TWI621871B - Window film and flexible display including the same - Google Patents

Abstract

The present invention provides a window film and a flexible display comprising a window film. The window film comprises a base layer, a window coating formed on one surface of the base layer; and a back coating layer formed on the other surface of the base layer, wherein the window coating layer is composed of a window coating layer comprising a terpene resin The article is formed and the window film has an elastic modulus of about 1,000 MPa or greater on the backcoat layer and a pencil hardness of about 6H or above 6H on the adhesive layer.

Description

Window film and flexible display comprising the window film

Korean Patent Application No. 10-2015-0109216 filed on July 31, 2015, Korean Patent Application No. 10-2015-0122152, filed on August 28, 2015, and The priority of Korean Patent Application No. 10-2016-0027328, filed on Jan. 7, the entire disclosure of which is incorporated herein by reference.

The present invention relates to a window film and a flexible display comprising the window film.

The window film is placed on the outermost side of the optical display. Therefore, a window film is required to have good light transmittance and high pencil hardness. Such window films can be mounted to various components of the display via an adhesive layer. In a structure in which the window film is mounted on the adhesive layer, the window film may be affected by a decrease in pencil hardness. The window film comprises a base layer and a coating formed of a curable resin. Depending on the base layer and/or curable resin, the window film may have a high yellow index such that the window film may appear yellow. Therefore, the display screen may provide poor image quality. The window film can be processed on the reel. If the window film has a high sheet resistance and static electricity may be generated, there is a problem that handling the roll is difficult. This problem may become more severe if the antistatic treatment of the window film base layer is difficult.

Recently, a flexible display having high folding and unfolding flexibility has been developed by replacing a glass substrate or a high-hardness substrate of a typical display with a flexible film. In a flexible display, not only a substrate but also various components are required to have flexibility. There is also a need for a window film for a flexible display that has good flexibility. A window film having a low window on its opposite side can be advantageously used to provide good flexibility.

An example of the prior art is disclosed in Korean Patent Publication No. 2011-0087497A.

According to an aspect of the invention, a window film includes a base layer, a window coating formed on one surface of the base layer, and a back coat layer formed on the other surface of the base layer, wherein the window coating layer is used for including a terpene resin The composition of the window coating is formed, and the window film has an elastic modulus of about 1,000 MPa or more on the back coat layer and a pencil hardness of about 6H or higher on the adhesive layer.

According to an embodiment of the invention, the window film has a pencil hardness of about 6H or higher.

According to an embodiment of the invention, the window film has a radius of curvature of a pressing direction of about 10.0 mm or less and a radius of curvature of a stretching direction of about 20.0 mm or less.

According to an embodiment of the invention, the window film has a Martens hardness of from about 50 Newtons/mm to about 200 Newtons/mm on the backcoat layer.

According to an embodiment of the invention, the window coating has a thickness of from about 5 microns to about 150 microns.

According to an embodiment of the invention, the back coat layer has a thickness of from about 1 micron to about 100 microns.

According to an embodiment of the invention, the adhesive layer has a storage modulus of from about 10 kPa to about 50 kPa at 25 °C.

According to an embodiment of the invention, the window film further comprises at least one of a binder layer and a support layer.

According to an embodiment of the invention, the adhesive layer included in the window film has a thickness of from about 10 microns to about 100 microns.

According to an embodiment of the invention, the support layer is a film formed of the same resin as the resin of the base layer.

According to an embodiment of the invention, the window coating is formed directly on one surface of the base layer and the back coating layer is formed directly on the other surface of the base layer.

According to an embodiment of the invention, the window film further comprises an adhesive layer formed between the base layer and the back coat layer.

According to an embodiment of the invention, the window film further comprises a stack of adhesive layers and a support layer formed between the base layer and the back coat layer.

At least one of the base layer, the window coating, and the back coat layer includes a dye having a maximum absorption wavelength of from about 500 nm to about 650 nm.

According to an embodiment of the invention, the dye has a maximum absorption wavelength of from about 550 nanometers to about 620 nanometers.

According to an embodiment of the invention, the dye comprises cyanine, porphyrin, arylmethane, squarylium, azomethine, oxonol. At least one of azo, xanthene, melocyanine, and vanadium dye.

According to an embodiment of the invention, the dye is contained in the back coat layer, and in terms of solid content, the dye is present in the composition for the back coat layer in an amount of from about 0.001% by weight to about 15% by weight.

According to an embodiment of the invention, the dye is contained in the back coat layer, and the back coat layer is formed of a composition for the back coat layer, and the composition for the back coat layer includes a dye, a UV curable group-containing resin, Crosslinker and initiator.

According to an embodiment of the present invention, the UV curable group-containing resin includes at least one of a (meth)acrylic resin having a UV curable group and a fluorene oxide resin having a UV curable group.

According to an embodiment of the invention, the back coat layer has a thickness of about 100 nanometers or less.

According to an embodiment of the invention, the back coat layer contains a dye, and the back coat layer further includes at least one of an antioxidant and an antistatic agent.

According to an embodiment of the present invention, the base layer is formed of at least one of a polyester resin, a polycarbonate resin, a poly(meth)acrylate resin, a polystyrene resin, a polyamide resin, and a polyimide resin. .

According to an embodiment of the invention, the window film further comprises an adhesive layer formed on a lower surface of the back coat layer.

According to an embodiment of the invention, the window film has a yellow index of from about -2.5 to about 3.5.

According to an embodiment of the invention, the window film has a b* value of from about -2.5 to about 2.5.

According to an embodiment of the invention, the window coating is formed directly on one surface of the base layer, the back coating layer is formed directly on the other surface of the base layer, the dye is contained in the back coating layer, and the base layer comprises polyimine Resin film.

According to one aspect of the invention, a flexible display comprises a window film as set forth above.

The present invention provides a window film having a high pencil hardness on both the glass substrate and the adhesive layer. The present invention provides a window film having good optical properties such as light transmittance. The present invention provides a window film having good flexibility. The present invention provides a window film that exhibits good flexibility in its opposite direction. The present invention provides a window film having a low yellow index to prevent the window film from appearing yellow. The present invention provides a window film having a high pencil hardness. The present invention provides a window film which has high heat resistance to exhibit a lower yellow index change even after standing at a high temperature for a long period of time, and thus can be used in a display. The present invention provides a window film that has good antistatic properties to exhibit good roll stability.

Embodiments of the present invention will be described in detail with reference to the accompanying drawings. It is to be understood that the invention is not limited to the following examples and may be practiced in various ways. In the drawings, the parts that are not related to the description will be omitted for the sake of clarity. Throughout the specification, like elements will be referred to by like figure symbols.

In this document, spatially relative terms such as "upper side" and "lower side" are defined with reference to the drawings. Therefore, it should be understood that the term "upper surface" may be used interchangeably with the term "lower surface." In addition, when an element such as a layer or film is referred to as being "on" another element, it can be placed directly on the other element, or an intervening element can be present. On the other hand, when an element is referred to as being "directly" placed on another element, there is no intervening element therebetween.

As used herein, the term "UV curable group" means an epoxy group; a (meth) acrylate group; a (meth) acrylamide group; a vinyl group; an alicyclic epoxy group; a glycidyloxy group; Oxetane; or having an epoxy group, a (meth) acrylate group, a (meth) acrylamide group, a vinyl group, an alicyclic epoxy group, a glycidoxy group or an oxetane a C ₁ to C ₆ alkyl group or a C ₅ to C ₁₀ cycloalkyl group.

Unless otherwise stated, the term "substituted" means that at least one hydrogen atom of a functional group is substituted with a hydroxy group, an unsubstituted C ₁ to C ₁₀ alkyl group, a C ₁ to C ₁₀ alkoxy group, C ₃ to C ₁₀ cycloalkyl, C ₆ to C ₂₀ aryl, C ₇ to C ₂₀ arylalkyl, benzophenone, C ₁ to C ₁₀ alkyl substituted C ₆ to C ₂₀ aryl or C ₁ to C ₁₀ alkyl substituted by C ₁ to C ₁₀ alkoxy.

As used herein, the term "(meth)acryloyl" means "acryloyl" and/or "methacryl".

As used herein, "Ec" means (3,4-epoxycyclohexyl)ethyl, "Me" means methyl, "Et" means ethyl, and "Gp" means 3-glycidoxy. Propyl, and "Op" means 3-oxetanylpropyl.

In this paper, "pencil hardness on the adhesive layer" is measured according to JIS K5400 using a pencil hardness tester (Heidon) to measure the window coating of the window film, wherein the window film is placed on the substrate (for example, glass). The layer of adhesive (thickness: 50 microns) on the substrate was placed such that the window coating was placed on the outermost side. In the measurement of pencil hardness, a pencil of 6B to 9H (Mitsubishi Co., Ltd.) was used. Specifically, 1 kg pencil load on the window coating, 45° scratch angle (angle between pencil and window coating), 60 mm/min scrap rate, 19.6 Newton pencil press and 10.0 The pencil hardness is measured under the condition of a millimeter pencil scale. When the window coating has one or more scratches after 5 tests using a pencil, the pencil hardness is measured again using another pencil having a lower pencil hardness than the previous pencil, and the pencil hardness is repeatedly measured five times. Thereafter, the maximum value of the pencil hardness of all scratches on the window coating was observed as the pencil hardness of the window coating. In the measurement of "pencil hardness on the adhesive layer", the "adhesive layer" may have a storage modulus of 10 kPa to 50 kPa at 25 ° C and a glass transition temperature of -60 ° C to -20 ° C. Agent layer. To prepare a sample for measuring the modulus of storage on the adhesive layer, the composition for the adhesive layer was applied to a release film and allowed to stand at 35 ° C and 45% RH for 24 hours to form a 50 micron thick adhesive. membrane. After removing the release film from each of the adhesive films, 8 adhesive films were stacked and cut into circular samples having a thickness of 400 μm and a diameter of 8 mm. Here, Physica MCR501 (Antonpa Co., Ltd. (Anton) was used at 25 ° C under a condition of 1 rad/sec with respect to a sample on a disc having a diameter of 8 mm. Parr Co., Ltd.)) measures the storage modulus of the adhesive layer while increasing the temperature from -50 ° C to 100 ° C.

In this paper, "pencil hardness" is measured according to JIS K5400 using a pencil hardness tester (Xindong) on a window coating of a window film, wherein the window film is placed on a substrate (for example, a glass substrate) so that the window coating is placed at the most Outside. In the measurement of the pencil hardness, a pencil of 6B to 9H (Mitsubishi Co., Ltd.) was used. Specifically, 1 kg pencil load on the window coating, 45° scratch angle (angle between pencil and window coating), 60 mm/min scratch rate, 19.6 Newton pencil pressure, and 10.0 mm The pencil hardness is measured under the condition of a pencil scale. When the coating has one or more scratches after 5 tests using a certain pencil, the pencil hardness is measured again using another pencil having a lower hardness than the previous pencil, and after repeatedly measuring the pencil hardness five times, The maximum value of the pencil hardness of all five scratches not observed on the window coating was regarded as the pencil hardness of the window coating.

In this paper, "the elastic modulus of the window film" and "the Martens hardness of the window film" mean that a layer of adhesive (thickness: 50 μm) can be formed on the glass substrate and in the adhesive layer. On the sample prepared by stacking the window film, a constant force of 200 millinewtons (mN) was applied to the outermost layer of the sample for 20 seconds by using a microindenter (Vickers indenter) at 25 ° C, followed by a slow shift of 5 seconds. And relax the value measured in 20 seconds. Here, the adhesive layer is the same as the adhesive layer used in the pencil hardness measurement. When the outermost layer of the sample is a window coating, the values are referred to as 'elastic modulus on the window coating' and 'Martens hardness on the window coating'. When the outermost layer of the sample is a back coat, the value is referred to as 'the elastic modulus on the back coat' and the 'Martens hardness on the back coat'. When the outermost layer of the sample is the base layer, the values are referred to as 'elastic modulus on the base layer' and 'Martens hardness on the base layer'.

As used herein, the term "radius of curvature" means when a window film sample is wound around a fixture for testing the radius of curvature (Mandela flexing tester, Coretech Co., Ltd.). On)), keep winding for 5 seconds or more, unwind, and then visually observe whether the sample cracks, the minimum radius of the crack-free fixture on the window film sample. Herein, when the sample is wound on the jig such that the window coating of the window film contacts the jig surface, the radius of curvature of the pressing direction is measured, and when the sample is wound on the jig such that the base layer of the window film contacts the jig, The radius of curvature of the tensile direction is measured.

In this paper, the term "yellow index" of the window film means that under the D65 light source, at 2° (the angle between the window coating and the light source), a colorimeter (CM-3600d, Konica Minolta Limited) is used. Company (Konica Minolta Co., Ltd.), the value of the yellow index 1925 [Recalc) relative to the window film. Herein, the "yellow index" of the base layer is measured by the same method as the method of measuring the yellow index of the window film.

In this paper, the “b* value” is based on the D65 source, at 2° (the angle between the window coating and the light source), using a colorimeter (CM-3600d, Konica Minolta Co., Ltd.). The value measured on the window film.

Next, a window film according to an embodiment of the present invention will be described with reference to FIG. 1 is a cross-sectional view of a window film in accordance with an embodiment of the present invention.

Referring to FIG. 1, a window film 100 according to an embodiment may include a base layer 110, a window coating 120, and a back coat layer 130. The window film 100 includes a back coat layer 130 to exhibit high pencil hardness on the adhesive layer.

The base layer 110 supports the window film 100 while improving the mechanical strength of the window film 100.

The base layer 110 may be formed of a non-flexible film or may be formed of a flexible film to improve the flexibility of the window film 100. The base layer 110 may be formed of an optically transparent resin. Specifically, the optically transparent resin may comprise at least one of polyester resins, including polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate. Ester, polycarbonate resin, poly(meth)acrylate resin (including poly(methyl methacrylate)), polystyrene resin, polyamide resin, and polyimide resin. Preferably, a polyimide resin is used. The base layer 110 can have a thickness of from about 10 microns to about 150 microns, especially from about 30 microns to about 100 microns, more specifically from about 40 microns to about 80 microns. Within this thickness range, the base layer 100 can be used for a window film.

