WO2013180185A1 - Highly reflecting mirror - Google Patents

Highly reflecting mirror Download PDF

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Publication number
WO2013180185A1
WO2013180185A1 PCT/JP2013/064940 JP2013064940W WO2013180185A1 WO 2013180185 A1 WO2013180185 A1 WO 2013180185A1 JP 2013064940 W JP2013064940 W JP 2013064940W WO 2013180185 A1 WO2013180185 A1 WO 2013180185A1
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Prior art keywords
layer
oxide
glass substrate
thickness
zinc oxide
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PCT/JP2013/064940
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French (fr)
Japanese (ja)
Inventor
奈緒子 岡田
信孝 青峰
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旭硝子株式会社
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Priority to JP2014518706A priority Critical patent/JPWO2013180185A1/en
Publication of WO2013180185A1 publication Critical patent/WO2013180185A1/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/08—Mirrors
    • G02B5/0816—Multilayer mirrors, i.e. having two or more reflecting layers
    • G02B5/085—Multilayer mirrors, i.e. having two or more reflecting layers at least one of the reflecting layers comprising metal
    • G02B5/0858—Multilayer mirrors, i.e. having two or more reflecting layers at least one of the reflecting layers comprising metal the reflecting layers comprising a single metallic layer with one or more dielectric layers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S23/00—Arrangements for concentrating solar-rays for solar heat collectors
    • F24S23/70—Arrangements for concentrating solar-rays for solar heat collectors with reflectors
    • F24S23/82—Arrangements for concentrating solar-rays for solar heat collectors with reflectors characterised by the material or the construction of the reflector
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/40—Solar thermal energy, e.g. solar towers

Definitions

  • the present invention relates to a high reflector.
  • High reflection mirrors having high reflectivity for light in a predetermined wavelength range have been used in various fields.
  • Patent Document 1 discloses a high-reflection mirror having a high reflectance in the visible light region, which can be applied to a projection television or the like.
  • Patent Document 2 discloses a high-reflection mirror for a secondary mirror of a solar thermal power generation apparatus that can obtain a high reflectance in a wavelength range of 400 nm to 2500 nm.
  • Patent Document 3 discloses a reflecting mirror that uses a nitride film and has excellent durability such as moisture resistance.
  • a solar thermal power generation system including a primary mirror and a secondary mirror (both linear Fresnel type and tower type systems are of this type)
  • the reflected sunlight is applied to the secondary mirror, where it is reflected again and collected on the heat storage member.
  • solar energy is accumulate
  • the reflectance of the primary mirror and the secondary mirror at the wavelength of sunlight is an extremely important characteristic that affects the efficiency of the system.
  • the secondary mirror is disposed in the vicinity of the heat storage member that accumulates solar thermal energy, the secondary mirror is also required to have heat resistance.
  • the high-reflection mirror for the secondary mirror of the solar thermal power generation system described in Patent Document 2 described above has a high refractive index layer on the first side of the glass substrate in order to obtain high reflectance in the wavelength region of sunlight.
  • the alternating layers of the low refractive index layer are disposed so as to have a total of 70 to 90 layers, for example, and the alternating layer of the high refractive index layer and the low refractive index layer is provided on the second side of the glass substrate, for example, It is configured by installing so as to have a total of 70 to 90 layers.
  • the high reflection mirror described in Patent Document 1 has a problem that although it has a relatively small number of layers (5-layer structure), it is difficult to apply to a curved surface shape. That is, since the high reflection mirror described in Patent Document 1 is assumed to be applied to a planar member, the configuration of the high reflection mirror described in Patent Document 1 is similar to that of a secondary mirror of a solar power generation device. When applying to a curved surface shape, there may arise a problem that a uniform layer cannot be formed.
  • the reflector described in Patent Document 3 described above has good durability such as moisture resistance, but has a problem in durability against heat resistance because the film thickness of the silver film is thin.
  • this reflecting mirror is a reflecting mirror on a film substrate, and is not applied to a glass substrate.
  • the present invention has been made in view of such a background.
  • the present invention has high reflectance in a wavelength region of 300 nm to 2500 nm, has heat resistance, and can be applied to a curved surface shape.
  • An object is to provide a high-reflection mirror.
  • a high reflection mirror constituted by laminating a plurality of layers
  • the glass substrate has a first surface and is made of glass having a sodium oxide (Na 2 O) content of 4% by weight or less
  • a first layer, a second layer, a third layer, a fourth layer, and a fifth layer are laminated in this order
  • the first layer has a thickness of 200 mm or more, and includes at least one selected from the group consisting of a metal nitride, a metal oxide, and a metal oxynitride
  • the second layer comprises silver or a silver alloy
  • the third layer comprises zinc oxide
  • the fourth layer has an optical constant of a refractive index of 1.55 or less and an extinction coefficient of 0.001 or less at a wavelength of 400 to 1500 nm, and includes silicon oxide.
  • the fifth layer has an optical constant of a refractive index of 1.7 or more and an extinction coefficient of 0.01 or less at a wavelength of 400 to 1500 nm, and silicon nitride, aluminum nitride, silicon oxynitride, aluminum oxynitride, titanium oxide.
  • a high reflector comprising at least one selected from the group consisting of niobium oxide, zirconium oxide, tantalum oxide, zinc oxide, tin oxide, and hafnium oxide.
  • the first layer is composed of zinc oxide containing a first metal species, and the first metal species is selected from the group consisting of titanium, aluminum, tin and gallium. It may be at least one selected.
  • the third layer is composed of zinc oxide containing a second metal species, and the second metal species is selected from the group consisting of titanium, aluminum, tin and gallium. May be at least one.
  • the second layer may have a thickness of 1000 to 3000 mm.
  • the third layer may have a thickness of 10 to 100 mm.
  • the fourth layer may have a thickness of 300 to 1500 mm.
  • the fifth layer may have a thickness of 300 to 1500 mm.
  • the present invention provides a secondary mirror for a solar thermal power generation system, which has a high reflection mirror having the above-described characteristics.
  • a highly reflective mirror that has high reflectivity in the wavelength range of 300 nm to 2500 nm, has heat resistance, and can be applied to curved surface shapes.
  • FIG. 1 shows a schematic cross-sectional view of an example of a highly reflecting mirror according to the present invention.
  • the high reflection mirror 100 is configured by laminating a plurality of layers on an upper portion of a glass substrate 110.
  • the glass substrate 110 has a first surface 115, and the first surface 115 includes a first layer 120, a second layer 130, a third layer 140, and a fourth layer. Five layers of the layer 150 and the fifth layer 160 are sequentially stacked.
  • the first layer 120 has a role of improving adhesion between the glass substrate 110 and the second layer 130 and a role of preventing diffusion of oxygen and / or alkali components from the glass substrate to the silver film.
  • the second layer 130 contains silver and has a role of effectively reflecting light in the wavelength region of sunlight.
  • the third layer 140 has a role of improving the adhesion between the second layer 130 and the fourth layer 150, and oxygen in the atmosphere diffuses into the silver film during the formation of the fourth layer. It has a role to suppress.
  • the fourth layer 150 is provided as a low refractive index film having a lower refractive index than the fifth layer 160.
  • the fifth layer 160 is provided as a high refractive index film having a higher refractive index than the fourth layer 150. By laminating the fifth layer 160 having a high refractive index on the fourth layer 150 having a low refractive index, the reflectivity of the high reflecting mirror 100 as a whole can be increased.
  • the high reflecting mirror 100 according to the present invention is characterized in that the sodium content in the glass substrate 110 is suppressed to 4% by weight or less.
  • the high reflecting mirror 100 according to the present invention is characterized in that the first layer 120 has a thickness of 200 mm or more.
  • the sodium content itself in the glass substrate 110 is significantly reduced.
  • the first layer 120 that functions as an adhesion improving layer is formed of a relatively thick layer of 200 mm or more, it can also function as a sodium ion diffusion barrier of the glass substrate 110.
  • the high reflecting mirror 100 according to the present invention is capable of sodium from the glass substrate 110 side to the second layer containing silver even when exposed to a relatively high temperature (eg, 300 ° C. to 350 ° C.) Can be significantly suppressed. For this reason, the high reflective mirror 100 by this invention can exhibit high heat resistance.
  • a relatively high temperature eg, 300 ° C. to 350 ° C.
  • the high reflection mirror 100 is configured by forming a laminated film of only five layers on one surface (first surface 115) of the glass substrate 110. Therefore, unlike the high reflection mirror of Patent Document 2, it is not necessary to stack 70 to 90 layers on both sides of the glass substrate, and a high reflection mirror having a relatively simple and low cost configuration can be obtained. it can.
  • the first layer 120 has a thickness of 200 mm (20 nm) or more.
  • Such a relatively thick layer can be uniformly formed even on a curved surface, unlike the high reflection mirror described in Patent Document 1 having a relatively thin underlayer.
  • the highly reflective mirror 100 by this invention can be provided appropriately also in the form of a curved surface shape.
  • Glass substrate 110 The type of glass substrate 100 is not particularly limited as long as it is made of glass having a sodium oxide (Na 2 O) content of 4 wt% or less.
  • the glass substrate 100 may be, for example, non-alkali metal glass, AN100, or the like.
  • the thickness of the glass substrate 100 is not particularly limited, but may be in the range of 0.5 mm to 8.0 mm, for example, from the viewpoint of the strength and ease of use of the high reflection mirror.
  • the shape of the glass substrate 110 is not particularly limited.
  • the glass substrate 110 may be flat or curved.
  • the first layer 120 has a role of improving the adhesion between the glass substrate 110 and the second layer 130.
  • the first layer 120 is composed of at least one selected from the group consisting of metal nitrides, metal oxides, and metal oxynitrides.
  • the first layer has a thickness of 200 mm or more.
  • the upper limit of the thickness of the first layer is not particularly limited.
  • the first layer 120 may be a single layer or a plurality of layers.
  • the second layer 130 is a layer containing silver.
  • the reflectance of light in the wavelength region of sunlight 300 nm to 2500 nm
  • the dependency of the reflectance on the incident angle can be reduced.
  • the second layer 130 may be an alloy of silver and gold or an alloy of palladium.
  • the contents of gold and palladium in the alloy may be in the range of 0.5% to 5% by mass.
  • the second layer 130 may have a thickness in the range of 1000 to 3000 mm.
  • the third layer 140 has a role of improving the adhesion between the second layer 130 and the fourth layer 150.
  • the third layer 140 may be made of zinc oxide containing the second metal species.
  • the second metal species is at least one selected from the group consisting of titanium, aluminum, tin, and gallium. By containing the second metal species, the adhesion between the second layer 130 and the fourth layer 150 can be further improved.
  • the third layer 140 may be a single layer or a plurality of layers.
  • the third layer 140 may have a thickness in the range of 10 to 100 mm.
  • the fourth layer 150 is made of a material having a lower refractive index than the fifth layer 160.
  • the fourth layer 150 may have an optical constant with a refractive index of 1.55 or less and an extinction coefficient of 0.001 or less at a wavelength of 550 nm.
  • the fourth layer 150 may be made of silicon oxide. Further, it may be made of a composite oxide containing silicon oxide and aluminum oxide.
  • the fourth layer 150 may have a thickness in the range of 300 to 1500 mm.
  • the fifth layer 160 is made of a material having a higher refractive index than that of the fourth layer 150.
  • the fifth layer 160 has an optical constant of a refractive index of 1.7 or more and an extinction coefficient of 0.01 or less.
  • the fifth layer 160 may be composed of silicon nitride, aluminum nitride, silicon oxynitride, aluminum oxynitride, niobium oxide, zirconium oxide, tantalum oxide, hafnium oxide, titanium oxide, zinc oxide, and / or tin oxide.
  • the fifth layer 160 may be a composite oxynitride.
