KR20230030865A - Composition for forming polyamideimide film, method for preparing the same and uses thereof - Google Patents

Abstract

The present disclosure relates to a composition for forming a polyamideimide film, a method for preparing the same, and uses thereof. A composition for forming a polyamideimide film according to an embodiment of the present invention implements excellent heat resistance without deterioration of the optical properties of colorlessness and transparency, and at the same time, provides flexibility and excellent bendability, thereby being usefully employed for a polyamideimide film and a display device including the same. The composition for forming a polyamideimide film comprises a polyamic acid or polyamideimide comprising a structural unit derived from diamine, a structural unit derived from a dianhydride, and a structural unit derived from diacid dichloride; and a mixed solvent including an amide-based solvent and a hydrocarbon-based solvent.

Description

Composition for forming polyamideimide film, method for preparing the same and uses thereof {Composition for forming polyamideimide film, method for preparing the same and uses thereof}

The present disclosure relates to a composition for forming a polyamideimide film, a method for preparing the same, and a use thereof.

Recently, weight reduction, slimming, and flexibility of display devices have been considered important. Since glass substrates, which have been widely used in existing displays, have the disadvantages of being heavy, brittle, inflexible, and difficult to process continuously, applying a polymer substrate that is light, flexible, and capable of continuous processing by replacing glass substrates to flexible displays Research is actively under way. Among them, polyamideimide (PAI), which is a polymer that is easy to synthesize and has excellent heat resistance and chemical resistance, is mainly used.

Substrate materials for next-generation display devices should be accompanied by improved flexibility and mechanical properties for application to foldable or flexible display devices as well as excellent optical properties. Furthermore, flexible devices involve high-temperature processes. In particular, in the case of organic light emitting diode (OLED) devices using a low temperature polysilicon (LTPS) process, the process temperature is close to 350 ℃ or more and 500 ℃, so excellent heat resistance is required. .

On the other hand, the color of conventional polyamideimide is brown or yellow, which is due to the electron transfer complex (CTC) caused by intra-molecular and inter-molecular interactions of polyamideimide. is the main cause This lowers the light transmittance of the "polyamideimide" film and increases the birefringence, which affects the visibility of the display device.

In order to solve this problem, colorless and transparent polyamideimide may be prepared by combining or changing monomers having various structures to reduce the CTC effect. However, optical properties and heat resistance are in a trade-off relationship with each other, and such an attempt has inevitably resulted in extremely general results of deterioration in functionality or deterioration in heat resistance even when the optical properties of polyamideimide are improved. Accordingly, studies on improving color transparency and optical properties are being continued to the extent that heat resistance and mechanical properties of polyamideimide are not greatly deteriorated, but there are limits to satisfying all of them.

Therefore, it is necessary to develop a display substrate material that can replace tempered glass by implementing improved optical properties and satisfying both excellent heat resistance without deteriorating colorless and transparent performance.

One embodiment of the present invention provides a composition for forming a polyamideimide film capable of realizing excellent optical properties and excellent heat resistance at the same time.

Another embodiment of the present invention provides a method for preparing a composition for forming a polyamideimide film capable of achieving excellent optical properties and excellent heat resistance at the same time.

Another embodiment of the present invention provides a polyamideimide film obtained by curing the composition for forming a polyamideimide film, and a cover window for a display device or a display device including the polyamideimide film.

A composition for forming a polyamideimide film according to an embodiment of the present invention includes a structural unit derived from diamine, a structural unit derived from dianhydride, and a structural unit derived from diacid dichloride, including polyamic acid or polyamideimide ; and

A mixed solvent containing an amide-based solvent and a hydrocarbon-based solvent; including,

A composition for forming a polyamideimide film satisfying the following formula 1,

The structural unit derived from the diamine includes a structural unit derived from a compound represented by Formula 1 below; The structural unit derived from the dianhydride includes a structural unit derived from a compound represented by Formula 2 below; The structural unit derived from the diacid dichloride may be a composition for forming a polyamideimide film including a structural unit derived from any one of a compound represented by Formula 3 and a compound represented by Formula 4 below.

[Formula 1]

,

,

[Formula 2]

,

,

[Formula 3]

,

,

[Formula 4]

,

,

[Equation 1]

5,000 ≤ _VPAI ≤ 15,000

In Equation 1 above,

V _PAI is the viscosity of the composition for forming a polyamideimide film when the solid content is 17% by weight relative to the total weight of the composition for forming a polyamideimide film, and the viscosity is measured by a Brookfield rotational viscometer at 25 ° C. with a 52Z spindle It is the viscosity (unit: cp) measured based on Torque 80% 2 minutes using

A method for preparing a composition for forming a polyamideimide film according to an embodiment of the present invention includes diamine including the compound represented by Formula 1, dianhydride including the compound represented by Formula 2, and preparing a polyamic acid solution by reacting diacid dichloride containing any one of the compound represented by Chemical Formula 3 and the compound represented by Chemical Formula 4 (step i); and

adjusting the viscosity by introducing a hydrocarbon-based solvent to satisfy Equation 1 (step ii); can include

The polyamideimide film according to one embodiment of the present invention may be obtained by curing the composition for forming a polyamideimide film according to one embodiment of the present invention.

The method for manufacturing a polyamideimide film according to one embodiment of the present invention may include applying a composition for forming a polyamideimide film according to one embodiment of the present invention to a substrate and then heat-treating it.

A cover window for a display device according to one embodiment of the present invention may include a polyamideimide film according to one embodiment of the present invention; and a coating layer formed on the polyamideimide film.

A display device according to one embodiment of the present invention may include a polyamideimide film according to one embodiment of the present invention.

Since the composition for forming a polyamideimide film according to one embodiment of the present invention inhibits the interaction between polyamic acid and a mixed solvent and significantly reduces the packing density between molecules during curing, the colorless and transparent performance is deteriorated. It is possible to provide a polyamideimide film capable of realizing excellent optical properties and excellent heat resistance at the same time without being In addition, the composition for forming a polyamideimide film according to one embodiment of the present invention uses a mixed solvent containing an amide-based solvent and a hydrocarbon-based solvent, so that the viscosity of the composition can be significantly lowered even if it contains a high solid content. Therefore, it can be applied to the thin film coating process with high solid content and low viscosity, and the desired physical properties can be effectively implemented.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, this invention may be implemented in many different forms, and is not limited to the embodiments described herein. Also, it is not intended to limit the scope of protection defined by the claims.

In addition, technical terms and scientific terms used in the description of the present invention may have meanings commonly understood by those of ordinary skill in the art to which this invention belongs, unless otherwise defined.

Throughout the specification describing the present invention, the phrase "includes" a certain element means that a part may further include other elements, not excluding other elements unless otherwise stated. can

Hereinafter, unless otherwise specifically defined herein, "combination thereof" may mean mixing or copolymerization of constituents.

Unless otherwise specified herein, "A and/or B" may mean an aspect including A and B at the same time, or may mean an aspect selected from A and B.

