5g radio wave transmission-type solar radiation-shielding highly visible light transmissive glass

Abstract

To provide a 5G radio wave transmission-type solar radiation-shielding highly visible light transmissive glass which has a high visible light transmittance and excellent solar radiation shielding ability and ultraviolet shielding ability, and through which radio waves in the Sub6 band (frequency: 4.5 GHz band and 3.7 GHz band) and the millimeter wave band (28 GHz band) used for a fifth generation mobile communication system pass.SOLUTION: On the surface of a single glass sheet, a mixture coating is formed having a thickness from 2 μm to 4.5 μm inclusive and containing fine composite tungsten oxide particles represented by a general formula MxWOy and fine antimony-doped tin oxide (SnO2:Sb) particles. The ratio of the antimony-doped tin oxide (SnO2:Sb) to MxWOy is from 0.5 wt.% to 1.5 wt.% inclusive. The molar ratio x of a metal M to tungsten W is in the range of 0.8-1.1. The metal M includes at least aluminum (Al), tin (Sn), and zinc (Zn).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a solar-shading, high-visible-light-transmitting glass that can be used as a single pane, blocks ultraviolet rays from sunlight, blocks most light in the near-infrared region, and has high visible light transmittance, and is also 5G radio-wave-transmitting, solar-shading, high-visible-light-transmitting glass that transmits radio waves in the 28 GHz frequency band, which is the millimeter wave band used in fifth-generation mobile communication systems, and the 4.5 GHz frequency band and the 3.7 GHz frequency band, which are the Sub6 band. Note that the frequency range of the 28 GHz band is 27.0 GHz to 29.5 GHz, the frequency range of the 4.5 GHz band is 4.4 GHz to 4.9 GHz, and the frequency range of the 3.7 GHz band is 3.6 GHz to 4.2 GHz, and these points are well known and obvious to those skilled in the art. [Background technology]

[0002] Solar-shading glass that can be used as a single pane includes heat-absorbing glass and heat-reflecting glass. Heat-absorbing glass contains coloring components in the raw materials of the glass to enhance absorption of heat rays, and improves heat-blocking properties by absorbing 30-40% of solar radiation (heat rays). However, because the raw materials contain coloring components, the transmittance of visible light also decreases, and the thicker the glass, the darker the color becomes. There are also heat-absorbing glass with a visible light transmittance as high as 70%, but in that case the transmittance of heat rays also increases. It also transmits most of the 380nm ultraviolet rays.

[0003] On the other hand, heat-reflecting glass is made by coating the glass surface with a heat-reflecting film, which is mainly made of a metal film. It has better heat-blocking performance than heat-absorbing glass, but its visible light reflectance is also high, so its visible light transmittance is generally less than 50%. It also transmits most of the 380 nm ultraviolet light. Another problem is that the heat-reflecting film coating reflects radio waves.

[0004] Low-E glass coated with a special metal film has become popular in recent years. It has high transmittance in the visible light range, ensuring transparency, and its low solar transmittance means it is expected to improve heat insulation in the summer. However, because the special metal film corrodes, it cannot be used as a single pane, and is only used as one pane of double-glazed glass, with the coating facing the air layer.

[0005] Furthermore, recent research has shown that such Low E glass attenuates millimeter waves of 28 GHz, which are used in next-generation (5th generation) mobile communication systems, to 1 / 10,000 (Non-Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-229388 [Patent Document 2] WO2013-147029 publication [Patent Document 3] Japanese Patent Application Publication No. 2018-039713 [Patent Document 4] Japanese Patent Application Publication No. 7-10609 [Patent Document 5] Japanese Patent Application Publication No. 9-100139 [Non-patent literature]

[0007] [Non-Patent Document 1] https: / / xtech.nikkei.com / atcl / nxt / column / 18 / 00001 / 05529 / Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention realizes 5G radio wave-transmitting glass that makes it easier to bring 5G radio waves in the 28 GHz frequency band, which is the millimeter wave band of 5G radio waves used in fifth-generation mobile communication systems, and the 4.5 GHz and 3.7 GHz frequency bands, which are the Sub6 bands, indoors from outdoors.It also provides ``5G radio wave-transmitting, solar radiation-shading, high visible light transmission glass'' that blocks most of the sunlight, which contains a lot of heat rays, blocks ultraviolet light, and conversely transmits most of the visible light.

