KR20240011496A - Cover window for foldable display and foldable display device including the same - Google Patents

Abstract

The present invention includes a first laminate including a first hard coating layer and a first light-transmitting substrate, and a second laminate sequentially including a second hard coating layer, a second light-transmitting substrate, and a third hard coating layer. It relates to a cover window for a foldable display and a foldable display device including the same.

Description

Cover window for foldable display and foldable display device including the same {COVER WINDOW FOR FOLDABLE DISPLAY AND FOLDABLE DISPLAY DEVICE INCLUDING THE SAME}

The present invention relates to a cover window for a foldable display and a foldable display device including the same.

Recently, with the development of mobile devices such as smartphones and tablet PCs, there is a demand for thinner and slimmer display substrates. Glass or tempered glass is generally used as a material with excellent mechanical properties for the display window or front panel of such mobile devices. However, glass and tempered glass are heavy, resulting in increased weight of mobile devices, and are easily damaged by external impacts. Additionally, their low flexibility limits their application to flexible or foldable display devices.

Plastic resin is being researched as a material to replace glass. Plastic resin is lightweight, has little risk of breaking, and is flexible, making it more suitable for lightweighting and flexible mobile devices. Representative examples include polyethylene terephthalate (PET), polyethersulfone (PES), polyethylene naphthalate (PEN), polyacrylate (PAR), polycarbonate (PC), polyimide (PI), and polyamideimide (PAI). However, substrates using these plastic resins have problems with insufficient impact resistance, hardness, and scratch resistance compared to glass materials. Accordingly, methods are being attempted to supplement high hardness, impact resistance, and wear resistance by coating a resin composition on a plastic resin substrate to form a hard coating layer.

For example, UV-curable curable resins are mainly used as hard coatings for foldable display substrates. However, conventional curable resins have a high shrinkage rate when cured, and as a result, severe curl occurs, so they must be coated with a thin coating, which limits their impact resistance to low.

The present invention has improved high hardness, impact resistance, and scratch resistance, so it can replace tempered glass cover windows, and there is almost no damage to the film even by repeated bending or folding operations, so it can be used in bendable, flexible, rollable, or folder applications. We provide a cover window for a foldable display that can be easily applied to mobile devices or display devices.

Additionally, the present invention provides a foldable display device including a cover window for the foldable display.

In this specification, a first laminate including a first hard coating layer and a first light-transmissive substrate; and a second laminate sequentially including a second hard coating layer, a second light-transmissive substrate, and a third hard coating layer.

Additionally, this specification provides a foldable display device including a cover window for the foldable display.

Hereinafter, a cover window for a foldable display according to a specific embodiment of the invention and a foldable display device including the same will be described in more detail.

In this specification, “foldable” means a state of flexibility that does not cause cracks of 3 mm or more in length when wound around a cylindrical mandrel with a diameter of 5 mm, Therefore, the optical laminated film can be applied as a cover film for a bendable, flexible, rollable, or foldable display.

Additionally, in this specification, “(meth)acrylate” includes both acrylate and methacrylate.

Additionally, in this specification, curing includes both photocuring and thermal curing.

In addition, in this specification, the weight average molecular weight (Mw) and the number average molecular weight (Mn) mean the 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 of polystyrene equivalent measured by the GPC method, commonly known analysis devices, detectors such as differential refractive index detectors, and analytical columns can be used, and the commonly applied temperature Conditions, solvent, and flow rate can be applied. Specific examples of the measurement conditions include a temperature of 30°C, chloroform solvent, and a flow rate of 1 mL/min. For a specific example of the above measurement conditions, a Waters PL-GPC220 instrument was used using a Polymer Laboratories PLgel MIX-B 300 mm long column, the evaluation temperature was 160°C, and 1,2,4-trichlorobenzene was used as a solvent. The flow rate is 1 mL/min, the sample is prepared at a concentration of 10 mg/10 mL, and then supplied in an amount of 200 μL. The values of Mw and Mn can be obtained respectively using a calibration curve formed using a polystyrene standard. . Nine types of molecular weights of polystyrene standards were used: 2,000 / 10,000 / 30,000 / 70,000 / 200,000 / 700,000 / 2,000,000 / 4,000,000 / 10,000,000.

In this specification, the terms first and second are used to describe various components, and the terms are used only for the purpose of distinguishing one component from other components.

Additionally, in this specification, the term “substituted or unsubstituted” refers to deuterium; halogen group; Nitrile group; nitro group; hydroxyl group; carbonyl group; ester group; imide group; amino group; Phosphine oxide group; Alkoxy group; Aryloxy group; Alkylthioxy group; Arylthioxy group; Alkyl sulphoxy group; Aryl sulfoxy group; silyl group; boron group; Alkyl group; Cycloalkyl group; alkenyl group; Aryl group; Aralkyl group; Aralkenyl group; Alkylaryl group; Alkylamine group; Aralkylamine group; heteroarylamine group; Arylamine group; Arylphosphine group; or substituted or unsubstituted with one or more substituents selected from the group consisting of heterocyclic groups containing one or more of N, O and S atoms, or substituted or unsubstituted with two or more of the above-exemplified substituents linked. . For example, “a substituent group in which two or more substituents are connected” may be a biphenyl group. That is, the biphenyl group may be an aryl group, or it may be interpreted as a substituent in which two phenyl groups are connected.

According to one embodiment of the invention, a first laminate including a first hard coating layer and a first light-transmissive substrate; And a second laminate sequentially including a second hard coating layer, a second light-transmitting substrate, and a third hard coating layer. A cover window for a foldable display including a can be provided.

The present inventors have conducted research on the cover window of a foldable display device, and the cover window includes a first laminate including a first hard coating layer and a first light-transmissive substrate, a second hard coating layer, a second light-transmissive substrate, and In the case of including a second laminate sequentially including a third hard coating layer, high hardness, impact resistance, and scratch resistance can be exhibited, and there is little damage to the film even by repeated bending or folding operations, making it bendable. , the invention was completed after confirming that it can be easily applied to flexible, rollable, or foldable mobile devices, display devices, etc.

