Patent Application
20180194912
This application claims the benefit of Korean Patent Application No. 10-2015-0135730 filed on Sep. 24, 2015 and Korean Patent Application No. 10-2016-0120100 filed on Sep. 20, 2016 with the Korean Intellectual Property Office, the disclosures of which are herein incorporated by reference in their entirety.
The present invention relates to a photocurable coating composition, a low refractive layer, and an anti-reflective film. More specifically, the present invention relates to a photocurable coating composition capable of providing a low refractive layer that has low reflectance and high light transmittance, and can simultaneously realize high scratch resistance and a high anti-pollution property, and an anti-reflective film that can increase screen sharpness of a display device and yet exhibits excellent mechanical properties.
In general, in flat panel display devices such as a PDP, an LCD, etc., an anti-reflective film is installed so as to minimize reflection of incident light from the outside.
Methods for minimizing the reflection of light include a method of using a dispersing filler such as inorganic fine particles, etc. in a resin, coating it on a substrate film, and forming unevenness (anti-glare: AG coating), a method of using light interference by forming multiple layers having different refractive indexes on a substrate film (anti-reflective: AR coating), a method of using them together, etc.
Among them, in the case of AG coating, although the absolute amount of reflected light is equivalent to common hard coatings, a low reflection effect can be obtained by reducing the amount of light entering the eyes using light scattering through unevenness. However, since the AG coating lowers screen sharpness due to the surface unevenness, recently, many studies have progressed on the AR coating.
As a film using the AR coating, those having a multi-layered structure in which a hard coating layer (high refractive index layer), a low refractive coating layer, etc. are stacked on a substrate film are being commercialized. However, since the method of forming multiple layers separately conducts the processes of forming each layer, it has a disadvantage in terms of lowered scratch resistance due to weak interlayer adhesion (interface adhesion). Accordingly, in order to reduce the absolute reflection amount of incident light from the outside and improve scratch resistance of the surface, many studies are being progressed, but the resulting property improvement degree is unsatisfactory.
It is an object of the present invention to provide a photocurable coating composition capable of providing a low refractive layer that has low reflectance and high light transmittance, and that can simultaneously realize high scratch resistance and a high anti-pollution property.
It is another object of the present invention to provide a low refractive layer that has low reflectance and high light transmittance, and that can simultaneously realize high scratch resistance and a high anti-pollution property.
It is still another object of the present invention to provide an anti-reflective film that can increase screen sharpness of a display device and yet exhibits excellent mechanical properties.
A photocurable coating composition for forming a low refractive layer, including: a photopolymerizable compound; inorganic fine particles; two or more kinds of fluorine-containing compounds including photoreactive functional groups; and a photopolymerization initiator, is provided herein.
A low refractive layer including the photocured product of the photocurable coating composition is also provided herein.
An anti-reflective film including the low refractive layer, and a hard coating layer formed on one side of the low refractive layer, is also provided herein.
Hereinafter, a photocurable coating composition, a low refractive layer, and an anti-reflective film according to specific embodiments of the present invention will be explained in detail.
As used herein, a photopolymerizable compound commonly designates a compound that causes a polymerization reaction if light, for example, visible rays or ultraviolet rays, is irradiated thereto.
Herein, a fluorine-containing compound means a compound including at least one fluorine atom in the compound.
Herein, (meth)acryl includes both an acryl and a methacryl.
Herein, (co)polymer includes both a copolymer and a homopolymer.
Herein, silica hollow particles mean silica particles derived from a silicon compound or an organosilicon compound, wherein an empty space exists on the surface and/or inside of the silica particles.
According to one embodiment of the present invention, a photocurable coating composition for forming a low refractive layer including: a photopolymerizable compound; inorganic fine particles; two or more kinds of fluorine-containing compounds including photoreactive functional groups; and a photopolymerization initiator, wherein the two or more kinds of fluorine-containing compounds including photoreactive functional groups have different fluorine contents according to the kind, is provided.
The present inventors confirmed through experiments that by using a photocurable coating composition including two or more kinds of fluorine-containing compounds including photoreactive functional groups, a low refractive layer that can realize low reflectance and high light transmittance, can improve abrasion resistance or scratch resistance, and can simultaneously secure an excellent anti-pollution property, and an anti-reflective film including the same, may be provided, and completed the present invention.
A low refractive layer prepared from the photocurable coating composition of the above embodiment can increase sharpness of the screen of a display device, and yet has excellent scratch resistance and a high anti-pollution property, and thus can be easily applied for the manufacturing processes of display devices or polarization plates without significant limitations.
Previously, in order to improve scratch resistance of a low refractive layer included in an anti-reflective film, a method of adding various particles of a nanometer size (for example silica, alumina, zeolite, etc.) was mainly attempted. However, when nanometer-sized particles are used, it is difficult to increase scratch resistance while lowering the reflectance of a low refractive layer, and due to the nanometer sized particles, the anti-pollution property of the surface of the low refractive layer is significantly deteriorated.
To the contrary, since the photocurable coating composition of the above embodiment includes two or more kinds of fluorine-containing compounds including photoreactive functional groups, the finally prepared low refractive layer and anti-reflective film may have lower reflectance and improved light transmittance, and can improve mechanical properties such as scratch resistance, etc., and can simultaneously secure a high anti-pollution property against external pollutants.
Specifically, due to the properties of the fluorine atom included in the fluorine-containing compound including a photoreactive functional group, the interaction energy of the low refractive layer and anti-reflective film prepared from the photocurable coating composition with liquids or organic materials may be lowered, and thus the amount of pollutant transcribed to the low refractive layer and anti-reflective film can be significantly reduced, the transcribed pollutant can be prevented from remaining on the surface, and the pollutant itself can be easily removed.
