CN111542562A - Method for preparing polyamic acid and polyamic acid, polyimide resin and polyimide film prepared therefrom - Google Patents

Abstract

The present invention relates to a method for preparing polyamic acid, and polyamic acid, polyimide resin, and polyimide film prepared therefrom, and more particularly, to developing a polyimide composition from which a polyimide film having an improved linear thermal expansion coefficient is manufactured by changing to a batch injection method when one type of diamine is injected.

Description

Preparation method of polyamic acid and polyamic acid, polyimide resin and polyimide film prepared therefrom

technical field

The present disclosure relates to a preparation method of a polyamic acid and the polyamic acid, polyimide resin and polyimide film prepared thereby.

Background technique

Generally, a polyimide (PI) film is a film formed of a polyimide resin, which is a highly heat-resistant resin obtained by combining an aromatic dianhydride with an aromatic diamine or an aromatic Diisocyanate is solution-polymerized to prepare a polyamic acid derivative, which is prepared by imidization of the polyamic acid derivative by ring-closure dehydration at a high temperature.

This polyimide film is used in a wide range of electronic materials such as semiconductor insulating films, TFT-LCD electrode protection films, and flexible printed circuit boards due to excellent mechanical properties, heat resistance, and electrical insulating properties.

However, the polyimide resin has a brown/yellow color due to its high aromatic ring density, and has low transmittance and yellow-based color in the visible light region, thereby reducing light transmittance and increasing birefringence, making it less Suitable for use as optical components.

US Patent Nos. 4,595,548, No. 4,603,061, No. 4,645,824, No. 4,895,972, No. 5,218,083, No. 5,093,453, No. 5,218,077, No. 5,367,046, No. 5,338,826, No. 5,986,036, and No. 6,232,428, and Korean Patent Laid-Open Publication No. 2003-0009437 reports the preparation of polyimides with novel structures by using linkers such as -O-, -SO ₂ - or CH ₂ - linked to meta positions instead of Monomers having a curved structure at the para position, or aromatic dianhydride and aromatic diamine monomers having substituents such as -CF ₃ , thus have improved transmittance and color transparency without significant deterioration in thermal properties. However, such polyimide is not suitable for use as a material for display devices such as OLED, TFT-LCD and flexible displays in terms of mechanical properties, heat resistance and birefringence.

SUMMARY OF THE INVENTION

technical problem

Therefore, an object of the present disclosure is to provide a preparation method of a polyamic acid capable of improving linear thermal expansion while maintaining optical properties by using the same raw materials and their amounts as conventional compositions, and changing the feeding method coefficient; provide polyamic acid, polyimide resin and polyimide film prepared by the preparation method; and provide an image display device including the polyimide film.

Technical solutions

In order to solve the above-mentioned technical problems, according to one aspect of the present disclosure, there is provided a method for preparing a polyamic acid, comprising: supplying a method comprising: 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFDB) (2,2'-bis(trifluoromethyl)diaminobiphenyl (TFDB) 2'-bis(trifluoromethyl)benzidine) and dianhydrides containing pyromellitic dianhydride (1,2,4,5-mellitic dianhydride (PMDA)); and supplies containing 2,2'- Diamines containing bis(trifluoromethyl)diaminobiphenyl (TFDB) and selected from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 3,3,4 , at least one dianhydride of 4-biphenyltetracarboxylic dianhydride (BPDA).

The molar ratio of PMDA to at least one selected from 6FDA and BPDA is 90 to 25:10 to 75.

The molar ratio of PMDA to 6FDA is 90 to 70:10 to 30.

The molar ratio of PMDA to BPDA is 90 to 25:10 to 75.

The molar ratio of PMDA, 6FDA to BPDA is 90 to 50:5 to 30:5 to 20.

The preparation method also includes further supplying at least one selected from the group consisting of 9,9-bis(4-aminophenyl)fluorene (FDA) and 9,9-bis(3-fluoro-4-aminophenyl)fluorene (FFDA). One as a diamine.

Based on the total moles of diamine, the selected from 9,9-bis(4-aminophenyl)fluorene (FDA) and 9,9-bis(3-fluoro-4-aminophenyl)fluorene (FFDA) At least one is added in an amount of 1 mol % to 20 mol %.

In another aspect of the present disclosure, there is provided a polyamic acid comprising: a block structure having repeating units derived from 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFDB) and derived from homophenylene repeating units of tetracarboxylic dianhydride (1,2,4,5-mellitic dianhydride (PMDA)); and block structures, having a derived from 2,2'-bis(trifluoromethyl)diaminobiphenyl ( Repeating units of TFDB) and derived from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 3,3,4,4-biphenyltetracarboxylic dianhydride (BPDA) at least one of the repeating units.

The molar ratio of PMDA in the first block structure to at least one selected from 6FDA and BPDA in the second block structure is 90 to 25:10 to 75.

The molar ratio of PMDA in the first block structure to 6FDA in the second block structure is 90 to 70:10 to 30.

