Polyimide film, substrate for display device, touch panel, solar cell and optical device and electronic device using the same

Abstract

The present invention relates to a polyimide film satisfying excellent heat resistance, optical properties, and mechanical properties, and to a substrate for a display device, a substrate for a touch panel, a substrate for a solar cell, an optical device, and an electronic device using the same.

Description

Technology Field

[0001] The present invention relates to a polyimide film satisfying excellent heat resistance, optical properties, and mechanical properties, and to a substrate for a display device, a substrate for a touch panel, a substrate for a solar cell, an optical device, and an electronic device using the same. Background Technology

[0002] As various flexible displays and electronic products advance, substrate materials previously used as glass are being replaced by organic plastic films. In particular, the display device market is focusing its attention on so-called flexible display devices, which apply flexible substrates to flat-panel displays. The application of these flexible display devices is being considered primarily for mobile devices such as smartphones, and their application fields are gradually expanding.

[0003] A representative material for such organic plastic films is polyimide, which is suitable for the high-temperature process of LTPS. A flexible substrate that can be used for manufacturing flexible TFTs can be produced by polymerizing a homopolymer mainly mixed with polyamic acid (PAA), polyamic acid ester (PAE), and soluble polyimide (SPI), applying it to a substrate, and then performing an inorganic monolayer or multilayer metal lamination process.

[0004] However, general transparent polyimides have very poor heat resistance reliability due to structural factors and have limitations such as yellowing caused by amine-based solvents in high-temperature processes.

[0005] Recently, there is a growing need for high-heat-resistant transparent polyimide materials to position cameras inside the panel, driven by the demand for eco-friendly products and the realization of full-screen displays, which is a challenging task for displays. The problem to be solved

[0006] The present invention relates to a polyimide film satisfying excellent heat resistance, optical properties, and mechanical properties.

[0007] In addition, the present invention is intended to provide a substrate for a display device, a substrate for a touch panel, a substrate for a solar cell, an optical device, and an electronic device using the polyimide film. means of solving the problem

[0008] To solve the above problem, the present specification provides a polyimide film comprising a polyimide resin including a reaction product of a monomer composition, wherein the monomer composition comprises a 1,4-phenylenediamine composition including 1,4-phenylenediamine, 1,3-phenylenediamine, and 1,2-phenylenediamine, and a tetracarboxylic acid dianhydride, and wherein the 1,3-phenylenediamine and 1,2-phenylenediamine are contained in an amount of 40 ppm or less relative to the weight of the 1,4-phenylenediamine composition.

[0009] In this specification, a substrate for a display device comprising the polyimide film is also provided.

[0010] In addition to the present specification, a substrate for a touch panel comprising the polyimide film is provided.

[0011] In addition to the present specification, a substrate for a solar cell comprising the polyimide film is provided.

[0012] The present specification also provides an optical device comprising the polyimide film.

[0013] The present specification also provides an electronic device comprising the polyimide film.

[0014] The following describes in more detail a polyimide film according to a specific embodiment of the invention and a substrate for a display device, a substrate for a touch panel, a substrate for a solar cell, an optical device, and an electronic device using the same.

[0016] Unless explicitly stated otherwise in this specification, technical terms are used merely to refer to specific embodiments and are not intended to limit the invention.

[0017] The singular forms used in this specification include plural forms unless the phrases clearly indicate otherwise.

[0018] As used in this specification, the meaning of 'includes' specifies certain characteristics, regions, integers, steps, actions, elements, and / or components, and does not exclude the existence or addition of other specific characteristics, regions, integers, steps, actions, elements, components, and / or groups.

[0019] Also, in this specification, terms including ordinal numbers such as 'first' and 'second' are used for the purpose of distinguishing one component from another and are not limited by said ordinal numbers. For example, within the scope of the present invention, the first component may also be named the second component, and similarly, the second component may be named the first component.

[0020] The present invention will be described in more detail below.

[0022] 1. Polyimide film

[0023] According to one embodiment of the invention, a polyimide film may be provided, comprising a polyimide-based resin including a reaction product of a monomer composition, wherein the monomer composition comprises a 1,4-phenylenediamine composition including 1,4-phenylenediamine, 1,3-phenylenediamine, and 1,2-phenylenediamine, and a tetracarboxylic acid dianhydride, and wherein the 1,3-phenylenediamine and 1,2-phenylenediamine are contained in an amount of 40 ppm or less relative to the weight of the 1,4-phenylenediamine composition.

[0024] The inventors confirmed through experiments that, as in the polyimide film of the above embodiment, if a 1,4-phenylenediamine composition containing 1,3-phenylenediamine and 1,2-phenylenediamine at a weight of 40 ppm or less relative to the weight of the 1,4-phenylenediamine composition is used as a monomer, the content of isomer impurities such as 1,3-phenylenediamine and 1,2-phenylenediamine is extremely reduced, and the purity of 1,4-phenylenediamine can be increased to 99.99%, thereby improving various physical properties of the polyimide film synthesized therefrom, and thus completed the invention.

[0025] In particular, the invention was completed after confirming through experiments that most of the 1,4-phenylenediamines used in the past exhibited a purity of 99.90%, which was inferior to the present invention in all aspects of heat resistance, optical properties, and mechanical properties.

