Polyimide precursor, polyimide precursor composition, polyimide film, preparation method and use thereof

Abstract

The present invention provides a polyimide precursor, a polyimide precursor solution, a polyimide film, and a preparation method and use thereof. According to an exemplary embodiment of the present invention, a polyimide film having excellent heat resistance and satisfying transparency and low linear thermal expansion coefficient can be provided, so it can be usefully applied to the field of flexible displays requiring high dimensional stability, etc.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the priority of Korean Patent Application No. 10-2020-0085890 filed on July 13, 2020, in the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The invention relates to a polyimide precursor, a polyimide precursor solution, a polyimide film, a preparation method and use thereof. Background Art

[0004] Polyimide is considered to be a highly heat-resistant, lightweight and flexible material. Aromatic polyimide is attracting attention as a resin with excellent thermal dimensional stability in the field of polyimide. Polyimide film is a molded body composed of aromatic polyimide with a rigid and linear chemical structure, and is widely used in fields requiring high thermal dimensional stability (low linear thermal expansion coefficient), such as base films of flexible printed circuit boards and interlayer insulating films of semiconductors. However, since aromatic polyimide with a low linear thermal expansion coefficient is strongly colored by intramolecular conjugation and intramolecular / intermolecular charge transfer interactions, it is difficult to apply aromatic polyimide to optical applications. In addition, since the intermolecular force of polyimide is very strong, it lacks processability.

[0005] Meanwhile, a flexible device is manufactured by applying a polyimide precursor composition on a conveyor plate and curing the composition to form a film, completing the device through subsequent processes such as thin film transistor (TFT) and organic film deposition, and then separating the completed device from the conveyor plate. Flexible devices involving high temperature processes themselves require high heat resistance at high temperatures. In particular, when using a thin film transistor process of low temperature polycrystalline silicon (LTPS), the process temperature may be close to 500°C. Therefore, even during high temperature treatment, the polyimide film formed as a film on the conveyor plate should not be thermally decomposed due to hydrolysis and meet high heat resistance. In addition, transparency after processing and storage stability should be ensured.

[0006] Therefore, there is a need to develop novel polyimides that can satisfy high heat resistance and also prevent hydrolysis to exhibit excellent chemical resistance and storage stability and improve optical / mechanical properties to fabricate flexible devices. Summary of the invention

[0007] Embodiments of the present invention provide a polyimide precursor and a polyimide precursor solution for providing a polyimide film having excellent heat resistance and satisfying transparency and a low linear thermal expansion coefficient, and a method for preparing the same.

[0008] Another embodiment of the present invention provides a method for preparing a polyimide film using a polyimide precursor solution.

[0009] Another embodiment of the present invention provides a polyimide film that can be usefully applied to a field requiring high dimensional stability and a multilayer structure including the polyimide film.

[0010] Still another embodiment of the present invention provides an optoelectronic device and a flexible display including the polyimide film.

[0011] In one general aspect, the polyimide precursor solution includes: a polyimide precursor derived from a tetracarboxylic dianhydride represented by Chemical Formula 1:

[0012] [Chemical formula 1]

[0013]

[0014] in

[0015] Q 1 is a single bond, -C(=O)-, -C(=O)O-, -C(=O)NH-, -NR′-, -S-, -SO 2 -、-CH 2 -, or a combination thereof, wherein R′ is hydrogen or a C1-C10 alkyl group;

[0016] R 1 and R 2 are independently halogen, hydroxyl, mercapto, nitro, cyano, C1-C10 alkyl, C1-C10 alkoxy, C6-C20 aryl, or a combination thereof, or may be connected to adjacent substituents to form a ring;

[0017] n and m are each independently an integer selected from 0 to 4, and when n and m are integers of 2 or more, R 1 and R 2 May be the same as or different from each other.

[0018] In the polyimide precursor solution, the tetracarboxylic dianhydride may be selected from the compounds represented by the following Chemical Formula 2 to Chemical Formula 5:

[0019] [Chemical formula 2]

[0020]

[0021] [Chemical formula 3]

[0022]

[0023] [Chemical formula 4]

[0024]

[0025] [Chemical formula 5]

[0026]

[0027] in

[0028] R 1 , R 2 , R′, n and m are as defined in Formula 1 above.

[0029] In the polyimide precursor solution, the polyimide precursor solution may include: a polymeric component including tetracarboxylic dianhydride represented by Chemical Formula 1 and diamine; and an organic solvent.

[0030] In the polyimide precursor solution, the diamine may include a unit represented by the following Chemical Formula 6:

[0031] [Chemical formula 6]

[0032]

[0033] in

[0034] R 3 is hydrogen, C1-C10 alkyl or C1-C10 fluoroalkyl;

[0035] p is an integer of 1 or 2.

[0036] In the polyimide precursor solution, the organic solvent may be selected from amides.

[0037] In the polyimide precursor solution, the organic solvent may be N,N-diethylacetamide, N,N-diethylformamide, N-ethylpyrrolidone, N,N-dimethylpropionamide, N,N-diethylpropionamide, or a combination thereof.

[0038] In the polyimide precursor solution, tetracarboxylic dianhydride selected from the compounds represented by the following Chemical Formula 7 and Chemical Formula 8 may also be included as a polymerization component:

[0039] [Chemical formula 7]

[0040]

[0041] [Chemical formula 8]

[0042]

[0043] in

[0044] Q 2 and Q 3 is a single bond, -O-, -C(=O)-, -C(=O)O-, -C(=O)NH-, -NR'-, -S-, -SO2 -, phenylene or a combination thereof, wherein R′ is hydrogen or a C1-C10 alkyl group.

[0045] In another general aspect, a polyimide precursor derived from a tetracarboxylic dianhydride represented by Chemical Formula 1 and a diamine is provided.

[0046] The polyimide precursor may include a repeating unit represented by the following chemical formula a:

[0047] [Chemical formula a]

[0048]

[0049] in

[0050] Q 1 is a single bond, -C(=O)-, -C(=O)O-, -C(=O)NH-, -NR′-, -S-, -SO 2 -、-CH 2 -,

[0051] or a combination thereof, wherein R′ is hydrogen or a C1-C10 alkyl group;

[0052] R a and R b are independently hydrogen or C1-C10 alkyl;

[0053] R 1 and R 2 are independently halogen, hydroxyl, mercapto, nitro, cyano, C1-C10 alkyl, C1-C10 alkoxy, C6-C20 aryl, or a combination thereof, or may be connected to adjacent substituents to form a ring;

[0054] R 3 is hydrogen, C1-C10 alkyl or C1-C10 fluoroalkyl;

[0055] p is an integer of 1 or 2;

[0056] n and m are each independently an integer selected from 0 to 4, and when n and m are integers of 2 or more, R 1 and R 2 May be the same as or different from each other.

[0057] The polyimide precursor may include 10 to 100 mol % of the repeating unit represented by Chemical Formula a based on the total repeating units.

[0058] In another general aspect, the polyimide film may include a repeating unit represented by the following chemical formula b:

[0059] [Chemical formula b]

[0060]

[0061] in

[0062] Q 1 is a single bond, -C(=O)-, -C(=O)O-, -C(=O)NH-, -NR′-, -S-, -SO 2 -、-CH 2 -,

[0063] or a combination thereof, wherein R′ is hydrogen or a C1-C10 alkyl group;

[0064] R 1 and R 2 are independently halogen, hydroxyl, mercapto, nitro, cyano, C1-C10 alkyl, C1-C10 alkoxy, C6-C20 aryl, or a combination thereof, or may be connected to adjacent substituents to form a ring;

[0065] R 3 is hydrogen, C1-C10 alkyl or C1-C10 fluoroalkyl;

[0066] p is an integer of 1 or 2;

[0067] n and m are each independently an integer selected from 0 to 4, and when n and m are integers of 2 or more, R 1 and R 2 May be the same as or different from each other.

[0068] The polyimide film may also include a repeating unit represented by the following chemical formula c or chemical formula d:

[0069] [Chemical formula c]

[0070]

[0071] [Chemical formula d]

[0072]

[0073] in

[0074] R 3 is hydrogen, C1-C10 alkyl or C1-C10 fluoroalkyl;

[0075] p is an integer of 1 or 2.

[0076] The polyimide film may have a coefficient of thermal expansion (CTE) of 50 ppm / ° C. or less at 100-450° C.

[0077] The polyimide film may have a YI according to ASTM E313 of 15 or less, a haze according to ASTM D1003 of 2 or less, and a total light transmittance within a range of 380-780 nm according to ASTM D1746 of 80% or more.

[0078] The polyimide film may have a modulus of 5.0 or more according to ASTM D882 and an elongation of 15% or more.

