Semi-transparent low dielectric polyimide film and method for producing the same

Abstract

The present invention provides a polyimide film having a dielectric loss factor (Df) of 0.003 or less, a haze of 3.5% or less, a light transmittance of 45% or more, and a glass transition temperature (Tg) of 300°C or more and less than 320°C, and a method for producing the polyimide film.

Description

[Technical Field]

[0001] The present invention relates to a polyimide film that is semi-transparent yet exhibits low dielectric properties, 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, polyimide has been attracting attention as a highly functional polymer material in the fields of electricity, electronics, optics, etc. due to its excellent insulating properties, i.e., excellent electrical properties such as low dielectric constant. Recently, with the trend toward lighter and / or smaller electronic products, highly integrated, flexible, thin circuit boards have been actively developed. Such thin circuit boards tend to have a structure in which a circuit containing metal foil is formed on a polyimide film that has excellent heat resistance, low temperature resistance, and insulating properties, yet is easily flexible.

[0003] Flexible metal clad laminates are mainly used for such thin circuit boards, such as flexible copper clad laminates (FCCLs), which use thin copper foils as the metal foil. Polyimides are also used as protective films and insulating films for thin circuit boards. Meanwhile, as electronic devices are increasingly equipped with a variety of functions, they are required to have high computing speeds and communication speeds. To meet this demand, thin circuit boards capable of high-speed communication at high frequencies have been developed.

[0004] 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. However, in the case of ordinary polyimides, the dielectric properties are currently not at a level that is good enough to maintain sufficient insulation for high-frequency communications. In addition, it is known that the lower the dielectric properties of the insulator, the more it can reduce undesirable stray capacitance and noise generation in thin circuit boards, thereby significantly eliminating the causes of communication delays.

[0005] Therefore, the low dielectric properties of polyimide are currently recognized as the most important factor in the performance of thin circuit boards. In particular, in the case of high-frequency communications, dielectric dissipation inevitably occurs due to polyimide. The dielectric dissipation factor (Df) indicates the degree of electrical energy wasted in a thin circuit board and is closely related to the signal transmission delay that determines the communication speed. Therefore, maintaining the dielectric dissipation factor of polyimide as low as possible is recognized as an important factor in the performance of thin circuit boards. In addition, as products that require the use of transparent insulating substrates, such as transparent displays, are being developed one after another, the need for polyimides with a certain degree of transparency (low haze) is increasing.

[0006] To improve the transparency of dark brown polyimide films, conventional methods include restricting the movement of π electrons using weak electron-accepting dianhydrides or weak electron-donating diamines, reducing the CTC effect by introducing bulky substituents or asymmetric or nonplanar structures into the main chain, and inhibiting the formation of π electron resonance structures by introducing aliphatic anhydrides or aliphatic diamines. However, these methods not only reduce the thermal stability and mechanical properties of the polyimide film, but also increase its dielectric constant, limiting its use in areas requiring low dielectric properties. Furthermore, since monomers with complex structures and high unit costs are mainly used, the raw material costs for transparent polyimide films are relatively high. Therefore, there is a need to develop a polyimide film that has a certain degree of transparency while maintaining the inherent thermal stability and mechanical properties of polyimide and at the same time has low dielectric properties. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Republic of Korea Patent Publication No. 2003-0027249 Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, in order to solve the above problems, an object of the present invention is to provide a semi-transparent polyimide film with low dielectric properties and a method for producing the same. In particular, it is an object of the present invention to provide a low-cost polyimide film having low dielectric constant and translucent (low haze) properties by using a combination of ordinary monomers rather than monomers with complex structures. Therefore, a substantial object of the present invention is to provide specific examples thereof. [Means for solving the problem]

[0009] To achieve the above object, one embodiment of the present invention comprises: (a) polymerizing a first dianhydride acid component, a second dianhydride acid component, and a diamine component in an organic solvent to produce a polyamic acid; (b) forming a film of the precursor composition containing the polyamic acid on a support, and then imidizing the film; the first dianhydride acid component is any one selected from the group consisting of oxydiphthalic dianhydride (ODPA), biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), and benzophenonetetracarboxylic dianhydride (BTDA); the second dianhydride acid component is any one selected from the group consisting of oxydiphthalic dianhydride (ODPA), biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), and benzophenonetetracarboxylic dianhydride (BTDA); the diamine component is at least one selected from the group consisting of paraphenylenediamine (PPD), diaminodiphenyl ether (ODA), m-tolidine, 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,4-bis(3-aminophenoxy)benzene (TPE-Q), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 4,4'-diaminobenzanilide, and 3,5-diaminobenzoic acid (DABA); The polyimide film has a dielectric loss factor (Df) of 0.003 or less and a haze of 3.5% or less. A method for producing a polyimide film is provided. (However, the first dianhydride acid component and the second dianhydride acid component are different from each other.)

