TWI837970B - Polyamic acid composition and polyimide film prepared with the same - Google Patents

Abstract

The present disclosure relates to a polyamic acid composition comprising: a polyamic acid comprising, as a polymerization unit, at least one selected from a dianhydride monomer represented by Chemical Formula 1 and a diamine monomer represented by Chemical Formula 2 or Chemical Formula 3; an imidazole-based compound; an epoxy-based compound; and an organic solvent, and a polyimide comprising the same. The polyamic acid composition of the present disclosure and the polyimide comprising the same have excellent mechanical properties such as strength and elongation while maintaining a low yellow index and excellent thermal properties.

Description

Polyamide compound and polyimide film prepared therefrom

The present disclosure relates to a polyamic acid composition and a polyimide film prepared therefrom. Specifically, the present disclosure relates to a polyamic acid composition used for manufacturing a display substrate and a polyimide film as a cured product of polyamic acid.

Displays of various types and sizes, from small displays such as mobile phones to LCD or plasma TVs or outdoor billboards (public information displays (PIDS) and digital information displays (DIDs)). In particular, as society develops into the era of popularization, that is, the advanced knowledge and information society, the demand for portable devices with simplicity and mobility is booming. In contrast, the technology of flexible displays that are thinner, lighter, easier to carry, and can be folded like paper and rolled up like a scroll is emerging and is becoming a new growth engine business.

In such an environment, polyimide films prepared by curing and imidizing polyamide (prepared by polymerizing dianhydride monomers and diamine monomers) have excellent heat resistance, chemical resistance, mechanical strength, electrical properties, and dimensional stability, and are therefore widely used in the fields of electrical/electronic devices, semiconductors, etc. In particular, people are paying more and more attention to using films as substrate materials for flexible displays.

However, in order to use the film for display applications, it needs to have high transparency, high mechanical strength, optical properties, yellowing index and mechanical properties, while being free of micro defects such as curling or cracks caused by folding.

Therefore, there is a need to develop polyimide with a low yellowing index that is suitable for application in flexible substrates and maintains excellent thermal properties such as heat resistance while having excellent strength and elongation.

[Technical topic] The purpose of this disclosure is to provide a polyamide compound having excellent elongation and strength while maintaining a low yellowing index and excellent thermal properties, and a polyimide film prepared therefrom.

In addition, another object of the present disclosure is to provide a flexible display device using the polyimide film as a substrate.

[Technical means] The present disclosure may have various variations and may have multiple embodiments, so specific embodiments will be described in detail as shown in the accompanying drawings. However, these descriptions are not intended to limit the present disclosure to specific embodiments, but should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present disclosure.

The terms used in this case are only used to describe specific embodiments and are not intended to limit the present disclosure. Unless the context clearly indicates otherwise, singular expressions include plural expressions. In this case, terms such as "including", "having", etc. are intended to indicate the presence of the features, quantities, steps, operations, components, and combinations thereof described in the specification. It should be understood that these terms do not preemptively exclude the possibility of the presence or addition of one or more other features or quantities, steps, operations, components, parts, or combinations thereof.

When an amount, concentration or other value or parameter is given by listing a range, a preferred range or a preferred upper limit, and a preferred lower limit, it should be understood that all ranges formed from any pair of any range upper limit or preferred value and any range lower limit or preferred value are specifically disclosed, regardless of whether the range is disclosed individually.

When numerical ranges are described herein, unless otherwise stated, the ranges are not limited to the endpoints, and the scope of the present disclosure within the range is not limited to the specific values recited when defining the range.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meanings as commonly understood by persons of ordinary skill in the art to which the present disclosure belongs. Terms defined in commonly used dictionaries should be understood to have meanings consistent with those in the relevant technical context and should not be interpreted as ideal or overly formalized meanings unless clearly defined in the present case. The following will describe specific details for implementing the present disclosure.

The present disclosure relates to a polyamino acid composition.

In one general aspect of the present disclosure, the polyamine composition may include: polyamine, including, as a polymerizable unit, at least one selected from the following: a dianhydride monomer represented by Chemical Formula 1 and a diamine monomer represented by Chemical Formula 2 or Chemical Formula 3: [Chemical Formula 1] [Chemical formula 2] [Chemical formula 3] Imidazole-based compounds; epoxy-based compounds; and organic solvents.

