Polyamic acid, polyimide, resin film, and metal-clad laminate

Abstract

To provide a polyimide capable of contributing to carbon neutral, circular economy and sustainable product development and having both heat resistance and mechanical strength in an excellent range, and to provide a polyamic acid giving a resin film and a metal-clad laminate using the polyimide.SOLUTION: A polyamic acid containing an acid anhydride residue derived from an acid anhydride component and a diamine residue derived from a diamine component, wherein the acid anhydride residue derived from the acid anhydride component represented by the following formula (1) is contained in an amount of 10 mol% or more based on all acid anhydride residues, and the diamine residue derived from 2,2 ' - dimethyl-4, 4 ' - diaminobiphenyl is contained in an amount of 10 mol% or more based on all diamine residues: SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polyamic acid, a polyimide obtained by imidizing the polyamic acid, and a resin film and a metal-clad laminate using the polyimide. [Background technology]

[0002] In recent years, with the advancement of miniaturization, weight reduction, and space-saving of electronic devices, there has been an increasing demand for flexible printed circuits (FPCs) that are thin, lightweight, flexible, and highly durable even when repeatedly bent. Because FPCs allow for three-dimensional, high-density packaging even in limited spaces, their applications are expanding to include wiring for moving parts in electronic devices such as hard disk drives (HDDs), DVD players, and smartphones, as well as cables and connectors. Most FPCs are manufactured by forming circuits on the metal layer of a metal-clad laminate, which is made by laminating a metal layer made of metal foil or other materials with an insulating resin substrate (insulating resin layer).

[0003] Polyimide films are widely used in various fields due to their excellent properties, including heat resistance, cold resistance, chemical resistance, electrical insulation, and mechanical strength. Taking advantage of their particularly excellent heat resistance and high rigidity, polyimide films are widely used as insulating resin layers in FPCs. Electronic devices, in particular, are expected to continue to become more functional and smaller in size. Therefore, for example, there is likely to be an increasing need for multilayered FPCs. Furthermore, as the housings of electronic devices such as mobile phones and smartphones become thinner, there is a growing demand for thinner circuit boards. Therefore, as the insulating resin layer becomes thinner due to the thinner circuit boards themselves, polyimide films used as insulating resin layers must have a higher mechanical strength, i.e., a higher modulus of elasticity, to prevent wrinkles during pattern processing and transportation.

[0004] Polyimides are manufactured using raw material monomers such as tetracarboxylic dianhydrides and diamine compounds. These raw materials have often been produced from petrochemical-derived materials. However, against the backdrop of global warming and the depletion of petroleum resources, there is a growing global demand for environmentally friendly materials made from bio-based materials, such as plants. The use of bio-based materials can significantly contribute to carbon neutrality by reducing the use of fossil resources such as petroleum, and can also contribute to the promotion of a circular economy and the creation of a sustainable society. In this context, there is also a growing demand for sustainable product development.

[0005] In response to these backgrounds and recent demands for polyimides, Patent Document 1 proposes a polyimide material that has excellent heat resistance, optical properties, and dielectric properties while increasing its biobased content by using a tetracarboxylic dianhydride synthesized from a biobased raw material, a cellulose derivative such as isosorbide or isomannide, and a trimellitic anhydride. However, the polyimide described in Patent Document 1 leaves room for further improvement in the aforementioned properties, such as heat resistance and mechanical strength. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2023 / 027031 [Patent Document 2] Japanese Patent Application Publication No. 2023-163314 [Patent Document 3] Chinese Patent Application Publication No. 116425976 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, as a result of intensive research, the inventors of the present application discovered that, in developing a polyimide that is preferably used as an insulating resin layer in an FPC, it is possible to achieve both excellent heat resistance and mechanical strength while using bio-based raw materials by using specific compounds as the acid anhydride component and diamine component that constitute the polyimide, and further adjusting the amounts used to fall within specific ranges, and thus completed the present invention.

[0008] Therefore, an object of the present invention is to provide a polyamic acid that provides a polyimide that has both heat resistance and mechanical strength. Another object of the present invention is to provide a resin film and a metal-clad laminate using such a polyimide. Still another object of the present invention is to provide a polyamic acid, a polyimide, a resin film, and a metal-clad laminate that can contribute to carbon neutrality, a circular economy, and sustainable product development.

[0009] Regarding tetracarboxylic dianhydrides, which are raw materials for polyimides, polyimides using specific tetracarboxylic dianhydrides such as those used in Patent Document 1 have also been proposed in prior art other than Patent Document 1 (Patent Documents 2 and 3). However, the polyimide proposed in Patent Document 2 has further improved the problems of elongation and elastic modulus of polyimides using dimer acid diamines disclosed in the prior art, and since the use of dimer diamine is essential in Patent Document 2 as well, there are problems with quality stability and the heat resistance is insufficient.On the other hand, the polyimide proposed in Patent Document 3 is shown to have high transparency and heat resistance by using a semi-aromatic dianhydride monomer having an ester group and an isosorbide structure as a raw material, but there is room for further improvement in the heat resistance and mechanical strength. [Means for solving the problem]

