KR20080055531A - Colorless polyimide film - Google Patents

Abstract

A colorless and transparent polyimide film is provided to be superior in mechanical properties and heat stability, and to be usable for various applications such as a protective layer of a solar battery and a flexible display substrate. A polyimide film has an average transmittance of 85% or more at 380-780 nm as transmittance of the polyimide film having a thickness of 50-100 micron is measured by a UV spectrometer, and a degree of yellowing of 15 or less. The polyimide film has an optical density less than 50 at 420 nm, a dielectric constant of 3.0 or less at 1 GHz, and an average linear expansion coefficient of 50 ppm or less at 50-200 °C, and an elastic modulus of 3.0 GPa or more.

Description

Colorless and transparent polyimide film {Colorless polyimide film}

1 is a photograph taken with a polyimide film obtained in Example 1 of the present invention on a document,

FIG. 2 is a photograph of a polyimide film obtained in Comparative Example 1 placed on a document. FIG.

The present invention relates to a colorless transparent polyimide film.

In general, a polyimide (PI) film is a film of a polyimide resin. The polyimide resin is a solution polymerization of an aromatic dianhydride and an aromatic diamine or an aromatic diisocyanate to prepare a polyamic acid derivative, followed by ring dehydration at high temperature. The high heat resistant resin manufactured by imidation is called. In order to prepare a polyimide resin, pyromellitic dianhydride (PMDA) or biphenyltetracarboxylic dianhydride (BPDA) is mainly used as an aromatic dianhydride component, and oxydianiline (ODA), p-phenylene diamine (p-PDA), m-phenylene diamine (m-PDA), methylenedianiline (MDA), bisaminophenylhexafluoropropane (HFDA), etc. are mainly used.

Polyimide resin is an insoluble and insoluble ultra high heat resistant resin, and has excellent characteristics such as heat oxidation resistance, heat resistance, radiation resistance, low temperature property, chemical resistance, and so on. It is used in a wide range of fields for electronic materials such as insulating films, semiconductors, electrode protective films of TFT-LCDs, and recently, it has been used in transparent electrode films and the like by containing conductive fillers in the display materials and films such as optical fibers and liquid crystal alignment films or by coating the surfaces thereof.

However, polyimide resins are colored brown or yellow due to the high aromatic ring density, and thus have a low transmittance in the visible region and a yellow-based color, which makes it difficult to be used in applications requiring transparency due to low light transmittance.

In order to solve this problem, a method of polymerizing the monomer and the solvent by high purity has been attempted, but the improvement of the transmittance is not large.

U.S. Patent No. 553480 describes a method of using an aliphatic ring-based dianhydride component instead of an aromatic dianhydride, and compared to the purification method, there was an improvement in transparency and color when solution or film was formed, but also an improvement in permeability. There was a limit to the high permeability was not satisfactory, and also resulted in degradation of thermal and mechanical properties.

See also U.S. Pat.Nos. 4,595,548,4603061, 4,464,824,4895972, 52,18083, 5,345,3, 52,18077, 53,670, 46,337. 5986036, 6262328 and Korean Patent Laid-Open No. 2003-0009437 disclose monomers having a curved structure connected to a linking group, such as -O-, -SO2-, CH2-, etc. to the m-position rather than the p-position, or -CF3. There have been reports of a novel polyimide structure having improved permeability and color transparency by using aromatic dianhydride dianhydride and an aromatic diamine monomer having substituents such as the like, but the thermal properties are not significantly reduced. Yellowness and visible light transmittance have been insufficient to be used as a semiconductor insulating film, a TFT-LCD insulating film, an electrode protective film, and a base layer for a flexible display.

Accordingly, an object of the present invention is to provide a polyimide film having colorless transparency and excellent mechanical properties and thermal stability properties.

The present invention for achieving the above object provides a polyimide film having an average transmittance of 85% or more and a yellowing degree of 15 or less at 380 to 780 nm when measuring transmittance with a UV spectrometer based on a film thickness of 50 to 100 μm. .

The polyimide film has an average transmittance of 88% or more at 551 to 780 nm and a transmittance of at least 88% at 550 nm and a transmittance of 85% at 500 nm, based on a film thickness of 50 to 100 μm, when measuring transmittance with a UV spectrometer. The transmittance is 50% or more at 420 nm.

The polyimide film has an optical density of less than 50 at 420 nm based on a film thickness of 50 to 100 μm.

The polyimide resin for preparing the polyimide film is 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (FDA), 4- (2,5-di) as an aromatic dianhydride. Oxotetrahydrofuran-3-yl) -1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride (TDA) and 4,4 '-(4,4'-isopropyl It includes at least one selected from liddenephenoxy) bis (phthalic anhydride) (HBDA), characterized in that it comprises at least one component represented by the formula (1) as an aromatic diamine.

<Formula 1>

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Among the structures selected.

The polyimide film is characterized by a dielectric constant of 3.0 or less at 1 GHz.

The polyimide film has an average linear expansion coefficient (CTE) of 50 ppm or less at 50 to 200 ° C.

The polyimide film has an elastic modulus of 3.0 GPa or more.

