| 摘要 |
<p>PROBLEM TO BE SOLVED: To solve the problems of preventing damage and coping even with a stain and the secular deterioration, by making hard to be broken even when repeatedly used, by enhancing strength by applying reinforcement to a back cover, since there is a case of occasionally damaging the back cover due to frequently pulling the back cover when taking out a file from a book shelf in a back-width adjustable extension file, and since there is a case of frequently damaging by repeatedly using when a main factor of damaging the back cover is that a construction material of the back cover is made of paper.SOLUTION: An aesthetic appearance is protected and made hard to be broken by reinforcing a part or the whole of a paper back cover.</p> |
