Abstract: A retroreflective marking material is disclosed comprising a sheet having at least some light-transmitting portions, a light-refracting surface on one side, and a plurality of trihedral light-reflecting units of three mutually perpendicular facets on the other side adapted to be adhered to a working site. The light-reflecting units are oriented to reflect light having relatively high angles of incidence with respect to the sheet. The marking material may be used as a tape for marking roads or as a vertical sign and is effective whether wet or dry. Optionally, the sheet or tape has light-receptors which rise above the tape and are spaced apart along one direction of the tape, and the trihedral light-reflecting units are substantially opposite the light-receptors. Preferably, the light-reflecting units have the shape of a triangular-based pyramid, and the marking material retroreflects light in two opposite directions.

Abstract: A retroreflector and a process for preparing it are disclosed characterized in that the retroreflector has a retroreflecting area consisting of rows of integrated, trihedral, light-reflecting units of varying geometric configurations which are so arranged as to provide substantially the same wide angle response to incident light throughout the entire retroreflective area. Essentially, the widths of adjacent rows of trihedral, light-reflecting units vary to form a pattern which may be repeated throughout the retroreflective area.

Abstract: A combined friction modifier and reinforcing agent and friction materials containing it are disclosed in which the combined modifier and reinforcing agent comprises a substantially amorphous, unstable, finely divided glass convertible in response to heat generated by the friction material during use to a devitrified, crystallized, friable state which separates from the amorphous, unstable glass in a substantially non-smearing particulate form.

Abstract: A molding pin is disclosed adapted to form a light-reflecting area in a reflector having a tri-faceted forming end provided with the configuration of three adjacent facets of a rectangular parallelepiped. The three facets are mutually perpendicular to each other, and at least two of the facets are rectangular with two adjacent sides of each rectangle being unequal. In use, the pin may be combined with other like pins to form a bundle from which a reflector or reflector mold is made.

Abstract: A multi-sided retroreflective body is disclosed having at least two retroreflective faces adapted to intercept light. Each reflective face is tilted in the same general direction about a lower portion angularly away from a vertical plane and is angularly related in a horizontal plane with respect to another vertical plane disposed substantially at right angles to the direction of such light. All four angles are so interrelated as to make the faces substantially optically equivalent, such that light retroreflected by the faces is directed in return paths substantially parallel to that of the intercepted light. Preferably, the reflective faces have light-reflecting units formed from three mutually perpendicular surfaces. In this case, a related advantage results in that all of the faces of the retroreflective body may be formed with the same forming tool without affecting their optical equivalence.

Abstract: A retroreflector of improved efficiency is disclosed comprising, in one form, a light-transmitting sheet adapted in use to be disposed in an angled position such that a normal to the sheet is at an angle of about 5.degree. to about 85.degree. from an incident beam of light. The sheet has front and back opposed, substantially parallel faces. The front face is substantially smooth and defines a light-refracting surface. The back face has a plurality of light-reflecting units. Each unit comprises three mutually perpendicular surfaces defining a trihedral angle of a rectangular parallelepiped and positioned with respect to the front face that the body diagonal of the rectangular parallelepiped is within an angle of 15.degree. of incident light refracted by the front face.

Abstract: A retroreflective device is disclosed comprising a convex-concavo lens having a cube-corner array extending across its concavity. The device returns in the same direction from which it is received a large proportion of incident light. The lens body is adapted with respect to reflected light to indicate a larger than actual area of the cube-corner array. The retroreflective device may be used as a marker, such as a roadmarker, the convex side of the lens body being exposed to receive the incident light.