JP3229182B2 - Conductive polysilane composition and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a conductive composition using an organosilicon polymer as a base polymer and a method for producing the same.

[0002]

2. Description of the Related Art It has been found that when polyacetylene is doped with an electron-accepting substance or an electron-donating substance, a charge-transfer formation reaction takes place and high electrical conductivity based on electron conduction is developed. Organic polymer compounds such as polypyrrole, polyaniline, and polythiophene have attracted attention as conductive materials for forming highly conductive thin films.

However, such organic high molecular compounds are insoluble and infusible or have poor shapeability. In addition, when a thin film is formed by a gas phase polymerization method or an electrolytic polymerization method, the shape of the obtained thin film is restricted by the shape of a reaction vessel or an electrode, or when doping an electron accepting substance or an electron donating substance, With deterioration.

[0004] The use of organosilicon polymers having a Si-Si bond skeleton, such as polysilane, as conductive materials has also been studied. Mori et al. Succeeded in synthesizing N-carbazolyl-substituted linear polysilane and obtained a conductive material having a volume resistivity of 7.7 × 10 ² Ωcm by doping with iodine (Synthetic Metals 73, 1995., p113). To 116, JP-A-6-128488). Ishikawa et al. Succeeded in synthesizing a diethynylenedipyridylenedisilanylene polymer, and obtained a conductive material having a volume resistivity of 7.1 × 10 ³ Ωcm by doping with iodine or ferric chloride (Organ).
ometallics 1995, 14, p714-720). All of these polymers are difficult to synthesize due to the need to introduce a special substituent. In addition, as an example of a similar organosilicon polymer which is not polysilane, Tamao and Ito et al. Report a thiophene-silole copolymer exhibiting a conductivity of 1 × 10 ³ Ωcm in volume resistivity (Japanese Patent Laid-Open No. Hei 6 (1994)). -100669 and JP-A-6-166746
Reference).

On the other hand, Hayase et al. Can obtain a polysilane composition having high photosensitivity because a polysilane chain can be broken by adding an onium salt to a linear polysilane and exposing the same to light. It reports that patterning is possible (Japanese Patent Laid-Open No. 5-23038).
No. 0). The composition disclosed herein is a photosensitive composition, and does not disclose the improvement in conductivity of polysilane.

In general, synthesis of polysilane requires synthesis or purification of a specific organic group-substituted chlorosilane as a raw material in advance, and furthermore, a large amount of alkali metal must be used for a condensation reaction. In addition, when the amount of a specific substituent bonded to a silicon atom of polysilane greatly contributes to its conductivity, a complicated method for selectively synthesizing a polysilane having a controlled content of the substituent is required. is necessary. Therefore, it is difficult to provide a polysilane-based highly conductive composition by a simple operation. As described above, none of the above reports disclose improving conductivity by adding an onium salt to polysilane and then doping with an oxidizing substance.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to use polysilane, which is easy to synthesize and handle, as a base polymer.
Soluble in solvent, good shapeability to thin film of any shape,
An object of the present invention is to provide a highly conductive silicon-based polymer composition which can be prepared by a simple operation and has little deterioration, and a method for producing the same.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, it has been found that a polysilane to which an onium salt is added is soluble in an organic solvent and has a thin film of an arbitrary shape. Unexpectedly, by doping with an oxidizing substance such as iodine,
The inventors have found that the deterioration of the composition is small and that the conductivity of the composition is remarkably improved as compared with the case where an oxidizing substance is doped without adding an onium salt, thereby completing the present invention.

That is, the gist of the present invention is a conductive polysilane composition characterized by doping an oxidizing substance to polysilane to which onium salts are added.

