KR102075734B1 - Polyamideimide copolymers and colorless and transparent polyamideimide film comprising the same - Google Patents

Abstract

The present invention relates to a polyamideimide copolymer and to a colorless transparent polyamideimide copolymer film comprising the same. The polyamideimide copolymer according to the present invention makes it possible to provide a polyamideimide film having excellent scratch resistance and colorless transparency. Such polyamideimide films can be suitably used as cover films of various flexible or foldable devices.

Description

POLYAMIDEIMIDE COPOLYMERS AND COLORLESS AND TRANSPARENT POLYAMIDEIMIDE FILM COMPRISING THE SAME

The present invention relates to a polyamideimide copolymer and to a colorless transparent polyamideimide 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 the formation of charge transfer complex (CTC) of π electrons present in the imide chain.

A method of limiting the movement of π electrons by introducing a strong electron attracting group such as 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 bent structure or aliphatic ring compound, and the film produced using the same still has limitations showing poor mechanical properties.

On the other hand, in recent years, in order to improve the scratch resistance of polyimide, the polyamide-imide copolymer which introduce | transduced the polyamide unit structure is developed.

However, polyamideimide copolymers tend to haze easily when they are coated to form films due to their high crystallinity.

This haze property of the polyamideimide film is more severely expressed as the thickness of the film and affects the yellow index (Y.I.), and there is a need for a method for improving the film.

The present invention is to provide a polyamideimide copolymer having excellent scratch resistance and colorless transparency.

The present invention also provides a colorless transparent polyamideimide film comprising the polyamideimide copolymer.

According to the invention,

An imide of a polyamic acid copolymerized with an aromatic diamine monomer, an aromatic dianhydride monomer and an acyl chloride monomer, wherein the molar ratio of (the aromatic diamine monomer) to (the aromatic dianhydride monomer and the acyl chloride monomer) is 1 There is provided a polyamideimide copolymer, which is from 1.02 to 1: 1.10.

According to the present invention, there is also provided a polyamideimide film comprising the polyamideimide copolymer.

Hereinafter, a polyamideimide copolymer and a polyamideimide 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 "comprising" embodies a particular characteristic, region, integer, step, operation, element and / or component, and other specific characteristics, region, integer, step, operation, element, component and / or group. It does not exclude the presence or addition of.

I. Polyamideimide Copolymers

According to one embodiment of the invention,

As imide of polyamic acid copolymerized with an aromatic diamine monomer, an aromatic dianhydride monomer and an acyl chloride monomer,

(Aromatic diamine monomer): The polyamideimide copolymer whose molar ratio of (the said aromatic dianhydride monomer and the said acyl chloride monomer) is 1: 1.02-1: 1.10 is provided.

As a result of continuous studies by the inventors, in the formation of the polyamideimide copolymer using the aromatic diamine monomer, the aromatic dianhydride monomer and the acyl chloride monomer, the sum of the aromatic dianhydride monomer and the acyl chloride monomer is added to the aromatic diaa. It has been found that when applied at a higher molar ratio than the monomer, it is possible to form a copolymer having excellent scratch resistance and low yellowness.

In the formation of the polyamideimide copolymer, diamine and dianhydride are generally applied in a molar ratio of 1: 1. However, in the present invention, the sum of the aromatic dianhydride monomer and the acyl chloride monomer is applied in an excess molar ratio than the aromatic diamine monomer. Accordingly, the polyamideimide copolymer according to the present invention may exhibit low yellowness while having an equivalent or higher pencil hardness than the polyamideimide copolymer to which the molar ratio of 1: 1 is applied. And such polyamideimide copolymer makes it possible to provide a colorless transparent polyamideimide film with excellent scratch resistance.

According to an embodiment of the invention, the polyamideimide copolymer is an imide of polyamic acid copolymerized with the aromatic diamine monomer, the aromatic dianhydride monomer and the acyl chloride monomer.

The polyamic acid may be a block copolymer or a random copolymer.

For example, the polyamic acid block copolymer may include a first unit structure derived from copolymerization of the aromatic diamine monomer and the aromatic dianhydride monomer; And a second unit structure derived from copolymerization of the aromatic diamine monomer and the acyl chloride monomer.

In addition, the polyamic acid random copolymer, the polyamideimide copolymer may include a unit structure in which the aromatic diamine monomer, the aromatic dianhydride monomer and the acyl chloride monomer each form an amide bond and randomly copolymerized Can be.

