POLYAMIDE RESIN FILM AND RESIN LAMINATE USING THE SAME

Abstract

The present invention relates to a polyamide resin film having improved light resistance by minimizing color difference variation rate due to long-term ultraviolet irradiation, and a resin laminate using the same.

Claims

1. A polyamide resin film in which a color difference variation rate (Eab.sub.1) value on the 1st day (n=1) of ultraviolet irradiation according to the following Mathematical Formula 1 is 2.5 or less:
Eab.sub.n={(L.sub.n−L.sub.n−1).sup.2+(a.sub.n−a.sub.n−1).sup.2+(b.sub.n−b.sub.n−1).sup.2}.sup.1/2  [Mathematical Formula 1] wherein, L.sub.n−1 is a lightness index of the polyamide resin film on the (n−1)th day of ultraviolet irradiation, a.sub.n−1 and b.sub.n−1 are color coordinates of the polyamide resin film on the (n−1)th day of ultraviolet irradiation, L.sub.n is a lightness index of the polyamide resin film on the n-th day of ultraviolet irradiation, and a.sub.n and b.sub.n are color coordinates of the polyamide resin film on the n-th day of ultraviolet irradiation.

2. The polyamide resin film of claim 1, wherein a lightness index L.sub.1 of the polyamide resin film on the 1.sup.st day of ultraviolet irradiation is at least 93.

3. The polyamide resin film of claim 1, wherein a color coordinate a.sub.1 of the polyamide resin film on the 1.sup.st day of ultraviolet irradiation is −1.5 or more, and b.sub.1 is 4 or less.

4. The polyamide resin film of claim 1, wherein the color difference variation rate (Eab.sub.5) value on the 5th day (n=5) of ultraviolet irradiation according to the Mathematical Formula 1 is 0.2 or less.

5. The polyamide resin film of claim 1, wherein the color difference variation rate (Eab.sub.1) value on the 1.sup.st day (n=1) of ultraviolet irradiation according to the Mathematical Formula 1 is 20 times or less the color difference variation rate (Eab.sub.10) value on the 10th day (n=10) of ultraviolet irradiation according to the Mathematical Formula 1.

6. The polyamide resin film of claim 1, wherein after irradiating the polyamide resin film with ultraviolet rays for 1 day, a yellowness index measured according to ASTM E313 is 7 or less.

7. The polyamide resin film of claim 1, wherein a difference between a yellowness index measured according to ASTM E313 after irradiating the polyamide resin film with ultraviolet rays for 10 days, and a yellowness index measured according to ASTM E313 after irradiating the polyamide resin film with ultraviolet rays for 1 day, is 2.5 or less.

8. The polyamide resin film of claim 1, wherein the polyamide resin film has a retardation (Rth) value in the thickness direction at a wavelength of 550 nm of −8000 nm or more and −3000 nm or less, and a moisture absorption rate according to the following Mathematical Formula 2 is 0.5% or more and 7.0% or less:
Moisture Absorption Rate (%)=(W1−W2)*100/W2  [Mathematical Formula 2] wherein in the Mathematical Formula 2, W1 is a weight measured by impregnating the polyamide resin film in ultrapure water for 24 hours, and W2 is a weight measured by drying the polyamide resin film at 150° C. for 30 minutes after the impregnation.

9. The polyamide resin film of claim 1, wherein the polyamide resin film has a retardation (Rth) value in the thickness direction at a wavelength of 550 nm of −6000 nm or more and −3000 nm or less.

10. The polyamide resin film of claim 1, wherein a haze measured according to ASTM D1003 for a specimen having a thickness of 45 or more and 55 or less is 3.0% or less.

11. The polyamide resin film of claim 1, wherein the polyamide resin film includes a polyamide resin containing aromatic amide repeating units derived from a combination of an aromatic diacyl compound and an aromatic diamine compound; and an ultraviolet light stabilizer.

12. The polyamide resin film of claim 11, wherein the polyamide resin includes a first polyamide segment containing a repeating unit represented by Chemical Formula 1, or a block comprised thereof: ##STR00013## in the Chemical Formula 1, Ar.sub.1 is a substituted or unsubstituted arylene group having 6 to 20 carbon atoms, or a substituted or unsubstituted heteroarylene group having 2 to 20 carbon atoms.

13. The polyamide resin film of claim 12, wherein the first polyamide segment has a number average molecular weight of 100 g/mol or more and 5000 g/mol or less.

