Optical laminate, image display device having the same, and method for manufacturing optical laminate

Abstract

This invention provides an optical laminate, an image display device comprising the same, and a method for manufacturing the optical laminate. The optical laminate includes a saponified cellulose-based resin film, a polarizer adhered to one side of the cellulose-based resin film, and a protective layer formed on the other side of the cellulose-based resin film. The protective layer is formed from a protective layer forming composition comprising a light-transmitting resin having a viscosity of 5,000 cp or higher at 60°C, a photoinitiator, and a solvent. The light-transmitting resin includes a photocurable (meth)acrylate oligomer. By introducing a high-viscosity protective layer onto the saponified cellulose-based resin film, the optical laminate of this invention ensures the adhesion and performance of the functional coating.

Description

Technical Field

[0001] The present invention relates to an optical laminate, an image display device having the same, and a method for manufacturing the optical laminate. More specifically, it relates to an optical laminate that can ensure adhesion and maintain the performance of the functional coating when a functional coating is laminated on a cellulose-based substrate film, an image display device having the same, and a method for manufacturing the optical laminate. Background Technology

[0002] Image display devices such as liquid crystal displays, plasma displays, electroluminescent displays, touch panels, electronic paper, and tablet computers contain expensive optical films such as polarizers. To prevent damage to these optical films, cellulose-based protective films are often laminated on the surface of the polarizers.

[0003] In recent years, image display devices have been required to exhibit superior durability, visibility, and a variety of other performance characteristics. Therefore, polarizing plates with structures that further incorporate functional coatings are being researched to provide users with the performance they desire.

[0004] However, in order to improve the fit between the polarizer and the polarizer when manufacturing such a polarizing plate, the polarizer is attached to the saponified side of the cellulose membrane with the functional coating after saponification. In this case, the performance of the functional coating is often degraded during the saponification process.

[0005] Korean Patent Publication No. 10-2014-0057484 discloses an antistatic hard coating film that is formed using an antistatic agent containing a quaternary ammonium salt and an ionizing radiation-curable resin containing a polyfunctional acrylate compound having an isocyanuric acid backbone and a (meth)acryloyl group of 15 functions. This allows the hard coating to maintain its properties even when subjected to saponification treatment with an alkaline aqueous solution.

[0006] However, since the functional coatings attached to such hard coatings are also saponified, there is a problem that the performance degradation of the functional coatings cannot be fundamentally prevented. Summary of the Invention

[0007] The problem to be solved

[0008] One object of the present invention is to provide an optical laminate in which a functional coating laminated on a cellulose-based substrate film can maintain both adhesion and original performance.

[0009] Another object of the present invention is to provide an image display device having the above-described optical laminate.

[0010] Another object of the present invention is to provide a method for manufacturing the above-described optical laminate.

[0011] Methods for solving problems

[0012] On one hand, the present invention provides an optical laminate comprising a saponified cellulose-based resin film, a polarizer adhered to one side of the cellulose-based resin film, and a protective layer formed on the other side of the cellulose-based resin film.

[0013] The aforementioned protective layer is formed by a protective layer forming composition comprising a transparent resin having a viscosity of 5,000 cp or higher at 60°C, a photoinitiator, and a solvent.

[0014] The aforementioned transparent resin contains a light-curable (meth)acrylate oligomer.

[0015] In one embodiment of the present invention, the above-mentioned photocurable (meth)acrylate oligomer may contain polyester acrylate.

[0016] In one embodiment of the present invention, the above-mentioned light-transmitting resin may further comprise a compound represented by the following chemical formula 1.

[0017] [Chemical Formula 1]

[0018]

[0019] In the above formula,

[0020] The sum of n and m is 2.

[0021] In one embodiment of the present invention, the mixing ratio of the above-mentioned polyester acrylate to the compound represented by chemical formula 1 may be from 60:40 to 80:20 by weight.

[0022] In one embodiment of the present invention, one or more functional coatings selected from hard coating, anti-reflective layer and conductive layer may be further formed on the above-mentioned protective layer.

[0023] On the other hand, the present invention provides an image display device having the above-described optical laminate.

[0024] In another aspect, the present invention provides a method for manufacturing an optical laminate, comprising:

[0025] (a) The step of saponifying the cellulose resin membrane;

[0026] (b) The step of attaching the polarizer to one side of the saponified cellulose resin film;

[0027] (c) The step of coating the protective layer forming composition onto the other side of the above-mentioned cellulose resin film to form a protective layer.

[0028] The above-mentioned protective layer forming composition includes a light-transmitting resin having a viscosity of 5,000 cp or higher at 60°C, a photoinitiator, and a solvent.

[0029] The aforementioned transparent resin contains a light-curable (meth)acrylate oligomer.

[0030] Invention Effects

[0031] The optical laminate of the present invention ensures the adhesion and performance of the functional coating by coating a high-viscosity protective layer on a saponified cellulose resin film. Detailed Implementation

[0032] The present invention will now be described in more detail.

[0033] One embodiment of the present invention relates to an optical laminate comprising a saponified cellulose-based resin film, a polarizer adhered to one side of the cellulose-based resin film, and a protective layer formed on the other side of the cellulose-based resin film.

[0034] The aforementioned protective layer is formed by a protective layer forming composition comprising a transparent resin having a viscosity of 5,000 cp or higher at 60°C, a photoinitiator, and a solvent.

[0035] The aforementioned transparent resin contains a light-curable (meth)acrylate oligomer.