The polyimide film is characterized in that 50% cut off wavelength (400 nm or less) when measuring transmittance with a UV spectrometer.

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

The polyimide film of the present invention is formed by filming a polyimide resin produced by copolymerizing a diamine component and a dianhydride component, and is particularly a colorless and transparent polyimide film.

The polyimide film prepared in the present invention preferably has an average transmittance of 85% or more at 380 to 780 nm when measuring transmittance with a UV spectrophotometer based on a film thickness of 50 to 100 μm, and based on a film thickness of 50 to 100 μm. It is preferable that yellowness is 15 or less.

Furthermore, when measuring transmittance with UV spectrometer based on film thickness of 50-100 μm, the average transmittance at 551-780 nm is 88% or more, the transmittance is 88% or more at 550 nm, the transmittance is 85% or more at 500 nm, and 420 nm. It is preferable that the transmittance is at least 50%.

The polyimide film of the present invention that satisfies the above-mentioned transmittance and yellowing degree is used for diffusion plates and coating films in protective films or TFT-LCDs, which are limited in use due to the yellow color of existing polyimide films, such as in interlayers and gates in TFT-LCDs. It can be used in fields requiring transparency such as insulator and liquid crystal alignment film, and it is possible to manufacture high-contrast TFT-LCD by contributing to increase of aperture ratio when applying transparent polyimide as liquid crystal alignment film. It can also be used for flexible display substrates.

In addition, the polyimide film of the present invention has an optical density of less than 50 at 420 nm based on a film thickness of 50 to 100 μm, and the polyimide film satisfying the optical density and the transmittance is a refractive index which is a scattering phenomenon of light passing through the film. It is possible to reduce the birefringence and the retardation (because the distortion of the color, size, position, etc. of the object through the film) becomes smaller, so that the above-mentioned transparency can be used.

The aromatic dianhydrides used for this purpose are not particularly limited, but 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (FDA), 4- (2,5-dioxotetra) Hydrofuran-3-yl) -1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride (TDA) and 4,4 '-(4,4'-isopropylidenedephenoxy It is preferable to include one or more selected from c) bis (phthalic anhydride) (HBDA).

In addition, although the aromatic diamine used by this invention is not specifically limited, It is preferable to further include the component represented by following formula (1).

<Formula 1>

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Selected structure.

The dianhydride component and the diamine component described above are dissolved in an organic solvent in an equimolar amount to react to prepare a polyamic acid solution.

Although the conditions at the time of reaction are not specifically limited, The reaction temperature is preferably -20 to 80 ° C, and the reaction time is preferably 2 to 48 hours. Moreover, it is more preferable that it is inert atmosphere, such as argon and nitrogen, at the time of reaction.

The organic solvent for the solution polymerization of the monomers described above is not particularly limited as long as it is a solvent in which the polyamic acid is dissolved. Known reaction solvents selected from m-cresol, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), acetone, diethyl acetate One or more polar solvents are used. In addition, low boiling point solutions such as tetrahydrofuran (THF), chloroform or low absorbing solvents such as γ-butyrolactone may be used.

The content 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 content of the organic solvent is preferably 50 to 95% by weight of the total polyamic acid solution, and more preferably 70 to 90% by weight. It is more preferable that is.

In addition, when preparing a polyimide film using a polyamic acid solution, a filler may be added to the polyamic acid solution for the purpose of improving various properties such as the sliding property, thermal conductivity, conductivity, and corona resistance of the polyimide film. Although it does not specifically limit as a filler, As a preferable specific example, a silica, titanium oxide, layered silica, carbon nanotube, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica, etc. are mentioned.

The particle diameter of the filler may vary depending on the characteristics of the film to be modified and the type of filler to be added, but is not particularly limited, but in general, the average particle diameter is preferably 0.001-50 μm, and preferably 0.005-25 μm. It is more preferable, More preferably, it is good that it is 0.01-10 micrometers. In this case, the modification effect of a polyimide film tends to appear, and favorable surface property, electroconductivity, and a mechanical characteristic can be acquired in a polyimide film.

Moreover, it does not specifically limit as it can fluctuate also with the film characteristic to be modified, filler particle diameter, etc. about the addition amount of the said filler. Generally, it is preferable that the addition amount of a filler is 0.001-20 weight part with respect to 100 weight part of polyamic-acid solutions, More preferably, it is 0.01-10 weight part.

The addition method of a filler is not specifically limited, For example, the method of adding to a polyamic-acid solution before superposition | polymerization or after superposition | polymerization, the method of kneading a filler using 3 rolls etc. after completion | finish of polyamic acid polymerization, the dispersion liquid containing filler The method of preparing and mixing this into a polyamic-acid solution, etc. are mentioned.

The method of manufacturing a polyimide film from the obtained polyamic-acid solution is not specifically limited, A conventionally well-known method can be used. As a method of imidating a polyamic-acid solution, a thermal imidation method and a chemical imidation method are mentioned, It is more preferable to use a chemical imidation method. The chemical imidization method is a method of applying an imidization catalyst represented by a dehydrating agent represented by acid anhydrides such as acetic anhydride and tertiary amines such as isoquinoline, β-picolin and pyridine to the polyamic acid solution. The thermal imidation method may be used in combination with the chemical imidization method, and the heating conditions may vary depending on the type of the polyamic acid solution, the thickness of the film, and the like.

