Window Film Research Articles

Climate change and thermo-solar patterns of office buildings with/without window films in extreme hot-arid climate of Kuwait

This research attempts to develop a systematic method to address climate changes by studying temperature-humidity patterns as the two major meteorological parameters and to moderate these effects using a commercially available window film on interior windows of an office building with double-glazing. A three-floor educational building at Australian College of Kuwait (ACK) was equipped with temperature, humidity and illuminance sensors for two similar size offices, one with 3 M Neutral 20 window films. Total readings of 50,000 entries from each sensor was recorded every 3 min by a home-designed microprocessor-based logging system for three months of June, July, and August 2019. In parallel, the ACK building was simulated in EnergyPlus and DesignBuilder software and calibrated with the experimental measurements. Histograms and a probability density function (PDF) of temperature and humidity are built by a representative rational function as a model of main climate parameters variations. By examining min-mean-max values of data, it is observed that the office with window films has increased indoor humidity and, in most instances, reduced temperature by 2–5 °C compared to double-glazed bare windows which can significantly reduce cooling loads in extreme hot-arid climates. Simulation results are presented on the energy saved and the reduced CO2 footprints by applying the solar window films in the ACK building.

Transparent and Flexible SiOC Films on Colorless Polyimide Substrate for Flexible Cover Window.

We fabricated transparent and flexible silicon oxycarbide (SiOC) hard coating (HC) films on a colorless polyimide substrate to use as cover window films for flexible and foldable displays using a reactive roll-to-roll (R2R) sputtering system at room temperature. At a SiOC thickness of 100 nm, the R2R-sputtered SiOC film showed a high optical transmittance of 87.43% at a visible range of 400 to 800 nm. The R2R-sputtered SiOC films also demonstrated outstanding flexibility, which is a key requirement of foldable and flexible displays. There were no cracks or surface defects on the SiOC films, even after bending (static folding), folding (dynamic folding), twisting, and rolling tests. Furthermore, the R2R-sputtered SiOC film showed good scratch resistance in a pencil hardness test (550 g) and steel wool test under a load of 250 g. To test the impact protection ability, we compared the performance of thin-film heaters (TFHs) and oxide-semiconductor-based thin-film transistors (TFTs) with and without SiOC cover films. The similar performance of the TFHs and TFTs with the SiOC cover window films demonstrate that the R2R-sputtered SiOC films offer promising cover window films for the next generation of flexible or foldable displays.

A patterned phase-changing vanadium dioxide film stacking with VO2 nanoparticle matrix for high performance energy-efficient smart window applications

A vanadium dioxide (VO2) based solid-to-solid phased changing material has been attracting great interest in smart window applications. However, achieving high solar modulation and high transparency simultaneously in visible light is the major challenge for the practical application of this smart material. To resolve this issue, in this paper, a smart film composed of a VO2 nanoparticle matrix and a patterned VO2 film is presented. Numerical modeling and electromagnetic simulation are carried out to characterize the performance in terms of solar modulation and luminous transmittance, and a parametric study is carried out to optimize the proposed smart window film. Compared with the VO2 nanoparticle matrix, the proposed structure can obtain 23% solar modulation and 57% luminous transmittance but with a much thinner thickness, which will significantly reduce the cost and fabrication complexity and extend the environment stability.

Seeking Balance: Conservation Values and the Artist’s Voice

ABSTRACT Traditional exhibition standards in museums may be challenged when an artist assumes an active role in determining the display parameters of a work or exhibition. Particularly with art created since the mid-twentieth century, artists have increasingly conceived their work to encompass aspects of its display environment and have deliberately blurred the boundaries between viewer and art. Finding ways to mediate the desires of the artist and the conditions that would best protect the physical object can be a challenge. Methods for this process may include light-reducing window films, creative exhibition design, and the use of exhibition copies. However, in recent years there has been an increasing reliance on waivers, signed by the owner, that acknowledge a departure from traditional display guidelines and absolves the museum of any consequences. This practice, while legal, raises ethical concerns as to the role and obligations of the conservator charged with the preservation of the work. Drawing from case studies at the Whitney Museum of American Art, this paper explores ways that conservators can continue to provide guidance as we operate in these non-traditional settings.

