Low dielectric polyimide film and method for manufacturing the same

Abstract

This invention relates to a polyimide film and a method for manufacturing the same. The polyimide film is manufactured by imidizing a polyamic acid solution containing an acid dianhydride component and a diamine component. The acid dianhydride component comprises biphenyl dianhydride (BPDA) and pyromellitic dianhydride (PMDA), and the diamine component comprises m-toluidine and p-phenylenediamine (PPD). Based on a total diamine content of 100 mol%, the content of m-toluidine is 30 mol% to 50 mol%, and the content of p-phenylenediamine is 50 mol% to 70 mol%.

Description

Technical Field

[0001] This invention relates to a low-dielectric polyimide film with improved dielectric properties and a method for manufacturing the same. Background Technology

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

[0003] In particular, due to its excellent insulation properties, namely its excellent electrical properties such as low dielectric constant, it has attracted much attention as a high-functionality polymer material in the fields of electrical, electronic and optical engineering.

[0004] In recent years, with the trend of electronic products towards lightweighting and miniaturization, thin circuit boards with high integration and flexibility have been actively developed.

[0005] Such thin circuit boards tend to be used in most cases to form circuits containing metal foil on polyimide films that have excellent heat resistance, low temperature resistance and insulation properties and are easy to bend.

[0006] As such thin circuit boards, flexible metal foil laminates are mainly used, such as flexible copper foil laminates (FCCLs) that use thin copper plates as metal foils. In addition, polyimide is also used as a protective film, insulating film, etc. for thin circuit boards.

[0007] On the other hand, as various functions have been integrated into electronic devices in recent years, these electronic devices are required to have fast computing and communication speeds. In order to meet this requirement, thin circuit boards capable of high-speed communication at high frequencies are being developed.

[0008] However, in reality, the dielectric properties of typical polyimides are not yet good enough to maintain adequate insulation in high-frequency communications.

[0009] In addition, it is well known that the lower the dielectric properties of an insulator, the more it can reduce the generation of unwanted parasitic capacitance and noise in thin circuit boards, thereby greatly solving the problem of communication delay.

[0010] Therefore, in practice, polyimide with low dielectric properties is considered the most important factor affecting the performance of thin circuit boards.

[0011] In particular, in the case of high-frequency communication, dielectric dissipation is inevitable through polyimide. The dielectric dissipation factor (Df) refers to the degree of energy waste in thin circuit boards and is closely related to the signal transmission delay that determines the communication speed. Therefore, keeping the dielectric dissipation factor of polyimide as low as possible is also considered an important factor affecting the performance of thin circuit boards.

[0012] Furthermore, the more moisture a polyimide film contains, the higher its dielectric constant and the greater its dielectric loss factor. While polyimide films are suitable as materials for thin circuit boards due to their excellent inherent properties, their relatively high susceptibility to moisture due to the polar imide groups can potentially reduce their insulating properties.

[0013] Therefore, in practice, there is a need to develop polyimide films that maintain the unique mechanical, thermal, and chemical resistance properties of polyimide at a certain level while having low dielectric properties, especially low dielectric loss factor.

[0014] Existing technical documents

[0015] Patent documents

[0016] (Patent Document 1) Korean Patent Publication No. 10-2015-0069318 Summary of the Invention

[0017] Technical issues

[0018] The purpose of this invention is to provide a polyimide film with high heat resistance, low dielectric properties and low moisture absorption, and a method for manufacturing the same.

[0019] Therefore, the actual object of the present invention is to provide specific embodiments thereof.

[0020] Methods for solving problems

[0021] For the purposes described above, one embodiment of the present invention provides a polyimide film manufactured by imidizing a polyamic acid solution containing 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 m-toluidine and p-phenylenediamine (PPD).

[0022] Based on a total content of 100 mol% for the above-mentioned diamine components, the content of the above-mentioned meta-toluidine is 30 mol% to 50 mol% and the content of the above-mentioned p-phenylenediamine is 50 mol% to 70 mol%.

[0023] In one embodiment, based on a total dianhydride content of 100 mol%, the content of biphenyl dianhydride can be 45 mol% or more and 65 mol% or less, and the content of pyromellitic dianhydride (PMDA) can be 35 mol% or more and 55 mol% or less.

[0024] In one embodiment, the polyimide film may comprise a block copolymer consisting of two or more blocks.

