KR102060190B1 - Polyimide-based random copolymers and polyimide-based film comprising the same - Google Patents

Abstract

The present invention relates to a polyimide random copolymer and a polyimide film comprising the same. The polyimide random copolymer according to the present invention makes it possible to provide a polyimide film which is colorless and transparent and exhibits excellent elongation.

Description

Polyimide random copolymer and polyimide film containing the same {POLYIMIDE-BASED RANDOM COPOLYMERS AND POLYIMIDE-BASED FILM COMPRISING THE SAME}

The present invention relates to a polyimide random copolymer and a polyimide film comprising the same.

Aromatic polyimide resins are mostly polymers having an amorphous structure and exhibit excellent heat resistance, chemical resistance, electrical properties, and dimensional stability due to their rigid chain structure. Such polyimide resins are widely used as electrical / electronic materials.

However, polyimide resins have many limitations in use because they have a dark brown limitation due to CTC (charge transfer complex) formation of π electrons present in the imide chain.

A method of limiting the transfer of π electrons by introducing a strong electron attracting group such as a trifluoromethyl (-CF ₃ ) group to remove the limitation and obtain a colorless transparent polyimide resin; A method of reducing the formation of the CTC by introducing a sulfone (-SO _2- ) group, an ether (-O-) group, or the like into a main chain to form a curved structure; Alternatively, a method of introducing an aliphatic ring compound to inhibit resonance structure formation of π electrons has been proposed.

However, the polyimide resin according to the above proposals is difficult to exhibit sufficient heat resistance by the curved structure or the aliphatic ring compound, and the film produced using the same still has a limit showing low elongation.

The present invention is to provide a polyimide-based random copolymer that is colorless transparent and exhibits excellent elongation.

The present invention is to provide a polyimide film containing the polyimide random copolymer.

According to the invention,

A first repeating unit represented by Formula 1 below;

A second repeating unit represented by Formula 2 below; And

A divalent and trivalent linking group represented by the following formula (3), connecting a plurality of the second repeating units

A polyimide-based random copolymer is provided, comprising:

[Formula 1]

In Chemical Formula 1,

R ¹ is the same or different in each repeating unit, and each independently a single bond, -O-, -S-, -C (= 0)-, -CH (OH)-, -S (= 0) ₂ -, -Si (CH ₃ ) ₂ -,-(CH ₂ ) _p- (where 1≤p≤10),-(CF ₂ ) _q- (where 1≤q≤10), -C (CH ₃ ) ₂ -, -C (CF ₃ ) _2- , -C (= 0) NH-, or an aromatic organic group having 6 to 30 carbon atoms;

R ² is each independently hydrogen, halogen, hydroxy group, ether group having aliphatic organic group having 1 to 10 carbon atoms, silyl group having three aliphatic organic groups having 1 to 10 carbon atoms, aliphatic organic group having 1 to 10 carbon atoms, or 6 carbon atoms An aromatic organic group having from 20 to 20;

n1 and m1 are each independently 0 to 3;

[Formula 2]

In Chemical Formula 2,

R ³ is the same or different at each repeating unit, and each independently is a single bond, -O-, -S-, -S (= O) _2- , -Si (CH ₃ ) _2- , carbon number 1 to 30 Aliphatic organic groups, alicyclic organic groups having 3 to 30 carbon atoms, aromatic organic groups having 6 to 30 carbon atoms, heterocyclic groups having 2 to 30 carbon atoms, or fluorenyl groups having 13 to 20 carbon atoms;

R ⁴ is each independently -CF ₃ , -CCl ₃ , -CBr ₃ , -CI ₃ , -F, -Cl, -Br, -I, -NO ₂ , -CN, -COCH ₃ , or -CO ₂ C ₂ H ₅ ;

E ¹ and E ² are each independently a single bond, —NH— or —C (═O) —;

n2 and m2 are each independently 1-4;

[Formula 3]

및

And

In Chemical Formula 3,

Z ¹ is a divalent linking group derived from one or more compounds selected from the group consisting of diacyl halides, diamines and dicarboxylic acids,

Z ² is a trivalent linking group derived from one or more compounds selected from the group consisting of triacyl halides, triamines and tricarboxylic acids.

According to the present invention, there is provided a polyimide film comprising the polyimide random copolymer.