A window coating 120 is formed on one surface of the base layer 110 to maintain optical characteristics of the window film 100, such as transmittance and haze, while improving the pencil hardness of the window film 100. In addition, the window coating 120 has good flexibility to allow the window film 100 to be used not only in non-flexible displays but also in flexible displays. The window coating 120 may be formed directly on the base layer 110. As used herein, "directly formed on" means that an intervening layer such as an adhesive layer is not interposed between the window coating 120 and the base layer 110. The window coating 120 can have a thickness of from about 5 microns to about 150 microns, especially from about 20 microns to about 100 microns, from about 20 microns to about 80 microns, from about 30 microns to about 80 microns, or from about 30 microns to about 50 microns. Within this thickness range, the window film can exhibit good flexibility and high pencil hardness on the adhesive layer.

Window film 100 can have a modulus of elasticity of from about 2,000 MPa to about 4,000 MPa on window coating 120 and a Martens hardness of from about 150 Newtons/mm to about 300 Newtons/mm on window coating 120. Within these ranges, the window film has a high pencil hardness on the adhesive layer and can exhibit good flexibility.

The window coating 120 may be formed of a composition for a window coating containing a terpene resin. Therefore, the composition for the window coating can obtain a window film having high pencil hardness and good flexibility. The composition for the window coating may comprise a terpene resin, a curable monomer, and an initiator.

Next, the composition for the window coating will be described in more detail.

The terpene resin can form a matrix of the window coating 120 and can improve the flexibility and pencil hardness of the window film 100. The terpene-based resin may contain a decane resin having a UV curable group.

In one embodiment, a decane resin having a UV curable group can be prepared via hydrolysis and condensation of an organic decane having a UV curable group and an alkoxyalkyl group. Specifically, the organic decane having a UV curable group and an alkoxyalkyl group can be represented by Formula 1, but is not limited thereto: <Formula 1> R ¹ -R ⁴ -Si(OR ² ) _m (R ³ ) _3-m , wherein R ¹ is an epoxy group; (meth) acrylate group; (meth) acryl amide group; vinyl group; C ₁ to C ₆ alkyl group having an alicyclic epoxy group; meth) acrylate groups C ₁ to C ₆ alkyl; C having a (meth) acrylamide group ₁ to C ₆ alkyl group; or a vinyl group having a C ₁ to C ₆ alkyl group; R ² is a C ₁ to C ₁₀ alkyl; R ³ is C ₁ to C ₁₀ alkyl, C ₃ to C ₂₀ cycloalkyl, C ₆ to C ₂₀ aryl or C ₇ to C ₂₀ arylalkyl; R ⁴ is a single bond Or C ₁ to C ₁₀ alkyl; and m is an integer from 1 to 3. In Formula 1, "an alicyclic epoxy group" is intended epoxidized C ₃ to C ₆ cycloalkyl or C ₃ having an epoxidized to C ₆ cycloalkyl, a C ₁ to C ₁₀ alkyl group. In Formula 1, "single bond" means that R ¹ and Si are directly bonded to each other without R ^{4 in} Formula 1.

Specifically, the organodecane having a UV curable group and an alkoxyalkylalkyl group may comprise 2-(3,4-epoxycyclohexyl)ethyltrimethoxynonane (2-(3,4-epoxycyclohexyl)). Ethyltrimethoxysilane), 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, (meth)acryloxypropyltrimethoxydecane (meth) acryloxypropyltrimethoxysilane, at least one of (meth) acryloyloxypropyltriethoxysilane and vinyltrimethoxysilane, but is not limited thereto.

Hydrolysis and condensation are typically known to those skilled in the art. Specifically, hydrolysis and condensation can be carried out by mixing an organic decane having a UV curable group and an alkoxyalkyl group with a solvent. The hydrolysis and condensation may be carried out at room temperature for about 12 hours to about 7 days, and may be carried out at about 60 ° C to about 100 ° C for about 2 hours to about 72 hours in order to accelerate the reaction, but is not limited thereto. The solvent is not subject to specific restrictions. Specifically, the solvent may include at least one of water, methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, and methoxypropanol. The rate of hydrolysis and condensation can be controlled by the addition of a catalyst. The catalyst may comprise an acid catalyst such as hydrochloric acid, acetic acid, hydrogen fluoride, nitric acid, sulfuric acid, chlorosulfonic acid and iodic acid; a ruthenium catalyst such as ammonia, potassium hydroxide, sodium hydroxide, cesium hydroxide and imidazole; an ion exchange resin, Such as Amberite (IRA-400, IRA-67, etc.).

The decane resin having a UV curable group can be produced by hydrolysis and condensation of a mixture of an organic decane having a UV curable group and an alkoxyalkyl group with an organodecane having a different alkoxyalkyl group. The organodecane having a different alkoxyalkyl group may contain an organic germane which does not contain a UV curable group. Specifically, an organodecane having a different alkoxyalkylene group can be represented by Formula 2: <Formula 2> Si(OR ⁵ ) _n (R ⁶ ) _4-n , (wherein R ⁵ is a C ₁ to C ₁₀ alkyl group ; R ⁶ is unsubstituted C ₁ to C ₂₀ alkyl, C ₃ to C ₈ cycloalkyl, C ₃ to C ₂₀ alkenyl, C ₂ to C ₂₀ alkynyl, C ₆ to C ₂₀ aryl, halogen , C halogen having ₁ to C ₁₀ alkyl group, an amino group, an amino group having a C ₁ to C ₁₀ alkyl group, a mercapto group, C ₁ to C ₁₀ ether group, a carbonyl group, a carboxylate group or a nitro group; and n is 1 to 4 integer).

In Formula 2, "halogen" means fluorine, chlorine, iodine or bromine. Specifically, the organodecane compound of Formula 2 may contain tetramethoxydecane, tetraethoxydecane, methyltrimethoxydecane, methyltriethoxydecane, methyltripropoxydecane, and dimethyl Dimethoxy decane, dimethyl diethoxy decane, phenyl trimethoxy decane, diphenyl dimethoxy decane, diphenyl diethoxy decane, triphenyl methoxy decane, three Phenyl ethoxy decane, ethyl triethoxy decane, propyl ethyl trimethoxy decane, 3-aminopropyl trimethoxy decane, 3-aminopropyl triethoxy decane, chloropropyl trimethoxy At least one selected from the group consisting of decane and chloropropyltriethoxydecane.

In another embodiment, the decane resin having a UV curable group may comprise a decane resin represented by Formula 3: <Formula 3> (R ⁷ SiO _3/2 ) _x (R ⁸ SiO _3/2 And _y (R ⁹ R ¹⁰ SiO _2/2 ) _z , wherein R ⁷ and R ⁸ are each independently a UV curable group and are different from each other; and R ⁹ and R ¹⁰ are each independently hydrogen, a UV curable group, a substituted or unsubstituted C ₁ to C ₂₀ alkyl group or a substituted or unsubstituted C ₅ to C ₂₀ cycloalkyl group; and 0 < x ≤ 1, 0 ≤ y < 1, 0 ≤ z < 1, x+y+z=1.

R ⁷ and R ⁸ provide crosslinking characteristics, and are each independently a C ₁ to C ₆ alkyl group having an alicyclic epoxy group, a glycidoxy group or an oxetane group or a C ₅ to C ₁₀ naphthenic group. More, especially ((3,4-epoxycyclohexyl)methyl) group, ((3,4-epoxycyclohexyl)ethyl) group, ((3,4-epoxy ring) a hexyl)propyl) group, a (3-glycidoxypropyl) group, a (3-oxetanylmethyl) group, a (3-oxetanylethyl) group or (3) -Oxetanepropyl) group. R ⁹ and R ¹⁰ further provide cross-linking properties and flexibility to the window coating 120, and are each independently C ₁ to each having an alicyclic epoxy group, glycidoxy group or oxetane group C ₆ alkyl or C ₅ to C ₁₀ cycloalkyl; substituted or unsubstituted C ₁ to C ₁₀ alkyl, more especially (3,4-epoxycyclohexyl)methyl, (3,4- Epoxycyclohexyl)ethyl, (3,4-epoxycyclohexyl)propyl, glycidoxypropyl, methyl or ethyl.

In one embodiment, the fluorene oxide resin having a UV curable group may comprise a fluorene oxide resin represented by any one of Formula 3-1 to Formula 3-3: <Formula 3-1> R ⁷ SiO _{3/ 2} <Formula 3-2> (R ⁷ SiO _3/2 ) _x (R ⁸ SiO _3/2 ) _y <Formula 3-3> (R ⁷ SiO _3/2 ) _x (R ⁹ R ¹⁰ SiO _2/2 ) _z In the formula 3-1 to the formula 3-3, R ⁷ , R ⁸ , R ⁹ and R ¹⁰ are the same as defined in the formula 3, and 0<x<1, 0<y<1, 0<z<1 , x + y = 1 and x + z = 1. In particular, x can range from about 0.20 to about 0.999; y can range from about 0.001 to about 0.80; and z can range from about 0.001 to about 0.80. In particular, x can range from about 0.20 to about 0.99; y can range from about 0.01 to about 0.80; and z can range from about 0.01 to about 0.80, more particularly x can range from about 0.50 to about 0.99. y may range from about 0.01 to about 0.50; and z may range from about 0.01 to about 0.50, still more particularly x may range from about 0.90 to about 0.97; y may range from about 0.03 to about 0.10; z can range from about 0.03 to about 0.10. Within these ranges, the window film can have high pencil hardness and good flexibility. Specifically, the silicone resin may contain siloxane silicone resin T siloxane units represented by EcSiO _3/2 siloxane and silicone resins composed of T GpSiO _3/2 units represented by at least one. Further, the decane resin may be a decane resin including (EcSiO _3/2 ) _x (GpSiO _3/2 ) _y (0<x<1, 0<y<1, x+y=1) Compound. Further, the decane resin may contain any one of the compounds represented by Formula 3-3A to Formula 3-3L, respectively, but is not limited thereto: <Form 3-3A> (EcSiO _3/2 ) _x ((Me) ₂ SiO _2/2 ) _z <Formula 3-3B> (EcSiO _3/2 ) _x (MeEtSiO _2/2 ) _z <Formula 3-3C> (GpSiO _3/2 ) _x ((Me) ₂ SiO _2/2 ) _z <Formula 3-3D> (GpSiO _3/2 ) _x (MeEtSiO _2/2 ) _z <Form 3-3E> (OpSiO _3/2 ) _x ((Me) ₂ SiO _2/2 ) _z <Formula 3-3F> (OpSiO _3/2 ) _x (MeEtSiO _2/2 ) _z <Formula 3-3G> (EcSiO _3/2 ) _x (EcMeSiO _2/2 ) _z <Form 3-3H> (EcSiO _3/2 ) _x (GpMeSiO _{2 /2} ) _z <Form 3-3I> (GpSiO _3/2 ) _x (EcMeSiO _2/2 ) _z <Form 3-3J> (GpSiO _3/2 ) _x (GpMeSiO _2/2 ) _z <Form 3-3K> (OpSiO _3/2 ) _x (EcMeSiO _2/2 ) _z <Formula 3-3L> (OpSiO _3/2 ) _x (GpMeSiO _2/2 ) _z (where 0<x<1, 0<z<1 and x+ z=1).

In particular, x can range from about 0.20 to about 0.999, and z can range from about 0.001 to about 0.80, more particularly x can range from about 0.20 to about 0.99, and z can range from about 0.01 to about 0.80. Further, still more particularly x may be in the range of from about 0.50 to about 0.99, and z may be in the range of from about 0.01 to about 0.50, still more particularly x may be in the range of from about 0.90 to about 0.97, and z may be in the range of from about 0.03 to about Within the range of 0.10.

The decane resin having a UV curable group may have a weight average molecular weight of from about 1,000 g/m to about 15,000 g/mole. The decane resin having a UV curable group may have a polydispersity index (PDI) of from about 1.0 to about 3.0. Within these ranges of weight average molecular weight and polydispersity index, the composition can improve the pencil hardness and transparency of the window film via dense crosslinking of the decane resin.

Represented by the formula 3 having a UV curable silicone resin, siloxane groups may be provided alone alkoxy Silane R ⁷ SiO _3/2 R provided via a separate alkoxy silane-containing or ⁷ SiO _3/2, provided R ⁸ It is prepared by hydrolysis and condensation of a mixture of _alkoxydecane of SiO _3/2 and at least one of alkoxydecanes providing R ⁹ R ¹⁰ SiO _2/2 . Hydrolysis and condensation are typically known to those skilled in the art. Specifically, hydrolysis and condensation may be carried out at room temperature for about 12 hours to about 7 days, and may be carried out at about 60 ° C to about 100 ° C for about 2 hours to about 72 hours in order to accelerate the reaction, but is not limited thereto. The solvent is not subject to specific restrictions. Specifically, the solvent may include at least one of water, methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, and methoxypropanol. The rate of hydrolysis and condensation can be controlled by the addition of a catalyst. The catalyst may comprise an acid catalyst such as hydrochloric acid, acetic acid, hydrogen fluoride, nitric acid, sulfuric acid, chlorosulfonic acid and iodic acid; a ruthenium catalyst such as ammonia, potassium hydroxide, sodium hydroxide, cesium hydroxide and imidazole; an ion exchange resin, Such as Abilite IRA-400, IRA-67 and so on.

The curable monomer is crosslinked with the terpene resin to increase the pencil hardness of the window film while controlling the viscosity of the composition for the window coating to improve workability. The curable monomer may include at least one of an epoxy group-containing monomer, an acid anhydride group-containing monomer, and an oxetane group-containing monomer. The epoxy-containing monomer may comprise a photocurable monomer comprising at least one epoxy group. The epoxy group may contain an epoxy group such as a glycidyl group and an organic group containing an epoxy group. The epoxy monomer may comprise an alicyclic epoxy monomer, an aromatic epoxy monomer, an aliphatic epoxy monomer, a hydrogenated epoxy monomer, or a mixture thereof. The alicyclic epoxy monomer is a monomer having one or more epoxy groups in the C ₃ to C ₁₀ alicyclic ring, for example, 3,4-epoxycyclohexylmethyl-3', 4'- Epoxycyclohexane carboxylate, but is not limited thereto. The aromatic epoxy monomer may contain bisphenol A, bisphenol F, phenol novolac, cresol novolac, glycidyl ether of triphenylmethane, tetraglycidyl methylene aniline or the like. The aliphatic epoxy monomer may comprise 1,4-butanediol glycidyl ether, 1,6-hexanediol diglycidyl ether, etc., and the hydrogenated epoxy monomer is obtained by hydrogenation of an aromatic epoxy monomer and may Contains hydrogenated bisphenol A diglycidyl ether. The acid anhydride group-containing monomer may include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylnadic anhydride, chlorendic anhydride, and pyromellitic anhydride. At least one of them. The oxetane-containing monomer may comprise 3-methyloxetane, 2-methyloxetane, 3-oxetanol, 2-methylene oxetane, 3,3-oxetanyl mercaptan, 4-(3-methyloxetan-3-yl)benzonitrile, N-(2,2-dimethylpropyl)3-methyl 3-oxo-butaneamine, N-(1,2-dimethylbutyl)-3-methyl-3-oxetanamine, (3-ethyloxycyclobutane-3 -yl)methyl methacrylate, 3-ethyl-3-hydroxymethyl-oxetane, 2-ethyloxycyclobutane, xylene dioxetane and 3-ethyl-3 At least one of -[[(3-ethyloxycyclobutane-3-yl)methoxy]methyl]oxetane.

