Polyimide film having low dielectric and high heat resistance characteristics and method for manufacturing same

Abstract

The present invention provides a polyimide film which is obtained by imidizing a polyamic acid solution containing an acid dianhydride component and a diamine component, and which has a dielectric loss factor (Df) of 0.0025 or less, a glass transition temperature (Tg) of 240 DEG C or more, and a heat resistance (Tg) of 3,000 or more. The acid dianhydride component contains two or more elements selected from the group consisting of biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), and p-phenylene bis (trimellitate dianhydride) (TAHQ), and the diamine component contains one or more elements selected from the group consisting of diaminodiphenyl ether (ODA), p-phenylenediamine (PPD), and m-toluidine (mTD).

Description

Technical Field

[0001] The present invention relates to a polyimide film having both excellent low dielectric properties and excellent heat resistance. Background Art

[0002] Polyimide (PI) is a polymer material based on an imide ring with excellent chemical stability and a rigid aromatic main chain, and has the highest level of heat resistance, chemical resistance, electrical insulation, chemical resistance, and weather resistance among organic materials.

[0003] In particular, due to its excellent insulating properties, that is, excellent electrical properties such as a low dielectric constant, it has attracted attention as a highly functional polymer material in the electrical, electronic, and optical fields.

[0004] In recent years, as electronic products have been moving toward lighter weight and smaller size, thin circuit substrates with high integration and flexibility have been actively developed.

[0005] Such thin circuit boards tend to have a structure in which a circuit including a metal foil is formed on a polyimide film which has excellent heat resistance, low temperature resistance, and insulation properties and is easily bendable.

[0006] As such a thin circuit board, a flexible metal foil laminate, for example, a flexible copper clad laminate (FCCL) using a thin copper plate as a metal foil is mainly used. In addition, polyimide is also used as a protective film, an insulating film, etc. of a thin circuit board.

[0007] On the other hand, as various functions are built into electronic devices in recent years, the electronic devices are required to have fast computing speeds and communication speeds. In order to meet this demand, thin circuit boards capable of high-speed communication at high frequencies are being developed.

[0008] In order to achieve high-frequency and high-speed communication, a high-impedance insulator that can maintain electrical insulation even at high frequencies is required. Since the impedance is inversely proportional to the frequency and dielectric constant (Dk) formed in the insulator, the dielectric constant should be as low as possible to maintain insulation even at high frequencies.

[0009] However, the reality is that conventional polyimide has not yet achieved a level of dielectric properties excellent enough to maintain sufficient insulation in high-frequency communications.

[0010] In addition, it is well known that the lower the dielectric property of an insulator, the more it can reduce the generation of unwanted stray capacitance and noise in a thin circuit substrate, thereby solving the problem of communication delay to a great extent.

[0011] Therefore, in fact, polyimide with low dielectric properties is considered to be the most important factor affecting the performance of thin circuit substrates.

[0012] In particular, in the case of high-frequency communication, dielectric dissipation caused by polyimide will inevitably occur. The dielectric dissipation factor (Df) refers to the degree of power waste in a thin circuit substrate and is closely related to the signal transmission delay that determines the communication speed. Therefore, keeping the dielectric dissipation factor of polyimide as low as possible is also considered to be an important factor affecting the performance of thin circuit substrates.

[0013] In addition, the more moisture a polyimide film contains, the greater the dielectric constant and the higher the dielectric loss factor. As for polyimide film, due to its excellent inherent properties, it is suitable as a material for thin circuit boards, but due to the polar imide group, it may be relatively fragile to moisture, which may lead to a decrease in insulation properties.

[0014] Therefore, the actual situation is that it is necessary to develop a polyimide film having dielectric properties, especially a low dielectric loss tangent, while maintaining the mechanical properties, thermal properties, and highly adhesive surface properties peculiar to polyimide at a certain level.

[0015] [Prior art literature]

[0016] [Patent Document]

[0017] (Patent Document 1) Korean Patent Publication No. 10-2021-0055230 Summary of the invention

[0018] Technical issues

[0019] Therefore, in order to solve the above-mentioned problems, an object is to provide a polyimide film having both excellent low dielectric and heat-resistant properties.

