PARK, Sang Wook (104-903 Gyodong LG Apt, 617 Mabuk-dong Giheung-gu, Yongin-si, Gyeonggi-do 446-912, KR)
PARK, Hyo Jun (104 Croba Vill, Jukjeon-dong Suji-gu, Yongin-si, Gyeonggi-do 448-160, KR)
JUNG, Hak Gee (101-303 Jugong 1 Danji, Sinjeong MaeulPungdeokcheon 2-dong, Suji-gu, Yongin-si, iliGyeonggi-do 448-172, KR)
PARK, Sang Wook (104-903 Gyodong LG Apt, 617 Mabuk-dong Giheung-gu, Yongin-si, Gyeonggi-do 446-912, KR)
PARK, Hyo Jun (104 Croba Vill, Jukjeon-dong Suji-gu, Yongin-si, Gyeonggi-do 448-160, KR)
[CLAIMS]
[Claim l]
A polyimide film, which is manufactured from a polymer of aromatic dianhydride and aromatic diamine, and has average transmittance of 85% or more at 380-780 nm according to measurement of transmittance using a UV spectrophotometer, and a yellowing index of 15 or less, based on a film thickness of 50-100 ,Mn.
[Claim 2] The polyimide film according to claim 1, which has average transmittance of 88% or more at 551-780 nm, transmittance of 88% or more at 550 nm, transmittance of 85% or more at 500 nm, and transmittance of 50% or more at 420 nm, according to measurement of transmittance using a UV spectrophotometer, based on the film thickness of 50-100 μm.
[Claim 3]
The polyimide film according to claim 1, which has an optical density of less than 50 at 420 nm, based on the film thickness of 50-100 [M-
[Claim 4]
The polyimide film according to claim 1, wherein the aromatic dianhydride comprises one or a mixture of two or more selected from among 2,2-bis(3,4- dicarboxyphenyl) hexafluoropropane dianhydride (6-FDA), 4-
(2, 5-dioxotetrahydrofuran-3-yl) -1,2,3,4- tetrahydronaphthalene-l,2-dicarboxylic anhydride (TDA), and 4, 4' - (4, 4'-isopropylidenediphenoxy)bis (phthalic anhydride)
(HBDA) .
[Claim 5]
The polyimide film according to claim 1, wherein the aromatic diamine comprises one or a mixture of two or more selected from among oxydianiline (ODA), l,3-bis(3- aminophenoxy) benzene (APB-133) , l,3-bis(4- aminophenoxy) benzene (APB-134), l,4-bis(4- aminophenoxy) benzene (APB-144), bis (3-aminophenyl) sulfone (3-DDS), bis ( 4-aminophenyl) sulfone (4-DDS) , 2,2'- bis (trifluoromethyl)-4,4'-diaminobiphenyl (2,2'-TFDB), 3, 3' -bis (trifluoromethyl)-4,4'-diaminobiphenyl (3,3'-TFDB) , 2, 2' -bis [4 ( 4-aminophenoxy) phenyl ] hexafluoropropane (4- BDAF) , 2, 2' -bis [3 (3-aminophenoxy) phenyl] hexafluoropropane (3-BDAF), 4, 4' -bis (3-aminophenoxy) diphenylsulfone (DBSDA), and 2, 2-bis[ 4- (4-aminophenoxy) phenyl] propane (β-HMDA) .
[Claim 6]
The polyimide film according to claim 1, which has a dielectric constant of 3.0 or less at 1 GHz, based on the film thickness of 50-100 μm. [Claim 7]
The polyimide film according to claim 1, which has an average coefficient of thermal expansion of 50 ppm or less at 50~200 ° C, based on the film thickness of 50-100 μm.
[Claim 8]
The polyimide film according to claim 1, which has a modulus of 3.0 GPa or more, based on the film thickness of 50-100 μm-
[Claim 9] The polyimide film according to claim 1, which has a 50% cut-off wavelength of 400 nm or less, according to measurement of transmittance using a UV spectrophotometer, based on the film thickness of 50-100 μm.
[Claim lθ] A substrate for a display, comprising the polyimide film of any one of claims 1 to 9. |
[DESCRIPTION]
[invention Title]
POLYIMIDE FILM
[Technical Field] The present invention relates to a polyimide film that is colorless and transparent.
