Abstract: 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. In an oil-based ball-point pen, the refill is disposed in a barrel cylinder. An oil-based ball-point pen ink composition including a specific salt-forming dye, polyvinyl butyral resin, and an aromatic alcohol can be utilized in the refill.

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: The present invention is a ballpoint pen tip in which a tip end portion of a tip body, which includes a ball holding chamber configured to hold a ball, an ink circulation hole formed in a center of a bottom wall of the ball holding chamber, and a plurality of ink circulation grooves extending radially from the ink circulation hole, is caulked inside, so that a part of the ball held in the ball holding chamber projects from a tip end edge and the ball is rotatably held, wherein: 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 to be 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 circulat

Abstract: A ballpoint pen tip includes a ball and a ball holder for rotatably holding the ball. The ball includes a ball body and a first carbonaceous film formed so as to cover a surface of the ball body. The first carbonaceous film has carbon atoms and oxygen atoms bonded to some of the carbon atoms. The ratio of carbon atoms bonded to oxygen atoms to the total carbon atoms at a surface of the first carbonaceous film is equal to or greater than 0.1.

Abstract: A niobium powder can be used to manufacture a niobium capacitor of excellent electrical properties The niobium powder when formed into a sintered body of 3.15 to 3.9 g/cm3 density exhibits a capacitance (CV value at a formation voltage of 20V) ranging from 80 to 240 kCV/g and a CV retention of 57% or higher. With respect to the production of the niobium powder, the employed potassium niobate fluoride has a water content of 1000 ppm or less as determined from the amount of water generated upon heating at 600° C. according to the Karl Fischer method.