Blended polyimide film and method for producing same

Abstract

The present invention provides a polyimide film that has a dielectric constant (Dk) of 3.5 or less and a dielectric loss factor (Df) of 0.003 or less, measured at 10 GHz, after being left in an environment of 85°C and 85% RH for 24 hours.

Description

[Technical Field]

[0001] The present invention relates to a blended polyimide film having excellent low dielectric properties and mechanical strength in high temperature and high humidity environments, and a method for producing the same. [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. 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 fields of electricity, electronics, and optics. Recently, as electronic products have become lighter and smaller, flexible thin circuit boards with high integration density have been actively developed. Such thin circuit boards tend to be constructed in such a way that a circuit containing metal foil is formed on a polyimide film that has excellent heat resistance, low temperature resistance, and insulating properties, and is also flexible.

[0003] Flexible metal clad laminates are mainly used for such thin circuit boards, such as flexible copper clad laminates (FCCL), which use thin copper foil as the metal foil. Polyimides are also sometimes used as protective films and insulating films for thin circuit boards. Meanwhile, as electronic devices now have a variety of built-in functions, they are required to have high calculation speeds and communication speeds. To meet this demand, thin circuit boards capable of high-speed communication at high frequencies have been developed. To realize high-frequency, high-speed communications, 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.

[0004] However, in the case of ordinary polyimides, the dielectric properties are not at a level excellent enough to maintain sufficient insulation in high frequency communications. In addition, the lower the dielectric properties of the insulator, the less stray capacitance and noise that are undesirable in thin circuit boards can be generated, and the greater the chance of communication delays. Therefore, the low dielectric properties of polyimide are recognized as the most important factor in the performance of thin circuit boards. In particular, in the case of high frequency communication, dielectric dissipation inevitably occurs due to polyimide. The dissipation factor (Df) refers to the degree of electrical energy wastage in a thin circuit board and is closely related to the signal transmission delay that determines communication speed. Maintaining the dielectric loss factor of polyimide as low as possible is also recognized as an important factor in the performance of thin circuit boards. In addition, the more moisture a polyimide film contains, the larger its dielectric constant becomes, increasing its dielectric loss factor. While polyimide film is suitable as a material for thin circuit boards due to its excellent inherent properties, its polar imide group can make it relatively vulnerable to moisture, which can lead to a deterioration in its insulating properties. Therefore, even in high temperature or humid environments, the mechanical properties specific to polyimide are maintained at a certain level. Therefore, there is a need to develop polyimide films that can maintain low dielectric properties while maintaining high thermal conductivity. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Korean Patent Publication No. 10-2021-0055230 Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, in order to solve the above problems, an object of the present invention is to provide a blended polyimide film that has excellent low dielectric properties and improved mechanical strength even in high temperature and humid environments, and a method for producing the same. [Means for solving the problem]

[0007] To achieve the above object, one embodiment of the present invention provides a polyimide film having a dielectric constant (Dk) of 3.5 or less and a dielectric loss factor (Df) of 0.003 or less, measured at 10 GHz after being left in an environment of 85°C and 85% RH for 24 hours. Another embodiment of the present invention provides a multilayer film comprising the polyimide film of the present application. Yet another embodiment of the present invention provides a flexible metal foil laminate comprising the polyimide film of the present application and an electrically conductive metal foil. Yet another embodiment of the present invention provides an electronic component including the flexible metal foil laminate of the present application. [Effects of the Invention]

[0008] As described above, the polyimide film of the present invention, which is prepared by imidizing a polyamic acid solution composed of specific components and specific composition ratios, maintains excellent low dielectric properties and mechanical strength even under high temperature and humid conditions, and is useful in various fields where such properties are required, particularly electronic components such as flexible metal foil laminates. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in more detail. Prior to this, the terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, in accordance with the principle that an inventor can appropriately define the concept of a term in order to best explain his or her invention. 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 represent the technical idea of ​​the present invention, and that there may be various equivalents and modifications that can replace them at the time of this application.

