Optical laminate and image display device including the same

Abstract

The present invention provides an optical laminate and an image display device comprising the same, the optical laminate comprising glass, a first hard coat layer formed on the glass, and a second hard coat layer formed on the first hard coat layer, the first hard coat layer is formed from a first hard coat composition containing an epoxy acrylic resin and an epoxy silane coupling agent, and the second hard coat layer is formed from a second hard coat composition containing a translucent resin. The optical laminate and the image display device including the same according to the present invention are capable of improving device reliability when applied to a flexible display due to little generation of curl or crack due to curing shrinkage and excellent adhesion, pen usability, curl characteristics, water contact angle, and scratch resistance.

Description

Technical Field

[0001] The present invention relates to an optical laminate and an image display device including the same. Background Art

[0002] In recent years, image display devices such as liquid crystal display (LCD) devices or organic light emitting display (OLED) devices have been continuously thinned and flexibilized. The above image display devices are widely used in various smart devices characterized by portability, such as smart phones, tablet PCs, and various wearable devices. In such flexible displays, a glass substrate layer having physical properties such as high transparency, hardness, and bending characteristics is required.

[0003] On the other hand, for an outer cover window for a flexible display, when it is frequently folded or when it receives an impact above a limit, the problem of breakage of the outer cover glass often occurs. In addition, in order to prevent the outer cover glass from being damaged, a method of forming a thick protective coating has been proposed, but if an acrylic oligomer having a high hardness is thickly coated, there is a disadvantage of curling caused by severe curing shrinkage.

[0004] Korean Registered Patent Publication No. 10-2336592 provides a resin composition for coating a flexible outer cover window and a flexible outer cover window characterized in that a resin layer based on the resin composition for coating a flexible outer cover window is formed on one or both sides of the flexible outer cover window.

[0005] However, the above flexible outer cover window has disadvantages of curling or cracking when a thick film is formed from an acrylic oligomer.

[0006] Therefore, in reality, there is a need to develop an optical laminate in which curling or cracking caused by curing shrinkage is less likely to occur even when an acrylic oligomer is thickly coated.

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: Korean Registered Patent Publication No. 10-2336592 Summary of the Invention

[0010] Problems to be Solved

[0011] In order to solve the above problems, an object of the present invention is to provide an optical laminate in which curling or cracking caused by curing shrinkage is less likely to occur even at a thickness above a certain level.

[0012] Specifically, an object of the present invention is to provide an optical laminate having high hardness, excellent adhesion, pen usability, curling characteristics, water contact angle, and scratch resistance, and an image display device including the same.

[0013] However, the problems to be solved by the present invention are not limited to the above-mentioned problems, and those of ordinary skill in the art should be able to understand other problems not mentioned based on the following description.

[0014] Means for Solving the Problems

[0015] To achieve the above technical problems, the present invention provides an optical laminate including glass, a first hard coat formed on the glass, and a second hard coat formed on the first hard coat. The first hard coat is formed from a first hard coat composition containing an epoxy acrylate resin and an epoxy silane coupling agent, and the second hard coat is formed from a second hard coat composition containing a light-transmissive resin.

[0016] In the present invention, the thickness of the glass may be 10 to 100 μm.

[0017] In the present invention, the thickness of the first hard coat may be 10 to 30 μm.

[0018] In the present invention, the thickness of the second hard coat may be 3 to 20 μm.

[0019] In the present invention, any one or more of the first hard coat composition and the second hard coat composition may further contain an additive.

[0020] In the present invention, the additive may include one or more selected from the group consisting of silicone-based leveling agents, ultraviolet stabilizers, and heat stabilizers.

[0021] In the present invention, any one or more of the first hard coat composition and the second hard coat composition may further contain an initiator and a solvent.

[0022] In the present invention, based on the total weight of the composition, the first hard coat composition may contain 20 to 80 parts by weight of an epoxy acrylate resin, 1 to 30 parts by weight of an epoxy silane coupling agent, 0.1 to 10 parts by weight of an initiator, and 50 to 98 parts by weight of a solvent.

[0023] In the present invention, based on the total weight of the composition, the second hard coat composition may contain 1 to 80 parts by weight of a light-transmissive resin, 0.1 to 10 parts by weight of an initiator, and 50 to 98 parts by weight of a solvent.

[0024] In the present invention, the above epoxy silane coupling agent may include one or more selected from 3-glycidoxypropyl dimethoxysilane, 3-glycidoxypropyl trimethoxysilane, 8-glycidoxy octyl trimethoxysilane, and 2-(3,4-epoxycyclohexyl) ethyl trimethoxysilane.

[0025] In the present invention, the above light-transmissive resin may include one or more selected from 2-hydroxyethyl (meth)acrylate, 2-hydroxyisopropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, caprolactone ring-opening hydroxyacrylate, pentaerythritol tri / tetra(meth)acrylate, and dipentaerythritol penta / hexa(meth)acrylate.

[0026] The present invention is characterized in that the above glass, first hard coat, and second hard coat may be directly formed in contact with each other without including an additional layer.

