Systems for generating a permanent image and image template

Abstract

System for generating a permanent image including: - comprising one image template (10): - a first layer (1) which has at least one motif (2) and - a second hydrochromic layer (3) arranged on the first layer (1) and - a transparent liquid with a boiling point of more than 150 °C at 1000 hPa atmospheric pressure.

Description

Description

[0001] The present invention relates to systems for generating a permanent image. Furthermore, the present invention also relates to an image template that can be used to generate an image.

[0002] So-called water-based coloring books for children have been available on the market for many years. A water-based coloring book is a coloring book in which images are created by applying water. The images created with water are initially invisible on the unused pages of the coloring book, but are covered by an opaque, usually white, matting hydrochromic layer that becomes transparent upon contact with water, revealing the image beneath the hydrochromic layer. The effect used in these coloring books is also known as the "wet reveal" effect, and hydrochromic inks can be purchased from companies such as "coates."

[0003] A disadvantage of commercially available systems with hydrochromic layers, such as the coloring books mentioned above, is that the effect of making the image or motif beneath the hydrochromic layer visible is temporary and only lasts until the applied water has evaporated. While this allows the coloring book to be reused, it cannot permanently create the image underlying the system.

[0004] Based on this prior art, it is an object of the present invention to provide systems for generating a permanent image. Furthermore, it is an object of the present invention to provide an image template with which an image can be generated reversibly or permanently.

[0005] The objects are achieved by the features of the independent claims. The dependent claims contain advantageous developments and refinements of the invention.

[0006] According to a first aspect of the present invention, the object of creating a permanent image is achieved by a first system comprising an image template and a transparent liquid. The image template comprises a first layer and a second layer and may comprise further layers. The first layer is the layer that produces the final image. It comprises at least one motif, which can be of any desired shape, color, size, and design. Two or more motifs can also be combined in the first layer.

[0007] The second layer, which is in the form of a second hydrochromic layer, is arranged on top of the first layer. The second layer can partially or even completely cover the first layer. It acts as a matting layer, which is particularly opaque and thus has a whitish color, thus covering the motif(s) of the first underlying layer, so that the motif(s) are not visible in this state.

[0008] For the purposes of the present invention, a hydrochromic layer is understood to be a layer that changes its appearance from opaque to transparent upon contact with water. The second hydrochromic layer is formed, in particular, from a hydrochromic ink that is applied to the first layer and dried. Hydrochromic inks are commercially available, for example under the trade name PF 70 / 32 from Coates. The second hydrochromic layer can also comprise motifs. However, this is not mandatory. To encourage the application of the transparent liquids, motifs are preferably also present in the second hydrochromic layer to promote the application of the transparent liquid in specific areas of the second hydrochromic layer.

[0009] However, unlike conventional water-based coloring books, which use water, the first system according to the invention comprises a transparent liquid with a boiling point of at least 150 °C at 1000 hPa atmospheric pressure. The higher the boiling point of the transparent liquid, the more permanent the image is.

[0010] A transparent liquid within the meaning of the present invention is understood not only to mean a liquid with a boiling point of at least 150°C at 1000 hPa air pressure, but also a liquid with sufficiently high transparency. To this end, the liquid has, in particular, a transmittance of 0.02% to less than 100%. The transmittance refers to the quotient of outgoing light intensity / incident light intensity and is measured photometrically using light with a wavelength between 400 and 800 nm, for example, at 550 nm. The higher the transmittance, the greater the transparency of the liquid and the clearer the motif of the first layer appears beneath the then transparent second layer.

[0011] If the transparent liquid described above is applied to the surface of the second hydrochromic layer, the hydrochromic layer becomes transparent, losing its opacity or inherent color and thus also its matting effect, allowing the motif(s) of the first layer beneath the hydrochromic layer to shine through. Because the transparent liquid has a boiling point of at least 150°C, it evaporates more slowly than water, so the transparency of the second layer is permanently maintained, and thus the motif(s) of the first layer are also permanently visible.

