High transmission and low dielectric polyimide film and manufacturing method thereof

Abstract

The present invention provides a polyimide film and a method for manufacturing the polyimide film, wherein the polyamic acid solution is obtained by imidizing a dianhydric acid component comprising two or more selected from the group consisting of benzophenone tetracarboxylic dianhydride (BTDA), biphenyltetracarboxylic dianhydride (BPDA), and pyromellitic dianhydride (PMDA), and a diamine component comprising paraphenylene diamine (PPD), wherein, based on a total content of 100 mol% of the diamine component, the content of paraphenylene diamine is 70 mol% or more and 100 mol% or less, and based on a total content of 100 mol% of the dianhydric acid component, the content of biphenyltetracarboxylic dianhydride is 50 mol% or more and less than 100 mol%, the dielectric loss rate (Df) is 0.003 or less, and the light transmittance at a wavelength of 550 nm is 15% or more and 50% or less.

Description

Technology Field

[0001] The present invention relates to a high-transmittance, low-dielectric polyimide film and a method for manufacturing the same. Background Technology

[0002] Polyimide (PI) is a polymer material based on imide rings with excellent chemical stability and a rigid aromatic main chain, possessing the highest levels of heat resistance, chemical resistance, electrical insulation, chemical resistance, and weather resistance among organic materials. In particular, due to its excellent electrical properties, such as outstanding insulation characteristics—specifically low dielectric constant—it is gaining attention as a high-performance polymer material in fields ranging from electrical, electronic, and optical.

[0003] Recently, as electronic products become lighter and smaller, highly integrated and flexible thin circuit boards are being actively developed. There is a growing trend to utilize structures in which circuits containing metal foil are formed on a polyimide film that is easily bendable while possessing excellent heat resistance, low-temperature resistance, and insulation properties. Flexible metal foil laminates are primarily used for these thin circuit boards; for example, Flexible Copper Clad Laminate (FCCL), which uses a thin copper plate as the metal foil, is included. In addition, polyimide is also utilized as a protective film or insulating film for thin circuit boards.

[0004] Meanwhile, as various functions are increasingly integrated into electronic devices, fast processing and communication speeds are required. To meet this demand, thin circuit boards capable of high-speed communication at high frequencies are being developed. To realize high-frequency high-speed communication, an insulator with high impedance capable of maintaining electrical insulation even at high frequencies is required. Since impedance is inversely proportional to the frequency formed in the insulator and the dielectric constant (Dk), the dielectric constant must be as low as possible to maintain insulation even at high frequencies.

[0005] However, in the case of conventional polyimides, the dielectric properties are not excellent enough to maintain sufficient insulation in high-frequency communication.

[0006] Furthermore, it is known that the lower the dielectric properties of an insulator, the more effectively it can reduce the occurrence of undesirable stray capacitance and noise in thin circuit boards, thereby significantly resolving the causes of communication delays. Consequently, polyimides with low dielectric properties are currently recognized as a critical factor in the performance of thin circuit boards.

[0007] In particular, in the case of high-frequency communication, dielectric dissipation through polyimide inevitably occurs. The dielectric dissipation factor (Df) represents the degree of electrical energy waste in thin circuit boards and is closely related to signal transmission delay, which determines communication speed; therefore, maintaining the dielectric dissipation factor of polyimide as low as possible is recognized as an important factor in the performance of thin circuit boards.

[0008] In addition, as the market for FCCL utilizing high-transmittance PI expands for applications such as AoD (Always On Display), smart windows, and transparent antennas, there is a demand for polyimide films with improved light transmittance. However, conventional polyimide films have a yellowish tint due to the high density of aromatic rings, resulting in low transmittance in the visible light region and making it difficult to achieve high light transmittance. Furthermore, when fillers are included in the film to improve driving performance, the light transmittance of the film decreases further due to the light-blocking effect caused by the included fillers, making it difficult to use in fields requiring transparency.

[0009] To address these issues, there is a need to develop polyimide materials with improved light transmittance and dielectric properties (Df) suitable for the application of high-speed transmission materials. The problem to be solved

[0010] Accordingly, the purpose is to provide a polyimide film having high light transmittance and low dielectric properties, and a method for manufacturing the same, in order to solve the above-mentioned problems.

[0011] Another objective of the present invention is to provide a method for manufacturing the polyimide film.

[0012] Another objective of the present invention is to provide a multilayer film comprising the polyimide film and a thermoplastic resin layer.

[0013] Another objective of the present invention is to provide a flexible metal foil laminate comprising the polyimide film and an electrically conductive metal foil.

[0014] Another objective of the present invention is to provide an electronic component comprising the flexible metal foil laminate. means of solving the problem

[0015] The present invention is capable of various modifications and may have various embodiments, and specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the invention to specific embodiments, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0016] The terms used in this application are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, terms such as "comprising" or "having" are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0017] Where in this specification, when a quantity, concentration, or other value or parameter is given as an enumeration of a range, a preferred range, a preferred upper limit, and a preferred lower limit, it should be understood that any pair of any upper range limit or preferred value and any lower range limit or preferred value specifically discloses 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 the range is disclosed separately.

[0018] Where a range of numerical values ​​is mentioned in this specification, unless otherwise stated, the range and the scope of the parent invention within that range are not intended to be limited to the specific value mentioned when defining the range.

[0019] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0020] In this specification, "anhydrous acid" is intended to include its precursor or derivative, which may not technically be an anhydrous acid but nevertheless will react with a diamine to form a polyamic acid, which can then be converted into a polyimide.