[0027] The present invention can be applied to flexible displays.

[0028] In addition, the present invention improves an image display device including the above optical laminate.

[0029] Advantages of the Invention

[0030] In the optical laminate of the present invention and an image display device including the same, curling or cracks caused by curing shrinkage are less likely to occur, and the adhesion, pen usability, curling characteristics, water contact angle, and scratch resistance are excellent. Therefore, when applied to a flexible display, the device reliability can be improved.

[0031] In addition, the optical laminate of the present invention does not include an additional substrate between the glass and the hard coat, but is directly formed in contact with each other. Therefore, the process for bonding each substrate layer can be omitted, and the manufacturing process can be simplified compared with the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The laminated structure of an optical laminate according to an embodiment of the present invention is illustrated.

[0033] The meanings represented by the respective symbols are as follows:

[0034] 100: Optical laminate,

[0035] 110: Glass,

[0036] 120a: First hard coat,

[0037] 120b: Second hard coat. DETAILED DESCRIPTION

[0038] The present invention relates to an optical laminate and an image display device including the same. The optical laminate includes glass, a first hard coat formed on the glass, and a second hard coat formed on the first hard coat. The first hard coat is formed from a first hard coat composition containing an epoxy acrylate resin and an epoxy silane coupling agent, and the second hard coat is formed from a second hard coat composition containing a light-transmissive resin.

[0039] Hereinafter, preferred embodiments of the present invention will be described in detail. However, these examples are provided illustratively to more specifically explain the present invention, and it is obvious to those of ordinary skill in the art that the scope of the present invention is not limited by these examples.

[0040] The terms used in this specification are intended to describe the embodiments and are not intended to limit the present invention. In this specification, unless otherwise specifically mentioned in the context, the singular form also includes the plural form. For example, the "hard coat" used in this specification may refer to at least one of the first hard coat and the second hard coat.

[0041] The terms "comprises" and / or "comprising" used in this specification are used in the sense of not excluding the presence or addition of one or more other elements, steps, operations, and / or components other than the recited elements, steps, operations, and / or components. Throughout the specification, the same reference numerals refer to the same components.

[0042] The term "transparent" used in this specification means that the transmittance of visible light is 70% or more or 80% or more.

[0043] Figure 1 The laminated structure of the optical laminate according to an embodiment of the present invention is shown. As Figure 1 shown, the optical laminate 100 of the present invention may have a structure formed by glass 110, a first hard coat 120a formed on the glass 110, and a second hard coat 120b formed on the first hard coat, that is, the outermost layer.

[0044] The optical laminate of the present invention can have both hardness and flexibility to be applied to a window for a flexible display.

[0045] <Optical laminate>

[0046] The optical laminate of the present invention may include glass and a hard coat, and preferably, may include a first hard coat and a second hard coat. More specifically, the optical laminate of the present invention may include glass, a first hard coat formed on the glass, and a second hard coat formed on the first hard coat. The first hard coat may be formed from a first hard coat composition containing an epoxy acrylate resin and an epoxy silane coupling agent, and the second hard coat may be formed from a second hard coat composition containing a light-transmissive resin.

[0047] Glass 110

[0048] The above glass is intended to support the subsequent hard coat 120 and other substrates or panels in place of the conventional glass substrate, and may be composed of either thin glass or curved glass for the display of an electronic device. The thin glass may include flat glass and flexible glass.

[0049] As the glass 110 according to an embodiment of the present invention, any transparent glass can be used without limitation, and preferably, silicate glass can be used. The above silicate glass is a glass mainly composed of anhydrous silicic acid (silicon dioxide) existing in the form of silica sand. Since the structure of the above silicate glass has a very high density and a very strong bond with oxygen and water, it shows a low transmittance and is preferably used as a display substrate.

[0050] In addition, the glass for the above substrate is preferably thin glass (Thin Glass, TG) with a thickness of 10 to 300 μm. Different from the conventional glass, in order to have excellent bending resistance that does not break even when bent or folded for use in a flexible display substrate, a thickness of 100 μm or less is more preferable. Glass with a thickness less than 10 μm has a problem of being easily broken during the process.

[0051] The optical laminate of the present invention may include additional substrate layers such as the subsequent hard coat 120 to ensure the durability of the glass 110. Generally, an adhesive layer or an adhesive layer is included to form or bond the substrate layer, but according to the optical laminate of the present invention, it is characterized in that it is formed by direct contact without including an additional substrate layer for bonding the hard coat, thereby simplifying the manufacturing process compared with the conventional laminate.

[0052] Hard coat 120

[0053] As Figure 1 shown, the hard coat of the present invention may include a first hard coat 120a and a second hard coat 120b.

[0054] According to an embodiment of the present invention, the first hard coat 120a is characterized by being formed from a first hard coat composition containing an epoxy acrylate resin and an epoxy silane coupling agent. By including an epoxy acrylate resin and an epoxy silane coupling agent, adhesion to the glass 110 can be ensured, and low curl and high hardness characteristics can be ensured. The second hard coat 120b is characterized by being formed from a second hard coat composition containing a light-transmissive resin.