The polyamic acid solution was heated at 80-200 ° C. on the support, preferably 100-180 ° C. to activate the dehydrating agent and the imidization catalyst, thereby partially curing and drying the polyamic acid film in a gel state to obtain the gel from the support, and the gel The film of a state is heated at 200-400 degreeC for 5 to 400 second, and a polyimide film is obtained.

Although the thickness of the polyimide film obtained is not specifically limited, It is preferable that it is the range of 10-250 micrometers, More preferably, it is 25-150 micrometers.

In addition, the polyimide film of the present invention preferably has a dielectric constant of 3.0 or less at 1 GHz, which makes it possible to use a passivation film in a semiconductor.

Meanwhile, the polyimide film of the present invention preferably has an average linear expansion coefficient (CTE) of 50 ppm or less at 50 to 200 ° C., and when the polyimide film is more than 50 ppm, the polyimide in the process of raising a thin film transistor (TFT) on the film (TFT ARRAY) In case of using film, alignment is not matched in electrode doping process because the film shrinks / expands according to process temperature change, and the film does not maintain horizontality (flattening), resulting in warpage. There is a problem. Therefore, the smaller the CTE value, the more precise TFT processing is possible.

In addition, the polyimide film of the present invention preferably has an elastic modulus of 3.0 GPa or more. In this case, the polyimide film may be more easily applied to a roll-to-roll manufacturing process for a flexible display substrate. When the polyimide film is used as a flexible display and a substrate film for FCCL, it undergoes a roll-to-roll process, and the film is subjected to tension between winding and unrolling between rolls, and has an elastic modulus of less than 3.0 GPa. This is because breakage of the film occurs when a film having a value is used.

The polyimide film of the present invention preferably has a 50% cut off wavelength of 400 nm or less when measuring transmittance with a UV spectrometer. Therefore, the polyimide film of the present invention can be used as a surface protective film such as a solar cell.

On the other hand, the polyimide resin of the present invention has a stable pretilt angle when used as a liquid crystal alignment film. The pretilt angle refers to an angle in which the liquid crystal is set up in advance in order to increase the response speed against the voltage when the liquid crystals are arranged in a predetermined direction by applying a voltage to the liquid crystal. The liquid crystal alignment layer including the polyimide resin of the present invention is 0 Since a stable pretilt angle of ˜2 μs is exhibited, the present invention can be applied as an alignment film for an IPS (In-Plane Switching) mode requiring a pretilt angle of less than 2 μs.

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

<Example 1>

The reactor was filled with 34.1904 g of N, N-dimethylacetaamide (DMAc) while passing nitrogen through a 100 ml 3-Neck round bottom flask equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller and a cooler. After lowering the temperature to 0 ° C., 4.1051 g (0.01 mol) of 6-HMDA was dissolved to maintain this solution at 0 ° C. 4.4425 g (0.01 mol) of 6-FDA was added thereto and stirred for 1 hour to completely dissolve 6-FDA. At this time, the concentration of the solid was 20% by weight, after which the solution was left at room temperature and stirred for 8 hours. At this time, the solution viscosity at 23 degreeC was obtained the polyamic-acid solution of 2400poise.

After completion of the reaction, the polyamic acid solution obtained was cast to a thickness of 500㎛ ~ 1000㎛ by using a doctor blade on a glass plate and dried in a vacuum oven for 1 hour at 40 ℃, 2 hours at 60 ℃ to obtain a self standing film A polyimide film having a thickness of 50 μm and 100 μm was obtained by heating at 80 ° C. for 3 hours at 100 ° C., 1 hour at 100 ° C., 1 hour at 200 ° C., and 30 minutes at 300 ° C. in a high temperature furnace oven.

<Example 2>

6-HMDA 2.87357g (0.007mol) was dissolved in 32.2438g of N, N-dimethylacetaamide (DMAc) in Example 1, 4-449 DS (0.003mol) of 4-DDS was completely dissolved, and 6-FDA was dissolved. 4.4425 g (0.01 mol) was added and stirred for 1 hour to completely dissolve 6-FDA. At this time, the concentration of the solid was 20% by weight, after which the solution was left at room temperature and stirred for 8 hours. At this time, the polyamic-acid solution whose solution viscosity in 23 degreeC is 2300 poise was obtained.

Thereafter, a polyimide film was prepared in the same manner as in Example 1.

<Example 3>

In Example 1, 4.1051 g (0.01 mol) of 6-HMDA was dissolved in 32.4623 g of N, N-dimethylacetaamide (DMAc), and 3.1097 g (0.007 mol) of 6-FDA was added, followed by 0.90078 g (0.003 of TDA). mol) was added and stirred for 1 hour to completely dissolve 6-FDA and TDA. At this time, the concentration of the solid was 20% by weight, after which the solution was left at room temperature and stirred for 8 hours. At this time, the polyamic-acid solution whose solution viscosity in 23 degreeC is 2200 poise was obtained.

