The present invention relates to a method of tagging a substrate with a covert, spectroscopically detectable security feature, wherein a liquid treatment composition comprising at least one acid is deposited onto a substrate, which comprises at least one external surface comprising a salifiable alkaline or alkaline earth compound.

The present invention discloses a water-induced anti-counterfeiting paper and a preparation method thereof, belonging to the field of anti-counterfeiting technology of paper. The water-induced anti-counterfeiting paper consists of a base paper layer and an anti-counterfeiting label thereon. The anti-counterfeiting label is a colorless, invisible pattern or character, and does not have any effect on the appearance of the base paper. When contacting with water, a transparency of a location where the paper has the anti-counterfeiting label increases, and thereby a character or a pattern appears. After drying, the character or the pattern disappears, and the paper reverted to normal. The water-induced anti-counterfeiting paper may be prepared by method of printing the anti-counterfeiting label at a surface of the base paper by processes such as printing, code-spurting and inkjet printing according to requirements. Compared with the existing anti-counterfeiting surface-printing technology and other anti-counterfeiting embedment technology, the water-induced anti-counterfeiting paper is low in cost, the process is simple, and is not easy to be imitated; and its identification method is simple, its anti-counterfeiting effect is remarkable, and detection is repeatable.

The present invention discloses a water-induced anti-counterfeiting paper and a preparation method thereof, belonging to the field of anti-counterfeiting technology of paper. The water-induced anti-counterfeiting paper consists of a base paper layer and an anti-counterfeiting label thereon. The anti-counterfeiting label is a colorless, invisible pattern or character, and does not have any effect on the appearance of the base paper. When contacting with water, a transparency of a location where the paper has the anti-counterfeiting label increases, and thereby a character or a pattern appears. After drying, the character or the pattern disappears, and the paper reverted to normal. The water-induced anti-counterfeiting paper may be prepared by method of printing the anti-counterfeiting label at a surface of the base paper by processes such as printing, code-spurting and inkjet printing according to requirements. Compared with the existing anti-counterfeiting surface-printing technology and other anti-counterfeiting embedment technology, the water-induced anti-counterfeiting paper is low in cost, the process is simple, and is not easy to be imitated; and its identification method is simple, its anti-counterfeiting effect is remarkable, and detection is repeatable.

The invention generally relates to a security sheet or document having one or more enhanced watermarks. In one exemplary embodiment, the inventive security sheet or document is a single-ply paper that is made up of a paper layer including one or more watermarks, and a micro-optic security device (e.g., a patch or thread) that at least partially covers an upper or face portion of the watermark(s). The overlying patch or thread increases the durability of the watermark(s), thereby allowing for the watermark(s) as well as reduced fiber density areas therein to be made larger, and further allowing for the reduced fiber density areas to be made thinner. In a preferred embodiment, the micro-optic security device projects one or more synthetic images that coordinate or link in with the watermark design(s). In a more preferred embodiment, the micro-optic security device offers a machine detectable/readable feature in the form of enhanced IR-brightness, especially when measured in transmission. As will be readily appreciated, the inventive security sheet or document offers greatly improved counterfeit-resistance.

The invention generally relates to a security sheet or document having one or more enhanced watermarks. In one exemplary embodiment, the inventive security sheet or document is a single-ply paper that is made up of a paper layer including one or more watermarks, and a micro-optic security device (e.g., a patch or thread) that at least partially covers an upper or face portion of the watermark(s). The overlying patch or thread increases the durability of the watermark(s), thereby allowing for the watermark(s) as well as reduced fiber density areas therein to be made larger, and further allowing for the reduced fiber density areas to be made thinner. In a preferred embodiment, the micro-optic security device projects one or more synthetic images that coordinate or link in with the watermark design(s). In a more preferred embodiment, the micro-optic security device offers a machine detectable/readable feature in the form of enhanced IR-brightness, especially when measured in transmission. As will be readily appreciated, the inventive security sheet or document offers greatly improved counterfeit-resistance.