  • the fifth layer 160 may have a thickness in the range of 300 to 1500 mm.
  • the fifth layer 160 may be a single layer or a plurality of layers.
  • the high reflecting mirror 100 has the combination of the fourth layer 150 and the fifth layer 160 only once.
  • the high reflecting mirror 100 may have a combination of the fourth layer 150 and the fifth layer 160 a plurality of times. That is, the combination of the fourth layer and the fifth layer may be arranged any number of times on the combination of the fourth layer 150 and the fifth layer 160.
  • the high reflecting mirror 100 according to the present invention as shown in FIG. 1 can be manufactured, for example, by applying a sputtering method using a metal target and a metal oxide target to a glass substrate.
  • a glass substrate 110 is prepared.
  • the first layer 110 is formed on the glass substrate 110 by a sputtering method using an oxide target or a metal target (such as oxide or zinc metal).
  • a second layer is formed on the first layer 110 by sputtering using a silver or silver alloy target.
  • a third layer is formed on the second layer by a sputtering method using a zinc oxide target. Note that in this case, in order to suppress the oxidation of the second layer, it is preferable to perform the film formation in an atmosphere in which an oxidizing gas such as oxygen does not exist.
  • the content of the oxidizing gas in the sputtering gas is preferably 10% by volume or less.
  • a fourth layer is formed on the third layer by a reactive sputtering method using a metal silicon target doped with boron.
  • a fifth layer is formed on the fourth layer by a reactive sputtering method using an oxide target or a metal target (oxidized or metallic titanium, oxidized or metallic niobium, or the like).
  • an alternating current (AC) or direct current (DC) sputtering method can be used as the sputtering method.
  • the DC sputtering method includes a pulse DC sputtering method.
  • AC sputtering or pulse DC sputtering is effective in preventing abnormal discharge.
  • AC or DC reactive sputtering is effective in that a dense film can be formed.
  • the sputtering method is superior in that it can form a film on a large-area substrate and has a small deviation in film thickness distribution.
  • the high reflection mirror 100 according to the present invention as shown in FIG. 1 can be manufactured.
  • the high reflecting mirror 100 according to the present invention can be applied as a secondary mirror of a solar thermal power generation system, for example.
  • a solar thermal power generation system such as a linear Fresnel type or a tower type includes a primary mirror and a secondary mirror, and uses high-temperature and high-pressure using thermal energy obtained by collecting sunlight irradiated on these mirrors. Steam is generated, and electricity is generated using this steam.
  • the secondary mirror since the secondary mirror is disposed in the vicinity of the heat generation part of the solar thermal power generation system, the secondary mirror requires heat resistance in addition to high reflection characteristics in the wavelength range of sunlight (300 nm to 2500 nm). Is done.
  • the high reflecting mirror 100 according to the present invention is characterized by having a high reflectivity in the wavelength range of sunlight (300 nm to 2500 nm) and relatively good heat resistance. Therefore, the high reflection mirror 100 according to the present invention can be significantly applied to the secondary mirror of the solar thermal power generation system.
  • the high reflecting mirror 100 according to the present invention can be configured with a relatively small number of layers and has a relatively simple structure. Therefore, the secondary mirror of the solar thermal power generation system configured with the high reflection mirror 100 according to the present invention has a relatively simple configuration and can be manufactured at a relatively low cost.
  • Example 1 A cleaned glass substrate was placed in the vacuum chamber, and each film was sequentially formed by the method described below to prepare a high reflector sample.
  • alkali-free glass having a length of 100 mm ⁇ width of 100 mm ⁇ thickness of 0.5 mm was used.
  • the sodium content in this glass substrate is almost zero.
  • targets 1 to 5 The following five types of targets (targets 1 to 5) were prepared as targets: (Target 1) Zinc oxide target added with gallium oxide (gallium oxide content 5.7 mass%, zinc oxide content 94.3 mass%), (Target 2) Silver alloy target (gold content 2 mass%, silver content 98 mass%) to which gold is added, (Target 3) Metallic silicon target (boron-doped polycrystalline target, silicon content 99.999 mass%), (Target 4) Titanium oxide target (content of titanium oxide 99.9% by mass).
  • the surface sizes of the targets 1 to 4 were 177.8 mm ⁇ 381 mm, respectively.
  • Each of these targets 1 to 4 was installed at a position opposite to the glass substrate, the inside of the vacuum chamber was evacuated to 2 ⁇ 10 ⁇ 3 Pa, and the following film formation was performed.
  • Step 1 Formation of zinc oxide film
  • a gallium-doped zinc oxide film was formed on a glass substrate by DC sputtering.
  • Argon gas flow rate 400 sccm
  • the input power was 0.25 kW.
  • the thickness of the obtained gallium-doped zinc oxide film was 200 mm.
  • the composition of the gallium-doped zinc oxide film was almost the same as that of the target 1.
  • Step 2 Formation of silver alloy film
  • a silver alloy film was formed on a glass substrate having a gallium-doped zinc oxide film by DC sputtering using the target 2.
  • Argon gas flow rate 400 sccm
  • the input power was 1 kW.
  • the thickness of the obtained silver alloy film was 1200 mm.
  • the composition of the silver alloy film was almost the same as that of the target 2.
  • Step 3 Formation of second zinc oxide film
  • Argon gas flow rate 400 sccm
  • the input power was 0.25 kW.
  • the thickness of the obtained gallium-doped zinc oxide film was 50 mm.
  • the composition of the gallium-doped zinc oxide film was almost the same as that of the target 1.
  • Step 4 Formation of silicon oxide film
  • a silicon oxide film was formed on the second zinc oxide film by using the target 3 by pulse DC reactive sputtering.
  • oxygen gas flow rate 240 sccm
  • argon gas flow rate 160 sccm
  • the thickness of the obtained silicon oxide film was 500 mm.
  • Step 5 Formation of titanium oxide film
  • a titanium oxide film was formed on the silicon oxide film by pulse DC sputtering using the target 4.
  • oxygen gas flow rate 20 sccm
  • argon gas flow rate 380 sccm
  • the input power was 2 kW and the frequency was 40 kHz.
  • the thickness of the obtained titanium oxide film was 950 mm.
  • Example 1 a sample of a high reflection mirror in which five layers were laminated on a glass substrate (hereinafter referred to as “sample according to Example 1”) was obtained.
  • Example 2 A sample of the high reflection mirror according to Example 2 (hereinafter referred to as “sample according to Example 2”) was produced by the same method as Example 1. However, in Example 2, Pyrex glass (registered trademark) having a thickness of 3 mm was used as the glass substrate. Other conditions are the same as in the first embodiment.
  • sodium oxide (Na 2 O) content of the glass in the substrate is 4 wt%.
  • Example 3 A sample of the high reflection mirror according to Example 3 (hereinafter referred to as “sample according to Example 3”) was produced by the same method as in Example 1. However, in Example 3, a silicon nitride film was formed on the silicon oxide film by a pulse DC reactive sputtering method using a boron-doped metal silicon target as the fifth layer. Nitrogen gas (flow rate 120 sccm) and argon gas (flow rate 280 sccm) were used as the sputtering gas, and the input power was 1 kW. The thickness of the obtained silicon nitride film was 500 mm. Other conditions are the same as in the first embodiment.
  • Example 4 A cleaned glass substrate was placed in the vacuum chamber, and each film was sequentially formed by the method described below to prepare a high reflector sample.
  • alkali-free glass having a length of 100 mm ⁇ width of 100 mm ⁇ thickness of 0.5 mm was used.
  • the sodium content in this glass substrate is almost zero.
  • targets 1 to 4 The following four types of targets (targets 1 to 4) were prepared as targets: (Target 1) Zinc oxide target added with gallium oxide (gallium oxide content 5.7 mass%, zinc oxide content 94.3 mass%), (Target 2) Silver alloy target (gold content 2 mass%, silver content 98 mass%) to which gold is added, (Target 3) Metallic silicon target (boron-doped polycrystalline target, silicon content 99.999 mass%), (Target 4) Metal silicon and aluminum alloy target (silicon content 90 mass%, aluminum content 10 mass%).
  • the surface sizes of the targets 1 to 4 were 70 mm ⁇ 200 mm, respectively.
  • Each of these targets 1 to 4 was installed at a position opposite to the glass substrate, the inside of the vacuum chamber was evacuated to 2 ⁇ 10 ⁇ 3 Pa, and the following film formation was performed.
  • Step 1 Formation of silicon aluminum nitride film
  • a silicon aluminum nitride film was formed on the glass substrate by the pulse DC reactive sputtering method using the target 4.
  • Argon gas flow rate 70 sccm
  • nitrogen gas flow rate 30 sccm
  • the input power was 0.5 kW.
  • the thickness of the obtained silicon aluminum nitride film was 200 mm.
  • Step 2 Formation of zinc oxide film
  • a gallium-doped zinc oxide film was formed on the silicon aluminum nitride film by DC sputtering using the target 1.
  • Argon gas flow rate 100 sccm
  • the input power was 0.1 kW.
  • the thickness of the obtained gallium-doped zinc oxide film was 15 mm.
  • the composition of the gallium-doped zinc oxide film was almost the same as that of the target 1.
  • Step 3 Formation of silver alloy film
  • a silver alloy film was formed on the glass substrate having the gallium-doped zinc oxide film by DC sputtering using the target 2.
  • Argon gas flow rate 100 sccm
  • the input power was 0.5 kW.
  • the thickness of the obtained silver alloy film was 1200 mm.
  • the composition of the silver alloy film was almost the same as that of the target 2.
  • Step 4 Formation of second zinc oxide film
  • a gallium-doped zinc oxide film was formed on the silver alloy film by DC sputtering.
  • Argon gas flow rate 100 sccm
  • the input power was 0.1 kW.
  • the thickness of the obtained gallium-doped zinc oxide film was 15 mm.
  • the composition of the gallium-doped zinc oxide film was almost the same as that of the target 1.
  • Step 5 Formation of second silicon aluminum nitride film
  • a silicon aluminum nitride film was formed on the second zinc oxide film by using the target 4 by pulse DC reactive sputtering.
  • Nitrogen gas flow rate 30 sccm
  • argon gas flow rate 70 sccm
  • the input power was 0.5 kW.
  • Step 6 Formation of silicon oxide film
  • a silicon oxide film was formed on the second silicon aluminum nitride film by the pulse DC reactive sputtering method using the target 4.
  • oxygen gas flow rate 60 sccm
  • argon gas flow rate 40 sccm
  • the input power was 0.5 kW.
  • the thickness of the obtained silicon oxide film was 500 mm.
  • Step 7 Formation of third silicon aluminum nitride film
  • a silicon aluminum nitride film was formed on the silicon oxide film by the pulse DC reactive sputtering method using the target 4.
  • Nitrogen gas flow rate 30 sccm
  • argon gas flow rate 70 sccm
  • the input power was 0.5 kW.
  • the thickness of the obtained silicon aluminum nitride film was 500 mm.
  • Example 5 A sample of the high reflection mirror according to Example 5 (hereinafter referred to as “sample according to Example 5”) was produced in the same manner as in Example 4. However, in Example 5, in Step 2 of Example 4, a glass substrate was obtained by pulse DC sputtering using an alloy target of nickel and chromium (nickel content: 50 mass%, chromium content: 50 mass%). A nichrome film was formed thereon. Argon gas (flow rate 100 sccm) was used as the sputtering gas, and the input power was 0.05 kW. Other conditions are the same as in Example 4. The thickness of the obtained nichrome film was 15 mm.
  • Comparative Example 1 A sample of a high reflection mirror according to Comparative Example 1 (hereinafter referred to as “sample according to Comparative Example 1”) was produced by the same method as in Example 1. However, in Comparative Example 1, soda lime glass having a thickness of 3 mm was used as the glass substrate. Other conditions are the same as in the first embodiment.