Daylighting performance analysis of a facade combining daylight-redirecting window film and automated roller shade

Daylighting provides a wide range of benefits for buildings and occupants, including light energy saving and a direct connection to the outdoors. Excessive sunlight can be eliminated using automatically controlled roller shades, and distribution can be improved by sending light to the back of a room using daylight redirecting films. These technologies can be combined in a multi-sectional facade to maximize its potential in serving different functions (light energy saving, glare prevention, and views). This paper aims to evaluate daylight redirecting film's effectiveness when combined with automatically controlled roller shades by analyzing daylight availability, glare prevention, and visibility through the facade. We also aim to provide a guide for designing a multi-sectional facade system.We conducted a parametric study scheme using a workflow based on Radiance's three-phase method. The evaluated design elements included the dimensions of the daylight redirecting film, and the properties of two glazing systems (top and middle sections) and shading fabrics. Besides daylighting availability and glare, we created a view index to evaluate the facade's “see-through” throughout a year.The results indicated that the film-to-wall ratio is the most critical design element in the scheme. An increased glass transmittance in the top section could result in higher daylight availability, while a decreased glass transmittance in the middle section could provide more outdoor views. Finally, we created a multi-sectional facade design guide to help designers understand potential trade-offs between different materials.

Distribution of Polycyclic Aromatic Hydrocarbons (PAHs) in Indoor/Outdoor Window Films and the Indoor Film/Air Partition of Northeastern Chinese College Dormitories

Distribution of Polycyclic Aromatic Hydrocarbons (PAHs) in Indoor/Outdoor Window Films and the Indoor Film/Air Partition of Northeastern Chinese College Dormitories

Transparent window film with embedded nano-shades for thermoregulation

Every year, more than 20% of the energy consumption in the United States and more than 10% of the global consumption is used towards HVAC (Heating, Ventilating, Air-Conditioning) systems in buildings. Although continued efforts in advancing renewable energy, efficient appliances, and smart building systems are desired, the most critical factors that cause extensive indoor energy consumption are thermal leakage and thermal waste generation. We demonstrate a smart window film that allows natural lighting with a clear view while blocking oblique incident sunlight to make the building interior cooler without using electricity or generating heat. Building upon the concept of, often overlooked, traditional window shades and privacy window films, we emphasize and elevate the application and impact of using magnetically arranged nanoscale material for energy conservation purpose in buildings. By embedding vertically aligned Ni flakes (VANF) in a polymer matrix film, nanoscale mirror array serve as shades to block the high-angled incident sunlight, blocking approximately 73% of total solar irradiance and bringing down the indoor temperature by 1.92 °C during the daytime in a model house while providing nearly 90% transparency. Global application was simulated by applying the respective solar angle and intensity at selected latitudes, indicating their potential. This passively energy-conserving smart film is a low cost, maintenance free, and simple product for users and easy-to-manufacture product for the industry.

Influence of shell materials on the optical performance of VO2 core–shell nanoparticle–based thermochromic films

VO2 nanoparticle–based thermochromic films have shown great promise for applications in smart windows because of their relatively high luminous transmittance and solar modulation ability. To improve the lifetime of VO2 nanoparticles, environmentally stable oxide materials such as TiO2, SiO2, and ZnO have been utilized as protecting shells. However, the shell material changes the optical performance of the thermochromic films because of the variation of the dielectric environment of the VO2 nanoparticles. In this work, the effective medium theory is coupled with the transfer matrix method to study the influence of the optical constants of the shell materials and the shell thickness on the luminous transmittance and solar modulation ability of the VO2 core–shell nanoparticle–based thermochromic films. The calculation results showed that it is challenging to simultaneously improve both the luminous transmittance and the solar modulation ability of core–shell structures. With the refractive index of the shell material being between 1.6 and 2.3 (e.g. ZnO and Cr2O3), there exists an optimal shell thickness to obtain the maximum solar modulation ability. The results reported in this study can be exploited to guide the design and development of high-performance VO2 core–shell nanoparticle–based thermochromic smart window films.

Ultraviolet-reflective film applied to windows reduces the likelihood of collisions for two species of songbird.