[0079] The polyimide film may have a coefficient of thermal expansion of 50 ppm / ° C. or less at 100-450° C.; a YI according to ASTM E313 of 15 or less; a haze according to ASTM D1003 of 2 or less; an average light transmittance in the range of 380-780 nm according to ASTM D1746 of 80% or more; and a modulus according to ASTM D882 of 8.0 or less and an elongation of 15% or more.

[0080] In another general aspect, a multilayer structure includes the polyimide film described above.

[0081] In another general aspect, an optoelectronic device includes the above-described polyimide film as a flexible substrate.

[0082] In another general aspect, a flexible display includes the above-described polyimide film as a flexible substrate.

[0083] In another general aspect, a method of preparing a polyimide film includes applying and coating the above-mentioned polyimide precursor solution on a substrate, followed by heat treatment.

[0084] In the method of preparing a polyimide film, the heat treatment may include a first heat treatment performed at a temperature of 100° C. or less; a second heat treatment performed at a temperature higher than 100° C. and lower than 300° C.; and a third heat treatment performed at a temperature higher than 300° C. and lower than 500° C.

[0085] In the method of preparing a polyimide film, the polyimide precursor solution may include a solid content of 10 to 13 wt % based on the total weight.

[0086] Other features and aspects will be apparent from the following detailed description, drawings, and claims. DETAILED DESCRIPTION

[0087] In this specification, unless otherwise defined, all technical terms and scientific terms have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein are only for effectively describing a specific example and are not intended to limit the present invention.

[0088] Unless otherwise indicated in the context, a singular form used in this specification may also include a plural form.

[0089] In addition, the units used in this specification are based on weight unless otherwise specified. For example, unless otherwise defined, the unit of % or ratio refers to weight % or weight ratio, and weight % refers to the weight % of any component in the total composition.

[0090] In addition, the numerical range used in this specification includes all values ​​within the range including the lower limit and the upper limit, the increments and spans within the defined range derived in some form of logic, all double limit values, and all possible combinations of upper and lower limits within the numerical range defined in different forms. Unless otherwise defined in the specification of the present invention, values ​​that may exceed the numerical range due to experimental errors or rounding of numerical values ​​are also included in the defined numerical range.

[0091] Unless otherwise stated, the term "comprising" in the present specification may be an open term implying the further inclusion of other components rather than the exclusion of other components.

[0092] The term "derived" in this specification means that at least one functional group of a compound is modified, and specifically may include a modified form or a evolved form (leased form) of the functional group and / or leaving group of the compound according to the reaction. In addition, when the structures derived from different compounds are the same, it may include a case where the structure derived from any one compound has the same structure as the structure derived from any other compound.

[0093] The term "polyimide precursor solution" in this specification refers to a composition for preparing polyimide, specifically, a polyimide precursor refers to a polymer including a structural unit having an amic acid portion, and may be equivalent to polyamic acid. In addition, the polyimide precursor solution may also be used as a composition for preparing polyamideimide.

[0094] The term "polyimide film" in the present specification is a molded body of polyimide derived from a polyimide precursor solution and may be equivalent to polyimide.

[0095] The term "halogen" in the present specification refers to a fluorine (F), chlorine (Cl), bromine (Br) or iodine (I) atom.

[0096] The term "alkyl group" in the present specification is an organic group derived from an aliphatic hydrocarbon by removing one hydrogen, and may include a straight chain form and a branched chain form.

[0097] The term "alkoxy" in the present specification means *-O-alkyl, and the alkyl group has the same meaning as above.

[0098] The terms "haloalkyl" and "haloalkoxy" in this specification refer to an alkyl or alkoxy group in which one hydrogen is replaced by a halogen.

[0099] The term "aryl group" in the present specification is an organic group derived from an aromatic hydrocarbon by removing one hydrogen, including a single ring or a condensed ring system, or even in the form of multiple aromatic groups connected by a single bond.

[0100] The present inventors have conducted in-depth research on optically transparent polyimides having excellent thermal dimensional stability and high Tg values, and found that a more rigid linear structure is introduced into the mother core skeleton of tetracarboxylic dianhydride, and fluorene is included, thereby not only satisfying significantly improved thermal dimensional stability but also increasing transparency. That is, the present inventors confirmed that the polyimide derived from tetracarboxylic dianhydride having such structural characteristics also satisfies a low linear thermal expansion coefficient and has excellent transparency and heat resistance, thereby proposing the present invention.

[0101] Hereinafter, exemplary embodiments of the present invention will be described in more detail.

[0102] The polyimide precursor solution according to the exemplary embodiment of the present invention may include a polyimide precursor derived from tetracarboxylic dianhydride represented by the following Chemical Formula 1, which is a novel tetracarboxylic dianhydride.

[0103] [Chemical formula 1]

[0104]

[0105] in

[0106] Q 1 is a single bond, -C(=O)-, -C(=O)O-, -C(=O)NH-, -NR′-, -S-, -SO 2 -、-CH 2 -, or a combination thereof, wherein R′ is hydrogen or a C1-C10 alkyl group;

[0107] R 1 and R 2 are independently halogen, hydroxyl, mercapto, nitro, cyano, C1-C10 alkyl, C1-C10 alkoxy, C6-C20 aryl, or a combination thereof, or may be connected to adjacent substituents to form a ring;

[0108] n and m are each independently an integer selected from 0 to 4, and when n and m are integers of 2 or more, R 1 and R 2 May be the same as or different from each other.

[0109] By satisfying the above structure, the polyimide precursor derived from tetracarboxylic dianhydride according to the exemplary embodiment of the present invention can satisfy excellent thermal dimensional stability. That is, heat resistance can be excellent. In addition, the intermolecular packing density can be increased to provide a polyimide film with increased transparency and reduced yellow index. However, when Q in Chemical Formula 1 1 When the oxygen atom is present, intramolecular bending occurs, and the polyimide derived therefrom has a reduced rigid structural property. 1 Polyimide having a carbon atom (wherein carbon atom is an oxygen atom) has low thermal dimensional stability.

[0110] The tetracarboxylic dianhydride may be selected from the compounds represented by the following Chemical Formula 2 to Chemical Formula 5:

[0111] [Chemical formula 2]

[0112]

[0113] [Chemical formula 3]

[0114]

[0115] [Chemical formula 4]

[0116]

[0117] [Chemical formula 5]

[0118]

[0119] in

[0120] R 1 and R 2 are independently halogen, hydroxyl, mercapto, nitro, cyano, C1-C10 alkyl, C1-C10 alkoxy, C6-C20 aryl, or a combination thereof, or may be connected to adjacent substituents to form a ring; and

[0121] R' is hydrogen or C1-C4 alkyl;

[0122] n and m are each independently an integer selected from 0 to 4, and when n and m are integers of 2 or more, R 1 and R 2 May be the same as or different from each other.

[0123] For example, a tetracarboxylic dianhydride having a mother core skeleton derived from spirobifluorene, such as the compound represented by Chemical Formula 2, may have further improved heat resistance and thus also have excellent processability.

[0124] As an example, the compounds represented by Chemical Formula 3 to Chemical Formula 5 have a further improved yellowness index (YI) and excellent total light transmittance in the region of 380-780 nm, thereby providing a polyimide film having a low thermal expansion coefficient and high transparency.

[0125] The polyimide precursor solution according to an exemplary embodiment of the present invention may include a polyimide precursor derived from tetracarboxylic dianhydride, wherein in Chemical Formula 1, R 1 and R 2 They may be independently halogen, hydroxyl, mercapto, nitro, cyano, C1-C10 alkyl, C1-C10 alkoxy, C6-C20 aryl, C1-C10 haloalkyl or C1-C10 haloalkoxy, and n and m may be independently integers selected from 0-2.

[0126] As an example, in Chemical Formula 2 to Chemical Formula 5, R 1 and R 2 They may be independently halogen, hydroxyl, mercapto, nitro, cyano, C1-C10 alkyl, C1-C10 alkoxy, C6-C20 aryl, C1-C10 haloalkyl or C1-C10 haloalkoxy, and n and m may be independently integers selected from 0-2.

[0127] In the polyimide precursor solution according to an exemplary embodiment of the present invention, in Chemical Formula 1, R 1 and R 2 They may independently be halogen, hydroxyl, mercapto, nitro, cyano, C1-C4 alkyl, C1-C4 alkoxy, C6-C18 aryl, C1-C4 haloalkyl or C1-C4 haloalkoxy, and n and m may independently be integers selected from 0-2.

[0128] As an example, in Chemical Formula 2 to Chemical Formula 5, R 1 and R 2 They may independently be halogen, hydroxyl, mercapto, nitro, cyano, C1-C4 alkyl, C1-C4 alkoxy, C6-C18 aryl, C1-C4 haloalkyl or C1-C4 haloalkoxy, and n and m may independently be integers selected from 0-2.

