Study On Recycling Technology Of Waste LCD ITO Glass

In2007, the worldwide shipments of the liquid crystal displays (LCDs) surpassedthe traditional cathode ray tubes (CRTs) for the first time and LCDs have been graduallyreplacing the traditional CRTs. With the continuous depletion of global resources, therecycling of the waste electrical and electronic products has aroused people’s wideconcern. Many domestic and foreign research institutions have attached greatimportance to the recycling and reuse of the abandoned LCDs. With ITO glass ofTFT-LCD as studying object, the recycling technology of ITO glass has been studied inthe dissertation.Firstly, the leaching characteristics of ITO glass in LCDs were analyzed based ondynamics and thermodynamics. After determining the pH value that must be met by theleaching of coating, the dissolution properties of ITO coating were studied from threeaspects: the study of the solubility of ITO glass in different acid systems, the study ofthe best acidity of ITO glass’ being leached and the study of the relationship between theparticle size of ITO glass and the dissolution rate of ITO. The experimental results showthat ITO has good solubility characteristics in acidic solution，8mol/L is the best acidconcentration and the grain size of ITO glass has less relationship with dissolution rateof ITO.Secondly, based on the physical properties, chemical compositions andmanufacturing process of ITO glass substrate, HF was used to clean the surface of theglass substrate. The results show that all the coating layers can be removed when theITO glass was leached in hydrofluoric acid solution (HF: H2O=1:2) for about120min.The recycled ITO glass substrate was used to manufacture new glass specimen and thecharacteristics of the recycled glass specimen were tested. The testing results show thatthe recycled ITO glass has the advantages of small density, high hardness, low thermalexpansion coefficient, light weight and good mechanical properties，and is worthy ofbeing recycled.Lastly, according to the conventional extracting process of rare and precious metalindium, using hydrofluoric acid solution to corrode and dissolve the surface of ITOglass, enriching and concentrating the solution which contains indium, the replacementliquid was got. Sponge indium was separated out by aluminum sheet from thepreoperative liquid. Smelting the sponge indium with molten sodium hydroxide, the crude indium was got with the purity of93%and the high purity indium was refined bymeans of electrolysis.