[0010] In this specification, the singular expression includes the plural expression unless the context clearly dictates otherwise. In this specification, the terms "comprises," "includes," "comprises," "has," and the like are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, and should be understood as not precluding the presence or additional possibility of one or more other features, numbers, steps, components, or combinations thereof. When an amount, concentration, or other value or parameter is given herein by listing a range, preferred range, or upper preferred value and a lower preferred value, it should be understood that this specifically discloses all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, whether or not a range is otherwise disclosed. Where a range of numerical values ​​is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all constants 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.

[0011] As used herein, "dianhydride acid" is intended to include precursors or derivatives thereof, which may not technically be dianhydrides, but which nevertheless react with diamines to form polyamic acids, which may also be converted to polyimides. As used herein, "diamine" is intended to include precursors or derivatives thereof, which may not technically be diamines, but which nonetheless will react with dianhydrides to form polyamic acids, which may also be converted to polyimides. In this specification, when numerical ranges are indicated as "a to b" or "a to b," "to" and "to" are defined as ≧a and ≦b.

[0012] The polyimide film according to the present invention may have a dielectric constant (Dk) of 3.5 or less and a dielectric loss factor (Df) of 0.003 or less, measured at 10 GHz after being left in an environment of 85°C and 85% RH for 24 hours. For example, after being left in an environment of 85°C and 85% RH for 24 hours, the dielectric constant measured may be 3.13 or more and 3.49 or less, and the dielectric loss factor may be 0.0026 or more and 0.0029 or less. That is, the polyimide film of the present invention can maintain excellent low dielectric properties even in high temperature and humid environments.

[0013] In one embodiment, the polyimide film is a polyimide film made of 1,4-phenylenebis(trimellitic acid monoester) dianhydride (p-phenylenebis(trimellitate The polyamic acid solution may be obtained by imidizing a polyamic acid solution containing a dianhydride acid component including 3,3,4,4-biphenyltetracarboxylic dianhydride (3,3,4,4-biphenyltetracarboxylic dianhydride (BPDA) and m-tolidine. The polyimide chain derived from 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, which can strengthen intermolecular interactions.

[0014] Such a structure has the effect of preventing hydrogen bonding with water, which has an effect of reducing the moisture absorption rate, and can maximize the effect of reducing the moisture absorption of the polyimide film. The dianhydride content is particularly important for polyimide films to simultaneously satisfy appropriate elasticity and moisture absorption. For example, as the content of biphenyltetracarboxylic dianhydride (BPDA) decreases, it becomes more difficult to expect low moisture absorption due to the CTC structure. In addition, the 1,4-phenylenebis(trimellitic acid monoester) dianhydride contains ester bonds, which can contribute to improving the low dielectric properties of polyimide films.

[0015] On the other hand, m-tolidine has a methyl group that is particularly hydrophobic, and therefore can contribute to the low moisture absorption properties of the polyimide film. The moisture absorption rate indicates the amount of water contained in a material, and it is generally known that when the moisture absorption rate is high, the dielectric constant and dielectric loss factor increase. When water vapor or the like is absorbed into a polyimide film, the water exists in a liquid state, and in such a case, the dielectric constant and dielectric loss factor of the polyimide film can increase dramatically.

[0016] That is, even a small amount of moisture absorption can cause a sudden change in the dielectric constant and dielectric loss factor of a polyimide film. Therefore, by improving the low moisture absorption property of the polyimide film, the low dielectric property of the polyimide film can be improved, and therefore the dianhydride acid component and diamine component of the polyimide film of the present application can contribute to the low dielectric and low moisture absorption properties of the polyimide film.

