DE112012004012T5 - safety device - Google Patents

Abstract

An optical safety device (10, 700) is provided which includes a transparent or translucent substrate (15, 705), at least a first array of repeating elements (20, 720) in or on a first side (16, 706) of the substrate (15). 15, 705), at least a second array of repeating elements (30, 730) on a second side of the substrate. The second array of repeating elements (20, 720) is substantially in register with the first array of elements (30, 730), wherein upon viewing the device from the first side, a first image (130, 725) is visible and when viewed the device from the second side of a second image (200, 735) is visible. The brightness or color values of repeating picture elements (30; 720, 730) on at least one side of the substrate may be modulated area-wise to produce a gray scale or color image. In a preferred embodiment, the first array of repeating elements in or on a first side of the substrate is an array of focussing elements (20) and the second array of repeating elements in or on the second side of the substrate is an array of picture elements (30) are substantially identical in shape to one another so that upon viewing the device from the first side an enlarged image is visible including at least one enlarged version of the pixel shape, and when viewing the device from the second side the gray value or color image is visible is. In another embodiment, the repetitive elements of both the first and second arrays are partially or completely opaque pixels (720, 730) forming the first and second images (725, 735, respectively).

Description

FIELD OF THE INVENTION

The present invention is directed to optical security devices, their use in security documents, and methods of making same.

DEFINITIONS

The security document

As used herein, the term security document encompasses all types of documents and stamps and identification documents, including, but not limited to, means of payment such as banknotes or coins, credit cards, checks, passports, identity cards, securities and stock certificates, driver's licenses, title deeds, travel documents such as airline or train tickets, and tickets Entry tickets, birth, death and marriage certificates and study books.

Transparent windows and half windows

As used herein, the term window refers to a transparent (i.e., transparent) or translucent area in the security document delimited from the substantially opaque area being printed on. The window may be fully transparent so as to allow the substantially unimpaired passage of light, or it may be partially transparent or translucent, thus allowing the partial passage of light without, however, being able to clearly see objects through the window area.

A window area may be formed in a polymeric security document having at least one layer of transparent polymeric material and one or more opacifying layers disposed on at least one side of a transparent polymeric substrate by omitting at least one opacifying layer in the area forming the window area. When opacifying layers are applied to both sides of a transparent substrate, a fully transparent window can be formed by omitting the opacifying layers on both sides of the transparent substrate in the window area.

A partially transparent or translucent area, hereinafter referred to as "half window", may be formed in a polymeric security document having opacifying layers on both sides by omitting the opacifying layers on only one side of the security document in the window area, so that the "half window "Is not fully transparent, but lets some light through, without objects through the half window can be clearly seen.

Alternatively, it is possible to fabricate the substrates from a substantially opaque material, such as paper or fiber material, with a liner of transparent plastic material placed in a cutout or recess in the paper or fibrous substrate to form a transparent window or translucent one Semi-window area form.

Opacity-enhancing layers

One or more opacifying layers may be applied to a transparent substrate to increase the opacity of the security document. An opacifying layer is designed such that L _T <L ₀ , where L _{0 is} the amount of light incident on the document and L _{T is} the amount of light transmitted through the document. An opacifying layer may comprise one or more of a variety of different opacifying coatings. For example, the opacifying layers may comprise a pigment, such as titanium dioxide, dispersed in a binder or support of thermally activated crosslinkable polymer material. Alternatively, a substrate of transparent plastic material could be sandwiched between opacifying layers of paper or another partially or substantially opaque material onto which indicia may subsequently be printed or otherwise applied.

Focus size or focal length H

As used herein, the term focal point size (or focus distance) refers to the dimensions, usually an effective diameter or width, of the geometric distribution of points at which rays that refract through a lens cross an object plane at a particular viewing angle to cut. The focal point size can be derived from theoretical calculations, beam simulations or actual measurements.

Focal length f

In the present specification, when used with respect to a microlens in a lens array, the focal length means the distance from the apex of the microlens to the position of the focal point determined by the location of the lens Maximum power density distribution when collimated radiation is incident from the lens side of the array (see T. Miyashita "Standardization for microlenses and microlens arrays" (2007) Japanese Journal of Applied Physics 46, p. 5391).

Test thickness t

The test thickness is the distance from the vertex of a small lens on one side of the transparent or translucent material to the surface of the opposite side of the translucent material on which the picture elements are substantially coincident with the object plane.

Lens frequency and pitch

The lens frequency of a lens array is the number of small lenses over a given distance on the surface of the lens array. The pitch is the distance between the vertex of a small lens and the vertex of the adjacent small lens. In a uniform lens arrangement, pitch and lens frequency are in inverse proportion.

