Abstract: A stencil printing ink is described, comprising 0.5 to 20% by weight pigment, 5 to 30% by weight extender pigment, 0.5 to 5% by weight water-soluble polymer (the viscosity of its 10% aqueous solution is at least 40 cps), 3 to 15% by weight (calculated as solids) o/w type resin emulsion, 5 to 20% by weight polyhydric alcohol and water. This ink can produce printed images without being affected by printing conditions such as temperature and application pressure. Thus, it is suitably used in stencil printing for non-professional or unskilled people.

Abstract: A method for producing a reversible thermochromic display composed of multiple, overlapping color images. In accordance with the invention, a plurality of overlapping colored image layers are formed on a support, at least one of which layers provides a reversible thermochromic image. Each of the images on the various layers has a different visual density, and at least one reversible thermochromic image changes color at a temperature below or above a predetermined temperature and provides a color which is more intense and more easily discernible than the colors of the other ones of the images.

Abstract: A writing pen wherein a valve element is operated to supply a writing nib held in a pen holder with ink from an ink reservoir is disclosed. The pen is characterized by having an ink guide stem between the writing nib and the valve element and a small ink-retaining space that is provided at least between the rear end of the nib and the front end of the ink guide stem.

Abstract: A ball-point pen tip provided with a tubular ink guide portion formed of metal. The ink guide portion is formed with radial projections extending radially inwardly produced by the pressing deformation of the metal tube. These projections define capillary channels between neighbouring projections and a ball seat at their radially oriented surfaces. An ink guide stem disposed in the tubular ink guide portion has one end in contact with at least one of the projections, and has the other end confronting with an ink supply stem inserted in a holder. The holder and the ink guide portion provide a socket of the pen tip. Such pen tip is applied to a ball-point pen which includes an ink reservoir adapted to be connected to said ink supply stem. Such ball-point pen employs an aqueous solution based low viscosity ink.

Abstract: A composite pen tip that comprises a core member inserted through a tubular casing to form an axial ink flow channel between the inner surface of the tubular casing and the core member. The core member is made of a material more wear-resistant than the tubular casing and the front ends of the core member and tubular casing are substantially flush with each other to form a level writing face. The tubular casing and the core member are curved in substantially the same form in at least one area in the axial direction and in substantially the same area so that said core member contacts the inner surface of said casing in the location of said curving and frictional contact thereat maintains said core front casing but permits said core to slide backward as said casing wears.

Abstract: An aqueous ink composition, suitable for use in writing instruments including an ink passage made of a plastic material, consisting essentially of water, a water-soluble dye and a naphthalene derivative as essential ingredients and a glycol or a polyglycol as a moisture-retaining agent, a very small amount of a surface active agent as a penetrant, an anti-mold agent and other additives as optional ingredients. The naphthalene derivative imparts affinity for the plastic material.

Abstract: An excellent thermochromic material exhibiting a sharp and reversible metachromatism at temperatures within a range of from -40.degree. to 80.degree. C can be formed from (A) an electron-donating, chromatic organic compound; (B) a compound containing a phenolic hydroxyl group; (C) a compound selected from the group consisting of higher aliphatic monovalent alcohols; and (D) a compound selected from the group consisting of higher aliphatic monovalent acid alcohol esters. The excellent thermochromic characteristics of such a thermochromic material can be further improved when it is occluded in fine microcapsules having a size not exceeding 50 .mu.. Thermochromic polymers, thermochromic printing inks, thermochromic writing instruments, thermochromic paints and thermochromic sheets having excellent thermochromatic characteristics and wide utility can be prepared from such a thermochromic material or microencapsulated thermochromic material.