  • the sodium content of oxidation in this glass substrate is 14% by weight.
  • Comparative Example 2 A sample of a high reflection mirror according to Comparative Example 2 (hereinafter referred to as “sample according to Comparative Example 2”) was produced by the same method as in Example 1. However, in Comparative Example 2, the thickness of the gallium-doped zinc oxide film formed in Step 1 was 150 mm. Other conditions are the same as in the first embodiment.
  • the heat resistance evaluation test was carried out by holding each sample at a predetermined temperature for a predetermined time and measuring the reflectance of the sample after the heat treatment.
  • the heat treatment temperatures were 300 ° C, 350 ° C, and 400 ° C.
  • FIG. 2 summarizes the reflectance measurement results before and after heat treatment for each sample.
  • the vertical axis reflectivity is shown as solar energy reflectivity: Re.
  • the solar energy reflectance: Re is a value calculated according to ISO 9050-2003. Specifically, the measured value of the spectral absolute reflectance (300 nm to 2500 nm) is overlapped indicating the standard spectral distribution of solar radiation. It means a weighted average value multiplied by a coefficient.
  • the solar energy reflectivity is the heat treatment in any of the heat treatment of 168 hours at 300 ° C., the heat treatment of 72 hours at 350 ° C., and the heat treatment of 72 hours at 400 ° C. You can see that there has been little change from before. Similarly, in the samples according to Examples 2 to 5, the solar energy reflectance after the heat treatment under each condition is almost the same as that before the heat treatment.
  • the solar energy reflectance tends to decrease due to the heat treatment.
  • the solar energy reflectance after heat treatment at 300 ° C. for 168 hours is about 2% lower than the value before heat treatment, and the solar energy reflectance after heat treatment at 350 ° C. for 72 hours is Compared to the value, it decreased by about 14%.
  • the heat processing for 72 hours at 400 degreeC is not implemented.
  • the solar energy reflectance tends to decrease due to the heat treatment.
  • the solar energy reflectance after heat treatment at 300 ° C. for 168 hours is 2% lower than the value before heat treatment
  • the solar energy reflectance after 72 hours at 400 ° C. is lower than the value before heat treatment.
  • FIG. 3 shows the change in reflectivity of the samples according to Examples 1 to 5 after being held at a temperature of 350 ° C. for each time.
  • the vertical axis indicates the same solar energy reflectance as Re in FIG.
  • FIG. 3 shows the results of Comparative Example 1 and Comparative Example 2 after holding at 350 ° C. for 72 hours at the same time.
  • the present invention can be used for a secondary mirror in a solar thermal power generation system such as a linear Fresnel type or a tower type.
  • High Reflector according to the Present Invention 110 Glass Substrate 115 First Surface 120 First Layer 130 Second Layer 140 Third Layer 150 Fourth Layer 160 Fifth Layer

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Abstract

A highly reflecting mirror which is configured by laminating a plurality of layers on a glass substrate. The glass substrate has a first surface and is configured of glass that has a sodium oxide content of 4% by weight or less; and first to fifth layers are sequentially laminated in this order on the first surface of the glass substrate. The first layer has a thickness of 200 Å or more and contains at least one substance that is selected from the group consisting of metal nitrides, metal oxides and metal oxynitrides; the second layer contains silver or a silver alloy; the third layer contains zinc oxide; the fourth layer contains silicon oxide and has such optical constants as a refractive index of 1.55 or less and an extinction coefficient of 0.001 or less at a wavelength of 400-1,500 nm; and the fifth layer contains a specific compound and has such optical constants as a refractive index of 1.7 or more and an extinction coefficient of 0.01 or less at a wavelength of 400-1,500 nm.

Description

高反射鏡High reflector
　本発明は、高反射鏡に関する。 The present invention relates to a high reflector.
　所定の波長域の光に対して高い反射率を有する高反射鏡は、従来より、様々な分野で使用されている。 High reflection mirrors having high reflectivity for light in a predetermined wavelength range have been used in various fields.
　例えば、特許文献１には、プロジェクションテレビ等に適用することが可能な、可視光領域において高い反射率を有する高反射鏡が開示されている。 For example, Patent Document 1 discloses a high-reflection mirror having a high reflectance in the visible light region, which can be applied to a projection television or the like.
　また、特許文献２には、４００ｎｍ～２５００ｎｍの波長域において高い反射率が得られる、太陽熱発電装置の二次ミラ－用の高反射鏡が開示されている。 Further, Patent Document 2 discloses a high-reflection mirror for a secondary mirror of a solar thermal power generation apparatus that can obtain a high reflectance in a wavelength range of 400 nm to 2500 nm.
　また、特許文献３には、窒化膜を使用した、耐湿性等の耐久性に優れる反射鏡が開示されている。 Further, Patent Document 3 discloses a reflecting mirror that uses a nitride film and has excellent durability such as moisture resistance.
特許第４４２８１５２号明細書Japanese Patent No. 4428152 特開２０１０－５５０５８号公報JP 2010-55058 A 国際公開第２００７－００７５７０号International Publication No. 2007-007570
　近年、太陽光を集光することにより得られる熱エネルギーを利用して発電を行う、太陽熱発電システムが注目されている。太陽熱発電システムの種類としては、リニアフレネル型およびタワー型など、各種形態が存在する。 In recent years, solar power generation systems that generate power using thermal energy obtained by concentrating sunlight have attracted attention. There are various types of solar thermal power generation systems such as a linear Fresnel type and a tower type.
　このうち、一次ミラーおよび二次ミラーを備えるタイプの太陽熱発電システム（リニアフレネル型およびタワー型のシステムは、いずれもこのタイプである）では、まず、太陽光は、一次ミラーに照射され、ここで反射される。次に、この反射された太陽光は、二次ミラーに照射され、ここで再度反射され、蓄熱部材に集光される。これにより、蓄熱部材において、太陽光エネルギーが熱エネルギーとして蓄積される。従って、この熱エネルギーを利用して、高温高圧蒸気を発生させることにより、発電を行うことができる。 Of these, in a solar thermal power generation system including a primary mirror and a secondary mirror (both linear Fresnel type and tower type systems are of this type), first, sunlight is applied to the primary mirror, where Reflected. Next, the reflected sunlight is applied to the secondary mirror, where it is reflected again and collected on the heat storage member. Thereby, solar energy is accumulate | stored as thermal energy in a thermal storage member. Therefore, electric power can be generated by generating high-temperature and high-pressure steam using this thermal energy.
　以上の動作原理から明らかなように、上記のタイプの太陽熱発電システムにおいて、一次ミラーおよび二次ミラーの太陽光の波長における反射率は、システムの効率を左右する極めて重要な特性となる。 As is apparent from the above operating principle, in the solar thermal power generation system of the above type, the reflectance of the primary mirror and the secondary mirror at the wavelength of sunlight is an extremely important characteristic that affects the efficiency of the system.
　さらに、二次ミラーは、太陽熱エネルギーを蓄積する蓄熱部材の近傍に配置されるため、二次ミラーには耐熱性も要求される。 Furthermore, since the secondary mirror is disposed in the vicinity of the heat storage member that accumulates solar thermal energy, the secondary mirror is also required to have heat resistance.
　前述の特許文献２に記載の太陽熱発電システムの二次ミラ－用の高反射鏡は、太陽光の波長域において高い反射率を得るため、ガラス基板の第１の側に、高屈折率層と低屈折率層の交互繰り返し層を、例えば合計７０～９０層となるように設置するとともに、ガラス基板の第２の側にも、高屈折率層と低屈折率層の交互繰り返し層を、例えば合計７０～９０層となるように設置することにより構成される。 The high-reflection mirror for the secondary mirror of the solar thermal power generation system described in Patent Document 2 described above has a high refractive index layer on the first side of the glass substrate in order to obtain high reflectance in the wavelength region of sunlight. For example, the alternating layers of the low refractive index layer are disposed so as to have a total of 70 to 90 layers, for example, and the alternating layer of the high refractive index layer and the low refractive index layer is provided on the second side of the glass substrate, for example, It is configured by installing so as to have a total of 70 to 90 layers.
　しかしながら、このような高反射鏡は、層数が多く、構成が複雑すぎる上、製造コストが高くなるという問題がある。 However, such a high reflection mirror has a problem that the number of layers is large, the configuration is too complicated, and the manufacturing cost is high.
　従って、より簡単な構成を有する太陽熱発電装置の二次ミラ－用の高反射鏡に対するニーズがある。 Therefore, there is a need for a high-reflection mirror for a secondary mirror of a solar thermal power generation device having a simpler configuration.
　一方、前述の特許文献１に記載の高反射鏡は、比較的層数は少ないものの（５層構造）、曲面形状に適用することは難しいという問題がある。すなわち、特許文献１に記載の高反射鏡は、平面形状の部材に対する適用を想定しているため、特許文献１に記載の高反射鏡の構成を、太陽熱発電装置の二次ミラ－のような曲面形状に適用しようとした場合、均一な層を形成することができないという問題が生じ得る。 On the other hand, the high reflection mirror described in Patent Document 1 has a problem that although it has a relatively small number of layers (5-layer structure), it is difficult to apply to a curved surface shape. That is, since the high reflection mirror described in Patent Document 1 is assumed to be applied to a planar member, the configuration of the high reflection mirror described in Patent Document 1 is similar to that of a secondary mirror of a solar power generation device. When applying to a curved surface shape, there may arise a problem that a uniform layer cannot be formed.
　また、前述の特許文献３に記載の反射鏡は、耐湿性等の耐久性は良いものの、銀膜の下地膜の膜厚が薄く、耐熱性に対する耐久性には問題がある。また、この反射鏡は、フィルム基板上の反射鏡であり、ガラス基板に適用されたものではない。 In addition, the reflector described in Patent Document 3 described above has good durability such as moisture resistance, but has a problem in durability against heat resistance because the film thickness of the silver film is thin. Moreover, this reflecting mirror is a reflecting mirror on a film substrate, and is not applied to a glass substrate.
　本発明は、このような背景に鑑みなされたものであり、本発明では、３００ｎｍ～２５００ｎｍの波長域において高い反射率を有し、耐熱性を有するとともに、曲面形状にも適用することが可能な、高反射鏡を提供することを目的とする。 The present invention has been made in view of such a background. In the present invention, the present invention has high reflectance in a wavelength region of 300 nm to 2500 nm, has heat resistance, and can be applied to a curved surface shape. An object is to provide a high-reflection mirror.
　本発明では、ガラス基板上に、複数の層を積層することにより構成された高反射鏡であって、
　前記ガラス基板は、第１の表面を有し、酸化ナトリウム（Ｎａ２Ｏ）含有量が４重量％以下のガラスで構成され、
　前記ガラス基板の第１の表面には、第１の層、第２の層、第３の層、第４の層、第５の層がこの順に積層され、
　前記第１の層は、２００Å以上の厚さを有し、金属窒化物、金属酸化物、および金属酸窒化物からなる群から選定された少なくとも一つを含み、
　前記第２の層は、銀または銀合金を含み、
　前記第３の層は、酸化亜鉛を含み、
　前記第４の層は、波長４００～１５００ｎｍにおいて、屈折率１．５５以下、消衰係数０．００１以下の光学定数を有し、酸化ケイ素を含み、
　前記第５の層は、波長４００～１５００ｎｍにおいて、屈折率１．７以上、消衰係数０．０１以下の光学定数を有し、窒化ケイ素、窒化アルミニウム、酸窒化ケイ素、酸窒化アルミニウム、酸化チタン、酸化ニオブ、酸化ジルコニウム、酸化タンタル、酸化亜鉛、酸化スズ、および酸化ハフニウムからなる群から選定された少なくとも一つを含むことを特徴とする高反射鏡が提供される。 In the present invention, on a glass substrate, a high reflection mirror constituted by laminating a plurality of layers,
The glass substrate has a first surface and is made of glass having a sodium oxide (Na 2 O) content of 4% by weight or less,
On the first surface of the glass substrate, a first layer, a second layer, a third layer, a fourth layer, and a fifth layer are laminated in this order,
The first layer has a thickness of 200 mm or more, and includes at least one selected from the group consisting of a metal nitride, a metal oxide, and a metal oxynitride,
The second layer comprises silver or a silver alloy;
The third layer comprises zinc oxide;
The fourth layer has an optical constant of a refractive index of 1.55 or less and an extinction coefficient of 0.001 or less at a wavelength of 400 to 1500 nm, and includes silicon oxide.
