| 摘要 |
The invention is capable of maintaining the planar view curve profile of the elastic membranous member of the back-contacting surface while enabling the maintenance of a stable and comfortable seated posture. The side frame members (13C) of a backrest frame (13) are formed substantially as obtuse angles with the bend towards the front when viewed from the side. The upper frame member (13A) is formed, in planar view, as an arc that protrudes towards the back. An elastic membranous member (14) is stretched so that when viewed from the side, the intermediate position curves gently towards the front, substantially forming an obtuse angle. Paired left and right shape-maintaining members (17), each slanting outward and upward, connect the lower frame member (13B) near the left and right sides to the bends (13a) in the left and right side frame members. The lower parts of both the left and right sides of the elastic membranous member are supported by the shape-maintaining members.
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