This application claims priority to and the benefit of Korean Patent Application No. 10-2012-0155600 filed in the Korean Intellectual Property Office on Dec. 27, 2012, and Korean Patent Application No. 10-2013-0122278 filed in the Korean Intellectual Property Office on Oct. 14, 2013, the entire content of each of which is incorporated herein by reference.
1. Technical Field
The present invention relates to a transparent conductor and an apparatus including the same.
2. Description of the Related Art
Transparent conductors are used as electrode films in touch screen panels, which are included in display apparatuses, flexible displays and the like. Accordingly, transparent conductors have been actively studied in recent years. Transparent conductors should have good properties such as transparency, surface resistance and the like, and also should be flexible for extension to application ranges, such as those of flexible displays. A film, in which indium tin oxide (ITO) films are stacked on two (or both) surfaces of a base film including a polyethylene terephthalate (PET) film, can be used as a transparent conductor. Because the ITO films are deposited on the base film by dry deposition, the ITO films are economical and exhibit good transparency. However, due to certain properties of ITO, ITO films have inherently high resistance and poor flexibility.
Recently, a transparent conductor, in which a conductive layer including metal nanowires such as silver nanowires and the like has been formed and developed. Such a transparent conductor has an advantage of good flexibility. However, because a transparent conductor having a conductive layer including only metal nanowires has high haze, such a transparent conductor has poor optical properties.
In accordance with one aspect according to an embodiment of the present invention, a transparent conductor may include: a base layer; a first coating layer on the base layer and having conductivity; and a second coating layer on the first coating layer, wherein the base layer, the first coating layer and the second coating layer have refractive indexes of R1, R2 and R3, respectively, at a wavelength of 380 nm to 780 nm, and the transparent conductor has a difference (i.e., R1−R2) between R1 and R2 of about 0.05 to about 0.20, and a difference (i.e., R2−R3) between R2 and R3 of about 0.01 to about 0.2.
In accordance with another aspect according to another embodiment of the present invention, a transparent conductor may include: a base layer; a first coating layer on the base layer and having conductivity; and a second coating layer on the first coating layer, wherein the transparent conductor has a haze of about 0.01% to about 1.0% and a surface resistance of about 50Ω/□ to about 150Ω/□.
In accordance with a further aspect according to another embodiment of the present invention, an apparatus may include the transparent conductor.
The above and other aspects, features and advantages of embodiments of the invention will become more apparent by reference to the following detailed description when considered together with the accompanying drawings, in which:
Certain embodiments of the present invention will be described with reference to the accompanying drawings. It should be understood that the present invention may be modified in different ways and is not limited to the following embodiments. In the drawings, elements irrelevant to the description of embodiments of the invention will be omitted for clarity. Like components will be denoted by like reference numerals throughout the specification. As used herein, terms such as “upper side” and “lower side” are defined with reference to the accompanying drawings. Thus, it will be understood that the term “upper side” can be used interchangeably with the term “lower side”. As used herein, the term “(meth)acrylate” may refer to acrylates and/or methacrylates. Also, in the context of the present application, when a first element is referred to as being “on” a second element, it can be directly on the second element or be indirectly on the second element with one or more intervening elements interposed therebetween.
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The transparent conductor may exhibit transparency in the range of visible light, for example, at a wavelength of 400 nm to 700 nm. In one embodiment, the transparent conductor may have a haze of about 1.0% or less, for example, about 0.01% to about 1.0%, and a total light transmittance of about 90% or more, for example, about 90% to about 95%, as measured using a haze meter at a wavelength of 400 nm to 700 nm. Within any of the foregoing ranges, the transparent conductor can be used as a transparent conductor.
The transparent conductor may have a surface resistance (e.g., sheet resistance) of about 150Ω/□ or less, for example, about 50Ω to about 150Ω/□, or about 50Ω/□ to about 100Ω/□, as measured using a 4-point probe tester. Within any of the foregoing ranges, due to low surface resistance, the transparent conductor can be used as an electrode film for touch panels, and can be applied to large area touch panels.