This polyamic acid forms the polyamideimide copolymer which has an imide bond and an amide bond simultaneously by imidation.

In particular, according to an embodiment of the present invention, the sum of the aromatic dianhydride monomer and the acyl chloride monomer may be included in a molar ratio of 1: 1.02 to 1:10 with respect to the aromatic diamine monomer, while having excellent scratch resistance. It may be desirable to form a colorless transparent copolymer.

That is, in the polyamideimide copolymer, the molar ratio of (the aromatic diamine monomer): (the aromatic dianhydride monomer and the acyl chloride monomer) may be applied as 1: 1.02 to 1: 1.10.

Preferably, the molar ratio of (the aromatic diamine monomer): (the aromatic dianhydride monomer and the acyl chloride monomer) is 1: 1.02 or more, or 1: 1.03 or more, or 1: 1.04 or more; And less than or equal to 1: 1.10, or less than or equal to 1: 1.09, or less than or equal to 1: 1.08, or less than or equal to 1: 1.07, or less than or equal to 1: 1.06, or less than or equal to 1: 1.

If the molar ratio is less than 1: 1.02 (eg, a molar ratio of 1: 1, or an excess of diamine), the pencil hardness grade may be lowered, resulting in a lower scratch resistance and higher yellow index. Therefore, it is preferable that the said molar ratio is 1: 1.02 or more.

However, when the aromatic dianhydride monomer and the acyl chloride monomer are used in excess of the necessary amount, the polymer chain is low molecular weight, which shows high crystallinity during coating, drying and curing of the varnish, resulting in opacity or deterioration in flex resistance. Problems such as and the like may appear. Therefore, the molar ratio is preferably 1: 1.10 or less.

And, preferably, the aromatic dianhydride is 25 mol% or more, or 30 mol% or more with respect to the total moles of the aromatic dianhydride monomer and the acyl chloride monomer; And it may be advantageous to express the above-described properties to be included in 40 mol% or less, or 35 mol% or less.

Meanwhile, according to an embodiment of the present invention, the aromatic diamine monomer is 2,2'-bis (trifluoromethyl) -4,4'-biphenyldiamine (2,2'-bis (trifluoromethyl) -4 , 4'-biphenyldiamine) may be preferably applied.

As the aromatic dianhydride monomer, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (3,3', 4,4'-biphenyltetracarboxylic dianhydride) may be preferably applied.

In addition, the acyl chloride monomer is composed of isophthaloyl chloride (terephthaloyl chloride), terephthaloyl chloride (terephthaloyl chloride) and 4,4'-biphenyl dicarbonyl chloride (4,4'-biphenyl dicarbonyl chloride) At least one compound selected from the group may be preferably applied. More preferably, the acyl chloride monomer isophthaloyl chloride (terephthaloyl chloride), terephthaloyl chloride (terephthaloyl chloride) and 4,4'-biphenyl dicarbonyl chloride (4,4'-biphenyl dicarbonyl chloride) Can be applied.

The aromatic diamine monomer 2,2'-bis (trifluoromethyl) -4,4'-biphenyldiamine (2,2'-bis (trifluoromethyl) -4,4'-biphenyldiamine) and the aromatic diane The 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (3,3', 4,4'-biphenyltetracarboxylic dianhydride) which is a hydride monomer is described above by copolymerization with the acyl chloride monomer. It can be advantageously applied to express properties.

On the other hand, the polymerization conditions for forming the polyamic acid copolymerized with the aromatic diamine monomer, aromatic dianhydride monomer and acyl chloride monomer are not particularly limited.

Preferably, the polymerization for forming the polyamic acid may be carried out by solution polymerization under an inert atmosphere of 0 to 100 ℃.

As a solvent for the formation of the polyamic acid, N, N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, acetone, N-methyl-2-pyrrolidone, tetrahydrofuran, chloroform, gamma-butyrolactone, etc. This can be used.

Imidization after formation of the polyamic acid can be carried out thermally or chemically. For example, compounds such as acetic anhydride and pyridine may be used for chemical imidization.

According to an embodiment of the invention, the polyamideimide copolymer has a weight average molecular weight of 10,000 to 1,000,000 g / mol, or 50,000 to 1,000,000 g / mol, or 50,000 to 500,000 g / mol, or 50,000 to 300,000 g / mol. Can be.