Thereafter, a polyimide film was prepared in the same manner as in Example 1.

<Example 4>

In Example 1, 2.87357 g (0.007 mol) of 6-HMDA was dissolved in 30.5158 g of N, N-dimethylacetamide (DMAc), and 0.7449 g (0.003 mol) of 4-DDS was completely dissolved. 6-FDA 3.1097g (0.007mol) was added and TDA 090078g (0.003mol) was added and stirred for 1 hour to completely dissolve 6-FDA and TDA. At this time, the concentration of the solid was 20% by weight, after which the solution was left at room temperature and stirred for 8 hours. At this time, the polyamic-acid solution whose solution viscosity in 23 degreeC is 2000 poise was obtained.

Thereafter, a polyimide film was prepared in the same manner as in Example 1.

<Example 5>

After filling 35.07 g of N, N-dimethylacetaamide (DMAc) in Example 1, the temperature of the reactor was lowered to 0 ° C. and 4.325 g (0.01 mol) of DBSDA was dissolved to maintain this solution at 0 ° C. 4.4425 g (0.01 mol) of 6-FDA was added thereto and stirred for 1 hour to completely dissolve 6-FDA. At this time, the concentration of the solid was 20% by weight, after which the solution was left at room temperature and stirred for 8 hours. At this time, the solution viscosity at 23 degreeC was obtained the polyamic-acid solution of 2100 poise.

Thereafter, a polyimide film was prepared in the same manner as in Example 1.

<Example 6>

In Example 5, 1.2975 g (0.003 mol) of DBSDA was dissolved in 29.9124 g of N, N-dimethylacetaamide (DMAc), and dissolved completely by adding 1.7381 g (0.007 mol) of 3-DDS, followed by 6-FDA. 4.4425 g (0.01 mol) was added and stirred for 1 hour to completely dissolve 6-FDA. At this time, the concentration of the solid was 20% by weight, after which the solution was left at room temperature and stirred for 8 hours. At this time, the polyamic-acid solution whose solution viscosity in 23 degreeC is 1800 poise was obtained.

Thereafter, a polyimide film was prepared in the same manner as in Example 1.

<Example 7>

After filling 30.5792 g of N, N-dimethylacetaamide (DMAc) in Example 1, the temperature of the reactor was lowered to 0 ° C. and 3.2023 g (0.01 mol) of 2,2′-TFDB was dissolved to dissolve the solution at 0 ° C. Was maintained. 4.4425 g (0.01 mol) of 6-FDA was added thereto and stirred for 1 hour to completely dissolve 6-FDA. At this time, the concentration of the solid was 20% by weight, after which the solution was left at room temperature and stirred for 8 hours. At this time, the solution viscosity at 23 degreeC was obtained the polyamic-acid solution of 2400poise.

Thereafter, a polyimide film was prepared in the same manner as in Example 1.

<Example 8>

In Example 7, 2,2′-TFDB 1.60115g (0.005mol) was dissolved in 32.3846g of N, N-dimethylacetaamide (DMAc), and 6525H (2.0525g (0.005mol)) of 6-HMDA was completely dissolved. Thereafter, 4.4425 g (0.01 mol) of 6-FDA was added and stirred for 1 hour to completely dissolve 6-FDA. At this time, the concentration of the solid was 20% by weight, after which the solution was left at room temperature and stirred for 8 hours. At this time, the polyamic-acid solution whose solution viscosity in 23 degreeC is 2300 poise was obtained.

Thereafter, a polyimide film was prepared in the same manner as in Example 1.

Example 9

In Example 7, 2,2′-TFDB 2.24161 g (0.007 mol) was dissolved in 27.98796 g of N, N-dimethylacetaamide (DMAc), and 0.7449 g (0.003 mol) of 4-DDS was completely dissolved. Thereafter, 3.1097 g (0.007 mol) of 6-FDA was added thereto, and 0.90078 g (0.003 mol) of TDA was added thereto, followed by stirring for 1 hour to completely dissolve 6-FDA and TDA. At this time, the concentration of the solid was 20% by weight, after which the solution was left at room temperature and stirred for 8 hours. At this time, the polyamic-acid solution whose solution viscosity in 23 degreeC is 2000 poise was obtained.

Thereafter, a polyimide film was prepared in the same manner as in Example 1.

<Example 10>

After filling 32.5132 g of N, N-dimethylacetaamide (DMAc) in Example 1, the temperature of the reactor was lowered to 0 ° C. and 2.9233 g (0.01 mol) of APB-133 was dissolved and maintained at 0 ° C. 5.205 g (0.01 mol) of 6-HBDA was added and stirred for 1 hour to completely dissolve 6-HBDA. At this time, the concentration of the solid was 20% by weight, after which the solution was left at room temperature and stirred for 8 hours. At this time, the polyamic-acid solution whose solution viscosity in 23 degreeC is 2000 poise was obtained.

Thereafter, a polyimide film was prepared in the same manner as in Example 1.