Hereinafter, unless otherwise specifically defined herein, "polymer" may include oligomers and polymers, and may include homopolymers and copolymers. The copolymers may include alternating polymers and block copolymers. It may include a polymer, a random copolymer, a branched copolymer, a crosslinked copolymer, or both.

Hereinafter, unless otherwise specified herein, "polyamic acid" refers to a polymer including a structural unit having an amic acid moiety, and "polyamideimide" refers to an amide moiety and an imide moiety. It may mean a polymer including a structural unit having

Hereinafter, unless otherwise specifically defined herein, the polyamideimide film may be a film containing polyamideimide, and specifically, after solution polymerization of a dianhydride compound and diacid dichloride in a diamine compound solution to prepare a polyamic acid, It may be a highly heat-resistant film prepared by imidization by ring-closing dehydration at a high temperature.

Hereinafter, as long as there is no specific definition in this specification, "Mura phenomenon" may be interpreted as encompassing all distortion phenomena caused by light that may be caused at a specific angle. For example, in a display device including a polyamideimide film, distortion due to light, such as a blackout phenomenon in which a screen appears black, a hotspot phenomenon, or a rainbow phenomenon having iridescent spots, may be mentioned.

Hereinafter, unless otherwise defined herein, when a part such as a layer, film, thin film, region, plate, etc. is said to be “on” or “on” another part, this is not only the case where it is “directly on” the other part, but also It may also include the case where there is another part in the middle.

Hereinafter, a composition for forming a polyamideimide film according to an embodiment of the present invention will be described.

A composition for forming a polyamideimide film according to an embodiment of the present invention (hereinafter, also referred to as a composition for forming a polyamideimide film) is composed of a structural unit derived from diamine, a structural unit derived from dianhydride, and a diacid dichloride. Polyamic acid or polyamideimide containing derived structural units; and

A mixed solvent containing an amide-based solvent and a hydrocarbon-based solvent; including,

The structural unit derived from the diamine includes a structural unit derived from a compound represented by Formula 1 below; The structural unit derived from the dianhydride includes a structural unit derived from a compound represented by Formula 2 below; The structural unit derived from the diacid dichloride may be a composition for forming a polyamideimide film including a structural unit derived from any one of a compound represented by Formula 3 and a compound represented by Formula 4 below.

In addition, the composition for forming a polyamideimide film according to an embodiment of the present invention may satisfy Equation 1 below. Although not intending to be bound by a specific theory, a composition for forming a polyamideimide film that satisfies the above conditions may be advantageously applied to a thin film process when forming a film, and when cured, it inhibits the packing density of the polyamideimide film and forms an amorphous (amorphous) film. ) so that the optical properties may be improved.

[Formula 1]

,

,

[Formula 2]

,

,

[Formula 3]

,

,

[Formula 4]

,

,

[Equation 1]

5,000 ≤ _VPAI ≤ 15,000

In Equation 1 above,

V _PAI is the viscosity of the composition for forming a polyamideimide film when the solid content is 17% by weight relative to the total weight of the composition for forming a polyamideimide film, and the viscosity is measured by a Brookfield rotational viscometer at 25 ° C. with a 52Z spindle It is the viscosity (unit: cp) measured based on Torque 80% 2 minutes using

The viscosity (V _PAI ) of the composition for forming a polyamideimide film according to an embodiment of the present invention is 5,000 cp to 13,000 cp, 6,000 cp to 13,000 cp, 15,000 cp or less, 13,000 cp or less, 11,000 cp or less, or 10,000 cp may be below. Accordingly, the composition for forming a polyamideimide film containing a high solid content can be more easily applied to a thin film process, and a polyamideimide film having better colorless and transparent performance, optical properties, and heat resistance can be provided. In this case, the solid content may be the polyamic acid and/or polyamideimide.

The composition for forming a polyamideimide film according to an embodiment of the present invention can be used as a polymerization solvent for polyamic acid (hereinafter, also referred to as a polyamideimide precursor) and/or polyamideimide by changing solvent conditions. Optical properties and heat resistance can be improved at the same time by applying a non-polar solvent having little affinity with polyamideimide. Specifically, the composition for forming a polyamideimide film according to one embodiment of the present invention includes polyamic acid and/or polyamideimide; polar solvent; and non-polar solvents; can include The polar solvent may be a hydrophilic solvent, for example, may have affinity with polyamic acid and/or polyamideimide, and may be, for example, an amide-based solvent. In addition, the non-polar solvent may have little affinity with polyamic acid and/or polyamideimide, and may be, for example, a hydrocarbon-based solvent.

The composition for forming a polyamideimide film according to an embodiment of the present invention uses a mixed solvent containing an amide-based solvent and a hydrocarbon-based solvent, thereby preventing intermolecular interactions between polymers and/or polymers and solvents. Interactions can be effectively inhibited, and during curing, the packing density between molecules is significantly lowered, so that optical and mechanical properties can be simultaneously improved. Furthermore, by using the mixed solvent, the viscosity of the composition for forming a polyamideimide film can be reduced while having a high solid content. Therefore, the composition for forming a polyamideimide film according to one embodiment of the present invention has a low viscosity while containing a high solid content, so that a thin film can be more easily formed by a solution process, and mechanical properties and heat resistance are reduced. It is possible to provide a polyamideimide film having excellent yellowness without having to do so.

In the composition for forming a polyamideimide film according to one embodiment of the present invention, the amide-based solvent refers to a compound containing an amide moiety. The amide-based solvent may be a cyclic compound or a chain compound, and specifically, may be a chain compound. The chain-like compound may have, specifically, 2 to 15 carbon atoms, and more specifically, 3 to 10 carbon atoms. The amide-based solvent may include a N,N-dialkylamide moiety, and the dialkyl groups may exist independently, or may be fused with each other to form a ring, or at least one alkyl group of the dialkyl groups may form another molecule in the molecule. A ring may be formed by fusion with a substituent, and for example, at least one alkyl group of the dialkyl group may be fused with an alkyl group connected to the carbonyl carbon of the amide moiety to form a ring. Here, the ring may be a 4 to 7-membered ring, for example, a 5- to 7-membered ring, and for example, a 5- or 6-membered ring. The alkyl group may be, for example, a C _1-10 alkyl group, such as a C _1-8 alkyl group, such as methyl or ethyl. More specifically, the amide-based solvent is not limited as long as it is generally used for polyamic acid polymerization, but, for example, dimethylpropionamide, diethylpropionamide, dimethylacetylamide, diethylacetamide, dimethylformamide, methyl It may include pyrrolidone, ethylpyrrolidone, octylpyrrolidone, or a combination thereof, and may specifically include dimethylpropionamide.

