Polyamide-Imide Film

Abstract

Provided is a polyamide-imide film including: a polyamide-imide resin and a porphyrin-based dye. The polyamide-imide film has excellent optical properties, and, in particular, may maintain an excellent yellow index even in a repeated temperature change environment.

Claims

1. A polyamide-imide film comprising: a polyamide-imide resin and a porphyrin-based dye, the polyamide-imide film having a yellow index (YI) of 2 or less and ΔYI.sub.heat of 0.3 or less, wherein ΔYI.sub.heat is, when a heat resistance test is performed, a yellow index change value of the polyamide-imide film before and after the heat resistance test, in which in one cycle, the polyamide-imide film is allowed to stand at 80° C. for 2 hours and then to stand at 25° C. for 2 hours, and 200 cycles are carried out repeatedly.

2. The polyamide-imide film of claim 1, wherein the polyamide-imide film has a light transmittance in a visible light area of 88% or more based on 80 μm and a haze of 0.8% or less.

3. The polyamide-imide film of claim 2, wherein the polyamide-imide film has a b* value of −1.3 to 1.3.

4. The polyamide-imide film of claim 1, wherein the polyamide-imide film has a modulus of 3 GPa or more and an elongation at break of 10% or more.

5. The polyamide-imide film of claim 1, wherein the polyamide-imide resin is a copolymerized product of an aromatic diamine, a dianhydride, and an aromatic dicarboxylic acid or a derivative thereof.

6. The polyamide-imide film of claim 5, wherein the aromatic diamine includes a fluorine-based aromatic diamine.

7. The polyamide-imide film of claim 5, wherein the dianhydride includes a fluorine-based aromatic dianhydride and a non-fluorine-based aromatic dianhydride.

8. The polyamide-imide film of claim 5, wherein the dianhydride includes a fluorine-based aromatic dianhydride and an alicyclic dianhydride.

9. The polyamide-imide film of claim 1, wherein a content of the porphyrin-based dye is 0.0001 to 0.005 parts by weight with respect to 100 parts by weight of the polyamide-imide resin.

10. The polyamide-imide film of claim 1, wherein a maximum absorption wavelength in a visible light area of the porphyrin-based dye is 570 to 599 nm in a MEK solvent.

11. The polyamide-imide film of claim 10, wherein a molar absorption coefficient at the maximum absorption wavelength in a visible light area of the porphyrin-based dye is 10,000 to 1,000,000 L/mol.Math.cm.

12. The polyamide-imide film of claim 10, wherein a full width at half maximum (FWHM) for a maximum absorption peak of the porphyrin-based dye is 100 nm or less.

13. The polyamide-imide film of claim 1, wherein a solubility of the porphyrin-based dye in N,N-dimethylacetatmide (DMAc) is 0.5 wt % or more.

14. The polyamide-imide film of claim 1, wherein the porphyrin-based dye has a residual mass at 300° C. of 90% or more as measured at a heating condition of 20° C./min under a nitrogen atmosphere.

Description

EXAMPLE 1

[0097] Methylene chloride and 2,2′-bis(trifluoromethyl)benzidine (TFMB) were added to a reactor and sufficiently stirred under a nitrogen atmosphere, terephthaloyl dichloride (TPC) was added thereto, and stirring was performed for 6 hours. Here, a mole ratio of TPC:TFMB introduced was 3:4, and a solid content was adjusted to 10 wt %.

[0098] Thereafter, a reaction product was precipitated using an excessive amount of methanol and filtered to obtain a solid content, which was dried under vacuum at 50° C. for 6 hours to prepare a polyamide-based oligomer. The formula weight (FW) of the prepared polyamide-based oligomer was 1670 g/mol.

[0099] Next, N,N-dimethylacetamide (DMAc), 100 mol of the prepared polyamide-basedoligomer, and 28.6 mol of TFMB were introduced to the reactor and stirring was sufficiently performed.

[0100] Thereafter, 64.3 mol of 4,4′-hexafluoroisopropylidene diphthalic anhydride (6FDA) and 64.3 mol of biphenyl tetracarboxylic dianhydride (BPDA) were sequentially introduced to the reactor and stirred, and were polymerized at 40° C. for 10 hours.

[0101] Subsequently, each of pyridine and acetic anhydride was introduced to the reactor at 2.5 times mole (321.5 mol) of the total introduced dianhydride, and stirred at 60° C. for 1 hour. Here, the solid content was adjusted to 12%.

[0102] After completing the reaction, CNef-P591 available from CFC Teramate, which is a porphyrin-based dye, was diluted in DMAc, which was introduced at 20 ppm relative to the solid content.

[0103] The viscosity of the finally prepared polyamide-imide was 100,000 cps, as measured at 25° C. using a Brookfield viscometer.

[0104] The thus-prepared polyamide-imide solution was subjected to solution casting on a glass substrate using an applicator. Thereafter, heat treatment was performed in a vacuum oven at 100° C. for 30 minutes, 200° C. for 30 minutes, and 280° C. for 10 minutes, and then the product was cooled at room temperature.

[0105] The polyamide-imide film formed on the glass substrate was separated from the substrate. The thickness of the prepared polyamide-imide film was 80 μm, the modulus thereof was 5.5 GPa, and the elongation at break thereof was 15%. In addition, as a result of measuring the light transmittance at a specific wavelength for the prepared polyamide film, the light transmittance at 590 nm was shown to be lower than the average value of the light transmittance at 540 nm and the light transmittance at 640 nm by 1.2%, and the light transmittance at 630 nm was shown to be lower than the light transmittance at 680 nm by 0.9%.