[0009] To function as solar-shading glass, it is necessary for it to have high solar heat-shielding performance and at the same time high visible light transmittance. In particular, to function as a window for a house or building, it is necessary for it to be transparent and transmit much of the visible light while blocking sunlight.

[0010] It is difficult for such solar-shading glass to satisfy the performance requirements of an ultraviolet transmittance of 2.0% or less, a visible light transmittance of 60% or more, and a solar radiation transmittance of 35% or less.

[0011] The present invention aims to satisfy these solar radiation and visible light performance requirements while also allowing 5G radio waves to pass through. Specifically, "allowing 5G radio waves to pass through" means that even after radio waves in the 28 GHz frequency band (millimeter wave band) and the 4.5 GHz and 3.7 GHz frequency bands (Sub6 band) pass through the solar radiation-shading, high visible light transmittance glass of the present invention, the strength of the radio waves in the 28 GHz frequency band remains at least two-thirds (66.7% or more) (this corresponds to a voltage attenuation rate of the radio waves of 3.5 dB or less), and the strength of the radio waves in the Sub6 band frequency range remains at least 75% (this corresponds to a voltage attenuation rate of the radio waves of 2.5 dB or less). [Means for solving the problem]

[0012] In order to solve the above-mentioned problems of the prior art, the present invention provides a glass substrate in which a mixed coating of composite tungsten oxide particles represented by the general formula MxWOy and antimony-doped tin oxide (SnO2:Sb) particles is formed on the surface of a single sheet of glass to a thickness of 2 μm to 4.5 μm, the ratio of the antimony-doped tin oxide (SnO2:Sb) to MxWOy is 0.5 wt% to 1.5 wt%, the molar ratio x of the metal M to tungsten W is in the range of 0.8 to 1.1, and the metal M is contained in a small amount. This 5G radio wave-transmitting, solar radiation-shielding, high visible light transmittance glass contains at least aluminum (Al), tin (Sn), and zinc (Zn), and has optical properties of an ultraviolet transmittance of 2.0% or less, a visible light transmittance of 60% or more, and a solar radiation transmittance of 35% or less. Furthermore, the radio wave attenuation rate for the 28 GHz frequency band, which is the millimeter wave band used in 5th generation mobile communication systems, is 3.5 dB or less, and the radio wave attenuation rate for the Sub6 band, which is also used in 5th generation mobile communication systems, is 2.5 dB or less.

[0013] In the present invention, the metal M in the composite tungsten oxide MxWOy in the mixed coating of composite tungsten oxide particles represented by the general formula MxWOy and antimony-doped tin oxide (SnO2:Sb) particles substitutes for tungsten atoms in the tungsten oxide or exists as a solid solution in the tungsten oxide, thereby causing oxygen deficiency and converting pentavalent tungsten ions W 5+ This efficiently generates the metal M, thereby promoting the near-infrared light absorption effect, i.e., the heat-shielding effect, of tungsten oxide. In the present invention, it is essential that the metal M contains Al, Sn, and Zn, but in addition to these, potassium (K), yttrium (Y), zirconium (Zr), magnesium (Mg), nickel (Ni), manganese (Mn), calcium (Ca), strontium (Sr), europium (Eu), niobium (Nb), and iron (Fe) may also be contained.

[0014] In the present invention, the molar ratio X of metal M to tungsten W is preferably 0.8 to 1.1. It has been found that if X exceeds 1.1, the amount of metal ions becomes excessive, resulting in a decrease in visible light transmittance, and conversely, if X is less than 0.8, the generation of pentavalent tungsten ions becomes insufficient, resulting in an increase in solar transmittance.

[0015] In the present invention, the composite tungsten oxide contains Zn as the metal M other than W, and further contains at least Al and Sn. These effects enable the composite tungsten oxide to have an ultraviolet blocking effect in addition to a near-infrared absorbing effect.