Further, in the process of forming the low refractive layer and anti-reflective film, the reactive functional groups included in the fluorine-containing compounds including photoreactive functional groups act as crosslinkers, thereby increasing physical durability, scratch resistance, and thermal stability of the low refractive layer and anti-reflective film.
Particularly, by using two or more kinds of the fluorine-containing compounds including photoreactive functional groups, a higher synergistic effect can be obtained compared to the case of using one kind of fluorine-containing compound including a photoreactive functional group, and specifically, more improved surface properties such as anti-pollution and slip properties, etc. can be realized while securing higher physical durability and scratch resistance.
The two or more kinds of fluorine-containing compounds including photoreactive functional groups may be classified according to the fluorine content range, and specifically, the two or more kinds of fluorine-containing compounds including photoreactive functional groups may have different fluorine content ranges according the kind.
Due to the properties arising from the fluorine-containing compound having a higher fluorine content among the two or more kinds of fluorine-containing compounds including photoreactive functional groups, the low refractive layer and anti-reflective film prepared from the photocurable coating composition may have a more improved anti-pollution property while securing lower reflectance. In addition, the fluorine-containing compound having a lower fluorine content among the two or more kinds of fluorine-containing compounds including photoreactive functional groups may further increase compatibility with other components included in the photocurable coating composition, and furthermore, allows the finally manufactured low refractive layer and anti-reflective film to have higher physical durability and scratch resistance and to have a homogeneous surface property and a high surface slip property as well as an improved anti-pollution property.
More specifically, the two or more kinds of fluorine-containing compounds including photoreactive functional groups may be divided on the basis of the fluorine content of 25 wt %. The content of fluorine included in each fluorine-containing compound including a photoreactive functional group can be confirmed through commonly known analysis methods, for example, IC [Ion Chromatograph] analysis.
For example, the two or more kinds of fluorine-containing compounds including photoreactive functional groups may include a first fluorine-containing compound including a photoreactive functional group and including 25 to 60 wt % of fluorine.
The two or more kinds of fluorine-containing compounds including photoreactive functional groups may include a second fluorine-containing compound including a photoreactive functional group and including fluorine in the content of 1 wt % or more and less than 25 wt %.
As the photocurable coating composition includes 1) a first fluorine-containing compound including a photoreactive functional group and including 25 to 60 wt % of fluorine, and 2) a second fluorine compound including a photoreactive functional group and including fluorine in the content of 1 wt % or more and less than 25 wt %, more improved surface properties such as anti-pollution property and slip property, etc. can be realized while securing higher physical durability and scratch resistance, compared to the case of using one kind of fluorine-containing compound including a photoreactive functional group.
Specifically, due to the first fluorine-containing compound having a higher fluorine content, the finally manufactured low refractive layer and anti-reflective film may have a more improved anti-pollution property while securing lower reflectance, and due to the second fluorine-containing compound having a lower fluorine content, compatibility with other components included in the photocurable coating composition can be increased, and the finally manufactured low refractive layer and anti-reflective film may have higher physical durability and scratch resistance, and have a homogeneous surface property and a high slip property as well as an improved anti-pollution property.
The fluorine content difference between the first fluorine-containing compound and the second fluorine-containing compound may be 5 wt % or more. When the fluorine content difference between the first fluorine-containing compound and the second fluorine-containing compound is 5 wt % or more, or 10 wt % or more, the effect resulting from each of the first fluorine-containing compound and the second fluorine-containing compound may be further maximized, and thus the synergistic effect resulting from the use of the first fluorine-containing compound and the second fluorine-containing compound together may increase.
The terms first and second are intended to specify constructional elements referred to, and the order or importance, etc. are not limited thereby.
Although the weight ratio of the first fluorine-containing compound and the second fluorine-containing compound is not specifically limited, the weight ratio of the second fluorine-containing compound to the first fluorine-containing compound may be 0.01 to 0.5, and preferably 0.01 to 0.4, so that the finally manufactured low refractive layer and anti-reflective film may have a homogeneous surface property as well as more improved scratch resistance and anti-pollution property.
In each of the two or more kinds of fluorine-containing compounds including photoreactive functional groups, one or more photoreactive functional groups may be included or substituted, and the photoreactive functional group means a functional group capable of participating in a polymerization reaction by the irradiation of light, for example, irradiation of visible light or UV. The photoreactive functional group may include various functional groups known to be capable of participating in a polymerization reaction by the irradiation of light, and specific examples thereof may include a (meth)acrylate group, an epoxide group, a vinyl group, or a thiol group.
The two or more kinds of fluorine-containing compounds including photoreactive functional groups may respectively have a weight average molecular weight (in terms of polystyrene measured by GPC) of 2000 to 200,000, and preferably 5000 to 100,000.
If the weight average molecular weight of the fluorine-containing compounds including photoreactive functional groups is too small, in the photocurable coating composition of the above embodiment, the fluorine-containing compounds may not be uniformly and effectively arranged on the surface and may be positioned inside, and thus the anti-pollution property of the low refractive layer and anti-reflective film may be deteriorated and the crosslinking density inside of the low refractive layer and anti-reflective film may be lowered, thus deteriorating mechanical properties such as total strength or scratch resistance, etc.
Further, if the weight average molecular weight of the fluorine-containing compounds including photoreactive functional groups is too high, compatibility with other components in the photocurable coating composition of the above embodiment may be decreased, and the haze of the finally manufactured low refractive layer and anti-reflective film may increase or the light transmittance may be lowered, and the strength of the low refractive layer and anti-reflective film may also be deteriorated.