Hereinafter, a polyimide random copolymer and a polyimide film including the same according to embodiments of the present invention will be described in detail.

Prior to this, the terminology is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention unless expressly stated otherwise.

As used herein, the singular forms “a”, “an” and “the” include plural forms as well, unless the phrases clearly indicate the opposite.

As used herein, the meaning of "includes" specifies a particular property, region, integer, step, operation, element, and / or component, and other specific properties, region, integer, step, operation, element, component, and / or group. It does not exclude the presence or addition of.

In this specification, terms including ordinal numbers such as 'first' and 'second' are used for the purpose of distinguishing one component from other components and are not limited by the ordinal number. For example, within the scope of the present invention, the first component may also be referred to as the second component, and similarly, the second component may be referred to as the first component.

I. Polyimide Random Copolymer

According to one embodiment of the invention,

A first repeating unit represented by Formula 1 below;

A second repeating unit represented by Formula 2 below; And

A divalent and trivalent linking group represented by the following formula (3), connecting a plurality of the second repeating units

A polyimide-based random copolymer is provided, comprising:

[Formula 1]

In Chemical Formula 1,

R ¹ is the same or different in each repeating unit, and each independently a single bond, -O-, -S-, -C (= 0)-, -CH (OH)-, -S (= 0) ₂ -, -Si (CH ₃ ) ₂ -,-(CH ₂ ) _p- (where 1≤p≤10),-(CF ₂ ) _q- (where 1≤q≤10), -C (CH ₃ ) ₂ -, -C (CF ₃ ) _2- , -C (= 0) NH-, or an aromatic organic group having 6 to 30 carbon atoms;

R ² is each independently hydrogen, halogen, hydroxy group, ether group having aliphatic organic group having 1 to 10 carbon atoms, silyl group having three aliphatic organic groups having 1 to 10 carbon atoms, aliphatic organic group having 1 to 10 carbon atoms, or 6 carbon atoms An aromatic organic group having from 20 to 20;

n1 and m1 are each independently 0 to 3;

[Formula 2]

In Chemical Formula 2,

R ³ is the same or different at each repeating unit, and each independently is a single bond, -O-, -S-, -S (= O) _2- , -Si (CH ₃ ) _2- , carbon number 1 to 30 Aliphatic organic groups, alicyclic organic groups having 3 to 30 carbon atoms, aromatic organic groups having 6 to 30 carbon atoms, heterocyclic groups having 2 to 30 carbon atoms, or fluorenyl groups having 13 to 20 carbon atoms;

R ⁴ is each independently -CF ₃ , -CCl ₃ , -CBr ₃ , -CI ₃ , -F, -Cl, -Br, -I, -NO ₂ , -CN, -COCH ₃ , or -CO ₂ C ₂ H ₅ ;

E ¹ and E ² are each independently a single bond, —NH— or —C (═O) —;

n2 and m2 are each independently 1-4;

[Formula 3]

및

And

In Chemical Formula 3,

Z ¹ is a divalent linking group derived from one or more compounds selected from the group consisting of diacyl halides, diamines and dicarboxylic acids,

Z ² is a trivalent linking group derived from one or more compounds selected from the group consisting of triacyl halides, triamines and tricarboxylic acids.

As a result of continuous research by the present inventors, a polyimide-based randomized polymer was introduced by introducing a kinked type moiety into a linear polyimide chain, and by introducing a brancher, a compound having three reactive substituents. It was confirmed that the copolymer can be colorless and transparent but exhibit excellent elongation.

In particular, the brancher may impart a network structure to the copolymer, and a network of a more robust and stable structure may be formed in the copolymer by irregular random copolymerization of monomers including the same. As such, the robust and stable network structure imparted with the kinked type residue enables the polyimide random copolymer to be colorless and transparent, and exhibit improved elongation.

The polyimide random copolymer provided in the present invention may include a first repeating unit represented by Chemical Formula 1; A second repeating unit represented by Formula 2; And divalent and trivalent linking groups represented by Formula 3, which connect a plurality of the second repeating units.

[Formula 1]

In the first repeating unit represented by Formula 1, R ¹ is the same or different from each other, and each independently a single bond, -O-, -S-, -C (= O)-, -CH (OH)-, -S (= O) _2- , -Si (CH ₃ ) ₂ -,-(CH ₂ ) _p- (where 1≤p≤10),-(CF ₂ ) _q- (where 1≤ q ≦ 10), —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, —C (═O) NH—, or an aromatic organic group having 6 to 30 carbon atoms.

