CN114651036A

CN114651036A - Polyimide film having improved dimensional stability and method for preparing the same

Info

Publication number: CN114651036A
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: 2022-06-21
Anticipated expiration: 2040-11-12
Also published as: KR20210057936A; WO2021096245A3; CN114651036B; WO2021096245A2; KR102346587B1

Abstract

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

Description

Polyimide film having improved dimensional stability and method for preparing the same

Technical Field

The present invention 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.

In addition, the polymer has attracted attention as a high-functional polymer material from the microelectronic field to the optical field because of its excellent electrical characteristics such as insulation properties and low permittivity.

For example, in the field of microelectronics, a thin circuit board having high integration and flexibility is actively developed due to weight reduction and size reduction of electronic products, and thus polyimide having very excellent heat resistance, low temperature resistance and insulation properties and being easily bent tends to be 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 called a Flexible metal foil Laminate in a broad sense, and when a thin Copper plate is used as the metal foil, it is also called a Flexible Copper Clad Laminate (FCCL) in a narrow sense.

As a method for producing the flexible metal foil laminate, for example, (i) a casting method, a method of casting (cast) on a metal foil or coating polyamic acid as a polyimide precursor and then imidizing; (ii) a metallization method in which a metal layer is directly provided on a polyimide film by sputtering or plating; and (iii) a lamination method of joining a polyimide film and a metal foil by a thermoplastic polyimide with heat and pressure.

Among them, the lamination method has advantages 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 an apparatus for performing lamination, a roll lamination apparatus or a double belt press apparatus that continuously laminates while feeding a roll-shaped material is used. Among them, a heat roll lamination method using a heat roll lamination device can be more preferably used from the viewpoint of productivity.

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

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

That is, when the lamination is performed at a high temperature, the storage modulus of the polyimide film is greatly lowered at a high temperature, the polyimide film is loosened at a low storage modulus, and the polyimide film is likely not to exist in a flat shape after the lamination is completed. 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 to be noted that the glass transition temperature of the polyimide film is significantly lower than the temperature at the time of lamination. In particular, in the above case, since the polyimide film has a high viscosity at the temperature at which the lamination is performed, there is a possibility that a relatively large dimensional change is accompanied, and therefore, the appearance quality of the polyimide film after the lamination may be degraded.

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), a method of preparing a three-layer polyimide film by coating a polyamic acid solution on a surface of a polyimide film and drying (imidizing) the coated polyimide film may be mentioned, but a process of preparing a polyimide film, a process of coating a surface of a polyimide film and drying (imidizing) the coated polyimide film are required, and a plurality of processes are required, thereby increasing the cost (cost-up) (for example, see patent document 1).

Further, as the three-layer polyimide film of the two-layer FPC, a method of simultaneously casting a polyamic acid solution on a support in a plurality of layers, peeling the polyimide film from the support after drying, and performing heat treatment to prepare a three-layer polyimide film may be mentioned, but there is also a case where a portion of the polyimide layer directly in contact with the support is adhered to the support or a difference in peel strength occurs between the polyimide layer in contact with the support and the polyimide layer on the opposite side thereof (for example, see patent documents 2 and 3).

Therefore, there is an urgent need for a technique capable of greatly improving the dimensional stability (uniformity) of a polyimide film by solving the problems as described above.

Documents of the prior art

Patent document

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

Patent document 2: japanese laid-open patent publication No. Hei 7-214637 (published: 8/15/1995)

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

Disclosure of Invention

Technical problem to be solved by the invention

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

Means for solving the problems

According to an aspect of the present invention, there is provided a polyimide film obtained by subjecting a polyamic acid solution including a dianhydride component and a diamine component to an imidization reaction, the dianhydride component comprises Benzophenone Tetracarboxylic Dianhydride (BTDA), biphenyl tetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA), the diamine component comprises diaminodiphenyl ether (ODA), p-phenylenediamine (PPD) and 3, 5-diaminobenzoic acid (DABA), wherein the content of the diaminodiphenyl ether is 10 mol% or more and 30 mol% or less based on 100 mol% of the total content of the diamine component, the content of the p-phenylenediamine 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 the nano silica particles are contained in an amount of 5 to 25 wt%.

