Heat-ray-reflecting substrate, method for producing same, and window glass

Abstract

The present invention pertains to a heat-ray-reflecting substrate provided with a dielectric substrate and a heat-ray-reflecting film provided on at least one main surface of the dielectric substrate, the heat-ray-reflecting substrate being characterized in that: at least a part of the at least one main surface has a radio-wave-transmitting region in a plan view; the radio-wave-transmitting region is provided with a slit portion in which the heat-reflecting film is not present, and in the radio-wave-transmitting region, the solar radiation heat acquisition rate (g0) obtained by a predetermined method in a region not including the slit portion and the solar radiation heat acquisition rate (g1) in a region including the slit portion satisfy a specific relationship.

Description

Technical Field

[0001] The present invention relates to a heat-reflecting substrate and a method for manufacturing the same, and a window glass. Background Art

[0002] Heat-reflecting glass, which is formed by forming a coating containing a conductive layer such as metal on the glass surface, reflects not only heat rays but also radio waves. When used as window glass for vehicles such as cars and trains, it will hinder communication from the inside of the vehicle to the outside. In particular, it is required to transmit radio waves from mobile phones (800MHz to 2GHz) and keyless entry (Japan, the United States: 315MHz, Europe: 433.92MHz).

[0003] Therefore, as a method for transmitting radio waves used for communication, there is a method of digging out the applied heat-ray reflective film to transmit the radio waves, but there are many problems such as color unevenness caused by digging out. In addition, as a technology for transmitting radio waves, there is a frequency selective surface (FSS (Frequency Selective Surface)) provided with two slits orthogonal to the heat-ray reflective film.

[0004] Patent Documents 1 and 2 describe heat-reflecting glass having such FSS.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2010-068154

[0006] Patent Document 2: International Publication No. 2020 / 054762

[0007] However, in the heat reflective glass described in Patent Documents 1 and 2, the slits for imparting radio wave transmittance reduce the coverage area of ​​the heat reflective film, resulting in reduced heat insulation performance. Therefore, there is room for further improvement from the perspective of improving heat insulation performance. Summary of the invention

[0008] The present invention has been made in view of the above problems, and an object of the present invention is to provide a heat-reflective substrate which has excellent radio wave transmittance and excellent heat-reflective performance.

[0009] As a result of intensive studies, the inventors of the present invention have found that the above-mentioned problems can be solved by configuring a heat-reflecting substrate so as to cause optical scattering in the slit portions, thereby completing the present invention.

[0010] That is, the present invention adopts the following structure.

[0011] [1] A heat ray reflecting substrate comprising: a dielectric substrate; and a heat ray reflecting film provided on at least one main surface of the dielectric substrate, wherein:

[0012] At least a portion of the at least one main surface has a radio wave transparent region when viewed from above,

[0013] The radio wave transparent area includes a slit portion without a heat-ray reflecting film.

[0014] In the radio wave transparent area, the solar radiation heat acquisition rate g0 in the area not including the slit portion and the solar radiation heat acquisition rate g1 in the area including the slit portion satisfy the following formula (a):

[0015] g1<(1-f2)·g0+f2α···(a)

[0016] In this formula, f2 is the designed aperture ratio, and α is the solar radiation heat acquisition rate of the dielectric substrate.

[0017] [2] The heat-reflecting substrate according to [1], wherein

[0018] In the radio wave transparent area,

[0019] The visual transmittance Tv0 in the region not including the slit portion and the visual transmittance Tv1 in the region including the slit portion satisfy the relationship of Tv1<Tv0.

[0020] [3] The heat-reflecting substrate according to [1] or [2], wherein

[0021] The radio wave transparent area transmits radio waves of a target frequency by more than -20 dB.

[0022] [4] The heat-reflecting substrate according to [3], wherein

[0023] The target frequency is 700 MHz to 100 GHz.

[0024] [5] The heat-reflecting substrate according to any one of [1] to [4], wherein

[0025] In the radio wave transparent area,

[0026] When g1=β((1-f2)·g0+fα), β<0.995 is satisfied.

[0027] [6] The heat-reflecting substrate according to any one of [1] to [5], wherein

[0028] The solar radiation heat acquisition rate g0 in the region excluding the slit portion is 0.7 or less.

[0029] [7] The heat-reflecting substrate according to any one of [1] to [6], wherein

[0030] In the radio wave transparent region, the haze in the region including the slit portion is at least twice the haze in the region not including the slit portion.

[0031] [8] The heat-reflecting substrate according to any one of [1] to [7], wherein

[0032] When the radio wave transparent region includes the slit portion having a grid-like slit pattern, the slit width is 20 to 100 μm and the slit interval is 0.2 to 14 mm.

[0033] [9] A window glass, wherein:

[0034] A heat-reflecting substrate according to any one of [1] to [8].

[0035]

[10] A method for producing a heat reflective substrate, the method for producing a heat reflective substrate according to any one of [1] to [8], wherein:

[0036] The slit portion is formed using nanosecond laser.

[0037] According to the present invention, it is possible to provide a heat reflective substrate which imparts excellent radio wave transmittance and has good heat reflective performance, a method for producing the heat reflective substrate, and a window glass including the heat reflective substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a diagram showing one embodiment of the heat reflective substrate of the present invention. Figure 1 (A) is a top view of the heat-reflecting substrate. Figure 1 (B) is an enlarged view of the cross section at line XX of (A).

[0039] Figure 2 This is a diagram showing one embodiment of the slit portion in the heat reflective substrate of the present invention.

