KR20230037862A - 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. The composition for forming a polyamideimide film according to an embodiment of the present invention has excellent mechanical properties without deterioration in colorless and transparent optical properties, thereby being usefully utilized in a polyamideimide film or a display device including the same. The composition for forming a polyamideimide film comprises polyamic acids or polyamideimides, including structural units derived from diamines, structural units derived from dianhydrides, and structural units derived from diacid dichlorides; and additives.

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.

Polyamide-imide film is attracting attention as a next-generation material that can replace tempered glass as a material for display device substrates and cover windows. However, in order to apply the polyamideimide film to a display device, it is essential to improve the inherent yellowness characteristic and impart colorless and transparent performance. Furthermore, since mechanical properties must be improved in order to be applicable to foldable or flexible display devices, the performance requirements of polyamideimide films for display devices are gradually increasing.

To this end, studies to reduce the CTC effect by combining or changing monomers of various structures are continuing, but there is still a limit in that yellowness increases as the thickness of the film increases as the residual yellow color appears. In addition, a method of adding additives to polyamideimide films has been proposed, but access is difficult due to problems in the manufacturing process, and there is a limit to solving the deterioration of excellent mechanical properties inherent in polyamideimide instead of securing transparency. There is a situation.

Therefore, it satisfies transparency and mechanical properties at the same time so that it can be applied to various display material fields, including substrates of display devices as well as cover window replacement materials, while having excellent optical properties and preventing degradation of inherent excellent mechanical properties. It is necessary to develop technology for polyamideimide films that can further expand the

One embodiment of the present invention provides a colorless and transparent composition for forming a polyamideimide film having no optical stains, excellent visibility, heat resistance and mechanical properties without deterioration of optical properties.

Another embodiment of the present invention provides a method for preparing a composition for forming a polyamideimide film having no optical stains, excellent visibility, heat resistance and mechanical properties without deteriorating colorless and transparent optical properties.

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 additives;

The additive may include inorganic nanoparticles; multifunctional (meth)acrylic compounds; and at least one of blue-based pigments and dyes, wherein the inorganic nanoparticles may be included in an amount of 5% to 40% by weight based on the solid content of polyamic acid or polyamideimide, and the multifunctional (meth)acrylic The compound may be included in an amount of 2% to 10% by weight based on the solid content of the polyamic acid or polyamideimide,

The structural unit derived from the diamine includes a structural unit derived from a compound represented by Formula 1 below, and 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 diacid dichloride may include a structural unit derived from any one of a compound represented by Chemical Formula 3 and a compound represented by Chemical Formula 4 below.

[Formula 1]

,

,

[Formula 2]

,

,

[Formula 3]

,

,

[Formula 4]

.

.

A method for preparing a composition for forming a polyamideimide film according to an embodiment of the present invention includes preparing a reaction product of diamine and diacid dichloride;

preparing a polyamic acid solution by adding and reacting the reaction product of the diamine and diacid dichloride and dianhydride to a reaction medium containing at least one of blue-based pigments and dyes; and

In the polyamic acid solution, 5% to 40% by weight of inorganic nanoparticles based on the solid content of polyamic acid or polyamideimide, and 2% to 10% by weight of polyfunctional (meth)acrylic based on the solid content of polyamic acid and polyamideimide Injecting a compound; can include,

The diamine includes a compound represented by Formula 1 below, the dianhydride includes a compound represented by Formula 2 below, and the diacid dichloride includes a compound represented by Formula 3 below and a compound represented by Formula 4 below. It may include any one.

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.

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.

The composition for forming a polyamideimide film according to one embodiment of the present invention and the polyamideimide film prepared using the same can implement colorless and transparent optical properties even in a thickness range having mechanical strength similar to that of tempered glass. In addition, the composition for forming a polyamideimide film according to an embodiment of the present invention and the polyamideimide film prepared using the same have excellent optical properties, and display quality and visibility are remarkably improved, as well as flexibility and mechanical properties. It is excellent and can be usefully applied for optical purposes such as a foldable display device or a flexible display device.

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, 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, as long as there is no specific definition in this specification, “(meth)acryl” may be used as a meaning including both “methacryl” and “acryl”.

Hereinafter, unless otherwise specifically defined herein, "multifunctional (meth)acrylic crosslinked polymer" may mean a crosslinked polymer formed by crosslinking multifunctional (meth)acrylic compounds having a (meth)acrylic group, and the multifunctional The (meth)acrylic crosslinking polymer may or may not include a (meth)acrylic group, for example, a (meth)acrylate group.

