Transparent substrate provided with a multiplayer thin film coating having improved thermal and chemical stability

Abstract

The present invention relates to a transparent substrate having a multilayer thin film coating, wherein the multilayer thin film coating comprises an infrared reflective layer and a metal oxide layer, the metal oxide layer is disposed in direct contact with at least one of the two sides of the infrared reflective layer, the infrared reflective layer comprises a silver alloy, the silver alloy comprises a resistant metal, and the metal oxide layer is made of an oxide of a metal comprising a resistant metal.

Description

Technology Field

[0001] The present invention relates to a transparent substrate having a multilayer thin film coating. In particular, it relates to a transparent substrate having a multilayer thin film coating comprising an infrared reflective layer having improved thermal and chemical stability, and a multi-glazing unit comprising such transparent substrate. Background Technology

[0002] Low-emissivity glass, or Low-E glass, features a multilayer thin-film coating containing a low-emissivity layer composed of a metal with high reflectivity in the infrared region, such as silver (Ag). Since this low-emissivity glass can reflect infrared radiation among incident rays, it is a functional building material that brings about energy savings in buildings by blocking solar radiation entering the interior in summer and conserving heating radiation escaping to the exterior in winter. Emissivity indicates the degree to which glass reflects infrared energy of long wavelengths (2,500 to 40,000 nm); the lower the emissivity, the better the infrared reflection, reflecting more infrared energy. Consequently, heat transfer is reduced, the thermal transmittance is lowered, and the insulation effect is enhanced. For example, while ordinary uncoated glass has an emissivity of approximately 0.84, low-emissivity glass can have an emissivity of approximately 0.10.

[0003] In general, low-emissivity glass, which uses glass as a transparent substrate, can use metals such as gold, silver, and aluminum as the material for the low-emissivity layer; however, silver is mainly used considering its high infrared reflectivity and visible light transmission performance. However, low-emissivity layers using silver have the disadvantage that they oxidize easily in the external air, causing a rapid decrease in infrared reflection properties or a change in the color of the coating. Silver oxidation can also easily occur during the glass strengthening process, which requires high-temperature heat treatment of 600 to 700 degrees. Furthermore, low-emissivity layers using silver can react with sulfide gases in the air to turn the surface black, or can be easily corroded by acid rain containing salt or with a low pH.

[0004] Conventionally, to protect such silver-based low-emissivity layers, a metal protective layer such as NiCr and a dielectric stack were laminated on both sides of the low-emissivity layer to prevent oxidation of the silver. However, metals such as NiCr have the problem of absorbing infrared radiation and negatively affecting emissivity. Additionally, the dielectric stack includes a zinc oxide layer as a dielectric layer for crystal growth to promote silver crystallization and lower emissivity; however, since the zinc oxide layer is sensitive to acids and moisture and can negatively affect the stability of the low-emissivity glass, it is desirable to avoid using such a zinc oxide layer.

[0005] FIG. 1 illustrates a cross-sectional view of low-emissivity glass having a multilayer thin film coating (10) according to the prior art.

[0006] In the prior art, silver (Ag) is used as an infrared reflective layer (11), and a metal protective layer (12) is placed on both sides or one side of the infrared reflective layer (11) to prevent oxidation or corrosion of the silver. The metal protective layer (12) is made of a metal or alloy including titanium, nickel, chromium, and niobium, and a nickel-chromium alloy is mainly used.

[0007] The multilayer thin film coating (10) has dielectric stacks (13) placed on both sides of an infrared reflective layer (11), and the dielectric stacks (13) are composed of a plurality of dielectric layers composed of metal oxide, metal nitride, or metal oxynitride, so that the optical properties of the multilayer thin film coating or stress within the thin film can be controlled.

[0008] Additionally, the dielectric stack (13) disposed between the transparent substrate (G) and the infrared reflective layer (11) may include a zinc oxide layer, and the zinc oxide layer can further lower the emissivity by promoting the crystal growth of the silver layer. However, as described above, such a zinc oxide layer has the disadvantage of being sensitive to acid and moisture.

