MANUFACTURING METHOD OF CONTINUOUS TRANSPARENT POLYIMIDE FILM FOR DISPLAY

Abstract

A manufacturing method of a continuous transparent polyimide film for a display includes the following steps providing a roll-to-roll polyimide film; providing a polyimide precursor, which is coated on the polyimide film; and baking the polyimide precursor at a baking temperature that is at least 20° C. higher than a glass transition temperature of the transparent polyimide film, such that the transparent polyimide film has an optical transmittance of greater than 85%, a chromaticity (b*) of less than 2, and a standard deviation of three axial refractive indices of the transparent polyimide film is less than 0.0012. Thus, the transparent polyimide film with reduced light leakage can be obtained.

Claims

1. A manufacturing method of a continuous transparent polyimide film for a display, comprising the following steps: providing a polyimide film set on a continuous process; providing a transparent polyimide precursor coated on the polyimide film; and baking the transparent polyimide precursor at a baking temperature from 200° C. to 300° C. to form a transparent polyimide film with an optical transmittance of greater than 85% and a chromaticity (b*) of less than 2, wherein the baking temperature is at least 20° C. higher than a glass transition temperature of the transparent polyimide film, and a standard deviation of three axial refractive indices (n.sub.x, n.sub.y, n.sub.z) of the transparent polyimide film is less than 0.00120.

2. The manufacturing method of continuous transparent polyimide film for display of claim 1, wherein the transparent polyimide precursor is a transparent polyamic acid solution or a transparent polyimide solution.

3. The manufacturing method of continuous transparent polyimide film for display of claim 1, wherein the transparent polyimide precursor has an inherent viscosity (intrinsic viscosity) of greater than 1.

4. The manufacturing method of continuous transparent polyimide film for display of claim 1, wherein the transparent polyimide precursor is obtained by the polymerization of a diamine and a dianhydride, wherein the diamine is composed of 4,4′-bis(4-aminophenoxy) diphenyl sulfone (pBAPS), 4,4′-bis(3-aminophenoxy) diphenyl sulfone (mBAPS), 1,3-bis(3-aminophenoxy)benzene (APB-N), 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane (HFBAPP), 4,4′-diaminodiphenyl sulfone (44DDS), 3,3′-diaminodiphenyl sulfone (33DDS), 2,2′-di(trifluoromethyl)benzidine (TFMB), Bicyclo[2.2.1]heptane dimethylamine (NBDA), 2,2′-bis(trifluoromethyl)-4,4′-diaminophenyl ether (6FODA), 2,2-bis(3-amino-4-hydroxyphenyl) hexafluoropropane (6FAP), 2,2-bis(4-aminophenyl) hexafluoropropane (Bis-A-AF), 4,4′-[1,4-phenyl bis(oxygen)]bis[3-(trifluoromethyl)aniline] (FAPB), 5(6)-amino-1-(4-aminophenyl)-1,3,3-trimethylindane (TMDA), 9,9-bis(4-aminophenyl) fluorene (BAFL), m-phenylenediamine (mPDA) or a combination thereof.

5. The manufacturing method of continuous transparent polyimide film for display of claim 1, wherein the transparent polyimide precursor is obtained by the polymerization of a diamine and a dianhydride, wherein the dianhydride is composed of 4,4-hexafluoroisopropylphthalic anhydride (6FDA), bisphenol A diether dianhydride (BPADA), 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), 3,3,4,4-diphenyl sulfone tetracarboxylic dianhydride (DSDA), 4,4′-oxydiphthalic anhydride (ODPA), 3,3′,4,4′-diphenyl ketonetetracarboxylic dianhydride (BTDA), 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA), bicyclic[2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BTA), hexahydro-4,8-ethano-1H, 3H-benzo[1,2-c:4,5-c′]difuran-1,3,5,7-tetrone (BODA), 2,3,3′,4′-biphenyltetracarboxylic dianhydride (α-BPDA) or a combination thereof.

6. The manufacturing method of continuous transparent polyimide film for display of claim 1, wherein the transparent polyimide film has a thickness ranging from 5 to 25 um.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 is a schematic view of the conventional transparent polyimide film used in a touch panel for a display.

[0008] FIG. 2 is a schematic view showing a manufacturing method of a continuous transparent polyimide film for a display according to the present invention.