[0026] Specifically, the monomer composition may include 1,4-phenylenediamine, 1,3-phenylenediamine, and 1,2-phenylenediamine, and may include a 1,4-phenylenediamine composition in which 1,3-phenylenediamine and 1,2-phenylenediamine are contained at a weight of 40 ppm or less relative to the weight of the 1,4-phenylenediamine composition.

[0027] The above 1,4-phenylenediamine composition is a composition comprising 1,4-phenylenediamine, 1,3-phenylenediamine, and 1,2-phenylenediamine, wherein 1,4-phenylenediamine is the main component, and 1,3-phenylenediamine and 1,2-phenylenediamine, which are isomers of 1,4-phenylenediamine, may be partially included or not included as impurities.

[0028] Specifically, the 1,4-phenylenediamine composition may contain 1,3-phenylenediamine and 1,2-phenylenediamine at a concentration of 40 ppm or less, or 35 ppm or less, or 30 ppm or less, or 0 ppm or more, or 1 ppm or more, or 0 ppm or more and 40 ppm or less, or 0 ppm to 35 ppm, or 0 ppm to 30 ppm, or 1 ppm to 40 ppm, or 1 ppm to 35 ppm, or 1 ppm to 30 ppm, or 1 ppm to 30 ppm, based on the weight of the 1,4-phenylenediamine composition.

[0029] The above ppm has the meaning of parts per million, which is 1 / 1,000,000. For example, 1,3-phenylenediamine and 1,2-phenylenediamine at a weight of 40 ppm or less relative to the weight of the above 1,4-phenylenediamine composition means a content ratio of 1,3-phenylenediamine and 1,2-phenylenediamine of 4 parts by weight or less relative to 1,000,000 weight of the above 1,4-phenylenediamine composition.

[0030] Although there is no specific standard for the weight of the 1,4-phenylenediamine composition used to measure the ppm unit, for example, the content of 1,3-phenylenediamine and 1,2-phenylenediamine contained therein can be measured based on 10 mg of the 1,4-phenylenediamine composition and converted into parts per million.

[0031] That is, in the above 1,4-phenylenediamine composition, the total weight of the 1,3-phenylenediamine and 1,2-phenylenediamine may be 40 ppm or less, or 35 ppm or less, or 30 ppm or less, or 0 ppm or more, or 1 ppm or more, or 0 ppm or more and 40 ppm or less, or 0 ppm to 35 ppm, or 0 ppm to 30 ppm, or 1 ppm to 40 ppm, or 1 ppm to 35 ppm, or 1 ppm to 30 ppm, or 1 ppm to 30 ppm.

[0032] The above 1,3-phenylenediamine and 1,2-phenylenediamine are structural isomers of 1,4-phenylenediamine, and as they have a bent structure compared to 1,4-phenylenediamine which has a linear structure, there is a problem with poor packing of the polyimide main chain. As a result, a decrease in the degree of polymerization and a deterioration in the physical properties of the polyimide film obtained at the end may occur.

[0033] Accordingly, if the above 1,3-phenylenediamine and 1,2-phenylenediamine are contained in an amount exceeding 40 ppm relative to the weight of the above 1,4-phenylenediamine composition, the content of impurities, such as 1,3-phenylenediamine and 1,2-phenylenediamine isomers, increases, and the purity of 1,4-phenylenediamine decreases to 99.90% or less, which may have a negative effect on the physical properties of the polyimide film.

[0034] More specifically, the 1,4-phenylenediamine composition may contain 1,3-phenylenediamine at a concentration of 20 ppm or less, or 15 ppm or less, or 0 ppm or more, or 1 ppm or more, or 0 ppm to 20 ppm, or 0 ppm to 15 ppm, or 1 ppm to 20 ppm, or 1 ppm to 15 ppm, based on the weight of the 1,4-phenylenediamine composition.

[0035] The above 1,4-phenylenediamine composition may contain 1,2-phenylenediamine at a concentration of 20 ppm or less, or 15 ppm or less, or 0 ppm or more, or 1 ppm or more, or 0 ppm to 20 ppm, or 0 ppm to 15 ppm, or 1 ppm to 20 ppm, or 1 ppm to 15 ppm, based on the weight of the above 1,4-phenylenediamine composition.

[0036] Meanwhile, the above 1,4-phenylenediamine composition may contain 1,4-phenylenediamine with a purity of 99.95% to 100%, or 99.96% to 100%, or 99.97% to 100%, or 99.98% to 100%, or 99.99% to 100% or less, or 99.95% or more, or 99.96% or more, or 99.97% or more, or 99.98% or more, or 99.99% or more, or 100% or less. If the purity of the above 1,4-phenylenediamine is less than 99.95%, the content of impurities, such as 1,3-phenylenediamine and 1,2-phenylenediamine isomers, increases, which may lead to a decrease in the degree of polymerization and have an adverse effect on the physical properties of the polyimide film.

[0037] Meanwhile, the monomer composition may include a tetracarboxylic acid dianhydride. The tetracarboxylic acid dianhydride can react with the 1,4-phenylenediamine composition described above to synthesize a polyamic acid, a polyamic acid ester, or a polyimide.

