Poly(amide-imide) copolymer composition and colorless and transparent poly(amide-imide) film comprising the same

Abstract

A poly(amide-imide) copolymer composition comprising an imide of a polyamic acid and an ultraviolet stabilizer, and a colorless and transparent poly(amide-imide) film including the composition. The poly(amide-imide) copolymer composition according to the present disclosure makes it possible to provide a poly(amide-imide) film exhibiting excellent scratch resistance, UV shielding property, and UV weather resistance while being colorless and transparent. This film can be suitably used as a cover film of various flexible or foldable devices.

Claims

1. A poly(amide-imide) film consisting essentially of: a poly(amide-imide) copolymer resulting from copolymerizing an aromatic diamine monomer, an aromatic dianhydride monomer, and an aromatic dicarbonyl monomer; and an ultraviolet stabilizer, wherein the aromatic dicarbonyl monomer is contained in an amount of at least 50 mol % based on the total moles of the aromatic dianhydride monomer and the aromatic dicarbonyl monomer, and the aromatic dicarbonyl monomer consists of 0 to 35 mol % of 4,4′-biphenyldicarbonyl chloride, 5 to 40 mol % of isophthaloyl chloride, and 60 to 95 mol % of terephthaloyl chloride, based on the total moles of the aromatic dicarbonyl monomer, and wherein the film at a thickness of 50±2 μm has a pencil hardness measured according to ASTM D3363 of a 2H grade or more and a modulus of 6.5 GPa or more measured according to ASTM D882.

2. The poly(amide-imide) film of claim 1, wherein a rate of change (dT/dλ) of light transmittance (T) with respect to a wavelength (λ) in a light transmittance range of 10% to 80% and in a wavelength range of 350 nm to 450 nm is 2.8 to 4.0 at a film thickness of 50±2 μm.

3. The poly(amide-imide) film of claim 1, wherein a rate of change (dT/dλ) of light transmittance (T) with respect to a wavelength (λ) in a light transmittance range of 10% to 80% and in a wavelength range of 350 nm to 450 nm is 2.9 to 3.9 at a film thickness of 50±2 μm.

4. The poly(amide-imide) film of claim 1, wherein the ultraviolet stabilizer is at least one compound selected from the group consisting of a benzophenone-based ultraviolet absorber, a benzotriazole-based ultraviolet absorber, a salicylate-based ultraviolet absorber, a cyanoacrylate-based ultraviolet absorber, a nickel complex salt ultraviolet absorber, and a hindered amine-based light stabilizer (HALS).

5. The poly(amide-imide) film of claim 1, wherein the ultraviolet stabilizer is contained in an amount of 0.1 to 15 parts by weight based on 100 parts by weight of the poly(amide-imide)copolymer.

6. The poly(amide-imide) film of claim 1, wherein the aromatic dianhydride monomer is contained in an amount of 25 mol % or less based on the aromatic diamine monomer.

7. The poly(amide-imide) film of claim 1, wherein the aromatic diamine monomer is at least one compound selected from the group of 2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine and 2,2′-dimethyl-4,4′-diaminobiphenyl.

8. The poly(amide-imide) film of claim 1, wherein the aromatic dianhydride monomer is at least one compound selected from the group of 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride and cyclobutane-1,2,3,4-tetracarboxylic dianhydride.

9. The poly(amide-imide) film of claim 1, wherein a rate of change (dT/dλ) of light transmittance (T) with respect to a wavelength (λ) in a light transmittance range of 10% to 80% and in a wavelength range of 350 nm to 450 nm is 3.0 to 3.8 at a film thickness of 50±2 μm.

10. The poly(amide-imide) film of claim 1, wherein a rate of change (dT/dλ) of light transmittance (T) with respect to a wavelength (λ) in a light transmittance range of 10% to 80% and in a wavelength range of 350 nm to 450 nm is 3.3 to 3.5 at a film thickness of 50±2 μm.

11. The poly(amide-imide) film of claim 1, wherein the film has an initial yellow index (YI.sub.0) measured according to ASTM D1925 of 3.5 or less at a film thickness of 50±2 μm.

12. The poly(amide-imide) film of claim 11, wherein the film at a film thickness of 50±2 μm has a coefficient of thermal expansion of 15 ppm/° C. or less.