[0012] The boiling point of the transparent liquid is not specifically limited and can be as high as desired, as long as it is at least 150 °C, measured at an air pressure of 1000 hPa.

[0013] There are no other restrictions on the transparent liquid. However, the transparent liquid should not contain any substances that could dissolve or disperse the image in the first layer, as otherwise the image will "bleed" upon contact with the transparent liquid, making it harder to see.

[0014] The first system according to the invention is characterized by a simple and efficient composition by which a prefabricated image comprising at least one motif contained in the first layer can be made permanently visible.

[0015] According to the invention, a second system for generating a permanent image is also described.

[0016] Like the first system, the second system also comprises an image template, which, like the image template, can be designed in the first system. Thus, with regard to the image template and the effects to be achieved by the second system, reference is made to the first system described above. The second system differs from the first system in that no transparent liquid as disclosed above is used to make the motif(s) of the first layer permanently visible under the second hydrochromic layer, but rather a mixture is provided which comprises at least one solvent and at least one binder. The proportion of the binder, based on the total mass of the mixture, is at least 20% by mass, and the binder is dissolved or dispersed in the solvent. It is essential that the mixture forms a transparent film after the evaporation of any volatile substances it may contain.For this purpose, the binder has a minimum film-forming temperature below room temperature (25 °C).

[0017] In other words, the mixture or the resulting film is characterized by a high degree of transparency, which, as with the transparent liquid described above, ranges from 0.02% to less than 100%. This transparency is maintained at least in the "dried" state of the mixture, in which the binder forms a film.

[0018] Without being bound by theory, after drying, the mixture either lies in the form of a dried transparent layer on the second hydrochromic layer, or the mixture is absorbed by the hydrochromic layer, and the dried transparent film fills the spaces between the opaque particles contained in the second hydrochromic layer, thus resulting in a permanent transparency of the hydrochromic layer. The transparency is measured as described above for the transparent liquid.

[0019] The solvent in the mixture is not specifically limited and can, for example, be selected from water, alcohols, esters, and any mixtures thereof, and the like. Preferably, the solvent, if not water, is a water-soluble or water-miscible solvent. For the purposes of the present invention, a water-soluble or water-miscible solvent is understood to mean a solvent that has a solubility in water of more than 30 vol.% at 25°C and does not form a separate phase under these conditions.

[0020] The binder is also not specifically restricted, and any binder, especially polymeric binders such as natural or synthetic polymers, can be used. Examples include celluloses, pectins, xanthan gum or other gums, polyurethanes, polyacrylates, polyolefins, and epoxy resins, which can be present individually or in mixtures with other polymers.

[0021] The effect of changing the opacity of the second hydrochromic layer to a transparency of the second hydrochromic layer by applying water to the second hydrochromic layer is known. What has not been recognized is that permanent transparency, and thus a permanent translucence of the motif(s) of the first layer through the transparent second hydrochromic layer, can be achieved by using a solvent in the form of a mixture with at least one binder.

[0022] Without being bound by theory, it is assumed that by using the mixture, the refractive index is adjusted to the refractive index of the first layer, so that the second layer changes its appearance from opaque to transparent. In other words, it is assumed that the transparent liquid or the solvent / binder mixture fills the spaces between the individual particles of the second hydrochromic layer, thus reducing light scattering in the second hydrochromic layer. Consequently, the opacity decreases, and the second hydrochromic layer thus becomes more transparent. This then leads to the motif of the first layer shining through.

[0023] The permanent transparency, which is also responsible for creating the permanent image, results from the low (or virtually nonexistent) evaporation rate of the binder. To achieve this, the binder content, based on the total mass of the mixture, is at least 20% by mass, and in particular, it is in the range of 30 to 70% by mass, and especially 35 to 65% by mass, to achieve good flowability of the mixture so that it spreads evenly over the second hydrochromic layer.

[0024] The second system can also produce a permanently visible image using a hydrochromic layer.

