Abstract: A ballpoint pen tip including a metallic pipe having a plurality of inwardly projecting portions at a neighborhood of a front end portion of the pipe at regular intervals, and a front end edge portion at a front end of the pipe, and a ball rotatably held between the front end edge portion and the plurality of inwardly projecting portions, wherein the pipe satisfies a relation of A/T.ltoreq.5.8 where A is an outer diameter of the ball and T is a thickness 10 of the pipe, and also the relation of B/T.ltoreq.2.3 where B is a diameter of a virtual inscribing circle contacting a top of the plurality of inwardly projecting portions and T is the same as above.

Abstract: A ballpoint pen tip including a metallic pipe having a plurality of inwardly projecting portions at a neighborhood of a front end portion of the pipe at regular intervals, and a front end edge portion at a front end of the pipe, and a ball rotatably held between the front end edge portion and the plurality of inwardly projecting portions, wherein the pipe satisfies a relation of A/T.ltoreq.5.8 where A is an outer diameter of the ball and T is a thickness 10 of the pipe, and also the relation of B/T.ltoreq.2.3 where B is a diameter of a virtual inscribing circle contacting a top of the plurality of inwardly projecting portions and T is the same as above.

Abstract: There is provided aqueous ink of high viscosity for writing instrument, capable of maintaining stable dispersed or dissolved state of the coloring material even after a prolonged period and exhibiting high fluidity under a shearing force applied by the writing operation in the ball point pen.The ink contains, as essential components, a coloring material, succinoglycan which is an organic acid-modified heteropolysaccharide composed of glucose and galactose as component monosaccharides, and aqueous medium in which water constitutes at least 50 wt. %.