lcd module light bleed manufacturer
Backlight bleed is characterized as light leaking around the edges or corners of an LCD. This is due to the way these displays work; they use a light behind the panel that faces the display.
Backlight bleeding is simply some of the backlight leaking through. There are no ways to completely remove this, though it can be reduced in some scenarios. If you have too much backlight bleeding, you might be able to RMA your display.
Your LED LCD, whether it’s a TV or a monitor, uses a LED backlight to create the image through the liquid crystal display panel. Some of that light might not get entirely blocked around the display’s bezels, which results in backlight bleeding.
Generally, some minor backlight bleeding is expected due to the nature of the display technology, and it is entirely tolerable given you won’t even notice it most of the time.
However, sometimes the backlight bleeding can be rather eye-searing and, in this case, you may be able to return your display and get a new model or a refund depending on the manufacturer’s RMA policy.
The flashlighting issue, as the name suggests, looks as if someone’s pointing a flashlight at the screen, thus creating bright patches at the corners of the screen.
In short, if you are experiencing too much backlight bleeding, you should try to RMA your display. In case the display manufacturer won’t accept it, you will have to get a new monitor/TV, preferably with an OLED panel that doesn’t suffer from these issues (but has other drawbacks).
In case the backlight bleeding doesn’t bother you in real use, it’s not worth returning or replacing the display as another unit might have even worse backlight bleeding or other defects, such as dead or stuck pixels.
Unlike backlight bleeding, the intensity of IPS glow can be reduced by changing the angle or the distance you’re looking at the screen or by decreasing screen brightness and adding bias lighting behind the screen.
Many will assume bleed is normal, or bleed is no big deal. That is who most manufacturers cater to, unfortunately. An example would be my brother-in-law ... I checked out his lousy TN display, and noticed he didn"t even run it at the correct resolution. I corrected it for him, explained why running an LCD at the wrong res matters... yet he didn"t care. He just liked the fact that text was big and the monitor was bright.
In this post I’ll talk about pressure stains and light leaks and if you’d like it will be a pleasure for me to tell about other defects in the next post!
Light leak/ bleed is backlight shining through where it is not supposed to. Most often it can be seen on edges of the screen and in some cases as smaller spots in various areas.
Backlight is at the back of the screen and it allows you to see the actual picture as otherwise you would have to use a flashlight to see anything:) if one of the layers is slightly misaligned from the edge it creates light leakage in that area.
looks like a small bright spot or some times similar to a normal light leak and are caused by some internal components like screws or sharp board edges in the monitor/tablet/phone pressing against some of the panel layers causing them to stretch and letting more light to go through. In some cases pressure applied at the factory by workers during assembly can cause a pressure stain.
Electronic/structural function is not achieved, such as display isabnormal, speaker output sound distorted, battery cannot be charged,the expansion interface /UI no function, buttons no function, LED indicator lights’ status is incorrect, imperfect paintwork etc.There is bias on electronic/structural function, such as the display brightness is not up to the standard, speaker volume is soft, structure gap exceeds the standard etc.
from 1,00,000 screens 50% have no visually identifiable light leak from a typical end user viewing distance. 25% have minor light leak that can be seen. 20% have average light leak that most people would find annoying. 5% have SEVERE light leak.
*Some of you might think that calculation above is unfair as it does not include RMA (consumer return) costs. While it’s true! In the end of the day not so many people go for service and often times light leak is a grey zone in warranty of the product. *
If you produce lighting systems for products, you may be wondering how to fix backlight bleed on an overlay. Backlight bleed can be a frustrating issue, but there are some things you can do to reduce it. Read on to learn more about light guide design, backlight bleed and ways to reduce it.
Think of backlight bleed as an annoying leak. When you add graphic overlays to devices, every icon within the overlay is individually lit by an LED bulb behind it. Ideally, when a user touches a single icon, it lights up but the rest of the screen remains dark.
The issue is that light naturally wants to go everywhere. When a user pushes one icon on the screen, other icons will brighten because the LED light is spilling over into other sections of the screen.
Backlight bleed is more common in capacitive touch applications. Many of these devices contain graphic overlays that have multiple icons or buttons. Given the thinness of these applications and the minimal space between the icons and LEDs behind them, uncontrolled light leaks across the overlay.
While some minor backlight bleed is expected and even tolerable, it can also be too apparent. It even leads users to assume their devices are malfunctioning or broken.
We’ve helped our clients minimize backlight bleed with years of experimentation and finetuning. Our innovative light guide design adds different design features for better backlight control.
Cutout design – A cost-effective option to decrease light bleed is to make cuts with our in-house lasers directly into the light guides. These cutouts allow for better light blockage and control. While some light escapes the guide, it won’t spill over into unintended areas of the overlay.
Housing (with ribs) design – We’ve developed another solution that leverages white plastic housing with “ribs” or raised features that slide into the cutouts of the light guide. The housing ribs reflect light back into the light guide instead of letting it pass through any air gaps and into the neighboring section. The downside to this option is that the plastic housing adds more weight to the light guide, so it’s not always ideal for ultra-thin applications.
Foam design – Instead of housing ribs, we insert black foam to absorb escaping light. While this design is similar to a light guide with housing, the foam isn’t bulky and you can maintain a thin assembly.
Overmold design – Our overmold design is multiple small light guides with cutouts, fused together with a plastic molding to block backlight bleed. This process allows for no additional components (housings or foam) to be added to the assembly while still blocking light bleed. While this option is highly effective, it does require additional mold tooling and design, which makes it more expensive.
The right light guide design depends on your project requirements, volume and budget. However, it can be difficult to make the smartest decision without a B2B custom light guide partner on your side.
Our lighting experts help determine which option will deliver the absolute best results. We use our optical software to simulate where backlight bleed may occur within a given graphic overlay. This is just one way we work closely with you during a light guide design engagement.
Light leak or backlight bleeding is often noticeable around the edges or the sides of a screen. Especially while it is displaying a dark background or is in a dark environment.
