Non-fluorine polyimide-based high-strength, high-light-resistant, transparent, flexible optical film material and its manufacturing method

Abstract

The present invention relates to a non-fluorinated polyimide resin having a structure of the following chemical formula 1, having excellent optical and mechanical properties, a method for manufacturing the same, and a film and a display device comprising the non-fluorinated polyimide resin. [Chemical Formula 1]

Description

Technology Field

[0001] The present invention relates to a non-fluorinated polyimide, a method for manufacturing the same, and a film and a display device comprising the non-fluorinated polyimide. Background Technology

[0003] Fluorinated polyimide is an important industrial material in which advanced companies overseas, including those in Japan, possess key know-how and patents, to the extent that it was designated as one of Japan's top three regulated items.

[0004] These fluorinated polyimides are special materials capable of producing high-hardness, transparent, flexible optical films that can replace glass; they are high-value core materials that are technically challenging and cannot be replaced by other polymer materials in the development of flexible displays.

[0005] However, due to regulations on perfluoroalkyl and polyfluoroalkyl substances (PFAS) that have recently been receiving great attention worldwide, the possibility is growing that fluorinated polyimides cannot be applied to next-generation displays in the future.

[0006] Accordingly, in order to successfully develop eco-friendly future displays, there is an urgent need to develop a non-fluorinated polyimide-based high-hardness transparent flexible optical film that can replace glass and has a fluorine content of 0%.

[0008] Conventional polyimides form a unique structure known as charge transfer complexes (CTCs). While these CTCs provide excellent mechanical properties, they simultaneously lower the bandgap energy, leading to severe degradation of optical properties, such as a high yellow index.

[0009] Therefore, there is a need to develop a new paradigm of materials with a fluorine content of 0% to overcome the trade-off between the mechanical and optical properties of polyimide and to comply with PFAS regulations.

[0011] Accordingly, the present invention was completed by developing a non-fluorinated polyimide-based high-strength, high-light-resistant transparent flexible optical film material and process technology, as a result of efforts to develop a new non-fluorinated polyimide, which has (1) excellent mechanical properties and optical properties simultaneously, (2) excellent bending reliability, and (3) can solve the problem of low light resistance, which is a chronic problem of non-fluorinated polyimides. Prior art literature

[0013] Republic of Korea Patent Publication No. 10-2024-0098938 Republic of Korea Patent Registration No. 10-2705540 Republic of Korea Patent Registration No. 10-2704985 Republic of Korea Patent Registration No. 10-2475436 The problem to be solved

[0014] The problem that the present invention aims to solve is to provide a non-fluorinated polyimide resin having excellent mechanical properties, optical properties, light resistance, and flexural reliability.

[0015] Another problem that the present invention aims to solve is to provide a method for manufacturing a non-fluorinated polyimide resin according to the present invention.

[0016] Another problem that the present invention aims to solve is to provide a composition for forming a high-strength, high-light-resistant transparent flexible optical film comprising a non-fluorinated polyimide resin according to the present invention.

[0017] Another problem that the present invention aims to solve is to provide a high-strength, high-light-resistant transparent flexible optical film comprising a non-fluorinated polyimide resin according to the present invention, and a display device comprising such a film. means of solving the problem

[0019] To solve the above problem, the present invention provides a non-fluorinated polyimide comprising the structure of the following chemical formula 1.

[0020] [Chemical Formula 1]

[0021]

[0022] In the above chemical formula 1,

[0023] The above X is a substituted or unsubstituted C6 to C 30 A C3 to C2 having a divalent aromatic organic group, wherein the aromatic organic group exists alone; two or more are joined to form a condensed ring; or two or more aromatic rings are single-bonded, substituted, or unsubstituted. 10 Cycloalkylene group, substituted or unsubstituted C6 to C 15 It is connected by functional groups that are arylene groups, -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O)2-, -Si(CH3)2-, -(CH2)p- (where 1≤p≤10), -C(CH3)2-, -C(=O)NH-, or a combination of two or more of these, and

[0024] The above Y is substituted or unsubstituted C4 to C 30 A tetravalent aromatic organic group comprising, said aromatic organic group, existing alone; two or more joined to form a condensed ring; or two or more aromatic rings having single bonds, substituted, or unsubstituted C3 to C 10 Cycloalkylene group, substituted or unsubstituted C6 to C 15 It is connected by functional groups that are arylene groups, -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O)2-, -Si(CH3)2-, -(CH2)p- (where 1≤p≤10), -C(CH3)2-, -C(=O)NH-, or a combination of two or more of these, and

[0025] The above x and y are each integers greater than or equal to 1.