[0010] That is, the present invention is as follows. [1] A polyamic acid containing an acid anhydride residue derived from an acid anhydride component and a diamine residue derived from a diamine component, The acid anhydride component represented by the following formula (1) accounts for 10 mol % or more of the total acid anhydride residues: A polyamic acid characterized by containing 10 mol % or more of diamine residues derived from 2,2'-dimethyl-4,4'-diaminobiphenyl relative to all diamine residues. [ka] [2] The polyamic acid according to [1], wherein the molar ratio of the acid anhydride residues derived from the acid anhydride component represented by formula (1) to the diamine residues derived from the 2,2'-dimethyl-4,4'-diaminobiphenyl is 10 to 80 mol %. [3] The polyamic acid according to [1], characterized in that it contains acid anhydride residues derived from pyromellitic dianhydride and / or acid anhydride residues derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride in an amount of 20 to 90 mol % based on the total acid anhydride residues. [4] The polyamic acid according to [1], characterized in that it contains acid anhydride residues derived from pyromellitic anhydride and / or acid anhydride residues derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride in an amount of 60 to 90 mol % based on the total acid anhydride residues. [5] The polyamic acid according to [4], characterized in that the polyamic acid contains acid anhydride residues derived from pyromellitic anhydride in an amount of 60 to 90 mol % based on the total acid anhydride residues. [6] The polyamic acid according to [1], characterized in that it contains diamine residues derived from 2,2'-dimethyl-4,4'-diaminobiphenyl in an amount of 70 mol % or more based on the total diamine residues. [7] A polyimide obtained by imidizing the polyamic acid according to any one of [1] to [6]. [8] A resin film containing a polyimide obtained by imidizing the polyamic acid according to any one of [1] to [6]. [9] The resin film according to [8], characterized in that the thermal deformation rate at 200°C to 260°C measured by thermomechanical analysis (TMA) is 2% or less.

[10] The resin film according to [8], characterized in that the thermal expansion coefficient is 10 ppm / K or more and 40 ppm / K or less.

[11] The resin film according to [8], characterized in that the glass transition temperature is 280°C or higher.

[12] The resin film according to [8], characterized in that the 5% weight loss temperature is 400°C or higher.

[13] A metal-clad laminate comprising an insulating resin layer consisting of a single layer or multiple layers and a metal layer laminated on at least one surface of the insulating resin layer, A metal-clad laminate, characterized in that the insulating resin layer contains the resin film described in [8]. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a polyimide that combines excellent heat resistance and mechanical strength, a resin film and a metal-clad laminate using the polyimide, and a polyamic acid that provides these. Furthermore, the polyamic acid and polyimide according to the present invention are produced using an acid anhydride component obtained from a bio-based raw material, and therefore can contribute to carbon neutrality, a circular economy, and the development of sustainable products. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a graph showing the displacement measured by thermomechanical analysis (TMA) for the polyimide films of Example 7 and Comparative Example 2. The solid line shows the results of Example 7, and the dashed line shows the results of Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described.

[0014] <Polyamic acid, polyimide> The polyamic acid of the present embodiment is a precursor of polyimide, and is composed of an acid anhydride residue, which is a tetravalent group derived from a tetracarboxylic dianhydride (hereinafter sometimes simply referred to as "acid anhydride") component, and a diamine residue, which is a divalent group derived from a diamine compound (hereinafter sometimes simply referred to as "diamine") component. When the combination of these components is considered as one repeating unit, the polyamic acid is composed of a polymer of this repeating unit. The composition can be controlled by adjusting the amount (molar ratio) of the acid anhydride component and the diamine component charged.

[0015] The polyimide of the present embodiment is obtained by imidizing the polyamic acid, and contains a specific acid anhydride residue and a specific diamine residue.

[0016] For example, polyamic acids are typically obtained by dissolving approximately equimolar amounts of a specific acid anhydride component and a diamine component in an organic solvent and then polymerizing the mixture by stirring at a temperature typically ranging from 0 to 100°C for 30 minutes to 24 hours. During the reaction, the reaction components are dissolved so that the resulting precursor is in a concentration of 5 to 30% by weight, preferably 10 to 20% by weight, in the organic solvent. Examples of organic solvents used in the polymerization reaction include N,N-dimethylformamide, N,N-dimethylacetamide (DMAC), N-methyl-2-pyrrolidone, 2-butanone, dimethyl sulfoxide, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme, triglyme, and γ-butyrolactone. Two or more of these solvents can also be used in combination, and aromatic hydrocarbons such as xylene and toluene can also be used in combination.

[0017] In the synthesis of polyamic acid and polyimide, the acid anhydride component and the diamine component may each be used alone or in combination of two or more. By selecting the types of acid anhydride component and diamine component, or by selecting the respective molar ratios when two or more acid anhydrides or diamines are used, physical properties such as thermal conductivity, thermal expansion, heat resistance, adhesiveness, glass transition temperature, and mechanical strength can be controlled.