A stacked body including the first coating layer and the second coating layer may be a transparent conductive film or a transparent electrode film, and may be used as a transparent electrode film of touch panels, E-paper or solar cells. The stacked body including the first coating layer and the second coating layer has a thickness of about 0.09 μm to about 0.3 μm, for example, about 0.1 μm to about 0.2 μm, but the stacked body is not limited thereto. Within any of the foregoing ranges, the stacked body including the first coating layer and the second coating layer can be used as a transparent electrode film of touch panels including flexible touch panels.
Because the transparent conductor includes the second coating layer, which is a low refractive index layer having a low refractive index of about 1.30 to about 1.50, for example, about 1.30, 1.31, 1.32, 1.33, 1.34, 1.35, 1.36, 1.37, 1.38, 1.39, 1.40, 1.41, 1.42, 1.43, 1.44, 1.45, 1.46, 1.47, 1.48, 1.49, or 1.50 at a wavelength of 380 nm to 780 nm, on (e.g., formed on) the first coating layer having (e.g., exhibiting) conductivity, the transparent conductor can have low haze and high transmittance (e.g., high light transmittance), and thus, the transparent conductor exhibits improved optical properties while providing (e.g., securing) low surface resistance and high flexibility.
Hereinafter, the transparent conductor according to embodiments of the invention will be described in more detail.
The base layer may have a refractive index R1 of about 1.50 to about 1.70, for example, 1.50, 1.51, 1.52, 1.53, 1.54, 1.55, 1.56, 1.57, 1.58, 1.59, 1.60, 1.61, 1.62, 1.63, 1.64, 1.65, 1.66, 1.67, 1.68, 1.69, or 1.70 at a wavelength of 380 nm to 780 nm.
Within any of the foregoing ranges, the base layer has a suitable (e.g., an appropriate) refractive index relative to that of the first coating layer, which can include a metal nanowire, and thus, can improve transparency of the transparent conductor.
The base layer may have a thickness of about 10 μm to about 100 μm. Within this range, the transparent conductor can be used as a transparent electrode film.
The base layer may include retardation films or non-retardation films. In one embodiment, the base layer may include polycarbonate, polyester including polyethylene terephthalate (PET), polyethylene naphthalate and the like, polyolefin, cyclic olefin polymer, polysulfone, polyimide, silicone, polystyrene, polyacryl, and polyvinyl chloride films, but the base layer is not limited thereto.
The base layer may further include functional layers stacked on one surface or two (e.g., both) surfaces thereof. The functional layers may include hard coating layers, anti-corrosive layers, anti-glare coating layers, adhesion promoters, oligomer elusion prevention layers, and the like, but the functional layers are not limited thereto.
The first coating layer may have a refractive index R2 of about 1.35 to about 1.70, about 1.40 to about 1.60, or, for example, 1.40, 1.41, 1.42, 1.43, 1.44, 1.45, 1.46, 1.47, 1.48, 1.49, 1.50, 1.51, 1.52, 1.53, 1.54, 1.55, 1.56, 1.57, 1.58, 1.59, or 1.60 at a wavelength of 380 nm to 780 nm. Within any of the foregoing ranges, since the first coating layer has a suitable (e.g., an appropriate) refractive index relative to that of the second coating layer, the transparent conductor can have low haze and high transmittance (e.g., high light transmittance), and thus, exhibit improved optical properties.
The first coating layer may have a thickness of about 0.1 μm to about 0.2 μm. Within this range, the transparent conductor can be used as a film for touch panels.
The first coating layer may be conductive (e.g., exhibit conductivity). For example, the first coating layer may be a conductive layer including metal nanowires, and for example, may include a conductive nanowire network formed from metal nanowires. As a result, the first coating layer can impart conductivity to the transparent conductor. For example, the first coating layer may be formed from a composition for a first coating layer including metal nanowires.
The metal nanowires may form a conductive network and thus impart conductivity to the first coating layer and provide good pliablility and flexibility.
