Shulou(Shulou.com)11/24 Report--

The original title: "Buy a mobile phone, don't forget to pay attention to this!" "

When choosing a mobile phone, what parameters do you pay most attention to?

Screen size, screen style, or camera resolution? .

I wonder if any students have paid attention to the material of the mobile phone screen?

We use mobile phones to play games, browse videos and watch live broadcasts. Those who are in close contact with each other are all mobile phone screens.

The material of the mobile phone screen directly affects the overall feeling of our mobile phone use.

What types of mobile phone screen materials are there in the market?

At present, the mainstream screen materials on the market are divided into two categories:

LCD (Liquid Crystal Display, LCD) screen

OLED (Organic Light-Emitting Diode, organic light emitting diode) screen

So what's the difference between these two materials? Which one should we choose when we buy?

Let's take a look at how LCD and OLED screens are implemented.

We all know that the screen is made up of thousands of pixels, and each pixel is made up of three sub-pixels of red, green and blue. The various colors seen on the LCD and OLED screens are mixed into a variety of colors by adjusting the light and shade of the three sub-pixels of red, green and blue.

On current LCD and OLED screens, each sub-pixel has at least 256 levels of brightness, that is, these three sub-pixels can be mixed into more than 1600 million colors.

So how are LCD and OLED implemented respectively?

LCD screen LCD screen can not work without backlight layer (emitting white light) and liquid crystal layer (adjusting light brightness).

To better understand how the LCD screen works, let's take a look at the structure of the LCD screen, as shown in the following figure.

The backlight layer includes a reflector, a light guide plate, a LED lamp, a diffusion film and a prism film.

Reflector: similar to the reflector when taking a picture, reflecting the light back to improve the brightness of the screen.

Light guide plate: converts the line light source emitted by the LED lamp into a surface light source to make the screen brightness uniform.

Diffusion film: similar to a soft light lamp when taking a picture, diffusing the light to make the light softer.

Prism film: filter out the light that does not conform to the angle, so that the light angle is more standardized.

Liquid crystal layer and other layers of materials also play an indispensable role in the display of LCD.

Bottom (vertical) polarizer: only vertical light is allowed to pass through, and the rest of the light is filtered out.

TFT (Thin Film Transistor, thin film field effect transistor): adjust the voltage of each sub-pixel (red, green and blue) to adjust the distortion of liquid crystal molecules, thereby controlling the brightness of the sub-pixel.

Alignment film: used to hold liquid crystal.

Liquid crystal layer: like a regulating valve, it controls the amount and direction of light.

Common electrode: used to apply voltage to the liquid crystal layer to maintain the voltage of the entire pixel.

Color filter film: composed of red, green and blue, so that the LCD screen can show a variety of colors.

Top (horizontal) polarizer: only horizontal light is allowed to pass through, and the rest is filtered out.

From the following dynamic diagram, you can see the specific implementation process of the LCD screen.

1. When we light up the screen, the LED starts to emit white light, passing through the light guide plate, converting the line light source into a surface light source, making the light uniform and illuminating the entire screen (at the same time, the reflector on the left reflects the light back, increasing the overall brightness).

two。 The light passes through the diffusion film, allowing the light to spread, making the area larger and softening the light.

3. The light passes through the prism film, and only the light in accordance with the angle will be emitted, making sure that the light is going in the right direction.

4. The light passes through the vertical polarizer at the bottom, allowing only the light in the vertical direction to pass through, filtering out the light in other directions.

5. TFT controls the voltage of each sub-pixel according to the need of color display, and the voltage affects the distortion of liquid crystal molecules, thus controlling the brightness and direction of light passing through the liquid crystal layer.

6. The sub-pixel light passing through the liquid crystal layer passes through the color filter, and then through the horizontal polarizer at the top, the desired color is seen on the screen.

OLED screen OLED screen uses organic self-luminous material, does not need the backlight layer like LCD screen, also does not need to control the amount of light out of the liquid crystal layer, as long as it is powered on, the organic self-luminous layer can emit light, the screen can be bright, so OLED is like a screen with countless small color light bulbs (a sub-pixel is similar to a small light bulb), each small light bulb can be controlled independently.

The structure of the OLED screen is shown in the following figure.

The role of the layers of material that make up the OLED screen:

Plastic substrate: used to support the OLED screen.

Electrode: used to apply voltage to the light-emitting layer.

Luminous layer: the luminous layer of each sub-pixel is similar to a small light bulb, which can emit the light needed by the screen as needed.

Compared with the structure of the LCD,OLED screen, there are fewer devices, which is much simpler. As a result, how OLED pixels work becomes simple.

1. When a voltage is applied at both ends of the electrode, the electrons combine in the luminous layer, and the red, green and blue sub-pixels emit light.

two。 After mixing the light of red, green and blue sub-pixels, you get all kinds of colors on the screen.

Comparing the advantages and disadvantages of LCD screen and OLED screen, we can see that the core difference between LCD screen and OLED screen is that the OLED screen has no backlight layer and liquid crystal layer, and all the pixels glow by themselves, while the LCD screen needs the backlight layer to illuminate.

Because OLED has less backlight layer and liquid crystal layer than LCD, OLED has the following advantages over LCD:

Screen thickness: the OLED can be made thinner than the LCD screen, which helps to control the overall thickness of the phone, while the thinner OLED screen allows the addition of more components to improve other performance.

