KR20200071461A - Polyimide Film with Improved Thermal Conductivity and Method for Preparing The Same - Google Patents

Abstract

The present invention provides a polyimide film comprising a polyimide resin and a thermally conductive filler, wherein the ratio of the average particle diameter of the thermally conductive filler to the thickness of the polyimide film (= average particle diameter/thickness) is 0.3 to 0.5.

Description

Polyimide Film with Improved Thermal Conductivity and Method for Preparing The Same}

The present invention relates to a polyimide film having improved thermal conductivity and a method for manufacturing the same.

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

On the other hand, electric and electronic devices or parts that accumulate a large amount of information and process and transmit such information at a high speed are actively being developed in accordance with the trend of high informatization, and polyimide is based on its excellent physical properties. It is widely used as a protective film.

Recently, in order to prevent performance degradation of electrical/electronic devices or components due to heat generation of electronic devices, research into polyimide films having effective heat dissipation properties has been actively conducted.

However, since the amorphous part occupies most of the polyimide in terms of crystal structure, although there are some differences depending on other structures, the thermal conductivity is not usually high. In particular, the polyimide in the form of a film has a low thermal conductivity in the thickness direction, and various studies have been conducted to improve the thermal conductivity in the thickness direction of the polyimide film to enable effective heat dissipation.

One example of this is to add a thermally conductive material such as graphene or metal having excellent thermal conductivity in a polyamic acid solution, which is a precursor of polyimide, and then film it to prepare a polyimide film having improved thermal conductivity in the thickness direction. Is to do.

However, in order to improve the thermal conductivity in the thickness direction of the polyimide film to a significant level, it is necessary to use such a thermally conductive material with a fairly high content, in which case the prepared polyimide film is brittle brittle (brittle) ), and at the same time may be accompanied by a decrease in mechanical properties such as modulus.

Moreover, since these thermally conductive materials do not disperse well in a polyamic acid solution, the thermally conductive material present in excess can more easily aggregate to form a large number of aggregates, and these aggregates are exposed through the film surface to the polyimide film. It may cause defects in appearance, such as projections.

Therefore, there is a high need for a technology that can fundamentally solve these problems.

An object of the present invention is to provide a polyimide film in which the thermal conductivity in the thickness direction is remarkably improved, even if a thermally conductive filler is used in a limited amount falling within the scope of the present invention. At the same time, the polyimide film of the present invention has excellent modulus and can prevent appearance defects due to the thermally conductive filler. In particular, by defining the ratio of the average particle diameter of the thermally conductive filler to the thickness of the polyimide film, when the calculated value satisfies the numerical range defined in the present invention, the polyimide film has excellent effects as described above. It may be desirable to implement.

Accordingly, the present invention has a practical purpose in providing a specific embodiment for its implementation.

In one embodiment, the present invention is a polyimide film comprising a polyimide resin and a thermally conductive filler,

The ratio of the average particle diameter of the thermally conductive filler to the thickness of the polyimide film (= average particle diameter/thickness) is 0.3 to 0.5,

There is provided a polyimide film having a thermal conductivity in the thickness direction of the polyimide film of 0.5 W/m·K or more and a modulus of 5.0 GPa or more.

In one embodiment, the present invention provides a method of making the polyimide film.

In one embodiment, an electronic device comprising the polyimide film is provided.

Hereinafter, embodiments of the invention will be described in more detail in the order of “polyimide film” and “polyimide film production method” according to the present invention.

Prior to this, the terms or words used in the present specification and claims should not be construed as being limited to ordinary or lexical meanings, and the inventor appropriately explains the concept of terms in order to explain his or her invention in the best way. Based on the principle that it can be defined, it should be interpreted as meanings and concepts consistent with the technical spirit 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 spirit of the present invention, and various equivalents and modifications that can replace them at the time of this application It should be understood that examples may exist.

In this specification, a singular expression includes a plural expression unless the context clearly indicates otherwise. In this specification, the terms "include", "have" or "have" are intended to indicate the presence of implemented features, numbers, steps, elements, or combinations thereof, one or more other features or It should be understood that the existence or addition possibilities of numbers, steps, elements, or combinations thereof are not excluded in advance.

As used herein, "dianhydride (dianhydride)" is intended to include its precursors or derivatives, which may not technically be dianhydrides, but will nevertheless react with diamines to form polyamic acids. And this polyamic acid can be converted back to polyimide.

“Diamine” as used herein is intended to include precursors or derivatives thereof, which may not technically be diamines, but will nevertheless react with dianhydrides to form polyamic acids, which are polyamic The acid can be converted back to polyimide.

Where an amount, concentration, or other value or parameter herein is given as an enumeration of ranges, preferred ranges, or preferred upper and lower limits, any upper limit of any pair of any pair, regardless of whether the ranges are disclosed separately or It should be understood to specifically disclose all ranges that can be formed with preferred values and any lower range limits or desirable values. When a range of numerical values is referred to herein, unless stated otherwise, such as unless there is a limiting term such as greater than, less than, the range is intended to include the endpoint and all integers and fractions within the range. It is intended that the scope of the invention not be limited to the specific values recited when defining a range.

