Conference PaperPDF Available

ReLCD recycling and re-use of LCD panels

Authors:
Bernd Kopacek at TU Wien
Bernd Kopacek
Download full-text PDF
Read full-text
Download citation

Abstract and Figures

Nowadays more and more consumers substitute their conventional TV-sets and computer monitors by LCD panels. In the near future huge amounts of LCDs will start coming back to recycling. As LCDs with hazardous mercury backlight lamps are used an appropriate recycling technology has to be implemented.
Figures - uploaded by Bernd Kopacek
Author content
All figure content in this area was uploaded by Bernd Kopacek
Content may be subject to copyright.
Content uploaded by Bernd Kopacek
Author content
All content in this area was uploaded by Bernd Kopacek
Content may be subject to copyright.
Proceedings of the 19th Waste Management Conference of the IWMSA (WasteCon2008).
6 – 10th October 2008. Durban, South Africa. ISBN Number: 978-0-620-40434-1
ReLCD: RECYCLING AND
RE-USE OF LCD PANELS
KOPACEK B
SAT, Austrian Society for Systems Engineering and Automation, Austria (bernd.kopacek@sat-
research.at)
ABSTRACT
Nowadays more and more consumers substitute their conventional TV-sets and computer
monitors with LCD panels. In the near future huge amounts of LCDs will start coming back to
recycling. As LCDs with hazardous mercury backlight lamps are used an appropriate recycling
technology has to be implemented.
KEYWORDS
LCD, Recycling, Re-Use
INTRODUCTION
Liquid Crystal Displays (LCDs) are widely used in notebooks, organizers, mobile phones, pocket
calculators, measuring and control instruments, electronic games, hand-held miniature TVs,
audio-video equipment, large signboards, automotive displays and more and more for PC
monitors and TVs.
According to a study from Stanford Resources (San Jose, California) the annual value of
LCD-products reached 35 billion EUR in 2002, about 30% of this within the European Union,
representing a total area of 2,1 million m² Liquid Crystal Displays. An annual increase rate of
about 15% is estimated for the next years (up to 4,1 million m² in 2005).
As LCDs are already on the market for several years, larger quantities of the more than 2,5
billion LCDs are coming into their End-of-Life stage for treatment. In 2005 this figure will become
even more dramatic - 40.000 tons of LCD-modules contained in 2 million tons of waste electrical
and electronic equipment (WEEE) or about 30% of total WEEE within EU. An amount which is
representing 400 million EUR costs for incineration.
434
Currently the only method used to deal with redundant LCD units is incineration or landfill.
Both are expensive and cause emissions into the atmosphere (global warming) respectively
water contamination (Class II) and difficulties in biodegradation. Up to now there is no recycling
solution for LC-Displays available.
As a consequence European Commission requests the disassembly of LCDs with an area
bigger than 100 cm² in the Directive 2002/96/EC of the European Parliament and of the Council
on Waste Electrical and Electronic Equipment (WEEE Directive) of February 13, 2003.
Structure and material composition of LCD
The definition of “LCD“ describes the sandwich composed of the two glass plates with
connected polymers (for example polarizers, colour filters) and the sealed liquid crystal mixture
in between the two glass plates. This definition does not include the backlight unit, the printed
circuit board, cables and frame which are part of the LCD module. Figure 1Error! Reference
source not found. shows the structure of a liquid crystal display.
Figure 1. Structure of LCD
Glass plates
The plate at LCD panel is a glass substrate with a transparent metal coating for the electrodes
of the display. In LCDs usually soda lime type glass is used, but in some cases it can be a more
expensive borosilicate type. The thickness of glass substrate is 0,4 - 1,1 mm.
Polarizer and orientation layers
The outer surface of both glass substrates are coated with polarizer layers made of
polycarbonate with the thickness of 0,2 mm. On the top of electrodes, the orientation layer can
be found. The orientation layer ensures the specific starting orientation in the unstressed state.
435
Usually hydrocarbon polymers, such as polyvinyl alcohol or heat resistant polyimide are applied.
The thickness of this layer is 30 to 100 nm.
Electrode
The transparent conductive coating is a thin layer of a metal, such as gold, silver, or tin.
