TW201817776A - Transparent polyimide precursor resin composition with improved resin stability and heat resistance, method for manufacturing polyimide film using the same, and polyimide film prepared therefrom - Google Patents

Abstract

The present invention relates to a transparent polyamic acid precursor resin composition having superior mechanical property, high heat resistance and a low coefficient of thermal expansion and showing no clouding phenomenon during solution casting by optimizing an aromatic diamine and an acid dianhydride to improve heat resistance and mechanical property and optimizing an organic solvent to prevent clouding phenomenon, a method of preparing a polyimide film using the same and a polyimide film prepared therefrom.

Description

Transparent polyimide precursor resin composition with improved resin stability and heat resistance, method for producing polyimide film using the same, and polyimide film prepared therefrom

FIELD OF THE INVENTION The present invention relates to a transparent polyimide precursor resin composition having superior mechanical properties, high heat resistance and low thermal expansion coefficient, and which does not show white turbidity during solution casting, and a method for preparing polyimide using the same. Method of film and a polyimide film prepared from the same. The present invention can be applied to flexible display substrate materials and semiconductor materials.

BACKGROUND OF THE INVENTION Flexible polymer materials are attracting attention as substrate materials for flexible displays of next-generation display devices.

Generally, organic light emitting diode (OLED) displays are used as the flexible device, and TFT processing with a high processing temperature (300-500ºC) is used. Polymer materials that can tolerate this high processing temperature are very limited. Among them, polyimide (PI) resin with superior heat resistance is mainly used.

Organic light-emitting diode (OLED) displays are manufactured by coating a resin on a glass substrate and thermally curing the resin to obtain a film, and then separating the film from the glass substrate after a series of steps. . During this manufacturing process, the stability of the resin applied to the glass substrate at room temperature is important. If the stability of the resin cannot be ensured, a uniform film may not be obtained after curing due to resin agglomeration, turbidity phenomenon, etc., which may cause defects. Defects may also be caused by high temperature thermal shock during the TFT deposition process. Therefore, a polyimide (PI) resin having excellent resin stability at room temperature, high heat resistance, and low coefficient of thermal expansion (CTE) is needed.

Korean Patent Publication No. 2015-108812 discloses a polyamic acid solution, which has superior thermal characteristics such as a low thermal expansion rate and a high pyrolysis temperature, and thus can be used as a base layer or a protective layer of a display device, and a film using the same. However, because the stability of the resin cannot be ensured, a uniform film cannot be obtained after curing, and defects may occur due to resin agglomeration, turbidity, and the like.

Korean Patent Publication No. 2013-35691 discloses a composition and method for preparing a polyfluorene-fluorene imine copolymer film. However, due to the production of by-products and the need to remove the by-products, the economic benefits are limited.

Therefore, there is a need for a polyimide composition having high heat resistance, a low thermal expansion coefficient, superior mechanical strength, and good resin stability, and a preparation method through a relatively simple process. References to related technologies

(Patent Document 1) 1: Korean Patent Publication No. 2015-108812. (Patent Document 2) 2: Korean Patent Publication No. 2013-35691.

Technical Problem In order to solve the above problems, the inventors of the present invention have found a composition of an aromatic diamine and an acid dianhydride compound, which is more effective for preparing a polyimide film having improved heat resistance and optimized mechanical properties. , And a composition of an organic solvent, which can prevent white turbidity. As a result, they have found a polyimide precursor resin composition having superior transparency and resin stability, high heat resistance and low thermal expansion coefficient than the existing polyimide film, and have completed the present invention.

Accordingly, the present invention aims to provide a polyimide precursor resin composition, which can be used as a substrate material for a flexible display, which has transparency, superior resin stability, high heat resistance, and a low thermal expansion coefficient.

The present invention also aims to provide a method for preparing a polyimide resin film using the composition.

