Synthetic image device and manufacturing method therefore

Abstract

A synthetic image device (1) comprises an array (10) of line focusing elements (11), an image layer (20) having linear extending cells (22), and a coloured background layer assembly (25). A limited part of the image layer is visible through the array of line focusing elements. Each cell comprises at least three sub-cells (24A-C). The at least three sub-cells having individual visual- contrast creating patterns (21), forming sub-images. Composed images, associated with a set composed by one sub-image from each cell, are visible from different viewing angles. The composed images together present a movement effect. The coloured background layer assembly covers a surface facing away from the image layer. The background layer assembly has a first colouring (28A), visible through the image layer. The first colouring presents a colour varying over the extension of the background layer assembly in registry with movement effects. A producing method is also disclosed.

Description

[0001] SYNTHETIC IMAGE DEVICE AND MANUFACTURING METHOD THEREFORE

[0002] TECHNICAL FIELD

[0003] The present technology relates in general to synthetic image devices and manufacturing methods thereof and in particular to synthetic image devices based on arrays of line focusing elements.

[0004] BACKGROUND

[0005] Synthetic image devices have for a long time been used e.g. as security items on valuable items, such as bank notes, or as eye-catching features, e.g. in labels. Common for these applications is that the synthetic image devices are difficult to copy but may still provide easily detectable features used to verify the authenticity of the item to which it is adhered.

[0006] If synthetic image devices are to be incorporated or attached to thin articles, such as a bank note, the thickness of the synthetic image device has to be small. In synthetic image devices based on arrays of microlenses, the size of the microlenses and the image features of the image layers that the microlenses depict has to be very small. Smaller sizes in turn put higher requests on registration between image features of the image layers and microlenses. The small size also put some restrictions on what manufacturing methods that can be used.

[0007] Many kinds of optical effects have been used, comprising e.g. switching between different images, “unlogical” movement of images or simple animations. Colour shifts have also been used for enhancing different effects.

[0008] In the published European patent EP 2 707 228 Bl, a lenticular lens device is presented in which the image strips present a cyclically repeating sequence from an image of a first form into an image of a second form and then back, upon changing the viewing angle. The combined image sequences present a contiguous variation in the image form. The cyclic change can for instance be an expansion / contraction or a shape change.

[0009] In the published European patent EP 3 307 553 Bl, a manufacturing method for synthetic image devices is disclosed, where a first metal layer acts as a mask layer for any background colour layer. The background colour layer may have different zones of different colours. Since the first metal layer provides the fine geometrical structures, the background layers can be printed by less demands on precision and size.

[0010] In the published international patent application WO 2018 / 037208 Al, a lenticular device having a mask layer is disclosed. The mask layer has transparent pixels defining different images across the lenticular axis. The different images will be viewable in different tilting directions of the lenticular device. The mask layer overlaps a colour layer, in which stripes of different colours are provided in a direction transverse to the lenticular axis. The transparent pixels of the mask layer define which colours of the colour layer that will be seen by the viewer. By having narrow colour lines, narrower than the resolution of the human eye, the colour experienced by the user will be a mix of the colours admitted by the transparent pixels. By selecting the transparent pixel position along the lenticular axis, any mix of the provided colours may be obtained, giving rise to multicoloured images. However, there has to be a very accurate aligning between the mask layer and the colour layer. Furthermore, the provision of different colours also leads to a contrast that is worse than for monochrome images.

[0011] In the published US patent application US 2023 / 0166556 Al, manufacturing of moire magnification devices is presented. Here it is mentioned that the colour of an image visible for a viewer preferably is constant or invariable concerning hue, saturation and / or transparency, but that different colours can be utilized in different parts of the device. There are still requests for utilizing the optical effects of a synthetic image device in even more eye-catching ways.

[0012] SUMMARY

[0013] A general object is to enhance the appearance of optical effects in thin synthetic image devices.

[0014] The above object is achieved by methods and devices according to the independent claims. Preferred embodiments are defined in dependent claims.

[0015] In general words, in a first aspect, a synthetic image device comprises an array of line focusing elements, an image layer and a coloured background layer assembly. The line focusing elements are lenticular lenses or linear rows of non-lenticular lenses. The line focusing elements extend in a longitudinal direction. The image layer has linearly extending cells extending in the longitudinal direction and having a width in a transverse direction, perpendicular to the longitudinal direction, that is equal to a pitch of the array of line focusing elements in the transverse direction. The image layer is positioned in parallel to the array of line focusing elements and at a distance relative to the array of line focusing elements such that a limited part of the image layer becomes visible when the image layer is viewed through the array of line focusing elements. Each cell comprises at least three sub-cells, provided side-by-side in the transverse direction. The at least three sub-cells of the image layer have individual visual-contrast creating patterns, forming sub-images. At least three composed images, each associated with a set composed by one sub-image from each cell, are visible from different viewing angles in the transverse direction. The at least three composed images together present a movement effect upon changing the viewing angles. The coloured background layer assembly covers a surface of the image layer facing away from the array of line focusing elements. The background layer assembly has a first colouring, visible from the image layer. The first colouring presents a colouring variation over the extension of the background layer assembly. The colouring variation is provided in registry with the movement effect of the composed images.

[0016] In a second aspect, a method of producing a synthetic image device comprises providing an array of line focusing elements, directly or via an additional film, to a first surface of a base film. The line focusing elements are lenticular lenses or linear rows of non-lenticular lenses. The line focusing elements extend in a longitudinal direction. An image layer is provided to a second surface, opposite to the first surface, of the base film. The image layer is provided to have linearly extending cells extending in said longitudinal direction and having a width in a transverse direction, perpendicular to said longitudinal direction, that is equal to a pitch of said array of line focusing elements in said transverse direction. A thickness of the base film and the additional film(s), if any, and the pick-up film, if any, is adapted such that a limited part of the image layer becomes visible when the image layer is viewed through the array of line focusing elements. Each cell is provided to comprise at least three sub-cells, provided side-by side in the transverse direction. The at least three sub-cells of the image layer have individual visual-contrast creating patterns, forming sub-images. At least three composed images, each associated with a set composed by one sub-image from each cell, are visible from different viewing angles in the transverse direction. The at least three composed images together present a movement effect upon changing the viewing angles. A surface of the image layer facing away from the array of line focusing elements is covered with a coloured background layer assembly. The background layer assembly has a first colouring, visible from the image layer. The covering further comprises presenting the first colouring with a colouring variation over the extension of the background layer assembly. The covering further comprises providing the colouring variation to be in registry with the movement effect of the composed images. One advantage with the proposed technology is that an easily apprehended combined movement and color effect can be presented for a viewer. Other advantages will be appreciated when reading the detailed description.