[0026] In addition, the present invention

[0027] 1) A step of synthesizing a non-fluorinated amide oligomer by reacting a diamine mixture composed of 4,4′-diaminodiphenyl sulfone (4,4′-DDS) and 3,3′-diaminodiphenyl sulfone (3,3′-DDS) with terephthaloyl chloride (TPCL);

[0028] 2) a step of synthesizing a non-fluorinated polyimide precursor by reacting the non-fluorinated amide oligomer of step 1) with any one selected from the group consisting of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), and mixtures thereof; and

[0029] 3) a step of synthesizing a non-fluorinated polyimide by chemically imidizing the non-fluorinated polyimide precursor of step 2) above; the present invention provides a method for manufacturing a non-fluorinated polyimide, comprising: a step of synthesizing a non-fluorinated polyimide.

[0030] In addition, the present invention provides a composition for forming a non-fluorinated polyimide film comprising a non-fluorinated polyimide according to the present invention.

[0031] In addition, the present invention provides a non-fluorinated polyimide film comprising a non-fluorinated polyimide according to the present invention.

[0032] In addition, the present invention provides a method for manufacturing a non-fluorinated polyimide film, comprising the process of dissolving a solid portion of the non-fluorinated polyimide according to the present invention in a solvent to prepare a non-fluorinated polyimide resin solution, and then coating the solution onto a substrate and drying it to manufacture a non-fluorinated polyimide film.

[0033] In addition, the present invention provides a display device comprising a non-fluorinated polyimide film according to the present invention. Effects of the invention

[0035] The non-fluorinated polyimide-based film according to the present invention simultaneously possesses excellent mechanical properties and optical properties, has excellent bending reliability, and has high light resistance.

[0036] The non-fluorinated polyimide-based film material and manufacturing process technology according to the present invention can contribute to strengthening national competitiveness and increasing the localization rate by achieving the localization of functional polyimide materials currently dependent on advanced countries abroad, creating new high-value-added markets related to next-generation displays and electronic products, and reducing dependence on advanced countries abroad for related core components. Brief explanation of the drawing

[0038] Figure 1 is a figure showing the synthesis process of embodiments of the present invention. Figure 2 is a figure showing the synthesis process of comparative examples of the present invention. FIG. 3 is a graph showing the mechanical properties of Examples 1 to 4 and Comparative Examples 1 to 2 of the present invention. FIG. 4 is a graph showing the light transmittance of Examples 1 to 4 and Comparative Examples 1 to 2 of the present invention. FIG. 5 is a graph showing the yellowness (YI) of Examples 1 to 4 of the present invention. Figure 6 is a figure showing the results of the dynamic bending reliability test of Example 4 of the present invention. Specific details for implementing the invention

[0039] The present invention will now be described in detail. Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings. Instead, based on the principle that the inventor may appropriately define the concepts of terms to best describe their invention, they must be interpreted in a meaning and concept consistent with the technical spirit of the present invention.

[0040] Therefore, it should be understood that the embodiments described in this specification are merely the most preferred embodiments of the invention and do not represent all of the technical ideas of the invention, and that various equivalents and modifications that can replace them may exist at the time of filing this application.

[0042] The present invention provides a non-fluorinated polyimide comprising the structure of the following chemical formula 1.