The present invention also aims to provide a polyimide resin film prepared by the preparation method. Based on a film thickness of 10-15 μm, the film has a glass transition temperature of 300 ° C or higher and is in the range of 100 to 300 ° C. A thermal expansion coefficient of 25 ppm / ºC or lower, a transmittance of 85% or higher at a wavelength of 550 nm, and a yellowing index (YI) of 7 or lower at a wavelength of 550 nm. Technical solutions

The invention provides a transparent polyimide precursor resin composition with improved resin stability and high heat resistance, which contains an aromatic diamine component, an acid dianhydride compound, and an organic solvent, wherein the aromatic diamine Component (A) contains 2,2'-bis (trifluoromethyl) -4,4'-diamine biphenyl (TFMB) as a fluorinated aromatic diamine monomer, as the second one having a fluorenamine group N- (4-aminophenyl) -4-amine benzamidine (DBA) or a mixture thereof, which is an amine monomer; the acid dianhydride compound (B) contains 4 as a fluorinated aromatic acid dianhydride. , 4 '-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and pyromelite dianhydride (PMDA) or 3,3,4,4'-biphenyl as non-fluorinated aromatic acid dianhydride A mixture of tetracarboxylic dianhydride (BPDA); and the organic solvent (C) is a mixture of γ-butyrolactone (GBL) and N-methyl-2-pyrrolidone (NMP), γ-butyrolactone ( GBL) is a mixture with 3-methoxy-N, N-dimethylpropanamide (DMPA) or 3-methoxy-N, N-dimethylpropanamide (DMPA) alone.

The present invention also provides a method for preparing a transparent polyimide resin film. The method comprises preparing a film by heat treating a polyamidic acid solution prepared from the composition.

The invention also provides a polyimide resin film prepared by the preparation method. Based on a film thickness of 10-15 μm, the film has a glass transition temperature of 300 ° C or higher and a range of 100 ppm to 300 ° C / 25 ppm / Thermal expansion coefficient of ºC or lower, transmittance of 85% or higher at a wavelength of 550 nm, and a yellowing index (YI) of 7 or lower at a wavelength of 550 nm. Beneficial effect

The present invention provides a polyimide precursor resin composition, which has superior resin stability at room temperature compared to existing polyamidic acid solutions, and does not show white turbidity during solution casting. When formed into a film through thermal curing, the composition exhibits superior mechanical, optical, and heat resistance characteristics. Therefore, the present invention can be applied to flexible display substrate materials, semiconductor materials, and the like.

In addition, the present invention remains competitive in the existing method of preparing a polyamic acid solution, as the process of removing by-products is not required.

Carrying out the method of the present invention The polyimide precursor resin composition of the present invention (hereinafter referred to as "polyamic acid composition") provides a transparent polyimide having high heat resistance, a low coefficient of thermal expansion, and superior mechanical strength. The amine film is used to optimize the composition of the aromatic diamine and the acid dianhydride compound to improve heat resistance and mechanical properties, and to optimize the composition of the organic solvent so that the phenomenon of white turbidity does not occur, and by optimizing the amount of use. The polyimide precursor composition of the present invention, that is, the "polyacid composition" refers to a composition for preparing a polyamic acid solution (which is used to prepare a polyimide film). .

More specifically, the polyamidic acid composition of the present invention contains an aromatic diamine component and an aromatic diamine component (A), which contains a fluorinated aromatic diamine, a diamine compound having a fluorene group, or A mixture thereof; an acid dianhydride compound (B) containing a fluorinated aromatic acid dianhydride and a non-fluorinated aromatic acid dianhydride compound; an organic solvent (C) containing γ-butyrolactone (GBL) With N-methyl-2-pyrrolidone (NMP) or 3-methoxy-N, N-dimethylpropanamide (DMPA); and a reaction catalyst (D). These components are detailed below. (A) Aromatic diamine component

In the present invention, the aromatic diamine component contains 2,2'-bis (trifluoromethyl) -4,4'-diamine biphenyl (TFMB) as a fluorinated aromatic diamine monomer, as N- (4-aminophenyl) -4-amine benzamidine (DBA) or a mixture thereof, which is a diamine monomer having an amidino group.

More specifically, the content of 2,2'-bis (trifluoromethyl) -4,4'-diamine biphenyl (TFMB) as a fluorinated aromatic diamine monomer based on the total diamine compound It may be 30-100 mol%, and the content of the N- (4-aminophenyl) -4-amine benzamidine (DBA) may be 5-50 mol% based on the entire diamine compound. A non-fluorinated aromatic diamine may additionally be included as a balance.

When the aromatic diamine component (A) contains a fluorinated aromatic diamine having a fluorine substituent, a polyfluorene with superior optical characteristics can be obtained due to the charge transfer between the fluorine substituents in the molecular chain. Imine film.