[0129] The tetracarboxylic dianhydride according to an exemplary embodiment of the present invention may include a polyimide precursor derived from tetracarboxylic dianhydride, wherein in Chemical Formula 1, R 1 and R 2 It can be independently halogen, nitro, cyano, C1-C4 alkyl, C1-C4 alkoxy, C6-C12 aryl, C1-C4 haloalkyl or C1-C4 haloalkoxy, and n and m can be independently integers selected from 0-2, and satisfy 0≤n+m≤2.

[0130] As an example, in Chemical Formula 2 to Chemical Formula 5, R 1 and R 2 It can be independently halogen, nitro, cyano, C1-C4 alkyl, C1-C4 alkoxy, C6-C12 aryl, C1-C4 haloalkyl, or C1-C4 haloalkoxy, and n and m can be independently integers selected from 0-2 and satisfy 0≤n+m≤2.

[0131] For example, in Chemical Formula 5, R′ may be hydrogen or a C1-C4 alkyl group.

[0132] As an example, R 1 and R 2 One of the fluorene rings may be substituted at position 2 or position 7 or at both positions. 1 and R 2 A substituent of may be substituted at a designated position of the following Chemical Formula 1-1. In this case, it may be more effective in terms of mechanical strength and flexibility.

[0133] [Chemical formula 1-1]

[0134]

[0135] in

[0136] Q 1 is a single bond, -NR′-, -S- or -SO 2 -, wherein R′ is hydrogen or C1-C4 alkyl;

[0137] R 1 and R 2 They are independently halogen, nitro, cyano, C1-C4 alkyl, C1-C4 alkoxy, C6-C12 aryl, C1-C4 haloalkyl or C1-C4 haloalkoxy, and n and m are independently integers selected from 0-2 and satisfy 0≤n+m≤2.

[0138] As an example, in Chemical Formula 1-1, R 1 or R 2 It may be a halogen selected from fluorine, chlorine, bromine and iodine; an alkyl selected from methyl, ethyl, propyl and butyl; an alkoxy selected from methoxy, ethoxy, propoxy and butoxy; and an aryl selected from phenyl and naphthyl.

[0139] Tetracarboxylic dianhydride may include at least one or two or more selected from the following structures:

[0140]

[0141]

[0142] Wherein Ph is phenyl.

[0143] Furthermore, another exemplary embodiment of the present invention may be a method of preparing the above-mentioned tetracarboxylic dianhydride.

[0144] Specifically, the method for preparing tetracarboxylic dianhydride according to an exemplary embodiment of the present invention may include dehydrating and cyclizing a compound represented by the following chemical formula A in the presence of a dehydrating agent:

[0145] [Chemical formula A]

[0146]

[0147] in

[0148] Q 1 is a single bond, -C(=O)-, -C(=O)O-, -C(=O)NH-, -NR′-, -S-, -SO 2 -、-CH 2 -

[0149] or a combination thereof, wherein R′ is hydrogen or a C1-C10 alkyl group;

[0150] R 1 and R 2 are independently halogen, hydroxyl, mercapto, nitro, cyano, C1-C10 alkyl, C1-C10 alkoxy, C6-C20 aryl, or a combination thereof, or may be connected to adjacent substituents to form a ring;

[0151] n and m are each independently an integer selected from 0 to 4, and when n and m are integers of 2 or more, R 1 and R 2 May be the same as or different from each other.

[0152] As an example, the dehydrating agent may be an acid anhydride.

[0153] As an example, the acid anhydride may be selected from acetic anhydride, phthalic anhydride, maleic anhydride, and the like, and preferably, may include acetic anhydride.

[0154] As an example, the dehydrating agent may also include one or more selected from pyridine, isoquinoline, triethylamine and the like.

[0155] As an example, the dehydrating agent may be introduced in an amount of 2 to 10 mol relative to 1 mol of the compound represented by Chemical Formula A.

[0156] For example, the dehydration and cyclization steps can be carried out at 60-130°C for 2-12 hours.

[0157] An embodiment of a method for preparing tetracarboxylic dianhydride according to another exemplary embodiment of the present invention may be as shown in the following Reaction Formula 1, but various modifications may be made through common organic synthesis methods, of course.

[0158] [Reaction 1]

[0159]

[0160] Furthermore, another exemplary embodiment of the present invention is use of the above-mentioned tetracarboxylic dianhydride, and specific embodiments thereof will be described later.

[0161] A first embodiment of the present invention may be a composition including tetracarboxylic dianhydride represented by Chemical Formula 1.

[0162] The second embodiment of the present invention may be a polyimide precursor solution including a polyimide precursor derived from tetracarboxylic dianhydride represented by Chemical Formula 1. Specifically, the polyimide precursor may be a polyamic acid obtained by reacting a polymerization component including tetracarboxylic dianhydride represented by Chemical Formula 1 and a diamine.

[0163] A third embodiment of the present invention may be a polyimide precursor solution including a polyimide precursor derived from a tetracarboxylic dianhydride represented by Chemical Formula 1, and the polyimide precursor of the tetracarboxylic dianhydride may be a polyamic acid further including tetracarboxylic dianhydride known in the art.

[0164] A fourth embodiment of the present invention may be the above-mentioned first to third embodiments further including an organic solvent.

[0165] Specifically, the composition or solution of the first to fourth embodiments described above can be used to provide a polyimide film. In addition, the composition or solution of the first to fourth embodiments described above can be used to provide a polyamideimide film.

[0166] As described above, according to the present invention, a polyimide film having high transparency and heat resistance and having excellent thermal dimensional stability due to a substrate whose stress is not increased even when heat-treated at high temperatures can be provided. In particular, according to the present invention, a polyimide film having a low linear thermal expansion coefficient can be provided even without tetracarboxylic dianhydride known in the art. In addition, when tetracarboxylic dianhydride known in the art is further included, a polyimide film having a more significantly reduced linear thermal expansion coefficient can be provided.

[0167] The composition or polyimide precursor solution according to the exemplary embodiment of the present invention may be one or a mixture of two or more selected from ketones such as γ-butyrolactone, 1,3-dimethyl-2-imidazolidinone, methyl ethyl ketone, cyclohexanone, cyclopentanone and 4-hydroxy-4-methyl-2-pentanone; aromatic hydrocarbons such as toluene, xylene, tetramethylbenzene; alcohol ethers (cellosolves) such as ethylene glycol monoethyl ether, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol diethyl ether and triethylene glycol monoethyl ether; alcohol ethers such as ethyl acetate Acetates such as butyl acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate and dipropylene glycol monomethyl ether acetate; alcohols such as ethanol, propanol, ethylene glycol, propylene glycol, carbitol; amides such as N,N-dimethylpropionamide (DMPA), N,N-diethylpropionamide (DEPA), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N,N-dimethylformamide (DMF), N,N-diethylformamide (DEF), N-methylpyrrolidone (NMP), N-ethylpyrrolidone (NEP) and N,N-dimethylmethoxyacetamide.

[0168] As an example, the organic solvent may be one or a mixture of two or more selected from the above-mentioned amides.

[0169] As an example, the organic solvent may have a boiling point below 300° C. Specifically, for example, the organic solvent may be N,N-diethylformamide (DEF), N,N-diethylacetamide (DEAc), N-ethylpyrrolidone (NEP), N,N-dimethylpropionamide (DMPA), N,N-diethylpropionamide (DEPA), or a combination thereof.

[0170] The polyimide precursor solution according to the exemplary embodiment of the present invention may include aromatic diamine.

[0171] Specifically, the aromatic diamine according to the present invention may include a unit represented by the following Chemical Formula 6:

[0172] [Chemical formula 6]

[0173]

[0174] in

[0175] R 3 is hydrogen, C1-C10 alkyl or C1-C10 fluoroalkyl;

[0176] p is an integer of 1 or 2.

[0177] As an example, the aromatic diamine may be a linear aromatic diamine, and specifically, may be selected from the compounds represented by the following Chemical Formula 6-1 and Chemical Formula 6-2. Here, of course, the aromatic diamine may be used alone or as a mixture of two or more.

[0178] [Chemical formula 6-1]

[0179]

[0180] [Chemical formula 6-2]

[0181]

[0182] in

[0183] R 3 are independently hydrogen, C1-C10 alkyl or C1-C10 fluoroalkyl.

[0184] As an example, the aromatic diamine may be a fluorine-based aromatic diamine including a fluoroalkyl group.

[0185] As an example, the aromatic diamine may be a compound represented by Chemical Formula 6-1 or Chemical Formula 6-2, wherein R 3 are independently C1-C7 fluoroalkyl.