[0010] Another embodiment of the present invention provides a polyimide film manufactured by the above manufacturing method. Yet another embodiment of the present invention is a laminate comprising the polyimide film and a thermoplastic resin layer, A multilayer film is provided. Yet another embodiment of the present invention comprises the polyimide film and an electrically conductive metal foil. A flexible metal foil laminate is provided. Yet another embodiment of the present invention comprises the flexible metal foil laminate: Provides electronic components. Yet another embodiment of the present invention is a dielectric loss factor (Df) of 0.003 or less, Haze is 3.5% or less. A polyimide film is provided. [Effects of the Invention]

[0011] As described above, the present invention provides a polyimide film containing characteristic components in a specific composition ratio and a manufacturing method thereof to provide a low-cost polyimide film having low dielectric and translucent (low haze) properties, which can be usefully applied to various fields requiring such properties, particularly electronic components such as flexible metal foil laminates. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, the embodiments of the present invention will be described in more detail in the order of "polyimide film" and "method for producing polyimide film" according to the present invention. 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 describe 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 entire 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. In this specification, the singular includes the plural unless the context clearly indicates otherwise. It should be understood that in this specification, the terms "comprises," "has," "comprises," "has," and the like are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0013] When an amount, concentration, or other value or parameter is given herein as a range, a preferred range, or a list of upper and lower preferred values, it should be understood to specifically disclose all ranges formed by any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether the ranges are 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 integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values ​​recited when defining a range. 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 are again converted to polyimides. As used herein, "diamine" is intended to include precursors or derivatives thereof, which may not technically be diamines, but which nevertheless react with dianhydrides to form polyamic acids, which are again converted to polyimides. can be.

[0014] The polyimide film according to one embodiment of the present invention may have a dielectric loss factor (Df) of 0.003 or less and a haze of 3.5% or less. Even if a polyimide film is produced using a monomer that is the same as or similar to that of the present invention, if the dielectric loss factor does not fall within the above range, it is difficult to ensure low dielectric properties. At the same time, if the haze does not fall within the above range, light transmitted through the film is excessively diffused, making it difficult to achieve translucency of the film. Preferably, the dielectric loss factor (Df) may be 0.0029 or less, and the haze may be 3.3% or less. Therefore, while a typical low dielectric polyimide film is very dark brown and has almost no transparency, the polyimide film has the technical advantages of having low dielectric properties while also having low haze and semi-transparency. The polyimide film may have a light transmittance of 45% or more and a glass transition temperature (Tg) of 300°C or more but less than 320°C. Therefore, the polyimide film of the present invention has the technical advantage of having high light transmittance and a glass transition temperature that allows it to be used as an insulating film for flexible metal foil laminates. Preferably, the glass transition temperature (Tg) may be 305°C or less.

[0015] In one embodiment, the polyimide film comprises a first dianhydride acid component selected from the group consisting of 4,4'-Oxidiphthalic dianhydride (ODPA), 3,3',4,4'-Biphenyltetracarboxylic dianhydride (BPDA), Pyromellitic anhydride (PMDA), and 3,3',4,4'-Benzophenonetetracarboxylic dianhydride (BTDA); a second dianhydride acid component selected from the group consisting of oxydiphthalic dianhydride (ODPA), biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), and benzophenonetetracarboxylic dianhydride (BTDA); and It is obtained by the imidization reaction of one or more diamine components selected from the group consisting of paraphenylenediamine (p-Phenylenediamine, PPD), diaminodiphenyl ether (4,4'-oxydianiline, ODA), m-tolidine, 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,4-bis(3-aminophenoxy)benzene (TPE-Q), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 4,4'-diaminobenzanilide, and 3,5-diaminobenzoic acid (DABA).