Specifically, the cover window for the foldable display may include a first laminate including a first hard coating layer and a first light-transmissive substrate, and the first laminate may be located on the viewing side of the foldable display device. You can. The cover window for the foldable display including the first laminate may have excellent impact resistance and scratch resistance.

In addition, the cover window for the foldable display includes a second laminate sequentially including a second hard coating layer, a second light-transmissive substrate, and a third hard coating layer, and the second laminate is attached to the first laminate. Compared to this, it can be located closer to the display element. The cover window for the foldable display including the second laminate may exhibit high hardness and have excellent impact resistance and scratch resistance.

The first hard coating layer included in the first laminate has a thickness of 1 ㎛ or more and 20 ㎛ or less, 2 ㎛ or more and 18 ㎛ or less, 4 ㎛ or more and 16 ㎛ or less, 5 ㎛ or more and 14 ㎛ or less, or 8 ㎛ or more and 12 ㎛ or less. You can. If the thickness of the first hard coating layer is too thick, it is more likely to break when folded, and if the thickness of the first hard coating layer is too thin, the hardness may be poor even if folding properties are secured.

The second hard coating layer and the third hard coating layer included in the second laminate each independently have a thickness of 20 ㎛ or more and 100 ㎛ or less, 25 ㎛ or more and 90 ㎛ or less, 30 ㎛ or more and 80 ㎛ or less, and 35 ㎛ or more 70 ㎛. Hereinafter, it may be 40 ㎛ or more and 60 ㎛ or less. If the thickness of the second hard coating layer and/or the third hard coating layer is excessively thick, it is more likely to break when folded. If the thickness of the second hard coating layer and/or the third hard coating layer is excessively thin, even if folding properties are secured, the hardness and Impact resistance may be poor. Also, the above The second hard coating layer and the third hard coating layer may have the same or different thicknesses.

The first hard coating layer, the second hard coating layer, and the third hard coating layer included in the cover window according to the above embodiment may include polysiloxane and an elastomer including a repeating unit containing an epoxy group-containing functional group. For example, the first hard coating layer, the second hard coating layer, and the third hard coating layer may include 100 parts by weight of polysiloxane containing 70 mol% or more of a repeating unit containing an epoxy group-containing functional group, and 20 to 80 parts by weight of an elastic polymer. .

For example, the first hard coating layer, the second hard coating layer, and the third hard coating layer may include polysiloxane including a repeating unit including the epoxy group-containing functional group. Specifically, the polysiloxane includes a repeating unit including an epoxy group-containing functional group. The unit may be included in an amount of 70 mol% or more, 70 mol% or more and 100 mol% or less, or 80 mol% or more and 99 mol% or less. If the content of repeating units containing epoxy group-containing functional groups contained in the polysiloxane is less than 70 mol%, there is a problem in that the hard coating layer has difficulty showing sufficient surface hardness due to a decrease in curing density.

Meanwhile, 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 the following formula (1).

[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 it is a substituted or unsubstituted alkylene group having 1 to 6 carbon atoms.

The functional group represented by Formula 1 includes an epoxy group, which not only improves the high hardness, impact resistance, and scratch resistance of the cover window, but also causes almost no damage to the film even by repeated bending or folding operations, making it bendable and flexible. , rollable, or foldable mobile devices, or display devices, etc.

For example, the epoxy group-containing functional group represented by Formula 1 is R _a is methylene, ethylene, propylene, allylene, -R _b -CH=CH-COO-R _c -, -R _d -OCO-CH=CH- It may be 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 glycidoxypropyl group, or a glycidoxybutyl group.

In addition, the alicyclic epoxy group is not limited thereto, but for example, epoxycyclopentyl group, epoxycyclopentylmethyl group, epoxycyclopentylethyl group, epoxycyclopentylpropyl group, epoxycyclopentylbutyl group, epoxycyclohexyl group, epoxy It may be a cyclohexylmethyl group, an epoxycyclohexylethyl group, an epoxycyclohexylpropyl group, or an epoxycyclohexylbutyl group.

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

[Formula 2]

(R ¹ SiO _3/2 ) _a (R ² SiO _3/2 ) _b (O _1/2 R) _c

In Formula 2,

R ¹ is the epoxy group-containing functional group, and contains at least 70 mol% of repeating units containing a substituent of R ¹ based on the total molar content of Formula 2,

R ² is a substituted or unsubstituted alkyl group with 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkyl group with 3 to 20 carbon atoms, a substituted or unsubstituted alkenyl group with 2 to 20 carbon atoms, or a substituted or unsubstituted alkenyl group with 2 to 20 carbon atoms. alkynyl group, substituted or unsubstituted aryl group having 6 to 20 carbon atoms, substituted or unsubstituted arylalkyl group having 7 to 20 carbon atoms, substituted or unsubstituted alkylaryl group having 7 to 20 carbon atoms, epoxy group, hydrogen atom, amino group , mercapto group, ether group, ester group, carbonyl group, carboxyl group, (meth)acrylate or sulfone group,

R is a hydrogen atom or an alkyl group having 1 to 20 carbon atoms,

a / (a + b) ≥ 0.7,

a is a positive number,

b and c are each independently 0 or a positive number.

The polysiloxane represented by Formula 2 includes a silsesquioxane unit of (R ¹ SiO _3/2 ) as a T3 unit.

In the silsesquioxane structural unit of (R ¹ SiO _3/2 ), R ¹ is a functional group represented by the formula 1, which is 70 mol% or more, 70 to 100 mol%, based on the total molar content of the formula 2. It may be included in mol%, or 80 to 100 mol%. If the content of the functional group represented by Formula 1 is less than 70 mol%, there is a problem in that the hard coating layer has difficulty showing sufficient surface hardness due to a decrease in curing density.

