JP2024505263A - High thickness multilayer polyimide film and its manufacturing method - Google Patents

Abstract

The present invention includes two or more polyimide unit films having a thickness of 50 μm or more and including a polyimide core layer and an adhesive layer laminated on one or both sides of the polyimide core layer, and the two or more polyimide units A multilayer polyimide film and a method for producing the same are disclosed, in which the films are adhesively laminated via the adhesive layer.

Description

The present invention relates to a high-thickness polyimide unit film, a multilayer polyimide film containing the same, and a method for producing the same.

Recent electronic devices are becoming lighter, smaller, thinner, and more highly integrated, which causes them to generate a lot of heat. Such heat may shorten the life of the product or cause malfunctions or malfunctions. Therefore, thermal management for electronic equipment has emerged as an important concern.

Graphite sheets have higher thermal conductivity than metal sheets such as copper and aluminum, and are attracting attention as heat dissipation members for electronic devices. In particular, research is actively underway on high-thickness graphite sheets that are advantageous in terms of heat capacity compared to thin graphite sheets (for example, graphite sheets having a thickness of about 40 μm or less).

The graphite sheet can be manufactured by various methods, for example, by carbonizing and graphitizing a polymer film. In particular, polyimide film is attracting attention as a polymer film for producing graphite sheets due to its excellent mechanical, thermal, dimensional stability, and chemical stability.

In order to produce a high-thickness graphite sheet, the production of a high-thickness polyimide film (for example, a polyimide film with a thickness of about 100 μm or more) must be preceded by casting a polyamic acid solution and heat-treating the polyimide film. With the conventional method of manufacturing a film, it is difficult to uniformly cure the inside and outside, resulting in layer splitting, bubbles, etc., making it difficult to manufacture a high-thickness polyimide film. In addition, when manufacturing a high-thickness polyimide film by bonding two or more polyimide films using an adhesive, heat resistance problems of the adhesive layer may occur during the process where the polyimide film is exposed to high temperature heat due to carbonization and graphitization. There was a problem in that layer separation phenomenon and graphitization did not progress in the adhesive layer, making it impossible to manufacture a high-thickness graphite sheet.

Alternatively, double-sided tape can be used to laminate two or more thin graphite sheets to produce high-thickness graphite sheets; There was a problem of lowering conductivity.

Republic of Korea Patent Publication No. 2017-0049912

An object of the present invention is to provide a high-thickness polyimide unit film and a multilayer polyimide film containing the same.

Another object of the present invention is to provide a method for manufacturing multilayer polyimide films.

In order to achieve the above object, an embodiment of the present invention is such that the ratio of the slope of the plastic deformation zone to the slope of the elastic deformation zone (the slope of the plastic deformation zone/the slope of the elastic deformation zone) is 0.025 or less. ,
Provides polyimide films.
(However, the plastic deformation section corresponds to the section from the deformation rate (Elongation) of 30% to just before breakage in the stress-strain curve of the polyimide film, and the elastic deformation zone corresponds to the section from the deformation rate (Elongation) of 30% to just before breakage. (This corresponds to an area where the percentage is 3% or less.)

Another embodiment of the present invention includes a polyimide core layer containing the polyimide film, and an adhesive layer laminated on one or both sides of the polyimide core layer,
The adhesive layer contains an imide group,
The thickness is 50 μm or more,
Provides a polyimide unit film.

Still another embodiment of the present invention is produced by laminating two or more of the polyimide unit films,
A multilayer polyimide film is provided.

Still another embodiment of the present invention includes the step of forming two or more polyimide unit films each having an adhesive layer laminated and integrated on one or both surfaces of the polyimide core layer;
Laminating the two or more polyimide unit films so that they can be bonded together via the adhesive layer;
a step of thermocompression bonding the two or more laminated polyimide unit films,
The thickness of the polyimide unit film is 50 μm or more,
A method of manufacturing a multilayer polyimide film is provided.

The present invention has the effect of providing a high-thickness polyimide unit film, a multilayer polyimide film containing the same, and a method for producing the same.

1 is a stress-strain curve (SS-curve) of a polyimide film according to a manufacturing example of the present invention, and is a graph showing a plastic deformation section and an elastic deformation section. FIG. 1 is a schematic diagram of a multilayer polyimide film according to an embodiment of the present invention. FIG. 1 is a schematic diagram of a multilayer polyimide film according to an embodiment of the present invention. 1 is a photograph showing the plasticity results of polyimide films of Production Examples 1 and 2 of the present invention and Comparative Production Example 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments and examples of the present invention will be described in detail so that those having ordinary knowledge in the technical field to which the present invention pertains can easily implement them. However, the invention may be implemented in a variety of different forms and is not limited to the embodiments and examples described herein. Throughout this specification, when a part is said to "include" a certain component, this does not mean that it excludes other components, but can further include other components, unless there is a specific statement to the contrary. do.

In this specification, the singular expression includes the plural expression unless the context clearly indicates otherwise.

In interpreting the constituent elements, they shall be construed to include margins of error, even if not explicitly stated otherwise.

In this specification, "~" in "a to b" indicating a numerical range is defined as ≧a and ≦b.

In the polyimide film according to one aspect of the present invention, the ratio of the slope of the plastic deformation zone to the slope of the elastic deformation zone (slope of the plastic deformation zone/slope of the elastic deformation zone) may be 0.025 or less, preferably 0. It may be .023 or less.

The plastic deformation section corresponds to the section from elongation of 30% to just before breakage in the stress-strain curve (SS-curve) of the polyimide film shown in FIG. The section corresponds to the section where the deformation rate is 3% or less.

On the other hand, the ratio of the slope of the plastic deformation section to the slope of the elastic deformation section of the polyimide film (the slope of the plastic deformation section/the slope of the elastic deformation section) may be 0.01 or more.

