Adhesive composition, adhesive sheet formed therefrom, and optical element

Abstract

The present invention provides an adhesive composition capable of blocking blue light in a target wavelength band at an excellent level, preventing changes in initial adhesion and optical properties due to external environmental factors, particularly heat, humidity, and UV light, and being widely applied in the optical field.

Description

TECHNICAL FIELD

[0001] The present application relates to an adhesive composition, more particularly, to an adhesive composition suitable for manufacturing an adhesive sheet excellent in blocking properties and durability for blue light in a target wavelength range, an adhesive sheet formed therefrom, and an optical element. BACKGROUND

[0002] The so-called blue light refers to blue light of a wavelength band of 380 nm to 500 nm, including a UV region of 380 to 400 nm and a visible light region of 400 to 500 nm which is violet, indigo, and blue, and has high energy due to a short wavelength, and thus is also called high-energy visible light (HEV light).

[0003] It is known that the above-described blue light is light that causes changes in hormones that regulate a person's mood, sleep-wake cycle, and thus has been applied to phototherapy for treating depression or insomnia. However, on the other hand, blue light is stronger in energy than other wavelengths of visible light, and thus constricts the pupil, overworks the eye muscles, and thus increases eye fatigue, which can induce tension in the eyes and the muscles around the eyes, and further cause stiffness in the surrounding muscles such as the shoulders and the neck. In addition, due to the strong energy, it can reach the inside of the eye, which causes inflammation of the conjunctiva and the cornea, damages the lens and the retina of the eye, and various problems such as reduction in the secretion of a sleep-inducing hormone (melatonin) and reduction in sleep quality have been reported when continuously exposed to blue light.

[0004] On the other hand, modern people are in an environment in which they cannot live without electronic devices such as smartphones, notebook computers, tablet computers, computer monitors, TVs, etc. in their daily lives, and accordingly, the frequency and duration of exposure to blue light by users are also increasing, and thus concerns about the harmful effects of blue light are rapidly increasing.

[0005] Accordingly, various attempts to control blue light emitted from display devices in various electronic devices have been continuously made in recent years. As an example, an adhesive sheet is introduced which exists in a state in which various optical films having optical and / or physical protection functions are laminated with the adhesive sheet interposed therebetween in a display device, and imparts a function of blocking a target wavelength band. However, such adhesive sheets mostly mainly perform UV blocking that can block a wavelength band close to 380 nm or 400 nm, rather than blocking a blue light wavelength band, and an adhesive sheet capable of blocking blue light in a target blue light wavelength band, particularly a wavelength band adjacent to the ultraviolet wavelength region and wide enough, has not been developed.

[0006] Furthermore, even if a blue light blocking function is provided, external environmental factors such as UV rays, heat, and humidity can cause changes in the optical function of the blue light blocking function or adhesive properties, thus failing to ensure sufficient durability.

[0007] Therefore, the actual situation is that there is an urgent need to develop an adhesive sheet that can block blue light emission wavelengths at an excellent level, especially blue light in a sufficiently wide wavelength band adjacent to the ultraviolet wavelength region, and has durability that can prevent changes in initial physical properties due to external environmental factors. Summary of the Invention

[0008] Technical issues

[0009] The present invention has been proposed in view of the above-mentioned problems, and its object is to provide an adhesive composition, an adhesive sheet formed therefrom, and an optical element, wherein the adhesive composition blocks blue light within a sufficiently wide target wavelength band adjacent to the ultraviolet wavelength region at an excellent level, and has durability that prevents changes in the adhesiveness and optical properties of the initial design due to external environmental factors.

[0010] Solutions to Problems

[0011] To solve the above problems, the present invention provides an adhesive composition comprising an adhesive component and a light absorber, wherein an adhesive layer formed from the adhesive composition satisfies the following conditions (a) and (b).

[0012] As condition (a), the transmittance at a wavelength of 470 nm is 60% or more, and the transmittance at a wavelength of 440 nm is 20% or less. As condition (b), the slope of the transmittance spectrum in the region from 20% to 60% is 3.0 or more.

[0013] According to one embodiment of the present invention, the adhesive component may include an acrylic copolymer having one or more functional groups of hydroxyl group and carboxyl group.

[0014] In addition, a cross-linking agent may be included.

[0015] In addition, the light absorber may include one or more compounds represented by the following Chemical Formula 1 and Chemical Formula 2.

[0016] [Chemical Formula 1]

[0017]

[0018] In Chemical Formula 1, R1 is an alkyl group having 3 to 20 carbon atoms or an aryl group having 6 to 12 carbon atoms.

