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Nowadays, the pictures of liquid crystal display products on the market are getting clearer and more refined, but not all screens are so excellent. So how does the LCD screen distinguish between good and bad screens? This involves a concept, the classification of LCD screens. Different display application scenarios, choose different LCD screen grades, so as to match the screen that is most suitable for your product. Generally, the grades of LCD liquid crystal screens can be roughly divided into A grade, B grade, and C grade. LCD panel manufacturers also divide A-level panels into two levels, A+ and A, which are mainly aimed at products with higher display quality requirements.

Classification of LCD screens——A+ grade LCD screens So what is the basis for distinguishing LCD screen levels? Usually the LCD screen industry judges the level of LCD screens based on the number of dead pixels on the LCD screen. First of all, let's introduce a concept: LCD screen dead pixels. We all know that the LCD screen can be subdivided into each sub-pixel, and the sub-pixels can display black and white and the three primary colors of red, green and blue. The dead pixel of the LCD screen means that no matter what the image displayed on the LCD screen is, a certain sub-pixel on the screen will always display the same color. Dead pixels can be roughly divided into two categories, one is that the sub-pixels are always black no matter how the screen is, called dark spots, and the other is that as long as the screen is turned on, there will always be bright spots, called bright spots. Generally speaking, dead pixels on the screen cannot be repaired, and can only be repaired by replacing the entire screen.

Knowing the concept of LCD screen dead pixels, let's roughly introduce the division of LCD screen levels:

A+ grade LCD screen: LCD screen without any dead pixels is called A+ grade LCD screen. Through the professional test software test, there is no bright spot in the power-on state, and there is no dark spot behind the display screen, and the display screen is stable and smooth. A+ grade LCD screen is the highest quality LCD screen, suitable for display fields that require extremely high display quality, such as LCD monitors, vehicle displays, medical displays, etc.

A-level LCD screen: The total number of dead pixels does not exceed 3, and there is only one bright spot at most, and the bright spot is not in the central area of the screen. We call it an A-level LCD screen. The screen display is still high-quality and smooth, and generally there will be no obvious dead pixels during use. General application and LCD TV, home appliance display and other fields.

B-level LCD screen: The total number of dead pixels does not exceed 5, and there are only 2 bright spots at most, and the bright spots are not in the central area of the screen, which is called B-level LCD screen. The brightness of the screen is relatively uneven, and the color saturation is relatively insufficient. Most cheap LCD monitors use this kind of B-level panel, and the cost is relatively cheap.

TFT LCD screens are now widely used in various fields, covering every corner of our daily life. We all know that some LCD screens are large in size, such as tablet computers and home appliances, and some are relatively small in size, such as handheld devices and smart wearables. Then let's analyze from the perspective of LCD screen size, and briefly introduce the application fields of LCD screens of various sizes.

Industrial handheld devices: such as infrared ranging, infrared thermal imaging cameras, temperature measurement, noise measurement, etc., the size of the LCD screen is between 2.0 inches and 5.0 inches. This type of equipment requires the screen to be visible in the sun. wide operating temperature.

ATM/POS machine: products that charge by swiping cards and scanning. The size of the LCD screen is 3.5 to 5.0 inches, and the screen is required to have a high-definition touch screen.

Car gauge LCD screen: used in car instrumentation, car central control, the size of the LCD screen is 7.0 inches to 10.1 inches, the car gauge screen requires capacitive multi-touch, has ultra-wide operating temperature, shock resistance, ultra-wide viewing angle, LCD screen with high brightness and high definition.

Industrial equipment: such as small processing equipment, numerical control equipment, etc., the size of the LCD screen is 7.0 inches to 10.1 inches, and the screen is required to be touch-sensitive, shock-resistant, impact-resistant, and stable.

Medium-sized medical equipment: such as syringe pumps, ECG monitors, fetal heart rate monitors, ventilators, etc., the size of the LCD screen is 7.0 inches to 10.1 inches, and the screen is required to have an ultra-wide viewing angle and a long lifespan.