[0040] Figure 3 It is a figure which shows the slit part in one embodiment of this invention. DETAILED DESCRIPTION

[0041] Hereinafter, the present invention will be described in detail, but the present invention is not limited to the following embodiments and can be implemented in any modified manner without departing from the gist of the present invention.

[0042] In addition, “to” indicating a numerical range is used to mean that the numerical values ​​described before and after it are included as the lower limit and the upper limit.

[0043] In the following drawings, the same reference numerals are sometimes used to describe components and parts that play the same role, and repeated descriptions are sometimes omitted or simplified. In addition, the embodiments described in the drawings are schematic for the purpose of clearly describing the present invention, and do not necessarily accurately represent the size and scale of the actual product.

[0044] 《Heat-ray reflecting substrate》

[0045] The heat reflective substrate of the present embodiment comprises a dielectric substrate and a heat reflective film provided on at least one main surface of the dielectric substrate, at least a portion of at least one main surface has a radio wave transparent region when viewed from above, the radio wave transparent region has a slit portion where no heat reflective film is present, and in the radio wave transparent region, a solar radiation heat acquisition rate g0 in a region excluding the slit portion and a solar radiation heat acquisition rate g1 in a region including the slit portion satisfy the following formula (a),

[0046] g1<(1-f2)·g0+f2α…(a) In this formula, f2 is the designed aperture ratio, and α is the solar radiation heat acquisition rate of the dielectric substrate.

[0047] Figure 1 FIG. 1 is a diagram showing an embodiment of a heat-reflecting substrate of the present invention. Figure 1 (A) is a top view of the heat-reflecting substrate. Figure 1 (B) is an enlarged view of the cross section at line XX of (A).

[0048] The heat reflective substrate 10 of the present embodiment includes a dielectric substrate 11 and a heat reflective film 13 provided on at least one main surface of the dielectric substrate 11 , and at least a portion of the at least one main surface has a radio wave transparent region A in a plan view.

[0049] <Dielectric substrate>

[0050] The dielectric substrate in this embodiment is not particularly limited as long as it is a substrate composed of a dielectric, and for example, a glass substrate such as sodium-lime glass, alkali-free glass, or quartz glass can be used. The glass substrate can also be subjected to physical strengthening treatment or chemical strengthening treatment. In addition, the glass substrate can be composed of a single piece of glass, or can be composed by laminating a plurality of glasses with a resin film (resin film) or the like interposed therebetween.

[0051] In addition, the dielectric substrate in the present embodiment is not limited to a glass substrate, and may be, for example, a substrate made of resin (resin substrate), a composite substrate formed by laminating a resin substrate and a glass substrate, etc. As the resin substrate, for example, substrates composed of acrylic resins such as polymethyl methacrylate, aromatic polycarbonate resins such as polyphenylene carbonate, aromatic polyester resins such as polyethylene terephthalate (PET), etc. may be cited.

[0052] The shape of the dielectric substrate in this embodiment is not particularly limited, and may be flat or curved. In addition, the thickness of the dielectric substrate in this embodiment is not particularly limited, and can be appropriately adjusted according to desired strength, lightness, etc.

[0053] The physical properties such as radio wave transmittance and heat reflectivity of the dielectric substrate in this embodiment are not particularly limited as long as the effects of the present invention are achieved, and may be appropriately adjusted according to the physical properties required for the heat reflective substrate to be finally obtained.

[0054] For example, the radio wave transmission loss of the dielectric substrate in this embodiment for a 28 GHz radio wave is preferably 4 dB or less, more preferably 3 dB or less, and even more preferably 2 dB or less. The radio wave transmission loss can be measured by a free space method.

[0055] In addition, the solar radiation heat acquisition rate of the dielectric substrate in this embodiment is preferably 0.8 or less, more preferably 0.75 or less, and further preferably 0.7 or less. The solar radiation heat acquisition rate of the dielectric substrate is calculated by optical calculation based on the spectral spectrum and emissivity measured in accordance with ISO9050 (2003) standard.

[0056] When a glass substrate is used as the dielectric substrate in this embodiment, the specific gravity of the glass substrate is preferably 2.4 or more and 3.0 or less. In addition, the Young's modulus of the glass substrate is preferably 60 GPa or more and 100 GPa or less. In addition, the average thermal expansion coefficient of the glass substrate from 50°C to 350°C is preferably 50×10 -7 / ℃ and above 120×10 -7 / °C or less. As long as the glass substrate satisfies these physical property requirements, it can be sufficiently suitably used as a window material.

[0057] <Heat reflective film>

[0058] The heat radiation reflective film of the present embodiment is not particularly limited as long as it can impart a function of reflecting heat radiation to the heat radiation reflective substrate. A typical example of a film that can impart a function of reflecting heat radiation is a conductive film.

[0059] In this specification, a "conductive film" refers to, for example, a film having a resistivity of 10 at 20°C. 0[Ω·cm] or less. The composition of the conductive film is not particularly limited, but for example, it is preferably composed mainly of metals such as silver, aluminum, indium tin oxide (ITO), tin oxide doped with at least one of fluorine and antimony (SnO2: F, Sb), titanium nitride, niobium nitride, chromium nitride, zirconium nitride, and hafnium nitride (hereinafter also referred to as "conductive film component group A") having excellent heat ray reflectivity. In addition, in this specification, the main component refers to a component whose content is 50 atomic % or more relative to all constituent components. That is, the conductive film of this embodiment contains at least one selected from the conductive film component group A, and the content of the conductive film component group A in the conductive film of this embodiment is preferably 50 atomic % or more in total.

