JP2017071734A - Heat-resistant polybenzobisoxazole film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film that achieves both high heat resistance and high elongation.SOLUTION: A film has a polybenzobisoxazole polymer that has structure A having a specific aromatic structure having a plurality of phenyl groups represented by a biphenyl structure, and structure B having a specific aromatic structure having a single phenyl group, with a molar ratio between the structure A and the structure B (A:B) of 0.8:0.2-0.3:0.7.SELECTED DRAWING: None

Description

  The present invention relates to a polybenzobisoxazole film having high heat resistance that can withstand even in an environment of 530 ° C. or higher and high elongation.

A polybenzobisoxazole (PBO) resin film is known as an ultra-high heat resistant resin film. Among them, for example, PBO used for flexible device applications requiring a heat resistant temperature of 530 ° C. or higher has a structure composed only of an aromatic and heterocyclic structure and has a high elongation as a film. Required.
Examples of the film having PBO composed of only aromatic and heterocyclic structures (hereinafter referred to as aromatic PBO) include the films described in Non-Patent Document 1, Non-Patent Document 2, and Patent Document 1. These films have a heat resistance of over 530 ° C., but an elongation of 2.0 to 3.5%. Thus, aromatic PBO has high heat resistance, but its rigidity is low due to its rigidity.

A film composed of a copolymer structure of aromatic PBO is described in Patent Document 2. The film exhibits high heat resistance with a 10% weight loss temperature of 600 ° C. or higher, but there is no description regarding the elongation.
Regarding the production method for forming aromatic PBO into a film, for example, a method of polymerizing polyphosphoric acid, methanesulfonic acid or the like as a solvent and then removing the solvent (Patent Document 3); synthesizing a precursor soluble in an organic solvent; And the method (Nonpatent literature 1 and Nonpatent literature 2) etc. which remove an organic solvent after forming into a film by the casting method using this precursor are known.

JP 2008-179705 A JP 2004-231874 A Japanese Patent Laid-Open No. 63-210138

Macromolecules 2014, 47, pp 2088-2095. Macromolecules 2012, 45, pp4247-4253

Many conventional aromatic PBO films having a structure exhibiting high heat resistance are known, but both have high heat resistance and good elongation, and can be easily formed into a film. No film has been proposed. For this reason, for example, when used for a substrate of a flexible device requiring a process temperature of 530 ° C. or higher, there is a problem that the heat resistance is satisfied but the elongation is insufficient. Further, according to the production method using polyphosphoric acid, methanesulfonic acid or the like as the solvent, if the removal of the solvent is performed by the casting method, a furnace having a high acid resistance at a high temperature is required, so that usable conditions are limited.
The present invention has been made in response to the above problems, and an object thereof is to provide a film in which high heat resistance and high elongation are compatible. Furthermore, an object of this invention is to provide the manufacturing method of the said film which can perform a film forming process easily.

The present inventor has intensively studied to achieve the above object. As a result, it has been found that aromatic PBO having a plurality of specific types of structures can achieve both high heat resistance and high elongation. Moreover, it discovered that the said film could be easily manufactured by forming into a film via the precursor which can be melt | dissolved in an organic solvent.
That is, the present invention is as follows.

｛式（Ｉ）中のＸ^１は、下記の構造群：

より選択される。｝

｛式（ＩＩ）中のＸ^２は、下記の構造群：

より選択される。｝

[1] At least one structure A selected from the group consisting of a structure represented by the following general formula (I) and a structure represented by the following general formula (II);
The structure B represented by the following general formula (III) has a molar ratio (A: B) between the structure A and the structure B of 0.8: 0.2 to 0.3: 0.7. A film comprising a polymer (P).

{X ¹ in Formula (I) is the following structural group:

More selected. }

{X ² in Formula (II) is the following structural group:

More selected. }

［３］ 前記構造Ａが、下記一般式（Ｖ）で表される構造を含む、［１］又は［２］に記載のフィルム。

[2] The film according to [1], wherein the structure B includes a structure represented by the following general formula (IV).

[3] The film according to [1] or [2], wherein the structure A includes a structure represented by the following general formula (V).

