Multilayer polyimide film and method for producing same

Abstract

The invention provides a multilayer polyimide film and a manufacturing method thereof. The multilayer polyimide film comprises a core layer; and a first surface layer and a second surface layer respectively formed on one outer surface of the core layer and the surface opposite to the outer surface, wherein the surface hardness measured by a nanoindenter is 0.4 GPa or more and 0.6 GPa or less.

Description

Technical Field

[0001] The present invention relates to a multi-layer polyimide film having excellent dimensional stability and adhesion, and more particularly, to a multi-layer polyimide film having high surface hardness and minimizing the reduction in adhesion between room temperature adhesion and heat-resistant adhesion, 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] The polyimide film has attracted much attention as a material for various electronic devices that require the above characteristics.

[0004] Microelectronic components using polyimide films can be, for example, flexible ultra-thin circuit boards with high circuit integration, in order to cope with the lightweight and miniaturization of electronic products. The polyimide film is particularly widely used as an insulating film for ultra-thin circuit boards.

[0005] The structure of the above ultra-thin circuit board is generally to form a circuit including a metal foil on an insulating film. Generally speaking, such an ultra-thin circuit board is called a flexible metal foil clad laminate. When a thin copper plate is used as the metal foil, in a narrow sense, it is also called a flexible copper clad laminate (FCCL).

[0006] As a method for manufacturing a flexible metal foil clad laminate, for example: (i) a casting method in which a polyamic acid as a polyimide precursor is cast or coated on a metal foil and then imidized; (ii) a metallization method in which a metal layer is directly provided on a polyimide film by sputtering; and (iii) a lamination method in which a polyimide film and a metal foil are joined by using thermoplastic polyimide with heat and pressure.

[0007] Especially the metallization method, for example, is a method for producing a flexible metal foil clad laminate by sputtering a metal such as copper on a polyimide film with a thickness of 20 μm to 38 μm and sequentially depositing a tie layer and a seed layer. It has advantages in ultra-fine circuits with a pitch of 35 μm or less for forming circuit patterns, and is widely used for manufacturing flexible metal foil clad laminates for COF (chip on film).

[0008] The polyimide film used in the flexible metal foil laminate based on the metallization method needs to have high dimensional stability and adhesion to the sputtered metal foil. However, the polyimide film with high dimensional stability usually has the problem of low adhesion to the sputtered metal foil.

[0009] Therefore, there is an urgent need for a polyimide film that simultaneously has high dimensional stability and excellent adhesion to the sputtered metal foil.

[0010] In particular, there is an increasing need to minimize the problem of reduced adhesion to the sputtered metal foil due to dimensional changes of the polyimide film during the sputtering process and subsequent processes.

[0011] The matters described in the above background art are used to help understand the background of the invention, and may include matters of prior art that are not known to those of ordinary skill in the art of this technology.

[0012] [Prior Art Documents]

[0013] [Patent Documents]

[0014] Patent Document 1: Korean Patent Publication No. 10-2020-0120515. Summary of the Invention

[0015] [Technical Problem]

[0016] Therefore, an object of the present invention is to provide a multi-layer polyimide film that simultaneously has high dimensional stability and excellent adhesion.

[0017] In particular, an object is to provide a multi-layer polyimide film with excellent surface hardness that minimizes the problem of reduced adhesion to the sputtered metal foil during the sputtering process and subsequent processes.

[0018] However, the problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those of ordinary skill in the art from the following description.

[0019] [Technical Solution]

[0020] One aspect of the present invention aimed at achieving the above object provides a multi-layer polyimide film, including: a core layer; and

[0021] A first surface layer and a second surface layer respectively formed on one outer surface of the above core layer and the opposite surface of the above outer surface;

[0022] The surface hardness measured by a nanoindenter is 0.4 GPa or more and 0.6 GPa or less.

[0023] On the other hand, the present invention provides a flexible metal foil laminate including the above-mentioned multi-layer polyimide film and a conductive metal foil.

[0024] On yet another aspect, the present invention provides an electronic component including the above-mentioned flexible metal foil laminate.

[0025] [Advantages of the Invention]

[0026] By providing a multi-layer polyimide film in which the ratio of the dianhydride and diamine components is adjusted, the present invention provides a multi-layer polyimide film having excellent dimensional stability and adhesiveness.

[0027] Such a multi-layer polyimide film can be applied to various fields of multi-layer polyimide films that require excellent dimensional stability and adhesiveness. For example, it can be applied to a flexible metal foil laminate manufactured by a metallization method or an electronic component including such a flexible metal foil laminate. Detailed Embodiments

[0028] The terms or words used in this specification and the claims should not be construed in accordance with their ordinary meanings or dictionary definitions. Instead, based on the principle that "the inventor can appropriately define the concept of terms in order to best explain his own invention", they should only be construed as meanings and concepts that conform to the technical idea of the present invention.

[0029] Therefore, the configurations of the embodiments described in this specification are merely one of 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 variations that can replace it 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 "comprising", "including" or "having" are used to specify the presence of features, numbers, steps, components 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, components or combinations thereof is not precluded in advance.

[0031] In this specification, "dianhydride" means including its precursors or derivatives, which may not technically be dianhydrides, but nevertheless react with diamines to form polyamic acids, which can be transformed into polyimides again.