Ideally, light leakage must not be inspected in a dark room. All Dell monitors are inspected as per industry standard with 150-Lux ambient lighting (similar to typical office lighting). However, for gaming monitors, ambient lighting is 70 Lux. Any visual inspection must be done in the same manner to help with the troubleshooting process.
NOTE: This article provides information about common issues that are seen on LCD screens. It is not something specific to a particular Dell computer but is something that can be seen on any LCD screen by any manufacturer.
Before proceeding to the troubleshooting section of this article, you must identify the issue that you are experiencing. Identify the light leak or light bleed issue using the examples below and ensure that this is the correct article for you.
The last thing you want on your monitor is light leaking around its edges. This is referred to as backlight bleeding. The backlight bleed test will help you determine if your monitor has this defect or no.
In many cases, you will not notice that your screen is suffering from too much light bleed until you use it in a dark room. Continue reading to learn more about a bleed test such as this, what causes this defect and how to prevent it.
Backlight bleeding is a screen defect that is likely to occur in new LCD displays that utilize a light source from the panel. The LCD panel itself is supposed to block out the excess backlight that is not needed when displaying an image/video.
Unfortunately, not all the light is blocked by the panel and as a result, light leaks around the edges of the frame. This is known as backlight bleeding and it can affect image/video clarity and spoil your gaming experience.
This is a type of backlight bleeding that is found on the corners of your monitor. In a serious case, the edges of the screen receive much more lighting whereas the center remains dimmer than on a normal monitor.
This is when there’re irregular patches of light still visible with a full black image screen. This type of backlight bleeding is more prevalent in larger displays than small ones.
The most common type of backlight bleed occurs along the edges of the screen. If you suspect your flat panel display suffers from possible backlight bleeding, you need to first make sure that you’re not mistaking it for an (In-Plane Switching) IPS glow.
If you’re not sure whether it’s a backlight bleed or IPS glow experience, it"s time for you to run a backlight bleed test. To perform the bleed test, follow these steps;
1. Turn off the room lights before you begin the bleed test. A dark room and a black screen/monitor make it easy to see if it is an IPS glow or backlight bleed.
3. Open a pitch-black image or black screen and search whether there are spots of light being emitted around the edges of the monitor or at the corners. If you don’t notice any backlight bleed issue or IPS glow, then your monitor is good.
There is also a website, lightbleedtest that you can use to bleed test this defect. Apart from a bleed test on your monitors, you can use them for your laptops and mobile phones.
This is a glow effect that appears along with the corners of an IPS screen especially when viewing dark/black content. It is the downside of IPS technologies that have a backlighting system to display images/video.
IPS displays are a type of LCD panel. IPS (In-Plane Switching) refers to the way molecules inside the liquid crystal display are positioned or oriented. IPS monitors are designed to widen the viewing angle without the image changing in color accuracy or contrast.
Depending on how long the image has stood still, burn-in can be remedied or reduced in some cases. You can do this by turning the screen off for at least 48 hours and then showing a white screen for a few days, for example with an image or screen saver. Set your background lighting low to save the LEDs. It"s often worth trying, but if the damage is too bad, this trick won"t work anymore either.
No matter how expensive an IPS panel is, it"s still an IPS panel and as such, it"s susceptible to the limitations and lighting-related defects that may arise as a result of;Both flashing and clouding can occur as a result of panel warping if the gaming monitor crews are too tight.
The above reasons cause pressure inside the LCD resulting in the disruption of liquid crystal alignments inside the panel. This damages the panel which causes light leaking in some areas much more than other parts.
The last thing you want to see after unpacking and powering your gaming monitor is a backlight bleed. Luckily for you, backlight bleeding can be treated in most cases. So, if light has started to creep through your monitor recently, do the following;Don’t try to fix it yourself first but rather get your monitor replaced. In case, it"s still covered by the warranty. Some companies will not accept it if it’s tampered with or the seal is broken.
2. Next, slightly loosen the screws at the back of your display. This should stop the problem. Turn on the display to see whether the backlight bleeding has stopped.
3. If not, switch it off again and then take the microfiber cloth and gently rub the areas where the backlight bleeding appears; in a circular pattern. You should only apply moderate pressure for the screen to warp slightly.
Unfortunately, massaging your monitor isn’t guaranteed to fix the screen 100% no matter how often you do it. In this case, the best thing to do is to make the backlight bleeding much more manageable.
If your monitor has a backlight bleed, one of the ways to remedy is to adjust the display brightness to around 30% to reduce the intensity of the bleed. Right away, your problem will be solved.
Some cases of backlight bleed are serious; if the warranty is still valid, take it back for replacement. Or, get a new quality display model with higher standards or zero/less backlight bleed.
OLED displays are completely immune to this problem since they don’t use a backlight. However, OLED monitors are expensive compared to regular monitors.
To ensure you don’t get a monitor with severe backlight bleed, buy the best one with minimal or less backlight bleeding. Make sure to read user reviews and see if other people are complaining about the excessive glow on the model that you are interested in before you purchase it.
Be careful with your monitor. Avoid situations that will cause harm on your display as this can damage or put a strain on its frame leading to backlight bleeding.
Some techies apply electrical insulation tape on the edges of the panel to block the excess lighting. Try it and am sure it will work on your monitor.
Check your display to ensure the screen is properly seating in its frame. If not, fix it by twisting it back into place and then check if the backlight bleeding problem has stopped.
To check for backlight bleed (commonly referred to as light bleed) on your display, play a full screen video or open a pitch-black image. Backlight bleed is the light that appears around the edges of the screen or in the corners.
Backlight bleed is a common issue with LCD displays, and unfortunately, there"s not much that can be done to fix it. The best solution is usually to try and adjust the viewing angle of the screen so that the bleed is less noticeable.
Backlight bleed is not always a defect, but it can be an indication of a defect. If there is too much light bleed from the backlight, it can cause a washed-out image on the screen. This is usually caused by a faulty or loose connection between the backlight and the screen.
ALL LED and LCD televisions, regardless of price or manufacturer, suffer from varying degrees of backlight bleed. Unfortunately, because the manufacturing process for these panels is significantly cheaper, it is extremely difficult to find a superior plasma television these days, as almost no one mass produces them.