In the composition for forming a polyamideimide film according to one embodiment of the present invention, the hydrocarbon-based solvent may be a non-polar molecule as described above. The hydrocarbon solvent may be a compound composed of carbon and hydrogen. For example, the hydrocarbon-based solvent may be aromatic or aliphatic, and may be, for example, a cyclic compound or a chain compound, but specifically, may be a cyclic compound. Here, when the hydrocarbon solvent is a cyclic compound, it may include a single ring or a polycyclic ring, and the polycyclic ring may be a condensed ring or a non-fused ring, but specifically may be a single ring. The hydrocarbon-based solvent may have 3 to 15 carbon atoms, for example, 6 to 15 carbon atoms, and for example, 6 to 12 carbon atoms. The hydrocarbon-based solvent may be a substituted or unsubstituted C _3-15 cycloalkane, a substituted or unsubstituted C _6-15 aromatic compound, or a combination thereof. Here, the cycloalkane may include cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, or a combination thereof, and the aromatic compound may include benzene, naphthalene, or a combination thereof. The hydrocarbon-based solvent may be a cycloalkane unsubstituted or substituted with at least one C _1-5 alkyl group, an aromatic compound unsubstituted or substituted with at least one C _1-5 alkyl group, or a combination thereof. Cycloalkanes and aromatic compounds are each as described above. The C _1-5 alkyl group may be, for example, a C _1-3 alkyl group, for example, a C _1-2 alkyl group, and more specifically, a methyl group, but is not limited thereto. In addition, the hydrocarbon-based solvent may further include oxygen as needed. For example, when the hydrocarbon example solvent includes oxygen, it may include a ketone group or a hydroxyl group, and may be, for example, cyclopentanone, cresol, or a combination thereof. Specifically, the hydrocarbon-based solvent may include benzene, toluene, cyclohexane, cyclopentanone, cresol, or a combination thereof, but is not limited thereto.

More specifically, the polyamideimide film-forming composition according to an embodiment of the present invention includes a mixed solvent including an amide-based solvent including dimethylpropionamide and a hydrocarbon-based solvent selected from toluene, benzene, and cyclohexane. it could be

The hydrocarbon-based solvent according to one embodiment of the present invention may be added after polymerization of polyamic acid or polyamideimide.

Accordingly, the composition for forming a polyamideimide film according to one embodiment of the present invention may exhibit different intermolecular behavior and interactions from those of simply adding a mixed solution in the polyamic acid polymerization step. For example, in the step of polymerizing polyamic acid, when the hydrocarbon-based solvent is mixed, high molecular weight polyamic acid may not be obtained because it acts as a factor that hinders polymerization. On the other hand, in the composition for forming a polyamideimide film according to an embodiment of the present invention, after obtaining a polyamic acid and/or polyamideimide having a sufficient high molecular weight, a hydrocarbon-based solvent is mixed, thereby causing intermolecular interactions between polymers and/or It can act as a catalyst that weakens the strong interaction between the polymer and the solvent, and can obtain desired optical properties during subsequent curing. Here, by sequentially using the amide-based solvent and the hydrocarbon-based solvent, the interaction between the polyamic acid, which is a polyamideimide precursor, and the solvent can be adjusted to a more appropriate range. Here, the regulation may mean inhibition.

The composition for forming a polyamideimide film according to an embodiment of the present invention may include the amide-based solvent and the hydrocarbon-based solvent in a weight ratio of 8:2 to 5:5, specifically, 7.5:2.5 to 5 :5, or a weight ratio of 7.5:2.5 to 5.5:4.5. By including the amide-based solvent and the hydrocarbon-based solvent in the above weight ratio, more excellent optical properties can be realized, and the reactivity of diamine and dianhydride can be maintained excellently, and packing density between molecules during curing of the composition for forming a polyamideimide film can be suitably inhibited and rendered amorphous. Accordingly, it is possible to provide a polyamideimide film having a further improved yellowness without deteriorating heat resistance and mechanical properties.

The structural unit derived from the diacid dichloride included in the composition for forming a polyamideimide film according to an embodiment of the present invention is 5 mol% to 100 mol% when the content of the structural unit derived from the diamine is 100 mol%. 50 mol%. Or, for example, 10 mol% to 50 mol%, 10 mol% to 40 mol%, 5 mol% to 40 mol%, or 20 mol% to 40 mol%. Here, the structural unit derived from diacid dichloride may be a structural unit derived from any one of a compound represented by Formula 3 and a compound represented by Formula 4, and the structural unit derived from diamine, Specifically, it may be a structural unit derived from a compound represented by Formula 1. The composition for forming a polyamideimide film according to an embodiment of the present invention includes a diacid dichloride-derived structural unit in the above range based on 100 mol% of a diamine-derived structural unit, so that it is more transparent and A polyamideimide film having a low retardation in the thickness direction and excellent mechanical properties such as high modulus can be manufactured. Accordingly, it may be possible to implement optical and mechanical properties equal to or superior to those of tempered glass.

The molar ratio of the structural unit derived from the dianhydride and the structural unit derived from the diacid dichloride included in the composition for forming a polyamideimide film according to an embodiment of the present invention may be 95:5 to 50:50. Or, for example, 90:10 to 50:50, 90:10 to 60:40, 95:5 to 60:40, or 80:20 to 60:40. Here, the structural unit derived from the dianhydride may specifically be a structural unit derived from a compound represented by Chemical Formula 2, and the structural unit derived from the diacid dichloride may be specifically derived from a compound represented by Chemical Formula 3 and Chemical Formula 4 It may be a structural unit derived from any one of the compounds represented by The composition for forming a polyamideimide film according to an embodiment of the present invention includes a structural unit derived from dianhydride and a structural unit derived from diacid dichloride in the molar ratio, so that it is more transparent and has a lower thickness direction retardation. And it is possible to prepare a polyamideimide film having excellent mechanical properties such as high modulus. Accordingly, it may be possible to implement optical and mechanical properties equal to or superior to those of tempered glass.

In addition, the diamine is PDA (p-phenylenediamine), m-PDA (m-phenylenediamine), 4,4'-ODA (4,4'-oxydianiline), 3,4'- ODA (3,4'-oxydianiline), BAPP (2,2-bis (4- [4-aminophenoxy] -phenyl) propane), TPE-Q (1,4-bis (4-aminophenoxy ) Benzene), TPE-R (1,3-bis (4-aminophenoxy) benzene), BAPB (4,4'-bis (4-aminophenoxy) biphenyl), BAPS (2,2-bis ( 4-[4-aminophenoxy]phenyl)sulfone), m-BAPS (2,2-bis(4-[3-aminophenoxy]phenyl)sulfone), HAB (3,3'-dihydroxy-4 ,4'-diaminobiphenyl), TB (3,3-dimethylbenzidine), m-TB (2,2-dimethylbenzidine), TFMB (2,2-bistrifluoromethylbenzidine), 6FAPB (1, 4-bis(4-amino-2-trifluoromethylphenoxy)benzene), 6FODA (2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether), APB(1 ,3-bis(3-aminophenoxy)benzene),1,4-ND(1,4-naphthalenediamine), 1,5-ND(1,5-naphthalenediamine), DABA(4,4' -diaminobenzanilide), 6-amino-2-(4-aminophenyl)benzoxazole, 5-amino-2-(4-aminophenyl)benzoxazole, etc. Yes, but is not limited thereto.

