EA041197B1 - RADIO TRANSPARENT SUBSTRATE - Google Patents

Description

The field of technology to which the invention belongs

The present invention relates to a radio-transmitting substrate.

State of the art

In recent years, it has become common practice to reduce the consumption of electricity, such as moderate use of air conditioners or the like for cooling, in order to prevent global warming. Accordingly, an attempt has been made to give the function of reflecting infrared radiation (thermal radiation) to the window panes of vehicles, buildings, etc., so as to thereby reduce the inflow of heat from sunlight into the interior of vehicles or buildings.

Examples of methods for imparting an infrared reflective function to window panes or the like include a method in which a thin film including a metal having an infrared reflective function such as silver is formed on a substrate such as glass.

For example, Patent Document 1 discloses a laminated glass structure including a glass sheet and a thermal reflective film placed on one major surface of the glass sheet, the thermal reflective film including a metal layer containing silver as a main component.

List of cited literature Patent literature

Patent Document 1: JP-A-2015-3388

The essence of the invention Technical problem

In a case where such a substrate having a function of reflecting infrared radiation is used, for example, as a window pane, it is necessary that the substrate has a high transparency to radio waves having predetermined frequencies. Conventional substrates having an infrared reflective function exhibit high transparency to radio waves used in conventional communication channels, which have relatively low frequencies, and thus do not pose a significant problem in terms of transparency. However, there is a problem in that transparency for radio waves having frequencies ranging from several hundred megahertz to tens of gigahertz, such as radio waves for use in recent fourth generation mobile communication systems (hereinafter referred to as 4G) or fifth generation mobile communication systems (hereinafter referred to as 5G) is insufficient compared to the transparency for radio waves that have frequencies in traditional bands.

In light of these circumstances, it is an object of the present invention to provide a radio-transparent substrate having excellent transparency also for radio waves having frequencies from about a few hundred megahertz to tens of gigahertz for 4G or 5G applications.

Solution of a problem

The radio wave-permeable substrate according to the present invention, which solves the problem, includes a dielectric substrate and, on at least one major surface of the dielectric substrate, a thermal radiation reflective film including an electrically conductive film, and an opening where the electrically conductive film is absent in plan view, wherein at least a portion of at least one major surface in plan view is a radio-wave-permeable area, and the radio-wave-permeable area is an area where every 1 sq. cm unit area satisfies the following expression (a):

L>802.6xS-503.7(a).

(In the expression (a), L represents the total length (unit: mm/cm ² ) of the boundary between the heat reflective film and the hole in the unit area, and S represents the proportion of the area occupied by the heat reflective film in the unit area).

In one embodiment of the present invention, the radio wave permeable region may satisfy the following expression (b):

Z>(-Z'+Z'xS'+0.3)/S' (b).

(In the expression (B), Z represents the solar reflectance of the thermal reflective film, Z' represents the solar reflectance of the aperture, and S' represents the ratio of the area of the thermal reflective film to the area of the radio wave transmission area).

In one embodiment of the present invention, the radio wave-permeable region may satisfy the following expression (c):

AE<60.3xD'°' ⁶² (c).

(In the expression (c), Δε represents the color contrast between the heat radiation reflective film and the hole, and D represents the width (unit: mm) of the hole.)

In one embodiment of the present invention, the radio-permeable region may have a radio wave transmission loss of 3 dB or less when transmitting radio waves having a frequency

- 1 041197

GHz.

In one embodiment of the present invention, the openings may be multiple parallel lines or a lattice structure.

In one embodiment of the present invention, the radio-transparent substrate may include a radio-impermeable region on at least a portion of one major surface of the dielectric substrate, wherein the radio-impervious region is an area where every 1 sq. see unit area including the radio-opaque area satisfies the following expression (d):

L<802.6*S-503.7 (d) (In the expression (d), L represents the total length (unit: mm/cm ² ) of the boundary between the heat-reflecting film and the hole in the unit area, and S represents the area ratio, occupied by a film reflecting thermal radiation in a single area).

In one embodiment of the present invention, the electrically conductive film may include at least one metal selected from the group consisting of silver and aluminum, in a total amount of 50 at.% or more.

In one embodiment of the present invention, the dielectric substrate may be exposed in the hole.

In one embodiment of the present invention, the dielectric substrate may have a radio wave transmission loss of 4 dB or less when transmitting radio waves having a frequency of 28 GHz.

In one embodiment of the present invention, the electrically conductive film may have a thickness of 1 to 100 nm.

In one embodiment of the present invention, the heat reflective film may include at least one metal oxide layer and a metal nitride layer, wherein the metal oxide layer and the metal nitride layer are different from the electrically conductive film.

In one embodiment of the present invention, the electrically conductive film may have a configuration in which the electrically conductive film is sandwiched between layers including at least one of a metal oxide layer or a metal nitride layer.

In one embodiment of the present invention, the dielectric substrate may include multiple glass substrates, and multiple glass substrates are layered on top of each other with a polymer film placed between them.

Advantageous results of the invention

According to the present invention, a radio wave-permeable substrate having excellent transparency also for radio waves having frequencies from about a few hundred megahertz to tens of gigahertz is provided for 4G or 5G applications.

Brief description of the figures

Fig. 1 illustrates one embodiment of a radio-transparent substrate according to the present invention. (A) is a plan view, and (B) is an enlarged cross-sectional view taken along line X-X in (A).

Fig. 2 illustrates another embodiment of a radio-transparent substrate according to the present invention.

Fig. 3 illustrates another further embodiment of a radio wave-permeable substrate according to the present invention.

Description of embodiments of the invention

The following is a detailed explanation of the embodiments of the present invention. The present invention is not limited to the embodiments explained below. In the drawings, elements or areas having similar functions are often identified by similar numbers or symbols. Duplicative explanations are often omitted or simplified. The embodiments shown in the drawings have been presented schematically in order to more clearly explain the present invention, and the dimensions or scales of the actual products are not always accurately depicted.

Fig. 1 illustrates one embodiment of a radio-transparent substrate according to the present invention. (A) is a plan view, and (B) is an enlarged cross-sectional view taken along line X-X in (A).

The radio wave-permeable substrate 10 according to this embodiment includes a dielectric substrate 11 and a thermal radiation reflective film 13 on at least one major surface of the dielectric substrate 11, and has an opening 14 on said at least one major surface where the thermal radiation reflective film 13 is absent. top view. In the radio-wave-permeable substrate 10 according to this embodiment, the plural portions of the heat-reflecting film 13 and the holes 14, which have been placed adjacent in plan view, constitute the radio-wave-permeable region. As will be indicated later, the hole 14 does not have an electrically conductive film in it, which is part of the thermal radiation reflective film 13.

The radio-permeable area is the area where every 1 square centi

- 2 041197 unit area meter satisfies the expression (a).

L>802.6xS-503.7(a) (In the expression (a), L represents the total length (in units: mm/cm ² ) of the boundary between the thermal radiation reflective film and the hole in the unit area, and S represents the proportion of the area occupied reflecting thermal radiation film in a single region).

The radio wave-permeable substrate according to this embodiment, which has the configuration shown above, has excellent transparency also for radio waves having frequencies from about a few hundred megahertz to tens of gigahertz. Features of the radio wave-permeable substrate according to this embodiment are explained in detail below.

Dielectric substrate

The dielectric substrate in this embodiment is not particularly limited as long as it is a substrate composed of a dielectric. For example, a glass substrate made of soda-lime glass, alkali-free glass, quartz glass, etc. can be used. The glass substrate may be subjected to a physical strengthening treatment or a chemical strengthening treatment. The glass substrate may be composed of a single glass sheet, or may be configured as multiple glass sheets layered on top of each other with a resin film (polymer film) or the like placed therebetween.

The dielectric substrate in this embodiment is not limited to glass substrates, and may be a resin substrate (resin substrate) or the like, for example. Examples of the polymer substrate include substrates made from acrylic polymers such as polymethyl methacrylate, aromatic polycarbonate polymers such as polyphenylene carbonate, and aromatic polyester polymers such as polyethylene terephthalate (PET).

The shape of the dielectric substrate in this embodiment is also not particularly limited, and may be a planar shape or a curved shape. The thickness of the dielectric substrate in this embodiment is also not particularly limited, and can be appropriately adjusted according to desired strength, light weight, and so on.

The properties of the dielectric substrate in this embodiment, such as transmission characteristics of radio waves and reflection characteristics of thermal radiation, are also not particularly limited as long as the effect of the present invention is achieved. Such properties can be adjusted according to the characteristics required for the resulting radio-transparent substrate.

For example, the dielectric substrate in this embodiment has a radio wave transmission loss when transmitting 28 GHz radio waves, preferably 4 dB or less, more preferably 3 dB or less, even more preferably 2 dB or less. The transmission loss of radio waves can be determined by the method which is described later in the examples.