Generally tin-oxide, indium-oxide, or their alloys are used because these materials constitute a
hard layer. In the industry the most preferred electrode material is the indium-tin oxide (ITO,
In2O3.SnO2) because of reasonable costs and eligible transparency. Accessible information
about Indium Tin Oxide electrode layer used in Liquid Crystal Displays and other applications
(e.g. solar cells) are the following:
• Thickness: 30-80 nm;
• Density: ~7,1-7,2 g/cm³;
• Typical In2O3:SnO2 ratio (by weight): 95:5-85:15, depends on application
Liquid crystals
Liquid crystals are used as mixtures typically containing between 10 and 25 single compounds.
These mixtures are composed of chemically quite similar compounds. Some of the compounds
only differ in their alkyl or alkoxy side chains by varying number of carbon atoms (homologous
compounds). The thickness of liquid crystal layer is about 5 μm, and the volume of it is about
350 mg in a 15” display. One the most important manufacturer, Merck KgaA, has confirmed that
the liquid crystals supplied by them don’t contain any of the substances mentioned in the EU
Directive 200/95/EC of 27 January 2003 on Restriction of the use of certain hazardous
substances in electrical and electronic equipment. Despite this, liquid crystals are known to be
hazardous to water (water contamination class II) and very difficult to biodegrade (0 – 30%
within 28 days).
Colour filter layer
The light passes through a colour filter layer, which is a key component for making colour
images. Colour filters’ pixel has red, green, and blue colour elements, and black matrix is
located between the colours to avoid leakage of light. The colour filter layer must be as smooth
as possible for maximal colour purity. The black matrix is usually made of chromium, chrome-
oxide, or black resins. Colour filter is usually an organic or inorganic polymeric material
(gelatine, casein, polyvinyl alcohol, acrylic, epoxy, polyester and polyimide) with pigments.
Pigments usually have carboxyl-, amino-, or sulfon groups. For example dianthraquinone (red)
or copper phthalocyanine (green or blue) is used. The thickness of colour filter layer is between
0,7 - 2,5 μm, and the pigments are under 0,1 μm.
Backlight unit
About 90% of LCDs use backlight unit. Backlight unit consists of light source, reflector, light
guide plate, and diffuser. Several technologies are used in backlight units, e.g. there are
electroluminescent, light emitting diode, and cold cathode fluorescent lamps. In most backlight
units the light source is a fluorescent tube because it offers low power consumption and very
bright white light. The reflector is usually a polymer film with a thickness of 25 μm coated with
Ag or Ag-alloys with a thickness of 150 nm. The polymer film is made of PET (polyethylene
terephthalate), and contains UV-ray absorbing agents to prevent UV-ray originating
degradation.
OBJECTIVE
Currently the only way to deal with End-of-Life LCDs is disposing them in waste incinerators or
landfills. Incineration of LCDs causes the same volatile products and residues as incineration of
municipal waste. Among other compounds, these emissions, due to the possible content of
liquid crystals of chlorine, could be made up of dioxins and furans, very toxic substances that
436
are currently under discussion. Furthermore, it is assumed that under high thermal conditions
there will be breakdown products that can be toxic. On the other hand, landfilling is not
ecologically efficient since it has been researched that large LCDs possess a backlight
containing mercury and the battery of small LCDs may also contain mercury or cadmium,
substances classified as toxic due to its accumulative effects in both human body and
environment. Therefore an eco-efficient disassembly and recycling technology for end of life
LCDs that fulfils the WEEE-Directive of the European Commission has to be implemented.
ReLCD went in several areas beyond the unsatisfactory state-of-the-art. The objectives
were:
• To find a cheap and fast test methodology to verify if the obsolete or excess LCDs are
still working
• To develop a technology to refurbish the working LCDs and re-integrate them into repair
and in exemptions also in production processes
• To find a test method to detect hazardous substances in LC-mixtures
• To develop an eco-efficient disassembly and recycling technology for the non-working
LCDs that fulfils the WEEE-Directive of the European Commission
• To research possible enhancements to the existing LCD design and production in order
to come to a more sustainable life-cycle of LCDs (publication of guidelines)
• Building up a pilot plant incorporating and testing the developed technologies
By all these measures decrease the amount going to landfill or incineration as well as
decrease the threats to the environment and mankind of today’s state-of-the-art technology.
