A water-based ballpoint pen contains an aqueous ink composition in which resin particles having an average particle diameter of at least 0.3 μm are blended. The water-based ballpoint pen is provided with a ballpoint pen tip including a writing ball. The writing ball is formed from a mixture that includes a hard phase component comprising tungsten carbide, a binder phase component comprising cobalt and nickel, and chromium.

A water-based ballpoint pen contains an aqueous ink composition in which resin particles having an average particle diameter of at least 0.3 μm are blended. The water-based ballpoint pen is provided with a ballpoint pen tip including a writing ball. The writing ball is formed from a mixture that includes a hard phase component comprising tungsten carbide, a binder phase component comprising cobalt and nickel, and chromium.

Provided is an ink composition for water-based ballpoint pens, which can provide excellent low-viewing angle visibility on a dark-colored writing surface and drawing lines with good luster. The ink composition for water-based ballpoint pens according to the present invention includes at least an aluminum pigment and titanium oxide-enclosing resin particles having an average particle size from 0.5 to 3 μm.

Provided is an ink composition for water-based ballpoint pens, which can provide excellent low-viewing angle visibility on a dark-colored writing surface and drawing lines with good luster. The ink composition for water-based ballpoint pens according to the present invention includes at least an aluminum pigment and titanium oxide-enclosing resin particles having an average particle size from 0.5 to 3 μm.

[Problems] Provided are a highly marketable reversibly thermochromic composition that provides a black color during color development by using a fluoran derivative having a specific structure as an electron-donating color-developing organic compound, turns colorless during decoloration, and is excellent in contrast between a colored state and a decolored state and a microcapsule pigment encapsulating the same.

[Solution] Disclosed are a reversibly thermochromic composition including: (a) a fluoran derivative having a specific structure as an electron-donating color-developing organic compound; (b) an electron-accepting compound; and (c) a reaction medium which reversibly induces an electron transfer reaction between the component (a) and the component (b) in a specific temperature range, and a reversibly thermochromic microcapsule pigment encapsulating the same.

[Problems] Provided are a highly marketable reversibly thermochromic composition that provides a black color during color development by using a fluoran derivative having a specific structure as an electron-donating color-developing organic compound, turns colorless during decoloration, and is excellent in contrast between a colored state and a decolored state and a microcapsule pigment encapsulating the same.

[Solution] Disclosed are a reversibly thermochromic composition including: (a) a fluoran derivative having a specific structure as an electron-donating color-developing organic compound; (b) an electron-accepting compound; and (c) a reaction medium which reversibly induces an electron transfer reaction between the component (a) and the component (b) in a specific temperature range, and a reversibly thermochromic microcapsule pigment encapsulating the same.

An erasable aqueous non-thermochromic writing ink having core-shell dye microparticles, wherein the core of the core-shell dye microparticles has an organic solvent immiscible with water and at least one dye soluble in the organic solvent and the shell includes a resin component.

There is also a writing instrument containing the ink, a process of preparation of the ink and the use of the core-shell dye microparticles as the only coloring agent in the ink.

An erasable aqueous non-thermochromic writing ink having core-shell dye microparticles, wherein the core of the core-shell dye microparticles has an organic solvent immiscible with water and at least one dye soluble in the organic solvent and the shell includes a resin component.

There is also a writing instrument containing the ink, a process of preparation of the ink and the use of the core-shell dye microparticles as the only coloring agent in the ink.

The present disclosure relates to pens comprising a non-aqueous writing ink comprising a solvent, a coloring agent, a resin, a gelling agent, and a homo or copolymer of vinylpyrrolidone, wherein the gelling agent is a mixture of silica particles and of a fatty acid amide wax, and wherein the homo or copolymer of vinylpyrrolidone is present in amounts of between about 0.05 and about 0.6 wt.-%, relative to the total weight of the ink.

The present disclosure relates to pens comprising a non-aqueous writing ink comprising a solvent, a coloring agent, a resin, a gelling agent, and a homo or copolymer of vinylpyrrolidone, wherein the gelling agent is a mixture of silica particles and of a fatty acid amide wax, and wherein the homo or copolymer of vinylpyrrolidone is present in amounts of between about 0.05 and about 0.6 wt.-%, relative to the total weight of the ink.