The molar ratio of PMDA in the first block structure to BPDA in the second block structure is 90 to 25:10 to 75.

The molar ratio of PMDA in the first block structure, 6FDA in the second block structure, and BPDA in the second block structure is 90 to 50:5 to 30:5 to 20.

The block structure has repeating units derived from TFDB and repeating units derived from at least one selected from 6FDA and BPDA, and further comprises repeating units derived from 9,9-bis(4-aminophenyl)fluorene (FDA) and 9 , a repeating unit of at least one of 9-bis(3-fluoro-4-aminophenyl)fluorene (FFDA).

The content of the at least one selected from FDA and FFDA is 1 mol % to 20 mol % based on the total moles of diamine.

In another aspect of the present disclosure, a polyimide resin prepared from the polyamic acid is provided.

In another aspect of the present disclosure, a polyimide film prepared from the polyimide resin is provided.

The thermal expansion coefficient of the polyimide film at 50°C to 350°C is 30 ppm/°C or less, the transmittance at 550 nm measured with a UV spectrometer is 85% or more, and the yellowness is 10 or less.

In another aspect of the present disclosure, an image display device including the polyimide film is provided.

beneficial effect

The present disclosure provides a method for preparing a polyamic acid, and a polyamic acid, a polyimide resin, and a polyimide film prepared by the method, wherein the polyamic acid is formed into a film or membrane) with an improved coefficient of linear thermal expansion while maintaining yellowness and transmittance.

specific implementation

In one aspect, the present disclosure relates to a method for preparing a polyamic acid, comprising: supplying a diamine comprising 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFDB) and a diamine comprising pyromellitic acid Dianhydrides of anhydrides (1,2,4,5-mellitic dianhydride (PMDA)); and diamines containing 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFDB) and diamines containing Dimethicone of at least one selected from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 3,3,4,4-biphenyltetracarboxylic dianhydride (BPDA) anhydride.

The present disclosure can obtain the effect of improving the coefficient of linear thermal expansion while maintaining excellent optical properties by supplying, for example, a first supply and a second supply of one type of diamine at least once under specific conditions.

Hereinafter, the present disclosure will be described in more detail.

The method for producing a polyamic acid according to one embodiment preferably includes supplying a diamine containing 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFDB) and a diamine containing pyromellitic dianhydride (1,2 , dianhydride of 4,5-benzenetetracarboxylic dianhydride (PMDA)); and a second supply comprising a diamine of 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFDB) and a diamine comprising a group selected from 2 , a dianhydride of at least one of 2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 3,3,4,4-biphenyltetracarboxylic dianhydride (BPDA).

The molar ratio of PMDA to at least one selected from 6FDA and BPDA is 90 to 25:10 to 75, preferably 90 to 30:10 to 70.

When the molar ratio of PMDA to at least one selected from 6FDA and BPDA does not fall within the above-defined range, there are problems that the yellowness is 10 or more and the thermal expansion coefficient is 30 ppm/°C or more.

Throughout the specification, diamines containing 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFDB) and pyromellitic dianhydride (1,2,4,5-mellitic acid diamine) were supplied The dianhydride (PMDA)) may be referred to as the "first supply", supplying a diamine comprising 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFDB) and a diamine comprising 2,2- The dianhydride of at least one of bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 3,3,4,4-biphenyltetracarboxylic dianhydride (BPDA) may be referred to as " secondary supply". However, this is not intended to limit the feeding sequence, but merely to distinguish the feeding steps from each other.

At this time, supplying at least two selected from at least one of 6FDA and BPDA in the second feeding process refers to the total amount of dianhydride added during the second feeding relative to the PMDA during the first feeding. Moore.

In addition, when 6FDA is selected and supplied from at least one selected from 6FDA and BPDA in the second feeding, the molar ratio of PMDA in the first feeding to 6FDA in the second feeding is 90 to 70:10 to 30, preferably 90 to 75:10 to 25.

When the molar ratio of PMDA at the time of first feeding to 6FDA at the time of second feeding does not fall within the range defined above, more specifically, when the ratio of PMDA is higher than the range, there may be a very high coefficient of linear thermal expansion. Low but very high yellowness problem, while when the ratio of 6FDA is above the range, there may be the advantage of very low yellowness, but there may also be a problem of increased linear thermal expansion coefficient.

In addition, when BPDA is selected and supplied from at least one selected from 6FDA and BPDA during the second feeding, the molar ratio of PMDA during the first feeding to BPDA during the second feeding is 90 to 25:10 to 75, preferably 85 to 30:15 to 70.

When the molar ratio of PMDA at the first feeding time to BPDA at the second feeding time does not fall within the above-defined range, more specifically, when the ratio of PMDA is higher than the range, there may be a very high coefficient of linear thermal expansion. Low but very high yellowness problem, while when the proportion of BPDA is above the range, there may be an advantage of very low yellowness compared to PMDA, but there may also be a problem of increased coefficient of linear thermal expansion.

