Polyamide-imide film
One embodiment may provide a polyamide-imide film which is colorless and transparent while having an adequate level of solubility and excellent mechanical properties, the polyamide-imide film comprising a polyamide-imide polymer formed by polymerizing an aromatic diamine compound, an aromatic dianhydride compound and a dicarbonyl compound, wherein, for a square cross-section of 1 cm×1 cm and a thickness of 30 um to 100 mm, the polyamide-imide film has a dissolution time of 5-60 minutes in 10 ml of dimethylacetamide (DMAc), and for a thickness of 50 mm, the polyamide-imide film has a yellowness of at most 5, a haze of at most 2%, a permeability of at least 85% and a modulus of at least 5.0 GPa.
1. A polyamide-imide film, which comprises a polyamide-imide polymer formed by polymerizing an aromatic diamine compound, an aromatic dianhydride compound, and a dicarbonyl compound, wherein a dissolution time for which the polyamide-imide film in a square of 1 cm×1 cm and in a thickness of 30 μm to 100 μm is dissolved in 10 ml of dimethylacetamide (DMAc) is 5 to 60 minutes, wherein the polyamide-imide film has a yellow index of 5 or less, a haze of 2% or less, a transmittance of 85% or more, and a modulus of 5.0 GPa or more, based on a thickness of 50 μm, the aromatic dianhydride compound comprises 2,2′-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6-FDA), wherein the aromatic diamine compound comprises 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (TFDB), wherein the dicarbonyl compound comprises at least two different dicarbonyl compounds, wherein the dicarbonyl compound comprises terephthaloyl chloride (TPC), 1,1′-biphenyl-4,4′-dicarbonyl dichloride (BPDC), or a combination thereof, and
wherein a molar ratio of the imide repeat unit to the amide repeat unit is from 50:50 to 20:80.
2. The polyamide-imide film of claim 1 , wherein the dissolution time is 10 minutes to 50 minutes.
3. The polyamide-imide film of claim 2 , wherein the dissolution time is 20 minutes to 40 minutes.
4. The polyamide-imide film of claim 1 , which has a yellow index of 3 or less, a haze of 1% or less, a transmittance of 88% or more, a modulus of 5.5 GPa or more, and a surface hardness of HB or higher, based on a thickness of 50 μm.
5. The polyamide-imide film of claim 1 , wherein an amount of increase in haze of the polyamide-imide film is 20% to 50% measured according to a surface solubility measurement method which includes placing the surface of the polyamide-imide film on a flat surface, rubbing the surface of the polyamide-imide film back and forth 10 times with a cotton swab soaked in DMAc at a force of 0.1 N and at a speed of 5 cm/sec, and then measuring the amount of increase in haze.
6. A polyamide-imide film, which comprises a polyamide-imide polymer formed by polymerizing an aromatic diamine compound, an aromatic dianhydride compound, and a dicarbonyl compound, and which has a yellow index of 5 or less, a haze of 2% or less, a transmittance of 85% or more, and a modulus of 5.0 GPa or more, based on a thickness of 50 μm, wherein the aromatic diamine compound comprises 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (TFDB), wherein the aromatic dianhydride compound comprises 2,2′-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6-FDA), wherein the dicarbonyl compound comprises at least two different dicarbonyl compounds, wherein the dicarbonyl compound comprises terephthaloyl chloride (TPC), 1,1′-biphenyl-4,4′-dicarbonyl dichloride (BPDC), or a combination thereof, wherein a molar ratio of the imide repeat unit to the amide repeat unit is from 50:50 to 20:80, and wherein an amount of increase in haze of the polyamide-imide film is 20% to 50% measured according to a surface solubility measurement method which includes placing the surface of the polyamide-imide film on a flat surface, rubbing back and forth 10 times the surface with a cotton swab soaked in DMAc at a force of 0.1 N and at a speed of 5 cm/sec, and then measuring the amount of increase in haze.
7. The polyamide-imide film of claim 6 , wherein the amount of increase in haze is 25% to 40%.
8. The polyamide-imide film of claim 6 , which has a yellow index of 3 or less, a haze of 1% or less, a transmittance of 88% or more, a modulus of 5.5 GPa or more, and a surface hardness of HB or higher, based on a thickness of 50 μm.
9. The polyamide-imide film of claim 6 , which is prepared by a process comprising: polymerizing the aromatic diamine compound, the aromatic dianhydride compound, and the least two dicarbonyl compounds to prepare a polyamide-imide polymer solution having a viscosity of 150,000 to 350,000 cps; extruding and casting the polymer solution; and then drying and thermally treating the cast polymer solution.