The fifth layer has an optical constant of a refractive index of 1.7 or more and an extinction coefficient of 0.01 or less at a wavelength of 400 to 1500 nm, and silicon nitride, aluminum nitride, silicon oxynitride, aluminum oxynitride, titanium oxide. There is provided a high reflector comprising at least one selected from the group consisting of niobium oxide, zirconium oxide, tantalum oxide, zinc oxide, tin oxide, and hafnium oxide.
　ここで、本発明による高反射鏡において、前記第１の層は、第１の金属種を含む酸化亜鉛で構成され、前記第１の金属種は、チタン、アルミニウム、スズおよびガリウムからなる群から選定された少なくとも一つであっても良い。 Here, in the high reflector according to the present invention, the first layer is composed of zinc oxide containing a first metal species, and the first metal species is selected from the group consisting of titanium, aluminum, tin and gallium. It may be at least one selected.
　また、本発明による高反射鏡において、前記第３の層は、第２の金属種を含む酸化亜鉛で構成され、前記第２の金属種は、チタン、アルミニウム、スズおよびガリウムからなる群から選定された少なくとも一つであっても良い。 In the high reflector according to the present invention, the third layer is composed of zinc oxide containing a second metal species, and the second metal species is selected from the group consisting of titanium, aluminum, tin and gallium. May be at least one.
　また、本発明による高反射鏡において、前記第２の層は、１０００Å～３０００Åの厚さを有しても良い。 In the high reflector according to the present invention, the second layer may have a thickness of 1000 to 3000 mm.
　また、本発明による高反射鏡において、前記第３の層は、１０Å～１００Åの厚さを有しても良い。 In the high reflector according to the present invention, the third layer may have a thickness of 10 to 100 mm.
　また、本発明による高反射鏡において、前記第４の層は、３００Å～１５００Åの厚さを有しても良い。 In the high reflector according to the present invention, the fourth layer may have a thickness of 300 to 1500 mm.
　また、本発明による高反射鏡において、前記第５の層は、３００Å～１５００Åの厚さを有しても良い。 In the high reflector according to the present invention, the fifth layer may have a thickness of 300 to 1500 mm.
　さらに、本発明では、太陽熱発電システム用の二次ミラーであって、前述のような特徴を有する高反射鏡を有する二次ミラーが提供される。 Furthermore, the present invention provides a secondary mirror for a solar thermal power generation system, which has a high reflection mirror having the above-described characteristics.
　本発明では、３００ｎｍ～２５００ｎｍの波長域において高い反射率を有し、耐熱性を有するとともに、曲面形状にも適用することが可能な、高反射鏡を提供することができる。 In the present invention, it is possible to provide a highly reflective mirror that has high reflectivity in the wavelength range of 300 nm to 2500 nm, has heat resistance, and can be applied to curved surface shapes.
本発明による高反射鏡の一例の概略的な断面図を示した図である。It is the figure which showed schematic sectional drawing of an example of the high reflective mirror by this invention. 各高反射鏡サンプルにおける熱処理前後の反射率（日射エネルギー反射率Ｒｅ）を示したグラフである。It is the graph which showed the reflectance (sunlight energy reflectance Re) before and behind heat processing in each high reflector sample. 各高反射鏡サンプルにおける熱処理前後の反射率（日射エネルギー反射率Ｒｅ）を示したグラフである。It is the graph which showed the reflectance (sunlight energy reflectance Re) before and behind heat processing in each high reflector sample.
　以下、図面を参照して、本発明について詳しく説明する。 Hereinafter, the present invention will be described in detail with reference to the drawings.
　図１には、本発明による高反射鏡の一例の概略的な断面図を示す。 FIG. 1 shows a schematic cross-sectional view of an example of a highly reflecting mirror according to the present invention.
　図１に示すように、本発明による高反射鏡１００は、ガラス基板１１０の上部に、複数の層を積層することにより構成される。 As shown in FIG. 1, the high reflection mirror 100 according to the present invention is configured by laminating a plurality of layers on an upper portion of a glass substrate 110.
　より具体的には、ガラス基板１１０は、第１の表面１１５を有し、この第１の表面１１５には、第１の層１２０、第２の層１３０、第３の層１４０、第４の層１５０、第５の層１６０の５層が、順次積層される。 More specifically, the glass substrate 110 has a first surface 115, and the first surface 115 includes a first layer 120, a second layer 130, a third layer 140, and a fourth layer. Five layers of the layer 150 and the fifth layer 160 are sequentially stacked.
　第１の層１２０は、ガラス基板１１０と第２の層１３０の間の密着性を改善する役割、および酸素および／またはアルカリ成分のガラス基板から銀膜への拡散を防止する役割を有する。 The first layer 120 has a role of improving adhesion between the glass substrate 110 and the second layer 130 and a role of preventing diffusion of oxygen and / or alkali components from the glass substrate to the silver film.
　第２の層１３０は、銀を含み、太陽光の波長域の光を有効に反射させる役割を有する。 The second layer 130 contains silver and has a role of effectively reflecting light in the wavelength region of sunlight.
　第３の層１４０は、第２の層１３０と第４の層１５０の間の密着性を改善する役割、および第４層の成膜の際に、雰囲気中の酸素が銀膜に拡散することを抑制する役割を有する。 The third layer 140 has a role of improving the adhesion between the second layer 130 and the fourth layer 150, and oxygen in the atmosphere diffuses into the silver film during the formation of the fourth layer. It has a role to suppress.
　第４の層１５０は、第５の層１６０に比べて屈折率が低い、低屈折率膜として提供される。 The fourth layer 150 is provided as a low refractive index film having a lower refractive index than the fifth layer 160.
　第５の層１６０は、第４の層１５０に比べて屈折率が高い、高屈折率膜として提供される。屈折率が低い第４の層１５０の上に屈折率が高い第５の層１６０を積層することにより、高反射鏡１００全体としての反射率を高めることができる。 The fifth layer 160 is provided as a high refractive index film having a higher refractive index than the fourth layer 150. By laminating the fifth layer 160 having a high refractive index on the fourth layer 150 having a low refractive index, the reflectivity of the high reflecting mirror 100 as a whole can be increased.
　ここで、通常の高反射鏡では、高温環境に晒された場合、ガラス基板に含まれるナトリウムが銀を含む層の方に拡散し、これにより銀を含む層が劣化し、反射率が低下する場合がある。 Here, in a normal high-reflection mirror, when exposed to a high temperature environment, sodium contained in the glass substrate diffuses toward the silver-containing layer, thereby deteriorating the silver-containing layer and lowering the reflectance. There is a case.
　これに対して、本発明による高反射鏡１００は、ガラス基板１１０におけるナトリウム含有量が４重量％以下に抑制されているという特徴を有する。また、本発明による高反射鏡１００は、第１の層１２０が２００Å以上の厚さを有するという特徴を有する。 On the other hand, the high reflecting mirror 100 according to the present invention is characterized in that the sodium content in the glass substrate 110 is suppressed to 4% by weight or less. The high reflecting mirror 100 according to the present invention is characterized in that the first layer 120 has a thickness of 200 mm or more.
　すなわち、本発明による高反射鏡１００では、ガラス基板１１０におけるナトリウム含有量自身が、有意に少なくなっている。また、密着性改善層として機能する第１の層１２０は、２００Å以上の比較的厚い層で形成されるため、ガラス基板１１０のナトリウムイオンの拡散バリアとしても機能することができる。 That is, in the high reflector 100 according to the present invention, the sodium content itself in the glass substrate 110 is significantly reduced. In addition, since the first layer 120 that functions as an adhesion improving layer is formed of a relatively thick layer of 200 mm or more, it can also function as a sodium ion diffusion barrier of the glass substrate 110.
　このような特徴により、本発明による高反射鏡１００は、比較的高い温度（例えば、３００℃～３５０℃）に晒されても、ガラス基板１１０側から、銀を含む第２の層へのナトリウムの拡散を有意に抑制することができる。このため、本発明による高反射鏡１００は、高い耐熱性を発揮することができる。 Due to such a feature, the high reflecting mirror 100 according to the present invention is capable of sodium from the glass substrate 110 side to the second layer containing silver even when exposed to a relatively high temperature (eg, 300 ° C. to 350 ° C.) Can be significantly suppressed. For this reason, the high reflective mirror 100 by this invention can exhibit high heat resistance.
　また、本発明による高反射鏡１００は、最も単純な構成の場合、ガラス基板１１０の一方の表面（第１の表面１１５）に、わずか５層の積層膜を形成することにより構成される。従って、特許文献２の高反射鏡のように、ガラス基板の両面のそれぞれに、７０～９０もの層を積層する必要がなくなり、比較的単純で、低コストな構成の高反射鏡を得ることができる。 In the simplest configuration, the high reflection mirror 100 according to the present invention is configured by forming a laminated film of only five layers on one surface (first surface 115) of the glass substrate 110. Therefore, unlike the high reflection mirror of Patent Document 2, it is not necessary to stack 70 to 90 layers on both sides of the glass substrate, and a high reflection mirror having a relatively simple and low cost configuration can be obtained. it can.
　さらに、本発明による高反射鏡１００において、第１の層１２０は、２００Å（２０ｎｍ）以上の厚さを有する。このような比較的厚い層は、比較的薄い下地層を有する特許文献１に記載の高反射鏡とは異なり、曲面状の表面に対しても、均一に形成することができる。このため、本発明による高反射鏡１００は、曲面形状の形態でも、適正に提供することができる。 Furthermore, in the high reflection mirror 100 according to the present invention, the first layer 120 has a thickness of 200 mm (20 nm) or more. Such a relatively thick layer can be uniformly formed even on a curved surface, unlike the high reflection mirror described in Patent Document 1 having a relatively thin underlayer. For this reason, the highly reflective mirror 100 by this invention can be provided appropriately also in the form of a curved surface shape.
　次に、本発明による高反射鏡１００を構成する各部分について、詳しく説明する。 Next, each part constituting the highly reflective mirror 100 according to the present invention will be described in detail.
　（ガラス基板１１０）
　ガラス基板１００は、酸化ナトリウム（Ｎａ２Ｏ）含有量が４重量％以下のガラスで構成される限り、その種類は、特に限られない。 (Glass substrate 110)
The type of glass substrate 100 is not particularly limited as long as it is made of glass having a sodium oxide (Na 2 O) content of 4 wt% or less.
　ガラス基板１００は、例えば、無アルカリ金属ガラス、ＡＮ１００等であっても良い。 The glass substrate 100 may be, for example, non-alkali metal glass, AN100, or the like.
　ガラス基板１００の厚さは、特に限られないが、高反射鏡の強度や使いやすさの点から、例えば０．５ｍｍ～８．０ｍｍの範囲であっても良い。 The thickness of the glass substrate 100 is not particularly limited, but may be in the range of 0.5 mm to 8.0 mm, for example, from the viewpoint of the strength and ease of use of the high reflection mirror.