[Background Art]
Generally, polyimide (PI) resin refers to highly heat-resistant resin obtained by ring closure and dehydration of polyamic acid at high temperature, which is obtained by solution polymerization of aromatic dianhydride and aromatic diamine or aromatic diisocyanate. For the preparation of the polyimide resin, the aromatic dianhydride includes, for example, pyromellitic dianhydride (PMDA) or biphenyl tetracarboxylic dianhydride (BPDA) , and the aromatic diamine includes, for example, oxydianiline
(ODA) , p-phenylene diamine (p-PDA) , m-phenylene diamine (m-
PDA) , methylene dianiline (MDA) , and bisaminophenylhexafluoropropane (HFDA) . Since polyimide resin, which is insoluble, infusible and super high heat resistant, has superior properties, including heat and oxidation resistance, radiation resistance, cryogenic resistance properties, and chemical
resistance, it has been used in various fields, including advanced heat resistant materials, such as automobile materials, aircraft materials, or spacecraft materials, and electronic materials, such as insulation coating agents, insulating films, semiconductors, or electrode protective films of TFT-LCDs . Recently, polyimide resin has been used as display materials, such as optical fibers or liquid crystal alignment layers, and transparent electrode films, which are constructed by mixing conductive fillers with polymers or applying conductive fillers to the surface of polymer films .
However, a high aromatic ring density and a charge transfer interaction of polyimide resin cause it to be colored brown or yellow, undesirably resulting in Low transmittance in the visible light range. Such yellow or brown color of polyimide resin makes it difficult to apply it to the fields requiring transparency.
In order to solve such problems, attempts to realize methods of purifying a monomer and a highly pure solvent in order to be polymerized have been made, but the improvement in transmittance was not large .
US Patent No. 5053480 discloses a method of using an alicyclic dianhydride component instead of the aromatic dianhydride. Although this method improves transparency and color in a solution phase or a film phase compared to the purification methods, the improvement in transmittance is
limited, and therefore high transmittance is not realized, and also, the thermal and mechanical properties thereof are deteriorated.
In US Patent Nos . 4595548, 4603061, 4645824, 4895972, 5218083, 5093453, 5218077, 5367046, 5338826, 5986036, and 6232428, and Korean Unexamined Patent Publication No. 2003- 0009437, there have been reports related to the preparation of polyimide, having a novel structure, which is improved in terms of transmittance and color transparency within a range in which the thermal properties are not greatly decreased, using aromatic dianhydride and aromatic diamine monomers, having a linker, such as -O-, -SO 2 -, or CH 2 -, a bent structure due to connection not at the p-position but at the m-position, or a substituent, such as -CF 3 . However, such a polyimide can be confirmed to have mechanical properties, a yellow index, and visible light transmittance insufficient for use in semiconductor insulating films, TFT-LCD insulating films, electrode protective films, and flexible display substrates.
[Disclosure]
[Technical Problem]
Accordingly, the present invention provides a polyimide film, which is colorless and transparent and exhibits superior properties, including mechanical properties and heat stability.
[Technical Solution]
According to a preferred embodiment of the present invention, there is provided a polyimide film, which is manufactured from a polymer of aromatic dianhydride and aromatic diamine, and has average transmittance of 85% or more at 380-780 run according to measurement of transmittance using a UV spectrophotometer, and a yellowing index of 15 or less, based on a film thickness of 50-100 IM.
The polyimide film according to the embodiment may have average transmittance of 88% or more at 551-780 nm, transmittance of 88% or more at 550 nm, transmittance of
85% or more at 500 nm, and transmittance of 50% or more at
420 nm, according to measurement of transmittance using a
UV spectrophotometer, based on the film thickness of 50-100 [M-
The polyimide film according to the embodiment may have an optical density of less than 50 at 420 nm, based on the film thickness of 50-100 μm.
In the polyimide film according to the embodiment, the aromatic dianhydride may comprise one or a mixture of two or more selected from among 2,2-bis(3,4- dicarboxyphenyl) hexafluoropropane dianhydride (6-FDA), 4-
(2, 5-dioxotetrahydrofuran-3-yl) -1,2,3,4- tetrahydronaphthalene-l,2-dicarboxylic anhydride (TDA), and 4,4'-(4,4'-isopropylidenediphenoxy)bis (phthalic anhydride)
(HBDA) .
In the polyimide film according to the embodiment, the aromatic diamine may comprise one or a mixture of two or more selected from among oxydianiline (ODA), l,3-bis(3- aminophenoxy) benzene (APB-133) , l,3-bis(4- aminophenoxy) benzene (APB-134), l,4-bis(4- aminophenoxy) benzene (APB-144), bis (3-aminophenyl) sulfone
(3-DDS), bis (4-aminophenyl) sulfone (4-DDS) , 2,2'- bis (trifluoromethyl)-4,4'-diaminobiphenyl (2,2'-TFDB) , 3, 3' -bis (trifluoromethyl ) -4 , 4 ' -diaminobiphenyl (3, 3' -TFDB) ,
2,2'-bis[4 (4-aminophenoxy) phenyl] hexafluoropropane (4-
BDAF) , 2, 2' -bis [3 (3-aminophenoxy) phenyl] hexafluoropropane
(3-BDAF) , 4, 4' -bis (3-aminophenoxy) diphenylsulfone (DBSDA) , and 2, 2-bis [4- (4-aminophenoxy) phenyl] propane (6-HMDA) . The polyimide film according to the third embodiment may have a dielectric constant of 3.0 or less at 1 GHz based on the film thickness of 50-100 μm.