Perhaps a billion birds die annually from colliding with residential and commercial windows. Therefore, there is a societal need to develop technologies that reduce window collisions by birds. Many current window films that are applied to the external surface of windows have human-visible patterns that are not esthetically preferable. BirdShades have developed a short wavelength (ultraviolet) reflective film that appears as a slight tint to the human eye but should be highly visible to many bird species that see in this spectral range. We performed flight tunnel tests of whether the BirdShades external window film reduced the likelihood that two species of song bird (zebra finch, Taeniopygia guttata and brown-headed cowbird, Molothrus ater) collide with windows during daylight. We paid particular attention to simulate the lighting conditions that birds will experience while flying during the day. Our results indicate a 75–90% reduction in the likelihood of collision with BirdShades-treated compared with control windows, in forced choice trials. In more ecologically relevant comparison between trials where all windows were either treated or control windows, the estimated reduction in probability of collision was 30–50%. Further, both bird species slow their flight by approximately 25% when approaching windows treated with the BirdShades film, thereby reducing the force of collisions if they were to happen. Therefore, we conclude that the BirdShades external window film will be effective in reducing the risk of and damage caused to populations and property by birds’ collision with windows. As this ultraviolet-reflective film has no human-visible patterning to it, the product might be an esthetically more acceptable low cost solution to reducing bird-window collisions. Further, we call for testing of other mitigation technologies in lighting and ecological conditions that are more similar to what birds experience in real human-built environments and make suggestions for testing standards to assess collision-reducing technologies.

84‐5: Late‐News‐Paper: Flexible Cover Window Film with Improved Optical Clarity

SK Innovation and SK ie technology have developed and commercialized cover window films (FCW®) composed of functional coatings on transparent polyimide (PI) film for a foldable displays. We report on the development of PI film with high visual clarity, which can provide glass‐like feel to public users. Advances were achieved by engineering drying kinetics on the process of film fabrication, and the technology is applied to the commercial product of transparent PI film.

Highly conducting and transparent low-E window films with high figure of merit values based on RF sputtered Al and In co-doped ZnO

In this work, we have studied the correlation between the electrical, optical and plasma properties of RF sputtered 1 at.% Al and In co-doped ZnO (AIZO) thin films with thickness 210–1590 nm in a comprehensive manner. The lattice strain of the hexagonal wurtzite ZnO structure decreases as the film thickness increases. The lowest resistivity of 8.9 × 10−4 Ω-cm is obtained for the 930 nm thick film with an electron concentration and mobility values of 3.96 × 1020 cm−3 and 17.7 cm2/Vs respectively. Optical transmission value is ~85%–90% in the range 400–700 nm for all the films. Most notably the figure of merit value of 2.65 × 10−2 Ω−1 for the 930 nm thick film is the highest among all the reports on AIZO films till date. High transparency in the visible region as well as higher reflectivity in the NIR region (with a plasma frequency of 8.2 × 1014 Hz) indicates its promising application in the low-E window.

Electrochromic Thin Films Based on NiAl Layered Double Hydroxide Nanoclusters for Smart Windows and Low-Power Displays

To develop electrochromic thin films for smart windows and low-power displays, homogeneous thin films were produced by spin coating colloidal NiAl layered double hydroxide (LDH) nanocluster solutions on a fluorine-doped tin oxide (FTO) glass substrate. The nano-LDH dispersion was synthesized via a facile one-step epoxide mediated process at room temperature. In situ relative transmittance measurements at 400 nm, recorded during potential scans in cyclic voltammetry or differential pulse chronoamperometry, showed the electrochromic behavior of the homogeneous thin films. The impact of various parameters on the electrochromic properties of the films was detailed, such as the thickness of the film, the nature of the electrolyte, and the presence of electroactive anions. The electrochromic properties, namely, the change in transmittance (ΔT) and the bleaching reversibility, were greatly improved using alkaline metal hydroxide as the electrolyte and in the presence of Fe(CN)64–. The performances that we reached from the deposition of nanoclusters can be advantageously compared to the literature with ΔT = 70% and fast and good reversibility. Upon calcination, the NiAl-LDH film converted into mixed oxides (NiO and NiAl2O4). The higher the calcination temperature, the lower was the ΔT value. The presence of porosity within the thin films, through the introduction of sacrificial polymeric beads and then decomposition at 400 °C, was investigated, highlighting an enhancement of the ΔT value attributed to better accessibility to the nickel redox sites.