[0032] In this specification, "diamine" means including its precursors or derivatives, which may not technically be diamines, but nevertheless react with dianhydrides to form polyamic acids, which can be transformed into polyimides again.

[0033] In this specification, when a quantity, concentration, or other value or parameter is given by listing a range, a preferred range, or a preferred upper limit value and a preferred lower limit value, regardless of whether the range is disclosed independently, 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.

[0034] When a range of values is mentioned in this specification, as long as it is not stated differently, the range is meant to include its endpoints and all integers and fractions within the range. It is meant that the scope of the present invention is not limited to the specific values mentioned when defining the range.

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

[0036] A multilayer polyimide film according to an embodiment of the present invention may include a core layer and a first surface layer and a second surface layer respectively formed on one outer surface of the core layer and the opposite surface of the outer surface. The surface hardness measured by a nanoindenter may be 0.4 GPa or more and 0.6 GPa or less.

[0037] That is, the above multilayer polyimide film may be a multilayer polyimide film having a three-layer structure in which a first surface layer and a second surface layer are respectively formed on one outer surface of the core layer and the opposite surface of the outer surface with the core layer as the center.

[0038] The above core layer of the multilayer polyimide film may impart excellent dimensional stability to the multilayer polyimide film, and the above first surface layer and second surface layer may impart excellent surface properties (surface hardness and adhesion) to the multilayer polyimide film to improve the performance of the flexible metal foil laminate.

[0039] For example, the hardness of the above surface may be 0.45 GPa or more and 0.55 GPa or less.

[0040] If it exceeds the above range of surface hardness, the vapor deposition of the metal foil becomes difficult, and the room-temperature adhesion of the above multilayer polyimide film becomes weak. If it is lower than the above range of surface hardness, the thermal stability and heat-resistant adhesion of the above multilayer polyimide film will decrease.

[0041] In one embodiment, the coefficient of thermal expansion of the above multilayer polyimide film may be 2.0 ppm / °C or more and 5.0 ppm / °C or less, and the coefficient of moisture absorption expansion may be 3.0 ppm / %RH or more and 6.0 ppm / %RH or less.

[0042] For example, the above thermal expansion coefficient can be 3.0 ppm / °C or less, 4.0 ppm / °C or less, and the above moisture absorption expansion coefficient can be 4.0 ppm / %RH or more, 5.0 ppm / %RH or more.

[0043] If it exceeds or is lower than the above range of the thermal expansion coefficient and / or the moisture absorption expansion coefficient, the process error in the sputtering process increases, and the performance of the flexible metal foil laminate will deteriorate.

[0044] In particular, if it exceeds the above range of the thermal expansion coefficient, the heat resistance stability of the vapor-deposited metal foil and the polyimide film will deteriorate. If it is lower than the above range of the thermal expansion coefficient, the adhesion of the above polyimide film to the metal foil at room temperature will deteriorate.

[0045] In one implementation example, the adhesion of the above multi-layer polyimide film to the metal foil at room temperature can be 0.6 kgf / cm or more and 0.9 kgf / cm or less, and the heat-resistant adhesion to the metal foil can be 0.3 kgf / cm or more and 0.6 kgf / cm or less.

[0046] The above adhesion at room temperature can be the adhesion between the polyimide film and the metal foil measured at room temperature (15 - 25°C) after a metal foil (e.g., copper foil) is laminated on the above polyimide film through a sputtering process.

[0047] In addition, the above heat-resistant adhesion can be the adhesion between the polyimide film and the metal foil measured after being placed at a high temperature (100 - 200°C) for a long time (100 - 300 hours) after a metal foil (e.g., copper foil) is laminated on the above polyimide film through a sputtering process.

[0048] As an example, the above adhesion at room temperature can be 0.6 kgf / cm or more and 0.83 kgf / cm or less, and the above heat-resistant adhesion can be 0.45 kgf / cm or more and 0.50 kgf / cm or less.

[0049] If it exceeds or is lower than the above range of the adhesion at room temperature and / or the heat-resistant adhesion, problems will occur in the production process of the product using the above multi-layer polyimide film.

[0050] In one implementation example, the adhesion reduction rate represented by the following mathematical formula 1 can be 50% or less.

[0051] [Mathematical formula 1]

[0052] Adhesion reduction rate (%) = [(Adhesion at room temperature to the metal foil - Heat-resistant adhesion to the metal foil) / Adhesion at room temperature to the metal foil] * 100

[0053] In one implementation example, the above-mentioned core layer of the multi-layer polyimide film in this case can be obtained by subjecting a polyamic acid solution containing a dianhydride component and a diamine component to an imidization reaction. Among them, the above-mentioned dianhydride component includes biphenyltetracarboxylic dianhydride (3,3',4,4'-biphenyltetracarboxylic dianhydride, BPDA) and pyromellitic dianhydride (pyromellitic dianhydride, PMDA), and the above-mentioned diamine component includes p-phenylene diamine (p-phenylene diamine, PPD) and m-tolidine (m-tolidine, MTD).

