Planar heating element, article comprising same, and method for manufacturing planar heating element

Abstract

Disclosed are a planar heating element, an article comprising same, and a method for manufacturing the planar heating element. The planar heating element comprises: a substrate: a hard coating layer located on the upper side of the substrate; a first conductive oxide layer located on the upper side of the hard coating layer; a metal layer located on the upper side of the first conductive oxide layer; a second conductive oxide layer located on the upper side of the metal layer; and an electrode layer disposed to be in contact with the substrate, the hard coating layer, the first conductive oxide layer, the metal layer, and the second conductive oxide layer.

Description

Surface heating element, article including the same, and method for manufacturing the surface heating element

[0001] The present disclosure relates to a surface heating element, an article including the same, and a method for manufacturing the surface heating element.

[0002] Surface heating elements are structures that generate radiant heat through voltage. Surface heating elements are pollution-free, energy-efficient, and quiet, making them ideal for a wide range of applications, including automotive windshields, refrigerator front display cases, smart glass, bathroom mirrors, and industrial heating.

[0003] Planar heaters are manufactured by applying a conductive material to one surface of an insulating substrate to form a layer, which operates by generating heat when a voltage is applied. Examples of conductive materials used include graphene, silver nanowires, metal mesh, and indium tin oxide (ITO). However, planar heaters containing only these conductive material layers struggle to achieve the high heat generation efficiency, long-term reliability, and uniform heat generation characteristics required for diverse applications.

[0004] Therefore, to solve these problems, there is a need for a novel surface heating element having a novel structure, an article including the same, and a method for manufacturing the surface heating element.

[0005] One aspect is to provide a novel structured planar heating element that satisfies all of the following characteristics: improved transmittance, excellent heat generation efficiency even under low voltage, stable corrosion resistance even under high temperature and high humidity environments, low curl height, and no thermal wrinkles.

[0006] Another aspect is to provide an article comprising the above surface heating element.

[0007] Another aspect is to provide a method for manufacturing the above-mentioned surface heating element.

[0008] According to one aspect,

[0009] substrate;

[0010] A hard coating layer positioned on the upper portion of the substrate;

[0011] A first conductive oxide layer positioned on top of the hard coating layer;

[0012] A metal layer positioned on top of the first conductive oxide layer;

[0013] a second conductive oxide layer positioned on top of the metal layer; and

[0014] A surface heating element is provided, comprising: an electrode layer arranged to be in contact with the substrate, the hard coating layer, the first conductive oxide layer, the metal layer, and the second conductive oxide layer.

[0015] The above hard coating layer may include one or more types of resin selected from acrylate resin, thiol resin, urethane resin, and epoxy resin.

[0016] The thickness of the above hard coating layer may be 0.1 ㎛ to 5 ㎛.

[0017] The above metal layer may be a metal selected from Ag, Au, Pt, Al, Cu, Cr, V, Mg, Ti, Sn, Pb, Pd, W or an alloy thereof.

[0018] The first conductive oxide layer and the second conductive oxide layer may be oxides selected from ZTO (zinc tin oxide), IGZO (indium gallium zinc oxide), ZAO (zinc aluminum oxide), IZO (indium zinc oxide), ZnO (zinc oxide), and combinations thereof.

[0019] The thicknesses of the first conductive oxide layer and the second conductive oxide layer may each be less than 30 nm to 100 nm.

[0020] The above substrate is a transparent substrate and may have a thickness of 50 ㎛ to 200 ㎛.

[0021] The surface resistance at room temperature can be less than 20 Ω / □.

[0022] The change rate of surface resistance before and after being left for 360 hours under 85℃ and 85% relative humidity can satisfy the following equation 1:

[0023] [Formula 1]

[0024] [(AB) / A] x 100 ≤ 3%

[0025] Among the foods,

[0026] A is the surface resistance (Ω / □) before being left for 360 hours at 85℃ and 85% relative humidity,

[0027] B is the surface resistance (Ω / □) after being left for 360 hours at 85℃ and 85% relative humidity.

[0028] Visible light transmittance may be greater than 60%, and haze may be less than 1.1.

[0029] On another note,

[0030] An article comprising the aforementioned surface heating element is provided.

[0031] According to another aspect,

[0032] Steps to prepare the substrate;

[0033] A step of applying a composition for forming a hard coating layer to one surface of the substrate and photocuring it to form a hard coating layer;

[0034] A step of sequentially forming a first conductive oxide layer, a metal layer, and a second conductive oxide layer by depositing the hard coating layer on one side opposite to the substrate; and

[0035] A method for manufacturing a planar heating element is provided, including a step of arranging an electrode layer so as to be in contact with the substrate, the hard coating layer, the first conductive oxide layer, the metal layer, and the second conductive oxide layer.

[0036] A planar heater according to one aspect has corrosion resistance with no change in surface resistance even under high temperature and high humidity environments, including a hard coating layer between a substrate and a first conductive oxide layer. The planar heater has excellent heat generation efficiency even under low voltage, including a metal layer between the first conductive oxide layer and the second conductive oxide layer. The planar heater has high visible light transmittance, low haze, low average curl height, and no thermal wrinkles. Therefore, articles including the planar heater can be widely used in various fields.

[0037] Figure 1 is a cross-sectional schematic diagram of a structure included in a surface heating element according to one embodiment.

[0038] Figure 2 is a cross-sectional schematic diagram of a surface heating element according to one embodiment.

[0039] Hereinafter, with reference to examples and drawings of the present invention, a surface heating element, an article including the same, and a method for manufacturing the surface heating element will be described in detail. These examples are provided solely as examples to more specifically illustrate the present invention, and it will be apparent to those skilled in the art that the scope of the present invention is not limited by these examples.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In case of conflict, the present specification, including its definitions, shall prevail.

