PLANAR SEALING ELEMENT

Abstract

The present invention relates to a planar sealing element (1) for application to a substrate (2), comprising a carrier layer (3) and several functional layers (4), the functional layers (4) comprising at least one colour display layer (5) and an adhesion-controlling layer (6), the sealing element (1) furthermore comprising an adhesive layer (8) for attachment to the substrate (2), the functional layers (4) being arranged between the carrier layer (3) and the adhesive layer (8), wherein the carrier layer (3) is at least partially detachable from the functional layers (4) in order to bring the sealing element (1) from a first state (9) to a second state (10), with the second state (10) not being convertible into the first state (9), the sealing element (1) in the second state (10) comprising a peeled-off layer (11), comprising at least the at least partially detached carrier layer (3), and a residue (12), comprising at least the adhesive layer (8) and at least parts of the at least one colour display layer (5), the carrier layer (3) being made of paper, wherein it is envisaged, according to the invention, that the carrier layer (3) is translucent so that the peeled-off layer (11), in at least one area when the peeled-off layer (11) is arranged congruently on the residue (12), has a different colour impression than the same area of the carrier layer (3) in the first state (9) in a viewing direction toward the carrier layer (3).

Claims

1. A planar sealing element for application to a substrate, comprising a carrier layer and several functional layers, the functional layers comprising at least one colour display layer and an adhesion-controlling layer, the sealing element further comprising an adhesive layer for attachment to the substrate, the functional layers being arranged between the carrier layer and the adhesive layer, wherein the carrier layer is at least partially detachable from the functional layers in order to bring the sealing element from a first state to a second state, with the second state not being convertible into the first state, the sealing element in the second state comprising a peeled-off layer, comprising at least the at least partially detached carrier layer, and a residue, comprising at least the adhesive layer and at least parts of the at least one colour display layer, the carrier layer being made of paper, wherein the carrier layer is translucent so that the peeled-off layer, in at least one area in which no or only small portions of the at least one colour display layer adhere when the peeled-off layer is arranged congruently on the residue, has a different colour impression than the same area of the carrier layer in the first state in a viewing direction toward the carrier layer.

2. A planar sealing element according to claim 1, wherein all layers are transparent or have translucency at least in a congruent surface area.

3. A planar sealing element according to claim 1, wherein the adhesive layer and/or the functional layers is/are opaque at least in a congruent surface area.

4. A planar sealing element according to claim 1, wherein the area of the peeled-off layer with no or only small portions of the at least one colour display layer adhere to when the peeled-off layer is arranged congruently on the residue has a colour distance Delta E (?E) of more than 0 to 7.0 as compared to the same area of the carrier layer in the first state in a viewing direction toward the carrier layer.

5. A planar sealing element according to claim 3, wherein the area of the peeled-off layer with no or only small portions of the at least one colour display layer adhered to when the peeled-off layer is arranged congruently on the residue has a colour distance Delta E (?E) of at least 0 to 90 as compared to the same area of the carrier layer in the first state in a viewing direction toward the carrier layer.

6. A planar sealing element according to claim 1, wherein the carrier layer is made of calendered paper.

7. A planar sealing element according to claim 1, wherein the sealing element further comprises a second adhesion-controlling layer between the carrier layer and the adhesive layer in order to tear out at least parts of the at least one colour display layer when the carrier layer is being detached and to adhere them to the carrier layer.

8. A planar sealing element according to claim 1, wherein the carrier layer has a mass per unit area in the range from 8 g/m.sup.2 to 150 g/m.sup.2.

9. A planar sealing element according to claim 1, further comprising a further carrier layer arranged between the functional layers and the adhesive layer or between two functional layers.

10. A planar sealing element according to claim 1, wherein the sealing element is a label.

11. A planar sealing element according to claim 1, wherein the sealing element is an adhesive tape.

12. A planar sealing element according to claim 1, wherein a siliconized cover layer made of paper or plastic is arranged on the adhesive layer on the side facing away from the functional layers to provide protection for the adhesive layer.