　ガラス基板１１０の形状は、特に限定されない。ガラス基板１１０は、平面上であっても、曲面状であっても良い。 The shape of the glass substrate 110 is not particularly limited. The glass substrate 110 may be flat or curved.
　（第１の層１２０）
　第１の層１２０は、前述のように、ガラス基板１１０と第２の層１３０との間の密着性を向上させる役割を有する。 (First layer 120)
As described above, the first layer 120 has a role of improving the adhesion between the glass substrate 110 and the second layer 130.
　第１の層１２０は、金属窒化物、金属酸化物、および金属酸窒化物からなる群から選定された少なくとも一つで構成される。 The first layer 120 is composed of at least one selected from the group consisting of metal nitrides, metal oxides, and metal oxynitrides.
　第１の層は、２００Å以上の厚さを有する。第１の層の厚さの上限は、特に限られない。第１の層１２０は、単層であっても、複数層で構成されても良い。 The first layer has a thickness of 200 mm or more. The upper limit of the thickness of the first layer is not particularly limited. The first layer 120 may be a single layer or a plurality of layers.
　（第２の層１３０）
　第２の層１３０は、前述のように、銀を含む層である。第２の層１３０に銀を含有させることで、太陽光の波長域（３００ｎｍ～２５００ｎｍ）における光の反射率を高め、入射角による反射率の依存性を低減させることができる。 (Second layer 130)
As described above, the second layer 130 is a layer containing silver. By including silver in the second layer 130, the reflectance of light in the wavelength region of sunlight (300 nm to 2500 nm) can be increased, and the dependency of the reflectance on the incident angle can be reduced.
　第２の層１３０は、銀と金の合金であっても良く、パラジウムとの合金であっても良い。この場合、合金中の金およびパラジウムの含有量は、０．５％～５質量％の範囲であっても良い。 The second layer 130 may be an alloy of silver and gold or an alloy of palladium. In this case, the contents of gold and palladium in the alloy may be in the range of 0.5% to 5% by mass.
　第２の層１３０は、１０００Å～３０００Åの範囲の厚さを有しても良い。 The second layer 130 may have a thickness in the range of 1000 to 3000 mm.
　（第３の層１４０）
　第３の層１４０は、前述のように、第２の層１３０と第４の層１５０の間の密着性を向上させる役割を有する。 (Third layer 140)
As described above, the third layer 140 has a role of improving the adhesion between the second layer 130 and the fourth layer 150.
　第３の層１４０は、第２の金属種を含む酸化亜鉛で構成されても良い。ここで、第２の金属種は、チタン、アルミニウム、スズおよびガリウムからなる群から選定された少なくとも一つである。第２の金属種を含有することにより、第２の層１３０と第４の層１５０の間の密着性をいっそう改善できる。第３の層１４０は、単層であっても、複数層で構成されても良い。 The third layer 140 may be made of zinc oxide containing the second metal species. Here, the second metal species is at least one selected from the group consisting of titanium, aluminum, tin, and gallium. By containing the second metal species, the adhesion between the second layer 130 and the fourth layer 150 can be further improved. The third layer 140 may be a single layer or a plurality of layers.
　第３の層１４０は、１０Å～１００Åの範囲の厚さを有しても良い。 The third layer 140 may have a thickness in the range of 10 to 100 mm.
　（第４の層１５０）
　第４の層１５０は、第５の層１６０に比べて、屈折率の低い材料で構成される。例えば、第４の層１５０は、波長５５０ｎｍにおいて屈折率１．５５以下、消衰係数０．００１以下の光学定数を有しても良い。また、例えば、第４の層１５０は、酸化ケイ素で構成されても良い。また、酸化ケイ素と酸化アルミニウムを含む複合酸化物からなるものでも良い。 (Fourth layer 150)
The fourth layer 150 is made of a material having a lower refractive index than the fifth layer 160. For example, the fourth layer 150 may have an optical constant with a refractive index of 1.55 or less and an extinction coefficient of 0.001 or less at a wavelength of 550 nm. For example, the fourth layer 150 may be made of silicon oxide. Further, it may be made of a composite oxide containing silicon oxide and aluminum oxide.
　第４の層１５０は、３００Å～１５００Åの範囲の膜厚を有しても良い。 The fourth layer 150 may have a thickness in the range of 300 to 1500 mm.
　（第５の層１６０）
　第５の層１６０は、第４の層１５０に比べて、屈折率の高い材料で構成される。例えば、第５の層１６０は、屈折率１．７以上、消衰係数０．０１以下の光学定数を有する。第５の層１６０は、窒化ケイ素、窒化アルミニウム、酸窒化ケイ素、酸窒化アルミニウム、酸化ニオブ、酸化ジルコニウム、酸化タンタル、酸化ハフニウム、酸化チタン、酸化亜鉛、および／または酸化スズで構成されても良い。また、第５の層１６０は、複合酸窒化物であっても良い。 (Fifth layer 160)
The fifth layer 160 is made of a material having a higher refractive index than that of the fourth layer 150. For example, the fifth layer 160 has an optical constant of a refractive index of 1.7 or more and an extinction coefficient of 0.01 or less. The fifth layer 160 may be composed of silicon nitride, aluminum nitride, silicon oxynitride, aluminum oxynitride, niobium oxide, zirconium oxide, tantalum oxide, hafnium oxide, titanium oxide, zinc oxide, and / or tin oxide. . The fifth layer 160 may be a composite oxynitride.
　第５の層１６０は、３００Å～１５００Åの範囲の厚さを有しても良い。 The fifth layer 160 may have a thickness in the range of 300 to 1500 mm.
　第５の層１６０は、単層であっても、複数層で構成されても良い。 The fifth layer 160 may be a single layer or a plurality of layers.
　なお、図１の例では、高反射鏡１００は、第４の層１５０および第５の層１６０の組み合わせを、１回だけ有する。ただし、これは、一例であって、高反射鏡１００は、第４の層１５０および第５の層１６０の組み合わせを、複数回有しても良い。すなわち、第４の層１５０および第５の層１６０の組み合わせの上に、任意の回数で、第４の層および第５の層の組み合わせを配置しても良い。第４の層１５０および第５の層１６０の組み合わせを、複数回繰り返すことにより、さらに反射率を向上させた高反射鏡を形成することができる。 In the example of FIG. 1, the high reflecting mirror 100 has the combination of the fourth layer 150 and the fifth layer 160 only once. However, this is only an example, and the high reflecting mirror 100 may have a combination of the fourth layer 150 and the fifth layer 160 a plurality of times. That is, the combination of the fourth layer and the fifth layer may be arranged any number of times on the combination of the fourth layer 150 and the fifth layer 160. By repeating the combination of the fourth layer 150 and the fifth layer 160 a plurality of times, it is possible to form a highly reflective mirror with further improved reflectivity.
　（本発明による高反射鏡１００の製造方法について）
　図１に示したような本発明による高反射鏡１００は、例えば、ガラス基板に対して、金属ターゲットおよび金属酸化物ターゲットを用いたスパッタリング法を適用することにより、製造することができる。 (About the manufacturing method of the high reflective mirror 100 by this invention)
The high reflecting mirror 100 according to the present invention as shown in FIG. 1 can be manufactured, for example, by applying a sputtering method using a metal target and a metal oxide target to a glass substrate.
　以下、本発明による高反射鏡１００の製造方法の一例について説明する。 Hereinafter, an example of a method for manufacturing the high reflecting mirror 100 according to the present invention will be described.
　本発明による高反射鏡１００をスパッタリング法により製造する際には、まず、ガラス基板１１０が準備される。 When manufacturing the highly reflective mirror 100 according to the present invention by the sputtering method, first, a glass substrate 110 is prepared.
　次に、このガラス基板１１０上に、第１の層１１０を、酸化物ターゲットまたは金属ターゲット（酸化または金属亜鉛等）を用いたスパッタリング法により形成する。 Next, the first layer 110 is formed on the glass substrate 110 by a sputtering method using an oxide target or a metal target (such as oxide or zinc metal).
　次に、第１の層１１０の上に、銀または銀合金のターゲットを用いたスパッタリング法により、第２の層を形成する。 Next, a second layer is formed on the first layer 110 by sputtering using a silver or silver alloy target.
　次に、第２の層上に、亜鉛酸化物ターゲットを用いたスパッタリング法により、第３の層を形成する。なお、この際には、第２の層の酸化を抑制するため、酸素等の酸化性ガスが存在しない雰囲気で成膜を行うことが好ましい。第３の層を形成する場合、スパッタガス中の酸化性ガスの含有量は、１０体積％以下であることが好ましい。 Next, a third layer is formed on the second layer by a sputtering method using a zinc oxide target. Note that in this case, in order to suppress the oxidation of the second layer, it is preferable to perform the film formation in an atmosphere in which an oxidizing gas such as oxygen does not exist. When forming the third layer, the content of the oxidizing gas in the sputtering gas is preferably 10% by volume or less.
　次に、第３の層上に、ボロンをドーピングした金属シリコンターゲットを用いた反応性スパッタリング法により、第４の層を形成する。 Next, a fourth layer is formed on the third layer by a reactive sputtering method using a metal silicon target doped with boron.
　次に、第４の層上に、酸化物ターゲットまたは金属ターゲット（酸化または金属チタン、酸化または金属ニオブ等）を用いた反応性スパッタリング法により、第５の層を形成する。 Next, a fifth layer is formed on the fourth layer by a reactive sputtering method using an oxide target or a metal target (oxidized or metallic titanium, oxidized or metallic niobium, or the like).
　スパッタリング法としては、交流（ＡＣ）または直流（ＤＣ）スパッタリング法を用いることができる。ＤＣスパッタリング法は、パルスＤＣスパッタリング法を含む。ＡＣスパッタリング法またはパルスＤＣスパッタリング法は、異常放電の防止の点で有効である。また、緻密な膜を形成できる点では、ＡＣまたはＤＣ反応性スパッタリング法が有効である。また、蒸着法と比較して、スパッタリング法は大面積の基板に成膜でき、かつ膜厚の分布の偏差が小さい点で優れている。 As the sputtering method, an alternating current (AC) or direct current (DC) sputtering method can be used. The DC sputtering method includes a pulse DC sputtering method. AC sputtering or pulse DC sputtering is effective in preventing abnormal discharge. In addition, AC or DC reactive sputtering is effective in that a dense film can be formed. Further, compared with the vapor deposition method, the sputtering method is superior in that it can form a film on a large-area substrate and has a small deviation in film thickness distribution.
　これにより、図１に示したような本発明による高反射鏡１００を製造することができる。 Thereby, the high reflection mirror 100 according to the present invention as shown in FIG. 1 can be manufactured.
　本発明による高反射鏡１００は、例えば、太陽熱発電システムの二次ミラーとして適用することができる。 The high reflecting mirror 100 according to the present invention can be applied as a secondary mirror of a solar thermal power generation system, for example.
　一般に、リニアフレネル型またはタワー型等の太陽熱発電システムは、一次ミラーおよび二次ミラーを備え、これらのミラーに照射される太陽光を集光することにより得られる熱エネルギーを利用して、高温高圧蒸気を発生させ、この蒸気により発電を行う。ここで、二次ミラーは、太陽熱発電システムの熱発生部分の近傍に配置されるため、二次ミラーには、太陽光の波長域（３００ｎｍ～２５００ｎｍ）における高い反射特性の他、耐熱性も要求される。 Generally, a solar thermal power generation system such as a linear Fresnel type or a tower type includes a primary mirror and a secondary mirror, and uses high-temperature and high-pressure using thermal energy obtained by collecting sunlight irradiated on these mirrors. Steam is generated, and electricity is generated using this steam. Here, since the secondary mirror is disposed in the vicinity of the heat generation part of the solar thermal power generation system, the secondary mirror requires heat resistance in addition to high reflection characteristics in the wavelength range of sunlight (300 nm to 2500 nm). Is done.