｛式（ＶＩ）中のＸ^１は式（Ｉ）中のＸ^１と同じであり、Ｒ^１及びＲ^２は、それぞれ独立に、水素原子、シリル基、及びアルキル基のいずれかを示す。｝

｛式（ＶＩＩ）中のＸ^２は式（ＩＩ）中のＸ^２と同じであり、Ｒ^３及びＲ^４は、それぞれ独立に、水素原子、シリル基、及びアルキル基のいずれかを示す。｝

｛式（ＶＩＩＩ）中のＲ^５及びＲ^６は、それぞれ独立に、水素原子、シリル基、及びアルキル基のいずれかを示す。｝ [4] At least one structure C selected from the group consisting of a structure represented by the following general formula (VI) and a structure represented by the following general formula (VII);
The method according to any one of [1] to [3], including a step of obtaining the polymer (P) from a precursor having a structure D represented by the following general formula (VIII): A method for producing a film.

^{{X 1} in formula (VI) are the same as ^{X 1} in formula (I), ^{R 1} and ^{R 2} each independently represent any one of a hydrogen atom, a silyl group and an alkyl group. }

^{{X 2} in the formula (VII) is the same as ^{X 2} in formula (II), ^{R 3} and ^{R 4} each independently represent any one of a hydrogen atom, a silyl group and an alkyl group. }

{R ⁵ and R ^{6 in} Formula (VIII) each independently represent a hydrogen atom, a silyl group, or an alkyl group. }

[5] The method for producing a film according to [4], wherein the polystyrene-equivalent weight average molecular weight (Mw) of the precursor measured using gel permeation chromatography is 10,000 or more.
[6] The method for producing a film according to [4] or [5], including a step of dissolving the precursor in a solvent and casting on a substrate to form a precursor film.

[7] The method for producing a film according to [6], wherein the solvent for dissolving the precursor is an organic solvent.
[8] The method for producing a film according to any one of [4] to [7], including a step of heating the precursor at 200 ° C. or more and 600 ° C. or less to form a benzoxazole ring.

The film having an aromatic PBO structure of the present invention has high heat resistance and high elongation. Moreover, the said film can be easily manufactured by forming into a film via the precursor which can melt | dissolve in an organic solvent.
It is not clear why the structure of the present invention has a high elongation despite having a rigid structure. The present inventor speculates that the effect is due to the coexistence of a structure having a single phenyl group and a structure having a plurality of phenyl groups (eg, biphenyl structure, terphenyl structure, etc.). That is, by containing a single phenyl group structure and a plurality of phenyl group structures at the same time, it becomes possible to take a three-dimensional structure with a large free volume, which is considered to lead to an improvement in elongation. .

｛式（Ｉ）中のＸ^１は、下記の構造群：

より選択される。｝

｛式（ＩＩ）中のＸ^２は、下記の構造群：

より選択される。｝

Hereinafter, embodiments of the present invention will be described in detail.
The film of the present invention comprises at least one structure A selected from the group consisting of a structure represented by the following general formula (I) and a structure represented by the following general formula (II):
The polymer (P) which has the structure B represented by the said general formula (III) is included.

{X ¹ in Formula (I) is the following structural group:

More selected. }

{X ² in Formula (II) is the following structural group:

More selected. }

重合体（Ｐ）における構造Ａ中に占める上記一般式（Ｖ）で表される構造の割合は、全構造Ａに対して、５０モル％以上であることが好ましく、７０モル％以上であることがより好ましく、９０モル％以上であることが更に好ましく、特に好ましくは構造Ａが上記一般式（Ｖ）で表される構造のみから成る場合である。 [Structure A]
The structure A used in the present invention is at least one structure selected from the group consisting of the structure represented by the general formula (I) and the structure represented by the general formula (II). The structure A may be a kind of structure or may be composed of a plurality of structures.
Of these structures, the structure A is particularly preferably a structure represented by the following general formula (V).

The proportion of the structure represented by the general formula (V) in the structure A in the polymer (P) is preferably 50 mol% or more, and 70 mol% or more with respect to the entire structure A. Is more preferably 90 mol% or more, and particularly preferably when the structure A consists only of the structure represented by the general formula (V).

