WO2019194386A1 - Polyimide film for preparing flexible metal foil-clad laminate and flexible metal foil-clad laminate comprising same - Google Patents

Abstract

The present invention provides a polyimide film prepared by imidizing a polyamic acid derived from the polymerization of: a diamine monomer comprising first diamine represented by chemical formula (1) and second diamine represented by chemical formula (2); and pyromellitic dianhydride (PMDA). The dielectric constant (Dk) is 3.4 or lower, and the dielectric loss rate (Df) is 0.005 or lower.

Description

Polyimide film for manufacturing flexible metal laminate and flexible metal laminate comprising same

The present invention relates to a polyimide film for producing a flexible metal laminate and a flexible metal laminate comprising the same.

Polyimide (PI) is a polymer having the highest level of heat resistance, chemical resistance, electrical insulation, chemical resistance and weather resistance among organic materials, based on an imide ring having a high chemical stability with a rigid aromatic backbone. Material.

Accordingly, polyimide is in the spotlight as an insulating material for microelectronic components in which the above characteristics are strongly required.

Examples of the microelectronic component include a thin circuit board having a high degree of circuit integration and a flexible circuit board to cope with light weight and miniaturization of electronic products. The polyimide is widely used as an insulating film of a thin circuit board.

For reference, a thin circuit board generally has a structure in which a circuit including a metal foil is formed on a polyimide film, and such a thin circuit board is also referred to as a flexible metal foil clad laminate in a broad sense.

Meanwhile, as various functions are recently embedded in electronic devices, fast computing speeds and communication speeds are required for the electronic devices, and thin circuit boards capable of high-speed communication at high frequencies of 2 GHz or more have been developed to satisfy these requirements.

In order to realize high frequency high speed communication, an insulator having a high impedance capable of maintaining electrical insulation even at high frequencies is required.

Since the impedance is inversely related to the frequency and dielectric constant (Dk) formed in the insulator, the dielectric constant should be as low as possible to maintain insulation at high frequencies.

However, in the case of the conventional polyimide, the dielectric constant is not high enough to maintain sufficient insulation in the high frequency communication of about 3.4 to 3.6, and for example, the insulation is partially provided in the thin circuit board having the high frequency communication of 2 GHz or more. Or there is a possibility of total loss.

In addition, as the dielectric constant of the insulator is lowered, it is possible to reduce undesirable stray capacitance and noise in the thin circuit board, and it is known that the cause of communication delay can be largely eliminated. As low as possible, the dielectric constant is considered to be the most important factor in the performance of thin circuit boards.

Another thing to note is that for high frequency communication above 2 GHz, dielectric dissipation through polyimide inevitably occurs.

Dielectric dissipation factor (Df) refers to the degree of waste of electrical energy in thin circuit boards and is closely related to the signal propagation delays that determine the communication speed, so that the dielectric loss rate of polyimide is as low as possible. It is recognized as an important factor for the performance of the substrate.

Therefore, the development of a polyimide film having a relatively low dielectric constant and dielectric loss rate is required.

It is an object of the present invention to provide a polyimide film having a relatively low dielectric constant and dielectric loss rate and a flexible metal laminate having the same.

According to one aspect of the present invention, a polyimide film prepared by combining a specific diamine monomer containing a nonpolar aliphatic moiety and a pyromellitic dianhydride, and imidizing the polyimide film is prepared in a polyimide polymer chain. Based on the special structure containing the nonpolar aliphatic moiety, it is possible to suppress moisture absorption which adversely affects the dielectric constant and the dielectric loss rate.

According to another aspect, the flexible metal laminate comprising the polyimide film is a circuit capable of high-speed communication at a high frequency based on the relatively low dielectric constant and dielectric loss rate of the polyimide film while having a desired glass transition temperature It can be implemented as.

Therefore, the present invention has a substantial object to provide a specific embodiment thereof.

The present invention to achieve the above object,

A diamine monomer comprising a first diamine represented by the following formula (1) and a second diamine represented by the following formula (2); And

It provides a polyimide film prepared by imidizing a polyamic acid derived from polymerization of pyromellitic dianhydride (PMDA), having a dielectric constant (Dk) of 3.4 or less and a dielectric loss factor (Df) of 0.005 or less. .

(One)

(2)

In the case of the polyimide film according to the present invention, the dielectric loss ratio is also improved at the same time while having the desired glass transition temperature and dielectric constant, so that the insulation reliability is high even at a high frequency and signal transmission delay can be minimized.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the invention will be described in more detail in the order of "polyimide film", "manufacturing method of polyimide film" and "flexible metal laminate board" according to the present invention.

Prior to this, terms or words used in the present specification and claims should not be construed as being limited to the common or dictionary meanings, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention.

Therefore, the configuration of the embodiments described herein is only one of the most preferred embodiments of the present invention and does not represent all of the technical idea of the present invention, various equivalents and modifications that may be substituted for them at the time of the present application It should be understood that examples may exist.