In addition, the polysiloxane may further include a (R ² SiO _3/2 ) silsesquioxane unit as a T3 unit along with the (R ¹ SiO _3/2 ) silsesquioxane unit described above. The silsesquioxane unit of (R ² SiO _3/2 ) can improve the surface hardness characteristics of the hard coating layer by increasing the curing density of polysiloxane.

The R ² is specifically a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aryl group having 6 to 12 carbon atoms, or a substituted or unsubstituted carbon number. It may be selected from the group consisting of an arylalkyl group having 7 to 12 carbon atoms, a substituted or unsubstituted alkylaryl group having 7 to 12 carbon atoms, an epoxy group, and a hydrogen atom. Among these, in that the surface hardness characteristics of the hard coating layer can be further improved by further increasing the curing density of polysiloxane, the R ² is more specifically composed of an acrylic group, a methacrylic group, a vinyl group, an allyl group, an epoxy group, and an oxetane group. It may be an alkyl group with 1 to 6 carbon atoms, an aryl group with 6 carbon atoms, or an epoxy group, which is unsubstituted or substituted with one or more substituents selected from the group. Meanwhile, the epoxy group is a functional group containing an oxirane ring and includes an alicyclic epoxy group, an aliphatic epoxy group, and an aromatic epoxy group, but excludes the epoxy group-containing functional group represented by Formula 1 above.

Additionally, the polysiloxane may include a structural unit of (O _1/2 R). By including the above structural units, flexibility can be improved while maintaining excellent hardness characteristics. The R may specifically be a hydrogen atom or an alkyl group having 1 to 12 carbon atoms. More specifically, it may be a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, such as a methyl group, ethyl group, propyl group, isopropyl group, butyl group, or isobutyl group. It may be a straight chain or branched alkyl group of 4 to 4.

Polysiloxane containing the above-described structural units is obtained by hydrolysis of the siloxane monomer of each structural unit, specifically, an alkoxysilane having a functional group of Formula 1, or an alkoxysilane having a functional group of Formula 1 and a heterogeneous alkoxysilane. It can be manufactured by a condensation reaction, where the molar ratio of each constituent unit can be controlled by controlling the content ratio of the alkoxysilane. Specifically, in Formula 2, a, b, and c are (R ¹ SiO _3/2 ) unit, (R ² SiO _3/2 ) unit, and (O _1/2 R) unit respectively constituting the polysiloxane. It represents the molar ratio, and may be 0<a<1, 0≤b<1, and 0≤c<1.

In addition, the polysiloxane contains the structural unit of (R ¹ SiO _3/2 ) in an amount of 70 mol% or more based on the total amount of T units constituting the polysiloxane, that is, 100 mol%, under the condition of satisfying the content range of each structural unit described above. , more specifically, by containing it at 70 mol% or more and 100 mol% or less, the cured density increases when forming a hard coating film, and as a result, the optical laminated film can exhibit significantly improved surface hardness (when expressed in molar ratio, 0.7 ≤ a / (a + b) ≤ 1). If the molar content of the (R ¹ SiO _3/2 ) structural unit in the polysiloxane is less than 70 mol%, it is difficult for the hard coating layer to exhibit sufficient surface hardness due to a decrease in cured density. More specifically, the structural unit of (R ¹ SiO _3/2 ) may be included in an amount of 70 mol% or more and 100 mol% or less, or 85 mol% or more and 100 mol% or less with respect to the total amount of T units, that is, 100 mol%. You can.

In addition, when the polysiloxane further includes the structural unit of (R ² SiO _3/2 ), it may be included in a molar ratio corresponding to b (0<b<1), and more specifically, 0<b<0.5 Alternatively, it may further include structural units of (R ² SiO _3/2 ) in a molar ratio satisfying 0.01≤b≤0.5, more specifically, 0.1≤b≤0.3. When the structural unit of (R ² SiO _3/2 ) is included in the above content range, the surface hardness characteristics of the hard coating layer can be improved by increasing the curing density of polysiloxane.

In addition, when the polysiloxane further contains the (O _1/2 R) structural unit, it may be included in a molar ratio corresponding to c (0<c<1), more specifically, 0<c<0.5, More specifically, the molar ratio satisfying 0.01≤c≤0.3 or 0.01≤c≤0.05 may further include (O _1/2 R) units. When the (O _1/2 R) unit is included in the above content range, flexibility can be improved while maintaining excellent hardness characteristics.

Additionally, under conditions that meet the above-described content range, the total molar ratio (a+b+c) of each structural unit included in the polysiloxane may be 1. Meanwhile, the content of each structural unit constituting the polysiloxane can be determined by measuring a ¹ H-NMR or ²⁹ Si-NMR spectrum.

Meanwhile, the polysiloxane may have an equivalent weight of an epoxy group-containing functional group of Formula 1 of 2.5 to 6.3 g/eq or 3.0 to 6e/eq. If the equivalent weight of the functional group represented by Formula 1 is too small, it may be difficult to achieve sufficient pencil pressing hardness of 3H or more, and if it is too large, the problem of reduced bending prevention properties occurs. The equivalent weight of these functional groups is the molecular weight of polysiloxane divided by the number of functional groups, and can be analyzed by H-NMR or chemical titration.

In addition, the weight average molecular weight, number average molecular weight, molecular weight distribution, etc. of the polysiloxane can be adjusted by controlling the reaction rate using reaction temperature, amount of catalyst, type of solvent, etc. during production. It may have a weight average molecular weight of 50,000 g/mol or less, 1,500 g/mol or more and 45,000 g/mol or less, 2,000 g/mol or more and 40,000 g/mol or less, and 2,500 g/mol or more and 35,000 g/mol or less. By having a weight average molecular weight in the above range, superior hardness and impact resistance characteristics can be exhibited. If the weight average molecular weight is too low, hardness and impact resistance may not be realized but rather ductility may develop, and if the weight average molecular weight is too high, although high hardness may be achieved, there is a risk that film processability may be reduced.

