KR102271023B1 - Polyamic acid, Polyimide, Polyimide Film and Display Device Comprising Thereof and mothod of preparing the Polyamic acid - Google Patents

Abstract

The present invention relates to a polyamic acid, polyimide, polyimide film, an image display device including the same, and a method for producing a polyamic acid, wherein the film according to the present invention has a low linear thermal expansion coefficient of 10 ppm/℃ or less and a low linear thermal expansion coefficient of 350℃ or more. It has the effect of improving yellowness while having a glass transition temperature.

Description

Polyamic acid, polyimide, polyimide film, image display device including the same, and method of manufacturing polyamic acid {Polyamic acid, Polyimide, Polyimide Film and Display Device Comprising Thereof and method of preparing the Polyamic acid}

The present invention relates to a polyamic acid, polyimide, and polyimide film with improved yellowness while having a low linear thermal expansion coefficient of 10 ppm/℃ or less and a glass transition temperature of 350° C. or more, an image display device including the same, and a method for manufacturing polyamic acid it's about

In general, a polyimide (PI) film is a film formed of a polyimide resin, and the polyimide resin is obtained by solution polymerization of an aromatic dianhydride and an aromatic diamine or an aromatic diisocyanate to prepare a polyamic acid derivative, followed by ring closure dehydration at high temperature. It refers to a high heat-resistant resin manufactured by imidization.

Because such polyimide films have excellent mechanical, heat resistance and electrical insulation properties, they are used in a wide range of electronic materials such as semiconductor insulating films, TFT-LCD electrode protective films, and flexible printed wiring circuit boards.

However, the polyimide resin is colored brown and yellow due to its high aromatic ring density, so it has low transmittance in the visible light region, shows a yellow color, low light transmittance, and has a large birefringence, making it difficult to use as an optical member. have.

U.S. Patent Nos. 4595548, 4603061, 4645824, 4895972, 5218083, 5093453, 5218077, 5367046, 5338826. No. 5986036, No. 6232428 and Korean Patent Laid-Open No. 2003-0009437 disclose that -O-, -SO ₂ -, CH ₂ -, etc., is a monomer of a bent structure connected to the m-position, not the p-position, or -CF ₃ There is a report of manufacturing a polyimide having a novel structure with improved transmittance and color transparency to the extent that thermal properties are not significantly reduced by using an aromatic dianhydride dianhydride and an aromatic diamine monomer having a substituent such as -CF 3 In terms of mechanical properties, heat resistance, and birefringence, the results were insufficient for use as a material for display devices such as OLED, TFT-LCD, and flexible display.

In the polyimide prepared in the present invention, diamine having a benzidine structure is introduced to improve yellowness while maintaining similar heat resistance of colored PI, and also, by combining monomers included in diamine and dianhydride in an appropriate ratio, 10 ppm/℃ An object of the present invention is to provide a polyamic acid, polyimide, and polyimide film with improved yellowness while having a low coefficient of linear thermal expansion and a glass transition temperature of 350° C. or higher, an image display device including the same, and a method of manufacturing the polyamic acid.

In order to solve the above problems, a preferred embodiment of the present invention is a polyamic acid comprising a repeating unit derived from diamine and a repeating unit derived from dianhydride, wherein the repeating unit derived from diamine is bistrifluoromethyl It includes a repeating unit derived from benzidine and a repeating unit derived from m-phenylenediamine, and the repeating unit derived from m-phenylenediamine is 10 to 20 moles based on 100 mol% of the repeating unit derived from diamine. %, and the repeating unit derived from dianhydride includes a repeating unit derived from pyromellitic acid dianhydride and a repeating unit derived from biphenyl tetracarboxylic dianhydride, and the biphenyl The repeating unit derived from tetracarboxylic dianhydride is a polyamic acid included in a molar ratio of 1:1 to 1.5 with respect to the repeating unit derived from the m-phenylenediamine.

The repeating unit derived from the diamine is characterized in that it further comprises 1 to 10 mol% of the repeating unit derived from bisfluoroaminophenyl fluorene based on 100 mol% of the repeating unit derived from the diamine.

The repeating unit derived from the diamine comprises more than 10 mol% and not more than 20 mol% of the total amount of the repeating unit derived from the m-phenylenediamine and the repeating unit derived from the bisfluoroaminophenyl fluorene do it with

Another preferred embodiment of the present invention is a polyimide comprising a repeating unit derived from diamine and a repeating unit derived from dianhydride, wherein the repeating unit derived from diamine is a repeating unit derived from bistrifluoromethyl benzidine a unit and a repeating unit derived from m-phenylenediamine, and the repeating unit derived from m-phenylenediamine is included in an amount of 10 to 20 mol% based on 100 mol% of the repeating unit derived from the diamine. and the repeating unit derived from dianhydride includes a repeating unit derived from pyromellitic acid dianhydride and a repeating unit derived from biphenyl tetracarboxylic dianhydride, and the biphenyl tetracarboxylic dianhydride The repeating unit derived from hydride is a polyimide included in a molar ratio of 1:1 to 1.5 compared to the repeating unit derived from the m-phenylenediamine.

The repeating unit derived from the diamine is characterized in that it further comprises 1 to 10 mol% of the repeating unit derived from bisfluoroaminophenyl fluorene based on 100 mol% of the repeating unit derived from the diamine.

The repeating unit derived from the diamine comprises more than 10 mol% and not more than 20 mol% of the total amount of the repeating unit derived from the m-phenylenediamine and the repeating unit derived from the bisfluoroaminophenyl fluorene do it with

Another preferred embodiment of the present invention is a polyimide film comprising the above-described polyimide.

Another preferred embodiment of the present invention is an image display device comprising the above-described polyimide film.

Another preferred embodiment of the present invention comprises the steps of preparing a diamine solution by adding and dissolving diamine containing bistrifluoromethyl benzidine and m-phenylenediamine in a solvent (S1); It is a method for producing a polyamic acid comprising the step (S2) of adding and reacting dianhydride including biphenyl tetracarboxylic dianhydride and pyromellitic acid dianhydride to the diamine solution prepared in step S1.

In step S2, biphenyl tetracarboxylic dianhydride is added to the diamine solution prepared in step S1 for a primary reaction, followed by secondary reaction by adding pyromellitic acid dianhydride.

The first reaction in step S2 is characterized in that it is carried out at 25 to 30 ℃ for 3 to 5 hours.

The secondary reaction in step S2 is characterized in that it is carried out at 25 to 40 ℃ for 12 to 20 hours.

According to the present invention, after forming a film or film, it is possible to provide a polyimide film having improved yellowness and transmittance while having heat resistance similar to that of colored PI.

