Polyimide film of multilayer structure and method for manufacturing the same

Abstract

The present invention provides a multilayer polyimide film and a method for manufacturing the same. The multilayer polyimide film comprises a first skin layer and a second skin layer formed on one outer surface of a core layer and an opposite surface of the outer surface, respectively, and has an adhesion strength of 0.8 kgf / cm or more to a copper foil.

Description

Technical Field

[0001] This invention relates to a multilayer polyimide film with excellent dimensional stability and excellent adhesion, and more specifically, to a multilayer polyimide film with high thermal and moisture dimensional stability and excellent adhesion, and a method for manufacturing the same. Background Technology

[0002] Polyimide (PI) is a polymeric material based on a rigid aromatic backbone and an imide ring with excellent chemical stability. It has the highest level of heat resistance, reagent resistance, electrical insulation, chemical resistance, and weather resistance among organic materials.

[0003] Polyimide films have attracted much attention as a material for various electronic devices that require the above-mentioned properties.

[0004] As an example of microelectronic components using polyimide films, one can cite thin circuit boards with high circuit integration and flexibility, which are needed to meet the requirements of lightweighting and miniaturization of electronic products. Polyimide films are particularly widely used as insulating films for thin circuit boards.

[0005] The aforementioned thin circuit board is generally a structure in which a circuit containing a metal foil is formed on an insulating film. In a broad sense, such a thin circuit board is called a flexible metal foil laminate. When a thin copper plate is used as the metal foil, it is also called a flexible copper foil laminate (FCCL) in a narrow sense.

[0006] Methods for manufacturing flexible metal foil laminates include, for example: (i) a casting method in which polyamic acid, as a precursor of polyimide, is cast or coated onto a metal foil and then imidized; (ii) a metallization method in which a metal layer is directly deposited on a polyimide film by sputtering; and (iii) a lamination method in which a polyimide film is bonded to a metal foil by using thermoplastic polyimide and heat and pressure.

[0007] In particular, the metallization method, which involves sputtering a metal such as copper onto a polyimide film with a thickness of 20 to 38 μm and then sequentially depositing a tie layer and a seed layer to produce a flexible metal foil laminate, is advantageous for forming ultra-fine circuits with a circuit pattern pitch of less than 35 μm and is widely used in the manufacture of flexible metal foil laminates for chip-on-film (COF) applications.

[0008] The polyimide film used in flexible metal foil laminates produced by metallization must possess high dimensional stability. Dimensional stability is typically determined by thermal dimensional stability, expressed as the coefficient of thermal expansion; however, moisture dimensional stability, expressed as the coefficient of hygroscopic expansion, is becoming increasingly important, just as much as thermal dimensional stability.

[0009] That is, the demand for polyimide films with excellent thermal dimensional stability and moisture dimensional stability is constantly increasing. However, when designing polyimide films with low thermal expansion coefficient and high thermal dimensional stability, the problem of reduced moisture dimensional stability will occur.

[0010] In addition, polyimide films with high dimensional stability often have the problem of reduced adhesion to sputtered metal coatings.

[0011] Therefore, there is an urgent need for a polyimide film that not only has high thermal dimensional stability and high moisture dimensional stability but also excellent adhesive strength.

[0012] The matters described in the background section above are intended to aid in understanding the background of the invention and may include matters that are not known to those skilled in the art.

[0013] Existing technical documents

[0014] Patent documents

[0015] Patent Document 1: Korean Patent Publication No. 10-2012-0133807 Summary of the Invention

[0016] Technical issues

[0017] Therefore, the object of the present invention is to provide a polyimide multilayer film that simultaneously possesses high thermal dimensional stability, high moisture dimensional stability, and excellent adhesive strength.

[0018] However, the problems to be solved by the present invention are not limited to those mentioned above, and those skilled in the art should be able to clearly understand other problems not mentioned from the following description.

[0019] Methods for solving problems

[0020] To achieve the objectives described above, one aspect of the present invention provides a multilayer polyimide film comprising a first skin layer and a second skin layer respectively formed on an outer surface of a core layer and on an opposing surface of the outer surface.