13. A planar sealing element according to claim 1, wherein the planar sealing element has punchings in order to render manipulation more difficult by a complete detachment or to enable easier cutting through the sealing element for opening a packaging.

14. A system made of a planar sealing element and a packaging object for goods, the sealing element comprising a carrier layer and several functional layers, the functional layers comprising at least one colour display layer and an adhesion-controlling layer, the sealing element further comprising an adhesive layer for attachment to a substrate, the functional layers being arranged between the carrier layer and the adhesive layer, wherein the carrier layer is at least partially detachable from the functional layers in order to bring the sealing element from a first state to a second state, with the second state not being convertible into the first state, the sealing element in the second state comprising a peeled-off layer, comprising at least the at least partially detached carrier layer, and a residue comprising at least the adhesive layer and at least parts of the at least one colour display layer, the carrier layer being made of paper, wherein the carrier layer is translucent so that the peeled-off layer, in at least one area in which no or only small portions of the at least one colour display layer adhere when the peeled-off layer is arranged congruently on the residue, has a different colour impression than the same area of the carrier layer in the first state in a viewing direction toward the carrier layer.

15. A system according to claim 14, wherein all layers are transparent or have translucency at least in a congruent surface area so that identification of information for goods, which is attached underneath the adhesive layer on the surface of the packaging element, is possible at least in a partial area.

16. A system according to claim 14, wherein the sealing element has opacity so that identification of information for goods, which is attached underneath the adhesive layer on the surface of the packaging element, is not possible at least in a partial area.

17. A planar sealing element according to claim 4, wherein the area of the peeled-off layer with no or only small portions of the at least one colour display layer adhere to when the peeled-off layer is arranged congruently on the residue has a colour distance Delta E (?E) of about 0.1 to about 5.0 as compared to the same area of the carrier layer in the first state in a viewing direction toward the carrier layer.

18. A planar sealing element according to claim 4, wherein the area of the peeled-off layer with no or only small portions of the at least one colour display layer adhere to when the peeled-off layer is arranged congruently on the residue has a colour distance Delta E (?E) of about 0.1 to about 3.0, as compared to the same area of the carrier layer in the first state in a viewing direction toward the carrier layer.

19. A planar sealing element according to claim 5, wherein the area of the peeled-off layer with no or only small portions of the at least one colour display layer adhered to when the peeled-off layer is arranged congruently on the residue has a colour distance Delta E (?E) of about 7 to about 50 as compared to the same area of the carrier layer in the first state in a viewing direction toward the carrier layer.

20. A planar sealing element according to claim 8, wherein the carrier layer has a mass per unit area in the range from 30 g/m.sup.2 to 120 g/m.sup.2, or of 50 g/m.sup.2.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0134] The invention will now be explained in further detail using exemplary embodiments.

[0135] The drawings are exemplary and are intended to outline the idea of the invention, but are in no way intended to restrict or even exhaustively represent it.

[0136] Therein:

[0137] FIG. 1 shows the schematic structure of a planar sealing element according to the invention with an adhesion-controlling layer,

[0138] FIG. 2 shows the first (FIG. 2A) and second (FIG. 2B) states of the planar sealing element of FIG. 1,

[0139] FIG. 3 shows the schematic structure of a sealing element according to the invention with two adhesion-controlling layers,

[0140] FIG. 4 shows the first (FIG. 4A) and second (FIG. 4B) states of the planar sealing element of FIG. 3.

WAYS OF IMPLEMENTING THE INVENTION

[0141] FIG. 1 shows the roughly schematic structure of a simple embodiment of a planar sealing element 1 according to the invention, with all successive layers being shown one below the other.

[0142] The structure of a sealing element according to the invention is described below in a first direction 25 starting from the carrier layer 3 in the direction of the adhesive layer 8.

[0143] The planar sealing element 1 comprises a carrier layer 3 and an adhesive layer 8. The functional layers 4 are arranged between the carrier layer 3 and the adhesive layer 8. In this embodiment, the functional layers 4 comprise a colour display layer 5, an intermediate layer 24 and a first adhesion-controlling layer 6. The carrier layer 3 and the adhesive layer 8 each have two sides, with one of them facing the functional layers 4 and one of them facing away from the functional layers 4.