[0186] As an example, the aromatic diamine may be a compound represented by Chemical Formula 6-1 or Chemical Formula 6-2, wherein R 3 are independently C1-C3 fluoroalkyl.

[0187] The polyimide precursor solution according to the exemplary embodiment of the present invention may include tetracarboxylic dianhydride (such as the compound represented by Chemical Formula 2) having a mother core skeleton derived from spirobifluorene in terms of imparting excellent processability and further improved heat resistance.

[0188] In terms of achieving further improved yellowness index (YI) and excellent total light transmittance in the range of 380-780 nm, the polyimide precursor solution according to the exemplary embodiment of the present invention may include one or more tetracarboxylic dianhydrides selected from the compounds represented by Chemical Formula 3 to Chemical Formula 5.

[0189] In terms of achieving further improved mechanical strength and flexibility, the polyimide precursor solution according to an exemplary embodiment of the present invention may include a tetracarboxylic dianhydride of Chemical Formula 1-1, wherein R 1 or R 2 It is a C1-C4 alkyl group.

[0190] The polyimide precursor solution according to the exemplary embodiment of the present invention may further include a tetracarboxylic dianhydride selected from compounds represented by the following Chemical Formula 7 and Chemical Formula 8 known in the art as a polymerization component:

[0191] [Chemical formula 7]

[0192]

[0193] [Chemical formula 8]

[0194]

[0195] in

[0196] Q 2 and Q 3 is a single bond, -O-, -C(=O)-, -C(=O)O-, -C(=O)NH-, -NR'-, -S-, -SO 2 -, phenylene or a combination thereof, wherein R′ is hydrogen or a C1-C10 alkyl group.

[0197] The polyimide precursor solution according to the exemplary embodiment of the present invention may include tetracarboxylic dianhydride represented by Chemical Formula 1 as a polymer component and diamine as described above. Specifically, the polymer component may include tetracarboxylic dianhydride represented by Chemical Formula 1 in the range of 0.9-1.1 based on 1 mol of diamine.

[0198] In addition, when the polyimide precursor solution according to the exemplary embodiment of the present invention further includes tetracarboxylic dianhydride known in the art as described above, the molar ratio of the total content of the tetracarboxylic dianhydride represented by Chemical Formula 1 and the tetracarboxylic dianhydride known in the art to the content of the diamine may be 1:0.99 to 0.99:1, specifically 1:0.98 to 0.98:1.

[0199] In addition, when the polyimide precursor solution according to the exemplary embodiment of the present invention further includes tetracarboxylic dianhydride known in the art as described above, the tetracarboxylic dianhydride represented by Chemical Formula 1 may be included in an amount of 10-99 mol % based on the total content of the tetracarboxylic dianhydride represented by Chemical Formula 1 and tetracarboxylic dianhydride known in the art. In addition, the tetracarboxylic dianhydride represented by Chemical Formula 1 may be included in an amount of 10-90 mol %, 20-50 mol % or 20-30 mol %.

[0200] Specifically, the polyimide precursor solution according to the exemplary embodiment of the present invention may include a polyimide precursor including a repeating unit represented by the following chemical formula a, which is a polymerization product of the above-mentioned polymerization components, that is, polyamic acid:

[0201] [Chemical formula a]

[0202]

[0203] in

[0204] Q 1 is a single bond, -C(=O)-, -C(=O)O-, -C(=O)NH-, -NR′-, -S-, -SO 2 -、-CH 2 -,

[0205] or a combination thereof, wherein R′ is hydrogen or a C1-C10 alkyl group;

[0206] R a and R b are independently hydrogen or C1-C10 alkyl;

[0207] R 1 and R 2 are independently halogen, hydroxyl, mercapto, nitro, cyano, C1-C10 alkyl, C1-C10 alkoxy, C6-C20 aryl, or a combination thereof, or may be connected to adjacent substituents to form a ring;

[0208] R 3 is hydrogen, C1-C10 alkyl or C1-C10 fluoroalkyl;

[0209] p is an integer of 1 or 2;

[0210] n and m are each independently an integer selected from 0 to 4, and when n and m are integers of 2 or more, R 1 and R 2 May be the same as or different from each other.

[0211] As an example, based on the total weight, the polyimide precursor solution according to the exemplary embodiment of the present invention may have a solid content of 10-40 wt%, 10-30 wt%, 10-20 wt%, or 10-13 wt% containing a polyimide precursor, the polyimide precursor including a repeating unit represented by chemical formula a. Here, the solid content may be the content of the polyamic acid, and the remaining amount may be the amount of the organic solvent.

[0212] For example, the polyimide precursor solution according to an exemplary embodiment of the present invention may have a viscosity that satisfies 2,000-10,000cps. The viscosity may satisfy specifically 8,000cps or less, more specifically 7,000cps or less. When such a viscosity range is met, the deformation efficiency during processing of the polyimide film is excellent, thereby providing advantages in processing. Therefore, a more uniform surface can be achieved, which is preferred. Here, viscosity refers to a value measured by piling up a sample at room temperature (25°C), using a Brookfield RVDV-III viscometer No. 52 rotor and performing a stabilization operation for 2 minutes at a torque value of 80%.

[0213] The polyimide precursor solution according to the exemplary embodiment of the present invention can be obtained by polymerizing the above-mentioned polymer components to prepare a polyamic acid including a repeating unit represented by Chemical Formula a and then performing imidization. For example, imidization can be performed by a chemical imidization method or a thermal imidization method.

[0214] The imidization according to the exemplary embodiment of the present invention can be carried out by a thermal imidization method. By such a method, when imidization is carried out by heating at a high temperature, uniform mechanical physical properties can be given to the entire film. Specifically, the polyimide film according to the exemplary embodiment of the present invention can be prepared by a preparation method including applying and coating the above-mentioned polyimide precursor solution and then performing a heat treatment.

[0215] As an example, the heat treatment may be performed at a temperature below 500°C.

[0216] As an example, the heat treatment may include: a first heat treatment performed at a temperature below 100°C; a second heat treatment performed at above 100°C and below 300°C; and a third heat treatment performed at above 300°C and below 500°C, but is not limited thereto.

[0217] As an example, the substrate may be a glass substrate, a metal substrate or a plastic substrate, without particular limitation. The substrate may be a glass substrate having excellent thermal and chemical stability during imidization and curing of the polyimide precursor solution and which can be easily separated without damaging the polyimide film formed after curing.

[0218] As an example, the method of applying and coating is not particularly limited, but for example, any one or more methods selected from spin coating, dip coating, spray coating, die coating, rod coating, roll coating, meniscus method, flexography method, screen printing, bead coating method, air knife coating, reverse roll coating, blade coating, casting coating method, and gravure coating method can be used.

[0219] As an example, after the heat treatment step, a drying step and a step of separating from the substrate may be further included.

[0220] As an example, the molecular weight of the polyamic acid including the repeating unit represented by Chemical Formula a is not particularly limited, but, as an example, when the weight average molecular weight is within the range of 20,000-150,000 g / mol, better physical properties may be obtained.

[0221] In addition, the polyimide precursor solution according to the exemplary embodiment of the present invention may further include additives such as a leveling agent, a flame retardant, an adhesion improver, inorganic particles, an antioxidant, a UV inhibitor, and a plasticizer.

[0222] Specifically, the polyimide film prepared from the polyimide precursor solution according to the exemplary embodiment of the present invention, that is, the polyimide may include a repeating unit represented by the following chemical formula b:

[0223] [Chemical formula b]

[0224]

[0225] in

[0226] Q 1 is a single bond, -C(=O)-, -C(=O)O-, -C(=O)NH-, -NR′-, -S-, -SO 2 -、-CH 2 -,

[0227] or a combination thereof, wherein R′ is hydrogen or a C1-C10 alkyl group;

[0228] R 1 and R 2 are independently halogen, hydroxyl, mercapto, nitro, cyano, C1-C10 alkyl, C1-C10 alkoxy, C6-C20 aryl, or a combination thereof, or may be connected to adjacent substituents to form a ring;

[0229] R 3 is hydrogen, C1-C10 alkyl or C1-C10 fluoroalkyl;

[0230] p is an integer of 1 or 2;

[0231] n and m are each independently an integer selected from 0 to 4, and when n and m are integers of 2 or more, R 1 and R 2 May be the same as or different from each other.

[0232] In addition, the polyimide film according to the exemplary embodiment of the present invention may further include a repeating unit represented by the following Chemical Formula c or Chemical Formula d:

[0233] [Chemical formula c]

[0234]

[0235] [Chemical formula d]

[0236]

[0237] in

[0238] R 3 is hydrogen, C1-C10 alkyl or C1-C10 fluoroalkyl;

[0239] p is an integer of 1 or 2.