　本発明による高反射鏡１００は、太陽光の波長域（３００ｎｍ～２５００ｎｍ）において高い反射率を有する上、比較的良好な耐熱性を有するという特徴を有する。従って、本発明による高反射鏡１００は、太陽熱発電システムの二次ミラーに、有意に適用することができる。 The high reflecting mirror 100 according to the present invention is characterized by having a high reflectivity in the wavelength range of sunlight (300 nm to 2500 nm) and relatively good heat resistance. Therefore, the high reflection mirror 100 according to the present invention can be significantly applied to the secondary mirror of the solar thermal power generation system.
　また、本発明による高反射鏡１００は、比較的少ない層数で構成することができ、比較的単純な構造を有する。従って、本発明による高反射鏡１００で構成された太陽熱発電システムの二次ミラーは、比較的単純な構成となり、比較的安価に製造することが可能となる。 Also, the high reflecting mirror 100 according to the present invention can be configured with a relatively small number of layers and has a relatively simple structure. Therefore, the secondary mirror of the solar thermal power generation system configured with the high reflection mirror 100 according to the present invention has a relatively simple configuration and can be manufactured at a relatively low cost.
　以下、本発明の実施例について説明する。 Hereinafter, examples of the present invention will be described.
　（実施例１）
　真空槽内に清浄化したガラス基板を設置し、以下に示す方法で各膜を順次成膜することにより、高反射鏡サンプルを作製した。 Example 1
A cleaned glass substrate was placed in the vacuum chamber, and each film was sequentially formed by the method described below to prepare a high reflector sample.
　ガラス基板には、縦１００ｍｍ×横１００ｍｍ×厚さ０．５ｍｍの無アルカリガラスを使用した。このガラス基板中のナトリウム含有量は、ほぼ０である。 For the glass substrate, alkali-free glass having a length of 100 mm × width of 100 mm × thickness of 0.5 mm was used. The sodium content in this glass substrate is almost zero.
　ターゲットとして、以下の５種類のターゲット（ターゲット１～５）を準備した：
（ターゲット１）酸化ガリウムを添加した酸化亜鉛ターゲット（酸化ガリウムの含有率５．７質量％、酸化亜鉛の含有率９４．３質量％）、
（ターゲット２）金を添加した銀合金ターゲット（金の含有率２質量％、銀の含有率９８質量％）、
（ターゲット３）金属シリコンターゲット（ボロンドープの多結晶ターゲット、シリコンの含有率９９．９９９質量％）、
（ターゲット４）酸化チタンターゲット（酸化チタンの含有率９９．９質量％）。 The following five types of targets (targets 1 to 5) were prepared as targets:
(Target 1) Zinc oxide target added with gallium oxide (gallium oxide content 5.7 mass%, zinc oxide content 94.3 mass%),
(Target 2) Silver alloy target (gold content 2 mass%, silver content 98 mass%) to which gold is added,
(Target 3) Metallic silicon target (boron-doped polycrystalline target, silicon content 99.999 mass%),
(Target 4) Titanium oxide target (content of titanium oxide 99.9% by mass).
　ターゲット１～４における表面のサイズは、それぞれ１７７．８ｍｍ×３８１ｍｍであった。 The surface sizes of the targets 1 to 4 were 177.8 mm × 381 mm, respectively.
　これらのターゲット１～４を、それぞれ、ガラス基板の対向位置に設置し、真空槽内を２×１０－３Ｐａまで排気し、以下の成膜を行った。 Each of these targets 1 to 4 was installed at a position opposite to the glass substrate, the inside of the vacuum chamber was evacuated to 2 × 10 −3 Pa, and the following film formation was performed.
　（ステップ１：酸化亜鉛膜の形成）
　ターゲット１を用いて、ＤＣスパッタリング法により、ガラス基板上にガリウムドープ酸化亜鉛膜を成膜した。スパッタリングガスには、アルゴンガス（流速４００ｓｃｃｍ）を使用した。投入電力は、０．２５ｋＷとした。 (Step 1: Formation of zinc oxide film)
Using the target 1, a gallium-doped zinc oxide film was formed on a glass substrate by DC sputtering. Argon gas (flow rate 400 sccm) was used as the sputtering gas. The input power was 0.25 kW.
　得られたガリウムドープ酸化亜鉛膜の厚さは、２００Åであった。ガリウムドープ酸化亜鉛膜の組成は、ターゲット１とほぼ同等であった。 The thickness of the obtained gallium-doped zinc oxide film was 200 mm. The composition of the gallium-doped zinc oxide film was almost the same as that of the target 1.
　（ステップ２：銀合金膜の形成）
　ステップ１による残存ガスを排気後、ターゲット２を用いて、ＤＣスパッタリング法により、ガリウムドープ酸化亜鉛膜を有するガラス基板上に、銀合金膜を成膜した。スパッタリングガスには、アルゴンガス（流速４００ｓｃｃｍ）を使用した。投入電力は、１ｋＷとした。 (Step 2: Formation of silver alloy film)
After exhausting the residual gas in Step 1, a silver alloy film was formed on a glass substrate having a gallium-doped zinc oxide film by DC sputtering using the target 2. Argon gas (flow rate 400 sccm) was used as the sputtering gas. The input power was 1 kW.
　得られた銀合金膜の厚さは、１２００Åであった。銀合金膜の組成は、ターゲット２とほぼ同等であった。 The thickness of the obtained silver alloy film was 1200 mm. The composition of the silver alloy film was almost the same as that of the target 2.
　（ステップ３：第２の酸化亜鉛膜の形成）
　ステップ２による残存ガスを排気後、ターゲット１を用いて、ＤＣスパッタリング法により、銀合金膜上に、ガリウムドープ酸化亜鉛膜を成膜した。スパッタリングガスには、アルゴンガス（流速４００ｓｃｃｍ）を使用した。投入電力は、０．２５ｋＷとした。 (Step 3: Formation of second zinc oxide film)
After exhausting the residual gas in step 2, using the target 1, a gallium-doped zinc oxide film was formed on the silver alloy film by DC sputtering. Argon gas (flow rate 400 sccm) was used as the sputtering gas. The input power was 0.25 kW.
　得られたガリウムドープ酸化亜鉛膜の厚さは、５０Åであった。ガリウムドープ酸化亜鉛膜の組成は、ターゲット１とほぼ同等であった。 The thickness of the obtained gallium-doped zinc oxide film was 50 mm. The composition of the gallium-doped zinc oxide film was almost the same as that of the target 1.
　（ステップ４：酸化ケイ素膜の形成）
　ステップ３による残存ガスを排気後、ターゲット３を用いて、パルスＤＣ反応性スパッタリング法により、第２の酸化亜鉛膜上に、酸化ケイ素膜を成膜した。スパッタリングガスには、酸素ガス（流速２４０ｓｃｃｍ）およびアルゴンガス（流速１６０ｓｃｃｍ）を使用した。投入電力は、２ｋＷとし、周波数は、２０ｋＨｚとした。 (Step 4: Formation of silicon oxide film)
After exhausting the residual gas in step 3, a silicon oxide film was formed on the second zinc oxide film by using the target 3 by pulse DC reactive sputtering. As the sputtering gas, oxygen gas (flow rate 240 sccm) and argon gas (flow rate 160 sccm) were used. The input power was 2 kW, and the frequency was 20 kHz.
　得られた酸化ケイ素膜の厚さは、５００Åであった。 The thickness of the obtained silicon oxide film was 500 mm.
　（ステップ５：酸化チタン膜の形成）
　ステップ４による残存ガスを排気後、ターゲット４を用いて、パルスＤＣスパッタリング法により、酸化ケイ素膜上に、酸化チタン膜を成膜した。スパッタリングガスには、酸素ガス（流速２０ｓｃｃｍ）およびアルゴンガス（流速３８０ｓｃｃｍ）を使用した。投入電力は、２ｋＷとし、周波数は、４０ｋＨｚとした。 (Step 5: Formation of titanium oxide film)
After exhausting the residual gas in step 4, a titanium oxide film was formed on the silicon oxide film by pulse DC sputtering using the target 4. As the sputtering gas, oxygen gas (flow rate 20 sccm) and argon gas (flow rate 380 sccm) were used. The input power was 2 kW and the frequency was 40 kHz.
　得られた酸化チタン膜の厚さは、９５０Åであった。 The thickness of the obtained titanium oxide film was 950 mm.
　以上の処理により、ガラス基板上に、５つの層が積層された高反射鏡のサンプル（以下、「実施例１に係るサンプル」と称する）が得られた。 Through the above treatment, a sample of a high reflection mirror in which five layers were laminated on a glass substrate (hereinafter referred to as “sample according to Example 1”) was obtained.
　（実施例２）
　実施例１と同様の方法により、実施例２に係る高反射鏡のサンプル（以下、「実施例２に係るサンプル」と称する）を作製した。ただし、この実施例２では、ガラス基板として、厚さ３ｍｍのパイレックスガラス（登録商標）を使用した。その他の条件は、実施例１と同様である。 (Example 2)
A sample of the high reflection mirror according to Example 2 (hereinafter referred to as “sample according to Example 2”) was produced by the same method as Example 1. However, in Example 2, Pyrex glass (registered trademark) having a thickness of 3 mm was used as the glass substrate. Other conditions are the same as in the first embodiment.
　なお、このガラス基板中の酸化ナトリウム（Ｎａ２Ｏ）含有量は、４重量％である。 Incidentally, sodium oxide (Na 2 O) content of the glass in the substrate is 4 wt%.
　（実施例３）
　実施例１と同様の方法により、実施例３に係る高反射鏡のサンプル（以下「実施例３に係るサンプル」と称する）を作製した。ただし、この実施例３では、第５の層として、ボロンドープ金属シリコンターゲットを用いて、パルスＤＣ反応性スパッタリング法により、酸化ケイ素膜上に窒化ケイ素膜を成膜した。スパッタリングガスには、窒素ガス（流速１２０ｓｃｃｍ）およびアルゴンガス（流速２８０ｓｃｃｍ）を使用し、投入電力は１ｋＷとした。得られた窒化ケイ素膜の厚さは５００Åであった。その他の条件は、実施例１と同様である。 (Example 3)
A sample of the high reflection mirror according to Example 3 (hereinafter referred to as “sample according to Example 3”) was produced by the same method as in Example 1. However, in Example 3, a silicon nitride film was formed on the silicon oxide film by a pulse DC reactive sputtering method using a boron-doped metal silicon target as the fifth layer. Nitrogen gas (flow rate 120 sccm) and argon gas (flow rate 280 sccm) were used as the sputtering gas, and the input power was 1 kW. The thickness of the obtained silicon nitride film was 500 mm. Other conditions are the same as in the first embodiment.
　（実施例４）
　真空槽内に清浄化したガラス基板を設置し、以下に示す方法で各膜を順次成膜することにより、高反射鏡サンプルを作製した。 (Example 4)
A cleaned glass substrate was placed in the vacuum chamber, and each film was sequentially formed by the method described below to prepare a high reflector sample.
　ガラス基板には、縦１００ｍｍ×横１００ｍｍ×厚さ０．５ｍｍの無アルカリガラスを使用した。このガラス基板中のナトリウム含有量は、ほぼ０である。 For the glass substrate, alkali-free glass having a length of 100 mm × width of 100 mm × thickness of 0.5 mm was used. The sodium content in this glass substrate is almost zero.