The starter can cure the terpene resin and the curable monomer to form a window coating. The initiator may comprise at least one of a photocationic initiator, a cationic thermal initiator, and a photoradical initiator.

Photocationic cation initiators accelerate curing by generating cations upon irradiation with light and may comprise typical photocationic initiators. The photocationic initiator can comprise a salt of a cation and an anion. Examples of the cation may include a diaryl fluorene such as diphenyl fluorene, 4-methoxydiphenyl fluorene, bis(4-methylphenyl)fluorene, (4-methylphenyl) [4-(2) -Methylpropyl)phenyl]anthracene, bis(4-t-butylphenyl)anthracene, bis(dodecylphenyl)anthracene, etc.; triarylsulfonium such as triphenylsulfonium and diphenyl-3 - thiophenoxyphenyl hydrazine; bis[4-(diphenyldihydrothio)phenyl] sulfide; etc.; bis[4-(bis(4-(2-hydroxyethyl)phenyl)) Hydrogenthio)-phenyl]sulfide; (η5-2,4-cyclopentadien-1-yl)[(1,2,3,4,5,6-η)-(1-methyl Base) benzene] iron (1+) and the like. Examples of the anion may include tetrafluoroborate (BF _4- ), hexafluoroborate (PF _6- ), hexafluoroantimonate (SbF _6- ), hexafluoroarsenate (AsF _6- ), and hexachloroantimonate ( SbCl _6- ) and so on.

The cationic thermal initiator may comprise 3-methyl-2-butenyltetramethylene hydrazine, hydrazine, hydrazine, hydrazine, hydrazine, hydrazine, tetrabutylphosphine, ethyltriphenylphosphonium bromide, and benzoic acid. Methyl dimethylamine, dimethylamino cresol, triethanolamine, N-n-butylimidazole, 2-ethyl-4-methylimidazole, and the like. Examples of the anion may include tetrafluoroborate (BF _4- ), hexafluorophosphate (PF _6- ), hexafluoroantimonate (SbF _6- ), hexafluoroarsenate (AsF _6- ), and hexachloroantimonate ( SbCl6-) and so on.

Photoradical initiators accelerate curing by generating free radicals upon irradiation with light and may comprise typical photoradical initiators. In particular, the photoradical initiator may comprise at least one of phosphorus, triazine, acetophenone, benzophenone, thioxanthone, benzoin, and a fluorene radical initiator.

The composition for the window coating may have a viscosity of from about 1 centipoise (cP) to about 3,000 centipoise at 25 °C. Within this range, the composition for the window coating can exhibit good coatability and wettability to help form a window coating.

The composition for the window coating may comprise from about 65% by weight to about 95% by weight of the terpene resin, from about 4% by weight to about 30% by weight of the curable monomer, based on the total weight of the composition for the window coating. And from about 0.1% to about 10% by weight of the starter. Within this range of contents, the composition can improve the flexibility and pencil hardness of the window coating. As used herein, the expression "in terms of solid content" means the remainder of the composition that does not contain a solvent.

In terms of solid content, the composition for the window coating may comprise 100 parts by weight of a terpene resin; from about 1 part by weight to about 20 parts by weight of the curable monomer, especially from about 1 part by weight to about 15 parts by weight; From 0.1 part by weight to about 20 parts by weight, especially from about 0.5 part by weight to about 10 parts by weight of the starter. Within this range of contents, the composition can improve the flexibility and pencil hardness of the window coating.

The composition for the window coating may further comprise typical additives. The additive may include at least one of an antistatic agent, a leveling agent, an antioxidant, a stabilizer, and a coloring agent.

The composition for the window coating may further comprise a solvent such as methyl ethyl ketone.

The composition for the window coating may further comprise nanoparticle. Nanoparticles increase the modulus of elasticity on the window coating and the Martens hardness on the window coating. The nanoparticle may include at least one of cerium oxide, aluminum oxide, zirconium oxide, and titanium oxide, but is not limited thereto. Nanoparticles can be surface treated with an anthrone compound. Nanoparticles can have, but are not limited to, any shape and size. Specifically, the nanoparticles may include particles having a circular shape, a sheet shape, an amorphous shape, and the like. The nanoparticles may have an average particle diameter of from about 1 nanometer to about 200 nanometers, especially from about 5 nanometers to about 50 nanometers, more particularly from about 10 nanometers to about 30 nanometers. Within this range, the nanoparticles can improve the hardness of the window film without adversely affecting the surface roughness and transmittance of the window film. The nanoparticles may be present in an amount of from about 0.1 part by weight to about 100 parts by weight, particularly from about 1 part by weight to about 80 parts by weight, based on 100 parts by weight of the oxime resin. Within this range, the nanoparticles can increase the pencil hardness of the window film on the adhesive layer while reducing the surface roughness of the window coating.

As used herein, the expression "in terms of solids content" means the remainder of the composition that does not contain a solvent.

The back coat layer 130 is formed on the other surface of the base layer 110 and can improve the pencil hardness of the window film on the adhesive layer. FIG. 1 shows a structure in which a base layer 110 is directly formed on a back coat layer 130. As used herein, "directly formed on" means that an intervening layer such as an adhesive layer is not interposed between the base layer 110 and the back coat layer 130.

Backcoat layer 130 can have a thickness of from about 1 micron to about 100 microns, especially from about 2 microns to about 50 microns, more specifically from about 2 microns to about 20 microns. Within this thickness range, the back coat can be used in the window film and exhibit good flexibility, and the window film can have a high pencil hardness on the adhesive layer.

Window film 100 can have an elastic modulus of about 1,000 megapascals or greater than 1,000 megapascals, especially from about 1,000 megapascals to about 2,000 megapascals, on backcoat layer 130. Window film 100 can have a Martens hardness of from about 50 Newtons/mm to about 200 Newtons/mm on backcoat layer 130. Within these ranges, the window film has a high pencil hardness on the adhesive layer and can exhibit good flexibility.

The back coat layer 130 may be formed of a composition for a back coat layer comprising a UV curable group-containing resin, a crosslinking agent, and an initiator. Next, the composition for the back coat layer will be described.

The UV curable group-containing resin can be cured with a crosslinking agent to form a matrix of the back coating layer 130. Specifically, the UV curable group-containing resin may include at least one of a (meth)acrylic resin having a UV curable group and a siloxane oxide having a UV curable group.

The (meth)acrylic resin having a UV curable group may contain a monofunctional to hexafunctional (meth)acrylic resin. The (meth)acrylic resin having a UV curable group may comprise a copolymer of a mixture comprising an alkyl (meth) acrylate, a hydroxyl group-containing (meth) acrylate, a carboxylic acid group (A) At least one of an acrylic monomer, an alicyclic (meth) acrylate-containing, heteroalicyclic (meth) acrylate-containing, and aromatic-containing (meth) acrylate. Specifically, the alkyl group-containing (meth) acrylate may be a (meth) acrylate containing an unsubstituted C ₁ to C ₁₀ alkyl group. The hydroxyl group-containing (meth) acrylate may be a C ₁ to C ₁₀ alkyl group containing a (meth) acrylate having at least one hydroxyl group. The carboxylic acid group-containing (meth)acrylic monomer may be (meth)acrylic acid. The alicyclic (meth) acrylate may be a C ₅ to C ₁₀ alicyclic (meth) acrylate. The heteroalicyclic (meth) acrylate may be a C ₃ to C ₁₀ heteroalicyclic (meth) acrylate containing nitrogen, oxygen or sulfur. The aromatic group-containing (meth) acrylate may be a C ₆ to C ₂₀ aryl group or a C ₇ to C ₂₀ aryl alkyl (meth) acrylate.

The (meth)acrylic resin having a UV curable group may contain a di- or higher functional group, especially a difunctional to hexafunctional urethane (meth)acrylic resin. The urethane (meth)acrylic resin can be prepared by a typical carbamate synthesis reaction of at least one polyol, at least one polyisocyanate compound, and a (meth) acrylate containing at least one hydroxyl group. The polyol may comprise at least one of an aromatic polyether polyol, an aliphatic polyether polyol, an alicyclic polyether polyol, a polyester polyol, a polycarbonate polyol, and a polycaprolactone polyol. The polyisocyanate compound is a compound containing two or more than two isocyanate groups, and may contain toluene diisocyanate, xylene diisocyanate, naphthalene diisocyanate, phenyl diisocyanate, diphenylmethane diisocyanate, biphenylene Diisocyanate, hexane diisocyanate, isophorone diisocyanate or an adduct thereof. The (meth) acrylate containing at least one hydroxyl group is a C ₁ to C ₁₀ (meth) acrylate having at least one hydroxyl group, and may especially comprise 2-hydroxyethyl (meth) acrylate or 1,4-butane Alcohol (meth) acrylate. Specifically, the urethane (meth) acrylate resin may contain a hexafunctional aliphatic urethane (meth) acrylate resin.

The decane resin having a UV curable group may contain a decane resin represented by Formula 3.

The resin containing the UV curable group may have a weight average molecular weight of from about 500 g/mol to about 8,000 g/mol, especially from about 1,000 g/mol to about 5,000 g/mol. Within this range, the window film can have high pencil hardness and good flexibility.

The crosslinker can be cured with the UV curable group-containing resin to form a matrix of the back coat while increasing the pencil hardness of the window film on the back coat. Specifically, the crosslinking agent may contain at least one of a di-hexafunctional (meth)acrylic monomer, the aforementioned epoxy monomer, the aforementioned anhydride monomer, and the aforementioned oxetane monomer. The di-hexa-functional (meth)acrylic monomer may comprise at least one selected from the group consisting of difunctional (meth) acrylates such as 1,4-butanediol di(meth) acrylate, 1,6- Hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, neopentyl glycol adipate di(meth)acrylate , dicyclopentenyl di(meth)acrylate, dicyclopentenyl di(meth)acrylate modified with caprolactone, di(meth)acrylate modified with ethylene oxide, isocyanuric acid (Meth) propylene methoxyethyl ester, allylated bis(meth) acrylate cyclohexyl ester, tricyclodecane dimethanol (meth) acrylate, dicyclopentane di (meth) acrylate dihydroxy Methyl ester, ethylene oxide modified hexahydrophthalic acid di(meth) acrylate, tricyclodecane dimethanol (meth) acrylate, neopentyl glycol modified trimethyl propane bis ( Methyl) acrylate, adamantane di(meth) acrylate and 9,9-bis[4-(2-propenyloxyethoxy)phenyl]fluoro; trifunctional acrylate such as trimethylol Propane tri (meth) acrylate, second season Pentaerythritol tri(meth)acrylate, propionic acid modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide modified trimethylolpropane tris(methyl) An acrylate, a trifunctional urethane (meth) acrylate, a tris(meth) propylene oxiranyl ethyl isocyanurate, and a C ₁ to C ₅ alkoxy group (eg, an ethoxy group, a propoxy or butoxy) alkoxylated trifunctional (meth) acrylate such as propoxylated glycerol tri(meth) acrylate and ethoxylated trimethylolpropane tri(methyl) Acrylate; tetrafunctional acrylate such as diglycerol tetra(meth)acrylate and pentaerythritol tetra(meth)acrylate; pentafunctional acrylate such as dipentaerythritol penta (meth) acrylate; and hexafunctional acrylate, Such as dipentaerythritol hexa (meth) acrylate, caprolactone modified dipentaerythritol hexa (meth) acrylate and urethane (meth) acrylate (such as isocyanate monomer and trimethylolpropane tri ( The reaction product of methyl) acrylate).

In terms of solid content, the crosslinking agent may be from about 1 part by weight to about 70 parts by weight, especially from about 5 parts by weight to about 65 parts by weight, based on 100 parts by weight of the UV curable group-containing resin, and about 5 parts by weight to about It is present in an amount of from 50 parts by weight, from about 10 parts by weight to about 60 parts by weight, or from about 15 parts by weight to about 40 parts by weight. Within this range, the composition can increase the pencil hardness of the window film on the adhesive layer.

The initiator is used to cure the UV curable group-containing resin and the crosslinking agent, and may include at least one of the photocationic initiator, the cationic thermal initiator, and the photoradical initiator described above.

In terms of solid content, the starter may be from about 0.1 part by weight to about 10 parts by weight, especially from about 1 part by weight to about 10 parts by weight, or about 1 part by weight, based on 100 parts by weight of the UV curable group-containing resin. An amount of about 7 parts by weight is present. Within this range, the composition for the back coat layer can be sufficiently cured and the transparency of the window film caused by the remaining starter can be prevented from being lowered.

The composition for the back coat layer may further contain nano particles. Nanoparticles can increase the elastic modulus and Martens hardness of the back coating. In the composition for the back coat layer, the nano particles may be from about 0.1 part by weight to about 100 parts by weight, particularly about 1 part by weight, based on 100 parts by weight of the UV curable group-containing resin. An amount of about 80 parts by weight is present. Within this range, the composition for the back coat layer can increase the pencil hardness of the window film on the adhesive layer while reducing the surface roughness of the back coat layer.

The composition for the back coat layer may further contain typical additives. The additive may comprise at least at least a dye, a UV absorber, a reaction inhibitor, an adhesion promoter, a thixotropic agent, a conductivity imparting agent, a color modifier, a stabilizer, an antistatic agent, an antioxidant, and a leveling agent. One, but not limited to.

Next, a window film according to another embodiment of the present invention will be described with reference to FIG. 2 is a cross-sectional view of a window film in accordance with another embodiment of the present invention.

Referring to FIG. 2, the window film 200 according to this embodiment may include a base layer 110, a window coating 120, a back coat layer 130, and an adhesive layer 140. The window film 200 according to this embodiment is substantially the same as the window film 100 according to the above embodiment except that the window film further includes the adhesive layer 140. The adhesive layer 140 provides another improvement in the coupling between the base layer 110 and the back coat layer 130. In the following, the adhesive layer 140 will be described in more detail.

