Field of the invention

The present invention relates to methods of manufacturing image articles, and image articles manufactured thereby.

Background to the invention

Image articles are known which comprise embossed or Braille images on a substrate. Generally, these image articles comprise a plain substrate on which a raised image has been applied by applying a three-dimensional material, image-wise over the coating, to produce the raised image.

These image articles are generally manufactured by specialist companies, utilising relatively expensive apparatus and techniques. The manufacture of embossed or Braille image articles in smaller premises, or even domestically, is rare due to the prohibitive expense of commercially available equipment.

Furthermore, the three-dimensional materials used in known Braille and embossed image manufacturing are relatively expensive, and require specialist apparatus to cut or mould into the desired image before application to a substrate.

It would be advantageous to provide a method of manufacturing embossed and Braille images, which utilises domestic and commercially available printing equipment. It would furthermore be advantageous to provide a method of manufacturing Braille and embossed images which does not utilise solid three-dimensional material to provide the raised images.

It would furthermore be advantageous to provide a method of manufacturing a raised image on an image article, in which the image effects an optically variable image, which when viewed from one angle is a negative of the image, and when viewed from a second angle is a positive of the image, with viewing angles in between revealing no image.

It is therefore an aim of preferred embodiments of the present invention to overcome or mitigate at least one problem in the prior art, whether expressly disclosed here or not.

Summary of the invention

According to a first aspect of the present invention there is provided a method of manufacturing an image article, the method comprising:

(a) providing a substrate; (b) coating at least a portion of a surface of the substrate with a hydrophilic polymer; and (c) effecting raising or expansion of at least a portion of the hydrophilic polymer from the surface of the substrate to create one or more raised image areas.

Suitably, raising of the polymer from the surface or expansion of the polymer, is effected by generating a gas beneath, within or on the polymer. Raising of the hydrophilic polymer may be effected by expansion of the polymer due to gas bubbles forming in the polymer matrix, thus causing the dimensions of the polymer to increase and form raised areas out of the plane of the coating. Alternatively or additionally raising of the polymer may be effected by stretching of the polymer due to formation of gas within or beneath the polymer coating and hence, the stretched polymer may be lifted away from the surface by gas. The stretched polymer spaced from the surface may then harden in that configuration. In effect, the raising of the polymer may be effected by one or a mixture of bubbling of the polymer to effect expansion, or stretching or expansion of the polymer by "blowing out" the polymer with a gas .

Suitably, the substrate is a sheet material, which may be planar or otherwise. The substrate may comprise any suitable material, such as paper, card, wood, glass, metal (including alloy), ceramic, stone, mineral, including mineral-based paper, plastics, hair and keratinous substances, composite, polymeric, or textile material, for example. Suitable textile material includes leather, cotton, synthetic textiles such as polyester, nylon or rayon, linen, flax, hemp, jute and silk.

Preferred substrates are sheets of card, paper, plastics, textile materials or metal.

Suitable plastics materials include polyurethanes, polyesters, poly vinyl chlorides, polyamides, and mixtures and co-polymers thereof. The hydrophilic polymer may be a water-soluble polymer or a water-dispersible polymer. Preferably the polymer is a water-soluble polymer.

Suitably the hydrophilic polymer is present in an aqueous solution or as a dispersion in an aqueous medium.

The hydrophilic polymer may be a polymer selected from polyvinyl alcohol, polyvinylpyrrolidone, polyvinylacetate, polyacrylic acid, polyacrylates, active acrylic polymers, gelatins, carboxyalkylcelluloses, alginates, guar gum, locust bean gum, polymeric surfactants and polyols.

Preferably the hydrophilic polymer is polyvinylalcohol .

Preferably the hydrophilic polymer is laid down as a coating in an aqueous medium in step (b) , preferably as an aqueous solution or aqueous dispersion. Preferably the coating is substantially dried, and may be dried by allowing the solvent to evaporate at ambient conditions, or by heating, for example.

Suitably the aqueous medium is printed onto the substrate, more preferably ink-jet printed, for example using a Hewlett Packard DeskJet series of printers.

The aqueous medium may include further ingredients such as, for example, humectants, fragrances, surfactants, dyes, pigments (or other colouring agents), co-solvents, preservatives and the like. A dye or pigment to present in the coating effects a coloured coating and subsequent raising of areas of the coating during or after step (c) may effect multi-tone images. Preferably raising or expansion of the hydrophilic polymers effected by contacting the coating with a gas.

Step (c) may comprise applying an agent capable of generating a gas on application of a stimulus, to at least a portion of the coating. Preferably the agent is image- wise applied. The agent may comprise a compound, for example, diazo compounds, which generate a gas on application of heat as the stimulus. Thus when step (c) comprises applying an agent capable of generating a gas on application of a stimulus, preferably the method comprises step (d) of applying the stimulus to the agent. The stimulus will depend on the agent used, but may for example, be heat, radiation, a chemical compound capable of reacting with the agent to form a gas, or any combination thereof.

