Advanced Imaging


Advanced Imaging Magazine

Updated: January 12th, 2011 10:01 AM CDT

The Shape of Things to Come

Falling in love with heart-shaped (and other non-traditional) LCDs
heart-shaped LCD
© NEC Electronics America
Figure 2
© NEC Electronics America
Figures 1 and 2: Conventional layouts for driving the row and columns are oriented in horizontal gate and vertical data lines as shown in Figure 1 (left). The complexity of the heart shape, specifically where the indentation occurs, requires driving both the gate and data lines from two sides of the display. The illustration shown in Figure 2 (right) shows the gate and line drivers separated with one edge sharing a driver of each type.
Figure 3
© NEC Electronics America
Figure 3: This design technique could be applied to many different and eye-catching shapes, such as the outline of a ship, a car or possibly a rain drop.

By Robert Dunhouse, NEC Electronics America

Liquid crystal displays (LCDs) are entwined in our everyday lives. They are the vehicle by which we visually communicate entertainment, diagnostic and analytical information. They offer many advantages compared to older technologies such as cathode ray tubes (CRTs), including thin profiles, bright displays, lighter weights and lower power consumption.

As with most display technologies, LCDs primarily come in only two types: rectangular and square. But in today's world, we are surrounded by a variety of complex shapes and forms. Fitting a rectangular display into a design with complex shapes is a compromise at best. Instead, what if a display could be designed to fit the end application, rather than the application having to be shaped to fit the display? Automotive systems, for example, are a likely application for LCDs in non-traditional shapes.

Many cars use curved hoods to protect the instrument panels from direct sunlight and to minimize blinding surface reflections that could interfere with a driver's vision. Although instrument clusters include a speedometer that typically is round in shape, some designers now are replacing those mechanical speedometers with LCDs that simulate the same analog functionality. The curved hood and the round speedometer are examples of complex shapes that must be adapted to incorporate a rectangular or square display. This creates two challenges. The first is how to fit a square display under a curved hood. The second is how to use a square display as a round simulation of an analog speedometer.

Today, these challenges are overcome by designing the instrument pod to be slightly larger than the square display and masking the viewable area of the display with a round overlay. However, these approaches restrict the overall image size that can be realized and, from a component cost, are more expensive due to the amount of materials wasted. By using a round or semicircular-shaped display, automotive designers could better match the instrument pod size, or allow room so that additional instrumentation could be fitted. Alternatively, using a fitted display also could allow designers to increase image size without a change in the overall size of the instrument pod. Recognition for the potential of nontraditional-shaped displays is beginning to emerge. To date, the challenges surrounding this type of LCD design have been significant. However, companies such as NEC LCD Technologies are driving innovations to help resolve some of these issues.

As a demonstration of its design capability, NEC LCD Technologies, Ltd. (Kawasaki, Kanagawa, Japan), introduced the first prototype of a heart-shaped LCD module at the 2008 Society for Information Display (SID) Symposium. The display illustrates rounded edges, which could not be achieved based on conventional amorphous-silicon thin-film transistor (TFT) driver ICs, as they are rectangular in shape and would need to be mounted on the glass substrate. Creating nonrectangular driver ICs using this technology can only be done through an expensive and prohibitive splicing procedure. System-on-glass (SOG) technology composed of low-temperature polycrystalline silicon thin-film transistors (LTPS TFTs) was used to form the display drivers directly on the glass substrate. The advantage is that both the TFT pixel array and its drivers are patterned and built up simultaneously on a single glass substrate, allowing for nonrectangular TFT drivers that can follow the overall form of the display. This highly integrated design also allows for a very small bezel surround.

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