The polyamic acid composition prepared according to the present disclosure has excellent thermal properties unique to polyimide, a low yellowing index, and excellent mechanical properties such as strength and elongation. Therefore, the polyamic acid composition is suitable as a display material, and the polyimide film as a cured product of the polyamic acid composition is beneficial as a display substrate material.

In the present disclosure, the compound represented by Chemical Formula 1 is referred to as norbornane-2-spiro-α-cyclopentanone-α′-spiro-2″-norbornane-5,5″,6,6″-tetracarboxylic acid dianhydride (CpODA). CpODA may be a mixture of stereoisomers or may be a specific stereoisomer. The stereoisomers are not particularly limited, but preferred stereoisomers may include trans-endo-endo-norbornane-2-spiro-α-cyclopentanone-α′-spiro-2″-norbornane-5,5″,6,6″-tetracarboxylic dianhydride (CpODA-tee) and cis-endo-endo-norbornane-2-spiro-α-cyclopentanone-α′-spiro-2″-norbornane-5,5″,6,6″-tetracarboxylic dianhydride (CpODA-tee). CpODA-cee). (CpODA) (CpODA-tee) (CpODA-cee)

In one embodiment, at least 50 mol% or more, even more preferably, 63 mol% or more of CpODA may be CpODA-tee. In another exemplification, at least 30 mol% or more, even more preferably, at least 37 mol% or more of CpODA may be CpODA-cee. In another exemplification, the total amount of CpODA-tee and CpODA-cee in CpODA may be at least 80 mol% or more, even more preferably, 83 mol% or more, but the content range is not limited thereto.

In the present disclosure, the compound represented by Chemical Formula 2 is referred to as 4,4'-diaminobenzanilide (DABAN), and the compound represented by Chemical Formula 3 is referred to as N,N'-bis(4-aminophenyl)benzene-1,4-dicarboxamide (DATA).

In the present disclosure, the polyamine composition may further include a dianhydride monomer as shown in Chemical Formula 4, and may have a polymerized unit associated with the dianhydride monomer: [Chemical Formula 4]

The compound represented by Chemical Formula 4 is called (4arH,8acH)-decahydro-1t,4t:5c,8c-dimethanonaphthalene-2c,3c,6c,7c-tetracarboxylic dianhydride (DNDAxx).

In the present disclosure, the dianhydride monomer represented by Chemical Formula 4 may comprise 20 mol % or less, preferably 15 mol % or less, 13 mol % or less, 10 mol % or less, 8 mol % or less, 7 mol % or less, 5 mol % or less, 3 mol % or less, or 2 mol % or less, or 0 mol % of the total dianhydride monomer component ratio.

In the present disclosure, the diamine monomer represented by Chemical Formula 2 may comprise 70 mol% or more of the total diamine monomer component ratio, the lower limit of the ratio may be, for example, 75 mol%, 78 mol%, 80 mol%, 82 mol%, 85 mol%, 87 mol%, 90 mol%, 92 mol%, 94 mol%, 95 mol%, 97 mol%, 99 mol%, or 100 mol% or more, and the upper limit of the ratio may be, for example, 100 mol%, 99 mol%, 98 mol%, 97 mol%, 96 mol%, 95 mol%, 94 mol%, 93 mol%, 92 mol%, 91 mol%, 90 mol%, or 88 mol% or less.

In the present disclosure, by using an imidazole-based compound suitable for polyimide, polyimide with excellent mechanical properties such as transparency, elongation and brittleness (strength) can be prepared.

In the present disclosure, the imidazole compound may include 2-phenylimidazole, benzimidazole, 1,2-dimethylimidazole, 1-methylimidazole, 2-methylimidazole, and imidazole, or a combination thereof. Preferably, the imidazole compound may be 2-phenylimidazole or benzimidazole, and more preferably, 2-phenylimidazole.

