KR102047345B1 - Polyimide and Methods for Preparing the Same - Google Patents

Abstract

The present invention relates to a polyimide film and a method for producing the same, wherein a monomer containing a functional group selected from the group consisting of a biphenyl group, a benzoxazole group and an oxy group is added during polymerization of an aromatic dianhydride and an aromatic diamine, thereby providing high heat resistance. The present invention relates to a polyimide film and a method of manufacturing the same, which have improved properties and tensile strength and elongation.

Description

Polyimide film and its manufacturing method {Polyimide and Methods for Preparing the Same}

The present invention relates to a polyimide film and a method for producing the same, which have high heat resistance and have improved tensile strength and elongation.

It is entering the ubiquitous era where information can be exchanged anywhere, anytime, anywhere, and digital convergence is rapidly progressing, where computers, communications and information appliances are converged or combined. Accordingly, the importance of a display that serves as an interface between the electronic information device and the human being is increasing. At the same time, the demand for high brightness and high definition image information has become stronger, and the corresponding large screen liquid crystal display, plasma display, and organic light emitting diode (OLED) are competing. have.

Recently, a thin, light, bendable or bendable display has been attracting attention, and in order to implement a display having such characteristics, a substrate of a new material having flexibility is required in place of an existing glass substrate. In order to realize such a flexible property, the use of a monomer having a flexible chain lattice such as -O-, SO _2- , CH _2- , or the use of a monomer having a bent structure connected to the m-position rather than the p-position is very high. Although there can be characteristics, there is a problem of reducing the natural high heat resistance of the polyimide.

The type of flexible display currently developed is OLED or TFT LCD, and a display is driven by mounting a TFT-like structure on a flexible polymer material substrate. By structuring and finally raising the electrode, a unit device for driving a display is constructed. However, the device fabrication process is often performed at a high temperature, so that the dimensions of the polymer material substrate are easily deformed and thermally deformed when the device is manufactured. There was a problem to use it as a substrate.

The main object of the present invention is to provide a polyimide film having optimum mechanical properties, in particular high tensile strength and tensile elongation, and a method of manufacturing the same, while maintaining the inherent high heat resistance of the polyimide resin.

The present invention also provides a display device comprising the polyimide film.

In order to achieve the above object, an embodiment of the present invention comprises the steps of copolymerizing aromatic dianhydride and aromatic diamine to obtain a polyamic acid; And imidating the obtained polyamic acid on a support, and containing at least one functional group selected from the group consisting of a benzoxazole group, a biphenyl group, and an oxy group before copolymerization of the aromatic dianhydride and aromatic diamine. It provides a method for producing a polyimide film comprising the step of adding a monomer to.

In a preferred embodiment of the present invention, the monomer containing a functional group selected from the group consisting of the benzoxazole group, biphenyl group and oxy group, may be included in 20 to 90 mol% with respect to the total aromatic dianhydride or total aromatic diamine. .

In a preferred embodiment of the present invention, the monomer containing a functional group selected from the group consisting of benzoxazole group, biphenyl group and oxy group is aminobenzooxazole (2- (4-Aminophenyl) -6-aminobenzoxazole, Ar2), It may be at least one selected from the group consisting of biphenyl tetracarboxylic dianhydride (3,3 ', 4,4'-biphenyltetracarboxylic acid dianhydride, BPDA) and oxydianiline (4,4'-oxydianiline).

In a preferred embodiment of the present invention, the method may further include the step of introducing an alkoxy silane compound before or after copolymerization of the aromatic dianhydride and aromatic diamine.

In a preferred embodiment of the present invention, the alkoxy silane compound is tetramethoxy silane (TMOS), tetraethoxy silane (TEOS), tetrabutoxy silane (Tetrabutoxy silane (TBS), amino propyl tree It may be at least one selected from the group consisting of ethoxy silane (3-Aminopropyl triethoxy silane (APTES)) and aminopropyl trimethoxy silane (APTMS).

In one preferred embodiment of the present invention, the alkoxy silane compound may be included in 0.1 to 5.0 mol% relative to the total aromatic diamine.

