Abstract: Retroreflective prisms are formed with windows thereon by removing a portion of the prism mold on one prism pair leaving the apex of the prism intact. In this manner smaller prisms are formed adjacent larger prisms. Optionally, the optical axis of the prisms may be tilted with respect to one another, preferably in a negative direction. The smaller prisms with windows provide increased brightness and optimize the retroreflection light.

Abstract: A method and apparatus for forming "seamless" retroreflective sheeting is described. At least two mold surfaces are used, each having alternate areas of arrays of prism recesses and spaces. In a first step, prisms are formed in one of the mold surfaces and applied to a base film or web. Next, prisms are formed on the second mold surface and applied to the spaced areas left in the first step.

Abstract: A durable reusable polymeric mold for casting a microstructure sheet having an array of prism elements and a method for forming the microstructure sheet are disclosed. A polymeric mold has a facet side and a base side including an array of prism elements upon which an radiation cured sheet can be formed. A protective surface layer can be formed on the facet side of the polymeric mold. The protective surface layer is sufficiently opaque to radiation to protect the polymeric mold from damage when the curable sheet is formed and is sufficiently bonded to the polymeric mold to allow the cured sheet to be removed from the protective surface layer while not substantially removing the protective surface layer from the polymeric mold. The microstructure sheet can be used as a retroreflective structure.

Abstract: A retroreflective structure and a method for forming the structure are disclosed. The structure has a window side and a facet side. The facet side has a plurality of steps with treads and risers intersecting at an angle. The risers include an array of retroreflective elements. Preferably, the elements are cube-corner prisms.

Abstract: A retroreflective structure having prism elements and a method for making the structure are disclosed. The retroreflective structure is formed of an extensible, elastomeric film and a rigid, non-extensible array of retroreflective prism elements. The array is bonded to the elastomeric film, thereby forming a retroreflective structure which can be significantly stretched without significantly diminishing the retroreflective properties of the structure.

Abstract: Retroreflective sheet material is produced by forming sheet material with closely spaced retroreflective formations on one face and depositing on this face silver and copper atoms having high kinetic energy to provide a reflective metallic deposit comprising a base layer of metallic silver and an overlying layer of metallic copper. An organic protective coating is thereafter applied over the reflective metallic deposit. Light rays passing through the front face of the body enter the retroreflective formations, impinge upon the interface provided by the silver base layer and are retroreflected therefrom. As a result, the sheet material exhibits a bright white appearance in daylight as well as a bright white coloration at night when an incandescent beam impinges thereon.

Abstract: A flexible retroreflective sheet material is formed by adhering a first face of a first flexible synthetic resin sheet material to a synthetic resin second sheet material by a first adhesive which preferentially adheres to the second sheet material. On the second face of said first sheet material are thereafter formed closely spaced retroreflective microprisms having a height of 0.001-0.010 inches. A second adhesive is applied to the second face of said first sheet and firmly engages therewith. A flexible backing material is adhered to the second adhesive over the second face. Lastly, the second sheet material and first adhesive are stripped from the first sheet material to produce a firmly bonded flexible composite sheet material comprised of the adhesively bonded first sheet material and backing material. The retroreflective microprisms may be coated with a reflective metal deposit or surrounded by air to provide a retroreflective interface.

Abstract: A relatively flexible retroreflective band for adhesive bonding about a support structure comprises a length of retroreflective sheeting formed into a continuous band with the outer portion of the band including retroreflective formations adapted to retroreflect light rays impinging thereon. An adhesive coating is disposed on the inner surface of the band to bond the band to a support structure, and a water-soluble release coating is superposed on the adhesive coating to prevent substantially contact of the adhesive coating with other surfaces. When it is desired to assemble the band onto a support structure, water is applied to dissolve the release coating and, while the adhesive coating is still wet with water, the band is slid over the support structure to the desired position.

Abstract: A retroreflective material providing a visual coloration includes a body member with microprisms on its rear surface. Some of the microprisms have a retroreflective interface and the remainder have a colored non-reflective coating thereon. As a result, light rays entering the front face which impinge upon the prisms with the retroreflective interface are redirected so that they exit the material in a parallel path. Light rays which travel to the color coated prisms are refracted from those prisms and impart a visual coloration to the material in daylight and ambient light.