[0144] As illustrated in FIG. 1, a further colour display layer 17 can be present below the colour display layer 5 in order to obtain a special colour effect in the residue 12 (see FIGS. 2A, 2B). In addition, a further carrier layer 26, preferably made of paper, could also be present in order to reinforce the planar sealing element 1. Without the further colour display layer 17 and the further carrier layer 26, the simplest embodiment variant from Example 1, as mentioned above, would be present.

[0145] In this case, the carrier layer 3 of the planar sealing element 1 is produced from highly calendered paper. In the present example, the mass per unit area of the paper amounts to 50 g/m.sup.2. In general, however, the paper used can have a mass per unit area of 8 g/m.sup.2 to 150 g/m.sup.2, preferably of 50 g/m.sup.2. Furthermore, it has a translucency of 70%. In general, however, the paper used can, of course, also have a translucency that is higher than 70%.

[0146] The functional layers 4 and the adhesive layer 8 can have a transparent or likewise a translucent design. In this case, it becomes possible to read information arranged on the substrate 2 in the first and second states. Alternatively, the functional layers 4 and the adhesive layer 8 can have an opaque design. In this case, it is achieved that information arranged below the adhesive layer 8 and on the substrate 2 is not readable, but is completely covered. Furthermore, the colour appearance of the sealing element 1 is not disturbed by the substrate 2, either.

[0147] Due to the fact that the carrier layer 3 is produced from paper, it is possible to dispose of or, respectively, recycle the planar sealing element 1 together with the substrate 2 (see FIGS. 2A and 2B). That is to say, the substrate 2 will preferably be paper, cardboard, paperboard or corrugated cardboard. Of course, sealing elements 1 according to the invention could also be applied to other substrates 2, such as, for example, glass, metal or plastic, in order to achieve a high level of protection against manipulation by liquids.

[0148] The colour display layer 5 of the functional layers 4 is a commercially available varnish (a UV-curing or water-based varnish) or a printing ink, and the adhesion-controlling layer 6 is a so-called transparent release varnish, which comprises at least one silicone and/or at least one wax.

[0149] The adhesive layer 8 comprises a commercially available adhesive composition. In the present case, this is an acrylic-based or rubber-based pressure-sensitive adhesive, which can be, for example, dispersed, dissolved in solvent or applied as a hot melt. Alternatively, a heat-sealing adhesive could also be used to create a solid connection between the sealing element 1 and the surface of the substrate 2. As an alternative, a wet glue can be used. Other adhesives with advantageous recycling properties can also be used.

[0150] The adhesive layer 8 serves for the attachment of the planar sealing element 1 to any kind of substrate 2. The substrate 2 is preferably a packaging carton. Preferably, the adhesion to the substrate 2 of the sealing element 1 according to the invention by means of the adhesive layer 8 is so strong that the sealing element 1 can only forcibly be detached from the substrate 2 and will remain partially on the substrate 2 even during a detachment process of the sealing element 1, which will be described later.

[0151] In addition, the sealing element 1 can herein also include siliconization on the carrier layer 3 on the side facing away from the functional layers 4. Or the sealing element 1 can have a siliconized cover layer made of paper or plastic on the adhesive layer 8, on the side facing away from the functional layers 4, to provide protection for the adhesive layer. However, the presence of such a siliconization or siliconized cover layer is not mandatory. The siliconized cover layer can be produced from siliconized, highly calendered paper to allow a sealing element 1 to be wound up. The siliconized cover layer simultaneously functions as a support for the sealing element 1 before it is glued to the item to be sealed. This means that the siliconized cover layer allows the sealing element to be stored and delivered in a first state. In an even simpler variant of the sealing element 1 according to the invention, two functional layers 4 are arranged between the carrier layer 3 and the adhesive layer 8, the first functional layer 4 being an adhesion-controlling layer 6 and the second functional layer being a transparent or coloured colour display layer 5. In this case, the carrier layer 3 then serves as a colour display layer, since the carrier layer 3 made of paper is not completely transparent, but is translucent, i.e., appears milky and cloudy, and changes its colour impression between the first 9 and the second state 10.

