JP4891411B2 - Polyimide resin, liquid crystal alignment film and polyimide film using the same - Google Patents

Description

  The present invention relates to a colorless and transparent polyimide resin, a liquid crystal alignment film and a polyimide film using the same.

In general, a polyimide (PI) resin is obtained by solution polymerization of an aromatic dianhydride component and an aromatic diamine component or an aromatic diisocyanate component to produce a polyamic acid derivative, followed by ring-closing dehydration at high temperature and imidization. It refers to a high heat resistant resin obtained by In order to produce a polyimide resin, pyromellitic dianhydride (PMDA) or biphenyltetracarboxylic dianhydride (BPDA) is used as an aromatic dianhydride component, and an oxygen diamine component is used as an oxygen diamine component. Aniline (ODA), p-phenylenediamine (p-PDA), m-phenylenediamine (m-PDA), methylenedianiline (MDA), bisaminophenylhexafluoropropane (HFDA) and the like are used.
Polyimide resin is an insoluble, infusible and ultra-high heat resistant resin, and has excellent properties such as heat resistance, oxidation resistance, radiation resistance, low temperature characteristics and chemical resistance. It is used in a wide range of fields including heat-resistant advanced materials such as aviation materials and spacecraft materials, and electronic materials such as insulating coating agents, insulating films, semiconductors, and electrode protection films for TFT-LCDs. Recently, polyimide resin is also used in display materials such as optical fibers and liquid crystal alignment films, and transparent electrode films made by mixing polymers and conductive fillers or applying conductive fillers to the surface of polymer films. It is used.
However, polyimide resins are colored brown or yellow due to high aromatic ring density and charge transfer interactions, which undesirably has low transmittance in the visible region. The yellow or brown color of the polyimide resin makes it difficult to apply to fields where transparency is required.
In order to solve such a problem, a method of purifying a monomer and a high-purity solvent for polymerization was attempted, but the improvement in transmittance was not great.

U.S. Pat. No. 5,053,480 discloses a method using an alicyclic dianhydride component in place of an aromatic dianhydride. This method improves the transparency and color in the solution phase or film phase as compared to the purification method described above, but there is a limit to the improvement in the transmittance and does not realize a high transmittance. Degradation of characteristics is caused.
In addition, U.S. Pat. No. 5986036, No. 6232428, and Korean Patent Publication No. 2003-0009437 are based on linking groups such as —O—, —SO ₂ —, CH ₂ —, and the like in the m-position instead of the p-position. Use of aromatic dianhydride having a bent structure or a substituent such as —CF ₃ and an aromatic diamine monomer, and improving transparency and color transparency within a range in which thermal characteristics are not greatly deteriorated There is a report that the polyimide of the structure was manufactured, but this polyimide is a semiconductor insulating film, TFT-LCD insulating film, electrode protective film, Mechanical properties to use the fine flexible display substrate for that yellowing degree and visible light transmittance is insufficient checked.

US Pat. No. 5,053,480 US Pat. No. 4,595,548 U.S. Pat. No. 4,603,061 US Pat. No. 4,645,824 US Pat. No. 4,895,972 US Pat. No. 5,218,083 US Pat. No. 5,093,453 U.S. Pat. No. 5218077 US Pat. No. 5,367,046 US Pat. No. 5,338,826 US Pat. No. 5,986,036 US Pat. No. 6,232,428 Korean Patent Publication No. 2003-0009437

  Therefore, the present invention provides a colorless and transparent polyimide resin excellent in physical properties such as mechanical properties and thermal stability, and a liquid crystal alignment film and a polyimide film using the same.