The metal nanowires may exhibit better dispersibility than metal nanoparticles due to a shape of the nanowires. In addition, the metal nanowires may significantly decrease surface resistance (e.g., sheet resistance) of the first coating layer, as compared to a layer formed from metal nanoparticles, due to a difference between a shape of the nanoparticles and a shape of the nanowires.
The metal nanowires have an ultrafine line shape having a specific cross-section. For example, the metal nanowires may have a ratio (e.g., L/d, aspect ratio) of length (L) to diameter (d) of the cross-section of about 10 to about 1,000. Within this range, the metal nanowires can realize a highly conductive network even at low density of the nanowires (e.g., at low nanowire concentration), and allow the transparent conductor to have low surface resistance. For example, the metal nanowires may have an aspect ratio of about 500 to about 1,000, or about 500 to about 700.
The metal nanowires may have the diameter (d) of the cross-section of greater than about 0 nm and 100 nm or less. Within this range, the metal nanowires can secure high L/d, and thus, provide (e.g., realize) a transparent conductor having high conductivity (e.g., high electrical conductivity) and low surface resistance. For example, the metal nanowires may have the diameter (d) of the cross-section of about 30 nm to about 100 nm, or about 60 nm to about 100 nm.
The metal nanowires may have a length (L) of about 20 μm or more. Within this range, the metal nanowire can secure high L/d (e.g., high aspect ratio), and thus, provide (e.g., realize) a conductive film having high conductivity (e.g., high electrical conductivity) and low surface resistance. For example, the metal nanowire may have a length (L) of about 20 μm to about 50 μm.
The metal nanowires may include nanowires prepared from any suitable metal. For example, the metal nanowires may include silver nanowires, copper nanowires, gold nanowires, and mixtures thereof, but the metal nanowires are not limited thereto. For example, in some embodiments, the metal nanowires include silver nanowires or a mixture including the silver nanowires, but the metal nanowires are not limited thereto.
The metal nanowires may be prepared by any suitable method typically used in the art, or the metal nanowires may be a commercially available product. For example, the metal nanowires may be prepared through reduction of a metal salt (for example, silver nitrate, AgNO3) in the presence of a polyol and poly(vinyl pyrrolidone). In some embodiments, the metal nanowires may be a commercially available product (for example, ClearOhm Ink., available from Cambrios Co., Ltd.).
The composition for the first coating layer may further include a solvent for ease of formation of a coating layer and ease of coating the first coating layer on the base film. The solvent may include a main solvent and a co-solvent. The main solvent may include water, acetone and the like, or mixtures thereof, and the co-solvent may include alcohols, such as methanol and the like, or mixtures thereof, for miscibility of water and acetone. However, the main solvent and co-solvent are not limited thereto.
As an overcoating layer, the second coating layer can improve adhesion of the first coating layer to the base film. In addition, as a low refractive index coating layer, the second coating layer can allow the transparent conductor to have low haze and high transmittance (e.g., high light transmittance) as compared with existing transparent conductors, and thus, improve optical properties of the transparent conductor while providing (e.g., securing) good electrical properties and flexibility of the transparent conductor. In one embodiment, the second coating layer may have a refractive index R3 of about 1.30 to about 1.50, or for example, 1.30, 1.31, 1.32, 1.33, 1.34, 1.35, 1.36, 1.37, 1.38, 1.39, 1.40, 1.41, 1.42, 1.43, 1.44, 1.45, 1.46, 1.47, 1.48, 1.49, or 1.50, at a wavelength of 380 nm to 780 nm. Within any of the foregoing ranges, the second coating layer can decrease haze of the transparent conductor and improve transmittance (e.g., light transmittance) thereof.
The second coating layer has a thickness of about 0.05 μm to about 0.2 μm, for example, from about 0.05 μm to about 0.1 μm. Within any of the foregoing ranges, the transparent conductor can be used as a film for touch panels.
The second coating layer may be formed from a composition including a fluorine-containing monomer or a polymer thereof. For example, the second coating layer may be formed from a composition including (C1) a fluorine-containing monomer or a polymer thereof, (C2) a non-fluorine monomer, and (C3) an initiator.
