Optical laminate and image display device including the same

Abstract

To provide an optical laminate where there is less occurrence of curls and cracks due to hardening shrinkage for even a certain thickness or greater, and an image display device including the optical laminate.SOLUTION: Provided are an optical laminate 100 including a glass 110, a first hard coat layer 120a formed on the glass, and a second hard coat layer 120b formed on the first hard coat layer 120a, and an image display device including the optical laminate. The first hard coat layer 120a is formed from a first hard coat composition including an epoxy acrylic resin and an epoxysilane coupling agent, and the second hard coat layer 120b is formed from a second hard coat component including a light transmissive resin.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Recently, thinning and flexibility of image display devices such as liquid crystal display (LCD) devices or organic light emitting display (OLED) devices have been continuing. The image display devices are widely applied to various smart devices characterized by portability, ranging from smart phones and tablet PCs to various wearable devices. Such flexible displays require a glass substrate layer having physical properties such as high transparency, hardness, and warpage characteristics.

[0003] On the other hand, in the case of a cover window for a flexible display, when frequent folding or an impact beyond the limit is applied, the problem of cracking of the cover glass may frequently occur. Also, a method of forming a thick protective coating to prevent breakage of the cover glass has been proposed, but when a hard acrylic oligomer is thickly coated, there is a disadvantage that severe curling occurs due to curing shrinkage.

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

[0005] However, the flexible cover window has disadvantages such as curling or cracking during thick film formation with an acrylic oligomer.

[0006] Therefore, at present, it is necessary to develop an optical laminate in which curling and cracking due to curing shrinkage are less likely to occur even when thick coating is performed using an acrylic oligomer.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] An object of the present invention is to provide an optical laminate in which curling and cracking due to curing shrinkage are less likely to occur even at a thickness equal to or greater than a certain level in order to solve the above-described problems.

[0009] Specifically, an object of the present invention is to provide an optical laminate that is excellent in adhesion, pen usability, curling characteristics, water contact angle, and scratch resistance while having high hardness, and an image display device including the same.

[0010] However, the problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

Means for Solving the Problems

[0011] In order to achieve the above technical problems, the present invention provides an optical laminate including glass, a first hard coat layer formed on the glass, and a second hard coat layer formed on the first hard coat layer, wherein the first hard coat layer is formed of a first hard coat composition including an epoxy acrylic resin and an epoxy silane coupling agent, and the second hard coat layer is formed of a second hard coat composition including a light-transmitting resin.

[0012] In the present invention, the thickness of the glass may be 10 to 100 μm. In the present invention, the thickness of the first hard coat layer may be 10 to 30 μm.

[0013] In the present invention, the thickness of the second hard coat layer may be 3 to 20 μm. 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.

[0014] In the present invention, the additive may contain one or more selected from the group consisting of a silicone leveling agent, an ultraviolet stabilizer, and a heat stabilizer.

[0015] 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.

[0016] In the present invention, the first hard coat composition may contain, based on the total weight of the composition, 20 to 80 parts by weight of an epoxy acrylic 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.

[0017] In the present invention, the second hard coat composition may contain, based on the total weight of the composition, 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.

[0018] In the present invention, the epoxy silane coupling agent may contain one or more selected from 3-glycidoxypropyl dimethoxysilane, 3-glycidoxypropyl trimethoxysilane, 8-glycidoxy octyl trimethoxysilane, and 2-(3,4-epoxy cyclohexyl) ethyl trimethoxysilane.

[0019] In the present invention, the light-transmissive resin may contain 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.

[0020] In the present invention, the glass, the first hard coat layer, and the second hard coat layer may be characterized in that they do not contain another layer and are formed in direct contact with each other.

[0021] The present invention may be for application to a flexible display. Further, the present invention provides an image display device including the optical laminate.

Advantages of the Invention

[0022] The optical laminate according to the present invention and the image display device including the same generate few curls and cracks due to curing shrinkage, and are excellent in adhesion, pen usability, curl characteristics, water contact angle, and scratch resistance, and the device reliability is improved when applied to a flexible display.