[0152] FIG. 2 shows that the planar sealing element 1 according to the invention as per FIG. 1 is transferred from a first state 9, see FIG. 2A, to a second state 10, see FIG. 2B. It should be noted that the black colouring merely serves to better illustrate the colour change according to the invention and is not to be equated with the adhesion-controlling layer 6. In the first state 9, a sealing element 1 according to the invention is glued to a substrate 2 and closed, i.e., it has not been tampered with. Therefore, the sealing element 1 appears in its entirety, for example, as a cloudy, dark blue to a viewer who looks at the carrier layer 3 from the outside, since the colour display layer 5 is dark blue. Of course, it cannot be ruled out that the sealing element 1 according to the invention exhibits other colours or even colour combinations in the first state 9 and also in the second state 10. In the present exemplary embodiment, it is therefore a sealing element 1 that appears opaque to a viewer. However, it cannot be ruled out that the functional layers 4 and the adhesive layer 8 have a transparent or, respectively, translucent design so that the sealing element 1 appears see-through or, respectively, translucid to a viewer. Of course, other colours are excluded neither in the opaque nor in the transparent or, respectively, translucent embodiment.

[0153] The sealing element 1 according to the invention is transferred to a second state 10 by being opened. In a second state 10, both a residue 12 and a layer 11 that has been peeled off at least partially are visible. The residue 12 is the parts of the functional layers 4 remaining on the substrate 2 and the adhesive layer 8. The peeled-off layer 11 is the parts of the functional layers 4 that have been detached at least partially and the carrier layer 3.

[0154] As a result of the at least partial detachment of functional layers 4, what can now be seen in the residue 12 because of the existing adhesion-controlling layer 6, which produces an easily detachable connection between the colour display layer 5 and the carrier layer 3, is the dark blue colour layer, which is now coloured a little more intensely dark blue, while the peeled-off layer 11 appears milky-white. This means that the adhesion-controlling layer (the release varnish layer) 6 separates the carrier layer 3 and the colour display layer 5 from each other.

[0155] However, due to the adhesion-controlling layer 6, it also becomes impossible to apply the peeled-off layer 11 back onto the residue 12 without this being noticed. Hence, manipulation is already virtually impossible. If the peeled-off layer 11 is placed back congruently onto the residue 12, the residue 12 would appear in a lighter dark blue when viewed through the peeled-off layer 11.

[0156] The difference between colours is determined by the colour distance Delta E (?E), which represents the coordinate difference in the L*a*b or Luv colour space. Since these colour spaces are visually equidistant, this value can therefore be used for the visible difference between two colours. For this purpose, measurements were conducted in the L*a*b space, as standardized, for example, in EN ISO 11664-4 ColorimetryPart 4: CIE 1976 L*a*b* Colour space. The L*a*b space is a three-dimensional colour space in which the brightness value L* is perpendicular to the colour plane (a*,b*). Each colour in the colour space is defined by a colour location having the Cartesian coordinates {L*, a*, b*}. On the a* axis, green and red lie opposite each other, the b* axis runs between blue and yellow. The L* axis describes the brightness (luminance) of the colour with values from 0 (black) to 100 (white).

[0157] In the first state 9, the present sealing element 1, which comprises opaque functional layers 4 or, respectively, an opaque adhesive layer 8, appears in a cloudy dark blue with the values {L*=47.33, a*=12.49, b*=?33, 22}. In the second state 10, when the peeled-off layer 11 is placed congruently back onto the residue 12 and is glued thereon by pressing through the effect of the adhesion-controlling layer 6 and the peeled-off layer 11 is viewed from above, the latter appears in a dark blue with the values {L*=55.74, a*=6.89, b*=?22.51}, thus, in any case, whiter. The difference is therefore ?L*=8.41, ?a*=?5.6, ?b*=10.71, and the Euclidean distance is thus ?E*Lab=14.72. The layer 11 that has been glued back on therefore appears whiter than the sealing element 1 in the first state 9.

