LCD LED QLED OLED knowledge

Come, Xiao Bian one by one to reveal their face.

The initial LCD

LCD TV is the abbreviation of Liquid Crystal Display. Its full name is LCD screen and it is the ancestor of LCD TV. Usually used electronic calculator screen is used more basic liquid crystal display.

What is LCD?

In general, there are three states of matter, solid state, such as stone, liquid state, such as water, and gaseous state, such as air. Some substances are in a state between a solid and a liquid state, which is called a liquid crystal state. Generally, this liquid crystal substance is called a liquid crystal. Crystal molecules are generally neatly arranged, liquids will be arranged in a disorderly manner, and the liquid crystals will be regularly arranged by external influences.

Adding an electric field to the liquid crystal causes the liquid crystal to be affected by the electric field and the angle will rotate regularly. If we project a light through the liquid crystal at this time, then as long as the magnitude of the electric field is controlled, the light transmitted through the liquid crystal will change as the electric field changes.

Through this principle, as long as the regular change of the signal image controls the voltage of each pixel of the LCD screen, the image can be displayed through the LCD screen. However, this can only show black and white images. If you want to display colored images, you only need to add three RGB filters to each pixel. You can achieve the effect of displaying color images by combining RGB brightness and darkness.

Usually look at the LCD screen carefully. After each pixel is enlarged, you can see that it consists of three red, green, and blue cells. The three red, green, and blue modules are three filters that control one RGB signal per pixel.

In fact, in order to improve the display effect, the liquid crystal screen will add two polarizers with vertical gratings between the liquid crystal modules. The following is the structural schematic diagram of the liquid crystal screen.

The backlight passes through the vertical grating and enters the liquid crystal layer. Because the liquid crystal is deflected by the electric field, the light will be refracted and then emitted through the horizontal grating. Become a pixel signal display.

LCD screen structure principle

The backlight determines the brightness of the LCD screen. The requirements for the backlight of the LCD TV are relatively high, and the power consumption of the backlight often accounts for more than 2/3 of the power consumption of the entire device. Therefore, an efficient backlight can greatly reduce the overall power consumption of the LCD TV.

The backlight of the LCD monitor was originally used as a backlight source for the CCFL. The Chinese name is a compact energy-saving lamp, which is like a reduced-size fluorescent tube.

CCFL tube

However, CCFL lamps have certain defects. For example, the use of CCFL lamps will darken at both ends for a long time, resulting in non-uniform backlighting, and AC power must be used, resulting in relatively complex backlight modules and relatively high power consumption. With the development of technology, gradually replaced by LED lamps with low voltage, low power consumption, low heat, and stable performance.

LCD's brother LED

The name of the LED is called a light emitting diode. LCD TVs and LED TVs are not much different, but their backlights have changed. The former CCFL backlights were too bulky and costly, so some people used light-emitting diodes to replace them. Such diodes are small and long-lived, so LED TVs The volume can be smaller and the appearance of the TV can be designed more beautifully.

LED light backlight

QLED, LCD's best younger brother

QLED LCD TV is the quantum dot TV we often say. In fact, compared with the previous LCD, LED, there is no much difference, or make a fuss about the backlight source.

Quantum Dots (QDs) are tiny inorganic nanocrystals that are invisible to the naked eye. Whenever you are stimulated by light, quantum dots emit very pure colored light. Backlights using quantum dot materials are currently the most pure color backlights. Quantum-dot TV uses the purest quantum dot light source as the backlight source, and it is a revolutionary implementation of the full-color display, which can restore the image color more realistically.

Quantum dot backlight

Strong opponent OLED

OLED, whose full name is Organic Light Emitting Diode, was discovered in the laboratory by Tang Qingyun, a Chinese-American professor born in Hong Kong in 1947. OLEDs have self-luminous properties, using a very thin coating of organic materials and a glass substrate that emits light when current passes through them.

OLED TVs are not part of the LCD TV family. Each pixel on the screen emits light. No separate backlight or color filter is required. Each OLED pixel can be assigned three colors: red, green, and blue. The simplest thing to understand is a small, colorful LED lamp that can be freely controlled.

Due to the special properties of OLEDs, it is not necessary to cover the light source like the LCD when displaying black. It is only necessary to make the pixels go out and not light up, which is why the OLED contrast is nearly infinite; the OLED has almost no visibility of the liquid crystal. The angle problem can be said to be a full viewing angle; the response time is one thousandth of an LCD, and there is absolutely no streaking phenomenon in the displayed moving picture; the OLED can be manufactured on substrates made of different materials and can be made into a flexible flexible display.

However, many revolutionary advantages of OLED, from LG in January 2013 took the lead in the introduction of 55-inch OLED TV, has not yet replaced the LCD TV to become the mainstream of the market.

The main reasons are:

Short life, far below the life of LCD and LED;

It is difficult to achieve mass production of large-size screens, resulting in an extremely high cost, which is almost several times that of ordinary LCD TVs;

Color purity is not enough, resulting in color gamut can not match the LCD TV.

These technical defects have caused OLEDs to be unable to be widely used in a short period of time. However, with the development of technologies, after these problems are solved, OLEDs will be the trend of display technologies.

As for ULED, GLED, these two are concepts that Hisense and Skyworth have come up with. There is no universal standard. This article will not be introduced.