[0017] BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The invention, together with further objects and advantages thereof, may best be understood by making reference to the following description taken together with the accompanying drawings, in which:

[0019] FIG. 1A schematically shows a top view of an image layer of a synthetic image device according to the prior art; and

[0020] FIG. IB schematically shows a side view of an array of line focusing elements according to the prior art;

[0021] Fig. 1C schematically shows an exemplifying synthetic image device according to the prior art;

[0022] Fig ID schematically shows another top view of an image layer of a synthetic image device according to Fig 1C;

[0023] Fig 1 E schematically shows another exemplifying synthetic image device according to the prior art;

[0024] Fig IF schematically shows another top view of an image layer of a synthetic image device according to Fig IE;

[0025] Fig 1G schematically shows another exemplifying synthetic image device according to the prior art;

[0026] Fig 2A schematically shows an exemplifying embodiment of a synthetic image device according to the present invention;

[0027] Fig 2B schematically shows a top view of an image layer of a synthetic image device as seen through the viewing angle shown in Fig 2A;

[0028] Fig 2C schematically shows another exemplifying embodiment of a synthetic image device according to the present invention;

[0029] Fig 2D schematically shows a top view of an image layer of a synthetic image device as seen through the viewing angle in Fig 2C;

[0030] Fig 2E schematically shows another exemplifying embodiment of a synthetic image device according to the present invention; Fig 2F schematically shows a top view of an image layer of a synthetic image device as seen through the viewing angle in Fig 2E;

[0031] Fig 3 A schematically shows an overlay illustration of three different views of another exemplifying embodiment of a synthetic image device according to the present invention;

[0032] Fig 3B schematically shows a top view of a coloured background layer assembly being a part of the synthetic image device in Fig 3A;

[0033] Figs 3C-E schematically show three views of the synthetic image device according to Fig. 3A;

[0034] Fig 4 schematically shows another exemplifying embodiment of a synthetic image device according to the present invention;

[0035] Fig 5A schematically shows an exemplifying embodiment of a synthetic image device according to the present invention having two colours in a coloured background layer assembly;

[0036] Fig 5B schematically shows another exemplifying embodiment of a synthetic image device according to the present invention having two colours in a coloured background layer assembly;

[0037] Fig 5C schematically shows another exemplifying embodiment of a synthetic image device according to the present invention having translucent ink in the image layer;

[0038] Fig 6 schematically shows another exemplifying embodiment of a synthetic image device according to the present invention; and

[0039] Fig 7 is an exemplifying flow chart illustrating a method of producing a synthetic image device.

[0040] DETAILED DESCRIPTION

[0041] Throughout the drawings, the same reference numbers are used for similar or corresponding elements.

[0042] For a better understanding of the proposed technology, it may be useful to begin with a brief overview of the basic features of a synthetic image device based on an array of line focusing elements. Figure 1A illustrates a view of a part of an image layer 20 of a synthetic image device 1. The image layer 20 has linearly extending cells 22 extending in a longitudinal direction L. The cells 22, each has a width W in a transverse direction T, perpendicular to the longitudinal direction L. Each cell 22 comprises in this embodiment three sub-cells 24A, 24B, 24C, provided side- by side in the transverse direction. In other embodiments, more than three sub-cells can be used. The sub-cells 24A, 24B, 24C of the image layer 20 have individual visual-contrast creating patterns, preferably patterns of micro geometrical structures 21, forming sub-images, in the figure illustrated as hatchings. The micro geometrical structures 21 may cover the entire sub-cell or a part thereof. Note that part illustrated in the figure is only a very small portion of the entire synthetic image device and furthermore that the size of the features in the figure is enormously exaggerated compared to typical synthetic image devices, where the width W of the cells 22 typically may be less than 200pm, and preferably much less than that. These figures are provided for illustrating the basic operation.

[0043] Figure IB illustrates a part of an array 10 of line focusing elements 11 of a synthetic image device 1. In this embodiment, the line focusing elements 11 are lenticular lenses 12. As will be discussed further below, the line focusing elements 11 may alternatively be linear rows of non-lenticular lenses. The line focusing elements extend in the longitudinal direction L and a pitch of the array of line focusing elements 11 in the transverse direction T is essentially equal to the width W of the cells in the image layer 20, c.f. figure 1A.

[0044] In a preferred embodiment, the synthetic device 1 has a thickness smaller or equal to 200 pm. Preferably, the synthetic device 1 has a thickness smaller or equal to 50 pm.

[0045] In a preferred embodiment, the width W in the transverse direction T of the cells 22 is smaller or equal to 100 pm. Preferably, the width W in the transverse direction T of the cells 22 is smaller or equal to 20 pm. Most preferably, the width W in the transverse direction T of the cells 22 is smaller or equal to 10 pm.

[0046] As illustrated in a cross-sectional view in Figure 1C, in the synthetic image device 1, the image layer 20 is positioned in parallel to the array 10 of line focusing elements 11 and at a distance D relative to the array 10 of line focusing elements 11 such that a limited part of the image layer 20 becomes visible when the image layer 20 being viewed through the array 10 of line focusing elements 11. The dotted lines in the figure illustrates a viewing direction from the left side, which selects the sub-cells 24C to be viewed through the array 10 of line focusing elements 11.

[0047] The result of such a viewing angle is illustrated in Figure ID. The figure illustrates the appearance of the synthetic image device 1 as seen from the side of the array 10 of line focusing elements 11. The respective sub-cells of the different cells of the image layer are viewed to occupy the entire width of the associated focusing element 11, forming a slightly enlarged sub-image 24C*. A composed image 23 is thus created and associated with a set composed by one sub-image 24C* from each cell of the image layer. The composed image 23 in this figure is thus visible when the image layer is viewed through the array 10 of line focusing elements 11 in the angle in the transverse direction T illustrated in Figure 1C.

