CN112154173B

CN112154173B - Polyimide film with low dielectric constant and low hygroscopicity and preparation method thereof

Info

Publication number: CN112154173B
Application number: CN201880093505.3A
Authority: CN
Inventors: 李吉男; 崔祯烈; 金纪勋; 白承烈
Original assignee: Polyimide Advanced Materials Co ltd
Current assignee: Polyimide Advanced Materials Co ltd
Priority date: 2018-05-18
Filing date: 2018-10-24
Publication date: 2023-03-28
Anticipated expiration: 2038-10-24
Also published as: KR20190132123A; WO2019221343A1; KR102164458B1; CN112154173A

Abstract

The present invention provides a polyimide film comprising: an aliphatic polyimide resin; an aromatic polyimide resin; and microspheres (microspherers) having pores, wherein the aliphatic polyimide resin contains at least one of a chain aliphatic hydrocarbon group and a cyclic aliphatic hydrocarbon group.

Description

Polyimide film with low dielectric constant and low hygroscopicity and preparation method thereof

Technical Field

The present invention relates to a polyimide film having a low dielectric constant and low hygroscopicity, and a method for preparing the same.

Background

In recent years, with the high performance and high functionality of computers and communication devices, the introduction of advanced information transmission techniques to network these electronic devices has been rapidly advanced, and as a part of these, processing due to the increase in the amount of information transmitted and high frequency of signals for high-speed transmission techniques have been performed for these electronic devices or communication devices configuring the networks.

While conventional high-frequency signals of 1MHz or more are mainly used for limited wireless communication, for example, aircraft or satellite communication, and recently, are also used for electronic devices such as mobile phones or wireless local area networks, electronic devices for high-speed transmission capable of high-speed communication with high-frequency signals of 10GHz or more are actively being developed due to demands for higher operation speed and communication speed.

In order to realize such high-frequency high-speed communication, it is required to overcome the problem of signal delay or transmission loss occurring in a component (for example, a high-speed transmission circuit board) of an electronic apparatus mounted in a communication apparatus. The signal delay (RC delay) is expressed as a product of capacitance (C) between metal wirings and resistance (R) of the wirings, which is increased in proportion to the square root of the dielectric constant of an insulator, and as recent electronic devices tend to be miniaturized and highly integrated, there is a problem in that the entire signal transmission is further delayed due to propagation delay (propagation delay) or crosstalk noise (crosstalk noise). In addition, the transmission loss is distinguished into a conductor loss and a dielectric loss, which are proportional to the dielectric constant and the dielectric loss of an insulator and tend to increase as the frequency increases.

That is, since the high-frequency characteristics of the high-speed transmission electronic device are closely related to the dielectric characteristics of the insulating layer, it is necessary to use an insulating material having a very low dielectric constant for high-frequency high-speed communication. Conventionally, it is known that a fluororesin (PTFE) is a resin having the most excellent high-frequency characteristics among polymer materials, and substrates using a fluororesin have been standardized in U.S. Military Specifications and Standards (MIL) in 1975 and used in aviation, aerospace, and Military, but since PTFE is a thermoplastic resin having a glass transition temperature close to room temperature, it has insufficient dimensional stability against heat, poor mechanical strength and thermal conductivity, requires a special plating pretreatment step, and has problems in moldability (high temperature of 350 ℃ or higher) and processability.

Therefore, in recent years, the availability of polyimide resins for high-speed transmission electronic devices has been studied.

In general, a polyimide resin refers to a high temperature resistant resin prepared by solution polymerization of an aromatic dianhydride and an aromatic diamine or an aromatic diisocyanate to prepare a polyamic acid derivative, followed by dehydration of ring closure at high temperature and imidization, and is a polymer material having the highest levels of heat resistance, chemical resistance, electrical insulation, and weather resistance among organic materials, based on a rigid aromatic main chain and an imide ring having very excellent chemical stability, and particularly, has advantages of relatively stable dielectric constant over the entire frequency range and high insulation breakdown voltage, and is attracting attention as an insulating material for electronic devices for high-speed communication.

However, polyimide materials themselves have a high moisture absorption rate due to their characteristics, and despite having excellent physical properties as described above, there are prescribed limitations on the expression of a low dielectric constant, and in order to overcome this problem, studies on the enhancement of performance of polyimides, particularly on the reduction of a dielectric constant and the reduction of a dielectric loss tangent, which are electrical characteristics corresponding to the increase in frequency, have been actively conducted in recent years.

For example, as an attempt to reduce the dielectric constant of a polyimide resin, a polyimide composition containing a fluorine resin and a method for producing the same have been proposed, which is characterized in that, in the presence of a surfactant polymer containing fluorine atoms in fluorine resin powder, an aromatic polyimide obtained from an aromatic tetracarboxylic acid component containing biphenyltetracarboxylic acid as a main component and an aromatic diamine component is uniformly dissolved in an organic polar solvent capable of dissolving the aromatic polyimide, but with respect to a polyimide to which a fluorine-containing surfactant or the like is added, the dielectric constant or dielectric loss tangent can be reduced to a predetermined level due to the effect of the fluorine resin, but the fluorine-containing surfactant, dispersant or the like generally increases the dielectric constant and dielectric loss tangent, and there is a limitation that it is difficult to sufficiently improve the electrical characteristics.

On the other hand, a method for producing a polyimide film has been proposed, in which specific particles are dispersed in a polyimide resin precursor solution and then imidized to obtain a polyimide resin in order to reduce the dielectric constant, but these particles have not only a problem in the process such as difficulty in uniform input but also a problem in that the polyimide film produced therefrom exhibits a dielectric constant of only 2.5 to 3.0 levels at 1GHz and has a predetermined limitation in achieving a desired level of low dielectric constant in a higher frequency band (for example, 10GHz or more).

In addition, even if these particles are dispersed in a solvent, there are problems that the solution is charged during storage and the storage stability is deteriorated due to the difference in specific gravity, for example, layer separation from the polyimide resin precursor occurs.

Therefore, it is required to develop a polyimide film which is excellent in input and storage stability and can realize a low dielectric constant in a frequency band higher than that of the conventional polyimide film.

Disclosure of Invention

Technical problem to be solved by the invention

The purpose of the present invention is to provide a polyimide film which has excellent input and storage stability and relatively low dielectric constant and moisture absorption rate, and a method for producing the same.

According to an aspect of the present invention, a polyimide film is produced in a manner including an aliphatic polyimide resin containing at least one of a chain aliphatic hydrocarbon group or a cyclic aliphatic hydrocarbon group, respectively, and microspheres having pores.