[0025] Unless otherwise stated in the following statements, the advantages, beneficial effects, further developments and configurations apply to both the first system and the second system.

[0026] Acrylic resins, alkyd resins, polyurethane resins and polyester resins are readily miscible or dispersible in water and are also characterized by very good adhesive properties and are therefore preferably used in the mixture of the second system.

[0027] In order to create a permanently visible image, the first layer advantageously comprises a plastic-based medium, a fiber-based medium or a textile-based medium. A plastic-based medium is understood in particular to be media that are in the form of a more or less thick layer or film. This can be, for example, packaging films but also items of clothing and parts thereof. A fiber-based medium is understood to be media that comprise fibers of any kind. The fibers can be synthetic, natural or nature-identical. Particularly common fiber-based media are fleece, paper and cardboard, with paper and cardboard comprising in particular cellulose fibers. Textile media is understood in particular to be woven, braided, warp-knitted or knitted media that are used in particular for items of clothing, furniture and home accessories.The materials used for this purpose are not limited in detail and can also be synthetic, natural or nature-identical.

[0028] The motif(s) of the first layer can preferably be applied to the plastic-based medium described above, the fiber-based medium, or the textile-based medium. Printing processes such as offset printing are particularly suitable for this. These printing processes produce the motifs with particular accuracy and long-lasting stability.

[0029] As already stated above, the design of the motif(s) of the first layer is essentially unlimited. Preferably, the motif(s) are formed in one or more colors. This allows the motif to stand out particularly well from the medium of the first layer and also from the second layer, which is formed in particular with white or opaque color.

[0030] According to a further advantageous development, the second hydrochromic layer is formed from a dried hydrochromic ink applied to the first layer. In other words, a hydrochromic ink known in the prior art and commercially available can be used to produce the second hydrochromic layer, which forms the second hydrochromic layer after drying off any solvents. "Drying" here refers not only to the evaporation of solvents, but also to curing, such as curing with UV rays. Any method of fixing the second hydrochromic layer to the first layer is suitable.

[0031] Preferably, a hydrochromic ink usable for the present invention comprises at least one solvent, at least one binder, and at least one pigment for forming the second hydrochromic layer, wherein the binder can be selected from acrylic resins, alkyd resins, polyurethane resins, and polyester resins, and wherein the pigment is selected from sodium aluminum silicates, amorphous silicas, clay, gypsum, aluminum oxides, talc (magnesium silicate), and metal carbonates. Preferably, no further pigments are included to improve transparency upon contact with the transparent liquid or mixture. Furthermore, the binder is advantageously of the same type as the binder used in the mixture, since in this way the refractive indices of the second layer and the mixture can be particularly well matched, and the transparency of the second hydrochromic layer can be improved.Pigment particle sizes range from 1 to 35 µm. The particle size refers to the D50 value, which is measured in suspension using dynamic light scattering.

[0032] The hydrochromic layer is particularly advantageous when applied by a screen printing process, since the screen printing process allows a suitable layer thickness of the hydrochromic layer to be adjusted particularly well.

[0033] In order to expose the motif(s) of the first layer for a particularly long time and thus permanently through the transparency of the second layer, the transparent liquid preferably has a vapor pressure of less than 1000 hPa at 20°C.

[0034] Transparent liquids selected from vegetable oils, synthetic oils, petroleum-based oils, glycols, alcohols, glycol ethers, glycol esters, silicone oils, and any mixtures thereof are particularly suitable due to their easy availability, high boiling point, low vapor pressure, and ease of use. Vegetable oils are particularly preferred due to their sustainability and environmental friendliness.

[0035] For the reasons stated above, the transparent liquid is further preferably selected from sunflower oil, rapeseed oil, linseed oil, walnut oil, olive oil, ester oils, such as in particular isopropyl myristate and isopropyl palmitate, paraffin oils, glycerin, polydimethylsiloxane and any mixtures thereof.

