Multilayer polyimide film and method for producing the same

Abstract

The present invention provides a multilayer polyimide film comprising a core layer and a first skin layer and a second skin layer formed on one outer surface and the opposite surface of the core layer, respectively, and having a surface hardness of 0.4 GPa to 0.6 GPa as measured with a nanoindenter, and a method for manufacturing the same.

Description

[Technical Field]

[0001] The present invention relates to a multilayer polyimide film having excellent dimensional stability and adhesive strength, and more particularly to a multilayer polyimide film having high surface hardness and minimal decrease in adhesive strength between room temperature adhesive strength and heat resistant adhesive strength, and a method for manufacturing the same. [Background technology]

[0002] Polyimide (PI) is a polymeric material based on imide rings, which have excellent chemical stability and 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. Polyimide films have been attracting attention as materials for a variety of electronic devices that require the above-mentioned properties.

[0003] Examples of microelectronic components to which polyimide films are applied include thin, flexible circuit boards with high circuit integration density that can accommodate the trend toward lighter and smaller electronic products, and polyimide films are particularly widely used as insulating films for thin circuit boards. The thin circuit board generally has a structure in which a circuit including a metal foil is formed on an insulating film, and such a thin circuit board is broadly called a flexible metal foil clad laminate (FMC), and when a thin copper plate is used as the metal foil, it is more narrowly called a flexible copper clad laminate (FCCL).

[0004] Examples of methods for producing flexible metal foil laminates include (i) a casting method in which polyamic acid, a precursor of polyimide, is cast or applied onto metal foil and then imidized; (ii) a metallizing method in which a metal layer is formed directly on a polyimide film by sputtering; and (iii) a lamination method in which a polyimide film and metal foil are bonded together by heat and pressure using a thermoplastic polyimide. In particular, the metallizing method is a method for producing flexible metal foil laminates by sputtering a metal such as copper onto a polyimide film having a thickness of, for example, 20 to 38 μm, and then sequentially depositing a tie layer and a seed layer. This method is advantageous for forming ultra-fine circuits with a circuit pattern pitch of 35 μm or less, and is widely used to manufacture flexible metal foil laminates for COF (chip on film). Polyimide films used in flexible metal foil laminates produced by the metallization method must have high dimensional stability and adhesive strength with sputtered metal foil. However, polyimide films with high dimensional stability usually have the problem of reduced adhesive strength with sputtered metal foil.

[0005] Therefore, there is a strong demand for a polyimide film that simultaneously has high dimensional stability and excellent adhesion to sputtered metal foils. In particular, there is a growing need to minimize the decrease in adhesive strength between the polyimide film and the sputtered metal foil due to dimensional changes in the polyimide film during the sputtering process and subsequent processes. The matters described in the above background art are intended to help understand the background of the invention, and may include matters that are not prior art already known to those with ordinary skill in the field to which this technology belongs. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Korean Patent Publication No. 10-2020-0120515 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, an object of the present invention is to provide a multilayer polyimide film that has high dimensional stability and excellent adhesive strength at the same time. In particular, the present invention aims to provide a multilayer polyimide film that has excellent surface hardness and minimizes the decrease in adhesive strength with sputtered metal foil during the sputtering process and subsequent processes. However, the problems to be solved by the present invention are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0008] In order to achieve the above object, one aspect of the present invention is a polymerizable composition comprising: a core layer; a first skin layer and a second skin layer formed on one outer surface of the core layer and the opposite surface of the outer surface, respectively; The surface hardness measured by a nanoindenter is 0.4 GPa or more and 0.6 GPa or less. A multilayer polyimide film is provided.

[0009] Another aspect of the present invention provides a flexible metal foil laminate comprising the multilayer polyimide film and an electrically conductive metal foil.

[0010] Yet another aspect of the present invention provides an electronic component comprising the flexible metal foil laminate. [Effects of the Invention]

[0011] The present invention provides a multilayer polyimide film in which the composition ratio of dianhydride acid and diamine components is adjusted, thereby providing a multilayer polyimide film that is excellent not only in surface hardness and dimensional stability but also in adhesive strength. Such a multilayer polyimide film can be applied to various fields requiring a multilayer polyimide film with excellent dimensional stability and adhesive strength, such as flexible metal foil laminates manufactured by a metallizing method or electronic components including such flexible metal foil laminates. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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 the inventor can appropriately define the concept of the 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.

