Polyamic acid composition and polyimide containing same

Abstract

The present application relates to a polyamic acid composition and a polyimide containing the same, and provides a polyamic acid composition having a high concentration of polyamic acid solids, low viscosity, and excellent heat resistance, dimensional stability, and mechanical properties after curing, as well as excellent electrical properties, and a polyimide and polyimide film produced therefrom.

Description

[Technical field]

[0001] Cross-reference to related applications This application claims the benefit of priority to Korean Patent Application No. 10-2020-0155543 filed on November 19, 2020, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] Technical Field The present application relates to polyamic acid compositions and polyimides containing the same. [Background technology]

[0003] Polyimide (PI) is a thermally stable polymeric material based on a rigid aromatic main chain. Due to the chemical stability of the imide ring, it has excellent mechanical properties such as strength, chemical resistance, weather resistance, and heat resistance.

[0004] Moreover, polyimide has excellent electrical properties such as insulating properties and low dielectric constant, and is in the spotlight as a highly functional polymeric material applicable to a wide range of industrial fields such as electronics, communications, and optics. The insulating layer (insulating coating) that covers the conductor is required to have excellent insulating properties, adhesion to the conductor, heat resistance, mechanical strength, etc. Furthermore, in electrical equipment that requires high voltage, such as a motor used at high voltage, a high voltage is applied to the insulated wire that constitutes the electrical equipment, and partial discharge (corona discharge) is likely to occur on the surface of the insulating coating. The occurrence of corona discharge causes a localized temperature rise and the generation of ozone or ions, which results in deterioration of the insulating coating of the insulated wire, which can cause early insulation breakdown and shorten the life of the electrical equipment.

[0005] Recently, as various electronic devices become thinner, lighter, and smaller, much research has been conducted into using thin, lightweight, and flexible polyimide films as insulating materials for circuit boards or display substrates that can replace glass substrates for displays.

[0006] In particular, in the case of polyimide films used for circuit boards or display substrates manufactured at high process temperatures, it is necessary to ensure higher levels of dimensional stability, heat resistance and mechanical properties.

[0007] One method for ensuring such physical properties is to increase the molecular weight of polyimide.

[0008] The more imide groups there are in a molecule, the more the heat resistance and mechanical properties of the polyimide film can be improved. Since the proportion of imide groups increases as the polymer chain becomes longer, producing a polyimide with a high molecular weight is advantageous in terms of ensuring physical properties.

[0009] In order to produce a polyimide having a high molecular weight, it is common to produce a polyamic acid, which is a precursor thereof, at a high molecular weight and then imidize the polyamic acid through a heat treatment.

[0010] However, as the molecular weight of the polyamic acid increases, the viscosity of the polyamic acid solution in which the polyamic acid is dissolved in a solvent increases, decreasing the flowability, and causing a problem of extremely poor process handleability.

[0011] In addition, in order to reduce the viscosity of the polyamic acid while maintaining the molecular weight of the polyamic acid, it is possible to consider a method of decreasing the solid content and increasing the solvent content. However, in this case, a large amount of solvent needs to be removed during the curing process, which increases the manufacturing cost and process time.

[0012] Therefore, there is a strong need for research into a polyimide film that satisfies not only heat resistance and mechanical properties but also electrical properties of the polyimide produced from the polyamic acid solution, while maintaining low viscosity and satisfying processability even if the solid content of the polyamic acid solution is high. Summary of the Invention [Problem to be solved by the invention]

[0013] The present application provides a polyamic acid composition having a high concentration of polyamic acid solids and low viscosity, and having excellent heat resistance, dimensional stability, and mechanical properties as well as excellent electrical properties after curing, and a polyimide and polyimide film produced therefrom. [Means for solving the problem]

[0014] The present application relates to a polyamic acid composition. The polyamic acid composition according to the present application may include a polyamic acid including a dianhydride monomer component and a diamine monomer component as polymerization units, and a solvent. The solvent may include a first solvent and a second solvent that is a component different from the first solvent. The solvent may be an organic solvent. The polyamic acid composition according to the present application has a dielectric constant of 3.5 or less at 120 Hz after curing, and a surface resistivity of 2.35×10 measured at 23° C. and 50% relative humidity according to the ASTM D257 standard after curing. 14 The upper limit of the dielectric constant may be, for example, 3.48, 3.45, 3.43, 3.4, 3.37, 3.35, 3.33, 3.32, 3.3, 3.25, 3.23, 3.2, 3.1, or 3.05 or less, and the lower limit may be, for example, 1.0, 2.0, 2.5, 2.8, 3.0, 3.1, or 3.15 or more. The lower limit of the surface resistivity may be, for example, 2.35×10 14 , 2.38×10 14 , 2.4×10 14 , 2.45×10 14 , 2.48×10 14 , 2.5×10 14 , 2.65×10 14 , 2.68×10 14 , 2.7×10 14 , 2.75×10 14 , 2.8×10 14 , 3×10 14 , 3.5×10 14 , 4×10 14 , 4.5×10 14 , 5×10 14 , 5.3×10 14, 5.5×10 14 , or 5.6 × 10 14 Ω or more, with an upper limit of, for example, 10×10 14 , 9×10 14 , 8×10 14 , 7×10 14 , 6×10 14 , 5.8×10 14 , 5.6×10 14 , 5.3×10 14 , 5×10 14 , 4.5×10 14 , 4×10 14 , 3.5×10 14 , 3×10 14 , 2.8×10 14 , or 2.6 × 10 14 The present application provides a polyamic acid composition that has a low viscosity and ensures processability by adjusting the physical properties together with the composition, and has excellent heat resistance, dimensional stability, and mechanical properties as well as excellent electrical properties after curing.