Home medical products: blood pressure meters, blood glucose meters, thermometers, etc., the size of the LCD screen is 2.8 inches to 5.0 inches, requiring the screen to be impact-resistant and have a wide viewing angle.

Instruments and meters: oscilloscope, optical time domain, optical cable survey, smart scale, etc., the size of the LCD screen is 3.5 to 7.0 inches, and the viewing angle of the screen is required to be wide.

Industrial tablet equipment: man-machine interface, outdoor handheld tablet, etc., the size of the LCD screen is 7.0 to 10.1 inches, and the LCD screen is required to have high resolution, shock resistance, and impact resistance.

LCD screen application field Smart home: smart switch panel, air conditioner panel, background music wall host, etc., the size of the LCD screen is 3.5 to 7.0 inches, and the screen is required to have an ultra-wide viewing angle and a long life.

Nautical equipment: GPS navigator, console instrument, etc., the size of the LCD screen is 7.0 to 10.1 inches, and the screen is required to have an ultra-wide operating temperature, be visible in the sun, and have a long life.

Household appliances: white goods, kitchen appliances, etc., the size of the LCD screen is 3.5 to 10.1 inches, and the LCD screen is required to have a wide viewing angle and a long life.

Elevator equipment: floor panel, elevator inner panel, LCD screen size is 4.3 to 8.0 inches, and the LCD screen is required to have a wide viewing angle and a long life.

What is the soft screen of an lcd display liquid? Which is a hard screen, first of all, let's introduce their concepts. The hard screen technology of LCD adopts a horizontal arrangement as the arrangement structure of liquid crystal molecules. When encountering external pressure, the molecular structure sinks slightly downwards, but the overall molecules are still horizontal. LCD hard screens are mainly IPS panels. The soft screen technology of LCD adopts vertical arrangement as the arrangement structure of liquid crystal molecules. When the finger crosses the LCD panel, "ripples" will appear at the same time, and the LCD soft screen is mainly a VA panel.

Let's analyze the difference between LCD hard screen and soft screen:

1. The arrangement of liquid crystal molecules is different: the IPS hard screen is a parallel arrangement of molecules, and the VA soft screen is a vertical arrangement of molecules. This will affect the response time of the screen. The inclination angle of the initial alignment direction of the soft screen liquid crystal molecules relative to the direction of the electric field is extremely small, and most of the liquid crystal molecules need to be rotated by nearly 90 degrees during the driving process; while the liquid crystal molecule alignment of the hard screen horizontal alignment technology generally has an inclination angle of 5 degrees compared to the direction of the electric field Above, only need to rotate 80 degrees during the driving process, and most of the liquid crystal molecules do not need to rotate to the limit angle during the driving process. Therefore, the response time of the LCD hard screen is better than that of the soft screen.

2. The surface of the LCD panel is different: VA soft screen is an LCD panel without a protective film. IPS hard screen is to add a layer of transparent resin material with a high hardness on the LCD screen to protect the outer film. In fact, the fundamental difference between an LCD hard screen and a soft screen is that the surface of the screen is coated or uncoated.

The difference between LCD hard screen and soft screen 3. Differences in viewing angle: viewing angle is an important indicator of LCD screens, especially for large-size screens, the differences in brightness, contrast, and color between front and side viewing angles will greatly affect the viewing experience. The VA soft screen vertical alignment technology uses 4-domain pixel electrodes to use liquid crystal molecules to flip in 4 directions to improve the performance of the viewing angle. There are still a lot of deficiencies in shifting, and the use of compensation films is still not optimistic. The IPS hard screen technology adopts an 8-domain design and applies different voltages to two 4-domain partitions in a pixel to increase the dispersion of the liquid crystal molecule arrangement and improve the color shift. The horizontal alignment technology of the IPS hard screen is determined by innate genes. In addition to its advantages in viewing angle, it can achieve a side viewing angle display effect far exceeding that of a VA soft screen without using a compensation film.

