Polyimide, polyimide varnish, polyimide thin film

Abstract

The objective of this invention is to provide a polyimide material that uses biological resources as raw materials, exhibits excellent heat resistance, and possesses excellent optical and dielectric properties. This invention provides a polyimide having repeating units as shown in the following general formula (1), and having a glass transition temperature (Tg) of 210°C or higher as determined by thermomechanical analysis. In the formula, R1 independently represents a straight-chain or branched alkyl group with 1 to 6 carbon atoms, a cyclic alkyl group with 5 or 6 carbon atoms, a straight-chain or branched alkoxy group with 1 to 6 carbon atoms, a cyclic alkoxy group with 5 or 6 carbon atoms, an aryl group with 6 to 8 carbon atoms, an aryloxy group with 6 to 8 carbon atoms, a straight-chain or branched haloalkyl group with 1 to 6 carbon atoms, or a halogen atom, n independently represents an integer from 0 to 3, and A represents a divalent group as shown in the following general formula (5) or a divalent organic group containing a cyclic aliphatic group with 4 to 30 carbon atoms. In the formula, R2 independently represents a straight-chain or branched-chain alkyl group with 1 to 6 carbon atoms, a cyclic alkyl group with 5 or 6 carbon atoms, a straight-chain or branched-chain alkoxy group with 1 to 6 carbon atoms, a cyclic alkoxy group with 5 or 6 carbon atoms, an aryl group with 6 to 8 carbon atoms, an aryloxy group with 6 to 8 carbon atoms, a straight-chain or branched-chain haloalkyl group with 1 to 6 carbon atoms, or a halogen atom, m independently represents an integer from 0 to 4, p, q and r represent 0 or 1, X represents a direct bond, oxygen atom, sulfur atom, sulfonyl (-SO2-), carbonyl (-CO-), acetamyl (-NHCO-), ester (-OCO-), alkylene group with 1 to 15 carbon atoms, fluorinated alkylene group with 2 to 15 carbon atoms, cycloalkylene group with 5 to 15 carbon atoms, phenylene or fumonisinyl, and * represents the bond position.

Description

Technical Field

[0001] The present invention relates to a polyimide obtained by using a tetracarboxylic dianhydride having an ester bond, and a polyimide varnish and a polyimide film obtained therefrom. The tetracarboxylic dianhydride is synthesized from a dianhydrohexitol such as isosorbide or isomannide, which is a raw material derived from biological resources, and a trimellitic anhydride. Prior Art

[0002] From the viewpoints of physical and chemical heat resistance, electrical insulation, mechanical properties, flame retardancy, and simplicity of manufacturing steps, polyimide is frequently used as a highly reliable material in today's super engineering plastics. Most of the tetracarboxylic dianhydride or diamine compounds, which are raw material monomers of polyimide, are manufactured from raw materials derived from petrochemicals. Polyimide derived from petrochemicals becomes one of the factors for greenhouse gas emissions because of its relatively high carbon content derived from petroleum. Furthermore, since petroleum, which is the raw material for petrochemical products, is naturally formed over hundreds of thousands of years, it can be said that petrochemical products are non-renewable products. On the other hand, biobased plastics using biological resources such as plants as raw materials are considered effective for constructing a sustainable low-carbon society because the carbon in their materials is derived from carbon dioxide fixed by plants. However, most biobased plastics have poor heat resistance or mechanical properties, so their uses are limited, and there is a problem that it is difficult to use them as engineering plastics. In order to widely apply biobased plastics to the most advanced uses such as displays or transparent substrates, they must have excellent heat resistance, chemical stability, environmental stability, and further excellent optical properties, dielectric properties, and mechanical properties. [Prior Art Documents] [Patent Documents]

[0003] Patent Document 1: Specification of Chinese Patent Application Publication No. 101648958 Summary of the Invention Problems to be Solved by the Invention

[0004] The problem of the present invention is to provide a polyimide material using biological resources as raw materials, having excellent heat resistance, and having excellent optical properties and dielectric properties. Means for Solving the Problems

[0005] In order to solve the above-mentioned problem, the inventors conducted careful research and found that the problem could be solved by using polyimide obtained by synthesizing tetracarboxylic acid dianhydride with ester bonds from dihydrohexitol of isosorbide or dehydromannitol and trimellitic anhydride, thus completing the present invention.

[0006] The present invention is described below. 1. A polyimide having repeating units as shown in the general formula (1) below, and having a glass transition temperature (Tg) of 210°C or higher as determined by thermomechanical analysis. In the formula, R1 independently represents a straight-chain or branched alkyl group with 1 to 6 carbon atoms, a cyclic alkyl group with 5 or 6 carbon atoms, a straight-chain or branched alkoxy group with 1 to 6 carbon atoms, a cyclic alkoxy group with 5 or 6 carbon atoms, an aryl group with 6 to 8 carbon atoms, an aryloxy group with 6 to 8 carbon atoms, a straight-chain or branched haloalkyl group with 1 to 6 carbon atoms, or a halogen atom; n independently represents an integer from 0 to 3; A represents a divalent group as shown in the following general formula (5), or a divalent organic group containing a cyclic aliphatic group with 4 to 30 carbon atoms. In the formula, R2 independently represents a straight-chain or branched-chain alkyl group with 1 to 6 carbon atoms, a cyclic alkyl group with 5 or 6 carbon atoms, a straight-chain or branched-chain alkoxy group with 1 to 6 carbon atoms, a cyclic alkoxy group with 5 or 6 carbon atoms, an aryl group with 6 to 8 carbon atoms, an aryloxy group with 6 to 8 carbon atoms, a straight-chain or branched-chain haloalkyl group with 1 to 6 carbon atoms, or a halogen atom; m independently represents an integer from 0 to 4; p, q, and r represent 0 or 1; X represents a direct bond, an oxygen atom, a sulfur atom, a sulfonyl group (-SO2-), a carbonyl group (-CO-), an amino group (-NHCO-), an ester group (-OCO-), an alkylene group with 1 to 15 carbon atoms, a fluorinated alkylene group with 2 to 15 carbon atoms, a cycloalkylene group with 5 to 15 carbon atoms, a phenyl group, or a fumonisin group; and * represents the bond position. 2. The polyimide as described in 1. has one or more repeating units selected from the repeating units shown in general formulas (2) to (4) below. In general formulas (2) to (4), R1, n, and A are defined in the same way as in general formula (1). 3. The polyimide as described in 1. has repeating units as shown in the following general formula (2), In the formula, R1, n, and A are defined in the same way as in general formula (1). 4. The polyimide as described in 1 or 2, having two or more repeating units selected from the repeating units shown in the aforementioned general formulas (2) to (4). 5. The polyimide as described in 4, which has repeating units as shown in the aforementioned general formula (2) and the aforementioned general formula (4). 6. The polyimide as described in 5, wherein the molar ratio of the repeating unit shown in the aforementioned general formula (2) to the repeating unit shown in the aforementioned general formula (4) is in the range of (2):(4)=99:1 to 50:50. 7. The polyimide as described in 1, wherein the content of the repeating unit shown in the aforementioned general formula (1) is more than 15 mol% of the total polyimide. 8. A polyimide varnish comprising the polyimide as described in 1. and an organic solvent. 9. A polyimide film comprising the polyimide as described in 1. 10. A polyimide having repeating units as shown in the following general formula (1), and having a thermal decomposition temperature (Td) of 350°C or higher when the residue weight percentage, as determined by thermogravimetric analysis based on the weight at 100°C, is 95%. In the formula, R1 independently represents a straight-chain or branched-chain alkyl group with 1 to 6 carbon atoms, a cyclic alkyl group with 5 or 6 carbon atoms, a straight-chain or branched-chain alkoxy group with 1 to 6 carbon atoms, a cyclic alkoxy group with 5 or 6 carbon atoms, an aryl group with 6 to 8 carbon atoms, an aryloxy group with 6 to 8 carbon atoms, a straight-chain or branched-chain haloalkyl group with 1 to 6 carbon atoms, or a halogen atom, n independently represents an integer from 0 to 3, and A represents a divalent organic group. 11. The polyimide as described in 10, having one or more repeating units selected from the repeating units shown in general formulas (2) to (4) below, In general formulas (2) to (4), R1, n, and A are defined in the same way as in general formula (1). 12. The polyimide as described in 10, which has repeating units as shown in the following general formula (2), In the formula, R1, n, and A are defined in the same way as in general formula (1). 13. The polyimide as described in 10 or 11, having two or more repeating units selected from the repeating units shown in the aforementioned general formulas (2) to (4). 14. The polyimide as described in 13, which has repeating units as shown in the aforementioned general formula (2) and the aforementioned general formula (4). 15. The polyimide as described in 14, wherein the molar ratio of the repeating unit shown in the aforementioned general formula (2) to the repeating unit shown in the aforementioned general formula (4) is in the range of (2):(4)=99:1 to 50:50. 16. The polyimide as described in 10, wherein A in the aforementioned general formulas (1) to (4) is a divalent organic group containing an aromatic ring, or a divalent organic group containing a straight-chain, branched-chain, or cyclic aliphatic group. 17. The polyimide as described in 16, wherein the divalent organic group containing an aromatic ring in A of the aforementioned general formulas (1) to (4) is a divalent group as shown in the following general formula (5), In the formula, R2 independently represents a linear or branched alkyl group having 1 to 6 carbon atoms, a cyclic alkyl group having 5 or 6 carbon atoms, a linear or branched alkoxy group having 1 to 6 carbon atoms, 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, a linear or branched haloalkyl group having 1 to 6 carbon atoms, or a halogen atom; m independently represents an integer of 0 or 1 to 4; p, q, and r represent 0 or 1; X represents a direct bond, an oxygen atom, a sulfur atom, a sulfonyl group (-SO2-), a carbonyl group (-CO-), an amide group (-NHCO-), an ester group (-OCO-), an alkylene group having 1 to 15 carbon atoms, a fluoroalkylene group having 2 to 15 carbon atoms, a cycloalkylene group having 5 to 15 carbon atoms, a phenylene group, or a vinylene group; * respectively represents a bonding position. 18. The polyimide according to 16., wherein the divalent organic group containing a linear, branched, or cyclic aliphatic group is a divalent organic group containing a linear or branched aliphatic group having 1 to 30 carbon atoms or a cyclic aliphatic group having 4 to 30 carbon atoms. 19. The polyimide according to 10., wherein the content of the repeating unit represented by the general formula (1) is 15 mol% or more of the whole polyimide. 20. A polyimide varnish containing the polyimide according to 10. and an organic solvent. 21. A polyimide film containing the polyimide according to 10. Advantages of the Invention

[0007] With the polyimide of the present invention, a material can be provided that uses resources from organisms as raw materials, sufficiently has the heat resistance required for polyimide resins, and has excellent optical properties and dielectric properties. Brief Explanation of the Drawings

