KR20220076336A - Optical laminate, cover window for flexible display device and flexible display device - Google Patents

Abstract

The present invention provides an optical laminate capable of replacing a conventional tempered glass cover window and exhibiting excellent impact resistance and bending properties, optical properties and mechanical properties, a cover window of a flexible display device including the same, and a flexible display device including the same it's about

Description

Optical laminate, a cover window of a flexible display device, and a display device {OPTICAL LAMINATE, COVER WINDOW FOR FLEXIBLE DISPLAY DEVICE AND FLEXIBLE DISPLAY DEVICE}

The present invention relates to an optical laminate, a cover window of a flexible display device, and a display device.

Recently, with the development of mobile devices such as smartphones and tablet PCs, thinning and slimming of substrates for displays are required. Glass or tempered glass is generally used as a material having excellent mechanical properties for a window or a front panel for a display of such a mobile device. However, glass causes a mobile device to become heavy due to its own weight, has a problem of breakage due to external impact, and has low flexibility, which limits its application to flexible or foldable display devices.

Therefore, plastic resins are being researched as materials that can replace glass. The plastic resin composition is lightweight and less prone to breakage, so it is suitable for the trend of pursuing lighter mobile devices.

Meanwhile, materials for foldable cover windows include Ultra Thin Glass (UTG), colorless polyimide (CPI), and polyethylene terephthalate (PET).

However, the UTG has a problem in that small pieces of glass may be scattered due to cracking or grinding because the UTG is weak to impact. In the case of transparent polyimide, the YI is high, the screen has wrinkles, and the hardness is low, so a hard coating is required.

In addition, many attempts have been made to replace the hard coating substrate with polyethylene terephthalate (PET). In this case, it has excellent mechanical properties and moisture barrier properties and a relatively low unit price. However, since polyethylene terephthalate has a very large birefringence, it may cause polarization distortion between the polarizer and the liquid crystal, and rainbow spots may occur, so retardation improvement is required. Therefore, a hard coating is needed to compensate for the low bending properties and impact resistance.

However, even when hard coating using UTG, CPI, and PET was performed, the desired level of folding properties and impact resistance were not exhibited.

For example, a hard coating for a foldable display substrate is focused on implementing surface hardness and scratch resistance in order to secure mechanical properties comparable to conventional glass. However, when this is applied to a film for a foldable display, there is a problem in that the hard coating film is broken due to poor flexibility.

The present invention can replace a tempered glass cover window such as UTG and CPI, which are considered to be conventional cover windows, and includes a light-transmitting material having excellent optical and mechanical properties, and a hard coating layer having excellent impact resistance and bending properties. It is to provide a thick film type hard coating laminate for use.

In addition, the present invention is an optical laminate for a flexible display device that can be easily applied to a bendable, flexible, rollable, or foldable mobile device, or a display device, etc. because there is little damage to the film even by repeated bending or folding operation. is to provide

Another object of the present invention is to provide a cover window of a flexible display device including the optical laminate.

Another object of the present invention is to provide a flexible display device including a cover window of the flexible display device including the optical laminate.

In the present specification, the light-transmitting substrate; and a hard coating layer positioned on at least one surface of the light-transmitting substrate;

The hard coating layer includes a cured product of polysiloxane and an elastic polymer,

The laminate has an elastic recovery rate of 70% or more measured by the nanoindentation method, and the Vickers hardness (HV) value measured when indenting with a 12mN load by indentation (triangular pyramid tip) to the surface of the hard coating layer is 2 It provides an optical laminate that is not less than 40 and not more than:

[Equation 1]

Rin = (nx - ny) × d

(In Equation 1, nx and ny are the refractive indices in the x-axis direction and the y-axis direction, respectively, and d is the thickness of the film)

In addition, the present invention provides a cover window of a flexible display device including the optical laminate.

In addition, the present specification provides a flexible display device including a cover window of the flexible display device.

Hereinafter, an optical laminate, a cover window of a flexible display device, and a flexible display device according to specific embodiments of the present invention will be described in more detail.

As used herein, "flexible" means a state having a degree of flexibility that does not cause cracks with a length of 5 mm or more when wound on a cylindrical mandrel having a diameter of 5 mm, and thus, The hard coating film may be applied as a cover film (window) of a bendable, flexible, rollable, or foldable display.

In addition, in this specification, "(meth)acrylate" is meant to include both acrylates and methacrylates.

In addition, in this specification, the weight average molecular weight (Mw) and the number average molecular weight (Mn) mean a molecular weight in terms of polystyrene (unit: Da (Dalton)) measured by gel permeation chromatography (GPC). In the process of measuring the weight average molecular weight in terms of polystyrene measured by the GPC method, a commonly known analyzer and a detector such as a differential refraction detector and a column for analysis may be used, and the temperature at which it is normally applied Conditions, solvents, and flow rates can be applied. Specific examples of the measurement conditions include a temperature of 30° C., tetrahydrofuran (THF), and a flow rate of 1 mL/min.

Also, as used herein, the term "substituted or unsubstituted" refers to deuterium; halogen group; nitrile group; nitro group; hydroxyl group; carbonyl group; ester group; imid; amino group; a phosphine oxide group; alkoxy group; aryloxy group; an alkyl thiooxy group; arylthioxy group; an alkyl sulfoxy group; arylsulfoxy group; silyl group; boron group; an alkyl group; cycloalkyl group; alkenyl group; aryl group; aralkyl group; aralkenyl group; an alkylaryl group; an alkylamine group; an aralkylamine group; heteroarylamine group; arylamine group; an aryl phosphine group; Or N, O, and S atom means that it is substituted or unsubstituted with one or more substituents selected from the group consisting of a heterocyclic group containing one or more, or substituted or unsubstituted, two or more of the above-exemplified substituents are linked. . For example, "a substituent in which two or more substituents are connected" may be a biphenyl group. That is, the biphenyl group may be an aryl group, and may be interpreted as a substituent in which two phenyl groups are connected.

는 다른 치환기에 연결되는 결합을 의미한다.In this specification,

means a bond connected to another substituent.

According to one embodiment of the invention, a light-transmitting substrate; and a hard coating layer positioned on at least one surface of the light-transmissive substrate; including a laminate, wherein the laminate has an elastic recovery rate of 60% or more measured by the nanoindentation method, and the surface of the hard coating layer An optical laminate having a Vickers hardness (HV) value of 2 or more and 40 or less when indented by indentation (triangular pyramid tip) with a load of 12 mN can be provided:

[Equation 1]

Rin = (nx - ny) Х d

(In Equation 1, nx and ny are the refractive indices in the x-axis direction and the y-axis direction, respectively, and d is the thickness of the film)

The present inventors conducted research on a laminate applicable to a cover window of a flexible display device that can replace the existing tempered glass cover window such as UTG and CPI and satisfy all optical properties, impact resistance and bending properties, a light-transmissive substrate capable of controlling properties and polysiloxane on the light-transmitting substrate; And an optical laminate comprising a hard coating layer (ie, hard coating film) made of a composition including an elastic copolymer, while exhibiting high hardness and excellent flexibility, excellent optical and mechanical properties, and also repeated bending or The invention was completed after confirming that the film can be easily applied to a cover window such as a bendable, flexible, rollable, or foldable mobile device or a display device because there is almost no damage to the film even by a folding operation.