[0020] Solution to the problem

[0021] In order to achieve the above-mentioned purpose, one embodiment of the present invention provides a polyimide film, which is manufactured by imidizing a polyamic acid solution containing an acid dianhydride component and a diamine component, wherein the above-mentioned acid dianhydride component contains two or more selected from the group consisting of biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA) and p-phenylenebis(trimellitate anhydride) (TAHQ), and the above-mentioned diamine component contains two or more selected from the group consisting of diaminodiphenyl ether (ODA), p-phenylenediamine (PPD) and m-tolidine (mTD).

[0022] The acid dianhydride component of the polyimide film must contain biphenyltetracarboxylic dianhydride and p-phenylenebis(trimellitic dianhydride).

[0023] Another embodiment of the present invention provides a polyimide film, based on the total content of the above-mentioned acid dianhydride components as 100 mol%, the content of the above-mentioned biphenyltetracarboxylic dianhydride (BPDA) is greater than 30 mol% and less than 70 mol%, the content of the above-mentioned pyromellitic dianhydride (PMDA) is less than 40 mol%, and the content of the above-mentioned paraphenylene bis(trimellitic dianhydride) (TAHQ) is greater than 15 mol% and less than 35 mol%.

[0024] Another embodiment of the present invention provides a polyimide film, based on 100 mol % of the total content of the above-mentioned diamine components, the content of the above-mentioned diaminodiphenyl ether (ODA) is less than 35 mol %, the content of the above-mentioned p-phenylenediamine (PPD) is less than 55 mol %, and the content of the above-mentioned m-tolidine is more than 45 mol %.

[0025] Still another embodiment of the present invention provides a polyimide film including a block copolymer composed of two or more blocks.

[0026] Another embodiment of the present invention provides a polyimide film, which includes a block copolymer having a first block and a second block, wherein the first block is obtained by subjecting the above-mentioned acid dianhydride component including para-phenylene bis(trimellitic dianhydride) (TAHQ) to an imidization reaction with a diamine component including meta-tolidine (mTD) and diaminodiphenyl ether (ODA), and the second block is obtained by subjecting the above-mentioned acid dianhydride component including biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) to an imidization reaction with a diamine component including meta-tolidine (mTD) and para-phenylenediamine (PPD).

[0027] Another embodiment of the present invention provides a polyimide film having a dielectric loss tangent (Df) of 0.0025 or less and a glass transition temperature (Tg) of 240° C. or more.

[0028] Another embodiment of the present invention provides a method for manufacturing a polyimide film, which includes: a step of polymerizing an acid dianhydride component and a diamine component to manufacture a polyamic acid solution; and a step of imidizing the above-mentioned polyamic acid solution, wherein the above-mentioned acid dianhydride component includes two or more selected from the group consisting of biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA) and p-phenylenebis(trimellitate anhydride) (TAHQ), and the above-mentioned diamine component includes two or more selected from the group consisting of diaminodiphenyl ether (ODA), p-phenylenediamine (PPD) and m-tolidine (mTD).

[0029] The acid dianhydride component in the method for producing a polyimide film must contain biphenyltetracarboxylic dianhydride and p-phenylenebis(trimellitic dianhydride).

[0030] Another embodiment of the present invention provides a method for manufacturing a polyimide film, wherein, based on the total content of the above-mentioned acid dianhydride components as 100 mol%, the content of the above-mentioned biphenyltetracarboxylic dianhydride (BPDA) is greater than 30 mol% and less than 70 mol%, the content of the above-mentioned pyromellitic dianhydride (PMDA) is less than 40 mol%, and the content of the above-mentioned paraphenylene bis(trimellitic dianhydride) (TAHQ) is greater than 15 mol% and less than 35 mol%.

[0031] Another embodiment of the present invention provides a method for manufacturing a polyimide film, wherein, based on 100 mol % of the total content of the diamine components, the content of the diaminodiphenyl ether (ODA) is less than 35 mol %, the content of the p-phenylenediamine (PPD) is less than 55 mol %, and the content of the m-tolidine is greater than 45 mol %.

[0032] Another embodiment of the present invention provides a method for producing a polyimide film, wherein the polyimide film has a dielectric loss factor (Df) of 0.0025 or less and a glass transition temperature (Tg) of 240° C. or more.

[0033] Still another embodiment of the present invention provides a multi-layer film comprising the polyimide film.

[0034] Still another embodiment of the present invention provides a multi-layer film including the polyimide film and a thermoplastic resin layer.

[0035] Still another embodiment of the present invention provides a flexible metal foil laminate including the polyimide film and a conductive metal foil.

