Low dielectric polyimide film with improved dimensional stability and method for manufacturing the same

Abstract

The present invention provides a low-dielectric polyimide film with excellent dimensional stability and heat resistance, comprising a block copolymer containing a first block and a second block. The first block is obtained by imidizing an acid dianhydride component containing biphenyl dianhydride (BPDA) with a diamine component containing p-phenylenediamine (PPD). The second block is obtained by imidizing an acid dianhydride component containing benzophenone tetracarboxylic dianhydride (BTDA) and pyromellitic dianhydride (PMDA) with a diamine component containing m-tolidine.

Description

Technical Field

[0001] This invention relates to a low-dielectric polyimide film with improved heat resistance (especially glass transition temperature characteristics) and dimensional stability (especially thermal dimensional stability) 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 structures where circuits containing metal foil are formed on polyimide films that have excellent heat resistance, low temperature resistance, and insulation properties and are easily flexible.

[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] To achieve high-frequency, high-speed communication, insulators with high impedance are required that can maintain electrical insulation even at high frequencies. Impedance is inversely proportional to the frequency at which the insulator is formed and its dielectric constant (Dk). Therefore, to maintain insulation at high frequencies, the dielectric constant should be as low as possible.

[0009] However, in reality, the dielectric properties of typical polyimides are not yet good enough to maintain adequate insulation in high-frequency communications.

[0010] 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.

[0011] Therefore, in practice, polyimide with low dielectric properties is considered the most important factor affecting the performance of thin circuit boards.

[0012] 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.

[0013] 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.

[0014] In particular, in the case of conventional low-dielectric polyimide films, there is a problem of decreased heat resistance due to a lower glass transition temperature. This reduction in heat resistance makes it difficult to manufacture films with the desired morphology.

[0015] Increasing the glass transition temperature of the polyimide film to improve this results in a decrease in dielectric properties (an increase in the dielectric loss factor). Furthermore, the reduced coefficient of thermal expansion due to the higher glass transition temperature leads to mismatching with the copper foil during the fabrication of flexible copper clad laminates (FCCLs).

[0016] Therefore, in reality, there is a need to develop polyimide films that maintain the unique mechanical and thermal properties of polyimide at a certain level while having low dielectric properties, especially low dielectric loss factor.

[0017] [Existing Technical Documents]

[0018] [Patent Literature]

[0019] (Patent Document 1) Korean Patent Publication No. 10-2015-0069318 Summary of the Invention

[0020] Technical issues

[0021] Therefore, in order to solve the problems mentioned above, a polyimide film with both high dimensional stability and low dielectric properties and a method for manufacturing the same are provided.

[0022] Therefore, the actual object of the present invention is to provide specific embodiments thereof.

[0023] Methods for solving problems

[0024] One embodiment of the present invention for achieving the objectives described above provides a polyimide film comprising a block copolymer containing a first block and a second block.

[0025] The first block mentioned above is obtained by imidizing an acid dianhydride component containing biphenyltetracarboxylic dianhydride (BPDA) with a diamine component containing p-phenylenediamine (PPD).

[0026] The second block is obtained by imidizing an acid dianhydride component containing benzophenonetetracarboxylic dianhydride (BTDA) and pyromellitic dianhydride (PMDA) with a diamine component containing m-tolidine.

[0027] Based on a total diamine content of 100 mol% in the first block and the second block, the content of meta-toluidine can be between 15 mol% and 45 mol%, and the content of p-phenylenediamine can be between 55 mol% and 85 mol%.

[0028] In addition, based on the total content of dianhydride components of the first block and the second block being 100 mol%, the content of benzophenone tetracarboxylic dianhydride can be 20 mol% or more and 55 mol% or less, the content of biphenyl tetracarboxylic dianhydride can be 25 mol% or more and 55 mol% or less, and the content of pyromellitic tetracarboxylic dianhydride can be 15 mol% or more and 30 mol% or less.

[0029] The dielectric loss factor (Df) of the above-mentioned polyimide film can be below 0.004, the coefficient of thermal expansion (CTE) can be below 19ppm / ℃, and the glass transition temperature (Tg) can be above 330℃.