The fluorine-containing monomer or polymer thereof may lower a refractive index of the second coating layer, and thus, allow the transparent conductor to have low haze and high transmittance, while forming a film of the second coating layer after curing.
The fluorine-containing monomer or polymer thereof may have a refractive index of about 1.30 to about 1.50 at a wavelength of 380 nm to 780 nm. Within any of the foregoing ranges, the second coating layer can have a low refractive index.
The fluorine-containing monomer may have a molecular weight of about 300 g/mol to about 10,000 g/mol, for example, about 500 g/mol to about 1,000 g/mol, or, for example, about 500, 600, 700, 800, 900, or 1,000 g/mol. Within any of the foregoing ranges, a uniform film of the second coating layer having a low refractive index can be formed and the transparent conductor can have low haze.
The fluorine-containing polymer formed from a fluorine-containing monomer may have a weight average molecular weight of about 10,000 g/mol to about 20,000 g/mol. Within this range, a uniform film of the second coating layer having a low refractive index can be formed and the transparent conductor can have low haze.
The fluorine-containing monomer may include a monomer having fluorine and at least two functional groups (for example, (meth)acrylate groups, or fluorine-containing (meth)acrylate groups) in one molecule.
Fluorine may be present in the fluorine-containing polymer in an amount of about 50% by weight (wt %) to about 90 wt %, for example, about 50, 60, 70, 80, or 90 wt %, based on the total weight of the fluorine-containing polymer formed from the fluorine-containing monomer. Within any of the foregoing ranges, the transparent conductor can exhibit decreased haze and improved transmittance (e.g., improved light transmittance).
The fluorine-containing monomer may include, for example, a pentaerythritol backbone, a dipentaerythritol backbone, a trimethylolpropane backbone, a ditrimethyloipropane backbone, a cyclohexyl backbone, a linear backbone, or a mixture thereof, but the fluorine-containing monomer is not limited thereto.
For example, the fluorine-containing monomer may be represented by any of Formulae 1 to 19:
In Formula 19, A is a fluorine-containing C1 to C20 hydrocarbon group; B is an acrylate group, methacrylate group, fluorine-substituted acrylate group, or fluorine-substituted methacrylate group; n is an integer from 1 to 6; and m is an integer from 1 to 16.
In Formula 19, the “hydrocarbon group” may be an alkyl group or an alkylene group.
The fluorine-containing monomer or polymer thereof may be present in the composition for forming the second coating layer in an amount of about 2 wt % to about 95 wt %, for example, about 5 wt % to about 91 wt %, for example, about 2 wt % to about 50 wt %, or, for example, about 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 wt %, based on the total weight of solids in the composition for forming the second coating layer. Within any of the foregoing ranges, the fluorine-containing monomer or polymer thereof can provide a second coating layer having a low index of refraction, and thus, allow the transparent conductor to have low haze and high transmittance (e.g., high light transmittance).
The fluorine-containing monomer or polymer thereof may be present in the composition for forming the second coating layer in an amount of about 2 parts by weight to about 95 parts by weight, for example, about 5 parts by weight to about 95 parts by weight, based on 100 parts by weight of (C1)+(C2). Within any of the foregoing ranges, the second coating layer can form a uniform film, and thus, allow the transparent conductor to exhibit low haze and improved transmittance (e.g., improved light transmittance).
The non-fluorine monomer is free from fluorine (e.g., completely free from fluorine) and may include a monofunctional or polyfunctional monomer having a curing reaction group, for example, a (meth)acrylate group. The non-fluorine monomer may be polymerization-cross-linked (e.g., cross-linked through polymerization) with the fluorine-containing monomer or polymer thereof through processes of heating and curing the composition, and thus, may form the second coating layer.
The non-fluorine monomer may have a refractive index of about 1.30 to about 1.50, for example, 1.30, 1.31, 1.32, 1.33, 1.34, 1.35, 1.36, 1.37, 1.38, 1.39, 1.40, 1.41, 1.42, 1.43, 1.44, 1.45, 1.46, 1.47, 1.48, 1.49, or 1.50 at a wavelength of 380 nm to 780 nm. Within any of the foregoing ranges, the non-fluorine monomer can provide (e.g., realize) a second coating layer having a suitably (e.g., sufficiently) low refractive index.
