KR20170026076A - Window film and display apparatus comprising the same - Google Patents

Abstract

Provided are a window film and a display apparatus comprising the same. The window film comprises: a substrate layer; a window coating layer formed on one surface of the substrate layer; and a back coating layer formed on the other surface of the substrate layer. The window coating layer is formed with a composition of a window coating layer having a silicon-based resin. Moreover, at least one of the substrate layer, the window coating layer, and the back coating layer has a dye of which a maximum absorption wavelength is 500-650 nm.

Description

FIELD OF THE INVENTION The present invention relates to a window film,

The present invention relates to a window film and a display device including the window film.

The window film is located at the outermost portion of the optical display device. The window film comprises a substrate layer and a window coating layer formed on the substrate layer. Therefore, the window film should have good transparency and pencil hardness. The window film includes a base layer and a coating layer formed of a curable resin. The window film may have a yellowing degree according to the base layer and / or the curing resin, so that yellow can be visually recognized, and when processed at a high temperature for a long time, the yellowing degree can be increased. In recent years, a flexible display device having flexibility capable of being folded and unfolded while replacing a glass substrate or a hardened substrate with a film in a display device has been developed. Window films should also be flexible. If the flexibility of the window film is low due to its low radius of curvature in both directions, the possibility of using the window film may increase.

The background art of the present invention is disclosed in Korean Patent Publication No. 2011-0087497.

A problem to be solved by the present invention is to provide a window film which is low in yellowness so that yellow can not be seen, has good optical properties, and has high pencil hardness.

Another object of the present invention is to provide a window film having good heat resistance and flexibility.

The window film of the present invention comprises a base layer, a window coating layer formed on one side of the base layer, and a back coating layer formed on the other side of the base layer, wherein the window coating layer is a composition for a window coating layer comprising a silicone resin And at least one of the substrate layer, the window coating layer, and the back coating layer may include a dye having a maximum absorption wavelength of 500 nm to 650 nm.

The display device of the present invention may include the window film.

The present invention provides a window film which is low in yellowness so that yellow is not visible, has good optical properties and has high pencil hardness.

The present invention provides a window film having excellent heat resistance and flexibility.

1 is a cross-sectional view of a window film according to an embodiment of the present invention.
2 is a cross-sectional view of a window film according to another embodiment of the present invention.
3 is a cross-sectional view of a flexible display device according to an embodiment of the present invention.
4 is a cross-sectional view according to an embodiment of the display unit of FIG.
5 is a cross-sectional view of a flexible display device according to another embodiment of the present invention.
6 is a cross-sectional view of a flexible display device according to another embodiment of the present invention.

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and the same names are used for the same or similar components throughout the specification.

The terms "upper" and "lower" in this specification are defined with reference to the drawings, wherein "upper" may be changed to "lower", "lower" What is referred to as "on" may include not only superposition, but also intervening other structures in the middle. On the other hand, what is referred to as "directly on" or "directly above"

As used herein, "UV curable group" means an epoxy group; (Meth) acrylate groups; (Meth) acrylamide groups; Vinyl group; Alicyclic epoxy group; Glycidoxin timing; An oxetane group; Means a C1 to C6 alkyl group or a C5 to C10 cycloalkyl group having an epoxy group, (meth) acrylate group, (meth) acrylamide group, vinyl group, alicyclic epoxy group, glycidoxy group or oxetane group. "Ec" represents a (3,4-epoxycyclohexyl) ethyl group, "Gp" represents a 3-glycidoxypropyl group, "Op" represents a cycloalkyl group of 3 Oxetanylpropyl group, "Me" is a methyl group, and "Et" is an ethyl group.

As used herein, "(meth) acrylic" means acrylic and / or methacrylic, and "substituted" means that at least one hydrogen atom in the functional group is a hydroxyl group, an unsubstituted C1 to C10 alkyl group, C10 alkoxy group, C3 to C10 cycloalkyl group, C6 to C20 aryl group, C7 to C20 arylalkyl group, benzophenone group, C6 to C20 aryl group substituted with C1 to C10 alkyl group, or C1 to C10 Means a C1 to C10 alkyl group substituted with an alkoxy group and "halogen " means fluorine, chlorine, iodine or bromine.

The "yellow index" of the window film in the present specification is measured using a color difference meter (CM-3600d, Konica Minolta) at 2 DEG (angle between the window coating layer and the light source) yellow index Measured 1925 [Recal] value. In the present specification, the "yellowness degree" of the base layer is measured in the same manner as the yellow color of the window film.

In the present specification, "b ^* " is measured using a chromatic meter (CM-3600d, Konica Minolta) at 2 DEG (angle between the window coating layer and the light source) using a D65 light source for the window film.

Hereinafter, 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 according to an embodiment of the present invention.

1, a window film 100 according to an exemplary embodiment of the present invention may include a base layer 110, a window coating layer 120, and a back coating layer 130, and may include a base layer 110, a window coating layer 120 And the back coating layer 130 may include a dye (not shown in FIG. 1). A window film comprising a non-glass plastic substrate layer and a window coating layer formed of a curable resin may have a high yellowness and thus may be visibly yellowish on the front and / or sides. However, since the window film 100 according to the present embodiment includes a dye, the yellowness is low so that the yellow can not be seen. Specifically, the window film 100 may have a yellowness value of -2.5 to 3.5, more specifically -1.5 to 1.5. Within this range, the yellow film may not be visible even when viewed from the front and / or side of the window film. And, the window film 100 according to this embodiment can have a b ^{* of} from -2.5 to 2.5, more specifically from -1.5 to 1.5, more specifically from -0.5 to 1.5, by including a dye. Within this range, the yellow film may not be visible even when viewed from the front and / or side of the window film.

In one embodiment, the dye may be included in the back coating layer 130. Therefore, the window film 100 according to the present embodiment has a low yellowness of the window film 100 without lowering the optical characteristics of the substrate layer 110, the window coating layer 120, and the window film 100, The transparency is good and the yellow is not visible. In addition, since the window coating layer 120 of the window film according to the present embodiment does not contain a dye, the degree of crosslinking of the window coating layer 120 is high, so that the pencil hardness can be high.

The base layer 110 can support the window film 100 and increase the mechanical strength of the window film 100. [ The substrate layer 110 may be a non-flexible film, but it is also possible to improve the flexibility of the window film 100 with a flexible film. The base layer 110 may have a yellowness value of 1 to 9. In particular, the window film 100 including the substrate layer 110 having a yellowness value of 3 or more may have a low yellowness of the window film 100 due to the back coating layer 130 including the dye. The base layer 110 may be formed of an optically transparent resin. Specifically, the resin is selected from the group consisting of a polyester resin including polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polybutylene naphthalate and the like, polycarbonate resin, poly (meth) acrylate including polymethylmethacrylate and the like A resin, a polystyrene resin, a polyamide resin, and a polyimide resin. The base layer 110 may have a thickness of 10 占 퐉 to 150 占 퐉, specifically 30 占 퐉 to 100 占 퐉, more specifically, 40 占 퐉 to 90 占 퐉. It can be used in the window film in the above range.

In one embodiment, the substrate layer may comprise a film formed of a polyimide resin. Therefore, the base layer 110 has high heat resistance, and the heat resistance of the window film 100 can be increased. The substrate layer formed of the polyimide resin has a high yellowness of 5 or more, but the window film 100 of the present embodiment may contain a dye to lower the yellowness of the window film 100 as a whole.

