Evaluation of indentation induced residual stress on the surface of substrate glasses for display

Residual stress field around a Vickers diamond indentation was studied in three commercial glasses with different strain points (T_s = 635°C, 570°C and 511°C, respectively). The basis of the experimental technique is to use cracks from a small indentation as a microprobe to measure the residual stress at a specific point around a large indentation and to study the change of the residual stress by heat treatment. Residual tensile and compressive stresses around a large indentation produced by applying the load of 19.6 N were distributed up to a distance of about 400 μm from the indentation center. For all specimens, the tensile and compressive stresses were about 10 MPa and -50 MPa∼ -30 MPa, respectively, at a distance of 200 μm from the indentation center. The residual stresses decreased by heat treatment at temperatures as low as 300°C below the strain point and became zero by keeping the indented specimen at temperatures close to the strain point of each glass, for 7.2 ks. The resistance to decrease in residual stresses against temperature was in the order Si-B-Al-O (T_s = 635°C) > Si-Al-O (T_s = 570°C) > Si-Ca-Na-O (T_s = 511°C) glass. The results were discussed based on the difference of the mobility of constituent ions and flow of glasses.