13. The poly(amide-imide) film of claim 1, wherein the film at a thickness of 50±2 μm has transmittance of 88.0% or more with respect to visible light having a wavelength of 550 nm, and transmittance of 15.0% or less with respect to ultraviolet light having a wavelength of 388 nm.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

(1) Hereinafter, preferred examples are provided for better understanding. However, these examples are for illustrative purposes only, and the invention is not intended to be limited by these examples.

Example 1

(2) In a 1000 mL 4-neck round flask (reactor) equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller, and a condenser, 42.5 g of N,N-dimethylacetamide was placed while slowly flowing nitrogen therein, the temperature of the reactor was adjusted to 25° C., and then 3.0441 g (0.00951 mol) of 2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine was added thereto to be completely dissolved. While maintaining the temperature of the solution at 25° C., 0.0839 g (0.00029 mol) of 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride was added thereto to be dissolved.

(3) After the temperature of the solution was cooled down to −10° C., 0.3281 g (0.00162 mol) of isophthaloyl chloride and 1.5439 g (0.0076 mol) of terephthaloyl chloride were added thereto and stirred to obtain a polyamic acid solution having a solid content of 10 wt %.

(4) N,N-dimethylacetamide was added to the polyamic acid solution to dilute the solid content to 5 wt % or less, and then the solid content was precipitated using 2 L of methanol.

(5) The precipitated solid content was filtered and then dried at 100° C. under vacuum for 6 hours or more to obtain a poly(amide-imide) copolymer in the form of a solid (weight average molecular weight: 112,481 g/mol).

(6) The poly(amide-imide) copolymer and 2-(2′-hydroxy-5′-tert-octylphenyl)benzotriazole (Tinuvin 329, BASF; 5 parts by weight based on 100 parts by weight of the solid content copolymer) were dissolved in N,N-dimethylacetamide to obtain a poly(amide-imide) copolymer composition having a solid content of 15 wt %.

Example 2

(7) In a 1000 mL 4-neck round flask (reactor) equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller, and a condenser, 42.5 g of N,N-dimethylacetamide was placed while slowly flowing nitrogen therein, the temperature of the reactor was adjusted to 25° C., and then 2.9569 g (0.00923 mol) of 2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine was added thereto to be completely dissolved. While maintaining the temperature of the solution at 25° C., 0.5434 g (0.00185 mol) of 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride was added thereto to be dissolved.

(8) After the temperature of the solution was cooled down to −10° C., 0.1875 g (0.00092 mol) of isophthaloyl chloride and 1.3122 g (0.0064 mol) of terephthaloyl chloride were added thereto and stirred to obtain a polyamic acid solution having a solid content of 10 wt %.

(9) N,N-dimethylacetamide was added to the polyamic acid solution to dilute the solid content to 5 wt % or less, and then the solid content was precipitated using 2 L of methanol.

(10) The precipitated solid content was filtered and then dried at 100° C. under vacuum for 6 hours or more to obtain a poly(amide-imide) copolymer in the form of a solid (weight average molecular weight: 97,146 g/mol).

(11) The poly(amide-imide) copolymer and 2-(2′-hydroxy-5′-tert-octylphenyl)benzotriazole (Tinuvin 329, BASF; 5 parts by weight based on 100 parts by weight of the solid content copolymer) were dissolved in N,N-dimethylacetamide to obtain a poly(amide-imide) copolymer composition having a solid content of 15 wt %.

Example 3

(12) In a 1000 mL 4-neck round flask (reactor) equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller, and a condenser, 42.5 g of N,N-dimethylacetamide was placed while slowly flowing nitrogen therein, the temperature of the reactor was adjusted to 25° C., and then 2.5391 g (0.01196 mol) of 2,2′-dimethyl-4,4′-diaminobiphenyl was added thereto to be completely dissolved. While maintaining the temperature of the solution at 25° C., 0.1056 g (0.00036 mol) of 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride was added thereto to be dissolved.

(13) After the temperature of the solution was cooled down to −10° C., 0.4128 g (0.00203 mol) of isophthaloyl chloride and 1.9426 g (0.00957 mol) of terephthaloyl chloride were added thereto and stirred to obtain a polyamic acid solution having a solid content of 10 wt %.

(14) N,N-dimethylacetamide was added to the polyamic acid solution to dilute the solid content to 5 wt % or less, and then the solid content was precipitated using 2 L of methanol.

