The present invention is in the field of wetness/fluid indicators. More specifically this invention relates to wetness/fluid indicating ink which indicates the presence of fluid by color change. This is especially useful in diapers, wound dressings, home construction uses, and other areas where it is desired to detect the presence of fluids.
Prior art discloses several methods for indicating wetness with a color change. U.S. Pat. No. 4,231,370 to Mroz et al. discloses a pH change/color change wetness indicator which is a solid mixture dispersed in an adhesive. U.S. Pat. No. 4,022,211 to Timmons et al. discloses a water soluble coloring agent which is visible when a diaper is dry, but which disappears when a diaper becomes wet. U.S. Pat. No. 3,952,746 to Summers discloses the use of humidity indicator paper mounted on an absorbent area of the diaper. U.S. Pat. No. 4,327,731 to Powell discloses moisture activated enzymatic systems and chromogens or pigment producing agents used as wetness detectors. U.S. Pat. Nos. 3,759,261 to Wang and 4,192,311 to Felfoldi disclose masked color layers which become visible when intervening layers become wet. U.S. Pat. No. 4,931,051 to Castello discloses a wetness indicator that includes a solid hydratable salt as an active ingredient to detect and visually signal the presence of water.
Many pH indicators may be unreliable. The other methods disclosed are also complicated to manufacture, as most require binding agents of some kind, and/or several manufacturing steps for implementation into a finished product
A simple, non-toxic wetness/fluid indicator is desired which would be able to be utilized with minimal manufacturing steps, for detection of almost any type of fluid.