The adhesive layer 140 is formed between the base layer 110 and the back coat layer 130 and the base layer 110 and the back coat layer 130 may be attached to each other.

The adhesive layer 140 can have a thickness of from about 10 microns to about 100 microns, especially from about 20 microns to about 80 microns, more specifically from about 30 microns to about 50 microns.

The adhesive layer 140 may be formed of a composition for a binder layer comprising a (meth)acrylic adhesive resin and a curing agent.

The (meth)acrylic adhesive resin may comprise a (meth)acrylic copolymer of a monomer mixture comprising an alkyl (meth)acrylic acid-containing monomer, a hydroxyl group-containing (meth)acrylic acid monomer, and a fat-containing resin. At least one of a cycloalkyl (meth)acrylic monomer, a heteroalicyclic (meth)acrylic acid-containing monomer, and a carboxylate-containing (meth)acrylic monomer.

The alkyl-containing (meth)acrylic monomer may comprise a (meth) acrylate containing an unsubstituted C ₁ to C ₁₀ alkyl group. The hydroxyl group-containing (meth)acrylic monomer may comprise a (meth) acrylate having a C ₁ to C ₁₀ alkyl group and having at least one hydroxyl group. The alicyclic (meth)acrylic acid-containing monomer may comprise a C ₃ to C ₁₀ alicyclic (meth) acrylate. The heteroalicyclic (meth)acrylic acid-containing monomer may contain a C ₃ to C ₁₀ heteroalicyclic (meth) acrylate containing nitrogen, oxygen or sulfur. The carboxylate-containing (meth)acrylic monomer may comprise (meth)acrylic acid.

The curing agent may include at least one of an isocyanate curing agent, an epoxy resin curing agent, a quinone imine curing agent, and a metal chelate curing agent. These curing agents can be used singly or in combination. With respect to the solid content, the curing agent may be from about 0.1 part by weight to about 10 parts by weight, particularly from about 0.1 part by weight to about 1 part by weight based on 100 parts by weight of the (meth)acrylic adhesive resin in the composition for the adhesive layer. The amount of serving exists.

The composition for the adhesive layer may further comprise a decane coupling agent. The decane coupling agent can further improve the adhesion of the composition for the adhesive layer. As the decane coupling agent, one or more typical decane coupling agents can be used. Specifically, the decane coupling agent may comprise at least one selected from the group consisting of ruthenium compounds containing an epoxy resin structure, such as 3-glycidoxypropyltrimethoxydecane, 3-glycidyloxy group. Propylmethyldimethoxydecane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxydecane; an anthracene compound containing a polymerizable unsaturated group, such as vinyltrimethoxydecane, ethylene a triethoxy decane and (meth) propylene methoxy propyl trimethoxy decane; and an amino group-containing hydrazine compound such as 3-aminopropyltrimethoxy decane, 3-aminopropyltriethoxy decane N-(2-Aminoethyl)-3-aminopropyltrimethoxydecane and N-(2-aminoethyl)-3-aminopropylmethyldimethoxydecane. With respect to the solid content, the decane coupling agent may optionally be used in an amount of about 10 parts by weight or less, particularly about 1 part by weight based on 100 parts by weight of the (meth)acrylic adhesive resin in the composition for the adhesive layer. It is present in an amount of less than 1 part by weight. Within this range, the decane coupling agent can exhibit good bonding strength.

Next, a window film according to another embodiment of the present invention will be described with reference to FIG. 3 is a cross-sectional view of a window film in accordance with another embodiment of the present invention.

Referring to FIG. 3, the window film 300 according to this embodiment may include a window coating 120, a base layer 110, an adhesive layer 140, a support layer 150, and a back coat layer 130. The window film 300 according to this embodiment is substantially the same as the window film 200 according to the above embodiment except that the support layer 150 is further formed between the adhesive layer 140 and the back coat layer 130. The support layer 150 increases the pencil hardness of the window film on the adhesive layer. Hereinafter, the support layer 150 will be described in more detail.

A support layer 150 is formed between the adhesive layer 140 and the back coat layer 130 to promote the formation of the adhesive layer 140 and the back coat layer 130 of the window film 300 while improving the pencil hardness of the window film 300 on the adhesive layer.

The support layer 150 may be formed of a resin that is the same as or different from the resin of the base layer 110. Specifically, the resin may comprise at least one of a polyester resin comprising polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polynaphthalene Butylene formate, polycarbonate resin, poly(meth)acrylate resin (including poly(methyl methacrylate)), polystyrene resin, polyamide resin, and polyimide resin. Support layer 150 can have a thickness of from about 10 microns to about 200 microns, especially from about 20 microns to about 150 microns, more specifically from about 50 microns to about 100 microns.

Next, a window film according to still another embodiment of the present invention will be described with reference to FIG. 4 is a cross-sectional view of a window film in accordance with yet another embodiment of the present invention.

Referring to FIG. 4, the window film 400 according to this embodiment may include a window coating 120, a base layer 110, a back coat layer 130, and an adhesive layer 140. The window film 400 according to this embodiment is substantially the same as the window film 100 according to the above embodiment except that the adhesive layer 140 is further formed on the lower surface of the back coat layer 130. The adhesive layer 140 allows the window film 400 to be directly attached to a display element, particularly a polarizing plate, a conductive film, or an upper surface of an organic light emitting diode.

Next, a window film according to still another embodiment of the present invention will be described with reference to FIG. Figure 5 is a cross-sectional view of a window film in accordance with yet another embodiment of the present invention.

Referring to FIG. 5, the window film 500 according to this embodiment may include a window coating 120, a base layer 110, and a back coat layer 130a, which may contain a dye (not shown in FIG. 5). A window film comprising a base layer formed of a plastic material instead of glass and a window coating formed of a curable resin having a high yellow index and thus a yellow window film may be viewed on the front surface and/or the side surface thereof. In contrast, the window film 500 according to this embodiment contains a dye to have a low yellow index and thus can prevent yellowing on the front surface and/or the side surface thereof. In particular, window film 500 can have a yellow index of from about -2.5 to about 3.5, more specifically from about -1.5 to about 1.5. Within this range, the window film can prevent yellowing when viewed by the naked eye on its front surface and/or side surface. Additionally, window film 500 in accordance with this embodiment contains a dye and thus has a b* value of from about -2.5 to about 2.5, more specifically from about -1.5 to about 1.5, and more specifically from about -0.5 to about 1.5. Within this range, the window film can prevent yellowing when viewed by the naked eye on its front surface and/or side surface. Although FIG. 5 shows a structure in which the dye is contained in the back coat layer 130a, the dye may be included in at least one of the base layer, the window coat layer, and the back coat layer.

The dye may be included in the back coat layer 130a. Therefore, the window film 500 according to this embodiment has a low yellow index to exhibit good transmittance and can prevent yellowing, while the optical characteristics of the base layer 110, the window coating 120, and the window film 500 are not lowered. Further, in the window film 500 according to this embodiment, the window coating 120 may be free of dye to have a high degree of crosslinking, thereby providing high pencil hardness.

The base layer 110 is the same as the base layer of the window film 100 according to the above embodiment. In one embodiment, the base layer 110 can have a yellow index of from about 1 to about 9. Specifically, if the base layer 110 of the window film 500 has a yellow index of about 3 or greater than 3, the yellowness index of the window film 500 may be lowered because the back coat layer 130a contains a dye. In one embodiment, the base layer may comprise a film formed of a polyimide resin. Therefore, the base layer 110 has high heat resistance, thereby improving the heat resistance of the window film 500. Although the base layer formed of the polyimide resin has a high yellow index of about 5 or more, the window film 500 according to this embodiment contains a dye, thereby lowering the total yellowness index of the window film 500.

The window coating 120 is the same as the window coating of the window film 100 described above.

A back coat layer 130a is formed on the other surface of the base layer 110 to support the window film 500. FIG. 5 shows a structure in which the back coat layer 130a is directly formed on the base layer 110. As used herein, "directly formed on" means that an intervening layer such as an adhesive layer is not interposed between the base layer 110 and the back coat layer 130. The back coat layer 130a may contain a dye. Since the back coat layer 130a contains a dye, the yellowness index of the window film 500 can be lowered to prevent the window film 500 from appearing yellow, while the optical properties of the base layer 110, the window coat layer 120, and the window film 500 are not lowered.

The back coat layer 130a may have about 5 microns or less, especially about 300 nanometers or less, more specifically about 100 nanometers or less, more specifically about 60 nanometers to about 80 nanometers, for example A thickness of about 10 nm to about 30 nm. Within this thickness range, the back coat 130a can be used in the window film and can exhibit good flexibility.

The back coat layer 130a may be formed of a composition for a back coat layer containing a UV curable group-containing resin, a crosslinking agent, a starter, and a dye. The UV curable group-containing resin, the crosslinking agent, and the initiator are the same as those of the window film according to the embodiment. Therefore, the following description will be given only for the dye.

The dye can be placed at a location on the back coat 130a. For example, the dye may be distributed throughout the back coat layer 130a, or may be provided in the form of a single layer or multiple layers. The dye may have a maximum absorption wavelength of from about 500 nanometers to about 650 nanometers, especially from about 550 nanometers to about 620 nanometers. Within this range, the dye can reduce the yellowness index of the window film, while the optical properties of the base layer, window coating, and window film are not reduced. As used herein, "maximum absorption wavelength" means the wavelength at the maximum absorption peak, that is, the wavelength indicating the maximum absorbance in the absorbance curve depending on the wavelength. The dye may comprise at least one of a metal dye and a metal-free non-metal dye having a maximum absorption wavelength of from about 500 nanometers to about 650 nanometers. The metal dye may have a maximum absorption wavelength of from about 500 nanometers to about 650 nanometers, especially from about 550 nanometers to about 620 nanometers, and comprises a metal. Specifically, the metal dye may contain at least one of a metal complex of vanadium, chromium, and manganese, but is not limited thereto. For example, the metal dye can be a bound heterocyclic vanadium complex. The non-metallic dye may have a maximum absorption wavelength of from about 500 nanometers to about 650 nanometers, especially from about 550 nanometers to about 620 nanometers, and does not comprise a metal. Specifically, the non-metal dye may comprise a cyanine dye, a porphyrin dye (including tetraaza porphyrin), an aryl methane dye, an aryl phthalocyanine dye, a azomethine dye, an oxonol dye. At least one of an azo dye, an arylene dye, a xanthene dye, and a merocyanine dye, but is not limited thereto. In the composition for the back coat layer, the dye may be from about 0.001% by weight to about 15% by weight, especially about 0.01% by weight to about the total weight of the composition for the back coat layer. It is present in an amount of 5% by weight, more particularly from about 0.1% by weight to about 3% by weight. Within this range, the window film prevents yellowing and reduced light transmission.

Although not shown in FIG. 5, the window film may further include an adhesive layer on the lower surface of the back coat layer 130a so that the window film may be directly attached to the display element, particularly a polarizing plate, a conductive film or an organic light emitting diode. Wait on the upper surface. The adhesive layer is the same as the adhesive layer described above.

Next, a window film according to still another embodiment of the present invention will be described.

The window film according to this embodiment is substantially the same as the above, except that the back coat layer of the window film according to this embodiment may further contain an antioxidant to reduce the yellow index change after a long time of treatment at a high temperature via improved heat resistance. The window film 500 of the example is the same. In particular, the window film according to this embodiment has a yellow index change of about 1.5 or less, especially about 1.0 or less, more specifically about 0.1 to about 1.0, as calculated by Equation 1. Within this range, the window film can exhibit good heat resistance and can therefore be used in displays: <Equation 1> Yellow index change = (YI'-YI), (where YI is the initial yellowness index of the window film and YI' is The yellowness index of the window film after standing at 80 ° C for 1,000 hours).

The window film according to this embodiment has a YI of from about -0.5 to about 3.5, especially from about 0.5 to about 2.0.

The antioxidant may include at least one of a phenolic antioxidant, a phosphorus antioxidant (including a phosphate antioxidant), a thioether antioxidant, and an amine antioxidant. Specifically, the phenolic antioxidant may comprise pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, octadecyl-3-(3,5-di- tert-Butyl-4-hydroxyphenyl)propionate, N,N'-1,6-hexanediylbis[3,5-bis(1,1-dimethylethyl)-4-hydroxyl] Phenylbenzamine, etc. The phosphorus antioxidant may comprise tris(2,4-di-tert-butylphenyl)phosphite), bis(2,3-di-tert-butyl-6-methylphenyl)- Ethyl-phosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, 2,2',2"-nitro[triethyl-tris[3,3',5, 5'-tetra-tert-butyl-1,1'-biphenyl-2,2'-diyl]phosphite], etc. The thioether antioxidant may comprise dodecyl-3,3'- Thiodipropionate, octadecyl 3,3'-thiodipropionate, etc. The amine antioxidant may comprise styrenated diphenylamine, dioctyldiphenylamine, naphthylamine, etc. The antioxidant may be present in an amount of from about 0.1 part by weight to about 20 parts by weight, particularly from about 1 part by weight to about 10 parts by weight, per 100 parts by weight of the UV curable group-containing resin. Within this range, the antioxidant may not be affected The heat resistance is improved in the case of a dye.

Next, a window film according to still another embodiment of the present invention will be described.

The window film according to this embodiment is substantially the same as the window film 500 according to the above embodiment except that the back coat layer of the window film according to this embodiment may further contain an antistatic agent. Therefore, the window film according to this embodiment hardly generates static electricity in a wound state on the reel to provide good workability, even when including a base layer having difficulty in antistatic treatment and having low surface resistance, The base layer is treated with a separate antistatic treatment to provide an antistatic effect. For example, the window film has a surface resistance of about 1 × 10 ¹⁰ Ω/□ or less than 1 × 10 ¹⁰ Ω/□, for example, about 1 × 10 ⁵ Ω/□ to about 5 × 10 ⁹ Ω/□, as in the back. Measured on the coating. Within this range, the window film provides good antistatic properties and good roll stability. The antistatic agent may comprise a typical antistatic agent such as a conductive polymer, a quaternary ammonium salt, a phosphonium salt, a sulfonate, an alkylamine compound, a fatty ester, an alkyl beet, a metal oxide such as antimony tin oxide, and the like. . Specifically, at least one of a conductive polymer, a quaternary ammonium salt, and a metal oxide such as antimony tin oxide may be included together with the dye in the back coat layer to provide an antistatic effect while reducing the yellowness index of the window film. The window film is not rendered yellow. The conductive polymer may comprise a water-soluble polyethylene dioxythiophene (PEDOT) which is a polythiophene-based polymer. More specifically, polyethylene dihydroxythiophene (PEDOT) having a molecular weight of 150,000 g/mole to 200,000 g/mol and doped with polystyrene sulfonate (PSS) as a dopant can be used. . The quaternary ammonium salt may comprise a quaternary ammonium salt such as tetrabutylammonium, wherein four C ₁ to C ₁₀ alkyl groups are substituted. The antistatic agent may be from about 0.001 parts by weight to about 30 parts by weight, especially from about 0.01 parts by weight to about 20 parts by weight, more specifically from about 0.1 parts by weight to about 15 parts by weight, based on 100 parts by weight of the UV curable group-containing resin. Still more particularly present in an amount from about 0.5 parts by weight to about 10 parts by weight. Within this range, the antistatic agent can improve heat resistance without affecting the dye.

