Methods and apparatus for embossing a precision optical pattern in a resinous sheet or laminate

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 the step of:
• (g) reheating said embossed sheeting and film to a temperature in the range of about 180.degree. F. to 200.degree. F., thereby to relieve any strain in said film caused by cooling thereof at said cooling station.

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.

Apparatus for continuousy 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;
• means for thereafter stripping said superimposed film and sheeting from said embossing element;
• and
• means for reheating said superimposed sheeting and film to a temperature in the range of 180.degree. F. to 200.degree. F. after stripping thereof from said embossing element.