According to the first aspect of the present invention, it is produced by polymerizing an aromatic dianhydride component and an aromatic diamine component, and 2,2-bis (3,4-dicarboxyphenyl) is used as the aromatic dianhydride component. Hexafluoropropane dianhydride (6-FDA) and 4- (2,5-dioxotetrahydrofuran-3-yl) -1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic dianhydride (TDA) ) And 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl (2,2′-TFDB), 3,3′-bis (trifluoromethyl) -4 as an aromatic diamine component , 4′-diaminobiphenyl (3,3′-TFDB), 4,4′-bis (3-aminophenoxy) diphenylsulfone (DBSDA), bis (3-aminophenyl) sulfone (3-DDS), and A polyimide resin comprising one or a mixture of two or more selected from bis (4-aminophenyl) sulfone (4-DDS) is provided.
The polyimide resin according to the first aspect includes 2,2′-bis [4 (4-aminophenoxy) phenyl] hexafluoropropane (4-BDAF), 2,2′-bis [3 (3) as an aromatic diamine component. -Aminophenoxy) phenyl] hexafluoropropane (3-BDAF), 1,3-bis (3-aminophenoxy) benzene (APB-133), 1,3-bis (4-aminophenoxy) benzene (APB-134) , 1,4-bis (4-aminophenoxy) benzene (APB-144), and 2,2-bis [4- (4-aminophenoxy) phenyl] propane (6-HMDA) Or you may further contain 2 or more types of mixtures.
In the first embodiment, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6-FDA) is used in an amount of 1 to 99 mol% based on the total amount of the aromatic dianhydride component. May be used.
In the polyimide resin according to the first embodiment, 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl (2,2′-TFDB), 3,3′-bis (trifluoromethyl)- 4,4′-diaminobiphenyl (3,3′-TFDB), 4,4′-bis (3-aminophenoxy) diphenylsulfone (DBSDA), bis (3-aminophenyl) sulfone (3-DDS), and bis One or a mixture of two or more selected from (4-aminophenyl) sulfone (4-DDS) may be used in an amount of 10 to 90 mol% based on the total amount of the diamine component.

According to the 2nd aspect of this invention, the liquid crystal aligning film containing the said polyimide resin is provided.
The liquid crystal alignment film according to the second aspect may have a pretilt angle of 0 to 2 °.
According to the 3rd aspect of this invention, the polyimide film containing the said polyimide resin is provided.

The polyimide film according to the third aspect has an average transmittance at 380 to 780 nm of 85% or more and an average transmittance at 551 to 780 nm when the transmittance is measured with a UV spectrometer based on a film thickness of 50 to 100 μm. May be 88% or more.
When the transmittance of the polyimide film according to the third aspect is measured with a UV spectrometer based on a film thickness of 50 to 100 μm, the transmittance at 550 nm is 88% or more, the transmittance at 500 nm is 85% or more, and the transmittance at 420 nm. The degree may be 50% or more.
The polyimide film according to the third aspect may have a yellowing degree of 15 or less based on a film thickness of 50 to 100 μm.
The polyimide film according to the third aspect may have a dielectric constant of 3.0 or less at 1 GHz based on a film thickness of 50 to 100 μm.
The polyimide film according to the third aspect may have an average coefficient of thermal expansion (CTE) at 50 to 200 ° C. of 50 ppm or less based on a film thickness of 50 to 100 μm.
The polyimide film according to the third aspect may have an elastic modulus of 3.0 GPa or more based on a film thickness of 50 to 100 μm.
The polyimide film according to the third aspect may have a 50% cut-off wavelength by UV of 400 nm or less based on a film thickness of 50 to 100 μm.

  Since the present invention is colorless and transparent and has excellent physical properties such as mechanical properties and thermal stability, various fields such as semiconductor insulating films, TFT-LCD insulating films, passivation films, liquid crystal alignment films, optical communication materials, A polyimide resin that can be used for a protective film for a solar cell, a flexible display substrate, and the like, and a liquid crystal alignment film and a polyimide film using the polyimide resin can be provided.

FIG. 1 shows a liquid crystal alignment film manufactured using the polyimide resin of the present invention.

Hereinafter, the present invention will be described in more detail.
The present invention is directed to a polyimide resin composed of a copolymer of a diamine component and a dianhydride component, and a liquid crystal alignment film and a polyimide film using the polyimide resin. The liquid crystal alignment film and the polyimide film used are directed.

For this purpose, the aromatic dianhydride component used is 2,2-bis (3,4-dicarboxyxyphenyl) hexafluoropropane dianhydride (6-FDA), and 4- (2,5- Dioxotetrahydrofuran-3-yl) -1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride (TDA) is essential.
At this time, the FDA component is used in an amount of 1 to 99 mol%, preferably 10 to 90 mol%, based on the total amount of the dianhydride component.
This makes it possible to produce polyamic acids that are transparent, have high visible light transmission, low UV absorption and yellowing, and high viscosity.

