LCD monitors are not unfamiliar to people, and you can see them in color-screen mobile phones, laptops and digital cameras that you usually see. If you buy a laptop and find that there is a bright spot on the LCD after using it, you will definitely find a business "theory". If you can't agree with the business, you will even resolve it with the Consumers Association. But in this case, if the two parties do not negotiate well, the Consumers Association often has no good solutions. Because the current national quality standards for the bright spots of liquid crystal displays are still blank, for now, it is up to each manufacturer to decide whether the "bright spots" problem is a quality problem like the above assumption. The standards customized by each manufacturer are not the same, ranging from "0 bright spots" to "7 bright spots" as qualified standards. There is even no place for quality testing, because the country has not yet issued testing standards. The lag in the introduction of quality and testing standards has affected the rights and interests of consumers and the popularity of LCD products. The author calls on relevant departments to issue quality and testing standards for LCD products as soon as possible. Many consumers pay attention to response time, price, warranty, and panel conditions when purchasing LCD monitors. But do you know that even behind the information that you think you have clearly understood, there are still many unclear questions.
Response time
The National Electronic Computer Quality Supervision and Inspection Center recently inspected LCD monitors. Among more than 10 brands and 22 models of products, one model of the monitor cannot be powered on normally, and the actual test index of the 12 models of products exceeds the indicated index. , The sample response time qualified rate is only 42%. Among them, the actual response time indicator of individual products is 26.6 milliseconds, but in the stated indicators, it is nominally 16 milliseconds. The National Electronic Computer Quality Supervision and Inspection Center pointed out that the actual test indicators of response time for most samples more or less exceeded the stated indicators, which shows that the problem of untrue indicator of the response time indicators of the liquid crystal display is more prominent. Among them, response time and point defect (level of liquid crystal panel) have become the hot spots of speculation by some manufacturers and consumers.
For such a low pass rate in this test, the person in charge of the LCD manufacturer believes that the response time indicated by the manufacturer is the peak value of the display speed that the LCD can achieve under certain circumstances, not the average speed. For the response time, the manufacturer generally calculates it according to the typical value and the maximum value. The nominal response time on the display is actually a response speed in the ideal state of the display. The response time is divided into "rising response time" plus "falling response time", that is, the time it takes for a pixel to change from black to white (rising), and then from white to black (falling). The corresponding time on the product label should be the total value of the rise time plus the fall time. However, some businesses only mark the rise (or fall) response time as the response time of the liquid crystal.
The industry still lacks standards for testing the response time of liquid crystals. This means that manufacturers can choose different methods to indicate the response time of their products. The lack of standards for the classification of LCD panels is often hidden in the familiar slogans such as AA-level panels and A+-level panels. According to reports, the number of dead pixels, bright spots and dark spots of the LCD panel, as well as indicators such as color purity and viewing angle, constitute the three levels of A, B, and C of the LCD panel. However, different LCD panel manufacturers have different grading conditions for their products: some manufacturers define LCD panels with less than 3 "point defects" as Class A, and some manufacturers define LCD panels with 5 or less "point defects" The panel is defined as Class A, and LCD panels without any "point defects" are also classified as Class A++, Class A+, and so on.
For the time being, there is no unified domestic standard for panel grade classification, but everyone in the industry formulates their own standards according to some default rules. For example, what you call A-level panels are panels that have outstanding performance in terms of viewing angle, contrast, and brightness. Although the "industry standard" has defined the panel grade, the industry believes that in this case, it is difficult for consumers to determine the grade and quality of the panel. More importantly, the division of A and B panels by panel manufacturers does not simply depend on the number of dead pixels, but starts from comprehensive indicators such as uniform brightness and color saturation. In this way, consumers have no way to start. In addition, some manufacturers only stated that they use Class A panels in their publicity, but they did not explain how they are defined. The National Computer Quality Supervision and Inspection Center stated that it is precisely because different LCD panel manufacturers have inconsistent requirements for the corresponding conditions of A, B, and C levels. There is confusion among consumers.
Standards lagging consumers' rights and interests are difficult to guarantee
It is understood that the existing GBT9813-2000 "General Specifications for Microcomputers" Appendix C "LCD Dead Pixel Acceptance Standards", SJT11292-2003 "General Specifications for Computer Liquid Crystal Displays" Appendix A "Acceptable Failure Points" is for computer LCD monitors The dead pixels or failure points ("white dots" or "black dots") are clearly defined. Among them, the maximum applicable size of GBT9813-2000 "General Specification for Microcomputers" is only 14 inches, so it has been lagging behind the current LCD market development. The "General Specification for Computer Liquid Crystal Displays" released in 2003 has been in line with the international standard ISO13406-2. However, as an industry standard, it remains to be seen when it will become a national standard.
In the absence of new national or industry standards, all LCD manufacturers should uniformly implement the current international standard ISO13406-2, which was updated in 2001 to identify the sensitive performance indicators of LCD products to avoid causing market sales. Caused confusion in propaganda.
However, even the nearest ISO13406-2 standard to us is inevitably lagging. ISO13406-2 stipulates that 15-inch LCD monitors cannot have more than one bright spot, one dark spot, and three color points. However, it is obvious that since the 13406-2 standard was formulated earlier, when encountering large-size LCD displays such as 17-inch and 19-inch products, consumers will encounter an awkward situation: according to the ISO13406-2Class2 standard calculation 17 The inch LCD monitor allows 2 bright spots, 2 dark spots and 6 color dots. For users, it is obviously unacceptable to have 10 dead pixels on a monitor. Therefore, for manufacturers who have consistently adopted Class2, either Class1 standards must be implemented on large-screen displays, which is relatively easy to do according to current technical capabilities, or a new quality grading standard needs to be formulated. Therefore, some people in the industry believe that the current domestic and international LCD standards have been relatively lagging behind. The calculation of the number of dead pixels and whether the response time should be based on grayscale and other indicators are worthy of more detailed research.
