Polyamide-imide resin, polyamide-imide resin film, window, display substrate, and flexible display device

Abstract

The invention discloses polyamide-imide resin, a polyamide-imide resin film, a window, a display substrate and a flexible display device. The polyamide-imide resin is obtained by copolymerization of a first monomer, a second monomer and a third monomer, the first monomer is tetracarboxylic dianhydride, the second monomer is a diacid derivative represented by formula (1), # imgabs0 #, R1 represents a cycloalkyl group, X represents a halogen atom, and the third monomer is diamine. According to the present invention, the polyamideimide resin and the polyamideimide resin film are transparent and exhibit excellent thermal stability, excellent mechanical properties and optical properties, and small dimensional change, and can be used in various fields such as windows, display substrates, touch panels, flexible display substrates, TFT insulating films, and the like.

Description

Technical Field

[0001] The present invention relates to the field of new polymer materials, and in particular to a polyamide-imide resin and a polyamide-imide resin film, a window, a display substrate and a flexible display device. Background Art

[0002] Polyimide refers to a polymer containing an imide bond on the main chain, and is one of the organic polymer materials with excellent comprehensive performance. The heat-resistant temperature of polyimide materials is above 400°C, with high insulation, very small dielectric constant and dielectric loss, and good chemical properties. Therefore, polyimide shows the possibility of application in many fields. However, polyimide is not easy to dissolve and melt, so the processability as a material is poor. Due to the poor processability, polyimide materials are mainly prepared by a two-stage process: first, diamine and tetracarboxylic dianhydride as monomers are polymerized to prepare a polyamic acid solution (i.e., a polyimide precursor). Then, the polyimide material is prepared by a thermal method (heating) or a chemical method (adding a dehydrating agent, a catalyst, etc.).

[0003] Ordinary polyimide is a highly heat-resistant polymer that is insoluble and infusible. It has excellent properties such as thermal oxidation resistance, heat resistance, radiation resistance, low temperature resistance, and chemical resistance. It can be used in a wide range of fields such as automotive materials, aerospace materials and other heat-resistant cutting-edge materials, insulating coating materials, insulating film materials, semiconductors, TFT-LCD electrode protection films and other electronic materials.

[0004] However, polyimide may appear brown or yellow due to charge transfer interactions caused by high aromatic ring density, resulting in low transmittance in the visible light region. Since ordinary polyimide has a large birefringence index, it is difficult to use it in optical components.

[0005] In order to make the conventional colored polyimide transparent, the transparency can be achieved by introducing a tortuous linking group or a relatively large free volume side chain into the main chain to suppress the intramolecular or intermolecular charge transfer interaction.

[0006] For example, Patent Document 1 proposes a copolyamide-imide film having excellent thermal, mechanical and optical properties and a method for producing the copolyamide-imide film, which is limited to a composition of 2,2'-bis(trifluoromethyl)benzidine, 4,4'-(hexafluoroisopropyl)diphthalic anhydride and terephthalic acid chloride. Although the copolyamide-imide film has excellent average transmittance and thermal linear expansion coefficient, the YI (Yellowness Index) value is still large.

[0007] Patent Document 2 proposes a transparent polyamide-imide resin and a film using the same which is excellent in thermal stability, mechanical properties and birefringence and can be used for a plastic display substrate, etc., and is limited to a composition of 2,2'-bis(trifluoromethyl)benzidine, 4,4'-(hexafluoroisopropyl)diphthalic anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, cyclobutanetetracarboxylic dianhydride and / or cyclopentanetetracarboxylic dianhydride, terephthalic acid chloride and / or isophthalic acid chloride. Although the polyamide-imide resin has excellent transmittance, thermal linear expansion coefficient and birefringence, the YI value is still large.

[0008] Patent document 3 proposes a polyamide-imide film, the molecular structure of which includes a first block obtained by copolymerizing a monomer containing a dialdehyde and a diamine and a second block obtained by copolymerizing a monomer containing an aromatic dicarbonyl compound and an aromatic diamine, and the molar ratio of the first block to the second block is 5:1 to 1:1. Among them, the first polyimide block has a higher degree of copolymerization than the second polyamide block. Although the polyamide-imide film has excellent transmittance, birefringence, etc., the YI and thermal linear expansion coefficient are still relatively large.