In this aspect, the aliphatic polyimide resin can effectively act to suppress the dielectric constant and the moisture absorption rate, a polyimide film having a lower dielectric constant can be realized by the microspheres having pores, and a method for producing a polyimide film having improved input and storage stability can be provided.

According to another aspect of the present invention, an electronic device for high-speed transmission containing a polyimide film can realize high-speed communication at a high frequency of 10GHz based on the relatively low dielectric constant of the polyimide film.

Finally, the above-mentioned prior art problems can be solved according to an aspect of the present invention.

In view of the above, a substantial object of the present invention is to provide a specific embodiment thereof.

Means for solving the problems

In order to achieve the above object, the present invention may provide a polyimide film comprising: an aliphatic polyimide resin; an aromatic polyimide resin; and microspheres (microspherers) having pores, wherein the aliphatic polyimide resin contains at least one of a chain aliphatic hydrocarbon group and a cyclic aliphatic hydrocarbon group.

The present invention can also provide a method for preparing a polyimide film, the method comprising:

a step of polymerizing an aliphatic diamine monomer and an aliphatic dianhydride monomer in an organic polar solvent to prepare an aliphatic polyamic acid solution;

a step of polymerizing an aromatic diamine monomer and an aromatic dianhydride monomer in an organic polar solvent to prepare an aromatic polyamic acid solution;

a step of adding microspheres to the aliphatic polyamic acid solution to prepare an aliphatic polyamic acid microsphere dispersion;

a step of mixing an aromatic polyamic acid solution in the aliphatic polyamic acid microsphere dispersion to prepare a precursor composition; and

a step of performing a heat treatment at a temperature of 200 to 450 ℃ after film-forming and drying the precursor composition on a support to prepare a gel film to prepare a polyimide film in which the polyamic acid precursor is imidized.

The present invention can also provide an electronic device for high-speed transmission, which comprises the polyimide film.

Hereinafter, embodiments of the present invention will be described in further detail in the order of "polyimide film" and "method for producing polyimide film" of the present invention.

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

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

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

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

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

When an amount, concentration, or other value or parameter is given herein as either a range, preferred range, or an enumeration of an upper range limit and a lower range limit, regardless of whether ranges are separately disclosed, it should be understood that all ranges that can be formed from any upper range limit or preferred value in any pair, as well as any lower range limit or preferred value, are specifically disclosed. When a range of numerical values is referred to herein, unless otherwise indicated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is intended that the scope of the invention not be limited to the particular values mentioned in defining the range.

Polyimide film

The polyimide film according to the present invention is characterized by comprising: an aliphatic polyimide resin; an aromatic polyimide resin; and microspheres (microspherers) having pores, wherein the aliphatic polyimide resin contains at least one of a chain aliphatic hydrocarbon group and a cyclic aliphatic hydrocarbon group.

Wherein the aliphatic polyimide resin is derived from an aliphatic polyamic acid polymerized from an aliphatic diamine monomer and an aliphatic dianhydride monomer, the aromatic polyimide resin is derived from an aromatic polyamic acid polymerized from an aromatic diamine monomer and an aromatic dianhydride monomer, and the polyimide film is prepared by imidizing a precursor composition comprising the aliphatic polyamic acid, the aromatic polyamic acid, and microspheres having pores.

As an example, the polyimide film may have a dielectric constant (a) of 3.0 or less and a moisture absorption rate (b) of 1.5% or less at 10 GHz.

In connection with this, when the polyimide film of the present invention satisfies all the conditions of the above-described dielectric constant (a) and moisture absorption rate (b), it can be used as an insulating film which can minimize signal delay and transmission loss based on excellent insulation stability even when used in an electric signal transmission circuit for transmitting signals at high frequencies of 10GHz or more in electronic devices for high-speed transmission.

The following will explain the above 2 conditions in detail.

< dielectric constant >

As is well known, permittivity (Permittivity) is an important characteristic value that represents electrical characteristics of a dielectric (or insulator), i.e., a nonconductor, and is not an electrical characteristic of Direct Current (DC) current, but is directly related to Alternating Current (AC) current, particularly characteristics of alternating electromagnetic waves.

In an insulator (for example, a polyimide film), the +, -moment components, which are generally scattered in random directions, are aligned according to an alternating current change of an electromagnetic field applied from the outside. That is, these moment components change according to the direction of change of the electromagnetic field, and the electromagnetic wave can be propagated inside even a non-conductor.

The degree of movement in response to the torque inside the substance can be expressed as a dielectric constant in response to such a change in the external electromagnetic field, and a high dielectric constant means that electric power transmission is good, so that a lower dielectric constant of an insulator such as a polyimide film is preferable.

That is, the dielectric constant of a general polyimide film is higher than a level capable of maintaining sufficient insulation to perform high frequency communication, however, in the polyimide film of the present invention, as an example, the dielectric constant at 10GHz may be 3.0 or less, preferably, 2.6 or less, and the lower limit thereof may be at least 2.2. It can be seen that the polyimide film exhibits a desirable dielectric constant as an insulator when considering the engineering properties of the polyimide film to the highest level.

On the other hand, even if all the conductors are separated from each other, there is always capacitive coupling (capacitive coupling) caused by an electric field between them, and even if the layers of the multilayer substrate are electrically separated from each other, this is merely an open circuit (open circuit) for direct current, and actually, it can be considered that a capacitor of a specific value is connected between them.

At this time, the capacitor has a property that the impedance decreases as the frequency of the current or voltage across the capacitor increases, and this value can be expressed as follows.

-impedance = 1/(2 x pi f C); where f is frequency, C = capacitance.

-C = e S/d; where e is the dielectric constant, S is the conductor area, and d is the distance.

Generally, on a scale of a visible degree or a degree capable of being operated by bare hands, no matter how close two conductors are placed, a capacitance value (faraday) between them is difficult to deviate from a pico (pico) unit, and a conventional PCB is also such that C between layers is small, and insulation between layers can be maintained even if a circuit operates at a high frequency of a prescribed degree, however, in the case of an electronic apparatus for high speed transmission operating at a high frequency of, for example, 10GHz or more in a frequency of GIGA (GIGA) unit, as shown in the above formula, it is difficult to maintain insulation due to a decrease in impedance caused by high frequency, and therefore, in selecting an insulator, a material having a low dielectric constant, that is, a material having a low dielectric constant is used as much as possible to minimize electrostatic coupling and capacitance (i.e., impedance).