And, when the fluorinated aromatic diamine is mixed with the N- (4-aminophenyl) -4-amine benzamidine (DBA), due to the rigidity of the aromatic structure and the amidine structure, it can be obtained Polyimide film with superior heat resistance and low thermal expansion coefficient.

Compared to using the fluorinated aromatic diamine alone, when the fluorinated aromatic diamine is used together with the N- (4-aminephenyl) -4-amine benzamidine as the aromatic diamine component It is possible to obtain a polyimide film having improved thermal characteristics while maintaining optical characteristics.

If the fluorinated aromatic diamine is a fluorine-containing aromatic diamine, it may be one or more selected from the group consisting of: 2,2'-bis (trifluoromethyl) -4,4 ' -Diamine biphenyl (TFMB), bis (aminohydroxyphenyl) hexafluoropropane (DBOH), bis (aminephenoxyphenyl) hexafluoropropane (4BDAF), 2,2'-bis (trifluoromethyl) -4,3'-diamine biphenyl and 2,2'-bis (trifluoromethyl) -5,5'-diamine biphenyl.

More specifically, in the present invention, 2,2'-bis (trifluoromethyl) -4,4'-diamine biphenyl (TFMB) can be used, which can improve both transmittance and heat resistance characteristics.

Based on 100 mole% of all diamine compounds, when the amount of TFMB is 30-100 mole%, more specifically 50-90 mole%, due to the charge between the fluorine substituents in the molecular chain The transfer can further improve the optical characteristics of the polyfluorene film.

And, in the present invention, not only the fluorinated aromatic diamine monomer such as TFMB, but also the non-fluorinated aromatic diamine monomer. The total amount of the fluorinated aromatic diamine and the non-fluorinated aromatic diamine is 100 mole%.

For the superior heat resistance and low thermal expansion coefficient of polyfluorene imide resin, compounds having or capable of forming a fluorene structure may be included. The compound capable of forming an amidine structure may be an acid halide or a dicarboxylic acid compound. Examples include one or more selected from the group consisting of: terephthaloyl chloride (TPC), isophthaloyl dichloride (IPC), 1,3-adamantane dicarbonyl dichloride (ADC) , 5-norbornene-2,3-dicarbonyl chloride (NDC), 4,4'-benzidine dichloride (BDC), 1,4-naphthalenedicarboxylic acid dichloride (1,4-NaDC) , 2,6-naphthalenedicarboxylic acid dichloride (2,6-NaDC), 1,5-naphthalenedicarboxylic acid dichloride (1,5-NaDC), terephthalic acid (TPA), isophthalic acid Formic acid (IPA), phthalic acid (PA), 4,4'-biphenyldicarboxylic acid (BDA), and naphthalenedicarboxylic acid (NaDA).

However, these compounds may cause by-products such as HCl, H ₂ O, and the like while they form the amidine structure, and may cause a reduction in the membrane characteristics of the amidine film.

Accordingly, in the present invention, in order to introduce the amidine group into the molecular chain without generating a by-product, the N- (4-aminophenyl) -4-amine benzamidine (DBA ) As a diamine compound having an amidine group, thereby providing superior heat resistance and a low thermal expansion coefficient. Based on the diamine compound as 100 mole%, the content of the N- (4-aminophenyl) -4-amine benzamidine (DBA) may be 5-50 mole%, more specifically 5- 20 mol%, however, it is not limited to this. (B) acid dianhydride compound

The aromatic acid dianhydride compound of the present invention contains 20-80 mole% of a fluorinated aromatic acid dianhydride and 80-20 mole% of a non-fluorinated aromatic acid dianhydride compound.

In the present invention, when the fluorinated aromatic acid dianhydride and the non-fluorinated aromatic acid dianhydride compound are used in combination, the optical properties and heat resistance of the polyfluorene imide film can be improved at the same time. The fluorinated aromatic acid dianhydride can be used to prepare a polyfluorene imine film having superior optical characteristics due to its fluorine substituent, and the aromatic acid dianhydride can be prepared to have superior heat resistance due to its rigid molecular structure. Of polyimide film.