[0025] For example, a block copolymer may be included, comprising a first block and a second block, wherein the first block is obtained by imidizing an acid dianhydride component containing biphenyl dianhydride with a diamine component containing m-tolidine and p-phenylenediamine, and the second block is obtained by imidizing an acid dianhydride component containing biphenyl dianhydride and pyromellitic dianhydride with a diamine component containing m-tolidine.

[0026] The glass transition temperature (Tg) of the above-mentioned polyimide film can be above 300℃, and the dielectric loss factor (Df) can be below 0.003.

[0027] In addition, the moisture permeability can be 0.02 g / m³. 2 For temperatures below 1000 μm, the coefficient of thermal expansion can be 15 to 18 ppm / ℃.

[0028] Another embodiment of the present invention provides a method for manufacturing a polyimide film, comprising: (a) a step of polymerizing a first acid dianhydride component and a first diamine component in an organic solvent to manufacture a first polyamic acid;

[0029] (b) The step of polymerizing the second acid dianhydride component and the second diamine component in an organic solvent to produce the second polyamic acid;

[0030] (c) the step of copolymerizing the first and second polyamic acids in an organic solvent to produce a third polyamic acid; and

[0031] (d) The step of imidizing the precursor composition containing the above-mentioned third polyamic acid after it has been formed on a support.

[0032] The aforementioned first and second acid dianhydride components each contain one or more components selected from the group consisting of biphenyl dianhydride (BPDA) and pyromellitic dianhydride (PMDA).

[0033] The aforementioned first and second diamine components each contain one or more components selected from the group consisting of m-toluidine and p-phenylenediamine (PPD).

[0034] Based on a total content of 100 mol% for the first and second diamine components, the content of the meta-toluidine is 30 mol% to 50 mol%, and the content of the p-phenylenediamine is 50 mol% to 70 mol%.

[0035] In addition, the present invention provides a multilayer film comprising the above-described polyimide film and thermoplastic resin layer.

[0036] In addition, the present invention provides a flexible metal foil laminate comprising the above-mentioned polyimide film and conductive metal foil.

[0037] In addition, electronic components comprising the aforementioned flexible metal foil laminate are provided.

[0038] Invention Effects

[0039] The polyimide film of the present invention uses a specific acid dianhydride component and a specific diamine component in a specific molar ratio, thereby minimizing moisture absorption and moisture permeability and exhibiting low dielectric properties and high heat resistance.

[0040] Furthermore, the present invention includes a polyimide film as described above, which enables high-speed communication at a high frequency of 10 GHz or higher, and thus can be effectively applied to electronic components such as flexible metal foil laminates. Detailed Implementation

[0041] Best practice

[0042] Hereinafter, embodiments of the present invention will be described in more detail in the order of "polyimide film" and "method for manufacturing polyimide film".

[0043] Prior to this, the terms or vocabulary used in this specification and the scope of the claims should not be interpreted as having their usual or dictionary meanings, but should be interpreted based on the principle that the inventor can appropriately define the concepts of the terms to best illustrate the invention, and in accordance with the meanings and concepts consistent with the technical ideas of the invention.

[0044] 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.

[0045] 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 a feature, number, step, constituent element, or combination thereof, and do not presuppose the presence or additional possibility of more than one other feature, number, step, constituent element, or combination thereof.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] The polyimide film of the present invention is manufactured by imidizing a polyamic acid solution containing an acid dianhydride component and a diamine component.

[0051] The aforementioned dianhydride component may include one or more components selected from the group consisting of biphenyl dianhydride (BPDA) and pyromellitic dianhydride (PMDA).

[0052] The aforementioned diamine component may include one or more components selected from the group consisting of m-tolidine and p-phenylenediamine (PPD).

[0053] For example, the polyimide film of the present invention can be obtained by subjecting an acid dianhydride component containing biphenyl dianhydride (BPDA) and pyromellitic dianhydride (PMDA) to an ammonium acid solution containing m-tolidine and p-phenylenediamine (PPD) via an imidization reaction.

[0054] The present invention can achieve the crystallinity of the membrane by using the above-mentioned biphenyl tetracarboxylic dianhydride (BPDA) and m-tolidine.

[0055] According to one embodiment of the present invention, based on a total diamine content of 100 mol%, the content of meta-toluidine can be 0 mol% or more and 50 mol% or less, and the content of p-phenylenediamine can be 50 mol% or more and 70 mol% or less.

