JPH11349305A - Production of carbonaceous film and film to be treated - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a carbonaceous film without defects in physical properties due to the formation, etc., of holes and having a homogeneous composition by carbonizing a precursor into which a functional group containing boron is introduced into the skeletal structure of a polyimide by heat treatment. SOLUTION: A polyimide is used as a precursor of a carbonaceous film and a functional group containing boron is introduced into the skeletal structure of the polyimide. The objective carbonaceous film containing nitrogen and the boron is produced by carbonizing the precursor by heat treatment. The polyimide used as the precursor regulatively precontains the nitrogen in the molecule and is frequently used as the precursor of a highly oriented carbonaceous material. When the functional group containing the boron is introduced into the precursor, the precursor is readily carbonized by the heat treatment and the nitrogen and boron are more densely and uniformly contained in the resultant carbonaceous film. The kind of the functional group containing the boron is not especially limited.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a carbon film obtained by carbonizing an organic polymer compound, and more particularly to a precursor for obtaining such a carbon film.

[0002]

2. Description of the Related Art When a part of carbon in a carbon material is replaced with boron or nitrogen, the carbon material changes not only in chemical properties such as oxidation resistance, but also in electrical, magnetic and mechanical properties. ,
Diversity as a material is expanded.

For example, a polyimide thin film is known as a precursor of a highly oriented carbon material. Previously, the inventor
Such a polyimide thin film contains intramolecular nitrogen,
It was reported that about 1 at% of nitrogen remained at a carbonization temperature of about 00 ° C (H. Konno, T. Nakahashi and
M. Inagaki, Carbon, 35, 669 (1997); T. Nakahashi,
H. Konno and M. Inagaki, Solid State Ionics, in pr
ess).

The inventor of the present invention has reported that the residual nitrogen
It has been reported that trace amounts remain even after graphitization at 00 ° C, which greatly affects the magnetoresistance and Hall coefficient of thin films (M.I.
nagaki, H. Tachikawa, T. Nakahashi, H. Konno and
Y. Hishiyama, Carbon, in press).

[0005] Materials with a high content of boron and nitrogen are BC
It is called an N compound, and synthesis by various methods has been attempted. Also, it is known that even when boron or nitrogen is doped in a small amount into graphite or the like, it greatly changes the physical properties of the graphite or the like, and various implantation methods have been tried.

[0006]

The simplest method for producing a carbon film containing nitrogen and boron is to form a film by mixing a boron compound with a polymer compound containing nitrogen.
There is a method of heating this in an inert gas atmosphere to carbonize.

However, in such a method, fine pores may be formed in the obtained carbon film, or a thin film having an inhomogeneous composition may be formed.

According to the study of the present inventor, in such a method, it is considered that components containing boron and nitrogen are diffused by heat treatment, and in order to obtain a uniform carbon film containing nitrogen and boron, it is necessary to use a heat treatment or the like. It was found that a device was required [Kano, Oka, Inagaki, Preparation of B and N-containing carbon thin film from polyimide (I). Proceedings of the 65th Annual Meeting of the Electrochemical Society of Japan, p. 317, 3K01, (1998)].

An object of the present invention is to obtain a carbon film having a uniform composition without physical defects due to generation of pores or the like by heat treatment of a precursor of a highly oriented carbon material.

[0010]

According to the present invention, in obtaining a carbon film containing nitrogen and boron, a precursor of the carbon film is made of polyimide, and the functional group containing boron has a skeleton structure of the polyimide. And a method for producing a carbon film, wherein the precursor is carbonized by heat treatment.

The present invention is also a precursor for obtaining a carbon film containing nitrogen and boron, wherein the precursor comprises polyimide, and the functional group containing boron is introduced into the skeleton structure of the polyimide. The present invention relates to a precursor for obtaining a carbon film, wherein the precursor is carbonized by heat treatment.

According to the present invention, a heterogeneous atom other than a carbon atom introduced into one organic compound and such a heterogeneous atom mixed as a separate organic compound show a difference in carbonization behavior. Attributable to what was found.

The inventor of the present invention has proposed that a polyimide containing nitrogen in a molecule is carbonized after introducing a functional group containing boron into its skeleton structure, so that the polyimide containing nitrogen and boron is more densely and homogeneously contained. The present inventors have found that a carbon film can be obtained, and completed the present invention.

In the present invention, boron and nitrogen are more likely to form a carbon film by introducing a functional group containing boron into the skeleton structure of the polyimide than by simply mixing the boron compound and the polyimide to carbonize. It was found that it was settled inside efficiently.

According to the present invention, a part of the carbon in the carbon film is homogeneously replaced by boron and nitrogen, and the chemical properties such as oxidation resistance and the electrical, magnetic and mechanical properties are improved. An excellent carbon film can be obtained.