[0016] In the present invention, the thickness of the mixed coating of composite tungsten oxide microparticles represented by the general formula MxWOy and antimony-doped tin oxide (SnO2:Sb) applied to the single-pane glass must be 2 μm or more and 4.5 μm or less. If it is less than 2 μm, the ultraviolet ray blocking property and the solar radiation blocking property will decrease. If it exceeds 4.5 μm, the visible light transmittance will decrease (yellowing will occur) and the film will become more uneven, causing bumps on the surface. When the thickness of the mixed coating is in the range of 2 μm or more and 4.5 μm or less, the ultraviolet ray transmittance will be 2.0% or less, the solar radiation transmittance will be 35% or less, and the visible light transmittance will be 60% or more.

[0017] In the present invention, composite tungsten oxide microparticles forming a mixed coating of composite tungsten oxide microparticles represented by the general formula MxWOy and antimony-doped tin oxide (SnO2:Sb) microparticles can be prepared using known methods such as those disclosed in Patent Document 1. Specifically, tungsten oxide hydrate (H2WO4) or the like can be used as the tungsten oxide raw material, zinc acetate dihydrate (Zn(CH3COO)2·2H2O) or the like can be used as the zinc oxide raw material, aluminum sulfate hydrate (Al2(SO4)3·16H2O) or the like can be used as the aluminum oxide raw material, and tin chloride dihydrate (SnCl2·2H2O) or the like can be used as the tin oxide raw material. A solution containing these raw materials in a predetermined ratio is stirred uniformly and then fired at a temperature of approximately 650°C in an inert gas atmosphere, thereby obtaining composite tungsten oxide microparticles that are uniform at the molecular level.

[0018] In the present invention, the antimony-doped tin oxide (SnO:Sb) particles that form a mixed coating of composite tungsten oxide particles represented by the general formula MxWOy and antimony-doped tin oxide (SnO:Sb) particles can be prepared using, for example, the method disclosed in Patent Document 2.

[0019] The mixed coating of composite tungsten oxide microparticles represented by the general formula MxWOy and antimony-doped tin oxide (SnO2:Sb) microparticles of the present invention can be formed by dispersing 30 to 33 wt% of the composite tungsten oxide microparticles and 0.2 to 0.5% of antimony-doped tin oxide in a mixed solution containing 27 to 30 wt% dipropylene glycol methyl ether acetate, 10 to 13 wt% ethyl acetate, 9 to 11 wt% propylene glycol methyl ether acetate, 7 to 9 wt% methacrylate copolymer, and 3 to 4 wt% silane copolymer as a solvent, thoroughly stirring the mixture, and then applying the resulting mixture to the surface of a plate glass using a slit coater to a thickness of 2 μm to 4.5 μm.

[0020] The antimony-doped tin oxide fine particles of the present invention can be selected from commercially available products. In the examples of the present invention, tin oxide with a doping ratio of antimony of 5 mol % was used.

[0021] In the present invention, the composite tungsten oxide microparticles are preferably spherical and have an average particle size of 50 nm or less. By achieving a spherical average particle size of 50 nm or less, the composite tungsten oxide microparticles are well dispersed, resulting in a coating with minimal scattering of visible light. Furthermore, because the microparticles are small and uniformly dispersed without forming aggregates, the functionality of the microparticles is improved, maintaining high visible light transmittance, improving solar radiation blocking properties, and reducing haze. Furthermore, this high dispersion without forming aggregates is also believed to contribute to improving the transmittance of 5G radio waves. However, achieving an average particle size of 40 nm or less is not easy, and in practice, composite tungsten oxide microparticles with an average particle size of 40 nm to 60 nm are used. The average particle size of the composite tungsten oxide microparticles was determined using the method disclosed in paragraph

[0050] of Patent Document 3 by the inventors.