[0048] Figure IE illustrates the synthetic image device 1, indicated to be viewed in another angle in the transverse direction T. In this viewing angle, the array 10 of line focusing elements 11 here depicts the sub-cells 24B. The result is illustrated in Figure IF, where a new composed image 23 is seen based on enlarged sub-image 24B*.

[0049] Figure 1G illustrates the synthetic image device 1, indicated to be viewed in yet another angle in the transverse direction T. In this viewing angle, the array 10 of line focusing elements 11 here depicts the sub-cells 24A. The result is illustrated in Figure 1H, where a new composed image 23 is seen based on enlarged sub-image 24A*.

[0050] As a summary, the image layer 20 is positioned in parallel to the array 10 of line focusing elements 11. The distance D relative to the array 10 of line focusing elements 11 is such that a limited part of the image layer 20 becomes visible when the image layer 20 is viewed through the array 10 of line focusing elements 11. Composed images 23 are seen, in this embodiment three, where each composed image 23 is associated with a set composed by one sub-image 24A-C from each cell 22. The composed image 23 are thus visible from different viewing angles in the transverse direction T.

[0051] As mentioned above, the line focusing elements 11 can be constituted by linear rows of non-lenticular lenses 13, as illustrated in Figure II. The non-lenticular lenses 13 will, in addition to the focusing effect in the transverse direction T, also provide a focusing effect in the longitudinal direction. However, if the subimages 24A-C have a variation in the longitudinal direction L that has typical sizes that are larger than the size of the non-lenticular lenses 13, this will not influence the composed image considerably. Thus, for composed images with large structures non-lenticular lenses 13 will give essentially the same result as line focusing elements 11 constituted by lenticular lenses.

[0052] The composed images 23 can in a general application be any type of composed images 23. If the composed images 23 are considerably different, the viewer will experience a relatively abrupt shift between the different composed images 23 when tilting the synthetic image device 1 in the transverse direction T. However, in many applications of security, some type of moving images are used. This can be achieved by having composed images that are related to each other, changing in position, direction, size and / or shape in small steps between neighbouring sub-cells. In the present technology, the composed images, at least three, together present a movement effect upon changing the viewing angles. Such a movement effect could e.g. be grow, shrink, rotation, translation etc. The figures 1A- 1I illustrate only four cells and four line focusing elements in a very enlarged scale for illustrational purpose. However, in a typical synthetic image device, there are typically hundreds or thousands of cells and corresponding line focusing elements.

[0053] With reference to Figure 2A, a first embodiment of a part of the synthetic image device 1 of the present invention is illustrated. Similarly to the prior art described above, the synthetic image device 1 in Figure 2A, the image layer 20 is positioned in parallel to the array 10 of line focusing elements 11 and at a distance D relative to the array 10 of line focusing elements 11 such that a limited part of the image layer 20 becomes visible when the image layer 20 being viewed through the array 10 of line focusing elements 11. The dotted lines in the figure illustrates a viewing direction from the left side, which selects the sub-cells 24C to be viewed through the array 10 of line focusing elements. Further, the synthetic image device 1 illustrated in Figure 2A comprises a coloured background layer assembly 25 which is applied on a surface of the image layer 20 facing away from the array 10 of line focusing elements 11. The coloured background layer assembly 25 has a first colouring 28A, visible from the image layer 20. In this embodiment, the first colouring 28A presents a colour intensity, which in this exemplifying embodiment, is represented by different distances in the hatching. The colour intensity of the first colouring 28A varies over the extension of the coloured background layer assembly 25, and in this particular embodiment the colour intensity varies in the transverse direction T as can be seen by the shifting hatching distances. On the right side of the coloured background layer assembly 25, the colour intensity is high, and on the left side of the coloured background layer assembly 25 the colour intensity is low. Further, the colour intensity of the first colouring 28A in Figure 2A, varies continuously over the extension of the background layer assembly 25. Put differently, in the transverse direction over the extension of the coloured background layer assembly 25 from the right side to the left side, the colour intensity is decreasing continuously. Moreover, in the transverse direction over the extension of the coloured background layer assembly 25 from the left side to the right side the colour intensity is increasing continuously. This is illustrated by the shifting hatching distances in Figure 2A. Since the first colouring 28A is visible through the image layer 20, when there is no micro geometrical structures present, the first colouring 28A and its colour intensity variation, will be visible through some of the subcells 24A, 24B, 24C in the image layer 20. In Figure 2A, a set of sub-cells 24C are depicted by the array 10 of line focusing elements 11 due to the specific viewing angle and thus forming a set of sub-images for a viewer. The composed image 23 is created from this set of sub-images seen through the array 10 of line focusing elements 11 in the viewing angle in Figure 2A. Since the first colouring 28A is visible through image layer 20 at least for the cell at the far right side, the first colouring 28A contributes in forming the set of sub-images. The resulting composed image 23 will be coloured in areas not being occupied by any image and have a colour intensity variation according to the first colouring 28A and its colour intensity variation over the plane of the synthetic image device 1.

[0054] The first colouring may, as an alternative or complement, present other types of colouring variations. For instance, the spectral distribution of the first colouring may vary over the extension of the coloured background layer assembly. Other alternatives are discussed further below.

[0055] The interface between the image layer 20 and the coloured background layer assembly 25 is shown as a flat surface in Figure 2A. If the visual-contrast creating patterns 21 are micro geometrical structures, this interface could typically not be flat, but follow the geometry of the micro geometrical structures. Depending on the nature of the background layer assembly 25, the visual-contrast creating patterns 21 can be partially or totally coated by the coloured background layer assembly 25. In some cases, the visualcontrast creating patterns 21 can also be embedded in the coloured background layer assembly 25. Alternatively, one or more transparent or semitransparent layers can also be arranged between the image layer 20 and the coloured background layer assembly 25.