[0055] Referring Figure 1 , the first hard coat 120a can be formed on the glass 110, and the second hard coat 120b can be formed on the first hard coat 120a, that is, the outermost layer of the optical laminate. Even without an additional substrate layer such as an adhesive layer, the first hard coat 120a ensures adhesion between substrates and provides impact resistance.

[0056] In addition, the optical laminate of the present invention and an image display device using the same ensure sufficient impact resistance even without using a separate protective film. That is, even when pressure is applied to the display surface with a pen, the thin film glass does not break, so pen usability can be greatly improved.

[0057] In addition, each of the first hard coat composition and the second hard coat composition may independently further contain one or more selected from the group consisting of an additive, an initiator, and a solvent. The additive may include one or more selected from the group consisting of a silicone-based leveling agent, an ultraviolet stabilizer, and a heat stabilizer. As an example, the first hard coat can be manufactured from a hard coat composition containing an epoxy acrylate resin, an epoxy silane coupling agent, a silicone-based leveling agent, an initiator, and a solvent, and the second hard coat can be manufactured from a hard coat composition containing a light-transmissive resin, a silicone-based leveling agent, an initiator, and a solvent.

[0058] Epoxy acrylate resin

[0059] The epoxy acrylate resin has an epoxy group and an acryloyl group in the molecule as thermosetting and photocuring functional groups, and there are partially esterified epoxy (meth)acrylates. As commercially available products, the following can be used: SMP-220AP-E5 of Kyoeisha Chemical Co., Ltd. which is a photocurable acrylate polymer type having an acryloyl group and an epoxy group; 3000A-E5, 3000AD-E5, 3000AL-E5 of Kyoeisha which are partially esterified epoxy bisphenol A types having an epoxy group and an acryloyl group; 3000M-E5, 3000MD-E5, 3000ML-E5 which are partially esterified epoxy bisphenol A types having an epoxy group and a methacryloyl group.

[0060] With respect to 100 parts by weight of the above-mentioned first hard coating composition as a whole, the content of the above-mentioned epoxy acrylate resin is preferably 20 to 80 parts by weight. When it is less than 20 parts by weight, there is a problem that thick film coating cannot be performed and the hardness decreases. When it is more than 80 parts by weight, there is a problem that the solubility of the composition decreases and the viscosity increases, making it difficult to ensure coatability.

[0061] Epoxy silane coupling agent

[0062] The above-mentioned epoxy silane coupling agent refers to a compound having an epoxy group in the organic reaction group of the silane coupling agent. Specifically, it refers to a compound in which R1 in the structure of x -Si-(OR2) 4-x contains an epoxy group on R1 (X is an integer of 1 to 3, and R2 is an alkyl group such as methyl, ethyl, or propyl). For example, the above-mentioned epoxy silane coupling agent may include one or more selected from 3-glycidoxypropyl dimethoxysilane, 3-glycidoxypropyl trimethoxysilane, 8-glycidoxy octyl trimethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyl trimethoxysilane.

[0063] As commercially available products of the above-mentioned epoxy silane coupling agent, KBM-303, KBM-402, KBM-403, KBM-4803, KBE-402, KBE-403, X-12-981S, X-12-984S, KR-516, KR-517, etc. of Shin-Etsu Chemical Co., Ltd. can be used.

[0064] With respect to 100 parts by weight of the above-mentioned hard coating composition as a whole, the content of the above-mentioned epoxy silane coupling agent is preferably 1 to 30 parts by weight, and more preferably 3 to 20 parts by weight. By including the epoxy silane coupling agent within the above range, the adhesion to glass can be improved and flexibility can be imparted to the hard coating. When it is less than the above range, there is a problem that the adhesion to glass cannot be sufficiently ensured. When it is more than the above range, there is a concern that the compatibility is poor and the optical properties deteriorate due to scattering.

[0065] Light-transmissive resin

[0066] The above-mentioned light-transmitting resin is a photocurable resin, and the photocurable resin may include a photocurable (meth)acrylate oligomer and a photopolymerizable monomer.

[0067] In the present invention, “(meth)acryloyl-” refers to “methacryloyl-”, “acryloyl-” or both of them.