[0022] In the present invention, the mixing ratio of antimony-doped tin oxide particles in the mixed coating of composite tungsten oxide particles represented by the general formula MxWOy and antimony-doped tin oxide (SnO2:Sb) particles is 0.5 to 1.5 parts per 100 parts of composite tungsten oxide particles when forming this coating with a particle size of 2 μm to 4.5 μm. If the mixing ratio is less than 0.5 parts, the appearance of the mixed coating deteriorates. On the other hand, if the mixing ratio exceeds 1.5 parts, the visible light transmittance of the mixed coating gradually decreases. Note that in the present invention, the emissivity of the mixed coating of the composite tungsten oxide particles and the antimony-doped tin oxide (SnO2:Sb) particles is not measured or taken into consideration.

[0023] The mixed coating of the composite tungsten oxide and the antimony-doped tin oxide is applied to the surface of a glass plate using a slit coater to obtain a wet coating, which is then evacuated to a pressure of 10 Pa in 30 seconds and then heated in an oven set to 100°C for approximately 8 minutes to form a coating consisting of composite tungsten oxide microparticles and antimony-doped tin oxide microparticles, making it possible to produce the 5G radio wave-transmitting, solar radiation-shading, and highly visible light transmittance glass of the present invention.

[0024] The high visible light transmittance means 60% or more for 5G radio wave-transmitting, solar radiation-shielding, high visible light transmittance glass coated with a mixed coating of composite tungsten oxide microparticles and antimony-doped tin oxide microparticles, making it suitable for use as window glass for homes and buildings.

[0025] Furthermore, "excellent solar radiation shielding properties" means that the 5G radio wave-transmitting, highly heat-shielding, and highly visible light-transmitting glass of the present invention can satisfy the performance requirements of an ultraviolet radiation transmittance of 2.0% or less and a solar radiation transmittance of 35% or less. To date, there has been no example of achieving such low solar radiation transmittance and ultraviolet radiation shielding while maintaining high visible light transmittance. The 5G radio wave-transmitting, highly heat-shielding, and highly visible light-transmitting glass of the present invention can satisfy both of these properties when the thickness of the mixed coating is 2 μm or more and 4.5 μm or less.

[0026] In the 5G radio wave-transmitting, solar-shading, highly visible light-transmitting glass of the present invention, high radio wave transmittance for 5G radio waves means that the attenuation rate of radio waves in the 28 GHz frequency band, which is the millimeter wave band, is not more than one-third (3.5 dB or less), and the attenuation rate of radio waves in the 4.5 GHz frequency band and the 3.7 GHz frequency band, which are the Sub6 band, is not more than 25% (2.5 dB or less). Conversely, this means that even after passing through the 5G radio wave-transmitting, solar-shading, highly visible light-transmitting glass of the present invention, the transmittance of radio waves in the 28 GHz band is 66.7% or more in terms of radio wave intensity, and the transmittance of radio waves in the 4.5 GHz band and the 3.7 GHz band is 75% or more in terms of radio wave intensity. It was found that the high radio wave transmittance for 5G radio waves was satisfied when the film thickness of the mixed coating of composite tungsten oxide microparticles and antimony-doped tin oxide microparticles was 4.5 μm or less.

[0027] The sheet glass that can be used for the 5G radio wave-transmitting, solar radiation-shading, and highly visible light-transmitting glass of the present invention may be float sheet glass, which is a common clear glass. Furthermore, to enhance heat shielding properties, heat-absorbing glass such as green glass may also be used.

[0028] Here, in order to clarify the features of the present invention, advantages of the present invention will be explained in comparison with some known examples.

[0029] Patent Document 4 discloses heat-blocking glass, which is made by coating green glass that absorbs heat rays and ultraviolet rays with a low-emissive film made of a multilayer film including a silver layer and having a normal emissivity of 0.2 or less. The glass has excellent solar radiation blocking properties (40% or less), relatively high visible light transmittance (67-69%), and thermal insulation properties, but there is no mention of radio wave transmittance, and because it uses a multilayer film including a highly conductive silver layer, it is thought to reflect radio waves used in fifth-generation mobile communication systems.