The window coating layer 120 is formed on one side of the base layer 110 to secure the optical characteristics of the window film 100 such as transmittance or haze and to increase the pencil hardness and flexibility of the window film 100, It can be used not only for a display device but also for a flexible display device. The window coating layer 120 may be formed directly on the substrate layer 110. The "directly formed" means that no adhesive layer or the like is interposed between the window coating layer 120 and the substrate layer 110. The thickness of the window coating layer 120 may be 5 占 퐉 to 150 占 퐉, specifically, 20 占 퐉 to 100 占 퐉, more specifically, 30 占 퐉 to 80 占 퐉. Within this range, flexibility of the window film may be good.

The window coating layer 120 may be formed of a composition for a window coating layer containing a silicone resin. Therefore, the composition for the window coating layer can realize a window film having high pencil hardness and excellent flexibility. The composition for the window coating layer may comprise a silicone-based resin, a curable monomer and an initiator. Hereinafter, the composition for the window coating layer will be described in detail.

The silicone resin forms a matrix of the window coating layer 120 and can increase the flexibility and the pencil hardness of the window film 100. The silicone-based resin may include a siloxane resin having a UV-curable group. The siloxane resin having a UV-curable group may include a siloxane resin represented by the following formula:

≪ Formula 1 >

(R ¹ SiO _3/2 ) _x (R ² SiO _3/2 ) _y (R ³ R ⁴ SiO _2/2 ) _z

Wherein R ¹ and R ² are independently a UV-curable group, R ¹ and R ² are different from each other, and R ³ and R ⁴ are each independently hydrogen, a UV-curable group, an unsubstituted or substituted C1 to C20 0 < y < 1, 0? Z < 1, and x + y + z = 1.

R ¹ and R ² are each independently a C1 to C6 alkyl group or a C5 to C10 cycloalkyl group having an alicyclic epoxy group, a glycidoxy group or an oxetane group, more specifically a (3,4- Epoxycyclohexyl) methyl group, (3,4-epoxycyclohexyl) ethyl group, (3,4-epoxycyclohexyl) ethyl group, (3,4-epoxycyclohexyl) propyl) group, a 3-glycidoxypropyl group, 3-oxetanylethyl group, 3-oxetanylethyl group, 3-oxetanylpropyl group and the like can be mentioned. R ³ and R ⁴ are each independently selected from a C1 to C6 alkyl group or a C5 to C10 cycloalkyl group having an alicyclic epoxy group, a glycidoxy group, or an oxetane group, and which provides crosslinking and flexibility to the window coating layer 120, (C1-C10) alkyl group, more preferably an unsubstituted or substituted C1-C10 alkyl group, more specifically a (3,4-epoxycyclohexyl) methyl group, Propyl group, isopropyl group, methyl group or ethyl group.

In one embodiment, the siloxane resin having a UV-curable group may be a siloxane resin represented by any of the following formulas (1-1) to (1-3):

&Lt; Formula 1-1 >

R ¹ SiO _3/2

(1-2)

(R ¹ SiO _3/2 ) _x (R ² SiO _3/2 ) _y

<Formula 1-3>

(R ¹ SiO _3/2 ) _x (R ³ R ⁴ SiO _2/2 ) _z

R ¹ , R ² , R ³ and R ⁴ are as defined in Formula 1 and 0 <x <1, 0 <y <1, 0 <z <1, x + y = 1, and x + z = 1. Specifically, 0.20? X? 0.999, 0.001? Y? 0.80, and 0.001? Z? 0.80 can be satisfied, and specifically 0.20? X? 0.99, 0.01? Y? 0.80, Specifically, 0.50? X? 0.99, 0.01? Y? 0.50, 0.01? Z? 0.50, more specifically 0.90? X? 0.97, 0.03? Y? 0.10, and 0.03? Z? In this range, the pencil hardness and flexibility of the window film can be good. Specifically, the siloxane resins may include one or more of the siloxane resin with a T unit represented by T a siloxane resin, GpSiO _3/2 units represented by EcSiO _3/2. The siloxane resin may be a siloxane resin containing (EcSiO _3/2 ) _{x (} GpSiO _3/2 ) _y (0 <x <1, 0 <y <1, x + y = 1). In addition, the siloxane resin may include, but is not limited to, any one of the following formulas (1-3A) to (1-3L);

<Formula 1-3A>

_{(EcSiO 3/2) x ((Me} ) 2 SiO 2/2) z

<Formula 1-3B>

(EcSiO3 / ₂ ) _x (MeEtSiO2 _{/ 2} ) _z

<Formula 1-3C>

(GpSiO _3/2 ) _x ((Me) ₂ SiO _2/2 ) _z

<Formula 1-3D>

(GpSiO _3/2 ) _x (MeEtSiO _2/2 ) _z

<Formula 1-3E>

(OpSiO _3/2 ) _x ((Me) ₂ SiO _2/2 ) _z

<Formula 1-3F>

(OpSiO _3/2 ) _x (MeEtSiO _2/2 ) _z

<Formula 1-3G>

(EcSiO3 / ₂ ) _x (EcMeSiO2 _{/ 2} ) _z

<Formula 1-3H>

(EcSiO3 / ₂ ) _x (GpMeSiO2 _{/ 2} ) _z

<Formula 1-3I>

(GpSiO _3/2 ) _x (EcMeSiO _2/2 ) _z

<Formula 1-3J>

(GpSiO _3/2 ) _x (GpMeSiO _2/2 ) _z

<Formula 1-3K>

(OpSiO _3/2 ) _x (EcMeSiO _2/2 ) _z

<Formula 1-3L>

(OpSiO _3/2 ) _x (GpMeSiO _2/2 ) _z

(0 <x <1, 0 <z <1, x + z = 1 in the above formulas 1-3A to 1-3L).

The siloxane resin having a UV-curable group may have a weight average molecular weight of 1,000 to 15,000. The siloxane resin having a UV-curable group may have a polydispersity index (PDI) of 1.0 to 3.0. The pencil hardness and transparency can be increased through dense crosslinking of the siloxane resin network in the weight average molecular weight and polydispersity range.

A siloxane resin having a UV-curing of the formula (1) R ¹ SiO _3/2 alkoxysilane alone to provide a, or R ¹ SiO _3/2 alkoxysilane and R to provide _² SiO _^3/2 alkoxysilane, R ³ to provide a R ⁴ SiO _2/2 And hydrolysis and condensation reaction of a monomer mixture containing at least one of alkoxysilanes. Hydrolysis and condensation reactions are commonly known to those skilled in the art. Specifically, the hydrolysis and condensation reaction may be carried out at room temperature for 12 hours to 7 days, and may be carried out at 60 to 100 ° C for 2 to 72 hours to promote the reaction, but the present invention is not limited thereto. The solvent is not particularly limited and may specifically include at least one of water, methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol and methoxypropanol. The hydrolysis and condensation reaction may further comprise a catalyst for controlling the reaction rate. The catalyst may be an acid catalyst such as hydrochloric acid, acetic acid, hydrogen fluoride, nitric acid, sulfuric acid, chlorosulfonic acid, or iodic acid; Basic catalysts such as ammonia, potassium hydroxide, sodium hydroxide, barium hydroxide and imidazole; Amberite IRA-400, IRA-67, and the like can be used.