The non-fluorine monomer may have a molecular weight of about 250 g/mol to about 1,000 g/mol. Within this range, since the non-fluorine monomer has an appropriate number of functional groups, the second coating layer does not suffer from hardness deterioration.
For example, the non-fluorine monomer may include dipentaerythritol hexa(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, di(trimethylolpropane)tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, glycerol tri(meth)acrylate, ethyleneglycol di(meth)acrylate, neopentylglycol di(meth)acrylate, hexanediol di(meth)acrylate, trimethylolpropane di(meth)acrylate, dipentaerythritol penta(meth)acrylate, pentaerythritol tri(meth)acrylate, cyclodecane dimethanol di(meth)acrylate, or a mixture thereof, but the non-fluorine monomer is not limited thereto.
The non-fluorine monomer may be present in the composition for forming the second coating layer in an amount of about 0.1 wt % to about 95 wt %, for example, about 0.2 wt % to about 40 wt % or about 8 wt % to about 92 wt %, based on the total weight of solids in the composition for forming the second coating layer. Within any of the foregoing ranges, the second coating layer can maintain external appearance thereof, and exhibit improved adhesion to the base layer and physical properties.
In one embodiment, the composition for forming the second coating layer may include a mixture of a hexafunctional monomer and a trifunctional monomer as the non-fluorine monomer. The mixture may include about 0.1 wt % to about 99.9 wt %, for example, about 0.1 wt % to about 90 wt % of the hexafunctional monomer, and about 0.1 wt % to about 99.9 wt %, for example, about 0.1 wt % to about 10 wt % of the trifunctional monomer, based on the total weight of the mixture. Within any of the foregoing ranges, the transparent conductor can provide (e.g., secure) adhesion between the base layer and the second coating layer, and can exhibit low haze and high transmittance (e.g., high light transmittance).
The non-fluorine monomer may be present in the composition for forming the second coating layer in an amount of about 5 parts by weight to about 98 parts by weight, for example, about 5 parts by weight to about 95 parts by weight, based on 100 parts by weight of (C1)+(C2). Within any of the foregoing ranges, the second coating layer can exhibit improved adhesion to the base layer and improved physical properties.
The initiator may be any suitable initiator without limitation as long as the initiator can absorb light at an absorption wavelength of about 150 nm to about 500 nm to induce (e.g., exhibit) photoreaction. For example, the initiator may include phosphine oxide initiators, α-hydroxyketone initiators, and the like, but the initiator is not limited thereto. For example, the initiator may include bis-acyl-phosphine oxide (BAPO), diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), 1-hydroxycyclohexylphenylketone, and mixtures thereof, but the initiator is not limited thereto.
The initiator may be present in the composition for forming the second coating layer in an amount of about 0.1 wt % to about 10 wt %, for example, about 0.1 wt % to about 5 wt %, based on the total weight of solids in the composition for the second coating layer in terms of solid content. Within any of the foregoing ranges, a monomer can be suitably (e.g., sufficiently) cured without the residual initiator.
The initiator may be present in the composition for forming the second coating layer in an amount of about 0.01 parts by weight to about 5 parts by weight, for example, about 0.1 parts by weight to about 1 part by weight, based on 100 parts by weight of (C1)+(C2). Within any of the foregoing ranges, a cured film of the second coating layer can exhibit adhesion to the base layer and chemical resistance.
The composition for forming the second coating layer may further include hollow silica fine particles. The hollow silica fine particles may improve a strength of the second coating layer. The hollow silica fine particles may be subjected to surface modification (e.g., surface treated) with a fluorine-containing resin. As a result, the second coating layer can have a lower refractive index.
The hollow silica fine particles may be present in the composition for forming the second coating layer in an amount of about 0.1 parts by weight to about 10 parts by weight, based on 100 parts by weight of solids in the composition for forming the second coating layer. The hollow silica fine particles may have an average particle diameter of about 30 nm to about 60 nm. Within this range, the second coating layer can exhibit good transparency.