[0030] Patent Document 5 aims to obtain a glass plate that effectively balances transparency, mirror properties, and heat insulation properties with a simple film structure, is friendly to people and the environment, has excellent livability, exhibits a deep green glass surface reflection color tone, and has radio wave transmittance. The glass plate is made of a laminated film that is formed on one surface of a transparent glass substrate, from the glass surface side, with a first layer of an Sn oxide thin film having a film thickness of 10 nm to 200 nm, and a second layer on the first layer of at least one thin film selected from the group consisting of Ti, SUS, NiCr metals and nitrides containing these metals as main components, having a film thickness of 1 nm to 15 nm and a surface resistivity of 1 kΩ / Ω or more, and a further Sn oxide thin film having a film thickness of 30 nm to 200 nm on the second layer, and the film thickness of either the first or third layer is 70 nm to 200 nm. Furthermore, the cited reference discloses a glass sheet with improved livability, which exhibits a highly saturated green glass surface reflection color tone with an excitation purity of 10% or more in the visible light wavelength range of light reflected from the glass surface. Regarding radio wave transmittance, this reference only states that the surface resistance of the thin film was 1 to 5 kΩ / □, but it is unclear whether 5G radio waves can be transmitted through it. Moreover, if a visible light transmittance of 50 to 70% is to be achieved, the solar radiation transmittance becomes a high value of 50 to 60%, resulting in extremely poor solar radiation blocking properties.

[0031] As already mentioned, Low-E glass coated with a low-emissivity film has excellent solar radiation shielding properties, but because the film is corrosive, it is limited to use as a single sheet of glass that constitutes double-glazing. Even in such cases, in order to transmit radio waves used for communication, etc., it was necessary to form the low-emissivity film as a discontinuous film in a spotted or island pattern, or to provide notches to allow the radio waves to pass through. However, in the present invention, the mixed coating of the composite tungsten oxide microparticles and the antimony-doped tin oxide microparticles does not need to be in such a discontinuous form or to provide notches. [Effects of the Invention]

[0032] The 5G radio wave-transmitting, solar-shading, high visible light transmission glass of the present invention exhibits excellent solar radiation shading properties, with an ultraviolet radiation transmittance of 2.0% or less and a solar radiation transmittance of 35% or less, while maintaining a high visible light transmittance of 60% or more. Furthermore, the transmission loss for the 28 GHz frequency band of the millimeter wave band, which is the 5G radio waves used in fifth-generation mobile communication systems, can be reduced to 3.5 dB or less, and the transmission loss for the 4.5 GHz and 3.7 GHz frequency bands of the Sub6 band can be reduced to 2.5 dB or less. These factors make the 5G radio wave-transmitting, solar-shading, high visible light transmission glass of the present invention extremely suitable for use as window glass in future homes and buildings.

[0033] Although the present invention relates to single-pane glass, the mixed coating of composite tungsten oxide microparticles and antimony-doped tin oxide microparticles applied to the radio wave-transmitting, solar radiation-shading, high visible light transmittance glass of the present invention can be applied to tempered glass to impart 5G radio wave-transmitting, solar radiation-shading, high visible light transmittance properties to the tempered glass. Furthermore, the 5G radio wave-transmitting, solar radiation-shading, high visible light transmittance glass of the present invention can be used as one of the panes of glass that make up double-glazing or laminated glass. In this way, double-glazing or laminated glass can also be endowed with the performance of 5G radio wave-transmitting, solar radiation-shading, and high visible light transmittance. [Brief explanation of the drawings]

[0034] [Figure 1] FIG. 1 is a diagram showing the spectral optical properties of the 5G radio wave-transmitting, high-heat-shielding, and high-visible light-transmitting glass of the present invention. [Figure 2] FIG. 1 is a diagram showing the radio wave transmittance in the millimeter wave band of the 5G radio wave-transmitting, solar radiation-shielding, highly visible light-transmitting glass of the present invention (air is used as a reference). [Figure 3] FIG. 1 is a diagram showing the radio wave attenuation rate in the millimeter wave band of the 5G radio wave-transmitting, solar radiation-shielding, highly visible light-transmitting glass of the present invention (the difference from that of air). [Figure 4] FIG. 1 is a diagram showing the radio wave transmittance in the Sub6 band of the 5G radio wave-transmitting, high-heat-shielding, and high-radio wave-transmitting glass of the present invention (air is used as a reference). [Figure 5] FIG. 1 is a diagram showing the radio wave attenuation rate in the Sub6 band of the 5G radio wave-transmitting, highly heat-shielding, and highly visible light-transmitting glass of the present invention (the difference from that in air). DETAILED DESCRIPTION OF THE INVENTION