In one embodiment of the present disclosure, when at least two selected from at least one of 6FDA and BPDA are supplied in the second feeding process, PMDA in the first feeding, 6FDA in the second feeding The molar ratio to BPDA in the second feed is more preferably 90 to 50:5 to 30:5 to 20.

When the molar ratio of PMDA at the first feeding time to 6FDA and BPDA at the second feeding time does not fall within the above-defined range, there are problems that the yellowness is 10 or more and the thermal expansion coefficient is 30 ppm/°C or more.

In the present disclosure, the dianhydride containing PMDA is fed first and then the dianhydride containing at least one selected from 6FDA and BPDA is fed than the dianhydride containing at least one selected from 6FDA and BPDA is fed first and then the dianhydride containing PMDA is fed The dianhydride is more preferable because the thermal expansion coefficient and yellowness can be improved.

That is, in one embodiment of the present disclosure, it is more preferable to first supply a diamine comprising 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFDB) and a diamine comprising pyromellitic dianhydride ( 1,2,4,5-Mellitic acid dianhydride (PMDA)), then a diamine containing 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFDB) and a diamine containing A dianhydride of at least one of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 3,3,4,4-biphenyltetracarboxylic dianhydride (BPDA), This is because the physical properties of the present disclosure can be further improved.

In addition, at the time of the second feeding, 9,9-bis(4-aminophenyl)fluorene (FDA) and 9,9-bis(3-fluoro-4-aminophenyl)fluorene (FFDA) may also be fed. ) as a diamine. When at least one selected from FDA and FFDA is further supplied, the effect of improving the glass transition temperature can be obtained.

The content of at least one selected from FDA and FFDA is 1 mol % to 20 mol %, preferably 1 mol % to 10 mol %, based on the total moles of diamines. When the content of at least one selected from FDA and FFDA does not fall within the above range, more specifically, when the content is less than 1 mol %, there may be little effect of improving the glass transition temperature due to the low content, while When the content exceeds 20 mol %, there may be problems of increased yellowness and deterioration of thermal expansion coefficient.

In one embodiment of the present disclosure, the preparation method may further include: after the second supply, a third supply of bis(2,2'-bis(trifluoromethyl)diaminobiphenyl) (TFDB) Amine and containing at least one selected from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 3,3,4,4-biphenyltetracarboxylic dianhydride (BPDA) kind of dianhydride.

The diamine and dianhydride fed in the third feeding process can be appropriately adjusted and added within the molar ratio range of the diamine and dianhydride fed in the first feeding and the second feeding process.

In addition to TFDB, FDA, and FFDA, the diamine used in one embodiment of the present disclosure may also include a diamine selected from the group consisting of 4,4'-diaminodiphenyl ether (ODA), p-phenylenediamine (pPDA), m- Phenylenediamine (mPDA), p-methylenediphenylamine (pMDA), methylenediphenylamine (mMDA), 1,3-bis(3-aminophenoxy)benzene (133APB), 1,3-bis (4-Aminophenoxy)benzene (134APB), 2,2'-bis[4(4-aminophenoxy)phenyl]hexafluoropropane (4BDAF), 2,2'-bis(3-aminobenzene) base) hexafluoropropane (33-6F), 2,2'-bis(4-aminophenyl)hexafluoropropane (44-6F), bis(4-aminophenyl)sulfone)(4DDS), bis(3 -Aminophenylsulfone) (3DDS), 1,3-cyclohexanediamine (13CHD), 1,4-cyclohexanediamine (14CHD), 2,2-bis[4-(4-aminophenoxy) -Phenyl]propane (6HMDA), 2,2-bis(3-amino-4-hydroxy-phenyl)-hexafluoropropane (6FAP) and 4,4'-bis(3-aminophenoxy)diphenyl At least one of sulfone (DBSDA), but not limited thereto.

Meanwhile, in addition to PMDA, 6FDA and BPDA, the dianhydride used in the present disclosure may further include a group selected from 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4- Tetralin-1,2-dicarboxylic anhydride (TDA), 3,3,4,4-benzophenonetetracarboxylic dianhydride (BTDA), 4,4-oxodiphthalic dianhydride (ODPA) ), bis(3,4-dicarboxyphenyl)dimethyl-silane dianhydride (SiDA), 4,4-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride (BDSDA) , sulfonyl diphthalic anhydride (SO ₂ DPA), cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA) and 4,4'-(4,4'-isopropylidene At least one of diphenoxy)bis(phthalic anhydride) (6HBDA), but not limited thereto.

In one embodiment of the present disclosure, the diamine and dianhydride components described above are used in the polymerization reaction.

The reaction conditions are not particularly limited, but the reaction temperature is preferably 0°C to 80°C, and the reaction time is preferably 2 hours to 48 hours. Furthermore, the reaction is more preferably carried out under an inert gas atmosphere such as argon or nitrogen.

