Patent Application
20060170849
1. Field of Invention
The invention relates to a LCD panel and, in particular, to a transflective LCD panel.
2. Related Art
The liquid crystal display (LCD) technology includes both the reflective type and the transmissive type. The former does not need a backlight source. It uses a reflective plate attached into the LCD panel to reflect external light. One of its advantages is energy conservative (only a fraction of power needed for the transmissive LCD). Its major drawback is that it is hard to view the screen in a darker environment and its contrast is worse. Therefore, it usually uses a front light source as its auxiliary source. However, when the environmental light is not sufficient, the purely reflective LCD has inferior contrast and brightness. On the other hand, the transmissive LCD has a weaker contrast when the environmental light is too strong. Therefore, it would be ideal to make the transflective type of LCD panels by combining both technologies. Such LCD panels have the advantages of both types, using external light when it is strong and turning on the backlight when the environment is dark.
For portable electronic device displays, such as those on mobile phones and PDA's, the primary concern is low voltage and power consumption. Therefore, for those that are not featuring animations, TN/STN displays are the best choices. However, when implementing the transflective type of structures on conventional TN displays, the thickness of the liquid crystal layer is fixed while the light paths of transmissive and reflective light are different. Therefore, the reflective images have an inferior quality. It is thus difficult to have both transmissive and reflective display on a conventional TN display.
To increase the quality of reflective images, one has to insert a dual gap structure. That is, one builds a reflective structure inside the liquid crystal layer to control the light paths of the transmissive and reflective light. However, this method complicates the manufacturing process and the product structure. Moreover, normal transflective LCD often has some brightness attenuation when light travels through the reflective structure, resulting in limited applications.
In view of the foregoing problems in the prior art, the invention provides a transflective LCD panel which, along with a backlight structure of the transmissive LCD panel and polarizers with compensation films added to the top and bottom of the LCD panel structure, generates both transmissive and reflective effects.
The backlight module is the primary element of the transmissive LCD panel to provide the LCD panel a homogeneous light source with high brightness and wide viewing angle. The basic principle is to convert a commonly used point or line light source into a highly bright and homogeneous plane light source through an effective mechanism. The normal backlight structure uses linear cold cathode fluorescent tube. The light enters a light guide plate or via a reflector to reflect it into light guide plate. The function of the light guide plate is to control the direction of the light beam to increase and homogenize its brightness. One can use an organic light guide plate with high transmissivity and make reflective dots on the plate surface. Through the reflective dot design, light beams undergo several times of total reflections and deflections, thereby homogeneously distributing light on the plate to form a plane light source.
The disclosed transflective LCD panel combines the backlight structure and two pieces of polarizers with compensation films to produce image reflection effects. Its structure includes a first transparent substrate, a second transparent substrate, a liquid crystal material, a first polarizer, a second polarizer, a backlight structure, and a gap between the first and second transparent substrates. The TN liquid crystal material is filled in the gap. The first and second transparent substrates are imposed a voltage on the TN liquid crystal material through several electrodes formed on their surfaces. The first transparent substrate has a first polarizer. The second transparent substrate has a second polarizer. These two polarizers have a compensation film with a delay of one-quarter wavelength. The backlight structure is formed on the surface of the first transparent substrate that is in contact with the exterior for providing an incident beam. The incident beam penetrates through the first transparent substrate and emits via the second transparent substrate, forming penetrating images. At the same time, the external incident light can enter through the second transparent substrate. Using the backlight structure design and two polarizers with compensation films, image reflection effects can be achieved on the second transparent substrate.
The twisting angle of the TN liquid crystal material is between 0 and 50 degrees. The transimission axis of the first and second polarizers are perpendicular to each other. The angle between the slow axis of the compensation film and the transmission axis of the polarizer is 45 degrees. To enhance the contrast and image quality of the transmissive display panel, one can also form an anti-reflective (AR) layer on the display panel.
The invention will become more fully understood from the detailed figures given hereinbelow, and thus are not limitative of the present invention, and wherein:
The invention discloses a transflective liquid crystal display (LCD) panel. It combines a backlight structure and polarizers with compensation films to achieve the transmissive and reflective displays on a transmission type panel.
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To increase the contrast and quality of transmissive images, one can form an anti-reflection (AR) coating on the side of the display panel, reducing extra light reflected by metal signal lines in the LCD panel. The AR coating can be formed on the surface of the second transparent substrate using a specially processed black matrix. The black matrix can be made from black resin or Cr/CrOX.
The disclosed transflective LCD panel can produce transmissive and reflective images without needing any reflector or dual gap structure. As it does not require any reflector, no attenuation occurs to the transmissive light and the light usage efficiency in the transmissive mode is enhanced.
Certain variations would be apparent to those skilled in the art, which variations are considered within the spirit and scope of the claimed invention.