[0036] Still another embodiment of the present invention provides an electronic component including the flexible metal foil laminate.

[0037] Effects of the Invention

[0038] As described above, the present invention provides a polyimide film having low dielectric properties and high heat resistance, which is produced by imidizing a polyamic acid solution composed of specific components and a specific composition ratio, and can be effectively applied to various fields requiring such properties, especially electronic components such as flexible metal foil laminates. DETAILED DESCRIPTION

[0039] Hereinafter, embodiments of the present invention will be described in more detail.

[0040] Prior to this, the terms or words used in this specification and claims should not be interpreted limited to the usual meanings or in dictionaries, but should only be interpreted based on the inventor's ability to appropriately define the concepts of the terms to explain the principles of his invention in the best way, and in accordance with the meanings and concepts that are consistent with the technical ideas of the present invention.

[0041] Therefore, the embodiments described in this specification are merely the most preferred embodiments of the present invention and do not represent all technical ideas of the present invention. Therefore, it should be understood that various equivalents and modifications that can replace these embodiments may exist when this application is filed.

[0042] In this specification, unless the context clearly provides otherwise, expressions in the singular include expressions in the plural. In this specification, it should be understood that the terms "comprising", "having" or "having" are intended to specify the existence of implemented features, numbers, steps, constituent elements or combinations thereof, and do not preclude the existence or additional possibility of one or more other features, numbers, steps, constituent elements or combinations thereof.

[0043] In the present specification, when the amount, concentration or other value or parameter is given as a range, a preferred range or a preferred upper limit and a preferred lower limit, it should be understood that any pair of all ranges formed by any upper range limit or preferred value and any lower range limit or preferred value are specifically disclosed regardless of whether the range is disclosed separately.

[0044] Where numerical ranges are mentioned in this specification, unless otherwise stated, the ranges are intended to include the endpoints and all integers and fractions therein. The scope of the present invention is not intended to be limited to the specific values ​​mentioned when defining a range.

[0045] In this specification, "dianhydride" is intended to include precursors or derivatives thereof, which, although they may not technically be dianhydrides, will still react with diamines to form polyamic acids, which can again be converted into polyimides.

[0046] In this specification, "diamine" is intended to include precursors or derivatives thereof, which, although they may not technically be diamines, will still react with the dianhydride to form a polyamic acid which can again be converted into a polyimide.

[0047] The polyimide film of the present invention can be manufactured by imidizing a polyamic acid solution containing an acid dianhydride component and a diamine component, wherein the acid dianhydride component can include two or more selected from the group consisting of biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA) and para-phenylene bis(trimellitic dianhydride) (TAHQ), and the diamine component can include two or more selected from the group consisting of diaminodiphenyl ether (ODA), para-phenylenediamine (PPD) and meta-tolidine (mTD).

[0048] The acid dianhydride component may essentially include biphenyltetracarboxylic dianhydride and p-phenylenebis(trimellitic dianhydride).

[0049] For example, the polyimide film can be prepared by imidizing a polyamic acid containing an acid dianhydride component and a diamine component as follows: (1) a polyamic acid containing an acid dianhydride component composed of p-phenylene bis(trimellitic dianhydride) (TAHQ) and biphenyltetracarboxylic dianhydride (BPDA) and a diamine component composed of m-tolidine (mTD), diaminodiphenyl ether (ODA) and p-phenylenediamine (PPD); (2) a polyamic acid containing an acid dianhydride component composed of p-phenylene bis(trimellitic dianhydride) (TAHQ), biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) and a diamine component composed of m-tolidine (mTD) and p-phenylenediamine (PPD); (3) a polyamic acid comprising an acid dianhydride component consisting of p-phenylene bis(trimellitic dianhydride) (TAHQ), biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) and a diamine component consisting of m-tolidine (mTD) and diaminodiphenyl ether (ODA); or (4) a polyamic acid comprising an acid dianhydride component consisting of p-phenylene bis(trimellitic dianhydride) (TAHQ), biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) and a diamine component consisting of m-tolidine (mTD), diaminodiphenyl ether (ODA) and p-phenylenediamine (PPD).

