Discover the new and share the fun~
We all know that the current mobile phone screen market is dominated by OLED, but we can still often see LCDs, such as in the iPhone 11.
In life, we often hear the uncompromising phrase “LCD will never be a slave,” but it is often mixed with complaints about “OLED burn-in and eye strain.”
01
Different Light Emission Principles
To explore the pros and cons of the two, we must first understand that they are fundamentally different products with different light emission principles.
LCD, translated from English, means “Liquid Crystal Display Technology,” which dominated the market for nearly 20 years before the emergence of OLED.
LCD’s light emission primarily depends on its backlight layer, which does not have light-emitting characteristics. Since the backlight is only white, a color filter layer is needed to project the three primary colors.
At the same time, to control the ratio of red, green, and blue colors, a liquid crystal layer that adjusts the voltage must be added between the backlight layer and the color filter.
Now looking at OLED screens, unlike LCDs, OLED uses self-emitting technology, meaning that when current passes through, countless tiny light-emitting pixel points can emit light on their own (each pixel consists of red, green, and blue sub-pixels).
02
Pros and Cons of LCD and OLED
Display Colors
As mentioned earlier, LCD has a liquid crystal layer that cannot be completely turned off, so when displaying black, light still passes through the liquid crystal layer, resulting in a grayish color formed by various colors.
In contrast, OLED screens can emit pure black since the pixels turn off when displaying black.
In terms of color display, OLED screens have more pure and vibrant colors, while LCDs, due to the presence of the color filter layer, naturally have lower color saturation than OLEDs.
Thickness
OLED screens do not require a backlight layer and liquid crystal layer, allowing them to be thinner than LCD screens and also flexible, resulting in narrower bezels and chins on mobile phones.
The popular COP and COF packaging in recent years is precisely due to this, including waterfall screens and curved screens launched by various manufacturers rely on the flexibility of OLED screens.
Additionally, the under-screen fingerprint sensor has always been an advantage unique to OLED screens. The principle of under-screen fingerprint recognition is that the optical fingerprint module below the screen emits a beam of light, illuminates the fingerprint through the screen, and then reflects back. OLED’s high light transmittance and self-emitting characteristics significantly reduce interference from other light sources, which LCD screens cannot match.
LCD’s under-screen fingerprint technology only made breakthroughs in the past two years, but it has only been a solution without mass production models available.
▲Huawei LCD under-screen fingerprint engineering machine
Flicker
Previously, OLED screens used PWM dimming, which changes the screen brightness by alternating between turning the screen on and off. Since the on-off cycle is fast enough to exceed the human eye’s perception range, the flicker is generally not noticeable at high brightness, only visible under a camera lens. However, at low brightness, flicker becomes more apparent, and sensitive individuals may experience discomfort due to flicker.
Fortunately, the Android camp has begun to popularize DC dimming since last year, which changes the panel circuit’s power to adjust the screen brightness via software algorithms, significantly reducing the flicker issue on OLED screens. Some manufacturers, like Redmi, have even introduced hardware DC dimming, integrating self-developed algorithms into the screen driver IC.
Burn-in
If OLED screen flicker has almost been overcome, then “burn-in” is another hard injury that is difficult to solve for OLED.
“Burn-in” also known as “ghosting,” is fundamentally due to the different lifespans of the light-emitting components. The lifespans of the red, green, and blue sub-pixels in an OLED panel are not the same, and the wavelengths and required currents also differ, so when displaying fixed content for a long time, the blue pixels age faster than the other two, leading to color shifts and leaving “pixel remnants.”
Even the iPhone cannot escape this common problem, as Apple states on its official website that burn-in or color changes are normal variations of OLED screens.
Pixel Arrangement
In LCD screens, a standard RGB pixel arrangement is used, where the red, green, and blue pixels are tightly adjacent, resulting in good precision and clear edges when displaying content.
In OLED screens, due to the inconsistent lifespans of the three sub-pixels, they cannot be made the same size. Generally, the areas of blue and red sub-pixels are increased to extend their lifespans.
However, this leads to a lower overall pixel density, as effective sub-pixels are reduced by about one-third. In other words, for the same 1080p resolution, an LCD screen can be considered as true 1080p, while on a Samsung OLED screen, the actual pixels may only be 80% of 1080p, and for domestically produced screens with other arrangements, this number is even lower.
Thus, Samsung has always insisted on using 2K resolution on its flagship models.
It can be seen that even though OLED screens are about to replace LCD screens today, there are still many imperfections. LCD screens still lag behind in many aspects, and both are bound to have their pros and cons.
Therefore, new screen technologies will inevitably emerge in the future to replace both.
03
Mini LED (the best transitional product)
Starting with the iPhone X, Apple initiated the trend of OLED mobile phone screens, and many believe that the next trend in mobile phone screens will be the mini LED technology that Apple is set to use in the iPad Pro.
Mini LED refers to diodes that are smaller than 0.2mm. This means that compared to LCD, mini LED panels will use more LEDs, which can provide good wide color gamut performance, high contrast, high dynamic range, and local dimming capabilities, with a lifespan that will also be longer than OLED screens.
In fact, the Pro Display XDR released by Apple in 2019 used 576 blue LED areas as the backlight layer. Although Apple did not label this backlight system as mini LED technology, industry insiders believe it is already a trial application of mini-LED-like technology.
Analyst Guo Mingqi previously stated that Apple plans to produce four to six products with mini-LED displays in the next two to three years, with the iPad Pro being the first to arrive.
04
Micro LED (the ultimate goal)
If mini LED is an upgraded continuation of LCD (since both are backlight technologies), then Micro LED is an upgraded continuation of OLED, as Micro LED also uses self-emitting technology.
▲Samsung Micro LED 4K TV, 75 inches
Micro LED can make LED units smaller than 100μm, far smaller than OLED and mini-LED. It also uses inorganic gallium nitride materials, which last longer and do not have burn-in issues.
Theoretically, its brightness can be 30 times greater than that of OLED screens, with significant improvements in response speed, resolution, and color saturation, and it also consumes less power than existing screens.
At the CES shows in 2018 and 2019, Samsung showcased several Micro LED TVs. Meanwhile, Apple acquired a MicroLED research company as early as 2014.
It is widely believed that Apple will first introduce microLED screens in the Apple Watch smartwatches.
Currently, mini LED has already been applied in many displays, while Micro LED, which has a more complex manufacturing process and superior experience, still has a long way to go before it becomes mainstream.