[0036] In order to better distribute the transparent liquid or mixture over the second hydrochromic layer, the systems according to the invention can further comprise an application device. To improve the spreadability of the transparent liquid or mixture, the transparent liquid or mixture is preferably provided in a writing device or a painting device. The writing device or painting device can thus be part of the system. For this purpose, the writing device or painting device comprises, in particular, a reservoir which contains the transparent liquid or mixture and from which the transparent liquid or mixture can be conveyed for application. The reservoir can simply be a storage container in which the transparent liquid is present in unbound form, or it can also be a fiber reservoir.Suitable application devices include markers with a fiber reservoir and tip, "free ink" markers with a free liquid reservoir and a valve system for dispensing, or markers with free ink in a reservoir with an associated compensation element for pressure and heat equalization. Alternatively, the transparent liquid or mixture can also be applied with brushes, rollers, rags, sponges, or similar devices.

[0037] To particularly effectively prevent the transparent liquid or mixture from flowing off or spreading and thus promote the permanence of the generated image, the image template preferably comprises a barrier layer beneath the first layer or between the first layer and the second hydrochromic layer. For the purposes of the present invention, a barrier layer is understood to mean a layer characterized by low porosity and low absorption capacity for the transparent liquid or mixture, so that the transparent liquid or mixture is not absorbed by the barrier layer and its polarity is, in particular, contrary to the polarity of the transparent liquid or mixture.

[0038] The barrier layer can be made of a transparent material, such as polypropylene, PVC, polyester, and the like. The barrier layer prevents the transparent liquid or mixture from being absorbed by the substrate of the image, which could compromise the permanence of the image. The barrier layer does not necessarily have to be a film. It is also conceivable to place a barrier layer above or below the image using printing techniques.

[0039] Advantageously, according to one embodiment, the systems according to the invention also comprise a transparent film arranged between the first layer and the second hydrochromic layer. The transparent film can be designed as the aforementioned barrier layer, but can also be an alternative or additional transparent film. The use of a transparent film has the advantage that the hydrochromic layer can be applied directly to the film and can thus be produced in a separate step. Furthermore, the use of the transparent film in the production of the image template protects the motif of the first layer.

[0040] A transparent film, as defined by the invention, is a film with a transmission of 0.02% to less than 100%. Transmission refers to the ratio of outgoing light intensity to incident light intensity and is measured photometrically with light with a wavelength between 400 and 800 nm, for example, at 550 nm. The higher the transmission, the greater the transparency of the transparent film.

[0041] The material of the transparent layer is not specifically limited. Due to their durability and mechanical stability, plastic-based films have proven particularly advantageous. Among these, films containing polyolefins, especially polypropylene or a polypropylene copolymer, such as a propylene / ethylene copolymer, are particularly preferred. This is due, among other things, to their permanent transparency, meaning they have a low tendency to yellow, which allows the motif to be particularly well-illustrated.

[0042] The transparent film may adhere due to electrostatic interactions between the first layer and the hydrochromic layer.

[0043] However, it is also advantageous if there is an adhesive layer between the transparent film and the first layer, or if the transparent film is self-adhesive on a surface facing the first layer. This enables a more stable bond between the first motif layer and the second hydrochromic layer.

[0044] If an adhesive layer is present, it preferably comprises an acrylate-based adhesive, a pressure-sensitive adhesive, a hot-melt adhesive, or a light-cured adhesive. These adhesives are characterized by high user-friendliness, ease of use, and good adhesive properties and are therefore preferred. Particularly suitable adhesives are PUR adhesives, polyolefin copolymers, and polyvinyl acetate adhesives, such as the Vinnapas adhesives from Wacker AG.

[0045] A further aspect of the invention also relates to an image template for generating an image. The image template comprises a first layer having at least one motif, a second hydrochromic layer, and a transparent film arranged between the first layer and the second hydrochromic layer. With regard to the individual components of the image template, reference is also made to the statements regarding the image template according to the first and second systems for generating a permanent image.

