Abstract: Provided is a paper diaper which is safe to a wearer thereof and also has additional values of, for example, developing a plurality of colors and providing a practical effect of instantaneously detecting that the wearer has urinated, or the like. In a paper diaper 11 including a back sheet 13 for covering an outer side of an absorption body 14 for absorbing urine, an indicator portion 15 containing a colorless color-developing agent formed of an electron-donating coloration compound is formed by application on a wide range of an inner surface of the back sheet 13, and a color development assisting agent 16 is provided on the indicator portion 15. The color development assisting agent 16 is dissolved in the urine to contact the indicator portion 15, thus to cause the indication portion 15 to develop a color.

Abstract: Provided is a paper diaper which is safe to a wearer thereof and also has additional values of, for example, developing a plurality of colors and providing a practical effect of instantaneously detecting that the wearer has urinated, or the like. In a paper diaper 11 including a back sheet 13 for covering an outer side of an absorption body 14 for absorbing urine, an indicator portion 15 containing a colorless color-developing agent formed of an electron-donating coloration compound is formed by application on a wide range of an inner surface of the back sheet 13, and a color development assisting agent 16 is provided on the indicator portion 15. The color development assisting agent 16 is dissolved in the urine to contact the indicator portion 15, thus to cause the indication portion 15 to develop a color.

Abstract: A writing board system comprises a white board having a writing surface for receiving a written mark thereupon, a liquid tank filled with water liquid for erasing the written mark from the writing surface, an applicator for applying the liquid in the liquid tank onto the writing surface, and a writing implement having an ink including at least one electron donative coloring compound selected from the group consisting of 2-{2-[4-(dodecyloxy)-3-metoxyphenl]-ethenyl}quinoline, 3-cyclohexylamino-6-chlorofluoran, 3-diethyl amino benzo [a]-fluoran, 3-(4-diethylamino-2-etoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphtha lide, 3.3 bis(4-diethylamino-2-etoxyphenyle)-4- azaphthalide, and 3-cyclohexyl methyl amino-6-methyl-7-anilinofluoran, and an electron acceptive developing compound selected from the group consisting of zinc salicylate and bisphenol A.

Abstract: A writing instrument contains, in its own container, a color ink agent mixing at least one electron donative coloring compound and one electron acceptive developing compound. The electron donative coloring compound is selected from a group composed of crystal violet lactone; malachite green lactone; 1,3-dimethyl-6-diethylaminofluoran 6-diethylamino-benzo[.alpha.]-fluoran; 3-cyclohexyl methylamino-6-methyl-7-anilinofluoran; benzoyl leucomethylene blue; ethyl leucomethylene blue; methoxybenzoyl leucomethylene blue; 2-(phenylimino ethanedilidene)-3,3-trimethyl-indoline; 1,3,3-trimethyl-indolino-7'-chloro-.beta.-naphthospiropyran; di-.beta.-naphthospiropyran; N-acetylauramlne; N-phenylauramine; and rhodamine B lactam. The electron acceptive developing compound is selected from a group composed of zinc salicylate and bisphenol A.

Abstract: A printed matter is printed by a ink containing a color coupler that is chromatized from a substantially invisible colorless state to a colored state by means of a color coupling additive applied by an applicator. The color coupler is at least one electron donative coloring compound selected from a group A composed of crystal violet lactone; malachite green lactone; 1.3-dimethyl-6-diethylaminofluoran; 6-diethylamino-benzo[.alpha.]-fluoran; 3-cyclohexyl methylamino-6-methyl-7-anilinofluoran; benzoyl leucomethylene blue; ethyl leucomethylene blue; methoxybenzoyl leucomethylene blue; 2-(phenylimino ethanedilidene)-3.3-trimethyl-indoline; 1.3.3-trimethyl-indolino-7'-chloro-.beta.-naphthospiropyran; di-.beta.-naphthospiropyran; N-acetylauramine; N-phenylauramine; and rhodamine B lactam. The color coupling additive is at least one electron acceptive developing compound selected from a group B composed of zinc salicylate, bisphenol A and inorganic and organic acids.

Abstract: In the color changing print of this invention, plural areas are printed by using plural types of color changing inks which develop into different colors from the substantially invisible colorless state by reaction with a color changing agent. By the emergence of print from colorlessness and by giving changes in the appearing colors, unexpectedness and entertainingness are provided so that an attractive education may be realized.

Abstract: Printed matters are disclosed, which are printed with the coloring ink that is able to do the short-time fading at which time the color is losen of itself in a relatively short time after once having developed color by interacting with the coloring assistant containing the pH-adjusting agent which loses effect with the passage of time due to the volatility or the desiccation, and further that is able to redevelop color and repeat the above-mentioned short-time fading each time when the above-mentioned coloring assistant is made to act thereon a plural number of times; and which printed matters are suitably used for printing invisibly, for example, the spaces for answers being to stand abreast of the visibly printed spaces for questions in question books.

Abstract: A print of this invention has a color-forming area and a discoloring area. The color-forming area is printed by an ink containing a first color-changing agent which changes from substantially invisible colorlessness to visibleness by applying a color former. The discoloring area is printed by an ink containing a second color-changing agent which changes a from substantially invisible colorlessness to visibleness by applying the color former and returns to invisible colorlessness state as the time passes naturally after changing its color.

Abstract: A coaster of this invention comprises an upper sheet having transparency and permeability, a printed sheet provided with a color-changing area of which surfaces faces the upper sheet, and a color former for changing the color-changing area. The color-changing area is printed by an ink containing a color-changing agent which changes from substantially invisible colorless state to a visible color state by applying a color former. The color former is set in the coaster such a way that the color former can melt out for applying to the color-changing agent by means of water permeating through the upper sheet.

Abstract: A representing utensil for use in making an invisibly depicted matter visible again which houses a coloring assistant in its own container is disclosed, wherein the coloring assistant is able to make a colorlessly depicted matter develop color and, after its coloring, do the short-time fading at which time the color is losen of itself in a relatively short time by acting on the depicted matter with the aid of a coloring agent, and further is able to make the depicted matter do repeat the recoloring and the short-time fading each time when the coloring assistant acts on the depicted matter a plural number of times.