Such an optical laminate includes a thick-film hard coating layer that satisfies both impact resistance and bending properties on a light-transmitting substrate that satisfies specific parameter properties capable of controlling optical properties and mechanical properties, thereby satisfying impact resistance and folding properties while satisfying impact resistance and folding properties Optically excellent, when applied as a cover window of a flexible display device, all of the optical properties, mechanical properties, and folding performance of the foldable display device can be improved.

Specifically, the optical laminate according to the embodiment includes a light-transmitting substrate capable of controlling optical and mechanical properties; and a hard coating layer formed on at least one surface of the light-transmitting substrate. As it has a laminated structure comprising, optical and mechanical properties are excellent, and impact resistance and bending properties can also be improved.

Conventional tempered glass cover windows mainly use materials such as UTG and CPI, but they are weak to impact or have low hardness, so even if they are hard coated, they do not exhibit the desired level of foldability and impact resistance.

Accordingly, the optical laminate of the embodiment can control optical properties and mechanical properties by using a light-transmitting substrate that satisfies specific parameter properties, and includes a hard coating layer having excellent impact resistance and bending properties on the light-transmitting substrate. can In addition, the optical laminate may exhibit a luminance characteristic equivalent to that of the conventional one.

In particular, as the light-transmitting substrate according to the embodiment uses an optical polyester film having a specific in-plane retardation that can prevent rainbow generation and distortion, excellent mechanical properties and bending properties while satisfying excellent optical properties etc. can be shown.

In the optical laminate according to the exemplary embodiment, a hard coat layer may be formed on a light-transmitting substrate by using a composition for forming a hard coat layer including polysiloxane and an elastomer.

The composition for forming a hard coating layer according to the embodiment may include polysiloxane including an epoxy group-containing functional group.

The epoxy group-containing functional group is not particularly limited as long as it is a functional group containing an epoxy group, but may be, for example, any one selected from the group consisting of an alicyclic epoxy group and a functional group represented by Formula 1 below.

[Formula 1]

In Formula 1,

R _a is a substituted or unsubstituted alkylene group having 1 to 6 carbon atoms, a substituted or unsubstituted alkenylene group having 2 to 20 carbon atoms, a substituted or unsubstituted alkynylene group having 2 to 20 carbon atoms, -R _b -CH= CH-COO-R _c -, -R _d -OCO-CH=CH-R _e -, -R _f OR _g -, -R _h COOR _i -, or -R _j OCOR _k -;

R _b to R _k are each independently, a single bond; or a substituted or unsubstituted C 1 to C 6 alkylene group.

The functional group represented by Chemical Formula 1 includes an epoxy group, and not only improves the physical properties of high hardness and scratch resistance of the hard coating film and the cover window including the same, but also causes almost no damage to the film even by repeated bending or folding operations. It can be easily made to a bendable, flexible, rollable, or foldable mobile device, a display device, or the like.

For example, in the epoxy group-containing functional group represented by Formula 1, R _a is methylene, ethylene, propylene, allylene, -R _b -CH=CH-COO-R _c -, -R _d -OCO-CH=CH- R _e -, -R _f OR _g -, -R _h COOR _i -, or -R _j OCOR _k -.

For example, in Formula 1, R _b to R _k may be a single bond, methylene, ethylene, propylene, or butylene.

For example, R _a may be methylene, ethylene, or -R _f OR _g -, where R _f and R _g may be a direct bond, methylene or propylene.

For example, the functional group represented by Formula 1 is not limited thereto, but may be a glycidoxy group, a glycidoxymethyl group, a glycidoxyethyl group, a glycidoxypropyl group, or a glycidoxybutyl group.

In addition, the alicyclic epoxy group is not limited thereto, but may be, for example, epoxycyclohexyl or epoxycyclopentyl.

The polysiloxane may contain 70 mol% or more, 70 to 100 mol%, or 80 to 100 mol% of the repeating unit including the epoxy group-containing functional group, and in particular, the alicyclic epoxy group and the functional group represented by Formula 1 The repeating unit including any one functional group selected from the group may be included in an amount of 70 mol% or more, 70-100 mol%, or 80-100 mol%. If the content of the repeating unit including the epoxy group-containing functional group is less than 70 mol%, there is a problem in that it is difficult for the hard coating film to exhibit sufficient surface hardness due to a decrease in curing density.

In addition, the polysiloxane may have an equivalent weight of the epoxy group-containing functional group of 2.5 to 6.3 mmol/g or 3.0 to 6 mmol/g. When the equivalent weight of the epoxy group-containing functional group is too small, a problem of a decrease in hardness occurs due to a decrease in film density, and when the equivalent weight of the epoxy group-containing functional group is excessively large, there is a problem of brittleness. The equivalent weight of these functional groups is a value obtained by dividing the molecular weight of the polysiloxane by the number of functional groups, and can be analyzed by H-NMR or chemical titration.

In addition, the polysiloxane may be represented by the following formula (2).

[Formula 2]

(R ¹ SiO _3/2 ) _a (R ² SiO _3/2 ) _b (R ³ R ⁴ SiO _2/2 ) _c (R ⁵ R ⁶ R ⁷ SiO _1/2 ) _d (SiO _4/2 ) _e ( O _1/2 R ⁸ ) _f

In Formula 2,

R ¹ to R ⁷ are each independently hydrogen, an epoxy group-containing functional group, amino group, mercapto group, ether group, ester group, carbonyl group, carboxyl group, (meth)acrylate, sulfone group, substituted or unsubstituted C1 to C20 Alkyl group, substituted or unsubstituted C3 to C20 cycloalkyl group, substituted or unsubstituted C2 to C20 alkenyl group, substituted or unsubstituted C2 to C20 alkynyl group, substituted or unsubstituted C2 to C20 An alkoxy group, a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, a substituted or unsubstituted arylalkyl group having 7 to 20 carbon atoms, or a substituted or unsubstituted alkylaryl group having ⁷ to 20 carbon atoms, but R At least one of ⁷ may be the epoxy group-containing functional group.