[0056] The resulting composed image 23 of such viewing angle as in Figure 2A, is illustrated with reference to Figure 2B. The dotted horizontal line corresponds to the position of the cross-section of Figure 2A. The figure 2B illustrates the appearance of the synthetic image device 1 as seen from the side of the array 10 of line focusing elements 11. The composed image 23 is created in the same way as described for the composed image 23 in Figure ID, i.e. the respective sub-cells of the different cells of the image layer are viewed to occupy the entire width of the associated focusing element 11, forming a slightly enlarged subimage 24C*. In areas in the cells where no micro geometrical structures are present, the background layer assembly 25 becomes visible and contributes to an area 26 of the sub-image24C*. A composed image 23 is thus created and associated with a set composed by one sub-image 24C* from each cell of the image layer. The composed image 23 in Figure 2B is thus visible when the image layer is viewed through the array 10 of line focusing elements 11 in the angle in the transverse direction T illustrated in Figure 2A. A difference in this embodiment compared to the prior art is that in each sub-cell 24A, 24B, 24C of each cell 22 in the image layer 20 where micro geometrical structures are missing, a certain colour intensity of the first colouring 28A is visible through the image layer 20. This is because the coloured background layer assembly 25 covers the surface of the image layer 1 facing away from the array 10 of line focusing elements 11. Thus, the first colouring 28A and the colour intensity variation are visible through the image layer 20 and is contributing to the forming the composed image 23. The underlaying colour intensity is thus be perceived in parts of each associated composed image 23 associated to specific viewing angles.

[0057] As shown in Figures 2A and 2B, the colour intensity of the first colouring 28A may be increasing or decreasing over the area of the synthetic image device. In synthetic image devices having composed images that together present a movement effect upon changing the viewing angles, it has been found that an eye-catching effect may be enhanced by use of background colours. If the colour intensity variation of the background layer assembly 25 is provided in registry with the movement effect of the composed images 23, a viewer will experience the movement effect more powerful.

[0058] This means that the variation of the colour intensity of the background coloured layer assembly is not primarily restricted to any particular direction. Rather, in different embodiments as will be discussed further, the colour intensity of the coloured background layer assembly 25 may vary in any direction of a plane of the coloured background layer assembly 25 as long as it is in registry with a direction of a movement effect of the series of combined images 23 provided.

[0059] Figure 2C illustrates a synthetic image device 1 indicated to be viewed in another angle in the transverse direction T. As already described for the embodiments above, different viewing angles of the array 10 of line focusing elements 11 depicts different sub-cells 24A, 24B, 24C, forming a set of subimages* which results in that the user perceives different composed images depending on the set of sub-images. Since the first colouring 28A of the coloured background layer assembly only is seen at places where the image layer 20 lacks micro geometrical structures, different colour intensities of the first colouring 28A may appear depending on the appearance of the different sub-cells 24 contributing to the composed images 23 viewed from specific angles in the transverse direction T. In the embodiment illustrated in Figure 2C, the sub-cells 24B are depicted as a result of the viewing angle specified by the dotted lines. Thus, a resulting composed image 23 will be formed and associated by a set of sub-images associated with sub-cells 24B. Since the sub-cells 24B of the two cell at the left side lacks micro geometrical structures, the first colouring 28A with its colour intensity at that location will be visible in the composed image 23. The resulting composed image 23 of the indicated viewing angle in Figure 2C is illustrated with reference to Figure 2D. The respective sub-cells of the cells of the image layer are viewed to occupy the entire width of the associated focusing element 11, forming a slightly enlarged part image 24B*. The composed image 23 in Figure 2D, is associated with a set composed of subimages 24B* associated to each sub-cell 24B depicted by the viewing angle of the image layer 22 in Figure 2C.

[0060] The composed image 23 acts as a discriminator or control layer for presenting the background colour. The first colouring of the background layer assembly 25 covers the surface of the image layer 20, however, corresponding areas 26A and 26B, where the first colouring 28A is seen by the viewer are restricted to areas not occupied by the composed image 23. In area 26A, a high intensity of the first colouring 28A is experienced, whereas in area 26B, a low intensity of the first colouring 28A is seen by the viewer. As can be seen, the respective composed image 23 in Figure 2B and 2D are different since the viewing angles in Fig 2A and 2C depicts different sub-cells 24, forming different set of subimages 24*. The sub-images also decide what parts of the coloured background layer assembly 25 that are seen in the respective composed image 23.

[0061] When comparing the images seen in Figure 2B and 2D, there is a difference in position of the depicted triangle, causing an impression of a movement in the direction to the left in the figures. The composed images together present a movement effect upon changing the viewing angles. The colour intensity variation of the background layer assembly 25 is provided in registry with the movement effect of the composed images 23, i.e. the background intensity decreased in the direction of the movement of the depicted triangle. A viewer will thus experience the movement effect in a more powerful way.

[0062] In the above embodiments, the colour intensities of the coloured background layer assembly 25 have varied continuously. However, the colour intensity of the first colouring 28A of the coloured background layer assembly 25 may also vary non-continuously over the image layer 20. In yet another embodiment illustrated in Figure 2E, the colour intensity of the first colouring 28A in the coloured background layer assembly 25 varies stepwise. However, regardless of whether the intensity variation is continuous or stepwise, a main gradient direction is present.

[0063] The resulting composed image 23 of the exemplifying embodiment shown in Figure 2E is illustrated in Figure 2F. In the composed image 23, two areas 26C and 26D of the first colouring are seen. It can furthermore be seen that the colour intensity of the first colouring varies between the two areas 26C, 26D, according to the intensity variation of the underlying coloured background layer 25.

[0064] As in previous description, in the figures 2A-2F only four cells and four line focusing elements are illustrated and in a very enlarged scale. This is for illustrational purposes. However, in a typical synthetic image device, there are typically hundreds or thousands of cells and corresponding line focusing elements.

[0065] As mentioned above, the eye-catching property of a movement effect caused by a series of combined images 23 can be enhanced by a background colour behaviour. In Figure 3A is a synthetic image device 1 illustrated. In this illustration, three composed images 23D, 23E and 23F as seen in three different viewing angles are indicated. In reality, these three images cannot be seen at the same time. However, when the synthetic image device 1 is tilted, the appearance may switch between these images, which in turn gives an impression of a movement, illustrated in the figure by the arrows.

[0066] Figure 3B illustrates an associated coloured background layer assembly 25. Here the first colouring 28A is presented with differing intensities over the surface. In this embodiment, the highest intensity is provided in the middle of the coloured background layer assembly 25, and the intensity decreases outwards. There is a thus an intensity gradient, illustrated by the arrows in the figure. One can here notice that the gradient direction is in registry with the movement direction as illustrated in Figure 3A.

