Blended polyimide film and manufacturing method thereof

Abstract

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

Description

Technical Field

[0001] The present invention relates to a blended polyimide film having excellent low dielectric properties and mechanical strength in a high-temperature and high-humidity environment and a method for manufacturing the same. Background Art

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

[0003] Especially due to its excellent insulating properties, that is, excellent electrical properties such as a low dielectric constant, it has attracted much attention as a high-functional polymer material in the fields of electricity, electronics, and even optics.

[0004] Recently, with the lightening and miniaturization of electronic products, highly integrated and flexible thin circuit boards are being actively developed.

[0005] Such thin circuit boards tend to make extensive use of a structure in which a circuit including a metal foil is formed on a polyimide film having excellent heat resistance, low-temperature resistance, and insulating properties and being easily bent.

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

[0007] On the other hand, recently, with the incorporation of various functions in electronic devices, the above-mentioned electronic devices require fast instruction cycles and communication speeds. To meet such requirements, thin circuit boards capable of achieving high-speed communication at high frequencies are being developed.

[0008] To achieve high-frequency and high-speed communication, an insulator with a high impedance that can maintain electrical insulation even at high frequencies is required. Impedance has an inverse relationship with the frequency and dielectric constant (Dk) formed in the insulator. Therefore, even at high frequencies, in order to maintain insulation, the dielectric constant should be reduced as much as possible.

[0009] However, for ordinary polyimide, the dielectric properties are not excellent enough to maintain sufficient insulating properties in high-frequency communication.

[0010] In addition, it is also known that the lower the dielectric properties of the insulator, the more it can reduce the occurrence of unwanted stray capacitance and noise in the thin circuit board, and can largely eliminate the cause of communication delay.

[0011] Therefore, polyimide with low dielectric properties is considered the most important factor in the performance of thin circuit boards.

[0012] Especially for high-frequency communication, dielectric loss caused by polyimide is bound to occur. The dielectric dissipation factor (Df) means the degree of power waste of the 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 also considered an important factor in the performance of thin circuit boards.

[0013] In addition, the more moisture the polyimide film contains, the greater the dielectric constant and the higher the dielectric dissipation factor. Regarding the polyimide film, due to its excellent inherent properties, it is suitable as a material for thin circuit boards. However, on the contrary, it is relatively vulnerable to moisture due to the polar imide groups, and thus the insulation properties will deteriorate.

[0014] Therefore, there is an urgent need to develop a polyimide film that can maintain low dielectric properties while keeping the unique mechanical properties of polyimide at a given level even in high-temperature or high-humidity environments.

[0015] [Prior Art Documents]

[0016] [Patent Documents]

[0017] Patent Document 1: Korean Patent Publication No. 10-2021-0055230. Summary of the Invention

[0018] [Technical Problem]

[0019] Therefore, in order to solve the above problems, an object of the present invention is to provide a blended polyimide film and a method for manufacturing the same, which have excellent low dielectric properties and improved mechanical strength even in high-temperature and high-humidity environments.

[0020] [Technical Solution]

[0021] In order to achieve the above object, an embodiment of the present invention provides a polyimide film having a dielectric constant (Dk) of 3.5 or less and a dielectric dissipation factor (Df) of 0.003 or less when measured at 10 GHz after being placed in an environment of 85°C and 85% RH for 24 hours.

[0022] Another embodiment of the present invention provides a multilayer film including the polyimide film of the present case.

[0023] Another embodiment of the present invention provides a flexible metal-clad laminate including the polyimide film of the present case and a conductive metal foil.

[0024] Another embodiment of the present invention provides an electronic component including the flexible metal-clad laminate of the present case.

[0025] [Advantages of the Invention]

[0026] As described above, the polyimide film manufactured by imidizing a polyamic acid solution composed of specific components and specific ratios maintains excellent low dielectric characteristics and mechanical characteristics even in a high-temperature and high-humidity environment, and thus can be usefully applied to various fields requiring these characteristics, particularly electronic components such as flexible metal-clad laminates. Detailed Embodiments

[0027] Hereinafter, embodiments of the present invention will be described in more detail.

