Post on 04-Apr-2018
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How can we recycle LCD monitor
Ana-Marija (Mia Viki)
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LCD (liquid-crystal-display) monitors
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LCD (liquid-crystal-display) monitors
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LCD (liquid-crystal-display) monitors
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Liquid crystalls
Liquid crystalls can be found in nature aroundus, but also in many electronic devices andapplications
It represents a state of materie whichcombines properties form both liquid andcrystalls
We can divide liquid crystalls into threegroups: thermotropic, liotropic andmetallotropic
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Liquid crystalls
Thermotropic liquid crstalls are build from
organic molecules and depending on
temperature can exchibit in different phases
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Thermotropic liquid crystalls
Molecules are in so called nematic phase
Combines from cilinder organic moleculeswhich can move freely
Although they do not posses arranged crystall
structure , the cilinders are merging andtrying to hold on arranged system in one
direction
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Smectic phase of liquid crystalls
In smectic phase , crystalls poses higher level of
inner arrangment then in nematic phase
It combines of layer that can slide across one
another
Phases between layers haves properties of liquid
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Smectic phase
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Chiral phase
Chiral molecules are turning in parallel in one
direction and in that way they are saving
longterm arrangement
The consiquences of turning angle from center
of rotation is optical propertie like Bragg
reflexion
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Chiral phase
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Usage of liquid crystall
The usage of liquid crystalls comes from the
fact that we have permanent electrical dipoles
whose orientation in space is determened by
orientation of molecules
Using outside electrical field we can influence
on inner arrangement of crystalls and
consiquentually on their optical preferences
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Main components of LCD monitor
Liquid crystall
Glass
Thin transistor film
Conducting electrodes
Color filters
Polarizators
Background light Reflective background
Plastical components
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Components of LCD screen
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LCD
LCD-display is based on liquid crystalls that arebound between two glasses substrates withpolarizator form outer side
On inner side of the glass substrate there is athin transistor film on one part glass substrateand color filter on another glass substrate
Exeption transistor and color filter on innerside , we also have conducting electrodes andand orientation films
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Making of picture
Depending about presence or nonpresenceof electric currence , the liquid crystalls arearranging themselves in such matter that they
combine with polarizators making light topass or not to pass
The light that comes from background lightsource is regulated when passing throughsample of color filter on inner side od thefront glass substrate
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Materials and chemical composits
1. Liquid crystalls
LCD display usually combines 10 -25 components
because only one doesnt fulfill complex
properties that LCD demands
From first discovery of liquid crystalls , we have a
knowledge for about more than 20 000
compounds that have nematic phase: some ofthem are anisilidenparaaminophenylacetate
(APAPA) and 4-n-penthyl -4-ciano-biphenyl(PCB)
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Materials and chemical composits
2008. , about 69 % of LC was made by german
company Merck KggA which patented about
2500 LC mixtures
Compounds that have been used in LC
mixtures are usually poliaromatic polimers
with 14 to 30 carbon atoms on which we
selectively add atoms of O, N, F, Br or Cl.
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LCDElectrodes
Conductive electrodes are from inner part of
glass substrates
Electrodes are made from transparent
conducting layer made from indium-tin oxides
(ITO) .ITO is a mixture of indium(III) oxide
(In2O3) and tin(IV) oxide (SnO2) in relate to
90:10
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LCDElectrodes
The position of electrodes in shematics for LCD screen
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Color filters
Color filter are made from black matrix,
surface layer,RGB pattern and conductive
electrode (ITO)
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Color filter
Color filter
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Polarizators
Polarizators are settled on outer side of glasssubstrate
These are special filters which allow onlypolarized light to pass, to be more acurate ,
fotons who are vibrating in only one plane They are made from layer films , begining from
layer of polyethilen tereftalate (PET) , then layerof celulose threeacetate, then layer of polyvinylalcohole impregnated with iodine or nonspecificcolors, then another layer of celulosethreeacetate and ends up with PET layer
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Polarizators
PET layer
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Polarizators
Celulose threeacetate
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Polarizators
Polarizators with polyvinyl alcohole and
impregnated iodine are also called H-cells
In later time , it is common to use polyvinyl
chains which can be derived from
dehydratation of polyvinyl alcoholethose are
called K-cells
In LCD screens there is one vertical and one
horizontal polarizator
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Background lighthing
In all LCD monitors there are fluorescentlamps, which are used to light up thebackground of screen and they represent the
only active light source Fluorescent light source is a glass tube which
produces white light . In the inner part of glasstube there is a mercury sample under lowpressure who is emitting UV radiance whenbeing in ionized form
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Background lighthing
The inner part of flourescent source is painted
by phosphor
Phosphore is capable of apsorbing energy and
to emitt one in a form of visible radiance
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Glass
Glass is combined with many sodium and
other alkali ions which can move freely on the
surface of the glass
To avoid those kind of efects , we are using
borsilicium glass or glass painted by a layer of
silicium oxide
Silicium oxide is preventing ions to react with
moisture from air
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Plastical components
The most simple solution is to use transparent
plastical surfaces for lighter LCD
Plastical components will make screen easier ,
but cheap plastical components will disperse
light more then glass and can react chemicaly
with molecules of liquid crystalls
Plastical components are also used for making
of outer screen frame
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Recycle of LCD materials
With growing production of LCD screens we
also have growing amount of their disposal
,and to taking care of represents a large
ecological issue
Liquid crystalls which are made of aromatic
rings supstituited with halogen atoms produce
very toxical products dangerous forenviroment (dioxanes, furans..etc..)
