Abstract: [Problem to be Solved] Provided are: an oil-based ball-point pen refill having the excellent concentration of a written trace, excellent performance against ink dripping, and an excellent feeling of writing; an oil-based ball-point pen using the oil-based ball-point pen refill; and an ink composition that is preferably used in the oil-based ball-point pen refill and the oil-based ball-point pen. [Solution] An oil-based ball-point pen refill includes a ball-point pen tip in which a ball is held, in which the ball-point pen tip is mounted on a leading end of an ink housing cylinder, an ink composition including a coloring agent consisting of a dye, an organic solvent, and polyvinyl butyral resin is housed in the ink housing cylinder, the arithmetic mean roughness of a surface of the ball is 0.1 to 15 nm, the content of the polyvinyl butyral resin is 50 mass % or more based on the total mass of the whole resin, and an ink viscosity is 5000 to 50000 mPa·s.

Abstract: A ballpoint pen tip is provided in which a curved contact surface, which has a curvature different from a curvature of the ball, is provided on the bottom wall of the ball holding chamber, and the ball is in contact with a contact part which is a part of the contact surface; and between the ball and the contact surface, a first gap is formed to extend from a side of the ink circulation hole up to the contact part such that the first gap gradually narrows from the side of the ink circulation hole, and a second gap is formed to extend from a distal side of an ink circulation groove up to the contact part such that the second gap gradually narrows from the distal side of the ink circulation groove.

Abstract: Provided are: an oil-based ink composition for a ball-point pen having a favorable feeling of writing, the favorable deepness of a written trace, favorable light resistance, favorable ink stability over time, and favorable pigment dispersibility; and an oil-based ball-point pen refill using the oil-based ink composition. An oil-based ink composition for a ball-point pen comprising at least a dye, a pigment, and an organic solvent, wherein the dye is at least one salt-forming dye selected from the group consisting of salt-forming dyes of alkylbenzene sulfonic acids and xanthene-based basic dyes, salt-forming dyes of alkylbenzene sulfonic acids and triarylmethane-based basic dyes, and salt-forming dyes of alkylbenzene sulfonic acids and azomethine-based basic dyes.

Abstract: Disclosed is a decolorizable electrophotographic toner, including: a binder resin; and a colorant which contains at least a color developable compound and a color developing agent and is covered with an outer shell so as to have a capsule structure, wherein the number ratio of particles having an equivalent circle diameter of 0.6 ?m or more and 2.5 ?m or less of the toner when measured using a flow particle image analyzer after the toner is dispersed in an aqueous medium at a ratio of 0.08% by weight and the resulting dispersion is subjected to a stirring treatment in which stirring is performed at 5000 rpm for 30 minutes using a homogenizer (T-25 digital ULTRA-TURRAX (manufactured by IKA Japan K.K., provided with a shaft generator S25N-10G)) is 30% by number or less.

Abstract: The invention aims at providing a solid writing material that does not adversely affect the color changing property of script and can obtain sufficient strength. This aim is achieved by the solid writing material that includes: a reversible thermochromic microcapsuled pigment encapsulating a temperature-sensitive color-changeable color-memorizing composition; an excipient; and a resin; the temperature-sensitive color-changeable color-memorizing composition including at least (a) an electron-donating coloring organic compound, (b) an electron accepting compound and (c) a reaction medium effecting reversibly an electron transfer reaction between the (a) and (b) components in a specific temperature range; wherein the excipient or the resin includes a styrene-structure-containing polymer.

Abstract: A thermochromic writing instrument contains a thermochromic ink, wherein a writing body is accommodated in a barrel movably in a longitudinal direction, an operation portion is provided on the outer surface of the barrel, a pen tip of the writing body is constituted so as to be projectable/retractable from/into a front-end hole of the barrel by operating the operation portion, the thermochromic ink is contained in the inside of the writing body, the pen tip capable of ejecting the thermochromic ink is provided at the front end of the writing tool, and a friction portion capable of thermally changing the color of the handwriting of the thermochromic ink by the frictional heat generated when the handwriting is rubbed with the friction portion is provided on the outer surface of the barrel.

Abstract: A thermochromic writing instrument contains a thermochromic ink, wherein a writing body is accommodated in a barrel movably in a longitudinal direction, an operation portion is provided on the outer surface of the barrel, a pen tip of the writing body is constituted so as to be projectable/retractable from/into a front-end hole of the barrel by operating the operation portion, the thermochromic ink is contained in the inside of the writing body, the pen tip capable of ejecting the thermochromic ink is provided at the front end of the writing tool, and a friction portion capable of thermally changing the color of the handwriting of the thermochromic ink by the frictional heat generated when the handwriting is rubbed with the friction portion is provided on the outer surface of the barrel.

Abstract: When the rear axial cylinder (3) is rotated, the cam cylinder (17) is also rotated, thereby the cam protrusion (18a) moves forward by means of the functions of the cam groove (17a) and the slit (18b), so that the slider (18) moves forward to cause the writing body (14) to move forward against a biasing force by the biasing member (15). The slider (18) has the hollow body (18m), the coil spring (18c) and the flange body (18f). The O-ring (19) is provided on the outer circumference of the flange body (18f).

Abstract: A thermochromic writing instrument 1 including a writing body 9, storing a thermochromic ink therein, stored in a barrel 2; an operation body provided in the barrel 2 to be operated to longitudinally move the writing body 9; a nib 91 of the writing body 9 configured to be capable of appearing from a front end of the writing instrument, wherein the writing instrument 1 further includes a friction unit 10, 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 7 as the operation body, the friction unit 10 is provided at a rear end of the barrel 2, and the clip body 7 is provided in an area other than the rear end of the barrel 2.

Abstract: Provided are: an oil-based ink composition for a ball-point pen having a favorable feeling of writing, the favorable deepness of a written trace, favorable light resistance, favorable ink stability over time, and favorable pigment dispersibility; and an oil-based ball-point pen refill using the oil-based ink composition. An oil-based ink composition for a ball-point pen comprising at least a dye, a pigment, and an organic solvent, wherein the dye is at least one salt-forming dye selected from the group consisting of salt-forming dyes of alkylbenzene sulfonic acids and xanthene-based basic dyes, salt-forming dyes of alkylbenzene sulfonic acids and triarylmethane-based basic dyes, and salt-forming dyes of alkylbenzene sulfonic acids and azomethine-based basic dyes.

Abstract: [Object] To provide a reversibly thermochromic composition free from accidental discoloration by heat conducting from the opposite side writing surface or by self-heating due to quick writing; and also to provide a solid writing material and a writing ink composition comprising that composition. [Means to solve the problem] A reversibly thermochromic composition comprising a combination of: (a) a reversibly thermochromic component capable of being discolored or decolored by heat and (b) a component for controlling heat conducting to the reversibly thermochromic component; and also a solid writing material and a writing ink composition comprising that composition.