[0028] Prior to this, terms or words used in this specification and the claims should not be construed as being limited to their ordinary meanings or dictionary meanings. Based on the principle that "the inventor can appropriately define the concept of terms in order to describe his own invention in the best way", they should only be construed as meanings and concepts consistent with the technical idea of the present invention.

[0029] Therefore, the configurations of the embodiments described in this specification are merely the best embodiments of the present invention and do not entirely represent the technical idea of the present invention. Therefore, it should be understood that there may be various equivalents and modification examples that can replace them at the time of this application.

[0030] In this specification, unless the context clearly indicates otherwise, singular expressions include plural expressions. In this specification, terms such as "comprises", "includes" or "has" are intended to specify the presence of the features, numbers, steps, elements or combinations thereof to be implemented, and it should be understood that the presence or additional possibility of one or more other features or numbers, steps, elements or combinations thereof is not precluded in advance.

[0031] In this specification, when ranges, preferred ranges or preferred upper limit values and preferred lower limit values are given for amounts, concentrations, or other values or parameters, regardless of whether the ranges are independently disclosed, it should be understood that all ranges formed by any upper range limit value or preferred value and any lower range limit value or preferred value of any pair are specifically disclosed.

[0032] When a range of values is recited in this specification, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within the range. The scope of the present invention is not intended to be limited to the specific values recited when defining the range.

[0033] In this specification, "dianhydride" is intended to include its precursors or derivatives, which may not technically be dianhydrides, but nevertheless will react with diamines to form polyamic acids, which can be converted again into polyimides.

[0034] 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 be converted again into polyimides.

[0035] In this specification, in "a to b" and "a~b" representing a numerical range, "to" and "~" are defined as ≥a and ≤b.

[0036] The polyimide film of 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 when measured at 10 GHz after being placed in an environment of 85°C and 85% RH for 24 hours.

[0037] For example, the dielectric constant measured after being placed in an environment of 85°C and 85% RH for 24 hours 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.

[0038] That is, the polyimide film of this case can maintain excellent low dielectric properties even in high temperature and high humidity environments.

[0039] In one implementation example, the above polyimide film can be obtained by subjecting a polyamic acid solution containing a dianhydride component and a diamine component to an imidization reaction, wherein the above dianhydride component includes p-phenylenebis(trimellitate anhydride) (TAHQ) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), and the above diamine component includes m-tolidine.

[0040] The polyimide chain derived from the above-mentioned biphenyltetracarboxylic dianhydride (BPDA) has a structure called a charge transfer complex (CTC), that is, a regular linear structure in which an electron donor and an electron acceptor are arranged close to each other, which can strengthen intermolecular interaction.

[0041] This structure has the effect of preventing hydrogen bonding with moisture, thus affecting the reduction of the moisture absorption rate, and can maximize the effect of reducing the moisture absorption of the polyimide film.

[0042] For the polyimide film to simultaneously satisfy appropriate elasticity and moisture absorption rate, the content ratio of the dianhydride is particularly important. For example, the lower the content ratio of biphenyltetracarboxylic dianhydride (BPDA), the more difficult it is to expect the low moisture absorption rate caused by the above-mentioned CTC structure.

[0043] In addition, the above-mentioned p-phenylene-bis(phthalic anhydride) contains an ester bond, which helps to improve the low dielectric properties of the polyimide film.

[0044] On the other hand, m-toluidine especially has a hydrophobic methyl group, which can contribute to the low moisture absorption characteristics of the polyimide film.

[0045] The moisture absorption rate is a ratio representing the amount of moisture contained in the material. Generally, when the moisture absorption rate is high, it is reported that the dielectric constant and the dielectric loss factor increase.

[0046] In a state where water vapor and the like are absorbed by the polyimide film, water exists in a liquid state. At this time, the dielectric constant and the dielectric loss factor of the polyimide film can increase dramatically.

[0047] That is, even if only a small amount of moisture is absorbed, the dielectric constant and the dielectric loss factor of the polyimide film will change sharply.

[0048] Therefore, by improving the low moisture absorption characteristics of the polyimide film, the low dielectric properties of the polyimide film can be improved. Thus, the dianhydride component and the diamine component of the polyimide film in this case can contribute to the low dielectric and low moisture absorption characteristics of the polyimide film.

