Patent ID: 7754312

Claim:
A hollow structure plate formed by fusing a plurality of hollow protrusions that are projected in each of two thermoplastic resin sheets with end faces of the hollow protrusions facing against one another, wherein said hollow protrusions are truncated cone-shaped, wherein a ratio between a total area of lower base portions of said hollow protrusions and an area of liner portions of the thermoplastic resin sheets is in a range from 0.3 to 0.58, wherein the lower base portions of said hollow protrusions are open portions of said hollow protrusions which are opposite to the end faces of the hollow protrusions, and the liner portions of the thermoplastic resin sheets are portions of the thermoplastic resin sheets in which the hollow protrusions are not formed, wherein a rising angle of a side face of each of said hollow protrusions in a vertical plane including a central axis of the hollow protrusion is in a range from 50 degrees to 70 degrees, and wherein a bending elasticity gradient of said hollow structure plate is equal to or greater than 420 N/cm.