Here, the single bond means a case of chemically bonding to simply connect the groups R ¹ of the next amount in the formula (1).

And, the aromatic organic group having 6 to 30 carbon atoms is present alone; Two or more are joined to each other to form a condensed ring; Two or more single bonds, -O-, -S-, -C (= O)-, -CH (OH)-, -S (= O) _2- , -Si (CH ₃ ) ₂ -,-( CH ₂ ) _p- (where 1≤p≤10),-(CF ₂ ) _q- (where 1≤q≤10), -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -C Connected by (= O) NH-.

In the first repeating unit represented by Formula 1, R ² is each independently hydrogen, halogen, hydroxy group, ether group having an aliphatic organic group having 1 to 10 carbon atoms, silyl group having three aliphatic organic groups having 1 to 10 carbon atoms, An aliphatic organic group having 1 to 10 carbon atoms or an aromatic organic group having 6 to 20 carbon atoms.

In the first repeating unit represented by Formula 1, n1 and m1 are each independently an integer of 0 to 3.

Specifically, the first repeating unit represented by Formula 1 may be selected from the group represented by the following structural formula:

,

,

,

,

,

,

,

,

,

,

,

,

.

.

[Formula 2]

In the second repeating unit represented by Chemical Formula 2, R ³ is the same as or different from each other in each repeating unit, and each independently a single bond, O, S, S (= 0) ₂ , Si (CH ₃ ) ₂ , An aliphatic organic group having 1 to 30 carbon atoms, an alicyclic organic group having 3 to 30 carbon atoms, an aromatic organic group having 6 to 30 carbon atoms, a heterocyclic group having 2 to 30 carbon atoms, or a fluorenyl group having 13 to 20 carbon atoms.

Here, the single bond refers to a case where R ³ in Chemical Formula 2 is a chemical bond that simply connects groups adjacent to each other.

In the second repeating unit represented by Formula 2, R ⁴ is an electron withdrawing group, and each independently -CF ₃ , -CCl ₃ , -CBr ₃ , -CI ₃ , -F, -Cl,- Br, —I, —NO ₂ , —CN, —COCH ₃ , or —CO ₂ C ₂ H ₅ .

In the second repeating unit represented by Formula 2, E ¹ and E ² are each independently a single bond, -NH-, or -C (= 0)-. Here, the single bond means a case where E ¹ or E ² is a chemical bond that simply connects the repeating unit of Formula 2 with the left or right repeating unit.

In the second repeating unit represented by Formula 2, n2 and m2 are each independently an integer of 1 to 4.

Specifically, the second repeating unit represented by Formula 2 may be selected from the group represented by the following structural formula:

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,

;

;

E ¹ and E ² in the structural formula are as defined in Chemical Formula 2, respectively.

[Formula 3]

및

And

In Formula 3, Z ¹ is a divalent linking group derived from at least one compound selected from the group consisting of diacyl halides, diamines and dicarboxylic acids; Z ² is a trivalent linking group derived from one or more compounds selected from the group consisting of triacyl halides, triamines and tricarboxylic acids.

Specifically, Z ¹ isophthaloyl dichloride, terephthaloyl chloride, isophthalic acid, isophthalic acid, terephthalic acid, benzene-1,3- Diamine (benzene-1,3-diamine), benzene-1,4-diamine, pyrimidine-2,5-diamine, pyrimidine-2 Pyrimidine-2,4-diamine, cyclohexane-1,3-diamine, and cyclohexane-1,4-diamine It may be a divalent linking group derived from one or more compounds selected from the group consisting of.

Preferably, Z ¹ may be selected from the group represented by the following structural formula:

,

,

,

,

,

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,

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.

,

.

And, Z ² is a benzene-1,3,5-tricarbonyl trichloride (benzene-1,3,5-tricarbonyl trichloride), benzene-1,3,5-tricarboxylic acid (benzene-1, 3,5-tricarboxylic acid), benzene-1,3,5-triamine, benzene-1,2,4-triamine ), Cyclohexane-1,3,5-triamine, cyclohexane-1,2,4-triamine, and pyridine It may be a trivalent linking group derived from one or more compounds selected from the group consisting of pyrimidine-2,4,6-triamine.

