A colour laser markable article includes at least a first and a second laser markable layer including, respectively, a first infrared dye IR-1 having an absorption maximum in the infrared region .sub.max(IR-1) and a second infrared dye IR-2 having an absorption maximum in the infrared region .sub.max(IR-2), characterized in that the colour laser markable layers further include a Diffusion Hindered Molecular Assembly (DHMA) which contains a leuco dye.

A colour laser markable composition includes at least a first and a second Diffusion Hindered Molecular Assembly (DHMA), each including a leuco dye and, respectively, a first and second sensitizer. With the laser markable composition, at least two different colours may be formed in a single layer.

A laser markable composition includes (a) an aqueous medium; (b) a leuco dye; (c) an optothermal converting agent; and (d) a colour developing agent, characterized in that the colour developing agent is a polymer particle capable of forming an acid upon exposure to heat.

A laser markable composition includes (a) an aqueous medium; (b) polymeric particles dispersed in the aqueous medium; (c) a colour developing agent or colour developing agent precursor; and (d) an optothermal converting agent; characterized in that a leuco dye is covalently bonded to the polymeric particles.

A method for producing a security document, with a thermographic substrate wherein the thermographic substrate is caused to undergo a color change depending on temperature effect in at least one first region A film element is arranged in such a way that the film element is arranged between the at least one first region of the thermographic substrate and a thermal print head. At least one first item of information is introduced by means of the thermal print head by activation of the color change in the at least one first region of the thermographic substrate, wherein the thermal print head, during the introduction of the at least one first item of information is in contact with the film element in such a way that the temperature effect causing the activation of the color change is transferred from the thermal print head through the film element to the at least one first region of the thermographic substrate.

A carrier for applying confidential data includes a substrate and a background applied to the substrate, in particular a concealment background, including an irregular configuration of characters. The characters are formed of a transparent non-chromogenic printing ink which phosphoresces under UV light. A data carrier having applied confidential data is also provided.

A colour laser markable laminate includes a colour laser markable layer including a leuco dye and an infrared absorbing compound, an optional adhesive layer, a polymeric support, an optional outerlayer, wherein the colour laser markable layer further includes an acid scavenger. The support, the optional adhesive layer, or the optional outer layer includes a UV absorbing compound.

An information recording medium having a front surface and a back surface has a first color developing layer, a second color developing layer and a third color developing layer. The first color developing layer develops yellow at a temperature not less than a first threshold value. The second color developing layer is arranged at the back surface side with respect to the first color developing layer. The second color developing layer develops magenta at a temperature not less than a second threshold value that is lower than the first threshold value. The third color developing layer is arranged at the front surface side with respect to the first color developing layer. The third color develops cyan at a temperature not less than a third threshold value that is higher than the first threshold value.

A forgery prevention medium includes a substrate and a specific invisible material layer directly or indirectly laminated on the substrate, having a specific invisible material reversibly and visually recognized through a predetermined process disposed thereon in a plane shape, and having a part of the specific invisible material inactivated in accordance with a visualized image pattern.

The present invention relates to a method for creating a hidden pattern on a substrate, wherein a liquid treatment composition comprising at least one acid is deposited by inkjet printing onto a substrate, which comprises at least one external surface comprising a salifiable alkaline or alkaline earth compound.