The organic solvent used for the solution polymerization of the monomer is not particularly limited as long as it is a solvent capable of dissolving the polyamic acid. Use selected from known reaction solvents such as m-cresol, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethylsulfoxide (DMSO) , acetone, ethyl acetate, diethylformamide (DEF), diethylacetamide (DEA), propylene glycol monomethyl ether (PGME), propylene glycol monomethyl ether acetate (PGMEA), ethyl lactate, 3- At least one polar solvent among methoxy-N,N-dimethylpropionamide and 3-butoxy-N,N-methylpropionamide. In addition, a low-boiling point solvent such as tetrahydrofuran (THF) or chloroform, or a low-absorptive solvent such as γ-butyrolactone may be used. The solvent is not limited to the types of the above-mentioned solvents, and the above-mentioned solvents may be used alone or in combination of two or more according to the purpose.

The content of the organic solvent is not particularly limited, however, with respect to the entire polyamic acid solution, the content of the organic solvent is preferably 50 to 95% by weight, more preferably 70 to 90% by weight, in order to obtain a suitable The molecular weight and viscosity of the polyamic acid solution.

In another aspect, the present disclosure relates to a polyamic acid comprising: a first block structure having repeating units derived from 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFDB) and derived from homogenous Repeating units of pyromellitic dianhydride (1,2,4,5-mellitic dianhydride (PMDA)); and a second block structure with derived from 2,2'-bis(trifluoromethyl)diamino Repeating units of biphenyl (TFDB) and derived from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 3,3,4,4-biphenyltetracarboxylic dianhydride A repeating unit of at least one of (BPDA).

The polyamic acid is preferably produced by the production method described above.

The polyamic acid produced by the above-described production method contains a first block structure and a second block structure, each of which contains a specific content of one type of diamine obtained by supplying one type of diamine in a batch manner, Thereby, the effect of improving the coefficient of linear thermal expansion while avoiding deterioration of yellowness and transmittance is provided as compared with the polyamic acid prepared by the conventional method including supplying one type of diamine at a time.

The molar ratio of PMDA in the first block structure to at least one selected from 6FDA and BPDA in the second block structure is 90 to 25:10 to 75, preferably 90 to 30:10 to 70.

When the molar ratio of PMDA in the first block structure to at least one selected from 6FDA and BPDA in the second block structure does not fall within the range defined above, there may be a yellowness of 10 or more or a thermal expansion coefficient It is a problem of 30 ppm/°C or more.

In addition, the molar ratio of PMDA in the first block structure to 6FDA in the second block structure is 90 to 70:10 to 30, preferably 90 to 75:10 to 25.

When the molar ratio of PMDA in the first block structure to 6FDA in the second block structure does not fall within the range defined above, more specifically, when the ratio of PMDA is higher than the range, there may be linear thermal expansion The coefficient is very low but the yellowness is very high, and when the ratio of 6FDA is higher than the range, there may be an advantage of very low yellowness, but there may also be a problem of an increase in the coefficient of linear thermal expansion.

In addition, the molar ratio of PMDA in the first block structure to BPDA in the second block structure is 90 to 25:10 to 75, preferably 85 to 30:15 to 70.

When the molar ratio of PMDA in the first block structure to BPDA in the second block structure does not fall within the range defined above, more specifically, when the ratio of PMDA is higher than the range, there may be linear thermal expansion The coefficient is very low but the yellowness is very high, and when the proportion of BPDA is higher than the range, there may be an advantage of very low yellowness compared to PMDA, but there may be a problem that the coefficient of linear thermal expansion increases.

In one embodiment of the present disclosure, the molar ratio of PMDA in the first block structure, 6FDA in the second block structure, and BPDA in the second block structure is preferably 90 to 50:5 to 30:5 to 20, more preferably 90 to 55:5 to 30:5 to 15.

When the molar ratio of PMDA in the first block structure to 6FDA and BPDA in the second block structure does not fall within the above-defined range, there are problems that the yellowness is 10 or more and the thermal expansion coefficient is 30 ppm/°C or more.

In addition, the block structure having a repeating unit derived from TFDB and a repeating unit derived from at least one selected from 6FDA and BPDA may further comprise a repeating unit derived from 9,9-bis(4-aminophenyl)fluorene (FDA) and A repeating unit of at least one of 9,9-bis(3-fluoro-4-aminophenyl)fluorene (FFDA). When the block structure further contains at least one selected from FDA and FFDA, the effect of improving the glass transition temperature can be obtained.

The content of the at least one selected from FDA and FFDA is preferably 1 mol % to 20 mol %, preferably 1 mol % to 10 mol %, based on the total moles of diamines. When the content of at least one selected from FDA and FFDA does not fall within the above range, more specifically, when the content is less than 1 mol %, there may be little effect of improving the glass transition temperature due to the low content, while When the content exceeds 20 mol %, there may be problems of deterioration of yellowness and thermal expansion coefficient.