[0021] The adhesion to copper foil is above 0.8 kgf / cm.

[0022] Another aspect of the present invention provides a flexible metal foil laminate comprising the above-mentioned multilayer polyimide film and conductive metal foil.

[0023] Another aspect of the present invention provides an electronic component comprising the above-described flexible metal foil laminate.

[0024] Invention Effects

[0025] This invention provides a polyimide film with excellent thermal dimensional stability, moisture dimensional stability, and adhesion by adjusting the composition ratio and reaction ratio of acid dianhydride and diamine components.

[0026] Such polyimide films can be applied in a variety of fields that require polyimide films with excellent dimensional stability and adhesion, such as flexible metal foil laminates manufactured by metallization or electronic components containing such flexible metal foil laminates. Detailed Implementation

[0027] The terms or vocabulary used in this specification and the claims should not be limited to their ordinary or dictionary meanings, but should be interpreted based on the principles that the inventors can appropriately define to best illustrate their invention, and in accordance with the meanings and concepts consistent with the technical ideas of this invention.

[0028] Therefore, the embodiments described in this specification are only one of the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. It should be understood that at the time of filing this application, there may be many equivalents and modifications that can replace these embodiments.

[0029] In this specification, unless the context clearly specifies otherwise, singular expressions include plural expressions. It should be understood in this specification that terms such as “comprising,” “possessing,” or “having” are intended to specify the presence of features, numbers, steps, constituent elements, or combinations thereof, and do not presuppose the presence or additional possibilities of more than one other feature, number, step, constituent element, or combination thereof.

[0030] In this specification, “acid dianhydride” is intended to include its precursors or derivatives, which, although technically not acid dianhydrides, can still react with diamines to form polyamic acid, which can then be converted back into polyimide.

[0031] In this specification, "diamine" is intended to include its precursors or derivatives, which, although technically they may not be diamines, can still react with dianhydrides to form polyamic acid, which can then be converted back into polyimide.

[0032] In this specification, when quantities, concentrations, or other values ​​or parameters are given as a range, a preferred range, or a preferred upper limit and a preferred lower limit, it should be understood that any pair of ranges formed by any upper limit or preferred value and any lower limit or preferred value is specifically disclosed, regardless of whether the range is disclosed individually.

[0033] Where a range of values ​​is mentioned in this specification, unless otherwise stated, the range is intended to include the endpoints and all integers and fractions within that range. The scope of this invention is not intended to be limited to the specific values ​​mentioned when defining the range.

[0034] According to one embodiment of the present invention, a multilayer polyimide film comprises a first skin layer and a second skin layer respectively formed on an outer surface of a core layer and an opposite surface of the outer surface, and the adhesion force to copper foil can be 0.8 kgf / cm or more.

[0035] That is, the above-mentioned multilayer polyimide film can be a multilayer polyimide film with a three-layer structure, having 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.

[0036] On the other hand, the composition and layer ratio of the first and second epidermal layers can be the same or different.

[0037] In addition, the thicknesses of the first and second epidermal layers can be the same or different.

[0038] The aforementioned copper foil can be formed on one or more sides of the multilayer polyimide film of this application by sputtering-electroplating.

[0039] In one embodiment, the thermal expansion coefficient in the traverse direction (TD) of the above-mentioned multilayer polyimide film can be above 2.0 ppm / ℃ and below 6.0 ppm / ℃, and the moisture absorption expansion coefficient in the traverse direction (TD) can be above 3.0 ppm / RH% and below 6.0 ppm / RH%.

[0040] The coefficient of thermal expansion in the traverse direction (TD) can be, for example, above 2.5 ppm / ℃ and below 6.0 ppm / ℃.

[0041] In addition, the hygroscopic expansion coefficient in the traverse direction (TD) can be, for example, above 4.5ppm / RH% and below 6.0ppm / RH%.