[0013] In this specification, the singular includes the plural unless the context clearly indicates otherwise. It should be understood that in this specification, the terms "comprise," "comprise," or "have" 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.

[0014] As used herein, "dianhydride acid" is intended to include precursors or derivatives thereof, which may not technically be dianhydrides, but which nevertheless will react with diamines to form polyamic acids, which can be converted back to polyimides.

[0015] As used herein, "diamine" is intended to include precursors or derivatives thereof, which may not technically be diamines, but which nevertheless must react with dianhydrides to form polyamic acids, which can then be converted back to polyimides.

[0016] 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 ranges are otherwise disclosed.

[0017] 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.

[0018] In this specification, the terms "from" and "to" in "from a to b" and "a to b" that indicate a numerical range are defined as ≧a and ≦b.

[0019] A multilayer polyimide film according to one embodiment of the present invention may include a core layer, a first skin layer formed on one outer surface of the core layer, and a second skin layer formed on the opposite outer surface of the core layer, and may have a surface hardness of 0.4 GPa to 0.6 GPa as measured by a nanoindenter. That is, the multilayer polyimide film may have a three-layer structure in which a first skin layer and a second skin layer are formed on one outer surface of the core layer and on the opposite surface of the core layer, respectively.

[0020] The core layer of the multilayer polyimide film imparts excellent dimensional stability to the multilayer polyimide film, and the first and second skin layers impart excellent surface properties (surface hardness and adhesive strength) to the multilayer polyimide film, thereby improving the performance of the flexible metal foil laminate. For example, the surface hardness may be 0.45 GPa or more and 0.55 GPa or less. If the surface hardness exceeds the above range, deposition of metal foil becomes difficult, resulting in a weakened room temperature adhesive strength of the multilayer polyimide film. If the surface hardness is below the above range, the thermal stability and heat-resistant adhesive strength of the multilayer polyimide film may be reduced.

[0021] In one embodiment, the multilayer polyimide film may have a thermal expansion coefficient of 2.0 ppm / ° C. to 5.0 ppm / ° C. and a hygroscopic expansion coefficient of 3.0 ppm / % RH to 6.0 ppm / % RH. For example, the thermal expansion coefficient may be 3.0 ppm / °C or less, or 4.0 ppm / °C or less, and the hygroscopic expansion coefficient may be 4.0 ppm / %RH or more, or 5.0 ppm / %RH or more. If the thermal expansion coefficient and / or hygroscopic expansion coefficient is above or below the above range, the process error during the sputtering process increases, which may result in a deterioration in the performance of the flexible metal foil laminate. In particular, if the thermal expansion coefficient exceeds the range, the heat resistance stability of the deposited metal foil and polyimide film may decrease, and if the thermal expansion coefficient is below the range, the room temperature adhesive strength between the polyimide film and metal foil may decrease.

[0022] In one embodiment, the multilayer polyimide film may have a room temperature adhesive strength to a metal foil of 0.6 kgf / cm or more and 0.9 kgf / cm or less, and a heat resistant adhesive strength to a metal foil of 0.3 kgf / cm or more and 0.6 kgf / cm or less. The room temperature adhesive strength may be the adhesive strength between the polyimide film and a metal foil (e.g., copper foil) laminated on the polyimide film by a sputtering process and then measured at room temperature (15 to 25°C). The heat-resistant adhesive strength may also be the adhesive strength between the polyimide film and a metal foil (e.g., copper foil) laminated on the polyimide film by a sputtering process, and then left at a high temperature (100 to 200°C) for a long period of time (100 to 300 hours), and then measured. For example, the room temperature adhesive strength may be 0.6 kgf / cm or more and 0.83 kgf / cm or less, and the heat resistant adhesive strength may be 0.45 kgf / cm or more and 0.50 kgf / cm or less. If the room temperature and / or heat resistant adhesive strength is above or below the range, problems may occur in the production process of products to which the multilayer polyimide film is applied.

[0023] In one embodiment, the adhesive strength reduction rate expressed by the following Equation 1 may be 50% or less. [Number 1] Adhesion strength reduction rate (%) = [(room temperature adhesion strength with metal foil - heat resistant adhesion strength with metal foil) / room temperature adhesion strength with metal foil] * 100

[0024] In one embodiment, the core layer of the multilayer polyimide film of the present application is obtained by imidizing a polyamic acid solution containing a dianhydride acid component including biphenyltetracarboxylic dianhydride (3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) and a diamine component including p-phenylene diamine (PPD) and m-tolidine (MTD).