[0056] Preferably, the content of the above-mentioned meta-toluidine can be more than 30 mol% and less than 50 mol%. Such meta-toluidine is particularly characterized by hydrophobic methyl groups, which can thus contribute to the low moisture absorption properties of the polyimide film.

[0057] In this invention, when the diamine component includes meta-toluidine and p-phenylenediamine within the above-mentioned content range, it has low dielectric properties and can exhibit low transmission loss characteristics even at high frequencies.

[0058] Based on a total dianhydride content of 100 mol%, the content of biphenyl dianhydride (BPDA) can be between 45 mol% and 65 mol%, and the content of pyromellitic dianhydride (PMDA) can be between 35 mol% and 55 mol%.

[0059] Preferably, the content of biphenyl dianhydride (BPDA) can be 45 mol% to 55 mol%, and the content of pyromellitic dianhydride (PMDA) can be 45 mol% to 55 mol%. When the dianhydride components include both biphenyl dianhydride and pyromellitic dianhydride (PMDA) within the aforementioned content range, the mechanical properties of the polyimide film can be improved, and heat resistance suitable for manufacturing flexible metal foil laminates can be ensured. Furthermore, it has the advantage of helping to ensure desired levels of dielectric loss factor and moisture permeability.

[0060] In this invention, the polyimide chain derived from biphenyl dianhydride 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, thus enhancing intermolecular interaction.

[0061] This structure prevents the formation of hydrogen bonds with moisture, thus maximizing the reduction of moisture permeability of the polyimide membrane.

[0062] Furthermore, the pyromellitic dianhydride included as the aforementioned dianhydride component has a relatively rigid structure, which can impart suitable elasticity to the polyimide film, and is therefore preferred from this perspective.

[0063] To ensure that the polyimide film simultaneously achieves suitable elasticity and moisture absorption, the ratio of dianhydride content is particularly important. For example, the lower the ratio of biphenyltetracarboxylic dianhydride, the less likely it is to be expected to achieve the low moisture absorption resulting from the aforementioned CTC structure.

[0064] 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.

[0065] In the dianhydride component, at the same molecular weight, the increase in the content of pyromellitic dianhydride can be understood as an increase in intramolecular imide groups. This can be interpreted as a relative increase in the proportion of imide groups derived from pyromellitic dianhydride in the polyimide polymer chain compared to the proportion of imide groups derived from biphenyl dianhydride.

[0066] 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 a low moisture absorption rate.

[0067] Conversely, if the content of pyromellitic dianhydride is reduced, the rigid structure component is relatively reduced, and the mechanical properties of the polyimide film may decrease below the desired level.

[0068] For this reason, when the content of biphenyl dianhydride is higher than the above range, the mechanical properties of the polyimide film decrease, and the heat resistance level suitable for manufacturing flexible metal foil laminates cannot be guaranteed.

[0069] Conversely, when the content of biphenyl dianhydride is below the above range or the content of pyromellitic dianhydride is above the above range, it is difficult to achieve appropriate levels of dielectric constant, dielectric loss factor, and moisture absorption rate, and therefore the results are unsatisfactory.

[0070] In one embodiment, the polyimide film may comprise a block copolymer consisting of two or more blocks, for example, it may comprise two blocks.

[0071] Each of the above two blocks can be: a first block obtained by imidizing a dianhydride component containing biphenyltetracarboxylic dianhydride with a diamine component containing m-tolidine and p-phenylenediamine; and a second block obtained by imidizing a dianhydride component containing biphenyltetracarboxylic dianhydride and pyromellitic dianhydride with a diamine component containing m-tolidine.

[0072] Thus, the first and second blocks mentioned above can be formed by the imidization reaction of their respective specific monomers.

[0073] The polyimide film of the present invention comprises a first block that has film-forming processability and low dielectric properties through heat resistance and a second block that enhances the low dielectric properties through crystallinity, thereby exhibiting the target high heat resistance, low dielectric properties and low moisture absorption properties.

[0074] For example, when forming the first block described above, the contents of biphenyltetracarboxylic dianhydride, m-tolidine, and p-phenylenediamine can be appropriately adjusted as needed to ensure high heat resistance and low dielectric properties. That is, the polyimide film of the present invention can ensure a glass transition temperature (Tg) above 300°C and a dielectric loss factor (Df) below 0.003, thus exhibiting high heat resistance and low dielectric properties.

