Structure, Principle, and Advantages of Samsung QD Display
According to the Korean media TheLec report on 27th, November 2020, Samsung Display will start the trial of the QD-OLED (Quantum Dot-Organic Light Emitting Diode) production line (Q1) in early December. This will be a turning point for Samsung Electronics to move into the QD display market by fully withdrawing from the LCD industry. At the time, Samsung Display said it will wrap up building the line by the end of the year and begin mass production in 2021.
Today, Samsung Display official news brings more highlights, principle, Advantages of QD-OLED display, and comparison with a traditional display. Here is Samsung Display’s Official text (translated).
In 1829, German physicist Carl Brown developed a CRT display named after him, and then the TV began to mass-produce in earnest, starting in the United States in the 1940s. In the 2000s, various technologies such as slim CRT, projection display, PDP, and LCD competed in the market. However, LCD, which occupied the superiority in various aspects such as productivity, size diversity, and price competitiveness, is still the mainstream in the large display market. However, the development of display technology did not stop at LCD, and it is creating a transition to a new era as it leads to the development of various new technologies such as QD (quantum dot), OLED, and micro-LED.
Among them, QD Display, which Samsung Display is developing as next-generation large-sized display technology, has a variety of product competitiveness and is preparing to take the throne by overcoming competing technologies as LCD did in the past. From now on, I will introduce what kind of product/technology QD Display (Quantum Dot Display) has and what kind of competitiveness it has.
Structure and light emission principle of QD display
Before looking at the structure of the QD display, let’s first look at the structure of LCDs that we commonly see. This is because it is easier to understand the structure of the QD display by comparing it with the structure of the LCD.
Since LCD is not a self-luminous method, a light source that emits light called a backlight unit (BLU) is required, and various sheets and films are used on the BLU to efficiently use the light from this light source. And on top of it, a thin film transistor (TFT) layer, which is an electronic circuit layer that controls liquid crystal, a liquid crystal layer that controls the amount of light per pixel, and separates the light into RGB (Red, Green, Blue). It is composed of various layers, including a color filter (CF) layer and a polarizing plate that sends light in one direction. Through this complex layer, light efficiency decreases significantly, and the product is bound to get heavier and thicker.
However, the QD display, which is a self-luminous display, has a simpler and more efficient structure than the LCD. The QD display is largely divided into three layers. First, the TFT layer, which is an electronic circuit that controls the emission source layer, second, the emission source that emits blue light, and third, the QD emission layer that emits light by converting the blue light, which is the emission source, into red and green Configured.
QD display uses blue, which has the strongest light energy, as a light source, so it can achieve relatively bright luminance. In addition, blue light with strong energy can emit light of color with low energy physically, so it is advantageous to use QD devices to emit different light. The light generated from the light-emitting source reaches another self-luminous layer, the QD light-emitting layer. At this time, the QD element converts its own color to emit light by receiving the energy of the blue light, thus maximizing the efficiency of light utilization.
In particular, Samsung Display’s QD display technology, unlike LCD, is not only implemented on a structurally simple principle but is also a front-emitting method that efficiently utilizes light, thus minimizing the reduction in light efficiency. As such, light is used efficiently, and the product can be made light and thin, showing various performance advantages compared to other large display products.
Then, from now on, let’s take a closer look at the outstanding image quality and performance of QD Display.
Advantages of QD Display
The advantage of QD Display is large, QD to the advantages, the advantages of the Blue light-emitting source, the advantages of the differentiated technology of Samsung display only do so in three can distinguish explanation. First, let’s take a look at the four areas that are counted as the strengths of QD Display: Color Gamut, Color Volume, Viewing angle, Perceived luminance.
- Color Gamut
The blue light generated from the blue light source of the QD display has a very high color purity, and the RG (Red, Green) produced by the QD device receiving this light also has a very high color purity. High color purity means that each color of RGB is not mixed with other colors around the light spectrum, and only produces light of a specific wavelength as accurately as possible. Therefore, the accuracy of the colors that can be expressed by combining RGB increases, which means that the area of color expression through color combinations is also widened.
Thanks to this high color purity, QD Display is considered one of the technologies with the widest range of color expression among existing displays. No display in the world can express all the colors we see, but QD displays can show colors closest to what we see with our eyes.
Most TVs on the market currently express about 70% (based on BT.2020) in the color gamut of visible light that our eyes can see, but it is predicted that QD displays will be able to express about 80~90%. It’s possible. The color gamut that the display can express in this way is called Color Gamut, and the QD display currently has the widest color gamut.
- Color Volume
However, the screens that the display shows are not the same brightness, but various brightnesses. So, in addition to simply expressing what percentage of the color gamut, it is also very important how many colors can be expressed according to the screen brightness. This color expressive power according to brightness is called Color Volume.
The QD display can express a very wide range of colors at any brightness, from dark to light. Based on BT.2020 Color Volume, a typical large display can represent less than 60%, but a QD display can represent about 80% or more.
- Viewing angle
The light has straightness. When the display shows an image, the light has straightness as well. So, the brightness of the screen changes, and the color changes according to the viewing angle of the display. Due to the nature of this display, you experience deterioration in image quality in many cases, such as when several people are viewing together or doing other activities (cooking, exercising, etc.) and viewing from a location other than the front.
However, due to the characteristic of QD that emits light uniformly in all directions, the QD display minimizes the change in image quality depending on the viewing angle. At 60 degrees from the front, the luminance ratio of the front side compared to the brightness of the front side is generally less than 40% for the LCD, while the QD display is about 70% or more, which is the smallest change in luminance depending on the viewing angle compared to other large displays.
- Perceived Luminance
When a user perceives the brightness of a display, it is affected not only by the actual physical brightness of the display but also by the expressiveness of black and the color saturation. In this way, the perceived brightness that the user feels is called perceived brightness.
As shown in the picture above, you can see that the box with the same luminance looks different depending on the contrast of the background. This phenomenon is called the simultaneous contrast effect, and the better the display represents black, the brighter the luminance will appear.
In addition, even if the color has the same luminance, the brightness feels different according to the type of color, and the higher the saturation of the same type of color, the brighter it feels. This phenomenon is called the H·K effect (Helmholtz·Kohlrausch effect).
Looking at the photo above, there is no significant difference between the left and right of the actual display’s measured luminance. However, the right side looks brighter to our eyes. It is the QD display’s excellent black expression and wide color expression that makes us perceive it brighter than the actual brightness of the display itself.
So far, for the first time about what is a QD display, we have looked at the structure of the QD display and the advantages of the QD display implemented by the QD characteristics. Since there are still many advantages of QD display to be introduced, next time we will look at the advantages of blue self-luminous characteristics and the advantages of QD display implemented by Samsung Display’s unique differentiated technology.