[0016] Additionally, the first dianhydride acid component and the second dianhydride acid component may be different from each other. For example, the first dianhydride acid component may be biphenyltetracarboxylic dianhydride (BPDA), the second dianhydride acid component may be oxydiphthalic dianhydride (ODPA), and the diamine component may be paraphenylenediamine (PPD). In one embodiment, the content of the first dianhydride acid component is 40 mol % or more and 95 mol % or less, based on 100 mol % of the total content of the dianhydride acid components in the polyimide film. The content of the second dianhydride acid component may be 5 mol % or more and 60 mol % or less. Preferably, based on 100 mol% of the total content of dianhydride acid components in the polyimide film, the content of the first dianhydride acid may be 45 mol% or more and 80 mol% or less, and the content of the second dianhydride acid may be 15 mol% or more and 50 mol% or less.

[0017] If the content of the first dianhydride is less than 40 mol% and more than 95 mol%, or if the content of the second dianhydride is less than 5 mol% and more than 60 mol%, based on 100 mol% of the total content of the dianhydride components, the dielectric loss factor may increase, resulting in a deterioration in dielectric properties, or the mechanical properties of the polyimide film may be deteriorated. In one embodiment, the polyimide film further comprises 5 mol% or less of a third dianhydride acid component, based on 100 mol% of the total dianhydride acid component of the polyimide film; The third dianhydride acid component may be any one selected from the group consisting of oxydiphthalic dianhydride (ODPA), biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), and benzophenonetetracarboxylic dianhydride (BTDA). Additionally, the third dianhydride acid component may be different from the first dianhydride acid component and the second dianhydride acid component.

[0018] For example, the third dianhydride acid may be a pyromellitic dianhydride, which may be used to adjust the viscosity during the preparation of polyamic acid. Meanwhile, the polyimide chain derived from biphenyltetracarboxylic dianhydride, which can be used as the dianhydride acid component of the polyimide film, 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, thereby strengthening the intermolecular interaction of the polyimide.

[0019] This structure has the effect of preventing hydrogen bonding with moisture, which has an effect of reducing the moisture absorption rate, thereby maximizing the effect of reducing the moisture absorption of the polyimide film. For a polyimide film to simultaneously satisfy appropriate elasticity and moisture absorption, the content ratio of the dianhydride is particularly important. For example, as the content ratio of biphenyltetracarboxylic dianhydride decreases, it becomes difficult to expect low moisture absorption due to the CTC structure. In addition, oxydiphthalic dianhydride, which can be used together with biphenyltetracarboxylic dianhydride as the dianhydride acid component of the polyimide film, contains two benzene rings corresponding to the aromatic moiety, just like biphenyltetracarboxylic dianhydride, and is expected to have an even lower moisture absorption rate. In this regard, polyimide films that satisfy both the dielectric loss factor (Df) and glass transition temperature requirements can be used as insulating films for flexible metal foil laminates. Furthermore, even when the manufactured flexible metal foil laminates are used as electrical signal transmission circuits that transmit signals at high frequencies of 10 GHz or higher, the insulation stability of the flexible metal foil laminates can be ensured and signal transmission delays can be minimized.

[0020] The dielectric loss factor (Df) will be explained in detail below. <Dielectric loss factor> "Dielectric loss factor" refers to the force dissipated by a dielectric (or insulator) when molecular friction impedes molecular motion caused by an alternating electric field. The dielectric loss factor is an index that indicates the ease of charge loss (dielectric loss) and is commonly used. The higher the dielectric loss factor, the easier it is to lose charge, and conversely, the lower the dielectric loss factor, the harder it is to lose charge. In other words, the dielectric loss factor is a measure of power loss, but when the dielectric loss factor is The lower the value, the more the signal transmission delay caused by power loss is alleviated and the faster the communication speed can be maintained. This is a strong requirement for polyimide films, which are insulating films, and the polyimide film according to the present invention may have a dielectric loss factor of 0.003 or less at a very high frequency of 10 GHz.