Polyimide film

The polyimide film according to the present invention may include a polyimide resin and a thermally conductive filler, and the ratio of the average particle diameter of the thermally conductive filler to its thickness (=average particle diameter/thickness) is 0.3 to 0.5, specifically 0.3 to 0.48, more specifically 0.31 to 0.45, and in particular 0.32 to 0.42.

Specifically, the polyimide film of the present invention that satisfies the above ratio has a thermal conductivity in the thickness direction at room temperature of 0.5 W/m·K or more, specifically 0.6 W/m·K or more, and more specifically 0.7 W It can be excellent at /m·K or more, particularly 0.74 W/m·K or more, and includes 5.0 GPa or more, particularly 5.5 GPa or more, and more particularly 7.0 GPa or more, particularly including a thermally conductive filler. It can have a modulus of compliance of 7.1 GPa or more.

The polyimide film of the present invention may have a thermally conductive filler dispersed throughout the polyimide resin, and may be formed of a composite structure in which the thermally conductive filler and the polyimide resin act as fillers and matrices, respectively.

In such a composite structure, the thermally conductive filler can act as a heat conduction medium that transfers heat applied to the polyimide film inside the film. However, even if the polyimide film includes a thermally conductive filler, it usually shows a tendency to improve the thermal conductivity in the planar direction, and the thermal conductivity improvement in the thickness direction may be insignificant. This is because, typically, polyimide polymer chains are oriented in the planar direction, so it is easy to conduct heat in a planar direction along the polymer chain, whereas it is relatively inconvenient to conduct through the polymer chain and the chain. do.

On the other hand, when the ratio according to the present invention is satisfied, the thermal conductivity in the thickness direction of the polyimide film can be remarkably improved. This forms a thermal conduction path that works optimally in the thickness direction in the relationship with the polymer chain in the polyimide film containing the thermal conductivity filler that satisfies the ratio, and at the same time, a plurality of thermal conduction paths are combined to thermal conductivity in the thickness direction. It is assumed that this is due to the formation of a kind of network that favors improvement.

This will be clearly demonstrated in the'detailed contents for carrying out the invention', but if the ratio falls below the range defined in the present invention, even if the thermally conductive filler is included in excess, the thermal conductivity in the thickness direction is desired. It may not be improved to the level, on the contrary, when it exceeds the above range, the modulus may be lowered and there is a problem in film forming properties, which is not preferable.

The specific configuration of the polyimide film for achieving the above is described in detail through the following non-limiting examples.

In one specific example, the thermally conductive filler is selected from the group consisting of aluminum oxide (Al ₂ O ₃ ), boron nitride (BN), aluminum nitride (AlN), silicon carbide (SiC), and magnesium oxide (MgO) 1 It may be a species or a mixture of two or more, and specifically, aluminum oxide.

In one specific example, the average particle diameter (D50) of the thermally conductive filler may be 2.5 to 20 μm, specifically 3 to 19 μm, and more specifically 3 to 16 μm.

When the average particle diameter of the thermally conductive filler is less than the range defined in the present invention, it is not preferable because the specific surface area is excessively increased on the basis of the entire thermally conductive filler to cause agglomeration of particles. On the contrary, when the particles are made of relatively large particles exceeding the above range, the number of particles settling by gravity in the polyamic acid solution may increase, which means that the particles forming the thermally conductive filler are a part of the polyimide film. It is undesirable because it may be present in a biased manner, which may cause defects in the appearance of the film.

In one specific example, the polyimide film may include 2 to 9 parts by weight, specifically 3 to 9 parts by weight, and particularly 5 to 9 parts by weight of a thermally conductive filler relative to 100 parts by weight of the polyimide resin. have.

The polyimide film containing a thermally conductive filler below the above range is difficult to include a heat conduction path sufficient to form a'network that can advantageously act in the thickness direction' described above, and thus a desired level of thickness direction heat conduction Degree may not be achieved. On the contrary, the polyimide film containing a thermally conductive filler exceeding the above range has a slight improvement in the thermal conductivity in the thickness direction as compared to the case of belonging to the above range, whereas a modulus deterioration may occur and the thermally conductive filler may be present in excess. Appearance defects may occur.

The thickness of the polyimide film may be selected in a range in which the ratio as described above can be satisfied. However, when it is excessively thin, it is not desirable to form a polyamic acid solution, which is a precursor of the film, because it is difficult, and when it is excessively thick, It is not preferable because the thermal conductivity in the thickness direction may be lowered.

Accordingly, the present invention provides a desirable thickness of the polyimide film, specifically, the thickness may be 5 to 60 μm, specifically 7 to 55 μm, and more specifically 7 to 50 μm, and the 7 to 50 Even in the range of μm, the lower limit may be 7 μm or 9 μm or 12 μm or 14 μm, and the upper limit may be 50 μm or 47 μm or 45 μm.

On the other hand, the polyimide resin,

100 parts by weight of the first polyimide resin; And

2 to 8 parts by weight of a second polyimide resin,

The second polyimide resin may have a relatively high crystallinity compared to the first polyimide resin.

In general, the more crystalline the polymer, the more advantageous it may be in terms of thermal conductivity. Conversely, the amorphous polymer may have relatively poor thermal conductivity. Such crystallinity can be quantitatively expressed using a degree of crystallinity.

Conventional polyimide resin is an amorphous polymer, and the polyimide film produced therefrom may also be considered to be substantially amorphous.