Specifically, the fluorine-containing compounds including photoreactive functional groups may include one or more selected from the group consisting of: i) aliphatic compounds or alicyclic compounds substituted with one or more photoreactive functional groups, in which at least one carbon is substituted with one or more fluorine atoms; ii) heteroaliphatic compounds or heteroalicyclic compounds substituted with one or more photoreactive functional groups, in which at least one hydrogen is substituted with fluorine, and at least one carbon is substituted with silicon; iii) a polydialkyl siloxane-based polymer (for example, a polydimethyl siloxane-based polymer) substituted with one or more photoreactive functional groups, in which at least one silicon is substituted with one or more fluorine atoms; iv) polyether compounds substituted by one or more photoreactive functional groups, in which at least one hydrogen is substituted with fluorine; and mixtures or copolymers of two or more of i) to iv).
The photocurable coating composition may include, based on 100 parts by weight of the photopolymerizable compound, 20 to 300 parts by weight of the two or more kinds of fluorine-containing compounds including photoreactive functional groups. The content of the two or more kinds of fluorine-containing compounds including photoreactive functional groups in the photopolymerizable compound is based on the total content of the two or more kinds of fluorine-containing compounds including photoreactive functional groups.
If the two or more kinds of fluorine-containing compounds including photoreactive functional groups are excessively added compared to the photopolymerizable compound, the coatability of the photocurable coating composition of the above embodiment may be deteriorated, or the low refractive layer obtained from the photocurable coating composition of the above embodiment may not have sufficient durability or scratch resistance. In addition, if the content of the two or more kinds of fluorine-containing compounds including photoreactive functional groups is too small compared to the photopolymerizable compound, the low refractive layer obtained from the photocurable coating composition of the above embodiment may not have sufficient mechanical properties such as anti-pollution property or scratch resistance, etc.
The fluorine-containing compound including a photoreactive functional group may further include silicon or a silicon-containing compound. That is, the fluorine-containing compound including a photoreactive functional group may optionally contain silicon or a silicon-containing compound inside, and specifically, the content of silicon in the fluorine-containing compound including a photoreactive functional group may be 0.1 wt % to 20 wt %.
The content of silicon or a silicon-containing compound respectively included in the fluorine-containing compound including a photoreactive functional group can be confirmed through commonly known analysis methods, for example ICP [Inductively Coupled Plasma] analysis.
The silicon included in the fluorine-containing compound including a photoreactive functional group may increase compatibility with other components included in the photocurable coating composition, and thus may prevent the generation of haze in the finally prepared low refractive layer, thereby increasing transparency, and furthermore, may improve the slip property of the surface of the finally prepared low refractive layer or anti-reflective film, thereby increasing scratch resistance.
Meanwhile, if the content of silicon in the fluorine-containing compound including a photoreactive functional group becomes too high, compatibility between other components included in the photocurable coating composition of the above embodiment and the fluorine-containing compounds may be deteriorated, and thus the finally prepared low refractive layer or anti-reflective film may not have sufficient light transmittance or anti-reflective performance and the anti-pollution property of the surface may be deteriorated. The photocurable coating composition may further include polysilsesquioxane substituted with one or more reactive functional groups. The polysilsesquioxane substituted with one or more reactive functional groups has reactive functional groups on the surface, and thus may increase mechanical properties, for example, scratch resistance of the binder resin or coating formed by photocuring of the photocurable coating composition.
When previously known fine particles such as silica, alumina, zeolite, etc. are used, only the strength of a film or coating is increased, while when the polysilsesquioxane substituted with one or more reactive functional groups is used, not only the strength of the finally prepared low refractive layer or anti-reflective film may be increased, but also cross-links may be formed throughout the whole area of the film, thus improving surface strength and scratch resistance together.
The photocurable coating composition may include, based on 100 parts by weight of the photopolymerizable compound, 0.5 to 60 parts by weight, or 1.5 to 45 parts by weight, of the polysilsesquioxane substituted with one or more reactive functional groups.
If the content of the polysilsesquioxane substituted with one or more reactive functional groups is too low compared to the photopolymerizable compound in the photocurable coating composition, it may be difficult to sufficiently secure scratch resistance of the binder resin or coating formed by photocuring of the photocurable coating composition. Further, if the content of the polysilsesquioxane substituted with one or more reactive functional groups is too low compared to the photopolymerizable compound in the photocurable coating composition, transparency of the low refractive layer or anti-reflective film prepared from the photocurable coating composition may be deteriorated, and scratch resistance may be deteriorated.
The reactive functional group substituted in the polysilsesquioxane may include one or more functional groups selected from the group consisting of alcohol, amine, carboxylic acid, epoxide, imide, (meth)acrylate, nitrile, norbornene, olefin [allyl, cycloalkenyl, or vinyldimethylsilyl, etc.], polyethylene glycol, thiol, and vinyl groups, and preferably, may be epoxide or (meth)acrylate.
More specific examples of the reactive functional group may include (meth)acrylates, C1-20 alkyl (meth)acrylates, C3-20 cycloalkyl epoxides, and C1-10 alkyl cycloalkane epoxides.
The alkyl (meth)acrylate means that another part of the ‘alkyl’ that is not bonded to (meth)acrylate is a bonding site, the cycloalkyl epoxide means that another part of the tycloalkyr that is not bonded to epoxide is a bonding site, and the alkyl cycloalkane epoxide means that another part of the ‘alkyl’ that is not bonded to cycloalkane epoxide is a bonding site.