II. Polyamideimide film

According to another embodiment of the invention, there is provided a colorless transparent polyamideimide film comprising the polyamideimide copolymer described above.

As described above, the present inventors have continued to study the formation of polyamideimide copolymers using aromatic diamine monomers, aromatic dianhydride monomers and acyl chloride monomers, When the sum is applied at a higher molar ratio than the aromatic diamine monomer, it was confirmed that a copolymer having excellent scratch resistance and low yellowness can be formed.

As a result, the film including the polyamideimide copolymer can be used as a material of various molded articles requiring high scratch resistance and colorless transparency. For example, the polyamideimide film may be suitably used as a display substrate, a display protective film, a touch panel, a cover film of a flexible or foldable device.

The polyamideimide film can be produced by conventional methods such as dry method and wet method using the polyamideimide copolymer. For example, the polyamideimide film may be obtained by coating a solution containing the copolymer on an arbitrary support to form a membrane, and evaporating the solvent from the membrane to dry it. If necessary, stretching and heat treatment of the polyamideimide film may be performed.

As the polyamideimide film is prepared using the polyamideimide copolymer, the polyamideimide film may exhibit colorless and transparent properties while having excellent scratch resistance.

Specifically, the polyamideimide film may exhibit a pencil hardness of 2H or higher, or 3H or higher, measured according to ASTM D3363 at a thickness of 30 ± 2 μm.

In addition, the polyamideimide film has a thickness of 30 ± 2 ㎛, measured in accordance with ASTM D1925 3.20 or less, or 3.15 or less, or 3.10 or less, 3.05 or less, or 3.00 or less, or 2.90 or less, or 2.80 or less, or Yellow index (YI) of 2.70 to 3.20, or 2.75 to 3.15.

The polyamideimide copolymer according to the invention makes it possible to provide a colorless transparent polyamideimide film while having excellent scratch resistance. Such polyamideimide films can be suitably used as cover films of various flexible or foldable devices.

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

Fill 42.5 g of N, N-dimethylacetamide while slowly passing nitrogen through a 100 mL 4-neck round flask (reactor) equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller, and a cooler, and the reactor temperature To 25 ° C., followed by 4.3158 g (0.013477) of 2,2'-bis (trifluoromethyl) -4,4'-biphenyldiamine (2,2'-bis (trifluoromethyl) -4,4'-biphenyldiamine) mol) was added to dissolve completely. 1.2689 g (0.004313 mol) of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (3,3', 4,4'-biphenyltetracarboxylic dianhydride) was added while maintaining the temperature of the solution at 25 ° C. It was added and stirred for a certain time to dissolve and react.

After cooling the solution to -10 ° C, 0.5472 g (0.002695 mol) of isophthaloyl chloride and 1.3681 g (0.006739 mol) of terephthaloyl chloride were added and stirred. , The polyamic acid solution of 15 weight% of solid content concentration was obtained.

Dimethyl acetamide was added to the polyamic acid solution to dilute the concentration of solids to 5 wt% or less, and then the solids were precipitated with 10 L of methanol.

The precipitated solid was filtered and dried in vacuo at 100 ° C. for at least 6 hours to obtain a polyamideimide copolymer in the form of a solid (weight average molecular weight about 118,800 g / mol).

Example  2

Fill 42.5 g of N, N-dimethylacetamide while slowly passing nitrogen through a 100 mL 4-neck round flask (reactor) equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller, and a cooler, and the reactor temperature To 25 ° C. and then 4.2802 g (0.013366) of 2,2′-bis (trifluoromethyl) -4,4′-biphenyldiamine (2,2′-bis (trifluoromethyl) -4,4′-biphenyldiamine) mol) was added to dissolve completely. 1.2831 g (0.004361 mol) of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (3,3', 4,4'-biphenyltetracarboxylic dianhydride) was added while maintaining the temperature of the solution at 25 ° C. It was added and stirred for a certain time to dissolve and react.

After cooling the solution to -10 ° C, 0.5534 g (0.002726 mol) of isophthaloyl chloride and 1.3834 g (0.006814 mol) of terephthaloyl chloride were added and stirred. , The polyamic acid solution of 15 weight% of solid content concentration was obtained.