[0023] In addition, the optical laminate according to the present invention does not contain another base material between the glass and the hard coat layer, is formed in direct contact, and can omit the process for joining each base material layer, and the manufacturing process can be simplified compared with the conventional one.

Brief Description of the Drawings

[0024]

Figure 1

Embodiments for Carrying Out the Invention

[0025] The present invention relates to an optical laminate and an image display device including the same, which include glass, a first hard coat layer formed on the glass, and a second hard coat layer formed on the first hard coat layer, wherein the first hard coat layer is formed of a first hard coat composition including an epoxy acrylic resin and an epoxy silane coupling agent, and the second hard coat layer is formed of a second hard coat composition including a light-transmissive resin.

[0026] Hereinafter, preferred embodiments of the present invention will be described in detail. However, these examples are merely presented as examples for more specifically explaining the present invention, and it will be apparent to those having ordinary knowledge in the art that the scope of the present invention is not limited by these examples.

[0027] The terms used in this specification are for explaining the embodiments and are not intended to limit the present invention. In this specification, the singular form also includes the plural form unless otherwise specifically mentioned in the text. For example, the "hard coat layer" used in this specification may mean at least one hard coat layer of the first hard coat layer and the second hard coat layer.

[0028] As used in this specification, "comprises" and / or "comprising" are used in the sense that they do not exclude the presence or addition of one or more other components, steps, operations and / or elements other than the recited components, steps, operations and / or elements. The same reference numerals refer to the same components throughout the specification.

[0029] As used in this specification, "transparent" means that the transmittance of visible light is 70% or more or 80% or more.

[0030] FIG. 1 is a diagram showing the laminated structure of an optical laminate according to an embodiment of the present invention. As shown in FIG. 1, the optical laminate 100 of the present invention may have a structure in which a glass 110, a first hard coat layer 120a formed on the glass 110, and a second hard coat layer 120b are formed on the first hard coat layer, that is, at the outermost corner.

[0031] The optical laminate of the present invention can simultaneously have hardness and flexibility in order to be applied to a window for a flexible display.

[0032] <Optical laminate> The optical laminate of the present invention includes a glass and a hard coat layer, and preferably may include a first hard coat layer and a second hard coat layer. More specifically, the optical laminate of the present invention includes a 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 of a first hard coat composition containing an epoxy acrylic resin and an epoxy silane coupling agent, and the second hard coat layer may be formed of a second hard coat composition containing a light-transmitting resin.

[0033] Glass 110 The glass is for supporting the hard coat layer 120 and other base materials or panels described later in place of an existing glass substrate, and may be made of either thin glass or curved glass for a display of an electronic device. The thin glass may include flat glass and flexible glass.

[0034] 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 silicate glass is a glass mainly composed of anhydrous silicic acid (silica) naturally existing in the form of silica sand. The structure of the silicate glass has a very high density and a very strong bond with oxygen and water, so it shows a low transmittance and is preferable for use as a display substrate.

[0035] Also, the thickness of the glass used for the substrate is preferably thin glass (Thin Glass, TG) with a thickness of 10 to 300 μm. Different from existing glass, in order to be used for a flexible display substrate, it further preferably has a thickness of 100 μm or less in order to have excellent flexural resistance characteristics such that it does not break even when bent or curved. Glass with a thickness thinner than 10 μm has a problem of being easily broken during the process.

[0036] The optical laminate according to the present invention can include additional substrate layers such as a hard coat layer 120 described later in order 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. According to the optical laminate of the present invention, it is characterized in that it does not include another substrate layer for bonding the hard coat layer and is formed by direct contact, and the manufacturing process can be simplified compared to conventional laminates.

[0037] Hard coat layer 120 The hard coat layer of the present invention can include a first hard coat layer 120a and a second hard coat layer 120b as shown in FIG. 1.

[0038] According to an embodiment of the present invention, the first hard coat layer 120a is formed of a first hard coat composition including an epoxy acrylic resin and an epoxy silane coupling agent. By including the epoxy acrylic resin and the 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 layer 120b is formed of a second hard coat composition including a light-transmitting resin.