[0009] FIG. 3 shows a transparent polyimide film manufactured according to the present invention.

[0010] FIG. 4 is a flow chart showing a manufacturing method of a continuous transparent polyimide film for a display according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0011] To facilitate understanding of the object, characteristics and effects of this present disclosure, embodiments together with the attached drawings for the detailed description of the present disclosure are provided.

[0012] With reference to FIGS. 2-4, the present invention provides a manufacturing method of a continuous transparent polyimide film for a display, which includes the following steps.

[0013] Providing a polyimide film 20 for a continuous process (S1); and providing a transparent polyimide precursor 22 (S2), which is coated on the polyimide film 20 (S3), wherein the polyimide precursor 22 may be a polyamic acid solution or a polyimide solution.

[0014] Baking the polyimide precursor 22 (S4). The baking temperature has to be at least 20° C. higher than a glass transition temperature of the transparent polyimide film 24. After film formation of the transparent polyimide film 24, the polyimide film 20 is removed (S5) to obtain the transparent polyimide film 24 having an optical transmittance of greater than 85% and a chromaticity (b*) of less than 2. The standard deviation of the three axial refractive indices of the transparent polyimide film 24 is less than 0.00120, which results in low light leakage.

[0015] Because the present invention coats the transparent polyimide precursor 22 on the polyimide film 20, it will not be affected by the biaxial extension when baking to form the transparent polyimide 24, so the difference between the refractive indices of the film surface in the x-axis direction and the film surface in the y-axis direction won't be too large. Also, the baking temperature is higher than the glass transition temperature of the transparent polyimide film 14 by more than 20 degrees such that the polyimide molecular segments can be rearranged to reduce the difference between the refractive indices of the film surface in the z-axis, x-axis and y-axis directions, thereby reducing the light leakage.

[0016] The polyimide precursor may be a polyamic acid solution or a polyimide solution.

[0017] The inherent viscosity (intrinsic viscosity) of the polyimide precursor 22 needs to be greater than 1 to ensure that the polyimide film has a certain degree of mechanical properties. In addition, the polyimide precursor is obtained by the polymerization of a diamine and a dianhydride, wherein the diamine is composed of 4,4′-bis(4-aminophenoxy) diphenyl sulfone (pBAPS), 4,4′-bis(3-aminophenoxy) diphenyl sulfone (mBAPS), 1,3-bis(3-aminophenoxy)benzene (APB-N), 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane (HFBAPP), 4,4′-diaminodiphenyl sulfone (44DDS), 3,3′-diaminodiphenyl sulfone (33DDS), 2,2′-di(trifluoromethyl)benzidine (TFMB), Bicyclo[2.2.1]heptane dimethylamine (NBDA), 2,2′-bis(trifluoromethyl)-4,4′-diaminophenyl ether (6FODA), 2,2-bis(3-amino-4-hydroxyphenyl) hexafluoropropane (6FAP), 2,2-bis(4-aminophenyl) hexafluoropropane (Bis-A-AF), 4,4′-[1,4-phenyl bis(oxygen)]bis[3-(trifluoromethyl)aniline] (FAPB), 5(6)-amino-1-(4-aminophenyl)-1,3,3-trimethylindane (TMDA), 9,9-bis(4-aminophenyl) fluorene (BAFL), m-phenylenediamine (mPDA) or a combination thereof.

[0018] The dianhydride may be composed of 4,4-hexafluoroisopropylphthalic anhydride (6FDA), bisphenol A diether dianhydride (BPADA), 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), 3,3,4,4-diphenyl sulfone tetracarboxylic dianhydride (DSDA), 4,4′-oxydiphthalic anhydride (ODPA), 3,3′,4,4′-diphenyl ketonetetracarboxylic dianhydride (BTDA), 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA), bicyclic[2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BTA), hexahydro-4,8-ethano-1H, 3H-benzo[1,2-c:4,5-c′]difuran-1,3,5,7-tetrone (BODA), 2,3,3′,4′-biphenyltetracarboxylic dianhydride (α-BPDA) or a combination thereof. In addition, the transparent polyimide film has a thickness ranging from 5 to 25 um.