14. The polyamide resin film of claim 12, wherein the polyamide resin further includes a second polyamide segment containing a repeating unit represented by Chemical Formula 2, or a block comprised thereof: ##STR00014## in the Chemical Formula 2, Ar.sub.2 is a substituted or unsubstituted arylene group having 6 to 20 carbon atoms, or a substituted or unsubstituted heteroarylene group having 2 to 20 carbon atoms.

15. The polyamide resin film of claim 14, wherein based on the total repeating units contained in the polyamide resin, a content of the repeating unit represented by Chemical Formula 1 is 60 mol % to 95 mol %, and a content of the repeating unit represented by Chemical Formula 2 is 5 mol % to 40 mol %.

16. The polyamide resin film of claim 14, wherein the first polyamide segment and the second polyamide segment form a backbone chain including an alternating repeating unit represented by Chemical Formula 3: ##STR00015## in the Chemical Formula 3, A is the first polyamide segment, and B is the second polyamide segment.

17. The polyamide resin film of claim 16, wherein the alternating repeating unit represented by Chemical Formula 3 is a repeating unit represented by Chemical Formula 4: ##STR00016## in the Chemical Formula 4, Ar.sub.1 and Ar.sub.2 are each independently a substituted or unsubstituted arylene group having 6 to 20 carbon atoms, or a substituted or unsubstituted heteroarylene group having 2 to 20 carbon atoms, a1 and a2 are each independently an integer of 1 to 10, and b1 and b2 are each independently an integer of 1 to 5.

18. The polyamide resin film of claim 11, wherein the ultraviolet light stabilizer includes one or more compounds selected from the group consisting of a triazine-based UV absorber, a triazole-based UV absorber, and a HALS-based UV absorber.

19. The polyamide resin film of claim 18, wherein the triazole-based UV absorber includes a compound represented by Chemical Formula 11: ##STR00017## in the Chemical Formula 11, R.sub.1 and R.sub.2 are each independently hydrogen or an alkyl group having 1 to 20 carbon atoms.

20. A resin laminate comprising: a substrate including the polyamide resin film of claim 1; and a hard coating layer formed on at least one side of the substrate.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0184] FIG. 1 shows a .sup.13C-NMR spectrum of the polyamide resin obtained in (1) of Example 1.

[0185] FIG. 2 shows a .sup.13C-NMR spectrum of the polyamide resin obtained in (1) of Example 2.

[0186] Hereinafter, embodiments of the present invention will be described in more detail by way of examples. However, these examples are presented for illustrative purposes only, and are not intended to limit the scope of the present invention.

Preparation Example: Preparation of Acyl Chloride Complex

Preparation Example 1

[0187] 569.5 g (2.803 mol) of terephthaloyl chloride (TPC; melting point: 83° C.) and 100.5 g (0.495 mol) of isophthaloyl chloride (IPC: melting point: 44° C.) were added to a 1000 mL 4-neck round flask (reactor) equipped with a stirrer, a nitrogen injection device, a dropping funnel and a temperature controller, and the mixture was melt-kneaded at 100° C. for 3 hours and then cooled at 0° C. for 12 hours to prepare a complex of acylchloride (specifically, terephthaloyl chloride and isophthaloyl chloride).

[0188] Subsequently, the acyl chloride complex was grinded with a jaw crusher to prepare a powder having an average particle size of 5 mm.

Preparation Example 2

[0189] An acylchloride complex was prepared in the same manner as in Preparation Example 1, except that 549.4 g (2.704 mol) of terephthaloyl chloride (TPC: melting point: 83° C.) and 120.6 g (0.594 mol) of isophthaloyl chloride (IPC: melting point: 44° C.) were added.

Example: Preparation of Polyamide Resin and Polyamide Resin Film

Example 1

[0190] (1) Polyamide Resin

[0191] 262 g of N,N-dimethylacetamide (DMAc) was filled into a 500 mL 4-neck round flask (reactor) equipped with a stirrer, a nitrogen injection device, a dropping funnel and a temperature controller while slowly blowing nitrogen into the reactor. Then, the temperature of the reactor was adjusted to 0° C., and 14.153 g (0.0442 mol) of 2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine (TFDB) was added and dissolved.