Lens width W

The width of a miniature lens in a microlens array is the distance from one edge of the miniature lens to the opposite edge of the miniature lens. In a lens array with hemispherical or semi-cylindrical small lenses, the width and diameter of the lens are identical.

Radius of curvature R

The radius of curvature of a small lens is the distance from a point on the surface of the lens to a point at which the perpendicular to the lens surface intersects a straight line perpendicular through the apex of the lenslet (lens axis).

Slack s

The sag of a small lens (also referred to as a lens thickness) is the distance from the vertex to a point on the axis intersected by the shortest straight line coming from the edge of a small lens passing through the axis.

Refractive index n

The refractive index of a medium n is the ratio of the speed of light in the vacuum to the speed of light in the medium. The refractive index n of a lens determines the magnitude of the refraction of light rays that reach the lens surface according to Snell's law: n ₁ × Sin (α) = n × Sin (θ), where: α is the angle between an incident beam and the perpendicular at the point of incidence on the lens surface; θ is the angle between the refracted ray and the perpendicular at the point of incidence; and n ₁ is the refractive index of air (for n ₁ , the value 1 can be used as an approximation).

Conic constant P

The conic constant P is a quantity used to describe conic sections and is used in geometrical optics to specify lenses: spherical (P = 1), elliptic (0 <P <1 or P> 1), parabolic (P = 0) and hyperbolic (P <0). Occasionally the letter K for the conical constant is also found in the literature. The relation of K to P is K = P - 1.

beam angle

The lobe angle of a lens is the total viewing angle formed by the lens.

Abbe number

The Abbe number of a transparent or translucent material is a measure of the dispersion (wavelength dependence of the refractive index) of the material. An appropriately selected Abbe number for a lens can help minimize color errors.

BACKGROUND OF THE INVENTION

The present invention aims to provide a security device with an attractive appearance, which can be produced economically and at the same time ensures increased security against counterfeiting.

It is known to use arrays of microlenses that are arranged to focus on corresponding arrays of identical microimages to achieve optically variable effects. A particularly striking effect can be achieved by a slight registration deviation of the microlenses and microimages, so that a series of moiré stripes are produced. The moiré stripes take the form of enlarged versions of the microimages. This effect, termed "moiré magnification," has been described in the past by Hutley et al. (Pure and Applied Optics 3, pp 133-142, 1994) and by Amidror ("The Theory of the Moire Phenomenon," Kluwer, Dordrecht, 2000). described.

When a transparent (transparent) or translucent material is used as the substrate for a security device or for a security document, the corresponding substrates are suitable as carriers for devices of the above-mentioned type. For example, it is possible to apply the microimages on one side of the substrate and apply the microlenses on the opposite side of the substrate, thereby functioning as an optical spacer, such as in FIG US 5712731 described.

An alternative way of producing a security device or security document with moiré magnification effect is to provide a separate raster in the form of a microlens array. The grid may be an independent element or built-in part of the security device or security document and positioned by folding the document in register with the microimages located elsewhere on the document.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided an optical safety device comprising:
a transparent or translucent substrate,
at least a first array of repeating elements in or on a first side of the substrate,
at least a second array of repeating elements on a second side of the substrate,
wherein the at least one second array of repeating elements is substantially in register with the at least one first array of elements,
and wherein, when the device is viewed from the first side, a first image is visible and when the device is viewed from the second side, a second image is visible.

Preferably, the repeating elements on at least one side of the substrate are modulated in regions according to the brightness or color values of corresponding areas of an underlying gray scale or color image.

In one embodiment, the repeating elements may be amplitude modulated on at least one side of the substrate. In another embodiment, the thickness or area of the repeating elements may be modulated on at least one side of the substrate.

The first and / or second image may be optically variable. In one embodiment, the first image may be an optically variable image and the second image may be an optically invariant image.

In another embodiment, both the first and second images may be optically invariant images.

The optical security device may include on or in at least one side of the substrate two or more arrays of repeating elements.

The repeating elements on at least one side of the substrate may be embossed elements. In one embodiment, the embossed elements on at least one side of the substrate form repeating picture elements. In this case, each imprinted picture element has a depth and the depth is preferably modulated in regions.

The repeating elements on at least one side of the substrate may be printed picture elements. In another embodiment, the repeating elements are printed pixels on both sides of the substrate.

The repeating elements on at least one side of the substrate may be picture element-forming diffraction structures or structures in the sub-wavelength range. The diffraction or subwavelength structures may be surrounded by a non-diffractive background.

