Polyamide-imide film

Abstract

The present invention relates to a polyamide-imide film comprising a polyamide-imide resin and a porphyrin-based dye. The polyamide-imide film of the present invention has excellent optical properties, and in particular has the characteristic of being able to maintain an excellent yellow index in an environment where the temperature changes repeatedly.

Description

Technical Field

[0001] The present invention relates to a polyamideimide film containing a dye. Background Art

[0002] The highly heat-resistant polyimide resin is a highly heat-resistant resin prepared by preparing a polyamic acid derivative by solution polymerization of an aromatic diamine and an aromatic dianhydride, and then imidizing the polyamic acid derivative by chemical curing and / or thermal curing.

[0003] This polyimide resin has excellent properties in terms of high heat resistance, thermal oxidation resistance, radiation resistance, low temperature characteristics, chemical resistance, etc., and is therefore used in a wide range of fields, such as heat-resistant cutting-edge materials such as automotive materials, aviation materials, and spacecraft materials, as well as electronic materials such as insulating coating agents, insulating films, semiconductors, and electrode protective films for TFT-LCDs.

[0004] Furthermore, there is a trend in recent years to employ the polyimide resin in various fields such as optical fibers, display materials such as liquid crystal alignment films, transparent electrode films, transparent displays, and flexible displays.

[0005] However, the polyimide film prepared from the highly heat-resistant polyimide resin is characterized by being colored brown or yellow due to the high aromatic ring density. Therefore, in order to use the polyimide film in a field requiring transparency, the yellow index (YI) must be improved.

[0006] Therefore, it has been proposed to include dyes or pigments in polyimide films. However, when dyes and pigments are used, the yellowness index and light transmittance conflict with each other, so there is a problem that light transmittance decreases when the yellowness index is improved.

[0007] In addition, due to the solubility and dispersibility of dyes and pigments, the light transmittance and haze characteristics of the polyimide film may be reduced. Therefore, it is difficult to provide a polyimide film having excellent light transmittance, yellow index and haze.

[0008] In particular, in order to use a polyimide film in the field of displays, it is necessary to maintain the yellowness index even under repeated temperature changes, for example, under repeated changes between high temperature and normal temperature.

[0009] Therefore, it is necessary to develop a polyimide film having excellent optical properties and maintaining an excellent yellow index even in an environment where the temperature changes repeatedly. Summary of the invention

[0010] Technical issues to be solved

[0011] An object of the present invention is to provide a polyimide film having excellent optical properties and maintaining an excellent yellow index even in an environment where the temperature changes repeatedly.

[0012] Technical Solution

[0013] In order to achieve the above object, the present invention provides a polyamide-imide film, which comprises a polyamide-imide resin and a porphyrin-based dye, wherein the yellowness index (YI) of the polyamide-imide film is less than 2, △YI 热 (△YI heat ) is less than 0.3.

[0014] Among them, △YI 热 It refers to the change in the yellowness index of the polyamideimide film before and after the heat resistance test when the heat resistance test is repeated 200 times in which the polyamideimide film is allowed to stand at 80°C for 2 hours and then at 25°C for 2 hours.

[0015] In one embodiment of the present invention, the light transmittance of the polyamide-imide film in the visible light region may be 88% or more and the haze may be 0.8% or less based on 80 μm.

[0016] In one embodiment of the present invention, the b* value of the polyamideimide film may be -1.3 to 1.3.

[0017] In one embodiment of the present invention, the modulus of the polyamide-imide film may be greater than 3 GPa, and the elongation at break may be greater than 10%.

[0018] In one embodiment of the present invention, the polyamide-imide resin may be a copolymer of an aromatic diamine, a dianhydride, and an aromatic dicarboxylic acid or a derivative of an aromatic dicarboxylic acid.

[0019] In one embodiment of the present invention, the aromatic diamine may include a fluorine-based aromatic diamine.

[0020] In one embodiment of the present invention, the dianhydride may include a fluorine-based aromatic dianhydride and a non-fluorine-based aromatic dianhydride.

[0021] In one embodiment of the present invention, the dianhydride may include a fluorine-based aromatic dianhydride and an alicyclic dianhydride.

[0022] In one embodiment of the present invention, the content of the porphyrin-based dye may be 0.0001-0.005 parts by weight relative to 100 parts by weight of the polyamide-imide resin.

[0023] In one embodiment of the present invention, the maximum absorption wavelength of the porphyrin-based dye in the visible light region in the MEK solvent may be 570-599 nm.

[0024] In one embodiment of the present invention, the molar absorption coefficient of the porphyrin-based dye at the maximum absorption wavelength in the visible light region may be 10,000-1,000,000 L / mol·cm.