As used herein, the singular forms "a", "an" and "the" include plural forms unless the context clearly indicates otherwise. As used herein, the terms "comprise", "comprise" or "have" are intended to indicate that there is a feature, number, step, component, or combination thereof, that is, one or more other features, It should be understood that it does not exclude in advance the possibility of the presence or addition of numbers, steps, components, or combinations thereof.

Polyimide film

Polyimide film according to the present invention,

A diamine monomer comprising a first diamine represented by the following formula (1) and a second diamine represented by the following formula (2); And

It is prepared by imidating a polyamic acid derived from the polymerization of pyromellitic dianhydride (PMDA), and has a dielectric constant (Dk) of 3.4 or less and a dielectric loss ratio (Df) of 0.005 or less.

(One)

(2)

Wherein in formula (1), R 1 and R 2 are each independently a C ₁ -C ₆ alkyl group or a C ₁ -C ₆ alkoxy group;

In formula (2), R 3 is —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, — (CH ₂ ) _{n 1} —, or —O (CH ₂ ) _{n 2} O—, wherein n 1 and n 2 Are each independently an integer of 1 to 10.

Such polyimide film,

(a) the dielectric constant (Dk) is 3.4 or less,

(b) the dielectric loss factor (Df) is 0.005 or less,

(c) the moisture absorption is 2.3% by weight or less,

(d) Glass transition temperature (Tg) is 320 degreeC or more.

In this regard, in the case of the polyimide film that satisfies all the above four conditions, it can be used as an insulating film for the flexible metal laminate, and the manufactured flexible metal laminate is used as an electrical signal transmission circuit for transmitting signals at a high frequency of 2 GHz or more. Even if it is, its insulation stability can be ensured, and signal propagation delay can also be minimized.

The polyimide film having all four of these conditions is a novel polyimide film which has not been known so far, and the four conditions will be described in detail below.

<Genetic constant>

Permittivity is an important characteristic value that represents the electrical properties of a dielectric (or insulator), that is, a non-conductor. The permittivity is not directly representative of the electrical properties of a DC current, but is directly related to the characteristics of AC currents, especially AC electromagnetic waves. Known.

In the insulator (for example, a polyimide film), the + and-moment components, which are normally scattered in a random direction in general, are aligned with an alternating current change of an electromagnetic field applied outside the insulator. In other words, the moment components are changed in accordance with the change direction of the electromagnetic field, it is possible to enable the progress of electromagnetic waves inside even the non-conductor.

For such a change in the external electromagnetic field, the degree of sensitivity and how sensitively the moment inside the material reacts can be expressed as permittivity.

This permittivity can be intuitively interpreted through relative permittivity, which means that the dielectric constant of each dielectric is proportional to air 1, and the imaginary number in the calculation of the relative dielectric constant is calculated. The exclusion and real expression is the dielectric constant (Dk).

Higher dielectric constants mean better electrical energy transfer, and insulators such as polyimide films are preferred as the dielectric constants are lower.

Nevertheless, it has already been explained that conventional polyimide films are not at a level sufficient to maintain sufficient insulation in high frequency communication.

This is evident when compared to the dielectric constant of liquid crystal polymers. In the case of liquid crystal polymers, the dielectric constant is known to be about 2.9 to 3.3, which is much better than an insulator compared to a conventional polyimide having most dielectric constants. can see.

On the other hand, the polyimide film according to the present invention may have a dielectric constant close to or lower than the dielectric constant of the liquid crystal polymer, specifically, a dielectric constant of 3.4 or less, specifically, 3.0 or less, and the lower limit thereof may be at least 2.8. have.

It can be seen that this is an ideal form as an insulator, recalling the highest level of engineering properties of the polyimide film.

The meaning of these dielectric constants is explained in detail.

Even though all conductors are separated from each other, there is always capacitive coupling between them, and even if the layers and layers of the multilayer board are electrically separated from each other, they are actually only open circuits for direct current. It can be seen that an arbitrary capacitor is connected in between.

On the other hand, the capacitor has a property of lowering the impedance as the frequency of the current or voltage at both ends thereof, the value can be expressed as follows.

Impedance = 1 / (2 * π * f * C); Where f is frequency and C = capacitance.

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

In general, on a scale that can be seen and handled barely, no matter how close the two conductors are, the capacitance value (farad, farad) between them is unlikely to deviate from the pico unit. It is so small that even if the circuit operates at some high frequency, the insulation between layers can be well maintained.

On the other hand, in a special case such as a communication device operating at a frequency of GIGA, for example, a high frequency of 2 GHz, it may be difficult to maintain insulation because the frequency is so high that the impedance is low.

Therefore, when selecting an insulator, materials with the lowest possible dielectric constant should be used to minimize electrostatic coupling and capacitance (ie impedance).

Accordingly, the polyimide film according to the present invention has a relatively low dielectric constant as described above, and thus is easy to maintain insulation even at a frequency in a giga (GIGA) unit, for example, communication equipment operating at a very high frequency of 10 GHz. There is an advantage.

Dielectric loss rate

By "dielectric loss factor" is meant the force dissipated by the dielectric (or insulator) when the friction of the molecules interferes with the molecular motion caused by the alternating electric field.