[0039] Referring to FIG. 1, the first hard coat layer 120a is formed on the glass 110, and the second hard coat layer 120b can be formed on the first hard coat layer 120a, that is, at the outermost corner of the optical laminate. The first hard coat layer 120a ensures adhesion between substrates and imparts impact resistance without a layer such as another substrate layer such as an adhesive layer.

[0040] In addition, the optical laminate according to the present invention and the image display device to which this is applied ensure sufficient impact resistance even when another protective film is not applied, and the thin film glass does not break even when pressure is applied to the surface of the display with a pen, thereby greatly improving the usability of the pen.

[0041] Furthermore, each of the first hard coat composition and the second hard coat composition may further include 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, a heat stabilizer, and the like. As an example, the first hard coat layer can be produced from a hard coat composition containing an epoxy acrylic resin, an epoxy silane coupling agent, a silicone-based leveling agent, an initiator, and a solvent, and the second hard coat layer can be produced from a hard coat composition containing a light-transmitting resin, a silicone-based leveling agent, an initiator, and a solvent.

[0042] Epoxy acrylic resin The epoxy acrylic resin has an epoxy group and an acrylic group as thermosetting and photocuring functional groups in the molecule, and examples include partially esterified epoxy (meth)acrylate. As commercially available products, SMP-220AP-E5 from Kyoeisha Chemical Co., Ltd. which has an acrylic group and an epoxy group as a photocurable acrylic polymer type, 3000A-E5, 3000AD-E5, 3000AL-E5 from Kyoeisha which have an epoxy group and an acrylic group as a partially esterified epoxy bisphenol A type, 3000M-E5, 3000MD-E5, 3000ML-E5 which have an epoxy group and a methacrylic group as a partially esterified epoxy bisphenol A type can be used.

[0043] The epoxy acrylic resin is preferably contained in an amount of 20 to 80 parts by weight based on 100 parts by weight of the entire first hard coat composition. When the amount is less than 20 parts by weight, it is impossible to form a thick film coating and the hardness decreases. When the amount exceeds 80 parts by weight, the solubility of the composition decreases, the viscosity increases, and it is difficult to ensure coatability.

[0044] Epoxysilane coupling agent The epoxysilane coupling agent means a compound having an epoxy group in the organic reaction group of the silane coupling agent. Specifically, in the structure of R1 x -Si-(OR2) 4-x it means a compound containing an epoxy group in R1. (X is an integer of 1 to 3, and R2 is an alkyl group such as methyl, ethyl, or propyl.) For example, the epoxysilane 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.

[0045] As commercially available products of the epoxysilane 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.

[0046] The epoxysilane coupling agent may preferably be contained in an amount of 1 to 30 parts by weight, more preferably 3 to 20 parts by weight, based on 100 parts by weight of the entire hard coat composition. By containing the epoxysilane coupling agent within the above range, the adhesion to glass can be improved and flexibility can be imparted to the hard coat layer. When it is less than the above range, there is a problem that sufficient adhesion to glass cannot be ensured. When it exceeds the above range, the compatibility is not good and the optical properties may be deteriorated by scattering.

[0047] Light-transmitting resin The light-transmissive resin is a photocurable resin, and the photocurable resin can contain a photocurable (meth)acrylate oligomer and a photopolymerizable monomer.

[0048] In the present invention, “(meth)acryl-” refers to “methacryl-”, “acryl-”, or both of them.

[0049] The photocurable (meth)acrylate oligomer usually uses epoxy (meth)acrylate, urethane (meth)acrylate, etc., and urethane (meth)acrylate is more preferred. Urethane (meth)acrylate can be produced by reacting a polyfunctional (meth)acrylate having a hydroxy group in the molecule with a compound having an isocyanate group in the presence of a catalyst. Specific examples of the (meth)acrylate having a hydroxy group in the molecule include 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, and one or more selected from the group can be selected. Specific examples of the compound having an isocyanate group include 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, tetramethylxylene-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 a trimethanepropanol adduct toluene diisocyanate, and one or more selected from the group can be selected.