For this reason, the polyimide film of the present invention comprises an aliphatic polyimide resin and microspheres having pores, thereby having a relatively low dielectric constant as described above. Specifically, the aliphatic polyimide resin has a very low dielectric constant in view of its lower specific gravity, molecular density, polarity, and possibility of forming a charge transfer complex compared to the aromatic polyimide resin, and the microspheres having air holes can further reduce the dielectric constant by utilizing the electrical characteristics of air.

Therefore, the polyimide film of the present invention has an advantage that insulation can be easily maintained even in high-speed transmission electronic devices and the like that operate at a frequency of GIGA (GIGA) units, for example, at a high frequency of 10GHz or more.

< moisture absorption Rate >

The moisture absorption rate is a ratio indicating the amount of moisture absorbed by a material. It is known that the dielectric constant generally increases when the moisture absorption rate is high, and is 100 or more when water is in a solid state, about 80 when water is in a liquid state, and 1.0059 when water is vapor in a gas state.

Therefore, although water in a water vapor state does not substantially affect the dielectric constant of the polyimide film, the dielectric constant of the polyimide film may be rapidly increased when water is absorbed in a liquid state by the polyimide film. That is, even when only a small amount of water is absorbed, the dielectric constant of the polyimide film may change rapidly, and the dielectric constant may increase significantly.

Therefore, it can be seen that the low moisture absorption rate is a physical property necessary for using the polyimide film as an insulating film.

As an example, the polyimide film of the present invention has a moisture absorption rate of 1.5% or less, and the lower limit thereof may be at least 0.8, and such moisture absorption rate is achieved due to the structural characteristics of the polyimide film of the present invention.

This is described in more detail hereinafter, but it is predicted that this is because the polyimide film of the present invention contains an aliphatic polyimide resin, and the molecular structure of the aliphatic polyimide resin contains at least one of a nonpolar chain aliphatic hydrocarbon group or a cyclic aliphatic hydrocarbon group.

As described above, the polyimide film according to the present invention satisfies the above-mentioned 2 conditions, and thus can secure insulation stability even at high frequencies, thereby making it possible to minimize signal delay and transmission loss.

Here, the description will be made in more detail by the 'embodiment mode', but it is presumed that the polyimide resin and the micro-spheres exist in the polyimide film in at least one state selected from the following states:

a first state (A) in which the microspheres are coated on the surface;

a second state (B) in which the microspheres are physically bound to polymer chains of the polyimide resin; and

a third state (C) in which the microspheres are chemically bonded to the polymer chains of the polyimide resin.

The first state may be a result of inhibiting layer separation by promoting mixing and/or dispersion of the aliphatic polyamic acid and the microsphere. This structure allows pores of the microspheres to be uniformly dispersed in the polyimide film to uniformly reduce the dielectric constant, thereby providing an advantage that a low dielectric constant can be achieved in a high frequency region.

The second state may be a state in which the microspheres are physically entangled with polymer chains of the polyimide resin. Such a structure may be in a shape in which the microspheres are fixed on the polymer chains of the polyimide resin, and thus may provide advantages similar to those of the first state.

Also, the third state is a state in which the microspheres are chemically bonded to at least a part of the polymer chains of the polyimide resin, and can provide similar advantages to the first state or the second state.

On the other hand, as described above, the aliphatic polyimide resin may include at least one of a chain aliphatic hydrocarbon group or a cyclic aliphatic hydrocarbon group.

As an example, the chain aliphatic hydrocarbon group contains a group selected from C ₁ To C ₃₀ Alkyl radical, C ₂ To C ₃₀ Alkenyl radical, C ₂ To C ₃₀ Alkynyl, C ₁ To C ₃₀ Alkylene radical, C ₂ To C ₃₀ Alkenylene and C ₂ To C ₃₀ At least one aliphatic organic group of the group consisting of alkynylene groups,

the cyclic aliphatic hydrocarbon group may contain one or more groups selected from C ₃ To C ₃₀ Cycloalkyl, C ₃ To C ₃₀ Cycloalkenyl radical, C ₃ To C ₃₀ Cycloalkynyl group, C ₃ To C ₃₀ Cycloalkylene radical, C ₆ To C ₃₀ Cycloalkylene radical and C ₃ To C ₃₀ At least one cycloaliphatic organic group of the group consisting of cycloalkynylene groups.

<xnotran> , , (CHDA), 2,2- [ (4- ) ] (BAPP), 2,2- [4- (4- ) ] (HFBAPP), 4,4'- (MCA), 4,4' - (2- ) (MMCA), 1,3- (DAA), 3,3'- -1,1' - (DADA), (isophorone diamine), 4,4'- (4,4' -Diaminodicyclohexyl methane), 3,3'- -4,4' - (3,3 '-Dimethyl-4,4' -Diaminodicyclohexyl methane) 3,3',5,5' - -4,4'- (3,3', 5,5'-Tetramethyl-4,4' -Diaminodicyclohexyl methane) , , (CHDA). </xnotran>

More specifically, the Cyclohexanediamine (CHDA) may be, for example, at least one selected from the group consisting of 1,2-Cyclohexanediamine (1, 2-Cyclohexanediamine), 1,3-Cyclohexanediamine (1, 3-Cyclohexanediamine), 1,4-Cyclohexanediamine (1, 4-Cyclohexanediamine), N, N '-Dimethyl-1,2-Cyclohexanediamine (N, N' -Dimethyl-1, 2-Cyclohexanediamine), 4-Methyl-1,3-Cyclohexanediamine (4-Methyl-1, 3-Cyclohexanediamine), (R, 2R) -N, N, N ', N' -Tetramethyl-1,2-Cyclohexanediamine ((R, 2R) -N, N ', N' -tetra-Methyl-1, 2-Cyclohexanediamine), and N, N '-dipropylcyclohexanediamine (N, N' -dipropylcyclohexanediamine).

As described above, based on the above advantages, the polyimide film of the present invention comprising an aliphatic polyimide resin prepared from a diamine monomer comprising at least one of a chain aliphatic hydrocarbon group or a cyclic aliphatic hydrocarbon group and a dianhydride monomer and microspheres can have a low dielectric constant and a low moisture absorption rate even at high frequencies.

However, in spite of the above advantages, it is not preferable in the present invention to contain an excessive amount of the aliphatic polyimide resin in an amount out of the limited range.

Specifically, when the content of the aliphatic polyimide resin is in the range defined in the present invention, the aforementioned advantages may be expressed, but if it is out of this range, the mechanical strength or heat resistance of the polyimide film may be drastically reduced in terms of physical properties, and the film forming properties, such as surface defects, thermal wrinkles, film forming defects, and the like, may also be reduced in the film forming step in terms of engineering properties.