In one embodiment, the slope of the plastic deformation section of the polyimide film may be 0.05 GPa or less.

On the other hand, the slope of the plastic deformation section of the polyimide film may be 0.020 GPa or more. The slope of the plastic deformation section of the polyimide film may be preferably 0.027 GPa or more, more preferably 0.030 GPa or more.

Moreover, the slope of the elastic deformation section of the polyimide film may be 2.1 GPa or more. The inclination of the elastic deformation section of the polyimide film may be preferably 2.11 GPa or more.

On the other hand, the slope of the elastic deformation section of the polyimide film may be 3.0 GPa or less.

If the ratio of the plastic deformation section to the elastic deformation section of the polyimide film and/or the slope of the plastic deformation section of the polyimide film exceeds or falls below the above range, sintering (graphitization) for producing a graphite sheet is not easy. .

In other words, a multilayer polyimide film produced by laminating polyimide unit films becomes extremely thick and cannot be easily fired (graphitized), making it difficult to manufacture graphite sheets. You need to use layers.

In order to facilitate firing, it is necessary to suppress the progress of imidization of the polyimide used as the core layer, and this can be achieved by adjusting the amount of heat during the production of the polyimide.

In one embodiment, the polyimide film may have a tensile strength of 200 MPa or less, preferably 195 MPa or less.

Moreover, the tensile strength of the polyimide film may be 170 MPa or more.

This is because as a result of adjusting the amount of heat to facilitate firing, the tensile strength of the polyimide film is affected and becomes lower.

Dianhydride monomers for producing the polyimide film of the present invention include pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3',4,4' -Biphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 2,3,3', 4-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 3,4 , 9,10-perylenetetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)propane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1 -Bis(3,4-dicarboxyphenyl)ethane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)ethane dianhydride, oxydiphthalic dianhydride Bis(3,4-dicarboxyphenyl)sulfone dianhydride, p-phenylene bis(trimellitic monoester anhydride), ethylene bis(trimellitic monoester anhydride), bisphenol A bis(trimellitic acid monoester anhydride) Mellitic acid monoester acid anhydride), derivatives thereof, or combinations thereof may be used, and the diamine monomers include 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4 , 4'-oxydianiline, 3,4'-oxydianiline, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(3 -aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenylpropane, 4,4'-methylenedianiline, 3,3 '-Methylene dianiline, benzidine, 3,3'-dichlorobenzidine, 4,4'-diaminodiphenylsulfide, 3,3'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenyl ether , 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 1,5-diaminonaphthalene, 4,4'-diaminodiphenyldiethylsilane, 4,4'-diaminodiphenylsilane, 4,4'-diaminodiphenyl Ethylphosphine oxide, 4,4'-diaminodiphenyl N-methylamine, 4,4'-diaminodiphenyl N-phenylamine, 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene, 1, 2-diaminobenzene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, or derivatives thereof, or combinations thereof can be used.

A polyimide unit film according to another aspect of the present invention includes a polyimide core layer containing the polyimide film, and an adhesive layer laminated on one or both sides of the polyimide core layer, the adhesive layer having an imide base. The thickness of the polyimide unit film may be 50 μm or more.

For example, the polyimide unit film may have a thickness of 50 μm to 500 μm, in another example, 100 μm to 300 μm, and in another example, 125 μm to 250 μm, but is not limited thereto.

In one embodiment, in the polyimide unit film, the ratio of the thickness of the polyimide core layer to the thickness of the adhesive layer may be 1:0.004 to 1:0.095.

That is, when the polyimide unit film has an adhesive layer laminated only on one side of the polyimide core layer, the ratio of the thickness of the polyimide core layer to the thickness of the adhesive layer is 1:0.004 to 1:0. It may be .095.

Further, when the polyimide unit film has adhesive layers laminated on both sides of the polyimide core layer, the thickness of the polyimide core layer and the thickness of the adhesive layer (the total thickness of the adhesive layers laminated on both sides) The ratio may be 1:0.008 to 1:0.19.

In one embodiment, the adhesive layer may have a glass transition temperature (Tg) of 300°C or lower, and the polyimide core layer may have a glass transition temperature (Tg) of 350°C or higher.

In particular, the polyimide core layer may include a non-thermoplastic polyimide, and the adhesive layer may include a thermoplastic polyimide. Preferably, the polyimide core layer consists of only a non-thermoplastic polyimide, and the adhesive layer , consisting only of thermoplastic polyimide.

In one embodiment, the polyimide core layer and the adhesive layer are formed from dianhydride monomers and diamine monomers. For example, the polyimide core layer and the adhesive layer can be manufactured by imidizing a polyamic acid formed by a reaction between a dianhydride monomer and a diamine monomer. The types of dianhydride monomers and diamine monomers that can be used to form the polyimide core layer and the adhesive layer may be the dianhydride monomers and diamine monomers described above; Various monomers commonly used in the field of manufacturing polyimide films can be used without any particular limitation.

As an example, the polyimide core layer is formed by reacting 100 mol% of pyromellitic dianhydride (PMDA) as a dianhydride monomer and 100 mol% of 4,4'oxydianiline (ODA) as a diamine monomer. It can be formed by Further, the adhesive layer contains 100 mol% of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) as a dianhydride monomer and 4,4'oxydianiline as a diamine monomer. (ODA) 100 mol%.