[0025] In one embodiment of the present invention, the full width at half maximum (FWHM) of the porphyrin-based dye with respect to the maximum absorption peak may be 100 nm or less.

[0026] In one embodiment of the present invention, the solubility of the porphyrin-based dye in N,N-dimethylacetamide (DMAc) may be 0.5 wt % or more.

[0027] In one embodiment of the present invention, the residual mass of the porphyrin-based dye at 300° C. measured under a nitrogen atmosphere at a temperature increase condition of 20° C. / min may be 90% or more.

[0028] Beneficial Effects

[0029] The present invention can provide a polyamide-imide film having excellent optical properties and maintaining an excellent yellow index even in an environment where the temperature changes repeatedly. DETAILED DESCRIPTION

[0030] In the present specification, "-based dye" may refer to a compound having a "-group" and its derivatives. For example, "porphyrin-based dye" may refer to porphyrin and a compound having porphyrin as a parent and a substituent bonded to porphyrin.

[0031] In the present specification, the "fluorine-based compound" may refer to a compound including a fluorine-containing substituent, for example, a compound including a fluorine group, a trifluoromethyl group, or the like.

[0032] As described above, in order to use a polyimide film in a field requiring transparency, for example, in the field of displays, it is necessary to improve the yellow index (YI) of the polyimide film.

[0033] Therefore, in order to improve the yellowness index of the polyimide film, a method of adding a dye or a pigment has been proposed in the past. However, when a dye or a pigment is added, the yellowness index and the light transmittance become in a conflicting relationship with each other, so there is a problem that the light transmittance decreases when the yellowness index is improved.

[0034] In addition, due to the solubility and dispersibility of dyes and pigments, the haze characteristics and light transmittance of the polyimide film may be reduced. Therefore, it is difficult to provide a polyimide film having excellent light transmittance, yellow index and haze.

[0035] In particular, in order to use a polyimide film in the field of displays, it is necessary to maintain the yellowness index even in an environment where the temperature changes repeatedly, for example, even under repeated changes between high temperature and normal temperature.

[0036] Therefore, our research team has continued to study to solve the above problems. As a result, we found that when a polyimide film is prepared by including a specific polyimide resin and a specific dye, it not only has excellent optical properties, but also can maintain an excellent yellow index in an environment with repeated temperature changes.

[0037] Specifically, the present invention relates to a polyimide film including a resin having a polyamide-imide structure as a specific polyimide resin, and including a porphyrin-based dye as a specific dye.

[0038] That is, the present invention relates to a polyamideimide film including a polyamideimide resin and a porphyrin-based dye.

[0039] The polyamide-imide film of the present invention comprises a polyamide-imide resin and a porphyrin-based dye, and thus has excellent optical properties, and in particular has a feature of maintaining an excellent yellowness index even in an environment where the temperature changes repeatedly.

[0040] Specifically, the yellowness index (YI) of the polyamide-imide film of the present invention may be 2 or less, ΔYI 热 It may be 0.3 or less.

[0041] Among them, △YI 热 It refers to the change in the yellowness index of the polyamideimide film before and after the heat resistance test when the heat resistance test is repeated 200 times in which the polyamideimide film is allowed to stand at 80°C for 2 hours and then at 25°C for 2 hours.

[0042] In some embodiments, the yellowness index of the polyamide-imide film may be 1.8 or less, more preferably 1.7 or less, and even more preferably 1.6 or less.

[0043] In addition, in some embodiments, the △YI of the polyamide-imide film is 热 It may be 0.2 or less, more preferably 0.1 or less, and even more preferably 0.05 or less. As can be confirmed in the embodiments described below, the polyamide-imide film of one embodiment of the present invention is characterized by having a ΔYI of 0.04. 热 , thus showing the characteristic of maintaining an excellent yellowness index even in an environment with temperature changes.

[0044] In one embodiment of the present invention, the light transmittance of the polyamide-imide film in the visible light region may be 88% or more and the haze may be 0.8% or less based on 80 μm.

[0045] In some embodiments, the light transmittance of the polyamide-imide film in the visible light region based on 80 μm may be 89% or more, more preferably 90% or more. In addition, the haze may be 0.7% or less, more preferably 0.6% or less.

[0046] In one embodiment of the present invention, the b* value of the polyamideimide film may be -1.3 to 1.3, more preferably -1.0 to 1.0, and further preferably -0.5 to 0.5. When b* exceeds 1.3, the polyamideimide film may appear yellow, and when b* is less than -1.3, the polyamideimide film may appear blue, so satisfying the above range is conducive to improving the color.

[0047] In one embodiment of the present invention, the modulus of the polyamide-imide film may be 3 GPa or more, more preferably 4 GPa or more, and further preferably 5 GPa or more, and the elongation at break of the polyamide-imide film may be 10% or more, more preferably 15% or more, and further preferably 20% or more. In this case, in fields requiring excellent optical properties and excellent mechanical and physical properties, for example, in the field of flexible displays, more favorable advantages may be achieved.