[0036] One embodiment of the optical laminate of the present invention, by attaching a polarizer to one side of a saponified cellulose-based resin film, includes on the other side a protective layer formed using a light-transmitting resin containing a photocurable (meth)acrylate oligomer and having a viscosity of 5,000 cp or higher at 60°C, thereby maintaining high adhesion of the functional coating formed on the protective layer. Furthermore, the optical laminate of one embodiment of the present invention allows the formation of a functional coating on the saponified cellulose-based resin film, thus preventing performance degradation of the functional coating caused by the saponification process.

[0037] In one embodiment of the present invention, the cellulose-based resin film is a resin film composed of cellulose and fatty acid esters. Any resin film whose adhesion to the polarizer can be improved through saponification can be used without particular limitation. Specific examples include cellulose triacetate resin, cellulose diacetate resin, cellulose tripropionate resin, and cellulose dipropionate resin, among which cellulose triacetate (triacetyl cellulose) resin with excellent transparency and adhesion is preferred.

[0038] The thickness of the cellulose resin film can be 30~100μm, more preferably 40~80μm.

[0039] Since the surface of cellulose-based resin films, especially triacetylcellulose films, is hydrophobic, they exhibit poor adhesion to polyvinyl alcohol films, which are mainly used as polarizers. Therefore, the above-mentioned saponification treatment aims to improve the adhesion between cellulose-based resin films and polarizers through surface modification.

[0040] The above saponification process can be carried out by known methods, such as immersing the triacetylcellulose membrane in an alkaline solution, washing it with water, and then drying it.

[0041] Examples of alkaline solutions used in the above-mentioned saponification process include aqueous solutions of sodium hydroxide, potassium hydroxide, etc., or alkaline aqueous solutions in which various organic solvents such as alcohol have been added. There are no particular limitations on the saponification conditions, but an aqueous solution with a concentration of 0.1 to 10N is preferred, and a concentration of 1 to 2N is more preferred. The temperature of the alkaline aqueous solution is preferably 0 to 100°C, more preferably 40 to 60°C. The saponification time is typically 1 to 120 seconds, preferably 10 to 40 seconds.

[0042] The aforementioned polarizer can be obtained by swelling, dyeing, crosslinking, stretching, washing and drying a polarizer forming film commonly used in the art.

[0043] The aforementioned polarizer-forming film can be any film that can be stained by a dichroic substance, such as iodine, and its type is not particularly limited. Examples include polyvinyl alcohol (PVA) films, dehydrated polyvinyl alcohol films, dehydrochlorinated polyvinyl alcohol films, polyethylene terephthalate films, ethylene-vinyl acetate copolymer films, ethylene-vinyl alcohol copolymer films, cellulose films, and their partially saponified films. Among these, polyvinyl alcohol-based films are preferred due to their excellent effect in enhancing the uniformity of in-plane polarization and their excellent affinity for iodine staining.

[0044] The bonding of the aforementioned cellulose-based resin film to the polarizer can be achieved using an adhesive, and any adhesive known in the art can be used without particular limitation. Specifically, examples include isocyanate-based, polyvinyl alcohol-based, gelatin-based, vinyl polymer-based, latex-based, and water-soluble polyester-based adhesives. Both aqueous and non-aqueous adhesives can be used, but aqueous adhesives are preferred, specifically, they may contain 0.5 to 60% by weight of solid components.

[0045] In one embodiment of the present invention, the protective layer is formed from a protective layer forming composition comprising a transparent resin having a viscosity of 5,000 cp or more at 60°C, preferably 5,000 to 7,000 cp, a photoinitiator, and a solvent, wherein the transparent resin comprises a photocurable (meth)acrylate oligomer.

[0046] In one embodiment of the present invention, the above-mentioned photocurable (meth)acrylate oligomer may contain polyester acrylate.

[0047] The aforementioned polyester acrylate can be manufactured by reacting a polyester polyol with acrylic acid according to methods known in the art.

[0048] The aforementioned polyester acrylates may be, for example, one or more selected from the group consisting of polyester monoacrylate, polyester diacrylate, polyester tetraacrylate, polyester hexaacrylate, polyester pentaerythritol triacrylate, polyester pentaerythritol tetraacrylate, and polyester pentaerythritol hexaacrylate, but are not limited thereto. Difunctional polyester acrylates are particularly preferred from the perspective of suppressing surface haze and ensuring adhesion.

[0049] In one embodiment of the present invention, in addition to the above-mentioned polyester acrylate, the above-mentioned light-transmitting resin may also contain a compound represented by the following chemical formula 1.

[0050] [Chemical Formula 1]

[0051]

[0052] In the above formula,

[0053] The sum of n and m is 2.

[0054] When the above-mentioned polyester acrylate and the compound represented by Formula 1 are used in combination, the mixing ratio of the polyester acrylate to the compound represented by Formula 1, on a weight basis, can be 60:40 to 80:20, preferably 65:35 to 75:25.

[0055] In one embodiment of the present invention, the content of the light-transmitting resin may be 1 to 60% by weight, preferably 10 to 50% by weight, relative to 100% by weight of the entire composition for forming the protective layer. If the content of the light-transmitting resin is less than 1% by weight, the thickness of the coating becomes too thin and it is difficult to achieve sufficient hardness improvement. When it is greater than 60% by weight, there is a problem that the thickness of the coating becomes too thick, resulting in increased curling.