  On the other hand, the aromatic diamine component used in the present invention is 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl (2,2′-TFDB), 3,3′-bis (tri Fluoromethyl) -4,4′-diaminobiphenyl (3,3′-TFDB), 4,4′-bis (3-aminophenoxy) diphenylsulfone (DBSDA), bis (3-aminophenyl) sulfone (3-DDS ), And a mixture of two or more selected from bis (4-aminophenyl) sulfone (4-DDS).

  In addition, aromatic diamine components include 2,2′-bis [4 (4-aminophenoxy) phenyl] hexafluoropropane (4-BDAF), 2,2′-bis [3 (3-aminophenoxy) phenyl]. Hexafluoropropane (3-BDAF), 1,3-bis (3-aminophenoxy) benzene (APB-133), 1,3-bis (4-aminophenoxy) benzene (APB-134), 1,4-bis One or a mixture of two or more selected from (4-aminophenoxy) benzene (APB-144) and 2,2-bis [4- (4-aminophenoxy) phenyl] propane (6-HMDA) Can further be included.

  In this case, the 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl (2,2′-TFDB), 3,3′-bis (trifluoromethyl) -4,4′-diamino is used. Biphenyl (3,3′-TFDB), 4,4′-bis (3-aminophenoxy) diphenylsulfone (DBSDA), bis (3-aminophenyl) sulfone (3-DDS), and bis (4-aminophenyl) One or a mixture of two or more selected from sulfone (4-DDS) can be used in an amount of 10 to 90 mol%, preferably 20 to 80 mol%, based on the total amount of the diamine component. Thereby, high transparency and transparency can be realized, and electrical characteristics, thermal characteristics and mechanical characteristics can be improved.

The dianhydride component and the diamine component are dissolved in an equimolar amount in an organic solvent and then reacted to produce a polyamic acid solution.
Although reaction conditions are not specifically limited, For example, reaction temperature is -20-80 degreeC, and reaction time is 2-48 hours. The reaction is preferably carried out under an inert atmosphere such as argon or nitrogen.
The organic solvent for the monomer solution polymerization reaction described above is not particularly limited as long as it is a solvent that dissolves polyamic acid. As a known reaction solvent, 1 selected from m-cresol, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), acetone and diethyl acetate More than one type of polar solvent is useful. In addition, a low-boiling point solution such as tetrahydrofuran (THF) or chloroform, or a low-absorbing solvent such as γ-butyrolactone can be used.
The amount of the organic solvent is not particularly limited, but in order to obtain an appropriate molecular weight and viscosity of the polyamic acid solution, the amount of the organic solvent is preferably 50 to 95% by weight, more preferably 70 to 70% by weight based on the total amount of the polyamic acid solution. 90% by weight.
The polyamic acid solution thus produced is imidized to produce a polyimide resin having a glass transition temperature of 200 to 350 ° C.

  In order to form a liquid crystal alignment film using the polyamic acid produced from the monomer, the polyamic acid is spin-coated or roll-coated on a glass substrate (generally ITO glass), then 80 ° C./5 minutes, Through a thermosetting process at 250 ° C./20 minutes, the solvent is removed and at the same time polyimide is formed. Thereby, a thin film (usually about 10 to 1000 nm) is formed on the glass substrate. At this time, the prepared polyamic acid solution is diluted to an appropriate coating solution viscosity of 10 to 50 cps and used for improving coating property or surface flatness and process applicability. At this time, the solvent used for dilution is not limited to the solvent used for polymerization. Known diluent solvents include polar solvents such as N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), γ-butyrolactone, and 2-n-butoxyethanol. Can be used alone or in admixture.

In order to be useful for the formation of a liquid crystal alignment film, the polyamic acid coating solution prepared from the monomer can be manufactured by one or more methods selected from the manufacturing methods listed below:
1. A method using a polyamic acid solution,
2. A method in which a polyamic acid polymer is polyimideized through heat and / or chemical curing and then precipitated for the formation of a resin, and then dissolved in an organic solvent, thereby obtaining a solution as a coating solution;
3.2. A method of subjecting the polyamic acid polymer to heat and / or chemical curing for polyimidization (without resinification), thereby obtaining a coating liquid,
4.1. And 2. Or 3. A method of mixing a solution of form, thereby obtaining a coating liquid,
5.1. To the polyamic acid solution of 2. A method of obtaining a coating liquid by adding (dissolving) the resin produced by the method of 1.
In addition, the coating solution produced by the above method can be subjected to two or more stages of filtration using a filter having a pore size selected within a range of 0.1 to 5 μm and an ion filter immediately before the coating process. .