An aromatic acid dianhydride having a fluorine substituent may be used as the fluorinated aromatic acid dianhydride, for example, one or more selected from the group consisting of: 4,4 '-(hexafluoroisopropylidene Group) diphthalic anhydride (6FDA) and 4,4 '-(4,4'-hexafluoroisopropylidene diphenoxy) bis (phthalic anhydride) (6-FDPDA). More specifically, in the present invention, 6FDA is used as the fluorinated aromatic acid dianhydride.

The content of the fluorinated aromatic acid dianhydride may be 20-80 mol%, more specifically 40-70 mol%, based on 100 mol% of the total acid dianhydride. A polyimide film with high transmittance and low yellowing index can be achieved in this example.

An aromatic acid dianhydride without the introduction of a fluorine substituent may be used as the non-fluorinated aromatic acid dianhydride, such as one or more selected from the group consisting of pyromelite dianhydride (PMDA), 3, 3 ', 4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3', 4,4'-diphenylketone tetracarboxylic dianhydride (BTDA), 4,4'-oxydiphthalide Acid anhydride (ODPA), 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] propane dianhydride (BPADA), 3,3 ', 4,4'-diphenylphosphonium tetracarboxylic acid di Anhydride (DSDA) and ethylene glycol bis (4-trimellitic anhydride) (TMEG). More specifically, in the present invention, PMDA, BPDA or a mixture thereof is used as the non-fluorinated aromatic acid dianhydride.

Based on 100 mol% of the total acid dianhydride, the non-fluorinated aromatic acid dianhydride can be used in an amount of 80-20 mol%, more particularly 30-50 mol%, and the polymer can be improved at the same time. The imine film has heat resistance and maintains high transmittance and low yellowing index. (C) Organic solvents

In the present invention, the organic solvent may be a polar solvent such as m-cresol, N-methyl-2-pyrrolidone (NMP), N, N-dimethylformamide (DMF), dimethylacetamidine Amine (DMAc), dimethylsulfinium (DMSO); low boiling point solvents, such as diethyl acetate (DEA), 3-methoxy-N, N-dimethylpropanamide (DMPA), etc .; tetrahydrofuran (THF), chloroform, etc .; or a low water-absorbent solvent, such as γ-butyrolactone (GBL).

The organic solvent used in the present invention plays an important role in improving the phenomenon of white turbidity. The turbidity phenomenon can be confirmed from FIGS. 1-3. Figure 1 shows that the organic solvent consisting of 70 mol% GBL and 30 mol% NMP is stable (no white turbidity) when the polyamic acid solution is cast on a glass substrate at room temperature, and Figure 2 shows that Organic solvent consisting of Molar% GBL and 30 Molar% DMPA is stable at room temperature (no cloudiness). In contrast, FIG. 3 shows that the organic solvent consisting of 100 mole% NMP alone becomes cloudy.

Accordingly, in the present invention, in order to improve the turbidity phenomenon, it is necessary to use a mixture of γ-butyrolactone (GBL) and N-methyl-2-pyrrolidone (NMP), γ- A mixture of butyrolactone (GBL) and 3-methoxy-N, N-dimethylpropanamide (DMPA) or 3-methoxy-N, N-dimethylpropanamide (DMPA) alone.

More specifically, 30-70 mole% of gamma-butyrolactone (GBL) and 70-30 mole% of N-methyl-2-pyrrolidone (NMP) or 3-methoxy-N can be used As the organic solvent, N-dimethylpropylamine (DMPA) was used. More specifically, 50-70 mole% of gamma-butyrolactone (GBL) and 30-50 mole% of N-methyl-2-pyrrolidone (NMP) or 3-methoxy-N can be used , N-dimethylpropanamide (DMPA). Alternatively, 100 mol% of γ-butyrolactone (GBL) may be used alone. (D) Reaction catalyst

The polyamic acid composition of the present invention may further include one or more reaction catalysts selected from the group consisting of trimethylamine, xylene, pyridine, and quinoline, depending on the reactivity, but not It must be limited to this. In addition, when necessary, the polyamic acid composition may contain a small amount of additives, such as a plasticizer, an antioxidant, a flame retardant, a dispersant, within a range that does not seriously affect the purpose and efficacy of the present invention. Viscosity control agents, leveling agents, etc.

