JP7769114B2 - Multilayer polyimide film and its manufacturing method - Google Patents

Description

The present invention relates to a multilayer polyimide film that has excellent dimensional stability and adhesive strength, and more specifically to a multilayer polyimide film that has high dimensional stability against both heat and moisture and excellent adhesive strength, and a method for producing the same.

Polyimide (PI) is a polymeric material based on imide rings, which have excellent chemical stability along with a rigid aromatic main chain, and has the highest levels of heat resistance, chemical resistance, electrical insulation, chemical resistance, and weather resistance among organic materials.
Polyimide films have been attracting attention as materials for a variety of electronic devices that require the above-mentioned properties.
Examples of microelectronic components to which polyimide films are applied include thin circuit boards that are flexible and have a high degree of circuit integration, allowing for the reduction in the weight and size of electronic products. Polyimide films are particularly widely used as insulating films for thin circuit boards.
The thin circuit board generally has a structure in which a circuit including a metal foil is formed on an insulating film, and such a thin circuit board is broadly called a flexible metal foil clad laminate (FMC), and when a thin copper foil is used as the metal foil, it is more narrowly called a flexible copper clad laminate (FCCL).

Examples of methods for producing flexible metal foil laminates include (i) a casting method in which polyamic acid, a precursor of polyimide, is cast or coated onto a metal foil and then imidized; (ii) a metallizing method in which a metal layer is formed directly on a polyimide film by sputtering; and (iii) a lamination method in which a polyimide film and a metal foil are bonded together by heat and pressure via a thermoplastic polyimide.
In particular, the metallizing method is a method for producing flexible metal foil laminates by sputtering a metal such as copper on a polyimide film having a thickness of, for example, 20 to 38 μm, and sequentially depositing a tie layer and a seed layer. This method is advantageous for forming ultra-fine circuits with a circuit pattern pitch of 35 μm or less, and is widely used to produce flexible metal foil laminates for COF (chip on film).
Polyimide films used in metallizing flexible metal foil laminates must have high dimensional stability. Dimensional stability is usually measured by the thermal expansion coefficient, but dimensional stability against moisture, measured by the hygroscopic expansion coefficient, is becoming increasingly important.
That is, there is an increasing demand for polyimide films that have excellent thermal dimensional stability and moisture dimensional stability. However, when a polyimide film is actually designed to have a structure with a low thermal expansion coefficient and high thermal dimensional stability, a problem arises in that the dimensional stability against moisture is low.
Furthermore, polyimide films, which have a high degree of dimensional restriction, usually have the problem of reduced adhesive strength with sputtered metal plating.
Therefore, there is a strong demand for polyimide films that not only have high thermal dimensional stability and high dimensional stability against moisture, but also have excellent adhesive strength.
The matters described in the above background art are intended to help understand the background of the invention, and may include matters that are not prior art already known to those with ordinary skill in the field to which this technology belongs.

Republic of Korea Patent Publication No. 10-2012-0133807

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a polyimide multilayer film that has high dimensional stability against heat and moisture, as well as excellent adhesive strength.
However, the problems to be solved by the present invention are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, one aspect of the present invention includes a first skin layer and a second skin layer formed on one outer surface of a core layer and on an opposite surface of the outer surface, respectively;
The adhesive strength to copper foil is 0.8 kgf/cm or more.
A multilayer polyimide film is provided.

Another aspect of the present invention is a multilayer polyimide film comprising the multilayer polyimide film and an electrically conductive metal foil.
A flexible metal foil laminate is provided.

Yet another aspect of the present invention includes the flexible metal foil laminate,
Provides electronic components.

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

The terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of the present invention, in accordance with the principle that the inventor can appropriately define the concept of the term in order to best describe his or her invention.
Therefore, it should be understood that the configuration of the embodiment described in this specification is merely one of the most preferred embodiments of the present invention and does not represent the entire technical idea of the present invention, and that there may be various equivalents and modifications that can replace them at the time of this application.

