Polyimide film having low dielectric constant and high heat resistance and method for producing the same

Abstract

The present invention provides a polyimide film obtained by imidizing a polyamic acid solution containing a dianhydride acid component including two or more selected from the group consisting of biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), and p-phenylene bis(trimellitate anhydride) (TAHQ), and a diamine component including one or more selected from the group consisting of oxydianiline (ODA), paraphenylenediamine (PPD), and m-tolidine (mTD), and 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.

Description

[Technical field]

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

[0002] Polyimide (PI) is a polymeric material based on imide rings, which have excellent chemical stability along with a rigid aromatic main chain, and has the highest levels of heat resistance, chemical resistance, electrical insulation, chemical resistance, and weather resistance among organic materials.

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

[0004] 2. Description of the Related Art Recently, with the trend towards lighter and smaller electronic products, flexible thin circuit boards with high integration density have been actively developed.

[0005] Such thin circuit boards tend to have a structure in which a circuit containing metal foil is formed on a polyimide film that has excellent heat resistance, low temperature resistance and insulating properties, but is also easily flexible.

[0006] Flexible metal clad laminates are mainly used for such thin circuit boards, and an example is Flexible Copper Clad Laminate (FCCL), which uses a thin copper plate as a metal foil. Polyimide is also used as a protective film and insulating film for thin circuit boards.

[0007] Meanwhile, as electronic devices are increasingly equipped with a variety of functions, they are required to have high computing and communication speeds. To meet this demand, thin circuit boards capable of high-speed communication at high frequencies have been developed.

[0008] To realize high-frequency and high-speed communication, insulators with high impedance that can maintain electrical insulation even at high frequencies are required. Since impedance is inversely proportional to the frequency and dielectric constant (Dk) formed in the insulator, the dielectric constant must be as low as possible to maintain insulation even at high frequencies.

[0009] However, in the case of ordinary polyimide, the dielectric properties are not currently at a level excellent enough to maintain sufficient insulation for high-frequency communications.

[0010] In addition, it is known that the lower the dielectric properties of the insulator, the less unwanted stray capacitance and noise can be generated in thin circuit boards, which can largely eliminate the causes of communication delays.

[0011] Therefore, the low dielectric properties of polyimide are currently recognized as the most important factor in the performance of thin circuit boards.

[0012] In particular, in the case of high frequency communication, dielectric dissipation due to polyimide inevitably occurs. The dielectric dissipation factor (Df) indicates the degree of electrical energy wasted in a thin circuit board 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 recognized as an important factor in the performance of thin circuit boards.

[0013] In addition, the more moisture a polyimide film contains, the larger its dielectric constant becomes and the higher its dielectric loss factor becomes. Although polyimide film is suitable as a material for thin circuit boards due to its excellent inherent properties, it is relatively vulnerable to moisture due to its polar imide group, which can cause its insulating properties to deteriorate.

[0014] Therefore, there is a need to develop a polyimide film having dielectric properties, particularly a low dielectric loss factor, while maintaining a certain level of the mechanical properties, thermal properties and highly adhesive surface properties inherent to polyimides. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] Republic of Korea Patent Publication No. 10-2021-0055230 Summary of the Invention [Problem to be solved by the invention]

[0016] In order to solve the above problems, an object of the present invention is to provide a polyimide film having both excellent low dielectric and heat resistance properties. [Means for solving the problem]

[0017] In order to achieve the above object, one embodiment of the present invention relates to a dianhydride component including two or more selected from the group consisting of biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), and p-phenylenebis(trimellitate anhydride) (TAHQ); The present invention provides a polyimide film produced by imidizing a polyamic acid solution containing a diamine component including two or more members selected from the group consisting of oxydianiline (ODA), paraphenylenediamine (PPD), and m-tolidine (mTD).

[0018] However, the dianhydride acid component of the polyimide film necessarily contains biphenyltetracarboxylic dianhydride and p-phenylenebis(trimellitate anhydride).