When the liquid crystal alignment film is formed using the polyimide resin of the present invention, a stable pretilt angle is realized. The term “pretilt angle” refers to an angle at which the liquid crystal is slightly tilted in advance in order to increase the response speed to the voltage when applying a voltage to the liquid crystal and arranging the liquid crystal in a certain direction. Since the liquid crystal alignment film containing the polyimide resin of the present invention exhibits a stable pretilt angle of 0 to 2 °, it can be applied as an alignment film for an IPS (In-Plane Switching) mode that requires a pretilt angle of less than 2 °. .
Furthermore, when manufacturing a polyimide film using the polyamic acid solution,

A filler can be added to the polyamic acid solution for the purpose of improving various properties such as slidability, thermal conductivity, conductivity, and corona resistance of the polyimide film. The filler is not particularly limited, and specific examples include silica, titanium oxide, layered silica, carbon nanotube, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica and the like.
The particle size of the filler varies depending on the properties of the film to be modified and the type of filler to be added, and is not particularly limited, but generally the average particle size is 0.001 to 50 μm, preferably 0.005 to 25 μm, Preferably it is 0.01-10 micrometers. In this case, the modification effect of the polyimide film is likely to appear, and good surface properties, conductivity and mechanical properties can be obtained in the polyimide film.
Further, the addition amount of the filler is not particularly limited and varies depending on the film characteristics to be modified, the particle size of the filler, and the like. Generally, the addition amount of the filler is 0.001 to 20 parts by weight, preferably 0.01 to 10 parts by weight with respect to 100 parts by weight of the polyamic acid solution.
The method of adding the filler is not particularly limited, but includes, for example, a method of adding to the polyamic acid solution before or after polymerization, a method of kneading the filler using a 3-roll mill after completion of polyamic acid polymerization, and a filler. Examples thereof include a method of mixing the dispersion with a polyamic acid solution.

The method for producing a polyimide film from the obtained polyamic acid solution is not particularly limited, and a commonly known method can be used. Examples of the method for imidizing the polyamic acid solution include a thermal imidization method and a chemical imidization method, but it is preferable to use a chemical imidization method. In the chemical imidization method, a polyhydric acid solution is applied with a dehydrating agent such as an acid anhydride (for example, acetic acid anhydride) and an imidization catalyst such as a tertiary amine (for example, isoquinoline, β-picoline, pyridine). It is. A thermal imidization method may be used in combination with the chemical imidization method. The heating conditions can vary depending on the type of polyamic acid solution and the thickness of the film.
The polyamide acid solution is partially cured and dried by heating the polyamic acid solution on the support at 80 to 200 ° C., preferably 100 to 180 ° C. to activate the dehydrating agent and imidization catalyst, and then the gel polyamide The acid film is peeled off from the support, and the gel film is heated at 200 to 400 ° C. for 5 to 400 seconds to obtain a polyimide film.
The thickness of the obtained polyimide film is not particularly limited, but is 10 to 250 μm, preferably 25 to 150 μm in consideration of the application field.
When the transmittance of a polyimide film manufactured in the present invention is measured with a UV spectrometer based on a film thickness of 50 to 100 μm, the transmittance at 550 nm is 88% or more, the transmittance at 500 nm is 85% or more, and at 420 nm. The transmittance is 50% or more. Furthermore, the average transmittance at 380 to 780 nm is preferably 85% or more, and the average transmittance at 551 to 780 nm is preferably 88% or more.
Moreover, it is preferable that a yellowing degree is 15 or less on the basis of film thickness 50-100micrometer.