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

The average diameter of the nano silicon dioxide particles can be 5-50 nm.

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 Coefficients of Thermal Expansion (CTE) in a main orientation direction and a sub-orientation direction orthogonal to the main orientation direction of 2 to 7 ppm.

According to still another aspect of the present invention, there is provided a method for preparing a polyimide film, the method including: a first step (a) of polymerizing a dianhydride component comprising Benzophenone Tetracarboxylic Dianhydride (BTDA), biphenyl tetracarboxylic dianhydride (BPDA), and pyromellitic dianhydride (PMDA) and a diamine component comprising diaminodiphenyl ether (ODA), p-phenylenediamine (PPD), and 3, 5-diaminobenzoic acid (DABA) in an organic solvent to prepare 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 diaminodiphenyl ether is 10 mol% or more and 30 mol% or less, the content of p-phenylenediamine is 50 mol% or more and 70 mol% or less, and the content of 3, 5-diaminobenzoic acid is 5 mol% or more and 25 mol% or less, based on 100 mol% of the total content of the diamine component.

According to another aspect of the present invention, 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 invention is to provide a specific embodiment thereof.

ADVANTAGEOUS EFFECTS OF INVENTION

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

Detailed Description

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

Before this, the terms or words used herein and in the claims of the invention should not be construed as being limited to their ordinary or dictionary meanings, but interpreted as having meanings and concepts conforming to the technical spirit of the present invention on the basis of the principle that the inventor can appropriately define the concepts of the terms in order to explain his invention in the best way.

Therefore, it should be understood that the structure of the embodiment described herein is only one of the preferred embodiments of the present invention and does not represent all the technical spirit of the present invention, so that various equivalent substitutions and modifications can be made with respect to the present application.

As used herein, the singular forms "a", "an" and "the" include plural forms unless the context clearly dictates otherwise. It will be understood that, in this document, the terms "comprising", "including", "having" or "with", etc., are intended to specify the presence of stated features, steps, structural elements, or combinations thereof, and do not preclude the presence or addition of one or more other features or numbers, steps, structural elements, or combinations thereof.

When an amount, concentration, or other value or parameter is given herein as either a range, preferred range or an enumeration of upper preferable values and lower preferable values, regardless of whether ranges are separately disclosed, it is to be understood that all ranges that can be formed from any upper limit value or preferred value in any pair, as well as any lower limit value or preferred value of ranges, are specifically disclosed.

When a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is intended that the scope of the invention not be limited to the particular values mentioned in defining the range.

"dianhydride" is intended herein to include precursors or derivatives thereof which may not technically be a dianhydride, but which will also react with a diamine to form a polyamic acid which can be converted back to a polyimide.

"diamine" is intended herein to include precursors or derivatives thereof, which may not be technically a diamine, but which will also react with a dianhydride to form a polyamic acid which can be converted back to a polyimide.

The polyimide film according to the present invention is obtained by subjecting a polyamic acid solution containing a dianhydride component and a diamine component to an imidization reaction, the dianhydride component comprises Benzophenone Tetracarboxylic Dianhydride (BTDA), biphenyl tetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA), the diamine component comprises diaminodiphenyl ether (ODA), p-phenylenediamine (PPD) and 3, 5-diaminobenzoic acid (DABA), wherein the content of the diaminodiphenyl ether is 10 mol% or more and 30 mol% or less based on 100 mol% of the total content of the diamine component, the content of p-phenylenediamine is 50 to 70 mol%, the content of 3, 5-diaminobenzoic acid is 5 to 25 mol%, and the nano-silica particles are contained in an amount of 5 to 25 wt%.