Meanwhile, the polysilsesquioxane substituted with one or more reactive functional groups may further include one or more unreactive functional groups selected from the group consisting of a C1-20 linear or branched alkyl group, a C6-20 cyclohexyl group, and a C6-20 aryl group, in addition to the above-explained reactive functional groups. As the polysilsesquioxane is substituted with a reactive functional group and an unreactive functional group on the surface, in the polysilsesquioxane substituted with one or more reactive functional groups, a siloxane bond (—Si—O—) is formed inside of the molecule and is not exposed outside, and thus compatibility with other organic materials may be further increased, and the siloxane bond is strongly formed between the reactive functional groups or other organic materials and is not separated by external pressure, and thus may function as a strong support inside of the binder resin or coating formed by photocuring of the photocurable coating composition, and thereby the strength or scratch resistance of the finally prepared low refractive layer or anti-reflective film may be significantly increased.
Meanwhile, the polysilsesquioxane may be represented by (RSiO15)n (wherein n is 4 to 30 or 8 to 20), and may have various structures such as random, ladder, cage, partial cage, etc.
However, in order to increase the properties and qualities of the low refractive layer and anti-reflective film prepared from the photocurable coating composition of the above embodiment, polyhedral oligomeric silsesquioxane that is substituted with one or more reactive functional groups and has a cage structure may be used as the polysilsesquioxane substituted with one or more reactive functional groups.
And, more preferably, the polyhedral oligomeric silsesquioxane that is substituted with one or more reactive functional groups and has a cage structure may include 8 to 20 silicon atoms in the molecule.
Further, in the polyhedral oligomeric silsesquioxane having a cage structure, at least one silicon atom may be substituted with a reactive functional group, and remaining silicon atoms that are not substituted with a reactive functional group may be substituted with unreactive functional groups.
As at least one silicon of the polyhedral oligomeric silsesquioxane having a cage structure is substituted with a reactive functional group, the mechanical properties of the binder resin or coating formed by photocuring of the photocurable coating composition may be improved, and furthermore, as remaining silicons are substituted with unreactive functional groups, molecular structural steric hindrance appears, thus significantly lowering the frequency or probability of a siloxane bond (—Si—O—) being exposed outside, and thus compatibility with other organic materials may be further increased, and the siloxane bond is strongly formed between the reactive functional groups or other organic materials and is not separated by external pressure, and thus may function as a strong support inside of the binder resin or coating formed by photocuring of the photocurable coating composition, and thereby the strength or scratch resistance of the finally prepared low refractive layer or anti-reflective film may be significantly increased.
Examples of the polyhedral oligomeric silsesquioxane (POSS) that is substituted with one or more reactive functional groups and has a cage structure may include POSS substituted with one or more alcohols such as TMP diolisobutyl POSS, cyclohexanediol isobutyl POSS, 1,2-propanediollsobutyl POSS, octa(3-hydroxy-3-methylbutyldimethylsiloxy) POSS, etc.; POSS substituted with one or more amines such as aminopropylisobutyl POSS, aminopropylisooctyl POSS, aminoethylaminopropyl isobutyl POSS, N-phenylaminopropyl POSS, N-methylaminopropyl isobutyl POSS, octaammonium POSS, aminophenylcyclohexyl POSS, aminophenylisobutyl POSS, etc.; POSS substituted by one or more carboxylic acids such as maleamic acid-cyclohexyl POSS, maleamic acid-isobutyl POSS, octa maleamic acid POSS, etc.; POSS substituted with one or more epoxides such as epoxycyclohexylisobutyl POSS, epoxycyclohexyl POSS, glycidyl POSS, glycidylethyl POSS, glycidylisobutyl POSS, glycidylisooctyl POSS, etc.; POSS substituted with one or more imides such as POSS maleimide cyclohexyl, POSS maleimide isobutyl, etc.; POSS substituted with one or more (meth)acrylates such as acryloisobutyl POSS, (meth)acrylisobutyl POSS, (meth)acrylate cyclohexyl POSS, (meth)acrylate isobutyl POSS, (meth)acrylate ethyl POSS, (meth)acrylethyl POSS, (meth)acrylate isooctyl POSS, (meth)acrylisooctyl POSS, (meth)acrylphenyl POSS, (meth)acryl POSS, acrylo POSS, etc.; POSS substituted with one or more nitrile groups such as cyanopropylisobutyl POSS, etc.; POSS substituted with one or more norbornene groups such as norbornenylethylethyl POSS, norbornenylethylisobutyl POSS, norbornenylethyl disilanoisobutyl POSS, trisnorbornenyl isobutyl POSS, etc.; POSS substituted with one or more vinyl groups such as allylisobutyl POSS, monovinylisobutyl POSS, octacyclohexenyldimethylsilyl POSS, octavinyldimethylsilyl POSS, octavinyl POSS, etc.; POSS substituted with one or more olefins such as allylisobutyl POSS, monovinylisobutyl POSS, octacyclohexenyldimethylsilyl POSS, octavinyldimethylsilyl POSS, octavinyl POSS, etc.; POSS substituted with C5-30 PEG; POSS substituted by one or more thiol groups such as mercaptopropylisobutyl POSS or mercaptopropylisooctyl POSS, etc.; and the like.
Meanwhile, the photopolymerizable compound included in the photocurable coating composition of the embodiment may form a binder resin of the prepared low refractive layer. Specifically, the photopolymerizable compound may include monomers or oligomers including (meth)acrylate or vinyl groups. More specifically, the photopolymerizable compound may include monomers or oligomers including one or more, or two or more, or three or more (meth)acrylate or vinyl groups.