[0008] FIG. 1 is a diagram showing the ATR (Attenuated Total Reflection) infrared absorption spectrum of the polyimide film (film thickness: about 15 μm) obtained in Example 1. FIG. 2 is a diagram showing the ATR infrared absorption spectrum of the polyimide film (film thickness: about 15 μm) obtained in Example 2. FIG. 3 is a diagram showing the ATR infrared absorption spectrum of the polyimide film (film thickness: about 15 μm) obtained in Example 3. FIG. 4 is a diagram showing the ATR infrared absorption spectrum of the polyimide film (film thickness: about 15 μm) obtained in Example 4. Figure 5 shows the ATR infrared absorption spectrum of the polyimide film (approximately 15 μm thick) obtained in Example 5. Figure 6 shows the ATR infrared absorption spectrum of the polyimide film (approximately 15 μm thick) obtained in Example 6. Figure 7 shows the ATR infrared absorption spectrum of the polyimide film (approximately 15 μm thick) obtained in Example 7. Figure 8 shows the ATR infrared absorption spectrum of the polyimide film (approximately 15 μm thick) obtained in Example 8. Figure 9 shows the ATR infrared absorption spectrum of the polyimide film (approximately 15 μm thick) obtained in Example 9. Figure 10 shows the ATR infrared absorption spectrum of the polyimide film (approximately 15 μm thick) obtained in Example 10. Figure 11 shows the ATR infrared absorption spectrum of the polyimide film (approximately 15 μm thick) obtained in Example 11. Figure 12 shows the 1H-NMR spectrum of the polyimide film obtained in Example 1 in a solution of deuterated dimethyl monoxide (DMSO-d6). Figure 13 shows the 1H-NMR spectrum of the polyimide film obtained in Example 2 in DMSO-d6 solution. Figure 14 shows the 1H-NMR spectrum of the polyimide film obtained in Example 3 in DMSO-d6 solution. Figure 15 shows the 1H-NMR spectrum of the polyimide film obtained in Example 4 in DMSO-d6 solution. Figure 16 shows the 1H-NMR spectrum of the polyimide film obtained in Example 5 in DMSO-d6 solution. Figure 17 shows the 1H-NMR spectrum of the polyimide film obtained in Example 6 in DMSO-d6 solution. Figure 18 shows the 1H-NMR spectrum of the polyimide film obtained in Example 7 in DMSO-d6 solution. Figure 19 shows the 1H-NMR spectrum of the polyimide film obtained in Example 8 in DMSO-d6 solution. Figure 20 shows the 1H-NMR spectrum of the polyimide film obtained in Example 9 in DMSO-d6 solution. Figure 21 shows the 1H-NMR spectrum of the polyimide film obtained in Example 10 in DMSO-d6 solution. Figure 22 shows the 1H-NMR spectrum of the polyimide film obtained in Example 11 in DMSO-d6 solution. Figure 23 is a graph showing the thermomechanical analysis (TMA) of the polyimide film obtained in Example 1. Figure 24 is a graph showing the thermomechanical analysis (TMA) of the polyimide film obtained in Example 2. Figure 25 is a graph showing the thermomechanical analysis (TMA) of the polyimide film obtained in Example 3. Figure 26 is a graph showing the thermomechanical analysis (TMA) of the polyimide film obtained in Example 4. Figure 27 is a graph showing the thermomechanical analysis (TMA) of the polyimide film obtained in Example 5. Figure 28 is a graph showing the thermomechanical analysis (TMA) of the polyimide film obtained in Example 6. Figure 29 is a graph showing the thermomechanical analysis (TMA) of the polyimide film obtained in Example 7. Figure 30 is a graph showing the thermomechanical analysis (TMA) of the polyimide film obtained in Example 8. Figure 31 is a graph showing the thermomechanical analysis (TMA) of the polyimide film obtained in Example 9. Figure 32 is a graph showing the thermomechanical analysis (TMA) of the polyimide film obtained in Example 10. Figure 33 is a graph showing the thermomechanical analysis (TMA) of the polyimide film obtained in Example 11. Figure 34 is a graph showing the thermogravimetric analysis (TGA) of the polyimide film obtained in Example 1. Figure 35 is a graph showing the thermogravimetric analysis (TGA) of the polyimide film obtained in Example 2. Figure 36 is a graph showing the thermogravimetric analysis (TGA) of the polyimide film obtained in Example 3. Figure 37 is a graph showing the thermogravimetric analysis (TGA) of the polyimide film obtained in Example 4. Figure 38 is a graph showing the thermogravimetric analysis (TGA) of the polyimide film obtained in Example 5. Figure 39 is a graph showing the thermogravimetric analysis (TGA) of the polyimide film obtained in Example 6. Figure 40 is a graph showing the thermogravimetric analysis (TGA) of the polyimide film obtained in Example 7. Figure 41 is a graph showing the thermogravimetric analysis (TGA) of the polyimide film obtained in Example 8. Figure 42 is a graph showing the thermogravimetric analysis (TGA) of the polyimide film obtained in Example 9. Figure 43 is a graph showing the thermogravimetric analysis (TGA) of the polyimide film obtained in Example 10. Figure 44 is a graph showing the thermogravimetric analysis (TGA) of the polyimide film obtained in Example 11. Figure 45 is a spectrum showing the ultraviolet and visible light transmittance of the polyimide film obtained in Example 1. Figure 46 is a spectrum showing the ultraviolet and visible light transmittance of the polyimide film obtained in Example 2. Figure 47 is a spectrum showing the ultraviolet and visible light transmittance of the polyimide film obtained in Example 3. Figure 48 is a spectrum showing the ultraviolet and visible light transmittance of the polyimide film obtained in Example 4. Figure 49 is a spectrum showing the ultraviolet and visible light transmittance of the polyimide film obtained in Example 5. Figure 50 is a spectrum showing the ultraviolet and visible light transmittance of the polyimide film obtained in Example 6. Figure 51 is a spectrum showing the ultraviolet and visible light transmittance of the polyimide film obtained in Example 7. Figure 52 is a spectrum showing the ultraviolet and visible light transmittance of the polyimide film obtained in Example 8. Figure 53 is a spectrum showing the ultraviolet and visible light transmittance of the polyimide film obtained in Example 9. Figure 54 is a spectrum showing the ultraviolet and visible light transmittance of the polyimide film obtained in Example 10. Figure 55 is a spectrum showing the ultraviolet and visible light transmittance of the polyimide film obtained in Example 11. Figure 56 is a graph showing the wavelength dependence of the refractive index (nTE, nTM, nav) and birefringence (Δn) of the polyimide film obtained in Example 1. Figure 57 is a graph showing the wavelength dependence of the refractive index (nTE, nTM, nav) and birefringence (Δn) of the polyimide film obtained in Example 2. Figure 58 is a graph showing the wavelength dependence of the refractive index (nTE, nTM, nav) and birefringence (Δn) of the polyimide film obtained in Example 3. Figure 59 is a graph showing the wavelength dependence of the refractive index (nTE, nTM, nav) and birefringence (Δn) of the polyimide film obtained in Example 4. Figure 60 is a graph showing the wavelength dependence of the refractive index (nTE, nTM, nav) and birefringence (Δn) of the polyimide film obtained in Example 5. Figure 61 is a graph showing the wavelength dependence of the refractive index (nTE, nTM, nav) and birefringence (Δn) of the polyimide film obtained in Example 6. Figure 62 is a graph showing the wavelength dependence of the refractive index (nTE, nTM, nav) and birefringence (Δn) of the polyimide film obtained in Example 7. Figure 63 is a graph showing the wavelength dependence of the refractive index (nTE, nTM, nav) and birefringence (Δn) of the polyimide film obtained in Example 8. Figure 64 is a graph showing the wavelength dependence of the refractive index (nTE, nTM, nav) and birefringence (Δn) of the polyimide film obtained in Example 9. Figure 65 is a graph showing the wavelength dependence of the refractive index (nTE, nTM, nav) and birefringence (Δn) of the polyimide film obtained in Example 10. Figure 66 is a graph showing the wavelength dependence of the refractive index (nTE, nTM, nav) and birefringence (Δn) of the polyimide film obtained in Example 11. Figure 67 is a spectrum showing the circular dichroism (CD) of the polyimide film (approximately 1 μm thick) obtained in Example 1. Figure 68 is a spectrum showing the circular polarimetric ellipticity (CD) of the polyimide film (approximately 1 μm thick) obtained in Example 2. Figure 69 is a spectrum showing the circular polarimetric ellipticity (CD) of the polyimide film (approximately 1 μm thick) obtained in Example 3. Figure 70 is a spectrum showing the circular polarimetric ellipticity (CD) of the polyimide film (approximately 1 μm thick) obtained in Example 9. Figure 71 is a spectrum showing the circular polarimetric ellipticity (CD) of the polyimide film (approximately 1 μm thick) obtained in Example 10. Figure 72 is a spectrum showing the circularly polarized dichroic ellipticity (CD) of the polyimide film (approximately 1 μm thick) obtained in Example 11. Implementation

[0009] The polyimide of the present invention has repeating units as shown in general formula (1), and the glass transition temperature (Tg) obtained by thermomechanical analysis is 210°C or higher. In the formula, R1 independently represents a straight-chain or branched alkyl group with 1 to 6 carbon atoms, a cyclic alkyl group with 5 or 6 carbon atoms, a straight-chain or branched alkoxy group with 1 to 6 carbon atoms, a cyclic alkoxy group with 5 or 6 carbon atoms, an aryl group with 6 to 8 carbon atoms, an aryloxy group with 6 to 8 carbon atoms, a straight-chain or branched haloalkyl group with 1 to 6 carbon atoms, or a halogen atom; n independently represents an integer from 0 to 3; and A represents a divalent group as shown in the following general formula (5) or a divalent organic group containing a cyclic aliphatic group with 4 to 30 carbon atoms. In the formula, R2 independently represents a straight-chain or branched-chain alkyl group with 1 to 6 carbon atoms, a cyclic alkyl group with 5 or 6 carbon atoms, a straight-chain or branched-chain alkoxy group with 1 to 6 carbon atoms, a cyclic alkoxy group with 5 or 6 carbon atoms, an aryl group with 6 to 8 carbon atoms, an aryloxy group with 6 to 8 carbon atoms, a straight-chain or branched-chain haloalkyl group with 1 to 6 carbon atoms, or a halogen atom; m independently represents an integer from 0 to 4; p, q, and r represent 0 or 1; X represents a direct bond, an oxygen atom, a sulfur atom, a sulfonyl group (-SO2-), a carbonyl group (-CO-), an amino group (-NHCO-), an ester group (-OCO-), an alkylene group with 1 to 15 carbon atoms, a fluorinated alkylene group with 2 to 15 carbon atoms, a cycloalkylene group with 5 to 15 carbon atoms, a phenyl group, or a fumonisin group; and * represents the bond position. The polyimide of the present invention preferably has one or more repeating units selected from the repeating units shown in the following general formulas (2) to (4). In general formulas (2) to (4), R1, n, and A are defined in the same way as in general formula (1). Among them, the special series has repeating units as shown in general formula (2). Examples of cases having two or more repeating units selected from the repeating units shown in general formulas (2) to (4) include: cases having repeating units shown in general formulas (2) and (3), cases having repeating units shown in general formulas (2) and (4), cases having repeating units shown in general formulas (3) and (4), and cases having repeating units shown in general formulas (2), (3) and (4). Among these, the polyimide obtained when it has repeating units as shown in general formulas (2) and (4) is preferred from the viewpoints of excellent light transmittance and reduced birefringence (Δn). In this case, the molar ratio of the repeating units shown in general formula (2) to those shown in general formula (4) is preferably in the range of (2):(4) = 99:1 to 50:50, more preferably in the range of (2):(4) = 90:10 to 60:40, and even more preferably in the range of (2):(4) = 80:20 to 60:40.

[0010] In general formulas (1) to (4), R1 series independently represents a straight-chain or branched alkyl group having 1 to 6 carbon atoms, a cyclic alkyl group having 5 or 6 carbon atoms, a straight-chain or branched alkoxy group having 1 to 6 carbon atoms, 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, a straight-chain or branched haloalkyl group having 1 to 6 carbon atoms, or a halogen atom. Preferably, the alkyl group is a straight-chain or branched chain with 1 to 4 carbon atoms, or a haloalkyl group is a straight-chain or branched chain with 1 to 4 carbon atoms, or a halogen atom, especially preferably a straight-chain or branched chain haloalkyl group or a halogen atom with 1 to 4 carbon atoms, and most preferably a trifluoromethyl or fluorine atom.

[0011] In general formulas (1) to (4), n independently represents an integer from 0 to 3, either 1 or 0. Preferably, n is 0, 1 or 2, especially 0 or 1, and most preferably 0.

[0012] In the above general formula (5), R2 independently represents a straight-chain or branched alkyl group having 1 to 6 carbon atoms, a cyclic alkyl group having 5 or 6 carbon atoms, a straight-chain or branched alkoxy group having 1 to 6 carbon atoms, 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, a straight-chain or branched haloalkyl group having 1 to 6 carbon atoms, or a halogen atom. Preferably, the alkyl group is a straight-chain or branched-chain alkyl group having 1 to 4 carbon atoms, a haloalkyl group having 1 to 4 carbon atoms, or a halogen atom, more preferably a straight-chain or branched-chain haloalkyl group having 1 to 4 carbon atoms, even more preferably a straight-chain or branched-chain haloalkyl group having 1 to 4 carbon atoms, and especially preferably trifluoromethyl. When R2 in general formula (5) is a trifluoromethyl or other haloalkyl group, the charge mobility of the electronic states formed in the substrate state by the diamine compound site and the trimellitic acid site of the tetracarboxylic dianhydride site decreases, and the light absorption end shifts from the visible region to the ultraviolet region. Therefore, a polyimide with high light transmittance in the visible region, as well as low refractive index, small dielectric constant, and small dielectric loss tangent, can be obtained, which is advantageous. Here, the so-called light absorption end refers to the wavelength at which the absorbance increases sharply in the ultraviolet and visible light transmittance spectrum of the polyimide film. In general formula (5), m independently represents an integer from 0 or 1 to 4, preferably 0, 1 or 2, and even more preferably 0 or 1. In general formula (5), p represents 0 or 1, preferably 1. When p in general formula (5) is 0, there are 2 bonding positions on the aromatic ring on the left side of general formula (5). In this case, general formula (5) is as shown in general formula (5') below. In the formula, R2, m, and q are defined in the same way as in general formula (5). In general formula (5), q and r represent 0 or 1 independently, with 0 being preferred. When p and q in general formula (5) are 0 (when q in general formula (5') is 0), that is, when the aromatic ring in the formula is a benzene ring, it is preferable that the two bond positions indicated by * are in the para or meta position of the benzene ring. Among them, when the two bond positions indicated by * are in the meta position of the benzene ring, due to the bent structure of the meta-extended benzene bond, the electron donation from the diamine compound is reduced and the intermolecular aggregation of polyimide is hindered, so the charge-transfer light absorption is shortened to a shorter wavelength. Therefore, a polyimide with high light transmittance in the visible region and low refractive index can be obtained, which is preferable. In general formula (5), X represents a direct bond, an oxygen atom, a sulfur atom, a sulfonyl group (-SO2-), a carbonyl group (-CO-), a amide group (-NHCO-), an ester group (-OCO-), an alkylene group with 1 to 15 carbon atoms, a fluorinated alkylene group with 2 to 15 carbon atoms, a cycloalkylene group with 5 to 15 carbon atoms, a phenylene group, or a phenylene group. Preferably, the X represents a direct bond, an oxygen atom, a sulfur atom, a sulfonyl group (-SO2-), a carbonyl group (-CO-), a amide group (-NHCO-), an ester group (-OCO-), an alkylene group with 2 to 12 carbon atoms, a fluorinated alkylene group with 2 to 12 carbon atoms, a cycloalkylene group with 5 to 12 carbon atoms, a phenyl ethylene group, or a phenylene group, and even more preferably, a direct bond, an oxygen atom, a sulfur atom, a sulfonyl group (-SO2-), a carbonyl group (-CO-), a amide group (-NHCO-), or a phenylene group (-NHCO-). O-), ester group (-OCO-), alkylene group with 2 to 8 carbon atoms, fluorinated alkylene group with 2 to 8 carbon atoms, cycloalkylene group with 6 to 12 carbon atoms, phenyl ethylene or genistein, preferably directly bonded, oxygen atom, sulfur atom, sulfonyl group (-SO2-), acetamino group (-NHCO-), ester group (-OCO-), alkylene group with 2 to 4 carbon atoms, fluorinated alkylene group with 2 to 4 carbon atoms, cycloalkylene group with 6 to 9 carbon atoms or genistein. The bonding position of acetamino group (-NHCO-) ​​or ester group (-OCO-) is not limited; for example, acetamino group may also include "-CONH-". The aforementioned cycloalkylene groups with 5 to 15 carbon atoms may also contain alkyl groups as branched chains. Specific examples of cycloalkylene groups include: cyclopentylene (5 carbon atoms), cyclohexylene (6 carbon atoms), 3-methylcyclohexylene (7 carbon atoms), 4-methylcyclohexylene (7 carbon atoms), 3,3,5-trimethylcyclohexylene (9 carbon atoms), cycloheptanylene (7 carbon atoms), and cyclododecylene (12 carbon atoms), etc.