According to one embodiment of the present invention, in the polyamic acid comprising a repeating unit derived from diamine and a repeating unit derived from dianhydride, the repeating unit derived from diamine is bistrifluoromethyl benzidine (2,2 '-bis(trifluoromethyl)benzidine, TFDB) and a repeating unit derived from m-phenylene diamine (mPDA), and the m-phenylene diamine (meta-phenylene diamine, The repeating unit derived from mPDA) is included in an amount of 10 to 20 mol% based on 100 mol% of the repeating unit derived from the diamine, and the repeating unit derived from the dianhydride is pyromellitic acid dianhydride (1 A repeating unit derived from ,2,4,5-benzene tetracarboxylic dianhydride, pyromellicticacid dianhydride, PMDA) and a repeating unit derived from biphenyl tetracarboxylic dianhydride (3,3,4,4-Biphenyltetracarboxylic dianhydride, BPDA) Including, the repeating unit derived from the biphenyl tetracarboxylic dianhydride (3,3,4,4-Biphenyltetracarboxylic dianhydride, BPDA) is 1:1 to the repeating unit derived from the m-phenylenediamine A polyamic acid contained in a molar ratio of 1.5 may be provided.

As used herein, the term “derived repeating unit” means that the monomers for forming the polymer are linked to each other and the structure of the monomer appears repeatedly in the polymer. This is a term widely used in the field to which the present invention belongs. For example, polyethylene is a polymer having a repeating unit derived from ethylene, and the structure of the ethylene monomer is repeatedly displayed in the polyethylene polymer while the ethylene monomers are connected to each other.

The polyamic acid according to the present invention is a repeating unit derived from diamine, and a repeating unit derived from bistrifluoromethyl benzidine (2,2'-bis(trifluoromethyl)benzidine, TFDB) and m-phenylene diamine (meta-phenylene diamine). , mPDA), and the repeating unit derived from dianhydride is a repeating unit derived from pyromellitic acid dianhydride (1,2,4,5-benzene tetracarboxylic dianhydride, pyromellicticacid dianhydride, PMDA). and a repeating unit derived from biphenyl tetracarboxylic dianhydride (3,3,4,4-Biphenyltetracarboxylic dianhydride, BPDA).

As the diamine, other diamines may be included in addition to bistrifluoromethyl benzidine (2,2'-bis(trifluoromethyl)benzidine, TFDB) and m-phenylene diamine (mPDA), for example, oxydiamine Aniline (4,4'-Oxydianiline, ODA), p-phenylene diamine (pPDA), p-methylene diamine (pMDA), m-methylene diamine (meta-Methylene Diamine, mMDA) ), bisaminophenoxybenzene (1,3-bis(3-aminophenoxy) benzene, 133APB), bisaminophenoxybenzene (1,3-bis(4-aminophenoxy) benzene, 134APB), bisaminophenoxyphenyl hexa Fluoropropane (2,2'-bis[4(4-aminophenoxy)phenyl]hexafluoropropane, 4BDAF), bisaminophenyl hexafluoropropane (2,2'-bis(3-aminophenyl)hexafluoropropane, 33-6F), Bis aminophenyl hexafluoropropane (2,2'-bis (4-aminophenyl) hexafluoropropane, 44-6F), bis aminophenyl sulfone (bis (4-aminophenyl) sulfone, 4DDS), bis aminophenyl sulfone (bis (3) - aminophenyl)sulfone, 3DDS), cyclohexanediamine (1,3-Cyclohexanediamine, 13CHD), cyclohexanediamine (1,4-Cyclohexanediamine, 14CHD), bisaminophenoxyphenylpropane (2,2-Bis[4-( 4-aminophenoxy)-phenyl]propane, 6HMDA), bisaminohydroxyphenyl hexafluoropropane (2,2-Bis(3-amino-4-hydroxy-phenyl)-hexafluoropropane, DBOH), bisaminophenoxy diphenyl Sulfone (4,4'-Bis(3-amino phenoxy) diphen yl sulfone, DBSDA) bisaminophenyl fluorene (9,9-Bis(4-aminophenyl)fluorene, FDA), bisfluoroaminophenyl fluorene (9,9-Bis(3-fluoro-4-aminophenyl)fluorene, FFDA), etc., and is not limited to the types mentioned herein.

The dianhydride is pyromellitic acid dianhydride (1,2,4,5-benzene tetracarboxylic dianhydride, pyromellicticacid dianhydride, PMDA), biphenyl tetracarboxylic dianhydride (3,3,4,4-Biphenyltetracarboxylic dianhydride) , BPDA) may include other dianhydrides, for example, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA), 4- (2,5-dioxo) Tetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride (TDA), benzophenone tetracarboxylic dianhydride (3,3,4 ,4-Benzophenone tetracarboxylic dianhydride, BTDA), oxydiphthalic dianhydride (4,4-Oxydiphthalic dianhydride, ODPA), biscarboxyphenyl dimethyl silane dianhydride ( Bis(3,4dicarboxyphenyl)dimethyl-silane dianhydride, SiDA), Bis dicarboxyphenoxy diphenyl sulfide dianhydride (4,4-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride, BDSDA), sulfonyldiphthalic anhydride (SO ₂ DPA), cyclobutane tetra Cyclobutane-1,2,3,4-tetracarboxylic dianhydride, CBDA, isopropylideneiphenoxy bis phthalic anhydride (4,4'-(4,4'-Isopropylidenediphenoxy)bis (phthalic anhydride), 6HBDA), and the like, but is not limited to the above-mentioned types.

The polyamic acid of the present invention is a repeating unit derived from bistrifluoromethyl benzidine (2,2'-bis(trifluoromethyl)benzidine, TFDB), a repeating unit derived from m-phenylene diamine (mPDA) , a repeating unit derived from pyromellitic acid dianhydride (1,2,4,5-benzene tetracarboxylic dianhydride, pyromellicticacid dianhydride, PMDA) and biphenyl tetracarboxylic dianhydride (3,3,4,4-Biphenyltetracarboxylic When a repeating unit derived from dianhydride, BPDA) is included, it can have a high glass transition temperature by m-phenylenediamine, and the effect of improving yellowness compared to PMDA can be obtained by adding BPDA.

The repeating unit derived from the m-phenylene diamine (mPDA) may be included in an amount of 10 to 20 mol% based on 100 mol% of the repeating unit derived from the diamine. When the content of the repeating unit derived from the m-phenylenediamine is less than 10 mol%, there is a problem that there is little effect on improving heat resistance because the ratio is relatively small, and when it exceeds 20 mol%, yellowness due to structural characteristics There is an increasing problem.

The repeating unit derived from the biphenyl tetracarboxylic dianhydride (3,3,4,4-Biphenyltetracarboxylic dianhydride, BPDA) has a molar ratio of 1:1 to 1.5 compared to the repeating unit derived from the m-phenylenediamine. may be included. That is, the molar ratio of the repeating unit derived from m-phenylenediamine to the repeating unit derived from biphenyl tetracarboxylic dianhydride (3,3,4,4-Biphenyltetracarboxylic dianhydride, BPDA) is 1:1 to 1.5. It is preferable to include a repeating unit derived from biphenyl tetracarboxylic dianhydride (3,3,4,4-Biphenyltetracarboxylic dianhydride, BPDA) as the content. When the molar ratio of the repeating unit derived from the biphenyl tetracarboxylic dianhydride is less than 1 molar ratio, there is a small problem in improving the yellowness, and when it exceeds 1.5 molar ratio, it has a high coefficient of linear thermal expansion. There is a problem in that the coefficient of linear thermal expansion increases.