For example, as the dianhydride monomer for forming the polyimide core layer and the adhesive layer, pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 2,3 , 3',4-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride , 3,4,9,10-perylenetetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)propane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride , 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)ethane dianhydride, Oxydiphthalic dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, p-phenylene bis (trimellitic acid monoester anhydride), ethylene bis (trimellitic acid monoester acid anhydride), bisphenol A bis (trimellitic acid monoester acid anhydride), a derivative thereof, or a combination thereof is used as a diamine monomer such as 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4 , 4'-oxydianiline, 3,4'-oxydianiline, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(3 -aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenylpropane, 4,4'-methylenedianiline, 3,3 '-Methylene dianiline, benzidine, 3,3'-dichlorobenzidine, 4,4'-diaminodiphenylsulfide, 3,3'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenyl ether , 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 1,5-diaminonaphthalene, 4,4'-diaminodiphenyldiethylsilane, 4,4'-diaminodiphenylsilane, 4,4'-diaminodiphenyl Ethylphosphine oxide, 4,4'-diaminodiphenyl N-methylamine, 4,4'-diaminodiphenyl N-phenylamine, 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene, 1, 2-diaminobenzene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, or derivatives thereof, or combinations thereof can be used.

In one embodiment, the dianhydride monomer for forming the non-thermoplastic polyimide core layer includes pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4-biphenyltetracarboxylic dianhydride, oxydiphthalic anhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride Acid dianhydride or a combination thereof is used, and diamine monomers include 4,4'-oxydianiline, 3,4'-oxydianiline, p-phenylenediamine, m-phenylenediamine, 4, 4'-methylene dianiline, 3,3'-methylene dianiline, or a combination thereof can be used. In this case, it is possible to form a polyimide layer with excellent orientation, and it has excellent properties during carbonization and graphitization. Graphite sheets having thermal conductivity can be formed, but are not limited thereto.

In one embodiment, the dianhydride monomer for forming the thermoplastic polyimide adhesive layer includes 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4 - using biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, or a combination thereof, and as the diamine monomer, 4,4'-oxydianiline , 3,4'-oxydianiline, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 1 , 4-bis(3-aminophenoxy)benzene, or a combination thereof.

As an example, the polyimide core layer is formed by reacting 100 mol% of pyromellitic dianhydride (PMDA) as a dianhydride monomer and 100 mol% of 4,4'oxydianiline (ODA) as a diamine monomer. It can be formed by Further, the adhesive layer contains 100 mol% of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) as a dianhydride monomer and 4,4'oxydianiline as a diamine monomer. (ODA) 100 mol%.

In one embodiment, any known film lamination method can be used to manufacture the polyimide unit film.

For example, a coating method, a bonding sheet method, a coextrusion method, etc. can be applied. The coating method is a method in which an adhesive layer is formed to a certain thickness on a polyimide core layer manufactured by a conventional method, and then dried to produce a polyimide unit film.

The bonding sheet method is a method of manufacturing a polyimide unit film by simultaneously introducing a polyimide core film and a sheet-shaped adhesive layer film (bonding sheet) into a calendaring process.

Further, the coextrusion method is a method of manufacturing a polyimide unit film by simultaneously forming an adhesive layer and a polyimide core layer using a coextrusion die in the step of casting a polyamic acid solution onto a metal support layer.

A multilayer polyimide film according to another aspect of the present invention can be manufactured by laminating two or more of the polyimide unit films.

The thickness of the multilayer polyimide film can be easily controlled by adjusting the thickness (for example, the thickness of the polyimide core layer, the thickness of the adhesive layer), the number, etc. of the polyimide unit films to be laminated. For example, in order to satisfy a predetermined thickness, a multilayer polyimide film is made of two or more polyimide unit films (e.g., 2, 3, 4, 5, 6, 7, 8, 9). , 10 sheets, 11 sheets, 12 sheets, 13 sheets, 14 sheets, or 15 sheets or more), other examples are 2 sheets to 1,000 sheets, still other examples are 2 sheets to 100 sheets, still other examples are 2 sheets. It can be formed by stacking 2 to 50 sheets, or as another example, 2 to 10 sheets.

That is, the multilayer polyimide film includes two or more polyimide unit films each including a polyimide core layer and an adhesive layer laminated on one or both surfaces of the polyimide core layer. The polyimide unit film may be adhesively laminated via the adhesive layer.

For example, when the adhesive layer is a thermoplastic polyimide layer, it can be easily adhered by thermocompression bonding or the like, and has excellent adhesive strength.

In one embodiment, the multilayer polyimide film may have a thickness of 100 μm or more.

For example, the multilayer polyimide film may have a thickness of 100 μm to 20,000 μm, in other examples 150 μm to 2,000 μm, and in still other examples 200 μm to 1,000 μm, but is not limited thereto. isn't it.

In one embodiment, each polyimide unit film included in the multilayer polyimide film may be the same or different from each other. For example, the polyimide unit films may have the same or different polyimide core layer and/or adhesive layer material (for example, polyimide precursor component, content of the component), thickness, and the like.

In addition, when the polyimide unit film is laminated on both sides of a polyimide core layer made of non-thermoplastic polyimide and has an adhesive layer containing a thermoplastic polyimide layer, the thermoplastic polyimide layers of each adhesive layer may be the same or different from each other. good.

Furthermore, the non-thermoplastic polyimide layer and/or the thermoplastic polyimide layer contained in the polyimide unit film may consist of a single layer or a plurality of layers.

In one embodiment, the thermoplastic polyimide layers included in each polyimide unit film may be made of the same material, and in this case, the adhesive strength between the thermoplastic polyimide layers is superior, and the peeling prevention effect during post-processing is more effective. It can be excellent, but is not limited to this.

FIG. 2 is a diagram schematically illustrating a multilayer polyimide film 100 according to an embodiment of the invention. Referring to FIG. 2, the multilayer polyimide film 100 includes polyimide unit films 110 and 120 including polyimide core layers 111 and 121 and adhesive layers 112 and 122 laminated on one surface of the polyimide core layers 111 and 121. Optionally, between the polyimide unit films 110 and 120, one or more polyimide unit films (not shown) including a polyimide core layer and adhesive layers laminated on both sides of the polyimide core layer are provided. (eg, 2, 3, 4, 5, 6, 7, 8, 9, or 10 or more).

