KR20090019306A - Colorless polyimide film - Google Patents

Abstract

A colorless polyimide film is provided to ensure excellent thermal stability and mechanical property and to be useful for a semiconductor insulating film, TFT-LCD insulating layer, passivation film, liquid crystal alignment film, the material for the optical communication, a protective film for a solar battery and a flexible display substrate. A colorless polyimide film comprises aromatic dianhydride and aromatic diamine as a main material, and has yellowness of 5.0 or less based on the film thickness of 25~100 micrometer and the whiteness of 60 or greater.

Description

Colorless and transparent polyimide film {Colorless polyimide film}

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 in electronic materials such as insulating films, semiconductors, electrode protective films of TFT-LCDs, and recently, it is used in display materials such as optical fibers and liquid crystal alignment films, and also in transparent electrode films by containing conductive fillers in the films or coating them on surfaces. have.

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. No. 5986036, 6262328 and Korean Patent Publication No. 2003-0009437 are monomers having a curved structure connected to a linking group, such as -O-, -SO _2- , CH ₂ -and the m-position rather than the p-position A report has been made of a novel polyimide structure having improved transmittance and color transparency using aromatic dianhydride dianhydrides having substituents such as -CF ₃ and aromatic diamine monomers, without increasing the thermal properties significantly. Mechanical properties, 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 flexible displays.

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

Accordingly, the present invention includes aromatic dianhydride and aromatic diamine as main components, and has a yellowness of 5.0 or less and a whiteness of 60 based on a film thickness of 25 to 100 μm. The above polyimide film can be provided.

In the embodiment, the polyimide film may have an average transmittance of 85% or more at 380 to 780 nm when measuring transmittance with a UV spectrometer based on a film thickness of 25 to 100 μm.

In the embodiment, the polyimide film may have a transmittance of 88% or more at 550 nm and a transmittance of 70% or more at 440 nm when measured for transmittance with a UV spectrometer based on a film thickness of 25 to 100 μm.

In the embodiment, the polyimide film may have a 50% cut off wavelength of 400 nm or less when measuring transmittance with a UV spectrometer.

In the embodiment, the polyimide film may have an L value of 90 or more, a value of 5 or less, and b value of 5 or less when the color coordinate is measured by a UV spectrometer based on a film thickness of 25 to 100 μm.

In the above embodiment, the diamine and dianhydride are polymerized under a first solvent to obtain a polyamic acid solution, the obtained polyamic acid solution is imidized, and then the imidized solution is introduced into a second solvent, filtered and dried to obtain a polyamic acid solution. The polyimide solution obtained by obtaining the solid content of the mid resin and dissolving the obtained polyimide resin solid content in the first solvent may be formed into a film through a film forming process.

In the above embodiment, the second solvent may have a lower polarity than the first solvent.

In this embodiment, the first solvent is m-crosol, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), acetone, At least one selected from diethyl acetate, and the second solvent may be at least one selected from water, alcohols, ethers and ketones.

In this embodiment the polyimide film is 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (FDA), 4- (2,5-dioxotetrahydro) as aromatic dianhydride. Furan-3-yl) -1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride (TDA), 4,4 '-(4,4'-isopropylidenediphenoxy Bis (phthalic anhydride) (HBDA), 3,3 '-(4,4'-oxydiphthalic dianhydride) (ODPA) and 3,4,3', 4'-biphenyltetracar It may be one containing one or more selected from the cyclic dianhydride (BPDA).

In this embodiment the polyimide film is 2,2-bis [4- (4-aminophenoxy) -phenyl] propane (6HMDA), 2,2'-bis (trifluoromethyl) -4, as aromatic diamine. 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 (3DDS), bis (4-aminophenyl) sulfone (4DDS), 1,3-bis (3-amino Phenoxy) benzene (APB-133), 1,4-bis (4-aminophenoxy) benzene (APB-134), 2,2'-bis [3 (3-aminophenoxy) phenyl] hexafluoropropane (3-BDAF), 2,2'-bis [4 (4-aminophenoxy) phenyl] hexafluoropropane (4-BDAF), and oxydianiline (ODA). .

In another aspect, the present invention can provide a display device substrate comprising the polyimide film.

INDUSTRIAL APPLICABILITY The present invention is colorless and transparent, and has excellent mechanical and thermal stability properties, which can be used in various fields such as semiconductor insulating film, TFT-LCD insulating film, passivation film, liquid crystal alignment film, optical communication material, solar cell protective film, and flexible display substrate Polyimide resins and films can be provided.