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

In order to apply the polyimide film to a display device, it may be very important to improve the inherent yellowness of the polyimide film and impart colorless and transparent performance. In order to solve this problem, research on reducing the CTC effect and preparing colorless and transparent polyimide through a combination of monomers of various structures has been continued. However, the transparent polyimide film prepared by the above method may still show residual yellow color, and there is a limitation that yellowness increases as the thickness of the film increases.

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 by including additives, it is possible to implement colorless and transparent optical properties even in a thickness range having mechanical strength similar to that of tempered glass.

In this case, the structural unit derived from the diamine includes a structural unit derived from a compound represented by Formula 1 below, and 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 include 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 additive may include any one or more of inorganic nanoparticles, multifunctional (meth)acrylic compounds, and blue-based pigments and dyes.

[Formula 1]

,

,

[Formula 2]

,

,

[Formula 3]

,

,

[Formula 4]

.

.

The inorganic nanoparticles may be included in an amount of 5% to 40% by weight based on the solid content of polyamic acid and/or polyamideimide. The weight % of the inorganic nanoparticles is not necessarily limited to the above range, and for example, 5% to 43% by weight, 10% to 40% by weight, 15% by weight based on the solid content of polyamic acid and / or polyamideimide. % to 40% by weight, 20% to 40% by weight, or 25% to 40% by weight. By adding the inorganic nanoparticles in the above amount, a polyamideimide film having a more transparent, low thickness direction retardation, and excellent mechanical properties can be provided. Here, the polyamic acid and/or polyamideimide solid content may mean polyamic acid and/or polyamideimide.

The inorganic nanoparticles may include, for example, silica, zirconium oxide, titanium oxide, zinc oxide, zinc sulfide, chromium oxide, barium titanate, or a combination thereof.

The average diameter of the inorganic nanoparticles is not necessarily limited to a specific range, but may be 5 nm to 50 nm, or, for example, 5 nm to 30 nm, or 5 nm to 20 nm.

The inorganic nanoparticles may be mixed with the polyamideimide resin in a form dispersed in an organic solvent, and may be a surface-treated material to improve dispersibility.

The polyfunctional (meth)acrylic compound may be included in an amount of 2% to 10% by weight based on the solid content of polyamic acid and/or polyamideimide. The weight % of the polyfunctional (meth)acrylic compound is not necessarily limited to the above range, and is, for example, 2% to 13% by weight, 3% to 10% by weight, based on the solid content of polyamic acid or polyamideimide, 4% to 10% by weight, or 5% to 10% by weight. By adding the multifunctional (meth)acrylic compound in the above content, a polyamideimide film having a more transparent and low thickness direction retardation and excellent mechanical properties can be provided. Here, the polyamic acid and/or polyamideimide solid content may mean polyamic acid and/or polyamideimide.

The multifunctional (meth)acrylic compound is a compound having a multifunctional (meth)acrylic group, and the (meth)acrylic group may be, for example, a (meth)acrylate group. The multifunctional (meth)acrylic compound is, for example, trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, 1,2,4-cyclohexanetetra(meth)acrylate, pentaglycerol tri (meth)acrylate, pentaerythritol tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipenta Erythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tripentaerythritol tri(meth)acrylate, tripentaerythritol hexa(meth)acrylate, polyfunctional urethane (meth)acrylate , polyfunctional polyester (meth)acrylate, or a combination thereof.

Alternatively, the multifunctional (meth)acrylic compound may further include an alkylene group, an ether group, a urethane group, an ester group, or a combination thereof.

The multifunctional (meth)acrylic compound according to one embodiment of the present invention may form a multifunctional (meth)acrylic crosslinked polymer through subsequent heating, and the crosslinked polymer is the multifunctional (meth)acrylic compound. This may be crosslinked in whole or in part, but is not necessarily limited thereto. In addition, the multifunctional (meth)acrylic crosslinking polymer may be dispersed in a composition for forming a polyamideimide film to form a composite. However, the bond between the multifunctional (meth)acrylic crosslinking polymer and the polyamideimide polymer may not include a chemical bond, and for example, the multifunctional (meth)acrylic crosslinking polymer and the polyamideimide polymer may covalently bond with each other. It may not be.

