| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain a middle core material which is light and has air permeability and heat retaining property. SOLUTION: Grooves 13 and 15 are respectively arranged on the front surface 12 and the rear surface 14 of a planar object 11 made of a foamed synthetic resin. The total sum of the depths h1 and h2 of both grooves 13 and 15 is made to be larger than the thickness H of the planar object 11 and, communication holes 16 which communicate with both grooves are disposed at places where the grooves 13 on the front surface cross the grooves 15 on the rear surface.</p> |