For this reason, as an example, in the present invention, the aliphatic polyamic acid may be included by 5 to 30 wt%, and specifically may be included by 10 to 20 wt%, with respect to the total solid weight of the aliphatic polyamic acid and the aromatic polyamic acid.

When it is less than the range, the dielectric constant and the moisture absorption rate are not reduced to a desired degree, whereas when it is more than the range, engineering properties such as film forming property and the like are lowered due to a lower glass transition temperature, so that it is not preferable.

In addition, the viscosity of the aliphatic polyamic acid may be 2000cP to 20000cP, specifically may be 3000cP to 15000cP, more specifically may be 5000cP to 10000cP.

When the viscosity of the aliphatic polyamic acid is less than the range, layer separation from the microspheres may occur, and is not preferable in terms of input and storage stability, whereas when it is greater than the range, mixing and/or dispersion with the microspheres may be difficult.

On the other hand, the microspheres having gas pores may be contained in an amount of 3 to 10 wt%, specifically 5 to 7 wt%, based on the total weight of the solids of the aliphatic polyamic acid and the aromatic polyamic acid.

When it is less than the range, voids formed in the polyimide film by the microspheres are reduced, and thus the electrical characteristics of air cannot be sufficiently realized, and thus a desired degree of low dielectric constant cannot be realized, whereas when it is more than the range, the microspheres are aggregated to cause defects on the surface of the film, and the inclusion of an excessive amount of microspheres may also adversely affect the mechanical properties of the polyimide film.

As an example, the microspheres may have an average particle size of 1 μm to 20 μm, specifically 10 μm to 20 μm, and more specifically 16 μm to 20 μm.

When the average particle diameter is less than the range, it is not preferable because it is difficult to prepare particles having pores to deteriorate the engineering properties, and on the contrary, when it is more than the range, problems may occur due to the content range of the microspheres described above.

Such microspheres having pores may contain, for example, at least one selected from the group consisting of silica, alumina, titania, zeolite, boron oxide, and glass, and specifically may be, but not limited to, borosilicate glass.

On the other hand, the aromatic polyimide resin can be prepared by a polymerization reaction of 1 or more kinds of aromatic diamine monomers and 1 or more kinds of aromatic dianhydride monomers in an organic solvent.

The aromatic diamine monomer may be at least one selected from the group consisting of 4-phenylenediamine (PPD), 4' -Oxydianiline (ODA), 3,4' -oxydianiline, 4' -Malondialdehyde (MDA), and 1, 3-bis (4-aminophenoxy) benzene (TPE-R), which may be used alone or in combination of 2 or more as needed.

The aromatic dianhydride monomer may be at least one selected from the group consisting of pyromellitic dianhydride (PMDA), biphenyltetracarboxylic dianhydride (BPDA), oxydiphthalic anhydride (ODPA), and benzophenonetetracarboxylic dianhydride (BTDA), and these may be used alone or in combination of 2 or more, as required.

Preparation method of polyimide film

The polyimide film of the present invention is obtained from a solution of an aliphatic polyamic acid and an aromatic polyamic acid, which are precursors of polyimide.

Such a polyamic acid solution is prepared by stirring a polyamic acid organic solvent solution prepared by dissolving a monomer compound in which a diamine monomer and a dianhydride monomer are mixed in a substantially equimolar amount in an organic solvent under controlled temperature conditions until polymerization of the aromatic dianhydride monomer and the aromatic diamine monomer is completed.

As an example, the polyamic acid solution is generally obtained at a solid content of 5 to 35% by weight, preferably, at a concentration of 10 to 30% by weight. For this range of concentration, the polyamic acid solution attains the appropriate molecular weight and solution viscosity.

The solvent used for synthesizing the polyamic acid is not particularly limited, and any solvent may be used as long as it can dissolve the polyamic acid, but an amide-based solvent is preferable. Specifically, the solvent may be an organic polar solvent, specifically, an aprotic polar solvent (aproticpolarsolvent), and for example, one or more selected from the group consisting of N, N '-Dimethylformamide (DMF), N' -dimethylacetamide, N-methyl-pyrrolidone (NMP), γ -butyrolactone (GBL), and Diglyme (Diglyme) may be used, but not limited thereto, and two or more thereof may be used alone or in combination as necessary.

In one example, at least one of N, N-dimethylformamide or N, N-dimethylacetamide may be preferably used as the solvent.

Therefore, in order to obtain the polyimide film of the present invention, a preferable production method is to prepare an aliphatic polyamic acid and an aromatic polyamic acid solution obtained by the following steps and imidize them.

Therefore, the invention provides a preparation method of the polyimide film.

The preparation method can comprise the following steps:

a step of performing a heat treatment at a temperature of 200 to 450 ℃ after forming a film of the precursor composition on a support and drying to prepare a gel film, to prepare a polyimide film in which the polyamic acid precursor is imidized.

As an example, the microspheres may be blended 3 to 5 times at 2000RPM to 5000RPM, 5 minutes to 10 minutes each, at 0 ℃ to 10 ℃ and added to the aliphatic polyamic acid solution.

In accordance with the present invention, in the polyimide film thus prepared, the polyimide resin and the microspheres may be made to exist in at least one state selected from the group consisting of:

a first state (A) in which the microspheres are coated on the surface;

a second state (B) in which the microspheres are physically bonded to the polymer chains of the polyimide resin; and

That is, mixing the microspheres in the aliphatic polyamic acid solution having relatively low hygroscopicity and then mixing the aliphatic polyamic acid microsphere dispersion and the aromatic polyamic acid solution makes mixing and/or dispersion of the microspheres easy, and the microspheres can be uniformly dispersed inside the polyimide resin based on excellent input stability to maximize the electrical characteristics of air, so that a low dielectric constant of the polyimide film can be achieved even at high frequencies.

Also, storage stability problems such as layer separation of the aliphatic polyamic acid microsphere dispersion can be solved.

The polyamic acid precursor composition prepared according to the steps has a molecular structure in a shape to which a part of chains having physical properties different from each other is attached. By adjusting the position and length of the partial chain and the kind and content of the monomer constituting the partial chain, it is possible to more precisely adjust physical properties, such as dielectric constant, moisture absorption rate, etc., of the polyimide film obtained by imidizing the polyamic acid precursor.

On the other hand, in the "precursor composition preparation process", a filler may be added to improve various characteristics of the thin film, such as slidability, thermal conductivity, electrical conductivity, corona resistance, coil hardness. The filler to be added is not particularly limited, but preferable examples thereof include silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, and mica.

The particle size of the filler is not particularly limited, and may be determined according to the characteristics of the film to be modified and the kind of the filler to be added. In general, the average particle diameter is from 0.05 μm to 20 μm, preferably from 0.1 μm to 10 μm, more preferably from 0.1 μm to 5 μm, and particularly preferably from 0.1 μm to 3 μm.

