CN114651036B

CN114651036B - Polyimide film with improved dimensional stability and method for preparing same

Info

Publication number: CN114651036B
Application number: CN202080077421.8A
Authority: CN
Inventors: 李吉男; 金纪勋
Original assignee: Polyimide Advanced Materials Co ltd
Current assignee: Polyimide Advanced Materials Co ltd
Priority date: 2019-11-13
Filing date: 2020-11-12
Publication date: 2023-10-24
Anticipated expiration: 2040-11-12
Also published as: WO2021096245A2; CN114651036A; WO2021096245A3; KR102346587B1; KR20210057936A

Abstract

The present application provides a polyimide film obtained by imidizing a polyamic acid solution including a dianhydride component including Benzophenone Tetracarboxylic Dianhydride (BTDA), biphenyl tetracarboxylic dianhydride (BPDA), and pyromellitic dianhydride (PMDA), and a diamine component including diaminodiphenyl ether (ODA), p-phenylene diamine (PPD), and 3, 5-diaminobenzoic acid (DABA), and including 5 to 25 wt% of nano silica particles, and a method for preparing the same.

Description

Polyimide film with improved dimensional stability and method for preparing same

Technical Field

The present application relates to a polyimide film having improved dimensional stability and a method for preparing the same.

Background

Polyimide (PI) is a polymer material having thermal stability based on a hard aromatic main chain, and has excellent mechanical strength, chemical resistance, weather resistance, and heat resistance based on chemical stability of an imide ring.

Further, the polymer material has been attracting attention as a high-functional polymer material from the microelectronics field to the optical field because of its excellent electrical characteristics such as insulation characteristics and low permittivity.

For example, in the microelectronics field, a thin circuit board having high integration and flexibility is being actively developed due to weight reduction and miniaturization of electronic products, and thus polyimide having very excellent heat resistance, low temperature resistance and insulating properties and being easily bent is being used as a protective film of the thin circuit board.

Such a thin circuit board generally has a structure in which a circuit including a metal foil is formed on a polyimide film, and is referred to as a flexible metal foil laminate in a broad sense, and is also referred to as a flexible copper clad laminate (Flexible Copper Clad Laminate, FCCL) in a narrow sense when a thin copper plate is used as a metal foil as an example thereof.

Examples of the method for producing the flexible metal foil laminate include (i) a casting method, a method of casting (cast) a metal foil or coating a polyamide acid as a polyimide precursor thereon and then imidizing the metal foil; (ii) A metallization method, in which a metal layer is directly provided on a polyimide film by sputtering or electroplating; and (iii) a lamination method, a method of bonding a polyimide film and a metal foil by heat and pressure through a thermoplastic polyimide.

Among these, the lamination method has an advantage in that the applicable thickness range of the metal foil is wider than that of the casting method, and the apparatus cost is lower than that of the metallization method. As the apparatus for performing lamination, a roll lamination apparatus or a twin-belt pressing apparatus that continuously laminates while supplying a roll material is used. Among them, a heat roll lamination method using a heat roll lamination apparatus can be more preferably used from the viewpoint of productivity.

However, in the case of lamination, as described above, since the thermoplastic resin is used for adhesion of the polyimide film and the metal foil, it is necessary to apply heat of 300 ℃ or more to the polyimide film in order to exhibit heat sealability of the thermoplastic resin, and in some cases, it is necessary to apply heat of 400 ℃ or more as a temperature close to or higher than the glass transition temperature (Tg) of the polyimide film.

In general, it is known that the storage modulus of a viscoelastic body such as a polyimide film is significantly reduced in a temperature range exceeding the glass transition temperature, as compared with the storage modulus at normal temperature.

That is, when lamination requiring a high temperature is performed, the storage modulus of the polyimide film may be greatly reduced at a high temperature, and the polyimide film may be loosened at a low storage modulus, and after the lamination is completed, the polyimide film may not exist in a flat shape. In other words, in the case of the laminate, it can be said that the dimensional change of the polyimide film is relatively unstable.

It is also noted that the glass transition temperature of the polyimide film is significantly lower than the temperature at the time of lamination. Specifically, in the above case, since the polyimide film has high tackiness at the temperature at which lamination is performed, a relatively large dimensional change may be accompanied, and thus the appearance quality of the polyimide film may be degraded after lamination.

In addition, in the case of using the casting method, as a three-layer polyimide film of a two-layer flexible printed circuit board (FPC), there is exemplified a method of applying a polyamic acid solution on the surface of a polyimide film and drying (imidizing) to prepare a three-layer polyimide film, but a process of preparing a polyimide film, a process of applying and drying (imidizing) on the surface of a polyimide film, and a cost increase (cost-up) is caused due to a plurality of processes being required (for example, see patent document 1).