[0009] In addition, in conventional technology, transparent conductive oxides (TCOs) are sometimes used as a substitute for silver used in infrared reflective layers. Transparent conductive oxides refer to oxides that are optically transparent while possessing electrical conductivity; they are commonly used as materials for transparent electrodes and include ITO, FTO, and AZO. Due to their excellent optical and electrical properties, transparent conductive oxides can also be used as the low-emissivity layer in low-emissivity glass. However, these transparent conductive oxides have very high resistivity compared to metals such as silver, and since an average grain size of 257 nm is required for ITO and 190 nm for FTO, there is a problem in that a thickness more than 20 times greater than that of silver must be stacked to achieve the electrical resistance characteristics required for the low-emissivity layer. Furthermore, in the case of ITO, resistance increases sharply when heat-treated at temperatures above 200°C, making it unsuitable for applications requiring a strengthening process through heat treatment. The problem to be solved

[0010] The present invention aims to solve the aforementioned problems by providing a transparent substrate equipped with a multilayer thin film coating that improves the thermal and chemical stability of low-emissivity glass without reducing infrared reflection performance. means of solving the problem

[0011] A transparent substrate according to the present invention comprises a multilayer thin film coating, wherein the multilayer thin film coating includes an infrared reflective layer and a metal oxide layer, and the metal oxide layer is disposed in direct contact with at least one of the two sides of the infrared reflective layer. The infrared reflective layer comprises a silver alloy, the silver alloy comprises a resistant metal, and the metal oxide layer may be composed of an oxide of a metal comprising a resistant metal.

[0012] The resistant metal may include at least one of indium (In), titanium (Ti), gold (Au), platinum (Pt), palladium (Pd), copper (Cu), and nickel (Ni).

[0013] Preferably, the resistant metal is indium, and the silver alloy may contain 2 to 10 weight percent of indium based on the total weight.

[0014] Preferably, the resistant metal is titanium, and the silver alloy may contain 4 to 15 weight percent of titanium based on the total weight.

[0015] The thickness of the infrared reflective layer may be 1 to 30 nm, and the thickness of the metal oxide layer may be 5 to 30 nm.

[0016] According to one embodiment of the present invention, the multilayer thin film coating may further include a dielectric stack comprising at least one dielectric layer.

[0017] A dielectric stack may include a first dielectric stack and a second dielectric stack, the first dielectric stack may be disposed between a transparent substrate and an infrared reflective layer, and the second dielectric stack may be disposed on the opposite side of the transparent substrate with respect to the infrared reflective layer.

[0018] The dielectric layer may be composed of an oxide layer, a nitride layer, or an oxynitride layer containing one or more of titanium (Ti), hafnium (Hf), zirconium (Zr), niobium (Nb), zinc (Zn), bismuth (Bi), tin (Sn), and silicon (Si).

[0019] The multilayer thin film coating may include an additional infrared reflective layer. A multi-glazing unit comprising a transparent substrate having the aforementioned multilayer thin film coating can be formed. Effects of the invention

[0020] A transparent substrate having a multilayer thin film coating according to the present invention can maintain excellent infrared reflection capabilities while having improved thermal and chemical stability. Brief explanation of the drawing

[0021] FIG. 1 is a cross-sectional view of low-emissivity glass having a multilayer thin film coating according to the prior art. FIG. 2 is a cross-sectional view of a transparent substrate having a multilayer thin film coating according to an embodiment of the present invention. FIG. 3 is a cross-sectional view of a low-emissivity glass having a multilayer thin film coating including an additional infrared reflective layer according to an embodiment of the present invention. Figure 4 is a graph showing the change in resistance according to the doping ratio of the resistant metal. Figure 5 is a surface microscope image of a multilayer thin film coating before heat treatment. Figure 6 is a surface microscope image of a multilayer thin film coating after heat treatment. Specific details for implementing the invention

[0022] Hereinafter, embodiments according to the present invention are described in detail with reference to the attached drawings so that a person skilled in the art can easily practice the invention. However, the present invention may be embodied in various other forms and is not limited to the embodiments described herein.