Particularly, when the total weight of the polyimide film is 100 wt%, the content of the nano silica is 5 to 25 wt%. The nano silica forms a network with polyimide to suppress shrinkage and expansion occurring during film formation and control orientation deformation.

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

The average diameter of the nano silicon dioxide can be 5-50 nm.

When the average particle diameter of the nano-silica is less than the above range, the specific surface area based on the entire nano-silica increases, so that the particles constituting the nano-silica may be aggregated. Aggregation of the 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, the nano-silica having a larger average particle diameter exceeding the above range may sometimes cause a phenomenon in which more particles are settled in the polyamic acid by gravity. The nano silica particles precipitated and biased to any portion may be exposed through the surface of the polyimide film while forming protrusions.

The nano-silica has excellent dispersibility in polyamic acid, and particularly, the surface of the nano-silica can be subjected to surface modification to further improve the 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, which may be at least one of methoxy (methoxy), ethoxy (ethoxy), amino (amino), phenyl (phenyl), vinyl (vinyl), epoxy (epoxy), methacryloxy (methacryloxy), acryloxy (acryloxy), ureido (ureido), chloropropyl (chloropropyl), mercapto (mercapto), thio (sulfo), isocyanate (isocyanato) functional groups.

Polyimide chains derived from biphenyltetracarboxylic dianhydride have a structure called Charge Transfer Complex (CTC), that is, a regular linear structure in which an electron donor (electron donor) and an electron acceptor (electron acceptor) are arranged very close to each other, and enhance intermolecular interaction.

Furthermore, benzophenone tetracarboxylic dianhydride having a carbonyl group contributes to the expression of CTC as well as biphenyl tetracarboxylic dianhydride.

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

In addition, biphenyltetracarboxylic dianhydride and benzophenonetetracarboxylic dianhydride contain two benzene rings corresponding to aromatic moieties, while 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 imide groups in the molecule, i.e., a relative increase in the ratio of imide groups derived from pyromellitic dianhydride as compared to imide groups derived from biphenyl tetracarboxylic dianhydride and benzophenone tetracarboxylic dianhydride in the polyimide polymer chain.

If the content ratio of pyromellitic dianhydride is excessively reduced, the components of the rigid structure are relatively reduced, and thus the mechanical properties of the polyimide film may be reduced below a desired level.

Therefore, when the content of the biphenyltetracarboxylic dianhydride and the benzophenonetetracarboxylic dianhydride exceeds the above range, the mechanical characteristics of the polyimide film are deteriorated.

The strength of the polyimide film can be 300-365 MPa, and the elongation can be 30-50%. Especially physical properties such as elongation may be generally difficult to be compatible with previous strength at a preferred level, but the specific composition and composition ratio of the present invention may mainly act to express the preferred level of strength while suppressing the decrease in elongation.

In addition, the difference between the maximum value and the minimum value of the orientation degree (MOR) in the whole width of the product can be more than 0.01 and less than 0.05, and the difference between the Coefficient of Thermal Expansion (CTE) of the main orientation direction and the secondary orientation orthogonal to the main orientation direction can be 2-7 ppm.

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

The polyamic acid in the present invention can be prepared by the following method:

(1) a method of adding the whole amount of the diamine component to a solvent and then adding a dianhydride component so as to be approximately equimolar with the diamine component to carry out polymerization;

(2) a method of adding the whole amount of the dianhydride component to a solvent and then adding a diamine component so as to be approximately equimolar with the dianhydride component to carry out polymerization;

(3) a method in which a diamine component is partially added to a solvent, then a dianhydride component is partially mixed in an amount of about 95 to 105 mol% with respect to the reaction component, and then the remaining diamine component is added, and then the remaining dianhydride component is added to polymerize the diamine component and the dianhydride component in such an amount that the diamine component and the dianhydride component are substantially equimolar;