[0009] Prior art literature

[0010] Patent Document 1: Japanese Patent No. 5799172

[0011] Patent Document 2: Japanese Patent No. 6244470

[0012] Patent Document 3: Japanese Patent No. 6837974 Summary of the invention

[0013] In order to solve at least one of the technical problems existing in the prior art, the present invention provides a polyamide-imide resin and a polyamide-imide resin film, a window, a display substrate and a flexible display device.

[0014] Means for solving technical problems

[0015] A first aspect of the present invention provides a polyamide-imide resin obtained by copolymerizing a first monomer, a second monomer and a third monomer, wherein the first monomer is tetracarboxylic dianhydride, and the second monomer is a diacid derivative represented by the following formula (1):

[0016]

[0017] Among them, R 1 represents a cycloalkyl group, X represents a halogen atom, and the third monomer is a diamine.

[0018] In the above polyamide-imide resin, the third monomer is a diamine represented by the following formula (2):

[0019] NH2-R 2 -NH2···Formula (2)

[0020] Among them, R 2 It is a substituted or unsubstituted phenylene group having one or more ring structures. When the phenylene group has two or more ring structures, they are linked by a single bond, -O-, -S-, -C(=O)- or -CH(OH)-. When the phenylene group is substituted, the substituent is -CF3, -CCl3 or -CBr3.

[0021] In the polyamide-imide resin, the first monomer includes 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) as an essential component.

[0022] In the polyamide-imide resin, the first monomer further comprises one or more of 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), 4,4'-oxydiphthalic dianhydride (ODPA) and cyclobutanetetracarboxylic dianhydride (CBDA).

[0023] In the above polyamideimide resin, the second monomer is at least one selected from the group consisting of cyclosuccinoyl fluoride, cyclosuccinoyl chloride, cyclosuccinoyl bromide, cyclopentanoyl fluoride, cyclopentanoyl chloride, cyclopentanoyl bromide, cyclohexanoyl fluoride, cyclohexanoyl chloride, cyclohexanoyl bromide, cyclopeptanoyl fluoride, cyclopeptanoyl chloride, and cyclopeptanoyl bromide.

[0024] In the polyamide-imide resin, the second monomer is at least one selected from the group consisting of cyclopentanoyl chloride, cyclohexanoyl chloride, and cycloheptanedioyl chloride.

[0025] In the polyamide-imide resin, the molar ratio of the first monomer, the second monomer, and the third monomer is 0.2-0.8:0.8-0.2:1.

[0026] A second aspect of the present invention provides a polyamide-imide resin film formed from the above-mentioned polyamide resin, wherein the polyamide-imide film has a thickness of 10 to 100 μm and a yellowness index of 2.0 or less.

[0027] In the polyamide-imide resin film, the surface hardness is 3H or more.

[0028] A third aspect of the present invention provides a window comprising the polyamide-imide resin film.

[0029] A fourth aspect of the present invention provides a display substrate comprising the polyamide-imide resin film.

[0030] A fifth aspect of the present invention provides a flexible display device comprising the polyamide-imide resin film.

[0031] Technical Effects of the Invention

[0032] According to the present invention, a polyamide-imide resin and a polyamide-imide film can be provided which are transparent, exhibit excellent thermal stability and mechanical properties, are excellent in optical properties, and further have little dimensional change, and can be used in various fields such as windows, touch panels, flexible display substrates, and TFT insulating films. DETAILED DESCRIPTION

[0033] Hereinafter, the polyamide-imide resin and the polyamide-imide resin film and the method for producing the same according to the present invention will be described in detail.

[0034] Polyamide-imide resin

[0035] The polyamide-imide resin used in the present invention is obtained by polymerizing tetracarboxylic dianhydride, diamine, and a dicarboxylic acid derivative in a solvent.

[0036] <Tetracarboxylic dianhydride>

[0037] In the present embodiment, the tetracarboxylic dianhydride used is 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) as an essential component. As the tetracarboxylic dianhydride component, the essential component can be used in combination with one or more selected from 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), 4,4'-oxydiphthalic dianhydride (ODPA) and cyclobutanetetracarboxylic dianhydride (CBDA).