In addition, the polyamino acid composition of the present invention prepared by using the aromatic diamine component, the acid dianhydride compound, the organic solvent, and the reaction catalyst has a polyamine solution of 10-40. A solids content of 10% by weight, more specifically 10-25% by weight. When the solid content is less than 10% by weight, there is a limitation in increasing the film thickness. When the solid content exceeds 40% by weight, there is a limitation in controlling the viscosity of the polyamic acid resin. Therefore, the aforementioned range is used.

More specifically, the polyamine solution may include an organic solvent such that the solid content is 10-40% by weight, and 100 mol parts of the aromatic diamine component and 95- 105 mol parts of the acid dianhydride compound is prepared for 24-48 hours. The reaction temperature may vary with the monomers used.

More specifically, the acid dianhydride compound may be added in an amount exceeding -5 to 5 mol parts based on the aromatic diamine component in order to achieve the desired viscosity. This allows moderate viscosity control and ensures storage stability.

More specifically, the polyamic acid solution produced from the reaction may have a viscosity ranging from 1,000 to 7,000 cP. When the viscosity is less than 1,000 cP, it is difficult to obtain a desired thickness. When it exceeds 7,000 cP, it is not easy to obtain a uniform coating and effective solvent removal. Therefore, this range is preferable.

The transparent polyfluorene imide film of the present invention and its preparation method are described below. The present invention provides a transparent polyimide film prepared by using a polyamidic acid solution prepared by the above-mentioned polyamidic acid composition and subjecting it to thermal imidization. The polyamic acid solution of the present invention is viscous. It can be coated on a glass substrate by a suitable method and heat-treated to form a film. This coating can be performed by a non-limiting, generally used method. For example, spin coating, dip coating, solvent casting, slit coating, spray coating, and the like can be used, but are not limited thereto.

The polyamic acid composition of the present invention can be made into a polyimide film by heat treatment in a high-temperature ventilation oven. This heat treatment is performed at 100-450ºC under a nitrogen environment for 30-120 minutes. More specifically, membranes are available at temperature times of 100ºC / 30 minutes, 220ºC / 30 minutes, and 350ºC / 30 minutes. Under these conditions, the solvent can be removed adequately, and the properties of the film can be maximized through fluorene imidization.

Since the transparent polyfluorene imide film of the present invention is prepared by using the polyphosphonium acid composition, it exhibits high transparency and at the same time has a low thermal expansion coefficient.

The polyimide film of the present invention is based on a film thickness of 10-15 μm, has a glass transition temperature of 300ºC or higher, 25ppm / ºC or lower in the range of 100 to 300ºC, and more particularly 15ppm / ºC thermal expansion Coefficient, 85% or higher transmittance at a wavelength of 550 nm, and a yellowing index (YI) of 7 or lower, more specifically 5 or lower, at a wavelength of 550 nm. The polyimide film of the present invention can prevent the device on the substrate from causing defects due to expansion and shrinkage. Moreover, the polyimide film of the present invention can be applied to a flexible display due to its high light transmittance and low yellowing index.

The polyfluorene imide film of the present invention can be used in various applications. In particular, it can be provided as a substrate or a flexible display that requires high transparency and heat resistance, such as an OLED display, a liquid crystal display, a TFT display, a flexible printed circuit board, a flexible OLED surface light-emitting display, or an electronic paper display. Protective film.

The present invention will be explained in more detail through examples. The following examples are for illustrative purposes only, and the scope of the present invention is not limited by these examples. Comparative Example 1

In order to prepare the composition specified in Table 1, 2.547 g (0.024 mol) of PPD as a diamine monomer and 17.606 g (0.055 mol) of TFMB were dissolved in an organic composition of 142.1 g of NMP and 58.5 g of GBL. In a solvent, it takes 30 minutes to 1 hour in a nitrogen environment at room temperature. Then, after adding 24.798 g (0.056 mol) of 6FDA and 5.212 g (0.024 mol) of PMDA as dianhydride monomers, after 24 hours of polymerization, further add 83.6 g of GBL, and then stir for 24 hours (Reaction temperature: 30ºC, based on the total weight of the reaction solvent, the solid content is maintained at 15% by weight) to prepare a polyamic acid solution. The viscosity measured with a viscometer (Brookfield DV2T, SC4-27) was 5,700 cP. Comparative Example 2-3