The transparent conductor may be prepared from the base layer, the composition for forming the first coating layer, and the composition for forming the second coating layer using any suitable method commonly used in the art. For example, the composition for forming the first coating layer is coated onto a surface of the base layer, followed by drying and baking. Next, the composition for forming the second coating layer is coated onto the first coating layer, followed by drying, baking, and UV curing at about 500 mJ/cm2 or more, for example, about 500 mJ/cm2 to about 1000 mJ/cm2, thereby forming the second coating layer. The first and second coating layers are formed on a surface (e.g., at least one surface) of the base layer, and in some embodiments, are formed on only one surface thereof.
In
Each of the first and second coating layers 120, 130 may be patterned, for example, by wet etching and the like, but the method of patterning is not limited thereto.
Each of the first and second coating layers 120, 130 may be patterned, for example, by wet etching and the like, but the method of patterning is not limited thereto.
An apparatus according to an embodiment of the invention may include the transparent conductor according to an embodiment of the invention. Examples of the apparatus include, for example, optical display apparatuses including touch screen panels, flexible displays and the like, E-paper, solar cells, and the like, but the apparatus is not limited thereto.
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Hereinafter, embodiments of the present invention will be described with reference to some examples. However, it should be noted that these examples are provided for illustration only and are not to be construed in any way as limiting the present invention.
48 parts by weight of silver nanowires (Clearohm Ink., available from Cambrios Co., Ltd., aspect ratio: 500) was introduced into 52 parts by weight of ultrapure distilled water, followed by stirring, thereby preparing a composition for forming a first coating layer.
The components used in Examples and Comparative Examples were as follows.
(A) Fluorine-containing monomer or polymer thereof: (A1) AR-110 (available from DAIKIN Co., Ltd.), (A2) LINC-3A (available from KYOEISHA Co., Ltd., Formula 2)
(B) Non-fluorine monomer: (B1) Trimethylolpropane triacrylate (TMPTA), (B2) Dipentaerythritol hexaacrylate (DPHA)
(C) Initiator: Bis-acyl-phosphine oxide (BAPO, Darocure 819W, available from CIBA Co., Ltd.)
(D) Urethane acrylate
(E) Composition for first coating layer: The composition of Preparative Example
(F) Base layer: Polycarbonate film (thickness: 50 μm, refractive index at a wavelength of 550 nm: 1.63)
0.45 parts by weight of TMPTA and 0.01 parts by weight of the initiator were introduced into 95 parts by weight of propylene glycol monomethyl ether (PGME) as a solvent, and dissolved therein. Next, 4.5 parts by weight of AR-110 (available from DAIKIN Co., Ltd.) was added to the resulting solution and dissolved therein, thereby preparing a composition for forming a second coating layer. The composition for forming a first coating layer was coated onto the base layer using wire bar-coating, followed by drying in an oven at 80° C. for 2 minutes. Next, the composition for forming a second coating layer was coated onto the dried first coating layer using a spin coater, followed by drying in an oven at 80° C. for 2 minutes. The coating layers were subjected to UV curing at 500 mJ/cm2 in a nitrogen atmosphere, thereby preparing a transparent conductor.
0.21 parts by weight of TMPTA, 7.5 parts by weight of DPHA and 0.23 parts by weight of the initiator were introduced into 99 parts by weight of propylene glycol monomethyl ether (PGME) as a solvent, and then dissolved therein. Next, 0.5 parts by weight of LINC-3A (available from KYOEISHA Co., Ltd.) was added to the resulting solution and dissolved therein, thereby preparing a composition for forming a second coating layer. The composition for forming a first coating layer was coated onto the base layer by wire bar-coating, followed by drying in an oven at 80° C. for 2 minutes. Next, the composition for forming a second coating layer was coated onto the dried first coating layer using a spin coater, followed by drying in an oven at 80° C. for 2 minutes. The coating layers were subjected to UV curing at 500 mJ/cm2 in a nitrogen atmosphere, thereby preparing a transparent conductor.