In addition, in the present disclosure, based on 1 mol of the repeating unit of polyamine, the content of the imidazole compound may be 0.1 to 40 mol%. The lower limit of the ratio may be, for example, 0.5 mol%, 1.0 mol%, 1.5 mol%, 2 mol%, 2.5 mol%, 3 mol%, 3.5 mol%, 4.0 mol%, 4.5 mol%, 4.7 mol%, 4.9 mol%, 5.0 mol%, 5.2 mol%, 5.5 mol%, 6.0 mol%, 6.5 mol%, 7.0 mol%, 7.5 mol%, 8.0 mol%, 8.5 mol%, 9.0 mol%, 9.5 mol%, or 10 mol% or more, and the upper limit of the ratio may be, for example, 35 mol%, 30 mol%, 28 mol%, 26 mol%, 24 mol%, 22 mol%, 20 mol%, 18 mol%, 15 mol%, 12 mol%, or 10 mol% or less. When the content of the imidazole compound is too low, for example, when the content of the imidazole compound is less than 0.1 mol%, the mechanical properties such as elongation, brittleness, and strength may be reduced. On the other hand, when the content of the imidazole compound is too high, for example, when the content of the imidazole compound is greater than 40 mol%, the polyamine composition may have poor storage stability.

In the present disclosure, epoxy-based compounds are multifunctional epoxy compounds. The multifunctional epoxy compounds may include epoxy compounds having 2 to 4 epoxy functional groups, such as N,N'-N,N'-tetraglycidyl diamino diphenyl methane (TGDDM), bisphenol A diglycidyl ether (DGEBA), tetraglycidyl-meta-xylenediamine, tetraglycidyl-1,3-bisaminomethylcyclohexane, and trimethylolpropane triglycidyl ether (TMP), and preferably TGDDM. The polyamine composition prepared in the present disclosure contains an epoxy compound as an additive, so that the crosslinking density can be increased to have rigid mechanical properties.

In addition, in the present disclosure, based on 1 mol of repeating units of polyamide, the content of epoxy compound can be 0.01 to 1.0 mol%. The lower limit of the ratio can be, for example, 0.02 mol%, 0.03 mol%, 0.05 mol%, 0.07 mol%, or 0.09 mol% or more, and the upper limit of the ratio can be, for example, 0.9 mol%, 0.85 mol%, 0.8 mol%, 0.75 mol%, 0.7 mol%, 0.65 mol%, 0.6 mol%, 0.55 mol%, 0.5 mol%, 0.48 mol%, 0.45 mol%, 0.4 mol%, 0.35 mol%, or 0.3 mol% or less.

In the present disclosure, the strength of polyimide can be improved by adding an epoxy compound. However, based on 1 mol of repeating units of polyamide, when the content of the epoxy compound is less than 0.01 mol%, the effect of improving the strength of polyimide by adding the epoxy compound may not be significant. When the content is greater than 1.0 mol%, the physical properties may be reduced due to reduced solubility.

The polyamide composition disclosed herein can contain both an imidazole compound and an epoxy compound in the polyamide, so it can be expected to have high strength and excellent elongation at the same time. In particular, the polyimide disclosed herein exhibits high strength and excellent elongation as well as improved heat resistance and yellowing index by promoting imidization when a specific dianhydride monomer and a diamine monomer are mixed with an imidazole compound. In addition, the elongation is further improved by containing an epoxy compound such as TGDDM, thereby achieving polyimide with improved mechanical properties and excellent thermal properties suitable for being a display substrate material.

In the present disclosure, the organic solvent is not particularly limited as long as it can dissolve the polyamine, the imidazole compound and the epoxy compound, but can be, for example, an aprotic polar solvent, preferably, as the organic solvent, N-methyl-pyrrolidone (NMP), N,N'-dimethylformamide (DMF), N,N'-diethylformamide (DEF), N,N'-dimethylacetamide (DMAc), dimethylpropanamide (DMPA), N,N-diethylacetamide (685-91-6, N,N-diethylacetamide, DEAc), and 3-methoxy-N,N-dimethylpropanamide (53185-52-7, 3-methoxy-N,N-dimethylpropanamide, KJCMPA) or a combination thereof, but NMP is most preferably used.

In the present disclosure, the polyamine composition prepared in the present disclosure may have a weight average molecular weight of 1,000 g/mol to 100,000 g/mol. The lower limit of the weight average molecular weight may be 1,500 g/mol, 2,000 g/mol, 2,500 g/mol, or 3,000 g/mol or higher, and the upper limit of the weight average molecular weight may be 90,000 g/mol, 80,000 g/mol, 70,000 g/mol, 60,000 g/mol, 50,000 g/mol, 30,000 g/mol, 29,000 g/mol, or 28,500 g/mol or lower.