[0050] In one embodiment, based on the total content of the acid dianhydride component of 100 mol%, the content of the biphenyltetracarboxylic dianhydride (BPDA) can be 30 mol% to 70 mol%, the content of the pyromellitic dianhydride (PMDA) can be 40 mol% to 40 mol%, and the content of the p-phenylene bis (trimellitic dianhydride) (TAHQ) can be 15 mol% to 35 mol%. Preferably, the content of the biphenyltetracarboxylic dianhydride (BPDA) can be 35 mol% to 65 mol%, the content of the pyromellitic dianhydride (PMDA) can be 35 mol% to 35 mol%, and the content of the p-phenylene bis (trimellitic dianhydride) (TAHQ) can be 20 mol% to 35 mol%.

[0051] The polyimide chain derived from the biphenyltetracarboxylic dianhydride (BPDA) has a structure called a charge transfer complex (CTC), that is, a regular linear structure in which an electron donor and an electron acceptor are close to each other, which strengthens intermolecular interaction.

[0052] Such a structure has an effect of preventing the formation of hydrogen bonds with water, and thus can have an influence on reducing the moisture absorption rate and maximize the effect of reducing the hygroscopicity of the polyimide film.

[0053] In order to make the polyimide film satisfy both appropriate elasticity and moisture absorption rate, the content ratio of acid dianhydride is particularly important. For example, as the content ratio of biphenyltetracarboxylic dianhydride (BPDA) decreases, it will become increasingly difficult to expect the low moisture absorption rate brought by the above-mentioned CTC structure.

[0054] In addition, the above-mentioned biphenyltetracarboxylic dianhydride (BPDA) includes two benzene rings corresponding to the aromatic part, and pyromellitic dianhydride (PMDA) includes one benzene ring corresponding to the aromatic part.

[0055] The pyromellitic dianhydride (PMDA) is an acid dianhydride component having a relatively rigid structure, and is preferred from the viewpoint of being able to impart appropriate elasticity to the polyimide film.

[0056] When the same molecular weight is used as the benchmark, the increase in the content of the above-mentioned pyromellitic dianhydride (PMDA) can be understood as an increase in the imide groups in the molecule, which can be understood as that in the polyimide polymer chain, the ratio of the imide groups derived from the above-mentioned pyromellitic dianhydride (PMDA) is relatively increased compared with the imide groups derived from biphenyltetracarboxylic dianhydride (BPDA).

[0057] That is, for the entire polyimide film, an increase in the content of pyromellitic dianhydride can be regarded as a relative increase in imide groups, and therefore it is difficult to expect a low moisture absorption rate.

[0058] If the content of the biphenyltetracarboxylic dianhydride (BPDA) is higher than 70 mol %, the heat resistance of the polyimide film may be reduced when a flexible metal foil laminate is produced.

[0059] On the contrary, if the content of the biphenyltetracarboxylic dianhydride (BPDA) is less than 30 mol % or the content of the pyromellitic dianhydride (PMDA) is more than 40 mol %, it may be difficult to achieve appropriate levels of dielectric constant, low dielectric loss characteristics and glass transition temperature.

[0060] If the content of p-phenylenebis(trimellitic dianhydride) (TAHQ) is more than 35 mol %, it may be difficult to achieve a high glass transition temperature, and if it is less than 15 mol %, it may be difficult to achieve low dielectric loss characteristics.

[0061] In another embodiment, based on 100 mol% of the total content of the diamine component, the content of the diaminodiphenyl ether (ODA) may be 35 mol% or less, the content of the p-phenylenediamine (PPD) may be 55 mol% or less, and the content of the m-tolidine may be 45 mol% or more. Preferably, the content of the diaminodiphenyl ether (ODA) may be 30 mol% or less, the content of the p-phenylenediamine (PPD) may be 50 mol% or less, and the content of the m-tolidine may be 50 mol% or more.

[0062] The above-mentioned diaminodiphenyl ether (ODA) or the above-mentioned p-phenylenediamine (PPD) may not be contained at all.

[0063] Furthermore, the meta-tolidine may be essentially contained as the diamine component, and the content of the meta-tolidine may be, for example, 90 mol % or less, or 85 mol % or less.

[0064] The above-mentioned meta-tolidine has a methyl group that exhibits hydrophobicity, and thus contributes to the low hygroscopicity of the polyimide film.

[0065] If the content of the above-mentioned diaminodiphenyl ether (ODA) is greater than 35 mol%, not only the glass transition temperature will be lowered, but the low dielectric loss characteristics may also be reduced. If the content of the above-mentioned p-phenylenediamine (PPD) is greater than 55 mol%, there is a concern that the low dielectric loss characteristics may be reduced. If the content of the above-mentioned m-tolidine is less than 45 mol%, the low dielectric loss characteristics may be reduced.