The value of the dielectric loss rate is commonly used as an index indicating the ease of dissipation (dielectric loss), and the higher the dielectric loss rate, the easier the charge is to be lost. Conversely, the lower the dielectric loss rate, the more difficult it is to be lost. have.

That is, the dielectric loss rate is a measure of power loss. As the dielectric loss rate is lower, the signal transmission delay due to power loss is alleviated, and thus the communication speed can be maintained quickly.

This is a characteristic strongly required for polyimide films, which are insulating films, in which the polyimide film according to the invention has a dielectric loss factor of 0.005 or less, in particular 0.004 or less, more specifically, 0.003 under a fairly high frequency of about 2 GHz. It may be:

Hygroscopicity

A moisture absorption rate is a ratio which shows the moisture content which a material absorbs, and generally, it is known that dielectric constant and dielectric loss rate increase when moisture absorption rate is high.

Generally, when water is in the solid state, the dielectric constant is at least 100, in the liquid state, it is about 80, and in the gaseous water vapor, it is known as 1.0059.

That is, water present in the water vapor state other than the polyimide film does not substantially affect the dielectric constant and dielectric loss rate of the polyimide film.

However, when water vapor is absorbed in the polyimide film, it exists in a liquid state. In this case, the dielectric constant and dielectric loss rate of the polyimide film may increase dramatically.

That is, the dielectric constant and dielectric loss rate of the polyimide film may change rapidly even with a small amount of moisture absorption.

Therefore, keeping moisture absorption low can be seen as a very important factor for the polyimide film as an insulating film.

The polyimide film according to the present invention may have a moisture absorption of 2.3% by weight or less, in detail, 2.0% by weight or less, and more specifically 1.7% by weight or less, based on the total weight of the polyimide film. It is due to the structural features of the polyimide film according to the invention.

This will be described in more detail later, but it is expected that the non-polar part is included in the molecular structure of the polyimide film according to the present invention, and that the imide group close to hydrophilicity is occupied relatively low.

<Glass transition temperature>

In the present invention, the glass transition temperature can be obtained from the storage modulus and loss modulus measured by the dynamic viscoelasticity measuring device (DMA), and in detail, the top peak of tan δ which is the value of the calculated loss modulus divided by the storage modulus. ) Can be calculated as the glass transition temperature.

The glass transition temperature is related to the heat resistance of the polyimide film, and may be higher when considering the use of the insulating film.

However, in the polyimide film, the highest level of glass transition temperature, dielectric constant, and wireline loss rate are difficult to achieve. The reason is that the strong heat resistance of the polyimide film is due to the chemical stability of the imide group. It is expected to be due to a relatively weak point to moisture absorption.

On the other hand, the present invention provides a polyimide film in which both the glass transition temperature, the dielectric constant, and the streamline loss ratio are both at a desirable level. Specifically, the glass transition temperature of the polyimide film according to the present invention may be 320 ° C. or more. In detail, the temperature may be 320 ° C or higher and 380 ° C or lower, and particularly preferably 350 ° C or higher and 370 ° C or lower.

When the glass transition temperature is lower than the above range, when laminating, a large dimensional change may be accompanied because the viscosity of the polyimide film is relatively high. This is not preferable because it causes the appearance quality to be impaired.

On the other hand, when the glass transition temperature is higher than the above range, the temperature required to soften the core layer to a level sufficient to alleviate the thermal distortion is too high, so that the existing laminate apparatus cannot sufficiently relieve thermal stress, and the dimensional change is worsened. There is a possibility.

As described above, the polyimide film according to the present invention can be utilized as an insulating film for a flexible metal laminate, as well as satisfying all four conditions described above, and also ensures insulation stability even at high frequencies, and delays signal transmission. Can also be minimized.

As an embodiment of the present invention for the polyimide film having the above conditions, the dianhydride monomer, the diamine monomer and the blending ratio thereof are described in detail through the following non-limiting examples.

<Diamine Monomer>

In one specific example, the diamine monomer may be 50 mol% or more and 80 mol% or less, and 20 mol% or more and 50 mol% or less of the first diamine, based on the total number of moles thereof. .

For the second diamine, the molecular weight may be 400 g / mol to 600 g / mol, and for the first diamine, the molecular weight may be 200 g / mol to 250 g / mol.

Therefore, when the content of the second diamine is increased, the molecular weight of the polyimide polymer chain formed by imidating the polyamic acid may also increase.

In another aspect, the total molecular weight of one polyimide polymer chain increased with the content of the second diamine is such that the aromatic portion of the second diamine occupies most of the portion derived from the diamine monomer, while per second diamine molecule. Since only two amine groups are supplied, in the case of imide groups derived from the diamine, the proportion of the total molecular weight may be relatively reduced.

In other words, since the longer the length of one of the polyimide polymer chains described above, the aromatic moiety occupies most of the polyimide polymer chain, it is understood that the relative proportion of imide groups occupies relatively less in the entire polyimide polymer chain in which the polymer chain is repeated. Could be.