[0017] In one embodiment, in the polyimide film according to the present invention, the ratio of the mol% of the biphenyltetracarboxylic dianhydride (BPDA) to the mol% of the 1,4-phenylenebis(trimellitic acid monoester) dianhydride (TAHQ) (mol% of the biphenyltetracarboxylic dianhydride (BPDA) / mol% of the 1,4-phenylenebis(trimellitic acid monoester) dianhydride (TAHQ)) may be 1.5 or more and 2.9 or less, based on 100 mol% of the total content of the dianhydride acid components. If the content of biphenyltetracarboxylic dianhydride (BPDA) is too high or the content of 1,4-phenylenebis(trimellitic acid monoester) dianhydride (TAHQ) is too low, exceeding the above molar ratio, the low dielectric properties of the polyimide film may be reduced. Conversely, if the content of biphenyltetracarboxylic dianhydride (BPDA) is too low or the content of 1,4-phenylenebis(trimellitic acid monoester) dianhydride (TAHQ) is too high and falls below the above molar ratio, the mechanical strength of the polyimide film may be reduced.

[0018] In one embodiment, the polyimide film according to the present invention may contain 10 wt % or more and 40 wt % or less of a particulate polymer, based on 100 wt % of the total weight of the polyimide film. The particulate polymer may be a fluoropolymer or a liquid crystal polymer (LCP). The fluorine-based polymer may be at least one selected from the group consisting of polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-chlorotrifluoroethylene copolymer (TFE / CTFE), and ethylene-chlorotrifluoroethylene copolymer (ECTFE), but is not limited thereto.

[0019] Preferably, the fluorine-based polymer may be polytetrafluoroethylene (PTFE) or tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA). If the content of the particulate polymer exceeds the range of the present application, the dielectric properties may be improved, but the mechanical properties of the polyimide film may be reduced. If the content of the particulate polymer is below the range of the present application, the low dielectric properties of the polyimide film may be reduced. The particulate polymer contained in the polyimide film of the present invention may have an average particle size of 15 μm or less and a glass transition temperature or melting point of 100° C. or more. In one embodiment, the polyimide film according to the present application may have a moisture absorption rate of 0.4% or less and a tensile strength of 150 MPa or more.

[0020] For example, the moisture absorption rate may be 0.28% or more and 0.38% or less, and the tensile strength may be 158 MPa or more and 199 MPa or less. On the other hand, the polyimide film according to the present application may have a dielectric constant (Dk) of 3.5 or less and a dielectric loss factor (Df) of 0.002 or less, measured at 10 GHz after being left in a 23°C environment for 24 hours; a dielectric constant (Dk) of 3.5 or less and a dielectric loss factor (Df) of 0.0029 or less, measured at 28 GHz after being left in a 23°C environment for 24 hours; and a dielectric constant (Dk) of 3.5 or less and a dielectric loss factor (Df) of 0.0029 or less, measured at 40 GHz after being left in a 23°C environment for 24 hours. For example, after being left in a 23°C / 50% RH environment for 24 hours, the dielectric constant (Dk) measured at 10 GHz may be 3.13 or more and 3.49 or less, and the dielectric loss factor (Df) may be 0.0014 or more and 0.00178 or less.

[0021] Furthermore, after being left in a 23°C environment for 24 hours, the dielectric constant (Dk) measured at 28 GHz may be 3.13 or more and 3.49 or less, and the dielectric loss factor (Df) may be 0.00254 or more and 0.00285 or less, or after being left in a 23°C environment for 24 hours, the dielectric constant (Dk) measured at 40 GHz may be 3.13 or more and 3.49 or less, and the dielectric loss factor (Df) may be 0.00257 or more and 0.00288 or less. That is, the polyimide film of the present invention can maintain its low dielectric constant characteristics despite changes in ambient temperature and humidity, since there is no difference between the dielectric constant measured at 10 GHz after being left in a 23°C / 50% RH environment for 24 hours and the dielectric constant measured at 10 GHz after being left in an 85°C / 85% RH environment for 24 hours. Such low dielectric constant characteristics of the polyimide film of the present invention were maintained even when the frequency was changed during measurement.

