Optical film and image display device including the same

Abstract

The present invention relates to an optical film comprising a light-transmitting substrate and a light-transmitting functional layer formed on one or both sides of the light-transmitting substrate, the optical film having a spectral transmittance of less than 1% at a wavelength of 380 nm, a spectral transmittance of less than 10% at a wavelength of 410 nm, and a spectral transmittance of less than 15% at a wavelength of 440 nm, which efficiently blocks light in a wavelength range that is particularly harmful to the human body and has excellent light transmittance in a wavelength range that is not harmful to the human body so as not to affect visual characteristics, and an optical film and an image display device can be provided.

Description

[Technical Field]

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

[0002] Recently, image display devices such as smartphones, tablets, and personal computers display images by transmitting light emitted from a light source, and among these, blue light in the wavelength range of 380 to 495 nm has the shortest wavelength of visible light visible to the human eye and possesses strong energy close to that of ultraviolet light. This strong energy is not absorbed by the cornea or lens and reaches the retina, causing problems such as retinal damage, fatigue, and adverse effects on sleep.

[0003] Furthermore, recent studies have shown that blue light in the wavelength range of 415 to 455 nm creates a phototoxic risk to retinal pigment epithelial cells, as well as the death of photoreceptor cells.

[0004] Blue light, which is known to cause these problems, is also known as blue light, and various efforts are being made to block it.

[0005] Korean Patent Publication No. 10-2007-0035982 discloses a technology for providing sunglasses, lenses, optical filters, etc. as optical articles containing fullerene as a substance that absorbs blue light. However, when this technology is applied to an image display device, the blue light blocking performance deteriorates due to long-term exposure to a light source, so the intended effect cannot be achieved.

[0006] Therefore, there is a demand for the development of an optical film that can effectively block blue light in the harmful wavelength range of 415 to 455 nm while increasing the spectral transmittance of non-harmful wavelengths, and that is effective in blocking blue light when applied to image display devices. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Korean Patent Publication No. 10-2007-0035982 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention aims to improve the problems of the prior art by providing an optical film that effectively blocks wavelengths that are harmful to the human body, improves the transmittance of non-harmful light, and does not affect visual characteristics.

[0009] Another object of the present invention is to provide an image display device including the optical film. [Means for solving the problem]

[0010] To achieve the above object, the present invention provides an optical film comprising a light-transmitting substrate and a light-transmitting functional layer formed on one or both sides of the light-transmitting substrate, the optical film having a spectral transmittance of less than 1% at a wavelength of 380 nm, a spectral transmittance of less than 10% at a wavelength of 410 nm, and a spectral transmittance of less than 15% at a wavelength of 440 nm.

[0011] The present invention also provides an image display device including the optical film. [Effects of the Invention]

[0012] The present invention provides an optical film that efficiently blocks blue light in a wavelength range that is particularly harmful to the human body, has excellent light transmittance in a wavelength range that is not harmful to the human body, and does not affect visual characteristics, and can be applied to various areas for blocking blue light.

[0013] Furthermore, the present invention can provide an image display device that is effective in blocking blue light and has excellent visual characteristics. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention provides an optical film comprising a light-transmitting substrate and a light-transmitting functional layer formed on one or both sides of the light-transmitting substrate, the optical film having a spectral transmittance of less than 1% at a wavelength of 380 nm, a spectral transmittance of less than 10% at a wavelength of 410 nm, and a spectral transmittance of less than 15% at a wavelength of 440 nm.

[0015] The present invention also provides an image display device including the optical film. The present invention will be described in detail below.

[0016] <Optical film> The present invention relates to an optical film comprising a translucent substrate and a light-transmitting functional layer formed on one or both sides of the translucent substrate. Specifically, the present invention relates to an optical film that can block harmful blue light without affecting visual characteristics by blocking light of 455 nm or less, which is a wavelength range of blue light that is particularly harmful to the human body, and allowing sufficient transmission of light of 480 nm or more, which is a wavelength range that is not harmful to the human body.

[0017] In particular, conventionally, the wavelength range around 450 nm has not been known to be harmful to the human body, so the focus has been on blocking the wavelength range of 410 nm or less. However, through recent research, the inventors have confirmed that the wavelength range of 455 nm or less also falls within the blue light range that is harmful to the human body. Therefore, they have confirmed that it is possible to provide an optical film that effectively blocks light in the wavelength range of 455 nm or less, while also having excellent transmittance for light of 480 nm or more so as not to affect visual characteristics, and have completed the present invention.