In this case, hydrophobicity improves also about the whole polyimide film, and lower moisture absorption can be expected.

However, if the content of the second diamine is increased in consideration of only the moisture absorption rate, since the occupancy ratio of the imide group is reduced for the above reason, there is a fear that the heat resistance of the polyimide film due to the chemical stability of the imide group is considerably lowered.

For this reason, the present invention emphasizes that it is not desirable for the second diamine to exceed 50 mol%, based on the total moles of the diamine monomer.

In addition, for the opposite reason, when the second diamine is less than 20 mol% based on the total moles of the diamine monomer, the moisture absorption rate is not preferable because it does not reach a desired level.

In the case of the first diamine, the molecular weight is relatively low compared to the second diamine, the overall molecular weight of the diamine monomer can be adjusted to an appropriate level, which is understood to control the proportion of the aromatic moiety in one polyimide polymer chain. Can be.

The first diamine may also serve as another source of amine groups for forming imide groups, for a desired level of heat resistance.

When above or below the range of the content of the first diamine, adverse effects opposite to the second diamine may occur.

The polyimide polymer chain formed by imidating the polyamic acid may include an aliphatic moiety derived from R 1 and R 2 of the first diamine and R 3 of the second diamine.

Such aliphatic moieties may be appropriately selected to have non-polarity, and non-limiting examples of aliphatic moieties for understanding include -CH ₃ , -CF ₃ , and the like. As described above, since the aliphatic moieties derived from R1, R2, and R3 have nonpolarity, the hygroscopicity of the polyimide polymer chain can be reduced.

In another aspect, when the aliphatic moiety is included in the polyamic acid, the proportion of amic acid groups that significantly affect the increase in hygroscopicity throughout the polyamic acid may be relatively low. Therefore, it can act positively to lower the hygroscopicity of the polyimide film containing such polyamic acid.

Having already explained the close relationship between the dielectric constant and the dielectric loss rate, the aliphatic moieties derived from R1, R2, and R3 can be understood as the main factors for the polyimide film according to the present invention to have a low dielectric constant and a low dielectric loss rate. Could be.

In addition, the aliphatic moieties derived from R1, R2, and R3 improve nonpolarity and at the same time provide the desired level of flexibility in the polyimide film to reduce defect rates in the filming process and to produce levels suitable for producing flexible metal laminates. The glass transition temperature and thermal expansion coefficient of can be obtained.

In order to achieve the desired moisture absorption rate, dielectric constant, dielectric loss rate, flexibility, glass transition temperature, and coefficient of thermal expansion, the molecular weight of the aliphatic moiety is 5% to 20 based on the total molecular weight of one polyimide polymer chain. %, In detail, may be 6% to 17%.

When the molecular weight of the aliphatic portion exceeds the above range, the mechanical properties of the polyimide film are lowered, and it is difficult to attain a level of glass transition temperature and coefficient of thermal expansion suitable for producing a flexible metal laminate, and to be less than the above range. It is not desirable to achieve levels of moisture absorption, dielectric constant and dielectric loss rate.

In one specific example, the R1 and R2 may be an alkyl group having a non-polarity, while excluding excessive molecular weight occupancy of the aliphatic portion, in detail, each of the R1 and R2 may be a methyl group.

R3 may also be a substituent having a nonpolarity while excluding an excessively aliphatic molecular weight occupancy, and in detail, may be -C (CF ₃ ) ₂ -or -C (CH ₃ ) _2- .

In the case of -C (CF ₃ ) _2- , fluorine may contribute to lowering the dielectric constant and may express strong nonpolarity, which may be particularly preferable as R 3.

In one specific example, the first diamine may be 4,4'-diamino-2,2'-dimethylbiphenyl (4,4'-Diamino-2,2'-dimethylbiphenyl: m-Tolidine).

In another specific example, the second diamine is 2,2-bis [4- (4-aminophenoxyphenyl)] hexafluoropropane (2,2-Bis [4- (4-aminophenoxy phenyl)] hexafluoropropane: HFBAPP).

<Dianhydride monomer>

The foregoing has already described that the diamine monomer may have a relatively large molecular weight.

As the molecular weight of one polyimide polymer chain formed by imidation of the polyamic acid is excessively large (for example, 2000 or more per polymer chain), and as the chain length increases, relatively few imide groups may exist in the entire polyimide polymer chain. There is nothing else.

In this case, other mechanical properties such as heat resistance, storage modulus, loss modulus, and the like of the polyimide film are seriously lost, which is not preferable.

In consideration of this, the dianhydride monomer may be a monomer having a relatively small molecular weight.

Accordingly, pyromellitic dianhydride (PMDA) having a relatively low molecular weight of 218 may be preferred as dianhydride monomer.

The pyromellitic dianhydride (PMDA) may also be viewed as a dianhydride monomer having a relatively rigid structure.

It is well known that rigid monomers are suitable for high modulus.

Therefore, the pyromellitic dianhydride (PMDA) is preferable in that it can impart proper elasticity to the polyimide film prepared by imidating the polyamic acid.

