A method of forming a security document, comprises providing a thread comprising at least one region of heat-transformable material, this material having an optical effect which is transformable in response to applied heat. The thread is integrated with a document substrate material during a substrate forming process, so as to produce a security document substrate having at least one windowed region in which the thread is exposed at the substrate surface, and at least one bridge region in which the thread is not exposed. A patterned heat process is then applied, causing a structural modification in the heat-transformable layer of the thread so as to produce an observable optical effect representative of the heat pattern at one or more predetermined positions with respect to one or more of the said windowed region or bridge region. Security documents bearing threads with such optically transformable materials are also disclosed.

The invention relates to a security sheet or document having enhanced watermark(s). 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 for the reduced fiber density areas to be made thinner. In a preferred embodiment, the micro-optic security device projects synthetic image(s) 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.

The invention relates to a security sheet or document having enhanced watermark(s). 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 for the reduced fiber density areas to be made thinner. In a preferred embodiment, the micro-optic security device projects synthetic image(s) 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.

A security element, preferably a security wire, for a secure document, that may include a masking structure for reducing the visibility of a surface of the element when the latter is located inside the document or on the surface of the document, the masking structure comprising a nanometric filler and a multilayer interference pigment.

A security element, preferably a security wire, for a secure document, that may include a masking structure for reducing the visibility of a surface of the element when the latter is located inside the document or on the surface of the document, the masking structure comprising a nanometric filler and a multilayer interference pigment.

A security element, preferably a security wire, for a secure document, may include a masking structure for reducing the visibility of a surface of the element when the latter is located inside the document or on the surface thereof, the masking structure comprising a mixture of at least two nanometric fillers.

A security element, preferably a security wire, for a secure document, may include a masking structure for reducing the visibility of a surface of the element when the latter is located inside the document or on the surface thereof, the masking structure comprising a mixture of at least two nanometric fillers.

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 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.

A method for the secure protection of a portion of the surface of an official document bearing markings, in which: a transparent security layer (17) is selected, the layer including at least one semi-transparent printed image including at least one transparent binder and at least one thermochromic pigment (14, 13, 12, 11); the semi-transparent printed image reveals at least one semi-transparent visible pattern in a first non-activated state at least a first temperature, such that the markings can be seen through the image, the pattern not being visible in a second activated state at least a second temperature different from the first temperature. A device for the secure protection of a portion of the surface of an official document and such an official document are also described.