<Example 11>

After filling 28.8296 g of N, N-dimethylacetamide (DMAc) in Example 1, the temperature of the reactor was lowered to 0 ° C. and 2.0024 g (0.01 mol) of 3,3′-ODA was dissolved and maintained at 0 ° C. . 5.205 g (0.01 mol) of 6-HBDA was added and stirred for 1 hour to completely dissolve 6-HBDA. At this time, the concentration of the solid was 20% by weight, after which the solution was left at room temperature and stirred for 8 hours. At this time, the polyamic-acid solution whose solution viscosity in 23 degreeC is 2200 poise was obtained.

Thereafter, a polyimide film was prepared in the same manner as in Example 1.

<Example 12>

After filling 30.986 g of N, N-dimethylacetaamide (DMAc) in Example 1, the temperature of the reactor was lowered to 0 ° C. and 3.2023 g (0.01 mol) of 2,2′-TFDB was dissolved to dissolve the solution at 0 ° C. Was maintained. 6.64355g (0.007mol) of 6-HBDA was added, followed by 0.90078g (0.003mol) of TDA, followed by stirring for 1 hour to completely dissolve 6-HBDA and TDA. At this time, the concentration of the solid was 20% by weight, after which the solution was left at room temperature and stirred for 8 hours. At this time, the polyamic-acid solution whose solution viscosity in 23 degreeC is 2000 poise was obtained.

Thereafter, a polyimide film was prepared in the same manner as in Example 1.

Example 13

In Example 1, 30.94392 g of N, N-dimethylacetaamide (DMAc) was charged, and the temperature of the reactor was lowered to 0 ° C., followed by dissolving 1.55538 g (0.003 mol) of 4-BDAF to maintain the solution at 0 ° C. After 4-BDAF completely dissolved, 1.7381 g (0.007 mol) of 3-DDS was completely dissolved, and then 4.4425 g (0.01 mol) of 6-FDA was added and stirred for 1 hour to completely dissolve 6-FDA. At this time, the concentration of the solid was 20% by weight, after which the solution was left at room temperature and stirred for 8 hours. At this time, the polyamic-acid solution whose solution viscosity in 23 degreeC is 1900 poise was obtained.

Thereafter, a polyimide film was prepared in the same manner as in Example 1.

<Example 14>

In Example 1, 28.23036 g of N, N-dimethylacetaamide (DMAc) was charged, and the temperature of the reactor was lowered to 0 ° C., followed by dissolving 1.55538 g (0.003 mol) of APB-133 to maintain this solution at 0 ° C. After completely dissolving APB-133, 1.7381 g (0.007 mol) of 4-DDS was completely dissolved. Then, 4.4425 g (0.01 mol) of 6-FDA was added and stirred for 1 hour to completely dissolve 6-FDA. At this time, the concentration of the solid was 20% by weight, after which the solution was left at room temperature and stirred for 8 hours. At this time, the polyamic-acid solution whose solution viscosity in 23 degreeC is 1900 poise was obtained.

Thereafter, a polyimide film was prepared in the same manner as in Example 1.

<Example 15>

In Example 1, 27.20696 g of N, N-dimethylacetaamide (DMAc) was charged and the reactor temperature was lowered to 0 ° C., and 2.04631 g (0.007 mol) of APB-133 was dissolved to maintain this solution at 0 ° C. After APB-133 is completely dissolved, 3-DDS 0.7449g (0.003mol) is added to completely dissolve it, then 6-FDA 3.10975g (0.007mol) is added and TDA 0.90078g (0.003mol) is added for 1 hour. Was stirred to dissolve 6-FDA and TDA completely. At this time, the concentration of the solid was 20% by weight, after which the solution was left at room temperature and stirred for 8 hours. At this time, the polyamic-acid solution whose solution viscosity in 23 degreeC is 1900 poise was obtained.

Thereafter, a polyimide film was prepared in the same manner as in Example 1.

Comparative Example 1

In Example 1, 5.1846 g (0.01 mol) of 4-BDAF was dissolved in 38.5084 g of N, N-dimethylacetaamide (DMAc), and 4.4425 g (0.01 mol) of 6-FDA was added thereto, followed by stirring for 1 hour. 6-FDA was completely dissolved. At this time, the concentration of the solid was 20% by weight, after which the solution was left at room temperature and stirred for 8 hours. At this time, the polyamic-acid solution whose solution viscosity in 23 degreeC is 1300 poise was obtained.

Thereafter, a polyimide film was prepared in the same manner as in Example 1, and a polyimide film having a thickness of 25 μm, 50 μm, and 100 μm was obtained.

Comparative Example 2

In Example 1, 2.9233 g (0.01 mol) of APB-133 was dissolved in 29.4632 g of N, N-dimethylacetaamide (DMAc), and 4.4425 g (0.01 mol) of 6-FDA was added thereto, followed by stirring for 1 hour. 6-FDA was completely dissolved. At this time, the concentration of the solid was 20% by weight, after which the solution was left at room temperature and stirred for 8 hours. At this time, the polyamic-acid solution whose solution viscosity in 23 degreeC is 1200 poise was obtained.

Thereafter, a polyimide film was prepared in the same manner as in Comparative Example 1.