In addition, the polysiloxane may have a number average molecular weight (Mn) of 1,000 g/mol or more and 10,000 g/mol or less, 2,000 g/mol or more and 9,000 g/mol or less, or 3,000 g/mol or more and 8,000 g/mol or less, in addition to the Mw described above. there is. When the number average molecular weight condition is met, compatibility with other components in the hard coating layer is increased, surface hardness of the cured product is improved, and heat resistance and abrasion resistance of the cured product can be further improved. Meanwhile, the weight average molecular weight and number average molecular weight of the polysiloxane are standard polystyrene conversion values obtained by gel permeation chromatography.

In addition, the polysiloxane may have a molecular weight distribution (Mw/Mn) of 1.0 or more and 10.0 or less, 1.5 or more and 9.0 or less, 2.0 or more and 8.0 or less, and 3.0 or more and 7.0 or less. When the molecular weight distribution is within the above range, the effect of improving surface hardness and impact resistance is superior, and polysiloxane exists in a liquid form, making handling easy.

The hard coating layer includes an elastic polymer, and the elastic polymer provides stress resistance characteristics through the toughness of the hard coating layer to minimize shrinkage during curing, thereby improving bending characteristics and simultaneously improving flexibility such as bendability. and can improve hardness characteristics.

The content of the elastic polymer included in the hard coating layer is specifically, 20 to 80 parts by weight, 20 to 70 parts by weight of the elastic polymer, based on 100 parts by weight of polysiloxane containing 70 mol% or more of repeating units containing the epoxy group-containing functional group. , 20 to 60 parts by weight, 20 to 50 parts by weight, and 30 to 40 parts by weight. If the content of the elastic polymer is too high, there is a risk that the bending properties will be greatly reduced, and if the content of the elastic polymer is too small, the improvement effect due to the inclusion of the elastic polymer will not be sufficiently obtained, and there is a risk that the bending properties and flexibility will be reduced.

The elastic polymer is not limited thereto, but includes, for example, at least one selected from the group consisting of alkanediols having 1 to 20 carbon atoms, polyolefin polyols, polyester polyols, polycaprolactone polyols, polyether polyols, and polycarbonate polyols. can do. Compared to typical elastic polymers such as rubber, these elastic polymers can be cross-polymerized by ultraviolet irradiation and can achieve high hardness and flexibility without deteriorating other physical properties.

Among these, the elastic polymer may include polycaprolactone polyol, polycarbonate diol, or a mixture thereof. In particular, the polycaprolactone polyol contains an ester group and an ether group simultaneously in the repeating unit, so that it is combined with the polysiloxane. When used, it can exhibit superior effects in terms of flexibility, hardness, and impact resistance.

The polycaprolactone polyol may have a number average molecular weight (Mn) of 300 Da or more and 10,000 Da or less, 500 Da or more and 9,000 Da or less, 1,000 Da or more and 8,000 Da or less, and 2,000 Da or more and 7,000 Da or less. When the above-mentioned number average molecular weight conditions are met, compatibility with other components in the hard coating layer is increased, surface hardness of the cured product is improved, and heat resistance and abrasion resistance of the cured product can be further improved.

The hard coating layer may further include a reactive monomer containing one or more functional groups capable of crosslinking with the polysiloxane. The reactive monomer includes one or more functional groups capable of crosslinking with the polysiloxane described above, thereby lowering the viscosity of the polysiloxane to facilitate processability and improve coating adhesion.

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

In addition, reactive monomers containing one or more functional groups capable of crosslinking with the polysiloxane include, for example, bisphenol A diglycidyl ether, 4-vinylcyclohexene dioxide, cyclohexene vinyl monooxide, (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- Methylene oxetane, 3-methyl-3-hydroxymethyloxetane, 3-ethyl-3-hydroxymethyloxetane, 3,3-oxetanedimethanethiol, 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 bisoxetane, 3-ethyl-3[{(3-ethyloxetan-3-yl)methoxy}methyl]oxetane, (3-ethyloxetan-3-yl) It may include one or more selected from the group consisting of methyl methacrylate, and 4-[(3-ethyloxetan-3-yl)methoxy]butan-1-ol.

The weight ratio of polysiloxane and reactive monomer included in the hard coating layer may be 99:1 to 80:20, 97:3 to 85:15, or 95:5 to 90:10. If the polysiloxane is contained in an excessive amount compared to the reactive monomer, the improvement effect due to the inclusion of the reactive monomer may be minimal, and if the polysiloxane is contained in an excessively small amount compared to the elastomer, the viscosity of the polysiloxane is excessively lowered due to the excess reactive monomer, resulting in poor processability. This may actually deteriorate.

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

The acrylate-based compounds include 2-ethylhexyl acrylate, octadecyl acrylate, isodecyl acrylate, 2-phenoxyethyl acrylate, lauryl acrylate, stearyl acrylate, behenyl acrylate, and tridecyl meta. Crylate, nonylphenol ethoxylate 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, triphenyl glycol diacrylate, butanediol diacrylate , 1,3-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate Crylate, tetraethylene glycol, diacrylate, tetraethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, Diporo Pylene 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 pentacrylate, di Examples include trimethylolpropane tetraacrylate, alcohol sulfated tetraacrylate, etc., preferably pentaerythritol triacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, or Examples include multifunctional acrylate-based compounds such as pentaerythritol tetraacrylate, and any one or a mixture of two or more of these may be used.

In addition, acrylate-based oligomers such as polyester acrylate, polyether acrylate, urethane acrylate, or epoxy acrylate may be used, and any one or a mixture of two or more of these may be used. Among the acrylate-based compounds described above, urethane acrylate oligomer can be used more preferably considering the significant 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 there are less than 6 functional groups, the effect of improving hardness may be minimal, and if there are more than 9 functional groups, hardness may be excellent but viscosity may increase. In addition, the urethane (meth)acrylate oligomer may be used without limitation in the field, but is preferably a compound having at least one isocyanate group in the molecule and a (meth)acrylate compound having at least one hydroxy group in the molecule. Those prepared by reacting can 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 minimal, and if it exceeds 20 parts by weight, the effect of improving surface hardness may be hindered due to the excessive amount of the acrylate-based compound.

