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

Abstract

The present invention addresses the problem of providing 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. The problem is solved by forming, on the surface of a single glass sheet, a mixture coating having a thickness of 2-4.5 µm 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 0.5-1.5 wt%, the molar ratio x of a metal M to tungsten W is in the range of 0.8-1.1, and the metal M includes at least aluminum (Al), tin (Sn), and zinc (Zn).

Description

5G radio wave-transmitting, solar radiation-shielding, highly visible light-transmitting glass

[0001] The present invention relates to a solar-shading, high-visible-light-transmitting glass that can be used as a single pane, and that has high visible light transmittance while blocking ultraviolet rays from sunlight and most light in the near-infrared region, and that transmits radio waves in the 28 GHz frequency band, which is the millimeter wave band used in 5th generation mobile communication systems, and the 4.5 GHz frequency band and the 3.7 GHz frequency band, which are the Sub-6 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.

[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, since 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 glasses with a visible light transmittance as high as 70%, but in such cases the transmittance of heat rays also increases. They also transmit most of the 380 nm ultraviolet light.

[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. Its heat-blocking performance is higher than that of heat-absorbing glass, but its visible light reflectance is also high, so its visible light transmittance is generally 50% or less. 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, which has become popular in recent years and is coated with a special metal film, has high transmittance in the visible light range, ensuring transparency, and its low solar transmittance 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 film 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).

[0006] JP 2012-229388 WO 2013-147029 JP 2018-039713 JP 7-10609 JP 9-100139

[0007] https: / / xtech.nikkei.com / atcl / nxt / column / 18 / 00001 / 05529 /

[0008] The present invention realizes 5G radio wave-transmitting glass that makes it easier to take in radio waves from outdoors into indoors 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 frequency band and 3.7 GHz frequency band, which are the Sub-6 bands.It also provides ``5G radio wave-transmitting, solar radiation-shading, high visible light transmittance 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).

[0012] In order to solve the above-mentioned problems of the prior art, the present invention provides a method for forming 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 :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.

[0013] In the present invention, composite tungsten oxide particles represented by the general formula MxWOy and antimony-doped tin oxide (SnO ２ The metal M in the composite tungsten oxide MxWOy in the mixed coating of Sb) fine 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＋In the present invention, it is essential that the metal M contains Al, Sn, and Zn, but other than these, the metal M may contain potassium (K), yttrium (Y), zirconium (Zr), magnesium (Mg), nickel (Ni), manganese (Mn), calcium (Ca), strontium (Sr), europium (Eu), niobium (Nb), and iron (Fe).

[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 actions allow the composite tungsten oxide to have an ultraviolet blocking effect in addition to a near-infrared absorbing effect.

[0016] In the present invention, the composite tungsten oxide particles represented by the general formula MxWOy and antimony-doped tin oxide (SnO ２ The thickness of the mixed coating of Sb) needs to be 2 μm or more and 4.5 μm or less. If it is less than 2 μm, the ultraviolet ray shielding property and the solar radiation shielding property will decrease. If it exceeds 4.5 μm, the visible light transmittance will decrease (yellowing) and the unevenness of the film will increase, 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 particles represented by the general formula MxWOy and antimony-doped tin oxide (SnO ２Composite tungsten oxide microparticles that form a mixed coating of nanoparticles containing Sb (Sb) can be prepared using known methods such as those disclosed in Patent Document 1. Specifically, tungsten oxide hydrate (HWO) or the like can be used as the tungsten oxide raw material, zinc acetate dihydrate (Zn(CHCOO)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, composite tungsten oxide particles represented by the general formula MxWOy and antimony-doped tin oxide (SnO ２ Antimony-doped tin oxide (SnO) that forms a mixed coating of Sb) fine particles ２ The (Sb) fine particles can be prepared by using the method disclosed in Patent Document 2, for example.