[0023] To clearly explain the present invention, parts unrelated to the description have been omitted, and throughout the specification, the same or similar reference numerals are used for identical or similar components.

[0024] In addition, the size and thickness of each component shown in the drawing are arbitrarily represented for convenience of explanation, and the thickness of each layer is exaggerated.

[0025] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the content of this disclosure and are not interpreted in an ideal or highly formal sense unless otherwise defined.

[0026] Terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. That is, these terms are used solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section without departing from the scope of the present invention.

[0027] The technical terms used herein are for the reference of specific embodiments only and are not intended to limit the invention. The singular forms used herein include plural forms unless phrases clearly indicate otherwise. As used in the specification, the meaning of "comprising" specifies certain characteristics, areas, integers, steps, actions, elements, and / or components, and does not exclude the presence or addition of other characteristics, areas, integers, steps, actions, elements, and / or components.

[0028] When it is stated that one part is "on" or "on" another part, it may be directly on or on the other part, or there may be other parts interposed between them. In contrast, when it is stated that one part is "immediately on" or "directly on" another part, no other parts are interposed between them.

[0029] In this invention, the terms "emissivity" and "transmittance" are used as commonly known in the art. "Emissivity" is a measure indicating how much light at a given wavelength is absorbed and reflected. Generally, it satisfies the following equation.

[0030] (Emissivity) = 1 - (Reflectivity)

[0031] In architectural glass, the emissivity of the infrared spectrum, approximately 2500 to 50000 nm, is of significant importance.

[0032] FIG. 2 illustrates a cross-sectional view of a transparent substrate having a multilayer thin film coating (100) according to the present invention.

[0033] The transparent substrate (G) is not particularly limited, but is preferably made of a hard inorganic material such as glass or an organic material of a polymer substrate.

[0034] The infrared reflective layer (110) may include gold (Ag), copper (Cu), palladium (Pd), aluminum (Al), and silver (Ag) having infrared (IR) reflective properties. Specifically, the infrared reflective layer (110) includes a silver alloy, and the silver alloy is preferably an alloy based on silver that is doped with a predetermined resistant metal.

[0035] The resistant metal includes at least one of indium (In), titanium (Ti), gold (Au), platinum (Pt), palladium (Pd), copper (Cu), and nickel (Ni). Although the resistant metal increases the thermal and chemical stability of the infrared reflective layer, it can increase surface resistance and negatively affect infrared reflection performance, so it is necessary to control the proportion included in the alloy.

[0036] FIG. 4 shows the change in resistance according to the proportion of resistant metals included in the silver alloy. Generally, commercially available low-emissivity glass has a normalized resistivity (NR) of 40 to 80, but as can be seen in FIG. 4, the resistance increases to about 100 for an alloy containing 4 wt% indium and to about 150 for an alloy containing 6 wt% titanium. Therefore, in the case of a silver-indium alloy, it is preferable to include at least 2 wt% indium relative to the total weight of the alloy, with upper limits of 10 wt% or less, 8 wt% or less, 6 wt% or less, or 4 wt% or less. Meanwhile, in the case of a silver-titanium alloy, it is preferable to include at least 4 wt% titanium relative to the total weight of the alloy, with upper limits of 15 wt% or less, 12 wt% or less, 10 wt% or less, 8 wt% or less, or 6 wt% or less.

[0037] The thickness of the infrared reflective layer (110) may be 1 to 30 nm. If the thickness of the infrared reflective layer (110) is too thin, there may be insufficient infrared reflection, which may result in a higher solar heat gain coefficient (SHGC), and if the thickness is too thick, the transmitted color may move away from blue in the color coordinates and exhibit an undesirable color.

[0038] The multilayer thin film coating (100) includes a metal oxide layer, and the metal oxide layer may be disposed in direct contact with at least one of the two sides of the infrared reflective layer. The thickness of the metal oxide layer may be 5 to 30 nm.