The maximum absorption wavelength of the blue-based pigment or dye is not particularly limited as long as it includes the yellow-based wavelength range, but may be, for example, 520 nm to 650 nm, 550 nm to 650 nm, or 550 nm to 620 nm. . By using a pigment or dye having a maximum absorption wavelength within the above range, the blue or violet wavelength light absorption phenomenon of the polyamideimide film made of polyamic acid or polyamideimide containing the above structural units is effectively offset, Yellowness can be improved more effectively. Furthermore, by appropriately selecting the maximum absorption wavelength range of the inorganic pigment according to the type and composition of monomers used in preparing the composition for forming a polyamideimide film or the optical properties of the polyamideimide film, the yellowness, refractive index, and thickness of the film Even optical properties such as directional retardation can be further improved.

As the pigment, a blue-based pigment or a known pigment having a maximum absorption wavelength of 520 nm to 650 nm may be used without particular limitation, and examples thereof include natural minerals; or one or more metals or metal oxides thereof selected from zinc, titanium, lead, iron, copper, chromium, cobalt, molybdenum, manganese, and aluminum; it may be an inorganic pigment including. The pigment may be used by being included in a pigment dispersion along with a dispersant.

The average particle size of the inorganic pigment may be 30 nm to 100 nm. Alternatively, the average particle size is not necessarily limited, but may be, for example, 50 nm to 100 nm, or 70 nm to 100 nm. The average particle size of the inorganic pigment may be measured, for example, in a dispersion or in a polyamideimide film. Also, for example, the average particle size of the solid phase before dispersion of the pigment may be, for example, 10 nm to 70 nm, 30 nm to 70 nm, or 50 nm to 70 nm.

In order to improve the dispersibility of the pigment, means such as ultrasonic waves may be used, and a dispersing agent may be used. The dispersant is not particularly limited as long as it can prevent aggregation between pigments and improve the dispersibility and dispersion stability of the pigment, but, for example, a functional group adsorbed to the pigment and a functional group having high affinity to the dispersion medium (the organic solvent). It may have, and the quasi-acid may be determined by adjusting the balance of the two functional groups. Various types of the dispersant may be used according to the surface state of the pigment, which is a product to be dispersed. For example, the pigment dispersant according to one embodiment of the present invention may have an acidic functional group, and in this case, the acidic functional group may be adsorbed to the pigment. The acidic functional group may be, for example, carboxylic acid.

As the dye, a blue-based dye or a known dye having a maximum absorption wavelength of 520 nm to 650 nm may be used without particular limitation, and examples thereof include acid dyes, direct dyes, mordant dyes, and the like. Alternatively, compounds classified as having color in addition to pigments in the color index (published by The Society of Dyers and Coulurists) or known dyes described in dyeing notes (color dyeing yarns) may be exemplified. Alternatively, chemical structures include azo dyes, cyanine dyes, triphenylmethane dyes, phthalocyanine dyes, anthraquinone dyes, naphthoquinone dyes, quinoneimine dyes, methine dyes, azomethine dyes, squarylium dyes, acridine dyes, styryl dyes, coumarin dyes, quinoline dyes, nitro dyes, and indigo dyes.

The pigment according to one embodiment of the present invention may be 10 ppm to 1,500 ppm based on the solid content of polyamic acid and/or polyamideimide, or, for example, 100 ppm to 1,500 ppm, or 500 ppm to 1,500 ppm. . Here, the polyamic acid and/or polyamideimide solid content may mean polyamic acid and/or polyamideimide.

The dye according to one embodiment of the present invention may be 10 ppm to 500 ppm based on the solid content of polyamic acid and/or polyamideimide, or for example, 10 ppm to 300 ppm, 10 ppm to 200, 50 ppm to 200 ppm, or 80 ppm to 200 ppm. Here, the polyamic acid and/or polyamideimide solid content may mean polyamic acid and/or polyamideimide.

In one embodiment of the present invention, the additive may further include a conventional additive added to a polyamideimide film or a composition for forming a polyimide film, for example, a flame retardant, an adhesion enhancer, an antioxidant, and an ultraviolet inhibitor. Alternatively, a plasticizer may be further included.

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.