[0049] In one implementation example, for the polyimide film of the present invention, based on the total content of the above-mentioned dianhydride component being 100 mol%, the ratio of the mole% of the above-mentioned biphenyltetracarboxylic dianhydride (BPDA) to the mole% of the p-phenylene-bis(phthalic anhydride) (TAHQ) (the mole% of the biphenyltetracarboxylic dianhydride (BPDA) / mole% of the p-phenylene-bis(phthalic anhydride) (TAHQ)) can be 1.5 or more and 2.9 or less.

[0050] When the content of the above-mentioned biphenyltetracarboxylic dianhydride (BPDA) is too large or the content of p-phenylene-bis(trimellitic anhydride) (TAHQ) is too small and exceeds the above molar ratio, the low dielectric characteristics of the polyimide film will decline.

[0051] On the contrary, when the content of the above-mentioned biphenyltetracarboxylic dianhydride (BPDA) is too small or the content of p-phenylene-bis(trimellitic anhydride) (TAHQ) is too large and is lower than the above molar ratio, the mechanical strength of the polyimide film will decline.

[0052] In one implementation example, based on the total weight of the polyimide film of the present invention being 100% by weight, the polyimide film may contain 10% by weight or more and 40% by weight or less of particulate polymer.

[0053] The above-mentioned particulate polymer may be a fluoropolymer or a liquid crystal polymer (liquid crystal polymer, LCP).

[0054] The above-mentioned fluoropolymer can be used but is not limited to 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), and chlorotrifluoroethylene-ethylene copolymer (ECTFE).

[0055] Preferably, the above-mentioned fluoropolymer may be polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA).

[0056] When the above-mentioned particulate polymer exceeds the content range of this case, although the dielectric characteristics can be improved, the mechanical properties of the polyimide film will decline. When it is lower than the content range of this case, the low dielectric characteristics of the polyimide film will decline.

[0057] In addition, for the particulate polymer contained in the polyimide film of this case, its average particle size may be 15 μm or less, and its glass transition temperature or melting point may be 100 °C or more.

[0058] In one implementation example, the moisture absorption rate of the polyimide film of this case may be 0.4% or less, and the tensile strength may be 150 MPa or more.

[0059] For example, the above-mentioned moisture absorption rate may be 0.28% or more and 0.38% or less, and the above-mentioned tensile strength may be 158 MPa or more and 199 MPa or less.

[0060] On the other hand, the polyimide film in this case, after being placed in an environment of 23°C for 24 hours, may have a dielectric constant (Dk) measured at 10 GHz of 3.5 or less, and a dielectric loss rate (Df) of 0.002 or less. After being placed in an environment of 23°C for 24 hours, the dielectric constant (Dk) measured at 28 GHz may be 3.5 or less, and the dielectric loss rate (Df) may be 0.0029 or less. After being placed in an environment of 23°C for 24 hours, the dielectric constant (Dk) measured at 40 GHz may be 3.5 or less, and the dielectric loss rate (Df) may be 0.0029 or less.

[0061] For example, after being placed in an environment of 23°C / 50% RH 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 rate (Df) may be 0.0014 or more and 0.00178 or less.

[0062] In addition, after being placed in an environment of 23°C 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 rate (Df) may be 0.00254 or more and 0.00285 or less. After being placed in an environment of 23°C 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 rate (Df) may be 0.00257 or more and 0.00288 or less.

[0063] That is, the dielectric constant of the polyimide film in this case, measured at 10 GHz after being placed in an environment of 23°C / 50% RH for 24 hours, has no difference from the dielectric constant measured at 10 GHz after being placed in an environment of 85°C and 85% RH for 24 hours. Despite the changes in external temperature and humidity, it can still maintain the low dielectric constant characteristics.

[0064] When measuring the low dielectric constant characteristics of the polyimide film in this case, even if the frequency changes, they still remain unchanged.

[0065] In addition, the dielectric loss rate of the polyimide film in this case, measured at 10 GHz after being placed in an environment of 85°C and 85% RH for 24 hours, increases compared to the dielectric loss rate measured at 10 GHz after being placed in an environment of 23°C / 50% RH for 24 hours, but it can still exhibit a low dielectric loss characteristic of 0.003 or less.

