Revolutionizing In-Car Displays: The Rise of Mini LED Technology

With the development of autonomous driving and intelligent networking technologies, car displays have gradually become the core interactive interface of vehicles, allowing various controls beyond just driving through the screen. According to Omdia data, the global shipment of automotive displays reached 127 million units in 2020. The market outlook for in-car displays is optimistic; even with the constraints of chip shortages, some organizations predict that the pre-installed shipment volume may reach 148 million in 2021.

As the functionality and usage frequency of in-car displays rapidly increase, the quality of the displays themselves will significantly impact consumers’ evaluations of related vehicle models. Consumers, accustomed to the user experience of smartphones and other consumer electronics, will inevitably have the same expectations for in-car displays.

Therefore, in addition to the high and low-temperature resistance and long service life required for automotive standards, the requirements for brightness, picture quality, and other details of in-car displays are becoming increasingly high. For example, the current industry trends include high contrast, high dynamic HDR, and wide color gamut requirements.

Currently, in-car display panels are primarily of the LCD type, with a few using OLED displays. As industry demands for display quality increase, LCDs are revealing some of their inherent disadvantages due to their structure and imaging principles.

1. Composition and Imaging Principle of LCDs

The structure of LCD panels is quite complex, consisting of components such as glass substrates, liquid crystal layers, color filters, polarizers, light guides, and backlight modules. LCD refers to the liquid crystal layer, which is used to control the direction of light but does not emit light itself; it requires LED backlighting as a light source. Additionally, LCDs do not directly display images; they require color filters for imaging. The color filter consists of many pixel points, each containing red (R), green (G), and blue (B) sub-pixels. According to the basic concepts of color science, the RGB primary colors can combine into various colors based on different brightness ratios, and the combination of different colored pixel points forms the colorful images we see.

2. Drawbacks of LCDs

To preserve the twisting potential of liquid crystal molecules, there are gaps between the molecules in the liquid crystal layer of the LCD panel. When the LCD panel displays darker scenes, the liquid crystal layer cannot completely block the backlight source, resulting in insufficient purity of black imaging. The most direct impact is that the native contrast specifications of the panel are difficult to improve, generally only around 1000:1, with a maximum of 5000:1. Therefore, traditional LCDs struggle to meet the current high contrast and HDR display requirements for in-car displays.

To further enhance image performance, panel manufacturers are working on improving backlight technology, one of which is changing from global dimming to local dimming. However, this solution has a drawback; having too few zones can lead to severe halo effects.

Whether it’s the previously mentioned high contrast, dynamic HDR, or wide color gamut requirements, precise control over brightness and color in relevant areas of the display is necessary. To solve the LCD dilemma mentioned earlier, the optimal solution from a display technology perspective is to adopt revolutionary display technologies that eliminate the use of LCDs and filters, such as self-emissive OLED/Micro LED screens.

1. Advantages and Disadvantages of OLED

OLED screens emit light from organic layers, and each light-emitting point can be controlled sensitively through voltage, resulting in excellent color gamut, contrast, and HDR effects. However, OLED also has significant issues: high costs, low brightness, and a service life that is difficult to meet automotive requirements.

Audi 7-inch OLED provided by Samsung Display

2. Mini LED: LED Chips Sized 50~100µm

Micro LED technology miniaturizes LED lights to achieve display effects similar to OLEDs. Currently, the industry generally defines LED chips sized 50-100µm as Mini LED and those under 30µm as Micro LED. The key technical challenge in Micro LED production is the massive transfer process, and it seems that revolutionary breakthroughs in mass production are not likely in the short term. Therefore, Mini LED has begun to gain attention in the industry.

Currently, the commercial use of Mini LED is divided into two types: direct display or backlight. The direct display is temporarily used only in large-sized commercial displays, while for in-car displays, it is primarily used as backlighting. Mini LED backlighting does not have significant advantages in terms of thinness compared to traditional LCDs, but it is very suitable for in-car displays where thickness is not a strict requirement.

Huaxing’s official website announces a 48” 8K In-cell Touch AM Mini-LED backlit curved car screen

The backlight control of Mini LED also belongs to the local dimming approach mentioned earlier, which is a direct backlight method. However, since Mini LED sizes are very small and the number of zones is sufficient, for example, an 8-inch display can integrate thousands of LEDs, it allows for precise control of very small parts of the display.

The structure of the Mini LED backlight display previously exhibited by Tianma

Through precise light control, it is possible to achieve high contrast, dynamic display, thus greatly enhancing contrast, HDR, and color gamut. Additionally, using this backlighting solution not only makes the display image more realistic but also increases the overall screen brightness.

In summary, the advantages of Mini LED backlit screens are as follows:

Brightness, contrast, high HDR (what Apple calls XDR)
Wider color gamut, more saturated colors
Peak brightness increases 3-5 times (>1000nit)
Display lifespan extended by 3-5 times compared to OLED
Can save up to 80% more energy than OLED
Lower costs compared to OLED
Currently, there are a large number of LCD production lines that can be modified for mass production, reducing Mini LED product costs and ensuring capacity

Conclusion

I have discussed the current innovative display market with some industry professionals, and several viewpoints emerged:

1. The Local Dimming products of OLED and Mini LED backlighting represent a qualitative leap in display effects compared to traditional LCDs, with high-end models likely to start mass production next year.

2. Mini LED has advantages over OLED in terms of brightness and lifespan, and after the current production lines for Mini LED backlighting are modified, costs can significantly decrease, making further applications in mid-range brands and models possible.

3. From a technological standpoint, there seems unlikely to be a revolutionary breakthrough in OLED lifespan in the short term, while Mini LED backlighting extends the industry lifespan of LCD panels; in the field of in-car displays, Mini LED and OLED may coexist for a considerable time.

4. Major panel manufacturers such as Huaxing, Innolux, Tianma, and BOE are actively promoting the application of Mini LED in in-car displays.

2021 is the year of mass production for Mini LED, and its application is rapidly growing. How will the next generation of innovative display technology for in-car displays develop? We welcome you to join the Mini LED group for discussion. Friends from the industrial chain, including Jidu Auto, Tianma, BOE, Huaxing Optoelectronics, Hisense, Longteng Optoelectronics, and Longli Technology, have already joined.

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