Manufacturing Method Of Polyimide Film

The polyimide film of this invention is obtained from the polyamic-acid solution which is a precursor of polyimide.

The polyamic acid solution is obtained by dissolving a monomer compound blended in such a manner that the aromatic diamine monomer and the aromatic dianhydride monomer are substantially equimolar in an organic solvent, and the obtained polyamic acid organic solvent solution is prepared under controlled temperature conditions. It is prepared by stirring until the polymerization of the monomer is completed.

The polyamic acid solution is usually obtained at a solid content of 5 to 35% by weight, preferably at a concentration of 10 to 30% by weight.

In concentrations in this range, the polyamic acid solution obtains the appropriate molecular weight and solution viscosity.

The solvent for synthesizing the polyamic acid solution is not particularly limited, and any solvent may be used as long as it is a solvent in which the polyamic acid is dissolved, but is preferably an amide solvent.

Specifically, the solvent may be an organic polar solvent, and in detail, may be an aprotic polar solvent, for example, N, N'-dimethylformamide (DMF), N, It may be one or more selected from the group consisting of N'-dimethylacetamide, N-methyl-pyrrolidone (NMP), gamma butyrolactone (GBL), Diglyme (Diglyme), but is not limited thereto. It can be used individually or in combination of 2 or more types.

In one example, the solvent may particularly preferably be N, N-dimethylformamide and N, N-dimethylacetamide.

Thus, in order to obtain the polyimide film of the present invention, a production method of preparing a polyamic acid solution obtained through the following steps (a) to (c) and imidating the same is preferable.

Therefore, this invention provides the manufacturing method of a polyimide film.

The manufacturing method,

(a) adding the diamine monomer and the dianhydride monomer to an organic polar solvent,

(b) polymerizing the diamine monomer and the dianhydride monomer with each other in the organic polar solvent to obtain a polyamic acid,

(c) forming the polyamic acid on a support, followed by heat treatment at a temperature of 200 to 400 ° C. to obtain a polyimide film imidated with the polyamic acid.

However, depending on the type of monomer and the physical properties of the desired polyimide film, all monomers may be added in one step or the monomers may be sequentially added in step (a), and in this case, partial polymerization between monomers may occur. Of course.

The final polyamic acid prepared through the steps (a) to (b) has a molecular structure in which partial chains having different physical properties are connected.

The physical properties of the polyimide film obtained by imidating the polyamic acid by adjusting the position, length of the partial chain and the type and content of the monomer constituting the same, for example, dielectric constant, dielectric loss rate, glass transition temperature, moisture absorption rate You can fine tune your back.

In addition, in the "polyamic acid solution manufacturing process", the filler may be added for the purpose of improving various properties of the film, such as sliding, thermal conductivity, conductivity, corona resistance, loop hardness.

The filler to be added is not particularly limited, but preferred examples thereof include silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica and the like.

The particle size of the filler is not particularly limited and can be determined according to the film properties to be modified and the type of filler to be added.

In general, the average particle diameter may be from 0.05 to 100 μm, preferably from 0.1 to 75 μm, more preferably from 0.1 to 50 μm, particularly preferably from 0.1 to 25 μm.

If the particle size is less than this range, the modifying effect is less likely to appear. If the particle size is larger than this range, the surface properties may be largely impaired, or the mechanical properties may be greatly reduced.

The addition amount of the filler is not particularly limited, and can be determined by the film characteristics to be modified, the particle size of the filler, and the like.

In general, the addition amount of the filler may be 0.01 to 100 parts by weight, preferably 0.01 to 90 parts by weight, more preferably 0.02 to 80 parts by weight based on 100 parts by weight of polyimide.

If the amount of filler added is less than this range, the effect of modification by the filler is less likely to appear, and if it exceeds this range, mechanical properties of the film may be largely impaired.

The addition method of a filler is not specifically limited, Any known method can also be used.

As a method for producing a polyimide film by imidating the polyamic acid solution prepared as described above, a conventionally known method can be used.

Specifically, the thermal imidation method, the chemical imidation method, or the composite imidation method which used the thermal imidation method and the chemical imidation method together is mentioned.

The thermal imidization method is a method of imidizing a polyamic acid solution by heating only without using a catalyst such as a dehydrating agent. After forming a polyamic acid on a support, it is 40 to 400 degreeC, Preferably it is 40 to 300 degreeC It is a method of obtaining a polyimide film in which the polyamic acid is imidated by gradually increasing the temperature in the temperature range of 1 to 8 hours.

The chemical imidation method is a method of promoting imidization of a polyamic acid solution using a catalyst such as a dehydrating agent and / or an imidizing agent.

In the composite imidization method, a dehydrating agent and an imidization catalyst are added to a polyamic acid solution to form a film on a support, and then heated at 80 to 200 ° C, preferably 100 to 180 ° C, partially cured and dried, and then at 200 to 400 ° C. The polyimide film can be obtained by heating for 5 to 400 seconds.