[0019] Another embodiment of the present invention provides a polyimide film, in which the content of the biphenyltetracarboxylic dianhydride (BPDA) is 30 mol% or more and 70 mol% or less, the content of the pyromellitic dianhydride (PMDA) is 40 mol% or less, and the content of the p-phenylene bis(trimellitate anhydride) (TAHQ) is 15 mol% or more and 35 mol% or less, based on 100 mol% of the total content of the dianhydride acid components.

[0020] In yet another embodiment of the present invention, there is provided a polyimide film, in which the oxydianiline (ODA) content is 35 mol% or less, the paraphenylenediamine (PPD) content is 55 mol% or less, and the m-tolidine content is 45 mol% or more, based on 100 mol% of the total content of the diamine components.

[0021] Yet another embodiment of the present invention provides a polyimide film comprising a block copolymer consisting of two or more blocks.

[0022] Yet another embodiment of the present invention provides a polyimide film comprising a block copolymer including a first block obtained by imidization reaction of a dianhydride component containing p-phenylene bis(trimellitate anhydride) (TAHQ) with a diamine component containing m-tolidine (mTD) and oxydianiline (ODA), and a second block obtained by imidization reaction of a dianhydride component containing biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) with a diamine component containing m-tolidine (mTD) and paraphenylenediamine (PPD).

[0023] Yet another embodiment of the present invention provides a polyimide film having a dielectric loss factor (Df) of 0.0025 or less and a glass transition temperature (Tg) of 240° C. or more.

[0024] Yet another embodiment of the present invention provides a method for producing a polyimide film, comprising the steps of: polymerizing a dianhydride acid component including two or more selected from the group consisting of biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), and p-phenylenebis(trimellitate anhydride) (TAHQ) and a diamine component including two or more selected from the group consisting of oxydianiline (ODA), paraphenylenediamine (PPD), and m-tolidine (mTD) to produce a polyamic acid solution; and imidizing the polyamic acid solution.

[0025] The dianhydride acid component in the method for producing the polyimide film necessarily contains biphenyltetracarboxylic dianhydride and p-phenylenebis(trimellitate anhydride).

[0026] In still another embodiment of the present invention, there is provided a method for producing a polyimide film, wherein the content of the biphenyltetracarboxylic dianhydride (BPDA) is 30 mol% or more and 70 mol% or less, the content of the pyromellitic dianhydride (PMDA) is 40 mol% or less, and the content of the p-phenylene bis(trimellitate anhydride) (TAHQ) is 15 mol% or more and 35 mol% or less, based on 100 mol% of the total content of the dianhydride acid components.

[0027] In yet another embodiment of the present invention, the content of the oxydianiline (ODA) is 35 mol% or less, the content of the paraphenylenediamine (PPD) is 55 mol% or less, and the content of the m-tolidine is 45 mol% or more, based on 100 mol% of the total content of the diamine components. A method for producing a polyimide film is provided.

[0028] In yet another embodiment of the present invention, there is provided 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.

[0029] Yet another embodiment of the present invention provides a multilayer film comprising the polyimide film.

[0030] Yet another embodiment of the present invention provides a multilayer film comprising the polyimide film and a thermoplastic resin layer.

[0031] Yet another embodiment of the present invention provides a flexible metal foil laminate comprising the polyimide film and an electrically conductive metal foil.

[0032] Yet another embodiment of the present invention provides an electronic component comprising the flexible metal foil laminate. Effect of the Invention

[0033] 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 having specific components and a specific composition ratio, and is useful in various fields requiring such properties, particularly in electronic components such as flexible metal foil laminates. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] Hereinafter, embodiments of the present invention will be described in more detail.

[0035] Prior to this, the terms and words used in this specification and claims should not be interpreted limited to their ordinary or dictionary meanings, but should be interpreted with meanings and concepts that correspond to the technical ideas of the present invention, in accordance with the principle that an inventor can appropriately define the concepts of terms in order to explain his / her invention in the best possible way.