4. The pressing characteristics of the screen are different: when the LCD soft screen is lightly pressed with a finger or scratched with a fingernail, there will be obvious water ripples, but they will disappear after a while, and the image quality will not be affected. The hard-screen screen has a certain degree of stability, and there will be no obvious marks when you press it lightly with your fingers, which is good for screen protection, but the bonding process must be good enough.

5. The display effect is different: the soft screen has good color performance and a strong sense of layering, but the viewing angle is relatively poor, the touch will be distorted, and the high-speed motion picture is poor. The hard screen has a large viewing angle, fast response, and accurate color reproduction.

LCD circular liquid crystal screen - as the name implies, it is a round liquid crystal screen. Most of the LCD screen products we usually come into contact with are square or rectangular, and there are relatively few circular screens. But in recent years, with the change of people's aesthetics, more and more circular LCD screens have been used in various fields, such as smart watches, smart wall clocks, electric vehicle meters, car display meters and so on. Usually it is a relatively small size application scenario. Next, let us introduce the LCD circular LCD screen in detail.

Brief introduction of LCD circular LCD screen

In fact, the display principle of the LCD circular liquid crystal screen is the same as that of the conventional rectangular liquid crystal screen, but through the production technology of the liquid crystal glass and the adjustment of the screen parameters, the circular screen can display normally even in the circular state. The key to the decisive factor is the design and formulation of the drive scheme, that is, how to establish a good bridge between the circular LCD screen and the motherboard. Circular LCD screens are basically used on smart devices, and they pay more attention to the driving scheme and UI interface design scheme. Therefore, the circular LCD screen is actually an innovative, intelligent, and high-end LCD product. The display size is relatively small, commonly used are 2.1 inches, 2.36 inches, 3.4 inches, 6.2 inches and so on. Circular LCD screens also have their own unique common faults, such as dissatisfaction around the arc of the display screen, or white light around the arc.

LCD circular LCD screen parameter table

LCD circular LCD screen drawing Second, the application field of LCD circular liquid crystal screen

LCD circular liquid crystal screens are divided into large size and small size. Small size circular screens are more widely used, such as smart wear, smart watch, smart wall clock, electric vehicle instrument, car display instrument, smart home appliance, smart handheld device and so on. Large-size circular screens are also used, and the general size is more than 20 inches, such as new medical equipment, industrial equipment central control, museum exhibition halls, corporate meeting rooms, financial media centers, commercial places, etc. Please see the example diagram below.

LCD (Liquid Crystal Display) displays through the movement of liquid crystal molecules and backlighting, while OLED (Organic Light Emitting Diode) emits light once it is powered on.

So the main difference between them is that LCD displays need a backlight to illuminate the screen, while OLED displays can generate light by themselves.

Basic composition of LCD and OLED Compared with LCD displays, OLED does not require external light, so it can reduce the number of CCFL backlight modules, as well as TFT glass, C/F glass and a set of substrates. Due to these characteristics, the structure of the OLED display is simpler, lighter, and power-saving.

In the era of full screens, OLED displays are more popular. And this is also related to fingerprint recognition technology. Because this technology needs to see through the display, the thinner the display, the better. That's why OLED displays are favored. All in all, OLED displays are better for smartphones.

The structural difference between LCD and OLED However, not all OLED displays are perfect. LCD display has 3 panel types: TN panel, VA panel, IPS panel. There are also 2 types of OLED displays: AM active and PM passive. Although AMOLED plays a leading role in the market, the display effect of AMOLED still varies from manufacturer to manufacturer.

Why AMOLED have different display effects?

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P-array of AMOLED: When it comes to the shortcomings of AMOLED, the first thing people think of is the P-array, that is, the Pentile array. Samsung is the first company to mass-produce OLED panels and use P-array. The Galaxy S4 first used a P-array called Diamond Pixel, which took a different path from the standard RGB arrangement.