[0054] In addition, the above-mentioned first surface layer and second surface layer of the multi-layer polyimide film in this case are obtained by subjecting a polyamic acid solution containing a dianhydride component and a diamine component to an imidization reaction. Among them, the above-mentioned dianhydride component includes biphenyltetracarboxylic dianhydride and pyromellitic dianhydride, and the above-mentioned diamine component includes two or more selected from the group consisting of p-phenylene diamine, 4,4-oxydianiline (4,4-oxydianiline, ODA), and 1,3-bis(4-aminophenoxy)benzene (1,3-bis(4-aminophenoxy)benzene, TPE-R).

[0055] However, the above-mentioned core layer of the multi-layer polyimide film in this case may not contain 1,3-bis(4-aminophenoxy)benzene and 4,4-oxydianiline as diamines.

[0056] For example, as the diamine component of the above-mentioned first surface layer and second surface layer of the multi-layer polyimide film, a combination of p-phenylene diamine and 4,4-oxydianiline or a combination of p-phenylene diamine and 1,3-bis(4-aminophenoxy)benzene can be used.

[0057] On the other hand, the components and ratios of the above-mentioned first surface layer and the second surface layer may be the same or different.

[0058] The polyimide chain derived from biphenyltetracarboxylic dianhydride has a structure named charge transfer complex (CTC: Charge transfer complex), that is, a regular linear structure in which an electron donor (electron donnor) and an electron acceptor (electron acceptor) are arranged close to each other, strengthening the intermolecular interaction (intermolecular interaction).

[0059] In addition, pyromellitic dianhydride is a dianhydride component with a relatively rigid structure, which can endow the polyimide film with appropriate elasticity, so it is preferred.

[0060] On the other hand, biphenyltetracarboxylic dianhydride contains two benzene rings corresponding to the aromatic moiety. In contrast, pyromellitic dianhydride contains one benzene ring corresponding to the aromatic moiety.

[0061] In the dianhydride component, an increase in the content of pyromellitic dianhydride can be understood as an increase in the imide groups within the molecule when based on the same molecular weight. This can be understood as the ratio of the imide groups derived from the above-mentioned pyromellitic dianhydride relative to the imide groups derived from biphenyltetracarboxylic dianhydride increasing on the polyimide polymer chain.

[0062] The above-mentioned p-phenylenediamine is a rigid monomer. With an increase in the content of p-phenylenediamine, the synthesized polyimide has a more linear structure, which helps to improve the mechanical properties of the polyimide.

[0063] In addition, m-xylylenediamine particularly has a methyl group that exhibits hydrophobicity, which helps the polyimide film to have low moisture absorption characteristics, and the low moisture absorption characteristics are related to the dimensional stability against moisture.

[0064] In one implementation example, based on the total content of the above-mentioned dianhydride component in the core layer being 100 mol%, the content of biphenyltetracarboxylic dianhydride can be 40 mol% or more and 60 mol% or less, and the content of pyromellitic dianhydride can be 40 mol% or more and 60 mol% or less. Based on the total content of the above-mentioned diamine component in the core layer being 100 mol%, the content of p-phenylenediamine can be 50 mol% or more and 70 mol% or less, and the content of m-xylylenediamine can be 30 mol% or more and 50 mol% or less.

[0065] In addition, based on the total content of the above-mentioned dianhydride component in the surface layer being 100 mol%, the content of biphenyltetracarboxylic dianhydride can be 40 mol% or more and 98 mol% or less, and the content of pyromellitic dianhydride can be 2 mol% or more and 60 mol% or less. Based on the total content of the above-mentioned diamine component in the surface layer being 100 mol%, the content of p-phenylenediamine can be 40 mol% or more and 95 mol% or less, the content of diaminodiphenyl ether can be 30 mol% or less, and the content of 1,3-bis(4-aminophenoxy)benzene can be 60 mol% or less.

[0066] For example, based on the total content of the above-mentioned dianhydride component in the surface layer being 100 mol%, the content of biphenyltetracarboxylic dianhydride can be 50 mol% or more and 97 mol% or less, and the content of pyromellitic dianhydride can be 3 mol% or more and 50 mol% or less.

[0067] In addition, based on the total content of the diamine component in the above-mentioned surface layer being 100 mol%, the content of the above-mentioned p-phenylenediamine can be 55 mol% or more and 87 mol% or less, the content of the above-mentioned diaminodiphenyl ether can be 13 mol% or less, and the content of the above-mentioned 1,3-bis(4-aminophenoxy)benzene can be 45 mol% or less.

[0068] On the other hand, the ratio of the core layer thickness of the above-mentioned multilayer polyimide film to the sum of the thicknesses of the above-mentioned first surface layer and the second surface layer (core layer thickness: sum of the thicknesses of the first surface layer and the second surface layer) can be 15:1 to 5:1.

[0069] The thicknesses of the above-mentioned first surface layer and the second surface layer can be the same or different.

