Sony Details Backlight Units of its 3D LCD TVs

Sony Corp announced three series of its Bravia LCD TVs supporting 3D video. The HX900, HX800 and LX900 use white LEDs for the backlights of their LCD panels. The backlight unit of the HX900 series is located behind the LCD panel (direct type). And those of the HX800 and LX900 series are positioned at the lateral sides of their panels (edge-lit type).

HX900 Series
The backlight unit of the HX900 series consists of groups of white LEDs, and those groups of LEDs (as units) are attached to the back of the panel like tiles. The light-emitting part of the white LED is parallel to the panel, and it lights the back of the panel by using optical elements such as a light guide plate. "It is as if edge-lit LED backlights are vertically arrayed," Sony said. This structure enables to realize a slimmer LCD panel than the structure of a normal direct-type LED backlight with LEDs whose light-emitting part is vertical to the panel. Furthermore, by controlling the light emission of each unit of LEDs, it is possible to improve the contrast. The company declined to comment on the number of separately controlled areas and the number of white LEDs.

The "HX900" series (right), which has a direct-type LED backlight, and the "XR1" series (left), which features RGB-color LED backlight

HX800 Series
The HX800 series is equipped with Sony's edge-lit white LED backlight that has a local dimming function. White LEDs are arranged in lines at the upper and lower edges of the panel. And the light emissions of groups of white LEDs are separately controlled. Controllable areas are arranged in two lines in the vertical direction. Sony did not disclose the number in the horizontal direction but said that it is 10 or less and that the areas cannot be controlled as minutely as those of a direct-type LED backlight. The HX800 uses almost the same number of white LEDs and the same optical elements as the Bravia EX700 series announced in January 2010, the company said. Edge-lit white LED backlights with a local dimming function are also being developed by Sanken Electric Co Ltd and ChiMei Optoelectronics Corp.


The "HX800" series (right), which has an edge-lit backlight with a local dimming function, and an LCD TV with a normal edge-lit LED backlight (left)

LX900 Series
The LX900 series comes with a normal edge-lit LED backlight that does not have a local dimming function. The HX900 and LX900 series have a structure where the LCD panel unit and the glass plate on the surface are integrated by filling the gap between them with newly-developed resin. The structure is called "Opti Contrast Panel." Because of the integration, the reflection of backlight and the light from outside can be reduced compared with panels made by filling the gap between the LCD panel and glass plate with air. The surface of the glass plate is coated with an AR (antireflection) film.

By Shinya Saeki, Nikkei Electronics