Method of making a microprism master mold
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United States of America Patent
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Jan 4, 2000
Grant Date -
N/A
app pub date -
Jan 28, 1998
filing date -
Jul 28, 1995
priority date (Note) -
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Abstract
This invention relates to a method of making a microprism master mold which is suitable for use in the production of cube-corner retroreflectors, especially in the form of thin retroreflective sheeting, and permits the formation of hexagonal prism type microprisms having both high reflectivity and excellent angularity. This method is characterized in that, in making a cube-corner microprism master mold by stacking a plurality of flat sheets having two mutually parallel major surfaces, cutting V-shaped grooves on one lateral surface of the resulting flat sheet stack in a direction perpendicular to the major surfaces and at a fixed pitch to form a series of successive roof-shaped projections having a vertical angle of about 90.degree., and then shifting the flat sheets so that the vertices of the roof-shaped projections formed on each flat sheet meet the bottoms of the V-shaped grooves formed on an adjacent flat sheet. The flat sheets having a thickness of 50 to 500 .mu.m and made of a synthetic resin having a Rockwell hardness of not less than 70 are used.
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