[Equation 1]

5,000 ≤ _VPAI ≤ 40,000

In Equation 1 above,

V _PAI is the viscosity of the composition for forming a polyamideimide film when the solid content of polyamic acid or polyamideimide is 14% by weight with respect to the total weight of the composition for forming a polyamideimide film, and the viscosity is measured using a Brookfield rotational viscometer It is the viscosity (unit: cp) measured based on Torque 80% 2 minutes using a 52Z spindle at 25 ° C. The viscosity (V _PAI ) may be, for example, 5.000 cp to 30,000 cp, 5,000 cp to 25,000 cp, 5,000 cp to 20,000 cp, or 5,000 cp to 15,000 cp. 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 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.

In one embodiment of the present invention, the diacid dichloride-derived structural unit may be included in an amount of 5 mol% to 50 mol% based on 100 mol% of the diamine-derived structural unit. 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 polyamideimide film according to one embodiment of the present invention can have a more transparent and low thickness direction retardation by including structural units derived from diacid dichloride in the above range based on 100 mol% of structural units derived from diamine. and may have excellent mechanical properties such as high modulus and elongation at break. Accordingly, it may be possible to implement optical and mechanical properties equal to or superior to those of tempered glass.

In one embodiment of the present invention, the molar ratio of the structural unit derived from the dianhydride and the structural unit derived from 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 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 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 above molar ratio, so that it can be more transparent and have a low thickness direction retardation, and has high modulus. , can have excellent mechanical properties such as elongation at break. 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.

The polyamideimide film according to one embodiment of the present invention may be prepared from a polyamideimide resin including structural units derived from diamine, dianhydride, and diacid dichloride as exemplified above, wherein the polyamideimide resin is It may have a weight average molecular weight (Mw) of 10,000 g/mol to 80,000 g/mol, 10,000 g/mol to 70,000 g/mol, or 10,000 g/mol to 60,000 g/mol, but is not limited thereto.

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, or 10% to 25% by weight may be satisfied. Here, the solid content may be the polyamic acid and/or polyamideimide.

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

A method for preparing a composition for forming a polyamideimide film according to an embodiment of the present invention,

preparing a reaction product of diamine and diacid dichloride;

preparing a polyamic acid solution by adding a reaction product of diamine and diacid dichloride and dianhydride to a reaction medium containing at least one of blue-based pigments and dyes; and

In the polyamic acid solution, 5% to 40% by weight of inorganic nanoparticles based on the solid content of polyamic acid or polyamideimide, and 2% to 10% by weight of polyfunctional (meth)acrylic based on the solid content of polyamic acid and polyamideimide Injecting a compound; can include

The diamine may include a compound represented by Formula 1 below, the dianhydride may include a compound represented by Formula 2 below, and the diacid dichloride may include a compound represented by Formula 3 below and Formula 4 below. It may contain any one of the compounds shown.

[Formula 1]

,

,

[Formula 2]

,

,

[Formula 3]

,

,

[Formula 4]

.

.

The method for preparing a composition for forming a polyamideimide film according to an embodiment of the present invention may include preparing a diamine solution by mixing the diamine and a solvent, and then adding diacid dichloride to the diamine solution and reacting the mixture. there is.

The method for preparing a composition for forming a polyamideimide film according to an embodiment of the present invention may further include, after the step of preparing a polyamic acid solution, adjusting the viscosity by introducing an organic solvent to satisfy Equation 1 below. there is.

[Equation 1]

5,000 ≤ _VPAI ≤ 40,000

In Equation 1 above,

V _PAI is the viscosity of the composition for forming a polyamideimide film when the solid content of polyamic acid or polyamideimide is 14% by weight with respect to the total weight of the composition for forming a polyamideimide film, and the viscosity is measured using a Brookfield rotational viscometer It is the viscosity (unit: cp) measured based on Torque 80% 2 minutes using a 52Z spindle at 25 ° C.

In the method for preparing the composition for forming a polyamideimide film, the step of preparing the polyamic acid solution may be performed in an organic solvent, a polar solvent, specifically an amide-based solvent. The amide-based solvent may refer to a compound containing an amide moiety. The amide-based solvent may be aromatic or aliphatic, for example, aliphatic. Also, for example, the amide-based solvent may be a cyclic compound or a chain compound, specifically, may have 2 to 15 carbon atoms, for example, 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 polymerization of polyamic acid and/or polyamideimide, but examples thereof include dimethylpropionamide, diethylpropionamide, dimethylacetylamide, and diethylacetamide. , Dimethylformamide, methylpyrrolidone, ethylpyrrolidone, octylpyrrolidone, or a combination thereof, and may specifically include dimethylpropionamide.