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 of the present invention has a yellowness of 5.0 or less and a whiteness of 60 based on a film thickness of 25 to 100 μm. It is preferable that it is above.

The polyimide film of the present invention that satisfies the yellowness and the whiteness can be used for a use that was limited in use due to the yellow color of the existing polyimide film.

In addition, the polyimide film of the present invention preferably has an average transmittance of 85% or more at 380 to 780 nm when measuring transmittance with a UV spectrometer based on a film thickness of 25 to 100 μm, and furthermore, based on a film thickness of 25 to 100 μm. When measuring transmittance with a UV spectrometer, the transmittance is preferably 88% or more at 550 nm and 70% or more at 440 nm.

In addition, the polyimide film of the present invention preferably has an L value of 90 or more, a value of 5 or less, and b value of 5 or less when measured by color spectrometer with a UV spectrometer based on a film thickness of 25 to 100 μm.

The polyimide film of the present invention satisfying the transmittance and color coordinate measurement together with the yellowness and the whiteness is a use that has been limited in use due to the yellow color of the existing polyimide film, that is, a diffusion plate in a protective film or a TFT-LCD, etc. It can be used in applications requiring transparency such as coating layers such as TFT-LCDs, interlayers, gate insulators, and liquid crystal alignment films, and contributes to increase of the aperture ratio when the transparent polyimide is applied as liquid crystal alignment films to produce high-contrast TFT-LCDs. Is possible. It can also be used for flexible display substrates.

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

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), 4,4 '-(4,4'-isopropylidenediphenoxy Bis (phthalic anhydride) (HBDA), 3,3 '-(4,4'-oxydiphthalic dianhydride) (ODPA) and 3,4,3', 4'-biphenyltetracar It is preferable to include at least one selected from the cycloxian hydride (BPDA).

In addition, the aromatic diamine used in the present invention is not particularly limited, but 2,2-bis [4- (4-aminophenoxy) -phenyl] propane (6HMDA), 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 (3DDS), bis (4-aminophenyl) sulfone (4DDS), 1,3-bis ( 3-aminophenoxy) benzene (APB-133), 1,4-bis (4-aminophenoxy) benzene (APB-134), 2,2'-bis [3 (3-aminophenoxy) phenyl] hexa At least one selected from fluoropropane (3-BDAF), 2,2'-bis [4 (4-aminophenoxy) phenyl] hexafluoropropane (4-BDAF), and oxydianiline (ODA). It is preferable.

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 first 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.

Although not particularly limited with respect to the content of the first solvent, in order to obtain the molecular weight and viscosity of the appropriate polyamic acid solution, the content of the first solvent is preferably 50 to 95% by weight of the total polyamic acid solution, more preferably 70 ~ It is more preferable that it is 90 weight%.

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. In general, the average particle diameter is preferably 0.001 to 50 μm, and preferably 0.005 to 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.

As a method for preparing a polyimide film from the obtained polyamic acid solution, a conventionally known method may be used, that is, the polyamic acid solution may be cast on a support to imide to obtain a film.

The imidation method applied at this time can be applied in combination with the thermal imidation method, the chemical imidation method, the thermal imidation method, and the compound imidation method. The chemical imidization method is a method in which a dehydrating agent represented by acid anhydrides such as acetic anhydride and an imidization catalyst represented by tertiary amines such as isoquinoline, β-picoline and pyridine are introduced into a polyamic acid solution. In the case of using the thermal imidization method or the thermal imidization method together with the chemical imidization method, the heating conditions of the polyamic acid solution may vary depending on the kind of the polyamic acid solution, the thickness of the polyimide film to be produced, and the like.

When explaining the production example of the polyimide film in the case of using the thermal imidation method and the chemical imidation method more specifically, 80-200 degreeC, after casting a dehydrating agent and an imidation catalyst in a polyamic-acid solution, and casting on a support body, Preferably, the polyamic acid film in the gel state is obtained from the support after being partially cured and dried by heating at 100 to 180 ° C. to activate the dehydrating agent and the imidization catalyst, and the film in the gel state at 5 ° C. to 200 ° C. to 400 ° C. A polyimide film can be obtained by heating for 400 seconds.

On the other hand, in the present invention, it is also possible to produce a polyimide film from the obtained polyamic acid solution as follows. That is, after imidating the obtained polyamic acid solution, the imidized solution is added to the second solvent, filtered and dried to obtain a solid content of the polyimide resin, and the obtained polyimide resin solid content is dissolved in the first solvent. It can obtain through a film forming process using a polyimide solution.