The method of producing the polyimide resin by imidizing the above-mentioned polyamic acid is not particularly limited, and conventionally known methods may be followed. The method of imidizing the polyamic acid may be thermal imidization, chemical imidization, or a combination of thermal imidization and chemical imidization. Thermal imidization is preferred. More preferably, the solution obtained by chemical imidization is precipitated, purified, dried and then dissolved in a solvent before use. The type of solvent is the same as described above. Chemical imidization is a method in which a dehydrating agent represented by an acid anhydride such as acetic anhydride and an imidization catalyst represented by a tertiary amine such as isoquinoline, β-picoline or pyridine are applied to a polyamic acid solution . Thermal imidization may be used in combination with chemical imidization, and heating conditions may vary depending on the type of polyamic acid solution, the thickness of the film, and the like.

In another aspect, the present disclosure relates to a polyimide film prepared from the polyimide resin.

The polyimide film can also be obtained by the following method: imidizing the obtained polyamic acid solution, adding the imidized solution to the second solvent, precipitating, filtering and drying the obtained solution, A polyimide resin solid is obtained, and a film is formed using a polyimide solution obtained by dissolving the obtained polyimide resin solid in a first solvent.

That is, the above-mentioned polyamic acid is chemically imidized to prepare a polyimide resin, the polyimide resin is precipitated, dried and dissolved in a solvent to prepare a polyimide solution, the polyimide solution is It is coated onto a support, and the coated solution is allowed to form a film on the support by drying air and heat treatment.

The first solvent may be the same solvent as that used for the polymerization of the polyamic acid solution, and the second solvent may have a lower polarity than the first solvent, so as to obtain a solid polyimide resin, which is Specific examples may include at least one selected from the group consisting of water, alcohols, ethers, and ketones. In this case, the content of the second solvent is not particularly limited, but is preferably 5 to 20 times the weight of the polyamic acid solution.

The temperature at which the film is formed is preferably 250°C to 500°C, and the carrier used herein may be a glass plate, an aluminum foil, an endless stainless steel belt or a stainless steel drum, or the like.

The treatment time required for film formation depends on the temperature, the type of the carrier, the amount of the coated polyamic acid solution, and the mixing conditions of the catalyst, and is not limited to a predetermined time. Preferably, the film formation is performed for 5 minutes to 30 minutes.

The heat treatment temperature is 100°C to 500°C, and the treatment time is 1 minute to 30 minutes. After drying and imidization by heat treatment, the film is peeled off from the support.

The thickness of the obtained polyimide film is not particularly limited, but is preferably in the range of 10 μm to 250 μm, more preferably in the range of 10 μm to 100 μm.

Additionally, the term "polyimide" as used herein includes any polyimide-based polymer, such as polyimide-amide.

The thermal expansion coefficient at 50°C to 350°C of the polyimide film prepared in the present disclosure is preferably 30 ppm/°C or less.

The polyimide film prepared in the present disclosure has a transmittance at 550 nm of 85% or more, preferably 90% or more, wherein the transmittance is measured by a UV spectrometer based on a thickness of 10 μm to 100 μm.

In addition, the polyimide film has a yellowness of 10 or less, preferably 5 or less, based on a film thickness of 10 μm to 100 μm.

Hereinafter, the present disclosure will be described in more detail with reference to examples. These examples are provided only for a better understanding of the present disclosure, and should not be construed as limiting the scope of the present disclosure.

<Example 1>

To a 500 mL reactor equipped with a stirrer, nitrogen injector, dropping funnel, temperature controller and cooler as the reactor was added 273.882 g of N-methyl-2-pyrrolidone (NMP) while passing nitrogen through A reactor in which 28.821 g of TFDB was dissolved, and 19.631 g of PMDA was added thereto, followed by stirring for 3 hours. Then, 3.202 g of TFDB was dissolved therein, and 4.443 g of 6FDA was added thereto, after which the reaction was allowed to proceed for 15 hours. As a result, a polyamic acid solution having a solid content of 17% by weight was obtained. After the reaction was completed, the obtained solution was applied to a glass plate, treated with hot air at 80°C for 20 minutes, and then cured by isothermal treatment for 30 minutes when the temperature reached 370°C. Then, the resultant was slowly cooled and separated from the glass plate to obtain a polyimide film.

<Example 2>

To a 500 mL reactor equipped with a stirrer, nitrogen injector, dropping funnel, temperature controller and cooler as the reactor was added 284.922 g of N-methyl-2-pyrrolidone (NMP) while passing nitrogen through A reactor in which 25.618 g of TFDB was dissolved, and 17.450 g of PMDA was added thereto, followed by stirring for 3 hours. Then, 6.405 g of TFDB was dissolved therein, and 8.885 g of 6FDA was added thereto, after which the reaction was allowed to proceed for 15 hours. As a result, a polyamic acid solution having a solid content of 17% by weight was obtained. After the reaction was completed, the obtained solution was applied to a glass plate, treated with hot air at 80°C for 20 minutes, and then cured by isothermal treatment for 30 minutes when the temperature reached 370°C. Then, the resultant was slowly cooled and separated from the glass plate to obtain a polyimide film.

