A friction body is configured to discolor handwriting written with a thermochromic ink with frictional heat. The friction body includes a viscoelastic body, and has a Shore A hardness (based on JIS K 7215) immediately after start of contact of an indenter point of from 55 to 95.

Provided are 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.

A 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, 0.3≤P.sub.MC/(P.sub.PVP+P.sub.G)≤4, and 0.2≤P.sub.PVP/P.sub.G≤5, and a refill or an aqueous ballpoint pen incorporating the reversibly thermochromic aqueous ink composition.

Provided is a retractable writing instrument including a pen point, a barrel, and a clip. The pen point is configured to be in a state of projecting from the barrel or a state of being retracted into the barrel by sliding the clip in a longitudinal direction of the barrel. The clip includes a clip body extending in the longitudinal direction of the barrel, a ball portion provided on a front side of the clip body and projecting in a direction of a surface of the barrel, and a clip base provided on a rear side of the clip body and is configured to produce a biasing force in a direction of a surface of the barrel. The surface of the barrel includes a guide groove extending in the longitudinal direction of the barrel and provided with a pair of side surfaces to restrict lateral movement of the ball portion, and the guide groove has a through groove capable of causing the ball portion to be in a noncontact state in a direction of the biasing force at least when the pen point is in the retracted state.

A phonetic game system and method of operation can include: providing a card having a word thereon; and providing a marker for a player to write a misspelled version of the word and for marking the misspelled version of the word with an indication of a point based on the misspelled version of the word having a sound phonetically correct to an other player.

A phonetic game system and method of operation can include: providing a card having a word thereon; and providing a marker for a player to write a misspelled version of the word and for marking the misspelled version of the word with an indication of a point based on the misspelled version of the word having a sound phonetically correct to an other player.

A thermochromic writing instrument including a writing body, storing a thermochromic ink therein, stored in a barrel; an operation body provided in the barrel to be operated to longitudinally move the writing body; a nib of the writing body configured to be capable of appearing from a front end of the writing instrument, wherein the writing instrument 1 further includes a friction unit, for rubbing handwriting in the thermochromic ink and capable of thermally changing the color of the handwriting by frictional heat generated at that time, and at least one clip body as the operation body, the friction unit 10 is provided at a rear end of the barrel, and the clip body is provided in an area other than the rear end of the barrel.

A thermochromic writing instrument including a writing body, storing a thermochromic ink therein, stored in a barrel; an operation body provided in the barrel to be operated to longitudinally move the writing body; a nib of the writing body configured to be capable of appearing from a front end of the writing instrument, wherein the writing instrument 1 further includes a friction unit, for rubbing handwriting in the thermochromic ink and capable of thermally changing the color of the handwriting by frictional heat generated at that time, and at least one clip body as the operation body, the friction unit 10 is provided at a rear end of the barrel, and the clip body is provided in an area other than the rear end of the barrel.

To provide a reversibly thermochromic aqueous ink composition excellent in dispersion stability of a reversibly thermochromic microcapsule pigment and a writing instrument using the same. Disclosed is a reversibly thermochromic aqueous ink composition comprising a reversibly thermochromic microcapsule pigment encapsulating a reversibly thermochromic composition comprising (a) an electron-donating color-developing organic compound, (b) an electron-accepting compound, and (c) a reaction medium to determine an occurrence temperature of a coloring reaction of the component (a) and the component (b), and a vehicle comprising water and a specific gravity adjuster selected from the group consisting of an oxyacid belonging to Group 6 having an atomic weight of 90 to 185 or salt thereof.

To provide a reversibly thermochromic aqueous ink composition excellent in dispersion stability of a reversibly thermochromic microcapsule pigment and a writing instrument using the same. Disclosed is a reversibly thermochromic aqueous ink composition comprising a reversibly thermochromic microcapsule pigment encapsulating a reversibly thermochromic composition comprising (a) an electron-donating color-developing organic compound, (b) an electron-accepting compound, and (c) a reaction medium to determine an occurrence temperature of a coloring reaction of the component (a) and the component (b), and a vehicle comprising water and a specific gravity adjuster selected from the group consisting of an oxyacid belonging to Group 6 having an atomic weight of 90 to 185 or salt thereof.

A thermochromic ink writing instrument comprising a body extending along an axis, the body having a first end and a second end opposed to the first end along the axis, the first end being provided with a writing tip and with an eraser, wherein the writing tip is fed with thermochromic ink, wherein the writing tip is fixed with regard to the body and the eraser is movable along the axis with regard to the body, and the thermochromic ink writing instrument further comprising a helical-cam propelling mechanism configured to move the eraser along the axis between a retracted position and a protruding position.