In addition, as a three-layer polyimide film of a two-layer FPC, there is a method of preparing a three-layer polyimide film by casting a polyamic acid solution in a plurality of layers simultaneously on a support, peeling off the support after drying, and performing heat treatment, but there is also a case where a polyimide layer portion directly contacting the support is attached to the support or a difference in peel strength occurs between a polyimide layer contacting the support and a polyimide layer on the opposite side thereof (for example, see patent documents 2 and 3).

Therefore, a technology capable of greatly improving the dimensional stability (uniformity) of the polyimide film by solving the problems as described above is urgently needed.

Prior art literature

Patent literature

Patent document 1: japanese laid-open patent publication No. Hei 9-116254 (publication date: 1997, 5, 2 days)

Patent document 2: japanese laid-open patent publication No. Hei 7-214637 (publication date: 15 days of 8 months of 1995)

Patent document 3: japanese laid-open patent publication No. Hei 10-138318 (publication date: 5 month of 1998, 26 days)

Disclosure of Invention

Technical problem to be solved by the application

In order to solve the problems described above, an object of the present application is to provide a polyimide film containing nanosilica formed of specific components and specific composition ratios and having excellent dimensional stability, and a method for preparing the same.

Means for solving the technical problems

According to an aspect of the present application, there is provided a polyimide film obtained by imidizing a polyamic acid solution containing a dianhydride component including Benzophenone Tetracarboxylic Dianhydride (BTDA), biphenyl tetracarboxylic dianhydride (BPDA), and pyromellitic dianhydride (PMDA), and a diamine component including diaminodiphenyl ether (ODA), p-phenylene diamine (PPD), and 3, 5-diaminobenzoic acid (DABA), wherein the content of the diaminodiphenyl ether is 10 mol% or more and 30 mol% or less, the content of the p-phenylene diamine is 50 mol% or more and 70 mol% or less, the content of the 3, 5-diaminobenzoic acid is 5 mol% or more and 25 mol% or less, and nano silica particles are included, based on 100 mol% of the total content of the diamine component.

The content of benzophenone tetracarboxylic acid dianhydride may be 10 to 30 mol% based on 100 mol% of the total content of dianhydride components, the content of biphenyl tetracarboxylic acid dianhydride may be 40 to 70 mol%, and the content of pyromellitic acid dianhydride may be 10 to 50 mol%.

The average diameter of the nano-silica particles may be 5 to 50nm.

The polyimide film may have a strength of 300 to 365MPa, an elongation of 30 to 50%, a difference between a maximum value and a minimum value of the degree of orientation (MOR) of more than 0.01 and 0.05 or less, and a difference between a Coefficient of Thermal Expansion (CTE) in a main orientation direction and a secondary orientation direction orthogonal to the main orientation direction of 2 to 7ppm.

According to still another aspect of the present application, there is provided a method for preparing a polyimide film, the method comprising: a first step (a) of polymerizing a dianhydride component including Benzophenone Tetracarboxylic Dianhydride (BTDA), biphenyl tetracarboxylic dianhydride (BPDA), and pyromellitic dianhydride (PMDA) and a diamine component including diaminodiphenyl ether (ODA), p-phenylenediamine (PPD), and 3, 5-diaminobenzoic acid (DABA) in an organic solvent to prepare a polyamic acid; and a second step (b) of adding 5 to 25 wt% of nano silica particles to the polyamic acid of the first step and mixing, wherein the content of the diamine-based diphenyl ether is 10 to 30 mol% inclusive, the content of the p-phenylenediamine is 50 to 70 mol% inclusive, and the content of the 3, 5-diaminobenzoic acid is 5 to 25 mol% inclusive, based on 100 mol% of the total content of the diamine component.

According to another aspect of the present application, there are provided a multilayer film and a flexible metal foil laminate including the polyimide film and a thermoplastic resin layer or a conductive metal foil.

According to these aspects, the problems of the prior art can be solved, and a substantial object of the present application is to provide specific embodiments thereof.

ADVANTAGEOUS EFFECTS OF INVENTION

As described above, the present application provides a polyimide film having excellent dimensional stability by a polyimide film composed of specific components and specific composition ratios and including nano silica, and a method of preparing the same, and thus can be effectively applied to various fields in which these characteristics are required, particularly electronic parts such as flexible metal foil laminates.