[0041] Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.

[0042] The term "including" in this specification means that other components may be included rather than excluding other components unless specifically stated to the contrary.

[0043] The term "combination of these" as used herein means a mixture or combination of one or more of the described components, including, for example, a mixture, alloy, or composite of the components described above.

[0044] As used herein, the term "and / or" is meant to include any and all combinations of one or more of the items described herein. As used herein, the term "or" means "and / or." The expressions "at least one" or "one or more" preceding elements herein may modify the entire list of elements and do not mean that they modify individual elements described above.

[0045] When a component is referred to herein as being "on" or "over" another component, the component may be directly on the other component, or there may be intervening components between the components. Conversely, when a component is referred to as being "directly on" or "directly over" another component, there may not be intervening components.

[0046] Among the conventional methods for manufacturing planar heaters, there is a method of forming a metal layer by directly sputtering a metal such as Ag onto one surface of a substrate. When a planar heater having such a metal layer formed uses a substrate with high roughness, the metal such as Ag grows directly on the substrate with high roughness, resulting in a metal layer with high roughness. As a result, the conductive oxide layer laminated on the metal layer with high roughness has a reduced film quality and cannot function as a corrosion-preventing film, so the metal layer can easily corrode when used at high temperatures for a long time. Alternatively, there is a method of changing the type of material of the conductive oxide layer laminated on the metal layer. However, even if the type of material of the conductive oxide layer is changed, it is difficult to improve the performance of the corrosion-preventing film due to the high roughness of the conductive oxide layer.

[0047] Taking these points into consideration, the inventors of the present invention propose a novel planar heating element, an article including the same, and a method for manufacturing the planar heating element.

[0048] According to one embodiment, a planar heater includes: a substrate; a hard coating layer positioned on an upper portion of the substrate; a first conductive oxide layer positioned on an upper portion of the hard coating layer; a metal layer positioned on an upper portion of the first conductive oxide layer; a second conductive oxide layer positioned on an upper portion of the metal layer; and an electrode layer positioned so as to be in contact with the substrate, the hard coating layer, the first conductive oxide layer, the metal layer, and the second conductive oxide layer. Since the planar heater has the hard coating layer positioned between the substrate and the first conductive oxide layer, the first conductive oxide layer, the metal layer, and the second conductive oxide layer can be planarized, thereby providing stable corrosion resistance even when used for a long time in a high-temperature and high-humidity environment. Since the metal layer is positioned between the first conductive oxide layer and the second conductive oxide layer, the planar heater can have improved transmittance and excellent heat generation efficiency even under low voltage. At the same time, the planar heater structure has the characteristics of low curl height and no thermal wrinkles.

[0049] Fig. 1 is a cross-sectional schematic diagram of a structure included in a planar heating element according to an embodiment. Fig. 2 is a cross-sectional schematic diagram of a planar heating element according to an embodiment.

[0050] Referring to Fig. 1, a structure (100) included in a planar heating element according to one embodiment is a structure in which a substrate (11), a hard coating layer (21), a first conductive oxide layer (31), a metal layer (41), and a second conductive oxide layer (51) are sequentially laminated. Referring to Fig. 2, a planar heating element (100') according to one embodiment shows an electrode layer (61) formed by connecting the upper and lower ends of both ends so as to be in contact with the respective layers of the structure of Fig. 1.

[0051] The substrate (11) may be a film or a sheet. For example, the substrate (11) may be a film. The substrate (11) may be a film with excellent heat resistance that can withstand high temperatures. The substrate (11) may be a transparent substrate.

[0052] The substrate (11) may be a transparent polymer film. Examples of the substrate (11) may include, but are not limited to, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyarylate, polycarbonate, polyetherimide, polyamideimide, polyimide, or polybenzoxazole.

[0053] The substrate (11) may be a single layer. Alternatively, the substrate (11) may be a multilayer structure having two or more layers. When the substrate (11) is a multilayer structure having two or more layers, the polymer materials constituting each layer may be the same or different materials.

[0054] The thickness of the substrate (11) may be 50 ㎛ to 200 ㎛. If the thickness of the substrate (11) is less than 50 ㎛, thermal wrinkles may occur during the sputtering process, which may deteriorate the bonding properties. If the thickness of the substrate (11) exceeds 200 ㎛, the bonding properties may deteriorate due to high stiffness during bonding. The stiffness of the substrate (11) may be 5 N / mm to 81 N / mm.

[0055] The substrate (11) may undergo surface treatment such as plasma treatment or corona treatment to improve adhesion with the hard coating layer (21).

[0056] The hard coating layer (21) serves to planarize the first conductive oxide layer (31), the metal layer (41), and the second conductive oxide layer (51).

[0057] The hard coating layer (21) may include one or more types of resin selected from acrylate resin, thiol resin, urethane resin, and epoxy resin.

[0058] Acrylate resins include (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, silicone (meth)acrylate, etc., either singly or in combination of two or more.

[0059] For example, it may be a (meth)acrylate multifunctional (meth)acrylate. Examples of polyfunctional (meth)acrylates include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, glycerol tri(meth)acrylate, and triallyl(meth)acrylate.

[0060] The polyfunctional (meth)acrylate may contain an ethylene oxide (EO) or propylene oxide (PO) addition type polyfunctional (meth)acrylate. The addition type polyfunctional (meth)acrylate is a compound obtained by esterifying an ethylene oxide (EO) or propylene oxide (PO) addition type polyhydric alcohol with acrylic acid. Examples thereof include EO or PO modified glycerol triacrylate, EO or PO modified trimethylolpropane acrylate, EO or PO modified pentaerythritol tetraacrylate, and EO or PO modified dipentaerythritol hexaacrylate. When the content of EO or PO added is in the range of 5 to 20 moles per mole of the polyfunctional (meth)acrylate, appropriate flexibility can be imparted to the hard coating layer (21).

