Liquid Crystal Display Properties and Technology
Director (Vector Director)
The direction of orientation present in a liquid crystal, up or down to the bottom of the page, can be represented by a vertical arrow. There are always two possible choices to aim toward the principal. The two directions are equivalent in the liquid crystal, so any choice is good. The molecular direction of preferred orientation in liquid crystal mesophases.
Electric Field Influence
In general, liquid crystal molecules have permanent or induced electric dipoles, both along and across the long axis of the molecule. The molecule is oriented so that the larger of the two electric dipoles remains oriented along the direction of the electric field. The electric field vector causes the liquid crystal director to be oriented toward the field.
The electric field strength needed to guide the direction vector of a liquid crystal is relatively low, as the principal vector of a liquid crystal is usually free to orient in any direction. The higher the electric dipole of the molecule or the electric field, the greater the bias supply.
The result of applying a field is the deformation in the liquid crystal molecules near the surface and normal behavior of molecules away from it. A deformed liquid crystal is one whose director changes its direction from one point to another in the liquid crystal.
Display Characteristics
- Resolution: The term resolution is used broadly to describe the level of spatial detail of a screen. Most commonly, resolution is specified in pixels per unit length.
- Number of pixels represented horizontally and vertically. In the configuration of monitors, you can choose from several resolutions, with some more desirable than others depending on the size of the screen. A higher resolution means higher image quality. Note that the graphics card can limit the maximum resolution of a monitor.
- Refresh Rate: The refresh rate is the number of times the image is drawn per second, i.e., the number of times the electron beam sweeps the screen completely. In a CRT display, this is an important parameter as it relates to visual fatigue. If it is not high enough, there is a flickering effect of the image that many researchers see as causing visual fatigue. PDPs also need a continuous refresh to create a sense of continuity of the displayed image, but as the whole screen is updated at once, the eyestrain caused is less than that associated with CRTs.
- Response Time: Typically takes values of 25 ms in the case of liquid crystals inside an actual TFT screen to respond to the applied current, which is usually more than enough to trick the human eye into seeing fluid motion. The response times listed include an element of latency, when a pixel stays on for a short time after power is removed.
TFT Technology
TFT (Thin Film Transistor): A type of LCD flat panel display in which each pixel is controlled by one, two, three, or four transistors. TFT technology provides the best resolution of all current flat-screen techniques. TFT screens are sometimes called active-matrix LCDs.