For example, a multilayer polyimide film includes two first polyimide unit films including a polyimide core layer and an adhesive layer laminated on one side of the polyimide core layer, a polyimide core layer, and an adhesive layer laminated on both sides of the polyimide core layer. and one or more second polyimide unit films including an adhesive layer, the one or more second polyimide unit films are interposed between the two first polyimide unit films, and the first polyimide unit film is interposed between the two first polyimide unit films, and The polyimide unit film and the second polyimide unit film may be adhesively laminated via an adhesive layer included in the first polyimide unit film and the second polyimide unit film.

FIG. 3 is a diagram schematically illustrating a multilayer polyimide film 200 according to another embodiment of the present invention. Referring to FIG. 3, the multilayer polyimide film 200 includes polyimide unit films 210 and 220 including polyimide core layers 211 and 221 and adhesive layers 212 and 222 laminated on both sides of the polyimide core layers 211 and 221. Optionally, between the polyimide unit films 210 and 220, one or more polyimide unit films (not shown) including a polyimide core layer and adhesive layers on both sides of the polyimide core layer (for example, (2, 3, 4, 5, 6, 7, 8, 9 or 10 or more).

In one embodiment, the adhesive force between the laminated polyimide unit films of the multilayer polyimide film may be 0.3 kgf/cm or more, for example, 0.5 kgf/cm or more, and as another example, 0.3 kgf/cm or more. It may be 6 kgf/cm or more.

On the other hand, the adhesive force between the laminated polyimide unit films of the multilayer polyimide film may be 1.5 kgf/cm or less.

In one embodiment, when the multilayer polyimide film is heated at 600° C. or higher for 1 hour or less, interlayer separation does not occur between the laminated polyimide unit films. For example, the heating time during which interlayer separation does not occur is 50 minutes. Hereinafter, as another example, the time may be 30 minutes or less.

Further, the temperature at which interlayer separation does not occur between the laminated polyimide unit films may be, for example, 650° C. or higher, and as another example, 700° C. or higher.

Meanwhile, the temperature at which interlayer separation does not occur between the stacked polyimide unit films may be 3,000° C. or lower.

In one embodiment, the multilayer polyimide film may be for graphite sheet production.

The multilayer polyimide film has excellent adhesive strength between polyimide unit films, and when the multilayer polyimide film is carbonized and graphitized, a high thickness graphite sheet with excellent thermal conductivity can be produced without layer separation at the adhesive interface. Can be done.

When the multilayer polyimide film is used for producing a graphite sheet, the polyimide unit film may further include an inorganic filler, preferably a sublimable inorganic filler.

Here, the term "sublimable inorganic filler" can mean an inorganic filler that sublimes due to heat during the carbonization and/or graphitization process during the production of the graphite sheet. When the polyimide film contains a sublimable inorganic filler, voids are formed in the graphite sheet by the gas generated by sublimation of the sublimable inorganic filler during the manufacture of the graphite sheet, and this causes the sublimation gas generated during the manufacture of the graphite sheet to Not only can a high-quality graphite sheet be obtained through smooth evacuation, but also the flexibility of the graphite sheet can be improved, ultimately improving the handleability and moldability of the graphite sheet. Examples of sublimable inorganic fillers include, but are not limited to, calcium carbonate, dibasic calcium phosphate, barium sulfate, and the like.

The average particle diameter (D ₅₀ ) of the sublimable inorganic filler may be 0.05 μm to 5.0 μm (for example, 0.1 μm to 4.0 μm), and it is possible to obtain a high-quality graphite sheet within the above range. However, it is not limited to this.

The content of the sublimable inorganic filler may be 0.001 to 0.5 parts by weight based on 100 parts by weight of the polyimide film, and a high quality graphite sheet can be obtained within the above range, but it is not limited to this. It's not something you can do.

In one embodiment, both the polyimide core layer and the adhesive layer include a sublimable inorganic filler in the polyimide unit film. According to other embodiments, the adhesive layer may include a sublimable inorganic filler and the polyimide core layer may not include a sublimable inorganic filler, or vice versa.

A method for producing a multilayer polyimide film according to still another aspect of the present invention includes the steps of: forming two or more polyimide unit films each having an adhesive layer laminated and integrated on one or both surfaces of a polyimide core layer; The method may include the steps of: laminating unit films so that they can be bonded via the adhesive layer; and thermocompression bonding the two or more laminated polyimide unit films, wherein the thickness of the polyimide unit film is The polyimide core layer may include the polyimide film.

First, a polyimide unit film in which an adhesive layer is integrally laminated on one or both surfaces of a polyimide core layer can be formed by a known film lamination method.

The polyimide unit film is produced, for example, by manufacturing a non-thermoplastic polyimide layer precursor composition as the polyimide core layer, manufacturing a thermoplastic polyimide layer precursor composition as the adhesive layer, and manufacturing the non-thermoplastic polyimide layer precursor composition and The thermoplastic polyimide layer precursor composition may be prepared in the form of two or more layers on a support, dried to form a gel film, and the gel film may be heat-treated.

Non-thermoplastic polyimide layer precursor compositions are prepared, for example, by mixing a solvent, a diamine monomer, and a dianhydride monomer to form a polyamic acid solution; The method may further include adding a sublimable inorganic filler, a dehydrating agent, and/or an imidizing agent to the solution. The thermoplastic polyimide layer precursor composition is prepared, for example, by mixing a solvent, a diamine monomer, and a dianhydride monomer to form a polyamic acid solution; The method may further include adding a sublimable inorganic filler, a dehydrating agent, and/or an imidizing agent to the method. Regarding the diamine monomer, dianhydride monomer and sublimable inorganic filler, see what has been described above.