[0048] In one embodiment of the present invention, the light transmittance of the polyamide-imide film at 590 nm may be 0.5% to 1.5% lower than the average of the light transmittance at 540 nm and the light transmittance at 640 nm. When the deviation is greater than 1.5%, the color of the polyamide-imide film may become blue due to excessive light absorption, and when the deviation is less than 0.5%, the effect of improving the color may be minimal.

[0049] Furthermore, in one embodiment of the present invention, the light transmittance of the polyamideimide film at 630 nm may be 0.5% to 1.5% lower than the light transmittance at 680 nm.

[0050] In one embodiment of the present invention, the polyamide-imide resin may be a copolymer of: (a) an aromatic diamine; (b) a dianhydride; and (c) an aromatic dicarboxylic acid or a derivative of an aromatic dicarboxylic acid. That is, the polyamide-imide resin may contain a unit derived from an aromatic diamine, a unit derived from a dianhydride, and a unit derived from an aromatic dicarboxylic acid or a derivative of an aromatic dicarboxylic acid.

[0051] In one embodiment of the present invention, the polyamideimide resin may contain a fluorine-containing substituent. The fluorine-containing substituent may be, for example, a fluorine group, a trifluoromethyl group, etc. In this case, the dynamic bending properties and optical properties of the polyamideimide film may be more excellent.

[0052] In some embodiments, the polyamide-imide resin may contain a fluorine-containing substituent and an aliphatic ring (alicyclic structure). In this case, the polyamide-imide resin can provide a polyamide-imide film having more excellent mechanical physical properties, dynamic bending properties, and optical properties by combining with the porphyrin-based dye. In addition, a polyamide-imide film having the property of maintaining a particularly excellent yellow index in an environment where the temperature changes repeatedly can be provided.

[0053] In one embodiment of the present invention, the (a) aromatic diamine may include a fluorine-based aromatic diamine. The fluorine-based aromatic diamine may refer to an aromatic diamine containing a fluorine-containing substituent, such as an aromatic diamine containing a fluorine group, a trifluoromethyl group, etc. In this case, the optical properties of the polyamide-imide film can be improved.

[0054] In some embodiments, the fluorine-based aromatic diamine may include 2,2′-bis(trifluoromethyl)-benzidine (TFMB).

[0055] In one embodiment of the present invention, the (b) dianhydride may include fluorine-based aromatic dianhydride and non-fluorine-based aromatic dianhydride. Wherein, fluorine-based aromatic dianhydride may refer to an aromatic dianhydride containing a fluorine-containing substituent, and non-fluorine-based aromatic dianhydride may refer to an aromatic dianhydride not containing a fluorine-containing substituent. In this case, the polyamide-imide film can show more excellent mechanical and physical properties.

[0056] In one embodiment of the present invention, the (b) dianhydride may include aromatic dianhydride and alicyclic dianhydride, wherein the aromatic dianhydride may refer to a dianhydride including an aromatic ring structure, and the alicyclic dianhydride may refer to a dianhydride including an aliphatic ring structure.

[0057] In some embodiments, the (b) dianhydride may include fluorine-based aromatic dianhydride and alicyclic dianhydride. In this case, the polyamideimide film may exhibit more excellent optical characteristics and mechanical physical properties.

[0058] In some embodiments, the aromatic dianhydride can be any one or more selected from 4,4'-hexafluoroisopropylidene diphthalic anhydride (6FDA), biphenyltetracarboxylic anhydride (BPDA), oxydiphthalic anhydride (ODPA), sulfonyl diphthalic anhydride (SO2DPA), (isopropylidene diphenoxy) di(phthalic anhydride) (6HDBA), 4-(2,5-dioxytetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride (TDA), 1,2,4,5-benzenetetracarboxylic anhydride (PMDA), benzophenonetetracarboxylic anhydride (BTDA), bis(carboxyphenyl)dimethylsilane dianhydride (SiDA), bis(dicarboxyphenoxy)diphenyl sulfide dianhydride (BDSDA), etc.

[0059] In some embodiments, the alicyclic dianhydride can be any one or more selected from 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 5-(2,5-dioxotetrahydrofuranyl)-3-methylcyclohexene-1,2-dicarboxylic dianhydride (DOCDA), bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BTA), bicyclooctene-2,3,5,6-tetracarboxylic dianhydride (BODA), 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA), 1,2,4,5-cyclohexanetetracarboxylic dianhydride (CHDA), 1,2,4-tricarboxy-3-carboxymethylcyclopentane dianhydride (TMDA), 1,2,3,4-tetracarboxycyclopentane dianhydride (TCDA), and the like.