PROJECT RESULT
Although numerous manufacturers and various different types are available on the market the
characteristics important for dismantling are similar for all types. So a representative sample
was selected to find the most efficient treatment method. The aim was to separate the
hazardous backlight lamps from the panel.
About 90% of LCDs use backlight unit. Apart from manual dismantling some cutting
technologies were investigated.
If the backlight lamp - which represents just 2% of the total mass of the LCD – is not
extracted before, the whole screen has to be treated as hazardous waste. Therefore the goal of
the project has been to find a cheap technology for dismantling the backlight unit because the
remaining 98% of the mass can be easily treated in a conventional shredder for waste
electronics.
For separation of the backlight lamps the following treatment technologies methodologies
have been evaluated:
• Manual dismantling
• Water Jet Cutting
• Laser Cutting
• Circular Saw
A rough estimation of the processing costs and total treatment costs have been also
investigated.
437
The following parameters have been considered:
• Mean processing time
• Maintenance costs
• Personnel costs
• Material revenues
Although some alternative treatment technologies were investigated the best results were
achieved by manual dismantling. Both the costs per item and the quality assessment reach the
best results.
Especially the high investment costs of jet cutting and laser cutting result to an inefficient cost
trend especially for low volumes. After the amortisation time and huge volumes laser cutting can
be competitive to manual dismantling. As the recycling amount of LCDs for the next years is
hard to estimate high investment costs will also cause a high financial risk. Even more that more
and more producers use mercury-free backlight lamps. These do not have to be extracted and
the whole module can be recycled as “normal” WEEE (Waste from Electrical and Electronic
Equipment) in the future.
Sawing technologies like circular sawing or band sawing would be inefficient because of the
material composition of LCD panels. Although a huge variety of special designed saw blades
are available no one fits all requirements which are necessary to cut LCD panels. Especially the
content of glass result to difficulties and the lifetime of the sawing-blade is reduced heavily. The
short lifetime of the sawing equipment will result to very high variable costs. Hence sawing can
never be competitive to manual dismantling.
It can be also stated, that some manufactures already consider requirements for dismantling.
Our investigations show that already 40% of the panels are designed disassembly friendly. As
we expect a rising of the percentage in the future manual dismantling will become efficient
anymore. A percentage of 60% will reduce the mean dismantling time to 1,4 min. A dismantling
time of 1,4 min per panel prefer manual dismantling to other technologies (e.g.: Laser cutting …)
even in countries with high labour costs.
ACKNOWLEDGEMENT
The author would like to thank all partners in the research consortium as well as the European
Commission to enable the project by its funding.
438
... Zhuang et al. [10] reported that; in 2006, about 90% of the electronic displays on the global market were LCD/LEDs with their average life span estimated to be between 3 and 8 years [11][12][13][14]. With the continuous use of LCD/LEDs in most applications, the waste produced from electrical and electronic equipment is exponentially on the increase with the fastest rate of increase being observed in developing countries [15]. In a recent report published by the United Nations Environment Program entitled 'Waste Crime', 41.8 million metric tons of electronic waste were reported to have been produced globally in 2014 [16]. ...
... Some of the wastes from LCDs/LEDs contain valuable metals such as indium and gold, and some hazardous materials such as mercury and liquid crystals (LC) [4]. LC used in LCD/LED panels is made up of a mixture of 10-25 different types of LCs or molecules [14,15,19]. These LCs are highly stable, have low biodegradability and also contain large volumes of benzene rings, fluorine, chlorine, bromine, cyano-group, esters, and cyclohexyl. ...
... The differences in colour of the PLA-RLC composites indicate the effectiveness of this hybrid approach used in recovering the LCs as compared to other methods. This is because, most methods only extract the LC without purifying it, and those who tried purification, used fresh organic solvents to redissolve the extracted raw LC, and then went through the process of purification [7,11,15,20,22]. This is double cost as compared with our approach whereby the same LCorganic solvent solution is processed after the LC is extracted from the screens to obtain Fig. 2 shows FTIR spectra with all the functional groups of the RLC. ...