[0067] Figure 3C illustrates the synthetic image device 1 as seen in one viewing direction. A composed image 23D in the shape of three concentric rings is seen. Parts of the coloured background may be distinguished around the rings. Figure 3D illustrates the synthetic image device 1 as seen in another viewing direction. Now, the composed image 23E is visible, being three concentric rings of smaller sizes, respectively (meaning that each of the three rings is smaller than the corresponding ring in figure 3C). Again, parts of the coloured background are visible around the rings, these parts showing however colouring densities different than the parts in figure 3C. Figure 3E illustrates the synthetic image device 1 as seen in yet another viewing direction. The composed image 23F is now seen, being three concentric rings of even smaller sizes, respectively. Even in this case, parts of the coloured background are visible around the rings, these parts showing colouring densities different than the parts in figures 3C and 3D. The transformation from the composed imaged 23D via the composed image 23E to the composed image 23F gives an impression of shrinking rings. This shrinking is associated with a movement directed towards the middle of the synthetic image device 1. This direction is in registry with the intensity gradient direction of the coloured background layer assembly 25, in each part of the surface of the synthetic image device 1.

[0068] In other words, in one embodiment, the colour intensity variation is provided in registry with the movement effect of the composed images.

[0069] When tilting the synthetic image device 1, shrinking rings are experienced. At the same time, the areas between the rings are also experienced by the user as shrinking. In other words, these areas can be regarded as images with movement, the new background being the areas defined by the rings. As these images show a geometrical change coordinated with a colour intensity variation upon tilt, they create a powerful eye-catching effect. For a simple image animation, such as shrinking rings, a local movement direction can easily be determined. However, for more complex image objects, the movement in each separate point may vary a lot. In such cases, an average movement direction for a part image can be used as association for the intensity variation.

[0070] The enhancing effect of the intensity variation is not extremely dependent on that the directions are perfectly aligned. A gradient direction of the background layer assembly may differ from the direction of an associated movement. It is presently considered that a deviation of 30 degrees still will give an enhancement effect.

[0071] In other words, if the movement effect has, within a number of limited image part-areas, a respective associated movement direction, the gradient direction of the colour intensity variation of the background layer assembly in the respective image part areas preferably coincides within 30 degrees, more preferably within 15 degrees, with the associated movement direction.

[0072] In one embodiment, the colouring variation, e.g. the colour intensity variation, is provided in registry with the movement effect of the composed images in the longitudinal direction as well as in the transversal direction.

[0073] For the case illustrated in figures 3A-E, both the colour intensity variation of the background layer assembly and the movement direction in the composed images have a radial component, each having its own center. To obtain a satisfying optical effect, both centers must be registered in the longitudinal direction L and the transversal direction T. The requirement for this registration is, however, not in the micrometer scale, which would make the fabrication difficult. For a typical image size of a few millimeters, it was found that a registration in the order of 1-2 mm, or preferably 0, 1-0,2 mm is sufficient to create an appealing optical effect. The same registration is also needed when the movement effect is a rotation. For other movement effects, such as for example translations, these position registration requirements do not apply, just registration of directions.

[0074] The coloured background layer assembly 25 can be defined using common printing techniques including flexography, rotogravure, offset, typography, screen printing but also inkjet or laser printing. Several colors can be defined using these techniques, with the possibility of printing each color in register. In register means that each color can be applied at a precise position towards the other colors and possibly toward the image layer 20. In case of flexography or rotogravure printed in line, the registration between each color is in the range of 100 gm to 250 gm.

[0075] In one embodiment, flexography can be used to print up to four colors (quadrichromy) using 150 Ipi stochastic raster. The liquid ink is stored into cells of a ceramic anilox roller, transferred to raised areas of a polymer plate and finally transferred to the substrate. The volume of the anilox cells and the density of the printed dots determine the final experienced color.

[0076] With reference to Figure 4 a synthetic image device 1 is illustrated, where the colour intensity variation of the coloured background layer assembly 25 is provided by varying a density of the colour dots, e.g. printed dots. (In the figure, the illustrated density of the spots within the coloured background layer assembly 25 represents the density of spots as viewed from the backside of the synthetic image device, i.e. as seen from beneath in the figure.) In such an embodiment, the first colouring 28A of the coloured background layer assembly 25 is composed of colour dots 27. The colour dots 27 may be provided in different sizes by varying the diameter of the colour dots 27. Alternatively, the density of colour dots may be varied by changing the distance between the colour dots 27. In either approach, the density of colour dots 27 in a certain sub-cell 24 is varied. Further, in Figure 4 the density of colour dots 27 varies over the coloured background layer assembly 25. This variation may be continuous or, as illustrated, stepwise. In such an embodiment, the amount of colour dots 27 contained in an image-area is either increased or decreased in a direction of a plane of the coloured background layer assembly 25.

[0077] In other words, in one embodiment, the colour intensity variation of the background layer assembly is provided by varying a density of colour dots. In a further embodiment, the density of colour dots varies continuously over the background layer assembly. In another embodiment, the density of colour dots varies in density steps over the background layer assembly.

[0078] Furthermore, the colour dots 27 may have different geometric shapes, such as circular shapes, ellipsoid shapes, oval shapes, polygonal shapes or any other geometric shape. The skilled person in the art realizes that there are uncountable variations of shapes that may be utilized. The shapes of the colour dots may also be utilized to vary the density of colour dots in a certain image part-area. A larger amount of colour dots of a certain geometric shape may fit non-overlapping inside a cell 22 compared to another geometric shape, thereby giving a different average colour density. Alternatively, to further increase the amount of colour dots contain inside a cell 22, a combination of different geometric shapes may be utilized, such that e.g. some colour dots may be circular shaped, while some colour dots may be oval shaped or polygonal shaped.

[0079] The background layer assembly 25 which covers a surface of the image layer 20 facing away from the array of line focusing elements 10, may further comprises a second colouring 28B different from the first colouring 28A. This is further illustrated in yet another embodiment shown in Figure 5A. The second colouring 28B of the background layer assembly 25 is also visible in the image layer 20. The second colouring 28B and the first colouring 28A may be two significantly different colours, such as e.g. green and red, or blue and yellow. However, the second colouring 28B and the first colouring 28A may also be colours found close to each other in a color scheme, such as e.g. two shades of green, or two shades of red. In the exemplifying embodiment of the synthetic image device 1 shown in Figure 5A, the coloured background layer assembly 25 is composed of a first colour layer 25’ comprising the first colouring 28A, and a second colour layer 25” comprising the second colouring 28B. However, in other embodiments, such as e.g. the one illustrated in Figure 5B, the first colouring 28A and second colouring 28B may be comprised in the same colour layer.