[0022] Furthermore, the polyimide film of the present invention exhibits a dielectric loss factor measured at 10 GHz after being left in an 85°C, 85% RH environment for 24 hours, which increases compared to the dielectric loss factor measured at 10 GHz after being left in a 23°C / 50% RH environment for 24 hours. However, the film still exhibits low dielectric loss characteristics of 0.003 or less. For example, the dielectric loss factor of the polyimide film of the present application measured at 10 GHz after being left in an environment of 85°C and 85% RH for 24 hours may be higher by 90% or less (e.g., 60% or more and 86% or less) than the dielectric loss factor measured at 10 GHz after being left in an environment of 23°C and 50% RH for 24 hours, but still exhibits low dielectric loss characteristics of 0.003 or less.

[0023] On the other hand, the polyimide film of the present invention exhibits a dielectric loss factor of 0.003 or less after being left in a 23°C / 50% RH environment for 24 hours and measured at 28 GHz and 40 GHz, which increases compared to the dielectric loss factor measured at 10 GHz after being left in a 23°C / 50% RH environment for 24 hours. In this regard, the polyimide film of the present application, which satisfies the requirements for moisture absorption rate, tensile strength, dielectric constant, and dielectric loss factor, can be used as an insulating film for flexible thin metal laminates. Furthermore, even when the manufactured flexible metal foil laminates are used in electrical signal transmission circuits that transmit signals at high frequencies of 10 GHz or more, the insulation stability of the produced flexible metal foil laminates can be ensured and signal transmission delay can be minimized. In one embodiment, the polyimide film of the present application may be a random or block copolymer.

[0024] On the other hand, polyamic acid for producing the polyimide film of the present invention can be produced, 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 so that the amount is substantially equimolar to the diamine component, and polymerization is carried out. (2) The entire amount of the dianhydride acid component is placed in a solvent, and then the diamine component is mixed with the dianhydride acid component. Polymerization method in which the components are added so that they are qualitatively equimolar (3) A method in which a part of the diamine component is placed in a solvent, and then a part of the dianhydride component is mixed with the reaction components in a ratio of about 95 to 105 mol %, and then the remaining diamine component is added, followed by the remaining dianhydride component, so that the diamine component and the dianhydride component are substantially equimolar, and polymerization is carried out. (4) A method in which a dianhydride acid component is placed in a solvent, and then a portion of the diamine compound is mixed in a ratio of 95 to 105 mol % relative to the reaction components, and then another dianhydride acid component is added, followed by the remaining diamine component, so that the diamine component and the dianhydride acid component are substantially equimolar, and polymerization is carried out. (5) A method of forming a first composition by reacting a portion of the diamine component and a portion of the dianhydride acid component in a solvent so that one of them is in excess, and then forming a second composition by reacting a portion of the diamine component and a portion of the dianhydride acid component in another solvent so that one of them is in excess, and then mixing the first and second compositions to complete the polymerization. In this case, if the diamine component is in excess when forming the first composition, 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 then mixing the first and second compositions to polymerize so that the total diamine component and dianhydride acid component used in these reactions are substantially equimolar.

[0025] However, the polymerization method is not limited to the above example, and any known method may be used to produce the first and second polyamic acids. 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 biphenyltetracarboxylic dianhydride (BPDA) and 1,4-phenylenebis(trimellitic acid monoester) dianhydride (TAHQ) and a diamine component including m-tolidine (mTB) to prepare a polyamic acid solution, and imidizing the polyamic acid solution. In particular, the molar percentage of the biphenyltetracarboxylic dianhydride (BPDA) relative to the molar percentage of the 1,4-phenylenebis(trimellitic acid monoester) dianhydride (TAHQ) (molar percentage of the biphenyltetracarboxylic dianhydride (BPDA) / molar percentage of the 1,4-phenylenebis(trimellitic acid monoester) dianhydride (TAHQ)) may be 1.5 or more and 2.9 or less, based on 100 molar percentage of the total content of the dianhydride acid components.