[0030] Another embodiment of the present invention provides a method for manufacturing a polyimide film, comprising:

[0031] (a) A process for producing a first polyamic acid by polymerizing a first acid dianhydride component and a first diamine component in an organic solvent;

[0032] (b) A process for producing a second polyamic acid by polymerizing the second acid dianhydride component and the second diamine component in an organic solvent;

[0033] (c) The process of copolymerizing the first and second polyamic acids in an organic solvent to produce a third polyamic acid; and

[0034] (d) The process of imidizing the precursor composition containing the above-mentioned third polyamic acid after it has been formed on a support.

[0035] The aforementioned primary acid dianhydride component includes biphenyltetracarboxylic dianhydride (BPDA).

[0036] The aforementioned secondary acid dianhydride components include benzophenone tetracarboxylic dianhydride (BTDA) and pyromellitic tetracarboxylic dianhydride (PMDA).

[0037] The aforementioned first diamine component includes p-phenylenediamine (PPD).

[0038] The aforementioned second diamine component includes m-tolidine.

[0039] Invention Effects

[0040] As described above, the present invention provides a polyimide film with both thermal dimensional stability and low dielectric properties by forming a polyimide film with specific components and specific composition ratios and the method thereof, thereby enabling it to be effectively applied in a variety of fields that require these properties, especially 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 the implemented 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.

[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 a polyimide film containing a block copolymer, the block copolymer comprising a first block and a second block, wherein the first block is obtained by imidizing an acid dianhydride component containing biphenyltetracarboxylic dianhydride (BPDA) with a diamine component containing p-phenylenediamine (PPD).

[0051] The second block is obtained by imidizing an acid dianhydride component containing benzophenone tetracarboxylic dianhydride (BTDA) and pyromellitic tetracarboxylic dianhydride (PMDA) with a diamine component containing m-tolidine.

[0052] Based on a total diamine content of 100 mol% in the first block and the second block, the content of meta-toluidine can be between 15 mol% and 45 mol%, and the content of p-phenylenediamine can be between 55 mol% and 85 mol%.

[0053] Particularly preferred, the content of meta-toluidine can be more than 20 mol% and less than 40 mol%, and the content of p-phenylenediamine can be more than 60 mol% and less than 80 mol%.

[0054] Metatoluidine, in particular, has a hydrophobic methyl group, which contributes to the low moisture absorption properties of polyimide films.

[0055] In addition, based on the total content of dianhydride components of the first block and the second block being 100 mol%, the content of benzophenone tetracarboxylic dianhydride can be 20 mol% or more and 55 mol% or less, the content of biphenyl tetracarboxylic dianhydride can be 25 mol% or more and 55 mol% or less, and the content of pyromellitic tetracarboxylic dianhydride can be 15 mol% or more and 30 mol% or less.

[0056] Particularly preferred, the content of the above-mentioned benzophenone tetracarboxylic dianhydride can be more than 25 mol% and less than 50 mol%, the content of biphenyl tetracarboxylic dianhydride can be more than 30 mol% and less than 50 mol%, and the content of pyromellitic tetracarboxylic dianhydride can be more than 20 mol% and less than 27 mol%.

[0057] 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, thus enhancing the intermolecular interaction.

[0058] In addition, benzophenone tetracarboxylic dianhydride, which has a carbonyl group, also contributes to the expression of CTC, just like biphenyl tetracarboxylic dianhydride.

[0059] This structure prevents the formation of hydrogen bonds with moisture, thus maximizing the reduction of the hygroscopicity of the polyimide film.

[0060] In one specific example, the aforementioned dianhydride component may further include pyromellitic dianhydride. Pyromellitic dianhydride, as an acid dianhydride component with a relatively rigid structure, can impart moderate elasticity to the polyimide film, and is therefore preferred.

[0061] To ensure that the polyimide film simultaneously achieves adequate 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.

[0062] In addition, biphenyl dianhydride and benzophenone dianhydride contain two benzene rings corresponding to the aromatic moiety, while pyromellitic dianhydride contains one benzene ring corresponding to the aromatic moiety.

[0063] In the dianhydride component, when the molecular weight is the same, the increase in the content of pyromellitic dianhydride can be understood as an increase in intramolecular imide groups. This can be understood as the ratio of imide groups derived from the aforementioned pyromellitic dianhydride in the polyimide polymer chain being relatively increased compared to the ratio of imide groups derived from biphenyl dianhydride and benzophenone tetracarboxylic dianhydride.

[0064] 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.

[0065] Conversely, if the content of pyromellitic dianhydride is reduced, the rigid structure is relatively reduced, and the elasticity of the polyimide film may decrease below the desired level.

