Polyiamidemide Film and Flexible Display Panel Including the Same

Abstract

Provided are a polyamideimide film, a window cover film, and a display panel including the same. More specifically, a polyamideimide film including an amideimide structure derived from a dianhydride, a diamine, and an aromatic diacid dichloride is provided, wherein a chlorine content in the film is 5 to 33 ppm and a yellow index change amount ΔYI is 5 or less, the yellow index change amount being measured in accordance with ASTM E313 after repeating a process of irradiating 0.55 W/m.sup.2 of UVA at 340 nm at 40° C. for 20 hours and then blocking UVA for 4 hours three times.

Claims

1. A polyamideimide film comprising an amideimide structure derived from a dianhydride, a diamine, and an aromatic diacid dichloride, wherein a chlorine content in the film is 5 to 33 ppm and a yellow index change amount ΔYI satisfies the following equation, the yellow index change amount being measured in accordance with ASTM E313 after repeating a process of irradiating 0.55 W/m.sup.2 of UVA at 340 nm at 40° C. for 20 hours and then blocking UVA for 4 hours three times:
ΔYI≤5 wherein ΔYI is a yellow index after a UV weathering accelerated test—an initial yellow index.

2. The polyamideimide film of claim 1, wherein the polyamideimide film has the initial yellow index of 4 or less.

3. The polyamideimide film of claim 1, wherein the polyamideimide film has the initial yellow index of 2 or less and the ΔYI of 4 or less.

4. The polyamideimide film of claim 1, wherein a content of the aromatic diacid dichloride is 20 to 80 mol with respect to 100 mol of the diamine.

5. The polyamideimide film of claim 1, wherein the polyamideimide film has a modulus in accordance with ASTM D882 of 4 GPa or more and an elongation at break of 8% or more.

6. The polyamideimide film of claim 1, wherein the polyamideimide film has a light transmittance of 5% or more as measured at 388 nm in accordance with ASTM D1746, a total light transmittance of 87% or more as measured at 400 to 700 nm, a haze of 2.0% or less, and a b* value of 2.0 or less.

7. The polyamideimide film of claim 1, wherein the diamine includes a fluorine-based aromatic diamine.

8. The polyamideimide film of claim 1, wherein the dianhydride includes an aromatic dianhydride and a cycloaliphatic dianhydride.

9. The polyamideimide film of claim 8, wherein 10 to 50 mol of the aromatic dianhydride and 10 to 60 mol of the cycloaliphatic dianhydride are included with respect to 100 mol of the diamine.

10. The polyamideimide film of claim 8, wherein the cycloaliphatic dianhydride includes cyclobutanetetracarboxylic dianhydride (CBDA).

11. The polyamideimide film of claim 1, wherein a sum of the aromatic diacid dichloride and the dianhydride to the diamine has a mole ratio of 1:0.9 to 1.1.

12. The polyamideimide film of claim 1, wherein the polyamideimide film is formed of a block polyamideimide structure.

13. The polyamideimide film of claim 1, wherein the polyamideimide film includes a fluorine-based aromatic diamine-derived unit, an aromatic dianhydride-derived unit, a cycloaliphatic dianhydride-derived unit, and an aromatic diacid dichloride-derived unit.

14. The polyamideimide film of claim 1, wherein the polyamideimide film has a thickness of 10 to 500 μm.

15. A window cover film comprising: the polyamideimide film of claim 1; and a coating layer formed on one surface or both surfaces of the polyamideimide film.

16. The window cover film of claim 15, wherein the coating layer is any one or more selected from a hard coating layer, an antistatic layer, an anti-fingerprint layer, an antifouling layer, an anti-scratch layer, a low-refractive layer, an antireflective layer, and a shock absorption layer.

17. A flexible display panel comprising the polyamideimide film of claim 1.

Description

EXAMPLE 1

<Production of Polyamideimide-Based Film>

[0146] Terephthaloyl dichloride (TPC) and 2,2′-bis(trifluoromethyl)-benzidine (TFMB) were added to a mixed solution of dichloromethane and pyridine in a reactor, and stirring was performed at 25° C. for 2 hours under a nitrogen atmosphere. Here, a mole ratio of TPC:TFMB was 300:400, and a solid content was adjusted to 10 wt %. Thereafter, the reactant was precipitated in an excessive amount of methanol and filtered, and washed with water three times to obtain a solid content, which was dried under vacuum at 50° C. for 6 hours to obtain an oligomer, and the prepared oligomer had a formula weight (FW) of 1670 g/mol.