[0060] In order to make the heat-reflecting substrate have excellent heat-reflecting properties, the conductive film preferably contains at least one of silver and aluminum as the main component, and the conductive film more preferably contains silver as the main component (i.e. contains more than 50 atomic %), and further preferably contains more than 95 atomic % of silver.

[0061] In addition, the conductive film mainly composed of silver may also contain one or more additive elements such as gold, palladium, copper, bismuth, neodymium, platinum, etc. By making the conductive film mainly composed of silver contain such additive elements, the diffusion of silver can be suppressed and the moisture resistance can be improved. In addition, the additive elements are not limited to the elements exemplified above, and any elements can be added as long as the effect of the present invention is achieved.

[0062] In addition, the thickness of the heat-reflective film (conductive film) of this embodiment is not particularly limited, and can be appropriately adjusted according to the radio wave transmittance of the specified frequency required in the final heat-reflective substrate, heat-reflective property, visible light transmittance, appearance, etc. The thickness of the heat-reflective film is usually 1 nm or more, preferably 3 nm or more, more preferably 5 nm or more, and further preferably 6 nm or more. In addition, the thickness is preferably 100 nm or less, more preferably 50 nm or less, and further preferably 20 nm or less. The thickness is preferably 1 to 100 nm, for example.

[0063] In addition, the heat reflective film may be only one layer (single layer), or may be two layers, three layers, or other multiple layers. In the case of multiple layers of heat reflective film, they may be adjacent to each other in the thickness direction of the heat reflective film, or may be separated by sandwiching other films (other layers) described later between the layers. In addition, in the case of multiple layers of heat reflective film, the total thickness may be within the above range.

[0064] The heat ray reflecting substrate in the present embodiment may include a film (other film) different from the heat ray reflecting film within a range in which the effects of the present invention are exhibited.

[0065] The heat reflective substrate in this embodiment may include, for example, a metal oxide layer and a metal nitride layer, preferably at least one of the metal oxide layer and the metal nitride layer, as a film (other film) different from the heat reflective film. In particular, from the viewpoint of durability, it is preferred to have a layer structure in which the heat reflective film (conductive film) is sandwiched by the other layers such as the metal oxide layer and the metal nitride layer.

[0066] Examples of the metal oxide layer include layers of metal oxides mainly composed of aluminum oxide, zinc oxide, indium oxide, titanium oxide, niobium oxide, tin oxide, bismuth oxide, tantalum oxide, tungsten oxide, zirconium oxide, silicon oxide, etc. Among them, the metal oxide layer preferably contains zinc oxide as a main component from the viewpoint of good compatibility with silver, which is a preferred component of the conductive film, and improving the durability of the heat-ray reflective film (conductive film).

[0067] Examples of the metal nitride layer include a metal nitride layer mainly composed of silicon nitride (Si 3 N 4 ), aluminum nitride (AlN), and the like.

[0068] The method for forming the heat-ray reflective film is not particularly limited, and for example, physical vapor deposition (vacuum vapor deposition, ion plating, magnetron sputtering, etc.), chemical vapor deposition (thermal CVD, plasma CVD, optical CVD, etc.), ion beam sputtering, etc. can be used. When the film forming area is large, it is easy to control the uniformity of the thickness and the productivity is excellent, so DC magnetron sputtering, DC pulsed magnetron sputtering, or AC dual magnetron sputtering is preferred.

[0069] The heat reflective film in this embodiment may be formed directly on the dielectric substrate or indirectly. The method of indirectly forming the heat reflective film on the dielectric substrate is not particularly limited, but examples thereof include a method of attaching a resin film having the heat reflective film formed thereon to the dielectric substrate. In addition, in this embodiment, a commercial product having the heat reflective film formed on the dielectric substrate may be used.

[0070] In addition, Figure 1 In the embodiment shown, the heat-reflecting film 13 (and the slit portion 14) is formed on the entire main surface of one of the dielectric substrates 21, but it may be formed only on a portion. As an example, Figure 2 The figure shows a plan view of a heat reflective substrate 20 in which a heat reflective film 23 and slit portions 24 are provided on a portion of one main surface of a dielectric substrate 21 and the dielectric substrate 21 is exposed over a wide range in the other portion.

[0071] <Radio wave transparent area>

[0072] In this embodiment, the radio wave transparent region is a region having radio wave transparency by forming a predetermined pattern with the slit portion. The radio wave transparent region of this embodiment is formed on at least a portion of at least one main surface of the dielectric substrate in a plan view and has a slit portion without a heat radiation reflective film.

[0073] exist Figure 1 In the example of , a substantially parallel linear pattern formed by the slits 14 is formed on the entire surface of the main surface having the heat-ray reflecting film. Figure 1 In the example of FIG. 1 , the entire main surface of the heat-ray reflecting film 13 when viewed from above is the radio wave transparent area A. On the other hand, Figure 2 As exemplified above, a portion of the main surface on which the heat-ray reflecting film 13 is formed may be made into the radio wave transparent region A.

[0074] (Slit part)

[0075] The slit portion is a portion where at least the heat reflective film is discontinuously changed when the heat reflective substrate is viewed from above, and is divided by the heat reflective film. As for the form of the slit portion, for example, when the heat reflective substrate includes the heat reflective film and other layers, there is a form in which the heat reflective film and other layers are completely removed and the dielectric substrate becomes the uppermost surface. That is, the slit portion can be, for example, a form in which the dielectric substrate is exposed. In addition, if there is no conduction between the heat reflective films that divide the slit portion, part or almost all of the components of the heat reflective film may remain.