In this specification, the singular includes the plural unless the context clearly dictates otherwise. It should be understood that in this specification, the terms "comprise," "include," "comprise," or "have" are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

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

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

Whenever an amount, concentration, or other value or parameter is given herein as a range, a preferred range, or a list of upper and lower preferred values, it should be understood to specifically disclose all ranges formed by any pair of any upper range limit or preferred value, and any lower range limit or preferred value, regardless of whether ranges are otherwise disclosed.

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 not intended that the scope of the invention be limited to the specific values recited when defining the range.

A multilayer polyimide film according to one embodiment of the present invention may include a first skin layer and a second skin layer formed on one outer surface of the core layer and the opposite surface of the outer surface, respectively, and may have an adhesive strength to copper foil of 0.8 kgf/cm or more.

In other words, the multilayer polyimide film may be a three-layer polyimide film having a core layer at the center, with a first skin layer and a second skin layer formed on one outer surface of the core layer and on the opposite surface of the outer surface, respectively.

On the other hand, the components and composition ratios of the first skin layer and the second skin layer may be the same or different.
The first and second skin layers may have the same or different thicknesses. The copper foil is formed on at least one surface of the multilayer polyimide film by a sputter-electroplating method.

In one embodiment, the multilayer polyimide film may have a thermal expansion coefficient in the transverse direction (TD) of 2.0 ppm/°C or more and 6.0 ppm/°C or less, and a moisture expansion coefficient in the transverse direction (TD) of 3.0 ppm/RH% or more and 6.0 ppm/RH% or less.

The thermal expansion coefficient in the transverse direction (TD) may be, for example, 2.5 ppm/°C or more and 6.0 ppm/°C or less.

Furthermore, the moisture absorption expansion coefficient in the transverse direction (TD) may be, for example, 4.5 ppm/RH% or more and 6.0 ppm/RH% or less.

In one embodiment, the core layer of the multilayer polyimide film is obtained by imidizing a polyamic acid solution containing a dianhydride acid component including biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) and a diamine component including paraphenylenediamine (PPD) and m-tolidine.

Meanwhile, at least one of the first skin layer and the second skin layer is obtained by an imidization reaction of a polyamic acid solution containing a dianhydride acid component including two or more selected from the group consisting of biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, oxydiphthalic anhydride (ODPA), and benzophenonetetracarboxylic dianhydride (BTDA), and a diamine component including one or more selected from the group consisting of oxydianiline (ODA) and 1,3-bisaminophenoxybenzene (TPE-R).

For example, any one or more of the first skin layer and the second skin layer may use, as the dianhydride acid component, biphenyltetracarboxylic dianhydride and pyromelic dianhydride together, biphenyltetracarboxylic dianhydride, pyromelic dianhydride and oxydiphthalic anhydride together, or biphenyltetracarboxylic dianhydride, pyromelic dianhydride and benzophenonetetracarboxylic dianhydride together.
Also, for example, at least one of the first skin layer and the second skin layer may use only oxydianiline as the diamine component, or may use oxydianiline and 1,3-bisaminophenoxybenzene together.

In one embodiment, the core layer may have a biphenyltetracarboxylic dianhydride content of 40 mol% or more and 60 mol% or less, a pyromellitic dianhydride content of 40 mol% or more and 60 mol% or less, and a paraphenylenediamine content of 50 mol% or more and 70 mol% or less, and an m-tolidine content of 30 mol% or more and 50 mol% or less, based on a total content of 100 mol% of the dianhydride acid components.

In one embodiment, one or more of the first skin layer and the second skin layer may have, based on 100 mol% of the total content of the dianhydride acid components, a biphenyltetracarboxylic dianhydride content of 15 mol% or more and 85 mol% or less, a pyromellitic dianhydride content of 15 mol% or more and 60 mol% or less, an oxydiphthalic anhydride content of 35 mol% or less, and a benzophenonetetracarboxylic dianhydride content of 35 mol% or less, based on 100 mol% of the total content of the diamine components, an oxydianiline content of 20 mol% or more and 100 mol% or less, and a 1,3-bisaminophenoxybenzene content of 80 mol% or less.

