In this study, a new wet etching method and the solution for thinning the glass with the thickness below 100 μm were investigated. For the preparation of etching solution with low hydrofluoric acid, it was effective to use NH4HF2 as a main ingredient with addition of sulfuric acid. Flexibility of the etched glass was greatly improved at below 100 μm thickness. To confirm the possibility as flexible display substrate, the ultra thin grass with 50 μm thickness was coated with ITO (Indium Tin Oxide) transparent electrode and its electrical conductivity was investigated.