[0076] In addition, as long as the effect of the present invention is achieved, the form of the slit portion is not limited to the form having the dielectric substrate as the uppermost surface, and for example, it may be a form that does not include a heat ray reflective film but includes at least one layer of a layer other than the heat ray reflective film (other layer). That is, the slit portion may not have a heat ray reflective film, and only a layer other than the heat ray reflective film (for example, a film with a resistivity exceeding 100 [Ω·cm]) may be stacked on the dielectric substrate. For example, the slit portion may not have a heat ray reflective film, and a metal oxide layer or a metal nitride layer exemplified in the description of the other layer may be stacked on the dielectric substrate.

[0077] The inventors of the present invention discovered that in the radio wave transparent area, the solar radiation heat acquisition rate g0 in the area excluding the slit portion and the solar radiation heat acquisition rate g1 in the area including the slit portion satisfy the following formula (a), thereby obtaining a heat radiation reflecting substrate that has both radio wave transmittance and heat radiation reflection performance (thermal insulation performance).

[0078] g1<(1-f2)·g0+f2α…(a)

[0079] Here, f2 in formula (a) is the designed aperture ratio, and α is the solar radiation heat acquisition rate of the dielectric substrate, that is, the solar radiation heat acquisition rate of the dielectric substrate before the heat reflection film is provided.

[0080] The right side of formula (a) represents the theoretical value of g1. Generally, when a slit portion is formed to improve radio wave transmittance, the area ratio of the heat reflective film decreases, so the solar radiation heat acquisition rate increases, showing a trend of reduced heat insulation performance. However, the heat reflective substrate of this embodiment can also achieve a value lower than the solar radiation heat acquisition rate that should be obtained by forming the slit portion.

[0081] Here, the solar radiation heat acquisition rate α of the dielectric substrate is calculated by optical calculation based on the measurement of the spectral spectrum and emissivity in accordance with ISO9050 (2003) standards.

[0082] The solar radiation heat acquisition efficiency g0 is calculated by optical calculation by measuring the spectral spectrum and emissivity based on ISO9050 (2003) standards with the radio wave transparent region excluding the slit portion as the measurement region.

[0083] In addition, the solar radiation heat acquisition rate g1 is calculated by optical calculation by measuring the spectral spectrum and emissivity based on the ISO9050 (2003) standard, with the radio wave transmittance area including the slit part within ±10% relative to the designed opening rate f2 as the measurement area. The measurement area in the measurement of g1 can be, for example, a square area with a side having a length of 10 times or more of the maximum value of the slit interval.

[0084] In addition, the size of the measurement region in the measurement of g0 is not particularly limited unless the slit portion is included.

[0085] In the measurement of g1, the "designed aperture ratio f2" refers to the area ratio (%) of the designed slit portion calculated based on the slit width, slit interval, slit pattern, etc. per unit area of ​​the entire main surface of the heat reflective substrate provided with the heat reflective film.

[0086] In addition, the area ratio f1 (%) occupied by the slit portion in the radio wave transparent area is calculated by measuring with an optical microscope, etc. That is, in the measurement of the solar radiation heat acquisition rate g1, the position of the measurement area is adjusted using an optical microscope, etc., so that the deviation between the area ratio f1 occupied by the slit portion in the measurement area and the designed opening ratio f2 is within 10%, and the measurement is performed.

[0087] In addition, in the measurement of the solar radiation heat acquisition rates g1 and g0, it is necessary to consider the influence of light scattering at the slit portion. In addition, in the present embodiment, in order to suppress the influence of light scattering, in the optical measurement for calculating the solar radiation heat acquisition rates g1 and g0, the measurement substrate is not in contact with the integrating sphere of the light receiving portion, and the linear transmittance is measured.

[0088] The radio wave transparent region of the present embodiment preferably satisfies β<0.995 when g1=β((1-f2)·g0+f2α). When β<0.995, a more excellent heat insulating property is exhibited. β is more preferably β<0.985, and further preferably β<0.980.

[0089] The heat reflective substrate satisfying the above formula (a) is obtained by forming slit portions that cause optical scattering at the slit portions when light enters from the surface provided with the heat reflective film toward the opposite surface.

[0090] More specifically, by adjusting so that film residues remaining as the heat reflective film are left after cutting when the slit portion is formed, a heat reflective substrate satisfying formula (a) can be obtained. Figure 3 As shown in FIG. 1 , film residues at the slit portion are found on the side wall of the slit portion. Since film residues remain when the slit portion is formed, when light is incident from the surface on the side where the heat reflective film is provided toward the surface on the opposite side, optical scattering occurs at the side wall of the slit portion. As a result, light that should have been incident is scattered on the surface on the side where the heat reflective film is provided, thereby suppressing the reduction in heat insulation performance. As a result, both radio wave transmittance and heat insulation performance can be achieved.

[0091] In the manufacturing method of the heat-reflecting substrate of the present embodiment, the slit portion is formed by removing the heat-reflecting film using a nanosecond laser. Nanosecond laser is a method with low cost and high industrial applicability. In addition, compared with a femtosecond laser having a very short pulse width, the laser beam output by the nanosecond laser is long in duration, and the heat has a great influence on the heat-reflecting film. Therefore, by etching with a nanosecond laser, it is possible to form a slit portion while leaving film residues on the heat-reflecting film and generating appropriate deformation caused by heat, and it is possible to obtain a heat-reflecting substrate having both radio wave transmittance and heat insulation performance.

