To prevent bubbles from being formed to form a protective layer free from coating defects by suppressing the pressure of a coating material below a pressure of an atmospheric pressure plus 0.1MPa so as to reduce the gas amount dissolved in 1kg of the coating material to 0.1g or less in forming the protective layer on a substrate by controlling discharge from a nozzle.
In forming a protective layer, comparatively high coating material pressure is required before passage through a filter in a first liquid transfer line 6 is finished, but low coating material pressure is sufficient after the passage and for a second liquid transfer line 13. Particularly, because being once contained in an intermediate tank 5, the coating material is relieved to a low pressure. Pressure of pressurizing gas 8 and pressure in a diaphragm pump 9 are suppressed to a pressure of an atmospheric pressure plus 0.1MPa or less so that the amount of gas dissolved in the coating material is such that the content of gas dissolved in 1kg of the coating material is kept to 1.0g or less. Therefore, the coating material in the second liquid transfer line 13 and the coating material discharged onto an optical magnetic recording medium 12 is free from bubbles so that coating of a desired protective layer can be applied.
TAKEDA ATSUSHI
NAKANISHI TOSHIHARU