[0056] The protective layer forming composition of one embodiment of the present invention may further include a light-transmitting resin having a viscosity of less than 5,000 cp at 60°C, preferably 500 to 3,000 cp, for example, a monomer having (meth)acryloyl groups.

[0057] Specific examples of the monomers having a (meth)acryloyl group mentioned above may be selected from one or more of the group consisting of neopentyl glycol acrylate, 1,6-hexanediol di(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 tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, isooctyl methacrylate, isodecanyl methacrylate, stearyl methacrylate, tetrahydrofurfuryl methacrylate, phenoxyethyl methacrylate, and isobornol (meth)acrylate.

[0058] From the perspective of ensuring adhesion to the saponified substrate and crosslinking with the aforementioned polyester acrylate, pentaerythritol tri(meth)acrylate is particularly preferred.

[0059] The content of the monomer having (meth)acryloyl groups can be 40% by weight or less, for example, 3 to 40% by weight, relative to 100% by weight of the composition for forming the protective layer. If the content of the monomer having (meth)acryloyl groups is within the above range, the polymerization rate of the protective layer coating can be adjusted to an appropriate level to improve the adhesion to the functional coating formed on the protective layer, and therefore it is preferred from this perspective.

[0060] In one embodiment of the present invention, the photoinitiator is added to induce photocuring of the composition for forming the protective layer, and any photoinitiator used in this art can be used without limitation. For example, one or more photoinitiators selected from the group consisting of hydroxy ketones, amino ketones, hydrogen-abstracting photoinitiators, and combinations thereof can be used.

[0061] Specifically, as the aforementioned photoinitiator, one or more of the following can be used: 2-methyl-1-[4-(methylthio)phenyl]2-morpholinoacetone-1, diphenyl ketone, benzoyladium dimethyl 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-hydroxycyclohexylphenyl ketone, benzophenone, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, and combinations thereof.

[0062] In one embodiment of the present invention, the content of the photoinitiator may be about 0.1 to 10% by weight, preferably about 1 to 8% by weight, relative to 100% by weight of the entire composition for forming the protective layer. If the content of the photoinitiator is less than 0.1% by weight, the curing speed of the composition is slow, resulting in incomplete curing and a decrease in mechanical properties. If it is greater than 10% by weight, the coating may crack due to over-curing.

[0063] In one embodiment of the present invention, the solvent described above can dissolve or disperse the aforementioned components. Any solvent known in the art can be used without limitation. Preferably, solvents used include alcohols (methanol, ethanol, isopropanol, butanol, methyl cellosolve, ethyl cellosolve, etc.), ketones (methyl ethyl ketone, methyl butyl ketone, methyl isobutyl ketone, diethyl ketone, dipropyl ketone, cyclohexanone, etc.), acetates (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.), hexanes (hexane, heptane, octane, etc.), benzenes (benzene, toluene, xylene, etc.), and ethers (diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, diethylene glycol dibutyl ether, propylene glycol monomethyl ether, etc.). The solvents listed above can be used individually or in combination of two or more.

[0064] In one embodiment of the present invention, the content of the solvent, relative to 100% by weight of the entire composition for forming the protective layer, can be 10-95% by weight, preferably 30-95% by weight, and more preferably 40-80% by weight. If the content of the solvent is less than the above-mentioned content, not only will the viscosity be high and the operability reduced, but it may also be difficult to fully swell the substrate film. Conversely, when the content is greater than the above-mentioned range, there is a problem that the drying process consumes a lot of time, resulting in reduced economy.

[0065] In one embodiment of the present invention, the composition for forming the protective layer may further include additives such as leveling agents, ultraviolet stabilizers, and heat stabilizers.

[0066] The leveling agents mentioned above are components that impart smoothness and coatability to the coating film, and may include silicone-based leveling agents, fluorine-based leveling agents, acrylic polymer-based leveling agents, etc. These can be used alone or in combination of two or more.

[0067] Examples of silicone-based leveling agents include polyether-modified, polyester-modified, or aralkyl-modified organic polysiloxanes. In particular, from the perspective of controlling the surface tension of the protective layer, these silicone-based leveling agents may contain polyether-modified polysiloxanes.

[0068] The aforementioned polyether-modified polysiloxanes can be polysiloxanes modified with ethylene oxide, propylene oxide, butane oxide, or tetrahydrofuran, etc. Specifically, examples include polydialkylsiloxanes modified with ethylene oxide and / or propylene oxide (polydimethylsiloxane, polydiethylsiloxane, polydipropylsiloxane, polydibutylsiloxane, or polydipentylsiloxane, etc.). For instance, the aforementioned polyether-modified polysiloxanes can be side-chain type polyether-modified polydialkylsiloxanes, terminal type polyether-modified polydialkylsiloxanes, or side-chain terminal type polydialkylsiloxanes, etc.

[0069] Commercially available silicone-based leveling agents include, for example, those with the trade names BYK-300, BYK-302, BYK-306, BYK-307, BYK-320, BYK-325, BYK-330, BYK-331, BYK-333, BYK-337, BYK-341, BYK-344, BYK-345, BYK-346, BYK-348, BYK-377, BYK-378, BYK-UV3500, BYK-3510, and BYK-353. 0, BYK-3570 (manufactured by BYK), FZ-2118, FZ-77, FZ-2161 (manufactured by Toray Industries, Inc.), KP321, KP323, KP324, KP326, KP340, KP341 (manufactured by Shin-Etsu Chemical Co., Ltd.), TSF4440, TSF4441, TSF4445, TSF4450, TSF4446, TSF4452, TSF4453, TSF4460 (manufactured by Momentive Advanced Materials), etc.