[0092] However, the slit portion of the present embodiment may be formed by other methods as long as the heat ray reflecting film can be removed and optical scattering is imparted to the slit portion with respect to light incident from the surface on which the heat ray reflecting film is provided.

[0093] In etching using nanosecond laser, the processing conditions of the laser beam (eg, focus, scanning speed, etc.) can be appropriately set in consideration of the balance between the amount of film residue and the insulation, transparency, and heat insulation of the laser-processed area.

[0094] In the past, the laser beam was usually adjusted to the position where the slit width was the smallest on the surface of the etching object, that is, it was just focused. Here, after confirming the position where the slit width was the smallest, when etching was performed with the focus position located above the surface of the etching object, compared with the case where etching was performed with the focus adjusted to be just focused, more film residues in the slit portion were found, and there was a tendency for the heat-reflecting substrate to look slightly turbid. In addition, even when the focus was shifted from the position where the slit width was the smallest to the inside of the etching object, the same tendency was observed.

[0095] Until now, it has been believed that the insulation required for the slit portion cannot be ensured in such a condition with film residues, and therefore, a process of precisely focusing is usually performed in the formation of FSS, etc. The inventors of the present invention have found that by finely adjusting the focus of the laser beam at a pitch of 5 μm, conditions are met to obtain sufficient insulation as FSS even in the presence of film residues, which was previously believed to be unable to ensure insulation.

[0096] That is, by shifting the focusing condition of the laser beam from just focusing to the front and back, the amount of film residue at the slit portion can be adjusted. Moreover, if the film residue is too little, the heat insulation performance is reduced. In addition, if the film residue is too much to a certain amount, the insulation required as FSS cannot be obtained and the function as FSS cannot be performed. Therefore, by appropriately adjusting the focusing condition, the heat ray reflecting substrate of this embodiment can be obtained.

[0097] The shape of the slit portion, that is, the slit pattern, for example, may be a straight line, a grid, a curve, a zigzag shape, a concentric circle, a spiral, or a random line, but from the viewpoint of workability during formation, a linear shape is preferred, and a straight line is more preferred. In particular, in the case where the slit portion is formed by laser etching, a straight line slit portion extending in the first direction can be easily formed by transporting the substrate in the first direction while irradiating the heat reflective film with a fixed laser. In addition, for example, a straight line slit portion extending in the first direction and the second direction can also be easily formed by transporting the substrate in a second direction different from the first direction while irradiating the heat reflective film with a fixed laser.

[0098] From the perspective of the ease of manufacturing as described above, the shape of the slit portion in this embodiment is preferably a straight line extending in the first direction, or a combination of a straight line extending in the first direction and a straight line extending in the second direction. Specifically, the slit portion is preferably a plurality of parallel lines or a grid shape, and is preferably formed by alternately arranging a heat-ray reflective film of a specified width and a slit portion of a specified width in the width direction of the parallel lines or the grid shape to have periodicity, thereby cutting off radio waves of a specific frequency band or improving the radio wave transmittance of a target frequency.

[0099] For example, when observing the heat-reflecting substrate from above, the slit portions have a specified width and are straight or grid-like extending in one direction. A plurality of slits are arranged parallel to the width direction to form an electromagnetic wave transparent region, thereby increasing the electromagnetic wave transmittance to linear polarized waves orthogonal to the extension direction.

[0100] As described above, the specific frequency depends on the pattern formed by the heat reflective film, and therefore the slit width, the width between the slits, that is, the slit interval, and the slit pattern can be appropriately set according to the characteristics of the radio waves to be transmitted.

[0101] For example, when the frequency of the radio wave to be transmitted is 0.1 to 6 GHz, the slit portion preferably satisfies the following conditions.

[0102] Slit pattern: Grid

[0103] Slit spacing: 0.2~14mm

[0104] Slit width: 20~100μm

[0105] When the frequency of the radio wave to be transmitted is 0.1 to 40 GHz, the slit portion preferably meets the following conditions.

[0106] Slit pattern: Grid

[0107] Slit spacing: 0.2~2.4mm

[0108] Slit width: 20~100μm

[0109] In addition, the slit intervals of the slit portions formed in the heat ray reflecting film may be constant or different over the entire heat ray reflecting film.

[0110] In addition, the inventors of the present invention have found that, in the radio wave transparent region, when the visual transmittance (Tv0) in the region excluding the slit portion and the visual transmittance (Tv1) in the region including the slit portion satisfy the relationship Tv1<Tv0, a heat-ray reflecting substrate having particularly excellent heat-insulating performance can be obtained. That is, in this embodiment, the radio wave transparent region preferably satisfies the above relationship.

[0111] In the conventional heat reflective substrate, since the heat reflective film is removed at the slit portion, the visual transmittance increases, and becomes Tv1>Tv0. In contrast, in the present embodiment, the visual transmittance of the region including the slit portion is more likely to be lower than that of the region not including the slit portion. The reason for this is believed to be that the film residue exists at the slit portion, and thus the light that should be incident from the side where the heat reflective film is provided to the opposite side is more likely to be scattered on the side wall of the slit portion. By having the film residue at the slit portion, a heat reflective film having both excellent heat reflective performance and radio wave transmittance can be obtained.

[0112] The visual transmittances Tv0 and Tv1 are calculated by multiplying the transmittance (reflectance) at each wavelength by a coefficient corresponding to visibility based on JIS R 3106 (1998).

[0113] More specifically, the radio wave transparent region not including the slit portion is used as the measurement region, and the visual transmittance Tv0 is measured by the above method. Here, the size of the measurement region in the measurement of Tv0 is not particularly limited as long as it does not include the slit portion.