[0050] The photopolymerizable monomer is a commonly used photocurable functional group. For example, monomers used in the relevant technical field having an unsaturated group such as a (meth)acryloyl group, vinyl group, styryl group, allyl group, etc. in the molecule can be used without limitation. Among them, the (meth)acryloyl group is more preferable. More specifically, for example, monofunctional and / or polyfunctional (meth)acrylates can be mentioned. These can be used alone or in a mixture of two or more.

[0051] Specific examples of the monomer having the (meth)acryloyl group include 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 - cyclohexanetetra(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 hexatri(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, isobornyl (meth)acrylate. One or more can be selected from the group consisting of these.

[0052] The light-transmissive resin is not particularly limited, but it is preferably contained in an amount of 1 to 80 parts by weight based on 100 parts by weight of the entire hard coat composition. If it is less than 1 part by weight, it is difficult to achieve sufficient improvement in hardness, and if it exceeds 80 parts by weight, there is a problem of severe curling.

[0053] Additive In addition, the hard coat composition used for forming the hard coat layer according to the present invention can further contain additives such as a leveling agent, an ultraviolet stabilizer, and / or a heat stabilizer.

[0054] The leveling agent is a component that imparts smoothness and coatability to the coating film. As the leveling agent, those leveling agents commonly used in the industry can be applied, for example, silicone-based leveling agents, fluorine-based leveling agents, acrylic polymer-based leveling agents, and the like. These can be used alone or in combination of two or more, but are not necessarily limited thereto.

[0055] Commercially available products of the leveling agent include BYK-323, BYK-331, BYK-333, BYK-337, BYK-373, BYK-375, BYK-377, BYK-378, BYK-3530, BYK-3560, BYK-358N, BYK-361N from BYK Chemie; 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 from Degussa; FC-4430, FC-4432 from 3M, etc. can be used, but are not limited thereto, and those leveling agents commonly used in the industry can be applied.

[0056] The leveling agent may be contained in an amount of 0.1 to 1 part by weight with respect to 100 parts by weight of the hard coat composition, but is not limited thereto. However, when the leveling agent is contained within the above range with respect to the hard coat composition, there is an advantage that the smoothness and coating properties of the coating film can be maximized while maintaining excellent hardness and flexibility.

[0057] The ultraviolet stabilizer is a component that blocks or absorbs ultraviolet rays and prevents decomposition, discoloration, and cracking of the cured hard coat layer due to ultraviolet exposure.

[0058] Ultraviolet stabilizers include absorbers, quenchers, hindered amine light stabilizers (HALS) etc. classified by their mechanism of action; and phenyl salicylates (absorbers), benzophenone (absorber), benzotriazole (absorber), nickel derivatives (quenchers), radical scavengers etc. classified by their chemical structure. These can be used alone or in combination of two or more, and the type is not particularly limited as long as it is an ultraviolet stabilizer that does not significantly change the initial color of the hard coat layer.

[0059] As heat stabilizers, for example, as commercially applicable products, polyphenol-based primary heat stabilizers, phosphate-based and lactone-based secondary heat stabilizers can be used alone or in combination. These can be used alone or in combination of two or more. The ultraviolet stabilizer and the heat stabilizer can be used by appropriately adjusting the content within a level that does not affect the ultraviolet curability. Specifically, it is preferably contained in an amount of 0.1 to 3 parts by weight with respect to 100 parts by weight of the entire hard coat composition of the present invention.

[0060] The content of the additive can be appropriately adjusted and added within a range that does not inhibit the effects of the present invention.

[0061] Initiator The initiator can be used without limitation as long as it is used in the relevant 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.

[0062] Specifically, as the photoinitiator, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone-1, diphenyl ketone, benzyldimethyl ketal, 2-hydroxy-2-methyl-1-phenyl-1-one, 4-hydroxycyclophenyl ketone, 2,2-dimethoxy-2-phenyl-acetophenone, 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 one or more selected from the group consisting of combinations thereof can be used.

[0063] Such a photoinitiator is used in the range of 0.1 to 10 parts by weight, preferably 1 to 5 parts by weight, based on 100 parts by weight of the entire hard coat composition. If the content is less than the above range, the curing rate of the composition is slow, uncured occurs and the mechanical properties deteriorate. On the contrary, if it exceeds the above range, cracks may occur in the coating film due to overcuring.