[0018] The polyamic acid and polyimide of this embodiment may also contain a terminal blocking agent. Monoamines or dicarboxylic acids are preferred as terminal blocking agents. The amount of terminal blocking agent introduced is preferably 0.0001 to 0.1 mol per 1 mol of the acid anhydride component, and particularly preferably 0.001 to 0.05 mol. Examples of monoamine terminal blocking agents include methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, aniline, and 4-methylaniline. Of these, benzylamine and aniline are preferred. Dicarboxylic acid terminal blocking agents are preferably dicarboxylic acids, which may be partially ring-closed. Examples of recommended dicarboxylic acid terminal blocking agents include phthalic acid, phthalic anhydride, 4-chlorophthalic acid, tetrafluorophthalic acid, cyclopentane-1,2-dicarboxylic acid, and 4-cyclohexene-1,2-dicarboxylic acid. Of these, phthalic acid and phthalic anhydride are preferably used.

[0019] The synthesized polyamic acid is usually advantageously used as a reaction solvent solution, but it can be concentrated, diluted, or replaced with another organic solvent if necessary. Polyamic acid is also advantageously used because it generally has excellent solvent solubility. The method for imidizing polyamic acid is not particularly limited, and a suitable method is, for example, heat treatment in the solvent at a temperature of 80°C to 400°C for 1 to 24 hours.

[0020] Furthermore, although there are no limitations on the polyamic acid, it is preferable that the viscosity be in the range of 1,000 to 200,000 cP by adjusting the concentration and weight-average molecular weight Mw. If the viscosity is high, dilution can be achieved by adding a solvent. The weight-average molecular weight Mw of the polyamic acid is preferably, for example, in the range of 10,000 to 500,000, and more preferably in the range of 50,000 to 500,000. If the weight-average molecular weight is less than 10,000, the film tends to have reduced strength and become brittle. On the other hand, if the weight-average molecular weight exceeds 500,000, the viscosity increases excessively, which tends to cause defects such as uneven film thickness and streaks during coating.

[0021] The acid anhydride residue and the diamine residue contained in the polyamic acid and polyimide of the present embodiment will be collectively described below.

[0022] (Acid anhydride component, acid anhydride residue) First, the acid anhydride component used in the polyamic acid and polyimide of the present embodiment essentially contains an acid anhydride represented by the following general formula (1). [ka]

[0023] The acid anhydride represented by formula (1) is derived from dianhydrohexitol, such as isosorbide, isomannide, or isoidide, a cellulose derivative, and is derived from biological raw materials. This allows the provision of polyamic acids and polyimides that can contribute to carbon neutrality, the circular economy, and sustainable product development. Furthermore, these compounds have a bulky and rigid alicyclic structure, which can impart transparency and thermoplasticity. Formula (1) is shown without specifying the isomeric structures derived from isosorbide, isomannide, or isoidide, but specific examples are represented by the following formulas (1)-1 to (1)-3. (1)-1 represents isosorbide-bis(trimellitate anhydride) derived from isosorbide, (1)-2 represents isomannide-bis(trimellitate anhydride) derived from isomannide, and (1)-3 represents isoidide-bis(trimellitate anhydride) derived from isoidide. Among these, isosorbide is widely used in pharmaceuticals, and from the viewpoints of price, availability, etc., the use of compound (1)-1 is a preferred embodiment. [ka]

[0024] These compounds (1)-1 to (1)-3 can be produced by any conventionally known method, and the production method is not limited thereto. For example, they can be produced by reacting isosorbide, isomannide, or isoidide with a trimellitic anhydride compound such as trimellitic anhydride chloride. In the present embodiment, these compounds (1)-1 to (1)-3 can be used alone or in a mixture of two or more.

[0025] In the polyamic acid and polyimide of the present embodiment, the acid anhydride represented by formula (1) is contained in an amount of 10 mol % or more relative to the total 100 mol % of all acid anhydride components. That is, the acid anhydride residues derived from this acid anhydride are set to 10 mol % or more relative to the total 100 mol % of all acid anhydride residues in the polyamic acid and polyimide produced. If the acid anhydride component (acid anhydride residue) of formula (1) is less than 10 mol %, the amount (degree) of biomass in the polyamic acid and polyimide will be low, and effects such as carbon neutrality will not be fully achieved. Furthermore, the acid anhydride component of formula (1) also serves to impart flexibility to the molecular chain. If it is less than 10 mol %, the polyamic acid and polyimide may become brittle and have low elongation. On the other hand, as the acid anhydride component (acid anhydride residue) of formula (1) increases, the content of other acid anhydride components (acid anhydride residues) relatively decreases. Therefore, taking into consideration the blending of other acid anhydride components (acid anhydride residues) as described below, the content of the acid anhydride component (acid anhydride residue) of formula (1) is preferably 10 mol % or more and 80 mol % or less, more preferably 10 mol % or more and 60 mol % or less, even more preferably 10 mol % or more and 50 mol % or less, and still more preferably 20 mol % or more and 40 mol % or less.

[0026] In addition, in the polyamic acid and polyimide of this embodiment, it is a preferred embodiment to use pyromellitic dianhydride (PMDA) and / or 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) as the acid anhydride component (acid anhydride residue) other than that of formula (1). These other acid anhydride components control the molecular orientation in the polyimide, suppress an increase in the coefficient of thermal expansion (CTE), and improve heat resistance, thereby enabling the polyimide and resin film formed using the polyamic acid of this embodiment to have a lower CTE and improved heat resistance. They also contribute to an increase in the elastic modulus.