[0035] Examples of the present invention are described below in detail. Visible light transmittance (wavelength range: 380 nm to 780 nm), ultraviolet light transmittance (wavelength range: 300 nm to 380 nm), and solar radiation transmittance (wavelength range: 300 nm to 2500 nm) were measured at the Kanagawa Prefectural Institute of Industrial Science and Technology using a spectrophotometer UH-4150 manufactured by Hitachi, Ltd. Measurement of radio wave transmittance was also carried out at the Kanagawa Prefectural Institute of Industrial Science and Technology. [Example]

[0036] Composite tungsten oxide was prepared by weighing out tungsten oxide hydrate (H2WO4) as the tungsten oxide raw material, zinc acetate dihydrate (Zn(CH3COO)2·2H2O) as the zinc oxide raw material, aluminum sulfate hydrate (Al2(SO4)3·16H2O) as the aluminum oxide raw material, and tin chloride dihydrate (SnCl2·2H2O) as the tin oxide raw material in a molar fraction of 1:0.1:0.25:0.4, grinding them in a mortar to form a powder, and reducing and calcining them using known methods to obtain composite tungsten oxide microparticles. In this example, the molar ratio x of metal M to tungsten W is stoichiometrically 1.0.

[0037] In addition, when preparing the dispersion liquid for producing 5G radio wave-transmitting, highly visible light-transmitting glass, commercially available antimony-doped tin oxide (manufactured by Mitsubishi Materials Electronic Chemicals) was used. The antimony doping ratio was 5 mol%.

[0038] 31.7 wt% of the composite tungsten oxide microparticles and 0.3 wt% of antimony-doped tin oxide were dispersed in an organic solvent consisting of 31 wt% dipropylene glycol methyl ether acetate, 13 wt% ethyl acetate, 11 wt% propylene glycol methyl ether acetate, 9 wt% methacrylate copolymer, and 4 wt% silane polymer as a dispersant. To improve the dispersion, the mixture was stirred at 1000 rpm for 10 minutes to prepare a mixed dispersion of the composite tungsten oxide microparticles and antimony-doped tin oxide microparticles.

[0039] A small amount of baking soda powder was sprinkled on the surface of a 150mm wide x 150mm long x 3mm thick transparent glass plate (known as FL3), and the surface was cleaned by rubbing it with a sponge soaked in water. The baking soda on the glass surface was then completely washed off with water.

[0040] After cleaning the glass plate surface, the previously prepared mixed dispersion of composite tungsten oxide microparticles and antimony-doped tin oxide microparticles was applied to the glass substrate using a slit coater. A 120 μm coating gap was established between the slit and the glass substrate, and the coating nozzle was moved at a speed of 100 mm / s to form a wet film thickness of approximately 25 μm on the glass substrate. The wet film thickness refers to the film thickness including the solvent. The wet-coated glass substrate was then evacuated to 10 Pa over 30 seconds in a vacuum chamber, removed from the vacuum chamber, and heated in an oven at 100°C for 8 minutes to obtain a coated glass substrate with a mixed coating of composite tungsten oxide and antimony-doped tin oxide microparticles. The coating thickness was measured and found to be 4.5 μm, as expected.

