lcd module light bleed factory

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. *

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.

(1) When the quality of the panel is not good, or an accident occurs during the handling process, the panel is bent and deformed, which will cause serious backlight bleed problems. If this condition is detected before leaving the factory, it is usually prohibited from leaving the factory.

(2) Another reason is that when the TV is assembled, the fit between the frame and the panel is not high, resulting in slight light leakage. However, it is generally difficult to detect with the naked eye, and the phenomenon of backlight bleed can only be seen in a completely dark environment.

Although light leakage will not affect the basic functions of the display itself such as brightness, response speed, and lifespan. Slight backlight bleed is also acceptable, but when the light leakage is serious, some special screen displays may have poor results.

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 visible when viewing dark images in a darker environment. The amount of the IPS Glow depends on viewing angles, the distance to the IPS panel, the ambient light, monitor brightness settings as well as the manufacturing quality. Each individual unit will vary in terms of the IPS Glow. Backlight Bleeding does not change when viewing at an off angle. The IPS Glow is technology-related and can never be completely prevented or eliminated.

The IPS Glow and Backlight Bleeding can really be exhausting when buying a new monitor. It is most visible on the edges of an IPS monitor in a darker environment (and especially when combined with it higher monitor OSD brightness settings). It can appear with a brownish, light bluish, yellowish, or greyish tint and the amount and color can differ in each individual unit. Backlight bleeding refers to areas of bright light on the monitor that are primarily visible when viewing dark or black screens in the darker environment. These light areas usually appear along the edges or corners of the monitor.

Long answer: The IPS Glow is strongly depending on the viewing angle, on the distance, on the panel frame construction as well as on the ambient light. The brighter your environment, the less visible the IPS glow. The IPS Glow also can differ in terms of the IPS Glow color tint. Current WQHD high refresh rate gaming monitors have a brownish or bluish IPS Glow (depending on your individual unit) whereas 100Hz ultrawide gaming monitors have a more yellowish IPS Glow (LG Panel built in the Asus PG348Q, Acer X34A, Alienware AW3418DW, Acer X34P). Some other IPS panels with 60 Hz have a more white/grey tint in the IPS Glow. The IPS Glow is visible only in the corners/edged of a screen. However, the IPS Glow also is visible in bright image content or rather on a fully white screen when looking from an angle. At a harsher angle, it looks like the panel is coated with an oil filter.

The amount of backlight bleeding increases the more the panel frame pressures against the panel/display. It also can increase the amount of the IPS Glow when it pressures against the panel/display near the edged.

Backlight Bleeding otherwise occurs when the led backlit behind the panel or borders is placed faulty or when the panel frame construction causes too much pressure on the display. Unlike the IPS Glow, it does not depend on the distance to the monitor or the angle at which you look at the display. Sometimes, it is possible to lose the panel frame also a bit. In this case, you can observe that the amount of Backlight Bleed will decrease. However, Backlight Bleed often is visible also near the edged, because the panel frame at this part is mostly tighter and stiffer compared to the bottom center for example.

Already during the production, it is decided if a panel has bad, acceptable or very good IPS Glow and Backlight Bleed conditions. A panel has different layers included the anti-glare coating surface and the inner panel housing which is made out of metal. In the end, it depends on how well a panel is manufactured and how much pressure and tension the individual panel has. Incidentally, it is currently technically not possible to build an IPS panel without IPS Glow.

To test your individual unit for IPS Glow you simply just have to open a full black screen on your monitor and dim your ambient lights in your room (Lamps, lights from outside, windows etc.). The darker the room the more IPS Glow and Backlight Bleed you will be able to observe. You can follow this link where I have created a full black screen video on YouTube with a length of 30 minutes.

Monitor adjustments also are very important when using an IPS panel in a darker environment or in a pitch black room. Ensure that you set proper height AND tilt adjustments. While individual units differ, you can easily find out easily which height and tilt settings are the best for your monitor when opening the test video and darken the ambient light.

While the inner panel frame is out of medal and also have a bit sharper edges, in the worst case your credit card can lose some plastic pieces which will be stuck in the inner panel frame. The result out from this is that these plastic pieces will cause more panel pressure and more Backlight Bleed.

Different units from different manufacturers will have different constructions and closing mechanisms so that you have to figure out how to open your monitor model. In my case, with the Viewsonic XG2703-GS, removing the panel frame only helped a tiny bit in terms of Backlight Bleeding. Losing the inner panel frame is not really possible and even when I was able to increase the gap between the inner panel frame and the display it also sometimes has increased the Backlight Bleed, probably because the backside of the inner panel frame became more tension.

Returned the laptop to Best Buy for an exchange. In and out with a new one in 20 minutes. I checked the new one at the customer service counter before accepting it, and the display appeared to be fine, although I remarked to the customer service agent that the ambient light inside the store makes it difficult to closely examine the display. And sure enough, after taking it home and viewing it in a darker environment, the screen artifact is present in both lower corners, although much less pronounced. I want there to be no doubt about the nature of my complaint. There should be NO light bleed in this display. None. This defect is due solely to poor display construction and non-existent quality control.

Hey I just unboxed my brand new M1 iMac 2021. After installing Mac OS 12.1 (Monterey) coming from factory Big Sur I noticed some backlight bleed during start up black screen. I’ve seen worse but should I return it or keep it? Honestly I want to avoid returning it and have the hassle

Performance issues may occur if there is any type of damage that is caused to the display cables or the LCD screen. LCD screen may show that symptoms like LCD screen stops working, work intermittently, color mismatch, flickering, display horizontal or vertical lines if there is damage to the display cables or the LCD screen.