[0010]

DETAILED DESCRIPTION OF THE INVENTION The polysilane used in the present invention is preferably of the average formula (I):

Embedded image (Wherein R ¹ may be the same or different,
Represents a substituted or unsubstituted monovalent hydrocarbon group bonded to a silicon atom, part of which may be a hydrogen atom; R ² may be the same or different, and represents R ³ represents a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group bonded to an atom; R ³ represents a divalent substituted or unsubstituted hydrocarbon group or heterocyclic group bonded to two silicon atoms. And the main chain skeleton is composed of a Si—Si bond and, in some cases, a Si—R ³ —Si bond, a is 1.00 to 1.97, b is a positive number, and c is 0 ≦ c.
/(An+bn+c)≦0.3;
n represents a weight average molecular weight of the polysilane of 500 to 3,000.
000).

Such a polysilane may have a linear, branched, cyclic, or network-like polysilane skeleton, and may be partially dispersed in a molecule in the structure. The above-mentioned R ³ may be present between silicon atoms. However, since the deterioration and the molecular weight due to doping with an oxidizing substance are suppressed, a network structure is formed by the polysilane skeleton itself and / or R ³ . Is preferably formed.

Examples of such a polysilane include those represented by the general formula (II) or (III):

Embedded image Wherein R ¹ , R ² and R ³ are as described above; p, q and s are 0 or a positive integer, r is a positive integer, and p, q, r and s are as defined above. Average formula (I)
Be of a, b, the number to satisfy c and n; expression represents the number of silane units and R ^3, shown in does not mean a block copolymer), R ¹ Si units and need And a polysilane having a network skeleton crosslinked by R ³ .

R ¹ is a substituted or unsubstituted monovalent hydrocarbon group bonded to a silicon atom of polysilane, and is a straight-chain such as methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl, dodecyl, tetradecyl, octadecyl or the like. A chain or branched alkyl group; a cycloalkyl group such as cyclohexyl; an aralkyl group such as 2-phenylethyl and 2-phenylpropyl; an aryl group such as phenyl, tolyl, xylyl, and mesityl; an alkenyl group such as vinyl and allyl; Examples thereof include alkenylaryl groups such as p-vinylphenyl; and substituted hydrocarbon groups such as chloromethyl, trifluoropropyl, and methoxyphenyl, and some R ¹ may be a hydrogen atom. Among them, C1-C1 such as methyl, ethyl, propyl, butyl, pentyl, hexyl, etc.
6 alkyl groups, cyclohexyl groups and phenyl groups are preferred.

The number of R ^{1 in} the polysilane molecule is related to the degree of the network structure described above, and the ratio R ¹ / Si to silicon atom is preferably in the range of 1.00 to 1.97, 1.00 to 1.91 are more preferred.

R ² is a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group constituting OR ² bonded to a silicon atom. In addition to the hydrogen atom, methyl, ethyl, propyl, butyl, pentyl, hexyl , A linear or branched alkyl group such as dodecyl; a cycloalkyl group such as cyclohexyl; an aryl group such as phenyl, tolyl, xylyl, and mesityl;
And substituted hydrocarbon groups such as -ethoxyethyl and 2-butoxyethyl. For ease of synthesis and handling, alkyl groups having 1 to 4 carbon atoms such as methyl, ethyl, propyl and butyl and phenyl are preferable. The groups are preferred, and methyl and ethyl are most preferred. That is, O
R ² is most preferably a lower alkoxy group such as methoxy and ethoxy. Such an OR ² group may be bonded to any of the silicon atoms at the terminal, intermediate and branched positions of the polysilane molecular chain.

R ³ is a substituted or unsubstituted divalent hydrocarbon or heterocyclic group introduced between silicon atoms in a polysilane chain, in a form that crosslinks the polysilane chain, or in a network polysilane structure. Yes, it is preferable to exist in a dispersed state in the polysilane molecule. R ³ is an alkylene group such as methylene, ethylene, and trimethylene; a divalent saturated aliphatic hydrocarbon group such as butadienylene; an arylene group such as phenylene, naphthylene, 9,10-anthracenylene, and ferrosenylene; a divalent group such as xylylene Aromatic-substituted hydrocarbon groups; thienylene, dithienylene,
Examples of heterocyclic groups such as pyrrolylene and pyridinylene include biphenylene, triphenylene, and thienylene.
A divalent chain in which two or more aromatic rings or heterocyclic rings are repeatedly present may be used, and an aromatic hydrocarbon group or a heterocyclic ring is preferable from the viewpoint of ease of synthesis and conductivity of the composition. , 10-anthracenylene and thienylene are particularly preferred.