In the method for preparing a composition for forming a polyamideimide film according to an embodiment of the present invention, a blue-based pigment or dye may be added in a step of polymerizing polyamic acid and/or polyamideimide. Specifically, after preparing a diamine solution by reacting diamine and a solvent, diamino oligomer prepared by adding diacid dichloride to the prepared diamine solution and reacting thereto is prepared, and a reaction medium containing a blue pigment or dye is prepared. It can proceed to the step of dissolving by adding to. Meanwhile, the dye may be added in advance, added at the start of polymerization, or added after polymerization, and the order of addition is not limited. Meanwhile, in the case of a pigment, when the pigment is added and dispersed after polymerization of polyamic acid and/or polyamideimide is completed, the pigment cannot be uniformly dispersed and the optical properties of the polyamideimide film may be deteriorated. In contrast, the experiment was performed with the same composition as in Example 1 below, but the pigment dispersion was added after polymerization of polyamic acid and/or polyamideimide, and as a result, it was confirmed that the pigment was not dispersed at all. On the other hand, when a pigment or dye and a polyamic acid and/or polyamideimide monomer are added together in the step of polymerizing polyamic acid and/or polyamideimide, stable dispersibility of the pigment can be secured. That is, in the step of polymerizing polyamic acid and/or polyamideimide, the dispersibility of the dye or pigment in the composition for forming a polyamideimide film can be remarkably improved by adding the dye or pigment and the monomer together, and thus, curing Even after this, the yellowness can be improved without deterioration of the mechanical properties of the film.

In addition, in the method for preparing a composition for forming a polyamideimide film according to an embodiment of the present invention, the above description of the composition for forming a polyamideimide film may be applied.

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

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.

Since the polyamideimide film according to one embodiment of the present invention can implement a low retardation in the thickness direction while being transparent even at a thickness of 20 μm or more, and can further improve visibility, a cover window including the polyamideimide film is suitable for users. It can further reduce eye fatigue. In addition, even with a thickness of 20 μm or more, not only excellent optical properties as described above, but also mechanical strength can be further improved, so that dynamic bending characteristics are further improved and foldable display devices that repeat folding and unfolding operations repeatedly or It may be suitable for application as a cover window of 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 to 3.5, 1.5 to 3.5, 1.0 to 3.0, 1.5 to 3.0, 1.0 to 2.8, 1.5 to 2.8, or 2.0 to 3.0, but is not necessarily limited to the above range. . In addition, the polyamideimide film according to one embodiment of the present invention may have an elongation at break of 10% or more. Alternatively, the elongation at break may be, for example, 10% to 20%, 10% to 18%, 11% or more, 11% to 20%, or 10% to 16%, but is not necessarily limited to the above range. . The polyamideimide film according to one embodiment of the present invention satisfies both the yellowness and elongation at break, and thus can provide sufficient mechanical properties and durability to be applied to a cover window for a display.

In addition, the thickness of the polyamideimide film according to one embodiment of the present invention may be 20 μm to 500 μm. Alternatively, the thickness may be, for example, 20 μm to 300 μm, 20 μm to 250 μm, 20 μm to 200 μm, 20 μm to 150 μm, 20 μm to 100, 30 μm to 100 μm, or 20 μm to 80 μm. there is. In addition, the polyamideimide film according to one embodiment of the present invention may have an absolute value of retardation in the thickness direction at a wavelength of 550 nm of 800 nm or less. Or the thickness direction retardation is, for example, 600 nm or less, 200 nm to 600 nm, 200 nm to 500 nm, 250 nm to 600 nm, 250 nm to 550 nm, 300 nm to 600 nm, or 300 nm to 500 nm. However, it is not necessarily intended to be 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 modulus according to ASTM E111 of the polyamideimide film according to one embodiment of the present invention may be 3.5 GPa or more, 4.0 GPa or more, 4.3 GPa or more, or 4.0 GPa to 6.0 GPa.

The polyamideimide film according to one embodiment of the present invention satisfies the thickness direction retardation, yellowness, and elongation at break within the above ranges, thereby preventing image distortion caused by light and providing improved visibility. In addition, more uniform mechanical properties (elongation at break, etc.) and optical properties (e.g., retardation in the thickness direction) 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.

