KR102164474B1 - 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, and having a ratio of the average particle diameter of the thermally conductive filler to the thickness of the polyimide film (= average particle diameter/thickness) of 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 with improved thermal conductivity and a method of manufacturing the same.

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

Meanwhile, according to the trend of advanced information, electrical and electronic devices or parts that accumulate a large amount of information and process and transmit such information at high speed are being actively developed, and polyimide is based on its excellent physical properties. It is widely used as a protective film.

In recent years, in order to prevent deterioration of the performance of electric/electronic devices or parts due to heat generation of electronic devices, studies on polyimide films having effective heat dissipation properties have been actively conducted.

However, since polyimide occupies most of the amorphous portion in terms of the crystal structure, although there are some differences depending on other configurations, the thermal conductivity is not generally high. In particular, since the film-type polyimide has low thermal conductivity in the thickness direction, various studies are being 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 prepare a polyimide film with improved thermal conductivity in the thickness direction by adding a thermally conductive material such as graphene or metal having excellent thermal conductivity to a polyamic acid solution, which is a precursor of polyimide, and forming a film. 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 the thermally conductive material in a fairly high content. In this case, the manufactured polyimide film is brittle. ), and at the same time, mechanical properties such as modulus may be deteriorated.

Moreover, since these thermally conductive materials are not well dispersed in the 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 and are thus formed on the polyimide film. It may cause appearance defects such as projections.

Therefore, there is a high need for a technology that can fundamentally solve this problem.

It is an object of the present invention to provide a polyimide film in which the thermal conductivity in the thickness direction is remarkably improved even when the 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 can prevent appearance defects due to the thermally conductive filler while having excellent modulus. 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 value calculated through it 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 to provide 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,

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

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

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

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

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

Therefore, the configuration of the embodiments described in the present specification 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 application It should be understood that examples may exist.

In the present specification, expressions in the singular include plural expressions unless the context clearly indicates otherwise. In the present specification, terms such as "comprise", "include" or "have" are intended to designate the presence of implemented features, numbers, steps, components, or a combination thereof, and one or more other features or It is to be understood that the possibility of the presence or addition of numbers, steps, elements, or combinations thereof is not preliminarily excluded.

In the present specification, "dianhydride (dianhydride)" is intended to include its precursor or derivative, which may not be technically dianhydride, but nevertheless react with diamine to form polyamic acid. And this polyamic acid can be converted back to polyimide.

In the present specification "diamine" is intended to include precursors or derivatives thereof, which may not technically be diamines, but nevertheless will react with dianhydride to form polyamic acid, and this 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 a range, a preferred range, or a preferred upper and lower preferred value, any pair of any upper range limits, or It is to be understood that the preferred values and any lower range limits or all ranges that may be formed with preferred values are specifically disclosed. When a range of numerical values is referred to herein, unless otherwise stated, and unless there is a limiting term such as greater than or less than, the range is intended to include the end value and all integers and fractions within that range. It is intended that the scope of the invention is not limited to the specific values recited when defining the 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 (= average particle diameter/thickness) of the thermally conductive filler to the thickness thereof is 0.3 to 0.5, specifically 0.3 to It may be 0.48, more specifically 0.31 to 0.45, particularly specifically 0.32 to 0.42.

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

The polyimide film of the present invention may exist in a state in which the thermally conductive filler is dispersed throughout the polyimide resin, and may have a composite structure in which the thermally conductive filler and the polyimide resin act as a filler and a matrix, respectively.

In such a composite structure, the thermally conductive filler may act as a thermally conductive medium to transfer heat applied to the polyimide film inside the film. However, even if the polyimide film includes a thermally conductive filler, the thermal conductivity in the planar direction generally tends to be improved, and the thermal conductivity in the thickness direction may be insignificant. This is considered to be because, typically, since the polyimide polymer chain is oriented in the plane direction, heat is easily conducted along the polymer chain in the plane direction, whereas conduction between the polymer chain and the chain is relatively difficult. do.