The paraphenylenediamine of the present invention is a rigid monomer, and by increasing the content of paraphenylenediamine, the synthesized polyimide has a more linear structure, which contributes to improving the mechanical properties of the polyimide.

In addition, m-tolidine contains a methyl group that is particularly hydrophobic, contributing to the low moisture absorption properties related to the dimensional stability of polyimide film against moisture.

The polyimide chains derived from the biphenyltetracarboxylic dianhydride of the present invention have a structure known as a charge transfer complex (CTC), i.e., a regular linear structure in which the electron donor and electron acceptor are located close to each other, strengthening intermolecular interaction.

Such a structure has the effect of preventing hydrogen bonding with moisture, thereby reducing the moisture absorption rate and maximizing the effect of reducing the moisture absorption of the polyimide film, which affects the dimensional stability against moisture.

Furthermore, pyromellitic dianhydrides are preferred in that they are dianhydride acid components with a relatively rigid structure, which can impart appropriate elasticity to the polyimide film.

The dianhydride acid content ratio is important for polyimide film to have excellent dimensional stability. For example, the lower the biphenyltetracarboxylic dianhydride content ratio, the less likely it is that the low moisture absorption rate achieved by the CTC structure will be achieved, and dimensional stability against moisture will also decrease.

Furthermore, biphenyltetracarboxylic dianhydride contains two benzene rings corresponding to the aromatic portion, while pyromelitic dianhydride contains one benzene ring corresponding to the aromatic portion.

An increase in the content of pyromellitic dianhydride in the dianhydride acid component can be understood as an increase in the number of imide groups in the molecule when the same molecular weight is used as the basis. This can be understood as a relative increase in the proportion of imide groups derived from the pyromellitic dianhydride in the polyimide polymer chain compared to the imide groups derived from biphenyltetracarboxylic dianhydride.

In other words, an increase in the pyromellitic dianhydride content is seen as a relative increase in imide groups in the polyimide film as a whole, making it difficult to expect high dimensional stability against moisture due to a low moisture absorption rate.

Conversely, if the content ratio of pyromellitic dianhydride decreases, the relatively rigid structural components decrease, and the elasticity of the polyimide film may fall below the desired level.

For this reason, if the content of biphenyltetracarboxylic dianhydride exceeds the above range or the content of pyromellitic dianhydride falls below the above range, the dimensional stability of the polyimide film may decrease.

Conversely, if the content of the biphenyltetracarboxylic dianhydride is below the above range or the content of the pyromellitic dianhydride is above the above range, this may have an adverse effect on the dimensional stability of the polyimide film.

In the present invention, the polyamic acid can be produced, for example, by
(1) A method in which the entire amount of the diamine component is placed in a solvent, and then the dianhydride acid component is added in an amount substantially equimolar to the diamine component to polymerize it;
(2) A method in which the entire amount of the dianhydride acid component is placed in a solvent, and then the diamine component is added in an amount substantially equimolar to the dianhydride acid component to polymerize the resulting mixture;
(3) A method in which a part of the diamine component is placed in a solvent, and then a part of the dianhydride acid component is mixed with the reaction components in a ratio of about 95 to 105 mol %, and the remaining diamine component is added, and then the remaining dianhydride acid component is added successively to this, so that the diamine component and the dianhydride acid component are substantially equimolar, thereby polymerizing;
(4) A method in which a dianhydride acid component is placed in a solvent, and then a portion of the components in the diamine compound is mixed in a ratio of 95 to 105 mol % relative to the reaction components, and then another dianhydride acid component is added, followed by the addition of the remaining diamine component, so that the diamine component and the dianhydride acid component are substantially equimolar, thereby polymerizing the mixture;
(5) A method of forming a first composition by reacting some diamine components and some dianhydride acid components in a solvent so that one of them is in excess, and then forming a second composition by reacting some diamine components and some dianhydride acid components in another solvent so that one of them is in excess, and then mixing the first and second compositions to complete polymerization, in which if the diamine component is in excess when forming the first composition, the dianhydride acid component is made in excess in the second composition, and if the dianhydride acid component is in excess in the first composition, the diamine component is made in excess in the second composition, and the first and second compositions are mixed to polymerize the diamine components and dianhydride acid components used in the reactions in total so that they are substantially equimolar.