[0036] Therefore, it should be understood that the configuration of the embodiment described in this specification is merely one of the most preferred embodiments of the present invention and does not fully represent the technical ideas of the present invention, and that there may be various equivalents and modifications that can replace them at the time of this application.

[0037] In this specification, the singular expression includes the plural expression unless the context clearly indicates otherwise. It should be understood that in this specification, the terms "comprise", "comprise", "have" and the like are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, and do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0038] Whenever an amount, concentration, or other value or parameter is given herein as a range, a preferred range or a list of an upper preferred value and a lower preferred value, it should be understood to specifically disclose all ranges formed by any pair of any upper range limit or preferred value, and any lower range limit or preferred value, regardless of whether a range is otherwise disclosed.

[0039] Where a range of numerical values ​​is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values ​​recited when defining a range.

[0040] As used herein, "dianhydride acid" is intended to include precursors or derivatives thereof which may not technically be dianhydrides but which nevertheless must react with a diamine to form a polyamic acid which is then converted back to a polyimide.

[0041] As used herein, "diamine" is intended to include precursors or derivatives thereof, which may not technically be diamines, but which nevertheless must react with a dianhydride to form a polyamic acid, which is then converted back to a polyimide.

[0042] The polyimide film according to the present invention can be produced by imidizing a polyamic acid solution containing a dianhydride component including two or more selected from the group consisting of biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), and p-phenylene bis(trimellitate anhydride) (TAHQ), and a diamine component including two or more selected from the group consisting of oxydianiline (ODA), paraphenylenediamine (PPD), and m-tolidine (mTD).

[0043] However, the dianhydride acid component can necessarily contain biphenyltetracarboxylic dianhydride and p-phenylenebis(trimellitate anhydride).

[0044] For example, (1) a polyimide film produced by imidizing a polyamic acid containing a dianhydride acid component consisting of p-phenylene bis(trimellitate anhydride) (TAHQ) and biphenyl tetracarboxylic dianhydride (BPDA) and a diamine component consisting of m-tolidine (mTD), oxydianiline (ODA) and paraphenylenediamine (PPD); (2) a polyimide film produced by imidizing a polyamic acid containing a dianhydride acid component consisting of p-phenylene bis(trimellitate anhydride) (TAHQ), biphenyl tetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) and a diamine component consisting of m-tolidine (mTD) and paraphenylenediamine (PPD); (3) a polyimide film produced by imidizing a polyamic acid containing a dianhydride acid component consisting of p-phenylene bis(trimellitate anhydride) (TAHQ), biphenyl tetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) and a diamine component consisting of m-tolidine (mTD) and paraphenylenediamine (PPD); The polyimide film may be a polyimide film produced by imidizing a polyamic acid containing a dianhydride acid component consisting of bis(trimellitate anhydride) (TAHQ), biphenyltetracarboxylic dianhydride (BPDA), and pyromellitic dianhydride (PMDA) and a diamine component consisting of m-tolidine (mTD) and oxydianiline (ODA), or (4) a polyimide film produced by imidizing a polyamic acid containing a dianhydride acid component consisting of p-phenylenebis(trimellitate anhydride) (TAHQ), biphenyltetracarboxylic dianhydride (BPDA), and pyromellitic dianhydride (PMDA) and a diamine component consisting of m-tolidine (mTD), oxydianiline (ODA), and paraphenylenediamine (PPD).

[0045] In one embodiment, based on the total content of the dianhydride acid components being 100 mol%, the content of the biphenyltetracarboxylic dianhydride (BPDA) may be 30 mol% or more and 70 mol% or less, the content of the pyromellitic dianhydride (PMDA) may be 40 mol% or less, and the content of the p-phenylene bis(trimellitate anhydride) (TAHQ) may be 15 mol% or more and 35 mol% or less. Preferably, the content of the biphenyltetracarboxylic dianhydride (BPDA) may be 35 mol% or more and 65 mol% or less, the content of the pyromellitic dianhydride (PMDA) may be 35 mol% or less, and the content of the p-phenylene bis(trimellitate anhydride) (TAHQ) may be 20 mol% or more and 35 mol% or less.