[0158] FIG. 3 schematically shows the structural design of another embodiment of a planar sealing element 1 according to the invention. The design of a sealing element 1 according to the invention as per FIG. 3 is described below in a first direction 25 starting from the carrier layer 3 in the direction of the adhesive layer 8.

[0159] As usual, the planar sealing element comprises a carrier layer 3 and an adhesive layer 8. The carrier layer 3 is produced from calendered paper like in FIG. 1, and the adhesive layer 8 comprises the adhesive composition like in FIG. 1.

[0160] Viewed in the first direction 25, the adhesive layer 8 is the layer furthest away from the carrier layer 3, i.e., all functional layers 4 are arranged between the carrier layer 3 and the adhesive layer 8.

[0161] Viewed in the first direction 25, the carrier layer 3 serves as a colour layer due to its milky appearance in the sense that it changes its colour impression and appears even milkier in the second state 10 in places in which no colour of the colour display layer 5 adheres to it (i.e., in the area of symbol V). The positive of a V, which represents the at least one symbol 18 in the present embodiment of the sealing element 1, is then applied to the carrier layer 3. The symbol 18 is applied as the first adhesion-controlling layer 6. In the present case, the adhesion-controlling layer 6 is a transparent release varnish with at least one silicone and/or at least one wax, like in FIG. 1.

[0162] The first adhesion-controlling layer 6 causes the surface tension to be reduced so that adjacent functional layers 4, in the present case the carrier layer 3, stick to a reduced extent or not at all.

[0163] Furthermore, an intermediate layer 24 is arranged on said adhesion-controlling layer 6. It goes without saying that this intermediate layer 24 is optional and therefore does not necessarily have to be present in every embodiment according to the invention of the invention.

[0164] It also goes without saying that more additional layers might be present, such as further colour display layers and further adhesion-controlling layers.

[0165] The colour display layer 5 as a further layer is then arranged as the next functional layer 4 below the carrier layer 3.

[0166] Since the first adhesion-controlling layer 6 has been applied only in the area of the symbol 18, i.e., of the V, the colour display layer 5 and the intermediate layer 24 unite inseparably with the carrier layer 3 outside of the V. These layers can no longer be detached from each other subsequently when the sealing element 1 is being opened. In the area of the first adhesion-controlling layer 6, the layers 5, 24, in turn, bond together just in an easily detachable manner. It should be noted that, accordingly, the black layer in the figures does not correspond to the adhesion-controlling layer 6, but only serves for better illustration.

[0167] Next, the negative of the symbol 18, i.e., of the V, is arranged as a further adhesion-controlling layer 7 on the colour display layer 5. This adhesion-controlling layer 7 is likewise a transparent release varnish with at least one silicone and/or at least one wax, like in FIG. 1. Optionally, a further colour display layer 17 can be present below the adhesion-controlling layer 7 in order to obtain a special colour effect in the residue 12 (see FIG. 4) and/or to separate the further colour display layer 17 from the adhesive layer 8 if no further carrier layer 26 is present. An optional further carrier layer 26, preferably made of paper, can be provided to reinforce the planar sealing element 1 and could also separate the adhesion-controlling layer 7 from the adhesive layer 8 if no further colour display layer 17 is present.

[0168] The adhesive layer 8 is arranged last.

[0169] The functional layers 4 are therefore only partially inseparably connected to each other, while other functional layers 4 or, respectively, parts thereof are connected to each other just in an easily detachable manner, namely where the two adhesion-controlling layers 6,7 are located.

[0170] Also in connection with this embodiment of a sealing element 1 according to the invention, it should be noted that it can be an opaque sealing element 1, i.e., a sealing element 1 in which the functional layers 4 or, respectively, the adhesive layer 8 has/have an opaque design, or a translucent sealing element, i.e., in which the layers 4, 8 have a translucent design.