The polyimide film according to the third embodiment may have an average coefficient of thermal expansion of 50 ppm or less at 50-200 ° C, based on the film thickness of 50-100 μm.
The polyimide film according to the third embodiment may have a modulus of 3.0 GPa or more, based on the film thickness of 50-100 μm. The polyimide film according to the third embodiment may have a 50% UV cut-off wavelength of 400 nm or less,
based on the film thickness of 50~100 /an.
[Advantageous Effects]
The present invention can provide a polyimide resin that is colorless and transparent and has superior properties, including mechanical properties and heat stability, and that can thus be used in various fields, including semiconductor insulating films, TFT-LCD insulating films, passivation films, liquid crystal alignment layers, optical communication materials, protective films for solar cells, and flexible display substrates, and also provide a liquid crystal alignment layer and a polyimide film using the same.
[Description of Drawings] FIG. 1 is a photograph of the polyimide film of Example 1 placed on a piece of paper; and
FIG. 2 is a photograph of the polyimide film of Comparative Example 1 placed on a piece of paper .
[Best Mode] Hereinafter, a detailed description of the present invention will be given.
The polyimide film of the present invention is a film of polyimide resin prepared from a copolymer of diamine and
dianhydride, and in particular, is a colorless transparent polyimide film.
The polyimide film manufactured in the present invention has average transmittance of 85% or more at 380-780 nm according to measurement of transmittance using a UV spectrophotometer based on a film thickness of 50~100 μm, and has a yellowing index of 15 or less based on the film thickness of 50-100 μm.
Further, the polyimide film preferably has average transmittance of 88% or more at 551-780 nm, transmittance of 88% or more at 550 nm, transmittance of 85% or more at 500 nm, and transmittance of 50% or more at 420 nm, according to the measurement of transmittance using a UV spectrophotometer, based on the film thickness of 50-100 μm. The polyimide film of the present invention, satisfying the aforementioned transmittance and yellowing index, may be used in fields requiring transparency, in which it is difficult to apply a conventional polyimide film due to the yellow color thereof, including protective films, or diffusion sheets and coating films of TFT-LCDs, for example, interlayers, gate insulators, and liquid crystal alignment layers of TFT-LCDs. When the transparent polyimide is applied to a liquid crystal alignment layer, it contributes to an increase in porosity, thus enabling the fabrication of a TFT-LCD having a high contrast ratio, and may also be used for flexible display substrates.
The polyimide film of the present invention has an optical density of less than 50 at 420 nm based on the film thickness of 50-100 μm. The polyimide film satisfying the aforementioned optical density and transmittance decreases the refractive index, which indicates the degree of scattering of light passed through the film, and thus, as the distortion of the color, size, or position of a target through the film is decreased, birefringence and retardation are reduced. Therefore, the polyimide film of the present invention may be applied in fields requiring transparency.
To this end, the aromatic dianhydride used in the present invention is not particularly limited, but includes one or a mixture of two or more selected from among 2,2- bis (3, 4-dicarboxyphenyl)hexafluoropropane dianhydride (6- FDA) , 4- (2, 5-dioxotetrahydrofuran-3-yl) -1, 2, 3, 4- tetrahydronaphthalene-1, 2-dicarboxylic anhydride (TDA), and 4, 4' - (4, 4' -isopropylidenediphenoxy)bis (phthalic anhydride) (HBDA) . Also, the aromatic diamine used in the present invention is not particularly limited but includes one or a mixture of two or more selected from among oxydianiline
(ODA), l,3-bis(3-aminophenoxy) benzene (APB-133), l,3-bis(4- aminophenoxy) benzene (APB-134), l,4-bis(4- aminophenoxy) benzene (APB-144), bis (3-aminophenyl) sulfone (3-DDS), bis (4-aminophenyl) sulfone (4-DDS) , 2,2'-
bis (trifluoromethyl)-4,4'-diaminobiphenyl (2,2'-TFDB) , 3, 3' -bis (trifluoromethyl) -4, 4' -diaminobiphenyl (3, 3' -TFDB) , 2, 2' -bis [4 ( 4-aminophenoxy) phenyl] hexafluoropropane (4- BDAF) , 2,2' -bis [3 (3-aminophenoxy) phenyl] hexafluoropropane (3-BDAF) , 4, 4' -bis (3-aminophenoxy) diphenylsulfone (DBSDA), and 2, 2-bis [4- (4-aminophenoxy) phenyl] propane (β-HMDA) .
