Abstract: [Problems] To provide a reversibly thermochromic composition having excellent contrast between a colored state and a decolored state, and excellent light resistance, and a reversibly thermochromic microcapsule pigment encapsulating the reversibly thermochromic composition. [Solution] Disclosed is a reversibly thermochromic composition including: (a) an electron-donating color-developing organic compound; (b) a combination of a compound having a specific structure as an electron-accepting compound; and (c) a reaction medium which reversibly induces an electron transfer reaction between the component (a) and the component (b) in a specific temperature range, and a reversibly thermochromic microcapsule pigment encapsulating the reversibly thermochromic composition.

Abstract: [Problems] To provided are a reversibly thermochromic composition that shows black during color development by using a fluoran derivative having a specific structure as an electron-donating color-developing organic compound, turns colorless during decoloration, and is excellent in light resistance and a microcapsule pigment encapsulating the reversibly thermochromic composition. [Solution] Disclosed is a reversibly thermochromic composition including: (a) a fluoran derivative having a specific structure as an electron-donating color-developing organic compound; (b) a compound having a specific structure as an electron-accepting compound; and (c) a reaction medium which reversibly induces an electron transfer reaction between the component (a) and the component (b) in a specific temperature range, and a reversibly thermochromic microcapsule pigment encapsulating the reversibly thermochromic composition.

Abstract: Provided is a water-soluble sheet-like coloring material in which sheets are less likely to stick to each other, have appropriate self-standing property and flexibility, and can be quickly brought into a uniform state when dissolved in water. A water-soluble sheet-like coloring material including a film-forming water-soluble polymer; a dissolution accelerator; a colorant; and a moisture-retaining agent.

Abstract: [Problem] To provide an oil-based ink composition for ballpoint pens and also an oil-based ballpoint pen employing the composition. The ink composition inhibits a ball seat from wearing under high pen pressure (writing load: 300 to 500 gf), improves writing feeling, and is excellent in writing performance at the beginning of handwriting, in temporal stability and in ink followability. [means to solve the problem] An oil-based ink composition for ballpoint pens, comprising a colorant, an organic solvent, and a polyoxy-alkylene glyceryl ether.

Abstract: 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 PMC, PPVP, and PG, respectively, 0.3?PMC/(PPVP+PG)?4, and 0.2?PPVP/PG?5, and a refill or an aqueous ballpoint pen incorporating the reversibly thermochromic aqueous ink composition.

Abstract: [Problems] Provided are a highly marketable reversibly thermochromic composition that provides a black color during color development by using a fluoran derivative having a specific structure as an electron-donating color-developing organic compound, turns colorless during decoloration, and is excellent in contrast between a colored state and a decolored state and a microcapsule pigment encapsulating the same. [Solution] Disclosed are a reversibly thermochromic composition including: (a) a fluoran derivative having a specific structure as an electron-donating color-developing organic compound; (b) an electron-accepting compound; and (c) a reaction medium which reversibly induces an electron transfer reaction between the component (a) and the component (b) in a specific temperature range, and a reversibly thermochromic microcapsule pigment encapsulating the same.

Abstract: The present invention provides: a highly practical and safe oil-based ink composition for a writing board, said composition being capable of imparting high mark-erasability and having excellent resistance to drying up; and a marking pen incorporating the same. Specifically, the present invention provides: an oil-based ink composition for a writing board, said composition containing a pigment, an organic solvent, a resin, and at least one compound selected from compounds represented by general formula (1) or (2); and a marking pen obtained by incorporating the oil-based ink composition for a writing board. (In the formulae, R1-R4 each represent a C6-18 alkyl group or a C2-18 and O2-10 alkoxypolyglycol group.

Abstract: 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.

Abstract: 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.

Abstract: A writing instrument excellent in handwriting density and temporal stability. The writing instrument includes a ball-point pen tip attached to the front end portion of the ink storage cylinder; and a ball-point pen refill having an ink composition for a writing instrument loaded therein. The ink composition for the writing instrument is a thermochromic ink containing at least a thermochromic microcapsule pigment. The writing instrument includes a pressurization mechanism for applying a pressure to the back end of the ink composition for the writing instrument.

Abstract: The present invention provides an aqueous writing ink composition capable of forming handwriting having both opacity and transparency, also a writing implement using the composition, and further a process for producing the composition. The aqueous writing ink composition according to the present invention comprises a white pigment, resin particles containing styrene-acrylonitrile, a colorant, and a polysaccharide. The content of the white pigment X %, that of the resin particles Y1% and that of the polysaccharide Y2% satisfy the conditions of 0.1?X?7,??[1] 0.5<(Y1+Y2)/X, and??[2] 10?2.5X+(Y1+Y2)?40.

Abstract: A reversal magnetic display panel where the numbers of writes/erases repeated until the micro magnets in a dispersion liquid sealed in multiple small cells formed between substrates sediment in the lower part of the small cells by repeated writes/erases when the reversal magnetic display panel is used in a vertical position are increased and a favorable display/erase performance is achieved. Between substrates, a dispersion liquid containing a dispersion medium and a thickening agent as main components and further containing micro magnets the both sides of each of which are differently colored are sealed in. Writing is constituted by difference in contrast between the color of the reversed micro magnets and the color of the non-reversed ones. Hollow particles are mixed with the micro magnets so as to reduce the ratio of the specific gravity of the micro magnets to that of the liquid. The residual magnetization per unit mass of the micro magnets is 1.0 to 23.