[0066] On the other hand, the polyimide film of the present invention may include a block copolymer composed of two or more blocks, and may particularly include two blocks.

[0067] The polyimide film of the present invention may include a first block and a second block, wherein the first block is obtained by subjecting the above-mentioned acid dianhydride component containing paraphenylene bis(trimellitic dianhydride) (TAHQ) to an imidization reaction with a diamine component containing meta-tolidine (mTD) and diaminodiphenyl ether (ODA), and the second block is obtained by subjecting the above-mentioned acid dianhydride component containing biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) to an imidization reaction with a diamine component containing meta-tolidine (mTD) and para-phenylenediamine (PPD).

[0068] By adjusting the blocks of such a block copolymer, the polyimide film may have excellent dielectric loss factor (Df) characteristics due to the first block, and may increase the glass transition temperature due to the second block to ensure high temperature stability.

[0069] In one embodiment, the dielectric constant (Dk) of the polyimide film may be 3.5 or less, the dielectric loss factor (Df) may be 0.0025 or less, and the glass transition temperature (Tg) may be 240° C. or more.

[0070] In this regard, in the case of a polyimide film that simultaneously satisfies the dielectric constant (Dk), dielectric loss factor (Df), and glass transition temperature, it can be used as an insulating film for a flexible metal foil laminate. Moreover, even if the manufactured flexible metal foil laminate is used as an electrical signal transmission circuit that transmits signals at a high frequency of more than 10 GHz, the insulation stability of the flexible metal foil laminate can be ensured and the signal transmission delay can be minimized.

[0071] On the other hand, the production of polyamic acid can be exemplified by the following method:

[0072] (1) A method in which all diamine components are added to a solvent, and then an acid dianhydride component is added in a substantially equimolar amount to the diamine component to carry out polymerization;

[0073] (2) A method in which all of the acid dianhydride component is added to a solvent, and then the diamine component is added in a substantially equimolar amount to the acid dianhydride component to carry out polymerization;

[0074] (3) A method in which a portion of the diamine component is added to a solvent, a portion of the acid dianhydride component is mixed at a ratio of about 95 to 105 mol % relative to the reaction components, and then the remaining diamine component is added, followed by the remaining acid dianhydride component, thereby polymerizing the diamine component and the acid dianhydride component in substantially equimolar amounts;

[0075] (4) A method in which an acid dianhydride component is added to a solvent, a portion of the diamine compound is mixed at a ratio of about 95 to 105 mol % relative to the reaction components, the remaining acid dianhydride component is added, and then the remaining diamine component is added, thereby polymerizing the diamine component and the acid dianhydride component in a substantially equimolar ratio;

[0076] (5) A method of forming a first composition by reacting a portion of a diamine component with a portion of an acid dianhydride component in a solvent in which either one of the components is in excess, and forming a second composition by reacting a portion of a diamine component with a portion of an acid dianhydride component in another solvent in which either one of the components is in excess, and then mixing the first and second compositions to complete polymerization, wherein, when forming the first composition, if the diamine component is in excess, the acid dianhydride component is in excess in the second composition, and if the acid dianhydride component is in excess in the first composition, the diamine component is in excess in the second composition, thereby mixing the first and second compositions and polymerizing the diamine component and the acid dianhydride component used in their reaction in a substantially equimolar manner; etc.

[0077] However, the polymerization method is not limited to the above examples, and the first and second polyamic acids may be produced by any known method.

[0078] In one embodiment, the method for producing a polyimide film of the present invention includes: a step of polymerizing an acid dianhydride component and a diamine component to produce a polyamic acid solution; and a step of imidizing the above-mentioned polyamic acid solution, wherein the acid dianhydride component includes two or more selected from the group consisting of biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA) and p-phenylenebis(trimellitate anhydride) (TAHQ), and the diamine component includes two or more selected from the group consisting of diaminodiphenyl ether (ODA), p-phenylenediamine (PPD) and m-tolidine (mTD).

[0079] The acid dianhydride component may essentially include biphenyltetracarboxylic dianhydride and p-phenylenebis(trimellitic dianhydride).

[0080] The polyimide film can be produced by reacting and copolymerizing the acid dianhydride component and the diamine component in a predetermined order.