[0171] FIG. 4 shows that the planar sealing element 1 according to the invention as per FIG. 3 can be transferred from a first state 9, see FIG. 4A, to a second state 10, see FIG. 4B. It should be noted that the black colouring merely serves to better illustrate the colour change according to the invention and is not to be equated with the adhesion-controlling layer 6. In the first state 9, a sealing element 1 according to the invention is glued to a substrate 2 and closed, i.e., it has not been tampered with, and the symbol 18 is not identifiable for a viewer. Therefore, the sealing element 1 appears in its entirety, for example, as a cloudy, dark blue to a viewer who looks at the carrier layer 3 from the outside. In the present exemplary embodiment, it is therefore a sealing element 1 that appears opaque to a viewer, i.e., a sealing element in which the functional layers 4 and the adhesive layer 8 have an opaque design. However, it cannot be ruled out that the functional layers 4 and the adhesive layer 8 have a transparent or translucent design so that the sealing element 1 appears translucid to a viewer. Of course, it cannot be ruled out that the sealing element 1 according to the invention exhibits other colours or even colour combinations in the first state 9 and also in the second state 10. If the peeled-off layer 11 is placed back congruently onto the residue 12, the residue 12, as viewed through the V (symbol 18) of the peeled-of layer 11, would appear in a dark blue, but no longer in such an intense dark blue, i.e., in a lighter dark blue, as in the first state 9, which is due to the milky-white colouring of the carrier layer 3 or, respectively, in the remaining area of the peeled-off layer 11 where the dark blue colour indeed adheres to the carrier layer 3.

[0172] The difference in the colour impression essentially corresponds to the difference in the brightness values L*, as explained in FIG. 1.

[0173] The sealing element 1 according to the invention is transferred to a second state 10 by being opened. In a second state 10, both a residue 12 and a layer 11 that has been peeled off at least partially can be seen. The residue 12 is the parts of the functional layers 4 remaining on the substrate 2 and the adhesive layer 8. The peeled-off layer 11 is the parts of the functional layers 4 that have been detached at least partially and the carrier layer 3.

[0174] As a result of the at least partial detachment of functional layers 4, the symbol 18 is now visible in the residue 12 or, respectively, in the peeled-off layer 11 because of the two adhesion-controlling layers 6, 7, which produce an easily detachable connection between the colour display layer 5 and the positive of the symbol 18, i.e., the V in the present case, and the carrier layer 3. This means that the first adhesion-controlling layer (the release varnish layer) 6 separates the carrier layer 3 and the colour display layer 5 from each other and provides for the colour design of the symbol 18.

[0175] As already mentioned, the symbol 18 is designed as a V in FIGS. 3 and 4. However, it goes without saying that the symbol can basically have any shape or, respectively, that several symbols 18 can even be combined with one another.

[0176] However, due to the two adhesion-controlling layers 6, 7, it also becomes impossible to apply the peeled-off layer 11 back onto the residue 12 without this being noticed. Hence, unnoticed manipulation is already virtually impossible. In addition, the contrast is significantly enhanced in the second state 10, whereby the indication of a manipulation is facilitated for the user. This is due to the change in the colour distance Delta E (?E) that is visible to a user. This is particularly readily identifiable for a user since the colour distance Delta E (?E) of the section in which, in the second state 10, no colour of the at least one colour display layer 5 adheres is preferably different by 0 to 90, preferably by at least 7 to 50, in the second state 10 when the peeled-off layer 11 is arranged congruently on the residue 12, compared to the first state 9.

[0177] Due to the fact that the carrier layer 3 is furthermore produced from calendered paper, the possibility of manipulation is reduced even further, since paper is indeed tear-resistant enough to serve as a carrier layer 3 for the sealing element 1 according to the invention, but is not tear-resistant enough to be easily removed and, consequently, tampered with. In addition, the carrier layer 3 is deformed when being transferred to the second state 10, since thin paper or, respectively, carrier layers 3 made of paper generally tend(s) to have edges that curl up.