[0075] In addition, the crystallinity of the polyimide film can be adjusted by a second block containing biphenyltetracarboxylic dianhydride and m-tolidine, thereby minimizing moisture absorption and permeability and improving low dielectric properties.

[0076] Furthermore, the present invention achieves a coefficient of thermal expansion of 15 to 18 ppm / °C, similar to that of copper foil, by appropriately controlling the content of biphenyl dianhydride used in forming the second block as needed, thereby ensuring interlayer dimensional stability.

[0077] As described above, the glass transition temperature (Tg) of the polyimide film of the present invention can be 300°C or higher, and the dielectric loss factor (Df) can be 0.003 or lower. Furthermore, the moisture permeability can be 0.02 g / m³. 2 For the coefficient of thermal expansion, the value of the material can be 15 to 18 ppm / ℃.

[0078] In this regard, polyimide films that meet the above-mentioned dielectric loss factor (Df), glass transition temperature, moisture permeability and / or coefficient of thermal expansion range can be used as insulating films for flexible metal foil laminates. Moreover, even if the manufactured flexible metal foil laminate is used in electrical signal transmission circuits that transmit signals at high frequencies of 10 GHz or higher, its insulation stability can be ensured and signal transmission delay can be minimized.

[0079] The aforementioned "dielectric loss factor" refers to the force dissipated by a dielectric (or insulator) when molecular friction hinders molecular motion caused by an alternating electric field.

[0080] The dielectric loss factor is typically used as an index to represent the ease with which charge dissipates (dielectric loss). A higher dielectric loss factor means that the charge dissipates more easily, while a lower dielectric loss factor means that the charge dissipates less easily. In other words, the dielectric loss factor is a standard for measuring power loss. As the dielectric loss factor decreases, signal transmission delay caused by power loss can be reduced, while maintaining fast communication speeds.

[0081] This is a highly demanded aspect of polyimide films used as insulating films, and the polyimide film of the present invention can have a dielectric loss factor of less than 0.004 at a very high frequency of 10 GHz.

[0082] The moisture permeability mentioned above represents the amount of water contained in the material. Generally speaking, it is known that when the moisture permeability is high, the dielectric constant and dielectric loss factor increase.

[0083] Typically, it is known that the dielectric constant of water is above 100 when it is in a solid state, about 80 when it is in a liquid state, and 1.0059 when it is in a gaseous state of water vapor.

[0084] For example, when a polyimide film absorbs water vapor, the water exists in a liquid state, and the dielectric constant and dielectric loss factor of the polyimide film will be significantly increased.

[0085] That is, even absorbing only a trace amount of moisture can cause a drastic change in the dielectric constant and dielectric loss factor of a polyimide film.

[0086] The moisture permeability of the polyimide membrane of the present invention can be 0.02 g / m³. 2 The achievement of *days) / μm) below is attributed to the structural features of the polyimide film of the present invention.

[0087] This will be explained in more detail later, which seems to be due to the presence of nonpolar portions in the molecular structure of the polyimide film of the present invention.

[0088] As described above, the polyimide film of the present invention satisfies all the above conditions, and therefore can be used as an insulating film for flexible metal foil laminates. Moreover, it can ensure insulation stability even at high frequencies and minimize signal transmission delay.

[0089] In this invention, polyamic acid can be manufactured by the following methods:

[0090] (1) A method of polymerization in which all diamine components are added to a solvent and then acid dianhydride components are added in a manner that is substantially equimolar with the diamine components;

[0091] (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 a manner that is substantially equal in molar to the acid dianhydride components;

[0092] (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.

[0093] (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, so that the diamine component and the acid dianhydride component are polymerized in a substantially equimolar manner.

[0094] (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.

[0095] However, the polymerization method described above is not limited to the examples above, and the first to third polyamic acids can of course be manufactured using any known method.

[0096] In one specific example, the method for manufacturing the polyimide film of the present invention may include:

[0097] (a) The step of polymerizing the first acid dianhydride component and the first diamine component in an organic solvent to produce the first polyamic acid;

[0098] (b) The step of polymerizing the second acid dianhydride component and the second diamine component in an organic solvent to produce the second polyamic acid;

[0099] (c) the step of copolymerizing the first and second polyamic acids in an organic solvent to produce a third polyamic acid; and

[0100] (d) The step of imidizing the precursor composition containing the above-mentioned third polyamic acid after it has been formed on a support.