[0021] In the present invention, the polyamic acid 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 acid component is added in an amount substantially equimolar to the diamine component to polymerize it; (2) A method in which the entire amount of the dianhydride acid component is placed in a solvent, and then the diamine component is added in an amount substantially equimolar to the dianhydride acid component to polymerize it; (3) A method in which a part of the diamine component is placed in a solvent, and then a part of the dianhydride acid 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 acid component, so that the diamine component and the dianhydride acid component are substantially equimolar, thereby polymerizing; (4) A method in which a dianhydride acid component is placed in a solvent, and then a part of the components in the diamine compound is mixed in a ratio of 95 to 105 mol % relative to the reactants, 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, thereby polymerizing the mixture; (5) A method of forming a first composition by reacting some diamine components and some dianhydride acid components in a solvent so that one of them is in excess, and then forming a second composition by reacting some diamine components and some dianhydride acid components in another solvent so that one of them is in excess, and then mixing the first and second compositions to complete the polymerization, in which 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 components and dianhydride acid components used in these reactions are substantially equimolar. However, the polymerization method is not limited to the above examples, and it goes without saying that any known method can be used to produce the polyamic acid.

[0022] In one embodiment, a method for producing a polyimide film according to another aspect of the present invention includes the steps of: (a) polymerizing a first dianhydride acid component, a second dianhydride acid component, and a diamine component in an organic solvent to produce a polyamic acid; (b) forming a film of the precursor composition containing the polyamic acid on a support, and then imidizing the film; the first dianhydride acid component is any one selected from the group consisting of oxydiphthalic dianhydride (ODPA), biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), and benzophenonetetracarboxylic dianhydride (BTDA); the second dianhydride acid component is any one selected from the group consisting of oxydiphthalic dianhydride (ODPA), biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), and benzophenonetetracarboxylic dianhydride (BTDA); The diamine component may include at least one selected from the group consisting of paraphenylenediamine (PPD), diaminodiphenyl ether (ODA), m-tolidine, 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,4-bis(3-aminophenoxy)benzene (TPE-Q), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 4,4′-diaminobenzanilide, and 3,5-diaminobenzoic acid (DABA). Additionally, the first dianhydride acid component and the second dianhydride acid component may be different from each other. In one embodiment, in the process of producing the polyamic acid, after adding a diamine component, The polyimide film can be produced by first adding and polymerizing the first dianhydride acid component, and then adding and polymerizing the second dianhydride acid component.

[0023] The polyimide film produced using this addition order exhibited low dielectric and low haze properties. However, when the addition order was changed (especially when the order of adding the first dianhydride and the second dianhydride was changed), the dielectric loss value of the produced polyimide film increased, resulting in a decrease in low dielectric properties and a decrease in light transmittance. That is, the order in which the diamine component and the dianhydride component are added can affect the dielectric and optical properties of the produced polyimide film. The polymerization method of the polyamic acid as described above can be defined as a random polymerization method, and the polyimide film prepared from the polyamic acid of the present invention prepared by the above process can be preferably used in terms of optimizing the effects of the present invention, such as reducing the dielectric loss factor (Df) and moisture absorption rate and imparting low haze characteristics.

[0024] However, since the above polymerization method results in a relatively short length of the repeating units in the polymer chain, there may be a limit to the excellent properties of the polyimide chain derived from the dianhydride acid component. Therefore, in the present invention, the polyamic acid may be polymerized using 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 can be used, but an amide-based solvent is preferred. Specifically, the solvent may be an organic polar solvent, more specifically, an aprotic polar solvent, such as one or more selected from the group consisting of N,N-dimethylformamide (DMF), N,N-dimethylacetamide, N-methyl-pyrrolidone (NMP), gamma-butyrolactone (GBL), and diglyme, but is not limited thereto, and may be used alone or in combination of two or more types as needed.

[0025] In one example, N,N-dimethylformamide and N,N-dimethylacetamide are particularly preferably used as the solvent. Furthermore, in the polyamic acid production process, a filler may be added for the purpose of improving various film properties such as sliding properties, thermal conductivity, corona resistance, loop hardness, etc. The filler to be added is not particularly limited, but preferred examples include silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica, etc. The particle size of the filler is not particularly limited and may be determined depending on the film properties to be modified and the type of filler to be added. Generally, the average particle size is 0.05 to 100 μm, preferably 0.1 to 75 μm, more preferably 0.1 to 50 μm, and particularly preferably 0.1 to 25 μm.