[0041] The optical properties of the 5G radio wave-transmitting, solar-shading, high visible light transmission glass thus obtained were evaluated, and the results are shown in Figure 1. The visible light transmittance, visible light reflectance, solar transmittance, and solar reflectance calculated in accordance with JIS R3106:2019 are shown in Table 1. Note that near-infrared radiation refers to the wavelength range of 780 nm to 2500 nm, and the transmittance and reflectance in this range were calculated by multiplying them by a weighting factor, which represents the proportion of solar radiation. From the results shown in Table 1, the 5G radio wave-transmitting, solar-shading, high visible light transmission glass of the present invention had a visible light transmittance of 64.2%, a high value exceeding 60%, a solar transmittance of 25.4%, a low value below 35%, and a near-infrared transmittance of 2.9%, indicating that most of the 25.4% of the solar transmittance was due to visible light. Furthermore, the ultraviolet transmittance was 0.4%, indicating that almost all ultraviolet radiation was blocked. These performance characteristics are all highly suitable for use as windows in homes and buildings.

[0042] [Table 1]

[0043] Next, the radio wave transmittance of the 5G radio wave-transmitting, solar radiation-shading, high visible light transmittance glass of the example of the present invention was measured. Using a network analyzer, the ratio of received power was measured with the antennas facing each other when the glass was sandwiched between the glass plates and when they were not sandwiched between the plates (i.e., when air was present).

[0044] Figure 2 shows the measurement results for radio wave transmittance in the frequency range of 15 GHz to 40 GHz, which is the measurement range sandwiching the 28 GHz frequency band, which is the millimeter wave band. In Figure 2, S21 corresponds to the strength of the transmitted radio waves, with the thick solid line being the measurement result for this sample (described as heat-shielding glass alone as a legend), and the thin solid line showing the reference value when nothing is sandwiched between the antennas. For the sample of the example of the present invention, the deviation from the reference value is small, indicating little attenuation of radio waves.

[0045] Figure 3 shows the ratio of received power in the millimeter wave band (28 GHz frequency band) of a sample according to an embodiment of the present invention to the reference value of a state without glass, i.e., a state with only empty air. In other words, the radio wave attenuation rate is shown when the sample according to the present invention is sandwiched, with the air state being taken as 0 dB. Measurement results for the millimeter wave band (28 GHz frequency band), one of the frequencies of so-called 5G radio waves used in fifth-generation mobile communication systems, showed that the sample according to the embodiment of the present invention had an attenuation rate of 0.65 dB at 15 GHz. The attenuation rate then gradually increased toward 28 GHz, but at 28 GHz, the attenuation rate was 3.3 dB, indicating that approximately 68% of the radio waves were transmitted, resulting in a low radio wave attenuation rate. Above 28 GHz, the radio wave attenuation rate was 3.5 to 3.6 dB between 29.5 GHz and 31.5 GHz. Above 32 GHz, the attenuation rate gradually decreased, reaching 0.4 dB or less at 40 GHz.

[0046] Since listing all of this data would be enormous, the measurement results for the millimeter wave band for the sample of the present invention are shown in Table 2, in 0.5 GHz increments from 27 GHz to 29.5 GHz. It was found that the radio wave attenuation rate in the millimeter wave band was 3.5 dB or less.

[0047] [Table 2]

[0048] Next, the measurement results of radio wave transmittance in the Sub6 band, 4.5 GHz and 3.7 GHz frequency bands, are shown in Figures 4 and 5. The measured frequency range was 2 GHz to 18 GHz, which includes the Sub6 band. Figure 4 shows the measurement results comparing the reference value when no glass is sandwiched (when there is only air between the opposing antennas) with the glass of this example sandwiched (the sample of this example is indicated by the legend "heat-shielding glass alone"), and Figure 5 shows the difference between the measurement results of the sample of this example and the reference value.

[0049] The sample of the embodiment of the present invention exhibits radio wave attenuation of 1.3 dB at 2 GHz, 2.0 dB at 3.7 GHz, and 2.3 dB at 4.5 GHz, and then shows a maximum value of approximately 3.8 dB in the frequency range of 9 to 11 GHz.

[0050] For the samples according to the present invention, data on the attenuation rates in the 3.7 GHz and 4.5 GHz bands, which are radio waves used in 5G communications in the Sub6 band, is shown in Table 3. It was found that the radio wave attenuation rate in the Sub6 band for the samples according to the present invention was 2.5 dB or less.