Another embodiment of the invention comprises a unit structure derived from aromatic dianhydride and aromatic diamine, characterized in that it comprises a monomer containing at least one functional group selected from the group consisting of benzoxazole groups, biphenyl groups and oxy groups. A polyimide film is provided.

In another preferred embodiment of the present invention, the monomer containing a functional group selected from the group consisting of benzoxazole group, biphenyl group and oxy group is aminobenzooxazole (2- (4-Aminophenyl) -6-aminobenzoxazole, Ar2), It may be at least one selected from the group consisting of biphenyl tetracarboxylic dianhydride (3,3 ', 4,4'-biphenyltetracarboxylic acid dianhydride, BPDA) and oxydianiline (4,4'-oxydianiline).

In another preferred embodiment of the present invention, the polyimide film may further comprise an alkoxy silane compound.

In another preferred embodiment of the present invention, the alkoxy silane compound is tetramethoxy silane (TMOS), tetraethoxy silane (TEOS), tetrabutoxy silane (TBS), amino propyl tree It may be at least one selected from the group consisting of ethoxy silane (3-Aminopropyl triethoxy silane (APTES)) and aminopropyl trimethoxy silane (APTMS).

In another preferred embodiment of the present invention, the polyimide film has a coefficient of thermal expansion (CTE) of 5 ppm / ° C. or less at 50 to 540 ° C., based on a film thickness of 10 to 30 μm, and a tensile strength measured by the ISO 527-3 method. The strength is 350 MPa or more, and the tensile elongation measured by the ISO 527-3 method may be 15% or more.

Another embodiment of the present invention provides a substrate for a display device including the polyimide film.

The polyimide film according to the present invention has the best mechanical properties, especially high tensile strength and elongation, while maintaining the inherent high heat resistance of the polyimide resin, thus leading-edge industries such as electric / electronics, semiconductors, flat panel displays, automobiles, aerospace, etc. It is expected to be used as a high heat resistant mechanical part.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In general, the nomenclature used herein is well known and commonly used in the art.

Throughout this specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding the other components unless otherwise stated.

As used herein, the terms "about", "substantially", and the like, are used at, or in close proximity to, numerical values when manufacturing and material tolerances inherent in the meanings indicated are intended to aid the understanding of the invention. Accurate or absolute figures are used to assist in the prevention of unfair use by unscrupulous infringers.

In one aspect, the present invention provides a method for preparing a polyamic acid by copolymerizing an aromatic dianhydride and an aromatic diamine; And imidating the polyamic acid on a support, wherein the monomer contains at least one functional group selected from the group consisting of a benzoxazole group, a biphenyl group, and an oxy group before copolymerization of the aromatic dianhydride and the aromatic diamine. It relates to a method for producing a polyimide film comprising the step of introducing.

In another aspect, the present invention includes a monomer structure derived from an aromatic dianhydride and an aromatic diamine, and includes a monomer containing at least one functional group selected from the group consisting of a benzoxazole group, a biphenyl group, and an oxy group. It relates to a polyimide film to be used.

In still another aspect, the present invention relates to a substrate for a display device comprising the polyimide film.

Hereinafter, the present invention will be described in detail.

The present invention relates to a method for producing a polyimide film with improved mechanical properties, in particular tensile strength and elongation, while maintaining the inherent high heat resistance of the polyimide resin, and to a polyimide film produced by the method. A monomer containing at least one functional group selected from the group consisting of a benzoxazole group, a biphenyl group and an oxy group is added before copolymerization of the aromatic dianhydride and the aromatic diamine, thereby controlling the molecular arrangement in the polymer to obtain tensile strength of the polyimide film and Tensile elongation can be improved.

Conventionally, the preparation of polyimide film was imidized after polyamic acid polymerization using diamine and dianhydride in a 1: 1 equivalent ratio, but the preparation of the polyimide film of the present invention copolymerized aromatic dianhydride and aromatic diamine, but copolymerized. By imidizing by adding a monomer containing a functional group selected from the group consisting of c. Biphenyl group, benzoxazole group and oxy group, it is possible to prepare a high heat-resistant polyimide film having improved tensile strength and tensile elongation.