[0027] The content of PMDA and / or BPDA is preferably within the range of 20 to 90 mol %, based on 100 mol % of all acid anhydride components. It is more preferably within the range of 60 to 90 mol %. That is, the acid anhydride residues derived from these acid anhydrides are preferably within the range of 20 to 90 mol %, based on 100 mol % of all acid anhydride residues in the polyamic acid and polyimide to be produced, and more preferably within the range of 60 to 90 mol %. Of these, the use of PMDA is more preferred. The use of PMDA increases the imide group concentration and strengthens the interaction between molecular chains, thereby lowering the CTE and increasing the glass transition temperature (Tg) and thermal decomposition temperature, making this a more preferred embodiment. When PMDA is used, it is also preferably within the range of 20 to 90 mol %, based on 100 mol % of all acid anhydride components, and more preferably within the range of 60 to 90 mol %.

[0028] The third acid anhydride component other than the compound represented by formula (1), PMDA, or BPDA may be selected from any other tetracarboxylic acid anhydride component generally usable in the production of polyamic acid and polyimide, provided that it does not impair the effects and purposes of the present invention. However, aromatic tetracarboxylic acid dianhydrides are preferred. Anhydrides of tetracarboxylic acids having an aliphatic backbone may also be used. When these third acid anhydride components are used, they are preferably used in an amount of 50 mol % or less, more preferably 30 mol % or less, and even more preferably 10 mol % or less, of the total acid anhydride components.

[0029] (diamine component, diamine residue) The diamine component used in the polyamic acid and polyimide of this embodiment is 2,2'-dimethyl-4,4'-diaminobiphenyl (also known as m-tolidine, 2,2'-dimethylbenzidine, or 4,4'-diamino-2,2'-dimethylbiphenyl). This diamine component has a rigid biphenyl ring structure and methyl groups on the side chains of the two benzene rings. This strengthens intermolecular interactions, which is thought to reduce molecular chain movement and intramolecular rotation even when heated. This suppresses molecular chain motion, improving heat resistance, e.g., increasing the glass transition temperature (Tg), and suppressing thermal deformation. For example, this diamine component is thought to contribute to reducing thermal wrinkling during the manufacturing and transport of polyimide films and metal-clad laminates, as well as deformation and wrinkling during copper foil pressing.

[0030] To achieve these properties, the polyamic acid and polyimide of the present embodiment must contain the diamine component (2,2'-dimethyl-4,4'-diaminobiphenyl) in an amount of 10 mol % or more relative to 100 mol % of all diamine components. That is, the diamine residues derived from this diamine component must account for 10 mol % or more relative to 100 mol % of all diamine residues. The content of this diamine component (diamine residue) is preferably 50 mol % or more, more preferably 70 mol % or more, and even more preferably 100 mol % relative to 100 mol % of all diamine components (diamine residues).

[0031] As the diamine component other than those described above, any diamine component that can generally be used in the synthesis of polyimides can be selected and used as long as it does not impair the effects and objects of the present invention, but aromatic diamine compounds are preferred. For example, a diamine component that provides high flatness (e.g., one or more selected from the group consisting of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB), paraphenylenediamine (PPD), 4,4'-diaminobiphenyl (DAB), and 4,4'-diaminobenzanilide (DABA)) can be used, or a diamine component that provides flexibility (e.g., one or more selected from the group consisting of 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,4-bis(4-aminophenoxy)benzene (TPE-Q), 1,3-bis(3-aminophenoxy)benzene (APB), and 2,2'-bis[4-(4-aminophenoxy)phenyl]propane (BAPP)) can be used in combination. Diamine compounds having an aliphatic skeleton may also be used. When other diamine components are used, they are preferably used in an amount of 50 mol % or less, more preferably 30 mol % or less, and even more preferably 10 mol % or less of the total diamine components.

[0032] (Acid anhydride component / diamine component (molar ratio)) In the polyamic acid and polyimide of the present embodiment, the molar ratio of the acid anhydride component and diamine component used as essential components, that is, the molar ratio of the acid anhydride residue derived from the acid anhydride component represented by formula (1) to the diamine residue derived from the 2,2'-dimethyl-4,4'-diaminobiphenyl, is preferably within the range of 10 to 80 mol %. By setting the molar ratio of the essential components within this range, the proportion of biomass raw material derived from the compound of formula (1) can be relatively high, and heat resistance and elastic modulus can be improved.

[0033] (Other ingredients) The polyamic acid and polyimide of the present embodiment may contain fillers and other components, such as silicon dioxide, aluminum oxide, boron nitride, magnesium oxide, beryllium oxide, aluminum nitride, silicon nitride, aluminum fluoride, calcium fluoride, and metal salts of organic phosphinic acids, as needed, as long as the object of the present invention is not impaired. These components may be used alone or in combination of two or more.