[0015] In the present application, when a physical property is measured and temperature affects the physical property, the physical property may be measured at room temperature of 25° C. unless otherwise specified.

[0016] The present application may include a first solvent and a second solvent. As previously mentioned, the second solvent may be a different composition than the first solvent.

[0017] In one example, the first solvent may have a boiling point of 150° C. or more, and the second solvent may have a boiling point lower than that of the first solvent. That is, the first solvent may have a boiling point higher than that of the second solvent. The second solvent may have a boiling point in the range of 30° C. or more and less than 150° C. The lower limit of the boiling point of the first solvent may be, for example, 155° C., 160° C., 165° C., 170° C., 175° C., 180° C., 185° C., 190° C., 195° C., 200° C., or 201° C. or more, and the upper limit may be, for example, 500° C., 450° C., 300° C., 280° C., 270° C., 250° C., 240° C., 230° C., 220° C., 210° C., or 205° C. or less. The lower limit of the boiling point of the second solvent may be, for example, 35° C., 40° C., 45° C., 50° C., 53° C., 58° C., 60° C., or 63° C. or more, and the upper limit may be, for example, 148° C., 145° C., 130° C., 120° C., 110° C., 105° C., 95° C., 93° C., 88° C., 85° C., 80° C., 75° C., 73° C., 70° C., or 68° C. or less. In the present application, a polyimide having desired physical properties can be produced by using two solvents having different boiling points.

[0018] In one example, the second solvent may have a solubility of the dianhydride monomer of less than 1.5 g / 100 g. That is, the second solvent may have a solubility of the dianhydride monomer of less than 1.5 g / 100 g. The upper limit of the solubility range is, for example, 1.3 g / 100 g, 1.2 g / 100 g, 1.1 g / 100 g, 1.0 g / 100 g, 0.9 g / 100 g, 0.8 g / 100 g, 0.7 g / 100 g, 0.6 g / 100 g, 0.5 g / 100 g, 0.4 g / 100 g, 0.3 g / 100 g, 0.25 g / 100 g. , 0.23g / 100g, 0.21g / 100g, 0.2g / 100g or 0.15g / 100g or less, and the lower limit may be, for example, 0g / 100g, 0.01g / 100g, 0.05g / 100g, 0.08g / 100g, 0.09g / 100g or 0.15g / 100g or more. The present application can provide a polyamic acid composition having a desired physical property by including a second solvent having low solubility for the dianhydride monomer contained in the polymerized unit or the dianhydride monomer not polymerized. In the present application, when a physical property to be measured is a property that is affected by temperature, it may be measured at room temperature of 23°C unless otherwise specified.

[0019] In an embodiment of the present application, the first solvent may have a solubility for the dianhydride monomer of, for example, 1.5 g / 100 g or more. The lower limit of the solubility may be, for example, 1.6g / 100g, 1.65g / 100g, 1.7g / 100g, 2g / 100g, 2.5g / 100g, 5g / 100g, 10g / 100g, 30g / 100g, 45g / 100g, 50g / 100g, or 51g / 100g or more, and the upper limit may be, for example, 80g / 100g, 70g / 100g, 60g / 100g, 55g / 100g, 53g / 100g, 48g / 100g, 25g / 100g, 10g / 100g, 5g / 100g, or 3g / 100g or less. The first solvent may have a higher solubility than the second solvent.

[0020] The first solvent according to the present application is not particularly limited as long as it is a solvent in which polyamic acid can be dissolved. The first solvent may also be a polar solvent. For example, the first solvent may be an amide solvent such as N,N-dimethylformamide, N,N-dimethylacetamide, or N-methylpyrrolidone, and the first solvent may have an amide group or a ketone group in its molecular structure. The first solvent may have a lower polarity than the second solvent.

[0021] The first solvent may be an aprotic polar solvent, as an example. The second solvent may be an aprotic polar solvent or a protic polar solvent. The second solvent may have at least one polar functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an alkoxy group, an ester group, and an ether group. For example, the second solvent may include an alcohol-based solvent such as methanol, ethanol, 1-propanol, butyl alcohol, isobutyl alcohol, or 2-propanol, an ester-based solvent such as methyl acetate, ethyl acetate, or isopropyl acetate, a carboxylic acid solvent such as formic acid, acetic acid, propionic acid, butyric acid, or lactic acid, an ether-based solvent such as dimethyl ether, diethyl ether, diisopropyl ether, or dimethoxyethane methyl t-butyl ether, dimethyl carbonate, methyl methacrylate, or propylene glycol monomethyl ether acetic acid.

[0022] As described above, the present application may include both the first solvent and the second solvent. In this case, the first solvent may be contained in a content greater than that of the second solvent. The second solvent may be contained in a ratio of 0.01 to 10 parts by weight relative to 100 parts by weight of the first solvent. The lower limit of the content ratio may be, for example, 0.02 parts by weight, 0.03 parts by weight, 0.04 parts by weight, 0.1 parts by weight, 0.3 parts by weight, 0.5 parts by weight, 0.8 parts by weight, 1 part by weight, or 2 parts by weight or more, and the upper limit may be, for example, 8 parts by weight, 6 parts by weight, 5 parts by weight, 4.5 parts by weight, 4 parts by weight, 3 parts by weight, 2.5 parts by weight, 1.5 parts by weight, 1.2 parts by weight, 0.95 parts by weight, 0.4 parts by weight, 0.15 parts by weight, or 0.09 parts by weight or less.