(4) a method in which a dianhydride component is added to a solvent, a part of the diamine component is mixed in a proportion of 95 to 105 mol% with respect to the reaction component, and then the other dianhydride component is added, and then the remaining diamine component is continuously added so that the diamine component and the dianhydride component are polymerized in approximately equimolar amounts;

(5) a method of forming a first composition by reacting a part of a diamine component and a part of a dianhydride component in a solvent in either excess, and forming a second composition by reacting a part of a diamine component and a part of a dianhydride component in another solvent in either excess, followed by mixing the first and second compositions and completing the polymerization. In this case, when the first composition is formed, if the diamine component is excessive, the dianhydride component is excessive in the second composition, and if 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 whole diamine component and dianhydride component used in these reactions are approximately equimolar to each other to perform polymerization.

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

In one specific example, the method for preparing a polyimide film according to the present invention is characterized by comprising: a first step (a) of polymerizing a dianhydride component comprising Benzophenone Tetracarboxylic Dianhydride (BTDA), biphenyl tetracarboxylic dianhydride (BPDA), and pyromellitic dianhydride (PMDA) and a diamine component comprising diaminodiphenyl ether (ODA), p-phenylenediamine (PPD), and 3, 5-diaminobenzoic acid (DABA) in an organic solvent to prepare 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 diaminodiphenyl ether is 10 mol% or more and 30 mol% or less, the content of p-phenylenediamine is 50 mol% or more and 70 mol% or less, and the content of 3, 5-diaminobenzoic acid is 5 mol% or more and 25 mol% or less, based on 100 mol% of the total content of the diamine component.

The content of 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, and the content of pyromellitic dianhydride is 10 mol% or more and 50 mol% or less, based on 100 mol% of the total dianhydride component.

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 sub-orientation direction orthogonal to the main orientation direction of 2 to 7 ppm.

In the present invention, the polymerization method of polyamic acid as described above may be defined as any (random) polymerization method, and the polyimide film prepared from polyamic acid of the present invention prepared by the process as described above may be preferably applied in terms of the effect of the present invention of maximally improving dimensional stability.

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 can dissolve the polyamic acid, but an amide solvent is preferable.

Specifically, the solvent may be an organic polar solvent, specifically an aprotic polar solvent, and 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), and diethylene glycol (Diglyme), but is not limited thereto, and may be used alone or in combination of two or more thereof, as required.

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

In the step of preparing polyamic acid, a filler other than nano silica may be added to improve various properties of the thin 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 size of the filler is not particularly limited, and may be determined according to the characteristics of the film to be modified and the kind of the 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 μm, more preferably from 0.1 μm to 50 μm, and particularly preferably from 0.1 μm to 25 μm.

If the particle diameter is less than this range, the modification effect is hardly exhibited, and if the particle diameter is more than this range, the surface properties may be largely impaired and the mechanical properties may be largely degraded.

The amount of the filler to be added is not particularly limited, and may be determined by the film properties to be modified, the particle size 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, and more preferably 0.02 to 80 parts by weight, relative to 100 parts by weight of the polyimide.

If the amount of the filler added is less than this range, the effect of modifying the filler is hardly exhibited, and if the amount of the filler is more than 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.

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

Alternatively, the polyimide can be prepared by a complex imidization method combining a thermal imidization method and a chemical imidization method.

The thermal imidization is a method of initiating an imidization reaction by a heat source such as hot air or an infrared dryer without including 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 amic acid groups present in the gel film, specifically, 200 ℃ to 500 ℃, and more specifically, the amic acid groups present in the gel film may be imidized by heat-treating at a temperature ranging from 300 ℃ to 500 ℃.

However, some amic acid (about 0.1 to 10 mole percent) may also be imidized during the formation of the gel film, and for this purpose, the polyamic acid composition may be dried at variable temperatures ranging from 50 to 200 ℃, which is also included in the scope of the thermal imidization process described above.