Specific examples of the monomers or oligomers including (meth)acrylate may include pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tripentaerythritol hepta(meth)acrylate, thrylene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, trimethylolpropane tri(meth)acrylate, trimethylolpropane polyethoxy tri(meth)acrylate, trimethylolpropane trimethacrylate, ethylene glycol dimethacrylate, butanediol dimethacrylate, hexaethyl methacrylate, butyl methacrylate, or mixtures of two or more kinds thereof, or urethane modified acrylate oligomers, epoxide acrylate oligomers, etheracrylate oligomers, dendritic acrylate oligomers, or mixtures of two or more kinds thereof. Here, it is preferable that the molecular weight of the oligomer is 1000 to 10,000.
Specific examples of the monomers or oligomers including vinyl groups may include divinylbenzene, styrene, or paramethylstyrene.
Although the content of the photopolymerizable compound in the photocurable coating composition is not significantly limited, considering the mechanical properties of the finally prepared low refractive layer or anti-reflective film, the content of the photopolymerizable compound in the photocurable coating composition may be 10 wt % to 80 wt %. The solid content of the photocurable coating composition means only solid components excluding liquid components, for example, organic solvents, etc. that may be optionally included in the photocurable coating composition as described below.
Meanwhile, the photopolymerizable compound may further include fluorine-based (meth)acrylate-based monomers or oligomers, in addition to the above-explained monomers or oligomers. When the photopolymerizable compound further includes the fluorine-based (meth)acrylate-based monomers or oligomers, the weight ratio of the fluorine-based (meth)acrylate-based monomers or oligomers to the monomer or oligomers including (meth)acrylate or vinyl groups may be 0.1% to 10%.
Examples of the fluorine-based (meth)acrylate-based compound may include one or more compounds selected from the group consisting of the following Chemical Formulas 11 to 15.
In Chemical Formula 11, R1 is a hydrogen group or a C1-6 alkyl group, a is an integer of 0 to 7, and b is an integer of 1 to 3.
In Chemical Formula 12, c is an integer of 1 to 10.
In Chemical Formula 13, d is an integer of 1 to 11.
In Chemical Formula 14, e is an integer of 1 to 5.
In Chemical Formula 15, f is an integer of 4 to 10.
Meanwhile, the inorganic fine particles mean inorganic particles having a diameter of nanometer or micrometer units.
Specifically, the inorganic fine particles may be hollow silica particles having a number average particle diameter of 10 to 100 nm, nano-silica particles having a number average particle diameter of 1 to 50 nm, or a mixture thereof.
The hollow silica particles mean particles on the surface and/or inside of which an empty space exists. The hollow silica particles have a lower reflective index compared to the particles of which inside are filled, and thus may exhibit an excellent anti-reflective property.
The hollow silica particles may have a number average particle diameter of 10 to 100 nm, preferably 20 to 70 nm, and more preferably 30 to 70 nm, and the shape of the particles may preferably be spherical, but it may be amorphous.
The inorganic fine particles may include hollow silica particles having a number average particle diameter of 10 to 100 nm and nano-silica particles having a number average particle diameter of 1 to 50 nm. On each surface of the hollow silica particles and nano-silica particles, photocurable functional groups may be substituted.
The photocurable functional groups may include one or more selected from the group consisting of alcohol, amine, carboxylic acid, epoxide, imide, (meth)acrylate, nitrile, norbornene, olefin, polyethylene glycol, thiol, and vinyl groups.
And, the hollow silica particles may be included in the composition as a colloid dispersed in a predetermined dispersion medium. The colloid including the hollow silica particles may include an organic solvent as the dispersion medium.
The solid content of the hollow silica particles in the colloid of the hollow silica particles may be determined considering the content range of the hollow silica in the photocurable coating composition of the above embodiment or the viscosity of the photocurable coating composition, etc., and for example, the solid content of the hollow silica particles in the colloid may be 5 wt % to 60 wt %.
Here, as the organic solvent in the dispersion medium, alcohols such as methanol, isopropyl alcohol, ethylene glycol, butanol, etc.; ketones such as methylethylketone, methylisobutylketone, etc.; aromatic hydrocarbons such as toluene, xylene, etc.; amides such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone, etc.; esters such as ethyl acetate, butyl acetate, gamma butyrolactone, etc.; ethers such as tetrahydrofuran, 1,4-dioxane, etc.; or mixtures thereof may be included.
As the inorganic fine particles, nano-silica particles having a number average particle diameter of 1 to 50 nm, or 3 to 30 nm, may be used. The nano-silica particles mean solid silica particles of which insides are filled, contrary to the hollow silica particles.
By using the nano-silica particles, the low refractive layer prepared from the photocurable coating composition of the above embodiment may secure higher mechanical strength and scratch resistance. And, by including the nano-silica particles having a number average particle diameter of 1 to 50 nm, or 3 to 30 nm, in a predetermined content, phase separation of inorganic fine particles, etc. may occur, and thus the reflectance of the low refractive layer may be further lowered.
The photocurable coating composition may include, based on 100 parts by weight of the photopolymerizable compound, 10 to 400 parts by weight, or 20 to 200 parts by weight of the inorganic fine particles. If the inorganic fine particles are added in an excessive amount, the inorganic fine particles may be arranged on the surface of the finally prepared low refractive layer, and surface unevenness may be excessively generated, thus deteriorating the anti-pollution property.
As the photopolymerization initiator, any compounds known to be usable in a photocurable resin composition may be used without significant limitations, and specifically, a benzophenone-based compound, an acetophenone-based compound, a biimidazole-based compound, a triazine-based compound, an oxime-based compound, or mixtures of two or more kinds thereof may be used.
