Patent Application
20070085958
The present invention relates to liquid crystal displays, and particularly to a liquid crystal display having a plurality of common and pixel electrodes on both of substrates thereof.
A liquid crystal display (LCD) utilizes the optical and electrical anisotropy of liquid crystal molecules to produce an image. The liquid crystal molecules have a particular passive orientation when no voltage is applied thereto. However, in a driven state, the liquid crystal molecules change their orientation according to the strength and direction of the driving electric field. A polarization state of incident light changes when the light transmits through the liquid crystal molecules, due to the optical anisotropy of the liquid crystal molecules. The extent of the change depends on the orientation of the liquid crystal molecules. Thus, by properly controlling the driving electric field, an orientation of the liquid crystal molecules is changed and a desired image can be produced.
The first type of LCD developed was the TN (twisted nematic) mode LCD. Even though TN mode LCDs have been put into use in many applications, they have an inherent drawback that cannot be eliminated; namely, a very narrow viewing angle. By adding compensation films on TN mode LCDs, this problem can be mitigated to some extent. However, the cost of the TN mode LCD is increased. Therefore, a totally different driving means called IPS (in-plane switching) was proposed as early as 1974. Then in 1993, Hitachi Corporation filed its first US patent application concerning IPS, in which an IPS mode LCD was disclosed.
Referring to
When no voltage is applied to the common and pixel electrodes 141, 142, the long axes of the liquid crystal molecules is in the rubbing direction of the alignment layers 131, 132. Because the rubbing direction of the alignment layers 131, 132 is the same as the polarizing axis of the polarizer 122, light beams passing through the polarizer 122 can pass through the liquid crystal layer 113, and polarizing directions of the light beams do not change. Because the polarizing axes of the polarizers 121, 122 are perpendicular to each other, the light beams cannot pass through the polarizer 121, and are absorbed by the polarizer 121. Thus the IPS LCD 100 is in an “off” state, and cannot display images.
As shown in
However, because the common electrode 141 and the pixel electrode 142 are both disposed adjacent to the second substrate 112, and the liquid crystal layer 113 has a certain thickness, it is difficult for the electric field 114 between the common and pixel electrodes 141, 142 to grasp those liquid crystal molecules that are distal from the second substrate 112. Thus such liquid crystal molecules cannot be readily or fully twisted to a predetermined angle in the electric field 114, such that a viewing angle, a degree of chroma, and a transmission ratio of the IPS LCD 100 are decreased.
Therefore, a new LCD that can overcome the above-described problems is desired.
In a preferred embodiment, a liquid crystal display includes a first substrate, a second substrate opposite to the first substrate, a liquid crystal layer sandwiched between the first substrate and the second substrate, a plurality of first common electrodes and first pixel electrodes provided at the first substrate, and a plurality of second common electrodes and second pixel electrodes provided at the second substrate.
Other advantages and novel features will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
Referring to
The first substrate assembly 201 includes a first polarizer 221, a first substrate 211, a color filter 230, a first insulating layer 235, a first passivation layer 243, and a first alignment layer 231, disposed in that order from top to bottom. The first substrate assembly 201 further includes a plurality of first common electrodes 241 disposed on an inner surface of the color filter 230 and a plurality of first pixel electrodes 242 disposed on an inner surface of the first insulating layer 235. The first common electrodes 241 and the first pixel electrodes 242 are alternately arranged.
The second substrate assembly 202 includes a second alignment layer 232, a second passivation layer 244, a second insulating layer 236, a second substrate 212, and a second polarizer 222 disposed in that order, from top to bottom. The second substrate assembly 202 further includes a plurality of second common electrodes 251 disposed on an inner surface of the second substrate 212 and a plurality of second pixel electrodes 252 disposed on an inner surface of the second insulating layer 236. The second common electrodes 251 and the second pixel electrodes 252 are alternately arranged. Each second common electrode 251 corresponds to a respective first common electrode 241. Each second pixel electrode 252 corresponds to a respective first pixel electrode 242. Referring to
The first and second substrates 211, 212 are made from a transparent material, such as glass or quartz. The liquid crystal layer 213 includes a plurality of nematic-type liquid crystal molecules. The electrodes 241, 242, 251, 252 may be made from a transparent electrically conductive material such as indium-zinc-oxide (IZO) or indium-tin-oxide (ITO), or from material including any one or more items selected from the group consisting of aluminum, gold, silver, chromium, nickel, titanium, copper, molybdenum, niobium, and an electrically conductive alloy.
As shown in
In summary, the first common electrodes 241 and the first pixel electrodes 242, and the second common electrodes 251 and the second pixel electrodes 252, respectively produce two electric fields 214 in the liquid crystal layer 213. A combined strength of the electric fields 214 is uniformly distributed in the liquid crystal layer 213, so that all the liquid crystal molecules can be sufficiently twisted. In particular, all the liquid crystal molecules in each of pixel regions defined by the electrodes 241, 242, 251, 252 can be sufficiently and uniformly twisted. That is, even those liquid crystal molecules distal from either of the substrates 211, 212 can be grasped by the combined electric fields 214 produced by the electrodes 241, 242, 251, 252 and twisted to a predetermined angle. Thus a viewing angle, a degree of chroma, and a transmission ratio of the LCD 200 are improved.
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 |
|---|---|---|---|
| 200510100412.3 | Oct 2005 | TW | national |
