Patent ID: 6926458

Claim:
A ball-point pen refill comprising an ink storage tube, a tip fixed to an end of the ink storage tube, and a tail plug fixed at an end of the ink storage tube opposite to the tip; ink being filled in the space of the ink storage tube relatively near to the tip; pressuring gas being filled in the space of the ink storage tube relatively far from the tip; the ink being squeezed to flow toward the tip under the pressure of the pressuring gas; the tip comprising a ball and a holder for holding the ball; the ball being formed to have a surface roughness (Ra) of 0.010 μm to 0.080 μm; the holder having a ball house for housing the ball provided in the vicinity of its end opposite to the ink storage tube, and an ink guiding hole extending from its end opposite to the ball house to the ball house for supplying the ink; the ball house having a cylindrical side part and a conical bottom part decreasing its inner diameter in the direction toward the ink guiding hole; and a formula 1.01≦φB/φA≦1.11 being satisfied when φA is a diameter of the ball and φB is an inner diameter of the side part.