[0046] The polyimide chain derived from the biphenyltetracarboxylic dianhydride (BPDA) has a structure called a charge transfer complex (CTC), i.e., a regular linear structure in which the electron donor and electron acceptor are located close to each other, enhancing the intermolecular interaction.

[0047] Such a structure has the effect of preventing hydrogen bonding with moisture, and thus has the effect of lowering the moisture absorption rate, thereby maximizing the effect of lowering the moisture absorption of the polyimide film.

[0048] In order for the polyimide film to simultaneously satisfy the appropriate elasticity and moisture absorption rate, the content ratio of the dianhydride acid is particularly important. For example, the lower the content ratio of biphenyltetracarboxylic dianhydride (BPDA), the less likely it is that the low moisture absorption rate due to the CTC structure will be achieved.

[0049] Moreover, the biphenyltetracarboxylic dianhydride (BPDA) contains two benzene rings corresponding to the aromatic moiety, whereas the pyromellitic dianhydride (PMDA) contains one benzene ring corresponding to the aromatic moiety.

[0050] The pyromellitic dianhydride (PMDA) is preferred in that it is a dianhydride acid component having a relatively rigid structure and can impart suitable elasticity to the polyimide film.

[0051] The increase in the content of pyromellitic dianhydride (PMDA) can be understood as an increase in the imide groups in the molecule when the molecular weight is the same, and this can be understood as a relative increase in the ratio of imide groups derived from the pyromellitic dianhydride (PMDA) in the polyimide polymer chain compared to the imide groups derived from biphenyltetracarboxylic dianhydride (BPDA).

[0052] In other words, an increase in the content of pyromellitic dianhydride can be regarded as a relative increase in imide groups with respect to the entire polyimide film, which makes it difficult to expect a low moisture absorption rate.

[0053] If the content of biphenyltetracarboxylic dianhydride (BPDA) exceeds 70 mol %, the heat resistance of the polyimide film may decrease when manufacturing a flexible metal foil laminate.

[0054] Conversely, 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 an appropriate level of dielectric constant, low dielectric loss characteristics, and glass transition temperature.

[0055] In addition, if the content of p-phenylene bis(trimellitate anhydride) (TAHQ) exceeds 35 mol %, it may be difficult to achieve the glass transition temperature, and if it is less than 15 mol %, it may be difficult to achieve low dielectric loss characteristics.

[0056] In another embodiment, the content of the oxydianiline (ODA) may be 35 mol% or less, the content of the paraphenylenediamine (PPD) may be 55 mol% or less, and the content of the m-tolidine may be 45 mol% or more, based on the total content of the diamine components being 100 mol%. Preferably, the content of the oxydianiline (ODA) may be 30 mol% or less, the content of the paraphenylenediamine (PPD) may be 50 mol% or less, and the content of the m-tolidine may be 50 mol% or more.

[0057] The oxydianiline (ODA) or the paraphenylenediamine (PPD) may not be included at all.

[0058] Furthermore, the diamine component necessarily contains the m-tolidine, and the content of the m-tolidine may be, for example, 90 mol % or less, or 85 mol % or less.

[0059] The m-tolidine in particular has a methyl group that exhibits hydrophobicity, and contributes to the low moisture absorption properties of the polyimide film.

[0060] If the content of oxydianiline (ODA) exceeds 35 mol %, not only the glass transition temperature but also the low dielectric loss characteristics may decrease. If the content of paraphenylenediamine (PPD) exceeds 55 mol %, the low dielectric loss characteristics may decrease. If the content of m-tolidine is less than 45 mol %, the low dielectric loss characteristics may decrease.

[0061] On the other hand, the polyimide film of the present invention may contain a block copolymer consisting of two or more blocks, and in particular, may contain two blocks.