[0066] For example, the dielectric loss rate of the polyimide film in this case, measured at 10 GHz after being placed in an environment of 85°C and 85% RH for 24 hours, will increase within a range of less than 90% (for example, 60% or more and 86% or less) compared to the dielectric loss rate measured at 10 GHz after being placed in an environment of 23°C / 50% RH for 24 hours, but still can exhibit a low dielectric loss characteristic of 0.003 or less.

[0067] On the other hand, the dielectric loss rates of the polyimide film in this case, measured at 28 GHz and 40 GHz after being placed in an environment of 23°C / 50% RH for 24 hours, are higher than the dielectric loss rate measured at 10 GHz after being placed in an environment of 23°C / 50% RH for 24 hours, but still can exhibit a low dielectric loss characteristic of 0.003 or less.

[0068] In connection with this, for all polyimide films that satisfy the moisture absorption rate, tensile strength, dielectric constant, and dielectric loss rate, they can not only be used as insulating films for flexible metal foil laminates, but also when the manufactured flexible metal foil laminate is used as a telecommunication signal transmission circuit for transmitting signals at a high frequency of 10 GHz or more, its insulation stability can be ensured and the signal transmission delay can also be minimized.

[0069] In one implementation example, the polyimide film in this case can be a random or block copolymer.

[0070] On the other hand, the polyamic acid required for manufacturing the polyimide film in this case can be manufactured, for example, by the following methods:

[0071] (1) Method: Add the total amount of the diamine component to a solvent, and then add the dianhydride component so that it is substantially equimolar with the diamine component and carry out polymerization;

[0072] (2) Method: Add the total amount of the dianhydride component to a solvent, and then add the diamine component so that it is substantially equimolar with the dianhydride component and carry out polymerization;

[0073] (3) Method: After adding a part of the diamine component to a solvent, mix a part of the dianhydride component at a ratio of about 95 to 105 mol% with respect to the reaction components, then add the remaining diamine component, and then add the remaining dianhydride component to make the diamine component and the dianhydride component substantially equimolar and carry out polymerization;

[0074] (4) Method: After adding the dianhydride component to a solvent, mix a part of the diamine compound at a ratio of 95 to 105 mol% with respect to the reaction components, then add the other dianhydride component, and then add the remaining diamine component to make the diamine component and the dianhydride component substantially equimolar and carry out polymerization;

[0075] (5) A method in which a part of the diamine component and a part of the dianhydride component are reacted in a solvent to make one of them in excess to form a first composition, and in another solvent, a part of the diamine component and a part of the dianhydride component are reacted to make one of them in excess to form a second composition, and then the first and second compositions are mixed to complete the polymerization. At this time, when forming the first composition, if the diamine component is in excess, then in the second composition, the dianhydride component is made in excess; when the dianhydride component is in excess in the first composition, then in the second composition, the diamine component is made in excess. The first and second compositions are mixed so that the total diamine component and dianhydride component used in the reaction are substantially equimolar and polymerization is carried out.

[0076] However, the above polymerization method is not limited to the above examples, and obviously any known method can be used for the production of the above first to second polyamic acids.

[0077] In one implementation example, the method for manufacturing a polyimide film of the present invention includes: a step of polymerizing a dianhydride component containing biphenyltetracarboxylic dianhydride (BPDA) and p-phenylene-bis(trimellitate) dianhydride (TAHQ), and a diamine component containing m-toluidine (mTB) to produce a polyamic acid solution; and a step of imidizing the above polyamic acid solution.

[0078] Especially when the total content of the above dianhydride component is 100 mol%, the ratio of the molar% of the above biphenyltetracarboxylic dianhydride (BPDA) to the molar% of the p-phenylene-bis(trimellitate) dianhydride (TAHQ) (the molar% of the biphenyltetracarboxylic dianhydride (BPDA) / the molar% of the p-phenylene-bis(trimellitate) dianhydride (TAHQ)) can be 1.5 or more and 2.9 or less.

[0079] By reacting the above dianhydride component and diamine component in a predetermined order for polymerization, a polyimide film can be manufactured.

[0080] In addition, in the above polyimide manufacturing method, a step of adding 10% by weight or more and 40% by weight or less of a particulate polymer to the above polyamic acid solution and stirring may be included. The above particulate polymer may be a fluoropolymer or a liquid crystal polymer (LCP).