[0240] As described above, according to the exemplary embodiment of the present invention, a polyimide film having excellent optical properties, heat resistance, mechanical strength and flexibility can be provided by including a repeating unit derived from tetracarboxylic dianhydride represented by Chemical Formula 1. Therefore, the polyimide film can be used in various fields, such as element substrates, display cover substrates, optical films, integrated circuit (IC) packaging, electrodeposition films, multilayer flexible printed circuits (FRC), tapes, touch panels, and optical disc protective films.

[0241] According to the polyimide film of the exemplary embodiment of the present invention, that is, the polyimide may have a weight average molecular weight of 10,000-200,000 g / mol, 20,000-100,000 g / mol or 30,000-100,000 g / mol. In addition, the polyimide according to the present invention may have a molecular weight distribution (Mw / Mn) satisfying the range of 1.1-2.5. When the weight average molecular weight and molecular weight distribution of the polyimide are satisfied, the optical properties, heat resistance, mechanical strength, flexibility and other properties of the polyimide film are beneficial.

[0242] The polyimide film according to the exemplary embodiment of the present invention may have a thickness of 5 to 15 μm.

[0243] The polyimide film according to the exemplary embodiment of the present invention can have excellent heat resistance according to temperature change. Specifically, when in the above-mentioned thickness range, the primary heating process is carried out at a heating rate of 5°C / min in a temperature range of 100°C to 450°C, and then cooled at a cooling rate of 4°C / min in a temperature range of 400°C to 100°C, as a result of measuring the thermal expansion change pattern using a thermomechanical analyzer (TMA) (TMA450 can be obtained by TMA), the polyimide film can meet the thermal expansion coefficient (CTE) below 50ppm / °C. Specifically, the polyimide film can meet the thermal expansion coefficient (CTE) below 45ppm / °C, more specifically in the range of -15 to 45ppm / °C.

[0244] In the above thickness range, the polyimide film according to the exemplary embodiment of the present invention can satisfy the haze according to ASTM D1003 in the range of 2 or less, specifically 1 or less, more specifically 0.5 or less, and most specifically 0.01-0.3. Since such a haze value is satisfied, a polyimide film with improved transparency can be provided.

[0245] In addition, the polyimide film according to the exemplary embodiment of the present invention has excellent light transmittance and excellent yellow index, thereby showing significantly improved transparency and optical properties. Specifically, the polyimide film can have a YI of 15 or less according to ASTM E313 and a total light transmittance of 80% or more according to ASTM D1746 in the range of 380-780nm, more specifically a YI of 13 or less, and a total light transmittance of 85% or more, most specifically a YI of 11 or less, and a total light transmittance of 87%-99%.

[0246] Within the above thickness range, the polyimide film according to an exemplary embodiment of the present invention may have a modulus of 5.0 or more according to ASTM D882 and an elongation of 15% or more. Specifically, the polyimide film may have a modulus of 5.5 or more and an elongation of 15% or more, more specifically, a modulus of 6.0 or more and an elongation of 15% or more. When these characteristics are met, the polyimide film may have excellent rigidity and further ensure sufficient flexibility, thereby having flexibility to resist external impacts.

[0247] The polyimide film according to the exemplary embodiment of the present invention simultaneously satisfying all of the above-mentioned physical properties may be preferable, but the present invention is not limited thereto.

[0248] The polyimide film according to the exemplary embodiment of the present invention can simultaneously satisfy excellent optical properties, heat resistance, mechanical strength and flexibility through the rigid structure derived from the tetracarboxylic dianhydride represented by Chemical Formula 1. In particular, since the polyimide film can exhibit excellent heat resistance to heat shrinkage behavior that may occur in a high temperature process and also exhibit excellent colorless and transparent optical properties, the polyimide film can be used in various fields, such as element substrates, display substrates, optical films, integrated circuit (IC) packaging, electrodeposition films (adhesive films), multilayer flexible printed circuits (FRCs), tapes, touch panels, and optical disc protective films.

[0249] The polyimide film according to the exemplary embodiment of the present invention may be used in the form of being included as two or more layers.

[0250] Furthermore, another exemplary embodiment of the present invention may be an optoelectronic device and a flexible display including a polyimide film or a multilayer structure in the form of a polyimide film as a flexible substrate.

[0251] As examples, optoelectronic devices may be optical components, switches, light modulators, and are also suitable as high heat-resistant substrate materials requiring micro-patterning properties.

[0252] As an example, the flexible display may be applicable to a liquid crystal display device (LCD), an organic light emitting diode (OLED), etc., and particularly to an LED device using a low temperature polysilicon (LTPS) process requiring a high temperature process, but is not limited thereto.

[0253] The present invention is described below by specific examples and comparative examples of the present invention. The following examples are used to illustrate the technical concept of the present invention, and those skilled in the art will appreciate that the present invention is not limited thereto.

[0254] (Evaluation method)

[0255] 1. Coefficient of linear thermal expansion (CTE) and glass transition temperature (Tg)

[0256] The linear thermal expansion coefficient was measured according to thermomechanical analysis (TMA) using a thermomechanical analyzer (TMA) (available from TA Instrument, Discovery 450). The sample size was 5 mm×20 mm, the load was 0.02 N, and the heating rate was 5° C. / min. The CTE value was measured in the heating zone at a temperature of 100° C.-450° C.

[0257] The Tg value was measured in the heating region of 100° C. to 450° C. as the inflection point of the TMA graph.

[0258] 2. Haze

[0259] The haze was measured on a polyimide film having a thickness of 50 μm using a spectrophotometer (available from Nippon Denshoku, COH-400) according to the standard of ASTM D1003. The unit is %.

[0260] 3. Yellowness Index (YI)

[0261] The yellowness index was measured on a polyimide film having a thickness of 10 μm using a colorimeter (available from HunterLab, ColorQuest XE) according to the standard of ASTM E313.

[0262] 4. Total light transmittance

[0263] The total light transmittance was measured in % over the entire wavelength range of 380-780 nm on a polyimide film having a thickness of 10 μm using a spectrophotometer (available from SHIMADZU, MPC-3100) according to the standard of ASTM D1746.

[0264] 5. Modulus and elongation

[0265] The elongation is measured according to ASTM D882 using UTM3365 available from Instron under the condition of stretching a polyimide film of 10 μm thick, 40 mm long and 5 mm wide at 10 mm / min at 25° C. The unit of modulus is GPa, and the unit of elongation is %.

[0266] 6. Thickness

[0267] PAA was coated on 0.5T glass and cured to obtain a substrate, and the thickness of the substrate was measured using a film thickness meter (Alpha stepD500). The unit is μm.

[0268] 7. Viscosity

[0269] The viscosity may refer to a value measured by piling up a sample at room temperature (25° C.), using a Brookfield RVDV-III viscometer No. 52 spindle, allowing the sample to stand for 2 minutes when the torque value is 80%, and then stabilizing the sample, and the unit is cps.

[0270] 8.CR test (chemical resistance test)

[0271] Polyimide film curing conditions: multi-step (80℃ / 30 minutes, 220℃ / 30 minutes and 450℃ / 60 minutes)

[0272] ○: no film deformation, Δ: partial film deformation occurred, ×: film deformation occurred.

[0273] 9. Weight average molecular weight

[0274] The film was dissolved in a DMAc eluent containing 0.05 M LiBr. For GPC, a Waters GPC system, a Waters 1515 isocratic HPLC pump, and a Waters 2414 refractive index detector were used. For the chromatographic column, Olexis, Polypore, and mixed D columns were connected, and polymethyl methacrylate (PMMA STD) was used as a standard substance, and the analysis was performed at a flow rate of 1 mL / min at 35°C.

[0275] (Preparation Example 1)

[0276]

[0277] Step 1. Substance A

[0278] 3,4-dimethylphenylboronic acid (7.95 g, 53.0 mmol), 1,2-dibromo-4,5-dimethylbenzene (14 g, 53.0 mmol), triphenylphosphine (0.42 g, 1.59 mmol) and K 2 CO 3 (21.9 g, 159 mmol) was added to a mixed solution of 100 ml of degassed water and 70 ml of tetrahydrofuran (THF). The temperature was raised to 80°C and Pd(PPh 3 ) 4 (0.61 g, 0.53 mmol), stirred for 30 hours. Cooled to room temperature, the organic solvent was distilled off under reduced pressure, 100 ml of dichloromethane (DCM) and 50 ml of water were added, the organic layer was washed with water, and anhydrous MgSO 4 Remove water. Filter out MgSO 4 Afterwards, the solvent was removed and the resulting substance was separated by column chromatography to obtain substance A with a yield of 75%.