Preferably, Z ² may be selected from the group represented by the following structural formula:

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.

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.

According to an embodiment of the invention, at least a portion of the second repeating unit may have one end connected to the first repeating unit and the other end connected to the divalent or trivalent linking group.

Specifically, the polyimide random copolymer may include a repeating unit represented by Formula 4 below:

[Formula 4]

In Chemical Formula 4,

R ¹ , R ² , R ³ , R ⁴ , n1, m1, n2, m2, E ¹ , E ² , and Z ¹ are as defined in Chemical Formulas 1 to 3 above.

Preferably, the polyimide-based random copolymer may include a repeating unit represented by the following formula (5):

[Formula 5]

In Chemical Formula 5,

R ² , R ⁴ , n1, m1, n2, m2, E ¹ , E ² , and Z ¹ are as defined in Chemical Formulas 1 to 3 above.

More preferably, the polyimide-based random copolymer may include a repeating unit represented by the following formula (6):

[Formula 6]

In Chemical Formula 6,

R ² , R ⁴ , n1, m1, n2, and m2 are as defined in Chemical Formulas 1 to 3 above.

According to an embodiment of the present invention, at least a part of the repeating unit represented by Formula 4, 5 or 6 may be connected to the trivalent linking group at one end thereof.

Specifically, the polyimide random copolymer may include a repeating unit represented by Formula 7 below:

[Formula 7]

In Chemical Formula 7,

R ² , R ⁴ , n1, m1, n2, and m2 are as defined in Chemical Formulas 1 to 3 above.

In the polyimide random copolymer, the weight ratio of the first and second repeating units: the trivalent linking group may be 1: 0.00001 to 1: 0.01, preferably 1: 0.0001 to 1: 0.05.

As described above, the trivalent linking group is a branch that gives a network structure to the copolymer, and a network of a more robust and stable structure can be formed by irregular random copolymerization of monomers including the same.

Therefore, when too little of the trivalent linking group is included, the network structure may not be sufficiently formed in the copolymer, and the effect of improving physical properties may be insignificant. However, when too much of the trivalent linking group is included, gelation may occur during the polymerization process.

The polyimide-based random copolymer may have a higher molecular weight than a polyimide resin having a general linear structure as it has a robust and stable network. Specifically, the polyimide random copolymer may have a weight average molecular weight of 100,000 to 5,000,000 g / mol, preferably 150,000 to 2,500,000 g / mol, more preferably 150,000 to 1,000,000 g / mol.

The polyimide random copolymer may be suitably selected from a compound forming the first repeating unit, a compound forming the second repeating unit, a compound forming the divalent linking group, and a compound forming the trivalent linking group. Initiating the reaction by mixing in a solvent; And inducing a chemical imidization reaction by adding a compound such as acetic anhydride or pyridine to the reaction mixture of the above step.

Low temperature solution polymerization, interfacial polymerization, melt polymerization, solid phase polymerization, etc. may be used to prepare the polyimide random copolymer.

II. Polyimide film

According to another embodiment of the present invention, a polyimide film including the polyimide random copolymer described above is provided.

As described above, the inventors of the present inventors have found that a kinked type moiety is introduced into a polyimide chain having a linear structure, and a brancher, a compound having three reactive substituents, is introduced to polymerize the same. It was confirmed that the polyimide-based random copolymers were colorless and transparent and exhibited excellent elongation.

As a result, the polyimide film including the polyimide random copolymer may be used as a material for various molded articles requiring high elongation with colorless transparency. For example, the polyimide film may be applied to a display substrate, a display protective film, a touch panel, and the like.

The polyimide film may be prepared by a conventional method such as a dry method or a wet method using the polyimide random copolymer. For example, the polyimide film may be obtained by coating a solution including the copolymer on an arbitrary support to form a film, and drying the solvent by evaporating the solvent from the film. If necessary, stretching and heat treatment may be performed on the polyimide film.

The polyimide-based film may be colorless, transparent and have excellent elongation as manufactured using the polyimide-based random copolymer. Specifically, the polyimide film may exhibit a tensile elongation of 5% or more, preferably 5-10%, more preferably 6.5-10% based on ASTM D 882.