In the case of using a glass substrate as the dielectric substrate in this embodiment, the configurations shown below are preferable. The content of each component in the glass substrate is presented in mole percent based on oxides. Thus, by glass essentially free of a certain component, it is understood that the component was not deliberately added, except in the situation where the component inevitably entered the glass as an impurity.

The glass substrate preferably has a specific gravity of 2.4 or higher and 3.0 or less. The glass substrate preferably has a Young's modulus of 60 GPa or higher and 100 GPa or lower. The glass substrate preferably has an average coefficient of thermal expansion at a temperature of 50 to 350°C from 50x10 ^-7 /°C to 120x10 ^-7 /°C. In the case where the glass substrate satisfies these property requirements, the glass substrate is sufficiently suitable for use as a window glass material.

Preferably, the glass substrate contains at least a certain level of SiO ₂ for reasons of weather resistance. As a result, the glass substrate may have a specific gravity of 2.4 or higher. The specific gravity of the glass substrate is more preferably 2.45 or higher. In the case where the specific gravity of the glass substrate is 3.0 or less, the glass substrate is less prone to embrittlement and weight reduction is achieved. The specific gravity of the glass substrate is more preferably 2.6 or less.

In the case where the glass substrate has a high Young's modulus, the glass substrate is rigid and more suitable for automotive glazing applications, etc. The Young's modulus of the glass substrate is preferably 65 GPa or higher, more preferably 70 GPa or higher, even more preferably 72 GPa or higher. Increasing the content of SiO ₂ to increase the Young's modulus of the glass substrate results in poor fusibility. Thus, the proper values of Young's modulus are 100 GPa or less. The Young's modulus of the glass substrate is more preferably

- 3 041197 is 85 GPa or less, even more preferably 78 GPa or less.

In the case where the glass substrate has a high average coefficient of linear expansion, the glass substrate can be physically strengthened and is more suitable for window glass applications. The average coefficient of linear expansion at a temperature of 50°C to 350°C is more preferably 60x10 ^-7 /°C or higher, even more preferably 80x10 ^-7 /°C or higher. In the case where the glass substrate has an excessively high average coefficient of linear expansion, the glass sheet is prone to thermal stress due to temperature distribution therein in the forming step, the annealing step, or the physical strengthening step. This can cause thermal cracking of the sheet. In addition, there is an increased difference in expansion between such a glass substrate and metal window frames or the like, and the difference in expansion causes stresses and may lead to cracking. The average coefficient of linear expansion at a temperature of 50°C to 350°C is more preferably 110x10 ^-7 /°C or less, even more preferably 98x10'/C or less.

The glass substrate preferably has a T2 value of 1750° C. or lower. The glass substrate preferably has a T ₄ value of 1350°C or lower. The T ₄ -T _l value of the glass substrate is preferably -50° C. or higher. More preferably, the glass substrate has a T2 value of 1750°C or less, a T ₄ of 1350°C or less, and a T _{4 -Tl of} -50°C or more. In this specification, T2 denotes the temperature at which the glass has a viscosity of 102 (dPa-s), _T4 denotes the temperature at which the glass has a viscosity of ¹⁰⁴ (dPa-s), and _Tl denotes the liquidus temperature of the glass.

In the case where the T2 or _T4 value is higher than this temperature, it is difficult to produce a large sheet by the float method, the melt method, the drawing method, the downward drawing method, etc. The T2 value is preferably 1600°C or less, even more preferably 1500°C or less. The T ₄ value is preferably 1350°C or less, even more preferably 1200°C or less. For T ₂ and T ₄ there are no specific lower limits. However, for reasons of maintaining weather resistance and specific gravity of the glass, T ₂ is typically 1200°C or higher, and T ₄ is typically 800°C or higher. More preferably T ₂ is 1300°C or higher, even more preferably 1400°C or higher. More preferably T ₄ is 900°C or higher, even more preferably 1000°C or higher.

In view of the possibility of obtaining a glass substrate by the float method, the value of T ₄ -T _l is preferably -50°C or higher. In the case where the difference between them is less than -50°C, the glass may devitrify during glass formation, and this may cause problems in that the glass has reduced mechanical performance, reduced transparency, etc., making it impossible to obtaining glass with satisfactory quality. Therefore, such too low values of T ₄ -T _l are undesirable. The value of T ₄ -T _l is preferably 0°C or higher, even more preferably 20°C or higher.

The glass substrate preferably has a Tg value of 400°C or higher and 750°C or less. In this description, Tg means the glass transition temperature of the glass. In the case where the value of Tg is within the specified temperature range, the bending of this glass can be performed within the normal process conditions. In the case where the Tg is less than 400° C., this glass, although having satisfactory formability, has an alkali content that is too high or an alkaline earth metal content that is too high, and is therefore prone to such problems that the glass exhibits excessive thermal expansion and has reduced weather resistance, etc. There is also the possibility that this glass could devitrify at temperatures within the molding temperature range, making molding impossible. The Tg value is more preferably 450°C or higher, even more preferably 480°C or higher, particularly preferably 520°C or higher. In a case where the Tg value is too high, a higher temperature is required to bend the glass, thereby making manufacturing difficult. The Tg value is more preferably 600°C or less, even more preferably 550°C or less.

The glass substrate can be formed having reduced dielectric loss by adjusting the composition of the glass, thereby achieving high radio wave transmission. Likewise, the relative permittivity can also be adjusted by adjusting the composition, allowing the relative permittivity to be achieved according to the application.

The glass substrate preferably has a SiO ₂ content of 50% or more and 80% or less. The glass substrate preferably has an Al ₂ O ₃ content of 0% or more and 20% or less. SiO ₂ and Al ₂ O ₃ contribute to the improvement of Young's modulus, making it easier to provide the strength needed in building applications, automotive glass, etc. In the case where the content of Al ₂ O ₃ and/or SiO ₂ is too low, not only does it become difficult to provide weather resistance, but also the glass tends to have an average linear expansion coefficient that is too high and is prone to thermal cracking. Such too

- 4 041197 low levels of their content is therefore undesirable. In the case where the content of Al ₂ O ₃ and/or SiO 2 is too high, this glass has an increased melt viscosity, making glass production difficult.

Too high levels of their content are also undesirable. In addition, too high levels of Al2O ₃ may result in reduced radio wave transmission.

The content of SiO2 is more preferably 65% or more, even more preferably 70% or more, particularly preferably 72% or more. The content of SiO ₂ is more preferably 77% or less, even more preferably 75% or less.

The content of Al ₂ O ₃ is preferably 0.1% or higher from the standpoint of improving weather resistance. In order to keep the T ₂ viscosity of the glass low to facilitate glass production and improve radio wave transmission, the Al2O3 content is more preferably 5% or less, even more preferably 1% or less, particularly 0.5% or less.

For reasons of increasing radio wave transmission, it is preferable that SiO ₂ +Al ₂ O ₃ , that is, the total content of SiO ₂ and Al ₂ O ₃ , be 50% or more and 80% or less. Also, in order to keep glass viscosities T ₂ and T ₄ low to facilitate glass production, SiO ₂ +Al ₂ O ₃ is preferably lower, and thus preferably 80% or less. More preferably SiO ₂ +Al ₂ O ₃ is 76% or less, even more preferably 74% or less. However, in a case where the value of SiO ₂ +Al ₂ O ₃ is too low, the glass substrate might have reduced weather resistance and an average linear expansion coefficient that is too high. In view of this, the value of SiO ₂ +Al ₂ O ₃ is more preferably 65% or more, even more preferably 72% or more.

The glass substrate preferably has a B2O3 content of 0% or more and 15% or less. B ₂ O ₃ can be added to improve fusibility and to improve the strength of the glass. In addition, B2O3 exhibits the ability to increase the permeability to radio waves. In the case where the content of B2O3 is too high, the alkaline elements might be prone to volatilization during melting/forming, resulting in deterioration of the quality of the glass. In the case where the content of B ₂ O ₃ is too high, the glass has a reduced average coefficient of linear expansion, and physical strengthening becomes difficult. The B ₂ O ₃ content is more preferably 10% or less, even more preferably 3% or less, particularly preferably substantially free.

The glass substrate preferably has an MgO content of 0% or more and 20% or less. MgO is a component that promotes the melting of glass raw materials and improves weather resistance. The MgO content is preferably 0.1% or higher. In the case where the MgO content is 20% or less, this glass is less prone to devitrification. There are situations where MgO is also effective in increasing radio wave transmission. The MgO content is more preferably 4% or less, even more preferably 1% or less, particularly preferably 0.2% or less.