Dimethyl acetamide was added to the polyamic acid solution to dilute the concentration of solids to 5 wt% or less, and then the solids were precipitated with 10 L of methanol.

The precipitated solid was filtered and dried in vacuo at 100 ° C. for at least 6 hours to obtain a polyamideimide copolymer in the form of a solid (weight average molecular weight about 84,720 g / mol).

Comparative example  One

Fill 42.5 g of N, N-dimethylacetamide while slowly passing nitrogen through a 100 mL 4-neck round flask (reactor) equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller, and a cooler, and the reactor temperature To 25 ° C., followed by 4.3520 g of 2,2'-bis (trifluoromethyl) -4,4'-biphenyldiamine (2,2'-bis (trifluoromethyl) -4,4'-biphenyldiamine) mol) was added to dissolve completely. 1.2544 g (0.004264 mol) of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (3,3', 4,4'-biphenyltetracarboxylic dianhydride) was added while maintaining the temperature of the solution at 25 ° C. It was added and stirred for a certain time to dissolve and react.

After cooling the temperature of the solution to −10 ° C., 0.5410 g (0.002665 mol) of isophthaloyl chloride and 1.3525 g (0.00662 mol) of terephthaloyl chloride were added thereto, followed by stirring. , The polyamic acid solution of 15 weight% of solid content concentration was obtained.

Dimethyl acetamide was added to the polyamic acid solution to dilute the concentration of solids to 5 wt% or less, and then the solids were precipitated with 10 L of methanol.

The precipitated solid was filtered and dried in vacuo at 100 ° C. for at least 6 hours to obtain a polyamideimide copolymer in the form of a solid (weight average molecular weight about 128,117 g / mol).

Comparative example  2

Fill 42.5 g of N, N-dimethylacetamide while slowly passing nitrogen through a 100 mL 4-neck round flask (reactor) equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller, and a cooler, and the reactor temperature To 25 ° C., followed by 4.1434 g (0.012939) of 2,2'-bis (trifluoromethyl) -4,4'-biphenyldiamine (2,2'-bis (trifluoromethyl) -4,4'-biphenyldiamine) mol) was added to dissolve completely. 1.3376 g (0.004546 mol) of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (3,3', 4,4'-biphenyltetracarboxylic dianhydride) was added while maintaining the temperature of the solution at 25 ° C. It was added and stirred for a certain time to dissolve and react.

After cooling the solution to -10 ° C, 0.5769 g (0.002841 mol) of isophthaloyl chloride and 1.4422 g (0.007104 mol) of terephthaloyl chloride were added and stirred. , The polyamic acid solution of 15 weight% of solid content concentration was obtained.

Dimethyl acetamide was added to the polyamic acid solution to dilute the concentration of solids to 5 wt% or less, and then the solids were precipitated with 10 L of methanol.

The precipitated solid was filtered and dried in vacuo at 100 ° C. for at least 6 hours to obtain a polyamideimide copolymer in the form of a solid (weight average molecular weight about 31,777 g / mol).

Example  3

Fill 42.5 g of N, N-dimethylacetamide while slowly passing nitrogen through a 100 mL 4-neck round flask (reactor) equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller, and a cooler, and the reactor temperature To 25 ° C., followed by 4.2404 g (0.013242) of 2,2'-bis (trifluoromethyl) -4,4'-biphenyldiamine (2,2'-bis (trifluoromethyl) -4,4'-biphenyldiamine) mol) was added to dissolve completely. 1.2467 g (0.004237 mol) of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (3,3', 4,4'-biphenyltetracarboxylic dianhydride) was added while maintaining the temperature of the solution at 25 ° C. It was added and stirred for a certain time to dissolve and react.

Then, after cooling the temperature of the solution to -10 ℃, 0.5377 g (0.002648 mol) isophthaloyl chloride, 4,4'-biphenyl dicarbonyl chloride (4,4'-biphenyl dicarbonyl chloride) 0.4805 g (0.001721 mol) and 0.9947 g (0.004805 mol) of terephthaloyl chloride were added and stirred to obtain a polyamic acid solution having a solid content of 15% by weight.

Dimethyl acetamide was added to the polyamic acid solution to dilute the concentration of solids to 5 wt% or less, and then the solids were precipitated with 10 L of methanol.

The precipitated solid was filtered and dried in vacuo at 100 ° C. for at least 6 hours to obtain a polyamideimide copolymer in the form of a solid (weight average molecular weight about 97,441 g / mol).