[0043]

[0044] In the above chemical formula 1,

[0045] The above X is a substituted or unsubstituted C6 to C 30 A C3 to C2 having a divalent aromatic organic group, wherein the aromatic organic group exists alone; two or more are joined to form a condensed ring; or two or more aromatic rings are single-bonded, substituted, or unsubstituted. 10 Cycloalkylene group, substituted or unsubstituted C6 to C 15 It is connected by functional groups that are arylene groups, -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O)2-, -Si(CH3)2-, -(CH2)p- (where 1≤p≤10), -C(CH3)2-, -C(=O)NH-, or a combination of two or more of these, and

[0046] The above Y is substituted or unsubstituted C4 to C 30A tetravalent aromatic organic group comprising, said aromatic organic group, existing alone; two or more joined to form a condensed ring; or two or more aromatic rings having single bonds, substituted, or unsubstituted C3 to C 10 Cycloalkylene group, substituted or unsubstituted C6 to C 15 It is connected by functional groups that are arylene groups, -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O)2-, -Si(CH3)2-, -(CH2)p- (where 1≤p≤10), -C(CH3)2-, -C(=O)NH-, or a combination of two or more of these, and

[0047] The above x and y are each integers greater than or equal to 1.

[0049] Unless otherwise specified, the term "substitution" means that one or more hydrogen atoms of a functional group in a specific chemical formula are substituted with one or more substituents selected from the group consisting of a halogen atom (Br, Cl, or I), a hydroxyl group, a nitro group, a cyano group, an amino group {NH2, NH(R), or N(R')(R''), wherein R, R', and R'' are the same or different from each other and are each independently a C1 to C10 alkyl group}, an amidino group, a hydrazine group, a hydrazone group, a carboxyl group, an ester group, a ketone group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alicyclic organic group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, and a substituted or unsubstituted heterocyclic group, and said substituents may be connected to each other to form a ring.

[0050] Here, "ester group" refers to C2 to C 30 It refers to an ester group, specifically C2 to C 18 It refers to an ester group, and "alkyl group" refers to a C1 to C1 30 It refers to an alkyl group, and "aliphatic organic group" refers to a substituted or unsubstituted C3 to C 30Cycloalkyl group, substituted or unsubstituted C3 to C 30 Cycloalkenyl groups, or substituted or unsubstituted C3 to C 30 It refers to a tetracycloalkynyl group, specifically a substituted or unsubstituted C3 to C 15 Cycloalkyl group, substituted or unsubstituted C3 to C 15 Cycloalkenyl groups, or substituted or unsubstituted C3 to C 15 It refers to a cycloalkynyl group, and "aryl group" refers to C6 to C 30 It refers to an aryl group, specifically C6 to C 18 It refers to an aryl group, and "alkenyl group" refers to a C2 to C group containing one or more carbon-carbon double bonds. 30 It refers to an alkenyl group, specifically C2 to C 18 It means an alkenyl group, and "alkenyl group" refers to a C2 to C group containing one or more carbon-carbon triple bonds. 30 alkynyl groups, specifically C2 to C 18 It means an alkynyl group, and "heterocyclic group" refers to a substituted or unsubstituted C3 to C4 containing 1 to 3 heteroatoms selected from the group consisting of O, S, N, P, Si, and combinations thereof within a single ring. 30 cycloalkyl groups, substituted or unsubstituted C3 to C 30 cycloalkenyl groups of, substituted or unsubstituted C3 to C 30 The cycloalkynyl group of, or substituted or unsubstituted C6 to C 30 It refers to a heteroaryl group, specifically a substituted or unsubstituted C3 to C6 containing 1 to 3 heteroatoms selected from the group consisting of O, S, N, P, Si, and combinations thereof within a single ring. 15 cycloalkyl groups, substituted or unsubstituted C3 to C 15 cycloalkenyl groups of, substituted or unsubstituted C3 to C 15It means a cycloalkynyl group, or a substituted or unsubstituted C6 to C15 heteroaryl group.

[0051] X of the above chemical formula 1 is

[0052] It could be,

[0053] Y of the above chemical formula 1 is

[0054] or It could be.

[0056] In addition, the present invention

[0057] 1) A step of synthesizing a non-fluorinated amide oligomer by reacting a diamine mixture composed of 4,4′-diaminodiphenyl sulfone (4,4′-DDS) and 3,3′-diaminodiphenyl sulfone (3,3′-DDS) with terephthaloyl chloride (TPCL);

[0058] 2) a step of synthesizing a non-fluorinated polyimide precursor by reacting the non-fluorinated amide oligomer of step 1) with any one selected from the group consisting of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), and mixtures thereof; and

[0059] 3) a step of synthesizing a non-fluorinated polyimide by chemically imidizing the non-fluorinated polyimide precursor of step 2) above; the present invention provides a method for manufacturing a non-fluorinated polyimide, comprising: a step of synthesizing a non-fluorinated polyimide.