[0039] In the embodiment illustrated in FIG. 2, two metal oxide layers are included, wherein the first metal oxide layer (121) is disposed in direct contact with the lower surface of the infrared reflective layer (110), and the second metal oxide layer (122) is disposed in direct contact with the upper surface of the infrared reflective layer (110). The metal oxide layer may be composed of an oxide of a resistant metal doped into the silver alloy of the infrared reflective layer (110). For example, if the silver alloy is doped with indium, the metal oxide layer may be composed of indium tin oxide (ITO), and if the silver alloy is doped with titanium, the metal oxide layer may be composed of titanium dioxide (TiO2). When the same metal is used for the infrared reflective layer and the metal oxide layer, it is possible to ensure the thermal and chemical stability of the infrared reflective layer while simultaneously minimizing the increase in emissivity caused by increased resistance compared to pure silver. That is, since the infrared reflective layer and the metal oxide layer have the same metal element, the resistance metal migrates preferentially over silver (Ag) due to the common element effect, thereby suppressing the oxidation of silver. Therefore, when the metal oxide layer is placed in direct contact with the infrared reflective layer, it is possible to protect the infrared reflective layer without using a conventional metal protective layer (NiCr).

[0040] The multilayer thin film coating (100) may include a dielectric stack comprising at least one dielectric layer. The dielectric layer may be composed of an oxide layer, a nitride layer, or an oxynitride layer comprising one or more of titanium (Ti), hafnium (Hf), zirconium (Zr), niobium (Nb), zinc (Zn), bismuth (Bi), tin (Sn), and silicon (Si). For example, the dielectric layer may include silicon nitride (Si3N4). The dielectric stack may be 5 to 50 nm in size.

[0041] In the embodiment illustrated in FIG. 2, the multilayer thin film coating (100) comprises a first dielectric stack (131) and a second dielectric stack (132), the first dielectric stack (131) is positioned between a transparent substrate (G) and an infrared reflective layer (110), and the second dielectric stack (132) is positioned on the opposite side of the transparent substrate (G) with respect to the infrared reflective layer (110). The second dielectric stack (132) may be thicker than the first dielectric stack (131), for example, the thickness ratio of the second dielectric stack (132) to the first dielectric stack (131) may be 1.1:1 to 1.4:1. In this way, by adjusting the thickness ratio of the first dielectric layer (131) and the second dielectric layer (132), it is possible to control the optical properties of the transparent substrate by controlling the reflective color of the multilayer thin film coating or by increasing the visible light transmittance.

[0042] According to one embodiment of the present invention, the multilayer thin film coating may include an additional infrared reflective layer. In the embodiment illustrated in FIG. 3, the multilayer thin film coating (200) includes two infrared reflective layers (210). A metal oxide layer (220) is disposed on both sides of each infrared reflective layer (210). A dielectric stack (230) comprising at least one dielectric layer is disposed between the transparent substrate (G) and the lower infrared reflective layer, between the lower infrared reflective layer and the upper infrared reflective layer, and above the upper infrared reflective layer, respectively, so as to control the optical properties of the multilayer thin film coating or control stress within the thin film.

[0044] Performance comparison experiment

[0045] To compare the chemical resistance, thermal stability, and resistance of thin film multilayer coatings, thin film multilayer coatings were formed on a transparent substrate with a stacked structure as shown in Table 1 below. A 5 mm thick clear glass (manufactured by LX Glass) was used as the transparent substrate.