[0101] The first and second acid dianhydride components mentioned above may each include one or more components selected from the group consisting of biphenyl dianhydride (BPDA) and pyromellitic dianhydride (PMDA).

[0102] Furthermore, the aforementioned first and second diamine components are characterized in that they contain one or more of the group consisting of m-tolidine and p-phenylenediamine (PPD).

[0103] Based on a total content of 100 mol% for the first and second diamine components, the content of the meta-toluidine can be 30 mol% or more and 50 mol% or less, and the content of the p-phenylenediamine can be 50 mol% or more and 70 mol% or less.

[0104] In addition, based on the total content of the first acid dianhydride component and the second acid dianhydride component of 100 mol%, the content of the biphenyl dianhydride can be more than 45 mol% and less than 65 mol%, and the content of pyromellitic dianhydride (PMDA) can be more than 35 mol% and less than 55 mol%.

[0105] Preferably, the first polyamic acid may contain an acid dianhydride component containing biphenyltetracarboxylic dianhydride and a diamine component containing m-tolidine and p-phenylenediamine, and the second polyamic acid may contain an acid dianhydride component containing biphenyltetracarboxylic dianhydride and pyromellitic dianhydride and a diamine component containing m-tolidine.

[0106] In this invention, the polymerization method of polyamic acid as described above can be defined by any random polymerization method. The polyimide film manufactured from the polyamic acid of this invention produced by the process described above is preferably used to maximize the effects of this invention in reducing dielectric loss factor (Df), moisture absorption and moisture permeability.

[0107] 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.

[0108] 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.

[0109] Specifically, the solvent mentioned above 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.

[0110] In one example, the solvents described above may particularly preferably be N,N-dimethylformamide and N,N-dimethylacetamide.

[0111] 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 loop hardness. There are no particular limitations on the fillers added; preferred examples include silica, titanium dioxide, alumina, silicon nitride, boron nitride, dicalcium phosphate, calcium phosphate, and mica.

[0112] 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.

[0113] If the particle size is below the above range, it is not easy to show the 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.

[0114] Furthermore, there is no particular limitation on the amount of filler added; it can be determined based on the desired membrane characteristics and filler particle size. 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.

[0115] 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.

[0116] In the manufacturing method of the present invention, the polyimide film can be manufactured by thermal imidization and chemical imidization.

[0117] Alternatively, it can be manufactured by a combined imidization method that combines thermal imidization and chemical imidization.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] The glass transition temperature (Tg) of the polyimide film of the present invention manufactured according to the manufacturing method described above can be 320°C or higher, the moisture absorption rate can be 0.4% or lower, and the dielectric loss factor (Df) can be 0.004 or lower.

[0124] The present invention provides a multilayer film comprising the above-mentioned polyimide film and thermoplastic resin layer, and a flexible metal foil laminate comprising the above-mentioned polyimide film and conductive metal foil.

[0125] For example, a thermoplastic polyimide resin layer can be used as the aforementioned thermoplastic resin layer.

[0126] The metal foil used is not particularly limited. 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.

[0127] 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.

[0128] 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.

[0129] The flexible metal foil laminate of the present invention can be a structure in which a metal foil is laminated on one side of the polyimide film, or a structure in which an adhesive layer containing thermoplastic polyimide is attached to one side of the polyimide film and the metal foil is laminated in the state of being attached to the adhesive layer.

[0130] The present invention also provides an electronic component comprising the above-described flexible metal foil laminate as an electrical signal transmission circuit. The above-described electrical signal transmission circuit can be an electronic component that transmits signals at a high frequency of at least 2 GHz, specifically at a high frequency of at least 5 GHz, and more specifically at a high frequency of at least 10 GHz.

[0131] The aforementioned electronic components may be, for example, communication circuits for portable terminals, communication circuits for computers, or communication circuits for spacecraft, but are not limited thereto.

[0132] Implementation

[0133] The following detailed description of the invention's function and effects will be provided through specific embodiments. However, these embodiments are merely illustrative and the scope of the claims is not limited thereto.

[0134] <Example 1>

[0135] In a 500 ml reactor equipped with a stirrer and nitrogen injection / exhaust pipe, DMF was added simultaneously with nitrogen injection. After setting the reactor temperature to 30°C, m-toluidine (m-tolidine) and p-phenylenediamine (p-phenylenediamine) as diamine components, and biphenyltetracarboxylic dianhydride (biphenyltetracarboxylic dianhydride) as acid dianhydride component, and complete dissolution was confirmed. Under a nitrogen atmosphere, the temperature was raised to 40°C while stirring continuously for 120 minutes to produce a first polyamic acid with a viscosity of 200,000 cP at 23°C.

