Patent Application
20080106680
The present invention relates to liquid crystal displays (LCDs), and especially to a transflective liquid crystal display device.
LCD devices have the advantages of portability, low power consumption, and low radiation, and because of this they have been widely used in various portable information products such as notebooks, personal digital assistants (PDAs), video cameras, and the like. Furthermore, LCD devices are considered to have the potential to completely replace CRT (cathode ray tube) monitors and televisions.
A transmissive LCD device displays images using light from a back light device, and is usable under any ambient light conditions. Because the transmissive LCD device requires a back light having high brightness, it has high power consumption. Further, the back light device can not be used for a long time.
Unlike the transmissive LCD device, a reflective LCD device utilizes ambient light beams from a natural light source or from an external artificial light source. The reflective LCD device can be used for a long time. However, the reflective LCD device is useless when the weather is unfavorable or when the external light source is not available.
To overcome the problems described above, a transflective LCD device has been developed. The transflective LCD device can compensate for the respective shortcomings of the reflective LCD device and the transmissive LCD device. That is, the transflective LCD device can selectively provide a reflective or transmissive mode, depending on the prevailing needs of users.
In the reflective mode, an ambient light ray from an external light source such as natural sunlight passes through the color filter 5, the first electrode layer 6, the first aligning film 7, the liquid crystal layer 8, the second aligning film 17 in that order, and is then reflected by the reflective region 161 of the second electrode layer 16 to pass back through the second aligning film 17, the liquid crystal layer 8, the first aligning film 7, the first electrode layer 6, and the color filter 5 in that order. That is the ambient light ray passes through the color filter 5 twice.
In the transmissive mode, light beams from the backlight module 18 transmit through the transmission region 162 of the second electrode layer 16, the second aligning film 17, the liquid crystal layer 8, the first aligning film 7, the first electrode layer 6, and the color filter 5 in that order. That is the ambient light ray passes through the color filter 5 once.
Because the light beams passes through the color filter 5 twice when the LCD device 10 works in the reflective mode, and the light beams passes through the color filter 5 once when the LCD device 10 works in the transmissive mode, the reflective mode has a better color purity than the transmissive mode in the transflective LCD device 10. That is, there is a difference in color purity as between the reflective mode and the transmissive mode.
What is needed, is an LCD device that can overcome the above-described deficiencies.
In one preferred embodiment, an exemplary transflective liquid crystal display device has a liquid crystal panel, and a backlight module adjacent to the second color filter substrate. The liquid crystal panel includes a first color filter substrate, a thin film transistor substrate, a second color filter substrate, a first liquid crystal layer being provided between the first color filter substrate and the TFT substrate, and a second liquid crystal layer being provided between the second color filter substrate and the TFT substrate.
Other advantages and novel features will become more apparent from the following detailed description of preferred embodiments when taken in conjunction with the accompanying drawings.
Reference will now be made to the drawings to describe the preferred embodiments in detail.
Referring to
The liquid crystal panel 20 includes a first color filter substrate 210, a thin film transistor (TFT) substrate 220, and a second color filter substrate 230. A first liquid crystal layer 240 is provided between the first color filter substrate 210 and the TFT substrate 220, and a second liquid crystal layer 250 is provided between the second color filter substrate 230 and the TFT substrate 220. The first and the second liquid crystal layers 240, 250 have a substantially same thickness.
Each of the first and second color filter substrates 210, 230 has a color filter layer (not shown). The two color filter layers each have a plurality of color units, having a substantially same arrangement and corresponding to each other. In addition, two out surfaces of the first and second color filter substrates 210, 230 respectively have a polarizer (not shown) disposed thereat, which polarizing axles are perpendicular to each other.
The first color filter substrate 210 further has a first common electrode layer 260, and a first aligning film 281, disposed at an inner surface of the first color filter substrate 210 in that order from top to bottom, adjacent to the first liquid crystal layer 240. And the second color filter substrate 230 further has a second common electrode layer 265, and a fourth aligning film 284, disposed at an inner surface of the second color filter substrate 230 in that order from bottom to top, adjacent to the second liquid crystal layer 240. The first and the fourth aligning films 281, 284 have two aligning directions, same to each other.
The TFT substrate 220 has two thin film transistor arrays, respectively disposed at two opposite surfaces of the TFT substrate 220. The two thin film transistor arrays have a substantially same arrangement. The TFT substrate 220 has a first pixel electrode layer (not labeled) and a second aligning film 282, disposed at an external surface thereof adjacent to the first liquid crystal layer 240, and further has a second pixel electrode layer (not labeled) and a third aligning film 283, disposed at an external surface thereof adjacent to the second liquid crystal layer 250. The second and the third aligning films 282, 283 have two aligning directions, same to each other. The first pixel electrode layer includes a plurality of first pixel electrode units 221, which is transflective electrode, having a transmission region 224 and a reflective region 225, alternately disposed thereof. When a voltage is provided thereat, the first pixel electrode layer and the first common electrode layer 260 can form an electrical filed to control the rotation of the first liquid crystal layer 240 to realize the image display. The second pixel electrode layer has a plurality of second pixel units 222, which is transparent pixel electrode. When a voltage is provided thereat, the second pixel electrode layer and the second common electrode layer 265 can form an electrical filed to control the rotation of the second liquid crystal layer 250 to realize the image display.
The first color filter substrate 210, the TFT substrate 220, and the first liquid crystal layer 240 therebetween define a plurality of pixel regions 270. Each pixel region 270 has a transmissive region 271, corresponding to the transmission region 224 of the first pixel electrode unit 221, and a reflective region 273, corresponding to the reflective region 225 of the first pixel electrode unit 221.
When ambient light rays are enough, the transflective LCD device 20 works in a reflective mode. The external light rays pass through the first color filter substrate 210 and the first liquid crystal layer 240, and then are reflected by the reflective region 225 to pass back through the first liquid crystal layer 240, and the first color filter substrate 210 to realize the image display. Thus the external light rays transmit through the first color filter substrate 210 twice. When ambient light rays are insufficient, the transflective LCD device 20 works in a transmissive mode. The transflective LCD device 20 utilizes the backlight module 29 to provide light beams to the liquid crystal panel 20. The light beams from the backlight module 29 transmit through the second color filter substrate 230, the second liquid crystal layer 250, the TFT substrate 220, the first liquid crystal layer 240 and the first color filter substrate 210 in that order to realize the image display. The light beams thereof respectively transmit through the first and the second color filter substrates 210, 230, that is the light beams passes through two color filter substrates. Because the first and the second color filter substrates 210, 230 have a same arrangement of color filter layers thereof, and the TFT substrate 220 has two same arrangement of the two TFT arrays disposed at two opposite external surface of the TFT substrate 220, and the first and the second liquid crystal layers 240, 250 have a same thickness, and the first and the fourth aligning films 281, 284 have a same aligning direction, and the second and the third aligning films 282, 283 have a same aligning direction, the light beams respectively work in the reflective mode and the transmissive mode have a same optical path. Thus, the two light beams respectively working in the reflective mode and the transmissive mode have a substantially same color purity.
Referring to
Further or alternative embodiments may include the followings. In one example, a reflective layer can be disposed between a pixel electrode and an aligning film. In further example, a transflective film is provided at least one of the external surfaces of the TFT substrate. The reflective region corresponds to a reflective part of the transflective film. That is the LCD device utilizes the reflective part of the transflective film to realize working in the reflective mode, instead of the transflective electrode and the reflective layer.
It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 95136311 | Sep 2006 | TW | national |