The polyimide film of the present invention that satisfies the above-mentioned transmittance and yellowing degree is difficult to use due to the yellow color of the existing polyimide film, and is required to be transparent, i.e., a protective film, or diffusion in a TFT-LCD. It can be used for a plate and a coating film (for example, an interlayer of a TFT-LCD, a gate insulating film, a liquid crystal alignment film, etc.), and has an opening when the transparent polyimide is applied to the liquid crystal alignment film. This contributes to an increase in the rate and enables the production of a TFT-LCD with a high contrast ratio, and the polyimide film of the present invention can be used for a flexible display substrate.
In addition, the polyimide film of the present invention has a dielectric constant of 1 or less at 1 GHz, and can be used as a passivation film in a semiconductor.
The polyimide film of the present invention has an average coefficient of thermal expansion (CTE) at 50 to 200 ° C. of 50 ppm or less. When the CTE exceeds 50 ppm, the polyimide film contracts or expands in accordance with the change in process temperature when applied to a TFT array (TFT array) process in which a thin film transistor (TFT) is placed on the film. Alignment is not realized. Moreover, there exists a problem that a film cannot maintain horizontal (flattening) property and distortion generate | occur | produces. Therefore, the smaller the CTE value, the more precise TFT process is possible.
The polyimide film of the present invention has an elastic modulus of 3.0 GPa or more. In this case, application to a roll-to-roll manufacturing process for a flexible display substrate is even easier. When a polyimide film is used as a flexible display and a substrate film for FCCL, a roll-to-roll process is performed. At this time, since the film receives tension from winding and unwinding from the roll, the use of a film having an elastic modulus of less than 3.0 GPa may cause breakage of the film.
The polyimide film of the present invention has a 50% cutoff wavelength of 400 nm or less when the transmittance is measured with a UV spectrometer. Therefore, the polyimide film of the present invention can also be used as a surface protective film for solar cells and the like.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, these Examples do not limit the scope of the present invention.
<Example 1>

After charging 33.5386 g of N, N-dimethylacetamide (DMAc) while passing nitrogen through a 100 mL 3-neck round bottom flask reactor equipped with stirrer, nitrogen injector, dropping funnel, temperature controller and concentrator The reactor temperature was lowered to 0 ° C. There, 3.69222 g (0.007 mol) of 4-BDAF and 0.7449 g (0.003 mol) of 3-DDS were dissolved, and this solution was maintained at 0 ° C. After adding 3.1097 g (0.007 mol) of 6-FDA and 0.90078 g (0.003 mol) of TDA to the solution, the mixture was left for 1 hour until 6-FDA and TDA were completely dissolved. Stir. The solid content was 20% by weight. The resulting solution was stirred at room temperature for 8 hours to obtain a polyamic acid solution having a viscosity at 23 ° C. of 2200 cps.
Thereafter, the obtained polyamic acid solution was cast on a glass substrate to a thickness of 500 μm to 1000 μm using a doctor blade, and dried in a vacuum oven at 40 ° C. for 1 hour and 60 ° C. for 2 hours. After obtaining a self supporting film, the film was heated at a rate of 5 ° C./min for 3 hours at 80 ° C. for 3 hours, 100 ° C. for 1 hour, 200 ° C. for 1 hour, 300 ° C. using a high temperature oven. For 30 minutes to obtain polyimide films having thicknesses of 50 μm and 100 μm.

<Example 2>
As in Example 1, 3.69222 g (0.007 mol) of 4-BDAF was dissolved in 33.5386 g of DMAc, and 0.7449 g (0.003 mol) of 4-DDS was added thereto to be completely dissolved. I let you. To the solution, 3.1097 g (0.007 mol) of 6-FDA and 0.90078 g (0.003 mol) of TDA were sequentially added and stirred for 1 hour until 6-FDA and TDA were completely dissolved. The concentration of the solid content of the solution was 20% by weight. Thereafter, the solution was stirred at room temperature for 8 hours to obtain a polyamic acid solution having a viscosity at 23 ° C. of 2100 cps.
Thereafter, a polyimide film was produced in the same manner as in Example 1.

<Example 3>
As in Example 1, 2.04631 g (0.007 mol) of APB-133 was dissolved in 27.20696 g of DMAc,
449 g (0.003 mol) of 3-DDS was added thereto and completely dissolved. To the solution, 3.10975 g (0.007 mol) of 6-FDA and 0.90078 g (0.003 mol) of TDA were sequentially added and stirred for 1 hour until 6-FDA and TDA were completely dissolved. The concentration of the solid content of the solution was 20% by weight. Thereafter, the solution was stirred at room temperature for 8 hours to obtain a polyamic acid solution having a viscosity at 23 ° C. of 1900 cps.
Thereafter, a polyimide film was produced in the same manner as in Example 1.