[0025] The first and second skin layers of the multilayer polyimide film of the present application are obtained by imidizing a polyamic acid solution containing a dianhydride acid component including biphenyltetracarboxylic dianhydride and pyromellitic dianhydride, and a diamine component including two or more members selected from the group consisting of paraphenylenediamine, oxydianiline (4,4-oxydianiline, ODA), and 1,3-bis(4-aminophenoxy)benzene (TPE-R).

[0026] However, the core layer of the multilayer polyimide film of the present application does not necessarily need to contain the diamine 1,3-bisaminophenoxybenzene and oxydianiline. For example, the diamine components of the first and second skin layers of the multilayer polyimide film can be a combination of paraphenylenediamine and oxydianiline, or a combination of paraphenylenediamine and 1,3-bisaminophenoxybenzene.

[0027] On the other hand, the first skin layer and the second skin layer may have the same or different components and composition ratios.

[0028] The polyimide chains derived from biphenyltetracarboxylic dianhydride have 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, strengthening the intermolecular interaction. Furthermore, pyromellitic dianhydride is a dianhydride acid component having a relatively rigid structure, and is preferred in that it can impart appropriate elasticity to the polyimide film.

[0029] On the other hand, biphenyltetracarboxylic dianhydride contains two benzene rings corresponding to the aromatic moiety, whereas pyromelitic dianhydride contains one benzene ring corresponding to the aromatic moiety.

[0030] An increase in the content of pyromellitic dianhydride in the dianhydride acid component can be understood as an increase in the number of imide groups in the molecule based on the same molecular weight, which can be understood as a relative increase in the ratio of imide groups derived from the pyromellitic dianhydride in the polyimide polymer chain compared to the imide groups derived from biphenyltetracarboxylic dianhydride.

[0031] As the content of paraphenylenediamine is increased as a rigid monomer, the synthesized polyimide has a more linear structure, which can contribute to improving the mechanical properties of the polyimide.

[0032] Furthermore, m-tolidine has a methyl group that exhibits hydrophobicity, and can contribute to the low moisture absorption property related to the dimensional stability of the polyimide film against moisture.

[0033] In one embodiment, based on 100 mol% of the total content of the dianhydride acid components in the core layer, the content of the biphenyltetracarboxylic dianhydride may be 40 mol% or more and 60 mol% or less, the content of the pyromellitic dianhydride may be 40 mol% or more and 60 mol% or less, based on 100 mol% of the total content of the diamine components in the core layer, the content of the paraphenylenediamine may be 50 mol% or more and 70 mol% or less, and the content of the m-tolidine may be 30 mol% or more and 50 mol% or less.

[0034] Furthermore, based on 100 mol% of the total content of the dianhydride acid components in the skin layer, the content of the biphenyltetracarboxylic dianhydride may be 40 mol% or more and 98 mol% or less, the content of the pyromellitic dianhydride may be 2 mol% or more and 60 mol% or less, and based on 100 mol% of the total content of the diamine components in the skin layer, the content of the paraphenylenediamine may be 40 mol% or more and 95 mol% or less, the content of the oxydianiline may be 30 mol% or less, and the content of the 1,3-bisaminophenoxybenzene may be 60 mol% or less.

[0035] For example, based on 100 mol% of the total content of the dianhydride acid components in the skin layer, the content of the biphenyltetracarboxylic dianhydride may be 50 mol% or more and 97 mol% or less, and the content of the pyromellitic dianhydride may be 3 mol% or more and 50 mol% or less. Furthermore, based on 100 mol% of the total content of the diamine components in the skin layer, the content of the paraphenylenediamine may be 55 mol% or more and 87 mol% or less, the content of the oxydianiline may be 13 mol% or less, and the content of the 1,3-bisaminophenoxybenzene may be 45 mol% or less.

[0036] Meanwhile, the multilayer polyimide film may have a ratio of the thickness of the core layer to the sum of the thicknesses of the first and second skin portions (thickness of the core layer: sum of the thicknesses of the first and second skin portions) of 15:1 to 5:1.