Gas generation may be effected by the reaction of two or more agents applied in step (c) , or may be effected by reaction of an agent applied in step (c) with an agent present in the coating laid down in step (b) . Thus step (b) may comprise coating both a hydrophilic polymer and a compound capable of reacting with another compound subsequently applied to the coating to generate a gas.

Suitable gases arranged to be generated include carbon dioxide, nitrogen, oxygen, sulphur dioxide, chloroform and the like, for example.

Step (b) may comprise coating a hydrophilic polymer and first agent capable of reacting with a second agent to form a gas to the substrate, and step (c) may comprise image-wise applying a second agent capable of reacting with the first agent to generate a gas, to the coating.

Preferably the first agent is an acid, more preferably a non-volatile acid, and the second agent is an agent capable of reacting with the acid to generate a gas.

The acid may be any suitable acid, including organic acids, inorganic acids and the like. Suitably the acid is an organic acid. Suitable organic acids include citric acid, lactic acid, malic acid, maleic acid, oxalic acid, tartaric acid, and mixtures thereof.

The agent capable of reacting with the acid to generate a gas may comprise a water soluble salt, such as carbonate or bicarbonate, or a sulphite, for example. Suitable carbonates include alkali metal carbonates, especially sodium and potassium carbonate, ammonium bicarbonate, and substituted amine carbonates.

Preferably the coating of hydrophilic polymer is dried after step (b) .

Suitably, gas generation on, within or beneath the coating is effected such that different amounts of gas are generated at different areas of the coating. Thus, this differential gas generation effects differential raising or expansion of the polymer to effect different elevation of raised polymer on different areas of the coating.

Suitably the image article is a printing form, an electronic part or a mask to a printing form or electronic part. The differential generation of gas effects differential elevation of raised areas of the hydrophilic polymer to produce a 3-D image. The degree of elevation can be incrementally changed to produce photographically equivalent images which vary according to viewing angle. For example, if viewed at a glancing angle to the substrate (preferably less than 45°) the image may be seen as a negative image, whereas if viewed at just off perpendicular to the substrate the image may be seen as positive; other viewing angles may reveal no image. If sufficient elevation occurs, then the degree of raising of the polymer is sufficient to enable a Braille reader to interpret the image by touch alone.

The method enables the manufacture of embossed, Braille and optically variable images .

Preferably the image article is allowed to stand for at least 12 hours, preferably 24 hours, more preferably 36 hours before use, in order that complete gas generation is achieved and thus, that the image areas may be completely raised.

According to a second aspect of the present invention there is provided a method of manufacturing an image article, the method comprising:

(a) providing a substrate; (b) coating at least a portion of a surface of the substrate with a hydrophilic polymer and a first agent capable of generating a gas by reaction with a second agent; and (c) image-wise applying a second agent capable of reacting with the first agent to generate a gas, to the coating.

The amount of gas generated in step (c) may be controlled by varying the amount of second agent applied to an area of the coating. The second agent is preferably present in solution and the amount of second agent applied to the coating controlled by varying the amount of solution applied to the coating. The amount of solution may be controlled image-wise, such that different amounts of solution are applied across different areas of the coating.

Suitably the second agent applied to the coating in step (c) is printed onto the coating, more preferably ink-jet printed, for example, using a Hewlett Packard DeskJet series of printers.

Suitably the substrate, hydrophilic polymer, first and second agents are as described hereinbefore.

According to a third aspect of the invention there is provided a method of manufacturing an image article, the method comprising:

(a) providing a substrate; (b) coating at least a portion of a surface of the substrate with a hydrophilic polymer; (c) image-wise applying an agent capable of generating a gas upon contact with a stimulus, to the coating; and (d) applying the stimulus to the agent capable of generating a gas. According to a fourth aspect of the invention there is provided an image article manufactured by the method of the first, second or third aspects of the invention.

Suitably the hydrophilic polymer, substrate, agent capable of generating a gas upon contact with a stimulus and stimulus are as described hereinabove .

EXAMPLES

The various aspects of the invention will now be described by way of example.