Thermochromic properties of composite materials made from polylactic acid reinforced with recovered liquid crystals from waste LCD/LED laptops screens
Article
  • Jul 2022
  • OPT MATER
The use of flat panel displays has permeated daily life since the breakthrough in the usage of liquid crystals (LCs) in display technology. However, the presence of chemical compositions such us cyano-groups, benzene, fluorine, cyclohexyl, etc., in LCs has potential adverse effects on humans and their environment as well. The environmental issue can be resolved by recovering the LCs for use in different applications. In this study, solvent extraction recovery process was directly used to simultaneously recover and purify LCs from waste liquid crystal display (LCD)/light emitting diode (LED) screens of laptops. The physicochemical (Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC)) and morphological properties (scanning electron microscopy (SEM)) of the purified and unpurified recovered liquid crystals (RLCs) were compared. The RLCs were incorporated in polylactic acid (PLA) using 0, 5, 10, 15, 20, 25 and 30 wt% of RLC. Thermochromic properties of the formulated PLA-RLC composites were studied from room temperature (25 °C) to 100 °C using a colorimeter. The changes in colour with change in temperature were measured and recorded. A recovery rate of 92.46% LCs was obtained from the laptop screens, making the purification process very effective as ascertained by the physicochemical characterization techniques. The difference in crystallinity of the purified and unpurified RLCs was 2.55% with the solid to liquid crystalline transition temperatures of the purified and unpurified RLCs being 45 °C and 65 °C, respectively. The thermochromic studies of the formulated PLA-RLC composites showed an appreciable colour change with temperature improvements in all the colour variables (i.e., the lightness, a* and b*). The colour changes were however not visible to the eyes due to the small energy difference (ΔE*) values. The implication of the results is that the RLC from waste screens of LCDs/LEDs exhibits enhanced thermochromic properties when different purification stages are used.
View
... LCD monitors hold general structure, though its contents may vary with manufactures to manufactures. Kopacek [7] reported that LCDs contains different components such as glass plates, polarizer, electrode, liquid crystals, colour filter layer and backlight unit. Moreover, the study also pointed out, LCD products possibly contain toxic elements such as mercury or cadmium therefore an efficient method should be applied during recycling. ...
... Presence of certain hazardous materials such as brominated flame retardants or heavy metals opposes the mechanical recycling as well as reprocessing of plastics recovered from WEEE [18,29,30]. However EDAX analysis performed on the r-PMMA material indicates that they does not contains any brominated flame retardants and other toxic elements as discussed by Kopacek [7], which suggest the recycling possibilities of the r-PMMA without any toxic concern. Figure 3 represents EDAX spectrum for both virgin and recycled PMMA material. ...
Investigation into the mechanical and thermal properties of poly(methyl methacrylate) recovered from light guidance panels with a focus on future remanufacturing and sustainable waste management
Article
Full-text available
  • Dec 2017
The potential of light guidance panels (LGPs) in the field of recycling technology has not explored to meet its full efficiency in the recovering of polymeric component from it. As consequences such components are either incinerated or used for land filling purposes. Therefore, this work aims to address the recycling and reutilization of poly(methyl methacrylate) (PMMA) recovered from light guidance panels used in the liquid crystal displays (LCDs). Fourier transform infrared (FTIR) analysis, resin identification code (RIC) and density methods confirm the presence of PMMA as the major polymer used in LGPs. Additionally, energy dispersive spectroscopy (EDAX) analysis reveals the absence of heavy metals and flame retardants in collected PMMA. Furthermore, mechanical, thermal and morphological characteristics of recovered PMMA were compared with its corresponding virgin material, which confirms the further recyclability of recovered PMMA from LGPs.
View
... The transparent conductive coating is made up of a thin layer of metals, that can be gold, silver or tin. Generally, indium and tin oxide and their alloys are used because of their lower price; moreover, they form a very hard layer and own an eligible transparency (Kopacek, 2008). As widely known, indium oxide(III) is coupled with tin(IV) oxide (indium-tin oxide) with a typical composition of 90%wt In 2 O 3 and 10%wt SnO 2 in LCDs (Swain et al., 2016). ...
... They only differ in alkyl or alkoxy side chains by varying the number of carbon atoms. The thickness of liquid crystal layer is about 5 lm (Kopacek, 2008). ...