[0042] In one embodiment, the core layer of the multilayer polyimide film can be obtained by performing an imidization reaction on a polyamic acid solution containing an acid dianhydride component and a diamine component, wherein the acid dianhydride component includes biphenyl dianhydride (BPDA) and pyromellitic dianhydride (PMDA), and the diamine component includes p-phenylenediamine (PPD) and m-tolidine.

[0043] On the other hand, any one or more of the first epidermal layer and the second epidermal layer can be obtained by imidizing a polyamic acid solution containing an acid dianhydride component and a diamine component, wherein the acid dianhydride component comprises two or more selected from the group consisting of biphenyl dianhydride, pyromellitic dianhydride, oxydiphthalic anhydride (ODPA) and benzophenone tetracarboxylic dianhydride (BTDA), and the diamine component comprises one or more selected from the group consisting of diaminodiphenyl ether (ODA) and 1,3-diaminophenoxybenzene (TPE-R).

[0044] For example, either or more of the first epidermal layer and the second epidermal layer may use biphenyl dianhydride and pyromellitic dianhydride simultaneously, or biphenyl dianhydride, pyromellitic dianhydride and oxydiphthalic anhydride simultaneously, or biphenyl dianhydride, pyromellitic dianhydride and benzophenone dianhydride simultaneously as acid dianhydride components.

[0045] Alternatively, for example, either or more of the first epidermal layer and the second epidermal layer may use only diaminodiphenyl ether, or both diaminodiphenyl ether and 1,3-diaminophenoxybenzene as diamine components.

[0046] In one embodiment, based on a total content of 100 mol% of the aforementioned dianhydride components in the core layer, the content of the aforementioned biphenyltetracarboxylic dianhydride can be 40 mol% or more but less than 60 mol% and the content of the aforementioned pyromellitictetracarboxylic dianhydride can be 40 mol% or more but less than 60 mol%; based on a total content of 100 mol% of the aforementioned diamine components, the content of the aforementioned p-phenylenediamine can be 50 mol% or more but less than 70 mol% and the content of the aforementioned meta-toluidine can be 30 mol% or more but less than 50 mol%.

[0047] In one embodiment, based on a total content of 100 mol% of the acid dianhydride components in either the first epidermal layer or the second epidermal layer, the content of the biphenyl dianhydride may be 15 mol% or more and 85 mol% or less, the content of the pyromellitic dianhydride may be 15 mol% or more and 60 mol% or less, the content of the oxydiphthalic anhydride may be 35 mol% or less, the content of the benzophenone tetracarboxylic dianhydride may be 35 mol% or less, and based on a total content of 100 mol% of the diamine components, the content of the diaminodiphenyl ether may be 20 mol% or more and 100 mol% or less, and the content of 1,3-diaminophenoxybenzene may be 80 mol% or less.

[0048] The p-phenylenediamine of this invention is a rigid monomer, and the synthesized polyimide will have a more linear structure as the p-phenylenediamine content increases, which helps to improve the mechanical properties of the polyimide.

[0049] In addition, meta-toluidine, especially because it has a hydrophobic methyl group, contributes to the low moisture absorption properties of polyimide films related to moisture dimensional stability.

[0050] The polyimide chain derived from biphenyl dianhydride of the present invention has a structure known as a charge transfer complex (CTC), which is a regular linear structure in which the electron donor and electron acceptor are close to each other, thereby enhancing the intermolecular interaction.

[0051] This structure prevents the formation of hydrogen bonds with moisture, thus reducing the hygroscopicity and maximizing the effect of reducing the hygroscopicity of the polyimide film that affects the dimensional stability of moisture.

[0052] In addition, pyromellitic dianhydride is an acid dianhydride component with a relatively rigid structure, and is preferred from the perspective of imparting appropriate elasticity to the polyimide film.

[0053] The ratio of dianhydride to biphenyl dianhydride is crucial for ensuring excellent dimensional stability of polyimide films. For example, as the ratio of biphenyl dianhydride decreases, the low moisture absorption rate expected from the aforementioned CTC structure becomes less desirable, and the dimensional stability of moisture content also declines.

[0054] In addition, biphenyl dianhydride contains two benzene rings corresponding to the aromatic moiety, while pyromellitic dianhydride contains one benzene ring corresponding to the aromatic moiety.