Detailed Description

Hereinafter, embodiments of the present application will be described in more detail in the order of "polyimide film" and "method for producing polyimide film" according to the present application.

Before this, the terms or words used herein and in the scope of the application claimed should not be construed as limited to their usual or dictionary meanings, but interpreted as meanings and concepts conforming to the technical spirit of the present application on the basis of the principle that the inventor can properly define terms in order to explain his application in the best manner.

Therefore, it should be understood that the structure of the embodiments described herein is only one embodiment among the preferred embodiments of the present application and does not represent all technical spirit of the present application, so various equivalent substitutions and modifications may be made in terms of the present application.

As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. It will be understood that the terms "comprises," "comprising," "includes," "including" or "having," etc., when used herein, are intended to specify the presence of stated features, integers, steps, components, or groups thereof, but do not preclude the presence or addition of one or more other features or integers, steps, components, or groups thereof.

Where an amount, concentration, or other value or parameter is given as either a range, preferred range, or an enumeration of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges which might be formed from any pair of any upper value or preferred value and any lower value or preferred value, regardless of whether ranges are separately disclosed.

When numerical ranges are referred to herein, unless otherwise indicated, the ranges are intended to include the endpoints thereof, and all integers and fractions within the range. The scope of the application is not intended to be limited to the particular values mentioned when defining the scope.

"dianhydride" is herein intended to include precursors or derivatives thereof, which may not be technically dianhydrides, but which also react with diamines to form polyamic acids, which can be reconverted to polyimides.

"diamine" is herein intended to include precursors or derivatives thereof, which may not be diamine in the art, but which also react with dianhydride to form a polyamic acid which can be reconverted to a polyimide.

The polyimide film according to the present application is obtained by imidizing a polyamic acid solution containing a dianhydride component including Benzophenone Tetracarboxylic Dianhydride (BTDA), biphenyl tetracarboxylic dianhydride (BPDA), and pyromellitic dianhydride (PMDA), and a diamine component including diaminodiphenyl ether (ODA), p-phenylene diamine (PPD), and 3, 5-diaminobenzoic acid (DABA), wherein the content of the diaminodiphenyl ether is 10 mol% or more and 30 mol% or less, the content of the p-phenylene diamine is 50 mol% or more and 70 mol% or less, and the content of the 3, 5-diaminobenzoic acid is 5 mol% or more and 25 mol% or less, and contains 5-25 wt% of nano silica particles, based on 100 mol% of the total content of the diamine component.

In particular, the nano silica content is comprised between 5 and 25% by weight, when the total weight of the polyimide film is 100% by weight. The nano silica forms a network with polyimide to suppress shrinkage and expansion occurring during film formation and to control alignment deformation.

That is, the nano-silica may have a spherical shape, and when the content of the nano-silica is less than 5 wt%, it is not advantageous to improve thermal properties and strength. In particular, dimensional stability decreases (increase in the difference in degree of orientation (MOR) and increase in the difference in Coefficient of Thermal Expansion (CTE) between the main orientation direction and the sub orientation direction orthogonal to the main orientation direction). In addition, when the content of nano silica exceeds 25 wt%, elongation is reduced, and thus a problem occurs in the process.

The average diameter of the nano-silica may be 5 to 50nm.

When the average particle diameter of the nanosilica is smaller than the above range, the specific surface area based on the whole nanosilica increases, so that particles constituting the nanosilica may aggregate. Aggregation of nano-silica particles may cause defects in the shape protruding from the polyimide surface.

If the average particle diameter of the nano-silica exceeds the above range, the smoothness of the polyimide film may be lowered. On the other hand, nano-silica having a larger average particle diameter exceeding the above range may sometimes cause a phenomenon in which more particles settle in the polyamic acid due to gravity. The nano-silica particles precipitated and biased to any portion may form protrusions while being exposed through the surface of the polyimide film.

The nano-silica has excellent dispersibility in polyamic acid, and particularly, the surface of the nano-silica may be surface-modified to further improve compatibility with polyimide forming a network. The surface modification is mainly performed by a reaction with a silane compound, but is not limited thereto.

The silane compound includes a functional group, and the functional group may be at least one of methoxy (method), ethoxy (method), amino (amino), phenyl (phenyl), vinyl (vinyl), epoxy (epoxy), methacryloxy (metacryloxy), acryloxy (acryl), ureido (ureido), chloropropyl (chloropropyl), mercapto (mercapto), thio (sulfofido), and isocyanate (isocyanato) functional groups.

