Polyimide film and its manufacturing method

Abstract

The present invention provides a polyimide film having a surface hardness of 0.4 GPa or more and 0.6 GPa or less as measured by nanoindentation, and a method for producing the same.

Description

[Technical Field]

[0001] The present invention relates to a polyimide film having excellent dimensional stability and adhesive strength, and more particularly to a 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 a rigid aromatic main chain and imide rings, which are extremely chemically stable, and has the highest level of heat resistance, chemical resistance, electrical insulation, chemical resistance, and weather resistance among organic materials. Polyimide film has been attracting attention as a material for a variety of electronic devices that require the above-mentioned properties. Examples of microelectronic components to which polyimide films are applied include thin, flexible circuit boards that have a high degree of circuit integration and are suitable for the reduction in weight and size of electronic products. Polyimide films are widely used, particularly 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 sometimes more narrowly called a flexible copper clad laminate (FCCL).

[0003] Examples of manufacturing methods for flexible metal foil laminates include (i) a casting method in which polyamic acid, a precursor of polyimide, is cast or applied onto a 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 a metal foil are bonded together by heat and pressure through 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).

[0004] Polyimide films used in flexible metal foil laminates made by the metallizing 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. Therefore, there is a strong demand for a polyimide film that simultaneously has high dimensional stability and excellent adhesive strength to sputtered metal foil. In particular, there is an increasing 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 aid in understanding the background of the invention, and may include matters that are not conventional art already known to those having ordinary skill in the art to which this technology pertains. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Korean Patent Publication No. 10-2020-0120515 Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, an object of the present invention is to provide a polyimide film that has high dimensional stability and excellent adhesive strength at the same time. In particular, the present invention aims to provide a 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]

[0007] In order to achieve the above object, one aspect of the present invention is a surface hardness measured by nanoindentation of 0.4 GPa or more and 0.6 GPa or less. A polyimide film is provided. Another aspect of the present invention is a method for producing a polyamic acid by polymerizing a dianhydride component including biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) and a diamine component including two or more selected from the group consisting of paraphenylenediamine (PPD), oxydianiline (ODA), and 1,3-bisaminophenoxybenzene (TPE-R) in an organic solvent; and (b) imidizing the polyamic acid; A method for producing a polyimide film is provided. Another aspect of the present invention is a laminate comprising the polyimide film and an electrically conductive metal foil. A flexible metal foil laminate is provided. Another aspect of the present invention includes the flexible metal foil laminate. Provides electronic components. [Effects of the Invention]

[0008] The present invention provides a polyimide film in which the composition ratio and reaction ratio of dianhydride and diamine components are adjusted, thereby providing a polyimide film with excellent dimensional stability and adhesive strength. Such polyimide films are applicable to various fields where polyimide films with excellent dimensional stability and adhesive strength are required, 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

[0009] The terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted as meanings and concepts that are consistent with the technical idea of the present invention, based on the principle that an inventor can appropriately define the concepts of terms in order to best explain his or her invention. Therefore, it should be understood that the configuration of the embodiment described in this specification is merely one of the most preferred embodiments of the present invention and does not represent the technical idea of the present invention, and that at the time of filing this application, there may be various equivalents and modifications that can replace them. In this specification, the singular includes the plural unless the context clearly dictates otherwise. In this specification, the terms "comprise," "comprise," "have," and the like are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, and should be understood as not precluding the presence or additional possibility of one or more other features, numbers, steps, components, or combinations thereof.

[0010] As used herein, "dianhydride acid" is intended to include precursors or derivatives thereof, which may not technically be dianhydrides, but which nevertheless react with diamines to form polyamic acids, which can be converted back to polyimides. As used herein, "diamine" is intended to include precursors or derivatives thereof, which may not technically be diamines, but which nevertheless react with dianhydrides to form polyamic acids, which can then be converted back to polyimides. Whenever an amount, concentration, or other value or parameter is listed herein as a range, a preferred range, or an upper preferred value and a lower preferred value, it should be understood that this specifically discloses all ranges formed by any pair of any upper value or preferred value and any lower value or preferred value, regardless of whether a range is otherwise disclosed.