[0037] The thickness of each of the first and second skin portions may be the same or different.

[0038] 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 component is mixed with the reaction components in a ratio of about 95 to 105 mol %, and then the remaining diamine component is added, and then the remaining dianhydride component is added successively to this, so that the diamine component and the dianhydride component are substantially equimolar, thereby polymerizing; (4) A method in which a dianhydride acid component is placed in a solvent, and then a portion 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 made in excess in the second composition, and if the dianhydride acid component is in excess in the first composition, the diamine component is made in excess in the second composition, and then mixing the first and second compositions, and polymerizing the resulting mixture so that the total amount of diamine components and dianhydride acid components used in these reactions is substantially equimolar.

[0039] In the present invention, the above-described polyamic acid polymerization method can be defined as a random polymerization method, and a polyimide film prepared from the polyamic acid of the present invention prepared by the above-described process can be preferably applied in terms of maximizing the effects of the present invention, such as improving dimensional stability and chemical resistance. However, since the above polymerization method produces a polymer chain with a relatively short repeating unit length, there may be a limit to the excellent properties of the polyimide chain derived from the dianhydride acid component. Therefore, the polyamic acid polymerization method that is particularly preferably used in the present invention is block polymerization.

[0040] 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 organic solvent may be an organic polar solvent, more specifically, an aprotic polar solvent, or may be, for example, 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 kinds as needed. In one example, N,N-dimethylformamide and N,N-dimethylacetamide are particularly preferably used as the organic solvent.

[0041] In addition, in the manufacturing process of polyamic acid, properties such as sliding properties, thermal conductivity, corona resistance, and loop hardness are required. Fillers may be added to improve various properties of any film. The fillers to be added are not particularly limited, but preferred examples include silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica, etc.

[0042] 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. 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.

[0043] The amount of filler to be added is not particularly limited and may be determined depending on the film properties to be modified, the particle size of the filler, etc. Generally, the amount of filler to be 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 will be difficult to achieve, and if it exceeds this range, the mechanical properties of the film may be significantly impaired. The method of adding the filler is not particularly limited, and any known method may be used.

[0044] 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.

[0045] 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. 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 %) can be 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.

[0046] In the case of chemical imidization, a polyimide film can be produced using a dehydrating agent and an imidizing agent by methods known in the art.

[0047] Here, the term "dehydrating agent" refers to a substance that promotes the ring-closure reaction by dehydrating the polyamic acid, and non-limiting examples thereof include aliphatic acid anhydrides, aromatic acid anhydrides, N,N'-dialkylcarbodiimides, halogenated lower aliphatic acids, halogenated lower fatty acid anhydrides, arylphosphonic dihalides, and thionyl halides. Among these, aliphatic acid anhydrides are preferred from the standpoints of availability and cost, and non-limiting examples thereof include acetic anhydride (or acetic anhydride, AA), propionic acid anhydride, and lactic acid anhydride, which can be used alone or in combination of two or more.

[0048] The "imidizing agent" is an imidizing agent having the effect of promoting the ring-closing reaction of polyamic acid. The term "tertiary amine" refers to a substance, and may be, for example, an imine-based component such as an aliphatic tertiary amine, an aromatic tertiary amine, or a heterocyclic tertiary amine. Among these, heterocyclic tertiary amines are preferred from the viewpoint of reactivity as a catalyst. Non-limiting examples of heterocyclic tertiary amines include quinoline, isoquinoline, β-picoline (BP), pyridine, etc., which may be used alone or in combination of two or more.

[0049] The amount of the dehydrating agent added is preferably within a range of 0.5 to 5 mol, and particularly preferably 1.0 to 4 mol, per mol of amic acid groups in the polyamic acid, and the amount of the imidizing agent added is preferably within a range of 0.05 to 2 mol, and particularly preferably 0.2 to 1 mol, per mol of amic acid groups in the polyamic acid. If the amounts of the dehydrating agent and imidizing agent are below the above ranges, chemical imidization may be insufficient, cracks may form in the produced polyimide film, and the mechanical strength of the film may be reduced.If the amounts of these agents added are above the above ranges, imidization may proceed too rapidly, making film casting difficult or the produced polyimide film may exhibit brittle properties, which is undesirable.

[0050] 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.