重合体（Ｐ）における構造Ｂ中に占める上記一般式（ＩＶ）で表される構造の割合は、全構造Ｂに対して、３０モル％以上であることが好ましく、５０モル％以上であることがより好ましく、７０モル％以上であることが更に好ましく、特に好ましくは構造Ｂが上記一般式（ＩＶ）で表される構造のみから成る場合である。 [Structure B]
Structure B used in the present invention is a structure represented by the above general formula (III). The structure B may be a kind of structure or may be composed of a plurality of structures.
Of these structures, the structure B is particularly preferably a structure represented by the following general formula (IV).

The proportion of the structure represented by the general formula (IV) in the structure B in the polymer (P) is preferably 30 mol% or more, and 50 mol% or more with respect to the total structure B. Is more preferably 70 mol% or more, and particularly preferably when the structure B is composed of only the structure represented by the general formula (IV).

[Polymer (P)]
The polymer (P) is characterized by having both the structure A and the structure B. The form in which the structure A and the structure B are contained in the polymer (P) is not limited. Specifically, for example, an alloy structure in which a polymer composed of structure A and a polymer composed of structure B exist independently and are mixed; copolymerization in such a manner that structure A and structure B are randomly linked A random copolymer structure; a block copolymer structure in which a chain of structure A and a chain of structure B are bonded; an alternating copolymer structure in which structures A and B are alternately present; one or more of the above copolymer structures For example, a graft copolymer structure formed by comb-like bonding.

  In order to obtain a film having both high heat resistance and high elongation, the content ratio of the structure A and the structure B in the polymer (P) is important. When the content ratio of the structure A is too high, the number of benzene rings capable of intermolecular bonding becomes too large, so that gel is generated at the time of film formation and a uniform film may not be obtained. If the content ratio of the structure B is too high, the elongation may be low due to the rigidity of the structure B. Therefore, the content molar ratio (A: B) of the structure A and the structure B needs to be 0.8: 0.2 to 0.3: 0.7, preferably 0.7: 0.3 to 0. .3: 0.7, more preferably 0.6: 0.4 to 0.4: 0.6.

｛式（ＶＩ）中のＸ^１は式（Ｉ）中のＸ^１と同じであり、式中、Ｒ^１及びＲ^２は、それぞれ独立に、水素原子、シリル基、及びアルキル基のいずれかを示す。｝

｛式（ＶＩＩ）中のＸ^２は式（ＩＩ）中のＸ^２と同じであり、Ｒ^３及びＲ^４は、それぞれ独立に、水素原子、シリル基、及びアルキル基のいずれかを示す。｝

｛式（ＶＩＩＩ）中のＲ^５及びＲ^６は、それぞれ独立に、水素原子、シリル基、及びアルキル基のいずれかを示す。｝ [precursor]
The polymer (P) in the present invention includes at least one structure C selected from the group consisting of a structure represented by the following general formula (VI) and a structure represented by the following general formula (VII):
It can be obtained from a precursor having the structure D represented by the following general formula (VIII).

^{{X 1} in formula (VI) are the same as ^{X 1} in the formula (I), wherein, ^{R 1} and ^{R 2} are each independently a hydrogen atom, a silyl group or an alkyl group Show. }

^{{X 2} in the formula (VII) is the same as ^{X 2} in formula (II), ^{R 3} and ^{R 4} each independently represent any one of a hydrogen atom, a silyl group and an alkyl group. }

{R ⁵ and R ^{6 in} Formula (VIII) each independently represent a hydrogen atom, a silyl group, or an alkyl group. }

R ¹ , R ² , R ³ , R ⁴ , R ⁵ , and R ⁶ in the above structural formulas (VII) and (VIII) are each contained to improve the solubility of the precursor in an organic solvent. The most suitable form can be selected according to the structure. Specifically, for example, hydrogen atom; silyl group such as trimethylsilyl group, triethylsilyl group, triisopropylsilyl group, tert-butyldimethylsilyl group, tert-butyldiphenylsilyl group; methyl group, ethyl group, propyl group, isopropyl And alkyl groups such as butyl, isobutyl, tert-butyl, pentyl, and hexyl. Among these, a trimethylsilyl group, a tert-butyldimethylsilyl group, a methyl group, or an isopropyl group is particularly preferable because of high solubility of the precursor.