A polyamic acid solution was prepared in the same manner as in Comparative Example 1, but the composition of the organic solvent was changed according to the instructions in Table 1. Example 1-5

A polyamic acid solution was prepared in the same manner as in Comparative Example 1, but the composition of the organic solvent was changed according to the instructions in Table 1. Experimental example 1 : Measurement of physical properties (1) Evaluation of white turbidity at room temperature

The polyamic acid solution prepared in Examples 1-5 and Comparative Examples 1-3 was dropped on a glass plate and applied to a predetermined thickness (15 μm after heat treatment with 15% solids using a bar coater). Content and 100 μm solution thickness). After maintaining at a temperature of 25ºC and a humidity of> 90% for 30 minutes, observe the phenomenon of white turbidity. The degree of turbidity was evaluated with a score from 0 to 5 (0: no turbidity, 5: severe turbidity). (2) Preparation of film and evaluation of physical properties

This polyamic acid solution was coated on a glass plate using a bar coater, and then heat-treated in a high-temperature convection oven. The heat treatment is performed in a nitrogen environment at a temperature time of 100ºC / 30 minutes, 220ºC / 30 minutes, and 350ºC / 30 minutes. The physical properties of the obtained film were measured according to the methods described below. The results are provided in Table 2. (a) Transmission and retardation

The transmittance was measured using a UV-Vis NIR spectrophotometer at 550 nm, while the in-plane light retardation (R _o ) and out-of-plane light retardation (R _th ) were measured using retarders (RETs-100, Otsuka). (b) Yellowing Index (YI)

The yellowing index is measured using a colorimeter (LabScan XE). (c) Haze

Haze is measured using a haze meter (HAZE-GARD, Toyoseiki). (d) Thermal characteristics

The glass transition temperature (T _g ) and the coefficient of thermal expansion (CTE) of the film were measured using TMA 402 F3 (Netzsch). Measure the linear thermal expansion coefficient in tension mode with the force set to 0.05N and the temperature increased from 30ºC to 350ºC at a rate of 5ºC / min. Take the average value from 100 to 300ºC. Thermal degradation temperature (T _d , 1%) was measured using TG 209 F3 (Netzsch). (e) Mechanical characteristics

The mechanical properties of the film were measured using UTM (Instron). A film sample with a width of 10 mm and a clamping interval of 100 mm was stretched at a rate of 50 mm / min and measured. Table 1

It can be seen from Table 1 that when a 70:30 (mole%) mixture of GBL and NMP was used as the organic solvent in Example 1, no cloudiness was observed at room temperature after the solution was cast on a glass plate.

Moreover, when a mixture of GBL and DMPA was used in Example 2-4, or when DMPA was used alone in Example 5, no white turbidity was observed.

Because GBL is less likely to absorb water, when the GBL content increases, it can more effectively prevent white turbidity. DMPA also has the effect of preventing white turbidity for the same reason. In addition, the optical, thermal, and mechanical characteristics of this film were comparable to those of Comparative Examples 1-3.

Therefore, it can be seen that when GBL and NMP or GBL and DMPA are used as the organic solvent according to the content of the present invention, the stability of the resin at room temperature can be ensured without degrading the film characteristics. Comparative Example 4

In order to prepare the composition specified in Table 2, 21.186 g (0.066 mol) of TFMB as a diamine monomer was dissolved in an organic solvent composed of 86.7 g of NMP and 117.3 g of GBL, in a nitrogen environment at room temperature. 30 minutes to 1 hour. Then, after adding 29.881g (0.067mol) of 6FDA as dianhydride monomer, after 24 hours of polymerization, further add 85.0g of GBL, and then stir for 24 hours (reaction temperature: 30ºC, based on the reaction solvent) The solid content was maintained at 15% by weight based on the total weight) to prepare a polyamidic acid solution. The viscosity measured with a viscometer (Brookfield DV2T, SC4-27) was 4,200 cP. Example 6

To prepare the composition specified in Table 2, 2.589 g (0.024 mol) of PPD as a diamine monomer and 17.899 g (0.056 mol) of TFMB were dissolved in a composition consisting of 86.7 g of NMP and 117.3 g of GBL In an organic solvent, in a nitrogen environment at room temperature for 30 minutes to 1 hour. Then, after adding 25.210g (0.057 mol) of 6FDA and 5.299g (0.024 mol) of PMDA as dianhydride monomers, after 24 hours of polymerization, further add 85.0g of GBL, and then stir for 24 hours (Reaction temperature: 30ºC, based on the total weight of the reaction solvent, the solid content is maintained at 15% by weight) to prepare a polyamic acid solution. The viscosity measured with a viscometer (Brookfield DV2T, SC4-27) was 6,400 cP. Example 7

