JP7253215B2 - Polyimide, polyimide varnish, polyimide thin film - Google Patents

Description

The present invention is a polyimide obtained by using a tetracarboxylic dianhydride having an ester bond synthesized from dianhydrohexitol such as isosorbide and isomannide, which are raw materials of biological resources, and trimellitic anhydrides, and It relates to polyimide varnishes and polyimide films obtained therefrom.

Polyimide is frequently used among current super engineering plastics as a highly reliable material in terms of physical and chemical heat resistance, electrical insulation, mechanical properties, flame retardancy, and simplicity of manufacturing process.
Tetracarboxylic dianhydrides and diamine compounds, which are raw material monomers for polyimides, are often produced from raw materials derived from petrochemicals. Petrochemically-derived polyimides contribute to greenhouse gas emissions due to their high petroleum-derived carbon content. Furthermore, petrochemicals are non-renewable products because they are naturally formed over hundreds of thousands of years from petroleum, which is their raw material.
On the other hand, bio-based plastics, which are made from bio-based resources such as plants, are said to be effective in building a sustainable low-carbon society because the carbon in the material is derived from the carbon dioxide fixed by the plants. ing. However, most bio-based plastics are inferior in heat resistance and mechanical properties, so their applications are limited, and there is a problem that they are difficult to use as engineering plastics.
In order to widely apply bio-based plastics to cutting-edge applications such as displays and transparent substrates, it is necessary to have excellent heat resistance, chemical stability, and environmental stability, as well as excellent optical properties, dielectric properties, and mechanical properties. Must have properties.

Chinese Patent Application Publication No. 101648958

An object of the present invention is to provide a polyimide material having excellent heat resistance and excellent optical properties and dielectric properties while using biological resources as raw materials.

As a result of intensive studies for solving the above problems, the present inventors have found that tetracarboxylic acid dianhydrides having an ester bond, which are synthesized from dianhydrohexitols such as isosorbide and isomannide, and trimellitic anhydrides, The inventors have found that the obtained polyimide can solve these problems, and completed the present invention.

（式中、Ｒ_１は、各々独立して炭素原子数１～６の直鎖状又は分岐鎖状のアルキル基、炭素原子数５又は６の環状のアルキル基、炭素原子数１～６の直鎖状又は分岐鎖状のアルコキシ基、炭素原子数５又は６の環状のアルコキシ基、炭素原子数６～８のアリール基、炭素原子数６～８のアリールオキシ基、炭素原子数１～６の直鎖状又は分岐鎖状のハロゲン化アルキル基、又はハロゲン原子を示し、ｎは、各々独立して０又は１～３の整数を示し、Ａは、下記一般式（５）で表される２価の基若しくは炭素原子数４～３０の環状の脂肪族基を含む２価の有機基を示す。）

（式中、Ｒ_２は、各々独立して炭素原子数１～６の直鎖状又は分岐鎖状アルキル基、炭素原子数５又は６の環状アルキル基、炭素原子数１～６の直鎖状又は分岐鎖状のアルコキシ基、炭素原子数５又は６の環状のアルコキシ基、炭素原子数６～８のアリール基、炭素原子数６～８のアリールオキシ基、炭素原子数１～６の直鎖状又は分岐鎖状のハロゲン化アルキル基、又はハロゲン原子を示し、ｍは、各々独立して０又は１～４の整数を示し、ｐ、ｑ及びｒは、０又は１を示し、Ｘは、直接結合、酸素原子、硫黄原子、スルホニル基（－ＳＯ_２－）、カルボニル基（－ＣＯ－）、アミド基（－ＮＨＣＯ－）、エステル基（－ＯＣＯ－）、炭素原子数１～１５のアルキリデン基、炭素原子数２～１５のフッ素含有アルキリデン基、炭素原子数５～１５のシクロアルキリデン基、フェニレン基又はフルオレニリデン基を示し、＊は、各々結合位置を示す。）
２．下記一般式（２）～（４）で表される繰り返し単位から選択される１つ以上の繰り返し単位を有する、１．に記載のポリイミド。

（一般式（２）～（４）中、Ｒ_１、ｎ、Ａは、一般式（１）の定義と同じである。）
３．下記一般式（２）で表される繰り返し単位を有する、１．に記載のポリイミド。

（式中、Ｒ_１、ｎ、Ａは、一般式（１）の定義と同じである。）
４．前記一般式（２）～（４）で表される繰り返し単位から選ばれる２つ以上の繰り返し単位を有する、１．又は２．に記載のポリイミド。
５．前記一般式（２）及び前記一般式（４）で表される繰り返し単位を有する、４．に記載のポリイミド。
６．前記一般式（２）で表される繰り返し単位と前記一般式（４）で表される繰り返し単位とのモル比率が、（２）：（４）＝９９：１～５０：５０の範囲である、５．に記載のポリイミド。
７．前記一般式（１）で表される繰り返し単位の含有量が、ポリイミド全体の１５モル％以上である、１．に記載のポリイミド。
８．１．に記載のポリイミドと有機溶媒を含む、ポリイミドワニス。
９．１．に記載のポリイミドを含む、ポリイミド薄膜。
１０．下記一般式（１）で表される繰り返し単位を有し、熱重量分析による１００℃での重量を基準値とした残渣重量率が９５％になる熱分解温度（Ｔｄ）が、３５０℃以上であるポリイミド。

（式中、Ｒ_１は、各々独立して炭素原子数１～６の直鎖状又は分岐鎖状のアルキル基、炭素原子数５又は６の環状のアルキル基、炭素原子数１～６の直鎖状又は分岐鎖状のアルコキシ基、炭素原子数５又は６の環状のアルコキシ基、炭素原子数６～８のアリール基、炭素原子数６～８のアリールオキシ基、炭素原子数１～６の直鎖状又は分岐鎖状のハロゲン化アルキル基、又はハロゲン原子を示し、ｎは、各々独立して０又は１～３の整数を示し、Ａは、２価の有機基を示す。）
１１．下記一般式（２）～（４）で表される繰り返し単位から選択される１つ以上の繰り返し単位を有する、１０．に記載のポリイミド。

（一般式（２）～（４）中、Ｒ_１、ｎ、Ａは、一般式（１）の定義と同じである。）
１２．下記一般式（２）で表される繰り返し単位を有する、１０．に記載のポリイミド。

（式中、Ｒ_１、ｎ、Ａは、一般式（１）の定義と同じである。）
１３．前記一般式（２）～（４）で表される繰り返し単位から選ばれる２つ以上の繰り返し単位を有する、１０．又は１１．に記載のポリイミド。
１４．前記一般式（２）及び前記一般式（４）で表される繰り返し単位を有する、１３．に記載のポリイミド。
１５．前記一般式（２）で表される繰り返し単位と前記一般式（４）で表される繰り返し単位とのモル比率が、（２）：（４）＝９９：１～５０：５０の範囲である、１４．に記載のポリイミド。
１６．前記一般式（１）～（４）におけるＡが、芳香環を含む２価の有機基又は直鎖状、分岐鎖状若しくは環状の脂肪族基を含む２価の有機基である、１０．に記載のポリイミド。
１７．前記一般式（１）～（４）におけるＡの芳香環を含む２価の有機基が、下記一般式（５）で表される２価の基である、１６．に記載のポリイミド。

（式中、Ｒ_２は、各々独立して炭素原子数１～６の直鎖状又は分岐鎖状アルキル基、炭素原子数５又は６の環状アルキル基、炭素原子数１～６の直鎖状又は分岐鎖状のアルコキシ基、炭素原子数５又は６の環状のアルコキシ基、炭素原子数６～８のアリール基、炭素原子数６～８のアリールオキシ基、炭素原子数１～６の直鎖状又は分岐鎖状のハロゲン化アルキル基、又はハロゲン原子を示し、ｍは、各々独立して０又は１～４の整数を示し、ｐ、ｑ及びｒは、０又は１を示し、Ｘは、直接結合、酸素原子、硫黄原子、スルホニル基（－ＳＯ_２－）、カルボニル基（－ＣＯ－）、アミド基（－ＮＨＣＯ－）、エステル基（－ＯＣＯ－）、炭素原子数１～１５のアルキリデン基、炭素原子数２～１５のフッ素含有アルキリデン基、炭素原子数５～１５のシクロアルキリデン基、フェニレン基又はフルオレニリデン基を示し、＊は、各々結合位置を示す。）
１８．直鎖状、分岐鎖状若しくは環状の脂肪族基を含む２価の有機基が、炭素原子数１～３０の直鎖状又は分岐鎖状の脂肪族基若しくは炭素原子数４～３０の環状の脂肪族基を含む２価の有機基である、１６．に記載のポリイミド。
１９．前記一般式（１）で表される繰り返し単位の含有量が、ポリイミド全体の１５モル％以上である、１０．に記載のポリイミド。
２０．１０．に記載のポリイミドと有機溶媒を含む、ポリイミドワニス。
２１．１０．に記載のポリイミドを含む、ポリイミド薄膜。 The present invention is as follows.
1. A polyimide having a repeating unit represented by the following general formula (1) and having a glass transition temperature (Tg) of 210° C. or higher as determined by thermomechanical analysis.

(wherein R ₁ is each independently a linear or branched alkyl group having 1 to 6 carbon atoms, a cyclic alkyl group having 5 or 6 carbon atoms, a straight alkyl group having 1 to 6 carbon atoms, chain or branched alkoxy group, cyclic alkoxy group having 5 or 6 carbon atoms, aryl group having 6 to 8 carbon atoms, aryloxy group having 6 to 8 carbon atoms, aryloxy group having 1 to 6 carbon atoms represents a linear or branched halogenated alkyl group or a halogen atom, n is each independently an integer of 0 or 1 to 3, and A is 2 represented by the following general formula (5) A divalent organic group including a valent group or a cyclic aliphatic group having 4 to 30 carbon atoms.)

(wherein R ₂ is each independently a linear or branched alkyl group having 1 to 6 carbon atoms, a cyclic alkyl group having 5 or 6 carbon atoms, a linear alkyl group having 1 to 6 carbon atoms, or a branched alkoxy group, a cyclic alkoxy group having 5 or 6 carbon atoms, an aryl group having 6 to 8 carbon atoms, an aryloxy group having 6 to 8 carbon atoms, or a straight chain having 1 to 6 carbon atoms represents a branched or branched halogenated alkyl group or a halogen atom, m each independently represents an integer of 0 or 1 to 4, p, q and r represent 0 or 1, X is direct bond, oxygen atom, sulfur atom, sulfonyl group (--SO ₂ --), carbonyl group (--CO--), amide group (--NHCO--), ester group (--OCO--), alkylidene having 1 to 15 carbon atoms group, a fluorine-containing alkylidene group having 2 to 15 carbon atoms, a cycloalkylidene group having 5 to 15 carbon atoms, a phenylene group or a fluorenylidene group, and * indicates a bonding position.)
2. 1. having one or more repeating units selected from repeating units represented by the following general formulas (2) to (4); Polyimide according to.

(In general formulas (2) to (4), R ₁ , n, and A are the same as defined in general formula (1).)
3. 1. Having a repeating unit represented by the following general formula (2); Polyimide according to.

(In the formula, R ₁ , n, and A are the same as defined in general formula (1).)
4. 1. Having two or more repeating units selected from the repeating units represented by the general formulas (2) to (4); or 2. Polyimide according to.
5. 4. having repeating units represented by the general formulas (2) and (4); Polyimide according to.
6. The molar ratio of the repeating unit represented by the general formula (2) and the repeating unit represented by the general formula (4) is in the range of (2):(4)=99:1 to 50:50. 5. Polyimide according to.
7. 1. The content of the repeating unit represented by the general formula (1) is 15 mol % or more of the entire polyimide. Polyimide according to.
8.1. A polyimide varnish containing the polyimide and an organic solvent according to .
9.1. A polyimide thin film comprising the polyimide according to .
10. It has a repeating unit represented by the following general formula (1), and the thermal decomposition temperature (Td) at which the residue weight ratio becomes 95% based on the weight at 100 ° C. by thermogravimetric analysis is 350 ° C. or higher. some polyimide.

(wherein R ₁ is each independently a linear or branched alkyl group having 1 to 6 carbon atoms, a cyclic alkyl group having 5 or 6 carbon atoms, a straight alkyl group having 1 to 6 carbon atoms, chain or branched alkoxy group, cyclic alkoxy group having 5 or 6 carbon atoms, aryl group having 6 to 8 carbon atoms, aryloxy group having 6 to 8 carbon atoms, aryloxy group having 1 to 6 carbon atoms represents a linear or branched halogenated alkyl group or a halogen atom, each n independently represents an integer of 0 or 1 to 3, and A represents a divalent organic group.)
11. 10. having one or more repeating units selected from repeating units represented by the following general formulas (2) to (4); Polyimide according to.

(In general formulas (2) to (4), R ₁ , n, and A are the same as defined in general formula (1).)
12. 10. having a repeating unit represented by the following general formula (2); Polyimide according to.

(In the formula, R ₁ , n, and A are the same as defined in general formula (1).)
13. 10. having two or more repeating units selected from the repeating units represented by the general formulas (2) to (4); or 11. Polyimide according to.
14. 13. having repeating units represented by the general formulas (2) and (4); Polyimide according to.
15. The molar ratio of the repeating unit represented by the general formula (2) and the repeating unit represented by the general formula (4) is in the range of (2):(4)=99:1 to 50:50. , 14. Polyimide according to.
16. 10. A in the general formulas (1) to (4) is a divalent organic group containing an aromatic ring or a divalent organic group containing a linear, branched or cyclic aliphatic group; Polyimide according to.
17. 16. The divalent organic group containing an aromatic ring of A in the general formulas (1) to (4) is a divalent group represented by the following general formula (5). Polyimide according to.

(wherein R ₂ is each independently a linear or branched alkyl group having 1 to 6 carbon atoms, a cyclic alkyl group having 5 or 6 carbon atoms, a linear alkyl group having 1 to 6 carbon atoms, or a branched alkoxy group, a cyclic alkoxy group having 5 or 6 carbon atoms, an aryl group having 6 to 8 carbon atoms, an aryloxy group having 6 to 8 carbon atoms, or a straight chain having 1 to 6 carbon atoms represents a branched or branched halogenated alkyl group or a halogen atom, m each independently represents an integer of 0 or 1 to 4, p, q and r represent 0 or 1, X is direct bond, oxygen atom, sulfur atom, sulfonyl group (--SO ₂ --), carbonyl group (--CO--), amide group (--NHCO--), ester group (--OCO--), alkylidene having 1 to 15 carbon atoms group, a fluorine-containing alkylidene group having 2 to 15 carbon atoms, a cycloalkylidene group having 5 to 15 carbon atoms, a phenylene group or a fluorenylidene group, and * indicates a bonding position.)
18. A divalent organic group containing a linear, branched or cyclic aliphatic group is a linear or branched aliphatic group having 1 to 30 carbon atoms or a cyclic group having 4 to 30 carbon atoms 16. A divalent organic group containing an aliphatic group; Polyimide according to.
19. 10. The content of the repeating unit represented by the general formula (1) is 15 mol % or more of the entire polyimide. Polyimide according to.
20.10. A polyimide varnish containing the polyimide and an organic solvent according to .
21.10. A polyimide thin film comprising the polyimide according to .

With the polyimide according to the present invention, it is possible to provide a material having excellent optical properties and dielectric properties while having sufficient heat resistance required for polyimide resins while using biological resources as raw materials.