[0061] The thiol resin may be, for example, a multifunctional thio(meth)acrylate resin. For example, the multifunctional thio(meth)acrylate resin can be obtained by adding a multifunctional thiol compound, a hydroxy-containing ethylenically unsaturated compound, and an isocyanate group-containing (meth)acrylate compound. The multifunctional thiol compound is not limited as long as it contains two or more thiol groups (-SH) at the terminal. Hydroxyl-containing ethylenically unsaturated compounds include, but are not limited to, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, polyethylene glycol mono (meth)acrylate, polypropylene glycol mono (meth)acrylate, polyethylene glycol-propylene glycol mono (meth)acrylate, polyethylene glycol-tetramethylene glycol mono (meth)acrylate, polypropylene glycol-polybutylene glycol mono (meth)acrylate, polycaprolactone mono (meth)acrylate, hydroxyethyl vinyl ether, and diethylene glycol monovinyl ether, which may be used alone or in combination of two or more thereof. Examples of (meth)acrylate compounds containing an isocyanate group include, but are not limited to, 2-isocyanateethyl (meth)acrylate, 3-isocyanatepropyl (meth)acrylate, etc.

[0062] The urethane-based resin may be urethane (meth)acrylate. The urethane (meth)acrylate may be a multifunctional urethane (meth)acrylate. For example, the multifunctional urethane (meth)acrylate may be a multifunctional urethane (meth)acrylate containing a cyclohexyl group. For example, the multifunctional urethane (meth)acrylate containing a cyclohexyl group may be prepared by a condensation reaction of a diisocyanate containing a cyclohexyl group and a multifunctional (meth)acrylate containing a hydroxy group. The diisocyanate containing a cyclohexyl group may be, but is not limited to, 1,4-cyclohexyl diisocyanate, isophorone diisocyanate, or 4,4-dicyclohexylmethane diisocyanate, either singly or in combination of two or more thereof. The multifunctional (meth)acrylate containing a hydroxy group may be trimethylolpropane di(meth)acrylate, pentaerythritol tri(meth)acrylate, or dipentaerythritol penta(meth)acrylate, either alone or in combination of two or more thereof, but is not limited thereto.

[0063] The epoxy resin may include, but is not limited to, epoxy acrylate, siloxane resin having an alicyclic epoxy group, etc.

[0064] The thickness of the hard coating layer (21) may be 0.1 ㎛ to 5 ㎛. For example, the thickness of the hard coating layer (21) may be 0.1 ㎛ to 5 ㎛, or 0.1 ㎛ to 4 ㎛, or 0.1 ㎛ to 3 ㎛, or 0.5 ㎛ to 5 ㎛, or 0.5 ㎛ to 4 ㎛, or 0.5 ㎛ to 3 ㎛, or 1 ㎛ to 5 ㎛, or 1 ㎛ to 4 ㎛, or 1 ㎛ to 3 ㎛. If the thickness of the hard coating layer (21) is less than 0.1 ㎛, a flat layer may not be formed, and crystals may occur. If the thickness of the hard coating layer (21) is more than 5 ㎛, the height of the curl may increase, which may reduce the cohesion of the planar heating element (100').

[0065] The first conductive oxide layer (31) and the second conductive oxide layer (51) may be transparent conductive oxide layers. The first conductive oxide layer (31) and the second conductive oxide layer (51) may be oxides selected from zinc tin oxide (ZTO), indium gallium zinc oxide (IGZO), zinc aluminum oxide (ZAO), indium zinc oxide (IZO), zinc oxide (ZnO), and combinations thereof. For example, the first conductive oxide layer (31) and the second conductive oxide layer (51) may be zinc tin oxide (ZTO).

[0066] The thickness of the first conductive oxide layer (31) and the second conductive oxide layer (51) may be 30 nm to less than 100 nm, respectively. If the thickness of the first conductive oxide layer (31) and the second conductive oxide layer (51) is within the above range, the transmittance of the planar heating element (100') may be improved and the surface resistance may be reduced, thereby providing excellent heat generation efficiency.

[0067] The metal layer (21) positioned between the first conductive oxide layer (31) and the second conductive oxide layer (51) may be a metal selected from Ag, Au, Pt, Al, Cu, Cr, V, Mg, Ti, Sn, Pb, Pd, W, or an alloy thereof. For example, the metal layer (21) may be Ag having high electrical conductivity or an alloy of Ag and the above-described metals. The metal layer (21) may have improved corrosion resistance even under high temperature and high humidity environments due to the flattening of the hard coating layer (21) on the lower surface of the first conductive oxide layer (31), thereby reducing roughness, and may have excellent heat generation efficiency even under low voltage.

[0068] The thickness of the metal layer (21) may be 5 nm to 20 nm. For example, the thickness of the metal layer (21) may be 7 nm to 20 nm, or 10 nm to 20 nm. If the thickness of the metal layer (21) is within the above range, it may have high visible light transmittance and low surface resistance, thereby achieving excellent heat generation efficiency even under low voltage.

[0069] The electrode layer (61) can be arranged to be in contact with the substrate (11), the hard coating layer (21), the first conductive oxide layer (31), the metal layer (41), and the second conductive oxide layer (51). The electrode layer (61) functions as a current path. The electrode layer (61) can be formed to connect and contact the upper and lower portions of both ends of the structure (100). The electrode layer (61) can be formed of a conductive material. For example, the conductive material can be a metal, a conductive metal nitride, a conductive metal oxide, or a combination thereof. For example, the conductive material can be a metal such as Cu.