[0114] The visual transmittance Tv1 is measured in the same manner as described above, with the radio wave transmittance region as the measurement region and adjusted to include a slit portion within ±10% relative to the designed opening ratio f2 in the measurement region. The measurement region is preferably, for example, a square region with one side having a length of at least 10 times the maximum value of the slit interval. When measuring Tv1, the area ratio f1 occupied by the slit portion in the measurement region can be measured using an optical microscope or the like. Here, the "designed opening ratio f2" is as described above.

[0115] In addition, in the radio wave transmittance region, the above Tv0 is preferably 50% or more, more preferably 60% or more, and further preferably 70% or more. When Tv0 is 50% or more, a heat-reflecting substrate having excellent transparency can be obtained. In addition, from the viewpoint of achieving both transparency and heat-reflecting properties, Tv0 is preferably 90% or less. Tv0 is preferably 50 to 90%, for example.

[0116] In addition, in the radio wave permeability region, the above Tv1 is preferably 50% or more, more preferably 60% or more, and further preferably 70% or more. When Tv1 is 50% or more, a heat-reflecting substrate having excellent transparency can be obtained. In addition, from the viewpoint of achieving both transparency and heat-reflecting properties, Tv1 is preferably 90% or less. Tv1 is preferably 50 to 90%, for example.

[0117] In the heat reflective substrate of the present embodiment, in the radio wave transparent region, preferably, [Haze in the region including the slit portion] is at least twice as large as [Haze in the region not including the slit portion].

[0118] The heat reflective substrate of this embodiment shows excellent heat insulation performance when [Haze in the region including the slit portion] is more than twice [Haze in the region not including the slit portion] in the radio wave transparent region. This is because, in the region including the slit portion, when light is incident from the side facing the opposite side of the heat reflective film, light scattering occurs at the slit portion, so that the haze increases, resulting in improved heat insulation performance.

[0119] In the present embodiment, the [Haze in the region including the slit portion] of the radio wave transparent region is preferably 3 times or more of the [Haze in the region excluding the slit portion], and further preferably 4 times or more. In addition, in order to ensure the beauty of the heat-reflecting substrate, the [Haze in the region including the slit portion] is preferably 8 times or less of the [Haze in the region excluding the slit portion], and further preferably 7.5 times or less, and further preferably 7 times or less. The [Haze in the region including the slit portion] is preferably 3 to 8 times of the [Haze in the region excluding the slit portion].

[0120] The haze was measured using a haze meter in accordance with JIS K 7136 (2000).

[0121] More specifically, [Haze in the area not including the slit portion] is measured by the above method using the radio wave transmittance area not including the slit portion as the measurement area. Here, the size of the measurement area in the measurement of [Haze in the area not including the slit portion] is not particularly limited as long as the slit portion is not included.

[0122] In addition, [Haze in the area including the slit portion] is measured in the same manner as the above method, with the radio wave transparent area as the measurement area, and adjusted to include a slit portion within ±10% relative to the designed opening ratio f2 in the measurement area. The measurement area is preferably, for example, an area in the shape of a square having one side with a length that is more than 10 times the maximum value of the slit interval. At this time, the area ratio f1 occupied by the slit portion in the measurement area can be measured by an optical microscope or the like. Here, the "designed opening ratio f2" is as described above.

[0123] <Features>

[0124] The heat reflective substrate of the present embodiment preferably has the following characteristics.

[0125] The radio wave permeability region of the present embodiment preferably has a large amount of radio wave permeability at the target frequency, and more specifically, preferably allows the radio wave of the target frequency to be permeated by more than -20dB. By allowing the radio wave of the target frequency to be permeated by more than -20dB, excellent radio wave permeability is displayed. The radio wave permeability region more preferably allows the radio wave of the target frequency to be permeated by more than -15dB, and further preferably by more than -10dB. The permeability or transmittance can be measured, for example, by a free space method.

[0126] In addition, the target frequency is preferably 700 MHz to 100 GHz, and more preferably a radio wave in a frequency band of 1 GHz to 40 GHz including the Sub6 band (3.6 to 6 GHz), quasi-millimeter wave band (24 GHz to 30 GHz), and millimeter wave band (30 GHz to 300 GHz).

[0127] In addition, the heat reflective substrate of the present embodiment only needs to have a transmittance of -20 dB or more at any of the above-mentioned target frequencies.

[0128] In addition, in the heat-reflecting substrate of the present embodiment, for example, the radio wave transmission loss for the radio wave of frequency 28 GHz in the radio wave transmission area is preferably 3 dB or less, more preferably 2 dB or less, and further preferably 1 dB or less. In addition, the radio wave transmission loss for the radio wave of frequency 79 GHz is also preferably 3 dB or less, more preferably 2 dB or less, and further preferably 1 dB or less.

[0129] In addition, the radio wave transmission loss for radio waves with a frequency of 28 GHz (79 GHz) in the radio wave transmission region is a value obtained by subtracting the radio wave transmission loss of the dielectric substrate for radio waves with a frequency of 28 GHz (79 GHz) from the radio wave transmission loss of the heat-reflecting substrate as a whole for radio waves with a frequency of 28 GHz (79 GHz) in the radio wave transmission region. The radio wave transmission loss refers to a value measured by a free space method, for example.

[0130] Thus, the radio wave transmission loss for radio waves with frequencies of 28 GHz and 79 GHz is described as an example, but it is not limited to the 28 GHz band and the 79 GHz band. It is preferable to obtain the same radio wave transmission loss as described above in the frequency band of about several hundred MHz to 100 GHz.