Backlight bleeding occurs when light from the backlight of your monitor escapes through the screen"s edges. The light that was supposed to shine through the black screen now escapes along the edges, creating an uneven lighting pattern on the screen.
Both LCD and LED displays use backlighting, either via liquid crystals or light-emitting diodes. However, emissive OLED and MicroLED displays don"t use backlighting, so you won"t experience backlight bleed with these two display types.
Backlight bleeding occurs when the layers which make up the monitor or TV screen become misaligned. When this happens, pressure forms inside the display, which changes the alignment of the components that emit light. This misalignment directs light in the wrong direction and leads to backlight bleeding.
Even if cleaning the screen doesn"t work immediately, give it at least 24 hours to dry and settle before turning on the screen and testing to see if the backlight feed resolves.
If you"re stuck with a monitor or TV that"s not under warranty, another option is to turn down the brightness. Adjust the brightness down on your laptop or your TV so that it"s just low enough, so the backlight bleed issue fades away. This step isn"t an ideal solution, but it allows you to keep using the display without the problem.
Another quick fix is applying electrical tape to the very edge of the display. Doing this will reattach loose sections of the screen edge, which typically leads to backlight escaping from the edges of the screen.
Room lighting always has an impact on your TV viewing or PC gaming. Watching the display in a dark room can make the issue appear worse, so while this doesn"t count as a "fix," you can try to brighten the lights in the room, and you may not even notice the problem.
Use a screwdriver to loosen the screws on the back of the monitor or TV frame. You won"t have to open the display like you would if you were trying to repair it. Just loosen the screws and slightly twist the screen. When the frame screws are too tight, it can cause backlight bleed.
If the backlight bleed issue is too severe for any of the more straightforward fixes and there"s no warranty, you may need to resort to buying a new TV or a new laptop.
It depends on how much you"re willing to tolerate. Some bleed is normal when the screen is at full brightness, but it may be less noticeable if you dim the screen.
If your TV has a blue tint, it could be due to faulty cable connections or a defective LED backlight. Some TVs have a slight blue tint when operating normally.
Sometimes. All LCD screens have some backlight bleed at first, but as the pressure around the panel weakens with use, it will become less noticeable. If you"ve had your device for a while, the backlight bleed probably isn"t going away.
Glass substrate with ITO electrodes. The shapes of these electrodes will determine the shapes that will appear when the LCD is switched ON. Vertical ridges etched on the surface are smooth.
A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers. Liquid crystals do not emit light directlybacklight or reflector to produce images in color or monochrome.seven-segment displays, as in a digital clock, are all good examples of devices with these displays. They use the same basic technology, except that arbitrary images are made from a matrix of small pixels, while other displays have larger elements. LCDs can either be normally on (positive) or off (negative), depending on the polarizer arrangement. For example, a character positive LCD with a backlight will have black lettering on a background that is the color of the backlight, and a character negative LCD will have a black background with the letters being of the same color as the backlight. Optical filters are added to white on blue LCDs to give them their characteristic appearance.
LCDs are used in a wide range of applications, including LCD televisions, computer monitors, instrument panels, aircraft cockpit displays, and indoor and outdoor signage. Small LCD screens are common in LCD projectors and portable consumer devices such as digital cameras, watches, calculators, and mobile telephones, including smartphones. LCD screens have replaced heavy, bulky and less energy-efficient cathode-ray tube (CRT) displays in nearly all applications. The phosphors used in CRTs make them vulnerable to image burn-in when a static image is displayed on a screen for a long time, e.g., the table frame for an airline flight schedule on an indoor sign. LCDs do not have this weakness, but are still susceptible to image persistence.
Each pixel of an LCD typically consists of a layer of molecules aligned between two transparent electrodes, often made of Indium-Tin oxide (ITO) and two polarizing filters (parallel and perpendicular polarizers), the axes of transmission of which are (in most of the cases) perpendicular to each other. Without the liquid crystal between the polarizing filters, light passing through the first filter would be blocked by the second (crossed) polarizer. Before an electric field is applied, the orientation of the liquid-crystal molecules is determined by the alignment at the surfaces of electrodes. In a twisted nematic (TN) device, the surface alignment directions at the two electrodes are perpendicular to each other, and so the molecules arrange themselves in a helical structure, or twist. This induces the rotation of the polarization of the incident light, and the device appears gray. If the applied voltage is large enough, the liquid crystal molecules in the center of the layer are almost completely untwisted and the polarization of the incident light is not rotated as it passes through the liquid crystal layer. This light will then be mainly polarized perpendicular to the second filter, and thus be blocked and the pixel will appear black. By controlling the voltage applied across the liquid crystal layer in each pixel, light can be allowed to pass through in varying amounts thus constituting different levels of gray.
The chemical formula of the liquid crystals used in LCDs may vary. Formulas may be patented.Sharp Corporation. The patent that covered that specific mixture expired.
Most color LCD systems use the same technique, with color filters used to generate red, green, and blue subpixels. The LCD color filters are made with a photolithography process on large glass sheets that are later glued with other glass sheets containing a TFT array, spacers and liquid crystal, creating several color LCDs that are then cut from one another and laminated with polarizer sheets. Red, green, blue and black photoresists (resists) are used. All resists contain a finely ground powdered pigment, with particles being just 40 nanometers across. The black resist is the first to be applied; this will create a black grid (known in the industry as a black matrix) that will separate red, green and blue subpixels from one another, increasing contrast ratios and preventing light from leaking from one subpixel onto other surrounding subpixels.Super-twisted nematic LCD, where the variable twist between tighter-spaced plates causes a varying double refraction birefringence, thus changing the hue.
LCD in a Texas Instruments calculator with top polarizer removed from device and placed on top, such that the top and bottom polarizers are perpendicular. As a result, the colors are inverted.
