SOLAR LIGHT MANAGEMENT

Abstract

A translucent construction element comprising a layer of translucent substrate, which contains a surface structured with nanoplanes of inclined angle relative to the substrate plane, and coated with an interrupted metallic layer covering at least a part of said nanoplanes, is characterized by a high density of interruptions in the metallic layer of low thickness; the periodicity of interruptions in the metallic layer generally is from the range 50 to 1000 nm and the thickness of the metallic layer typically is from the range 1 to 50 nm. The construction element may be integrated, for example, into windows, plastic films or sheets or glazings, especially for the purpose of light management.

Claims

1-16. (canceled)

17. A translucent construction element comprising a layer of translucent substrate, which contains a surface structured with nanoplanes of inclined angle relative to the substrate plane, and coated with an interrupted metallic layer covering at least a part of said nanoplanes, characterized in that the thickness of the metallic layer is from the range 1 to 50 nm and the metallic layer is interrupted in one dimension with a periodicity of interruptions in the range 50 to 1000 nm and realizes a duty cycle from the range 0.25 to 0.7; wherein the metallic layer contains a metal selected from the group consisting of silver, gold, copper, and platinum; wherein the metallic layer is covered by a transparent medium in the form of an encapsulating layer or has an underlayer, the underlayer comprising an enhancement material selected from the group consisting of Ti, Cr, Ni, silver oxides, and PEDOT-PSS is contained between the substrate and the interrupted metallic layer; or wherein the metallic layer is covered by a transparent medium in the form of an encapsulating layer, and has an underlayer, the underlayer comprising an enhancement material selected from the group consisting of Ti, Cr, Ni, silver oxides, and PEDOT-PSS is contained between the substrate and the interrupted metallic layer; and wherein the translucent construction element or device permits transmission of at least 10% solar radiation energy in the range of 400 to 700 nm.

18. The translucent construction element of claim 17, wherein the nanoplanes on the substrate surface are provided in form of a grating of depth from the range 30 to 1000 nm, wherein the grating has a sinusoidal, trapezoidal, triangular or rectangular cross section.

19. The translucent construction element of claim 17, wherein the inclined angle relative to the substrate plane is from the range 10 to 90°.

20. The translucent construction element according to claim 17, wherein the metallic layer contains silver.

21. The translucent construction element according to claim 17, wherein the substrate is glass or polymeric materials selected from the group consisting of thermoplastic polymers and UV-cured polymers, polycarbonates, polyesters, polyvinylbutyrate, polyolefines, polyetherimides, polyetherketones, polyethylene naphthalates, polyimides, polystyrenes, polyoxymethylene, polyvinylchloride, low refractive index composite materials, hybrid polymers, radiation-curable compositions, and combinations thereof.

22. The translucent construction element according to claim 17, wherein the substrate comprises a polymer film or sheet, and/or or a glass sheet, each of which is flat or bent.

23. The translucent construction element of claim 17 wherein: the substrate comprises a glass sheet including the interrupted metallic layer on at least a part of its surface, wherein the interrupted metallic layer is directly attached to the glass surface; or wherein the translucent construction element is embedded in the transparent medium comprising the substrate and an encapsulating medium, where the substrate and the encapsulating medium are selected from the group consisting of thermoplastic polymers, UV-cured polymers, polycarbonates, polyesters, polyvinylbutyrate, polyolefines, polyetherimides, polyetherketones, polyethylene naphthalates, polyimides, polystyrenes, polyoxymethylene, polyvinylchloride, low refractive index composite materials, hybrid polymers, radiation-curable compositions, and combinations thereof.

24. The translucent construction element according to claim 17, wherein the interrupted metallic layer has an aspect ratio from 1:5 to 5:1.

25. The translucent construction element according to claim 17, wherein the translucent construction element permits transmission of at least 30% of solar radiation energy in the range of 400 to 700 nm.

26. The translucent construction element according to claim 17, wherein the translucent construction element is a façade element or architectural window.

27. A method for seasonal heat and/or light management for reducing entry of IR radiation and/or modifying entry of visible or ultraviolet light through a window into the interior space of a building, the method comprising integrating the translucent construction element according to claim 17 into thebuilding.

28. A building comprising the translucent construction element according to claim 17, wherein the translucent construction element is integrated in the building's facade with its grating lines alignedhorizontally.

29. A device comprising an interrupted metallic layer on the surface of a transparent substrate, characterized in that the surface is structured with nanoplanes of inclined angle relative to the substrate plane and carrying a metal coating on at least a part of said nanoplanes, where the periodicity of interruptions in the metallic layer is from the range 50 to 1000 nm and the thickness of the metal coating is from the range 1 to 50 nm.