[0011] Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all constants and fractions within the range. It is not intended that the scope of the invention be limited to the specific values recited when defining a range. In the present specification, when numerical ranges are indicated as "a to b" or "a to b," "to" and "to" are defined as ≧a and ≦b. The polyimide film according to an embodiment of the present invention may have a surface hardness of 0.4 GPa or more and 0.6 GPa or less as measured by nanoindentation.

[0012] For example, the surface hardness may be 0.45 GPa or more, 0.5 GPa or more, or 0.55 GPa or more. If the surface hardness exceeds the above range, deposition of a metal foil may become difficult, and the room temperature adhesive strength of the polyimide film may be weakened. If the surface hardness is below the above range, the thermal stability and heat-resistant adhesive strength of the polyimide film may be reduced. In one embodiment, the polyimide film may have room temperature adhesive strength to the metal foil of 0.6 kgf / cm or more and 0.9 kgf / cm or less, and heat resistant adhesive strength to the metal foil of 0.3 kgf / cm or more and 0.5 kgf / cm or less.

[0013] 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 through a sputtering process and then measured at room temperature (15 to 25°C). The heat-resistant adhesive strength may be measured by laminating a metal foil (e.g., copper foil) on the polyimide film through a sputtering process, leaving the polyimide film at a high temperature (100 to 200°C) for a long period of time (100 to 300 hours), and then measuring the adhesive strength between the polyimide film and the metal foil. 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.

[0014] If the room temperature and / or heat resistant adhesive strength is above or below the range, problems may occur in the manufacturing process of products to which the polyimide film is applied. In one embodiment, the adhesive strength reduction rate expressed by the following mathematical formula 1 may be 50% or less, and the thermal expansion coefficient may be more than 1 ppm / °C and 15 ppm / °C or less. [Mathematical formula 1] Adhesive strength reduction rate (%) = [(room temperature adhesive strength with metal foil - heat resistant adhesive strength with metal foil) / room temperature adhesive strength with metal foil] x 100 The adhesive strength reduction rate is, for example, 45% or less, 40% or less, 35% or less, 30% or less, 2 It may be 5% or less, or 20% or less.

[0015] On the other hand, the thermal expansion coefficient may be, for example, 4.5 ppm / °C or more and 10 ppm / °C or less. If the thermal expansion coefficient exceeds the above range, the heat resistance of the deposited metal foil and polyimide film may be reduced, and if the thermal expansion coefficient is below the above range, the room temperature adhesive strength between the polyimide film and metal foil may be reduced. In one embodiment, the polyimide film of the present application is obtained by imidizing a polyamic acid solution containing a dianhydride component including biphenyltetracarboxylic dianhydride (3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) and a diamine component including two or more selected from the group consisting of paraphenylenediamine (PPD), oxydianiline (ODA), and 1,3-bisaminophenoxybenzene (TPE-R).

[0016] However, the polyimide film of the present application may not contain 3,3',4,4'-Benzophenone tetracarboxylic dianhydride (BTDA) and 4,4'-Oxydiphthalic anhydride (ODPA) as dianhydride acid components. The polyimide film of the present invention may not contain m-tolidine (MTD) as a diamine component. For example, the diamine component of the polyimide film may be a combination of paraphenylenediamine and oxydianiline, or a combination of paraphenylenediamine and 1,3-bisaminophenoxybenzene (TPE-R).

[0017] The polyimide chain derived from biphenyltetracarboxylic dianhydride has a structure called a charge transfer complex (CTC), i.e., a regular linear structure in which the electron donor and electron acceptor are located close to each other, strengthening intermolecular interactions. 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. On the other hand, biphenyltetracarboxylic dianhydride contains two benzene rings that correspond to the aromatic moiety, while pyromelitic dianhydride contains one benzene ring that corresponds to the aromatic moiety.