[0068] The above-mentioned photocurable (meth)acrylate oligomers are usually epoxy (meth)acrylate, urethane (meth)acrylate, etc., and urethane (meth)acrylate is more preferred. Urethane (meth)acrylate can be produced from a polyfunctional (meth)acrylate having a hydroxyl group in the molecule and a compound having an isocyanate group in the presence of a catalyst. As specific examples of the (meth)acrylate having a hydroxyl group in the molecule, one or more selected from the group consisting of 2-hydroxyethyl (meth)acrylate, 2-hydroxyisopropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, caprolactone ring-opening hydroxyacrylate, pentaerythritol tri / tetra (meth)acrylate, and dipentaerythritol penta / hexa (meth)acrylate can be used. In addition, as specific examples of the compound having an isocyanate group, one or more selected from the group consisting of 1,4-diisocyanatobutane, 1,6-diisocyanatohexane, 1,8-diisocyanatooctane, 1,12-diisocyanatododecane, 1,5-diisocyanato-2-methylpentane, trimethyl-1,6-diisocyanatohexane, 1,3-bis(isocyanatomethyl)cyclohexane, trans-1,4-cyclohexene diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), isophorone diisocyanate, toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, xylene-1,4-diisocyanate, tetramethyldimethylbenzene-1,3-diisocyanate, 1-chloromethyl-2,4-diisocyanate, 4,4'-methylenebis(2,6-dimethylphenyl isocyanate), 4,4'-oxybis(phenyl isocyanate), a trifunctional isocyanate derived from hexamethylene diisocyanate, and tolylene diisocyanate adduct of trimethane propanol can be used.

[0069] The above-mentioned photopolymerizable monomers can be used without limitation to monomers used in the art that have unsaturated groups such as (meth)acryloyl, vinyl, styryl, allyl, etc. in the molecule as photocurable functional groups, and among them, (meth)acryloyl is more preferred. More specifically, for example, monofunctional and / or polyfunctional (meth)acrylates can be cited. They can be used alone or in combination of two or more.

[0070] Regarding the above-mentioned monomers having (meth)acryloyl groups, as specific examples, one or more selected from the group consisting of neopentyl glycol acrylate, 1,6-hexanediol (meth)acrylate, propylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, 1,2,4-cyclohexane tetrakis(meth)acrylate, pentaglycerol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tripentaerythritol tri(meth)acrylate, tripentaerythritol hexakis(meth)acrylate, bis(2-hydroxyethyl)isocyanurate di(meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, isooctyl (meth)acrylate, isodecyl (meth)acrylate, stearyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, phenoxyethyl (meth)acrylate, and isobornyl (meth)acrylate can be used.

[0071] The above-mentioned light-transmissive resin is not particularly limited, and preferably contains 1 to 80 parts by weight relative to 100 parts by weight of the whole hard coat composition. When it is less than 1 part by weight, there is a problem that it is difficult to achieve sufficient hardness improvement, and when it is more than 80 parts by weight, there is a problem that curling is aggravated.

[0072] Additive

[0073] In addition, the hard coat composition used in the formation of the hard coat of the present invention may further contain additives such as a leveling agent, an ultraviolet stabilizer, and / or a heat stabilizer.

[0074] The leveling agent is a component that imparts smoothness and coatability to the coating film.

[0075] As the leveling agent, leveling agents commonly used in the art can be applied. For example, silicone-based leveling agents, fluorine-based leveling agents, acrylic polymer-based leveling agents, etc. can be cited. They can be used alone or in combination of two or more, but are not necessarily limited thereto.

[0076] As commercially available products of the above leveling agents, BYK-323, BYK-331, BYK-333, BYK-337, BYK-373, BYK-375, BYK-377, BYK-378, BYK-3530, BYK-3560, BYK-358N, BYK-361N of BYK Chemie GmbH can be used; TEGO Glide 410, TEGO Glide 411, TEGO Glide 415, TEGO Glide 420, TEGO Glide 432, TEGO Glide 435, TEGO Glide 440, TEGO Glide 450, TEGO Glide 455, TEGO Rad 2100, TEGO Rad 2200N, TEGO Rad 2250, TEGO Rad 2300, TEGO Rad 2500 of Evonik Degussa GmbH; FC-4430, FC-4432 of 3M Company, etc. However, it is not limited thereto, and leveling agents commonly used in the art can be applied.

[0077] With respect to 100 parts by weight of the hard coat composition, the content of the leveling agent can be 0.1 to 1 part by weight, but it is not limited thereto. However, when the content of the above leveling agent is within the above range with respect to the above hard coat composition, it has the advantages of being able to maximize the smoothness and coatability of the coating film and maintaining excellent hardness and flexibility.

[0078] An ultraviolet stabilizer is a component that blocks or absorbs ultraviolet rays and prevents the cured hard coat from decomposing, discoloring, and crumbling due to exposure to ultraviolet rays.

[0079] As the ultraviolet stabilizer, absorbers, quenchers, hindered amine light stabilizers (HALS), etc. classified according to the action mechanism can be used; or phenyl salicylates (absorbers), benzophenone (absorber), benzotriazole (absorber), nickel derivatives (quenchers), radical scavengers, etc. classified according to the chemical structure; etc. They can be used alone or in combination of two or more, and the types are not particularly limited as long as they are ultraviolet stabilizers that do not cause a significant change in the initial color of the hard coat.

[0080] As a heat stabilizer, for example, polyphenols as a primary heat stabilizer, phosphate esters and lactones as secondary heat stabilizers in commercially available products can be used alone or in combination. They can be used alone or in combination of two or more. The above ultraviolet stabilizers and heat stabilizers can be used by appropriately adjusting the content at a level that does not affect the ultraviolet curability. Specifically, with respect to 100 parts by weight in total of the hard coat composition of the present invention, the content is preferably 0.1 to 3 parts by weight.