The photopolymerization initiator may be used in the content of 1 to 100 parts by weight, based on 100 parts by weight of the photopolymerizable compound. If the content of the photopolymerization initiator is too small, material that is not cured in the step of photocuring of the photocurable coating composition and remains may be generated. If the content of the photopolymerization initiator is too large, unreacted initiator may remain as impurities or a cross-linking degree may be lowered, and thus the mechanical properties of the prepared film may be deteriorated or reflectance may significantly increase.
The photocurable coating composition may further include an organic solvent.
Non-limiting examples of the organic solvent may include, for example, ketones, alcohols, acetates, ethers, and mixtures of two or more kinds thereof.
Specific examples of the organic solvent may include ketones such as methylethylketone, methylisobutylketone, acetylacetone, or isobutylketone, etc.; alcohols such as methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, or t-butanol, etc.; acetates such as ethyl acetate, i-propyl acetate, or polyethylene glycol monomethylether acetate, etc.; ethers such as tetrahydrofuran or propylene glycol monomethylether, etc.; and mixtures of two or more kinds thereof.
The organic solvent may be added when mixing the components included in the photocurable coating composition, or each component may be added while being dispersed in or mixed in the organic solvent. If the content of the organic solvent in the photocurable coating composition is too small, flowability of the photocurable coating composition may be deteriorated, and thus faults such as stripes, etc. may be generated in the finally prepared film. And, if the organic solvent is excessively added, the solid content may decrease, and thus coating and film formation may not be sufficiently achieved, thus deteriorating the properties or surface property of the film and generating faults in the process of drying and curing. Thus, the photocurable coating composition may include an organic solvent such that the total solid concentration of the included components may become 1 to 50 wt %, or 2 to 20 wt %.
According to another embodiment of the present invention, a low refractive layer including the photocured product of the above-described photocurable coating composition may be provided.
As explained above, a low refractive layer obtained from the photocurable coating composition including two or more kinds of fluorine-containing compounds including photoreactive functional groups may realize low reflectance and high light transmittance, can improve abrasion resistance or scratch resistance, and can simultaneously secure an excellent anti-pollution property against external pollutants.
The low refractive layer prepared from the photocurable coating composition including two or more kinds of fluorine-containing compounds including photoreactive functional groups may have lowered interaction energy with an organic material, and thus the amount of pollutant transcribed to the low refractive layer and anti-reflective film can be significantly reduced, the transcribed pollutant can be prevented from remaining on the surface, and the pollutant itself can be easily removed.
By using two or more kinds of the fluorine-containing compounds including photoreactive functional groups in the photocurable coating composition for forming a low refractive layer, a higher synergistic effect can be obtained compared to the case of using one kind of fluorine-containing compound including a photoreactive functional group, and specifically, more improved surface properties such as anti-pollution and slip property, etc. can be realized while securing higher physical durability and scratch resistance.
Meanwhile, the two or more kinds of fluorine-containing compounds including photoreactive functional groups may be classified according to the fluorine content range, and specifically, the two or more kinds of fluorine-containing compounds including photoreactive functional groups may have different fluorine content ranges according the kind. The actions or effects resulting from the use of the two or more kinds of fluorine-containing compounds including photoreactive functional groups are as explained above with regard to the photocurable coating composition for forming a low refractive layer of the above embodiment.
And, the low refractive layer may include a part derived from polysilsesquioxane substituted with one or more reactive functional groups that may be further included in the photocurable coating composition of the above embodiment, wherein the polysilsesquioxane substituted with one or more reactive functional groups has reactive functional groups on the surface, and thus may increase the strength of the low refractive layer formed by photocuring of the photocurable coating composition of the above embodiment or an anti-reflective film including the same, and may form cross-links throughout the whole area of the low refractive layer or anti-reflective film, thereby improving surface strength and scratch resistance together.
Further, the polysilsesquioxane substituted with one or more reactive functional groups includes a siloxane bond (—Si—O—) inside of the molecule, wherein the siloxane bond is not exposed outside even in the process of photocuring of the photocurable coating composition of the above embodiment to form a low refractive layer, and thus the siloxane bond is strongly formed between the reactive functional groups or other organic materials and is not separated by external pressure, and thus may function as a strong support inside of the binder resin or coating formed by photocuring of the photocurable coating composition, thereby significantly increasing the strength or scratch resistance of the finally prepared low refractive layer or anti-reflective film.
Specifically, the low refractive layer may include a binder resin including a cross-linked (co)polymer of a photopolymerizable compound and two or more kinds of fluorine-containing compounds including photoreactive functional groups, and inorganic fine particles dispersed in the binder resin.
In addition, as the photocurable coating composition for forming a low refractive layer may further include polysilsesquioxane substituted with one or more reactive functional groups, the binder resin included in the low refractive layer may further include a cross-linked (co)polymer of a photopolymerizable compound, two or more kinds of fluorine-containing compounds including photoreactive functional groups, and polysilsesquioxane substituted with one or more reactive functional groups.
The low refractive layer may be obtained by applying the photocurable coating composition on a predetermined substrate and photocuring the applied product. Specific kinds or thicknesses of the substrate are not particularly limited, and substrates known to be used for the preparation of a low refractive layer or anti-reflective film may be used without specific limitations.
For the application of the photocurable coating composition, commonly used methods and apparatuses may be used without specific limitations, and for example, bar coating such as using a Meyer bar, etc., gravure coating, 2-roll reverse coating, vacuum slot die coating, 2-roll coating, etc. may be used.
The low refractive layer may have a thickness of 1 nm to 300 nm, or 50 nm to 200 nm. Thus, the thickness of the photocurable coating composition applied on the predetermined substrate may be about 1 nm to 300 nm, or 50 nm to 200 nm.