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

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 in the heat treatment step is not necessarily performed in a specific temperature range, but, for example, at a temperature of 280 ° C. or more and 350 ° C. or less for 10 minutes It may be carried out for 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 arise. 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 temperature of the drying step is not necessarily performed within a specific temperature range, but may be performed at a temperature of, for example, 50 °C to 150 °C, 50 °C to 130 °C, 60 °C to 100 °C, or about 80 °C.

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 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 embodiment of the present invention may be a multilayer structure including the polyamideimide film according to any one of the above embodiments 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.

One embodiment of the present invention may be a display device including the polyamideimide film according to any one of the above embodiments 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.

<Measurement method>

1. Yellow Index (YI)

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

2. Modulus and elongation at break

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. The unit of modulus is Gpa, and the unit of elongation at break is %.

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.

< Example 1>

Preparation of composition for forming polyamideimide film

253 g of dimethylpropionamide (DMPA) was charged into a reactor under a nitrogen atmosphere. While maintaining the temperature of the reactor at 25 ° C, 2,2'-bis (trifluoromethyl) -benzidine (TFMB) was added and stirred for 6 hours to dissolve and react. Then, 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 to obtain a white powder.

The obtained white powder was put into a reactor under nitrogen atmosphere again with DMPA and a solvent mixed with 1,200 ppm of a pigment dispersion (5% by weight in DMAc, OP-1803B, Toyoink) having an average particle size of 90 nm in the dispersion and dissolved. After, 9,9-bis (3,4-dicarboxyphenyl) fluorene dianhydride (9,9-Bis (3,4-dicarboxyphenyl) fluorene dianhydride, BPAF) was added, dissolved and reacted with stirring for 12 hours To prepare a polyamic acid resin composition. At this time, the molar ratio of each monomer TFMB:BPAF:TPC was adjusted to be as shown in Table 1 below, and the solid content was adjusted to 14% by weight. Then, based on the polyamic acid or polyamideimide solid content of the polyamic acid resin composition, silica particles (SSD 330T, DMAc 30% by weight, Renko, 15 nm) 25% by weight and dipentaerythritol hexaacrylate (Dipentaerythritol Hexaacrylate, DPHA ) (M500, Miwon) was added and stirred for 5 hours to prepare a polyamideimide film forming composition.

Manufacture of polyamideimide film

On one surface of a glass substrate (1.0T), the above-obtained composition for forming a polyamideimide film was applied with an applicator, cured by heating at 80 ° C for 30 minutes and then at 300 ° C for 15 minutes in a nitrogen atmosphere, and curing the glass substrate. It was peeled off to prepare a polyamideimide film having a thickness of 50 μm.

< Example 2>

A composition for forming a polyamideimide film of Example 2 was prepared in the same manner as in Example 1, except that the weight % of DPHA, a multifunctional acrylic compound, was changed as shown in Table 2 below, and the same as in Example 1. In this way, a polyamideimide film of Example 2 having a thickness of 50 μm was prepared.

< Example 3>

After polymerization in the same manner as in Example 1 except for the step of adding the pigment dispersion containing the pigment, silica particles (SSD 330T, DMAc 30% by weight, Renko, 15 nm) 40% by weight and DPHA (M500, Miwon) 5 A polyamideimide film-forming composition of Example 3 was prepared by adding 120 ppm of dye (SI1001, KISCO) diluted by weight % and 5% and then stirring for 5 hours. Then, a polyamideimide film of Example 3 having a thickness of 50 μm was prepared in the same manner as in Example 1.

< Example 4 and Example 5>

Example 4 in the same manner as in Example 1, except that Isophthaloyl chloride (IPC) was used instead of TPC in Example 1, and the weight% of silica particles and DPHA were changed as shown in Table 2 below. And the composition for forming a polyamideimide film of Example 5 was prepared, and the polyamideimide films of Examples 4 and 5 having a thickness of 50 μm were prepared in the same manner as in Example 1.

< Example 6>

The composition for forming a polyamideimide film of Example 6 was prepared in the same manner as in Example 3, except that IPC was used instead of TPC in Example 3, and the composition having a thickness of 50 μm was prepared in the same manner as in Example 3. A polyamideimide film of Example 6 was prepared.