[0055] In the dianhydride component, when the molecular weight is the same, the increase in the content of pyromellitic dianhydride can be understood as the increase of imide groups in the molecule. This can be understood as the ratio of imide groups from the aforementioned pyromellitic dianhydride to imide groups from biphenyl dianhydride in the polyimide polymer chain is relatively increased.

[0056] That is, the increase in the content of pyromellitic dianhydride can also be regarded as a relative increase in the number of imide groups relative to the overall polyimide film, so it is difficult to expect high moisture dimensional stability due to low moisture absorption.

[0057] Conversely, if the content of pyromellitic dianhydride is reduced, the rigid structure is relatively reduced, and the elasticity of the polyimide film can be reduced to below the desired level.

[0058] For this reason, when the content of biphenyl dianhydride is higher than the above range or the content of pyromellitic dianhydride is lower than the above range, the dimensional stability of the polyimide film will decrease.

[0059] Conversely, if the content of biphenyl dianhydride is below the above range or the content of pyromellitic dianhydride is above the above range, it will also have an adverse effect on the dimensional stability of the polyimide film.

[0060] In this invention, polyamic acid can be manufactured by, for example, the following methods:

[0061] (1) A method of polymerization in which all diamine components are added to a solvent and then acid dianhydride components are added in substantially equal molar amounts to the diamine components;

[0062] (2) A method of polymerization in which all the acid dianhydride components are added to the solvent, and then the diamine components are added in substantially equal molar amounts to the acid dianhydride components;

[0063] (3) After adding a portion of the diamine component to the solvent, a portion of the acid dianhydride component is mixed relative to the reaction component at a ratio of about 95 to 105 mol%, and then the remaining diamine component is added, followed by the remaining acid dianhydride component, so that the diamine component and the acid dianhydride component are polymerized in a substantially equimolar manner.

[0064] (4) After adding the acid dianhydride component to the solvent, a portion of the diamine compound is mixed relative to the reaction component at a ratio of about 95 to 105 mol%, then other acid dianhydride components are added, followed by the addition of the remaining diamine component, thereby polymerizing the diamine component and the acid dianhydride component in a substantially equimolar manner.

[0065] (5) A method in which a portion of a diamine component and a portion of an acid dianhydride component are reacted in a solvent in excess of either component to form a first composition, and a portion of a diamine component and a portion of an acid dianhydride component are reacted in another solvent in excess of either component to form a second composition, and the first and second compositions are then mixed and polymerization is completed, wherein, in forming the first composition, if the diamine component is in excess, the acid dianhydride component is in excess in the second composition, and if the acid dianhydride component is in excess in the first composition, the diamine component is in excess in the second composition, thereby mixing the first and second compositions and polymerizing the total diamine component and the acid dianhydride component used in their reaction in a substantially equimolar manner; etc.

[0066] In this invention, the polymerization method of polyamic acid as described above can be defined by random polymerization. The polyimide film manufactured from the polyamic acid of this invention produced by the process described above can be preferably used to maximize the effects of this invention in improving dimensional stability and chemical resistance.

[0067] However, the above-described polymerization method results in shorter repeating units within the polymer chain, which may limit the utilization of the various excellent properties of the polyimide chain derived from the dianhydride component. Therefore, block polymerization is a particularly preferred polymerization method for polyamic acid in this invention.

[0068] On the other hand, there are no particular limitations on the solvent used to synthesize polyamic acid; any solvent can be used as long as it dissolves polyamic acid, with amide-based solvents being preferred.

[0069] Specifically, the aforementioned organic solvent can be an organic polar solvent, more specifically, it can be an aprotic polar solvent, for example, it can be one or more selected from the group consisting of N,N-dimethylformamide (DMF), N,N-dimethylacetamide, N-methylpyrrolidone (NMP), γ-butyrolactone (GBL), and diethylene glycol dimethyl ether (Diglyme), but is not limited thereto, and can be used alone or in combination as needed.