[0279] HRMS (EI, m / z): [M+] C16H13Br, calculated value 288.05; found value 269.16

[0280] 1 H-NMR (ppm,CDCl 3 ):7.44(1H,s),7.15-7.20(3H,m),7.10(1H,s),2.33(6H,s),2.29(3H,s),2.25(3H,s).

[0281]

[0282] Step 2. Substance B

[0283] Substance A (5.65 g, 19.5 mmol) was dissolved in 80 ml of anhydrous tetrahydrofuran (THF) under nitrogen atmosphere, and n-butyl lithium (9.37 ml of 2.5 M hexane solution, 23.4 mmol) was slowly added at -78 °C over 1 hour. Anhydrous CO was passed into the solution. 2 The reaction was continued for 4 hours, 60 ml of water was added to terminate the reaction, and the organic solvent was removed by distillation under reduced pressure. 100 ml of water and 50 ml of DCM were added, the aqueous layer was washed with DCM, 0.1 N HCl solution was added to the aqueous layer to make the pH reach 4, and then the precipitated organic matter was extracted with ether. The water was removed with anhydrous magnesium sulfate, filtered, the solvent was removed, and the obtained substance was separated by column chromatography to obtain substance B with a yield of 65%.

[0284] HRMS (EI, m / z): [M+] C17H18O2, calculated value 254.13; found value 255.32

[0285] 1 H-NMR (ppm,CDCl 3 ):7.75(1H,s),7.12-7.15(3H,m),7.07(1H,s),2.34(s,6H),2.31(6H,s).

[0286]

[0287] Step 3. Substance C

[0288] Substance B (4.73 g, 18.6 mmol) was dissolved in 50 g MeSO under nitrogen atmosphere. 3 H and stirred at 50°C for 18 hours. The reactant was poured into 500 ml of water at 0°C, and the resulting solid was filtered and recrystallized with methanol (MeOH) to obtain substance C with a yield of 85%.

[0289] HRMS (EI, m / z): [M+] C17H16O, calculated value 236.12; found value 237.25

[0290] 1 H-NMR (ppm,CDCl 3 ):7.24(2H,s),2.33(6H,s),2.28(6H,s).

[0291]

[0292] Step 4. Substance D

[0293] 2-Bromo-1,1′-biphenyl (4.0 g, 17.16 mmol) was dissolved in 80 ml of anhydrous tetrahydrofuran (THF) under nitrogen atmosphere, and n-butyl lithium (7.5 ml of 2.5 M hexane solution, 18.7 mmol) was slowly added at -78°C over 10 minutes. After stirring for 1 hour, substance C (3.69 g, 15.6 mmol) was added to the reaction, and stirred for 12 hours while warming to room temperature. 80 ml of water was added, the solvent was removed under reduced pressure, and 100 ml of dichloromethane (DCM) was added to extract the organic matter. The reaction mixture was stirred for 12 hours with anhydrous MgSO 4 The water was removed, filtered, the solvent was removed, and the resulting substance was added to 50 ml of acetic acid at 0°C. 1 ml of 35 wt% HCl was added, heated to reflux for 4 hours, and then stirred at room temperature for 1 hour. The reactant was poured into 200 ml of ice water, the resulting solid was filtered, precipitated with methanol (MeOH) and stirred to obtain substance D with a yield of 87%.

[0294] HRMS (EI, m / z): [M+] C29H24, calculated value 372.19; found value 373.05

[0295] 1 H-NMR (ppm,CDCl 3 ):7.84-7.91(4H,m),7.59(2H,s),6.73-6.80(4H,m),6.49(2H,s),2.35(6H,s),2.11(6H,s).

[0296]

[0297] Step 5. Substance E

[0298] Substance D (3.95 g, 10.6 mmol) was dissolved in a mixed solvent of 50 ml pyridine (Py) and 50 ml water, and KMnO dissolved in 100 ml water was slowly added over 4 hours. 4 (33.5 g, 212 mmol). After heating under reflux for 6 hours, the solid matter was filtered off and the temperature was lowered to room temperature to remove the solvent. 0.1 N HCl solution was added to the aqueous layer to adjust the pH value to 4, and the precipitated solid matter was filtered out and dried to obtain substance E with a yield of 80%.

[0299] HRMS (EI, m / z): [M+] C29H16O8, calculated value 492.08; found value 493.00

[0300] 1 H-NMR (ppm, D 2 O):7.97(8H,s),7.91(4H,s).

[0301]

[0302] Step 6. Substance F

[0303] Substance E (3.80 g, 7.72 mmol) was dissolved in acetic anhydride (100 ml) under nitrogen atmosphere, heated to reflux for 6 hours, and then cooled to room temperature. The generated solid was filtered out and washed with acetic anhydride to obtain substance F with a yield of 90%.

[0304] HRMS (EI, m / z): [M+] C29H12O6, calculated value 456.06; found value 457.11

[0305] (Preparation Example 2)

[0306]

[0307] Step 1. Substance G

[0308] Substance A (5.0 g, 17.47 mmol) was dissolved in 100 ml of anhydrous tetrahydrofuran (THF), the temperature was lowered to -78 °C, and then n-butyl lithium (7.6 ml of 2.5 M hexane solution, 18.8 mmol) was slowly added over 10 minutes. After stirring for 1 hour, 9H-thioxanthen-9-one (3.375 g, 15.9 mmol) was added to the reaction, and stirred for 12 hours while warming to room temperature. 100 ml of water was added, the solvent was removed under reduced pressure, and 100 ml of dichloromethane (DCM) was added to extract the organic matter. The reaction mixture was stirred for 12 hours with anhydrous MgSO 4 The water was removed, the solvent was filtered off, and the resulting substance was added to 50 ml of acetic acid at 0°C. 1 ml of 35 wt% HCl was added, heated to reflux for 4 hours, and then stirred at room temperature for 1 hour. The reactant was poured into 200 ml of water, the generated solid was filtered, precipitated with MeOH and stirred, thereby obtaining substance G with a yield of 88%.

[0309] HRMS (EI, m / z): [M+] C29H24S, calculated value 404.16; found value 405.15

[0310]

[0311] Step 2. Substance H

[0312] Substance G (4.6 g, 10.88 mmol) was dissolved in 100 ml of acetic acid, and 9 ml of 30 wt% H 2 O 2The temperature was raised to 100°C, stirred for 8 hours, and then cooled to room temperature. The generated solid material was filtered out, further washed with 20 ml of acetic acid and 20 ml of heptane, and dried to obtain material H with a yield of 89%.

[0313] HRMS (EI, m / z): [M+] C29H24S, calculated value 404.16; found value 405.15

[0314]

[0315] Step 3. Substance I

[0316] Substance H (4.0 g, 9.89 mmol) was dissolved in a mixed solvent of 50 ml pyridine (Py) and 50 ml water, and KMnO dissolved in 100 ml water was slowly added over 4 hours. 4 (31.6 g, 200 mmol). After heating under reflux for 6 hours, the solid matter was filtered off and the temperature was lowered to room temperature to remove the solvent. 0.1 N HCl solution was added to the aqueous layer to adjust the pH value to 4, and the precipitated solid matter was filtered out and dried to obtain substance I with a yield of 85%.

[0317] HRMS (EI, m / z): [M+] C29H16O10S, calculated value 556.05; found value 557.04

[0318]

[0319] Step 4. Substance J

[0320] Substance I (3.6 g, 6.47 mmol) was dissolved in acetic anhydride (80 ml) under nitrogen atmosphere, heated to reflux for 6 hours, and then cooled to room temperature. The resulting solid was filtered, washed with acetic anhydride, and dried to obtain substance J with a yield of 90%.

[0321] HRMS (EI, m / z): [M+] C29H12O6, calculated value 556.05; found value 557.03

[0322] (Preparation Example 3)

[0323]

[0324] Step 1. Substance K

[0325] Under nitrogen atmosphere, 2-bromo-4′-tert-butyl-1,1′-biphenyl (5.0 g, 17.29 mmol) was dissolved in 80 ml of anhydrous tetrahydrofuran (THF), the temperature was lowered to -78°C, and then n-butyl lithium (7.6 ml of 2.5 M hexane solution, 18.8 mmol) was slowly added over 10 minutes. After stirring for 1 hour, substance C (3.73 g, 15.8 mmol) was added to the reaction, and stirred for 12 hours while warming to room temperature. 80 ml of water was added, the solvent was removed under reduced pressure, and 100 ml of dichloromethane (DCM) was added to extract the organic matter. The reaction mixture was stirred for 12 hours with anhydrous MgSO 4 The water was removed, the solvent was filtered off, and the resulting substance was added to 50 ml of acetic acid at 0°C. 1 ml of 35 wt% HCl was added, heated to reflux for 4 hours, and then stirred at room temperature for 1 hour. The reactant was poured into 200 ml of water at 0°C, the generated solid was filtered out, precipitated with methanol (MeOH) and stirred, thereby obtaining substance K with a yield of 85%.