[0019] [Chemical Formula 2]

[0020]

[0021] In Chemical Formula 2, R2 is an alkyl group having 3 to 20 carbon atoms or an aryl group having 6 to 12 carbon atoms.

[0022] Furthermore, in the above condition (a), the transmittance at a wavelength of 470 nm may be 90% or more, and the transmittance at a wavelength of 440 nm may be 5% or less.

[0023] In addition, in each of the compound represented by Chemical Formula 1 and the compound represented by Chemical Formula 2, the number of carbon atoms of R1 and R2 may be independently 3 to 8.

[0024] Furthermore, the light absorber may be contained in an amount of 0.2 to 2.0% by weight based on the weight of the adhesive layer formed from the adhesive composition.

[0025] The present invention also provides an adhesive sheet including an adhesive layer formed from the adhesive composition of the present invention.

[0026] The present invention also provides an optical element including an optical film and the adhesive sheet of the present invention disposed on at least one surface of the optical film.

[0027] According to one embodiment of the present invention, the optical film may be one selected from the group consisting of an absorbing polarizing film, a phase difference film diffuser, a light collecting film, a reflecting polarizing film, a protective film and a TAC film.

[0028] Effects of the Invention

[0029] The adhesive composition of the present invention is capable of blocking blue light within a sufficiently wide target wavelength band adjacent to the ultraviolet wavelength region at an excellent level, and can form an adhesive sheet having heat resistance, moisture and heat resistance, and light resistance that prevents changes in the optical and adhesive properties of the initial design due to external environmental factors, particularly heat, humidity, and UV light. Therefore, the formed adhesive sheet can be used alone or in combination with various optical films to realize a variety of optical elements. DETAILED DESCRIPTION

[0030] The following describes the embodiments of the present invention in detail so that those skilled in the art can easily implement the present invention. The present invention can be implemented in various ways and is not limited to the embodiments described here.

[0031] The adhesive composition of one embodiment of the present invention includes an adhesive component and a light absorber. The adhesive layer formed by the above-mentioned adhesive composition satisfies conditions (a) and (b). As condition (a), the transmittance at a wavelength of 470nm is greater than 60%, and the transmittance at a wavelength of 440nm is less than 20%. As condition (b), the slope of the transmittance region from 20% to 60% in the transmittance spectrum is greater than 3.0.

[0032] First, condition (a) will be described. The transmittance of the adhesive layer formed from the adhesive composition at a wavelength of 470 nm can be 60% or greater, preferably 90% or greater. This allows for high transmittance at 470 nm or, for example, blue light in the 470-500 nm wavelength range to achieve sufficient brightness and minimize or prevent color distortion. If the transmittance of the adhesive layer at 470 nm is less than 60%, the adhesive layer may reduce the brightness of the light source, causing color distortion.

[0033] Furthermore, the adhesive layer can have a transmittance of 20% or less at 440 nm, preferably 5% or less. This allows for high blocking properties for blue light, for example, at 440 nm or in the 400-440 nm wavelength range. This helps prevent various harmful effects of blue light, such as retinal damage and hormonal abnormalities, by blocking blue light in the high-energy, low-wavelength range. If the transmittance at 440 nm exceeds 20%, the average transmittance in the target wavelength range, including 440 nm, such as 400-440 nm, increases, potentially making it difficult to adequately block blue light.

[0034] In addition, as condition (b), the slope of the area with a transmittance of 20% to 60% in the transmittance spectrum can be 3.0 or more, preferably 3.2 or more. By satisfying the above slope of 3.0 or more in condition (b), the blue wavelength region band that satisfies the transmittance of less than 20% has a low average transmittance, and the blue wavelength region band that satisfies the transmittance of more than 60% tends to have a high average transmittance, which is conducive to simultaneously showing the blocking of blue light in the target wavelength region and the transmission characteristics of blue light wavelength regions outside it. Further, when the above slope is 3.0 or more, changes in optical properties and / or adhesive properties caused by UV light and humidity can be minimized, especially changes in transmittance in the blue wavelength region band that must be blocked due to heat. If the above slope in condition (b) is less than 3.0, the brightness may be reduced or the blue light blocking of the target wavelength band may be negligible, and the optical properties and / or adhesive properties may change significantly due to external environmental factors.

[0035] At this time, regarding the slope of the transmittance T1 (%) to T2 (%) region defined in condition (b), the wavelength at which the transmittance Tx (%) corresponding to the y-axis of the transmittance spectrum is achieved is defined as λ Tx (nm), the slope of the transmittance range from T1 (%) to T2 (%) is calculated according to the following mathematical formula 1.