[0192] 8.972 g (0.0442 mol) of the acyl chloride complex powder obtained in Preparation Example 1 was added thereto and stirred, and subjected to amide formation reaction at 0° C. for 12 hours.

[0193] After completion of the reaction, N,N-dimethylacetamide (DMAc) was added to dilute the solution to a solid content of 5% or less, and the resultant was precipitated with 1 L of methanol. The precipitated solids were filtered and then dried at 100° C. under vacuum for 6 hours or more to prepare a solid-state polyamide resin.

[0194] It was confirmed through .sup.13C-NMR shown in FIG. 1 that the polyamide resin obtained in (1) of Example 1, contained 85 mol % of the first repeating unit obtained by an amide reaction of terephthaloyl chloride (TPC) and 2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine (TFDB) and 15 mol % of the second repeating unit obtained by an amide reaction of isophthaloyl chloride (IPC) and 2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine (TFDB).

[0195] (2) Polyamide Resin Film

[0196] The polyamide resin obtained in (1) of Example 1, and Tinuvin 329 (UV blocking agent) 5 phr (5 parts by weight relative to 100 parts by weight of polyamide resin) were dissolved in N,N-dimethylacetamide to prepare about 10% (w/v) polymer solution.

[0197] The polymer solution was applied onto a polyimide substrate film (UPILEX-75s, UBE), and the thickness of the polymer solution was uniformly adjusted using a film applicator.

[0198] Then, after drying for 15 minutes at 80° C. Mathis oven, it was cured at 250° C. for 30 minutes while flowing nitrogen, and then peeled from the substrate film to obtain a polyamide resin film (thickness: 50 ).

Example 2

[0199] (1) Polyamide Resin

[0200] A polyamide resin was prepared in the same manner as in (1) of Example 1, except that the acyl chloride complex powder obtained in Preparation Example 2 was used instead of the acyl chloride complex powder obtained in Preparation Example 1.

[0201] It was confirmed through .sup.13C-NMR shown in FIG. 2 that the polyamide resin obtained in (1) of Example 2, contained 82 mol % of the first repeating unit obtained by an amide reaction of terephthaloyl chloride (TPC) and 2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine (TFDB), and 18 mol % of the second repeating unit obtained by an amide reaction of isophthaloyl chloride (IPC) and 2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine (TFDB).

[0202] (2) Polyamide Resin Film

[0203] A polyamide resin film (thickness: 50 ) was prepared in the same manner as in (2) of Example 1, except that the polyamide resin obtained in (1) of Example 2 was used instead of the polyamide resin obtained in (1) of Example 1.

Comparative Example: Preparation of Polyamide Resin and Polyamide Resin Film

Comparative Example 1

[0204] A polyamide resin and a polyamide resin film (thickness: 49 ) were prepared in the same manner as in Example 1, except that Tinuvin 329 was not added as the UV blocking agent.

Reference Example: Preparation of Polyamide Resin

Reference Example 1

[0205] A polyamide resin was prepared in the same manner as in (1) of Example 1, except that instead of the acyl chloride complex powder obtained in Preparation Example 1, 7.358 g (0.0362 mol) of terephthaloyl chloride (TPC) and 1.615 g (0.0080 mol) of isophthaloyl chloride (IPC were added simultaneously to perform an amide formation reaction.

Reference Example 2

[0206] A polyamide resin was prepared in the same manner as in (1) of Example 1, except that instead of the acyl chloride complex powder obtained in Preparation Example 1, 7.358 g (0.0362 mol) of terephthaloyl chloride (TPC) was first added, and then 1.615 g (0.0080 mol) of isophthaloyl chloride (IPC) was added sequentially at about 5 minute intervals to perform an amide formation reaction.

Reference Example 3

[0207] A polyamide resin was prepared in the same manner as in (1) of Example 1, except that instead of the acyl chloride complex powder obtained in Preparation Example 1, 1.615 g (0.0080 mol) of isophthaloyl chloride (IPC) was first added, and then 7.358 g (0.0362 mole) of terephthaloyl chloride (TPC) was added sequentially at about 5 minute intervals to perform an amide formation reaction.

Reference Example 4

[0208] 262 g of N,N-dimethylacetamide (DMAc) was filled into a 500 mL 4-neck round flask (reactor) equipped with a stirrer, a nitrogen injection device, a dropping funnel and a temperature controller while slowly blowing nitrogen into the reactor. Then, the temperature of the reactor was adjusted to 0° C., and then 7.358 g (0.0362 mol) of terephthaloyl chloride (TPC) and 1.615 g (0.0080 mol) of isophthaloyl chloride (IPC) were added and dissolved.