The solvent is not particularly limited as long as it can dissolve the polyamic acid. For example, the solvent can include an aprotic polar solvent. Examples of aprotic polar solvents include amide solvents such as N,N'-dimethylformamide (DMF) and N,N'-dimethylacetamide (DMAc), and phenolic solvents such as p-chlorophenol and o-chlorophenol. Solvents include N-methyl-pyrrolidone (NMP), gamma-butyrolactone (GBL), and Diglyme, which can be used alone or in combination of two or more. Optionally, auxiliary solvents such as toluene, tetrahydrofuran (THF), acetone, methyl ethyl ketone (MEK), methanol, ethanol, water, etc. can also be used to adjust the solubility of the polyamic acid.

According to one embodiment, the polyamic acid solution has a solids content, i.e., the weight percentage of diamine monomer and dianhydride monomer relative to the total weight of diamine monomer, dianhydride monomer and solvent. may be, for example, 5 to 35% by weight, and as another example 10 to 30% by weight. The polyamic acid solution may have a molecular weight and viscosity suitable for forming a film within the above range, but is not limited thereto.

According to one embodiment, the polyamic acid solution for forming the non-thermoplastic polyimide layer may have a viscosity of 100,000 cP to 500,000 cP at 23°C. Within the above range, while the polyamic acid has a predetermined molecular weight, it is possible to have excellent processability when forming a polyimide film. Here, "viscosity" can be measured using a HAAKE Mars viscometer. For example, the viscosity of the polyamic acid solution may be 150,000 cP to 450,000 cP at 23°C, as another example 200,000 cP to 400,000 cP, and still another example 220,000 cP to 350,000 cP. , but is not limited to this.

According to one embodiment, the polyamic acid solution for forming the thermoplastic polyimide layer may have a viscosity of 1,000 cP to 500,000 cP at 23°C. While the polyamic acid has a predetermined molecular weight within the above range, it has excellent processability when forming a polyimide film, and can be thermocompression bonded at an appropriate temperature and pressure. Here, "viscosity" can be measured using a HAAKE Mars viscometer. For example, the viscosity of the polyamic acid solution at 23° C. may be 1,000 cP to 100,000 cP, as another example 1,000 cP to 50,000 cP, and still another example 5,000 cP to 50,000 cP. , but is not limited to this.

According to one embodiment, the polyamic acid for forming the non-thermoplastic polyimide layer may have a weight average molecular weight of 50,000 g/mol to 500,000 g/mol. The above range may be advantageous for producing graphite sheets with better thermal conductivity. Here, the "weight average molecular weight" can be measured using gel chromatography (GPC) using polystyrene as a standard sample. For example, the weight average molecular weight of the polyamic acid may be 150,000 g/mol to 500,000 g/mol, and as another example, 100,000 g/mol to 400,000 g/mol, but is not limited thereto. isn't it.

According to one embodiment, the polyamic acid for forming the thermoplastic polyimide layer may have a weight average molecular weight of 5,000 g/mol to 500,000 g/mol, but is not limited thereto. The above range may be advantageous for producing graphite sheets with better thermal conductivity. Here, the "weight average molecular weight" can be measured using gel chromatography (GPC) using polystyrene as a standard sample.

The dehydrating agent is one that promotes the ring-closing reaction by dehydrating polyamic acid, and includes, for example, aliphatic acid anhydrides, aromatic acid anhydrides, N,N'-dialkylcarbodiimides, halogenated lower aliphatic halides, Examples include halogenated lower fatty acid anhydrides, allylphosphonic acid dihalides, and thionyl halides, and these can be used alone or in combination of two or more. Among them, from the viewpoint of availability and cost, aliphatic acid anhydrides such as acetic anhydride, propionic anhydride, and lactic anhydride can be used alone or in combination of two or more. The dehydrating agent is used in an amount of 0.5 to 5 moles per mole of amic acid group in polyamic acid.
It is added in a molar amount (for example, 1 mol to 4 mol), and sufficient imidization is possible within the above range, and it may be advantageous for casting into a film, but it is not limited thereto.

The imidizing agent is one that promotes the ring-closing reaction of polyamic acid, and includes, for example, aliphatic tertiary amine, aromatic tertiary amine, and heterocyclic tertiary amine. Among these, heterocyclic tertiary amines can be used from the viewpoint of reactivity as a catalyst. Examples of heterocyclic tertiary amines include quinoline, isoquinoline, β-picoline, and pyridine, which can be used alone or in combination of two or more. The imidizing agent is added in an amount of 0.05 mol to 3 mol (for example, 0.2 mol to 2 mol) per mol of the amic acid group in the polyamic acid, and sufficient imidization is possible within the above range, It may be advantageous to cast into a film, but is not limited thereto.

Thereafter, the non-thermoplastic polyimide layer precursor composition and the thermoplastic polyimide layer precursor composition can be formed into two or more layers of film on a support and dried to form a gel film.

Any known manufacturing method can be used to manufacture a film having two or more layers, such as a coating method, a bonding sheet method, a coextrusion method, and the like.

In particular, when manufacturing using coextrusion, the non-thermoplastic polyimide layer precursor composition and the thermoplastic polyimide layer precursor composition are simultaneously supplied to an extrusion molding machine having an extrusion molding die of two or more layers, and the A gel film can be produced by coextruding the two compositions into a film having two or more layers from the discharge port of a die and drying the film.

More specifically, a non-thermoplastic polyimide layer precursor composition and a thermoplastic polyimide layer precursor composition are simultaneously supplied to a molding die for two or more layers, and the two extrusion molding dies discharged from the extrusion molding die for two or more layers are After the composition is continuously formed into a film shape on a support, a self-supporting gel film is produced by heating and drying (for example, 30 ° C. to 300 ° C.), and after separating the gel film from the support. A polyimide film can be obtained by processing at a high temperature (for example, 50° C. to 700° C.). As the molding die for two or more layers, various known structures can be used, and for example, a T-die for producing a multilayer film (for example, a feed block T-die or a multi-manifold T-die) can be used.