Security threads or stripes include a substrate and i) a first optically variable layer imparting a first different color impression at different viewing angles, ii) a second optically variable layer imparting a second different color impression at different viewing angles, iii) a first color constant layer having a color matching the color impression of the first or second optically variable layer at a first viewing angle, iv) a second color constant layer having a color matching the color impression of the first or second optically variable layer at a second viewing angle, and v) one or more material-free regions, wherein the first optically variable layer, the second optically variable layer, the first color constant layer, the second color constant layer and the one or more material-free regions are jointly visible from one side of the security thread or stripe.

Security threads or stripes include a substrate and i) a first optically variable layer imparting a first different color impression at different viewing angles, ii) a second optically variable layer imparting a second different color impression at different viewing angles, iii) a first color constant layer having a color matching the color impression of the first or second optically variable layer at a first viewing angle, iv) a second color constant layer having a color matching the color impression of the first or second optically variable layer at a second viewing angle, and v) one or more material-free regions, wherein the first optically variable layer, the second optically variable layer, the first color constant layer, the second color constant layer and the one or more material-free regions are jointly visible from one side of the security thread or stripe.

The invention generally relates to a security sheet or document having one or more enhanced watermarks. In one exemplary embodiment, the inventive security sheet or document is a single-ply paper that is made up of a paper layer including one or more watermarks, and a micro-optic security device (e.g., a patch or thread) that at least partially covers an upper or face portion of the watermark(s). The overlying patch or thread increases the durability of the watermark(s), thereby allowing for the watermark(s) as well as reduced fiber density areas therein to be made larger, and further allowing for the reduced fiber density areas to be made thinner. In a preferred embodiment, the micro-optic security device projects one or more synthetic images that coordinate or link in with the watermark design(s). In a more preferred embodiment, the micro-optic security device offers a machine detectable/readable feature in the form of enhanced IR-brightness, especially when measured in transmission. As will be readily appreciated, the inventive security sheet or document offers greatly improved counterfeit-resistance.

The invention generally relates to a security sheet or document having one or more enhanced watermarks. In one exemplary embodiment, the inventive security sheet or document is a single-ply paper that is made up of a paper layer including one or more watermarks, and a micro-optic security device (e.g., a patch or thread) that at least partially covers an upper or face portion of the watermark(s). The overlying patch or thread increases the durability of the watermark(s), thereby allowing for the watermark(s) as well as reduced fiber density areas therein to be made larger, and further allowing for the reduced fiber density areas to be made thinner. In a preferred embodiment, the micro-optic security device projects one or more synthetic images that coordinate or link in with the watermark design(s). In a more preferred embodiment, the micro-optic security device offers a machine detectable/readable feature in the form of enhanced IR-brightness, especially when measured in transmission. As will be readily appreciated, the inventive security sheet or document offers greatly improved counterfeit-resistance.

There is described a substrate (S) for security documents, such as banknotes, comprising one or more paper layers (11, 12) and a polymer layer (20) which is made to adhere to a side of at least one of the paper layers (11, 12), which polymer layer (20) is substantially transparent in at least one region of the substrate (S) which is not covered by the paper layer or layers (11, 12) so as to form a substantially transparent window (W) in the substrate (S) which is formed and closed by the polymer layer (20). The polymer layer (20) exhibits in the region of the window (W) a thickness (T) which is greater than a thickness (t) of the polymer layer (20) outside of the region of the window (W). The thickness (T) of the polymer layer (20) in the region of the window (W) is substantially equal to the added thickness of the paper layer or layers (11, 12) and of the polymer layer (20) outside of the region of the window (W) so that the substrate (S) exhibits a substantially uniform and constant thickness (T). The substrate (S) further comprises a micro-optical structure (30), in particular a lens structure, which is disposed in the region of the window (W) on at least one side of the polymer layer (20).