In the present disclosure, the polyamide composition prepared in the present disclosure may have a solid content of 5wt% to 30wt%. The lower limit of the weight percentage of the solid content may be 5wt%, 8wt%, 9wt%, 10wt%, 15wt%, 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, or 29wt% or more, and the upper limit of the weight percentage of the solid content may be 29wt%, 27wt%, 25wt%, 23wt%, 21wt%, 20wt%, 19wt%, or 18wt% or less. By adjusting the solid content of the polyamide composition, the increase in viscosity can be controlled and the process time in the curing process can be shortened.

In the present disclosure, the viscosity of the polyamino acid composition may be in the range of 1,000 to 10,000 millipoise, which is measured at a temperature of 23° C. and a shear rate of 1 s ⁻¹ . For example, the upper limit of the viscosity may be 10,000, 8,000, 5,000, 4,700, 4,500, 4,000, 3,800, 3,700, 3,500, 3,300, 3,200, 3,100, or 3,000 or less, and the lower limit thereof is not particularly limited but may be 1,200, 1,500, 2,000, or 2,500 or more. The viscosity can be measured using, for example, a Haake Rheostress 600 manufactured by Thermo Fisher Scientific Inc., and the measurement is performed under the conditions of a shear rate of 1 s ^-1 , a temperature of 23° C., and a plate gap of 1 mm. The present disclosure can provide a precursor composition with excellent processing properties by adjusting the viscosity range.

In addition, the present disclosure provides a polyimide, which is a cured product of the polyamic acid composition. The polyimide can be prepared into a film for physical property analysis.

Therefore, in another aspect of the present disclosure, a polyimide film comprising a cured product of the polyamic acid composition is provided.

In the present disclosure, it is confirmed that the glass decomposition temperature (Tg) can ensure mechanical properties while predicting thermal properties, in addition to the coefficient of thermal expansion (CTE) and the glass transition temperature (Td), which are mainly used as criteria for judging the thermal properties of polyimide.

In the present disclosure, polyamide may have a thermal expansion coefficient in the range of 3ppm/°C to 20ppm/°C, for example, the upper limit of the thermal expansion coefficient may be 19ppm/°C, 18ppm/°C, 16ppm/°C, 14ppm/°C, 12ppm/°C, 10ppm/°C, or 8ppm/°C or less, and the lower limit thereof may be, for example, 4ppm/°C, 4.5ppm/°C, 5.0ppm/°C, 5.5ppm/°C, 6.0ppm/°C, 6.5ppm/°C, or 7ppm/°C or more. In one embodiment, the thermal expansion coefficient may be measured at 100°C to 400°C. For the measurement of the thermal expansion coefficient, a thermodynamic analyzer Q400 manufactured by TA Instruments, Inc., may be used. Specifically, the thermal expansion coefficient can be determined by making polyimide into a film, cutting the film into a size of 2 mm wide and 10 mm long, and then applying a tension of 0.05 Newton to the polyimide film in a nitrogen atmosphere, and measuring the slope of the section from 100°C to 350°C by increasing the temperature from room temperature to 400°C at a rate of 10°C/min and then cooling again at a rate of 10°C/min.

In addition, in the present disclosure, the glass transition temperature of the polyamine composition may be in the range of 370° C. or higher, for example, the lower limit of the glass transition temperature may be 375° C., 380° C., 385° C., or 390° C. or higher, and the upper limit of the glass transition temperature may be 600° C. or lower. The glass transition temperature can be measured at 10° C./min on a polyimide prepared by curing the polyamine composition using a thermodynamic analyzer.

