1. Field of Invention
The invention relates to a two-screen LCD panel and, in particular, to a double-sided LCD panel that uses a single panel to implement dual display.
2. Related Art
Among so many electronic devices, having a light weight and a compact size becomes the primary concern for planar displays. In addition to the continuous improvement in the reaction speed, resolution, and screen quality of the displays, engineers also pursue for breakthroughs in functions and display modes. For example, the market is recently advertising the dual display mode function in consumer electronics. That is, the screen is simultaneously sent to two output devices (such as CRT screens and LCD panels). This method does not only extend the screen space to a wilder view field, it can also function as a real-time monitoring system for quickly job switching and processing more work.
Since the LCD panel has become the main power on the display market. Therefore, how to make an electronic system simultaneously drive two output devices through a circuit design has been the main research topic of all manufacturers. However, most dual display systems use two independent liquid crystal displays (LCD""s) to make a set of dual display. This method requires twice as much cost and space as a single LCD. Moreover, it does not satisfy the need for lightness and compactness. Consequently, developing a better dual display is an important subject.
In terms of the modern LCD technology, the reflective LCD""s include the reflective type and the transflective type. The former does not need a backlit source. It utilizes a reflective plate attached on the LCD panel to reflect external light. Its advantage is being very power-effective (only a small fraction of the transparent LCD""s). Its drawback, however, is that the screen is not easy to view in a dimmer environment and has a worse contrast. Therefore, it normally uses a front light source as the auxiliary light source. Nevertheless, the contrast and brightness of a purely reflective type LCD are greatly reduced when the environment is not bright enough. The purely transparent type LCD usually has an insufficient contrast when the environment is too bright. Therefore, it would be better if one can combine the auxiliary backlit source and the transparent technology to form the transflective LCD that has the advantages of both the transparent and reflective LCD""s. When the external light is sufficient, the transflective type display uses the external light. When the external light is too dim, the backlit source is turned on. Therefore, this is a wonderful solution of saving energy and providing auxiliary light. Currently, how to combine existing display technologies to make dual display monitors is an important issue in the industry, but is nonetheless seldom studied.
To achieve the above-mentioned objective, the invention uses a transflective LCD panel along with a light-emitting device to make a dual display LCD panel. One surface of the transflective panel uses the transparent mode for display, while the other surface uses the reflective mode. At the same time, the LCD panel in the transparent mode uses the light-emitting device as a backlit source. The reflective mode uses the light-emitting device as the front light source only when the environment is dark.
The disclosed double-sided LCD includes a transflective display panel, which is comprised of a first transparent substrate, a second transparent substrate, several electrodes, a partial reflective layer, and a liquid crystal material. A space is inserted between the first transparent substrate and the second transparent substrate. The liquid crystal material fills up this space. The electrodes are formed on the first transparent substrate and the second transparent substrate for imposing a voltage on the liquid crystal material. The partial reflective layer is formed on the surface of the second transparent substrate for allowing part of the incident light to be reflected by the reflective layer and to go out through the first transparent substrate. This forms a reflective display panel. The rest of the incident light penetrates through the reflective layer and comes out from the second transparent substrate, forming a transparent display panel. A light-emitting device is provided at the interface between the first transparent substrate and the external environment for providing the incident light. It simultaneously functions as the front light source of the reflective display panel and the backlit source of the transparent display panel. The light-emitting device can be made of a light source and a light-guiding plate. The light-guiding plate is put at one side of the reflective display panel. The light source emits light toward the light-guiding plate for providing a homogeneous incident beam of light.
In addition, the invention further contains several thin film transistors (TFT""s) for controlling the electrodes and the voltage they impose on the liquid crystal material. The invention may also contain a polarizer and a phase-difference wavelength plate attached on the reflective display panel and the transparent display panel, respectively, for blocking unnecessary incident and environmental light. At the same time, to increase the contrast and image quality of the transparent display panel, an anti-reflective (AR) mask can be formed on the sides of the transparent display panel.