[0021] In this specification, "diamine" is intended to include its precursors or derivatives, which may not technically be diamines but nevertheless will react with dianhydrides to form polyamic acids, which can then be converted into polyimides.

[0022] Specific details for implementing the above invention are described below.

[0023] High transmittance, low dielectric polyimide film of the present invention

[0024] The present invention is obtained by imidizing a polyamic acid solution comprising a dianhydric acid component including two or more selected from the group consisting of benzophenone tetracarboxylic dianhydride (BTDA), biphenyl tetracarboxylic dianhydride (BPDA), and pyromellitic dianhydride (PMDA), and a diamine component including paraphenylenediamine (PPD).

[0025] Based on a total content of 100 mol% of the above diamine components, the content of the paraphenylene diamine is 70 mol% or more and 100 mol% or less, and

[0026] Based on a total content of 100 mol% of the above anhydrous acid component, the content of the above biphenyltetracarboxylic dianhydride is 50 mol% or more and less than 100 mol%, and

[0027] The dielectric loss rate (Df) is 0.003 or less, and

[0028] A polyimide film having a light transmittance of 15% or more and 50% or less at a wavelength of 550 nm is provided.

[0029] The above diamine component may additionally include m-tolidine. m-tolidine has a particularly hydrophobic methyl group, which contributes to the low moisture absorption characteristics of the polyimide film and the resulting low dielectric properties of the polyimide film.

[0030] Based on a total content of 100 mol% of the above diamine components, the content of m-tolidine may be 30 mol% or less, or may not be included at all. For example, the lower limit may be greater than 0 mol%, 1.0 mol% or more, 2.0 mol% or more, 3.0 mol% or more, 4.0 mol% or more, 5.0 mol% or more, 6.0 mol% or more, 7.0 mol% or more, 8.0 mol% or more, 9.0 mol% or more, 10.0 mol% or more, 11.0 mol% or more, 12.0 mol% or more, 13.0 mol% or more, 14.0 mol% or more, 15.0 mol% or more, 15.5 mol% or more, 16.0 mol% or more, 16.5 mol% or more, 17.0 mol% or more, 17.5 mol% or more, 18.0 mol% or more, 18.5 mol% or more, or 19.0 mol% or more. In addition, the upper limit may be 27.5 mol%, 25 mol% or less, 22.5 mol% or less, or 20 mol% or less.

[0031] Based on a total content of 100 mol% of the above diamine components, the content of the paraphenylenediamine may be 70 mol% or more and 100 mol%, and for example, the above diamine components may be composed of 100 mol% of paraphenylenediamine. In addition, the upper limit may be less than 100 mol%, 99.0 mol% or less, 98.0 mol% or less, 97.0 mol% or less, 96.0 mol% or less, 95.0 mol% or less, 94.0 mol% or less, 93.0 mol% or less, 92.0 mol% or less, 91.0 mol% or less, 90.0 mol% or less, 89.5 mol% or less, 89.0 mol% or less, 88.5 mol% or less, 88.0 mol% or less, 87.5 mol% or less, 87.0 mol% or less, 86.5 mol% or less, 86.0 mol% or less, 85.5 mol% or less, or 85.0 mol% or less. In addition, the lower limit may be 72.5 mol% or more, 75 mol% or more, 77.5 mol% or more, 80 mol% or more, 82.5 mol% or more, or 85 mol% or more.

[0032] Based on a total content of 100 mol% of the above diamine components, if the content of paraphenylenediamine is used at less than 70 mol% or the content of m-tolidine is used at more than 30 mol%, the light transmittance becomes excessively high and is undesirable.

[0033] PPD, which can be used as the diamine component of the above-mentioned polyimide film, is a rigid monomer; as the content of paraphenylenediamine (PPD) increases, the synthesized polyimide acquires a more linear structure, contributing to the improvement of mechanical properties such as the elastic modulus of the polyimide. Additionally, m-tolidine can suppress charge transfer complexes (CTCs) originating from the conjugated electron system located in the imide main chain, thereby inhibiting the formation of resonance structures and increasing transparency, which can contribute to improving the optical properties of the polyimide resin. Therefore, as the content of PPD increases, crystallinity increases and CTCs increase, improving dielectric properties, but transmittance decreases. Conversely, as the content of m-tolidine increases, CTCs decrease and transmittance increases; however, if the ratio exceeds a certain level, it impairs dielectric properties and is undesirable. In other words, the ratio of diamine content is particularly important for the polyimide film to simultaneously satisfy appropriate light transmittance and low dielectric properties.

[0034] Based on the total content of the above anhydrous acid component of 100 mol%, the content of the above biphenyltetracarboxylic dianhydride may be 50 mol% or more and less than 100 mol%. For example, the upper limit may be 99.0 mol% or less, 98.0 mol% or less, 97.0 mol% or less, 96.0 mol% or less, 95.0 mol% or less, 94.0 mol% or less, 93.0 mol% or less, 92.0 mol% or less, 91.0 mol% or less, 90.0 mol% or less, 89.0 mol% or less, 88.0 mol% or less, 87.0 mol% or less, 86.0 mol% or less, 85.0 mol% or less, 84.5 mol% or less, 84.0 mol% or less, 83.5 mol% or less, 83.0 mol% or less, 82.5 mol% or less, 82.0 mol% or less, 81.5 mol% or less, 81.0 mol% or less, 80.5 mol% or less, or 80.0 mol% or less, and the lower limit may be 50.1 mol% or more, It may be 50.2 mol% or more, 50.3 mol% or more, 50.4 mol% or more, or 50.5 mol% or more.