[0038] <Diamine>

[0039] In this embodiment, the diamine used can be selected from one or a combination of two or more of 2,2'-bis(trifluoromethyl)benzidine (TFMB), p-phenylenediamine (PPD), m-phenylenediamine (MPD), 4,4'-diaminodiphenyl ether (4,4'-ODA), 3,4'-diaminodiphenyl ether (3,4'-ODA), and 4,4'-methylenedianiline (4,4'-DABA), but is not limited thereto. The diamine can also be selected from p-methylenedianiline (pMDA), m-methylenedianiline (mMDA), 1,3-bis(3-aminophenoxy)benzene (133APB), 1,3-bis(4-aminophenoxy)benzene (134APB), 2,2'-bis[4(4-aminophenoxy)phenyl]hexafluoropropane (4BDAF), 2,2'-bis(3-aminophenyl)hexafluoropropane (33-6F), 2,2'-bis(4-aminophenyl)hexafluoropropane (44-6F), bis(4-aminophenyl)sulfone (4DDS), bis(3-aminophenyl)sulfone (4DDS), bis(4 ...3-aminophenyl) The invention can be used as the preparation method of the present invention. The invention can be used as the preparation method of the present invention. The invention can be used as the preparation method of the present invention. The invention can be used as the preparation method of the present invention.

[0040] <Dicarboxylic acid derivatives>

[0041] In this embodiment, the dicarboxylic acid derivative used can be selected from one or a combination of two or more of cyclosuccinic acid fluoride (1,2-cyclosuccinic acid fluoride, 1,3-cyclosuccinic acid fluoride), cyclosuccinic acid chloride (1,2-cyclosuccinic acid chloride, 1,3-cyclosuccinic acid chloride), cyclosuccinic acid bromide (1,2-cyclosuccinic acid bromide, 1,3-cyclosuccinic acid bromide), cyclopentanedioyl fluoride (1,2-cyclopentanedioyl fluoride, 1,3-cyclopentanedioyl fluoride), cyclopentanedioyl chloride (1,2-cyclopentanedioyl chloride, 1,3-cyclopentanedioyl chloride), cyclopentanedioyl bromide (1,2-cyclopentanedioyl bromide, 1,3-cyclopentanedioyl bromide), cyclohexanedioyl chloride (1,2-cyclohexanedioyl chloride, 1,3-cyclohexanedioyl chloride, 1,4-cyclohexanedioyl chloride), and cyclohexanedioyl bromide (1,2-cyclohexanedioyl bromide, 1,3-cyclohexanedioyl bromide, 1,4-cyclohexanedioyl bromide). Preferably, the dicarboxylic acid derivative used can be selected from one or a combination of two or more of 1,2-cyclohexanediyl chloride, 1,3-cyclohexanediyl chloride, and 1,4-cyclohexanediyl chloride.

[0042] <Solvent>

[0043] According to the manufacturing method of polyamide-imide resin of the present invention, the solvent used is selected from one or more mixed solvents of solvents such as N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), acetone, ethyl acetate, diethylformamide (DEF), diethylacetamide (DEA), propylene glycol monomethyl ether (PGME), meta-cresol. In addition, low boiling point solutions such as tetrahydrofuran (THF), chloroform or low absorption solvents such as gamma-butyrolactone can also be used. More preferably, the solvent is DMAc or NMP, or a mixed solvent of the two.

[0044] ·Production method of polyamide-imide resin

[0045] The method for producing the polyamide-imide resin of the present invention includes the following two methods: (1) a method including an imidization step of reacting a diamine and a tetracarboxylic dianhydride in a solvent, reacting the diamine and a dicarboxylic acid derivative, and then causing a chemical imidization reaction in the presence of an imidization catalyst; and (2) a method including an imidization step of reacting a diamine and a dicarboxylic acid derivative in a solvent, reacting the diamine and a tetracarboxylic dianhydride, and then causing a chemical imidization reaction in the presence of an imidization catalyst. The target polyamide-imide resin can be obtained by any of the methods.

[0046] <Molar Ratio of Diamine, Tetracarboxylic Acid Component, and Dicarboxylic Acid Derivative>

[0047] According to the method for producing the polyamide-imide resin of the present invention, the tetracarboxylic dianhydride and dicarboxylic acid derivatives as the acid components can be made to be substantially equimolar with the diamine component (preferably the molar ratio of [tetracarboxylic dianhydride + dicarboxylic acid derivative] / [diamine] is 0.900 to 1.100). More preferably, it is 0.900 to 0.990. The amount of solvent can be determined according to the solid content of the generated polyamic acid solution, preferably, the solid content of the polyamic acid solution is 5wt% to 50wt%, more preferably 10wt% to 25wt%.