The optical effect of a TN device in the voltage-on state is far less dependent on variations in the device thickness than that in the voltage-off state. Because of this, TN displays with low information content and no backlighting are usually operated between crossed polarizers such that they appear bright with no voltage (the eye is much more sensitive to variations in the dark state than the bright state). As most of 2010-era LCDs are used in television sets, monitors and smartphones, they have high-resolution matrix arrays of pixels to display arbitrary images using backlighting with a dark background. When no image is displayed, different arrangements are used. For this purpose, TN LCDs are operated between parallel polarizers, whereas IPS LCDs feature crossed polarizers. In many applications IPS LCDs have replaced TN LCDs, particularly in smartphones. Both the liquid crystal material and the alignment layer material contain ionic compounds. If an electric field of one particular polarity is applied for a long period of time, this ionic material is attracted to the surfaces and degrades the device performance. This is avoided either by applying an alternating current or by reversing the polarity of the electric field as the device is addressed (the response of the liquid crystal layer is identical, regardless of the polarity of the applied field).
Displays for a small number of individual digits or fixed symbols (as in digital watches and pocket calculators) can be implemented with independent electrodes for each segment.alphanumeric or variable graphics displays are usually implemented with pixels arranged as a matrix consisting of electrically connected rows on one side of the LC layer and columns on the other side, which makes it possible to address each pixel at the intersections. The general method of matrix addressing consists of sequentially addressing one side of the matrix, for example by selecting the rows one-by-one and applying the picture information on the other side at the columns row-by-row. For details on the various matrix addressing schemes see passive-matrix and active-matrix addressed LCDs.
LCDs are manufactured in cleanrooms borrowing techniques from semiconductor manufacturing and using large sheets of glass whose size has increased over time. Several displays are manufactured at the same time, and then cut from the sheet of glass, also known as the mother glass or LCD glass substrate. The increase in size allows more displays or larger displays to be made, just like with increasing wafer sizes in semiconductor manufacturing. The glass sizes are as follows:
Until Gen 8, manufacturers would not agree on a single mother glass size and as a result, different manufacturers would use slightly different glass sizes for the same generation. Some manufacturers have adopted Gen 8.6 mother glass sheets which are only slightly larger than Gen 8.5, allowing for more 50 and 58 inch LCDs to be made per mother glass, specially 58 inch LCDs, in which case 6 can be produced on a Gen 8.6 mother glass vs only 3 on a Gen 8.5 mother glass, significantly reducing waste.AGC Inc., Corning Inc., and Nippon Electric Glass.
In 1922, Georges Friedel described the structure and properties of liquid crystals and classified them in three types (nematics, smectics and cholesterics). In 1927, Vsevolod Frederiks devised the electrically switched light valve, called the Fréedericksz transition, the essential effect of all LCD technology. In 1936, the Marconi Wireless Telegraph company patented the first practical application of the technology, "The Liquid Crystal Light Valve". In 1962, the first major English language publication Molecular Structure and Properties of Liquid Crystals was published by Dr. George W. Gray.RCA found that liquid crystals had some interesting electro-optic characteristics and he realized an electro-optical effect by generating stripe-patterns in a thin layer of liquid crystal material by the application of a voltage. This effect is based on an electro-hydrodynamic instability forming what are now called "Williams domains" inside the liquid crystal.
In the late 1960s, pioneering work on liquid crystals was undertaken by the UK"s Royal Radar Establishment at Malvern, England. The team at RRE supported ongoing work by George William Gray and his team at the University of Hull who ultimately discovered the cyanobiphenyl liquid crystals, which had correct stability and temperature properties for application in LCDs.
The idea of a TFT-based liquid-crystal display (LCD) was conceived by Bernard Lechner of RCA Laboratories in 1968.dynamic scattering mode (DSM) LCD that used standard discrete MOSFETs.
On December 4, 1970, the twisted nematic field effect (TN) in liquid crystals was filed for patent by Hoffmann-LaRoche in Switzerland, (Swiss patent No. 532 261) with Wolfgang Helfrich and Martin Schadt (then working for the Central Research Laboratories) listed as inventors.Brown, Boveri & Cie, its joint venture partner at that time, which produced TN displays for wristwatches and other applications during the 1970s for the international markets including the Japanese electronics industry, which soon produced the first digital quartz wristwatches with TN-LCDs and numerous other products. James Fergason, while working with Sardari Arora and Alfred Saupe at Kent State University Liquid Crystal Institute, filed an identical patent in the United States on April 22, 1971.ILIXCO (now LXD Incorporated), produced LCDs based on the TN-effect, which soon superseded the poor-quality DSM types due to improvements of lower operating voltages and lower power consumption. Tetsuro Hama and Izuhiko Nishimura of Seiko received a US patent dated February 1971, for an electronic wristwatch incorporating a TN-LCD.
In 1972, the concept of the active-matrix thin-film transistor (TFT) liquid-crystal display panel was prototyped in the United States by T. Peter Brody"s team at Westinghouse, in Pittsburgh, Pennsylvania.Westinghouse Research Laboratories demonstrated the first thin-film-transistor liquid-crystal display (TFT LCD).high-resolution and high-quality electronic visual display devices use TFT-based active matrix displays.active-matrix liquid-crystal display (AM LCD) in 1974, and then Brody coined the term "active matrix" in 1975.
In 1972 North American Rockwell Microelectronics Corp introduced the use of DSM LCDs for calculators for marketing by Lloyds Electronics Inc, though these required an internal light source for illumination.Sharp Corporation followed with DSM LCDs for pocket-sized calculators in 1973Seiko and its first 6-digit TN-LCD quartz wristwatch, and Casio"s "Casiotron". Color LCDs based on Guest-Host interaction were invented by a team at RCA in 1968.TFT LCDs similar to the prototypes developed by a Westinghouse team in 1972 were patented in 1976 by a team at Sharp consisting of Fumiaki Funada, Masataka Matsuura, and Tomio Wada,
In 1983, researchers at Brown, Boveri & Cie (BBC) Research Center, Switzerland, invented the passive matrix-addressed LCDs. H. Amstutz et al. were listed as inventors in the corresponding patent applications filed in Switzerland on July 7, 1983, and October 28, 1983. Patents were granted in Switzerland CH 665491, Europe EP 0131216,
The first color LCD televisions were developed as handheld televisions in Japan. In 1980, Hattori Seiko"s R&D group began development on color LCD pocket televisions.Seiko Epson released the first LCD television, the Epson TV Watch, a wristwatch equipped with a small active-matrix LCD television.dot matrix TN-LCD in 1983.Citizen Watch,TFT LCD.computer monitors and LCD televisions.3LCD projection technology in the 1980s, and licensed it for use in projectors in 1988.compact, full-color LCD projector.