In addition to the above ingredients, the hard coating layer may independently additionally include one or more commonly used additives such as antioxidants, surfactants, anti-yellowing agents, inorganic fillers, lubricants, coating aids, and antifouling agents.

The first light-transmitting substrate included in the first laminate and the second light-transmitting substrate included in the second laminate each independently have a thickness of 30 ㎛ or more and 200 ㎛ or less, 35 ㎛ or more and 180 ㎛ or less, and 40 ㎛. It may be 150 ㎛ or less, 45 ㎛ or more and 120 ㎛ or less, or 50 ㎛ or more and 100 ㎛ or less. If the thickness of the first light-transmitting substrate and/or the second light-transmitting substrate is too thick, it is likely to break when folded, and if the thickness of the first light-transmitting substrate and/or the second light-transmitting substrate is too thin, even if folding properties are secured, Poor hardness may occur.

The first light-transmitting substrate and/or the second light-transmitting substrate may include a transparent plastic resin. Specific examples of the plastic resin include polyester resin, cellulose resin, polycarbonate resin, acrylic resin, styrene resin, polyolefin resin, polyimide resin, polyethersulfone resin, and sulfone resin. Any one or a mixture of two or more of these may be used. Additionally, in order to improve the impact resistance, high hardness, and scratch resistance of the cover window, the first light-transmitting substrate and/or the second light-transmitting substrate may be a polyester film.

For example, the first light-transmitting substrate and/or the second light-transmitting substrate may be polyethyleneterephthalate (PET), cyclic olefin copolymer (COC), polyacrylate (PAC), Polycarbonate (PC), polyethylene (PE), polymethylmethacrylate (PMMA), polyetheretherketone (PEEK), polyethylenenaphthalate (PEN), polyetherimide , PEI), polyimide (PI), polyamideimide (PAI), and triacetylcellulose (TAC).

Meanwhile, the support base layer may be a single layer, or may have a multi-layer structure of two or more layers made of the same or different materials. For example, the support base layer is a multilayer structure of polyethylene terephthalate (PET), a multilayer structure formed by co-extrusion of polymethyl methacrylate (PMMA)/polycarbonate (PC), or polymethyl methacrylate (PMMA). It may be a single-layer structure containing a copolymer of polycarbonate (PC).

In addition, the support base layer may be surface treated by plasma and/or corona as needed, and the method is not specifically proposed and may be performed according to a common method.

In the cover window for a foldable display according to the above embodiment, a first adhesive layer may be interposed between the first and second laminates.

Additionally, the first light-transmissive substrate of the first laminate and the first adhesive layer may be in contact with each other. The second or third hard coating layer of the second laminate may be in contact with the first adhesive layer. Accordingly, the cover window is sequentially stacked with a first hard coating layer/first light-transmitting substrate/first adhesive layer/second hard coating layer/second light-transmitting substrate/third hard coating layer, or a first hard coating layer/third hard coating layer. 1 Light-transmitting substrate/first adhesive layer/third hard coating layer/second light-transmitting substrate/second hard coating layer may be sequentially laminated.

Additionally, the cover window may further include a second adhesive layer formed on one surface of the second laminate facing the first laminate. Accordingly, the second adhesive layer may be in contact with the second hard coating layer of the second laminate or may be in contact with the third hard coating layer. In addition, the cover window may be sequentially stacked with a first hard coating layer/first light-transmitting substrate/first adhesive layer/second hard coating layer/second light-transmitting substrate/third hard coating layer/second adhesive layer, or a first hard coating layer/second adhesive layer. Hard coating layer/first light-transmitting substrate/first adhesive layer/third hard coating layer/second light-transmitting substrate/second hard coating layer/second adhesive layer may be sequentially laminated.

In addition, the first and second adhesive layers may each independently have a thickness of 5 ㎛ or more, 10 ㎛ or more, 15 ㎛ or more, 20 ㎛ or more, and 50 ㎛ or less, 45 ㎛ or less, 40 ㎛ or less, 35 ㎛ or less, and 30 ㎛ or less. It may be ㎛ or less. If the thickness of the first adhesive layer and/or the second adhesive layer is too thin, there is a problem in that sufficient folding properties required for display panel assembly cannot be secured, and if the thickness of the first adhesive layer and/or the second adhesive layer is too thin, If it is thick, excessive lamination of the soft adhesive layer may cause appearance defects such as adhesive peeling.

In addition, the first adhesive layer and/or the second adhesive layer may be implemented as an adhesive or adhesive film, and are not particularly limited as long as they are known in the art, but may include, but are not limited to, optically clear adhesive (OCA), It may include one or more selected from the group consisting of Pressure Sensitive Adhesive (PSA), Super View Resin (SVR), and Optically Clear Resin (OCR).

Additionally, the first adhesive layer and/or the second adhesive layer may further include one or more layers depending on the specific purpose and structure of the cover window.

The cover window according to the above embodiment may have a total thickness of 150 ㎛ or more and 450 ㎛ or less, 180 ㎛ or more and 400 ㎛ or less, 200 ㎛ or more and 350 ㎛ or less, and 220 ㎛ or more and 300 ㎛ or less. If the overall thickness of the cover window is too thick, it is more likely to break when folded. If the overall thickness of the cover window is too thin, hardness and impact resistance may be poor even if folding properties are secured.

The cover window according to the above embodiment may further include a release film. The release film may be formed on the second adhesive layer. As the release film, those known in the art may be used. For example, a polyethylene terephthalate (PET) film may be used. In addition, the release film is preferably a PET film with a release force of about 10 g/in to facilitate release, but is not limited to this. The optical laminated film including the release film is easy to attach to an adherend after removing the release film, thereby ensuring convenience when applied to a flexible display device, etc.