In addition, the polyamic acid according to the present invention is a repeating unit derived from diamine, and a repeating unit derived from bistrifluoromethyl benzidine (2,2'-bis(trifluoromethyl)benzidine, TFDB) and m-phenylenediamine (meta- In addition to the repeating unit derived from phenylene diamine, mPDA), it may further include a repeating unit derived from bisfluoroaminophenyl fluorene (9,9-Bis(3-fluoro-4-aminophenyl)fluorene, FFDA).

The polyamic acid of the present invention is a repeating unit derived from bistrifluoromethyl benzidine (2,2'-bis(trifluoromethyl)benzidine, TFDB) and a repeating unit derived from m-phenylene diamine (mPDA) In addition, the FFDA raw material with a high glass transition temperature is introduced by including a repeating unit derived from bisfluoroaminophenyl fluorene (9,9-Bis(3-fluoro-4-aminophenyl)fluorene, FFDA). It is possible to obtain the effect of further improving the

The repeating unit derived from the bisfluoroaminophenyl fluorene (9,9-Bis(3-fluoro-4-aminophenyl)fluorene, FFDA) is 1 to 10 mol% based on 100 mol% of the repeating unit derived from diamine is included in the content of When the content of the bisfluoroaminophenyl fluorene is less than 1 mol%, there is a problem that there is little effect, and when it exceeds 10 mol%, the mechanical properties of the polyimide film are deteriorated due to the characteristics of the FFDA raw material, and the coefficient of linear thermal expansion There is an increasing problem.

The repeating unit derived from the diamine may include the total amount of the repeating unit derived from the m-phenylenediamine and the repeating unit derived from the bisfluoroaminophenyl fluorene in an amount greater than 10 mol% and less than or equal to 20 mol%. . When the total amount of the repeating unit derived from m-phenylenediamine and the repeating unit derived from bisfluoroaminophenyl fluorene is 10 mol% or less, the effect of improving the glass transition temperature physical properties cannot be obtained, and 20 mol% If it exceeds, there is a problem in that yellowness and thermal expansion coefficient increase as mentioned above.

According to another embodiment of the present invention, in the polyimide comprising a repeating unit derived from diamine and a repeating unit derived from dianhydride, the repeating unit derived from diamine is derived from bistrifluoromethyl benzidine. It includes a repeating unit and a repeating unit derived from m-phenylenediamine, and the repeating unit derived from m-phenylenediamine is 10 to 20 mol% based on 100 mol% of the repeating unit derived from the diamine. The repeating unit derived from dianhydride includes a repeating unit derived from pyromellitic acid dianhydride and a repeating unit derived from biphenyl tetracarboxylic dianhydride, and the biphenyl tetracarboxylic The repeating unit derived from dianhydride may provide a polyimide included in a molar ratio of 1:1 to 1.5 compared to the repeating unit derived from the m-phenylenediamine.

The polyimide according to the present invention is a repeating unit derived from diamine, and a repeating unit derived from bistrifluoromethyl benzidine (2,2'-bis(trifluoromethyl)benzidine, TFDB) and m-phenylene diamine (meta-phenylene diamine). , mPDA), and the repeating unit derived from dianhydride is a repeating unit derived from pyromellitic acid dianhydride (1,2,4,5-benzene tetracarboxylic dianhydride, pyromellicticacid dianhydride, PMDA). and a repeating unit derived from biphenyl tetracarboxylic dianhydride (3,3,4,4-Biphenyltetracarboxylic dianhydride, BPDA).

As the diamine, other diamines may be included in addition to bistrifluoromethyl benzidine (2,2'-bis(trifluoromethyl)benzidine, TFDB) and m-phenylene diamine (mPDA), for example, oxydiamine Aniline (4,4'-Oxydianiline, ODA), p-phenylene diamine (pPDA), p-methylene diamine (pMDA), m-methylene diamine (meta-Methylene Diamine, mMDA) ), bisaminophenoxybenzene (1,3-bis(3-aminophenoxy) benzene, 133APB), bisaminophenoxybenzene (1,3-bis(4-aminophenoxy) benzene, 134APB), bisaminophenoxyphenyl hexa Fluoropropane (2,2'-bis[4(4-aminophenoxy)phenyl]hexafluoropropane, 4BDAF), bisaminophenyl hexafluoropropane (2,2'-bis(3-aminophenyl)hexafluoropropane, 33-6F), Bis aminophenyl hexafluoropropane (2,2'-bis (4-aminophenyl) hexafluoropropane, 44-6F), bis aminophenyl sulfone (bis (4-aminophenyl) sulfone, 4DDS), bis aminophenyl sulfone (bis (3) - aminophenyl)sulfone, 3DDS), cyclohexanediamine (1,3-Cyclohexanediamine, 13CHD), cyclohexanediamine (1,4-Cyclohexanediamine, 14CHD), bisaminophenoxyphenylpropane (2,2-Bis[4-( 4-aminophenoxy)-phenyl]propane, 6HMDA), bisaminohydroxyphenyl hexafluoropropane (2,2-Bis(3-amino-4-hydroxy-phenyl)-hexafluoropropane, DBOH), bisaminophenoxy diphenyl Sulfone (4,4'-Bis(3-amino phenoxy) diphe nyl sulfone, DBSDA) bisaminophenyl fluorene (9,9-Bis(4-aminophenyl)fluorene, FDA), bisfluoroaminophenyl fluorene (9,9-Bis(3-fluoro-4-aminophenyl)fluorene, FFDA), etc., and is not limited to the types mentioned herein.

The dianhydride is pyromellitic acid dianhydride (1,2,4,5-benzene tetracarboxylic dianhydride, pyromellicticacid dianhydride, PMDA), biphenyl tetracarboxylic dianhydride (3,3,4,4-Biphenyltetracarboxylic dianhydride) , BPDA) may include other dianhydrides, for example 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA), 4- (2,5-dioxo) Tetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride (TDA), benzophenone tetracarboxylic dianhydride (3,3,4 ,4-Benzophenone tetracarboxylic dianhydride, BTDA), oxydiphthalic dianhydride (4,4-Oxydiphthalic dianhydride, ODPA), biscarboxyphenyl dimethyl silane dianhydride (Bis(3,4dicarboxyphenyl)dimethyl-silane dianhydride, SiDA), Bis dicarboxyphenoxy diphenyl sulfide dianhydride (4,4-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride, BDSDA), sulfonyldiphthalic anhydride (SO ₂ DPA), cyclobutane tetra Cyclobutane -1,2,3,4 - tetracarboxylic dianhydride, CBDA, isopropylideneiphenoxy bis phthalic anhydride (4,4'-(4,4'-Isopropylidenediphenoxy)bis (phthalic anhydride), 6HBDA), etc., but is not limited to the above-mentioned types.