[0147] N,N-dimethylacetamide (DMAc), 100 mol of the oligomer, and 28.6 mol of 2,2′-bis(trifluoromethyl)-benzidine (TFMB) were added to the reactor and sufficient stirring was performed. After confirming that the solid raw material was completely dissolved, fumed silica (surface area of 95 m.sup.2/g, <1 μm) was added to DMAc at a content of 1000 ppm relative to the solid content, and added to the reactor after being dispersed using ultrasonic waves. 64.3 mol of cyclobutanetetracarboxylic dianhydride (CBDA) and 64.3 mol of 4,4′-hexafluoroisopropylidene diphthalic anhydride (6FDA) were subsequently added, sufficient stirring was performed, and the mixture was polymerized at 40° C. for 10 hours. The solid content was 20% at this time. Subsequently, each of pyridine and acetic anhydride was added sequentially at 2.5-fold relative to the total content of dianhydride, and stirring was performed at 60 ° C. for 12 hours.

[0148] After the polymerization was finished, the polymerization solution was precipitated in an excessive amount of methanol and filtered to obtain a solid content, which was dried under vacuum at 50° C. for 8 hours to obtain polyamideimide powder. The powder was diluted and dissolved at 20 wt % in DMAc to prepare a polyamideimide-based resin solution.

[0149] The polyimide-based resin solution was applied on a glass substrate using an applicator, dried at 80° C. for 30 minutes and 100° C. for 1 hour, and cooled to room temperature to produce a film. Thereafter, a stepwise heat treatment was performed at a heating rate of 20° C./min at 100 to 200° C. and 250 to 300° C. for 2 hours.

[0150] The thus-produced polyamideimide film had a thickness of 48 μm, a chlorine content of 33 ppm, a total light transmittance of 90.1%, a haze of 0.33%, a yellow index (YI) of 1.7, a b* value of 1.1, a modulus of 7.3 GPa, an elongation at break of 24.1%, a weight average molecular weight of 325,000 g/mol, a polydispersity index (PDI) of 2.2, and a pencil hardness of HB/750 g. After the UV weathering accelerated test, it was confirmed that the yellow index was 4.7, which was increased by 3 as compared with the initial value.

EXAMPLE 2

[0151] A film was produced in the same manner as in Example 1, except that a mole ratio of TPC:TFMB was 200:400.

[0152] The thus-produced polyamideimide film had a thickness of 52 μm, a chlorine content of 14 ppm, a total light transmittance of 90.4%, a haze of 0.28%, a yellow index (YI) of 1.5, a b* value of 1.0, a modulus of 8.5 GPa, an elongation at break of 20.5%, a weight average molecular weight of 310,000 g/mol, a polydispersity index (PDI) of 2.6, and a pencil hardness of HB/750 g. After the UV weathering accelerated test, it was confirmed that the yellow index was 4.3, which was increased by 2.8 as compared with the initial value.

EXAMPLE 3

[0153] A film was produced in the same manner as in Example 1, except that a mole ratio of TPC:TFMB was 120:400.

[0154] The physical properties of the thus-produced polyamideimide film were a thickness of 50 μm, a chlorine content of 25 ppm, a total light transmittance of 90.3%, a haze of 0.31%, a yellow index (YI) of 1.8, a b* value of 1.2, a modulus of 7.9 GPa, an elongation at break of 19.5%, a weight average molecular weight of 300,000 g/mol, a polydispersity index (PDI) of 2.1, and a pencil hardness of HB/750 g. After the UV weathering accelerated test, it was confirmed that the yellow index was 4.8, which was increased by 3 as compared with the initial value.

EXAMPLE 4

[0155] A film was produced in the same manner as in Example 1, except that 100 mol of the oligomer and 28.6 mol of 2,2′-bis(trifluoromethyl)-benzidine (TFMB) were used and 128.6 mol of 4,4′-hexafluoroisopropylidene diphthalic anhydride (6FDA) was used in the preparation of polyamideimide.

[0156] The thus-produced polyamideimide film had a thickness of 42 μm, a chlorine content of 6 ppm, a total light transmittance of 90.5%, a haze of 0.26%, a yellow index (YI) of 1.7, a b* value of 1.2, a modulus of 7.9 GPa, an elongation at break of 24.5%, a weight average molecular weight of 340,000 g/mol, a polydispersity index (PDI) of 2.1, and a pencil hardness of HB/750 g. After the UV weathering accelerated test, it was confirmed that the yellow index was 4.6, which was increased by 2.9 as compared with the initial value.