[0038] The specific examples of the above tetracarboxylic acid dianhydrides are not significantly limited, and various tetracarboxylic acid dianhydrides widely used in the field of polyimide synthesis, even if not exemplified in this specification, can be applied without limitation.

[0039] However, to explain by extremely specific example, the above tetracarboxylic acid dianhydride may include a multiphenylene-based aromatic tetracarboxylic acid dianhydride having 12 or more and 20 or fewer carbon atoms. An example of the above multiphenylene-based aromatic tetracarboxylic acid dianhydride having 12 or more and 20 or fewer carbon atoms is 3,3',4,4'-biphenyltetracarboxylic acid dianhydride.

[0040] In addition, the tetracarboxylic acid dianhydride may include a norbornene-based alicyclic tetracarboxylic acid dianhydride having 21 or more carbon atoms. Examples of the norbornene-based alicyclic tetracarboxylic acid dianhydride having 21 or more carbon atoms include norbornene-2-spiro-α-cyclopentanone-α′-spiro-2″-norbornene-5,5″,6,6″-tetracarboxylic acid dianhydride.

[0041] The above monomer composition may be used without limitation with various monomers, additives, etc., necessary for the synthesis of polyimide-based resins as needed, even if not exemplified in this specification.

[0042] Meanwhile, the polyimide film may comprise a polyimide-based resin containing a reaction product of the monomer composition described above. The reaction product refers to a material obtained through various reaction processes that induce a change in the molecular structure of the monomer in the monomer composition.

[0043] Specifically, a bond between the nitrogen atom of the amino group and the carbon atom of the anhydride group can be formed through a polymerization reaction between the terminal anhydride group (-OC-O-CO-) of the tetracarboxylic acid dianhydride contained in the monomer composition and the terminal amino group (-NH2) of the 1,4-phenylenediamine composition. Then, a polyimide resin can be synthesized by carrying out an imide ring formation reaction through heat treatment of the polymerization product.

[0044] That is, the reaction product of the monomer composition may include any one of the polymerization reaction product of the monomer composition, the imide of the polymerization reaction product, or a mixture thereof. In this case, the polymerization reaction product of the monomer composition may include a polyamic acid or a polyamic acid ester. Additionally, the imide of the polymerization reaction product may include a polyimide.

[0045] That is, the reaction product of the above monomer composition may include polyamic acid, polyamic acid ester, or polyimide.

[0046] More specifically, the reaction product of the monomer composition may include any one of a polyimide repeating unit represented by the following chemical formula 1, a precursor repeating unit thereof, or a mixture thereof.

[0047] [Chemical Formula 1]

[0048]

[0049] In the above chemical formula 1, X1 is a tetravalent functional group, and Y1 is a divalent functional group derived from a 1,4-phenylenediamine composition.

[0050] In the above chemical formula 1, X1 is a functional group derived from the tetracarboxylic acid dianhydride contained in the monomer composition. Additionally, Y1 is a functional group derived from the 1,4-phenylenediamine composition contained in the monomer composition. The details regarding the tetracarboxylic acid dianhydride and the 1,4-phenylenediamine composition are as described above for the monomer composition.

[0051] The polymerization reaction product of the above monomer composition may include a polyamic acid or a polyamic acid ester, and the polyamic acid or polyamic acid ester may include a precursor repeating unit of a polyimide repeating unit represented by the above chemical formula 1.

[0052] In addition, the imid of the polymerization reaction product of the monomer composition may include a polyimide, and the polyimide may include a polyimide repeating unit represented by the chemical formula 1.

[0053] Meanwhile, the above-mentioned polyimide film may include a polyimide-based resin containing a reaction product of the monomer composition described above.

[0054] Polyimide-based resins may include resins composed solely of polyimide repeating units, or resins containing polyimide repeating units.

[0055] That is, the above polyimide-based resin may include polyimide resin, or polyamic acid resin, polyamic acid ester resin, etc., which are precursor polymers of polyimide resin. That is, the above polyimide-based resin may include one or more selected from the group consisting of polyamic acid repeating units, polyamic acid ester repeating units, and polyimide repeating units. That is, the above polyimide-based resin may include one type of polyamic acid repeating unit, one type of polyamic acid ester repeating unit, one type of polyimide repeating unit, or a copolymer in which two or more of these repeating units are mixed.

[0056] One or more repeating units selected from the group consisting of the above polyamic acid repeating unit, polyamic acid ester repeating unit, and polyimide repeating unit can form the main chain of the above polyimide-based resin.

[0057] In addition, the polyimide-based resin may include a copolymer in which polyimide repeating units and various other polymer repeating units are mixed. For example, it may include a polyamideimide resin in which polyimide repeating units and polyamide repeating units are mixed.

[0058] The weight-average molecular weight (GPC measurement) of the above polyimide-based resin is not significantly limited, but, for example, is 1000 g / mol or more, or 10000 g / mol or more. Also, it is 200000 g / mol or less, or 200000 g / mol or less. Additionally, it may be 1000 g / mol to 200000 g / mol, or 10000 g / mol to 200000 g / mol.

