a) From the pen tip

a-1) In case the pen tip is destroyed

The pen tip has a very delicate structure in which a fine ball is assembled at the tip of a thin metal pipe. Therefore, even if you penetrate an object with a pen tip or drop it from the pen tip onto the floor, the pen tip will be damaged, in some cases the pen tip will deform and the ink may leak out.

• If you write with the pen at too much of an angle, the part holding the ball wears on the paper surface, and as with the case where the pen tip got scratched, ink may leak out. The ball pen transfers the ink of the pen to paper by rotating the ball on paper. For that reason it is ideal to write at an angle greater than 60 ° when the ball rotates.

• Multicolor ballpoint pens are equipped with the refill of each color at a position away from the center of the barrel. Therefore, when the pen tip is extended, the pen tip of each color becomes "slightly oblique" toward the center of the barrel. In the above picture, the yellow line shows the center of the barrel, the red dashed line shows the center of the pen tip (the side close to the writing surface). As a result, even with an angle at which writing can be done without problem even with a single-function pen, with "multicolor ballpoint pen" "only the refill on the side close to the writing surface" becomes the further angle, may wear out on the paper surface, causing ink leakage.