In the present invention, the above-described polyamic acid polymerization method can be defined as a random polymerization method, and polyimide films produced from the polyamic acid of the present invention produced by the above-described process are preferably applicable in that they maximize the effects of the present invention, which are to improve dimensional stability and chemical resistance.

However, this polymerization method produces polymers with relatively short repeating units in the polymer chains described above, which may limit the ability of the polyimide chains derived from the dianhydride acid component to exhibit their excellent properties. Therefore, the polyamic acid polymerization method that is particularly suitable for use in the present invention is block polymerization.

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

In one example, N,N-dimethylformamide and N,N-dimethylacetamide are particularly preferred organic solvents.

Furthermore, in the polyamic acid manufacturing process, fillers may be added to improve various film properties such as sliding properties, thermal conductivity, corona resistance, and loop hardness. There are no particular limitations on the fillers added, but preferred examples include silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, and mica.

The particle size of the filler is not particularly limited and can be determined based on the film properties to be modified and the type of filler to be added. Generally, the average particle size is 0.05 to 100 μm, preferably 0.1 to 75 μm, more preferably 0.1 to 50 μm, and especially preferably 0.1 to 25 μm.

If the particle size is below this range, the modifying effect will be difficult to achieve, and if it exceeds this range, the surface properties may be significantly damaged or the mechanical properties may be significantly reduced.

Furthermore, there are no particular restrictions on the amount of filler added, and it can be determined based on the film properties to be modified and the particle size of the filler. Generally, the amount of filler added is 0.01 to 100 parts by weight, preferably 0.01 to 90 parts by weight, and more preferably 0.02 to 80 parts by weight, per 100 parts by weight of polyimide.

If the amount of filler added is below this range, the modifying effect of the filler will be difficult to achieve, and if it exceeds this range, the mechanical properties of the film may be significantly damaged. There are no particular restrictions on the method of adding the filler, and any known method may be used.

In the manufacturing method of the present invention, polyimide films are produced by thermal imidization and chemical imidization.

It may also be produced using a hybrid imidization method in which thermal imidization and chemical imidization are performed in parallel.

The thermal imidization method is a method in which a chemical catalyst is not used and the imidization reaction is induced by a heat source such as hot air or an infrared dryer.
The thermal imidization method may involve heat-treating the gel film at a variable temperature in the range of 100 to 600°C to imidize the amic acid groups present in the gel film, specifically at 200 to 500°C, and more specifically at 300 to 500°C to imidize the amic acid groups present in the gel film.
However, even during the process of forming the gel film, a portion of the amic acid (approximately 0.1 mol % to 10 mol %) is imidized. For this reason, the polyamic acid composition can be dried at a variable temperature ranging from 50°C to 200°C, which also falls within the category of the thermal imidization method.

In the case of chemical imidization, polyimide films can be produced using dehydrating agents and imidizing agents by methods known in the industry.

As an example of the composite imidization method, a polyimide film can be produced by adding a dehydrating agent and an imidization agent to a polyamic acid solution, heating it at 80 to 200°C, preferably 100 to 180°C, partially curing and drying it, and then heating it at 200 to 400°C for 5 to 400 seconds.

Meanwhile, the multilayer polyimide film of the present invention described above is manufactured using one or more of the following methods: coextrusion or coating.