[0026] If the particle size is below this range, the modifying effect is less likely to be achieved, whereas if it exceeds this range, the surface properties may be significantly damaged and the mechanical properties may be significantly reduced. The amount of filler to be added is not particularly limited, and may be determined depending on the film properties that need to be modified, the particle size of the filler, and the like. Generally, the amount of filler added is 0.01 to 100 parts by weight, preferably 0.01 to 90 parts by weight, and more preferably 0.02 to 80 parts by weight, per 100 parts by weight of polyimide. If the amount of filler added is below this range, the modifying effect of the filler is unlikely to be achieved, while if it exceeds this range, the mechanical properties of the film may be significantly impaired. There are no particular limitations on the method of adding the filler, and any known method may be used.

[0027] In the production method of the present invention, the polyimide film can be produced by a thermal imidization method or a chemical imidization method. Alternatively, the imidation layer may be produced by a hybrid imidation method in which thermal imidization and chemical imidization are performed in parallel. The thermal imidization method is a method in which a chemical catalyst is not used and the imidization reaction is induced by a heat source such as hot air or an infrared dryer.

[0028] The thermal imidization method can imidize the amic acid groups present in the gel film by heat-treating the gel film at a variable temperature in the range of 100 to 600°C, specifically 200 to 500°C, more specifically 300 to 500°C. However, even during the process of forming the gel film, a portion of the amic acid (approximately 0.1 mol % to 10 mol %) is imidized. For this reason, the polyamic acid composition can be dried at a variable temperature in the range of 50°C to 200°C, which also falls within the category of the thermal imidization method. In the case of chemical imidization, polyimide films can be produced using a dehydrating agent and an imidizing agent by methods known in the art. As an example of the composite imidization method, a polyimide film can be produced by adding a dehydrating agent and an imidization agent to a polyamic acid solution, heating the solution at 80 to 200°C, preferably 100 to 180°C, partially curing and drying the solution, and then heating the solution at 200 to 400°C for 5 to 400 seconds.

[0029] The polyimide film of the present invention produced by the above-described production method may have a dielectric loss factor (Df) of 0.003 or less, a haze of 3.5% or less, a light transmittance of 45% or more, and a glass transition temperature (Tg) of 300°C or more but less than 320°C. The present invention provides a multilayer film comprising the above-mentioned polyimide film and a thermoplastic resin layer, and a flexible metal foil laminate comprising the above-mentioned polyimide film and an electrically conductive metal foil. As the thermoplastic resin layer, for example, a thermoplastic polyimide resin layer can be used. The metal foil to be used is not particularly limited, but when the flexible metal foil laminate of the present invention is used for electronic or electrical equipment, the metal foil may be, for example, copper or a copper alloy, stainless steel or an alloy thereof, nickel or a nickel alloy (including alloy 42), or aluminum or an aluminum alloy.

[0030] In general, copper foils such as rolled copper foils and electrolytic copper foils are widely used in flexible metal foil laminates, and are also preferably used in the present invention. Furthermore, 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, the thickness of the metal foil is not particularly limited, and may be any thickness that allows it to exhibit sufficient functionality depending on its intended use. 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.

[0031] The present invention also provides an electronic component including the flexible metal foil laminate as an electrical signal transmission circuit, which may be an electronic component that transmits signals at a high frequency of at least 2 GHz, particularly at least 5 GHz, and even more particularly at least 10 GHz. The electronic component may be, for example, but 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]

[0032] The functions and effects of the present invention will be described in more detail below through specific examples of the present invention, but these examples are presented only as examples of the present invention and do not define the scope of the invention.