The window film according to the embodiment may have a pencil hardness of about 6H or higher than 6H, especially about 6H to about 8H on the glass substrate. Within this range, the window film has no difference in pencil hardness on the glass substrate and the adhesive layer, thereby providing high applicability.

The window film according to the embodiment may have a radius of curvature of about 10.0 mm or less, especially about 0.1 mm to about 5.0 mm in the pressing direction, and about 20.0 mm or less than 20.0 mm in the stretching direction, especially about 0.1 mm. To a radius of curvature of about 10.0 mm. Within these ranges, the window film has good flexibility and can be used as a flexible window film. The window film according to the embodiment has a lower radius of curvature in both the pressing direction and the stretching direction, and thus can exhibit good flexibility in its opposite side, thereby maintaining high applicability.

The window film according to the described embodiment is optically transparent and can be used in a transparent display. In particular, in the visible light region, particularly in the wavelength range from about 400 nm to about 800 nm, the window film has a transmittance of about 88% or higher, especially about 88% to about 100%, and Haze of about 2% or less, especially about 0.1% to about 2%. Within this range, the window film is transparent.

The window film according to the embodiment has a thickness of from about 50 microns to about 300 microns. Within this range, window films can be used in optical displays.

Next, a flexible display according to an embodiment of the present invention will be described with reference to FIGS. 6 and 7. Figure 6 is a cross-sectional view of a flexible display in accordance with one embodiment of the present invention, and Figure 7 is a cross-sectional view of one embodiment of the display unit of the flexible display shown in Figure 6.

Referring to FIG. 6, a flexible display 600 according to an embodiment includes a display unit 650a, an adhesive layer 660, a polarizing plate 670, a touch screen panel 680, and a flexible window film 690. The flexible window film 690 can comprise a window film in accordance with an embodiment of the present invention.

The display unit 650a is for driving the flexible display 600, and may include a substrate and an optical device including an OLED, an LED, or an LCD formed on the substrate. Figure 7 is a cross-sectional view of one embodiment of the display unit of the flexible display shown in Figure 6. Referring to FIG. 7, the display unit 650a may include a lower substrate 610, a thin film transistor 616, an organic light emitting diode 615, a planarization layer 614, a protective layer 618, and an insulating layer 617.

The lower substrate 610 supports the display unit 650a and may be formed using a thin film transistor 616 and an organic light emitting diode 615. The lower substrate 610 may also be equipped with a flexible printed circuit board (FPCB) for driving the transparent electrode structure. The flexible printed circuit board may be further equipped with a timing controller for driving the organic light emitting diode array, the power supply, and the like.

The lower substrate 610 may include a substrate formed of a flexible resin. Specifically, the lower substrate 610 may include a flexible substrate such as a germanium substrate, a polyimide substrate, a polycarbonate substrate, and a polyacrylate substrate, but is not limited thereto.

In the display area of the lower substrate 610, a plurality of primitive domains are defined by crossing a plurality of driving wires (not shown) and a plurality of sensor wires (not shown), and each of the primitive domains may Formed with an array of organic light emitting diodes, each of which includes a thin film transistor 616 and an organic light emitting diode 615 coupled to the thin film transistor 616. In the non-display area of the lower substrate 610, a gate driver that applies an electrical signal to the driving wires may be formed in a gate-in panel form. The panel gate driving unit is formed on one side or both sides of the display area.

The thin film transistor 616 controls a current (which flows through the semiconductor by applying an electric field perpendicular to the current), and may be formed on the lower substrate 610. The thin film transistor 616 may include a gate electrode 610a, a gate insulating layer 611, a semiconductor layer 612, a source electrode 613a, and a drain electrode 613b. The thin film transistor 616 may be an oxide thin film transistor using an oxide such as indium gallium zinc oxide (IGZO), ZnO, and TiO as the semiconductor layer 612, and an organic thin film transistor using an organic material as a semiconductor layer. An amorphous germanium thin film transistor using amorphous germanium as a semiconductor layer or a polycrystalline germanium thin film transistor using polycrystalline germanium as a semiconductor layer.

The planarization layer 614 covers the thin film transistor 616 and the circuit portion 610b to flatten the upper surfaces of the thin film transistor 616 and the circuit portion 610b so that the organic light emitting diode 615 can be formed thereon. The planarization layer 614 may be formed of a spin-on-glass (SOG) film, a polyimide polymer or a polyacrylic acid polymer, but is not limited thereto.

The organic light emitting diode 615 obtains a display image via self-emission, and may include a first electrode 615a, an organic light emitting layer 615b, and a second electrode 615c, which are stacked in the stated order. The adjacent organic light emitting diodes may be separated from each other by the insulating layer 617. The organic light emitting diode 615 may have a bottom emission type structure in which light generated by the organic light emitting layer 615b is emitted via a lower substrate; or a top emission type structure in which light from the organic light emitting layer 615b is emitted via the upper substrate.

The protective layer 618 covers the organic light emitting diode 615 to protect the organic light emitting diode 615. The protective layer 618 may be formed of an inorganic insulating material such as SiOx (1≤x≤2), SiNx (1≤x≤1.33), SiC, SiON, SiONC, and amorphous carbon (aC); or organic Insulating materials such as acrylates, epoxy polymers, yttrium imide polymers, and the like. Specifically, the protective layer 618 may include an encapsulation layer in which the inorganic material layer and the organic material layer are sequentially stacked one or more times.

Referring again to FIG. 6, the adhesive layer 660 is used to attach the display unit 650a to the polarizing plate 670, and may be formed of a binder composition comprising a (meth) acrylate resin, a curing agent, Starting agent and decane coupling agent.

The polarizing plate 670 can realize internal light polarization or prevent external light from being reflected to obtain a display image or can improve the contrast of the display image. The polarizing plate 670 may be composed only of a polarizer. Alternatively, the polarizing plate 670 may include a polarizer and a protective film formed on one or both surfaces of the polarizer. Alternatively, the polarizing plate 670 may include a polarizer and a protective coating formed on one or both surfaces of the polarizer. As the polarizer, the protective film, and the protective coating, a typical polarizer, a typical protective film, and a typical protective coating known in the art can be used.

The touch screen panel 680 generates an electrical signal by detecting a change in capacitance when a human body or a conductor such as a stylus touches the touch screen panel 680, and the display unit 650a can be driven by such an electrical signal. The touch screen panel 680 is formed by patterning a flexible conductor, and may include a first sensor electrode and a second sense each formed between the first sensor electrode and crossing the first sensor electrode Detector electrode. The touch screen panel 680 may include a conductive material such as a metal nanowire, a conductive polymer, and a carbon nanotube, but is not limited thereto.

Window film 690 is formed as the outermost layer of flexible display 600 to protect the display.

Although not shown in FIG. 6, an adhesive layer may be further formed between the polarizing plate 670 and the touch screen panel 680 and/or between the touch screen panel 680 and the window film 690 to enhance the polarizing plate and the touch type. Bonding between the screen panel and the window film. The adhesive layer may be formed of a binder composition comprising a (meth)acrylic resin, a curing agent, a starter, and a decane coupling agent. In addition, although not shown in FIG. 6, a polarizing plate may be disposed under the display unit 650a to achieve internal light polarization.

Next, a flexible display according to another embodiment of the present invention will be described with reference to FIG. Figure 8 is a cross-sectional view of a flexible display in accordance with another embodiment of the present invention.

Referring to FIG. 8, a flexible display 700 according to this embodiment includes a display unit 650a, a touch screen panel 680, a polarizing plate 670, and a flexible window film 690, which may include a window film in accordance with an embodiment of the present invention. The flexible display 700 according to this embodiment is substantially the same as the flexible display according to the above embodiment except that the touch screen panel 680 is directly formed on the display unit 650a. In this embodiment, the touch screen panel 680 can be formed with the display unit 650a. Therefore, since the touch screen panel 680 is disposed on the display unit 650a while being formed together with the display unit 650a, the flexible display 700 according to this embodiment has a smaller size than the flexible display according to the above embodiment. Thickness to provide better visibility. In this embodiment, the touch screen panel 680 may be formed by deposition, but is not limited thereto.

Although not shown in FIG. 8, it may be further formed between the display unit 650a and the touch screen panel 680, between the touch screen panel 680 and the polarizing plate 670, and/or between the polarizing plate 670 and the window film 690. The adhesive layer enhances the bond between the polarizing plate, the touch screen panel, and the window film. The adhesive layer may be formed of a binder composition comprising a (meth)acrylic resin, a curing agent, a starter, and a decane coupling agent. In addition, although not shown in FIG. 8, a polarizing plate may be disposed under the display unit 650a to improve the image quality of the display by realizing internal light polarization.

Next, a flexible display according to another embodiment of the present invention will be described with reference to FIG. 9 is a cross-sectional view of a flexible display in accordance with another embodiment of the present invention.

Referring to Figure 9, a flexible display 800 in accordance with this embodiment includes a display unit 650b, an adhesive layer 660, and a flexible window film 690, which may include a window film in accordance with an embodiment of the present invention. The flexible display 800 according to this embodiment is substantially the same as the flexible display according to the above embodiment except that the flexible display can be driven only by the display unit 650b and does not include the polarizing plate and the touch screen panel.

The display unit 650b may include a substrate and an optical device including an OLED, an LED, or an LCD formed on the substrate. The display unit 650b may further include a touch screen panel therein.

Although a flexible display including a window film according to an embodiment of the present invention has been described above, it should be understood that the window film according to an embodiment of the present invention can also be applied to a non-flexible display.

Hereinafter, the present invention will be described in more detail with reference to some examples. However, it should be noted that these examples are provided for illustration only and are not to be construed as limiting the invention in any way.

Instance

Preparation example 1 : composition for window coating

By using 70.0 g of a composition containing a siloxane-containing resin having a UV curable group (Hybrimer, solid content: 90% by weight, anthraquinone resin, epoxy monomer, and photocationic initiation) a mixture of the agents, Solip Co., Ltd. and 30.0 g of methyl ethyl ketone were placed in a flask, followed by stirring for 30 minutes and removing bubbles for 30 minutes to prepare a composition for the window coating. .

Preparation example 2 : composition for back coating

By placing 12.0 g of urethane acrylate (UA7619, Entis Co., Ltd.), 7.2 g of dipentaerythritol hexaacrylate (Entetsu Co., Ltd.), and 30.0 g of methyl ethyl ketone in a flask The composition for the back coat layer was then prepared by stirring for 30 minutes. 0.7 g of Irgacure 184 (BASF) was further added to the mixture, followed by stirring for 30 minutes.

Preparation example 3 : composition for back coating

10.6 g of urethane acrylate (HX-920UV, Kyoeisha Co., Ltd.), 2.1 g of dipentaerythritol hexaacrylate (Entetsu Co., Ltd.), and 8.5 g of cerium oxide nanoparticle were stirred by stirring. Particle sol (Optisol-SST650U, solid content: 50% by weight, average particle diameter of cerium oxide nanoparticles: 12 nm, cerium oxide nanoparticle content: 4.3 g, Lanke Co., Ltd. ( Ranco Co., Ltd.)) and 10.0 g of methyl ethyl ketone were mixed for 30 minutes. 0.4 g of Yanjiao 184 (BASF) was further added to the mixture, followed by stirring for 30 minutes to prepare a composition for the back coat layer.

Preparation example 4 : composition for back coating

100 g including 95 mol% of 2-(3,4-epoxycyclohexyl)ethyltriethoxydecane (Shin-Etsu Co., Ltd.) and 5 mol% of dimethyl A monomer mixture of dimethoxy decane (UMT Co., Ltd.) was placed in a 500 ml 3-necked flask. 0.5 mol% KOH and 1.48 mol% water were added to the hydrazine monomer mixture, followed by stirring at 25 ° C for 1 hour, and then at 70 ° C for 2 hours. A The decane resin was prepared to have a solid content of 90% by weight by removing the remaining solvent using a vacuum distillation apparatus. The decane resin has a weight average molecular weight of 5,000 g/mole as measured by gel permeation chromatography. Prepared by mixing 100 grams of the prepared decane resin, 10 grams of crosslinkable monomer (CY-179), 2 grams of starter (Banjia 250, BASF), and 60 grams of methyl ethyl ketone. The composition of the back coating.

Preparation example 5 : composition for the adhesive layer

By placing 200 g of an acrylic adhesive resin (PS-06HE, Soken Co., Ltd.), 0.3 g of a curing agent (L-45, Kosei Co., Ltd.), and 30 g of ethyl acetate in a flask, and then The composition for the adhesive layer was prepared by stirring for 30 minutes. The adhesive layer formed from this composition had a storage modulus of 25 kPa at 25 ° C and a glass transition temperature of -42 ° C. To prepare a sample for measuring the storage modulus of the adhesive layer, the composition for the adhesive layer was applied to a release film and allowed to stand at 35 ° C and 45% RH for 24 hours to form a 50 micron thick adhesive. membrane. Next, after removing the release film from each of the adhesive films, 8 adhesive films were stacked and cut into circular samples having a thickness of 400 μm and a diameter of 8 mm. The storage modulus of the adhesive layer was measured using a Fesica MCR501 (Antonpa Co., Ltd.) at 25 ° C under a condition of 1 rad/sec with respect to a sample on a disc having a diameter of 8 mm. Increase the temperature from -50 ° C to 100 ° C.