The siloxane resin having a UV-curable group may include, but is not limited to, a compound represented by the following formula (2) alone or a siloxane resin prepared by a hydrolysis and condensation reaction of a mixture of a compound represented by the following formula :

(2)

R ⁵ -R ⁸ -Si (OR ⁶ ) _m (R ⁷ ) _3-m

(Wherein R ⁵ is a UV curable group, R ⁶ is a C1 to C10 alkyl group, R ⁷ is a C1 to C10 alkyl group, a C3 to C20 cycloalkyl group, a C6 to C20 aryl group, or a C7 to C20 R ⁸ is a single bond or an alkylene group having from 1 to 10 carbon atoms, and m is an integer of from 1 to 3,

(3)

Si (OR ⁹ ) _n (R ¹⁰ ) _{4 -n}

(Wherein R ⁹ is an alkyl group having 1 to 10 carbon atoms, R ¹⁰ is an unsubstituted C1 to C20 alkyl group, a C3 to C8 cycloalkyl group, a C3 to C20 alkenyl group, a C2 to C20 alkynyl group, a C6 A C1 to C10 alkyl group, a C1 to C10 alkyl group, a C1 to C10 ether group, a carbonyl group, a carboxylic acid group and a nitro group, each of which has from 1 to 20 carbon atoms, 1 to 4).

"Single bond" in formula (2) means that R ⁵ and Si are directly connected without R ⁸ in formula (2). Specifically, the compound of formula (2) is preferably selected from 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyl tri (Meth) acryloxypropyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane, (meth) acryloxypropyltrimethoxysilane, (meth) acryloyloxypropyltriethoxysilane ), Vinyltrimethoxysilane, but is not limited thereto.

Specifically, the compound of formula (III) may be used in combination with at least one compound selected from the group consisting of tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, Dimethyldimethoxysilane, dimethyldiethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, diphenyldimethoxysilane, diphenyldimethoxysilane, Triphenylmethoxysilane, triphenylethoxysilane, ethyltriethoxysilane, propylethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, triphenylmethoxysilane, , 3-aminopropyltriethoxysilane, chloropropyltrimethoxysilane (ch chloropropyltrimethoxysilane, chloropropyltrimethoxysilane, and chloropropyltriethoxysilane.

The curable monomer is crosslinked with the silicone resin to increase the pencil hardness of the window film and control the viscosity of the composition for the window coating layer to facilitate the 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 group-containing monomer may include a photocurable monomer containing at least one epoxy group. The epoxy group may include an epoxy group, an organic group containing an epoxy group, for example, a glycidyl group. The epoxy monomer may include 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 at least one epoxy group in an alicyclic ring of C3 to C10, for example, 3,4-epoxycyclohexylmethyl-3 ', 4'-epoxycyclohexanecarboxylate (3,4- epoxycyclohexylmethyl-3 ', 4'-epoxycyclohexane carboxylate), but are not limited thereto. Aromatic epoxy monomers include bisphenol A, bisphenol F, and phenol novolac, cresol novolac, glycidyl ether of triphenylmethane, , Tetraglycidyl methyleneaniline, and the like. The aliphatic epoxy monomer may be 1,4-butanediol glycidyl ether, 1,6-hexanediol diglycidyl ether, or the like. The hydrogenated epoxy monomer may be a hydrogenated bisphenol A diglycidyl ether or the like obtained by hydrogenating an aromatic epoxy monomer. The acid anhydride group-containing monomer may be selected from the group consisting of phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylnadic anhydride, chlorendic anhydride, , Pyromellitic anhydride, and the like. Oxetane group-containing monomers include 3-methyloxetane, 2-methyloxetane, 3-oxetanol, 2-methyleneoxetane, 3 3-oxetanemethanethiol, 4- (3-methyloxetane-3-yl) benzonitrile, N- ( (2,2-dimethylpropyl) 3-methyl-3-oxetaneamine, N- (1,2-dimethylbutyl) -3-methyl 3-methyl-3-oxetaneamine, (3-ethyloxetane-3-yl) methyl methacrylate, N- methylmethacrylate, 3-ethyl-3-hydroxymethyl-oxetane, 2-ethyloxetane, xylenebisoxetane, 3- One of ethyl-3 - [[(3-ethyloxetan-3-yl) methoxy] methyl] oxetane Or more.

The initiator may cure the silicone resin and the curable monomer to form a window coating layer. The initiator may include at least one of a light-ion initiator, a cationic thermal polymerization initiator, and a photo radical initiator.

The Gwangyang ionic initiator generates cations by light irradiation to catalyze curing, and the Gwangyang ion initiator may include a conventional Gwangyang ion initiator. Gwangyang ionic initiator may include salts of cations and anions. Specific examples of the cation include diphenyliodonium, 4-methoxydiphenyliodonium, bis (4-methylphenyl) iodonium, and 4-methylphenyl [4 (4-methylphenyl) iodonium, bis (4-tert-butylphenyl) iodonium, iodonium and bis (dodecylphenyl) iodonium; diphenyl iodonium, triphenylsulfonium, diphenyl-3-iodophenylsulfonium iodonium, thiophenoxyphenylsulfonium), bis [4- (diphenylsulfonyl) phenyl] sulfide, bis [4- (di (4- Phenyl] sulfo) -phenyl] sulfide), (? -5-2,4-cyclopentadiene) -phenyl] sulfide (bis [4- Yl) [(1,2,3,4,5,6-eta) - (1-methylethyl) benzene] iron (1 + (1,2,3,4,5,6-.eta.) - (1- methylethyl) benzene] iron (1+)). Specific examples of the anion include tetrafluoroborate (BF ₄ ^- ), hexafluoroborate (PF ₆ ^- ), hexafluoroantimonate (SbF ₆ ^- ), hexafluoroarsenate hexafluoroarsenate, AsF ₆ ^- ), and hexachloroantimonate (SbCl ₆ ^- ). Cationic thermal polymerization initiators include 3-methyl-2 butenyltetramethylenesulfonium, ytterbium, samarium, erbium, dysprosium, lanthanum lanthanum, tetrabutylphosphonium, ethyltriphenylphosphonium bromide salt, benzyldimethylamine, dimethylaminomethylphenol, triethanolamine, Nn- N-butylimidazole, 2-ethyl-4-methylimidazole, and the like. Specific examples of the anion include tetrafluoroborate (BF ₄ ^- ), hexafluorophosphate (PF ₆ ^- ), hexafluoroantimonate (SbF ₆ ^- ), hexafluoroarsenate (AsF ₆ ^- And chlorantimonate (SbCl ₆ ^- ). The photo-radical initiator can generate a radical by light irradiation to catalyze the curing, and the photo-radical initiator can include a conventional photo-radical initiator. Specifically, the photo radical initiator may be at least one selected from the group consisting of phosphorous, triazine, acetophenone, benzophenone, thioxanthone, benzoin, oxime, , And a phenyl ketone system.

The composition for the window coating layer may have a viscosity of 1 cps to 3000 cps at 25 占 폚. In the above range, the composition for a window coating layer is excellent in coatability and coating property, and a window coating layer can be easily formed.

The composition for the window coating layer may comprise from 65% to 95% by weight of a solids based silicone resin, from 4% to 30% by weight of a curable monomer, and from 0.1% to 10% by weight of an initiator. In this range, the flexibility of the window coating layer and the pencil hardness can be increased. As used herein, the term "solids basis" refers to the entirety excluding the solvent.

The composition for the window coating layer comprises 100 parts by weight of the solid base silicone resin, 1 part by weight to 20 parts by weight, specifically 1 part by weight to 15 parts by weight of the curable monomer, 0.1 part by weight to 20 parts by weight, specifically 0.5 part by weight to 10 parts by weight can do. In this range, the flexibility of the window coating layer and the pencil hardness can be increased.