[0023] In one example, as described above, the polyamic acid composition of the present application may include a second solvent, and the second solvent may be included in the range of 0.01 to 10 wt% in the entire polyamic acid composition. The lower limit of the content of the second solvent may be, for example, 0.015 wt%, 0.03 wt%, 0.05 wt%, 0.08 wt%, 0.1 wt%, 0.3 wt%, 0.5 wt%, 0.8 wt%, 1 wt%, or 2 wt% or more, and the upper limit may be, for example, 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5.5 wt%, 5.3 wt%, 5 wt%, 4.8 wt%, 4.5 wt%, 4 wt%, 3 wt%, 2.5 wt%, 1.5 wt%, 1.2 wt%, 0.95 wt%, or 0.4 wt% or less. The first solvent may be included in the range of 60 to 95 wt% in the entire polyamic acid composition. The lower limit of the content of the first solvent may be, for example, 65 wt%, 68 wt%, 70 wt%, 73 wt%, 75 wt%, 78 wt%, or 80 wt%, and the upper limit may be, for example, 93 wt%, 90 wt%, 88 wt%, 85 wt%, 83 wt%, 81 wt%, or 79 wt%. The polyamic acid composition according to the present application includes a dianhydride monomer component and a diamine monomer component, and the two monomers form a polymerization unit with each other, but a part of the dianhydride monomer is ring-opened by the organic solvent and cannot participate in the polymerization reaction. The dianhydride monomer that is ring-opened without polymerization acts as a dilution monomer and can adjust the viscosity of the entire polyamic acid composition to be relatively low. The dianhydride monomer having a ring-opening structure can participate in the reaction during the imidization reaction to realize the desired polyimide.

[0024] In one embodiment, the dianhydride monomer may include a monomer having a ring-opening structure that is not polymerized with a monomer contained in a polymerization unit. That is, the dianhydride monomer may be partially or partially contained in the polymerization unit, and the dianhydride monomer not contained in the polymerization unit may have a ring-opening structure by the solvent according to the present application. In the polyamic acid composition according to the present application, the dianhydride monomer may be present in the form of an aromatic carboxylic acid having two or more carboxylic acids without being polymerized, and the aromatic carboxylic acid may be present as a monomer before curing, thereby reducing the viscosity of the entire polyamic acid composition and improving processability. The aromatic carboxylic acid having two or more carboxylic acids increases the length of the entire polymer chain by polymerizing the dianhydride monomer to the main chain after curing, and such a polymer may have excellent heat resistance, dimensional stability, and mechanical and electrical properties.

[0025] Specifically, during heat treatment of the polyamic acid composition for imidization into polyimide, the aromatic carboxylic acid having two or more carboxylic acids undergoes a ring-closing dehydration reaction to become a dianhydride monomer, and reacts with the terminal amine group of the polyamic acid chain or the polyimide chain to increase the length of the polymer chain. As a result, the dimensional stability and thermal stability at high temperatures of the produced polyimide film can be improved, and the mechanical properties at room temperature can be improved.

[0026] As described above, the polyamic acid composition of the present application may include polymerized units of a diamine monomer and a dianhydride monomer. In this specification, the polyimide precursor composition may be used interchangeably with the polyamic acid composition or the polyamic acid solution.

[0027] The dianhydride monomer that can be used in the preparation of the polyamic acid solution may be an aromatic tetracarboxylic acid dianhydride, and the aromatic tetracarboxylic acid dianhydride may be pyromellitic dianhydride (or PMDA), 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (or BPDA), 2,3,3',4'-biphenyltetracarboxylic acid dianhydride (or a-BPDA), oxydiphthalic acid dianhydride (or ODPA), diphenylsulfate ... Sulfon-3,4,3',4'-tetracarboxylic acid dianhydride (or DSDA), bis(3,4-dicarboxyphenyl)sulfide dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride, 2,3,3',4'-benzophenone tetracarboxylic acid dianhydride, 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride (or BTDA), bis(3,4-dicarboxyphenyl)methane dianhydride Anhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, p-phenylene bis(trimellitic acid monoester anhydride), p-biphenylene bis(trimellitic acid monoester anhydride), m-terphenyl-3,4,3',4'-tetracarboxylic acid dianhydride, p-terphenyl-3,4,3',4'-tetracarboxylic acid dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(3,4 Examples of such dianhydrides include 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, 2,2-bis[(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, and 4,4'-(2,2-hexafluoroisopropylidene)diphthalic acid dianhydride.

[0028] The dianhydride monomers may be used alone or in combination of two or more, as necessary, and may include, for example, pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), oxydiphthalic dianhydride (ODPA), 4,4-(hexafluoroisopropylidene)diphthalic anhydride (6-FDA), p-phenylenebis(trimellitate anhydride) (TAHQ), or 2,2-bis[(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA).