[0060] In the present invention, the (c) aromatic dicarboxylic acid or the derivative of the aromatic dicarboxylic acid can be polymerized with the (a) aromatic diamine to form an amide structure within the chain, thereby providing a polyamideimide film having more excellent optical properties and mechanical properties.

[0061] In some embodiments, the (c) aromatic dicarboxylic acid or the derivative of aromatic dicarboxylic acid may be benzene, biphenyl or naphthalene substituted with two carboxylic acid groups or carboxylic acid derivatives. The carboxylic acid derivative may contain an acid chloride group (-COCl).

[0062] In some embodiments, the (c) aromatic dicarboxylic acid or the derivative of an aromatic dicarboxylic acid may be an aromatic dichloride. For example, the aromatic dichloride may be any one or more selected from isophthaloyl dichloride (IPC), terephthaloyl dichloride (TPC), [1,1'-Biphenyl]-4,4'-dicarbonyl dichloride (BPC), 1,4-naphthalene dicarboxylic dichloride (NPC), 2,6-naphthalenedicarboxylic dichloride (NTC), 1,5-naphthalene dicarboxylic dichloride (NEC), and the like.

[0063] In one embodiment of the present invention, the polyamide-imide resin containing a fluorinated substituent and an aliphatic ring can be prepared by a two-step polymerization reaction. For example, the two-step polymerization reaction may include the following steps: polymerizing a first fluorinated aromatic diamine and an aromatic dicarboxylic acid or a derivative of an aromatic dicarboxylic acid (e.g., an aromatic diacyl chloride) to prepare a polyamide-based oligomer (step 1); and polymerizing the polyamide-based oligomer, a second fluorinated aromatic diamine, an aromatic dianhydride, and an alicyclic dianhydride to prepare a polyamic acid (step 2). Afterwards, the polyamic acid is imidized to prepare the polyamide-imide resin. The first fluorinated aromatic diamine and the second fluorinated aromatic diamine may be the same as or different from each other.

[0064] As described above, when the polyamide-imide resin is prepared by a two-step polymerization reaction, a polyamide-based oligomer having an amine group at the end is prepared in step 1, and the polyamide-based oligomer can play the role of a monomer in step 2. In this case, a block-type polyamide-imide resin having a polyamide-based block can be prepared. Such a block-type polyamide-imide resin is characterized by having improved optical properties, mechanical physical properties, etc. In addition, it has the advantage of a wide range of choices of coating solvents due to the diversity of solubility.

[0065] In some embodiments, the polyamide-based oligomer, the second fluorine-based aromatic diamine, the aromatic dianhydride and the alicyclic dianhydride can be subjected to solution polymerization in the step of preparing the polyamic acid. The organic solvent that can be used in the solution polymerization can be, for example, any one or more selected from dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), ethyl cellosolve, methyl cellosolve, acetone, ethyl acetate, m-cresol, etc.

[0066] In some embodiments, the method of imidizing the polyamic acid can be, for example, chemical imidization of the polyamic acid using pyridine and acetic anhydride. In addition, then, at a temperature below 150°C, preferably below 100°C, specifically, at a temperature of 50-150°C, imidization can also be performed using an imidization catalyst and a dehydrating agent. In this case, compared to a method of imidizing by heat at high temperature, uniform mechanical and physical properties can be imparted to the entire polyamide-imide film.

[0067] In this case, the imidization catalyst may be, for example, any one or more selected from pyridine, isoquinoline, β-quinoline, etc. In addition, the dehydrating agent may be, for example, any one or more selected from acetic anhydride, phthalic anhydride, maleic anhydride, etc.

[0068] In some embodiments, the polyamide-imide resin may be prepared by mixing additives such as flame retardants, tackifiers, inorganic particles, antioxidants, UV inhibitors, and plasticizers into the polyamic acid.

[0069] In some embodiments, in step 1, the first fluorinated aromatic diamine and the aromatic dicarboxylic acid or the derivative of the aromatic dicarboxylic acid may be used in a molar ratio of 1:0.5 to 1:1, more preferably in a molar ratio of 1:0.5 to 1:0.8.

[0070] In some embodiments, in step 2, the ratio of the total moles of the polyamide-based oligomer and the second fluorine-based aromatic diamine to the total moles of the aromatic dianhydride and the alicyclic dianhydride may be 1:0.9 to 1:1.1, more preferably 1:1.

[0071] In some embodiments, in step 2, the amount of the polyamide-based oligomer used may be 30 mol% or more, preferably 50 mol% or more, and more preferably 70 mol% or more relative to the total molar number of the polyamide-based oligomer and the second fluorine-based aromatic diamine. In this case, the optical properties and mechanical properties of the polyamide-imide film may be further improved. The invention is not limited thereto.

