| 摘要 |
A method of making a watermarked polymeric sheet includes forcing a web (22) of a polymeric material, selectively irradiating portions of the web (22) with electromagnetic radiation, and stretching the web to Form a sheet (26) having increased length and/or width. The watermarked polymeric sheet (26) has a plurality of indentations in at least one surface thereof, in areas corresponding to the irradiated portions of the web. The indentations form a watermark comprising areas of increased translucency, which is visible by transmitted light.
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