CaO, SrO and/or BaO may be contained in certain amounts in the glass substrate to make the glass have reduced dielectric loss. The content of CaO is preferably 0% or more and 20% or less. The content of SrO is preferably 0% or more and 15% or less. The content of BaO is preferably 0% or more and 15% or less. In the case where the glass substrate contains CaO, SrO and/or BaO, the glass may have improved fusibility. The content of CaO is more preferably 3% or higher, and such levels of CaO content reduce the dielectric loss of the glass to improve radio wave transmission. In addition, adding CaO in an amount of 3% or more also leads to an improvement in glass fusibility (lower T ₂ and lower T ₄ ). The CaO content is more preferably 8% or more, even more preferably 11% or more. By controlling the CaO content to 20% or less, the SrO content to 15% or less and the BaO content to 15% or less, the increase in the specific gravity of the glass is prevented and the strength and low brittleness are maintained. For reasons of preventing glass brittleness, the CaO content is more preferably 15% or less, even more preferably 12% or less. The SrO content is more preferably 3% or less, even more preferably substantially free. The content of BaO is more preferably 3% or less, even more preferably substantially free.

In this description, RO represents the total content of MgO, CaO, SrO and BaO. The glass substrate preferably has an RO of 0% or more and 20% or less. In the case where its RO is 20% or less, this glass substrate has improved weather resistance. The RO value of the glass substrate is more preferably 16% or less, even more preferably 13% or less.

For reasons of reducing the T2 and T4 viscosities of the glass during manufacture, or for reasons of increasing the Young's modulus, the RO value of the glass substrate is preferably above 0%, more preferably 5% or more, even more preferably 10% or more.

For reasons of preventing glass devitrification during melting or molding

- 5 041197 glass, the total content of MgO and CaO (MgO+CaO) is preferably 0% or more and 20% or less. More preferably, MgO+CaO is 15% or less, even more preferably 13% or less. However, in a case where the MgO+CaO value is too low, the viscosity of the glass at the time of melting or molding might be too high, making it difficult to manufacture. In view of this, the value of MgO+CaO is preferably 4% or more, even more preferably 10% or more.

The glass substrate preferably has a Na ₂ O content of 0% or more and 18% or less. Na ₂ O and K2O are components that improve glass fusibility, and more preferably, the glass substrate contains 0.1% or more of Na ₂ O and 0.1% or more of K2O. This facilitates the regulation of T ₂ to 1750°C or below, and T ₄ to 1350°C or below. The introduction of Na ₂ O allows chemical strengthening of the glass. The content of Na ₂ O is more preferably 4% or more, even more preferably 6% or more.

In the case where the Na2O content is too high, the glass substrate has an average linear expansion coefficient that is too high, and tends to thermal crack. The content of Na2O is preferably 16% or less, even more preferably 10% or less, particularly preferably 8% or less.

The glass substrate preferably has a K2O content of 0% or more and 18% or less. K2O is a component that improves the fusibility of glass, and more preferably, the glass substrate contains 0.1% or more of K2O. This facilitates the regulation of T ₂ to 1750°C or below and T ₄ to 1350°C or below. The content of K2O is more preferably 2% or more, even more preferably 5% or more.

In the case where the content of K2O is too high, the glass substrate has an average linear expansion coefficient that is too high and is prone to thermal cracking. In the case where the content of K2O exceeds 18%, the glass substrate has reduced weather resistance. Thus, such too high levels of K2O are undesirable. The content of K2O is preferably 16% or less, even more preferably 12% or less, particularly preferably 8% or less.

In the case where the glass substrate contains both Na ₂ O and K ₂ O, the glass substrate can have improved weather resistance while maintaining fusibility. Therefore, it is preferable to introduce both of them. Their incorporation is often also effective in increasing radio wave transmission. In the case where the content of Na ₂ O and/or K 2 O is too low, this glass cannot have an increased average coefficient of linear expansion, and cannot be thermally strengthened. By adjusting the content of Na ₂ O and/or K 2 O so that it is within a predetermined range, the glass substrate is made suitable as a material for window panes that are in excellent agreement with other details. From the standpoint of radio wave transmission, by adjusting the content so that it is within a predetermined range, high radio wave transmission can be obtained.

The glass substrate preferably has a Li ₂ O content of 0% or more and 18% or less. Li ₂ O is a component that improves the fusibility of glass and makes it easier to increase the Young's modulus to help improve the strength of the glass. The glass substrate containing Li ₂ O can be chemically strengthened. The introduction of Li ₂ O is often also effective in increasing radio wave transmission. In the case where Li ₂ O is contained, its content may be 0.1% or more, or it may be 1% or more, or it may be 3% or more.

In the case where the content of Li2O is too high, devitrification or phase separation might occur during glass production, making production difficult. The content of Li2O is more preferably 10% or less. Li2O can reduce the coefficient of thermal expansion, making the glass unsuitable for physical strengthening. Therefore, it is undesirable that the glass substrate for use as automobile window glass has an excessively high content of Li2O. In view of this, the content of Li2O is more preferably 7% or less, even more preferably 3% or less, particularly preferably substantially free.

In this description, R2O represents the sum of alkali metal oxides. Generally, R2O means the total content of Li ₂ O, Na ₂ O and K ₂ O. The R2O value of the glass substrate is preferably 4% or more and 20% or less. In the case where its R ₂ O value is 20% or less, this glass substrate has improved weather resistance. The R2O value of the glass substrate is more preferably 18% or less, even more preferably 15% or less.

For reasons of reducing the viscosities of T2 and T4 glass during manufacture, its R2O value is preferably 4% or higher. Its R2O value is more preferably 9% or more, even more preferably 13% or more, particularly preferably 14% or more.

The glass substrate preferably has a ZrO ₂ content of 0% or more and 5% or less. ZrO ₂ has the effect of reducing the viscosity of the glass melt, promoting melting, and can contribute to improvements in heat resistance and chemical resistance. In the case where the ZrO2 content is too high, the glass could have an increased liquidus temperature and an increased average coefficient of linear expansion. The content of ZrO ₂ is more preferably 1.0% or less, more

- 6 041197 more preferably it is essentially not contained.

The glass substrate preferably has an Fe2O3 content of 0.001% or more and 5% or less. In the case where the content of Fe2O3 is less than 0.001%, this glass substrate would not only be unsuitable for use in applications where thermal barrier properties are required, but it would also become necessary that expensive raw materials having low iron content. Therefore, such too low Fe2O3 levels are undesirable. In addition, by adjusting the content of Fe2O3 to 0.001% or more, heat radiation during glass melting can be prevented from reaching the bottom of the melting furnace in an unnecessarily large amount, thereby increasing the load on the melting basin. The Fe ₂ O ₃ content is more preferably 0.01% or more, even more preferably 0.05% or more.

In the case where the Fe2O3 content exceeds 5%, radiation heat transfer could be prevented, making it difficult to melt the raw materials. In addition, in a case where the content of Fe2O3 is too high, the light transmittance in the visible region could be reduced, making the glass substrate unsuitable for use as a glazing for automobiles. The content of Fe2O3 is more preferably 1% or less, even more preferably 0.3% or less.

The glass substrate preferably has a TiO2 content of 0.001% or more and 5% or less. By adjusting the content of TiO2 so as to be within this range, formation of a layer of bubbles on the surface of the molten glass can be prevented in the manufacture of the glass substrate. When a layer of bubbles is formed, the molten glass tends to be less efficient in heating and cleaning, resulting in poor production performance. The titanium compound can be added as a defoamer to the bubble layer formed on the surface of the molten glass to thin or eliminate the bubble layer formed on the surface of the molten glass. The titanium compound enters the molten glass and becomes present as TiO2. The content of TiO2 is more preferably 0.05% or higher. Since TiO2 exhibits absorption in the ultraviolet range, it is preferable to add a titanium compound in the case where it is desirable not to transmit ultraviolet radiation. In this case, the TiO ₂ content may be more preferably 0.1% or more, even more preferably 0.5% or more. However, too high levels of TiO2 can lead to an increase in the liquidus temperature, causing devitrification. In addition, a glass substrate having too high a TiO2 content may exhibit absorption in the visible region, resulting in a yellow coloration. Therefore, it is preferable to adjust the TiO2 content to 5%. The content of TiO2 is more preferably 0.5% or less, even more preferably 0.2% or less.

In the case where water is present in the glass substrate, the glass substrate has a reduced near-infrared light transmittance because water exhibits absorption in the near-infrared region, and this glass substrate is unsuitable for use in devices for emitting infrared rays (for example, laser radars). ). The water content of glass can generally be expressed in terms of the e-OH value. The e-OH value of the glass substrate is preferably 0.5 mm ^-1 or less, more preferably 0.3 mm ^-1 or less, even more preferably 0.2 mm ^-1 or less. The e-OH value can be obtained using the following equation from the light transmission coefficient of glass measured on an FT-IR instrument (Fourier Transform Infrared Spectrometer).