[0070] The surface heating element (100') may have a surface resistance of 20 Ω / □ or less at room temperature.

[0071] The surface heating element (100') can have a surface resistance change rate before and after being left at 85°C and 85% relative humidity for 360 hours that satisfies the following equation 1:

[0072] [Formula 1]

[0073] [(AB) / A] x 100 ≤ 3%

[0074] Among the foods,

[0075] A is the surface resistance (Ω / □) before being left for 360 hours at 85℃ and 85% relative humidity,

[0076] B is the surface resistance (Ω / □) after being left for 360 hours at 85℃ and 85% relative humidity.

[0077] For example, the surface resistance change rate of the surface heating element (100') before and after being left at 85°C and 85% relative humidity for 360 hours may be 2% or less, 1% or less, or 0%.

[0078] The surface heating element (100') may have a visible light transmittance of 60% or more and a haze of 1.1 or less.

[0079]

[0080] Articles according to another embodiment may include the surface heating element (100') described above. Examples of the articles include automotive windshields, refrigerator front display cases, smart glasses, bathroom mirrors, industrial heating, smart farms, fish tanks, coats, medical devices, etc.

[0081] Another embodiment of a method for manufacturing a surface heating element may include the steps of: preparing a substrate; applying a composition for forming a hard coating layer to one surface of the substrate and photocuring the composition to form a hard coating layer; depositing the hard coating layer on one surface opposite to the substrate to sequentially form a first conductive oxide layer, a metal layer, and a second conductive oxide layer; and arranging an electrode layer so as to be in contact with the substrate, the hard coating layer, the first conductive oxide layer, the metal layer, and the second conductive oxide layer.

[0082] First, prepare the substrate described above.

[0083] Next, a composition for forming a hard coating layer is applied to one surface of the substrate and photocured to form a hard coating layer. The composition for forming a hard coating layer may include the above-described resin, photoinitiator, and solvent. The photoinitiator may be used without particular limitation as long as it is an initiator usable in the relevant technical field. For example, photoinitiators include acetophenones such as 4-phenoxydichloroacetophenone, 4-t-butyldichloroacetophenone, 4-t-butyltrichloroacetophenone, diethoxyacetophenone, 2-hydroxy-2-methyl-l-phenylpropan-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-l-one, 1-(4-dodecylphenyl)-2-hydroxy-2-methylpropan-1-one, 4-(2-hydroxyethoxy)-phenyl(2-hydroxy-2-propyl)ketone, and 1-hydroxycyclohexylphenyl ketone; benzoins such as benzoin, benzoin methyl ether, benzoin ethyl ether, and benzyl dimethyl ketal; acylphosphine oxides, and titanocene compounds; Examples thereof include benzophenones such as benzophenone, benzoylbenzoic acid, benzoylbenzoic acid methyl ether, 4-phenylbenzophenone, hydroxybenzophenone, 4-benzol-4'-methyldiphenyl sulfide, and 3,3'-methyl-4-methoxybenzophenone; and thioxanthones such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2, 4-dimethylthioxanthone, and isopropylthioxanthone. The photoinitiator may be used alone or in combination of two or more. The photoinitiator may be included in an amount of 0.1 to 10 wt% based on the total solid content weight of the hard coating composition. If the photoinitiator is less than 0.1 wt%, curing does not progress sufficiently, and improvement in the mechanical properties and adhesion of the hard coating layer formed by the hard coating composition cannot be expected. If the photoinitiator exceeds 10 wt%, poor adhesion, cracking, and curling may occur due to curing shrinkage.

[0084] Any solvent used in the art may be used without particular limitation. For example, the solvent may include alcohols such as methanol, ethanol, isopropanol, butanol, and propylene glycol methoxy alcohol; ketones such as methyl ethyl ketone, methyl butyl ketone, methyl isobutyl ketone, diethyl ketone, and dipropyl ketone; acetates such as methyl acetate, ethyl acetate, butyl acetate, and propylene glycol methoxy acetate; cellosolves such as methyl cellosolve, ethyl cellosolve, and propyl cellosolve; hydrocarbons such as n-hexane, n-heptane, benzene, toluene, and xylene; and ethers such as propylene glycol monomethyl ether. The solvent may be 5 to 90 wt% or 20 to 70 wt% based on the total weight of the hard coating composition. If the solvent content is less than 5 wt%, the viscosity of the hard coating composition may increase, reducing workability. If the solvent content exceeds 90 wt%, it is difficult to control the thickness of the hard coating layer, and dry spots may occur, resulting in a deteriorated appearance.

[0085] If desired, the hard coating composition may additionally contain inorganic particles, leveling agents, or stabilizers.

[0086] Inorganic particles can be uniformly formed in a hard coating layer formed of a hard coating composition to further improve mechanical properties such as wear resistance, scratch resistance, and pencil hardness. The inorganic particles may have an average particle diameter of 1 to 100 nm, or may be 5 to 50 nm. If the average particle diameter of the inorganic particles is less than 1 nm, agglomeration may occur within the hard coating composition, making it impossible to form a uniform hard coating layer. In addition, if the average particle diameter of the inorganic particles exceeds 100 nm, the optical properties and mechanical properties of the hard coating layer may deteriorate. The inorganic particles may be metal oxides. For example, the inorganic particles may be Al2O3, SiO2, ZnO, ZrO2, BaTiO3, TiO2, Ta2O5, Ti3O5, ITO, IZO, ATO, ZnO-Al, Nb2O3, SnO, MgO, or a combination thereof. For example, the inorganic particles may be Al2O3, SiO2, ZrO2, or a combination thereof. The inorganic particles may be present in an amount of 5 to 40 wt%, or 6 to 35 wt%, based on the total weight of the solid content of the hard coating composition. If the inorganic particles are present in an amount of less than 5 wt%, the mechanical properties of the hard coating composition, such as abrasion resistance, scratch resistance, and pencil hardness, may not be improved. If the inorganic particles are present in an amount exceeding 40 wt%, the curability of the hard coating composition may be hindered, resulting in a deterioration in the mechanical properties and a deterioration in the appearance of the hard coating layer. If the inorganic particles are present in an amount exceeding 40 wt%, the curability of the hard coating composition may be hindered, resulting in a deterioration in the mechanical properties and a deterioration in the appearance of the hard coating layer.