[0019] The composite tungsten oxide particles represented by the general formula MxWOy and antimony-doped tin oxide (SnO ２ The mixed coating of the Sb) fine particles can be formed by dispersing 30 to 33 wt % of the composite tungsten oxide fine particles and 0.2 to 0.5% of antimony-doped tin oxide in a mixed solution of 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 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 particles with a doping ratio of antimony of 5 mol % were 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 little scattering of visible light. Furthermore, because the microparticles have a small particle size and are uniformly dispersed without forming aggregates, the functionality of the microparticles is improved, maintaining high visible light transmittance, improving solar radiation shielding properties, and reducing the haze factor. Furthermore, this high dispersion without forming aggregates is also thought to contribute to improving the transmittance of 5G radio waves. However, it is not easy to achieve an average particle size of 40 nm or less for composite tungsten oxide microparticles, 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 composite tungsten oxide particles represented by the general formula MxWOy and antimony-doped tin oxide (SnO ２ The mixing ratio of antimony-doped tin oxide fine particles in a mixed coating of the composite tungsten oxide fine particles and the antimony-doped tin oxide (SnO) fine particles is 0.5 to 1.5 parts per 100 parts of composite tungsten oxide fine particles when the coating is formed to have a size of 2 μm or more and 4.5 μm or less. If the amount is less than 0.5 parts, the appearance of the mixed coating deteriorates. On the other hand, if the amount exceeds 1.5 parts, the visible light transmittance of the mixed coating gradually decreases. In the present invention, the mixed coating of the composite tungsten oxide fine particles and the antimony-doped tin oxide (SnO) fine particles is 0.5 to 1.5 parts per 100 parts of composite tungsten oxide fine particles. ２ The emissivity of the mixed coating of Sb: particulates was not measured or taken into account.

[0023] A 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, and then the glass is evacuated to a vacuum of 10 Pa in 30 seconds, and then heated in an oven set to a temperature of 100°C for approximately 8 minutes to form a coating of composite tungsten oxide microparticles and antimony-doped tin oxide microparticles, thereby making it possible to produce the 5G radio wave-transmitting, solar radiation-shielding, and highly visible light transmittance glass of the present invention.

[0024] The high visible light transmittance means 60% or more in the 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, and is 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. In the 5G radio wave-transmitting, highly heat-shielding, and highly visible light-transmitting glass of the present invention, when the thickness of the mixed coating is 2 μm or more and 4.5 μm or less, both of these properties can be satisfied.

[0026] In the 5G radio wave-transmitting, solar radiation-shading, high visible light transmission glass of the present invention, high radio wave transmission 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 Sub-6 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 radiation-shading, high visible light transmission 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 transmission 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, high visible light transmittance glass of the present invention may be float sheet glass, which is a common clear glass. In addition, heat-absorbing glass such as green glass may be used to improve heat insulation.

[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 a low-radiation film made of a multilayer film containing a silver layer and having a normal emissivity of 0.2 or less on heat-ray and ultraviolet-absorbing green glass. The glass has excellent solar radiation blocking properties (40% or less), relatively high visible light transmittance (67-69%), and heat insulation properties, but there is no mention of radio wave transmittance, and because it uses a multilayer film containing 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, and is composed of a laminated film formed on one surface of a transparent glass substrate, from the glass surface side, of a first layer having a film thickness of 10 nm to 200 nm, 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 on the second layer having a film thickness of 30 nm to 200 nm, and either the first or third layer having a film thickness of 70 nm to 200 nm. Furthermore, the cited reference discloses a glass sheet with improved livability, which exhibits a highly saturated green-colored 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 the thin film. Moreover, if a visible light transmittance of 50 to 70% is to be achieved, the solar radiation transmittance becomes as high as 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 shape, or to provide notches for transmitting the radio waves. 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.

[0032] The 5G radio wave-transmitting, solar radiation-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 suppressed to 3.5 dB or less, and the transmission loss for the 4.5 GHz and 3.7 GHz frequency bands of the Sub-6 band can be suppressed to 2.5 dB or less. For these reasons, the 5G radio wave-transmitting, solar radiation-shading, high visible light transmission glass of the present invention is 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 provided with the performance of 5G radio wave-transmitting, solar radiation-shading, and high visible light transmittance.

