| 摘要 |
PROBLEM TO BE SOLVED: To provide a direct liquid feed type writing instrument capable of visually recognizing a residue of an ink liquid. SOLUTION: The direct liquid feed type writing instrument A stores a raw ink. In this case, a critical surface tension of an entire or a partial inner wall surface of an ink tank 10 contacted with an ink 11 is smaller than a surface tension of the ink 11, and an contact angle of an overall or a partial inner wall surface of the tank 10 contacted with the ink 11 to the ink 11 is 30 deg. or more at 25 deg.C. Thus, since visibility of the ink residue and continuity of its visible effect are excellent and it is not necessary to surface treat or the like, a complicated following step is not required, and its manufacturing cost is low. |