Example 1

[0019] Manufacturing of Polyimide Precursor

[0020] 4.933 kg of mBAPS (0.0114 mol) was added into 30 kg of N,N-dimethylacetamide (DMAc). After all the mBAPS was dissolved, 5.067 kg of 6FDA (0.0114 mol) was slowly added under the controlled temperature of 25° C. Stirring was performed for a certain period of time to dissolve and react, and the temperature of the solution was maintained at 25° C. Finally, the polyimide precursor with a solid content of 25% was obtained.

[0021] Manufacturing of Transparent Polyimide Film

[0022] The above-mentioned polyimide precursor added with an appropriate amount of acetic anhydride and 3-picoline was coated on the polyimide film by a continuous process. After baking at a temperature not exceeding 300° C., a composite film of the transparent polyimide film and the polyimide film was obtained. The transparent polyimide was removed to obtain the transparent polyimide film.

Example 2

[0023] Manufacturing of Polyimide Precursor

[0024] 4.538 kg of mBAPS (0.0105 mol) was added into 30 kg of N,N-dimethylacetamide (DMAc). After all the mBAPS was dissolved, 5.434 kg of 6FDA (0.0104 mol) was slowly added under the controlled temperature of 25° C. Stirring was performed for a certain period of time to dissolve and react, and the temperature of the solution was maintained at 25° C. Finally, the polyimide precursor with a solid content of 25% was obtained.

[0025] Manufacturing of Transparent Polyimide Film

[0026] The above-mentioned polyimide precursor added with an appropriate amount of acetic anhydride and 3-picoline was coated on the polyimide film by a continuous process. After baking at a temperature not exceeding 260° C., a composite film of the transparent polyimide film and the polyimide film was obtained. The transparent polyimide was removed to obtain the transparent polyimide film.

Example 3

[0027] Manufacturing of Polyimide Precursor

[0028] 2.932 kg of pBAPS (0.0068 mol) was added into 20 kg of N,N-dimethylacetamide (DMAc). After all the pBAPS was dissolved, 1.807 kg of 6FDA (0.0041 mol) was slowly added. 1.046 kg of NBDA and 10 kg of DMAc were evenly mixed and then slowly poured into the above mixture of pBAPS and 6FDA. Afterwards, 4.216 kg of 6FDA was slowly added and stirred for a certain period of time to dissolve and react, and the temperature of the solution was maintained at 25° C. Finally, the polyimide precursor with a solid content of 25% was obtained.

[0029] Manufacturing of Transparent Polyimide Film

[0030] The above-mentioned polyimide precursor added with an appropriate amount of acetic anhydride and 3-picoline was coated on the polyimide film by a continuous process. After baking at a temperature not exceeding 290° C., a composite film of the transparent polyimide film and the polyimide film was obtained. The transparent polyimide was removed to obtain the transparent polyimide film.

Comparative Example 1

[0031] Manufacturing of Polyamic Acid

[0032] 4.933 kg of mBAPS (0.0114 mol) was added into 30 kg of N,N-dimethylacetamide (DMAc). After all the mBAPS was dissolved, 5.067 kg of 6FDA (0.0114 mol) was slowly added under the controlled temperature of 25° C. Stirring was performed for a certain period of time to dissolve and react, and the temperature of the solution was maintained at 25° C. Finally, the polyimide precursor with a solid content of 25% was obtained.

[0033] Manufacturing of Transparent Polyimide Film

[0034] The above-mentioned polyimide precursor added with an appropriate amount of acetic anhydride and 3-picoline was coated on the polyimide film by a continuous process. After baking at a temperature not exceeding 260° C., a composite film of the transparent polyimide film and the polyimide film was obtained. The transparent polyimide was removed to obtain the transparent polyimide film.

Comparative Example 2

[0035] Manufacturing of Polyimide Precursor

[0036] 4.538 kg of mBAPS (0.0105 mol) was added into 30 kg of N,N-dimethylacetamide (DMAc). After all the mBAPS was dissolved, 5.434 kg of 6FDA (0.0104 mol) was slowly added under the controlled temperature of 25° C. Stirring was performed for a certain period of time to dissolve and react, and the temperature of the solution was maintained at 25° C. Finally, the polyimide precursor with a solid content of 25% was obtained.