The co-extrusion method involves filling a reservoir with a polyamic acid solution or a polyimide resin produced by imidizing the polyamic acid solution, extruding the solution in multiple layers onto a casting belt using a co-extrusion die, and then curing the extrusion to produce a multi-layer polyimide film. This method is highly productive and ensures high interfacial adhesion reliability by blending different types of polyimide resins at the interfaces.
For example, a method for producing a multilayer polyimide film of the present invention includes a first filling step of filling a first storage tank with a first solution, which is a first polyamic acid solution or a first polyimide resin produced by imidizing the first polyamic acid solution; a second filling step of filling a second storage tank with a second solution, which is a second polyamic acid solution or a second polyimide resin produced by imidizing the second polyamic acid solution; a co-extrusion step of co-extruding the first and second solutions through a co-extrusion die having a first flow path connected to the first storage tank, a second flow path connected to the second storage tank, and a third flow path connected to the second storage tank, respectively; and a curing step of curing the co-extruded first and second solutions.

The first polyamic acid solution is used to form the core layer and is preferably produced by polymerizing a dianhydride acid component containing biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) with a diamine component containing paraphenylenediamine (PPD) and m-tolidine.

The second polyamic acid solution is used to form the first and second skin layers, and is preferably produced by polymerizing a dianhydride acid component containing two or more selected from the group consisting of biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, oxydiphthalic anhydride (ODPA), and benzophenonetetracarboxylic dianhydride (BTDA), and a diamine component containing one or more selected from the group consisting of oxydianiline (ODA) and 1,3-bisaminophenoxybenzene (TPE-R).

On the other hand, when the first polyamic acid solution is used as the first solution and the second polyamic acid solution is used as the second solution, it is preferable to further include an imidization step of imidizing the first and second solutions co-extruded before the curing step.

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

There are no particular limitations on the metal foil used, but when the flexible metal foil laminate of the present invention is used for electronic or electrical equipment, the metal foil may contain, for example, copper or copper alloy, stainless steel or its alloy, nickel or nickel alloy (including 42 alloy), aluminum or aluminum alloy.

In general, flexible metal foil laminates often use copper foils such as rolled copper foil and electrolytic copper foil, and these can also be preferably used in the present invention. Furthermore, the surface of these metal foils may be coated with an anti-rust layer, a heat-resistant layer, or an adhesive layer.

In the present invention, there are no particular limitations on the thickness of the metal foil, as long as it is thick enough to perform its function adequately depending on the application.

The flexible metal foil laminate according to the present invention may have a structure in which metal foil is laminated on at least one surface of the multilayer polyimide film.

The functions and effects of the invention will be described in more detail below through specific manufacturing examples and examples of the invention. However, these manufacturing examples and examples are presented merely as examples of the invention and do not limit the scope of the invention.

Manufacturing Example: Manufacturing of Multilayer Polyimide Film <br/> A dianhydride acid and a diamine component were selected from biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), oxydiphthalic anhydride (ODPA), benzophenonetetracarboxylic dianhydride (BTDA), paraphenylenediamine (PPD), m-tolidine (MTD), 1,3-bisaminophenoxybenzene (TPE-R), and oxydianiline (ODA), and were polymerized to prepare a first polyamic acid solution used to manufacture the core layer.
A dianhydride acid and a diamine component were selected from biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, oxydiphthalic anhydride, benzophenonetetracarboxylic dianhydride, paraphenylenediamine, m-tolidine, 1,3-bisaminophenoxybenzene, and oxydianiline, and polymerized to produce a second polyamic acid solution to be used in the production of the first and second skin layers.
The first polyamic acid solution and the second polyamic acid solution prepared above were co-extruded by a co-extrusion method, imidized, and then cured to produce a multilayer polyimide film having a core layer and a first skin layer and a second skin layer formed therearound.
Here, however, the core layer was produced by co-extruding a first polyamic acid solution, and the first and second skin layers were produced by co-extruding a second polyamic acid solution.
In preparing the polyamic acid, the solvent may be an aprotic polar solvent, typically an amide-based solvent, such as N,N'-dimethylformamide, N,N'-dimethylacetamide, N-methyl-pyrrolidone, or a combination thereof.
The dianhydride acid and diamine components may be added in the form of powder, lump, or solution. It is preferred that they are added in the form of powder at the beginning of the reaction to allow the reaction to proceed, and then added in the form of a solution to adjust the polymerization viscosity.
The resulting polyamic acid solution is mixed with an imidization catalyst and a dehydrating agent and then applied to a support.
Examples of catalysts that can be used include tertiary amines (for example, isoquinoline, β-picoline, pyridine, etc.), and examples of dehydrating agents include, but are not limited to, acid anhydrides.