On the other hand, dehydrating agents are, for example, aliphatic acid anhydride, aromatic acid anhydride, N, N'-dialkylcarbodiimide, halogenated lower aliphatic, halogenated lower fatty acid anhydride, arylphosphonic acid dihalide, and thionyl halide, or And mixtures of two or more thereof.

Among them, aliphatic acid anhydrides such as acetic anhydride, propionic anhydride, and lactic anhydride, or a mixture of two or more thereof can be preferably used in view of ease of availability and cost.

In addition, as an imidation agent, an aliphatic tertiary amine, an aromatic tertiary amine, a heterocyclic tertiary amine, etc. are used, for example.

Among them, those selected from heterocyclic tertiary amines are particularly preferably used in view of reactivity as a catalyst.

Specifically, quinoline, isoquinoline, β-picolin, pyridine and the like are preferably used.

When the chemical imidation method is used in the imidization step, the imidization step is performed by applying the film forming composition containing the polyamic acid solution on a support, and heat treating the film to a temperature range of 40 ° C. to 300 ° C. on the support. And a step of peeling the gel film from the support and further heating the gel film to imidize and dry the remaining amic acid (hereinafter also referred to as "firing process"). Do.

Each process mentioned above is demonstrated in detail below.

In order to manufacture a gel film, first, a dehydrating agent and / or an imidating agent are mixed in a polyamic-acid solution at low temperature, and a composition for film forming is obtained.

Although the said dehydrating agent and the imidating agent are not specifically limited, The compound illustrated above can be selected and used.

Moreover, in the said gel film manufacturing process, it can also mix in a polyamic-acid solution using the hardening | curing agent containing a chemical conversion agent and an imidation catalyst, and can also obtain a composition for film forming.

It is preferable to exist in the range of 0.5-5 mol with respect to 1 mol of amic acid groups in polyamic acid, and, as for the addition amount of a dehydrating agent, it is more preferable to exist in the range of 1.0-4 mol.

Moreover, it is preferable that it is in the range of 0.05-3 mol with respect to 1 mol of amic acid groups in polyamic acid, and, as for the addition amount of the imidating agent, it is especially preferable that it is in the range of 0.2-2 mol.

If the dehydrating agent and the imidating agent are less than the above ranges, the chemical imidation may be insufficient, and may break during firing or the mechanical strength may decrease.

Moreover, when these amounts exceed the said range, since imidation advances rapidly and it may become difficult to cast in a film form, it is not preferable.

On the other hand, the film forming composition is then cast in a film form on a support such as a glass plate, an aluminum foil, an endless stainless belt, or a stainless drum.

Thereafter, the film forming composition is heated on a support in a temperature range of 80 ° C to 200 ° C, preferably 100 ° C to 180 ° C.

By doing so, the dehydrating agent and the imidizing agent are activated, and partially hardening and / or drying occurs, thereby forming a gel film.

Then, it peels from a support body and obtains a gel film.

The gel film is in the intermediate stage of curing from polyamic acid to polyimide and is self supporting.

Flexible Copper Clad Laminates

This invention provides the flexible metal foil laminated board containing the polyimide film mentioned above and an electrically conductive metal foil.

Although it does not specifically limit as metal foil to be used, When using the flexible metal foil laminated board of this invention for an electronic device or an electrical device use, it is copper or a copper alloy, stainless steel or its alloys, nickel or a nickel alloy (alloy 42, for example). And metal foil including aluminum or an aluminum alloy.

In general flexible metal foil laminated sheets, copper foil, such as a rolled copper foil and an electrolytic copper foil, is used abundantly, and can also be used suitably also in this invention.

Moreover, the antirust layer, a heat resistant layer, or an adhesive layer may be apply | coated to the surface of these metal foils.

It does not specifically limit about the thickness of the said metal foil in this invention, What is necessary is just a thickness which can exhibit sufficient function according to the use.

In the flexible metal laminate sheet according to the present invention, a metal foil is laminated on one surface of the polyimide film, or an adhesive layer containing thermoplastic polyimide is added to one surface of the polyimide film, and the metal foil is attached to the adhesive layer. It may be a laminated structure.

The present invention also provides an electronic component comprising the flexible metal laminate sheet as an electrical signal transmission circuit.

The electrical signal transmission circuit may be an electronic component that transmits a signal at a high frequency of at least 2 GHz, specifically at a high frequency of at least 5 GHz, and more particularly at a high frequency of at least 10 GHz.

The electronic component 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.

Hereinafter, the operation and effects of the invention will be described in more detail with reference to specific examples of the invention. However, these embodiments are only presented as an example of the invention, whereby the scope of the invention is not determined.

<Example 1>

PMDA was added to DMF in the reaction system maintained at 10 degreeC in the molar ratio shown in following Table 1, and it stirred for 1 hour.

After visually confirming the dissolution, m-tolidine was added in the molar ratio shown in Table 1, dissolved, and HFBAPP was added in the molar ratio shown in Table 1, and stirred for 1 hour to prepare a polyamic acid.