[0034] <Resin film> The resin film of the present embodiment has a single or multiple polyimide layers, at least one of which is made of a polyimide obtained by imidizing the polyamic acid of the present embodiment, and may be a film (sheet) made of an insulating resin, or may be an insulating resin film laminated on a substrate such as a resin sheet, such as a copper foil, a glass plate, a polyimide film, a polyamide film, or a polyester film.

[0035] As described above, the resin film of this embodiment essentially uses the acid anhydride component of formula (1), which is a biologically derived raw material. This allows for the production of polyimides and resin films with relatively high biomass content (or biomass content), and they also have excellent low thermal expansion and heat resistance. The coefficient of thermal expansion (CTE) is typically 80 ppm / K or less, preferably 70 ppm / K or less, more preferably 50 ppm / K or less, even more preferably 40 ppm / K or less, even more preferably 10 ppm / K to 40 ppm / K, sufficiently preferably 20 ppm / K to 40 ppm / K, and most preferably 20 ppm / K to 30 ppm / K. Controlling the CTE within this range can suppress deformation such as curling and ensure high dimensional stability. Here, CTE is the average value of the thermal expansion coefficients in the MD and TD directions of the resin film.

[0036] In particular, with regard to heat resistance, a low thermal deformation rate is preferable, contributing to the suppression of thermal wrinkles during the manufacturing and transport of metal-clad laminates, as well as deformation and wrinkles during copper foil pressing. The thermal deformation rate can be determined by measuring the displacement that occurs when the temperature is raised from 200°C to 260°C using thermomechanical analysis (TMA), as described in the Examples. The thermal deformation rate is preferably 2% or less, more preferably 1.5% or less, and even more preferably 1.0% or less. Since it is most preferable that no thermal deformation occurs, there is no lower limit, but for the resin film of this embodiment, it is usually 0.05% or more. The reason for measuring the displacement from 200°C to 260°C is that the manufacturing process of metal-clad laminates often reaches high temperatures above 200°C, and comparing at temperatures below the glass transition temperature makes it easier to compare thermal film deformation. Furthermore, because the lamination temperature of bonding films in the manufacturing process of flexible printed circuit boards is also exposed to high temperatures around 200°C, measurements are performed under stricter conditions of 200°C to 260°C. In a particularly preferred embodiment, the thermal deformation rate is adjusted by adjusting the content of the essential diamine component described above.

[0037] Regarding heat resistance, in a thermal decomposition test, the resin film of the present embodiment preferably has a 5% thermal weight loss temperature (Td5) of 390° C. or higher, more preferably 400° C. or higher, even more preferably 405° C. or higher, and even more preferably 410° C. or higher. By controlling the temperature within such a range, the resin film has sufficient heat resistance even when used as a main component of an FPC.

[0038] Regarding heat resistance, the resin film of the present embodiment may have a glass transition temperature (Tg) of 275° C. or higher, and preferably has heat resistance of 280° C. or higher, more preferably 290° C. or higher, even more preferably 300° C. or higher, still more preferably 310° C. or higher, and most preferably 320° C. or higher.

[0039] Furthermore, the resin film of this embodiment is preferably one in which the modulus of elasticity is adjusted by adjusting the content of the other acid anhydride components described above. The modulus of elasticity is preferably 3.0 GPa or more, more preferably 3.5 GPa or more, even more preferably 4.0 GPa or more, still more preferably 5.0 GPa or more, and most preferably 6.0 GPa or more.

[0040] The overall thickness of the resin film of this embodiment is preferably within the range of 2 to 100 μm, and more preferably within the range of 4 to 50 μm. If the thickness is less than 2 μm, problems such as wrinkles in the metal foil are likely to occur during the transport process during the production of the metal-clad laminate. On the other hand, if the thickness exceeds 100 μm, there is a tendency for problems to occur in terms of toughness, flexibility, and productivity.

[0041] Examples of methods for forming the polyimide (layer) and resin film of this embodiment include: [1] a method of coating a support substrate (e.g., a metal layer) with a polyamic acid solution, drying the solution, and then imidizing the polyamic acid to produce a resin film (hereinafter referred to as the casting method); [2] a method of coating a support substrate with a polyamic acid solution, drying the solution, peeling the polyamic acid gel film from the support substrate, and then imidizing the polyamic acid to produce a resin film. Furthermore, when the polyimide layer is made up of multiple polyimide layers, examples of the manufacturing method include: [3] a method of repeatedly coating a support substrate with a polyamic acid solution and drying the solution, followed by imidization (hereinafter referred to as the sequential coating method); and [4] a method of simultaneously coating a support substrate with a polyamic acid layer structure by multilayer extrusion, drying the layer, and then imidizing the layer (hereinafter referred to as the multilayer extrusion method). From the viewpoint of controlling dimensional stability and adhesion to the metal layer, it is preferable to form the polyimide layer (resin film and the insulating resin layer and metal-clad laminate using the same, which will be described later) by the casting method or the sequential coating method.

[0042] The method for applying the polyamic acid solution (or polyimide solution) to the substrate is not particularly limited, and it can be applied using a coater such as a comma, die, knife, or lip. When forming a multilayer polyimide layer, a method in which the polyamic acid solution (or polyimide solution) is repeatedly applied to the substrate and dried is preferred. The insulating resin layer (described below) in this embodiment may be formed from only a single polyimide layer, or may be formed from multiple polyimide layers.