In another embodiment, the repeating elements on at least one side of the substrate are non-diffractive pixels surrounded by a background region comprising a diffraction or sub-wavelength grating structure, wherein a background region of the image on that side of the substrate exhibits an optically variable color effect ,

In a preferred embodiment, the at least one first array of repeating elements in or on a first side of the substrate is an array of focusing elements and the at least one second array of repeating elements in or on the second side of the substrate is an array of pixels one another have substantially identical shape, wherein the picture elements of the at least one second array are modulated in regions according to the brightness or color values of corresponding areas of an underlying gray value or color image, so that when viewing the device from the first side of an enlarged image is visible, the includes at least one enlarged version of the pixel shape, and when viewing the device from the second side, the halftone image or color image is visible.

According to a second aspect, the present invention provides an optical safety device comprising:
a transparent or translucent substrate,
an array of focusing elements in or on a first side of the substrate and
at least one array of repeating picture elements having a substantially identical shape to one another and arranged in or on a second side of the substrate,
the array of repeating pixels being substantially in register with the array of focusing elements,
and wherein the picture elements are modulated in regions according to the brightness or color values of corresponding areas of an underlying gray scale or color image so that when the device is viewed from the first page an enlarged image including at least one enlarged version of the pixel shape is visible Viewing the device from the second page of the gray scale or color image is visible.

Preferably, the picture elements are amplitude modulated. In a preferred form of the invention, the amplitude modulation takes place in that the line thicknesses or area contents of the picture elements are varied.

Alternatively, the picture elements may be frequency-modulated. For example, it is possible for the repeating pixels to have substantially the same overall period as the array of focussing elements, but omitted in some areas to produce brightness variations when viewing the second side of the device. This can result in a slightly degraded quality of the enlarged image, but provide better contrast for viewing the gray scale or color image.

Thus, the effect produced by the safety device includes a moiré magnification effect when the device is viewed from the first side while the device, when viewed from the opposite side (unexpected for a transparent region), has a completely different optical effect, such as creates an optically invariable image (for example, a portrait). This combination of two different types of optical effects within the same area of the device provides a more recognizable security feature with increased security over known security devices.

The device is also easier to manufacture because an array of picture elements placed in a single surface of the device, applied in a single manufacturing step (eg, by embossing), can be used to produce two different effects.

In a particularly preferred embodiment, the enlarged image is an optically variable image and the gray value or color image is an optically invariable image.

The interaction of diffractive and non-diffractive elements can produce a monochromatic macroscale image. Under conditions of illumination with multiple or diffused light sources, the image appears as a negative (contrast-reversed) image of the underlying image in the case of top light and as a positive image of the underlying image in transmitted light. Usually, a purely diffractive device would produce a very weak image with low diffraction power under such light conditions and be so weak under certain conditions that it is no longer recognizable.

The optical security device may include two or more array of repeating pixels. Thus, for example, when viewing a first region of the device from the first side, an enlarged image may be visible, while viewing a second region of the device from the first side, a second, different, enlarged image is visible. When the device is viewed from the second side, a tonal gray value or color image is visible. Thus, adding more arrays of repeating pixels increases the complexity of the visual effect produced by the device and makes counterfeiting even more difficult.

In a preferred embodiment, the focal length of the focusing elements in an object plane located on the second side of the device is about the same, or in the range of 20%, of the width of the picture elements. This allows the use of larger picture elements for a given substrate thickness while still providing the desired image magnification effect.

The enlargement of the picture elements in the enlarged picture is preferably controlled by the array of focusing elements and the array of picture elements in the pitch and / or in the rotational direction having a deviation from one another.

The picture elements in one embodiment are embossed picture elements, but the picture elements may also be printed picture elements. Embossed picture elements are particularly preferred since a higher resolution can be achieved with embossing processes, which produces a sharper magnified image when the device is viewed from the first side is looked at. In a method in which the picture elements are subjected to amplitude modulation, each embossed picture element has a depth, and the depth is modulated in regions.

Printing methods can also be used if the printing resolution is high enough for the picture elements to fit under the focusing elements.

In a particularly preferred embodiment, the picture elements comprise diffraction or subwavelength grating elements which are surrounded by a non-diffractive background area, wherein the enlarged picture shows an optically variable color effect. The picture elements may alternatively be non-diffractive picture elements surrounded by a background area comprising diffraction or subwavelength grating elements, a background area of the magnified image exhibiting an optically variable color effect.

A "sub-wavelength" grid element, or zero-order grid element, is a surface-raised or surface-buried microstructure that produces light only in the zeroth diffraction order when illuminated with a light of a given wavelength. Generally, these zeroth-order structures have a period below the desired incident wavelength of light. For this reason, zeroth-order diffraction gratings are sometimes referred to as sub-wavelength gratings.