3-OH \u003d (1 / X) 1o _ё10 (T _A / Tv) [mm- ¹ ]

X - sample thickness [mm]

T _A - light transmission coefficient [%] at a reference wavenumber of 4000 cm ^-1

TB is the minimum light transmission coefficient [%] near the wave number of the absorption band of the hydroxyl group of 3600 cm ^-1 .

For reasons of improving the heat-shielding performance of the glass substrate, in this embodiment, the e-OH value of the glass is preferably 0.05 mm ^-1 or higher, more preferably 0.10 mm ^-1 or higher, even more preferably 0.15 mm ^-1 or higher .

Thermal reflective film

The radio wave-permeable substrate according to this embodiment includes a thermal radiation reflective film, and the thermal radiation reflective film includes an electrically conductive film. This radio-transparent substrate thus performs the function of reflecting thermal radiation. The heat reflective film may include other layers than the electrically conductive film as long as the effect of the present invention is achieved. Hereinafter, layers other than the electrically conductive film in the thermal radiation reflective film are often referred to as other layers.

In this description, the term electrically conductive film means a film having an electrical resistivity at 20° C. of 10° [Ω-cm] or less. The electrically conductive film is not particularly limited in terms of its components. However, it is preferable that

- 7 041197 the electrically conductive film included, for example, a metal having excellent thermal radiation reflection characteristics such as silver, aluminum, indium tin oxide (ITO), tin oxide doped with fluorine and/or antimony (SnO2:F, Sb), nitride titanium, niobium nitride, chromium nitride, zirconium nitride, and hafnium nitride (hereinafter also referred to as the group A component of the electrically conductive film) as the main component. In this description, the term main component used for a substance means that the content of this substance is 50 at.% or higher relative to all constituent components. That is, it is preferable that the electrically conductive film in this embodiment includes at least one substance selected from the group A components of the electrically conductive film, and that the total content of the electrically conductive film group A component in the electrically conductive film in this embodiment is 50 at.% or more .

For reasons of enabling the radio wave-permeable region to have excellent thermal radiation reflection characteristics, the electrically conductive film preferably includes at least one of silver or aluminum as a main component, and the electrically conductive film more preferably includes silver as a main component (i.e., the film includes 50 at.% or more of silver), and even more preferably includes 95 at.% or more of silver.

The electrically conductive film including silver as the main component may contain one or more additional elements such as gold, palladium, copper, bismuth, neodymium, and platinum. By adding such additional elements to an electrically conductive film including silver as a main component, diffusion of silver can be prevented and moisture resistance can be improved. The additional elements are not limited to the above as examples, and any desired elements may be added as long as the effect of the present invention is achieved.

The thickness of the electrically conductive film in this embodiment is not particularly limited. The thickness can be appropriately adjusted according to the transparency to radio waves having a predetermined frequency, thermal reflection characteristics, transparency to visible light, appearance, etc., which are required for the resulting radio wave-permeable substrate. The thickness of the electrically conductive film may generally be 1 nm or more, and preferably 3 nm or more, more preferably 5 nm or more, even more preferably 6 nm or more. Its thickness is preferably 100 nm or less, more preferably 50 nm or less, even more preferably 20 nm or less. The electrically conductive film may be composed of only one layer (single layer structure), or may be composed of multiple layers, such as two or three layers. In the case where multiple layers are present, these layers may be adjacent to each other in the thickness direction of the electrically conductive film, or may be separated from each other by another layer placed between them. In the case where the electrically conductive film is composed of multiple layers, the total thickness may be within the range shown above.

As mentioned above, the heat reflective film in this embodiment may include layers (other layers) other than the electrically conductive film, as long as the effect of the present invention is achieved.

The radio wave-permeable substrate according to this embodiment may include, for example, a metal oxide layer or a metal nitride layer. Preferably, the radio wave-permeable substrate includes at least one of a metal oxide layer and a metal nitride layer. In particular, for reasons of durability, it is preferable that the heat reflective film has a layered configuration in which the electrically conductive film is sandwiched between said other layers, such as metal oxide layers or metal nitride layers. Examples of the metal oxide layers include layers of metal oxides including alumina, zinc oxide, indium oxide, titanium oxide, niobium oxide, tin oxide, bismuth oxide, tantalum oxide, tungsten oxide, zirconium oxide, silicon oxide, or the like, as the base component. Of these, a metal oxide layer including zinc oxide as a main component is preferable because zinc oxide is satisfactorily compatible with silver, which is a preferred component of the electrically conductive film, and is able to increase the strength of the electrically conductive film. Examples of the metal nitride layers include metal nitride layers containing silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN), or the like as a main component.

Methods for forming a thermal radiation reflective film are not particularly limited. For example, methods of physical vapor deposition (vacuum deposition, ion sputtering, magnetron sputtering, etc.), chemical vapor deposition (thermal CVD, plasma CVD, photochemical CVD, etc.), ion beam sputtering can be applied. , or the like. In the case where the film is deposited over a large area, it is preferable to use DC magnetron sputtering (D.C.), pulsed D.C magnetron sputtering, or alternating current (A.C.) dual magnetron sputtering, since these methods provide easy control of thickness uniformity and have excellent

- 8 041197 processing performance.

The heat reflective film in this embodiment can be directly or indirectly formed on a dielectric substrate. Methods for directly forming a thermal radiation reflective film on a dielectric substrate are not particularly limited. Examples thereof include a method in which a polymer film on which a thermal radiation reflective film has been formed is deposited on a dielectric substrate.

In the embodiment shown in FIG. 1, the thermal reflective film 13 (and holes 14) is formed on the entire main surface of the dielectric substrate 21. However, the thermal reflective film may be formed on only a portion of the main surface. One example is shown in FIG. 2 which is a plan view of the radio wave-permeable substrate 20 as an embodiment in which the heat reflective film 23 and holes 24 are placed on a part of one major surface of the dielectric substrate 21, and in which the dielectric substrate 21 is exposed in the remaining large portion.

Hole

The hole is a portion where, at least in plan view, there is no electrically conductive film, and is separated by a thermal radiation reflective film. In the case where the thermal radiation reflective film includes both the electrically conductive film and layers other than the electrically conductive film, examples of the aperture configuration include a configuration in which there is a portion where the electrically conductive film and all layers other than the electrically conductive film have been removed and where the dielectric the substrate constitutes the outermost surface. That is, examples of the opening configuration include a configuration in which a dielectric substrate is exposed.

The hole configuration is not limited to the configuration in which there is a portion where the dielectric substrate constitutes the outermost surface. For example, the configuration may be such that the hole does not include an electrically conductive film, but includes at least one other layer than the electrically conductive film, while the effect of the present invention is achieved. Namely, there is no electrically conductive film in the hole, and only at least one layer (a film having electrical resistivity higher than 10° [Ω-cm]) other than the electrically conductive film can be layered on the dielectric substrate. For example, there is no electrically conductive film in the hole, and an oxide layer or a nitride layer, such as those shown above to clarify the other layers, may be layered on the dielectric substrate.

In the embodiment shown in FIG. 1, the radio wave-permeable region has openings which, in plan view, are multiple parallel lines (hereinafter also referred to simply as parallel lines). However, the openings are not limited to linear portions, and may be circular or elliptical portions, dots, etc., for example.

In the case where the openings are linear, the openings may form, for example, a lattice pattern, a curved line, may be zigzag, or a pattern of irregular lines other than straight lines. For example, examples of straight holes include holes in which each hole has an outer shape that is a rectangle or parallelogram.

Methods for forming the radio wave-permeable region (hole formation methods) in this embodiment are not particularly limited. Examples thereof include a method in which a continuous (solid) thermal radiation reflective film is formed on a given area of the surface of the dielectric substrate without leaving a hole, and then the thermal radiation reflective film is partially removed; and a method in which a heat-reflecting film is formed only on a given area of the surface of the dielectric substrate, thereby obtaining a radio-wave-permeable area.

Examples of methods for partially removing a thermal reflective film include laser etching and photolithography. Examples of methods for forming a hole including layers other than the electrically conductive film by partially removing only the electrically conductive film (or without depositing the electrically conductive film) include a method in which the electrically conductive film is partially removed by photolithography, laser etching, etc., and then others are deposited. layers.

In addition, examples of methods for forming a thermal reflection film only on a given portion of the surface of the dielectric substrate include a method in which a portion of the dielectric substrate where the thermal reflection film is not formed (a portion where a hole is formed) is covered (masked) with a sheet or plate, and then form a film reflecting thermal radiation.

The holes are preferably linear, more preferably straight, for reasons of hole formation efficiency. Particularly in the case of forming holes in a method in which the heat-reflecting film is partially removed by laser etching, straight-line holes extending in the first direction can be easily formed by drawing the substrate in the first direction while irradiating the heat-reflecting film.