[0070] In the present invention, for example, the following methods can be used to manufacture polyamic acid:

[0071] (1) A method in which the entire amount of the diamine component is added to a solvent, and then the dianhydride component is added to substantially equimolar with the diamine component and polymerization is carried out;

[0072] (2) A method in which the entire amount of the dianhydride component is added to a solvent, and then the diamine component is added to substantially equimolar with the dianhydride component and polymerization is carried out;

[0073] (3) A method in which a part of the diamine component is added to a solvent, and then, relative to the reaction components, a part of the dianhydride component is mixed at a ratio of about 95 to 105 mol%, the remaining diamine component is added, and then the remaining dianhydride component is added to make the diamine component and the dianhydride component substantially equimolar and polymerization is carried out;

[0074] (4) A method in which the dianhydride component is added to a solvent, and then, relative to the reaction components, a part of the diamine compound is mixed at a ratio of 95 to 105 mol%, the other dianhydride component is added, and then the remaining diamine component is added to make the diamine component and the dianhydride component substantially equimolar and polymerization is carried out;

[0075] (5) A method in which a part of the diamine component reacts with a part of the dianhydride component 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 reacts with a part of the dianhydride component to make one of them in excess to form a second composition, and then the first composition and the second composition are mixed to complete 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 in excess, and when the dianhydride component is in excess in the first composition, then in the second composition, the diamine component is in excess. The first composition and the second composition are mixed so that the total diamine component and dianhydride component used in the reaction are substantially equimolar and polymerization is carried out.

[0076] In the present invention, the polymerization method of the polyamic acid as described above can be defined as a random polymerization method. The polyimide film manufactured from the polyamic acid of the present invention through the process as described above is preferably applicable in maximizing the effects of improving the dimensional stability and chemical resistance of the present invention.

[0077] However, since the length of the repeating units in the polymer chain described above is relatively short, there are limitations in exhibiting various excellent properties of the polyimide chain derived from the dianhydride component. Therefore, the polymerization method of the polyamic acid that can be particularly preferably utilized in the present invention can be a block polymerization method.

[0078] On the other hand, the solvent for synthesizing the polyamic acid is not particularly limited, and any solvent can be used as long as it can dissolve the polyamic acid, but an amide solvent is preferably used.

[0079] Specifically, the above organic solvent can be an organic polar solvent, and in detail, it can be an aprotic polar solvent. For example, it can be one or more selected from the group consisting of N,N-dimethylformamide (DMF), N,N-dimethylacetamide, N-methylpyrrolidone (NMP), γ-butyrolactone (GBL), and diglyme, but is not limited thereto, and can be used alone or in combination of two or more as needed.

[0080] In one example, N,N-dimethylformamide and N,N-dimethylacetamide can be particularly preferably used as the above organic solvent.

[0081] In addition, in the process of manufacturing the polyamic acid, a filler can also be added for the purpose of improving various film properties such as slidability, thermal conductivity, corona resistance, and ring hardness. The added filler is not particularly limited, and as a preferred example, it can be, for example, silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica, etc.

[0082] The particle size of the filler is not particularly limited, and can be determined according to the film properties to be modified and the type of filler added. Generally, the average particle size is from 0.05 μm to 100 μm, preferably from 0.1 μm to 75 μm, more preferably from 0.1 μm to 50 μm, and particularly preferably from 0.1 μm to 25 μm.

[0083] If the particle size is below this range, it is difficult to exhibit the modification effect, and if it exceeds this range, there are cases where the surface property is severely damaged or the mechanical properties are significantly reduced.

[0084] In addition, the addition amount of the filler is not particularly limited and can be determined according to the film properties to be modified, the particle size of the filler, etc. Generally, the addition amount of the filler is 0.01 to 100 parts by weight, preferably 0.01 to 90 parts by weight, more preferably 0.02 to 80 parts by weight, based on 100 parts by weight of the polyimide.

[0085] If the addition amount of the filler is below this range, it is difficult to exhibit the modification effect of the filler. If it exceeds this range, there is a possibility that the mechanical properties of the film will be greatly damaged. The method of adding the filler is not particularly limited, and any known method can also be used.

[0086] In the manufacturing method of the present invention, the polyimide film can be manufactured by a thermal imidization method and a chemical imidization method.

[0087] In addition, it can also be manufactured by a composite imidization method using both the thermal imidization method and the chemical imidization method.

[0088] The so-called above-mentioned thermal imidization method is a method of inducing an imidization reaction by using a heat source such as a hot air or an infrared dryer without using a chemical catalyst.

[0089] The above-mentioned thermal imidization method can perform heat treatment on the above-mentioned gel film at a variable temperature in the range of 100°C to 600°C to imidize the amide groups present in the gel film. Specifically, it can be performed at 200°C to 500°C, and more specifically, at 300°C to 500°C to imidize the amide groups present in the gel film.

[0090] However, during the formation of the gel film, a part (about 0.1 mol% to 10 mol%) of the amide acid is also imidized. Therefore, the polyamic acid composition can be dried at a variable temperature in the range of 50°C to 200°C, which can also be included in the scope of the above-mentioned thermal imidization method.

[0091] Regarding the chemical imidization method, a polyimide film can be manufactured by using a dehydrating agent and an imidizing agent according to a method well-known in the art.

[0092] Among them, the so-called "dehydrating agent" refers to a substance that promotes the cyclization reaction by dehydrating the polyamic acid. As non-limiting examples thereof, aliphatic acid anhydrides, aromatic acid anhydrides, N,N'-dialkylcarbodiimides, halogenated lower aliphatics, halogenated lower fatty acid anhydrides, arylphosphine dihalides, and thionyl halides can be mentioned. Among them, from the viewpoints of availability and cost, aliphatic acid anhydrides are preferred. As non-limiting examples thereof, acetic anhydride (or acetic anhydride, AA), propionic anhydride, and lactic anhydride can be mentioned, and they can be used alone or in combination of two or more.