[0029] In a specific example of the present application, the dianhydride monomer may include a dianhydride monomer having one benzene ring and a dianhydride monomer having two or more benzene rings. The dianhydride monomer having one benzene ring and the dianhydride monomer having two or more benzene rings may be included in a molar ratio of 20-60 mol% and 40-90 mol%; 25-55 mol% and 45-80 mol%; or 35-53 mol% and 48-75 mol%, respectively. By including the dianhydride monomer, the present application can realize both excellent adhesive strength and desired mechanical properties.

[0030] The diamine monomers that can be used in the production of the polyamic acid solution are aromatic diamines, and can be exemplified by the following classifications: 1) Diamines having a relatively rigid structure, such as 1,4-diaminobenzene (or paraphenylenediamine, PDA), 1,3-diaminobenzene, 2,4-diaminotoluene, 2,6-diaminotoluene, and 3,5-diaminobenzoic acid (or DABA); 2) Diaminodiphenyl ethers such as 4,4'-diaminodiphenyl ether (or oxydianiline, ODA), 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane (methylenediamine), 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-dicarboxy-4,4'-diaminodiphenyl phenylmethane, 3,3',5,5'-tetramethyl-4,4'-diaminodiphenylmethane, bis(4-aminophenyl)sulfide, 4,4'-diaminobenzanilide, 3,3'-dichlorobenzidine, 3,3'-dimethylbenzidine (or o-tolidine), 2,2'-dimethylbenzidine (or m-tolidine), 3,3'-dimethoxybenzidine, 2,2'-dimethoxybenzidine, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3 '-Diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,3'-diamino-4,4'-dichlorobenzophenone, 3,3'-diamino-4,4'-dimethoxybenzophenone, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane diamines having two benzene nuclei in their structure, such as ethane, 4,4'-diaminodiphenylmethane, 2,2-bis(3-aminophenyl)propane, 2,2-bis(4-aminophenyl)propane, 2,2-bis(3-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 2,2-bis(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 3,3'-diaminodiphenyl sulfoxide, 3,4'-diaminodiphenyl sulfoxide, 4,4'-diaminodiphenyl sulfoxide, etc.; 3) 1,3-bis(3-aminophenyl)benzene, 1,3-bis(4-aminophenyl)benzene, 1,4-bis(3-aminophenyl)benzene, 1,4-bis(4-aminophenyl)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene (or TPE-Q), 1,4-bis(4-aminophenoxy)benzene (or TPE-Q), 1,3-bis(3-aminophenoxy)-4-trifluoromethylbenzene, 3,3'-diamino-4-(4-phenyl)phenoxybenzophenone, 3,3'-diamino-4,4'-di(4-phenylphenoxy)benzophenone diamines having three benzene nuclei in their structure, such as 1,3-bis(3-aminophenylsulfide)benzene, 1,3-bis(4-aminophenylsulfide)benzene, 1,4-bis(4-aminophenylsulfide)benzene, 1,3-bis(3-aminophenylsulfone)benzene, 1,3-bis(4-aminophenylsulfone)benzene, 1,4-bis(4-aminophenylsulfone)benzene, 1,3-bis[2-(4-aminophenyl)isopropyl]benzene, 1,4-bis[2-(3-aminophenyl)isopropyl]benzene, 1,4-bis[2-(4-aminophenyl)isopropyl]benzene, and the like; 4) 3,3'-bis(3-aminophenoxy)biphenyl, 3,3'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, 4,4'-bis(4-aminophenoxy)biphenyl, bis[3-(3-aminophenoxy)phenyl]ether, bis[3-(4-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, bis[3-(3-aminophenoxy)phenyl]ketone, bis[3-(4-aminophenoxy)phenyl] bis[4-(3-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]ketone, bis[3-(3-aminophenoxy)phenyl]sulfide, bis[3-(4-aminophenoxy)phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[3-(3-aminophenoxy)phenyl]sulfone, bis[3-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone phenyl]sulfone, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[3-(3-aminophenoxy)phenyl]methane, bis[3-(4-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(4-aminophenoxy)phenyl]methane, 2,2-bis[3-(3-aminophenoxy)phenyl]propane, 2,2-bis[3-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, Diamines having four benzene nuclei in their structure, such as 2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane (BAPP), 2,2-bis[3-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, and 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane.

[0031] In one example, the diamine monomer according to the present application may include 1,4-diaminobenzene (PPD), 1,3-diaminobenzene (MPD), 2,4-diaminotoluene, 2,6-diaminotoluene, 4,4'-diaminodiphenyl ether (ODA), 4,4'-methylenediamine (MDA), 4,4-diaminobenzanilide (4,4-DABA), N,N-bis(4-aminophenyl)benzene-1,4-dicarboxamide (BPTPA), 2,2-dimethylbenzidine (M-TOLIDINE), 2,2-bis(trifluoromethyl)benzidine (TFDB), 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (HFBAPP) or 2,2'-bis(trifluoromethyl)benzidine (TFMB).

[0032] In one specific example, the polyamic acid composition may contain 9 to 35 wt%, 10 to 33 wt%, 10 to 30 wt%, 15 to 25 wt%, or 18 to 23 wt% of solids based on the total weight. By adjusting the solids content of the polyamic acid composition to be relatively high, the present application can control an increase in viscosity while maintaining the physical properties after curing at a desired level, and prevent an increase in manufacturing costs and process time that would be required to remove a large amount of solvent during the curing process.