If the particle diameter is less than this range, it is difficult to exhibit an improvement effect, and if the particle diameter is greater than this range, the surface properties may be largely impaired and the mechanical properties may be largely degraded.

The amount of the filler to be added is not particularly limited, and may be determined by the film properties to be improved, the particle size of the filler, or the like. In general, the filler is added in an amount of 0.01 to 10 parts by weight, preferably 0.01 to 5 parts by weight, and more preferably 0.02 to 1 part by weight, relative to 100 parts by weight of the polyimide resin.

If the amount of the filler added is less than this range, the improvement effect due to the filler hardly occurs, and if the amount of the filler is more than this range, the mechanical properties of the film may be greatly impaired. The method of adding the filler is not particularly limited, and a known specific method can be used.

For the method of preparing a polyimide film by imidizing the precursor composition prepared as described above, a known method can be used.

Specific examples of such imidization include a thermal imidization method, a chemical imidization method, and a composite imidization method using both the thermal imidization method and the chemical imidization method, and these methods are more specifically described by the following non-limiting examples.

< thermal imidization method >

The thermal imidization method is a method of causing an imidization reaction by hot air or a heat source such as an infrared dryer in addition to a chemical catalyst, and may include:

a step of drying the precursor composition to form a gel film; and

and a step of heat-treating the gel film to obtain a polyimide film.

Among these, the gel film can be understood as a film intermediate having a self-supporting property in an intermediate step of converting from polyamic acid to polyimide.

The step of forming the gel film may be casting the precursor composition in the form of a film on a support such as a glass plate, an aluminum foil, a circulating (end) stainless steel belt or a stainless steel drum, and then drying the precursor composition on the support at a variable temperature ranging from 50 ℃ to 200 ℃, particularly from 80 ℃ to 150 ℃.

Thus, partial curing and/or drying may occur in the precursor composition to form a gel film, and the gel film may be obtained by peeling the formed gel film from the support.

The thickness and size of the polyimide film obtained in the subsequent heat treatment process may be adjusted according to circumstances, and the gel film may be stretched to improve orientation, wherein the stretching process may be performed in at least one of a machine transport direction (MD) and a Transverse Direction (TD) with respect to the machine transport direction.

After the gel film thus obtained is set in a tenter, heat treatment is performed at a variable temperature ranging from 50 ℃ to 500 ℃, specifically from 150 ℃ to 500 ℃ to remove water, residual solvent, and the like remaining in the gel film, and almost all of the remaining amic acid groups are imidized, whereby the polyimide film of the present invention can be obtained.

According to circumstances, the polyimide film obtained as described above may be heated and processed for 5 to 400 seconds at a temperature of 300 to 600 ℃ to further cure the polyimide film, and this step may also be performed under a predetermined tension in order to relax internal stress that may remain in the obtained polyimide film.

< chemical imidization method >

The chemical imidization method is a method of adding a dehydrating agent and/or an imidizing agent to a precursor composition to promote imidization of an amide group.

The "dehydrating agent" means a material which promotes the ring-closure reaction by the dehydration action with respect to the polyamic acid, and as a non-limiting example thereof, aliphatic acid anhydrides, aromatic acid anhydrides, N' -dialkylcarbodiimides, halogenated lower aliphatic acid anhydrides, dihalogenated aryl phosphines, and halogenated sulfinyl groups, etc. can be exemplified. Among them, aliphatic acid anhydrides are preferable in terms of convenience and cost, and non-limiting examples thereof include Acetic Anhydride (AA), propionic anhydride, and lactic anhydride, and these may be used alone or in combination of two or more.

The "imidizing agent" means a material having an effect of promoting a ring-closing reaction with respect to the polyamic acid, and may be an imine component such as an aliphatic tertiary amine, an aromatic tertiary amine, or a heterocyclic tertiary amine. Among these, heterocyclic tertiary amines may be preferable from the viewpoint of reactivity as a catalyst. As non-limiting examples of the heterocyclic tertiary amine, quinoline, isoquinoline, β -picoline, pyridine, and the like may be cited, and these may be used alone or in combination of two or more.

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

If the amount of the dehydrating agent and the imidizing agent is less than the above range, chemical imidization may be insufficient, resulting in cracks in the polyimide film to be produced and a decrease in the mechanical strength of the film. Also, if their addition amount is more than the above range, imidization proceeds excessively rapidly, and in this case, it may be difficult to express brittleness (brittle) in a polyimide film cast or prepared in the form of a film.

< Complex imidization method >

A complex imidization method, which further performs a thermal imidization method based on a chemical imidization method, may be utilized for the preparation of a polyimide film.

Specifically, the complex imidization method may include: chemical imidization processes, adding dehydrating agents and/or imidizing agents to the precursor composition at low temperatures; and a thermal imidization process of drying the precursor composition to form a gel film, and heat-treating the gel film.

In performing the chemical imidization method process, the kinds and addition amounts of the dehydrating agent and the imidizing agent may be appropriately selected according to the description of the aforementioned chemical imidization method.

In forming the gel film, the precursor composition containing the dehydrating agent and/or the imidizing agent is cast in the form of a film on a support such as a glass plate, an aluminum foil, a circulating (end) stainless steel belt or a stainless steel tub, and then the precursor composition on the support is dried at 50 to 200 ℃, particularly at a variable temperature in the range of 80 to 150 ℃. In these processes, a chemical conversion agent and/or an imidizing agent is used as a catalyst so that amide groups can be quickly converted into imide groups.

After the gel film thus obtained is fixed in a tenter, heat treatment is performed at a temperature ranging from 50 ℃ to 700 ℃, specifically from 150 ℃ to 600 ℃ to remove water, catalyst, residual solvent, and the like remaining in the gel film, imidizing most of the remaining amic acid groups, and thus the polyimide film of the present invention can be obtained. In the heat treatment as described above, the dehydrating agent and/or the imidizing agent also serve as a catalyst, so that amide groups can be rapidly converted into imide groups, thereby making it possible to achieve a high imidization rate.

According to circumstances, the polyimide film obtained as described above may be heated and processed for 5 to 400 seconds at a temperature of 400 to 500 ℃ to further cure the polyimide film, and this step may also be performed under a predetermined tension in order to relax internal stress that may remain in the obtained polyimide film.

The invention also provides electronic equipment for high-speed transmission, which comprises the polyimide film.

The electronic device for high-speed transmission may be an electronic device that transmits signals at a high frequency of at least 2GHz, specifically at a high frequency of at least 5GHz, more specifically at a high frequency of at least 10 GHz.