[0046] division Stacked structure (nm) Comparative Example 1 Glass / ITO (158) Comparative Example 2 Glass / FTO(600) Comparative Example 3 Glass / Ag(30) Comparative Example 4 Glass / ITO(10) / Ag(30) / ITO(10) Comparative Example 5-1 Glass / Ag98In2(30) Comparative Example 5-2 Glass / Ag96In4(30) Comparative Example 5-3 Glass / Ag92In8(30) Comparative Example 5-4 Glass / Ag98Ti2(30) Comparative Example 5-5 Glass / Ag94Ti6(30) Comparative Examples 5-6 Glass / Ag88Ti12(30) Example 1 Glass / ITO(10) / Ag98In2(30) / ITO(10) Example 2 Glass / ITO(10) / Ag96In4(30) / ITO(10) Example 3 Glass / ITO(10) / Ag92In8(30) / ITO(10) Example 4 Glass / TiO2(10) / Ag94Ti6(30) / TiO2(10)

[0047] Comparative Example 1 used a product from Geomatec, and Comparative Example 2 used a product from Pilkington. Comparative Example 3 deposited a single film of pure Ag on clear glass using DC sputtering, and Comparative Example 4 also deposited ITO, Ag, and ITO sequentially using DC sputtering.

[0048] Comparative Examples 5-1 to 5-6 used a silver alloy as the infrared reflective layer, but did not include a metal oxide layer.

[0049] Examples 1 to 4 used a silver alloy as the infrared reflective layer, and formed oxide layers of a resistant metal doped into the silver alloy on both sides of the infrared reflective layer.

[0050] In Comparative Examples 5-1 to 5-6 and Examples 1 to 4, the proportion of the silver alloy is expressed in weight%, for example, in Comparative Example 5-1, the silver alloy consists of a weight ratio of Ag : In = 98 : 2. The numbers in parentheses indicate the thickness of each layer, and the unit is nm.

[0051] The resistance, chemical resistance, and surface quality of the comparative example and the example were evaluated before and after heat treatment, respectively.

[0052] Resistance was measured using a sheet resistance meter from NAGY, and the surface of the coating was analyzed using an Olympus U-TO0.5XC-3 microscope. To evaluate chemical resistance, each test specimen was immersed in a mixture of H2SO4 0.01N and 10 wt% NaCl aqueous solutions, and the time required for white spots and color changes to appear on the thin film surface was measured.

[0053] Table 2 shows the resistance, resistivity, and chemical resistance of each coating before heat treatment, and Table 3 shows the resistance, resistivity, and chemical resistance of each coating after heat treatment.

[0054] Before heat treatment Resistance (ohm / □) Resistivity (NR) Chemical resistance (min) Comparative Example 1 10.0 1580 Over 10,000 Comparative Example 2 13.3 7980 Over 10,000 Comparative Example 3 1.2 36 Less than 1 Comparative Example 4 1.2 36 Less than 1 Comparative Example 5-1 2.5 75 30 Comparative Example 5-2 3.5 105 30 Comparative Example 5-3 5.4 162 30 Comparative Example 5-4 1.9 57 10 Comparative Example 5-5 4.9 147 45 Comparative Examples 5-6 10.5 315 60 Example 1 2.6 78 210 Example 2 3.7 111 210 Example 3 5.0 150 330 Example 4 5.1 153 360

[0055] After heat treatment Resistance (ohm / □) Resistivity (NR) Chemical resistance (min) Comparative Example 1 51.2 8090 Over 10,000 Comparative Example 2 13.8 8280 Over 10,000 Comparative Example 3 Unmeasurable Unmeasurable Less than 1 Comparative Example 4 13.6 407 Less than 1 Comparative Example 5-1 2.7 81 45 Comparative Example 5-2 4.1 123 45 Comparative Example 5-3 6.2 186 45 Comparative Example 5-4 Unmeasurable Unmeasurable Less than 1 Comparative Example 5-5 3.1 93 180 Comparative Examples 5-6 4.5 135 Over 7200 Example 1 1.9 57 45 Example 2 2.8 84 45 Example 3 2.0 60 45 Example 4 2.3 69 Over 7200

[0056] Figures 5 and 6 show microscopic observations of the surfaces of Comparative Examples 3, 4, 5-1 to 5-6 and Examples 1 to 4, where Figure 5 shows the surface before heat treatment and Figure 6 shows the surface after heat treatment.