In addition, the cover window is a third hard coating layer (or first hard coating layer) at a 90° angle so that the third hard coating layer (or first hard coating layer) faces each other with a gap of 5 mm in the middle of the third hard coating layer (or first hard coating layer). When folding and unfolding the inside of the first hard coating layer (1st hard coating layer) 50,000 times at a speed of 1 time per second, it shows bending durability at a level where cracks of 1 mm or more do not occur.

In addition, the cover window is a third hard coating layer (or first hard coating layer) at a 90° angle so that the third hard coating layer (or first hard coating layer) faces each other with a gap of 5 mm in the middle of the third hard coating layer (or first hard coating layer). When folding and unfolding the inside of the first hard coating layer 50,000 times at a speed of 1 time per second at -20°C, it shows bending durability to the extent that no cracks of 1 mm or more occur.

Figure 1 schematically shows a method for evaluating dynamic bending properties.

Referring to Figure 1, cover window After placing it horizontally with the floor, the gap between the folded parts in the middle of the cover window is 5 mm, and both sides of the cover window are folded and unfolded at 90 degrees with respect to the floor, repeating 50,000 times at a speed of 1 time per second. Durability against bending can be measured. At this time, in order to keep the distance between the folded parts constant, for example, the optical laminated film is placed in contact with a rod with a diameter (R) of 5 mm, the remaining part of the cover window is fixed, and both sides of the cover window are centered around the rod. You can repeat folding and unfolding. Additionally, the folded portion is not particularly limited as long as it is inside the cover window. For measurement convenience, the central portion of the optical laminated film may be folded so that the remaining two sides of the cover window excluding the folded portion are symmetrical.

In this dynamic bending characteristic evaluation, the cover window does not generate cracks larger than 1 cm, larger than 3 mm, or larger than 1 mm even after bending more than 50,000 times, and virtually no cracks occur. In particular, the first hard coating layer of the optical laminated film can be folded inward, the third hard coating layer can be folded inward, or the second adhesive layer can be folded inward, and no cracks occur no matter which layer is folded inward. . Therefore, the risk of cracks occurring even under actual use conditions such as repeated folding, rolling, or bending is very low, making it suitable for use as a cover window for a foldable display device.

The cover window having the above-described structure and configuration can form first, second, and third hard coat layers by applying the resin composition for forming a hard coat layer to one or both sides of the first and second light-transmissive substrates and then curing it. there is. Resin compositions for forming a hard coating layer that form the first, second, and third hard coating layers may be the same or different.

The composition and weight ratio of polysiloxane, elastomer, reactive monomer, etc. contained in the resin composition for forming the hard coating layer are as described above.

Additionally, the resin composition for forming the hard coating layer may further include an initiator. The initiator may be a photopolymerization or thermal polymerization initiator well known in the field, and its type is not greatly limited. For example, the photopolymerization initiator is aryl sulfonium hexafluoroantimonate salt, aryl sulfonium hexafluorophosphate salt, diphenyldiodonium hexafluorophosphate salt, diphenyldiodonium hexaantimonium salt. , ditorililiodonium hexafluorophosphate salt, and 9-(4-hydroxyethoxyphenyl)cyanthreneium hexafluorophosphate salt, but is not limited thereto. The thermal polymerization initiator is 3-methyl-2-butenyltetramethylenesulfonium hexafluoroantimonate salt, ytterbium trifluoromethene sulfonate salt, samarium trifluoromethene sulfonate salt, and erbium trifluoromethene salt. Sulfonate salt, disprosium trifluoromethenesulfonate salt, lanthanum trifluoromethenesulfonate salt, tetrabutylphosphonium metensulfonate salt, ethyltriphenylphosphonium bromide salt, benzyldimethylamine, dimethyl It may include, but is not limited to, one or more selected from the group consisting of aminomethylphenol, triethanolamine, N-n-butylimidazole, and 2-ethyl-4-methylimidazole.

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 total content of the composition. If the initiator content is less than 0.1% by weight, only surface hardening occurs or epoxy curing does not occur sufficiently, resulting in low hardness. If it exceeds 10% by weight, cracks and peeling may occur due to the fast curing speed.

The resin composition for forming the hard coating layer can be used as solvent-free if there are no problems in the process, but optionally an organic solvent may be added to control the viscosity and fluidity of the composition and increase the applicability of the composition during coating. It can be included.

When the organic solvent is further included, the organic solvent may include alcohol-based solvents such as methanol, ethanol, isopropyl alcohol, and butanol; Alkoxy alcohol-based solvents such as 2-methoxyethanol, 2-ethoxyethanol, 1-methoxy-2-propanol, and diacetone alcohol; Ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl propyl ketone, and cyclohexanone; Polyamidoimide corrosive solvents such as dimethylacetamide and diethylacetamide; 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-based 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, aromatic solvents such as benzene, toluene, and xylene can be used individually or in combination.

In addition, the resin composition for forming a hard coating layer may further include antioxidants, surfactants, anti-yellowing agents, inorganic fillers, lubricants, coating aids, anti-fouling agents, etc. in addition to the ingredients described above. In addition, the content can be variously adjusted within a range that does not deteriorate the physical properties, so it is not particularly limited, but may be included, for example, at 0.1 to 10% by weight based on 100% by weight of the total content of the composition.

For example, the antioxidant is used to suppress the oxidation reaction resulting from the polymerization initiator, and may include one or more mixtures selected from the group consisting of phenolic, phosphate, amino, thioester, etc. It may not be limited. The surfactant may be a 1- to 2-functional fluorine-based acrylate, a fluorine-based surfactant, or a silicone-based surfactant. At this time, the surfactant may be included in the cross-linked copolymer in a dispersed or cross-linked form. Additionally, the anti-yellowing agent may include benzophenone-based compounds or benzotriazole-based compounds.

The application process of the resin composition for forming the hard coating layer may be performed by known methods such as die coater, air knife, reverse roll, spray, blade, casting, gravure, spin coating, or bar coating.