[0061] In the above manufacturing method, in step 1), 4,4′-diaminodiphenyl sulfone (4,4′-diaminodiphenyl sulfone; 4,4'-DDS) and 3,3′-diaminodiphenyl sulfone (3,3′-diaminodiphenyl sulfone; 3,3′-DDS) can be mixed in a molar ratio of 1:99 to 99:1.

[0062] In the above manufacturing method, in step 1), the diamine mixture and terephthaloyl chloride (TPCL) can be mixed in a molar ratio of 1:99 to 99:1.

[0063] In the above manufacturing method, in step 2), any one selected from the group consisting of a non-fluorinated amide oligomer and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), and mixtures thereof may be mixed in a molar ratio of 1:99 to 99:1, and it is more preferable to mix in a molar ratio of 9:1 to 7:3.

[0064] In the above manufacturing method, the imidation method in step 3) mainly includes thermal imidation and chemical imidation methods.

[0065] The above thermal imidation method includes, for example, a method of imidizing a non-fluorinated polyimide precursor by applying heat up to 250 to 500°C. At this time, to promote imidation, a dehydrating ring-closing agent, a ring-closing catalyst, or two or more of these may be added to the non-fluorinated polyimide precursor dissolved in an organic solvent. The dehydrating ring-closing agent or ring-closing catalyst may be, for example, a tertiary amine such as pyridine, triethylamine, tributylamine, or isoquinoline; or an acid anhydride such as acetic anhydride, propionic anhydride, or benzoic anhydride.

[0066] The above chemical imidation method includes, for example, a method of obtaining a direct polyimide by heating the non-fluorinated polyimide precursor to 100°C or higher or 180°C or higher in the presence of a catalyst such as tributylamine, triethylamine, triphenyl phosphite, isoquinoline, or pyridine (25 parts by weight or less of the total reactant) or a dehydration catalyst such as p-toluenesulfonic acid (25 parts by weight or less of the total reactant) as needed. Additionally, there is a method of removing the ring at a relatively low temperature (room temperature to 100°C) by adding a dehydration ring-removing agent such as acetic anhydride, propionic anhydride, benzoic anhydride, or a carbodiimide compound such as dicyclohexylcarbodiimide, and, if needed, a ring-removing catalyst such as pyridine, isoquinoline, imidazole, or triethylamine to the non-fluorinated polyimide precursor.

[0067] After the above imidization is performed, the resulting product can be obtained as a solid by precipitating and grinding it in an excess amount of solvent.

[0068] In the above manufacturing method, the step of adding the imidized non-fluorinated polyimide resin to an excess amount of ethanol and stirring and filtering it to obtain a high-purity solid may be further included. At this time, the step of adding the imidized non-fluorinated polyimide resin to ethanol and stirring may be performed for 1 to 48 hours. The obtained high-purity non-fluorinated polyimide resin may be dried at 60 to 250°C for 12 to 96 hours.

[0070] In addition, the present invention provides a composition for forming a non-fluorinated polyimide film comprising a non-fluorinated polyimide according to the present invention.

[0071] In addition, the present invention provides a non-fluorinated polyimide film comprising a non-fluorinated polyimide according to the present invention.

[0072] In addition, the present invention provides a method for manufacturing a non-fluorinated polyimide film, comprising the process of dissolving a solid portion of the non-fluorinated polyimide according to the present invention in a solvent to prepare a non-fluorinated polyimide resin solution, and then coating the solution onto a substrate and drying it to manufacture a non-fluorinated polyimide film.

[0073] The above non-fluorinated polyimide film can be manufactured by precipitating and grinding a non-fluorinated polyimide resin according to one embodiment of the present invention in excess water to obtain a solid, then proceeding with a solvent exchange process to obtain a high-purity polyimide resin solid, and dissolving the solid in a solvent to form a non-fluorinated polyimide resin solution, which is then coated and dried on a substrate.

[0074] The method of coating the above-mentioned composition for forming a non-fluorinated polyimide resin on a substrate may use any conventional method known in the art without limitation, such as spin coating, dip coating, solvent casting, slot die coating, spray coating, etc.

