Thermal control of transmittance/diffraction states of holographic structures composed of polymer and liquid crystal phases

Kakiuchida, Hiroshi; Tazawa, Masato; Yoshimura, Kazuyoshi; Ogiwara, Akifumi

doi:10.1016/j.solmat.2010.05.040

Cited by 23 publications

(17 citation statements)

References 16 publications

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“…An exotic example of a dynamic heat control element using organics are holographic polymer dispersed liquid crystals . These films are quite angularly dependent, and while can be efficient on excluding IR light at specific incident angles, they are generally transparent at other incident angles, which makes control of diffuse light difficult.…”

Section: Dynamic Ir Regulating Windowmentioning

confidence: 99%

Infrared Regulating Smart Window Based on Organic Materials

Khandelwal

Schenning

Debije

2017

Advanced Energy Materials

336

220

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(IR), here defined as light with wavelengths between 700 nm and 2500 nm, accounts for around 50% of the total energy emitted by the sun reaching Earth (Figure 1b), [3,4] and this light produces interior heating but is invisible to the unaided eye.The absorption of sunlight by building materials and passage of IR through transparent surfaces such as windows is responsible for much of the interior overheating of office rooms, automobile interiors, greenhouses, and other similar spaces. The use of artificial cooling and heating systems will only increase with the continued influence of global climate change, with energy used for cooling systems surpassing energy used for heating around the year 2070, and a 40 fold increase in air cooling energy use is expected by 2100. [5] By controlling the influx of radiant heat transfer, calculations show that more than 50% of the energy used in lighting, heating and cooling could be saved by deploying better control systems over only 18% of available window stock. [6] In areas with human inhabitants employing windows, more aspects must be considered than simply reducing the use of energy in the room: any switchable window used in, for example, a commercial office space has several other requirements that must be met before it may be installed. Among these requirement are reasonably fast switching speeds [7] (although for IR control, relatively longer times compared to visible light switching should be acceptable), good optical transparency with minimum haze, an acceptable device lifetime, [8] and functionality over a range of exterior temperatures. Controlling the excess of solar energy without compromising the visible transparency of the window is an important consideration for human health: maintaining inside/outside contact and daylighting are vital in retaining well-being and productivity, as well as providing economic and aesthetic gain by reducing the need for artificial lighting systems. [9,10] These are challenging goals for a window to realize.A number of materials have been developed over the past few decades to maintain indoor temperatures. Many of these focus on the opaque structural building elements like walls and roofing. [10][11][12][13] Other solutions target the transparent window, employing external mechanical shutters and blinds, [14] phase change materials (PCMs), [15] thermochromic materials, [16] aerogels, [17] trapped gas in fluid membranes, [18] and even phononic materials, [19] among other options. Indeed, controlling heat passage through the window in response to changing climate conditions is a great challenge; ideally, one would accomplish Windows are vital elements in the built environment that have a large impact on the energy consumption in indoor spaces, affecting heating and cooling and artificial lighting requirements. Moreover, they play an important role in sustaining human health and well-being. In this review, we discuss the next generation of smart windows based on organic materials which can change their properties by reflecting or trans...

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Section: Dynamic Ir Regulating Windowmentioning

confidence: 99%

Infrared Regulating Smart Window Based on Organic Materials

Khandelwal

Schenning

Debije

2017

Advanced Energy Materials

336

220

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“…Note that T(λ) denotes transmittance as functions of wavelength (λ) and temperature, Φ sol (λ) is the spectral solar irradiance for air mass 1.5, and Φ lum (λ) is the standard luminous efficiency function for photonic vision, and related to the transparency of materials 19 . Figure 2 shows the normalized spectra in solar ray expressed by Φ sol (slash mark) and Φ lum (cross mark) which are the spectral solar irradiance for air mass and the standard luminous efficiency function of wavelength for photonic vision.…”

Section: Performance Indicators For a Solar-ray Controllermentioning

confidence: 99%

“…Holographic polymer dispersed liquid crystal (HPDLC), which was originally proposed for optoelectronic devices such as projection displays, optical switches, and tunable lasers, is expected to be applicable to a diffractive type of thermodriven light controller 19 . As shown in Fig.…”

Section: Thermal Control Of Diffraction Wavelength By Hpdlc Gratingsmentioning

confidence: 99%

Thermo-driven light controller by using thermal modulation of diffraction wavelength in holographic polymer dispersed liquid crystal grating

Ogiwara

Kakiuchida

2014

SPIE Proceedings

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A microperiodic structure composed of polymer and liquid crystal (LC) phases, called holographic polymer dispersed liquid crystal (HPDLC), was fabricated based on a photo-induced phase separation technique by laser interferometric exposure. The diffraction wavelength of HPDLC gratings formed by different LC composites and grating structures was experimentally investigated by spectroscopic measurements as a function of temperature at around 30 °C. The HPDLC gratings composed of nematic LC having low nematic to isotropic temperature (T NI ) and film thickness of 25 μm showed the switch of diffraction wavelength between visible and infrared lights by the change of temperature. The optical characteristics achieved in HPDLC gratings are expected to be applicable for the basis of diffractive type of thermodriven light controller which can supply visibility constantly for solar-ray control windows.

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“…Their high efficiencies are mainly determined by the particle size, shape and formula. 16,17 However, they commonly possess reectivity in the full light band, unlike the LC ones with a reection band that can be regulated. 18,19 For the latter one, either a reliable polymer-stabilized LC (PSLC) or a sensitive polymer-dispersed LC (PDLC) smart window is generally dependent on the LC phase transition under the stimulus of applied physical signals to change the overall optical properties.…”

Section: Introductionmentioning

confidence: 99%