Comparative Example 3

In Example 1, 2.4830 g (0.01 mol) of 3-DDS was dissolved in 27.702 g of N, N-dimethylacetaamide (DMAc), and 4.4425 g (0.01 mol) of 6-FDA was added thereto, followed by stirring for 1 hour. 6-FDA was completely dissolved. At this time, the concentration of the solid was 20% by weight, after which the solution was left at room temperature and stirred for 8 hours. At this time, the polyamic-acid solution whose solution viscosity in 23 degreeC is 1300 poise was obtained.

Thereafter, a polyimide film was prepared in the same manner as in Comparative Example 1.

<Comparative Example 4>

In Example 1, 2.4830 g (0.01 mol) of 4-DDS was dissolved in 27.702 g of N, N-dimethylacetamide (DMAc), and 4.4425 g (0.01 mol) of 6-FDA was added thereto, followed by stirring for 1 hour. 6-FDA was completely dissolved. At this time, the concentration of the solid was 20% by weight, after which the solution was left at room temperature and stirred for 8 hours. At this time, the polyamic-acid solution whose solution viscosity in 23 degreeC is 1400 poise was obtained.

Thereafter, a polyimide film was prepared in the same manner as in Comparative Example 1.

Comparative Example 5

In Example 1, 3,3′-ODA 2.0024 g (0.01 mol) was dissolved in 25.7796 g of N, N-dimethylacetamide (DMAc), and 6 hours were added 4.4425 g (0.01 mol) of 1-FDA, followed by 1 hour. Was stirred to dissolve 6-FDA completely. At this time, the concentration of the solid was 20% by weight, after which the solution was left at room temperature and stirred for 8 hours. At this time, the polyamic-acid solution whose solution viscosity in 23 degreeC is 1600 poise was obtained.

Thereafter, a polyimide film was prepared in the same manner as in Comparative Example 1.

Comparative Example 6

In Example 1, 2.002 g (0.01 mol) of ODA was dissolved in 16.7344 g of N, N-dimethylacetaamide (DMAc), and 2.1812 g (0.01 mol) of PMDA was added thereto, followed by stirring for 1 hour to completely dissolve PMDA. I was. At this time, the concentration of the solid was 20% by weight, after which the solution was left at room temperature and stirred for 8 hours. At this time, the polyamic-acid solution whose solution viscosity in 23 degreeC is 2500 poise was obtained.

Thereafter, a polyimide film was prepared in the same manner as in Comparative Example 1.

The physical properties of the polyimide films prepared in Examples and Comparative Examples were measured as follows and are shown in Tables 1 to 4 below.

(1) Permeability and 50% blocking wavelength

In the film prepared in Example, visible light transmittance and 50% blocking wavelength were measured using a UV spectrometer (Varian, Cary 100).

On the other hand, the yellow letters and lines were printed on the document printed with a 50 μm-thick polyimide film prepared in Example 1 and Comparative Example 6 and shown in Fig. 1 and 2, respectively.

(2) yellowing degree

Yellowing degree was measured by ASTM E313 standard.

(3) optical density (OD)

The optical density was computed from following formula 1.

<Equation 1>

Where l is the film thickness, A _λ is the absorbance at wavelength λ, T is the transmittance, Io is the intensity of incident light, and I is the intensity of transmitted light.

(4) elastic modulus

The measurement was performed according to JIS K 6301 using Instron's Universal Testing Machine Model 1000.

(5) Glass transition temperature (Tg)

The glass transition temperature was measured using a differential scanning calorimeter (DSC, TA Instrument, Q200).

(6) coefficient of linear expansion (CTE)

The coefficient of linear expansion at 50-200 ° C. was measured using TMA (TA Instrument, Q400) according to TMA-Method.

(7) permittivity

Permittivity was measured according to ASTM D-150 standard.