According to one embodiment, the non-thermoplastic polyimide layer and the thermoplastic polyimide layer of the polyimide unit film may be in direct contact. Here, "direct contact" can mean that no other layer is interposed between the non-thermoplastic polyimide layer and the thermoplastic polyimide layer.

Examples of the support include a glass plate, aluminum foil, an endless stainless steel belt, and a stainless steel drum. Drying is performed at a temperature of, for example, 30°C to 300°C (for example, 80°C to 200°C, another example is 100°C to 180°C, still another example is 100°C to 150°C), but is not limited thereto. It's not something you can do. The drying time is, for example, 1 minute to 10 minutes, another example is 2 minutes to 7 minutes, and still another example is 2 minutes to 5 minutes, but is not limited thereto.

In some cases, a step of stretching the gel film may be included in order to adjust the thickness and size of the finally obtained polyimide unit film and improve the orientation, and the stretching may be performed by MD (machine direction). and TD (transverse direction). This stretching process must be performed at a low temperature of less than 50° C. in order to smoothly align the polymer. This is because at a temperature of 50° C. or higher, the imidization reaction is promoted and the orientation of the polymer is hindered.

Thereafter, the gel film can be heat-treated to produce a polyimide unit film. By heat-treating the gel film, most of the amic acid groups remaining in the gel film are imidized, and a polyimide film can be obtained. The heat treatment temperature is 50°C to 700°C, for example 150°C to 600°C, another example is 200°C to 600°C, still another example is 350°C to 500°C, still another example is 400°C to 450°C. However, it is not limited to this. The heat treatment time is, for example, 1 minute to 20 minutes, another example is 1 minute to 10 minutes, and still another example is 2 minutes to 8 minutes, but is not limited thereto.

Next, two or more polyimide unit films can be laminated such that they can be bonded together via an adhesive layer (eg, a thermoplastic polyimide layer). More specifically, the respective polyimide unit films can be laminated so that the adhesive layers face each other.

Next, two or more laminated polyimide unit films can be thermocompression bonded. Thermocompression bonding is performed, for example, at a pressure of 0.1 MPa to 30 MPa and a temperature of 250° C. to 450° C. for 10 seconds to 150 seconds, but is not limited thereto.

According to one embodiment, the thermoplastic polyimide layers of the polyimide unit film (for example, when two polyimide unit films are included, the thermoplastic polyimide layer of one polyimide unit film and the thermoplastic polyimide layer of the other polyimide unit film) They may be in direct contact with each other via a plastic polyimide layer).

The multilayer polyimide film produced as described above is obtained by thermocompression bonding two or more polyimide unit films each having an adhesive layer laminated and integrated on one or both surfaces of a polyimide core layer, and adhesively laminated via the adhesive layer. , polyimide unit film can be bonded with excellent adhesive strength.

Such excellent adhesive strength can be converted into a high-thickness graphite sheet with excellent thermal conductivity without layer separation at the adhesive interface when the multilayer polyimide film is used for carbonization for graphite sheets and/or during graphitization.

According to yet another aspect of the present invention, there is provided a graphite sheet manufactured from the multilayer polyimide film described above or a multilayer polyimide film manufactured by the manufacturing method described above. Such graphite sheets have a thickness of 50 μm or more, such as 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm or 200 μm or more, as other examples from 50 μm to 4,000 μm, and still other examples from 50 μm to 500 μm. However, it can have excellent thermal conductivity.

According to one embodiment, the graphite sheet has a thermal conductivity of 500 W/m·K or higher (e.g., 500 W/m·K, 600 W/m·K, 700 W/m·K, 800 W/m·K, 900 W/m·K, m・K, 1,000W/m・K, 1,100W/m・K, 1,200W/m・K, 1,300W/m・K, 1,400W/m・K or 1,500W/m・K K or higher). For example, the thermal conductivity of the graphite sheet may be 500 W/m·K to 2,000 W/m·K, and as another example, 1,000 W/m·K to 2,000 W/m·K, It is not limited to this.

The graphite sheet described above can be manufactured by various methods commonly used in the graphite sheet manufacturing field. For example, graphite sheets can be produced by carbonizing and graphitizing the multilayer polyimide film described above.

"Carbonization" is a process of thermally decomposing the polymer chains of a polyimide film to form a preliminary graphite sheet containing amorphous carbon bodies, non-crystalline carbon bodies, and/or amorphous carbon bodies. The method may include the step of raising and maintaining the temperature of the film from room temperature to a maximum temperature in the range of 1,000°C to 1,500°C over 10 to 30 hours under reduced pressure or an inert gas atmosphere, It is not limited to this. Optionally, due to the high orientation of carbon, pressure can be applied to the polyimide film using a hot press or the like during carbonization, and the pressure at this time is, for example, 5 kg/cm ² or more, and another example is 15 kg/cm 2 or more. cm ² or more, and as another example, it may be 25 kg/cm ² or more, but is not limited thereto.

Graphitization is a process in which the carbon of an amorphous carbon body, amorphous carbon body, and/or amorphous carbon body is rearranged to form a graphite sheet, e.g., a preliminary graphite sheet is selectively deactivated. The method may include, but is not limited to, raising and maintaining the temperature from room temperature to a maximum temperature in the range of 2,500°C to 3,000°C over a period of 2 to 30 hours in a gas atmosphere. do not have. Optionally, due to the high orientation of carbon, pressure can be applied to the preliminary graphite sheet using a hot press or the like during graphitization, and the pressure at this time is, for example, 100 kg/ ^cm2 or more, as another example. The weight may be 200 kg/cm ² or more, and as another example, 300 kg/cm ² or more, but is not limited thereto.

