Patent Application
20070272896
The foregoing aspects become better understood by reference to the following drawings, wherein:
One embodiment of the present invention provides a nematic liquid crystal composition applied to a multiplexed twisted nematic electro-optical display. The nematic liquid crystal composition includes the mixture of at least two components with different characteristics, for example, a first component with the first twist-related characteristics and second component with the second twist-related characteristics. For example, the first twist-related characteristic is a first positive optical anisotropy higher than a second optical anisotropy of the second twist-related characteristic. Alternatively, the first twist-related characteristic is a first dielectric anisotropy higher than a second dielectric anisotropy of the second twist-related characteristic. The mixture includes from 75% to 90% of the first component in the total weight of the mixture which is used for the main body of the nematic liquid crystal display media to transmit incident light, and from 25% to 10% of the second component in the total weight of the mixture which is used for adjusting or compensating the twisted-related characteristics.
The second component selected to adjust the values of the dielectric anisotropy or the optical anisotropy is for preventing the fast refractive index change from influencing the quality of the image especially the view angle dependency. Please refer to
The nematic liquid crystal composition is formed from mixing the first component and the second component in proper proportion. Next, the mixture temperature is raised to the phase transition temperature and then lowered to room temperature. After the foregoing processes, the nematic liquid crystal composition is still a homogenous alignment compound as the first component and the second component. Therefore, when the nematic liquid crystal composition is filled between the two substrates and applied a proper voltage, the twisted nematic electro-optical effect is presented.
The first component and the second component may be individually selected from the group of compounds represented by formulas (1), (2), and (3) as follow:
Wherein the R and the T in the formulas (1), (2), and (3) are individual the optional substituted group in which the dipole moment of the T group is stronger than the R group. R, for example, may be alkyl, aryl, and alkenyl and the T may be substituted by the group of the 2,3,4-trifluorobenzo-, the group of the 2,3,4-trifluorobenzo-oxo-difluoromethyl, and the group of the 3,5-difluoro-4-methoxylbenzo. Alternatively the R may be substituted by the straight-chain or branched alkyl group, and the T may be substituted by straight-chain or branched of the alkyl.
Another one embodiment of the present invention provides an active matrix liquid crystal display with the mixture of the liquid crystal compound. Shown in
Similar as the weight ratios of the first embodiment, the layer of nematic liquid crystal of the second embodiment may include the first component from 90% to 75% and the second component from 10% to 25% by the ratio based on the total weight of the layer of nematic liquid crystal. In an active matrix LCD, the non-linear switching elements are addressed in a multiplex scheme. They charge to the TFT of a pixel from a matrix driving circuit in the limited time they are active. Then they become inactive until they are addressed again in the next cycle. Accordingly, the liquid crystal molecules may show short response time and reduced viscosity. For example, the large positive dielectric anisotropy of at least +3.5 recommend, increasing the voltage holding ratio up to 98%, and the positive dielectric anisotropy or the optical anisotropy of the second component must be less than the positive dielectric anisotropy or the optical anisotropy of the first component.
In the present invention, when applied a driving voltage to the TFTs of the pixels at least two different inclinations of the nematic liquid crystal show in the pixels of the active matrix LCD. The driving voltage is referred to as a gray level voltage to control the intensity of light transmitted through the pixels. A gray level voltage is generally known as any driving voltage greater than threshold voltage up to about 1.0 to 4.5 volts, and used to generate dissimilar shades of color so as to create different colors and images. The higher the gray voltage is applied across to the nematic liquid crystal of selected said pixels, the weaker the intensity of light transmitted is.
While the invention is susceptible to various modifications and alternative forms, a specific example thereof has been shown in the drawings and is herein described in detail. It should be understood, however, that the invention is not to be limited to the particular form disclosed, but to the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 95118280 | May 2006 | TW | national |