[0059] The polyimide-based resin according to the present invention can exhibit excellent colorless and transparent properties while maintaining characteristics such as heat resistance and mechanical strength due to its rigid structure, and can be used in various fields such as substrates for devices, cover substrates for displays, optical films, circuit boards, IC (integrated circuit) packages, adhesive films, multilayer FRC (flexible printed circuit), tapes, touch panels, and protective films for optical discs.

[0060] Meanwhile, the above polyimide film may have a yellowness index (YI) measured on a specimen having a thickness of 9.5 μm or more, or 10.5 μm or less, or 9.5 μm to 10.5 μm, which is 20 or less, or 5 or less, or 0.1 or more, or 1 or more, or 0.1 to 20, or 1 to 20, or 0.1 to 5, or 1 to 5. As the yellowness index (YI) measured on a specimen having a thickness of 9.5 μm or more, or 10.5 μm or less, or 9.5 μm to 10.5 μm decreases to 20 or less, the polyimide film can achieve excellent optical properties by ensuring transparency.

[0061] The above yellow index can be measured from a polyimide film sample of 9.5 μm or more, 10.5 μm or less, or 9.5 μm to 10.5 μm. When the thickness of the polyimide film increases or decreases by a specific amount, the physical properties measured in the polyimide film can also change by a certain amount.

[0062] The above polyimide film may have a coefficient of thermal expansion (CTE) measured on a specimen having a thickness of 9.5 μm or more, or 10.5 μm or less, or 9.5 μm to 10.5 μm, which is 12 ppm / ℃ or less, or 10 ppm / ℃ or less, or 0.1 ppm / ℃ or more, or 0.1 ppm / ℃ to 12 ppm / ℃, or 0.1 ppm / ℃ to 10 ppm / ℃. Specifically, the above polyimide film may have a coefficient of thermal expansion in the range of 100 ℃ to 250 ℃ that is 12 ppm / ℃ or less, or 10 ppm / ℃ or less, or 0.1 ppm / ℃ or more, or 0.1 ppm / ℃ to 12 ppm / ℃, or 0.1 ppm / ℃ to 10 ppm / ℃. The above range of 100 ℃ or higher and 250 ℃ or lower may refer to a temperature range of 100 ℃ or higher and 250 ℃ or lower.

[0063] The above coefficient of thermal expansion is the change in thermal expansion measured by a TMA (TA's Q400) when the polyimide film sample is subjected to a first heating process at a heating rate of 1 ℃ / min to 10 ℃ / min or 4 ℃ / min to 6 ℃ / min in a temperature range of 100 ℃ to 250 ℃, with the film pulling force set to 0.01 N or more and 0.1 N or less, or 0.01 N or more and 0.05 N or less, and then cooled at a cooling rate of 1 ℃ / min to 10 ℃ / min or 3 ℃ / min to 5 ℃ / min in a temperature range of 250 ℃ to 100 ℃.

[0064] The coefficient of thermal expansion can be measured from a polyimide film sample having a thickness of 9.5 μm or more, 10.5 μm or less, or 9.5 μm to 10.5 μm. When the thickness of the polyimide film increases or decreases by a specific amount, the physical properties measured in the polyimide film can also change by a certain amount.

[0065] As the above polyimide film satisfies a coefficient of thermal expansion of 12 ppm / ℃ or less in the range of 100 ℃ to 250 ℃, sufficient heat resistance is secured even in a polyimide film obtained by high-temperature curing, so when this is used as a plastic substrate, the plastic substrate is prevented from being damaged by heat when heat-treating the metal layer formed on the plastic substrate, and warpage in the metal thin film formed on the plastic substrate can also be suppressed.

[0066] The above polyimide film may have a transmittance at a wavelength of 470 nm measured on a specimen having a thickness of 9.5 μm or more, or 10.5 μm or less, or 9.5 μm to 10.5 μm, which is 70% or more, or 85% or more, or 100% or less, or 90% or less, or 70% to 100%, or 70% to 90%, or 85% to 100%, or 85% to 90%. As the transmittance at a wavelength of 470 nm measured on a specimen having a thickness of 9.5 μm or more, or 10.5 μm or less, or 9.5 μm to 10.5 μm, increases to 70% or more, the polyimide film can achieve excellent optical properties by securing transparency.

[0067] The above transmittance can be measured from a polyimide film sample of 9.5 μm or more, 10.5 μm or less, or 9.5 μm to 10.5 μm. When the thickness of the polyimide film increases or decreases by a specific amount, the physical properties measured in the polyimide film can also change by a certain amount.

[0068] The above polyimide film may have a tensile modulus of 5 GPa or more, or 8 GPa or more, or 9 GPa or more, or 10.5 μm or less, or 9.5 μm to 10.5 μm, measured for a specimen having a thickness of 5.5 μm or more, or 8 GPa or more, or 9 GPa or more, or 10 GPa or more, or 15 GPa or less, or 5 GPa to 15 GPa, or 8 GPa to 15 GPa, or 9 GPa to 15 GPa, or 10 GPa to 15 GPa.

[0069] The above polyimide film may have a tensile strength of 200 MPa or more, 300 MPa or more, 500 MPa or more, 700 MPa or less, 200 MPa to 700 MPa, or 300 MPa to 700 MPa, or 500 MPa to 700 MPa, or 500 MPa to 700 MPa, when measured on a specimen having a thickness of 9.5 μm or more, or 10.5 μm or less, or 9.5 μm to 10.5 μm.