[0018] More specifically, the present invention provides an optical film comprising a light-transmitting substrate and a light-transmitting functional layer formed on one or both sides of the light-transmitting substrate, the optical film having a spectral transmittance of less than 1% at a wavelength of 380 nm, a spectral transmittance of less than 10% at a wavelength of 410 nm, and a spectral transmittance of less than 15% at a wavelength of 440 nm.

[0019] By satisfying the spectral transmittance for the above wavelength range, the present invention can provide an optical film that has excellent blocking properties for blue light that is harmful to the human body.

[0020] Furthermore, the present invention can provide an optical film having a spectral transmittance of 70% or more at a wavelength of 480 nm, which can appropriately block blue light in the range that is harmful to the human body, thereby preventing harm to the human body, and can provide an optical film that does not affect the color of the display screen when applied to an image display device.

[0021] The optical film of the present invention that satisfies the above transmittance may have a blue light ratio (BLR) represented by the following formula 1 of 21% or less, and preferably 20% or less.

[0022] [Formula 1]

[0023]

number

[0024] If the ratio of blue light represented by the above formula 1 exceeds 21%, it is not preferable because it means that light in the blue light region that is harmful to the human body is not blocked but is transmitted.

[0025] Furthermore, the optical film of the present invention may have a spectral transmittance of 70% or more at 480 nm so as to block blue light that is harmful to the human body while not affecting the transmission of blue light sources. Light in the wavelength range of 455 nm or less, which is a blue light source in the wavelength range harmful to the human body, is blocked without being able to smoothly transmit, and the transmittance of blue light in the wavelength range of 480 nm or more that does not affect the human body is excellent, and it can be seen that blue light sources are well expressed.

[0026] Translucent base material The light-transmitting substrate of the present invention may be a film excellent in transparency, mechanical strength, thermal stability, moisture-blocking properties, isotropy, etc. Specific examples include films made of thermoplastic resins such as polyester-based resins such as polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate, and polybutylene terephthalate; cellulose-based resins such as diacetyl cellulose and triacetyl cellulose; polycarbonate-based resins; acrylate-based resins such as polymethyl (meth)acrylate and polyethyl (meth)acrylate; styrene-based resins such as polystyrene and acrylonitrile-styrene copolymers; polyolefin-based resins such as polyethylene, polypropylene, polyolefins having a cyclo- or norbornene structure, and ethylene-propylene copolymers; vinyl chloride-based resins; arylate-based resins; polyoxymethylene-based resins; and epoxy resins. Films made of blends of these thermoplastic resins can also be used. Films made of thermosetting or ultraviolet-curable resins such as (meth)acrylic, urethane, acrylic urethane, epoxy, and silicone-based resins can also be used.

[0027] In one embodiment, the translucent substrate may have a thickness of 50 μm to 150 μm. If the translucent substrate is less than 50 μm thick, it may not be able to properly support the light-transmitting functional layer, and if it is more than 150 μm thick, the excessive thickness may increase the overall film thickness, resulting in a decrease in transmittance or flexibility of the optical film.

[0028] Light-transparent functional layer The light-transmitting functional layer of the present invention is a layer having the function of satisfying the above-mentioned spectral transmittance, blue light proportion, and yellowness, and may be formed, for example, using a light-transmitting functional layer-forming composition containing the photocurable compound, photoinitiator, and absorber described below.

[0029] That is, the light-transmitting functional layer of the present invention preferably has a spectral transmittance of less than 1% at a wavelength of 380 nm, less than 10% at a wavelength of 410 nm, and less than 15% at a wavelength of 440 nm.Moreover, the light-transmitting functional layer of the present invention more preferably has a spectral transmittance of 70% or more at a wavelength of 480 nm.

[0030] Furthermore, the light-transmitting functional layer of the present invention preferably has a blue light ratio (BLR) represented by the following formula 1 of 21% or less, more preferably 20% or less.

[0031] [Formula 1]

[0032]

number

[0033] Furthermore, the light-transmitting functional layer of the present invention may have a spectral transmittance of 70% or more at 480 nm so as to block blue light that is harmful to the human body and not affect the transmission of blue light sources. Based on this, it can be seen that the transmittance in the blue light wavelength range of 480 nm or more that does not affect the human body is excellent, and blue light sources are well expressed.

[0034] In one embodiment, the light-transmitting functional layer may have a thickness of 10 μm or less. When the thickness of the light-transmitting functional layer is 10 μm or less, the desired spectral transmittance for each wavelength can be appropriately satisfied, which is preferable.

