Are LCD Screens Dangerous?

 

 

LCD (liquid crystal display) consumes much less power, and is lighter, thinner than CRT (Cathode Ray Tube). It is the most popular display technology in the world now.  It has been widely used in mobile phones, tablets, TVs, laptops, computer monitors, ATMs, Kiosks, home appliances, IoT, automotive, solar panels etc. The sizes are getting bigger and the quantities are getting more. There are a lot of worries about if LCD screens safe or even dangerous or any affect for the climate change? There was little research on it. There are several articles on the internet with contradictory information.  It is important to look at the safety issue from a viewing angle from a LCD panels professional manufacturer.  In order to have deep understand of the question, we have to have a deep understanding of the LCD basis. As most of the big size LCDs are color display, we will focus on TFT LCDs.

Introduction to LCD Displays: TFT LCD Structure and How it works

TFT LCD Display (Thin-Film-Transistor Liquid Crystal Display) technology has a sandwich-like structure with liquid crystal material filled between two glass plates. Two polarizer filters, color filters (RGB, red/green/blue)and two alignment layers determine exactly the amount of light is allowed to pass and which colors are created. Each pixel in an active matrix is paired with a transistor that includes capacitor which gives each sub-pixel the ability to retain its charge, instead of requiring an electrical charge sent each time it needed to be changed.  The TFT layer controls light flow a color filter displays the color and a top layer houses your visible screen. See Fig.1 for  TFT LCD structure.

 

Fig.1 TFT LCD Display Structure

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. 

The pixels of TFT displays are determined by the underlying density (resolution) of the color matrix and TFT layout. The more pixels the higher detail is available. Available screen size, power consumption, resolution, interface (how to connect) define the TFT displays.

TFT screen itself can’t emit light like OLED display, it has to be used with a back-light of white bright light to generate the picture. Newer panels utilize LED backlight (light emitting diodes) to generate their light and therefore utilize less power and require less depth by design.

TFT display module includes TFT display screen, LED backlight and driving circuitry.

OK, let’s analyze one layer by another.

-Polarizers: Actually, polarizer is made of several layers of normal plastic. Mostly they are PVA ( Polyvinyl alcohol ) and TAC (three cellulose acetate film). Both are normal safe polymer. Most of the plastic nowadays has  flame retardants to prevent from catching fire.Fig. 2 Polarizer Structure

 – Glass: Normally, there are two kinds of glass used: Soda lime and alkalinebosicate. Both are safe.-TFT: It’s kind of semiconductor which mainly has silicon and metal (gold, aluminum etc.). They are safe.

 – Color Filter: They are very thin and are made of polymers of photoresist. The process is done by photolithography method. They are safe.

 – Driving Circuitry: LCD’s driving circuitry has no material different from other electronics. It has IC (Integrated circuit) and PCB (Printed Circuit Board).

 – Backlight and Liquid Crystal Material: Both are the most suspicious. We will dive deep into these two parts.

Mercury Vapors

Some internet articles claimed that the LCD screen uses mercury to generate visible light as part of the viewing process. It is the reason that there is a chance that vapors could escape where the screen becomes cracked. While the mercury levels are generally low, there is a risk of side effects such as allergic reactions, skin rashes and even birth defects.

To our understanding, it is a false statement. From our above structure analyze, LCD screen doesn’t contain mercury at all.  LCD screen can’t light itself; it has to use light source to help it to be seen. The light sources can be sunlight, surrounding light or we can make backlight at the back of the LCD screens.

There are two kinds of backlight: LED (Light Emitting Diode) backlight and CCFL (Cold Cathode Fluorescent Lamp) backlight. Both are widely used for our normal lighting at home. If LCD screen and mercury have to be related. It can be the CCFL which contains toxic metals and their salts, including mercury to produce fluorescent light. But you might notice that most of LCD manufacturers advertise LED displays which are LED backlighted LCD displays.  Orient Display stopped using CCFL as backlight 15 years again and we are 100% RoHS (Restriction of Hazardous Substances Directive) Compliance for whole factory including raw materials, process and products.

Fig. 3 ROHS Compliant

 

Liquid Crystal Material

Liquid crystal is a state between liquid (like water) and crystal/solid (like ice). Although we have liquid crystal displays around us, most of people never see what liquid crystal materials look like. Actually, commercial liquid crystal materials look like milk. But you can’t drink it.

Fig. 4 A Bottle of Liquid Crystal Materials

Liquid Crystal monomers don’t have protein. Their chemical structures look like below. The effect of these chemicals shows in MSDS (Material Safety Data Sheet).

Fig. 5 Liquid Crystal Material Typical Formula

 

Environmental Impacts

Some researchers have a deep study into chemicals used in LCD display and the result is as below:

– In Proceedings of the National Academy of Sciences, Giesy’s research team assembled and analyzed a comprehensive list of 362 commonly used liquid crystal monomers gathered from 10 different industries and examined each chemical for its potential toxicity. When inhaled or ingested, these toxic chemicals can build up in the body over time with toxic effects, potentially causing digestive problems and other health issues.

-“These chemicals are semi-liquid and can get into the environment at any time during manufacturing and recycling, and they are vaporized during burning,” said University of Saskatchewan environmental toxicologist and lead author John Giesy in a press release. “Now we also know that these chemicals are being released by products just by using them.”

-The researchers found the specific monomers isolated from the smartphones were potentially hazardous to animals and the environment. In lab testing, the chemicals were found to have properties known to inhibit animals’ ability to digest nutrients and to disrupt the proper functioning of the gallbladder and thyroid–similar to dioxins and flame retardants which are known to cause toxic effects in humans and wildlife.

-To be clear, the researchers didn’t observe any adverse health effects from the accumulation of liquid crystals in the human body; they only found that these crystals do in fact leak from devices, and that they have the potential to be toxic. “We don’t know yet whether this a problem, but we do know that people are being exposed, and these chemicals have the potential to cause adverse effects,” said Giesy.

OK, relax. If you understand the research statement above correctly and combine our understanding of liquid crystal materials. The results are:

-Any artificial chemicals have potential hazard to human health. If you read the notes of your prescription drug, the statement is likely more alarming than above.

-Don’t burn your LCDs, just like you can’t burn your battery, your wires or gasoline. Any vapor can be hazard.

-If you crack LCD screens and find the liquid crystal leakage, don’t panic. Just remember that the liquid crystal materials might not be more toxic than your detergents for stove or washroom. Just wash your hands with soup throughout. Never try to play with it or even worse to taste it. The liquid of the cracked computer screen will not evaporate, no emissions worries.

-Any electronics has environment impact and can’t be used landfills. If you want to get rid of old LCD monitors or LCD TVs, give them to electronic collection stations. Let’s the professionals to handle them. They will extract some precious metals/parts and make them into something useful or at least not hazard. FYI, liquid crystal materials are retrievable. 

 

Other Impacts 

-Will LCD screen emit ultraviolet radiation or blue light?

No, LCD screen doesn’t emit light itself. It uses LED backlight to produce visible light which doesn’t have the either UV or Blue light wavelengths.

-My Samsung uhd 65-inch LCD TV cracked. Can it be repaired? .

No, the LCD is made by glass which can’t be repaired. Please send the TV to your local waste management company for recycling.

-I heard that LCD screen can damage ozone layer, is it true?

Many year ago, LCD manufacturing process used hydro-fluorocarbons as solvent, which can damage ozone layer. Now, it is prohibited to use this chemical.