[0070] In one example, the aforementioned organic solvents may particularly preferably be N,N-dimethylformamide and N,N-dimethylacetamide.

[0071] In addition, fillers can be added during the polyamic acid manufacturing process to improve various film properties such as lubricity, thermal conductivity, corona resistance, and Knoop hardness. There are no particular limitations on the fillers added, but preferred examples include silica, titanium dioxide, alumina, silicon nitride, boron nitride, dicalcium phosphate, calcium phosphate, and mica.

[0072] The particle size of the filler is not particularly limited, but can be determined according to the desired membrane characteristics and the type of filler added. Generally, the average particle size is 0.05 to 100 μm, preferably 0.1 to 75 μm, more preferably 0.1 to 50 μm, and particularly preferably 0.1 to 25 μm.

[0073] If the particle size is below the above range, it is not easy to show a modification effect; if it is above the above range, it may sometimes cause significant damage to the surface properties or a significant decrease in mechanical properties.

[0074] Furthermore, there is no particular limitation on the amount of filler added; it can be determined based on the membrane characteristics to be modified or the particle size of the filler. Generally, the amount of filler added is 0.01 to 100 parts by weight relative to 100 parts by weight of polyimide, preferably 0.01 to 90 parts by weight, and more preferably 0.02 to 80 parts by weight.

[0075] If the filler content is below the above range, the modification effect brought about by the filler will not be easily observed; if it is above the above range, the mechanical properties of the membrane may be significantly damaged. There are no particular limitations on the method of adding the filler; any known method can be used.

[0076] In the manufacturing method of the present invention, the polyimide film can be manufactured by thermal imidization and chemical imidization.

[0077] Alternatively, it can be manufactured by a combined imidization method that combines thermal imidization and chemical imidization.

[0078] The aforementioned thermal imidization method is a method that eliminates chemical catalysts and uses heat sources such as hot air or infrared dryers to induce the imidization reaction.

[0079] In the above-described thermal imidization method, the gel membrane can be heat-treated at a variable temperature ranging from 100 to 600°C to imidize the amyl acid groups present in the gel membrane. More specifically, the heat treatment can be performed at 200 to 500°C, and more specifically, at 300 to 500°C to imidize the amyl acid groups present in the gel membrane.

[0080] However, a portion of the amic acid (about 0.1 mol% to 10 mol%) may also undergo imidization during the formation of the gel film. For this purpose, the polyamic acid composition can be dried at a variable temperature ranging from 50°C to 200°C, which also falls under the category of the above-mentioned thermal imidization method.

[0081] In the case of chemical imidization, polyimide films can be manufactured using dehydrating agents and imidizing agents in accordance with methods known in the art.

[0082] As an example of the composite imidization method, a dehydrating agent and an imidizing agent can be added to a polyamic acid solution, and then partially cured and dried by heating at 80 to 200°C, preferably at 100 to 180°C, and then heated at 200 to 400°C for 5 to 400 seconds, thereby producing a polyimide film.

[0083] On the other hand, the multilayer polyimide film of the present invention described herein can be manufactured by any one or more of co-extrusion or coating.

[0084] Co-extrusion is a method of filling a storage tank with a polyamic acid solution or a polyimide resin made by imidizing it, then using a co-extrusion die to extrude multiple layers on a cast tape, and finally curing to produce a multi-layered polyimide film. Due to its high productivity and the mixing of different types of polyimide resins at the interfaces, it can ensure high interfacial adhesion reliability.

[0085] For example, the manufacturing method of the multilayer polyimide film of the present invention can be carried out by including the following steps: a first filling step, in which a first polyamic acid solution or a first polyimide resin, i.e., a first solution, is filled into a first storage tank; a second filling step, in which a second polyamic acid solution or a second polyimide resin, i.e., a second solution, is filled into a second storage tank; a co-extrusion step, in which the first solution and the second solution are co-extruded through a co-extrusion die formed inside 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 respectively connected to the second storage tank; and a curing step, in which the co-extruded first solution and the second solution are cured.