At this time, at least one of R ¹ to R ⁷ includes the epoxy group-containing functional group, and the repeating unit including the epoxy group-containing functional group is 70 mol relative to the total molar ratio content of all repeating units of the polysiloxane represented by Formula 2 % or more, 70 to 100 mol%, or 80 to 100 mol% may be included. When the content of the repeating unit including the epoxy group-containing functional group is less than 70 mol%, there is a problem in that it is difficult for the hard coating film to exhibit sufficient surface hardness due to a decrease in curing density.

In addition, in Formula 2, R ⁸ may be a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

It may be 0<a≤1, 0≤b≤1, 0≤c≤1, 0≤d≤1, 0≤e≤1, and 0<f≤1.

The (R ¹ SiO _3/2 ) structural unit and (R ² SiO _3/2 ) structural unit included in the polysiloxane are T units, and the T unit refers to a structural unit in which three siloxane bonds are formed. Polysiloxane containing such a T unit may increase the curing density to improve the surface hardness properties of the hard coating film.

The molar ratio of the (R ¹ SiO _3/2 ) structural unit and the (R ² SiO _3/2 ) structural unit as the T unit is a and b, respectively, and the molar ratio of the T unit to 100 mol% of the total polysiloxane of Formula 2 may be 70 to 100 mol%, 80 to 99.9 mol%, 85 to 99 mol%, 90 to 98 mol% (ie, 0.7≤a+b≤1, 0.8≤a+b≤0.999, 0.85≤a+ b≤0.99, or 0.9≤a+b≤0.98). In addition, the ratio of a and b may be 1:0 to 1, 1:0.01 to 0.9, 1:0.05 to 0.7, or 1:1 to 0.5, and when the ratio of a and b is 1:0 , a may have a molar ratio of 0.7≤a≤1, 0.8≤a≤0.999, 0.85≤a≤0.99, or 0.9≤a≤0.98.

In addition, the (R ³ R ⁴ SiO _2/2 ) constituent unit included in the polysiloxane is a D unit, and the D unit refers to a constituent unit in which two siloxane bonds are formed. The molar ratio of the (R ³ R ⁴ SiO _2/2 ) constituent unit is c, and the molar ratio of the D unit to the polysiloxane total molar ratio content of Formula 1 is 0≤c≤1, 0.01≤c<0.3, or 0.05≤ c≤0.2.

In addition, the (R ⁵ R ⁶ R ⁷ SiO _1/2 ) structural unit included in the polysiloxane is an M unit, and the M unit means a structural unit in which one siloxane bond is formed. The molar ratio of the (R ⁵ R ⁶ R ⁷ SiO _1/2 ) structural unit is d, and the molar ratio of the M unit to the polysiloxane total molar ratio content of Formula 1 is 0≤d≤1, 0.01≤d<0.3, or 0.05≤d≤0.2.

In addition, the sum (c+d) of the molar ratio of the (R ³ R ⁴ SiO _2/2 ) structural unit and the (R ⁵ R ⁶ R ⁷ iO _1/2 ) structural unit is 0≤c+d<0.3, 0.01≤ c+d≤0.29, 0.05≤c+d≤0.25, or 0.07≤c+d≤0.23.

Specifically, R ¹ is an epoxy group-containing functional group, R ² to R ⁷ are hydrogen, amino group, mercapto group, ether group, ester group, carbonyl group, carboxyl group, (meth) acrylate, sulfone group, methyl group, ethyl group, propyl group, It may be a t-butyl group, a cyclohexyl group, a methoxy group, an ethoxy group, a propoxy group, a t-butoxy group, a phenyl group, a naphthalene group, and the like.

The polysiloxane may include a (SiO _4/2 ) structural unit, which is a structural unit in which four siloxane bonds are formed. In addition, the molar ratio of the (SiO _4/2 ) constituent unit is e, and e may be 0≤e≤1, 0.01≤e<0.3, or 0.05≤e≤0.2.

In addition, the polysiloxane (O _1/2 R ⁸ ) may include a structural unit, and the polysiloxane including this may improve flexibility while maintaining excellent hardness properties. In addition, the molar ratio of the (O _1/2 R ⁸ ) structural unit is f, and f may be 0<f≤1, 0.01≤f<0.3, or 0.05≤f≤0.2.

R ⁸ may be a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and more specifically, a hydrogen atom, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, and the like.

Polysiloxane including the above-mentioned structural units may be prepared by hydrolysis and condensation reaction between the siloxane monomer of each structural unit, specifically, one type of alkoxysilane alone, or one type of alkoxysilane and a different type of alkoxysilane. , In this case, the molar ratio of each constituent unit can be controlled by controlling the content ratio of the alkoxysilane. In addition, the molar ratio of each structural unit which comprises the said polysiloxane can be calculated|required by ¹ H-NMR or ²⁹ Si-NMR spectrum measurement.

The polysiloxane may have a weight average molecular weight (Mw), a number average molecular weight (Mn), a molecular weight distribution, etc. controlled by controlling the reaction temperature using a reaction temperature, an amount of catalyst, a kind solvent, etc. The molecular weight may be from 1,000 to 50,000, from 1,500 to 45,000, or from 2,000 to 40,000. If the weight average molecular weight of the polysiloxane is too low, hardness may not be realized but rather ductility may be expressed.

In addition, the polysiloxane may have a number average molecular weight (Mn) of 1,000 to 10,000, 1,500 to 9,000, or 2,000 to 8,000. When the above-described number average molecular weight condition is satisfied, compatibility with other components in the composition is increased, surface hardness is improved, and abrasion resistance can be further improved.

In addition, the polysiloxane may have a molecular weight distribution (Mw/Mn) of 1.0 to 10.0, 1.1 to 8.0, or 1.2 to 6.0. When it has a molecular weight distribution within the above range, the surface hardness improvement effect is more excellent, and the polysiloxane is present in a liquid phase, so handling may be easy. The weight average molecular weight and number average molecular weight of the polysiloxane are standard polystyrene conversion values by gel permeation chromatography.

The polysiloxane may be included in an amount of 60 to 95 parts by weight, 65 to 90 parts by weight, or 70 to 85 parts by weight based on 100 parts by weight of the composition for forming a hard coat film. If the content of the polysiloxane is too large, the hardness of the finally manufactured hard coating film is increased, but the bending properties are lowered, so that cracks may occur due to repeated bending operations. have.

The elastic polymer including the polyester polyol can minimize shrinkage during curing by imparting stress resistance properties through the toughness of the hard coating layer, and as a result, improve flexural properties, and at the same time improve flexibility such as flexibility, hardness characteristics can be improved.

A weight ratio of the polysiloxane and the elastomer may be 100: 20 to 80. That is, the content of the elastic polymer included in the hard coating layer is specifically, 20 to 80 parts by weight, or 30 to 60 parts by weight, based on 100 parts by weight of polysiloxane containing 70 mol% or more of the repeating unit including the epoxy group-containing functional group, Or 40 to 55 parts by weight may be included. When the content of the elastomer including the polyester polyol is excessively greater than 80 parts by weight, there is a risk that the bending properties are greatly reduced, and when the content of the elastomer is too small, less than 20 parts by weight, the improvement effect due to the inclusion of the elastomer is not sufficiently obtained, and there is a possibility that the bending characteristics and flexibility may decrease.