[0093] In addition, the so-called imidizing agent refers to a substance having the effect of promoting the cyclization reaction with polyamic acid, and examples thereof may include imine components such as aliphatic tertiary amines, aromatic tertiary amines, and heterocyclic tertiary amines. Among them, from the perspective of reactivity as a catalyst, heterocyclic tertiary amines are preferred. Non-limiting examples of heterocyclic tertiary amines may include, for example, quinoline, isoquinoline, β-methylpyridine (BP), pyridine, etc., which may be used alone or in combination of two or more.

[0094] The addition amount of the dehydrating agent is preferably within the range of 0.5 to 5 moles, particularly preferably within the range of 1.0 to 4 moles, relative to 1 mole of the amic acid group in the polyamic acid. In addition, the addition amount of the imidizing agent is preferably within the range of 0.05 to 2 moles, particularly preferably within the range of 0.2 to 1 mole, relative to 1 mole of the amic acid group in the polyamic acid.

[0095] If the above dehydrating agent and imidizing agent are below the above range, chemical imidization is insufficient, cracks will form on the manufactured polyimide film, and the mechanical strength of the film will also decrease. In addition, if these addition amounts exceed the above range, imidization will proceed too quickly. At this time, it will be difficult to cast into a film form or the manufactured polyimide film will exhibit brittle characteristics, so it is not recommended.

[0096] As an example of the composite imidization method, after adding a dehydrating agent and an imidizing agent to a polyamic acid solution, it can be heated at 80°C to 200°C, preferably at 100°C to 180°C. After partial curing and drying, it is heated at 200°C to 400°C for 5 to 400 seconds, thereby a polyimide film can be manufactured.

[0097] On the other hand, the multi-layer polyimide film of the present invention described so far can be manufactured by any one or more of co-extrusion or coating.

[0098] The co-extrusion method is a method of manufacturing a multi-layer polyimide film with a high productivity by filling a polyamic acid solution or a polyimide resin manufactured by imidizing it into a storage tank, extruding multiple layers on a casting belt using a co-extrusion die, and then curing. Different types of polyimide resins between interfaces can be miscible to ensure high interface adhesion reliability.

[0099] For example, the method for manufacturing a multilayer polyimide film of the present invention may include: a first filling step of filling a first storage tank with a first polyamic acid solution or a first polyimide resin (i.e., a first solution) obtained by imidizing the first polyamic acid solution; a second filling step of filling a second storage tank with a second polyamic acid solution or a second polyimide resin (i.e., a second solution) obtained by imidizing the second polyamic acid solution; a co-extrusion step of co-extruding the first solution and the second solution through a co-extrusion die formed inside a first flow path connected to the first storage tank, a second flow path and a third flow path respectively connected to the second storage tank; and a curing step of curing the co-extruded first solution and second solution.

[0100] The first polyamic acid solution constituting the above core layer can be manufactured by polymerizing a dianhydride component containing biphenyltetracarboxylic dianhydride and pyromellitic dianhydride with a diamine component containing p-phenylenediamine and m-xylylenediamine in a solvent.

[0101] On the other hand, the second polyamic acid solution constituting the above first surface layer and second surface layer can be manufactured by polymerizing a dianhydride component containing biphenyltetracarboxylic dianhydride and pyromellitic dianhydride with two or more diamine components selected from the group consisting of p-phenylenediamine, diaminodiphenyl ether, and 1,3-bis(4-aminophenoxy)benzene in a solvent.

[0102] Based on the total content of the above dianhydride component of the first polyamic acid being 100 mol%, the content of biphenyltetracarboxylic dianhydride can be 40 mol% or more and 60 mol% or less, and the content of pyromellitic dianhydride can be 40 mol% or more and 60 mol% or less. Based on the total content of the above diamine component being 100 mol%, the content of p-phenylenediamine can be 50 mol% or more and 70 mol% or less, and the content of m-xylylenediamine can be 30 mol% or more and 50 mol% or less.

[0103] On the other hand, based on the total content of the above dianhydride component of the second polyamic acid being 100 mol%, the content of biphenyltetracarboxylic dianhydride can be 40 mol% or more and 98 mol% or less, and the content of pyromellitic dianhydride can be 2 mol% or more and 60 mol% or less. Based on the total content of the above diamine component being 100 mol%, the content of p-phenylenediamine can be 40 mol% or more and 95 mol% or less, the content of diaminodiphenyl ether can be 30 mol% or less, and the content of 1,3-bis(4-aminophenoxy)benzene can be 60 mol% or less.

[0104] The present invention provides a flexible metal foil laminate including the above polyimide film and a conductive metal foil.

[0105] The metal foil to be used is not particularly limited. For example, when the multilayer film of the present invention is used for electronic devices or electrical equipment applications, 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.

[0106] 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 surfaces of these metal foils.

[0107] In the present invention, the thickness of the above-mentioned metal foil is not particularly limited, as long as it is a thickness that can fully exert its function according to its use.