In the present disclosure, the polyimide obtained by curing the polyamic acid composition may have a thermal decomposition temperature of 470°C or higher at a loss of 5 wt%. The thermal decomposition temperature can be measured using a thermogravimetric analyzer (Q50) manufactured by TA Instruments, Inc., Taiwan, USA. In a specific example, the polyimide obtained by curing the polyamic acid composition is heated to 150°C at a rate of 10°C/min in a nitrogen atmosphere, and then kept at this temperature for 30 minutes to remove moisture, and then the temperature can be raised to 600°C at a rate of 10°C/min to measure the temperature at which 5 wt% weight loss occurs. The lower limit of the thermal decomposition temperature can be, for example, 470°C, 475°C, 480°C, 482°C, 484°C, 486°C, 488°C, 490°C, 492°C, 494°C, 496°C, 498°C, 500°C, 505°C, 506°C, 507°C, 508°C, 509°C, or 510°C or higher, and the upper limit thereof can be, for example, 800°C, 750°C, 700°C, 650°C, 630°C, or 600°C or lower.

In addition, the elongation of the polyimide obtained by curing the polyamic acid composition is 6% or more, such as 7%, 8%, 9%, 10% or more, and the upper limit of the elongation is not particularly limited, but may be 40% or less. The elongation can be measured by curing the polyamic acid composition into a polyimide film, cutting the polyimide film into a size of 10 mm wide and 40 mm long, and then using an Instron 5564 UTM device from Instron Corp. and measuring the elongation by ASTM D-882 method.

In the present disclosure, the film-like polyimide obtained by curing the polyamic acid composition has a thickness of 10±0.5 microns, and when the yellowing index (YI) is measured, the yellowing index is 10 or less, preferably 7 or less, more preferably 5 or less, and more preferably 3.5 or less. When the polyimide film is used in a light-transmitting portion such as a display substrate, the polyimide film needs to have transparency, more precisely, colorless (achromatic) transparency. This means that the smaller the absolute value of the yellowing index, the closer the color of the film is to colorless (achromatic). If the yellowing index is 10 or less, particularly preferably 5 or less, when measured at a film thickness of 10±0.5 microns, the generally required colorlessness can be ensured. In addition, as the film thickness increases, the yellowing index also tends to increase. Furthermore, the yellowing index is preferably 0 or greater.

In the present disclosure, with respect to the strength of polyimide obtained by curing a polyamic acid composition, the degree of improvement in strength can be measured by fixing a polyimide film having a width of 50 mm, a length of 50 mm, and a thickness of 10±0.5 μm, repeatedly folding and bending the film, and visually observing cracks and breaks to confirm the extent of cracks and breaks according to the number of folding times.

In another aspect of the present disclosure, a polyamine composition is provided, comprising: a polyamine, comprising, as a polymerizable unit, a dianhydride monomer represented by Chemical Formula 1 and a diamine monomer represented by Chemical Formula 2: [Chemical Formula 1] [Chemical formula 2] 2-phenylimidazole; N-methylpyrrolidone (NMP) and N,N'-tetraglycidyldiaminodiphenylmethane (TGDDM).

The contents of 2-phenylimidazole as the imidazole compound and TGDDM as the epoxy compound are the same as described above.

In another aspect of the present disclosure, a polyamine composition is provided, comprising: a polyamine, comprising, as a polymerizing unit, a dianhydride monomer represented by Chemical Formula 1 and a diamine monomer represented by Chemical Formula 2 or Chemical Formula 3: [Chemical Formula 1] [Chemical formula 2] [Chemical formula 3] 2-phenylimidazole; N-methylpyrrolidone (NMP) and N,N'-tetraglycidyldiaminodiphenylmethane (TGDDM).

Here, 90 mol% of the diamine monomer represented by Chemical Formula 2 and 10 mol% of the diamine monomer represented by Chemical Formula 3 may be included in the total diamine monomer component.

In addition, the contents of 2-phenylimidazole as the imidazole compound and TGDDM as the epoxy compound are the same as described above.

In another aspect of the present disclosure, the polyamine composition prepared in the present disclosure may include: a polyamine having a repeating unit represented by Chemical Formula 5; an imidazole compound; an epoxy compound; and an organic solvent: [Chemical Formula 5] In Chemical Formula 5, _R1 and _R2 are the same or different and each independently represents a hydrogen atom, a _C1 - _C6 alkyl group or a _C3 - _C9 alkylsilyl group; In the entire repeating unit of the polyamide represented by Chemical Formula 5, 70 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more, and even more preferably 100 mol% of the A portion is a structure derived from the dianhydride monomer represented by Chemical Formula 1; and [Chemical Formula 1] In the entire repeating unit of the polyamine represented by Chemical Formula 5, the W portion is a derivative structure of a diamine monomer represented by Chemical Formula 2 and/or Chemical Formula 3. Here, 70 mol% or more, preferably 80 mol% or more, and more preferably 90 mol% or more of the W portion is a derivative structure of a diamine monomer represented by Chemical Formula 2: [Chemical Formula 2] [Chemical formula 3]

The types and contents of the imidazole compound, epoxy compound and organic solvent are the same as those described above.