[0070] In one embodiment of the present invention, the leveling agent content can be 0.01 to 10% by weight relative to 100% of the total composition for forming the protective layer. If the leveling agent content is less than the above range, it is difficult to achieve sufficient smoothness of the optical film; if it is greater than the above range, the hardness and scratch resistance of the optical film may also be reduced.

[0071] The aforementioned UV stabilizers are components that block or absorb ultraviolet rays to prevent the cured coating from decomposing, discoloring, or cracking due to exposure to ultraviolet rays.

[0072] The aforementioned UV stabilizers are classified according to their mechanism of action into absorbers, quenchers, and hindered amine light stabilizers (HALS). Additionally, based on their chemical structure, they can be categorized into phenyl salicylate (absorber), benzophenone (absorber), benzotriazole (absorber), nickel derivatives (quenchers), and radical scavengers. There are no particular limitations on the use of these UV stabilizers as long as they do not significantly alter the initial color of the coating.

[0073] In addition, heat stabilizers can be used individually or in combination in commercially available products as the main heat stabilizer (polyphenols), phosphite-based heat stabilizers, and lactone-based heat stabilizers (phosphite-based heat stabilizers).

[0074] The content of the aforementioned UV stabilizers and heat stabilizers can be appropriately adjusted to ensure that they do not affect UV curability.

[0075] In one embodiment of the present invention, the protective layer can be formed by coating the above-described protective layer forming composition onto a saponified cellulose resin film and then UV curing it after drying.

[0076] The above-mentioned protective layer forming composition can be applied to the substrate layer using known methods such as die coating machine, air knife, reverse roller, spraying, doctor blade, casting, gravure, microgravure, spin coating, etc.

[0077] After applying the above-mentioned protective layer forming composition onto the resin film, the volatiles are evaporated at a temperature of 30-150°C for 10 seconds to 1 hour, more specifically 30 seconds to 30 minutes, and then cured by UV light. The UV light irradiation intensity can specifically be about 0.01-10 J / cm². 2 More specifically, it can be 0.1~2 J / cm 2 .

[0078] At this point, the thickness of the formed protective layer can be specifically 1~30μm, more specifically 3~20μm. When the thickness of the protective layer is within the above range, excellent hardness, bending resistance and curling properties can be obtained.

[0079] In one embodiment of the present invention, the optical laminate may further include one or more functional coatings selected from hard coating, anti-reflective layer and conductive layer on the above-mentioned protective layer.

[0080] The aforementioned hard coating preferably exhibits excellent hardness, sufficient strength after the film layer is formed, and excellent light transmittance. Examples of resins for forming the hard coating include thermosetting resins, thermoplastic resins, UV-curable resins, electron beam-curable resins, and two-component mixed resins. Among these, UV-curable resins are preferred, as they are capable of efficiently forming a hard coating through simple processing operations during UV-curing treatment.

[0081] Examples of UV-curable resins include polyester, acrylic, urethane, amide, silicone, and epoxy resins, encompassing UV-curable monomers, oligomers, and polymers. Preferred UV-curable resins are those with UV-polymerizable functional groups, including resins containing acrylic monomers or oligomers having two or more, particularly three to six, of these functional groups. A UV polymerization initiator is also incorporated into the resin.

[0082] There are no particular limitations on the method for forming the hard coating layer; any suitable method can be used. For example, a method can be used to apply the hard coating composition onto the aforementioned protective layer, dry it, and then cure it. The hard coating composition can be applied using suitable methods such as fountain coating, die coating, casting, spin coating, fountain metering, gravure coating, etc. Furthermore, in the coating process, the aforementioned hard coating composition is preferably diluted with common solvents such as toluene, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, isopropanol, and ethanol to prepare a solution. There are no particular limitations on the thickness of the hard coating layer, but it is preferably 0.5 to 30 μm, and particularly preferably 3 to 15 μm.

[0083] The aforementioned anti-reflective layer is a film that minimizes the reflectivity of external light and maximizes the contrast (white brightness / black brightness) to maximize image quality.

[0084] The anti-reflective layer can be made of any suitable composition. As a representative composition, it can be a single-layer thin film with a low refractive index layer or a multi-layer thin film composed of a low refractive index layer and a high refractive index layer stacked in sequence.

[0085] In this invention, a low-refractive-index layer refers to a low-refractive-index coating having a refractive index of 1.38 to 1.48 and a thickness of 0.05 to 10.0 μm, and a high-refractive-index layer refers to a high-refractive-index coating having a refractive index of 1.58 to 1.70 and a thickness of 30 to 100 nm. The aforementioned low-refractive-index and high-refractive-index layers are formed by drying and curing a coating solution containing an adhesive resin with an ionizing-ray curable resin as its main component and inorganic microparticles for refractive index adjustment, using conventional methods. For example, a low-refractive-index layer can be obtained by further adding inorganic microparticles with low refractive index, such as silica or hollow silica microparticles with a particle size of 0.001 μm to 0.2 μm, to a coating solution. On the other hand, a high-refractive-index layer can be obtained by further adding microparticles with high refractive index, such as antimony oxide particles containing tin, antimony oxide particles containing zinc, indium tin oxide particles, zinc oxide / alumina particles, or antimony oxide particles, to a coating solution.