[0108] The flexible metal foil laminate of the present invention can have a structure in which a metal foil is laminated on one side of the above-mentioned polyimide film or an adhesive layer containing a thermoplastic polyimide is attached to one side of the above-mentioned polyimide film, and the lamination is carried out in a state where the above-mentioned metal foil is attached to the adhesive layer.

[0109] The present invention also provides an electronic component including the above-mentioned flexible metal foil laminate as a signal transmission circuit.

[0110] The functions and effects of the invention will be described in more detail below through specific embodiments of the invention. However, such embodiments are only presented as examples of the invention, and the scope of the invention is not limited thereby.

[0111] Production Example 1: Production of the core layer (first composition)

[0112] While injecting nitrogen into a 500 ml reactor equipped with a stirrer and a nitrogen injection / discharge tube, DMF was introduced. After setting the reactor temperature to 30°C, p-phenylenediamine (PPD) and biphenyltetracarboxylic dianhydride (BPDA) were dissolved, and then the temperature of the reactor was raised to 40°C while continuing to stir for 120 minutes to polymerize them.

[0113] Then, m-tolidine (MTD) and pyromellitic dianhydride (PMDA) were further added to the prepared polymer solution of p-phenylenediamine and biphenyltetracarboxylic dianhydride, and polymerization was continued by heating and stirring to obtain a first composition containing a first polyamic acid solution.

[0114] Production Example 2: Production of the first surface layer and the second surface layer (second composition)

[0115] While injecting nitrogen into a 500-ml reactor equipped with a stirrer and a nitrogen injection / discharge pipe, DMF was introduced. After setting the reactor temperature to 30 °C, as diamine components, a part of p-phenylenediamine (PPD), m-tolidine (MTD), 1,3-bis(4-aminophenoxy)benzene (TPE-R), and diaminodiphenyl ether (ODA) was selected and introduced. As dianhydride components, biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) were introduced and it was confirmed that they were completely dissolved.

[0116] Then, under a nitrogen atmosphere, while heating to raise the reactor temperature to 40 °C, stirring was continued for 120 minutes, and a second composition containing a second polyamic acid solution was obtained.

[0117] Production Example 3: Production of the multilayer polyimide film

[0118] The first composition prepared in Preparation Example 1 above was introduced into the first storage tank of the coextrusion die, and the second composition prepared in Preparation Example 2 above was introduced into the second storage tank.

[0119] Then, coextrusion was carried out in the order of the second composition, the first composition, and the second composition on the endless belt to form the precursor composition into a film with a thickness of about 35 μm. At this time, when the first composition was extruded from the first storage tank, a mixture of isoquinoline, dimethylformamide, and acetic anhydride was mixed from the catalyst storage tank.

[0120] Next, heat treatment was carried out at a temperature of about 150 °C, and it was heated again from 150 °C to 600 °C in a high-temperature tenter, and then cooled at 25 °C, and a multilayer polyimide film having a first surface layer / core layer / second surface layer structure was obtained.

[0121] [Examples and Comparative Examples]

[0122] As shown in Table 1 and Table 2 below, the components and ratios of the first polyamic acid for manufacturing the core layer and the second polyamic acid for manufacturing the surface layer were adjusted respectively, and multilayer polyimide films were manufactured according to Preparation Examples 1 to 3.

[0123] The thickness of the core layer was 32 μm, and the thicknesses of the first surface layer and the second surface layer were 1.5 μm respectively.

[0124] However, in Comparative Examples 1 to 4, single-layer polyimide films were prepared. That is, after preparing the second polyamic acid according to Preparation Example 2, 3 moles of acetic anhydride and 1 mole of isoquinoline were added per mole of amic acid group to the prepared polyamic acid solution to obtain a precursor composition for the polyimide film.

[0125] The above-described precursor composition for a polyimide film was cast on a SUS plate using a doctor blade and dried at 110°C for 4 minutes to produce a gel film.

[0126] After separating the above gel film from the SUS plate, it was heat-treated at 280°C for 4 minutes and then heat-treated at 380°C for 4 minutes to produce a polyimide film having a thickness of 35 μm.

[0127] The thickness of the produced polyimide film was measured using a film thickness measuring instrument (Electric Film thickness tester) of Anritsu Corporation.

[0128] [Table 1]

[0129]

[0130] [Table 2]

[0131]

[0132] Production Example 4: Production of the flexible metal foil laminate

[0133] On the (multilayer) polyimide films of Examples 1 to 3 and Comparative Examples 1 to 6 produced according to Production Examples 1 to 3, a copper film having a thickness of about 80 to 300 nm was vapor-deposited by sputtering as a copper seed layer for an electroplating electrode, and a copper conductive layer having a thickness of about 8 to 9 μm was formed by electroplating.

[0134] (1) Measurement of surface hardness

[0135] After cutting the (multilayer) polyimide films of Examples 1 to 3 and Comparative Examples 1 to 6 produced according to Production Examples 1 to 3 into a width of 100 mm and a length of 100 mm, the surface hardness was measured using an iNano nanoindentation instrument of KLA-Tenco Corporation that can measure the force applied to the probe during pressing the probe on the sample.