[0036] [Mathematical formula 1]

[0037]

[0038] On the other hand, the slope within the predetermined transmittance region in the above-mentioned transmittance spectrum can be adjusted by one or a combination of two or more factors including the type and content of the light absorber contained in the adhesive composition described later for forming the adhesive layer, the thickness of the formed adhesive layer, and the content of the absorber, and the present invention is not particularly limited to this.

[0039] The adhesive layer according to one embodiment of the present invention that satisfies the above-mentioned optical properties may be formed from an adhesive composition including an adhesive component and a light absorber.

[0040] The adhesive component can be any adhesive component that has adhesive properties, does not affect the properties of the light transmitted, and can accommodate the light absorber described below without causing physical or chemical effects on the light absorber. As an example, the adhesive component can include acrylic, urethane, and silicone adhesive components that meet the above requirements and are well known as adhesive components in the optical field. Among them, acrylic adhesive components are preferred in terms of light transmittance and cost.

[0041] The above-mentioned acrylic adhesive component may contain an acrylic copolymer as a main component. Here, the so-called main component refers to, for example, 55% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more of the acrylic copolymer based on the weight of the acrylic adhesive component.

[0042] The acrylic (co)polymer may contain polymerized units of an alkyl (meth)acrylate monomer. Considering cohesive strength, glass transition temperature, and adhesive properties, for example, an alkyl (meth)acrylate monomer having an alkyl group of 1 to 14 carbon atoms may be used. Examples of the alkyl group include 2 to 14 carbon atoms, 3 to 14 carbon atoms, 4 to 14 carbon atoms, 4 to 12 carbon atoms, or 4 to 8 carbon atoms, and such an alkyl group may be linear or branched. Such monomers may include one or more of the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, sec-butyl (meth)acrylate, pentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-ethylbutyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, lauryl (meth)acrylate, and / or tetradecyl (meth)acrylate. Furthermore, considering the influence of factors such as the glass transition temperature on adhesion, n-butyl acrylate may be used as an example.

[0043] Furthermore, the content of the alkyl (meth)acrylate monomer having an alkyl group having 1 to 14 carbon atoms is 60 to 99% by weight, preferably 90 to 99% by weight, relative to 100% by weight of all monomers used in the production of the acrylic copolymer. If the content of the alkyl (meth)acrylate monomer having an alkyl group having 1 to 14 carbon atoms is less than 60% by weight, the viscosity of the adhesive composition may increase, while if it exceeds 99% by weight, adhesive strength may be poorly exhibited.

[0044] In addition, as additional polymerized units, polymerized units of copolymerizable monomers having polar functional groups may be further included to improve cohesion, etc. The above-mentioned copolymerizable monomers having polar functional groups may refer to monomers such as the above-mentioned (meth) alkyl acrylate monomers that can be copolymerized with compounds that form acrylic polymers. In addition, the copolymerizable monomers having polar functional groups may refer to monomers that can provide polar functional groups on the side chains or ends of the copolymers after copolymerization to form acrylic copolymers. Here, the above-mentioned polar functional groups may be, for example, functional groups that can react with the cross-linking agent described later by heating to form a cross-linked structure or that play a role in improving the wettability of the adhesive layer. As the above-mentioned polar functional groups, for example, hydroxyl groups, carboxyl groups or their anhydride groups, acid groups such as sulfonic acid groups or phosphoric acid groups, glycidyl groups, amino groups or isocyanate groups may be exemplified.

[0045] The aforementioned copolymerizable monomers having polar groups and hydroxyl groups may be monomers that contain both a site copolymerizable with other monomers forming an acrylic polymer and a hydroxyl group, and that can provide a hydroxyl group to the acrylic copolymer after copolymerization. Examples of such monomers include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, or 8-hydroxyoctyl (meth)acrylate. Preferred examples include 4-hydroxybutyl acrylate, 2-hydroxyethyl (meth)acrylate, and 4-hydroxybutyl vinyl ether.

[0046] In addition, as a copolymerizable monomer having a hydroxyl group but lacking a site copolymerizable with other monomers, hydroxyalkylene glycol (meth)acrylates such as 2-hydroxyethylene glycol (meth)acrylate and 2-hydroxypropylene glycol (meth)acrylate can also be used. In particular, when the cross-linking agent described later is a polyfunctional isocyanate compound, hydroxybutyl acrylate is preferably used as the copolymerizable monomer having a hydroxyl group from the viewpoint of ensuring reactivity with the cross-linking agent and wettability of the adhesive layer.