The dianhydride and the diamine are dissolved in equivalent molar amounts in an organic solvent and are then reacted, thus preparing a polyamic acid solution. The reaction conditions are not particularly limited, but include a reaction temperature of -20~80 ° C and a reaction time of 2-48 hours. Furthermore, the reaction is preferably conducted in an inert atmosphere of argon or nitrogen. The organic solvent that is used for the solution polymerization of the monomers is not particularly limited, as long as polyamic acid can be dissolved therein. As known reaction solvents, useful are one or more polar solvents selected from among m-cresol, N-methyl-2-pyrrolidone (NMP) , dimethylformamide (DMF), dimethylacetamide (DMAc), dimethylsulfoxide (DMSO), acetone, and diethylacetate. In addition, a low-boiling-point solvent, such as tetrahydrofuran (THF) or chloroform, or a low-absorbing- solvent, such as γ-butyrolactone, may be used. The amount of the organic solvent is not particularly limited, but is preferably 50-95 wt%, and more preferably
70-90 wt%, based on the total amount of the polyamic acid solution, in order to realize appropriate molecular weight and viscosity of a polyamic acid solution.
In addition, when a polyimide film is manufactured using the polyamic acid solution, a filler may be added to the polyamic acid solution so as to improve various properties of the polyimide film, including sliding properties, heat conductivity, electrical conductivity, and corona resistance. The filler is not particularly limited, but specific examples thereof include silica, titanium oxide, layered silica, carbon nanotubes, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, and mica.
The particle size of the filler may vary depending on the properties of the film to be modified and the type of filler to be added, and is not particularly limited. The average particle size thereof is preferably set within 0.001-50 μm, more preferably 0.005-25 (M 1 and still more preferably 0.01-10 μm. In this case, the polyimide film may be easily and effectively modified and may also exhibit good surface properties, e Lectrical conductivity, and mechanical properties.
The amount of the filler may vary depending on the properties of the film to be modified and the particle size of the filler, and is not particularly limited. The filler is added in an amount of 0.001-20 parts by weight, and
preferably 0.01-10 parts by weight, based on 100 parts by weight of the polyamic acid solution.
The method of adding the filler is not particularly limited, but includes, for instance, adding the filler to the polyamic acid solution before or after polymerization, kneading the filler using a 3 roll mill after completion of the polymerization of polyamic acid, or mixing a dispersion solution containing the filler with the polyamic acid solution. The method of manufacturing the polyimide film from the polyamic acid solution thus obtained is not particularly limited, and any conventionally known methods may be used. The imidization of the polyamic acid solution includes, for example, thermal imidization and chemical imidization. Particularly useful is chemical imidization. Chemical imidization is conducted by adding a dehydrating agent, including acid anhydride, such as acetic anhydride, and an imidization catalyst, including tertiary amine, such as isoquinoline, β-picoline, or pyridine, to the polyamic acid solution. The chemical imidization may be conducted along with the thermal imidization, and heating conditions may vary depending on the type of polyamic acid solution and the thickness of the film.
The polyimide film is obtained by heating the polyamic acid solution on a substrate at 80-200 ° C, and preferably 100~180 ° C to activate the dehydrating agent and
the imidization catalyst, performing partial curing and drying to obtain a polyamic acid film in a gel state, separating the polyamic acid film from the substrate, and heating the film in a gel state at 200~400 ° C for 5-400 sec. The thickness of the polyimide film thus obtained is not particularly limited, but is preferably set within
10-250 μm, and more preferably 25-150 //m, in consideration of the application field thereof.
The polyimide film of the present invention has a dielectric constant of 3.0 or less at 1 GHz, and may thus be used as a semiconductor passivation film.
The polyimide film of the present invention has an average coefficient of thermal expansion (average CTE) of
50 ppm or less at 50-200 ° C. In the case where the average CTE exceeds 50 ppm, the polyimide film may shrink or expand, depending on the variation in process temperatures, when applied to a TFT array process for placing a TFT on the film, resulting in unrealized alignment in an electrode doping process. Further, the film does not remain flat, and thus may warp. Hence, as the CTE is decreased, the TFT process may be more accurately conducted.
The polyimide film of the present invention has a modulus of 3.0 GPa or more. In this case, the polyimide film may be more easily applied to a roll-to-roll process for a flexible display substrate. When the polyimide film is used as a substrate film for flexible displays and
FCCLs, a roll-to-roll process is conducted. At this time, because the film is subjected to tension when it is wound on and released from the rolls, a film having a modulus of less than 3.0 GPa may break down. The polyimide film of the present invention has a 50% cut-off wavelength of 400 run or less according to the measurement of transmittance using a UV spectrophotometer. Therefore, the polyimide film of the present invention may be used as a surface protective film for solar cells.