The polyimide of the present invention is a repeating unit derived from bistrifluoromethyl benzidine (2,2'-bis(trifluoromethyl)benzidine, TFDB), a repeating unit derived from m-phenylene diamine (mPDA) , a repeating unit derived from pyromellitic acid dianhydride (1,2,4,5-benzene tetracarboxylic dianhydride, pyromellicticacid dianhydride, PMDA) and biphenyl tetracarboxylic dianhydride (3,3,4,4-Biphenyltetracarboxylic When a repeating unit derived from dianhydride, BPDA) is included, it can have a high glass transition temperature by m-phenylenediamine, and the effect of improving yellowness compared to PMDA can be obtained by adding BPDA.

The repeating unit derived from the m-phenylene diamine (mPDA) may be included in an amount of 10 to 20 mol% based on 100 mol% of the repeating unit derived from the diamine. When the content of the repeating unit derived from the m-phenylenediamine is less than 10 mol%, there is a problem that there is little effect on improving heat resistance because the ratio is relatively small, and when it exceeds 20 mol%, yellowness due to structural characteristics There is an increasing problem.

The repeating unit derived from the biphenyl tetracarboxylic dianhydride (3,3,4,4-Biphenyltetracarboxylic dianhydride, BPDA) has a molar ratio of 1:1 to 1.5 compared to the repeating unit derived from the m-phenylenediamine. may be included. That is, the molar ratio of the repeating unit derived from m-phenylenediamine to the repeating unit derived from biphenyl tetracarboxylic dianhydride (3,3,4,4-Biphenyltetracarboxylic dianhydride, BPDA) is 1:1 to 1.5. It is preferable to include a repeating unit derived from biphenyl tetracarboxylic dianhydride (3,3,4,4-Biphenyltetracarboxylic dianhydride, BPDA) as the content. When the molar ratio of the repeating unit derived from the biphenyl tetracarboxylic dianhydride is less than 1 molar ratio, there is a small problem in improving the yellowness, and when it exceeds 1.5 molar ratio, it has a high coefficient of linear thermal expansion. There is a problem in that the coefficient of linear thermal expansion increases.

In addition, the polyimide according to the present invention is a repeating unit derived from diamine, and a repeating unit derived from bistrifluoromethyl benzidine (2,2'-bis(trifluoromethyl)benzidine, TFDB) and m-phenylenediamine (meta-). In addition to the repeating unit derived from phenylene diamine, mPDA), it may further include a repeating unit derived from bisfluoroaminophenyl fluorene (9,9-Bis(3-fluoro-4-aminophenyl)fluorene, FFDA).

The polyimide of the present invention is a repeating unit derived from bistrifluoromethyl benzidine (2,2'-bis(trifluoromethyl)benzidine, TFDB) and a repeating unit derived from m-phenylene diamine (mPDA) In addition, the FFDA raw material with a high glass transition temperature is introduced by including a repeating unit derived from bisfluoroaminophenyl fluorene (9,9-Bis(3-fluoro-4-aminophenyl)fluorene, FFDA). It is possible to obtain the effect of further improving the

The repeating unit derived from the bisfluoroaminophenyl fluorene (9,9-Bis(3-fluoro-4-aminophenyl)fluorene, FFDA) is 1 to 10 mol% based on 100 mol% of the repeating unit derived from diamine is included in the content of When the content of the bisfluoroaminophenyl fluorene is less than 1 mol%, there is little effect, and when it exceeds 10 mol%, the mechanical properties of the polyimide film are deteriorated due to the characteristics of the FFDA raw material, and the coefficient of linear thermal expansion is increased. there is a problem.

The repeating unit derived from the diamine may include the total amount of the repeating unit derived from the m-phenylenediamine and the repeating unit derived from the bisfluoroaminophenyl fluorene in an amount greater than 10 mol% and less than or equal to 20 mol%. . When the total amount of the repeating unit derived from m-phenylenediamine and the repeating unit derived from bisfluoroaminophenyl fluorene is 10 mol% or less, the effect of improving the glass transition temperature physical properties cannot be obtained, and 20 mol% If it exceeds, there is a problem in that yellowness and thermal expansion coefficient increase as mentioned above.

According to another embodiment of the present invention, a polyimide film including the above-described polyimide may be provided.

The polyimide film preferably has a coefficient of thermal expansion of 10 ppm/° C. or less at 50 to 350° C.

The polyimide film preferably has a transmittance of 85% or more at 550 nm when the transmittance is measured with a UV spectrometer based on a thickness of 10 to 100 µm. Furthermore, the average transmittance at 380 to 780 nm is 80% or more, and it is preferable that the average transmittance is 85% or more at 550 to 780 nm.

In addition, the polyimide film preferably has a yellowness of 15 or less based on a film thickness of 10 to 100 μm.

The polyimide film of the present invention that satisfies the above light transmittance, yellowness, and heat resistance can be used in a protective film or a diffusion plate and coating film in TFT-LCD, such as TFT-LCD, which has been restricted due to the yellow color of the existing polyimide film. It can be used in fields that require transparency such as interlayer, gate insulator, and liquid crystal alignment film, and when the above transparent polyimide is applied as a liquid crystal alignment film, it contributes to an increase in the aperture ratio, making it possible to manufacture high contrast TFT-LCD. In addition, it can be used as a flexible display substrate and a hard coating film that replaces glass in the existing display.

The above-described physical properties such as coefficient of thermal expansion, transmittance, yellowness, etc. are measured when the thickness of the film is within the range of 10 to 100 μm, for example, 11 μm, 12 μm, 13 μm, … It may be measured as a film having a thickness of 100 μm or the like, and when each film within the thickness is measured, all of the above physical property ranges may be satisfied. In this case, the thickness range of the film corresponds to the measurement method for measuring the physical properties, and unless otherwise specified, it is not meant to limit the thickness of the film. In addition, the polyimide film according to the present invention is characterized in that it satisfies all of the above physical properties, that is, thermal expansion coefficient, transmittance, yellowness, and the like.

According to another embodiment of the present invention, it is possible to provide an image display device including the above-described polyimide film.

According to another embodiment of the present invention, a diamine containing bistrifluoromethyl benzidine and m-phenylenediamine is added and dissolved in a solvent to prepare a diamine solution (S1); It provides a method for producing a polyamic acid comprising the step (S2) of adding and reacting dianhydride including biphenyl tetracarboxylic dianhydride and pyromellitic acid dianhydride to the diamine solution prepared in step S1 above (S2) can do.

