Abstract: A method of forming a coloured substrate, comprising applying to or incorporating within the substrate a diacetylene compound, and exposing the substrate to (i) a first, activating stimulus that converts the diacetylene compound from an unreactive to a reactive form, and (ii) a second stimulus that causes the reactive form of the diacetylene compound to polymerize and form the coloured substrate, wherein the diacetylene compound reverts to its unreactive form on removal of the activating stimulus and is of formula I: Y—C?C—C?C—(CH2)n-T-Q-Z (I) wherein: n=an odd integer; T=CO, CS or a bond; Q=NH, S, O, OCONH, NHCONH, NH—CHE-CONH, NHCOO or NHCSNH wherein E is H or a C1-20 alkyl group; Z=H or a hydrocarbon group containing 1 to 20 carbon atoms; Y=H or any group comprising at least one carbon atom.

Abstract: A method of forming an image on a substrate, which comprises applying to the substrate an activatable color forming compound wherein said activatable color forming compound is initially unreactive but becomes reactive upon activation; activating said color forming compound in the areas of the substrate where the image is to be formed, and, reacting the activated color forming compound into its colored form to produce an image. A substrate imaged using this method is also provided.

Abstract: A method of manufacturing a paper substrate comprising a color former which is capable undergoing a light activated color change reaction, wherein the color former is applied to the paper substrate during the manufacture of said paper substrate, and the color former is a metal oxyanion or a molecular organic. A paper substrate obtainable by this method is also provided.

Abstract: The invention relates to a method of marking a substrate comprising treating the substrate with a boron compound and a charrable agent, and, irradiating the areas of the substrate to be marked such that those areas change colour. Marked substrates obtainable by this method are also provided.

Abstract: A method of forming an image on a substrate, which comprises applying to the substrate an activatable colour forming compound wherein said activatable colour forming compound is initially unreactive but becomes reactive upon activation; activating said colour forming compound in the areas of the substrate where the image is to be formed, and, reacting the activated colour forming compound into its coloured form to produce an image. A substrate imaged using this method is also provided.

Abstract: The invention relates to a method of marking a substrate comprising treating the substrate with a boron compound and a charrable agent, and, irradiating the areas of the substrate to be marked such that those areas change colour. Marked substrates obtainable by this method are also provided.

Abstract: A method of manufacturing a paper substrate comprising a colour former which is capable undergoing a light activated colour change reaction, wherein the colour former is applied to the paper substrate during the manufacture of said paper substrate, and the colour former is a metal oxyanion or a molecular organic. A paper substrate obtainable by this method is also provided.

Abstract: The invention relates to a method of storing information in or on an article, wherein the article comprises a colour former which is selectively irradiated to produce a multi-coloured code comprising at least three different colours. Also provided by the invention is an article comprising a multi-coloured code comprising at least three different colours, obtainable by the method of the invention.

Abstract: A method of forming an invisible indicium on an article that comprises an outer opaque layer and an inner, laser-imageable layer, which comprises (5) irradiating the article with a laser, whereby the laser radiation passes through the opaque layer, and causes the laser-imageable layer to change colour. The article can be scanned, as a security check.

Abstract: A data storage medium comprising recording information in the form of a track of data points, the colour of each data point being selected from at least three different colours, wherein the recording information is disposed on a substrate which comprises a colour forming composition, wherein said colour forming comprises a colour former which is susceptible to changing to at least three different colours when irradiated with a laser, wherein the colour former is a leuco dye, a diacetylene or a carbazole. Methods of forming the data storage medium and methods of reading the medium are also provided.