Understanding display options

Ever wondered about the benefits of different display technologies. Varitronix UKs engineering manager, Robert Hill, explains all Industrial and automotive display applications present a diverse range of requirements. Although mono LCD displays remain almost ubiquitous, alternative technologies are available, all offering benefits.
Monochrome LCD
Historically, monochrome LCD remains the most significant range in Varitronixs technology portfolio. Low power consumption, versatility in size and colour, plus ruggedness and reliability suit this technology to industrial applications such as factory automation and test equipment. The technology is ideal for applications seeking a cost effective solution while displaying basic content.
Monochrome LCM
LCD modules suit customers looking for a more complete solution than just the LCD glass. Options include chip-on-glass, chip-on-board and tab formats. Depending on the application, dimensions and design, this route can simplify integration into existing systems.
Free shape LCD
A new development for mono LCD, free shape LCD displays suit for specialist applications across many markets. No longer limited by rectangular or square displays, free shape LCD technology can create displays in any shape, including a circle. Product thickness, batch size and precision are improving steadily.
Colour STN
Colour Supertwisted Nematic Displays (CSTN) offer full colour reproduction at a lower cost than TFT-LCD. This technology is popular in telecommunication devices such as mobile phones and digital audio players where high volume full colour displays are desirable at a lower cost than TFT. Applications involving fast changing data, such as counters, plotters and video playback, may not be suitable as response times are often too slow.
Automotive grade STN (DSTN)
Impressively reliable and rugged with extreme operating temperatures between -40 to 80oC, DSTN suits automotive and industrial applications where everyday use involves extreme temperatures. An extra LCD cell compensates light dispersion giving clearer images and improved readability.
Similar to DSTN, except a special liquid crystal polymer film is used instead of a second LCD cell. This gives the display the same properties in a thinner footprint.

Double active STN
In DSTN an extra dummy LCD cell is used to compensate light dispersion. In double active STN this extra cell is an active display too, allowing reproduction of twp different images. This suits niche industrial, automotive and consumer applications where one dot matrix or segment series is not enough.
Small to medium sized TFT panels are available as standard products or with semi or full customisation. TFT gives high brightness, excellent contrast ratios, wide viewing angles and fast response times, perfect for colour reproduction of moving images, pictograms, charts and video. Displays are available with analogue or digital interfaces and options including widescreen, interface boards, polarisers and touchscreen capability. A process called index matching enhances viewing where optical glue is applied between the two pieces of glass. Tests have shown a 400 per cent increase in brightness and improved sunlight readability.

Mono TFT
Utilising the same technology as full colour TFT, mono TFT keeps the same positive characteristics (wide viewing angle, fast response etc) but offers contrast ratios to 1,000:1 in negative display mode. The technology suits automotive and industrial application where colour is not a prerequisite but clear viewing is imperative for safety. Driving requirements are less complex than full colour TFT.
Improved Black Nematic (IBN) display technology offers an alternative to standard mono LCD. For applications requiring exceptional contrast ratios, the negative mode (white on black) is well suited, offering a contrast ratio of approximately 500:1, far greater than mono LCD. IBN technology works like TN, except the liquid crystal molecules are vertically aligned. This also enhances viewing angle. IBN is ideal for simple interfaces such as industrial counters and automotive instrument clusters.
Bi-stable Cholesteric technology doesnt require any power to drive the display. Power is only required when information is refreshed and changed. No backlight is needed and viewing angles are extremely wide. The display improves in direct sunlight and is available in many colour combinations. This makes BCD ideal for replacing signage such as information boards and shelf labels. The panel is sensitive to mechanical pressure and requires protection.