<Example 4>
As in Example 1, 2.04631 g (0.007 mol) of APB-133 was dissolved in 27.20696 g of DMAc, and 0.7449 g (0.003 mol) of 4-DDS was added thereto and completely dissolved. I let you. To the solution, 3.10975 g (0.007 mol) of 6-FDA and 0.90078 g (0.003 mol) of TDA were sequentially added and stirred for 1 hour until 6-FDA and TDA were completely dissolved. The solid content was 20% by weight. Thereafter, the solution was stirred at room temperature for 8 hours to obtain a polyamic acid solution having a viscosity at 23 ° C. of 1950 cps.
Thereafter, a polyimide film was produced in the same manner as in Example 1.

<Example 5>
As in Example 1, 2.241161 g (0.007 mol) of 2,2′-TFDB was dissolved in 27.98796 g of DMAc, and 0.7449 g (0.003 mol) of 3-DDS was added thereto. It was completely dissolved. To the solution, 3.1097 g (0.007 mol) of 6-FDA and 0.90078 g (0.003 mol) of TDA were sequentially added and stirred for 1 hour until 6-FDA and TDA were completely dissolved. The concentration of the solid content of the solution was 20% by weight. Thereafter, the solution was stirred at room temperature for 8 hours to obtain a polyamic acid solution having a viscosity at 23 ° C. of 2000 cps.
Thereafter, a polyimide film was produced in the same manner as in Example 1.

<Example 6>
As in Example 1, 2.241161 g (0.007 mol) of 2,2′-TFDB and 0.7449 g (0.003 mol) of 4-DDS were added to 27.98796 g of DMAc and completely dissolved. It was. To the solution, 3.1097 g (0.007 mol) of 6-FDA and 0.90078 g (0.003 mol) of TDA were sequentially added and stirred for 1 hour until 6-FDA and TDA were completely dissolved. The solid content was 20% by weight. Thereafter, the solution was stirred at room temperature for 8 hours to obtain a polyamic acid solution having a viscosity at 23 ° C. of 2000 cps.
Thereafter, a polyimide film was produced in the same manner as in Example 1.

<Comparative Example 1>
As in Example 1, 5.1846 g (0.01 mol) of 4-BDAF was dissolved in 38.5084 g of DMAc, and then 4.4425 g (0.01 mol) of 6-FDA was added. The solution was stirred for 1 hour until 6-FDA was completely dissolved. The solid content was 20% by weight. Thereafter, the solution was stirred at room temperature for 8 hours to obtain a polyamic acid solution having a viscosity at 23 ° C. of 1300 cps.
Then, the polyimide film was manufactured by the method similar to Example 1, and the polyimide film of thickness 25micrometer, 50micrometer, and 100micrometer was obtained.

<Comparative Example 2>
Similarly to Example 1, 2.9233 g (0.01 mol) of APB-133 was dissolved in 29.4632 g of DMAc, and 4.4425 g (0.01 mol) of 6-FDA was added thereto. The solution was stirred for 1 hour until 6-FDA was completely dissolved. The solid content was 20% by weight. Thereafter, the solution was stirred at room temperature for 8 hours to obtain a polyamic acid solution having a viscosity at 23 ° C. of 1200 cps.
Thereafter, a polyimide film was produced in the same manner as in Comparative Example 1.

<Comparative Example 3>
In the same manner as in Example 1, 2.4830 g (0.01 mol) of 3-DDS was dissolved in 27.702 g of DMAc, and 4.4425 g (0.01 mol) of 6-FDA was added thereto. Stir for 1 hour until completely dissolved. The concentration of the solid content of the solution was 20% by weight. Thereafter, the solution was stirred at room temperature for 8 hours to obtain a polyamic acid solution having a viscosity at 23 ° C. of 1300 cps.
Thereafter, a polyimide film was produced in the same manner as in Comparative Example 1.