[0075] The above drying can be performed, for example, at 50 to 400 ℃ for 10 to 360 minutes.

[0077] In addition, the present invention provides a display device comprising a non-fluorinated polyimide film according to the present invention.

[0078] The above-mentioned non-fluorinated polyimide film can be used in various fields, and in particular, it can be utilized as a substrate and protective film for flexible displays such as organic light-emitting diode (OLED) displays, liquid crystal displays, TFT substrates, flexible printed circuit boards, flexible OLED surface lighting substrates, and substrate materials for electronic paper, where high transparency and heat resistance are required.

[0080] Hereinafter, the present invention will be described in detail with reference to examples to aid in understanding. However, the embodiments according to the present invention may be modified in various different forms, and the scope of the present invention should not be interpreted as being limited to the following embodiments. The embodiments of the present invention are provided to more completely explain the present invention to those with average knowledge in the art.

[0082] <Examples 1 to 4>

[0083] To prepare the example, a non-fluorinated amide oligomer was first synthesized by reacting a diamine mixture composed of 4,4'-diaminodiphenyl sulfone (4,4′-diaminodiphenyl sulfone; 44DDS) and 3,3′-diaminodiphenyl sulfone (3,3′-diaminodiphenyl sulfone; 33DDS) with terephthaloyl chloride (TPCL). Subsequently, a non-fluorinated polyimide precursor was synthesized by further reacting it with 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) alone, a dianhydride mixture consisting of BPDA and 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), or CBDA dianhydride alone. Then, a non-fluorinated polyimide was synthesized using a chemical imidation method.

[0084] A solid portion of the above-mentioned non-fluorinated polyimide was dissolved in a solvent to form a non-fluorinated polyimide resin solution. A non-fluorinated polyimide film was prepared by coating the solution onto a glass substrate using a casting method and drying it.

[0086] <Comparative Examples 1 ~ 2>

[0087] To prepare a comparative example, a conventional fluorinated polyimide precursor was synthesized by reacting 2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diamine (TFDB) alone with 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) alone or with a mixture of 6FDA and BDPA. Then, a conventional fluorinated polyimide was synthesized using a chemical imidation method.

[0088] A fluorinated polyimide resin solution was formed by dissolving the solid portion of the above fluorinated polyimide in a solvent. A fluorinated polyimide film was prepared by coating and drying the solution onto a glass substrate using a casting method.

[0090] Components and composition ratios of the examples and comparative examples Sample Chemical composition diamine Diasilhalide Imusumul TFBD 44DDS 33DDS TPCL 6FDA BPDA CBDA mol% Comparative Example 1 100 100 Comparative Example 2 100 80 20 Example 1 60 40 70 30 Example 2 60 40 70 20 10 Example 3 60 40 70 10 20 Example 4 60 40 70 30

[0092] <Experimental Example 1> Measurement of mechanical properties, optical properties, light resistance, and flexural reliability

[0093] As a result of comparative analysis using a Universal Testing Machine (UTM) and a colorimeter on the polyimide films prepared in Examples 1 to 4 and Comparative Examples 1 to 2, it was found that all examples not only exhibited excellent optical properties comparable to all comparative examples but also possessed improved mechanical properties compared to the comparative examples. Through this, it was confirmed that the non-fluorinated polyimide-based optical film developed in the present invention possesses excellent optical properties and improved mechanical properties simultaneously by overcoming the inherent trade-off between optical properties and mechanical properties of conventional polyimide materials.

[0094] In addition, after exposing all examples to UV for 72 hours and comparing the yellowness index before and after UV exposure, it was found that the difference in yellowness index was less than 3 for all of them, and in particular, in the case of Comparative Example 4, the difference in yellowness index was less than 1. Through this, it was confirmed that the non-fluorinated polyimide-based optical film developed in the present invention has excellent light resistance, unlike conventional non-fluorinated polyimide-based optical films.

[0095] In addition, as a result of conducting a dynamic bending reliability test of Example 4 under conditions of a bending radius of 1.5 mm and a bending radius of 180 degrees, it was found that no damage occurred to the surface even after undergoing more than 500,000 folding / unfolding cycles. Through this, it was confirmed that the non-fluorinated polyimide-based optical film developed in the present invention has excellent bending reliability. Industrial applicability

[0097] The non-fluorinated polyimide-based high-strength transparent flexible optical film according to the present invention, which can replace glass, a core material of flexible displays, can be applied to displays and electronic components having various complex form factors such as foldable, rollable, wearable, and stretchable displays, as well as to advanced materials and components in future mobility.