<Example 3>

To a 500 mL reactor equipped with a stirrer, nitrogen injector, dropping funnel, temperature controller and cooler as the reactor was added 295.963 g of N-methyl-2-pyrrolidone (NMP) while passing nitrogen through A reactor in which 22.416 g of TFDB was dissolved, and 15.268 g of PMDA was added thereto, followed by stirring for 3 hours. Then, 9.607 g of TFDB was dissolved therein, and 13.328 g of 6FDA was added thereto, after which the reaction was allowed to proceed for 15 hours. As a result, a polyamic acid solution having a solid content of 17% by weight was obtained. After the reaction was completed, the obtained solution was applied to a glass plate, treated with hot air at 80°C for 20 minutes, and then cured by isothermal treatment for 30 minutes when the temperature reached 370°C. Then, the resultant was slowly cooled and separated from the glass plate to obtain a polyimide film.

<Example 4>

To a 500 mL reactor equipped with a stirrer, nitrogen injector, dropping funnel, temperature controller and cooler as the reactor was added 295.963 g of N-methyl-2-pyrrolidone (NMP) while passing nitrogen through A reactor in which 9.607 g of TFDB was dissolved, and 13.328 g of 6FDA was added thereto, followed by stirring for 3 hours. Then, 22.416 g of TFDB was dissolved therein, and 15.268 g of PMDA was added thereto, after which the reaction was allowed to proceed for 15 hours. As a result, a polyamic acid solution having a solid content of 17% by weight was obtained. After the reaction was completed, the obtained solution was applied to a glass plate, treated with hot air at 80°C for 20 minutes, and then cured by isothermal treatment for 30 minutes when the temperature reached 370°C. Then, the resultant was slowly cooled and separated from the glass plate to obtain a polyimide film.

<Example 5>

To a 500 mL reactor equipped with a stirrer, nitrogen injector, dropping funnel, temperature controller and cooler as the reactor was added 281.419 g of N-methyl-2-pyrrolidone (NMP) while passing nitrogen through A reactor in which 16.012 g of TFDB was dissolved, and 10.906 g of PMDA was added thereto, followed by stirring for 3 hours. Then, 16.012 g of TFDB was dissolved therein, and 14.711 g of BPDA was added thereto, after which the reaction was allowed to proceed for 15 hours. As a result, a polyamic acid solution having a solid content of 17% by weight was obtained. After the reaction was completed, the obtained solution was applied to a glass plate, treated with hot air at 80°C for 20 minutes, and then cured by isothermal treatment for 10 minutes when the temperature reached 350°C. Then, the resultant was slowly cooled and separated from the glass plate to obtain a polyimide film.

<Example 6>

To a 500 mL reactor equipped with a stirrer, nitrogen injector, dropping funnel, temperature controller and cooler as a reactor was added 283.076 g of N,N-dimethylacetamide (DMAc) while allowing nitrogen Through the reactor, 13.450 g of TFDB was dissolved therein, and 9.161 g of PMDA was added thereto, followed by stirring for 3 hours. Then, 23.825 g of TFDB and 1.384 g of FFDA were dissolved therein, and 22.949 g of BPDA was added thereto, after which the reaction was allowed to proceed for 15 hours. As a result, a polyamic acid solution having a solid content of 20% by weight was obtained. After the reaction was completed, the obtained solution was applied to a glass plate, treated with hot air at 80°C for 20 minutes, and then cured by isothermal treatment for 10 minutes when the temperature reached 350°C. Then, the resultant was slowly cooled and separated from the glass plate to obtain a polyimide film.

<Example 7>

To a 500 mL reactor equipped with a stirrer, nitrogen injector, dropping funnel, temperature controller and cooler as a reactor was added 288.638 g of N-methyl-2-pyrrolidone (NMP) while passing nitrogen through A reactor in which 22.416 g of TFDB was dissolved, and 15.268 g of PMDA was added thereto, followed by stirring for 3 hours. Then, 9.607 g of TFDB was dissolved therein, and 8.885 g of 6FDA was added thereto, after which the reaction was allowed to proceed for 3 hours. Finally, 2.942 g of BPDA was added thereto, after which the reaction was allowed to proceed for 15 hours. As a result, a polyamic acid solution having a solid content of 17% by weight was obtained. After the reaction was completed, the obtained solution was applied to a glass plate, treated with hot air at 80°C for 20 minutes, and then cured by isothermal treatment for 30 minutes when the temperature reached 370°C. Then, the resultant was slowly cooled and separated from the glass plate to obtain a polyimide film.

<Example 8>

To a 500 mL reactor equipped with a stirrer, nitrogen injector, dropping funnel, temperature controller and cooler as a reactor was added 288.638 g of N-methyl-2-pyrrolidone (NMP) while passing nitrogen through A reactor in which 22.416 g of TFDB was dissolved, and 15.268 g of PMDA was added thereto, followed by stirring for 3 hours. Then, 6.405 g of TFDB was dissolved therein, and 8.885 g of 6FDA was added thereto, after which the reaction was allowed to proceed for 3 hours. Finally, 3.202 g of TFDB was dissolved therein and 2.942 g of BPDA was added thereto, after which the reaction was allowed to proceed for 15 hours. As a result, a polyamic acid solution having a solid content of 17% by weight was obtained. After the reaction was completed, the obtained solution was applied to a glass plate, treated with hot air at 80°C for 20 minutes, and then cured by isothermal treatment for 30 minutes when the temperature reached 370°C. Then, the resultant was slowly cooled and separated from the glass plate to obtain a polyimide film.