[0081] In one embodiment, based on the total content of the acid dianhydride component of 100 mol%, the content of the biphenyltetracarboxylic dianhydride (BPDA) can be 30 mol% to 70 mol%, the content of the pyromellitic dianhydride (PMDA) can be 40 mol% to 40 mol%, and the content of the p-phenylene bis (trimellitic dianhydride) (TAHQ) can be 15 mol% to 35 mol%. Preferably, the content of the biphenyltetracarboxylic dianhydride (BPDA) can be 35 mol% to 65 mol%, the content of the pyromellitic dianhydride (PMDA) can be 35 mol% to 35 mol%, and the content of the p-phenylene bis (trimellitic dianhydride) (TAHQ) can be 20 mol% to 35 mol%.

[0082] In another embodiment, based on 100 mol % of the total content of the diamine components, the content of the diaminodiphenyl ether (ODA) may be 35 mol % or less, the content of the p-phenylenediamine (PPD) may be 55 mol % or less, and the content of the m-tolidine may be 45 mol % or more.

[0083] Preferably, the content of the diaminodiphenyl ether (ODA) may be 30 mol % or less, the content of the p-phenylenediamine (PPD) may be 50 mol % or less, and the content of the m-tolidine may be 50 mol % or more.

[0084] The above-mentioned diaminodiphenyl ether (ODA) or the above-mentioned p-phenylenediamine (PPD) may not be contained at all.

[0085] Furthermore, the meta-tolidine may be essentially contained as the diamine component, and the content of the meta-tolidine may be, for example, 90 mol % or less, or 85 mol % or less.

[0086] In the present invention, the polymerization method of the polyamic acid as described above can be a random polymerization method. From the perspective of maximizing the effect of the present invention of reducing the dielectric loss factor (Df) and moisture absorption rate, a polyimide film made from the polyamic acid of the present invention produced by the process as described above can be preferably used.

[0087] However, the above-mentioned polymerization method can make the length of the repeating unit in the polymer chain described above shorter, so there may be limitations in exerting the various excellent properties of the polyimide chain derived from the acid dianhydride component. Therefore, the polymerization method of the polyamic acid that can be particularly preferably used in the present invention can be a block polymerization method.

[0088] The solvent used for synthesizing the polyamic acid is not particularly limited, and any solvent can be used as long as it can dissolve the polyamic acid, and an amide-based solvent is preferred.

[0089] The polyimide film manufactured by the method for manufacturing a polyimide film may have a dielectric constant (Dk) of 3.5 or less, a dielectric loss tangent (Df) of 0.0025 or less, and a glass transition temperature (Tg) of 240° C. or more.

[0090] In one embodiment of the present invention, there are provided a multilayer film including the polyimide film, a multilayer film including the polyimide film and a thermoplastic resin layer, and a flexible metal foil laminate including the polyimide film and a conductive metal foil.

[0091] As the thermoplastic resin layer, for example, a thermoplastic polyimide resin layer can be used.

[0092] The metal foil used is not particularly limited, but when the flexible metal foil laminate of the present invention is used in electronic equipment or electrical equipment, for example, it can be a metal foil containing copper or copper alloy, stainless steel or its alloy, nickel or nickel alloy (including 42 alloy), aluminum or aluminum alloy.

[0093] In common flexible metal foil laminates, copper foils such as rolled copper foil and electrolytic copper foil are often used, and they can also be preferably used in the present invention. In addition, the surfaces of these metal foils can also be coated with a rust-proof layer, a heat-resistant layer or an adhesive layer.

[0094] In the present invention, the thickness of the metal foil is not particularly limited as long as it is a thickness that can sufficiently exhibit a function according to the intended use.

[0095] The flexible metal foil laminate of the present invention may be a structure in which a metal foil is laminated on one side of the polyimide film, or a structure in which an adhesive layer containing thermoplastic polyimide is attached to one side of the polyimide film and the metal foil is laminated with the adhesive layer attached thereto.

[0096] In addition, according to one embodiment of the present invention, the flexible metal foil laminate may be an electronic component including the above-mentioned flexible metal foil laminate as an electric signal transmission circuit. The above-mentioned electric signal transmission circuit may be an electronic component that transmits signals at a high frequency of at least 2 GHz, specifically at a high frequency of at least 5 GHz, and more specifically at a high frequency of at least 10 GHz.