[0072] In some embodiments, in step 2, aromatic dianhydride and alicyclic dianhydride may be used in a molar ratio of 3:7 to 8:2. In this case, the transparency, yellowness index, mechanical properties, etc. of the polyamide-imide film may be improved.

[0073] In another embodiment of the present invention, the polyamide-imide resin comprising a fluorinated substituent and an aliphatic ring can be prepared by a one-step polymerization reaction. For example, the one-step polymerization reaction may include the following steps: a derivative (e.g., aromatic diacyl chloride) of a fluorinated aromatic diamine, an aromatic dianhydride, an alicyclic dianhydride and an aromatic dicarboxylic acid or an aromatic dicarboxylic acid is polymerized to prepare polyamic acid. Afterwards, the polyamic acid is imidized to prepare the polyamide-imide resin. In this case, random polyamide-imide resins can be prepared. Random polyamide-imide resins may differ from the above-mentioned block-type polyamide-imide resins in terms of solvent sensitivity caused by differences in optical properties, mechanical physical properties, and surface energy, but this also belongs to the scope of the present invention.

[0074] At this time, 40 moles or more of the aromatic dianhydride can be used relative to 100 moles of the fluorinated aromatic diamine, and more preferably 50 to 80 moles of the aromatic dianhydride can be used. In addition, 10 to 60 moles of the alicyclic dianhydride can be used relative to 100 moles of the fluorinated aromatic diamine.

[0075] In addition, the ratio of the mole number of the fluorine-based aromatic diamine to the total mole number of the aromatic dianhydride, the alicyclic dianhydride and the aromatic diacid chloride may be 1:0.9 to 1:1.1, and more preferably may be 1:1.

[0076] In the present invention, the porphyrin-based dye refers to a cyan or purple porphyrin-based dye known in the art. The porphyrin-based dye can be combined with the above-mentioned polyamide-imide resin to achieve excellent light transmittance, yellow index and haze. In particular, the polyamide-imide film can show the characteristics of maintaining an excellent yellow index in an environment where the temperature changes repeatedly.

[0077] In one embodiment of the present invention, the maximum absorption wavelength of the porphyrin-based dye in the visible light region in the MEK solvent may be above 570 nm, more preferably 570-599 nm. In this case, the yellowness index, b*, etc. of the polyamide-imide film may be further improved.

[0078] Absorbance can be expressed as A=abC (a: molar absorption coefficient; b: path length; C: molar concentration) according to Beer's Law. That is, the larger the molar absorption coefficient value of the dye, the better it can absorb light, which can be beneficial to improve the effect of the yellow index. However, when the molar absorption coefficient value of the dye is too large, there is a problem of reduced transmittance of the polyamide-imide film. In addition, when the molar absorption coefficient value of the dye is too small, the effect of improving the color is insufficient, so a relatively large amount of dye needs to be used. In this case, the transmittance of the polyamide-imide film may be reduced.

[0079] Therefore, in one embodiment of the present invention, the molar absorption coefficient of the porphyrin-based dye at the maximum absorption wavelength in the visible light region may be 10,000-1,000,000 L / mol·cm.

[0080] In one embodiment of the present invention, the full width at half maximum (FWHM) of the porphyrin-based dye for the maximum absorption peak may be less than 100 nm, more preferably less than 50 nm. In this case, only light of a specific color can be selectively removed, thereby having the advantage of being able to selectively adjust the specific color of the polyamide-imide film.

[0081] In one embodiment of the present invention, the molar absorption coefficient of the porphyrin-based dye at 470 nm may be 50,000 L / mol·cm or less. In this case, light of other wavelengths other than the specific wavelength to be removed can be absorbed to a minimum extent, thereby further selectively adjusting the specific color of the polyamide-imide film.

[0082] In one embodiment of the present invention, the solubility of the porphyrin-based dye in N,N-dimethylacetamide (DMAc) can be more than 0.5 % by weight. More preferably, the solubility of the porphyrin-based dye in DMAc can be more than 3 % by weight. In this case, the porphyrin-based dye can be evenly distributed in the polyamide-imide film. Therefore, the polyamide-imide film with uniform color can be prepared.

[0083] Hereinafter, the method for producing the polyamide-imide film of the present invention will be described.

[0084] The polyamideimide film of the present invention can be prepared by coating a polyamideimide resin solution containing the polyamideimide resin, the porphyrin-based dye and a solvent on a substrate and then drying or drying and stretching. That is, the polyamideimide film can be prepared by a solution casting method.

