LG Display Co Ltd developed a reflective LCD panel that can display different images on front and back sides of the glass substrate and unveiled it at SID2008.
With the adoption of a reflective type electrically controlled birefringence (ECB) display mode, the panel can eliminate the need for a backlight and provide a higher outdoor visibility. Thus, the panel is intended for use in mobile devices, according to the company. For example, the new LCD panel can simultaneously function as the main and sub displays on a mobile phone, the company said.
The ECB mode is a display method based on the birefringence effect of liquid crystal cells, which is used for the standard reflective and semi-transmissive LCD panels.
Two major modifications were made to display images on both sides. First, a new reflective layer is arranged in the color filter substrate. When the images are viewed from the TFT array substrate side, the layer reflects incoming light. On the other hand, when viewed from the side of the color filter as in the case of the existing LCD panels, the light is reflected by the reflection electrode formed on the TFT array.
Another major improvement relates to the structure of the TFT array. The company formed two transistors in one pixel in order to display different images on both sides of the panel.
LG Display reportedly prototyped 2.2- and 15-inch LCD panels with the new structure. Both panels feature a reflectivity of 20%. The 2.2-inch prototype has a resolution of 160 x 120 and an aperture ratio of 43%, according to the company. The RGB three colors are arranged in a stripe pattern.
The 15-inch prototype reportedly has a resolution of 2048 x 1536 and an aperture ratio of 46%. It employs a sub-pixel arrangement with four colors, consisting of R, G and B and the additional white (W) (See related article).
These prototypes were not presented at the exhibition site or at the author's interview.