[0018] In the dianhydride acid component, an increase in the pyromellitic dianhydride content can be understood as an increase in the imide groups in the molecule based on the same molecular weight, which can be understood as a relative increase in the proportion of imide groups derived from the pyromellitic dianhydride in the polyimide polymer chain compared to the imide groups derived from biphenyltetracarboxylic dianhydride. In one embodiment, based on 100 mol% of the total content of the dianhydride acid components, the content of the biphenyltetracarboxylic dianhydride is 40 mol% to 99 mol%, the content of the pyromellitic dianhydride is 1 mol% to 60 mol%, based on 100 mol% of the total content of the diamine components, the content of the paraphenylenediamine is 40 mol% to 95 mol%, the content of the oxydianiline is 30 mol% or less, and the content of the 1,3-bisaminophenoxybenzene is 60 mol% to 80 mol%, based on 100 mol% of the total content of the diamine components. It may be mol % or less. For example, based on 100 mol% of the total content of the dianhydride acid components, 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.

[0019] Furthermore, based on 100 mol% of the total content of the diamine components, 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. Among the dianhydride acid component and diamine component, when the content of short-chain monomers such as paraphenylenediamine and pyromellitic dianhydride increases, the surface hardness of the polyimide film tends to increase and the thermal expansion coefficient tends to decrease. Meanwhile, when the content of the monomer having a flexible structure, such as oxydianiline or biphenyltetracarboxylic dianhydride, among the dianhydride acid component and the diamine component, increases, the surface hardness of the polyimide film tends to decrease and the thermal expansion coefficient tends to increase.

[0020] 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;

[0021] (4) A method in which a dianhydride acid component is placed in a solvent, and then a part of the diamine compound is mixed in a ratio of 95 to 105 mol % relative to the reaction components, and then another dianhydride acid component is added, followed by the remaining diamine component, so that the diamine component and the dianhydride acid component are substantially equimolar, thereby polymerizing the mixture; (5) A method of forming a first composition by reacting a portion of the diamine component and a portion of the dianhydride acid component in a solvent so that one of them is in excess, and then forming a second composition by reacting a portion of the diamine component and a portion of the dianhydride acid component in another solvent so that one of them is in excess, and then mixing the first and second compositions to complete the polymerization. In this case, if the diamine component is in excess when forming the first composition, the dianhydride acid component is in excess in the second composition, and if the dianhydride acid component is in excess in the first composition, the diamine component is in excess in the second composition, and then mixing the first and second compositions to polymerize so that the total diamine component and dianhydride acid component used in these reactions are substantially equimolar. However, the polymerization method is not limited to the above example, and it goes without saying that any known method may be used to produce polyamic acid.

[0022] In one specific example, the method for producing a polyimide film according to the present invention includes: (a) preparing a polyamic acid by polymerizing a dianhydride component including biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) and a diamine component including two or more selected from the group consisting of paraphenylenediamine (PPD), oxydianiline (ODA), and 1,3-bisaminophenoxybenzene (TPE-R) in an organic solvent; and (b) imidizing the polyamic acid. In one embodiment, based on 100 mol% of the total content of the dianhydride acid components, the content of the biphenyltetracarboxylic dianhydride may be 40 mol% to 99 mol% and the content of the pyromellitic dianhydride may be 1 mol% to 60 mol%. Based on 100 mol% of the total content of the diamine components, the content of the paraphenylenediamine may be 40 mol% to 95 mol%, 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.

[0023] Meanwhile, the surface hardness of the polyimide film measured by nanoindentation may be 0.4 GPa or more and 0.6 GPa or less, the room temperature adhesive strength to a metal foil may be 0.6 kgf / cm or more and 0.9 kgf / cm or less, and the heat-resistant adhesive strength to a metal foil may be 0.3 kgf / cm or more and 0.5 kgf / cm or less. 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 to the effects of the present invention, such as improving mechanical properties, heat resistance, and chemical resistance.

[0024] On the other hand, the solvent for synthesizing the polyamic acid is not particularly limited, and any solvent that can dissolve the polyamic acid can be used, but an amide-based solvent is preferred. Specifically, the solvent may be an organic polar solvent, more specifically, an aprotic polar solvent, such as one or more selected from the group consisting of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methyl-pyrrolidone (NMP), p-chlorophenyl, o-chlorophenyl, N-methyl-pyrrolidone (NMP), gamma-butyrolactone (GBL), and diglyme, but is not limited thereto, and may be used alone or in combination as needed.