In addition, after applying each resin composition, a process for curing may be performed, and the curing may be performed through heat curing or light curing according to a conventional method. Heat treatment or light irradiation conditions for the heat curing and light curing can be appropriately controlled by adjusting the wavelength range, light amount, or heat treatment temperature depending on the type of initiator.

According to another embodiment of the invention, a foldable display device including a cover window for the foldable display may be provided.

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

Meanwhile, the foldable display device may be, 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. It can be a device (rollable display or foldable display).

For example, in the organic light emitting diode (OLED) display device, the cover window of the foldable organic light emitting diode display device may be located on the outer part in the direction from which light or the screen comes, and a cathode that provides electrons. , an electron transport layer, an emission layer, a hole transport layer, and an anode that provides holes may be formed sequentially. 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 foldable display, the cathode and anode electrodes and each component may be made of a material having a predetermined elasticity.

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

Meanwhile, the rollable display device may have various structures depending on the field of application and specific form, and includes, for example, a cover window, a touch panel, a polarizer, a barrier film, a light-emitting device (OLED device, etc.), a transparent substrate, etc. It could be a structure.

Another example of the foldable display device includes a pair of polarizers facing each other; A thin film transistor, a color filter, and a liquid crystal cell sequentially stacked between the pair of polarizers; and a liquid crystal display device including a backlight unit.

In the display device, the optical laminated film may be provided on the outermost surface of the display panel on the viewer side or the backlight side.

According to the present invention, a cover window for a foldable display with high hardness, excellent impact resistance, and scratch resistance, and a foldable display device including the same can be provided.

In addition, the cover window exhibits improved bending characteristics and has excellent flexibility, high hardness, impact resistance, and scratch resistance. In particular, the film is hardly damaged even by repeated bending or folding operations, making it bendable. , can be usefully applied to flexible, rollable, or foldable mobile devices, display devices, front panels of various instrument panels, and display units.

Figure 1 schematically shows a method for evaluating dynamic bending properties.
Figure 2 compares the color change of pressure-sensitive paper when evaluating the impact resistance of the cover windows of Examples and Comparative Examples.

The invention is explained 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.

<Manufacturing example>

Preparation Example 1: Preparation of polysiloxane

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

Next, a basic catalyst (trimethylammonium hydroxide; TMAH) was added to the resulting mixed solution in an amount of 1 part by weight based on 100 parts by weight of the silane monomer and reacted at 100°C for 2 hours to produce glycidoxypropyl modified silicone (hereinafter referred to as glycidoxypropyl modified silicone). Polysiloxane A of the following composition containing 100 mol% GP) was prepared (Mw: 2,800 g/mol, glycidoxypropyl group equivalent: 6.0 g/eq).

(R ¹ SiO _3/2 ) _a (R ² SiO _3/2 ) _b (O _1/2 R) _c (2)

(In Formula 2, R ¹ is a glycidoxypropyl group (in Formula 1, R _a is -R _b OR _c -, R _b is a propylene group, and R _c is a methylene group), and R is a hydrogen atom or It is a methyl group, a=0.97, b=0, c=0.03)

Preparation Example 2: Preparation of resin composition for forming hard coating layer

100 g of polysiloxane prepared in Preparation Example 1, 20 g of polycaprolactone diol as an elastic polymer (number average molecular weight: 2000 Da, Sigma Aldrich), and 10 g of bisphenol A diglycidyl ether as a reactive monomer (Mn: 340 g) /mol, Sigma Aldrich Co.), 3 g of Irgacure as a photoinitiator, and 11.2 g of 2-butanone as a solvent were mixed to prepare a resin composition for forming a hard coating layer.

<Examples and Comparative Examples>

Example 1

The resin composition for forming a hard coating layer prepared in Preparation Example 2 was applied to one side of a polyethylene terephthalate film of 15 cm was formed to manufacture a first laminate.

Thereafter, the resin composition for forming a hard coating layer prepared in Preparation Example 2 was applied to one side of a polyethylene terephthalate film of 15 cm A hard coating layer was formed. Then, the resin composition for forming a hard coating layer prepared in Preparation Example 2 was applied to the other side of the polyethylene terephthalate film and photocured by irradiating ultraviolet rays using a lamp to form a third layer with a thickness of 40 ㎛. A hard coating layer was formed to prepare a second laminate.

A first adhesive layer (Material: Pressure Sensitive Adhesive (PSA), Manufacturer: LG Chemical) with a thickness of 25 ㎛ is laminated on the polyethylene terephthalate film of the first laminate, and then, the second laminate is The second hard coating layer was laminated so as to be in contact with the first adhesive layer. Afterwards, a second adhesive layer (material: pressure sensitive adhesive (PSA)) with a thickness of 25 ㎛ was laminated on the third hard coating layer of the second laminate to prepare a cover window.

Comparative Example 1

The resin composition for forming a hard coating layer prepared in Preparation Example 2 was applied to one side of a polyethylene terephthalate film of 15 cm was formed. Thereafter, a first adhesive layer (Material: Pressure Sensitive Adhesive (PSA), Manufacturer: LG Chemical) with a thickness of 25 ㎛ was laminated on the other side of the polyethylene terephthalate film, and a 15 cm x 20 layer was applied to the first adhesive layer. After laminating glass (UTG; Ultra Thin Glass) with a thickness of 60 ㎛ and a thickness of 60 ㎛, a second adhesive layer (Material: Pressure Sensitive Adhesive (PSA), Manufacturer: LG Chemical) with a thickness of 25 ㎛ is applied to the other side of the glass. By stacking, a cover window was manufactured.

Comparative Example 2

The resin composition for forming a hard coating layer prepared in Preparation Example 2 was applied to one side of a polyimide film (PI) of 15 cm A hard coating layer was formed. Afterwards, a 25 ㎛ adhesive layer (material: pressure sensitive adhesive (PSA), manufacturer: LG Chemical) was laminated on the other side of the polyimide film to manufacture a cover window.