The electronic device may be, for example, a communication circuit for a portable terminal, a communication circuit for a computer, or a communication circuit for aerospace, but is not limited thereto.

Detailed Description

Hereinafter, the action and effect of the invention will be further described by way of specific examples of the invention. However, such embodiments are presented only as examples of the present invention and do not thereby determine the scope of the invention as claimed.

< Experimental example 1> evaluation of moisture absorption rate, dielectric constant and film Forming Property of polyimide film

< examples 1 to 1>

Preparation examples 1 to 1: preparation of aliphatic polyamic acid solution

450g of N, N-dimethylacetamide (DMAc) was added as a polar solvent to a 1L reactor under a nitrogen atmosphere.

Next, after setting the temperature inside the reactor to 25 ℃, 16.87g of 1,3-Cyclohexanediamine (CHDA) was added as an aliphatic diamine monomer and stirred for about 30 minutes to confirm that the diamine monomer was dissolved in the solvent, 33.13g of 1,2,4, 5-cyclohexanedicarboxylic dianhydride (HPMDA) was gradually added as an aliphatic dianhydride monomer and the amount added was adjusted so that the final viscosity became 5000cP to 10000cP.

After the completion of the charging, stirring was performed for 1 hour while maintaining the temperature, thereby preparing a polymerized aliphatic polyamide acid solution having a final viscosity of 8000 CP.

Preparation examples 1 to 2: preparation of aliphatic polyamic acid microsphere dispersion

After 60g of the aliphatic polyamic acid solution prepared in preparation example 1-1, 42g of a 10% crude solution of borosilicate glass (product name: scotchlite, 3M) having an average particle diameter of 16 μ M as microspheres having pores, and 0.2g of N, N-Dimethylformamide (DMF) for concentration control were added to a 1L reactor, the mixture was stirred at 10 ℃ for 5 minutes at 2500RPM to prepare an aliphatic polyamic acid microsphere dispersion.

Preparation examples 1 to 3: preparation of aromatic polyamic acid solution

425g of N, N-Dimethylformamide (DMF) were added as a polar solvent in a 1L reactor under a nitrogen atmosphere.

Next, after the temperature in the reactor was set to 25 ℃, 12.41g of 4,4' -Oxydianiline (ODA) and 11.92g of 1, 4-phenylenediamine (PPD) were added as aromatic diamine monomers and stirred for about 30 minutes to confirm that the diamine monomers were dissolved in the solvent, 50.67g of biphenyltetracarboxylic dianhydride (BPDA) was gradually added as aromatic dianhydride monomers, and the addition amount was adjusted so that the final viscosity became 150000cP to 200000cP.

After the completion of the charging, stirring was performed for 1 hour while maintaining the temperature, thereby preparing an aliphatic polyamic acid solution polymerized at a final viscosity of 180000 CP.

Preparation examples 1 to 4: preparation of Polyamic acid precursor compositions

In 100g of the aromatic polyamic acid solution prepared in preparation examples 1 to 3 and a catalyst mixture solution (5.67 g of isoquinoline, 17.92g of acetic anhydride, 6.41g of n, n-dimethylformamide) using a high shear mixer, 30g of the aliphatic polyamic acid microsphere dispersion prepared in preparation examples 1 to 2 was mixed at 0 ℃ for 1 minute to 2 minutes, thereby preparing a polyamic acid precursor composition.

< examples 1 and 2>

Polyamic acid precursor compositions were prepared in the same manner as in example 1-1, except that the addition amount was changed so as to contain 5 wt% of the microspheres, as shown in table 1 below.

< examples 1 to 3>

Polyamic acid precursor compositions were prepared in the same manner as in example 1-1, except that the addition amounts were changed to include 20 wt% of aliphatic polyamic acid and 5 wt% of microspheres, as shown in table 1 below.

< examples 1 to 4>

A polyamic acid precursor composition was prepared in the same manner as in example 1-1, except that the addition amounts were changed so as to include 30 wt% of aliphatic polyamic acid and 10 wt% of microspheres, as shown in table 1 below.

< examples 1 to 5>

A polyamic acid precursor composition was prepared in the same manner as in example 1-1, except that the addition amount was adjusted to include 5 wt% of aliphatic polyamic acid and 3 wt% of microspheres, as shown in table 1 below.

< examples 1 to 6>

Polyamic acid precursor compositions were prepared in the same manner as in example 1-1, except that borosilicate glass having an average particle diameter of 20 μm was used in an amount of 3% by weight, as shown in Table 1 below.

< examples 1 to 7>

A polyamic acid precursor composition was prepared in the same manner as in example 1-1, except that 22.06g of 2, 2-bis [ (4-aminophenoxy) phenyl ] propane (BAPP) was used as an aliphatic diamine monomer in place of 1,3-cyclohexanediamine, and 27.94g of 2, 2-bis [4- (3, 4-dicarboxyphenoxy) phenyl ] propane dianhydride (BPADA) was used as an aliphatic dianhydride monomer in place of 1,2,4, 5-cyclohexanetetracarboxylic dianhydride.

< examples 1 to 8>

A polyamic acid precursor composition was prepared in the same manner as in example 1-1, except that 25.88g of 4,4' -Methylenebiscyclohexylamine (MCA) was used as the aliphatic diamine monomer in place of 1,3-cyclohexanediamine, and 24.12g of cyclobutane-1, 2,3, 4-tetracarboxylic dianhydride (CBDA) was used as the aliphatic dianhydride monomer in place of 1,2,4, 5-cyclohexanetetracarboxylic dianhydride.

< comparative example 1>

A polyamic acid precursor composition was prepared in the same manner as in example 1-1, except that the addition amount was changed so as to contain 3 wt% of aliphatic polyamic acid and 1 wt% of microspheres, as shown in table 1 below.

< comparative examples 1 and 2>

A polyamic acid precursor composition was prepared in the same manner as in example 1-1, except that the addition amounts were changed so as to contain 40 wt% of aliphatic polyamic acid and 15 wt% of microspheres, as shown in table 1 below.

< comparative examples 1 to 3>

Polyamic acid precursor compositions were prepared in the same manner as in example 1-1, except that the addition amount was changed so as to contain 1 wt% of microspheres, as shown in table 1 below.

< comparative examples 1 to 4>

A polyamic acid precursor composition was prepared in the same manner as in example 1-1, except that the addition amount was changed so as to contain 3 wt% of aliphatic polyamic acid as shown in table 1 below.