[0085] In one embodiment of the present invention, relative to the polyamide-imide resin of 100 weight parts, the content of the porphyrin-based dye can be 0.0001-0.005 weight part, more preferably can be 0.001-0.003 weight part. Relative to the polyamide-imide resin of 100 weight parts, when the content of the porphyrin-based dye exceeds 0.005 weight part, due to excessive light absorption, the transmittance of the polyamide-imide film may be reduced, and may be blue. In addition, relative to the polyamide-imide resin of 100 weight parts, when the content of the porphyrin-based dye is less than 0.0001 weight part, the effect of improving the color of the yellow index, b*, etc. may be very small.

[0086] In the present invention, the time point for mixing the porphyrin-based dye and the polyamide-imide resin is not particularly limited. That is, for example, the porphyrin-based dye can be added during the process of preparing polyamic acid, immediately after preparing polyamic acid, during imidization of polyamic acid after preparing polyamic acid, or after completing imidization of polyamic acid.

[0087] In some embodiments, when mixing the porphyrin-based dye and the polyamide-imide resin (or polyamic acid), the porphyrin-based dye solution may be prepared by first dissolving the porphyrin-based dye in a solvent such as DMAc, and then mixing the porphyrin-based dye solution with the polyamide-imide resin (or polyamic acid).

[0088] In some embodiments, the substrate may be glass, stainless steel, film, etc. In addition, the coating may be performed by, for example, a die coater, air knife coating, reverse roll coating, spray coating, blade coating, casting, gravure coating, spin coating, etc.

[0089] In the present invention, the thickness of the polyamide-imide film may be, for example, 10-250 μm, but is not limited thereto.

[0090] Examples and comparative examples of the present invention are described below. However, the following examples are merely one embodiment of the present invention, and the present invention is not limited to the following examples.

[0091] [Measurement methods of physical properties]

[0092] (1) Modulus and elongation at break

[0093] The prepared film was cut into 80 μm thickness, 50 mm width and 10 mm length to prepare a test piece. The modulus and elongation at break of the test piece were measured using UTM 3365 of Instron at 25° C. under the condition of stretching at 50 mm / min according to ASTM D882.

[0094] (2) Light transmittance (total light transmittance; TT)

[0095] The light transmittance of the prepared film was measured as follows: Based on a thickness of 80 μm, the light transmittance was measured in the visible light region using COH-400 manufactured by Nippon Denshoku according to ASTM D1003.

[0096] In addition, the transmittance at a specific wavelength was measured using UV-3600 manufactured by Shimadzu Corporation.

[0097] (3) Yellowness Index (YI)

[0098] The yellowness index of the prepared film was measured as follows: with a thickness of 80 μm as a reference, the measurement was carried out according to ASTM E313 standard using ColorQuest XE (Mode type: Total transmission, Area view: 0.375 inches (in.), UV filter: Nominal) manufactured by HunterLab.

[0099] (4) Haze

[0100] The haze of the prepared film was measured as follows: the haze was measured using COH-400 manufactured by Nippon Denshoku Industries Co., Ltd. based on a thickness of 80 μm in accordance with ASTM D1003.

[0101] (5)Lab color coordinates (b*)

[0102] The b* value of the prepared film was measured as follows: with a thickness of 80 μm as a reference, the measurement was performed according to ASTM E313 standard using a ColorQuest XE (mode type: full transmission, area view: 0.375 inch, UV filter: nominal) from HunterLab.

[0103] (6) Heat resistance (△YI 热 )

[0104] The prepared film was cut into a thickness of 80 μm, a width of 40 mm and a length of 40 mm to prepare a test piece. A heat resistance test was performed by repeating 200 steps of standing the test piece in an oven at 80° C. for 2 hours and then standing at 25° C. for 2 hours.

[0105] After the heat resistance test is completed, the yellowness index of the test piece is measured according to the method (3) to confirm the change value of the yellowness index of the test piece before and after the heat resistance test (△YI 热 ).

[0106] [Example 1]

[0107] Dichloromethane and 2,2'-bis(trifluoromethyl)-benzidine (TFMB) were added to the reactor and stirred well under a nitrogen atmosphere, and then terephthaloyl chloride (TPC) was added and stirred for 6 hours. At this time, the molar ratio of TPC:TFMB added was set to 3:4, and the solid content was adjusted to 10 wt%.

[0108] Then, the reaction product was precipitated with excess methanol and filtered to obtain a solid, which was then vacuum dried at 50° C. for more than 6 hours to prepare a polyamide-based oligomer having a molecular weight (Formula Weight, FW) of 1670 g / mol.

[0109] Next, N,N-dimethylacetamide (DMAc), 100 mol of the prepared polyamide-based oligomer, and 28.6 mol of TFMB were added to the reactor and fully stirred.