[0087] A leveling agent is added to improve the smoothness and applicability of the coating film when applying the composition, and a silicone leveling agent, a fluorine-based leveling agent, an acrylic leveling agent, etc. can be used. The leveling agent can be included in an amount of 3 to 5 wt% based on the total weight of the hard coating composition.

[0088] Stabilizers can be divided into UV stabilizers and heat stabilizers.

[0089] Since the surface of the hard coating composition cured by continuous exposure to ultraviolet rays decomposes, discolors, and crumbles, a UV stabilizer can be used to protect the surface of the coating by blocking or absorbing ultraviolet rays.

[0090] UV stabilizers can be categorized into absorbers, quenchers, and hindered amine light stabilizers (HALS) based on their mechanism of action. Furthermore, they can be categorized based on their chemical structure into phenyl salicylate absorbers, benzophenone absorbers, benzotriazole absorbers, nickel derivative quenchers, and radical scavengers. There are no particular limitations on the type of UV stabilizer, as long as it does not significantly alter the initial color of the hard coating layer formed using the hard coating composition.

[0091] Heat stabilizers are commercially applicable products, and the primary heat stabilizers are polyphenol-based, and the secondary heat stabilizers are phosphite-based and lactone-based, which can be used alone or in combination. The UV stabilizers and heat stabilizers can be used by adjusting the content appropriately so as not to affect UV curability, and can be included in an amount of 0.1 to 3 wt% based on the total weight of the hard coating composition.

[0092] The method for applying the hard coating layer is not particularly limited, but examples thereof include die coaters such as fountain dies and slot dies, roll coaters such as gravure coaters and comma coaters, bar coaters, dip coaters, spin coaters, and spray coaters.

[0093] Examples of the active energy rays irradiated during photocuring include visible light, ultraviolet rays, infrared rays, X-rays, α-rays, β-rays, γ-rays, and electron rays. Ultraviolet rays may be used as the active energy ray because it has a high curing reaction speed and excellent energy efficiency. The accumulated irradiation dose of the active energy ray is, for example, approximately 50 to 10,000 mJ / cm2, and can be set according to the type and mixing amount of the photopolymerization initiator, the thickness of the hard coating layer, etc.

[0094] The temperature during photocuring may be 35°C or higher to reduce the amount of curl, and the temperature during photocuring may be 150°C or lower to avoid reducing transparency due to heat. In some cases, heating may be performed after photocuring to increase the curing speed and reduce uncured material, thereby suppressing changes in the amount of curl. The heating temperature may be, for example, 35°C to 180°C. The heating time may be, for example, about 10 seconds to 60 minutes.

[0095] Next, a first conductive oxide layer, a metal layer, and a second conductive oxide layer are sequentially formed by depositing on one side of the hard coating layer opposite the substrate. Any deposition method available in the relevant technical field can be used. For example, sputtering, magnetron sputtering, etc. can be used as the deposition method.

[0096] Finally, a step of arranging an electrode layer so as to be in contact with the substrate, the hard coating layer, the first conductive oxide layer, the metal layer, and the second conductive oxide layer is included. The electrode layer may be formed using, but is not limited to, a transparent metal such as Cu, Ag, nanowires / paste, an oxide transparent electrode such as ITO, ZnO, SnO2, or a non-oxide transparent electrode such as carbon nanotubes or graphene.

[0097]

[0098] Hereinafter, the present invention will be described in more detail by way of examples, but the scope of the present invention is not limited by the examples.

[0099]

[0100] [Example]

[0101]

[0102] Example 1: Preparation of a surface heating element

[0103] A polyethylene terephthalate (PET) transparent substrate with a thickness of approximately 125 μm was prepared.

[0104] Separately, 100 parts by weight of UV-curable acrylate resin (solid content 100 wt%, EA-4000, Kellon), and 1-hydroxy-cyclohexyl-phenyl ketone photoinitiator (Irgacure ® A mixture of 5 parts by weight of 184, Ciba was diluted with a propylene glycol monomethyl ether solvent to prepare a composition for forming a hard coating layer having a solid content of 30% by weight.

[0105] The composition for forming the hard coating layer is applied to one side of the substrate using a bar coater, dried at 80°C for 1 minute, and then exposed to 300 mJ / cm2 using a high-pressure mercury ultraviolet lamp. 2 A hard coating layer of approximately 1 μm in thickness was formed by irradiating and photocuring under the conditions of accumulated light intensity.

[0106] A magnetron sputtering process was performed on the upper surface of the hard coating layer using an 8-inch ZTO (zinc tin oxide, ZnO: SnO2 weight ratio = 9: 1) Ag (purity 99.99%) target. A structure was manufactured in which a first conductive oxide layer with a thickness of about 40 nm, a metal layer with a thickness of about 12 nm, and a second conductive oxide layer with a thickness of about 40 nm were sequentially formed on the upper surface of the hard coating layer by depositing ZTO / Ag / ZTO.

[0107] At this time, the magnetron sputtering process was performed as follows.

[0108] High-purity Ar gas of 50 sccm was injected into the chamber at room temperature. 300 W of RF power was supplied to the ZTO (zinc tin oxide, ZnO: SnO2 weight ratio = 9: 1) target, and 400 W of DC power was supplied to the Ag (99.99% purity) target. The substrate was rotated at a speed of 5 rpm to control the uniformity of the thin film.