Example  4

Fill 42.5 g of N, N-dimethylacetamide while slowly passing nitrogen through a 100 mL 4-neck round flask (reactor) equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller, and a cooler, and the reactor temperature After adjusting to 25 ° C., 4.2046 g (0.01313) of 2,2'-bis (trifluoromethyl) -4,4'-biphenyldiamine (2,2'-bis (trifluoromethyl) -4,4'-biphenyldiamine) mol) was added to dissolve completely. 1.2604 g (0.004284 mol) of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (3,3', 4,4'-biphenyltetracarboxylic dianhydride) was added while maintaining the temperature of the solution at 25 ° C. It was added and stirred for a certain time to dissolve and react.

Then, after cooling the temperature of the solution to -10 ℃, 0.5436 g (0.002677 mol) isophthaloyl chloride, 4,4'-biphenyl dicarbonyl chloride (4,4'-biphenyl dicarbonyl chloride) 0.4858 g (0.00174 mol) and 1.0056 g (0.004953 mol) of terephthaloyl chloride were added and stirred to obtain a polyamic acid solution having a solid content of 15% by weight.

Dimethyl acetamide was added to the polyamic acid solution to dilute the concentration of solids to 5 wt% or less, and then the solids were precipitated with 10 L of methanol.

The precipitated solid was filtered and dried in vacuo at 100 ° C. for at least 6 hours to obtain a polyamideimide copolymer in the form of a solid (weight average molecular weight about 74,998 g / mol).

Comparative example  3

Fill 42.5 g of N, N-dimethylacetamide while slowly passing nitrogen through a 100 mL 4-neck round flask (reactor) equipped with a stirrer, a nitrogen injector, a dropping funnel, a temperature controller, and a cooler, and the reactor temperature After adjusting to 25 ° C., 4.2769 g (0.013356) of 2,2'-bis (trifluoromethyl) -4,4'-biphenyldiamine (2,2'-bis (trifluoromethyl) -4,4'-biphenyldiamine) mol) was added to dissolve completely. 1.2328 g (0.00419 mol) of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (3,3', 4,4'-biphenyltetracarboxylic dianhydride) was added while maintaining the temperature of the solution at 25 ° C. It was added and stirred for a certain time to dissolve and react.

After cooling the temperature of the solution to −10 ° C., 0.5317 g (0.002619 mol) of isophthaloyl chloride, 4,4′-biphenyl dicarbonyl chloride (4,4′-biphenyl dicarbonyl chloride) 0.4751 g (0.001702 mol) and 0.9836 g (0.004845 mol) of terephthaloyl chloride were added and stirred to obtain a polyamic acid solution having a solid content of 15% by weight.

Dimethyl acetamide was added to the polyamic acid solution to dilute the concentration of solids to 5 wt% or less, and then the solids were precipitated with 10 L of methanol.

The precipitated solid was filtered and dried in vacuo at 100 ° C. for at least 6 hours to obtain a polyamideimide copolymer in solid form (weight average molecular weight about 98,777 g / mol).

Content (mol) TFDB BPDA IPC TPC BPC Example 1 0.013477 0.004313 0.002695 0.006739 - Example 2 0.013366 0.004361 0.002726 0.006814 - Comparative Example 1 0.013900 0.004264 0.002665 0.006620 - Comparative Example 2 0.012939 0.004546 0.002841 0.007104 - Example 3 0.013242 0.004237 0.002648 0.004805 0.001721 Example 4 0.013130 0.004284 0.002677 0.004953 0.001740 Comparative Example 3 0.013356 0.004190 0.002619 0.004845 0.001702

* TFDB: 2,2'-Bis (trifluoromethyl) -4,4'-biphenyldiamine

* BPDA: 3,3 ', 4,4'-Biphenyltetracarboxylic dianhydride

IPC: Isophthaloyl chloride

TPC: Terephthaloyl chloride

* BPC: 4,4'-Biphenyl dicarbonyl chloride

Example  5

The copolymer obtained in Example 1 was dissolved in dimethylacetamide to prepare a polymer solution of about 25% (w / V). Pour the polymer solution on a plastic substrate (UPILEX-75s, UBE) and uniformly adjust the thickness of the polymer solution using a film applicator and dry in a Matiz oven at 80 ° C. for 10 minutes, and then flow the nitrogen at 30 ° C. at 30 ° C. Curing for minutes gave a polyamideimide film with a thickness of 31.2 μm peeled off the substrate.