The carbon film according to the present invention is promising as a functional carbon material, and is expected to be applied to products such as lithium secondary batteries, sensors, and semiconductors.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail with reference to the drawings. In the present invention, polyimide is used as a precursor of the carbon film. A functional group containing boron is introduced into the skeleton structure of this polyimide. The carbon film containing nitrogen and boron according to the present invention is obtained by heat-treating this precursor to carbonize it.

The polyimide used as a precursor of the carbon film in the present invention contains nitrogen in the molecule in advance and is most often used as a precursor of a highly oriented carbon material.

As the precursor of the carbon film according to the present invention,
Similar to polyimide, various polymer films are also useful. Such polymer materials include various organic polymer compounds such as polyparaphenylene vinylene, polyoxadiazole, polyparaphenylene terephthalamide, and polyacrylonitrile.

In the present invention, a functional group containing boron is introduced into the skeleton structure of the precursor. Such a precursor is easily carbonized by heat treatment, and nitrogen and boron are more densely and uniformly contained in the obtained carbon film.

The type of the functional group containing boron is not particularly limited. Therefore, functional groups having various structures can be introduced according to the skeleton structure of the precursor according to the present invention.

The polyimide used in the present invention is known as a precursor of a highly oriented carbon material, and contains nitrogen in the molecule regularly. One of such polymer compounds is pyromellitic dianhydride (PMDA) and 4,4'-
There is a type in which a liquid polyamic acid obtained by polymerizing diaminodiphenyl ether (DDE) is dehydrated and imidized at 200 ° C. to form a thin film.

In the present invention, such a polyimide is used as a precursor of a carbon film. In the polyimide, a functional group containing boron is introduced into the skeleton structure of the polyimide. Such a functional group containing boron can be introduced before synthesizing the precursor of the carbon film according to the present invention.

In the present invention, a functional group containing boron is introduced into a raw material monomer of an organic high molecular compound containing nitrogen in the molecule, the raw material monomer is polymerized, and the organic high molecular compound containing nitrogen and boron in the skeleton is obtained. Is synthesized into a precursor, and the precursor is carbonized by heat treatment, whereby a carbon film can be obtained.

For example, in the present invention, DDE is used as a raw material monomer, a functional group containing boron is introduced into this monomer, and this is polymerized with PMDA to form a polyamic acid, and the polyamic acid containing boron in the molecule is used. Can be imidated to produce a boron-containing polyimide.

In this case, a compound in which a functional group containing boron is introduced at position 2 of DDE is synthesized, and a polyamic acid can be synthesized using the compound. FIG. 1 is a structural formula of DDE substituted with an example of a functional group containing boron.

As described above, when polyimide is used as a precursor of the carbon film, a functional group containing boron introduced into DDE as shown in FIG. 1 can be used. Such a functional group can be relatively easily introduced into DDE, and the compound after the introduction has excellent chemical stability. In addition, such a functional group, when polymerizing to synthesize a polyamic acid,
Relatively hard to get in the way.

However, such a boron-containing polyamic acid may not be able to obtain a sufficient degree of polymerization required for casting on a glass substrate or the like. DDE is
This is because, when a functional group containing boron is introduced at the position 2 or the like, the amino group may easily fall off, making it difficult to synthesize with high purity.

In such a case, a boron-containing polyamic acid having a sufficient degree of polymerization can be obtained by studying the conditions for synthesizing DDE into which a functional group containing boron has been introduced, or by increasing the purity by purification.

Alternatively, a boron-containing polyimide film having a high degree of polymerization can be obtained by mixing the boron-containing polyamic acid obtained in a state of a low degree of polymerization with an ordinary polyamic acid in an equimolar amount and imidizing the mixture. Then, if this thin film is carbonized at a temperature of 1200 ° C. or the like, a dense and uniform carbon film containing boron and nitrogen can be obtained.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings based on examples and comparative examples. Example 1 In this example, a polyimide film containing boron in a molecule (PI-P) was prepared using a raw material into which a functional group containing boron was introduced.
B) was prepared, and the carbonization behavior of this film was examined.

As shown in FIG. 1, 4,4'-diaminodiphenyl substituted at position 2 by a functional group containing boron.
lether (DDE) was synthesized, and Pyromell was synthesized.
It polymerized with itic dianhydride (PMDA) to prepare a boron-containing polyamic acid.

In this preparation, boron-containing DDE and PMDA were combined with N, N-dimethylacetam.
The solution was dissolved in an equimolar amount in ide (DMAc), and the mixture was stirred and polymerized for 3 hours while cooling with water. However, a sufficient degree of polymerization was not obtained. For this reason, in the following imidization, this boron-containing polyamic acid and a normal polyamic acid prepared from normal DDE and PMDA not substituted with a boron-containing functional group are equimolarly mixed, and these are mixed. It was imidized.

