LCD panels equipped with a built-in touch sensor are drawing people's attention at FPD International 2007.
While the technology itself had already been proposed, technical development has been intensifying because the improvement of user interfaces using touch sensors is regarded as an important factor in device development.
Sharp Corp exhibited the LCD panel with a built-in optical sensor, which was unveiled in August 2007. In this product, a photodiode is formed for each pixel by using the LCD panel production process.
The diode is used to detect the changes in light intensity caused when the panel is touched. In this way, the product functions as a touch panel or a scanner. This mechanism is similar to the technology developed by Toshiba Matsushita Display Technology Co Ltd (See related article 1).
Sharp, however, improved the image recognition algorithms, thereby making it possible to use the panel in a various luminance conditions (0-100,000 lx).
Toshiba Matsushita Display Technology's panel is the same as that exhibited last year. The biggest problem of this panel is the detection sensitivity that varies depending on the ambient light.
While promoting the technical development to solve this problem, the company is considering the adoption of the capacitance and resistance detection type sensors in addition to the optical sensor. This is quite contrary to Sharp's strategy focused only on the optical sensor.
Samsung Electronics Co Ltd of Korea exhibited a 12.1-inch WXGA panel featuring the touch panel function. The product is manufactured based on the Integrated Touch Sensor Technology (iTSP) in which a resistance sensor is formed in each pixel of LCD panel.
Compared with the existing method where a touch screen is attached on the panel, the thickness of the LCD module can be reduced from 7.8mm to 4.8mm. Along with the 12.1-inch panel, a 7-inch WVGA panel based on the same technology is on display.
AU Optronics Corp (AUO) of Taiwan exhibited its In-Cell Multi-Touch Panel, a 4.3-inch LCD panel with a built-in touch sensor (See related article 2). The company is showcasing panels with two kinds of sensors, namely the capacitance and the resistance detection type sensors. The product can simultaneously detect up to five points.