Structures C and D in the precursor give structures A and B in the polymer (P), respectively, by the heating step described later. Therefore, the content and content ratio of the structures C and D in the precursor should be appropriately designed according to the desired structure of the polymer (P).
The weight average molecular weight (Mw) of the precursor is preferably 10,000 or more and 1,000,000 or less. If the weight average molecular weight is 10,000 or more, the self-supporting property of the film is improved, and if the weight average molecular weight is 1,000,000 or less, dissolution in a solvent becomes easy. More preferably, it is 30,000 or more and 700,000 or less, and further preferably 50,000 or more and 500,000 or less.
This weight average molecular weight is a polystyrene equivalent value measured by gel permeation chromatography.

The precursors as described above can be synthesized by a known method except that monomers giving structures C and D are used. Specifically, the precursor can be obtained by a polycondensation reaction between an aromatic diamine having a predetermined structure or a derivative thereof and an aromatic dicarboxylic acid having a predetermined structure or a derivative thereof.
Examples of the aromatic diamine that gives the structure C represented by the above formula (VI) or a derivative thereof include a compound group represented by the following formula (VI-a);
Examples of the aromatic dicarboxylic acid or derivative thereof that gives the structure C represented by the above formula (VI) include a compound group represented by the following formula (VI-b);
Examples of the aromatic diamine that gives the structure C represented by the formula (VII) or a derivative thereof include a compound group represented by the following formula (VII-a);
Examples of the aromatic dicarboxylic acid or a derivative thereof that gives the structure C represented by the formula (VII) include a compound group represented by the following formula (VII-b);
Each can be mentioned.

The structure D represented by the above formula (VIII) is selected from one or more selected from the group of compounds represented by the above formula (VI-a) and the compound group represented by the following formula (VIII-b) Can be obtained by reaction with one or more of the above.

Examples of the solvent used for the polycondensation reaction as a precursor synthesis include inorganic solvents such as polyphosphoric acid, methanesulfonic acid, sulfuric acid, trifluoroacetic acid, and dimethylsulfuric acid; and m-cresol, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, γ-butyrolactone, N, N-dimethylsulfoxide, acetone, diethyl acetate, ethyl acetate, butyl acetate, isopropyl acetate, ethylene glycol, glycerin, methyl ethyl ketone, methyl isobutyl ketone, One or more selected from organic solvents such as dioxane, cyclohexanone, toluene, tetrahydrofuran, methylene chloride, chloroform, acetonitrile, pyridine and trichloroethylene are useful. Due to the high solubility of the raw materials for synthesis and the precursors obtained, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, γ-butyrolactone, and N, N-dimethylsulfoxide It is more preferable to use one or more selected from the group.

[Film Forming Method]
The film of this invention can be preferably formed by heating the precursor film which consists of said precursor, and producing | generating a benzoxazole ring.
The precursor film in the present invention is formed by coating a precursor solution obtained by dissolving the precursor in a solvent on an appropriate support to form a coating film, and then removing the solvent from the coating film. Can be formed.
As the coating method, a known coater can be used. Specific examples include coating using an applicator, die coater, blade coater, wire bar coater, air knife coater, dip coater, comma knife coater, spray coater, curtain coater, spin coater and the like. These can be implemented by one kind or a combination of two or more kinds as required.

As a preferable support used for coating, for example, glass substrate (Eagle XG, manufactured by Corning), SUS substrate, Upilex film (SX50, manufactured by Ube Industries), Kapton film (manufactured by Toray DuPont), polycarbonate film, PET A film etc. are mentioned.
As an example of a method for forming a film of the present invention from a precursor film, a cast method in which a coating film of a precursor solution formed on a support using the above-described method is heated on the support. And a method of producing a benzoxazole ring while removing an organic solvent from the coating film. As an example of the process of changing from the precursor structure to the benzoxazole ring structure, there is a method in which the precursor is used as a film and annealed in the film state to obtain an aromatic PBO film. At this time, from the viewpoint of the heat resistance of the support, it is possible to select whether or not the support is used and the type of the support in accordance with the temperature during annealing.