<Experimental example>

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

1. Impact resistance evaluation

A 0.5T glass plate was placed under the cover window of the examples and comparative examples, and pressure-sensitive paper (Prescale LLW, Fujifilm) was placed under the 0.5T glass plate. A 45.5 g spherical ball was freely dropped from a position of 15 cm in height on the cover window, and impact resistance was evaluated from the color change of the pressure-sensitive paper on the falling side.

The color change of the pressure-sensitive paper was scanned with a pressure image analysis system (Fuji Film, FPD-8010 J) and then the pressure distribution according to area was compared. At this time, Figure 2 shows the pressure-sensitive paper when evaluating the impact resistance of the cover window of the examples and comparative examples. This is a comparison of color changes. The relative comparison between the pressure distribution analyzed by the pressure image analysis system and Comparative Example 2 is shown in Table 1 below.

2. Pencil hardness evaluation

For the first hard coating layer of the cover window of the above examples and comparative examples, a pencil was fixed at a load of 750 g and an angle of 45°, as in the JIS K 5600 5-4 measurement method, and then applied at a speed of 5 mm/sec for each pencil hardness. The pencil was scratched a total of 5 times at 20 mm each to determine whether it was scratched with the naked eye, and the maximum pencil hardness at which no surface damage occurred more than 3 times was measured.

At this time, in order to exclude the effect of pressing by the adhesive layer and evaluate it, the specimen was aged at 100°C for 10 minutes and then the hardness was checked.

3. Scratch resistance evaluation

For the first hard coating layer of the cover window of the above examples and comparative examples, a load of 1 kg was applied to steel wool (#0000) and the material was reciprocated 5000 times at a speed of 100 mm/sec, and the presence or absence of scratches was visually confirmed. If no scratches were observed with the naked eye, it was judged as ‘○’, and if scratches were observed, specifically, if one or more scratches of 1 mm or more were observed, it was judged as ‘X’.

4. Evaluation of dynamic bending properties

Figure 1 is a diagram schematically showing a method for evaluating dynamic bending characteristics of a cover window according to an embodiment of the present invention.

The cover window was laser cut to a size of 80 x 140 mm to minimize micro cracks at the edge area. Place the laser-cut film on the measuring equipment, place the second adhesive layer on the inside (in the case of Comparative Example 2, the adhesive layer is on the inside), and ensure that the gap (inner curvature diameter) of the folded area is 5 mm, and at -20 ° C. Both sides of the film were folded and unfolded at 90 degrees with respect to the bottom surface, repeated 50,000 times in a continuous motion (the speed at which the film is folded is once per second), and bending resistance was evaluated according to the following standards.

○: No cracks occur

X: crack occurs

Example 1 Comparative Example 1 Comparative example 2 impact resistance MPa 0.67 0.77 0.78 Relative comparison (compared to Comparative Example 2) 86% 99% 100% pencil hardness B HB 5H Scratch resistance ○ ○ ○ Dynamic bending properties ○ ○ ○

According to Table 1, it was confirmed that the cover window of Example 1 had excellent pencil hardness, scratch resistance, and dynamic bending characteristics, as well as excellent impact resistance. On the other hand, it was confirmed that Comparative Examples 1 and 2 had inferior impact resistance compared to Example 1.

Claims (15)

A first laminate including a first hard coating layer and a first light-transmissive substrate; and
A cover window for a foldable display comprising; a second laminate sequentially including a second hard coating layer, a second light-transmissive substrate, and a third hard coating layer.
According to paragraph 1,
A cover window for a foldable display in which a first adhesive layer is interposed between the first and second laminates.
According to paragraph 2,
A cover window for a foldable display, further comprising a second adhesive layer formed on one surface of the second laminate opposite the first laminate.
According to paragraph 2,
A cover window for a foldable display, wherein the first light-transmissive substrate and the first adhesive layer are in contact with each other.
According to paragraph 1,
The first hard coating layer is a cover window for a foldable display having a thickness of 1 ㎛ or more and 20 ㎛ or less.
According to paragraph 1,
The cover window for a foldable display, wherein the second hard coating layer and the third hard coating layer each independently have a thickness of 20 ㎛ or more and 100 ㎛ or less.
According to paragraph 3,
A cover window for a foldable display, wherein the first adhesive layer and the second adhesive layer each independently have a thickness of 5 ㎛ or more and 50 ㎛ or less.
According to paragraph 1,
A cover window for a foldable display, wherein the first light-transmitting substrate and the second light-transmitting substrate each independently have a thickness of 30 ㎛ or more and 200 ㎛ or less.
According to paragraph 1,
A cover window for a foldable display, wherein the total thickness of the cover window for the foldable display is 150 ㎛ or more and 450 ㎛ or less.
According to paragraph 1,
A cover window for a foldable display, wherein the first light-transmitting substrate and the second light-transmitting substrate are polyester films.
According to paragraph 1,
The first hard coating layer, the second hard coating layer, and the third hard coating layer include 100 parts by weight of polysiloxane containing 70 mol% or more of a repeating unit containing an epoxy group-containing functional group, and 20 to 80 parts by weight of an elastic polymer. A cover for a foldable display window.
According to clause 11,
The polysiloxane has a weight average molecular weight of 1,000 g/mol or more and 50,000 g/mol or less, a number average molecular weight of 1,000 g/mol or more and 10,000 g/mol or less, and a molecular weight distribution of 1.0 or more and 10.0 or less. A cover window for a foldable display.
According to clause 11,
A cover window for a foldable display, wherein the elastomer includes polycaprolactone polyol having a number average molecular weight of 300 Da or more and 10,000 Da or less.
According to paragraph 1,
When folding and unfolding the inside of the third hard coating layer at a 90° angle so that the third hard coating layer faces each other with a gap of 5 mm in the middle of the third hard coating layer 50,000 times at a speed of 1 time per second, a crack of 1 mm or more occurs. A cover window for foldable displays that does not occur.
A foldable display device comprising a cover window for a foldable display according to claim 1.