| 摘要 |
PROBLEM TO BE SOLVED: To provide a pipe type ballpoint pen capable of providing a sufficient ink outflow property in writing, and providing a secure sealing property between a calking part and a ball in non-writing over a long term.SOLUTION: A ballpoint pen tip 2 includes a ball holding part for rotatably holding a ball 6 by a calking part 4 formed by pressing and deforming a dwindling tip of a metallic pipe 3 to the inner side in a radial direction, and a plurality of inward projecting parts 5 formed by pressing and deforming a sidewall in the vicinity of the tip of the pipe 3 to the inner side in the radial direction. Difference between a maximum inner diameter B of the ball holding part and a diameter A of the ball 6 is set ≥25 μm. An annular projecting surface part 4a having an inner diameter gradually decreasing toward the front side is formed on an inner peripheral surface of the calking part 4. The ball 6 is tightly fitted to the annular projecting surface part 4a of the calking part 4 by forward energization of an elastic body 11 in non-writing. A carbonaceous film is formed on each of a surface of the annular projecting surface part 4a and/or the surface of the ball 6. The carbonaceous film has carbon atoms and oxygen atoms bonded to the carbon atoms. |