[0109] As shown in Fig. 2, the upper and lower ends of the structure were respectively connected and attached with Cu tape so as to be in contact with the substrate, the hard coating layer, the first conductive oxide layer, the metal layer, and the second conductive oxide layer, thereby forming an electrode layer. A planar heating element was manufactured comprising a structure of substrate (approximately 125 μm) / hard coating layer (approximately 1 μm) / first conductive oxide layer (approximately 40 nm) / metal layer (approximately 12 nm) / second conductive oxide layer (approximately 40 nm) and an electrode layer in contact with these structures.

[0110]

[0111] Example 2: Preparation of a surface heating element

[0112] A planar heating element was manufactured by using a structure of substrate (about 50 μm) / hard coating layer (about 1 μm) / first conductive oxide layer (about 40 nm) / metal layer (about 12 nm) / second conductive oxide layer (about 40 nm) and an electrode layer in contact with these structures in the same manner as in Example 1, except that a polyethylene terephthalate (PET) transparent substrate with a thickness of about 50 μm was used and a hard coating layer with a thickness of about 3 μm was formed.

[0113]

[0114] Example 3: Preparation of a surface heating element

[0115] A planar heating element was manufactured by the same method as Example 1, except that a hard coating layer having a thickness of about 3 μm was formed, and comprising a structure of a substrate (about 125 μm) / hard coating layer (about 3 μm) / first conductive oxide layer (about 40 nm) / metal layer (about 12 nm) / second conductive oxide layer (about 40 nm) and an electrode layer in contact with these structures.

[0116]

[0117] Example 4: Preparation of a surface heating element

[0118] A planar heating element was manufactured by using a structure of a substrate (about 200 μm) / hard coating layer (about 1 μm) / first conductive oxide layer (about 40 nm) / metal layer (about 12 nm) / second conductive oxide layer (about 40 nm) and an electrode layer in contact with these structures in the same manner as in Example 1, except that a polyethylene terephthalate (PET) transparent substrate having a thickness of about 200 μm was used.

[0119]

[0120] Example 5: Preparation of a surface heating element

[0121] A planar heating element was manufactured by the same method as Example 1, except that a hard coating layer having a thickness of about 5 μm was formed, and comprising a structure of a substrate (about 125 μm) / hard coating layer (about 5 μm) / first conductive oxide layer (about 40 nm) / metal layer (about 12 nm) / second conductive oxide layer (about 40 nm) and an electrode layer in contact with these structures.

[0122]

[0123] Example 6: Preparation of a surface heating element

[0124] A surface heating element was manufactured by the same method as Example 1, except that the thickness of the second conductive oxide layer was formed to be about 70 nm, and comprised of a structure of substrate (about 125 μm) / hard coating layer (about 1 μm) / first conductive oxide layer (about 40 nm) / metal layer (about 12 nm) / second conductive oxide layer (about 70 nm) and an electrode layer in contact with these structures.

[0125]

[0126] Example 7: Preparation of a surface heating element

[0127] A surface heating element was manufactured by the same method as Example 1, except that the thickness of the metal layer was formed to be about 20 nm, and comprised of a structure of a substrate (about 125 μm) / hard coating layer (about 1 μm) / first conductive oxide layer (about 40 nm) / metal layer (about 20 nm) / second conductive oxide layer (about 40 nm) and an electrode layer in contact with these structures.

[0128]

[0129] Example 8: Preparation of a surface heating element

[0130] A surface heating element was manufactured by the same method as Example 1, except that the thickness of the metal layer was formed to be about 7 nm, and comprised of a structure of a substrate (about 125 μm) / hard coating layer (about 1 μm) / first conductive oxide layer (about 40 nm) / metal layer (about 20 nm) / second conductive oxide layer (about 40 nm) and an electrode layer in contact with these structures.

[0131]

[0132] Comparative Example 1: Manufacturing of a surface heating element

[0133] A planar heating element was manufactured by using a structure of a substrate (about 25 μm) / hard coating layer (about 1 μm) / first conductive oxide layer (about 40 nm) / metal layer (about 12 nm) / second conductive oxide layer (about 40 nm) and an electrode layer in contact with these structures in the same manner as in Example 1, except that a polyethylene terephthalate (PET) transparent substrate having a thickness of about 25 μm was used.

[0134]

[0135] Comparative Example 2: Manufacturing of a Planar Heating Element

[0136] A planar heating element was manufactured by the same method as Example 1, except that a hard coating layer was not formed, and the structure was composed of a substrate (about 125 μm) / first conductive oxide layer (about 40 nm) / metal layer (about 12 nm) / second conductive oxide layer (about 40 nm) and an electrode layer in contact with these structures.

[0137]

[0138] Comparative Example 3: Manufacturing of a Planar Heating Element

[0139] A planar heating element was manufactured by the same method as Example 1, except that a hard coating layer having a thickness of about 0.05 μm was formed, and comprising a structure of a substrate (about 125 μm) / hard coating layer (about 0.05 μm) / first conductive oxide layer (about 40 nm) / metal layer (about 12 nm) / second conductive oxide layer (about 40 nm) and an electrode layer in contact with these structures.

[0140]

[0141] Comparative Example 4: Manufacturing of a surface heating element

[0142] A planar heating element was manufactured by the same method as Example 1, except that a hard coating layer having a thickness of about 8 μm was formed, and comprising a structure of a substrate (about 125 μm) / hard coating layer (about 8 μm) / first conductive oxide layer (about 40 nm) / metal layer (about 12 nm) / second conductive oxide layer (about 40 nm) and an electrode layer in contact with these structures.