[0326] HRMS (EI, m / z): [M+] C33H32, calculated value 428.25; found value 428.20

[0327]

[0328] Step 2. Substance L

[0329] Substance K (3.95 g, 9.22 mmol) was dissolved in a mixed solvent of 50 ml pyridine (Py) and 50 ml water, and KMnO dissolved in 100 ml water was slowly added over 4 hours. 4 (31.0 g, 190 mmol). After heating under reflux for 6 hours, the solid matter was filtered off and the temperature was lowered to room temperature to remove the solvent. 0.1 N HCl solution was added to the aqueous layer to adjust the pH value to 4, and the precipitated solid matter was filtered out and dried to obtain substance L with a yield of 81%.

[0330] HRMS (EI, m / z): [M+] C33H24O8, calculated value 548.15; found value 548.12

[0331]

[0332] Step 3. Substance M

[0333] Under nitrogen atmosphere, substance L (3.00 g, 5.47 mmol) was dissolved in acetic anhydride (80 ml), heated to reflux for 6 hours, and then cooled to room temperature. The generated solid was filtered out and washed with acetic anhydride to obtain substance M with a yield of 90%.

[0334] HRMS (EI, m / z): [M+] C33H20O6, calculated value 512.13; found value 513.12

[0335] (Example 1)

[0336] TFMB (0.999) / Preparation Example 1 (1.0), unit: molar ratio

[0337] 176 g of N,N-dimethylpropionamide (DMPA) was filled in a stirrer in which a nitrogen gas flow was flowing, and then 14.03 g of 2,2′-bis(trifluoromethyl)-4,4′-biphenylenediamine (TFMB) was dissolved while the reactor temperature was maintained at 25° C. 20 g of the novel monomer 1 (Preparation Example 1, substance F) was added thereto at the same temperature, and stirred for a certain time while the monomer was dissolved. Thereafter, DMPA was added so that the solid concentration was 13% by weight, thereby preparing a polyimide precursor solution 1. The viscosity of the polyimide precursor solution 1 was 4,500 cp.

[0338] (Example 2)

[0339] TFMB (0.999) / Preparation Example 1 (0.2) / PMDA (0.8), unit: molar ratio

[0340] 175 g of N,N-dimethylpropionamide (DMPA) was filled in a stirrer in which a nitrogen stream was flowing, and then 18.33 g of 2,2′-bis(trifluoromethyl)-4,4′-biphenylenediamine (TFMB) was dissolved while the reactor temperature was maintained at 25° C. 5.22 g of the novel monomer 1 (Preparation Example 1, substance F) and 10 g of pyromellitic dianhydride (PMDA) were added thereto at the same temperature, and stirred for a certain time while the monomers were dissolved. Thereafter, DMPA was added so that the solid concentration of the polyimide precursor solution was 13% by weight, thereby preparing a polyimide precursor solution 2. The viscosity of the polyimide precursor solution 2 was 5,200 cp.

[0341] (Example 3)

[0342] TFMB (0.999) / Preparation Example 2 (1.0), unit: molar ratio

[0343] 169 g of N,N-dimethylpropionamide (DMPA) was filled in a stirrer in which a nitrogen gas flow was flowing, and then 12.29 g of 2,2′-bis(trifluoromethyl)-4,4′-biphenylenediamine (TFMB) was dissolved while the reactor temperature was maintained at 25° C. 20 g of the novel monomer 2 (Preparation Example 2, Material J) was added thereto at the same temperature, and stirred for a certain time while the monomer was dissolved. Thereafter, DMPA was added so that the solid concentration was 13% by weight, thereby preparing a polyimide precursor solution 3. The viscosity of the polyimide precursor solution 3 was 4,200 cp.

[0344] (Example 4)

[0345] TFMB (0.999) / Preparation Example 3 (1.0), unit: molar ratio

[0346] 170 g of N,N-dimethylpropionamide (DMPA) was filled in a stirrer in which a nitrogen gas flow was flowing, and then 12.48 g of 2,2′-bis(trifluoromethyl)-4,4′-biphenylenediamine (TFMB) was dissolved while the reactor temperature was maintained at 25° C. 20 g of the novel monomer 3 (Preparation Example 3, substance M) was added thereto at the same temperature, and stirred for a certain time while the monomer was dissolved. Thereafter, DMPA was added so that the solid concentration was 13% by weight, thereby preparing a polyimide precursor solution 4. The viscosity of the polyimide precursor solution 4 was 4,300 cp.

[0347] (Example 5)

[0348] TFMB (0.999) / Preparation Example 2 (0.2) / PMDA (0.8), unit: molar ratio

[0349] 180 g of N,N-dimethylpropionamide (DMPA) was filled in a stirrer in which a nitrogen stream was flowing, and then 18.33 g of 2,2′-bis(trifluoromethyl)-4,4′-biphenylenediamine (TFMB) was dissolved while the reactor temperature was maintained at 25° C. 5.96 g of the novel monomer 2 (Preparation Example 2, Material J) and 10 g of pyromellitic dianhydride (PMDA) were added thereto at the same temperature, and stirred for a certain time while the monomers were dissolved. Thereafter, DMPA was added so that the solid concentration was 13% by weight, thereby preparing a polyimide precursor solution 5. The viscosity of the polyimide precursor solution 5 was 5,200 cp.

[0350] (Example 6)

[0351] TFMB (0.999) / Preparation Example 3 (0.2) / PMDA (0.8), unit: molar ratio

[0352] 179 g of N,N-dimethylpropionamide (DMPA) was filled in a stirrer in which a nitrogen stream was flowing, and then 18.33 g of 2,2′-bis(trifluoromethyl)-4,4′-biphenylenediamine (TFMB) was dissolved while the reactor temperature was maintained at 25° C. 5.87 g of novel monomer 3 (Preparation Example 3, substance M) and 10 g of pyromellitic dianhydride (PMDA) were added thereto at the same temperature, and stirred for a certain time while the monomers were dissolved. Thereafter, DMPA was added so that the solid concentration was 13% by weight, thereby preparing a polyimide precursor solution 6. The viscosity of the polyimide precursor solution 6 was 5,200 cp.

[0353] (Comparative Example 1)

[0354] TFMB(0.999) / BPAF(1.0), unit: molar ratio

[0355] 173 g of N,N-dimethylpropionamide (DMPA) was filled in a stirrer in which a nitrogen gas flow was flowing, and then 13.96 g of 2,2′-bis(trifluoromethyl)-4,4′-biphenylenediamine (TFMB) was dissolved while the reactor temperature was maintained at 25° C. 20 g of 9,9′-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF) was added thereto at the same temperature, and stirred for a certain time while dissolving the compound. Thereafter, DMPA was added so that the solid concentration was 13% by weight, thereby preparing a polyimide precursor solution A. The viscosity of the polyimide precursor solution A was 4,200 cp.

[0356] (Comparative Example 2)

[0357] TFMB (0.999) / BPAF (0.2) / PMDA (0.8), unit: molar ratio

[0358] 175 g of N,N-dimethylpropionamide (DMPA) was filled in a stirrer in which a nitrogen stream was flowing, and then 18.33 g of 2,2′-bis(trifluoromethyl)-4,4′-biphenylenediamine (TFMB) was dissolved while the reactor temperature was maintained at 25° C. 5.25 g of 9,9′-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF) and 10 g of pyromellitic dianhydride (PMDA) were added thereto at the same temperature, and stirred for a certain time while dissolving the compound. Thereafter, DMPA was added so that the solid concentration was 13% by weight, thereby preparing a polyimide precursor solution B. The viscosity of the polyimide precursor solution B was 4,600 cp.

[0359] (Preparation of polyimide film)

[0360] Each of the polyimide precursor solutions of Examples 1 to 6 and Comparative Examples 1 and 2 was spin-coated on a glass substrate. The glass substrate coated with the polyimide precursor solution was placed in an oven, heated at a rate of 4°C / min, kept at 80°C for 30 minutes, kept at 220°C for 30 minutes, and kept at 450°C for 1 hour to perform a curing process. After the curing was completed, the glass substrate was immersed in water to form a film on the glass substrate, the film was peeled off, and dried in an oven at 100°C to prepare a polyimide film.

[0361] The physical properties of the polyimide film prepared by the above method were measured by the above evaluation method, as shown in Table 1 below:

[0362] [Table 1]

[0363]

[0364] As shown in Table 1 above, in Examples 1, 3 and 4 of the tetracarboxylic dianhydride-derived polyimide film of the present invention, the thermal expansion coefficient is 35-43 ppm / °C, the haze is 0.1-0.2, the yellowness index (YI) is 7.2-7.5, the total light transmittance is 88-90%, the modulus is 6.1-6.8, and the elongation is 15-27%, and the measured properties of each item are at a similar level.

