tft display burn in factory
TFT LCD image retention we also call it "Burn-in". In CRT displays, this caused the phosphorus to be worn and the patterns to be burnt in to the display. But the term "burn in" is a bit misleading in LCD screen. There is no actual burning or heat involved. When you meet TFT LCD burn in problem, how do you solve it?
Burn in is a noticeable discoloration of ghosting of a previous image on a display. It is caused by the continuons drive of certain pixels more than other pixels. Do you know how does burn in happen?
When driving the TFT LCD display pixels Continously, the slightly unbalanced AC will attract free ions to the pixels internal surface. Those ions act like an addition DC with the AC driving voltage.
Those burn-in fixers, screen fixer software may help. Once the Image Retention happened on a TFT, it may easy to appear again. So we need to take preventive actions to avoid burn in reappearing.
For normal white TFT LCD, white area presenting minimal drive, black area presenting maximum drive. Free ions inside the TFT may are attracted towards the black area (maximum drive area)
When the display content changed to full screen of 128(50%) gray color, all the area are driving at the same level. Those ions are free again after a short time;
If you"ve ever left your LCD monitor on a single static screen for an extended period, say 24 hours or more, and then changed the on-screen image and seen a "ghost" of the previous screen, you"ve experienced Image Persistence. You can also sometimes see this phenomenon while traveling through an airport and seeing the flight status monitors. The good news is that the persistence is not permanent, unlike previous technologies such as plasma displays or CRTs.
The previous technologies of plasma displays and CRTs are phosphor-based, and extended static images create a "burn-in" that affects the properties of the phosphor material and create permanent damage. The damage is called burn-in, whereas static image "ghosts" on an LCD are Image Persistence. Image Persistence is not permanent damage and is reversible. Modern LCDs include design, driver ICs and chemical improvements that minimize these effects.
To understand why image persistence happens, we must first understand the basic structure of an LCD TFT. Within the TFT, a voltage is applied to the liquid crystal material to align or twist the crystals in each pixel to allow light to pass through or block light, thus creating the on-screen image. By allowing a static image to remain on screen for an extended duration, the polarity of that voltage on the crystals remains. During this time, ions within the liquid crystal fluid will migrate to either the + or – electrode of the transistor (source or drain). As these ions accumulate on the electrodes, the voltage applied to the crystals to align or twist is no longer sufficient to completely change the image on-screen, resulting in a "ghost effect" from the previous image.
The best method for preventing Image Persistence is to avoid having any static images on the screen for an extended time. If the image changes periodically, the ion flow will never have an opportunity to accumulate on any internal electrode. However, depending upon the use of the display, it is not always possible to avoid static images on the screen. In cases such as these, there are steps that you can do to reduce the chance of persistence.
Switching off the displayduring periods of inactivity (sleeping mode) and arousing at necessary image changes would also be reflected as a positive side effect providing lower power consumption.
Panel manufacturers specifically test for the phenomenon and have designed the TFT cell and improved the purity of the liquid crystal fluid to minimize any effect of image persistence.
If you have a project that is considering taking advantage of any display technology, US Micro Products can provide a solution designed for your application. Send us an email at sales@usmicroproducts.com.
In my application, the same data will/can be kept on the TFT LCD display for a long time e.g couple of days or even for months and I can"t run any screen saver. I have read that this causes pixel burn or damage.
Does your Company offer any solution in terms of Industrial Grade Displays for Panel Monitoring with long long life ( Back-light as well as pixel safety)?.
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LCD (liquid crystal display) is the most widely used display technology. They are used for automotive, appliance, telecommunication, home appliance, industrial, consumer electronic, military etc. But LCD displays have some drawbacks, such as slow response, narrow viewing angle, lower contrast etc. One annoying phenomenon often complained about by users is image sticking.
If a fixed image remains on a display for a long period of time, the faint outline of that image will persist on the screen for some time before it finally disappears. Normally, it happens to LCD and plasma screens, but for the purpose of our discussion, we will focus on TFT LCD displays. Image sticking is also referred to as “image persistence”, “image retention”, “ghosting” or “burn-in image.”
