To solve the problem that ink can leak through a hole temporarily made in an ink follower fluid layer and the ink follower fluid layer is broken by boiling of the ink to eject the ink due to movement of gas passing through the layer to go out caused by expansion of the gas when the gas dissolved in ink and entrained in the ink during the filling of the ink is disposed under a vacuum condition in the manufacturing process, for the purpose of preventing a bubble from being entrained in a print head during printing.

This ink tank performs a process for applying a centrifugal force to the ink and the ink follower fluid so that the gas is compressed by the layer of the ink follower fluid, and then the gas is passed through the layer the ink follower to be discharged to the outside by being dispersed therein by the pressure. The layer of the ink follower fluid is placed on the interface of the ink.