<Comparative Example 4>
In the same manner as in Example 1, 2.4830 g (0.01 mol) of 4-DDS was dissolved in 27.702 g of DMAc, and 4.4425 g (0.01 mol) of 6-FDA was added thereto. The solution was stirred for 1 hour until 6-FDA was completely dissolved. The concentration of the solid content of the solution was 20% by weight. Thereafter, the solution was stirred at room temperature for 8 hours to obtain a polyamic acid solution having a viscosity at 23 ° C. of 1400 cps.
Thereafter, a polyimide film was produced in the same manner as in Comparative Example 1.

<Comparative Example 5>
In the same manner as in Example 1, 2.0024 g (0.01 mol) of 3,3′-ODA was dissolved in 25.7796 g of DMAc, and 4.4425 g (0.01 mol) of 6-FDA was added. The resulting solution was stirred for 1 hour until 6-FDA was completely dissolved. The solid content was 20% by weight. Thereafter, the solution was stirred at room temperature for 8 hours to obtain a polyamic acid solution having a viscosity at 23 ° C. of 1600 cps.
Thereafter, a polyimide film was produced in the same manner as in Comparative Example 1.

<Comparative Example 6>
As in Example 1, 2.0024 g (0.01 mol) of 4,4′-ODA was dissolved in 16.7344 g of DMAc and obtained after adding 2.812 g (0.01 mol) of PMDA. The solution was stirred for 1 hour until the PMDA was completely dissolved. The solid content was 20% by weight. Thereafter, the solution was stirred at room temperature for 8 hours to obtain a polyamic acid solution having a viscosity of 2500 poise at 23 ° C.
Thereafter, a polyimide film was produced in the same manner as in Comparative Example 1.

The physical properties of the polyimide films produced in these examples and comparative examples were measured as follows and are shown in Tables 1 to 5.
(1) Transmittance and 50% cut-off wavelength The films produced in the examples were measured for visible light transmittance and 50% cut-off wavelength using a UV spectrometer (Varian, Cary 100).
(2) Yellowing degree Yellowing degree was measured according to ASTM E313 standard.
(3) Elastic modulus It measured based on JISK6301 using Universal Testing Machine Model 1000 of Instron.
(4) Glass transition temperature (Tg)
The glass transition temperature was measured using a differential scanning calorimeter (DSC, TA Instrument, Q200).
(5) Coefficient of thermal expansion (CTE)
The thermal expansion coefficient at 50 to 200 ° C. was measured by TMA method using TMA (TA Instrument, Q400).
(6) Dielectric constant The dielectric constant was measured based on ASTM D-150 standard.
(7) Pretilt angle
After diluting the polyamic acid solutions of Examples and Comparative Examples with γ-butyrolactone as a diluent solvent so that the solution viscosity becomes 10 to 50 cps, filters and ions having sizes of 2 μm, 0.45 μm, and 0.2 μm Filtration was performed using a filter, and a glass substrate (ITO Glass) was coated (coating conditions: spin coating, 400 to 4,000 rpm, 10 to 40 seconds). Thereafter, after a thermosetting process at 80 ° C. for 5 minutes and then at 250 ° C. for 20 minutes, the solvent was removed and at the same time polyimideization was performed to form a thin film (thickness 100 nm) on the glass substrate. The coated glass substrates 1 and 2 are used as upper and lower plates, and liquid crystal molecules 4 are injected into the space between the glass substrates 1 and 2 to produce a liquid crystal cell including the liquid crystal layer 5 (see FIG. 1). The pretilt angle of each liquid crystal cell was measured using (Crystal Rotation Method). The results are shown in Table 5.

As a result of evaluating physical properties such as transmittance and yellowing degree, the polyimide film of the present invention has a transmittance of 88% or more at 550 nm in the visible light region and 85% or more at 500 nm, despite the thickness of 50 μm and 100 μm. It was 50% or more at 420 nm. Further, the average transmittance at 380 to 780 nm was 85% or more, the average transmittance at 551 to 780 nm was 88% or more, and the yellowing degree was constantly low. Thereby, it was confirmed that the polyimide film of the present invention is very transparent.
In the comparative example, the average transmittance in the visible light region at 380 to 780 nm was not more than 85% regardless of the thickness. In Comparative Example 6, it was impossible to form a film having a thickness of 90 μm or more.
The polyimide film manufactured according to the embodiment of the present invention has a wavelength of 400 nm or less at which the transmittance is 50%, and uses a colorless and transparent polyimide film having excellent visible light transmittance as a surface protective film for solar cells or the like. It can be used. Furthermore, since the average thermal expansion coefficient of the polyimide is 50 ppm or less, it has excellent dimensional stability, and since the elastic modulus is 3.0 GPa or more, it has film characteristics applicable to a roll-to-roll process, The present invention can be applied to a TFT process for manufacturing a flexible display substrate material and an active drive type display element. Moreover, since a dielectric constant is 3.0 or less, it can be used as a semiconductor passivation film.
Since the liquid crystal alignment film manufactured with the polyimide resin of the present invention has a pretilt angle of 2 ° or less, it can also be used as an alignment film for IPS mode.

