Die head and liquid coater

1. A die head for forming a coating film, the die head comprising a tip portion for continuously discharging a coating solution to form the coating film on a substrate and configured to retain a bead of the coating solution in a gap formed between the substrate and the tip portion during a relative movement of the substrate with respect to the die head in a predetermined moving direction, wherein

the tip portion comprises:

a feed slot which is positioned at a downstream side of the tip portion in the moving direction of the substrate and continuously feeds the coating solution;

a gas suction slot which is positioned at an upstream side of the tip portion in the moving direction of the substrate and suctions a gas so as to create a vacuum in a vicinity of an upstream edge of the bead with respect to the moving direction of the substrate; and

a gas ejection slot which is positioned between the feed slot and the gas suction slot and ejects a gas toward the upstream edge of the bead positioned on an upstream side from an aperture of the feed slot so as to prevent an inflow of the coating solution into the gas suction slot, wherein

a direction in which the gas ejection slot ejects the gas is one of a perpendicular direction with respect to a surface of the substrate or an inclined direction with respect to the surface of the substrate toward the upstream side of the tip portion in the moving direction of the substrate, and

an aperture plane of the feed slot, an aperture plane of the gas ejection slot, an aperture plane of the gas suction slot, a plane of the tip portion between the aperture plane of the gas ejection slot and the aperture plane of the gas suction slot, and a plane of the tip portion between the aperture plane of the feed slot and an aperture plane of the gas ejection slot are arranged on a same plane.

2. The die head according to claim 1 , wherein a distance between the feed slot and the gas ejection slot is at least 0.3 mm, and a distance between the gas ejection slot and the gas suction slot is between 0.05 mm and 15 mm.

3. The die head according to claim 1 , wherein the gas ejection slot ejects the gas in the perpendicular direction with respect to the surface of the substrate.

4. The die head according to claim 1 , wherein the gas ejection slot ejects the gas in the inclined direction with respect to the surface of the substrate toward the upstream side of the tip portion in the moving direction of the substrate.

5. The die head according to claim 4 , wherein an inclination angle of the inclined direction in which the gas ejection slot ejects the gas with respect to a normal of the substrate surface is between 1° and 75°.

6. A liquid coater comprising the die head according to claim 1 .