Bendability: due to the existence of LCD backlight layer and LCD layer, the thick LCD screen can not be greatly bent, while the light and thin OLED screen can be bent at will. Under the limitation of the size of the phone, you can achieve the display effect of a larger screen through curved screen, folding screen and so on.

Color: because the liquid crystal layer of LCD can not be completely closed, when LCD shows black, there will still be part of the light passing through the filter, so the black of LCD is actually a mixture of white and black gray, just like a white flashlight shooting through a black film, the light passing through the film will not become pure black light, but gray with a sharp decline in brightness. When OLED displays black, you can directly turn off the pixels in the black area, which can achieve the effect of pure black.

Contrast refers to the ratio of white to black, the higher the contrast, the thicker and brighter the color of the picture. Because the black of LCD is not pure black, so the contrast is difficult to do. While OLED can achieve pure black, that is, black is almost zero, then the contrast can be infinite in theory. So OLED display is like oil painting, the color is pure and delicate, LCD display is like watercolor strokes, the color is hazy and elegant.

Power consumption: each pixel (small light bulb) of OLED works independently, it lights up what needs to be displayed and goes out when it doesn't need to be displayed, while LCD has full backlight no matter what color it displays, so OLED saves more power than LCD.

Of course, OLED is not perfect, and it also has the following shortcomings compared with LCD,OLED:

The screen life is relatively short: LCD screen uses inorganic material, OLED screen uses organic material, and the aging rate of inorganic material is much slower than that of organic material, so the service life of OLED screen is shorter than LCD screen.

Screen burning: each pixel of the OLED screen is self-luminous, while the LCD screen is bright as a whole, so the working time of each pixel of the OLED screen is different, which may lead to the phenomenon of uneven aging of the pixels on the screen. Burning screen refers to the phenomenon of residual shadow on the screen. However, it takes a very long process to burn the screen. In general, as long as the brightness of the phone is not too high during daily use, and the phone screen does not display a picture for a long time, there is no problem for the OLED screen to be used for several years.

Screen flash: the screen needs to be controlled for brightness. For most LCD screens, you can directly adjust the voltage of the backlight layer to control the brightness (DC (Direct Current) dimming), while the OLED screen can not control the brightness by adjusting the voltage, you need to constantly switch the screen to control the brightness (PWM (Pulse Width Modulation) dimming), that is, the screen brightness flickers, which may make the eyes feel uncomfortable. But when the frequency of the switch is high enough, the action of the switch on the screen can not be felt by the naked eye.

We can see that LCD and OLED have their own advantages and disadvantages, so it is not appropriate to directly claim that who will be better, so there are a large number of mobile phones on the market.

Here, we synthesize the performance-to-price ratio of mobile phones and other factors to make a simple comparison between LCD and OLED screens.

The classification of LCD screen and OLED screen students who have paid attention to the materials of mobile phone screens must have noticed that in addition to LCD and OLED, there are also some letter combinations such as TFT, IPS, SLCD, AMOLED, and so on, which do not represent different screen materials, but different display technologies of LCD and OLED. In general, the common LCD display technologies are: TFT, IPS, SLCD. Common OLED display technologies are: AMOLED, Super AMOLED.

In order to distinguish different display technologies, we briefly introduce the implementation and effect of each display technology.

LCD common display technology TFT (Thin Film Transistor, thin film field effect transistor): there is a semiconductor switch for each pixel, and each pixel can be directly controlled by a point pulse, so each pixel is relatively independent and can be controlled continuously, which not only improves the reaction speed of the display screen, but also accurately controls the display color levels, so the TFT liquid crystal has real color, good brightness, strong layering and bright color. But it also consumes more electricity.

IPS (In-Plane Switching, plane conversion), also known as "Super TFT", the display effect is transparent, bright, can be viewed from a large angle, can achieve a visual angle of close to 180 °, and touch no water lines, environmental protection and power saving.

SLCD (Splice Liquid Crystal Display, splicing special LCD screen) is a complete splicing display unit and an advanced version of LCD. It is characterized by warmer color, more realistic, more natural, suitable for human eyes and long service life.

OLED common display technology AMOLED (Active Matrix OLED, active OLED) uses active luminous technology, that is, every pixel on the screen can not only display color, but also has the characteristic of self-luminous. In this way, not all the pixels on the screen are glowing in any kind of background, and the pixels in pure black places are neither displayed nor glowing, which saves electricity to a great extent and protects the mobile phone screen very well. AMOLED's self-illuminating technology makes the screen more colorful and brighter, making it possible to see the screen clearly even outdoors during the day. At the same time, thinner AMOLED has faster response speed, wider vision and higher contrast.

Super AMOLED: compared to AMOLED, Super AMOLED removes the glass cover, making the panel thinner than AMOLED. Because of the lack of a barrier, the screen touch is more sensitive and the color is brighter. At the same time, Super AMOLED has a good performance in visual angle, display fineness and bright color saturation.

With regard to the content of common mobile phone screen materials, the editor has introduced here today. I believe you also have a certain understanding of your own mobile phone screen, and you also have some parameter guidance when choosing and buying mobile phones.

Of course, in addition to the materials mentioned in this article, there are ASV, NOVA, TN and other materials on the market used in mobile phones of different manufacturers, which will not be introduced today.

This article comes from the official account of Wechat: ZTE documents (ID:ztedoc), author: Ye

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