[0051] Meanwhile, the multilayer polyimide film of the present invention described above can be produced by one or more of the following methods: coextrusion or coating.

[0052] The co-extrusion method involves filling a reservoir with a polyamic acid solution or a polyimide resin produced by imidizing the polyamic acid solution, extruding the solution in multiple layers onto a casting belt using a co-extrusion die, and then curing the extrusion to produce a multi-layer polyimide film. This method is highly productive and ensures high interfacial adhesion reliability by blending different types of polyimide resins at the interfaces.

[0053] For example, a method for producing a multilayer polyimide film of the present invention may include a first filling step of filling a first reservoir with a first solution, which is a first polyamic acid solution or a first polyimide resin produced by imidizing the first polyamic acid solution; a second filling step of filling a second reservoir with a second solution, which is a second polyamic acid solution or a second polyimide resin produced by imidizing the second polyamic acid solution; a co-extrusion step of co-extruding the first and second solutions through a co-extrusion die formed therein with a first flow path connected to the first reservoir, a second flow path connected to the second reservoir, and a third flow path connected to the second reservoir, respectively; and a curing step of curing the co-extruded first and second solutions.

[0054] The first polyamic acid solution constituting the core layer can be produced by polymerizing a dianhydride acid component containing biphenyltetracarboxylic dianhydride and pyromellitic dianhydride and a diamine component containing paraphenylenediamine and m-tolidine in a solvent.

[0055] On the other hand, the second polyamic acid solution constituting the first and second skin layers can be produced by polymerizing, in a solvent, a dianhydride acid component including biphenyltetracarboxylic dianhydride and pyromellitic dianhydride, and a diamine component including two or more selected from the group consisting of paraphenylenediamine, oxydianiline, and 1,3-bisaminophenoxybenzene.

[0056] The first polyamic acid may have a biphenyltetracarboxylic dianhydride content of 40 mol% or more and 60 mol% or less, a pyromellitic dianhydride content of 40 mol% or more and 60 mol% or less, and a paraphenylenediamine content of 50 mol% or more and 70 mol% or less, and a m-tolidine content of 30 mol% or more and 50 mol% or less, based on 100 mol% of the total content of the diamine components.

[0057] On the other hand, based on 100 mol% of the total content of the dianhydride acid components in the second polyamic acid, the content of the biphenyltetracarboxylic dianhydride may be 40 mol% or more and 98 mol% or less, the content of the pyromellitic dianhydride may be 2 mol% or more and 60 mol% or less, based on 100 mol% of the total content of the diamine components, the content of the paraphenylenediamine may be 40 mol% or more and 95 mol% or less, the content of the oxydianiline may be 30 mol% or less, and the content of the 1,3-bisaminophenoxybenzene may be 60 mol% or less.

[0058] The present invention provides a flexible metal foil laminate comprising the above-mentioned polyimide film and an electrically conductive metal foil.

[0059] The metal foil to be used is not particularly limited, but for example, when the multilayer film of the present invention is used for electronic or electrical equipment, the metal foil may be 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.

[0060] In general, copper foils such as rolled copper foils and electrolytic copper foils are often 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.

[0061] 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.

[0062] 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.

[0063] The present invention also provides an electronic component including the flexible metal foil laminate as an electrical signal transmission circuit. [Example]

[0064] 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 determine the scope of the invention.

[0065] Preparation Example 1: Preparation of core layer (first composition) 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. Paraphenylenediamine (PPD) and biphenyltetracarboxylic dianhydride (BPDA) were dissolved in the reactor, and the temperature was then raised to 40°C under heating while stirring continuously for 120 minutes to polymerize the mixture. Then, the prepared polymer solution of paraphenylenediamine and biphenyltetracarboxylic dianhydride was added with m-tolidine (MTD) and Pyromellitic dianhydride (PMDA) was additionally added, and polymerization was carried out by continuing heating and stirring, to obtain a first composition containing a first polyamic acid solution.

[0066] Preparation Example 2: Preparation of the first and second skin layers (second composition) DMF was added to a 500 ml reactor equipped with a stirrer and nitrogen inlet / outlet tubes while injecting nitrogen. The reactor temperature was set to 30°C, and then a portion of the diamine components, paraphenylenediamine (PPD), m-tolidine (MTD), 1,3-bisaminophenoxybenzene (TPE-R), and oxydianiline (ODA), was selected and added, and biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) were added as dianhydride components, and complete dissolution was confirmed. Thereafter, the temperature of the reactor was raised to 40° C. under a nitrogen atmosphere, and stirring was continued for 120 minutes while heating, to obtain a second composition containing a second polyamic acid solution.