As the diamine, other diamines may be included in addition to bistrifluoromethyl benzidine (2,2'-bis(trifluoromethyl)benzidine, TFDB) and m-phenylene diamine (mPDA), for example, oxydiamine Aniline (4,4'-Oxydianiline, ODA), p-phenylene diamine (pPDA), p-methylene diamine (pMDA), m-methylene diamine (meta-Methylene Diamine, mMDA) ), bisaminophenoxybenzene (1,3-bis(3-aminophenoxy) benzene, 133APB), bisaminophenoxybenzene (1,3-bis(4-aminophenoxy) benzene, 134APB), bisaminophenoxyphenyl hexa Fluoropropane (2,2'-bis[4(4-aminophenoxy)phenyl]hexafluoropropane, 4BDAF), bisaminophenyl hexafluoropropane (2,2'-bis(3-aminophenyl)hexafluoropropane, 33-6F), Bis aminophenyl hexafluoropropane (2,2'-bis (4-aminophenyl) hexafluoropropane, 44-6F), bis aminophenyl sulfone (bis (4-aminophenyl) sulfone, 4DDS), bis aminophenyl sulfone (bis (3) - aminophenyl)sulfone, 3DDS), cyclohexanediamine (1,3-Cyclohexanediamine, 13CHD), cyclohexanediamine (1,4-Cyclohexanediamine, 14CHD), bisaminophenoxyphenylpropane (2,2-Bis[4-( 4-aminophenoxy)-phenyl]propane, 6HMDA), bisaminohydroxyphenyl hexafluoropropane (2,2-Bis(3-amino-4-hydroxy-phenyl)-hexafluoropropane, DBOH), bisaminophenoxy diphenyl Sulfone (4,4'-Bis(3-amino phenoxy) diphen yl sulfone, DBSDA) bisaminophenyl fluorene (9,9-Bis(4-aminophenyl)fluorene, FDA), bisfluoroaminophenyl fluorene (9,9-Bis(3-fluoro-4-aminophenyl)fluorene, FFDA), etc., and is not limited to the types mentioned herein.

The dianhydride is pyromellitic acid dianhydride (1,2,4,5-benzene tetracarboxylic dianhydride, pyromellicticacid dianhydride, PMDA), biphenyl tetracarboxylic dianhydride (3,3,4,4-Biphenyltetracarboxylic dianhydride) , BPDA) may include other dianhydrides, for example, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA), 4- (2,5-dioxo) Tetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride (TDA), benzophenone tetracarboxylic dianhydride (3,3,4 ,4-Benzophenone tetracarboxylic dianhydride, BTDA), oxydiphthalic dianhydride (4,4-Oxydiphthalic dianhydride, ODPA), Bis(3,4-dicarboxyphenyl)dimethyl-silane dianhydride, SiDA ), bis-dicarboxyphenoxy diphenyl sulfide dianhydride (4,4-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride, BDSDA), sulfonyldiphthalic anhydride (SO ₂ DPA), cyclo Butane tetracarboxylic dianhydride (Cyclobutane -1,2,3,4 - tetracarboxylic dianhydride, CBDA), isopropylideneiphenoxy bis phthalic anhydride (4,4'-(4,4'-Isopropylidenediphenoxy) )bis(phthalic anhydride), 6HBDA), etc., but is not limited to the above-mentioned types.

First, diamine containing bistrifluoromethyl benzidine and m-phenylenediamine is added and dissolved in a solvent to prepare a diamine solution (S1).

In step S1, the m-phenylenediamine may be added in an amount of 10 to 20 mol% based on 100 mol% of the diamine. When the content of the repeating unit derived from the m-phenylenediamine is added to less than 10 mol%, there is a problem that the ratio is relatively small, so there is little effect in improving heat resistance, and when it exceeds 20 mol%, yellowness due to structural characteristics There is an increasing problem.

When preparing the diamine solution in step S1, in addition to bis trifluoromethyl benzidine (2,2'-bis (trifluoromethyl) benzidine, TFDB) and m-phenylene diamine (mPDA), bis fluoro Aminophenyl fluorene (9,9-Bis(3-fluoro-4-aminophenyl)fluorene, FFDA) may be further added.

The bisfluoroaminophenyl fluorene may be further added in an amount of 1 to 10 mol% based on 100 mol% of the diamine. When the content of the bisfluoroaminophenyl fluorene is added less than 1 mol%, there is a problem that there is little effect, and when it exceeds 10 mol%, the mechanical properties of the polyimide film are deteriorated due to the characteristics of the FFDA raw material, and the coefficient of linear thermal expansion There is an increasing problem.

When preparing the diamine solution in step S1, the total amount of the m-phenylenediamine and the bisfluoroaminophenyl fluorene may be added in an amount of more than 10 mol% and not more than 20 mol%. When the total amount of the m-phenylenediamine and the bisfluoroaminophenyl fluorene is 10 mol% or less, there is a problem that the glass transition temperature is not improved, and when it exceeds 20 mol%, as mentioned above, yellowness and coefficient of thermal expansion There is an increasing problem.

The solvent is m-cresol, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), acetone, diethyl acetate, diethylform At least one polar solvent selected from amide (DEF), diethylacetamide (DEA), propylene glycol monomethyl ether (PGME), and propylene glycol monomethyl ether acetate (PGMEA) is used. In addition, a low-boiling-point solution such as tetrahydrofuran (THF), chloroform, or a low-absorption solvent such as γ-butyrolactone may be used. It is not limited to the above-mentioned types, and these solvents may be used alone or in two or more types depending on the purpose.

The content of the solvent is not particularly limited, but for the degree of polymerization and the convenience of the process, the content of the solvent is preferably 70 to 95% by weight of the total diamine solution, more preferably 75 to 90% by weight. .

Then, dianhydride including biphenyl tetracarboxylic dianhydride and pyromellitic acid dianhydride is added to the diamine solution prepared in step S1 and reacted (S2).

In step S2, the biphenyl tetracarboxylic dianhydride is preferably added in a molar ratio of 1:1 to 1.5 with respect to the repeating unit derived from the m-phenylenediamine. That is, the molar ratio of m-phenylenediamine to biphenyl tetracarboxylic dianhydride (3,3,4,4-Biphenyltetracarboxylic dianhydride, BPDA) is 1:1 to 1.5. Ride (3,3,4,4-Biphenyltetracarboxylic dianhydride, BPDA) is preferably added.

When the content of the biphenyl tetracarboxylic dianhydride is added in less than 1 molar ratio, there is a small problem in improving yellowness, and when it exceeds 1.5 molar ratio, it has a high coefficient of linear thermal expansion, so the linear thermal expansion of the polyimide composition There is a problem that the coefficient increases.

The conditions for the reaction in step S2 are not particularly limited, but the reaction temperature is preferably 0 to 80° C., and the reaction time is preferably 2 to 48 hours. In addition, it is more preferable to use an inert gas atmosphere such as argon or nitrogen during the reaction.

In the step S2 according to the present invention, it is preferable to perform a primary reaction by adding biphenyl tetracarboxylic dianhydride to the diamine solution prepared in step S1, and then to perform a secondary reaction by adding pyromellitic acid dianhydride. desirable.

The first reaction in step S2 is preferably carried out at 25 to 30 ℃ for 3 to 5 hours. When the primary reaction is carried out under the above conditions, there is an effect that a sufficient reaction can be achieved for the polymerization of the polyamic acid to proceed.

The secondary reaction in step S2 is preferably carried out at 25 to 40 ℃ for 12 to 20 hours. When the primary reaction is carried out under the above conditions, there is an effect that a sufficient reaction can be achieved for the polymerization of the polyamic acid to proceed.

A method for producing a polyimide film from the polyamic acid obtained by the above-described production method is not particularly limited, and a conventionally known method can be used. Although the thermal imidation method and the chemical imidation method are mentioned as a method of imidating the said polyamic acid, it is more preferable to use the chemical imidation method. More preferably, the solution subjected to the chemical imidization method is precipitated, purified, dried, and then dissolved again in a solvent before use. This solvent is the same as the solvent mentioned above. Chemical imidization is a method of applying a dehydrating agent represented by an acid anhydride such as acetic anhydride and an imidization catalyst represented by tertiary amines such as isoquinoline, β-picoline, and pyridine 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.