[0143]

[0144] Comparative Example 5: Manufacturing of a Planar Heating Element

[0145] A planar heating element was manufactured by the same method as Example 1, except that the second conductive oxide layer was not formed, and comprised of a structure of a substrate (about 125 μm) / hard coating layer (about 1 μm) / first conductive oxide layer (about 40 nm) / metal layer (about 12 nm) and an electrode layer in contact with these structures.

[0146]

[0147] Comparative Example 6: Manufacturing of a surface heating element

[0148] A surface heating element was manufactured by the same method as Example 1, except that the thickness of the second conductive oxide layer was formed to be about 100 nm, and comprised of a structure of substrate (about 125 μm) / hard coating layer (about 1 μm) / first conductive oxide layer (about 40 nm) / metal layer (about 12 nm) / second conductive oxide layer (about 100 nm) and an electrode layer in contact with these structures.

[0149]

[0150] Comparative Example 7: Manufacturing of a surface heating element

[0151] A surface heating element was manufactured by the same method as Example 1, except that the thickness of the metal layer was formed to 30 nm, and comprised of a structure of a substrate (about 125 μm) / hard coating layer (about 1 μm) / first conductive oxide layer (about 40 nm) / metal layer (about 12 nm) / second conductive oxide layer (about 40 nm) and an electrode layer in contact with these structures.

[0152]

[0153] Comparative Example 8: Manufacturing of a surface heating element

[0154] A planar heating element was manufactured by the same method as Example 1, except that the structure was formed with ITO 150 nm instead of ZTO / Ag / ZTO, and comprised of a structure of substrate (about 125 μm) / hard coating layer (about 1 μm) / ITO layer (about 150 nm) and an electrode layer in contact with these structures.

[0155]

[0156] Comparative Example 9: Manufacturing of a surface heating element

[0157] A surface heating element was manufactured by the same method as Example 1, except that the thickness of the metal layer was formed to be 5 nm, and comprised of a structure of a substrate (about 125 μm) / hard coating layer (about 1 μm) / first conductive oxide layer (about 40 nm) / metal layer (about 12 nm) / second conductive oxide layer (about 40 nm) and an electrode layer in contact with these structures.

[0158]

[0159] Evaluation Example 1: Physical Property Evaluation

[0160] The physical properties of the surface heating elements manufactured in Examples 1 to 8 and Comparative Examples 1 to 9 were evaluated as follows. The results are shown in Tables 1 and 2 below, respectively.

[0161]

[0162] (1) Stiffness of substrate (N / mm) - Compatibility of planar heating element

[0163] The stiffness of each planar heating element was measured to evaluate the compatibility of the planar heating element. The stiffness was measured using a bending / stiffness tester (4171S, Thwing-Albert).

[0164] (2) Thickness of hard coating layer (㎛)

[0165] The thickness of the hard coating layer was measured for each surface heating element. The thickness of the hard coating layer was measured five times using a micrometer (Mitutoyo), and the average value was calculated.

[0166] (3) Surface resistance change rate (%) - Corrosion resistance

[0167] For each surface heating element, the surface resistance was measured three times before and after leaving it for 360 hours at 85°C and 85% relative humidity using a temperature and humidity chamber (PR-1J, ESPEC), and the average value was calculated. The surface resistance was measured using a 4-point probe (RC2175, EDTM).

[0168] From this, the change rate of surface resistance for each surface heating element was calculated according to the following equation 1-1, and the corrosion resistance of the surface heating element was evaluated:

[0169] [Formula 1-1]

[0170] [(AB) / A] x 100

[0171] Among the foods,

[0172] A is the surface resistance (Ω / □) before being left for 360 hours at 85℃ and 85% relative humidity,

[0173] B is the surface resistance (Ω / □) after being left for 360 hours at 85℃ and 85% relative humidity.

[0174] (4) Visible light transmittance (%) and haze

[0175] Each surface heating element was cut into 4 cm x 4 cm samples. Visible light transmittance and haze were measured for the samples. Visible light transmittance and haze were measured using a haze meter (NDH-5000W, NIPPON DENSHOKU).

[0176] (5) Average curl height (cm)

[0177] Each surface heating element was cut into a size of 10 cm x 10 cm to make a sample. The sample was placed on a stone plate, and the height of the curl generated from the floor at the four vertices was measured using a steel ruler, and the average value was obtained.

[0178] (6) Whether or not thermal wrinkles occur

[0179] The appearance of each surface of the heating element was observed and the occurrence of thermal wrinkles was determined using the following criteria.

[0180] O: One or more thermal wrinkles occur

[0181] X: No thermal wrinkles

[0182] (7) Surface resistance according to metal layer thickness

[0183] When depositing the metal layer of each planar heating element, samples were prepared by varying the deposition time under the same conditions. For the above samples, the surface resistance was measured three times using a 4-point probe (RC2175, EDTM) to determine the change in surface resistance according to the metal layer thickness.

[0184] (8) Fever temperature

[0185] Each surface heating element was cut to a size of 10 cm x 10 cm to create a sample. A voltage of 8 V was applied to the electrodes of the sample using a power supply (ex-60, ODA), and the heating temperature was measured using an infrared camera (E76, FLIR).

[0186]

[0187]

[0188] Referring to Table 1, the planar heaters manufactured by Examples 1 to 8 had a substrate thickness of 50 μm to 200 μm, a substrate rigidity of 5.11 N / mm to 80.71 N / mm, a hard coating layer thickness of 1 μm to 5 μm, a metal layer thickness of 7 nm to 20 nm, and a second conductive oxide layer thickness of 40 nm to 70 nm. In addition, the planar heaters manufactured by Examples 1 to 8 had a surface resistance change rate of 0% under a high-temperature and high-humidity environment, a heating temperature of 45 ℃ to 150 ℃ after application of 8 V voltage, a visible light transmittance of 62.1% to 85.1%, a haze of 0.69 to 1.1, an average curl height of 3.3 cm, and no thermal wrinkles occurred.

