Modern materials and products
We will be looking at the structural composition, application and advantages/ disadvantages of the following modern materials and products used by the graphics industry:
Liquid crystal displays (LCDs)
Phosphorescent pigments
Electroluminescent (EL) lighting
We will be looking at the structural composition, application and advantages/ disadvantages of the following modern materials and products used by the graphics industry:
Liquid crystal displays (LCDs)
Phosphorescent pigments
Electroluminescent (EL) lighting
Liquid crystal displays (LCDs)
![Picture](/uploads/1/1/1/3/11139306/943751836.gif?814)
LCD (liquid crystal display) is the technology used for displays in notebook and other smaller computers. Like light-emitting diode (LED) and gas-plasma technologies, LCDs allow displays to be much thinner than cathode ray tube (CRT) technology. LCDs consume much less power than LED and gas-display displays because they work on the principle of blocking light rather than emitting it.
An LCD display is made up of a thin layer of liquid crystals arranged in a matrix (or grid) of a million or more pixels (picture elements), which are themselves made up of three sub-pixels aligned to a colour filter for each of the primary colours; red, green and blue. This layer is sandwiched between the two glass plates, which are covered in a matrix of electrodes and transistors (electronic switches), each coated with a polarising filter. The two polarising layers only allow light vibrating in one direction to pass through them, one allows horizontally vibrating light through and the other passes vertically vibrating light.
The light source in an LCD is its backlight so this unpolarized light becomes vertically polarized as it passes through the first polarizing filter at the back of the display. The other polarizing layer on the front sheet of glass is horizontally polarized, so ordinarily the now vertically polarized light coming from backlight can't pass through it. The role of the liquid crystal layer in the middle of the display is to rotate the vertically polarized light travelling through it by ninety degrees so it can pass through the front, horizontally polarized filter. By varying the voltage applied to the liquid crystal sub-pixels the amount they twist the light changes, allowing more light of each colour though as a greater voltage is applied.
Individual pixel colours are produced by the combination of the primary colours produced by each sub pixel, with the pixel's overall brightness is produced by the sub-pixels relative intensities. Many thousands of these pixel units operating together in the display combine to produce the image you see.
Phosphorescent pigments
![Picture](/uploads/1/1/1/3/11139306/289820058.jpg?320)
Phosphorescent pigments glow in the dark. They are able to absorb light energy and store it. This stored energy is released as light energy over a period of time.
Phosphorescent pigments are useful for watch faces that glow in the dark. They may also be used in fire safety signs placed near fire extinguishers. In the event of a fire, the position of the fire extinguishers can be seen, even if the lights fail.
Phosphorescent pigments are useful for watch faces that glow in the dark. They may also be used in fire safety signs placed near fire extinguishers. In the event of a fire, the position of the fire extinguishers can be seen, even if the lights fail.
Electroluminescent (EL) lighting
![Picture](/uploads/1/1/1/3/11139306/986780046.jpg?331)
To put it simply EL lamps or "high field electroluminescent" lamps use electric current directly through a phosphor to make light. Unlike most lamps, they can be shaped to be extremely flat, or in narrow wire-like shapes.
Electroluminescence or "EL" is the non-thermal conversion of electrical energy into light energy. This phenomenon is used in EL lamps, LEDs, and OLEDs.
Advantages:
-Low wattage
-Long life
-No external circuitry required (no ballast needed to limit current, it can be plugged directly into AC power and will self-regulate power through it's own resistivity)
-Can be manufactured into flat flexible panels, narrow strings, and other small shapes
-Can be made into waterproof computer monitors which are more durable and light weight than LCDs or Plasma screens.
-Not directional like LCDs when used as a computer monitor, looks good at all angles
-EL displays can handle an impressive -60 C to 95 C temperature range, which LCD monitors cannot do
Disadvantages:
-Not practical for general lighting of large areas due to low lumen output of phosphors (so far)
-Poor lumens per watt rating, however typically the lamp is not used for high lumen output anyway
-Reduced lumen output over time, although newer technologies are better than older phosphors on this point
-Flexible flat EL sheets wear out as they get flexed, durability is being worked on
-The lamps can use significant amount of electricity: 60-600 volts
-Typical EL Needs a converter when used with DC sources such as on watches (to create higher frequency AC power, this is audible)
Electroluminescence or "EL" is the non-thermal conversion of electrical energy into light energy. This phenomenon is used in EL lamps, LEDs, and OLEDs.
Advantages:
-Low wattage
-Long life
-No external circuitry required (no ballast needed to limit current, it can be plugged directly into AC power and will self-regulate power through it's own resistivity)
-Can be manufactured into flat flexible panels, narrow strings, and other small shapes
-Can be made into waterproof computer monitors which are more durable and light weight than LCDs or Plasma screens.
-Not directional like LCDs when used as a computer monitor, looks good at all angles
-EL displays can handle an impressive -60 C to 95 C temperature range, which LCD monitors cannot do
Disadvantages:
-Not practical for general lighting of large areas due to low lumen output of phosphors (so far)
-Poor lumens per watt rating, however typically the lamp is not used for high lumen output anyway
-Reduced lumen output over time, although newer technologies are better than older phosphors on this point
-Flexible flat EL sheets wear out as they get flexed, durability is being worked on
-The lamps can use significant amount of electricity: 60-600 volts
-Typical EL Needs a converter when used with DC sources such as on watches (to create higher frequency AC power, this is audible)