[0097] By controlling the high hygroscopicity of the polyimide film that affects the above-mentioned electric signal transmission loss, it is possible to achieve optimization of the transmission loss at a frequency of 10 GHz or higher and a dielectric loss factor (Df) of 0.0025 or less.

[0098] The electronic component may be, for example, a communication circuit for a portable terminal, a communication circuit for a computer, or a communication circuit for a spacecraft, but is not limited thereto.

[0099] Implementation

[0100] The following describes the functions and effects of the invention in more detail through specific embodiments of the invention. However, these embodiments are provided only as examples of the invention, and the scope of the claims of the invention is not limited thereto.

[0101] Production Example (Production of Polyimide Film)

[0102] DMF was added to a 500 ml reactor equipped with a stirrer and a nitrogen injection / exhaust tube while injecting nitrogen. After setting the reactor temperature to 30° C., the diamine monomer and the acid dianhydride monomer were added in a predetermined order and confirmed to be completely dissolved.

[0103] Then, under a nitrogen atmosphere, stirring was continued for 120 minutes while the temperature of the reactor was heated to 40° C., thereby producing a block-copolymerized polyamic acid.

[0104] The content of the catalyst and the dehydrating agent were adjusted and added to the polyamic acid thus produced to prepare a polyimide precursor composition, and then the defoamed polyimide precursor composition was applied to a glass substrate using a spin coater. Thereafter, the gel film was dried at 120° C. for 30 minutes in a nitrogen atmosphere to produce a gel film, and the gel film was heated to 450° C. at a rate of 2° C. / min, and heat-treated at 450° C. for 60 minutes, and then cooled to 30° C. at a rate of 2° C. / min to obtain a polyimide film.

[0105] Examples 1 to 5 and Comparative Examples 1 to 4

[0106] The polyimide films were produced according to the production examples described above, except that the contents of the acid dianhydride component and the diamine component in Examples 1 to 5 and Comparative Examples 1 to 4 were adjusted as shown in Table 1 below.

[0107] [Table 1]

[0108]

[0109] For the polyimide films respectively produced in Examples 1 to 5 and Comparative Examples 1 to 4 as shown in Table 1 above, the dielectric constant, dielectric loss tangent, and glass transition temperature were measured and shown in Table 2 below.

[0110] [Table 2]

[0111]

[0112] The dielectric constant (Dk), dielectric loss tangent (Df), and glass transition temperature of the produced polyimide film were measured as follows.

[0113] (1) Dielectric constant measurement

[0114] The dielectric constant (Dk) was measured at 10 GHz using a SPDR measuring instrument from Keysight.

[0115] (2) Dielectric loss factor measurement

[0116] The dielectric loss factor (Df) was measured by using ENA (Vector Network Analyzer) of Deutsche Telekom by a cavity resonance method (SPDR) on a film placed in a 23° C. / 50% RH environment for 24 hours.

[0117] (3) Determination of glass transition temperature

[0118] The glass transition temperature (Tg) was obtained by determining the loss modulus and storage modulus of each film using DMA and measuring the inflection point in the tangent graph thereof.

[0119] As shown in Table 2, the polyimide film manufactured according to the embodiment of the present invention not only has a dielectric loss factor (Df) characteristic of less than 0.0025, but also has a glass transition temperature (Tg) of 240° C. or more and excellent thermal stability.

[0120] In addition, the dielectric constant (Dk) of the polyimide films of all Examples and Comparative Examples except Comparative Example 3 of the present invention was 3.5 or less.

[0121] Such results are achieved by the components and composition ratios specified in the present application, and it can be seen that the content of each component plays a decisive role.

[0122] On the other hand, it can be confirmed that the dielectric loss factor of the polyimide films of Comparative Examples 2 to 4 is higher than that of the polyimide films of Examples 1 to 5, and only the dielectric loss factor of the polyimide film of Comparative Example 1 is lower than that of the polyimide films of Examples 1 to 5, but it shows a very low glass transition temperature, so the heat resistance is greatly reduced.

[0123] Therefore, it is expected that the polyimide films of Examples 1 to 5 are suitable for practical use in electronic components because they have both low dielectric loss tangent characteristics and high heat resistance.

[0124] The above description has been made with reference to the embodiments of the present invention. However, a person skilled in the art in the art to which the present invention belongs should be able to make various applications and modifications within the scope of the present invention based on the above contents.