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

[0035] Examples of the present invention are described below in detail. Visible light transmittance (wavelength range: 380 nm to 780 nm), ultraviolet 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.

[0036] The composite tungsten oxide was prepared by weighing out tungsten oxide hydrate (HWO) as the tungsten oxide raw material, zinc acetate dihydrate (Zn(CHCOO)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 ratio of 1:0.1:0.25:0.4, grinding them in a mortar to form a powder, and reducing and calcining them by a known method 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, in preparing the dispersion liquid for preparing the 5G radio wave-transmitting and highly visible light-transmitting glass, commercially available antimony-doped tin oxide (manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.) was used as the antimony-doped tin oxide. The doping ratio of antimony 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% of dipropylene glycol methyl ether acetate, 13 wt% of ethyl acetate, 11 wt% of propylene glycol methyl ether acetate, 9 wt% of methacrylate copolymer, and 4 wt% of 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 sodium bicarbonate powder was sprinkled on the surface of a transparent glass plate (so-called FL3) measuring 150 mm wide x 150 mm long x 3 mm thick, and the surface was cleaned by rubbing with a sponge moistened with water. The sodium bicarbonate powder on the glass surface was then completely washed off with water.

[0040] After cleaning the surface of the glass plate, the previously prepared mixed dispersion of composite tungsten oxide microparticles and antimony-doped tin oxide microparticles was applied to the surface using a slit coater. A coating gap of 120 μm was provided between the slit and the glass substrate, and the coating nozzle was moved at a speed of 100 mm / sec 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 in a vacuum chamber over 30 seconds, removed from the vacuum chamber, and heated in an oven at 100°C for 8 minutes to obtain a coated glass substrate bearing a mixed coating of composite tungsten oxide and antimony-doped tin oxide microparticles. The coating thickness was measured to be 4.5 μm, as expected.

[0041] The optical properties of the 5G radio wave transmitting, solar radiation-shading, high visible light transmittance 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 that 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 radiation-shading, high visible light transmittance 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%, which was found to be extremely low, with most of the 25.4% solar transmittance being due to visible light. Furthermore, the ultraviolet transmittance was 0.4%, indicating that almost all ultraviolet radiation was blocked. These properties are all extremely suitable for use as windows for homes and buildings.

[0042]

[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, with the antennas facing each other, to measure the received power ratio between when the glass was sandwiched and when it was not sandwiched (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, the thick solid line is the measurement result for this sample (described as heat-shielding glass alone as a legend), and the thin solid line is the reference value when nothing is sandwiched between the antennas. For the samples 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, gradually increasing toward 28 GHz, but only 3.3 dB at 28 GHz, indicating that approximately 68% of the radio waves were transmitted, indicating 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 samples of the present invention in the millimeter wave band are shown in Table 2, from 27 GHz to 29.5 GHz in 0.5 GHz increments. It was found that the radio wave attenuation rate in the millimeter wave band was 3.5 dB or less.

[0047]

[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 result when the glass of this example is sandwiched (the sample of this example is indicated by the legend "heat-shielding glass alone" in the figure), and Figure 5 shows the difference between the measurement result 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 for 5G communication in the Sub-6 band, is shown in Table 3. It was found that the radio wave attenuation rate in the Sub-6 band for the samples according to the present invention was 2.5 dB or less.

[0051]

[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 radio waves are transmitted, and at least 75% or more of Sub6 band radio waves are transmitted.

[0053]

[0054] The composite tungsten oxide particles and antimony-doped tin oxide (SnO ２ Since the thickness of the mixed coating of Sb) fine particles was 4.5 μm, it is considered that if the thickness of the coating is 2 μm or more and 4.5 μm or less, 5G radio wave transmission characteristics at least equal to or greater than the evaluation results shown in Table 4 can be obtained.

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

Claims

1. A composite tungsten oxide particle 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, and highly visible light-transmitting glass according to claim 1 or 2, wherein the composite tungsten oxide microparticles have an average particle size of 40 nm to 60 nm.

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