[0017] During polysilane R ^3, by R ³ is present in particular aromatic group or a heterocyclic group, to increase the conductivity of the polysilane composition, impart solubility in a solvent, the thin film of the polysilane It can be performed more easily and uniformly. In this case, the number c of R ³ is 30% of the total number of substituents an + bn + c in the polysilane.
It is preferably at most 0.1%, more preferably 0.1% to 20%. As the ratio increases, the conductivity of the polysilane can be increased. However, when the ratio exceeds 30%, it becomes difficult to obtain a solid polysilane having a high molecular weight, and a stable thin film having good physical properties cannot be formed.

The weight average molecular weight of the polysilane is not particularly limited as long as the polysilane is soluble in a solvent and a solid film can be formed. The range of 3,000,000 is preferred, 1,000 to 1,000,000 is more preferred, and 2,500 to 100,000 is particularly preferred.

The polysilane used in the present invention, in particular, the network skeleton polysilane, can be produced by using a known polysilane synthesis method. For example, by using a desalting condensation reaction of organochlorosilanes with sodium metal (Wurtz method), the mixing ratio of organochlorosilanes as a raw material is adjusted to control the degree of the network of the molecular skeleton. Can be obtained.

Further, by utilizing the disproportionation reaction of alkoxydisilanes, it is possible to synthesize a polysilane having a network-like skeleton having various organic substituents under mild conditions (Japanese Patent Application Laid-Open No. 4-31727, JP-A-6-57002 and K. Kabeta et al., Chem. Lett., 1994, p835-838.
reference). Furthermore, it is also possible to obtain a polysilane having R ³ introduced between two silicon atoms (Chem. Lett., 1
994, 119-120). Although these are described for an alkoxy group-containing polysilane, it would be easy for those skilled in the art to apply this to a polysilane having an OR ² group other than the alkoxy group.

In the present invention, the onium salt added to the polysilane is an essential component for imparting high conductivity to the polysilane composition of the present invention. As such an onium salt, an iodonium salt and a sulfonium salt are preferable. For example, one or more compounds having the molecular structures listed below can be used.

[0022]

Embedded image

[0023]

Embedded image

Among these onium salts, the following compounds are preferred from the viewpoint of easy handling and imparting excellent conductivity to the composition after doping.

[0025]

Embedded image

The amount of the onium salt to be added varies depending on the type of the onium salt with respect to 100 parts by weight of the polysilane, but is usually 1 to 200 parts by weight, preferably 30 to 12 parts by weight.
0 parts by weight, and in the case of (p-dodecylbenzene) iodonium hexafluoroantimonate, more preferably 30 to 60 parts by weight. If the amount is less than 1 part by weight, the effect of imparting high conductivity to the composition is not sufficient, and if the amount exceeds 200 parts by weight, the film formability deteriorates.

The polysilane to which the onium salt has been added can be dissolved in an appropriate solvent to prepare a treatment liquid for forming a thin film on the surface of the substrate. As the solvent, any of a nonpolar solvent and a polar solvent may be used.
Heptane, n-hexane, toluene, xylene, benzene, dimethylformamide, tetrahydrofuran, diethyl ether, chloroform and the like can be mentioned, but a polar solvent such as tetrahydrofuran is preferable because polysilane is easily dissolved. The amount of the solvent for obtaining good workability is usually 50 to 10,000 parts by weight, preferably 500 parts by weight, per 100 parts by weight of the polysilane.
2,000 parts by weight.