1 is a diagram showing an ATR infrared absorption spectrum of a polyimide thin film (about 15 μm thick) obtained in Example 1. FIG. 2 is a diagram showing an ATR infrared absorption spectrum of a polyimide thin film (about 15 μm thick) obtained in Example 2. FIG. FIG. 10 is a diagram showing an ATR infrared absorption spectrum of a polyimide thin film (about 15 μm thick) obtained in Example 3; FIG. 10 is a diagram showing an ATR infrared absorption spectrum of a polyimide thin film (film thickness of about 15 μm) obtained in Example 4; FIG. 10 is a diagram showing an ATR infrared absorption spectrum of a polyimide thin film (film thickness of about 15 μm) obtained in Example 5; FIG. 10 is a diagram showing an ATR infrared absorption spectrum of a polyimide thin film (about 15 μm thick) obtained in Example 6; FIG. 10 is a diagram showing an ATR infrared absorption spectrum of a polyimide thin film (about 15 μm thick) obtained in Example 7; FIG. 10 is a diagram showing an ATR infrared absorption spectrum of a polyimide thin film (film thickness of about 15 μm) obtained in Example 8; FIG. 10 is a diagram showing an ATR infrared absorption spectrum of a polyimide thin film (about 15 μm thick) obtained in Example 9; FIG. 10 is a diagram showing an ATR infrared absorption spectrum of a polyimide thin film (about 15 μm thick) obtained in Example 10; FIG. 11 is a diagram showing an ATR infrared absorption spectrum of a polyimide thin film (about 15 μm thick) obtained in Example 11; 1 is a diagram showing a ¹ H-NMR spectrum of a deuterated dimethylsulfoxide (DMSO-d ₆ ) solution of a polyimide thin film obtained in Example 1. FIG. 1 is a diagram showing the ¹ H-NMR spectrum of a DMSO-d ₆ solution of the polyimide thin film obtained in Example 2. FIG. 1 is a diagram showing the ¹ H-NMR spectrum of a DMSO-d ₆ solution of a polyimide thin film obtained in Example 3. FIG. FIG. 10 shows the ¹ H-NMR spectrum of a DMSO-d ₆ solution of the polyimide thin film obtained in Example 4; FIG. 10 is a diagram showing the ¹ H-NMR spectrum of a DMSO-d ₆ solution of the polyimide thin film obtained in Example 5; FIG. 10 is a diagram showing the ¹ H-NMR spectrum of a DMSO-d ₆ solution of the polyimide thin film obtained in Example 6; FIG. 10 is a diagram showing the ¹ H-NMR spectrum of a DMSO-d ₆ solution of the polyimide thin film obtained in Example 7; FIG. 10 is a diagram showing the ¹ H-NMR spectrum of a DMSO-d ₆ solution of the polyimide thin film obtained in Example 8; FIG. 10 is a diagram showing the ¹ H-NMR spectrum of a DMSO-d ₆ solution of the polyimide thin film obtained in Example 9; FIG. 10 is a diagram showing the ¹ H-NMR spectrum of a DMSO-d ₆ solution of the polyimide thin film obtained in Example 10; FIG. 10 is a diagram showing the ¹ H-NMR spectrum of a DMSO-d ₆ solution of the polyimide thin film obtained in Example 11; 1 is a diagram showing a thermomechanical analysis (TMA) chart of a polyimide thin film obtained in Example 1. FIG. 3 is a diagram showing a thermomechanical analysis (TMA) chart of the polyimide thin film obtained in Example 2. FIG. FIG. 4 is a diagram showing a thermomechanical analysis (TMA) chart of the polyimide thin film obtained in Example 3. FIG. FIG. 4 is a diagram showing a thermomechanical analysis (TMA) chart of the polyimide thin film obtained in Example 4. FIG. FIG. 10 is a diagram showing a thermomechanical analysis (TMA) chart of the polyimide thin film obtained in Example 5. FIG. FIG. 10 is a diagram showing a thermomechanical analysis (TMA) chart of the polyimide thin film obtained in Example 6. FIG. FIG. 10 is a diagram showing a thermomechanical analysis (TMA) chart of the polyimide thin film obtained in Example 7; FIG. 10 is a diagram showing a thermomechanical analysis (TMA) chart of the polyimide thin film obtained in Example 8. FIG. FIG. 10 is a diagram showing a thermomechanical analysis (TMA) chart of the polyimide thin film obtained in Example 9. FIG. FIG. 10 is a diagram showing a thermomechanical analysis (TMA) chart of the polyimide thin film obtained in Example 10; FIG. 10 is a diagram showing a thermomechanical analysis (TMA) chart of the polyimide thin film obtained in Example 11; 1 is a diagram showing a thermogravimetric analysis (TGA) chart of a polyimide thin film obtained in Example 1. FIG. 2 is a diagram showing a thermogravimetric analysis (TGA) chart of the polyimide thin film obtained in Example 2. FIG. FIG. 3 is a diagram showing a thermogravimetric analysis (TGA) chart of the polyimide thin film obtained in Example 3. FIG. FIG. 4 is a diagram showing a thermogravimetric analysis (TGA) chart of the polyimide thin film obtained in Example 4. FIG. FIG. 10 is a diagram showing a thermogravimetric analysis (TGA) chart of the polyimide thin film obtained in Example 5. FIG. FIG. 10 is a diagram showing a thermogravimetric analysis (TGA) chart of the polyimide thin film obtained in Example 6. FIG. FIG. 10 is a diagram showing a thermogravimetric analysis (TGA) chart of the polyimide thin film obtained in Example 7; FIG. 10 is a diagram showing a thermogravimetric analysis (TGA) chart of the polyimide thin film obtained in Example 8. FIG. FIG. 10 is a diagram showing a thermogravimetric analysis (TGA) chart of the polyimide thin film obtained in Example 9. FIG. FIG. 10 is a diagram showing a thermogravimetric analysis (TGA) chart of the polyimide thin film obtained in Example 10; FIG. 11 is a diagram showing a thermogravimetric analysis (TGA) chart of the polyimide thin film obtained in Example 11; 2 is a diagram showing the spectrum of the ultraviolet/visible light transmittance of the polyimide thin film obtained in Example 1. FIG. 3 is a diagram showing the spectrum of ultraviolet/visible light transmittance of the polyimide thin film obtained in Example 2. FIG. FIG. 10 is a diagram showing the spectrum of the ultraviolet/visible light transmittance of the polyimide thin film obtained in Example 3; FIG. 10 is a diagram showing the spectrum of the ultraviolet/visible light transmittance of the polyimide thin film obtained in Example 4; FIG. 10 is a diagram showing the spectrum of ultraviolet/visible light transmittance of the polyimide thin film obtained in Example 5; FIG. 10 is a diagram showing the spectrum of the ultraviolet/visible light transmittance of the polyimide thin film obtained in Example 6; FIG. 10 is a diagram showing the spectrum of the ultraviolet/visible light transmittance of the polyimide thin film obtained in Example 7; FIG. 10 is a diagram showing the spectrum of the ultraviolet/visible light transmittance of the polyimide thin film obtained in Example 8; FIG. 10 is a diagram showing the spectrum of ultraviolet/visible light transmittance of the polyimide thin film obtained in Example 9. FIG. FIG. 10 is a diagram showing the spectrum of the ultraviolet/visible light transmittance of the polyimide thin film obtained in Example 10; FIG. 10 is a diagram showing the spectrum of the ultraviolet/visible light transmittance of the polyimide thin film obtained in Example 11; 1 is a diagram showing wavelength dependence of refractive indices (n _TE , n _TM , n _av ) and birefringence (Δn) of a polyimide thin film obtained in Example 1. FIG. 4 is a diagram showing wavelength dependence of refractive indices (n _TE , n _TM , n _av ) and birefringence (Δn) of the polyimide thin film obtained in Example 2. FIG. FIG. 10 is a graph showing the wavelength dependence of the refractive indices (n _TE , n _TM , n _av ) and birefringence (Δn) of the polyimide thin film obtained in Example 3; FIG. 10 is a graph showing the wavelength dependence of the refractive indices (n _TE , n _TM , n _av ) and birefringence (Δn) of the polyimide thin film obtained in Example 4; FIG. 10 is a graph showing the wavelength dependence of refractive indices (n _TE , n _TM , n _av ) and birefringence (Δn) of a polyimide thin film obtained in Example 5; FIG. 10 is a diagram showing the wavelength dependence of the refractive indices (n _TE , n _TM , n _av ) and birefringence (Δn) of the polyimide thin film obtained in Example 6; FIG. 10 is a graph showing the wavelength dependence of the refractive indices (n _TE , n _TM , n _av ) and birefringence (Δn) of the polyimide thin film obtained in Example 7; FIG. 10 is a diagram showing the wavelength dependence of refractive indices (n _TE , n _TM , n _av ) and birefringence (Δn) of a polyimide thin film obtained in Example 8; FIG. 10 is a graph showing the wavelength dependence of refractive indices (n _TE , n _TM , n _av ) and birefringence (Δn) of a polyimide thin film obtained in Example 9; FIG. 10 is a diagram showing the wavelength dependence of the refractive indices (n _TE , n _TM , n _av ) and birefringence (Δn) of the polyimide thin film obtained in Example 10; FIG. 10 is a diagram showing the wavelength dependence of the refractive indices (n _TE , n _TM , n _av ) and birefringence (Δn) of the polyimide thin film obtained in Example 11; 1 is a diagram showing a spectrum showing the circular dichroism ellipticity (CD) of a polyimide thin film (thickness: about 1 μm) obtained in Example 1. FIG. 2 is a diagram showing a spectrum showing circular dichroism ellipticity (CD) of a polyimide thin film (thickness: about 1 μm) obtained in Example 2. FIG. FIG. 10 is a diagram showing a spectrum showing the circular dichroism ellipticity (CD) of the polyimide thin film (thickness: about 1 μm) obtained in Example 3; FIG. 10 is a diagram showing a spectrum showing the circular dichroism ellipticity (CD) of the polyimide thin film (thickness: about 1 μm) obtained in Example 9; FIG. 10 is a diagram showing a spectrum showing the circular dichroism ellipticity (CD) of the polyimide thin film (thickness: about 1 μm) obtained in Example 10; FIG. 10 is a diagram showing a spectrum showing the circular dichroism ellipticity (CD) of the polyimide thin film (thickness: about 1 μm) obtained in Example 11;

（式中、Ｒ_１は、各々独立して炭素原子数１～６の直鎖状又は分岐鎖状のアルキル基、炭素原子数５又は６の環状のアルキル基、炭素原子数１～６の直鎖状又は分岐鎖状のアルコキシ基、炭素原子数５又は６の環状のアルコキシ基、炭素原子数６～８のアリール基、炭素原子数６～８のアリールオキシ基、炭素原子数１～６の直鎖状又は分岐鎖状のハロゲン化アルキル基、又はハロゲン原子を示し、ｎは、各々独立して０又は１～３の整数を示し、Ａは、下記一般式（５）で表される２価の基若しくは炭素原子数４～３０の環状の脂肪族基を含む２価の有機基を示す。）

（式中、Ｒ_２は、各々独立して炭素原子数１～６の直鎖状又は分岐鎖状アルキル基、炭素原子数５又は６の環状アルキル基、炭素原子数１～６の直鎖状又は分岐鎖状のアルコキシ基、炭素原子数５又は６の環状のアルコキシ基、炭素原子数６～８のアリール基、炭素原子数６～８のアリールオキシ基、炭素原子数１～６の直鎖状又は分岐鎖状のハロゲン化アルキル基、又はハロゲン原子を示し、ｍは、各々独立して０又は１～４の整数を示し、ｐ、ｑ及びｒは、０又は１を示し、Ｘは、直接結合、酸素原子、硫黄原子、スルホニル基（－ＳＯ_２－）、カルボニル基（－ＣＯ－）、アミド基（－ＮＨＣＯ－）、エステル基（－ＯＣＯ－）、炭素原子数１～１５のアルキリデン基、炭素原子数２～１５のフッ素含有アルキリデン基、炭素原子数５～１５のシクロアルキリデン基、フェニレン基又はフルオレニリデン基を示し、＊は、各々結合位置を示す。）
本発明のポリイミドは、下記一般式（２）～（４）で表される繰り返し単位から選択される１つ以上の繰り返し単位を有することが好ましい。

（一般式（２）～（４）中の、Ｒ_１、ｎ、Ａは、一般式（１）の定義と同じである。）
この中でも一般式（２）で表される繰り返し単位を有することが特に好ましい。
一般式（２）～（４）で表される繰り返し単位から選ばれる２つ以上の繰り返し単位を有する場合として、例えば、一般式（２）及び一般式（３）で表される繰り返し単位を有する場合、一般式（２）及び一般式（４）で表される繰り返し単位を有する場合、一般式（３）及び一般式（４）で表される繰り返し単位を有する場合、一般式（２）、一般式（３）及び一般式（４）で表される繰り返し単位を有する場合が挙げられる。
この中でも、一般式（２）及び一般式（４）で表される繰り返し単位を有する場合に得られるポリイミドが、光透過性に優れる観点及び複屈折（Δｎ）の低下の観点から好ましい。この時の一般式（２）で表される繰り返し単位と一般式（４）で表される繰り返し単位とのモル比率は、（２）：（４）＝９９：１～５０：５０の範囲が好ましく、（２）：（４）＝９０：１０～６０：４０の範囲がより好ましく、（２）：（４）＝８０：２０～６０：４０の範囲がさらに好ましい。 The polyimide of the present invention has a repeating unit represented by the general formula (1) and has a glass transition temperature (Tg) of 210° C. or higher as determined by thermomechanical analysis.

(wherein R ₁ is each independently a linear or branched alkyl group having 1 to 6 carbon atoms, a cyclic alkyl group having 5 or 6 carbon atoms, a straight alkyl group having 1 to 6 carbon atoms, chain or branched alkoxy group, cyclic alkoxy group having 5 or 6 carbon atoms, aryl group having 6 to 8 carbon atoms, aryloxy group having 6 to 8 carbon atoms, aryloxy group having 1 to 6 carbon atoms represents a linear or branched halogenated alkyl group or a halogen atom, n is each independently an integer of 0 or 1 to 3, and A is 2 represented by the following general formula (5) A divalent organic group including a valent group or a cyclic aliphatic group having 4 to 30 carbon atoms.)

(wherein R ₂ is each independently a linear or branched alkyl group having 1 to 6 carbon atoms, a cyclic alkyl group having 5 or 6 carbon atoms, a linear alkyl group having 1 to 6 carbon atoms, or a branched alkoxy group, a cyclic alkoxy group having 5 or 6 carbon atoms, an aryl group having 6 to 8 carbon atoms, an aryloxy group having 6 to 8 carbon atoms, or a straight chain having 1 to 6 carbon atoms represents a branched or branched halogenated alkyl group or a halogen atom, m each independently represents an integer of 0 or 1 to 4, p, q and r represent 0 or 1, X is direct bond, oxygen atom, sulfur atom, sulfonyl group (--SO ₂ --), carbonyl group (--CO--), amide group (--NHCO--), ester group (--OCO--), alkylidene having 1 to 15 carbon atoms group, a fluorine-containing alkylidene group having 2 to 15 carbon atoms, a cycloalkylidene group having 5 to 15 carbon atoms, a phenylene group or a fluorenylidene group, and * indicates a bonding position.)
The polyimide of the present invention preferably has one or more repeating units selected from repeating units represented by the following general formulas (2) to (4).

(R ₁ , n, and A in general formulas (2) to (4) are the same as defined in general formula (1).)
Among these, it is particularly preferable to have a repeating unit represented by the general formula (2).
In the case of having two or more repeating units selected from repeating units represented by general formulas (2) to (4), for example, having repeating units represented by general formulas (2) and (3) When having repeating units represented by general formulas (2) and (4), when having repeating units represented by general formulas (3) and (4), general formula (2), A case of having a repeating unit represented by general formula (3) or general formula (4) is included.
Among these, polyimides obtained when having repeating units represented by general formulas (2) and (4) are preferable from the viewpoint of excellent light transmittance and reduction in birefringence (Δn). At this time, the molar ratio of the repeating unit represented by the general formula (2) and the repeating unit represented by the general formula (4) is in the range of (2):(4) = 99:1 to 50:50. The range of (2):(4)=90:10 to 60:40 is more preferred, and the range of (2):(4)=80:20 to 60:40 is even more preferred.

R ₁ in general formulas (1) to (4) is each independently a linear or branched alkyl group having 1 to 6 carbon atoms, a cyclic alkyl group having 5 or 6 carbon atoms, a carbon atom linear or branched alkoxy group having 1 to 6 carbon atoms, cyclic alkoxy group having 5 or 6 carbon atoms, aryl group having 6 to 8 carbon atoms, aryloxy group having 6 to 8 carbon atoms, carbon It represents a linear or branched halogenated alkyl group having 1 to 6 atoms, or a halogen atom.
Among them, a linear or branched alkyl group having 1 to 4 carbon atoms, a linear or branched halogenated alkyl group having 1 to 4 carbon atoms, or a halogen atom is preferable, and 1 carbon atom A linear or branched halogenated alkyl group of ∼4 or a halogen atom is more preferable, and a trifluoromethyl group or a fluorine atom is particularly preferable.

n in general formulas (1) to (4) each independently represents an integer of 0 or 1 to 3. Among them, 0, 1 or 2 is preferable, 0 or 1 is more preferable, and 0 is particularly preferable.

（式中、Ｒ_２、ｍ、ｑは一般式（５）の定義と同じである。）
一般式（５）におけるｑ、ｒは、各々独立して０又は１を示し、０が好ましい。
一般式（５）におけるｐ及びｑが０である場合（一般式（５’）におけるｑが０である場合）、すなわち式中の芳香環がベンゼン環である場合に、＊で表される２つの結合位置がベンゼン環のパラ位又はメタ位の位置関係にあることが好ましい。その中でも、メタ位の位置関係にあると、ｍ－フェニレン結合の屈曲した構造を有することから、ジアミン化合物に由来する部位の電子供与性が低下し、かつポリイミドの分子間の凝集を阻害して、電荷移動性の光吸収が短波長化するために、可視域における高い光透過性を有する他、低い屈折率を有するポリイミドが得られることから好ましい。
一般式（５）におけるＸは、直接結合、酸素原子、硫黄原子、スルホニル基（－ＳＯ_２－）、カルボニル基（－ＣＯ－）、アミド基（－ＮＨＣＯ－）、エステル基（－ＯＣＯ－）、炭素原子数１～１５のアルキリデン基、炭素原子数２～１５のフッ素含有アルキリデン基、炭素原子数５～１５のシクロアルキリデン基、フェニレン基又はフルオレニリデン基を示す。中でも、直接結合、酸素原子、硫黄原子、スルホニル基（－ＳＯ_２－）、カルボニル基（－ＣＯ－）、アミド基（－ＮＨＣＯ－）、エステル基（－ＯＣＯ－）、炭素原子数２～１２のアルキリデン基、炭素原子数２～１２のフッ素含有アルキリデン基、炭素原子数５～１２のシクロアルキリデン基、フェニルエチリデン基又はフルオレニリデン基が好ましく、直接結合、酸素原子、硫黄原子、スルホニル基（－ＳＯ_２－）、カルボニル基（－ＣＯ－）、アミド基（－ＮＨＣＯ－）、エステル基（－ＯＣＯ－）、炭素原子数２～８のアルキリデン基、炭素原子数２～８のフッ素含有アルキリデン基、炭素原子数６～１２のシクロアルキリデン基、フェニルエチリデン基又はフルオレニリデン基がより好ましく、直接結合、酸素原子、硫黄原子、スルホニル基（－ＳＯ_２－）、アミド基（－ＮＨＣＯ－）、エステル基（－ＯＣＯ－）、炭素原子数２～４のアルキリデン基、炭素原子数２～４のフッ素含有アルキリデン基、炭素原子数６～９のシクロアルキリデン基又はフルオレニリデン基が特に好ましい。なお、アミド基（－ＮＨＣＯ－）やエステル基（－ＯＣＯ－）の結合位置は限定されず、例えば、アミド基は「－ＣＯＮＨ－」も含む。
前記炭素原子数５～１５のシクロアルキリデン基は、分岐鎖としてのアルキル基を含んでいてもよい。シクロアルキリデン基としては、具体的には、例えば、シクロペンチリデン基（炭素原子数５）、シクロヘキシリデン基（炭素原子数６）、３－メチルシクロヘキシリデン基（炭素原子数７）、４－メチルシクロヘキシリデン基（炭素原子数７）、３，３，５－トリメチルシクロヘキシリデン基（炭素原子数９）、シクロヘプチリデン基（炭素原子数７）、シクロドデカニリデン基（炭素原子数１２）等が挙げられる。 R ₂ in the above general formula (5) is each independently a linear or branched alkyl group having 1 to 6 carbon atoms, a cyclic alkyl group having 5 or 6 carbon atoms, or a linear or branched alkoxy group, cyclic alkoxy group having 5 or 6 carbon atoms, aryl group having 6 to 8 carbon atoms, aryloxy group having 6 to 8 carbon atoms, 1 to 6 carbon atoms represents a straight-chain or branched-chain halogenated alkyl group or a halogen atom.
Among them, a linear or branched alkyl group having 1 to 4 carbon atoms, a linear or branched halogenated alkyl group having 1 to 4 carbon atoms, or a halogen atom is preferable, and 1 carbon atom ~ 4 linear or branched halogenated alkyl group, or more preferably a halogen atom, more preferably a linear or branched halogenated alkyl group having 1 to 4 carbon atoms, trifluoromethyl group is particularly preferred.
When R ₂ in the general formula (5) is a halogenated alkyl group such as a trifluoromethyl group, a site derived from a diamine compound and a site derived from trimellitic acid of a tetracarboxylic dianhydride are formed in the ground state. Polyimide with low refractive index, small dielectric constant, and small dielectric loss tangent, in addition to high optical transparency in the visible region, because the charge mobility of the electronic state is reduced and the light absorption edge moves from the visible region to the ultraviolet region. is obtained, which is preferable. Here, the light absorption edge refers to the wavelength at which the absorbance sharply rises in the ultraviolet/visible light transmittance spectrum of the polyimide thin film.
Each m in the general formula (5) independently represents an integer of 0 or 1 to 4, preferably 0, 1 or 2, more preferably 0 or 1.
p in the general formula (5) represents 0 or 1, preferably 1; When p in general formula (5) is 0, there are two bonding positions on the left aromatic ring in general formula (5). In such a case, general formula (5) is expressed as general formula (5') below.

