DISPLAYS & UIS
OLED vs TFT LCD
The latest printed OLED panels, in comparison with a contemporary TFT LCD display module, provide significant performance advantages in terms of contrast ratio, colour gamut, response time and luminance characteristics. The leading features of printed OLED displays include:
Contrast ratio
Contrast ratio is defined as a measure of the ratio of the luminance of the brightest shade of white to that of the darkest shade of black a display can produce. More so than colour, resolution or other aspects of image quality, contrast has the biggest impact on image performance. Printed OLED displays can now achieve contrast ratios of 1,000,000: 1 which enables highly saturated, deep, dark black levels and whiter whites. A typical TFT LCD contrast ratio is 1000:1.
Colour gamut
The colour gamut of a display is defined as the range of colour that a display can reproduce within the full spectrum of colours that are visible to the human eye. The sRGB gamut is a standard colour space created for use on monitors, printers, scanners, and digital cameras, and defines the chromaticity coordinates of red, green, and blue (RGB) within the CIE 1931 Chromaticity diagram. Printed OLED displays supporting a 10-bit colour depth can now deliver 138% of the sRGB colour gamut, which enables highly accurate and deeply saturated colour reproduction. In comparison, TFT LCD typically supports a sRGB colour gamut of 100%.
Response time
Response time represents one of the most important specifications for flat panel displays and determines how quickly a pixel switches to an active ‘on’ state and then switches to an inactive ‘off’ state. A faster response time will minimise ghosting and blur effects, and how consistent the display image appears to the viewer. Printed OLED displays have a response time of just 0.1mS, which is significantly fast (>100 times) than a typical TFT LCD at 15mS.
Energy efficiency
OLED is a self-illuminating emissive display technology - each individual picture element (pixel) emits light that can be switched on/off independently - no backlight is needed. A TFT LCD operates in the same way as a shutter mechanism - light can only pass through the LCD cell when a pixel is switched ‘on’ and active. A backlight unit (BLU), which consumes power and as a result generates heat, is required to enable the display image to be viewed.
Blue light emission
The display screens of monitors, laptops, smartphones, and other digital devices emit significant amounts of blue light. High-energy blue light has a short wavelength and scatters easily. The human eye is not very effective at blocking blue light, which passes through the eye and reaches the retina. Prolonged exposure to excessive amounts of blue light can lead to damage of the light sensitive cells in the retina. Printed OLED displays offer a more user-friendly solution with a reduction in blue light emissions of up to 40% when compared with a TFT LCD.
Form factor
The OLED printing manufacturing process creates a simple, effective, exceptionally thin OLED structure with a total display thickness of just 1.3mm. A 32-inch printed OLED display panel has a weight of just 1kg. An equivalent TFT LCD display panel will weigh significantly more, typically 4-8kg.
These product characteristics are ideally suited for high-end monitors, in-vehicle systems, medical diagnostics, professional broadcast equipment and entertainment systems.
A bright future for OLED
JOLED was established in 2015, combining the OLED display development divisions of Sony and Panasonic, with the goal of developing and commercialising high performance medium-size printed OLED displays. This initial goal has now been achieved with commercially viable printed OLED displays providing outstanding optical performance and superb blur-free image quality now entering the market. The innovative printing process now enables the efficient and effective production of medium sized OLED display panels from 10 to 32-inch.
What next?
The printing process developed by JOLED also lends itself to the development and production of flexible OLED substrates. With an ultra-thin profile, a flexible, high- performance, full colour OLED display could be realised for practical use in the not-too- distant future.
Review Display Systems
https://review-displays.co.uk/
JULY/AUGUST 2021 | ELECTRONICS TODAY 37
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