[0365] In addition, in Examples 2, 5 and 6 in which the polyimide film further includes repeating units derived from pyromellitic dianhydride (PMDA), the coefficient of thermal expansion is 6.5-8.3 ppm / °C, the haze is 0.1, the yellowness index (YI) is 7.4-10.8, the total light transmittance is 87-88%, the modulus is 7.1-7.5, and the elongation is 23-29%, and the measured properties of each item are at similar levels.

[0366] Such effects are significantly improved heat resistance, optical characteristics, and mechanical characteristics compared to Comparative Example 1 or 2.

[0367] According to an exemplary embodiment of the present invention, a polyimide film can be provided, which has high transparency and heat resistance and has excellent thermal dimensional stability due to a substrate whose stress does not increase even when heat-treated at high temperatures. In addition, the polyimide film according to an exemplary embodiment of the present invention is optically very good, has reduced optical anisotropy and achieves uniform transmittance to total light.

[0368] According to an exemplary embodiment of the present invention, a colorless and transparent polyimide film can be provided. The polyimide film according to an exemplary embodiment of the present invention has excellent heat resistance, mechanical strength and flexibility, and can be used in various fields, such as device substrates, flexible display substrates, optical films, integrated circuit (IC) packaging, adhesive films, multilayer flexible printed circuits (FPC), tapes, touch panels and optical disc protective films.

[0369] Specifically, the polyimide film according to the exemplary embodiment of the present invention i) may satisfy a coefficient of thermal expansion (CTE) of 50 ppm / °C or less at 100-450°C, ii) may satisfy a YI of 15 or less according to ASTM E313, a haze of 2 or less according to ASTM D1003, and an average light transmittance of 80% or more in the range of 380-780 nm according to ASTM D1746, iii) may satisfy a modulus of 8.0 or less according to ASTM D882 and an elongation of 15% or more, or may satisfy these properties simultaneously.

[0370] In the above, although the present invention has been described by specific matters and specific exemplary embodiments, they are provided only to help the overall understanding of the present invention. Therefore, the present invention is not limited to the specific matters of the exemplary embodiments, and those skilled in the art to which the present invention belongs can make various modifications and changes according to the description.

[0371] Therefore, the spirit of the present invention should not be limited to the above-described exemplary embodiments, and the appended claims and all contents modified equivalent to or equivalent to the claims are intended to fall within the scope and spirit of the present invention.

Claims

1. A polyimide precursor solution, comprising: a polyimide precursor derived from a tetracarboxylic dianhydride represented by the following chemical formula 2: [Chemical formula 2] in R 1 and R 2 are independently halogen, hydroxyl, mercapto, nitro, cyano, C1-C10 alkyl, C1-C10 alkoxy, C6-C20 aryl, or a combination thereof, or may be connected to adjacent substituents to form a ring; and n and m are each independently an integer selected from 0 to 4, and when n and m are integers of 2 or more, R 1 and R 2 May be the same as or different from each other.

2. The polyimide precursor solution according to claim 1, wherein the polyimide precursor solution comprises: A polymeric component comprising a tetracarboxylic dianhydride represented by Chemical Formula 2 and a diamine; and organic solvents.

3. The polyimide precursor solution according to claim 2, wherein the diamine comprises a unit represented by the following Chemical Formula 6: [Chemical formula 6] in R 3 is hydrogen, C1-C10 alkyl or C1-C10 fluoroalkyl; and p is an integer of 1 or 2. The polyimide precursor solution according to claim 2 , wherein the organic solvent is selected from amides. 5 . The polyimide precursor solution according to claim 4 , wherein the organic solvent is N,N-diethylacetamide, N,N-diethylformamide, N-ethylpyrrolidone, N,N-dimethylpropionamide, N,N-diethylpropionamide, or a combination thereof.

6. The polyimide precursor solution according to claim 2, further comprising a tetracarboxylic dianhydride selected from the compounds represented by the following Chemical Formula 7 and Chemical Formula 8 as a polymerization component: [Chemical formula 7] [Chemical formula 8] in Q 2 and Q 3 is a single bond, -O-, -C(=O)-, -C(=O)O-, -C(=O)NH-, -NR'-, -S-, -SO2-, phenylene or a combination thereof, wherein R' is hydrogen or a C1-C10 alkyl group.

7. A polyimide precursor derived from tetracarboxylic dianhydride and diamine represented by the following Chemical Formula 1: [Chemical formula 1] in Q 1 is a single bond; R 1 and R 2 are independently halogen, hydroxyl, mercapto, nitro, cyano, C1-C10 alkyl, C1-C10 alkoxy, C6-C20 aryl, or a combination thereof, or may be connected to adjacent substituents to form a ring; and n and m are each independently an integer selected from 0 to 4, and when n and m are integers of 2 or more, R 1 and R 2 May be the same as or different from each other.

8. The polyimide precursor according to claim 7, wherein the polyimide precursor comprises a repeating unit represented by the following chemical formula a: [Chemical formula a] in Q 1 is a single bond; R a and R b are independently hydrogen or C1-C10 alkyl; R 1 and R 2 are independently halogen, hydroxyl, mercapto, nitro, cyano, C1-C10 alkyl, C1-C10 alkoxy, C6-C20 aryl, or a combination thereof, or may be connected to adjacent substituents to form a ring; R 3 is hydrogen, C1-C10 alkyl or C1-C10 fluoroalkyl; p is an integer of 1 or 2; and n and m are each independently an integer selected from 0 to 4, and when n and m are integers of 2 or more, R 1 and R 2 May be the same as or different from each other. 9 . The polyimide precursor according to claim 8 , wherein the polyimide precursor comprises 10 to 100 mol % of the repeating unit represented by Chemical Formula a based on the total repeating units.

10. A polyimide film comprising a repeating unit represented by the following chemical formula b: [Chemical formula b] in Q 1 is a single bond; R 1 and R 2 are independently halogen, hydroxyl, mercapto, nitro, cyano, C1-C10 alkyl, C1-C10 alkoxy, C6-C20 aryl, or a combination thereof, or may be connected to adjacent substituents to form a ring; R 3 is hydrogen, C1-C10 alkyl or C1-C10 fluoroalkyl; p is an integer of 1 or 2; and n and m are each independently an integer selected from 0 to 4, and when n and m are integers of 2 or more, R 1 and R 2 May be the same as or different from each other.

11. The polyimide film according to claim 10, wherein the polyimide film further comprises a repeating unit represented by the following chemical formula c or chemical formula d: [Chemical formula c] [Chemical formula d] in R 3 is hydrogen, C1-C10 alkyl or C1-C10 fluoroalkyl; and p is an integer of 1 or 2. 12 . The polyimide film according to claim 10 , wherein the polyimide film has a thermal expansion coefficient of 50 ppm / ° C. or less at 100 to 450° C.

13. The polyimide film according to claim 10, wherein the polyimide film has Yellowness index according to ASTM E313 below 15; A haze according to ASTM D1003 of 2 or less; and 80% or more total light transmittance in the range of 380-780nm according to ASTM D1746.

14. The polyimide film according to claim 10, wherein The polyimide film has a modulus of 5.0 or more according to ASTM D882 and an elongation of 15% or more.

15. The polyimide film according to claim 10, wherein the polyimide film has a thermal expansion coefficient of 50 ppm / °C or less at 100-450°C; Yellowness index according to ASTM E313 below 15; Haze according to ASTM D1003 of 2 or less; An average light transmittance of 80% or more in the range of 380-780 nm according to ASTM D1746; and Modulus according to ASTM D882 of 8.0 or less and elongation of 15% or more.

16. A multilayer structure comprising the polyimide film according to any one of claims 10 to 15.

17. A photovoltaic device comprising the polyimide film according to any one of claims 10 to 15 as a flexible substrate.

18. A flexible display comprising the polyimide film according to any one of claims 10 to 15 as a flexible substrate.

19. A method for preparing a polyimide film, comprising: The polyimide precursor solution according to any one of claims 1 to 6 is applied and coated on a substrate, and then heat-treated.

20. The method for preparing a polyimide film according to claim 19, wherein the heat treatment comprises: The first heat treatment is carried out at a temperature below 100°C; A second heat treatment at a temperature higher than 100°C and lower than 300°C; and The third heat treatment is performed at a temperature higher than 300°C and lower than 500°C. 21 . The method for preparing a polyimide film according to claim 19 , wherein the polyimide precursor solution comprises a solid content of 10-13 wt % based on the total weight.

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