[0070] The above polyimide film may have a tensile elongation of 10% or more, 14% or more, 15% or more, or 20% or less, or 10% to 20%, or 14% to 20%, or 15% to 20%, or 15% to 20%, measured on a specimen having a thickness of 9.5 μm or more, or 10.5 μm or less, or 9.5 μm to 10.5 μm or less.

[0071] The above tensile modulus, tensile strength, and tensile elongation can be measured from the polyimide film sample having a thickness of 9.5 μm or more, 10.5 μm or less, or 9.5 μm to 10.5 μm. When the thickness of the polyimide film increases or decreases by a specific amount, the physical properties measured in the polyimide film can also change by a certain amount.

[0072] Meanwhile, the polyimide film of the above embodiment may include a cured product of the polyimide-based resin. Specifically, the polyimide film of the above embodiment may include a cured product in which the polyimide-based resin is cured at a temperature of 400°C or higher. The cured product refers to a material obtained through a curing process of a resin composition containing the polyimide-based resin, and the curing process may be carried out at a temperature of 400°C or higher, 500°C or lower, or between 400°C and 500°C.

[0073] More specifically, examples of methods for synthesizing the polyimide film are not significantly limited, and for example, a method for manufacturing a film may be used, comprising the steps of: applying a resin composition containing the polyimide-based resin to a substrate to form a film (Step 1); drying the film (Step 2); and heat-treating the dried film to cure it (Step 3).

[0074] Step 1 above is a step of forming a coating film by applying a resin composition containing the aforementioned polyimide-based resin to a substrate. The method of applying the resin composition containing the polyimide-based resin to the substrate is not particularly limited, and methods such as screen printing, offset printing, flexographic printing, and inkjet printing may be used.

[0075] Furthermore, the resin composition containing the above-mentioned polyimide-based resin may be dissolved or dispersed in an organic solvent. In such a form, for example, when the polyimide-based resin is synthesized in an organic solvent, the solution may be the resulting reaction solution itself, or it may be the reaction solution diluted with another solvent. Also, when the polyimide-based resin is obtained as a powder, it may be dissolved in an organic solvent to form a solution.

[0076] Specific examples of the above organic solvents include toluene, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 2-pyrrolidone, N-ethylpyrrolidone, N-vinylpyrrolidone, dimethyl sulfoxide, tetramethylurea, pyridine, dimethylsulfone, hexamethyl sulfoxide, gamma-butyrolactone, 3-methoxy-N,N-dimethylpropanamide, 3-ethoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, 1,3-dimethyl-imidazolidinone, ethylamyl ketone, methylnonyl ketone, methyl ethyl ketone, methyl isoamyl ketone, methyl isopropyl ketone, cyclohexanone, ethylene carbonate, Examples include propylene carbonate, diglaime, 4-hydroxy-4-methyl-2-pentanone, ethylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol monopropyl ether, ethylene glycol monopropyl ether acetate, ethylene glycol monoisopropyl ether, ethylene glycol monoisopropyl ether acetate, ethylene glycol monobutyl ether, ethylene glycol monobutyl ether acetate, etc. These may be used alone or in combination.

[0077] The resin composition containing the above-mentioned polyimide-based resin may contain a solid content in an amount that has an appropriate viscosity, taking into account processability such as applicability during the film formation process. For example, the content of the composition can be adjusted so that the total resin content is 5% by weight or more, or 25% by weight or less, or 5% to 25% by weight, or 20% by weight or less, or 15% by weight or less, or 5% to 20% by weight, or 5% to 15% by weight.

[0078] In addition, the resin composition containing the polyimide-based resin may further include other components in addition to the organic solvent. As a non-limiting example, when the resin composition containing the polyimide-based resin is applied, additives may be further included that can improve the uniformity of film thickness or surface smoothness, improve adhesion to the substrate, change the dielectric constant or conductivity, or increase density. Examples of such additives include surfactants, silane compounds, dielectric or crosslinking compounds, etc.

[0079] Step 2 above is a step of drying a coating film formed by applying a resin composition containing the polyimide-based resin to a substrate.

[0080] The drying step of the above coating film can be carried out by a heating means such as a hot plate, a hot air circulation furnace, or an infrared furnace, and can be performed at a temperature of 50°C or higher, or 150°C or lower, or 100°C or lower, or 50°C to 150°C, or 50°C to 100°C.

[0081] Step 3 above is a step of curing the dried coating film by heat treatment. At this time, the heat treatment may be carried out by a heating means such as a hot plate, a hot air circulation furnace, or an infrared furnace, and may be performed at a temperature of 400°C or higher, 500°C or lower, or 400°C to 500°C.

[0082] The thickness of the above polyimide film is not significantly limited, but can be freely adjusted, for example, to 0.01 μm or more, or 1000 μm or less, or within the range of 0.01 μm to 1000 μm.

[0084] 2. Substrate for display device

[0085] Meanwhile, according to another embodiment of the invention, a substrate for a display device comprising a polyimide film of the first embodiment may be provided. The details regarding the polyimide film may include all the details described above in the first embodiment.

[0086] The display device including the above substrate may be a liquid crystal display device (LCD), an organic light emitting diode (OLED), a flexible display, or a rollable display or foldable display, but is not limited thereto.