[0081] The above additives can be added by appropriately adjusting the content within a range that does not impair the effects of the present invention.

[0082] Initiator

[0083] The above initiators can be used without limitation as long as they are initiators used in the technical field. For example, one or more selected from the group consisting of hydroxyketones, aminoketones, hydrogen abstraction type photoinitiators and combinations thereof can be used.

[0084] Specifically, as the above photoinitiator, one or more selected from the group consisting of 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone-1, benzophenone, benzil dimethyl ketal, 2-hydroxy-2-methyl-1-phenyl-1-one, 4-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenylacetophenone, anthraquinone, fluorene, triphenylamine, carbazole, 3-methylacetophenone, 4-chloroacetophenone, 4,4-dimethoxyacetophenone, 4,4-diaminobenzophenone, 1-hydroxycyclohexyl phenyl ketone, benzophenone, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide and combinations thereof can be used.

[0085] With respect to 100 parts by weight of the entire hard coat composition, such a photoinitiator is used in the range of 0.1 to 10 parts by weight, preferably 1 to 5 parts by weight. If the content is less than the above range, the curing rate of the composition may be slow and uncured, resulting in a decrease in mechanical properties. On the contrary, if it is greater than the above range, cracks may occur in the coating film due to overcuring.

[0086] Solvent

[0087] The above solvent is a substance that can dissolve or disperse the above-mentioned components, and can be used without limitation as long as it is a solvent known as a coating-forming composition solvent in the technical field.

[0088] As the solvents that can be used, it is preferable to use alcohol-based solvents (such as methanol, ethanol, isopropyl alcohol, butanol, methyl cellosolve, ethyl cellosolve, etc.), ketone-based solvents (such as methyl ethyl ketone, methyl butyl ketone, methyl isobutyl ketone, diethyl ketone, dipropyl ketone, cyclohexanone, etc.), acetate-based solvents (such as ethyl acetate, propyl acetate, n-butyl acetate, tert-butyl acetate, methyl cellosolve acetate, ethyl cellosolve acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, methoxybutyl acetate, methoxypentyl acetate, etc.), hexane-based solvents (such as hexane, heptane, octane, etc.), benzene-based solvents (such as benzene, toluene, xylene, etc.), ether-based solvents (such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, diethylene glycol dibutyl ether, propylene glycol monomethyl ether, etc.), and the like. The solvents exemplified above can be used alone or in combination of two or more.

[0089] With respect to 100 parts by weight of the entire hard coat composition, 50 to 98 parts by weight of such a solvent is used. If the content of the above solvent is less than the above content, the viscosity is high and the workability deteriorates. Moreover, it may not be possible to reduce the thickness of the hard coat, resulting in a decrease in flexibility. On the contrary, if it is greater than the above range, there is a problem that the desired coating film thickness cannot be formed, and the coating liquid flows out during the drying process to contaminate the reverse side of the glass or the film, resulting in the generation of streaks. Therefore, it is necessary to appropriately adjust within the above range.

[0090] The hard coat can be manufactured by a method known in the art. The thicknesses of the first hard coat and the second hard coat are not particularly limited. The thickness of the first hard coat is preferably 5 to 100 μm, more preferably 10 to 30 μm. The thickness of the second hard coat is preferably 3 to 20 μm, more preferably 5 to 15 μm. If the thickness is within the above range, more excellent hardness and flexibility can be exhibited. If the thicknesses of the first hard coat and the second hard coat deviate from the above range, there is a problem that sufficient hardness and curling characteristics cannot be ensured.

[0091] The optical laminate of the embodiment of the present invention can form the first hard coat 120a through the steps of coating the first hard coat composition on the glass 110, drying, and UV curing, and then can form the second hard coat 120b through the steps of coating the second hard coat composition on the above first hard coat 120a and then drying and UV curing in the same manner as the first hard coat.

[0092] The step of drying the above optical laminate can be carried out using heating tools such as a hot plate, a hot air circulation furnace, an infrared furnace, etc., and can be carried out at a temperature of 50 to 150 °C or 50 to 100 °C.

[0093] In the step of curing the above optical laminate, 50 to 1000 mJ / cm 2, preferably 200 to 800 mJ / cm 2 of actinic rays such as UV rays. In particular, by performing primary curing weakly at a level of 50 to 600 mJ / cm 2 in the formation step of forming the first hard coat 120a and irradiating UV with a high light quantity of 300 to 800 mJ / cm 2 in the step of forming the second hard coat 120b, the adhesion between the second hard coat and the first hard coat can be further enhanced. As the light source used during irradiation, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, an argon laser, etc. can be used, and X-rays, electron rays, etc. can also be used as needed.

[0094] <Image display device>

[0095] Embodiments of the present invention provide an image display device including the above optical laminate.