However, the polyimide film of the present invention further comprises a second polyimide resin having a high degree of crystallinity compared to the first polyimide resin, so that the polyimide film may include a crystalline portion, and compared to a conventional polyimide film. It can have a high crystallinity.

For reference, it is not easy to measure the crystallinity of polyimide resins of different compositions constituting a polyimide film separately and compare the size or degree of crystallinity between polyimide resins, but it is possible to measure the crystallinity of the polyimide film itself. . Therefore, when the crystallinity of the polyimide film increases as the content of the second polyimide resin increases in the polyimide film, it can be confirmed that the second polyimide resin has greater crystallinity than the first polyimide resin. have.

The crystallinity of the polyimide resin is greatly influenced by the composition of the monomers constituting it, but the crystallinity may vary depending on the polymerization method in addition to the composition. For example, in the process of polymerizing the precursor polyamic acid in the process of preparing a polyimide resin, some molecular structures may be arranged in a regular state according to viscosity, and thus a difference may occur in the degree of crystal formation.

In summary, in the present invention, the crystallinity of the polyimide film may vary according to the content of the second polyimide resin in the polyimide film, and also, depending on the viscosity of the second polyamic acid which is the precursor of the second polyimide resin. The crystallinity of the polyimide film prepared from may be different.

At least a portion of the second polyimide resin forms a crystal, and the crystal and the thermally conductive filler may have a structure that forms a heat conduction path with respect to a thickness direction in the film.

In the present invention, the crystal is a structure in which a part of the polyimide chain included in the second polyimide resin is regularly arranged, for example, radially regular arrangements from the central nucleus of the crystal in two-dimensional or three-dimensional directions. The structure in which the polyimide chains are regularly arranged in a circular or spherical shape in which crystals are grown, but the specific shape or shape is not limited.

Crystals as described above may be present in a myriad of numbers in the polyimide film, may include a part of the amorphous part between the crystal part and the crystal part, it is also possible that the amorphous part and the crystal part are present separately.

This structure is different from the structure of a general polyimide film in which a thermally conductive filler is dispersed between amorphous polyimide resins in a polyimide film, and the crystal has a thermal conductivity path in the thickness direction of the thermally conductive filler and film in the polyimide film. As can be formed, it is possible to improve the thermal conductivity in the thickness direction of the polyimide film according to the present invention.

However, despite the above advantages, it is not desirable that the second polyimide resin is unconditionally contained in the polyimide film.

Specifically, when the content of the second polyimide resin in the polyimide film is at a certain level, the above advantages may be exhibited, but beyond this, the advantage in terms of improving the thermal conductivity may be enhanced, but the polyimide film may have the above advantages. This is because there are too many crystals and the elongation of the polyimide film may drop rapidly.

That is, it is important that the polyimide film includes an appropriate amount of the first polyimide resin and the second polyimide resin so that the mechanical properties and the thermal conductivity of the polyimide film are compatible. Accordingly, the present invention has described the preferred content of the first polyimide resin and the second polyimide resin, the polyimide film of the present invention may have a crystallinity of 40% to 80%, and an elongation of 30% or more.

In one specific example, the first polyimide resin,

It is produced by imidizing a first polyamic acid prepared by polymerization of a first diamine monomer and a first dianhydride monomer,

The second polyimide resin may be prepared by imidizing a second polyamic acid prepared by polymerization of a second diamine monomer and a second dianhydride monomer.

The first dianhydride monomer may include at least one selected from the group consisting of pyromellitic dianhydride (PMDA), oxydiphthalan hydride (ODPA), and benzophenone tetracarboxylic dianhydride (BTDA). Including,

The first diamine monomer is 1,4-diaminobenzene (or paraphenylenediamine, PDA, PPD), 1,3-diaminobenzene (MPD), 2,4-diaminotoluene, 2,6-diamino Toluene, 3,5-diaminobenzoic acid (DABA), 4,4'-diaminodiphenyl ether (or oxydianiline, ODA), 3,4'-diaminodiphenyl ether, 4,4'- Diaminodiphenylmethane (or 4,4'-methylenedianiline, MDA), 3,3'-dimethylbenzidine (or o-tolidine, o-tolidine), 2,2'-dimethylbenzidine (or m-tol Lidine, m-tolidine) and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP).

The second dianhydride monomer is 3,3',4,4'-biphenyltetracarboxylic dianhydride,

The second diamine monomer may be 1,3-bis(4-aminophenoxy)benzene (TPE-R) and/or 1,4-bis(3-aminophenoxy)benzene (TPE-Q).

The TPE-based diamine is a monomer containing three benzene rings, and is a monomer having excellent chemical resistance, and may play a major role in increasing the crystallinity of the polymer.

Manufacturing method of polyimide film

The present invention provides a method for producing a polyimide film.

The manufacturing method of the present invention,

Polymerizing the polyamic acid;

Preparing a precursor composition by mixing the polyamic acid and a thermally conductive filler; And

It may include the step of imidizing the precursor composition to obtain a polyimide film.

In one specific example, the step of polymerizing the polyamic acid,

Polymerizing the first dianhydride monomer and the first diamine monomer in a first organic solvent to produce a first polyamic acid; And

And polymerizing the second dianhydride monomer and the second diamine monomer in the second organic solvent to produce a second polyamic acid,

The polyamic acid may include the first polyamic acid and the second polyamic acid.