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

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

The composition for the window coating layer may further comprise nanoparticles. Nanoparticles can increase the pencil hardness of window films. The nanoparticles may include, but are not limited to, one or more of silica, aluminum oxide, zirconium oxide, and titanium oxide. The nanoparticles may also be surface treated with a silicone compound. Nanoparticles are not limited in shape and size. Specifically, the nanoparticles may include spherical, plate-like, amorphous, etc. particles. The nanoparticles may have an average particle size of 1 nm to 200 nm, specifically 5 nm to 50 nm, more specifically 10 nm to 30 nm. The pencil hardness of the window film can be increased without affecting the surface roughness and transparency of the window coating layer in the above range. The nano-particles may be contained in an amount of 0.1 to 100 parts by weight, specifically 1 to 80 parts by weight, based on 100 parts by weight of the solid-based silicone resin. In the above range, the pencil hardness of the window film can be increased and the surface roughness of the window coating layer can be lowered.

The back coating layer 130 may be formed on the other surface of the base layer 110 to support the window film 100. FIG. 1 shows a case where a back coating layer 130 is formed directly on a base layer 110. This "directly formed" means that no adhesive layer is interposed between the substrate layer 110 and the back coat layer 130. [ The back coating layer 130 may include a dye. The back coating layer 130 includes a dye to lower the yellowing degree of the window film 100 without lowering the optical characteristics of the base layer 110, the window coating layer 120 and the window film 100, As shown in FIG. The back coating layer 130 may be formed of a composition for a back coating layer containing a dye, a resin having a UV curable group, a crosslinking agent, and an initiator. Hereinafter, the composition for the back coat layer will be described.

The dye may be contained in the back coating layer 130 at an arbitrary position. For example, the dye may be dispersed throughout the back coating layer 130, or may be contained in a single layer or a multilayer shape. The dyes having a maximum absorption wavelength of 500 nm to 650 nm, specifically 550 nm to 620 nm, may be used. Within this range, the yellowness of the window film can be lowered without lowering the optical properties of the base layer, window coating layer and window film. Herein, the term "maximum absorption wavelength" refers to a wavelength indicating the maximum absorption peak, that is, a wavelength giving the maximum absorbance in an absorbance curve according to the wavelength. The dye may include one or more of metal dyes including metal, non-metal dyes not including metal, having a maximum absorption wavelength of 500 nm to 650 nm. The metal dye may include a dye having a maximum absorption wavelength of 500 nm to 650 nm, specifically, from 550 nm to 620 nm and containing a metal. Specifically, the metal dye may include at least one of metal complexes such as vanadium, chromium, manganese, and the like, but is not limited thereto. For example, the metal dye can be a heterocyclic vanadium complex. The non-metallic dye may include a dye having a maximum absorption wavelength of 500 nm to 650 nm, specifically, 550 nm to 620 nm and not containing a metal. Specifically, the non-metallic dyes include porphyrine-based, arylmethane-based, squarylium-based, azomethine-based pigments including cyanine based, tetraazaporphyrine, But are not limited to, one or more of an oxonol system, an azo system, an arylidene system, a xanthene system, and a merocyanine system, . The dye may be contained in an amount of 0.001 to 15% by weight, specifically 0.01 to 5% by weight, more specifically 0.1 to 3% by weight, based on the solid content of the composition for the back coat layer. In the above range, the yellow of the window film is not visually observed, and the decrease of the transparency of the window film can be prevented.

The resin having a UV curable group may be cured with a crosslinking agent to form a matrix of the back coating layer 130. Specifically, the resin having a UV curable group may include at least one of (meth) acrylic resin having a UV curable group, siloxane resin having a UV curable group. The (meth) acrylic resin having a UV-curable group may include monofunctional to hexafunctional (meth) acrylic resins. The (meth) acrylic resin having a UV-curable group is preferably a (meth) acrylic ester having an alkyl group, a (meth) acrylic acid ester having a hydroxyl group, a (meth) acrylic monomer having a carboxylic acid group, a (meth) acrylate having an alicyclic group, (Meth) acrylic acid ester having an aromatic group, a (meth) acrylic acid ester having an aromatic group, and the like. Specifically, the (meth) acrylic acid ester having an alkyl group may be a (meth) acrylic acid ester having an unsubstituted C1 to C10 alkyl group. The (meth) acrylic acid ester having a hydroxyl group may be a (meth) acrylic acid ester having a C1 to C10 alkyl group having at least one hydroxyl group. The (meth) acrylic monomer having a carboxylic acid group may be (meth) acrylic acid. The (meth) acrylic acid ester having an alicyclic group may be a (meth) acrylic acid ester having a C5 to C10 alicyclic group. The (meth) acrylic acid ester having a heteroalicyclic group may be a (meth) acrylic acid ester having a C3 to C10 heteroalicyclic group having nitrogen, oxygen or sulfur. The (meth) acrylic acid ester having an aromatic group may be a (meth) acrylic acid ester having a C6 to C20 aryl group or a C7 to C20 arylalkyl group. The (meth) acrylic resin having a UV-curable group may contain a bifunctional or hexafunctional or multifunctional urethane (meth) acrylic resin specifically. The urethane (meth) acrylic resin may be a urethane (meth) acrylic resin prepared by a conventional urethane synthesis reaction of at least one polyol, at least one polyisocyanate compound, and at least one hydroxyl group-containing (meth) acrylate. At this time, the polyol may include 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 having two or more isocyanate groups, and examples thereof include tolylene diisocyanate, xylene diisocyanate, naphthalene diisocyanate, phenylene diisocyanate, diphenylmethane diisocyanate, biphenyl diisocyanate, hexane diisocyanate, isophorone diisocyanate, Or adducts thereof. The (meth) acrylate containing a hydroxyl group is a C1 to C10 (meth) acrylic acid ester having at least one hydroxyl group, specifically 2-hydroxyethyl (meth) acrylate, 1,4-butanediol (meth) . Specifically, the urethane (meth) acrylic resin may include a six-functional aliphatic urethane (meth) acrylate resin. The siloxane resin having a UV-curable group may include the siloxane resin represented by the above formula (1). The resin having a UV-curable group may have a weight average molecular weight of 500 to 8,000, specifically 1,000 to 5,000. Within this range, the pencil hardness of the window film may be high and flexibility may be good.

The crosslinking agent may be cured with a resin having a UV curable group to form a matrix of the back coating layer and to increase the pencil hardness of the window film. Specifically, the cross-linking agent may include at least one of a bifunctional to hexafunctional (meth) acrylic monomer, an epoxy monomer described above, an acid anhydride monomer described above, and an oxetane monomer described above. The (meth) acrylic monomer having two or more functional groups may be 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, dicyclopentanyl di (meth) acrylate, caprolactone modified dicyclopentenyl di (meth) Acrylate, di (meth) acryloxyethyl isocyanurate, allyl cyclohexyl di (meth) acrylate, tricyclodecane dimethanol (meth) acrylate, dimethylol dicyclopentanedi (Meth) acrylate, neopentyl glycol-modified trimethylpropane di (meth) acrylate, adamantane (meth) acrylate, (meth) acrylate including adamantane di (meth) acrylate or 9,9-bis [4- (2-acryloyloxyethoxy) phenyl] fluorene and the like; (Meth) acrylate, dipentaerythritol tri (meth) acrylate, propionic acid modified dipentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propylene oxide modified trimethylol (Meth) acrylate, propoxylated trimethylolpropane tri (meth) acrylate, propoxylated trimethylolpropane tri (meth) acrylate, trifunctional urethane (Meth) acrylates including trifunctional (meth) acrylates alkoxylated with C1 to C5 alkoxy groups such as methoxy (meth) acrylate (e.g., ethoxy, propoxy or butoxy groups); Tetrafunctional (meth) acrylates such as diglycerin tetra (meth) acrylate or pentaerythritol tetra (meth) acrylate; Pentafunctional (meth) acrylates such as dipentaerythritol penta (meth) acrylate; And reaction products of dipentaerythritol hexa (meth) acrylate, caprolactone modified dipentaerythritol hexa (meth) acrylate or urethane (meth) acrylate (e.g., isocyanate monomer and trimethylolpropane tri (meth) acrylate) (Meth) acrylate of hexafunctional (meth) acrylate.

