| 摘要 |
<p>A push button type ballpoint pen which is free from ink leakage from a writing tip, prevents ink from being drawn-in by an impact when a push button is operated and has a good writing performance, the ballpoint pen comprising a ballpoint pen refill (3) having a ballpoint pen tip (7) disposed at the tip end side of an ink storing cylinder (8) and a ball (9) rotatably embraced at the tip end of the tip (7), and a push-button advancing/retracting mechanism (5, 6) for advancing and retracting the tip end of the tip (7) to/from the tip opening (2a) of a barrel (2), the ink storing cylinder (8) being directly filled therein with a water color ink (15) containing therein a shear viscosity reducing agent and having a viscosity of 900 to 2500 mPa.s at a shear rate of 1.9 sec-1 in a measuring environment of 20 °C, a flow path constricting portion (20) having an area of 0.4 to 0.8 mm2 at a section crossing at right angles the axis of the ink storing cylinder (8) and restricting the flow rate of the water color ink (15) being provided on a flow path through which the ink (15) in the cylinder (8) flows up to the ball (9).</p> |