<Comparative Example 1>

To a 500 mL reactor equipped with a stirrer, nitrogen injector, dropping funnel, temperature controller and cooler as the reactor was added 268.362 g of N-methyl-2-pyrrolidone (NMP) while passing nitrogen through A reactor in which 32.023 g of TFDB was dissolved, and 20.721 g of PMDA was added thereto, followed by stirring for 3 hours. Then, 2.221 g of 6FDA was added thereto, after which the reaction was allowed to proceed for 15 hours. As a result, a polyamic acid solution having a solid content of 17% by weight was obtained. After the reaction was completed, the obtained solution was applied to a glass plate, treated with hot air at 80°C for 20 minutes, and then cured by isothermal treatment for 30 minutes when the temperature reached 370°C. Then, the resultant was slowly cooled and separated from the glass plate to obtain a polyimide film.

<Comparative Example 2>

To a 500 mL reactor equipped with a stirrer, nitrogen injector, dropping funnel, temperature controller and cooler as the reactor was added 295.963 g of N-methyl-2-pyrrolidone (NMP) while passing nitrogen through A reactor into which 32.023 g of TFDB was dissolved, and 15.268 g of PMDA was added thereto, followed by stirring for 3 hours. Then, 13.328 g of 6FDA was added thereto, after which the reaction was allowed to proceed for 15 hours. As a result, a polyamic acid solution having a solid content of 17% by weight was obtained. After the reaction was completed, the obtained solution was applied to a glass plate, treated with hot air at 80°C for 20 minutes, and then cured by isothermal treatment for 30 minutes when the temperature reached 370°C. Then, the resultant was slowly cooled and separated from the glass plate to obtain a polyimide film.

<Comparative Example 3>

To a 500 mL reactor equipped with a stirrer, nitrogen injector, dropping funnel, temperature controller and cooler as the reactor was added 295.963 g of N-methyl-2-pyrrolidone (NMP) while passing nitrogen through A reactor in which 32.023 g of TFDB was dissolved, and 13.328 g of 6FDA was added thereto, followed by stirring for 3 hours. Then, 15.268 g of PMDA was added thereto, followed by stirring for 15 hours. As a result, a polyamic acid solution having a solid content of 17% by weight was obtained. After the reaction was completed, the obtained solution was applied to a glass plate, treated with hot air at 80°C for 20 minutes, and then cured by isothermal treatment for 30 minutes when the temperature reached 370°C. Then, the resultant was slowly cooled and separated from the glass plate to obtain a polyimide film.

<Comparative Example 4>

To a 500 mL reactor equipped with a stirrer, nitrogen injector, dropping funnel, temperature controller and cooler as a reactor was added 301.483 g of N-methyl-2-pyrrolidone (NMP) while passing nitrogen gas through A reactor in which 32.023 g of TFDB was dissolved, and 14.178 g of PMDA was added thereto, followed by stirring for 3 hours. Then, 15.549 g of 6FDA was added thereto, followed by stirring for 15 hours. As a result, a polyamic acid solution having a solid content of 17% by weight was obtained. After the reaction was completed, the obtained solution was applied to a glass plate, treated with hot air at 80°C for 20 minutes, and then cured by isothermal treatment for 30 minutes when the temperature reached 370°C. Then, the resultant was slowly cooled and separated from the glass plate to obtain a polyimide film.

The physical properties of the polyimide films prepared in Examples and Comparative Examples were evaluated by the following methods, and the results are shown in Table 1 below.

(1) Measurement of transmittance (TT)

The transmittance was measured three times at 550 nm using a UV spectrometer (Cotica Minolta CM-3700d) and the average value is shown in Table 1.

(2) Measurement of yellowness (Y.I.)

Yellowness was measured using a UV spectrometer (Konita Minolta, CM-3700d) according to ASTM E313 standard.

(3) Measure the coefficient of thermal expansion (CTE)

The coefficient of linear thermal expansion from 50°C to 350°C was measured twice using TMA (TA Instrument, Q400) according to the TMA method. The size of the sample is 4mm×24mm, the load is 0.02N, and the heating rate is 10°C/min. After heat treatment, residual stress may remain on the formed film. Therefore, the residual stress is completely removed by the first run, thereby providing the second order value as the actual measurement value.

[Table 1]

When the Examples and Comparative Examples are compared with each other, it can be seen from Table 1 that Examples 1 to 8 in which TFDB is supplied in a batch manner satisfy excellent yellowness, transmittance and linear thermal expansion coefficient. On the other hand, Comparative Example 1 had significantly deteriorated transmittance, while Comparative Examples 2 to 4 had significantly deteriorated coefficients of linear thermal expansion.