(15) The precipitated solid content was filtered and then dried at 100° C. under vacuum for 6 hours or more to obtain a poly(amide-imide) copolymer in the form of a solid (weight average molecular weight: 132,481 g/mol).

(16) The poly(amide-imide) copolymer and 2-(2′-hydroxy-5′-tert-octylphenyl)benzotriazole (Tinuvin 329, BASF; 5 parts by weight based on 100 parts by weight of the solid content copolymer) were dissolved in N,N-dimethylacetamide to obtain a poly(amide-imide) copolymer composition having a solid content of 15 wt %.

Example 4

(17) In a 1000 mL 4-neck round flask (reactor) equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller, and a condenser, 42.5 g of N,N-dimethylacetamide was placed while slowly flowing nitrogen therein, the temperature of the reactor was adjusted to 25° C., and then 3.0612 g (0.00956 mol) of 2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine was added thereto to be completely dissolved. While maintaining the temperature of the solution at 25° C., 0.0562 g (0.00029 mol) of cyclobutane-1,2,3,4-tetracarboxylic dianhydride was added thereto to be dissolved.

(18) After the temperature of the solution was cooled down to −10° C., 0.3299 g (0.00163 mol) of isophthaloyl chloride and 1.5526 g (0.00765 mol) of terephthaloyl chloride were added thereto and stirred to obtain a polyamic acid solution having a solid content of 10 wt %.

(19) N,N-dimethylacetamide was added to the polyamic acid solution to dilute the solid content to 5 wt % or less, and then the solid content was precipitated using 2 L of methanol.

(20) The precipitated solid content was filtered and then dried at 100° C. under vacuum for 6 hours or more to obtain a poly(amide-imide) copolymer in the form of a solid (weight average molecular weight: 122,681 g/mol).

(21) The poly(amide-imide) copolymer and 2-(2′-hydroxy-5′-tert-octylphenyl)benzotriazole (Tinuvin 329, BASF; 5 parts by weight based on 100 parts by weight of the solid content copolymer) were dissolved in N,N-dimethylacetamide to obtain a poly(amide-imide) copolymer composition having a solid content of 15 wt %.

Example 5

(22) In a 1000 mL 4-neck round flask (reactor) equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller, and a condenser, 42.5 g of N,N-dimethylacetamide was placed while slowly flowing nitrogen therein, the temperature of the reactor was adjusted to 25° C., and then 1.6961 g (0.0053 mol) of 2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine and 1.1244 g (0.0053 mol) of 2,2′-dimethyl-4,4′-diaminobiphenyl were added thereto to be completely dissolved. While maintaining the temperature of the solution at 25° C., 0.0935 g (0.00032 mol) of 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride was added thereto to be dissolved.

(23) After the temperature of the solution was cooled down to −10° C., 0.365 g (0.0018 mol) of isophthaloyl chloride and 1.7205 g (0.00847 mol) of terephthaloyl chloride were added thereto and stirred to obtain a polyamic acid solution having a solid content of 10 wt %.

(24) N,N-dimethylacetamide was added to the polyamic acid solution to dilute the solid content to 5 wt % or less, and then the solid content was precipitated using 2 L of methanol.

(25) The precipitated solid content was filtered and then dried at 100° C. under vacuum for 6 hours or more to obtain a poly(amide-imide) copolymer in the form of a solid (weight average molecular weight: 133,224 g/mol).

(26) The poly(amide-imide) copolymer and 2-(2′-hydroxy-5′-tert-octylphenyl)benzotriazole (Tinuvin 329, BASF; 5 parts by weight based on 100 parts by weight of the solid content copolymer) were dissolved in N,N-dimethylacetamide to obtain a poly(amide-imide) copolymer composition having a solid content of 15 wt %.

Example 6

(27) In a 1000 mL 4-neck round flask (reactor) equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller, and a condenser, 42.5 g of N,N-dimethylacetamide was placed while slowly flowing nitrogen therein, the temperature of the reactor was adjusted to 25° C., and then 3.0547 g (0.00954 mol) of 2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine was added thereto to be completely dissolved. While maintaining the temperature of the solution at 25° C., 0.0281 g (0.0001 mol) of 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride was added thereto to be dissolved.

(28) After the temperature of the solution was cooled down to −10° C., 0.368 g (0.00181 mol) of isophthaloyl chloride and 1.5493 g (0.00763 mol) of terephthaloyl chloride were added thereto and stirred to obtain a polyamic acid solution having a solid content of 10 wt %.