Each of the first organic solvent and the second organic solvent may be an aprotic polar solvent. As a non-limiting example of the aprotic polar solvent, amide solvents such as N,N'-dimethylformamide (DMF), N,N'-dimethylacetamide (DMAc), p-chlorophenol, o-chloro And phenol-based solvents such as phenol, N-methyl-pyrrolidone (NMP), gamma brotirolactone (GBL) and digrime, and these may be used alone or in combination of two or more.

The method for polymerizing the first polyamic acid and the second polyamic acid is, for example,

(1) a method in which the total amount of the diamine monomer is placed in an organic solvent, and then the dianhydride monomer is added to be substantially equimolar with the diamine monomer and polymerized;

(2) a method in which the total amount of the dianhydride monomer is placed in an organic solvent, and then the diamine monomer is added to be substantially equimolar with the dianhydride monomer to polymerize;

(3) After adding some components of the diamine monomer in an organic solvent, after mixing some components of the dianhydride monomer with respect to the reaction component at a ratio of about 95 mol% to 105 mol%, the remaining diamine monomer components are added thereto. A method in which the remaining dianhydride monomer components are added successively to make the diamine monomer and the dianhydride monomer substantially equimolar;

(4) After placing the dianhydride monomer in an organic solvent, after mixing some components of the diamine compound with respect to the reaction component in a ratio of 95 mol% to 105 mol, other dianhydride monomer components are added and successively the remaining diamine A method of polymerization by adding a monomer component such that the diamine monomer and the dianhydride monomer become substantially equimolar; And

(5) Some diamine monomer components and some dianhydride monomer components are reacted in an organic solvent so as to be in excess, thereby forming a first polymer, and some diamine monomer components and some dianhydride monomer components in another organic solvent. As a method for reacting such that one is in excess to form a second polymer, mixing the first and second polymers, and completing the polymerization, wherein the diamine monomer component is excessive when forming the first polymer. , In the second polymerized product, an excess of the dianhydride monomer component, and in the case of the excess of the dianhydride monomer component in the first polymerized product, in the second polymerized product, the diamine monomer component is added in excess, and the first and second polymerized products are mixed. And a method in which the total diamine monomer component and the dianhydride monomer component used in these reactions are substantially equimolar and polymerized.

However, the above method is an example for helping the implementation of the present invention, and the scope of the present invention is not limited to them, and any known method can be used.

Meanwhile, the step of obtaining the polyimide film may include forming a polyimide film by imidizing the gel film after forming the precursor composition on a support and drying the gel film.

Specific examples of the imidization method include a thermal imidization method, a chemical imidization method, or a complex imidization method using a combination of the thermal imidization method and a chemical imidization method, and examples thereof include the following non-limiting examples. This will be described in more detail.

<Thermal imidization method>

The thermal imidization method is a method of excluding chemical catalysts and inducing an imidization reaction with a heat source such as hot air or an infrared dryer.

Drying the precursor composition to form a gel film; And

The heat treatment of the gel film may include a process of obtaining a polyimide film.

Here, the gel film can be understood as a film intermediate having self-supporting properties in an intermediate step for conversion from polyamic acid to polyimide.

In the process of forming the gel film, the precursor composition is cast in a film form on a support such as a glass plate, aluminum foil, endless stainless belt, or stainless drum, and then the precursor composition on the support is 50°C to 250°C, Specifically, it may be to dry at a variable temperature in the range of 50 ℃ to 200 ℃.

Accordingly, a gel film may be formed by partial curing and/or drying of the precursor composition. Then, the gel film can be obtained by peeling from the support.

In some cases, a process of stretching the gel film may be performed in order to control the thickness and size of the polyimide film obtained in the subsequent heat treatment process and to improve the orientation, and the stretching is performed in the machine transport direction (MD) and the machine transport direction. It may be performed in at least one of the lateral direction for (TD).

The gel film thus obtained is fixed to a tenter and then heat-treated at a variable temperature in the range of 50°C to 800°C, specifically 150°C to 650°C, to remove water, residual solvents, etc. remaining in the gel film, and remain. By imidizing almost all the amic acid groups, the polyimide film of the present invention can be obtained.

In some cases, the polyimide film obtained as described above may be heated to a temperature of 400°C to 650°C for 5 seconds to 400 seconds to further harden the polyimide film, and may remain inside the obtained polyimide film. It can also be done under a given tension to relieve stress.

<Chemical imidation method>

The chemical imidization method is a method of promoting imidization of the amic acid group by adding a dehydrating agent and/or an imidizing agent to the precursor composition.

Here, the term “dehydrating agent” refers to a substance that promotes a cyclization reaction through dehydration of a polyamic acid, and as a non-limiting example, an aliphatic acid anhydride, an aromatic acid anhydride, N,N' -Dialkyl carbodiimide, lower halogenated aliphatic, lower halogenated patty acid anhydride, aryl phosphonic dihalide, thionyl halide, and the like. Of these, aliphatic acid anhydrides may be preferred from the viewpoint of ease of availability and cost, and non-limiting examples include acetic anhydride (AA), propionic acid anhydride, and lactic acid anhydride. Etc. are mentioned, These can be used individually or in mixture of 2 or more types.