After the chemical imidization method, it is precipitated, dried, dissolved in a solvent, and applied to a support. The applied solution is formed into a film on the support by dry air and heat treatment. The film forming temperature condition of the coated film is preferably 300 ~ 500 ℃, and a glass plate, an aluminum foil, a circulation stainless belt, a stainless drum, etc. can be used as a support body.

The processing time required for film formation depends on the temperature, the type of support, the amount of the applied polyamic acid solution, and the mixing conditions of the catalyst, and is not limited to a certain time. Preferably, it is good to carry out in the range between 5 minutes and 30 minutes.

The heat treatment temperature is between 100 and 500°C, and the treatment time is between 1 and 30 minutes. After completion of drying and imidization by heat treatment, it is peeled off from the support.

The residual volatile content of the heat-treated film is 5% or less, preferably 3% or less.

Although the thickness of the polyimide film obtained is not specifically limited, It is preferable that it is the range of 10-100 micrometers.

Hereinafter, the present invention will be described in more detail through examples, but the scope of the present invention is not limited to the following examples.

<Example 1>

As a reactor, 278.606 g of N-methyl-2-pyrrolidone (NMP) was filled in a 500 ml reactor equipped with a stirrer, nitrogen injection device, dropping funnel, temperature controller and cooler while passing nitrogen, and then 28.180 g (0.088 mol) of TFDB was added. After dissolution, 2.379 g (0.022 mol) of mPDA was dissolved. Then, 9.709 g (0.033 mol) of BPDA was added and reacted for 4 hours, and 16.795 g (0.077 mol) of PMDA was added and reacted for 15 hours. As a result, a polyamic acid solution having a solid content of 17 wt% was obtained. After completion of the reaction, the obtained solution was applied to a glass plate, treated with hot air at 80° C. for 20 minutes, and cured to 350° C. Then, it cooled gradually, isolate|separated from the glass plate, and obtained the polyimide film.

< Example 2>

As a reactor, 274.519 g of N-methyl-2-pyrrolidone (NMP) was filled in a 500 ml reactor equipped with a stirrer, nitrogen injection device, dropping funnel, temperature controller and cooler while passing nitrogen, and then 28.180 g (0.088 mol) of TFDB was added. After dissolution, 2.379 g (0.022 mol) of mPDA was dissolved. Then, 6.473 g (0.022 mol) of BPDA was added and reacted for 4 hours, and 19.195 g (0.088 mol) of PMDA was added and reacted for 15 hours. As a result, a polyamic acid solution having a solid content of 17 wt% was obtained. After completion of the reaction, the obtained solution was applied to a glass plate, treated with hot air at 80° C. for 20 minutes, and cured to 350° C. Then, it cooled gradually, isolate|separated from the glass plate, and obtained the polyimide film.

< Example 3>

As a reactor, 276.002 g of N-methyl-2-pyrrolidone (NMP) was filled with nitrogen passing through a 500 ml reactor equipped with a stirrer, nitrogen injection device, dropping funnel, temperature controller and cooler, and then 28.180 g (0.088 mol) of TFDB was added. After dissolution, 2.379 g (0.0209 mol) of mPDA and 0.423 g (0.0011 mol) of FFDA were dissolved. Then, 6.473 g (0.022 mol) of BPDA was added and reacted for 4 hours, and 19.195 g (0.088 mol) of PMDA was added and reacted for 15 hours. As a result, a polyamic acid solution having a solid content of 17 wt% was obtained. After completion of the reaction, the obtained solution was applied to a glass plate, treated with hot air at 80° C. for 20 minutes, and cured to 350° C. Then, it cooled gradually, isolate|separated from the glass plate, and obtained the polyimide film.

< Example 4>

As a reactor, after filling 281.938 g of N-methyl-2-pyrrolidone (NMP) while passing nitrogen through a 500 ml reactor equipped with a stirrer, nitrogen injection device, dropping funnel, temperature controller and cooler, 28.180 g (0.088 mol) of TFDB was added. After dissolution, 1.784 g (0.0165 mol) of mPDA and 2.114 g (0.0055 mol) of FFDA were dissolved. Then, 6.473 g (0.022 mol) of BPDA was added and reacted for 4 hours, and 19.195 g (0.088 mol) of PMDA was added and reacted for 15 hours. As a result, a polyamic acid solution having a solid content of 17 wt% was obtained. After completion of the reaction, the obtained solution was applied to a glass plate, treated with hot air at 80° C. for 20 minutes, and cured to 350° C. Then, it cooled gradually, isolate|separated from the glass plate, and obtained the polyimide film.

< comparative example 1>

As a reactor, 272.910 g of N-methyl-2-pyrrolidone (NMP) was filled in a 500 ml reactor equipped with a stirrer, nitrogen injection device, dropping funnel, temperature controller and cooler while passing nitrogen, and then 26.419 g (0.0825 mol) of TFDB was added. After dissolution, 2.974 g (0.0275 mol) of mPDA was dissolved. Then, 9.709 g (0.033 mol) of BPDA was added and reacted for 4 hours, and 16.795 g (0.077 mol) of PMDA was added and reacted for 15 hours. As a result, a polyamic acid solution having a solid content of 17 wt% was obtained. After completion of the reaction, the obtained solution was applied to a glass plate, treated with hot air at 80° C. for 20 minutes, and cured to 350° C. Then, it cooled gradually, isolate|separated from the glass plate, and obtained the polyimide film.

< comparative example 2>

As a reactor, after filling 295.691 g of N-methyl-2-pyrrolidone (NMP) while passing nitrogen into a 500 ml reactor equipped with a stirrer, nitrogen injection device, dropping funnel, temperature controller and cooler, 33.464 g (0.1045 mol) of TFDB was added. After dissolution, 0.595 g (0.0055 mol) of mPDA was dissolved. Then, 9.709 g (0.033 mol) of BPDA was added and reacted for 4 hours, and 16.795 g (0.077 mol) of PMDA was added and reacted for 15 hours. As a result, a polyamic acid solution having a solid content of 17 wt% was obtained. After completion of the reaction, the obtained solution was applied to a glass plate, treated with hot air at 80° C. for 20 minutes, and cured to 350° C. Then, it cooled gradually, isolate|separated from the glass plate, and obtained the polyimide film.

< comparative example 3>

As a reactor, 272.475 g of N-methyl-2-pyrrolidone (NMP) was filled in a 500 ml reactor equipped with a stirrer, nitrogen injection device, dropping funnel, temperature controller and cooler while passing nitrogen, and then 28.180 g (0.0088 mol) of TFDB was added. After dissolution, 2.379 g (0.022 mol) of mPDA was dissolved. Then, 4.855 g (0.0165 mol) of BPDA was added and reacted for 4 hours, and 20.394 g (0.0935 mol) of PMDA was added and reacted for 15 hours. As a result, a polyamic acid solution having a solid content of 17 wt% was obtained. After completion of the reaction, the obtained solution was applied to a glass plate, treated with hot air at 80° C. for 20 minutes, and cured to 350° C. Then, it cooled gradually, isolate|separated from the glass plate, and obtained the polyimide film.