[0209] 14.153 g (0.0442 mol) of 2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine (TFDB) in powder form was added thereto and stirred, and subjected to amide formation reaction at 0° C. for 12 hours.

[0210] After completion of the reaction, N,N-dimethylacetamide (DMAc) was added to dilute the solution to a solid content of 5% or less, and the resultant was precipitated with 1 L of methanol. The precipitated solids were filtered and then dried at 100° C. under vacuum for 6 hours or more to prepare a solid-state polyamide resin.

Experimental Example 1

[0211] A specimen of 5 cm*5 cm size was prepared using the polyamide resin films obtained in Examples and Comparative Examples. The specimen was irradiated with an ultraviolet light having a light amount of 1.1 w/m.sup.2 and a wavelength of 340 nm by a 40 W lamp using a QUV Accelerated Weathering Tester of Q-Lab Corporation at a temperature of 50° C. for a total of 10 days. The lightness index (L), color coordinates (a.sub.n, b.sub.n) and yellowness index (YI.sub.n) on the n-th day (n is an integer of 1 to 10) of ultraviolet irradiation were measured every day using a Shimadzu UV-2600 UV-vis spectrometer.

[0212] Specifically, the lightness index (L) and the color coordinate (a, b) mean values in the coordinate axes representing the intrinsic colors, respectively. L has a value of 0 to 100, a value closer to 0 indicates black colors, and a value closer to 100 indicates white colors, a has positive (+) and negative (−) values with respect to 0 wherein the positive (+) means reddish colors, and the negative (−) means greenish. b has positive (+) and negative (−) values with respect to 0 wherein the positive (+) means yellowish colors, and the negative (−) means bluish colors.

[0213] The yellowness index (YI), the lightness index (L) and the color coordinate (an, b.sub.n) were measured according to ASTM E313 using a Shimadzu UV-2600 UV-vis spectrometer.

[0214] Further, the color difference variation rate (Eab.sub.n) on the n-th day (n is an integer of 1 to 10) of ultraviolet irradiation was calculated according to the following Mathematical Formula and shown in Tables 1 to 6 below.

Eab.sub.n={(L.sub.n−L.sub.n−1).sup.2+(a.sub.n−a.sub.n−1).sup.2+(b.sub.n−b.sub.n−1).sup.2}.sup.1/2  [Mathematical Formula]

[0215] wherein,

[0216] L.sub.n−1 is a lightness index of the polyamide resin film on the (n−1)th day (n is an integer of 1 to 10) of ultraviolet irradiation,

[0217] a.sub.n−1 and b.sub.n−1 are color coordinates of the polyamide resin film on the (n−1)th day (n is an integer of 1 to 10) of ultraviolet irradiation,

[0218] L.sub.n is a lightness index of the polyamide resin film on the n-th day (n is an integer of 1 to 10) of ultraviolet irradiation, and

[0219] a.sub.n and b.sub.n are color coordinates of the polyamide resin film on the n-th day (n is an integer of 1 to 10) of ultraviolet irradiation.

TABLE-US-00001 TABLE 1 Polyamide Resin Film of Example 1 Day Lightness Color Color Yellowness Color difference (n) index(L.sub.n) coordinate(a.sub.n) coordinate(b.sub.n) index(YI.sub.n) variation rate(Eab.sub.n)  0 95.51 −0.53 1.69 3.08 —  1 95.74 −0.65 2.15 3.86 0.52811  2 95.74 −0.74 2.46 4.37 0.32027  3 95.78 −0.84 2.73 4.80 0.29319  4 95.79 −0.87 2.81 4.94 0.08559  5 95.79 −0.90 2.90 5.08 0.09500  6 95.80 −0.93 2.98 5.21 0.08602  7 95.80 −0.96 3.06 5.35 0.08544  8 95.83 −0.96 3.02 5.27 0.05000  9 95.83 −0.99 3.11 5.41 0.09487 10 95.83 −1.02 3.20 5.55 0.09487