On the other hand, when the above ratio according to the present invention is satisfied, the thermal conductivity of the polyimide film in the thickness direction can be remarkably improved. This is because the thermally conductive filler satisfying the above ratio forms a heat conduction path that optimally acts in the thickness direction in relation to the polymer chain in the polyimide film containing the same, and at the same time, a plurality of thermal conduction paths are combined to provide thermal conductivity in the thickness direction. It is presumed to be due to the formation of a kind of network that works favorably for improvement.

This will be clearly demonstrated in the'Specific Contents for Carrying out the Invention', but if the ratio is less than the range limited by the present invention, the thermal conductivity in the thickness direction is desired even if an excessive amount of the thermally conductive filler is included. It may not be improved to the level, and on the contrary, if it exceeds the above range, the modulus may be lowered and there is a problem in film forming property, which is not preferable.

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

In one specific example, the thermally conductive filler is 1 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). It may be a species or a mixture of two or more, and specifically, it may be 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.

If the average particle diameter of the thermally conductive filler is less than the range defined in the present invention, the specific surface area is excessively increased based on the entire thermally conductive filler, which may cause aggregation of particles, which is not preferable. On the contrary, in the case of particles having a relatively large size beyond the above range, the number of particles settled by gravity in the polyamic acid solution may increase, which means that the particles forming the thermally conductive filler are part of the polyimide film. It is not preferable because it is biased to exist, which may cause appearance defects 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, in particular 5 to 9 parts by weight, based on 100 parts by weight of the polyimide resin, a thermally conductive filler. have.

A polyimide film that is less than the above range and contains a thermally conductive filler is difficult to include a heat conduction path sufficient to form the'network that can act advantageously in the thickness direction' described above. Degrees may not be achieved. On the contrary, the polyimide film containing a thermally conductive filler beyond the above range exhibits insignificant improvement in thermal conductivity in the thickness direction compared to the case falling within the above range, whereas a decrease in modulus may occur, and is caused by an excessively present thermally conductive filler. Appearance defects may occur.

The thickness of the polyimide film may be selected within a range that can satisfy the ratio as described above, but if it is excessively thin, it is difficult to form a polyamic acid solution, which is a precursor of the film. It is not preferable because the thermal conductivity in the thickness direction may decrease.

Accordingly, the present invention provides a preferred thickness of the polyimide film, and specifically, the thickness may be 5 to 60 µm, specifically 7 to 55 µm, 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 a first polyimide resin; And

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

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

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

A typical polyimide resin is an amorphous polymer, and a polyimide film prepared therefrom can 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 contain a crystalline portion, compared to a conventional polyimide film. It can have a high degree of crystallinity.

For reference, it is not easy to separate and measure the crystallinity of polyimide resins of different compositions that make up the polyimide film and to 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 higher crystallinity than the first polyimide resin. have.

The crystallinity of the polyimide resin is greatly influenced by the composition of the monomer constituting it, but the crystallinity may vary depending on the polymerization method other than the composition. For example, in the process of polymerizing the precursor polyamic acid during the manufacturing process of the polyimide resin, some molecular structures may be arranged in a regular state depending on the viscosity, and a difference may occur in the degree to which crystals are formed.

In summary, in the present invention, the degree of crystallinity of the polyimide film may vary depending on the content of the second polyimide resin in the polyimide film, and also, depending on the viscosity of the second polyamic acid, which is a precursor of the second polyimide resin, The crystallinity of the polyimide film produced from may vary.

At least a portion of the second polyimide resin may form a crystal, and the crystal and the thermally conductive filler may have a structure in which a thermal conduction path is formed in a film in a thickness direction.

In the present invention, the crystal is a structure in which some of the polyimide chains included in the second polyimide resin are regularly arranged, for example, in a radially regular arrangement from the central nucleus of the crystal in a two-dimensional or three-dimensional direction. A structure in which polyimide chains are regularly arranged in a growing, crystal shape in a circular or spherical shape may be exemplified, but the specific shape or shape is not limited.