[0046] With the image template according to the invention, an image can be created, for example, by using a liquid to make the hydrochromic layer "transparent", so that the underlying motif of the first layer is visible. To "make it transparent", for example, a transparent liquid as described for the first aspect of the invention or a mixture containing at least one solvent and at least one binder, as described for the second aspect of the invention, can be used. This use is then characterized in that a permanent image is created using the image template. If, on the other hand, water or an aqueous liquid that evaporates at 25 °C and ambient air pressure is used, the image is only temporarily visible and disappears again after the liquid dries. The hydrochromic layer then becomes opaque again.

[0047] The transparent layer can be designed as an additional so-called barrier layer or can also be used to apply the hydrochromic layer directly to it. In the context of the present invention, a barrier layer is understood to be a layer characterized by low porosity and low absorption capacity for the liquids for "making transparent" the motif in the first layer, so that the liquid is not absorbed by the barrier layer and its polarity is, in particular, contrary to the polarity of the liquid. If the transparent layer is used as a carrier for the hydrochromic layer, this has the advantage that a layer arrangement comprising a hydrochromic layer and a transparent film can be applied to or arranged on any motif layer and, if necessary, can be reused successively on different motif-containing first layers.

[0048] Due to its excellent mechanical properties, the transparent film is preferably a plastic-based film, particularly comprising a polyolefin, particularly polypropylene, or a polypropylene copolymer, such as a propylene / ethylene copolymer. The transparent film can be self-adhesive, particularly on the surface adjacent to the first layer.

[0049] Alternatively or additionally, the image template comprises an adhesive layer arranged between the transparent film and the first layer to improve the adhesion of the first layer to the hydrochromic second layer provided with the transparent film. The adhesive layer can be of any design and must merely be suitable for establishing sufficient adhesion to the first layer.

[0050] For particularly good adhesion, the adhesive layer preferably comprises an acrylate-based adhesive, a pressure-sensitive adhesive, a hot-melt adhesive, or a light-cured adhesive. Particularly suitable adhesives are PUR adhesives, polyolefin copolymers, and polyvinyl acetate adhesives, such as the Vinnapas adhesives from Wacker AG.

[0051] In addition, but not as part of the present invention, a method for producing an image template for generating an image is also described. The image template can, for example, be the image template according to the invention described above. The image template comprises a first layer having at least one motif, a second hydrochromic layer, and a transparent film arranged between the first layer and the second hydrochromic layer. With regard to the components of the image template, additional reference is made to the image template according to the invention and the systems according to the invention for generating a permanent image.

[0052] The method for producing an image template first comprises a step of applying the second hydrochromic layer to the transparent film and a step of bonding the transparent film to the first layer. The two steps can be carried out in any order. The application of the hydrochromic layer to the transparent film is not specifically restricted and can, in particular, be applied using a printing process. In the simplest case, the bonding of the transparent film to the first layer can be achieved by electrostatic attraction between the film and the first layer. Alternatively, the film can also be self-adhesive, at least on the surface that is to be bonded to the first layer, so that bonding can be achieved by simply bringing the first layer into contact with the self-adhesive surface of the transparent film.

[0053] The process creates an image template. By applying a liquid to the hydrochromic layer to make the hydrochromic layer transparent, an image becomes visible. This image is the motif of the first layer beneath the hydrochromic layer and the transparent film. Among other things, the transparent film can act as a barrier to the liquid, preventing it from soaking through the first layer, which can lead to reduced image quality. The transparent film can also serve as a carrier for the second hydrochromic layer, thus facilitating the production of the image template.

[0054] Furthermore, the method for producing an image template advantageously also comprises a step of applying an adhesive layer to the transparent film before the step of bonding the transparent film to the first layer. The adhesive layer can be applied before or after the hydrochromic layer is applied to the transparent film. The adhesive layer serves to improve the adhesion between the transparent film bearing the hydrochromic layer and the first layer, thus resulting in a layer bond in the image template that is also mechanically stable.