In addition, the monomer containing a functional group selected from the group consisting of the biphenyl group, benzoxazole group and oxy group is aminobenzoxazole (2- (4-Aminophenyl) -6-aminobenzoxazole, Ar2), biphenyl tetracarboxylic dian It may be at least one selected from the group consisting of hydride (3,3 ', 4,4'-biphenyltetracarboxylic acid dianhydride, BPDA) and oxydianiline (4,4'-oxydianiline).

Such a monomer including a functional group selected from the group consisting of a biphenyl group, a benzoxazole group and an oxy group in its molecular structure may have a linking group such as (C ₆ H ₅ ) _2- , C ₇ H ₅ NO-, -O- Since the bent structure is connected to the m-position instead of the position, the mechanical properties can be improved by controlling the molecular arrangement within the extent that the heat resistance and the dimensional stability are not significantly reduced.

The monomer containing a functional group selected from the group consisting of the biphenyl group, the benzoxazole group and the oxy group may be used in an amount of 20 to 90 mol% with respect to the total aromatic dianhydride or the total aromatic diamine, and preferably in terms of workability and cost At 30 to 70 mol%. If a monomer containing a functional group selected from the group consisting of a biphenyl group, a benzoxazole group and an oxy group is used in an amount of less than 20 mol% with respect to the total aromatic dianhydride or the total aromatic diamine, it may be carbonized in a high temperature film forming process. In the case of exceeding 90 mol%, the viscosity may increase rapidly during polymerization to cause gelation. In this case, the content of the total aromatic dianhydride and the total aromatic diamine containing the monomer may be used in about 1: 1 molar ratio.

As the aromatic dianhydride used in the present invention, any aromatic dianhydride that can be commonly used in the production of polyimide can be used without limitation, and for example, pyromellitic dianhydride (1,2,4,5- Benzene tetracarboxylic dianhydride (PMDA), benzophenone tetracarboxylic dianhydride (BTDA), biscarboxyphenyl dimethyl silane dianhydride (SiDA), bis dicarboxyphenoxy diphenyl sulfide dianhydride (BDSDA ), Sulfonyl diphthalic hydride (SO ₂ DPA) and the like can be mentioned, but is not limited thereto.

The aromatic diamine used in the present invention can be used without limitation as long as it is a diamine that can be used conventionally in the preparation of polyimide, and examples thereof include oxydianiline (ODA), p-phenylenediamine (pPDA), and m-phenylenediamine. (mPDA), p-methylenediamine (pMDA), m-methylenediamine (mMDA), 4-aminophenylbenzamide (APBA), and the like, may be mentioned alone or two or more thereof. It is not.

In addition, the preparation of the polyimide film of the present invention may further include the step of introducing an alkoxy silane compound before or after the polyamic acid polymerization, the alkoxy silane compound is tetramethoxy silane (TMOS), tetra Among tetraethoxy silaneTEOS, tetrabutoxy silane (TBS), aminopropyl triethoxy silane (APTES) and aminopropyl trimethoxy silane (APTMS) It may be one or more selected. Such alkoxy silane compounds may further improve tensile strength and tensile elongation while maintaining inherent heat resistance of the film by crosslinking.

In this case, the alkoxy silane compound may be used in an amount of 0.1 to 5.0 mol% based on the total aromatic diamine in order to further improve the properties of tensile strength and elongation without disturbing the bonding structure of the polymer resin.

In preparing the polyimide film according to the present invention, in the step of copolymerizing at least three monomers including aromatic dianhydride and aromatic diamine, at least three monomers are dissolved in a solvent and reacted to prepare a polyamic acid solution.

The reaction conditions are not particularly limited, but the reaction temperature is preferably -20 to 80 ° C, and the reaction time is preferably 2 to 48 hours. Moreover, it is more preferable that it is inert atmosphere, such as argon and nitrogen, at the time of reaction.