(In the formula, R ₂ , m, and q are the same as defined in general formula (5).)
q and r in general formula (5) each independently represent 0 or 1, with 0 being preferred.
When p and q in general formula (5) are 0 (when q in general formula (5′) is 0), i.e., when the aromatic ring in the formula is a benzene ring, 2 represented by * It is preferable that the two bonding positions are in the para-position or meta-position relationship of the benzene ring. Among them, when it is in a meta-positional relationship, since it has a bent structure of m-phenylene bond, the electron donating property of the site derived from the diamine compound is reduced, and the aggregation between polyimide molecules is inhibited. In addition to having high light transmittance in the visible region, polyimide having a low refractive index can be obtained because the wavelength of light absorbed by charge transfer is shortened.
X in the general formula (5) is a direct bond, an oxygen atom, a sulfur atom, a sulfonyl group ( _--SO.sub.2-- ), a carbonyl group (--CO--), an amide group (--NHCO--), an ester group (--OCO--). , an alkylidene group having 1 to 15 carbon atoms, a fluorine-containing alkylidene group having 2 to 15 carbon atoms, a cycloalkylidene group having 5 to 15 carbon atoms, a phenylene group or a fluorenylidene group. Among them, a direct bond, an oxygen atom, a sulfur atom, a sulfonyl group ( _--SO.sub.2-- ), a carbonyl group (--CO--), an amide group (--NHCO--), an ester group (--OCO--), and 2 to 12 carbon atoms. alkylidene group, fluorine-containing alkylidene group having 2 to 12 carbon atoms, cycloalkylidene group having 5 to 12 carbon atoms, phenylethylidene group or fluorenylidene group are preferable, direct bond, oxygen atom, sulfur atom, sulfonyl group (-SO _2- ), a carbonyl group (-CO-), an amide group (-NHCO-), an ester group (-OCO-), an alkylidene group having 2 to 8 carbon atoms, a fluorine-containing alkylidene group having 2 to 8 carbon atoms, A cycloalkylidene group having 6 to 12 carbon atoms, a phenylethylidene group or a fluorenylidene group is more preferable, and a direct bond, an oxygen atom, a sulfur atom, a sulfonyl group (—SO ₂ —), an amide group (—NHCO—), an ester group ( —OCO—), an alkylidene group having 2 to 4 carbon atoms, a fluorine-containing alkylidene group having 2 to 4 carbon atoms, a cycloalkylidene group having 6 to 9 carbon atoms, or a fluorenylidene group are particularly preferred. The bonding position of the amide group (--NHCO--) or the ester group (--OCO--) is not limited, and for example, the amide group includes "--CONH--".
The cycloalkylidene group having 5 to 15 carbon atoms may contain an alkyl group as a branched chain. Specific examples of the cycloalkylidene group include a cyclopentylidene group (having 5 carbon atoms), a cyclohexylidene group (having 6 carbon atoms), a 3-methylcyclohexylidene group (having 7 carbon atoms), 4 -methylcyclohexylidene group (7 carbon atoms), 3,3,5-trimethylcyclohexylidene group (9 carbon atoms), cycloheptylidene group (7 carbon atoms), cyclododecanylidene group (carbon number of atoms 12) and the like.

The divalent organic group containing a cyclic aliphatic group having 4 to 30 carbon atoms is preferably a divalent hydrocarbon group containing a cyclic aliphatic group having 4 to 30 carbon atoms. A divalent hydrocarbon group including an aliphatic group may contain a halogen atom such as fluorine. Further, it is more preferably a cyclic divalent aliphatic saturated hydrocarbon group having 4 to 30 carbon atoms, more preferably a cyclic divalent aliphatic saturated hydrocarbon group having 6 to 20 carbon atoms. A cyclic divalent aliphatic saturated hydrocarbon group having 6 to 12 carbon atoms is particularly preferable, and such a divalent aliphatic saturated hydrocarbon group may contain a halogen atom such as fluorine.
Specific examples of the divalent organic group containing a cyclic aliphatic group having 4 to 30 carbon atoms include a bis(1,4-cyclohexylene)methylene group and trans-1,4-cyclohexane-diyl. cis-1,4-cyclohexane-diyl group, cyclohexane-1,4-bismethylene group, bicyclo[2.2.1]heptane-2,5-bismethylene group, bicyclo[2.2.1]heptane-2 , 6-bismethylene group, bicyclo[2.2.2]octane-1,4-diyl group, decahydronaphthalene-1,4-diyl group, tricyclo[5.2.1.0]decane-3,8- bismethylene group, adamantane-1,3-diyl group, isopropylidenedicyclohexane-4,4'-diyl group, hexafluoroisopropylidenedicyclohexane-4,4'-diyl group and the like.
In the case of a divalent organic group containing a cyclic aliphatic group having 4 to 30 carbon atoms, the site derived from the diamine compound in the polyimide and the site derived from the trimellitic acid of the tetracarboxylic dianhydride are in the ground state. In order to reduce the charge mobility of the electronic state formed in and the light absorption edge moves from the visible range to the ultraviolet range, a polyimide having high optical transparency in the visible range and a low refractive index can be obtained. preferable. Among these, a trans-1,4-cyclohexane-diyl group and a cis-1,4-cyclohexane-diyl group are more preferable.

（式中、Ｗは４価の有機基（但し、下記一般式（７）で表される４価の基を除く）を示し、Ａは一般式（１）の定義と同じである。）

（式中、Ｒ_１及びｎは一般式（１）の定義と同じであり、＊は結合位置を示す。） As long as the polyimide of the present invention contains the repeating unit represented by the general formula (1), it may have other skeletons as long as the effect of the present invention is not impaired.
For example, it may have a repeating unit represented by the following general formula (6).

(Wherein, W represents a tetravalent organic group (excluding the tetravalent group represented by the following general formula (7)), and A has the same definition as in general formula (1).)

(Wherein, R ₁ and n are the same as defined in general formula (1), and * indicates the bonding position.)

（式中、Ｖは、直接結合、酸素原子、硫黄原子、スルホニル基（－ＳＯ_２－）、カルボニル基（－ＣＯ－）、アミド基（－ＮＨＣＯ－）、エステル基（－ＯＣＯ－）、炭素原子数１～１５のアルキリデン基、炭素原子数２～１５のフッ素含有アルキリデン基、炭素原子数５～１５のシクロアルキリデン基、フェニレン基、フルオレニリデン基又は下記一般式（９）で表される２価の基を示し、ａは０又は１を示し、＊は結合位置を示す。）

（式中、Ｒ_３は、各々独立して炭素原子数１～６の直鎖状又は分岐鎖状のアルキル基、炭素原子数５又は６の環状のアルキル基、炭素原子数１～６の直鎖状又は分岐鎖状のアルコキシ基、炭素原子数５又は６の環状のアルコキシ基、炭素原子数６～８のアリール基、炭素原子数６～８のアリールオキシ基、炭素原子数１～６の直鎖状又は分岐鎖状のハロゲン化アルキル基、又はハロゲン原子を示し、Ｕは、直接結合、酸素原子、硫黄原子、スルホニル基（－ＳＯ_２－）、カルボニル基（－ＣＯ－）、アミド基（－ＮＨＣＯ－）、エステル基（－ＯＣＯ－）、炭素原子数１～１５のアルキリデン基、炭素原子数２～１５のフッ素含有アルキリデン基、炭素原子数５～１５のシクロアルキリデン基、フェニレン基、フルオレニリデン基を示し、ｂは各々独立して０又は１～４の整数を示し、ｃ、ｄ、ｅ、及びｆは、各々独立に０又は１を示し、＊は結合位置を示す。）

（式中、Ｒ_４は、各々独立して水素原子若しくはメチル基を示し、Ｒ_５は、各々独立して直接結合又は炭素原子数１～３のアルキレン基を示し、＊は結合位置を示す。）
一般式（１０）におけるＲ_５は、直接結合であることが好ましい。

（式中、Ｒ_６は、二重結合もしくはカルボニル基を含んでもよい４価の脂肪族基を示し、＊は結合位置を示す。）
一般式（１１）における、二重結合もしくはカルボニル基を含んでもよい４価の脂肪族基は、二重結合もしくはカルボニル基を含んでもよい炭素原子数３～２０の４価の脂肪族基であることが好ましい。具体的には、例えば、下記構造式で表される基が挙げられる。

（式中、＊は結合位置を示す。） The tetravalent organic group of W in the repeating unit represented by the general formula (6) is a structure represented by the following general formula (8), a structure represented by the following general formula (10), or the following general formula ( It is preferably one or more of the structures represented by 11).

(Wherein, V is a direct bond, an oxygen atom, a sulfur atom, a sulfonyl group (—SO ₂ —), a carbonyl group (—CO—), an amide group (—NHCO—), an ester group (—OCO—), a carbon an alkylidene group having 1 to 15 atoms, a fluorine-containing alkylidene group having 2 to 15 carbon atoms, a cycloalkylidene group having 5 to 15 carbon atoms, a phenylene group, a fluorenylidene group or a divalent represented by the following general formula (9) represents a group, a represents 0 or 1, and * represents a bonding position.)

(wherein R ₃ is each independently a linear or branched alkyl group having 1 to 6 carbon atoms, a cyclic alkyl group having 5 or 6 carbon atoms, a straight alkyl group having 1 to 6 carbon atoms, chain or branched alkoxy group, cyclic alkoxy group having 5 or 6 carbon atoms, aryl group having 6 to 8 carbon atoms, aryloxy group having 6 to 8 carbon atoms, aryloxy group having 1 to 6 carbon atoms A linear or branched halogenated alkyl group or a halogen atom, U is a direct bond, an oxygen atom, a sulfur atom, a sulfonyl group ( _--SO.sub.2-- ), a carbonyl group (--CO--), an amide group (-NHCO-), an ester group (-OCO-), an alkylidene group having 1 to 15 carbon atoms, a fluorine-containing alkylidene group having 2 to 15 carbon atoms, a cycloalkylidene group having 5 to 15 carbon atoms, a phenylene group, represents a fluorenylidene group, b each independently represents an integer of 0 or 1 to 4, c, d, e, and f each independently represents 0 or 1, and * represents a bonding position.)

(In the formula, each R ₄ independently represents a hydrogen atom or a methyl group, each R ₅ independently represents a direct bond or an alkylene group having 1 to 3 carbon atoms, and * represents a bonding position. )
_R5 in general formula (10) is preferably a direct bond.

(In the formula, _R6 represents a tetravalent aliphatic group which may contain a double bond or a carbonyl group, and * represents the bonding position.)
In the general formula (11), the tetravalent aliphatic group which may contain a double bond or a carbonyl group is a tetravalent aliphatic group having 3 to 20 carbon atoms which may contain a double bond or a carbonyl group. is preferred. Specific examples include groups represented by the following structural formulas.

(In the formula, * indicates the bonding position.)

When the polyimide of the present invention has a repeating unit other than the repeating unit represented by the general formula (1), the content of the repeating unit represented by the general formula (1) is 15 mol% or more of the total polyimide. The content is preferably 50 mol% or more, more preferably 70 mol% or more, and particularly preferably 90 mol% or more. In addition, the repeating units of the general formula (1) may be arranged regularly, or may be randomly present in the polyimide.
Even when the repeating unit represented by the general formula (1) is a repeating unit represented by the general formula (2), (3) or (4) among them, the range of mol % is the same, and the general formula ( In the case of having two or more repeating units selected from the repeating units represented by 2), (3) or (4), the total is in the same mol% range.

The polyimide of the present invention has a glass transition temperature of 210° C. or higher as determined by thermomechanical analysis, and has sufficient heat resistance required as a polyimide resin. The glass transition temperature is preferably 220° C. or higher, more preferably 230° C. or higher, and particularly preferably 240° C. or higher.

The polyimide of the present invention preferably has a thermal decomposition temperature (Td) of 350° C. or higher at which the residual weight percentage becomes 95% based on the weight at 100° C. determined by thermogravimetric analysis. It is more preferably 370° C. or higher, still more preferably 390° C. or higher, and particularly preferably 400° C. or higher.

（一般式（１２）及び一般式（１４）中のＲ_１及びｎ並びに、一般式（１３）及び一般式（１４）中のＡは、一般式（１）の定義と同じである。） The method for producing the polyimide of the present invention is not particularly limited. It can be produced through a step of reacting equimolarly to obtain a polyimide precursor (polyamic acid) represented by the following general formula (14) and a step of imidizing the polyimide precursor.

(R ₁ and n in general formulas (12) and (14) and A in general formulas (13) and (14) are the same as defined in general formula (1).)

As a specific example thereof, the tetracarboxylic dianhydride represented by the above general formula (12) is isosorbide-bis(trimellitate anhydride) (compound (a)), and is represented by the above general formula (13). The following reaction formula shows the production method when the diamine compound is 1,4-diaminocyclohexane (compound (b)). The compound (a) and the compound (b) are polymerized to obtain a polyimide precursor (polyamic acid) (compound (c)) having the following repeating unit, which is imidized to obtain the desired repeating unit below It is possible to obtain a polyimide (compound (d)) having

（一般式（１５）、（１２）におけるＲ_１及びｎは、一般式（１）の定義と同じである。） The tetracarboxylic dianhydride represented by the general formula (12) can be produced by a conventionally known method, and is not limited to the production method. For example, as represented by the following reaction formula, dianhydrohexitol such as isosorbide, isomannide and isoidide are reacted with trimellitic anhydride represented by general formula (15) such as trimellitic anhydride chloride. can be manufactured by

(R ₁ and n in general formulas (15) and (12) are the same as defined in general formula (1).)

なお、式（ｉ）で表される化合物はイソソルビド－ビス（トリメリテートアンハイドライド）であり、式（ｉｉ）で表される化合物はイソイジド－ビス（トリメリテートアンハイドライド）であり、式（ｉｉｉ）で表される化合物はイソマンニド－ビス（トリメリテートアンハイドライド）である。以下、各々、化合物（ｉ）、化合物（ｉｉ）、化合物（ｉｉｉ）と称する場合がある。
これらの中でも、式（ｉ）で表される化合物が特に好ましい。
本発明のポリイミドの製造方法において、一般式（１２）で表されるテトラカルボン酸二無水物を１種のみを用いてもよいし、２種以上を併用してもよい。 R ₁ and n in general formula (12) are the same as defined in general formula (1), and preferred embodiments are also the same.
Specific examples of the tetracarboxylic dianhydride represented by the general formula (12) include compounds represented by the following formulas (i) to (iii).

The compound represented by formula (i) is isosorbide-bis(trimellitate anhydride), the compound represented by formula (ii) is isoidide-bis(trimellitate anhydride), and the formula ( The compound represented by iii) is isomannide-bis(trimellitate anhydride). Hereinafter, they may be referred to as compound (i), compound (ii), and compound (iii), respectively.
Among these, the compound represented by formula (i) is particularly preferred.
In the method for producing a polyimide of the present invention, the tetracarboxylic dianhydride represented by the general formula (12) may be used singly or in combination of two or more.

A in general formula (13) has the same definition as in general formula (1), and preferred embodiments are also the same.
Specifically, the diaminediamine compound in which A in the general formula (13) is a divalent group represented by the general formula (5), when p in the general formula (5) is 0, For example, p-phenylenediamine (PPD), m-phenylenediamine (MPD), 2,4-diaminotoluene, 2,5-diaminotoluene, 2,4-diaminoxylene, 1,4-diaminodurene, 1,4- Diaminobenzenes such as diamino-2-phenylbenzene, 1,3-diamino-4-phenylbenzene, 1,3-diamino-5-phenylbenzene, 5-trifluoromethyl-1,3-phenylenediamine (TFMPD); diaminonaphthalenes such as 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, and 2,7-diaminonaphthalene;
Among these, m-phenylenediamine (MPD), 2,4-diaminotoluene, 2,4-diaminoxylene, 1,3-diamino-4-phenylbenzene, 1,3-diamino-5-phenylbenzene, 5-tri Fluoromethyl-1,3-phenylenediamine (TFMPD) and the like are preferable, and m-phenylenediamine (MPD) and 5-trifluoromethyl-1,3-phenylenediamine (TFMPD) are more preferable.
When p in the general formula (5) is 1, for example, 2,2′-diaminobiphenyl, 3,3′-diaminobiphenyl, 4,4′-diaminobiphenyl, 2,2′-dimethyl-4,4′ -diaminobiphenyls such as 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl (2,2'-bis(trifluoromethyl)benzidine;TFDB);3,3'-diaminodiphenyl ether, Diaminodiphenyl ethers such as 3,4'-diaminodiphenyl ether and 4,4'-diaminodiphenyl ether; Diaminodiphenyls such as 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide and 4,4'-diaminodiphenyl sulfide sulfides; diaminodiphenylsulfones such as 3,3′-diaminodiphenylsulfone, 3,4′-diaminodiphenylsulfone and 4,4′-diaminodiphenylsulfone; 3,3′-diaminobenzophenone, 3,4′-diaminobenzophenone, Diaminobenzophenones such as 4,4′-diaminobenzophenone; Bis(aminophenyl)alkanes such as bis(3-aminophenyl)methane, bis(4-aminophenyl)methane and 2,2-bis(4-aminophenyl)propane 2,2-bis(3-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 2,2-bis(4-aminophenyl)-1,1,1,3,3 bis(aminophenyl)cycloalkanes such as 1,1-bis(4-aminophenyl)cyclohexane; 4,4″-diamino-p-terphenyl , 4,4''-diamino-m-terphenyl and other diaminoterphenyls, 9,9-bis(4-aminophenyl)fluorene, 9,9-bis(4-amino-3-fluorophenyl)fluorene, etc. and bis(aminophenyl)fluorene.
Among the diamine compounds represented by the general formula (13), 2,2′-bis(trifluoromethyl)benzidine (TFDB) and 5-trifluoromethyl-1,3-phenylenediamine (TFMPD) are preferred.

Specifically, the diamine compound represented by the general formula (13) in which A in the general formula (13) is a divalent organic group containing a cyclic aliphatic group having 1 to 30 carbon atoms is , for example, 4,4′-methylenebis(cyclohexylamine), trans-1,4-diaminocyclohexane, cis-1,4-diaminocyclohexane, 1,4-cyclohexanebis(methylamine), 2,5-bis(amino methyl)bicyclo[2.2.1]heptane, 2,6-bis(aminomethyl)bicyclo[2.2.1]heptane, bicyclo[2.2.2]octane-1,4-diamine, decahydro-1 ,4-naphthalenediamine, 3,8-bis(aminomethyl)tricyclo[5.2.1.0]decane, 1,3-diaminoadamantane, 2,2-bis(4-aminocyclohexyl)propane, 2,2 -bis(4-aminocyclohexyl)hexafluoropropane. Among these, trans-1,4-diaminocyclohexane and cis-1,4-diaminocyclohexane are preferred.
Only one kind of the diamine compound represented by the general formula (13) may be used, or two or more kinds thereof may be used in combination.

In the case where the polyimide of the present invention further has a repeating unit represented by the general formula (6), in addition to the tetracarboxylic dianhydride represented by the general formula (12), the general formula (12) It can be produced by using an acid dianhydride used as a polyimide monomer other than the tetracarboxylic dianhydride represented.

