FEATURE DISPLAYS & UIS DISPLAY TECHNOLOGY OPTIONS:
THERE BUT NOT ALWAYS CLEARLY SEEN With such a wide range of displays now available, it is important to be able to identify high-quality products, which are suited to their specific markets. Here CDSexplores some of the options available
A
lthough there has been significant growth in the larger format TFT
Displays such as Samsung’s Public Information (PID) displays including some amazing applications like Digital Bus shelters in London, small format displays including PMOLEDs, AMOLEDs, Monochrome LCDs and TFTs have a huge market share and will continue to be utilised in many interesting and innovative applications such as crypto currency wallets, etc. Although OLEDs are used in a limited
number of applications such as Smartphone displays such as the Samsung Galaxy J6, improvement in the technology and wider acceptance of the lifetime etc. there will be a wide-ranging increase in uses and applications as new products are created. In addition to the optimisation of
standard monochrome TN (narrow viewing angle, STN (wider viewing angle) and FSTN (retardation film) based technologies, niche technologies such as Improved Black Nematic Display (IBN) are also available and very popular in automotive applications or products where high ambient conditions can be an issue. Linked to sunlight readability CDS also offer the option of optical bonding which incorporates, applying an optical gel between the LCD and the touchscreen or top cover glass to limit the refraction of light within the cell which distinctively improves the visibility on the screen when exposed to direct sunlight or high ambient conditions. For clarification, when looking at the
differences between TN and STN, the difference lies in the angle in which the liquid crystal is twisted. TN is twisted at an angle of 900
angle between 90 and 2700
, while STN can have an . This
provides a higher contrast than twisted nematic (TN) displays. With the change of twisted angle and different angles of polarizer film, STN can display yellow- green, blue and grey modes. STN is superior to TN in more duty cycles and excellent opto-electro functions. STN also requires less power and is less expensive to manufacture than TFT LCDs for example, another popular type of LCD. However, STN displays typically
10 OCTOBER 2018 | ELECTRONICS
monochrome displays to show basic information such as gas testing equipment, fire alarms etc. and that is a stable market. The big growth in small TFT LCDs is in full colour where resolutions and viewing angles (IPS, MVA etc.) have improved dramatically but also the optimised interfaces such as MiPi or RGB up to 24 Bit making interfacing easier and cleaner. With more users wanting interactivity,
suffer from relatively lower image quality and slower response time than TFT displays limiting it for certain uses. STN displays are still used in some inexpensive mobile phones and informational screens of some digital products but are dramatically being replaced by colour TFT displays as the cost of those has reduced and the quality increased.
TRUE COLOUR ENHANCEMENT FSTN has special retardation films added with the rear polarizer to make up for the interfering colour of STN so that a true colour can be seen. Different angles of the film can create more options, i.e. positive, white/grey background with black font; negative, black background with grey/white font. Other options with filters etc. are also available. Despite more applications moving to full colour many applications still only need
Figure 1: 17.3 inch 4k displays
small colour TFTs are also incorporating Projected Capacitive PCAP single touch and multitouch touchscreens, which have replaced resistive touchscreens in many applications, although 4 and 5 wire analogue resistive still have their place, where for example users need to wear gloves in extreme low temperatures for example.
APPLICATION SPECIFIC Many applications cannot use standard off the shelf displays so CDS offers a full custom solution service which can mean that companies can choose such aspects of the display including size, brightness (up to 2500cd), high resolutions, contrast, viewing angle, depth, touchscreen (USB and I2
C), Figure 2: Letter box TFT
interface (MiPi, SSD1963, RGB etc.), lifetime of backlight (e.g. 100K hours), low power, integrated keyboard, and format (square or rectangle, or even circular. This service opens many new opportunities for designers and developers that they may not have had before and although there will be NRE tooling charges involved for large volume projects this is not prohibitive. CDS is currently working on a project for 1 million pieces, so large projects that need this service and support are available in the UK and globally. There are many technical variations
and options, which is why CDS say it is critical to have a close relationship to the customer and really understand the application and requirements to ensure the optimum solution is delivered.
CDS
www.crystal-display.com e:
info@crystal-display.com
/ ELECTRONICS
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