[0013] The aforementioned divalent organic group containing a cyclic aliphatic group with 4 to 30 carbon atoms is preferably a hydrocarbon group containing a cyclic aliphatic group with 4 to 30 carbon atoms. The divalent hydrocarbon group containing this aliphatic group may also contain halogen atoms such as fluorine. In addition, it is particularly preferred to be a cyclic divalent aliphatic saturated hydrocarbon group with 4 to 30 carbon atoms, more preferably a cyclic divalent aliphatic saturated hydrocarbon group with 6 to 20 carbon atoms, and especially preferably a cyclic divalent aliphatic saturated hydrocarbon group with 6 to 12 carbon atoms. The divalent aliphatic saturated hydrocarbon group may also contain halogen atoms such as fluorine. The aforementioned divalent organic groups containing cyclic aliphatic groups with 4 to 30 carbon atoms can be specifically listed as follows: bis(1,4-cyclohexyl)methylene, trans-1,4-cyclohexane-diyl, cis-1,4-cyclohexane-diyl, cyclohexane-1,4-dimethyl, bicyclo[2.2.1]heptane-2,5-dimethyl, bicyclo[2.2.1]heptane-2,6-dimethyl, bicyclo[2.2.2]octane-1,4-diyl, decahydronaphthalene-1,4-diyl, tricyclo[5.2.1.0]decane-3,8-dimethyl, adamantane-1,3-diyl, isopropylidene dicyclohexane-4,4'-diyl, hexafluoroisopropylidene dicyclohexane-4,4'-diyl, etc. In the case of divalent organic groups containing cyclic aliphatic groups with 4 to 30 carbon atoms, the charge mobility of the electronic states formed in the substrate state by the diamine compound site and the trimellitic acid site from the tetracarboxylic dianhydride in the polyimide is reduced, and the light absorption end shifts from the visible region to the ultraviolet region. Therefore, a polyimide with high light transmittance in the visible region and low refractive index can be obtained, which is preferable. Among them, trans-1,4-cyclohexane-diyl and cis-1,4-cyclohexane-diyl are particularly preferred.

[0014] If the polyimide of the present invention contains the repeating unit shown in the above general formula (1), it may also have other skeletons without impairing the effect of the present invention. It may have repeating units, for example, as shown in the following general formula (6). In the formula, W represents a tetravalent organic group (except for the tetravalent group shown in the general formula (7) below), and A is defined in the same way as in the general formula (1). In the formula, R1 and n are defined in the same way as in general formula (1), and * indicates the position of the bond.

[0015] The tetravalent organic group of W in the repeating unit shown in general formula (6) is preferably one or more of the structures shown in general formula (8), general formula (10), or general formula (11). In the formula, V represents a direct bond, oxygen atom, sulfur atom, sulfonyl (-SO2-), carbonyl (-CO-), acetamyl (-NHCO-), ester (-OCO-), alkylene with 1 to 15 carbon atoms, fluorinated alkylene with 2 to 15 carbon atoms, cycloalkylene with 5 to 15 carbon atoms, phenylene, fumonisin, or a divalent group as shown in the following general formula (9), a represents 0 or 1, and * represents the bond position. In the formula, R3 independently represents a straight-chain or branched alkyl group with 1 to 6 carbon atoms, a cyclic alkyl group with 5 or 6 carbon atoms, a straight-chain or branched alkoxy group with 1 to 6 carbon atoms, a cyclic alkoxy group with 5 or 6 carbon atoms, an aryl group with 6 to 8 carbon atoms, an aryloxy group with 6 to 8 carbon atoms, a straight-chain or branched haloalkyl group with 1 to 6 carbon atoms, or a halogen atom; U represents a direct bond, an oxygen atom, a sulfur atom, a sulfonyl group (-SO2-), a carbonyl group (-CO-), an amino group (-NHCO-), an ester group (-OCO-), an alkylene group with 1 to 15 carbon atoms, a fluorinated alkylene group with 2 to 15 carbon atoms, a cycloalkylene group with 5 to 15 carbon atoms, a phenyl group, or a fumonisin; b independently represents an integer from 0 to 4; c, d, e, and f independently represent 0 or 1; and * represents the bond position. In the formula, R4 independently represents a hydrogen atom or a methyl group, R5 independently represents a direct bond or an alkyl group with 1 to 3 carbon atoms, and * indicates the bond position. In general formula (10), R5 is preferably a direct bond. In the formula, R6 represents a double bond or a tetravalent aliphatic group that may contain a carbonyl group, and * indicates the bond position. The double bond in general formula (11) may be a tetravalent aliphatic group containing a carbonyl group, preferably a tetravalent aliphatic group with 3 to 20 carbon atoms in the double bond or containing a carbonyl group. Specifically, examples of groups represented by the following structural formulas can be listed. In the formula, * indicates the location of the bond.

[0016] When the polyimide of the present invention has repeating units other than those shown in general formula (1), the content of the repeating units shown in general formula (1) is preferably 15 mol% or more of the total polyimide, more preferably 50 mol% or more, even more preferably 70 mol% or more, and particularly preferably 90 mol% or more. Furthermore, the repeating units of the above general formula (1) can be arranged regularly or exist randomly in the polyimide. In the case of repeating units shown in general formula (1), when the repeating units are shown in general formula (2), (3) or (4), the range of moles is the same. When there are two or more repeating units selected from repeating units shown in general formula (2), (3) or (4), the total is the same range of moles.

[0017] The polyimide of this invention has a glass transition temperature of 210°C or higher, determined by thermomechanical analysis, which sufficiently provides the heat resistance required for polyimide resins. This glass transition temperature is preferably 220°C or higher, more preferably 230°C or higher, and particularly preferably 240°C or higher.

[0018] The thermal decomposition temperature (Td) of the polyimide of the present invention, determined by thermogravimetric analysis, when the residue weight percentage based on the weight at 100°C is 95%, is preferably 350°C or higher, more preferably 370°C or higher, even more preferably 390°C or higher, and particularly preferably 400°C or higher.

[0019] The method for manufacturing the polyimide of the present invention is not particularly limited. For example, it can be manufactured by the following steps: reacting a tetracarboxylic acid dianhydride of the following general formula (12) with a substance of a diamine compound of the following general formula (13) in an isomolar manner to obtain a precursor (polyamide) of the polyimide of the following general formula (14); and imidizing the polyimide precursor. R1 and n in general formula (12) and general formula (14), and A in general formula (13) and general formula (14), are the same as those defined in general formula (1).

[0020] A specific example is the manufacturing method of a tetracarboxylic acid dianhydride represented by the above general formula (12) being isosorbide-bis(triphenylamine) (compound (a)) and a diamine compound represented by the above general formula (13) being 1,4-diaminocyclohexane (compound (b)). The reaction formula is shown below. Compound (a) and compound (b) are polymerized to obtain a polyimide precursor (polyamide) having the following repeating unit (compound (c)), and then imidized to obtain a polyimide (compound (d)) belonging to the target compound having the following repeating unit.

[0021] The tetracarboxylic acid dianhydride shown in general formula (12) can be manufactured by conventionally known methods, and the method of manufacture is not limited. As shown in the following reaction formula, for example, it can be manufactured by reacting isosorbide, dehydromannitol, isoidide (a disohydrohexitol), and trimellitic anhydride, etc., with trimellitic anhydride of general formula (15). The R1 and n series in general formulas (15) and (12) are defined in the same way as in general formula (1).

[0022] The R1 and n series in general formula (12) are defined in the same way as in general formula (1), and the better mode is also the same. The tetracarboxylic acid dianhydrides represented by general formula (12) can be specifically listed as compounds represented by formulas (i) to (iii) below. The compound represented by formula (i) is isosorbitol-bis(triphenyltrihydric anhydride), the compound represented by formula (ii) is iso-idolitol-bis(triphenyltrihydric anhydride), and the compound represented by formula (iii) is dehydromannitol-bis(triphenyltrihydric anhydride). These compounds are sometimes referred to as compound (i), compound (ii), and compound (iii) respectively. Of these, the compound represented by formula (i) is particularly preferred. In the method for manufacturing polyimide of the present invention, the tetracarboxylic acid dianhydride shown in general formula (12) may be used only one type or in combination with two or more types.

[0023] The A series in general formula (13) is defined in the same way as in general formula (1), and the preferred mode is also the same. In general formula (13), A represents a diamine compound with a divalent group as shown in general formula (5). Specifically, when p in general formula (5) is 0, examples include: p-phenylenediamine (PPD), m-phenylenediamine (MPD), 2,4-diaminotoluene, 2,5-diaminotoluene, 2,4-diaminoxylene, and 1,4-diaminodimethylamine (1,4-Dia Diaminobenzenes such as minodurene, 1,4-diamino-2-phenylbenzene, 1,3-diamino-4-phenylbenzene, 1,3-diamino-5-phenylbenzene, and 5-trifluoromethyl-1,3-phenylenediamine (TFMPD: 5-Trifluoromethyl-1,3-phenylenediamine); and diaminonaphthalenes such as 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, and 2,7-diaminonaphthalene. Preferred ingredients include m-phenylenediamine (MPD), 2,4-diaminotoluene, 2,4-diaminoxylene, 1,3-diamino-4-phenylbenzene, 1,3-diamino-5-phenylbenzene, and 5-trifluoromethyl-1,3-phenylenediamine (TFMPD), with m-phenylenediamine (MPD) and 5-trifluoromethyl-1,3-phenylenediamine (TFMPD) being particularly preferred. When p in general formula (5) is 1, examples include: 2,2'-diaminobiphenyl, 3,3'-diaminobiphenyl, 4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (2,2'-bis(trifluoromethyl)benzidine; TFDB), etc., which are diaminobiphenyl derivatives; 3,3'-diaminobiphenyl Diaminodiphenyl ethers such as phenyl ether, 3,4'-diaminodiphenyl ether, and 4,4'-diaminodiphenyl ether; diaminodiphenyl sulfides such as 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, and 4,4'-diaminodiphenyl sulfide; diaminodiphenyl sulfides such as 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, and 4,4'-diaminodiphenyl sulfone; 3 Diaminodiphenyl ketones such as 3'-diaminodiphenyl ketone, 3,4'-diaminodiphenyl ketone, and 4,4'-diaminodiphenyl ketone; 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 and 2,2-bis(4-aminophenyl) Diaminophenyl hexafluoropropanes such as 1,1-bis(4-aminophenyl)cyclohexane; diaminophenyl cycloalkanes such as 4,4"-diamino-p-triphenyl and 4,4"-diamino-meta-triphenyl; and diaminophenyl derivatives such as 9,9-bis(4-aminophenyl)furan and 9,9-bis(4-amino-3-fluorophenyl)furan. Among the diamine compounds represented by general formula (13), 2,2'-bis(trifluoromethyl)benzidine (TFDB) and 5-trifluoromethyl-1,3-phenylenediamine (TFMPD) are preferred.

[0024] When A in general formula (13) is a divalent organic group containing a cyclic aliphatic group with 1 to 30 carbon atoms, the diamine compounds represented by general formula (13) can be specifically listed as follows: 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-naphthyldiamine, 3,8-bis(aminomethyl)tricyclo[5.2.1.0]decane, 1,3- The preferred formulations are trans-1,4-diaminocyclohexane, 2,2-bis(4-aminocyclohexyl)propane, and 2,2-bis(4-aminocyclohexyl)hexafluoropropane. The diamine compound shown in general formula (13) may be used with only one or with two or more compounds.

[0025] The polyimide of the present invention further includes the repeating unit shown in general formula (6). In addition to the tetracarboxylic acid dianhydride shown in general formula (12), the polyimide can be manufactured by using an acid dianhydride other than the tetracarboxylic acid dianhydride shown in general formula (12) as a monomer for polyimide.

[0026] The tetracarboxylic dianhydride used as a monomer for polyimide, other than the tetracarboxylic dianhydride shown in general formula (12), is preferably the tetracarboxylic dianhydride shown in general formulas (16) to (18) described below. The tetracarboxylic acid dianhydride shown in general formula (16) is a compound represented by the following structural formula. In the formula, V and a are defined in the same way as in general formula (8). Specifically, when a is 0, the tetracarboxylic dianhydride is pyromellitic dianhydride. When a is 1, examples include: 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 3,3',4,4'-diphenylsulfide tetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfide tetracarboxylic dianhydride, 3,3',4,4'-diphenylketone tetracarboxylic dianhydride, 4,4'-(hexafluoroisopropyl)bis(phthalic acid) dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)phthalic anhydride, 1,3-bis(3,4-dicarboxyphenoxy)phthalic anhydride, 4,4'-bis(3,4- Dicarboxyphenoxy)biphenyl dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)-3,3'-dimethylbiphenyl dianhydride, bis[4-(3,4-dicarboxyphenoxy)phenyl]ether dianhydride, bis[4-(3,4-dicarboxyphenoxy)phenyl]cyclohexane 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]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]pyranodianhydride, Hydroquinone-bis(triphenylamine), Resorcinol-bis(triphenylamine) 1,5-Dihydroxynaphthalene-bis(triphenyltrihydric anhydride), 2,6-Dihydroxynaphthalene-bis(triphenyltrihydric anhydride), 2,7-Dihydroxynaphthalene-bis(triphenyltrihydric anhydride), 4,4'-Dihydroxybiphenyl-bis(triphenyltrihydric anhydride), 4,4'-Dihydroxy-3,3'-dimethylbiphenyl-bis(triphenyltrihydric anhydride), 4, 4'-Dihydroxy-2,2',3,3',5,5'-Hexamethylbiphenyl-bis(triphenyltrihydride), 4,4'-Dihydroxydiphenyl ether-bis(triphenyltrihydride), 4,4'-Dihydroxydiphenyl sulfide-bis(triphenyltrihydride), 4,4'-Dihydroxydiphenyl sulfide-bis(triphenyltrihydride), 4,4'-Dihydroxydiphenyl ketone-bis(triphenyltrihydride), 1,1'-bis(4-hydroxyphenyl)ethane -bis(triphenyltrihydride), 2,2'-bis(4-hydroxyphenyl)propane-bis(triphenyltrihydride), 2,2'-bis(4-hydroxy-3-methylphenyl)propane-bis(triphenyltrihydride), 2,2'-bis(4-hydroxyphenyl)hexafluoropropane-bis(triphenyltrihydride), 1,1'-bis(4-hydroxyphenyl)cyclohexane-bis(triphenyltrihydride), 1,1'-bis(4-hydroxyphenyl)-3,3,5-Trimethylcyclohexane-bis(triphenyltrihydric anhydride), 1,1'-bis(4-hydroxyphenyl)cyclodecane-bis(triphenyltrihydric anhydride), 9,9'-bis(4-hydroxy-3-methylphenyl)furan-bis(triphenyltrihydric anhydride).