[0096] For example, the above optical laminate can be inserted inside the image display device and thus coexist with a polarizing layer or a touch sensor layer.

[0097] The above image display device includes various image display devices such as a liquid crystal display device, an electroluminescent display device, a plasma display device, a field emission display device, etc., and can be a flexible display device having flexibility and bending characteristics.

[0098] In this case, the optical laminate of the embodiments of the present invention can be more effectively used as a window or a window laminate of the flexible display device. Through the interaction between the glass and the hard coat included in the optical laminate of the embodiments of the present invention, the flexibility and durability of the window can be improved simultaneously, and antistatic performance can also be achieved together. Thereby, for example, the impact resistance and abrasion resistance of the above flexible display device can be improved, and damage such as cracks and peeling can also be prevented during bending.

[0099] Hereinafter, embodiments of the present invention will be specifically described. However, the present invention is not limited by the embodiments disclosed below and can be implemented in various different ways. These embodiments are only provided to make the disclosure of the present invention complete and to fully inform those of ordinary skill in the technical field to which the present invention pertains of the scope of the invention. The present invention is only defined by the scope of the claims. Unless otherwise noted, "%" and "parts" are mass % and mass parts, respectively.

[0100] Production Example: Production of Hard Coat Composition

[0101] Production Example 1

[0102] 40 parts by weight of epoxy acrylate (Kyoeisha, SMP-220AP-E5), 5 parts by weight of epoxy silane coupling agent (Shin-Etsu, KBM-403), 50 parts by weight of propylene glycol monomethyl ether, 2.25 parts by weight of photoacid generator (Irgacure 250), 2.25 parts by weight of photo radical initiator (1-hydroxycyclohexyl phenyl ketone), and 0.5 part by weight of silicone leveling agent (BYK, BYK-UV3530) were mixed using a blender and then filtered using a PP material filter to produce the first hard coat composition.

[0103] Production Example 2

[0104] 5 parts by weight of dendritic acrylate (Mihara Special Chemicals, SP1106), 40 parts by weight of dipentaerythritol hexaacrylate (Mihara Special Chemicals, Miramer M600), 50 parts by weight of methyl ethyl ketone, 3 parts by weight of 1-hydroxycyclohexyl phenyl ketone, 3 parts by weight of fluorine-based leveling agent (DAC-HP, Daikin), and 2 parts by weight of antistatic agent ATO dispersion (methyl ethyl ketone dispersion) were mixed using a blender and then filtered using a PP material filter to produce the second hard coat composition.

[0105] Production Example 3

[0106] 45 parts by weight of epoxy acrylate (Kyoeisha, SMP-220AP-E5), 50 parts by weight of propylene glycol monomethyl ether, 2.25 parts by weight of photoacid generator (Irgacure 250), 2.25 parts by weight of photo radical initiator (1-hydroxycyclohexyl phenyl ketone), and 0.5 part by weight of silicone leveling agent (BYK, BYK-UV3530) were mixed using a blender and then filtered using a PP material filter to produce the first hard coat composition.

[0107] Production Example 4

[0108] 40 parts by weight of epoxy acrylate (Kyoeisha, SMP-220AP-E5), 5 parts by weight of epoxy silane coupling agent (Shin-Etsu, KBM-4803), 50 parts by weight of propylene glycol monomethyl ether, 2.25 parts by weight of photoacid generator (Irgacure 250), 2.25 parts by weight of photo radical initiator (1-hydroxycyclohexyl phenyl ketone), and 0.5 part by weight of silicone leveling agent (BYK, BYK-UV3530) were mixed using a blender and then filtered using a PP material filter to produce the first hard coat composition.

[0109] Example and Comparative Example: Production of Optical Laminate

[0110] The hard coat compositions of Production Examples 1 to 4 were laminated in the order and thickness described in Table 1 below to produce the optical laminates of the examples and comparative examples.

[0111] Specifically, in the case of Examples 1 to 4, after coating the hard coat composition of Production Example 1 on thin glass, the solvent was dried at 90°C for 2 minutes. Nitrogen was blown onto the dried coating film, and UV was irradiated at a light quantity of 500 mJ / cm 2 to form a first hard coat (HC1). After coating the hard coat composition of Production Example 2 on the formed first hard coat, the solvent was dried at 90°C for 2 minutes. Nitrogen was blown onto the dried coating film, and UV was irradiated at a light quantity of 500 mJ / cm 2 to form a second hard coat (HC2), thereby producing the final optical laminate.

[0112] In the case of Example 5, after coating the hard coat composition of Production Example 4 on thin glass, the solvent was dried at 90°C for 2 minutes. Nitrogen was blown onto the dried coating film, and UV was irradiated at a light quantity of 500 mJ / cm 2 to form a first hard coat (HC1). After coating the hard coat composition of Production Example 2 on the formed first hard coat, the solvent was dried at 90°C for 2 minutes. Nitrogen was blown onto the dried coating film, and UV was irradiated at a light quantity of 500 mJ / cm 2 to form a second hard coat (HC2), thereby producing the final optical laminate.