As a method of forming a thin film of polysilane to which an onium salt is added, the polysilane is dissolved in the above-mentioned solvent, and then applied on a substrate and left at normal pressure or reduced pressure at normal temperature, or Heat to evaporate the solvent,
A method of obtaining a polysilane thin film is generally used. Examples of the application method include dipping and spin coating, and it is preferable to use spin coating.

The polysilane thin film thus obtained can be doped with an oxidizing substance to obtain a conductive polysilane composition.

The oxidizing substance used in the present invention includes:
Halogens such as chlorine, bromine and iodine; transition metal chlorides such as tin chloride and ferric chloride; antimony pentafluoride;
It is preferable to use iodine or ferric chloride because Lewis acids such as arsenic pentafluoride are effective, safe and easy to handle.

The amount of the oxidizing substance used for doping is usually 1 to 1,000 parts by weight, preferably 10 to 100 parts by weight, based on 100 parts by weight of polysilane. If the amount is less than 1 part by weight, high conductivity cannot be imparted to the composition,
If the amount exceeds 1,000 parts by weight, the film-forming properties are poor, and the resulting polysilane film tends to have defects.

As the doping method, for example, (a) a gas phase (dry) doping method in which a polysilane thin film is exposed to a vapor atmosphere of an oxidizing substance such as iodine or ferric chloride; A wet doping method in which polysilane is immersed in a solution in which iron or the like is dissolved in an inert solvent; and (c) using a solvent in which iodine and polysilane are commonly dissolved, dissolving polysilane in a solution in which iodine is dissolved; There is a simultaneous doping method in which the film is formed into a film or a thin film by dry film forming from the same, and simultaneously doping is performed, and either of them can be used.

The gas phase doping method controls the temperature of the dopant atmosphere and the partial pressure of the dopant,
The doping rate can be controlled. Generally, doping is performed at a temperature of a dopant atmosphere of -30 to 20.
It can be performed in the range of 0 ° C. If the temperature is lower than −30 ° C., the doping rate is low, and if the temperature exceeds 200 ° C., polysilane is deteriorated during doping, which is not preferable. The dopant partial pressure is preferably in the range of 1 Torr to 5 atm. 1To
If the pressure is less than rr, the doping rate is generally low, and increasing the pressure beyond 5 atm has no particular effect.

As the inert solvent used in the wet doping method, a solvent that does not react with iodine and deactivate the ability as an electron acceptor compound is used. Examples of such a solvent include aliphatic hydrocarbons such as hexane, octane, petroleum ether and cyclohexane; aromatic hydrocarbons such as benzene, toluene and xylene; ethers such as diethyl ether and tetrahydrofuran; Esters; alcohols such as methanol and ethanol; aprotic polar solvents such as dimethylformamide and dimethylsulfoxide; and nitromethane, nitrobenzene, and acetonitrile. Among them, a solvent such as tetrahydrofuran is a good solvent for polysilane, and is particularly suitable for the simultaneous doping method. In this case, doping and film formation can be performed simultaneously by dissolving polysilane in a solution containing a dopant, casting the solution, and then drying. Drying after casting can be performed at a temperature of 0 to 150 ° C. under normal pressure or reduced pressure.

A radical generator may be further added to the composition of the present invention.

[0036]

According to the present invention, a polysilane composition having high conductivity up to 10 ² Ωcm, particularly a thin film thereof, can be obtained by a simple and quick operation. The conductive polysilane composition provided by the present invention can improve the conductivity of the polysilane composition by changing the types and amounts of additives contained therein. The conductivity can also be controlled by changing the skeleton structure and the substituent of the polysilane. The addition of an additive such as an iodonium salt or a sulfonium salt has an effect of stably maintaining the conductivity of the polysilane.

The conductive composition of the present invention, in addition to the features described above, is easy to handle and has good shapeability. Therefore, it is extremely useful as a material widely applicable to the electronics field such as photoconductive materials and conductive materials. Useful.