[0035] <Composition for forming a light-transparent functional layer> The light-transmitting functional layer of the present invention may be formed using a composition for forming a light-transmitting functional layer, which includes a photocurable compound, a photoinitiator, and an absorber, thereby satisfying the aforementioned spectral transmittance, blue light ratio, and yellowness index that are the objectives of the present invention.

[0036] photocurable compound The photocurable compound may include a photocurable (meth)acrylate oligomer and monomer.

[0037] The photocurable (meth)acrylate oligomer typically includes epoxy (meth)acrylate, urethane (meth)acrylate, etc., with urethane (meth)acrylate being more preferred. Urethane (meth)acrylate can be produced from a polyfunctional (meth)acrylate having a hydroxy group in the molecule and a compound having an isocyanate group in the presence of a catalyst. Specific examples of the (meth)acrylate having a hydroxy group in the molecule include one or more selected from the group consisting of 2-hydroxyethyl (meth)acrylate, 2-hydroxyisopropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, caprolactone ring-opened hydroxyacrylate, pentaerythritol tri / tetra(meth)acrylate mixture, and dipentaerythritol penta / hexa(meth)acrylate mixture. Specific examples of the compound having an isocyanate group include 1,4-diisocyanate butane, 1,6-diisocyanate hexane, 1,8-diisocyanate octane, 1,12-diisocyanate dodecane, 1,5-diisocyanate-2-methylpentane, trimethyl-1,6-diisocyanate hexane, 1,3-bis(isocyanatemethyl)cyclohexane, trans-1,4-cyclohexene diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), isophorone diisocyanate, and triisocyanate. The isocyanate may be one or more selected from the group consisting of toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, xylene-1,4-diisocyanate, tetramethylxylene-1,3-diisocyanate, 1-chloromethyl-2,4-diisocyanate, 4,4'-methylenebis(2,6-dimethylphenylisocyanate), 4,4'-oxybis(phenylisocyanate), trifunctional isocyanates derived from hexamethylene diisocyanate, and trimethanepropanol adduct toluene diisocyanate.

[0038] The monomer is a commonly used one, and has an unsaturated group such as a (meth)acryloyl group, a vinyl group, a styryl group, or an aryl group in the molecule as a photocurable functional group, with a (meth)acryloyl group being more preferred among them.

[0039] Specific examples of the monomer having a (meth)acryloyl group include neopentyl glycol acrylate, 1,6-hexanediol (meth)acrylate, propylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, 1,2,4-cyclohexane tetra(meth)acrylate, pentaglycerol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, and dipentaerythritol tri(meth)acrylate. and the alkyl acrylate may be one or more selected from the group consisting of bis(2-hydroxyethyl)isocyanurate di(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tripentaerythritol tri(meth)acrylate, tripentaerythritol hexatri(meth)acrylate, bis(2-hydroxyethyl)isocyanurate di(meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, isooctyl (meth)acrylate, iso-decyl (meth)acrylate, stearyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, phenoxyethyl (meth)acrylate, and isoborneol (meth)acrylate.

[0040] The photocurable (meth)acrylate oligomers and monomers exemplified above can be used alone or in combination of two or more.

[0041] The content of the photocurable compound is not particularly limited, but may be 1 to 80 wt %, preferably 1 to 50 wt %, based on the total weight of the composition for forming the light-transmitting functional layer. If it is less than 1 wt %, it is difficult to achieve sufficient improvement in hardness, and if it exceeds 80 wt %, curling may become severe.

[0042] Photoinitiator The photoinitiator may be any photoinitiator commonly used in the art, and may be at least one selected from the group consisting of hydroxyketones, aminoketones, hydrogen-removal photoinitiators, and combinations thereof.

[0043] Specifically, the photoinitiator may be at least one selected from the group consisting of 2-methyl-1-[4-(methylthio)phenyl]2-morpholinepropanone-1, diphenyl ketone, benzil 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.

[0044] The photoinitiator is used in an amount of 0.1 to 10 wt %, preferably 1 to 5 wt %, based on the total weight of the composition for the light-transmitting functional layer. If the content is less than this range, the curing speed of the composition will be slowed, resulting in under-curing and reduced mechanical properties. Conversely, if the content exceeds this range, over-curing may result in cracks in the coating film.

[0045] absorbent The composition for forming a light-transmitting functional layer included in the optical film according to one embodiment of the present invention may contain an absorbent, and simultaneously contains a first absorbent having a maximum absorption wavelength at a wavelength of 400 nm and a second absorbent having a maximum absorption wavelength at a wavelength of 420 nm. That is, by including the first absorbent and the second absorbent having maximum absorption wavelengths at different wavelengths, the above-mentioned spectral transmittance, blue light ratio, and yellowness index can be satisfied.