[0035] Based on the total content of the above anhydrous acid component of 100 mol%, the content of the above benzophenone tetracarboxylic dianhydride may be 5 mol% or more and 50 mol% or less. For example, the upper limit may be 49.0 mol% or less, 48.0 mol% or less, 47.0 mol% or less, 46.0 mol% or less, 45.0 mol% or less, 44.0 mol% or less, 43.0 mol% or less, 42.0 mol% or less, 41.0 mol% or less, 40.0 mol% or less, 39.0 mol% or less, 38.0 mol% or less, 37.5 mol% or less, 37.0 mol% or less, 36.5 mol% or less, 36.0 mol% or less, 35.5 mol% or less, or 35.0 mol% or less, and the lower limit may be 6.0 mol% or more, 7.0 mol% or more, 7.5 mol% or more, 8.0 mol% or more, 8.5 mol% or more, 9.0 mol% or more, 9.5 mol% or more, or 10.0 mol% or more.

[0036] Based on a total content of 100 mol% of the above anhydrous acid components, the content of the above pyromellitic dianhydride may be 50 mol% or less, or may not be included at all. For example, the upper limit may be 49.0 mol% or less, 48.0 mol% or less, 47.0 mol% or less, 46.0 mol% or less, 45.0 mol% or less, 44.0 mol% or less, 43.0 mol% or less, 42.0 mol% or less, 41.0 mol% or less, 40.0 mol% or less, 39.5 mol% or less, 39.0 mol% or less, 38.5 mol% or less, or 38.0 mol% or less, and the lower limit may be 1.0 mol% or more, 3.0 mol% or more, 5.0 mol% or more, 7.0 mol% or more, 10.0 mol% or more, 13.0 mol% or more, 15.0 mol% or more, 18.0 mol% or more, 20.0 mol% or more, 22.0 mol% or more, 25.0 mol% or more, 27.0 mol% or more, It may be 30.0 mol% or more, 32.0 mol% or more, or 34.0 mol% or more. The above pyromellitic dianhydride may also be used to control viscosity when manufacturing polyamic acid.

[0037] Based on the total content of the above dianhydric acid component of 100 mol%, if the content of the above biphenyltetracarboxylic dianhydride is used at less than 50 mol% or the content of the above benzophenonetetracarboxylic dianhydride is used at less than 5 mol% and more than 50 mol%, the dielectric loss rate increases, which may lead to a decrease in dielectric properties or a decrease in the mechanical properties of the polyimide film.

[0038] Meanwhile, the polyimide chain derived from BPDA, which can be used as the dianhydric acid component of the above polyimide film, has a structure named a charge transfer complex (CTC), that is, a regular linear structure in which electron donors and electron acceptors are located close to each other, and accordingly strengthens the intermolecular interaction of the polyimide.

[0039] In addition, BTDA, which has a carbonyl group, also contributes to the expression of CTCs, just like BPDA. Since this structure has the effect of preventing hydrogen bonding with moisture, it influences the reduction of moisture absorption, thereby maximizing the effect of reducing the hygroscopicity of polyimide films.

[0040] In addition, PMDA may be additionally included as the above-mentioned dianhydric acid component. PMDA is a dianhydric acid component with a relatively rigid structure, which is desirable in that it can impart appropriate elasticity to the polyimide film. The content ratio of the dianhydric acid is particularly important for the polyimide film to simultaneously satisfy appropriate elasticity and moisture absorption.

[0041] For example, as the content ratio of BPDA decreases, it becomes difficult to expect a low moisture absorption rate due to the CTC structure. Additionally, while BPDA and BTDA contain two benzene rings corresponding to the aromatic portion, PMDA contains one benzene ring corresponding to the aromatic portion. An increase in the PMDA content in the dianhydric acid component can be understood as an increase in the imide groups within the molecule based on the same molecular weight; this can be understood as a relative increase in the proportion of imide groups derived from PMDA in the polyimide polymer chain compared to the imide groups derived from BPDA and BTDA. In other words, an increase in PMDA content can be viewed as a relative increase in imide groups for the entire polyimide film, making it difficult to expect a low moisture absorption rate. Conversely, if the content ratio of PMDA decreases, the component with a relatively rigid structure decreases, which may cause the mechanical properties of the polyimide film to degrade below the desired level.

[0042] For this reason, if the content of BPDA and BTDA exceeds the above range, the mechanical properties of the polyimide film deteriorate, and heat resistance suitable for manufacturing a flexible metal foil laminate cannot be secured. Conversely, if the content of BPDA and BTDA falls below the above range or the content of PMDA exceeds the above range, it is undesirable because it is difficult to achieve a suitable level of dielectric constant, dielectric loss rate, and moisture absorption rate.

[0043] In one embodiment, the polyimide film is obtained by imidizing a dianhydric acid component comprising biphenyltetracarboxylic dianhydride (BPDA) and benzophenonetetracarboxylic dianhydride (BTDA) with a diamine component comprising paraphenylene diamine (PPD), wherein the content of paraphenylene diamine is 100 mol%, and based on the total content of the dianhydric acid component of 100 mol%, the content of biphenyltetracarboxylic dianhydride is 60 mol% or more and 75 mol% or less, and the content of benzophenonetetracarboxylic dianhydride is 25 mol% or more and 40 mol% or less. Preferably, the content of biphenyltetracarboxylic dianhydride may be 62 mol% or more and 70 mol% or less, or 64 mol% or more and 68 mol% or less, and preferably, the content of benzophenonetetracarboxylic dianhydride may be 30 mol% or more and 38 mol% or less, or 32 mol% or more and 36 mol% or less.