[0062] The polyimide film of the present invention can include a first block obtained by imidization reaction between a dianhydride component containing p-phenylene bis(trimellitate anhydride) (TAHQ) and a diamine component containing m-tolidine (mTD) and oxydianiline (ODA), and a second block obtained by imidization reaction between a dianhydride component containing biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) and a diamine component containing m-tolidine (mTD) and paraphenylenediamine (PPD).

[0063] By adjusting the blocks of the block copolymer in this way, the polyimide film can have excellent dielectric loss factor (Df) characteristics due to the first block, and at the same time, the second block can increase the glass transition temperature and ensure high temperature stability.

[0064] In one embodiment, the polyimide film may have a dielectric constant (Dk) of 3.5 or less, a dielectric loss factor (Df) of 0.0025 or less, and a glass transition temperature (Tg) of 240° C. or more.

[0065] In this regard, polyimide film that satisfies all the required dielectric constant (Dk), dielectric loss factor (Df), and glass transition temperature can be used as an insulating film for flexible metal foil laminates. Even if the manufactured flexible metal foil laminates are used as electrical signal transmission circuits that transmit signals at high frequencies of 10 GHz or more, the insulation stability can be ensured and delays in signal transmission can be minimized.

[0066] On the other hand, the production of polyamic acid can be carried out, for example, by (1) A method in which the entire amount of the diamine component is placed in a solvent, and then the dianhydride component is added in an amount substantially equimolar to the diamine component to polymerize the mixture; (2) A method in which the entire amount of the dianhydride component is placed in a solvent, and then a diamine component is added in an amount substantially equimolar to the dianhydride component to polymerize the diamine component; (3) A method in which a part of the diamine component is placed in a solvent, a part of the dianhydride component is mixed with the reaction components in a ratio of about 95 to 105 mol %, the remaining diamine component is added, and the remaining dianhydride component is added continuously thereto, so that the diamine component and the dianhydride component are substantially equimolar, thereby polymerizing the mixture; (4) A method in which a dianhydride component is placed in a solvent, a portion of the diamine compound is mixed with the reaction components in a ratio of 95 to 105 mol %, and then another dianhydride component is added, followed by the remaining diamine component, so that the diamine component and the dianhydride component are substantially equimolar, thereby polymerizing the mixture; (5) A method of forming a first composition by reacting some diamine components and some dianhydride acid components in a solvent so that one of them is in excess, and forming a second composition by reacting some diamine components and some dianhydride acid components in another solvent so that one of them is in excess, and then mixing the first and second compositions to complete polymerization, in which if the diamine component is in excess when the first composition is formed, the dianhydride acid component is in excess in the second composition, and if the dianhydride acid component is in excess in the first composition, the diamine component is in excess in the second composition, and the first and second compositions are mixed to polymerize so that the total diamine components and dianhydride acid components used in these reactions are substantially equimolar.

[0067] However, the polymerization method is not limited to the above examples, and the first and second polyamic acids can be produced by any known method.

[0068] In one embodiment, a method for producing a polyimide film according to the present invention includes the steps of: polymerizing a dianhydride acid component including two or more selected from the group consisting of biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), and p-phenylenebis(trimellitate anhydride) (TAHQ) and a diamine component including two or more selected from the group consisting of oxydianiline (ODA), paraphenylenediamine (PPD), and m-tolidine (mTD) to produce a polyamic acid solution; and imidizing the polyamic acid solution.

[0069] However, the dianhydride acid component can necessarily contain biphenyltetracarboxylic dianhydride and p-phenylenebis(trimellitate anhydride).

[0070] The dianhydride acid component and the diamine component can be reacted in a specific order to copolymerize and produce a polyimide film.

