Smart Glass Applications with Polymer Dispersed Liquid Crystal (PDLC) Technology
How PDLC Technology Works
Liquid crystal applications are a familiar technology for numeric and flat panel displays. Liquid crystal display, or LCD, is the most popular flat panel display technology, seen in portable computers, cell phones, calculators, digital clocks, gas pumps, and watches, etc. In LCD, applied electricity changes the shape of liquid crystals to allow light to pass through individual elements, thus forming images, figures, and numbers on the displays.
Image courtesy of Glass Apps.
Liquid crystals respond to an electrical charge to morph the glass from opaque to clear.
Source: http://www.glass-apps.com
Polymer dispersed liquid crystal is simply micro droplets of liquid crystals encapsulated in a polymer matrix. The liquid crystals respond to an electrical charge. In a static state, the liquid crystal molecules remain in a randomized configuration that refracts the light that enters the mixture, making it appear opaque. When electricity is applied, the molecules line up the direction of the electric field, allowing light to pass through what is now essentially a transparent surface. When electrical charge is deactivated, liquid crystal droplets again become randomly oriented, the incoming light is again heavily scattered and does not pass through in a straightforward manner, resulting in fully blocked images.
Case Study:
Conference Room Doesn’t Monopolize Sweeping Views and Natural Light
Photo courtesy of Apigee
When considering the office build-out of San Francisco Bay Area software company Apigee, project manager Sonia Li considered the company’s philosophy and ethos.
“Understanding the Apigee culture, which inspires an open, collaborative work environment, was an important element of the project,” Li says.
She also noted the office space’s physical attributes, which includes a wall of windows offering panoramic views of downtown San Jose.
Siting the boardroom to capitalize on the stunning views made a lot of sense. The natural light and far-reaching views would create a pleasant environment for conferences and meetings. And many studies have shown that natural light improves morale and productivity. Even views have been found to increase mental and emotional wellbeing.
However, a conference room along the bank of windows would block the views and light from the interior spaces, thereby depriving those using the conference room of the room’s beneficial assets. With this dilemma, Li came up with unique solutions: She designed a conference room with walls made of switchable glass.
When the electrically controlled glass is switched to clear, the natural light and broad views radiate deep into the interior spaces as though the conference room wasn’t there. That setting could be used when no conference or board meeting is in session, or when a gathering does not require privacy.
On the other hand, when a meeting in the boardroom requires privacy, the glass fronts and doors turn from clear to opaque with the flick of a switch. Because of the technology of the glass, made with polymer dispersed liquid crystal (PDLC), the opaque status of the glass does not block light, but still allows natural light to flood though the panels. Other switchable glass technologies, such as suspended particle devices (SPD), would have blocked the natural light and yet not provided full privacy.
According to Li, the PDLC switchable glass is comparable budget wise to electric shades, but “the impact is a lot more modern, stylish, and chic.”
Many of Apigee's employees consider the switchable glass walls to be one of the coolest features in the office.
Types of PDLC Switchable Glass
Smart glass with PDLC technology is available in two separate products that help to solve distinct design problems.
Image courtesy of Glass Apps
The layer containing indium tin oxide (ITO) conducts the electricity that stimulates the liquid crystals.
Laminated Switchable PDLC Glass
Laminated switchable glass is typically used for new construction projects or renovations where glass may be replaced. In this case, switchable film is sandwiched between two sheets of glass and two sheets of interlayer adhesive. Indium tin oxide (ITO) is a clear conductor that is coated on the inside of PET plastic films, which are sandwiched around the LC droplets encapsulated in a polymer matrix. PET/ITO films conduct the electrical current that causes the liquid crystals to align and thus render the glass transparent. Glass can be made to almost any thickness (5/16” to + for Insulated Units) and specification required (i.e. tempered, low-iron, etc.).
Self-adhesive Switchable PDLC Film
Self-adhesive switchable film is typically used for retrofit applications. Switchable adhesive film has an adhesive side that is dry applied to the surface of any smooth glass surface (similar to a smart phone screen protector) and can be easily installed in the field. The outer surface of the film is hard coated and scratch resistant. Copper mesh tabs on the top or sides connect the conductive layer to electrical wires soldered on by the installer, covered by a silicone bead, and attached to a power source. The electrical current can be controlled by a wall switch, home automation or smart phone app.
With the knowledge of how PDLC technology works, we’ll next examine the benefits it brings.
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