[Solvents that can be used to form a film]
The solvent that can be used for preparing the precursor solution is not particularly limited as long as it is a solvent that dissolves the precursors having the structures C and D. For example, inorganic solvents such as polyphosphoric acid, methanesulfonic acid, sulfuric acid, trifluoroacetic acid, dimethyl sulfuric acid; and m-cresol, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, γ -Butyrolactone, N, N-dimethyl sulfoxide, acetone, diethyl acetate, ethyl acetate, butyl acetate, isopropyl acetate, ethylene glycol, glycerin, methyl ethyl ketone, methyl isobutyl ketone, dioxane, cyclohexanone, toluene, tetrahydrofuran, methylene chloride, chloroform, acetonitrile, One or more selected from organic solvents such as pyridine and trichlorethylene are useful. Among these, an organic solvent is preferable from the viewpoint of acid resistance of the apparatus. Furthermore, due to the high solubility of the precursors having structures C and D, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, γ-butyrolactone, and N, N-dimethyl It is more preferable to use one or more selected from the group consisting of sulfoxides.

[Optional components of precursor solution]
In addition to the precursor and the organic solvent, the precursor solution may contain an acid, a base, or a salt for the purpose of facilitating PBO film formation. In addition, for the purpose of suppressing weight change before and after conversion from the precursor film to the film of the present invention, inorganic fibers such as carbon fibers, glass fibers, silica, metal oxides, and carbon nanotubes; inorganic fillers may be added. Is possible. Further, an antifoaming agent, a dispersion stabilizer, a surfactant, a viscosity modifier, a corrosion inhibitor, etc. can be added to the precursor solution.

[Heating temperature for forming PBO film]
In forming the PBO film, the temperature at the time of heating (annealing) simultaneously with removing the solvent from the precursor film or after removing the solvent is preferably 200 ° C. or more and 600 ° C. or less. If it is 200 ° C. or higher, the formation of a benzoxazole ring proceeds, and if it is 600 ° C. or lower, the amount of heat necessary for heating the heater is reduced, so that the process load can be reduced. The heating temperature is more preferably 350 ° C. or higher and 550 ° C. or lower.
Here, for example, heating is performed while gradually rising from about 50 ° C., the solvent is removed from the precursor coating film to form a precursor film, and the precursor structure of the precursor film is converted into a benzoxazole ring. It is also a preferred embodiment to carry out the process stepwise or continuously.

Yield of benzoxazole ring (cyclization ratio) is, for example, the appearance of the peak of 1,270cm in IR measurement ^-1 (C-C stretching), 1,255Cm ^-1 disappearance of the peak of the (C-C stretch) It can be determined from the ratio, etc. In order to satisfy the heat resistance of 530 ° C. or higher, a higher cyclization rate is desirable. Specifically, the cyclization rate is preferably 50 mol% or more, more preferably 70 mol% or more, still more preferably 90 mol% or more, and particularly preferably 100%. is there.

  Hereinafter, the present invention will be described in detail by examples. However, the present invention is not limited by the following examples.

<Raw materials used for synthesis>
The raw materials used for the synthesis are as follows.
N-methyl-2-pyrrolidone: commercially available ultra-dehydrated N-methyl-2-pyrrolidone manufactured by Wako Pure Chemical Industries, Ltd. “NMP”
N, N-dimethylformamide: commercially available ultra-dehydrated N, N-dimethylformamide, “DMF” manufactured by Wako Pure Chemical Industries, Ltd.
γ-Butyrolactone, a commercial product, manufactured by Wako Pure Chemical Industries, “GBL”
4,6-Diaminoresorcinol dihydrochloride, a commercial product, manufactured by Sigma-Aldrich, "DAR"
tert-Butyldimethylchlorosilane, commercially available, manufactured by TCI, “TBSCl”
Triethylamine, a commercial product, manufactured by TCI, “TEA”
Terephthalyl chloride, commercial product, TCI's Isophthalyl chloride, commercial product, TCI's 4,4'-biphenyl carbonyl chloride, commercial product, TCI

<Synthesis of 4,6-Di (tert-butyldimethylsilylamino) -1,3-di (tert-butyldimethylsiloxy) benzene (TBS-DAR)>
The synthesis was performed using a four-necked flask equipped with a stirring blade and a dropping funnel.
In the four-necked flask, 230 mL of DMF, 4.3 g of DAR, and 40 g of TEA were charged under nitrogen and dissolved by stirring. Thereafter, 30 g of TBSCl was dropped from the dropping funnel at 4 ° C., and the reaction was carried out at room temperature for 12 hours. The precipitated solid was collected by filtration and washed with distilled water. The collected solid was dried under reduced pressure at 80 ° C. to obtain 11 g of TBS-DAR.
The obtained TBS-DAR was analyzed using ¹ H NMR and ¹³ C NMR (manufactured by JEOL, 400 MHz). The analysis results are shown below.
¹ H NMR (CDCl ₃ , δ ppm): 6.26 (s, 1H), 6.22 (s, 1H), 3.62 (s, 2H), 0.96 (d, 36H), 0.20 ( d, 24H)
¹³ C NMR (CDCl ₃ , δ ppm): 133.7, 132.8, 102.3, 102.5, 26.4, 26.0, 18.2, 17.9, −4.0, −4. 1