[0044] In addition, in one embodiment, the polyimide film is obtained by imidizing a dianhydric acid component comprising biphenyltetracarboxylic dianhydride (BPDA) and benzophenonetetracarboxylic dianhydride (BTDA) with a diamine component comprising paraphenylenediamine (PPD) and m-tolidine, and based on a total content of 100 mol% of the diamine component, the content of m-tolidine is 10 mol% or more and 30 mol% or less, and the content of paraphenylenediamine is 70 mol% or more and 90 mol% or less, and based on a total content of 100 mol% of the dianhydric acid component, the content of biphenyltetracarboxylic dianhydride is 65 mol% or more and 85 mol% or less, and the content of benzophenonetetracarboxylic dianhydride is 15 mol% or more and 35 mol% or less. Preferably, the content of m-tolydine may be 15 mol% or more and 25 mol% or less, or 18 mol% or more and 22 mol% or less, and preferably, the content of paraphenylenediamine may be 75 mol% or more and 85 mol% or less, or 78 mol% or more and 82 mol% or less. Also preferably, the content of biphenyltetracarboxylic dianhydride may be 70 mol% or more and 80 mol% or less, or 73 mol% or more and 77 mol% or less, and preferably, the content of benzophenonetetracarboxylic dianhydride may be 20 mol% or more and 30 mol% or less, or 23 mol% or more and 27 mol% or less.

[0045] In addition, in one embodiment, the polyimide film is obtained by imidizing a dianhydric acid component comprising biphenyltetracarboxylic dianhydride (BPDA), benzophenonetetracarboxylic dianhydride (BTDA), and pyromellitic dianhydride (PMDA) with a diamine component comprising paraphenylene diamine (PPD) and m-tolidine, wherein, based on a total content of 100 mol% of the diamine component, the content of m-tolidine is 15 mol% or more and 40 mol% or less, and the content of paraphenylene diamine is 60 mol% or more and 85 mol% or less, and based on a total content of 100 mol% of the dianhydric acid component, the content of biphenyltetracarboxylic dianhydride is 50 mol% or more and 65 mol% or less, and the content of benzophenonetetracarboxylic dianhydride is 10 mol% or more and 20 mol% or less. The content of pyromellitic dianhydride may be 25 mol% or more and 45 mol% or less. Preferably, the content of m-tolydine may be 20 mol% or more and 35 mol% or less, or 22 mol% or more and 32 mol% or less, and preferably, the content of paraphenylenediamine may be 65 mol% or more and 80 mol% or less, or 68 mol% or more and 78 mol% or less. Also preferably, the content of biphenyltetracarboxylic dianhydride may be 50 mol% or more and 60 mol% or less, or 50.5 mol% or more and 55 mol% or less, and preferably, the content of benzophenonetetracarboxylic dianhydride may be 11 mol% or more and 18 mol% or less, or 12 mol% or more and 15 mol% or less, and preferably, the content of pyromellitic dianhydride may be 30 mol% or more and 40 mol% or less, or 33 mol% or more and 38 mol% or less.

[0046] The above polyimide film may include a block copolymer composed of 1 to 3 blocks.

[0047] For example, the polyimide film may comprise a block copolymer comprising a first block obtained by imidizing a dianhydric acid component including biphenyltetracarboxylic dianhydride and benzophenonetetracarboxylic dianhydride with a diamine component including paraphenylene diamine.

[0048] In addition, the polyimide film may comprise a block copolymer comprising: a first block obtained by imidizing a dianhydric acid component including biphenyltetracarboxylic dianhydride and benzophenonetetracarboxylic dianhydride with a diamine component including paraphenylene diamine; and a second block obtained by imidizing a dianhydric acid component including biphenyltetracarboxylic dianhydride with a diamine component including m-tolidine.

[0049] In addition, the polyimide film may comprise a block copolymer comprising: a first block obtained by imidizing a dianhydric acid component including biphenyltetracarboxylic dianhydride and benzophenonetetracarboxylic dianhydride with a diamine component including paraphenylene diamine; and a second block obtained by imidizing a dianhydric acid component including biphenyltetracarboxylic dianhydride and pyromellitic dianhydride with a diamine component including m-tolidine.

[0050] In addition, the polyimide film may comprise a block copolymer comprising: a first block obtained by imidizing a dianhydric acid component including biphenyltetracarboxylic dianhydride and benzophenonetetracarboxylic dianhydride with a diamine component including paraphenylene diamine; and a second block obtained by imidizing a dianhydric acid component including pyromellitic dianhydride with a diamine component including m-tolidine.

[0051] The above polyimide film may have a thickness of 1 to 50 μm, preferably 5 to 40 μm, and more preferably 10 to 30 μm.

[0052] The "dielectric loss rate" of the present invention refers to the force dissipated by a dielectric (or insulator) when friction between molecules hinders molecular motion caused by an alternating electric field. The value of the dielectric loss rate is commonly used as an index indicating the ease of charge loss (dielectric loss); the higher the dielectric loss rate, the easier it is for charge to be lost, while conversely, the lower the dielectric loss rate, the more difficult it is for charge to be lost. In other words, since the dielectric loss rate is a measure of power loss, the lower the dielectric loss rate, the more the signal transmission delay caused by power loss is mitigated, allowing the communication speed to be maintained at a fast rate.

[0053] The polyimide film according to the present invention may have a dielectric loss rate (Df) of 0.003 or less, preferably less than 0.003, under a very high frequency of 10 GHz.

