The same LCD panel, TV spreads so why?

When we buy TV, we often encounter this situation. The same size TV with the same brand, are using the same panel, see the presentation of the hardware and software used is also not much difference, but often the price is a difference of several thousand There is also a difference in picture quality. Why is this? In fact, we often overlook a part that occupies a large proportion of the cost of LCD TVs. This is the backlight. The backlight not only plays an important role in the picture quality of the LCD TV, but at the same time, the different backlight sources also have a great impact on the cost/price of the TV.


Straight down and side entry, two ways of LED backlighting

We all know that there are many backlight types for display devices, such as EL, CCFL, and LED. Of course, with the popularity and development of LCD TVs, LEDs have become the most suitable backlight for current TVs. LED's working principle and light concept are not much to say here, from the perspective of the color of the backlight source, LED is divided into white LED backlight source and RGB-LED backlight source, RGB-LED backlight source is obviously better color, picture quality Stronger, but the price is exaggerated, so the vast majority of LCD TVs on the market use a white LED backlight.

In addition, the LED backlight source can also be distinguished according to the installation method, one is called direct type, and the other is called side type. In the direct type, the LED light emitting die is disposed evenly behind the liquid crystal panel (screen surface) as a light source, so that the backlight can be uniformly transmitted to the entire screen; and the side type is to arrange the LED die around the LCD screen. The edge, and then with the light guide plate, when the LED backlight module emits light, the light emitted from the edge of the screen is transmitted through the light guide plate to the area in the center of the screen, so that there is enough backlight as a whole, allowing the liquid crystal screen to display the picture.

In short, in the backlight system, the direct type is a light source in which the dots are arranged as a surface, and the lateral type is a light source in which a dot is arranged as a line. Both of these methods have their own advantages and have a great impact on the final performance of television.


Side-entry is to set the light bar (light source) at the edge of the screen. There are many LED lights on each light bar. The direct type backlight means that the back of the screen is covered with LED lights. The number of LED lights is much more.

Image quality and thickness, direct and lateral advantages

The advantage of the direct type is that it can set different backlight module authority areas. Theoretically, each LED can independently control the brightness, but the line and design cost is not easy. Therefore, in actual products, the design of sub-regional control is often adopted so that each area can independently adjust the brightness. The more LED lights are used by the direct light source, the more areas the backlight divides and the better the picture quality of the TV. For example, Toshiba's new generation of high-end 4K TV Z20X series backlight area up to 200 or more, each area can independently adjust the brightness, the effect is naturally better, of course, the cost is also high and bizarre.

The direct backlight is a surface light source placed behind the screen, so it has inherent advantages in brightness uniformity, and more critical is its light leakage control is better. And the direct type backlight can adjust the screen brightness in a local area, make the bright part brighter and the dark part darker, so its contrast effect is stronger than the side-entry type backlight, and the energy saving effect is also relatively good. In addition, due to the limitations of the installation method, the side-entry backlight can only use white LEDs, while the direct type can use white LEDs and RGB-LED backlights. If RGB-LED backlights are used, then the gamut value Direct-lit backlights will also outperform edge-lit backlights. However, because of the cost, direct-lit RGB-LED backlights will only be used in high-end products.


High-end direct-light TV backlight form

Side-entry backlight is actually installed in the panel on the four sides of the LED light bar (only two left and right, up and down about four), and then use the light guide to send the edge of the light to the central area of ​​the screen. This approach naturally has an adverse effect on brightness uniformity and light leakage, but its greatest benefits are twofold. First, the cost is low, the light guide plate and the LED light bar are not expensive, and the second is because the LED light is distributed on the side of the screen. , so the thickness of the LCD TV can be made very thin.

In addition, with the improvement of technology and the increase in the number of LED strips used, side-edge light sources have gradually improved in image quality. For example, the increase in the number of light bars and the improvement of the light guide plate can achieve each row (column) screen. The regional light control, the birth of quantum dot technology and the improvement of panel color also make the side-entry products not inferior to the direct-type products in the color gamut value (of course, the color transition and perception are worse than the high-end direct-down TV).


Side-entry light back TV

It is worth mentioning that the quality of LCD TVs is not necessarily better than that of LCD TVs. We can only say that the quality limit of the direct backlight mode is higher than the edge quality of the edge backlight. Some manufacturers of direct-down TV if you use less LED lights, the backlight area is not divided, the picture quality is not stronger than the mainstream side-entry TV, such as Lenovo has previously launched below 3,000 yuan direct-lit backlight LCD Television is not outstanding in quality. For those high-end direct-view TVs, if thousands of LED lights are used at all times, then the effect will definitely be stronger than that of the side-entry TVs (the number of side-in LEDs is only a few hundred.)

See the thickness, check the information, teach you to identify the direct type and side-entry TV

As we said, looking at the backlight only, we can't actually make arbitrary conclusions about the quality of the TV. However, it is still very important to understand what kind of backlighting a TV is using. This at least allows us to be aware of the truthfulness of the company’s publicity. For example, a TV uses an edge-type backlight and the price is relatively low. If this TV boasts about what intelligent light control and area control light it has, it will make little sense. Here we briefly talk about several ways of distinguishing between direct type and side-entry type LCD TVs.

The first is to see the thickness. The current market speculation about their own thin-thin TV, almost all of the side-entry backlight, because only the side-entry backlight can be done thin, the kind of thinnest but more than 1 cm thickness, direct type is difficult in any case Do it. Of course, if the user wants to select a TV with a good picture quality and a thin thickness, he can only choose the edge-lit backlight LCD TV or the OLED TV.

In addition, to understand what kind of LCD TV backlight, you can also go to the official website of the TV to view. In general, the domestic TV brand official website will not specify some of its own TV backlighting methods (unless for publicity), but the foreign brand specifications are relatively clear, such as the direct type backlight will be clearly expressed as "Backlight:Direct" And the edge-type backlight will be clearly expressed as "Backlight:Edge". It is worth mentioning that some domestic models of foreign brands will also clearly describe their own backlight source in the manual. For example, in Sony's domestic 4K TV specification, it clearly describes the different models and sizes used. Backlight mode.


Thinner TVs are usually side-entry backlights

Finally, we emphasize again that whether it is a side-entry or direct-type backlight, in fact, high-end low-end TV has been adopted, the key is to look at the manufacturer's own technology and cost, different backlighting TV, picture quality is not absolute Of course, high-end direct-lit backlight TVs are certainly relatively expensive. To be sure, the picture quality and quality of LCD TVs is definitely a penny-a-goods product. Perhaps high-end LCD TVs have a certain premium. However, the current Internet brands' low-priced products are absolutely impossible and traditional high-end LCD TVs. Competition quality.

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