[0110] Thereafter, 64.3 mol of 4,4′-hexafluoroisopropylidene diphthalic anhydride (6FDA) and 64.3 mol of biphenyltetracarboxylic dianhydride (BPDA) were sequentially added to the reactor and stirred, and polymerized at 40° C. for 10 hours.

[0111] Next, pyridine and acetic anhydride were added to the reactor in an amount of 2.5 times (321.5 mol) the total amount of dianhydride added, respectively, and stirred at 60° C. for 1 hour. At this time, the solid content was adjusted to 12% by weight.

[0112] After the reaction was completed, CNef-P591 from CFC Teramate, a porphyrin-based dye, was diluted in DMAc and added at 20 ppm based on the solid content.

[0113] When measured at 25° C. using a Brookfield viscometer, the viscosity of the finally prepared polyamideimide was 100,000 cps.

[0114] The prepared polyamideimide solution was solution-casted on a glass substrate using an applicator, and then heat-treated at 100° C. for 30 minutes, at 200° C. for 30 minutes, and at 280° C. for 10 minutes in a vacuum oven, and then cooled at room temperature.

[0115] The polyamide-imide film formed on the glass substrate was separated from the substrate. The thickness of the prepared polyamide-imide film was 80 μm, the modulus was 5.5 GPa, and the elongation at break was 15%. In addition, the transmittance of the prepared polyamide film at a specific wavelength was measured, and the transmittance at 590 nm showed a value 1.2% lower than the average value of the transmittance at 540 nm and the transmittance at 640 nm, and the transmittance at 630 nm showed a value 0.9% lower than the transmittance at 680 nm.

[0116] For the prepared polyamide-imide film, transmittance, YI, b*, haze and ΔYI were measured according to the measurement method. 热 , and are recorded in Table 1.

[0117] [Example 2]

[0118] Except that cyclobutanetetracarboxylic dianhydride (CBDA) was added instead of BPDA, a polyamide-imide film having a thickness of 80 μm was prepared by the same method as in Example 1. The modulus of the prepared polyamide-imide film was 5.4 GPa, and the elongation at break was 21.5%. In addition, the transmittance of the prepared polyamide film at a specific wavelength was measured, and the transmittance at 590 nm showed a value 1.0% lower than the average value of the transmittance at 540 nm and the transmittance at 640 nm, and the transmittance at 630 nm showed a value 0.9% lower than the transmittance at 680 nm.

[0119] For the prepared polyamide-imide film, transmittance, YI, b*, haze and ΔYI were measured according to the measurement method. 热 , and are recorded in Table 1.

[0120] [Comparative Example 1]

[0121] A polyamideimide film having a thickness of 80 μm was prepared by the same method as in Example 1 except that the dye was not added after the reaction.

[0122] For the prepared polyamide-imide film, transmittance, YI, b*, haze and ΔYI were measured according to the measurement method. 热 , and are recorded in Table 1.

[0123] [Comparative Example 2]

[0124] A polyamideimide film having a thickness of 80 μm was prepared by the same method as in Example 1 except that 500 ppm of a pigment (Shepherd Company, Cobalt and Aluminum Blue, maximum absorption wavelength: 603 nm) was added instead of the dye.

[0125] For the prepared polyamide-imide film, transmittance, YI, b*, haze and ΔYI were measured according to the measurement method. 热 , and are recorded in Table 1.

[0126] [Comparative Example 3]

[0127] A polyamideimide film having a thickness of 80 μm was prepared by the same method as in Example 1 except that Sumiplast Violet B manufactured by Sumitomo Corporation was added as an anthraquinone-based dye instead of the porphyrin-based dye.

[0128] For the prepared polyamide-imide film, transmittance, YI, b*, haze and ΔYI were measured according to the measurement method. 热 , and are recorded in Table 1.

[0129] [Comparative Example 4]

[0130] A polyamideimide film having a thickness of 80 μm was prepared by the same method as in Example 1 except that FASTOGEN Blue CA5380 manufactured by DIC Corporation was added as a phthalocyanine-based dye instead of the porphyrin-based dye.

[0131] For the prepared polyamide-imide film, transmittance, YI, b*, haze and ΔYI were measured according to the measurement method. 热 , and are recorded in Table 1.

[0132] [Comparative Example 5]

[0133] A polyimide film having a thickness of 80 μm was prepared by the same method as in Example 1, except that TPC was not added and TFMB, 6FDA and BPDA were added in a molar ratio of 1:0.5:0.5.

[0134] For the prepared polyimide film, transmittance, YI, b*, haze and ΔYI were measured according to the measurement method. 热 , and are recorded in Table 1.