[0033] <Production example> DMF was added to a 500 ml reactor equipped with a stirrer and nitrogen inlet / outlet tubes while injecting nitrogen, and the temperature of the reactor was set to 30°C or less. Then, paraphenylenediamine as the diamine component, biphenyltetracarboxylic dianhydride as the first dianhydride component, and oxydiphthalic dianhydride as the second dianhydride component were added, and it was confirmed that they were completely dissolved. The diamine component and dianhydride acid component were added in the following order: paraphenylenediamine (PPD), biphenyltetracarboxylic dianhydride (BPDA), and oxydiphthalic dianhydride (ODPA). The temperature was raised to 40°C under a nitrogen atmosphere, and the mixture was stirred for 120 minutes. After that, a 10% solution of pyromellitic dianhydride (PMDA) was added in portions to adjust the viscosity, producing a polyamic acid solution with a viscosity of 200,000 cP at 23°C. The prepared polyamic acid solution was spun at a high speed of 1,500 rpm or more to remove air bubbles. The degassed polyimide precursor composition was then coated onto a glass substrate using a spin coater. It was then dried under a nitrogen atmosphere at 120°C for 30 minutes to prepare 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. The polyimide film was then peeled off from the glass substrate by dipping in distilled water. The thickness of the polyimide film was 25-30 μm. The thickness of the polyimide film was measured using an Anritsu Electric Film Thickness Tester.

[0034] <Examples 1 to 4 and Comparative Examples 1 to 3> In the production examples, the components and their contents were changed as shown in Table 1 below to produce the respective polyimide films. In Comparative Examples 2 and 3, the compositions and composition ratios were the same as those in Examples 1 and 4, respectively, but the diamine component and dianhydride acid component were added in the following order: paraphenylenediamine, oxydiphthalic dianhydride, and biphenyltetracarboxylic dianhydride. That is, the order of adding oxydiphthalic dianhydride and biphenyltetracarboxylic dianhydride was reversed from that in Examples 1 and 4. [Table 1]

[0035] <Experimental Example> Evaluation of dielectric loss factor, haze, light transmittance and glass transition temperature The polyimide films produced in Examples 1 to 6 and Comparative Examples 1 to 3 were measured for dielectric loss factor, haze, light transmittance, and glass transition temperature, and the results are shown in Table 2 below. (1) Measurement of dielectric loss factor The dielectric loss factor (Df) was measured by drying the prepared film at 130°C for 30 minutes, then aging it for 24 hours in a thermo-hygrostat maintained at 23°C and 50% relative humidity.Then, the dielectric properties were measured at a frequency of 10 GHz using a Keysight ENA with a Split Post Dielectric Resonator (SPDR) measurement method. (2) Haze measurement Haze was measured using a HunterLab device according to ASTM E308 standard. (3) Measurement of light transmittance The light transmittance was measured at 400-700 nm using a HunterLab device according to the ASTM D1003 standard. (4) Measurement of glass transition temperature Glass transition temperature (T g ) was measured using DMA to determine the loss modulus and storage modulus of each film, and the inflection point on the tangent graph was measured as the glass transition temperature. [Table 2]

[0036] As shown in Table 2, the polyimide films prepared according to the examples of the present invention exhibited a dielectric loss factor of 0.003 or less, which is significantly lower than that of the polyimide films of the comparative examples. That is, the dielectric loss factors of the polyimide films of Comparative Examples 1 to 3 all exceeded 0.003. The glass transition temperatures of the polyimide films produced according to the examples of the present invention were all equal to or higher than 300°C and lower than 320°C.

[0037] In addition, the haze of the polyimide films manufactured according to the examples of the present invention was measured to be 3.5% or less. In contrast, Comparative Example 1, which did not contain oxydiphthalic dianhydride, exhibited a high haze of 7.1% and a low light transmittance of 40%. On the other hand, in Comparative Examples 2 and 3, in which the order of adding the first and second dianhydride acid components was reversed from that of Examples 1 and 4, the measured haze was 2.7% and 5.9%, respectively, which was higher than that of Examples 1 and 4 with the same composition ratio.

[0038] The polyimide films of Comparative Examples 2 and 3 were measured to have light transmittances of 35% and 24%, respectively, which were lower than those of Examples 1 and 4. In other words, it was confirmed that even for polyimide films with the same composition and composition ratio as those in the examples, not only did the low dielectric (low dielectric loss factor) characteristics deteriorate depending on the order in which the dianhydride acid components were added, but the light transmittance characteristics also deteriorated. Therefore, it has been found that the inherent low dielectric loss, haze, light transmittance, and glass transition temperature of the polyimide film of the present application can be achieved by the specified components, composition ratio, and production method (particularly, the order of adding the dianhydride acid components) of the present application, and that the polyimide film is suitable for use in electronic components in which signal transmission is performed at high frequencies in the gigabit range. In contrast, the polyimide films of Comparative Examples 1 to 3, which have compositions or manufacturing methods different from those of the Examples, are expected to be difficult to use in electronic components in which signal transmission is performed at high frequencies in the gigabit range in terms of at least one of the dielectric loss factor, haze, light transmittance, and glass transition temperature. The present invention has been described above with reference to the preferred embodiments thereof. Those skilled in the art will be able to make various applications and modifications within the scope of the present invention based on the above content. [Industrial Applicability]