In addition, "imide agent" means a substance having an effect of promoting a ring-closure reaction to a polyamic acid, for example, an imine-based component such as an aliphatic tertiary amine, an aromatic tertiary amine, and a heterocyclic tertiary amine. Can be. Of these, heterocyclic tertiary amines may be preferable from the viewpoint of reactivity as a catalyst. Non-limiting examples of heterocyclic tertiary amines include quinoline, isoquinoline, β-picoline (BP), pyridine and the like, and these may be used alone or in combination of two or more.

It is preferable that the addition amount of a dehydrating agent is in the range of 0.5 to 5 mol with respect to 1 mol of the amic acid group in polyamic acid, and it is particularly preferable to be in the range of 1.0 mol to 4 mol. Further, the amount of the imidizing agent added is preferably in the range of 0.05 mol to 2 mol with respect to 1 mol of the amic acid group in the polyamic acid, and particularly preferably in the range of 0.2 mol to 1 mol.

When the dehydrating agent and the imidizing agent fall below the above range, chemical imidization is insufficient, cracks may be formed in the polyimide film to be produced, and mechanical strength of the film may also be lowered. In addition, if these addition amounts exceed the above range, imidization may proceed excessively rapidly, and in this case, it is difficult to cast in the form of a film, or the prepared polyimide film may exhibit brittle characteristics, which is not preferable. not.

<Composite imidization method>

In conjunction with the chemical imidization method described above, a complex imidization method in which a thermal imidization method is further performed can be used for the production of a polyimide film.

Specifically, the complex imidization method includes a chemical imidation process of adding a dehydrating agent and/or an imidizing agent to a precursor composition at a low temperature; And drying the precursor composition to form a gel film and heat-treating the gel film.

When performing the chemical imidization process, the type and amount of the dehydrating agent and the imidizing agent may be appropriately selected as described in the previous chemical imidization method.

In the process of forming the gel film, a precursor composition containing a dehydrating agent and/or an imidizing agent is cast in a film form on a support such as a glass plate, aluminum foil, endless stainless belt, or stainless drum, and then on the support. The precursor composition is dried at variable temperatures ranging from 50°C to 250°C, specifically 50°C to 200°C. In this process, chemical converting agents and/or imidizing agents can act as catalysts to rapidly convert the amic acid groups to imide groups.

In some cases, a process of stretching the gel film may be performed in order to control the thickness and size of the polyimide film obtained in the subsequent heat treatment process and to improve the orientation, and the stretching is performed in the machine transport direction (MD) and the machine transport direction. It may be performed in at least one of the lateral direction for (TD).

The gel film thus obtained is fixed to a tenter, and then heat-treated at a variable temperature in the range of 50°C to 800°C, specifically 150°C to 650°C to remove water, catalyst, residual solvent, etc. remaining in the gel film, By imidizing almost any remaining amic acid group, the polyimide film of the present invention can be obtained. In such a heat treatment process, a dehydrating agent and/or an imidizing agent acts as a catalyst, so that the amic acid group can be rapidly converted to an imide group, thereby realizing a high imidization rate.

In some cases, the polyimide film obtained as described above may be heated to a temperature of 400°C to 650°C for 5 seconds to 400 seconds to further harden the polyimide film, and may remain inside the obtained polyimide film. It can also be done under a given tension to relieve stress.

The polyimide film according to the present invention includes a thermally conductive filler, and the ratio of the average particle diameter of the thermally conductive filler to its thickness (=average particle diameter/thickness) comprises 0.3 to 0.5.

In the case of a polyimide film in which such a ratio is satisfied, a thermally conductive filler in the film can form a thermally conductive path that works optimally with respect to the thickness direction along with the polyimide polymer chain, and at the same time, a plurality of thermally conductive paths are formed with the polymer chain. It can be combined to form a network suitable for improving the thermal conductivity in the thickness direction. Based on these characteristics, the polyimide film of the present invention has a particularly excellent thermal conductivity in the thickness direction.

The polyimide film according to the present invention also includes a polyimide resin comprising a first polyimide resin and a second polyimide resin having a relatively high crystallinity.

Such a polyimide film may have a crystal structure that is advantageous for improving the thermal conductivity in the thickness direction, which works in combination with the above-described thermal conductivity filler and the advantage according to the ratio to the film thickness, thereby improving the thermal conductivity in the thickness direction of the film. It can be improved further.

Hereinafter, the operation and effects of the invention will be described in more detail through specific examples of the invention. However, these examples are only presented as examples of the invention, and the scope of the invention is not thereby determined.

<Example 1>

Preparation Example a: Preparation of first polyamic acid

After introducing nitrogen into a 500 ml reactor equipped with a stirrer and a nitrogen injection and discharge pipe while introducing 407.5 g of DMF and setting the temperature of the reactor to 25°C, 13.26 g of ODA and 21.48 g of PPD were added and completely dissolved. After confirmation, PMDA was added in 57.76 g portions, and a first polyamic acid having a solid content of 18.5 wt% and a viscosity at 23° C. of 250,000 to 300,000 cP was prepared.

Preparation Example b: Preparation of precursor composition

After setting the temperature of the reactor to 50° C., the first polya was prepared from a crude solution containing 5 parts by weight of aluminum oxide and DMF having an average particle diameter of 3 μm with respect to 100 parts by weight of the first polyamic acid solid (100 g) and DMF. The precursor composition was prepared by mixing with mixed acid and stirring for 1 hour while maintaining the temperature.