(29) N,N-dimethylacetamide was added to the polyamic acid solution to dilute the solid content to 5 wt % or less, and then the solid content was precipitated using 2 L of methanol.

(30) The precipitated solid content was filtered and then dried at 100° C. under vacuum for 6 hours or more to obtain a poly(amide-imide) copolymer in the form of a solid (weight average molecular weight: 112,481 g/mol).

(31) The poly(amide-imide) copolymer and 2-(2′-hydroxy-5′-tert-octylphenyl)benzotriazole (Tinuvin 329, BASF; 5 parts by weight based on 100 parts by weight of the solid content copolymer) were dissolved in N,N-dimethylacetamide to obtain a poly(amide-imide) copolymer composition having a solid content of 15 wt %.

Comparative Example 1

(32) In a 1000 mL 4-neck round flask (reactor) equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller, and a condenser, 42.5 g of N,N-dimethylacetamide was placed while slowly flowing nitrogen therein, the temperature of the reactor was adjusted to 25° C., and then 3.0441 g (0.00951 mol) of 2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine was added thereto to be completely dissolved. While maintaining the temperature of the solution at 25° C., 0.0839 g (0.00029 mol) of 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride was added thereto to be dissolved.

(33) After the temperature of the solution was cooled down to −10° C., 0.8685 g (0.00428 mol) of isophthaloyl chloride and 1.0035 g (0.00494 mol) of terephthaloyl chloride were added thereto and stirred to obtain a polyamic acid solution having a solid content of 10 wt %.

(34) Dimethylacetamide was added to the polyamic acid solution to dilute the solid content to 5 wt % or less, and then the solid content was precipitated using 2 L of methanol.

(35) The precipitated solid content was filtered and then dried at 100° C. under vacuum for 6 hours or more to obtain a poly(amide-imide) copolymer in the form of a solid (weight average molecular weight: 92,554 g/mol).

(36) The poly(amide-imide) copolymer and 2-(2′-hydroxy-5′-tert-octylphenyl)benzotriazole (Tinuvin 329, BASF; 5 parts by weight based on 100 parts by weight of the solid content copolymer) were dissolved in N,N-dimethylacetamide to obtain a poly(amide-imide) copolymer composition having a solid content of 15 wt %.

Comparative Example 2

(37) A poly(amide-imide) copolymer composition having a solid content of 15 wt % was obtained in the same manner as in Comparative Example 1, except that 2-(2′-hydroxy-5′-tert-octylphenyl)benzotriazole was not added thereto.

Comparative Example 3

(38) In a 1000 mL 4-neck round flask (reactor) equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller, and a condenser, 42.5 g of N,N-dimethylacetamide was placed while slowly flowing nitrogen therein, the temperature of the reactor was adjusted to 25° C., and then 2.9569 g (0.00923 mol) of 2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine was added thereto to be completely dissolved. While maintaining the temperature of the solution at 25° C., 0.05434 g (0.00185 mol) of 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride was added thereto to be dissolved.

(39) After the temperature of the solution was cooled down to −10° C., 0.0562 g (0.00028 mol) of isophthaloyl chloride and 1.4435 g (0.00711 mol) of terephthaloyl chloride were added thereto and stirred to obtain a polyamic acid solution having a solid content of 10 wt %.

(40) Dimethylacetamide was added to the polyamic acid solution to dilute the solid content to 5 wt % or less, and then the solid content was precipitated using 2 L of methanol.

(41) The precipitated solid content was filtered and then dried at 100° C. under vacuum for 6 hours or more to obtain a poly(amide-imide) copolymer in the form of a solid (weight average molecular weight: 112,481 g/mol).

(42) The poly(amide-imide) copolymer and 2-(2′-hydroxy-5′-tert-octylphenyl)benzotriazole (Tinuvin 329, BASF; 5 parts by weight based on 100 parts by weight of the solid content copolymer) were dissolved in N,N-dimethylacetamide to obtain a poly(amide-imide) copolymer composition having a solid content of 15 wt %.

