| 摘要 |
The invention relates to improvements in security substrates and in particular to fibrous security substrates, such as paper, incorporating a watermark. The security substrate comprises a fibrous base layer, having a normal base fibre density, said base layer incorporating a watermark consisting of a plurality of alphanumeric characters. Each character comprises dark and/or light regions, the dark regions being formed by more densely deposited fibres than the normal base fibre density and the light regions being formed by less densely deposited fibres than the normal base fibre density. The density of the fibres in any region is substantially uniform such that there is no gradual change of tone between the light and dark regions. Each dark and light region adjoins at least one light and dark region respectively and an area of normal fibre density.
|