Production Example c: Preparation of polyimide film

The precursor composition was deaerated through a high-speed rotation of 1,500 rpm or more. Thereafter, the defoamed precursor composition was applied to the glass substrate using a spin coater. Then, under a nitrogen atmosphere and dried at a temperature of 120° C. for 30 minutes, a gel film was prepared, the gel film was heated to a rate of 2° C./min to 450° C., heat-treated at 450° C. for 60 minutes, and up to 30° C. Cooling at a rate of 2°C/min yielded a polyimide film. Thereafter, the polyimide film was peeled from the glass substrate by dipping in distilled water.

The prepared polyimide film contained 100 parts by weight of the first polyimide resin and 5 parts by weight of aluminum oxide, the thickness was 9 μm, and the ratio of the aluminum oxide D50 to the film thickness (D50/thickness) was 0.33.

For reference, the thickness of the polyimide film was measured by using an Anritsu electric film thickness tester.

<Example 2>

A polyimide film having a thickness of 7 μm and a ratio of 0.42 was prepared using the same method as in Example 1, except that the coating amount of the precursor composition was adjusted in Preparation Example c to change the thickness and ratio of the film.

<Example 3>

In Preparation Example b, aluminum oxide having an average particle diameter of 5 μm was used, and except that the coating amount of the precursor composition was adjusted in Production Example c, the thickness was 14 μm and the ratio was 0.36 using the same method as in Example 1. A polyimide film was prepared.

<Example 4>

In Production Example b, aluminum oxide having an average particle diameter of 5 μm was used, and except that the coating amount of the precursor composition was adjusted in Production Example c, the thickness was 12 μm and the ratio was 0.42 using the same method as in Example 1. A polyimide film was prepared.

<Example 5>

In Production Example b, aluminum oxide having an average particle diameter of 16 μm was used, and except that the coating amount of the precursor composition was adjusted in Production Example c, the thickness was 50 μm and the ratio was 0.32 using the same method as in Example 1. A polyimide film was prepared.

<Example 6>

Aluminum oxide having an average particle diameter of 16 μm was used in Production Example b, and the thickness was 45 μm and the ratio was 0.36, using the same method as in Example 1, except that the coating amount of the precursor composition was adjusted in Production Example c. A polyimide film was prepared.

<Example 7>

Production Example a': Preparation of first polyamic acid

After introducing nitrogen into a 500 ml reactor equipped with a stirrer and a nitrogen injection and discharge pipe while introducing 407.5 g of DMF and setting the temperature of the reactor to 25°C, 13.26 g of ODA and 21.48 g of PPD were added and completely dissolved. After confirmation, PMDA was added in 57.76 g portions, and a first polyamic acid having a solid content of 18.5 wt% and a viscosity at 23° C. of 250,000 to 300,000 cP was prepared.

Production Example b': Preparation of second polyamic acid

While introducing nitrogen into a 500 ml reactor equipped with a stirrer and a nitrogen injection/discharge tube, 425 g of DMF was added, the temperature of the reactor was set to 30° C., and 37.38 g of TPE-R and 37.62 g of BPDA were completely dissolved. Was confirmed. After heating the temperature to 40° C. under a nitrogen atmosphere and stirring was continued for 120 minutes, a second polyamic acid solution having a solid content of 15% by weight and a viscosity at 23° C. of 130,000 to 150,000 cP was prepared.

Preparation Example c': Preparation of precursor composition

After setting the temperature of the reactor to 50°C, 100 g of the first polyamic acid and 7.5 g of the second polyamic acid were mixed to prepare a polyamic acid mixed solution.

In the polyamic acid mixture solution, a crude solution (9.73 g) containing 5 parts by weight of aluminum oxide and DMF having an average particle diameter of 3 µm with respect to 100 parts by weight of solid content (100 g) is mixed with the polyamic acid mixture solution, and the temperature is maintained. While stirring for 1 hour to prepare a precursor composition.

Production Example d': Preparation of polyimide film

The precursor composition was deaerated through a high-speed rotation of 1,500 rpm or more. Thereafter, the defoamed precursor composition was applied to the glass substrate using a spin coater. Then, under a nitrogen atmosphere and dried at a temperature of 120° C. for 30 minutes, a gel film was prepared, the gel film was heated to a rate of 2° C./min to 450° C., heat-treated at 450° C. for 60 minutes, and up to 30° C. Cooling at a rate of 2°C/min yielded a polyimide film. Thereafter, the polyimide film was peeled from the glass substrate by dipping in distilled water.

The prepared polyimide film contains 100 parts by weight of a first polyimide resin, 7.5 parts by weight of a second polyimide resin, and 5 parts by weight of aluminum oxide, and has a thickness of 9 μm, and the ratio of aluminum oxide D50 to film thickness (D50/ Film) was 0.33.

<Comparative Example 1>

A polyimide film having a thickness of 15 μm and a ratio of 0.2 was prepared using the same method as in Example 1, except that the coating amount of the precursor composition was adjusted in Preparation Example c.

<Comparative Example 2>

In Example b, the weight part of aluminum oxide was changed as shown in Table 1, and except that the coating amount of the precursor composition was adjusted in Preparation Example c, the thickness was 25 μm and the ratio was 0.12 using the same method as in Example 1. A polyimide film was prepared.