[0037] Manufacturing of Transparent Polyimide Film

[0038] The above-mentioned polyimide precursor added with an appropriate amount of acetic anhydride and 3-picoline was coated on the polyimide film by a continuous process. After baking at a temperature not exceeding 220° C., a composite film of the transparent polyimide film and the polyimide film was obtained. The transparent polyimide was removed to obtain the transparent polyimide film.

Comparative Example 3

[0039] Manufacturing of Polyimide Precursor

[0040] 2.932 kg of pBAPS (0.0068 mol) was added into 20 kg of N,N-dimethylacetamide (DMAc). After all the pBAPS was dissolved, 1.807 kg of 6FDA (0.0041 mol) was slowly added. 1.046 kg of NBDA and 10 kg of DMAc were evenly mixed and then slowly poured into the above mixture of pBAPS and 6FDA. Afterwards, 4.216 kg of 6FDA was slowly added and stirred for a certain period of time to dissolve and react, and the temperature of the solution was maintained at 25° C. Finally, the polyimide precursor with a solid content of 25% was obtained.

[0041] Manufacturing of Transparent Polyimide Film

[0042] The above-mentioned polyimide precursor added with an appropriate amount of acetic anhydride and 3-picoline was coated on the polyimide film by a continuous process. After baking at a temperature not exceeding 270° C., a composite film of the transparent polyimide film and the polyimide film was obtained. The transparent polyimide was removed to obtain the transparent polyimide film.

Comparative Example 4

[0043] Manufacturing of Polyamic Acid

[0044] 24.665 kg of mBAPS (0.057 mol) was added into 150 kg of N,N-dimethylacetamide (DMAc). After all the mBAPS was dissolved, 25.335 kg of 6FDA (0.057 mol) was slowly added under the controlled temperature of 25° C. Stirring was performed for a certain period of time to dissolve and react, and the temperature of the solution was maintained at 25° C. Finally, the polyimide precursor with a solid content of 25% was obtained.

[0045] Manufacturing of Transparent Polyimide Film

[0046] The above-mentioned polyimide precursor was added with an appropriate amount of acetic anhydride and 3-picoline. After baking at a temperature not exceeding 260° C. by a continuous process, a transparent polyimide film was obtained.

[0047] The optical properties of the transparent polyimide films obtained in the following examples were measured using the following methods:

[0048] Refractive index: AXOMETRICS polarization measuring equipment was used for measurement.

[0049] Chromaticity b*: Model NE-4000 instrument manufactured by Nippon Denshoku was used for measurement according to ASTM E313 standard.

[0050] Light transmittance: Model NDH-2000N instrument manufactured by Nippon Denshoku was used for measurement according to ISO 14782 standard.

[0051] Test results of the polymerization method of Examples and Comparative Examples

TABLE-US-00001 Poly- imide Tg Baking carrier Dianhydride Diamine ° C. Temp. Ex. 1 w 6FDA mBAPS — 241 300 Ex. 2 w BPADA mBAPS — 200 260 Ex. 3 w 6FDA NBDA.sub.50 pBAPS.sub.50 268 290 Comp. w 6FDA mBAPS — 241 260 Ex. 1 Comp. w BPADA mBAPS — 200 220 Ex. 2 Comp. w 6FDA NBDA pBAPS 268 270 Ex. 3 Comp. w/o 6FDA mBAPS — 241 260 Ex. 4

TABLE-US-00002 Refractive index TT n.sub.x n.sub.y n.sub.z St. Dev. b* % Ex. 1 1.620161 1.620153 1.618186 0.00114 1 89 Ex. 2 1.661753 1.661759 1.660988 0.00044 0.9 88 Ex. 3 1.589423 1.589419 1.587397 0.00117 1.7 89 Comp. 1.618292 1.618291 1.615317 0.00172 1 89 Ex. 1 Comp. 1.661245 1.661238 1.659101 0.00124 0.9 88 Ex. 2 Comp. 1.589495 1.589499 1.587406 0.00121 1.5 89 Ex. 3 Comp. 1.618392 1.616601 1.615107 0.00165 1.1 89 Ex. 4

[0052] The contents of the above examples are provided for illustrating the present invention in detail. However, those examples are for illustration only and are not intended to limit the present invention. People having ordinary skill in the art should understand that various changes or modifications made to the present invention without departing from the scope defined by the appended claims still fall within a part of the present invention.