RGB type and P array Simply put, the RGB type arranges the sub-pixels of the three primary colors of red, green, and blue evenly, and the RGB sub-pixels are not evenly arranged in the P array, but share pixels, so the actual pixel density of the P array is higher than that of the RGB Low. This has led to the fact that even at the same resolution, the P-array OLED display is not as clear as RGB, so it is often called "big fruit color-changing screen".

With the rapid development of electric vehicles, the number of supporting charging piles is also increasing. We can see them everywhere in residential parking lots, public parking lots, and high-speed service areas, and TFT LCD screens have become an important carrier of human-computer interaction for charging piles. The LCD screen on the charging pile can display important data such as charging capacity, electricity cost, and required time. We can complete the corresponding charging operation by swiping the card on the human-computer interaction interface. So how to choose the type of LCD screen used on the charging pile, and what customization requirements are there?

Charging pile LCD display Customization requirements for charging pile LCD screen

The TFT LCD screen on the charging pile can be customized according to the site conditions, generally considering factors such as size, brightness, waterproofing, climate conditions, and electromagnetic interference. Usually, there are some customization requirements as follows.

High brightness requirements: Most charging piles are installed outdoors, and the brightness requirements of display screens must be higher than those indoors. Generally, we need to choose bright outdoor screen products with screen brightness greater than 900 cd/m2 and LCD backlight service life greater than 50,000 hours. The core technology of high-brightness LCD screens lies in the packaging process of LED backlights and energy efficiency. If the packaging process and energy efficiency are not up to standard, the heat generated during the use of the high-brightness screen will be greater, which will affect the use effect and service life of the screen. The outdoors itself is a very hot environment, plus the heat generated by the screen itself, so the LCD screen of the charging pile needs heat dissipation technology to reduce the temperature of the backlight and ensure the normal operation of the backlight so that the screen can be used normally. Usually, we add graphene to the back cover of the outdoor screen, which can have a good heat absorption and heat dissipation effect. In addition, using high-quality LED backlights with high energy efficiency to save energy and reduce heat generation is also an important outdoor high-brightness screen solution.

Wide working temperature requirements: The outdoor ambient temperature varies greatly with the seasons, and the charging process will also generate heat. Therefore, the outdoor charging pile screen needs to be equipped with a TFT LCD display with a wide operating temperature. The working environment temperature of the charging pile is generally: -20°C ~ +50°C, and for the selection of the temperature range of the LCD screen, it needs to be wider than this ambient temperature, generally -20°C ~ +70°C, if the outdoor environment is relatively harsh In some places, you can choose a wide temperature LCD screen from -30°C to +85°C.

Other requirements: The working environment of outdoor charging piles is affected by the weather, such as bright sun and heavy rain, so the LCD screen has the requirements of waterproof, dustproof, UV-proof, and external impact resistance; in addition, the charging pile will be charged during charging. There is serious electromagnetic interference, and the display screen must have a certain degree of anti-electromagnetic interference in order to be used normally. Usually, we need to carry out standard electromagnetic compatibility tests on products. https://www.hemlcd.com/products/tft/

With the rapid development of automobile technology, people's experience of using a car is not only limited to the driving texture, but the onboard display system has attracted more and more attention. Most of the car LCD screens currently on the market are LCD screens. Due to the special use environment of the vehicle display, the screen is generally required to be moisture-proof, dust-proof, anti-glare, visible under high-brightness sunlight, and resistant to high and low temperatures. These can be said to be the most basic requirements for on-board display and combined with physical buttons, it is a qualified on-board display product.