The organic solvent for the polymerization reaction of the polyamic acid solution is not particularly limited as long as it is a solvent in which the polyamic acid is dissolved. Known reaction solvents selected from m-cresol, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), acetone, diethyl acetate One or more polar solvents are used. In addition, low boiling point solutions such as tetrahydrofuran (THF), chloroform or low absorbing solvents such as γ-butyrolactone may be used.

Although not particularly limited with respect to the content of the organic solvent, in order to obtain the molecular weight and viscosity of the appropriate polyamic acid solution, the organic solvent is preferably 50 to 95% by weight of the total polyamic acid solution, more preferably 70 to 90% by weight It is more preferable.

The polyimide resin prepared by imidating the polyamic acid solution prepared as described above preferably has a glass transition temperature of 500 ° C. or higher in consideration of thermal stability. The glass transition temperature of the above or the following was measured by increasing the temperature of 10 ℃ / min from 25 ℃ to 500 ℃ using the DSC of the manufacturer Perkin Elmer.

That is, since the polyimide film according to the present invention exhibits a glass transition temperature (Tg) of 300 ° C. or higher and low thermal expansion rate, TFTs and the like can be produced at a temperature of 300 ° C. or higher, which is advantageous for pattern formation, and without support. Since it can be fixed on the surface, the smoothness can be easily maintained, which may be a material that is very advantageous for implementing a flexible display.

As a method for producing a polyimide film from the polyamic acid solution described above, a method that simulates a flexible display manufacturing process may be used, and a method of imidizing the polyamic acid solution after uniformly applying it to a support may be mentioned. That is, the display device manufacturing process generally proceeds in the order of sequentially stacking electrodes and display parts on the upper surface of the base layer. In one method of applying the polyamic acid solution as the base layer, the polyamic acid solution is coated on a separate support. And imidation to produce an imidization film, and after performing a display element lamination process according to a conventional method on the imidization film, a method of finally peeling off the support. In this case, the plastic material in the form of a film may be advantageous in terms of improving the flatness of the substrate layer compared with the substrate.

In addition, the polyimide film obtained by applying the polyamic acid solution on the parts laminated on the display element and imidizing can be applied as a protective layer. At this time, the polyamic acid solution is preferably a viscosity of 50 ~ 4,000poise in consideration of coating workability and coating uniformity.

The imidation method applicable to the polyimide film formation can be applied in combination with a thermal imidization method, a chemical imidization method, or a thermal imidization method and a chemical imidization method. The chemical imidization method is a method of imidizing a polyamic acid solution by imidating a dehydrating agent represented by an acid anhydride such as acetic anhydride and an imidization catalyst represented by tertiary amines such as isoquinoline, β-picolin and pyridine.

In the case of using the thermal imidization method or the thermal imidization method together with the chemical imidization method, the heating conditions of the polyamic acid solution may vary depending on the kind of the polyamic acid solution, the required imidization film thickness, and the like.

In the case where the thermal imidization method is used, an example of an imidization film formation method will be described in more detail. After casting a polyamic acid solution on a support, it is heated to 80 to 200 ° C., partially cured and dried, and then 250 to 600. A polyimide film can be obtained by heating at 5 degreeC for 5 to 400 second.

In addition, in the case of using the thermal imidization method and the chemical imidization method together, an example of the imidization film formation method will be described in more detail. After the dehydrating agent and the imidization catalyst are added to the polyamic acid solution, it is cast on a separate support. The polyimide film can be obtained by heating at 80-200 ° C, preferably 100-180 ° C to activate the dehydrating agent and imidization catalyst, partially curing and drying, and then heating at 200-570 ° C for 5-400 seconds.

A display element component or the like may be sequentially laminated on the imidization film as described above, and a solution in which a dehydrating agent and an imidization catalyst is added to the polyamic acid solution is applied onto the display element component, and then an imidization film is formed. It can be applied as a protective layer.