<Precursor synthesis of Example 1>
The reaction was carried out using a four-necked flask equipped with a stirring blade and a dropping funnel.
In the four-necked flask, 10 g of TBS-DAR was dissolved in 33 g of NMP under nitrogen. Next, a solution obtained by dissolving 1.7 g of acid chloride Terephtharyl chloride and 2.3 g of 4,4′-biphenylcarbonyl chloride in 20 g of GBL was dropped into a TBS-DAR solution cooled to 4 ° C. from a dropping funnel for 5 hours. The reaction was performed. After completion of the reaction, the obtained solution was put into special grade methanol (manufactured by Wako Pure Chemical Industries, Ltd.) for reprecipitation, and the solid was collected by filtration. The recovered solid was washed sequentially with special grade methanol and distilled water and dried under reduced pressure at 80 ° C.
The formation of the desired precursor was confirmed by measuring the molecular weight using gel permeation chromatography (GPC).

<Precursor synthesis of Example 2>
The desired precursor was obtained in the same manner as in Example 1 except that 1.4 g of Terephthalyl chloride and 2.8 g of 4,4′-Biphenyldivinyl chloride were used as the acid chloride.

<Precursor synthesis of Comparative Example 1>
A desired precursor was obtained in the same manner as in Example 1 except that 3.4 g of Terephthalyl chloride was used as the acid chloride.

<Precursor synthesis of Comparative Example 2>
A desired precursor was obtained in the same manner as in Example 1 except that 1.7 g of Terephthalyl chloride and 1.7 g of Isophthalyl chloride were used as the acid chloride.

<Precursor synthesis of Comparative Example 3>
A desired precursor was obtained in the same manner as in Example 1 except that 4.7 g of 4,4′-Biphenyldicbonyl chloride was used as the acid chloride.

<Precursor synthesis of Comparative Example 4>
A desired precursor was obtained in the same manner as in Example 1 except that 0.3 g of Terephthalyl chloride and 4.2 g of 4,4′-Biphenyldylcarbonyl chloride were used as acid chlorides.

<Precursor synthesis of Comparative Example 5>
A desired precursor was obtained in the same manner as in Example 1 except that 0.9 g of Terephtharyl chloride and 2.7 g of 4,4′-biphenylcarbonyl chloride were used as the acid chloride.

<Method for evaluating precursor molecular weight>
The weight average molecular weight (Mw) of the precursor was measured under the following conditions using gel permeation chromatography (GPC). As the solvent, N, N-dimethylformamide (manufactured by Wako Pure Chemical Industries, Ltd., for high performance liquid chromatograph) was used, and 24.8 mol / L lithium bromide monohydrate (manufactured by Wako Pure Chemical Industries, Ltd.) before the measurement. , Purity 99.5%) and 63.2 mol / L phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd., for high performance liquid chromatograph) were used. A calibration curve for calculating the weight average molecular weight was prepared using standard polystyrene (manufactured by Tosoh Corporation). Other conditions are as follows.
Column: TSK-GEL SUPER HM-H
Flow rate: 0.5 mL / min Column temperature: 40 ° C
Pump: PU-2080 (manufactured by JASCO)
Detector: RI-2031Plus (RI: differential refractometer, manufactured by JASCO) and UV-2075Plus (UV-Vis: UV-visible absorptiometer, manufactured by JASCO)