[0055] Also described, but not part of the present invention, is a method for producing a permanent image. The method comprises a step of forming an at least two-layer image template comprising a first layer having at least one motif and further comprising a second hydrochromic layer arranged on the first layer.

[0056] The second hydrochromic layer can be created using a hydrochromic ink. The hydrochromic layer can also be applied to a transparent film, which then acts like the barrier layer described above. A second hydrochromic layer thus formed can then be bonded to the first layer, for example, using an adhesive.

[0057] Then, a transparent liquid having a boiling point of at least 150 °C, measured at 1000 hPa air pressure, or a mixture containing at least one solvent and at least one binder dissolved or dispersed in the solvent, and wherein a proportion of binder, based on the total mass of the mixture, is at least 20 mass%, is applied to the second hydrochromic layer.

[0058] In the areas where the transparent liquid or mixture is applied to the second layer, the opacity of the second layer changes to transparent, so that the motif(s) of the first layer lying beneath the second layer and covered by the second layer become visible in these areas due to the transparency of the second layer.

[0059] The method is easy to apply without requiring significant technical effort and allows for the creative creation of a permanent image that is initially invisible. With regard to the embodiments of the method, reference is also made to the systems according to the invention.

[0060] In the method, the second hydrochromic layer advantageously comprises a transparent film, in particular a plastic-based film, and the method comprises a step of bonding the transparent film to the first layer. The bonding step can depend on the material of the transparent film. In the simplest case, the bonding of the transparent film to the first layer is achieved by electrostatic interaction. If the plastic used for the film is in particular a polyolefin, and in particular polypropylene or a copolymer comprising polypropylene, the transparent film can also be characterized by self-adhesive properties, at least on the surface that is bonded to the first layer, so that the bonding can be carried out by bringing the first layer into contact with the transparent film. If necessary, pressure and / or heat can also be applied to improve the bonding.

[0061] In order to improve the bond formation and thus also the layer bond in the image template, the method preferably also comprises a step of applying an adhesive, in particular an acrylate-based adhesive, a pressure-sensitive adhesive, a hot-melt adhesive or a light-curing adhesive, to a surface of the transparent film and a step of bonding the adhesive layer comprising the adhesive to the first layer.

[0062] Also described, but not part of the invention, is the use of a transparent liquid having a boiling point of at least 150°C, measured at 1000 hPa air pressure, or of a mixture containing at least one solvent and at least one binder, wherein the binder is dissolved or dispersed in the solvent and a binder content of at least 20% by mass, based on the total mass of the mixture. The transparent liquid or mixture is used with the aim of producing a permanent image from an image template comprising a first layer having at least one motif and a second hydrochromic layer arranged on the first layer. The image can be produced by the method disclosed above and thus by applying the transparent liquid or mixture. - Example -

[0063] Below, a recipe is given for components for forming a first layer according to the invention and for components for forming a second layer according to the invention. First layer:

[0064] The first layer (motif-bearing) is a cardboard surface (white) printed with corresponding motifs using the following ingredients: - 10 mass% color pigment (e.g. HelioBeit LW 305, HelioBeit-LW 905 from Helio Beit or others) - 30% by weight polymer dispersion Esacote AC 200 (from Lamberti surface treatment) - 0.3 mass% defoamer BYK-019 (from BYK) - 2 mass% wetting agent DisperBYK-168 (from BYK) - 0-4 mass% RheoBYK-425 (to adjust the rheology properties; from BYK) - Rest: Water Second layer: - 50 mass% Bayhydrol UV 2720 / 1 (from Covestro AG); aqueous UV varnish - 15% by mass Dorkafill H (kaolin; from Dorfner) - 15% by mass MinTalc 97-05 (talc; from Nobelmin) - 3 mass% Irgacure 500 (photoinitiator; from BASF) - 3 mass% Byk 348 (wetting aid; from BYK) - 0-3 mass% rheology additive to adjust the appropriate viscosity (see above) - Rest: Water

[0065] The components of the second layer can optionally be mixed in a ratio of 10:1 (based on mass%) with polyisocyanate (e.g. Bayhydur 305) to obtain a 2-component system with increased abrasion resistance.