（式中、Ｖ及びａは、一般式（８）の定義と同じである。）
このようなテトラカルボン酸二無水物として、具体的には、ａが０である場合、ピロメリット酸二無水物である。ａが１である場合、具体的には、例えば、３，３’，４，４’－ビフェニルテトラカルボン酸二無水物、４，４’－オキシジフタル酸無水物、３，３’，４，４’－ジフェニルスルフィドテトラカルボン酸二無水物、３，３’，４，４’－ジフェニルスルホンテトラカルボン酸二無水物、３，３’，４，４’－ベンゾフェノンテトラカルボン酸二無水物、４，４’－（ヘキサフルオロイソプロピリデン）ビス（フタル酸）二無水物、１，４－ビス（３，４－ジカルボキシフェノキシ）ベンゼン二無水物、１，３－ビス（３，４－ジカルボキシフェノキシ）ベンゼン二無水物、４，４’－ビス（３，４－ジカルボキシフェノキシ）ビフェニル二無水物、４，４’－ビス（３，４－ジカルボキシフェノキシ）－３，３’－ジメチルビフェニル二無水物、ビス［４－（３，４－ジカルボキシフェノキシ）フェニル］エーテル二無水物、ビス［４－（３，４－ジカルボキシフェノキシ）フェニル］スルホン二無水物、２，２－ビス［４－（３，４－ジカルボキシフェノキシ）フェニル］プロパン二無水物、２，２－ビス［４－（３，４－ジカルボキシフェノキシ）フェニル］ヘキサフルオロプロパン二無水物、１，１－ビス［４－（３，４－ジカルボキシフェノキシ）フェニル］シクロヘキサン二無水物、１，１－ビス［４－（３，４－ジカルボキシフェノキシ）フェニル］シクロデカン二無水物、１，１－ビス［４－（３，４－ジカルボキシフェノキシ）フェニル］－３，３，５－トリメチルシクロヘキサン二無水物、９，９－ビス［４－（３，４－ジカルボキシフェノキシ）－３－メチルフェニル］フルオレン二無水物、ハイドロキノン－ビス（トリメリテートアンハイドライド）、レゾルシノール－ビス（トリメリテートアンハイドライド）、１，５－ジヒドロキシナフタレン－ビス（トリメリテートアンハイドライド）、２，６－ジヒドロキシナフタレン－ビス（トリメリテートアンハイドライド）、２，７－ジヒドロキシナフタレン－ビス（トリメリテートアンハイドライド）、４，４’－ジヒドロキシビフェニル－ビス（トリメリテートアンハイドライド）、４，４’－ジヒドロキシ－３，３’－ジメチルビフェニル－ビス（トリメリテートアンハイドライド）、４，４’－ジヒドロキシ－３，３’，５，５’－テトラメチルビフェニル－ビス（トリメリテートアンハイドライド）、４，４’－ジヒドロキシ－２，２’，３，３’，５，５’－ヘキサメチルビフェニル－ビス（トリメリテートアンハイドライド）、４，４’－ジヒドロキシジフェニルエーテル－ビス（トリメリテートアンハイドライド）、４，４’－ジヒドロキシジフェニルスルフィド－ビス（トリメリテートアンハイドライド）、４，４’－ジヒドロキシジフェニルスルホン－ビス（トリメリテートアンハイドライド）、４，４’－ジヒドロキシベンゾフェノン－ビス（トリメリテートアンハイドライド）、１，１’－ビス（４－ヒドロキシフェニル）エタン－ビス（トリメリテートアンハイドライド）、２，２’－ビス（４－ヒドロキシフェニル）プロパン－ビス（トリメリテートアンハイドライド）、２，２’－ビス（４－ヒドロキシ－３－メチルフェニル）プロパン－ビス（トリメリテートアンハイドライド）、２，２’－ビス（４－ヒドロキシフェニル）ヘキサフルオロプロパン－ビス（トリメリテートアンハイドライド）、１，１’－ビス（４－ヒドロキシフェニル）シクロヘキサン－ビス（トリメリテートアンハイドライド）、１，１’－ビス（４－ヒドロキシフェニル）－３，３，５－トリメチルシクロヘキサン－ビス（トリメリテートアンハイドライド）、１，１’－ビス（４－ヒドロキシフェニル）シクロデカン－ビス（トリメリテートアンハイドライド）、９，９’－ビス（４－ヒドロキシ－３－メチルフェニル）フルオレン－ビス（トリメリテートアンハイドライド）が挙げられる。 As the tetracarboxylic dianhydride used as a polyimide monomer other than the tetracarboxylic dianhydride represented by the general formula (12), tetracarboxylic acid represented by the general formulas (16) to (18) described later An acid dianhydride is preferred.
The tetracarboxylic dianhydride represented by general formula (16) is a compound represented by the following structural formula.

(Wherein, V and a are the same as defined in general formula (8).)
Specifically, such a tetracarboxylic dianhydride is pyromellitic dianhydride when a is 0. When a is 1, specifically, for example, 3,3′,4,4′-biphenyltetracarboxylic dianhydride, 4,4′-oxydiphthalic anhydride, 3,3′,4,4 '-diphenyl sulfide tetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 4, 4'-(Hexafluoroisopropylidene)bis(phthalic acid) dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,3-bis(3,4-dicarboxyphenoxy ) benzene dianhydride, 4,4′-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, 4,4′-bis(3,4-dicarboxyphenoxy)-3,3′-dimethylbiphenyl dianhydride anhydride, bis[4-(3,4-dicarboxyphenoxy)phenyl]ether dianhydride, bis[4-(3,4-dicarboxyphenoxy)phenyl]sulfone dianhydride, 2,2-bis[4 -(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride, 1,1-bis[4 -(3,4-dicarboxyphenoxy)phenyl]cyclohexane dianhydride, 1,1-bis[4-(3,4-dicarboxyphenoxy)phenyl]cyclodecane dianhydride, 1,1-bis[4-( 3,4-dicarboxyphenoxy)phenyl]-3,3,5-trimethylcyclohexane dianhydride, 9,9-bis[4-(3,4-dicarboxyphenoxy)-3-methylphenyl]fluorene dianhydride , hydroquinone-bis (trimellitate anhydride), resorcinol-bis (trimellitate anhydride), 1,5-dihydroxynaphthalene-bis (trimellitate anhydride), 2,6-dihydroxynaphthalene-bis (trimellitate anhydride) tate anhydride), 2,7-dihydroxynaphthalene-bis (trimellitate anhydride), 4,4'-dihydroxybiphenyl-bis (trimellitate anhydride), 4,4'-dihydroxy-3,3'- Dimethylbiphenyl-bis(trimellitate anhydride), 4,4′-dihydroxy-3,3′,5,5′-tetramethylbiphenyl-bis(trimellitate anhydride), 4,4′-dihydroxy-2 ,2′,3,3′,5,5′-hexamethylbiphenyl-bis(trimellitate anhydride), 4,4′-dihydroxydiphenyl ether-bis(trimellitate anhydride), 4,4′-dihydroxy Diphenylsulfide-bis(trimellitate anhydride), 4,4'-dihydroxydiphenylsulfone-bis(trimellitate anhydride), 4,4'-dihydroxybenzophenone-bis(trimellitate anhydride), 1,1 '-bis(4-hydroxyphenyl)ethane-bis(trimellitate anhydride), 2,2'-bis(4-hydroxyphenyl)propane-bis(trimellitate anhydride), 2,2'-bis( 4-hydroxy-3-methylphenyl)propane-bis(trimellitate anhydride), 2,2′-bis(4-hydroxyphenyl)hexafluoropropane-bis(trimellitate anhydride), 1,1′- bis(4-hydroxyphenyl)cyclohexane-bis(trimellitate anhydride), 1,1′-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane-bis(trimellitate anhydride), 1 , 1′-bis(4-hydroxyphenyl)cyclodecane-bis(trimellitate anhydride), 9,9′-bis(4-hydroxy-3-methylphenyl)fluorene-bis(trimellitate anhydride). be done.

（式中、Ｒ_４、Ｒ_５は、一般式（１０）の定義と同じである。）
一般式（１７）で表されるテトラカルボン酸二無水物として、Ｒ_５が直接結合である場合、具体的には、例えば、シクロブタン－１，２，３，４－テトラカルボン酸二無水物、１，３－ジメチルシクロブタン－１，２，３，４－テトラカルボン酸二無水物、１，２，３，４－テトラメチルシクロブタン－１，２，３，４－テトラカルボン酸二無水物が挙げられる。また、Ｒ_５の一方が直接結合で、他方が炭素原子数１～３のアルキレン基である場合は、具体的には、例えば、シクロペンタン－１，２，３，４－テトラカルボン酸二無水物、シクロヘキサン－１，２，３，４－テトラカルボン酸二無水物が挙げられる。また、Ｒ_５が炭素原子数１～３のアルキレン基である場合、具体的には、例えば、シクロヘキサン－１，２，４，５－テトラカルボン酸二無水物が挙げられる。
この中でも、Ｒ_５が直接結合である、シクロブタン－１，２，３，４－テトラカルボン酸二無水物、１，３－ジメチルシクロブタン－１，２，３，４－テトラカルボン酸二無水物、１，２，３，４－テトラメチルシクロブタン－１，２，３，４－テトラカルボン酸二無水物が好ましい。 The tetracarboxylic dianhydride represented by general formula (17) is a compound represented by the following structural formula.

(Wherein, R _{4 and} R ₅ are the same as defined in general formula (10).)
Specific examples of the tetracarboxylic dianhydride represented by the general formula (17) when R ₅ is a direct bond include cyclobutane-1,2,3,4-tetracarboxylic dianhydride, 1,3-dimethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride, 1,2,3,4-tetramethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride be done. Further, when one of R ₅ is a direct bond and the other is an alkylene group having 1 to 3 carbon atoms, specifically, for example, cyclopentane-1,2,3,4-tetracarboxylic dianhydride and cyclohexane-1,2,3,4-tetracarboxylic dianhydride. Further, when R ₅ is an alkylene group having 1 to 3 carbon atoms, specific examples thereof include cyclohexane-1,2,4,5-tetracarboxylic dianhydride.
Among these, cyclobutane-1,2,3,4-tetracarboxylic dianhydride, 1,3-dimethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride, wherein R ₅ is a direct bond, 1,2,3,4-Tetramethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride is preferred.

（式中、Ｒ_６は、一般式（１１）の定義と同じである。）
一般式（１８）で表されるテトラカルボン酸二無水物として、具体的には、例えば、下記構造式で表される化合物が挙げられ、かかる態様が好ましい。

The tetracarboxylic dianhydride represented by general formula (18) is a compound represented by the following structural formula.

(Wherein, R ₆ has the same definition as in general formula (11).)
Specific examples of the tetracarboxylic dianhydride represented by the general formula (18) include compounds represented by the following structural formulas, and such an embodiment is preferred.

Only one kind of tetracarboxylic dianhydride used as a polyimide monomer other than the tetracarboxylic dianhydride represented by the general formula (12) may be used, or two or more kinds thereof may be used in combination.

（式中、Ｒ_１は、各々独立して炭素原子数１～６の直鎖状又は分岐鎖状のアルキル基、炭素原子数５又は６の環状のアルキル基、炭素原子数１～６の直鎖状又は分岐鎖状のアルコキシ基、炭素原子数５又は６の環状のアルコキシ基、炭素原子数６～８のアリール基、炭素原子数６～８のアリールオキシ基、炭素原子数１～６の直鎖状又は分岐鎖状のハロゲン化アルキル基、又はハロゲン原子を示し、ｎは、各々独立して０又は１～３の整数を示し、Ａは、２価の有機基を示す。） Another aspect of the polyimide of the present invention has a repeating unit represented by the following general formula (1), and is pyrolyzed to a residue weight rate of 95% based on the weight at 100 ° C. by thermogravimetric analysis The temperature (Td) is 350° C. or higher.

(wherein R ₁ is each independently a linear or branched alkyl group having 1 to 6 carbon atoms, a cyclic alkyl group having 5 or 6 carbon atoms, a straight alkyl group having 1 to 6 carbon atoms, chain or branched alkoxy group, cyclic alkoxy group having 5 or 6 carbon atoms, aryl group having 6 to 8 carbon atoms, aryloxy group having 6 to 8 carbon atoms, aryloxy group having 1 to 6 carbon atoms represents a linear or branched halogenated alkyl group or a halogen atom, each n independently represents an integer of 0 or 1 to 3, and A represents a divalent organic group.)

（一般式（２）～（４）中、Ｒ_１、ｎ、Ａは、一般式（１）の定義と同じである。）
この中でも一般式（２）で表される繰り返し単位を有することが特に好ましい。
一般式（２）～（４）で表される繰り返し単位から選ばれる２つ以上の繰り返し単位を有する場合として、例えば、一般式（２）及び一般式（３）で表される繰り返し単位を有する場合、一般式（２）及び一般式（４）で表される繰り返し単位を有する場合、一般式（３）及び一般式（４）で表される繰り返し単位を有する場合、一般式（２）、一般式（３）及び一般式（４）で表される繰り返し単位を有する場合が挙げられる。
この中でも、一般式（２）及び一般式（４）で表される繰り返し単位を有する場合に得られるポリイミドが、光透過性に優れる観点及び複屈折（Δｎ）の低下の観点から好ましい。この時の一般式（２）で表される繰り返し単位と一般式（４）で表される繰り返し単位とのモル比率は、（２）：（４）＝９９：１～５０：５０の範囲が好ましく、（２）：（４）＝９０：１０～６０：４０の範囲がより好ましく、（２）：（４）＝８０：２０～６０：４０の範囲がさらに好ましい。 The polyimide of the present invention preferably has one or more repeating units selected from repeating units represented by the following general formulas (2) to (4).

(In general formulas (2) to (4), R ₁ , n, and A are the same as defined in general formula (1).)
Among these, it is particularly preferable to have a repeating unit represented by the general formula (2).
In the case of having two or more repeating units selected from repeating units represented by general formulas (2) to (4), for example, having repeating units represented by general formulas (2) and (3) When having repeating units represented by general formulas (2) and (4), when having repeating units represented by general formulas (3) and (4), general formula (2), A case of having a repeating unit represented by general formula (3) or general formula (4) is included.
Among these, polyimides obtained when having repeating units represented by general formulas (2) and (4) are preferable from the viewpoint of excellent light transmittance and reduction in birefringence (Δn). At this time, the molar ratio of the repeating unit represented by the general formula (2) and the repeating unit represented by the general formula (4) is in the range of (2):(4) = 99:1 to 50:50. The range of (2):(4)=90:10 to 60:40 is more preferred, and the range of (2):(4)=80:20 to 60:40 is even more preferred.

R ₁ in general formulas (1) to (4) is each independently a linear or branched alkyl group having 1 to 6 carbon atoms, a cyclic alkyl group having 5 or 6 carbon atoms, a carbon atom linear or branched alkoxy group having 1 to 6 carbon atoms, cyclic alkoxy group having 5 or 6 carbon atoms, aryl group having 6 to 8 carbon atoms, aryloxy group having 6 to 8 carbon atoms, carbon It represents a linear or branched halogenated alkyl group having 1 to 6 atoms, or a halogen atom.
Among them, a linear or branched alkyl group having 1 to 4 carbon atoms, a linear or branched halogenated alkyl group having 1 to 4 carbon atoms, or a halogen atom is preferable, and 1 carbon atom A linear or branched halogenated alkyl group of ∼4 or a halogen atom is more preferable, and a trifluoromethyl group or a fluorine atom is particularly preferable.

n in general formulas (1) to (4) each independently represents an integer of 0 or 1 to 3. Among them, 0, 1 or 2 is preferable, 0 or 1 is more preferable, and 0 is particularly preferable.

A in the general formulas (1) to (4) represents a divalent organic group. A divalent organic group containing an aromatic ring or a divalent organic group containing a linear, branched or cyclic aliphatic group is preferred.

（式中、Ｒ_２は、各々独立して炭素原子数１～６の直鎖状又は分岐鎖状アルキル基、炭素原子数５又は６の環状アルキル基、炭素原子数１～６の直鎖状又は分岐鎖状のアルコキシ基、炭素原子数５又は６の環状のアルコキシ基、炭素原子数６～８のアリール基、炭素原子数６～８のアリールオキシ基、炭素原子数１～６の直鎖状又は分岐鎖状のハロゲン化アルキル基、又はハロゲン原子を示し、ｍは、各々独立して０又は１～４の整数を示し、ｐ、ｑ及びｒは、０又は１を示し、Ｘは、直接結合、酸素原子、硫黄原子、スルホニル基（－ＳＯ_２－）、カルボニル基（－ＣＯ－）、アミド基（－ＮＨＣＯ－）、エステル基（－ＯＣＯ－）、炭素原子数１～１５のアルキリデン基、炭素原子数２～１５のフッ素含有アルキリデン基、炭素原子数５～１５のシクロアルキリデン基、フェニレン基又はフルオレニリデン基を示し、＊は、各々結合位置を示す。） The divalent organic group containing an aromatic ring is preferably a divalent organic group containing an aromatic ring having 6 to 8 carbon atoms.
More preferably, the divalent organic group containing the aromatic ring is a divalent group represented by the following general formula (5).

(wherein R ₂ is each independently a linear or branched alkyl group having 1 to 6 carbon atoms, a cyclic alkyl group having 5 or 6 carbon atoms, a linear alkyl group having 1 to 6 carbon atoms, or a branched alkoxy group, a cyclic alkoxy group having 5 or 6 carbon atoms, an aryl group having 6 to 8 carbon atoms, an aryloxy group having 6 to 8 carbon atoms, or a straight chain having 1 to 6 carbon atoms represents a branched or branched halogenated alkyl group or a halogen atom, m each independently represents an integer of 0 or 1 to 4, p, q and r represent 0 or 1, X is direct bond, oxygen atom, sulfur atom, sulfonyl group (--SO ₂ --), carbonyl group (--CO--), amide group (--NHCO--), ester group (--OCO--), alkylidene having 1 to 15 carbon atoms group, a fluorine-containing alkylidene group having 2 to 15 carbon atoms, a cycloalkylidene group having 5 to 15 carbon atoms, a phenylene group or a fluorenylidene group, and * indicates a bonding position.)

（式中、Ｒ_２、ｍ、ｑは一般式（５）の定義と同じである。）
一般式（５）におけるｑ、ｒは、各々独立して０又は１示し、０が好ましい。
一般式（５）におけるｐ及びｑが０である場合（一般式（５’）におけるｑが０である場合）、すなわち式中の芳香環がベンゼン環である場合に、＊で表される２つの結合位置がベンゼン環のパラ位又はメタ位の位置関係にあることが好ましい。その中でも、メタ位の位置関係にあると、ｍ－フェニレン結合の屈曲した構造を有することから、ジアミン化合物に由来する部位の電子供与性が低下し、かつポリイミドの分子間の凝集を阻害して、電荷移動性の光吸収が短波長化するために、可視域における高い光透過性を有する他、低い屈折率を有するポリイミドが得られることから好ましい。
一般式（５）におけるＸは、直接結合、酸素原子、硫黄原子、スルホニル基（－ＳＯ_２－）、カルボニル基（－ＣＯ－）、アミド基（－ＮＨＣＯ－）、エステル基（－ＯＣＯ－）、炭素原子数１～１５のアルキリデン基、炭素原子数２～１５のフッ素含有アルキリデン基、炭素原子数５～１５のシクロアルキリデン基、フェニレン基又はフルオレニリデン基を示す。中でも、直接結合、酸素原子、硫黄原子、スルホニル基（－ＳＯ_２－）、カルボニル基（－ＣＯ－）、アミド基（－ＮＨＣＯ－）、エステル基（－ＯＣＯ－）、炭素原子数１～１２のアルキリデン基、炭素原子数２～１２のフッ素含有アルキリデン基、炭素原子数５～１２のシクロアルキリデン基、フェニルエチリデン基又はフルオレニリデン基が好ましく、直接結合、酸素原子、硫黄原子、スルホニル基（－ＳＯ_２－）、カルボニル基（－ＣＯ－）、アミド基（－ＮＨＣＯ－）、エステル基（－ＯＣＯ－）、炭素原子数１～８のアルキリデン基、炭素原子数２～８のフッ素含有アルキリデン基、炭素原子数６～１２のシクロアルキリデン基、フェニルエチリデン基又はフルオレニリデン基がより好ましく、直接結合、酸素原子、硫黄原子、スルホニル基（－ＳＯ_２－）、アミド基（－ＮＨＣＯ－）、エステル基（－ＯＣＯ－）、炭素原子数１～４のアルキリデン基、炭素原子数２～４のフッ素含有アルキリデン基、炭素原子数６～９のシクロアルキリデン基又はフルオレニリデン基が特に好ましい。なお、アミド基（－ＮＨＣＯ－）やエステル基（－ＯＣＯ－）の結合位置は限定されず、例えば、アミド基は「－ＣＯＮＨ－」も含む。
前記、炭素原子数５～１５のシクロアルキリデン基は、分岐鎖としてのアルキル基を含んでいてもよい。シクロアルキリデン基としては、具体的には、例えば、シクロペンチリデン基（炭素原子数５）、シクロヘキシリデン基（炭素原子数６）、３－メチルシクロヘキシリデン基（炭素原子数７）、４－メチルシクロヘキシリデン基（炭素原子数７）、３，３，５－トリメチルシクロヘキシリデン基（炭素原子数９）、シクロヘプチリデン基（炭素原子数７）、シクロドデカニリデン基（炭素原子数１２）等が挙げられる。 R ₂ in the above general formula (5) is each independently a linear or branched alkyl group having 1 to 6 carbon atoms, a cyclic alkyl group having 5 or 6 carbon atoms, or a linear or branched alkoxy group, cyclic alkoxy group having 5 or 6 carbon atoms, aryl group having 6 to 8 carbon atoms, aryloxy group having 6 to 8 carbon atoms, 1 to 6 carbon atoms represents a straight-chain or branched-chain halogenated alkyl group or a halogen atom.
Among them, a linear or branched alkyl group having 1 to 4 carbon atoms, a linear or branched halogenated alkyl group having 1 to 4 carbon atoms, or a halogen atom is preferable, and 1 carbon atom ~ 4 linear or branched halogenated alkyl group, or more preferably a halogen atom, more preferably a linear or branched halogenated alkyl group having 1 to 4 carbon atoms, trifluoromethyl group is particularly preferred.
When R ₂ in the general formula (5) is a halogenated alkyl group such as a trifluoromethyl group, a site derived from a diamine compound and a site derived from trimellitic acid of a tetracarboxylic dianhydride are formed in the ground state. Polyimide with low refractive index, small dielectric constant, and small dielectric loss tangent, in addition to high optical transparency in the visible region, because the charge mobility of the electronic state is reduced and the light absorption edge moves from the visible region to the ultraviolet region. is obtained. Here, the light absorption edge refers to the wavelength at which the absorbance sharply rises in the ultraviolet/visible light transmittance spectrum of the polyimide thin film.
Each m in the general formula (5) independently represents an integer of 0 or 1 to 4, preferably 0, 1 or 2, more preferably 0 or 1.
p in the general formula (5) represents 0 or 1, preferably 1; When p in general formula (5) is 0, there are two bonding positions on the left aromatic ring in general formula (5). In such a case, general formula (5) is expressed as general formula (5') below.