Examples of the elastic polymer include alkanediol, polyolefin polyol, polyester polyol, polycaprolactone polyol, polyether polyol or polycarbonate polyol having 1 to 20 carbon atoms, and any one or mixture of two or more thereof may be used. . These elastomers can be crosslinked and polymerized by UV irradiation compared to conventional elastomers such as rubber, and high hardness and flexibility can be realized without lowering other properties. Among them, the elastic polymer may be polycaprolactonediol or polycarbonate diol, and in particular, the polycaprolactonediol may be used.

According to one embodiment, the polyester polyol included in the elastic polymer may be polycaprolactone polyol. The polycaprolactone polyol contains an ester group and an ether group at the same time in the repeating unit and is repeated, thereby exhibiting superior effects in terms of flexibility, hardness, and impact resistance when used in combination with the polysiloxane.

In addition, the elastic polymer may have a number average molecular weight (Mn) of 500 to 10,000 Da, more specifically, 1,000 to 5,000 Da. When the above-described number average molecular weight condition is satisfied, compatibility with other components in the resin composition for forming a coating layer is increased, the surface hardness of the cured product is improved, and the heat resistance and abrasion resistance of the cured product can be further improved.

The composition for forming a hard coating layer of the embodiment may further include an initiator. The type of the initiator is not particularly limited as long as it is a photopolymerization initiator, but may be, for example, an initiator having a maximum absorbance at a wavelength of 200 nm to 280 nm. For example, the initiator may be an initiator having a maximum absorbance at a wavelength of 210 nm to 270 nm or 220 nm to 260 nm.

When the initiator has the maximum absorbance at a wavelength of less than 200 nm, compatibility with the curing lamp wavelength may decrease, and the degree of curing may be reduced. It deteriorates, and cracks may occur due to repeated bending or folding operations.

The initiator is, for example, 4-phenoxydichloroacetphenone, 4-t-butyldichloroacetphenone, 4-t-butyltrichloroacetphenone, diethoxyacetphenone, 2-hydroxy-2-methyl-1 -Phenylpropan-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 1-(4-dodecylphenyl)-2-hydroxy-2-methyl acetphenones such as propan-1-one, 4-(2-hydroxyethoxy)-phenyl (2-hydroxy-2-propyl) ketone, and 1-hydroxycyclohexylphenyl ketone; benzoins such as benzoin, benzoin methyl ether, benzoin ethyl ether, and benzyl dimethyl ketal; acylphosippin oxides; titanocene compounds; Benzos such as benzophenone, benzoylbenzoic acid, benzoylbenzoic acid methyl ether, 4-phenylbenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyldiphenylsulfide, and 3,3'-methyl-4-methoxybenzophenone phenones; and thioxanthone such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, and isopropylthioxanthone. can be used by

The initiator may be included in an amount of 0.1 to 10% by weight, 0.5 to 5% by weight, or 1 to 4% by weight based on 100% by weight of the composition for forming the hard coating layer. If the content of the initiator is less than 0.1% by weight, only surface hardening or epoxy curing may not occur sufficiently, so that the hardness may be low, and if it exceeds 10% by weight, cracks and peeling may occur due to a fast curing rate.

The composition for forming the hard coating layer can be used as a solvent-free if there is no problem in the process, but optionally further includes an organic solvent to control the viscosity and fluidity of the composition during coating and increase the applicability of the composition can do.

When the organic solvent is further included, the organic solvent may include an alcohol-based solvent such as methanol, ethanol, isopropyl alcohol, or butanol; alkoxy alcohol solvents such as 2-methoxyethanol, 2-ethoxyethanol, and 1-methoxy-2-propanol; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl propyl ketone, and cyclohexanone; Propylene glycol monopropyl ether, propylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethyl glycol monoethyl ether, diethyl glycol monopropyl ether , ether solvents such as diethyl glycol monobutyl ether and diethylene glycol-2-ethylhexyl ether; acetate-based solvents such as propylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, and diethylene glycol monoethyl ether acetate; Alternatively, an aromatic solvent such as benzene, toluene, or xylene may be used alone or in combination.

The hard coating layer included in the optical laminate according to the exemplary embodiment may further include a reactive monomer including at least one functional group crosslinkable with the polysiloxane. The reactive monomer may include at least one functional group crosslinkable with the polysiloxane described above, thereby lowering the viscosity of the polysiloxane to facilitate processability and improve coating adhesion.

The reactive monomer may include at least one selected from the group consisting of a functional group crosslinkable with the polysiloxane, for example, an alicyclic epoxy group, a glycidyl group, and an oxetanyl group.

In addition, the reactive monomer comprising at least one functional group crosslinkable with the polysiloxane is, for example, bisphenol A diglycidyl ether, 4-vinylcyclohexene dioxide, cyclohexene vinyl monoxide, (3,4-epoxycyclohexyl ) methyl 3,4-epoxycyclohexylcarboxylate, 3,4-epoxycyclohexylmethyl methacrylate, 3,4-epoxycyclohexanecarboxylate, 2- (3,4-epoxycyclohexyl)-1, 3-dioxolane, bis(3,4-epoxycyclohexylmethyl)adipate, p-butyl phenol glycidyl ether, butyl glycidyl ether, cresyl glycidyl ether, allyl glycidyl ether, phenyl glycidyl ether Cydyl ether, diglycidyl ether, butanediol diglycidyl ether, limonene dioxide, diethylene glycol diglycidyl ether, 3-methyloxetane, 2-methyloxetane, 3-oxetanol, 2- Methyleneoxetane, 3-methyl-3-hydroxymethyloxetane, 3-ethyl-3-hydroxymethyloxetane, 3,3-oxetane dimanethiol, 2-ethylhexyloxetane, 4- (3 -Methyloxetan-3-yl)benzonitrile, N-(2,2-dimethylpropyl)-3-methyl-3-oxetanemethanamine, N-(1,2-dimethylbutyl)-3-methyl- 3-oxetanemethanamine, xylene bis oxetane, 3-ethyl-3[{(3-ethyloxetan-3-yl)methoxy}methyl]oxetane, (3-ethyloxetan-3-yl) methyl methacrylate, and at least one selected from the group consisting of 4-[(3-ethyloxetan-3-yl)methoxy]butan-1-ol.

The weight ratio of the polysiloxane and the reactive monomer included in the hard coating layer may be 99:1 to 80:20, 97:3 to 85:5, or 95:5 to 90:10. When the polysiloxane is included in an excessive amount compared to the reactive monomer, the improvement effect due to the inclusion of the reactive monomer may be insignificant. Rather, it may be lowered.

