HURME, Eero (Iirismäki 10 A, Espoo, FI-02230, FI)
| CLAIMS 1. A method for manufacturing an indicator, cha racte r i zed in that the method comprises a step of partially coating an optical grating structure that is variable as a function of moisture, light or pressure and fabricated on a substrate with a transparent protective coating wherein the refractive index is more than 1.55 to form a patterned grating pattern on the grating structure. 2. The method according to claim 1, cha ra ct e r i z e d in that the optical grating structure is coated with a protective coating so that in a non- reacted state of the indicator the grating pattern of the optical grating structure is completely displayed and in a reacted state of the indicator the grating pattern of the optical grating structure is displayed only in the area that is coated with the protective coating of the grating structure. 3. The method according to any one of claims 1 to 2, cha ra ct e r i z e d in that the protective coating is solvent-based. 4. The method according to any one of claims 1 to 2, cha ract e r i z ed in that the protective coating is water-based. 5. The method according to any one of claims 1 to 4, cha ra c t e r i z e d in that the optical grating structure is fabricated on the substrate by hot pressing, laser technique or UV lithography. 6. The method according to any one of claims 1 to 5, cha rac t e r i z ed in that the protective coating is fabricated by flexographic printing, inkjet printing or the rotogravure technique. 7. An indicator, cha ract e r i z ed in that the indicator is manufactured by partially coating an optical grating structure that is variable as a function of moisture, light or pressure and fabricated on a substrate with a transparent protective coating wherein the refractive index is more than 1.55 to form a patterned grating pattern on the grating structure. 8. The indicator according to claim 7, cha ra ct e r i z ed in that the optical grating structure is coated with a protective coating so that in a non-reacted state of the indicator the grating pattern of the optical grating structure is completely displayed and in a reacted state of the indicator the grating pattern of the optical grating structure is displayed only in the area that is coated with the protective coating of the grating structure. 9. The indicator according to any one of claims 7 to 8, cha ra ct e r i z ed in that the pro- tective coating is solvent-based. 10. The indicator according to any one of claims 7 to 8, cha ra ct e r i z ed in that the protective coating is water-based. 11. The indicator according to any one of claims 7 to 10, cha ra ct e r i z ed in that the optical grating structure is fabricated on the substrate by hot pressing, laser technique or UV lithography. 12. The indicator according to any one of claims 7 to 11, cha ra ct e r i z ed in that the protective finish is fabricated by flexographic printing, inkjet printing or the rotogravure technique. 13. Use of the indicator according to any one of claims 7 to 12 in a package for detecting a change caused by moisture, light or pressure. |
FIELD OF THE INVENTION
The invention relates to the method defined in the preamble of claim 1, to the indicator defined in the preamble of claim 7, and to the use defined in claim 13.
PRIOR ART
New innovations and technical solutions relating to traceability, authenticity detection and convenience of use in packages and packaged products are in a key position especially in pharmaceutical, cosmetic, food, tobacco and electronic products.
The state of the art in coatings of a high refractive index have been disclosed e.g. in published patent applications US2005276980, US20080024847 and EP1268197. Publications US2005276980 and US20080024847 disclose for example the coating of grating structures to be used in security applications with coatings having a high refractive index.
Publication WO 2007042176 discloses a holographic device that is used to indicate a counterfeit/authenticity. The device comprises an optical grating structure that is variable as a function of temperature and completely coated with a protective coating.
OBJECTIVE OF THE INVENTION
An objective of the invention is to disclose a new method for manufacturing an indicator. Furthermore, an objective of the ' invention is to disclose a new indicator wherein the optical grating structure is partially coated with a protective coating. Further- more, an objective of the invention is to disclose the use of the indicator.
SUMMARY OF THE INVENTION
The method according to the invention is characterized by what has been presented in claim 1.
The indicator according to the invention is characterized by what has been presented in claim 7.
The use according to the invention is charac- terized by what has been presented in claim 13.
The method according to the invention for manufacturing an indicator comprises a step of partially coating an optical grating structure that is variable as a function of moisture, light or pressure and fabricated on a substrate with a transparent protective coating wherein the refractive index is more than 1.55 to form a patterned grating pattern on the grating structure.
The indicator according to the invention is manufactured by partially coating an optical grating structure that is variable as a function of moisture, light or pressure and fabricated on a substrate with a transparent protective coating wherein the refractive index is more than 1.55 to form a patterned grating pattern on the grating structure.
Transparent in this context means that the protective coating transmits at least approximately 70%, preferably at least approximately 90%, N of the incident visible light.
According to one embodiment of the invention the optical grating structure is coated in the method with a protective coating so that in a non-reacted state of the indicator the grating pattern of the optical grating structure is completely displayed and in a reacted state of the indicator the grating pattern of the optical grating structure is displayed only in the area that is coated with the protective coating of the grating structure.