[0038]

The present invention will be described in more detail with reference to the following synthesis examples, examples and comparative examples. In these examples, all parts are parts by weight, and physical property values are values at 25 ° C. The present invention is not limited by these examples.

Synthesis Example 1 (Synthesis of network-structured polysilane) Under a dry argon gas flow, 50 parts of 1,2-dimethyl-1,1,2,2-tetraethoxydisilane was placed in a flask equipped with a condenser and a stirrer. Was added thereto, and 1.5 parts of sodium ethoxide was added thereto.
Heated for 0 hours. After cooling, the solid content was removed by suction filtration, and the filtrate was slowly poured into 1,000 parts of anhydrous methanol to reprecipitate a white solid. The solid collected by filtration by suction filtration was washed with anhydrous ethanol and dried under reduced pressure to obtain 5 parts of a polysilane having a network-like molecular skeleton. As a result of ¹ H NMR measurement of the obtained polysilane, the presence of a methyl group and an ethoxy group was confirmed, and the ratio was 10: 1. The molecular weight in terms of polystyrene by GPC was 3,300.

Synthesis Example 2 (Synthesis of Thienylene Group-Containing Network-Shaped Polysilane) A flask equipped with a cooling tube and a stirrer was charged with 2 parts by weight of 2,5-dibromothiophene under a stream of dry argon, and 100 parts of tetrahydrofuran was added. And the temperature was adjusted to −78 ° C. with a dry ice-acetone bath. To this was added a 1.8 M n-hexane solution of n-butyllithium.
Five parts were added dropwise, and the mixture was stirred for 1 hour. This is 1,2
-Dimethyl-1,1,2,2-tetraethoxydisilane (50 parts) was charged, heated to room temperature, and then heated at 100 ° C. for 20 hours with stirring. After cooling, the solid content was removed by suction filtration, and the filtrate was slowly poured into 1,000 parts of anhydrous methanol to reprecipitate a white solid. The solid separated by suction filtration was washed with anhydrous ethanol and dried under reduced pressure to obtain 6 parts of polysilane having a network structure. As a result of ¹ H NMR measurement of the obtained polysilane, the presence of a methyl group, an ethoxy group and a thienylene group was confirmed, and the ratio was 85: 13: 2. The molecular weight in terms of polystyrene by GPC was 11,000.

Synthesis Example 3 (Synthesis of anthracenylene group-containing polysilane having a network structure) A flask equipped with a cooling tube and a stirrer was charged with 6 parts of 9,10-dibromoanthracene under a stream of dry argon, and 100 parts of tetrahydrofuran was added. After melting, the temperature was adjusted to −78 ° C. with a dry ice-acetone bath. To this was added a 1.8 M n-hexane solution of n-butyllithium.
Five parts were added dropwise, and the mixture was stirred for 1 hour. This is 1,2
-Dimethyl-1,1,2,2-tetraethoxydisilane (50 parts) was charged, the temperature was raised to room temperature, and 1 part was stirred.
Heat at 00 ° C. for 20 hours. After cooling, the solid content was removed by suction filtration, and the filtrate was slowly poured into 1,000 parts of anhydrous methanol to reprecipitate a white solid. The solid separated by suction filtration was washed with anhydrous ethanol and dried under reduced pressure to obtain 7 parts of polysilane having a network structure. As a result of ¹ H NMR measurement of the obtained polysilane, the presence of a methyl group, an ethoxy group and a 9,10-anthracenylene group was confirmed, and the ratio was 78: 18: 4.
The molecular weight in terms of polystyrene by GPC was 2,700.

