초록 ▼

Disclosed herein are an improved method and apparatus for continuously embossing a repeating pattern of precise detail, in particular, cube-corner type reflector elements, on one surface of a single sheet or on one surface of a laminate of transparent thermoplastic materials, to form retroreflective

Disclosed herein are an improved method and apparatus for continuously embossing a repeating pattern of precise detail, in particular, cube-corner type reflector elements, on one surface of a single sheet or on one surface of a laminate of transparent thermoplastic materials, to form retroreflective sheeting. A continuous embossing tool in the form of a flexible thin metal belt or cylinder has on its outer surface an embossing pattern which is the reverse of the precision optical pattern to be formed. The embossing tool is continously moved at a predetermined speed along a closed course through a heating station where the temperature of a portion of the embossing tool is raised to be above the glass transition temperature of the sheeting or laminate and a cooling station where the heated portion of the embossing tool is cooled while in a relatively planar condition to be below that glass transition temperature. The sheeting is continuously moved at the predetermined speed from a supply thereof into engagement with the embossing pattern on the tool and is pressed thereagainst continuously at a plurality of pressure points sequentially spaced along the heating station, with the one surface of the sheeting confronting and engaging the embossing pattern until the sheeting is raised above its glass transition temperature and conforms to the embossing pattern on the one face. The sheeting is maintained in engagement with the tool until the tool passes through the cooling station and the sheeting is lowered below its glass transition temperature and the pattern solidifies. The sheeting thereafter is stripped from the tool and next passed through a reheating station where the embossed sheeting is heated to an annealing temperature where the stresses formed in the thermoplastic material during cooling are relieved, while preserving and enhancing the precision optical pattern previously formed.

대표청구항 ▼

An improved method for continuously embossing a precision optical pattern requiring sharp angles and flatness of faces in certain detail on one surface of a continuous resinous sheeting material, the method being performed with the aid of a generally cylindrical endless metal embossing element havin

An improved method for continuously embossing a precision optical pattern requiring sharp angles and flatness of faces in certain detail on one surface of a continuous resinous sheeting material, the method being performed with the aid of a generally cylindrical endless metal embossing element having an inner surface and an outer surface, the outer surface having a precision optical embossing pattern which is the reverse of the precision optical pattern to be formed on one surface of said sheeting, and wherein the method includes the steps of: (a) continuously moving the endless embossing element along a closed course through a heating station, where said embossing element is heated through its inner surface to a predetermined temperature and then to a cooling station where said embossing element is cooled below said predetermined temperature; (b) continuously feeding onto said embossing element as it passes through a part of said heating station superimposed resinous film and sheeting materials, said resinous materials of said film and said sheeting each having different glass transition temperatures, said sheeting being in direct contact with the outer precision patterned surface of said embossing tool; (c) continuously heating said embossing element to said predetermined temperature at said heating station, said temperature being greater than the glass transition temperature of said sheeting and less than the glass transition temperature of said resinous film; (d) pressing said superimposed film and sheeting against said embossing element at a plurality of pressure points sequentially spaced along said heating station with one surface of said sheeting confronting and engaging said precision optical pattern on said embossing element until said one surface of said sheeting conforms to said precision optical embossing pattern; (e) continuously passing said embossing element and said superimposed film and sheeting through said cooling station where the temperature of said embossing element and said sheeting is lowered below said sheeting glass transition temperature, with said film serving to substantially continuously maintain said sheeting in engagement with said embossing element through the heating station and through said cooling station; and (f) continuously stripping said superimposed layer of film and embossed sheeting from said embossing element, said film being later strippable from the other face of said sheeting without destroying said optical pattern formed on said one face of said sheeting, the improvement comprising: (g) said cooling step being substantially effected while said superimposed film and sheeting and embossing tool are disposed in a generally planar condition, thereby to achieve an increase in the optical efficiency of the embossed sheeting. Apparatus for continuously embossing a precision optical pattern on one surface of transparent resinous material or materials, said apparatus comprising: embossing means including a continuous seamless embossing tool in the form of a thin metal element having an inner surface and an outer surface, said outer surface having a precision optical embossing pattern thereon which is the reverse of the precision optical pattern to be formed in the resinous material; means for continuously moving said embossing element along a closed course; means for introducing superimposed film and sheeting of resinous materials onto said embossing element with one face of said sheeting in direct contact with said optical pattern on said embossing element; heating means for raising the temperature of said embossing pattern to be above the glass transition temperature of said sheeting and below the glass transition temperature of said film while said embossing element is in a first portion of its course; cooling means for lowering the temperature of said sheeting to be below said glass transition temperature while said element and said sheeting are in a generally planar condition in their course, thereby to rigidify said precision pattern while in an undistorted condition; a plurality of pressure means sequentially spaced along said first portion of said course for pressing said superimposed film and sheeting against said embossing element with said one surface of said sheeting confronting and engaging said embossing pattern until said one surface conforms to said embossing pattern, with said film serving to substantially continuously maintain said sheeting in engagement with said embossing element until the latter passes said second portion of said course; and means for thereafter stripping said superimposed film and sheeting from said embossing element.