However, with the intelligent development of in-vehicle display technology, the screen will not stay at the stage of physical buttons. The in-vehicle touch screen is currently developing rapidly. Representatives of a series of new energy models such as Tesla, Weilai, and Xiaopeng, even All the physical buttons have been abandoned, and a whole car touch LCD screen is used to integrate all functions. Car touch screens and car touch screens will be the development trend and future of car displays.

car touch screen Most car touch screens use capacitive touch technology, and the technical characteristics of capacitive touch screens have also been introduced in our previous articles. Capacitive touch screens are different from resistive touch screens. The biggest advantage is high touch accuracy, fast response, and support for multi-point touch. , to support larger screen sizes.

First of all, let's talk about the large size of the car's capacitive touch screen. Today's car touch screens are becoming larger and larger. Large-size car screens can not only integrate more functions on the screen, but also fully display the menu, and greatly improve the presentation of visual effects. Traditional car companies such as Toyota and Volkswagen have increased the size of the touch screen to more than 10 inches, and new energy vehicles such as Tesla and Weilai have even increased the size of the touch screen to more than 15 inches. Capacitive touch modules can be customized in various sizes, especially for large-sized car touch screens, which can fit perfectly. Therefore, the capacitive touch screen is the first choice for large-size vehicle displays at present.

Secondly, let's talk about the multi-touch of the capacitive touch screen. How is multi-touch implemented? Specifically, the screen is divided into blocks, and a group of mutual capacitance modules is set in each block to work independently so that the capacitive screen can independently detect the touch conditions in each area, and after processing, realize multi-touch. Multi-touch is very useful in the application of car touch screens, especially when zooming in and out of map navigation, it is very convenient.

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In the use of some outdoor equipment, due to environmental reasons, the brightness of the screen is usually required to be very high. Such as handheld infrared thermometers, outdoor commercial screens, etc. This requires us to use an outdoor bright LCD screen as the screen of the device. Next, let's focus on the concept and characteristics of outdoor bright LCD screens.

1. The concept of the outdoor bright LCD screen

The so-called outdoor high-brightness LCD screen, as the name suggests, first of all, it is brighter than ordinary LCD screens. The maximum brightness of an ordinary LCD screen is within 500 units, and the backlight source uses CCFL, which cannot be seen clearly outdoors. The reason why the outdoor high-brightness LCD screen can be used outdoors is to increase the brightness of its backlight. LED backlight is used, which is similar to or even higher than outdoor brightness. Generally, it needs to be higher than 500 units, and some can even reach the highest. 2000nits brightness, so that the outdoor LCD screen can be clearly displayed. Secondly, due to the variability of the outdoor environment, to ensure that the screen can operate normally without hindrance in various environmental conditions, the outdoor high-brightness screen must also have multiple functions such as wide temperature range, dustproof, and waterproof.

Outdoor bright LCD screen Second, the characteristics of the outdoor bright LCD screen

The outdoor high-brightness LCD screen has many advantages such as high brightness, high resolution, long life, wide temperature range, waterproof and dustproof. The most important feature is, of course, the high brightness, which is above 500nits. Using high-efficiency LED backlight modules, not only the brightness and contrast are greatly improved, but also the display effect and lifespan are also greatly improved. In this way, it is visible and readable in outdoor sunlight and has an ultra-wide brightness range.

Secondly, the resolution is also a very important indicator. It refers to the number of pixels that can be displayed in the horizontal and vertical directions on the screen. High resolution can make the picture more delicate and display more important information on the screen.

Wide temperature characteristics of the outdoor bright LCD screen. The outdoor environment is changeable, ranging from high-temperature exposure to ultra-low temperature. Therefore, the screen used outdoors must have the characteristics of a wide temperature range, and the working temperature and storage temperature of the screen must reach the range of -30°C to 85°C. Only by paying attention to high and low-temperature design can the failure of outdoor high-brightness LCD screens be reduced.

Dustproof and waterproof performance of outdoor high-brightness LCD screen. In addition to the cold winter and hot summer, there is also dust and water outdoors. The waterproof and dustproof outdoor screen is generally designed together with the whole machine, and special attention should be paid to the selection of materials to prevent the screen from entering water and dust.

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