　ターゲットとして、以下の４種類のターゲット（ターゲット１～４）を準備した：
（ターゲット１）酸化ガリウムを添加した酸化亜鉛ターゲット（酸化ガリウムの含有率５．７質量％、酸化亜鉛の含有率９４．３質量％）、
（ターゲット２）金を添加した銀合金ターゲット（金の含有率２質量％、銀の含有率９８質量％）、
（ターゲット３）金属シリコンターゲット（ボロンドープの多結晶ターゲット、シリコンの含有率９９．９９９質量％）、
（ターゲット４）金属シリコンとアルミニウムの合金ターゲット（シリコンの含有率９０質量％、アルミニウムの含有率１０質量％）。 The following four types of targets (targets 1 to 4) were prepared as targets:
(Target 1) Zinc oxide target added with gallium oxide (gallium oxide content 5.7 mass%, zinc oxide content 94.3 mass%),
(Target 2) Silver alloy target (gold content 2 mass%, silver content 98 mass%) to which gold is added,
(Target 3) Metallic silicon target (boron-doped polycrystalline target, silicon content 99.999 mass%),
(Target 4) Metal silicon and aluminum alloy target (silicon content 90 mass%, aluminum content 10 mass%).
　ターゲット１～４における表面のサイズは、それぞれ７０ｍｍ×２００ｍｍであった。 The surface sizes of the targets 1 to 4 were 70 mm × 200 mm, respectively.
　これらのターゲット１～４を、それぞれ、ガラス基板の対向位置に設置し、真空槽内を２×１０－３Ｐａまで排気し、以下の成膜を行った。 Each of these targets 1 to 4 was installed at a position opposite to the glass substrate, the inside of the vacuum chamber was evacuated to 2 × 10 −3 Pa, and the following film formation was performed.
　（ステップ１：シリコンアルミ窒化膜の形成）
　ターゲット４を用いて、パルスＤＣ反応性スパッタリング法により、ガラス基板上にシリコンアルミ窒化膜を成膜した。スパッタリングガスには、アルゴンガス（流速７０ｓｃｃｍ）および窒素ガス（流速３０ｓｃｃｍ）を使用した。投入電力は、０．５ｋＷとした。 (Step 1: Formation of silicon aluminum nitride film)
A silicon aluminum nitride film was formed on the glass substrate by the pulse DC reactive sputtering method using the target 4. Argon gas (flow rate 70 sccm) and nitrogen gas (flow rate 30 sccm) were used as the sputtering gas. The input power was 0.5 kW.
　得られたシリコンアルミ窒化膜の厚さは、２００Åであった。 The thickness of the obtained silicon aluminum nitride film was 200 mm.
　（ステップ２：酸化亜鉛膜の形成）
　ステップ１による残存ガスを排気後、ターゲット１を用いて、ＤＣスパッタリング法により、シリコンアルミ窒化膜上に、ガリウムドープ酸化亜鉛膜を成膜した。スパッタリングガスには、アルゴンガス（流速１００ｓｃｃｍ）を使用した。投入電力は、０．１ｋＷとした。 (Step 2: Formation of zinc oxide film)
After exhausting the residual gas in step 1, a gallium-doped zinc oxide film was formed on the silicon aluminum nitride film by DC sputtering using the target 1. Argon gas (flow rate 100 sccm) was used as the sputtering gas. The input power was 0.1 kW.
　得られたガリウムドープ酸化亜鉛膜の厚さは、１５Åであった。ガリウムドープ酸化亜鉛膜の組成は、ターゲット１とほぼ同等であった。 The thickness of the obtained gallium-doped zinc oxide film was 15 mm. The composition of the gallium-doped zinc oxide film was almost the same as that of the target 1.
　（ステップ３：銀合金膜の形成）
　ステップ２による残存ガスを排気後、ターゲット２を用いて、ＤＣスパッタリング法により、ガリウムドープ酸化亜鉛膜を有するガラス基板上に、銀合金膜を成膜した。スパッタリングガスには、アルゴンガス（流速１００ｓｃｃｍ）を使用した。投入電力は、０．５ｋＷとした。 (Step 3: Formation of silver alloy film)
After exhausting the residual gas in Step 2, a silver alloy film was formed on the glass substrate having the gallium-doped zinc oxide film by DC sputtering using the target 2. Argon gas (flow rate 100 sccm) was used as the sputtering gas. The input power was 0.5 kW.
　得られた銀合金膜の厚さは、１２００Åであった。銀合金膜の組成は、ターゲット２とほぼ同等であった。 The thickness of the obtained silver alloy film was 1200 mm. The composition of the silver alloy film was almost the same as that of the target 2.
　（ステップ４：第２の酸化亜鉛膜の形成）
　ステップ３による残存ガスを排気後、ターゲット１を用いて、ＤＣスパッタリング法により、銀合金膜上に、ガリウムドープ酸化亜鉛膜を成膜した。スパッタリングガスには、アルゴンガス（流速１００ｓｃｃｍ）を使用した。投入電力は、０．１ｋＷとした。 (Step 4: Formation of second zinc oxide film)
After exhausting the residual gas in step 3, using the target 1, a gallium-doped zinc oxide film was formed on the silver alloy film by DC sputtering. Argon gas (flow rate 100 sccm) was used as the sputtering gas. The input power was 0.1 kW.
　得られたガリウムドープ酸化亜鉛膜の厚さは、１５Åであった。ガリウムドープ酸化亜鉛膜の組成は、ターゲット１とほぼ同等であった。 The thickness of the obtained gallium-doped zinc oxide film was 15 mm. The composition of the gallium-doped zinc oxide film was almost the same as that of the target 1.
　（ステップ５：第２のシリコンアルミ窒化素膜の形成）
　ステップ４による残存ガスを排気後、ターゲット４を用いて、パルスＤＣ反応性スパッタリング法により、第２の酸化亜鉛膜上に、シリコンアルミ窒化素膜を成膜した。スパッタリングガスには、窒素ガス（流速３０ｓｃｃｍ）およびアルゴンガス（流速７０ｓｃｃｍ）を使用した。投入電力は、０．５ｋＷとした。 (Step 5: Formation of second silicon aluminum nitride film)
After exhausting the residual gas in Step 4, a silicon aluminum nitride film was formed on the second zinc oxide film by using the target 4 by pulse DC reactive sputtering. Nitrogen gas (flow rate 30 sccm) and argon gas (flow rate 70 sccm) were used as the sputtering gas. The input power was 0.5 kW.
　得られた窒化ケイ素膜の厚さは、３５Åであった。
（ステップ６：酸化ケイ素膜の形成）
　ステップ５による残存ガスを排気後、ターゲット４を用いて、パルスＤＣ反応性スパッタリング法により、第２のシリコンアルミ窒化膜上に、酸化ケイ素膜を成膜した。スパッタリングガスには、酸素ガス（流速６０ｓｃｃｍ）およびアルゴンガス（流速４０ｓｃｃｍ）を使用した。投入電力は、０．５ｋＷとした。 The thickness of the obtained silicon nitride film was 35 mm.
(Step 6: Formation of silicon oxide film)
After exhausting the residual gas in step 5, a silicon oxide film was formed on the second silicon aluminum nitride film by the pulse DC reactive sputtering method using the target 4. As the sputtering gas, oxygen gas (flow rate 60 sccm) and argon gas (flow rate 40 sccm) were used. The input power was 0.5 kW.
　得られた酸化ケイ素膜の厚さは、５００Åであった。 The thickness of the obtained silicon oxide film was 500 mm.
　（ステップ７：第３のシリコンアルミ窒化素膜の形成）
　ステップ６による残存ガスを排気後、ターゲット４を用いて、パルスＤＣ反応性スパッタリング法により、酸化ケイ素膜上に、シリコンアルミ窒化素膜を成膜した。スパッタリングガスには、窒素ガス（流速３０ｓｃｃｍ）およびアルゴンガス（流速７０ｓｃｃｍ）を使用した。投入電力は、０．５ｋＷとした。 (Step 7: Formation of third silicon aluminum nitride film)
After exhausting the residual gas in step 6, a silicon aluminum nitride film was formed on the silicon oxide film by the pulse DC reactive sputtering method using the target 4. Nitrogen gas (flow rate 30 sccm) and argon gas (flow rate 70 sccm) were used as the sputtering gas. The input power was 0.5 kW.
　得られたシリコンアルミ窒化膜の厚さは、５００Åであった。 The thickness of the obtained silicon aluminum nitride film was 500 mm.
　以上の処理により、ガラス基板上に、７つの層が積層された高反射鏡のサンプル（以下、「実施例４に係るサンプル」と称する）が得られた。
（実施例５）
　実施例４と同様の方法により、実施例５に係る高反射鏡のサンプル（以下「実施例５に係るサンプル」と称する）を作製した。ただし、この実施例５では、実施例４のステップ２において、ニッケルとクロムの合金ターゲット（ニッケルの含有率５０質量％、クロムの含有率５０質量％）を用いてパルスＤＣスパッタリング法により、ガラス基板上にニクロム膜を成膜した。スパッタリングガスにはアルゴンガス（流速１００ｓｃｃｍ）を使用し、投入電力は０．０５ｋＷとした。その他の条件は、実施例４と同様である。得られたニクロム膜の厚さは、１５Åであった。 Through the above processing, a sample of a high-reflection mirror in which seven layers were laminated on a glass substrate (hereinafter referred to as “sample according to Example 4”) was obtained.
(Example 5)
A sample of the high reflection mirror according to Example 5 (hereinafter referred to as “sample according to Example 5”) was produced in the same manner as in Example 4. However, in Example 5, in Step 2 of Example 4, a glass substrate was obtained by pulse DC sputtering using an alloy target of nickel and chromium (nickel content: 50 mass%, chromium content: 50 mass%). A nichrome film was formed thereon. Argon gas (flow rate 100 sccm) was used as the sputtering gas, and the input power was 0.05 kW. Other conditions are the same as in Example 4. The thickness of the obtained nichrome film was 15 mm.
　（比較例１）
　実施例１と同様の方法により、比較例１に係る高反射鏡のサンプル（以下、「比較例１に係るサンプル」と称する）を作製した。ただし、この比較例１では、ガラス基板として、厚さ３ｍｍのソーダライムガラスを使用した。その他の条件は、実施例１と同様である。 (Comparative Example 1)
A sample of a high reflection mirror according to Comparative Example 1 (hereinafter referred to as “sample according to Comparative Example 1”) was produced by the same method as in Example 1. However, in Comparative Example 1, soda lime glass having a thickness of 3 mm was used as the glass substrate. Other conditions are the same as in the first embodiment.
　なお、このガラス基板中酸化のナトリウム含有量は、１４重量％である。 In addition, the sodium content of oxidation in this glass substrate is 14% by weight.
　（比較例２）
　実施例１と同様の方法により、比較例２に係る高反射鏡のサンプル（以下「比較例２に係るサンプル」と称する）を作製した。ただし、この比較例２では、ステップ１において形成されたガリウムドープ酸化亜鉛膜の厚さは、１５０Åであった。その他の条件は、実施例１と同様である。 (Comparative Example 2)
A sample of a high reflection mirror according to Comparative Example 2 (hereinafter referred to as “sample according to Comparative Example 2”) was produced by the same method as in Example 1. However, in Comparative Example 2, the thickness of the gallium-doped zinc oxide film formed in Step 1 was 150 mm. Other conditions are the same as in the first embodiment.
　（評価）
　前述の方法で作製した各サンプルを用いて、耐熱性評価試験を実施した。 (Evaluation)
A heat resistance evaluation test was carried out using each sample produced by the method described above.
　耐熱性評価試験は、各サンプルを所定の温度に所定の時間保持し、熱処理後のサンプルの反射率を測定することにより実施した。熱処理温度は、３００℃、３５０℃、および４００℃とした。 The heat resistance evaluation test was carried out by holding each sample at a predetermined temperature for a predetermined time and measuring the reflectance of the sample after the heat treatment. The heat treatment temperatures were 300 ° C, 350 ° C, and 400 ° C.