In addition, the dianhydride is, if necessary, PMDA (pyromellitic dianhydride), BPDA (3,3',4,4'-biphenyltetracarboxylic dianhydride), BTDA (3,3',4, 4'-benzophenone tetracarboxylic dianhydride), ODPA (4,4'-oxydiphthalic anhydride), BPADA (4,4'-(4,4'-isopropylbiphenoxy) bipe talic anhydride), DSDA (3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride), 6FDA (2,2'-bis-(3,4-dicarboxylphenyl) hexafluoro Propane dianhydride), TMHQ (p-phenylene bistrimelictic monoester anhydride), ESDA (2,2'-bis(4-hydroxyphenyl)propanedibenzoate-3,3',4, 4'-tetracarboxylic dianhydride), NTDA (naphthalene tetracarboxylic dianhydride), or a combination thereof may be further included.

In addition, the diacid dichloride is BPC (1,1'-biphenyl-4,4'-dicarbonyl dichloride), NPC (1,4-naphthalenedicarboxylic dichloride), NTC (2 ,6-naphthalenedicarboxylic dichloride), NEC (1,5-naphthalenedicarboxylic dichloride), or a combination thereof may be further included.

A composition for forming a polyamideimide film according to an embodiment of the present invention includes polyamic acid and/or polyamideimide including structural units derived from diamine, dianhydride, and diacid dichloride as exemplified above. The weight average molecular weight (Mw) of the polyamic acid and/or polyamideimide is not particularly limited, but may be 10,000 g/mol or more, specifically, 20,000 g/mol or more, and more specifically, 25,000 g/mol to 80,000 g/mol. g/mol. By having a weight average molecular weight within the above range, it is possible to provide a film having more excellent optical properties and mechanical strength, and less curling.

The solid content of the composition for forming a polyamideimide film according to an embodiment of the present invention is 40% by weight or less, 10% to 40% by weight, 35% by weight or less based on the total weight of the composition for forming a polyamideimide film. , 30% by weight or less, 10% by weight to 25% by weight, or 15% by weight to 25% by weight may be satisfied. Here, the solid content may be the polyamic acid and/or polyamideimide.

In general, in the case of polyamideimide, the viscosity tends to increase as the solid content concentration increases. For example, when the polyamic acid and/or polyamideimide are dissolved in a common amide-based solvent alone, the viscosity of the solution is Higher than about 15,000 cp. Here, the viscosity of the solution means the viscosity when the solid content is 17% by weight based on the total weight of the solution. When the thin film is manufactured by a solution process, for example, a coating process, if the flow of the polymer is poor due to high viscosity, it is difficult to remove air bubbles and mura may occur during coating. On the other hand, the composition for forming a polyamideimide film according to an embodiment of the present invention uses a mixed solvent containing an amide-based solvent and a hydrocarbon-based solvent, so that the viscosity of the composition is significantly reduced even if it contains a high solid content of 17% by weight or more. can be lowered Accordingly, defects occurring during a solution process, for example, a coating process, can be effectively prevented, and more improved optical properties can be implemented. In addition, since it has a high solids content without defects occurring during the coating process, it may be commercially advantageous.

Hereinafter, a method for preparing a composition for forming a polyamideimide film according to an embodiment of the present invention will be described.

A composition for forming a polyamideimide film according to an embodiment of the present invention comprises a diamine including a compound represented by Formula 1 below, a dianhydride including a compound represented by Formula 2 below, and a composition represented by Formula 3 below in an amide-based solvent. preparing a polyamic acid solution by reacting a diacid dichloride containing any one of a compound represented by Formula 4 and a compound represented by Formula 4 below (step i); and

Step of adjusting the viscosity by introducing a hydrocarbon-based solvent to satisfy the following formula 1 (step ii); It can be prepared by a method including.

[Formula 1]

,

,

[Formula 2]

,

,

[Formula 3]

,

,

[Formula 4]

,

,

[Equation 1]

5,000 ≤ _VPAI ≤ 15,000

In Equation 1 above,

V _PAI is the viscosity of the composition for forming a polyamideimide film when the solid content is 17% by weight relative to the total weight of the composition for forming a polyamideimide film, and the viscosity is measured by a Brookfield rotational viscometer at 25 ° C. with a 52Z spindle It is the viscosity (unit: cp) measured based on Torque 80% 2 minutes using

Step i according to an embodiment of the present invention is a step of polymerizing a polyamic acid by mixing diamine, dianhydride, and diacid dichloride, dissolving diamine in an amide solvent, dissolving by adding diacid dichloride , dissolving by adding dianhydride, and reacting by stirring the reaction solution for 5 to 7 hours.

Step ii according to an embodiment of the present invention may be a step of additionally adding the above-described hydrocarbon solvent, stirring, and then adding a mixed solvent containing an amide-based solvent and a hydrocarbon-based solvent, through which polyamideimide A viscosity range of the film-forming composition may satisfy Equation 1 above. Specifically, 20% to 100% by weight, or 20% to 50% by weight of a hydrocarbon-based solvent based on the weight of the amide-based solvent in step i is additionally added at room temperature (25 ° C.) to stir for 15 to 20 hours stirring; and adding a mixed solvent including an amide-based solvent and a hydrocarbon-based solvent to satisfy Equation 1 after the stirring is completed. Although not wishing to be bound by a specific theory, a composition for forming a polyamideimide film that satisfies the above conditions may inhibit the packing density of the polyamideimide film and make it amorphous during curing. Accordingly, it is possible to provide a polyamideimide film having a further improved yellowness without deteriorating mechanical properties and heat resistance.

In addition, the composition for forming a polyamideimide film according to one embodiment of the present invention may exhibit different intermolecular behavior and interactions from those in which a mixed solution is simply added in the polyamic acid polymerization step. For example, if the hydrocarbon-based solvent is included in the step of polymerizing polyamic acid, it may not be possible to obtain high molecular weight polyamic acid by acting as a factor that hinders polymerization. On the other hand, in the composition for forming a polyamideimide film according to an embodiment of the present invention, polyamic acid of high molecular weight can be obtained by mixing a hydrocarbon-based solvent after obtaining polyamic acid and/or polyamideimide having a sufficient high molecular weight. there is. In addition, the hydrocarbon-based solvent may act as a catalyst to weaken intermolecular interactions between polymers and/or strong interactions between polymers and solvents, and desired optical properties may be obtained during subsequent curing.

In the method for preparing a composition for forming a polyamideimide film according to an embodiment of the present invention, the diacid dichloride may be used in an amount of 5 mol% to 50 mol% based on 100 mol% of the diamine. Or, for example, 10 mol% to 50 mol%, 10 mol% to 40 mol%, 5 mol% to 40 mol%, or 20 mol% to 40 mol%. Here, the diacid dichloride may be specifically any one of a compound represented by Formula 3 and a compound represented by Formula 4, and the diamine may be specifically a compound represented by Formula 1. In the method for preparing the composition for forming a polyamideimide film according to an embodiment of the present invention, by including diamine in the above range, it is possible to have a more transparent and low thickness direction retardation, and to have excellent mechanical properties such as high modulus and elongation at break. It is possible to prepare a composition for producing a polyamideimide film. Accordingly, it may be possible to implement optical and mechanical properties equal to or superior to those of tempered glass.