By measuring the thermal decomposition temperature, thermal expansion coefficient and glass transition temperature with weight percentage loss, it is confirmed that the polyimide according to the present disclosure has a low yellowing index level suitable for application in display substrates and maintains the excellent thermal properties unique to polyimide. In addition, by elongation measurement and brittleness analysis, it is shown that the polyimide according to the present disclosure has high strength and maintains excellent elongation at the same time.

The composition and content of the optimal polyamine composition according to the present disclosure are determined to achieve thermal properties, mechanical properties and transparency suitable for the display substrate as described above.

Therefore, the polyamic acid composition and the polyimide prepared therefrom according to the present disclosure can be advantageously used in substrates such as display substrates.

In another aspect of the present disclosure, the present disclosure provides a flexible display, which includes the polyimide film as a substrate, and the polyimide film is prepared from the polyamic acid composition.

[Advantageous Effects] The polyamine composition and the polyimide containing the polyamine composition disclosed herein can have excellent mechanical properties, such as strength and elongation, while maintaining a low yellowing index and excellent thermal properties.

The following examples are provided to help understand the present disclosure. In order to make it easier to understand the present disclosure, the following embodiments are provided, but the content of the present disclosure is not limited to these embodiments.

＜ Gather Acetyl Preparation of amino acid compositions ＞

Embodiment 1 : Poly Acetyl Amino acid combination

DABAN and N-methyl-2-pyrrolidone were placed in a reaction vessel filled with nitrogen, and the mixture was stirred at 50°C for 1 hour. CpODA was slowly added to the stirred solution, stirred at room temperature for 4 hours or more, and reacted until the viscosity did not change, thereby obtaining polyamine.

Based on 1 mol of the repeating unit of the polyamide, 20 mol% of 2-phenylimidazole was added as an imidazole compound, and based on 1 mol of the repeating unit of the polyamide, 0.08 mol% of TGDDM was added as an epoxy compound used as a crosslinking agent. Then, the obtained mixture was stirred at room temperature for 3 hours and reacted until the viscosity did not change, thereby preparing a polyamide composition.

Embodiment 2 to 11 : Poly Acetyl Amino acid combination

As shown in Table 1, the polyamine composition was prepared in the same manner as in Example 1, except that the content ratio of the imidazole compound and the content ratio of the epoxy compound were adjusted in addition to the monomer components and their content ratios.

[Table 1] Categories Dianhydride (mol%) Diamine (mol%) Imidazole compounds (mol%) Epoxy compounds (mol%) CpODA DABAN DATA 2-Phenylimidazole TGDDM Embodiment 1 100 90 10 20 0.08 Embodiment 2 100 90 10 10 0.08 Embodiment 3 100 90 10 20 0.48 Embodiment 4 100 90 10 5 0.03 Embodiment 5 100 90 10 5 0.08 Embodiment 6 100 90 10 5 0.16 Embodiment 7 100 100 - 20 0.07 Embodiment 8 100 100 - 20 0.14 Embodiment 9 100 100 - 5 0.07 Embodiment 10 100 100 - 10 0.07 Embodiment 11 100 100 - 20 0.07

The abbreviations of the compounds used in the following various examples are as follows. Norbornane-2-spiro-α-cyclopentanone-α′-spiro-2″-norbornane-5,5″,6,6″-tetracarboxylic dianhydride: CpODA 4,4'-diaminobenzanilide: DABAN N,N'-bis(4-aminophenyl)benzene-1,4-dimethylamide: DATA N-methylpyrrolidone: NMP

Experimental Examples. Acetyl Analysis of physical properties of polyimide prepared from amino acid composition.

＜ Preparation of polyimide for physical property measurement ＞

From each of the polyamine compositions prepared in Examples 1 to 11, air bubbles were removed by high-speed spinning at 1,500 rpm or more. Then, each defoamed polyamine composition was applied to a glass substrate using a spin coater.