[0086] On the other hand, the ionizing ray curable resin contained in the above coating solution preferably contains (meth)acrylic resin, polyurethane resin, polyester resin, polyether resin, olefin resin and polyimide resin in its skeleton structure, and may be a polymer oligomer of the above resin with 3 to 10 repeating units.

[0087] The aforementioned conductive layer is a layer formed from a composition containing a conductive substance.

[0088] The aforementioned conductive layer is formed from a conductive layer forming composition comprising a polythiophene-based conductive polymer and an alcohol solvent.

[0089] The aforementioned polythiophene-based conductive polymer can be poly(3,4-ethylenedioxythiophene), PEDOT (PEDOT:PSS), which is doped with poly(styrenesulfonate, PSS).

[0090] Poly(3,4-ethylenedioxythiophene) (PEDOT) has high conductivity and low resistance, which facilitates electron migration and gives it excellent conductivity.

[0091] The weight ratio of poly(3,4-ethylenedioxythiophene) (PEDOT) to poly(styrene sulfonate) (PSS) can be from 1:1 to 5.

[0092] The aforementioned polythiophene-based conductive polymers can be used either commercially available products or manufactured using methods known in the art.

[0093] Specifically, PEDOT:PSS can be manufactured by using PSS as a template to regulate charge balance through the oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT) in an aqueous phase. In PEDOT:PSS manufactured according to the above method, PEDOT forms very strong ionic bonds with the PSS polymer chains, thereby allowing it to be stably dispersed in the aqueous phase as polymeric gel particles without separating from each other.

[0094] The alcohol solvents mentioned above may include methanol, ethanol, isopropanol, and butanol, but are not limited to these.

[0095] The conductive layer can be formed by applying the conductive layer forming composition onto the protective layer, hard coating layer or antireflective layer and then thermally curing it after drying.

[0096] The above-mentioned conductive layer forming composition can be applied to the substrate using known methods such as die coating machine, air knife, reverse roller, spraying machine, doctor blade, casting, gravure, microgravure, spin coating, etc.

[0097] After the above-described conductive layer forming composition is applied to a substrate, it can be dried at 60-100°C for 1 to 10 minutes to form the conductive layer. This drying process can be performed, for example, by hot air drying.

[0098] One embodiment of the present invention relates to an image display device having the above-described optical laminate.

[0099] The image display device according to one embodiment of the present invention is applicable not only to conventional liquid crystal display devices, but also to various image display devices such as organic EL display devices, plasma display devices, and field emission display devices.

[0100] In addition to the optical laminates described above, the image display device of the present invention may also include configurations known in the art.

[0101] One embodiment of the present invention relates to a method for manufacturing the above-described optical laminate. The method for manufacturing the optical laminate according to one embodiment of the present invention includes:

[0102] (a) The step of saponifying the cellulose resin membrane;

[0103] (b) The step of attaching the polarizer to one side of the saponified cellulose resin film;

[0104] (c) The step of coating the protective layer forming composition onto the other side of the cellulose resin film to form a protective layer.

[0105] Specifically, in one embodiment of the manufacturing method of the optical laminate of the present invention, the cellulose resin film is first subjected to saponification treatment.

[0106] The types and thicknesses of the cellulose-based resin films described above are the same as those described in the optical laminates section above, and the saponification treatment of the cellulose-based resin films described above is the same as that described in the optical laminates section above. Therefore, specific details are omitted to avoid repetition.

[0107] Next, the polarizer is attached to one side of the saponified cellulose resin film.

[0108] The manufacturing methods and types of the polarizers described above are the same as those described in the optical laminates section, and the bonding of the cellulose resin film to the polarizer is also the same as that described in the optical laminates section. Therefore, specific details are omitted to avoid repetition.

[0109] Next, the protective layer forming composition is applied to the other side of the cellulose resin film to form a protective layer.

[0110] The above-mentioned protective layer forming composition includes a light-transmitting resin having a viscosity of 5,000 cp or more at 60°C, a photoinitiator, and a solvent, wherein the light-transmitting resin comprises a photocurable (meth)acrylate oligomer.

[0111] The composition and content of the light-transmitting resin, photoinitiator, and solvent having a viscosity of 5,000 cp or more at 60°C are the same as those described in the optical laminate above. Furthermore, the coating of the protective layer forming composition and the formation of the protective layer are the same as those described in the optical laminate above. Therefore, specific details are omitted to avoid repetition.

[0112] The method for manufacturing an optical laminate according to one embodiment of the present invention may further include the step of forming one or more functional coatings selected from the above-mentioned protective layer, such as a hard coating layer, an anti-reflective layer, and a conductive layer.

[0113] The hard coating, anti-reflective layer and conductive layer described above are the same as those described in the optical laminate above, so detailed descriptions are omitted to avoid repetition.

[0114] The present invention will now be described in more detail through examples, comparative examples, and experimental examples. It will be apparent to those skilled in the art that these examples, comparative examples, and experimental examples are merely illustrative of the invention, and the scope of the invention is not limited thereto.

[0115] Manufacturing Example 1: Manufacturing of a composition for forming a protective layer

[0116] A composition for forming a protective layer was prepared by mixing 37.4 parts by weight of difunctional polyester acrylate (MIRAMER PS2500, Meiyuan Special Chemicals, 6,000 cP at 60°C), 2.4 parts by weight of photoinitiator (Irgacure-184, Ciba), 0.2 parts by weight of leveling agent (BYK-3530, BYK), and 60 parts by weight of methyl ethyl ketone using a mixer and filtering the mixture using a PP filter.