[0046] Commercially available products of the first absorbent include Epolite 5663 and Epolite 5845 from Eporin Co., Ltd., FND-009 from Yamada Chemical Co., Ltd., ANTHRACURE UVS-1331, ANTHRACURE UVS-1101, ANTHRACURE UVS-581, and ANTHRACURE UVS-2171 from AWPC Co., Ltd., NK-10490, NK-10694, and NK-8997 from Hayashibara Co., Ltd., Bonasorb UA-3911 and Bonasorb UA-3912 from Orient Chemical Co., Ltd., NUV-400 from Toyo Ink Co., Ltd., ABS-400 and ABS-407 from Luxottica, and Tinuvin Carboprotect from BASF.

[0047] Commercially available products of the second absorbent include Epolite 5820, Epolite 5851, and Epolite 5636 from Eporin Co., Ltd., Tinuvin 970 from BASF, NUV-910 from Toyo Ink Co., Ltd., ABS-415, ABS-420, ABS-425, and ABS-426 from Luxottica, FDB-001 from Yada Chemical Co., Ltd., and NK-10396 and DYE2 from Hayashibara Co., Ltd.

[0048] The absorbent is contained in an amount of 0.1 to 10 wt %, preferably 0.5 to 5 wt %, based on the total weight of the composition for forming the light-transmitting functional layer. If the content is less than this range, the absorbency is insufficient, and if it exceeds this range, the liquid compatibility is reduced.

[0049] solvent The composition for a light-transmitting functional layer included in the optical film according to one embodiment of the present invention may contain a solvent. The solvent of the present invention is capable of dissolving or dispersing the above-mentioned composition, and any solvent known in the art as a solvent for a composition for forming a coating layer may be used without limitation.

[0050] Solvents that can be used in the composition for the light-transmitting functional layer of the present invention include alcohols (methanol, ethyl alcohol, 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, normal butyl acetate, tertiary butyl acetate, methyl cellosolve acetate, ethyl cellosolve acetate, propylene glycol monomethyl ether acetate), Preferred examples of solvents that can be used include solvents such as hexane, heptane, and octane, solvents such as benzene, toluene, and xylene, solvents such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, diethylene glycol dibutyl ether, and propylene glycol monomethyl ether. Each of the solvents exemplified above can be used alone or in combination of two or more.

[0051] The solvent is preferably included in an amount of 10 to 95 wt % based on the total weight of the composition for forming the light-transmitting functional layer. If the content of the solvent is less than the above range, the viscosity becomes high and workability becomes poor. Conversely, if the content of the solvent exceeds the above range, the drying process takes a long time, which reduces economic efficiency, and haze may occur.

[0052] additives The composition for a light-transmitting functional layer included in the optical film according to one embodiment of the present invention may further include an additive. The type of the additive may be determined according to the needs of a user and is not particularly limited in the present invention. For example, the composition may further include additives such as a labeling agent, an ultraviolet stabilizer, and a heat stabilizer.

[0053] The labeling agent is a component that imparts smoothness and coatability to the coating film. Examples of the labeling agent include silicone-based labeling agents, fluorine-based labeling agents, and acrylic polymer-based labeling agents. These can be used alone or in combination of two or more.

[0054] The content of the leveling agent may be 0.1 to 1% by weight based on the total weight of the composition for the light-transmitting functional layer, but is not limited thereto.

[0055] <Image display device> Meanwhile, the present invention provides an image display device including the above-mentioned optical film, which effectively blocks only blue light that is harmful to the human body without reducing the spectral transmittance of non-harmful wavelengths, thereby providing an image display device with excellent blue light blocking properties without affecting the color of the image display screen. [Example]

[0056] [Mode for carrying out the invention] The present invention will be described in more detail below based on examples. However, the embodiments of the present invention disclosed below are merely illustrative, and the scope of the present invention is not limited to these embodiments. The scope of the present invention is defined by the claims, and includes all modifications within the scope and meaning equivalent to the claims. In the following examples and comparative examples, "%" and "parts" indicating the content are by weight unless otherwise specified.