[0027] The tetracarboxylic acid dianhydride shown in general formula (17) is a compound represented by the following structural formula. In the formula, R4 and R5 are defined in the same way as in general formula (10). Regarding the tetracarboxylic dianhydrides represented by general formula (17), when R5 is a direct bond, examples include: cyclobutane-1,2,3,4-tetracarboxylic dianhydride, 1,3-dimethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride, and 1,2,3,4-tetramethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride. Furthermore, when one of R5 is a direct bond and the other is an alkyl group having 1 to 3 carbon atoms, examples include: cyclopentane-1,2,3,4-tetracarboxylic dianhydride and cyclohexane-1,2,3,4-tetracarboxylic dianhydride. Furthermore, when R5 is an alkyl group having 1 to 3 carbon atoms, examples include: cyclohexane-1,2,4,5-tetracarboxylic dianhydride. Among them, the preferred system R5 is directly bonded cyclobutane-1,2,3,4-tetracarboxylic dianhydride, 1,3-dimethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride, or 1,2,3,4-tetramethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride.

[0028] The tetracarboxylic acid dianhydride shown in general formula (18) is a compound represented by the following structural formula. In the formula, R6 is defined in the same way as in general formula (11). The tetracarboxylic acid dianhydride represented by general formula (18) can be specifically listed as, for example, compounds represented by the following structural formulas, preferably of this type.

[0029] Other than the tetracarboxylic dianhydride shown in general formula (12), the tetracarboxylic dianhydride used as a monomer for polyimide may be used alone or in combination with two or more.

[0030] Other forms of polyimide of the present invention have repeating units as shown in the following general formula (1), and the thermal decomposition temperature (Td) when the residue weight percentage based on the weight at 100°C is 95% as determined by thermogravimetric analysis is 350°C or higher. In the formula, R1 independently represents a straight-chain or branched-chain alkyl group with 1 to 6 carbon atoms, a cyclic alkyl group with 5 or 6 carbon atoms, a straight-chain or branched-chain alkoxy group with 1 to 6 carbon atoms, a cyclic alkoxy group with 5 or 6 carbon atoms, an aryl group with 6 to 8 carbon atoms, an aryloxy group with 6 to 8 carbon atoms, a straight-chain or branched-chain haloalkyl group with 1 to 6 carbon atoms, or a halogen atom, n independently represents an integer from 0 to 3, and A represents a divalent organic group.

[0031] The polyimide of the present invention preferably has one or more repeating units selected from the repeating units shown in the following general formulas (2) to (4). In general formulas (2) to (4), R1, n, and A are defined in the same way as in general formula (1). Among them, the special series has repeating units as shown in general formula (2), Examples of cases having two or more repeating units selected from the repeating units shown in general formulas (2) to (4) include: cases having repeating units shown in general formulas (2) and (3), cases having repeating units shown in general formulas (2) and (4), cases having repeating units shown in general formulas (3) and (4), and cases having repeating units shown in general formulas (2), (3) and (4). Among these, the polyimide obtained when it has repeating units as shown in general formulas (2) and (4) is preferred from the viewpoints of excellent light transmittance and reduced birefringence (Δn). In this case, the molar ratio of the repeating units shown in general formula (2) to those shown in general formula (4) is preferably in the range of (2):(4) = 99:1 to 50:50, more preferably in the range of (2):(4) = 90:10 to 60:40, and even more preferably in the range of (2):(4) = 80:20 to 60:40.

[0032] In general formulas (1) to (4), R1 series independently represents a straight-chain or branched alkyl group having 1 to 6 carbon atoms, a cyclic alkyl group having 5 or 6 carbon atoms, a straight-chain or branched alkoxy group having 1 to 6 carbon atoms, 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, a straight-chain or branched haloalkyl group having 1 to 6 carbon atoms, or a halogen atom. Preferably, the alkyl group is a straight-chain or branched chain with 1 to 4 carbon atoms, or a haloalkyl group is a straight-chain or branched chain with 1 to 4 carbon atoms, or a halogen atom, especially preferably a straight-chain or branched chain haloalkyl group or a halogen atom with 1 to 4 carbon atoms, and most preferably a trifluoromethyl or fluorine atom.

[0033] In general formulas (1) to (4), n independently represents an integer from 0 to 3, either 1 or 0. Preferably, n is 0, 1 or 2, especially 0 or 1, and most preferably 0.

[0034] In general formulas (1) to (4), A represents a divalent organic group. Preferably, it is a divalent organic group containing an aromatic ring, or a divalent organic group containing a straight-chain, branched-chain, or cyclic aliphatic group.

[0035] The aforementioned divalent organic groups containing aromatic rings are preferably divalent organic groups containing aromatic rings with 6 to 8 carbon atoms. The aforementioned divalent organic group containing an aromatic ring is preferably in the form of a divalent group as shown in the following general formula (5). In the formula, R2 independently represents a straight-chain or branched-chain alkyl group with 1 to 6 carbon atoms, a cyclic alkyl group with 5 or 6 carbon atoms, a straight-chain or branched-chain alkoxy group with 1 to 6 carbon atoms, a cyclic alkoxy group with 5 or 6 carbon atoms, an aryl group with 6 to 8 carbon atoms, an aryloxy group with 6 to 8 carbon atoms, a straight-chain or branched-chain haloalkyl group with 1 to 6 carbon atoms, or a halogen atom; m independently represents an integer from 0 to 4; p, q, and r represent 0 or 1; X represents a direct bond, an oxygen atom, a sulfur atom, a sulfonyl group (-SO2-), a carbonyl group (-CO-), an amino group (-NHCO-), an ester group (-OCO-), an alkylene group with 1 to 15 carbon atoms, a fluorinated alkylene group with 2 to 15 carbon atoms, a cycloalkylene group with 5 to 15 carbon atoms, a phenyl group, or a fumonisin group; and * represents the bond position.

[0036] In the above general formula (5), R2 independently represents a straight-chain or branched alkyl group having 1 to 6 carbon atoms, a cyclic alkyl group having 5 or 6 carbon atoms, a straight-chain or branched alkoxy group having 1 to 6 carbon atoms, 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, a straight-chain or branched haloalkyl group having 1 to 6 carbon atoms, or a halogen atom. Preferably, the alkyl group is a straight-chain or branched-chain alkyl group having 1 to 4 carbon atoms, a haloalkyl group having 1 to 4 carbon atoms, or a halogen atom, more preferably a straight-chain or branched-chain haloalkyl group having 1 to 4 carbon atoms, even more preferably a straight-chain or branched-chain haloalkyl group having 1 to 4 carbon atoms, and especially preferably trifluoromethyl. When R2 in general formula (5) is a trifluoromethyl or other haloalkyl group, the charge mobility of the electronic states formed in the substrate state by the diamine compound site and the trimellitic acid site of the tetracarboxylic dianhydride site decreases, and the light absorption end shifts from the visible region to the ultraviolet region. Therefore, a polyimide with high light transmittance in the visible region, as well as low refractive index, small dielectric constant, and small dielectric loss tangent, can be obtained, which is advantageous. Here, the so-called light absorption end refers to the wavelength at which the absorbance increases sharply in the ultraviolet and visible light transmittance spectrum of the polyimide film. In general formula (5), m independently represents an integer from 0 or 1 to 4, preferably 0, 1 or 2, and even more preferably 0 or 1. In general formula (5), p represents 0 or 1, preferably 1. When p in general formula (5) is 0, there are 2 bonding positions on the aromatic ring on the left side of general formula (5). In this case, general formula (5) is as shown in general formula (5') below. In the formula, R2, m, and q are defined in the same way as in general formula (5). In general formula (5), q and r represent 0 or 1 independently, with 0 being preferred. When p and q in general formula (5) are 0 (when q in general formula (5') is 0), that is, when the aromatic ring in the formula is a benzene ring, the two bond positions indicated by * are preferably in the para or meta position of the benzene ring. When in the meta position, due to the bent structure of the meta-extended benzene bond, the electron donation from the diamine compound is reduced and the intermolecular aggregation of polyimide is hindered, resulting in short wavelengths of charge-transfer light absorption. Therefore, polyimide with high light transmittance in the visible region and low refractive index can be obtained, which is preferred. In general formula (5), X represents a direct bond, an oxygen atom, a sulfur atom, a sulfonyl group (-SO2-), a carbonyl group (-CO-), an amino group (-NHCO-), an ester group (-OCO-), an alkylene group with 1 to 15 carbon atoms, a fluorinated alkylene group with 2 to 15 carbon atoms, a cycloalkylene group with 5 to 15 carbon atoms, a phenylene group, or a genistein group. Preferably, the bonds are direct bonds, an oxygen atom, a sulfur atom, a sulfonyl group (-SO2-), a carbonyl group (-CO-), an amino group (-NHCO-), an ester group (-OCO-), an alkylene group with 1 to 12 carbon atoms, a fluorinated alkylene group with 2 to 12 carbon atoms, a cycloalkylene group with 5 to 12 carbon atoms, a phenyl ethylene group, or a genistein group; particularly preferably, the bonds are direct bonds, an oxygen atom, a sulfur atom, a sulfonyl group (-SO2-), a carbonyl group (-CO-), an amino group (-NHCO-), or a phenylene group (-NHCO-). O-), ester group (-OCO-), alkylene group with 1 to 8 carbon atoms, fluorinated alkylene group with 2 to 8 carbon atoms, cycloalkylene group with 6 to 12 carbon atoms, phenyl ethylene or genistein, preferably directly bonded, oxygen atom, sulfur atom, sulfonyl group (-SO2-), acetamino group (-NHCO-), ester group (-OCO-), alkylene group with 1 to 4 carbon atoms, fluorinated alkylene group with 2 to 4 carbon atoms, cycloalkylene group with 6 to 9 carbon atoms or genistein. The bonding position of acetamino group (-NHCO-) ​​or ester group (-OCO-) is not limited; for example, acetamino group may also include "-CONH-". The aforementioned cycloalkylene groups with 5 to 15 carbon atoms may also contain alkyl groups as branched chains. Specific examples of cycloalkylene groups include: cyclopentylene (5 carbon atoms), cyclohexylene (6 carbon atoms), 3-methylcyclohexylene (7 carbon atoms), 4-methylcyclohexylene (7 carbon atoms), 3,3,5-trimethylcyclohexylene (9 carbon atoms), cycloheptanylene (7 carbon atoms), and cyclododecylene (12 carbon atoms), etc.

[0037] The aforementioned divalent organic groups containing straight-chain, branched-chain, or cyclic aliphatic groups are preferably divalent organic groups containing straight-chain or branched-chain aliphatic groups with 1 to 30 carbon atoms, or cyclic aliphatic groups with 4 to 30 carbon atoms. Furthermore, it is particularly preferred to be a hydrocarbon group containing a straight-chain or branched-chain divalent aliphatic group with 2 to 20 carbon atoms, or cyclic divalent aliphatic groups with 4 to 20 carbon atoms, wherein the hydrocarbon group may also contain halogen atoms such as fluorine atoms. More preferably, it is a straight-chain or branched-chain divalent aliphatic saturated hydrocarbon group with 2 to 20 carbon atoms, or cyclic divalent aliphatic saturated hydrocarbon group with 4 to 20 carbon atoms; especially preferably, it is a straight-chain or branched-chain divalent aliphatic hydrocarbon group with 6 to 20 carbon atoms, or cyclic divalent aliphatic hydrocarbon group with 6 to 20 carbon atoms, wherein the aliphatic hydrocarbon group may also contain halogen atoms such as fluorine atoms. The aforementioned divalent organogroups containing linear, branched, or cyclic aliphatic groups can be specifically listed as follows: methylene, 1,2-epenylethyl, 1,3-epenylpropyl, 1,4-epenylbutyl, 1,5-epenylpentyl, 1,6-epenylhexyl, 1,7-epenylheptyl, 1,8-epenyloctyl, 1,9-epenylnonyl, bis(1,4-epenylcyclohexyl)methylene, trans-1,4-cyclohexane-diyl, cis-1,4-cyclohexane-diyl, cyclohexane-1 ,4-Dimethyl, bicyclo[2.2.1]heptane-2,5-dimethyl, bicyclo[2.2.1]heptane-2,6-dimethyl, bicyclo[2.2.2]octane-1,4-diyl, decahydronaphthalene-1,4-diyl, tricyclo[5.2.1.0]decane-3,8-dimethyl, adamantane-1,3-diyl, isopropylidene dicyclohexane-4,4'-diyl, hexafluoroisopropylidene dicyclohexane-4,4'-diyl, etc. Among them, those with an alicyclic skeleton include trans-1,4-cyclohexane-diyl, cis-1,4-cyclohexane-diyl, cyclohexane-1,4-dimethyl, bicyclo[2.2.1]heptane-2,5-dimethyl, bicyclo[2.2.1]heptane-2,6-dimethyl, bicyclo[2.2.2]octane-1,4-diyl, decahydronaphthalene-1,4-diyl, tricyclo[5.2.1.0]decane-3,8-dimethyl, and adamantane-1 3-diyl, isopropylidene dicyclohexane-4,4'-diyl, hexafluoroisopropylidene dicyclohexane-4,4'-diyl, etc., are preferred because the charge mobility of the electronic states formed in the substrate state by the diamine compound site and the trimellitic acid site of the tetracarboxylic dianhydride is reduced, and the light absorption end shifts from the visible region to the ultraviolet region. Therefore, polyimides with high light transmittance in the visible region and low refractive index can be obtained. Among them, trans-1,4-cyclohexane-diyl and cis-1,4-cyclohexane-diyl are particularly preferred.

[0038] If the polyimide of the present invention contains the repeating unit shown in the above general formula (1), it may also have other skeletons without impairing the effect of the present invention. It may have repeating units, for example, as shown in the following general formula (6). In the formula, W represents a tetravalent organic group (except for the tetravalent group shown in the general formula (7) below), and A is defined in the same way as in the general formula (1). In the formula, R1 and n are defined in the same way as in general formula (1), and * indicates the position of the bond.

