Let you buy with confidence: a complete guide to LCD TV panels

LCD TV Panel Concept and classification

The LCD panel is the display system of the LCD TV and the core component of the entire TV. The LCD panel can largely determine the brightness , contrast , color, and viewing angle of the LCD display . The LCD panel is developing very fast. The LCD panel part is closely related to the LCD display. Its production, quality, market environment and other factors are related to the quality, price and market trend of the LCD display itself, because about 80% of the cost of an LCD display is concentrated on the panel.

In terms of panel types, the current LCD panel manufacturers mainly include Sharp, Samsung, LG, AUO , Chimei Innolux, etc. The wide viewing angle technology of LCD TV panels is divided into TN+Film (soft screen) camp, IPS (hard screen) camp and VA (soft screen) camp. Each of them has its own advantages. Let's take a closer look.

1. TN+Film viewing angle expansion film (soft screen) This technology is still based on the traditional TN mode liquid crystal, but a film-sticking process is added during the manufacturing process. The biggest feature of TN+Film wide-angle technology is its low price, low technical entry threshold, and wide application. In general, TN panels are products with obvious advantages and disadvantages. They are cheap, have a small number of output gray levels, and have a fast deflection speed of liquid crystal molecules, which makes it easy to improve their response time. Its advantage is that its response time can meet the requirements of the game. Its obvious disadvantages are that the viewing angle is not ideal and the color performance is not realistic. Therefore, the LCD monitors using TN panels sold in the market now generally use improved TN+FILM (compensation film) to make up for the shortcomings of the TN panel in terms of viewing angle. At the same time, the use of color dithering technology also enables the TN panel, which can only display 260,000 colors, to obtain a display capacity of 16.2M.

2. The biggest selling point of IPS (In Plane Switching) wide viewing angle technology (hard screen) is that its two electrodes are on the same plane, unlike other liquid crystal modes where the electrodes are arranged in three dimensions on the upper and lower surfaces. Since the electrodes are on the same plane, the liquid crystal molecules are always parallel to the screen regardless of the state, which will reduce the aperture ratio and reduce the transmittance, so IPS applications on LCD TVs will require more backlights. The black it restores is slightly worse than PVA , so it is necessary to rely on optical film compensation to achieve better black; another feature of IPS mode LCD displays is that if you observe at a 45-degree angle, you will see a grayscale reversal phenomenon similar to the TN mode, which can be used as a sign to identify IPS. IPS also has the disadvantages of slow response time and difficulty in improving contrast. (S-IPS and AS-IPS are improved versions of IPS technology)

VA panels are the most commonly used panel type in high-end LCDs. The 16.7M color number and large viewing angle are the capital of this type of panel for high-end positioning. At the same time, VA can be divided into MVA panels and PVA panels.

1. In the MVA (Multi-domain Vertical Alignment ) (soft screen) mode LCD display, the long axis of the liquid crystal molecules is not parallel to the screen like the TN mode when no power is applied, but perpendicular to the screen, and each pixel is composed of multiple such vertically oriented liquid crystal molecules.

2. PVA (Patterned Vertical Alignment) wide viewing angle technology (soft screen). PVA wide viewing angle technology also belongs to the category of VA technology. In fact, it is very similar to MVA and can be said to be a deformation of MVA. PVA uses transparent ITO electrodes to replace the liquid crystal layer protrusions in MVA. The transparent electrode can obtain a better aperture ratio and minimize the waste of backlight. This mode greatly reduces the possibility of "bright spots" appearing on the LCD panel. Its status in the era of LCD TVs is equivalent to the "long tube" in the era of picture tube TVs. Samsung's main PVA mode wide viewing angle technology is widely adopted by Japanese and American manufacturers due to its strong production capacity and stable quality control system. At present, this technology is widely used in mid-to-high-end LCD TVs. (S-PVA is an improved version of PVA technology)

4. CPA (Continuous Pinwheel Alignment) mode wide viewing angle technology (soft screen). Strictly speaking, CPA mode wide viewing angle technology also belongs to the VA camp. Each liquid crystal molecule is arranged in a flame-like manner radiating toward the central electrode. Since the electric field on the pixel electrode changes continuously, this wide viewing angle mode is called the "continuous flame-like arrangement" mode. CPA is promoted by Sharp, the "father of liquid crystal". It should be noted here that the ASV that Sharp has always promoted does not actually refer to a specific wide viewing angle technology. It refers to the products that have adopted TN+Film, VA, and CPA wide viewing angle technologies as ASV. In fact, only the CPA mode is the wide viewing angle technology pioneered by Sharp itself, and the products of this mode are basically equivalent to MVA and PVA. In other words, Sharp brand LCD TVs may not use CPA mode LCD panels produced by Sharp itself. It may use VA mode panels from Taiwanese manufacturers or LCD panels from other manufacturers.

Teach you how to identify various types of LCD panels

The LCD screens on the market are divided into three categories: the best quality is Sharp screen; the second is LCD screens produced by Japanese and Korean manufacturers, such as Samsung Sony LCD screens (S-LCD panels) and LG.Philips LCD screens (LPL panels); and the last is screens produced by Taiwanese manufacturers, such as AUO and Chimei. They all have their own liquid crystal materials and panel structures, and their advantages and disadvantages are also different! The following introduces the characteristics and identification methods of several common LCD panels.

Sharp screen

Sharp screen, the top-level LCD panel, uses ASV technology and the ExtraView LCD panel launched by NEC. It is characterized by true color reproduction and excellent viewing angle, and is a well-known king in the LCD market.