<Comparative Example 3>

In Production Example b, aluminum oxide having an average particle diameter of 5 μm was used, and except that the coating amount of the precursor composition was adjusted in Production Example c, the thickness was 25 μm and the ratio was 0.2 using the same method as in Example 1. A polyimide film was prepared.

<Comparative Example 4>

The same method as in Example 1 was used except that aluminum oxide having an average particle diameter of 5 μm in Preparation Example b was used, and the weight part of aluminum oxide was changed as shown in Table 1, and the coating amount of the precursor composition was adjusted in Preparation Example c. A polyimide film having a thickness of 30 µm and a ratio of 0.17 was produced.

<Comparative Example 5>

Aluminum oxide having an average particle diameter of 16 µm was used in Production Example b, and the thickness was 70 µm and the ratio was 0.23, using the same method as in Example 1, except that the coating amount of the precursor composition was adjusted in Production Example c. A polyimide film was prepared.

<Comparative Example 6>

The same method as in Example 1 was used except that aluminum oxide having an average particle diameter of 16 µm was used in Production Example b, and the weight part of aluminum oxide was changed as shown in Table 1, and the coating amount of the precursor composition was adjusted in Production Example c. A polyimide film having a thickness of 85 μm and a ratio of 0.19 was prepared.

<Comparative Example 7>

A polyimide film having a thickness of 9 μm and a ratio of 0.56 was prepared in the same manner as in Example 1, except that aluminum oxide having an average particle diameter of 5 μm was used in Production Example b.

<Comparative Example 8>

In Production Example b, aluminum oxide having an average particle diameter of 16 μm was used, and except that the coating amount of the precursor composition was adjusted in Production Example c, the thickness was 25 μm and the ratio was 0.64 using the same method as in Example 1. A polyimide film was prepared.

<Comparative Example 9>

A polyimide film having a thickness of 9 µm and a ratio of 0.33 was prepared using the same method as in Example 1, except that the weight part of aluminum oxide in Production Example b was changed as shown in Table 1.

<Comparative Example 10>

In Production Example b, aluminum oxide having an average particle diameter of 5 μm was used, and the weight portion of aluminum oxide was changed as shown in Table 1, and the coating thickness of the precursor composition was controlled in Production Example c to change the film thickness and proportion as shown in Table 1. Except for that, a polyimide film having a thickness of 12 μm and a ratio of 0.42 was prepared using the same method as in Example 1.

Aluminum oxide D50
(㎛) Aluminum oxide content
(Parts by weight) PI film thickness
(㎛) ratio
(Aluminum oxide D50/
PI film thickness) Example 1 3 5 9 0.33 Example 2 3 5 7 0.42 Example 3 5 5 14 0.36 Example 4 5 5 12 0.42 Example 5 16 5 50 0.32 Example 6 16 5 45 0.36 Example 7 3 5 9 0.33 Comparative Example 1 3 5 15 0.20 Comparative Example 2 3 10 25 0.12 Comparative Example 3 5 5 25 0.20 Comparative Example 4 5 10 30 0.17 Comparative Example 5 16 5 70 0.23 Comparative Example 6 16 10 85 0.19 Comparative Example 7 5 5 9 0.56 Comparative Example 8 16 5 25 0.64 Comparative Example 9 3 One 9 0.33 Comparative Example 10 5 12 12 0.42

<Experimental Example 1: Physical property test of polyimide film>

The physical properties of the polyimide films prepared in Examples 1 to 7 and Comparative Examples 1 to 10 were tested in the following manner, and the results are shown in Table 2.

(1) Evaluation of thermal conductivity: the thermal diffusivity in the thickness direction of the polyimide film was measured by a laser flash method using a thermal diffusivity measuring equipment (model name LFA 447, Netsch), and the density (weight/ Volume) and specific heat (specific heat measurement using DSC) to calculate the thermal conductivity.

(2) Modulus

Modulus was measured using the Instron 5564 model, by the method set forth in ASTM D882.

(3) Elongation

Elongation was measured by the method set forth in ASTM D1708.

Thickness direction thermal conductivity
(W/mK) Modulus
(GPa) Elongation
(%) Example 1 0.535 5.5 65 Example 2 0.745 7.2 60 Example 3 0.618 5.7 59 Example 4 0.756 7.1 54 Example 5 0.541 5.1 57 Example 6 0.621 5.8 51 Example 7 0.726 6.9 48 Comparative Example 1 0.251 2.9 70 Comparative Example 2 0.189 2.7 62 Comparative Example 3 0.279 3.0 68 Comparative Example 4 0.231 2.8 72 Comparative Example 5 0.246 3.2 62 Comparative Example 6 0.215 2.7 66 Comparative Example 7 0.923 3.7 30 Comparative Example 8 1.112 3.4 26 Comparative Example 9 0.212 2.6 74 Comparative Example 10 0.245 3.1 27

It can be seen that the polyimide film according to the embodiment has not only a high thermal conductivity in the thickness direction, but also a desirable level of mechanical properties such as modulus and elongation.

Comparative Examples 1 to 6 in which the ratio of the thermal conductive filler D50 to the thickness of the film is outside the scope of the present invention shows a significantly lower level than the examples, and the ratio acts decisively to improve the thermal conductivity in the thickness direction. Can be seen.