In a nitrogen atmosphere, the temperature was raised from room temperature to 400°C at a rate of 4°C/min, the product was heat treated at 400°C for 60 minutes, and then cooled to 30°C at a rate of 4°C/min, thereby obtaining a 10±0.5 μm thin film of polyimide.

Experimental Examples 1 ：Thickness measurement

The thickness of the polyimide prepared according to the aforementioned embodiment was measured using a film thickness tester manufactured by Anritsu Corporation.

Experimental Examples 2 ：Viscosity measurement

For the polyamine composition prepared in the example, the viscosity was measured using a Haake Rheostress 600 manufactured by Thermo Fisher Scientific Inc. under the conditions of a shear rate of 1 s ^-1 , a temperature of 23° C., and a plate gap of 1 mm.

Experimental Examples 3 ：Yellowing index measurement

For the polyimide prepared according to the aforementioned examples, the yellowing index was measured using a colorimeter from Hunter Lab.

Experimental Examples 4 : Thermal decomposition temperature with weight percentage loss （ Thermal Decomposition Temperature, Td ）

Using a thermogravimetric analyzer Q50 manufactured by TA Instruments, the polyimide film was heated to 150°C in a nitrogen atmosphere at a rate of 10°C/min, then kept at that temperature for 30 minutes to remove moisture. The temperature was then raised to 600°C at a rate of 10°C/min, and the temperature at which the weight loss was 5% was measured.

Experimental Examples 5 : Thermal expansion coefficient ( Coefficient of Thermal Expansion , CTE ) Measurement

A thermomechanical analyzer Q400 manufactured by TA Instruments was used. Specifically, a thin film of polyimide was cut into a size of 2 mm in width and 10 mm in length. A tension of 0.05 Newton was applied to the polyimide film in a nitrogen atmosphere, and the temperature was increased from room temperature to 400°C at a rate of 10°C/min, and then cooled again at a rate of 10°C/min, thereby measuring the cross-sectional slope from 100°C to 350°C.

Experimental Examples 6 : Glass transition temperature ( Glass Transition Temperature, Tg ）

The polyimide film prepared from the polyamic acid composition of the example was measured using a thermomechanical analyzer (TMA) with the rapid expansion point at 10° C./min as the starting point.

Experimental Examples 7 : Elongation

The polyimide film prepared from the polyamic acid composition of the example was cut into a size of 10 mm in width and 40 mm in length, and the elongation was measured using an Instron 5564 UTM apparatus from Instron Corp. according to the ASTM D-882 method.

Experimental Examples 8 ：Intensity analysis

For the polyimide film prepared from the polyamic acid composition of the embodiment, the polyimide film was cut into a size of 50 mm in width and 50 mm in length (thickness 10 mm), and the strength of each polyimide film was analyzed by aligning the two ends of the film, repeatedly folding (180°) and bending the film, and observing cracks and breaks with the naked eye. The film was folded 5 times or more, and the case where there were no cracks and breaks was judged as A+, and the case where it was folded 5 times or more but had small cracks was judged as A-, and it could be folded up to 3 times, but if it broke in the subsequent folding, it was judged as B+, and it could be folded up to 2 times, but if it broke in the subsequent folding, it was judged as B-.

[Table 2] Categories Solid content (%) Viscosity (cmP) Thickness(μm) Yellowing Index (YI) Td 5% (℃) CTE (ppm/℃) Tg (℃) Elongation(%) Brittleness (strength) Embodiment 1 18 2,890 9.8 3.4 506 7 393 9 A ^- Embodiment 2 18 2,890 10.0 3.8 508 9 405 8 A ^- Embodiment 3 18 2,890 10.0 3.9 506 10 392 9 A ^- Embodiment 4 18 2,890 10.3 3.5 508 7 400 7 B ⁺ Embodiment 5 18 2,890 10.0 3.4 508 7 390 8 B ⁺ Embodiment 6 18 2,890 10.1 3.4 508 8 383 7 B ⁺ Embodiment 7 18 4,530 10.1 3.1 506 9 393 9 A ^- Embodiment 8 18 4,530 9.8 3.0 507 9 386 8 A ^- Embodiment 9 18 4,530 10.0 3.2 511 8 397 7 B ⁺ Embodiment 10 18 4,530 9.7 2.9 509 9 391 6 B ⁺ Embodiment 11 18 4,530 10.2 3.1 507 9 386 7 B ⁺

The specification omits details that can be fully recognized and inferred by a person skilled in the art to which the present disclosure belongs. In addition to the specific examples described in the specification, various modifications can be made within the scope of not changing the technical spirit or basic structure of the present disclosure. Therefore, the present disclosure can be implemented in a manner different from that specifically described and illustrated herein, and a person skilled in the art to which the present disclosure belongs will understand these manners.

