HIGH-STRENGTH TRANSPARENT POLYAMIDIMIDE AND METHOD FOR PREPARING SAME

Abstract

The present invention provides a polyamidimide film which maintains transparency and has highly enhanced mechanical properties and heat resistance. The polyamidimide shows excellent transparency, heat resistance, mechanical strength and flexibility and thus can be used in various fields such as substrates for devices, cover substrates for displays, optical films, integrated circuit (IC) packages, adhesive films, multi-layer flexible printed circuits (FPC), tapes, touch panels and protective films for optical disks.

Claims

1. Polyamide-imide containing a repeating structure of the following Formula 1a and a repeating structure of the following Formula 1b together: ##STR00020## wherein, X.sub.1 is a tetravalent organic group of the following Formula 2 derived from tetracarboxylic dianhydride, ##STR00021## X.sub.2 is a divalent organic group derived from the compound of the following Formula 3, ##STR00022## wherein, Z is one selected from a hydroxyl group (OH), a halide group selected from Cl, Br, F and I, and a C.sub.1-5 alkoxyl group (OR), Y.sub.1 and Y.sub.2 are a divalent organic group derived from diamine, and at least one thereof contains a divalent organic group of the following Formula 4: ##STR00023## wherein, R.sub.1 and R.sub.2 are each independently a substituent selected from a halogen atom comprising F, Cl, Br and I, a hydroxyl group (OH), a thiol group (SH), a nitro group (NO.sub.2), a cyano group, a C.sub.1-10 alkyl group, a C.sub.1-4 halogenoalkoxyl group, a C.sub.1-10 halogenoalkyl group, and a C.sub.6-20 aryl group, Q is selected from the group consisting of a single bond, O, CR.sub.18R.sub.19, C(O), C(O)O, C(O)NH, S, SO.sub.2, a phenylene group and a combination thereof, wherein R.sub.18 and R.sub.19 are each independently selected from the group consisting of a hydrogen atom, a C.sub.1-10 alkyl group and a C.sub.1-10 fluoroalkyl group.

2. The polyamide-imide according to claim 1, wherein the divalent organic group of the Formula 4 is selected from the compounds of the following Formula 4a to Formula 4d: ##STR00024##

3. The polyamide-imide according to claim 1, wherein the repeating structure of the Formula 1a and the repeating structure of the Formula 1b are polymerized at molar ratio of 1:5 to 1:1.

4. The polyamide-imide according to claim 1, wherein the repeating structure of the Formula 1a and the repeating structure of the Formula 1b are polymerized in the form of a random copolymer.

5. The polyamide-imide according to claim 1, wherein the compounds of the Formula 1a and the Formula 1b contains the repeating structures of the following Formula 1a-1 and Formula 1b-1: ##STR00025##

6. A method for manufacturing the polyamide-imide of claim 1 comprising the following steps of: stirring a solution of diamine containing the compound of the following Formula 4; adding tetracarboxylic dianhydride containing the structure of the following Formula 2 and the compound of the following Formula 3 to the diamine solution followed by reacting thereof to prepare a polyamide-imide precursor; and imidizing the polyamide-imide precursor: ##STR00026## wherein, Z is one selected from a hydroxyl group (OH), a halide group selected from Cl, Br, F and I, and a C.sub.1-5 alkoxyl group (OR), ##STR00027## wherein, R.sub.1 and R.sub.2 are each independently a substituent selected from a halogen atom comprising F, Cl, Br and I, a hydroxyl group (OH), a thiol group (SH), a nitro group (NO.sub.2), a cyano group, a C.sub.1-10 alkyl group, a C.sub.1-4 halogenoalkoxyl group, a C.sub.1-10 halogenoalkyl group, and a C.sub.6-20 aryl group, Q is selected from the group consisting of a single bond, O, CR.sub.18R.sub.19, C(O), C(O)O, C(O)NH, S, SO.sub.2, a phenylene group and a combination thereof, wherein R.sub.18 and R.sub.19 are each independently selected from the group consisting of a hydrogen atom, a C.sub.1-10 alkyl group and a C.sub.1-10 fluoroalkyl group.

7. The method for manufacturing the polyamide-imide according to claim 6, wherein the tetracarboxylic dianhydride of the Formula 2 and the compound of the Formula 3 are added at molar ratio of 1:5 to 1:1.

8. The method for manufacturing the polyamide-imide according to claim 6, wherein the compounds of the Formula 2 and the Formula 3 and the diamine of the Formula 4 are reacted at molar ratio of 1:1.1 to 1.1:1.