Example 1 Card and paper substrates (white 160gm"2 card supplied by Vanguard, UK, and white 80gdm~2 paper, supplied by Niceday, UK) were coated with an aqueous solution containing poly (vinyl alcohol) (50gdπf3, supplied by Aldrich, UK) and citric acid (as a first agent capable of generating a gas by reaction with a second agent) (lOOgdπf 3, supplied by Aldrich, UK) using a K-bar and allowed to dry at room temperature. The pre-coated papers produced were ink-jet printed with an aqueous solution containing sodium carbonate (as a second agent capable of generating a gas by reaction with the first agent) (lOOgdrrf3, supplied by Aldrich, UK) and N-methylmorpholine-N-oxide (250gdm~3, supplied by Aldrich, UK) and the printed sample allowed to stand at room temperature during which time the ink-jet printed areas gradually rose. A photographic quality image was achieved, which gradually improved in quality over the next 2-3 days. The resulting prints obtained exhibited optically variable image properties; the prints exhibiting a positive grey-scale image when viewed from one angle, a negative image when viewed from a second angle and finally disappeared from view when observed from a third angle.

Example 2 The process described in Example 1 was repeated, but in this case a series of dots corresponding to the Braille alphabet was printed. On standing, a raised series of dots was achieved, which could be readily detected by touch.

Example 3 The process described in Example 1 was repeated, but in this case sodium trichloroacetate (lOOgdirf3, BASF) was incorporated in the paper pre-treatment solution in place of the citric acid originally present. The coated papers were ink-jet printed with sodium carbonate and N- methylmorpholine-N-oxide, as in Example 1. The ink-jet printed samples were dried at 1000C, during which time small amounts of chloroform and carbon dioxide were generated, which in turn created a raised 'blown' image. The prints were similar in quality and properties to those achieved in Example 1.

Example 4 Paper was pre-treated as in Example 1, but in this case the citric acid was omitted. An ink was prepared containing sodium trichloroacetate (lOOgdπT3, BASF) and N- methylmorpholine-N-oxide (250gdm~3, Aldrich) . Ink-jet printing with sodium carbonate, followed by drying at 1000C produced small amounts of chloroform and carbon dioxide which created a raised λblown' image. . The prints were similar in quality and properties to those achieved in Example 1.

Example 5 A stabilised diazoamine compound was synthesised via the method described below. Sulphanilic acid (13.3g, O.lmole, Aldrich UK) was dissolved in distilled water (100ml), concentrated hydrochloric acid (30cm3) was added and the resulting solution was cooled to 0-5°C. Sodium nitrite (7g, O.lmole, Aldrich UK) was dissolved in distilled water (50ml) and added dropwise to the sulphanilic acid solution over 20 minutes. After stirring for a further 20 minutes, sulphamic acid (Aldrich UK) was added until a negative result with starch iodide paper was obtained. This solution was added to a mixture of N-methyltaurine (16. Ig, O.lmole, Aldrich UK) and sodium carbonate (3Og, Aldrich UK) . The stabilised diazoamine was precipitated by the addition of sodium chloride and collected by filtration.

Paper and card substrates were pre-coated and then ink-jet printed in a similar manner to the process described in Example 1, but in this case the stabilised diazoamine was used to replace the sodium carbonate present in the ink- jet ink formulation. Once printed, the diazoamine regenerated the original diazonium salt due to the acidic nature of the pre-coated paper and on heating decomposed to generate nitrogen gas, which in turn created a raised 'blown' image. The prints achieved were similar in quality and properties to those achieved in Example 1. Thus the diazoamine generates a gas on application of a stimulus in the form of heat.

Example 6 The process described in Example 1 was repeated, but in this case the aqueous solution ink-jet printed onto the treated substrate contained sodium sulphite (lOOgdm"3) in place of the sodium carbonate present in the original solution of Example 1. Once printed, sodium sulphite decomposed due to the acidic nature of the pre-coated paper and liberated sulphur dioxide gas, which in turn created a raised λblown' image. The prints achieved were similar in quality and properties to those achieved in Example 1.

Example 7 Card (white, lβOgirf2, supplied by Vanguard, UK) and paper (white, 80gm~2, supplied by Niceday, UK) substrates were coated with an aqueous solution containing poly (vinyl alcohol) (50gdm~3, supplied by Aldrich, UK), citric acid (lOOgdπf3, supplied by Aldrich, UK) and urea (200gdrrf3, supplied by Aldrich, UK) using a K-bar and allowed to dry at room temperature. The pre-coated papers produced were ink-jet printed with an aqueous solution containing sodium nitrite (50gdm~3, supplied by Aldrich, UK) and N- methylmorpholine-N-oxide (250gdm~3, supplied by Aldrich, UK) and the printed sample allowed to stand at room temperature during which time the ink-jet printed areas gradually rose due to the generation of nitrogen gas. A photographic quality image was achieved, which gradually improved in quality over the next 2-3 days. The resulting prints obtained exhibited optically variable image properties; the prints exhibiting a positive grey-scale image when viewed from one angle, a negative image when viewed from a second angle and finally disappeared from view when observed from a third angle. The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings) , and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) , may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment (s) . The invention extend to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.