[0087] The above display device may have various structures depending on the application field and specific form, and may include, for example, a structure including a cover plastic window, a touch panel, a polarizer, a barrier film, a light-emitting element (OLED element, etc.), a transparent substrate, etc.

[0088] The polyimide film of the above-described embodiment can be used for various purposes, such as a substrate, an external protective film, or a cover window in various display devices, and more specifically, can be applied as a substrate.

[0089] For example, the substrate for the display device may have a structure in which a device protection layer, a transparent electrode layer, a silicon oxide layer, a polyimide film, a silicon oxide layer, and a hard coating layer are sequentially laminated.

[0090] The above transparent polyimide substrate may include a silicon oxide layer formed between the transparent polyimide film and the cured layer to further improve solvent resistance, moisture permeability, and optical properties, and the silicon oxide layer may be formed by curing polysilazane.

[0091] Specifically, the silicon oxide layer may be formed by coating and drying a solution containing polysilazane and then curing the coated polysilazane prior to the step of forming a coating layer on at least one surface of the transparent polyimide film.

[0092] A substrate for a display device according to the present invention can provide a transparent polyimide cover substrate having excellent bending characteristics and impact resistance, as well as solvent resistance, optical characteristics, moisture permeability, and scratch resistance by including the above-described device protection layer.

[0094] 3. Substrates for touch panels, substrates for solar cells

[0095] Meanwhile, according to another embodiment of the invention, a substrate for a touch panel or a substrate for a solar cell comprising the polyimide film of the other embodiment may be provided. The details regarding the polyimide film may include all the details described above in the first embodiment.

[0096] The polyimide film of the above-described embodiment can be used for various purposes, such as a substrate, an external protective film, or a cover window in a touch panel or solar cell, and more specifically, it can be applied as a substrate.

[0097] The configuration and manufacturing method of the above-mentioned touch panel or solar cell may utilize technology known in the art, except that the above-mentioned polyimide film is used for the purposes described above.

[0099] 4. Optical device

[0100] Meanwhile, according to another embodiment of the invention, an optical device comprising a polyimide film of the other embodiment may be provided. The details regarding the polyimide film may include all the details described above in the first embodiment.

[0101] The above optical device may include all types of devices utilizing properties realized by light, such as display devices. Specific examples of the above display devices include, but are not limited to, liquid crystal display devices (LCDs), organic light emitting diodes (OLEDs), flexible displays, or rollable or foldable displays.

[0102] The above optical device may have various structures depending on the application field and specific form, and may include, for example, a structure including a cover plastic window, a touch panel, a polarizer, a barrier film, a light-emitting element (such as an OLED element), a transparent substrate, etc.

[0103] The polyimide film of the other embodiment described above can be used for various purposes, such as a substrate, an external protective film, or a cover window in these various optical devices, and more specifically, can be applied to a substrate.

[0105] 5. Electronic devices

[0106] Meanwhile, according to another embodiment of the invention, an electronic device comprising a polyimide film of the other embodiment may be provided. The details regarding the polyimide film may include all the details described above in the first embodiment.

[0107] The above electronic device may include all types of devices utilizing properties implemented by electrical signals, such as semiconductor devices, communication equipment such as mobile phones, lighting devices, and batteries (secondary batteries, solar cells).

[0108] In the above electronic device, the polyimide film of the above embodiment may be used for various purposes such as a substrate, an interlayer insulating film, a solder resist, an external protective film, or a cover window, and the configuration and manufacturing method of the above electronic device may utilize techniques known in the art except that the polyimide film is used for the aforementioned purposes. Effects of the invention

[0109] According to the present invention, a polyimide film satisfying excellent heat resistance, optical properties, and mechanical properties, and a substrate for a display device, a substrate for a touch panel, a substrate for a solar cell, an optical device, and an electronic device using the same can be provided. Specific details for implementing the invention

[0110] The invention is described in more detail in the following examples. However, the following examples are merely illustrative of the invention, and the scope of the invention is not limited by the following examples.

[0112] <Preparation Example: Preparation of a Diamine Composition>

[0113] p-Nitrochlorobenzene (PNC) was prepared according to a general manufacturing method and then reacted with ammonia to prepare p-Nitroaniline (PNA), and 1,4-phenylenediamine (p-phenylenediamine, p-PDA) was synthesized through a hydrogenation reaction of the prepared PNA.

[0114] Subsequently, a 1,4-phenylenediamine composition with a purity of 99.99% was prepared by sublimation purification of the synthesized 1,4-phenylenediamine (p-PDA).

[0116] <Comparative Preparation Example: Preparation of Diamine Composition>

[0117] p-Nitrochlorobenzene (PNC) was prepared according to a general manufacturing method and then reacted with ammonia to prepare p-Nitroaniline (PNA), and 1,4-phenylenediamine (p-phenylenediamine, p-PDA, Sigma-Aldrich) with a purity of 99.00% was obtained by hydrogenating the prepared PNA.

[0118] Subsequently, the above 1,4-phenylenediamine (p-phenylenediamine, p-PDA) was recrystallized with ethanol to prepare a 1,4-phenylenediamine composition with a purity of 99.90%.