[0136] (2) Measurement of coefficient of thermal expansion

[0137] The coefficient of thermal expansion (CTE) was measured using a TA Instruments thermomechanical analyzer model Q400. After cutting the (multi-layer) polyimide films of Examples 1 to 3 and Comparative Examples 1 to 6 manufactured according to Production Example 1 into strips 4 mm wide and 20 mm long, a tension of 0.05 N was applied in a nitrogen atmosphere, and the temperature was raised from 30 °C to 400 °C at a rate of 10 °C / min and then cooled at the same rate. Meanwhile, the slope in the temperature range from 50 °C to 200 °C (the rate of dimensional change (ppm / °C) caused by the temperature change in the range from 50 °C to 200 °C) was measured.

[0138] (3) Measurement of coefficient of hygroscopic expansion

[0139] The coefficient of hygroscopic expansion (CHE) was measured as follows: A minimum weight (about 1 g for a 25 mm × 150 mm sample) was applied to prevent the (multi-layer) polyimide films of Examples 1 to 3 and Comparative Examples 1 to 6 manufactured according to Production Example 1 from loosening. In this state, the humidity was adjusted to 3% RH at 25 °C and the film was allowed to absorb moisture until fully saturated and the dimensions were measured. Then the humidity was adjusted to 90% RH, and after saturated moisture absorption in the same way, the dimensions were measured again. The rate of dimensional change was calculated from the two results.

[0140] (4) Measurement of adhesion at room temperature

[0141] Using the (multi-layer) polyimide films of Examples 1 to 3 and Comparative Examples 1 to 6 manufactured according to Production Examples 1 to 3, after applying a wet etching process to the flexible metal laminate manufactured according to Production Example 4 and etching it into rods 2 mm wide, the peel adhesion at room temperature was measured by a 90° peel test using a Universal Testing Machine at a tensile speed of 20 mm / min.

[0142] The above wet etching process was carried out in the following order: A rod-shaped coating film 2 mm wide was applied to the above flexible metal foil laminate, and an etching solution (ferric chloride [iron(III) chloride]) was sprayed to etch the metal, thereby forming a rod-shaped pattern. Then the coating film was removed.

[0143] (5) Measurement of heat-resistant adhesion

[0144] Using the (multi-layer) polyimide films of Examples 1 to 3 and Comparative Examples 1 to 6 manufactured according to Production Examples 1 to 3, after applying a wet etching process to the flexible metal laminate manufactured according to Production Example 4 and etching it into rods 2 mm wide, it was heat-treated at 150 °C for 168 hours.

[0145] The above wet etching process was carried out in the same manner as the measurement of the peel adhesion at room temperature.

[0146] Then, using a Universal Testing Machine, the heat-resistant adhesion was measured by a 90° peel test while stretching at a speed of 20 mm / min.

[0147] The surface hardness, coefficient of thermal expansion (CTE), coefficient of heat and moisture expansion (CHE), room-temperature adhesion, and heat-resistant adhesion of the (multi-layer) polyimide films of Examples 1 to 3 and Comparative Examples 1 to 6 measured by the above measurement method are shown in Table 3 below.

[0148] [Table 3]

[0149]

[0150] The measurement results show that the polyimide films of Examples 1 to 3 exhibit a surface hardness of 0.4 GPa or more and 0.6 GPa or less, a coefficient of thermal expansion of 2.0 ppm / °C or more and 5.0 ppm / °C or less, a coefficient of heat and moisture expansion of 3.0 ppm / %RH or more and 6.0 ppm / %RH or less, a room-temperature adhesion of 0.6 kgf / cm or more and 0.9 kgf / cm or less, a heat-resistant adhesion of 0.3 kgf / cm or more and 0.6 kgf / cm or less, and an adhesion reduction characteristic of 50% or less.

[0151] In contrast, for the (multi-layer) polyimide films of Comparative Examples 1 to 6, one or more of the surface hardness, coefficient of thermal expansion, coefficient of heat and moisture expansion, room-temperature adhesion, heat-resistant adhesion, and adhesion reduction characteristic do not meet the characteristic range of the multi-layer polyimide film of this case.

[0152] Specifically, compared with the multi-layer polyimide films of Examples 1 to 3 in which the polyimide film of Comparative Example 1 was used as the core layer, the surface hardness and room-temperature adhesion of the polyimide film of Comparative Example 1 do not meet the characteristic range of the multi-layer polyimide film of this case.

[0153] On the other hand, for the polyimide films of Comparative Examples 2 to 4, the same components and ratios as those of the surface layers of the multi-layer polyimide films of Examples 1 to 3 were used, and the coefficient of thermal expansion and / or coefficient of heat and moisture expansion of the polyimide films of Comparative Examples 2 to 4 do not meet the characteristic range of the multi-layer polyimide film of this case.

[0154] In addition, although the multi-layer polyimide film of Comparative Example 5 used the core layer of the multi-layer polyimide films of Examples 1 to 3, the types and contents of the surface layer components were different, and the surface hardness, coefficient of thermal expansion, and heat-resistant adhesion of the multi-layer polyimide film of Comparative Example 5 do not meet the characteristic range of the multi-layer polyimide film of this case.

[0155] On the other hand, the contents of the dianhydride component in the core layer and the types and contents of the diamine components in the surface layer of the multilayer polyimide film of Comparative Example 6 are different from those of the multilayer polyimide films of Examples 1 to 3. The surface hardness, coefficient of thermal expansion, adhesion at room temperature, and heat-resistant adhesion of the multilayer polyimide film of Comparative Example 6 cannot meet the characteristic range of the multilayer polyimide film of this case.