[0080] In the present embodiment, the second colour 28B in the second colour layer 25” have a colour intensity variation. The colour intensity variation of the second coloring 28B may vary over the extension of the background layer assembly 25. The second colouring 28B may comprise all aspects described for the first colouring 28A. However, the colour intensity variation of the second colouring 28B may be different from the colour intensity variation of the first colouring 28A. For example, the colour intensity of the second colouring 28B may vary continuously, or in density steps over the coloured background layer assembly 25. In Figures 5A and 5B, the colour intensity variation of the first colouring 28A and the colour intensity variation of the second colouring 28B varies continuously in opposite directions. In these embodiments, as illustrated, the intensity of the second colouring 28B increases from the right side to the left of the coloured background layer assembly 25, whilst the intensity of the first colouring 28A increases from the left side to the right of the background layer 25.

[0081] Even though the colour intensity variation of the second coloring 28B is different from the colour intensity variation of the first colouring 28A, the colour intensity variation of the second colouring 28B also varies in registry with the movement effect of the composed images 23. Furthermore, in another embodiment the colour intensity variation of the first colouring 28A and the colour intensity variation of said second colouring 28B are in mutual registration, and thus also in registry with the movement effect of the composed images 23. By having access to two colours, the background-promoted enhancement of the movement effect may also be based on a colour change. The ring arrangement of Figs. 3A-E can be used as an example system and provided with a background layer assembly 25 having two colours. For the first colour, the highest intensity is provided in the middle of the coloured background layer assembly 25, and the intensity decreases outwards, as shown in figure 3B. For the second colour, the lowest intensity is provided in the middle of the coloured background layer assembly 25, and the intensity increases outwards. When the user experiences the rings - and the areas between the rings - to shrink, he also experiences a coordinated change of colour or hue for the areas between the rings.

[0082] In another embodiment, the colouring variation in the coloured background layer assembly 25 can be created by a so-called colour-shifting layer. Such layer can for example be produced by using liquid crystals or thin-film structures composed of several sub-layers of metallic and dielectric materials. This embodiment however presents some limitation in the choice of the direction for the colouring variation, reducing the design freedom for the optical effects.

[0083] In one embodiment, the visual-contrast creating patterns of the image layer and the coloured background layer assembly may cooperate in providing colour effects. Figure 5C illustrates a synthetic image device 1 in which the visual-contrast creating patterns 21 are created by coloured ink that is translucent. The coloured background layer assembly 25 has another colour with a changing intensity. In areas where there are no parts of the visualcontrast creating patterns 21, the coloured background layer assembly 25 will be visible in the same manner as previous embodiments. However, in the subcell where the visual-contrast creating pattern 21 is present, the colour of the visual-contrast creating pattern 21 will, due to its translucent properties, be mixed with the colour of the coloured background layer assembly 25 below. If, as an example, the visual-contrast creating pattern 21 is made in a blue colour and the coloured background layer assembly 25 has a yellow colour, the composed image will have a blue colour at the parts where the coloured background layer assembly 25 has a low intensity. However, the composed image will present a gradually change into a green colour when going to parts where the background layer assembly 25 has a high intensity, since the combination of a blue and yellow will give a green appearance. In Figure 5C, the light coming from the left-most cell, illustrated by the hatched area 30A, will have an almost blue colour. The light coming from the second left-most cell, illustrated by the hatched area 30B, will have a green-blue colour. The light coming from the second right-most cell, illustrated by the hatched area 30C, will have a green colour. At the same time, the yellow colour, illustrated by the hatched area 30D, will be seen in areas where there is no visualcontrast creating pattern 21. Such combinations of colour intensity changes and pattern colour changes will increase the optical effect for a viewer even more.

[0084] Figure 6 illustrates the synthetic image device 1, in yet another embodiment where the background layer assembly 25 further comprises an additional layer 29. The first colouring 28A is situated between the additional layer 29 and the array 10 of line focusing elements 11. This additional layer can present different properties. For example, the additional layer 29 may be an opacifying layer providing the synthetic image device 1 with additional contrast and clarity, as it will prevent light from passing through the synthetic image device 1. This opacifying layer can for example be applied by rotogravure, or flexography or any suitable print technique. An opacifying layer may e.g. be a layer of a metal or a metal alloy. Alternatively, the opacifying layer may comprise a metallic ink. The metal or metal alloy increases the opacity of the opacifying layer, and potentially increasing the reflectivity of the surface of the opacifying layer. The metal or metal alloy may e.g. be aluminum. However, the person skilled in the art realizes that there are numerous of different metals and metal alloys that are useful for the purpose of increasing opacity and / or reflectivity of the opacifying layer. In another embodiment, the opacifying layer may comprise a metallic ink. Such metallic ink comprises metallic pigments. Using a metallic ink may be advantageous, apart from also having opaque and reflectivity enhancing properties, because it may give the opacifying layer a coloured or tinted appearance. For example, a mixture of zinc and copper pigments may give the filler layer a golden appearance, whilst silver pigments will give the filler layer a silver appearance.

[0085] The opacifying layer may also be composed of several sub-layers of metallic and dielectric materials producing a colour shifting effect. It is well known in the art that structural colors can be achieved by using a Fabry-Perot cavity constituted of a metal-dielectric-metal thin-film stack. The colour shifting happens when the angle of incidence of the light is changed, for example upon tilting of the optical device.

[0086] The additional layer 29 can also comprise security elements like fluorescent, phosphorescent, IR detectable and / or magnetic pigments. Of course, several additional layers 29 with different properties can be applied onto the background layer assembly 25.

[0087] The visual-contrast creating patterns 21 of the sub-cells 24 in the synthetic image device 1 illustrated in e.g. Figure 2A, may be provided as at least one of: printed ink, ink filled or coated recesses, deposit metal, holographic structures, photo-chromatic projections, laser engraving and refractive index differences, or a combination thereof. In yet another embodiment, the visualcontrast creating patterns 21 have a vertical dimension of 0.1 - 10 pm, preferably 1 - 4 pm.