The crosslinking agent is used in an amount of 1 part by weight to 70 parts by weight, specifically 5 parts by weight to 50 parts by weight, more specifically 10 parts by weight to 50 parts by weight, even more preferably 15 parts by weight to 40 parts by weight, based on 100 parts by weight of the resin having a UV- By weight. In this range, the pencil hardness of the window film can be increased.

The initiator cures the resin having the UV curable group and the cross-linking agent, and may include at least one of the above-described cationic ion initiator, cationic thermal polymerization initiator, and photo radical initiator. The initiator may be included in an amount of 0.1 part by weight to 10 parts by weight, specifically 1 part by weight to 7 parts by weight, based on 100 parts by weight of the resin having a UV-curable group. Within the above range, the composition for the back coating layer can be sufficiently cured, and the transparency of the window film due to the remaining amount of the initiator can be prevented from deteriorating.

The composition for the back coat layer may further comprise the nanoparticles. The nanoparticles may be contained in an amount of 0.1 part by weight to 100 parts by weight, specifically 1 part by weight to 80 parts by weight, based on 100 parts by weight of the resin having the UV-curable group in the composition for the back coating layer based on the solid content. Within the above range, the surface roughness of the back coating layer can be lowered, and the pencil hardness of the window film can be increased.

The composition for the back coat layer may further comprise a solvent such as methyl ethyl ketone.

The composition for the back coat layer may further comprise conventional additives. The additive may include at least one of a UV absorber, a reaction inhibitor, an adhesion improver, a thixotropic agent, a conductivity-imparting agent, a colorant-adjusting agent, a stabilizer, an antistatic agent, an antioxidant and a leveling agent.

The back coating layer 130 may have a thickness of 5 mu m or less, specifically 300 nm or less, more specifically 100 nm or less, more specifically 60 nm to 80 nm, for example, 10 nm to 30 nm. Within this range, it can be used for window films, and flexibility can be good.

Hereinafter, 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 according to another embodiment of the present invention.

2, a window film 200 according to an exemplary embodiment of the present invention includes a window film 200 according to an embodiment of the present invention, except that an adhesive layer 140 is further formed on a lower surface of the back coating layer 130 100). &Lt; / RTI &gt; Hereinafter, the adhesive layer 140 will be described. In one embodiment, the dye may be included in the back coating layer 130.

The adhesive layer 140 is formed on the lower surface of the back coating layer 130 so that the window film 200 can be adhered directly on a polarizing plate, a conductive film, an organic light emitting device, or the like. The thickness of the adhesive layer 140 may be 10 占 퐉 to 100 占 퐉, specifically 20 占 퐉 to 80 占 퐉, more specifically 30 占 퐉 to 50 占 퐉. The adhesive layer 140 may be formed of a composition for a pressure-sensitive adhesive layer containing a (meth) acrylic adhesive resin and a curing agent. The (meth) acrylic adhesive resin may be a (meth) acrylic monomer having an alkyl group, a (meth) acrylic monomer having a hydroxyl group, a (meth) acrylic monomer having an alicyclic group, a (meth) acrylic monomer having a heterocyclic group, (Meth) acryl-based copolymer of a monomer mixture containing at least one of (meth) acrylic monomers.

The (meth) acrylic monomer having an alkyl group may include an unsubstituted (meth) acrylic acid ester having an alkyl group having 1 to 10 carbon atoms. The (meth) acrylic monomer having a hydroxyl group may include a (meth) acrylic acid ester having an alkyl group having 1 to 10 carbon atoms and having at least one hydroxyl group. The (meth) acrylic monomer having an alicyclic group may include a (meth) acrylic acid ester having an alicyclic group having 3 to 10 carbon atoms. The (meth) acrylic monomer having a hetero-alicyclic group may include a (meth) acrylic acid ester having a heteroalicyclic group having 3 to 10 carbon atoms having at least one of nitrogen, oxygen, or sulfur. The (meth) acrylic monomer having a carboxylic acid group may include (meth) acrylic acid and the like. The curing agent may include at least one of an isocyanate curing agent, an epoxy curing agent, an imide curing agent, and a metal chelating curing agent. The curing agents may be used alone or in combination of two or more. The curing agent may be contained in an amount of 0.1 to 10 parts by weight, specifically 0.1 to 1 part by weight, based on 100 parts by weight of the (meth) acrylic adhesive resin in the composition for a pressure-sensitive adhesive layer on a solid basis. The composition for a pressure-sensitive adhesive layer may further comprise a silane coupling agent. The silane coupling agent can realize the effect of further increasing the stickiness. As the silane coupling agent, one or more commonly known silane coupling agents may be used. Specifically, the silane coupling agent is a silane coupling agent having an epoxy structure such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4-epoxycyclohexyl) Silane compounds; Silane compounds containing polymerizable unsaturated groups such as vinyltrimethoxysilane, vinyltriethoxysilane, and (meth) acryloxypropyltrimethoxysilane; Aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) Containing silane compounds such as dimethoxysilane, and the like. The silane coupling agent may be contained in an amount of 0 to 10 parts by weight, specifically 0 to 1 part by weight, based on 100 parts by weight of the solid (meth) acrylic adhesive resin in the composition for a pressure-sensitive adhesive layer. Adhesive strength may be good in the above range.

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

The window film according to the present exemplary embodiment may further include an antioxidant in the back coating layer to improve the heat resistance so that the amount of change in the heat yellowing degree during the long time treatment at a high temperature is reduced. ). Specifically, the window film according to this embodiment can have a change in the heat resistance yellowing degree of the following formula (1) to 1.5 or less, specifically 1.0 or less, more specifically 0.1 to 1.0. Within this range, it is good in heat resistance and can be used in a display device:

<Formula 1>

Heat yellowing degree change amount = (YI '- YI)

(YI 'is the initial yellowness of the window film and YI' is the yellowness after leaving the window film at 80 DEG C for 1000 hours).

In the window film according to this embodiment, YI 'may be -0.5 to 3.5, specifically 0.5 to 2.0.