[0066] For this reason, when the content of biphenyl dianhydride and benzophenone dianhydride is higher than the above range or the content of pyromellitic dianhydride is lower than the above range, the mechanical properties of the polyimide film are reduced, and the heat resistance level suitable for manufacturing flexible metal foil laminates cannot be guaranteed.

[0067] Conversely, when the contents of biphenyltetracarboxylic dianhydride and benzophenonetetracarboxylic dianhydride are below the above range or the contents of pyromellitic dianhydride are 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.

[0068] The dielectric loss factor (Df) of the above-mentioned polyimide film can be above 0.004, the coefficient of thermal expansion (CTE) can be below 19ppm / ℃, and the glass transition temperature (Tg) can be above 330℃.

[0069] Preferably, the dielectric loss factor (Df) of the polyimide film can be 0.0036 or less, the coefficient of thermal expansion (CTE) can be 13.9 ppm / ℃ or more and 18.8 ppm / ℃ or less, and the glass transition temperature (Tg) can be 335℃ or more and 355℃ or less.

[0070] The low dielectric loss factor and high glass transition temperature of the aforementioned polyimide film are ensured by optimizing the content ratio of biphenyltetracarboxylic dianhydride to p-phenylenediamine in the first block of the block copolymer. In particular, the improved heat resistance of the polyimide film due to the high glass transition temperature ensures the film-forming properties of the film.

[0071] Furthermore, by optimizing the content ratio of benzophenone tetracarboxylic dianhydride, pyromellitic tetracarboxylic dianhydride, and meta-toluidine in the second block of the block copolymer, the heat resistance and low dielectric properties of the polyimide film are further enhanced.

[0072] In particular, the range of the thermal expansion coefficient of the aforementioned low-dielectric polyimide film is consistent with the range of the thermal expansion coefficient of the copper foil, thus minimizing the mismatch with the copper foil during the manufacture of FCCL.

[0073] In this regard, when the dielectric loss factor (Df), glass transition temperature and coefficient of thermal expansion are all satisfied, the polyimide film can be used as an insulating film for flexible metal foil laminates. Moreover, even when 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.

[0074] The polyimide film that meets all the above conditions is a novel polyimide film that has not been known to date. The dielectric loss factor (Df) will be described in detail below.

[0075] <Dielectric loss factor>

[0076] The term "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.

[0077] 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.

[0078] This is a highly demanded aspect of the polyimide film used as an insulating film, 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.

[0079] In this invention, polyamic acid can be manufactured by the following methods:

[0080] (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;

[0081] (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;

[0082] (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.

[0083] (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.

[0084] (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 if the diamine component is in excess when forming the first composition, 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 to polymerize the total diamine component and acid dianhydride component used in their reaction in a substantially equimolar manner; etc.

[0085] 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.

[0086] In one specific example, the method for manufacturing the polyimide film of the present invention may include:

[0087] (a) A process for producing a first polyamic acid by polymerizing a first acid dianhydride component and a first diamine component in an organic solvent;

[0088] (b) A process for producing a second polyamic acid by polymerizing the second acid dianhydride component and the second diamine component in an organic solvent;

[0089] (c) The process of copolymerizing the first and second polyamic acids in an organic solvent to produce a third polyamic acid; and

[0090] (d) The process of imidizing the precursor composition containing the above-mentioned third polyamic acid after it has been formed on a support.

[0091] The aforementioned primary acid dianhydride component may include biphenyltetracarboxylic dianhydride (BPDA).

[0092] The aforementioned secondary acid dianhydride component may include benzophenone tetracarboxylic dianhydride (BTDA) and pyromellitic tetracarboxylic dianhydride (PMDA).

[0093] The aforementioned first diamine component may include p-phenylenediamine (PPD).

[0094] The aforementioned second diamine component may include m-tolidine.

[0095] Based on a total content of 100 mol% for the first and second diamine components mentioned above, the content of meta-toluidine can be between 15 mol% and 45 mol%, and the content of p-phenylenediamine can be between 55 mol% and 85 mol%.

[0096] In addition, based on the total content of the first acid dianhydride and the second acid dianhydride of the above, which is 100 mol%, the content of benzophenone tetracarboxylic dianhydride can be more than 20 mol% and less than 55 mol%, the content of biphenyl tetracarboxylic dianhydride can be more than 25 mol% and less than 55 mol%, and the content of pyromellitic tetracarboxylic dianhydride can be more than 15 mol% and less than 30 mol%.