In the case of the chemical imidization method, a polyimide film may be prepared by using a dehydrating agent and an imidizing agent according to a method known in the art. Wherein, the "dehydrating agent" means a substance which promotes ring closure reaction by dehydration of polyamic acid, and includes, as non-limiting examples thereof, aliphatic acid anhydride, aromatic acid anhydride, N' -dialkylcarbodiimide, halogenated lower aliphatic, halogenated lower fatty acid anhydride, arylphosphonic acid dihalide, thionyl halide, and the like. Among them, aliphatic acid anhydrides are preferable from the viewpoint of availability and cost, and non-limiting examples thereof include acetic anhydride (or acetic anhydride, AA), propionic anhydride, lactic acid anhydride, and the like, 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-closing reaction with respect to the polyamic acid, and may be an imide component, for example, an aliphatic tertiary amine, an aromatic tertiary amine, a heterocyclic tertiary amine, or the like. Among them, a heterocyclic tertiary amine 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 can be cited, and these may be used alone or in combination of two or more.

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

If the amount of the dehydrating agent and the imidizing agent is less than the above range, chemical imidization may be insufficient, resulting in formation of cracks in the polyimide film to be produced and reduction in mechanical strength of the film. Further, if the amount of addition is more than the above range, imidization proceeds too quickly, and in this case, it may be difficult to cast in the form of a film, or the polyimide film produced may be brittle (britle), which is not preferable.

As an example of the complex imidization method, a polyimide film can be produced by adding a dehydrating agent and an imidizing agent to a polyamic acid solution, heating the resulting solution at 80 to 200 ℃, preferably 100 to 180 ℃, partially curing the cured product, and drying the cured product, and then heating the cured product at 200 to 400 ℃ for 5 to 400 seconds.

The present invention 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 used.

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

In general, a copper foil such as a laminated copper foil or an electrolytic copper foil is generally used in the flexible metal foil laminate, and can be preferably used in the present invention. In addition, these metal foils may be coated with a rust-preventive layer, a heat-resistant layer or an adhesive layer on the surface.

In the present invention, the thickness of the metal foil is not particularly limited, and any thickness that can sufficiently function may be used according to the application.

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

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

Hereinafter, the action and effect of the invention will be further described by way of specific examples of the invention. However, such embodiments are merely provided as examples of the present invention, and do not limit the scope of the invention claimed herein.

Example 1

Preparation example 1: preparation of nano-silica

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

Preparation example 2: polymerization of nano-silica powdered polyamic acid (PAA)

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

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

Next, 22.9g of a PMDA 8% solution was added to obtain a varnish having a viscosity of 100000 cp. To the resulting varnish, 20g of a 20% nano-silica solution having an average diameter of 20nm was added to obtain 8.6% nano-silica dispersed polyamic acid (PAA).

Preparation example 3: preparation of polyimide film

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

Then, the film was peeled 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 having a thickness of 20 μm.

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 the following table 1.

TABLE 1

Experimental example: evaluation of physical Properties of polyimide film

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

1) Measurement of the 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 portion using MOA-7015 equipment of OSI (prince measuring device) corporation of Japan. 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 differs from the anisotropy of the sample, and therefore the ratio of the major axis to the minor axis of a polar coordinate (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) direction were measured using Instron UTM according to the method of ASTM D882.

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

When a 40mm by 40mm sample sampled from both ends of a mother roll was measured using a Q400 TMA apparatus of 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 tension of 0.05N, cooled at a rate of 10 ℃/min, heated again at 10 ℃/min at room temperature, and the thermal expansion coefficient in a range of 100 to 200 ℃ was measured to find the difference.

TABLE 2

As shown in Table 2, the strength of the polyimide films prepared according to the examples was 300 to 365MPa, the elongation was 30 to 50%, and the difference between the maximum value and the minimum value of the degree of orientation (MOR) was 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 secondary orientation direction perpendicular to the main orientation direction is 2 to 7 ppm.