The hard coating layer may further include an acrylate-based compound to improve surface hardness.

Examples of the acrylate-based compound include 2-ethylhexyl acrylate, octadecyl acrylate, isodecyl acrylate, 2-phenoxyethyl acrylate, lauryl acrylate, stearyl acrylate, behenyl acrylate, tridecyl meta Krylate, nonylphenolethoxylate monoacrylate, β-carboxyethyl acrylate, isobornyl acrylate, tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, 4-butylcyclohexyl acrylate, dicyclophene Tenyl acrylate, dicyclopentenyl oxyethyl acrylate, ethoxyethoxyethyl acrylate, ethoxylated monoacrylate, 1,6-hexanediol diacrylate, triphenylglycol diacrylate, butanediol diacrylate , 1,3-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate acrylate, tetraethylene glycol, diacrylate, tetraethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, diphoro Phylene glycol diacrylate, ethoxylated neopentyl glycol diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, penta Erythritol tetramethacrylate, pentaerythritol tetraacrylate, ethoxylated triacrylate, tris(2-hydroxyethyl)isocyanurate triacrylate, dipentaerythritol pentaacrylate, di and trimethylolpropane tetraacrylate, alcohol sylated tetraacrylate, and the like, preferably pentaerythritol triacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, or and polyfunctional acrylate-based compounds such as pentaerythritol tetraacrylate, and any one or a mixture of two or more thereof may be used. have.

In addition, there may be mentioned acrylate-based oligomers such as polyester acrylate, polyether acrylate, urethane acrylate, or epoxy acrylate, and any one or a mixture of two or more thereof may be used. Among the above-described acrylate-based compounds, urethane acrylate oligomer may be more preferably used in consideration of the remarkable effect of improving surface hardness when used in combination with the above-described polysiloxane.

The urethane acrylate oligomer may have 6 to 9 functional groups. If the functional group is less than 6, the effect of improving the hardness may be insignificant, and if it is more than 9, the hardness may be excellent, but the viscosity may increase. In addition, the urethane (meth)acrylate oligomer may be used without limitation those used in the art, but preferably a compound having at least one isocyanate group in the molecule and a (meth)acrylate compound having at least one hydroxyl group in the molecule One prepared by reacting may be used.

When the acrylate-based compound is further included, it may be included in an amount of 0.1 to 20 parts by weight, 1 to 15 parts by weight, or 5 to 10 parts by weight based on 100 parts by weight of the polysiloxane. If the content of the reactive monomer is less than 0.1 parts by weight, the improvement effect due to the inclusion of the acrylate-based compound is insignificant, and if it exceeds 20 parts by weight, the surface hardness improvement effect may be rather inhibited due to the excess acrylate-based compound.

In addition, the composition for forming the hard coating layer may further include an antioxidant, a surfactant, an inorganic filler, a lubricant, a coating aid, an antifouling agent, and the like, in addition to the above-described components. In addition, the content can be variously adjusted within a range that does not reduce the physical properties, so it is not particularly limited, but for example, it may be included in an amount of 0.1 to 10% by weight based on 100% by weight of the total content of the composition.

For example, the antioxidant is for inhibiting the oxidation reaction resulting from the cationic initiator, and may include one or more mixtures selected from the group consisting of phenolic, phosphate, amino, thioester, etc. may not be limited.

The surfactant may be a fluorine-based acrylate, a fluorine-based surfactant, or a silicone-based surfactant having 1-2 functional properties. In this case, the surfactant may be included in a dispersed or cross-linked form in the cross-linked copolymer.

Meanwhile, the optical laminate may include a light-transmitting substrate having specific parameter properties capable of controlling optical properties and mechanical properties so as to implement the above-described physical properties of the hard coating layer.

Such a light-transmitting substrate may include a transparent plastic resin.

More specifically, the light-transmitting substrate may be a polyester film having a plane-direction retardation value of 400 to 2000 nm represented by Equation 1 at a wavelength of 550 nm.

[Equation 1]

Rin = (nx - ny) Х d

(In Equation 1, nx and ny are the refractive indices in the x-axis direction and the y-axis direction, respectively, and d is the thickness of the film)

The polyester film may have a YI value of 1.5 or less, and a modulus measured according to ISO 527-3 may be 10 GPa or less. More specifically, the polyester film may have a YI value of 1.5 or less, and a modulus measured according to ISO 527-3 may be 10 GPa or 8 GPa or less, or 6 or less.

According to one embodiment, the polyester film may use polyethylene terephthalate (PET) that satisfies all of the above physical properties. That is, the polyester film has a plane-direction retardation value of 40 to 2000 nm represented by Formula 1 at a wavelength of 550 nm, a YI value of 1.5 or less, and a polyethylene terephthalate having a modulus measured according to ISO 527-3 of 10 Gpa or less. (PET).

In this case, the polyester film, specifically the PET film, needs to use an appropriate optical PET since the PET film itself is a birefringent material unlike other transparent optical films used in the prior art. In the case of non-optical PET, a rainbow appears due to a low plane-direction retardation, or a combination with other laminated optical films because the plane-direction retardation is too high may cause distortion. Therefore, in the present specification, an optical film in a range satisfying the in-plane retardation value expressed by Equation 1 that does not cause the above problem is used.

The polyester film satisfying the above physical properties can provide an economical optical laminate because it has excellent mechanical properties and moisture barrier properties as well as optical properties and is inexpensive. Accordingly, the Vickers hardness of the final optical laminate may satisfy the Vickers hardness (HV) value of 2 or more and 40 or less as described above.

In addition, the hard coating layer may be laminated on one or both surfaces of the light-transmitting substrate. In addition, when the hard coating layer is formed on both surfaces of the light-transmitting substrate, the two hard coating films may have the same composition or thickness, or may be different.

The light-transmitting substrate may be a single layer, or may have a multi-layered structure of two or more layers made of the same or different light-transmitting substrates. As the other light-transmitting substrate, cyclic olefin copolymer (COC), polyacrylate (PAC), polycarbonate (PC), polyethylene (PE), polymethyl methacrylate ( polymethylmethacrylate (PMMA), polyetheretherketone (PEEK), polyethylenenaphthalate (PEN), polyetherimide (PEI), polyimide (PI), polyamideimide (PAI) and It may include at least one of triacetylcellulose (TAC). In particular, the polyamide-imide film can be used as the support base layer because it has excellent flexibility and hardly causes damage to the film due to repeated bending.

For example, the light-transmitting substrate is a multilayer structure of polyethylene terephthalate (PET), a multilayer structure formed by coextrusion of polyethylene terephthalate (PET)/polycarbonate (PC), or polyethylene terephthalate (PET) and polycarbonate ( It may be a single-layer structure including a copolymer of PC).