[0097] In this invention, the polymerization method of polyamic acid as described above can be defined by random polymerization. From the perspective of maximizing the effects of this invention in reducing dielectric loss factor (Df) and moisture absorption, it is preferable to use a polyimide film made from the polyamic acid of this invention manufactured by the process described above.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] In one example, the solvents described above may particularly preferably be N,N-dimethylformamide and N,N-dimethylacetamide.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] In the manufacturing method of the present invention, the polyimide film can be manufactured by thermal imidization and chemical imidization.

[0108] Alternatively, it can be manufactured by a combined imidization method that combines thermal imidization and chemical imidization.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] The polyimide film of the present invention manufactured according to the manufacturing method described above can have a dielectric loss factor (Df) of 0.004 or less, a coefficient of thermal expansion (CTE) of 19 ppm / ℃ or less, and a glass transition temperature (Tg) of 330℃ or more.

[0115] 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.

[0116] For example, a thermoplastic polyimide resin layer can be used as the aforementioned thermoplastic resin layer.

[0117] 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.

[0118] 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.

[0119] In this invention, the thickness of the metal foil is not particularly limited, as long as it is thick enough to perform its function fully according to its purpose.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] Implementation

[0124] 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.

[0125] <Manufacturing Example>

[0126] In a 500ml reactor equipped with a stirrer and nitrogen injection / exhaust pipe, DMF was added simultaneously with nitrogen injection. After setting the reactor temperature below 30°C, p-phenylenediamine (as a diamine component) and biphenyltetracarboxylic 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 first polyamic acid with a viscosity of 200,000 cP at 23°C.

[0127] 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), benzophenone tetracarboxylic dianhydride (as acid dianhydrides), and pyromellitic tetracarboxylic dianhydride (as acid dianhydrides) 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.

[0128] 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.

[0129] The bubbles in the third polyamic acid produced above are removed by high-speed rotation at 1,500 rpm or higher. Then, the degassed polyimide precursor composition is coated onto a glass substrate using a spin coater. Subsequently, a gel film is produced by drying at 120°C for 30 minutes under a nitrogen atmosphere. The gel film is then 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.

[0130] 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.

[0131] <Examples 1 to 4 and Comparative Examples 1 to 5>

[0132] Manufacture according to the manufacturing example described above, adjusting the composition ratio of the acid dianhydride component to the diamine component as shown in Table 1 below.

[0133] In Comparative Example 3, 13 mol% and 15 mol% of benzophenone tetracarboxylic dianhydride were used in the manufacture of the first polyamic acid and the second polyamic acid, respectively.

[0134] [Table 1]

[0135]

[0136] <Experimental Example> Evaluation of Dielectric Loss Factor, Coefficient of Thermal Expansion, and Glass Transition Temperature

[0137] For the polyimide films manufactured in Examples 1 to 4 and Comparative Examples 1 to 5, respectively, the dielectric loss factor, coefficient of thermal expansion, and glass transition temperature were measured, and the results are shown in Table 2 below.

[0138] (1) Dielectric loss factor measurement

[0139] The dielectric loss factor (Df) was determined by placing the flexible metal foil laminate on a resistance tester (Agilent 4294A) for 72 hours.

[0140] (2) Determination of thermal expansion coefficient

[0141] 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.

[0142] (3) Glass transition temperature determination

[0143] 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.

[0144] [Table 2]

[0145] Df CTE (ppm / ℃) Tg (°C) Example 1 0.0036 18.8 335 Example 2 0.0035 15.8 345 Example 3 0.0032 15.7 338 Example 4 0.0034 13.9 352 Comparative Example 1 0.0044 9.4 360 Comparative Example 2 0.0049 8.4 360 Comparative Example 3 0.0047 4.5 369 Comparative Example 4 0.0024 14.5 305 Comparative Example 5 0.0044 10.2 337

[0146] As shown in Table 2 above, it can be confirmed that the polyimide film manufactured according to the embodiments of the present invention exhibits an extremely low dielectric loss factor of less than 0.004, and the coefficient of thermal expansion and glass transition temperature are at the desired levels.

