Why do white LED lights turn yellow?

Three different reasons for led panel lights turning yellow

Yellowing caused by the material change of the light guide plate itself

The LED chips are abnormal (mostly phosphor problems) causing yellowing.

The external use environment causes the stains attached to the light guide plate to penetrate into the light guide plate and cause yellowing.

 

1.Yellowing caused by the material change of the light guide plate itself

This is our true yellowing quality problem, and it is also the most common and serious yellowing problem in the market. When you turn on this ultra-thin panel light, a yellow area will appear in the middle of the light-emitting surface of the panel light. The light guide plate of PS material is the culprit of this problem.

The full name of PS is polystyrene. It is a relatively low-level transparent brittle glue in petrochemicals. Its specific gravity is only 1.047~1.049. When it is fully transparent, the light transmittance is 87%. It is the refractive index of a plastic second only to a PC. The second most transparent material. Compared with the PMMA light guide plate, the PS price will be much cheaper, but it is very easy to turn yellow in terms of weather resistance, and it is very easy to be brittle when it is extremely cold.

 

2.The LED chips are abnormal (mostly phosphor problems) causing yellowing

This situation mostly occurred around 2010. At that time, due to LED technology and illegal businesses cutting corners, some panel lights turned yellow. Some LED panel lights that were originally 5000-6500k cold white, after lighting up, the whole or part of the light emitted is yellowish and reddish. The phosphor usage ratio and chip packaging technology of led chips are the main reasons for this problem.

 

3.The external use environment causes the stains attached to the light guide plate to penetrate into the light guide plate and cause yellowing

As the outermost layer, the diffuser plate not only plays the role of the uniform light guide but also plays the role of blocking dirt and dust from contaminating the light guide plate. However, in actual use, many customers will ignore the influence of the external environment on the internal structure of the lamp, especially in some special use environments such as chemical factories, laboratories, and toilets and bathrooms that are often filled with water vapor. The special air components in these places tend to slowly penetrate into the inside of the lamp body through the side of the panel light, polluting the light guide plate, causing yellowing. Or, for example, the long-term corrosion of the diffuser by water vapor will also cause the surface of the panel light to yellow.

 

 

How to solve and avoid yellowing for led flat panel light?

 

1. Yellowing caused by the problem of the light guide plate itself

 

It can only be replaced with a new LED panel light.

When buying, you need to ask the LED panel light supplier the type and parameters of the light guide plate, the more detailed the better. The best light guide plate is a laser-dotted light guide plate made of PMMA. The LED panel light produced by this material will not show yellowing even if it is used for more than 6 years. Secondly, you can also choose a panel light made of PS material with anti-UV and anti-yellowing. Of course, the current market is more adopting new Backlit LED panel lights to replace edge-lit panel lights. Backlit panel light does not contain a light guide plate in structure, which also eliminates the biggest problem of light guide plate yellowing, and its cost is lower than side-lit.

 

 

2. For the yellowing of the color temperature caused by led chips

We can replace the internal lamp beads to improve this problem. Or replace it with a new LED panel light.

 

3.Yellowing caused by the external use environment

Generally, there are two situations. If it is only the yellowing caused by external dust or water stains attached to the surface of the diffuser for a long time, such as a non-waterproof panel light installed in the bathroom, then we can use low-concentration industrial alcohol to wipe the surface to change the yellowing Case. For the external use environment, the yellowing of the light guide plate inside the lamp body has been caused, and the panel light can only be replaced as a whole.