In the present invention, the polyimide film obtained as described above may be subjected to a heat treatment step once more. The temperature of the additional heat treatment step is preferably 100 ~ 500 ℃, the heat treatment time is preferably 1 minute to 30 minutes. The stable thermal properties of the coefficient of thermal expansion can be obtained by obtaining stable thermal stability by relieving the thermal hysteresis and residual stress remaining in the film through the heat treatment step once more on the polyimide film obtained as described above. The residual volatile content of the film after heat treatment is 5% or less, and preferably 3% or less.

Although the thickness of the polyimide film manufactured in this way is not specifically limited, It is preferable that it is the range of 10-100 micrometers, More preferably, it is 10-30 micrometers.

As described above, a polyimide film including three or more monomers containing an aromatic dianhydride and an aromatic diamine and an alkoxy silane compound may be prepared, and the polyimide film may have a film thickness of 10 to 30 μm. The coefficient of thermal expansion (CTE) at 50 ~ 540 ℃ is 5ppm / ℃ or less, the tensile strength measured by the ISO 527-3 method is 350MPa or more, the tensile elongation measured by the ISO 527-3 method is 15% or more Indicates.

The polyimide film exhibiting excellent thermal properties, tensile strength and tensile elongation can be applied to a substrate for a display device.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited to the following Examples.

<Example 1>

After the reactor was filled with 900 g of N, N-dimethylacetamide (DMAc) while passing nitrogen through a 1 L reactor equipped with a stirrer, a nitrogen injection device, a dropping funnel, a temperature controller, and a cooler, the temperature of the reactor was adjusted to 25 ° C., followed by diamine. 78.83 g (70 mol%) of Ar2 and 16.22 g (30 mol%) of diamine pPDA were dissolved to maintain this solution at 25 ° C. 76.33 g (70 mol%) of dianhydride PMDA and 44.25 g (30 mol%) of dianhydride BPDA were added thereto, followed by stirring for 24 hours to obtain a polyamic acid solution having a viscosity of 3120 poise. In this case, the viscosity of the polyamic acid solution is measured using a Brookfield bismeter.

In order to simulate and evaluate the use as a base layer or protective layer for a flexible display, the obtained polyamic acid solution was vacuum degassed, cooled to room temperature, cast to a thickness of 50 μm on a stainless plate, dried with hot air at 150 ° C. for 10 minutes, and It heated up to 450 degreeC, heated to 570 degreeC for 1 hour, and then cooled slowly and isolate | separated from the support body, and obtained the polyimide film of thickness 12micrometer.

<Example 2>

After the reactor was filled with 900 g of N, N-dimethylacetamide (DMAc) while passing nitrogen through a 1 L reactor equipped with a stirrer, a nitrogen injection device, a dropping funnel, a temperature controller, and a cooler, the temperature of the reactor was adjusted to 25 ° C., followed by diamine. 78.83 g (70 mol%) of Ar2, 15.68 g (29 mol%) of diamine pPDA and 1.05 g (1 mol%) of APTES were dissolved to maintain the solution at 25 ° C. 76.33 g (70 mol%) of dianhydride PMDA and 44.25 g (30 mol%) of dianhydride BPDA were added thereto, followed by stirring for 24 hours to obtain a polyamic acid solution having a viscosity of 3260 poise. In this case, the viscosity of the polyamic acid solution is measured using a Brookfield bismeter.

Thereafter, a polyimide film having a thickness of 11 μm was obtained in the same manner as in Example 1.

<Example 3>

After the reactor was filled with 900 g of N, N-dimethylacetamide (DMAc) while passing nitrogen through a 1 L reactor equipped with a stirrer, a nitrogen injection device, a dropping funnel, a temperature controller, and a cooler, the temperature of the reactor was adjusted to 25 ° C., followed by diamine. 78.83 g (70 mol%) of Ar2, 15.14 g (28 mol%) of diamine pPDA and 2.11 g (2 mol%) of APTES were dissolved to maintain the solution at 25 ° C. 76.33 g (70 mol%) of dianhydride PMDA and 44.25 g (30 mol%) of dianhydride BPDA were added thereto, followed by stirring for 24 hours to obtain a polyamic acid solution having a viscosity of 3260 poise. In this case, the viscosity of the polyamic acid solution is measured using a Brookfield bismeter.

