Seamless master and method of making same

1. A one-piece hollow cylindrical invertible elastomeric master having preselected irregular speckle pattern made by a method comprising:

(1) applying an effective amount of a liquid curable photosensitive medium to an external circumferential surface of an elongated cylindrical member defining a longitudinal axis and rotatable thereabout, and rotating the cylindrical member about its longitudinal axis, for forming along the exterior circumferential surface thereof a seamless layer of curable photosensitive medium of substantially uniform radial dimension;

(2) curing the layer of photosensitive medium on the elongated cylindrical member;

(3) exposing the cured layer of photosensitive medium substantially along the length and exterior circumferential surface thereof to a source of coherent light that has preselected irregular speckle imparted thereto and rotating the cylindrical member about its longitudinal axis, to produce an associated predetermined irregular speckle pattern in the exposed photosensitive medium along exterior circumferential surface of the photosensitive medium on the cylindrical member, whereupon the exposed photosensitive medium is subsequently able to be developed;

(4) fixing the irregularly exposed areas of the photosensitive medium as physical microstructures in the exposed photosensitive medium;

(5) applying along the exterior circumferential surface of the developed photosensitive material an effective amount of a curable elastomeric liquid;

(6) curing the elastomeric liquid, to produce an elongated invertible hollow cylindrical elastomeric member of a predetermined radial dimension that is in intimate contact with the speckle pattern recorded in the photosensitive material, thereby producing in the elastomeric member a seamless light-shaping diffuser surface where the elastomeric member is in intimate contact with the speckle pattern;

(7) separating the elongated invertible hollow cylindrical elastomeric member from the developed photosensitive material having the speckle pattern recorded therein, whereupon the invertible hollow cylindrical elastomeric member has the seamless light-shaping diffuser surface substantially along the length and inner circumferential surface thereof; and

(8) inverting the hollow cylindrical elastomeric member, for presenting the seamless light-shaping diffuser surface substantially along the length and exterior circumferential surface thereof, wherein the surface of light-shaping diffuser has a plurality of microstructures projecting therefrom, said microstructures having irregular lengths in the projecting direction, thereby producing the hollow cylindrical elastomeric master.

2. The master of claim 1 , wherein the photosensitive medium is formed to have a radial thickness of about one-micron to about one hundred microns.

3. The master of claim 1 , wherein the photosensitive medium is formed to have a radial thickness of about thirty-five microns.

4. The master of claim 1 , wherein curing of the photosensitive medium is effected by baking said medium at elevated temperature for about forty minutes to about two hours.

5. The master of claim 1 , wherein curing of the photosensitive medium is effected by baking said medium at a temperature of about 90 degrees C for about one hour to about two hours.

6. The master of claim 1 , wherein curing of the photosensitive medium is effected by baking said medium at a temperature of about 65 degrees C for about one hour.

7. The master of claim 1 , wherein the exposed photosensitive medium is developed by contacting said medium with an effective amount of a 10 weight % aqueous developer solution for a period of time ranging from about thirty seconds to about one minute.

8. The master of claim 1 , wherein the elastomeric liquid is cured by subjecting said elastomeric liquid to room temperature for a time period of about twenty-four hours.

9. The master of claim 1 , wherein the hollow cylindrical elastomeric member is formed to have a radial thickness of about 1/16 inches to about ⅛ inches.

10. The master of claim 1 , wherein the speckle pattern is a sinc function pattern.