[0117] Manufacturing Example 2: Manufacturing of a Composition for Forming a Protective Layer

[0118] A composition for forming a protective layer was prepared by mixing 18.7 parts by weight of trifunctional acrylate (MIRAMER M340, Meiyuan Special Chemicals, 1,000~1,800 cP at 25°C), 18.7 parts by weight of difunctional polyester acrylate (MIRAMER PS2500, Meiyuan Special Chemicals, 6,000 cP at 60°C), 2.4 parts by weight of photoinitiator (Irgacure-184, Ciba), 0.2 parts by weight of leveling agent (BYK-3530, BYK Corporation) and 60 parts by weight of methyl ethyl ketone using a mixer and filtering the mixture using a PP filter.

[0119] Manufacturing Example 3: Manufacturing of a Composition for Forming a Protective Layer

[0120] A composition for forming a protective layer was prepared by mixing 26.2 parts by weight of trifunctional acrylate (MIRAMER M340, Meiyuan Special Chemicals, 1,000~1,800 cP at 25°C), 11.2 parts by weight of difunctional polyester acrylate (MIRAMER PS2500, Meiyuan Special Chemicals, 6,000 cP at 60°C), 2.4 parts by weight of photoinitiator (Irgacure-184, Ciba), 0.2 parts by weight of leveling agent (BYK-3530, BYK Corporation) and 60 parts by weight of methyl ethyl ketone using a mixer and filtering the mixture using a PP filter.

[0121] Manufacturing Example 4: Manufacturing of Hard Coating Composition

[0122] A hard coating composition was prepared by mixing 46.7 parts by weight of hexafunctional urethane acrylate (UA-306I, Kyoei Co., Ltd.), 3 parts by weight of photoinitiator (Irgacure-184, Ciba), 0.3 parts by weight of leveling agent (BYK-307, BYK Corporation) and 50 parts by weight of methyl ethyl ketone using a mixer and filtering the mixture through a PP filter.

[0123] Manufacturing Example 5: Manufacturing of Hard Coating Composition

[0124] A hard coating composition was prepared by mixing 4.7 parts by weight of tetradecyl acrylate (Osaka Organic Chemicals, VISCOAT #1000), 42.1 parts by weight of hexafunctional urethane acrylate (UA-306I, Kyoei Co., Ltd.), 3 parts by weight of photoinitiator (Irgacure-184, Ciba), 1 part by weight of leveling agent (KY-1203, Shin-Etsu Co., Ltd.), and 49.2 parts by weight of methyl ethyl ketone using a mixer and filtering the mixture using a PP filter.

[0125] Manufacturing Example 6: Manufacturing of a Composition for Forming an Antireflective Layer

[0126] A composition for forming an antireflective layer was prepared by mixing 1 part by weight of hexafunctional urethane acrylate (Kyoeisha, UA-306I), 0.1 part by weight of photoinitiator (Irgacure-184, Ciba), 0.1 part by weight of leveling agent (BYK-307, BYK), 9 parts by weight of hollow silica with a size of 60 nm and 89.8 parts by weight of methyl ethyl ketone using a mixer and filtering the mixture using a PP filter.

[0127] Manufacturing Example 7: Manufacturing of a Composition for Forming a Conductive Layer

[0128] A composition for forming a conductive layer was prepared by mixing 18.2 parts by weight of PEDOT:PSS (Shin-Etsu Polymer, SAS-P) and 81.8 parts by weight of isopropanol using a mixer and filtering the mixture using a PP filter.

[0129] Manufacturing Example 8: Manufacturing of a Composition for Forming a Protective Layer

[0130] A composition for forming a protective layer was prepared by mixing 37.4 parts by weight of trifunctional acrylate (MIRAMER M340, Meiyuan Special Chemicals, 1,000~1,800 cP at 25°C), 2.4 parts by weight of photoinitiator (Irgacure-184, Ciba), 0.2 parts by weight of leveling agent (BYK-3530, BYK Corporation) and 60 parts by weight of methyl ethyl ketone using a mixer and filtering the mixture using a PP filter.

[0131] [Table 1]

[0132]

[0133] A-1: Difunctional polyester acrylate (MIRAMER PS2500, Meiyuan Special Chemicals, 6,000 cP at 60℃);

[0134] A-2: Trifunctional acrylate (MIRAMER M340, Meiyuan Special Chemicals, 1,000~1,800 cP at 25℃);

[0135] B: Irgacure-184 (Ciba Special Chemicals);

[0136] C-1: Leveling agent (BYK-3530, BYK Corporation);

[0137] C-2: Leveling agent (BYK-307, BYK Corporation);

[0138] C-3: Leveling agent (KY-1203, Shin-Etsu Chemical Co., Ltd.);

[0139] D-1: Methyl ethyl ketone;

[0140] D-2: Isopropanol;

[0141] Hexafunctional acrylates: urethane acrylates (UA-306I, Kyoei Co., Ltd.);

[0142] Tetradecanoic acrylate: VISCOAT #1000 (Osaka Organic Chemicals);

[0143] Conductive polymer: PEDOT:PSS (SAS-P, Shin-Etsu Polymer).