The content of the benzophenone tetracarboxylic acid dianhydride may be 10 to 30 mol% based on 100 mol% of the total content of the dianhydride component, the content of the biphenyl tetracarboxylic acid dianhydride may be 40 to 70 mol%, and the content of the pyromellitic acid dianhydride may be 10 to 50 mol%.

Polyimide chains derived from biphenyl tetracarboxylic dianhydride have a structure called a charge transfer complex (Charge transfer complex, CTC), i.e., a regular linear structure in which an electron donor (electron donnor) and an electron acceptor (electron acceptor) are disposed very close to each other, enhancing intermolecular interactions (intermolecular interaction).

In addition, benzophenone tetracarboxylic dianhydride having a carbonyl group contributes to expression of CTCs as well as biphenyl tetracarboxylic dianhydride.

In particular, pyromellitic dianhydride may also be contained as the dianhydride component. The pyromellitic dianhydride is a dianhydride component having a relatively rigid structure, and preferably can impart an appropriate elasticity to the polyimide film.

In addition, biphenyl tetracarboxylic dianhydride and benzophenone tetracarboxylic dianhydride contain two benzene rings corresponding to aromatic moieties, and pyromellitic dianhydride contains one benzene ring corresponding to aromatic moieties.

An increase in the content of pyromellitic dianhydride in the dianhydride component, when based on the same molecular weight, can be understood as an increase in the imide groups in the molecule, that is, a relative increase in the ratio of imide groups derived from pyromellitic dianhydride as compared with imide groups derived from biphenyl tetracarboxylic dianhydride and benzophenone tetracarboxylic dianhydride in the polyimide polymer chain.

If the content ratio of pyromellitic dianhydride is reduced too much, the composition of the rigid structure is relatively reduced, and thus the mechanical properties of the polyimide film may be lowered below a desired level.

Therefore, when the contents of the biphenyl tetracarboxylic dianhydride and the benzophenone tetracarboxylic dianhydride exceed the above ranges, the mechanical properties of the polyimide film are deteriorated.

The polyimide film may have a strength of 300 to 365MPa and an elongation of 30 to 50%. Physical properties such as elongation in particular may often be difficult to be compatible with previous strengths at preferred levels, but the specific compositions and composition ratios of the present application may act primarily to express a strength at a preferred level while inhibiting a decrease in elongation.

In addition, the difference between the maximum and minimum values of the degree of orientation (MOR) across the width of the product may be greater than 0.01 and 0.05 or less, and the difference between the Coefficient of Thermal Expansion (CTE) of the primary orientation direction and the secondary orientation orthogonal to the primary orientation direction may be 2 to 7ppm.

Wherein the main orientation refers to a direction expressed as a main orientation when the degree of orientation is measured.

The polyamic acid of the present application can be prepared by the following method:

(1) A method in which the entire amount of the diamine component is put in a solvent, and then the dianhydride component is added so as to be approximately equimolar with the diamine component, thereby polymerizing the diamine component;

(2) A method in which the entire amount of the dianhydride component is put in a solvent, and then a diamine component is added so as to be approximately equimolar with the dianhydride component, thereby polymerizing the dianhydride component;

(3) A method in which a part of the diamine component is added to the solvent, and then the remaining diamine component is added after mixing the part of the dianhydride component at a ratio of about 95 to 105 mol% relative to the reaction component, and then the remaining dianhydride component is added so that the diamine component and the dianhydride component are substantially equimolar to each other to polymerize the mixture;

(4) A method in which a dianhydride component is added to a solvent, a part of the components of a diamine compound is mixed at a ratio of 95 to 105 mol% relative to the reaction components, then another dianhydride component is added, and then the remaining diamine component is continuously added so that the diamine component and the dianhydride component are substantially equimolar to each other to polymerize the mixture;

(5) A method in which a part of the diamine component and a part of the dianhydride component are reacted in a solvent to form a first composition in excess, and a part of the diamine component and a part of the dianhydride component are reacted in another solvent to form a second composition, and after the first and second compositions are mixed and polymerization is completed. In this case, when the diamine component is excessive in forming the first composition, the dianhydride component is excessive in the second composition, when the dianhydride component is excessive in the first composition, the diamine component is excessive in the second composition, and the first and second compositions are mixed so that the entire diamine component and dianhydride component used in these reactions are substantially equimolar to perform polymerization.

However, the polymerization method is not limited to the above-described examples, and of course, any known method may be used for preparing the polyamic acid.