9. The method for manufacturing the polyamide-imide according to claim 6, wherein the compound of the Formula 3 is the compound of the following Formula 3a or Formula 3b: ##STR00028##

10. A high strength transparent polyamide-imide film comprising the polyamide-imide according to claim 1.

11. The high strength transparent polyamide-imide film according to claim 10, which has haziness (Haze) of 2 or lower and pencil strength of 2H or higher.

12. The high strength transparent polyamide-imide film according to claim 10, which has yellowness index (YI) of 5 or lower.

13. A cover substrate for a display comprising the polyamide-imide film according to claim 10.

14. The cover substrate for a display according to claim 13, which further comprises a device protection layer containing a urethane acrylate compound.

15. The cover substrate for a display according to claim 13, which has a structure wherein the device protection layer, a transparent electrode layer, a silicon oxide layer, the polyamide-imide film, a silicon oxide layer and a hard coating layer are stacked in order.

16. The cover substrate for a display according to claim 15, wherein the hard coating layer is a cured layer of polyisocyanate containing an acrylate group and 2 to 5 isocyanate groups.

17. The cover substrate for a display according to claim 15, wherein the silicon oxide layer is formed by coating a solution containing polysilazane and drying thereof followed by curing the coated polysilazane.

Description

BEST MODE CARRYING OUT THE INVENTION

[0106] The present invention will be explained in detail with reference to the following examples, including test examples. However, these examples are provided for illustrative purposes only and are not intended to limit the scope of the invention.

<Example 1>TFMB(1)/BPDA(0.5)_TPC(0.5)

[0107] N,N-dimethyl acetamide (DMAc) 200 g was filled in a reactor under nitrogen atmosphere, and then 2,2-bis(trifluoromethyl)-4,4-biphenyl diamine (TFMB) 21.7 g was dissolved while maintaining the temperature of the reactor to 25 C. 3,3,4,4-biphenyltetracarboxylic dianhydride (BPDA) 10 g was added to the TFMB solution at the same temperature, and dissolved with stirring for a predetermined period of time. After enough stirring, the temperature was lowered to 0 C., terephthaloyl chloride (TPC) 7 g was added thereto and stirring was continued to obtain a polyamide-imide precursor solution. Pyridine and acetic anhydride were added to the solution and stirred enough, and then precipitated with a mixture of methanol and water. The precipitated polyamide-imide powder was dried and dissolved in DMAc to obtain a polyamide-imide precursor solution of a solid content of 13%.

[0108] The composition solution was spin coated on a glass substrate in thickness of about 30 m. The polyamide-imide composition-coated glass substrate was placed in an oven, heated at a rate of 4 C./min, and then cured at 300 C. for 60 min. After completing the curing process, the film formed on the glass substrate was stripped from the substrate to obtain a film.

<Example 2>TFMB(1)/BPDA(0.4)_TPC(0.6)

[0109] The procedure of Example 1 was repeated except that the ratio of the BPDA and the TPC was 0.4 mol:0.6 mol.

<Example 3>TFMB(1)/BPDA(0.3)_TPC(0.7)

[0110] The procedure of Example 1 was repeated except that the ratio of the BPDA and the TPC was 0.3 mol:0.7 mol.

Test Example 1

[0111] Optical properties such as transmittance, yellow index (YI) and haziness of each polyamide-imide film manufactured in Examples 1 to 3 were measured, and the results are shown in the following Table 1.

[0112] Haziness was measured using a Haze Meter HM-150 by a method according to ASTM D1003.

[0113] Yellowness index (YI) was measured using a color difference meter (Color Eye 7000A).

[0114] In-plane retardation (R.sub.in) and thickness retardation (R.sub.th) of the film were measured using Axoscan.

[0115] Surface hardness was measured three times per pencil under a load of 750 gf using a pencil hardness tester according to the measuring standard JIS K5400, and then degrees of scratch and dent were observed to determine hardness.

TABLE-US-00001 TABLE 1 BPDA(0.5)/ BPDA(0.4)/ BPDA(0.3)/ TPC(0.5) TPC(0.6) TPC(0.7) Example 1 Example 2 Example 3 Thickness 33 31 32 (m) YI 3.4 3.1 2.9 Haze 0.83 0.79 0.75 R.sub.th 520 553 652 R.sub.in 67 67 67 Hardness 2H 2H 2H (750 gf) 1/3 0/3 0/3

[0116] From the results of Example 1 to Example 3, it can be found that the polyamide-imide according to the present invention has not only excellent haziness and yellowness index but also superior hardness.

