Feature: Displays Pixels per inch TFT LCD
Key features and benefits of display technologies
Power Consumption Brightness Cost
Pixels per inch OLED
Power Consumption Brightness Cost
Pixels per inch Micro LED
Display shrinkage – from mini to micro, and beyond
M
ini and micro LEDs are two display technologies that are becoming more widely used, in a diverse range of
applications. Here we will look at the current TFT LCD and OLED technologies and investigate the features and benefits of the emerging mini- and micro-LED displays.
TFT LCDs and OLEDs Te ubiquitous TFT (thin-film transistor) LCD has been a mainstay of design and development engineers for over three decades, extensively used in a broad range of industries and consumer applications. Significant enhancements have included wide viewing-angle technologies, such as IPS (in-plane switching) and MVA (multi- domain vertical alignment), and high brightness, long-life white LED backlights. TFT technology remains much the same as when first introduced, but it now benefits from highly-refined manufacturing
Power Consumption Brightness Cost
TFT LCD Type
Transmissive
Contrast Ratio Medium
Life Span Long
Response Time ms
OLED Type
self-emissive
Contrast Ratio High
Life Span Medium
Response Time µs
Micro LED Type
self-emissive
Contrast Ratio Very High
Life Span Long
Response Time ns
By Mike Fowle, Business Development Manager, Review Display Systems
techniques and high yield rates. On the other hand, the much-liked
OLED (organic light emitting diode) display technology has seen significant investment and commercial success in high-volume OEM markets, such as flat screen televisions and mobile phones, but remains rare in medium-size (5”-17”) display applications. OLED display technology provides
excellent optical performance: deeper, darker black levels, highly-saturated, vivid colour reproduction, enhanced contrast ratios and fast response times. Although OLED technology, materials and derivative development continue apace, these displays remain complex and expensive to make.
Micro LED – emerging potential A more recent, emerging display technology development is micro LED, considered by some industry analysts as a potential long-term successor to TFT and OLED displays. Micro LED is a direct drive, emissive (no backlight needed) display technology, constructed with an array of
50 July/August 2023
www.electronicsworld.co.uk
microscopic (2µm-50µm) LEDs forming the individual pixels. Tis enables higher image quality in direct-emission displays because each pixel is constructed of three subpixels – each composed of a red, green and blue micro LED. Manufacturing costs are reduced due to the simple physical structure of micro LED technology, whilst display resolutions and sizes can be scaled with relative ease. Micro LED also addresses an ongoing
technical issue of OLED technology: image retention, or screen burn-in. Due to the inherently different material properties of micro LED and OLED, individual micro LED pixels are at no risk of retaining static images, and operate without any significant degradation. Brightness levels up to 5,000 nits can be achieved with micro-LED displays – approximately five times the peak luminance of current OLED displays. Micro LED technology is already used in a
scaleable tile format, to build displays of any size and resolution. Applications range from small (smart watches), to medium-sized (handheld tablets) and very large (video wall displays).
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