According to one embodiment of the invention the optical grating structure is coated with a protec- tive coating so that in a non-reacted state of the indicator the grating pattern of the optical grating structure is completely displayed and in a reacted state of the indicator the grating pattern of the optical grating structure is displayed only in the area that is coated with the protective coating of the grating structure.
A non-reacted state of the indicator means that the indicator has not changed by the effect of moisture, light or pressure. A reacted state of the indicator means that the indicator has changed by the effect of moisture, light or pressure.
According to the invention the protective coating has a high refractive index. According to one preferred embodiment of the invention the refractive index of the protective coating is higher than the refractive index of the optical grating structure. According to another embodiment of the invention the refractive index of the protective coating is smaller than the refractive index of the optical grating structure.
According to one embodiment of the invention the protective coating is solvent-based. The protective coating may comprise for example toluene, xylene, acetone, ethanol, isopropanol, methanol, thinner, tri- chloroethylene and/or tall oil turpentine. According to another embodiment of the invention the protective coating is water-based. The protective coating normally includes salts and/or oxides of a metal and/or a semi-metal. According to one embodiment of the inven- tion the protective coating comprises one or more of the following: ZnS, Sb 2 S 3 , Fe 2 0 3 , PbO, ZnSe, CdS, Ti0 2 , PbCl 2 , Ce0 2 , Ta 2 0 5 , ZnO, CdO, Nd 2 0 3 , A1 2 0 3 , BiOCl, Sb 2 0 5 , I Ti0 2 -Zr0 2 -Sn0 2 and Zn0 2 Sb 2 0 5 .
According to one embodiment of the invention the thickness of the protective coating is 1 to 10 μπι.
According to one embodiment of the invention the optical grating structure is fabricated on the substrate by hot pressing, laser technique or UV lithography. The hot pressing may be performed with the embossing technique and/or any other hot pressing process known in the art. By hot pressing, the grating pattern is pressed onto the indicators. Any pattern may be fabricated as a light refracting grating. The grating pattern may be a line-shaped, round and/or angular pattern. The grating pattern used is preferably a pattern in which the change and/or disappearance of the grating is easily observable.
According to one embodiment of the invention the indicator material of the optical grating structure comprises any known indicator material. The indi- cator material may comprise for example a moisture absorbent, binder, hydrophilic salt, coloring agent, filler, additive and/or any other known agent and/or material used in indicators.
According to one embodiment of the invention the protective coating is fabricated by flexographic printing, inkjet printing or the rotogravure technique.
I According to one embodiment of the invention the substrate is a packaging material. According to another embodiment of the invention the substrate is a backing to be associated separately to the package. The indicator according to the invention may be formed by manufacturing it directly on the packaging material. In this case the optical grating structure may be fabricated directly on the package by hot pressing, laser technique or UV lithography at the time of pack- aging of before packaging the product. The indicator may also be formed by hot pressing, laser technique or UV lithography on a separate substrate backing which is associated to the package at the time of packaging. The material of the separate substrate backing is any packaging material known per se. The separate indicator is preferably in the form of a sticker and/or equivalent label which is easy to be associated to the package in connection with the packaging. Correspond- ingly, also the protective coating may be fabricated on the optical grating structure for example by flex- ographic printing, inkjet printing or the rotogravure technique.
The indicator associated to the packaging ma- terial or the separate indicator containing a finished optical grating structure that is partially coated with a protective coating should be kept in dry conditions. For the duration of its storage before taking to use, a film that protects against moisture and/or light and is fabricated from a material transmitting moisture and/or light to a very small extent or not at all may additionally be associated to the indicator.
The indicator is associated to the package before closing the package and it is reactive immedi- ately after the product has been packaged. According to one embodiment of the invention the optical grating structure is fabricated on a substrate that makes the change of the grating structure possible as the environmental factors change. The change of the grating structure may be for example expansion, contraction, wearing or melting. When the indicator reacts as a function of moisture, light or pressure, the part that is uncoated with the protective coating of the optical grating structure changes, while the part that is coated with the protective coating remains substantially invariable. The indicator associated to a pack- age reacts for example to moisture, light or change of pressure applied on the package from outside, - indicating by change of the optical grating effect the exposure of the package to moisture, light or change of pressure, respectively, for example due to opening or breaking of the package. The indicator reacts to moisture or light that penetrates inside through breaking of the package, indicating a leak. The indicator may also react to a risen storage temperature of the prod- uct. According to one embodiment of the invention the indicator reacts by the effect of change in pressure. According to one embodiment of the invention the indicator reacts by the effect of abrasion.
The invention relates further to the use of the indicator according to the invention in a package to detect a change caused by moisture, light or pressure .
The invention allows the addition of different identifiers and patterns on the optical grating structure. The protective coating that has a high refractive index and is fabricated by patterning on the grating structure protects the optical grating structure from changing at the coated area, whereas the optical grating structure changes or is destroyed in the area that is uncoated with the protective coating, for example as the moisture content rises or it is being rubbed by hand. An advantage of the indicator according to the invention over indicators of the prior art is the formation of the patterned grating structure allowed by the protective coating.