[0025] As an example, N,N-dimethylformamide and N,N-dimethylacetamide can be particularly preferably used as the solvent. In addition, in the polyamic acid production process, fillers other than nanosilica can be added to improve various film properties such as tribological properties, thermal conductivity, corona resistance, Knoop hardness, etc. The fillers to be added are not particularly limited, but preferred examples include titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica, etc. The particle size of the filler is not particularly limited and may be determined depending on the film properties to be modified and the type of filler to be added. Generally, the average particle size is 0.05 to 100 μm, preferably 0.1 to 75 μm, more preferably 0.1 to 50 μm, and particularly preferably 0.1 to 25 μm.

[0026] If the particle size is below this range, it becomes difficult to achieve the modifying effect, whereas if it exceeds this range, the surface properties may be significantly damaged or the mechanical properties may be significantly reduced. The amount of filler to be added is not particularly limited and may be determined depending on the film properties 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 is 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.

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

[0028] However, even during the process of forming the gel film, a portion of the amic acid (approximately 0.1 mol % to 10 mol %) may be imidized, and for this purpose, the polyamic acid composition may be dried at a variable temperature ranging from 50°C to 200°C, which also falls within the category of the thermal imidization method. In the chemical imidization method, polyimide films can be prepared using a dehydrating agent and an imidizing agent according to methods known in the art. Here, the term "dehydrating agent" refers to a substance that promotes a ring-closure reaction through dehydration of polyamic acid. Non-limiting examples of the dehydrating agent include aliphatic acid anhydrides, aromatic acid anhydrides, N,N'-dialkylcarbodiimides, halogenated lower aliphatic acid anhydrides, halogenated lower fatty acid anhydrides, arylphosphonic dihalides, and thionyl halides. Among these, aliphatic acid anhydrides are preferred in terms of availability and cost. Non-limiting examples of the aliphatic acid anhydrides include acetic anhydride (or acetic anhydride, AA), propionic acid anhydride, and lactic acid anhydride. These can be used alone or in combination.

[0029] The term "imidizing agent" refers to a substance that promotes the ring-closing reaction of polyamic acid, 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 in terms of their catalytic reactivity. Non-limiting examples of heterocyclic tertiary amines include quinoline, isoquinoline, β-picoline (BP), and pyridine, which may be used alone or in combination of two or more. The amount of the dehydrating agent added is preferably within a range of 0.5 to 5 mol, and particularly preferably within a range of 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 within a range of 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, the 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, the imidization may proceed too quickly, which may make it difficult to cast the film or the produced polyimide film may exhibit brittle properties, which is undesirable.

[0030] In one example of the composite imidization method, a dehydrating agent and an imidization agent are added to a polyamic acid solution, and the solution is heated at 80 to 200°C, preferably 100 to 180°C, partially cured and dried, and then heated at 200 to 400°C for 5 to 400 seconds to produce a polyimide film. The present invention provides a flexible metal foil laminate comprising the above-mentioned polyimide film and an electrically conductive metal foil. Provide a lamina. The metal foil used is not particularly limited, but for example, when the multilayer film of the present invention is used for electronic or electrical equipment applications, the metal foil may be copper or a copper alloy, stainless steel or its alloy, nickel or a nickel alloy (including 42 alloy), or aluminum or an aluminum alloy.

[0031] In general, copper foils such as rolled copper foils and electrolytic copper foils are often used in soft metal foil laminates, and can be preferably used in the present invention. In addition, the surface of these metal foils may be coated with an anti-rust layer, a heat-resistant layer, or an adhesive layer. In the present invention, the thickness of the metal foil is not particularly limited, and may be any thickness that can exhibit sufficient functionality depending on the application. 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. The present invention further provides an electronic component that includes the flexible metal foil laminate as an electrical signal transmission circuit. [Example]

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

[0033] Production Example 1: Production of polyimide film DMF was added to a 500 ml reactor equipped with a stirrer and nitrogen inlet / outlet tubes while injecting nitrogen, and the reactor temperature was set to 30°C. Then, a portion of the diamine components, such as paraphenylenediamine (PPD), m-tolidine (MTD), 1,3-bisaminophenoxybenzene (TPE-R), and oxydianiline (ODA), was selected and added, and a portion of the dianhydride components, such as biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), and oxydiphthalic anhydride (ODPA), was selected and added, and complete dissolution was confirmed.