In the imidization, the raw material is cast on a glass substrate and placed in a vacuum oven at 60 ° C. for 3 hours and at 120 ° C. for 2 hours.
After drying for an hour, the reaction was performed at 200 ° C. for 3 hours. The obtained polyimide film was separated from the glass substrate during imidization, and the film thickness became 50 μm. This polyimide film contains 0.91 at% of boron in calculation.

The carbonization of the polyimide film is carried out in a stream of Ar gas.
The temperature was raised to a constant temperature of 00 to 1200 ° C. at 400 K / h, and the heating was performed for 1 hour. About the obtained carbon thin film, XP
S, EPMA, SEM, elemental analysis (combustion method) and measurement of electric conductivity were performed. Carbonization is currently 600-
It is conducted in the range of 1200 ° C., but higher temperatures are under consideration.

Comparative Example 1 An ordinary polyamic acid was imidized by mixing borane with it.
Create a polyimide film (PI-B) mixed with boron,
The carbonization behavior of this film was studied.

PMDA and DDE not substituted with a boron-containing functional group were dissolved in DMAc in equimolar amounts and polymerized with stirring for 3 hours while cooling with water. In addition, D
Dihydroxyphenylbo dissolved in MAc
was added, and the mixture was further stirred and polymerized for 2 hours.
B-doped Polyamic acid was prepared.

This was cast on a glass substrate, dried in a vacuum oven at 60 ° C. for 3 hours and at 120 ° C. for 2 hours, and then imidized at 200 ° C. for 3 hours to obtain a commercially available Kapton-type polyimide having a thickness of 35 μm. A membrane was made. The carbonization was performed for 1 hour at a temperature of 400 K / h up to a constant temperature of 500 to 1600 ° C. in an Ar gas stream.

With respect to the obtained carbon thin film, XPS, EPMA, SEM, elemental analysis (combustion method) and measurement of electric conductivity were performed in the same manner as in Example 1.

Comparative Example 2 In Comparative Example 1, a polyimide film (PI) was prepared by imidizing ordinary polyamic acid without mixing borane, and the carbonization behavior of this film was examined in the same manner as in Example 1. .

[0041] Study Results Figure 2 is a plot of the intensity ratio of N1s and C1s spectrum of the surface by XPS with respect to carbonization temperatures. FIG. 3 is a graph in which the intensity ratio of the N1s and C1s spectra of the surface by XPS is plotted against the N / C molar ratio by elemental analysis.

As shown in FIG. 2, in the polyimide film (PI-B) mixed with boron, the residual ratio of N at 1000 ° C. or more was about twice that of the polyimide film (PI) not mixed.

Although not particularly shown in the figure, as a result of analyzing the N1s spectrum, in the PI-B, in addition to the tertiary amine-type nitrogen remaining at high temperatures at PI, BN-bonded nitrogen is generated. I knew I was doing it. This BN-bonded nitrogen was considered to be the cause of the increase in the amount of residual nitrogen.

As compared with the results of the elemental analysis, in the PI, the N / C molar ratio of the film surface almost coincided with the value of the elemental analysis, whereas in PI-B, the N / C mole ratio in the film inside was lower. / C molar ratio increased, and the B1s / C1s spectral intensity ratio of the surface did not tend to monotonously increase with the carbonization temperature.

Further, as a result of SEM observation, it was found that cracks were formed on the surface after carbonization at higher temperatures, and together with the results of the analysis, fragments containing nitrogen and boron became gas during carbonization and were desorbed. It was estimated that.

When the electric conductivity exceeds 900 ° C., Pl
-B decreased, but it was considered that this was mainly due to the occurrence of cracks.

In the EPMA measurement from the surface, the distribution of boron was almost uniform, but the boron mixing method by PI-B resulted in that it was very difficult to stably fix boron to the whole film up to a high temperature. Was.

From the examination results of Comparative Examples 1 and 2, it is considered that in the case of PI-B, the component containing borane was released from the surface as a gas during carbonization at a high temperature.
In order to obtain a uniform boron and nitrogen-containing carbon thin film, it was found that some measures such as heat treatment were required.

In the polyimide film (PI-PB) of Example 1 in which a functional group containing boron was introduced into the molecule, the change in the N1s / C1s spectral intensity ratio of the surface by XPS due to the carbonization temperature was shown in FIG. The tendency was exactly the same as that of -B, and the N1s peak of the BN bond type could be separated from 800 ° C.