In the method for preparing the composition for forming a polyamideimide film according to one embodiment of the present invention, the molar ratio of the dianhydride and the diacid dichloride may be 95:5 to 50:50. Or, for example, 90:10 to 50:50, 90:10 to 60:40, 95:5 to 60:40, or 80:20 to 60:40. Here, the dianhydride may specifically be a compound represented by Chemical Formula 2, and the diacid dichloride may be specifically any one of a compound represented by Chemical Formula 3 and a compound represented by Chemical Formula 4. In the method for preparing the composition for forming a polyamideimide film according to an embodiment of the present invention, by including dianhydride and diacid dichloride in the molar ratio, it is possible to have more transparency and low thickness direction retardation, and to have excellent mechanical properties such as high modulus. may have properties. Accordingly, it may be possible to implement optical and mechanical properties equal to or superior to those of tempered glass.

The polyamideimide film according to one embodiment of the present invention may be obtained by curing the composition for forming a polyamideimide film according to one embodiment of the present invention.

The polyamideimide film is a polyamideimide film including a polyamideimide polymer having a rigid structure by including structural units derived from any one of Formulas 1 and 2, and Formulas 3 and 4. Compared to this, the light distortion phenomenon can be further improved. For example, in the polyamideimide film according to one embodiment of the present invention, the structural unit derived from the dianhydride may not include a rigid structural unit. For example, it may not contain a structural unit derived from a dianhydride in which two anhydride groups are fused to one ring. The ring may be a single ring or a fused ring, and may be an aromatic ring, an aliphatic ring, or a combination thereof. Specifically, the structural unit derived from the dianhydride is a structural unit derived from pyromellitic dianhydride (PMDA), a structural unit derived from cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA), or a combination thereof.

Accordingly, since the polyamideimide film according to one embodiment of the present invention can realize a transparent and low retardation in the thickness direction even at a thickness of 30 μm or more and can further improve visibility, the cover including the polyamideimide film Windows can further reduce user's eye fatigue. In addition, even with a thickness of 30 μm or more, not only excellent optical properties as described above, but also mechanical strength such as modulus can be further improved, so that dynamic bending characteristics are further improved, resulting in foldables that repeat folding and unfolding operations repeatedly. It may be suitable for application as a cover window of a display device or a flexible display device.

The polyamideimide film according to one embodiment of the present invention may have a yellowness index (YI) of 3.5 or less according to ASTM E313. Alternatively, the yellowness may be, for example, 1.0 or more and 3.5 or less, 1.5 or more and 3.5 or less, 2.0 or more and 3.5 or less, 2.5 or more and 3.5 or less, 2.8 or more and 3.4 or less, 2.5 or more and 3.3 or less, or 3.0 or less, but necessarily limited to the above ranges. It's not what I want to do. In addition, the absolute value of the retardation in the thickness direction of the polyamideimide film according to one embodiment of the present invention at a wavelength of 550 nm is 600 nm or less, 200 nm to 600 nm, 200 nm to 500 nm, 250 nm to 600 nm, 250 nm It may be nm to 550 nm, 300 nm to 600 nm, or 300 nm to 500 nm, but is not necessarily limited to the above range. The retardation value in the thickness direction may be measured at normal temperature before heating the film, and the normal temperature may be a temperature in a state where the temperature is not artificially controlled. For example, the room temperature may be 20 °C to 40 °C, 20 °C to 30 °C, or 23 °C to 26 °C.

In addition, the polyamideimide film according to one embodiment of the present invention may have a thickness of 30 μm to 80 μm, 40 μm to 80 μm, 40 μm to 60 μm, or 50 μm to 80 μm. Further, the modulus according to ASTM E111 may be 4.0 GPa or higher, 4.0 GPa to 5.0 GPa, 4.1 GPa to 4.7 GPa, or 4.0 GPa to 4.5 GPa. As the polyamideimide film according to one embodiment of the present invention satisfies the above modulus, it can provide sufficient mechanical properties and durability to be applied to a cover window for a display.

As the polyamideimide film according to one embodiment of the present invention satisfies the thickness direction retardation, yellowness, and modulus within the above-described ranges, image distortion due to light may be prevented and thus improved visibility may be imparted. In addition, more uniform mechanical properties (modulus, etc.) and optical properties (thickness direction retardation, etc.) can be exhibited at the center and edges of the film, and film loss can be further reduced. In addition, since the polyamideimide film is flexible and has excellent bending properties, even if a predetermined deformation occurs repeatedly, the film is not deformed and/or damaged and can be more easily restored to its original shape. In addition, since the cover window including the polyamideimide film according to an embodiment of the present invention can have better visibility and can prevent the occurrence of fold marks and microcracks, it can be used in a foldable display device or a flexible display device. More excellent durability and long lifespan can be imparted.

The method for manufacturing a polyamideimide film according to one embodiment of the present invention may include applying a composition for forming a polyamideimide film according to one embodiment of the present invention to a substrate and then heat-treating it.

In the method for producing a polyamideimide film according to an embodiment of the present invention, the heat treatment of the heat treatment step may be performed at a temperature of 280 ° C. or more and 350 ° C. or less for 10 minutes to 60 minutes. When cured at a relatively low temperature, the yellowness may tend to be relatively low because the film receives less heat history, but when cured below the glass transition temperature (Tg), the orientation problem of the molecular structure causes a thickness direction retardation. Elevation problems may occur. The polyamideimide film according to one embodiment of the present invention is heat-treated at a temperature of 280 ° C to 350 ° C or 300 ° C to 350 ° C, thereby arranging the polymer chains more isotropically, thereby reducing the thickness direction retardation. In addition, the heat treatment may be performed for, for example, 10 minutes to 50 minutes, 10 minutes to 40 minutes, 10 minutes to 30 minutes, or 10 minutes to 20 minutes, but is not necessarily limited thereto. In addition, the thermal curing may be performed in, for example, a separate vacuum oven or an oven filled with an inert gas.

In addition, before the heat treatment step, a drying step may be additionally performed if necessary. The drying step may be performed at a temperature of 50 °C to 150 °C, 50 °C to 130 °C, 60 °C to 100 °C, or about 80 °C, but is not necessarily limited thereto.