Such crystals may exist in a myriad number of numbers in the polyimide film, and may include some amorphous portions between the crystal portions and the crystal portions, and independently an amorphous portion and a crystal portion may exist separately.

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

However, despite the above advantages, it is not preferable that the second polyimide resin is unconditionally included in a large amount 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 reinforced. This is because too many crystals are present, so that the elongation of the polyimide film may be rapidly decreased.

That is, it is important that the polyimide film contains an appropriate amount of the first polyimide resin and the second polyimide resin so that the mechanical properties and 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, and 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 prepared 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 is at least one selected from the group consisting of pyromellitic dianhydride (PMDA), oxydiphthalic anhydride (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 Ridine, m-tolidine) and 2,2-bis [4-(4-aminophenoxy) phenyl] propane (BAPP) may contain at least one selected from the group consisting of.

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, 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 of manufacturing a polyimide film.

The manufacturing method of the present invention,

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

Polymerizing a second dianhydride monomer and a second diamine monomer in a second organic solvent to prepare 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 Phenolic solvents such as phenol, N-methyl-pyrrolidone (NMP), gamma butyrolactone (GBL), and Diglyme, and these may be used alone or in combination of two or more.

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

(1) a method of polymerizing by putting the entire amount of the diamine monomer in an organic solvent, and then adding a dianhydride monomer so as to be substantially equimolar with the diamine monomer;

(2) a method of polymerizing by putting the entire amount of the dianhydride monomer in an organic solvent, and then adding the diamine monomer so as to be substantially equimolar with the dianhydride monomer;

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

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

(5) In an organic solvent, some diamine monomer components and some dianhydride monomer components are reacted so that any one is in excess to form a first polymer, and some diamine monomer components and some dianhydride monomer components in another organic solvent A method of forming a second polymer by reacting so that any one of the polymers is in excess, mixing the first and second polymers, and completing the polymerization. In this case, when the first polymer is formed, the diamine monomer component is excessive. , When the dianhydride monomer component is excessive in the second polymer, and the dianhydride monomer component is excessive in the first polymer, the diamine monomer component is excessive in the second polymer, and the first and second polymers are mixed. And a method of polymerization by making all the diamine monomer components and dianhydride monomer components used in these reactions substantially equimolar.

However, the above method is an example to aid in the implementation of the present invention, and the scope of the present invention is not limited thereto, and of course, any known method may be used.

Meanwhile, the step of obtaining the polyimide film may include forming a film of the precursor composition on a support and drying to prepare a gel film, and then imidizing the gel film to form a polyimide film.

Specific methods of such imidization include thermal imidation, chemical imidization, or a complex imidization method in which the thermal imidization and chemical imidization are used in combination, and the following non-limiting examples It will be described in more detail through.

<Thermal imidization method>

The thermal imidation method is a method of inducing an imidation reaction with a heat source such as hot air or an infrared dryer, excluding a chemical catalyst,

Drying the precursor composition to form a gel film; And

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, an aluminum foil, an endless stainless belt, or a stainless drum, and then the precursor composition on the support is 50°C to 250°C, Specifically, it may be dried 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 adjust the thickness and size of the polyimide film obtained in the subsequent heat treatment process and improve orientation, and the stretching may be performed in the machine transfer direction (MD) and the machine transfer direction. It may be performed in at least one of the transverse directions 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 and residual solvent remaining in the gel film, and Almost all of the amic acid groups can be imidized to obtain the polyimide film of the present invention.

In some cases, the polyimide film may be further cured by heating and finishing the polyimide film obtained as described above at a temperature of 400° C. to 650° C. for 5 to 400 seconds, and the interior may remain in the obtained polyimide film. It is also possible to do this under a certain tension to relieve the stress.

<Chemical imidization method>

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

Here, the "dehydrating agent" means a substance that promotes a ring closure reaction through a dehydration action on polyamic acid, and non-limiting examples thereof include an aliphatic acid anhydride, an aromatic acid anhydride, N,N' -Dialkylcarbodiimide, halogenated lower aliphatic, halogenated lower patty acid anhydride, aryl phosphonic dihalides, and thionyl halides. Among these, aliphatic acid anhydride may be preferable from the viewpoint of availability and cost, and non-limiting examples thereof include acetic anhydride (AA), propion acid anhydride, and lactic acid anhydride. And the like, and these may be used alone or in combination of two or more.