The polyimide random copolymer according to the present invention makes it possible to provide a polyimide film which is colorless and transparent and exhibits excellent elongation.

1 is an NMR spectrum of the polyimide random copolymer obtained in Example 1. FIG.

 Hereinafter, preferred embodiments will be presented to aid in understanding the invention. However, the following examples are only to illustrate the invention, not limited to the invention only.

Example  One

4.80 g (1 eq) of 2,2'-bis (trifluoromethyl) benzidine in 250 mL round flask equipped with dean-stark device and condenser ., 0.015 mol); 6.56 g (0.985 eq., 0.0148 mol) of 4,4 '-(hexafluoroisopropylidene) diphthalic anhydride; 1.5227 g (0.5 eq., 0.0075 mol) isophthaloyl dichloride; 0.039 g (0.01 eq., 0.00015 mol) of benzene-1,3,5-tricarbonyl trichloride; And 70 ml of dimethylacetamide was added, and the reaction was started at room temperature.

To the reaction mixture was added 14 mL (10 eq., 0.15 mol) of acetic anhydride and 12 mL (10 eq., 0.15 mol) of pyridine, followed by an oil bath at a temperature of 40 ° C. (oil bath) was stirred for 15 hours to proceed with the chemical imidization reaction.

After completion of the reaction, precipitated in water and ethanol to obtain a polyimide random copolymer containing the following repeating units (weight average molecular weight 185,000 g / mol).

¹ H NMR (CDCl ₃ , Standard TMS) δ (ppm): 10.854 (s), 8.644 (s), 8.256 (m), 8.162 (d), 8.044 (s), 8.017 (d), 7.851 (d) , 7.816 (m), 7.7 (d), 7.430 (d)

Comparative example  One

4.80 g (1 eq) of 2,2'-bis (trifluoromethyl) benzidine in 250 mL round flask equipped with dean-stark device and condenser ., 0.015 mol); 6.56 g (0.985 eq., 0.0148 mol) of 4,4 '-(hexafluoroisopropylidene) diphthalic anhydride; And 70 ml of dimethylacetamide was added, and the reaction was started at room temperature.

To the reaction mixture was added 14 mL (10 eq., 0.15 mol) of acetic anhydride and 12 mL (10 eq., 0.15 mol) of pyridine, followed by an oil bath at a temperature of 40 ° C. (oil bath) was stirred for 15 hours to proceed with the chemical imidization reaction.

After completion of the reaction, the resultant was precipitated in water and ethanol to obtain a polyimide random copolymer including the following repeating units (weight average molecular weight 107,000 g / mol).

Production Example  1 and 2

A film was prepared using the polyimide copolymer obtained in Example 1 (Preparation Example 1). Then, a film was prepared using the polyimide copolymer obtained in Comparative Example 1 (Preparation Example 2).

Specifically, the polyimide copolymer was dissolved in dimethylacetamide to prepare a polymer solution of about 25% (w / V). The polymer solution was poured onto a glass substrate, and the thickness of the polymer solution was uniformly adjusted using a film applicator, followed by drying in a vacuum oven at 100 ° C. for at least 12 hours to prepare a polyimide film having a thickness of 20 to 30 μm.

Test Example

The physical properties of the polyimide films of Preparation Examples 1 and 2 were measured by the following methods, and the results are shown in Table 1 below.

(1) Yellowness (%): The yellowness of the film was measured using a COH-400 Spectrophotometer (NIPPON DENSHOKU INDUSTRIES).

(2) Tensile elongation (%): The tensile elongation based on ASTM D 882 was measured using the universal testing machine. After fabricating a sample having a thickness (μm) * length (60mm) * width (6mm), an elongation was measured at an elongated length from the breaking point of the sample by applying a force in the tensile direction.

Preparation Example 1 Preparation Example 2 Yellow degree (%) 1.72 2.01 Tensile Elongation (%) 6.85 3.2

Referring to Table 1, it can be seen that the film according to Preparation Example 1 exhibits a lower yellowness and improved tensile elongation than the film of Preparation Example 2.

