Introduction

Liquid crystal glazing is the use of glass that allows you to switch between transparency and translucence at the push of a button. The secret of the transformation between clear glass and translucent glass is found in its ‘Liquid Crystal Sheet’. Liquid crystal glazing comprises laminated glass, with a minimum of two clear or coloured sheets of glass and a liquid crystal film, assembled between at least two plastic interlayers. In the ‘off’ state, the liquid crystals are not aligned, which prevents vision, yet allows light to pass through the glass. When is it switched ‘on’, the liquid crystals align, turning the glass transparent and allowing visibility. The change in transparency takes place within milliseconds.

A piece of glass can adjust the rate of light transmission by changing its transparency or colour. This process is called a ‘chromogenic’ one. There are several types of chromogenics, namely, electrochromic, photochromic, thermochromic and gasochromic etc. The most popular is electrochromic.

Electrochromic:

Electrochromic devices change light transmission properties in response to voltage and thus control the amount of light and heat passing through. In electrochromic windows, the electrochromic material changes its opacity. A burst of electricity is required for changing opacity, but once the change has been effectuated, no electricity is needed for maintaining the particular shade which has been reached.

Darkening occurs from the edges, moving inward, and is a slow process, ranging from several seconds to several minutes depending on window size. Electrochromic glass allows visibility even in the darkened state and thus preserves visible contact with the outside environment. It has been used in small-scale applications such as rearview mirrors.

Electrochromic technology also finds use in indoor applications - for example, for protection of objects under the glass of museum display cases and picture frame glass from the damaging effects of the ultraviolet and visible wavelengths of artificial light.

Two Types:

There are two types of electrochromic: PDLC (polymer dispersed liquid crystal) and SPD (suspension particle device). PDLC is more frequently used. 

1. Polymer Dispersed Liquid Crystal Glass (PDLC)

PDLC glass is a light control glass. It can regulate and adjust the light intensity or light transmission through the glass. Sometimes, it is referred to as intelligent glass, magic glass, privacy glass, smart glass or switchable glass.

2. Suspended Particle Device (SPD)

The liquid crystal Suspended Particle Device (SPD) contains molecular particles suspended in a solution between plates of glass. In their natural state, the particles move randomly and collide, blocking the direct passage of light. When energized, the particles align rapidly and the glazing becomes transparent. This type of switchable glazing can block up to about 90 percent of light.

Residential windows with liquid crystal glazing that switches from clear to milky white has been introduced in the U.S. Although the windows do not significantly reduce the amount of light transmission, they provide privacy by reducing transparency. This type of glazing requires a steady current to keep the glass in the clear state.

Applications

Liquid crystal glazing is designed for internal applications, including partitions, display cases and bank screens. Liquid crystal glass is a popular choice for the home, corporate environment, or anyplace where there is a need for privacy or protection. Switchable liquid crystal glass is a state-of-the-art glass that provides complete privacy on demand and is becoming popular with builders, designers, architects and consumers. By eliminating the need for shades, curtains or blinds, the liquid crystal in the glass also protects fine furnishings, carpets and displays from UV damage.

High net worth individuals, government bodies and corporate setups use polymer-dispersed liquid crystal regulating light glass to embellish their homes and offices. Disneyland amusement park also uses this kind of glass. It is even used in upper segment cars like the BMW.