[0047] In addition, examples of the copolymerizable monomer having a carboxyl group as the above-mentioned polar group include: monobasic acids such as (meth)acrylic acid and crotonic acid; dibasic acids such as maleic acid, itaconic acid, and fumaric acid, and their monoalkyl esters; 3-(meth)acryloylpropionic acid; succinic anhydride ring-opening adducts of 2-hydroxyalkyl (meth)acrylates having an alkyl group with 2 to 3 carbon atoms, succinic anhydride ring-opening adducts of hydroxyalkylene glycol (meth)acrylates having an alkyl group with 2 to 4 carbon atoms, and compounds formed by ring-opening addition of succinic anhydride to caprolactone adducts of 2-hydroxyalkyl (meth)acrylates having an alkyl group with 2 to 3 carbon atoms, etc. Among them, (meth)acrylic acid is preferred.

[0048] In addition, the copolymerizable monomer having an amide group as the above-mentioned polar group may include, for example, one or more of (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, and N-hydroxyethylacrylamide.

[0049] The copolymerizable monomer having an amino group as the polar group may include, for example, one or more of aminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and tert-butylaminoethyl (meth)acrylate.

[0050] The copolymerizable monomer having a glycidyl group as the polar group may include, for example, one or more of glycidyl (meth)acrylate and methylglycidyl (meth)acrylate.

[0051] In addition, as other copolymerizable monomers having polar groups, for example, there can be mentioned: cyano group-containing monomers such as acrylonitrile or methacrylonitrile; heterocyclic vinyl-based monomers such as N-vinyl-2-pyrrolidone, (meth)acryloylmorpholine, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrrole, N-vinylimidazole, and N-vinyloxazole; sulfonic acid group-containing monomers such as sodium vinyl sulfonate; phosphate group-containing monomers such as 2-hydroxyethylacryloyl phosphate; imide group-containing monomers such as cyclohexylmaleimide and isopropylmaleimide; isocyanate group-containing monomers such as 2-methacryloyloxyethyl isocyanate, etc.

[0052] Preferably, the copolymerizable monomer having a polar group may include one or more of a monomer having a hydroxyl group and a monomer having a carboxyl group. In this case, the content of one or more of the monomer having a hydroxyl group and the monomer having a carboxyl group may be 1 to 40% by weight, preferably 1 to 25% by weight, relative to 100% by weight of all monomers used in the manufacture of the acrylic copolymer. As another example, the content may be 1 to 10% by weight. On the other hand, if the content of one or more of the monomer having a hydroxyl group and the monomer having a carboxyl group is less than 1% by weight, the cohesive force of the adhesive may be reduced, resulting in decreased durability. If the content is greater than 40% by weight, the adhesive force may be reduced due to the high gel fraction, resulting in decreased durability.

[0053] On the other hand, the acrylic copolymer may contain a polyfunctional monomer. For example, it may contain one or more of hexanediol di(meth)acrylate, butanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol (meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, etc. In this case, the polyfunctional monomer may be 0.5% by weight or less, and more preferably 0 to 0.1% by weight, based on 100% by weight of all monomers used in the production of the acrylic copolymer.

[0054] The acrylic copolymer can be produced by known methods used in the production of acrylic copolymers. For example, bulk polymerization, solution polymerization, emulsion polymerization, or suspension polymerization can be used. Solution polymerization is preferred from the perspectives of transparency, water resistance, and cost. Furthermore, solvents, polymerization initiators, and chain transfer agents for molecular weight control commonly used in the production of acrylic copolymers can be used, and the present invention is not particularly limited thereto.

[0055] The weight average molecular weight (polystyrene equivalent, Mw) of the acrylic copolymer as measured by gel permeation chromatography (GPC) is preferably 50,000 to 2,000,000, more preferably 400,000 to 2,000,000. If the weight average molecular weight is less than 50,000, the cohesive force between the copolymers may be insufficient, leading to durability problems. If the weight average molecular weight is greater than 2,000,000, a large amount of dilution solvent may be required during coating to ensure process efficiency.

[0056] In addition, based on the total weight of the adhesive composition, the content of the adhesive component containing the above-mentioned acrylic copolymer is preferably 90% by weight to 99.99% by weight. If the content of the adhesive component containing the acrylic copolymer is less than 90% by weight, the cohesive force may be reduced, resulting in poor durability. When it is greater than 99.9% by weight, the viscosity of the adhesive composition may increase, making it difficult to exhibit adhesive strength.

[0057] In addition, according to one embodiment of the present invention, the adhesive composition may further include a cross-linking agent for cross-linking the adhesive components.