[0064] Solvent The solvent can dissolve or disperse the composition as mentioned above, and can be used without limitation as long as it is known as a solvent for a composition for forming a coating layer in the relevant technical field.

[0065] Possible solvents include alcohol-based (such as methanol, ethanol, isopropanol, butanol, methyl cellosolve, ethyl cellosolve, etc.), ketone-based (such as methyl ethyl ketone, methyl butyl ketone, methyl isobutyl ketone, diethyl ketone, dipropyl ketone, cyclohexanone, etc.), acetate-based (such as ethyl acetate, propyl acetate, normal butyl acetate, tertiary 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 (such as hexane, heptane, octane, etc.), benzene-based (such as benzene, toluene, xylene, etc.), ether-based (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, which can be preferably used. The solvents exemplified above can be used alone or in combination of two or more thereof.

[0066] Such solvents are used in an amount of 50 to 98 parts by weight based on 100 parts by weight of the whole hard coat composition. If the content of the solvent is less than the above content, not only will the viscosity be high and the workability be reduced, but also the thickness of the hard coat layer cannot be reduced, which may cause a decrease in flexibility. Conversely, if it exceeds the above range, a desired coating film thickness cannot be formed, and there is a problem that the coating liquid runs off during the drying process and contaminates the opposite surface of the glass or film, resulting in the occurrence of stains. Therefore, appropriate adjustment within the above range is necessary.

[0067] The hard coat layer may be manufactured by a method known in the art. The thicknesses of the first hard coat layer and the second hard coat layer are not particularly limited, but the thickness of the first hard coat layer may preferably be 5 to 100 μm, and more preferably 10 to 30 μm. The thickness of the second hard coat layer may preferably be 3 to 20 μm, and more preferably 5 to 15 μm. When the thickness is within the above range, better hardness and flexibility can be exhibited. When the thicknesses of the first hard coat layer and the second hard coat layer exceed the above range, there is a problem that sufficient hardness and curl characteristics cannot be ensured.

[0068] The optical laminate according to an embodiment of the present invention may be formed by coating a first hard coat composition on glass 110, and forming a first hard coat layer 120a through drying and UV curing steps. Thereafter, after coating a second hard coat composition on the first hard coat layer 120a, a second hard coat layer 120b may be formed through drying and UV curing steps similar to those of the first hard coat layer.

[0069] The step of drying the optical laminate can be carried out by heating means 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.

[0070] The step of curing the optical laminate is to irradiate active rays such as UV rays of 50 to 1000 mJ / cm 2 , preferably 200 to 800 mJ / cm 2 . In particular, the step of forming the first hard coat layer 120a is to perform weak primary curing at a level of 50 to 600 mJ / cm 2 , and the step of forming the second hard coat layer 120b is 300 to 800 mJ / cm 2By irradiating with strong light intensity of UV, the adhesion between the second hard coat layer and the first hard coat layer can be further strengthened. As the light source used for irradiation, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, an argon gas laser, etc. can be used, and in some cases, X-rays, electron beams, etc. can also be utilized.

[0071] <Image display device> An embodiment of the present invention provides an image display device including the above-described optical laminate.

[0072] For example, the above-described optical laminate may be inserted inside the image display device and included together with a polarizing layer or a touch sensor layer.

[0073] The 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 may be a flexible display device having flexibility and bending characteristics.

[0074] In this case, the optical laminate according to the embodiment of the present invention can be effectively applied to the window or window laminate of the flexible display device. Due to the interaction between the glass and the hard coat layer included in the optical laminate according to the embodiment of the present invention, both the flexibility and durability of the window are improved, and antistatic performance can be realized. As a result, for example, the impact resistance and abrasion resistance of the flexible display device are improved, and at the same time, damage such as cracks and peeling can be prevented even during bending.

Example

[0075] Hereinafter, embodiments of the present invention will be specifically described. However, the present invention is not limited to the embodiments disclosed below and can be realized in various different forms. Merely, these embodiments are provided to make the disclosure of the present invention complete and to fully inform those with ordinary knowledge in the technical field to which the present invention pertains of the scope of the invention. The present invention is defined only by the scope of the claims. "%" and "parts" are, unless otherwise specified, mass % and parts by mass, respectively.