(43) TABLE-US-00001 TABLE 1 UV stabilizer Poly(amide-imide) copolymer (mol %) (parts by TFDB m-TBHG BPDA CBDA IPC TPC weight) Example 1 50 — 1.5 — 8.5 40 5 Example 2 50 — 10  — 5 35 5 Example 3 — 50 1.5 — 8.5 40 5 Example 4 50 — — 1.5 8.5 40 5 Example 5 25 25 1.5 — 8.5 40 5 Example 6 50 — 0.5 — 9.5 40 5 Comp. Ex. 1 50 — 1.5 — 22.5 26 5 Comp. Ex. 2 50 — 1.5 — 22.5 26 — Comp. Ex. 3 50 — 10  — 1.5 38.5 5 TFDB: 2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine m-TBHG: 2,2′-dimethyl-4,4′-diaminobiphenyl BPDA: 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride CBDA: Cyclobutane-1,2,3,4-tetracarboxylic dianhydride IPC: Isophthaloyl chloride TPC: Terephthaloyl chloride

Example 7

(44) The poly(amide-imide) copolymer composition obtained in Example 1 was poured onto a plastic substrate (UPILEX-75s, UBE) and the thickness of the polymer solution was uniformly controlled using a film applicator. Then, it was dried in a Mathis oven at 80° C. for 10 minutes, and cured at 250° C. for 30 minutes while flowing nitrogen therein to obtain a poly(amide-imide) film having a thickness of 50.1 μm after being peeled from the substrate.

Example 8

(45) A film having a thickness of 50.2 μm was obtained in the same manner as in Example 7, except that the copolymer obtained in Example 2 was used in place of the copolymer obtained in Example 1.

Example 9

(46) A film having a thickness of 49.8 μm was obtained in the same manner as in Example 7, except that the copolymer obtained in Example 3 was used in place of the copolymer obtained in Example 1.

Example 10

(47) A film having a thickness of 52.1 μm was obtained in the same manner as in Example 7, except that the copolymer obtained in Example 4 was used in place of the copolymer obtained in Example 1.

Example 11

(48) A film having a thickness of 50.0 μm was obtained in the same manner as in Example 7, except that the copolymer obtained in Example 5 was used in place of the copolymer obtained in Example 1.

Example 12

(49) A film having a thickness of 50.3 μm was obtained in the same manner as in Example 7, except that the copolymer obtained in Example 6 was used in place of the copolymer obtained in Example 1.

Comparative Example 4

(50) A film having a thickness of 49.4 μm was obtained in the same manner as in Example 7, except that the copolymer obtained in Comparative Example 1 was used in place of the copolymer obtained in Example 1.

Comparative Example 5

(51) A film having a thickness of 49.8 μm was obtained in the same manner as in Example 7, except that the copolymer obtained in Comparative Example 2 was used in place of the copolymer obtained in Example 1.

Comparative Example 6

(52) A film having a thickness of 50.2 μm was obtained in the same manner as in

(53) Example 7, except that the copolymer obtained in Comparative Example 3 was used in place of the copolymer obtained in Example 1. However, the film of Comparative Example 6 was very hazy after curing, so the main properties of the experimental examples below were not evaluated.

Experimental Examples

(54) The following characteristics were measured or evaluated for the films of the Examples 7 to 12 and Comparative Examples 4 to 6, and the results are shown in Tables 2 to 4 below.

(55) (1) Pencil Hardness

(56) The pencil hardness of the films was measured in accordance with ASTM D3363 using a pencil hardness Tester. Specifically, pencils of varying hardness values were fixed to the tester and scratched on the film, and then, the degree of occurrence of scratches on the film was observed with the naked eye or with a microscope. When more than 70% of the total number of scratches were not observed, a value corresponding to the hardness of the pencil was evaluated as the pencil hardness of the film.

(57) (2) Yellow Index

(58) The initial yellow index (YI.sub.0) of the film was measured according to the method of ASTM D1925 using a UV-2600 UV-Vis Spectrometer (SHIMADZU).

(59) (3) UV weather Resistance

(60) The yellow index (YI.sub.3) of the film was measured in accordance with ASTM D1925 using a QUV Accelerated Weathering Tester (Q-LAB), after exposure of the film to ultraviolet light and water for 96 hours in accordance with ASTM G53 [Practice for Operating Light- and Water-Exposure Apparatus (Fluorescent UV-Condensation Type) for Exposure of Nonmetallic Materials].

(61) (4) Transmittance (T)

(62) The total light transmittance of the film was measured using a UV-VIS-NIR Spectrophotometer (SolidSpec-3700, SHIMADZU), and the transmittance with respect to visible light having a wavelength of 550 nm and the transmittance with respect to ultraviolet light having a wavelength of 388 nm are shown in the following tables.