[0135] [Table 1]

[0136] Light transmittance Haze b* YI <![CDATA[△YI 热 ]]> Example 1 88.4 0.76 0.79 1.97 0.08 Example 2 89.0 0.48 0.52 1.25 0.04 Comparative Example 1 89.3 0.81 1.45 3.46 0.16 Comparative Example 2 85.6 1.12 1.38 2.27 0.25 Comparative Example 3 87.8 0.86 0.83 2.13 0.56 Comparative Example 4 89.1 0.85 0.92 2.37 0.38 Comparative Example 5 88.0 0.81 1.80 3.78 0.32

[0137] With reference to Table 1, it can be confirmed that Examples 1 and 2 have a light transmittance of 88% or more, a haze of 0.8% or less, and a yellowness index (YI) of 2 or less, and thus are excellent in optical properties.

[0138] In particular, it can be confirmed that ΔYI of Example 1 and Example 2 热 The value is less than 0.1, and thus the property of maintaining the yellowness index even in an environment with temperature changes is remarkably excellent.

[0139] On the other hand, in the case of Comparative Example 1 in which no dye was added, a yellow index of 3.46 was shown, and thus it was confirmed that the optical properties were poor.

[0140] In the case of Comparative Example 2 in which a pigment was added instead of a dye, although the yellowness index was improved, it still exceeded 2, so the improvement was insufficient, and there was a problem that the light transmittance and haze characteristics were reduced.

[0141] In the case of Comparative Examples 3 and 4, anthraquinone-based dyes or phthalocyanine-based dyes were used, and although the yellowness index was improved, it still exceeded 2, and thus the improvement was insufficient.

[0142] In particular, in the case of Comparative Examples 3 and 4, ΔYI 热 The value exceeds 0.3, so there is a problem that the yellowness index decreases sharply in an environment where the temperature changes repeatedly.

[0143] In the case of Comparative Example 5, a polyimide film was used, but the yellow index was too high and ΔYI 热 The value also exceeds 0.3, and therefore the property of maintaining the yellowness index in an environment where the temperature changes repeatedly is poor.

[0144] As described above, the polyamideimide film of the present invention can show the unique effects of excellent optical characteristics and excellent yellowness index maintenance property in an environment where the temperature changes repeatedly by the combination of the polyamideimide resin and the porphyrin-based dye.

Claims

1. A polyamide-imide film comprising a polyamide-imide resin and a porphyrin-based dye, wherein the polyamide-imide film has a yellow index YI of 2 or less, ΔYI 热 is less than 0.1, where △YI 热 It refers to the change in the yellowness index of the polyamide-imide film before and after the heat resistance test when the heat resistance test is repeated 200 times, with the polyamide-imide film being allowed to stand for 2 hours at 80°C and then for 2 hours at 25°C as one step. The polyamide-imide resin is a copolymer of aromatic diamine, dianhydride and aromatic dicarboxylic acid or a derivative of aromatic dicarboxylic acid.

2. The polyamide-imide film according to claim 1, wherein The polyamide-imide film has a light transmittance in the visible light region of 88% or more and a haze of 0.8% or less based on 80 μm.

3. The polyamide-imide film according to claim 2, wherein The b* value of the polyamideimide film is from -1.3 to 1.

3.

4. The polyamide-imide film according to claim 1, wherein The polyamide-imide film has a modulus of 3 GPa or more and an elongation at break of 10% or more.

5. The polyamide-imide film according to claim 1, wherein The aromatic diamine includes a fluorine-based aromatic diamine.

6. The polyamide-imide film according to claim 1, wherein The dianhydride includes a fluorine-based aromatic dianhydride and a non-fluorine-based aromatic dianhydride.

7. The polyamide-imide film according to claim 1, wherein The dianhydride includes a fluorine-based aromatic dianhydride and an alicyclic dianhydride.

8. The polyamide-imide film according to claim 1, wherein The content of the porphyrin-based dye is 0.0001-0.005 parts by weight relative to 100 parts by weight of the polyamide-imide resin.

9. The polyamide-imide film according to claim 1, wherein The maximum absorption wavelength of the porphyrin-based dye in the visible light region in MEK solvent is 570-599 nm.

10. The polyamide-imide film according to claim 9, wherein The molar absorption coefficient of the porphyrin-based dye at the maximum absorption wavelength in the visible light region is 10000-1000000 L / mol cm.

11. The polyamide-imide film according to claim 9, wherein The porphyrin-based dye has a full width at half maximum (FWHM) of a maximum absorption peak of 100 nm or less.

12. The polyamide-imide film according to claim 1, wherein The solubility of the porphyrin-based dye in N,N-dimethylacetamide DMAc is greater than 0.5 weight %.

13. The polyamide-imide film according to claim 1, wherein The porphyrin-based dye has a residual mass at 300° C. measured under a nitrogen atmosphere at a temperature increase condition of 20° C. / min of 90% or more.