[0156] Therefore, it can be confirmed that the multilayer polyimide films of Examples 1 to 3 manufactured within the appropriate range of this case are excellent in surface hardness, thermal dimensional stability, dimensional stability against moisture, and adhesion to copper foil. However, when it exceeds the appropriate range of this case, it is difficult to fully meet the surface hardness, thermal dimensional stability, dimensional stability against moisture, and adhesion to copper foil of the multilayer polyimide film of this case.

[0157] That is, it can be confirmed that the multilayer polyimide film having excellent surface hardness, dimensional stability, and adhesion to copper foil and fully meeting various conditions applicable to the application field is the multilayer polyimide film manufactured within the appropriate range of this case.

[0158] The examples of the multilayer polyimide film and the manufacturing method of the multilayer polyimide film of the present invention only enable those of ordinary skill in the art to which the present invention pertains to easily implement the preferred embodiments of the present invention, and are not limited to the above embodiments. Therefore, the scope of the rights of the present invention is not limited thereby. Therefore, the true technical protection scope of the present invention should be determined according to the technical idea of the appended claims for patent. In addition, within the scope not exceeding the technical idea of the present invention, various substitutions, deformations, and changes can be realized, which is self-evident to those skilled in the art, and the parts that can be easily changed by those skilled in the art are also included in the scope of the rights of the present invention, which is self-evident.

[0159] Industrial Applicability

[0160] The present invention provides a multilayer polyimide film in which the ratio of the dianhydride and diamine components is adjusted, thereby providing a multilayer polyimide film having excellent surface hardness, dimensional stability, and adhesion.

[0161] Such a multilayer polyimide film can be applied to multiple fields of multilayer polyimide films that require excellent dimensional stability and adhesion. For example, it can be applied to flexible metal foil laminates manufactured by the metallization method or electronic components including such flexible metal foil laminates.

Claims

1. A multi-layer polyimide film, comprising: a core layer; a first surface layer and a second surface layer respectively formed on one outer surface of the core layer and the opposite surface of the outer surface, measuring the surface hardness of the multi-layer polyimide film with a nanoindenter to be 0.4 GPa or more and 0.6 GPa or less.

2. The multi-layer polyimide film according to claim 1, wherein The thermal expansion coefficient of the multi-layer polyimide film is 2.0 ppm / °C or more and 5.0 ppm / °C or less, and the moisture absorption expansion coefficient is 3.0 ppm / %RH or more and 6.0 ppm / %RH or less.

3. The multilayer polyimide film according to claim 1, wherein The normal temperature adhesion of the multi-layer polyimide film to the metal foil is 0.6 kgf / cm or more and 0.9 kgf / cm or less, and the heat-resistant adhesion to the metal foil is 0.3 kgf / cm or more and 0.6 kgf / cm or less.

4. The multilayer polyimide film according to claim 1, wherein, The core layer is obtained by subjecting a polyamic acid solution containing a dianhydride component and a diamine component to an imidization reaction, wherein the dianhydride component includes biphenyltetracarboxylic dianhydride and pyromellitic dianhydride, and the diamine component includes p-phenylenediamine and m-xylylenediamine; The first surface layer and the second surface layer are obtained by subjecting a polyamic acid solution containing a dianhydride component and a diamine component to an imidization reaction, wherein the dianhydride component includes biphenyltetracarboxylic dianhydride and pyromellitic dianhydride, and the diamine component includes two or more selected from the group consisting of p-phenylenediamine, diaminodiphenyl ether, and 1,3-bis(4-aminophenoxy)benzene.

5. The multilayer polyimide film according to claim 4, wherein, Based on the total content of the dianhydride component of the core layer being 100 mol%, the content of biphenyltetracarboxylic dianhydride is 40 mol% or more and 60 mol% or less, and the content of pyromellitic dianhydride is 40 mol% or more and 60 mol% or less. Based on the total content of the diamine component of the core layer being 100 mol%, the content of p-phenylenediamine is 50 mol% or more and 70 mol% or less, and the content of m-xylylenediamine is 30 mol% or more and 50 mol% or less.

6. The multi-layer polyimide film according to claim 4, wherein, Based on the total content of the dianhydride component of the first surface layer and the second surface layer being 100 mol%, the content of biphenyltetracarboxylic dianhydride is 40 mol% or more and 98 mol% or less, and the content of pyromellitic dianhydride is 2 mol% or more and 60 mol% or less. Based on the total content of the diamine component of the first surface layer and the second surface layer being 100 mol%, the content of p-phenylenediamine is 40 mol% or more and 95 mol% or less, the content of diaminodiphenyl ether is 30 mol% or less, and the content of 1,3-bis(4-aminophenoxy)benzene is 60 mol% or less.

7. The multilayer polyimide film according to any one of claims 1 to 6, wherein, The multi-layer polyimide film is manufactured according to any one or more selected from the group consisting of co-extrusion and coating.

8. A flexible metal foil laminate, comprising the multi-layer polyimide film according to any one of claims 1 to 6; and a conductive metal foil.

9. An electronic component, comprising the flexible metal foil laminate according to claim 8.

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