[0113] In the case of Comparative Example 1, after coating the hard coat composition of Production Example 2 on thin glass, the solvent was dried at 90°C for 2 minutes. Nitrogen was blown onto the dried coating film, and UV was irradiated at a light quantity of 500 mJ / cm 2 to form a hard coat, thereby producing the final optical laminate.

[0114] In the case of Comparative Example 2, after coating the hard coat composition of Production Example 1 on thin glass, the solvent was dried at 90°C for 2 minutes. Nitrogen was blown onto the dried coating film, and UV was irradiated at a light quantity of 500 mJ / cm 2 to form a hard coat, thereby producing the final optical laminate.

[0115] In the case of Comparative Example 3, after coating the hard coat composition of Production Example 2 on thin glass, the solvent was dried at 90°C for 2 minutes. Nitrogen was blown onto the dried coating film, and UV was irradiated at a light quantity of 500 mJ / cm 2 to form a hard coat, thereby producing the final optical laminate.

[0116] In the case of Comparative Example 4, after coating the hard coat composition of Production Example 3 on the thin glass, the solvent was dried at 90 °C for 2 minutes. Nitrogen was blown onto the dried coating film, and UV was irradiated at a light quantity of 500 mJ / cm 2 to form a first hard coat (HC1). After coating the hard coat composition of Production Example 2 on the thus-formed first hard coat, the solvent was dried at 90 °C for 2 minutes. Nitrogen was blown onto the dried coating film, and UV was irradiated at a light quantity of 500 mJ / cm 2 to form a second hard coat (HC2), thereby producing the final optical laminate.

[0117] [Table 1]

[0118] (Unit: μm)

[0119]

[0120]

[0121] Experimental Example

[0122] The physical properties of the optical laminates produced in Examples 1 to 5 and Comparative Examples 1 to 4 above were measured by the following method, and the results are shown in Table 2.

[0123] (1) Transmittance evaluation

[0124] The transmittance of the optical laminates of the above examples and comparative examples was measured using a haze meter HM-150N manufactured by Murakami Corporation.

[0125] (2) Haze evaluation

[0126] The haze of the optical laminates of the above examples and comparative examples was measured using a haze meter HM-150N manufactured by Murakami Corporation.

[0127] (3) Adhesion evaluation

[0128] With the hard coat surface facing upward, the optical laminates of the above examples and comparative examples were adhered to glass using a transparent adhesive, and then 100 squares were horizontally and vertically marked at 1 mm intervals on the hard coat surface using a cutter, and then a tape adhesion test was performed 3 times using a 3M tape.

[0129] <Evaluation criteria>

[0130] 5B: Not peeled off

[0131] 4B: Peeling less than 5%

[0132] 3B: Peeling 5% or more and less than 15%

[0133] 2B: Stripping is more than 15% and less than 35%

[0134] 1B: Stripping is 35% or more and less than 65%

[0135] 0B: Stripping is 65% or more

[0136] (4) Evaluation of pen usability

[0137] A polymer film laminate similar to the display panel structure is joined to the lower part of the optical laminate in the above-described examples and comparative examples and fixed with the hard coat facing upward. Then, under a 1 kg load, 5 tests are performed with a 3H hardness pencil for a length of 1 cm to evaluate the impact resistance.

[0138] The polymer film laminate similar to the display panel structure is manufactured by joining a 25 μm transparent adhesive / 75 μm polarizing film / 35 μm PI film / 25 μm transparent adhesive / 35 μm PI film so that the overall thickness becomes 195 μm. An evaluation specimen is prepared by joining the adhesive layer on the polarizing film side to the opposite surface of the hard coat of the optical laminate.

[0139] <Evaluation criteria>

[0140] ◎: The glass is not broken

[0141] ○: The hard coat is pressed down (recovered after 24 hours of pressing down)

[0142] △: The hard coat is pressed down (not recovered after 24 hours of pressing down)

[0143] X: The glass is broken

[0144] (5) Evaluation of curl characteristics

[0145] The optical laminates of the examples and comparative examples are placed at 25 °C and 50% relative humidity with the hard coat surface facing upward for 24 hours, and then the distances from the four vertices to the ground are measured and the average value is recorded. If it is reverse curl that curls in the opposite direction to the second hard coat surface, the thin glass is turned over and the distance between the ground and the vertex is measured and calculated.

[0146] <Evaluation criteria>

[0147] ◎: 5 mm or less

[0148] ○: Greater than 5 mm and less than 10 mm

[0149] △: 10 mm or more and less than 20 mm

[0150] X: 20 mm or more

[0151] (6) Evaluation of initial water contact angle

[0152] Using the DSA100 from KRUSS, the water contact angle of the coated surface of the optical laminates produced in the above Examples and Comparative Examples was measured.