[0120] <Example: Preparation of Polyimide Film>

[0121] Example 1

[0122] (1) Preparation of a polyimide precursor composition

[0123] After filling an organic solvent Diethylacetamide (DEAc) into a stirrer with a nitrogen stream, and maintaining the temperature of the reactor at 25°C, 0.735 mol of the 1,4-phenylenediamine composition of the preparation example was added and dissolved at the same temperature.

[0124] A polyimide precursor composition was obtained by adding 0.735 mol of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) as an anhydride to a solution to which the 1,4-phenylenediamine composition of the preparation example was added at the same temperature and stirring for 24 hours.

[0125] (2) Preparation of polyimide film

[0126] The above polyimide precursor composition was spin-coated onto a glass substrate. The glass substrate coated with the polyimide precursor composition was placed in an oven and heated at a rate of 5 ℃ / min, and a curing process was carried out by maintaining it at 80 ℃ for 30 minutes and at 460 ℃ for 30 minutes. After the curing process was completed, the glass substrate was immersed in water to peel off the film formed on the glass substrate, and the film was dried in an oven at 100 ℃ to produce a polyimide film with a thickness of approximately 10 μm.

[0128] Example 2

[0129] A polyimide film was prepared in the same manner as in Example 1 above, except that norbornane-2-spiro-α-cyclopentanone-α′-spiro-2″-norbornane-5,5″,6,6″-tetracarboxylic dianhydride (CpODA), represented by the following chemical formula a, was used instead of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) as the anhydride, and the maximum curing temperature was set to 400°C.

[0130] [Chemical formula a]

[0131]

[0133] <Comparative Example: Preparation of Polyimide Film>

[0134] Comparative Example 1

[0135] A polyimide precursor composition and a polyimide film were prepared in the same manner as in Example 1, except that the 1,4-phenylenediamine composition of the Comparative Preparation Example was used instead of the 1,4-phenylenediamine composition of the Preparation Example.

[0137] Comparative Example 2

[0138] A polyimide precursor composition and a polyimide film were prepared in the same manner as in Example 2 above, except that the 1,4-phenylenediamine composition of the Comparative Preparation Example was used instead of the 1,4-phenylenediamine composition of the Preparation Example.

[0140] <Experimental Example 1: Measurement of Physical Properties of Diamine Compositions Obtained in Preparation Examples and Comparative Preparation Examples>

[0141] Physical properties were measured from the 1,4-phenylenediamine compositions obtained in the above manufacturing examples and comparative manufacturing examples using the following method, and the results are shown in Table 1.

[0143] 1. Purity

[0144] Under atmospheric pressure and conditions of 20 to 30 °C, 5 to 20 mg of a 1,4-phenylenediamine composition was taken as a sample, dissolved in 1 ml of DMSO-d6 solvent, and then analyzed using an Agilent DD1 500 MHz NMR instrument 1 An H NMR spectrum was obtained. Using analysis software (MestReC), peaks of all detected substances, such as 1,4-phenylenediamine (p-PDA), 1,2-phenylenediamine (o-PDA), and 1,3-phenylenediamine (m-PDA), were each designated and integrated. Based on the peak integration values, the weight percentage ratio of 1,4-phenylenediamine (p-PDA) contained within 100 weight% of the sample was calculated and this was defined as the purity.

[0146] 2. Isomer content

[0147] Under atmospheric pressure and conditions of 20–30 °C, 10 mg of a 1,4-phenylenediamine composition was taken as a sample, dissolved in 1 ml of DMSO-d6 solvent, and then analyzed using an Agilent DD1 500 MHz NMR instrument 1An H NMR spectrum was obtained. Using analysis software (MestReC), peaks of all detected substances, such as 1,4-phenylenediamine (p-PDA), 1,2-phenylenediamine (o-PDA), and 1,3-phenylenediamine (m-PDA), were each designated and integrated. Based on the peak integration values, the weight ratio (ppm) of 1,2-phenylenediamine (o-PDA) and 1,3-phenylenediamine (m-PDA) contained within 100 wt% of the sample was calculated.

[0149] Measurement results of Experimental Example 1 of the Manufacturing Example and Comparative Manufacturing Example division water(%) Isomer content (ppm) o-PDA m-PDA Preparation Example 99.99 15 15 Comparative Manufacturing Example 99.90 440 440

[0150] <Experimental Example 2: Measurement of Physical Properties of Polyimide Films Obtained in Examples and Comparative Examples>

[0151] The physical properties of the polyimide films obtained in the above examples and comparative examples were measured by the following method, and the results are shown in Table 2.

[0153] 1. Transmittance

[0154] Transmittance at a wavelength of 470 nm was measured using a transmittance meter (model name HR-100, manufactured by Murakami Color Research Laboratory) in accordance with JIS K 7105.

[0156] 2. Yellow Index (YI)

[0157] The yellowness index of the polyimide film was measured using a color meter (Color-Eye 7000A from GRETAGMACBETH).

[0159] 3. Coefficient of Thermal Expansion (CTE)

[0160] The above film was prepared in a size of 5 x 20 mm, and the sample was loaded using an accessory. The actual measured length of the film was kept constant at 16 mm. The film was set to a pulling force of 0.02 N, and a first heating process was carried out at a heating rate of 5 ℃ / min in a temperature range of 100 ℃ to 250 ℃. Then, the change in thermal expansion was measured using a TMA (TA Q400) when cooling at a cooling rate of 4 ℃ / min in a temperature range of 250 ℃ to 100 ℃.