Hereinafter, the present invention will be explained in more detail with reference to Examples. However, this is presented as a preferred example of the present invention and should not be construed as limiting the present invention in any way.

Production Example 205.0 g of dimethylformamide was charged as a solvent into a reactor, and the temperature was adjusted to 20°C. To this, 21.5 g of 4,4'oxydianiline (ODA) was added as a diamine monomer, and then 23.4 g of pyromellitic dianhydride (PMDA) was added as a dianhydride monomer. , a polyamic acid solution with a viscosity of 230,000 cP was produced. Next, 39.5 g of acetic anhydride as a dehydrating agent, 4.8 g of β-picoline as an imidizing agent, and dibasic calcium phosphate (average particle size (D ₅₀ ): 2 A non-thermoplastic polyimide precursor solution was prepared by mixing 0.12 g of .5 μm) and 30.4 g of dimethylformamide as a solvent.

A non-thermoplastic polyimide precursor solution prepared using a film forming apparatus was formed into a film on an SUS plate (100SA, Sandvik) and dried to produce a gel film. The produced gel film was separated from the SUS plate and then heat-treated to produce a polyimide film.

During the heat treatment, the amount of heat was adjusted so that the maximum temperature during the heat treatment was 510 °C for Production Example 1, 520 °C for Production Example 2, and 550 °C for Production Comparative Example 1. A polyimide film of Example 1 was produced.

The tensile properties of the polyimide films of Production Examples 1 and 2 and Production Comparative Example 1 were measured according to ASTM D882, and the results are shown in a stress-strain curve in which the vertical axis is tensile strength (MPa) and the horizontal axis is deformation rate (%). (stress-strain curve), and as shown in Table 1 below, after measuring the slope of the plastic deformation section and the slope of the elastic deformation section, the ratio thereof was calculated.

The plastic deformation section corresponds to the stress-strain curve (st) of the polyimide film shown in FIG.
In a ress-strain curve (SS-curve), this corresponds to a section from a deformation rate (elongation) of 30% to just before breakage, and the elastic deformation section corresponds to a section where the deformation rate is 3% or less.

The slope of each section was derived by calculating the amount of change in tensile strength/the amount of change in deformation rate in each section, and at this time, for example, the deformation rate of 3% was calculated by changing it to 0.03.

The polyimide films of Production Examples 1 and 2 corresponded to the ratio of the slope of the plastic deformation zone to the slope of the elastic deformation zone (slope of the plastic deformation zone/slope of the elastic deformation zone) and within the range of the slope of the plastic deformation zone of the present application. However, in Comparative Manufacturing Example 1, the ratio of the slope of the plastic deformation zone to the slope of the elastic deformation zone (slope of the plastic deformation zone/slope of the elastic deformation zone) and the slope of the plastic deformation zone were out of the range of the present application. Moreover, the tensile strengths of the polyimide films of Production Examples 1 and 2 were 180 MPa and 191 MPa, respectively, which corresponded to 200 MPa or less.

On the other hand, the tensile strength of the polyimide film of Comparative Production Example 1 was measured to be about 210 MPa. The polyimide films of Production Examples 1 and 2 and Production Comparative Example 1 were heated to 1,200 °C at an average rate of 0.5 °C/min under argon gas using an electric furnace, and then maintained at the temperature for 3 hours. After that, the temperature was raised to 2,800° C. at an average rate of 1.0° C./min under argon gas, and the temperature was maintained for 1 hour to progress graphitization.

As shown in FIG. 4, the polyimide films of Production Example 1 and Production Example 2 had no problem with graphitization (FIGS. 4a and 4b, respectively), but the slope of the plastic deformation zone and the slope of the plastic deformation zone/ It was confirmed that the polyimide film of Manufacture Comparative Example 1, in which the slope of the elastic deformation zone was outside the range, was imidized too much, was not easy to sinter, and was not successfully graphitized (FIG. 4c).

Examples and experimental examples
Example 1
A non-thermoplastic polyimide precursor solution (used as a polyimide core layer) was produced in the same manner as in the production example described above.

A separate reactor was charged with 217.5 g of dimethylformamide as a solvent and the temperature was adjusted to 20°C. To this was added 4,4'oxydianiline (ODA) (13.2) g as a diamine monomer, and then 3,3',4,4'-biphenyltetracarboxylic acid was added as a dianhydride monomer. A polyamic acid solution with a viscosity of 10,000 cP was prepared by adding 19.3 g of acid dianhydride (BPDA). Next, 23.2 g of acetic anhydride as a dehydrating agent, 3.0 g of β-picoline as an imidizing agent, and dibasic calcium phosphate (average particle size (D ₅₀ ): 1.5 μm) and 18.6 g of dimethylformamide as a solvent were mixed to prepare a precursor solution for an adhesive layer (thermoplastic polyimide layer).

A three-layer extrusion die was provided so that the produced non-thermoplastic polyimide layer precursor solution and thermoplastic polyimide layer precursor solution were laminated and integrated on both sides of the non-thermoplastic polyimide layer. A film was formed on a SUS plate (100SA, Sandvik) using a film forming apparatus, and dried at 130° C. for 3 minutes to produce a gel film. After separating the manufactured gel film from the SUS plate, it was heat-treated at 420 to 550°C for 4 minutes to obtain a thermoplastic polyimide layer/non-thermoplastic polyimide layer/thermoplastic polyimide layer (thickness: 3 μm/46 μm/3 μm) structure. A polyimide unit film was produced.

The four produced polyimide unit films were laminated and then thermocompression bonded at 350° C. for 1 minute while applying a pressure of 20 MPa to produce a multilayer polyimide film having a thickness of 202 μm.

Experimental example 1
Using the multilayer polyimide film test piece produced in Example 1, the adhesive strength between polyimide unit films was measured. The adhesive force was measured by preparing a test piece with a width of 10 mm and a length of 100 mm, and then peeling one side at a 90° angle at a speed of 25 mm/min to measure the adhesive force.