[0058] The cross-linking agent improves the adhesion and durability of the adhesive layer, and is conducive to ensuring high-temperature reliability and shape retention. The cross-linking agent can be combined with a known cross-linking agent suitable for cross-linking the adhesive component, taking into account the specific type of the adhesive component. As an example, when the adhesive component is an acrylic copolymer, the cross-linking agent can be one or more of isocyanate, epoxy, melamine, peroxide, metal chelate, oxazoline, etc., preferably an isocyanate and / or epoxy cross-linking agent. The above-mentioned isocyanate system can use one or more of diisocyanate compounds such as toluene diisocyanate, xylene diisocyanate, 2,4-diphenylmethane diisocyanate, 4,4-diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, tetramethylxylene diisocyanate, and naphthalene diisocyanate; an adduct formed by reacting 1 mol of a polyol-based compound such as trimethylolpropane with 3 mol of a diisocyanate compound, an isocyanurate formed by self-condensation of 3 mol of a diisocyanate compound, a biuret formed by condensing a diisocyanate urea obtained from 2 mol of 3 mol of a diisocyanate compound with the remaining 1 mol of a diisocyanate, and triphenylmethane triisocyanate, a multifunctional isocyanate compound containing three functional groups such as methylene bistriisocyanate, etc.

[0059] The epoxy resins can be ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polytetramethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, resorcinol diglycidyl ether , 2,2-dibromoneopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol polyglycidyl ether, sorbitol polyglycidyl ether, diglycidyl adipate, diglycidyl phthalate, tris(glycidyl)isocyanurate, tris(glycidyloxyethyl)isocyanurate, 1,3-bis(N,N-glycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylenediamine, etc.

[0060] Furthermore, as the melamine, one or more of hexamethylolmelamine, hexamethoxymethylmelamine, hexabutoxymethylmelamine, and the like can be used.

[0061] On the other hand, the content of the crosslinking agent can be 0.1 to 15 parts by weight, preferably 0.1 to 5 parts by weight, relative to 100 parts by weight of the acrylic copolymer. If the content of the crosslinking agent is less than 0.1 parts by weight, the cohesive force of the formed adhesive layer may be reduced due to the reduced degree of crosslinking, resulting in reduced physical properties such as durability and cuttability. In addition, if the content of the crosslinking agent exceeds 15 parts by weight, the crosslinking reaction may proceed excessively, resulting in residual stress in the adhesive layer.

[0062] In addition, the adhesive composition may contain a light absorber so that the formed adhesive layer satisfies the above-mentioned optical properties. The light absorber may preferably contain one or more compounds represented by the following Chemical Formula 1 and Chemical Formula 2.

[0063] [Chemical Formula 1]

[0064]

[0065] In Chemical Formula 1, R1 is an alkyl group having 3 to 20 carbon atoms or an aryl group having 6 to 12 carbon atoms. More preferably, when R1 in Chemical Formula 1 is an alkyl group, the number of carbon atoms can be 3 to 8. The resulting adhesive layer can exhibit excellent target optical properties and durability, such as heat resistance, moisture resistance, and light resistance. If R1 in Chemical Formula 1 is an alkyl group with fewer than 3 carbon atoms, the compatibility of the adhesive components may be reduced, resulting in a significant decrease in the adhesion of the resulting adhesive layer. Furthermore, if R1 is an alkyl group with more than 20 carbon atoms, the molar absorption coefficient decreases, and the amount of light absorber required to achieve the desired optical properties may increase.

[0066] [Chemical Formula 2]

[0067]

[0068] In Formula 2, R2 is an alkyl group having 3 to 20 carbon atoms or an aryl group having 6 to 12 carbon atoms. More preferably, when R2 is an alkyl group, it has 3 to 8 carbon atoms. This can further facilitate the formation of the adhesive layer to achieve the desired optical properties and durability such as heat resistance, moisture resistance, and light resistance. If R2 is an alkyl group in Formula 2 with fewer than 3 carbon atoms, the compatibility of the adhesive components may be reduced, resulting in a significant decrease in the adhesion of the formed adhesive layer. Furthermore, if R1 is an alkyl group with more than 20 carbon atoms, the molar absorption coefficient decreases, and the content of the light absorber added to achieve the desired optical properties may increase.

[0069] In addition, between the compound represented by Chemical Formula 1 and the compound represented by Chemical Formula 2, the compound represented by Chemical Formula 1 may be more advantageous in terms of optical properties and durability.

[0070] On the other hand, the alkyl group having 3 to 20 carbon atoms used in the present specification means a monovalent hydrocarbon group of a straight chain or a branched chain having 3 to 20 carbon atoms, and includes, for example, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, and the like, but is not limited thereto.