TABLE-US-00002 TABLE 2 Polyamide Resin Film of Example 2 Day Lightness Color Color Yellowness Color difference (n) index(L.sub.n) coordinate(a.sub.n) coordinate(b.sub.n) index(YI.sub.n) variation rate(Eab.sub.n)  0 95.30 −0.39 1.38 2.60 —  1 95.70 −0.76 2.01 3.51 0.83295  2 95.77 −0.45 2.23 4.16 0.38652  3 95.80 −0.78 2.49 4.40 0.42379  4 95.93 −0.88 2.87 5.03 0.41229  5 95.95 −0.93 2.99 5.22 0.12627  6 95.86 −0.76 2.99 5.35 0.18736  7 95.55 −0.89 3.08 5.44 0.34459  8 95.87 −0.93 3.15 5.52 0.33000  9 95.83 −1.02 3.24 5.63 0.13342 10 95.85 −1.11 3.35 5.75 0.14353

TABLE-US-00003 TABLE 3 Polyamide Resin Film of Comparative Example 1 Day Lightness Color Color Yellowness Color difference (n) index(L.sub.n) coordinate(a.sub.n) coordinate(b.sub.n) index(YI.sub.n) variation rate(Eab.sub.n)  0 95.06 −0.24 1.47 2.89 —  1 95.77 −1.57 4.22 7.04 3.13616  2 95.80 −1.70 4.54 7.53 0.34670  3 95.82 −1.82 4.85 8.02 0.33302  4 95.85 −1.95 5.16 8.51 0.33749  5 95.79 −2.00 5.40 9.90 0.25239  6 95.80 −2.05 5.53 9.90 0.13964  7 95.80 −2.10 5.66 9.91 0.13928  8 95.81 −2.14 5.80 9.91 0.14595  9 95.81 −2.19 5.94 9.92 0.14866 10 95.82 −2.24 6.06 9.92 0.13038

[0220] As shown in Table 1, in the case of the polyamide resin film obtained in Example 1, it was confirmed that the color difference variation rate (Eab.sub.1) measured at the 1.sup.st day was as low as 0.52811, while the yellowness index (YI1) was measured to be as low as 3.86, hereby having excellent light resistance.

[0221] In addition, as shown in Table 2, in the case of the polyamide resin film obtained in Example 2, it was confirmed that the color difference variation rate (Eab.sub.1) measured on the 1.sup.st day was as low as 0.83295, while the yellowness index (YI1) was measured to be as low as 3.51, thereby having excellent light resistance.

[0222] On the other hand, as shown in Table 3, in the case of the polyamide resin film obtained in Comparative Example 1, it was confirmed that the color difference variation rate (Eab.sub.1) measured on the 1.sup.st day was 3.13616 which was significantly increased compared to Examples, and the yellowness index (YI1) was also measured to be as high as 7.04, thereby having poor light resistance compared to Examples.

Experimental Example 2

[0223] (1) Retardation (Rth) Value in Thickness Direction at Wavelength of 550 nm

[0224] The retardation (Rth) value in the thickness direction was determined by using the polymer film (length: 76 mm, width: 52 mm, and thickness: 13 ) prepared in each of Examples and Comparative Examples as a measuring sample, using a measuring apparatus manufactured by AXOMETRICS, Inc. under the trade name of “AxoScan”, inputting a value of a refractive index (the refractive index at a wavelength of 550 nm of the film obtained by the measurement of the refractive index described above) of each polymer film into the measuring apparatus, measuring the thickness-direction retardation value by using light at a wavelength of 550 nm under conditions of a temperature: 25° C. and a humidity: 40%; and then converting the measured value of the thickness-direction retardation value thus obtained (the value was measured according to the automatic measurement of the measuring apparatus) into a retardation value per 10 of the thickness of the film, and the results are shown in Table 4 below.

[0225] (2) Moisture Absorption Rate

[0226] The moisture absorption rate was calculated according to the following Mathematical Formula 2 and shown in Table 4 below.

Moisture Absorption Rate (%)=(W1−W2)*100/W2  [Mathematical Formula 2]

[0227] in Mathematical Formula 2, W1 is a weight measured by impregnating the polyamide resin film in ultrapure water for 24 hours, and W2 is a weight measured by drying the polyamide resin film after at 150° C. for 30 minutes after the impregnation.

