An ink composition for a water-based ballpoint pen in which, even in a case of an ink composition for a water-based ballpoint pen using a colored resin particle containing a pigment, the phenomenon of skipped strokes does not occur and writing defects are less likely to occur when writing at a high writing angle or under a high load. An example of the ink composition for a water-based ballpoint pen according to the present embodiment includes an ink composition for a water-based ballpoint pen that contains at least a urethane-based colored resin particle containing a pigment and having an average particle size of 0.3 to 2 μm and a naphthalenesulfonic acid-formaldehyde condensate.

An ink composition for a water-based ballpoint pen in which, even in a case of an ink composition for a water-based ballpoint pen using a colored resin particle containing a pigment, the phenomenon of skipped strokes does not occur and writing defects are less likely to occur when writing at a high writing angle or under a high load. An example of the ink composition for a water-based ballpoint pen according to the present embodiment includes an ink composition for a water-based ballpoint pen that contains at least a urethane-based colored resin particle containing a pigment and having an average particle size of 0.3 to 2 μm and a naphthalenesulfonic acid-formaldehyde condensate.

The present invention provides a water-based ink composition for a ballpoint pen that is less likely to cause bleeding of a written trace in writing, provides a favorable written trace without causing no blurring or line splitting, and excels in the storage stability of the ink composition; and a water-based ballpoint pen using the ink composition. A water-based ink composition for a ballpoint pen comprising water, a coloring agent, a copolymer having a specific structure; and a water-based ballpoint pen using the ink composition.

The present invention provides a water-based ink composition for a ballpoint pen that is less likely to cause bleeding of a written trace in writing, provides a favorable written trace without causing no blurring or line splitting, and excels in the storage stability of the ink composition; and a water-based ballpoint pen using the ink composition. A water-based ink composition for a ballpoint pen comprising water, a coloring agent, a copolymer having a specific structure; and a water-based ballpoint pen using the ink composition.

Provided is a dispersion liquid of colored resin fine particles for an aqueous ink having excellent stability and a sufficient drawn line intensity; an aqueous ink composition for a writing instrument such as felt-tip pens, marking pens, and ballpoint pens using the dispersion liquid of the colored resin fine particle as a colorant; and a writing instrument loaded with the composition. The dispersion liquid of colored resin fine particles for an aqueous ink includes colored resin fine particles dispersed in water, the colored resin fine particles composed of at least a cyclohexyl (meth)acrylate monomer, and a basic dye or an oil-soluble dye, in which the content of the cyclohexyl (meth)acrylate monomer is 30% by mass or more, and the content of the basic dye or the oil-soluble dye is 15% by mass or more based on the total polymer component constituting the colored resin fine particles.

An ink composition contains a carbon black and/or an organic pigment, water, a polysaccharide, two or more of diols, and particles of an acrylic resin. The two or more of diols include a first diol having from 5 to 7 carbon atoms and a second diol having from 1 to 4 carbon atoms, and a content of the first diol in the ink composition is 0.05 wt % or more.

An ink composition contains a carbon black and/or an organic pigment, water, a polysaccharide, two or more of diols, and particles of an acrylic resin. The two or more of diols include a first diol having from 5 to 7 carbon atoms and a second diol having from 1 to 4 carbon atoms, and a content of the first diol in the ink composition is 0.05 wt % or more.

An aqueous ink composition suitable for ballpoint pens may achieve excellent smooth writing without causing deterioration of the smooth writing and wear of a tip socket while colored resin particles encapsulating a pigment are used. An embodiment of such ink compositions is an aqueous ink composition suitable for ballpoint pens containing at least colored resin particles (A) encapsulating a pigment (a) and non-colored resin particles (B) containing no pigment.

An aqueous ink composition suitable for ballpoint pens may achieve excellent smooth writing without causing deterioration of the smooth writing and wear of a tip socket while colored resin particles encapsulating a pigment are used. An embodiment of such ink compositions is an aqueous ink composition suitable for ballpoint pens containing at least colored resin particles (A) encapsulating a pigment (a) and non-colored resin particles (B) containing no pigment.

Provided is an aqueous ink composition for writing instruments containing colored resin particles encapsulating a pigment, wherein the ink is not repelled when the aqueous ink composition for writing instruments is used to write on a paper face attached with hand fingers or the like, and achieves a uniform density in a drawn line and excellent writing capability. An embodiment of the aqueous ink composition for writing instruments is an aqueous ink composition for writing instruments containing at least a pigment (a) and colored resin particles (A) encapsulating the pigment (a).