[0071] Further, the aryl group having 6 to 12 carbon atoms used in the present specification can be a monovalent substituted or unsubstituted aryl group, and as an example, can be a phenyl group, a naphthyl group, a phenyl group substituted with an alkyl group having 1 to 4 carbon atoms of a straight chain or a branched chain.

[0072] Further, the content of the above-mentioned light absorber can be 0.2 to 2.0% by weight, and more preferably 0.3 to 0.5% by weight, based on the weight of the adhesive layer formed from the adhesive composition. If the content of the light absorber is less than 0.2% by weight, it can be difficult to exhibit the target optical properties. Further, when the content of the light absorber is more than 2.0% by weight, the adhesive properties can be impaired, or bleeding can occur and / or the durability of the adhesive layer can be impaired.

[0073] Further, the above-mentioned adhesive composition can further include a solvent. As the above-mentioned solvent, aromatic hydrocarbons such as toluene, benzene, xylene, and the like; aliphatic hydrocarbons such as cyclohexane, decaline, and the like; esters such as ethyl acetate, butyl acetate, and the like; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and the like; alcohols such as methanol, ethanol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, methyl cellosolve, ethyl cellosolve, butyl cellosolve, and the like; ethers such as tetrahydrofuran, dioxane, and the like; halogenated hydrocarbons such as dichloromethane, chloroform, carbon tetrachloride, and the like; dimethylformamide; dimethyl sulfoxide, and the like can be exemplified, and one or two or more kinds thereof can be used in combination.

[0074] On the other hand, in addition to the above-mentioned adhesive component, the light absorber, and the crosslinking agent which can be further included, the adhesive composition can further include a silane coupling agent, a tackifying resin, an antioxidant, a leveling agent, a surface lubricant, a dye, a pigment, an antifoaming agent, a filler, a plasticizer, a light stabilizer, a reaction initiator, an antistatic agent, a flame retardant, and the like as additives to adjust the adhesion, cohesion, tackiness, elastic modulus, glass transition temperature, and the like as needed according to the purpose.

[0075] Among them, it is preferable to include a silane coupling agent to exert the effect of improving the adhesion of the adhesive to the substrate, and an alkoxysilane including a functional group such as an amino group, an epoxy group, an acetoacetyl group, a polyalkylene glycol group, an acryl group, an alkyl group, and the like can be used. Further, the content of the above-mentioned silane coupling agent can be 0.1 to 2 parts by weight with respect to 100 parts by weight of the adhesive component, but is not limited thereto.

[0076] According to one embodiment of the present invention, an adhesive sheet may be formed by including an adhesive layer formed of the adhesive composition.

[0077] The adhesive layer can be formed by applying the adhesive composition to a predetermined thickness on the surface of the substrate using a known coating method and then drying it. In addition, when the adhesive composition contains a crosslinking agent, the adhesive layer can be in a C-stage state (dried and uncrosslinked), a B-stage state (dried and partially crosslinked), or a state in which the adhesive component is completely crosslinked after drying.

[0078] In this case, the thickness of the formed adhesive layer can be 3 to 100 μm, more preferably 5 to 100 μm. If the thickness of the adhesive layer is less than 3 μm, it may be difficult to exhibit sufficient adhesive properties, and the mechanical strength may be reduced. In addition, if the thickness of the adhesive layer exceeds 100 μm, the adhesion may be reduced.

[0079] The adhesive layer may be disposed on one or both sides of a transparent substrate to form an adhesive sheet or a double-sided adhesive sheet. In this case, the transparent substrate may be, for example, a plastic film having a thickness of 10 to 1,000 μm, although this is not particularly limited in the present invention. Furthermore, the adhesive layer may be formed as a substrate-less adhesive sheet without a separate transparent substrate. In this case, release films may be disposed on both sides of the adhesive layer to protect the surface of the adhesive layer.

[0080] In addition, the adhesive sheet may be disposed on one side or both sides of an optical film to form an optical element.

[0081] Here, the above-mentioned optical film can be a film that is well-known in the optical field for exhibiting optical properties and / or supplementing mechanical properties. As an example, it can be an absorbing polarizing film, a diffuser, a light-collecting film, a reflective polarizing film, a protective film, a phase difference film, a TAC film, etc. These can appropriately adopt well-known films, so the present invention is not particularly limited to this.

[0082] Implementation Method

[0083] The present invention is described in more detail by the following examples, which, however, do not limit the scope of the present invention and should be interpreted as helping to understand the present invention.