[0131] <Application>

[0132] The heat-reflecting substrate of the present embodiment is suitable for applications requiring heat-reflecting properties and radio wave transmittance. Such applications include, for example, window glass for building applications, or window glass (window glass, rear window glass, side window glass) for automobile applications, window glass for railway vehicle applications, etc.

[0133] Example

[0134] Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto. Examples 1 to 4 are Examples, and Example 5 is a Comparative Example.

[0135] [Manufacturing of heat-reflecting substrate]

[0136] (Example 1)

[0137] On a 2 mm thick sodium calcium glass (solar radiation heat acquisition rate α is 0.880), a multilayer film including a conductive layer containing Ag and a metal oxide layer containing zinc oxide was formed by sputtering so that the visual transmittance Tv0 became 87.1% and the solar radiation heat acquisition rate g0 became 0.640 as a laminate including a heat radiation reflective film. In the following table, the heat radiation reflective film structure of Example 1 is represented as "1Ag".

[0138] Next, a nanosecond laser (laser marker MD-X1520, manufactured by KEYENCE) was used to provide a grid-like slit portion with a slit width of 40 μm and a slit interval of 0.5 mm on the entire heat reflective film (100 mm × 100 mm), thereby obtaining a heat reflective substrate. In addition, the focusing condition in laser etching was to perform the etching in a state where the focus position was shifted upward by about 25 μm from the position where the slit width was the smallest on the surface of the heat reflective substrate (condition 1). In addition, the designed aperture ratio f2 is as shown in the table.

[0139] (Example 2)

[0140] A heat-reflecting substrate was produced in the same manner as in Example 1 except that the slit intervals of the slit portions were set as shown in Table 1. The designed aperture ratio f2 was as shown in the table.

[0141] (Example 3)

[0142] A heat reflective substrate was prepared in the same manner as in Example 1 except that the amount of Ag in the heat reflective film was doubled and the visual transmittance Tv0 and the solar radiation heat acquisition rate g0 were the values ​​shown in Table 1. In the following table, the heat reflective film structure of Example 3 is indicated as "2Ag".

[0143] (Example 4)

[0144] A heat-reflecting substrate was prepared in the same manner as in Example 3 except that the slit interval of the slit portion was as shown in Table 1.

[0145] (Example 5)

[0146] A heat reflective substrate was prepared in the same manner as in Example 3 except that the heat reflective film was formed so that the visual transmittance Tv0 had the value shown in Table 1 and laser etching was performed using a picosecond laser (GR50 manufactured by Spectra-Physics) under the following focusing conditions.

[0147] Focusing condition: Perform at the exact focus position (condition 2).

[0148] [Solar radiation heat acquisition rate]

[0149] For each heat-reflecting substrate, the surface provided with the radio wave transparent region was used as the measurement surface, and the spectral spectrum and the emissivity were measured in the radio wave transparent region of 10 mm × 10 mm excluding the slit portion using a spectrophotometer (manufactured by Hitachi High-Technologies Corporation, model U-4100) based on the ISO9050 (2003) standard, and calculated by optical calculation. In Table 1, it is indicated as "g0".

[0150] In addition, for the 10 mm × 10 mm radio wave transparent area including a part of the slit portion, the solar radiation heat acquisition rate was calculated by the same method as above. In Table 1, the obtained value is represented as "g1". In addition, in the measurement of g1, the area ratio f1 occupied by the slit portion in the above-mentioned area was measured using an optical microscope, and the measurement was performed so that the area ratio f1 occupied by the slit portion in the above-mentioned area was within ±10% relative to the designed opening ratio f2.

[0151] [Visual transmittance]

[0152] For each example of the heat reflective substrate, the transmittance (reflectance) of each wavelength was calculated in the radio wave transparent area of ​​10 mm×10 mm excluding the slit portion based on JIS R 3106 (1998) by multiplying the transmittance (reflectance) by a coefficient corresponding to visibility. In Table 1, the obtained value is indicated as "Tv0".

[0153] In the 10 mm × 10 mm radio wave permeability region including the slit portion, the visual transmittance was determined by the same method as described above. The obtained value is indicated as "Tv1" in Table 1. In addition, in the measurement of Tv1, the area ratio f1 occupied by the slit portion in the above region was measured using an optical microscope, and the measurement was performed so that the area ratio f1 occupied by the slit portion in the above region was within ±10% relative to the designed opening ratio f2.

[0154] [Haze value]

[0155] For each example of the heat reflective substrate, the haze was measured in a 10 mm x 10 mm radio wave transparent area excluding the slit portion using a haze meter (HZ-2 manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS K 7136 (2000). In Table 1, the obtained value is indicated as "Haze (no slit)".

[0156] In the 10mm×10mm radio wave permeability area including the slit portion, the Haze value was measured in the same manner as described above. In Table 1, the obtained value is expressed as "Haze (with slit)". In addition, in the measurement of "Haze (with slit)", the area ratio f1 occupied by the slit portion in the above-mentioned area is measured using an optical microscope, and the measurement is performed so that the area ratio f1 occupied by the slit portion in the above-mentioned area is adjusted to be within ±10% relative to the designed opening ratio f2. In addition, "~" in the table means approximately, and means within ±25% of the value immediately following it.

[0157] [Radio wave transmission characteristics at 28 GHz]

[0158] For each example of the heat reflective substrate, the transmission amount (S12) at 28 GHz was evaluated by a free space method in a radio wave transparent area of ​​100 mm×100 mm excluding the slit portion. In Table 1, the obtained value is indicated as "S12 dB at 28 GHz (no slit)".