[0144] Example 1: Fabrication of optical laminates

[0145] After saponifying an 80 μm thick triacetyl cellulose membrane, a polarizer was attached to one side using a modified polyvinyl alcohol adhesive to form a polarizing plate. The protective layer forming composition of Manufacturing Example 1 was then coated onto the other side of the saponified triacetyl cellulose membrane to a thickness of 3 μm and dried. The membrane was then irradiated with a UV cumulative light intensity of 600 mJ / cm² under a nitrogen atmosphere. 2 To manufacture optical laminates.

[0146] Example 2: Fabrication of Optical Laminates

[0147] The protective layer forming composition of Manufacturing Example 2 was used instead of the protective layer forming composition of Manufacturing Example 1. Otherwise, the optical laminate was manufactured in the same manner as in Example 1.

[0148] Example 3: Fabrication of Optical Laminates

[0149] The protective layer forming composition of Manufacturing Example 3 was used instead of the protective layer forming composition of Manufacturing Example 1. Otherwise, the optical laminate was manufactured in the same manner as in Example 1.

[0150] Example 4: Fabrication of Optical Laminates

[0151] After coating the protective layer formed in Example 2 above with a thickness of 5 μm onto the hard coating composition of Manufacturing Example 5 and drying it, the mixture was irradiated with UV cumulative light intensity of 600 mJ / cm under a nitrogen atmosphere. 2 To manufacture optical laminates.

[0152] Example 5: Fabrication of Optical Laminates

[0153] After coating the protective layer formed in Example 2 with a thickness of 5 μm onto the hard coating composition of Manufacturing Example 4 and drying it, the mixture was irradiated with a UV cumulative light intensity of 600 mJ / cm under a nitrogen atmosphere. 2 A hard coating is formed, and then the antireflective layer forming composition of Manufacturing Example 6 is coated on it with a thickness of 100 nm and dried. Then, it is irradiated with UV cumulative light intensity of 600 mJ / cm under a nitrogen atmosphere. 2 To manufacture optical laminates.

[0154] Example 6: Fabrication of Optical Laminates

[0155] The conductive layer forming composition of manufacturing example 7 was coated on the protective layer formed in example 2 above with a thickness of 100 nm and then thermosetting to manufacture an optical laminate.

[0156] Comparative Example 1: Fabrication of Optical Laminates

[0157] The protective layer forming composition of Manufacturing Example 8 was used instead of the protective layer forming composition of Manufacturing Example 1. Otherwise, the optical laminate was manufactured in the same manner as in Example 1.

[0158] Comparative Example 2: Fabrication of Optical Laminates

[0159] The hard coating composition of Manufacturing Example 5 was applied to replace the protective layer forming composition of Manufacturing Example 1, with a thickness of 5 μm. Otherwise, the optical laminate was manufactured in the same manner as in Example 1.

[0160] Comparative Example 3: Fabrication of Optical Laminates

[0161] After coating one side of a triacetylcellulose membrane with a thickness of 80 μm with the hard coating composition of Manufacturing Example 5 and drying it, the membrane was irradiated with a UV cumulative light intensity of 600 mJ / cm under a nitrogen atmosphere. 2 To form a hard coating, the triacetyl cellulose membrane with the hard coating is then saponified, and a polarizer is bonded to the other side using a modified polyvinyl alcohol adhesive to create an optical laminate.

[0162] Comparative Example 4: Fabrication of Optical Laminates

[0163] After saponifying an 80 μm thick triacetyl cellulose membrane, a polarizer was attached to one side using a modified polyvinyl alcohol adhesive to form a polarizing plate. Then, the hard coating composition of Manufacturing Example 4 was coated onto the other side of the saponified triacetyl cellulose membrane to a thickness of 5 μm and dried. The membrane was then irradiated with a UV cumulative light intensity of 600 mJ / cm² under a nitrogen atmosphere. 2 A hard coating is formed, and then the composition for forming the antireflective layer of Example 6 is coated on the hard coating to a thickness of 100 nm and dried. After drying, it is irradiated with UV cumulative light intensity of 600 mJ / cm under a nitrogen atmosphere. 2 To manufacture optical laminates.

[0164] Comparative Example 5: Fabrication of Optical Laminates

[0165] After coating one side of a triacetylcellulose membrane with a thickness of 80 μm with the hard coating composition of Manufacturing Example 4 and drying it, the membrane was irradiated with a UV cumulative light intensity of 600 mJ / cm under a nitrogen atmosphere. 2 A hard coating is formed, and then the antireflective layer forming composition of Manufacturing Example 6 is coated on the hard coating with a thickness of 100 nm and dried. Then, it is irradiated with a UV cumulative light intensity of 600 mJ / cm² under a nitrogen atmosphere. 2 After forming the anti-reflective layer, the triacetyl cellulose membrane with the hard coating and anti-reflective layer is saponified, and then a polarizer is bonded to the other side using a modified polyvinyl alcohol adhesive to create an optical laminate.

[0166] Comparative Example 6: Fabrication of Optical Laminates

[0167] The conductive layer forming composition of Manufacturing Example 7 was applied to replace the protective layer forming composition of Manufacturing Example 1 with a thickness of 100 nm, and then thermally cured to form a conductive layer. Otherwise, the optical laminate was manufactured in the same manner as in Example 1.

[0168] Comparative Example 7: Fabrication of Optical Laminates

[0169] The conductive layer forming composition of Manufacturing Example 7 was applied to replace the hard coating composition of Manufacturing Example 5 with a thickness of 100 nm and then thermally cured to form a conductive layer. Otherwise, the optical laminate was manufactured in the same manner as in Comparative Example 3.