[0071] In one embodiment, based on the total content of the dianhydride acid components being 100 mol%, the content of the biphenyltetracarboxylic dianhydride (BPDA) may be 30 mol% or more and 70 mol% or less, the content of the pyromellitic dianhydride (PMDA) may be 40 mol% or less, and the content of the p-phenylene bis(trimellitate anhydride) (TAHQ) may be 15 mol% or more and 35 mol% or less. Preferably, the content of the biphenyltetracarboxylic dianhydride (BPDA) may be 35 mol% or more and 65 mol% or less, the content of the pyromellitic dianhydride (PMDA) may be 35 mol% or less, and the content of the p-phenylene bis(trimellitate anhydride) (TAHQ) may be 20 mol% or more and 35 mol% or less.

[0072] In another embodiment, based on 100 mol% of the total content of the diamine components, the content of the oxydianiline (ODA) may be 35 mol% or less, the content of the paraphenylenediamine (PPD) may be 55 mol% or less, and the content of the m-tolidine may be 45 mol% or more.

[0073] Preferably, the content of the oxydianiline (ODA) may be 30 mol % or less, the content of the paraphenylenediamine (PPD) may be 50 mol % or less, and the content of the m-tolidine may be 50 mol % or more.

[0074] The oxydianiline (ODA) or the paraphenylenediamine (PPD) may not be included at all.

[0075] Furthermore, the diamine component necessarily contains the m-tolidine, and the content of the m-tolidine may be, for example, 90 mol % or less, or 85 mol % or less.

[0076] In the present invention, the polymerization method of the polyamic acid may be a random polymerization method, and the polyimide film prepared from the polyamic acid of the present invention prepared by the above process can be preferably applied in terms of maximizing the effect of the present invention, which is to reduce the dielectric loss factor (Df) and moisture absorption rate.

[0077] However, in the above polymerization method, the length of the repeating unit in the polymer chain is relatively short as described above, so that there may be a limit to the excellent properties of the polyimide chain derived from the dianhydride acid component. Therefore, the polymerization method of polyamic acid that can be particularly preferably used in the present invention may be a block polymerization method.

[0078] On the other hand, the solvent for synthesizing the polyamic acid is not particularly limited, and any solvent that dissolves the polyamic acid can be used, but an amide-based solvent is preferable.

[0079] The polyimide film produced by the method for producing a polyimide film may have a dielectric constant (Dk) of 3.5 or less, a dielectric loss factor (Df) of 0.0025 or less, and a glass transition temperature (Tg) of 240° C. or more.

[0080] In one embodiment according to 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 an electrically conductive metal foil.

[0081] The thermoplastic resin layer may be, for example, a thermoplastic polyimide resin layer.

[0082] The metal foil used is not particularly limited, but when the flexible metal foil laminate of the present invention is used for electronic or electrical equipment, the metal foil may be, for example, copper or a copper alloy, stainless steel or an alloy thereof, nickel or a nickel alloy (including alloy 42), aluminum or an aluminum alloy.

[0083] In general flexible metal foil laminates, copper foils such as rolled copper foils and electrolytic copper foils are often used, and are also preferably usable in the present invention. In addition, the surface of these metal foils may be coated with an anti-rust layer, a heat-resistant layer, or an adhesive layer.

[0084] In the present invention, the thickness of the metal foil is not particularly limited, and may be any thickness that allows the metal foil to exhibit sufficient function depending on the application.

[0085] The flexible metal foil laminate according to the present invention may have a structure in which a metal foil is laminated on one side of the polyimide film, or an adhesive layer containing a thermoplastic polyimide is added to one side of the polyimide film, and the metal foil is laminated in a state of being attached to the adhesive layer.

[0086] Meanwhile, according to one embodiment of the present invention, the flexible metal foil laminate may be an electronic component including the flexible metal foil laminate as an electric signal transmission circuit. The electric signal transmission circuit may be an electronic component that transmits a signal at a high frequency of at least 2 GHz, more specifically at a high frequency of at least 5 GHz, and even more specifically at a high frequency of at least 10 GHz.

[0087] By controlling the high moisture absorption of the polyimide film, which affects the transmission loss of the electrical signal, it is possible to optimize the transmission loss at frequencies of 10 GHz or more and achieve a dielectric loss factor (Df) of 0.0025 or less.

