Bistable nematic liquid crystal displays Static flat panel displays rely on materials whose color states are bistable. This means that the image they hold requires no energy to maintain, but instead requires energy to change.

Static flat panel displays rely on materials whose color states are bistable. This means that the image they hold requires no energy to maintain, but instead requires energy to change. This results in a much more energy efficient display, but with a tendency towards slow refresh rates which are undesirable in an interactive display. Examples:

• Electrophoretic displays.
• Bichromal ball displays.
• Interferometric modulator displays.
• Cholesteric displays.
• Bistable nematic liquid crystal displays.

Bistable flat panel displays are beginning deployment in limited applications (Cholesteric displays manufactured by Magink, in outdoor advertising; electrophoretic displays in e–book products from Sony and iRex; and bistable liquid crystal displays from ZBD in store shelf labels).

Dot–pitch of the LCD The dot pitch rating of a monitor tells you just how sharp the displayed image will be.

The following are important factors for evaluating television displays:

Display size: This refers to the diagonal length of the display and usually specified in inches.

Display resolution: This refers to the number of pixels in each dimension on a display. In general a higher resolution will yield a clearer, sharper image.

Dot pitch: This measures the size of an individual pixel, which includes the length of the subpixels and distances between subpixels. It can be measured as the horizontal or diagonal length of a pixel. A smaller dot pitch generally results in sharper images because there are more pixels in a given area. In the case of CRT based displays, pixels are not equivalent to the phosphor dots, as they are to the pixel triads in LC displays. Projection displays that use 3 monochrome CRTs do not have a dot structure, so this specification does not apply.

Mechanism of LCD The liquid-crystal display has the distinct advantage of having a low power consumption than the LED. It is typically of the order of micro watts in comparison to the order of milliwatts for LEDs.

A pixel on an LCD consists of multiple layers of components: two polarizing filters, two glass plates with electrodes and liquid crystal molecules. The liquid crystals are sandwiched between the glass plates and are in direct contact with the electrodes. The two polarizing filters are the outer layers in this structure. The polarity of one of these filters is oriented horizontally, while the polarity of the other filter is oriented vertically.

The electrodes are treated with a layer of polymer to control the alignment of liquid crystal molecules in a particular direction. These rod–like molecules are arranged to match the horizontal orientation on one side and the vertical orientation on the other, giving the molecules a twisted, helical structure. Twisted nematic liquid crystals are naturally twisted and are commonly used for LCDs because they react predictably to temperature variation and electric current.

Pixels on different display technologies LCDs with high resolutions, such as large-screen LCD televisions, require an active-matrix structure.

The electrodes on one side of the LCD are arranged in columns, while on the other side they are arranged in rows, forming a large matrix that controls every pixel. Each pixel is designated a unique row–column combination, and the pixel can be accessed by the control circuits using this combination. These circuits send charge down the appropriate row and column, effectively applying a voltage across the electrodes at a given pixel.

Simple LCDs such as those on digital watches can operate on what is called a passive–matrix structure, in which each pixel is addressed one at a time. This results in extremely slow response times and poor voltage control. A voltage applied to one pixel can cause the liquid crystals at surrounding pixels to untwist undesirably, resulting in fuzziness and poor contrast in this area of the image. LCDs with high resolutions, such as large–screen LCD televisions, require an active–matrix structure.

This structure is a matrix of thin–film transistors, each corresponding to one pixel on the display. The switching ability of the transistors allows each pixel to be accessed individually and precisely, without affecting nearby pixels. Each transistor also acts as a capacitor while leaking very little current, so it can effectively store the charge while the display is being refreshed.

Mechanism of MVA This technology results in wide viewing angles while boasting good contrast ratios and faster response times than those of TN and IPS displays.

Unlike the electrode arrangement in traditional TN displays, the two electrodes corresponding to a pixel are both on the same glass plate and are parallel to each other. The liquid crystal molecules do not form a helical structure and instead are also parallel to each other.

In its natural or "off " state, the molecule structure is arranged parallel to the glass plates and electrodes. Because the twisted molecule structure is not used in an IPS display, the angle at which light leaves a pixel is not as restricted, and therefore viewing angles and color reproduction are much improved compared to those of TN displays. However, IPS displays have slower response times. IPS displays also initially suffered from poor contrast ratios but has been significantly improved with the development of Advanced Super IPS.

Multi–domain Vertical Alignment (MVA)

In this type of display the liquid crystals are naturally arranged perpendicular to the glass plates but can be rotated to control light passing through. There are also pyramid–like protrusions in the glass substrates to control the rotation of the liquid crystals such that the light is channeled at an angle with the glass plate. This technology results in wide viewing angles while boasting good contrast ratios and faster response times than those of TN and IPS displays. The major drawback is a reduction in brightness.

Patterned Vertical Alignment (PVA): This type of display is a variation of MVA and performs very similarly, but with much higher contrast ratios.