The antioxidant may include at least one of a phosphorus-based antioxidant such as a phenol-based antioxidant and a phosphite-based antioxidant, a thioether-based antioxidant, and an amine-based antioxidant. Specifically, the phenolic antioxidant is pentaerythritol tetrakis (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, octadecyl- hydroxyphenyl) propionate, N, N'-1,6-hexanediylbis [3,5-bis (1,1-dimethylethyl) -4- hydroxy] benzenepropanimide -hexanediylbis [3,5-bis (1,1-dimethylethyl) -4-hydroxy] benzenepropanamide, the phosphorus antioxidant is tris (2,4-ditert-butylphenyl) phosphite -butylphenyl) phosphite, bis (2,3-di-tert-butylphenyl) -ethyl-phosphite, bis , 2,4-ditertbutylphenyl) pentaerythritoldiphosphite), 2,2 ', 2 "-nitrilo [triethyl-tris [3,3', 5,5 '-Tetra-tert-butyl-1,1 '-Biphenyl-2,2'-diyl] phosphite (2,2', 2 "-nitrilo [triethyl-tris [3,3 ', 5,5'- tetra-tertbutyl- 2,2'-diyl phosphite], thioether-based antioxidants include didodecyl-3,3'-thiodipropionate, dioctadecyl 3,3'-thiodi Dioctadecyl 3,3'-thiodipropionate, and amine antioxidants may include styrenated diphenylamine, dioctyldiphenylamine, naphthylamine, and the like. The antioxidant may be included in an amount of 0.1 part by weight to 20 parts by weight, specifically 1 part by weight to 10 parts by weight, based on 100 parts by weight of the resin having a UV curable group. Within the above range, the heat resistance may be improved without affecting the dye.

The window film according to the embodiments of the present invention may have a pencil hardness of 6H or more, specifically 6H to 8H. In this range, a window film can be used for an optical display device. In the window film according to the embodiments of the present invention, the radius of curvature in the compression direction is 10.0 mm or less, specifically 0.1 mm to 5.0 mm, and the radius of curvature in the tensile direction is 20.0 mm or less, specifically 0.1 mm to 10.0 mm. Flexibility is good in the above range, so that it can be used as a flexible window film. The window film according to the embodiments of the present invention has a low compression radius curvature radius and a small tensile radius of curvature, and thus flexibility in both sides of the window film is good, so that it is possible to use the window film. The window film according to the embodiments of the present invention may have a transmittance of 88% or more, specifically 88% to 100% and a haze of 2% or less, specifically 0.1% to 2%, in the visible light region specifically at a wavelength of 400 nm to 800 nm. It is transparent in the above range and can be used as a window film. The window film according to embodiments of the present invention may have a thickness of 50 to 300 mu m. And can be used in an optical display device in the above range.

Hereinafter, a flexible display device according to an embodiment of the present invention will be described with reference to FIGS. 3 and 4. FIG. FIG. 3 is a cross-sectional view of a flexible display device according to an embodiment of the present invention, and FIG. 4 is a cross-sectional view of an exemplary embodiment of the display unit of FIG.

3, the flexible display device 300 according to an exemplary embodiment of the present invention includes a display portion 350a, an adhesive layer 360, a polarizing plate 370, a touch screen panel 380, a flexible window film 390 , And the flexible window film 390 may comprise a window film according to embodiments of the present invention.

The display portion 350a is for driving the flexible display device 300 and may include an optical element including an OLED, an LED, or an LCD element formed on the substrate and the substrate. 4 is a cross-sectional view according to an embodiment of the display unit of FIG. 4, the display portion 350a may include a lower substrate 310, a thin film transistor 316, an organic light emitting diode 315, a planarization layer 314, a protection layer 318, and an insulation layer 317 have.

The lower substrate 310 supports the display portion 350a and the lower substrate 310 may have a thin film transistor 316 and an organic light emitting diode 315 formed thereon. A flexible printed circuit board (FPCB) for driving the touch screen panel 380 may be formed on the lower substrate 310. The flexible printed circuit board may further include a timing controller for driving the organic light emitting diode array, a power supply unit, and the like.

The lower substrate 310 may include a substrate formed of a flexible resin. The lower substrate 310 may include a flexible substrate such as a silicone substrate, a polyimide substrate, a polycarbonate substrate, or a polyacrylate substrate, but is not limited thereto .

A plurality of pixel regions are defined by a plurality of driving wirings (not shown) and sensor wirings (not shown) crossing the display region of the lower substrate 310, and thin film transistors 316 and thin film transistors 316 And an organic light emitting diode (OLED) 315 connected to the organic light emitting diode array. In a non-display area of the lower substrate, a gate driver for applying an electrical signal to the driving wiring may be formed in the form of a gate in panel. The gate-in panel circuit portion may be formed on one side or both sides of the display region.

The thin film transistor 316 may be formed on the lower substrate 310 by controlling a current flowing through the semiconductor by applying an electric field perpendicular thereto. The thin film transistor 616 may include a gate electrode 310a, a gate insulating film 311, a semiconductor layer 312, a source electrode 313a, and a drain electrode 313b. The thin film transistor 316 includes an oxide thin film transistor using an oxide such as indium gallium zinc oxide (IGZO), ZnO, or TiO.sub.2 as the semiconductor layer 312, an organic thin film transistor using an organic material as a semiconductor layer, an amorphous silicon An amorphous silicon thin film transistor to be used, or a polycrystalline silicon thin film transistor using polycrystalline silicon as a semiconductor layer.

The planarization layer 314 may cover the thin film transistor 316 and the circuit portion 310b so that the top surface of the thin film transistor 316 and the circuit portion 310b may be planarized to form the organic light emitting diode 315. [ The planarization layer 614 may be formed of a spin-on-glass (SOG) film, a polyimide-based polymer, a polyacrylic polymer, or the like, but is not limited thereto.

The organic light emitting diode 315 emits light by self-emission, and may include a first electrode 315a, an organic light emitting layer 315b, and a second electrode 315c stacked in that order. The adjacent organic light emitting diodes may be separated through an insulating film 317. [ The organic light emitting diode 315 may include a bottom emission structure in which light generated in the organic emission layer 315b is emitted through the bottom substrate or a front emission structure in which light generated in the organic emission layer 315b is emitted through the top substrate have.

The passivation layer 318 may cover the organic light emitting diode 315 to protect the organic light emitting diode 315. The passivation layer 318 may be formed of an inorganic material such as SiOx, SiNx, SiC, SiON, SiONC, and aC (amorphous carbon) Methacrylate, epoxy-based polymer, imide-based polymer, and the like. Specifically, the protective layer 318 may include an encapsulation layer in which a layer formed of an inorganic material and a layer formed of an organic material are sequentially stacked one or more times.

3, the adhesive layer 360 is formed of a pressure-sensitive adhesive composition comprising a (meth) acrylate resin, a curing agent, an initiator, and a silane coupling agent to adhere the display portion 350a and the polarizing plate 370 .

The polarizing plate 30 can implement the display or enhance the contrast ratio of the display by realizing the polarization of the inner light or preventing the reflection of the outer light. The polarizing plate may be composed of a polarizer alone. Or the polarizing plate may include a polarizing film and a protective film formed on one or both sides of the polarizing film. Or the polarizing plate may include a polarizer and a protective coating layer formed on one or both sides of the polarizer. The polarizer, the protective film, and the protective coating layer may be conventional ones known to those skilled in the art.

The touch screen panel 380 senses a change in capacitance generated when a conductor such as a human body or a stylus touches, and generates an electrical signal. The display unit 350a can be driven by this signal. The touch screen panel 380 is formed by patterning a flexible conductive conductive material. The touch screen panel 380 may include a first sensor electrode and a second sensor electrode formed between the first sensor electrode and the first sensor electrode. have. The conductor for the touch screen panel 380 may include, but is not limited to, metal nanowires, conductive polymers, carbon nanotubes, and the like.

The window film 390 may be formed at the outermost portion of the flexible display device 300 to protect the display device.