To prepare the composition specified in Table 2, 22.244 g (0.069 mol) of TFMB as a diamine monomer and 0.842 g (0.004 mol) of DBA were dissolved in 86.7 g of NMP and 117.3 g of GBL In an organic solvent, in a nitrogen environment at room temperature for 30 minutes to 1 hour. Then, after adding 23.063g (0.052mol) of 6FDA and 4.848g (0.022mol) of PMDA as dianhydride monomers, after 24 hours of polymerization, 85.0g of GBL was further added, and then stirred for 24 hours. (Reaction temperature: 30ºC, based on the total weight of the reaction solvent, the solid content is maintained at 15% by weight) to prepare a polyamic acid solution. The viscosity measured with a viscometer (Brookfield DV2T, SC4-27) was 4,800 cP. Example 8

In order to prepare the composition specified in Table 2, 24.320 g (0.076 mol) of TFMB as a diamine monomer was dissolved in an organic solvent composed of 86.7 g of NMP and 117.3 g of GBL. 30 minutes to 1 hour at temperature. Then, after adding 17.110g (0.038mol) of 6FDA and 5.035g (0.038mol) of PMDA as dianhydride monomers, after 24 hours of polymerization, further add 85.0g of GBL, and then stir for 24 hours (Reaction temperature: 30ºC, based on the total weight of the reaction solvent, the solid content is maintained at 15% by weight) to prepare a polyamic acid solution. The viscosity measured with a viscometer (Brookfield DV2T, SC4-27) was 6,600 cP. Example 9

In order to prepare the composition specified in Table 2, 2.094 g (0.019 mol) of PPD as diamine monomer, 18.610 g (0.058 mol) of TFMB and 0.881 g (0.004 mol) of DBA were dissolved in 86.7 g In an organic solvent composed of NMP and 117.3 g of GBL, in a nitrogen environment at room temperature for 30 minutes to 1 hour. Then, after adding 24.298 g (0.055 mol) of 6FDA and 5.115 g (0.023 mol) of PMDA as dianhydride monomers, after 24 hours of polymerization, further add 85.0 g of GBL, and then stir for 24 hours (Reaction temperature: 30ºC, based on the total weight of the reaction solvent, the solid content is maintained at 15% by weight) to prepare a polyamic acid solution. The viscosity measured with a viscometer (Brookfield DV2T, SC4-27) was 6,800 cP. Experimental Example 2 : Measurement of physical characteristics

In the same manner as in Experimental Example 1, the physical properties of the polyamic acid solutions prepared in Examples 6-9 and Comparative Example 4 were measured. The results are provided in Table 2. Table 2

It can be seen from Examples 6-8 in Table 2 that when the content of the acid dianhydride monomers PMDA and BPDA and the diamine monomer PPD and DBA increases, the transmittance and thermal characteristics are improved. As for Example 9 in which TFMB, PPD, and DBA are used as the diamine monomer at the same time, heat resistance characteristics and a low thermal expansion coefficient are achieved without generating by-products of DBA.

Therefore, the polyamic acid solution prepared according to the present invention can be provided as a transparent polyimide film, which is based on a film thickness of 10-15 μm, has a glass transition temperature of 300 ° C or higher, and ranges from 100 to 300 ° C. Internal thermal expansion coefficient of 25 ppm / ºC or lower, transmittance of 85% or higher at a wavelength of 550 nm, and a yellowing index (YI) of 7 or lower at a wavelength of 550 nm.

Accordingly, the polyimide film prepared according to the present invention satisfies the requirements of high transparency, good resin stability, high heat resistance, low thermal expansion coefficient, and superior mechanical characteristics, and can be widely used as a flexible display, such as OLED display, liquid crystal display, TFT display, flexible printed circuit board, flexible OLED surface light-emitting display or electronic paper display substrate or protective film.