In the method for producing a polyamideimide film of the present invention, if necessary, a step of applying the composition for forming a polyamideimide film on a substrate and then leaving it at room temperature may be further included. Through the leaving step, the optical properties of the film surface can be more stably maintained. Although not wishing to be bound by a particular theory, when the conventional composition for forming a polyamideimide film is subjected to such a leaving step before curing, the solvent absorbs moisture in the air, the moisture diffuses into the inside, and polyamic acid and/or polyamide is formed. By colliding with the mid, white turbidity may occur from the surface of the film, and aggregation may occur, resulting in coating non-uniformity. On the other hand, the composition for forming a polyamideimide film according to one embodiment of the present invention has the advantage of being free from cloudiness and agglomeration even when left in the air for a long time and securing a film having improved optical properties. The leaving step may be performed under room temperature and/or high humidity conditions. Here, the room temperature may be 40 °C or less, for example, 30 °C or less, for example, 25 °C or less, and more specifically, 15 °C to 25 °C, 20 °C to 25 °C. may be particularly preferred. In addition, the high humidity may be, for example, 50% or more, eg, 60% or more, eg, 70% or more, eg, 80% or more relative humidity. The leaving step may be performed for 1 minute to 3 hours, for example, 10 minutes to 2 hours, for example, 20 minutes to 1 hour.

In the method for producing a polyamideimide film according to an embodiment of the present invention, one or two or more additives selected from flame retardants, adhesion improvers, inorganic particles, antioxidants, ultraviolet inhibitors, and plasticizers are mixed with the polyamic acid solution to obtain a polyamide-imide film. Amidimide films can be prepared.

In addition, in the method for producing a polyamideimide film according to an embodiment of the present invention, the coating for forming the polyamideimide film may be used without limitation as long as it is commonly used in the related field. Non-limiting examples thereof include knife coating, dip coating, roll coating, slot die coating, lip die coating, and slide coating. coating) and curtain coating, etc., and the same type or different types may be sequentially applied one or more times.

The substrate may be used without limitation as long as it is commonly used in the field, and non-limiting examples thereof include glass; stainless; or polyethylene terephthalate, polyethylene naphthalate, polypropylene, polyethylene, cellulose triacetate, cellulose diacetate, poly(meth)acrylic acid alkyl ester, poly(meth)acrylic acid ester copolymer, polyvinyl chloride, polyvinyl alcohol, polycarbonate, plastic films such as polystyrene, cellophane, polyvinylidene chloride copolymer, polyamide, polyamideimide, vinyl chloride/vinyl acetate copolymer, polytetrafluoroethylene, and polytrifluoroethylene; etc. can be used.

Hereinafter, the use of the polyamideimide film according to one embodiment of the present invention will be described.

One aspect according to the present invention may be a multilayer structure including a polyamideimide film according to one embodiment of the present invention. For example, the polyamideimide film; And it may be a cover window for a display device including a coating layer positioned on the polyamideimide film. In addition, the multilayer structure may include a polyamideimide film including monomers having different compositions from the polyamideimide film according to the present invention, and two or more coating layers.

At this time, non-limiting examples of the coating layer may be a hard coating layer, an antistatic layer, an antifingerprint layer, an antifouling layer, an antiscratch layer, a low refractive index layer, an antireflection layer, an impact absorbing layer, or a combination thereof, but is not necessarily limited thereto. . In this case, the coating layer may have a thickness of 1 μm to 500 μm, 2 μm to 450 μm, or 2 μm to 200 μm, but is not limited thereto.

In addition, the multilayer structure according to one embodiment of the present invention may include the polyamideimide film of the present invention and a semiconductor layer formed on a substrate. Non-limiting examples of the semiconductor layer include low-temperature polysilicon (LTPS), low-temperature polyoxide (LTPO), indium tin oxide (ITO), and indium gallium zinc oxide (IGZO). For example, LTPS and / or may include LTPO. In the case of a display device using low temperature polysilicon (LTPS) and/or low temperature polycrystalline oxide (LTPO), the process temperature may approach 350 °C or more and 500 °C or less. In such a high-temperature process, thermal decomposition due to hydrolysis is likely to occur even for polyamideimide having excellent heat resistance. Therefore, in order to manufacture a flexible device for LTPS and/or LTPO, a material having excellent heat resistance that does not undergo thermal decomposition due to hydrolysis even in a high-temperature process is required. The polyamideimide film according to one embodiment of the present invention has excellent optical properties and heat resistance at the same time, so that it can be used in a display device for LTPS and/or LTPO.

Another aspect according to the present invention may be a display device including the polyamideimide film according to one embodiment of the present invention.

As described above, the polyamideimide film according to one embodiment of the present invention has excellent optical and mechanical properties, and can specifically exhibit sufficient retardation at various angles, so that a wide viewing angle is required. It can be applied in the industrial field.

For example, the display device is not particularly limited as long as it requires excellent optical properties, and a display panel suitable for this may be selected and provided. Specifically, it can be applied to a flexible display device, and non-limiting examples thereof include various image display devices such as a liquid crystal display device, an electroluminescence display device, a plasma display device, and a field emission display device, but are limited thereto it is not going to be

In addition, the display device including the polyamideimide film according to an embodiment of the present invention not only has excellent display quality, but also has a significantly reduced distortion caused by light, thereby preventing a rainbow phenomenon in which iridescent spots occur. Significantly improved, excellent visibility can minimize the fatigue of the user's eyes. In particular, as the screen size of the display device increases, there are many cases in which the screen is viewed from the side. When the polyamideimide film for cover window of the present invention is applied to a display device, visibility is excellent even when viewed from the side, so a large display device can be usefully applied to

Hereinafter, examples and experimental examples of the present invention will be specifically illustrated and described. However, Examples and Experimental Examples to be described later are merely illustrative of a part of the present invention, and the present invention is not limited thereto.

Physical properties of the present invention were measured as follows.

<Measurement method>

1. Viscosity (V _PAI )

The viscosity was measured by a late rheometer (Brookfield Co., LVDV-1II Ultra) by putting 0.5 μL of the composition for forming a polyamideimide film (solid concentration: 17% by weight) in a container, lowering the spindle, and adjusting the rpm at the point when the torque reached 80%. After waiting for 2 minutes, the viscosity value was measured when there was no change in torque. At this time, the viscosity was measured at a temperature of 25 °C using a 52Z spindle. The unit is cp.

2. Yellow Index (YI)

It was measured using a spectrophotometer (Nippon Denshoku Co., COH-5500) according to ASTM E313 standard.

3. Phase difference (Rth)

Measurements were made using an AxoScan (OPMF, Axometrics Inc.). The thickness direction retardation (Rth) was measured for a wavelength of 550 nm, and the thickness direction retardation at a wavelength of 550 nm was expressed as an absolute value. Unit is nm.

4. Modulus

According to ASTM E111, a specimen having a thickness of 50 μm, a length of 50 mm and a width of 10 mm was measured using Instron's UTM 3365 under the condition of pulling at 50 mm/min at 25 °C. Unit is Gpa.