< comparative examples 1 to 5>

Polyamic acid precursor compositions were prepared in the same manner as in example 1-1, except that the addition amount was changed so as to contain 15 wt% of microspheres, as shown in table 1 below.

< comparative examples 1 to 6>

A polyamic acid precursor composition was prepared in the same manner as in example 1-1, except that the addition amount was changed so as to include 40 wt% of aliphatic polyamic acid and 10 wt% of microspheres, as shown in table 1 below.

< comparative examples 1 to 7>

As shown in Table 1 below, a polyamic acid precursor composition was prepared in the same manner as in example 1-1, except that microspheres having an average particle diameter of 50 μm were added.

< comparative examples 1 to 8>

A polyamic acid precursor composition was prepared in the same manner as in example 1-1, except that spherical silica powder having no gas holes was used as microspheres having gas holes instead of borosilicate glass.

< comparative examples 1 to 9>

A polyamic acid precursor composition was prepared in the same manner as in example 1-1, except that the microspheres according to preparation examples 1-3 were not included, and the addition amount thereof was changed as in the following table 1 so as to include 40 wt% of aliphatic polyamic acid.

< comparative examples 1 to 10>

A polyamic acid precursor composition was prepared in the same manner as in example 1-1, except that the aliphatic polyamic acid and the microsphere according to preparation examples 1-1 and 1-3 were changed so as not to be included.

< comparative examples 1 to 11>

A polyamic acid precursor composition was prepared in the same manner as in example 1-1, except that the aliphatic polyamic acid according to preparation example 1-1 was not included, and the added amount thereof was changed as in the following table 1 so as to include 15% by weight of the microsphere.

< comparative examples 1 to 12>

A polyamic acid precursor composition was prepared in the same manner as in example 1-1, except that the aliphatic polyamic acid solution, the microspheres, and the aromatic polyamic acid solution in preparation examples 1-3 were mixed simultaneously using a high shear mixer.

TABLE 1

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The polyamic acid precursor compositions prepared in the examples 1-1 to 1-8 and the comparative examples 1-1 to 1-12 were respectively cast on a glass plate to a thickness of 500 μm using a doctor blade, and then dried at 120 ℃ for 5 minutes to prepare a gel film, and then subjected to a heat treatment in an oven (high temperature tenter) at 250 ℃ for 2 minutes and then in an oven at 450 ℃ for 4 minutes to prepare a polyimide film of 50 μm.

With respect to the polyimide film thus prepared, the moisture absorption rate and the dielectric constant were measured in the following manners, and the film forming properties thereof were visually observed, and the results thereof are shown in the following table 3.

1) Moisture absorption measurement

The polyimide film was cut into a square of 5cm × 5cm size according to astm d570 method to prepare a sample, and the weight was measured after drying the cut sample in an oven at 50 ℃ for 24 hours or more, and then the weight was measured again after immersing the sample, the weight of which had been measured, in water at 23 ℃ for 24 hours, wherein the difference between the obtained weights was expressed in% to measure the moisture absorption rate.

2) Dielectric constant measurement

The dielectric constant at 10GHz was measured using a SPDR measuring instrument from Keysight.

TABLE 2

	Dielectric constant	Moisture absorption Rate (%)	Film forming property
				Example 1-1	2.5	1.2	Good effect
Examples 1 to 2	2.9	1.2	Good effect
				Examples 1 to 3	2.8	0.9	Good effect
Examples 1 to 4	2.2	0.8	Good effect
				Examples 1 to 5	3.1	1.5	Good effect
Examples 1 to 6	2.7	1.2	Good effect
				Examples 1 to 7	2.5	1.1	Is good
Examples 1 to 8	2.5	1.0	Good effect
				Comparative example 1-1	3.3	1.7	Good effect
Comparative examples 1 to 2	2.0	0.7	Failure in film formation
				Comparative examples 1 to 3	3.3	1.2	Is good
Comparative examples 1 to 4	2.8	1.7	Good effect
				Comparative examples 1 to 5	2.1	1.2	Surface defect
Comparative examples 1 to 6	2.0	0.7	Film formation failure
				Comparative examples 1 to 7	2.1	1.2	Surface defect
Comparative examples 1 to 8	3.7	1.2	Is good
				Comparative examples 1 to 9	3.5	0.7	Thermal wrinkling occurs
Comparative examples 1 to 10	3.5	1.8	Good effect
				Comparative examples 1 to 11	2.0	1.8	Is good
Comparative examples 1 to 12	3.5	1.3	Good effect

As is clear from table 2, the polyimide film according to the examples of the present invention was found to have a significantly low moisture absorption rate and a significantly low dielectric constant, and to have excellent film-forming properties.

This result was achieved only by the combination of the aliphatic polyimide resin and the microspheres having pores, and it can be seen that the contents of the aliphatic polyimide resin and the microspheres play a critical role.

Specifically, the polyimide films in comparative examples which are outside the content ranges of the aliphatic polyamic acid and the microsphere of the invention, as compared to the polyimide films in examples, it was confirmed that they showed a significantly high dielectric constant, or even if the dielectric constant was reduced, there was a case where the film forming property such as occurrence of surface defects or thermal wrinkles was significantly reduced. Similarly, even when particles having no air holes are used or a polyimide film in which aliphatic and aromatic polyamic acids are mixed with microspheres has a poor dielectric constant and/or film-forming properties, it is found that it is substantially difficult to apply the polyimide film to an electronic device for transmitting a high-frequency signal.

< Experimental example 2> evaluation of input and storage stability of dispersion liquid of aliphatic polyamic acid microspheres

< preparation example 2-1>

An aliphatic polyamic acid microsphere dispersion was prepared in the same manner as in preparation examples 1-1 and 1-2, except that an aliphatic polyamic acid solution polymerized at a final viscosity of 5000CP was used, as shown in table 3 below.

< preparation examples 2 and 2>

An aliphatic polyamic acid microsphere dispersion was prepared in the same manner as in preparation examples 1-1 and 1-2, except that an aliphatic polyamic acid solution polymerized at a final viscosity of 10000CP was used, as shown in table 3 below.

< comparative preparation example 2-1>

An aliphatic polyamic acid microsphere dispersion was prepared in the same manner as in preparation examples 1-1 and 1-2, except that an aliphatic polyamic acid solution polymerized at a final viscosity of 1500CP was used, as shown in table 3 below.

< comparative preparation example 2-2>

An aliphatic polyamic acid microsphere dispersion was prepared in the same manner as in preparation examples 1-1 and 1-2, except that an aliphatic polyamic acid solution polymerized at a final viscosity of 15000CP was used, as shown in table 3 below.