In addition, the light-transmitting substrate may be plasma surface-treated if necessary, and the method is not particularly limited and may be performed according to a conventional method.

In addition, when the thickness of the light-transmitting substrate is excessively thick or thin, there are problems in surface hardness, lowering of impact resistance, or folding characteristics, and it may be preferable to appropriately set the range. For example, the light-transmitting substrate may have a thickness of 20 to 200 μm, 30 to 150 μm, or 50 to 120 μm.

In addition, the total thickness of the light-transmitting substrate and the hard coating layer may be 5 to 200 μm, 60 to 180 μm, 80 to 160 μm, or 100 to 150 μm. If the total thickness of the light-transmitting substrate and the hard coating layer is too thick, it is easy to break when folded, and if the thickness is too thin, even if the foldability is secured, the strength may be poor.

The optical laminate according to the exemplary embodiment includes: the light-transmitting substrate; and a thick film-type hard coating layer positioned on at least one surface of the light-transmitting substrate, thereby satisfying physical properties equivalent to or higher than that of the existing tempered glass cover window. Specifically, the optical laminate according to one embodiment has an elastic recovery rate of at least 60% or more measured by the nanoindentation method, and when indented with a 12mN load by indentation (triangular pyramid tip) to the surface of the hard coating layer The measured Vickers hardness (HV) value may be 2 or more and 40 or less.

More specifically, the optical laminate according to one embodiment has an elastic recovery rate of 70% or 80% or more measured by the nanoindentation method, and a 12mN load by indentation (triangular pyramid tip) with respect to the surface of the hard coating layer. The Vickers hardness (HV) value measured during indentation may be 5 or more and 30 or less.

At this time, when the Vickers hardness is 2 or less, the hardness is too low to compensate for the brittle characteristics of the supporting substrate of the optical laminate. It cannot absorb the impact of

Accordingly, according to another embodiment of the present invention, the cover window of the flexible display device including the optical laminate according to the embodiment may be provided.

The optical laminate or cover window is folded and unfolded inward of the hard coating layer at a 90° angle so that the hard coating layer faces each other with a gap of 2 mm in the middle of the hard coating layer, repeated 200,000 times at 25° C. at a rate of once per second No cracks occur when used, and there is almost no damage to the film even by repeated bending or folding operations. .

1 schematically shows a method for evaluating dynamic bending properties.

Referring to FIG. 1, after placing the cover window so that it is level with the floor, the gap between the folds in the middle of the cover window is 8 mm, and both sides of the cover window are folded and unfolded at a 90° angle with respect to the floor. Durability against bending can be measured by repeating 200,000 times at a rate of once per second at °C. At this time, in order to keep the distance between the folds constant, for example, place the cover window so that it touches a rod having a diameter (R) of 8 mm, fix the rest of the cover window, and cut both sides of the cover window with the rod as the center. You can take a method that repeats folding and unfolding. In addition, the folded portion is not particularly limited as long as it is inside the cover window, and for convenience of measurement, the central portion of the cover window may be folded so that both sides of the cover window except for the folded portion are symmetrical.

In the evaluation of the dynamic bending characteristics, cracks of 1 cm or more do not occur in the cover window even after bending for 200,000 times, and cracks do not occur substantially. Therefore, the possibility of cracks occurring even in actual use such as repeatedly folding, rolling, or bending is very low, and thus it can be suitably applied to a cover window of a flexible display device.

The cover window having the above-described structure and configuration may form the hard coating film by applying the composition for forming a hard coating layer on one surface of a light-transmitting substrate and then curing it. In addition, after the composition for forming the hard coat layer is applied to one surface of the light-transmitting substrate and cured to form an upper hard coat layer, a composition for forming a hard coat layer similar to or different from the composition for forming the hard coat layer is applied to the light-transmitting substrate. It can be applied to the other side and cured to form a lower hard coating layer.

The above-described application process may be performed by a known method such as a die coater, an air knife, a reverse roll, a spray, a blade, casting, gravure, spin coating, or bar coating.

In addition, after each resin composition is applied, a process for curing may be performed, and the curing may be performed by thermal curing or photocuring according to a conventional method. The heat treatment or light irradiation conditions for the thermosetting and photocuring may be appropriately controlled by adjusting the wavelength region and the amount of light, or the heat treatment temperature, depending on the type of the initiator.

According to another embodiment of the present invention, a flexible display device including a cover window of the flexible display device including the optical laminate of the embodiment may be provided.

The flexible display device includes a curved, bendable, flexible, rollable, or foldable mobile communication terminal, a smart phone, a touch panel of a tablet PC, and a wearable device. It may include both devices and various displays. According to various embodiments, the wearable device is an accessory type (eg, a watch, a ring, a bracelet, an anklet, a necklace, glasses, contact lenses, or a head-mounted-device (HMD)), a fabric or a clothing integrated type ( It may include at least one of: electronic clothing), body attachable (eg skin pad or tattoo), or bioimplantable (eg implantable circuit).

On the other hand, the flexible display device is, for example, a liquid crystal display (LCD) device, a light emitting diode (LED) display device, an organic light emitting diode (OLED) display device, a microelectromechanical system (MEMS) display device or a rollable display device (rollable display or foldable display).

For example, in the organic light emitting diode (OLED) display device, the cover window of the flexible organic light emitting diode display device may be positioned at an outer portion in a direction in which light or a screen is emitted, and a cathode providing electrons; An electron transport layer, an emission layer, a hole transport layer, and an anode providing holes may be sequentially formed. In addition, the organic light emitting diode (OLED) display may further include a hole injection layer (HIL) and an electron injection layer (EIL).

In order for the organic light emitting diode (OLED) display to function and operate as a flexible display, the cathode and anode electrodes and each component may be used as a material having a predetermined elasticity.

Another example of the flexible display device may be a rollable display or foldable display.

On the other hand, the retractable display device may have various structures depending on the field of application and specific form, for example, including a cover window, a touch panel, a polarizing plate, a barrier film, a light emitting device (OLED device, etc.), a transparent substrate, etc. can be a structure.

As another example of the flexible display device, a pair of polarizing plates facing each other; a thin film transistor, a color filter and a liquid crystal cell sequentially stacked between the pair of polarizing plates; And it may be a liquid crystal display device including a backlight unit.

In the display device, the cover window may be provided on the outermost surface of the viewer side or the backlight side of the display panel.

According to the present invention, an optical laminate capable of replacing a tempered glass cover window such as UTG, CPI, etc. and securing improved impact resistance, bendability, optical properties and mechanical properties compared to the prior art, and a flexible display device including the same A cover window of may be provided.