Examples and Comparative Examples As shown in Table 1 (core layer components and composition ratios) and Table 2 (skin layer components and composition ratios), the contents of the dianhydride acid component and the diamine component in the core layer and skin layer in Examples 1 to 6 and Comparative Examples 1 to 9 were adjusted to produce multilayer polyimide films according to the production examples.
The first and second skin layers of Examples 1 to 6 and Comparative Example 9 were manufactured to have the same composition and component ratio, and also to the same thickness.
However, Comparative Examples 1 to 8 correspond to single-layer polyimide films, and only the core layer was produced.

The coefficient of thermal expansion (CTE), coefficient of hydroscopic expansion (CHE), and adhesive strength of the produced polyimide film in the width direction were measured and are shown in Table 3 below.

(1) Measurement of the coefficient of thermal expansion The coefficient of thermal expansion (CTE) was measured using a TA Thermomechanical Analyzer (Model Q400). The manufactured multilayer polyimide film was cut into a width of 4 mm and a length of 20 mm. Under a nitrogen atmosphere, the film was heated from 30°C to 400°C at a rate of 10°C/min while applying a tension of 0.05 N. Then, the film was cooled again at a rate of 10°C/min, and the slope of the curve from 50°C to 200°C was measured.

(2) Measurement of the coefficient of moisture expansion (CHE). The coefficient of moisture expansion (CHE) was measured by adjusting the humidity to 3% RH at 25°C under a minimal load (approximately 1 g for a 25 mm x 150 mm sample) to prevent the multilayer polyimide film from becoming loose. The film was then allowed to absorb moisture until it was fully saturated, and the dimensions were measured. The humidity was then adjusted to 90% RH, and the film was allowed to absorb moisture until it was fully saturated. The dimensions were then measured, and the dimensional change rate was calculated from both results.

(3) Adhesion Measurement <br/> A copper thin film layer with a thickness of approximately 80-300 nm was deposited on the prepared multilayer polyimide film by sputtering as a copper seed layer for electroplating electrodes, and a copper conductive layer with a thickness of approximately 8-9 μm was formed by electroplating to prepare a flexible metal foil laminate for COF.
The flexible metal foil laminate was etched into a rod shape with a width of 2 mm by wet etching, and then subjected to a 90° peel test using a Universal Testing Machine to measure adhesive strength by pulling at a speed of 20 mm/min.