Although not shown in the present specification, according to the calculation of molecular orbital method by the present inventor, when boron and nitrogen are substituted in the carbon hexagonal plane, B is higher than that when boron and nitrogen are isolated. It has been found that the presence of -N bonds makes the energy more stable by orders of magnitude.
Abstracts of the 4th Annual Meeting of the Carbon Materials Society of Japan, Konno, Oka, Tachikawa, Inagaki, p. 302 (1997)].

From the above and the results of the examination of Example 1, the polyimide film (PI-PB) of Example 1 in which a functional group containing boron was introduced, regardless of the original state of boron, Was found to give a compound in which the BN bonds were dispersed in the carbon structure.

However, unlike PI-B, the ratio of BN-bonded boron and nitrogen in the N1s spectrum of PI-PB increases almost linearly with the carbonization temperature.
At 200 ° C., the amount was almost twice as large as that of tertiary amine type nitrogen.

Further, as shown in FIG.
Since the / C1s spectrum intensity ratio and the N / C molar ratio by elemental analysis showed a linear relationship, which was close to the case of PI, it was found that there was almost no difference in composition between the surface of the thin film after carbonization and the inside.

Further, although not particularly shown in the figure, the B1s / C1s spectrum intensity ratio on the surface also increased linearly from 800 ° C. with the carbonization temperature.

Although not particularly shown, when the BN bond type N1s spectrum intensity was plotted against the B1s intensity, an almost linear relationship was obtained. However, this graph did not pass through the zero point, and it was found that boron was slightly excessive on the surface, suggesting that boron other than the BN type was also present.

From the above results, it was found that the use of polyimide containing boron in the molecule can produce a carbon thin film containing different atoms more uniformly.

[0057]

According to the present invention, a more dense and homogeneous carbon film containing boron and nitrogen is produced by introducing boron into the skeleton structure of polyimide and carbonizing it by heat treatment. be able to.

The carbon film obtained by the present invention is expected to be used as a functional carbon material for products such as lithium secondary batteries, sensors, and semiconductors.

[Brief description of the drawings]

FIG. 1 is a structural formula of an exemplary substituted DDE according to the present invention.

FIG. 2 is a graph in which the intensity ratio of N1s and C1s spectra of the carbon film surface by XPS is plotted against the carbonization temperature.

FIG. 3 is a graph in which the intensity ratio of N1s and C1s spectra on the carbon film surface by XPS is plotted against the N / C molar ratio by elemental analysis.

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[Procedure amendment]

[Submission date] May 21, 1999

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

Patent application title: Method for producing carbon film and film to be treated

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claims

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[Claims]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0001

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[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon film obtained by carbonizing an organic polymer compound, and more particularly to a film to be treated for obtaining such a carbon film.

[Procedure amendment 4]

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[Correction target item name] 0009

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SUMMARY OF THE INVENTION It is an object of the present invention to obtain a carbon film having a uniform composition without physical defects due to generation of pores or the like by heat treatment of a film to be treated with a highly oriented carbon material.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0010

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[0010]

According to the present invention, when a carbon film containing nitrogen and boron is obtained by heat-treating a film to be treated, the film to be treated is made of polyimide. The present invention relates to a method for producing a carbon film, wherein a functional group containing is introduced into the skeleton structure of the polyimide, and the film to be treated is carbonized by the heat treatment.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0011

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The present invention is also a film to be treated for obtaining a carbon film containing nitrogen and boron by heat treatment, wherein the film to be treated is made of polyimide, and the functional group containing boron is a polyimide. Wherein the film to be treated is carbonized by the heat treatment, and is a film to be treated for obtaining a carbon film.

[Procedure amendment 7]

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[Correction target item name] 0023

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In the present invention, such a polyimide is used as a film to be treated. In such a polyimide, a functional group containing boron is introduced into the skeleton structure of the polyimide. Such a functional group containing boron can be introduced before synthesizing the target film of the present invention.

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0024

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In the present invention, a functional group containing boron is introduced into a raw material monomer of an organic high molecular compound containing nitrogen in the molecule, the raw material monomer is polymerized, and the organic high molecular compound containing nitrogen and boron in the skeleton is obtained. Are synthesized into a film to be processed, and the film to be processed is carbonized by heat treatment, whereby a carbon film can be obtained.

Claims (2)

[Claims] In obtaining a carbon film containing nitrogen and boron, a precursor of the carbon film is made of polyimide, and the functional group containing boron is introduced into a skeleton structure of the polyimide. A method for producing a carbon film, comprising carbonizing a body by heat treatment. 2. A precursor for obtaining a carbon film containing nitrogen and boron, wherein the precursor is made of polyimide, and the functional group containing boron is introduced into a skeleton structure of the polyimide. A precursor for obtaining a carbon film, wherein the precursor is carbonized by a heat treatment.