[0136] In a 500ml reactor equipped with a stirrer and nitrogen injection / exhaust pipe, NMP was added simultaneously with nitrogen injection. After setting the reactor temperature to 30°C, meta-toluidine (as a diamine component), biphenyltetracarboxylic dianhydride (as an acid dianhydride component), and pyromellitic dianhydride (as an acid dianhydride component) were added, and complete dissolution was confirmed. Under a nitrogen atmosphere, the temperature was raised to 40°C while stirring continuously for 120 minutes to produce a second polyamic acid with a viscosity of 200,000 cP at 23°C.

[0137] Next, under a nitrogen atmosphere, while heating the temperature to 40°C, the first and second polyamic acids were continuously stirred for 120 minutes to produce a third polyamic acid with a final viscosity of 200,000 cP at 23°C and containing diamine and dianhydride components as shown in Table 1 below.

[0138] The air bubbles in the third polyamic acid produced above are removed by high-speed rotation at 1,500 rpm or higher. Then, the polyamic acid and catalyst are mixed and stirred, and then cast into a film. The film is dried in a nitrogen atmosphere at a temperature of 90-200°C for 30 minutes to produce a gel film. The gel film is heated to 450°C at a rate of 2°C / min, heat-treated at 450°C for 60 minutes, and then cooled to 30°C at a rate of 2°C / min to obtain a polyimide film.

[0139] Then, the polyimide film was peeled off from the glass substrate by dipping it in distilled water. The thickness of the manufactured polyimide film was 15 μm. The thickness of the manufactured polyimide film was measured using an Electric Film Thickness Tester from Anritsu Corporation.

[0140] <Examples 2 to 4 and Comparative Examples 1 to 5>

[0141] In Example 1, the components and their contents were changed as shown in Table 1 below, and the polyimide film was otherwise manufactured using the same method as in Example 1.

[0142] [Table 1]

[0143]

[0144] Experimental Example

[0145] For the polyimide films manufactured in Examples 1 to 4 and Comparative Examples 1 to 5, the moisture permeability, dielectric loss factor, thermal properties (coefficient of thermal expansion and glass transition temperature) and film formation properties were evaluated, and the results are shown in Table 2 below.

[0146] (1) Moisture permeability

[0147] Moisture permeability was measured using a Permatran-W 3 / 33MA instrument at 38±2℃ and 100%RH (measurement standard according to ASTM F1249).

[0148] (2) Dielectric loss factor measurement

[0149] The dielectric loss factor (Df) was determined by placing the flexible metal foil laminate on a resistance tester (Agilent 4294A) for 72 hours.

[0150] (3) Determination of thermal expansion coefficient

[0151] The coefficient of thermal expansion (CTE) was determined using a TA Instruments Q400 thermomechanical analyzer. The polyimide film was cut into pieces 4 mm wide and 20 mm long. Under a nitrogen atmosphere, with a tension of 0.05 N, the temperature was increased from room temperature to 300 °C at a rate of 10 °C / min, and then cooled again at a rate of 10 °C / min. The slope of the temperature range from 100 °C to 200 °C was then measured.

[0152] (4) Glass transition temperature determination

[0153] Glass transition temperature (T) g Yes, the loss modulus and storage modulus of each film are determined using DMA, and the inflection point in their tangent plot is determined as the glass transition temperature.

[0154] (5) Film-forming characteristics (smoothness evaluation)

[0155] Film-forming properties were evaluated by visually observing the presence or absence of wrinkles in the polyimide films manufactured in the above examples and comparative examples. The results are shown in Table 2 below.

[0156] <Evaluation Criteria>

[0157] ○: No wrinkles appeared, and the membrane had a consistent smoothness.

[0158] X: Wrinkles appear, and the membrane's flatness is inconsistent.