In addition, the term "imidating agent" refers to a substance having an effect of promoting a ring closure reaction with respect to polyamic acid, and is an imine component such as an aliphatic tertiary amine, an aromatic tertiary amine, and a heterocyclic tertiary amine. I can. Among these, a heterocyclic tertiary amine may be preferable from the viewpoint of reactivity as a catalyst. Non-limiting examples of the heterocyclic tertiary amine include quinoline, isoquinoline, β-picoline (BP), pyridine, and the like, and these may be used alone or in combination of two or more.

The amount of the dehydrating agent added is preferably in the range of 0.5 to 5 moles, and particularly preferably in the range of 1.0 to 4 moles per 1 mole of the amic acid group in the polyamic acid. In addition, the amount of the imidizing agent added is preferably within the range of 0.05 to 2 moles, and particularly preferably within the range of 0.2 to 1 mole, per 1 mole of the amic acid group in the polyamic acid.

If the dehydrating agent and the imidizing agent are less than the above ranges, chemical imidization is insufficient, cracks may be formed in the polyimide film to be produced, and the mechanical strength of the film may be reduced. In addition, if the amount of these additions exceeds the above range, imidization may proceed excessively quickly, and in this case, it is difficult to cast into a film or the manufactured polyimide film may exhibit brittle characteristics, which is not preferable. not.

<Complex imidization method>

In connection with the above chemical imidization method, a composite imidization method in which a thermal imidization method is additionally performed can be used for the production of a polyimide film.

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

When performing the chemical imidization process, the types and amounts of the dehydrating agent and the imidizing agent may be appropriately selected as described in the above 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, an aluminum foil, an endless stainless belt, or a 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, a chemical converting agent and/or an imidizing agent may act as a catalyst to rapidly convert an amic acid group into an imide group.

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

The gel film thus obtained is fixed to a tenter and then heat-treated at a variable temperature ranging from 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 all remaining amic acid groups, the polyimide film of the present invention can be obtained. Even in such a heat treatment process, a dehydrating agent and/or an imidizing agent may act as a catalyst to rapidly convert an amic acid group into an imide group, thereby enabling a high imidation rate.

In some cases, the polyimide film may be further cured by heating and finishing the polyimide film obtained as described above at a temperature of 400° C. to 650° C. for 5 to 400 seconds, and the interior may remain in the obtained polyimide film. It is also possible to do this under a certain tension to relieve the 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 the thickness thereof (= average particle diameter/thickness) is 0.3 to 0.5.

In the case of a polyimide film that satisfies this ratio, the thermally conductive filler in the film can form a heat conduction path that works optimally in the thickness direction with the polyimide polymer chain, and at the same time, a plurality of heat conduction paths Combined, it is possible to form a network suitable for improving the thermal conductivity in the thickness direction. Based on these features, the polyimide film of the present invention has an advantage of particularly excellent thermal conductivity in the thickness direction.

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

Such a polyimide film may have a crystal structure that is advantageous for improving the thermal conductivity in the thickness direction, which acts in combination with the aforementioned thermal conductive 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 further improved.

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

<Example 1>

Preparation Example a: Preparation of the first polyamic acid

407.5 g of DMF was added while injecting nitrogen into a 500 ml reactor equipped with a stirrer and a nitrogen injection/discharging pipe. After setting the temperature of the reactor to 25° C., 13.26 g of ODA and 21.48 g of PPD were added. After confirmation, PMDA was divided into 57.76 g, 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., a crude liquid (9.73 g) containing 5 parts by weight of aluminum oxide and DMF having an average particle diameter of 3 μm per 100 parts by weight (100 g) of the first polyamic acid solid content was added to the first polyamic acid. Mixing with mixed acid and stirring for 1 hour while maintaining the temperature to prepare a precursor composition.