[0033] The polyamic acid composition of the present application may be a composition having low viscosity characteristics. The polyamic acid composition of the present application may be a composition having low viscosity characteristics at a temperature of 23° C. and 1 s -1The viscosity measured under the condition of a shear rate of 1 / s may be 50,000 cP or less, 40,000 cP or less, 30,000 cP or less, 20,000 cP or less, 10,000 cP or less, or 9,000 cP or less. The lower limit is not particularly limited, but may be 500 cP or more or 1000 cP or more. The viscosity may be measured, for example, using a Rheostress 600 manufactured by Haake Co., Ltd., and may be measured under the conditions of a shear rate of 1 / s, a temperature of 23° C., and a plate gap of 1 mm. The present application provides a precursor composition having excellent processability by adjusting the viscosity range, and a film or substrate having desired physical properties can be formed during the formation of the film or substrate.

[0034] In one embodiment, the polyamic acid composition of the present application may have a weight average molecular weight after curing in the range of 10,000 to 500,000 g / mol, 15,000 to 400,000 g / mol, 18,000 to 300,000 g / mol, 20,000 to 200,000 g / mol, 25,000 to 100,000 g / mol, or 30,000 to 80,000 g / mol. In the present application, the term weight average molecular weight refers to a value converted to standard polystyrene measured by GPC (Gel Permeation Chromatograph).

[0035] The polyamic acid composition according to the present application may further include inorganic particles. The inorganic particles may have an average particle size of, for example, 5 to 80 nm, and in a specific example, the lower limit may be 8 nm, 10 nm, 15 nm, 18 nm, 20 nm, or 25 nm or less, and the upper limit may be, for example, 70 nm, 60 nm, 55 nm, 48 nm, or 40 nm or less. In the present specification, the average particle size may be measured by D50 particle size analysis. In the present application, by adjusting the particle size range, compatibility with polyamic acid can be increased and the desired physical properties after curing can be realized.

[0036] The type of the inorganic particles is not particularly limited, and may include silica, alumina, titanium dioxide, zirconia, yttria, mica, clay, zeolite, chromium oxide, zinc oxide, iron oxide, magnesium oxide, calcium oxide, scandium oxide, or barium oxide. The inorganic particles of the present application may also include a surface treatment agent on the surface. The surface treatment agent may include, for example, a silane coupling agent. The silane coupling agent may be one or more selected from the group consisting of epoxy-based, amino-based, and thiol-based compounds. In particular, the epoxy-based compound may include glycidoxypropyl trimethoxysilane (GPTMS), the amino-based compound may include aminopropyl trimethoxysilane ((3-Aminopropyl)trimethoxysilane (APTMS), and the thiol-based compound may include mercaptopropyl-trimethoxysilane (MPTMS), but are not limited thereto. The surface treatment agent may include dimethyldimethoxysilane (DMDMS), methyltrimethoxysilane (MTMS), methyltriethoxysilane (MTES) or tetraethoxysilane (TEOS). In the present application, the surface of the inorganic particles may be treated with one type of surface treatment agent or may be surface-treated with two different types of surface treatment agents. In addition, the inorganic particles may be included in a range of 1 to 20 parts by weight with respect to 100 parts by weight of the polyamic acid. The lower limit of the content may be, for example, 3 parts by weight, 5 parts by weight, 8 parts by weight, 9 parts by weight or more, and the upper limit may be, for example, 18 parts by weight, 15 parts by weight, 13 parts by weight or less, and 8 parts by weight or less. In the present application, the inorganic particles are blended into the polyamic acid composition to improve dispersibility and miscibility, and to realize adhesion and heat resistance durability after curing.

[0037] The polyamic acid composition may have a coefficient of thermal expansion (CTE) after curing in the range of 40 ppm / ° C. or less. In one specific example, the upper limit of the CTE may be 40 ppm / °C, 35 ppm / °C, 30 ppm / °C, 25 ppm / °C, 20 ppm / °C, 18 ppm / °C, 15 ppm / °C, 13 ppm / °C, 10 ppm / °C, 8 ppm / °C, 7 ppm / °C, 6 ppm / °C, 5 ppm / °C, 4.8 ppm / °C, 4.3 ppm / °C, 4 ppm / °C, 3.7 ppm / °C, 3.5 ppm / °C, 3 ppm / °C, 2.8 ppm / °C, or 2.6 ppm / °C or less, and the lower limit may be, for example, 0.1 ppm / °C, 1 ppm / °C, 2.0 ppm / °C, 2.6 ppm / °C, 2.8 ppm / °C, 3.5 ppm / °C, or 4 ppm / °C or more. In one example, the thermal expansion coefficient may be measured at 100 to 450°C. The CTE can be measured using a TA thermomechanical analyzer, model Q400. After preparing a polyimide film and cutting it to a width of 2 mm and a length of 10 mm, the film is heated from room temperature to 500° C. at a rate of 10° C. / min while applying a tension of 0.05 N under a nitrogen atmosphere, and then cooled at a rate of 10° C. / min to measure the slope from 100° C. to 450° C.

[0038] The polyamic acid composition may have an elongation of 10% or more after curing, and in specific examples, may be 12% or more, 13% or more, 15% or more, 18% or more, 20-60%, 20-50%, 20-40%, 20-38%, 22-36%, 24-33%, or 25-29%. The elongation may be measured by curing the polyamic acid composition into a polyimide film, cutting the film into a width of 10 mm and a length of 40 mm, and then measuring the elongation according to ASTM D-882 method using an Instron 5564 UTM device manufactured by Instron Corporation.

