At present, the optical display and electronic consumer field has set off a wave of flexible AMOLED screens. After the first AMOLED production line of BOE has been mass-produced, some domestic manufacturers such as Huawei, Xiaomi and vivo intend to use flexible screens on their high-end mobile phones. However, from the current status of the industry where electronic products are generally not flexible, many high-end mobile phones have adopted flexible OLEDs. The author believes that the OLED screen has the natural advantages that traditional LCD screens do not have in terms of display quality. Rather than the advantages of OLED screens in terms of flexibility. However, due to high equipment costs and low yields, the production capacity of flexible OLED screens by companies such as Samsung and BOE is still limited, and it is difficult to meet the huge demand for high-quality displays in domestic and foreign markets in a short period of time. Liquid crystal displays, with their continuous improvement in image quality and sufficient production capacity, can still play an important role in the display market in the next few years. Image quality has always been an important focus of competition in the color TV industry. The new generation of quantum dot technology has the characteristics of “wide color gamut, high color capacity, pure chroma, long color”, which can truly restore 100% natural color and greatly enhance consumers' Quality experience. In recent years, TCL, the leading enterprise in the domestic color TV industry, has successively launched a number of primary color quantum dot TVs such as X2/X3/X6 through the continuous innovation in quantum dot display technology. The technology matures and innovates, breaking through the traditional LCD TV. The bottleneck in the color rendering effect, and promote the image quality upgrade of the color TV consumer market.
However, many readers will be puzzled and curious about such a high expression of "quantum dots." In this regard, this article will popularize some basic knowledge of liquid crystal display principle and quantum dot technology from a professional point of view!
1, the principle of liquid crystal display
The night crystal display is controlled by an electric signal to control the state of the polarized light. The light emitted by a general light source is natural light, that is, no light vector in any direction predominates in other directions. At any one time, we can decompose each light vector into two mutually perpendicular light vectors. If there is a light vector in one direction in the light, this light is polarized. Light hits the polarizer and only allows light in a particular direction to vibrate. A polarizer that obtains polarized light from natural light is called a polarizer, and a polarizer for verifying whether a certain light is polarized is called an analyzer. According to the law of Marius, the law of variation of the transmitted light intensity after the polarized light passes through the analyzer is: I out = I into cos2a.
The liquid crystal is sandwiched between two transparent conductive ITO films, and the electric fields on both sides can control the rotation of the liquid crystal molecules. The natural light emitted by the backlight passes through the polarizer and becomes polarized light in the vertical direction. In the TN mode liquid crystal cell without electric field, the optical anisotropy of the liquid crystal and the alignment of the liquid crystal molecules cause the polarization direction to change from vertical to horizontal, just in line with the transmission axis of the analyzer. monitor. When the electric field is not applied to the liquid crystal ends, the liquid crystal display mode in which the incident light can be transmitted is referred to as a "normal white" mode.
Similarly, if a controllable voltage is applied to the liquid crystal, the TN mode liquid crystal molecules change from a twisted alignment state to a vertically aligned state, and the polarization direction of the polarized light passes through the liquid crystal molecules at a certain angle with the transmission axis of the analyzer. It is known from Marius's law that the intensity of transmitted light after passing through the analyzer will be smaller as the angle increases. Therefore, the polarized light transmitted through the analyzer has different intensities, thus realizing multi-gray scale display.
2, quantum dot technology
A quantum dot is a nanoscale particle composed of a group II-VI element or a group III-V element (containing zinc, cadmium, and sulfur atoms), and has a particle diameter generally ranging from 1 to 10 nm. Since the electrons and holes are quantum confinement, the quantum confinement effect is remarkable, and the quantum dot particles are excited and the emission peak is extremely narrow, and the spectral purity is high. The emission spectrum of a quantum dot can be controlled by changing the particle size and chemical composition of the quantum dot so that its emission spectrum covers the entire visible region. The quantum dot technology is applied to a liquid crystal display, and is encapsulated on a backlight LED lamp cap by a quantum dot film, a quantum dot tube or as a phosphor. It is an excited excitation target of a blue LED, and is excited by a blue light spectrum. It will emit more pure red and green light. This allows the color gamut of the display to be as high as 100% or more, and its display effect is even comparable to that of an OLED display.
As an emerging technology, quantum dot materials still need improvement in terms of job stability. Under wet steam and high temperature conditions, the ability of quantum dot materials to emit red and green light is reduced, resulting in a blue-to-blue color shift in the display. In addition, quantum dot displays may contain heavy metals such as cadmium, which can contaminate the environment after being scrapped.
In addition to the quantum dot technology with significant color gamut effect, new technologies such as high dynamic range image, local dimming, Ram erase and motion image compensation have improved the display quality of LCD screens. This is the LCD screen in the display market. I have won a lot of chips in the place. Of course, the thin and flexible OLED screen is inevitably the development trend of the display, and the LCD screen with excellent image quality can be used as a necessary supplement for the OLED screen incapacity or in the specific environment.