Example  6

A film having a thickness of 30.8 μm was obtained in the same manner as in Example 5, except that the copolymer obtained in Example 2 was used instead of the copolymer obtained in Example 1.

Comparative example  4

A film having a thickness of 29.8 μm was obtained in the same manner as in Example 5, except that the copolymer obtained in Comparative Example 1 was used instead of the copolymer obtained in Example 1.

Comparative example  5

A film having a thickness of 29.8 μm was obtained in the same manner as in Example 5, except that the copolymer obtained in Comparative Example 2 was used instead of the copolymer obtained in Example 1.

Example  7

A film having a thickness of 31.2 μm was obtained in the same manner as in Example 5, except that the copolymer obtained in Example 3 was used instead of the copolymer obtained in Example 1.

Example  8

A film having a thickness of 31.4 μm was obtained in the same manner as in Example 5, except that the copolymer obtained in Example 4 was used instead of the copolymer obtained in Example 1.

Comparative example  6

A film having a thickness of 28.8 μm was obtained in the same manner as in Example 5, except that the copolymer obtained in Comparative Example 3 was used instead of the copolymer obtained in Example 1.

Test Example

The following properties were measured or evaluated for the films of Examples 5 to 8 and Comparative Examples 4 to 6, and the results are shown in Table 2 below.

(1) pencil hardness

Pencil Hardness Tester was used to measure the pencil hardness of the film according to the measuring method of ASTM D3363. Specifically, after fixing the pencils of various hardness to the tester and scratching the film, the degree of scratches on the film was observed by naked eye or microscope, and when not more than 70% of the total number of scratches, the hardness of the pencil Corresponding values were evaluated by the pencil hardness of the film.

(2) Yellow Index (Y.I.)

The yellowness index (Y.I.) of the film was measured using a UV-2600 UV-Vis Spectrometer (SHIMADZU) according to the measurement method of ASTM D1925.

Thickness (㎛) Pencil hardness Y.I. Example 5 31.2 2H 3.02 Example 6 30.8 2H 2.78 Comparative Example 4 29.8 2H 3.08 Comparative Example 5 29.8 - - Example 7 31.2 3H 3.12 Example 8 31.4 3H 2.88 Comparative Example 6 28.8 3H 3.22

Referring to Table 2, it was confirmed that the films of Examples 5 and 6 exhibited a lower yellow index while showing the same pencil hardness as compared to the film of Comparative Example 4, to which the same type of monomers were applied.

The film of Comparative Example 5 was not able to measure the physical property by haze and brittle after curing.

In addition, it was confirmed that the films of Examples 7 and 8 exhibited the same pencil hardness as the film of Comparative Example 6 to which monomers of the same type were applied, but also exhibited a low yellow index.

Claims (6)

As imides of polyamic acids copolymerized with aromatic diamine monomers, aromatic dianhydride monomers and acyl chloride monomers,
(Aromatic diamine monomer): The polyamideimide copolymer whose molar ratio of (the said aromatic dianhydride monomer and said acyl chloride monomer) is 1: 1.02-1: 1.10.
The method of claim 1,
The aromatic diamine monomer is a polyamide of 2,2'-bis (trifluoromethyl) -4,4'-biphenyldiamine (2,2'-bis (trifluoromethyl) -4,4'-biphenyldiamine) Mid copolymer.
The method of claim 1,
The aromatic dianhydride monomer is 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (3,3', 4,4'-biphenyltetracarboxylic dianhydride), polyamideimide copolymer.
The method of claim 1,
The acyl chloride monomer is selected from the group consisting of isophthaloyl chloride (terephthaloyl chloride), terephthaloyl chloride (terephthaloyl chloride) and 4,4'-biphenyl dicarbonyl chloride (4,4'-biphenyl dicarbonyl chloride) Polyamideimide copolymer, which is at least one compound.
A polyamideimide film comprising the polyamideimide copolymer of claim 1.
The method of claim 5, wherein
The film has a polyamideimide film having a pencil hardness of at least 2H measured according to ASTM D3363 and a yellowness index (YI) of 3.20 or less measured according to ASTM D1925 at a thickness of 30 ± 2 μm. .