[0076] Production Example: Production of Hard Coat Composition Production Example 1 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 (Irgacure250), 2.25 parts by weight of photo radical initiator (1-hydroxycyclohexyl phenyl ketone), 0.5 part by weight of silicone leveling agent (BYK, BYK-UV3530) were blended using a stirrer and filtered using a PP material filter to produce the first hard coat composition.

[0077] Production Example 2 5 parts by weight of dendrimer acrylate (Miwon Specialty Chemical, SP1106), 40 parts by weight of dipentaerythritol hexaacrylate (Miwon Specialty Chemical, 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), 2 parts by weight of antistatic agent ATO dispersion (methyl ethyl ketone dispersion) were blended using a stirrer and filtered using a PP material filter to produce the second hard coat composition.

[0078] Production Example 3 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), 0.5 part by weight of silicone leveling agent (BYK, BYK-UV3530) were blended using a stirrer and filtered using a PP material filter to produce a first hard coat composition.

[0079] Production Example 4 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), 0.5 part by weight of silicone leveling agent (BYK, BYK-UV3530) were blended using a stirrer and filtered using a PP material filter to produce a first hard coat composition.

[0080] Examples and Comparative Examples: Production of Optical Laminates The hard coat compositions of Production Examples 1 to 4 were laminated in the order and thickness shown in Table 1 below to produce optical laminates of Examples and Comparative Examples.

[0081] Specifically, in the case of Examples 1 to 4, after applying the hard coat composition of Production Example 1 on thin glass, the solvent was dried at 90°C for 2 minutes. The dried coating film was purged with nitrogen, and under nitrogen conditions, UV was irradiated with a light amount of 500 mJ / cm 2 to form a first hard coat layer (HC1). After applying the hard coat composition of Production Example 2 on the formed first hard coat layer, the solvent was dried at 90°C for 2 minutes. The dried coating film was purged with nitrogen, and under nitrogen conditions, UV was irradiated with a light amount of 500 mJ / cm 2 to form a second hard coat layer (HC2) and produce a final optical laminate.

[0082] In the case of Example 5, after applying the hard coat composition of Production Example 4 onto the thin glass, the solvent was dried at 90 °C for 2 minutes. The dried coating film was purged with nitrogen, and under nitrogen conditions, UV was irradiated with a light amount of 500 mJ / cm 2 to form the first hard coat layer (HC1). After applying the hard coat composition of Production Example 2 onto the formed first hard coat layer, the solvent was dried at 90 °C for 2 minutes. The dried coating film was purged with nitrogen, and under nitrogen conditions, UV was irradiated with a light amount of 500 mJ / cm 2 to form the second hard coat layer (HC2), and the final optical laminate was produced.

[0083] In the case of Comparative Example 1, after applying the hard coat composition of Production Example 2 onto the thin glass, the solvent was dried at 90 °C for 2 minutes. The dried coating film was purged with nitrogen, and under nitrogen conditions, UV was irradiated with a light amount of 500 mJ / cm 2 to form the hard coat layer, and the final optical laminate was produced.

[0084] In the case of Comparative Example 2, after applying the hard coat composition of Production Example 1 onto the thin glass, the solvent was dried at 90 °C for 2 minutes. The dried coating film was purged with nitrogen, and under nitrogen conditions, UV was irradiated with a light amount of 500 mJ / cm 2 to form the hard coat layer, and the final optical laminate was produced.

[0085] In the case of Comparative Example 3, after applying the hard coat composition of Production Example 2 onto the thin glass, the solvent was dried at 90 °C for 2 minutes. The dried coating film was purged with nitrogen, and under nitrogen conditions, UV was irradiated with a light amount of 500 mJ / cm 2 to form the hard coat layer, and the final optical laminate was produced.