[0162] 4. Tensile strength, tensile elongation, tensile modulus

[0163] The specimens were formed according to ASTM D638 Type V and measured at room temperature. The tensile strength (Tesile Stress, MPa) and tensile strain (Tesile Strain, %) at the fracture point were measured. The tensile modulus (Tesile Modulus, GPa) was calculated as the ratio of tensile stress to tensile strain of 5%.

[0165] Measurement results of Experimental Example 2 of the Examples and Comparative Examples division diamine anhydride Thickness (㎛) 470nm transmittance (%) YI CTE(ppm / ℃) Tensile elongation (%) Tensile modulus (GPa) Tensile strength (MPa) Example 1 Preparation Example BPDA 10.3 76 17.3 9.81 17.8 10.2 552 Comparative Example 1 Comparative Manufacturing Example BPDA 10.3 64 25 10.1 14.5 6.8 231 Example 2 Preparation Example CpODA 9.8 88.49 2.38 11.53 14.9 9.7 220 Comparative Example 2 Comparative Manufacturing Example CpODA 9.8 84 5.35 13.4 12.7 5 78

[0166] As shown in Table 2 above, in the case of the polyimide film of the example synthesized from the 99.99% purity 1,4-phenylenediamine (p-PDA) composition of the manufacturing example, it was confirmed that there were improvements in transmittance, optical properties of YI, heat resistance properties of CTE, and mechanical properties of tensile strength compared to the polyimide film of the comparative example synthesized from the 99.90% purity 1,4-phenylenediamine (p-PDA) composition of the comparative manufacturing example.

Claims

Claim 1 A polyimide film comprising a reaction product of a monomer composition, wherein the monomer composition comprises a 1,4-phenylenediamine composition including 1,4-phenylenediamine, 1,3-phenylenediamine, and 1,2-phenylenediamine; and a tetracarboxylic acid dianhydride; wherein the 1,3-phenylenediamine and 1,2-phenylenediamine are contained in an amount of 40 ppm or less relative to the weight of the 1,4-phenylenediamine composition, and the polyimide film has a coefficient of thermal expansion (CTE) of 12 ppm / ℃ or less and a tensile modulus of 5 GPa or more, measured on a specimen having a thickness of 9.5 μm to 10.5 μm. Claim 2 In claim 1, the 1,4-phenylenediamine composition is a polyimide film containing 1,3-phenylenediamine at a weight of 20 ppm or less relative to the weight of the 1,4-phenylenediamine composition. Claim 3 In claim 1, the 1,4-phenylenediamine composition is a polyimide film containing 1,2-phenylenediamine at a weight of 20 ppm or less relative to the weight of the 1,4-phenylenediamine composition. Claim 4 In claim 1, the 1,4-phenylenediamine composition is a polyimide film containing 1,4-phenylenediamine with a purity of 99.95% or higher. Claim 5 In claim 1, the polyimide film is a polyimide film having a yellowness index (YI) of 20 or less measured on a specimen having a thickness of 9.5 μm to 10.5 μm. Claim 6 delete Claim 7 In claim 1, the polyimide film is a polyimide film having a transmittance of 70% or more at a wavelength of 470 nm measured on a specimen having a thickness of 9.5 μm to 10.5 μm. Claim 8 delete Claim 9 In claim 1, the polyimide film is a polyimide film having a tensile strength of 200 MPa or more measured on a specimen having a thickness of 9.5 μm to 10.5 μm. Claim 10 In claim 1, the polyimide film is a polyimide film having a tensile elongation of 10% or more measured on a specimen having a thickness of 9.5 μm to 10.5 μm. Claim 11 In claim 1, the reaction product of the monomer composition comprises a polyimide film comprising any one of a polyimide repeating unit represented by the following Chemical Formula 1, a precursor repeating unit thereof, or a mixture thereof: [Chemical Formula 1] In the above chemical formula 1, X1 is a tetravalent functional group, and Y1 is a divalent functional group derived from the above 1,4-phenylenediamine composition. Claim 12 A polyimide film according to claim 1, wherein the reaction product of the monomer composition comprises any one of the polymerization reaction product of the monomer composition, the imide of the polymerization reaction product, or a mixture thereof. Claim 13 A polyimide film according to claim 1, wherein the tetracarboxylic acid dianhydride comprises a multiphenylene-based aromatic tetracarboxylic acid dianhydride having 12 to 20 carbon atoms. Claim 14 A polyimide film according to claim 1, wherein the tetracarboxylic acid dianhydride comprises a norbornene-based alicyclic tetracarboxylic acid dianhydride having 21 or more carbon atoms. Claim 15 A substrate for a display device comprising the polyimide film of claim 1. Claim 16 A substrate for a touch panel comprising the polyimide film of claim 1. Claim 17 A substrate for a solar cell comprising the polyimide film of claim 1. Claim 18 An optical device comprising the polyimide film of claim 1. Claim 19 An electronic device comprising the polyimide film of claim 1.

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