< comparative example 4>

As a reactor, 280.649 g of N-methyl-2-pyrrolidone (NMP) was filled in a 500 ml reactor equipped with a stirrer, nitrogen injection device, dropping funnel, temperature controller and cooler while passing nitrogen, and then 28.180 g (0.088 mol) of TFDB was added. After dissolution, 2.379 g (0.022 mol) of mPDA was dissolved. After that, BPDA 11.327g (0.0385mol) was added and reacted for 4 hours, PMDA 15.596 (0.0715mol) was added and reacted for 15 hours. As a result, a polyamic acid solution having a solid content of 17 wt% was obtained. After completion of the reaction, the obtained solution was applied to a glass plate, treated with hot air at 80°C for 20 minutes, and cured to 350°C. Then, it cooled gradually, isolate|separated from the glass plate, and obtained the polyimide film.

< comparative example 5>

As a reactor, 29.942 g (0.0935 mol) of TFDB was added after filling 284.301 g of N-methyl-2-pyrrolidone (NMP) while passing nitrogen through a 500 ml reactor equipped with a stirrer, nitrogen injection device, dropping funnel, temperature controller and cooler. After dissolution, 1.784 g (0.0165 mol) of mPDA was dissolved. Then, 9.709 g (0.033 mol) of BPDA was added and reacted for 4 hours, and 16.795 g (0.077 mol) of PMDA was added and reacted for 15 hours. As a result, a polyamic acid solution having a solid content of 17 wt% was obtained. After completion of the reaction, the obtained solution was applied to a glass plate, treated with hot air at 80° C. for 20 minutes, and cured to 350° C. Then, it cooled gradually, isolate|separated from the glass plate, and obtained the polyimide film.

< comparative example 6>

As a reactor, 289.996 g of N-methyl-2-pyrrolidone (NMP) was filled in a 500 ml reactor equipped with a stirrer, nitrogen injection device, dropping funnel, temperature controller and cooler while passing nitrogen, and then 31.703 g (0.099 mol) of TFDB was added. After dissolution, 1.190 g (0.011 mol) of mPDA was dissolved. Then, 9.709 g (0.033 mol) of BPDA was added and reacted for 4 hours, and 16.795 g (0.077 mol) of PMDA was added and reacted for 15 hours. As a result, a polyamic acid solution having a solid content of 17 wt% was obtained. After completion of the reaction, the obtained solution was applied to a glass plate, treated with hot air at 80° C. for 20 minutes, and cured to 350° C. Then, it cooled gradually, isolate|separated from the glass plate, and obtained the polyimide film.

< comparative example 7>

As a reactor, 270.432 g of N-methyl-2-pyrrolidone (NMP) was filled in a 500 ml reactor equipped with a stirrer, nitrogen injection device, dropping funnel, temperature controller and cooler while passing nitrogen, and then 28.180 g (0.088 mol) of TFDB was added. After dissolution, 2.379 g (0.022 mol) of mPDA was dissolved. Then, 3.236 g (0.011 mol) of BPDA was added and reacted for 4 hours, and 21.594 (0.099 mol) of PMDA was added and reacted for 15 hours. As a result, a polyamic acid solution having a solid content of 17 wt% was obtained. After completion of the reaction, the obtained solution was applied to a glass plate, treated with hot air at 80° C. for 20 minutes, and cured to 350° C. Then, it cooled gradually, isolate|separated from the glass plate, and obtained the polyimide film.

< comparative example 8>

As a reactor, 289.357 g of N-methyl-2-pyrrolidone (NMP) was filled while passing nitrogen through a 500 ml reactor equipped with a stirrer, nitrogen injection device, dropping funnel, temperature controller and cooler, and then 28.180 g (0.088 mol) of TFDB was added. After dissolution, 1.190 g (0.011 mol) of mPDA and 4.229 g (0.011 mol) of FFDA were dissolved. Then, 6.473 g (0.022 mol) of BPDA was added and reacted for 4 hours, and 19.195 g (0.088 mol) of PMDA was added and reacted for 15 hours. As a result, a polyamic acid solution having a solid content of 17 wt% was obtained. After completion of the reaction, the obtained solution was applied to a glass plate, treated with hot air at 80° C. for 20 minutes, and cured to 350° C. Then, it cooled gradually, isolate|separated from the glass plate, and obtained the polyimide film.

< comparative example 9>

As a reactor, 293.328 g of N-methyl-2-pyrrolidone (NMP) was filled in a 500 ml reactor equipped with a stirrer, nitrogen injection device, dropping funnel, temperature controller and cooler while passing nitrogen, and then 31.703 g (0.099 mol) of TFDB was added. After dissolution, 0.595 g (0.0055 mol) of mPDA and 2.114 g (0.0055 mol) of FFDA were dissolved. Then, 6.473 g (0.022 mol) of BPDA was added and reacted for 4 hours, and 19.195 g (0.088 mol) of PMDA was added and reacted for 15 hours. As a result, a polyamic acid solution having a solid content of 17 wt% was obtained. After completion of the reaction, the obtained solution was applied to a glass plate, treated with hot air at 80° C. for 20 minutes, and cured to 350° C. Then, it cooled gradually, isolate|separated from the glass plate, and obtained the polyimide film.

< comparative example 10>

As a reactor, 296.775 g of N-methyl-2-pyrrolidone (NMP) was filled while passing nitrogen through a 500 ml reactor equipped with a stirrer, nitrogen injection device, dropping funnel, temperature controller and cooler, and then 28.180 g (0.088 mol) of TFDB was added. After dissolution, 0.595 g (0.0055 mol) of mPDA and 6.343 g (0.0165 mol) of FFDA were dissolved. Then, 6.473 g (0.022 mol) of BPDA was added and reacted for 4 hours, and 19.195 g (0.088 mol) of PMDA was added and reacted for 15 hours. As a result, a polyamic acid solution having a solid content of 17 wt% was obtained. After completion of the reaction, the obtained solution was applied to a glass plate, treated with hot air at 80°C for 20 minutes, and cured to 350°C. Then, it cooled gradually, isolate|separated from the glass plate, and obtained the polyimide film.

< comparative example 11>

As a reactor, 276.242 g of N-methyl-2-pyrrolidone (NMP) was filled in a 500 ml reactor equipped with a stirrer, nitrogen injection device, dropping funnel, temperature controller and cooler while passing nitrogen, and then 26.419 g (0.0825 mol) of TFDB was added. After dissolution, 2.379 g (0.022 mol) of mPDA and 2.114 g (0.0055 mol) of FFDA were dissolved. Then, 6.473 g (0.022 mol) of BPDA was added and reacted for 4 hours, and 19.195 g (0.088 mol) of PMDA was added and reacted for 15 hours. As a result, a polyamic acid solution having a solid content of 17 wt% was obtained. After completion of the reaction, the obtained solution was applied to a glass plate, treated with hot air at 80° C. for 20 minutes, and cured to 350° C. Then, it cooled gradually, isolate|separated from the glass plate, and obtained the polyimide film.