Comparative Example 1

[0157] A reactor was filled with N,N-dimethylacetamide (DMAc) under a nitrogen atmosphere, 100 mol of 2,2′-bis(trifluoromethyl)-benzidine (TFMB) was added thereto, sufficient stirring was performed, 40 mol of 4,4′-hexafluoroisopropylidene diphthalic anhydride (6FDA) was added thereto, and sufficient stirring was performed until the materials were dissolved. Thereafter, 40 mol of cyclobutanetetracarboxylic dianhydride (CBDA) was added and sufficient stirring was performed until the materials were dissolved. Thereafter, 20 mol of terephthaloyl dichloride (TPC) was introduced and stirring was performed for 6 hours to carry out dissolution and reaction, thereby preparing a polyamic acid resin composition. Each monomer was adjusted to have a solid content of 6.5 wt %. Pyridine and acetic anhydride were sequentially added to the composition at 2.5-fold of the moles of the total dianhydrides, and were stirred at 60 ° C. for 1 hour. Thereafter, the solution was precipitated in an excessive amount of methanol and filtered to obtain a solid content, which was dried under vacuum at 50° C. for 6 hours to obtain polyamideimide powder. The powder was diluted and dissolved at 20 wt % in DMAc to prepare a composition.

[0158] The composition was cast on a glass substrate to form a film, which was then separated from the substrate. The thus-produced polyamideimide film had a thickness of 42 μm, a chlorine content of 48 ppm, a yellow index (YI) of 3.5, and a yellow index after a UV weathering accelerated test of 9, which was increased by 5.5 as compared with the initial value. In addition, the produced film had a modulus of 4 GPa and an elongation at break of 15.5%, which was low as compared with Example 1. In addition, it was confirmed that the film had a weight average molecular weight of 260,000 g/mol, a pencil hardness of Hb/750 g, a total light transmittance of 87.5%, and a haze of 1.5%.

COMPARATIVE EXAMPLE 2

[0159] A film was produced in the same manner as in Example 1, except that a process of mixing a polyamideimide-based resin solution with an excessive amount of water, performing filtration to obtain a resin, dissolving the obtained resin in a DMAc solution again, and precipitating the resin in an excessive amount of water was performed 5 times to obtain polyamideimide, which was dissolved in DMAc to produce a film.

[0160] The thus-produced film had a thickness of 52 μm, a chlorine content of 4 ppm, a total light transmittance of 90.1%, a haze of 0.8%, a yellow index (YI) of 3, a b* value of 1.2, a modulus of 5 GPa, and an elongation at break of 15%. After the UV weathering accelerated test, it was confirmed that the yellow index was 8, which was increased by 5.3 as compared with the initial value.

COMPARATIVE EXAMPLE 3

[0161] A film was produced in the same manner as in Example 1, except that after the polyamic acid oligomer was prepared, the oligomer was precipitated in an excessive amount of methanol and filtered to obtain a solid content, which was dried in vacuum at 90° C. for 48 hours to obtain an oligomer. The obtained film had a thickness of 52 μm, a chlorine content of 68 ppm, a total light transmittance of 89.5%, a haze of 1.1%, a yellow index (YI) of 4, a b* value of 1.2, a modulus of 5.5 GPa, an elongation at break of 16%, a weight average molecular weight of 260,000 g/mol, and a pencil hardness of HB/750 g. After the UV weathering accelerated test, it was confirmed that the yellow index was 11, which was increased by 7 as compared with the initial value.

TABLE-US-00001 TABLE 1 Chlorine Total light Yellow index Elongation content transmittance Haze After UV Modulus at break (ppm) (%) (%) Initially treatment ΔYI (GPa) (%) Example 1 33 90.1 0.33 1.7 4.7 3 7.3 24.1 Example 2 14 90.4 0.28 1.5 4.3 2.8 8.5 20.5 Example 3 25 90.3 0.31 1.8 4.8 3 7.9 19.5 Example 4 6 90.5 0.26 1.7 4.6 2.9 7.9 24.5 Comparative 48 87.5 1.5 3.5 9 5.5 4 15.5 Example 1 Comparative 4 90.1 0.8 3 8.3 5.3 5 15 Example 2 Comparative 68 89.5 1.1 4 11 7 5.5 16 Example 3

[0162] The polyamideimide film according to an exemplary embodiment of the present invention has a high transmittance to visible light to have excellent transparency and has excellent mechanical physical properties and thermal resistance, and thus, may provide physical properties appropriate for use as a window cover film of a flexible display panel.

[0163] In addition, the polyamideimide film has a low yellow index of 4 or less and has a small change in the yellow index even in the case of long-term exposure to ultraviolet rays, while satisfying transparency and mechanical physical properties as described above, and thus, may provide a film having excellent weatherability.

[0164] Hereinabove, although the present invention has been described by specified matters and specific exemplary embodiments, they have been provided only for assisting in the entire understanding of the present invention. Therefore, the present invention is not by the specific matters limited to the exemplary embodiments. Various modifications and changes may be made by those skilled in the art to which the present invention pertains from this description.

[0165] Therefore, the spirit of the present invention should not be limited to the above-described exemplary embodiments, and the following claims as well as all modified equally or equivalently to the claims are intended to fall within the scope and spirit of the invention.