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Recycle of LCD materials
The background light source posses largeamount of mercury , and batteries of smallLCD often have mercury and cadmium
Both elements , mercury and cadmium haveacumulative effect in human body andenviroment , and posses toxicity
Glasses used in LCD screen posses cadmiumand arsenic compounds so their recyclebecomes very important
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Recycling flourescent lamps
Flourescent lamps are made of 94% glass, 4%
metals and 2% phosporus pouder
Mercury is settled inside phosporus pouder
Mercury element is suffiecient to create
toxicity of 30 000 liters of water
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Recycling flourescent lamps
Comparison between flourescent tube from laptop and plain pencil
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Recycling flourescent lamps
Mercury can be depleted on specific mercury
deposits , but those places are very few
We can recycle mercury using vacuum
destillation
Unpure mercury can be destillated in twohead
pots and dried on 360 C , and using condenser
we can extract , condense and assemble pure
mercury in round pots
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Recycling flourescent lamps
Simple aparature for mercury destillation
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Glass recycling
The amount of glass deposits which is
collected on deposits in Taiwan in 2009. has
reached 0,52 million tons
Glass deposits can be recycled to produce
glass ceramics
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Glass recycling
Kitchen assemblance made from glass ceramics
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Glass recycling
Deposit glass is drilled ,homogenized and setin chasement under pressure
Dust particles are assembled in solid mass
using thermal process (the process ofsinteration)
Heating glass deposits we are removingorganic components and stabilize inorganiccomponents incorporating oxidescharacteristic for glass ceramics
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Glass recycling
On temp. from 800-950 OC , in 6 hours and
increasing temperature by 5C O /min we can
get very qualitative glass ceramics
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Recycling plastical components
Most of plastical components are not
biodegradible , but all plastical components
can be recycled
We can recycle plastical components using
pyrolithic procesess in pyrolithic reactors
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Recycling plastical components
Pyrolithic reactor
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Recycling plastical components
The process of pyrolise is a proces where we havedestillation of organic part from deposit withripping of chemical bounds (crecking) of largemolecules of material like plastics, rubber ,leather and similar materials
With the same process we can gain gas andliquid fuels
Gases gained from pyrolithic processes aremixture of :hydrogen , methane, carbonmonoxide and carbon dioxide
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Recycling plastical components
Liquid phase from process of pyrolize has
condensed burning oil whose composition
depends from different deposit material
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Recycling wires of electrical net
Like any other electronic devices we can also
recycle electric circle wires
Materials are first grinded to dust and then we
use chemical and physical processes to dissolvenobel metals in process called smeltingvery
similar to dissolving mineral composits
Using temperature and reductive chemicalagenses we can remove all components
exception metals like copper, gold and silver
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Rycling of liquid crystalls
Liquid crystalls are not easly biodegradible
We dont know much about recycling liquid
crystalls because most of them are under
patent protection and recycling tehniques are
still developing
Merck company recomends industrial burning
process for ecological measurment
l i l b k d f d i
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Ecological background of producing
LCD
Main ecological problem is process of making
LCD materials and their usage (they use lot of
electrical energy)
Factories manufacture several million tons of
waste waters
Those waste waters consists of large
spectrum of organic solvents like :DMSO,MEA, TMAH and chrome residues..
E l i l b k d f d i
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Ecological background of producing
LCD
Chrome is extremly cancerogenetic supstance
We have many methods which can resolveorganic solvents and can isolate dissolved
chromium in a form of chromium oxide fromwaste waters
In the process of production we use largeamount of SF6 (sulfur-flouride) gas andnatural gases which also contributes to globalwarm effect...
H h LCD i l
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How to change LCD materials
ecological issue
Main problem is mercury in flourescent lamps
We have new generation of LCD monitors who
doesnt have mercury , they are energetically
more effective and higher quality
Monitors that are using LED lamps as
background light source are capable off
creating much cleaner white light
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LIGHT EMITTING DIODE(LED)
LED is a semiconducting light source
They are available in many sizes and colors
Very restistant and long life
Recycling LED diode would mean to: induce more money for making glass
Reduce the amount of toxic metals in glass
New form of glasses donz have arsenic , antimonand barium resiudes , their are ligher and havebetter heat properties