Separation and recovery of glass, plastic and indium from spent LCD panels
Article
  • Dec 2016
The present paper deals with physico-mechanical pre-treatments for dismantling of spent liquid crystal displays (LCDs) and further recovery of valuable fractions like plastic, glass and indium. After a wide experimental campaign, two processes were designed, tested and optimized. In the wet process, 20%, 15% and 40% by weight of the feeding panels are recovered as plastic, glass and indium concentrate, respectively. Instead, in the dry process, only two fractions were separated: around 11% and 85% by weight are recovered as plastic and glass/indium mixture. Indium, that concentrated in the -212μm fraction, was completely dissolved by sulphuric acid leaching (0.75molL(-1) H2SO4 solution, 80°C, 10%vol H2O2, pulp density 10%wt/vol, leaching time 3h). 100% of indium can be extracted from the pregnant solution with 5%wt/vol Amberlite™ resin, at room temperature and pH 3 in 24h. Indium was thus re-extracted from the resin by means of a 2molL(-1) H2SO4 solution, at room temperature and S/L of 40%wt/vol.
View
... Used LCDs must be dismantled to break the plastic case, remove the backlight, and retrieve the LCD panels. Manual dismantling is reported to be the most efficient and cost-effective way to recover metals compared to the mechanical way (Kopacek, 2010). ...
Integration of Bioleaching and Biorefinery Technologies for the Recovery of Base and Critical Elements from Electronic Waste
Chapter
  • Feb 2024
Several profound societal changes such as the shift towards renewable energies have created an ever-increasing demand for base and critical metals. Electronic wastes constitute a significant secondary source of such elements and a potential environmental hazard if disposed of improperly. In contrast to traditional methods of recycling e-waste, biohydrometallurgy is an environmentally friendly, low-cost, and energy-efficient alternative. Although processes developed in laboratories display promising yields, it is still premature to implement these biotechnological strategies on a larger scale as the bioleaching and biorefinery mechanisms are still poorly understood. Moreover, very few studies focus on fully biological processes, and most opt for more efficient hybrid approaches. Thus, this book chapter compiles the optimal parameters reported in recent studies, from waste pre-treatment to metal biorecovery, along with insights to complete and close the biohydrometallurgical recycling loop.
View
... The problem is exacerbated by the economics of waste recovery, which suggest that the most costeffective method is manual disassembly. 6 Despite disputes over the toxicity of the components on LCDs, there is general agreement that they are poorly biodegradable, and are potentially significant water contaminants. ...
Current Screens
Chapter
  • Jan 2017
As mobile communication, social media, wireless networks, and flexible user interfaces become prominent topics in the study of media and culture, the screen emerges as a critical research area. This reader brings together insightful and influential texts from a variety of sources–theorists, researchers, critics, inventors, and artists–that explore the screen as a fundamental element not only in popular culture but also in our very understanding of society and the world. The Screen Media Reader is a foundational resource for studying the screen and its cultural impact. Through key contemporary and historical texts addressing the screen’s development and role in communications and the social sphere, it considers how the screen functions as an idea, an object, and an everyday experience. Reflecting a number of descriptive and analytical approaches, these essays illustrate the astonishing range and depth of the screen’s introduction and application in multiple media configurations and contexts. Together they demonstrate the long-standing influence of the screen as a cultural concept and communication tool that extends well beyond contemporary debates over screen saturation and addiction.
View
... 서 론 [1,2]. 폐 LCD용 판넬에서 발생되는 폐 붕규산유리의 재활용에 대해 이루어진 연구 사 례는 (i) 액정, 박막 등 불순물을 물리화학적 방법에 의해 제거한 후 유리의 재사용 [3][4][5], (ii) 야금공정, 용융공정, 소각공정, 시멘트 제조공 정 등 고온 공정에 복합적 사용 [6][7][8] 에서 확인될 수 있다. Figure 6은 B2O3의 첨가량을 달리하여 얻어진 붕규산 유리 발포체의 단면 사진이다. ...