- 9 041197 films with a fixed laser beam. In addition, the substrate can, for example, then be advanced in a second direction different from the first direction, while irradiating the heat-reflecting film with a fixed laser beam. Thus, straight holes extending along the first and second directions can be easily obtained.

For reasons of ease of manufacture as described above, it is preferred that the openings in this embodiment be straight lines extended in the first direction, or a combination of straight lines extended in the first direction and straight lines extended in the second direction. More specifically, it is preferred that the openings are either multiple parallel lines or form a lattice structure. This configuration is preferable because portions of the thermal radiation reflective film having a given width and holes having a given width have been alternately arranged along the width direction(s) of parallel lines or a grating structure to create periodicity, and thereby improve transparency for radio waves having preset frequencies.

For example, in the case where the openings in the top view of the radio wave-permeable substrate are either straight lines having a predetermined width and extending in one direction, or portions located in a lattice structure, and multiple of these portions are arranged along the width direction in parallel order to form a radio-transparent region, this radio-permeable region has increased transparency for linearly polarized waves perpendicular to the extension direction. Due to this, a radio-wave-permeable substrate having such a radio-wave-permeable region is advantageous in the case where high-performance transmission of predetermined linearly polarized waves is desired. More specifically, the above-described radio-permeable substrate tends to exhibit high transparency to vertically polarized radio waves when mounted perpendicular to the ground such that the extension direction of the straight or lattice holes is horizontal with respect to the ground.

Area permeable to radio waves

In this embodiment, the radio wave-permeable area is an area where every 1 sq. cm unit area satisfies the following expression (a) and is an area that has excellent transparency not only for radio waves in conventional applications, but also for radio waves having frequencies from about a few hundred megahertz to tens of gigahertz. This radio-permeable region exhibits better transparency especially for radio waves from 6 GHz to tens of gigahertz than conventional regions.

L>802.6><S-503.7 (a) (In the expression (a), L represents the total length (unit: mm/cm ² ) of the boundary between the heat-reflecting film and the hole in the unit area, and S represents the area ratio, occupied by a film reflecting thermal radiation in a single region).

The radio wave-permeable region in this embodiment may be formed on only one major surface of the dielectric substrate, or may be formed on both major surfaces. In the case where the radio wave-permeable region is formed on both major surfaces of the dielectric substrate, this embodiment may have a top-view configuration where the radio-wave-permeable region on one major surface partially or completely overlaps the radio-wave-permeable region on the other major surface, or may have a plan view configuration where the radio-transparent regions do not overlap with each other at all.

The inventors of the present invention have found that not only the proportion of the area occupied by the heat reflective film in the radio wave transparent area in plan view, namely the coverage amount of the heat reflective film, but also the total length of the boundaries between the heat reflective film and the holes in the radio wave transparent areas are a factor that affects the transmission characteristics of radio waves. The inventors of the present invention have found that the transmission characteristics of radio waves can be improved by increasing the overall length of the boundaries. When radio waves enter the radio-permeable area, an electromagnetic field is generated between sections of the electrically conductive film that face each other with a hole sandwiched between them, and radio waves are radiated again to the side opposite to the arrival surface. Thus, high transmission characteristics of radio waves are obtained. In addition, with an increase in the total length of the boundaries, the proportion of opposite sections of the electrically conductive film that face each other with a hole sandwiched between them increases. Thereby, generation of an electromagnetic field is stimulated, and the efficiency of re-radiation is increased, thereby improving the transmission characteristics of radio waves.

Based on this idea, the present inventors have found through experiments that the region that satisfies the expression (a) exhibits particularly satisfactory radio wave transmission characteristics, and exhibits excellent transparency also for radio waves having frequencies from about several hundred megahertz to tens of gigahertz. . The present invention has been made based on this discovered fact.

As long as the difference between the left side and the right side of the expression (a) [(left side)-(right side)], that is, {L-(802.6xS-503.7)}, exceeds 0, the expression (a) is satisfied. However, increasing the difference tends to make it easier to obtain better radio wave transmission characteristics. That is, it is preferable that the difference between the left side and the right side of the expression (a) [(left side)-(right side)] is larger. The difference is preferably 100 or more, more preferably 400 or more. In other words, it is more preferable that each 1 square centimeter of a unit area in the radio wave-permeable area in this embodiment satisfies the following expression (a-1), even more preferably satisfies the following expression (a-2).

L>802.6xS-403.7(a-l)

L>802.6xS-103.7 (a-2)

The values of the total length L of the boundaries between the thermal reflective film and the hole in the unit area, and the area fraction S occupied by the thermal reflective film in the unit area differ depending on the unit area within the considered radio-wave-permeable areas.

In the case where the value obtained by dividing the total length of the boundary between the heat-reflecting film and the hole in the entire radio-wave-permeable area by the area (unit: ^cm2 ) of the entire radio-wave-permeable area (hereinafter, this value is also called the average boundary length per unit area where the value obtained by dividing the total area of the heat-reflecting film in the radio-wave-transmissive area by the total area of the radio-wave-permeable area (hereinafter, this value is also referred to as the coverage amount of the radio-wave-permeable area of the heat-reflecting film ) is expressed by the symbol S', the values of L and S differ from L' and S' depending on the considered unit areas.

However, in the case where the holes are arranged at approximately regular intervals, and the widths of the holes and the heat reflective film are sufficiently small compared to the length of each side (i.e., 1 cm) of the unit regions, L and S are approximately the same as L ' and S', even when considering any single region in the radio wave-permeable region.

In this embodiment, S' is preferably 65% or more, more preferably 80% or more, even more preferably 90% or more. L' is preferably 100 mm/cm ² or more, more preferably 300 mm/cm ² or more, even more preferably 500 mm/cm ² or more. The difference between L and L' and the difference between S and S' are preferably within ±10%, more preferably within ±5%.

The present inventors have found that in the case where the radio wave-permeable region further satisfies the following expression (b), the radio wave-permeable region is particularly excellent also in terms of thermal radiation reflection characteristics, and a radio wave-permeable substrate is obtained that combines excellent radio wave transmission characteristics and characteristics of the reflection of thermal radiation. That is, in this embodiment, it is more preferable that the radio wave-permeable area satisfies the following expression (b).

Z>(-Z'+Z'xS'+0.3)/S' (b) (In expression (b), Z represents the solar reflectance of the thermal reflective film, Z' represents the solar reflectance of the hole, and S ' represents the amount of coverage of the radio-transparent area by the reflective film).

The above solar reflectance refers to the solar reflectance defined in JIS R3106 (1998). This standard also applies to solar reflectance, which is mentioned later. In the case where no heat reflective film is present in the hole, Z' corresponds to the solar reflectance of the dielectric substrate.

In this embodiment, for reasons of heat reflection characteristics, the radio wave-permeable area more preferably satisfies the following expression (b1), even more preferably satisfies the following expression (b-2), and particularly preferably satisfies the following expression (b-3).

Z>(-Z’+Z’xS’+0.35)/S’ (b-1)

Z>(-Z’+Z’xS’+0.4)/S’ (b-2)

Z>(-Z’+Z’xS’+0.43)/S’ (b-3)

In expressions (b-1), (b-2) and (b-3), Z represents the solar reflectance

- 11 041197 reflecting thermal radiation film, Z' represents the reflectance of the solar radiation of the hole, and S' represents the amount of coverage of the radio-transparent area of the reflective thermal radiation film.

The present inventors have found that in the case where the radio wave-permeable region further satisfies the following expression (c), the hole is less likely to be visually distinguishable, and the radio wave-permeable region has an excellent appearance. That is, in this embodiment, it is more preferable that the radio wave-permeable area satisfies the following expression (c).

ΔΕ<60.3χϋ-°' ⁶² (s)

In the expression (c), Δε represents the color contrast between the heat radiation reflective film and the hole, and D represents the width (unit: mm) of the hole.

That is, the smaller ΔΕ and the smaller D, the smaller the hole is visually distinguishable. In the case where the thermal radiation reflective film is not present in the hole, the surface of the hole corresponds to the dielectric substrate.

In this embodiment, for reasons of making the hole less likely to be visually distinguishable, the radio wave-permeable area more preferably satisfies the following expression (c-1), even more preferably satisfies the following expression (c-2), and particularly preferably satisfies the following expression (s-3).

AE<60.3xD-°' ⁶² -50 (s-1)

AE<60.3xD-°' ⁶² -150 (s-2)

AE<60.3xD-°> ⁶² -3 5 0 (s-3) (In terms of (s-1) to (s-3), ΔΕ represents the color contrast between the heat reflective film and the hole, and D represents the width (unit: mm) holes).

More specifically, the color difference ΔΕ between the thermal reflection film and the hole is the color difference between the thermal reflection film and the hole, which is determined by the following expression (c-i) according to the L*a*b* color coordinate system.