Indoor air partitioning of Synthetic Musk Compounds: Gas, particulate matter, house dust, and window film

Due to diversity of contaminants indoors and complexity in the physical structure of particulate matter, partition process of chemicals affects indoor concentration distribution. Synthetic Musk Compounds (SMCs) are ubiquitously found in household and personal care products, thus, in the environment. Exposure to SMCs is important for human health, therefore, their partitioning in indoor environmental media is a key issue. In this study, gas – particle, house dust, and window film partitioning of SMCs were investigated in an indoor micro-environment. In a sealed and unoccupied room, a polycyclic and nitro musk mixture was left for volatilization for an hour. Then, samples were collected using XAD-2 sandwiched between two PUF plugs, glass-fiber filter, and wipes for gas, PM10, window-film, house dust phases, respectively, for 145 h. Collected samples were analyzed using a GC–MS. Results demonstrated that SMC concentrations decreased over time, non-linearly. Six of the SMCs partitioned to PM10 with at least 10% at beginning of the experiment, whereas the number of compounds dropped to two at the end, showing that SMCs may partition well between the two phases but they tend to be in the gas phase. They were also detected in the film and dust phases but a decrease pattern similar to gas-particle was not observed. Spearman correlations indicate that the dust and film-associated concentrations were governed by similar processes but PM-associated concentrations were not. SMCs may be found in all phases, mainly in house dust in terms of mass among the studied media and unaccounted surface reservoirs. Therefore, their partitioning between indoor media has key implications for human exposure.

Facile preparation of wear-resistant and anti-fingerprint hard coating with chemisorption of fluorosilane by simple wet coating

Epoxy-siloxane hybrid hard coating (HC) has been reported to be applicable to foldable display cover window film due to its glass-like hardness and plastic-like flexibility, which are trade-off characteristics. In addition, to provide an anti-fingerprint (AF) function with abrasion resistance to HC, the addition of a durable hydrophobic function on the HC surface is essential. Herein, durable hydrophobic and abrasion resistant F-HC was reported by chemical adsorption of fluorosilane on HC with simple wet coating. TEOS-derived silica primer increased the hydroxyl groups (–OH) on surface of HC, then it improved the sol-gel condensation with fluorosilane. The fluoro-treatment reduced the coefficient of friction to maintain hydrophobicity (<10% of the initial water contact angle) and optical transparency (~90%) after 5000 cycles of a steel-wool test and 2000 cycles of an eraser abrasion test. Performance was dependent on plasma treatment, annealing condition, and pretreatment on the HC surface for the stronger chemisorption of fluorosilane.

Durability-enhanced vanadium dioxide thermochromic film for smart windows

Vanadium dioxide (VO2)–based thermochromic films are of great interest for energy-saving smart windows as they can dynamically change the solar transmittance as the ambient temperature changes. However, VO2 is thermodynamically unstable and could be easily oxidized by the oxygen and moisture in the ambient air. In this work, a durability-enhanced VO2 nanoparticle-polymer thermochromic film was proposed and fabricated using the blade coating method where the cross-linked and highly entangled poly(methyl methacrylate) (PMMA) chains with a molecular weight (~ 950,000) was adopted to block gas diffusion in the polymer matrix. It was shown that the developed VO2 nanoparticle film kept ~30% of its solar modulation ability after ~900 h of accelerated durability test in the aging environment with a temperature at 60 °C and ~95% relative humidity. This is ~4 times of the lifetime of the VO2 nanoparticles which are embedded in the non–cross-linked PMMA matrix with low molecular weight (~15,000). The cross-linked PMMA-VO2 film also showed a high luminous transmittance of ~50%, a high solar modulation ability of ~17%, and a low haze of ~11%. Our method provides an easy and effective strategy to improve the lifetime of VO2 nanoparticles, showing a promising pathway toward environmentally stable and easily scalable thermochromic films for energy-efficient smart windows.