(In the formula, R ₂ , m, and q are the same as defined in general formula (5).)
q and r in general formula (5) each independently represent 0 or 1, with 0 being preferred.
When p and q in general formula (5) are 0 (when q in general formula (5′) is 0), i.e., when the aromatic ring in the formula is a benzene ring, 2 represented by * It is preferable that the two bonding positions are in the para-position or meta-position relationship of the benzene ring. Among them, when it is in a meta-positional relationship, since it has a bent structure of m-phenylene bond, the electron donating property of the site derived from the diamine compound is reduced, and the aggregation between polyimide molecules is inhibited. In addition to having high light transmittance in the visible region, polyimide having a low refractive index can be obtained because the wavelength of light absorbed by charge transfer is shortened.
X in the general formula (5) is a direct bond, an oxygen atom, a sulfur atom, a sulfonyl group ( _--SO.sub.2-- ), a carbonyl group (--CO--), an amide group (--NHCO--), an ester group (--OCO--). , an alkylidene group having 1 to 15 carbon atoms, a fluorine-containing alkylidene group having 2 to 15 carbon atoms, a cycloalkylidene group having 5 to 15 carbon atoms, a phenylene group or a fluorenylidene group. Among them, a direct bond, an oxygen atom, a sulfur atom, a sulfonyl group ( _--SO.sub.2-- ), a carbonyl group (--CO--), an amide group (--NHCO--), an ester group (--OCO--), and 1 to 12 carbon atoms. alkylidene group, fluorine-containing alkylidene group having 2 to 12 carbon atoms, cycloalkylidene group having 5 to 12 carbon atoms, phenylethylidene group or fluorenylidene group are preferable, direct bond, oxygen atom, sulfur atom, sulfonyl group (-SO _2- ), a carbonyl group (-CO-), an amide group (-NHCO-), an ester group (-OCO-), an alkylidene group having 1 to 8 carbon atoms, a fluorine-containing alkylidene group having 2 to 8 carbon atoms, A cycloalkylidene group having 6 to 12 carbon atoms, a phenylethylidene group or a fluorenylidene group is more preferable, and a direct bond, an oxygen atom, a sulfur atom, a sulfonyl group (—SO ₂ —), an amide group (—NHCO—), an ester group ( —OCO—), an alkylidene group having 1 to 4 carbon atoms, a fluorine-containing alkylidene group having 2 to 4 carbon atoms, a cycloalkylidene group having 6 to 9 carbon atoms, or a fluorenylidene group are particularly preferred. The bonding positions of the amide group (--NHCO--) and the ester group (--OCO--) are not limited, and for example, the amide group includes "--CONH--".
The cycloalkylidene group having 5 to 15 carbon atoms may contain an alkyl group as a branched chain. Specific examples of the cycloalkylidene group include, for example, a cyclopentylidene group (having 5 carbon atoms), a cyclohexylidene group (having 6 carbon atoms), a 3-methylcyclohexylidene group (having 7 carbon atoms), 4 -methylcyclohexylidene group (7 carbon atoms), 3,3,5-trimethylcyclohexylidene group (9 carbon atoms), cycloheptylidene group (7 carbon atoms), cyclododecanylidene group (carbon number of atoms 12) and the like.

The divalent organic group containing a linear, branched or cyclic aliphatic group includes a linear or branched aliphatic group having 1 to 30 carbon atoms or an aliphatic group having 4 to 30 carbon atoms. A divalent organic group containing a cyclic aliphatic group is preferred. More preferably, it is a hydrocarbon group containing a linear or branched divalent aliphatic group having 2 to 20 carbon atoms or a cyclic divalent aliphatic group having 4 to 20 carbon atoms. , such hydrocarbon groups may contain halogen atoms such as fluorine atoms. It is more preferably a linear or branched divalent aliphatic saturated hydrocarbon group having 2 to 20 carbon atoms or a cyclic divalent aliphatic saturated hydrocarbon group having 4 to 20 carbon atoms, A linear or branched divalent aliphatic hydrocarbon group having 6 to 20 carbon atoms or a cyclic divalent aliphatic hydrocarbon group having 6 to 20 carbon atoms is particularly preferred, and such an aliphatic hydrocarbon The group may contain a halogen atom such as fluorine.
Specific examples of the divalent organic group containing a linear, branched or cyclic aliphatic group include a methylene group, a 1,2-ethylene group, a 1,3-propylene group, a 1,4 -tetramethylene group, 1,5-pentamethylene group, 1,6-hexamethylene group, 1,7-heptamethylene group, 1,8-octamethylene group, 1,9-nonamethylene group, bis(1,4- cyclohexylene)methylene group, trans-1,4-cyclohexane-diyl group, cis-1,4-cyclohexane-diyl group, cyclohexane-1,4-bismethylene group, bicyclo[2.2.1]heptane-2,5 -bismethylene group, bicyclo[2.2.1]heptane-2,6-bismethylene group, bicyclo[2.2.2]octane-1,4-diyl group, decahydronaphthalene-1,4-diyl group, tricyclo [5.2.1.0] Decane-3,8-bismethylene group, adamantane-1,3-diyl group, isopropylidenedicyclohexane-4,4′-diyl group, hexafluoroisopropylidenedicyclohexane-4,4 '-diyl group and the like.
Among them, trans-1,4-cyclohexane-diyl group, cis-1,4-cyclohexane-diyl group, cyclohexane-1,4-bismethylene group, bicyclo[2.2.1]heptane, having an alicyclic skeleton -2,5-bismethylene group, bicyclo[2.2.1]heptane-2,6-bismethylene group, bicyclo[2.2.2]octane-1,4-diyl group, decahydronaphthalene-1,4- diyl group, tricyclo[5.2.1.0]decane-3,8-bismethylene group, adamantane-1,3-diyl group, isopropylidenedicyclohexane-4,4'-diyl group, hexafluoroisopropylidenedicyclohexane -4,4'-diyl group and the like, the charge mobility of the electronic state formed in the ground state by the site derived from the diamine compound in the polyimide and the site derived from trimellitic acid in the tetracarboxylic dianhydride is reduced, Since the light absorption edge shifts from the visible region to the ultraviolet region, polyimide having high optical transparency in the visible region and a low refractive index can be obtained. Among these, a trans-1,4-cyclohexane-diyl group and a cis-1,4-cyclohexane-diyl group are more preferable.

（式中、Ｗは４価の有機基（但し、下記一般式（７）で表される４価の基を除く）を示し、Ａは一般式（１）の定義と同じである。）

（式中、Ｒ_１及びｎは一般式（１）の定義と同じであり、＊は結合位置を示す。） As long as the polyimide of the present invention contains the repeating unit represented by the general formula (1), it may have other skeletons as long as the effect of the present invention is not impaired.
For example, it may have a repeating unit represented by the following general formula (6).

(Wherein, W represents a tetravalent organic group (excluding the tetravalent group represented by the following general formula (7)), and A has the same definition as in general formula (1).)

(Wherein, R ₁ and n are the same as defined in general formula (1), and * indicates the bonding position.)

（式中、Ｖは、直接結合、酸素原子、硫黄原子、スルホニル基（－ＳＯ_２－）、カルボニル基（－ＣＯ－）、アミド基（－ＮＨＣＯ－）、エステル基（－ＯＣＯ－）、炭素原子数１～１５のアルキリデン基、炭素原子数２～１５のフッ素含有アルキリデン基、炭素原子数５～１５のシクロアルキリデン基、フェニレン基、フルオレニリデン基又は下記一般式（９）で表される２価の基を示し、ａは０又は１を示し、＊は結合位置を示す。）

（式中、Ｒ_３は、各々独立して炭素原子数１～６の直鎖状又は分岐鎖状のアルキル基、炭素原子数５又は６の環状のアルキル基、炭素原子数１～６の直鎖状又は分岐鎖状のアルコキシ基、炭素原子数５又は６の環状のアルコキシ基、炭素原子数６～８のアリール基、炭素原子数６～８のアリールオキシ基、炭素原子数１～６の直鎖状又は分岐鎖状のハロゲン化アルキル基、又はハロゲン原子を示し、Ｕは、直接結合、酸素原子、硫黄原子、スルホニル基（－ＳＯ_２－）、カルボニル基（－ＣＯ－）、アミド基（－ＮＨＣＯ－）、エステル基（－ＯＣＯ－）、炭素原子数１～１５のアルキリデン基、炭素原子数２～１５のフッ素含有アルキリデン基、炭素原子数５～１５のシクロアルキリデン基、フェニレン基、フルオレニリデン基を示し、ｂは各々独立して０又は１～４の整数を示し、ｃ、ｄ、ｅ、及びｆは、各々独立に０又は１を示し、＊は結合位置を示す。）

（式中、Ｒ_４は、各々独立して水素原子若しくはメチル基を示し、Ｒ_５は、各々独立して直接結合又は炭素原子数１～３のアルキレン基を示し、＊は結合位置を示す。）
一般式（１０）におけるＲ_５は、直接結合であることが好ましい。

（式中、Ｒ_６は、二重結合もしくはカルボニル基を含んでもよい４価の脂肪族基を示し、＊は結合位置を示す。）
一般式（１１）における、二重結合もしくはカルボニル基を含んでもよい４価の脂肪族基は、二重結合もしくはカルボニル基を含んでもよい炭素原子数３～２０の４価の脂肪族基であることが好ましい。具体的には、例えば、下記構造式で表される基が挙げられる。

（式中、＊は結合位置を示す。） The tetravalent organic group of W in the repeating unit represented by the general formula (6) is a structure represented by the following general formula (8), a structure represented by the following general formula (10), or the following general formula ( It is preferably one or more of the structures represented by 11).

(Wherein, V is a direct bond, an oxygen atom, a sulfur atom, a sulfonyl group (—SO ₂ —), a carbonyl group (—CO—), an amide group (—NHCO—), an ester group (—OCO—), a carbon an alkylidene group having 1 to 15 atoms, a fluorine-containing alkylidene group having 2 to 15 carbon atoms, a cycloalkylidene group having 5 to 15 carbon atoms, a phenylene group, a fluorenylidene group or a divalent represented by the following general formula (9) represents a group, a represents 0 or 1, and * represents a bonding position.)

(wherein R ₃ is each independently a linear or branched alkyl group having 1 to 6 carbon atoms, a cyclic alkyl group having 5 or 6 carbon atoms, a straight alkyl group having 1 to 6 carbon atoms, chain or branched alkoxy group, cyclic alkoxy group having 5 or 6 carbon atoms, aryl group having 6 to 8 carbon atoms, aryloxy group having 6 to 8 carbon atoms, aryloxy group having 1 to 6 carbon atoms A linear or branched halogenated alkyl group or a halogen atom, U is a direct bond, an oxygen atom, a sulfur atom, a sulfonyl group ( _--SO.sub.2-- ), a carbonyl group (--CO--), an amide group (-NHCO-), an ester group (-OCO-), an alkylidene group having 1 to 15 carbon atoms, a fluorine-containing alkylidene group having 2 to 15 carbon atoms, a cycloalkylidene group having 5 to 15 carbon atoms, a phenylene group, represents a fluorenylidene group, b each independently represents an integer of 0 or 1 to 4, c, d, e, and f each independently represents 0 or 1, and * represents a bonding position.)

(In the formula, each R ₄ independently represents a hydrogen atom or a methyl group, each R ₅ independently represents a direct bond or an alkylene group having 1 to 3 carbon atoms, and * represents a bonding position. )
_R5 in general formula (10) is preferably a direct bond.

(In the formula, _R6 represents a tetravalent aliphatic group which may contain a double bond or a carbonyl group, and * represents the bonding position.)
In the general formula (11), the tetravalent aliphatic group which may contain a double bond or a carbonyl group is a tetravalent aliphatic group having 3 to 20 carbon atoms which may contain a double bond or a carbonyl group. is preferred. Specific examples thereof include groups represented by the following structural formulas.

(In the formula, * indicates the bonding position.)

When the polyimide of the present invention has a repeating unit other than the repeating unit represented by the general formula (1), the content of the repeating unit represented by the general formula (1) is 15 mol% or more of the total polyimide. The content is preferably 50 mol% or more, more preferably 70 mol% or more, and particularly preferably 90 mol% or more. In addition, the repeating units of the general formula (1) may be arranged regularly, or may be randomly present in the polyimide.
Even when the repeating unit represented by the general formula (1) is a repeating unit represented by the general formula (2), (3) or (4) among them, the range of mol % is the same, and the general formula ( In the case of having two or more repeating units selected from the repeating units represented by 2), (3) or (4), the total is in the same mol% range.

The polyimide of the present invention has a thermal decomposition temperature (Td) of 350 ° C. or higher at which the weight of the residue at 100 ° C. as a reference value by thermogravimetric analysis is 95%, and has high thermal stability. Polyimide resin It has sufficient heat resistance required for The thermal decomposition temperature is preferably 370° C. or higher, more preferably 380° C. or higher, even more preferably 390° C. or higher, and particularly preferably 400° C. or higher.

（一般式（１２）及び一般式（１４）中のＲ_１及びｎ並びに、一般式（１３）及び一般式（１４）中のＡは、一般式（１）の定義と同じである。） The method for producing the polyimide of the present invention is not particularly limited. It can be produced through a step of reacting equimolarly to obtain a polyimide precursor (polyamic acid) represented by the following general formula (14) and a step of imidizing the polyimide precursor.

(R ₁ and n in general formulas (12) and (14) and A in general formulas (13) and (14) are the same as defined in general formula (1).)

As a specific example thereof, the tetracarboxylic dianhydride represented by the above general formula (12) is isosorbide-bis(trimellitate anhydride) (compound (a)), and is represented by the above general formula (13). The following reaction formula shows the production method when the diamine compound is 1,4-diaminocyclohexane (compound (b)). The compound (a) and the compound (b) are polymerized to obtain a polyimide precursor (polyamic acid) (compound (c)) having the following repeating unit, which is imidized to obtain the desired repeating unit below It is possible to obtain a polyimide (compound (d)) having

（一般式（１５）、（１２）におけるＲ_１及びｎは、一般式（１）の定義と同じである。） The tetracarboxylic dianhydride represented by the general formula (12) can be produced by a conventionally known method, and is not limited to the production method. For example, as represented by the following reaction formula, dianhydrohexitol such as isosorbide, isomannide and isoidide are reacted with trimellitic anhydride represented by general formula (15) such as trimellitic anhydride chloride. can be manufactured by

(R ₁ and n in general formulas (15) and (12) are the same as defined in general formula (1).)

なお、式（ｉ）で表される化合物はイソソルビド－ビス（トリメリテートアンハイドライド）であり、式（ｉｉ）で表される化合物はイソイジド－ビス（トリメリテートアンハイドライド）であり、式（ｉｉｉ）で表される化合物はイソマンニド－ビス（トリメリテートアンハイドライド）である。以下、各々、化合物（ｉ）、化合物（ｉｉ）、化合物（ｉｉｉ）と称する場合がある。
これらの中でも、式（ｉ）で表される化合物が特に好ましい。
本発明のポリイミドの製造方法において、一般式（１２）で表されるテトラカルボン酸二無水物を１種のみを用いてもよいし、２種以上を併用してもよい。 R ₁ and n in general formula (12) are the same as defined in general formula (1), and preferred embodiments are also the same.
Specific examples of the tetracarboxylic dianhydride represented by the general formula (12) include compounds represented by the following formulas (i) to (iii).

The compound represented by formula (i) is isosorbide-bis(trimellitate anhydride), the compound represented by formula (ii) is isoidide-bis(trimellitate anhydride), and the formula ( The compound represented by iii) is isomannide-bis(trimellitate anhydride). Hereinafter, they may be referred to as compound (i), compound (ii), and compound (iii), respectively.
Among these, the compound represented by formula (i) is particularly preferred.
In the method for producing a polyimide of the present invention, the tetracarboxylic dianhydride represented by the general formula (12) may be used singly or in combination of two or more.

A in general formula (13) has the same definition as in general formula (1), and preferred embodiments are also the same.
When A in general formula (13) is a divalent organic group containing an aromatic ring, the diamine compound represented by general formula (13) is a diamine compound containing an aromatic ring. The diamine compound containing an aromatic ring preferably has a divalent group represented by general formula (5). Specific examples of the diaminediamine compound containing an aromatic ring include p-phenylenediamine (PPD), m-phenylenediamine (MPD), 2,4- Diaminotoluene, 2,5-diaminotoluene, 2,4-diaminoxylene, 1,4-diaminodurene, 1,4-diamino-2-phenylbenzene, 1,3-diamino-4-phenylbenzene, 1,3- Diaminobenzenes such as diamino-5-phenylbenzene and 5-trifluoromethyl-1,3-phenylenediamine (TFMPD); 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2 , and diaminonaphthalenes such as 7-diaminonaphthalene.
Among these, m-phenylenediamine (MPD), 2,4-diaminotoluene, 2,4-diaminoxylene, 1,3-diamino-4-phenylbenzene, 1,3-diamino-5-phenylbenzene, 5-tri Fluoromethyl-1,3-phenylenediamine (TFMPD) and the like are preferable, and m-phenylenediamine (MPD) and 5-trifluoromethyl-1,3-phenylenediamine (TFMPD) are more preferable.
When p in the general formula (5) is 1, for example, 2,2′-diaminobiphenyl, 3,3′-diaminobiphenyl, 4,4′-diaminobiphenyl, 2,2′-dimethyl-4,4′ -diaminobiphenyls such as 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl (2,2'-bis(trifluoromethyl)benzidine;TFDB);3,3'-diaminodiphenyl ether, Diaminodiphenyl ethers such as 3,4'-diaminodiphenyl ether and 4,4'-diaminodiphenyl ether; Diaminodiphenyls such as 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide and 4,4'-diaminodiphenyl sulfide sulfides; diaminodiphenylsulfones such as 3,3′-diaminodiphenylsulfone, 3,4′-diaminodiphenylsulfone and 4,4′-diaminodiphenylsulfone; 3,3′-diaminobenzophenone, 3,4′-diaminobenzophenone, Diaminobenzophenones such as 4,4′-diaminobenzophenone; Bis(aminophenyl)alkanes such as bis(3-aminophenyl)methane, bis(4-aminophenyl)methane and 2,2-bis(4-aminophenyl)propane 2,2-bis(3-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 2,2-bis(4-aminophenyl)-1,1,1,3,3 bis(aminophenyl)cycloalkanes such as 1,1-bis(4-aminophenyl)cyclohexane; 4,4″-diamino-p-terphenyl , 4,4''-diamino-m-terphenyl and other diaminoterphenyls, 9,9-bis(4-aminophenyl)fluorene, 9,9-bis(4-amino-3-fluorophenyl)fluorene, etc. and bis(aminophenyl)fluorene.
Among the diamine compounds represented by the general formula (13), 2,2′-bis(trifluoromethyl)benzidine (TFDB) and 5-trifluoromethyl-1,3-phenylenediamine (TFMPD) are preferred.