In a specific example, the method of producing a polyimide film according to the present application is characterized by comprising: a first step (a) of polymerizing a dianhydride component including Benzophenone Tetracarboxylic Dianhydride (BTDA), biphenyl tetracarboxylic dianhydride (BPDA), and pyromellitic dianhydride (PMDA) and a diamine component including diaminodiphenyl ether (ODA), p-phenylenediamine (PPD), and 3, 5-diaminobenzoic acid (DABA) in an organic solvent to prepare a polyamic acid; and a second step (b) of adding 5 to 25 wt% of nano silica particles to the polyamic acid of the first step and mixing, wherein the content of the diamine-based diphenyl ether is 10 to 30 mol%, the content of the p-phenylenediamine is 50 to 70 mol%, and the content of the 3, 5-diaminobenzoic acid is 5 to 25 mol%, based on 100 mol% of the total content of the diamine component.

The content of benzophenone tetracarboxylic acid dianhydride is 10 to 30 mol% based on 100 mol% of the total content of dianhydride components, the content of biphenyl tetracarboxylic acid dianhydride is 40 to 70 mol%, and the content of pyromellitic acid dianhydride is 10 to 50 mol%.

The polyimide film may have a strength of 300 to 365MPa, an elongation of 30 to 50%, a difference between a maximum value and a minimum value of an orientation degree (MOR) of more than 0.01 and 0.05 or less, and a difference between a Coefficient of Thermal Expansion (CTE) in a main orientation direction and a secondary orientation direction orthogonal to the main orientation direction of 2 to 7ppm.

In the present application, the polymerization method of the polyamic acid as described above can be defined as an arbitrary (random) polymerization method, and the polyimide film of the present application prepared from the polyamic acid prepared by the process as described above can be preferably applied to the effect of the present application in which the dimensional stability is maximized.

On the other hand, the solvent used for synthesizing the polyamic acid is not particularly limited, and any solvent may be used as long as it is a solvent capable of dissolving the polyamic acid, but an amide-based solvent is preferable.

Specifically, the solvent may be an organic polar solvent, specifically an aprotic polar solvent, and for example, may be one or more selected from the group consisting of N, N-Dimethylformamide (DMF), N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), p-chlorophenol, o-chlorophenol, N-methylpyrrolidone (NMP), γ -butyrolactone (GBL), diethylene glycol (Diglyme), but is not limited thereto, and two or more may be used alone or in combination as required.

In one example, particularly preferably, N-dimethylformamide and N, N-dimethylacetamide can be used as the solvent.

In the process for producing polyamide acid, a filler other than nano silica may be added to improve various properties of the film such as slidability, thermal conductivity, corona resistance, and ring hardness. The filler to be added is not particularly limited, and preferable examples include titanium oxide, aluminum oxide, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica, and the like.

The particle diameter of the filler is not particularly limited, and may be determined according to the characteristics of the modified film and the kind of filler to be added. In general, the average particle diameter is from 0.05 μm to 100. Mu.m, preferably from 0.1 μm to 75. Mu.m, more preferably from 0.1 μm to 50. Mu.m, particularly preferably from 0.1 μm to 25. Mu.m.

If the particle diameter is smaller than this range, it is difficult to exhibit a modifying effect, and if the particle diameter is larger than this range, the surface properties may be impaired to a large extent, and the mechanical properties may be greatly reduced.

The amount of filler to be added is not particularly limited, and may be determined by the film characteristics to be modified, the particle diameter of the filler, and the like. In general, the filler is added in an amount of 0.01 to 100 parts by weight, preferably 0.01 to 90 parts by weight, more preferably 0.02 to 80 parts by weight, relative to 100 parts by weight of polyimide.

If the filler addition amount is less than this range, the modifying effect by the filler is hardly exhibited, and if the filler is more than this range, the mechanical properties of the film may be greatly impaired. The method of adding the filler is not particularly limited, and any known method may be used.

In the preparation method of the present application, the polyimide film may be prepared by thermal imidization and chemical imidization.

In addition, the compound imidization method may be prepared by combining a thermal imidization method and a chemical imidization method.

The thermal imidization method is a method of initiating imidization reaction with a heat source such as hot air or an infrared dryer without containing a chemical catalyst.

In the thermal imidization method, the gel film may be heat-treated at a variable temperature ranging from 100 ℃ to 600 ℃ to imidize the amide acid groups present in the gel film, specifically, from 200 ℃ to 500 ℃, and more specifically, the amide acid groups present in the gel film may be imidized by heat-treating at a temperature ranging from 300 ℃ to 500 ℃.

However, during the formation of the gel film, a part of the amic acid (about 0.1 mol% to 10 mol%) may be imidized, and for this purpose, the polyamic acid composition may be dried at a variable temperature in the range of 50℃to 200℃and may be included in the scope of the thermal imidization method described above.