1, 2: Glass substrate 3: Alignment film 4: Liquid crystal molecule 5: Liquid crystal layer α: Pretilt angle

Claims (14)

  It is produced from a polymer of an aromatic dianhydride component and an aromatic diamine component, and the aromatic dianhydride component is 2,2′-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6 -FDA) and 4- (2,5-dioxotetrahydrofuran-3-yl) -1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic dianhydride (TDA), said aromatic diamine The component is 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl (2,2′-TFDB), 3,3′-bis (trifluoromethyl) -4,4′-diaminobiphenyl ( 3,3′-TFDB), 4,4′-bis (3-aminophenoxy) diphenylsulfone (DBSDA), bis (3-aminophenyl) sulfone (3-DDS), and bis (4-a Nofeniru) sulfone (4-DDS) 1 kind or a mixture of two or more of, a polyimide resin selected from among.   The aromatic diamine component is 2,2′-bis [4 (4-aminophenoxy) phenyl] hexafluoropropane (4-BDAF), 2,2′-bis [3 (3-aminophenoxy) phenyl] hexafluoro. Propane (3-BDAF), 1,3-bis (3-aminophenoxy) benzene (APB-133), 1,3-bis (4-aminophenoxy) benzene (APB-134), 1,4-bis (4 -Aminophenoxy) benzene (APB-144) and 2,2-bis [4- (4-aminophenoxy) phenyl] propane (6-HMDA) The polyimide resin according to claim 1, wherein the polyimide resin is contained.   The 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6-FDA) is used in an amount of 1 to 99 mol% based on the total amount of aromatic dianhydride components. The polyimide resin according to claim 1.   2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl (2,2′-TFDB), 3,3′-bis (trifluoromethyl) -4,4′-diaminobiphenyl (3 , 3′-TFDB), 4,4′-bis (3-aminophenoxy) diphenylsulfone (DBSDA), bis (3-aminophenyl) sulfone (3-DDS), and bis (4-aminophenyl) sulfone (4 The polyimide resin according to claim 2, wherein one or a mixture of two or more selected from -DDS) is used in an amount of 10 to 90 mol% based on the total amount of the diamine component.   The liquid crystal aligning film containing the polyimide resin of any one of Claims 1-4.   The liquid crystal alignment film according to claim 5, wherein a pretilt angle is 0 to 2 °.   The polyimide film containing the polyimide resin of any one of Claims 1-4.   When the transmittance is measured with a UV spectrometer based on a film thickness of 50 to 100 μm, the average transmittance at 380 to 780 nm is 85% or more, and the average transmittance at 551 to 780 nm is 88% or more. The polyimide film according to claim 7.   When the transmittance is measured with a UV spectrometer based on a film thickness of 50 to 100 μm, the transmittance at 550 nm is 88% or more, the transmittance at 500 nm is 85% or more, and the transmittance at 420 nm is 50% or more. The polyimide film according to claim 7, which is characterized.   The polyimide film according to claim 7, wherein the degree of yellowing based on a film thickness of 50 to 100 µm is 15 or less.   The polyimide film according to claim 7, wherein a dielectric constant at 1 GHz based on a film thickness of 50 to 100 μm is 3.0 or less.   The polyimide film according to claim 7, wherein an average coefficient of thermal expansion (CTE) at 50 to 200 ° C. based on a film thickness of 50 to 100 μm is 50 ppm or less.   The polyimide film according to claim 7, wherein an elastic modulus based on a film thickness of 50 to 100 μm is 3.0 GPa or more.   The polyimide film according to claim 7, wherein a 50% cutoff wavelength by UV based on a film thickness of 50 to 100 μm is 400 nm or less.