When A in general formula (13) is a divalent organic group containing a linear, branched or cyclic aliphatic group, the diamine compound represented by general formula (13) is linear, It is a diamine compound having a branched or cyclic aliphatic group. Specific examples of such diamine compounds include 1,2-ethylenediamine, 1,3-propanediamine, 1,4-tetramethylenediamine, 1,5-pentamethylenediamine, and 1,6-hexamethylene. diamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 4,4′-methylenebis(cyclohexylamine), trans-1,4-diaminocyclohexane, cis-1, 4-diaminocyclohexane, 1,4-cyclohexanebis(methylamine), 2,5-bis(aminomethyl)bicyclo[2.2.1]heptane, 2,6-bis(aminomethyl)bicyclo[2.2. 1]heptane, bicyclo[2.2.2]octane-1,4-diamine, decahydro-1,4-naphthalenediamine, 3,8-bis(aminomethyl)tricyclo[5.2.1.0]decane, 1,3-diaminoadamantane, 2,2-bis(4-aminocyclohexyl)propane, and 2,2-bis(4-aminocyclohexyl)hexafluoropropane.
Among these, 4,4′-methylenebis(cyclohexylamine), trans-1,4-diaminocyclohexane, cis-1,4-diaminocyclohexane, 1,4-cyclohexanebis(methylamine), which have an alicyclic skeleton, 2,5-bis(aminomethyl)bicyclo[2.2.1]heptane, 2,6-bis(aminomethyl)bicyclo[2.2.1]heptane, bicyclo[2.2.2]octane-1, 4-diamine, decahydro-1,4-naphthalenediamine, 3,8-bis(aminomethyl)tricyclo[5.2.1.0]decane, 1,3-diaminoadamantane, 2,2-bis(4-amino Diamine compounds such as cyclohexyl)propane and 2,2-bis(4-aminocyclohexyl)hexafluoropropane are preferred, and trans-1,4-diaminocyclohexane and cis-1,4-diaminocyclohexane are more preferred.
Only one kind of the diamine compound represented by the general formula (13) may be used, or two or more kinds thereof may be used in combination.

In the case where the polyimide of the present invention further has a repeating unit represented by the general formula (6), in addition to the tetracarboxylic dianhydride represented by the general formula (12), the general formula (12) It can be produced by using an acid dianhydride used as a polyimide monomer other than the tetracarboxylic dianhydride represented.

（式中、Ｖ及びａは、一般式（８）の定義と同じである。）
このようなテトラカルボン酸二無水物として、具体的には、ａが０である場合、ピロメリット酸二無水物である。ａが１である場合、具体的には、例えば、３，３’，４，４’－ビフェニルテトラカルボン酸二無水物、４，４’－オキシジフタル酸無水物、３，３’，４，４’－ジフェニルスルフィドテトラカルボン酸二無水物、３，３’，４，４’－ジフェニルスルホンテトラカルボン酸二無水物、３，３’，４，４’－ベンゾフェノンテトラカルボン酸二無水物、４，４’－（ヘキサフルオロイソプロピリデン）ビス（フタル酸）二無水物、１，４－ビス（３，４－ジカルボキシフェノキシ）ベンゼン二無水物、１，３－ビス（３，４－ジカルボキシフェノキシ）ベンゼン二無水物、４，４’－ビス（３，４－ジカルボキシフェノキシ）ビフェニル二無水物、４，４’－ビス（３，４－ジカルボキシフェノキシ）－３，３’－ジメチルビフェニル二無水物、ビス［４－（３，４－ジカルボキシフェノキシ）フェニル］エーテル二無水物、ビス［４－（３，４－ジカルボキシフェノキシ）フェニル］スルホン二無水物、２，２－ビス［４－（３，４－ジカルボキシフェノキシ）フェニル］プロパン二無水物、２，２－ビス［４－（３，４－ジカルボキシフェノキシ）フェニル］ヘキサフルオロプロパン二無水物、１，１－ビス［４－（３，４－ジカルボキシフェノキシ）フェニル］シクロヘキサン二無水物、１，１－ビス［４－（３，４－ジカルボキシフェノキシ）フェニル］シクロデカン二無水物、１，１－ビス［４－（３，４－ジカルボキシフェノキシ）フェニル］－３，３，５－トリメチルシクロヘキサン二無水物、９，９－ビス［４－（３，４－ジカルボキシフェノキシ）－３－メチルフェニル］フルオレン二無水物、ハイドロキノン－ビス（トリメリテートアンハイドライド）、レゾルシノール－ビス（トリメリテートアンハイドライド）、１，５－ジヒドロキシナフタレン－ビス（トリメリテートアンハイドライド）、２，６－ジヒドロキシナフタレン－ビス（トリメリテートアンハイドライド）、２，７－ジヒドロキシナフタレン－ビス（トリメリテートアンハイドライド）、４，４’－ジヒドロキシビフェニル－ビス（トリメリテートアンハイドライド）、４，４’－ジヒドロキシ－３，３’－ジメチルビフェニル－ビス（トリメリテートアンハイドライド）、４，４’－ジヒドロキシ－３，３’，５，５’－テトラメチルビフェニル－ビス（トリメリテートアンハイドライド）、４，４’－ジヒドロキシ－２，２’，３，３’，５，５’－ヘキサメチルビフェニル－ビス（トリメリテートアンハイドライド）、４，４’－ジヒドロキシジフェニルエーテル－ビス（トリメリテートアンハイドライド）、４，４’－ジヒドロキシジフェニルスルフィド－ビス（トリメリテートアンハイドライド）、４，４’－ジヒドロキシジフェニルスルホン－ビス（トリメリテートアンハイドライド）、４，４’－ジヒドロキシベンゾフェノン－ビス（トリメリテートアンハイドライド）、１，１’－ビス（４－ヒドロキシフェニル）エタン－ビス（トリメリテートアンハイドライド）、２，２’－ビス（４－ヒドロキシフェニル）プロパン－ビス（トリメリテートアンハイドライド）、２，２’－ビス（４－ヒドロキシ－３－メチルフェニル）プロパン－ビス（トリメリテートアンハイドライド）、２，２’－ビス（４－ヒドロキシフェニル）ヘキサフルオロプロパン－ビス（トリメリテートアンハイドライド）、１，１’－ビス（４－ヒドロキシフェニル）シクロヘキサン－ビス（トリメリテートアンハイドライド）、１，１’－ビス（４－ヒドロキシフェニル）－３，３，５－トリメチルシクロヘキサン－ビス（トリメリテートアンハイドライド）、１，１’－ビス（４－ヒドロキシフェニル）シクロデカン－ビス（トリメリテートアンハイドライド）、９，９’－ビス（４－ヒドロキシ－３－メチルフェニル）フルオレン－ビス（トリメリテートアンハイドライド）が挙げられる。 As the tetracarboxylic dianhydride used as a polyimide monomer other than the tetracarboxylic dianhydride represented by the general formula (12), tetracarboxylic acid represented by the general formulas (16) to (18) described later An acid dianhydride is preferred.
The tetracarboxylic dianhydride represented by general formula (16) is a compound represented by the following structural formula.

(Wherein, V and a are the same as defined in general formula (8).)
Specifically, such a tetracarboxylic dianhydride is pyromellitic dianhydride when a is 0. When a is 1, specifically, for example, 3,3′,4,4′-biphenyltetracarboxylic dianhydride, 4,4′-oxydiphthalic anhydride, 3,3′,4,4 '-diphenyl sulfide tetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 4, 4'-(Hexafluoroisopropylidene)bis(phthalic acid) dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,3-bis(3,4-dicarboxyphenoxy ) benzene dianhydride, 4,4′-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, 4,4′-bis(3,4-dicarboxyphenoxy)-3,3′-dimethylbiphenyl dianhydride anhydride, bis[4-(3,4-dicarboxyphenoxy)phenyl]ether dianhydride, bis[4-(3,4-dicarboxyphenoxy)phenyl]sulfone dianhydride, 2,2-bis[4 -(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride, 1,1-bis[4 -(3,4-dicarboxyphenoxy)phenyl]cyclohexane dianhydride, 1,1-bis[4-(3,4-dicarboxyphenoxy)phenyl]cyclodecane dianhydride, 1,1-bis[4-( 3,4-dicarboxyphenoxy)phenyl]-3,3,5-trimethylcyclohexane dianhydride, 9,9-bis[4-(3,4-dicarboxyphenoxy)-3-methylphenyl]fluorene dianhydride , hydroquinone-bis (trimellitate anhydride), resorcinol-bis (trimellitate anhydride), 1,5-dihydroxynaphthalene-bis (trimellitate anhydride), 2,6-dihydroxynaphthalene-bis (trimellitate anhydride) tate anhydride), 2,7-dihydroxynaphthalene-bis (trimellitate anhydride), 4,4'-dihydroxybiphenyl-bis (trimellitate anhydride), 4,4'-dihydroxy-3,3'- Dimethylbiphenyl-bis(trimellitate anhydride), 4,4′-dihydroxy-3,3′,5,5′-tetramethylbiphenyl-bis(trimellitate anhydride), 4,4′-dihydroxy-2 ,2′,3,3′,5,5′-hexamethylbiphenyl-bis(trimellitate anhydride), 4,4′-dihydroxydiphenyl ether-bis(trimellitate anhydride), 4,4′-dihydroxy Diphenylsulfide-bis(trimellitate anhydride), 4,4'-dihydroxydiphenylsulfone-bis(trimellitate anhydride), 4,4'-dihydroxybenzophenone-bis(trimellitate anhydride), 1,1 '-bis(4-hydroxyphenyl)ethane-bis(trimellitate anhydride), 2,2'-bis(4-hydroxyphenyl)propane-bis(trimellitate anhydride), 2,2'-bis( 4-hydroxy-3-methylphenyl)propane-bis(trimellitate anhydride), 2,2′-bis(4-hydroxyphenyl)hexafluoropropane-bis(trimellitate anhydride), 1,1′- bis(4-hydroxyphenyl)cyclohexane-bis(trimellitate anhydride), 1,1′-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane-bis(trimellitate anhydride), 1 , 1′-bis(4-hydroxyphenyl)cyclodecane-bis(trimellitate anhydride), 9,9′-bis(4-hydroxy-3-methylphenyl)fluorene-bis(trimellitate anhydride). be done.

（式中、Ｒ_４、Ｒ_５は、一般式（１０）の定義と同じである。）
一般式（１７）で表されるテトラカルボン酸二無水物として、Ｒ_５が直接結合である場合、具体的には、例えば、シクロブタン－１，２，３，４－テトラカルボン酸二無水物、１，３－ジメチルシクロブタン－１，２，３，４－テトラカルボン酸二無水物、１，２，３，４－テトラメチルシクロブタン－１，２，３，４－テトラカルボン酸二無水物が挙げられる。また、Ｒ_５の一方が直接結合で、他方が炭素原子数１～３のアルキレン基である場合は、具体的には、例えば、シクロペンタン－１，２，３，４－テトラカルボン酸二無水物、シクロヘキサン－１，２，３，４－テトラカルボン酸二無水物が挙げられる。また、Ｒ_５が炭素原子数１～３のアルキレン基である場合、具体的には、例えば、シクロヘキサン－１，２，４，５－テトラカルボン酸二無水物が挙げられる。
この中でも、Ｒ_５が直接結合である、シクロブタン－１，２，３，４－テトラカルボン酸二無水物、１，３－ジメチルシクロブタン－１，２，３，４－テトラカルボン酸二無水物、１，２，３，４－テトラメチルシクロブタン－１，２，３，４－テトラカルボン酸二無水物が好ましい。 The tetracarboxylic dianhydride represented by general formula (17) is a compound represented by the following structural formula.

(In the formula, R ₄ and R ₅ are the same as defined in general formula (10).)
Specific examples of the tetracarboxylic dianhydride represented by the general formula (17) when R ₅ is a direct bond include cyclobutane-1,2,3,4-tetracarboxylic dianhydride, 1,3-dimethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride, 1,2,3,4-tetramethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride be done. Further, when one of R ₅ is a direct bond and the other is an alkylene group having 1 to 3 carbon atoms, specifically, for example, cyclopentane-1,2,3,4-tetracarboxylic dianhydride and cyclohexane-1,2,3,4-tetracarboxylic dianhydride. Further, when R ₅ is an alkylene group having 1 to 3 carbon atoms, specific examples thereof include cyclohexane-1,2,4,5-tetracarboxylic dianhydride.
Among these, cyclobutane-1,2,3,4-tetracarboxylic dianhydride, 1,3-dimethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride, wherein R ₅ is a direct bond, 1,2,3,4-Tetramethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride is preferred.

（式中、Ｒ_６は、一般式（１１）の定義と同じである。）
一般式（１８）で表されるテトラカルボン酸二無水物として、具体的には、例えば、下記構造式で表される化合物が挙げられ、かかる態様が好ましい。

The tetracarboxylic dianhydride represented by general formula (18) is a compound represented by the following structural formula.

(Wherein, R ₆ has the same definition as in general formula (11).)
Specific examples of the tetracarboxylic dianhydride represented by the general formula (18) include compounds represented by the following structural formulas, and such an embodiment is preferred.

Only one kind of tetracarboxylic dianhydride used as a polyimide monomer other than the tetracarboxylic dianhydride represented by the general formula (12) may be used, or two or more kinds thereof may be used in combination.

In the production of the polyimide of the present invention, the amount (total molar amount) of the diamine compound used is the total molar amount of the tetracarboxylic dianhydride compound being 1 mol, and the lower limit thereof is preferably 0.94 mol or more, more It is preferably 0.96 mol or more, more preferably 0.98 mol or more, particularly preferably 0.99 mol or more, and the upper limit is preferably 1.20 mol or less, more preferably 1.10 mol or less, and further It is preferably 1.05 mol or less, particularly preferably 1.02 mol or less.

A specific example of the polymerization reaction method for producing the polyimide of the present invention will now be described.
First, a diamine compound is dissolved in a polymerization solvent, and tetracarboxylic dianhydride is gradually added to this solution. Stir for 150 hours, preferably 1-72 hours. At this time, the monomer concentration is usually in the range of 5 to 50% by weight, preferably in the range of 10 to 40% by weight. By performing polymerization within such a monomer concentration range, a uniform polyimide precursor (polyamic acid) having a high degree of polymerization can be obtained. If the degree of polymerization of the polyimide precursor (polyamic acid) increases too much and the polymerization solution becomes difficult to stir, it can be diluted with the same solvent as appropriate. By carrying out the polymerization within the above monomer concentration range, the degree of polymerization of the polymer is sufficiently high, and the solubility of the monomer and polymer can be sufficiently ensured. If the polymerization is carried out at a concentration lower than the above range, the degree of polymerization of the polyimide precursor (polyamic acid) may not be sufficiently high. Insufficient dissolution may occur.

As the solvent used for polymerization of the polyimide precursor (polyamic acid), aprotic solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone and dimethylsulfoxide are preferred. Any solvent can be used without any problem as long as it dissolves the raw material monomers, the resulting polyimide precursor (polyamic acid), and the imidized polyimide, and the structure and type of the solvent are not particularly limited. Specifically, for example, amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone , ε-caprolactone, α-methyl-γ-butyrolactone, butyl acetate, ethyl acetate, isobutyl acetate, and other ester solvents; ethylene carbonate, propylene carbonate, and other carbonate solvents; diethylene glycol dimethyl ether, triethylene glycol, triethylene glycol dimethyl ether, and other glycols. phenolic solvents such as phenol, m-cresol, p-cresol, o-cresol, 3-chlorophenol, 4-chlorophenol, cyclopentanone, cyclohexanone, acetone, methyl ethyl ketone, diisobutyl ketone, methyl isobutyl ketone Ether solvents such as ketone solvents, tetrahydrofuran, 1,4-dioxane, dimethoxyethane, diethoxyethane, and dibutyl ether are included. Other general-purpose solvents include acetophenone, 1,3-dimethyl-2-imidazolidinone, sulfolane, dimethyl sulfoxide, propylene glycol methyl acetate, ethyl cellosolve, butyl cellosolve, 2-methyl cellosolve acetate, ethyl cellosolve acetate, butyl cellosolve acetate, butanol, ethanol. , xylene, toluene, chlorobenzene, terpene, mineral spirits, petroleum naphtha-based solvents and the like can also be used. Two or more of these solvents may be mixed and used.

In the polymerization reaction for producing the polyimide of the present invention, a silylating agent can be further used in order to make it difficult for the association of raw materials and the insolubilization (gelation) of the product to occur. Silylating agents that can be used are not particularly limited, but include, for example, N,O-bis(trimethylsilyl)acetamide, N,O-bis(trimethylsilyl)trifluoroacetamide and the like.

A method for imidizing the obtained polyimide precursor (polyamic acid) will be described.
For imidization, known imidization methods can be applied, for example, "thermal imidization method" for thermally ring-closing a polyimide precursor (polyamic acid) thin film, "solution "Thermal imidization method", "Chemical imidization method" using a dehydrating agent, and the like can be used as appropriate.
Specifically, in the "thermal imidization method", a polyimide precursor (polyamic acid) solution is cast on a substrate or the like and dried at 50 to 200 ° C., preferably 60 to 150 ° C. to form a polyimide precursor (polyamic acid ) After forming a thin film, it is heated in an inert gas or under reduced pressure at 150° C. to 400° C., preferably 200° C. to 380° C. for 1 to 12 hours to complete imidization by thermal dehydration ring closure. Inventive polyimides can be obtained.
Further, in the "solution thermal imidization method", a polyimide precursor (polyamic acid) solution to which a basic catalyst or the like is added is heated to 100 to 250°C in the presence of an azeotropic agent such as xylene, preferably 150 to 220°C. By heating for 5 to 12 hours, by-produced water is removed from the system to complete imidization, and the polyimide solution of the present invention can be obtained. Alternatively, a polyimide precursor (polyamic acid) solution in an amide solvent such as N,N-dimethylacetamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, under a stream of nitrogen, 150 to 220 ° C., preferably by heating at 165 to 205 ° C. for 0.5 to 2 hours, by-product water is partially removed from the system to complete imidation, and the polyimide solution of the present invention can be obtained. can.
In the "chemical imidization method", while stirring a polyimide precursor (polyamic acid) solution adjusted to an appropriate solution viscosity that is easy to stir with a mechanical stirrer, an anhydride of an organic acid, A dehydration cyclization agent (chemical imidization agent) composed of amines as a basic catalyst is added dropwise and stirred at 0 to 100° C., preferably 10 to 50° C. for 1 to 72 hours to chemically complete imidization. The organic acid anhydride that can be used at that time is not particularly limited, but examples thereof include acetic anhydride and propionic anhydride. Acetic anhydride is preferably used because it is easy to handle and purify as a reagent. As the basic catalyst, pyridine, triethylamine, quinoline and the like can be used, and pyridine is preferably used because of ease of handling and separation of reagents, but is not limited to these. The amount of the organic acid anhydride in the chemical imidizing agent is in the range of 1 to 10 times the theoretical amount of dehydration of the polyimide precursor (polyamic acid), preferably 1 to 5 times the mole. The amount of the basic catalyst is in the range of 0.1 to 2 mol, more preferably 0.1 to 1 mol, relative to the amount of the organic acid anhydride.