[0081] In the present invention, the polymerization method of the polyamic acid as described above may be a random polymerization method. The polyimide film produced from the polyamic acid of the present invention manufactured through the above process maximizes the effects of improving the tensile strength, reducing the moisture absorption rate, dielectric constant, and dielectric loss rate of the present invention, and can be preferably applied in this regard.

[0082] However, since the length of the repeating units in the polymer chain described above is made relatively short, there are limitations in exhibiting various excellent properties of the polyimide chain derived from the dianhydride component. Therefore, the polymerization method of polyamic acid that can be preferably used in the present invention can be a block polymerization method.

[0083] On the other hand, the solvent for synthesizing polyamic acid is not particularly limited, and any solvent can be used as long as it can dissolve polyamic acid, but an amide solvent is preferably used.

[0084] The polyimide film manufactured by the above manufacturing method of the 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) measured after being placed in an environment of 23°C / 50% RH for 24 hours may be 3.5 or less, and a dielectric loss factor (Df) may be 0.002 or less.

[0085] In particular, the polyimide film manufactured by the above manufacturing method of the polyimide film may have a moisture absorption rate of 0.4% or less, a tensile strength of 150 MPa or more, a dielectric constant (Dk) measured after being placed in an environment of 85°C / 85% RH for 24 hours may be 3.5 or less, and a dielectric loss factor (Df) may be 0.003 or less.

[0086] In one implementation example of the present invention, a flexible metal foil laminate is provided, including a multilayer film containing the above polyimide film, a multilayer film including the above polyimide film and a thermoplastic resin layer, and the above polyimide film and a conductive metal foil.

[0087] The above thermoplastic resin layer can be, for example, a thermoplastic polyimide resin layer.

[0088] The metal foil used is not particularly limited, but when the flexible metal foil laminate of the present invention is used for electronic devices or electrical device applications, for example, it can be a metal foil including copper or copper alloy, stainless steel or its alloy, nickel or nickel alloy (including 42 alloy), aluminum or aluminum alloy.

[0089] In ordinary flexible metal foil laminates, copper foils such as rolled copper foil and electrolytic copper foil are often used, and they can also be preferably used in the present invention. In addition, an anti-rust layer, a heat-resistant layer, or an adhesive layer can also be coated on the surface of these metal foils.

[0090] In the present invention, the thickness of the above metal foil is not particularly limited as long as it can fully exhibit its function according to its use.

[0091] The flexible metal foil laminate of the present invention may have a structure in which a metal foil is laminated on one side of the above polyimide film or an adhesive layer containing thermoplastic polyimide is attached to one side of the above polyimide film, and lamination is performed in a state where the metal foil is attached to the adhesive layer.

[0092] On the other hand, according to an embodiment of the present invention, it may be an electronic component including the above flexible metal foil laminate as a signal transmission circuit. The above signal transmission circuit may be an electronic component that transmits signals at a high frequency of at least 2 GHz, specifically, at a high frequency of at least 5 GHz, and more specifically, at a high frequency of at least 10 GHz.

[0093] The high moisture absorption of the polyimide film that affects the above signal transmission loss can be controlled to optimize the transmission loss at frequencies above 10 GHz.

[0094] The above electronic components may be, for example, communication circuits for portable terminals, communication circuits for computers, or communication circuits for aerospace applications, but are not limited thereto.

[0095] Hereinafter, the functions and effects of the invention will be described in more detail through specific embodiments of the invention. However, such embodiments are merely presented as examples of the invention, and the scope of the invention is not limited thereby.

[0096] Production Example (Production of Polyimide Film)

[0097] While injecting nitrogen into a 500 ml reactor equipped with a stirrer and a nitrogen injection / discharge pipe, DMF was introduced. After setting the temperature of the reactor to 30 °C, the molar ratio of p-phenylene-bis(trimellitic anhydride) (TAHQ) to biphenyltetracarboxylic dianhydride (BPDA) as the dianhydride component was adjusted to 1:1.5 - 2.9 and introduced, and then m-tolidine as the diamine component was introduced and confirmed to be completely dissolved.