Instance 1

The composition for window coating prepared in Preparation Example 1 was applied to one surface of a 75 μm thick transparent polyimide film using a bar coater, and dried in an oven at 80 ° C for 3 minutes, exposed UV light at 500 mJ/cm 2 was post-cured at 120 ° C for 24 hours. The composition for the back coat layer prepared in Preparation Example 2 was applied to the other surface of the transparent polyimide film using a bar coater. Next, the composition for the back coat layer was dried in an oven at 80 ° C for 2 minutes and exposed to 300 mJ/cm 2 of UV light under a nitrogen atmosphere to prepare a window-containing coating (thickness: 50 μm), A transparent polyimide film (thickness: 75 μm) and a back coat (thickness: 10 μm) window film were sequentially stacked in the stated order.

Instance 2

A window film was prepared in the same manner as in Example 1 except that the composition for the back coat layer of Preparation Example 3 was used instead of the composition for the back coat layer of Preparation Example 2.

Instance 3

A window film was prepared in the same manner as in Example 1 except that the composition for the back coat layer of Preparation Example 4 was used instead of the composition for the back coat layer of Preparation Example 2.

Instance 4

The composition for window coating prepared in Preparation Example 1 was applied to a surface of a 75 μm thick transparent polyimide film for the base layer using a bar coater, and dried at 80 ° C in an oven. After 3 minutes, it was exposed to 500 mJ/cm 2 of UV light and post-cured at 120 ° C for 24 hours. The composition for the adhesive layer prepared in Preparation Example 5 was applied to the other surface of the transparent polyimide film for the base layer using a bar coater, followed by drying at 80 ° C in an oven. Minutes to form a layer of adhesive. Next, the composition for the back coat layer prepared in Preparation Example 2 was applied to one surface of a 75 μm thick transparent polyimide film for the support layer using a bar coater, in an oven at 80 It was dried at ° C for 2 minutes, and exposed to 300 mJ/cm 2 of UV light under a nitrogen atmosphere to form a back coat layer on one surface of the transparent polyimide film for the support layer. The adhesive layer was attached to the other surface of the transparent polyimide film for the support layer, thereby preparing a transparent polyimide film (thickness) including a back coat layer (thickness: 20 μm) for the support layer : 75 μm), adhesive layer (thickness: 30 μm), transparent polyimide film (thickness: 75 μm) for the base layer, and window coating (thickness: 50 μm) window film, as stated The order is stacked in order.

Instance 5

A window film was prepared in the same manner as in Example 4, except that the composition for the back coat layer of Preparation Example 3 was used instead of the composition for the back coat layer of Preparation Example 2.

Instance 6

A window film was prepared in the same manner as in Example 4, except that the composition for the back coat layer of Preparation Example 4 was used instead of the composition for the back coat layer of Preparation Example 2.

Instance 7

The composition for window coating prepared in Preparation Example 1 was applied to one surface of a 75 μm thick transparent polyimide film using a bar coater, and dried in an oven at 80 ° C for 3 minutes, exposed UV light at 500 mJ/cm 2 was post-cured at 120 ° C for 24 hours. The composition for the adhesive layer prepared in Preparation Example 5 was applied to the other surface of the transparent polyimide film using a bar coater. Next, the composition for the adhesive layer was dried in an oven at 80 ° C for 2 minutes and exposed to 300 mJ/cm 2 of UV light under a nitrogen atmosphere to form a binder layer. The composition for the back coat layer of Preparation Example 3 was applied to one surface of a release film (polyethylene terephthalate film) using a bar coater, followed by drying at 80 ° C in an oven 2 Minutes and exposure to 300 mJ/cm 2 of UV light under a nitrogen atmosphere. A window film is prepared by attaching a binder layer to the back coat layer and removing the release film, which comprises a back coat layer (thickness: 10 μm), a binder layer (thickness: 30 μm), a polyimide film (thickness) : 75 microns) and window coating (thickness: 50 microns), which are sequentially stacked in the stated order.

Instance 8

A window film was prepared in the same manner as in Example 7 except that the composition for the back coat layer of Preparation Example 4 was used instead of the composition for the back coat layer of Preparation Example 3.

Comparative example 1

The composition for window coating prepared in Preparation Example 1 was applied to one surface of a 75 μm thick transparent polyimide film using a bar coater, and dried in an oven at 80 ° C for 3 minutes, exposed UV light at 500 mJ/cm 2 and post-curing at 120 ° C for 24 hours to prepare a transparent polyimide film having a window coating (thickness: 50 μm) and formed thereon (thickness: 75 Micron window film.

The characteristics of Table 1 of the window films of Examples 1 to 8 and Comparative Example 1 were evaluated.

Table 1 <TABLE border="1" borderColor="#000000" width="85%"><TBODY><tr><td></td><td> Comparative Example</td><td> Instance </ Td></tr><tr><td> 1 </td><td> 1 </td><td> 2 </td><td> 3 </td><td> 4 </td>< Td> 5 </td><td> 6 </td><td> 7 </td><td> 8 </td></tr><tr><td> pencil hardness</td><td> 8H </td><td> 8H </td><td> 8H </td><td> 8H </td><td> 8H </td><td> 8H </td><td> 8H < /td><td> 8H </td><td> 8H </td></tr><tr><td> pencil hardness on the adhesive layer</td><td> H </td>< Td> 8H </td><td> 8H </td><td> 8H </td><td> 6H </td><td> 8H </td><td> 8H </td><td> 6H </td><td> 6H </td></tr><tr><td> Haze (%) </td><td> 1.05 </td><td> 0.89 </td><td > 1.06 </td><td> 0.92 </td><td> 0.98 </td><td> 1.03 </td><td> 0.93 </td><td> 1.03 </td><td> 0.93 </td></tr><tr><td> total light transmittance (%) </td><td> 88.94 </td><td> 89.21 </td><td> 89.03 </td>< Td> 89.21 </td><td> 88.96 </td><td> 88.82 </td><td> 89.10 </td><td> 88.86 </td><td> 88.92 </td></tr ><tr><td> Radius of curvature</td><td> Pressurization direction (mm) </td><td> 5 </td><td> 5 </td><td> 5 </td> < Td> 5 </td><td> 5 </td><td> 5 </td><td> 5 </td><td> 5 </td><td> 5 </td></tr ><tr><td> Stretching direction (mm) </td><td> 10 </td><td> 10 </td><td> 10 </td><td> 10 </td>< Td> 10 </td><td> 10 </td><td> 10 </td><td> 10 </td><td> 10 </td></tr><tr><td> window Martens hardness on the coating (Newtons/mm) </td><td> 137 </td><td> 222 </td><td> 252 </td><td> 255 </td>< Td> 181 </td><td> 204 </td><td> 201 </td><td> 173 </td><td> 176 </td></tr><tr><td> window Elastic modulus on the coating (MPa) </td><td> 1718 </td><td> 2858 </td><td> 3103 </td><td> 3092 </td><td> 2149 </td><td> 2572 </td><td> 2510 </td><td> 2102 </td><td> 2096 </td></tr><tr><td> Back Coating Martens hardness (Newtons/mm) </td><td> - </td><td> 108 </td><td> 117 </td><td> 120 </td><td> 82 </td><td> 99 </td><td> 92 </td><td> 72 </td><td> 76 </td></tr><tr><td> Back Coating Elastic Modulus ( MPa) </td><td> - </td><td> 1484 </td><td> 1611 </td><td> 1592 </td><td> 1208 < /td><td> 1296 </td><td> 1285 </td><td> 1156 </td><td> 1182 </td> </tr><tr><td> Martens hardness on the base layer (Newtons/mm) </td><td> 58 </td><td> - </td><td> - </td> <td> - </td><td> - </td><td> - </td><td> - </td><td> - </td><td> - </td></ Tr><tr><td> Elastic modulus on the base layer (MPa) </td><td> 817 </td><td> - </td><td> - </td><td> - </td><td> - </td><td> - </td><td> - </td><td> - </td><td> - </td></tr></ TBODY></TABLE>

As shown in Table 1, the window film of the example exhibited good characteristics both in pencil hardness on the glass substrate and pencil hardness on the adhesive layer. Specifically, the window films of Examples 1 to 3, 5, and 6 have the same pencil hardness on the glass substrate and on the adhesive layer. Further, the window film including the example of the back coat layer has the same radius of curvature and thus exhibits good flexibility for use as a flexible window film, compared to the window film of Comparative Example 1 which does not include the back coat layer. Furthermore, the window film of the examples has low haze and good transmittance regardless of the presence or absence of a back coating.

In contrast, the window film of Comparative Example 1 which did not include the back coat layer had the pencil hardness on the same glass substrate as the example window film and the lower pencil hardness on the adhesive layer as compared with the case film of the example.

(1) Pencil hardness: Each of the window films prepared in the examples and the comparative examples was cut into a sample having a size of 50 mm × 50 mm (length × width), and a pencil hardness tester (New East - according to JIS K5400) was used. 14EW, Shinto Scientific Co., Ltd., measured the pencil hardness for the window coating of the window film. A pencil of 6B to 9H (Mitsubishi Co., Ltd.) was used. At 60 mm/min scraping speed, 19.6 Newton pencil pressing force, 45° scraping angle (angle between pencil and window coating), 1 kg pencil load, and 10.0 mm pencil scale Measure the pencil hardness. When the window coating has one or more scratches after 5 tests using a pencil, the pencil hardness is again measured using another pencil having a lower pencil hardness than the previous pencil. After repeatedly measuring the pencil hardness five times, the maximum value of the pencil hardness of all the five scratches not observed on the window coating was regarded as the pencil hardness of the window coating.

(2) Pencil hardness on the adhesive layer: The composition for the adhesive layer prepared in Preparation Example 5 was deposited on a 2T 堿 lime glass substrate and cured to form a 50 μm thick adhesive layer. A binder layer was attached to the back coat layer or the base layer of each of the window films prepared in the examples and the comparative examples to prepare a sample, and then the pencil hardness thereof was measured by the same method as (1).

(3) Haze and total light transmittance: The haze of each window film was measured using a NDH2000 (Nippon Denshoku Co., Ltd.) at a wavelength of 400 nm to 800 nm. And total light transmittance.

(4) Curvature radius: Each window film (width × length: 3 cm × 15 cm) was wound around a jig (Mandela Bending Tester, Touch Technology Co., Ltd.) for testing the radius of curvature, and the roll was kept. Winding for 5 seconds or more, and then unwinding from the fixture. Next, the window film was observed with the naked eye to determine whether or not the window film was cracked. Here, the radius of curvature of the pressurizing direction is measured under the condition that the window coating of the window film contacts the surface of the jig, and the radius of curvature of the stretching direction is measured under the condition that the base layer of the window film contacts the jig. The radius of curvature is measured while the diameter of the jig is gradually reduced from the maximum diameter, and the minimum radius of the jig that does not cause cracks on the window film is determined as the radius of curvature of the window film.

(5) Martens hardness on the window coating and elastic modulus on the window coating: at 25 ° C, using a Fischer HM2000LT micro indenter (Fisher Co., Ltd.) for each window The window coating of the film measures the Martens hardness and the modulus of elasticity. The composition for the adhesive layer prepared in Preparation Example 5 was deposited on a 2T tantalum lime glass substrate and cured to form a 50 micrometer thick adhesive layer. A layer of adhesive is attached to each of the window films such that the window coating of the window film is placed on the outermost side to prepare a sample in which the window film is attached to the layer of adhesive. Applying a constant force of 200 millinewtons to the window coating of the sample for 20 seconds by using a micro-indenter (Vickers indenter) with a vertical diamond pyramid shaped as a rectangular chassis, then slowly moving for 5 seconds and relaxing for 20 seconds. The Martens hardness and modulus of elasticity were measured.

(6) Martens hardness on the back coat layer and elastic modulus on the back coat layer: an adhesive layer is formed by the same method as (5), and attached to each window film to make the back of the window film The coating was placed on the outermost side to prepare a sample in which the window film was attached to the adhesive layer. The Martens hardness and the elastic modulus were measured by applying a constant force of 200 millinewtons to the back coating of the sample for 20 seconds in the same manner as in (5), followed by slow movement for 5 seconds and relaxation for 20 seconds.

(7) Martens hardness on the base layer and elastic modulus on the base layer: a binder layer is formed by the same method as (5), and attached to each window film so that the base layer of the window film is placed on the outermost side , thereby preparing a sample in which the window film is attached to the adhesive layer. The Martens hardness and the elastic modulus were measured by applying a constant force of 200 millinewtons to the base layer of the sample for 20 seconds in the same manner as in (5), followed by slow movement for 5 seconds and relaxation for 20 seconds.

Preparation example 6 : composition for back coating

3.6 g of a hexafunctional urethane acrylate (UP118, Entins Co., Ltd.) as a UV curable acrylic resin, 1.2 g of trimethylolpropane triacrylate as a trifunctional acryl oxime monomer (Entetsu Co., Ltd.) ), 94 g of methyl ethyl ketone and 0.05 g of porphyrazine dye (KCF Blue b), maximum absorption wavelength: 596 nm, Kyung-In Synthetic Co. And stirred for 30 minutes. 0.2 g of a photoinitiator (Yanjiao 184, BASF) was added to the mixture and stirred for 30 minutes to prepare a composition for the back coat layer.

Preparation example 7 : composition for back coating

3.6 g of a hexafunctional urethane acrylate (UP118, Entins Co., Ltd.) as a UV curable acrylic resin, 1.2 g of trimethylolpropane triacrylate as a trifunctional acryl oxime monomer (Entetsu Co., Ltd.) ), 94 g of methyl ethyl ketone and 0.05 g of porphyrazine dye (SK-D584, SK Chemical Co., Ltd., maximum absorption wavelength: 584 nm) were mixed and stirred for 30 minutes. 0.2 g of Yanjiao 184 (BASF) as a photoinitiator was added to the mixture and stirred for 30 minutes to prepare a composition for the back coat layer.

Preparation example 8 : composition for back coating

3.6 g of a hexafunctional urethane acrylate (UP118, Entins Co., Ltd.) as a UV curable acrylic resin, 1.2 g of trimethylolpropane triacrylate as a trifunctional acryl oxime monomer (Entetsu Co., Ltd.) ), 94 g of methyl ethyl ketone and 0.05 g of porphyrin dye (PD-311S, Yamamoto Chemicals Inc., maximum absorption wavelength: 584 nm) were mixed and stirred for 30 minutes. 0.2 g of Yanjiao 184 (BASF) as a photoinitiator was added to the mixture and stirred for 30 minutes to prepare a composition for the back coat layer.