[0039] The polyamic acid composition of the present application may have a modulus of elasticity in the range of 6.0 GPa to 11 GPa after curing. The lower limit of the modulus of elasticity may be, for example, 6.5 GPa, 7.0 GPa, 7.5 GPa, 8.0 GPa, 8.5 GPa, 9.0 GPa, 9.3 GPa, 9.55 GPa, 9.65 GPa, 9.8 GPa, 9.9 GPa, 9.95 GPa, 10.0 GPa, or 10.3 GPa or more, and the upper limit may be, for example, 10.8 GPa, 10.5 GPa, 10.2 GPa, or 10.0 GPa or less. The polyamic acid composition may have a tensile strength in the range of 300 MPa to 600 MPa after curing. The lower limit of the tensile strength may be, for example, 350 MPa, 400 MPa, 450 MPa, 480 MPa, 500 MPa, 530 MPa, or 540 MPa or more, and the upper limit may be, for example, 580 MPa, 570 MPa, 560 MPa, 545 MPa, 530 MPa, or 500 MPa or less. The elastic modulus and tensile strength may be measured by curing the polyamic acid composition to prepare a polyimide film, cutting the film into a width of 10 mm and a length of 40 mm, and then measuring the elastic modulus and tensile strength according to ASTM D-882 method using an Instron 5564 UTM device manufactured by Instron. The cross head speed may be measured at 50 mm / min.

[0040] In one example, the polyamic acid composition according to the present application may have a glass transition temperature after curing in the range of 350° C. or more. The upper limit of the glass transition temperature may be 800° C. or less or 700° C., and the lower limit may be 360° C., 365° C., 370° C., 380° C., 390° C., 400° C., 410° C., 420° C., 425° C., 430° C., 440° C., 445° C., 448° C., 450° C., 453° C., 455° C., or 458° C. or more. The glass transition temperature can be measured at 10° C. / min using TMA on a polyimide produced by curing the polyamic acid composition.

[0041] The polyamic acid composition according to the present application may have a 1 wt% thermal decomposition temperature of 500° C. or more after curing. The thermal decomposition temperature can be measured using a thermogravimetric analyzer Q50 model manufactured by TA. In a specific example, the polyimide obtained by curing the polyamic acid is heated to 150° C. at a rate of 10° C. / min in a nitrogen atmosphere, and then isothermal is maintained for 30 minutes to remove moisture. Thereafter, the temperature is raised to 600° C. at a rate of 10° C. / min, and the temperature at which a 1% weight loss occurs can be measured. The lower limit of the pyrolysis temperature may be, for example, 510°C, 515°C, 518°C, 523°C, 525°C, 528°C, 530°C, 535°C, 538°C, 545°C, 550°C, 560°C, 565°C, 568°C, 570°C, 580°C, 583°C, 585°C, 588°C, 590°C or 593°C or more, and the upper limit may be, for example, 800°C, 750°C, 700°C, 650°C or 630°C or less.

[0042] The polyamic acid composition according to the present application may have a light transmittance in the range of 50 to 80% in any one wavelength band in the visible light region (380 to 780 nm) after curing. The lower limit of the light transmittance may be, for example, 55%, 58%, 60%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, or 71% or more, and the upper limit may be, for example, 78%, 75%, 73%, 72%, 71%, 69%, 68%, 67%, 66%, 65%, or 64% or less.

[0043] The present application also relates to a method for producing the polyamic acid composition described above.

[0044] The preparation method may include a step of heating at least 50°C. The heating step may be, for example, 55°C or more, 58°C or more, 60°C or more, 63°C or more, 65°C or more, or 68°C or more, and the upper limit may be, for example, 100°C or less, 98°C or less, 93°C or less, 88°C or less, 85°C or less, 83°C or less, 80°C or less, 78°C or less, 75°C or less, 73°C or less, or 71°C or less. The present application may include a step of mixing an organic solvent and a dianhydride monomer component before the heating step. The present application may perform the above-mentioned heating step after the mixing, and therefore, heating may be performed in a state in which the organic solvent and the dianhydride monomer are included. The present application may have a desired polyamic acid structure by performing a heating step at a higher temperature than the conventional process, and the length of the entire polymer chain is increased after curing, and such a polymer may have excellent heat resistance, dimensional stability, and mechanical properties.

[0045] In an embodiment, the method for producing the polyamic acid composition of the present application can include, for example, the following polymerization method. For example, (1) a method in which the entire amount of the diamine monomer is placed in a solvent, and then a dianhydride monomer is added in an amount substantially equimolar to the diamine monomer to polymerize it; (2) A method in which the entire amount of the dianhydride monomer is placed in a solvent, and then a diamine monomer is added in an amount substantially equimolar to the dianhydride monomer to polymerize it; (3) A method in which a part of the diamine monomer components is put into a solvent, a part of the dianhydride monomer components is mixed with the reaction components in a ratio of about 95 to 105 mol %, and then the remaining diamine monomer components are added, and the remaining dianhydride monomer components are added successively thereto, so that the diamine monomer and the dianhydride monomer are polymerized in substantially equimolar amounts; (4) A method in which a dianhydride monomer is placed in a solvent, a part of a diamine compound is mixed in a ratio of 95 to 105 mol % relative to the reaction components, and then another dianhydride monomer component is added, followed by the remaining diamine monomer component, so that the diamine monomer and the dianhydride monomer are polymerized in substantially equimolar amounts; (5) A method of forming a first composition by reacting a part of a diamine monomer component and a part of a dianhydride monomer component in a solvent so that one of them is in an excess amount, and forming a second composition by reacting a part of a diamine monomer component and a part of a dianhydride monomer component in another solvent so that one of them is in an excess amount, and then mixing the first and second compositions to complete polymerization, in which, in this case, when the diamine monomer component is in excess when forming the first composition, the dianhydride monomer component is in excess in the second composition, and when the dianhydride monomer component is in excess in the first composition, the diamine monomer component is in excess in the second composition, and the first and second compositions are mixed to polymerize so that the total diamine monomer components and dianhydride monomer components used in these reactions are substantially equimolar.