[0125] Industrial Applicability

[0126] As described above, the present invention provides a polyimide film having low dielectric properties and high heat resistance, which is produced by imidizing a polyamic acid solution composed of specific components and a specific composition ratio, and can be effectively applied to various fields requiring such properties, especially electronic components such as flexible metal foil laminates.

Claims

1. A polyimide film produced by imidizing a polyamic acid solution containing an acid dianhydride component and a diamine component, The acid dianhydride component includes two or more selected from the group consisting of biphenyltetracarboxylic dianhydride BPDA, pyromellitic dianhydride PMDA and paraphenylene bis(trimellitic dianhydride) TAHQ, The diamine component includes two or more selected from the group consisting of diaminodiphenyl ether (ODA), p-phenylenediamine (PPD), and m-tolidine (mTD), in, The acid dianhydride component must contain biphenyltetracarboxylic dianhydride and p-phenylene bis(trimellitic dianhydride).

2. The polyimide film according to claim 1, based on the total content of the acid dianhydride components as 100 mol %, the content of the biphenyltetracarboxylic dianhydride BPDA is greater than 30 mol % and less than 70 mol %, the content of the pyromellitic dianhydride PMDA is less than 40 mol %, and the content of paraphenylene bis(trimellitic dianhydride) TAHQ is greater than 15 mol % and less than 35 mol %.

3. The polyimide film according to claim 1, wherein, based on 100 mol % of the total content of the diamine components, the content of the diaminodiphenyl ether (ODA) is 35 mol % or less, the content of the p-phenylenediamine (PPD) is 55 mol % or less, and the content of the m-tolidine is 45 mol % or more. The polyimide film according to claim 1 , comprising a block copolymer composed of two or more blocks.

5. The polyimide film according to claim 1, comprising a block copolymer having a first block and a second block, The first block is obtained by imidizing the acid dianhydride component including p-phenylenebis(trimellitic acid dianhydride) TAHQ with the diamine component including m-tolidine mTD and diaminodiphenyl ether ODA, The second block is obtained by subjecting the acid dianhydride component including biphenyltetracarboxylic dianhydride BPDA and pyromellitic dianhydride PMDA to an imidization reaction with a diamine component including meta-tolidine mTD and para-phenylenediamine PPD. The polyimide film according to claim 1 , wherein the dielectric loss tangent Df of the polyimide film is 0.0025 or less and the glass transition temperature Tg of the polyimide film is 240° C. or more.

7. A method for producing a polyimide film, comprising: A step of polymerizing an acid dianhydride component and a diamine component to produce a polyamic acid solution; as well as The step of imidizing the polyamic acid solution, The acid dianhydride component includes two or more selected from the group consisting of biphenyltetracarboxylic dianhydride BPDA, pyromellitic dianhydride PMDA and paraphenylene bis(trimellitic dianhydride) TAHQ, The diamine component includes two or more selected from the group consisting of diaminodiphenyl ether (ODA), p-phenylenediamine (PPD), and m-tolidine (mTD), The acid dianhydride component must contain biphenyltetracarboxylic dianhydride and p-phenylenebis(trimellitic dianhydride).

8. The method for producing a polyimide film according to claim 7, wherein, based on 100 mol % of the total content of the acid dianhydride components, the content of the biphenyltetracarboxylic dianhydride BPDA is greater than 30 mol % and less than 70 mol %, the content of the pyromellitic dianhydride PMDA is less than 40 mol %, and the content of paraphenylene bis(trimellitic dianhydride) TAHQ is greater than 15 mol % and less than 35 mol %.

9. The method for producing a polyimide film according to claim 7, wherein, based on 100 mol % of the total content of the diamine components, the content of the diaminodiphenyl ether (ODA) is 35 mol % or less, the content of the p-phenylenediamine (PPD) is 55 mol % or less, and the content of the meta-tolidine is 45 mol % or more. 10 . The method for producing a polyimide film according to claim 7 , wherein the polyimide film has a dielectric loss tangent Df of 0.0025 or less and a glass transition temperature Tg of 240° C. or more. 11 . A multilayer film comprising the polyimide film according to claim 1 .

12. The multilayer film according to claim 11, further comprising a thermoplastic resin layer. 13 . A flexible metal foil laminate comprising the polyimide film according to claim 1 and a conductive metal foil. 14 . An electronic component comprising the flexible metal foil laminate according to claim 13 .

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