Sharp LCD panel: The pixels are honeycomb or hexagonal, which is very distinctive and easy to see if you look carefully.

Samsung Sony S-LCD Panel

Soft screen panels are the most commonly used panel types in high-end LCDs. The 16.7M color number and large viewing angle are the capital of this type of panel's high-end positioning. At the same time, VA can be divided into MVA panels and PVA panels.

PVA Panel

1. In the MVA (Multi-domain Vertical Alignment) mode LCD panel, the long axis of the liquid crystal molecules is not parallel to the screen like the TN mode when no power is applied, but perpendicular to the screen, and each pixel is composed of multiple such vertically oriented liquid crystal molecules.

2. PVA (Patterned Vertical Alignment) wide viewing angle technology, PVA wide viewing angle technology also belongs to the category of VA technology, which can be said to be a deformation of MVA. PVA uses transparent ITO electrodes to replace the liquid crystal layer protrusions in MVA. The transparent electrode can obtain a better aperture ratio and minimize the waste of backlight.

The S-LCD panel is a PVA panel, Samsung's main PVA mode wide-viewing angle technology. If you look closely, you will see a half-pixel fish-scale image with thinner lines.

In fact, most of the mid- and low-end products on the market use Taiwanese screens. Most of the pixels on Taiwanese screens are in the shape of vertical strips, the viewing angle is small, and Taiwanese screens have almost no special features.

LCD panel bad pixels and bright spots and detection methods

LCD panels may have light leakage, bad pixels, bright spots and other phenomena. Light leakage mainly refers to the loose fit between the screen liquid crystal and the frame, which causes the light of the lamp to be transmitted. A bad pixel refers to a point that appears in any color background and still appears as a pure black or pure white pixel. Bright spots are also a type of bad pixel, which means that only one or two of the three liquid crystal boxes corresponding to the pixel drive tubes are faulty, and a pixel of one color among red, green and blue appears on a black background.

To detect whether there are problems such as bad pixels and bright spots, the five colors of red, green, blue, white and black are mainly used to examine the quality of the product. Among them, red, green and blue are the basic colors of television and are used to detect bright spots, while black and white can be used to detect bad pixels. Under a black background, pixels of one color among red, green and blue will appear; or pixels that should be red, green and blue will appear white. These can be judged as bright spots, which are also a type of bad pixels.

The common problem with bad pixels is that the colors are not controlled, only pure colors such as black and white are displayed, and the dark changes cannot be controlled to form an image.

1. After purchasing an LCD TV, be sure to check whether the LCD TV has bad pixels before confirming receipt. You can use a special test disc for testing, such as "AVIA", "Hivi Cast", "Digital Video Essentials", etc., which are available in general audio-visual stores.

2. Connect the TV to a laptop, and then display a solid black, solid white, or solid red, solid green, or solid blue background in full screen. Carefully check whether there are black, white, or different colored luminous spots under the solid color. If so, it means that the LCD TV has bad pixels and you should refuse to accept the product.

3. If there is no computer connection, you can first make 5 pure-color DVDs or put 5 large pure-color pictures in the USB , and test it by playing the DVD.

4. If the above methods are not feasible for you, you can also directly connect to cable TV and use a certain picture in the TV program to detect it through the TV's still image function.

In addition, you can also use professional testing software to test other indicators of LCD monitors. For example, NOKIA MONITOR TEST is a test program that consumers can carry with them on a disk. This software provides 15 options, including Geometry, Brightness and contrast, High Voltage , Colors, To control panel/display, Convergence, Focus, Resolution, Moire, Readability, Jitter, Sound, etc. For LCD monitors, except for the inability to test the response time, the other main performance parameters are clear at a glance, and the bad pixels that consumers are concerned about are not a problem. If there are problems with the color purity, contrast, and brightness of the display, the B-level and C-level panels will be exposed. LCD TVs
need to be cleaned after using them for a period of time, but there are also skills to clean the TV screen.

The surface of the LCD screen looks like a solid black screen, but in fact, the manufacturer will add a special coating on this layer of screen. The main function of this special coating is to prevent users from being reflected and glared by other light sources when using it, and at the same time enhance the color contrast effect of the LCD screen itself. However, because the coating materials used by different manufacturers are not the same, of course its durability will also vary.

LCD TV screen cleaning and maintenance knowledge

Therefore, when cleaning, users must not use any alkaline solution or chemical solution to wipe the screen surface, let alone water and alcohol solution. Do not use the following liquids and objects as cleaning products: alcohol, thinner, detergent, soap, washing powder, coarse fiber cloth, decontamination wax, knife and hard tools.

When cleaning the TV screen, you must choose professional cleaning cloth and cleaning liquid. You can buy a cleaning kit, which includes cleaning liquid and microfiber scratch-free cloth. The cleaning liquid will not damage the LCD surface coating, while the microfiber scratch-free cloth can effectively wipe away dust and fingerprints. When wiping, be sure to spray the cleaning liquid onto the cleaning cloth and wipe gently and regularly in the same direction.

Also, when cleaning, do not sprinkle water directly onto the surface of the display . Water entering the LCD will cause the screen to short-circuit. If moisture has entered the LCD, it should be placed in a warmer place to allow the moisture and organic compounds in it to evaporate. After cleaning, let it sit for 30 minutes, then turn on the power to remove moisture, otherwise the static electricity will be too strong and it will easily cause the TV to burn.

Also, don’t look at the large size of flat-panel TVs . LCD screens are fragile, even IPS hard screens are no exception, so avoid strong impact and vibration, and don’t put pressure on the screen surface.