3, an adhesive layer is further formed between the polarizing plate 370 and the touch screen panel 380 and / or between the touch screen panel 380 and the window film 390 to form a polarizing plate, a touch screen panel, Can be strengthened. The pressure-sensitive adhesive layer may be formed of a pressure-sensitive adhesive composition comprising a (meth) acrylate resin, a curing agent, an initiator, and a silane coupling agent. Further, although not shown in FIG. 3, a polarizing plate is further provided under the display unit 350a, so that polarized light can be realized.

Hereinafter, a flexible display device according to another embodiment of the present invention will be described with reference to FIG. 5 is a cross-sectional view of a flexible display device according to another embodiment of the present invention.

5, a flexible display device 400 according to another embodiment of the present invention includes a display portion 350a, a touch screen panel 380, a polarizing plate 370, and a flexible window film 390, The film 390 may comprise a window film according to embodiments of the present invention. Is substantially the same as the flexible display device according to the embodiment of the present invention, except that the touch screen panel 380 is directly formed on the display portion 350a. At this time, the touch screen panel 380 may be formed together with the display portion 350a. In this case, since the touch screen panel 380 is formed on the display unit 350a together with the display unit 350a, the thickness of the touch screen panel 380 can be thinner and brighter than that of the flexible display device according to an embodiment of the present invention. In this case, the touch screen panel 380 can be formed by deposition or the like, but is not limited thereto.

Although not shown in FIG. 5, between the display portion 350a and the touch screen panel 380 and / or between the touch screen panel 380 and the polarizer 370 and / or between the polarizer 370 and the window film 390 By further forming the adhesive layer, the mechanical strength of the display device can be increased. The pressure-sensitive adhesive layer may be formed of a pressure-sensitive adhesive composition comprising a (meth) acrylate resin, a curing agent, an initiator, and a silane coupling agent. Although not shown in FIG. 5, a polarizing plate is further provided under the display unit 350a to thereby guide polarized light to improve the display image.

Hereinafter, a flexible display device according to another embodiment of the present invention will be described with reference to FIG. 6 is a cross-sectional view of a flexible display device according to another embodiment of the present invention.

6, the flexible display device 500 according to another exemplary embodiment of the present invention includes a display portion 350b, an adhesive layer 360, and a flexible window film 390. The flexible window film 390 includes a flexible window film 390, May comprise a window film according to embodiments of the present invention. Is substantially the same as the flexible display device according to an embodiment of the present invention, except that only the display portion 350b is capable of driving the device and the polarizing plate and the touch screen panel are excluded.

The display portion 350b may include an LCD, an OLED, or an optical element including an LED element formed on the substrate, and the display portion 350b may further include a touch screen panel.

Although the flexible display device has been described above, the window films according to the present embodiments may be included in the non-flexible display device.

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

Manufacturing example  1: Composition for back coat layer

3.6 g of 6-functional urethane acrylate (ENTIS, UP118) as a UV curable acrylic resin, 1.2 g of trifunctional acrylic monomer trimethylolpropane triacrylate (ENTIS), 94 g of methyl ethyl ketone, a tetraazaporphyrin dyestuff (KCF Blue b, Kyungin Yang event, maximum absorption wavelength: 596 nm) were mixed and stirred for 30 minutes. To the resulting mixture was added 0.2 g of photopolymerization initiator Irgacure 184 (BASF) and further stirred for 30 minutes to prepare a composition for the back coat layer.

Manufacturing example  2 to Manufacturing example  5: Composition for back coat layer

A composition for a back coating layer was prepared in the same manner as in Preparation Example 1, except that the dyes shown in Table 1 were used instead of tetraazaporphyrin dyes (KCF Blue b, Kyungin Yang, maximum absorption wavelength: 596 nm).

Manufacturing example  6: Composition for back coat layer

3.6 g of 6-functional urethane acrylate (ENTIS, UP118) as a UV curable acrylic resin, 1.2 g of trifunctional acrylic monomer trimethylolpropane triacrylate (ENTIS), 94 g of methyl ethyl ketone, and tetraazaporphyrin dyes (KCF Blue b, glare amount occasion, maximum absorption wavelength: 596 nm) and 0.1 g of a phenolic antioxidant Irganox-1010 (BASF) were mixed and stirred for 30 minutes. To the resulting mixture was added 0.2 g of photopolymerization initiator Irgacure 184 (BASF) and further stirred for 30 minutes to prepare a composition for the back coat layer.

Manufacturing example  7 to Manufacturing example  10: Composition for back coat layer

A composition for a back coat layer was prepared in the same manner as in Preparation Example 6, except that the antioxidant shown in Table 2 was used in place of 0.1 g of the phenol antioxidant Irganox-1010.

Manufacturing example  11: window  Composition for coating layer

50 g of 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane (ShinEtsu, KBM-303) was placed in a 200 ml 3-neck flask. 0.5 mol% of KOH and 1.5 mol% of water were added to 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, and the mixture was stirred at 25 DEG C for 1 hour and then at 70 DEG C for 2 hours. The remaining solvent was removed by a vacuum distillation apparatus to prepare a silicone resin, and the solid content was adjusted to 90% by weight. The weight average molecular weight of the siloxane resin confirmed by gel permeation chromatography was 5,000. 100 g of the prepared siloxane resin, 15 g of curable monomer 3,4-epoxyclohexylmethyl 3 ', 4'-epoxycyclohexanecarboxylate (Ciba, CY-179), initiator diphenyliodonium hexafluorophosphate (Sigma Aldrich G) and 60 g of methyl ethyl ketone were mixed to prepare a composition for a window coating layer.

Example  One

3 ml of the composition for a back coating layer of Production Example 1 was coated on one surface of a transparent polyimide film (thickness: 75 占 퐉), spin-coated at 500 rpm for 20 seconds, dried in an oven at 80 占 폚 for 3 minutes, ² to form a back coating layer (thickness: 100 nm) on one side of the transparent polyimide film. On the other side of the transparent polyimide film, the composition for the window coating layer of Production Example 11 was applied by a bar coating applicator. 80 ℃ and dried in an oven for 3 minutes and exposed to ultraviolet light of 500mJ / cm ² in a nitrogen atmosphere, and then was cured at 120 ℃ for 24 hours, the window coating layer (thickness: 50㎛), a transparent polyimide film (thickness: 75㎛ ), And a back coating layer (thickness: 100 nm).

Example  2 to Example  5

A window film was prepared in the same manner as in Example 1, except that the composition for a back coat layer of the following Table 1 was used in place of the back coat layer composition of Production Example 1.

Example  6 - Example  10

A window film was prepared in the same manner as in Example 1, except that the composition for the back coat layer of the following Table 2 was used in place of the back coat layer composition of Production Example 1.

Comparative Example  One

On one side of a transparent polyimide film (thickness: 75 mu m), a composition for a window coating layer of Production Example 11 was applied by a bar coating applicator. The film was dried in an oven at 80 캜 for 3 minutes, exposed to ultraviolet light of 500 mJ / cm ² , and then post-cured at 120 캜 for 24 hours to obtain a window coating layer (thickness: 50 탆) and a transparent polyimide film A window film was prepared.

The properties of the window films of Examples and Comparative Examples were evaluated in Tables 1 and 2 below.

(1) Pencil hardness: The window films prepared in the above Examples and Comparative Examples were cut into a size of 50 x 50 mm, and a pencil hardness meter (Heidon-14EW, manufactured by SHINTO SCIENFITIF Co., Ltd.) By the JIS K5400 method. The pencil was a pencil from 6B to 9H from Mitsubishi. The pencil hardness was measured with a pencil drawing speed of 60 mm / min, a pencil pressing force of 19.61 N, an angle of 45 with the pencil and window coating layer, a pencil load of 1 kg, and a pencil scale of 10.0 mm. 5 times, and when scratches occurred more than once, the pencil hardness was measured using a pencil in the lower step. If no scratches were found in the 5th evaluation at the 5th evaluation, the pencil hardness was determined by the pencil hardness.

