| 摘要 |
<p>1424754 Light-transmissive retroreflective sheeting MINNESOTA MINING & MFG CO 22 Jan 1973 [24 Jan 1972 17 April 1972] 3269/73 Heading G2J Light-transmissive retroreflective sheeting is formed by an open web of filaments 17, Fig. 2 e.g. of nylon or metal, encased by transparent retroreflective microspheres 18 e.g. of glass or plastics, whereby the sheet may be placed between e.g. a road sign and a rear source of illumination so that the sign may be seen by light transmitted through the spaces in the web or by light reflected from the microspheres. The woven filaments having the desired denier and percentage of open area coated with a tacky transparent binder into which microspheres covered with reflective material, e.g. vapourized aluminium, or silver, are embedded, the binder hardened and the exposed reflective material removed, e.g. by etching. The web may be non-planar and, if of metal, may conduct electricity to generate heat for removing moisture in signs. In Fig. 4 (not shown) the open mesh fabric 23 with microspheres 24 is pressed into a light-transmissive polymer-based layer 25, preferably elastomeric to permit flexibility of the sheet, which may be pigmented to produce light diffusion or the figment may be phosphorescent or fluorescent, the layer being on a support or release sheet 26. In a further embodiment the layer 25 is allowed to penetrate the opening between the filaments to above the top of the filaments where the layer supports a transparent sheet out of contact with the microspheres. Additional microspheres of different refractive index may be embedded in the layer between the encased filaments.</p> |