< Example 1>

Preparation of composition for forming polyamideimide film

Put dimethylpropionamide (N,N-dimethylpropionamide, DMPA) and 2,2'-bis(trifluoromethyl)-benzidine (2,2'-Bis(trifluoromethyl)-benzidine, TFMB) in a reactor under a nitrogen atmosphere to sufficiently After stirring, terephthaloyl chloride (TPC) was added and stirred for 6 hours to dissolve and react. Thereafter, the reaction product obtained by precipitation and filtration using an excess of methanol was vacuum-dried at 50 ° C. for 6 hours or more, and then put in a reactor with DMPA again under a nitrogen atmosphere to dissolve, and then 9,9-bis (3,4-di Carboxyphenyl) fluorene dianhydride (9,9-Bis (3,4-dicarboxyphenyl) fluorene dianhydride, BPAF) was added and stirred for 12 hours to dissolve and react to prepare a polyamic acid resin composition. At this time, the molar ratio of each monomer TFMB:BPAF:TPC was set to 100:90:10.

After stirring for 6 hours, toluene was added at 25 °C and stirred for 18 hours. Thereafter, a mixed solvent of DPMA and toluene is added so that the solid content is 17% by weight based on the total weight of the composition and the toluene content in the composition is DMPA: toluene = 70% by weight: 30% by weight, thereby forming a polyamideimide film A composition was prepared.

Manufacture of polyamideimide film

On one surface of a glass substrate (1.0T), the obtained polyamideimide film-forming composition was applied with a meyer bar, dried at 80° C. for 15 minutes under a nitrogen atmosphere, and then cured by heating at 300° C. for 15 minutes, and cured on a glass substrate. A polyamideimide film having a thickness of 50 μm according to Example 1 was prepared by peeling from the

< Example 2 and Example 3>

The compositions for forming a polyamideimide film of Examples 2 and 3, respectively, were prepared in the same manner as in Example 1, except that the molar ratio of TFMB, BPAF, and TPC was changed as shown in Table 1 below, and Polyamideimide films of Example 2 and Example 3 each having a thickness of 50 μm were prepared in the same manner as in Example 1.

< Example 4 and Example 5>

In Example 1, isophthaloyl chloride (IPC) was used instead of TPC, and the molar ratio of TFMB, BPAF and IPC and the content of toluene were changed as shown in Table 1. The same method as in Example 1 above The compositions for forming polyamideimide films of Examples 4 and 5, respectively, were prepared, and polyamideimide films of Examples 4 and 5 having a thickness of 50 μm, respectively, were prepared in the same manner as in Example 1. .

< Example 6>

Except for changing the toluene content as shown in Table 1 below, the composition for forming a polyamideimide film of Example 6 was prepared in the same manner as in Example 1, except that the heat treatment temperature was changed as shown in Table 1 below. prepared a polyamideimide film of Example 6 having a thickness of 50 μm in the same manner as in Example 1.

< comparative example 1>

Preparation of composition for forming polyamideimide film

Put dimethylpropionamide (N,N-dimethylpropionamide, DMPA) and 2,2'-bis(trifluoromethyl)-benzidine (2,2'-Bis(trifluoromethyl)-benzidine, TFMB) in a reactor under a nitrogen atmosphere to sufficiently After stirring, terephthaloyl chloride (TPC) was added and stirred for 6 hours to dissolve and react. Thereafter, the reaction product obtained by precipitation and filtration using an excess of methanol was vacuum-dried at 50 ° C. for 6 hours or more, and then put in a reactor with DMPA again under a nitrogen atmosphere to dissolve, and then 9,9-bis (3,4-di Carboxyphenyl) fluorene dianhydride (9,9-Bis (3,4-dicarboxyphenyl) fluorene dianhydride, BPAF) was added and stirred for 12 hours to dissolve and react to prepare a polyamic acid resin composition. At this time, a polyamideimide film-forming composition was prepared by adjusting the molar ratio of each monomer TFMB:BPAF:TPC to 100:90:10 and adjusting the solid content to 15% by weight.

Manufacture of polyamideimide film

A polyamideimide film of Comparative Example 1 having a thickness of 50 μm was prepared in the same manner as in Example 1.

< comparative example 2 to comparative example 4>

Polyamideimide film-forming compositions of Comparative Examples 2 to 4 were prepared in the same manner as in Example 1, except that the molar ratio of TFMB, BPAF and TPC and the toluene content were changed as shown in Table 1 below, Polyamideimide films of Comparative Examples 2 to 4 each having a thickness of 50 μm were prepared in the same manner as in Example 1.

< comparative example 5>

In Example 1, the composition for forming a polyamideimide film of Comparative Example 5 was prepared in the same manner as in Example 1, except that IPC was used instead of TPC and the molar ratio of TFMB, BPAF and IPC was changed as shown in Table 1 below. and a polyamideimide film of Comparative Example 5 having a thickness of 50 μm was prepared in the same manner as in Example 1.

TFMB BPAF TPC IPC toluene
(weight%) heat treatment temperature
(℃) Example 1 100 90 10 - 30 300 Example 2 100 80 20 - 30 300 Example 3 100 60 40 - 30 300 Example 4 100 80 - 20 30 300 Example 5 100 60 - 40 25 300 Example 6 100 90 10 - 45 350 Comparative Example 1 100 90 10 - 0 300 Comparative Example 2 100 90 10 - 60 300 Comparative Example 3 100 90 10 - 15 300 Comparative Example 4 100 40 60 - 30 300 Comparative Example 5 100 90 - 60 30 300

< Experimental example > Evaluation of optical and mechanical properties

The viscosity, yellowness (YI), retardation (Rth) and modulus in the thickness direction of the polyamideimide films according to Examples 1 to 6 and Comparative Examples 1 to 5 were measured according to the above measurement method, and the following table 2.

Example No. One 2 3 4 5 6 thickness
(μm) 50 50 50 50 50 50 viscosity
(V _PAI , cp) 10,500 10,500 12,500 8,900 7,400 9,200 yellowness
(YI) 2.4 2.9 2.9 2.5 2.8 2.5 Rth
(550 nm) 340 440 420 290 301 330 modulus
(GPa) 4.1 4.2 4.4 4.0 4.0 4.0 Comparative Example No. One 2 3 4 5 thickness
(μm) 50 As the initial viscosity rises
Unable to polymerize 50 50 50 viscosity
(V _PAI , cp) 17,400 16,500 14,500 6,300 yellowness
(YI) 2.9 2.9 4.6 3.8 Rth
(550 nm) 383 380 1,010 400 modulus
(GPa) 4.2 4.2 4.8 3.9

As can be seen from Table 2, the diacid dichloride containing either TPC or IPC is included in the range of 5 mol% to 50 mol% based on 100 mol% of diamine, and the amide-based solvent and hydrocarbon-based The compositions for forming a polyamideimide film according to Examples 1 to 6 containing a mixed solvent containing a solvent had a viscosity of 15,000 cp or less, and the polyamideimide films prepared using them had a yellowness of 3.5 or less. And, the tensile strength was high with a modulus of 4.0 GPa or more according to ASTM E111, and the absolute value of the retardation in the thickness direction at a wavelength of 550 nm was 600 nm or less, and the mechanical and optical properties were excellent. Therefore, the polyamide-imide film prepared using the composition for forming a polyamide-imide film according to the embodiment improves reflection appearance and screen distortion in the visible ray region, is flexible, and has excellent bending characteristics, so that display It is suitable for application to a device, and is useful for application as a cover window of, for example, a foldable or flexible display device.