[Mode for Invention]
A better understanding of the present invention may be obtained through the following examples which are set forth to illustrate, but are not to be construed as the limit of the present invention. <Example 1>
While nitrogen was passed through a 100 ml three-neck round bottom flask reactor equipped with a stirrer, a nitrogen inlet, a dropping funnel, a temperature controller and a condenser, 32.4623 g of N, N-dimethylacetamide (DMAc) was loaded thereto, the temperature of the reactor was decreased to 0 ° C, 4.1051 g (0.01 mol) of 6-HMDA was dissolved therein. This solution was maintained at 0 ° C. To the solution, 3.1097 g (0.007 mol) of 6-FDA and 0.90078 g (0.003 mol) of TDA were added and the mixture was stirred for 1 hour till the 6-FDA and TDA were completely dissolved
The solid content was 20 wt% . The resulting solution was stirred at room temperature for 8 hours, thus producing a polyamic acid solution with a viscosity of 2200 cps at 23 ° C.
Thereafter, the polyamic acid solution was spread 500-1000 μm thick on a glass substrate using a doctor blade, and was then dried in a vacuum oven at 40 ° C for 1 hour and at 60 ° C for 2 hours, thus affording a self-supporting film.
The film was then cured in a high-temperature oven at 80 ° C for 3 hours, 100 ° C for 1 hour, 200 ° C for 1 hour, and 300 ° C for 30 min at a heating rate of 5 ° C/min, thereby affording polyimide films having a thickness of 50 μm and 100 JM.
<Example 2> As in Example 1, 4.1051 g (0.01 mol) of 6-HMDA was dissolved in 31.3106 g of DMAc, and this solution was maintained at 0 ° C. To the solution 2.2215 g (0.005 mol) of β-FDA and 1.5013 g (0.005 mol) of TDA were sequentially added thereto and the solution stirred for 1 hour the 6-FDA and TDA were completely dissolved. The solid content of the solution was 20 wt% . The solution was then stirred at room temperature for 8 hours, thus affording a polyamic acid solution having a viscosity of 2000 cps at 23 ° C.
Thereafter, polyimide films were manufactured in the same manner as in Example 1.
<Example 3>
As in Example 1, 4.1051 g (0.01 mol) of β-HMDA was dissolved in 30.15868 g of DMAc, and this solution was maintained at 0 ° C. To the solution 1.11275 g (0.003 mol) of
6-FDA and 2.10182 g (0.007 mol) of TDA were sequentially added the solution was stirred for 1 hour till the 6-FDA and TDA were completely dissolved. The solid content of the solution was 20 wt%. The solution was then stirred at room temperature for 8 hours, thus affording a polyamic acid solution having a viscosity of 1800 cps at 23 ° C.
Thereafter, polyimide films were manufactured in the same manner as in Example 1.
<Example 4>
As in Example 1, 2.87357 g (0.007 mol) of 6-HMDA was dissolved in 30.5158 g of DMAc, and 0.7449 g (0.003 mol) of 3-DDS was added thereto and completely dissolved. To the solution 3.1097 g (0.007 mol) of 6-FDA and 0.90078 g (0.003 mol) of TDA were sequentially added the solution was stirred for 1 hour till the 6-FDA and TDA were completely dissolved. The solid content of the solution was 20 wt%. The solution was then stirred at room temperature for 8 hours, thus affording a polyamic acid solution having a viscosity of 2000 cps at 23 ° C.
Thereafter, polyimide films were manufactured in the same manner as in Example 1.
<Example 5>
As in Example 1, 2.87357 g (0.007 mol) of 6-HMDA was dissolved in 30.5158 g of DMAc, and 0.7449 g (0.003 mol) of 4-DDS was added thereto and completely dissolved. To the solution 3.1097 g (0.007 mol) of 6-FDA and 0.90078 g (0.003 mol) of TDA were sequentially added the solution was stirred for 1 hour till the β-FDA and TDA were completely dissolved. The solid content of the solution was 20 wt% . The solution was then stirred at room temperature for 8 hours, thus affording a polyamic acid solution having a viscosity of 2000 cps at 23 ° C.
Thereafter, polyimide films were manufactured in the same manner as in Example 1.
<Example 6>
As in Example 1, 2.24161 g (0.007 mol) of 2,2'-TFDB and 0.7449 g (0.003 mol) of 3-DDS were dissolved in 27.98796 g of DMAc. To the mixture, 3.1097 g (0.007 mol) of 6-FDA and 0.90078 g (0.003 mol) of TDA were sequentially added and then the solution was stirred for 1 hour till the 6-FDA and TDA were completely dissolved. The solid content
was thus 20 wt%. The solution was then stirred at room temperature for 8 hours, thus affording a polyamic acid solution having a viscosity of 2000 cps at 23 ° C.