Preparation of Borosilicate Foamed Glass Body with Sound Absorption Characteristics by the Recycling Waste Liquid Crystal Display Glass
Article
  • Dec 2016
In this research, an alumino-borosilicate foamed glass with sound absorption property was prepared using the waste borosilicate glass obtained from the recycling process of waste liquid crystal display (LCD) panel. A 100 g of pulverized waste borosilicate glass with the particle size of under 325 mesh, was mixed with 0.3 g (wt/wt) of graphite, each 1.5 g (wt/wt) of Na2CO3, Na2SO4and CaCO3as a foaming agent, and 6.0 g (wt/wt) of H3BO3and 3.0 g (wt/wt) of Al2O3as a pore control agent. Following mixture was under the foaming process for 20 minutes at a foaming temperature of 950 ℃. The result yielded the foaming agent with 45% of the opened porosity and 0.5-0.7 of the sound absorbing coefficient. This alumino-borosilicate foamed glass with the sound absorption property showed excellent physical and mechanical properties such as density of 0.21 g/cm³, bending strength of 55 N/cm²and compression strength of 298 N/cm²which can be ideally used as sound absorption materials with heat-resisting and chemical-resisting property. © 2016 The Korean Society of Industrial and Engineering Chemistry. All rights reserved.
View
View
Acid leaching of indium from the screens of obsolete LCD monitors
Article
  • Feb 2020
Liquid crystal display (LCD) are present in televisions, computers and mobile phones, and in a variety of other electronic devices. These screens contain in your composition the element indium, considered a critical raw material. Thus, the objective of this work is to study the hydrometallurgical recovery of indium from LCD screens of televisions monitors, using ground samples without the previous removal of polarizing film of the glass layer. In addition, to study some parameters used in this indium recovery process. In this study, initially, the monitors were disassembled for the removal of LCD screens. After this, the LCD screens were broken into smaller parts and ground in a ball mill. After grinding, the samples were characterized by X-Ray Fluorescence (XRF). Subsequently, the leaching tests with aqua regia (HCl/HNO3, 3:1), HCl, HNO3 and H2SO4 were performed. In the leaching tests, variations in acid concentrations, temperature and time of leaching were analyzed. Results showed indium concentrations of 300 mg/kg in the ground samples. In leaching tests, the best results were obtained using H2SO4 0.5 M at room temperature (in 2 h) with extraction rate of 98.2 % and HCl 6 M at 60 °C (in 4 h) with extraction rate of 99.3 %. The high rates of indium extraction obtained indicate that it is not necessary to remove the polarizing film from the glass layer prior to the hydrometallurgical step. On the other hand, the results do not show a clear trend in relation to variations of analyzed parameters.
View
Attrition scrubbing for recovery of indium from waste liquid crystal display glass via selective comminution
Article
  • Jun 2017
  • J CLEAN PROD
More than three quarters of global indium consumption is used for the manufacture of liquid crystal displays (LCDs). These devices contain indium at concentrations that appear to be too low to be economically valorized by standard hydro- or pyrometallurgical methods under current market conditions. Because indium is a metal critical to many electronics and clean energy technologies, developing commercially viable processes for recovery indium from such end of life products is expected to offer societal benefit. While LCD screens contain indium at low levels, the surface confinement of indium in these devices makes abrasion an intriguing option for concentrating indium to industrially relevant levels. To that end, attrition scrubbing is investigated and shown capable of producing a concentrate upgraded in indium concentration by a factor of 10 with greater than 90% recovery of indium. The same process leaves the LCD glass cleaned of semiconductor elements that are viewed as impurities to the glass recycling sector. Relative economics of such a pretreatment process relative to direct chemical processing routes are presented.
View
Preparation of Feed Glass Materials for Producing a Foamed Borosilicate Glass Body from Waste LCD Panel
Article
  • Aug 2016
In this article, the foamed body of glass was manufactured from the waste borosilicate glass produced by wet pulverization process without additional pretreatment which can be used as a recycling method for waste LCD panel glass. Each 100 g of pulverized waste borosilicate glass with the size of less than 270 mesh were mixed with 0.3 weight fraction of carbon and 1.5 weight fraction of Na_2CO_3, Na_2SO_4 and CaCO_3 and let them foamed for 20 minutes at 950^{\circ}C to manufacture the foamed body having the density of less than 0.3g/cm^3. Additionally, adding SiO_2 or H_3BO_3 to the mixture enabled the foamed body to have efficient formation of open pores which showed the possibility for producing the foamed body with new functionalities such as sound absorption.
View
ResearchGate has not been able to resolve any references for this publication.