[0034] Thereafter, the temperature of the reactor was raised to 40° C. under a nitrogen atmosphere, and stirring was continued for 120 minutes to prepare a polyamic acid solution. To the polyamic acid solution thus prepared, 3 moles of asethenoic anhydride and 1 mole of isoquinoline per mole of amic acid group were added to obtain a precursor composition for a polyimide film. 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 380° C. for 8 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.

[0035] <Examples 1 to 3 and Comparative Examples 1 to 4> The contents of the diamine monomer and dianhydride monomer were adjusted as shown in Table 1. [Table 1]

[0036] Manufacturing Example 2: Manufacturing of flexible metal foil laminate On the polyimide films of Examples 1 to 3 and Comparative Examples 1 to 4 prepared according to Preparation Example 1, a copper thin film layer having a thickness of about 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 about 8 to 9 μm was formed by electroplating.

[0037] (1) Measurement of thermal expansion coefficient The coefficient of thermal expansion (CTE) was measured using a TA Thermomechanical Analyzer (Model Q400). Each of the polyimide films prepared in Preparation Example 1 and Comparative Examples 1 to 4 was cut into a 4 mm wide x 20 mm long piece. The polyimide films were heated from 30°C to 400°C at a rate of 10°C / min under a tension of 0.05 N in a nitrogen atmosphere, and then cooled at a rate of 10°C / min. The temperature gradient (the dimensional change rate (ppm / °C) due to temperature change in the range from 50°C to 200°C) was measured.

[0038] (2) Surface hardness measurement The polyimide films of Examples 1 to 3 and Comparative Examples 1 to 4 prepared by Preparation Example 1 were cut into a width of 100 mm and a length of 100 mm. Then, the probe was pressed into the sample, and the force applied to the probe was measured using an Inano tester manufactured by KLA-Tenco, which can measure the surface hardness. The surface hardness was measured using a nanoindenter (iNano Nanoindentor).

[0039] (3) Measurement of room temperature adhesive strength The flexible metal laminates prepared according to Preparation Example 2 using the polyimide films of Examples 1 to 3 and Comparative Examples 1 to 4 were etched into a 2 mm wide rod shape using a wet etching method, and then subjected to a 90° peel test using a universal testing machine at a pulling speed of 20 mm / min to measure the room temperature adhesive strength. The wet etching method was carried out by attaching a 2 mm wide rod-shaped coating film to the flexible sheet 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.

[0040] ( 4) Measurement of heat-resistant adhesive strength The flexible sheet metal laminates manufactured in Manufacturing Example 2 using the polyimide films of Examples 1 to 3 and Comparative Examples 1 to 4 were etched into a 2 mm wide road shape by wet etching. After the coating, the sample was heat treated at 150°C for 168 hours. The wet etching method was performed in the same manner as in the measurement of room temperature adhesive strength. Thereafter, 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 coefficient of thermal expansion (CTE), surface hardness, room temperature adhesive strength, and heat resistant adhesive strength of the polyimide films of Examples 1 to 3 and Comparative Examples 1 to 4 prepared by Preparation Example 1, measured by the above-mentioned measuring methods, are shown in Table 2 below. The decrease in adhesive strength calculated by the above-mentioned mathematical formula 1 is shown in Table 2 below. [Table 2]

[0041] As a result of the measurements, the polyimide films of Examples 1 to 3 exhibited a thermal expansion coefficient of more than 1 ppm / °C and less than 15 ppm / °C, a surface hardness of 0.4 GPa to 0.6 GPa, a room temperature adhesive strength of 0.6 kgf / cm to 0.9 kgf / cm, a heat-resistant adhesive strength of 0.3 kgf / cm to 0.5 kgf / cm, and a decrease in adhesive strength of 50% or less. In contrast, the polyimide films of Comparative Examples 1 to 4 did not satisfy the range of properties of the polyimide film of the present invention in terms of one or more of the thermal expansion coefficient, surface hardness, room temperature adhesive strength, heat-resistant adhesive strength, and adhesive strength reduction.