[0054] The "light transmittance" of the present invention can be used as an indicator to estimate and evaluate the degree of yellowness and transparency of the film. When the goal is to obtain a colorless, highly transparent polyimide film, a higher light transmittance is desirable, whereas for polyimide films requiring shielding or light blocking, a relatively lower light transmittance is desirable. Generally, conventional low-dielectric polyimide films absorb wavelengths of 380 nm to 500 nm (violet to blue light) in the visible light region, so they are yellowish-brown with almost no transparency, and are formed as films with high haze and very low light transmittance to achieve low dielectric properties. However, the polyimide film of the present invention can have high light transmittance while possessing low dielectric properties.

[0055] The polyimide film according to the present invention may have a light transmittance of 15% or more and 50% or less at a wavelength of 550 nm, for example, the upper limit may be less than 50%, 49.9% or less, 49.8% or less, 49.7% or less, 49.6% or less, 49.5% or less, 49.4% or less, 49.3% or less, 49.2% or less, 49.1% or less, 49.0% or less, 48.9% or less, 48.8% or less, 48.7% or less, or 48.6% or less. In addition, the lower limit may be 15.5% or more, 16.0% or more, 16.5% or more, 17.0% or more, 17.5% or more, 18.0% or more, 18.5% or more, 19.0% or more, 19.5% or more, 20.0% or more, 21.0% or more, 22.0% or more, 23.0% or more, 24.0% or more, 25.0% or more, 26.0% or more, 27.0% or more, 28.0% or more, 28.5% or more, or 29.0% or more. In this case, the light transmittance may be measured using a UV-Vis Spectrometer.

[0056] The present invention allows for the expression of dielectric properties while simultaneously exhibiting high transmittance compared to conventional low-dielectric polyimide by controlling the light transmittance of the polyimide film to the above range.

[0057] Even if a polyimide film is manufactured using a monomer identical or similar to that of the present invention, if the dielectric loss rate within the above range is not achieved, it is difficult to secure low dielectric properties, and at the same time, if the light transmittance within the above range is not achieved, the transmitted light through the film is excessively diffused, making it difficult to achieve appropriate transparency of the film.

[0058] In this regard, a polyimide film that satisfies both dielectric loss (Df) and light transmittance can be utilized as an insulating film for flexible metal foil laminates (FCCL). Furthermore, even if the manufactured flexible metal foil laminate (FCCL) is used as an electrical signal transmission circuit that transmits signals at high frequencies of 10 GHz or higher, its insulation stability can be ensured and signal transmission delay can be minimized. Additionally, as the FCCL market utilizing high-transmittance polyimide films expands, market dominance can be strengthened by possessing low dielectric properties while simultaneously maintaining transparency.

[0059] Method for manufacturing a high-transmittance, low-dielectric polyimide film of the present invention

[0060] The present invention comprises the steps of: (a) forming a polyamic acid solution on a support, the solution comprising a dianhydric acid component comprising two or more selected from the group consisting of benzophenone tetracarboxylic dianhydride (BTDA), biphenyltetracarboxylic dianhydride (BPDA), and pyromellitic dianhydride (PMDA), and a diamine component comprising paraphenylenediamine (PPD); and

[0061] (b) a step of producing a polyimide film by subjecting the above-described polyamic acid solution to an imidation reaction; comprising,

[0062] Based on a total content of 100 mol% of the above diamine components, the content of the paraphenylene diamine is 70 mol% or more and 100 mol% or less, and

[0063] Based on a total content of 100 mol% of the above anhydrous acid component, the content of the above biphenyltetracarboxylic dianhydride is 50 mol% or more and less than 100 mol%, and

[0064] The above polyimide film is,

[0065] The dielectric loss rate (Df) is 0.003 or less, and

[0066] A method for manufacturing a polyimide film having a light transmittance of 15% or more and 50% or less at a wavelength of 550 nm is provided.

[0067] In one embodiment, the polymerization method of the polyamic acid solution in step (a) can be defined as a random polymerization method. Since the length of the repeating unit within the polymer chain is relatively short in the random polymerization method, there may be limitations in exhibiting the excellent properties of each polyimide chain derived from the dianhydric 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.

[0068] The preparation of the polyamic acid solution of the present invention is, for example,

[0069] (1) A method of polymerizing by adding the entire amount of the diamine component into a solvent, and then adding the dianhydrous acid component in a manner substantially equimolar to the diamine component;

[0070] (2) A method of polymerizing by adding the entire amount of the dianhydric acid component into a solvent, and then adding a diamine component in a manner substantially equimolar to the dianhydric acid component;

[0071] (3) A method of polymerization in which some of the diamine components are added to a solvent, some of the dianhydric acid components are mixed with the reaction components in a ratio of 95 to 105 mol%, the remaining diamine components are added, and the remaining dianhydric acid components are added subsequently so that the diamine components and the dianhydric acid components are substantially equimolar;

[0072] (4) A method of polymerization in which a dianhydric acid component is placed in a solvent, some components of the diamine compound are mixed with the reaction components in a ratio of 95 to 105 mol%, another dianhydric acid component is added, and then the remaining diamine component is added so that the diamine component and the dianhydric acid component are substantially equimolar;

[0073] (5) A method of forming a first composition by reacting some diamine components and some dianhydric acid components in a solvent such that one of them is in excess, and forming a second composition by reacting some diamine components and some dianhydric acid components in another solvent such that one of them is in excess, and then mixing the first and second compositions and completing the polymerization, wherein when the diamine component is in excess when forming the first composition, the dianhydric acid component is in excess in the second composition, and when the dianhydric 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 so that the total diamine component and dianhydric acid component used in these reactions are substantially equimolar and polymerized, etc.

[0074] However, the above polymerization method is not limited to the examples above, and it goes without saying that any known method may be used to manufacture the polyamic acid.