[0098] No content

Claims

Claim 1 Non-fluorinated polyimide comprising the structure of Chemical Formula 1 below: [Chemical Formula 1] In the above Chemical Formula 1, X is a substituted or unsubstituted C6 to C 30 A C3 to C2 having a divalent aromatic organic group, wherein the aromatic organic group exists alone; two or more are joined to form a condensed ring; or two or more aromatic rings are single-bonded, substituted, or unsubstituted. 10 Cycloalkylene group, substituted or unsubstituted C6 to C 15 It is connected by functional groups that are arylene groups, -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O)2-, -Si(CH3)2-, -(CH2)p- (where 1≤p≤10), -C(CH3)2-, -C(=O)NH-, or a combination of two or more of these, and the above Y is a substituted or unsubstituted C4 to C 30 A tetravalent aromatic organic group comprising, said aromatic organic group, existing alone; two or more joined to form a condensed ring; or two or more aromatic rings having single bonds, substituted, or unsubstituted C3 to C 10 Cycloalkylene group, substituted or unsubstituted C6 to C 15 It is connected by functional groups that are arylene groups, -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O)2-, -Si(CH3)2-, -(CH2)p- (where 1≤p≤10), -C(CH3)2-, -C(=O)NH-, or a combination of two or more of these, and x and y are each integers greater than or equal to 1. Claim 2 In claim 1, X of the above chemical formula 1 is A non-fluorinated polyimide characterized by being. Claim 3 In claim 1, Y of the above chemical formula 1 is or A non-fluorinated polyimide characterized by being. Claim 4 1) a step of synthesizing a non-fluorinated amide oligomer by reacting a diamine mixture composed of 4,4′-diaminodiphenyl sulfone (4,4'-DDS) and 3,3′-diaminodiphenyl sulfone (3,3′-DDS) with terephthaloyl chloride (TPCL); 2) a step of reacting the non-fluorinated amide oligomer from step 1) with any one selected from the group consisting of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), and mixtures thereof to synthesize a non-fluorinated A method for manufacturing a non-fluorinated polyimide, comprising: a step of synthesizing a polyimide precursor; and 3) a step of chemically imidizing the non-fluorinated polyimide precursor of step 2) to synthesize a non-fluorinated polyimide. Claim 5 A method for preparing a non-fluorinated polyimide according to claim 4, characterized in that in step 1), 4,4′-diaminodiphenyl sulfone (4,4′-DDS) and 3,3′-diaminodiphenyl sulfone (3,3′-DDS) are mixed in a molar ratio of 1:99 to 99:

1. Claim 6 A method for preparing a non-fluorinated polyimide according to claim 4, characterized in that in step 1), the diamine mixture and terephthaloyl chloride (TPCL) are mixed in a molar ratio of 1:99 to 99:

1. Claim 7 A method for preparing a non-fluorinated polyimide according to claim 4, wherein in step 2), a non-fluorinated amide oligomer is mixed with any one selected from the group consisting of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), and mixtures thereof in a molar ratio of 1:99 to 99:

1. Claim 8 A composition for forming a non-fluorinated polyimide film comprising a non-fluorinated polyimide according to any one of claims 1 to 3. Claim 9 A non-fluorinated polyimide film comprising a non-fluorinated polyimide according to any one of claims 1 to 3. Claim 10 A method for manufacturing a non-fluorinated polyimide film, comprising: 1) a step of manufacturing a non-fluorinated polyimide according to any one of claims 4 to 7; 2) a step of manufacturing a non-fluorinated polyimide resin solution by dissolving the solid portion of the non-fluorinated polyimide in a solvent; and 3) a step of manufacturing a non-fluorinated polyimide film by coating the non-fluorinated polyimide resin solution onto a substrate and drying it. Claim 11 A display device comprising a non-fluorinated polyimide film according to claim 9. Claim 12 A display device according to claim 11, characterized in that the display device is a flexible display device.

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