AE={(AL*) ² +(Aa*) ² +(Ab*) ² } ^1/2 (ci)

In the expression (c-i), AL*, Aa* and Δb* represent the values defined by the following expressions from (c-ii) to (c-iv).

AE*=|E*(reflecting thermal radiation film)-E*(holes)| (c-ii) Aa*=|a*(thermal reflective film)-a*(holes)| (c-iii) AB*=|b*(thermal reflective film)-b*(holes)| (c-iv)

In the expressions (c-ii) to (c-iv), b*(thermal reflective film), a*(thermal reflective film) and b*(thermal reflective film) respectively represent the hues of the thermal reflective film according to L*a*b* color coordinate system.

In the expressions (c-ii) to (c-iv), b*(holes), a*(holes) and b*(holes) respectively represent hole hues according to the L*a*b* color coordinate system.

The value of AE can be determined by the method described in the examples.

In the case where the holes are lines, the width D of the hole means the width (thickness) of each line. In the case where the holes are dots, or are circular, elliptical, or the like, the width D of the hole means the shortest length of the line segments that can be drawn inside the hole, and which run through the center of gravity of the hole contour. That is, in the case where each hole is in the form of a square dot, the width D of the hole means the length of each side of the square. In the case where each hole is in the form of a rectangular point, the width D of the hole means the length of each smaller side of the rectangle. In the case where each hole is circular, the width D of the hole means the diameter of the circle. In the case where each hole is elliptical, the width D of the hole means the length of the minor axis of the ellipse.

Moreover, in the case where there are multiple holes of different widths in the radio wave-permeable region, the width of the hole having the largest width is taken as the hole width D in expression (c) to judge whether the radio wave-permeable region satisfies expression (c) or No.

Impenetrable area for radio waves

In this embodiment, the region of the radio wave-permeable substrate, which includes both the heat-reflecting film and the hole, may be entirely the radio-wave-permeable region, or may partially include the radio-impervious region. Hereinafter, the area of the radio wave-permeable substrate, which includes both the heat-reflecting film and the hole, other than the radio-wave-permeable area, is often referred to as the radio-wave impervious area.

- 12 041197

That is, although the entire surface area of the radio wave-permeable substrate as shown in FIG. 1 is a radio wave permeable region A, some of the surface of the radio wave permeable substrate may be a radio wave permeable region A, and the remainder of it may be a radio wave impervious region B, as in the radio wave permeable substrate 30 according to another embodiment. execution shown in Fig. 3.

The radio wave impervious area is the area which is in the area of the radio wave transparent substrate which includes the heat reflective film and the hole, and in which every 1 sq. cm of the unit area including said area satisfies the following expression (d)

L<802.6*S-503.7 (d)

In the expression (d), L represents the total length (unit: [mm/cm ² ]) of the boundary between the heat reflective film and the hole in the unit area, and S represents the proportion of the area occupied by the heat reflective film in the unit area.

The radio-impervious region may or may not have an opening. That is, the radio wave impermeable area may be an area in which a hole is formed such that expression (d) is satisfied, or it may be an area that includes a heat radiation reflective film only without creating a hole in it. However, it is preferable that the radio wave impervious area is a region that only includes a heat reflective film and does not include a hole, in order to enhance the heat reflection characteristics and prevent the radio wave transparent substrate from having a degraded appearance due to the hole. which is easily visible visually.

As described above, the radio-transparent substrate according to this embodiment may or may not include a radio-impermeable region.

For example, in a case where a large proportion of the radio wave-permeable substrate is to have radio wave transmission characteristics, it is often preferable that the entire surface of the radio wave-permeable substrate be a radio wave-permeable region and not contain a radio-impermeable region.

On the other hand, for example, in the case where a radio transceiver is to be placed on a portion of the radio wave-permeable substrate, the radio wave-permeable substrate is often configured such that only the area required for transmission by the transceiver is the radio wave-permeable region, and the remainder is a region impenetrable to radio waves.

Properties of a radio-transparent substrate

The radio-wave-permeable region of the radio-wave-permeable substrate according to this embodiment exhibits excellent transparency also, in particular, for radio waves having frequencies from about a few hundred megahertz to tens of gigahertz, and furthermore exhibits excellent transparency for radio waves having frequencies from about 6 GHz to tens of gigahertz. More specifically, in the radio wave-permeable substrate according to this embodiment, the radio wave-permeable region is less likely to suppress the transmission of radio waves having predetermined frequencies.

In the radio wave-permeable substrate according to this embodiment, the radio wave-permeable region has a transmission loss of radio waves having a frequency of 28 GHz, preferably 3 dB or less, more preferably 2 dB or less, even more preferably 1 dB or less. The transmission loss of ee when passing radio waves having a frequency of 79 GHz is likewise preferably 3 dB or less, more preferably 2 dB or less, even more preferably 1 dB or less.

The radio wave transmission loss of the radio-permeable region when transmitting radio waves having a frequency of 28 GHz (79 GHz) is the value obtained by subtracting the transmission loss of radio waves of a dielectric substrate when transmitting radio waves having a frequency of 28 GHz (79 GHz) from the transmission loss of radio waves of the entire transparent for the radio waves of the substrate inside the radio-wave-permeable region when passing radio waves having a frequency of 28 GHz (79 GHz).

Although the radio wave transparency of the radio wave transparent area has been explained above using its radio wave transmission loss when passing radio waves having frequencies of 28 GHz and 79 GHz as an example, radio waves are not limited to the 28 GHz band and the 79 GHz band. Preferably, the same transmission loss as shown above would be obtained by transmitting radio waves having frequencies in the range of about a few hundred megahertz to tens of gigahertz.

It is preferable that the radio wave-permeable substrate according to this embodiment has excellent thermal radiation reflection characteristics. The reflectance characteristics of thermal radiation can be evaluated in terms of solar reflectance, as defined in JIS R3106 (1998), for example. The solar reflectance of the radio-wave-permeable region of the radio-wave-permeable substrate according to this embodiment is preferably 30% or more, more preferably 35% or more, still

- 13 041197 more preferably 40% or more.

Examples

The present invention is explained in detail below with reference to examples, but the invention is not limited to the following examples.

Preparation of radio-transparent substrates

First, glass sheets were made as dielectric substrates. More specifically, the raw materials were placed in a platinum crucible so as to obtain in each case the compositions (unit: mol.%) of the glasses shown in Table. 1, and melted by heating at 1550° C. for 2 hours. Thereafter, the melts were poured onto a carbon plate in each case and cooled gradually, thereby obtaining seven kinds of glass sheets as Composition Examples 1 to 7. Both surfaces of each formed sheet were polished to obtain a glass sheet having a size of 100 mm x 100 mm and a thickness of 2.8 mm. In table. 1 shows the specific gravity, average coefficient of thermal expansion at 50 to 350° C., T ₂ , T ₄ , T _L values, glass transition temperature Tg and e-OH value of each glass sheet produced. In the table, the symbol - indicates that the characteristic has not been defined. The values determined from the compositions by calculations are shown in brackets.

Then the glass sheet with the composition of example 1 was washed and introduced into the spray device in the production line and into the loading lock chamber, which was evacuated to a vacuum degree of 2x10 ^-6 Torr (0.00027 Pa) or to a lower pressure. Then, the glass sheet was introduced into the spray chamber, and a tin-doped zinc oxide layer and an aluminum-doped zinc oxide layer were deposited on the surface of the glass sheet so that the total thickness of the two layers was 43.5 nm. Then sequentially deposited films in the following order: silver with a thickness of 12.5 nm; 2 nm titanium; an aluminum-doped zinc oxide, a tin-doped zinc oxide, and an aluminum-doped zinc oxide layer, in that order, with a total thickness of the three layers of 87.5 nm; 12.5 nm silver; 2 nm titanium; aluminum-doped zinc oxide and tin-doped zinc oxide in that order with a total thickness of two layers of 31.5 nm and 1 nm of titanium oxide. After the deposition, the multilayer structure was heat-treated in air at 730° C. for 4 minutes, thereby obtaining a glass sheet having a heat-reflecting film thereon.

Then, using a laser ablation apparatus, multiple linear holes were formed along the width direction in parallel at regular intervals over the entire area (100 mm x 100 mm) of the thermal reflective film so that the thermal reflective film had a width of 0.07 mm, and the holes had a width of 0.03 mm. Thus, the radio-wave-permeable substrate according to Example 1 was obtained. In addition, the radio-wave-permeable substrates of Examples 2 to 13 and Comparative Examples 1 to 9 were obtained in the same manner as in Example 1, except that the width of the heat reflective film and the width holes were changed to the values shown in table. 2.

