| 摘要 |
PROBLEM TO BE SOLVED: To provide a toothbrush capable of visually displaying the degraded state of bristles before the bristles are torn or bent under repeated use, regardless of the open state of bristle tips in the toothbrush using PTT (polytrimethylene terephthalate) bristles. SOLUTION: This toothbrush using the PTT bristles for a part or the whole of bristles inserted in a head part insertion face. The PTT bristle 10 is formed in double or triple sheath core structure comprising a core part 11 and sheath parts 12, 13, for instance. A region different in color or depth of color is formed in at least a part of the cross section of the PTT bristle 10 so that the color or depth of color of the bristle surface, or the area of the part different in color or depth of color taking up the bristle surface, is changed by wear caused by repeated use. Further, a boundary part changed in color or depth of color is set to a depth of 1-7.5% of a bristle radius from the bristle surface, and the region different in color or depth of color exists within 3 mm at least from the bristle tip. COPYRIGHT: (C)2005,JPO&NCIPI
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