[0057] Comparative Examples 1 and 2 use a transparent conductive oxide as an infrared reflective layer, so although the chemical resistance is excellent, the resistance is relatively too high, making it unsuitable for use as low-emission glass.

[0058] It can be seen that in Comparative Examples 3 and 4, the silver layer is completely oxidized after heat treatment and loses its electrical properties. In particular, it can be confirmed that Comparative Example 4, despite containing an indium oxide layer, has a resistivity of approximately 1000% after heat treatment compared to before heat treatment.

[0059] Comparative Examples 5-1 to 5-6 have a silver alloy single-film coating. In the case of the silver-indium alloy, the resistivity after heat treatment increased by about 12% compared to before heat treatment, and in the case of the silver-titanium alloy, the resistivity after heat treatment generally decreased, but when containing 2 wt% titanium, the resistivity increased excessively.

[0060] In Examples 1 to 4, it was confirmed that thermal stability was improved, with the resistivity of the silver-indium alloy decreasing by about 25 to 60% after heat treatment and the resistivity of the silver-titanium alloy decreasing by about 55% after heat treatment. In particular, in the case of Example 4, it was confirmed that chemical stability was significantly increased after heat treatment. Explanation of the symbols

[0061] G: Transparent material 10: Multilayer thin film coating 11: Infrared reflective layer 12: Metal protective layer 13: Genome Stack 100: Multilayer thin film coating 131: First Genome Stack 121: First metal oxide layer 110: Infrared reflective layer 122: Second metal oxide layer 132: Second Genome Stack 200: Multilayer thin film coating 210: Infrared reflective layer 220: Metal oxide layer 230: Genome Stack

Claims

Claim 1 A transparent substrate having a multilayer thin film coating, wherein the multilayer thin film coating comprises an infrared reflective layer and a metal oxide layer, wherein the metal oxide layer is disposed in direct contact with at least one of the two sides of the infrared reflective layer, wherein the infrared reflective layer comprises a silver alloy, wherein the silver alloy comprises indium (In), and wherein the metal oxide layer is composed of indium oxide. Claim 2 A transparent substrate having a multilayer thin film coating, wherein the multilayer thin film coating comprises an infrared reflective layer and a metal oxide layer, wherein the metal oxide layer is disposed in direct contact with at least one of the two sides of the infrared reflective layer, wherein the infrared reflective layer comprises a silver alloy, wherein the silver alloy comprises titanium (Ti), and wherein the metal oxide layer is composed of titanium oxide (TiO2). Claim 3 In claim 1, the silver alloy comprises 2 to 10 weight percent of indium based on the total weight, a transparent substrate. Claim 4 In paragraph 2, the silver alloy comprises 4 to 15 weight percent of titanium with respect to the total weight, a transparent substrate. Claim 5 A transparent substrate according to claim 1 or 2, wherein the thickness of the infrared reflective layer is 1 to 30 nm. Claim 6 A transparent substrate according to claim 1 or 2, wherein the thickness of the metal oxide layer is 5 to 30 nm. Claim 7 A transparent substrate according to claim 1 or 2, wherein the multilayer thin film coating further comprises a dielectric stack comprising at least one dielectric layer. Claim 8 In claim 7, the dielectric stack comprises a first dielectric stack and a second dielectric stack, wherein the first dielectric stack is disposed between a transparent substrate and an infrared reflective layer, and the second dielectric stack is disposed on the opposite side of the transparent substrate with respect to the infrared reflective layer. Claim 9 A transparent substrate according to claim 7, wherein the dielectric layer comprises an oxide layer, a nitride layer, or an oxynitride layer comprising one or more of titanium (Ti), hafnium (Hf), zirconium (Zr), niobium (Nb), zinc (Zn), bismuth (Bi), tin (Sn), and silicon (Si). Claim 10 In claim 7, the multilayer thin film coating comprises an additional infrared reflective layer, a transparent substrate. Claim 11 A multi-glazing unit comprising a transparent substrate according to claim 1 or 2.

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