[0098] Then, in a nitrogen atmosphere, the temperature of the reactor was raised to 40 °C and heated while continuously stirring for 120 minutes to produce polyamic acid.

[0099] After adjusting the content of the particulate polymer and adding it to the polyamic acid thus produced, stirring was performed to disperse it, and the contents of the catalyst and dehydrating agent were adjusted and added. After preparing a polyimide precursor composition in this way, the defoamed polyimide precursor composition was coated on a glass substrate using a spin coater. Then, it was dried in a nitrogen atmosphere at a temperature of 120 °C for 30 minutes to produce a gel film. The above gel film was heated to 450 °C at a rate of 2 °C / minute, heat-treated at 450 °C for 60 minutes, and cooled to 30 °C at a rate of 2 °C / minute to obtain a polyimide film.

[0100] Examples 1 to 10 and Comparative Examples 1 to 4

[0101] Manufacture was carried out according to the manufacturing examples described above, but the content of the particulate polymer was adjusted as shown in Table 1 below, and polyimide films of Examples 1 to 10 and Comparative Examples 1 to 4 were manufactured.

[0102] [Table 1]

[0103] Granular Polymer Content (wt%) Example 1 LCP 10 Example 2 LCP 20 Example 3 LCP 30 Example 4 LCP 40 Example 5 PTFE 10 Example 6 PTFE 20 Example 7 PTFE 30 Example 8 PFA 10 Example 9 PFA 20 Example 10 PFA 30 Comparative Example 1 LCP 50 Comparative Example 2 PTFE 50 Comparative Example 3 PFA 50 Comparative Example 4 - 0

[0104] For the polyimide films separately manufactured in Examples 1 to 10 and Comparative Examples 1 to 4, the tensile strength and moisture absorption rate were measured and shown in Table 2 below.

[0105] In addition, for the polyimide films separately manufactured in Examples 1 to 10 and Comparative Examples 1 to 4, the dielectric constant (Dk) and dielectric dissipation factor (Df) were measured and shown in Table 3 below.

[0106] [Table 2]

[0107] Tensile Strength (MPa) Moisture Absorption Rate (%) Example 1 199 0.38 Example 2 186 0.36 Example 3 173 0.34 Example 4 159 0.32 Example 5 194 0.36 Example 6 177 0.33 Example 7 158 0.29 Example 8 194 0.36 Example 9 177 0.32 Example 10 159 0.28 Comparative Example 1 146 0.3 Comparative Example 2 123 0.22 Comparative Example 3 120 0.21 Comparative Example 4 212 0.5

[0108] [Table 3]

[0109]

[0110] The measurement methods of the tensile strength, moisture absorption rate, dielectric constant (Dk), and dielectric dissipation factor (Df) of the manufactured polyimide films are as follows.

[0111] (1) Tensile strength measurement

[0112] Using a universal material testing machine (model name Instron 5564, Instron Corporation), the tensile strength of the sample was measured according to the method shown in ASTM D1708.

[0113] (2) Moisture absorption rate measurement

[0114] Prepare 2 test pieces of polyimide film (width 4 cm × length 25 cm), and dry them at 80 °C for 1 hour. Immediately after drying, place them in a constant temperature and humidity chamber at 23 °C and 50% RH. After leaving them for more than 24 hours, calculate from the weight change before and after as follows.

[0115] Moisture absorption rate (weight %) = [(weight after moisture absorption - weight after drying) / weight after drying] × 100

[0116] (3) Dielectric constant measurement

[0117] The dielectric constant (Dk) was measured at 10 GHz, 28 GHz, and 40 GHz after placing the polyimide film for 24 hours in an environment of 23°C / 50% RH using an Agilent SPDR meter.

[0118] In addition, the dielectric constant at 10 GHz was measured after placing the polyimide film for 24 hours in an environment of 85°C / 85% RH.

[0119] (4) Measurement of dielectric loss factor

[0120] The dielectric loss factor (Df) was measured at 10 GHz, 28 GHz, and 40 GHz after placing the polyimide film for 24 hours in an environment of 23°C using an Agilent ENA (vector network analyzer) with the SPDR (split post dielectric resonator) method.

[0121] In addition, the dielectric loss factor at 10 GHz was measured after placing the polyimide film for 24 hours in an environment of 85°C / 85% RH.