In the "solution thermal imidization method" and "chemical imidization method", the reaction solution contains components such as catalysts, chemical imidization agents, and by-product carboxylic acids (hereinafter referred to as impurities). It may be removed and purified. A known method can be used for purification. For example, the simplest method is a method in which the imidized reaction solution is dropped into a large amount of poor solvent while stirring to precipitate polyimide, and then the polyimide powder is recovered and washed repeatedly until impurities are removed. There is At this time, as the poor solvent that can be used, water, methanol, ethanol, isopropanol, and other alcohols, which can precipitate polyimide, efficiently remove impurities, and are easy to dry, are suitable. good. If the concentration of the polyimide solution when it is dropped into a poor solvent and precipitated is too high, the precipitated polyimide will become grains, and impurities may remain in the coarse particles. It may take a long time to dissolve. On the other hand, if the concentration of the polyimide solution is too low, a large amount of poor solvent is required, which is not preferable because the disposal of the waste solvent increases the environmental burden and increases the manufacturing cost. Therefore, the concentration of the polyimide solution when dropped into the poor solvent is 20% by weight or less, more preferably 10% by weight or less. The amount of the poor solvent used at this time is preferably equal to or more than the amount of the polyimide solution, preferably 1.5 to 3 times the amount.
The polyimide powder of the present invention can be obtained by recovering the obtained polyimide powder and removing the residual solvent by drying under reduced pressure, drying with hot air, or the like. The drying temperature and time are not limited as long as the temperature does not degrade the polyimide and the residual solvent does not decompose, and it is preferable to dry in the temperature range of 30 to 200° C. for 48 hours or less.

The polyimide of the present invention preferably has an intrinsic viscosity in the range of 0.1 to 10.0 dL/g, more preferably in the range of 0.2 to 5.0 dL/g.
Since the polyimide of the present invention is soluble in various organic solvents, it can be used as a polyimide varnish. As the organic solvent, a solvent can be selected according to the intended use and processing conditions of the varnish. For example, although not particularly limited, amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and dimethylsulfoxide can be used. Among these, amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide and N-methyl-2-pyrrolidone are preferably used from the viewpoint of solubility. Two or more of these solvents may be mixed and used.

The solid content concentration when the polyimide of the present invention is dissolved in a solvent to form a solution is preferably 5% by weight or more, although it depends on the molecular weight of the polyimide, the production method, and the product to be produced. If the solid content concentration is too low, it will be difficult to process the film to a sufficient film thickness. As a method for dissolving the polyimide contained in the material for melt processing of the present invention in a solvent, for example, the polyimide powder contained in the material for melt processing of the present invention is added while stirring the solvent, and dissolved in air or an inert gas. It can be dissolved in the temperature range from room temperature to the boiling point of the solvent for 1 to 48 hours to form a polyimide solution (varnish).
The resulting polyimide solution can be molded into various shapes by known methods. For example, when molding into a film, the polyimide solution is cast on a support such as a glass substrate using a doctor blade or the like, and is heated using a hot air dryer, an infrared drying oven, a vacuum dryer, an inert oven, or the like. Usually, it can be carried out by drying in the range of 40 to 350°C, preferably in the range of 50 to 250°C.

The polyimide of the present invention can be used for display devices (e.g., liquid crystal displays, plasma displays, organic EL displays, flexible displays, foldable displays, rollable displays, 3D displays), touch panels, organic EL lighting, solar cells, and the like. Materials for transparent substrates and cover films; materials for optical films (e.g., light guide plate, polarizing plate, polarizing plate protective film, retardation film, light diffusion film, viewing angle expansion film, reflective film, antireflection film, antiglare film, Brightness enhancement film, prism sheet, light guide film), insulating materials for electronic parts, materials for passivation films, buffer coat films, interlayer insulating films, etc. in semiconductor devices, flexible printed circuit boards, wiring board materials such as metal-clad laminates, It can be used for wire coating materials for aircraft, motors, generators, etc., luminescent materials for organic EL devices, optical sensor materials, optical radar materials, 3D display materials, and the like.

EXAMPLES The present invention will be specifically described below by way of examples, but the present invention is not limited to these examples.
The analysis method in the present invention is as follows.

<Analysis method>
1. Infrared absorption spectrum The infrared absorption spectrum of the polyimide thin film was measured using an FT/IR4200 Fourier transform infrared spectrophotometer (manufactured by JASCO Corporation) using an ATR (attenuated total reflection) method using a Ge prism. , a polyimide thin film sample (15 μm thick) was measured.

2. ¹ H-NMR spectrum The ¹ H-NMR spectrum of the polyimide thin film was obtained from JNM. A polyimide thin film sample was partially dissolved in deuterated dimethylsulfoxide (DMSO-d ₆ ) and measured using an ECP400 Fourier transform nuclear magnetic resonance spectrometer (manufactured by JEOL). TMS (tetramethylsilane) was used as a chemical shift reference.

3. Glass transition temperature: Tg
The glass transition temperature of the polyimide thin film was measured using a TMA60 thermomechanical analyzer (manufactured by Shimadzu Corporation) with a sample size of 5 mm in width, 10 mm in length, and a load of 5 g. After raising the temperature for the second time), it is cooled to 20 ° C. and further heated at 10 ° C./min (second temperature rise). (point of intersection of tangent lines after Tg).

4. Average linear thermal expansion coefficient: CTE
The average linear thermal expansion coefficient of the polyimide thin film was measured using a TMA60 thermomechanical analyzer (manufactured by Shimadzu Corporation) with a sample size of 5 mm in width, 10 mm in length, and a load of 5 g. After raising the temperature (first temperature rise), the temperature was cooled to 20° C. and further heated at 10° C./min (second temperature rise), and calculation was performed from the TMA curve during the second temperature rise. The coefficient of linear thermal expansion was obtained as an average value between 80 and 200°C.

5. Thermal decomposition temperature (nitrogen atmosphere): Td
The thermal decomposition temperature of the polyimide thin film is measured using a TG-DTA60 thermogravimetric analyzer (manufactured by Shimadzu Corporation) in a temperature rising process at a temperature rising rate of 10°C/min in a nitrogen atmosphere. The temperature at which the residue weight ratio becomes 95% was measured as the thermal decomposition temperature (Td). Higher values of these indicate higher thermal stability.

6. Ultraviolet/visible light transmittance The light transmittance of the polyimide thin film in the ultraviolet/visible region was measured using a V-670 ultraviolet/visible spectrophotometer (manufactured by JASCO Corporation) in the wavelength range of 250 to 800 nm. A polyimide thin film sample was measured. A Glan-Taylor polarizer with a high degree of polarization in the ultraviolet-visible region is inserted into the optical path for measurement to make it p-polarized, and the measurement sample is tilted to the optical path at a Brewster angle (approximately 60 degrees). By doing so, the influence of multiple reflections on the thin film surface is eliminated as much as possible.

7. Average refractive index: n _av and birefringence: Δn
The refractive index of the polyimide thin film was measured using a PC-2010 prism coupler (manufactured by Metricon) at wavelengths of 636 nm, 845 nm, 1310 nm and 1558 nm for polyimide thin film samples formed on silicon substrates. Here, by inserting a half-wave plate corresponding to each wavelength into the optical path and rotating the linear polarization plane of the laser beam, the direction parallel to the film surface (n _TE ) and the direction perpendicular to the film surface (film thickness direction) ( n _TM ) was measured. From these refractive indices, the average refractive index (n _av ² =(2n _TE ² +n _TM ² )/3) and birefringence (Δn=n _TE −n _TM ) of the polyimide film were calculated.

8. Dielectric constant (estimated value): ε _ref
The dielectric constant (estimated value) of the polyimide thin film was calculated as (ε _ref =1.1×n _av ² ) based on the average refractive index n _av at a wavelength of 1310 nm.

9. Permittivity, dielectric loss tangent (measured value)
The dielectric constant and dielectric loss tangent of the polyimide thin film were measured in TE mode at frequencies of 10 GHz and 20 GHz using a VNA network analyzer MS46122B (manufactured by Anritsu) and cavity resonators (10 GHz and 20 GHz) (manufactured by AET). . The measurement was carried out after the polyimide thin film was dried at 120° C. for 2 hours, and then under an environment of 23° C.±1° C. and 50% RH±5% for 24 hours and after humidity control.

10. Circular dichroism: CD
The circular dichroism (CD) of the polyimide thin film was measured using a J-1000 circular dichroism spectrometer (manufactured by JASCO Corporation) in the wavelength range of 190 to 500 nm. It was measured.

11. Solubility test The solubility of the polyimide thin film in a solvent was measured by adding 0.1 g of the polyimide thin film and 9.9 g of the solvent described in Table 3 (solid content concentration of 1% by weight) into a glass sample tube and mixing with a test tube mixer. The dissolution state was confirmed visually after stirring for 60 minutes. N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), dimethylsulfoxide (DMSO), γ-butyrolactone (GBL) were used as solvents. The evaluation results are "++" when dissolved at room temperature, "+" when dissolved by heating and maintaining uniformity even after standing to cool to room temperature, and "±" when swollen/partially dissolved. , and the case of insolubility is shown in Table 3 as "-".

<Synthesis Example 1> Synthesis of compound (i) (isosorbide-bis(trimellitate anhydride)) A four-necked flask equipped with a thermometer, a stirrer, and a condenser was charged with isosorbide and 30 times anhydrous dichloromethane, and the mixture was While stirring and dissolving, triethylamine was added in an amount of 1.1 times the moles of isosorbide, and trimellitic anhydride chloride was added in an amount of 2.1 times the moles of isosorbide. Stirred for an hour.
The resulting precipitate was filtered off, and the filtrate was slowly added dropwise to petroleum ether of 30 times volume to obtain a white solid. The resulting white solid was filtered off and dried at 80° C. under reduced pressure. The obtained white solid was dissolved in deuterated dimethyl sulfoxide (DMSO-d ₆ ) and analyzed by ¹ H-NMR, and identified as the target compound (i).

<Synthesis Example 2> Synthesis of compound (iii) (isomannide-bis(trimellitate anhydride)) A four-necked flask equipped with a thermometer, a stirrer, and a condenser was charged with isomannide and 38 times of anhydrous dimethylacetamide and mixed. While stirring and dissolving the liquid, triethylamine was added thereto in an amount of 1.1 times the moles of isomannide, and trimellitic anhydride chloride was added in an amount of 2.1 times the moles of isomannide. Stirred for 28 hours.
The resulting precipitate was filtered off, and the filtrate was slowly added dropwise to petroleum ether of 38 times volume to obtain a white solid. The resulting white solid was filtered off and dried at 80° C. under reduced pressure. The resulting white solid was dissolved in deuterated chloroform (CDCl ₃ ), analyzed by ¹ H-NMR, and identified as the target compound (iii).

<Example 1>
Under a nitrogen atmosphere, 0.571 g (5 mmol) of 1,4-cyclohexanediamine (DACH) and 1.29 g of N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) were added to a glass container with a lid, and dehydrated N,N 2.472 g (5 mmol) of compound (i) synthesized according to <Synthesis Example 1> was dissolved in 12.6 g of -dimethylacetamide (DMAc) and mixed several times, and dissolved while stirring with a magnetic stirrer. After that, the mixture was stirred at room temperature for 12 hours to obtain a polyamic acid solution as a polyimide precursor (solid concentration: 18.0% by weight). This polyamic acid solution was spread on a silicon substrate or a fused quartz substrate placed on a spin coater, and a film was formed by spin coating, and the substrate was moved into a heating furnace (inert oven). After that, it was dried at 70° C. for 50 minutes in a nitrogen stream, then heated to 280° C. at a rate of temperature increase of 3° C./min, held at 280° C. for 90 minutes, and then naturally cooled to room temperature. It was peeled off from the substrate to obtain a colorless and transparent polyimide thin film. In addition, the polyimide thin film prepared for the purpose of optical measurement (light transmittance, refractive index, circular dichroism) was used for the measurement without being peeled off from the substrate. The resulting polyimide thin film was stored in a dry desiccator. The structural formula of the polyimide of Example 1 is shown below.

<Example 2>
Under a nitrogen atmosphere, 1.601 g (5 mmol) of 2,2′-bis(trifluoromethyl)benzidine (TFDB) was dissolved in 12.9 g of dehydrated N,N-dimethylacetamide (DMAc) in a glass container with a lid, 2.472 g (5 mmol) of compound (i) was mixed in several portions and dissolved while stirring with a magnetic stirrer. After that, the mixture was stirred at room temperature for 12 hours to obtain a polyamic acid solution as a polyimide precursor (solid concentration: 24.0% by weight). This polyamic acid solution was spread on a silicon substrate or a fused quartz substrate placed on a spin coater, and a film was formed by spin coating, and the substrate was moved into a heating furnace. After that, it was dried at 70° C. for 50 minutes in a nitrogen stream, then heated to 280° C. at a rate of temperature increase of 3° C./min, held at 280° C. for 90 minutes, and then naturally cooled to room temperature. It was peeled off from the substrate to obtain a colorless and transparent polyimide thin film. In addition, the polyimide thin film prepared for the purpose of optical measurement (light transmittance, refractive index, circular dichroism) was used for the measurement without being peeled off from the substrate. The resulting polyimide thin film was stored in a dry desiccator. The structural formula of the polyimide of Example 2 is shown below.

<Example 3>
Under a nitrogen atmosphere, 1.00 g (5 mmol) of 4,4′-diaminodiphenyl ether (ODA) was dissolved in 17.0 g of dehydrated N,N-dimethylacetamide (DMAc) in a glass container with a lid, and compound (i)2 was obtained. .472 g (5 mmol) was mixed in several portions and dissolved while stirring with a magnetic stir bar. After that, the mixture was stirred at room temperature for 12 hours to obtain a polyamic acid solution as a polyimide precursor (solid concentration: 18.0% by weight). This polyamic acid solution was spread on a silicon substrate or a fused quartz substrate placed on a spin coater, and a film was formed by spin coating, and the substrate was moved into a heating furnace. Then, it was dried at 70° C. for 50 minutes in a nitrogen stream, then heated to 280° C. at a rate of temperature increase of 3° C./min, held at 280° C. for 90 minutes, and then naturally cooled to room temperature. It was peeled off from the substrate to obtain a pale yellow polyimide thin film. In addition, the polyimide thin film prepared for the purpose of optical measurement (light transmittance, refractive index, circular dichroism) was used for the measurement without being peeled off from the substrate. The resulting polyimide thin film was stored in a dry desiccator. The structural formula of the polyimide of Example 3 is shown below.

<Example 4> Example of compound (i): compound (iii) = 9:1 (molar ratio)) Under a nitrogen atmosphere, 2,2'-bis(trifluoromethyl)benzidine (TFDB) was added to a glass container with a lid. 1.60 g (5 mmol) was dissolved in 12.9 g of dehydrated N,N-dimethylacetamide (DMAc), mixed with 0.247 g (0.5 mmol) of compound (iii) and dissolved while stirring with a magnetic stir bar. . After that, the mixture was stirred at room temperature for 6 hours, and 0.225 g (4.5 mmol) of compound (i) was mixed in several portions and dissolved while stirring with a magnetic stirrer. After that, the mixture was stirred at room temperature for 12 hours to obtain a polyamic acid solution as a polyimide precursor (solid concentration: 24.0% by weight). This polyamic acid solution was spread on a silicon substrate or a fused quartz substrate placed on a spin coater, and a film was formed by spin coating, and the substrate was moved into a heating furnace. After that, it was dried at 70° C. for 50 minutes under a nitrogen stream, then heated to 280° C. at a heating rate of 3° C./min, held at 280° C. for 90 minutes, and then naturally cooled to room temperature. It was peeled off from the substrate to obtain a colorless and transparent polyimide thin film. In addition, the polyimide thin film prepared for the purpose of optical measurement (light transmittance, refractive index) was used for the measurement without being peeled off from the substrate. The resulting polyimide thin film was stored in a dry desiccator. The structural formula of the polyimide of Example 4 is shown below. The ratio of m and n in the following structural formula is 9:1.

<Example 5> Example of compound (i): compound (iii) = 8:2 (molar ratio)) Under a nitrogen atmosphere, 2,2'-bis(trifluoromethyl)benzidine (TFDB) was added to a glass container with a lid. 1.60 g (5 mmol) was dissolved in 12.9 g of dehydrated N,N-dimethylacetamide (DMAc), mixed with 0.494 g (1 mmol) of compound (iii) and dissolved while stirring with a magnetic stir bar. Then, the mixture was stirred at room temperature for 6 hours, and 1.977 g (4 mmol) of compound (i) was mixed in several portions and dissolved while stirring with a magnetic stirrer. After that, the mixture was stirred at room temperature for 12 hours to obtain a polyamic acid solution as a polyimide precursor (solid concentration: 24.0% by weight). This polyamic acid solution was spread on a silicon substrate or a fused quartz substrate placed on a spin coater, and a film was formed by spin coating, and the substrate was moved into a heating furnace. After that, it was dried at 70° C. for 50 minutes under a nitrogen stream, then heated to 280° C. at a heating rate of 3° C./min, held at 280° C. for 90 minutes, and then naturally cooled to room temperature. It was peeled off from the substrate to obtain a colorless and transparent polyimide thin film. In addition, the polyimide thin film prepared for the purpose of optical measurement (light transmittance, refractive index) was used for the measurement without being peeled off from the substrate. The resulting polyimide thin film was stored in a dry desiccator. Here, the structural formula of the polyimide of Example 5 is the same as the structural formula shown in Example 4, and the ratio of m to n is 8:2.

<Example 6>
A polyimide was produced by the same preparation method as in Example 4, except that the molar ratio of compound (i) and compound (iii) in Example 4 was changed to 7:3.

<Example 7>
A polyimide was produced by the same preparation method as in Example 4, except that the molar ratio of compound (i) and compound (iii) in Example 4 was changed to 6:4.

<Example 8>
A polyimide was produced by the same preparation method as in Example 4, except that the molar ratio of compound (i) and compound (iii) in Example 4 was changed to 5:5.

