PURPOSE: To obtain the title indicator which is excellent in handleability and blue color stability against moisture, by disposing on a substrate surface a coloring layer comprising a PVA resin, tungstic acid (salt) and glyoxal or methylol melamine.
CONSTITUTION: A mineral acid or an org. acid is added to an aq.soln. having a concn. of 5W10% obtd. by dissolving tungstic acid (salt) in water to adjust the pH of the soln. to 1W3, followed by heating. A PVA resin is added in an amt. of 1W5 times that of the tungstic acid (salt), dissolved and filtered while heating. The soln. is cooled to room temp., and glyoxal or methylol melamine is added in an amt. of 5.0W30wt.% based on the wt. of the PVA resin to obtain a coating soln. The coating soln. is applied to the surface of a substrate, such as polyethylene terephthalate film, in a thickness of, e.g., 100W200μ in a wet state, and dried to for a coloring layer. Thus, the title indicator is obtd.
OISO SHOJI
YAMAMURA SHIGEO
Next Patent: FLUORESCENT CLAY COMPOUND, PRODUCTION THEREOF AND PRODUCT USING THE COMPOUND