division Furtherance Molar ratio Thickness (㎛) Yellowing degree 50% blocking wavelength (nm) Modulus of elasticity (GPa) Tg (℃) CTE (ppm / ℃) Permittivity / 1 GHz Example One 6-FDA / 6-HMDA 10:10 50 1.59 384 3.13 252 46 2.79 2 6-FDA / 6-HMDA + 4-DDS 10: 7: 3 50 2.76 386 3.16 287 35 2.88 3 6-FDA + TDA / 6-HMDA 7: 3: 10 50 3.45 386 3.50 245 40 2.77 4 6-FDA + TDA / 6-HMDA + 4-DDS 7: 3: 7: 3 50 3.85 384 3.38 271 45 2.96 5 6-FDA / DBSDA 10:10 50 3.72 390 3.41 228 46 2.72 6 6-FDA / DBSDA + 3-DDS 10: 3: 7 50 3.77 386 3.80 246 42 2.83 7 6-FDA / 2,2′-TFDB 10:10 50 1.22 Less than 380 3.9 315 48 2.72 8 6-FDA / 2,2′-TFDB + 6-HMDA 10: 5: 5 50 5.23 394 3.4 265 45 2.73 9 6-FDA + TDA / 2,2′-TFDB + 4-DDS 7: 3: 7: 3 50 2.45 384 3.02 247 44 2.86 10 6-HBDA / APB-133 10:10 50 5.39 390 3.2 219 48 2.70 11 6-HBDA / 3,3'-ODA 10:10 50 5.16 392 3.21 231 45 2.71 12 6-HBDA + TDA / 2,2'-TFDB 7: 3: 10 50 2.87 386 3.26 236 47 2.78 13 6-FDA / 4-BDAF + 3-DDS 10: 3: 7 50 6.9 384 3.5 270 48.2 2.8 14 6-FDA / APB-133 + 4-DDS 10: 3: 7 50 3.9 384 3.5 274 43.7 2.91 15 6-FDA + TDA / APB-133 + 3-DDS 7: 3: 7: 3 50 4.6 388 3.0 212 46.7 2.70 Example One 6-FDA / 6-HMDA 10:10 100 2.49 387 3.23 - 43 - 2 6-FDA / 6-HMDA + 4-DDS 10: 7: 3 100 3.38 389 3.17 - 32 - 3 6-FDA + TDA / 6-HMDA 7: 3: 10 100 4.12 389 3.52 - 38 - 4 6-FDA + TDA / 6-HMDA + 4-DDS 7: 3: 7: 3 100 4.73 388 3.41 - 41 - 5 6-FDA / DBSDA 10:10 100 4.61 393 3.47 - 44 - 6 6-FDA / DBSDA + 3-DDS 10: 3: 7 100 4.67 390 3.86 - 40 - 7 6-FDA / 2,2′-TFDB 10:10 100 2.11 - 3.95 - 46 - 8 6-FDA / 2,2′-TFDB + 6-HMDA 10: 5: 5 100 6.11 396 3.47 - 43 - 9 6-FDA + TDA / 2,2′-TFDB + 4-DDS 7: 3: 7: 3 100 3.35 388 3.1 - 43 - 10 6-HBDA / APB-133 10:10 100 6.29 394 3.24 - 46 - 11 6-HBDA / 3,3'-ODA 10:10 100 6.31 397 3.29 - 42 - 12 6-HBDA + TDA / 2,2'-TFDB 7: 3: 10 100 3.67 388 3.31 - 46 - 13 6-FDA / 4-BDAF + 3-DDS 10: 3: 7 100 7.7 389 3.56 - 47.3 - 14 6-FDA / APB-133 + 4-DDS 10: 3: 7 100 5.0 388 3.54 - 43.1 - 15 6-FDA + TDA / APB-133 + 3-DDS 7: 3: 7: 3 100 5.8 393 3.12 - 46 -

division Furtherance Molar ratio Thickness (㎛) Transmittance Optical density (OD _λ ) 380 nm to 780 nm 551 nm to 780 nm 550 nm 500 nm 420 nm 550 nm 500 nm 420nm Comparative example One 6-FDA / 4-BDAF 10:10 25 82.8 90.0 87.2 86.0 63.1 23.79 26.20 79.98 2 6-FDA / APB-133 10:10 25 84.4 89.3 87.8 86.0 77.3 22.60 26.20 44.72 3 6-FDA / 3-DDS 10:10 25 84.3 88.6 89.7 88.6 66.5 18.88 21.02 70.87 4 6-FDA / 4-DDS 10:10 25 84.6 89.4 90.5 90.0 72.5 17.34 18.30 55.86 5 6-FDA / 3,3'-ODA 10:10 25 84.9 89.8 90.0 87.6 77.1 18.30 22.99 45.17 6 PMDA / ODA 10:10 25 56.6 85.2 73.0 35.0 0.05 54.67 182.37 1320 Comparative example One 6-FDA / 4-BDAF 10:10 50 82.2 89.7 86.8 85.1 60.0 12.29 14.01 44.36 2 6-FDA / APB-133 10:10 50 83.8 88.8 87.2 84.8 73.2 11.89 14.32 27.09 3 6-FDA / 3-DDS 10:10 50 83.7 88.2 89.1 87.6 63.1 10.02 11.49 39.99 4 6-FDA / 4-DDS 10:10 50 83.9 89.1 90.0 89.1 69.4 9.15 10.02 31.72 5 6-FDA / 3,3'-ODA 10:10 50 84.3 89.3 89.2 86.3 73.8 9.92 12.79 26.38 6 PMDA / ODA 10:10 50 56.0 84.5 69.2 33.1 0 31.97 96.03 - Comparative example One 6-FDA / 4-BDAF 10:10 100 81.6 89.2 86.3 84.3 51.2 6.39 7.41 29.07 2 6-FDA / APB-133 10:10 100 83.1 88.1 86.7 84.3 63.3 6.19 7.41 19.85 3 6-FDA / 3-DDS 10:10 100 83.1 87.8 88.5 87.0 53.5 5.30 6.04 27.16 4 6-FDA / 4-DDS 10:10 100 83.2 88.8 89.5 88.6 58.6 4.81 5.25 23.21 5 6-FDA / 3,3'-ODA 10:10 100 83.5 88.7 88.8 85.4 62.1 5.15 6.85 20.69 6 PMDA / ODA 10:10 100 - - - - - - - -