[0026] The dianhydride acid component and the diamine component are reacted in a predetermined order to copolymerize them, thereby producing a polyimide film. The method for producing polyimide may further include adding 10% by weight to 40% by weight of a particulate polymer to the polyamic acid solution and stirring the mixture. The particulate polymer may be a fluorine-based polymer or a liquid crystal polymer (LCP). In the present invention, the polymerization method of the polyamic acid may be a random polymerization method, and a polyimide film prepared from the polyamic acid of the present invention prepared by the above process can be preferably used from the viewpoint of maximizing the effects of increasing tensile strength and reducing moisture absorption rate, dielectric constant, and dielectric loss factor.

[0027] However, since the length of the repeating units in the polymer chain is relatively short in this polymerization method, there may be a limit to the excellent properties of the polyimide chain derived from the dianhydride acid component. Therefore, the polymerization method for polyamic acid particularly preferably used in the present invention may be a block polymerization method. On the other hand, the solvent for synthesizing the polyamic acid is not particularly limited, and any solvent that can dissolve the polyamic acid may be used, but an amide-based solvent is preferred. The polyimide film manufactured by the method for manufacturing a polyimide film has a moisture absorption rate of 0.4% or less, a tensile strength of 150 MPa or more, and is After being left for 24 hours, the measured dielectric constant (Dk) may be 3.5 or less and the dielectric loss factor (Df) may be 0.002 or less.

[0028] In particular, the polyimide film produced by the method for producing a polyimide film may have a moisture absorption rate of 0.4% or less, a tensile strength of 150 MPa or more, and a dielectric constant (Dk) of 3.5 or less and a dielectric loss factor (Df) of 0.003 or less, measured after being left in an environment of 85°C and 85% RH for 24 hours. 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 an electrically conductive metal foil. The thermoplastic resin layer may be, for example, a thermoplastic polyimide resin layer.

[0029] There are no particular limitations on the metal foil used, but when the flexible metal foil laminate of the present invention is used for electronic or electrical equipment applications, the metal foil may be, for example, copper or copper alloy, stainless steel or its alloy, nickel or nickel alloy (including 42 alloy), aluminum or aluminum alloy. In general, copper foils such as rolled copper foils and electrolytic copper foils are often used in flexible metal foil laminates, and these can also be preferably used in the present invention. The surface of these metal foils may be coated with an anti-rust layer, a heat-resistant layer, or an adhesive layer. In the present invention, there is no particular limitation on the thickness of the metal foil, and it may be of any thickness that can provide sufficient functionality depending on the application.

[0030] 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 in which 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 adhering to the adhesive layer. Meanwhile, according to one embodiment of the present invention, an electronic component may include the flexible metal foil laminate as an electrical signal transmission circuit, and the electrical signal transmission circuit may be an electronic component that transmits signals at a high frequency of at least 2 GHz, particularly at least 5 GHz, and more particularly at least 10 GHz. By controlling the high moisture absorption of the polyimide film, which affects the electrical signal transmission loss, it is possible to optimize the transmission loss at frequencies above 10 GHz. 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 industry. [Example]

[0031] The functions and effects of the invention will be described in more detail below through specific examples of the invention, but these examples are presented only as examples of the invention and do not determine the scope of the invention. Manufacturing example (manufacturing polyimide film) DMF was added to a 500 ml reactor equipped with a stirrer and nitrogen inlet / outlet tubes while injecting nitrogen. The reactor temperature was set to 30°C, and then 1,4-phenylenebis(trimellitic acid monoester) dianhydride (TAHQ) and biphenyltetracarboxylic dianhydride (BPDA) were added as dianhydride acid components in a molar ratio adjusted to 1:1.5-2.9, and m-tolidine was added as diamine component, and complete dissolution was confirmed. Thereafter, the temperature of the reactor was raised to 40° C. under a nitrogen atmosphere, and stirring was continued for 120 minutes while heating to produce polyamic acid. The particulate polymer is added to the polyamic acid thus produced while adjusting the content thereof, and the mixture is stirred. The mixture was stirred and dispersed, and the catalyst and dehydrating agent were added in controlled amounts to prepare a polyimide precursor composition, which was then coated onto a glass substrate using a spin coater. The degassed polyimide precursor composition was then dried at 120°C for 30 minutes under a nitrogen atmosphere to produce a gel film. The gel film was then 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.

