The rise of LED backlight means that the CCFL out?

A cafe owner recently encountered a headache, a 15 inch LCD screen three years ago cafes began to yellow, with two or three or even visible flicker definition has been greatly reduced, regardless of how to adjust the brightness is of no avail. In desperation, had to let the technical staff to open the inspection, only to find the culprit - backlight bad. Backlight module is an essential part of LCD tv. As is known to all, liquid crystal is a kind of material between liquid and crystal. The wonderful thing about liquid crystal is that it can change its molecular arrangement by the current, and it can control the amount of light passing through the liquid crystal. But the LCD itself does not emit light, so all of the LCD backlight. Backlight tube broken, do not change, it means that the whole machine scrapped.

CCFL cold cathode fluorescent lamp

LCD does not emit light, which determines the importance of LCD backlight application. From birth to now, LCD backlight for almost all of the cold cathode fluorescent lamp (Cold Cathode Fluorescent Lamps). This light source life is short, after 2 years of use, the screen will gradually turn dark yellow, poor quality of the production of CCFL backlight is often less than 3 years to scrap. Over the years, the domestic and international monitors manufacturers in order to enhance the performance of LCD TVs, are committed to exploring and developing new backlight. At present, the industry is more optimistic about LED backlight technology, and have launched a LED backlight computer monitors, LED backlight notebook, LED backlight LCD tv. So, the rise of LED backlight means that the elimination of CCFL? This paper tries to analyze the two aspects of technology and market demand, to answer the questions we are most concerned about. Technical analysis: LED technology is superior to the CCFLLCD backlight module, including the light source (CCFL or LED), light guide plate, reflector, diffuser, prism, frame, etc.. The backlight module light guide plate is often used in the production of poly (methyl methacrylate), which is used to convert the point (line) light source into a surface light source, and the light energy is derived, which plays a very important role in the uniform distribution of light intensity. The diffusion plate is composed of a plastic material (PET or PVC) which is added with organic or inorganic particles, and the utility model is used for guiding the light beam to the direction perpendicular to the LCD panel and homogenizing the light energy. Prism (film), which can reduce the solid angle, so as to improve brightness, and can further correct the beam to the vertical direction. CCFL backlight technology, a physical presence to highlight the drawbacks of CCFL is sealed inert gas Ne+Ar gas mixture in a glass tube, which contains trace mercury vapor (mg), and on the inner wall of the glass coated phosphor. CCFL through the electrodes at both ends of the lamp tube, so that the gaseous mercury in the lamp tube to stimulate the ultraviolet light on the wall of the impact of the fluorescent powder, thus emitting light. Its wavelength is determined by the characteristics of fluorescent material.

Working principle of CCFL fluorescent tube

LCD TV is currently widely used CCFL light source, both from the light emitting principle or from the physical structure, and we are very close to the daily use of fluorescent tubes. The utility model has the advantages of simple structure, small temperature rise on the surface of the lamp tube, high brightness of the lamp tube, and easy processing into various shapes. But the service life is short, containing mercury, narrow color gamut, can only reach 70% ~ NTSC of. For large size TV screens, CCFL's voltage rise and long pipe processing are also difficult. First, the most headaches is the short life. CCFL back light source service life is generally 15000 hours to 25000 hours, LCD (especially the LCD screen of notebook computer) using the longer the brightness decline more obvious, in the use of 2 ~ 3 years after dark, the screen will become yellow and LCD, which is the defect of CCFL service life for a shorter period caused. Second, limiting the LCD display color. Each pixel is composed of R, G, B three rectangular color blocks, and LCD display color performance depends entirely on the backlight module and color filter performance. Three color filter film of the default CCFL emits a white light and sunlight as uniform (three colors of the respective components), but the CCFL backlight module does not actually meet the design requirements, only can achieve the standard of NTSC 70%.

CCFL and LED color gamut

Third, the structure is complex, and the luminance uniformity is poor. Because of the cold cathode fluorescent lamp is not planar light source, so in order to achieve uniform output brightness backlight, LCD backlight modules need collocation diffuser, light guide plate, the reflecting plate and other auxiliary devices, but in the display of all white or all black screen, differences between the edge and the center of the screen brightness is very obvious. Fourth, large size, power consumption is not ideal. Since the CCFL backlight must include complex optical devices such as diffuser, reflector, and so on, the volume of LCD cannot be further reduced. In terms of power consumption, the use of CCFL as a backlight source of LCD is also not satisfactory, 14 inch LCD CCFL backlight often consumes 20W or more power. It is worth noting that in recent years domestic and foreign manufacturers for the shortcomings of the traditional CCFL made some improvement, seems to have reached a very high level, the manufacturers publicity is that the miraculous, such as SHARP's four wavelength backlight system, through the improvement of the performance of CCFL lamp fluorescent powder in the red light, spectral components the enhanced, so as to improve the color reduction effect to a certain extent; part of the products of SONY, Samsung and TCL are also equipped with a WCG-CCFL- wide color gamut CCFL light source, the color gamut range up to NTSC standard 85%; intelligent backlight adjustment technology of TOSHIBA is to change the CCFL lights up shortcomings, according to the picture intelligent adjusting backlight brightness