[0088] The visual-contrast creating patterns 21 of the sub-cells 24 in the synthetic image device 1 of the present invention, may also have a colour. This colour is different from the first colouring. In such an embodiment, a contrast between the visual-contrast creating patterns 21 and the first colouring of the coloured background layer assembly 25 is enhanced.

[0089] To even further enhance the contrast between the visual contrast-creating patterns 21 and the coloured background layer assembly 25, the visualcontrast creating patterns 21 may also have a colour that is one of black, white and metallic. The colour for the contrast creating patterns 21 may also vary over the device. Furthermore, the visual-contrast creating patterns 21 may be opaque. In any of these embodiments the contrast between the visual-contrast creating patterns 21 and the background layer assembly 25 is enhanced.

[0090] However, the visual-contrast creating patterns may also be at least partially translucent. This may be advantageous because it allows to adjust the contrast between the visual-contrast creating patterns and the first colouring and / or the second colouring of the coloured background layer assembly 25. In such embodiments, the first colouring will at least to a part penetrate through the visual-contrast creating patterns. The combined images will then have the appearance of partly translucent images, which partly diffuse a background colour.

[0091] Moreover, an embodiment of the synthetic image device 1 may further comprising a top coating 19, as indicated by a dotted line in Figure 6, arranged to cover a surface of the array of line focusing elements 10 facing away from the image layer 20. A top coating 19 is advantageous because it protects the synthetic image device 1 from debris, light-degradation and other environmental degradation.

[0092] With reference to Figure 7, a method of producing a synthetic image device 1, according to some embodiments, is illustrated. The method 1000 may for example be used to produce a synthetic image device 1 as described above with reference to previous figures.

[0093] The method 1000 comprising the steps of: At a first step 1010, providing, an array of line focusing elements, directly or via an additional film, to a first surface of a base film. The line focusing elements being one of lenticular lenses and linear rows of non-lenticular lenses, and the line focusing elements extend in a longitudinal direction.

[0094] At a second step 1020, the method 1000 comprises, providing, an image layer, directly or via a pick-up film, to a second surface, opposite to said first surface, of said base film. The image layer is provided to have linearly extending cells extending in said longitudinal direction and having a width in a transverse direction, perpendicular to the longitudinal direction, that is equal to a pitch of the array of line focusing elements in the transverse direction. A thickness of the base film and the additional film, if any, and the pick-up film, if any, is adapted such that a limited part of the image layer becomes visible when the image layer being viewed through the array of line focusing elements.

[0095] Each cell is provided to comprise at least three sub-cells, provided side-by side in the transverse direction. The at least three sub-cells of the image layer have individual visual-contrast creating patterns, preferably patterns of micro geometrical structures, forming sub-images. The at least three composed images, each associated with a set composed by one sub-image from each cell, are visible from different viewing angles in said transverse direction. The at least three composed images together present a movement effect upon changing said viewing angles.

[0096] At a third step 1030, the method 1000 comprising, covering, a surface of said image layer facing away from said array of line focusing elements with a coloured background layer assembly. The background layer assembly has a first colouring, visible from the image layer, and the step of covering comprises presenting the first colouring with a colouring variation over the extension of the background layer assembly, and the step of covering comprises providing said colouring variation being in registry with said movement effect of said composed images. In some embodiments, the colouring variation is a colour intensity variation.

[0097] The method according to the present disclosure may comprise further steps, illustrated by broken line boxes in Figure 7. For example, the method 1000 of producing a synthetic image device 1 may comprise the step of providing an image layer comprises one of:

[0098] At a step 1021, printing, the individual visual-contrast creating patterns directly or via a pick-up film to the first surface of the base film through a curing process. Or, another step 1022, embossing, the individual visual-contrast creating patterns as recesses and filling and / or coating the recesses. Or, another step 1023, engraving, the individual visual-contrast creating patterns by laser light. Or, another step 1024, depositing, the individual visual-contrast creating patterns by lamination.

[0099] The method 1000 of producing a synthetic image device 1, may comprise further steps illustrated by a broken line box in Figure 7. For example, at a step 1040, applying, an additional layer on a surface of the coloured background layer assembly facing away from the array of line focusing elements.

[0100] The method 1000 of producing a synthetic image device 1, may comprise further steps illustrated by a broken line box in Figure 7. For example, at a step 1050, applying, a top coating on a surface of the array of line focusing elements facing away from the image layer. Step 1050 can typically be done between steps 1010 and 1020, or between steps 1020 and 1030. Alternatively, the top coating can already be present on the focusing elements, if an additional film is used to transfer them to the surface of a base film under step 1010. The embodiments described above are to be understood as a few illustrative examples of the present invention. It will be understood by those skilled in the art that various modifications, combinations and changes may be made to the embodiments without departing from the scope of the present invention. In particular, different part solutions in the different embodiments can be combined in other configurations, where technically possible. The scope of the present invention is, however, defined by the appended claims.

Claims

CLAIMS1. A synthetic image device (1) comprising:- an array (10) of line focusing elements (11); said line focusing elements (11) being one of lenticular lenses (12) and linear rows of non-lenticular lenses (12); wherein said line focusing elements (11) extend in a longitudinal direction (L);- an image layer (20) having linearly extending cells (22) extending in said longitudinal direction (L) and having a width (W) in a transverse direction (T), perpendicular to said longitudinal direction (L), that is equal to a pitch of said array (10) of line focusing elements (11) in said transverse direction (T); said image layer (20) being positioned in parallel to said array (10) of line focusing elements (11) and at a distance (D) relative to said array (10) of line focusing elements (11) such that a limited part of said image layer (20) becomes visible when said image layer (20) being viewed through said array (10) of line focusing elements (11); wherein each cell (22) comprises at least three sub-cells (24A, 24B, 24C), provided side-by-side in said transverse direction (T); wherein said at least three sub-cells (24A, 24B, 24C) of said image layer (20) have individual visual-contrast creating patterns (21), forming subimages (24*); wherein at least three composed images (23), each associated with a set composed by one sub-image (24*) from each cell (22), are visible from different viewing angles in said transverse direction (T); wherein said at least three composed images (23) together present a movement effect upon changing said viewing angles; and- a coloured background layer assembly (25) covering a surface of said image layer (20) facing away from said array (10) of line focusing elements (11); wherein said background layer assembly (25) has a first colouring (28A), visible from said image layer (20), said first colouring (28A) presenting a colouring variation over the extension of the background layer assembly (25); andwherein said colouring variation being provided in registry with said movement effect of said composed images (23).