[0032] Examples 1 to 10 and Comparative Examples 1 to 4 Polyimide films of Examples 1 to 10 and Comparative Examples 1 to 4 were prepared according to the above-described Preparation Example, but by adjusting the content of particulate polymer as shown in Table 1 below. [Table 1]

[0033] The tensile strength and moisture absorption rate of the polyimide films prepared in Examples 1 to 10 and Comparative Examples 1 to 4 were measured and are shown in Table 2 below. In addition, the dielectric constant (Dk) and dielectric loss factor (Df) of each of the polyimide films prepared in Examples 1 to 10 and Comparative Examples 1 to 4 were measured and are shown in Table 3 below. [Table 2] [Table 3]

[0034] The tensile strength, moisture absorption rate, dielectric constant (Dk) and dielectric loss factor (Df) of the produced polyimide film were measured as follows. (1) Measurement of tensile strength The tensile strength of the samples was measured according to the method set forth in ASTM D 1708 using a universal material testing machine (model name Instron 5564, manufactured by Instron Corporation). (2) Measurement of moisture absorption rate Two polyimide film test pieces (4 cm wide × 25 cm long) were prepared and dried at 80°C for 1 hour. After drying, they were immediately placed in a constant temperature and humidity chamber at 23°C and %RH and left for at least 24 hours. The weight change before and after the drying was calculated using the following formula. Moisture absorption rate (wt%) = [(weight after moisture absorption - weight after drying) / weight after drying] x 100 (3) Measurement of dielectric constant The dielectric constant (Dk) was measured using a Keysight SPDR measuring instrument at 10 GHz, 28 GHz and 40 GHz after leaving the polyimide film in an environment of 23°C / 50% RH for 24 hours. Furthermore, the polyimide film was left in an environment of 85°C and 85% RH for 24 hours, and then the dielectric constant at 10 GHz was measured. (4) Measurement of dielectric loss factor The dielectric loss factor (Df) was measured at 10 GHz, 28 GHz, and 40 GHz using a Keysight ENA (Vector Network Analyzer) by the cavity resonance method (SPDR) after leaving the polyimide film in a 23°C environment for 24 hours.

[0035] Furthermore, the polyimide film was left in an environment of 85°C and 85% RH for 24 hours, and then the dielectric loss factor at 10 GHz was measured. As shown in Table 2, the polyimide films prepared in Examples 1 to 10 of the present invention had a tensile strength of 150 MPa or more and a moisture absorption rate of 0.4% or less. As shown in Table 3, the polyimide films of Examples 1 to 10 of the present invention not only exhibited a dielectric constant (Dk) of 3.5 or less and a dielectric loss factor (Df) of 0.0020 or less measured at 10 GHz after being left in a 23°C environment for 24 hours, but also exhibited a dielectric constant (Dk) of 3.5 or less and a dielectric loss factor (Df) of 0.0030 or less measured at 10 GHz after being left in a high temperature (85°C) and high humidity (85%) environment for 24 hours, demonstrating excellent low dielectric properties.

[0036] Furthermore, the polyimide films of Examples 1 to 10 of the present invention were able to achieve a dielectric constant (Dk) of 3.5 or less and a dielectric loss factor (Df) of 0.0029 or less when measured at 28 GHz after being left in a 23°C environment for 24 hours, and also achieved a dielectric constant (Dk) of 3.5 or less and a dielectric loss factor (Df) of 0.0029 or less when measured at 40 GHz after being left in a 23°C environment for 24 hours. In contrast, even though the dielectric constant (Dk) and dielectric loss factor (Df) of the polyimide films of Comparative Examples 1 to 3 were similar to those of the polyimide films of Examples 1 to 10, the tensile strength was less than 150 MPa.