[0039] As described above, the present invention provides a polyimide film containing characteristic components in a specific composition ratio and a manufacturing method thereof to provide a low-cost polyimide film having low dielectric and translucent (low haze) properties, which can be usefully applied to various fields requiring such properties, particularly electronic components such as flexible metal foil laminates.

Claims

1. A method for producing a polyimide film, comprising: (a) polymerizing a first dianhydride acid component, a second dianhydride acid component, and a diamine component in an organic solvent to produce a polyamic acid; (b) forming a film of the precursor composition containing the polyamic acid on a support, and then imidizing the film; the first dianhydride acid component is biphenyltetracarboxylic dianhydride (BPDA); the second dianhydride acid component is oxydiphthalic dianhydride (ODPA); the diamine component is paraphenylenediamine (PPD), In the step of preparing the polyamic acid, the diamine component is added, and then the first dianhydride acid component is added and polymerized first; Next, the second dianhydride acid component is introduced and polymerized, the content of the first dianhydride acid component is 48.5 mol% or more and 78 mol% or less, based on 100 mol% of the total content of dianhydride acid components in the polyimide film; the content of the second dianhydride acid component is 19 mol% or more and 48.5 mol% or less, and the content of paraphenylenediamine is 100 mol % based on 100 mol % of the diamine component of the polyimide film; The polyimide film has a dielectric loss factor (Df) of 0.003 or less at 10 GHz and a haze of 3.5% or less. A method for producing polyimide film.

2. The polyimide film has a light transmittance of 45% or more, A glass transition temperature (Tg) of 300°C or higher and lower than 320°C. The method for producing the polyimide film according to claim 1 .

3. The polyimide film further contains 5 mol% or less of a third dianhydride acid component based on 100 mol% of the total dianhydride acid component; The third dianhydride acid component is any one selected from the group consisting of pyromellitic dianhydride (PMDA) and benzophenone tetracarboxylic dianhydride (BTDA). The method for producing the polyimide film according to claim 1 .

4. A polyimide film, A polyimide comprising, as polymerized units, a dianhydride component and a diamine component, wherein the dianhydride component comprises a first dianhydride acid component and a second dianhydride acid component; the first dianhydride acid component is biphenyltetracarboxylic dianhydride (BPDA); the second dianhydride acid component is oxydiphthalic dianhydride (ODPA), and the diamine component is paraphenylenediamine (PPD); the content of the first dianhydride acid component is 48.5 mol% or more and 78 mol% or less, based on 100 mol% of the total content of dianhydride acid components in the polyimide film; the content of the second dianhydride acid component is 19 mol% or more and 48.5 mol% or less, and the content of paraphenylenediamine is 100 mol % based on 100 mol % of the diamine component of the polyimide film; The polyimide film has a dielectric loss factor (Df) of 0.003 or less at 10 GHz and a haze of 3.5% or less. Polyimide film.

5. A laminate comprising the polyimide film according to claim 4 and a thermoplastic resin layer. Multilayer film.

6. A laminate comprising the polyimide film of claim 4 and an electrically conductive metal foil. Flexible metal foil laminate.

7. The flexible metal foil laminate of claim 6, Electronic components.

8. The polyimide film has a light transmittance of 45% or more, A glass transition temperature (Tg) of 300°C or higher and lower than 320°C. The polyimide film according to claim 4.

9. The polyimide film further contains 5 mol% or less of a third dianhydride acid component based on 100 mol% of the total dianhydride acid component content of the polyimide film; The third dianhydride acid component is any one selected from the group consisting of pyromellitic dianhydride (PMDA) and benzophenone tetracarboxylic dianhydride (BTDA). The polyimide film according to claim 4.

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