[0088] The electronic component may be, for example, but is not limited to, a communication circuit for a mobile terminal, a communication circuit for a computer, or a communication circuit for an aerospace application. EXAMPLES

[0089] The functions and effects of the present invention will be described in more detail below through specific examples of the present invention, however, these examples are merely presented as examples of the present invention and do not define the scope of the invention.

[0090] Manufacturing example (manufacturing polyimide film) In a 500 ml reactor equipped with a stirrer and nitrogen inlet / outlet tubes, DMF is added while injecting nitrogen, the temperature of the reactor is set to 30°C, and then the diamine monomer and dianhydride monomer are added in a specified order and it is confirmed that they are completely dissolved.

[0091] Thereafter, the temperature of the reactor was raised to 40° C. under a nitrogen atmosphere, and stirring was continued for 120 minutes to prepare a block copolymerized polyamic acid.

[0092] A polyimide precursor composition was prepared by adding a catalyst and a dehydrating agent to the polyamic acid thus prepared, and the degassed polyimide precursor composition was applied to a glass substrate using a spin coater. The composition was then dried for 30 minutes at 120°C under a nitrogen atmosphere to prepare a gel film. The gel film was heated to 450°C at a rate of 2°C / min, heat-treated at 450°C for 60 minutes, and cooled to 30°C at a rate of 2°C / min to obtain a polyimide film.

[0093] Examples 1 to 5 and Comparative Examples 1 to 4 Polyimide films were produced according to the above-described production examples, and the contents of the dianhydride acid component and the diamine component in Examples 1 to 5 and Comparative Examples 1 to 4 were adjusted as shown in Table 1 below.

[0094] [Table 1]

[0095] As shown in Table 1, the dielectric constant, dielectric loss factor and glass transition temperature of the polyimide films prepared in Examples 1 to 5 and Comparative Examples 1 to 4 were measured, and the results are shown in Table 2 below.

[0096] [Table 2]

[0097] The dielectric constant (Dk), dielectric loss factor (Df) and glass transition temperature of the produced polyimide film were measured as follows.

[0098] (1) Measurement of dielectric constant The dielectric constant (Dk) was measured at 10 GHz using a Keysight SPDR measuring instrument.

[0099] (2) Measurement of dielectric loss factor The dielectric loss factor (Df) was measured by a cavity resonance method (SPDR) using a Keysight ENA (Vector Network Analyzer) after leaving the film in an environment of 23° C. / 50% RH for 24 hours.

[0100] (3) Measurement of glass transition temperature The glass transition temperature (Tg) was measured by determining the loss modulus and storage modulus of each film using DMA, and the inflection point in the tangent graph of these was taken as the glass transition temperature.

[0101] As shown in Table 2, the polyimide films prepared according to the embodiments of the present invention not only achieved a dielectric loss factor (Df) characteristic of less than 0.0025, but also had excellent thermal stability with a glass transition temperature (Tg) of 240° C. or higher.

[0102] On the other hand, the dielectric constant (Dk) of the polyimide films of all the Examples and Comparative Examples except Comparative Example 3 of the present invention was equal to or lower than 3.5.

[0103] This result is achieved by the components and composition ratios specified in this application, and it is understood that the content of each component plays a decisive role.

[0104] On the other hand, the dielectric loss factors of the polyimide films of Comparative Examples 2 to 4 were higher than those of the polyimide films of Examples 1 to 5. Only the polyimide film of Comparative Example 1 had a lower dielectric loss factor than the polyimide films of Examples 1 to 5. However, it was confirmed that the polyimide film showed a very low glass transition temperature and thus had a significantly reduced heat resistance.

[0105] From this, it could be predicted that the polyimide films of Examples 1 to 5 have both low dielectric loss properties and high heat resistance, and are suitable for practical application to electronic parts.