[0048] Polyamide-imide film

[0049] The polyamide-imide resin solution obtained by the method for manufacturing the polyamide-imide resin of the present invention is subjected to rod coating, slit coating, spin coating, electrostatic spinning, etc. to prepare a coating film of a desired shape. Then, in a nitrogen atmosphere, the solvent is removed by a heating method (step heating) to obtain a polyamide-imide film. Preferably, the heating method is step heating, and more preferably, the heating rate of the step heating is 2 to 10°C / min, and the process includes heating at 50 to 100°C and maintaining for 0.5 to 2 hours, and heating at 120 to 200°C. Maintain at 120 to 200°C for 0.5 to 1 hour, heat to 250 to 350°C, and maintain for 0.5 to 1 hour. The heating rates may be the same or different.

[0050] As an example, in a preferred embodiment, the step heating rate is 4-5°C / min, and the process includes heating at 60°C for 0.5 hours, heating at 130°C for 1 hour, and heating at 300°C for 0.5 hours.

[0051] The polyamide-imide film having a thickness of 10 to 100 μm obtained by the present invention can be suitably used for windows, touch panels, flexible display substrates, and TFT insulating films.

[0052] ·Example

[0053] In order to more clearly illustrate the present invention, the present invention is further described below with reference to preferred embodiments. For those skilled in the art, the following specific description is not intended to be limiting, but is intended to be used as an example and is not intended to limit the scope of protection of the present invention.

[0054] Next, the measurement method of the characteristics used in the following examples is shown.

[0055] <Film thickness measurement>

[0056] Five arbitrary locations of the polyamide-imide film were selected, and the thickness was measured using a micrometer (SSI-650 manufactured by Teclock).

[0057] <Total light transmittance measurement>

[0058] The total light transmittance of the polyamide-imide film was measured using a photometer (NDH7000SPII, manufactured by Nippon Denshoku Industries) in accordance with ISO13468-1.

[0059] <Yellowness Index (YI) Measurement>

[0060] The yellowness index of the polyamide-imide film was measured using a colorimeter (ZE7700, manufactured by Nippon Denshoku Industries) in accordance with ASTM E313.

[0061] <Measurement of coefficient of thermal expansion (CTE)>

[0062] Using a thermomechanical analyzer (ThermoplusEVO2TMA8311 manufactured by Rigaku Corporation), the sample was heated from room temperature to 300°C at a load of 50 mN and a heating rate of 10°C / min to remove residual stress. The sample was gradually cooled to room temperature and then heated again to 400°C to calculate the CTE at 50 to 300°C.

[0063] <Pencil hardness (H) measurement>

[0064] The pencil hardness of the polyamide-imide film was measured in accordance with JIS K5600-5-4 using a pencil made by Hi-uni Mitsubishi and a pencil hardness tester loaded with a weight of 750 g.

[0065] The abbreviations of the compounds used in the following examples are explained.

[0066] 6FDA: 4,4'-(hexafluoroisopropylidene)diphthalic anhydride

[0067] s-BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride

[0068] CBDA: Cyclobutanetetracarboxylic dianhydride

[0069] ODPA: 4,4'-oxydiphthalic dianhydride

[0070] TFMB: 2,2'-bis(trifluoromethyl)benzidine

[0071] HHTC: Cyclohexanediyl chloride

[0072] TPC: Terephthaloyl chloride

[0073] DMAc: N,N-dimethylacetamide

[0074] IPA: Isopropyl alcohol

[0075] Example 1

[0076] In a glass reaction container with a volume of 1L equipped with a stirrer and a nitrogen inlet / exhaust tube, 800g of DMAc was added as a solvent, and 40.40g (0.126 mol) of TFMB was added thereto, and stirred at 25°C for 1 hour to dissolve it. 22.45g (0.050 mol) of 6FDA was added to the solution, and stirred at 30°C for 12 hours to obtain a polyimide precursor solution. After adding 16.07g (0.076 mol) of HHTC to the polyimide precursor solution, 24.00g of pyridine and 31.00g of acetic anhydride were added, and stirred at 70°C for 1 hour to obtain a polyamide-imide resin solution. The solution was added to 5L of IPA, and the precipitated solid components were filtered and crushed, and then dried in a vacuum oven at 120°C for 12 hours to obtain 66.9g of polyamide-imide powder.