　図２には、各サンプルにおける熱処理前後の反射率測定結果をまとめて示す。 FIG. 2 summarizes the reflectance measurement results before and after heat treatment for each sample.
　なお、図２において、縦軸の反射率は、日射エネルギー反射率：Ｒｅで示した。この日射エネルギー反射率：Ｒｅは、ＩＳＯ９０５０－２００３に準じて算定される値であり、具体的には、分光絶対反射率（３００ｎｍ～２５００ｎｍ）の測定値に、日射の標準スペクトル分布を示す重化係数を乗じて加重平均した値を意味する。 In FIG. 2, the vertical axis reflectivity is shown as solar energy reflectivity: Re. The solar energy reflectance: Re is a value calculated according to ISO 9050-2003. Specifically, the measured value of the spectral absolute reflectance (300 nm to 2500 nm) is overlapped indicating the standard spectral distribution of solar radiation. It means a weighted average value multiplied by a coefficient.
　この結果から、実施例１に係るサンプルでは、３００℃における１６８時間の熱処理、３５０℃における７２時間の熱処理、および４００℃における７２時間の熱処理のいずれの熱処理においても、日射エネルギー反射率が、熱処理前とほとんど変化していないことがわかる。同様に、実施例２～実施例５に係るサンプルにおいても、各条件の熱処理後の日射エネルギー反射率は、熱処理前とほとんど変化していない。 From this result, in the sample according to Example 1, the solar energy reflectivity is the heat treatment in any of the heat treatment of 168 hours at 300 ° C., the heat treatment of 72 hours at 350 ° C., and the heat treatment of 72 hours at 400 ° C. You can see that there has been little change from before. Similarly, in the samples according to Examples 2 to 5, the solar energy reflectance after the heat treatment under each condition is almost the same as that before the heat treatment.
　一方、比較例１に係るサンプルの場合、熱処理によって日射エネルギー反射率は、低下する傾向にあることがわかる。例えば、３００℃における１６８時間の熱処理後の日射エネルギー反射率は、熱処理前の値に比べて２％程度低下しており、３５０℃における７２時間の熱処理後の日射エネルギー反射率は、熱処理前の値に比べて約１４％も低下した。なお、比較例１に係るサンプルでは、日射エネルギー反射率の低下傾向が顕著であるため、４００℃における７２時間の熱処理は、実施していない。 On the other hand, in the case of the sample according to Comparative Example 1, it can be seen that the solar energy reflectance tends to decrease due to the heat treatment. For example, the solar energy reflectance after heat treatment at 300 ° C. for 168 hours is about 2% lower than the value before heat treatment, and the solar energy reflectance after heat treatment at 350 ° C. for 72 hours is Compared to the value, it decreased by about 14%. In addition, in the sample which concerns on the comparative example 1, since the fall tendency of solar energy reflectance is remarkable, the heat processing for 72 hours at 400 degreeC is not implemented.
　同様に、比較例２に係るサンプルにおいても、熱処理によって日射エネルギー反射率は、低下する傾向にあることがわかる。例えば、３００℃における１６８時間の熱処理後の日射エネルギー反射率は、熱処理前の値に比べて２％低下しており、４００℃における７２時間後の日射エネルギー反射率は、熱処理前の値に比べて約７％も低下した。 Similarly, also in the sample according to Comparative Example 2, it can be seen that the solar energy reflectance tends to decrease due to the heat treatment. For example, the solar energy reflectance after heat treatment at 300 ° C. for 168 hours is 2% lower than the value before heat treatment, and the solar energy reflectance after 72 hours at 400 ° C. is lower than the value before heat treatment. About 7%.
　図３には、実施例１～実施例５に係るサンプルにおいて、３５０℃の温度で各時間保持した後の反射率の変化を示す。縦軸は、図２と同じ日射エネルギー反射率：Ｒｅで示した。なお、図３には、比較例１および比較例２における、３５０℃、７２時間保持後の結果を同時に示した。 FIG. 3 shows the change in reflectivity of the samples according to Examples 1 to 5 after being held at a temperature of 350 ° C. for each time. The vertical axis indicates the same solar energy reflectance as Re in FIG. FIG. 3 shows the results of Comparative Example 1 and Comparative Example 2 after holding at 350 ° C. for 72 hours at the same time.
　この図３から、比較例１および比較例２に係るサンプルでは、７２時間保持後に、反射率が大きく低下するのに対して、実施例１～実施例５に係るサンプルは、いずれも、最大１２０時間までの間、３５０℃の熱処理によって反射率がほとんど変化していないことがわかる。 From FIG. 3, in the samples according to Comparative Example 1 and Comparative Example 2, the reflectivity is greatly reduced after 72 hours, while all of the samples according to Examples 1 to 5 have a maximum of 120. It can be seen that the reflectance is hardly changed by the heat treatment at 350 ° C. until the time.
　このように、ガラス基板に含まれるナトリウムの含有量が高い比較例１に係るサンプルでは、耐熱性に問題があることがわかった。これに対して、ガラス基板に含まれるナトリウムの含有量が４質量％以下の実施例１～実施例５に係るサンプルでは、比較的良好な耐熱性を有することが確認された。 Thus, it was found that the sample according to Comparative Example 1 having a high content of sodium contained in the glass substrate has a problem in heat resistance. On the other hand, it was confirmed that the samples according to Examples 1 to 5 in which the content of sodium contained in the glass substrate was 4% by mass or less had relatively good heat resistance.
　また、第１の層の膜厚が１５０Åである比較例２に係るサンプルでは、ガラス基板に含まれるナトリウムの含有量が４％以下であるにもかかわらず、耐熱性に問題があることがわかった。これに対して、第１の層が２００Å以上である実施例１～実施例５に係るサンプルでは、比較的良好な耐熱性を有することが確認された。 Moreover, in the sample which concerns on the comparative example 2 whose film thickness of a 1st layer is 150 mm, it turns out that there is a problem in heat resistance, although the content of sodium contained in the glass substrate is 4% or less. It was. On the other hand, it was confirmed that the samples according to Examples 1 to 5 having the first layer of 200 mm or more have relatively good heat resistance.
　本発明は、リニアフレネル型またはタワー型等の太陽熱発電システムにおける二次ミラー等に利用することができる。 The present invention can be used for a secondary mirror in a solar thermal power generation system such as a linear Fresnel type or a tower type.
　本願は、２０１２年６月１日に出願した日本国特許出願２０１２－１２６４１１号に基づく優先権を主張するものであり、同日本国出願の全内容を本願の参照として援用する。 This application claims priority based on Japanese Patent Application No. 2012-126411 filed on June 1, 2012, the entire contents of which are incorporated herein by reference.
　１００　　本発明による高反射鏡
　１１０　　ガラス基板
　１１５　　第１の表面
　１２０　　第１の層
　１３０　　第２の層
　１４０　　第３の層
　１５０　　第４の層
　１６０　　第５の層
  100 High Reflector according to the Present Invention 110 Glass Substrate 115 First Surface 120 First Layer 130 Second Layer 140 Third Layer 150 Fourth Layer 160 Fifth Layer

Claims (8)

  1. 　ガラス基板上に、複数の層を積層することにより構成された高反射鏡であって、
    　前記ガラス基板は、第１の表面を有し、酸化ナトリウム（Ｎａ２Ｏ）含有量が４重量％以下のガラスで構成され、
    　前記ガラス基板の第１の表面には、第１の層、第２の層、第３の層、第４の層、第５の層がこの順に積層され、
    　前記第１の層は、２００Å以上の厚さを有し、金属窒化物、金属酸化物、および金属酸窒化物からなる群から選定された少なくとも一つを含み、
    　前記第２の層は、銀または銀合金を含み、
    　前記第３の層は、酸化亜鉛を含み、
    　前記第４の層は、波長４００～１５００ｎｍにおいて屈折率１．５５以下、消衰係数０．００１以下の光学定数を有し、酸化ケイ素を含み、
    　前記第５の層は、波長４００～１５００ｎｍにおいて屈折率１．７以上、消衰係数０．０１以下の光学定数を有し、窒化ケイ素、窒化アルミニウム、酸窒化ケイ素、酸窒化アルミニウム、酸化チタン、酸化ニオブ、酸化ジルコニウム、酸化タンタル、酸化スズ、酸化亜鉛、および酸化ハフニウムからなる群から選定された少なくとも一つを含むことを特徴とする高反射鏡。     A highly reflective mirror constructed by laminating a plurality of layers on a glass substrate,
    The glass substrate has a first surface and is made of glass having a sodium oxide (Na 2 O) content of 4% by weight or less,
    On the first surface of the glass substrate, a first layer, a second layer, a third layer, a fourth layer, and a fifth layer are laminated in this order,
    The first layer has a thickness of 200 mm or more, and includes at least one selected from the group consisting of a metal nitride, a metal oxide, and a metal oxynitride,
    The second layer comprises silver or a silver alloy;
    The third layer comprises zinc oxide;
    The fourth layer has an optical constant of a refractive index of 1.55 or less and an extinction coefficient of 0.001 or less at a wavelength of 400 to 1500 nm, and includes silicon oxide.
    The fifth layer has an optical constant of a refractive index of 1.7 or more and an extinction coefficient of 0.01 or less at a wavelength of 400 to 1500 nm, and silicon nitride, aluminum nitride, silicon oxynitride, aluminum oxynitride, titanium oxide, A high reflector comprising at least one selected from the group consisting of niobium oxide, zirconium oxide, tantalum oxide, tin oxide, zinc oxide, and hafnium oxide.
  2. 　前記第１の層は、第１の金属種を含む酸化亜鉛で構成され、前記第１の金属種は、チタン、アルミニウム、スズおよびガリウムからなる群から選定された少なくとも一つであることを特徴とする請求項１に記載の高反射鏡。 The first layer is made of zinc oxide containing a first metal species, and the first metal species is at least one selected from the group consisting of titanium, aluminum, tin, and gallium. The high reflector according to claim 1.
  3. 　前記第３の層は、第２の金属種を含む酸化亜鉛で構成され、前記第２の金属種は、チタン、アルミニウム、スズおよびガリウムからなる群から選定された少なくとも一つであることを特徴とする請求項１または２に記載の高反射鏡。 The third layer is composed of zinc oxide containing a second metal species, and the second metal species is at least one selected from the group consisting of titanium, aluminum, tin, and gallium. The high reflection mirror according to claim 1 or 2.
  4. 　前記第２の層は、１０００Å～３０００Åの厚さを有することを特徴とする請求項１乃至３のいずれか一つに記載の高反射鏡。 4. The high reflection mirror according to claim 1, wherein the second layer has a thickness of 1000 to 3000 mm.
  5. 　前記第３の層は、１０Å～１００Åの厚さを有することを特徴とする請求項１乃至４のいずれか一つに記載の高反射鏡。 The high reflection mirror according to any one of claims 1 to 4, wherein the third layer has a thickness of 10 to 100 mm.
  6. 　前記第４の層は、３００Å～１５００Åの厚さを有することを特徴とする請求項１乃至５のいずれか一つに記載の高反射鏡。 6. The high reflecting mirror according to claim 1, wherein the fourth layer has a thickness of 300 to 1500 mm.
  7. 　前記第５の層は、３００Å～１５００Åの厚さを有することを特徴とする請求項１乃至６のいずれか一つに記載の高反射鏡。 The high reflection mirror according to any one of claims 1 to 6, wherein the fifth layer has a thickness of 300 to 1500 mm.
  8. 　太陽熱発電システム用の二次ミラーであって、
    　前記請求項１乃至７のいずれか一つの高反射鏡を有する二次ミラー。     A secondary mirror for a solar thermal power generation system,
    A secondary mirror comprising the high reflecting mirror according to claim 1.
PCT/JP2013/064940 2012-06-01 2013-05-29 Highly reflecting mirror WO2013180185A1 (en)

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