When imidating the said polyamic-acid solution, it can apply in combination with the thermal imidation method, the chemical imidation method, the thermal imidation method, and the compound imidation method similarly to the above-mentioned. For example of specific imidization in the case of using the thermal imidization method and the chemical imidization method, a dehydrating agent and an imidization catalyst are added to the obtained polyamic acid solution, and heated at 20 to 180 ° C. for 1 to 12 hours to imide. Can be mad.

The first solvent may use the same solvent as the solvent used in the polymerization of the polyamic acid solution, and the second solvent may use a solvent that cannot dissolve the obtained polyamic acid polymer in order to obtain a solid content of the polyimide resin. In the solvent that can be applied to the principle of precipitation as a solid by using a lower polarity than the first solvent, specifically may be one or more selected from water, alcohols, ethers and ketones.

At this time, it is not particularly limited with respect to the content of the second solvent, it is preferable to use 5 to 20 times by weight relative to the weight of the prepared polyamic acid solution.

The conditions of drying after filtering the obtained polyimide resin solid content are preferable to dry at a temperature of 50-150 degreeC for 2 to 24 hours considering the boiling point of the 2nd solvent and the 1st solvent which will remain in solidified resin.

After the film forming process, the polyimide solution in which the polyimide resin solids are dissolved is cast on a support, and the polyimide resin is heated at a temperature rising rate of 1 to 10 ° C./min in a temperature range of 40 to 400 ° C., and heated for 1 minute to 8 hours. Obtain a mid film.

The polyimide film thus prepared may have a lower yellowness, a higher whiteness, and an improved transmittance.

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.

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 6HMDA was dissolved to maintain the solution at 0 ° C. 4.4425 g (0.01 mol) of 6FDA was added thereto and stirred for 1 hour to completely dissolve 6FDA. 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 adding 2 to 4 equivalents of acetic anhydride (Acetic oxide; tritran) and pyridine (Priridine) as a chemical curing agent, the polyamic acid solution was heated to a temperature within the range of 20 to 180 ° C. After imidating the polyamic acid solution by heating at a rate of 1 to 10 ° C./min at 2 to 10 hours, 30 g of the imidized solution was added to 300 g of water to precipitate, and the precipitated solid was filtered and pulverized. After finely powdered and dried in a vacuum drying oven at 80 to 100 ℃ for 2 to 6 hours to obtain a resin solid powder of about 8g. The obtained resin solid was dissolved in 32 g of DMAc or DMF, which is a polymerization solvent, to obtain a 20 wt% polyimide solution. This was heated for 2 to 8 hours while the temperature was raised at a rate of 1 to 10 ° C./min in a temperature range of 40 to 400 ° C. to obtain a polyimide film having a thickness of 50 μm and a thickness of 100 μm.

<Example 2>

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 6FDA was added thereto and stirred for 1 hour to completely dissolve 6FDA. 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 3>

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 6FDA was added thereto and stirred for 1 hour to completely dissolve 6FDA. 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 4>

In Example 1, 2.24161 g (0.007 mol) of 2,2′-TFDB was dissolved in 29.716 g of N, N-dimethylacetamide (DMAc), and 0.7449 g (0.003 mol) of 4DDS was completely dissolved. And 4.4425g (0.01mol) of 6FDA was added and stirred for 1 hour to completely dissolve 6FDA. 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

In Example 1, 2.2023 g (0.01 mol) of 2,2′-TFDB was dissolved in 33.6292 g of N, N-dimethylacetaamide (DMAc), and the solution was maintained at 0 ° C. 5.205 g (0.01 mol) of 6HBDA was added thereto, followed by stirring for 1 hour to completely dissolve 6HBDA. At this time, the concentration of the solid was 20% by weight, and then 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 2100 poise was obtained.

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

<Example 6>

In Example 1, 3.2023 g (0.01 mol) of 2,2′-TFDB was dissolved in 31.82 g of N, N-dimethylacetaamide (DMAc), and the solution was maintained at 0 ° C. 4.164 g (0.008 mol) of 6HBDA was added thereto, and 0.58844 g (0.002 mol) of BPDA was added thereto, followed by stirring for 1 hour to completely dissolve 6HBDA and BPDA. 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.