2. The synthetic image device ( 1) according to claim 1, characterized in that said colouring variation is a colour intensity variation.

3. The synthetic image device (1) according to claim 2, characterized in that said movement effect has, within a number of limited image part-areas, a respective associated movement direction, wherein a gradient direction of said colour intensity variation of said background layer assembly (25) in respective said image part area coincides within 30 degrees, preferably within 15 degrees, with said associated movement direction.

4. The synthetic image device (1) according to claim 2 or 3, characterized in that said colour intensity variation of said background layer assembly (25) is provided by varying a density of colour dots (27).

5. The synthetic image device according to claim 4, characterized in that said density of colour dots varies (27) continuously over said background layer assembly (25).

6. The synthetic image device according to claim 4, characterized in that said density of colour dots (27) varies in density steps over said background layer assembly (25).

7. The synthetic image device (1) according to any of the claims 1 to 6, characterized in that said colouring variation being provided in registry with said movement effect of said composed images (23) in said longitudinal direction (L) as well as in said transversal direction (T) .

8. The synthetic image device (1) according to any of the claims 1 to 7, characterized in that said background layer assembly (25) further comprises a second colouring (28B) different from said first colouring (28A).

9. The synthetic image device (1) according to claim 8, characterized in that said second colouring (28B) has a colour intensity variation, wherein said colour intensity variation of said second colouring (28B) is different from a colour intensity variation of said first colouring (28A), but in registry with said movement effect of said composed images (23).

10. The synthetic image device (1) according to claim 9, characterized in that said colour intensity variation of said first colouring (28A) and said colour intensity variation of said second colouring (28B) are in mutual registration.

11. The synthetic image device (1) according to claim 9 or 10, characterized in that said colour intensity variation of said first colouring (28A) and said colour intensity variation of said second colouring (28B) varies in opposite directions.

12. The synthetic image device (1) according to any of the claims 1 to 11, characterized in that said background layer assembly (25) further comprises additional layers (29).

13. The synthetic image device (1) according to any of the claims 1 to 12, characterized in that said visual-contrast creating patterns (21) are provided as at least one of:- printed ink,- ink filled or coated recesses,- deposited metal,- holographic structures,- Photo-chromatic projections,- laser engraving, and- refractive index differences.

14. The synthetic image device according to any of the claims 1 to 13, characterized in that said synthetic device (1) has a thickness smaller or equal to 200 pm, preferably smaller or equal to 50 pm.

15. The synthetic image device according to any of the claims 1 to 14, characterized in that said width (W) in said transverse direction (T) of said cells (22) is smaller or equal to 100 pm, preferably smaller or equal to 20 pm, and most preferably smaller or equal to 10 pm.

16. The synthetic image device (1) according to any of the claims 1 to 15, characterized in that said visual-contrast creating patterns (21) have a vertical dimension of 0. 1 - 10 pm, preferably 1 - 4 pm.

17. The synthetic image device (1) according to any of the claims 1 to 16, characterized in that said visual-contrast creating patterns (21) have a colour, different than a colour of said first colouring (28A).

18. The synthetic image device (1) according to any of the claims 1 to 17, characterized in that said visual-contrast creating patterns (21) have a colour being one of black, white and metallic.

19. The synthetic image device (1) according to any of the claims 1 to 18, characterized in that said visual-contrast creating patterns (21) are opaque.

20. The synthetic image device (1) according to any of the claims 1 to 18, characterized in that said visual-contrast creating patterns (21) are at least partially translucent.

21. The synthetic image device (1) according to any of the claims 1 to 20, characterized by a top coating (19) arranged to cover a surface of said array (10) of line focusing elements (11) facing away from said image layer (20).

22. A method of producing a synthetic image device, comprising the steps of:- providing (1010) an array (10) of line focusing elements (11), directly or via an additional film, to a first surface of a base film; said line focusing elements (11) being one of lenticular lenses (12) and linear rows of non-lenticular lenses (12); wherein said line focusing elements (11) extend in a longitudinal direction (L);- providing (1020) an image layer (20) opposite to said first surface, of said base film; said image layer (20) is provided to have linearly extending cells (22) extending in said longitudinal direction (L) and having a width in a transverse direction (T), perpendicular to said longitudinal direction (L), that is equal to a pitch of said array (10) of line focusing elements (11) in said transverse direction (T); wherein a thickness of said base film and said additional film, if any, and said pick-up film, if any, is adapted such that a limited part of said image layer (20) becomes visible when said image layer (20) being viewed through said array (10) of line focusing elements (11); wherein each cell (22) is provided to comprise at least three sub-cells (24A, 24B, 24C), provided side-by side in said transverse direction (T); wherein said at least three sub-cells (24A, 24B, 24C) of said image layer (20) have individual visual-contrast creating patterns (21), forming subimages (24*); wherein at least three composed images (23), each associated with a set composed by one sub-image (24*) from each cell (22), are visible from different viewing angles in said transverse direction (T); wherein said at least three composed images (23) together present a movement effect upon changing said viewing angles; and- covering (1030) a surface of said image layer (20) facing away from said array (10) of line focusing elements (11) with a coloured background layer assembly (25);wherein said background layer assembly (25) has a first colouring (28A), visible from said image layer (20), and wherein said step of covering comprises presenting said first colouring (28A) with a colouring variation over the extension of the background layer assembly (25); and wherein said step of covering comprises providing said colouring variation being in registry with said movement effect of said composed images (23).

23. The method according to claim 22, characterized in that said step of providing an image layer (20) comprises one of: printing (1021) said individual visual-contrast creating patterns (21) directly or via a pick-up film to said first surface of said base film through a curing process; embossing (1022) said individual visual-contrast creating patterns (21) as recesses and filling and / or coating said recesses; engraving (1023) said individual visual-contrast creating patterns (21) by laser light, and depositing (1024) said individual visual-contrast creating patterns (21) by lamination.

24. The method according to claim 22 or 23, characterized by comprising the further step of applying (1040) an additional layer on a surface of the coloured background layer assembly (25) facing away from the array (10) of line focusing elements (11).

25. The method according to any of the claims 22 to 24, characterized by comprising the further step of applying (1050) a top coating on a surface of the array ( 10) of line focusing elements (10) facing away from the image layer (20).

Images