[0043] <Metal-clad laminate> (metal layer) The material of the metal layer is not particularly limited, but examples include copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and alloys thereof. Among these, copper, iron, or nickel metal elements, or indium tin oxide (ITO) are preferred, and copper (copper foil) is more preferred. Both electrolytic copper foil and rolled copper foil can be used as the copper foil. The metal layer is selected to exhibit the properties required for the intended use, such as the conductivity of the metal layer, the optical transparency of the polyimide layer, and adhesion to the polyimide layer. The shape of the metal layer is not particularly limited, and may be processed appropriately depending on the application. A long roll-shaped metal foil is preferably used.

[0044] The thickness of the metal layer is not particularly limited, but is preferably 100 μm or less, more preferably in the range of 0.1 to 70 μm, and even more preferably in the range of 1 to 50 μm. For heat dissipation applications, such as those involving automotive applications, where large currents are often passed, a thicker metal layer (e.g., copper foil) is preferred to withstand the large current. On the other hand, if the metal layer is too thick, the flexibility and processability of the laminate substrate tend to decrease, and the weight also tends to increase.

[0045] (insulating resin layer) The metal-clad laminate of this embodiment comprises an insulating resin layer consisting of a single layer or multiple layers, and a metal layer laminated on at least one surface (one side) or both surfaces (both surfaces) of this insulating resin layer, and in a preferred embodiment, at least one layer of the insulating resin layer is constructed by including the above-mentioned resin film.

[0046] When the insulating resin layer includes a resin film composed of multiple polyimide layers, it may have a two-layer structure consisting of a polyimide layer (P1) directly laminated on the metal layer and a polyimide layer (P2) not directly laminated on the metal layer. As shown in the following exemplary configurations 1 to 4, it may have a three-layer structure, and a third polyimide layer (P3) may be laminated in the order of (P1) / (P2) / (P3). M1 and M2 represent metal layers, and M1 and M2 may be the same or different. The polyimide layer (P1) directly laminated on the metal layer and the third polyimide layer (P3) may have the same composition. For example, when multiple polyimide layers are formed by a casting method, a two-layer structure may be formed in which a polyimide layer (P1) that is directly laminated onto a metal layer from the cast side and a polyimide layer (P2) that is not directly laminated onto the metal layer are laminated in this order. Alternatively, a three-layer structure may be formed in which a polyimide layer (P1) that is directly laminated onto a metal layer from the cast side and a polyimide layer (P2) that is not directly laminated onto the metal layer are laminated in this order from the cast side. The term "cast side" here refers to the surface facing the support when forming the polyimide layer. The support may be the metal layer of a metal-clad laminate, glass, or the support used when forming a gel film, etc. The surface of multiple polyimide layers opposite the cast side is referred to as the "laminate side." Unless otherwise specified, a metal layer may or may not be laminated on the laminate side.

[0047] Configuration 1;M1 / P1 / P2 Configuration 2: M1 / P1 / P2 / P1 (or P3) Configuration 3: M1 / P1 / P2 / P1 (or P3) / M2 (or M1) Configuration 4: M1 / P1 / P2 / P1 (or P3) / P2 / P1 (or P3) / M2 (or M1)

[0048] The polyimide constituting the polyimide layer (P1) and the polyimide layer (P3) is preferably a thermoplastic polyimide, which improves the adhesiveness as an insulating resin layer and is suitable for use as an adhesive layer for a metal layer.

[0049] A preferred embodiment of the insulating resin layer comprises a thermoplastic polyimide layer (P1) and a non-thermoplastic polyimide layer (P2) made of a non-thermoplastic polyimide, and at least one of the non-thermoplastic polyimide layers (P2) has a polyimide layer (P1) that becomes a thermoplastic polyimide layer. That is, the polyimide layer (P1) is preferably provided on one or both sides of the non-thermoplastic polyimide layer.

[0050] The non-thermoplastic polyimide layer constitutes a low-thermal expansion polyimide layer, and the thermoplastic polyimide layer constitutes a high-thermal expansion polyimide layer. Here, a low-thermal expansion polyimide layer generally refers to a polyimide layer having a coefficient of thermal expansion (CTE) preferably in the range of 1 ppm / K to 25 ppm / K, more preferably in the range of 3 ppm / K to 25 ppm / K. A high-thermal expansion polyimide layer generally refers to a polyimide layer having a CTE preferably in the range of 35 ppm / K or more, more preferably in the range of 35 ppm / K to 80 ppm / K, and even more preferably in the range of 35 ppm / K to 70 ppm / K. A polyimide layer having a desired CTE can be obtained by appropriately changing the combination of raw materials used, the thickness, and the drying and curing conditions. In the resin film, insulating resin layer, and metal-clad laminate of this embodiment, since the polyimide and resin film of this embodiment described above have low thermal expansion and heat resistance as described above, it is a preferred embodiment that they are used to form a layer of the non-thermoplastic polyimide.