[0067] Production Example 3: Production of multilayer polyimide film The first composition prepared in Preparation Example 1 was placed in the first reservoir of the coextrusion die, and the second composition prepared in Preparation Example 2 was placed in the second reservoir. The second composition, the first composition, and the second composition were then co-extruded in this order onto an endless belt to form a precursor composition film having a thickness of about 35 micrometers, in such a way that the mixture of isoquinoline, dimethylformamide, and acetic anhydride from the catalyst reservoir was mixed with the first composition extruded from the first reservoir. Next, the film was heat-treated at a temperature of approximately 150°C, and then heated again in a high-temperature tenter from 150°C to 600°C, after which it was cooled to 25°C to obtain a multilayer polyimide film having a first skin layer / core layer / second skin layer structure.

[0068] [Examples and Comparative Examples] The compositions and composition ratios of the first polyamic acid for producing the core layer and the second polyamic acid for producing the skin layer were adjusted as shown in Tables 1 and 2 below, respectively, to produce multilayer polyimide films according to Production Examples 1 to 3. The core layer had a thickness of 32 μm, and the first and second skin layers each had a thickness of 1.5 μm.

[0069] However, single-layer polyimide films were produced in Comparative Examples 1 to 4. That is, after producing a second polyamic acid according to Production Example 2, 3 moles of acetic anhydride and 1 mole of isoquinoline per mole of amic acid group were added to the produced polyamic acid solution to obtain a precursor composition for a polyimide film.

[0070] The polyimide film precursor composition was cast onto a SUS plate using a doctor blade and dried at 110° C. for 4 minutes to prepare a gel film. The gel film was separated from the SUS plate and then heat-treated at 280° C. for 4 minutes and then at 380° C. for 4 minutes to prepare a polyimide film having a thickness of 35 μm. The thickness of the produced polyimide film was measured using an Anritsu Electric Film Thickness Tester.

[0071] [Table 1]

[0072] [Table 2]

[0073] Manufacturing Example 4: Manufacturing of flexible metal foil laminates On the (multilayer) polyimide films of Examples 1 to 3 and Comparative Examples 1 to 6 manufactured by Manufacturing Examples 1 to 3, a copper thin film layer having a thickness of approximately 80 to 300 nm was deposited by sputtering as a copper seed layer for an electroplating electrode, and a copper conductive layer having a thickness of approximately 8 to 9 μm was formed by electroplating.

[0074] (1) Surface hardness measurement The (multilayer) polyimide films of Examples 1 to 3 and Comparative Examples 1 to 6 prepared according to Preparation Examples 1 to 3 were cut to a width of 100 mm and a length of 100 mm, and the surface hardness was measured using a KLA-Tenco iNano Nanoindenter, which can measure the surface hardness by measuring the force applied to a probe while pressing the probe into a sample.

[0075] (2) Measurement of thermal expansion coefficient The coefficient of thermal expansion (CTE) was measured using a TA thermomechanical analyzer. Using a Q400 model analyzer, the (multilayer) polyimide films of Examples 1 to 3 and Comparative Examples 1 to 6 manufactured by Manufacturing Examples 1 to 3 were cut into a width of 4 mm and a length of 20 mm. Then, under a nitrogen atmosphere, the film was heated from 30°C to 400°C at a rate of 10°C / min while applying a tension of 0.05 N, and then cooled again at a rate of 10°C / min from 50°C to 200°C. The gradient of the section (the dimensional change rate (ppm / °C) due to the temperature change in the section from 50°C to 200°C) was measured.

[0076] (3) Measurement of moisture absorption expansion coefficient The coefficient of moisture expansion (CHE) was measured by adjusting the humidity to 3% RH at 25°C under a minimum load (approximately 1 g for a 25 mm × 150 mm sample) on the (multilayer) polyimide films of Examples 1 to 3 and Comparative Examples 1 to 6 produced by Production Examples 1 to 3 so as not to loosen them, allowing them to absorb moisture until they were completely saturated, and then measuring the dimensions. Thereafter, the humidity was adjusted to 90% RH, and after similarly allowing them to absorb moisture to saturation, the dimensions were measured, and the dimensional change rate was calculated from both results.