[0086] The first polyamic acid solution is intended to form a core layer, preferably manufactured by polymerizing an acid dianhydride component and a diamine component, wherein the acid dianhydride component comprises biphenyl dianhydride (BPDA) and pyromellitic dianhydride (PMDA), and the diamine component comprises p-phenylenediamine (PPD) and m-tolidine.

[0087] The second polyamic acid solution is used to form the first and second skin layers, preferably manufactured by polymerizing an acid dianhydride component and a diamine component, wherein the acid dianhydride component comprises two or more selected from the group consisting of biphenyl dianhydride, pyromellitic dianhydride, oxydiphthalic anhydride (ODPA), and benzophenone tetracarboxylic dianhydride (BTDA), and the diamine component comprises any one or more selected from the group consisting of diaminodiphenyl ether (ODA) and 1,3-diaminophenoxybenzene (TPE-R).

[0088] On the other hand, when using the first polyamic acid solution as the first solution and the second polyamic acid solution as the second solution, it is preferable to further include an imidization step of imidizing the co-extruded first and second solutions before the curing step.

[0089] The present invention provides a flexible metal foil laminate comprising the above-described multilayer polyimide film and conductive metal foil.

[0090] The metal foil used is not particularly limited, but when the flexible metal foil laminate of the present invention is used in electronic or electrical equipment applications, it may be, for example, a metal foil containing copper or copper alloy, stainless steel or its alloy, nickel or nickel alloy (including 42 alloy), aluminum or aluminum alloy.

[0091] In conventional flexible metal foil laminates, rolled copper foil or electrolytic copper foil is commonly used, and these types of copper foil are also preferred in this invention. Furthermore, the surface of these metal foils may be coated with an anti-rust layer, a heat-resistant layer, or an adhesive layer.

[0092] In this invention, the thickness of the metal foil is not particularly limited, as long as it is thick enough to perform its intended function.

[0093] The flexible metal foil laminate of the present invention can be a structure formed by laminating metal foil on at least one side of the above-mentioned multilayer polyimide film.

[0094] Implementation

[0095] The following describes the function and effects of the invention in more detail through specific manufacturing examples and embodiments. However, these manufacturing examples and embodiments are provided merely as illustrative examples of the invention, and the scope of the invention is not limited thereto.

[0096] Manufacturing example: Manufacturing of multilayer polyimide films

[0097] A first polyamic acid solution for manufacturing the core layer is prepared by selecting acid dianhydrides and diamine components from biphenyl dianhydride (BPDA), pyromellitic dianhydride (PMDA), oxydiphthalic anhydride (ODPA), benzophenone tetracarboxylic dianhydride (BTDA), p-phenylenediamine (PPD), m-tolidine (MTD), 1,3-diaminophenoxybenzene (TPE-R), and diaminodiphenyl ether (ODA) and subjecting them to polymerization.

[0098] A second polyamic acid solution for manufacturing the first and second skin layers is prepared by selecting acid dianhydrides and diamine components from biphenyl dianhydride, pyromellitic dianhydride, oxydiphthalic anhydride, benzophenone tetracarboxylic dianhydride, p-phenylenediamine, meta-toluidine, 1,3-diaminophenoxybenzene, and diaminodiphenyl ether and subjecting them to polymerization.

[0099] The first and second polyamic acid solutions prepared above are co-extruded by co-extrusion, and then imidized and cured to produce a multilayer polyimide film with a first skin layer and a second skin layer formed around the core layer.

[0100] Here, the core layer is manufactured by co-extruding a first polyamic acid solution, and the first and second skin layers are manufactured by co-extruding a second polyamic acid solution.

[0101] In manufacturing the above-mentioned polyamic acid, the solvent is generally an amide solvent, and an aprotic polar solvent can be used, such as N,N'-dimethylformamide, N,N'-dimethylacetamide, N-methylpyrrolidone, or combinations thereof.

[0102] Regarding the input form of the aforementioned dianhydride and diamine components, they can be added in powder, bulk, or solution form. It is preferred to add them in powder form at the initial stage of the reaction to carry out the reaction, and then add them in solution form to adjust the polymerization viscosity.