[0159] In the 100mm×100mm radio wave permeability area including the slit portion, the transmittance at 28GHz was measured in the same manner as above. In Table 1, the obtained value is expressed as "S12dB at 28GHz (with slit)". In addition, the area ratio f1 occupied by the slit portion in the above-mentioned area was measured by optical microscope measurement, and the area ratio f1 occupied by the slit portion in the above-mentioned area was adjusted to be within ±10% relative to the designed opening ratio f2, and the measurement was performed.

[0160] [Table 1]

[0161] Table 1

[0162] Example 1 Example 2 Example 3 Example 4 Example 5 Heat reflective film structure 1Ag 1Ag 2Ag 2Ag 2Ag Laser device Nanoseconds Nanoseconds Nanoseconds Nanoseconds Picoseconds Focus conditions Condition 1 Condition 1 Condition 1 Condition 1 Condition 2 Seam width 40μm 40μm 40μm 40μm 40μm Slit spacing 0.5mm 1mm 0.5mm 1mm 0.5mm pattern Lattice Lattice Lattice Lattice Lattice <![CDATA[Tv0[%]]]> 87.1 87.1 79.0 79.0 77.0 <![CDATA[Tv1[%]]]> 86.0 85.4 78.2 78.8 77.5 <![CDATA[g0]]> 0.640 0.640 0.463 0.463 0.463 <![CDATA[g1]]> 0.670 0.650 0.509 0.492 0.525 <![CDATA[f2]]> 0.143 0.078 0.143 0.078 0.143 <![CDATA[(1-f2)g0+f2α]]> 0.674 0.659 0.522 0.495 0.522 β 0.994 0.986 0.975 0.993 1.006 Haze (no seams) ＜0.5％ ＜0.5％ ＜0.5％ ＜0.5％ ＜0.5％ Haze (with slit) ～2％ ～2％ ～2％ ～2％ ～1％ S12dB at 28GHz (with slit) >-10dB >-10dB >-10dB >-10dB >-10dB S12dB at 28GHz (no slit) ~-30dB ~-30dB ~-30dB ~-30dB ~-30dB

[0163] According to the results in Table 1, the heat-reflecting substrates of Examples 1 to 4 as embodiments satisfy g1<(1-f2)·g0+f2α, showing excellent heat-insulating performance and radio wave transmittance. On the other hand, Example 5 as a comparative example satisfies g1>(1-f2)·g0+f2α, and its heat-insulating performance is inferior to that of Examples 1 to 4 as embodiments.

[0164] Above, various embodiments have been described, but the present invention is certainly not limited to this example. If it is a person skilled in the art, it is obvious that various variations or modifications can be thought of within the scope described in the claims, and these should certainly be understood to belong to the technical scope of the present invention. In addition, within the scope of not departing from the gist of the invention, the various constituent elements in the above-mentioned embodiments may also be combined arbitrarily.

[0165] In addition, this application is based on the Japanese patent application (Japanese Patent Application No. 2022-112708) filed on July 13, 2022, and its contents are cited as reference in this application.

[0166] Description of Reference Numerals

[0167] 10, 20...heat-ray reflecting substrate; 11, 21...dielectric substrate; 13, 23...heat-ray reflecting film; 14, 24...slit portion; A...radio wave transparent region.

Claims

1. A heat ray reflecting substrate comprising: a dielectric substrate and a heat ray reflecting film provided on at least one main surface of the dielectric substrate, characterized in that: At least a portion of the at least one main surface has a radio wave transparent region when viewed from above, The radio wave transparent area includes a slit portion without a heat-ray reflecting film. In the radio wave transparent area, the solar radiation heat acquisition rate g0 in the area not including the slit portion and the solar radiation heat acquisition rate g1 in the area including the slit portion satisfy the following formula (a): g1<(1-f2)·g0+f2α…(a) In this formula, f2 is the designed aperture ratio, and α is the solar radiation heat acquisition rate of the dielectric substrate.

2. The heat-reflecting substrate according to claim 1, characterized in that: In the radio wave transparent area, The visual transmittance Tv0 in the region not including the slit portion and the visual transmittance Tv1 in the region including the slit portion satisfy the relationship of Tv1<Tv0.

3. The heat-reflecting substrate according to claim 1, characterized in that: The radio wave transparent area transmits radio waves of a target frequency by more than -20 dB.

4. The heat-reflecting substrate according to claim 3, characterized in that: The target frequency is 700 MHz to 100 GHz.

5. The heat-reflecting substrate according to claim 1, characterized in that: In the radio wave transparent area, When g1=β((1-f2)·g0+fα), β<0.995 is satisfied.

6. The heat-reflecting substrate according to claim 1, characterized in that: The solar radiation heat acquisition rate g0 in the region excluding the slit portion is 0.7 or less.

7. The heat-reflecting substrate according to claim 1, characterized in that: In the radio wave transparent region, the haze in the region including the slit portion is at least twice the haze in the region not including the slit portion.

8. The heat-reflecting substrate according to claim 1, characterized in that: When the radio wave transparent region includes the slit portion having a grid-like slit pattern, the slit width is 20 to 100 μm and the slit interval is 0.2 to 14 mm.

9. A window glass, characterized in that: A heat-reflecting substrate according to any one of claims 1 to 8.

10. A method for producing a heat ray reflecting substrate, the method for producing a heat ray reflecting substrate according to any one of claims 1 to 8, characterized in that: The slit portion is formed using nanosecond laser.

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