[0077] The above 6.0 g of polyamide-imide powder was dissolved in 34 g of DMAc to obtain a polyamide-imide resin solution having a solid content of 15.0 mass % and a solution viscosity of 50.0 Pa·s. The polyamide-imide resin solution was cast on a glass substrate and heated in a vacuum furnace at 60° C. for 0.5 hour, at 130° C. for 1 hour, and at 230° C. for 0.5 hour to obtain a polyamide-imide film.

[0078] Table 1 shows the properties of the obtained polyamide-imide film.

[0079] Example 2

[0080] In a glass reaction container with a volume of 1L equipped with a stirrer and a nitrogen inlet / exhaust tube, 760g of DMAc was added as a solvent, and 40.40g (0.126 mol) of TFMB was added thereto, and stirred at 30°C for 1 hour to dissolve it. 11.22g (0.025 mol) of 6FDA was added to the solution, and stirred at 30°C for 12 hours to obtain a polyimide precursor solution. After adding 21.45g (0.101 mol) of HHTC to the polyimide precursor solution, 24.00g of pyridine and 31.00g of acetic anhydride were added, and stirred at 70°C for 1 hour to obtain a polyamide-imide resin solution. The solution was added to 5L of IPA, and the precipitated solid components were filtered and crushed, and then dried in a vacuum oven at 120°C for 12 hours to obtain 62.4g of polyamide-imide powder.

[0081] 6.0 g of the polyamide-imide powder was dissolved in 44.0 g of DMAc to obtain a polyamide-imide resin solution having a solid content of 12.0% by mass and a solution viscosity of 321.0 Pa·s. The polyamide-imide resin solution was cast on a glass substrate and heated in a vacuum furnace at 60° C. for 0.5 hour, at 130° C. for 1 hour, and at 230° C. for 0.5 hour to obtain a polyamide-imide film.

[0082] Table 1 shows the properties of the obtained polyamide-imide film.

[0083] Example 3

[0084] In a glass reaction container with an internal volume of 1 L equipped with a stirrer and a nitrogen inlet / exhaust tube, 780 g of DMAc was added as a solvent, and 40.40 g (0.126 mol) of TFMB was added thereto, and stirred at 30°C for 1 hour to dissolve it. 3.90 g (0.050 mol) of 6FDA and 9.94 g (0.050 mol) of ODPA were added to the solution, and stirred at 30°C for 12 hours to obtain a polyimide precursor solution. 5.35 g (0.025 mol) of HHTC was added to the polyimide precursor solution, and then 24.00 g of pyridine and 31.00 g of acetic anhydride were added, and stirred at 70°C for 1 hour to obtain a polyamide-imide resin solution. The solution was added to 5 L of IPA, and the precipitated solids were filtered and crushed, and then dried in a vacuum oven at 120°C for 12 hours to obtain 67.2 g of polyamide-imide powder.

[0085] 6.0 g of the polyamide-imide powder was dissolved in 24.0 g of DMAc to obtain a polyamide-imide resin solution having a solid content of 20.0% by mass and a solution viscosity of 2.4 Pa·s. The polyamide-imide resin solution was cast on a glass substrate and heated in a vacuum furnace at 60° C. for 0.5 hour, at 130° C. for 1 hour, and at 230° C. for 0.5 hour to obtain a polyamide-imide film.

[0086] Table 1 shows the properties of the obtained polyamide-imide film.

[0087] Example 4

[0088] In a glass reaction container with an internal volume of 1 L equipped with a stirrer and a nitrogen inlet / exhaust tube, 780 g of DMAc was added as a solvent, and 40.40 g (0.126 mol) of TFMB was added thereto, and the mixture was stirred at 30°C for 1 hour to dissolve. 22.45 g (0.051 mol) of 6FDA and 1.98 g (0.010 mol) of ODPA were added to the solution, and the mixture was stirred at 30°C for 12 hours to obtain a polyimide precursor solution. 13.90 g (0.065 mol) of HHTC was added to the polyimide precursor solution, and then 24.00 g of pyridine and 31.00 g of acetic anhydride were added, and the mixture was stirred at 70°C for 1 hour to obtain a polyamide-imide resin solution. The solution was added to 5 L of IPA, and the precipitated solids were filtered and crushed, and then dried in a vacuum oven at 120°C for 12 hours to obtain 62.2 g of polyamide-imide powder.