In the case of the chemical imidization method, the polyimide film may be prepared by using a dehydrating agent and an imidizing agent according to methods known in the art. Among them, the "dehydrating agent" refers to a substance that promotes a ring-closure reaction by dehydrating a polyamic acid, and includes aliphatic acid anhydride, aromatic acid anhydride, N' -dialkylcarbodiimide, halogenated lower aliphatic acid anhydride, arylphosphonic acid dihalide, thionyl halide, and the like, as non-limiting examples thereof. Among them, aliphatic acid anhydride is preferable from the viewpoint of ease of acquisition and cost, and as non-limiting examples thereof, acetic anhydride (or acetic anhydride, AA), propionic anhydride, lactic anhydride, and the like may be cited, and these may be used alone or in combination of two or more.

The "imidizing agent" means a substance having an effect of promoting a ring-closure reaction with respect to the polyamic acid, and may be an imine component such as an aliphatic tertiary amine, an aromatic tertiary amine, a heterocyclic tertiary amine, or the like. Among them, heterocyclic tertiary amines may be preferable from the viewpoint of reactivity of the catalyst. As non-limiting examples of the heterocyclic tertiary amine, quinoline, isoquinoline, β -picoline (BP), pyridine, and the like may be cited, and these may be used alone or in combination of two or more.

The amount of the dehydrating agent to be added is preferably in the range of 0.5 mol to 5 mol, particularly preferably in the range of 1.0 mol to 4 mol, relative to 1 mol of the amide groups in the polyamic acid. The amount of the imidizing agent to be added is preferably in the range of 0.05 to 2 moles, particularly preferably in the range of 0.2 to 1 mole, relative to 1 mole of the amide groups in the polyamic acid.

If the dehydrating agent and the imidizing agent are less than the ranges, chemical imidization may be insufficient, resulting in formation of cracks in the prepared polyimide film, and a decrease in mechanical strength of the film. And if the amount of them to be added is more than the range, imidization proceeds too fast, at which time it may be difficult to cast in the form of a film, or the polyimide film produced exhibits brittleness (brittle), and is not preferable.

As an example of the composite imidization method, after adding a dehydrating agent and an imidizing agent to a polyamic acid solution, heating at 80 to 200 ℃, preferably at 100 to 180 ℃, and after a part of hardening and drying, heating at 200 to 400 ℃ for 5 to 400 seconds to prepare a polyimide film.

The present application provides a multilayer film comprising the polyimide film and the thermoplastic resin layer as described above, and a flexible metal foil laminate comprising the polyimide film and the conductive metal foil as described above.

As the thermoplastic resin layer, a thermoplastic polyimide resin layer or the like can be applied.

The metal foil to be used is not particularly limited, but when the flexible metal foil laminate of the present application is used in electronic equipment or electrical equipment, for example, a metal foil containing copper or a copper alloy, stainless steel or an alloy thereof, nickel or a nickel alloy (alloy 42 is also included), aluminum or an aluminum alloy may be used.

In a typical flexible metal foil laminate, a copper foil such as a laminated copper foil or an electrolytic copper foil is commonly used, and can be preferably used in the present application. In addition, the surfaces of these metal foils may be coated with a rust preventive layer, a heat resistant layer, or an adhesive layer.

In the present application, the thickness of the metal foil is not particularly limited, and any thickness capable of sufficiently functioning can be used according to the application.

In the flexible metal foil laminate according to the present application, a metal foil is laminated on one surface of the polyimide film, or an adhesive layer containing a thermoplastic polyimide is added to one surface of the polyimide film, and may be a structure in which the metal foil is laminated in a state of being attached to the adhesive layer.

The application also provides an electronic component comprising the flexible metal foil laminate as an electronic signal transmission circuit.

Hereinafter, the operation and effect of the application will be further described by means of specific examples of the application. However, such embodiments are presented as examples of the application only and are not intended to limit the scope of the application as claimed thereby.

Example 1

Preparation example 1: preparation of nanosilicon dioxide

100 g of tetraethyl orthosilicate (TEOS) and 220 g of ethanol were mixed in a 1L reactor, and then a solution of 94 g of pure water, 0.85 g of aqueous ammonia and 30 g of ethanol was prepared at 60℃and reacted for 24 hours to synthesize nanosilica having an average diameter of 20nm, 5g of phenyltrimethoxysilane (PTMS, CAS No. 2996-92-1) was dissolved in 20g of ethanol to perform surface treatment, and then 114g of N, N-dimethylacetamide (DMAc) was added to remove ethanol and water by distillation under reduced pressure to obtain a 20% nanosilica (solvent DMAc) solution having an average diameter of 20 nm.