[0106] The present invention has been described above with reference to an embodiment thereof. However, a person having ordinary knowledge in the field to which the present invention pertains will be able to make various applications and modifications within the scope of the present invention based on the above content. [Industrial Applicability]

[0107] 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 having specific components and a specific composition ratio, and is useful in various fields requiring such properties, particularly in electronic components such as flexible metal foil laminates.

Claims

1. a dianhydride acid component including two or more selected from the group consisting of biphenyltetracarboxylic dianhydride (BPDA), pyromelitic dianhydride (PMDA), and p-phenylenebis(trimellitate anhydride) (TAHQ); and a diamine component including two or more selected from the group consisting of oxydianiline (ODA), paraphenylenediamine (PPD) and m-tolidine (mTD), Polyimide film. (However, the dianhydride acid component necessarily contains biphenyltetracarboxylic dianhydride and p-phenylenebis(trimellitate anhydride).)

2. Based on 100 mol% of the total content of the dianhydride acid components, the content of the biphenyltetracarboxylic dianhydride (BPDA) is 30 mol% or more and 70 mol% or less, the content of the pyromellitic dianhydride (PMDA) is 40 mol% or less, and the content of the p-phenylene bis(trimellitate anhydride) (TAHQ) is 15 mol% or more and 35 mol% or less. The polyimide film according to claim 1 .

3. the content of the oxydianiline (ODA) is 35 mol% or less, the content of the paraphenylenediamine (PPD) is 55 mol% or less, and the content of the m-tolidine is 45 mol% or more, based on 100 mol% of the total content of the diamine components; The polyimide film according to claim 1 .

4. Including block copolymers consisting of two or more blocks, The polyimide film according to claim 1 .

5. a first block obtained by imidization reaction of a dianhydride component containing p-phenylenebis(trimellitate anhydride) (TAHQ) with a diamine component containing m-tolidine (mTD) and oxydianiline (ODA); and a second block obtained by imidization reaction of a dianhydride component containing biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) with a diamine component containing m-tolidine (mTD) and paraphenylenediamine (PPD). The polyimide film according to claim 1 .

6. The polyimide film has a dielectric loss factor (Df) of 0.0025 or less, The glass transition temperature (Tg) is 240° C. or higher. The polyimide film according to claim 1 .

7. A step of polymerizing a dianhydride acid component including two or more selected from the group consisting of biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), and p-phenylenebis(trimellitate anhydride) (TAHQ) and a diamine component including two or more selected from the group consisting of oxydianiline (ODA), paraphenylenediamine (PPD), and m-tolidine (mTD) to produce a polyamic acid solution; and imidizing the polyamic acid solution. A method for producing a polyimide film. (However, the dianhydride acid component necessarily contains biphenyltetracarboxylic dianhydride and p-phenylenebis(trimellitate anhydride).)

8. Based on 100 mol% of the total content of the dianhydride acid components, the content of the biphenyltetracarboxylic dianhydride (BPDA) is 30 mol% or more and 70 mol% or less, the content of the pyromellitic dianhydride (PMDA) is 40 mol% or less, and the content of the p-phenylene bis(trimellitate anhydride) (TAHQ) is 15 mol% or more and 35 mol% or less. The method for producing a polyimide film according to claim 7 .

9. the content of the oxydianiline (ODA) is 35 mol% or less, the content of the paraphenylenediamine (PPD) is 55 mol% or less, and the content of the m-tolidine is 45 mol% or more, based on 100 mol% of the total content of the diamine components; The method for producing a polyimide film according to claim 7 .

10. The polyimide film has a dielectric loss factor (Df) of 0.0025 or less, The glass transition temperature (Tg) is 240° C. or higher. The method for producing a polyimide film according to claim 7 .

11. The polyimide film according to any one of claims 1 to 6, Multilayer film.

12. additionally comprising a thermoplastic resin layer; The multilayer film of claim 11.

13. The polyimide film according to any one of claims 1 to 6, an electrically conductive metal foil; Flexible metal foil laminate.

14. The flexible metal foil laminate of claim 13, Electronic components.

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