[0153] (7) Scratch resistance evaluation

[0154] After fixing the optical laminates produced in the above Examples and Comparative Examples with the coated surface facing upward, use steel wool (#0000) to reciprocally rub 10 times with a load of 250 g / cm 2 Then visually check whether scratches are generated on the surface of the optical laminate.

[0155] [Evaluation criteria]

[0156] ○: When observing transmission and reflection of the measurement part using a three-wavelength lamp, no scratches are seen or 10 or fewer scratches are seen.

[0157] X: When observing transmission and reflection of the measurement part using a three-wavelength lamp, more than 10 scratches are seen.

[0158] [Table 2]

[0159]

[0160] Referring to the experimental data in Table 2 above, in the case of Examples 1 to 5 of the optical laminate including two hard coat layers applying the present invention, excellent results were shown in adhesion, pen usability, curling characteristics, water contact angle, and scratch resistance evaluation. In the case of the optical laminates of Comparative Examples 1 to 3 including only one hard coat layer, one or more of the evaluation criteria in adhesion, pen usability, curling characteristics, water contact angle, and scratch resistance evaluation did not meet the present invention, and the physical properties suitable for an optical laminate for a flexible display were not exhibited.

[0161] In particular, in Comparative Examples 1 and 3 that do not include the first hard coating of the present invention, more than 65% peeling occurred in the adhesion evaluation, and the adhesion to glass was not sufficiently ensured. In the case of Comparative Example 2 that does not include the second hard coating of the present invention, scratches were confirmed in the scratch resistance evaluation. In addition, in the case of Comparative Example 1 that does not include the first hard coating of the present invention and the thickness of the second hard coating is 5 μm, glass breakage was confirmed in the pen usability evaluation and it is not suitable for the use of protecting glass. In addition, in the case of Comparative Example 2 that does not include the second hard coating of the present invention, hard coating depression occurred in the pen usability evaluation and it is not suitable for the use of protecting glass, and the measured water contact angle was less than 95°. In the case of Comparative Example 3 that does not include the first hard coating of the present invention and the thickness of the second hard coating is greater than 15 μm, curling due to severe curing shrinkage occurred in the curling property evaluation. In the case of Comparative Example 4 that does not include the epoxy silane coupling agent of the present invention, more than 65% peeling occurred in the adhesion evaluation, and the adhesion to glass was not sufficiently ensured, and it did not exhibit physical properties suitable for an optical laminate for a flexible display.

[0162] Therefore, it can be confirmed that the optical laminate of the present invention and the image display device using the same have less curling due to curing shrinkage even at a thickness of 15 μm or more, excellent adhesion, pen usability, water contact angle, and scratch resistance, and have the effect of improving the device reliability when applied to a flexible display.

Claims

1. An optical laminate comprising: Glass; a first hard coating layer formed on the glass; and a second hard coating layer formed on the first hard coating layer, The first hard coating layer is formed from a first hard coating composition comprising an epoxy acrylic resin and an epoxy silane coupling agent. The second hard coating layer is formed from a second hard coating composition including a light-transmitting resin. 2 . The optical layered body according to claim 1 , wherein the glass has a thickness of 10 to 100 μm. 3 . The optical layered body according to claim 1 , wherein the first hard coating layer has a thickness of 10 to 30 μm. 4 . The optical layered body according to claim 1 , wherein the second hard coating layer has a thickness of 3 to 20 μm. 5 . The optical layered body according to claim 1 , wherein at least one of the first hard coating composition and the second hard coating composition further comprises an additive. 6 . The optical laminate according to claim 5 , wherein the additive comprises at least one selected from the group consisting of a silicone-based leveling agent, a UV stabilizer, and a heat stabilizer. 7 . The optical laminate according to claim 1 , wherein at least one of the first hard coating composition and the second hard coating composition further comprises an initiator and a solvent.

8. The optical laminate according to claim 7, wherein the first hard coating composition comprises 20 to 80 parts by weight of epoxy acrylic resin, 1 to 30 parts by weight of epoxy silane coupling agent, 0.1 to 10 parts by weight of initiator and 50 to 98 parts by weight of solvent, relative to the total weight of the composition. 9 . The optical laminate according to claim 7 , wherein the second hard coating composition comprises 1 to 80 parts by weight of a light-transmitting resin, 0.1 to 10 parts by weight of an initiator, and 50 to 98 parts by weight of a solvent, based on the total weight of the composition. 10 . The optical laminate according to claim 1 , wherein the epoxysilane coupling agent comprises at least one selected from 3-glycidoxypropyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 8-glycidoxyoctyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

11. The optical laminate according to claim 1, wherein the light-transmitting resin comprises one or more selected from 2-hydroxyethyl (meth)acrylate, 2-hydroxyisopropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, caprolactone ring-opening hydroxy acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate and pentaerythritol hexa(meth)acrylate.

12. The optical layered body according to claim 1, wherein: The glass, the first hard coating layer, and the second hard coating layer are each formed in direct contact without involving additional layers. The optical laminate according to claim 1 , which is used in a flexible display. 14 . An image display device comprising the optical layered body according to claim 1 .

Images