[0147] That is, the range of the coefficient of thermal expansion is 13.9 to 18.8 ppm / ℃, which corresponds to the range below 19 ppm / ℃. This also corresponds to the range of the coefficient of thermal expansion of the copper foil used in FCCL (approximately 14 to 19 ppm / ℃), thus minimizing the mismatch between the polyimide film and the copper foil during FCCL manufacturing.

[0148] Furthermore, the glass transition temperature corresponds to 330°C or higher, thus confirming that the heat resistance of the polyimide film of the present invention is at a suitable level.

[0149] This result is achieved due to the specific components and composition ratios in this application, indicating that the content of each component plays a decisive role.

[0150] On the other hand, compared with the polyimide films of the examples, the polyimide films of Comparative Examples 1 to 5, which have different composition ratios from those of the examples, are expected to be difficult to use in electronic components that transmit signals at gigabit-level high frequencies in any one or more aspects of dielectric loss factor, coefficient of thermal expansion, and glass transition temperature.

[0151] 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.

[0152] Industrial availability

[0153] This invention provides a polyimide film with both thermal dimensional stability and low dielectric properties by forming a polyimide film with specific components and specific composition ratios and the method thereof, thereby enabling its effective application in a variety of fields that require these properties, especially electronic components such as flexible metal foil laminates.

Claims

1. A polyimide film comprising a block copolymer containing a first block and a second block, The first block is obtained by imidizing an acid dianhydride component containing biphenyltetracarboxylic dianhydride (BPDA) with a diamine component containing p-phenylenediamine (PPD). The second block is obtained by imidizing an acid dianhydride component containing benzophenone tetracarboxylic dianhydride (BTDA) and pyromellitic tetracarboxylic dianhydride (PMDA) with a diamine component containing meta-toluidine. Based on a total dianhydride content of 100 mol% in the first and second blocks, the content of benzophenone tetracarboxylic dianhydride is 20 mol% to 55 mol%, the content of biphenyl tetracarboxylic dianhydride is 25 mol% to 55 mol%, and the content of pyromellitic tetracarboxylic dianhydride is 15 mol% to 30 mol%. Based on a total diamine content of 100 mol% in the first block and the second block, the content of meta-toluidine is 20 mol% to 40 mol%, and the content of p-phenylenediamine is 60 mol% to 80 mol%.

2. The polyimide film according to claim 1, wherein the dielectric loss factor Df is 0.004 or less, the coefficient of thermal expansion CTE is 13.9 ppm / ℃ or more and 19 ppm / ℃ or less, and the glass transition temperature Tg is 330℃ or more and 355℃ or less.

3. A method for manufacturing a polyimide film, comprising: (a) A process for producing a first polyamic acid by polymerizing a first acid dianhydride component and a first diamine component in an organic solvent; (b) A process for producing a second polyamic acid by polymerizing the second acid dianhydride component and the second diamine component in an organic solvent; (c) The process of copolymerizing the first polyamic acid and the second polyamic acid in an organic solvent to produce the third polyamic acid; as well as (d) The process of imidizing the precursor composition containing the third polyamic acid after it has been formed into a film on a support. The first acid dianhydride component includes biphenyltetracarboxylic dianhydride (BPDA). The second acid dianhydride component includes benzophenone tetracarboxylic dianhydride (BTDA) and pyromellitic tetracarboxylic dianhydride (PMDA). The first diamine component includes p-phenylenediamine (PPD). The second diamine component includes meta-toluidine. Based on a total content of 100 mol% for the first and second acid dianhydrides, the content of benzophenone tetracarboxylic dianhydride is 20 mol% to 55 mol%, the content of biphenyl tetracarboxylic dianhydride is 25 mol% to 55 mol%, and the content of pyromellitic tetracarboxylic dianhydride is 15 mol% to 30 mol%. Based on a total content of 100 mol% for the first and second diamine components, the content of meta-toluidine is 20 mol% to 40 mol%, and the content of p-phenylenediamine is 60 mol% to 80 mol%.

4. The method for manufacturing a polyimide film according to claim 3, wherein the polyimide film has a dielectric loss factor Df of 0.004 or less, a coefficient of thermal expansion CTE of 13.9 ppm / ℃ or more and 19 ppm / ℃ or less, and a glass transition temperature Tg of 330℃ or more and 350℃ or less.

5. A multilayer film comprising a polyimide film as described in claim 1 or 2 and a thermoplastic resin layer.

6. A flexible metal foil laminate comprising the polyimide film and conductive metal foil as described in claim 1 or 2.

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

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