Metal plate

A method of inspecting a metal plate to be used for manufacturing a deposition mask by forming a plurality of through-holes in the metal plate, the method comprising:

• obtaining a plurality of samples from the metal plate;
• measuring a distance L1 between two measurement points on each sample before a heat treatment;
• measuring a distance L2 between the two measurement points on each sample after the heat treatment;
• a step of judging whether the following conditions (1) and (2) are satisfied:
• (1) an average value of a thermal recovery rates of the respective samples is not less than −10 ppm and not more than +10 ppm;
• and
• (2) a dispersion of the thermal recovery rates of the respective samples is not more than 20 ppm;
• wherein the thermal recovery rate F of each sample is defined by the following expression:
• F={(L1−L2)/L1}×106 (ppm),
• wherein the samples are obtained by cutting at least one sample metal plate, which is obtained by cutting the metal plate along a width direction of the metal plate, into two or more samples along a longitudinal direction of the metal plate;
• wherein the two measurement points on each sample are aligned along the longitudinal direction of the metal plate;
• wherein the heat treatment includes a first step of increasing a temperature of each sample from 25° C. to 300° C. for 30 minutes, a second step of keeping the temperature of each sample at 300° C. for 5 minutes, and a third step of decreasing the temperature of each sample from 300° C. to 25° C. for 60 minutes;
• and
• wherein the dispersion of the thermal recovery rates is a value obtained by multiplying a standard deviation of the thermal recovery rates of the respective samples by a factor of 3.