2 parts by weight of a urethane acrylate and 0.01 parts by weight of the initiator were introduced into 98 parts by weight of propylene glycol monomethyl ether (PGME) as a solvent, and then dissolved therein, thereby preparing a solution B. The composition for forming a first coating layer was coated onto the base layer by wire bar-coating, followed by drying in an oven at 80° C. for 1 minute and then baking in an oven at 120° C. for 1 minute. The solution B was coated onto the first coating layer by wire bar-coating, followed by drying in an oven at 80° C. for 1 minute and then baking in an oven at 120° C. for 1 minute. Next, the coating layers were subjected to UV curing at 500 mJ/cm2 in a nitrogen atmosphere, thereby preparing a transparent conductor, in which a 150 nm-thick conductive film including a cured product of the metal nanowires, the urethane acrylate and the initiator was stacked on one surface of the base film.
A transparent conductor was prepared as in Example 1 except that 5 parts by weight of TMPTA was used instead of 4.5 parts by weight of AR-110 (DAIKIN Co., Ltd.).
The transparent conductors prepared in Examples and Comparative Examples were evaluated as to the following properties. Results are shown in Table 1.
(1) Difference between refractive indexes: Refractive indexes of the coating layers were measured using an ellipsometer at a wavelength of 380 nm to 780 nm. From the measured results, a difference between refractive indexes was calculated. R1, R2 and R3 were the refractive indexes of the base layer, the first coating layer and second coating layer, respectively.
(2) Haze and Total light transmittance (%): Haze and total light transmittance were measured on the transparent conductors at a wavelength of 400 nm to 700 nm using a haze meter.
(3) Surface resistance (Ω/□): With 4 probes of a contact-type surface resistance tester MCP-T610 (available from Mitsubishi Chemical Analytech Co., Ltd.) contacting a surface of the second coating layer of each of the transparent conductors, surface resistance was measured after 10 seconds.
(4) IPA rubbing: After isopropanol (IPA) was dropped onto the second coating layer using pipettes and then rubbed ten times thereon using a wiper, change in external appearance and resistance of the second coating layer was observed. No change in both external appearance and resistance was evaluated as ‘Good’, and change in at least one of external appearance and resistance was evaluated as ‘Not Good (NG)’.
As shown in Table 1, the transparent conductors according to an embodiment of the invention, in which the second coating layer including a low refractive fluorine resin was formed, exhibited good optical properties due to low haze and high transmittance thereof, and had low surface resistance. Conversely, the transparent conductor of Comparative Example 1, in which the second coating layer was not formed and an overcoating layer including a urethane acrylate was formed, had high haze and high surface resistance, and thus could not realize effects of embodiments of the present invention. In addition, the transparent conductor of Comparative Example 2, in which the second coating layer free from a fluorine-containing monomer or polymer was formed, had high haze and suffered from problems in terms of chemical resistance and adhesion to the base layer. Further, when the transparent conductor included hollow silica coated with a low refractive resin, the transparent conductor had problems of increased surface resistance and high haze. Thus, according to embodiments of the invention, the transparent conductor has improved optical properties due to low haze and high transmittance thereof, exhibits good properties in terms of adhesion to the base layer, solvent resistance and flexibility, and has low surface resistance.
While certain embodiments of the present invention have been illustrated and described herein, it will be understood that various modifications, changes, alterations, and equivalent embodiments can be made by those skilled in the art without departing from the spirit and scope of the invention as defined by the following claims, and equivalents thereof. Throughout the text and claims, use of the word “about” reflects the penumbra of variation associated with measurement, significant figures, and interchangeability, all as understood by a person having ordinary skill in the art to which this disclosure pertains. Additionally, throughout this disclosure and the accompanying claims, it is understood that even those ranges that may not use the term “about” to describe the high and low values are also implicitly modified by that term, unless otherwise specified.
Number | Date | Country | Kind |
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10-2012-0155600 | Dec 2012 | KR | national |
10-2013-0122278 | Oct 2013 | KR | national |