Thereafter, a polyimide film having a thickness of 11 μm was obtained in the same manner as in Example 1.

<Example 4>

After the reactor was filled with 900 g of N, N-dimethylacetamide (DMAc) while passing nitrogen through a 1 L reactor equipped with a stirrer, a nitrogen injection device, a dropping funnel, a temperature controller, and a cooler, the temperature of the reactor was adjusted to 25 ° C., followed by diamine. 78.83 g (70 mol%) of Ar2, 14.60 g (27 mol%) of diamine pPDA and 3.17 g (3 mol%) of APTES were dissolved to maintain the solution at 25 ° C. 76.33 g (70 mol%) of dianhydride PMDA and 44.25 g (30 mol%) of dianhydride BPDA were added thereto, followed by stirring for 24 hours to obtain a polyamic acid solution having a viscosity of 3260 poise. In this case, the viscosity of the polyamic acid solution is measured using a Brookfield bismeter.

Thereafter, a polyimide film having a thickness of 12 μm was obtained in the same manner as in Example 1.

Comparative Example 1

After the reactor was filled with 900 g of N, N-dimethylacetamide (DMAc) while passing nitrogen through a 1 L reactor equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller and a cooler, the temperature of the reactor was adjusted to 25 ° C. and diamine Ar2 112.91 g (100 mol%) were dissolved to maintain this solution at 25 ° C. 109.06 g (100 mol%) of dianhydride PMDA was added thereto, followed by stirring for 24 hours to obtain a polyamic acid solution having a viscosity of 2950 poise. In this case, the viscosity of the polyamic acid solution is measured using a Brookfield bismeter.

Thereafter, a polyimide film having a thickness of 12 μm was obtained in the same manner as in Example 1.

Comparative Example 2

After the reactor was filled with 900 g of N, N-dimethylacetamide (DMAc) while passing nitrogen through a 1 L reactor equipped with a stirrer, a nitrogen injection device, a dropping funnel, a temperature controller and a cooler, the temperature of the reactor was adjusted to 25 ° C. and diamine pPDA 64.88 g (100 mol%) were dissolved to maintain this solution at 25 ° C. 130.11 g (100 mol%) of dianhydride PMDA was added thereto, followed by stirring for 24 hours to obtain a polyamic acid solution having a viscosity of 3050 poise. In this case, the viscosity of the polyamic acid solution is measured using a Brookfield bismeter.

In order to simulate and evaluate the use as a base layer or protective layer for a flexible display, the obtained polyamic acid solution was vacuum degassed, cooled to room temperature, cast to a thickness of 50 μm on a stainless plate, dried with hot air at 150 ° C. for 10 minutes, and It heated up to 450 degreeC, heated to 570 degreeC for 1 hour, stood slowly cooling, isolate | separating from the support body, but the film could not be obtained by brittle.

Comparative Example 3

After the reactor was filled with 900 g of N, N-dimethylacetamide (DMAc) while passing nitrogen through a 1 L reactor equipped with a stirrer, a nitrogen injection device, a dropping funnel, a temperature controller and a cooler, the temperature of the reactor was adjusted to 25 ° C. and diamine pPDA 64.88 g (100 mol%) were dissolved to maintain this solution at 25 ° C. 164.77 g (100 mol%) of dianhydride BPDA was added thereto and stirred for 24 hours to obtain a polyamic acid solution having a viscosity of 3190 poise. In this case, the viscosity of the polyamic acid solution is measured using a Brookfield bismeter.

In order to simulate and evaluate the use as a base layer or protective layer for a flexible display, the obtained polyamic acid solution was vacuum degassed, cooled to room temperature, cast to a thickness of 50 μm on a stainless plate, dried with hot air at 150 ° C. for 10 minutes, and It heated up to 450 degreeC, heated to 570 degreeC for 1 hour, stood slowly cooling, isolate | separating from the support body, but the film was carbonized and cannot be obtained.