<Example 9>
Under a nitrogen atmosphere, 1.761 g (10 mmol) of 5-trifluoromethyl-1,3-phenylenediamine (TFMPD) was dissolved in 21.2 g of dehydrated N,N-dimethylacetamide (DMAc) in a glass container with a lid, Compound (i) 4.944 g (10 mmol) was mixed in several portions and dissolved while stirring with a magnetic stirrer. After that, the mixture was stirred at room temperature for 12 hours to obtain a polyamic acid solution as a polyimide precursor (solid concentration: 24.0% by weight). This polyamic acid solution was spread on a silicon substrate or a fused quartz substrate placed on a spin coater, and a film was formed by spin coating, and the substrate was moved into a heating furnace. After that, it was dried at 70° C. for 50 minutes in a nitrogen stream, then heated to 280° C. at a rate of temperature increase of 3° C./min, held at 280° C. for 90 minutes, and then naturally cooled to room temperature. It was peeled off from the substrate to obtain a colorless and transparent polyimide thin film. In addition, the polyimide thin film prepared for the purpose of optical measurement (light transmittance, refractive index, circular dichroism) was used for the measurement without being peeled off from the substrate. The resulting polyimide thin film was stored in a dry desiccator. The structural formula of the polyimide of Example 9 is shown below.

<Example 10>
Under a nitrogen atmosphere, 1.081 g (10 mmol) of 1,4-phenylenediamine (PPD) was dissolved in 27.4 g of dehydrated N,N-dimethylacetamide (DMAc) in a glass container with a lid, and compound (i)4. 944 g (10 mmol) were mixed in several portions and dissolved while stirring with a magnetic stir bar. After that, the mixture was stirred at room temperature for 12 hours to obtain a polyamic acid solution as a polyimide precursor (solid concentration: 18.0% by weight). This polyamic acid solution was spread on a silicon substrate or a fused quartz substrate placed on a spin coater, and a film was formed by spin coating, and the substrate was moved into a heating furnace. After that, it was dried at 70° C. for 50 minutes under a nitrogen stream, then heated to 280° C. at a heating rate of 3° C./min, held at 280° C. for 90 minutes, and then naturally cooled to room temperature. It was peeled off from the substrate to obtain a pale yellow polyimide thin film. In addition, the polyimide thin film prepared for the purpose of optical measurement (light transmittance, refractive index, circular dichroism) was used for the measurement without being peeled off from the substrate. The resulting polyimide thin film was stored in a dry desiccator. The structural formula of the polyimide of Example 10 is shown below.

<Example 11>
A polyimide was produced by the same preparation method as in Example 10, except that 1,4-phenylenediamine (PPD) in Example 10 was replaced with its structural isomer, 1,3-phenylenediamine (MPD). The structural formula of the polyimide of Example 11 is shown below.

The physical properties of the polyimide thin films of Examples 1 to 11 evaluated as described below are summarized in Tables 1 and 2 below. In Table 1, T ₄₀₀ (%) and T ₄₅₀ (%) are the light transmittance (%) at wavelengths of 400 nm and 450 nm, respectively, and λ (T _95% ) is the light transmittance (%) of 95%. means a wavelength (nm) of

<Confirmation of completion of imidization reaction>
1 to 11 are diagrams showing Fourier transform ATR (attenuated total reflection) infrared absorption spectra of polyimide thin films (thickness: about 15 μm) obtained in Examples 1 to 11, respectively.
In FIGS. 1 to 11, the peak near 1760 cm ^-1 is the symmetrical stretching vibration of the two carbonyl carbons contained in the imide group, the peak near 1700 cm ^-1 is the asymmetric stretching vibration of the same carbonyl carbon, and the peak near 1370 cm ^-1 is the imide It is a signal attributed to the stretching vibration of the single bond between the ring nitrogen (N) and the 1-position carbon of the benzene ring or the 1-position carbon of the cyclohexyl group. In addition, in FIGS. 2 to 11, a peak attributed to the benzene ring C═C stretching vibration of the diamine moiety is observed near 1480 to 1510 cm ⁻¹ . On the other hand, no amide group peak, which is observed when imidization is not completed, is observed near 1670 cm ⁻¹ . Therefore, it was clarified that the thermal imidization reaction in Examples 1 to 11 was completed and a polyimide thin film was indeed obtained.

12 to 22 are ¹ H-NMR spectra of deuterated dimethylsulfoxide (DMSO-d ₆ ) solutions of the polyimide thin films of Examples 1 to 11. FIG.
In these FIGS. 12 to 22, * is TMS (reference substance), # is DMSO (solvent), + is water signal, 7.5 to 8.5 ppm signal is phenyl group hydrogen, 4.5 to 5 The 0.5 ppm signal is assigned to the hydrogen of the cycloaliphatic structure of isosorbide and isomannide. Here, the 4.9 ppm and 5.4 ppm peaks (†) observed in FIGS. 15 to 19 (Examples 4 to 8) are signals attributed to isomannide. It was confirmed that each polyimide copolymer contained 10 mol to 50 mol % of isomannide. Further, the signal of 4.2 ppm in Example 1 is attributed to the 1st-position hydrogen of the cyclohexyl group, and 1 to 3 ppm is attributed to hydrogens other than the 1st-position of the cyclohexyl group. All of the major signals in these spectra can be attributed to the structure of the polyimide, and only the signals observed when imidization is complete are observed. Therefore, it was clarified that the thermal imidization reaction in Examples 1 to 11 was completed and a polyimide thin film was indeed obtained. Since the polyimide of Example 10 has extremely low solubility in DMSO- _d6 , the spectral resolution is low and there is a lot of noise, but signals characteristic of its molecular structure are observed.

<Glass transition temperature (Tg) and average linear thermal expansion coefficient (CTE) measurement>
23 to 33 are charts of thermomechanical analysis (TMA) of the polyimide thin films (about 15 μm thick) of Examples 1 to 11. FIG. Table 1 shows the glass transition temperature (Tg) obtained from the intersection of the tangent line of the low temperature part (150 ° C. to 250 ° C.) and the tangent line of the high temperature part (270 ° C. to 275 ° C.), and the average line obtained at 80 ° C. to 200 ° C. The coefficient of thermal expansion (CTE) is indicated.
All of them have Tg in the range of 240° C. to 268° C., and it has been clarified that they have a sufficiently high Tg as a heat resistant resin. In addition, the CTE is 44 to 67 ppm/K, which is a standard or slightly smaller value for a polyimide having an isotropic chemical structure (Non-Patent Document 1: S. Ando et al., Macromolecular Chemistry and Physics, 2017, 1700354, (2017).).

<Thermal decomposition temperature measurement>
34 to 44 are charts of thermogravimetric analysis (TGA) of the polyimide thin films (about 15 μm thick) of Examples 1 to 11. FIG. Table 1 shows the thermal decomposition temperature (Td) at which the weight at 100° C. is taken as the reference value and the weight percentage of the residue is 95%. All of them have Td in the range of 400° C. to 417° C., and it has been clarified that they have a sufficiently high thermal decomposition temperature as a heat resistant resin.

<Ultraviolet and visible light transmittance evaluation>
45 to 55 are diagrams showing spectra of ultraviolet and visible light transmittance of the polyimide thin films of Examples 1 to 11 (deposited on a quartz substrate, about 10 μm thick).
Here, in the thin film obtained in Example 1, a slight turbidity (haze) due to minute scatterers present in the film was observed. Moreover, the thin films obtained in Examples 3 and 10 were transparent, but had a pale yellow color. All of the thin films obtained in other examples (Examples 2, 4 to 9, 11) were colorless and transparent, had a light transmittance of 97.5 to 99.1% at a wavelength of 450 nm, and had a light transmittance of 95%. % is in the range of 415 to 423 nm, and it has been found to have extremely high light transmittance over the entire visible light wavelength range (400 to 780 nm). This is because 1,4-cyclohexanediamine (DACH) used as a diamine compound forms an alicyclic skeleton, 2,2′-bis(trifluoromethyl)benzidine (TFDB) and 5-trifluoromethyl-1,3-phenylene Diamine (TFMPD) has a bulky and strongly electron-withdrawing trifluoromethyl group, and as a result, the site derived from the diamine compound of the polyimide and the site derived from the trimellitic acid of the tetracarboxylic dianhydride This is caused by the decrease in the charge mobility of the electronic state formed in the ground state and the shift of the light absorption edge from the visible region to the ultraviolet region. It should be noted that 10 to 50 mol% of isomannide-bis(trimellitate anhydride) was added compared to Example 2 in which isosorbide-bis(trimellitate anhydride) was synthesized alone as the tetracarboxylic dianhydride. The point is that the light transmittance is improved in all of Examples 4 to 8. This is probably because the strongly bent structure derived from isomannide inhibited the intermolecular aggregation of the polyimide, further suppressing the intermolecular charge transfer light absorption. In addition, the polyimide of Example 10 using 1,4-phenylenediamine (PPD) as the diamine compound exhibited a light yellow color, whereas the structural isomer 1,3-phenylenediamine (MPD) was used. The polyimide of Example 11 was colorless and transparent. In this case as well, due to the bent structure of the m-phenylene bond, the electron-donating property of the site derived from the diamine compound was lowered, and aggregation of the polyimide was inhibited. It is thought that it depends on what happened.
On the other hand, in the thin films obtained in Examples 3 and 10, the benzene ring site of the raw material diamine compound and the trimellitic acid site of the tetracarboxylic dianhydride are in the ground state, electron transfer from the former to the latter. Due to the state, it is thought that the pale yellow color is exhibited because it slightly absorbs violet to blue light in the visible short wavelength region.

<Evaluation of refractive index characteristics>
56 to 66 show the wavelength dependence of the refractive indices (n _TE , n _TM , n _av ) and birefringence (Δn) of the polyimide thin films of Examples 1 to 11 (film formed on a silicon substrate, about 15 μm thick). FIG. 4 is a diagram showing; Table 2 summarizes the average refractive index and birefringence measured at a wavelength of 1310 nm as representative values.
It was found that the polyimide thin films of Examples 1 to 11 exhibit a lower refractive index (1.555 to 1.603) than general-purpose wholly aromatic polyimide. This is probably because the isosorbide- or isomannide-derived alicyclic structure contained in the tetracarboxylic dianhydride used has a low polarizability and a large molecular volume.
Among them, the polyimide thin films of Examples 1, 2, 4 to 9, and 11 have a standard average refractive index n _av (1.65 ~ 1.71, Non-Patent Document 2: S. Ando et al., Japan Journal of Applied Physics, 41, 5254-5258, (2002)), significantly lower refractive index (1.555 to 1.588 ). This is considered to be due to the cyclohexyl group and trifluoromethyl group contained in the diamine compound used in addition to the alicyclic structure derived from isosorbide or isomannide. The reason why the refractive index of the polyimide of Example 11 is significantly lower than that of Example 10 is considered to be that the bent structure of the m-phenylene bond inhibits intermolecular aggregation, resulting in a decrease in density.
In addition, the polyimide thin films of Examples 1 to 11 have the standard birefringence (Δn) (0.026 to 0.170) at a wavelength of 1310 nm in the above general-purpose wholly aromatic polyimide, Non-Patent Document 3: Y. Terui et al., Journal of Polymer Science, 42, 2354-2366, (2004). This is also considered to be due to the alicyclic structure derived from isosorbide and isomannide, which lowers the average refractive index and inhibits molecular chain orientation and formation of aggregate structure.
Among them, the birefringence (Δn) of Examples 1, 3, 8, 9 and 11 was extremely low at 0.01 or less, which is attributed to the diamine compound used having a flexible molecular structure. In addition, isosorbide-bis (trimellitate anhydride) was added in an amount of 10 to 50 mol% compared with Example 2 in which isosorbide-bis (trimellitate anhydride) was synthesized alone as a tetracarboxylic dianhydride. There is a significant decrease in birefringence (Δn) at ~8, which is also attributed to the strongly bent structure derived from isomannide.
These properties indicate that the polyimides of Examples 1 to 11 are excellent as heat-resistant optical materials used for optical waveguides, lightwave circuits, and the like.

67-72 are circles of polyimide thin films (deposited on quartz substrates, about 1 μm thick) of Examples 1-3 and Examples 9-11, except for polyimide copolymers using two acid anhydrides. FIG. 3 is a spectrum showing the ellipticity of polarization dichroism (CD); Table 1 shows the positive/negative and wavelength of the Cotton effect in the CD spectrum.
The polyimide thin film of Example 1 has a wavelength of 238 nm, the polyimide thin film of Example 2 has a wavelength of 230 nm and 260 nm, the polyimide thin film of Example 3 has a wavelength of 232 nm and 264 nm, the polyimide thin film of Example 9 has a wavelength of 232 nm and 254 nm, and Example 10. The polyimide thin film of Example 11 shows distinct peaks at 230 nm and 274 nm, and the polyimide thin film of Example 11 at 234 nm and 254 nm, both corresponding to the negative Cotton effect, and the CD signals are positive and negative pairs. This suggests that these polyimide molecules retain the optical isomerism (chirality) structure of the isosorbide moiety in the solid state and form a helical structure. A transparent polymer thin film that forms a helical structure can express circularly polarized luminescence by combining it with an organic polymer that has fluorescent or phosphorescent luminescence (photoluminescence). It can be applied to luminescent materials, optical sensors, optical radars, and 3D displays.

<Dielectric property evaluation> (Estimated value)
As shown in Table 2, the dielectric constant (estimated value from the refractive index) (ε _ref ) of the polyimide thin films of Examples 1 to 11 was calculated from the above formula using the average refractive index, and was 2.66 to 2.87. was a small value. From this, it can be expected that the polyimide has excellent dielectric properties. Compared to the standard ε _ref (3.0 to 3.2, observation frequency 10 GHz, Non-Patent Document 4: PM Hergenrother, High Performance Polymers, 15, 3-45, (2003).) in the above wholly aromatic polyimide It was found that the dielectric constant was remarkably small.

<Dielectric property evaluation> (measured value)
Dielectric constants (measured values) (ε) and dielectric loss tangents (measured values) of polyimide thin films (thickness: about 15 μm) of Examples 2 to 11 at frequencies of 10 GHz (TE mode) and 20 GHz (TE mode) are summarized in Table 2. indicated.
Here, the polyimide of Example 1 was excluded from the measurement object because it was difficult to peel off a thin film having an area (50 mm×50 mm or more) required for dielectric measurement from the substrate. Dielectric constants (measured values, frequency 20 GHz) of the polyimide thin films of Examples 2 to 8 are 2.88 to 2.99, and dielectric loss tangents (measured values, frequency 10 GHz) are 0.0092 to 0.0129. It has a significantly lower dielectric constant and a smaller dissipation factor compared to . In particular, the polyimide thin films made of the copolymers of Examples 4 to 6 show the smallest dielectric constant and dielectric loss tangent among all the examples, which is the effect of the trifluoromethyl group of the fluorine-containing diamine compound (TFDB). In addition to this, it is thought to be due to the effect of suppressing molecular aggregation caused by the strongly bent structure of isomannide. On the other hand, the polyimide thin films of Examples 9 to 11 have a dielectric constant (measured value, frequency 20 GHz) of 3.11 to 3.25 and a dielectric loss tangent (measured value, frequency 10 GHz) of 0.0146 to 0.0172. Both showed relatively high values, but the values were equal or smaller than those of general-purpose polyimide.
Overall, these dielectric properties indicate that the polyimides of Examples 2 to 11 having isosorbide- and isomannide-derived structures are excellent as heat-resistant insulating materials for high-frequency substrates.

<Solubility evaluation of polyimide>
The solvent solubility of the polyimide thin films of Examples 1 to 11 is summarized in Table 3 below. In Table 3, "+" means readily soluble, "±" means poorly soluble, and "-" means insoluble.
The polyimide thin films obtained in Examples 2 and 4 to 9 were sufficiently soluble in N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), and dimethylsulfoxide (DMSO) by heating at 60°C. was found to show In particular, the polyimides of Examples 7 and 8, which are copolymers with relatively high isomannide fractions, showed sufficient solubility in γ-butyrolactone (GBL), but the other polyimides were slightly soluble in GBL. showed only moderate solubility. The polyimide thin film obtained in Example 1 exhibits solubility in DMAc and NMP by heating at 60° C., and is slightly soluble in DMSO, but a polyimide varnish dissolved in such an organic solvent can be obtained. It was found that the polyimide thin films obtained in Examples 3 and 11 show slight solubility in DMAc, NMP, and DMSO when heated at 100° C., but do not exhibit solubility in GBL. rice field.

Although the polyimide thin films of Examples 1 to 11 are bio-based polyimides made from biological resources, their heat resistance (Tg, thermal decomposition temperature) and linear thermal expansion coefficient are almost standard characteristics of polyimide. At the same time, it exhibits excellent features such as low refractive index, small birefringence, low dielectric constant (estimated value, measured value), and small dielectric loss tangent (measured value). In addition, the polyimides shown in Examples 2, 4 to 9, and 11 exhibit extremely high light transmittance (colorless transparency) in the entire wavelength range of visible light, and exhibit circular dichroism in the ultraviolet wavelength range and polar organic It exhibits good solubility in solvents.
Summarizing the above, it has been clarified that the polyimide according to the present invention has excellent properties as a high-performance industrial material, particularly as a functional optical material and a low dielectric constant material.

Claims (9)

A polyimide having a repeating unit represented by the following general formula (1) and having a glass transition temperature (Tg) of 210° C. or higher as determined by thermomechanical analysis.

(wherein R ₁ is each independently a linear or branched alkyl group having 1 to 6 carbon atoms, a cyclic alkyl group having 5 or 6 carbon atoms, a straight alkyl group having 1 to 6 carbon atoms, chain or branched alkoxy group, cyclic alkoxy group having 5 or 6 carbon atoms, aryl group having 6 to 8 carbon atoms, aryloxy group having 6 to 8 carbon atoms, aryloxy group having 1 to 6 carbon atoms represents a linear or branched halogenated alkyl group or a halogen atom, n is each independently an integer of 0 or 1 to 3, and A is 2 represented by the following general formula (5) A divalent organic group including a valent group or a cyclic aliphatic group having 4 to 30 carbon atoms.)

(wherein R ₂ is each independently a linear or branched alkyl group having 1 to 6 carbon atoms, a cyclic alkyl group having 5 or 6 carbon atoms, a linear alkyl group having 1 to 6 carbon atoms, or a branched alkoxy group, a cyclic alkoxy group having 5 or 6 carbon atoms, an aryl group having 6 to 8 carbon atoms, an aryloxy group having 6 to 8 carbon atoms, or a straight chain having 1 to 6 carbon atoms represents a branched or branched halogenated alkyl group or a halogen atom, m each independently represents an integer of 0 or 1 to 4, p, q and r represent 0 or 1, X is direct bond, oxygen atom, sulfur atom, sulfonyl group (-SO2-), carbonyl group (-CO-), amide group (-NHCO-), ester group (-OCO-), alkylidene group having 1 to 15 carbon atoms , a fluorine-containing alkylidene group having 2 to 15 carbon atoms, a cycloalkylidene group having 5 to 15 carbon atoms, a phenylene group or a fluorenylidene group, and * indicates a bonding position.) 2. The polyimide according to claim 1, which has one or more repeating units selected from repeating units represented by the following general formulas (2) to (4).

(In general formulas (2) to (4), R ₁ , n, and A are the same as defined in general formula (1).) 2. The polyimide according to claim 1, which has a repeating unit represented by the following general formula (2).

(In the formula, R ₁ , n, and A are the same as defined in general formula (1).) 3. The polyimide according to claim 2 , which has two or more repeating units selected from repeating units represented by formulas (2) to (4). 5. The polyimide according to claim 4, which has repeating units represented by the general formulas (2) and (4). The molar ratio of the repeating unit represented by the general formula (2) and the repeating unit represented by the general formula (4) is in the range of (2):(4)=99:1 to 50:50. The polyimide of claim 5. 2. The polyimide according to claim 1, wherein the content of the repeating unit represented by the general formula (1) is 15 mol % or more of the entire polyimide. A polyimide varnish comprising the polyimide of claim 1 and an organic solvent. A polyimide film comprising the polyimide of claim 1 .

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