Patent ID: 7168876

Claim:
A writing instrument for a water-metachromatic member which is capable of rendering different transparency between a water absorbed state and a water unabsorbed state and which comprises a support layer and a porous layer formed thereon, said porous layer comprising a binder resin and a fine-particle silicic acid fixed in a dispersed state in said binder resin: said writing instrument comprising: a cylindrical container capable of holding water therein, the container being formed with an opening at a tip end thereof to communicate the interior of the container with the exterior thereof; a rod-like pen point member formed of a fiber bunch and having a pen point at a tip end thereof and a rod-like body; a hollow cylindrical holder which directly holds said pen point member, said holder being formed at a tip end thereof with an opening through which the tip end of said pen point member is projected outwardly and at a rear end with a communication hole; gap forming means being provided between an inner peripheral surface of said cylindrical holder and an outer peripheral surface of the rod-like body of said pen point member to form a gap for generating a capillary force therebetween; means for hermetically and firmly connecting a tip end portion of said container and a rear end portion of said holder so that the holder is detachably held to said container through said opening; whereby, when said holder is held to said container through said connecting means, said pen point member, said holder and said container constitute, as one body, said writing instrument and water in the container is supplied through said communication hole of the rear end of said holder to said pen point member, and when said holder is detached from said container, said opening of said container is usable to supply water therethrough into the container.