30. The device of claim 29, wherein the inclined angle relative to the substrate plane is from the range 10 to 90°.

31. The device of claim 29, wherein the nanoplanes of inclined angle relative to the substrate plane are provided in form of a grating of periodicity from the range 50 to 1000 nm and of depth from the range 30 to 1000 nm, which grating is of sinusoidal, trapezoidal, triangular or rectangular cross section.

32. The translucent construction element according to claim 25, wherein the thickness of the metallic layer is from the range 5 to 30 nm and the metallic layer is interrupted in one dimension with a periodicity of interruptions in the range 50 to 250 nm and realizes a duty cycle from the range 0.3 to 0.7.

Description

EXAMPLES

Example 1: Simulation of Light Reflection by Structured Silver Layer in Glass

[0100] The device comprises a rectangular grating of the period 390 nm, grating depth of 300 nm and duty cycle of 0.5 as schematically shown in FIG. 4a (duty cycle is the ratio of the area covered by grating peaks to the total area). As encapsulation material, borosilicate glass BK7 is chosen, whose index of refraction is similar to plastics, resulting in the encapsulated device as shown in FIG. 4b. The thickness of the encapsulating glass is larger than 5 μm and has no effect on the optical properties of the device. The peaks of the rectangular grating are coated on all 3 sides (side-walls and top) by silver of 8 nm thickness. Optical properties of the device are simulated and optimized using the rigorous coupled wave analysis (RCWA). Details of the RCWA method, which represents an industry standard for the simulation of the optical properties of gratings, have been published inter alia in “Diffraction analysis of dielectric surface-relief gratings”, M. G. Moharam, JOSA A, 72, 1385-1392 (1982); and in “Light Propagation in Periodic Media” by Michel Neviere and Evgeny Popov, Marcel Dekker Inc.,

[0101] New York, 2003. The appearing visual color of the device is evaluated in transmission and reflection from the simulated spectra. Total solar transmittance (TTS, ISO 13837) and the transmission in the visible TVIS (ISO 9050) are calculated at various angles of incidence (relative to the plane of the grating and its cross section, each perpendicular to the direction of the grating, as shown in FIG. 1), from the zeroth order transmission and reflection. For the targeted application, the particular incidence angles of 0° (perpendicular incidence of light) and ±60° (grazing light) are considered.

[0102] Results (according to ISO 13837 and ISO 9050) are compiled in the below table;

TABLE-US-00001 TABLE TTS and TVIS depending on the incidence angle Angle T.sub.TS T.sub.VIS  0° 71% 79% ±60° 56% 78%
the resulting ratio T.sub.TS(0°)/T.sub.TS(60°) is 1.27.

[0103] FIGS. 10 and 11 show the device's transmission and reflection spectra for angles of incidence 0° and 60° thus obtained.

Example 2: Fabrication and Testing of a Structured Silver Layer

[0104] A device is prepared, which holds an asymmetric cross-section as illustrated in FIG. 5a and which is encapsulated in a dielectric material as illustrated in FIG. 5b. The device comprises a grating of period 370 nm, grating depth of 300 nm and a duty cycle of 0.4. As the metal, silver is chosen with target thickness of 14 nm. The encapsulation material is a UV curable resin (Lumogen® OVD 301 from BASF). The substrate is a borosilicate glass B270 sheet with a size of 50×50×0.7 mm.sup.3.

[0105] The device is prepared as follows: [0106] i) A layer of UV curable material (Lumogen® OVD 301 from BASF) of thickness 5-10 μm is applied to one side of the final glass substrate (size 50'50×0.7 mm) by drop-casting. The wet layer of UV curable material is embossed with a tool comprising a rectangular grating of dimension as described above and cured, in accordance with the method described by Gale et al., Optics and Lasers in Engineering 43, 373 (2005), section 2.3. The thickness of the UV curable material has no major effect on the optical properties in the wavelength range of interest. [0107] ii) The replicated grating is then exposed to physical vapour deposition of silver from the side using a thermal evaporator vacuum chamber. The silver thickness selected is 14 nm, evaporation angle is 45° such that only a part of the grating is metalized as illustrated in FIG. 5a. [0108] iii) Finally, the device is encapsulated by coating the structures with another layer of UV curable material (Lumogen® OVD 301 from BASF; approximately 10 micrometer; thickness of the UV curable material has no major effect on the optical properties at the wavelength range of interest) and finally covered with another sheet of glass of same size.