TABLE-US-00004 TABLE 4 Comparative Category Example 1 Example 2 Example 1 Thickness-direction −5853.056 −5264.015 −6883.246 retardation (Rth, nm) value Moisture absorption rate (%) 2.48 2.75 2.45

[0228] Referring to Table 4 above, it was confirmed that in the polyamide resin films of Examples satisfying the physical properties that a retardation (Rth) value in the thickness direction at a wavelength of 550 nm in an unstretched state was −5853.056 nm or more and −5264.015 or less and a moisture absorption rate according to Mathematical Formula 1 was 2.48% or more and 2.75% or less, the moisture penetration and the like can be prevented, and the mechanical strength can be improved depending on the orientation of the polymer in the film together with colorless and transparent optical properties. On the contrary, the polyamide resin films of Comparative Examples had a retardation (Rth) value in the thickness direction at a wavelength of 550 nm in the unstretched state of −6883.246 nm and a moisture absorption rate according to Mathematical Formula 1 of 2.45%, which was poor in comparison with Examples.

Experimental Example 3

[0229] The following characteristics were measured or evaluated for the polyamide resin films obtained in the above examples and comparative examples, and the results are shown in Table 5 below.

[0230] (1) Thickness: The thickness of the film was measured using a thickness measuring device.

[0231] (2) Haze: The haze value of the polyamide resin film was measured according to the ASTM D1003 test method using a COH-400 Spectrophotometer (NIPPON DENSHOKU INDUSTRIES).

[0232] (3) Bending Property: The folding endurance of the polyamide resin films was evaluated using an MIT type folding endurance tester. Specifically, a specimen (1 cm*7 cm) of the polyamide resin film was loaded into the folding endurance tester, and folded to an angle of 1350 at a rate of 175 rpm on the left and right sides of the specimen, with a radius of curvature of 0.8 mm and a load of 250 g, until the specimen was bended and fractured. The number of reciprocating bending cycles was measured as the folding endurance.

[0233] (4) Pencil Hardness: The pencil hardness of the polyamide resin films was measured according to the ASTM D3363 test method using a Pencil Hardness Tester. Specifically, varying hardness values of pencils were fixed to the tester and scratched on the polyamide resin film, and the degree of occurrence of a scratch on the polyamide resin 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 polyamide resin film.

[0234] The pencil hardness is increased in the order of B grade, F grade and H grade. Within the same grade, the higher the number, the higher the hardness. Within the grade, the higher the number, the higher the hardness.

TABLE-US-00005 TABLE 5 Comparative Category Example 1 Example 2 Example 1 Thickness(   ) 50 50 49 Haze(%) 0.76 0.45 0.97 Bending property (Cycle) 10225 13521 9785 Pencil hardness 4 H 3 H 4 H

[0235] Looking at Table 5 above, it was confirmed that the polyamide resin film of Examples had a low haze value of 0.45% to 0.76% at a thickness of about 50 , thereby exhibiting excellent transparency. It was also confirmed that it had a high pencil hardness of 3H to 4H grade and a folding endurance that was broken at the number of reciprocating bending cycles from 10225 to 13521, thereby securing excellent mechanical properties (scratch resistance and folding endurance).

Experimental Example 4

[0236] The following characteristics were measured or evaluated for the polyamide resins obtained in the above examples and reference examples, and the films obtained therefrom, and the results are shown in Table 6 below.

[0237] (1) Thickness: The thickness of the film was measured using a thickness measuring device.

[0238] (2) Haze: The haze value of the polyamide resin film was measured according to the ASTM D1003 test method using a COH-400 Spectrophotometer (NIPPON DENSHOKU INDUSTRIES).

[0239] (3) Molecular weight and polydispersity index (PDI): The weight average molecular weight (Mw) and the number average molecular weight (Mn) of the polyamide resin were measured by gel permeation chromatography (GPC, manufactured by Waters), and the polydispersity index (PDI) was calculated by dividing the weight average molecular weight by the number average molecular weight. Specifically, the measurement was performed using a 600 mm long column connecting two Polymer Laboratories PLgel MIX-B Columns (300 mm in length), through Waters 2605 Refractive Index (RI) Detector, wherein the evaluation temperature was 50 to 75° C. (about 65° C.), DMF 100 wt % solvent was used, the flow rate was 1 mL/min, and the sample was prepared at a concentration of 1 mg/mL and supplied in an amount of 100 μL for 25 minutes. The molecular weights could be determined using calibration curves formed using polystyrene standards. As the molecular weight of polystyrene standard products, 7 types of 3940/9600/31420/113300/327300/1270000/4230000 were used.