[0051] [Table 3]

[0052] The above measurement results were compiled and the extent to which radio waves in the millimeter wave band (28 GHz frequency band) and Sub6 band (4.5 GHz frequency band and 3.7 GHz frequency band) used in fifth generation mobile communication systems are attenuated in the examples of the present invention is summarized in Table 4. In the examples of the present invention, it was found that the attenuation rate was 3.0 dB to 3.5 dB at frequencies from 27.0 GHz to 29.5 GHz in the 28 GHz band, which is the millimeter wave band used in fifth generation mobile communication systems, the attenuation rate was 2.3 to 2.4 dB at frequencies from 4.4 GHz to 4.9 GHz in the 4.5 GHz band, which is the Sub6 band, and the attenuation rate was 2.0 dB to 2.2 dB at frequencies from 3.6 GHz to 4.2 GHz in the 3.7 GHz band, which is also the Sub6 band. In other words, it was found that at least 66.7% or more of millimeter wave band radio waves are transmitted, and at least 75% or more of Sub6 band radio waves are transmitted.

[0053] [Table 4]

[0054] The thickness of the mixed coating of the composite tungsten oxide microparticles and antimony-doped tin oxide (SnO2:Sb) microparticles on the 5G radio wave-transmitting, solar radiation-shielding, high visible light transmittance glass sample used to evaluate radio wave transmittance in this example was 4.5 μm. Therefore, if the thickness of the coating is 2 μm or more and 4.5 μm or less, it is thought that 5G radio wave transmittance characteristics at least equal to or greater than the evaluation results shown in Table 4 can be obtained.

[0055] Up until now, the relationship between radio wave attenuation and radio wave transmittance has been calculated using the following equation. The ratio of the voltage of the emitted radio wave to the voltage of the radio wave transmitted through the glass placed between the network analyzer to measure radio wave transmittance is the radio wave transmittance, and taking the logarithm of this and multiplying it by 20 gives the radio wave attenuation (dB), which corresponds to the radio wave received power ratio. For example, if 0.75 (75%) is substituted into this equation as the radio wave transmittance, the radio wave attenuation is calculated as -2.5 dB. This is expressed as a radio wave attenuation of 2.5 dB. As another example, if 0.667 (66.7%) is substituted for the radio wave transmittance, the result is -3.5 dB, which is expressed as a radio wave attenuation of 3.5 dB. Radio wave reception power ratio = Radio wave attenuation rate (dB) = 20log 10 [Radio wave transmittance] Radio wave transmittance = transmitted radio wave voltage (amplitude) / emitted radio wave voltage (amplitude)

Claims

1. On the surface of the single glass plate, composite tungsten oxide particles represented by the general formula MxWOy and antimony-doped tin oxide (SnO ２ A mixed coating of antimony-doped tin oxide (SnO) particles is formed to a thickness of 2 μm or more and 4.5 μm or less, ２ 5G radio wave transmitting, solar radiation-shielding, high visible light transmittance glass, characterized in that the ratio of MxWOy (MxWOy:Sb) to MxWOy is 0.5 wt % or more and 1.5 wt % or less, the molar ratio x of the metal M to tungsten W is in the range of 0.8 to 1.1, the metal M contains at least aluminum (Al), tin (Sn), and zinc (Zn), and the optical properties are an ultraviolet transmittance of 2.0% or less, a visible light transmittance of 60% or more, and a solar radiation transmittance of 35% or less, and further a radio wave attenuation rate of 3.5 dB or less in the 28 GHz frequency band, which is the millimeter wave band used in fifth-generation mobile communication systems, and a radio wave attenuation rate of 2.5 dB or less in the Sub-6 band also used in fifth-generation mobile communication systems.

2. The antimony-doped tin oxide (SnO ２ 2. The 5G radio wave transmitting, solar radiation-shielding, and highly visible light transmittance glass according to claim 1, wherein the doping ratio of Sb in the (Sb:Sb) is 5 mol %.

3. The 5G radio wave-transmitting, solar radiation-shielding, highly visible light transmittance glass according to claim 1 or 2, wherein the average particle size of the composite tungsten oxide microparticles is 40 nm to 60 nm.

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