Experimental study on the performance of solar window films in office buildings in Kuwait

This work examines the solar performance of double-glazed windows in four offices in ACK buildings with and without solar window film in actual working conditions. Window films are passive thin films stick to the interior or exterior of windows to effect various solar-optical impacts including energy saving, UV reduction, and increased thermal comfort. For this study, the 3M Neutral 20 and 70 are selected which are made of multilayer nanofilms of 220 SAN25/THV 95-nm thick reflective layers. Real-time measurements of temperature, humidity, and luminous were conducted in 5 min intervals over the months of June, July, and August 2019 and data stored through WiFi system in iClouds. Arduino-type microprocessors and various temperature-humidity, and LUX sensors were assembled and programmed to transfer and store data in real time. Exploring and analyzing the data collected for four offices with and without window films in summer of Kuwait, it is evident that window film has good potential to save water by preserving interior humidity to the level of human comfort, decrease interior temperature to save energy and reduce CO2 footprints, to restrict the solar UV rays to minimum level, and to reduce visual impacts of high solar luminous. The benefits and drawbacks of the selected window films are discussed here for the weather condition of Kuwait.

Highly robust and transparent flexible cover window films based on UV‐curable polysilsesquioxane nano sol

AbstractFlexible cover window films based on the ultraviolet‐curable polysilsesquioxane are prepared to have enhanced mechanical, optical properties, and bending performance. To figure out the factors determining those properties, post–treatment conditions are varied into the light source, temperature, and relative humidity. Then, the effect of such variables is examined in respect of surface hardness, yellow index (YI), and bending cycle reliability of flexible hard coating. Also, the effect of photoinitiator type in terms of their chemical structure is also investigated. Notably, the relative humidity and thermal treatment are more effective to enhance the mechanical properties rather than light exposure. Indeed, compared to that of reference condition, the cover windows treated with 99% relative humidity and thermal aging at 85°C exhibit improved surface hardness by 24.4 and 19.5%, respectively. However, only the relative humidity is rather effective to enhance the optical properties such as the YI by lowering to the most 2.6. The YI is also improved by varying the chemical structure of the photoinitiator. By virtue of post–treatment and a different photoinitiator, we could achieve flexible cover window films with bending reliability at bending radius of 3 mm for 100,000 cycles, showing good mechanical and optical properties simultaneously.

A Novel Method for Notable Reducing Phase Transition Temperature of VO2 Films for Smart Energy Efficient Windows.

Although Vanadium dioxide (VO2) has a potential application value for smart energy efficient windows because of its unique phase transition characteristic, there are still many obstacles that need to be overcome. One challenge is to reduce its high transition temperature (ζc = 68 °C) to near room temperature without causing its phase transition performance degradation. In this paper, a novel method was employed that covered a 3 nm ultra-thin heavy Cr-doped VO2 layer on the pure VO2 films. Compared with the as-grown pure VO2, obviously, phase transition temperature decreasing from 59.5 °C to 48.0 °C was observed. Different from previous doping techniques, almost no phase transition performance weakening occurred. Based on the microstructure and electrical parameters measurement results, the mechanism of ζc reducing was discussed. The upper ultra-thin heavy Cr-doped layer may act as the induced role of phase transition. With temperature increasing, carrier concentration increased from the upper heavy Cr-doped layer to the bottom pure VO2 layer by diffusion, and induced the carrier concentration reach to phase transition critical value from top to bottom gradually. The present method is not only a simpler technique, but also avoids expensive alloy targets.

Flexible Vertically Aligned Polymer Network Liquid Crystal Using Transferred Spacers Bonded by Photoreactive Mesogens for Smart Window Films

Proceedings of the International Display Workshops Volume 26 (IDW '19),Flexible Vertically Aligned Polymer Network Liquid Crystal Using Transferred Spacers Bonded by Photoreactive Mesogens for Smart Window Films

Flexible Vertically Aligned Polymer Network Liquid Crystal Using Transferred Spacers Bonded by Photoreactive Mesogens for Smart Window Films

Flexible Vertically Aligned Polymer Network Liquid Crystal Using Transferred Spacers Bonded by Photoreactive Mesogens for Smart Window Films