Laser irradiation apparatus

A laser irradiation apparatus comprising:

• (a) a laser oscillator configured to emit a laser beam to be irradiated on a workpiece of a plate shape;
• and
• (b) a flotation unit configured to float the workpiece by blowing and suctioning a gas, and including:
• (b1) a base including a pressurizing through-hole and a depressurizing through-hole formed therein;
• (b2) a porous plate located on an upper surface of the base and including a plurality of first through-holes formed therein;
• and
• (b3) an intermediate plate made of a metal located below the porous plate, accommodated inside the base and including a plurality of second through-holes formed therein, wherein
• the intermediate plate is shorter along a conveyance direction than the porous plate and the base,
• the porous plate is bonded to the base by a first adhesive layer, and the intermediate plate is bonded to the base by a second adhesive layer,
• the porous plate is disposed facing the workpiece,
• a pressurizing chamber configured to pressurize a gas is formed in a space between the porous plate and the intermediate plate,
• a depressurizing chamber configured to depressurize the gas is formed in a space between the base and the intermediate plate,
• the pressurizing through-hole is connected to the pressurizing chamber,
• each of the plurality of first through-holes is connected with a corresponding one of the plurality of second through-holes,
• the depressurizing through-hole and the second through-holes are connected to the depressurizing chamber,
• the gas is blown through the pressurizing through-hole and a pore of the porous plate,
• the gas is suctioned through the depressurizing through-hole, and the pluralities of first and second through-holes, and
• diameters of the plurality of first through-holes are larger than diameters of the plurality of second through-holes.