In addition, Comparative Examples 7, 8 is a case where the ratio has a large value outside the scope of the present invention, it can be confirmed that the modulus and elongation is greatly reduced.

From these results, it can be understood that the above ratios fall within the scope of the present invention, which plays a major role in achieving the desired thermal conductivity and mechanical properties in the thickness direction.

On the other hand, in Comparative Examples 9 and 10, although the above ratio was satisfied, when a small or excessive amount of thermally conductive filler was used, negative results were obtained, such as slight thermal conductivity in the thickness direction or a significant drop in modulus and elongation. . These results suggest that it is important to be used with caution in the content range of the present invention of thermally conductive fillers.

<Experimental Example 2: Crystallinity test of polyimide film>

For the polyimide film prepared in Example 7, crystallinity was analyzed using XRD (Rigaku Corporation, Ultima IV).

At this time, the crystallinity was calculated by the following equation (1), and the results are shown in Table 3 below.

(1)

(One)

In the equation (1), X _c is the crystallinity (%),

I _a is the area of amorphous scattering,

I _c is the area of crystalline scattering peaks.

Crystallinity
(%) Example 7 60

As shown in Table 3, Example 7 comprising the first polyimide resin and the second polyimide resin simultaneously exhibited a very high crystallinity, and when referring to the results of Table 2 above, the high crystallinity of the thickness direction It can be seen that it has a positive effect on improving the thermal conductivity.

Although described above with reference to embodiments of the present invention, those of ordinary skill in the art to which the present invention pertains will be able to make various applications and modifications within the scope of the present invention based on the above.

Claims (14)

A polyimide film comprising a polyimide resin and a thermally conductive filler,
The ratio of the average particle diameter of the thermally conductive filler to the thickness of the polyimide film (= average particle diameter/thickness) is 0.3 to 0.5,
The polyimide film whose thermal conductivity in the thickness direction of the said polyimide film is 0.5 W/m*K or more, and a modulus is 5.0 GPa or more. According to claim 1,
The polyimide film having an average particle diameter (D50) of the thermally conductive filler is 2.5 to 20 μm. According to claim 1,
The polyimide film, the thickness of the polyimide film is 5 to 60 ㎛. According to claim 1,
A polyimide film comprising 2 to 9 parts by weight of a thermally conductive filler relative to 100 parts by weight of the polyimide resin. According to claim 1,
The thermally conductive filler is one or two or more mixtures selected from the group consisting of aluminum oxide (Al ₂ O ₃ ), boron nitride (BN), aluminum nitride (AlN), silicon carbide (SiC), and magnesium oxide (MgO). Phosphorus, polyimide film. The method of claim 5,
The thermally conductive filler is aluminum oxide, polyimide film. According to claim 1,
The polyimide film has a crystallinity of 40% to 80% and an elongation of 30% or more. According to claim 1,
The polyimide resin,
100 parts by weight of the first polyimide resin; And
2 to 8 parts by weight of a second polyimide resin,
The second polyimide resin has a relatively high crystallinity compared to the first polyimide resin, a polyimide film. The method of claim 8,
The first polyimide resin is prepared by imidizing a first polyamic acid prepared by polymerizing a first diamine monomer and a first dianhydride monomer,
The second polyimide resin is a polyimide film produced by imidizing a second polyamic acid prepared by polymerization of a second diamine monomer and a second dianhydride monomer. The method of claim 9,
The first dianhydride monomer may be one or more selected from the group consisting of pyromellitic dianhydride (PMDA), oxydiphthalan hydride (ODPA), and benzophenone tetracarboxylic dianhydride (BTDA). Including,
The first diamine monomer is 1,4-diaminobenzene (or paraphenylenediamine, PDA, PPD), 1,3-diaminobenzene (MPD), 2,4-diaminotoluene, 2,6-diamino Toluene, 3,5-diaminobenzoic acid (DABA), 4,4'-diaminodiphenyl ether (or oxydianiline, ODA), 3,4'-diaminodiphenyl ether, 4,4'- Diaminodiphenylmethane (or 4,4'-methylenedianiline, MDA), 3,3'-dimethylbenzidine (or o-tolidine, o-tolidine), 2,2'-dimethylbenzidine (or m-tol A polyimide film comprising at least one member selected from the group consisting of lydine, m-tolidine) and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP). The method of claim 9,
The second dianhydride monomer is 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA),
The second diamine monomer is 1,3-bis(4-aminophenoxy)benzene (TPE-R) and/or 1,4-bis(3-aminophenoxy)benzene (TPE-Q), a polyimide film . A method for manufacturing the polyimide film according to claim 1,
Polymerizing the polyamic acid;
Preparing a precursor composition by mixing the polyamic acid and a thermally conductive filler; And
The method comprising the step of obtaining a polyimide film by imidizing the precursor composition. The method of claim 12,
The step of polymerizing the polyamic acid,
Polymerizing the first dianhydride monomer and the first diamine monomer in a first organic solvent to produce a first polyamic acid; And
And polymerizing the second dianhydride monomer and the second diamine monomer in the second organic solvent to produce a second polyamic acid,
The polyamic acid is a manufacturing method comprising the first polyamic acid and the second polyamic acid. An electronic device comprising the polyimide film according to claim 1.