Thereafter, polyimide films were manufactured in the same manner as in Example 1.
<Example 7>
As in Example 1, 2.24161 g (0.007 mol) of 2,2'-TFDB and 0.7449 g (0.003 mol) of 4-DDS were completely dissolved in 27.98796 g of DMAc. To the solution, 3.1097 g (0.007 mol) of 6-FDA and 0.90078 g (0.003 mol) of TDA were sequentially added and the solution was stirred for 1 hour till the 6-FDA and TDA were completely dissolved. The solid content was thus 20 wt%. The solution was then stirred at room temperature for 8 hours, thus affording a polyamic acid solution having a viscosity of 2000 cps at 23 ° C.
Thereafter, polyimide films were manufactured in the same manner as in Example 1.
<Example 8>
As in Example 1, 3.62922 g (0.007 mol) of 4-BDAF was dissolved in 33.5386 g of DMAc, and 0.7449 g (0.003 mol) of 3-DDS was added thereto and completely dissolvedTo the solution, 3.1097 g (0.007 molj of 6-FDA and 0.90078 g (0.003 mol) of TDA were sequentially added and the solution was stirred for 1 hour till the 6-FDA and TDA were
completely dissolved. The solid content was thus 20 wt%. The solution was then stirred at room temperature for 8 hours, thus affording a polyamic acid solution having a viscosity of 2200 cps at 23 ° C. Thereafter, polyimide films were manufactured in the same manner as in Example 1.
<Example 9> As in Example 1, 3.62922 g (0.007 mol) of 4-BDAF was dissolved in 33.5386 g of DMAc, and 0.7449 g (0.003 mol) of 4-DDS was added thereto and completely dissolved. To the solution 3.1097 g (0.007 mol) of β-FDA and 0.90078 g (0.003 mol) of TDA were sequentially added and the solution was stirred for 1 hour till the 6-FDA and TDA were completely dissolved. The solid content of the solution was 20 wt% . The solution was then stirred at room temperature for 8 hours, thus affording a polyamic acid solution having a viscosity of 2100 cps at 23 ° C. Thereafter, polyimide films were manufactured in the same manner as in Example 1.
<Example 10>
As in Example 1, 2.04631 g (0.007 mol) of APB-133 and 0.7449 g (0.003 mol) of 3-DDS were completely dissolved in
27.20696 g of DMAc. To the solution 3.10975 g (0.007 mol)
of 6-FDA and 0.90078 g (0.003 mol) of TDA were sequentially added and the resulting solution was stirred for 1 hour till the β-FDA and TDA were completely dissolved. The solid content of the solution was thus 20 wt%. The solution was then stirred at room temperature for 8 hours, thus affording a polyamic acid solution having a viscosity of 1900 cps at 23 ° C.
Thereafter, polyimide films were manufactured in the same manner as in Example 1.
<Example 11>
As in Example 1, 2.04631 g (0.007 mol) of APB-133 and 0.7449 g (0.003 mol) of 4-DDS were completely dissolved in 27.20696 g of DMAc. To the solution, 3.10975 g (0.007 mol) of 6-FDA and 0.90078 g (0.003 mol) of TDA were sequentially added and the mixture was stirred for 1 hour till the 6-FDA and TDA were completely dissolved. The solid content of the resulting solution was thus 20 wt%. The solution was then stirred at room temperature for 8 hours, thus affording a polyamic acid solution having a viscosity of 1950 cps at
23 ° C.
Thereafter, polyimide films were manufactured in the same manner as in Example 1.
<Example 12>
As in Example 1, 3.2023 g (0.01 ml) of 2,2'-TFDB was
completely dissolved in 30.986 g of DMAc. This solution was maintained at 0°C. To the solution , 3.64355 g (0.007 mol) of 6-HBDA and 0.90078 g (0.003 mol) of TDA were sequentially added and the mixture was stirred for 1 hour till the β-HBDA and TDA were completely dissolved. The solid content of the resulting solution was thus 20 wt%. The solution was then stirred at room temperature for 8 hours, thus affording a polyamic acid solution having a viscosity of 2000 cps at 23 ° C. Thereafter, polyimide films were manufactured in the same manner as in Example 1.
<Example 13> As in Example 1, 2.483 g (0.01 mol) of 4-DDS was dissolved in 28.1093 g of DMAc, and this solution was maintained at 0 ° C. To the solution 3.64355 g (0.007 mol) of 6-HBDA and 0.90078 g (0.003 mol) of TDA were sequentially added and the solution was stirred for 1 hour till the 6- HBDA and TDA were completely dissolved. The solid content of the solution was 20 wt% . The solution was then stirred at room temperature for 8 hours, thus affording a polyamic acid solution having a viscosity of 1800 cps at 23 ° C.