Examples 1 to 3 Using the polysilanes having a network structure obtained in Synthesis Examples 1 to 3, the polysilanes and bis (p-dodecylbenzene) iodonium hexafluoroantimonate were used at the compounding ratios shown in Table 1. Was dissolved in tetrahydrofuran to prepare a 10% by weight solution of polysilane. This was spin-coated on a glass plate on which a platinum electrode was deposited, and 50
The film was dried by heating at a reduced pressure of 2 ° C./2 Torr to form a thin film having a thickness of 1 μm. The volume resistivity of the thin film thus obtained was measured in a nitrogen atmosphere by a two-end needle method.
When it was 10 ¹² Ωcm or more, no conductivity was exhibited. When this was allowed to stand at 25 ° C. for 1 hour in a light-shielding container filled with solid iodine and replaced with dry nitrogen, the thin film was exposed to iodine vapor and the appearance of the thin film changed from transparent to brown. When the volume resistivity of the thin film was measured, as shown in Table 1, 3.
It showed a value of 4 × 10 ² Ωcm to 2.4 × 10 ³ Ωcm, and was observed to have excellent conductivity. These polysilane thin films stably maintained conductivity for 5 days or more.

Comparative Examples 1 to 3 Polysilane thin films were obtained in the same manner as in Examples 1 to 3, except that the same polysilane as in Examples 1 to 3 was used and no onium salt was added, as shown in Table 1. . When this was exposed to iodine vapor under the same conditions as in Examples 1 to 3, as shown in Table 1, the volume resistivity was 2.7 × 10 ³ to
It was 5.0 × 10 ⁵ , and only inferior conductivity was obtained as compared with the corresponding examples.

[0044]

[Table 1]

Example 4 Anthracenylene group-containing network-structured polysilane obtained in Synthesis Example 3 and p-methoxyphenyl (diphenyl) sulfonium fluoroantimony salt as an onium salt
A composition doped with iodine was obtained in the same manner as in Examples 1 to 3, except that the composition was used at a weight ratio of 1: 1. When its volume resistivity was measured, it showed a value of 5.7 × 10 ² Ωcm, indicating that it had excellent conductivity.

Example 5 Except for using the anthracenylene group-containing network-structured polysilane obtained in Synthesis Example 3 and bis (p-tert-butylphenyl) iodonium fluoroantimony salt as an onium salt in a weight ratio of 1: 1. In the same manner as in Examples 1 to 3, a composition doped with iodine was obtained. When its volume resistivity was measured, it showed a value of 3.8 × 10 ¹ Ωcm, indicating that it had excellent conductivity.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-8-134221 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 83/16 C08K 3/22 C08K 5 / 03 C08K 5/36 C08G 77/60

Claims (5)

(57) [Claims] 1. A conductive polysilane composition, characterized in that polysilane obtained by adding 1 to 200 parts by weight of an onium salt to 100 parts by weight of polysilane is doped with 1 to 1,000 parts by weight of an oxidizing substance. 2. The polysilane has an average formula (I): (Wherein R ¹ may be the same or different,
Represents a substituted or unsubstituted monovalent hydrocarbon group bonded to a silicon atom, part of which may be a hydrogen atom; R ² may be the same or different, and represents R ³ represents a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group bonded to an atom; R ³ represents a divalent substituted or unsubstituted hydrocarbon group or heterocyclic group bonded to two silicon atoms. And the main chain skeleton is composed of a Si—Si bond and, in some cases, a Si—R ³ —Si bond, a is 1.00 to 1.97, b is a positive number, and c is 0 ≦ c.
/(An+bn+c)≦0.3;
n represents a weight average molecular weight of the polysilane of 500 to 3,000.
The conductive polysilane composition according to claim 1, wherein the number is selected to be 0.000). 3. The conductive polysilane composition according to claim 1, wherein the onium salt is an iodonium salt or a sulfonium salt. 4. The conductive polysilane composition according to claim 1, wherein the oxidizing substance is iodine, ferric chloride, or antimony pentafluoride. 5. A method for producing a conductive polysilane composition, comprising forming a polysilane thin film to which an onium salt is added, and then doping with an oxidizing substance.