Claims (20)

A polyamine composition includes: a polyamine, including, as a polymerized unit, a dianhydride monomer represented by chemical formula 1, a diamine monomer represented by chemical formula 2, and a diamine monomer represented by chemical formula 3:

an imidazole-based compound, wherein the content of the imidazole-based compound is 1.5 to 40 mol based on 1 mol of the repeating unit of the polyamide; an epoxy-based compound, wherein the content of the epoxy-based compound is 0.01 to 1.0 mol based on 1 mol of the repeating unit of the polyamide; and an organic solvent. The polyamine composition of claim 1, wherein the imidazole compound is selected from at least one of the group consisting of 2-phenylimidazole, benzimidazole, 1,2-dimethylimidazole, 1-methylimidazole, 2-methylimidazole, and imidazole. The polyamide composition of claim 1, wherein the organic solvent is at least one selected from the group consisting of N-methylpyrrolidone (NMP), N,N'-dimethylformamide (DMF), N,N'-diethylformamide (DEF), N,N'-dimethylacetamide (DMAc), dimethylpropionamide (DMPA), N,N-diethylacetamide (DEAc), and 3-methoxy-N,N-dimethylpropionamide (KJCMPA). The polyamide composition of claim 1, wherein the epoxy compound is a multifunctional epoxy compound. The polyamide composition of claim 4, wherein the epoxy compound is selected from at least one of the group consisting of N,N'-N,N'-tetraglycidyl diaminodiphenylmethane (TGDDM), bisphenol A diglycidyl ether (DGEBA), tetraglycidyl-m-phenylenediamine, tetraglycidyl-1,3-diaminomethylcyclohexane, and trihydroxymethylpropane triglycidyl ether (TMP). The polyamine composition of claim 1, wherein the polyamine further comprises a dianhydride monomer represented by chemical formula 4:

The polyamide composition of claim 6, wherein the content of the dianhydride monomer represented by chemical formula 4 is 20 mol% or less of the total dianhydride monomer components. The polyamide composition of claim 1, wherein the content of the diamine monomer represented by chemical formula 2 is 70 mol% or more of the total diamine monomer components. The polyamine composition of claim 1, wherein the content of the imidazole compound is 2 to 30 mol% based on 1 mol of the repeating unit of the polyamine. The polyamine composition of claim 1, wherein the content of the epoxy compound is 0.02 to 0.8 mol% based on 1 mol of the repeating unit of the polyamine. The polyamine composition of claim 1, wherein the weight average molecular weight of the polyamine composition is in the range of 1,000 g/mol to 100,000 g/mol. For example, the polyamide composition of claim 1 has a solid content in the range of 5wt% to 30wt%. The polyamine composition of claim 1 has a viscosity in the range of 1,000 to 10,000 millipoise, wherein the viscosity is measured at a temperature of 23° C. and a shear rate of 1 s ⁻¹ . For example, the polyamide composition of claim 1 has a coefficient of thermal expansion (CTE) after curing in the range of 3ppm/℃ to 20ppm/℃. For example, the polyamide composition of claim 1 has a glass transition temperature (Tg) of 370°C or higher after curing. For example, the polyamide composition of claim 1 has a thermal decomposition temperature (Td) of 470°C or higher at which 5 wt% of the composition is lost after curing. For example, the polyamide composition of claim 1 has an elongation of 6% or more after curing. For example, the polyamide composition of claim 1 has a yellowing index (YI) of 10 or less after curing. A polyimide film, comprising a cured product of a polyamide composition as described in any one of claims 1 to 18. A flexible display device, comprising a polyimide film as claimed in claim 19 as a substrate.