[0086] In the case of Comparative Example 4, after applying the hard coat composition of Production Example 3 onto the thin glass, the solvent was dried at 90 °C for 2 minutes. The dried coating film was purged with nitrogen, and under nitrogen conditions, UV was irradiated with a light amount of 500 mJ / cm 2The first hard coat layer (HC1) was formed by irradiating UV with the light quantity of 2 . After applying the hard coat composition of Production Example 2 onto the formed first hard coat layer, the solvent was dried at 90°C for 2 minutes. The dried coating film was purged with nitrogen, and under nitrogen conditions, UV was irradiated with the light quantity of 500 mJ / cm

[0087]

Table 1

[0088] Experimental Example The physical properties of the optical laminates manufactured in Examples 1 to 5 and Comparative Examples 1 to 4 were measured by the following method, and the results are shown in Table 2.

[0089] (1) Transmittance evaluation The transmittance of the optical laminates of the Examples and Comparative Examples was measured using a haze meter HM-150N manufactured by Murakami Corporation.

[0090] (2) Haze evaluation The haze of the optical laminates of the Examples and Comparative Examples was measured using a haze meter HM-150N manufactured by Murakami Corporation.

[0091] (3) Adhesion evaluation After bonding the optical laminates of the Examples and Comparative Examples to glass using a transparent adhesive so that the hard coat surface faced upward, cuts were made on the hard coat surface with a cutter knife into 100 square shapes with a 1 mm interval vertically and horizontally, and then an adhesion test was performed 3 times using Nichiban tape.

[0092] <Evaluation criteria> 5B: Not peeled off 4B: Peeled off less than 5% 3B: Peeled off 5% or more and less than 15% 2B: Peeled off 15% or more and less than 35% 1B: Peeled off 35% or more and less than 65% 0B: Peeled off 65% or more (4) Pen usability evaluation A polymer film laminate fabricated to be similar to the display panel structure was bonded to the lower part of the optical laminates of the above Examples and Comparative Examples. After fixing the hard coat layer so that it faces upward, a 3H hardness pencil was used to conduct 5 tests with a length of 1 cm under a load of 1 kg to evaluate the impact resistance.

[0093] A polymer film laminate similar to the display panel structure was manufactured by bonding a 25-μm transparent adhesive / 75-μm polarizing film / 35-μm PI film / 25-μm transparent adhesive / 35-μm PI film to have an overall thickness of 195 μm. An evaluation sample was prepared by bonding the adhesive layer on the polarizing film side and the opposite surface of the hard coat layer of the optical laminate.

[0094] <Evaluation Criteria> ◎: The glass does not crack. ○: Pressing the hard coat layer (restoring the press after 24 hours) △: Pressing the hard coat layer (not restoring the press after 24 hours) X: The glass cracks. (5) Curl characteristic evaluation The optical laminates of the Examples and Comparative Examples were left for 24 hours under the conditions of 25 °C and 50% relative humidity with the surface of the hard coat layer facing upward. The distance between the four vertices separated from the bottom was measured and the average value was recorded. In the case of reverse curl where curl occurs in the opposite direction of the second hard coat layer surface, after turning over the thin glass, the distance between the bottom and the vertex was measured and calculated.

[0095] <Evaluation Criteria> ◎: 5 mm or less ○: More than 5 mm and less than 10 mm △: 10 mm or more and less than 20 mm X: 20 mm or more (6) Initial water contact angle evaluation The water contact angle of the coated surface of the optical laminates manufactured in the above Examples and Comparative Examples was measured (using DSA100 of KRUSS).

[0096] (7) Scratch resistance evaluation After fixing the coated surface of the optical laminate produced in the above Examples and Comparative Examples so that it faces upward, 250 g / cm 2 of load was reciprocally rubbed 10 times using steel wool (#0000), and it was visually confirmed whether scratches occurred on the surface of the optical laminate.

[0097] <Evaluation Criteria> ○: When the measurement part was observed by transmitting and reflecting it with a three-wavelength lamp, no scratches were visually recognized, or 10 or fewer scratches were visually recognized.

[0098] X: When the measurement part was observed by transmitting and reflecting it with a three-wavelength lamp, more than 10 scratches were visually recognized.