Thereafter, polyimide films were manufactured in the same manner as in Example 1.
<Example 14>
As in Example 1, 5.1846 g (0.01 mol) of 4-BDAF was dissolved in 38.9157 g of DMAc, and this solution was maintained at 0 ° C. To the solution 3.64355 g (0.007 mol) of 6-HBDA and 0.90078 g (0.003 mol) of TDA were sequentially added the solution was stirred for 1 hour till the 6-HBDA and TDA were completely dissolved. The solid content of the solution was 20 wt% . The solution was then stirred at room temperature for 8 hours, thus affording a polyamic acid solution having a viscosity of 2000 cps at 23 ° C.
Thereafter, polyimide films were manufactured in the same manner as in Example 1.
<Example 15> As in Example 1, 2.24161 g (0.007 mol) of 2,2'-TFDB and 0.7449 g (0.003 mol) of 4-DDS were completely dissolved in 30.3628 g of DMAc. This solution was maintained at 0 ° C. To the solution 3.6435 g (0.007 mol) of 6-HBDA and 0.96069 g (0.003 mol) of TDA were sequentially added thereto and stirred for 1 hour till the 6-HBDA and TDA were completely dissolved. The solid content of the solution was 20 wt%. The solution was then stirred at room temperature for 8 hours, thus affording a polyamic acid solution having a viscosity of 1700 cps at 23 ° C. Thereafter, polyimide films were manufactured in the ' same manner as in Example 1.
2L
<Example 16>
As in Example 1, 3.62922 g (0.007 mol) of 3-BDAF and
0.7449 g (0.003 mol) of 4-DDS were completely dissolved in 35.91324 g of DMAc. This solution was maintained at 0 ° C. To the solution 3.6435 g (0.007 mol) of 6-HBDA and 0.96069 g
(0.003 mol) of TDA were sequentially added thereto and stirred for 1 hour till the 6-HBDA and TDA were completely dissolved. The solid content of the solution was 20 wt%. The solution was then stirred at room temperature for 8 hours, thus affording a polyamic acid solution having a viscosity of 1700 cps at 23 ° C.
Thereafter, polyimide films were manufactured in the same manner as in Example 1.
<Example 17>
As in Example 1, 2.24161 g (0.007 mol) of 2,2'-TFDB and 1.55538 g (0.003 mol) of 3-BDAF was added thereto and completely dissolved in 33.60472 g of DMAc. This solution was maintained at 0 ° C. To the solution, 3.6435 g (0.007 mol) of 6-HBDA and 0.96069 g (0.003 mol) of TDA were sequentially added thereto and stirred for 1 hour till the 6-HBDA and TDA were completely dissolved. The solid content of the solution was 20 wt% . The solution was then stirred at room temperature for 8 hours, thus affording a polyamic acid solution having a viscosity of 1800 cps at 23 ° C.
Thereafter, polyimide films were manufactured in the same manner as in Example 1.
<Comparative Example 1> As in Example 1, 5.1846 g (0.01 mol) of 4-BDAF was dissolved in 38.5084 g of DMAc, after which 4.4425 g (0.01 moi) of β-FDA was added thereto. The solution was stirred for 1 hour till the 6-FDA was completely dissolved. The so Lid content was thus 20 wt%. The solution was then stirred at room temperature for 8 hours, thus affording a polyamic acid solution having a viscosity of 1300 cps at 23 ° C.
Thereafter, polyimide fi lnas were manufactured in the same manner as in Example 1, and the thicknesses thereof were 25 μm, 50 μm r and 100 μm.
Comparative Example 2>
As in Example 1, 2.9233 g (0.01 mol) of APB-133 was dissolved in 29.4632 g of DMAc, after which 4.4425 g (0.01 mol) of 6-FDA was added thereto. The solution was stirred for 1 hour till the 6-FDA was completely dissolved. The solid content was thus 20 wt%. The solution was then stirred at room temperature for 8 hours, thus affording a polyamic acid solution having a viscosity of 1200 cps at 23 ° C.
Thereafter, polyimide films were manufactured in the
same manner as in Comparative Example 1.
<Comparative Example 3>
As in Example 1, 2.4830 g (0.01 mol) of 3-DDS was dissolved in 27.702 g of DMAc, after which 4.4425 g (0.01 mol) of 6-FDA was added thereto. The solution was stirred for 1 hour till the 6-FDA was completely dissolved. The solid content was thus 20 wt% . The solution was then stirred at room temperature for 8 hours, thus affording a polyamic acid solution having a viscosity of 1300 cps at
23 ° C.