<Formation of film>
The precursor solid obtained by the above synthesis was dissolved in NMP at a concentration of 20% by mass to prepare a precursor solution.
After coating the above precursor solution on a glass substrate (Eagle XG, manufactured by Corning) using an applicator (manufactured by Tester Sangyo Co., Ltd.), it is performed in a hot air oven at 50 ° C. for 3 minutes, 60 ° C. for 3 minutes, 70 ° C. 10 , 80 ° C for 20 minutes, and 100 ° C for 10 minutes, and then heated and dried in a hot air oven under nitrogen from 200 ° C to 350 ° C every 50 ° C for 1 hour and 10 minutes. Obtained.
After peeling off the obtained film from the glass substrate, a film having a thickness of 11 μm in which the formation of the benzoxazole ring was completed by heating sequentially under conditions of 400 ° C. for 1 hour and 530 ° C. for 30 minutes under nitrogen. Obtained. Generation of benzoxazole ring, the appearance of the peak of 1,270cm in IR measurement ^-1 (C-C stretch) and were confirmed by complete disappearance of the peak of 1,255cm ^-1 (C-C stretch).
Evaluation was carried out using this film as a sample.

<Evaluation method of elongation>
Evaluation of elongation was carried out using a tensile testing machine (manufactured by A & D, RTG-1210).
Using a sample having a width of 3 mm and a length of 50 mm, the elongation was evaluated at a tensile speed of 100 mm / min. The analysis of elongation was performed by converting (length when the sample was cut-original length) / (original length) into percentage (%). The evaluation results are shown in Table 1.

<Evaluation method of heat resistance (weight change around 530 ° C. for 30 minutes)>
Evaluation of heat resistance was performed using TG-DTA (manufactured by Seiko Instruments Inc., EXSTAR6000).
The temperature profile of TG-DTA was maintained at 100 ° C. for 30 minutes, then heated to 530 ° C. at 10 ° C./minute, and then maintained at 530 ° C. for 30 minutes. The heat resistance was calculated by converting the rate of decrease in weight before and after holding at 530 ° C. for 30 minutes (weight after holding at 530 ° C. for 30 minutes / weight before holding at 530 ° C. for 30 minutes) into percentage (%). The evaluation results are shown in Table 1.

<Evaluation results of elongation and heat resistance>
From Table 1, it was verified that the samples obtained in Examples 1 and 2 were excellent in both elongation and heat resistance. On the other hand, the samples of Comparative Examples 1 to 5 were inferior to either or both of elongation and heat resistance, or film formation itself was impossible.

  The film of the present invention is suitable as a film used in applications requiring both heat resistance and elongation, such as for flexible device substrates and carbon membrane reinforcing substrates.

Claims (8)

At least one structure A selected from the group consisting of a structure represented by the following general formula (I) and a structure represented by the following general formula (II):
The structure B represented by the following general formula (III) has a molar ratio (A: B) between the structure A and the structure B of 0.8: 0.2 to 0.3: 0.7. A film comprising a polymer (P).

{X ¹ in Formula (I) is the following structural group:

More selected. }

{X ² in Formula (II) is the following structural group:

More selected. }

The film according to claim 1, wherein the structure B includes a structure represented by the following general formula (IV).

The film according to claim 1 or 2, wherein the structure A includes a structure represented by the following general formula (V).

At least one structure C selected from the group consisting of a structure represented by the following general formula (VI) and a structure represented by the following general formula (VII);
The process of obtaining the said polymer (P) from the precursor which has the structure D represented with the following general formula (VIII), The film of any one of Claims 1-3 characterized by the above-mentioned. Production method.

^{{X 1} in formula (VI) are the same as ^{X 1} in formula (I), ^{R 1} and ^{R 2} each independently represent any one of a hydrogen atom, a silyl group and an alkyl group. }

^{{X 2} in the formula (VII) is the same as ^{X 2} in formula (II), ^{R 3} and ^{R 4} each independently represent any one of a hydrogen atom, a silyl group and an alkyl group. }

{R ⁵ and R ^{6 in} Formula (VIII) each independently represent a hydrogen atom, a silyl group, or an alkyl group. }   The manufacturing method of the film of Claim 4 whose weight average molecular weight (Mw) of polystyrene conversion measured using the gel permeation chromatography about the said precursor is 10,000 or more.   6. The method for producing a film according to claim 4 or 5, comprising a step of dissolving the precursor in a solvent and casting on a substrate to form a precursor film.   The method for producing a film according to claim 6, wherein the solvent for dissolving the precursor is an organic solvent.   The manufacturing method of the film as described in any one of Claims 4-7 including the process of heating the said precursor at 200 to 600 degreeC and producing | generating a benzoxazole ring.