Preparation example 2: polymerization of nanosilica powdery polyamic acid (PAA)

389.92g of N, N-Dimethylformamide (DMF) was added as solvent to a 1L reactor under nitrogen.

Subsequently, after setting the temperature to 25 ℃, 9.16g of diaminodiphenyl ether (ODA), 15.28g of p-phenylenediamine (PPD), 3.16g of 3, 5-diaminobenzoic acid (DABA) were dissolved in this order, and then reacted with 30.55g of biphenyltetracarboxylic dianhydride (BPDA), 11.38g of Benzophenone Tetracarboxylic Dianhydride (BTDA), and 13.63g of pyromellitic dianhydride (PMDA) in this order.

Next, 22.9g of PMDA8% solution was added to obtain a varnish having a viscosity of 100000 cp. To the obtained varnish was added 20g of a 20% nano silica solution having an average diameter of 20nm to obtain 8.6% nano silica dispersed polyamic acid (PAA).

Preparation example 3: preparation of polyimide film

4.35g of Isoquinoline (IQ), 12.03g of Acetic Anhydride (AA) and 8.61g of DMF were added as a catalyst to the nano silica-dispersed polyamic acid prepared in the above-mentioned preparation example 2, and then uniformly mixed to prepare a precursor composition, which was cast on SUS plate (100 sa, sandvik) using a doctor blade, and dried at a temperature ranging from 100 ℃ to 200 ℃.

Then, the film was peeled off from the SUS plate and fixed on a pin frame and then transferred to a high temperature tenter.

After heating the film from 200 ℃ to 500 ℃ in a high temperature tenter, it was cooled to 25 ℃ and separated from the pin frame to prepare a polyimide film of 20 μm thickness.

Examples 2 to 5 and comparative examples 1 to 3

A polyimide film was prepared in the same manner as in example 1, except that the content of the nano silica solution added in example 1 was changed as shown in table 1 below.

TABLE 1

Experimental example: evaluation of physical Properties of polyimide film

For the polyimide films prepared in examples 1 to 5, comparative examples 1 to 3, respectively, the difference in degree of orientation (MOR), the difference in strength, elongation and Coefficient of Thermal Expansion (CTE) were measured in the following manner, and the results thereof are summarized in table 2 below.

1) Measurement of difference in MOR (degree of orientation)

The difference between the maximum and minimum values of MOR was calculated by measuring both side surfaces and the center using MOA-7015 equipment of OSI (prince measuring instruments) corporation of Japan. The MOR is an index indicating the degree of orientation of a film, because when a sample molded on a film or sheet is irradiated with microwaves, the transmission intensity of the absorbed microwaves is different from the anisotropy of the sample, and therefore the ratio of the major axis to the minor axis of the polar coordinates (orientation pattern) indicating the difference in transmission intensity is calculated as the MOR value and used as an index indicating the molecular orientation.

2) Measurement of Strength and elongation

The strength and elongation of the samples in the Machine Direction (MD) were measured according to the method of ASTM D882 using an Instron UTM.

3) Measurement of Coefficient of Thermal Expansion (CTE) differences

When a 40mm sample was measured using a Q400 TMA device from TA corporation, the main orientation direction and the sub orientation direction orthogonal to the main orientation direction were heated to 360 ℃ at a rate of 10 ℃/min under a tensile force of 0.05N, cooled at a rate of 10 ℃/min, then reheated at 10 ℃/min at room temperature, and the coefficient of thermal expansion was measured in a range of 100 to 200 ℃ to determine the difference.

TABLE 2

As shown in Table 2, the polyimide films prepared according to the examples each have a strength of 300 to 365MPa, an elongation of 30 to 50%, and a difference between the maximum value and the minimum value of the degree of orientation (MOR) of more than 0.01 and 0.05 or less. And, the difference between the Coefficient of Thermal Expansion (CTE) in the main orientation direction and the sub orientation direction orthogonal to the main orientation direction corresponds to 2 to 7ppm.

In the comparative example, it was found that at least one of the following physical properties was not satisfied.

Strength of 300-365 Mpa

Elongation of 30-50%

-difference between maximum and minimum values of degree of orientation (MOR) greater than 0.01 and less than 0.05

-a difference between a main orientation direction and a secondary orientation direction orthogonal to the main orientation direction in a thermal expansion Coefficient (CTE) of 2 to 7ppm

In comparative example 1, since nano silica is not used at all, it is shown that the elongation is more than 50%, and the difference between the degree of orientation and the Coefficient of Thermal Expansion (CTE) is very large compared with the examples, and thus the dimensional stability is low.