[0066] To illustrate the present invention, reference is made to the following description and the figures. Fig. 1 shows an excerpt from a conventional water coloring book, which can be purchased. Fig. 1A and Fig. 2A shows the initial state.

[0067] Shown in each case is the same two-layer image template, comprising a first layer and an overlying second hydrochromic layer. The first layer contains motifs concealed beneath the second hydrochromic layer. The first layer and the second hydrochromic layer are formed using the components listed above for producing the first and second layers. The second hydrochromic layer also contains motifs intended to encourage the user to apply water. The second hydrochromic layer is characterized by a certain opacity or color, which conceals the motifs of the first layer.

[0068] Fig. 1B and Fig. 2B each show the motifs of the first layer. According to a conventional process, the image template from Fig. 1A water was applied. This changed the color / opacity of the second hydrochromic layer to transparent, and the motifs of the first layer beneath the second hydrochromic layer became visible.

[0069] The same effect was observed in Fig. 2B, but using a transparent liquid with a boiling point of at least 150 °C at 1000 hPa atmospheric pressure. Paraffin oil, which had a boiling point of at least 150 °C, was applied as the transparent liquid.

[0070] The difference between the conventional system or procedure according to Fig. 1A to C and the system according to the invention or a method as described above according to Fig. 2A to C is shown when looking at Fig. 1C compared to Fig. 2C. Fig. 1C and Fig. 2C were recorded after 20 min of drying after application of water or paraffin oil. Fig. 1C shows the state again Fig. 1A, i.e. the motifs of the second hydrochromic layer, which are colored or opaque over the motifs of the now invisible first layer.

[0071] In comparison, Fig. 2C still contains the same motifs from the first layer Fig. 2B. The transparency of the second hydrochromic layer was maintained because the paraffin oil did not dry out and evaporate due to its high boiling point of at least 150 °C.

[0072] For the sake of completeness, Fig. 2D shows the state of the system according to the invention 96 hours after application of paraffin oil to the second hydrochromic layer. The motifs of the first layer are still visible. This means that, according to the invention, the image from the motifs of the first layer is permanently visible, while by applying water, after the water has dried off, the opacity or color of the second hydrochromic layer in the example of Fig. 1A to 1C.

[0073] Fig. Figure 3 shows a cross-sectional view of a layered image template 10 according to one embodiment. The image template 10 serves to generate an image and includes: - a first layer 1 having at least one motif 2, - a second hydrochromic layer 3 and - a transparent film 4 arranged between the first layer 1 and the second hydrochromic layer 3.

[0074] The transparent film 4 is a plastic-based film, which in particular comprises a polyolefin, and in particular polypropylene, or a copolymer of polypropylene, such as propylene / ethylene copolymer. To better bond the first layer 1 to the transparent film 4, the image template 10 also comprises an adhesive layer 5 arranged between the transparent film 4 and the first layer 1.

[0075] The adhesive layer may comprise, for example, an acrylate-based adhesive, a pressure-sensitive adhesive, a hot-melt adhesive or a light-cured adhesive, so that a stable layer composite is obtained in the image template 10.

[0076] Particularly advantageously, the second hydrochromic layer 3 is applied directly to the transparent film 4, preferably by means of a printing process, whereby the first layer 1 is not damaged in the further course of production of the image template 10 by bonding the transparent film 4 to the first layer 1.