[0106] The light transmittance, YI, b*, the haze, and ΔYI.sub.heat of the prepared polyamide-imide film were measured according to the measurement method and are shown in Table 1.

EXAMPLE 2

[0107] A polyamide-imide film having a thickness of 80 μm was prepared in the same manner as in Example 1, except that cyclobutene tetracarboxylic dianhydride (CBDA) was introduced instead of BPDA. The modulus of the prepared polyamide-imide film was 5.4 GPa, and the elongation at break thereof was 21.5%. In addition, as a result of measuring the light transmittance at a specific wavelength for the prepared polyamide film, the light transmittance at 590 nm was shown to be lower than the average value of the light transmittance at 540 nm and the light transmittance at 640 nm by 1.0%, and the light transmittance at 630 nm was shown to be lower than the light transmittance at 680 nm by 0.9%.

[0108] The light transmittance, YI, b*, the haze, and ΔYI.sub.heat of the prepared polyamide-imide film were measured according to the measurement method and are shown in Table 1.

Comparative Example 1

[0109] A polyamide-imide film having a thickness of 80 μm was prepared in the same manner as in Example 1, except that after completing the reaction, no dye was introduced.

[0110] The light transmittance, YI, b*, the haze, and ΔYI.sub.heat of the prepared polyamide-imide film were measured according to the measurement method and are shown in Table 1.

Comparative Example 2

[0111] A polyamide-imide film having a thickness of 80 μm was prepared in the same manner as in Example 1, except that 500 ppm of a pigment (Cobalt and Aluminum Blue available from Shepherd, maximum absorption wavelength: 603 nm) was introduced instead of a dye.

[0112] The light transmittance, YI, b*, the haze, and ΔYI.sub.heat of the prepared polyamide-imide film were measured according to the measurement method and are shown in Table 1.

Comparative Example 3

[0113] A polyamide-imide film having a thickness of 80 μm was prepared in the same manner as in Example 1, except that Sumiplast Violet B available from Sumitomo, which is an anthraquinone-based dye, was introduced instead of a porphyrin-based dye.

[0114] The light transmittance, YI, b*, the haze, and ΔYI.sub.heat of the prepared polyamide-imide film were measured according to the measurement method and are shown in Table 1.

Comparative Example 4

[0115] A polyamide-imide film having a thickness of 80 μm was prepared in the same manner as in Example 1, except that FASTOGEN Blue CA5380 available from DIC, which is a phthalocyanine-based dye, was introduced instead of a porphyrin-based dye.

[0116] The light transmittance, YI, b*, the haze, and ΔYI.sub.heat of the prepared polyamide-imide film were measured according to the measurement method and are shown in Table 1.

Comparative Example 5

[0117] A polyamide-imide film having a thickness of 80 μm was prepared in the same manner as in Example 1, except that TFMB, 6FDA, and BPDA were introduced at a mole ratio of 1:0.5:0.5, without introducing TPC.

[0118] The light transmittance, YI, b*, the haze, and ΔYI.sub.heat of the prepared polyimide film were measured according to the measurement method and are shown in Table 1.

TABLE-US-00001 TABLE 1 Light transmittance Haze b* YI ΔYI.sub.heat Example 1 88.4 0.76 0.79 1.97 0.08 Example 2 89.0 0.48 0.52 1.25 0.04 Comparative 89.3 0.81 1.45 3.46 0.16 Example 1 Comparative 85.6 1.12 1.38 2.27 0.25 Example 2 Comparative 87.8 0.86 0.83 2.13 0.56 Example 3 Comparative 89.1 0.85 0.92 2.37 0.38 Example 4 Comparative 88.0 0.81 1.80 3.78 0.32 Example 5

[0119] Referring to Table 1, Examples 1 and 2 showed the light transmittance of 88% or more, the haze of 0.8% or less, and the yellow index (YI) of 2 or less, and thus, excellent optical properties were confirmed.

[0120] In particular, in Examples 1 and 2, the ΔYI.sub.heat value was less than 0.1, and thus, it was confirmed that yellow index retention properties were significantly excellent even in a temperature change environment.

[0121] However, in Comparative Example 1 in which no dye was introduced, a yellow index of 3.46 was shown, and thus, it was confirmed that the optical properties were inferior.

[0122] In addition, in Comparative Example 2 in which a pigment was introduced instead of a dye, the yellow index was improved, but was still more than 2, and thus, was insignificantly improved, and the light transmittance and the haze properties were rather deteriorated.

[0123] In Comparative Examples 3 and 4, an anthraquinone-based or phthalocyanine-based dye was employed, and the yellow index was improved, but was still more than 2, and thus, was insignificantly improved.

[0124] In particular, in Comparative Examples 3 and 4, the ΔYI.sub.heat value was more than 0.3, and thus, the yellow index was rapidly lowered in a repeated temperature change environment.

[0125] In Comparative Example 5 in which a polyimide film was used, the yellow index was excessively high and the ΔYI.sub.heat value was more than 0.3, and thus, the yellow retention properties in a repeated temperature change environment were inferior.

[0126] As described above, the polyamide-imide film according to an exemplary embodiment of the present invention, which is a combination of a polyamide-imide resin and a porphyrin-based dye, may show a unique effect, that is, excellent optical properties and excellent yellow index retention properties in a repeated temperature change environment.