Preferably, the alignment electrodes 30 a and 30 b are made of a material such as copper (Cu), aluminum (Al), silver (Ag), an alloy of copper and titanium (Cu/Ti), an alloy of copper and chromium (Cu/Cr), an alloy of aluminum and titanium (Al/Ti), an alloy of aluminum and chromium (Al/Cr), an alloy of silver and titanium (Ag/Ti), or an alloy of silver and chromium (Ag/Cr).