In addition, the optical laminate and the cover window include a hard coating layer that satisfies excellent impact resistance and bending properties and a polyester film capable of controlling optical properties as a light-transmitting substrate, so that damage can be prevented even when an external impact is applied. , can exhibit excellent optical properties.

In particular, the optical laminate and the cover window are bendable, flexible, rollable, or foldable mobile devices because there is little damage to the film even by repeated bending or folding operations; It can be usefully applied to display devices, the front panel of various instrument panels, and the display unit.

1 schematically shows a method for evaluating dynamic bending properties.

The invention is described in more detail in the following examples. However, the following examples only illustrate the present invention, and the content of the present invention is not limited by the following examples.

Preparation Example 1: Preparation of polysiloxane (a)

In a 1000 mL 3-neck flask, 3-glycidoxypropyltrimethoxysilane (GPTMS, KBM-403™, Shinetsu Corporation), water and toluene as a silane monomer were added, mixed and stirred (GPTMS: water = 1 mol: 3 mol: 4 mol).

Next, 1 part by weight of a basic catalyst (trimethylammonium hydroxide; TMAH) was added to the resulting mixed solution with respect to 100 parts by weight of the silane monomer and reacted at 100° C. for 2 hours, glycidoxypropyl modified silicone (hereinafter referred to as glycidoxypropyl modified silicone) GP) polysiloxane (a) of the following composition containing 100 mol% was prepared (number average molecular weight: 2000 g/mol, molecular weight distribution (PDI): 1.4, glycidoxypropyl group equivalent: 6 mmol/g).

Preparation Example 2: Preparation of polysiloxane (b)

In a 1000mL 3-neck flask, 3-glycidoxypropyltrimethoxysilane (GPTMS, Shinetsu Corporation), phenyltrimethoxysilane (PTMS, Shinetsu Corporation), water and toluene (GPTMS:PTMS:water=0.5 mol:0.5 mol) : 3 mol) was mixed and stirred.

Next, 1 part by weight of a basic catalyst (trimethylammonium hydroxide; TMAH) was added to the resulting mixed solution with respect to 100 parts by weight of the silane monomer and reacted at 100 ° C. for 2 hours, glycidoxypropyl modified silicone (hereinafter referred to as glycidoxypropyl modified silicone) GP) an epoxy siloxane resin containing 50 mol% was prepared. (Mw: 2800 g/mol).

Preparation Examples 3 to 7

[Preparation of composition for forming hard coating layer]

Each mixture was mixed with methyl ethyl ketone (MEK) as a solvent by the formulation shown in Table 1 below (solid content 80%) to prepare compositions for forming a hard coat layer in Examples and Comparative Examples, respectively.

Preparation 3 Preparation 4 Production Example 5 Preparation 6 Preparation 7 polysiloxane a 100 g 100 g 100 g 100 g - b 100 g elastomer 10g 50 80 80 photoinitiator 3g 3g 3g 3g 3g Methyl ethyl ketone (MEK) 7g 7g 7g 7g 7g

- Polysiloxane a: Polysiloxane prepared in Preparation Example 1 - Polysiloxane b: Polysiloxane prepared in Preparation Example 2

- Elastomer: Mn = 2000, polycaprolactone diol from Sigma aldrich

- Photoinitiator (A): omnicat 250 (IGM resin)

<Examples and Comparative Examples>

[Optical laminate (manufacture of cover window)]

On one side of a polyethylene terephthalate (PET) or CPI film having a thickness of 15 cm × 20 cm and a thickness of 50 μm, the compositions for forming a hard coating layer of Preparation Examples 3 to 7 were applied and irradiated with ultraviolet rays using a lamp (irradiation dose: 500 mJ/cm 2 ) ) and photocuring to form a hard coating layer having the thickness shown in Table 2, a cover window (optical laminate) having the structure shown in Table 2 was prepared (Examples 1-2 and Comparative Examples 2-7).

In this case, as the hard coat layer of Comparative Example 1, a resin composition for forming an acrylic hard coat layer prepared by the following method was used.

30% by weight of acrylic functional polymer (product name: TMPTA, manufacturer: Miwon, weight average molecular weight: 296.3g/mol) and 60% by weight of polyfunctional acrylic oligomer (product name: UX-5000, manufacturer: Miwon), polyfunctional acrylic oligomer (Product name: CN8885NS Manufacturer: Sartomer) 20 g of a mixture, 0.6 g of Irgacure 184 as a photoinitiator, and 8 g of methyl ethyl ketone as a solvent were mixed to prepare a resin composition for forming an acrylic hard coating layer.

After that, the resin composition for forming the acrylic hard coating layer was applied to one side of a PET film having a thickness of 15 cm × 20 cm and a thickness of 50 μm, and UV rays were irradiated using a lamp (irradiation amount: 1,000 mJ/cm 2 ) to photocurate to a thickness of 10 μm. By forming a hard coat layer, the cover window (optical laminate) of Comparative Example 2 was prepared.

Example
One Example
2 comparative example
One comparative example
2 comparative example
3 comparative example
4 comparative example
5 comparative example
6 comparative example
7 hard coating layer composition production example
5 production example
5 acryl production example
3 production example
4 production example
6 production example
5 production example
7 production example
5 hard
coating layer
section
coating thickness
(μm) 30 50 10 50 50 50 50 50 50 Base film (㎛) PET1 PET1 PET1 PET1 PET1 PET1 CPI PET1 PET2 Total thickness (㎛) 110 150 70 150 150 150 150 150 150

-PET1: PET film having in-plane retardation value of 900 nm, YI 0.3, and modulus 5.2 GPa expressed by Equation 1 at a wavelength of 550 nm [Equation 1]

Rin = (nx - ny) Х d

(In Equation 1, nx and ny are the refractive indexes in the x-axis direction and the y-axis direction, respectively, and d is the thickness of the film)

-PET2: PET film having in-plane retardation value of 2200 nm, YI 0.3, and modulus 5 GPa expressed by Equation 1 at a wavelength of 550 nm

- Transparent polyimide film (CPI) (Kolon industry)

<Experimental example>

For the cover windows prepared in Examples and Comparative Examples, physical properties were measured by the following method, and the results are shown in Table 1 below.

1. Measurement of Vikers hardness

For the surface of the hard coating film of the cover window, Vickers hardness was measured using a Vickers hardness tester (Helmut Fischer, FISCHERSCOPE HM-2000). (indentation: Vickers triangular pyramid tip, 12mN)

Specifically, using a Vickers triangular pyramid indenter, a load was applied to the surface of the hard coating film of the cover window and indentation was measured after making an indentation mark.

2. Dynamic bending properties

1 schematically shows a method for evaluating dynamic bending properties.