<Comparative Example 4>

After the reactor was filled with 900 g of N, N-dimethylacetamide (DMAc) while passing nitrogen through a 1 L reactor equipped with a stirrer, a nitrogen injection device, a dropping funnel, a temperature controller, and a cooler, the temperature of the reactor was adjusted to 25 ° C., followed by diamine. 64.88 g (100 mol%) of pPDA was dissolved to maintain this solution at 25 ° C. 89.33 g (70 mol%) of dianhydride PMDA and 51.25 g (30 mol%) of dianhydride BPDA were added thereto, followed by stirring for 24 hours to obtain a polyamic acid solution having a viscosity of 3180 poise. In this case, the viscosity of the polyamic acid solution is measured using a Brookfield bismeter.

In order to simulate and evaluate the use as a base layer or protective layer for a flexible display, the obtained polyamic acid solution was vacuum degassed, cooled to room temperature, cast to a thickness of 50 μm on a stainless plate, dried with hot air at 150 ° C. for 10 minutes, and It heated up to 450 degreeC, heated to 570 degreeC for 1 hour, stood slowly cooling, isolate | separating from the support body, but the film was carbonized and cannot be obtained.

Comparative Example 5

After the reactor was filled with 900 g of N, N-dimethylacetamide (DMAc) while passing nitrogen through a 1 L reactor equipped with a stirrer, a nitrogen injection device, a dropping funnel, a temperature controller, and a cooler, the temperature of the reactor was adjusted to 25 ° C., followed by diamine. 64.88 g (100 mol%) of pPDA was dissolved to maintain this solution at 25 ° C. 61.44 g (50 mol%) of dianhydride PMDA and 88.17 g (50 mol%) of dianhydride BPDA were added thereto, followed by stirring for 24 hours to obtain a polyamic acid solution having a viscosity of 3100 poise. In this case, the viscosity of the polyamic acid solution is measured using a Brookfield bismeter.

In order to simulate and evaluate the use as a base layer or protective layer for a flexible display, the obtained polyamic acid solution was vacuum degassed, cooled to room temperature, cast to a thickness of 50 μm on a stainless plate, dried with hot air at 150 ° C. for 10 minutes, and The temperature was raised to 450 ° C., heated to 570 ° C. for 1 hour, and then slowly cooled to separate from the support, but the film was carbonized and could not be obtained.

The physical properties of the polyimide films prepared in Examples and Comparative Examples were evaluated by the following methods, and the results are shown in Tables 1 and 2 below.

(1) coefficient of thermal expansion (CTE)

The TMA (TA, Q400 TMA) was used to measure the coefficient of thermal expansion at 50 to 540 ° C for the first run, the second run, and twice according to the TMA-Method, except for the first run. The value was obtained.

(2) pyrolysis temperature

Pyrolysis temperature was measured by using a TGA measuring device of Perkin Elmer. Cut the polyimide film into 3mm × 3mm size and place it on a pre-treated and weighed fan, heat-treated at 110 ℃ for 30 minutes, cooled to room temperature, and then heated to 700 ℃ at a rate of 10 ℃ / min to reduce the weight. Measured. The pyrolysis temperature was calculated by setting the weight reduction ratio to 1% of the weight of the polyimide film initially loaded.

(3) Measurement of tensile strength and tensile elongation

Tensile strength (MPa) and tensile elongation (%) were measured at a tensile rate of 10 mm / min according to ISO 527-3.