[0077] (4) Measurement of room temperature adhesive strength The flexible metal laminate prepared in Preparation Example 4 using the (multilayer) polyimide films of Examples 1 to 3 and Comparative Examples 1 to 6 prepared in Preparation Examples 1 to 3 was etched into a rod shape with a width of 2 mm by a wet etching method, and then the room temperature adhesive strength was measured by pulling at a speed of 20 mm / min in a 90° peel test using a Universal Testing Machine. The wet etching method was carried out in the following order: attaching a rod-shaped coating film having a width of 2 mm to the flexible metal laminate, spraying an etching solution (ferric chloride [iron III chloride]) to perform metal etching to form a rod-shaped pattern, and then removing the coating film.

[0078] (5) Measurement of heat-resistant adhesive strength The flexible metal plate laminate produced in Production Example 4 using the (multilayer) polyimide films of Examples 1 to 3 and Comparative Examples 1 to 6 produced in Production Examples 1 to 3 was etched into a rod shape with a width of 2 mm by a wet etching method, and then heat-treated at 150°C for 168 hours. The wet etching method was carried out in the same manner as in the measurement of room temperature adhesive strength. Thereafter, a 90° peel test was performed using a Universal Testing Machine at a pulling speed of 20 mm / min to measure the room temperature adhesive strength.

[0079] The surface hardness, coefficient of thermal expansion (CTE), coefficient of hygrothermal expansion (CHE), room temperature adhesive strength and heat resistant adhesive strength of the (multilayer) polyimide films of Examples 1 to 3 and Comparative Examples 1 to 6 measured by the above-mentioned measuring methods are shown in Table 3 below.

[0080] [Table 3]

[0081] As a result of the measurement, the polyimide films of Examples 1 to 3 had a strength of 0.4 GPa or more and 0.6 GPa or less. The properties of the adhesive were: surface hardness of 2.0 ppm / ℃ to 5.0 ppm / ℃, coefficient of thermal expansion of 3.0 ppm / %RH to 6.0 ppm / %RH, room temperature adhesive strength of 0.6 kgf / cm to 0.9 kgf / cm, heat resistant adhesive strength of 0.3 kgf / cm to 0.6 kgf / cm, and adhesive strength reduction of 50% or less. In contrast, the (multilayer) polyimide films of Comparative Examples 1 to 6 were unable to satisfy the property ranges of the multilayer polyimide films of the present invention in terms of one or more of the surface hardness, thermal expansion coefficient, hygroscopic expansion coefficient, room temperature adhesive strength, heat-resistant adhesive strength, and adhesive strength reduction property. Specifically, the polyimide film of Comparative Example 1 did not satisfy the characteristic ranges of the multilayer polyimide film of the present invention in terms of surface hardness and room temperature adhesion strength, compared to the multilayer polyimide films of Examples 1 to 3 in which the polyimide film of Comparative Example 1 was used as a core layer.

[0082] On the other hand, the polyimide films of Comparative Examples 2 to 4, which used the same components and composition ratios as the skin layers of the multilayer polyimide films of Examples 1 to 3, respectively, did not have thermal expansion coefficients and / or hygroscopic expansion coefficients that satisfied the characteristic ranges of the multilayer polyimide films of the present invention. Furthermore, the multilayer polyimide film of Comparative Example 5, which used the core layer of the multilayer polyimide films of Examples 1 to 3 but had different types and contents of components in the skin layer, was unable to satisfy the property ranges of the multilayer polyimide film of the present invention in terms of surface hardness, thermal expansion coefficient, and heat-resistant adhesive strength.

[0083] On the other hand, the multilayer polyimide film of Comparative Example 6, which had a different content of dianhydride acid component in the core layer and a different type and content of diamine component in the skin layer from the multilayer polyimide films of Examples 1 to 3, did not satisfy the property ranges of the multilayer polyimide film of the present invention in terms of surface hardness, thermal expansion coefficient, room temperature adhesive strength, and heat resistant adhesive strength.