[0051] Here, non-thermoplastic polyimide generally refers to polyimide that does not soften or exhibit adhesiveness even when heated. In this embodiment, however, the storage modulus at 30°C measured using a dynamic viscoelasticity measuring device (DMA) is 1.0 × 109 Pa or more, and the storage modulus at 350°C is 1.0 × 10 9 The term "thermoplastic polyimide" refers to a polyimide having a storage modulus of 1.0×10 Pa or more at 30° C., as measured by DMA. In addition, thermoplastic polyimide (also referred to as "TPI") generally refers to a polyimide having a clearly identifiable glass transition temperature (Tg). In this embodiment, however, the term "TPI" refers to a polyimide having a storage modulus of 1.0×10 Pa or more at 30° C., as measured by DMA. 9 Pa or more, and the storage modulus at 300°C is 1.0 × 10 8 Polyimides with a modulus of less than 1 Pa are also referred to as polyimides.

[0052] <Metal-clad laminate manufacturing method> As described above, the metal-clad laminate of this embodiment is preferably formed by forming an insulating resin layer containing a resin film consisting of a single layer or multiple layers of polyimide on a metal layer as a supporting substrate by a casting method or a sequential coating method from the viewpoint of dimensional stability, etc. However, this is not particularly limited. For example, the metal-clad laminate may be prepared by preparing an insulating resin layer containing a resin film composed of a polyimide layer of this embodiment, sputtering a metal onto the insulating resin layer to form a seed layer, and then forming a metal layer by, for example, plating.

[0053] Alternatively, the insulating resin layer may be prepared by preparing an insulating resin layer containing the resin film of this embodiment and laminating a metal foil thereon by a method such as thermocompression bonding.

[0054] In these cases, the surface of the resin film may be subjected to a modification treatment such as plasma treatment in order to enhance the adhesion between the resin film and the metal layer.

[0055] Furthermore, when manufacturing a metal-clad laminate having metal layers on both sides, the metal layer can be laminated by means of thermocompression or the like, directly onto the polyimide layer of the single-sided metal-clad laminate obtained by the above-mentioned method, or after forming an adhesive layer that does not impair the properties such as transparency of the insulating resin layer as needed. The heat-pressing temperature when thermocompressing the metal layer is not particularly limited, but it is desirable that it be equal to or higher than the glass transition temperature of the polyimide layer adjacent to the metal layer used. The heat-pressing pressure is 1 to 500 kg / m, depending on the type of press equipment used. 2 It is desirable that the range is [Example]

[0056] The present invention will be specifically described below based on examples, but the present invention is not limited to the scope of these examples.

[0057] The abbreviations used in the examples represent the following compounds. ISS-TME: isosorbide bis(trimellitate anhydride) obtained in Synthesis Example 1 BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride PMDA: Pyromellitic dianhydride m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl TFMB: 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl TPE-R: 1,3-bis(4-aminophenoxy)benzene DMAc: N,N-dimethylacetamide

[0058] The properties evaluated in the examples were evaluated according to the following evaluation methods.

[0059] [Viscosity measurement] The viscosity of the polyamic acid solution was measured at 25°C using a cone-plate viscometer (manufactured by Tokimec Co., Ltd.) equipped with a thermostatic water bath.

[0060] [Weight average molecular weight (Mw)] Measurement was performed by gel permeation chromatography (manufactured by Tosoh Corporation, product name: HLC-8220GPC). Polystyrene was used as a standard substance, and N,N-dimethylacetamide was used as a developing solvent.

[0061] [Tensile modulus, tensile elongation] Test pieces of polyimide film (10 mm × 15 mm) were prepared, and tensile tests were performed using a Tensilon universal testing machine (Orientec Co., Ltd., RTA-250) at a tensile speed of 10 mm / min in accordance with IPC-TM-650, 2.4.19, to calculate the tensile modulus and tensile elongation.

[0062] [Thermal deformation rate, coefficient of thermal expansion (CTE)] The polyimide film obtained by etching the copper foil was cut into a size of 3 mm x 20 mm, and using a thermomechanical analyzer (Hitachi High-Tech Science Corporation, product name: TMA7100), the temperature was raised from 30°C to 260°C at a heating rate of 10°C / min while applying a load of 49 mN, and then the sample was held at that temperature for 10 minutes and then cooled at a rate of 10°C / min to determine the average thermal expansion coefficient (thermal expansion coefficient) from 250°C to 100°C. The thermal deformation rate was defined as the ratio (%) of the displacement occurring when the sample was heated from 200°C to 260°C to the length of the sample being measured. FIG. 1 shows measurement data (graph) of the displacement with respect to the temperature for the resin films according to Example 7 and Comparative Example 2.

[0063] [Thermal decomposition temperature (Td5)] A polyimide film weighing 10 to 20 mg was heated at a constant rate from 30°C to 550°C in a nitrogen atmosphere using a thermogravimetric analyzer (TG), and the weight change was measured. The weight at 200°C was set to zero, and the temperature at which the weight loss rate reached 5% was defined as the thermal decomposition temperature (Td5).