[0122] As shown in Table 2 above, the polyimide films manufactured according to Embodiments 1 to 10 of the present invention have a tensile strength of 150 MPa or more and a moisture absorption rate of 0.4% or less.

[0123] As shown in Table 3 above, the polyimide films of Embodiments 1 to 10 of the present invention not only achieve the characteristics of 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 placed for 24 hours in an environment of 23°C, but also achieve the characteristics of 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 placed for 24 hours in a high-temperature (85°C) and high-humidity (85%) environment, and have excellent low-dielectric characteristics.

[0124] In addition, the polyimide films of Embodiments 1 to 10 of the present invention can achieve the characteristics of 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 placed for 24 hours in an environment of 23°C, and can achieve the characteristics of 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 placed for 24 hours in an environment of 23°C.

[0125] In contrast, although the dielectric constants (Dk) and dielectric loss factors (Df) of the polyimide films of Comparative Examples 1 to 3 are similar to those of the polyimide films of Embodiments 1 to 10, the tensile strength is less than 150 MPa.

[0126] That is, compared with the polyimide films of Examples 1 to 10, the granular polymers in Comparative Examples 1 to 3 were used in excess, and the measured tensile strength had a lower value. From this, the following fact can be confirmed, that is, when the content of the granular polymer exceeds the scope of this case, the mechanical properties of the polyimide film deteriorate.

[0127] On the other hand, as shown in Comparative Example 4, when the granular polymer was not used, while the moisture absorption rate increased, the dielectric constant and the dielectric loss factor increased, and the low dielectric property deteriorated.

[0128] Such measurement results indicate that in order to adjust the dielectric properties and mechanical properties to an appropriate level, it is preferable to include the granular polymer in the content range selected according to the present invention.

[0129] From this, it can be predicted that the polyimide films of Examples 1 to 10 have both excellent low dielectric constant properties and mechanical properties, and are suitable for practical applications in electronic components.

[0130] The above has been described with reference to the embodiments of the present invention. However, as long as those of ordinary skill in the art to which the present invention pertains, various applications and modifications can be made based on the above content within the scope of the present invention. Detailed Description

[0132] The polyimide film manufactured by imidizing a polyamic acid solution composed of specific components and specific ratios according to the present invention maintains excellent low dielectric properties and mechanical properties even in a high-temperature and high-humidity environment, and thus can be usefully applied to various fields requiring these properties, especially electronic components such as flexible metal-clad laminates.

Claims

1. A polyimide film, wherein, The polyimide film has a dielectric constant (Dk) of 3.5 or less and a dielectric loss factor (Df) of 0.003 or less when measured at 10 GHz after being placed in an environment of 85°C and 85% RH for 24 hours.

2. The polyimide film according to claim 1, wherein The polyimide film is obtained by subjecting a polyamic acid solution containing a dianhydride component and a diamine component to an imidization reaction. Among them, the dianhydride component includes p-phenylene-bis(trimellitic acid anhydride) (TAHQ) and biphenyltetracarboxylic dianhydride (BPDA), and the diamine component includes m-tolidine.

3. The polyimide film according to claim 2, wherein, Based on the total content of the dianhydride component being 100 mol%, the ratio of the mol% of biphenyltetracarboxylic dianhydride (BPDA) to the mol% of p-phenylene-bis(trimellitic acid anhydride) (TAHQ) (mol% of BPDA / mol% of TAHQ) is 1.5 or more and 2.9 or less.

4. The polyimide film according to claim 2, wherein Based on the total weight of the polyimide film being 100 wt%, the polyimide film contains 10 wt% or more and 40 wt% or less of particulate polymer.

5. The polyimide film according to claim 4, wherein The particulate polymer includes 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), chlorotrifluoroethylene-ethylene copolymer (ECTFE), and liquid crystal polymer (LCP).

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

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

8. A multilayer film comprising the polyimide film according to any one of claims 1 to 7.

9. The multilayer film according to claim 8, wherein, The multilayer film further includes a thermoplastic resin layer.

10. A flexible metal foil laminate, comprising: The polyimide film according to any one of claims 1 to 7; and A conductive metal foil.

11. An electronic component comprising the flexible metal foil laminate according to claim 10.

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