[0089] 6.0 g of the polyamide-imide powder was dissolved in 24.0 g of DMAc to obtain a polyamide-imide resin solution having a solid content of 20.0% by mass and a solution viscosity of 42.0 Pa·s. The polyamide-imide resin solution was cast on a glass substrate and heated in a vacuum furnace at 60° C. for 0.5 hour, at 130° C. for 1 hour, and at 230° C. for 0.5 hour to obtain a polyamide-imide film.

[0090] Table 1 shows the properties of the obtained polyamide-imide film.

[0091] Example 5

[0092] In a glass reaction container with a volume of 1 L equipped with a stirrer and a nitrogen inlet / exhaust tube, 780 g of DMAc was added as a solvent, and 40.40 g (0.126 mol) of TFMB was added thereto, and stirred at 30°C for 1 hour to dissolve it. 44.85 g (0.101 mol) of 6FDA was added to the solution, and stirred at 30°C for 12 hours to obtain a polyimide precursor solution. After adding 5.36 g (0.025 mol) of HHTC to the polyimide precursor solution, 24.00 g of pyridine and 31.00 g of acetic anhydride were added, and stirred at 70°C for 1 hour to obtain a polyamide-imide resin solution. The solution was added to 5 L of IPA, and the precipitated solids were filtered and crushed, and then dried in a vacuum oven at 120°C for 12 hours to obtain 67.2 g of polyamide-imide powder.

[0093] 6.0 g of the polyamide-imide powder was dissolved in 24.0 g of DMAc to obtain a polyamide-imide resin solution having a solid content of 20.0% by mass and a solution viscosity of 6.9 Pa·s. The polyamide-imide resin solution was cast on a glass substrate and heated in a vacuum furnace at 60° C. for 0.5 hour, at 130° C. for 1 hour, and at 230° C. for 0.5 hour to obtain a polyamide-imide film.

[0094] Table 1 shows the properties of the obtained polyamide-imide film.

[0095] Comparative Example 1

[0096] In a glass reaction container with a volume of 1 L equipped with a stirrer and a nitrogen inlet / exhaust tube, 460.0 g of DMAc was added as a solvent, and 32.50 g (0.101 mol) of TFMB was added thereto, and stirred at 25°C for 1 hour to dissolve it. 44.88 g (0.101 mol) of 6FDA was added to the solution, and stirred at 25°C for 12 hours to obtain a polyimide precursor solution. 56.90 g of pyridine and 62.36 g of acetic anhydride were added to the polyimide precursor solution, and stirred at 70°C for 5 hours to obtain a polyamide-imide resin solution. The solution was added to 5 L of pure water, and the precipitated solid components were filtered and crushed, and then dried in a vacuum oven at 120°C for 12 hours to obtain 26.5 g of polyamide-imide powder.

[0097] 26.5 g of the polyamide-imide powder was dissolved in 177.0 g of DMAc to obtain a polyamide-imide resin solution having a solid content of 13.0% by mass and a solution viscosity of 1.0 Pa·s. The polyamide-imide resin solution was cast on a glass substrate and heated in a vacuum furnace at 60° C. for 0.5 hour, at 130° C. for 1 hour, and at 300° C. for 0.5 hour to obtain a polyamide-imide film.

[0098] Table 1 shows the properties of the obtained polyamide-imide film.

[0099] Comparative Example 2

[0100] 780.0 g of DMAc was added as a solvent to a glass reaction container with a capacity of 1 L equipped with a stirrer and a nitrogen inlet / exhaust tube, and 40.40 g (0.126 mol) of TFMB was added thereto, and the mixture was stirred at 30° C. for 1 hour to dissolve the mixture. 26.80 g (0.126 mol) of HHTC was added to the solution, and then 24.00 g of pyridine was added and stirred for 1 hour to obtain a polyimide resin solution. The solution was added to 5 L of IPA, and the precipitated solids were filtered and crushed, and then dried in a vacuum oven at 120° C. for 12 hours to obtain 60.24 g of polyamide-imide powder.