In Example 14, a glass sheet with the composition of Example 4 having a thickness of 1.8 mm was used. In the same way as in Example 1, a tin-doped zinc oxide layer and an aluminum-doped zinc oxide layer were deposited on the surface of a glass sheet so that the total thickness of the two layers was 50 nm. Then the films were deposited sequentially in the following order: silver with a thickness of 17.5 nm; 1 nm titanium; aluminum-doped zinc oxide, tin-doped zinc oxide, and aluminum-doped zinc oxide, in that order, with a total thickness of three layers of 80 nm; 9.5 nm silver; 1 nm titanium; aluminium-doped zinc oxide and tin-doped zinc oxide in that order with a total thickness of the two layers of 55 nm; 11.5 nm silver; 1 nm titanium; aluminium-doped zinc oxide and tin-doped zinc oxide in that order with a total thickness of the two layers of 28 nm; and 1 nm titanium oxide. After the deposition, the multilayer structure was heat-treated in air at 730° C. for 4 minutes, thereby obtaining a glass sheet having a heat-reflecting film thereon.

Then, using a laser ablation apparatus, multiple linear holes were formed along the width direction in parallel at regular intervals over the entire area (100 mm x 100 mm) of the thermal reflective film so that the thermal reflective film had a width of 0.2 mm, and the holes had a width of 0.099 mm. Thus, a radio-wave-permeable substrate was obtained according to example 14.

In Example 15, a glass sheet with the composition of Example 5 having a thickness of 1.8 mm was used. In the same way as in Example 14, a film reflecting thermal radiation was deposited. Thereafter, using a laser ablation apparatus, multiple linear holes were formed, arranged in a lattice pattern over the entire area (100 mm x 100 mm) of the thermal reflective film, so that the thermal reflective film had a width of 0.1 mm, and the holes had a width of 0. 05 mm. Thus, a substrate permeable to radio waves was obtained.

In Example 16, a glass sheet with the composition of Example 1 having a thickness of 8.0 mm was used. At a substrate temperature of 600° C., a 55 nm thick SiOC film and a 320 nm thick film of fluorine-doped tin oxide (SnO ₂ :F) were successively deposited by thermal CVD. Then, using a laser ablation machine, multiple linear holes were formed along the width direction in parallel at regular intervals over the entire area (100 mm x 100 mm) of the thermal radiation reflective film so that the thermal radiation reflective film had a width of 0.321 mm. , and the holes had a width of 0.030 mm. Thus, the radio-transparent substrate of example 14 was obtained.

In Example 17, a glass sheet with the composition of Example 1 having a thickness of 6.0 mm was used. In the same way as in Example 1, a 30 nm thick Al-doped silicon nitride film, a 30 nm thick chromium nitride film, and a 30 nm thick Al-doped silicon nitride film were successively deposited. Then, using a laser ablation apparatus, multiple linear holes were formed along the width direction in parallel at regular intervals over the entire area (100 mm x 100 mm) of the thermal reflective film, so that the thermal reflective film had a width of 0.128 mm, and the holes had width 0.030 mm. Thus, the radio-transparent substrate of example 17 was obtained.

As mentioned above, each of the radio wave-permeable substrate examples and comparative examples had a radio wave-permeable region formed over the entire surface (100 mm x 100 mm) in a top view of the radio wave-permeable substrate, as shown in FIG. 1.

Tab. 2 shows the width of the heat reflective film, the width D of the apertures, the coverage amount S' of the radio wave transmission area by the heat radiation of the film, and the average length L' of boundaries per unit area in the radio wave transmission area, in each of the examples and comparative examples.

In each of the Examples and Comparative Examples, all films formed in the holes were removed. That is, the glass sheet is exposed at the holes. Thus, in each of the Examples and Comparative Examples, the solar reflectance and the color of the holes are the same as the solar reflectance and the color of the glass sheet.

Measurement of solar reflectance and visible light transmittance

With respect to each of the radio-wave-permeable substrates of Examples and Comparative Examples, the surface where the radio-wave-permeable area was placed was examined using a spectrophotometer (U-4100, manufactured by Hitachi High-Technologies Corp.) to measure their solar reflectance and transmittance. visible light in accordance with JIS R3106 (1998). In addition, the glass sheet on which the electrically conductive film was completely formed, but no holes were placed, and the glass sheet on which no thermal radiation reflective film was placed were examined in a similar manner to measure the solar radiation reflection coefficient Z of the thermal radiation reflective film and the coefficient Z' solar reflection holes. The results are shown in table. 2.

Definition of color contrast

The glass sheet on which the thermal reflection film was completely formed but no holes were placed, and the glass sheet on which the heat reflection film was not placed were examined using a spectrophotometer (U-4100, manufactured by Hitachi High-Technologies Corp.) to measuring their light transmission coefficient within the wavelength range from 300 to 800 nm. In accordance with the JIS Z8729 standard, light from the illumination source C was directed to each glass sheet twice to measure the chromaticity of the transmitted light according to the L*a*b* color coordinate system. From the obtained chromaticity, the color contrast ΔΕ between the film reflecting thermal radiation and the holes was calculated. The results are shown in table. 2.

Evaluation with expressions (a), (b) and (c)

In table. 2 shows the differences between the left side and the right side [(left side)-(right side)] of each of the following expressions (a), (b) and (c) with respect to radio wave-permeable substrate examples and comparative examples.

L>802.6xS-503.7 (a)

Z>(-Z’+Z’xS’+0.3)/S’ (b)

ΔΕ<60.3χϋ-°> ⁶² (s)

Expressions (a) and (b) are satisfied in the case where the values shown in the table. 2 are values greater than 0. Expression (c) is satisfied in the case where the value shown in table. 2 is less than 0.

In each of the Examples and Comparative Examples, the holes were placed at regular intervals, and the widths of the holes and the heat reflective film were much smaller than 1 cm. ).

Determination of transmission loss of radio waves

The radio wave transmission loss of each resulting radio wave-permeable substrate was

- 15 041197 measured by the free space transmission loss measurement method as follows. The antennas were placed opposite each other, and the obtained radio-wave-permeable substrate was placed between them so that the direction of the extension of the holes was perpendicular to the polarization direction of the radio waves. The loss for a hole with a diameter of 100 mm, where no radio-transparent substrate was present, was taken as 0 dB to measure the transmission loss of radio waves when transmitting radio waves having a frequency of 28 GHz. In the same manner, the glass sheet itself was also separately examined for radio wave transmission loss, on which the heat-reflecting film was not formed. The radio wave transmission loss of the radio wave-permeable region in each of the radio wave-permeable substrate examples and comparative examples when transmitting radio waves having a frequency of 28 GHz was calculated from the measured values. Their results are shown in table. 2.

Table 1

Composition example Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Compound (mol.%) _SiO2 71.4 69.7 72.4 73.7 69.7 70.1 75.5 A1 ₂ 0z 1.0 0.9 1.5 0.1 0.9 0 oh, s B ₂ O ₃ 0.0 0 0 0 0 0 0 MgO 6.1 7 OD 0.1 7 7.3 0 Cao 8.7 9 I,5 11.5 9 9.3 6 SrO oh oh 0 0 0 0 0 0 VAO oh oh 0 0 0 0 0 0 TiO ₂ 0.02 0.05 0.05 0.05 0.05 0.01 0.05 _ZrO2 oh oh 0 0 0 0 0 0 _Li2O oh oh 0 0 0 0 0 6.0 _Na2O 12.5 12.6 7.2 7.2 6.6 8.6 6.0 _K2O o,h 0.6 7.2 7.2 6.6 4.6 6.0 _{Fe2O3 _} 0.03 0.2 0.004 0.15 0.1 0.06 0.18 Specific gravity 2.50 2.51 2.49 2.49 2.50 2.50 2.44 Average coefficient of linear expansion ( ^10-7 /°C) 89 92 96 97 (93) (94) 95 Young's modulus (GPa) 73 74 71 71 (72) (74) - T ₂ (°C) 1469 1464 464 1437 - - -

T ₄ (°С) 1045 1041 1050 1030 - - - _TL (°C) 1021 1008 990 900 - - - Tg (°C) 548 544 561 547 (560) (545) 457 β-ΟΗ (mm' ¹ ) 0.26 0.19 0.15 0.29 0.10 0.05 0.23

