The present invention relates to vertical alignment liquid crystal displays (LCDs), and particularly to a vertical alignment LCD having continuous domains.
Since LCDs are thin and light, consume relatively little electrical power, and do not cause flickering, they have helped spawn product markets such as for laptop personal computers. In recent years, there has also been great demand for LCDs to be used as computer monitors and even televisions, both of which are larger than the LCDs of laptop personal computers. Such large-sized LCDs in particular require that an even brightness and contrast ratio prevail over the entire display surface, regardless of observation angle.
Because the conventional TN (twisted nematic) mode LCD cannot easily satisfy these demands, a variety of improved LCDs have recently been developed. They include IPS (in-plane switching) mode LCDs, optical compensation TN mode LCDs, and MVA (multi-domain vertical alignment) mode LCDs. In MVA mode LCDs, each pixel is divided into multiple domains. Liquid crystal molecules of the pixel are vertically aligned when no voltage in applied, and are inclined in different directions according the domains they are in when a voltage is applied. In other words, in each pixel, the effective direction of the electric field in one domain is different from the effective direction of the electric field in a neighboring domain. Typical MVA mode LCDs have four domains in a pixel, and use protrusions and/or slits to form the domains.
However, the four-domain configuration can only compensate visual performance in four directions. The overall viewing angle characteristics of the MVA LCD 1 are still inherently limited, and the MVA LCD 1 cannot satisfactorily present a uniform display at all viewing angles.
The protrusions 211, 221 have an arcuate shape, and the center portions thereof according to a region 28 have a larger curvature. Therefore, when a voltage is applied to the electrodes and protrusions 211, 221, the liquid crystal molecules 26 in the region 28 are oriented essentially only in two directions. This means that in the region 28, projections of the liquid crystal molecules 26 on the substrates are aligned parallel to the polarizing axis of the polarizer of the LCD 2. That is, projections of the long axes of the liquid crystal molecules 26 on the substrates are parallel to the polarizing axis of the polarizer. In operation, ambient incident light becomes linearly-polarized light after passing through the first polarizer. The polarizing direction of the linearly-polarized light passing through the region 28 does not change, because of transmission along the long axes of the liquid crystal molecules 26. Accordingly, the light passing through the region 28 cannot pass though the second polarizer that has a polarizing axis perpendicular to that of the first polarizer. As a result, the region 28 is liable to form a dark area when the LCD 2 is used to display images.
What is needed, therefore, is a continuous domain vertical alignment LCD which can provide a uniform display at all viewing angles without any dark areas.
In a preferred embodiment, a continuous domain vertical alignment LCD includes a first substrate and a second substrate, liquid crystal molecules interposed therebetween, and a plurality of curved first and second protrusions disposed at insides of the first and second substrate respectively. Each of the first and second protrusions respectively defines a first curve portion having a first substantially rectilinear first part, and a second curve portion having a second substantially rectilinear second part. The first part connects to the corresponding second part.
The projections of the liquid crystal molecules affected by the parts projected to the second substrates are not parallel to the polarizing axis of the polarizer of the second substrates. Therefore, the LCD avoid yielding a dark area similar to that of the conventional LCD. Thus, the LCD provides a more even display performance at various different viewing angles compared to the conventional LCD.
Other advantages and novel features will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
Referring to
Each of the first protrusions 411 and the second protrusions 421 has a mainly arcuate shape, and a triangular cross-section. Each of the first protrusions 411 includes a first curve portion 481 and a second curve portion 482. The first curve portion 481 has a part 483, which is substantially rectilinear. The second curve portion 482 has a part 484, which is substantially rectilinear. The part 483 connects to the part 484. The second protrusions 421 have a shape similar to that of the first protrusions 411. That is, each of the second protrusions 421 includes a first curve portion 491 and a second curve portion 492. The first curve portion 491 has a part 493, which is substantially rectilinear. The second curve portion 492 has a part 494, which is substantially rectilinear. The part 483 connects to the part 484.
Typically, maximum widths of the first protrusions 411 are larger than maximum widths of the second protrusions 421. In the illustrated embodiment, the maximum width of the first protrusions 411 is about 10 microns, and the maximum width of the second protrusions 421 is about 7.5 microns.
When no voltage is applied to the LCD 4, most of the liquid crystal molecules 46 between the first substrate 41 and the second substrate 42 are aligned in vertical directions. Therefore light beams passing between the first and second substrates 41, 42 do not change their polarization states.
Also referring to
The visual effect of the LCD 4 is the sum of multiple smoothly continuous domains, except in the regions between the connecting parts 483, 484 of the first protrusions 411 and the connecting parts 493, 494 of the second protrusions 421. This is because all the parts 483, 484, 493, 494 are substantially rectilinear. In said regions, the orientations of the liquid crystal molecules 46 are affected by the parts 483, 484, 493, 494, and therefore projections of the liquid crystal molecules 46 on the substrates 41, 42 are not parallel to the polarizing axis of the second polarizer of the second substrate 42. Therefore the LCD 4 avoids yielding a dark display area corresponding to said regions, unlike in the case of the conventional LCD 2. Thus, the LCD 4 provides a more even display performance at various different viewing angles compared to the conventional LCD 2.
It is to be understood, however, that even though numerous characteristics and advantages of preferred embodiments have been set out in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the
Number | Date | Country | Kind |
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93122893 | Jul 2004 | TW | national |