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Display devices

General

Removing the luminescent layer from the screen glass

Within the collection and processing category of display devices, two basic types of devices are distinguished:

  • Tube-based devices (cathode-ray tube)
    Televisions, computer monitors, surveillance and security monitors
  • Flat-screen devices (which are thinner and do not rely on CRT technology), e.g. LCD screens (liquid crystal display) and plasma screens
    Televisions, computer monitors, laptops, educational and gaming computers, surveillance and security monitors

Currently, tube-based devices are more commonly seen in waste electrical and electronic equipment, but the proportion of flat-screen displays is expected to increase sharply in the next few years.

Recovering raw materials

Currently, tube-based devices are more commonly seen in waste electrical and electronic equipment. The following table presents the approximate proportion of different materials recovered in the processing of display devices:

Display devices Mass [t] Proportion [%]
Ferrous metals,
Non-ferrous metals
2.078 11,20
Screen glass 5.937 32,00
Cone glass 5.195 28,00
Plastics 2.672 14,40
Circuit boards 1.484 8,00
Electrolytic capacitor 223 1,20
Luminescent coating 6 0,03
Remainder 959 5,17
Total 18.553 100,00

Hazardous substance removal and disassembly

Professional disassembly of tube-based display devices proceeds in the following steps:

  • Disassemble rear panel and housing.
  • Remove printed circuit boards.
  • Allow air to enter the picture tube (the vacuum in the picture tube poses a risk of implosion).
  • Remove the electron beam unit, made of high-grade nickel-alloy steel.
  • Extract the toxic getter plate, which contains barium.
  • Separate the picture tube into screen glass and cone glass.

Output proportions from processing display devices

For tube-based devices, the screen coating (which contains toxic cadmium and yttrium compounds) must be removed.
To do this, the metal clamping ring is first removed from the picture tube, and hot wire is then used to separate the tube into two halves: the screen glass (barium glass) and the cone glass (lead glass). The metal shadow mask is removed as well. Finally, the screen coating is vacuumed off and captured in collection containers. The screen coating is stored in an underground disposal site.
Currently, most of the barium and lead glass from the picture tubes is used to make new display devices in Asia, and a smaller portion is also processed further for use in recycled building materials.
When flat-screen displays are disassembled, the LCD or other displays are separated from the housing components and gathered separated. Next, the printed circuit boards, accumulators and batteries are removed.
Liquid crystals from LCD screens can be used e.g. in metallurgical processes, replacing quartz sands.
The remaining frame components, made of ferrous metals, and the cooling components made of aluminium, are further sources of valuable materials.Flat-screen display devices contain a large proportion of plastics in their housings. These can generally be separated in the disassembly stage.