[0042] Therefore, it was confirmed that the multilayer polyimide films of Examples 1 to 3 produced within the appropriate ranges of the present invention were all excellent in thermal dimensional stability, moisture dimensional stability, and adhesion strength to copper foil, but that if the appropriate ranges of the present invention were not met, it would be difficult for the multilayer polyimide films of the present invention to satisfy all of the thermal dimensional stability, moisture dimensional stability, and adhesion strength to copper foil. In other words, it was confirmed that the multilayer polyimide film that has excellent dimensional stability and adhesion to copper foil and satisfies all of the various requirements applicable to various fields of application is a polyimide film manufactured within the appropriate range of the present invention. The examples of the polyimide film and method for manufacturing a 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 are not intended to limit the scope of the present invention. Therefore, the true technical scope of protection of the present invention should 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 alterations are possible within the scope of the present invention, and it is obvious that any changes that can be easily made by those skilled in the art are also included within the scope of the present invention. [Industrial Applicability]

[0043] The present invention provides a polyimide film in which the composition ratio and reaction ratio of dianhydride and diamine components are adjusted, thereby providing a polyimide film with excellent dimensional stability and adhesive strength. Such polyimide films are applicable to various fields where polyimide films with excellent dimensional stability and adhesive strength are required, such as flexible metal foil laminates manufactured by a metallizing method or electronic components including such flexible metal foil laminates.

Claims

1. A polyimide film having a surface hardness of 0.4 GPa or more and 0.6 GPa or less as measured by nanoindentation.

2. 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 0.5 kgf / cm or less. The polyimide film according to claim 1 .

3. The adhesive strength reduction rate expressed by the following mathematical formula 1 is 50% or less, The thermal expansion coefficient is more than 1 ppm / °C and less than or equal to 15 ppm / °C. The polyimide film according to claim 1 . [Mathematical formula 1] Adhesive strength reduction rate (%) = [(room temperature adhesive strength with metal foil - heat resistant adhesive strength with metal foil) / room temperature adhesive strength with metal foil] x 100

4. a dianhydride acid component comprising biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA); obtained by imidizing a polyamic acid solution containing a diamine component including two or more selected from the group consisting of paraphenylenediamine (PPD), oxydianiline (ODA), and 1,3-bisaminophenoxybenzene (TPE-R); The polyimide film according to claim 1 .

5. the content of the biphenyltetracarboxylic dianhydride is 40 mol% or more and 99 mol% or less, and the content of the pyromellitic dianhydride is 1 mol% or more and 60 mol% or less, based on 100 mol% of the total content of the dianhydride acid components; 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; The polyimide film according to claim 4.

6. (a) preparing a polyamic acid by polymerizing a dianhydride acid component including biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) and a diamine component including two or more selected from the group consisting of paraphenylenediamine (PPD), oxydianiline (ODA), and 1,3-bisaminophenoxybenzene (TPE-R) in an organic solvent; and (b) imidizing the polyamic acid; A method for producing polyimide film.

7. the content of the biphenyltetracarboxylic dianhydride is 40 mol% or more and 99 mol% or less, and the content of the pyromellitic dianhydride is 1 mol% or more and 60 mol% or less, based on 100 mol% of the total content of the dianhydride acid components; 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; The method for producing a polyimide film according to claim 6.

8. Surface hardness measured by nanoindentation ss) is 0.4 GPa or more and 0.6 GPa or less, 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 0.5 kgf / cm or less. The method for producing a polyimide film according to claim 6.

9. The adhesive strength reduction rate expressed by the following mathematical formula 1 is 50% or less, The thermal expansion coefficient is more than 1 ppm / °C and less than or equal to 15 ppm / °C. The method for producing a polyimide film according to claim 6. [Mathematical formula 1] Adhesive strength reduction rate (%) = [(room temperature adhesive strength with metal foil - heat resistant adhesive strength with metal foil) / room temperature adhesive strength with metal foil] x 100

10. A laminate comprising the polyimide film according to any one of claims 1 to 5 and an electrically conductive metal foil. Flexible metal foil laminate.

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

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