(2) Initial Yellowness Index: The yellow index 1925 [Recal] was measured using a colorimeter (CM-3600d, Konica Minolta) at a D65 light source 2 ° (angle between the window coating layer and the light source) with respect to the window film.

(3) Change in heat resistance yellowing degree: Initial yellowing degree was measured for the window film in the same manner as in (2). The window film was allowed to stand in an oven at 80 DEG C for 1000 hours, and then the yellowness degree was measured in the same manner as in (2), and the change in the heat yellowing degree was calculated according to the above formula (1).

(4) Total light transmittance, haze: The haze and the total light transmittance were measured for a window film using NDH2000 (NIPPON DENSHOKU) at a wavelength of 400 to 800 nm.

(5) Radius of curvature: A window film (width x length, 3 cm x 15 cm) was wound around a JIG for curvature radius testing (Mandela bending tester, Core Tech Co., Ltd.) Was visually evaluated as to whether or not a crack occurred. The radius of curvature in the compression direction is measured by bringing the window coating layer into contact with the JIG, and the radius of curvature in the tensile direction is measured by bringing the back coating layer or the base layer into contact with the JIG. Starting from the maximum radius of the JIG, The radius of curvature was determined as the minimum radius of JIG without cracks.

(6) b ^*: a color difference meter (CM-3600d, Konica Minolta, Inc.) at 2 ° (the angle of the window and the coating layer and the light source) by using a D65 light source for window film was measured b ^* value.

Comparative Example Example One One 2 3 4 5 Back coating layer - include include include include include Types of back coating layer - Production Example 1 Production Example 2 Production Example 3 Production Example 4 Production Example 5 dyes - Tetraaza porphyrin type ¹ Tetraazaporphyrin type ² Porphyrin series ³ Vanadium based ⁴ Tetraazaporphyrin + vanadium ⁵ Maximum absorption wavelength (nm) of dye - 596 584 584 593 595 Pencil hardness 8H 8H 8H 8H 8H 8H Initial yellow color 5.76 0.24 0.69 0.89 1.14 0.94 Change in heat yellowing degree 0.14 1.76 1.78 1.82 2.03 1.92 Total light transmittance (%) 88.94 89.24 89.28 89.00 89.08 88.82 Haze (%) 0.94 0.80 0.88 0.85 0.87 0.73 Radius of curvature Compression direction (mm) 5 5 5 5 5 5 Tensile direction (mm) 10 10 10 10 10 10 b ^* 3.39 0.42 0.48 0.61 0.67 0.63

1: KCF Blue b (Kyungin Yang event, maximum absorption wavelength: 596nm) 0.05g

2: SK-D584 (SK Chemical Co., maximum absorption wavelength: 584 nm) 0.05 g

3: PD-311S (manufactured by Yamamoto Chemical Co., Ltd., maximum absorption wavelength: 584 nm) 0.05 g

4: SK-D593 (SK Chemical Co., maximum absorption wavelength: 593 nm) 0.05 g

5: PANAX NEC 595 (Yukseon Chemical Co., maximum absorption wavelength: 595 nm) 0.05 g

Example 6 7 8 9 10 Back coating layer include include include include include Types of back coating layer Production Example 6 Production Example 7 Production Example 8 Production Example 9 Production Example 10 dyes Tetraaza porphyrin type ¹ Tetraaza porphyrin type ¹ Tetraaza porphyrin type ¹ Tetraaza porphyrin type ¹ Tetraaza porphyrin type ¹ Maximum absorption wavelength of dye (nm) 596 596 596 596 596 Antioxidant Phenolic ² Takeover ³ Thioether type ⁴ Phenolic + takeover ⁵ Phenol + thioether ⁶ Pencil hardness 8H 8H 8H 8H 8H Initial yellow color 0.24 0.25 0.22 0.23 0.26 Change in heat yellowing degree 0.56 0.72 0.81 0.14 0.21 Total light transmittance (%) 89.13 89.14 89.23 89.15 89.19 Haze (%) 0.69 0.84 0.91 0.79 0.81 Radius of curvature Compression direction (mm) 5 5 5 5 5 Tensile direction (mm) 10 10 10 10 10 b * 0.42 0.43 0.41 0.42 0.43

1: KCF Blue b (Kyungin Yang event, maximum absorption wavelength: 596nm) 0.05g

2: 0.1 g of Irganox-1010 (BASF)

3: Irgafos-168 (BASF) 0.1 g

4: 0.1 g of Irganox-PS800 (BASF)

5: A mixture of 0.1 g of Irganox-1010 (BASF) and 0.05 g of Irgafos-168 (BASF)

6: A mixture of 0.1 g of Irganox-1010 (BASF) and 0.05 g of Irganox-PS800 (BASF)

As shown in Table 1, the window film according to the embodiments of the present invention has a low yellowing degree and a b ^* range so that the yellow can not be visually observed, and has high total light transmittance and low haze, so that optical characteristics are good. The window film according to the embodiments of the present invention has a high pencil hardness and a low curvature radius and can be used as a window film of a flexible display device. On the other hand, Comparative Example 1, which does not include a dye, has a high yellowness value and a b ^* value deviates from the range of this invention, and therefore yellow can not be visually recognized as a window film. In addition, as shown in Table 2, the window film according to the embodiments of the present invention has high heat resistance and can be used as a display window film because the change in the heat resistance yellowing degree is low even after being left at a high temperature for a long time.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (13)

Substrate layer,
A window coating layer formed on one side of the substrate layer, and
And a back coating layer formed on the other surface of the substrate layer,
Wherein the window coating layer is formed of a composition for a window coating layer containing a silicone resin,
Wherein at least one of the substrate layer, the window coating layer and the back coating layer comprises a dye having a maximum absorption wavelength of from 500 nm to 650 nm.
The window film of claim 1, wherein the dye has a maximum absorption wavelength of 550 nm to 620 nm.
The dye according to claim 1, wherein the dye comprises at least one of a cyanine dye, a porphyrin dye, an arylmethane dye, a squarylium dye, an azomethane dye, an oxonol dye, an azo dye, a xanthan dye, a merocyanine dye, Window film, that is.
The method according to claim 1, wherein the dye is included in the back coating layer,
Wherein the dye is contained in an amount of 0.001 wt% to 15 wt% of the solid content of the composition for the back coat layer.
The window film according to claim 1, wherein the back coating layer has a thickness of 100 nm or less.
The window film according to claim 1, wherein the substrate 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.
The window film according to claim 1, wherein an adhesive layer is further formed on a lower surface of the back coating layer.
The window film of claim 1, wherein the window film has a b ^{* of} from about 2.5 to about 2.5.
The window film according to claim 1, wherein the window film has a compression direction radius of curvature of 10.0 mm or less and a tensile direction radius of curvature of 20.0 mm or less.
The method of claim 1, wherein the window film comprises the base layer, the window coating layer formed directly on one side of the base layer, and the back coating layer formed directly on the other side of the base layer, Wherein the base layer comprises a polyimide resin film.
The window film of claim 1, wherein the window coating layer further comprises an antioxidant.
12. The window film of claim 11, wherein the antioxidant comprises at least one of phenolic, phosphorous, thioether, and amine.
A flexible display device comprising the window film of any one of claims 1 to 12.

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