In 1990, under different titles, inventors conceived electro optical effects as alternatives to twisted nematic field effect LCDs (TN- and STN- LCDs). One approach was to use interdigital electrodes on one glass substrate only to produce an electric field essentially parallel to the glass substrates.Germany by Guenter Baur et al. and patented in various countries.Hitachi work out various practical details of the IPS technology to interconnect the thin-film transistor array as a matrix and to avoid undesirable stray fields in between pixels.
Hitachi also improved the viewing angle dependence further by optimizing the shape of the electrodes (Super IPS). NEC and Hitachi become early manufacturers of active-matrix addressed LCDs based on the IPS technology. This is a milestone for implementing large-screen LCDs having acceptable visual performance for flat-panel computer monitors and television screens. In 1996, Samsung developed the optical patterning technique that enables multi-domain LCD. Multi-domain and In Plane Switching subsequently remain the dominant LCD designs through 2006.South Korea and Taiwan,
In 2007 the image quality of LCD televisions surpassed the image quality of cathode-ray-tube-based (CRT) TVs.LCD TVs were projected to account 50% of the 200 million TVs to be shipped globally in 2006, according to Displaybank.Toshiba announced 2560 × 1600 pixels on a 6.1-inch (155 mm) LCD panel, suitable for use in a tablet computer,
In 2016, Panasonic developed IPS LCDs with a contrast ratio of 1,000,000:1, rivaling OLEDs. This technology was later put into mass production as dual layer, dual panel or LMCL (Light Modulating Cell Layer) LCDs. The technology uses 2 liquid crystal layers instead of one, and may be used along with a mini-LED backlight and quantum dot sheets.
Since LCDs produce no light of their own, they require external light to produce a visible image.backlight. Active-matrix LCDs are almost always backlit.Transflective LCDs combine the features of a backlit transmissive display and a reflective display.
CCFL: The LCD panel is lit either by two cold cathode fluorescent lamps placed at opposite edges of the display or an array of parallel CCFLs behind larger displays. A diffuser (made of PMMA acrylic plastic, also known as a wave or light guide/guiding plateinverter to convert whatever DC voltage the device uses (usually 5 or 12 V) to ≈1000 V needed to light a CCFL.
EL-WLED: The LCD panel is lit by a row of white LEDs placed at one or more edges of the screen. A light diffuser (light guide plate, LGP) is then used to spread the light evenly across the whole display, similarly to edge-lit CCFL LCD backlights. The diffuser is made out of either PMMA plastic or special glass, PMMA is used in most cases because it is rugged, while special glass is used when the thickness of the LCD is of primary concern, because it doesn"t expand as much when heated or exposed to moisture, which allows LCDs to be just 5mm thick. Quantum dots may be placed on top of the diffuser as a quantum dot enhancement film (QDEF, in which case they need a layer to be protected from heat and humidity) or on the color filter of the LCD, replacing the resists that are normally used.
WLED array: The LCD panel is lit by a full array of white LEDs placed behind a diffuser behind the panel. LCDs that use this implementation will usually have the ability to dim or completely turn off the LEDs in the dark areas of the image being displayed, effectively increasing the contrast ratio of the display. The precision with which this can be done will depend on the number of dimming zones of the display. The more dimming zones, the more precise the dimming, with less obvious blooming artifacts which are visible as dark grey patches surrounded by the unlit areas of the LCD. As of 2012, this design gets most of its use from upscale, larger-screen LCD televisions.
RGB-LED array: Similar to the WLED array, except the panel is lit by a full array of RGB LEDs. While displays lit with white LEDs usually have a poorer color gamut than CCFL lit displays, panels lit with RGB LEDs have very wide color gamuts. This implementation is most popular on professional graphics editing LCDs. As of 2012, LCDs in this category usually cost more than $1000. As of 2016 the cost of this category has drastically reduced and such LCD televisions obtained same price levels as the former 28" (71 cm) CRT based categories.
Monochrome LEDs: such as red, green, yellow or blue LEDs are used in the small passive monochrome LCDs typically used in clocks, watches and small appliances.
Mini-LED: Backlighting with Mini-LEDs can support over a thousand of Full-area Local Area Dimming (FLAD) zones. This allows deeper blacks and higher contrast ratio.
Today, most LCD screens are being designed with an LED backlight instead of the traditional CCFL backlight, while that backlight is dynamically controlled with the video information (dynamic backlight control). The combination with the dynamic backlight control, invented by Philips researchers Douglas Stanton, Martinus Stroomer and Adrianus de Vaan, simultaneously increases the dynamic range of the display system (also marketed as HDR, high dynamic range television or FLAD, full-area local area dimming).
The LCD backlight systems are made highly efficient by applying optical films such as prismatic structure (prism sheet) to gain the light into the desired viewer directions and reflective polarizing films that recycle the polarized light that was formerly absorbed by the first polarizer of the LCD (invented by Philips researchers Adrianus de Vaan and Paulus Schaareman),
A pink elastomeric connector mating an LCD panel to circuit board traces, shown next to a centimeter-scale ruler. The conductive and insulating layers in the black stripe are very small.
A standard television receiver screen, a modern LCD panel, has over six million pixels, and they are all individually powered by a wire network embedded in the screen. The fine wires, or pathways, form a grid with vertical wires across the whole screen on one side of the screen and horizontal wires across the whole screen on the other side of the screen. To this grid each pixel has a positive connection on one side and a negative connection on the other side. So the total amount of wires needed for a 1080p display is 3 x 1920 going vertically and 1080 going horizontally for a total of 6840 wires horizontally and vertically. That"s three for red, green and blue and 1920 columns of pixels for each color for a total of 5760 wires going vertically and 1080 rows of wires going horizontally. For a panel that is 28.8 inches (73 centimeters) wide, that means a wire density of 200 wires per inch along the horizontal edge.