[0109] The transmission and reflection spectra are measured by means of a photospectrometer. Since the Ag structure is asymmetric (see FIG. 1b), there are two directions under which measurements under 60° can be made (indicated as +60° and −60°). In the present case, measurements are taken at −60°. Since detection of 0° reflection (=perpendicular irradiation) it is not possible with the present equipment, the measurement is carried out under the small angle of 6°, where reflection intensity is nearly identical with exact normal reflection. FIG. 2 shows the transmission spectrum for an angle of incidence at 0°, and the reflection spectrum of the device thus obtained for an incidence angle of 6°. FIG. 3 shows the measurement for θ=−60°.

[0110] With the measured transmission and reflection spectra at 0° (6°) and −60°, the ISO numbers and transmission colours are evaluated and shown in the following table:

TABLE-US-00002 TABLE Percentage of T.sub.TS and T.sub.VIS and the color c depending of the illumination angle; *the color value c is based on the color space L*a*b and its coordinates a and b, with c = √a.sup.2 + b.sup.2. c is a measure for the color saturation angle θ T.sub.TS T.sub.VIS color c* 0° (6°) 58.0% 57.7% 22.2 −60° 47.8% 31.1% 17.5

[0111] ISO numbers are calculated according to the international standard ISO 9050 and 13837.

[0112] The ratio of T.sub.TS(0°)/T.sub.TS(−60°) is 1.21.

[0113] Using the UV-curable material NOA 61 or NOA 63 from Norland Products instead of Lumogen® OVD 301 leads to very similar results

[0114] The device shows a good angle sensitivity.

Example 3: Simulation of Light Reflection and Transmission for Short Period

[0115] Simulations are carried out using the same simulation tools as described in example 1. For simulated devices, the encapsulation material is poly(methyl methacrylate) (PMMA). The cross-section through the device is as illustrated in FIG. 5b. The period P of the devices is 190 nm with a horizontal grating orientation. Such a short grating period does not lead to light redirection by diffraction in the visible and near infrared wavelength range.

[0116] FIG. 12 illustrates the definition of the used geometrical grating parameters P, D, DC, d.sub.top and d.sub.side. The grating depths D are 160 nm and 180 nm and the duty cycle is 0.25. Silver is chosen for the metallic layer; silver layer thickness on top d.sub.top and on the side d.sub.side of the grating are according to the following Table 1.

TABLE-US-00003 TABLE 1 silver thicknesses d.sub.top, d.sub.side for the two devices D = 160 nm and D = 180 nm D [nm] d.sub.top [nm] d.sub.side [nm] 160 16.4 14.6 180 17.2 13.7

[0117] For the two devices having grating depths D=160 nm and D=180 nm, simulations are carried out and the calculated transmission and the reflection spectra at an incident light angles θ=0° and θ=60° are shown in FIGS. 13-16.

[0118] Based on these simulated transmission and reflection spectra, the transmittance numbers T.sub.TS, T.sub.VIS, the colors c depending on the incidence angle θ and the angle dependence ratio T.sub.VIS(0°), T.sub.VIS(60°) for each device are extracted as shown in Table 2.

TABLE-US-00004 depth D period P θ T.sub.TS T.sub.VIS color c T.sub.TS0°/T.sub.TS60° 160 190  0° 62.0% 72.1% 15.6 60° 48.5% 56.8% 23.4 1.28 180 190  0° 62.5% 73.4% 11.4 60° 46.6% 59.4% 13.1 1.34 Table 2 calculated transmittance numbers T.sub.TS, T.sub.VIS, the colors c and the angle dependence ratio T.sub.VIS(0°), T.sub.VIS(60°) for the two device cases D = 160 nm and D = 180 nm; the ISO numbers are calculated acording to the international standard ISO 9050 and ISO 13837

Example 4: Fabrication of Device with Short Period

[0119] The device shown in FIG. 17 is prepared in accordance with the fabrication procedure outlined in the description of example 1 (including thin film evaporation, plasma etching, galvanic step, UV replication, oblique silver evaporation and encapsulation) with the following exception: The cross-section through the UV embossed grating of the device is as illustrated in FIG. 5b; the period P of the device is 195 nm with a horizontal grating orientation, the grating depths is 180 nm, duty cycle is approx. 0.3 as shown in FIG. 17. Silver is used as a metal and the physical vapour deposition is set-up such that a silver thickness of 22 nm results for perpendicular evaporation; the evaporation is carried out, however, again at an oblique angle of 35°.

[0120] The measured transmission and the reflection spectra at incident light angle θ=0°(i.e. 6°, see explanation in example 2) and θ=−60° are shown in FIGS. 18 and 19.