(no)

Figure 1 shows the results of research on the phenomenon of white turbidity caused by the organic solvent (GBL: NMP = 70 mole%: 30 mole%) of the organic solvent of Example 1 during the casting of the polyamic acid solution on the glass substrate at room temperature (room temperature Stability). Fig. 2 shows the results of a study on the phenomenon of white turbidity caused by the organic solvent (GBL: DMPA = 70 mole%: 30 mole%) during the casting of a polyamic acid solution on a glass substrate at room temperature (room temperature Stability). FIG. 3 shows the results of a study on the cloudiness phenomenon (stability at room temperature) of the organic solvent (NMP 100 mole%) of Example 3 during the casting of a polyamic acid solution on a glass substrate at room temperature.

Claims (9)

A transparent polyimide precursor resin composition with improved resin stability and high heat resistance, comprising an aromatic diamine component, an acid dianhydride compound, and an organic solvent, wherein the aromatic diamine component ( A) Contains 2,2'-bis (trifluoromethyl) -4,4'-diamine biphenyl (TFMB) as a fluorinated aromatic diamine monomer, as a diamine monomer having a fluorenamine group N- (4-aminophenyl) -4-amine benzamidine (DBA) or a mixture thereof, the acid dianhydride compound (B) contains 4,4 'as a fluorinated aromatic acid dianhydride -(Hexafluoroisopropylidene) diphthalic anhydride (6FDA) and pyromelite dianhydride (PMDA) as non-fluorinated aromatic acid dianhydride or 3,3,4,4'-biphenyltetracarboxylic acid A mixture of dianhydride (BPDA) and the organic solvent (C) are a mixture of γ-butyrolactone (GBL) and N-methyl-2-pyrrolidone (NMP), and γ-butyrolactone (GBL) and A mixture of 3-methoxy-N, N-dimethylpropanamide (DMPA) or 3-methoxy-N, N-dimethylpropanamide (DMPA) alone. For example, the transparent polyfluorene imide precursor resin composition with improved resin stability and high heat resistance according to claim 1, wherein the aromatic diamine component (A) contains 30-100 based on the total diamine compound. Mole% of the 2,2'-bis (trifluoromethyl) -4,4'-diaminebiphenyl (TFMB), and 5-50 mole% of the N- (4-Aminephenyl) -4-amine benzamidine (DBA), and additionally a non-fluorinated aromatic diamine as a balance. For example, the transparent polyfluorene imide precursor resin composition with improved resin stability and high heat resistance according to claim 1, wherein the acid dianhydride compound (B) contains 20-80 moles of the entire acid dianhydride compound. Ear% of the fluorinated aromatic acid dianhydride includes 80-20 mole% of the non-fluorinated aromatic acid dianhydride based on the total acid dianhydride compound. For example, the transparent polyfluorene imide precursor resin composition with improved resin stability and high heat resistance of claim 1, wherein the organic solvent (C) contains 30-70 mol% of γ-butyrolactone (GBL) And 70-30 mole% of N-methyl-2-pyrrolidone (NMP) or 3-methoxy-N, N-dimethylpropanamide (DMPA). For example, the transparent polyimide precursor resin composition with improved resin stability and high heat resistance according to claim 1, wherein the polyimide precursor resin composition further comprises a member selected from the group consisting of One or more reaction catalysts (D): trimethylamine, xylene, pyridine and quinoline. A method for preparing a transparent polyimide resin film, wherein the method comprises preparing a film by heat-treating a polyamidic acid solution, the polyamidic acid solution being used as in any one of claims 1 to 5 Composition made. The method for preparing a transparent polyimide resin film according to claim 6, wherein the polyamic acid solution contains the organic solvent so that a solid content is 10-40% by weight, and 100 mol parts are mixed. The aromatic diamine component and 95-105 moles of the acid dianhydride compound are prepared. The method for preparing a transparent polyimide resin film according to claim 6, wherein the polyamidic acid solution has a viscosity of 1000-7000 cP. A polyimide resin film prepared by the method as claimed in claim 6, wherein the polyimide resin film has a glass transition temperature of 300ºC or higher based on a film thickness of 10-15 μm. A thermal expansion coefficient of 25 ppm / ºC or lower in a range of 100 to 300ºC, a transmittance of 85% or higher at a wavelength of 550nm, and a yellowing index (YI) of 7 or lower at a wavelength of 550nm.