The LCD panel is powered by LCD drivers that are carefully matched up with the edge of the LCD panel at the factory level. The drivers may be installed using several methods, the most common of which are COG (Chip-On-Glass) and TAB (Tape-automated bonding) These same principles apply also for smartphone screens that are much smaller than TV screens.anisotropic conductive film or, for lower densities, elastomeric connectors.
Monochrome and later color passive-matrix LCDs were standard in most early laptops (although a few used plasma displaysGame Boyactive-matrix became standard on all laptops. The commercially unsuccessful Macintosh Portable (released in 1989) was one of the first to use an active-matrix display (though still monochrome). Passive-matrix LCDs are still used in the 2010s for applications less demanding than laptop computers and TVs, such as inexpensive calculators. In particular, these are used on portable devices where less information content needs to be displayed, lowest power consumption (no backlight) and low cost are desired or readability in direct sunlight is needed.
STN LCDs have to be continuously refreshed by alternating pulsed voltages of one polarity during one frame and pulses of opposite polarity during the next frame. Individual pixels are addressed by the corresponding row and column circuits. This type of display is called response times and poor contrast are typical of passive-matrix addressed LCDs with too many pixels and driven according to the "Alt & Pleshko" drive scheme. Welzen and de Vaan also invented a non RMS drive scheme enabling to drive STN displays with video rates and enabling to show smooth moving video images on an STN display.
Bistable LCDs do not require continuous refreshing. Rewriting is only required for picture information changes. In 1984 HA van Sprang and AJSM de Vaan invented an STN type display that could be operated in a bistable mode, enabling extremely high resolution images up to 4000 lines or more using only low voltages.
High-resolution color displays, such as modern LCD computer monitors and televisions, use an active-matrix structure. A matrix of thin-film transistors (TFTs) is added to the electrodes in contact with the LC layer. Each pixel has its own dedicated transistor, allowing each column line to access one pixel. When a row line is selected, all of the column lines are connected to a row of pixels and voltages corresponding to the picture information are driven onto all of the column lines. The row line is then deactivated and the next row line is selected. All of the row lines are selected in sequence during a refresh operation. Active-matrix addressed displays look brighter and sharper than passive-matrix addressed displays of the same size, and generally have quicker response times, producing much better images. Sharp produces bistable reflective LCDs with a 1-bit SRAM cell per pixel that only requires small amounts of power to maintain an image.
Segment LCDs can also have color by using Field Sequential Color (FSC LCD). This kind of displays have a high speed passive segment LCD panel with an RGB backlight. The backlight quickly changes color, making it appear white to the naked eye. The LCD panel is synchronized with the backlight. For example, to make a segment appear red, the segment is only turned ON when the backlight is red, and to make a segment appear magenta, the segment is turned ON when the backlight is blue, and it continues to be ON while the backlight becomes red, and it turns OFF when the backlight becomes green. To make a segment appear black, the segment is always turned ON. An FSC LCD divides a color image into 3 images (one Red, one Green and one Blue) and it displays them in order. Due to persistence of vision, the 3 monochromatic images appear as one color image. An FSC LCD needs an LCD panel with a refresh rate of 180 Hz, and the response time is reduced to just 5 milliseconds when compared with normal STN LCD panels which have a response time of 16 milliseconds.
Samsung introduced UFB (Ultra Fine & Bright) displays back in 2002, utilized the super-birefringent effect. It has the luminance, color gamut, and most of the contrast of a TFT-LCD, but only consumes as much power as an STN display, according to Samsung. It was being used in a variety of Samsung cellular-telephone models produced until late 2006, when Samsung stopped producing UFB displays. UFB displays were also used in certain models of LG mobile phones.
Twisted nematic displays contain liquid crystals that twist and untwist at varying degrees to allow light to pass through. When no voltage is applied to a TN liquid crystal cell, polarized light passes through the 90-degrees twisted LC layer. In proportion to the voltage applied, the liquid crystals untwist changing the polarization and blocking the light"s path. By properly adjusting the level of the voltage almost any gray level or transmission can be achieved.
In-plane switching is an LCD technology that aligns the liquid crystals in a plane parallel to the glass substrates. In this method, the electrical field is applied through opposite electrodes on the same glass substrate, so that the liquid crystals can be reoriented (switched) essentially in the same plane, although fringe fields inhibit a homogeneous reorientation. This requires two transistors for each pixel instead of the single transistor needed for a standard thin-film transistor (TFT) display. The IPS technology is used in everything from televisions, computer monitors, and even wearable devices, especially almost all LCD smartphone panels are IPS/FFS mode. IPS displays belong to the LCD panel family screen types. The other two types are VA and TN. Before LG Enhanced IPS was introduced in 2001 by Hitachi as 17" monitor in Market, the additional transistors resulted in blocking more transmission area, thus requiring a brighter backlight and consuming more power, making this type of display less desirable for notebook computers. Panasonic Himeji G8.5 was using an enhanced version of IPS, also LGD in Korea, then currently the world biggest LCD panel manufacture BOE in China is also IPS/FFS mode TV panel.
In 2011, LG claimed the smartphone LG Optimus Black (IPS LCD (LCD NOVA)) has the brightness up to 700 nits, while the competitor has only IPS LCD with 518 nits and double an active-matrix OLED (AMOLED) display with 305 nits. LG also claimed the NOVA display to be 50 percent more efficient than regular LCDs and to consume only 50 percent of the power of AMOLED displays when producing white on screen.
This pixel-layout is found in S-IPS LCDs. A chevron shape is used to widen the viewing cone (range of viewing directions with good contrast and low color shift).
Vertical-alignment displays are a form of LCDs in which the liquid crystals naturally align vertically to the glass substrates. When no voltage is applied, the liquid crystals remain perpendicular to the substrate, creating a black display between crossed polarizers. When voltage is applied, the liquid crystals shift to a tilted position, allowing light to pass through and create a gray-scale display depending on the amount of tilt generated by the electric field. It has a deeper-black background, a higher contrast ratio, a wider viewing angle, and better image quality at extreme temperatures than traditional twisted-nematic displays.