[0075] In one specific example, a method for manufacturing a polyimide film according to the present invention is,

[0076] (a) A process of preparing a first polyamic acid by polymerizing a first dianhydric acid component and a first diamine component in an organic solvent;

[0077] (b) a process of preparing a second polyamic acid by polymerizing the second dianhydric acid component and the second diamine component in an organic solvent;

[0078] (c) a process of copolymerizing the first polyamic acid and the second polyamic acid in an organic solvent to produce a third polyamic acid; and

[0079] (d) a process including forming a film of the precursor composition containing the third polyamic acid on a support and then imidizing it, and

[0080] The first dianhydric acid component and the second dianhydric acid component each comprise one or more selected from the group consisting of benzophenone tetracarboxylic dianhydride (BTDA), biphenyl tetracarboxylic dianhydride (BPDA), and pyromellitic dianhydride (PMDA), and the first diamine component and the second diamine component may each comprise one or more selected from the group consisting of m-tolidine and paraphenylenediamine (PPD).

[0081] The content and composition of each component in the method for manufacturing a polyimide film are as described above in the polyimide film of the present invention.

[0082] In addition, the organic solvent for synthesizing polyamic acid is not particularly limited, and any organic solvent capable of dissolving polyamic acid can be used, but it is preferable that it be an amide-based solvent. Specifically, the organic solvent may be a polar solvent, and more specifically, an aprotic polar solvent. For example, it may be one or more selected from the group consisting of N,N-dimethylformamide (DMF), N,N-dimethylacetamide, N-methylpyrrolidone (NMP), gamma-butyrolactone (GBL), and Diglyme, but is not limited thereto, and may be used alone or in combination of two or more as needed.

[0083] In one embodiment, the solvent may particularly preferably be N,N-dimethylformamide or N,N-dimethylacetamide.

[0084] In the manufacturing method of the present invention, the polyimide film can be manufactured by the thermal imidation method and the chemical imidation method. The thermal imidation method is a method that induces an imidation reaction using a heat source, such as hot air or an infrared dryer, while excluding chemical catalysts. In addition, in the case of the chemical imidation method, the polyimide film can be manufactured using a dehydrating agent and an imidizing agent according to methods known in the art.

[0085] The polyimide film of the present invention manufactured according to the above manufacturing method may have a dielectric loss rate (Df) of 0.003 or less and a light transmittance of 15% or more and 50% or less at a wavelength of 550 nm.

[0086] Multilayer film comprising the polyimide film of the present invention, flexible metal laminate, and electronic component

[0087] The present invention provides a multilayer film comprising the aforementioned polyimide film and a thermoplastic resin layer, and a flexible metal foil laminate comprising the aforementioned polyimide film and an electrically conductive metal foil.

[0088] For example, a thermoplastic polyimide resin layer may be applied as the above thermoplastic resin layer.

[0089] Although the metal foil used is not particularly limited, when the flexible metal foil laminate of the present invention is used for electronic or electrical device applications, it may be a metal foil comprising, for example, copper or a copper alloy, stainless steel or an alloy thereof, nickel or a nickel alloy (including 42 alloys), or aluminum or an aluminum alloy.

[0090] In general flexible metal foil laminates, copper foils such as rolled copper foil and electrolytic copper foil are widely used, and can be preferably used in the present invention as well. In addition, an anti-corrosion layer, a heat-resistant layer, or an adhesive layer may be applied to the surface of these metal foils.

[0091] In the present invention, the thickness of the metal foil is not specifically limited, and it is sufficient as long as it is a thickness capable of performing a sufficient function according to its application.

[0092] 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 thermoplastic polyimide is added to one side of the polyimide film, and the metal foil is laminated while attached to the adhesive layer.

[0093] The present invention also provides an electronic component comprising the flexible metal foil laminate as an electrical signal transmission circuit. The electrical 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 more specifically at a high frequency of at least 10 GHz.

[0094] The above electronic component may be, for example, a communication circuit for a mobile terminal, a communication circuit for a computer, or a communication circuit for aerospace, but is not limited thereto. Effects of the invention

[0095] The polyimide film according to the present invention is composed of specific components and a specific composition ratio, thereby providing excellent effects such as low dielectric properties and high light transmittance. Furthermore, it can be usefully applied to electronic components such as thin circuit boards capable of high-speed communication and flexible metal foil laminates, where such characteristics are required. Specific details for implementing the invention

[0096] Examples are provided to aid in understanding the present invention. The following examples are provided merely to facilitate a better understanding of the invention, and the scope of the invention is not limited by these examples.

[0097] <Example 1> Preparation of Polyimide Film

[0098] In a 500 ml reactor equipped with a stirrer and a nitrogen injection / discharge pipe, nitrogen was injected while DMF was added, and the temperature of the reactor was set to 30°C or lower. Then, paraphenylenediamine (PPD) as a diamine component and biphenyltetracarboxylic dianhydride (BPDA) and benzophenonetetracarboxylic dianhydride (BTDA) as dianhydric acid components were added and it was confirmed that they were completely dissolved. At this time, the order of addition of the diamine component and dianhydric acid component was paraphenylenediamine (PPD), biphenyltetracarboxylic dianhydride (BPDA), and benzophenonetetracarboxylic dianhydride (BTDA).

[0099] Polyamic acid was prepared by raising the temperature to 40°C under a nitrogen atmosphere and continuing stirring for 120 minutes, and then having a viscosity of 200,000 cP at 23°C.