[0084] <Example 1>

[0085] 0.5 parts by weight of an isocyanate crosslinking agent (AK75) was mixed with 100 parts by weight of an adhesive component as an acrylic copolymer prepared by the following preparation example 1, and then 0.5% by weight of a light absorber as a compound represented by Chemical Formula 1-1 synthesized by the following preparation example 2 was added based on the weight of the formed adhesive layer to prepare an adhesive composition. The adhesive composition was applied to a 75 μm thick release-treated polyethylene terephthalate (PET) film using a rod coater. After drying at 100°C for 2 minutes, it was crosslinked at 23°C for 7 days to form an adhesive layer with a thickness of 20 μm. The release-treated PET film was placed on the remaining side to produce an adhesive sheet.

[0086] [Chemical Formula 1-1]

[0087]

[0088] *Preparation Example 1-Manufacture of Acrylic Copolymer

[0089] A monomer mixture consisting of 80% by weight of n-butyl acrylate, 10% by weight of methyl acrylate, 9% by weight of 4-hydroxybutyl acrylate, and 1% by weight of acrylic acid was placed in a 1L reactor with nitrogen reflux and a cooling device for easy temperature control. Then, 300% by weight of methyl ethyl ketone was added as a solvent. Nitrogen was then injected for 1 hour to replace the oxygen, and the temperature was maintained at 70°C. After the monomer mixture was uniformly stirred, 0.07 parts by weight of azobisisobutyronitrile (AIBN) was added as a reaction initiator based on 100 parts by weight of the acrylic monomers and the reaction was allowed to proceed for 8 hours to produce an acrylic copolymer with a weight-average molecular weight of 1.2 million.

[0090] *Preparation Example 2-Synthesis of Chemical Formula 1-1

[0091] After adding 100 ml of acetonitrile to a 1000 ml round-bottom flask, 4-morpholinobenzaldehyde (10 mmol, 1.91 g) and butyl cyanoacetate (15.0 mmol, 2.10 g) were added, and the mixture was stirred at room temperature for 30 minutes. Tetrabutylammonium hydroxide (10 mmol, 2.59 g) was further added, the temperature was raised to 70°C, and stirred for 1 hour. After the reaction, 3.2 g of the compound represented by Chemical Formula 1-1 was obtained by extraction and recrystallization.

[0092] 1H NMR (300MHz, CDCl3): 8.07(s,1H,HC=C-), 7.94(d,2H,Ar-H), 6.70(d,2H,Ar-H), 4.36(m,6H,-CH2-), 3.11(s,6H,-CH3), 1.39(t,3H,-CH3)ppm

[0093] <Example 2>

[0094] The production was carried out in the same manner as in Example 1, except that the light absorber was changed to the compound represented by Chemical Formula 2-1 synthesized in Preparation Example 3 below, to produce an adhesive composition, and an adhesive sheet was produced using the adhesive composition.

[0095] [Chemical Formula 2-1]

[0096]

[0097] *Preparation Example 3-Synthesis of Chemical Formula 2-1

[0098] After adding 100 ml of acetonitrile to a 1000 ml round-bottom flask, 1-(4-formylphenyl)pyrrolidine (10 mmol, 1.75 g) and butyl cyanoacetate (15.0 mmol, 2.10 g) were added, and the mixture was stirred at room temperature for 30 minutes. Tetrabutylammonium hydroxide (10 mmol, 2.59 g) was further added, the temperature was raised to 70°C, and stirred for 1 hour. After the reaction, 3.1 g of the compound represented by Chemical Formula 2-1 was obtained by extraction and recrystallization.

[0099] 1H NMR (300MHz, CDCl3): 8.05(s,1H,HC=C-), 7.96(d,2H,Ar-H), 6.72(d,2H,Ar-H), 4.38(m,6H,-CH2-), 3.11(d,4H,-CH2), 1.45(d,4H,-CH2), 1.36(t,3H,-CH3)ppm

[0100] <Comparative Examples 1 and 2>

[0101] The adhesive composition was produced in the same manner as in Example 1 except that the light absorber was changed to the compound represented by the following Chemical Formula 3 or the compound represented by the following Chemical Formula 4. An adhesive sheet was produced using the adhesive composition.

[0102] [Chemical Formula 3]

[0103]

[0104] [Chemical Formula 4]

[0105]

[0106] <Experimental Example 1>

[0107] The physical properties of the adhesive sheets produced in Examples and Comparative Examples were measured by the following methods. The results are shown in Table 1 below.

