Provided are: a ballpoint pen with which the amount of bending of the pen tip can be changed, wobbling does not occur, and a stable writing feel can be obtained; and a ballpoint pen with which, to make it possible to clearly change the thickness of the drawn line by the force applied when writing, lines of different thickness can be written with a single writing tip using the angle of the ballpoint pen tip. The ballpoint pen is provided with: a writing ball; a holder for holding the writing ball by means of a swaged section the tip of which has been swaged; an ink supply section for supplying ink to the holder; a shaft body inside which the ink supply section is held; and a tip shaft, which is connected to the tip of the shaft body and from which the holder protrudes during writing.

Provided are: a ballpoint pen with which the amount of bending of the pen tip can be changed, wobbling does not occur, and a stable writing feel can be obtained; and a ballpoint pen with which, to make it possible to clearly change the thickness of the drawn line by the force applied when writing, lines of different thickness can be written with a single writing tip using the angle of the ballpoint pen tip. The ballpoint pen is provided with: a writing ball; a holder for holding the writing ball by means of a swaged section the tip of which has been swaged; an ink supply section for supplying ink to the holder; a shaft body inside which the ink supply section is held; and a tip shaft, which is connected to the tip of the shaft body and from which the holder protrudes during writing.

A ballpoint pen 10 includes: a ballpoint pen tip 20 having a writing ball 30 and a holder 21 holding the writing ball 30; a shaft tube 12 to which the rear end part of the ballpoint pen tip 20 is mounted; and ink 40 accommodated in the shaft tube 12. The holder 21 has an ink guiding hole 26 formed from the rear end thereof toward the head end thereof and a ball house 22 formed with the inner circumference near the head end of the holder 21 expanded. The writing ball 30 is formed of a zirconia sintered body with the content of an aluminum element being less than 0.1 weight %, and the ink 40 contains inorganic particles 41.

A writing tip assembly for dispensing a free-flowing low-viscosity ink from a writing instrument may include a micro-spring, a writing ball configured to transfer ink to a substrate, and a second ball between the writing ball and the micro-spring. The second ball is configured to transfer ink to the writing ball. A writing instrument for dispensing a free-flowing low-viscosity ink includes an ink reservoir, the writing tip assembly, and a feeder fluidically coupling the ink reservoir to the writing tip assembly.

A system may include a writing instrument. The writing instrument may include a ceramic writing ball. The ceramic writing ball may include, relative to the total weight of the ceramic writing ball, about 1.0 wt.-% to about 14.6 wt.-% of one or more metal oxides selected from Y.sub.2O.sub.3, HfO, MgO, CaO and/or Ce.sub.2O.sub.3, and about 0.15 wt.-% to about 3.0 wt.-% Al.sub.2O.sub.3, and ZrO.sub.2 as balance.

A writing instrument includes a shaft barrel and a grip provided at part of the shaft barrel. The grip has a cylindrically shaped inside shaft part and a cylindrically shaped outside shaft part arranged at the outside of the inside shaft part, thinner than the inside shaft part, and made of a nonviscoelastic plastic. A space part is provided between the inside shaft part and the outside shaft part.

A writing tip assembly for dispensing a free-flowing low-viscosity ink from a writing instrument may include a micro-spring, a writing ball configured to transfer ink to a substrate, and a second ball between the writing ball and the micro-spring. The second ball is configured to transfer ink to the writing ball. A writing instrument for dispensing a free-flowing low-viscosity ink includes an ink reservoir, the writing tip assembly, and a feeder fluidically coupling the ink reservoir to the writing tip assembly.

A reversibly thermochromic aqueous ink composition having excellent writability and few problems such as aggregation of a colorant, an increase in viscosity of the composition, or a decrease in handwriting density, and a refill or an aqueous ballpoint pen using the reversibly thermochromic aqueous ink composition. The reversibly thermochromic composition is a reversibly thermochromic aqueous ink composition containing a reversibly thermochromic microcapsule pigment encapsulated in a microcapsule formed from an organic resin, an N-vinyl-2-pyrrolidone polymer, glycerin, and water, in which when contents (% by mass) of the reversibly thermochromic microcapsule pigment, the N-vinyl-2-pyrrolidone polymer, and the glycerin with respect to a total mass of the ink composition are P.sub.MC, P.sub.PVP, and P.sub.G, respectively, 0.3P.sub.MC/(P.sub.PVP+P.sub.G)4, and 0.2P.sub.PVP/P.sub.G5, and a refill or an aqueous ballpoint pen incorporating the reversibly thermochromic aqueous ink composition.

A reversibly thermochromic aqueous ink composition having excellent writability and few problems such as aggregation of a colorant, an increase in viscosity of the composition, or a decrease in handwriting density, and a refill or an aqueous ballpoint pen using the reversibly thermochromic aqueous ink composition. The reversibly thermochromic composition is a reversibly thermochromic aqueous ink composition containing a reversibly thermochromic microcapsule pigment encapsulated in a microcapsule formed from an organic resin, an N-vinyl-2-pyrrolidone polymer, glycerin, and water, in which when contents (% by mass) of the reversibly thermochromic microcapsule pigment, the N-vinyl-2-pyrrolidone polymer, and the glycerin with respect to a total mass of the ink composition are P.sub.MC, P.sub.PVP, and P.sub.G, respectively, 0.3P.sub.MC/(P.sub.PVP+P.sub.G)4, and 0.2P.sub.PVP/P.sub.G5, and a refill or an aqueous ballpoint pen incorporating the reversibly thermochromic aqueous ink composition.

A handheld writing instrument which dispenses a non-aqueous pigment-based writing ink. Being based on a non-aqueous writing ink, the writing instrument is less subject to issues of ink drying due to solvent evaporation, such as build-up of dried ink on the writing ink and smearing caused by dried ink agglomerations. Due to its high-laydown characteristics, the writing instrument provides a vivid intense color impression despite the use of pigments as coloring agents.