These results show that Examples 1 to 8 overcome the trade-off relationship between yellowness and coefficient of linear thermal expansion by supplying TFDB in a batch manner.

In addition, when the first dianhydride is PMDA and the second dianhydride is 6FDA, the content of PMDA is preferably higher than 65 mol % to provide a linear thermal expansion coefficient of 30 ppm/°C or less, and not higher than 90 mol % to prevent yellowness deterioration . In addition, the same effects as described above can be obtained even when the second dianhydride is BPDA. Even when FFDA is further applied, the linear thermal expansion coefficient can be improved by supplying TFDB in a batch manner. As can be seen from Examples 3 and 4, when the first supplied dianhydride is PMDA, the effect of improving the coefficient of linear thermal expansion is greater than when the first supplied dianhydride is 6FDA. Furthermore, it can be seen from Examples 7 and 8 that when the third dianhydride is applied, the linear thermal expansion coefficient is further improved as the batchwise addition of TFDB increases.

Claims (18)

1. A method of preparing a polyamic acid comprising:

supplying a diamine comprising 2,2' -bis (trifluoromethyl) diaminobiphenyl (TFDB) and a dianhydride comprising pyromellitic dianhydride (1,2,4, 5-pyromellitic dianhydride (PMDA)); and

diamines including 2,2' -bis (trifluoromethyl) diaminobiphenyl (TFDB) and dianhydrides including at least one selected from 2, 2-bis (3, 4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and 3,3,4, 4-biphenyltetracarboxylic dianhydride (BPDA) are supplied.

2. The production method according to claim 1, wherein a molar ratio of PMDA to at least one selected from 6FDA and BPDA is 90 to 25:10 to 75.

3. The method of claim 1, wherein the molar ratio of PMDA to 6FDA is 90 to 70:10 to 30.

4. The method of claim 1, wherein the molar ratio of PMDA to BPDA is 90 to 25:10 to 75.

5. The method of claim 1, wherein the molar ratio of PMDA, 6FDA to BPDA is 90 to 50:5 to 30:5 to 20.

6. The production method according to claim 1, further comprising further supplying at least one selected from the group consisting of 9, 9-bis (4-aminophenyl) Fluorene (FDA) and 9, 9-bis (3-fluoro-4-aminophenyl) fluorene (FFDA) as the diamine.

7. The production method according to claim 6, wherein the at least one selected from the group consisting of 9, 9-bis (4-aminophenyl) Fluorene (FDA) and 9, 9-bis (3-fluoro-4-aminophenyl) fluorene (FFDA) is added in an amount of 1 to 20 mol% based on the total mol of diamine.

8. A polyamic acid comprising:

a first block structure having a repeating unit derived from 2,2' -bis (trifluoromethyl) diaminobiphenyl (TFDB) and a repeating unit derived from pyromellitic dianhydride (1,2,4, 5-pyromellitic dianhydride (PMDA)); and

a second block structure having a repeating unit derived from 2,2' -bis (trifluoromethyl) diaminobiphenyl (TFDB) and a repeating unit derived from at least one selected from 2, 2-bis (3, 4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and 3,3,4, 4-biphenyltetracarboxylic dianhydride (BPDA).

9. The polyamic acid of claim 8, wherein the molar ratio of PMDA in the first block structure to at least one selected from the group consisting of 6FDA and BPDA in the second block structure is from 90 to 25:10 to 75.

10. The polyamic acid of claim 8, wherein the molar ratio of PMDA in the first block structure to 6FDA in the second block structure is from 90 to 70:10 to 30.

11. The polyamic acid of claim 8, wherein the molar ratio of PMDA in the first block structure to BPDA in the second block structure is from 90 to 25:10 to 75.

12. The polyamic acid of claim 8, wherein the molar ratio of PMDA in the first block structure, 6FDA in the second block structure, and BPDA in the second block structure is from 90 to 50:5 to 30:5 to 20.

13. The polyamic acid according to claim 8, wherein the block structure has a repeating unit derived from TFDB and a repeating unit derived from at least one selected from 6FDA and BPDA, and further comprises a repeating unit derived from at least one selected from 9, 9-bis (4-aminophenyl) Fluorene (FDA) and 9, 9-bis (3-fluoro-4-aminophenyl) fluorene (FFDA).

14. The polyamic acid according to claim 13, wherein the at least one selected from FDA and FFDA is contained in an amount of 1 to 20 mol% based on the total mol of the diamine.

15. A polyimide resin prepared from the polyamic acid according to claim 8.

16. A polyimide film prepared from the polyimide resin according to claim 15.

17. The polyimide film according to claim 16, wherein the polyimide film has a coefficient of thermal expansion of 30ppm/° c or less at 50 ℃ to 350 ℃, a transmittance of 85% or more at 550nm as measured by a UV spectrometer, and a yellowness of 10 or less.

18. An image display device comprising the polyimide film according to claim 16.