[0240] (4) Bending Property: The folding endurance of the films obtained from the polyamide resin was evaluated using an MIT type folding endurance tester. Specifically, a specimen (1 cm*7 cm) of the films obtained from the polyamide resins was loaded into the folding endurance tester, and folded to an angle of 135° at a rate of 175 rpm on the left and right sides of the specimen, with a radius of curvature of 0.8 mm and a load of 250 g, until the specimen was bended and fractured. The number of reciprocating bending cycles was measured as the folding endurance.

[0241] (5) Viscosity: Under a constant reflux system at 25±0.2° C., the viscosity of the solution containing polyamide resin (solvent: dimethylacetamide (DMAc), solid content: 10 wt %) was measured according to ASTM D 2196: test method of non-Newtonian materials by Brookfield DV-2T Rotational Viscometer. As Brookfield silicone standard oil, a number of standard solutions having a viscosity range of 5000 cps to 200000 cps was used. The measurement was performed with a spindle LV-4 (64), 0.3-100 RPM, and the unit was cps (mPa.Math.s).

[0242] (6) Pencil Hardness: The pencil hardness of the films obtained from the polyamide resin was measured according to the ASTM D3363 test method using a Pencil Hardness Tester. Specifically, varying hardness values of pencils were fixed to the tester and scratched on the polyamide resin film, and the degree of occurrence of a scratch on the films obtained from the polyamide resins 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 polyamide resin film.

[0243] The pencil hardness is increased in the order of B grade, F grade and H grade. Within the same grade, the higher the number, the higher the hardness. Within the grade, the higher the number, the higher the hardness.

TABLE-US-00006 TABLE 6 Reference Reference Reference Reference Category Example 1 Example 2 Example 1 Example 2 Example 3 Example 4 Thickness(μm) 49 50 51 51 50 50 Y.I. 2.89 2.68 8.55 25.10 4.59 2.28 T (%)@550 nm 88.50 88.75 85.63 75.94 87.57 88.82 T (%)@388 nm 71.0 75.3 51.01 31.62 65.04 74.24 Haze(%) 0.97 0.81 3.43 24.21 1.61 0.40 Mw(g/mol) 463000 512000 412000 350000 382000 321000 Bending 9785 12022 5210 785 4513 6351 property(Cycle) PDI 2.71 1.84 2.05 2.02 1.98 2.00 Viscosity(cps) 174000 110000 54000 24000 28000 18000 Pencil hardness 4H 3H 1H F 1H 2H

[0244] Looking at Table 6 above, the polyamide resin of Examples prepared using the acyl chloride composite powder according to Preparation Examples 1 to 2 had a high weight average molecular weight of 463000 g/mol to 512000 g/mol, and the relative viscosity was measured to be as high as 110000 cps to 174000 cps. Moreover, it was confirmed that the polymer resin film obtained from the polyamide resin of Examples had a low yellowness index of 2.68 to 2.89 and a low haze value of 0.81% to 0.97% at a thickness of about 50 thereby exhibiting excellent transparency. It was also confirmed that it had a high pencil hardness of 3H to 4H grade and a folding endurance that was broken at the number of reciprocating bending cycles from 9785 to 12022, thereby securing excellent mechanical properties (scratch resistance and folding endurance).

[0245] On the other hand, in the case of the polyamide resins of Reference Examples 1 to 3 in which the acyl chloride complex powder according to Preparation Examples 1 to 2 was not used in the synthesis process of the polyamide resin, the molecular weight was 321,000 g/mol to 412,000 g/mol which was decreased compared to Examples. The viscosity was 18,000 cps to 54,000 cps which was decreased compared to Examples. In addition, it was confirmed that the haze value was 1.61% to 24.21% which was increased compared to Examples, showing that the transparency was poor.

[0246] This is because, in Reference Examples 1, 2, and 3, due to the difference in solubility and reactivity between the TPC powder and the IPC powder, the block due to TPC is excessively formed, thereby increasing the crystallinity of the polyamide resin.

[0247] Meanwhile, it was confirmed that the polyamide resin of Reference Example 4, in which acyl chloride was dissolved in an amide solvent and treated as a solution, had a very low molecular weight of 321,000 g/mol, showing that the viscosity was reduced to 18000 cps than Examples. This is presumably because in Reference Example 4, deterioration due to moisture and hybridization with amide solvents occurred during the dissolution of acyl chloride.