Blue phase mode LCDs have been shown as engineering samples early in 2008, but they are not in mass-production. The physics of blue phase mode LCDs suggest that very short switching times (≈1 ms) can be achieved, so time sequential color control can possibly be realized and expensive color filters would be obsolete.
Some LCD panels have defective transistors, causing permanently lit or unlit pixels which are commonly referred to as stuck pixels or dead pixels respectively. Unlike integrated circuits (ICs), LCD panels with a few defective transistors are usually still usable. Manufacturers" policies for the acceptable number of defective pixels vary greatly. At one point, Samsung held a zero-tolerance policy for LCD monitors sold in Korea.ISO 13406-2 standard.
Dead pixel policies are often hotly debated between manufacturers and customers. To regulate the acceptability of defects and to protect the end user, ISO released the ISO 13406-2 standard,ISO 9241, specifically ISO-9241-302, 303, 305, 307:2008 pixel defects. However, not every LCD manufacturer conforms to the ISO standard and the ISO standard is quite often interpreted in different ways. LCD panels are more likely to have defects than most ICs due to their larger size. For example, a 300 mm SVGA LCD has 8 defects and a 150 mm wafer has only 3 defects. However, 134 of the 137 dies on the wafer will be acceptable, whereas rejection of the whole LCD panel would be a 0% yield. In recent years, quality control has been improved. An SVGA LCD panel with 4 defective pixels is usually considered defective and customers can request an exchange for a new one.
Some manufacturers, notably in South Korea where some of the largest LCD panel manufacturers, such as LG, are located, now have a zero-defective-pixel guarantee, which is an extra screening process which can then determine "A"- and "B"-grade panels.clouding (or less commonly mura), which describes the uneven patches of changes in luminance. It is most visible in dark or black areas of displayed scenes.
The zenithal bistable device (ZBD), developed by Qinetiq (formerly DERA), can retain an image without power. The crystals may exist in one of two stable orientations ("black" and "white") and power is only required to change the image. ZBD Displays is a spin-off company from QinetiQ who manufactured both grayscale and color ZBD devices. Kent Displays has also developed a "no-power" display that uses polymer stabilized cholesteric liquid crystal (ChLCD). In 2009 Kent demonstrated the use of a ChLCD to cover the entire surface of a mobile phone, allowing it to change colors, and keep that color even when power is removed.
In 2004, researchers at the University of Oxford demonstrated two new types of zero-power bistable LCDs based on Zenithal bistable techniques.e.g., BiNem technology, are based mainly on the surface properties and need specific weak anchoring materials.
Resolution The resolution of an LCD is expressed by the number of columns and rows of pixels (e.g., 1024×768). Each pixel is usually composed 3 sub-pixels, a red, a green, and a blue one. This had been one of the few features of LCD performance that remained uniform among different designs. However, there are newer designs that share sub-pixels among pixels and add Quattron which attempt to efficiently increase the perceived resolution of a display without increasing the actual resolution, to mixed results.
Spatial performance: For a computer monitor or some other display that is being viewed from a very close distance, resolution is often expressed in terms of dot pitch or pixels per inch, which is consistent with the printing industry. Display density varies per application, with televisions generally having a low density for long-distance viewing and portable devices having a high density for close-range detail. The Viewing Angle of an LCD may be important depending on the display and its usage, the limitations of certain display technologies mean the display only displays accurately at certain angles.
Temporal performance: the temporal resolution of an LCD is how well it can display changing images, or the accuracy and the number of times per second the display draws the data it is being given. LCD pixels do not flash on/off between frames, so LCD monitors exhibit no refresh-induced flicker no matter how low the refresh rate.
Brightness and contrast ratio: Contrast ratio is the ratio of the brightness of a full-on pixel to a full-off pixel. The LCD itself is only a light valve and does not generate light; the light comes from a backlight that is either fluorescent or a set of LEDs. Brightness is usually stated as the maximum light output of the LCD, which can vary greatly based on the transparency of the LCD and the brightness of the backlight. Brighter backlight allows stronger contrast and higher dynamic range (HDR displays are graded in peak luminance), but there is always a trade-off between brightness and power consumption.
Usually no refresh-rate flicker, because the LCD pixels hold their state between refreshes (which are usually done at 200 Hz or faster, regardless of the input refresh rate).
No theoretical resolution limit. When multiple LCD panels are used together to create a single canvas, each additional panel increases the total resolution of the display, which is commonly called stacked resolution.
LCDs can be made transparent and flexible, but they cannot emit light without a backlight like OLED and microLED, which are other technologies that can also be made flexible and transparent.
As an inherently digital device, the LCD can natively display digital data from a DVI or HDMI connection without requiring conversion to analog. Some LCD panels have native fiber optic inputs in addition to DVI and HDMI.
Limited viewing angle in some older or cheaper monitors, causing color, saturation, contrast and brightness to vary with user position, even within the intended viewing angle. Special films can be used to increase the viewing angles of LCDs.
Uneven backlighting in some monitors (more common in IPS-types and older TNs), causing brightness distortion, especially toward the edges ("backlight bleed").
Display motion blur on moving objects caused by slow response times (>8 ms) and eye-tracking on a sample-and-hold display, unless a strobing backlight is used. However, this strobing can cause eye strain, as is noted next:
As of 2012, most implementations of LCD backlighting use pulse-width modulation (PWM) to dim the display,CRT monitor at 85 Hz refresh rate would (this is because the entire screen is strobing on and off rather than a CRT"s phosphor sustained dot which continually scans across the display, leaving some part of the display always lit), causing severe eye-strain for some people.LED-backlit monitors, because the LEDs switch on and off faster than a CCFL lamp.
Fixed bit depth (also called color depth). Many cheaper LCDs are only able to display 262144 (218) colors. 8-bit S-IPS panels can display 16 million (224) colors and have significantly better black level, but are expensive and have slower response time.
