter the formed blue precipitate,
After thorough washing with methanol and water, white powdery polydimethylsilane was obtained. The electrical conductivity of this polydimethylsilane was 5×IQ-125/cm.

Next, polydimethylsilane 2. Og was placed in 10 cc of concentrated sulfuric acid and allowed to stand at room temperature for 24 hours to dissolve. after that.

A glass plate of 20 x 201 layers was placed horizontally on a hot plate in a nitrogen atmosphere and heated to 300°C.

Approximately 0.5 cc of the above sulfuric acid solution was dropped onto this glass plate.

A transparent film made of polydimethylsilane was obtained by volatilizing the sulfuric acid. 1 CI on the surface of this transparent film! Apply a pair of silver pastes with a distance of l.

When I measured the resistance between them, it was 103Ω/mouth.

The transparent film formed was found to be electrically conductive.

Example 2゜9.7g of Na pieces were placed in 120cc of anhydrous toluene, and 1
It was heated to 20°C and stirred. 12 cc of dimethyldichlorosilane purified by distillation and 16.1 cc of methylphenyldichlorosilane were added to this solution, and the mixture was heated under reflux for 10 hours. The generated purple precipitate was filtered and thoroughly washed with methanol and water to obtain a waxy compound.

Mix this into THF (tetrahydrofuran).

By removing the insoluble portion by centrifugation and further dropping the above THF solution into methanol.

A white polyphenylmethylsilane precipitate was obtained.

2 g of this polyphenylmethylsilane powder (conductivity 7 Xl0-12S/am) was mixed with 10 g of concentrated sulfuric acid.
20111 in the same manner as in Example 1.
A transparent film was formed on a x 20 am alumina substrate. The surface resistance of the film was lO4Ω/mouth.

Example 3 Polycyclohexylmethylsilane was synthesized in the same manner as in Example 1 using dimethyldichlorosilane and cyclohexylmethyldichlorosilane as synthesis raw materials. Powdered polycyclohexylmethylsilane (conductivity 5 Xl0-”S
/ca+) 2 g was dissolved in 10 cc of concentrated sulfuric acid, and a transparent film was formed on a glass substrate in the same manner as in Example 1. The surface resistance of the film was 104 Ω/hole.

Claims (1)

[Claims] Polysilane represented by the following formula [A] is dissolved in sulfuric acid,
A method for producing conductive polysilane, which comprises subsequently heating the sulfuric acid solution. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(A) (However, in the above formula, R^1 and R^2 are hydrogen, alkyl groups such as methyl group, ethyl group, propyl group, phenyl group, tolyl group, etc.) are allyl groups such as aryl groups and vinyl groups, and may be the same or different, but both cannot be hydrogen at the same time.)