Patent ID: 7104640

Claim:
A liquid container comprising: an accommodation portion to define a liquid accommodation space; a liquid supply portion to supply a liquid accommodated in the accommodation space to an outside; a mechanism to maintain or expand a volume of the accommodation space; and a one-way valve to allow an introduction of a gas from the outside into the accommodation space and prevent the liquid and gas from flowing out of the accommodation space to the outside; wherein the one-way valve includes: a flexible sheet formed of a resin material situated between a first chamber on the accommodation space side and a second chamber on the outside and having an area to secure a predetermined level of freedom of deflection; a plate-shaped valve closing member attached to the flexible sheet; and a valve mechanism to perform an open-close operation accompanied by a deflection of the flexible sheet, the degree of the flexible sheet deflection conforming to a pressure difference between the first chamber and the second chamber; wherein an area of the flexible sheet around an outer periphery of said plate-shaped valve closing member is formed with a plurality of undulated portions whose undulated forms are maintained in at least an operation range of the valve mechanism; and wherein the plurality of undulated portions are formed in a plurality of positions substantially along a circumference of said plate-shaped valve closing member.