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

(1) Measurement of transmittance

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

(3) Measurement of coefficient of thermal expansion (CTE)

Using TMA (TA Instrument, Q400), the coefficient of linear thermal expansion at 50-350° C. was measured twice according to the TMA-Method. The size of the specimen was 4 mm×24 mm, the load was 0.02 N, and the temperature increase rate was 10° C./min.

Since residual stress may remain in the film through heat treatment after forming the film, the residual stress is completely removed by the first run, and the second value is presented as an actual measurement value.

(4) Glass transition temperature (Tg) measurement

Using MA (TA Instruments, Q400), the size of the specimen was 4 mm × 24 mm, the load was 0.02 N, and the temperature increase rate was 10° C./min.

division Diamin Dianhydride Properties TFDB PDA FFDA PMDA BPDA thickness yellowness permeability CTE Tg Example One 80 20 - 70 30 10 12.15 86.92 7.79 350 2 80 20 - 80 20 10 14.37 86.59 4.72 360 3 80 19 One 80 20 10 12.45 86.71 5.17 360 4 80 15 5 80 20 10 11.67 87.18 6.82 370 comparative example One 75 25 - 70 30 10 10 14.62 11.29 355 2 95 5 - 70 30 10 10.22 86.05 not measurable 310 3 80 20 - 85 15 10 16.72 85.59 3.71 365 4 80 20 - 65 35 10 10.54 87.11 10.29 345 5 85 15 - 70 30 10 9.54 86.98 not measurable 335 6 90 10 - 70 30 10 7.87 87.22 not measurable 320 7 80 20 - 90 10 10 15.52 86.28 2.27 370 8 80 10 10 80 20 10 10.53 87.32 10.12 375 9 90 5 5 80 20 10 8.29 87.78 3.93 345 10 80 5 15 80 20 10 8.93 87.55 13.21 380 11 75 20 5 80 20 10 13.11 86.88 10.12 375

As shown in Table 1, the content of mPDA is preferably not more than 20 mol% to prevent a decrease in yellowness, and in the case of FFDA, although it has an effect of improving the glass transition temperature, CTE is also increased, so the content is within 10 mol% is appropriate In the case of BPDA, the preferred content varies depending on the ratio of diamine added above, but it is judged that it is desirable to add within 30 mol% as a whole. If it is higher than that, the yellowness is improved, but it was found that the CTE and glass transition temperature decrease.

Specifically, Comparative Example 1 had a problem in that the CTE was increased due to a high mPDA ratio, whereas Comparative Example 2 had a low mPDA ratio and thus the glass transition temperature was not improved, and Comparative Examples 3 and 7 were mPDA The BPDA ratio was low compared to the ratio, so there was a problem of high yellowness, and on the contrary, Comparative Examples 4 to 6 had a problem in that the CTE and the glass transition temperature were lowered because the BPDA ratio was high compared to the mPDA ratio. In addition, it was found that Comparative Examples 8 to 11 had a problem in that CTE or glass transition temperature was lowered because the ratio of the raw materials was not appropriate.

From this, it was found that in order to satisfy all the physical properties of transmittance, yellowness, coefficient of thermal expansion and glass transition temperature, the configuration of the present invention should be satisfied as in Examples 1 to 4.

Claims (12)

In the polyamic acid comprising a repeating unit derived from diamine and a repeating unit derived from dianhydride,
The repeating unit derived from the diamine includes a repeating unit derived from bistrifluoromethyl benzidine and a repeating unit derived from m-phenylenediamine, and the repeating unit derived from m-phenylenediamine is derived from the diamine It is included in an amount of 10 to 20 mol% based on 100 mol% of the repeated unit,
The repeating unit derived from dianhydride includes a repeating unit derived from pyromellitic acid dianhydride and a repeating unit derived from biphenyl tetracarboxylic dianhydride, and the biphenyl tetracarboxylic dianhydride The repeating unit derived from polyamic acid is included in a molar ratio of 1:1 to 1.5 compared to the repeating unit derived from the m-phenylenediamine. The method according to claim 1, wherein the repeating unit derived from diamine further comprises 1 to 10 mol% of the repeating unit derived from bisfluoroaminophenyl fluorene based on 100 mol% of the repeating unit derived from diamine. polyamic acid. According to claim 2, wherein the repeating unit derived from the diamine is a total amount of the repeating unit derived from m-phenylenediamine and the repeating unit derived from bisfluoroaminophenyl fluorene is more than 10 mol% 20 mol% Polyamic acid, characterized in that it contains the following. In the polyimide comprising a repeating unit derived from diamine and a repeating unit derived from dianhydride,
The repeating unit derived from the diamine includes a repeating unit derived from bistrifluoromethyl benzidine and a repeating unit derived from m-phenylenediamine, and the repeating unit derived from m-phenylenediamine is derived from the diamine It is included in an amount of 10 to 20 mol% based on 100 mol% of the repeated unit,
The repeating unit derived from dianhydride includes a repeating unit derived from pyromellitic acid dianhydride and a repeating unit derived from biphenyl tetracarboxylic dianhydride, and the biphenyl tetracarboxylic dianhydride The repeating unit derived from the polyimide is included in a molar ratio of 1:1 to 1.5 compared to the repeating unit derived from the m-phenylenediamine. 5. The method of claim 4, wherein the repeating unit derived from diamine further comprises 1 to 10 mol% of the repeating unit derived from bisfluoroaminophenyl fluorene based on 100 mol% of the repeating unit derived from diamine. polyimide. The method according to claim 5, wherein the repeating unit derived from diamine exceeds 10 mol% by 20 mol% of the total amount of the repeating unit derived from m-phenylenediamine and the repeating unit derived from bisfluoroaminophenyl fluorene Polyimide, characterized in that it contains the following. A polyimide film comprising the polyimide according to any one of claims 4 to 6. An image display device comprising the polyimide film according to claim 7. preparing a diamine solution by adding and dissolving a diamine including bis trifluoromethyl benzidine and m-phenylenediamine in a solvent (S1);
A step (S2) of reacting by adding a dianhydride containing biphenyl tetracarboxylic dianhydride and pyromellitic acid dianhydride to the diamine solution prepared in step S1,
In the step S1, the m-phenylenediamine is included in an amount of 10 to 20 mol% based on 100 mol% of the diamine,
The method for producing a polyamic acid comprising the biphenyl tetracarboxylic dianhydride in the step S2 in a molar ratio of 1:1 to 1.5 with respect to the repeating unit derived from the m-phenylenediamine. 10. The method of claim 9, wherein in step S2, biphenyl tetracarboxylic dianhydride is added to the diamine solution prepared in step S1 for a primary reaction, followed by a secondary reaction by adding pyromellitic acid dianhydride A method for producing a polyamic acid, characterized in that. The method of claim 10, wherein the first reaction in step S2 is carried out at 25 to 30° C. for 3 to 5 hours. The method of claim 10, wherein the secondary reaction in step S2 is carried out at 25 to 40° C. for 12 to 20 hours.