[0101] 6.0 g of the polyamide-imide powder was dissolved in 114.0 g of DMAc to obtain a polyamide-imide resin solution having a solid content of 5.0% by mass and a solution viscosity of 71.0 Pa·s. The polyamide resin solution was cast on a glass substrate and heated in a vacuum furnace at 60° C. for 0.5 hour, at 130° C. for 1 hour, and at 230° C. for 0.5 hour to obtain a polyamide-imide film.

[0102] Table 1 shows the properties of the obtained polyamide film.

[0103] Comparative Example 3

[0104] 780.0 g of DMAc was added as a solvent to a glass reaction container with a volume of 1 L equipped with a stirrer and a nitrogen inlet / exhaust tube, and 40.40 g (0.126 mol) of TFMB was added thereto, and the mixture was stirred at 30°C for 1 hour to dissolve. 3.90 g (0.013 mol) of ODPA, 11.20 g (0.038 mol) of s-BPDA, and 1.98 g (0.010 mol) of CBDA were added to the solution, and the mixture was stirred at 30°C for 12 hours to obtain a polyimide precursor solution. 24.00 g of pyridine and 31.00 g of acetic anhydride were added to the polyimide precursor solution, and the mixture was stirred at 70°C for 1 hour to obtain a polyamide-imide resin solution. The solution was added to 5 L of IPA, and the precipitated solids were filtered and crushed, and then dried in a vacuum oven at 120°C for 12 hours to obtain 60.4 g of polyamide-imide powder.

[0105] 6.0 g of the polyamide-imide powder was dissolved in 34.0 g of DMAc to obtain a polyamide-imide resin solution having a solid content of 15.0% by mass and a solution viscosity of 52.0 Pa·s. The polyamide-imide resin solution was cast on a glass substrate and heated in a vacuum furnace at 60° C. for 0.5 hour, at 130° C. for 1 hour, and at 230° C. for 0.5 hour to obtain a polyamide-imide film.

[0106] Table 1 shows the properties of the obtained polyamide-imide film.

[0107] [Table 1]

[0108]

[0109] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A polyamide-imide resin, characterized in that: The polyamide-imide resin is obtained by copolymerizing a first monomer, a second monomer and a third monomer. The first monomer is tetracarboxylic dianhydride, The second monomer is a diacid derivative represented by the following formula (1): Among them, R 1 represents a cycloalkyl group, X represents a halogen atom, The third monomer is a diamine.

2. The polyamide-imide resin according to claim 1, characterized in that The third monomer is a diamine represented by the following formula (2): NH2-R 2 -NH2···Formula (2) R 2 It is a substituted or unsubstituted phenylene group having one or more ring structures. When the phenylene group has two or more ring structures, they are linked by a single bond, -O-, -S-, -C(=O)- or -CH(OH)-. When the phenylene group is substituted, the substituent is -CF3, -CCl3 or -CBr3.

3. The polyamide-imide resin according to claim 1, characterized in that The first monomer has 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) as an essential component, Preferably, the first monomer further comprises one or more of 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), 4,4'-oxydiphthalic dianhydride (ODPA) and cyclobutanetetracarboxylic dianhydride (CBDA).

4. The polyamide-imide resin according to claim 1, characterized in that in, The second monomer is one or more selected from the group consisting of cyclosuccinyl difluoride, cyclosuccinyl dichloride, cyclosuccinyl dibromide, cyclopentanoyl difluoride, cyclopentanoyl dichloride, cyclopentanoyl dibromide, cyclohexanoyl difluoride, cyclohexanoyl dichloride, and cyclohexanoyl dibromide, Preferably, the second monomer is cyclopentanoyl chloride or cyclohexanoyl chloride.

5. The polyamide-imide resin according to claim 1, characterized in that: in, The ratio of the molar amount of the first monomer, the molar amount of the second monomer, and the molar amount of the third monomer used is 0.2-0.8:0.8-0.2:

1.

6. A polyamide-imide resin film, characterized in that: Molded from the polyamide-imide resin according to any one of claims 1 to 5, The polyamide-imide film has a thickness of 10 to 100 μm and a yellowness index of 2.0 or less.

7. The polyamide-imide resin film according to claim 6, characterized in that: The surface hardness is above 3H.

8. A window, characterized in that: The polyamide-imide resin film according to claim 6 or 7 is included.

9. A display substrate, characterized in that: The polyamide-imide resin film according to claim 6 or 7 is included.

10. A flexible display device, characterized in that: The polyamide-imide resin film according to claim 6 or 7 is included.

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