(63) (5) Slope of Ultraviolet Cut-Off

(64) The rate of change (dT/dλ) of light transmittance (T, %) in a wavelength range of 350 nm to 450 nm was measured, when the total light transmittance was measured using a UV-VIS-NIR Spectrophotometer (SolidSpec-3700, SHIMADZU).

(65) (6) Flexibility

(66) The folding endurance of the film was evaluated using an MIT-type folding endurance tester. Specifically, a specimen (1 cm*7 cm) of the film was loaded into the folding endurance tester, and bent at a speed of 175 rpm and an angle of 135° on the left and right sides of the specimen, with a radius of curvature of 0.8 mm and a load of 250 g. Then, the number of reciprocating bends (cycles) until fracture was measured.

(67) (7) Modulus

(68) The Modulus (GPa) was measured according to the method of ASTM D 882 using a Universal Testing Machine (Zwick/RoellZ0.5).

(69) (8) Coefficient of Thermal Expansion (CTE)

(70) The coefficient of thermal expansion at 50 to 300° C. was measured according to a TMA method (temperature elevation at 10° C./min, load of 100 mN) using TMA equipment (SDTA840, manufactured by Mettler Toledo).

(71) TABLE-US-00002 TABLE 2 Example 7 Example 8 Example 9 Pencil hardness 3H 3H 3H YI.sub.0 2.68 3.00 2.89 YI.sub.3 4.78 4.73 4.99 T (%) @ 388 nm 11.8 3.81 4.51 T (%) @ 550 nm 88.8 88.7 88.8 dT/dλ 3.5 3.4 3.4 Flexibility (cycle) 100,000 or 100,000 or 100,000 or more more more Modulus (GPa) 7.21 6.88 8.24 CTE (ppm/° C.) 12.1 13.8 6.7

(72) TABLE-US-00003 TABLE 3 Example 10 Example 11 Example 12 Pencil hardness 3H 3H 3H YI.sub.0 2.57 2.81 2.61 YI.sub.3 4.88 4.77 4.84 T (%) @ 388 nm 12.8 7.8 13.0 T (%) @ 550 nm 89.2 88.8 89.0 dT/dλ 3.5 3.3 3.4 Flexibility (cycle) 100,000 or 100,000 or 100,000 or more more more Modulus (GPa) 6.48 7.73 7.31 CTE (ppm/° C.) 11.4 9.8 11.7

(73) TABLE-US-00004 TABLE 4 Comparative Comparative Comparative Example 4 Example 5 Example 6 Pencil hardness 2B 2B — YI.sub.0 2.58 2.43 — YI.sub.3 5.38 12.20 — T (%) @ 388 nm 12.4 67.4 — T (%) @ 550 nm 88.9 89.1 — dT/dλ 3.0 2.5 Flexibility (cycle) 100,000 or 100,000 or 1000 or more more less Modulus (GPa) 5.1 5.1 — CTE (ppm/° C.) 21.1 20.4 —

(74) Referring to Tables 2 and 3, it was confirmed that all the films of Examples 7 to 12 exhibited high pencil hardness of a 3H grade, a low initial yellow index (YI.sub.0) of 3.0 or less, and a small ΔYI(=YI.sub.3−YI.sub.0) value of 2.5 or less.

(75) Particularly, the films of Examples 7 to 12 exhibited not only low transmittance with respect to ultraviolet light of 15% or less, but also a high slope of ultraviolet cut-off (dT/dλ) of 3.3 or more. In addition, the films of Examples 7 to 12 exhibited moduli of 6.5 GPa or more, and coefficients of thermal expansion of 15 ppm/° C. or less.

(76) On the other hand, referring to Table 4, the films of Comparative Examples 4 and 5 exhibited low pencil hardness of a 2B grade. In addition, the films of Comparative Examples 4 and 5 exhibited a high ΔYI(=YI.sub.3−YI.sub.0) value of 2.8 or more, and particularly, the film of Comparative Examples 5 exhibited very poor UV weather resistance.

(77) In addition, the films of Comparative Examples 4 and 5 exhibited lower moduli than that of the films of the examples, and coefficients of thermal expansion of 20 ppm/° C. or more.

(78) The film of Comparative Example 6 was very hazy after curing, and the main properties of the experimental examples were not evaluated.