The imidation promoter including acetic anhydride / isoquinoline / DMF (46% / 13% / 41% by weight) was added to the polyamic acid solution thus obtained at 50 parts by weight based on 100 parts by weight of the polyamic acid solution, and the obtained mixture was made of stainless steel. After application to the plate was cast using a 400 μm gap using a doctor blade and dried for 4 minutes with hot air in a 120 ℃ oven to prepare a gel film.

The gel film thus prepared was peeled off from the stainless steel plate and fixed with a frame pin. After heat-treating the frame on which the gel film was fixed at 400 ° C. for 7 minutes, the film was removed to obtain a polyimide film having an average thickness of 15 μm.

<Example 2>

A polyimide film having a thickness of 15 μm was obtained in the same manner as in Example 1 except that the molar ratio of m-tolidine and HFBAPP was changed as in Table 1.

<Example 3>

A polyimide film having a thickness of 15 μm was obtained in the same manner as in Example 1 except that the molar ratio of m-tolidine and HFBAPP was changed as in Table 1.

Comparative Example 1

A polyimide film having a thickness of 15 μm was obtained in the same manner as in Example 1 except that the molar ratio of m-tolidine and HFBAPP was changed as in Table 1.

Comparative Example 2

A polyimide film having a thickness of 15 μm was obtained in the same manner as in Example 1 except that the molar ratio of m-tolidine and HFBAPP was changed as in Table 1.

Comparative Example 3

A polyimide film having a thickness of 15 μm was obtained in the same manner as in Example 1 except that the molar ratio of m-tolidine and HFBAPP was changed as in Table 1.

<Comparative Example 4>

A polyimide film having a thickness of 15 μm was obtained in the same manner as in Example 1 except that ODA was added in the molar ratio shown in Table 1 instead of m-tolidine and HFBAPP.

Comparative Example 5

A polyimide film having a thickness of 15 μm was obtained in the same manner as in Example 1 except that ODA and PPD were added in the molar ratio shown in Table 1 instead of m-tolidine and HFBAPP.

Comparative Example 6

A polyimide film having a thickness of 15 μm was obtained in the same manner as in Example 1 except that PMDA and BPDA were added in the molar ratio shown in Table 1 instead of adding PMDA alone.

Comparative Example 7

A polyimide film having a thickness of 15 μm was obtained in the same manner as in Example 1 except that BPDA was added in the molar ratio shown in Table 1 instead of PMDA.

	Dianhydride monomer (mol%)		Diamine Monomer (mol%)
	PMDA	BPDA	m-Tolidine	HFBAPP	PPD	ODA
Example 1	100	-	70	30	-	-
Example 2	100	-	80	20	-	-
Example 3	100	-	50	50	-	-
Comparative Example 1	100	-	30	70	-	-
Comparative Example 2	100	-	90	10	-	-
Comparative Example 3	100	-	40	60	-	-
Comparative Example 4	100	-	-	-	-	100
Comparative Example 5	100	-	-	-	25	75
Comparative Example 6	50	50	70	30	-	-
Comparative Example 7	-	100	70	30	-	-

Experimental Example 1

The glass transition temperature and the moisture absorption rate of the polyimide film obtained as described above were measured in the following manner.

Thereafter, copper foil was roll-laminated on both sides of the polyimide film to prepare a flexible metal laminate, and the dielectric constant and dielectric loss rate were measured in the following manner.

The above results are shown in Table 2 below.

1) Glass transition temperature

For glass transition temperature, the loss modulus and storage modulus of each film were calculated using DMA, and the inflection point was measured by the glass transition temperature in the tangent graph.

2) moisture absorption rate

According to ASTM D570 method, a polyimide film was cut into squares having a size of 5 cm × 5 cm to prepare specimens. After soaking in water at 23 ° C. for 24 hours, the weight was again measured, and the moisture absorption rate was measured by expressing the difference in weight obtained as%.

3) Measurement of dielectric constant and dielectric loss rate

Dielectric constant and dielectric loss rate were measured by using a ohmmeter Agilent 4294A for 72 hours.

	Dielectric constant (Dk)	Dielectric loss rate (Df)	Glass transition temperature (℃)	Hygroscopicity (%)
Example 1	3.2	0.004	365	1.4
Example 2	3.3	0.005	371	1.6
Example 3	3	0.004	323	1.2
Comparative Example 1	2.8	0.004	280	1.2
Comparative Example 2	3.5	0.005	377	1.8
Comparative Example 3	2.9	0.004	302	1.3
Comparative Example 4	3.7	0.017	403	2.8
Comparative Example 5	3.7	0.017	422	3
Comparative Example 6	3.2	0.004	304	1.3
Comparative Example 7	3.1	0.004	297	1.1

As shown in Table 2, the polyimide film prepared according to the embodiment of the present invention can be confirmed that not only the moisture absorption rate, dielectric constant and dielectric loss rate is significantly lower, but also the desired glass transition temperature, as described above. Likewise, all of the following conditions are satisfied.

(a) the dielectric constant (Dk) is 3.4 or less,

(b) the dielectric loss factor (Df) is 0.005 or less,

(c) the moisture absorption is 2.3% by weight or less,

(d) Glass transition temperature (Tg) is 320 degreeC or more.