<Example 7>

In Example 1, 3.2023 g (0.01 mol) of 2,2′-TFDB was dissolved in 33.59 g of N, N-dimethylacetaamide (DMAc), and the solution was maintained at 0 ° C. 6.64355 g (0.007 mol) of 6HBDA was added thereto, and 1.551 g (0.003 mol) of ODPA was added thereto, followed by stirring for 1 hour to completely dissolve 6HBDA and ODPA. 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.

<Examples 8-14>

After obtaining a polyamic acid solution with the same composition as in Examples 1 to 7, respectively, the obtained polyamic acid solution was cast to a thickness of 500 μm to 1000 μm using a doctor blade on a glass plate, and then vacuum oven was used for 1 hour and 60 ° C. at 40 ° C. After drying at 2 ℃ for 2 hours to obtain a self standing film, it was heated at 80 ℃ for 3 hours at 100 ℃, 1 hour at 100 ℃, 1 hour at 200 ℃ and 30 minutes at 300 ℃ in a high temperature furnace. Polyimide films of 50 μm and 100 μm were obtained.

<Example 15>

In Example 1, 5.1846 g (0.01 mol) of 4-BDAF was dissolved in 38.5084 g of N, N-dimethylacetaamide (DMAc), and the solution was maintained at 0 ° C. 4.4425 g (0.01 mol) of 6FDA was added thereto, followed by stirring for 1 hour to completely dissolve 6FDA. 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.

After adding 2 to 4 equivalents of acetic anhydride (Acetic oxide; tritran) and pyridine (Priridine) as a chemical curing agent to the polyamic acid solution, After imidating the polyamic acid solution by heating at a rate of 1 to 10 ° C./min at 2 to 10 hours, 30 g of the imidized solution was added to 300 g of water to precipitate, and the precipitated solid was filtered and pulverized. After finely powdered and dried in a vacuum drying oven at 80 to 100 ℃ for 2 to 6 hours to obtain a resin solid powder of about 8g. The obtained resin solid was dissolved in 32 g of DMAc or DMF, which is a polymerization solvent, to obtain a 20 wt% polyimide solution. This was heated for 2 to 8 hours while the temperature was raised at a rate of 1 to 10 ° C./min in a temperature range of 40 to 400 ° C. to obtain a 25 μm thick polyimide film.

<Example 16>

In Example 1, 2.9233 g (0.01 mol) of APB-133 was dissolved in 29.4632 g of N, N-dimethylacetamide (DMAc), and the solution was maintained at 0 ° C. 4.4425 g (0.01 mol) of 6FDA was added thereto, followed by stirring for 1 hour to completely dissolve 6FDA. 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 25 μm thick polyimide film was prepared in the same manner as in Example 1.

<Example 17>

In Example 1, 2.0024 g (0.01 mol) of 3,3′-ODA was dissolved in 25.7796 g of N, N-dimethylacetamide (DMAc), and the solution was maintained at 0 ° C. 4.4425 g (0.01 mol) of 6FDA was added thereto, followed by stirring for 1 hour to completely dissolve 6FDA. 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 25 μm thick 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 6FDA was added thereto, followed by stirring for 1 hour to give 6FDA. 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.

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 Polyimide film having a thickness of 25 μm, 50 μm and 100 μm 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. Got.

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 6FDA was added thereto, followed by stirring for 1 hour. 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, 2.0024 g (0.01 mol) of 3,3′-ODA was dissolved in 25.7796 g of N, N-dimethylacetamide (DMAc), and 4.4425 g (0.01 mol) of 6FDA was added thereto, followed by stirring for 1 hour. 6FDA 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 1600 poise was obtained.

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

<Comparative Example 4>

In Example 1, 4,4′-ODA 2.0024 g (0.01 mol) 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. PMDA 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 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 and 2 below.

(1) Permeability and 50% blocking wavelength

The prepared film was measured for visible light transmittance and 50% blocking wavelength using a UV spectrometer (Varian, Cary 100).

On the other hand, on the document printed with yellow letters and lines, the photo is placed with a polyimide film having a thickness of 100 μm prepared in Example 1 and a polyimide film having a thickness of 25 μm prepared in Comparative Example 4, respectively, as shown in FIGS. 1 and 2. Indicated.

(2) yellowness

The prepared film was measured using a UV spectrometer (Varian, Cary 100) to measure the yellowness according to ASTM E313 standard.

(3) whiteness

The prepared film was measured for whiteness according to ASTM E313 using a UV spectrometer (Varian, Cary 100).

(4) color coordinates

The prepared film was measured according to ASTM E 1347-06 standard using a UV spectrometer (Varian, Cary 100), the light source (Illuminant) was based on the measured value by CIE D65.