< comparative example 1>

A composition for forming a polyamideimide film of Comparative Example 1 was prepared in the same manner as in Example 1, except that inorganic nanoparticles, a multifunctional acrylic compound, and a pigment were not added as additives in Example 1, and 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 and comparative example 3>

Polyamideimide of Comparative Example 2 and Comparative Example 3, respectively, in the same manner as in Example 1, except that the molar ratios of TFMB, BPAF and TPC and the weight % of the additives were changed as shown in Tables 1 and 2 below. A composition for film formation was prepared, and polyamideimide films of Comparative Examples 2 and 3 having a thickness of 50 μm were prepared in the same manner as in Example 1.

TFMB BPAF TPC IPC Example 1 100 60 40 - Example 2 100 60 40 - Example 3 100 60 40 - Example 4 100 60 - 40 Example 5 100 60 - 40 Example 6 100 60 - 40 Comparative Example 1 100 60 40 - Comparative Example 2 100 80 20 - Comparative Example 3 100 40 60 -

inorganic nanoparticles
(weight%) Multifunctional acrylic compound (% by weight) dyes
(ppm) pigment
(ppm) Example 1 25 5 - 1200 Example 2 25 10 - 1200 Example 3 40 5 120 - Example 4 25 5 - 1200 Example 5 25 10 - 1200 Example 6 40 5 120 - Comparative Example 1 - - - - Comparative Example 2 45 15 - 1200 Comparative Example 3 45 15 - 1200

< Experimental example > Evaluation of optical and mechanical properties

Yellowness (YI), elongation at break, retardation (Rth) in the thickness direction, and modulus of the polyamideimide films according to Examples 1 to 6 and Comparative Examples 1 to 3 were measured according to the above measurement method, It is shown in Table 3 below.

Example No. One 2 3 4 5 6 thickness
(μm) 50 50 50 50 50 50 yellowness
(YI) 2.7 2.4 2.7 2.4 2.2 2.3 elongation at break
(%) 15 11 11 15 11 10 Rth
(550 nm) 450 400 390 310 280 260 modulus
(GPa) 5.1 5.0 5.4 4.6 4.5 5.0 Comparative Example No. One 2 3 thickness
(μm) 50 50 50 yellowness
(YI) 3.4 4.0 3.9 elongation at break
(%) 15 2 3 Rth
(550 nm) 490 350 338 modulus
(GPa) 4.7 5.1 4.7

As can be seen from Table 3, prepared from a composition for forming a polyamideimide film containing a diamine containing TFMB, a dianhydride containing BPAF, and a diacid dichloride containing any one of TPC and IPC. The polyamideimide film further includes a blue-based dye or pigment, inorganic nanoparticles, and an acryl-based compound, so that the polyamideimide film has excellent elongation at break, modulus, and retardation, and is more yellow than the polyamideimide film according to Comparative Example 1. By having, it is possible to provide a film capable of remarkably improving display quality and visibility.

On the other hand, the polyamideimide films according to Comparative Examples 2 and 3, in which inorganic nanoparticles were used in excess of 40% by weight and acryl-based compounds were used in excess of 10% by weight, had yellowness compared to the polyamideimide films according to Examples. It was confirmed that not only the significantly increased, but also the elongation at break was inferior, making it unsuitable for producing a polyamideimide film having excellent optical and mechanical properties.

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, 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 additives;
The additive includes at least one of inorganic nanoparticles, multifunctional (meth)acrylic compounds, and blue-based pigments and dyes,
The inorganic nanoparticles are included in an amount of 5% to 40% by weight based on the solid content of polyamic acid or polyamideimide,
The multifunctional (meth)acrylic compound is included in an amount of 2% to 10% by weight based on the solid content of polyamic acid or polyamideimide,
The structural unit derived from the diamine includes a structural unit derived from a compound represented by Formula 1 below, and 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 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]