division Furtherance Molar ratio Thickness (㎛) Yellowing degree 50% blocking wavelength (nm) Modulus of elasticity (GPa) Tg (℃) CTE (ppm / ℃) Permittivity / 1 GHz Comparative example One 6-FDA / 4-BDAF 10:10 25 9.7 411 3.0 263 52.3 2.5 2 6-FDA / APB-133 10:10 25 5.5 395 3.05 206 47.1 2.7 3 6-FDA / 3-DDS 10:10 25 1.82 388 3.1 270 47 3.0 4 6-FDA / 4-DDS 10:10 25 1.68 382 3.1 310 46 3.1 5 6-FDA / 3,3'-ODA 10:10 25 5.29 396 3.0 244 41 2.73 6 PMDA / ODA 10:10 25 91.7 514 3.0 none 26 3.3 Comparative example One 6-FDA / 4-BDAF 10:10 50 11.2 413 3.06 - 51.1 - 2 6-FDA / APB-133 10:10 50 6.9 398 3.11 - 46.0 - 3 6-FDA / 3-DDS 10:10 50 2.95 392 3.16 - 45.3 - 4 6-FDA / 4-DDS 10:10 50 2.81 386 3.17 - 45.1 - 5 6-FDA / 3,3'-ODA 10:10 50 6.46 399 3.05 - 39.6 - 6 PMDA / ODA 10:10 50 × × 3.12 - 25.0 - Comparative example One 6-FDA / 4-BDAF 10:10 100 23.4 415 3.09 - 48.8 - 2 6-FDA / APB-133 10:10 100 14.2 401 3.14 - 44.5 - 3 6-FDA / 3-DDS 10:10 100 4.54 396 3.20 - 44.9 - 4 6-FDA / 4-DDS 10:10 100 4.26 390 3.22 - 44.6 - 5 6-FDA / 3,3'-ODA 10:10 100 14.26 405 3.13 - 39.1 - 6 PMDA / ODA 10:10 100 - - - - - -

As a result of the evaluation of the physical properties, the polyimide film of the present invention has an average transmittance of 85% or more at 380 to 780 nm and a yellowness of 15 or less, and an optical density of 420 nm at a film thickness of 50 μm and 100 μm. It can be seen that it is less than 50. In addition, it can be seen from FIG. 1 that the polyimide film satisfying the transmittance, yellowing degree and optical density of the present invention is transparent so that yellow letters and lines can be seen as it is.

In the case of the comparative example, the average transmittance in the visible ray region of 380 to 780 nm was not more than 85% regardless of the thickness, and especially in the case of Comparative Example 6, film formation was not possible with a thickness of 90 μm or more.

In addition, the polyimide film prepared according to the embodiment of the present invention is a colorless transparent polyimide film having excellent visible light transmittance with a wavelength of 400 nm or less, the transmittance of which is 50%, and can be used as a surface protective film such as a solar cell. Linear expansion coefficient is 50ppm or less, excellent dimensional stability, elastic modulus is 3.0GPa or more, has film characteristics applicable to roll-to-roll process, TFT for manufacturing substrate materials and flexible display devices Applicable to the process. Moreover, since the dielectric constant is 3.0 or less, it can be used as a semiconductor passivation film.

As described above, the present invention is colorless and transparent, and has excellent mechanical and thermal stability properties such as semiconductor insulating film, TFT-LCD insulating film, passivation film, liquid crystal alignment film, optical communication material, solar cell protective film, flexible display substrate, etc. Polyimide resins and films that can be used in a variety of applications can be provided.

Claims (10)

A polyimide film having an average transmittance of 85% or more and a yellowing degree of 15 or less when measured on a transmittance with a UV spectrometer based on a film thickness of 50 to 100 μm. The method of claim 1, When measuring transmittance with UV spectrometer based on film thickness 50 ~ 100㎛, average transmittance at 551 ~ 780nm is 88% or more, transmittance at 88% at 550nm, transmittance at least 85% at 500nm, at 420nm The transmittance | permeability is 50% or more, The polyimide film characterized by the above-mentioned. The method of claim 1, The optical density is less than 50 at 420 nm based on film thickness of 50-100 micrometers, The polyimide film characterized by the above-mentioned. The method of claim 1, As aromatic dianhydrides 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (FDA), 4- (2,5-dioxotetrahydrofuran-3-yl) -1, 2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride (TDA) and 4,4 '-(4,4'-isopropylidenedephenoxy) bis (phthalic anhydride Polyimide film comprising at least one selected from (HBDA). The method of claim 1, A polyimide film comprising at least one component represented by the following general formula (1) as an aromatic diamine. <Formula 1>

In which R is

,

,

,

,

,

,

,

,

,

,

,

,

And

Among the structures selected. The method of claim 1, The dielectric constant at 1GHz is 3.0 or less, The polyimide film characterized by the above-mentioned. The method of claim 1, The average linear expansion coefficient (CTE) in 50-200 degreeC is 50 ppm or less, The polyimide film characterized by the above-mentioned. The method of claim 1, Elastic modulus is 3.0 GPa or more, The polyimide film characterized by the above-mentioned. The method of claim 1, A polyimide film, characterized in that 50% cut off wavelength is 400 nm or less when measured by UV spectrometer. A display element substrate comprising the polyimide film of any one of claims 1 to 9.

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