[0189] Referring to Table 2, the planar heater manufactured by Comparative Example 1 had a substrate thickness of 25 μm, a substrate rigidity of 2.57 N / mm, and thermal wrinkles occurred on the surface. The planar heaters manufactured by Comparative Examples 2 and 3 were planar heaters that did not include a hard coating layer or had a thin thickness of 0.05 μm, and thus, under a high temperature and high humidity environment, the surface resistance change rates were high at 37% and 34%, respectively, which did not prevent corrosion, and the haze increased to 1.41 and 1.37, respectively, which reduced visibility. The planar heater manufactured by Comparative Example 4 was a planar heater that had a thick hard coating layer of 8 μm, and the average curl height increased to 19.2 cm, which reduced the lamination properties of the planar heater. The planar heater manufactured by Comparative Example 5 was a planar heater that did not include a second conductive oxide layer, and under a high temperature and humidity environment, the change rate of surface resistance rapidly increased to 16437%, and the visible light transmittance decreased to 59.5%. This is thought to be due to the failure to inhibit corrosion due to the absence of the second conductive oxide layer, which acts as a protective film to prevent corrosion and light scattering. The planar heater manufactured by Comparative Example 6 had a second conductive oxide layer that was 100 nm thick, and the visible light transmittance significantly decreased to 56.9% due to the absorption of visible light by the second conductive oxide layer. The planar heater manufactured by Comparative Example 7 had a metal layer that was 30 nm thick, and the surface resistance before and after standing decreased to 0.7 Ω / □, but the visible light transmittance significantly decreased to 16.3% due to the absorption of visible light by the metal layer. The surface heating element manufactured by Comparative Example 8 was a heating element using ITO with a thickness of 150 nm instead of the first conductive oxide layer / metal layer / second conductive oxide layer structure on the hard coating layer, and the surface resistance before and after leaving was high at 126.5 Ω / □ and 114.5 Ω / □, and the heating temperature after applying 8 V voltage was low at 24.8 ℃ and the haze was high at 3.6.The surface heating element manufactured by Comparative Example 9 had a thin metal layer of 5 nm, and the surface resistance and surface resistance change rate before and after standing were very high at 31.3 Ω / □, 817.3 Ω / □, and 2611%, respectively. After applying a voltage of 8 V, the heating temperature was low at 32.6 ℃, and the haze was high at 5.2.

[0190] From this, it can be confirmed that the planar heating element manufactured by Examples 1 to 8 satisfies all of the following characteristics: improved transmittance, excellent heating efficiency even under low voltage, stable corrosion resistance even under high temperature and high humidity environments, low curl height, and no occurrence of thermal wrinkles.

Claims

1. Substrate; A hard coating layer positioned on the upper portion of the substrate; A first conductive oxide layer positioned on top of the hard coating layer; A metal layer positioned on top of the first conductive oxide layer; a second conductive oxide layer positioned on top of the metal layer; and A surface heating element comprising an electrode layer arranged to be in contact with the substrate, the hard coating layer, the first conductive oxide layer, the metal layer, and the second conductive oxide layer.

2. In paragraph 1, A planar heating element, wherein the hard coating layer comprises at least one type of resin selected from an acrylate resin, a thiol resin, a urethane resin, and an epoxy resin.

3. In paragraph 1, A planar heating element having a thickness of the hard coating layer of 0.1 ㎛ to 5 ㎛.

4. In paragraph 1, A planar heating element, wherein the metal layer is a metal selected from Ag, Au, Pt, Al, Cu, Cr, V, Mg, Ti, Sn, Pb, Pd, W or an alloy thereof.

5. In paragraph 1, A planar heating element, wherein the first conductive oxide layer and the second conductive oxide layer are oxides selected from ZTO (zinc tin oxide), IGZO (indium gallium zinc oxide), ZAO (zinc aluminum oxide), IZO (indium zinc oxide), ZnO (zinc oxide), and combinations thereof.

6. In paragraph 1, A planar heating element, wherein the thicknesses of the first conductive oxide layer and the second conductive oxide layer are each less than 30 nm to 100 nm.

7. In paragraph 1, The above substrate is a transparent substrate and is a planar heating element having a thickness of 50 ㎛ to 200 ㎛.

8. In paragraph 1, A surface heating element having a surface resistance of 20 Ω / □ or less at room temperature.

9. In paragraph 1, A surface heating element whose surface resistance change rate before and after being left for 360 hours under 85℃ and 85% relative humidity satisfies the following equation 1: [Formula 1] [(AB) / A] x 100 ≤ 3% Among the foods, A is the surface resistance (Ω / □) before being left for 360 hours at 85℃ and 85% relative humidity, B is the surface resistance (Ω / □) after being left for 360 hours at 85℃ and 85% relative humidity.

10. In paragraph 1, A surface heating element having a visible light transmittance of 60% or more and a haze of 1.1 or less.

11. An article comprising a surface heating element according to any one of paragraphs 1 to 10.

12. Step for preparing the substrate; A step of applying a composition for forming a hard coating layer to one surface of the substrate and photocuring it to form a hard coating layer; A step of sequentially forming a first conductive oxide layer, a metal layer, and a second conductive oxide layer by depositing the hard coating layer on one side opposite to the substrate; and A method for manufacturing a surface heating element, comprising: a step of arranging an electrode layer so as to be in contact with the substrate, the hard coating layer, the first conductive oxide layer, the metal layer, and the second conductive oxide layer.

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