Claims

[1] System for generating a permanent image comprising: - an image template (10) comprising: - a first layer (1) having at least one motif (2) and - a second hydrochromic layer (3) arranged on the first layer (1) and - a transparent liquid with a boiling point of more than 150 °C at 1000 hPa atmospheric pressure. [2] System for generating a permanent image comprising: - an image template (10) comprising: - a first layer (1) having at least one motif (2) and - a second hydrochromic layer (3) arranged on the first layer (1) and - a mixture containing at least one solvent and at least one binder, wherein the binder is dissolved or dispersed in the solvent and a proportion of the binder, based on the total mass of the mixture, is at least 20% by mass. [3] The system of claim 2, wherein the binder is selected from acrylic resins, alkyd resins, polyurethane resins and polyester resins. [4] The system of any one of claims 1 to 3, wherein the first layer comprises a plastic-based medium, a fiber-based medium, or a textile-based medium. [5] System according to claim 4, wherein the motif is applied, in particular printed, to the plastic-based medium, the fiber-based medium or the textile-based medium. [6] System according to one of the preceding claims, wherein the motif is formed in one or more colors. [7] System according to one of the preceding claims, wherein the second hydrochromic layer (3) is formed from a dried hydrochromic ink applied to the first layer (1). [8] System according to claim 7, wherein the hydrochromic ink comprises at least one solvent, at least one binder and at least one pigment, wherein the binder is in particular selected from acrylic resins, alkyd resins, polyurethane resins and polyester resins and wherein the pigment is selected from sodium aluminum silicates, amorphous silicas, clay, gypsum, aluminum oxides, talc and metal carbonates. [9] System according to one of the preceding claims, wherein the hydrochromic layer (3) is a layer applied by a screen printing process. [10] System according to any one of claims 1 and 4 to 9, wherein the transparent liquid has a vapor pressure of less than 1000 hPa at 20°C. [11] System according to any one of claims 1 and 4 to 10, wherein the transparent liquid is selected from vegetable oils, synthetic oils, petroleum-based oils, glycols, glycol ethers, glycol esters, alcohols, silicone oils and any mixtures thereof. [12] System according to one of claims 1 and 4 to 11, wherein the transparent liquid is selected from sunflower oil, rapeseed oil, linseed oil, walnut oil, olive oil, ester oils, such as in particular isopropyl myristate and isopropyl palmitate, paraffin oils, glycerin, polydimethylsiloxane and any mixtures thereof. [13] A system according to any one of the preceding claims, wherein the transparent liquid or mixture is provided in a writing implement or a painting implement. [14] System according to one of the preceding claims, wherein the image template comprises a barrier layer under the first layer (1) or between the first layer (1) and the second hydrochromic layer (3). [15] System according to one of the preceding claims, wherein a transparent film (4) is arranged between the first layer (1) and the second hydrochromic layer (3). [16] System according to claim 15, wherein the transparent film (4) is a plastic-based film, which in particular comprises a polyolefin and in particular polypropylene or a copolymer of polypropylene. [17] System according to claim 15 or 16, wherein an adhesive layer (5) is present between the transparent film (4) and the first layer (1) or wherein the transparent film (4) is self-adhesive on a surface facing the first layer (1). [18] The system according to claim 17, wherein the adhesive layer (5) comprises an acrylate-based adhesive, a pressure-sensitive adhesive, a hot-melt adhesive or a light-cured adhesive. [19] Image template (10) for generating an image comprising: - a first layer (1) having at least one motif (2), - a second hydrochromic layer (3) and - a transparent film (4) arranged between the first layer (1) and the second hydrochromic layer (3). [20] Image template (10) according to claim 19, wherein the transparent film (4) is a plastic-based film, which in particular comprises a polyolefin and in particular polypropylene or a copolymer of polypropylene. [21] Image template (10) according to claim 19 or 20, further comprising an adhesive layer (5) arranged between the transparent film (4) and the first layer (1). [22] Image template (10) according to claim 21, wherein the adhesive layer (4) comprises an acrylate-based adhesive, a pressure-sensitive adhesive, a hot-melt adhesive or a light-cured adhesive. [23] Image template (10) according to claim 19 or 20, wherein the transparent film (4) is self-adhesive on a surface facing the first layer (1).

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