(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 50-250 ° C. was measured using TMA (TA Instrument, Q400) according to TMA-Method.

As a result of the physical property evaluation, it can be seen that the polyimide film of the present invention has a yellowness of 5.0 or less and a whiteness of 60 or more at a film thickness of 50 μm and 100 μm, and an average transmittance of 380 to 780 nm of not less than 85%. , The transmittance was over 88% at 550 nm, and the transmittance was over 70% at 440 nm. In addition, the L value was 90 or more, the a value was 5 or less, the b value was 5 or less, and the 50% blocking wavelength was 400 nm or less. As shown in FIG. 1, the polyimide film of the present invention can be seen that the yellow letters and lines are transparent enough to be seen as it is.

In addition, Examples 15 to 17 are the same composition as Comparative Examples 1 to 3, but there is a difference in the method of manufacturing a polyimide film, in the case of the polyimide film prepared by the manufacturing method of Examples 15 to 17 conventional It can be seen that the yellowness was decreased and the whiteness was increased as compared with Comparative Examples 1 to 3 prepared by the manufacturing method.

Meanwhile, in the case of Comparative Example 4, it was difficult to manufacture a film having a thickness of 75 μm or more as a conventional general manufacturing method, and as shown in FIG. It can be seen that it is a colored film that cannot be seen.

Accordingly, it can be seen that the polyimide film of FIG. 1 is 100 μm, and the polyimide film of FIG. 2 is 25 μm, but is more transparent despite the thickness of the polyimide film of the present invention of FIG. 1.

1 is a photograph taken with a polyimide film having a thickness of 100 μm obtained in Example 1 of the present invention on a document,

FIG. 2 is a photograph taken on a document having a polyimide film having a thickness of 25 μm obtained in Comparative Example 4. FIG.

Claims (12)

A polyimide film comprising an aromatic dianhydride and an aromatic diamine as main components and having a yellowness of 5.0 or less and a whiteness of 60 or more based on a film thickness of 25 to 100 μm. The method of claim 1, A polyimide film having an average transmittance of 85% or more at 380 to 780 nm when measuring transmittance with a UV spectrometer based on a film thickness of 25 to 100 μm. The method of claim 1, A polyimide film having a transmittance of 88% or more at 550 nm and a transmittance of 70% or more at 440 nm when measuring transmittance with a UV spectrometer based on a film thickness of 25 to 100 μm. 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. The method of claim 1, L value is 90 or more, a value is 5 or less, and b value is 5 or less, when measuring the color coordinate with UV spectrometer based on film thickness 25-100 micrometers. The method of claim 1, Diamine and dianhydride were polymerized under a first solvent to obtain a polyamic acid solution, and the obtained polyamic acid solution was imidized. To obtain a polyimide solution obtained by dissolving the obtained polyimide resin solid content in the first solvent through a film forming process. The method of claim 6, The second solvent is a polyimide film, characterized in that the polarity is lower than the first solvent. The method of claim 6, The first solvent is selected from m-crosol, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), acetone, diethyl acetate At least one, and the second solvent is at least one selected from water, alcohols, ethers and ketones polyimide film, characterized in that. 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), 4,4 '-(4,4'-isopropylidenediphenoxy) bis (phthalic anhydride ) (HBDA), 3,3 '-(4,4'-oxydiphthalic dianhydride) (ODPA) and 3,4,3', 4'-biphenyltetracarboxylic dianhydride (BPDA) A polyimide film comprising at least one selected. The method of claim 1, 2,2-bis [4- (4-aminophenoxy) -phenyl] propane (6HMDA), 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl (2 as aromatic diamine , 2′-TFDB), 3,3′-bis (trifluoromethyl) -4,4′-diaminobiphenyl (3,3′-TFDB), 4,4′-bis (3-aminophenoxy ) Diphenylsulfone (DBSDA), bis (3-aminophenyl) sulfone (3DDS), bis (4-aminophenyl) sulfone (4DDS), 1,3-bis (3-aminophenoxy) benzene (APB-133) , 1,4-bis (4-aminophenoxy) benzene (APB-134), 2,2'-bis [3 (3-aminophenoxy) phenyl] hexafluoropropane (3-BDAF), 2,2 A polyimide film comprising at least one selected from '-bis [4 (4-aminophenoxy) phenyl] hexafluoropropane (4-BDAF) and oxydianiline (ODA). The substrate for display elements containing the polyimide film of any one of Claims 1-10. The protective film containing the polyimide film of Claim 4.

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