- 16 041197

table 2

No. Width Width D S' [%] And solar reflectance Coefficient reflective holes [mm/ ^cm2 ] radiation [°/ 0 nt thermal [mm] Permeable reflective Glass skip radiation I am for thermal th sheet i visible film [mm] radio waves radiation Sveta (%) substrate film Example 1 0.070 0.030 70.00 2000 31.8 44.6 8.8 77.5 Example 2 0.270 0.030 90.00 667 40.1 80.8 Example 3 0.200 0.099 67.00 667 31.6 79.7 Example 4 0.079 0.030 72.50 1835 31.6 76.9 Example 5 0.128 0.030 81.00 1266 35.9 77.9 Example 6 0.196 0.030 86.70 885 38.9 78.7 Example 7 0.321 0.030 91.50 570 40.6 78.9 Example 8 0.286 0.215 57.10 399 29.8 81.4 Example 9 0.528 0.215 71.10 269 35.2 80.7 Example 10 0.862 0.216 80.00 186 38.1 79.9 Example I 0.127 0.215 37.10 585 22.1 81.7 Example 12 0.273 0.465 37.00 271 22.0 79.4 Example 13 0.615 0.464 57.00 185 29.8 78.9 Example 14 0.200 0.099 67.00 667 33.1 50.0 8.8 55.0 Example 15 0.100 0.050 66.67 1742 33.0 50.0 8.8 54.4 Example 16 0.321 0.030 91.50 570 30.8 33.1 8.8 52.1 Example 17 0.128 0.030 81.00 1266 32.5 38.7 8.8 19.7 Comparative 0.900 0.100 90.00 200 40.8 44.6 8.8 79.4 Example 1 Comparative 2,900 0.090 97.00 67 43.5 - Example 2 Comparative 1.551 0.030 98.10 127 45.5 - Example 3 Comparative 1.324 0.216 86.00 130 40.4 - Example 4 Comparative 2.179 0.216 91.00 84 40.9 - Example 5 Comparative 5.171 0.215 96.00 37 45.2 - Example 6 Comparative 1.857 0.464 80.00 86 36.5 - Example 7 Comparative 2.851 0.464 86.00 60 39.4 - Example 8 Comparative 1.551 0.030 98.10 127 44.0 79.0 Example 9 Example 1 6.49 1941.88 0.06 -524 0.4 1 2.8 Example 2 448.03 0.12 -524 1.0 Example 3 632.62 0.04 -247 0.6 Example 4 1756.68 0.07 -524 oh, s Example 5 1119.42 0.10 -524 0.5 Example 6 692.80 0.11 _ί 523 0.7 Example 7 339.12 0.13 526 1.2 Example 8 444.62 -0.01 - 50 0.6 Example 9 202.23 0.06 - 50 1.2 Example 10 47.32 0.09 - 50 2.2 Example I 790.73 -0.21 - 50 oh, s Example 12 478.11 -0.21 -WITH )0 0.4 Example 13 231.57 -0.01 -WITH )1 1.0 Example 14 9.18 448.03 0.18 -524 2.3 4 1.8

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Claims (10)

Example 15 9.18 703.41 0.18 -377 0.8 5 1.8 Example 16 6.57 339.12 0.01 -245 1.2 1 8.0 Example 17 44.60 1119.42 0.04 -486 0.8 6.0 Comparative Example 1 6.49 -18.64 0.12 -245 3.1 2.8 Comparative Example 2 -208.16 0.14 -262 AND 2 Comparative Example 3 -157.15 0.14 -523 8.0 Comparative Example 4 -56.58 θ,ιι -150 4.0 Comparative Example 5 -143.12 0.13 -150 7.8 Comparative Example 6 -229.66 0.14 -150 12.1 Comparative Example 7 -52.21 0.09 -91 5.1 Comparative Example 8 -126.20 oh and -91 9.5 Comparative Example 9 -157.15 0.14 -523 7.6 In the radio wave-permeable substrates of Comparative Examples 1 to 9 that did not satisfy expression (a), the radio wave-permeable regions in each case had a radio wave transmission loss above 3 dB when transmitting radio waves having a frequency of 28 GHz. These radio wave-permeable substrates had poor radio wave transmission characteristics. Meanwhile, evaluation of the radio wave-permeable substrates of Examples 1 to 17 that satisfied the expression (a) with respect to radio wave transmission loss gave results showing that the radio wave-permeable regions in each case had a radio wave transmission loss of 3 dB or less when radio waves were transmitted, having a frequency of 28 GHz. These radio wave-permeable substrates had excellent radio wave transmission characteristics. The radio wave-permeable substrates of Examples 1-7, 9, 10, and 13-17, which further satisfied expression (b), each had a relatively high solar reflectance and excellent thermal reflectance characteristics. In addition, the radio wave-pervious substrates of Examples 1 to 17 all satisfied expression (c), so that holes were less likely to be visually distinguishable, and these radio wave-permeable substrates had excellent appearance. With regard to the radio wave-permeable substrates obtained from the glass sheets with the compositions of Examples 2-7, the radio wave-permeable substrates also satisfying expression (a) gave results showing that the radio wave-permeable regions in each case have a radio wave transmission loss of 3 dB or less when passing radio waves having a frequency of 28 GHz. These radio wave-permeable substrates have excellent radio wave transmission characteristics. While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from its spirit and scope. This application is based on Japanese Patent Application filed on September 14, 2018 (Application No. 2018-172749) and Japanese Patent Application filed on October 26, 2018 (Application No. 2018-202102), the entire contents of which are hereby incorporated by reference. All references cited herein are incorporated herein by reference in their entirety. List of reference positions 10, 20, 30 - radio-transparent substrate 11, 21 - dielectric substrate 13, 23, 33 - film reflecting thermal radiation 14, 24, 34 - hole A - area permeable to radio waves B - area impenetrable to radio waves CLAIM 1. A radio-wave-permeable substrate, comprising a dielectric substrate and, on at least one main surface of the dielectric substrate, a thermal radiation reflecting film containing an electrically conductive film, and an opening where the electrically conductive film is absent in top view, - 18041197 wherein at least a portion of at least one major surface in plan view is a radio wave permeable region, wherein the radio wave permeable region is a region where each 1 cm ² of the unit region satisfies the expression (a) L>802.6xS-503.7 (a), in which L represents the total length (unit: mm/cm ² ) of the boundary between the heat radiation reflective film and the hole in the unit area, and S represents the proportion of the area occupied by the heat-reflecting film in a unit area, and the radio-wave-permeable area satisfies the following expression (b): Z>(-Z'+Z'xS'+0.3)/S' (b), in where Z represents the solar reflectance of the thermal reflective film, Z' represents the solar reflectance of the hole, and S' represents the ratio of the area of the heat-reflecting film to the area of the radio-wave-permeable region. 2. A radio wave-permeable substrate, comprising a dielectric substrate and, on at least one major surface of the dielectric substrate, a thermal radiation reflecting film containing an electrically conductive film, and an opening where the electrically conductive film is absent in top view, wherein at least a portion of at least one major of the top view surface is a radio-wave-permeable area, and the radio-wave-permeable area is an area where every 1 cm ² of the unit area satisfies the expression (a): L>802.6xS-503.7 (a), in which L represents the total length (unit: mm/cm ² ) of the boundary between the heat radiation reflective film and the hole in the unit area, and S represents the proportion of the area occupied by the heat-reflecting film in a unit area, and the radio-wave-transmitting area satisfies the following expression (c): AE<60.3xD' ^0.62 (c) in which AE represents the color contrast between the heat-reflecting film and hole and D represents the width (unit: mm) of the hole. 3. The radio wave-permeable substrate according to claim 1 or 2, wherein the radio wave-permeable region has a radio wave transmission loss of 3 dB or less when transmitting radio waves having a frequency of 28 GHz. 4. A radio wave-permeable substrate according to any one of claims 1 to 3, wherein the apertures are a plurality of parallel lines or a lattice structure. 5. A radio wave-permeable substrate according to any one of claims 1 to 4, comprising a radio wave impermeable region on at least a portion of at least one major surface of the dielectric substrate, the radio wave impervious region being a region where every 1 cm ² of a unit region , including the region impenetrable to radio waves, satisfies the expression (d) L<802.6xS-503.7 (d), in which L represents the total length (unit: mm/cm ² ) of the boundary between the heat radiation reflective film and the hole in the unit area, and S represents the proportion of the area occupied by the heat reflective film in a unit area. 6. The radio wave-permeable substrate according to any one of claims 1 to 5, wherein the electrically conductive film comprises at least one selected from the group consisting of silver, aluminum, indium tin oxide, tin oxide doped with at least one of fluorine and antimony, titanium nitride, niobium nitride, chromium nitride, zirconium nitride and hafnium nitride, in a total amount of 50 at.% or more. 7. A radio wave-permeable substrate according to any one of claims 1 to 6, wherein the dielectric substrate is exposed in the hole. 8. The radio wave-permeable substrate according to any one of claims 1 to 7, wherein the dielectric substrate has a radio wave transmission loss of 4 dB or less when transmitting radio waves having a frequency of 28 GHz. 9. The radio wave-permeable substrate according to any one of claims 1 to 8, wherein the electrically conductive film has a thickness of 1 to 100 nm. 10. The radio wave-permeable substrate according to any one of claims 1 to 9, wherein the heat reflective film comprises at least one metal oxide layer and a metal nitride layer, wherein -