Claims (8)

A first repeating unit represented by Formula 1 below;
A second repeating unit represented by Formula 2 below; And
A divalent and trivalent linking group represented by the following formula (3), connecting a plurality of the second repeating units
Including,
Wherein at least a portion of the second repeating unit has one end connected to the first repeating unit and the other end connected to the divalent or trivalent linking group:

[Formula 1]

In Chemical Formula 1,
R ¹ is the same or different in each repeating unit, and each independently a single bond, -O-, -S-, -C (= 0)-, -CH (OH)-, -S (= 0) ₂ -, -Si (CH ₃ ) ₂ -,-(CH ₂ ) _p- (where 1≤p≤10),-(CF ₂ ) _q- (where 1≤q≤10), -C (CH ₃ ) ₂ -, -C (CF ₃ ) _2- , -C (= 0) NH-, or an aromatic organic group having 6 to 30 carbon atoms;
R ² is each independently hydrogen, halogen, hydroxy group, ether group having aliphatic organic group having 1 to 10 carbon atoms, silyl group having three aliphatic organic groups having 1 to 10 carbon atoms, aliphatic organic group having 1 to 10 carbon atoms, or 6 carbon atoms An aromatic organic group having from 20 to 20;
n1 and m1 are each independently 0 to 3;

[Formula 2]

In Chemical Formula 2,
R ³ is the same or different at each repeating unit, and each independently is a single bond, -O-, -S-, -S (= O) _2- , -Si (CH ₃ ) _2- , carbon number 1 to 30 Aliphatic organic groups, alicyclic organic groups having 3 to 30 carbon atoms, aromatic organic groups having 6 to 30 carbon atoms, heterocyclic groups having 2 to 30 carbon atoms, or fluorenyl groups having 13 to 20 carbon atoms;
R ⁴ is each independently -CF ₃ , -CCl ₃ , -CBr ₃ , -CI ₃ , -F, -Cl, -Br, -I, -NO ₂ , -CN, -COCH ₃ , or -CO ₂ C ₂ H ₅ ;
E ¹ and E ² are each independently a single bond, —NH— or —C (═O) —;
n2 and m2 are each independently 1-4;

[Formula 3]

And

In Chemical Formula 3,
Z ¹ is a divalent linking group derived from one or more compounds selected from the group consisting of diacyl halides, diamines and dicarboxylic acids,
Z ² is a trivalent linking group derived from one or more compounds selected from the group consisting of triacyl halides, triamines and tricarboxylic acids.
delete The method of claim 1,
The polyimide random copolymer includes a repeating unit represented by the following formula (4),
At least a part of the repeating unit represented by Formula 4 is a polyimide-based random copolymer, the trivalent linking group is connected to one end thereof:
[Formula 4]

In Chemical Formula 4,
R ¹ , R ² , R ³ , R ⁴ , n1, m1, n2, m2, E ¹ , E ² , and Z ¹ are as defined in Chemical Formulas 1 to 3 above.
The method of claim 1,
Z ¹ isophthaloyl dichloride, terephthaloyl chloride, isophthalic acid, isophthalic acid, terephthalic acid, benzene-1,3-diamine -1,3-diamine), benzene-1,4-diamine, pyrimidine-2,5-diamine, pyrimidine-2,4- A group consisting of pyrimidine-2,4-diamine, cyclohexane-1,3-diamine, and cyclohexane-1,4-diamine A divalent linking group derived from one or more compounds selected from;
Z ² is benzene-1,3,5-tricarbonyl trichloride (benzene-1,3,5-tricarbonyl trichloride), benzene-1,3,5-tricarboxylic acid (benzene-1,3, 5-tricarboxylic acid), benzene-1,3,5-triamine, benzene-1,2,4-triamine, Cyclohexane-1,3,5-triamine, cyclohexane-1,2,4-triamine, and pyrimidine- A polyimide random copolymer, which is a trivalent linking group derived from at least one compound selected from the group consisting of 2,4,6-triamine (pyrimidine-2,4,6-triamine).
The method of claim 1,
The weight ratio of the first and second repeating units: the trivalent linking group is 1: 0.00001 to 1: 0.01, polyimide-based random copolymer.
The method of claim 1,
A polyimide random copolymer having a weight average molecular weight of 100,000 to 5,000,000 g / mol.
A polyimide film comprising the polyimide random copolymer of claim 1.
The method of claim 7, wherein
A polyimide based film having a tensile elongation of 5 to 10% based on ASTM D 882.

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