[0108] 1. Blue light blocking

[0109] The release films on both sides of the adhesive sheet were removed, and the transmittance spectrum from 200 nm to 500 nm was measured using a spectrophotometer (Shimadzu UV-2450). The transmittance at wavelengths of 440 nm and 470 nm was determined from the transmittance spectrum, and the slope of the transmittance range from 20% to 60% was calculated using the following formula 1.

[0110] [Mathematical formula 1]

[0111]

[0112] In formula 1, λ Tx (nm) refers to the wavelength that achieves the transmittance Tx (%) corresponding to the y-axis of the transmittance spectrum.

[0113] ○: Slope is 3.3 or higher

[0114] △: 2.9 or more and less than 3.3

[0115] X: less than 2.9

[0116] 2. Durability

[0117] After placing the prepared adhesive sheet between the polarizing plate and glass and bonding them together, they were stored in a constant temperature and humidity chamber at high temperature (80°C) and humidity (60°C / 90%) for 500 hours, respectively. The formation of bubbles was confirmed by visual observation and evaluated according to the following evaluation criteria.

[0118] <Evaluation Criteria>

[0119] ◎: Less than 2 bubbles or peeling

[0120] ○: There are 2 or more bubbles or peelings but less than 5 bubbles or peelings

[0121] △: 5 or more bubbles or peelings and less than 10

[0122] X: There are 10 or more bubbles or peeling

[0123] After the wet heat evaluation, the transmittance at a wavelength of 440 nm was measured, and the change in transmittance (ΔT 440 ), and then evaluated according to the following evaluation criteria.

[0124] [Mathematical formula 2]

[0125] Transmittance change (ΔT 440 , %) = transmittance after moisture resistance evaluation (T' 440 )-Transmittance before moisture resistance evaluation (T 440 )

[0126] <Evaluation Criteria>

[0127] ○: Transmittance change is 5% or less

[0128] △: Transmittance change is greater than 5% and less than 10%

[0129] X: Transmittance change is 10% or more

[0130] [Table 1]

[0131]

[0132]

[0133] Table 1 confirms that while Comparative Examples 1 and 2 exhibit excellent light transmittance at a wavelength of 470 nm, their transmittance at 440 nm is 91-93%, indicating little blue light blocking effect in the wavelength range below 450 nm. In contrast, Examples 1 and 2 exhibit only 1-3% transmittance at 440 nm, demonstrating superior blue light blocking effect in the wavelength range below 450 nm to Comparative Examples 1 and 2.

[0134] An embodiment of the present invention has been described above, but the concept of the present invention is not limited to the embodiment presented in this specification. Those skilled in the art who understand the concept of the present invention can easily propose other embodiments within the scope of the same concept by adding, changing, deleting or appending constituent elements, but this will also be considered to be within the scope of the concept of the present invention.

Claims

1. An adhesive composition comprising an adhesive component and a light absorber, The adhesive layer formed from the adhesive composition satisfies the following conditions (a) and (b): (a) The transmittance at a wavelength of 470 nm is 60% or more, and the transmittance at a wavelength of 440 nm is 20% or less; (b) The slope of the transmittance spectrum in the region from 20% to 60% is 3.0 or greater. 2 . The adhesive composition according to claim 1 , wherein the adhesive component comprises an acrylic copolymer having at least one functional group of a hydroxyl group and a carboxyl group. The adhesive composition according to claim 2 , further comprising a cross-linking agent.

4. The adhesive composition according to claim 1, wherein the light absorber comprises at least one of the compounds represented by the following Chemical Formula 1 and Chemical Formula 2: [Chemical Formula 1] In Chemical Formula 1, R1 is an alkyl group having 3 to 20 carbon atoms or an aryl group having 6 to 12 carbon atoms, [Chemical Formula 2] In Chemical Formula 2, R2 is an alkyl group having 3 to 20 carbon atoms or an aryl group having 6 to 12 carbon atoms. The adhesive composition according to claim 1 , wherein, under condition (a), the transmittance at a wavelength of 470 nm is 90% or more and the transmittance at a wavelength of 440 nm is 5% or less. 6 . The adhesive composition according to claim 4 , wherein in each of the compound represented by Chemical Formula 1 and the compound represented by Chemical Formula 2, the number of carbon atoms of R1 and R2 is independently 3 to 8. 7 . The adhesive composition according to claim 1 , wherein the content of the light absorber is 0.2 to 2.0 wt % based on the weight of the adhesive layer formed from the adhesive composition. 8 . An adhesive sheet comprising an adhesive layer formed from the adhesive composition according to claim 1 .

9. An optical element comprising: optical films; and The adhesive sheet according to claim 8, disposed on at least one surface of the optical film.

Images