Preparation example 9 : composition for back coating

3.6 g of a hexafunctional urethane acrylate (UP118, Entins Co., Ltd.) as a UV curable acrylic resin, 1.2 g of trimethylolpropane triacrylate as a trifunctional acryl oxime monomer (Entetsu Co., Ltd.) ), 94 g of methyl ethyl ketone and 0.05 g of vanadium dye (SK-D593, SK Chemical Co., Ltd., maximum absorption wavelength: 593 nm) were mixed and stirred for 30 minutes. 0.2 g of Yanjiao 184 (BASF) as a photoinitiator was added to the mixture and stirred for 30 minutes to prepare a composition for the back coat layer.

Preparation example 10 : composition for back coating

3.6 g of a hexafunctional urethane acrylate (UP118, Entins Co., Ltd.) as a UV curable acrylic resin, 1.2 g of trimethylolpropane triacrylate as a trifunctional acryl oxime monomer (Entetsu Co., Ltd.) A mixture of 94 g of methyl ethyl ketone and 0.05 g of a porphyrin dye and a vanadium dye (PANAX NEC 595, Ukseung Chemical Inc., maximum absorption wavelength: 595 nm) was mixed and stirred for 30 minutes. 0.2 g of Yanjiao 184 (BASF) as a photoinitiator was added to the mixture and stirred for 30 minutes to prepare a composition for the back coat layer.

Preparation example 11 : composition for window coating

50 g of 2-(3,4-epoxycyclohexyl)ethyltriethoxydecane (KBM-303, Shin-Etsu Chemical Co., Ltd.) was placed in a 200 ml 3-necked flask. 0.5 mol% KOH and 1.5 mol% water were added to the flask on the basis of 2-(3,4-epoxycyclohexyl)ethyltriethoxydecane, followed by stirring at 25 ° C for 1 hour and then Stir at 70 ° C for 2 hours. The fluorenone resin was prepared to have a solid content of 90% by weight by removing the remaining solvent using a vacuum distillation apparatus. The decane resin has a weight average molecular weight of 5,000 g/mole as measured by gel permeation chromatography. By mixing 100 g of the prepared decane resin, curable monomer, 15 g of 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate (CY-179) , Ciba Chemical Co., Ltd.), 2 g of diphenylphosphonium hexafluorophosphate (Sigma Aldrich Co., Ltd.) as a starter and 60 Gethyl ethyl ketone was used to prepare a composition for a window coating.

Instance 9

By applying 3 ml of the composition for the back coat layer prepared in Preparation Example 6 to one surface of a 75 μm thick transparent polyimide film, followed by spin coating at 500 rpm for 20 seconds, It was dried in an oven at 80 ° C for 3 minutes, and exposed to 300 mJ/cm 2 of UV light under a nitrogen atmosphere to form a back coat (thickness: 100 nm) on a 75 μm thick transparent polyimide film. On a surface. The composition for window coating prepared in Preparation Example 11 was applied to the other surface of the transparent polyimide film using a bar coater. Next, the composition for the window coating was dried in an oven at 80 ° C for 3 minutes, exposed to 500 m joules per square centimeter of UV light under a nitrogen atmosphere, and post-cured at 120 ° C for 24 hours to prepare. A window film comprising a window coating (thickness: 50 microns), a transparent polyimide film (thickness: 75 microns), and a back coat (thickness: 100 nm).

Instance 10

A window film was prepared in the same manner as in Example 9 except that the composition for the back coat layer of Preparation Example 7 was used instead of the composition for the back coat layer of Preparation Example 6.

Instance 11

A window film was prepared in the same manner as in Example 9 except that the composition for the back coat layer of Preparation Example 8 was used instead of the composition for the back coat layer of Preparation Example 6.

Instance 12

A window film was prepared in the same manner as in Example 9 except that the composition for the back coat layer of Preparation Example 9 was used instead of the composition for the back coat layer of Preparation Example 6.

Instance 13

A window film was prepared in the same manner as in Example 9 except that the composition for the back coat layer of Preparation Example 10 was used instead of the composition for the back coat layer of Preparation Example 6.

Comparative example 2

The composition for window coating prepared in Preparation Example 11 was applied to one surface of a transparent polyimide film (thickness: 75 μm) using a bar coater. Thereafter, the composition was dried in an oven at 80 ° C for 3 minutes, exposed to 500 mJ/cm 2 of UV light, and post-cured at 120 ° C for 24 hours to prepare a window coating (thickness: 50 μm). And a window film of a transparent polyimide film (thickness: 75 μm) formed thereon.

The characteristics of Table 1 of the window films of Examples 9 to 13 and Comparative Example 2 were evaluated.

Table 2 <TABLE border="1" borderColor="#000000" width="85%"><TBODY><tr><td></td><td> Comparative Example</td><td> Instance </ Td></tr><tr><td> 2 </td><td> 9 </td><td> 10 </td><td> 11 </td><td> 12 </td>< Td> 13 </td></tr><tr><td> Back Coating</td><td> - </td><td> Existence</td><td> Existence</td><td > Existence</td><td> Existence</td><td> Existence</td></tr><tr><td> Dye</td><td> - </td><td> Existence < /td><td> Existence</td><td> Existence</td><td> Existence</td><td> Existence</td></tr><tr><td> Maximum absorption wavelength of dye (nano) </td><td> - </td><td> 596 </td><td> 584 </td><td> 584 </td><td> 593 </td><td > 595 </td></tr><tr><td> pencil hardness</td><td> 8H </td><td> 8H </td><td> 8H </td><td> 8H </td><td> 8H </td><td> 8H </td></tr><tr><td> yellow index</td><td> 5.65 </td><td> 0.24 </ Td><td> 0.69 </td><td> 0.89 </td><td> 1.14 </td><td> 0.94 </td></tr><tr><td> total light transmittance (% ) </td><td> 88.94 </td><td> 89.24 </td><td> 89.28 </td><td> 89.00 </td><td> 89.08 </td><td> 88.82 < /td></tr><tr><td> Haze (%) </td><td> 0.94 </ Td><td> 0.80 </td><td> 0.88 </td><td> 0.85 </td><td> 0.87 </td><td> 0.73 </td></tr><tr>< Td> radius of curvature</td><td> direction of pressurization (mm) </td><td> 5 </td><td> 5 </td><td> 5 </td><td> 5 < /td><td> 5 </td><td> 5 </td></tr><tr><td> Stretching direction (mm) </td><td> 10 </td><td> 10 </td><td> 10 </td><td> 10 </td><td> 10 </td><td> 10 </td></tr><tr><td> b* value </td><td> 3.39 </td><td> 0.42 </td><td> 0.48 </td><td> 0.61 </td><td> 0.67 </td><td> 0.63 </ Td></tr></TBODY></TABLE>

As shown in Table 2, the window film of the example has a lower yellow index and b* value according to the present invention to prevent the window film from appearing yellow, and has a higher total light transmittance and a lower haze, thereby providing good optical characteristics. . Moreover, the window film of the example has a higher pencil hardness and a lower radius of curvature for use in a flexible display.

In contrast, the window film of Comparative Example 2, which does not contain a dye, has a higher yellow index and b* value of the present invention to allow the window film to appear yellow, and thus may not be used in a flexible display.

(1) Pencil hardness: Each of the window films prepared in the examples and the comparative examples was cut into a sample having a size of 50 mm × 50 mm (length × width), and a pencil hardness tester (New East - according to JIS K5400) was used. 14EW, Shendong Science Co., Ltd.) measures the pencil hardness for the window coating of the window film. A pencil of 6B to 9H (Mitsubishi Co., Ltd.) was used. At 60 mm/min scraping speed, 19.6 Newton pencil pressing force, 45° scraping angle (angle between pencil and window coating), 1 kg pencil load, and 10.0 mm pencil scale Measure the pencil hardness. When the window coating has one or more scratches after 5 tests using a pencil, the pencil hardness is again measured using another pencil having a lower pencil hardness than the previous pencil. After repeatedly measuring the pencil hardness five times, the maximum value of the pencil hardness of all the five scratches not observed on the window coating was regarded as the pencil hardness of the window coating.

(2) Yellow index: Under the D65 light source, at 2° (the angle between the window coating and the light source), using a colorimeter (CM-3600d, Konica Minolta Co., Ltd.), measured relative to the window film Yellow index 1925 [recalculation].

(3) Total light transmittance and haze: Total light transmittance and haze were measured by the same method as in Table 1.

(4) Curvature radius: The radius of curvature was measured by the same method as in Table 1.

(5) b* value: under the D65 light source, at 2° (the angle between the window coating and the light source), using a colorimeter (CM-3600d, Konica Minolta Co., Ltd.), relative to the window film Measure the b* value.

Preparation example 12 : composition for back coating

3.6 g of a hexafunctional urethane acrylate (UP118, Entins Co., Ltd.) as a UV curable acrylic resin, 1.2 g of trimethylolpropane triacrylate as a trifunctional acryl oxime monomer (Entetsu Co., Ltd.) ), 94 g of methyl ethyl ketone, 0.05 g of porphyrazine dye (KCF blue b, maximum absorption wavelength: 596 nm, Jingren Synthetic Co., Ltd.) and 0.1 g of Yankun Knox as a phenolic antioxidant ( Irganox) -1010 (BASF) was mixed and stirred for 30 minutes. 0.2 g of a photoinitiator (Yanjiao 184, BASF) was added to the mixture and stirred for 30 minutes to prepare a composition for the back coat layer.

Preparation example 13 To 16 : composition for back coating

A composition for a back coat layer was prepared in the same manner as in Production Example 12, except that the antioxidants listed in Table 3 were used instead of 0.1 g of Yankanokex-1010.

Preparation example 17 : composition for back coating

By dispersing 1.5 g of Baytron PH-500 (Bayer Co. Ltd., solid content: 1.2% by weight) which is a polyethylene dihydroxythiophene (PEDOTT:PSS) dispersion A first solution was prepared by mixing a solution of 17.4 g of ethanol with 17.4 g of ethoxyethanol for 10 minutes. 3.6 g of a hexafunctional urethane acrylate (UP118, Entins Co., Ltd.) as a UV curable acrylic resin, 1.2 g of trimethylolpropane triacrylate as a trifunctional acryl oxime monomer (Entetsu Co., Ltd.) ), 17.4 g of isopropyl alcohol, 17.4 g of ethoxyethanol, and 0.05 g of porphyrazine dye (KCF blue b, maximum absorption wavelength: 596 nm, Jingren Synthetic Co., Ltd.) were mixed and stirred for 30 minutes. 0.2 g of a photoinitiator (Yanjiao 184, BASF) was added to the mixture and stirred for 30 minutes to prepare a second solution. The first solution and the second solution were mixed and stirred for 30 minutes to prepare a composition for the back coat layer.

Preparation example 18 : composition for back coating

3.6 g of a hexafunctional urethane acrylate (UP118, Entins Co., Ltd.) as a UV curable acrylic resin, 1.2 g of trimethylolpropane triacrylate as a trifunctional acryl oxime monomer (Entetsu Co., Ltd.) ), 94 g of methyl ethyl ketone and 0.05 g of porphyrazine dye (KCF blue b, maximum absorption wavelength: 596 nm, Jingren Synthetic Co., Ltd.) were mixed and stirred for 30 minutes. 0.2 g of photoinitiator (Yanjia 184, BASF) and 0.45 g of quaternary ammonium antistatic agent (I-A2, solid content: 100% by weight, KOEI Co., Ltd.) were added to the mixture. It was stirred and stirred for 30 minutes to prepare a composition for the back coat layer.

Preparation example 19 : composition for back coating

3.6 g of a hexafunctional urethane acrylate (UP118, Entins Co., Ltd.) as a UV curable acrylic resin, 1.2 g of trimethylolpropane triacrylate as a trifunctional acryl oxime monomer (Entetsu Co., Ltd.) ), 37.2 g of methyl ethyl ketone, 55.8 g of 1-methoxy-2-propanol and 0.05 g of porphyrazine dye (KCF blue b, maximum absorption wavelength: 596 nm, Jingren Synthetic Co., Ltd.) And stirred for 30 minutes. 0.2 g of photoinitiator (Yanjiao 184, BASF) and 0.9 g of ATO sol antistatic agent (XJB-0187, solid content: 40% by weight, Pelnox Co., Ltd.) were added to The mixture was stirred for 30 minutes to prepare a composition for the back coat layer.

Instance 14

By applying 3 ml of the composition for the back coat prepared in Preparation Example 12 onto one surface of a 75 μm thick transparent polyimide film, followed by spin coating at 500 rpm for 20 seconds, in an oven It was dried at 80 ° C for 3 minutes and exposed to 300 mJ/cm 2 of UV light under a nitrogen atmosphere to form a back coat (thickness: 100 nm) on one surface of a 75 μm thick transparent polyimide film. . The composition for window coating prepared in Preparation Example 11 was applied to the other surface of the transparent polyimide film using a bar coater. Next, the composition for the window coating was dried in an oven at 80 ° C for 3 minutes, exposed to 500 m joules per square centimeter of UV light under a nitrogen atmosphere, and post-cured at 120 ° C for 24 hours to prepare. A window film comprising a window coating (thickness: 50 microns), a transparent polyimide film (thickness: 75 microns), and a back coat (thickness: 100 nm).

Instance 15 To instance 18

A window film was prepared in the same manner as in Example 14 except that the composition for the back coat layer as listed in Table 3 was used instead of the composition for the back coat layer of Example 12.

Instance 19 To instance twenty one

A window film was prepared in the same manner as in Example 14 except that the composition for the back coat layer as listed in Table 4 was used instead of the composition for the back coat layer of Preparation Example 12.

The characteristics of Tables 3 and 4 of the window films of Examples 15 to 18 were evaluated.

(1) Pencil hardness: Each of the window films prepared in the examples and the comparative examples was cut into a sample having a size of 50 mm × 50 mm (length × width), and a pencil hardness tester (New East - according to JIS K5400) was used. 14EW, Shinto Scientific Co., Ltd., measured the pencil hardness for the window coating of the window film. A pencil of 6B to 9H (Mitsubishi Co., Ltd.) was used. At 60 mm/min scraping speed, 19.6 Newton pencil pressing force, 45° scraping angle (angle between pencil and window coating), 1 kg pencil load, and 10.0 mm pencil scale Measure the pencil hardness. When the window coating has one or more scratches after 5 tests using a pencil, the pencil hardness is again measured using another pencil having a lower pencil hardness than the previous pencil. After repeatedly measuring the pencil hardness five times, the maximum value of the pencil hardness of all the five scratches not observed on the window coating was regarded as the pencil hardness of the window coating.

