High opacity permanent ink formulations comprising a solvent, a polymer-based opacifier, a coloring agent, a resin, and a humectant, wherein the ink formulation displays a viscosity of less than about 50 cP, are provided herein.

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.

Provided is a writing instrument suited to ballpoint pens, marking pens and the like in which a flow pressure of an ink applied to a pen tip is controlled to a fixed level to prevent an ink direct flow phenomenon reverse flow phenomenon. The above writing instrument comprises a pen tip disposed at a front part of an ink tank, an ink received in the ink tank, a follower filled at a rear part of the ink, and a capillary porous member provided with a capillary force, which is arranged at a space part between a rear part of the follower and a rear end part of the ink tank in a state in which the follower is filled, wherein the pen tip is sealed when a cap is put on the writing instrument.

Provided is a writing instrument suited to ballpoint pens, marking pens and the like in which a flow pressure of an ink applied to a pen tip is controlled to a fixed level to prevent an ink direct flow phenomenon reverse flow phenomenon. The above writing instrument comprises a pen tip disposed at a front part of an ink tank, an ink received in the ink tank, a follower filled at a rear part of the ink, and a capillary porous member provided with a capillary force, which is arranged at a space part between a rear part of the follower and a rear end part of the ink tank in a state in which the follower is filled, wherein the pen tip is sealed when a cap is put on the writing instrument.

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.

An ink composition having erasability contains at least colored resin particles having an average particle size of 5 to 15 m, a binder resin, and a solvent. A difference between a specific gravity of the colored resin particles and a specific gravity of components other than the colored resin particles is not less than 0.06 and not more than 0.7. The ink composition forms a film in which the binder resin enfolds the colored resin particles on a paper surface where the ink composition is ejected, without the colored resin particles settling on the paper surface.