An LCD screen includes a thin layer of liquid crystal material sandwiched between two electrodes on glass substrates, with two polarizers on each side. A polarizer is an optical filter that lets light waves of a specific polarization pass through while blocking light waves of other polarizations. The electrodes need to be transparent so the most popular material is ITO (indium tin oxide). Since an LCD can’t emit light itself, normally a backlight is placed behind an LCD screen in order to be seen in a dark environment. The light sources used for a backlight can be LED (light emitting diode) or CCFL (cold cathode fluorescent lamps). The LED backlight is the most popular. Of course, if you want a color display, a layer of RGB color filter can be made into an LCD cell. A touch panel can also be added in front of an LCD display.
When an electric field is applied to the liquid crystal molecules, they become untwisted. When the polarized light reaches the layer of liquid crystal molecules, the light passes straight through without being twisted. When it reaches the second polarizer, it will also pass through, meaning the viewer sees the display as bright. Because LCD technology uses electric fields instead of electric current (electron passes through), it has low power consumption.
The cause of LCD image sticking is due to an accumulation of ionic impurities inside the liquid crystal materials. When slight DC voltage occurs, the charged impurities will move the electrodes and build up a reversed voltage field. When the power is removed, the reversed voltage will kick in to make the LCD molecules twisted different from the other part of the LCD, which shows up as the image sticking. The longer the time, the more impurities will migrate, the larger the reversed voltage will be, and the imaging sticking will appear worse.
Using the black/white chess board image shown above: Static image it for 2 hours, then change to 50% gray for 1 min. Use an 8% neutral density filter to check if it is OK.
If a static image must be displayed, try to use block patterns instead of distinct border lines. Try to use medium gray hues and use colors that are symmetric to the middle grey level at the boundary of two different colors. Gradually shift the border lines once in a while.
For LCD manufacturers, try to protect liquid crystal materials exposed to the air by using nitrogen gas or dried air to avoid absorbing moisture that can create a huge amount of impurities in the liquid crystal material, as water is an excellent solvent. Controlling the humidity of the fab is also very important, as is selecting the right liquid crystal materials and their manufacturers. Different liquid crystal materials have different moisture absorbing abilities. Different liquid crystal material factories have different capabilities in terms of controlling impurities. Despite the fact that high purity can mean high in cost, using higher purity liquid crystal materials and designing the circuitry to get rid of DC in LCD display drivers can avoid an image sticking issue.
Unlike the “burn-in” issue common with CRTs, an image sticking issue is not permanent. It will eventually recover after some time. One way to expedite erasing a retained image is to have a screen on in an all-black pattern for 4-6 hours. If you want to make it even faster, the display can be put into an environment with a temperature of around 35 to 50°C for 1-2 hours. As this elevated temperature is within the working temperature range, it will not damage the LCD panels.
DGBELL"s burn-in chamber is widely applied to electronic and electric products, components and materials by constant high low temperature, temperature shock and rapid temperature change reliability test.
With high precision perfect external design, external with double sides cold rolled plate electrostatic powder coated material, internal with SUS#304 high temperature resistant stainless steel. Insulation material adopts fire resistant high strength glass fiber thermal insulating material. The Control system and control circuit all introduced with the famous brand.
DGBELL"s burn-in chamber is widely applied to electronic and electric products, components and materials by constant high low temperature, temperature shock and rapid temperature change reliability test.
With high precision perfect external design, external with double sides cold rolled plate electrostatic powder coated material, internal with SUS#304 high temperature resistant stainless steel. Insulation material adopts fire resistant high strength glass fiber thermal insulating material. The Control system and control circuit all introduced with the famous brand.
Steven Van Slyke and Ching Wan Tang pioneered the organic OLED at Eastman Kodak in 1979. The first OLED product was a display for a car stereo, commercialized by Pioneer in 1997. Kodak’s EasyShare LS633 digital camera, introduced in 2003, was the first consumer electronic product incorporating a full-color OLED display. The first television featuring an OLED display, produced by Sony, entered the market in 2008. Today, Samsung uses OLEDs in all of its smartphones, and LG manufactures large OLED screens for premium TVs. Other companies currently incorporating OLED technology include Apple, Google, Facebook, Motorola, Sony, HP, Panasonic, Konica, Lenovo, Huawei, BOE, Philips and Osram. The OLED display market is expected to grow to $57 billion in 2026.