[0100] The polyamic acid prepared above was degassed by high-speed rotation of 1,500 rpm or more. Subsequently, the degassed polyimide precursor composition was applied to a glass substrate using a spin coater. Then, a gel film was prepared by drying for 30 minutes at a temperature of 120°C under a nitrogen atmosphere, 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 (thickness 15 μm).

[0101] <Examples 2 to 4 and Comparative Examples 1 to 3> Preparation of Polyimide Film

[0102] In a 500 ml reactor equipped with a stirrer and a nitrogen injection / discharge pipe, nitrogen was injected while DMF was added, and the temperature of the reactor was set to 30°C or lower. Then, paraphenylenediamine (PPD) was added as a diamine component, and one or more of biphenyltetracarboxylic dianhydride (BPDA) and benzophenonetetracarboxylic dianhydride (BTDA) were added as dianhydric acid components, and it was confirmed that they were completely dissolved. After heating under a nitrogen atmosphere at 40°C and continuing stirring for 120 minutes, a first polyamic acid was prepared that exhibited a viscosity of 200,000 cP at 23°C.

[0103] DMF was introduced into a 500 ml reactor equipped with a stirrer and a nitrogen injection / discharge pipe while injecting nitrogen, and the temperature of the reactor was set to 30°C. Then, at least one of m-toluidine and 4,4'-diaminodiphenyl ether (ODA) was introduced as a diamine component, and at least one of biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) was introduced as a dianhydric acid component, and it was confirmed that they were completely dissolved. After heating under a nitrogen atmosphere at 40°C and continuing stirring for 120 minutes, a second polyamic acid was prepared that exhibited a viscosity of 200,000 cP at 23°C.

[0104] Next, the first polyamic acid and the second polyamic acid were heated to 40°C under a nitrogen atmosphere and stirred for 120 minutes, and a third polyamic acid was prepared that had a final viscosity of 200,000 cP at 23°C and contained a diamine component and a dianhydric acid component as shown in Table 1 below.

[0105] The third polyamic acid prepared above was degassed by high-speed rotation of 1,500 rpm or more. Subsequently, the degassed polyimide precursor composition was applied to a glass substrate using a spin coater. Then, a gel film was prepared by drying for 30 minutes at a temperature of 120°C under a nitrogen atmosphere, 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 (thickness 15 μm).

[0107] A polyimide film was prepared by adjusting the composition ratio of the dianhydric acid component and the diamine component as shown in Table 1 below.

[0108] Imususan component (mol%) Diamine component (mol%) Polyamic acid polymerization method BPDA (Moll%) BTDA (Moll%) PMDA (mol%) PPD (Moll%) m-Tolidine (mol%) ODA (mol%) Example 1 66 34 - 100 - - Block polymerization Example 2 75 25 - 80 20 - Block polymerization Example 3 51 13 36 75 25 - Block polymerization Example 4 51 13 36 70 30 - Block polymerization Comparative Example 1 57 - 43 70 30 - Block polymerization Comparative Example 2 40 - 57 15 70 15 Block polymerization Comparative Example 3 33 32 35 66 34 - Block polymerization

[0109] <Experimental Example>

[0110] Experimental Example 1: Analysis of Dielectric Properties and Light Transmittance

[0111] (1) Dielectric loss rate (Df)

[0112] For the polyimide films prepared according to Examples 1 to 4 and Comparative Examples 1 to 3, the dielectric loss (Df) was measured using the SPDR (split post dielectric resonator) method. An ENA Vector Network Analyzer (E5063A, Keysight) model was used, and a QWED product was used for the SPDR. To measure dielectric properties, the polyimide films of Examples 1 to 4 and Comparative Examples 1 to 3 were each prepared in a size of 50 mm x 50 mm and dried at 130°C for 30 minutes to remove moisture. After aging for 24 hours in a constant temperature and humidity chamber set to a 23°C / 50%RH environment, the dielectric properties of the 24-hour aged film samples were measured using an ENA instrument. The results are shown in Table 2 below.

[0113] (2) Permittivity (Dk)

[0114] For the polyimide films prepared according to Examples 1 to 4 and Comparative Examples 1 to 3, the dielectric constant at 10 GHz was measured using a Keysight SPDR (split post dielectric resonator) meter. The results are shown in Table 2 below.

[0115] (3) Light transmittance

[0116] For the polyimide films prepared according to Examples 1 to 4 and Comparative Examples 1 to 3, a Color Spectrometer (Hunter Lab, Ultrascan Pro) was used to measure the light transmittance at 550 nm based on ASTM D1003 standards. The results are shown in Table 2 below.

[0117] Dielectric properties (@10GHz, 23℃ 50%RH, 24h) Light transmittance (%, @550nm) Permittivity (Dk) Dielectric loss rate (Df) Example 1 3.6 0.0025 19.0 Example 2 3.6 0.0028 48.4 Example 3 3.6 0.0028 42.9 Example 4 3.7 0.0029 29.9 Comparative Example 1 3.6 0.0025 2.8 Comparative Example 2 3.4 0.0038 79.0 Comparative Example 3 3.6 0.0040 58.3

[0118] Referring to Table 2, the polyimide films according to Examples 1 to 4 of the present invention exhibit a significantly low dielectric loss rate (Df) of less than 0.003, and at the same time exhibit a high light transmittance of 15% or more and less than 50%.

[0119] Meanwhile, Comparative Example 1 showed a low dielectric loss rate (Df) but had a problem with significantly low light transmittance, and Comparative Examples 2 and 3 had a dielectric loss rate (Df) exceeding 0.003 and it was confirmed that the light transmittance also fell outside the range intended by the present invention.