TABLE 3

After the dispersion of microspheres of aliphatic polyamic acid prepared as described above was left to stand at room temperature for 1 day, whether or not layer separation occurred between aliphatic polyamic acid and borosilicate glass was visually observed, and the results thereof are shown in table 4 below.

TABLE 4

	Whether or not layer separation occurs
		Preparation examples 1 to 2	X
Preparation example 2-1	X
		Preparation examples 2 to 2	X
Comparative preparation example 2-1	O
		Comparative preparation examples 2 to 2	X

As is clear from table 4, although no layer separation was observed in the production examples in which the viscosity of the aliphatic polyamic acid satisfied the content range defined in the present invention, it was confirmed that the layer separation of the aliphatic polyamic acid and the borosilicate glass occurred in the comparative production example 2-1 in which the aliphatic polyamic acid having a relatively low viscosity of 1500cP was used, and it was found from the above results that the aliphatic polyamic acid microsphere dispersion according to the present invention was particularly excellent in storage stability.

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

Industrial applicability

The aliphatic polyamic acid contained in the polyimide film of the present invention can be effectively used to suppress the dielectric constant and the moisture absorption rate, and the dielectric constant can be further reduced by realizing the electrical characteristics of air by the microspheres having pores, and the microspheres form a network with the aliphatic polyamic acid, thereby not only improving the stability but also preventing the layer separation of the microspheres and the polyimide precursor solution even when the precursor composition solution is stored for a long time.

Therefore, the electronic device for high-speed transmission including the polyimide film according to the present invention can realize high-speed communication at a high frequency of 10 GHz.

The substantial advantage of the production method according to the present invention is that the foregoing polyimide film can be realized.

Claims

1. A polyimide film, comprising:

an aliphatic polyimide resin;

an aromatic polyimide resin; and

a microsphere having a pore, wherein the pore is formed by a porous structure,

the aliphatic polyimide resin contains at least one of a chain aliphatic hydrocarbon group or a cyclic aliphatic hydrocarbon group,

wherein the microspheres are present in at least one state selected from the group consisting of:

a first state (A) in which the microspheres are coated on the surface;

a third state (C) in which the microspheres are chemically bonded to the polymer chains of the polyimide resin,

wherein the aliphatic polyimide resin is derived from an aliphatic polyamic acid obtained by polymerizing an aliphatic diamine monomer and an aliphatic dianhydride monomer,

the aromatic polyimide resin is derived from an aromatic polyamic acid obtained by polymerizing an aromatic diamine monomer and an aromatic dianhydride monomer,

the polyimide film is prepared by imidizing a precursor composition comprising the aliphatic polyamic acid, the aromatic polyamic acid, and the microspheres having pores,

wherein the polyimide film comprises 5 to 30 wt% of the aliphatic polyamic acid with respect to the total solid weight of the aliphatic polyamic acid and the aromatic polyamic acid,

wherein the polyimide film is prepared by a method comprising:

2. The polyimide film according to claim 1,

the chain aliphatic hydrocarbon group contains a group selected from C ₁ To C ₃₀ Alkyl radical, C ₂ To C ₃₀ Alkenyl radical, C ₂ To C ₃₀ Alkynyl, C ₁ To C ₃₀ Alkylene radical, C ₂ To C ₃₀ Alkenylene and C ₂ To C ₃₀ At least one aliphatic organic group of the group consisting of alkynylene groups,

said cyclic aliphatic hydrocarbon group comprises a group selected from C ₃ To C ₃₀ Cycloalkyl radical, C ₃ To C ₃₀ Cycloalkenyl radical, C ₃ To C ₃₀ Cycloalkynyl, C ₃ To C ₃₀ Cycloalkylene radical, C ₆ To C ₃₀ Cycloalkylene radical and C ₃ To C ₃₀ At least one cycloaliphatic organic group of the group consisting of cycloalkynylene groups.

3. The polyimide film according to claim 1,

the aliphatic diamine monomer is at least one selected from the group consisting of cyclohexanediamine, 1,4-cyclohexanedi (methylamine), 2-bis [ (4-aminophenoxy) phenyl ] propane, 2-bis [4- (4-aminophenoxyphenyl) ] hexafluoropropane, 4 '-methylenebiscyclohexylamine, 4' -methylenebis (2-methylcyclohexylamine), 1, 3-adamantanediamine, and 3,3 '-diamino-1, 1' -bisadamantane,

the aliphatic dianhydride monomer is at least one selected from the group consisting of 1,2,4, 5-cyclohexane tetracarboxylic dianhydride, 2-bis [4- (3, 4-dicarboxyphenoxy) phenyl ] propane dianhydride, bicyclo [2, 2] oct-7-ene-2, 3,5, 6-tetracarboxylic dianhydride, and cyclobutane-1, 2,3, 4-tetracarboxylic dianhydride.

4. The polyimide film according to claim 1,

the aromatic diamine monomer is at least one selected from the group consisting of 1, 4-phenylenediamine, 4' -oxydianiline, 3,4' -oxydianiline, 4' -dimethyldiphenylamine and 1, 3-bis (4-aminophenoxy) benzene,

the aromatic dianhydride monomer is at least one selected from the group consisting of pyromellitic dianhydride (PMDA), biphenyl tetracarboxylic dianhydride (BPDA), oxydiphthalic anhydride (ODPA), and Benzophenone Tetracarboxylic Dianhydride (BTDA).

5. The polyimide film according to claim 1, wherein the microspheres are hollow or mesoporous (mesoporus) type microspheres.

6. The polyimide film according to claim 1, wherein the microspheres are contained in an amount of 3 to 10 wt% based on the total solid weight of the aliphatic polyamic acid and the aromatic polyamic acid.

7. The polyimide film according to claim 1, wherein the microspheres comprise at least one selected from the group consisting of silica, alumina, titania, zeolite, boria, and glass.

8. The polyimide film of claim 1, wherein the microspheres are borosilicate glass.

9. The polyimide film according to claim 1, wherein the microspheres have an average particle diameter of 1 to 20 μm.

10. The polyimide film according to claim 1, wherein the viscosity of the aliphatic polyamic acid is 2000cP to 20000cP.

11. The polyimide film according to claim 1, wherein the polyimide film has a dielectric constant of 3.0 or less and a moisture absorption rate of 1.5% or less at 10 GHz.

12. The polyimide film of claim 1 wherein the microspheres are blended 3 to 5 times at 2000RPM to 5000RPM, each time for 5 to 10 minutes, at a temperature of 0 ℃ to 10 ℃ and added to the aliphatic polyamic acid solution.

13. An electronic device for high-speed transmission, comprising the polyimide film according to claim 1.