AMOLED (Active Matrix Organic Light Emitting Diode) is a type of OLED display device technology. OLED is a type of display technology in which organic material compounds form the electroluminescent material, and active matrix is the technology behind the addressing of individual pixels.
An AMOLED display consists of an active matrix of OLED pixels generating light (luminescence) upon electrical activation that have been deposited or integrated onto a thin-film transistor (TFT) array, which functions as a series of switches to control the current flowing to each individual pixel.
Typically, this continuous current flow is controlled by at least two TFTs at each pixel (to trigger the luminescence), with one TFT to start and stop the charging of a storage capacitor and the second to provide a voltage source at the level needed to create a constant current to the pixel, thereby eliminating the need for the very high currents required for PMOLED.
TFT backplane technology is crucial in the fabrication of AMOLED displays. In AMOLEDs, the two primary TFT backplane technologies, polycrystalline silicon (poly-Si) and amorphous silicon (a-Si), are currently used offering the potential for directly fabricating the active-matrix backplanes at low temperatures (below 150 °C) onto flexible plastic substrates for producing flexible AMOLED displays. Brightness of AMOLED is determined by the strength of the electron current. The colors are controlled by the red, green and blue light emitting diodes. It is easier to understand by thinking of each pixel is independently colored, mini-LED.
IPS technology is like an improvement on the traditional TFT LCD display module in the sense that it has the same basic structure, but with more enhanced features and more widespread usability compared with the older generation of TN type TFT screen (normally used for low-cost computer monitors). Actually, it is called super TFT. IPS LCD display consists of the following high-end features. It has much wider viewing angles, more consistent, better color in all viewing directions, it has higher contrast, faster response time. But IPS screens are not perfect as their higher manufacturing cost compared with TN TFT LCD.
Utilizing an electrical charge that causes the liquid crystal material to change their molecular structure allowing various wavelengths of backlight to “pass-through”. The active matrix of the TFT display is in constant flux and changes or refreshes rapidly depending upon the incoming signal from the control device.
N2 - This paper describes a thorough investigation to identify the root cause of an LCD panel burn-in failure induced by an LCD source driver, which is observed in a large-scale LCD factory producing more than one million LCD panels per month. The investigation demonstrates the effectiveness of the circuit simulation to precisely locate the defective spot which is caused by a metal slice originated from outer rings of an LCD COG (chip-on-glass) source driver. With the aid of emission microscope (EMMI), Energy Dispersive Analysis X-Ray (EDAX), and Chip Probing (CP) tester, the root cause of the failure is well explained. The formation mechanism of metal slice from the outer rings is thoroughly studied. A solution to completely eliminate the source of metal slices from the outer rings during wafer processing is also proposed.
AB - This paper describes a thorough investigation to identify the root cause of an LCD panel burn-in failure induced by an LCD source driver, which is observed in a large-scale LCD factory producing more than one million LCD panels per month. The investigation demonstrates the effectiveness of the circuit simulation to precisely locate the defective spot which is caused by a metal slice originated from outer rings of an LCD COG (chip-on-glass) source driver. With the aid of emission microscope (EMMI), Energy Dispersive Analysis X-Ray (EDAX), and Chip Probing (CP) tester, the root cause of the failure is well explained. The formation mechanism of metal slice from the outer rings is thoroughly studied. A solution to completely eliminate the source of metal slices from the outer rings during wafer processing is also proposed.
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These recommendations for proper handling and cleaning will help prevent accidental damages and answer common questions related to display maintenance.
We explain the difference between permanent image burn-in and temporary image retention, and provide some tips for maintaining your display screens to help avoid burn-in.
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I would just turn down the brightness (for less power consumption and monitor longevity, the backlight has nothing to do with the "burn in") and leave a screen saver on overnight. On my monitor, once the screen is back to normal, it doesn"t come back for a while.
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