Comparative example 2 contains a smaller amount of nanosilica than in example, and thus is improved compared to comparative example 1, but the elongation is still more than 50%, and the difference in degree of orientation and Coefficient of Thermal Expansion (CTE) is very large compared to example, thus showing lower dimensional stability.

Comparative example 3 contains a larger amount of nanosilica than in the examples, and therefore, the difference in degree of orientation and the difference in Coefficient of Thermal Expansion (CTE) are significantly improved, but the strength and elongation are significantly reduced as compared with the examples.

From these results, it is understood that the above-described advantages of physical properties can be simultaneously exhibited when the specific compositions of the present application are coordinated within the scope defined by the present application.

This means that it is preferable to include nanosilica in the content range selected in the present application in order to balance the difference between the sum of strength, elongation and degree of orientation and the Coefficient of Thermal Expansion (CTE) to an appropriate level.

Although the foregoing has been described in detail with reference to the embodiments of the present application, those skilled in the art to which the present application pertains can make various applications and modifications within the scope of the present application based on the above.

Industrial applicability

The present application provides a polyimide film having excellent dimensional stability by a polyimide film composed of specific components and specific composition ratios and containing nanosilica, and a method for preparing the same, and thus can be effectively applied to various fields in which these characteristics are required, particularly electronic parts such as flexible metal foil laminates and the like.

Claims

1. A polyimide film, wherein the polyimide film is obtained by imidizing a polyamic acid solution comprising a dianhydride component comprising benzophenone tetracarboxylic acid dianhydride, biphenyl tetracarboxylic acid dianhydride, and pyromellitic acid dianhydride, and a diamine component comprising diaminodiphenyl ether, p-phenylenediamine, and 3, 5-diaminobenzoic acid,

wherein the content of the diamine-based diphenyl ether is 10 to 30 mol% inclusive, the content of the p-phenylenediamine is 50 to 70 mol% inclusive, the content of the 3, 5-diaminobenzoic acid is 5 to 25 mol% inclusive, based on 100 mol% of the total content of the diamine components,

comprising 5 to 25 wt.% of nano-silica particles,

wherein the average diameter of the nano silicon dioxide particles is 5-50 nm,

wherein the difference between the maximum value and the minimum value of the orientation degree is more than 0.01 and less than 0.05,

wherein the difference between the thermal expansion coefficients in the main orientation direction and the sub orientation direction orthogonal to the main orientation direction is 2 to 7ppm.

2. The polyimide film according to claim 1, wherein the polyimide film is formed by a process comprising the steps of, based on 100 mol% of the total content of the dianhydride component,

the content of the benzophenone tetracarboxylic dianhydride is 10 mol% or more and 30 mol% or less,

the content of biphenyl tetracarboxylic dianhydride is 40 mol% or more and 70 mol% or less,

the content of pyromellitic dianhydride is 10 mol% or more and 50 mol% or less.

3. The polyimide film according to claim 1, wherein the polyimide film has a strength of 300 to 400MPa and an elongation of 30 to 50%.

4. A method of preparing a polyimide film, the method comprising:

a first step (a) of polymerizing a dianhydride component including benzophenone tetracarboxylic dianhydride, biphenyl tetracarboxylic dianhydride, and pyromellitic dianhydride, and a diamine component including diaminodiphenyl ether, p-phenylenediamine, and 3, 5-diaminobenzoic acid in an organic solvent to prepare a polyamic acid; and

a second step (b) of adding 5 to 25 wt% of nano silica particles to the polyamic acid of the first step and mixing,

wherein the average diameter of the nano silicon dioxide particles is 5-50 nm,

5. The method for producing a polyimide film according to claim 4, wherein the polyimide film is produced by reacting the polyimide film with a solvent in an aqueous medium,

the content of pyromellitic dianhydride is 10 mol% or more and 50 mol% or less.

6. The method for producing a polyimide film according to claim 4, wherein the polyimide film has a strength of 300 to 365MPa and an elongation of 30 to 50%.

7. A multilayer film comprising the polyimide film according to any one of claims 1 to 3 and a thermoplastic resin layer.

8. A flexible metal foil laminate comprising the polyimide film of any one of claims 1 to 3 and a conductive metal foil.

9. An electronic component comprising the flexible metal foil laminate of claim 8.