[0121] Based on these measured transmission and reflection spectra the ISO transmittance numbers T.sub.TS, T.sub.VIS, the colors c depending on the incidence angle θ and the angle dependence ratio T.sub.VIS(0°), T.sub.VIS(−60°) were evaluated as shown in Table 3.

TABLE-US-00005 TABLE 3 Calculated transmittance numbers T.sub.TS, T.sub.VIS, the colors c and the angle dependence ratio T.sub.VIS(0°), T.sub.VIS(−60°) for the fabricated device of example 4; the ISO numbers are evaluated according to the international standard ISO 9050 and ISO 13837 device θ T.sub.TS T.sub.VIS color c T.sub.TS0°/T.sub.TS − 60° example 4  0° 58.0% 55.5%  4.9 −60° 45.9% 25.5% 13.7 1.26

BRIEF DESCRIPTION OF FIGURES

[0122] FIG. 1a: Perspective representation of the grated device indicating the plane of the grating comprising the interrupted metallic structure (x and y axis) and the incident light; the x-axis therein points in direction of the periodicity, the y-axis is parallel with the grating; the z-axis stands perpendicular on the substrate plane; i represents the incoming light forming an angle θ with the z-axis (θ=0°represents light falling perpendicularly on the window).

[0123] FIG. 1b: Cross-section through the device and the incidence angle of light under which transmission measurements are carried out (in the present case of example 2, −60° is chosen).

[0124] FIG. 2: Transmission and reflection spectra as detected for the device of example 2 for θ=0° incident angle (transmission, dashed line) and for θ=6° (reflection, solid line).

[0125] FIG. 3: Transmission (dashed line) and reflection (solid line) spectra as detected for the device of example 2 for θ=−60° incident angle.

[0126] FIG. 4: Cross-section of a device according to the present invention in air (FIG. 4a) and in encapsulated form (FIG. 4b; thick black lines symbolize the metallic cover).

[0127] FIG. 5: Cross-section of a representative device according to the present invention, as obtainable by metal deposition under an oblique angle (as in present example 2) in air (FIG. 5a) and encapsulated in a dielectric material (FIG. 5b; thick black lines symbolize the metallic cover).

[0128] FIG. 6: Cross-section of a device according to the present invention in air (FIG. 6a) and in encapsulated form (FIG. 6b; thick black lines symbolize the metallic cover) as obtainable after metal deposition from both sides of the grating and subsequent removal of the metal layer from the grating top.

[0129] FIG. 7: Cross-section of device comprising an underlayer of enhancement material (7a: in air; 7b: encapsulated; shaded lines symbolize the enhancement layer; thick black lines symbolize the metallic cover), and of device additionally comprising a cover layer (7c: in air; 7d: encapsulated; shaded lines in contact with substrate symbolize the enhancement layer; thick black lines symbolize the metallic cover; further shaded line symbolizes the cover layer).

[0130] FIG. 8: Alternative devices based on a sinusoidal grating in air (FIG. 8a) and in encapsulated form (FIG. 8b; thick black lines symbolize the metallic cover).

[0131] FIG. 9: Alternative devices based on a triangular grating in air (FIG. 9a) and in encapsulated form (FIG. 9b; thick black lines symbolize the metallic cover).

[0132] FIG. 10 shows the transmission and reflection spectra of a device as of present example 1 for an angle of incidence of 0°.

[0133] FIG. 11 shows the transmission and reflection spectra of a device as of present example 1 for an angle of incidence of 60°.

[0134] FIG. 12 cross-section through a single side metal grating device, with the indicated geometries: period P, grating depth D, duty cycle DC, metal thickness on top d.sub.top and metal thickness on side d.sub.side.

[0135] FIGS. 13 and 14 show the transmission and reflection spectra for the silver based device with: D=160 nm, P=190 nm, DC=0.25 and silver thicknesses according to Table 1; spectra shown are for θ=0° (FIG. 13) and for θ=60° (FIG. 14).

[0136] FIGS. 15 and 16 show the transmission and reflection spectra for the silver based device with: D=180 nm, P=190 nm, DC=0.25 and silver thicknesses according to Table 1; spectra shown are for θ=0° (FIG. 15) and for θ=60° (FIG. 16).

[0137] FIG. 17 shows the SEM image of a cross-section through a fabricated short period grating of example 4, with a grating period of 195 nm (spacing between the vertical bars) and a depth of 180 nm.

[0138] FIG. 18 shows the transmission and reflection spectra for the silver based device of example 4 for θ=0° (6°).

[0139] FIG. 19 shows the transmission and reflection spectra for the silver based device of example 4 for θ=−60°.