[0039] The tetravalent organic group of W in the repeating unit shown in general formula (6) is preferably one or more of the structures shown in general formula (8), general formula (10), or general formula (11). In the formula, V represents a direct bond, oxygen atom, sulfur atom, sulfonyl (-SO2-), carbonyl (-CO-), acetamyl (-NHCO-), ester (-OCO-), alkylene with 1 to 15 carbon atoms, fluorinated alkylene with 2 to 15 carbon atoms, cycloalkylene with 5 to 15 carbon atoms, phenylene, fumonisin, or a divalent group as shown in the following general formula (9), a represents 0 or 1, and * represents the bond position. In the formula, R3 independently represents a straight-chain or branched alkyl group with 1 to 6 carbon atoms, a cyclic alkyl group with 5 or 6 carbon atoms, a straight-chain or branched alkoxy group with 1 to 6 carbon atoms, a cyclic alkoxy group with 5 or 6 carbon atoms, an aryl group with 6 to 8 carbon atoms, an aryloxy group with 6 to 8 carbon atoms, a straight-chain or branched haloalkyl group with 1 to 6 carbon atoms, or a halogen atom; U represents a direct bond, an oxygen atom, a sulfur atom, a sulfonyl group (-SO2-), a carbonyl group (-CO-), an amino group (-NHCO-), an ester group (-OCO-), an alkylene group with 1 to 15 carbon atoms, a fluorinated alkylene group with 2 to 15 carbon atoms, a cycloalkylene group with 5 to 15 carbon atoms, a phenyl group, or a fumonisin; b independently represents an integer from 0 to 4; c, d, e, and f independently represent 0 or 1; and * represents the bond position. In the formula, R4 independently represents a hydrogen atom or a methyl group, R5 independently represents a direct bond or an alkyl group with 1 to 3 carbon atoms, and * indicates the bond position. In general formula (10), R5 is preferably a direct bond. In the formula, R6 represents a double bond or a tetravalent aliphatic group that may contain a carbonyl group, and * indicates the bond position. The double bond in general formula (11) may be a tetravalent aliphatic group containing a carbonyl group, preferably a tetravalent aliphatic group with 3 to 20 carbon atoms in the double bond or containing a carbonyl group. Specifically, examples of groups represented by the following structural formulas can be listed. In the formula, * indicates the location of the bond.

[0040] When the polyimide of the present invention has repeating units other than those shown in general formula (1), the content of the repeating units shown in general formula (1) is preferably 15 mol% or more of the total polyimide, more preferably 50 mol% or more, even more preferably 70 mol% or more, and particularly preferably 90 mol% or more. Furthermore, the repeating units of the above general formula (1) can be arranged regularly or exist randomly in the polyimide. When the repeating unit shown in general formula (1) is the same as the repeating unit shown in general formula (2), (3) or (4), the total is the same range of moles %. When there are two or more repeating units selected from the repeating units shown in general formula (2), (3) or (4), the total is the same range of moles %.

[0041] The polyimide of this invention, as determined by thermogravimetric analysis, has a thermal decomposition temperature (Td) of 350°C or higher when the residue weight percentage is 95% based on the weight at 100°C. It exhibits high thermal stability and sufficiently meets the heat resistance requirements of polyimide resins. This 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.

[0042] The method for manufacturing the polyimide of the present invention is not particularly limited. For example, it can be manufactured by the following steps: reacting a tetracarboxylic acid dianhydride of the following general formula (12) with a substance of a diamine compound of the following general formula (13) in an isomolar manner to obtain a precursor (polyamide) of the polyimide of the following general formula (14); and imidizing the polyimide precursor. R1 and n in general formula (12) and general formula (14), and A in general formula (13) and general formula (14), are the same as those defined in general formula (1).

[0043] A specific example is the manufacturing method of a tetracarboxylic acid dianhydride represented by the above general formula (12) being isosorbide-bis(triphenylamine) (compound (a)) and a diamine compound represented by the above general formula (13) being 1,4-diaminocyclohexane (compound (b)). The reaction formula is shown below. Compound (a) and compound (b) are polymerized to obtain a polyimide precursor (polyamide) having the following repeating unit (compound (c)), and then imidized to obtain the polyimide (compound (d)) having the following repeating unit as the target.

[0044] The tetracarboxylic acid dianhydride shown in general formula (12) can be manufactured by conventionally known methods, and there is no limitation to the manufacturing method. For example, it can be manufactured by reacting isosorbide, dehydrated mannitol, isotretinoin dihydrohexitol with trimellitic anhydride such as chlorinated trimellitic anhydride, as shown in the following reaction formula. The R1 and n series in general formulas (15) and (12) are defined in the same way as in general formula (1).

[0045] The R1 and n series in general formula (12) are defined in the same way as in general formula (1), and the better mode is also the same. The tetracarboxylic acid dianhydrides represented by general formula (12) can be specifically listed as compounds represented by formulas (i) to (iii) below. The compound represented by formula (i) is isosorbitol-bis(triphenyltrihydric anhydride), the compound represented by formula (ii) is iso-idolitol-bis(triphenyltrihydric anhydride), and the compound represented by formula (iii) is dehydromannitol-bis(triphenyltrihydric anhydride). These compounds are sometimes referred to as compound (i), compound (ii), and compound (iii) respectively. Of these, the compound represented by formula (i) is particularly preferred. In the method for manufacturing polyimide of the present invention, the tetracarboxylic acid dianhydride shown in general formula (12) may be used only one type or in combination with two or more types.

[0046] The A series in general formula (13) is defined in the same way as in general formula (1), and the preferred mode is also the same. When A in general formula (13) is a divalent organic group containing an aromatic ring, the diamine compound shown in general formula (13) is a diamine compound containing an aromatic ring. The diamine compound containing an aromatic ring preferably has a divalent group shown in general formula (5). Specifically, when p in general formula (5) is 0, examples include: p-phenylenediamine (PPD), m-phenylenediamine (MPD), 2,4-diaminotoluene, 2,5-diaminotoluene, 2,4-diaminoxylene, 1,4-diaminobenzene, 1,4-diamino-2-phenylbenzene, 1,3-diamino-4-phenylbenzene, 1,3-diamino-5-phenylbenzene, 5-trifluoromethyl-1,3-phenylenediamine (TFMPD), and other diaminobenzenes; 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,7-diaminonaphthalene, and other diaminonaphthalenes. Preferred ingredients include m-phenylenediamine (MPD), 2,4-diaminotoluene, 2,4-diaminoxylene, 1,3-diamino-4-phenylbenzene, 1,3-diamino-5-phenylbenzene, and 5-trifluoromethyl-1,3-phenylenediamine (TFMPD), with m-phenylenediamine (MPD) and 5-trifluoromethyl-1,3-phenylenediamine (TFMPD) being particularly preferred. When p in general formula (5) is 1, examples include: 2,2'-diaminobiphenyl, 3,3'-diaminobiphenyl, 4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (2,2'-bis(trifluoromethyl)benzidine; TFDB), etc., which are diaminobiphenyl derivatives; 3,3'-diaminobiphenyl Diaminodiphenyl ethers such as phenyl ether, 3,4'-diaminodiphenyl ether, and 4,4'-diaminodiphenyl ether; diaminodiphenyl sulfides such as 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, and 4,4'-diaminodiphenyl sulfide; diaminodiphenyl sulfides such as 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, and 4,4'-diaminodiphenyl sulfone; 3 Diaminodiphenyl ketones such as 3'-diaminodiphenyl ketone, 3,4'-diaminodiphenyl ketone, and 4,4'-diaminodiphenyl ketone; 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 and 2,2-bis(4-aminophenyl) Diaminophenyl hexafluoropropanes such as 1,1-bis(4-aminophenyl)cyclohexane; diaminophenyl cycloalkanes such as 4,4"-diamino-p-triphenyl and 4,4"-diamino-meta-triphenyl; and diaminophenyl derivatives such as 9,9-bis(4-aminophenyl)furan and 9,9-bis(4-amino-3-fluorophenyl)furan. Among the diamine compounds represented by general formula (13), 2,2'-bis(trifluoromethyl)benzidine (TFDB) and 5-trifluoromethyl-1,3-phenylenediamine (TFMPD) are preferred.

[0047] When A in general formula (13) is a divalent organic group containing a straight-chain, branched-chain, or cyclic aliphatic group, the diamine compound shown in general formula (13) is a diamine compound having a straight-chain, branched-chain, or cyclic aliphatic group. Such diamine compounds can be specifically listed as follows: 1,2-ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 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-naphthyldiamine, 3,8-bis(aminomethyl)tricyclo[5.2.1.0] Decane, 1,3-diaminocyclohexyl propane, 2,2-bis(4-aminocyclohexyl)propane, 2,2-bis(4-aminocyclohexyl)hexafluoropropane. Preferred compounds include diamine compounds with an alicyclic skeleton such as 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-naphthyldiamine, 3,8-bis(aminomethyl)tricyclo[5.2.1.0]decane, 1,3-diaminocyclohexane, 2,2-bis(4-aminocyclohexyl)propane, and 2,2-bis(4-aminocyclohexyl)hexafluoropropane, with trans-1,4-diaminocyclohexane and cis-1,4-diaminocyclohexane being particularly preferred. The diamine compound shown in general formula (13) may be used with only one or with two or more compounds.

[0048] The polyimide of the present invention further includes the repeating unit shown in general formula (6). In addition to the tetracarboxylic acid dianhydride shown in general formula (12), the polyimide can be manufactured by using an acid dianhydride other than the tetracarboxylic acid dianhydride shown in general formula (12) as a monomer for polyimide.

[0049] The tetracarboxylic dianhydride used as a monomer for polyimide, other than the tetracarboxylic dianhydride shown in general formula (12), is preferably the tetracarboxylic dianhydride shown in general formulas (16) to (18) described below. The tetracarboxylic acid dianhydride shown in general formula (16) is a compound represented by the following structural formula. In the formula, V and a are defined in the same way as in general formula (8). Specifically, when a is 0, the tetracarboxylic acid dianhydride is pyrocalcite dianhydride.When 'a' is 1, specific examples include: 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 3,3',4,4'-diphenylsulfide tetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfide tetracarboxylic dianhydride, 3,3',4,4'-diphenylketone tetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)bis(phthalic acid) dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)phthalic anhydride, 1,3-bis(3,4-dicarboxyphenoxy)phthalic anhydride, 4,4'-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)-3,3'-dimethylbiphenyl dianhydride, bis[4-(3,4-dicarboxyphenoxy) [4,4-(3,4-dicarboxyphenoxy)phenyl] ether dianhydride, bis[4-(3,4-dicarboxyphenoxy)phenyl] cyclohexane 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] dianhydride, hydroquinone-bis(triphenyltrihydride), resorcinol-bis(triphenyltrihydride), 1 5-Dihydroxynaphthalene-bis(triphenyltrihydric anhydride), 2,6-Dihydroxynaphthalene-bis(triphenyltrihydric anhydride), 2,7-Dihydroxynaphthalene-bis(triphenyltrihydric anhydride), 4,4'-Dihydroxybiphenyl-bis(triphenyltrihydric anhydride), 4,4'-Dihydroxy-3,3'-dimethylbiphenyl-bis(triphenyltrihydric anhydride), 4,4'-Dihydroxy-3,3',5,5'-tetramethylbiphenyl-bis(triphenyltrihydric anhydride), 4,4'-Dihydroxy-2,2',3,3',5,5'-hexamethylbiphenyl-bis(triphenyltrihydric anhydride), 4,4'-Dihydroxydiphenyl ether-bis(triphenyltrihydric anhydride), 4,4'-Dihydroxydiphenyl sulfide-bis(triphenyltrihydric anhydride), 4,4'-Dihydroxydiphenyl sulfide-bis(triphenyltrihydric anhydride), 4,4'-di ... Hydroxydiphenyl ketone-bis(triphenyltrihydric anhydride), 1,1'-bis(4-hydroxyphenyl)ethane-bis(triphenyltrihydric anhydride), 2,2'-bis(4-hydroxyphenyl)propane-bis(triphenyltrihydric anhydride), 2,2'-bis(4-hydroxy-3-methylphenyl)propane-bis(triphenyltrihydric anhydride), 2,2'-bis(4-hydroxyphenyl)hexafluoropropane-bis(triphenyltrihydric anhydride), 1,1'-bis(4-hydroxyphenyl)cyclohexane-bis(triphenyltrihydric anhydride), 1,1'-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane-bis(triphenyltrihydric anhydride), 1,1'-bis(4-hydroxyphenyl)cyclodecane-bis(triphenyltrihydric anhydride), 9,9'-bis(4-hydroxy-3-methylphenyl)furan-bis(triphenyltrihydric anhydride).

[0050] The tetracarboxylic acid dianhydride shown in general formula (17) is a compound represented by the following structural formula. In the formula, R4 and R5 are defined in the same way as in general formula (10). Regarding the tetracarboxylic dianhydrides represented by general formula (17), when R5 is a direct bond, examples include: cyclobutane-1,2,3,4-tetracarboxylic dianhydride, 1,3-dimethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride, and 1,2,3,4-tetramethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride. Furthermore, when one of R5 is a direct bond and the other is an alkyl group having 1 to 3 carbon atoms, examples include: cyclopentane-1,2,3,4-tetracarboxylic dianhydride and cyclohexane-1,2,3,4-tetracarboxylic dianhydride. Furthermore, when R5 is an alkyl group having 1 to 3 carbon atoms, examples include: cyclohexane-1,2,4,5-tetracarboxylic dianhydride. Among them, R5 is preferably a directly bonded cyclobutane-1,2,3,4-tetracarboxylic dianhydride, 1,3-dimethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride, or 1,2,3,4-tetramethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride.

[0051] The tetracarboxylic acid dianhydride shown in general formula (18) is a compound represented by the following structural formula. In the formula, R6 is defined in the same way as in general formula (11). The tetracarboxylic acid dianhydride represented by general formula (18) can be specifically listed as, for example, compounds represented by the following structural formulas, preferably of this type.

[0052] Other tetracarboxylic dianhydrides used as monomers for polyimides besides the tetracarboxylic dianhydride shown in general formula (12) may be used alone or in combination with two or more.

[0053] In the manufacture of the polyimide of the present invention, the amount of diamine compound used (total moles) is preferably 0.94 moles or more, more preferably 0.96 moles or more, even more preferably 0.98 moles or more, and particularly preferably 0.99 moles or more when the total mole amount of tetracarboxylic dianhydride compound is 1 mole. The upper limit is preferably 1.20 moles or less, more preferably 1.10 moles or less, even more preferably 1.05 moles or less, and particularly preferably 1.02 moles or less.