[0159] [Table 2]

[0160]

[0161] As can be confirmed from Table 2, the polyimide film manufactured according to the embodiments of the present invention exhibits an extremely low dielectric loss factor of less than 0.003, and the glass transition temperature is at the desired level. Furthermore, it can be confirmed that the moisture permeability also shows excellent results, and excellent smoothness is present without wrinkles, indicating good film-forming properties. Such results are achieved due to the specific components and composition ratios of this application, demonstrating that the content of each component plays a decisive role. Conversely, the polyimide films of Comparative Examples 1 to 5, compared to the embodiments, not only show higher measured dielectric loss factors or lower glass transition temperatures, but also exhibit lower moisture permeability. Furthermore, in the cases of Comparative Examples 2 and 4, it can be seen that the film's smoothness is inconsistent due to wrinkles, resulting in poor film-forming properties. Therefore, it can be predicted that the comparative examples are difficult to apply to electronic components that transmit signals at gigabit-level high frequencies.

[0162] The above description refers to embodiments of the present invention. However, those skilled in the art should be able to make various applications and modifications within the scope of the present invention based on the above description.

[0163] Production availability

[0164] The polyimide film of the present invention uses a specific acid dianhydride component and a specific diamine component in a specific molar ratio, thereby minimizing moisture absorption and moisture permeability and exhibiting low dielectric properties and high heat resistance.

[0165] Furthermore, by including the polyimide film as described above, the present invention enables high-speed communication at frequencies above 10 GHz, thereby making it effective for use in electronic components such as flexible metal foil laminates.

Claims

1. A polyimide film manufactured by imidizing a polyamic acid solution comprising an acid dianhydride component and a diamine component to form a block copolymer consisting of two or more blocks, wherein the acid dianhydride component is composed of biphenyl dianhydride (BPDA) and pyromellitic dianhydride (PMDA), and the diamine component is composed of meta-toluidine and p-phenylenediamine (PPD). in, The block copolymer comprises a first block and a second block. The first block is obtained by imidizing an acid dianhydride component composed of biphenyl dianhydride (BPDA) with a diamine component composed of meta-toluidine and p-phenylenediamine (PPD). The second block is obtained by imidizing an acid dianhydride component composed of biphenyl dianhydride (BPDA) and pyromellitic dianhydride (PMDA) with a diamine component composed of meta-toluidine. Based on a total dianhydride content of 100 mol%, the content of biphenyltetracarboxylic dianhydride is between 48 mol% and 60 mol%, and the content of pyromellitic dianhydride is between 40 mol% and 52 mol%. Based on a total diamine content of 100 mol%, the content of meta-toluidine is 34 mol% to 46 mol%, the content of p-phenylenediamine is 54 mol% to 66 mol%, and... The polyimide film has a glass transition temperature (Tg) of 300°C or higher and a dielectric loss factor (Df) of 0.003 or lower.

2. The polyimide membrane according to claim 1, wherein the moisture permeability is 0.02 g / (m³). 2 *day)) / μm and below.

3. The polyimide film according to claim 1 has a coefficient of thermal expansion of 15 to 18 ppm / ℃.

4. A method for manufacturing a polyimide film, comprising: (a) The step of polymerizing the first acid dianhydride component and the first diamine component in an organic solvent to produce the first polyamic acid; (b) The step of polymerizing the second acid dianhydride component and the second diamine component in an organic solvent to produce the second polyamic acid; (c) the step of copolymerizing the first and second polyamic acids in an organic solvent to produce a third polyamic acid; and (d) The step of imidizing the precursor composition containing the third polyamic acid after it has been formed on a support to form a block copolymer consisting of two or more blocks. The first polyamic acid is obtained by reacting an acid dianhydride component composed of biphenyl dianhydride (BPDA) with a diamine component composed of meta-toluidine and p-phenylenediamine (PPD), and the second polyamic acid is obtained by reacting an acid dianhydride component composed of biphenyl dianhydride (BPDA) and pyromellitic dianhydride (PMDA) with a diamine component composed of meta-toluidine. Based on a total content of 100 mol% for the first and second acid dianhydrides, the content of biphenyl dianhydride is 48 mol% to 60 mol%, and the content of pyromellitic dianhydride (PMDA) is 40 mol% to 52 mol%. Based on a total content of 100 mol% for the first and second diamine components, the content of meta-toluidine is 34 mol% to 46 mol%, the content of p-phenylenediamine is 54 mol% to 66 mol%, and... The polyimide film has a glass transition temperature (Tg) of 300°C or higher and a dielectric loss factor (Df) of 0.003 or lower.

5. A multilayer film comprising a polyimide film according to any one of claims 1-4 and a thermoplastic resin layer.

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

7. An electronic component comprising the flexible metal foil laminate of claim 6.

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