[0120] Therefore, it was found that the low dielectric properties and light transmittance of the polyimide film according to the present invention can be achieved by specific components and composition ratios, and that it is suitable for use in electronic components where signal transmission is performed at gigabit high frequencies.

[0122] The specification omits detailed descriptions of matters that can be sufficiently recognized and inferred by those skilled in the art of the present invention, and various modifications are possible within the scope of not altering the technical concept or essential configurations of the present invention, in addition to the specific examples described in this specification. Accordingly, the present invention may be implemented in a manner different from that specifically described and exemplified in this specification, and this is a matter that can be understood by those skilled in the art.

Claims

Claim 1 A polyamic acid solution is obtained by imidation reaction of a dianhydric acid component comprising two or more selected from the group consisting of benzophenone tetracarboxylic dianhydride (BTDA), biphenyl tetracarboxylic dianhydride (BPDA), and pyromellitic dianhydride (PMDA), and a diamine component comprising paraphenylene diamine (PPD); wherein, based on a total content of 100 mol% of the diamine component, the content of paraphenylene diamine is 70 mol% or more and 100 mol% or less; based on a total content of 100 mol% of the dianhydric acid component, the content of biphenyl tetracarboxylic dianhydride is 50 mol% or more and less than 100 mol%; the content of benzophenone tetracarboxylic dianhydride is 5 mol% or more and 50 mol% or less; and the content of pyromellitic dianhydride is 0 mol% or more and 40 mol%. A polyimide film having a dielectric loss (Df) of 0.003 or less and a light transmittance of 15% or more and 50% or less at a wavelength of 550 nm. Claim 2 A polyimide film according to claim 1, wherein the diamine component further comprises m-tolidine. Claim 3 A polyimide film according to claim 2, wherein the content of m-tolidine is 0 mole or more and 30 mole or less, based on a total content of 100 mole% of the diamine component. Claim 4 delete Claim 5 delete Claim 6 The polyimide film according to claim 1, wherein the polyimide film is obtained by imidizing a dianhydric acid component comprising biphenyltetracarboxylic dianhydride (BPDA) and benzophenonetetracarboxylic dianhydride (BTDA) and a diamine component comprising paraphenylene diamine (PPD), wherein the content of paraphenylene diamine is 100 mol%, and based on the total content of the dianhydric acid component of 100 mol%, the content of biphenyltetracarboxylic dianhydride is 60 mol% or more and 75 mol% or less, and the content of benzophenonetetracarboxylic dianhydride is 25 mol% or more and 40 mol% or less. Claim 7 The polyimide film according to claim 1, wherein the polyimide film is obtained by an imidation reaction of a dianhydric acid component comprising biphenyltetracarboxylic dianhydride (BPDA) and benzophenonetetracarboxylic dianhydride (BTDA) and a diamine component comprising paraphenylene diamine (PPD) and m-tolidine, wherein, based on a total content of 100 mol% of the diamine component, the content of m-tolidine is 10 mol% or more and 30 mol% or less, and the content of paraphenylene diamine is 70 mol% or more and 90 mol% or less, and based on a total content of 100 mol% of the dianhydric acid component, the content of biphenyltetracarboxylic dianhydride is 65 mol% or more and 85 mol% or less, and the content of benzophenonetetracarboxylic dianhydride is 15 mol% or more and 35 mol% or less. Claim 8 In claim 1, the polyimide film is obtained by imidizing a dianhydric acid component comprising biphenyltetracarboxylic dianhydride (BPDA), benzophenonetetracarboxylic dianhydride (BTDA), and pyromellitic dianhydride (PMDA) with a diamine component comprising paraphenylene diamine (PPD) and m-tolidine, wherein, based on a total content of 100 mol% of the diamine component, the content of m-tolidine is 15 mol% or more and 40 mol% or less, and the content of paraphenylene diamine is 60 mol% or more and 85 mol% or less, and based on a total content of 100 mol% of the dianhydric acid component, the content of biphenyltetracarboxylic dianhydride is 50 mol% or more and 65 mol% or less, and the content of benzophenonetetracarboxylic dianhydride is 10 mol% or more and 20 mol% or less. Polyimide film having a pyromellitic dianhydride content of 25 mol% or more and 45 mol% or less. Claim 9 (a) a step of forming a polyamic acid solution on a support comprising a dianhydric acid component including two or more selected from the group consisting of benzophenone tetracarboxylic dianhydride (BTDA), biphenyltetracarboxylic dianhydride (BPDA), and pyromellitic dianhydride (PMDA), and a diamine component including paraphenylene diamine (PPD); and (b) a step of producing a polyimide film by imidizing the formed polyamic acid solution; A method for manufacturing a polyimide film comprising, based on a total content of 100 mol% of the diamine component, the content of paraphenylene diamine is 70 mol% or more and 100 mol% or less, based on a total content of 100 mol% of the dianhydric acid component, the content of biphenyltetracarboxylic dianhydride is 50 mol% or more and less than 100 mol%, the content of benzophenonetetracarboxylic dianhydride is 5 mol% or more and 50 mol% or less, and the content of pyromellitic dianhydride is 0 mol% or more and 40 mol% or less, wherein the polyimide film has a dielectric loss rate (Df) of 0.003 or less and a light transmittance of 15% or more and 50% or less at a wavelength of 550 nm. Claim 10 A multilayer film comprising a polyimide film and a thermoplastic resin layer according to claim 1. Claim 11 A flexible metal foil laminate comprising a polyimide film according to claim 1 and an electrically conductive metal foil. Claim 12 Electronic components comprising a flexible metal foil laminate according to paragraph 11.

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