| 摘要 |
<p>[PROBLEMS] To bond a paper sheet containing no thermally fusible component with sufficient strength without forming a through hole, deteriorating texture and increasing the material cost. [MEANS FOR SOLVING PROBLEMS] While pressing a second paper sheet (11) containing no thermally fusible component against a first paper sheet (10) containing no thermally fusible component, an ultrasonic wave is applied to the press contact portion so that fibers of the second paper sheet (11) enter mechanically between fibers of the first paper sheet (10) thus forming a bonding portion without requiring thermal fusion.</p> |