The cover window was cut, but laser cut to a size of 80 x 140 mm to minimize micro-cracks in the edge area. Place the laser-cut film on the measuring device, put the hard coating film inside, and make the gap (inner curvature diameter) of the folded part 2 mm, and at room temperature, both sides of the film were folded at an angle of 90° with respect to the bottom surface The unfolding operation was repeated 200,000 times in a continuous operation (the film folding speed was once per second at 25° C.), and the dynamic bending characteristics were evaluated according to the following criteria.

OK: no cracks

NG: cracks

3. nIT Assessment

About the hard coating film of the cover window, The elastic recovery rate was measured by the following method.

For the surface of the hard coat layer of the optical laminate, Helmut Fischer, FISCHERSCOPE HM-2000) was measured with a vickers indenter. The applied load and speed were 12mN/12sec, and the maintenance time was 5 seconds.

The measurement principle was carried out by the load-removal method, and the elastic recovery factor was obtained by substituting the integral values of the elastic region and the plastic region in the indentation load-displacement curve obtained by this into Equation 2 below.

[Equation 2]

Elastic recovery rate = (W _elast integral value / (W _plast integral value + W _elast integral value)) × 100

In Equation 2 above,

The W _elast integral value corresponds to the integral value of the elastic region in the indentation load-displacement curve,

The W _plast integral value corresponds to the integral value of the plastic region in the indentation load-displacement curve.

4. Light resistance reliability evaluation

QUV (UVA-340) equipment was used to measure Y.I values before and after 96 hours of standing for Examples and Comparative Examples, and the results were compared.

<Evaluation criteria>

Good: ΔYI < 2 compared to initial YI

Bad: △YI > 2 compared to initial YI

Example comparative example One 2 One 2 3 4 5 6 7 hard coating layer composition production example
5 production example
5 acryl production example
3 production example
4 production example
6 production example
5 production example
7 production example
5 hard coating layer
section
coating thickness
(μm) 30 50 10 50 50 50 50 50 50 Base film (㎛) PET1 PET1 PET1 PET1 PET1 PET1 CPI PET1 PET2 Total thickness (㎛) 110 150 70 150 150 150 150 150 150 nIT (%) 83 89 55 68 70 95 84 76 73 Vickers hardness (HV) 16.3 9.8 77 40 26 1.4 9 53 50 Dynamic bending characteristics (folding properties) OK OK OK NG NG OK OK OK OK Color coordinate change (YI) <2.0 <2.0 <2.0 <2.0 <2.0 <2.0 >3.0 <2.0 <2.0

According to Table 3, Examples 1 and 2 contained a photocurable epoxy siloxane resin containing 70 mol% or more of a repeating unit including a glycidox group and a cured product of an elastomer, and physical properties equal to or higher than those of Comparative Examples 1 to 7 was shown. In particular, it was confirmed that Examples 1 and 2 have excellent elastic recovery characteristics, and can replace materials for foldable cover windows such as UTG and CIP because they can implement high hardness and excellent flexibility by satisfying impact resistance and bending characteristics. .

On the other hand, in Comparative Example 1, it was confirmed that the acrylic resin composition was used as the hard coating layer, and the elastic recovery rate as well as the hardness was poor. In addition, in Comparative Examples 2 and 3, cracks occurred during evaluation of dynamic bending properties at room temperature, and the hardness and elastic recovery were poor. In addition, Comparative Example 4 could not compensate for the brittle properties of the supporting substrate because the hardness was too low compared to Examples 1 and 2. In addition, in Comparative Example 5, it was confirmed that the YI was 3.0 or more and the color coordinate change amount was increased, and thus the light resistance reliability was poor. In addition, Comparative Example 6 used a hard coating layer material containing 70 mol% or less of a repeating unit (glycidoxypropyl group) including an epoxy group-containing functional group, and as in Comparative Examples 2 and 3, the hardness and elastic recovery were poor. . In addition, in Comparative Example 7, since the base film did not satisfy the in-plane retardation value of the present application, hardness and elastic recovery were poor compared to Examples 1 and 2.

Claims (12)

light transmissive substrate; and a hard coating layer positioned on at least one surface of the light-transmitting substrate;
The hard coating layer includes a cured product of polysiloxane and an elastic polymer,
The laminate has an elastic recovery rate of 70% or more measured by the nanoindentation method, and the Vickers hardness (HV) value measured when indented with a 12mN load by indentation (triangular pyramid tip) to the surface of the hard coating layer is 2 The optical laminated body which is 40 or more and 40 or less.
The method of claim 1,
The light-transmitting substrate is an optical laminate comprising a polyester film having a plane-direction retardation value of 40 to 2000 nm represented by the following formula 1 at a wavelength of 550 nm:
[Equation 1]
Rin = (nx - ny) Х d
(In Equation 1, nx and ny are the refractive indices in the x-axis direction and the y-axis direction, respectively, and d is the thickness of the film)
3. The method of claim 2,
The polyester film has a YI value of 1.5 or less, and an optical laminate having a modulus of 10 GPa or less measured based on ISO 527-3.
3. The method of claim 2,
The polyester film comprises polyethylene terephthalate (PET), an optical laminate.
The method of claim 1,
The weight ratio of the polysiloxane and the elastomer is 100: 20 to 80, the optical laminate.
The method of claim 1,
The polysiloxane is an optical laminate comprising at least 70 mol% of a repeating unit including an epoxy group-containing functional group.
7. The method of claim 6,
The epoxy group-containing functional group is any one selected from the group consisting of an alicyclic epoxy group and a functional group represented by the following Chemical Formula 1, the optical laminate.
[Formula 1]

In Formula 1,
R _a is a substituted or unsubstituted alkylene group having 1 to 6 carbon atoms, a substituted or unsubstituted alkenylene group having 2 to 20 carbon atoms, a substituted or unsubstituted alkynylene group having 2 to 20 carbon atoms, -R _b -CH= CH-COO-R _c -, -R _d -OCO-CH=CH-R _e -, -R _f OR _g -, -R _h COOR _i -, or -R _j OCOR _k -;
R _b to R _k are each independently, a single bond; or a substituted or unsubstituted C 1 to C 6 alkylene group.
The method of claim 1,
The elastic polymer is selected from the group consisting of alkanediol having 1 to 20 carbon atoms, polyolefin polyol, polyester polyol, polyether polyol, polycarbonate polyol, or a mixture thereof, the optical laminate.
The method of claim 1,
A crack does not occur when the hard coating layer is folded and unfolded 200,000 times at a rate of once per second at 25 ° C. sifter.
The method of claim 1,
The thickness of the light-transmitting substrate is 20 μm to 200 μm,
The thickness of the hard coating layer is 5㎛ to 200㎛, the optical laminate.
A cover window of a flexible display device including the optical laminate of claim 1 .
A flexible display device comprising a cover window of the flexible display device including the optical laminate according to claim 11 .

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