In the step of photocuring the photocurable coating composition, UV or visible light of a 200-400 nm wavelength may be irradiated, wherein the exposure amount may be preferably 100 to 4000 mJ/cm2. The exposure time is not specifically limited, and may be appropriately changed according to the exposure apparatus used, the wavelength of irradiated light rays, or the exposure amount.
In the step of photocuring the photocurable coating composition, nitrogen purging, etc. may be conducted so as to apply a nitrogen atmosphere condition.
The low refractive layer of the one embodiment may have mean reflectance of 1.5% or less, or 1.0% or less.
According to another embodiment of the invention, an anti-reflective film including the above-described low refractive layer, and a hard coating layer formed on one side of the low refractive layer, is provided.
The low refractive layer includes all the matters described in the above embodiments.
Meanwhile, as the hard coating layer, commonly known hard coating layers may be used without specific limitations.
One example of the hard coating layer may include a hard coating layer including a binder resin including a photocurable resin and high molecular weight (co)polymer with a weight average molecular weight of 10,000 or more, and organic or inorganic fine particles dispersed in the binder resin. The high molecular weight (co)polymer may be one or more selected from the group consisting of a cellulose-based polymer, an acryl-based polymer, a styrene-based polymer, an epoxide-based polymer, a nylon-based polymer, a urethane-based polymer, and a polyolefin-based polymer.
The photocurable resin included in the hard coating layer may be a polymer of photocurable compounds capable of inducing a polymerization reaction if light such as UV, etc. is irradiated thereto, as is commonly known in the art. Specifically, the photocurable resin may include one or more selected from the group consisting of: reactive acrylate oligomers such as urethane acrylate oligomers, epoxide acrylate oligomers, polyester acrylates, and polyether acrylates; and multifunctional acrylate monomers such as dipentaerythritol hexaacrylate, di pentaerythritol hydroxy pentaacrylate, pentaerythritol tetraacrylate, pentaerythritol triacrylate, trimethylene propyl triacrylate, propoxylated glycerol triacrylate, trimethylpropane ethoxy triacrylate, 1,5-hexanediol acrylate, propoxylated glycerol triacrylate, tripropylene glycol diacrylate, and ethylene glycol diacrylate.
The organic or inorganic fine particles may have a particle diameter of 1 to 10 μm.
The organic or inorganic fine particles may be organic fine particles selected from the group consisting of an acryl-based resin, a styrene-based resin, an epoxide resin, and a nylon resin, or inorganic fine particles selected from the group consisting of a silicon oxide, a titanium dioxide, an indium oxide, a tin oxide, a zirconium oxide, and a zinc oxide.
The hard coating film may be formed from an anti-glare coating composition including organic or inorganic fine particles, a photocurable resin, a photoinitiator, and a high molecular weight (co)polymer with a weight average molecular weight of 10,000 or more.
Meanwhile, another example of the hard coating film may include a hard coating film including a binder resin of a photocurable resin, and an antistatic agent dispersed in the binder resin.
The photocurable resin included in the hard coating layer may be a polymer of a photocurable compounds capable of inducing a polymerization reaction by the irradiation of light such as UV, etc., as is commonly known in the art. However, preferably, the photocurable compound may be multifunctional (meth)acrylate-based monomers or oligomers, wherein it is advantageous in terms of securing of the properties of the hard coating layer that the number of (meth)acrylate-based functional groups is 2 to 10, preferably 2 to 8, and more preferably 2 to 7. More preferably, the photocurable compound may be one or more selected from the group consisting of pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol hepta(meth)acrylate, tripentaerythritol hepta(meth)acrylate, thrylene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, trimethylol propane tri(meth)acrylate, and trimethylol propane polyethoxy tri(meth)acrylate.
The antistatic agent may be a quaternary ammonium salt compound, a conductive polymer, or a mixture thereof. Here, the quaternary ammonium salt compound may be a compound having one or more quaternary ammonium salt groups in the molecule, and a low molecular type or a high molecular type may be used without limitations. As the conductive polymer, a low molecular type or a high molecular type may be used without limitations, and it may be one commonly used in the technical field to which the present invention pertains, and thus the kind is not specifically limited.
The hard coating film including a binder resin of a photocurable resin and an antistatic agent dispersed in the binder resin may further include one or more compounds selected from the group consisting of alkoxy silane-based oligomers and metal alkoxide-based oligomers.
Although the alkoxy silane-based compound may be one commonly used in the art, preferably, it may include one or more compounds selected from the group consisting of tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methacryloxypropyltrimethoxysilane, glycidoxy propyl trimethoxy silane, and glycidoxy propyl triethoxy silane.
The metal alkoxide-based oligomer may be prepared by the sol-gel reaction of a composition including a metal alkoxide-based compound and water. The sol-gel reaction may be conducted by a method similar to the above-explained preparation method of an alkoxy silane-based oligomer.
However, since the metal alkoxide-based compound may rapidly react with water, the sol-gel reaction may be conducted by diluting the metal alkoxide-based compound in an organic solvent, and then slowly dripping water thereto. At this time, considering the reaction efficiency, it is preferable that the mole ratio of the metal alkoxide-based compound to water (based on metal ions) is controlled within a range of 3 to 170.
Here, the metal alkoxide-based compound may be one or more compounds selected from the group consisting of titanium tetra-isopropoxide, zirconium isopropoxide, and aluminum isopropoxide.