[0099]

Table 2

[0100] Referring to the experimental data in Table 2 above, in the case of Examples 1 to 5 to which the optical laminate including the two-layer hard coat layer according to the present invention was applied, all showed excellent results in the evaluation of adhesion, pen usability, curl characteristics, water contact angle, and scratch resistance. On the other hand, in the case of the optical laminates of Comparative Examples 1 to 3 including only a single-layer hard coat layer, one or more of the evaluation criteria for adhesion, pen usability, curl characteristics, water contact angle, and scratch resistance did not reach those of the present invention, and they could not show physical properties suitable for an optical laminate for a flexible display.

[0101] In particular, in the case of Comparative Examples 1 and 3 that do not include the first hard coat layer according to the present invention, more than 65% was peeled off 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 coat layer according to the present invention, scratches were confirmed in the scratch resistance evaluation. Also, in the case of Comparative Example 1 that does not include the first hard coat layer according to the present invention and the thickness of the second hard coat layer is 5 μm, it was confirmed that the glass was damaged in the pen usability evaluation and it was not suitable for the use of protecting the glass. Further, in the case of Comparative Example 2 that does not include the second hard coat layer according to the present invention, hard coat layer pressing occurred in the pen usability evaluation and it was not suitable for the use of protecting the glass, and the water contact angle was measured to be less than 95°. In the case of Comparative Example 3 that does not include the first hard coat layer according to the present invention and the thickness of the second hard coat layer exceeds 15 μm, severe curling due to curing shrinkage occurred in the curl property evaluation. In the case of Comparative Example 4 that does not include the epoxy silane coupling agent according to the present invention, more than 65% was peeled off in the adhesion evaluation and the adhesion to glass was not sufficiently ensured, and it could not exhibit physical properties suitable for an optical laminate for a flexible display.

[0102] Therefore, it can be confirmed that the optical laminate according to the present invention and the image display device to which the same is applied have an effect of less curling due to curing shrinkage even at a thickness of 15 μm or more, are excellent in adhesion, pen usability, water contact angle, and scratch resistance, and improve device reliability when applied to a flexible display.

Explanation of Reference Numerals

[0103] 100: Optical laminate 110: Glass 120a: First hard coat layer 120b: Second hard coat layer

Claims

1. Glass, a first hard coat layer formed on the glass, and a second hard coat layer formed on the first hard coat layer, wherein the first hard coat layer is formed of a first hard coat composition containing an epoxy acrylic resin and an epoxy silane coupling agent, and the second hard coat layer is formed of a second hard coat composition containing a light-transmitting resin, an optical laminate.

2. The thickness of the glass is 10 to 100 μm, the optical laminate according to Claim 1.

3. The thickness of the first hard coat layer is 10 to 30 μm, the optical laminate according to Claim 1.

4. The thickness of the second hard coat layer is 3 to 20 μm, the optical laminate according to Claim 1.

5. Any one or more of the first hard coat composition and the second hard coat composition further contains an additive, the optical laminate according to Claim 1.

6. The additive contains one or more selected from the group consisting of a silicone-based leveling agent, an ultraviolet stabilizer, and a heat stabilizer, the optical laminate according to Claim 5.

7. Any one or more of the first hard coat composition and the second hard coat composition further contains an initiator and a solvent, the optical laminate according to Claim 1.

8. The first hard coat composition, based on the total weight of the composition, contains 20 to 80 parts by weight of an epoxy acrylic 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, the optical laminate according to Claim 7.

9. The second hard coat composition, based on the total weight of the composition, contains 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, the optical laminate according to Claim 7.

10. The epoxy silane coupling agent contains one or more selected from 3-glycidoxypropyl dimethoxysilane, 3-glycidoxypropyl trimethoxysilane, 8-glycidoxy octyl trimethoxysilane, and 2-(3,4-epoxy cyclohexyl) ethyl trimethoxysilane, the optical laminate according to Claim 1.

11. The light-transmitting resin contains 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. The optical laminate according to claim 1. Claim 12 The glass, the first hard coat layer, and the second hard coat layer do not contain another layer and are formed in direct contact with each other. The optical laminate according to claim 1. Claim 13 The optical laminate according to claim 1, which is for application to a flexible display. Claim 14 An image display device including the optical laminate according to any one of claims 1 to 13.

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