[0103] The obtained polyamic acid solution can be mixed with an imidization catalyst and a dehydrating agent and coated onto a support.

[0104] Examples of catalysts used include tertiary amines (such as isoquinoline, β-methylpyridine, pyridine, etc.), and examples of dehydrating agents include acid anhydrides, but are not limited to these.

[0105] Examples and Comparative Examples

[0106] As shown in Table 1 (composition and layer ratio of the core layer) and Table 2 (composition and layer ratio of the skin layer) below, the contents of the acid dianhydride composition and the diamine composition of the core layer and skin layer in Examples 1 to 6 and Comparative Examples 1 to 9 were adjusted, and a multilayer polyimide film was manufactured according to the manufacturing example.

[0107] The composition and component ratio of the first and second epidermal layers of Examples 1 to 6 and Comparative Example 9 were made the same, and the thickness was also the same.

[0108] However, Comparative Examples 1 to 8 were single-layer polyimide films, with only the core layer manufactured.

[0109] [Table 1]

[0110]

[0111] [Table 2]

[0112]

[0113] The coefficient of thermal expansion (CTE), coefficient of hydroscopic expansion (CHE), and adhesive strength of the manufactured polyimide film were measured and are shown in Table 3 below.

[0114] [Table 3]

[0115]

[0116] (1) Determination of thermal expansion coefficient

[0117] The coefficient of thermal expansion (CTE) was determined as follows: A TA thermomechanical analyzer Q400 was used. The manufactured multilayer polyimide film was cut into pieces with a width of 4 mm and a length of 20 mm. Then, under a nitrogen atmosphere, the temperature was increased from 30 °C to 400 °C at a rate of 10 °C / min while applying a tension of 0.05 N. The slope in the range of 50 °C to 200 °C was measured while cooling it again at a rate of 10 °C / min.

[0118] (2) Determination of hygroscopic expansion coefficient

[0119] The hygroscopic expansion coefficient (CHE) was determined as follows: Under the condition of applying a minimal load (approximately 1 g for a 25 mm × 150 mm sample) in a way that prevents the manufactured multilayer polyimide film from collapsing, the humidity was adjusted to 3% RH at 25°C, and the film was allowed to absorb moisture until it was fully saturated and the dimensions were measured. Then, the humidity was adjusted to 90% RH, and the film was similarly allowed to absorb moisture until it was saturated and the dimensions were measured. Based on the results of both tests, the dimensional change rate was determined.

[0120] (3) Adhesion strength test

[0121] A copper thin film layer with a thickness of about 80-300 nm is deposited on the manufactured multilayer polyimide film by sputtering as a copper seed layer for electroplating electrodes. Then, a copper conductive layer with a thickness of about 8-9 μm is formed by electroplating, thereby producing a flexible metal foil laminate for COF.

[0122] The above-mentioned flexible metal foil laminate was etched into a 2mm wide rod using a wet etching method. Then, a 90° peel test was performed using a universal testing machine, and the adhesive strength was determined by stretching at a speed of 20mm / min.

[0123] The test results showed the following characteristics: the coefficient of thermal expansion in the width direction of the multilayer polyimide film of Examples 1 to 6 was 2.0 ppm / ℃ or more and 6.0 ppm / ℃ or less, the coefficient of hygroscopic expansion in the width direction was 3.0 ppm / RH% or more and 6.0 ppm / RH% or less, and the adhesion to copper foil was 0.8 kgf / cm or more.

[0124] In contrast, the polyimide films of Comparative Examples 1 to 8, which have different compositions and / or layer ratios from the examples and consist of only one layer, and the multilayer polyimide film of Comparative Example 9, fail to meet the requirements of the multilayer polyimide film of this application in terms of coefficient of thermal expansion, coefficient of hygroscopic expansion, and adhesion to copper foil.

[0125] Therefore, it can be confirmed that the multilayer polyimide films of Examples 1 to 6 manufactured within the appropriate scope of this application have excellent thermal dimensional stability, moisture dimensional stability and adhesion to copper foil. However, outside the appropriate scope of this application, it is not possible to satisfy all the thermal dimensional stability, moisture dimensional stability and adhesion to copper foil of the multilayer polyimide films of this application.