This result is achieved by the combination of specific diamine monomers derived from aliphatic moieties with PMDA having a relatively low molecular weight, and it can be seen that the content of each monomer plays a decisive role.

On the other hand, Comparative Examples 1 to 3 in which the content of the diamine monomer is out of the range according to the present invention can be seen that at least one of the moisture absorption rate, dielectric constant and dielectric loss rate, and glass transition temperature is significantly reduced.

In addition, it was also confirmed that Comparative Examples 4 and 5 having different diamine monomers from the Examples also had significant differences in dielectric constant, dielectric loss rate, and moisture absorption rate compared with the Examples.

In particular, Comparative Examples 4 and 5 show a significantly higher dielectric constant and dielectric loss rate compared to the examples, which can be expected to be difficult to use in electronic components in which signal transmission is performed at a high frequency in units of gigabytes.

In addition, the glass transition temperature of Comparative Examples 4 and 5 greatly exceeds the preferred range disclosed in the present invention, which has already been described as being able to work very disadvantageously in the processing of the polyimide film.

On the other hand, in the case of Comparative Example 6 containing only BPDA as both dianhydride monomer and PMDA and Comparative Example 7 including only BPDA, it can be seen that there is a significant difference in glass transition temperature compared to the Example.

Although described above with reference to embodiments of the present invention, those skilled in the art will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

As described above, the present invention has a relatively low hygroscopicity with a desired glass transition temperature due to the combination of specific dianhydride monomers, diamine monomers and their specific blending ratio, and the dielectric constant according to moisture absorption. And it can provide the polyimide film by which the dielectric loss rate raise was suppressed.

The present invention can also provide a flexible metal laminate that can be utilized as an electrical transmission circuit capable of high frequency communication of 2 GHz or more, including the polyimide film as described above.

Claims (14)

1. A diamine monomer comprising a first diamine represented by the following formula (1) and a second diamine represented by the following formula (2); And

   A polyimide film prepared by imidizing a polyamic acid derived from the polymerization of pyromellitic dianhydride (PMDA), having a dielectric constant (Dk) of 3.4 or less and a dielectric loss factor (Df) of 0.005 or less:

   

   (One)

   

   (2)

   R 1 and R 2 in the formula (1) are each independently a C ₁ -C ₆ alkyl group or a C ₁ -C ₆ alkoxy group;

   In formula (2), R 3 is —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, — (CH ₂ ) _{n 1} —, or —O (CH ₂ ) _{n 2} O—, wherein n 1 and n 2 Are each independently an integer of 1 to 10.
2. The method of claim 1,

   The polyimide film is a polyimide film having a glass transition temperature of 320 ℃ or more.
3. The method of claim 1,

   The polyimide film has a coefficient of thermal expansion (CTE) of 10 to 25 ppm / ℃ polyimide film.
4. The method of claim 1,

   Based on the total number of moles of the diamine monomer, the first diamine is at least 50 mol% to 80 mol%, the second diamine is at least 20 mol% to 50 mol% polyimide film.
5. The method of claim 1,

   The polyimide polymer chain formed by imidating the polyamic acid comprises an aliphatic moiety derived from R1 and R2 of the first diamine and R3 of the second diamine.
6. The method of claim 5,

   The molecular weight of the aliphatic moiety is 5% to 20% based on the total molecular weight of one polyimide polymer chain.
7. The method of claim 1,

   R 1 and R 2 are each a methyl group, and R 3 is —C (CF ₃ ) ₂ — or —C (CH ₃ ) ₂ —.
8. The method of claim 1,

   The first diamine is 4,4'-diamino-2,2'-dimethylbiphenyl (4,4'-Diamino-2,2'-dimethylbiphenyl: m-Tolidine) polyimide film.
9. The method of claim 1,

   The second diamine is 2,2-bis [4- (4-aminophenoxyphenyl)] hexafluoropropane (2,2-Bis [4- (4-aminophenoxy phenyl)] hexafluoropropane: HFBAPP) polyimide film .
10. As a method of manufacturing the polyimide film according to claim 1,

    Adding the diamine monomer and the dianhydride monomer to an organic polar solvent;

    Polymerizing the diamine monomer and the dianhydride monomer with each other in the organic polar solvent to obtain a polyamic acid; And

    After forming the polyamic acid on a support, a heat treatment at a temperature of 200 to 450 ℃ to obtain a polyimide film in which the polyamic acid is imidized manufacturing method of a polyimide film.
11. A flexible metal foil laminate comprising the polyimide film according to claim 1 and an electrically conductive metal foil.
12. The method of claim 11,

    Metal foil is laminated on one surface of the polyimide film,

    An adhesive layer containing a thermoplastic polyimide is added to one surface of the polyimide film, and the flexible metal foil laminate is laminated in a state where the metal foil is attached to the adhesive layer.
13. An electronic component comprising the flexible metal laminate according to claim 11 as an electrical signal transmission circuit.
14. The electronic component of claim 13, wherein the electrical signal transmission circuit transmits a signal at a high frequency of at least 2 GHz.