[0178] In addition, there is the solubility of paper in relation to liquids, whereby a manipulation of the sealing element 1 with the help of solvents becomes visible. This means that, if a packaging object provided with the sealing element 1 made of paper according to the invention is placed in water for manipulation purposes, the water can quickly penetrate through the carrier layer 3, whereby at least one of these layers 4, 5, 8 in the wet or moistened state detaches at least partially from the carrier layer 3 made of paper, but without changing from a first state 9 to a second state 10. If the carrier layer 3 is now removed, there will subsequently be a residue 12 and a peeled-off layer 11, with none of the functional layers 4 adhering to the carrier layer 3 at least in parts. If the carrier layer 3 is removed in the wet or damp state, the carrier layer 3 can no longer be connected to the functional layers 4 in such a way that the sealing element 1 can again be transferred functionally from a first state 9 to a second state 10 as soon as it has dried.

[0179] However, if the substrate 2 is a fibrous substrate, such as, for example, corrugated cardboard or carton, it may happen that the complete sealing element in the first state 9 is pulled off or, respectively, torn off the substrate 2 with the uppermost layer of the substrate 2. In this case, the planar sealing element 1 will indeed be functional again after drying, but it will no longer be located on the desired substrate 2 and parts of the substrate 2 will adhere to the adhesive layer 8, which hinders reuse of the sealing element 1.

[0180] In the event that the planar sealing element 1 is transferred from a first 9 to a second state 10 due to moisture, the residue 12 then comprises the adhesive layer 8 and all functional layers 4, while the peeled-off layer 11 comprises only the carrier layer 3 without a functional layer 4 or the carrier layer 3 as well as parts of the functional layers 4. However, subsequently, the carrier layer 3 can no longer be applied to the detached functional layers 4 in such a way that a transfer from the first state 9 to the second state 10 is enabled, since no new connection of the carrier layer 3 to the functional layers 4 can be established.

[0181] However, if the sealing element 1 is dried after moistening without having been transferred from a first state 9 to a second state 10 or otherwise having been damaged or tampered with, the functionality according to the invention is restored so that the sealing element 1 can again be transferred from a first state 9 to a second state 10, whereby the colour effect according to the invention can be perceived.

[0182] Furthermore, in the illustrated exemplary embodiments, it would be conceivable that the planar sealing element 1 according to the invention has a tab (not shown) which is connected to the carrier layer 3. Said tab makes it easier for a user to remove the carrier layer 3 or, respectively, to transfer the sealing element 1 according to the invention from the first state 9 to the second state 10.

[0183] In case it is desired that the peeled-off layer 11 does not separate completely from the remaining planar sealing element 1, an area can be provided at the edge of the sealing element in which area no adhesion-controlling layer 6, 7 is applied so that the colour display layer 5 unites inseparably with the carrier layer 3. Complete removal of the peeled-off layer 11 is therefore only possible by applying greater force, which, however, would normally damage the sealing element 1. The peeled-off layer 11 thus remains on the planar sealing element 1 in an undamaged state. As a result, the disappearance of the sealing element 1 into the environment is reduced. Therefore, the sealing element 1 can likewise be subject to mechanical recycling.

[0184] Furthermore, it is noted that the embodiment variants of the sealing element according to the invention can basically be implemented also with an opaque carrier layer.

LIST OF REFERENCE NUMERALS

[0185] 1 planar sealing element [0186] 2 substrate [0187] 3 carrier layer [0188] 4 functional layers [0189] colour display layer [0190] 6 first adhesion-controlling layer [0191] 7 second adhesion-controlling layer [0192] 8 adhesive layer [0193] 9 first state of the planar sealing element [0194] second state of the planar sealing element [0195] 11 peeled-offlayer [0196] 12 residue [0197] 13 - [0198] 14 - [0199] 15 - [0200] 16 - [0201] 17 additional colour display layer [0202] 18 symbol [0203] 19 - [0204] 24 intermediate layer [0205] first direction [0206] 26 additional carrier layer