[0170] Experimental Example 1:

[0171] The physical properties of the optical laminates manufactured in the above embodiments and comparative examples were measured as follows, and the results are shown in Tables 2 and 3 below.

[0172] (1) Water contact angle

[0173] After 2 μl of water was dropped onto the coating surface of the optical laminate manufactured in the above embodiments and comparative examples, the water contact angle was measured using a KRUSS DSA100.

[0174] (2) Fit

[0175] The optical laminates manufactured in the above embodiments and comparative examples were bonded to glass with the coating facing upwards using a transparent adhesive. Then, 100 square grids were formed on the coating surface using a cutting tool at 1mm intervals in both the transverse and longitudinal directions. Three adhesion tests were then performed using Mikibon tape. After rapid peeling at a 180-degree peel angle, the degree of coating peeling was visually observed, and the adhesion was evaluated according to the following evaluation criteria.

[0176] <Evaluation Criteria>

[0177] 5B: Not stripped;

[0178] 4B: Stripping percentage is higher than 0% and lower than 5%;

[0179] 3B: Stripping of more than 5% but less than 15%;

[0180] 2B: Stripping of 15% or more but less than 35%;

[0181] 1B: Stripping of 35% or more but less than 65%;

[0182] 0B: Stripping more than 65%.

[0183] (3) Reflectivity

[0184] After the optical laminates manufactured in the above embodiments and comparative examples were bonded to a black acrylic sheet to remove back reflection, the reflectivity was measured using an integrating sphere reflectance meter (CM-3700A, Konica Minolta).

[0185] (4) Scratch resistance

[0186] After fixing the optical laminates manufactured in the above manufacturing examples and comparative examples with the hard coating facing upwards using adhesive tape, steel wool (#0000) at 250 g / cm² was used. 2 After 3,500 cycles of cyclic rubbing under load, the measuring unit was subjected to transmission and reflection under a three-wavelength lamp to observe the scratches. Scratch resistance was evaluated according to the following criteria.

[0187] <Evaluation Criteria>

[0188] ○: No scratches or fewer than 5 scratches seen;

[0189] ×: More than 5 scratches are visible.

[0190] (5) Haze Measurement

[0191] The haze of the optical laminates manufactured in the above-described examples and comparative examples was measured using a haze meter (HM-150N, Murakami Corporation).

[0192] (6) Surface resistance

[0193] The surface resistance of the optical laminates manufactured in the above embodiments and comparative examples was measured using a CMT-100A device (AIT Corporation).

[0194] [Table 2]

[0195]

[0196] [Table 3]

[0197]

[0198] As shown in Table 2 above, the optical laminates of Examples 1 to 6, which form a protective layer on one side of a saponified cellulose resin film using a light-transmitting resin containing a photocurable (meth)acrylate oligomer and having a viscosity of 5,000 cp or more at 60°C, exhibit excellent coating adhesion and good coating performance retention.

[0199] Conversely, as shown in Table 3, it can be confirmed that the optical laminates of Comparative Examples 1 to 7, which did not use a light-transmitting resin containing a photocurable (meth)acrylate oligomer and having a viscosity of 5,000 cp or more at 60°C when forming a protective layer on one side of the saponified cellulose resin film, or did not form a protective layer, or were saponified after forming a coating on one side of the cellulose resin film, exhibited reduced coating adhesion or poor coating performance.

[0200] The foregoing has described specific parts of the present invention in detail. It will be apparent to those skilled in the art that such detailed description is merely a preferred embodiment, and the scope of the invention is not limited thereto. Those skilled in the art should be able to make various applications and modifications within the scope of the present invention based on the above description.

[0201] Therefore, the actual scope of the invention will be defined by the appended claims and their equivalents.

Claims

1. An optical laminate comprising a saponified cellulose-based resin film, a polarizer adhered to one side of the cellulose-based resin film, and a protective layer formed on the other side of the cellulose-based resin film. The protective layer is formed by a protective layer forming composition comprising a light-transmitting resin having a viscosity of 5,000 cp or higher at 60°C, a photoinitiator, and a solvent. The light-transparent resin comprises a light-curable (meth)acrylate oligomer.

2. The optical laminate according to claim 1, wherein the photocurable (meth)acrylate oligomer comprises polyester acrylate.

3. The optical laminate according to claim 2, wherein the light-transmitting resin further comprises a compound represented by chemical formula 1: Chemical Formula 1 In the formula, The sum of n and m is 2.

4. The optical laminate according to claim 3, wherein the mixing ratio of the polyester acrylate to the compound represented by chemical formula 1 is 60:40 to 80:20 by weight.

5. The optical laminate according to claim 1, wherein one or more functional coatings selected from hard coating, anti-reflective layer and conductive layer are further formed on the protective layer.

6. An image display device comprising an optical laminate according to any one of claims 1 to 5.

7. A method for manufacturing an optical laminate, comprising: (a) The step of saponifying the cellulose resin membrane; (b) The step of attaching the polarizer to one side of the saponified cellulose resin film; (c) The step of coating the protective layer forming composition onto the other side of the cellulose-based resin film to form a protective layer. The composition for forming the protective layer includes a transparent resin having a viscosity of 5,000 cp or higher at 60°C, a photoinitiator, and a solvent. The light-transparent resin comprises a light-curable (meth)acrylate oligomer.

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