On the other hand, the polyamideimide film of Comparative Example 1 prepared from a composition not containing a mixed solvent containing an amide-based solvent and a hydrocarbon-based solvent has a yellowness compared to the polyamideimide film of Example 1 having the same monomer molar ratio and heat treatment temperature. and thickness direction retardation increased significantly. In addition, the composition for forming a polyamideimide film of Comparative Example 2 including the mixed solvent but containing the hydrocarbon-based solvent in an amount of 60% by weight based on the total amount of the amide-based solvent and the hydrocarbon-based solvent has a high initial polymerization solid content, so that the solution viscosity is controlled. It was so high that polymerization was impossible. On the other hand, the composition of Comparative Example 3 containing 15% by weight of a hydrocarbon-based solvent was disadvantageous in the process because the viscosity was high and bubbles were not removed, and the prepared film had an uneven coating surface. Accordingly, the surface of the coating layer after curing was somewhat rough, so it was evaluated as defective, and it was confirmed that it was unsuitable for manufacturing a polyamideimide film. In addition, the polyamide-imide film-forming composition of Comparative Examples 4 and 5 containing either TPC or IPC as a diacid dichloride, but containing more than 50 mol% based on 100 mol% of diamine, polyamideimide film-forming composition Since the yellowness and retardation in the thickness direction of the amideimide film were greatly increased, excellent optical properties of the polyamideimide film could not be realized.

As described above, the present invention has been described by limited embodiments, but this is only provided to help a more general understanding of the present invention, and the present invention is not limited to the above embodiments, and conventional knowledge in the field to which the present invention belongs Those who have it can make various modifications and variations from these materials.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and it will be said that not only the claims to be described later, but also all modifications equivalent or equivalent to these claims belong to the scope of the present invention. .

Claims (19)

a polyamic acid or polyamideimide comprising a structural unit derived from diamine, a structural unit derived from a dianhydride, and a structural unit derived from diacid dichloride; and
A mixed solvent containing an amide-based solvent and a hydrocarbon-based solvent; including,
A composition for forming a polyamideimide film satisfying the following formula 1,
The structural unit derived from the diamine includes a structural unit derived from a compound represented by Formula 1 below; The structural unit derived from the dianhydride includes a structural unit derived from a compound represented by Formula 2 below; A composition for forming a polyamideimide film, wherein the structural unit derived from the diacid dichloride includes a structural unit derived from any one of a compound represented by Formula 3 and a compound represented by Formula 4:
[Formula 1]

,
[Formula 2]

,
[Formula 3]

,
[Formula 4]

,
[Equation 1]
5,000 ≤ _VPAI ≤ 15,000
In Equation 1 above,
V _PAI is the viscosity of the composition for forming a polyamideimide film when the solid content is 17% by weight relative to the total weight of the composition for forming a polyamideimide film, and the viscosity is measured by a Brookfield rotational viscometer at 25 ° C. with a 52Z spindle It is the viscosity (unit: cp) measured based on Torque 80% 2 minutes using
According to claim 1,
The amide-based solvent comprises dimethylpropionamide, a composition for forming a polyamideimide film.
According to claim 1,
The hydrocarbon-based solvent is a cyclic hydrocarbon-based solvent, a composition for forming a polyamideimide film.
According to claim 3,
The cyclic hydrocarbon-based solvent includes toluene, benzene, cyclohexane, or a combination thereof, a composition for forming a polyamideimide film.
According to claim 1,
The solid content of the composition for forming the polyamideimide film,
A composition for forming a polyamideimide film, which is included in 10% to 40% by weight based on the total weight of the composition for forming a polyamideimide film.
According to claim 1,
The composition for forming the polyamideimide film,
A composition for forming a polyamideimide film comprising the amide-based solvent and the hydrocarbon-based solvent in a weight ratio of 8:2 to 5:5.
According to claim 1,
The structural unit derived from the diacid dichloride is included in an amount of 5 mol% to 40 mol% based on 100 mol% of the structural unit derived from the diamine.
According to claim 1,
A composition for forming a polyamideimide film, wherein the molar ratio of the structural unit derived from the dianhydride and the structural unit derived from the diacid chloride is 95:5 to 50:50.
In an amide solvent, diamine including a compound represented by Formula 1 below, a dianhydride including a compound represented by Formula 2 below, and any one of a compound represented by Formula 3 and a compound represented by Formula 4 below Preparing a polyamic acid solution by reacting diacid dichloride containing diacid (step i); and
Step of adjusting the viscosity by introducing a hydrocarbon-based solvent to satisfy the following formula 1 (step ii); Method for producing a composition for forming a polyamideimide film comprising:
[Formula 1]

,
[Formula 2]

,
[Formula 3]

,
[Formula 4]

,
[Equation 1]
5,000 ≤ _VPAI ≤ 15,000
In Equation 1 above,
V _PAI is the viscosity of the composition for forming a polyamideimide film when the solid content is 17% by weight relative to the total weight of the composition for forming a polyamideimide film, and the viscosity is measured by a Brookfield rotational viscometer at 25 ° C. with a 52Z spindle It is the viscosity (unit: cp) measured based on Torque 80% 2 minutes using
According to claim 9,
In step ii,
Stirring by adding 25% to 100% by weight of a hydrocarbon-based solvent based on the weight of the amide-based solvent in step i; and
additionally introducing a mixed solvent including an amide-based solvent and a hydrocarbon-based solvent to satisfy Equation 1; A method for producing a composition for forming a polyamideimide film comprising a.
According to claim 9,
Based on 100 mol% of the diamine, the mol% of the diacid dichloride is 5 mol% to 40 mol%, a method for producing a composition for forming a polyamideimide film.
According to claim 9,
A method for producing a composition for forming a polyamideimide film, wherein the molar ratio of the dianhydride and the diacid chloride is 95:5 to 50:50.
A polyamideimide film obtained by curing the composition for forming a polyamideimide film according to any one of claims 1 to 8.
According to claim 13,
The polyamideimide film has a yellowness index (YI) of 3.5 or less according to ASTM E313, and an absolute value of a thickness direction retardation (Rth) at a wavelength of 550 nm of 600 nm or less.
According to claim 13,
The polyamideimide film has a thickness of 30 μm to 100 μm and a modulus according to ASTM E111 of 4 GPa or more.
A method for producing a polyamideimide film comprising applying the composition for forming a polyamideimide film according to any one of claims 1 to 8 on a substrate and then heat-treating it.
According to claim 16,
The heat treatment is performed at a temperature of 280 ℃ to 350 ℃ for 10 minutes to 60 minutes, a method for producing a polyamideimide film.
The polyamideimide film according to claim 13; and
A cover window for a display device comprising a coating layer formed on the polyamideimide film.
A display device comprising the polyamideimide film according to claim 13 .