[0046] The polymerization method is not limited to the above examples, and any known method can be used.

[0047] The step of preparing the polyamic acid composition may be carried out at 30 to 80°C.

[0048] The present application also relates to a polyimide comprising a cured product of the polyamic acid composition. The present application also provides a polyimide film comprising the polyimide. The polyimide film may be a polyimide film for a substrate, and in a specific example, may be a polyimide film for a TFT substrate.

[0049] The present invention also provides a method for producing a polyimide film, comprising the steps of forming a polyamic acid composition produced by the method for producing a polyamic acid composition on a support, drying the polyamic acid composition to produce a gel film, and curing the gel film.

[0050] Specifically, in the method for producing a polyimide film of the present invention, the step of forming a film of the polyimide precursor composition on a support and drying the film to form a gel film, and curing the gel film may be performed through the steps of drying the polyimide precursor composition formed on the support at a temperature of 20 to 120°C for 5 to 60 minutes to form a gel film, heating the gel film to 30 to 500°C at a rate of 1 to 8°C / min, heat-treating the gel film at 450 to 500°C for 5 to 60 minutes, and cooling the gel film to 20 to 120°C at a rate of 1 to 8°C / min.

[0051] The step of curing the gel film may be performed at 30 to 500° C. For example, the step of curing the gel film may be performed at 30 to 400° C., 30 to 300° C., 30 to 200° C., 30 to 100° C., 100 to 500° C., 100 to 300° C., 200 to 500° C., or 400 to 500° C.

[0052] The polyimide film has a thickness of 10 to 20 μm. For example, the polyimide film may have a thickness of 10 to 18 μm, 10 to 16 μm, 10 to 14 μm, 12 to 20 μm, 14 to 20 μm, 16 to 20 μm, or 18 to 20 μm.

[0053] The support may be, for example, an inorganic substrate. Examples of the inorganic substrate include a glass substrate and a metal substrate. It is preferable to use a glass substrate. The glass substrate may be, for example, soda-lime glass, borosilicate glass, or alkali-free glass, but is not limited thereto. Effect of the Invention

[0054] The present application provides a polyamic acid composition having a high concentration of polyamic acid solids and low viscosity, and having excellent heat resistance, dimensional stability, and mechanical properties as well as excellent electrical properties after curing, and a polyimide and a polyimide film produced therefrom.

[0055] <Best Mode for Carrying Out the Invention> The present invention will be described in more detail below based on examples according to the present invention and comparative examples not according to the present invention, but the scope of the present invention is not limited to the examples presented below. EXAMPLES

[0056] <Preparation of polyamic acid solution> Example 1 While injecting nitrogen into a 500 ml reactor equipped with a stirrer and a nitrogen inlet / outlet pipe, N-methyl-pyrrolidone (NMP, 99 wt%) was added as a first solvent, and then methanol (MeOH) was added as a second solvent at a ratio of 1 wt% as an additional solvent and stirred. The temperature of the reactor was set to 70°C, and biphenyltetracarboxylic acid dianhydride (BPDA) was added as a dianhydride monomer and reacted. Next, the temperature was lowered to 30°C under a nitrogen atmosphere, and para-phenylenediamine (PPD) as a diamine monomer was completely dissolved in the reaction solution and stirred quickly. Then, the mixture was heated at a temperature of 40°C and stirred for 120 minutes to produce a polyamic acid solution.

[0057] Examples 2 to 6 A polyamic acid solution was prepared in the same manner as in Example 1, except that the monomer and content ratio and the type and content ratio of the added solvent were adjusted as shown in Table 1.

[0058] Comparative Examples 1 to 6 A polyamic acid solution was prepared in the same manner as in Example 1, except that the monomer and content ratio were adjusted as shown in Table 1 and the second solvent was omitted.

[0059] [Table 1]

[0060] <Preparation of polyimide for physical property measurement> The polyamic acid compositions prepared in the examples and comparative examples were rotated at a high speed of 1,500 rpm or more to remove air bubbles. The degassed polyamic acid compositions were then coated on a glass substrate using a spin coater. The degassed polyamic acid compositions were then dried for 30 minutes at 120°C under a nitrogen atmosphere to prepare a gel film. The gel film was then heated to 450°C at a rate of 2°C / min, heat-treated at 450°C for 60 minutes, and cooled to 30°C at a rate of 2°C / min to obtain a polyimide film.

[0061] Then, the polyimide film was peeled off from the glass substrate by dipping in distilled water. The physical properties of the prepared polyimide film were measured using the following methods, and the results are shown in Table 2 below.

[0062] Experimental Example 1 - Dielectric constant The dielectric constant of the polyimides prepared in the examples and comparative examples was measured according to ASTM D150. Specifically, the dielectric constant was measured at 120 Hz, 23 (±3)°C and 45 (±5)% relative humidity using an LCR Meter (Agilent). The measured dielectric constants are shown in Table 2 below.