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

Strength of-300 to 365MPa

-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 in Coefficient of Thermal Expansion (CTE) between a primary orientation direction and a secondary orientation direction perpendicular to the primary orientation direction of 2 to 7ppm

Comparative example 1 shows that the elongation is more than 50% because nano silica is not used at all, and the dimensional stability is low because the difference between the degree of orientation and the Coefficient of Thermal Expansion (CTE) is very large compared to the examples.

Comparative example 2 contains a smaller amount of nano silica than example and thus is improved as compared to comparative example 1, but the elongation is still more than 50%, and the difference between the degree of orientation and the difference between the Coefficients of Thermal Expansion (CTE) is very large as compared to example and thus shows lower dimensional stability.

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

From this, it is understood that when the specific compositions of the present invention are coordinated within the range defined by the present invention, the advantages of the physical properties described above can be simultaneously exhibited.

This indicates that, in order to balance the difference in the sum of the strength, elongation, and degree of orientation and the Coefficient of Thermal Expansion (CTE) at an appropriate level, it is preferable to include nano silica in the content range selected in the present invention.

Although the present invention has been described in detail with reference to the embodiments thereof, those skilled in the art can make various applications and modifications within the scope of the present invention based on the above-described matters.

Industrial applicability

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

Claims

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

wherein the diaminodiphenyl ether is contained in an amount of 10 to 30 mol%, the p-phenylenediamine is contained in an amount of 50 to 70 mol%, the 3, 5-diaminobenzoic acid is contained in an amount of 5 to 25 mol%, based on 100 mol% of the total diamine component,

comprises 5 to 25 wt% of nano silica particles.

2. The polyimide film according to claim 1, wherein the dianhydride component is contained in an amount of 100 mol% based on the total content of the dianhydride component,

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

the content of the biphenyltetracarboxylic dianhydride is 40 to 70 mol%,

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

3. The polyimide film according to claim 1, wherein the nano silica particles may have an average diameter of 5 to 50 nm.

4. 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%.

5. The polyimide film according to claim 1, wherein a difference between a maximum value and a minimum value of the degree of orientation is more than 0.01 and 0.05 or less.

6. The polyimide film according to claim 1, wherein a difference between coefficients of thermal expansion in a main alignment direction and a sub-alignment direction orthogonal to the main alignment direction is 2 to 7 ppm.

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

a first step (a) of polymerizing a dianhydride component comprising benzophenone tetracarboxylic dianhydride, biphenyl tetracarboxylic dianhydride, and pyromellitic dianhydride and a diamine component comprising 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 diaminodiphenyl ether is contained in an amount of 10 to 30 mol%, the p-phenylenediamine is contained in an amount of 50 to 70 mol%, and the 3, 5-diaminobenzoic acid is contained in an amount of 5 to 25 mol%, based on 100 mol% of the total diamine component.

8. The method for producing a polyimide film according to claim 7, wherein the dianhydride component is selected from the group consisting of dianhydride components,

the content of the biphenyltetracarboxylic dianhydride is 40 to 70 mol%,

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

9. The method for producing a polyimide film according to claim 7, wherein the polyimide film has a strength of 300 to 365MPa and an elongation of 30 to 50%.

10. The method for preparing a polyimide film according to claim 7, wherein a difference between a maximum value and a minimum value of the degree of orientation is more than 0.01 and 0.05 or less, and a difference between coefficients of thermal expansion in a main orientation direction and a sub-orientation direction orthogonal to the main orientation direction may be 2 to 7 ppm.

11. A multilayer film comprising the polyimide film according to any one of claims 1 to 6 and a thermoplastic resin layer.

12. A flexible metal foil laminate comprising the polyimide film according to any one of claims 1 to 6 and a conductive metal foil.

13. An electronic component comprising the flexible metal foil laminate of claim 12.