Thereafter, polyimide films were manufactured in the same manner as in Comparative Example 1.
Comparative Example 4>
As in Example 1, 2.4830 g (0.01 mol) of 4-DDS was dissolved in 27.702 g of DMAc, after which 4.4425 g (0.01 mol) of 6-FDA was added thereto. The solution was stirred for 1 hour till the 6-FDA was completely dissoved. The solid content was thus 20 wt% . The solution was then stirred at room temperature for 8 hours, thus affording a polyamic acid solution having a viscosity of 1400 cps at
23 ° C.
Thereafter, polyimide films were manufactured in the same manner as in Comparative Example 1.
<Comparative Example 5>
As in Example 1, 2.0024 g (0.01 mol) of 3,3'-ODA was dissolved in 25.7796 g of DMAc, after which 4.4425 g (0.01 mol ) of 6-FDA was added thereto and the resulting solution was stirred for 1 hour till 6-FDA was completely dissoved. The solid content was thus 20 wt% . The solution was then stirred at room temperature for 8 hours, thus affording a polyamic acid solution having a viscosity of 1600 cps at 23 ° C. Thereafter, polyimide films were manufactured in the same manner as in Comparative Example 1.
<Comparative Example 6>
As in Example 1, 2.0024 g (0.01 mol) of 4,4'-ODA was dissolved in 16.7344 g of DMAc, after which 2.1812 g (0.01 mol) of PMDA was added thereto and the resulting solution was stirred for 1 hour till the PMDA was completely dissoved. The solid content was thus 20 wt% . The solution was then stirred at room temperature for 8 hours, thus affording a polyamic acid solution having a viscosity of
2500 poises at 23 ° C.
Thereafter, polyimide films were manufactured in the same manner as in Comparative Example 1.
The properties of the polyimide films manufactured in the above examples and comparative examples were measured
as follows. The results are summarized in Tables 1 to 4 below.
(1) Transmittance and 50% Cut-Off Wavelength Each of the polyimide films was measured for visible light transmittance and 50% cut-off wavelength using a UV spectrophotometer (Varian, CarylOO) .
The polyimide film of each of Example 1 and
Comparative Example 6, having a thickness of 50 μm, was placed on a piece of paper having yellow letters and lines printed thereon, and photographed. The results are shown in
FIGS. 1 and 2.
(2) Yellowing Index
The yellowing index was measured according to ASTM E313. (3) Optical Density (OD)
The optical density was calculated according to Equation 1 below: Equation 1
OD,= A. _ --11« w r [ - -L ic £ W (A) ] wherein 1 is the thickness of the film, Ax is absorbance at a wavelength of λ, T is transmittance, I 0 is intensity of incident light, and I is intensity of transmitted light. (4) Modulus The modulus was measured according to JIS K 6301 using a universal testing machine, Model 1000, available
from Instron.
(5) Glass Transition Temperature (Tg)
The glass transition temperature was measured using a differential scanning calorimeter (DSC, TA Instrument, Q200) .
(6) Coefficient of Thermal Expansion (CTE)
The CTE was measured at 50~200 ° C according to a TMδ method using a TMA (TA Instrument, Q400) .
(7) Dielectric Constant The dielectric constant was measured according to ASTM Dl50.
TABLE 1
TABLE 2
As is apparent from the results of measurement of the properties, the polyimide films of the present invention, having a thickness of 50 μm and 100 μm, had average transmittance of 85% or more at 380-780 nm, a yellowing index of 15 or less, and an optical density of less than 50 at 420 nm. As shown in FIG. 1, the polyimide film satisfying the aforementioned transmittance, yellowing index and optical density was transparent to the extent that yellow letters and lines printed on paper placed therebeneath could be seen.
In the comparative examples, there was no case in which the average transmittance of the film was 85% or more in the visible light range of 380~780 nm, regardless of the thickness thereof. In addition, in Comparative Example β, a polyimide film having a thickness of 90 μm or more could not be manufactured.
The polyimide films manufactured in the examples of the present invention had a wavelength of 400 nm or less, at which transmittance was 50%, ultimately realizing a colorless transparent polyimide film having superior visible light transmittance. Thus, the polyimide film of the present invention can be used as a surface protective film for solar cells. In addition, because the polyimide film has an average CTE of 50 ppm or less, it can exhibit high dimensional stability, and furthermore, can manifest
film properties, necessary for application to a roll-to- roll process, thanks to the modulus of 3.0 GPa or more thereof. Moreover, the polyimide film of the present invention can be applied to a TFT process for fabricating flexible display substrates and active displays, and also has a dielectric constant of 3.0 or less, thus enabling it to be used as a semiconductor passivation film.
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