Preparation c: Preparation of polyimide film

Air bubbles were removed by rotating the precursor composition at a high speed of 1,500 rpm or more. Thereafter, the degassed precursor composition was applied to the glass substrate using a spin coater. Thereafter, a gel film was prepared by drying in a nitrogen atmosphere and at a temperature of 120° C. for 30 minutes, and the gel film was heated to 450° C. at a rate of 2° C./min, heat-treated at 450° C. for 60 minutes, and then until 30° C. It cooled at a rate of 2° C./min to obtain a polyimide film. Thereafter, the polyimide film was peeled off 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, had a thickness of 9 µm, and the ratio of aluminum oxide D50 to the film thickness (D50/thickness) was 0.33.

For reference, the thickness of the polyimide film was measured using an Anritsu's Electric Film thickness tester.

<Example 2>

In order to change the thickness and ratio of the film, 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 amount of the precursor composition was adjusted in Preparation Example c.

<Example 3>

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

<Example 4>

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

<Example 5>

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

<Example 6>

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

<Example 7>

Preparation Example a': Preparation of the first polyamic acid

407.5 g of DMF was added while injecting nitrogen into a 500 ml reactor equipped with a stirrer and a nitrogen injection/discharging pipe. After setting the temperature of the reactor to 25° C., 13.26 g of ODA and 21.48 g of PPD were added. After confirmation, PMDA was divided into 57.76 g, 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 the second polyamic acid

While injecting nitrogen into a 500 ml reactor equipped with a stirrer and a nitrogen injection/discharging pipe, 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 added to completely dissolve it. It was confirmed. After the stirring was continued for 120 minutes while heating by raising the temperature to 40°C in a nitrogen atmosphere, a second polyamic acid solution having a solid content of 15% by weight and a viscosity of 130,000 to 150,000 cP at 23°C was prepared.

Preparation Example c': Preparation of a 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 this polyamic acid mixture solution, a crude liquid (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 (100 g) of solid content was mixed with the polyamic acid mixture solution, and the temperature was maintained. While stirring for 1 hour to prepare a precursor composition.

Preparation Example d': Preparation of polyimide film

Air bubbles were removed by rotating the precursor composition at a high speed of 1,500 rpm or more. Thereafter, the degassed precursor composition was applied to the glass substrate using a spin coater. Thereafter, a gel film was prepared by drying in a nitrogen atmosphere and at a temperature of 120° C. for 30 minutes, and the gel film was heated to 450° C. at a rate of 2° C./min, heat-treated at 450° C. for 60 minutes, and then until 30° C. It cooled at a rate of 2° C./min to obtain a polyimide film. Thereafter, the polyimide film was peeled off 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, has a thickness of 9 μm, and the ratio of aluminum oxide D50 to the 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 amount of the precursor composition was adjusted in Preparation Example c.

<Comparative Example 2>

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

<Comparative Example 3>

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

<Comparative Example 4>

In Preparation Example b, aluminum oxide having an average particle diameter of 5 µm was used, and the weight part of the aluminum oxide was changed as shown in Table 1, and the same method as in Example 1 was used, except that 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 prepared by using.

<Comparative Example 5>

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

<Comparative Example 6>

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

<Comparative Example 7>

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

<Comparative Example 8>

Using the same method as in Example 1, except that aluminum oxide having an average particle diameter of 16 µm was used in Preparation Example b, and the coating amount of the precursor composition was adjusted in Preparation Example c, the thickness was 25 µm and the ratio was 0.64. 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 Preparation Example b was changed as shown in Table 1.

<Comparative Example 10>

In Preparation Example b, aluminum oxide having an average particle diameter of 5 µm was used, and the weight part of the aluminum oxide was changed as shown in Table 1, and the film thickness and ratio were changed as shown in Table 1 by controlling the coating amount of the precursor composition in Preparation Example c. Except for this, 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
(Part 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>

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

(1) Thermal conductivity evaluation: The thermal diffusivity in the thickness direction of the polyimide film was measured by the laser flash method using a thermal diffusivity measuring equipment (model name LFA 447, Netsch), and the density (weight/ The thermal conductivity was calculated by multiplying by volume) and specific heat (a measure of specific heat using DSC).