The average adhesive force between the laminated polyimide unit films was measured to be 0.63 kgf/cm.

Experimental example 2
The glass transition temperature (Tg) of each of the polyimide core layer and adhesive layer of the polyimide unit film of Example 1 was measured. The glass transition temperature was determined by determining the loss modulus and storage modulus of each layer using DMA, and measuring the inflection point in the tangent graph as the glass transition temperature.

As a result of the measurement, the glass transition temperature of the polyimide core layer was 395°C, and the glass transition temperature of the adhesive layer was 280°C.

Experimental example 3
After heating the multilayer polyimide film test piece produced in Example 1 at 700° C. for 30 minutes in a heating furnace, the presence or absence of interlayer separation was confirmed using SEM, but no interlayer separation was observed.

Example 2
The multilayer polyimide film of Example 1 was heated to 1,200° C. at a rate of 1° C./min under nitrogen gas using an electric furnace, and then maintained at the temperature for 2 hours to be carbonized. Thereafter, the temperature was raised to 2,800°C at a rate of 20°C/min under argon gas, maintained at the temperature for 1 hour to graphitize, and then passed between two upper and lower metal rolls at room temperature. , a graphite sheet with a thickness of 100 μm was produced.

Experimental example 4
A test piece was produced by cutting the graphite sheet of Example 2 into a circle with a diameter of 25.4 mm, and the test piece was thermally diffused by a laser flash method using a thermal diffusivity measurement device (LFA467, Netsch). After measuring the thermal diffusivity, the thermal conductivity was determined by multiplying the measured value of the thermal diffusivity by the density and specific heat (theoretical value: 0.85 kJ/kg·K). As a result, it was confirmed that the graphite sheet of Example 2 had an excellent thermal conductivity of 1,030 W/m·K.

The embodiments of the manufacturing method of the present invention are merely preferred embodiments that enable those skilled in the art to easily carry out the present invention, and are limited to the embodiments described above. Therefore, the scope of the rights of the present invention is not limited thereby. Therefore, the true technical protection scope of the present invention must be determined by the technical spirit of the appended claims. Furthermore, it is obvious to those skilled in the art that various substitutions, modifications, and changes can be made without departing from the technical idea of the present invention, and portions that can be easily changed by a person skilled in the art also fall within the scope of the rights of the present invention. It is obvious that it is included.

The present invention has the effect of providing a high-thickness polyimide unit film, a multilayer polyimide film containing the same, and a method for producing the same.

Claims (14)

The ratio of the slope of the plastic deformation zone to the slope of the elastic deformation zone (slope of the plastic deformation zone/slope of the elastic deformation zone) is 0.025 or less,
Polyimide film.
(However, the plastic deformation section corresponds to the section from the deformation rate (Elongation) of 30% to just before breakage in the stress-strain curve of the polyimide film, and the elastic deformation zone corresponds to the section from the deformation rate (Elongation) of 30% to just before breakage. (This corresponds to an area where the percentage is 3% or less.) The slope of the plastic deformation section is 0.05 GPa or less,
The polyimide film according to claim 1. The slope of the elastic deformation section is 2.1 GPa or more,
The polyimide film according to claim 1. The tensile strength is 200 MPa or less,
The polyimide film according to claim 1. A polyimide core layer comprising the polyimide film according to claim 1;
an adhesive layer laminated on one or both sides of the polyimide core layer,
The adhesive layer contains an imide group,
The thickness is 50 μm or more,
Polyimide unit film. The thickness ratio of the polyimide core layer and the adhesive layer (thickness of the polyimide core layer: thickness of the adhesive layer) is 1:0.004 to 1:0.095.
The polyimide unit film according to claim 5. The glass transition temperature (Tg) of the adhesive layer is 300°C or less,
The polyimide core layer has a glass transition temperature (Tg) of 350°C or higher,
The polyimide core layer includes a non-thermoplastic polyimide,
The adhesive layer includes thermoplastic polyimide.
The polyimide unit film according to claim 5. The polyimide core layer contains pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4-biphenyltetracarboxylic dianhydride, oxydiphthalic acid a dianhydride monomer comprising anhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, or a combination thereof; 4,4'-oxydianiline, 3,4'-oxydianiline, p-phenylenediamine, m-phenylenediamine, 4,4'-methylenedianiline, 3,3'-methylenedianiline, or a combination thereof formed from diamine monomers containing
The polyimide unit film according to claim 5. The adhesive layer includes 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4-biphenyltetracarboxylic dianhydride, 3,3',4,4'- dianhydride monomers including benzophenone tetracarboxylic dianhydride, or combinations thereof, and 4,4'-oxydianiline, 3,4'-oxydianiline, 1,3-bis(4-aminophenoxy ) benzene, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, or a combination thereof. formed from mass,
The polyimide unit film according to claim 5. Produced by laminating two or more polyimide unit films according to any one of claims 5 to 9,
Multilayer polyimide film. The adhesive force between the laminated polyimide unit films is 0.3 kgf/cm or more,
The multilayer polyimide film according to claim 10. When heated at 600℃ or higher for 1 hour or less,
interlayer separation does not occur between the laminated polyimide unit films;
The multilayer polyimide film according to claim 10. For graphite sheet production,
The multilayer polyimide film according to claim 10. forming two or more polyimide unit films in which adhesive layers are laminated and integrated on one or both sides of the polyimide core layer;
laminating the two or more polyimide unit films so that they can be bonded together via the adhesive layer;
a step of thermocompression bonding the two or more laminated polyimide unit films,
The thickness of the polyimide unit film is 50 μm or more,
The polyimide core layer includes the polyimide film according to claim 1.
Method for manufacturing multilayer polyimide film.