[0084] Therefore, the multilayer polyimide films of Examples 1 to 3 produced within the appropriate ranges of the present application were all excellent in surface hardness, thermal dimensional stability, dimensional stability against moisture, and adhesion to copper foil. However, it was confirmed that if the appropriate ranges of the present application are exceeded, it would be difficult to satisfy all of the surface hardness, thermal dimensional stability, dimensional stability against moisture, and adhesion to copper foil of the multilayer polyimide film of the present application. In other words, it was confirmed that the multilayer polyimide film that has excellent surface hardness, dimensional stability, and adhesion to copper foil and satisfies all of the various requirements applicable to various fields of application is the multilayer polyimide film manufactured within the appropriate range of the present invention.

[0085] The examples of the multilayer polyimide film and the method for manufacturing the multilayer polyimide film of the present invention are merely preferred examples that will enable those skilled in the art to easily practice the present invention, and the present invention is not limited to the above examples, and the scope of the present invention is not limited by these examples. Therefore, the true technical scope of the present invention must be determined by the technical spirit of the appended claims. Furthermore, it is obvious to those skilled in the art that various substitutions, modifications, and changes are possible within the scope of the present invention, and it is obvious that parts that can be easily modified by those skilled in the art are also included in the scope of the present invention. [Industrial Applicability]

[0086] The present invention provides a multilayer polyimide film in which the composition ratio of dianhydride acid and diamine components is adjusted, thereby providing a multilayer polyimide film that is excellent not only in surface hardness and dimensional stability but also in adhesive strength. Such multilayer polyimide films are used in a variety of fields where multilayer polyimide films with excellent dimensional stability and adhesive strength are required, such as flexible films manufactured by a metallizing method. The present invention is applicable to flexible metal foil laminates or electronic components that include such flexible metal foil laminates.

Claims

1. A core layer; a first skin layer and a second skin layer formed on one outer surface of the core layer and the opposite surface of the outer surface, respectively; The surface hardness measured by a nanoindenter is 0.4 GPa or more and 0.6 GPa or less. Multilayer polyimide film.

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

3. The room temperature adhesive strength to the metal foil is 0.6 kgf / cm or more and 0.9 kgf / cm or less, The heat-resistant adhesive strength with the metal foil is 0.3 kgf / cm or more and 0.6 kgf / cm or less. The multilayer polyimide film according to claim 1 .

4. the core layer is obtained by imidizing a polyamic acid solution containing a dianhydride acid component including biphenyltetracarboxylic dianhydride and pyromellitic dianhydride and a diamine component including paraphenylenediamine and m-tolidine; the first skin layer and the second skin layer are obtained by imidizing a polyamic acid solution containing a dianhydride acid component including biphenyltetracarboxylic dianhydride and pyromellitic dianhydride, and a diamine component including two or more species selected from the group consisting of paraphenylenediamine, oxydianiline, and 1,3-bisaminophenoxybenzene; The multilayer polyimide film according to claim 1 .

5. the content of the biphenyltetracarboxylic dianhydride is 40 mol % or more and 60 mol % or less, and the content of the pyromellitic dianhydride is 40 mol % or more and 60 mol % or less, based on 100 mol % of the total content of the dianhydride acid components in the core layer; the content of the paraphenylenediamine is 50 mol % or more and 70 mol % or less, and the content of the m-tolidine is 30 mol % or more and 50 mol % or less, based on 100 mol % of the total content of the diamine components in the core layer; The multilayer polyimide film according to claim 4.

6. the content of the biphenyltetracarboxylic dianhydride is 40 mol% or more and 98 mol% or less, and the content of the pyromellitic dianhydride is 2 mol% or more and 60 mol% or less, based on 100 mol% of the total content of the dianhydride acid components in the first and second skin layers; the content of the paraphenylenediamine is 40 mol % or more and 95 mol % or less, the content of the oxydianiline is 30 mol % or less, and the content of the 1,3-bisaminophenoxybenzene is 60 mol % or less, based on 100 mol % of the total content of the diamine components in the first and second skin layers; The multilayer polyimide film according to claim 4.

7. The multilayer polyimide film is produced by one or more methods selected from the group consisting of coextrusion and coating. The multilayer polyimide film according to any one of claims 1 to 6.

8. A multilayer polyimide film comprising the multilayer polyimide film according to any one of claims 1 to 6 and an electrically conductive metal foil. Flexible metal foil laminate.

9. The flexible metal foil laminate of claim 8. Electronic components.

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