[0126] That is, it can be confirmed that the multilayer polyimide film that fully meets the requirements of various application fields while having excellent dimensional stability and adhesion to copper foil is a multilayer polyimide film manufactured within the appropriate scope of this application.

[0127] The embodiments of the multilayer polyimide film and the method for manufacturing the multilayer polyimide film of the present invention are merely preferred embodiments that enable those skilled in the art to readily implement the invention, and are not limited to the above embodiments. Therefore, they do not limit the scope of the invention. Thus, the true scope of protection of the present invention will be defined by the technical concept of the appended claims. Furthermore, it will be apparent to those skilled in the art that various substitutions, modifications, and alterations can be made without departing from the technical concept of the present invention; of course, parts that can be easily modified by those skilled in the art also fall within the scope of the present invention.

[0128] Industrial availability

[0129] This invention provides a polyimide film with excellent thermal dimensional stability, moisture dimensional stability, and adhesion by adjusting the composition ratio and reaction ratio of acid dianhydride and diamine components.

[0130] Such polyimide films can be applied in a variety of fields that require polyimide films with excellent dimensional stability and adhesion, such as flexible metal foil laminates manufactured by metallization or electronic components containing such flexible metal foil laminates.

Claims

1. A multilayer polyimide film comprising a first skin layer and a second skin layer respectively formed on an outer surface of a core layer and an opposing surface of the outer surface. The core layer is obtained by imidizing a polyamic acid solution containing dianhydride and diamine components. in, The dianhydride component comprises biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA), and the diamine component comprises p-phenylenediamine (PPD) and meta-toluidine. Based on a total dianhydride content of 100 mol% in the core layer, the content of biphenyl dianhydride is between 40 mol% and 60 mol%, and the content of pyromellitic dianhydride is between 40 mol% and 60 mol%. Based on a total diamine content of 100 mol% in the core layer, the content of p-phenylenediamine is 50 mol% to 70 mol%, and the content of meta-toluidine is 30 mol% to 50 mol%. The first and second epidermal layers are obtained by imidization of a polyamic acid solution containing dianhydride and diamine components. The dianhydride component comprises two or more selected from the group consisting of biphenyl dianhydride (BPDA), pyromellitic dianhydride (PMDA), oxydiphthalic anhydride (ODPA), and benzophenone tetracarboxylic dianhydride (BTDA); and the diamine component comprises any one or more selected from the group consisting of diaminodiphenyl ether (ODA) and 1,3-bis(4-aminophenoxy)benzene (TPE-R). Based on a total dianhydride content of 100 mol% in the first and second epidermal layers, the content of biphenyl dianhydride is 15 mol% to 85 mol%, the content of pyromellitic dianhydride is 15 mol% to 60 mol%, the content of oxydiphthalic anhydride is 35 mol% to 35 mol%, and the content of benzophenone tetracarboxylic dianhydride is 35 mol% to 35 mol%. Based on a total diamine content of 100 mol% in the first and second epidermal layers, the content of the diaminodiphenyl ether is between 20 mol% and 100 mol%, and the content of 1,3-bis(4-aminophenoxy)benzene is less than 80 mol%. The adhesion between the multilayer polyimide film and the copper foil is above 0.8 kgf / cm.

2. The multilayer polyimide film according to claim 1, wherein the coefficient of thermal expansion (TD) in the width direction is above 2.0 ppm / ℃ and below 6.0 ppm / ℃. The hygroscopic expansion coefficient of TD in the width direction is above 3.0ppm / RH% and below 6.0ppm / RH%.

3. The multilayer polyimide film according to claim 1 or 2, wherein the multilayer polyimide film is manufactured by one or more methods selected from the group consisting of co-extrusion and coating.

4. A flexible metal foil laminate comprising a multilayer polyimide film and a conductive metal foil as described in any one of claims 1 to 3.

5. An electronic component comprising the flexible metal foil laminate of claim 4.

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