Abstract: A microprism retroreflector material has a body portion with a planar front face and closely spaced microprisms extending thereacross in a plane spaced from and parallel to the front face. The microprisms are formed with three side surfaces disposed along three intersecting planes, and at least some of the microprisms have at least one side surface which is arcuate along one of the intersecting planes and over at least the major portion of its height. At least some adjacent pairs of microprisms have their prism axes tilted relative to the intersecting plane extending therebetween. The microprisms retroreflect light in six circumferentially spaced radially extending exit-energy patterns, and at least 70 percent of the retroreflected light is within a spread of not more than 0.6.degree. from the light rays impinging thereon.

Abstract: A retroreflective sheeting has microretroreflective formations on one surface which are partially metallized and partially exposed to the atmosphere about them. It is produced by forming a coating on microprism surface, and this coating includes a thin metallic deposit over substantially the entire surface and a second coating material over only a portion of the surface. The coated surface is then exposed to a solvent to remove the coating from its predominant area and leave the metal deposit on only a minor portion of the area. A backing sheet is then applied over the microprisms and bonded to the retroreflective sheeting so as to leave an air interface about the predominant area of the microprisms. As a result, some light rays are retroreflected by the metal deposit and some are retroreflected by the atmosphere interface. The sheeting exhibits daytime whiteness over the bulk of its surface area.

Abstract: A retroreflective laminar sheet assembly comprises base and cover sheets made from flexible synthetic plastic materials, and an array of interposed retroreflective film pieces seated within discrete cells formed therebetween. The sheets and film pieces of different compositions are used to afford a preselected balance of mechanical and optical properties, and the construction is such that distortion is minimized and flexibility of the assembly is maintained. The invention also provides novel methods by which such an assembly can be produced, which may take advantage of inherent or induced cohesive characteristics of the components employed.

Abstract: A retroreflective assembly includes a transparent polycarbonate housing of generally trapezoidal cross section. A channel extends upwardly from the base of the trapezoid, and the channel receives a vertically oriented strip of retroreflective sheet material. Planar side surfaces are provided at an angle with the vertical so that light from oncoming cars impinging on it will be directed downward to the retroreflective strip, whose top is spaced downward from the top of the housing to permit a thickness of material between the top of the channel on the top of the housing that is sufficient to afford structural strength to the housing. As a result, the image of the retroreflective strip is higher than its actual position, permitting relatively high visibility in a small structure of rugged construction.

Abstract: There are disclosed an apparatus and a method for continuously embossing synthetic plastic sheet material with precisely formed embossments in patterns repeating along the length thereof. The apparatus includes a movable polished belt upon which the sheet material is carried, and a series of molds are placed on the sheet material. As the sheet material and molds are advanced in steps through the apparatus, presses clamp the molds and belt against opposite surfaces of the sheet material and raise the temperature of the assembly to embossing temperature for the resin to cause the resin to flow into the mold cavities, and volatiles at the interface are dissolved in the resin. After the embossing step, the clamping pressure is released and this permits limited shrinkage of the mold and sheet material.

Abstract: A composite retroreflective sheet material with controlled stretch is provided by a strip of transparent retroreflective snythetic resin having cube corner formations on one surface thereof bonded to a longitudinally stretched flexible strip of backing material with the cube corners thereadjacent. The composite sheet material is puckered when in a relaxed state and is stretchable on a support surface with the elimination of the puckered condition indicating the proper degree of elongation without distortion of the cube corners. The backing material is stretched 3 - 15% at the time of bonding, and bonding is conveniently only along the longitudinal edges of the two strips. The exposed surface of the backing material may have a high friction or adhesive coating, and the faces of the cube corner formations may have a reflective coating.

Abstract: A retroreflective assembly is provided by a base having closely spaced retroreflective formations in its upper surface portion and a top member having closely spaced prism formations of the lower surface thereof and light directing formations on the upper surface thereof. Light rays impinging upon the assembly at an angle of less than 10 degrees are directed into the body of the top member by the light directing formations and pass into the prism formations which in turn direct light rays into the retroreflective formations of the base member. The retroreflective formations then retroreflective the light rays back into the prism formations and the light rays pass into the light directing formations on the upper surface and back towards the source. The composite structure is readily fabricated from synthetic plastic materials in its entirety or with glass bead retroreflective elements and can be sealed to provide a highly useful lane dividing strip for roadways and the like.