An advantage of the indicator according to the invention is that the part of the optical grating structure that is coated with the protective coating remains invariable as the ambient conditions change, while the part that is uncoated with the protecting coating reacts. The partial reaction of the optical grating structure to a change in the ambient conditions facilitates the observation of the change by a consumer .
According to one embodiment of the invention the change of the optical grating structure may be invisible to the eye, in which case the detection of the change may be performed for example by a laser pointer .
An advantage of the method according to the invention is that the protective coating may be pressed or printed flexibly by patterning during further processing of the product.
There is clearly a demand for indicators relating to the identification of the origin and authen- ticity of products and being printed or added in a sticker form to the product, ameliorating the convenience of using the product and promoting the sales of the product. The solution according to one embodiment of the invention offers a possibility to add a func- tional property already in the manufacturing process of the product by roll to roll mass production processes, so that the effect cannot be added to the product afterwards (authenticity application) . On the other hand, by printing the material of a high refrac- tive index on the grating for example by flexographic or inkjet printing, the information supplied by the indicator may be tailored also at a later stage, for example in connection with the formation of the end product.
The indicator manufactured according to the invention may be used for example in the following applications: In posters, stickers, envelopes and games, where the optical effect that is variable as a function of time may be used for information and promo- tional purposes. The indicator manufactured according to the invention may be used for example as a label that reacts to moisture in a soft drink bottle or a glass. In the so-called initial state, i.e. non-reacted state of the indicator, the diffractive grating structure may cover a large area. Pouring the cold soft drink in a glass provides condensation of moisture and for example appearance of the manufacturer's brand design on the label as an optical diffractive pattern.
The indicator manufactured according to the invention may be used for example as a label that reacts to moisture inside the cap of a bottle (e.g. a dry pharmaceutical preparation) . In the so-called initial state the diffractive grating structure may cover a large area. Opening the bottle and the consequent rising of the moisture content in the bottle provides partial disappearance of the grating structure and for example appearance of the manufacturer's brand design on the cap as an optical diffractive pattern.
The indicator manufactured according to the invention may be used for example as a label that reacts to temperature in a glass or a cup. In the so- called initial state the diffractive grating structure may cover a large area. Pouring a hot beverage in the glass provides rising of the temperature and for example appearance of the manufacturer's brand design on the label as an optical diffractive pattern.
The indicator manufactured according to the invention may be used for example for marketing, game and identifier applications. As the grating pattern of the grating structure is rubbed a pattern is formed (i.e. the remaining grating pattern).
The indicator manufactured according to the invention may be used for example as an indicator that expresses the opening, tampering and/or authenticity in packages. The embodiments of the invention presented above can be combined freely with each other. Many of the embodiments may be combined in order to form a new embodiment. The method, the product or the use to which the invention relates may include one or more of the above-mentioned embodiments of the invention. The embodiments of the invention may vary, even to a considerable degree, within the scope of the set of claims .
LIST OF FIGURES
In the following section, the invention will be described in detail by means of an example embodiment with reference to the accompanying drawing, in which
Fig. 1 presents an indicator manufactured by the method according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
For simplifying purposes the repeating elements of the invention are referred to by the same numerals in the following example.
Fig. 1 presents a cross section of an indicator manufactured on a substrate according to one em- bodiment of the invention. The indicator of the example comprises a substrate 3 which is for example a packaging material, e.g. polypropylene or other poly- olefin, polyterephthalate or other polyester, or a combination and/or mixture of these. Furthermore, the indicator comprises an optical grating structure 2 fabricated on the surface of the substrate 3 by hot pressing without metallization. In manufacturing for example an indicator that reacts as a function of moisture, the indicator material of the optical grat- ing structure consists for example of a hygroscopic polymer, e.g. polyvinyl alcohol, on which the grating pattern may be hot pressed as it is a thermoplastic agent, and a hydrophilic salt, e.g. a mixture of calcium chloride solution or other chloride salt. The hot pressed indicator forms a large number of equally spaced gratings, the distance between each grating (= the period of the gratings) and the height of the gratings being generally on the order of approximately 100 to 700 nanometers, but it may also be on the order of a few nanometers. The indicator additionally comprises a transparent solvent-based protective coating la, lb partially coated on the grating structure 2. For example, the increase of moisture shows on the optical grating structure 2 as an expansion in the volume of the indicator material, whereby the dimensions of the gaps in the grating change and the gaps eventually disappear, which expresses the increase of moisture over a certain limit. The reaction is irreversible. However, the increase of moisture does not affect the part of the grating structure that is coated with the protective coating la, lb and it remains invariable, i.e. non-reacted, while the part that is uncoated with the protective coating la, lb reacts. The disappearance of the part that is uncoated with the protective coat- ing la, lb indicates to a consumer that the product has been subject to ambient moisture, e.g. on the store shelf .
The invention is not limited merely to the exemplary embodiments referred- to above; instead, many variations are possible within the scope of the inventive idea defined by the claims.