[0037] That is, the polyimide films of Comparative Examples 1 to 3 were measured to have lower tensile strength values ​​because an excessive amount of particulate polymer was used compared to the polyimide films of Examples 1 to 10. This confirmed that when the content of particulate polymer exceeds the range of the present invention, the mechanical properties of the polyimide film are reduced. On the other hand, when no particulate polymer was used as in Comparative Example 4, the moisture absorption rate increased, and the dielectric constant and dielectric loss factor increased, resulting in a decrease in low dielectric properties.

[0038] These measurement results suggest that in order to adjust the dielectric properties and mechanical properties to appropriate levels, it is preferable to include the particulate polymer in the content range selected in the present invention. Based on this, it was predicted that the polyimide films of Examples 1 to 10 would have excellent low dielectric constant properties and mechanical properties, and would be suitable for practical application in electronic components. The present invention has been described above with reference to the embodiments thereof, but a person having ordinary knowledge in the field to which the present invention pertains can make various applications and modifications within the scope of the present invention based on the above content. [Industrial Applicability]

[0039] The present invention relates to a polyimide film produced by imidizing a polyamic acid solution composed of specific components and specific composition ratios, which has excellent low dielectric properties and mechanical properties even under high temperature and humid environments. The resulting laminated sheet can be used in a variety of fields where such properties are required, particularly in electronic components such as flexible metal foil laminates.

Claims

1. After being left in an environment of 85°C and 85% RH for 24 hours, the dielectric constant (Dk) measured at 10 GHz is 3.5 or less and the dielectric loss factor (Df) is 0.003 or less. Polyimide film.

2. The polyimide film is obtained by imidizing a polyamic acid solution containing a dianhydride acid component including 1,4-phenylenebis(trimellitic acid monoester) dianhydride (TAHQ) and biphenyltetracarboxylic dianhydride (BPDA) and a diamine component including m-tolidine. The polyimide film according to claim 1 .

3. a ratio of the mol% of the biphenyltetracarboxylic dianhydride (BPDA) to the mol% of the 1,4-phenylenebis(trimellitic acid monoester)dianhydride (TAHQ) (mol% of the biphenyltetracarboxylic dianhydride (BPDA) / mol% of 1,4-phenylenebis(trimellitic acid monoester)dianhydride (TAHQ)) based on 100 mol% of the total content of the dianhydride acid components is 1.5 or more and 2.9 or less; The polyimide film according to claim 2 .

4. The particulate polymer is contained in an amount of 10% by weight or more and 40% by weight or less, based on 100% by weight of the total weight of the polyimide film. The polyimide film according to claim 2 .

5. The particulate polymer comprises one or more selected from the group consisting of polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-chlorotrifluoroethylene copolymer (TFE / CTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), and liquid crystal polymer (LCP); The polyimide film according to claim 4.

6. The moisture absorption rate is 0.4% or less, The tensile strength is 150 MPa or more. The polyimide film according to claim 1 .

7. After being left in a 23°C environment for 24 hours, the dielectric constant (Dk) measured at 10 GHz is 3.5 or less, and the dielectric loss factor (Df) is 0.002 or less, After being left in a 23°C environment for 24 hours, the dielectric constant (Dk) measured at 28 GHz is 3.5 or less, and the dielectric loss factor (Df) is 0.0029 or less, After being left in a 23°C environment for 24 hours, the dielectric constant (Dk) measured at 40 GHz is 3.5 or less and the dielectric loss factor (Df) is 0.0029 or less. The polyimide film according to claim 1 .

8. The polyimide film according to any one of claims 1 to 7, Multilayer film.

9. Further comprising a thermoplastic resin layer, The multilayer film of claim 8.

10. The polyimide film according to any one of claims 1 to 7; and an electrically conductive metal foil; Flexible metal foil laminate.

11. The flexible metal foil laminate according to claim 10, Electronic components.

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