(2) Initial yellow index: Under the D65 light source, at 2° (the angle between the window coating and the light source), a colorimeter (CM-3600d, Konica Minolta Co., Ltd.) is used, relative to the window film. The yellow index is measured at 1925 [recalculation].

(3) Yellow index change: The initial yellow index of each window film was measured by the same method as (2). The window film was allowed to stand at 80 ° C for 1,000 hours in an oven, and then the yellow index was measured by the same method as (2). The yellow index change is calculated according to Equation 1.

(4) Haze and total light transmittance: The haze and total light transmittance of each window film were measured using a NDH2000 (Nippon Denshoku Co., Ltd.) at a wavelength of 400 nm to 800 nm.

(5) Curvature radius: Each window film (width × length: 3 cm × 15 cm) was wound around a jig (Mandela Bending Tester, Touch Technology Co., Ltd.) for testing the radius of curvature, and the roll was kept. Winding for 5 seconds or more, and then unwinding from the fixture. Next, the window film was observed with the naked eye to determine whether or not the window film was cracked. Here, the radius of curvature of the pressurizing direction is measured under the condition that the window coating of the window film contacts the surface of the jig, and the radius of curvature of the stretching direction is measured under the condition that the back coat or the base layer of the window film contacts the jig. The radius of curvature is measured while the diameter of the jig is gradually reduced from the maximum diameter, and the minimum radius of the jig that does not cause cracks on the window film is determined as the radius of curvature of the window film.

(6) b* value: under the D65 light source, at 2° (the angle between the window coating and the light source), using a colorimeter (CM-3600d, Konica Minolta Co., Ltd.), relative to the window film Measure the b* value.

(7) Surface resistance: The surface resistance was measured for the back coat of each window film at 22 ° C and 55% RH using a high ohmmeter (MCT-HT450, Mitsubishi).

(8) Static electricity: using an electrostatic voltmeter (SK-H050, KEYENCE Co., Ltd.) at a speed of 1 rpm, in a wound state, on a 400 mm wide reel Static electricity was measured for the back coat of each window film. The distance between the electrostatic voltmeter probe and the window film is set to 25 mm. Three measurements were taken and the average of the absolute values was obtained.

Table 3 <TABLE border="1" borderColor="#000000" width="85%"><TBODY><tr><td></td><td> Instance</td></tr><tr> <td> 14 </td><td> 15 </td><td> 16 </td><td> 17 </td><td> 18 </td></tr><tr><td> Back coating</td><td> Existence</td><td> Existence</td><td> Existence</td><td> Existence</td><td> Existence</td></tr ><tr><td> Back Coating Type </td><td> Preparation Example 12 </td><td> Preparation Example 13 </td><td> Preparation Example 14 </td><td> Preparation Example 15 </td><td> Preparation Example 16 </td></tr><tr><td> Dye</td><td> Tetraazaporphyrin Dye ¹</td ><td> Tetraazaporphyrin dye¹</td><td> Tetraazaporphyrin dye¹</td><td> Tetraazaindene Porphyrin dye ¹</td><td> tetraazaporphyrin dye¹</td></tr><tr><td> maximum absorption wavelength of dye (nano) </td><td> 596 </td><td> 596 </td><td> 596 </td><td> 596 </td><td> 596 </td></ Tr><tr><td> Antioxidants</td><td> Phenolic Antioxidants²</td><td> Phosphorus Antioxidants³</ Td><td> thioether antioxidant⁴</td><td> phenol+phosphorus antioxidant ⁵</td><td> Phenol+thioether antioxidant mixture⁶</td></tr><tr><td> pencil hardness< /td><td> 8H </td><td> 8H </td><td> 8H </td><td> 8H </td><td> 8H </td></tr><tr> <td> Initial Yellow Index</td><td> 0.24 </td><td> 0.25 </td><td> 0.22 </td><td> 0.23 </td><td> 0.26 </td> </tr><tr><td> Yellow index change</td><td> 0.56 </td><td> 0.72 </td><td> 0.81 </td><td> 0.14 </td>< Td> 0.21 </td></tr><tr><td> total light transmittance (%) </td><td> 89.13 </td><td> 89.14 </td><td> 89.23 </ Td><td> 89.15 </td><td> 89.19 </td></tr><tr><td> Haze (%) </td><td> 0.69 </td><td> 0.84 < /td><td> 0.91 </td><td> 0.79 </td><td> 0.81 </td></tr><tr><td> radius of curvature</td><td> pressure direction Mm) </td><td> 5 </td><td> 5 </td><td> 5 </td><td> 5 </td><td> 5 </td></tr> <tr><td> Stretch direction (mm) </td><td> 10 </td><td> 10 </td><td> 10 </td><td> 10 </td><td > 10 </td></tr><tr><td> b*value</td><td> 0.42 </td><td> 0.43 </td><td> 0.41 </td><td> 0.42 </td><td> 0.43 </td></tr></TBODY></TABLE> 1:0.05 g KCF blue b (maximum absorption wavelength: 596 nm, Jingren Synthetic Company) 2: 0.1 g Yanjia Nuokesi-1010 (BASF) 3: 0.1 gram Yanjiafu (Irgafos)-168 (BASF) 4 : 0.1g Yanjia Nokesi-PS800 (BASF) 5: 0.1g Yanjianuokesi-1010 (BASF) and 0.05g Yanjiafu-168 (BASF) mixture 6: 0.1g Yanjia Nokesi-1010 (BASF ) and a mixture of 0.05 g Yankanokes-PS800 (BASF)

Table 4 <TABLE border="1" borderColor="#000000" width="85%"><TBODY><tr><td></td><td> Comparative Example</td><td> Instance </ Td></tr><tr><td> 2 </td><td> 19 </td><td> 20 </td><td> 21 </td></tr><tr><td > Back Coating</td><td> - </td><td> Existence</td><td> Existence</td><td> Existence</td></tr><tr><td> Back Coating Type </td><td> - </td><td> Preparation Example 17 </td><td> Preparation Example 18 </td><td> Preparation Example 19 </td></tr> <tr><td> Dye</td><td> - </td><td> Tetraazaporphyrin dye¹</td><td> Tetraazaporphyrin dye< Sup>1</sup></td><td> tetraazaporphyrin dye¹</td></tr><tr><td> maximum absorption wavelength of dye (nano) ) </td><td> - </td><td> 596 </td><td> 596 </td><td> 596 </td></tr><tr><td> Antistatic Agent </td><td> - </td><td> Conductive Polymer </td><td> Quaternary Ammonium Salt</td><td> ATO </td></tr><tr><td> Pencil Hardness</td><td> 8H </td><td> 8H </td><td> 8H </td><td> 8H </td></tr><tr><td> Initial Yellow Index</td><td> 5.65 </td><td> 0.12 </td><td> 0.23 </td><td> 0.19 </td></tr><tr><td> Surface Resistance ( Ω/□) </td><td > 1.26 × 10¹⁴</td><td> 1.26 × 10⁶</td><td> 1.02 × 10⁹</ Td><td> 4.14 × 10⁹</td></tr><tr><td> Electrostatic (kV) </td><td> 300 </td><td> 0.9 </td><td> 1.5 </td><td> 2.3 </td></tr><tr><td> total light transmittance (%) </td><td> 88.94 </td>< Td> 89.22 </td><td> 89.26 </td><td> 89.10 </td></tr><tr><td> Haze (%) </td><td> 0.94 </td> <td> 0.81 </td><td> 0.72 </td><td> 0.94 </td></tr><tr><td> Curvature radius </td><td> Pressurization direction (mm) < /td><td> 5 </td><td> 5 </td><td> 5 </td><td> 5 </td></tr><tr><td> Stretching direction (mm ) </td><td> 10 </td><td> 10 </td><td> 10 </td><td> 10 </td></tr></TBODY></TABLE> 1: KCF blue b (maximum absorption wavelength: 596 nm, Jingren Synthetic Company)

As can be seen from Table 3, the window film of the example has high heat resistance to exhibit a lower yellow index change even after standing at a high temperature for a long period of time, and thus can be used in a display.

In addition, as can be seen from Table 4, the example window film has good antistatic resistance to exhibit good roll stability.

As shown in Table 1, Table 2, Table 3, and Table 4, the present invention provides a window film having a high pencil hardness on both the glass substrate and the adhesive layer. The present invention provides a window film having good optical properties such as light transmittance. The present invention provides a window film having good flexibility. The present invention provides a window film that exhibits good flexibility in its opposite direction. The present invention provides a window film having a low yellow index to prevent the window film from appearing yellow. The present invention provides a window film having a high pencil hardness. The present invention provides a window film which has high heat resistance to exhibit a lower yellow index change even after standing at a high temperature for a long period of time, and thus can be used in a display. The present invention provides a window film that has good antistatic properties to exhibit good roll stability.

It will be appreciated that various modifications, changes, and alterations and equivalents may be made without departing from the spirit and scope of the invention.

100‧‧‧ window film

110‧‧‧ grassroots

120‧‧‧Window coating

130‧‧‧Back coating

130a‧‧‧Back coating

140‧‧‧Binder layer

150‧‧‧Support layer

200‧‧‧ window film

300‧‧‧ window film

400‧‧‧ window film

500‧‧‧ window film

600‧‧‧Flexible display

610‧‧‧lower substrate

610a‧‧‧gate electrode

610b‧‧‧ circuit part

611‧‧‧gate insulation

612‧‧‧Semiconductor layer

613a‧‧‧Source electrode

613b‧‧‧汲electrode

616‧‧‧film transistor

614‧‧ ‧ flattening layer

615‧‧‧Organic Luminescent Diodes

615a‧‧‧first electrode

615b‧‧‧Organic light-emitting layer

615c‧‧‧second electrode

617‧‧‧Insulation

618‧‧‧Protective layer

650a‧‧‧ display unit

650b‧‧‧ display unit

660‧‧‧Binder layer

670‧‧‧Polar plate

680‧‧‧Touch screen panel

690‧‧‧Flexible window film

700‧‧‧Flexible display

800‧‧‧Flexible display

1 is a cross-sectional view of a window film in accordance with an embodiment of the present invention. 2 is a cross-sectional view of a window film in accordance with another embodiment of the present invention. 3 is a cross-sectional view of a window film in accordance with another embodiment of the present invention. 4 is a cross-sectional view of a window film in accordance with yet another embodiment of the present invention. Figure 5 is a cross-sectional view of a window film in accordance with yet another embodiment of the present invention. Figure 6 is a cross-sectional view of a flexible display in accordance with one embodiment of the present invention. 7 is a cross-sectional view of one embodiment of a display unit of the flexible display of FIG. 6. Figure 8 is a cross-sectional view of a flexible display in accordance with another embodiment of the present invention. 9 is a cross-sectional view of a flexible display in accordance with another embodiment of the present invention.

Claims (28)

A window film comprising: a base layer; a window coating formed on one surface of the base layer; and a back coating formed on the other surface of the base layer, wherein the window coating is used for window coating Forming the composition, the composition comprising a terpene resin, and wherein the window film has an elastic modulus of 1,000 MPa or more on the back coat layer and 6H or high on the adhesive layer Pencil hardness at 6H. The window film of claim 1, wherein the window film has a pencil hardness of 6H or higher. The window film of claim 1, wherein the window film has a radius of curvature of a pressing direction of 10.0 mm or less and a radius of curvature of a stretching direction of 20.0 mm or less. The window film of claim 1, wherein the window film has a Martens hardness of 50 Newtons/mm to 200 Newtons/mm on the back coating. The window film of claim 1, wherein the window coating has a thickness of from 5 micrometers to 150 micrometers. The window film of claim 1, wherein the back coat layer has a thickness of from 1 micron to 100 microns. The window film of claim 1, wherein the adhesive layer has a storage modulus of 10 kPa to 50 kPa at 25 °C. The window film of claim 1, further comprising: an adhesive layer formed on a lower surface of the back coat layer. The window film of claim 1, further comprising: at least one of a binder layer and a support layer. The window film of claim 9, wherein the adhesive layer included in the window film has a thickness of from 10 micrometers to 100 micrometers. The window film of claim 9, wherein the support layer is a film formed of the same resin as the resin of the base layer. The window film of claim 1, wherein the window coating is formed directly on one surface of the base layer and the back coating layer is formed directly on the other surface of the base layer. The window film of claim 1, further comprising: a binder layer formed between the base layer and the back coat layer. The window film of claim 1, further comprising: a stack of a binder layer and a support layer formed between the base layer and the back coat layer. The window film of claim 1, wherein at least one of the base layer, the window coating, and the back coat layer comprises a dye having a maximum absorption wavelength of from 500 nm to 650 nm. The window film of claim 15, wherein the dye has a maximum absorption wavelength of from 550 nm to 620 nm. The window film of claim 15, wherein the dye comprises cyanine, porphyrin, arylmethane, aryl phthalocyanine, imine, oxonium, azo, xanthene, merocyanine, and At least one of vanadium dyes. The window film of claim 15, wherein the dye is contained in the back coat layer, and the dye is present in an amount of 0.001% by weight to 15% by weight in terms of solid content. The composition of the back coating. The window film of claim 15, wherein the dye is contained in the back coat layer, and the back coat layer is formed of a composition for a back coat layer, the back coat layer The composition includes the dye, a UV curable group-containing resin, a crosslinking agent, and an initiator. The window film according to claim 19, wherein the UV curable group-containing resin comprises a (meth)acrylic resin having a UV curable group and a siloxane resin having a UV curable group. At least one of them. The window film of claim 15, wherein the back coat layer has a thickness of 100 nm or less. The window film of claim 15, wherein the dye is contained in the back coat layer, and the back coat layer further comprises at least one of an antioxidant and an antistatic agent. The window film of claim 15, wherein the base layer is composed of a polyester resin, a polycarbonate resin, a poly(meth)acrylate resin, a polystyrene resin, a polyamide resin, and a polyimine. At least one of the resins is formed. The window film of claim 15, further comprising: an adhesive layer formed on a lower surface of the back coat layer. The window film of claim 15, wherein the window film has a yellow index of from -2.5 to 3.5. The window film of claim 15, wherein the window film has a b* value of -2.5 to 2.5. The window film of claim 15, wherein the window coating is directly formed on one surface of the base layer, and the back coating layer is directly formed on the other surface of the base layer, The dye is contained in the back coat layer, and the base layer includes a film of a polyimide film. A flexible display comprising the window film of any one of clauses 1 to 27 of the patent application.