Example 4

[0117] 0.03 g (0.03 wt %) of amorphous silica particles having a OH group bound to the surface thereof were added to N,N-dimethyl acetamide (DMAc) at a dispersion concentration of 0.1%, and ultrasonic treatment was performed until the solvent became transparent, followed by dissolving 100 g of the polyamide-imide solid powder manufactured in Example 3 in 670 g of DMAc, thus obtaining a 13 wt % solution. The solution thus obtained was coated on a stainless plate, cast to the thickness of 340 m, and dried using hot air of 130 C. for 30 min, after which the resulting film was stripped from the stainless plate and then fixed to a frame with pins. The film-fixed frame was placed in a vacuum oven, slowly heated from 100 C. to 300 C. for 2 hrs, and then slowly cooled, and a polyamide-imide film was separated from the frame and then subjected to final thermal treatment at 300 C. for 30 min.

[0118] 10 g of polysilazane (OPTS25 20 wt %, Az Materials) was dissolved to 10 wt % in 10 ml of dibutyl ether (DBE), and the resulting solution was coated on one side of the polyamide-imide film by means of a wire, and dried at 80 C., thus forming a 0.5 m thick polysilazane film. Subsequently, the film was allowed to stand at room temperature for about 5 min, and then thermally cured at about 250 C., thus forming a 0.5 m thick silicon oxide.

[0119] 10 g of polyisocyanate (KLS-009 55 wt %, Natoco) was dissolved in 10 mL of PGMEA, and the resulting solution was coated on one side of the silicon oxide layer by means of a bar coater, and dried at 80 C., thus forming a 10 m thick coating film. Subsequently, two wavelengths of 312 nm and 365 nm were simultaneously irradiated at energy of 100 mW/cm.sup.2 for 10 sec using a UV curing machine, thus forming a 10 m thick hard coating layer.

[0120] Then, ITO was deposited on the other side of the silicon oxide layer opposite the hard coating layer using a sputter, thus forming a transparent electrode layer. 10 g of a urethane acrylate compound (KLH-100, Natoco) was dissolved in 10 g of methylethyl ketone (MEK), and then the resulting solution having the dissolved urethane acrylate compound was coated on the transparent electrode layer by means of a bar coater and then dried at 80 C., thus obtaining a coating film 10 m thick. Then, two wavelengths of 312 nm and 365 nm were simultaneously irradiated on the coating film at energy of 100 mW/cm.sup.2 for 10 sec using a UV curing machine, thus forming a 10 m thick device protection layer, ultimately manufacturing a cover substrate for a display wherein the device protection layer, the transparent electrode layer, the silicon oxide layer, the polyamide-imide film, the silicon oxide layer and the hard coating layer were stacked in order.

[0121] <Method for Evaluating Physical Properties>

[0122] Physical properties were measured according to the following methods, and the results are shown in Table 2.

[0123] (1) Yellowness Index (YI)

[0124] Yellowness index was measured by using a color difference meter (Color Eye 7000A).

[0125] (2) Water Permeability (Gm.sup.2/Day)

[0126] Water vapor transmission rate (WVTR) was measured by using a WVTR tester (MOCON/US/Aquatran-model-1).

[0127] (3) Pencil Hardness

[0128] A line 50 mm long was drawn five times on a sample with a Mitsubishi test pencil (UNI) at a rate of 180 mm/min under a load of 1 kg using an electric pencil hardness tester, after which pencil hardness was measured when there was no surface scratch.

[0129] (4) Adhesiveness

[0130] According to a standard test method (ASTM D3359), a sample was cross cut and taped.

[0131] (5) Flexibility

[0132] A sample was wound and unwound 10,000 times on and from a cylinder having a diameter of 10 mm, and cracking of the film was observed with the naked eyes and using a microscope. The case where no crack is present is represented by OK.

[0133] (6) Scratch Resistance

[0134] A sample was rubbed back and forth 500 times with a steelwool at a 100 mm length at a rate of 50 mm/sec under a load of 500 g, after which the number of scratches was counted with the naked eyes and using an optical microscope.

[0135] (7) Impact Resistance

[0136] A sample was placed on a 0.7 T glass and a ball was dropped at a height of 50 cm from the glass, and damage and cracking of the glass were observed with the naked eyes and using an optical microscope. The case where no fine crack is present is represented by OK.

TABLE-US-00002 TABLE 2 Scratch WVTR Pencil resistance Impact YI (gm.sup.2/day) hardness Adhesiveness Flexibility (Number) resistance Example 4 4 0.1 6H 5B OK 0 OK

[0137] Although specific embodiments of the present invention are described in detail as described above, it will be apparent to those skilled in the art that the specific description is merely desirable exemplary embodiment and should not be construed as limiting the scope of the present invention. Therefore, the substantial scope of the present invention is defined by the accompanying claims and equivalent thereof.