[0054] The following describes specific examples of the polymerization reaction method used to manufacture the polyimide of the present invention. First, the diamine compound is dissolved in a polymerization solvent. Then, tetracarboxylic dianhydride is slowly added to this solution, and stirring is performed using a mechanical stirrer at a temperature ranging from 0 to 100°C, preferably 20 to 60°C, for 0.5 to 150 hours, more preferably 1 to 72 hours. The monomer concentration at this time is typically in the range of 5 to 50% by weight, preferably 10 to 40% by weight. By polymerizing within this monomer concentration range, a homogeneous polyimide precursor (polyamide) with a high degree of polymerization can be obtained. If the degree of polymerization of the polyimide precursor (polyamide) increases excessively, making it difficult to stir the polymerization solution, it can be appropriately diluted using the same solvent. By polymerizing within the above-mentioned monomer concentration range, the degree of polymerization of the polymer is sufficiently increased, and the solubility of both the monomer and the polymer is adequately ensured. When polymerization is carried out at concentrations below the above range, the degree of polymerization of the polyimide precursor (polyamide) is sometimes not sufficiently increased. In addition, when polymerization is carried out at concentrations above the above monomer concentration range, the dissolution of the monomer or the resulting polymer is sometimes insufficient.

[0055] Solvents used in the polymerization of polyimide precursors (polyamide) are preferably aprotic solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and dimethyl sulfoxide. Any solvent can be used without problems as long as it can dissolve the raw monomer, the resulting polyimide precursor (polyamide), and the imidized polyimide. There are no particular limitations on the structure or type of the solvent. Specifically, examples include: acetamide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; ester solvents such as γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone, α-methyl-γ-butyrolactone, butyl acetate, ethyl acetate, and isobutyl acetate; carbonate solvents such as ethyl carbonate and propyl carbonate; diol solvents such as diethylene glycol dimethyl ether, triethylene glycol, and triethylene glycol dimethyl ether; phenol solvents such as phenol, m-cresol, p-cresol, o-cresol, 3-chlorophenol, and 4-chlorophenol; ketone solvents such as cyclopentanone, cyclohexanone, acetone, butanone, diisobutyl ketone, and methyl isobutyl ketone; and ether solvents such as tetrahydrofuran, 1,4-dioxane, dimethoxyethane, diethoxyethane, and dibutyl ether. Other general-purpose solvents may also be used: 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, turpentine, mineral concentrates, petroleum hydrocarbon solvents, etc. Two or more of these solvents may also be mixed for use.

[0056] In the polymerization reaction during the manufacture of the polyimide of this invention, a siliconeizing agent may be used to prevent the aggregates of raw materials or the insolubility (gelation) of the products. There are no particular limitations on the siliconeizing agents that can be used; examples include N,O-bis(trimethylsilyl)acetamide and N,O-bis(trimethylsilyl)trifluoroacetamide.

[0057] Next, the imidization method of the obtained polyimide precursor (polyamide) will be described. Imidination can be performed using generally known imidination methods, such as: "thermal imidination" which involves thermally closing the ring of a polyimide precursor (polyamide) film; "solution thermal imidination" which involves closing the ring of a polyimide precursor (polyamide) solution at high temperature; and "chemical imidization" which uses a dehydrating agent. Specifically, in the "thermal imidization method", a polyimide precursor (polyacrylic acid) solution is poured onto a substrate or the like and dried at 50 to 200°C, preferably 60 to 150°C, to form a polyimide precursor (polyacrylic acid) film. Then, 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 perform thermal dehydration and ring closure, thereby ending the imidization process and obtaining the polyimide of the present invention. Furthermore, in the "solution thermal imidization method," a polyimide precursor (polyacrylic acid) solution containing an alkaline catalyst is heated at 100 to 250°C, preferably 150 to 220°C, for 0.5 to 12 hours in the presence of an azeotropic agent such as xylene. This removes the byproduct water from the system, thus ending the imidization process and yielding the polyimide solution of the present invention. Alternatively, the polyimide precursor (polyacrylic acid) solution is heated in an amide solvent such as N,N-dimethylacetamide, N-methyl-2-pyrrolidone, or 1,3-dimethyl-2-imidazolidineone under a nitrogen gas flow at 150 to 220°C, preferably 165 to 205°C, for 0.5 to 2 hours. This partially removes the byproduct water from the system, thus ending the imidization process and yielding the polyimide solution of the present invention. In the "chemical imidization method," a polyimide precursor (polyamide) solution, adjusted to a suitable solution viscosity for easy stirring, is stirred using a mechanical stirrer or similar device. Simultaneously, a dehydrating ring-closing agent (chemical imidizing agent) composed of an anhydride of an organic acid and an amine acting as a basic catalyst is added dropwise. The mixture is stirred at 0 to 100°C, preferably 10 to 50°C, for 1 to 72 hours, thereby chemically completing the imidization. There are no particular limitations on the organic acid anhydride that can be used in this process; examples include acetic anhydride and propionic anhydride. Acetic anhydride is suitable for ease of reagent handling and purification. Furthermore, pyridine, triethylamine, and quinoline can be used as the basic catalyst. Pyridine is suitable for ease of reagent handling and separation, but the method is not limited to these. The amount of organic acid anhydride in the chemical imidizing agent is in the range of 1 to 10 moles of the theoretical dehydration amount of the polyimide precursor (polyamide), preferably in the range of 1 to 5 moles. In addition, the amount of alkaline catalyst is in the range of 0.1 to 2 moles relative to the amount of organic acid anhydride, preferably in the range of 0.1 to 1 mole.

[0058] In the "solution thermal imidization method" or "chemical imidization method," components such as catalysts or chemical imidizing agents, and carboxylic acids from byproducts (hereinafter referred to as impurities) are mixed into the reaction solution. These can be removed and the solution purified. Purification can be performed using generally known methods. For example, the simplest method involves stirring the imidized reaction solution while simultaneously adding a large amount of a poor solvent to precipitate polyimide. The polyimide powder is then recovered and the washing process is repeated until the impurities are removed. Suitable poor solvents for this method include water, methanol, ethanol, isopropanol, and other alcohols that precipitate polyimide, effectively remove impurities, and are easy to dry. Mixtures of these solvents can also be used. When the concentration of the polyimide solution during precipitation is too high due to the addition of a poor solvent, the precipitated polyimide may form granules, with impurities remaining in the coarse particles. There is also a concern that dissolving the resulting polyimide powder in the solvent may take a longer time. On the other hand, if the concentration of the polyimide solution is too low, a large amount of poor solvent is required, leading to an increased environmental burden from waste solvent disposal or higher manufacturing costs, which is undesirable. Therefore, the concentration of the polyimide solution when adding the poor solvent should be 20% by weight or less, preferably 10% by weight or less. In this case, the amount of poor solvent used should preferably be at least equal to, and 1.5 to 3 times, the amount of the polyimide solution. The obtained polyimide powder is recovered and residual solvent is removed by vacuum drying or hot air drying to obtain the polyimide of the present invention. There are no particular restrictions on the drying temperature and time, as long as the temperature will not cause the polyimide to deteriorate and the residual solvent will not decompose. It is preferred to dry for less than 48 hours in the temperature range of 30 to 200°C.

[0059] The intrinsic viscosity of the polyimide of the present invention is preferably in the range of 0.1 to 10.0 dl / g, and more preferably in the range of 0.2 to 5.0 dl / g. The polyimide of this invention is soluble in various organic solvents, thus it can be used to make polyimide varnishes. The organic solvent can be appropriately selected according to the intended use or processing conditions of the varnish. While not particularly limited, examples of amide solvents that can be used include: N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; and dimethyl sulfoxide, etc. From a solubility point of view, amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone are preferred. Two or more of these solvents can also be mixed for use.

[0060] The solids concentration when dissolving the polyimide of the present invention in a solvent to form a varnish varies depending on the molecular weight of the polyimide, the manufacturing method, or the processed product, but is preferably 5% by weight or more. If the solids concentration is too low, it is difficult to process to a sufficient film thickness; conversely, if the solids concentration is too high, the solution viscosity becomes too high, raising concerns about processing difficulties. A method for dissolving the polyimide contained in the melt-processing material of the present invention in a solvent is, for example, to add the polyimide powder contained in the melt-processing material of the present invention while stirring the solvent, and dissolve it in air or an inert gas at a temperature ranging from room temperature to below the boiling point of the solvent for 1 to 48 hours to form a polyimide solution (varnish). The obtained polyimide solution can be shaped into various forms using generally known methods. For example, when forming a film, the polyimide solution can be poured onto a support such as a glass substrate using a scraper, and then dried using a hot air dryer, infrared drying oven, vacuum dryer, inert gas oven, etc., typically in the range of 40 to 350°C, preferably in the range of 50 to 250°C.

[0061] The polyimide of this invention can be used in, for example: transparent substrates or cover films 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, etc.; optical film materials (e.g., light guide plates, polarizing plates, polarizing plate protective films, phase difference films, light diffusion films, viewing angle expansion films, reflective films, anti-reflective films, anti-glare films, brightness enhancement films, prisms, light guide films), insulating materials for electronic components, passivation films, buffer coating films, interlayer insulating films, etc. in semiconductor devices, flexible printed circuit boards, metal-clad laminates, etc., wiring board materials, wire coating materials for aircraft, motors, and generators, etc., light-emitting materials or light sensor materials for organic EL devices, materials for photoradar, materials for 3D displays, etc. [Example]

[0062] The present invention will be described in more detail below by way of examples, but the present invention is not limited to these examples. The analytical methods in this invention are described below.

[0063] <Analytical Methods> 1. Infrared absorption spectrum The infrared absorption spectra of polyimide films were determined using an FT / IR4200 Fourier transform infrared spectrophotometer (manufactured by Japan Spectrophotometer Co., Ltd.), and the ATR (Attenuated Total Reflection) method with a Ge prism was employed to measure the polyimide film sample (15 μm thick).

[0064] 2. 1H-NMR spectrum The 1H-NMR spectra of polyimide films were determined using a JNM.ECP400 Fourier transform nuclear magnetic resonance spectrometer (manufactured by JEOL). The polyimide film sample was partially dissolved in dimethyl deuteride (DMSO-d6) and the measurements were performed. The chemical shift reference system was TMS (tetramethylsilane).

[0065] 3. Glass transition temperature: Tg The glass transition temperature of the polyimide film was determined using a TMA60 thermomechanical analyzer (manufactured by Shimadzu Corporation). The sample was made with a width of 5 mm and a length of 10 mm, and the load was set to 5 g. The temperature was temporarily increased to 150 °C at 10 °C / min (first heating), then cooled to 20 °C, and then increased again at 10 °C / min (second heating). The temperature was determined by the tangent method of the TMA curve at the second heating (the intersection of the tangent in the glass state and the tangent after Tg).

[0066] 4. Average linear coefficient of thermal expansion: CTE (Coefficient of Thermal Expansion) The average linear coefficient of thermal expansion of the polyimide film was determined using a TMA60 thermomechanical analysis apparatus (manufactured by Shimadzu Corporation). The sample was made with a width of 5 mm and a length of 10 mm, and a load of 5 g. The temperature was temporarily increased to 150 °C at a rate of 10 °C / min (first heating), then cooled to 20 °C, and then increased again at a rate of 10 °C / min (second heating). The linear coefficient of thermal expansion was calculated from the TMA curve at the second heating. The average value between 80 and 200 °C was used.

[0067] 5. Thermal decomposition temperature (nitrogen atmosphere): Td The thermal decomposition temperature of polyimide film was determined using a TG-DTA60 thermogravimetric analyzer (manufactured by Shimadzu Corporation) under nitrogen atmosphere. The temperature at which the residue weight percentage, based on the weight at 100°C, reaches 95% was measured during a heating process. A higher value indicates higher thermal stability.

[0068] 6. Ultraviolet and visible light transmittance The light transmittance of polyimide films in the ultraviolet and visible regions was measured using a V-670 UV / Vis spectrophotometer (manufactured by Nippon Spectrophotometer Co., Ltd.) within the wavelength range of 250 to 800 nm on polyimide film samples deposited on a quartz substrate. A Glan-Taylor polarizer with high polarization in the ultraviolet-visible region was inserted into the measured optical path to generate p-polarized light. The sample was tilted at a Brewster angle (approximately 60 degrees) relative to the optical path to minimize the influence of multiple reflections on the film surface.

[0069] 7. Mean refractive index: nav and birefringence: Δn The refractive index of the polyimide film was measured using a PC-2010 prism coupler (manufactured by Metricon) at wavelengths of 636 nm, 845 nm, 1310 nm, and 1558 nm on polyimide film samples deposited on a silicon substrate. A half-wavelength plate corresponding to each wavelength was inserted into the optical path to rotate the linear polarizing surface of the laser light, and the refractive index was measured in the direction parallel to the film surface (nTE) and in the direction perpendicular to the film surface (film thickness direction) (nTM). From these refractive indices, the average refractive index (nav² = (2nTE² + nTM²) / 3) and birefringence (Δn = nTE - nTM) of the polyimide film were calculated.

[0070] 8. Dielectric constant (estimated value): εref The dielectric constant (estimated value) of the polyimide film is calculated based on the average refractive index nav at a wavelength of 1310 nm, using (εref = 1.1 × nav 2).

[0071] 9. Dielectric constant and dielectric loss tangent (measured values) The dielectric constant and dielectric loss tangent of the polyimide film were measured at frequencies of 10 GHz and 20 GHz using a VNA network analyzer MS46122B (Anritsu) and a cavity resonator (10 GHz, 20 GHz) (AET) in TE mode. Furthermore, the measurements were performed after the polyimide film was dried at 120°C for 2 hours and then conditioned for 24 hours at 23°C ± 1°C and 50% RH ± 5%.

[0072] 10. Circular polarization diachromaticity: CD The circular polarization dichroism (CD) of polyimide films was measured using a J-1000 circular dichroism dispersant (manufactured by Japan Spectrophotometer Co., Ltd.) within a wavelength range of 190 to 500 nm on polyimide film samples deposited on a quartz substrate.