Input lag, because the LCD"s A/D converter waits for each frame to be completely been output before drawing it to the LCD panel. Many LCD monitors do post-processing before displaying the image in an attempt to compensate for poor color fidelity, which adds an additional lag. Further, a video scaler must be used when displaying non-native resolutions, which adds yet more time lag. Scaling and post processing are usually done in a single chip on modern monitors, but each function that chip performs adds some delay. Some displays have a video gaming mode which disables all or most processing to reduce perceivable input lag.
Loss of brightness and much slower response times in low temperature environments. In sub-zero environments, LCD screens may cease to function without the use of supplemental heating.
The production of LCD screens uses nitrogen trifluoride (NF3) as an etching fluid during the production of the thin-film components. NF3 is a potent greenhouse gas, and its relatively long half-life may make it a potentially harmful contributor to global warming. A report in Geophysical Research Letters suggested that its effects were theoretically much greater than better-known sources of greenhouse gasses like carbon dioxide. As NF3 was not in widespread use at the time, it was not made part of the Kyoto Protocols and has been deemed "the missing greenhouse gas".
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Sony states that this is a common phenomenon on all LCD TVs.Backlight Bleed is when some screen areas are lighter than others due to spillover from a backlight or uneven backlighting.
Perhaps you still want to get an LED TV due to the lower price point. In that case, your best bet is to read reviews to determine if others are experiencing backlight bleed issues with a particular TV model.
When light bounces off any surface around the edges of the screen, it can result in Flashlighting, or extra light at the edges or corners, making the lighting of the LCD panel uneven.
Clouding occurs when layers of the screen become uneven due to misalignment, damage, pressure, or temperature changes. The misalignment results in the light not being evenly distributed.Flashlighting is the type of backlight bleed experienced at the corners or edges of a screen.
Backlight bleed goes by various names, including light leakage, screen bleed, light bleed, clouding, blooming, mura, banding, and un-uniform brightness.
Excessive LED backlight bleed can be caused by the following:Temperature changes result in materials expanding or contracting, including the LCD panel or frame.
Temperature changes may result in some components moving or warping slightly. Backlight bleeding could be reduced after either cooling down or warming up, depending on how the TV was designed.
Some possible ways to fix LED backlight bleed or make it less noticeable include:Give it time: Some new TVs experience an increase in backlight bleeding which can slowly disappear after a few weeks or months.
Reduce screen brightness: Reducing brightness can reduce the backlight intensity, which may cause the backlight bleeding to be less noticeable or even impact the screen"s temperature.
Enable local dimming or LED dynamic control if your TV supports it: Reduce backlight bleeding for darker scenes by dimming darker portions of the scene.
Some more extreme options, which may damage your TV and void your warranty:Loosen screws: Excessive pressure caused by over-tightened screws can result in flashlighting.
Use a microfiber cloth to gently rub the portion of the screen where the backlight bleeding is prominent: This may help with clouding by evening out an uneven LCD panel.
Take apart the TV and apply electrical tape around the edges of the LCD: While likely to void your warranty, this could reduce light escaping and reflecting around the edges of the screen.
If the backlight bleed is not too distracting, there"s nothing to worry about. Backlight bleed typically will not get worse over time on its own. However, frequently moving a TV around or improper handling could result in bending the tv frame or components, resulting in backlight bleed.
Some manufacturers do not allow returns based on general backlight bleeding, which is typical of LED backlighting. For example, Sony considers bleeding that is only visible on "black images and in a dark or very dim room" to be considered within specification. Are you experiencing backlight bleeding in bright scenes and a well-lit room? If so, you may be able to return the TV to your manufacturer for a replacement.
To determine the maximum amount of backlight bleed possible with a TV, you can: increase screen brightness, turn off auto-brightness, view the TV in a dark room, and disable local dimming. These are not settings for optimal viewing but can be used for testing the worst-case scenario.
It is a very common phenomenon that liquid crystal display panel and the frame are not tight enough that some lights are transmittance out. It is inevitable to some extent and only a matter of how serious it is. Low-end display panels are more serious, meanwhile, high-end display panels are better.
We must know the principles of LCD. Electrical-optical conversion is that the outer light transmittance is changed because the alignment direction of liquid crystal molecules is changed by the electrical field. LCD which is different from the direct view CRT is displaying digital images and vivid colors by using electrical-optical conversion and different excitation of R, G, B three colors.
Liquid crystal is sandwiched between two layers of glass where the upper layer is CF glass and the lower layer is TFT glass. The surface of two layers of glass is uneven. In order to grip and arrange the liquid crystal, the interface of two glasses is coated with a layer of PI (polyimide), and then it is rubbed by a cloth. Therefore, this kind of backlight bleeding is inevitable. But more often than not, they are invisible. Some panels have serious backlight bleeding problem because of poor quality or transportation problems that will be detected by productive process and could be avoided. Thus, it is obvious that the backlight bleeding problem of some liquid crystal display panels is not caused by this reason.
Second, the extrusion is caused by assembling LCD. This is the most important reason of backlight breeding. It is relatively loosing requirement, dirty environment and rough process for assembling LCD, compared with producing display panel. There is a slight leak between the display panel and the frame when LCD is assembled. But it is very difficult to be seen by naked eyes, and we can clearly see the backlight bleeding only in an all-black environment.
There is a law in our country that luminous flux of backlight bleeding must be less than 4 cd/㎡ in an all-black environment. In this condition, backlight bleeding will not affect the using time, the response time, the brightness and other aspects of LCD.
We should not pay much attention since backlight bleeding does not affect the use of LCD, and manufacturers may not obey the return policy. It is completely normal that there is a slight backlight bleeding in the assembling LCD. High-end LCD barely has any serious backlight bleeding situation because of the high-quality display panel, carefully assembly process and excellent display design. For example: EIZO and NEC.
If you buy a low-end LCD, you have to check the LCD very carefully, otherwise, the return of the product will not be allowed by the vendor even there is slight backlight bleeding. But if you by a high-end LCD, you don’t have to worry about backlight bleeding, because you can enjoy excellent after-sale service for a high-quality product.
The IPS Glow is a "glow" effect which is present on the corners of an IPS panel whereas Backlight Bleeding usually appears along the edges of a monitor. It is most