[0057] Production example: Production of a composition for a light-transmitting functional layer [Manufacturing Example 1] 49.5 parts by weight of hexafunctional urethane acrylate (Kyoeisha, UA-306I), 44 parts by weight of methyl ether ketone, 3.5 parts by weight of 1-hydroxycyclohexyl phenyl ketone, 0.5 parts by weight of a silicone labeling agent (BYK, BYK-UV3530), 2 parts by weight of a first absorber (Epolite 5663, Epolin Co., Ltd.), and 0.5 parts by weight of a second absorber (Epolite 5820, Epolin Co., Ltd.) were mixed using a mixer and filtered using a PP filter to produce a composition for a light-transmitting functional layer.

[0058] [Manufacturing Example 2] 50 parts by weight of hexafunctional urethane acrylate (Kyoeisha, UA-306I), 44 parts by weight of methyl ether ketone, 3.5 parts by weight of 1-hydroxycyclohexyl phenyl ketone, 0.5 parts by weight of a silicone-based labeling agent (BYK, BYK-UV3530), 1.5 parts by weight of a first absorber (Epolite 5663, Eporin), and 0.5 parts by weight of a second absorber (ABS420, LUXOTTICA) were mixed using a mixer and filtered using a PP filter to produce a composition for a light-transmitting functional layer.

[0059] [Manufacturing Example 3] 51 parts by weight of hexafunctional urethane acrylate (Kyoeisha, UA-306I), 44 parts by weight of methyl ether ketone, 3.5 parts by weight of 1-hydroxycyclohexyl phenyl ketone, 0.5 parts by weight of a silicone labeling agent (BYK, BYK-UV3530), and 1 part by weight of a second absorber (Yamada Co., Ltd., FDB-001) were mixed using a mixer and filtered using a PP filter to produce a composition for a light-transmitting functional layer.

[0060] [Manufacturing Example 4] 51 parts by weight of hexafunctional urethane acrylate (Kyoeisha, UA-306I), 44 parts by weight of methyl ether ketone, 3.5 parts by weight of 1-hydroxycyclohexyl phenyl ketone, 0.5 parts by weight of a silicone-based labeling agent (BYK, BYK-UV3530), and 1 part by weight of a first absorber (Bonasorb UA-3912, Orient Chemical Co., Ltd.) were mixed using a mixer and filtered using a PP filter to prepare a coating composition.

[0061] Examples and Comparative Examples: Production of Optical Films The light-transmitting functional layer compositions of Preparation Examples 1 to 4 were coated on a triacetyl cellulose (TAC) substrate so that the thickness after curing was the same as that in Table 1 below, and the solvent was dried to obtain a coating having a UV integrated dose of 500 mJ / cm. 2 The film was produced by irradiation.

[0062] Experimental example (1) Transmittance The transmittance of the optical films prepared in the examples and comparative examples at wavelengths of 380 nm, 410 nm, 440 nm, 480 nm and 500 nm was measured using UV-2600 (Shimadzu Corporation), and the results are shown in Table 1 below.

[0063] (2)BLR[%] The transmittance of the optical films prepared in the examples and comparative examples was measured using UV-2600 (Shimadzu Corporation) equipment, and the BLR value was calculated according to the following equation 1.

[0064] [Formula 1]

[0065]

number

[0066] [Table 1]

[0067] Referring to the results in Table 1, it can be seen that the optical films according to the embodiments of the present invention that satisfy the spectral transmittance at wavelengths of 380 nm, 410 nm, and 440 nm have BLR values ​​of 21% or less, and therefore have excellent blue light blocking performance.

[0068] It was also confirmed that the optical films of the examples of the present invention had spectral transmittances of 70% or more at wavelengths of 480 nm and 500 nm, and therefore, it was found that there was no problem with the transmission of blue light sources. [Industrial Applicability] The present invention provides an optical film that efficiently blocks blue light in a wavelength range that is particularly harmful to the human body, has excellent light transmittance in a wavelength range that is not harmful to the human body, and does not affect visual characteristics, and can be applied to various areas for blocking blue light.

Claims

1. An optical film comprising a light-transmitting substrate and a light-transmitting functional layer formed on one or both surfaces of the light-transmitting substrate, The spectral transmittance at a wavelength of 380 nm is less than 1%; The spectral transmittance at a wavelength of 410 nm is less than 10%; An optical film having a spectral transmittance of less than 15% at a wavelength of 440 nm.

2. 2. The optical film according to claim 1, which has a spectral transmittance of 70% or more at a wavelength of 480 nm.

3. The optical film according to claim 1 , wherein the light-transmitting functional layer has a thickness of 10 μm or less.

4. The optical film according to claim 1 , wherein the blue light ratio (BLR) represented by the following formula 1 is 21% or less: [Formula 1] [Equation 1]

5. An image display device comprising the optical film according to claim 1 .

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