[0073] 11. Solubility Test The solubility of polyimide film in solvents was assessed by loading 9.9 g (1 wt% solids concentration) of the solvent listed in Table 3, relative to 0.1 g of the polyimide film, into a glass sample tube. The tube was then stirred for 60 minutes using a test tube mixer, and the dissolution status was visually confirmed. The solvents used were N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), and γ-butyrolactone (GBL). The evaluation results were categorized as follows: "++" for dissolution at room temperature, "+" for dissolution upon heating and maintaining homogeneity even after cooling to room temperature, "±" for swelling / partial dissolution, and "-" for insolubility. These results are presented in Table 3.

[0074] <Synthetic Example 1> Synthesis of compound (i) (isosorbitol-bis(triphenyltrihydric anhydride)) Isosorbide and 30 times the amount of anhydrous dichloromethane were added to a four-necked flask equipped with a thermometer, stirrer, and cooling tube. While stirring the mixture to dissolve it, triethylamine was added at a ratio of 1.1 moles to isosorbide. Then trimellitic anhydride chloride at a ratio of 2.1 moles to isosorbide was added, and the mixture was stirred at 0°C for 20 hours. The precipitate was filtered off, and the filtrate was slowly added dropwise to 30 times its volume of petroleum ether to obtain a white solid. The white solid obtained by filtration was dried at 80°C under reduced pressure. The white solid obtained was dissolved in dimethyl deuteride (DMSO-d6) and analyzed by 1H-NMR to identify compound (i) as the target compound.

[0075] <Synthetic Example 2> Synthesis of compound (iii) (dehydrated mannitol-bis(triphenyltrihydric anhydride)) Dehydrated mannitol and 38 times the amount of anhydrous dimethylacetamide were added to a four-necked flask equipped with a thermometer, stirrer, and cooling tube. While stirring the mixture to dissolve it, triethylamine was added at a ratio of 1.1 moles to dehydrated mannitol. Then trimellitic anhydride chloride at a ratio of 2.1 moles to dehydrated mannitol was added, and the mixture was stirred at 20°C for 28 hours. The precipitate was filtered off, and the filtrate was slowly added dropwise to 38 times its volume of petroleum ether to obtain a white solid. The white solid obtained was filtered off and dried at 80°C under reduced pressure. The white solid obtained was dissolved in deuterated chloroform (CDCl3) and analyzed by 1H-NMR to identify it as compound (iii) of the target compound.

[0076] <Example 1> In 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 dissolved in 12.6 g of dehydrated N,N-dimethylacetamide (DMAc) in a covered glass container. The solution was then mixed in several portions with 2.472 g (5 mmol) of compound (i) synthesized according to <Synthesis Example 1> while stirring with a magnetic stirrer. The mixture was then stirred at room temperature for 12 hours to obtain a polyamide solution (solids concentration 18.0 wt%), which is a polyimide precursor. This polyamide solution was spread on a silicon substrate or fused silica substrate mounted on a spin coater to form a film by spin coating, and the entire film, including the substrate, was transferred to a heating furnace (inert gas oven). The film was then dried at 70°C for 50 minutes under a nitrogen atmosphere, followed by a heating rate of 3°C / min to 280°C, held at 280°C for 90 minutes, and then allowed to cool naturally to room temperature. A colorless and transparent polyimide film was obtained by peeling it off from the substrate. Polyimide films prepared for optical measurements (light transmittance, refractive index, circular polarization dichroism) were used for these measurements without being peeled off from the substrate. The obtained polyimide films were stored in a desiccator. The structural formula of the polyimide from Example 1 is shown below.

[0077] <Example 2> In 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 covered glass container. The solution was then mixed in several portions with 2.472 g (5 mmol) of compound (i) while stirring with a magnetic stirrer. The mixture was then stirred at room temperature for 12 hours to obtain a polyamide solution (solids concentration 24.0 wt%), which is a polyimide precursor. This polyamide solution was spread on a silicon substrate or fused silica substrate mounted on a spin coater to form a film, and the entire film, including the substrate, was transferred to a heating furnace. The film was then dried at 70°C for 50 minutes under a nitrogen atmosphere, followed by a heating rate of 3°C / min to 280°C, held at 280°C for 90 minutes, and then allowed to cool naturally to room temperature. A colorless and transparent polyimide film was obtained by peeling it off from the substrate. The polyimide film prepared for optical measurements (light transmittance, refractive index, circular polarization dichroism) was used for these measurements without being peeled off from the substrate. The obtained polyimide film was stored in a desiccator. The structural formula of the polyimide in Example 2 is shown below.

[0078] <Example 3> Under 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 covered glass container. Compound (i) 2.472 g (5 mmol) was mixed in several portions while stirring with a magnetic stirrer. The mixture was then stirred at room temperature for 12 hours to obtain a polyamide solution (solids concentration 18.0 wt%), which is a polyimide precursor. This polyamide solution was spread on a silicon substrate or fused silica substrate mounted on a spin coater to form a film by spin coating. The entire film, including the substrate, was then transferred to a heating furnace. The film was dried at 70°C for 50 minutes under a nitrogen atmosphere, followed by a heating rate of 3°C / min to 280°C, held at 280°C for 90 minutes, and then allowed to cool naturally to room temperature. A pale yellow polyimide film was obtained by peeling it off from the substrate. A polyimide film prepared for optical measurements (light transmittance, refractive index, circular polarization dichroism) was used for these measurements without being peeled off from the substrate. The obtained polyimide film was stored in a desiccator. The structural formula of the polyimide in Example 3 is shown below.

[0079] Example 4: Compound (i): Compound (iii) = 9:1 (Mohr's ratio) Under nitrogen atmosphere, in a covered glass container, 1.60 g (5 mmol) of 2,2'-bis(trifluoromethyl)benzidine (TFDB) was dissolved in 12.9 g of dehydrated N,N-dimethylacetamide (DMAc), and 0.247 g (0.5 mmol) of compound (iii) was mixed in while stirring with a magnetic stirrer. The mixture was then stirred at room temperature for 6 hours, and compound (i) 0.225 g (4.5 mmol) was mixed in several portions while stirring with a magnetic stirrer. The mixture was then stirred at room temperature for 12 hours to obtain a polyamide solution (solids concentration 24.0 wt%), which is a polyimide precursor. This polyamide solution was spread on a silicon substrate or fused silica substrate placed in a spin coater, and a film was formed by spin coating. The entire film, including the substrate, was then transferred into a heating furnace. The film was then dried at 70°C for 50 minutes under a nitrogen atmosphere, followed by a heating rate of 3°C / min to 280°C, held at 280°C for 90 minutes, and then allowed to cool naturally to room temperature. A colorless, transparent polyimide film was obtained by peeling it off from the substrate. Polyimide films prepared for optical measurements (light transmittance, refractive index) were used for these measurements without being peeled off from the substrate. The obtained polyimide films were stored in a desiccator. The structural formula of the polyimide in Example 4 is shown below. The ratio of m to n in the following structural formula is 9:1.

[0080] Example 5: Compound (i): Compound (iii) = 8:2 (Mohr's ratio) Under nitrogen atmosphere, in a covered glass container, 1.60 g (5 mmol) of 2,2'-bis(trifluoromethyl)benzidine (TFDB) was dissolved in 12.9 g of dehydrated N,N-dimethylacetamide (DMAc), and 0.494 g (1 mmol) of compound (iii) was mixed in while stirring with a magnetic stirrer. The mixture was then stirred at room temperature for 6 hours, and compound (i) 1.977 g (4 mmol) was mixed in several portions while stirring with a magnetic stirrer. The mixture was then stirred at room temperature for 12 hours to obtain a polyamide solution (solids concentration 24.0 wt%), which is a polyimide precursor. This polyamide solution was spread on a silicon substrate or fused silica substrate placed in a spin coater, and a film was formed by spin coating. The entire film, including the substrate, was then transferred into a heating furnace. The film was then dried at 70°C for 50 minutes under a nitrogen atmosphere, followed by a heating rate of 3°C / min to 280°C, held at 280°C for 90 minutes, and then allowed to cool naturally to room temperature. A colorless, transparent polyimide film was obtained by peeling it off from the substrate. Polyimide films prepared for optical measurements (light transmittance, refractive index) were used for these measurements without being peeled off from the substrate. The obtained polyimide films were stored in a desiccator. Here, the structural formula of the polyimide in Example 5 is the same as that shown in Example 4, with a m:n ratio of 8:2.

[0081] <Example 6> Except for changing the molar ratio of compound (i) to compound (iii) in Example 4 to 7:3, polyimide was prepared by the same modulation method as in Example 4.

[0082] <Example 7> Except for changing the molar ratio of compound (i) to compound (iii) in Example 4 to 6:4, polyimide was prepared by the same modulation method as in Example 4.

[0083] <Example 8> Except for changing the molar ratio of compound (i) to compound (iii) in Example 4 to 5:5, polyimide was prepared by the same modulation method as in Example 4.

[0084] <Example 9> Under 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 covered glass container. Compound (i) 4.944 g (10 mmol) was mixed in several portions while stirring with a magnetic stirrer. The mixture was then stirred at room temperature for 12 hours to obtain a polyamide solution (solids concentration 24.0 wt%), which is a polyimide precursor. This polyamide solution was spread on a silicon substrate or fused silica substrate mounted on a spin coater to form a film by spin coating. The entire film, including the substrate, was then transferred to a heating furnace. The film was dried at 70°C for 50 minutes under a nitrogen atmosphere, followed by a heating rate of 3°C / min to 280°C, held at 280°C for 90 minutes, and then allowed to cool naturally to room temperature. A colorless and transparent polyimide film was obtained by peeling it off from the substrate. A polyimide film prepared for optical measurements (light transmittance, refractive index, circular polarization dichroism) was used for these measurements without being peeled off from the substrate. The obtained polyimide film was stored in a desiccator. The structural formula of the polyimide in Example 9 is shown below.

[0085] <Example 10> Under 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 covered glass container, and 4.944 g (10 mmol) of compound (i) was mixed in several portions while stirring with a magnetic stirrer. The mixture was then stirred at room temperature for 12 hours to obtain a polyamide solution (solids concentration 18.0 wt%), which is a polyimide precursor. This polyamide solution was spread on a silicon substrate or fused silica substrate mounted on a spin coater to form a film by spin coating, and the entire film, including the substrate, was transferred to a heating furnace. The film was then dried at 70°C for 50 minutes under a nitrogen atmosphere, followed by a heating rate of 3°C / min to 280°C, held at 280°C for 90 minutes, and then allowed to cool naturally to room temperature. A pale yellow polyimide film was obtained by peeling it off from the substrate. The polyimide film prepared for optical measurements (light transmittance, refractive index, circular polarization dichroism) was used for these measurements without being peeled off from the substrate. The obtained polyimide film was stored in a desiccator. The structural formula of the polyimide in Example 10 is shown below.

[0086] <Example 11> Except that 1,4-phenylenediamine (PPD) in Example 10 was replaced with its structural isomer 1,3-phenylenediamine (MPD), the polyimide was prepared using the same modulation method as in Example 10. The structural formula of the polyimide of Example 11 is shown below.

[0087] For the polyimide films of Examples 1 to 11, the physical properties evaluated as described below are summarized and presented in Tables 1 and 2 below. In Table 1, T400 (%) and T450 (%) represent the light transmittance (%) at wavelengths of 400 nm and 450 nm, respectively, and λ (T95%) represents the wavelength (nm) at which the light transmittance (%) becomes 95%.

[0088] [Table 1]

[0089] [Table 2]

[0090] <Confirmation of the end of the imine reaction> Figures 1 to 11 are Fourier transform ATR (attenuated total reflectance) infrared absorption spectra of the polyimide films (approximately 15 μm thick) obtained in Examples 1 to 11, respectively. In Figures 1 to 11, the peak near 1760 cm⁻¹ represents the symmetric stretching vibration of the two carbonyl carbons contained in the amide group, the peak near 1700 cm⁻¹ represents the asymmetric stretching vibration of the same carbonyl carbon, and the peak near 1370 cm⁻¹ represents the stretching vibration signal of the single bond between the amide ring nitrogen (N) and the carbon at position 1 of the benzene ring or the carbon at position 1 of the cyclohexyl group. In addition, in Figures 2 to 11, peaks representing the C=C stretching vibration of the benzene ring belonging to the diamine group were observed near 1480 to 1510 cm⁻¹. On the other hand, the peak of the amide group observed before imidization was completed was not observed near 1670 cm⁻¹. Therefore, it can be concluded that the thermal imidization reaction in Examples 1 to 11 has been completed, and a polyamide film has been reliably obtained.

[0091] Figures 12 to 22 show the 1H-NMR spectra of deuterated dimethyl monoxide (DMSO-d6) solutions of polyimide films from Examples 1 to 11. In Figures 12 to 22, * represents TMS (reference material), # represents DMSO (solvent), + represents water signal, 7.5 to 8.5 ppm signal is phenyl hydrogen, and 4.5 to 5.5 ppm signal is attributed to hydrogens in the alicyclic structure of isosorbide and dehydromannitol. Here, the peaks (†) of 4.9 ppm and 5.4 ppm observed in Figures 15 to 19 (Examples 4 to 8) are signals attributed to dehydromannitol. Based on this intensity ratio, it has been confirmed that the polyimide copolymers of Examples 4 to 8 contain 10 mol to 50 mol% dehydromannitol, respectively. Furthermore, the 4.2 ppm signal in Example 1 is attributed to the hydrogen at the 1-position of the cyclohexyl group, and 1 to 3 ppm is attributed to hydrogens other than the 1-position of the cyclohexyl group. In these spectra, the main signals can all be attributed to the structure of the polyimide, and only the signal observed at the end of imidization is seen. Therefore, it can be concluded that the thermal imidization reaction in Examples 1 to 11 has been completed, and polyimide films have been reliably obtained. Regarding the polyimide in Example 10, due to its extremely low solubility in DMSO-d6, the spectral decomposition energy is low and there is a lot of noise, but characteristic signals of its molecular structure were observed.