[0064] [Glass transition temperature (Tg)] The resin film (10 mm x 22.6 mm) was heated from 20°C to 400°C at a rate of 10°C / min using a dynamic thermomechanical analyzer, and the dynamic viscoelasticity was measured to determine the glass transition temperature (Tan δ maximum value: °C).

[0065] (Synthesis Example 1) A four-necked flask equipped with a thermometer, stirrer, and condenser was charged with isosorbide and 30 times the amount of anhydrous dichloromethane, and the mixture was stirred to dissolve, followed by the addition of 1.1 moles of triethylamine relative to the isosorbide. Furthermore, 2.1 moles of trimellitic anhydride chloride relative to the isosorbide was added, and the mixture was stirred at 0°C for 20 hours. The resulting precipitate was filtered off, and the filtrate was slowly added dropwise to 30 volumes of petroleum ether to obtain a white solid. The resulting white solid was filtered off and dried under reduced pressure at 80°C. The resulting white solid was dissolved in deuterated dimethyl sulfoxide (DMSO-d6) and 1 Analysis by H-NMR identified the compound as the target compound, isosorbide-bis(trimellitate anhydride).

[0066] (Examples 1 to 16, Comparative Examples 1 and 2) To synthesize the polyamic acid solutions of Examples 1 to 16 and Comparative Examples 1 and 2, a 500 ml separable flask was charged with DMAc as a solvent under a nitrogen stream so as to obtain the solid content concentration shown in Table 1, and the diamine component and acid anhydride component (molar parts) shown in Table 1 were then added. The mixture was stirred at room temperature for 36 hours to carry out a polymerization reaction, thereby preparing a viscous solution of polyamic acid.

[0067] [Table 1]

[0068] Next, the polyamic acid solutions according to Examples 1 to 16 and Comparative Examples 1 and 2 prepared as shown in Table 1 were applied to copper foil (electrolytic copper foil, manufactured by Fukuda Metal Foil & Powder Co., Ltd., product name: CF-T49A-DS-HD2-12, thickness: 12 μm, Rz=1.2 μm) so that the thickness after curing was as shown in Table 2. The solution was then dried by heating at 90 to 140°C to remove the solvent. The temperature was then increased stepwise over 30 minutes within a temperature range of 130 to 360°C to produce metal-clad laminates (CCLs) in which an insulating resin layer made of a polyimide layer was laminated on the copper foil. To evaluate the properties of the polyimide layer in each metal-clad laminate, the copper foil was etched away to produce a resin film, which was then evaluated. The evaluation results are shown in Table 2.

[0069] [Table 2]

[0070] Although the embodiments of the present invention have been described in detail above for the purpose of illustration, the present invention is not limited to the above-described embodiments.

Claims

1. A polyamic acid containing an acid anhydride residue derived from an acid anhydride component and a diamine residue derived from a diamine component, The acid anhydride component represented by the following formula (1) accounts for 10 mol % or more of the total acid anhydride residues: A polyamic acid characterized by containing 10 mol % or more of diamine residues derived from 2,2'-dimethyl-4,4'-diaminobiphenyl based on the total diamine residues. 【Chemistry 1】

2. The polyamic acid according to claim 1, wherein the molar ratio of the acid anhydride residue derived from the acid anhydride component represented by formula (1) to the diamine residue derived from the 2,2'-dimethyl-4,4'-diaminobiphenyl is 10 to 80 mol %.

3. The polyamic acid according to claim 1, characterized in that it contains acid anhydride residues derived from pyromellitic dianhydride and / or acid anhydride residues derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride in an amount of 20 to 90 mol % based on the total acid anhydride residues.

4. 2. The polyamic acid according to claim 1, wherein the polyamic acid contains acid anhydride residues derived from pyromellitic dianhydride and / or acid anhydride residues derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride in an amount of 60 to 90 mol % based on the total acid anhydride residues.

5. 5. The polyamic acid according to claim 4, wherein the acid anhydride residues derived from pyromellitic anhydride are contained in an amount of 60 to 90 mol % based on the total acid anhydride residues.

6. 2. The polyamic acid according to claim 1, wherein the diamine residues derived from 2,2'-dimethyl-4,4'-diaminobiphenyl account for 70 mol % or more of the total diamine residues.

7. A polyimide obtained by imidizing the polyamic acid according to any one of claims 1 to 6.

8. A resin film comprising a polyimide obtained by imidizing the polyamic acid according to any one of claims 1 to 6.

9. 9. The resin film according to claim 8, wherein the thermal deformation rate at 200° C. to 260° C. is 2% or less when measured by thermomechanical analysis (TMA).

10. 9. The resin film according to claim 8, wherein the thermal expansion coefficient is 10 ppm / K or more and 40 ppm / K or less.

11. 9. The resin film according to claim 8, wherein the glass transition temperature is 280° C. or higher.

12. 9. The resin film according to claim 8, wherein the 5% weight loss temperature is 400°C or higher.

13. A metal-clad laminate comprising an insulating resin layer consisting of a single layer or multiple layers, and a metal layer laminated on at least one surface of the insulating resin layer, A metal-clad laminate, wherein the insulating resin layer comprises the resin film according to claim 8.

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