Meanwhile, the anti-reflective film may further include a substrate bonded to the other side of the hard coating layer. The substrate may be a transparent film having light transmittance of 90% or more and haze of 1% or less. The substrate may be made of triacetylcellulose, a cyclo olefin polymer, polyacrylate, polycarbonate, polyethylene terephthalate, etc. The thickness of the substrate film may be 10 to 300 μm considering productivity, etc. However, the present invention is not limited thereto.
According to the present invention, a photocurable coating composition capable of providing a low refractive layer that has both low reflectance and high light transmittance and simultaneously realizes high scratch resistance and a high anti-pollution property, a low refractive layer obtained from the photocurable coating composition, and an anti-reflective film that can increase sharpness of the screen of a display device and yet exhibits excellent mechanical properties, are provided.
Embodiments of the invention will be explained in the following examples in more detail. However, these examples are presented only as for illustration of the present invention, and the scope of the invention is not limited thereby.
(1) Preparation of a hard coating film (HD1) A salt type of antistatic hard coating liquid manufactured by KYOEISHA Company (solid content 50 wt %, product name: LJD-1000) was coated on a triacetyl cellulose film with a #10 Meyer bar and dried at 90 r for 1 minute, and then irradiated by UV at 150 mJ/cm2 to prepare a hard coating film (HD1) with a thickness of 5 μm.
30 g of pentaerythritol triacrylate, 2.5 g of a high molecular weight copolymer (BEAMSET 371, Arakawa, Epoxy Acrylate, molecular weight 40,000), 20 g of methylethylketone, and 0.5 g of a leveling agent (Tego Wet 270) were uniformly mixed, and then 2 g of acryl-styrene copolymer resin fine particles with a refractive index of 1.525 (volume average particle diameter: 2 μm, manufacturing company: Sekisui Plastics) was added to prepare a hard coating composition. The obtained hard coating composition was coated on a triacetyl cellulose film with #10 Meyer bar and dried at 90 r for 1 minute. The dried product was irradiated by UV at 150 mJ/cm2 to prepare a hard coating film with a thickness of 5 μm.
(1) Preparation of a Photocurable Coating Composition for Forming a Low Refractive Layer
The components of the following Tables 1 and 2 were mixed, and diluted in a solvent of MIBK (methyl isobutyl ketone) such that the solid content became 3 wt %.
(2) Preparation of a Low Refractive Layer and an Anti-Reflective Film (Examples and Comparative Examples)
On the hard coating films described in the following Tables 1 and 2, each photocurable coating composition for forming a low refractive layer obtained in Table 1 was coated with a #3 Meyer bar, and dried at 60 r for 1 minute. And, under nitrogen purging, the dried coating was irradiated by UV at 180 mJ/cm2 to form a low refractive layer with a thickness of 110 nm, thus preparing an anti-reflective film.
1) THRULYA 4320 (manufactured by Catalysts and Chemicals Co., Ltd.): a hollow silica dispersion (solid content 20 wt % in an MIBK solvent)
2) X71-1203M (manufactured by Shinetsu): a fluorine-containing compound including a photoreactive functional group (diluted to a solid content of 15 wt % in MIBK solvent, fluorine content of about 45 wt % in the solid content)
3) OPTOOL-AR110 (manufactured by Daikin): a fluorine-containing compound including a photoreactive functional group (diluted to a solid content of 15 wt % in MIBK solvent, fluorine content of about 60 wt % in the solid content)
4) RS537 (manufactured by DIC Corporation): a fluorine-containing compound including a photoreactive functional group (diluted to a solid content of 40 wt % in MIBK solvent, fluorine content of about 15 wt % in the solid content)
5) TU2323 (manufactured by JSR): a fluorine-containing compound including a photoreactive functional group (diluted to a solid content of 20 wt % in MIBK solvent, fluorine content of about 21 wt % in the solid content)
4) MA0701: polysilsesquioxane (manufactured by Hybrid Plastics)
5) MIBK-ST (manufactured by Nissan Chemical Industries, Ltd.): nano-silica dispersion, diluted to a solid content of 30% in MIBK solvent
For the anti-reflective films obtained in the examples and comparative examples, the following experiments were conducted.
1. Measurement of Mean Reflectance
One side of the above-prepared anti-reflective film was darkened, and then, using Solidspec 3700 (SHIMADZU), mean reflectances in a wavelength region of 480 nm to 780 nm were measured while applying a measuring mode when HD1 was used as a hard coating film, and a 100% T mode when HD2 was used as a hard coating film.
2. Measurement of Scratch Resistance
While steel wool was loaded and allowed to go back and forth 10 times at 27 reciprocations per minute, the surfaces of the anti-reflective films obtained in the examples and comparative examples were rubbed. The maximum load under which a scratch of 1 cm or less is observed with the unaided eye was measured.
3. Evaluation of Anti-Pollution Property
On the surface of the anti-reflective films obtained in the examples and comparative examples, straight lines were drawn with a black oil-based pen and rubbed with a clean wiper, and the rubbing times at which the lines were erased were confirmed to measure anti-pollution properties.
◯: erased at 10 or less rubbing times
Δ: erased at 11 to 20 rubbing times
X: erased at 21 or more rubbing times, or not erased
As shown in the Table 3, it was confirmed that the anti-reflective films of Examples 1 to 10 have low reflectances of 0.7% or less and relatively excellent scratch resistance, and simultaneously have an excellent anti-pollution property.
To the contrary, it was confirmed that the anti-reflective films of Comparative Examples 1 to 3 have high reflectance and relatively inferior scratch resistance, and could not secure a sufficient anti-pollution property.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2015-0135730 | Sep 2015 | KR | national |
| 10-2016-0120100 | Sep 2016 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2016/010525 | 9/21/2016 | WO | 00 |