ingredient Molar ratio (%) Pyrolysis temperature
(℃) Thermal expansion
(ppm / ℃) Example 1 AR2: pPDA / PMDA: BPDA 70: 30/70: 30 605 3.5 Example 2 AR2: pPDA: APTES / PMDA: BPDA 70: 29: 1/70: 30 611 2.1 Example 3 AR2: pPDA: APTES / PMDA: BPDA 70: 28: 2/70: 30 613 1.9 Example 4 AR2: pPDA: APTES / PMDA: BPDA 70: 27: 3/70: 30 608 2.5 Comparative Example 1 AR2 / PMDA 100/100 614 -0.21 Comparative Example 2 pPDA / PMDA 100/100 Not measurable Not measurable Comparative Example 3 pPDA / BPDA 100/100 Not measurable Not measurable Comparative Example 4 pPDA / BPDA: PMDA 100/70: 30 Not measurable Not measurable Comparative Example 5 pPDA / BPDA: PMDA 100/50: 50 Not measurable Not measurable

ingredient Molar ratio (%) The tensile strength
(MPa) Tensile elongation
(%) Example 1 AR2: pPDA / PMDA: BPDA 70: 30/70: 30 350 17 Example 2 AR2: pPDA: APTES / PMDA: BPDA 70: 29: 1/70: 30 367 18 Example 3 AR2: pPDA: APTES / PMDA: BPDA 70: 28: 2/70: 30 372 18 Example 4 AR2: pPDA: APTES / PMDA: BPDA 70: 27: 3/70: 30 369 17 Comparative Example 1 AR2 / PMDA 100/100 230 6 Comparative Example 2 pPDA / PMDA 100/100 Not measurable Not measurable Comparative Example 3 pPDA / BPDA 100/100 Not measurable Not measurable Comparative Example 4 pPDA / BPDA: PMDA 100/70: 30 Not measurable Not measurable Comparative Example 5 pPDA / BPDA: PMDA 100/50: 50 Not measurable Not measurable

As shown in Tables 1 and 2, Examples 2 to 2 prepared by further containing the polyimide film of Example 1 prepared using AR2 which is a monomer having a benzoxazole group as a diamine and APTES which is an alcohol silane compound. In the case of the polyimide film of 4, thermal decomposition temperature, thermal expansion coefficient, tensile strength and tensile elongation all showed excellent results, whereas Comparative Examples 1 to 5 were produced only by aromatic dianhydride and aromatic diamine, and produced a high temperature film. It was found to be unsuitable in high temperature processes because it could not withstand the process and caused pyrolysis

Therefore, it can be seen that the polyimide film of the present invention improves the tensile strength and tensile elongation while maintaining the high heat resistance of the conventional polyimide film, and thus can be usefully applied to a substrate for a display device requiring a certain level of strength. Could confirm.

All simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

Claims (12)

delete delete delete delete delete delete A polyimide film comprising a unit structure derived from an aromatic dianhydride and an aromatic diamine, and further comprising a monomer containing at least one functional group selected from the group consisting of a benzoxazole group and an oxy group,
The monomer containing the functional group is contained in 20 to 90 mol% relative to the total aromatic diamine, the monomer containing the benzoxazole group includes amino benzoxazole (2- (4-Aminophenyl) -6-aminobenzoxazole),
The polyimide film has a tensile elongation of 15% or more and a glass transition temperature of 300 ° C. or more, measured by the ISO 527-3 method.
8. The polyimide film of claim 7, wherein the oxy group is oxydianiline (4,4'-oxydianiline).
8. The polyimide film of claim 7, wherein the polyimide film further comprises an alkoxy silane compound.
The method of claim 9, wherein the alkoxy silane compound is tetramethoxy silane (TMOS), tetraethoxy silane (TEOS), tetrabutoxy silane (Tetrabutoxy silane (TBS), amino propyl triethoxy silane (3-Aminopropyl triethoxy silane, APTES) and aminopropyl trimethoxy silane (3-Aminopropyl trimethoxy silane, APTMS) polyimide film, characterized in that at least one member selected from the group consisting of.
According to claim 7, wherein the polyimide film has a coefficient of thermal expansion (CTE) of 5ppm / ℃ or less at 50 ~ 540 ℃ based on the film thickness 10 ~ 30㎛, tensile strength measured by the ISO 527-3 method 350MPa The polyimide film characterized by the above.
The substrate for display elements containing the polyimide film of any one of Claims 7-11.