[0063] Experimental Example 2 - Surface Resistance The surface resistance of the polyimides prepared in the examples and comparative examples was measured at 23° C. and 50% relative humidity according to ASTM D257 using the following measuring equipment and conditions. 1.Analyzer 1) Equipment name: Resistance Meter 2) Manufacturer and model: Agilent / 4339B 3)Measurement range: 1kΩ to 16PΩ 4) Basic accuracy: ±0.6% 2.Analysis Method 1) Test condition -Temperature: 23±3℃ 2) Specimen -110×110mm Film 3) Test method: ASTM D257 4)Source Voltage: 500V 5) Load Scale: 5kgf 6)Charge Time: 60 Sec.

[0064] Experimental Example 3 - Viscosity The viscosity of the polyimide precursor compositions prepared in the Examples and Comparative Examples was measured using a Haake Rheostress 600 at a shear rate of 1 / s, a temperature of 23° C., and a plate gap of 1 mm.

[0065] Experimental Example 4 - Glass Transition Temperature For the polyimide films prepared in the examples and comparative examples, the point at which the polyimide films suddenly expanded at 10° C. / min was measured using TMA as the on-set point.

[0066] Experimental Example 5-CTE Using a TA thermomechanical analyzer, model Q400, the polyimide film was cut to a width of 2 mm and a length of 10 mm, and then the film was heated from room temperature to 500°C at a rate of 10°C / min while applying a tension of 0.05 N under a nitrogen atmosphere, and then cooled at a rate of 10°C / min to measure the slope of the section from 100°C to the Tg temperature.

[0067] Experimental Example 6-1% by weight thermal decomposition temperature (Td) Using a TA thermogravimetric analyzer Q50 model, the polyimide film was heated to 150°C at a rate of 10°C / min under a nitrogen atmosphere, and then the temperature was maintained at the same temperature for 30 minutes to remove moisture.Then, the film was heated to 600°C at a rate of 10°C / min to measure the temperature at which a 1% weight loss occurred.

[0068]

Table 2

Claims

1. A polyimide including a cured product of a polyamic acid composition, the polyamic acid composition including a polyamic acid including a dianhydride monomer component and a diamine monomer component as polymerization units, and a solvent, the solvent including a first solvent and a second solvent that is a component different from the first solvent, The first solvent has a boiling point of 150° C. or higher, and the second solvent has a boiling point lower than that of the first solvent. The second solvent is contained in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the first solvent; The cured product has a dielectric constant of 3.5 or less at 120 Hz and a surface resistivity of 2.35×10 measured at 23° C. and 50% relative humidity according to ASTM D257 standard. １４ Ω or more, and The glass transition temperature of the cured product is in the range of 350° C. or higher. Polyimide.

2. 10. The polyimide of claim 1, wherein the second solvent has a solubility for the dianhydride monomer of less than 1.5 g / 100 g.

3. 2. The polyimide according to claim 1, wherein the second solvent has at least one polar functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an alkoxy group, an ester group, and an ether group.

4. 2. The polyimide according to claim 1, wherein the second solvent is contained in an amount ranging from 0.01 to 10% by weight in the total polyamic acid composition.

5. The polyimide of claim 1, wherein the polyamic acid composition contains, in addition to the monomers contained in the polymerization units, an unpolymerized dianhydride monomer having an open ring structure.

6. The polyimide according to claim 5 , wherein a dianhydride monomer having a ring-open structure participates in the imidization reaction.

7. 2. The polyimide of claim 1, wherein the diamine monomer comprises 1,4-diaminobenzene (PPD), 1,3-diaminobenzene (MPD), 2,4-diaminotoluene, 2,6-diaminotoluene, 4,4'-diaminodiphenyl ether (ODA), 4,4'-methylenediamine (MDA), 4,4-diaminobenzanilide (4,4-DABA), N,N-bis(4-aminophenyl)benzene-1,4-dicarboxamide (BPTPA), 2,2-dimethylbenzidine (M-TOLIDINE), 2,2-bis(trifluoromethyl)benzidine (TFDB), 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (HFBAPP) or 2,2'-bis(trifluoromethyl)benzidine (TFMB).

8. The dianhydride monomers are pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3,3', 2. The polyimide of claim 1, comprising 4'-biphenyltetracarboxylic dianhydride (a-BPDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), oxydiphthalic dianhydride (ODPA), 4,4-(hexafluoroisopropylidene)diphthalic anhydride (6-FDA), p-phenylenebis(trimellitate anhydride) (TAHQ) or 2,2-bis[(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA).

9. 2. The polyimide of claim 1, wherein the solids content of the polyamic acid composition is in the range of 9 to 35%.

10. The polyamic acid composition is heated at 23° C. for 1 s －１ 2. The polyimide of claim 1, having a viscosity in the range of 500 to 50,000 cP measured at a shear rate of 100 .mu.m.

11. 2. The polyimide according to claim 1, wherein the weight average molecular weight of the cured product is within the range of 10,000 g / mol to 500,000 g / mol.

12. The polyimide of claim 1 , wherein the polyamic acid composition further comprises inorganic particles.

13. 2. The polyimide according to claim 1, wherein the CTE (coefficient of thermal expansion) of the cured product is in the range of 40 ppm / ° C. or less.

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