.
According to claim 1,
The composition for forming a polyamideimide film, wherein the inorganic nanoparticles include silica, zirconium oxide, titanium oxide, zinc oxide, zinc sulfide, chromium oxide, barium titanate, or a combination thereof.
According to claim 1,
The average diameter of the inorganic nanoparticles is 5 nm to 50 nm, the composition for forming a polyamideimide film.
According to claim 1,
The multifunctional (meth)acrylic compound is trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, 1,2,4-cyclohexanetetra(meth)acrylate, pentaglycerol tri(meth)acrylate, Acrylates, pentaerythritol tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol tetra (meth)acrylate, dipentaerythritol hexa(meth)acrylate, tripentaerythritol tri(meth)acrylate, tripentaerythritol hexa(meth)acrylate, polyfunctional urethane (meth)acrylate, polyfunctional A composition for forming a polyamideimide film comprising polyester (meth)acrylate, or a combination thereof.
According to claim 1,
The multifunctional (meth)acrylic compound further comprises an alkylene group, an ether group, a urethane group, an ester group, or a combination thereof, the composition for forming a polyamideimide film.
According to claim 1,
The maximum absorption wavelength of the blue-based pigment or dye is 520 nm to 650 nm, the composition for forming a polyamideimide film.
According to claim 1,
The pigment is a natural mineral; or zinc, titanium, lead, iron, copper, chromium, cobalt, molybdenum, manganese, and one or more metals selected from aluminum or metal oxides thereof; an inorganic pigment comprising a composition for forming a polyamideimide film.
According to claim 1,
A composition for forming a polyamideimide film satisfying the following formula 1:
[Equation 1]
5,000 ≤ _VPAI ≤ 40,000
In Equation 1 above,
V _PAI is the viscosity of the composition for forming a polyamideimide film when the solid content of polyamic acid or polyamideimide is 14% by weight with respect to the total weight of the composition for forming a polyamideimide film, and the viscosity is measured using a Brookfield rotational viscometer It is the viscosity (unit: cp) measured based on Torque 80% 2 minutes using a 52Z spindle at 25 ° C.
According to claim 1,
The structural unit derived from the diacid dichloride is included in 5 mol% to 50 mol% based on 100 mol% of the structural unit derived from the diamine, the composition for forming a polyamideimide film.
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 dichloride is 95:5 to 50:50.
preparing a reaction product of diamine and diacid dichloride;
preparing a polyamic acid solution by adding and reacting the reaction product of the diamine and diacid dichloride and dianhydride to a reaction medium containing at least one of blue-based pigments and dyes; and
In the polyamic acid solution, 5% to 40% by weight of inorganic nanoparticles based on the solid content of polyamic acid or polyamideimide, and 2% to 10% by weight of polyfunctional (meth)acrylic based on the solid content of polyamic acid and polyamideimide Injecting a compound; including,
The diamine includes a compound represented by Formula 1 below, the dianhydride includes a compound represented by Formula 2 below, and the diacid dichloride includes a compound represented by Formula 3 below and a compound represented by Formula 4 below. Method for producing a composition for forming a polyamideimide film comprising any one:
[Formula 1]

,
[Formula 2]

,
[Formula 3]

,
[Formula 4]

.
According to claim 11,
The step of preparing the reaction product of the diamine and the diacid dichloride is to prepare a diamine solution by mixing the diamine containing the compound represented by Formula 1 and a solvent, and then to the diamine solution to obtain the compound represented by Formula 3 and the A method for preparing a composition for forming a polyamideimide film, comprising adding and reacting diacid dichloride containing any one of the compounds represented by Formula 4.
According to claim 11,
After the step of preparing a polyamic acid solution, a method for preparing a composition for forming a polyamideimide film, further comprising the step of adjusting the viscosity by introducing an organic solvent so as to satisfy Equation 1 below:
[Equation 1]
5,000 ≤ _VPAI ≤ 40,000
In Equation 1 above,
V _PAI is the viscosity of the composition for forming a polyamideimide film when the solid content of polyamic acid or polyamideimide is 14% by weight with respect to the total weight of the composition for forming a polyamideimide film, and the viscosity is measured using a Brookfield rotational viscometer It is the viscosity (unit: cp) measured based on Torque 80% 2 minutes using a 52Z spindle at 25 ° C.
A polyamideimide film obtained by curing the composition for forming a polyamideimide film according to any one of claims 1 to 10.
According to claim 14,
The polyamideimide film has a yellowness index (YI) of 3.5 or less according to ASTM E131 and an elongation at break of 10% or more.
According to claim 14,
The polyamideimide film has a thickness of 20 μm to 500 μm, and an absolute value of a thickness direction retardation (Rth) at a wavelength of 550 nm is 800 nm or less.
The polyamideimide film according to any one of claims 14 to 16; and
A cover window for a display device comprising a coating layer positioned on the polyamideimide film.
According to claim 17,
The coating layer is a hard coating layer, an antistatic layer, an anti-fingerprint layer, an antifouling layer, an anti-scratch layer, a low refractive index layer, an antireflection layer, an impact absorbing layer, or a combination thereof, a cover window for a display device.
A display device comprising the polyamideimide film according to any one of claims 14 to 16.