As a result of the measurements, the multilayer polyimide films of Examples 1 to 6 exhibited the following properties: a thermal expansion coefficient in the width direction of 2.0 ppm/°C or more and 6.0 ppm/°C or less, a hygroscopic expansion coefficient in the width direction of 3.0 ppm/RH% or more and 6.0 ppm/RH% or less, and an adhesive strength to copper foil of 0.8 kgf/cm or more.
In contrast, the polyimide films of Comparative Examples 1 to 8 and the multilayer polyimide film of Comparative Example 9, which were composed of only one layer and had different components and/or composition ratios from those of the Examples, were unable to satisfy the properties required of the multilayer polyimide film of the present invention in at least one of the thermal expansion coefficient, hygroscopic expansion coefficient, and adhesive strength to copper foil.
Therefore, the multilayer polyimide films of Examples 1 to 6, which were produced within the appropriate range of the present invention, were all excellent in thermal dimensional stability, dimensional stability against moisture, and adhesive strength to copper foil. However, it was confirmed that when the appropriate range of the present invention is exceeded, it is difficult for the multilayer polyimide films of the present invention to satisfy all of the thermal dimensional stability, dimensional stability against moisture, and adhesive strength to copper foil.
In other words, it was confirmed that the multilayer polyimide film that has excellent dimensional stability and adhesion to copper foil and satisfies all of the various conditions applicable to various fields of application is the multilayer polyimide film manufactured within the appropriate range of the present invention.

The examples of the multilayer polyimide film and method for manufacturing a multilayer polyimide film of the present invention are merely preferred examples that will enable those skilled in the art with ordinary skill in the art to easily practice the present invention. The present invention is not limited to the above-mentioned examples, and the scope of the present invention is not limited thereby. Therefore, the true technical scope of protection of the present invention must be determined by the technical spirit of the appended claims. Furthermore, it is obvious to those skilled in the art that various substitutions, modifications, and alterations are possible within the scope of the present invention, and it is self-evident that parts that can be easily modified by those skilled in the art are also included in the scope of the present invention.

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

Claims (4)

a first skin layer and a second skin layer formed on one outer surface of the core layer and on the opposite surface of the outer surface, respectively;
The core layer comprises a dianhydride acid component including biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA);
It is obtained by subjecting a polyamic acid solution containing a diamine component including paraphenylenediamine (PPD) and m-tolidine to an imidization reaction,
the core layer has, based on 100 mol% of the total content of the dianhydride acid components, a content of the biphenyltetracarboxylic dianhydride of 40 mol% or more and 60 mol% or less, a content of the pyromellitic dianhydride of 40 mol% or more and 60 mol% or less, based on 100 mol% of the total content of the diamine components, a content of the paraphenylenediamine of 50 mol% or more and 70 mol% or less, and a content of the m-tolidine of 30 mol% or more and 50 mol% or less,
At least one selected from the group consisting of the first skin layer and the second skin layer comprises a dianhydride acid component including at least two selected from the group consisting of biphenyltetracarboxylic dianhydride, pyromelic dianhydride, oxydiphthalic anhydride (ODPA), and benzophenonetetracarboxylic dianhydride (BTDA);
and a diamine component including at least one selected from the group consisting of oxydianiline (ODA) and 1,3-bisaminophenoxybenzene (TPE-R), and
In one or more of the first skin layer and the second skin layer, the content of the biphenyltetracarboxylic dianhydride is 15 mol% or more and 85 mol% or less, the content of the pyromellitic dianhydride is 15 mol% or more and 60 mol% or less, the content of the oxydiphthalic anhydride is 35 mol% or less, and the content of the benzophenonetetracarboxylic dianhydride is 35 mol% or less, based on 100 mol% of the total content of the dianhydride acid components.
the content of the oxydianiline is 20 mol % or more and 100 mol % or less, and the content of the 1,3-bisaminophenoxybenzene is 80 mol % or less, based on 100 mol % of the total content;
The adhesive strength to copper foil is 0.8 kgf/cm or more.
Multilayer polyimide film. a thermal expansion coefficient in the transverse direction (TD) of 2.0 ppm/°C or more and 6.0 ppm/°C or less;
The moisture expansion coefficient in the transverse direction (TD) is 3.0 ppm/RH% or more and 6.0 ppm/RH% or less.
The multilayer polyimide film according to claim 1 . A multilayer polyimide film comprising the multilayer polyimide film according to claim 1 or 2 and an electrically conductive metal foil.
Flexible metal foil laminate. The flexible metal foil laminate of claim 3 .
Electronic components.