(2) Modulus

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

(3) elongation

The elongation was measured by the method presented in ASTM D1708.

Thermal conductivity in thickness direction
(W/m·K) 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 not only has remarkably high thermal conductivity in the thickness direction, but also has desirable 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 out of the scope of the present invention, showed a significantly lower level compared to the examples, and the ratio acts decisively on the improvement of the thermal conductivity in the thickness direction. Can be seen.

In addition, Comparative Examples 7 and 8 are cases in which the ratio has a large value outside the scope of the present invention, and it can be seen that the modulus and elongation are significantly reduced.

From these results, it can be understood that the ratio falling within the scope of the present invention plays a major role in achieving both thermal conductivity in the thickness direction and mechanical properties at a desirable level.

On the other hand, in Comparative Examples 9 and 10, even though the above ratio was satisfied, a small amount or an excessive amount of the thermally conductive filler was used, and negative results were derived such that the thermal conductivity in the thickness direction was insignificant or the modulus and elongation were significantly reduced. . These results suggest that it is important to carefully use the thermally conductive filler in the content range of the present invention.

<Experimental Example 2: Crystallinity test of polyimide film>

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

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

(1)

(One)

In Equation (1), X _c is the degree of 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 including the first polyimide resin and the second polyimide resin at the same time exhibited a very high degree of crystallinity, and when referring to the results of Table 2 above, the high degree of crystallinity in the thickness direction It can be seen that it has a positive effect on the improvement of thermal conductivity.

Although the above description has been made with reference to the embodiments of the present invention, a person of ordinary skill in the field to which the present invention belongs will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

Claims (14)

As 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 thermal conductivity in the thickness direction of the polyimide film is 0.5 W/m·K or more, and the modulus is 5.0 GPa or more,
The polyimide resin,
100 parts by weight of a first polyimide resin; And
Including 2 to 8 parts by weight of a second polyimide resin,
The second polyimide resin is a polyimide film having a relatively high crystallinity compared to the first polyimide resin. The method of claim 1,
The average particle diameter (D50) of the thermally conductive filler is 2.5 to 20 μm, a polyimide film. The method of claim 1,
The polyimide film has a thickness of 5 to 60 μm. The method of claim 1,
A polyimide film comprising 2 to 9 parts by weight of a thermally conductive filler based on 100 parts by weight of the polyimide resin. The method of claim 1,
The thermally conductive filler is one or a mixture of two or more 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, a polyimide film. The method of claim 1,
The polyimide film has a crystallinity of 40% to 80% and an elongation of 30% or more. delete The method of claim 1,
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 prepared by imidizing a second polyamic acid prepared by polymerization of a second diamine monomer and a second dianhydride monomer, a polyimide film. The method of claim 9,
The first dianhydride monomer is at least one selected from the group consisting of pyromellitic dianhydride (PMDA), oxydiphthalic anhydride (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 Lidin, m-tolidine) and 2,2-bis [4- (4-aminophenoxy) phenyl] propane (BAPP) containing at least one selected from the group consisting of, a polyimide film. 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 . As a method for producing the polyimide film according to claim 1,
Polymerizing polyamic acid;
Preparing a precursor composition by mixing the polyamic acid and a thermally conductive filler; And
A method comprising the step of imidizing the precursor composition to obtain a polyimide film. The method of claim 12,
The step of polymerizing the polyamic acid,
Polymerizing a first dianhydride monomer and a first diamine monomer in a first organic solvent to prepare a first polyamic acid; And
Polymerizing a second dianhydride monomer and a second diamine monomer in a second organic solvent to prepare a second polyamic acid,
The polyamic acid comprises the first polyamic acid and the second polyamic acid. An electronic device comprising the polyimide film according to claim 1.