[0092] <Determination of Glass Transition Temperature (Tg) and Average Linear Coefficient of Thermal Expansion (CTE)> Figures 23 to 33 are graphs showing the thermomechanical analysis (TMA) of the polyimide films (approximately 15 μm thick) of Examples 1 to 11. Table 1 shows the glass transition temperature (Tg) obtained from the intersection of the tangent at the low temperature range (150°C to 250°C) and the tangent at the high temperature range (270°C to 275°C), and the average coefficient of linear thermal expansion (CTE) obtained from 80°C to 200°C. The Tg values ​​are all in the range of 240°C to 268°C, indicating that the Tg is sufficiently high for heat-resistant resins. In addition, the CTE is 44 to 67 ppm / K, which is considered to be standard or slightly lower for polyimides with isotropic chemical structures (Non-Patent Literature 1: S. Ando et al., Macromolecular Chemistry and Physics, 2017, 1700354, (2017).).

[0093] <Determination of Thermal Decomposition Temperature> Figures 34 to 44 are graphs showing the thermogravimetric analysis (TGA) of the polyimide films (approximately 15 μm thick) of Examples 1 to 11. Table 1 shows the thermal decomposition temperature (Td) when the residue weight percentage is 95% based on the weight at 100°C. Td is in the range of 400°C to 417°C, indicating a sufficiently high thermal decomposition temperature for a heat-resistant resin.

[0094] <Ultraviolet and Visible Light Transmittance Assessment> Figures 45 to 55 are spectra of the ultraviolet and visible light transmittance of the polyimide films (formed on a quartz substrate, approximately 10 μm thick) of Examples 1 to 11. In this example, the film obtained in Example 1 exhibited slight turbidity (haze) due to the presence of minute scatterers within the film. Furthermore, the films obtained in Examples 3 and 10 were transparent and pale yellow. The films obtained in the other examples (Examples 2, 4 to 9, 11) were all colorless and transparent, with a light transmittance of 97.5% to 99.1% at a wavelength of 450 nm, and a light transmittance of 95% at wavelengths ranging from 415 to 423 nm, indicating extremely high light transmittance across the entire visible light wavelength range (400 to 780 nm). This is due to the fact that 1,4-cyclohexanediamine (DACH), used as a diamine compound, has an alicyclic skeleton, while 2,2'-bis(trifluoromethyl)benzidine (TFDB) and 5-trifluoromethyl-1,3-phenylenediamine (TFMPD) have large and electron-attracting trifluoromethyl groups. As a result, the charge mobility of the electronic states formed in the substrate state of the polyimide from the diamine compound site and from the trimellitic acid site of the tetracarboxylic dianhydride is reduced, and the light absorption end shifts from the visible region to the ultraviolet region. It should be particularly noted that compared with Example 2, which was synthesized solely using isosorbide-bis(triphenylic anhydride) as the tetracarboxylic dianhydride, Examples 4 to 8, which added 10 to 50 mol% of dehydromannitol-bis(triphenylic anhydride), all showed improved light transmittance. This can be attributed to the strongly bent structure derived from dehydrated mannitol, which hinders the aggregation of polyimide molecules and further suppresses the light absorption due to intermolecular charge migration. Furthermore, the polyimide in Example 10, using 1,4-phenylenediamine (PPD) as the diamine compound, is pale yellow, while the polyimide in Example 11, using its structural isomer 1,3-phenylenediamine (MPD), is colorless and transparent. This can also be attributed to the bent structure of the intercalated benzene bond, which reduces the electron donation from the diamine compound site and hinders the aggregation of polyimide, thus suppressing the light absorption due to intramolecular and intermolecular charge migration. On the other hand, the films obtained in Examples 3 and 10 can be considered to be due to the fact that the benzene ring of the diamine compound belonging to the raw material and the trimellitic acid site of the tetracarboxylic acid dianhydride have an electronic state in which the former has charge migration from the latter to the latter in the substrate state, and only absorb some visible short-wavelength violet to blue light, so they appear pale yellow.

[0095] <Evaluation of Refractive Index Properties> Figures 56 to 66 are graphs showing the wavelength dependence of refractive index (nTE, nTM, nav) and birefringence (Δn) of the polyimide films (formed on silicon substrates, approximately 15 μm thick) of Examples 1 to 11. Table 2 summarizes and presents the average refractive index and birefringence measured at a wavelength of 1310 nm as representative values. Compared to commonly used fully aromatic polyimides, the polyimide films of Examples 1 to 11 exhibit a lower refractive index (1.555 to 1.603). This can be attributed to the alicyclic structure of isosorbide or dehydromannitol contained in the tetracarboxylic dianhydride used, which has a low fractionation and a large molecular volume. Among them, the polyimide films of Examples 1, 2, 4 to 9, and 11 exhibit significantly lower refractive indices (nav) at a wavelength of 1310 nm compared to the standard average refractive indices (nav) of general-purpose fully aromatic polyimides without alicyclic structures or fluorine (1.65 to 1.71, Non-Patent Literature 2: S. Ando et al., Japan Journal of Applied Physics, 41, 5254-5258, (2002)). This can be attributed to the alicyclic structure derived from isosorbide or dehydromannitol, as well as the presence of cyclohexyl or trifluoromethyl groups in the diamine compounds used. Furthermore, the significantly lower refractive index of the polyimide in Example 11 compared to that in Example 10 can be attributed to the reduced density caused by the bent structure of the intercalated benzene bonds, which hinders intermolecular aggregation. In addition, compared with the standard birefringence (Δn) of the aforementioned general-purpose fully aromatic polyimide at a wavelength of 1310 nm for the polyimide films of Examples 1 to 11 (0.026 to 0.170, Non-Patent Literature 3: Y. Terui et al., Journal of Polymer Science, 42, 2354-2366, (2004).), the polyimide films of Examples 1 to 11 showed significantly smaller birefringence (0.005 to 0.021). This can also be attributed to the alicyclic structures derived from isosorbide and dehydromannitol, which reduce the average refractive index and hinder the formation of molecular chain orientation or condensed structures. Among them, the birefringence (Δn) of Examples 1, 3, 8, 9, and 11 was extremely low, below 0.01, which is due to the flexible molecular structure of the diamine compounds used. In addition, compared with Example 2, which was synthesized using isosorbide-bis(triphenyltrihydric anhydride) alone as the tetracarboxylic dianhydride, the birefringence (Δn) of Examples 4 to 8, which added 10 to 50 mol% of dehydromannitol-bis(triphenyltrihydric anhydride), was significantly reduced, which can also be attributed to the strongly flexible structure derived from dehydromannitol. These characteristics demonstrate that the polyimide of Examples 1 to 11 has excellent properties as a heat-resistant optical material for use in optical waveguides or optical circuits.

[0096] Figures 67 to 72 show the ellipticity spectra of the circularly polarized dichroism (CD) of the polyimide films (approximately 1 μm thick) of Examples 1 to 3 and Examples 9 to 11, which exclude the use of two acid anhydrides in the polyimide copolymer. Table 1 shows the sign and wavelength of the Cotton effect in the CD spectrum. The polyimide film of Example 1 at 238 nm, the polyimide film of Example 2 at 230 nm and 260 nm, the polyimide film of Example 3 at 232 nm and 264 nm, the polyimide film of Example 9 at 232 nm and 254 nm, the polyimide film of Example 10 at 230 nm and 274 nm, and the polyimide film of Example 11 at 234 nm and 254 nm all exhibit clear peaks corresponding to the negative Cotton effect, with the CD signal being positive and negative pairs. This suggests that these polyimide molecules retain the optical anisotropy (palmartic) structure of the isosorbide portion in the solid state and form a helical structure. This can be considered as forming a transparent polymer film with a helical structure, which can exhibit circularly polarized light emission by being combined with organic polymers that have fluorescent or phosphorescent properties (photoluminescence). This can be applied to light-emitting materials or photosensors, photoradar, and 3D displays used in organic EL devices.

[0097] <Dielectric Property Evaluation> (Estimated Values) As shown in Table 2, the dielectric constant (estimated from the refractive index) (εref) of the polyimide films of Examples 1 to 11 was calculated from the above formula using the average refractive index, and is a relatively small value of 2.66 to 2.87. This result suggests that these are polyimides with excellent dielectric properties. Compared to the standard εref (3.0 to 3.2, observed at 10 GHz, Non-Patent Literature 4: PM Hergenrother, High Performance Polymers, 15, 3-45, (2003)) of the above-mentioned fully aromatic polyimides, this is a significantly smaller dielectric constant.

[0098] <Dielectric property evaluation> (measured values) The dielectric constant (measured value) (ε) and dielectric loss tangent (measured value) of the polyimide films (film thickness approximately 15 μm) of Examples 2 to 11 at frequencies of 10 GHz (TE mode) and 20 GHz (TE mode) are summarized in Table 2. Here, the polyimide of Example 1 was excluded from the test because it was difficult to peel off a film of the area (50 mm × 50 mm or more) required for dielectric measurement from the substrate. The dielectric constant (measured value, frequency 20 GHz) of the polyimide films of Examples 2 to 8 was 2.88 to 2.99, and the dielectric loss tangent (measured value, frequency 10 GHz) was 0.0092 to 0.0129, which are significantly lower than those of commonly used polyimides. In particular, the polyimide films composed of the copolymers of Examples 4 to 6 exhibited the smallest dielectric constant and dielectric loss tangent among all examples. This can be attributed to the effect of the trifluoromethyl group of the fluorinated diamine compound (TFDB), as well as the inhibitory effect of the molecular aggregation of the strongly bent structure of dehydromannitol. On the other hand, the dielectric constant (measured value, frequency 20 GHz) of the polyimide films of Examples 9 to 11 is 3.11 to 3.25, and the dielectric loss tangent (measured value, frequency 10 GHz) is 0.0146 to 0.0172. Both are relatively high values, but are equal to or smaller than those of commonly used polyimides. In summary, these dielectric properties demonstrate that the polyimides of Examples 2 to 11, having a structure derived from isosorbide and dehydromannitol, possess excellent properties as heat-resistant insulating materials in high-frequency substrates.

[0099] <Solubility Assessment of Polyimide> The solvent solubility of the polyimide films of Examples 1 to 11 is summarized and presented in Table 3 below. In Table 3, "+" means readily soluble, "±" means sparingly soluble, and "-" means insoluble. It is clear that the polyimide films obtained in Examples 2, 4 to 9 exhibit sufficient solubility relative to N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), and dimethyl sulfoxide (DMSO) upon heating at 60°C. In particular, the polyimides in Examples 7 and 8, which are copolymers with relatively high dehydrated mannitol fractions, also exhibit sufficient solubility relative to γ-butyrolactone (GBL). However, other polyimides show only slight solubility relative to GBL. The polyimide film obtained in Example 1, upon heating at 60°C, exhibits solubility relative to DMAc and NMP, and although slightly less soluble relative to DMSO, a polyimide varnish soluble in this organic solvent can be obtained. Furthermore, it can be seen that the polyimide films obtained in Examples 3 and 11, when heated to 100°C, showed only slight solubility relative to DMAc, NMP, and DMSO, and were difficult to dissolve, and showed no solubility relative to GBL.

[0100] [Table 3]

[0101] The polyimide films of Examples 1 to 11 represent bio-based polyimides made from biological resources. Their heat resistance (Tg, thermal decomposition temperature) and linear coefficient of thermal expansion are almost standard for polyimides. They also possess excellent properties such as low refractive index, low birefringence, low dielectric constant (estimated and measured values), and low dielectric loss tangent (measured value). Furthermore, the polyimides shown in Examples 2, 4 to 9, and 11 exhibit extremely high light transmittance (colorless transparency) across the entire visible light spectrum, and demonstrate circularly polarized dichroism and good solubility in polar organic solvents in the ultraviolet region. In summary, the polyimide system of the present invention possesses excellent properties for use as a high-performance industrial material, especially as a functional optical material or a low dielectric constant material.

Claims

1. A polyimide having repeating units as shown in the following general formula (1), and having a glass transition temperature (Tg) of 210°C or higher as determined by thermomechanical analysis, wherein R1 independently represents a straight-chain or branched alkyl group having 1 to 6 carbon atoms, a cyclic alkyl group having 5 or 6 carbon atoms, a straight-chain or branched alkoxy group having 1 to 6 carbon atoms, 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, a straight-chain or branched haloalkyl group having 1 to 6 carbon atoms, or a halogen atom, n independently represents an integer from 0 to 3, and A represents a divalent group as shown in the following general formula (5) or a divalent organic group containing a cyclic aliphatic group having 4 to 30 carbon atoms. In the formula, R2 independently represents a straight-chain or branched-chain alkyl group with 1 to 6 carbon atoms, a cyclic alkyl group with 5 or 6 carbon atoms, a straight-chain or branched-chain alkoxy group with 1 to 6 carbon atoms, a cyclic alkoxy group with 5 or 6 carbon atoms, an aryl group with 6 to 8 carbon atoms, an aryloxy group with 6 to 8 carbon atoms, a straight-chain or branched-chain haloalkyl group with 1 to 6 carbon atoms, or a halogen atom, m independently represents an integer from 0 to 4, p, q and r represent 0 or 1, X represents a direct bond, oxygen atom, sulfur atom, sulfonyl (-SO2-), carbonyl (-CO-), acetamyl (-NHCO-), ester (-OCO-), alkylene group with 1 to 15 carbon atoms, fluorinated alkylene group with 2 to 15 carbon atoms, cycloalkylene group with 5 to 15 carbon atoms, phenylene or fumonisinyl, and * represents the bond position.

2. The polyimide as described in claim 1, having one or more repeating units selected from the repeating units shown in general formulas (2) to (4) below, wherein R1, n, and A are defined in the same way as in general formula (1).

3. The polyimide as described in claim 1, which has repeating units as shown in the following general formula (2), wherein R1, n, and A are defined in the same way as in general formula (1).

4. The polyimide as described in claim 2, having two or more repeating units selected from the repeating units shown in the aforementioned general formulas (2) to (4).

5. The polyimide as described in claim 4, which has repeating units as shown in the aforementioned general formula (2) and the aforementioned general formula (4).

6. The polyimide as claimed in claim 5, wherein the molar ratio of the repeating unit shown in the aforementioned general formula (2) to the repeating unit shown in the aforementioned general formula (4) is in the range of (2):(4)=99:1 to 50:

50.

7. The polyimide as claimed in claim 1, wherein the content of the repeating unit shown in the aforementioned general formula (1) is more than 15 mol% of the total polyimide.

8. A polyimide varnish comprising the polyimide as described in claim 1 and an organic solvent.

9. A polyimide film comprising the polyimide as described in claim 1.

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