The use of diffraction or subwavelength grating elements (or non-diffractive picture elements in front of a (light) diffractive background) advantageously provides a device which provides a conspicuous visual effect in both specular reflection and diffuse light conditions or in dim lighting.

The focusing elements may be refractive microlenses. Alternatively, they may be Fresnel lenses, diffractive zone plates or photon screens. An exemplary photon screen is a screen having a series of apertures pseudo-randomized along the Fresnel zones of a Fresnel zone plate, such as in FIG US 7368744 described.

In a further preferred embodiment of the first aspect of the invention, the at least one first array of repeating elements in or on the first side are picture elements that form a first image, the at least one second array in or on the second side picture elements that form a second image form, wherein the picture elements of at least one of the first and second arrays of repeating elements are at least partially opaque, whereby the first image is visible from the first side when the device is viewed from the first side and the second image is visible from the second side when the device is viewed from the second side is.

According to a third aspect of the present invention, there is provided an optical safety device comprising:
a transparent or translucent substrate,
at least a first array of repeating pixels forming a first image in or on a first side of the substrate,
at least a second array of repeating pixels forming a second image on a second side of the substrate,
wherein the at least one second array of repeating pixels is substantially in register with the at least one first array of repeating pixels, and
the at least one first array and / or the at least one second array of repeating pixels are at least partially opaque,
wherein the first image is visible from the first side when the device is viewed from the first side, and the second image is visible when the device is viewed from the second side.

Preferably, the picture elements of both the first and second arrays are at least partially opaque. The picture elements of at least one of the arrays may be completely opaque. In one embodiment, the pixels of at least one of the arrays are partially opaque and partially transparent such that the first image and the second image combine to form a third image that is visible when the security device is viewed in transmitted light.

The pixels of at least one of the first and second arrays may be colored pixels that are modulated in regions according to the color or brightness values of corresponding regions of an underlying color image.

Alternatively or additionally, the picture elements of at least one of the first and second arrays can be gray-scale picture elements, which are modulated in regions according to the brightness values of corresponding areas of an underlying gray scale image.

The picture elements on at least one side of the substrate may be printed picture elements. The picture elements on both sides of the substrate may be printed picture elements. Alternatively, the picture elements may be imprinted picture elements on at least one side of the substrate. In other embodiments, the pixels may be on be at least one side of the substrate diffraction structures or structures in the sub-wavelength range.

In another embodiment, the repeating elements on at least one side of the substrate are non-diffractive pixels surrounded by a background region comprising a diffraction or sub-wavelength grating structure,
wherein a background area of the image, which becomes visible from this side when viewing the device, exhibits an optically variable color effect.

In a fourth aspect of the invention, there is provided a method of manufacturing a security device, comprising the steps of:
Forming at least a first array of repeating elements in or on a first side of a transparent or translucent substrate; and
Forming at least a second array of repeating elements in or on a second side of the substrate,
wherein the at least one second array of repeating elements is substantially in register with the at least one first array of repeating elements,
so that when viewing the device from the first page, a first image is visible and when viewing the device from the second side of a second image is visible.

Preferably, the method includes the step of: modulating the repeating elements on at least one side of the substrate by the brightness or color values of an underlying gray scale or color image. The method preferably includes the step of printing the repetitive elements on at least one side of the substrate to form repeating pixels. In one embodiment, the method includes the step of printing the repeating elements on both sides of the substrate to form repeating pixels. Various printing techniques can be used to print the repeating image elements, including offset, flexo, intaglio, and gravure. Simultaneous printing is a particularly preferred printing method that can be used to print register-repeating picture elements concurrently on opposite sides of a substrate.

The method may include the step of forming the repeating elements on at least one side of the substrate as diffractive pixels.

The method may include the step of embossing the repeating elements on at least one side of the substrate.

In a particularly preferred method, the step of forming the at least one first array of repeating elements and the step of forming the at least one second array of picture elements are performed substantially simultaneously.

In a fifth aspect of the invention, there is provided a method of manufacturing a security device, comprising the steps of:
Forming an array of focusing elements in or on a first side of a transparent or translucent substrate; and
Forming at least one array of repeating picture elements having a substantially identical shape to one another and arranged in or on a second side of the substrate,
the array of repeating pixels being substantially in register with the array of focusing elements,
and wherein the picture elements are modulated in regions according to the brightness values of corresponding areas of an underlying gray scale or color image,
such that when the device is viewed from the first side, at least one enlarged version of the pixel shape is visible, and when viewing the device from the second side, the gray value or color image is visible.

The method may include the further step of applying an embossable radiation-curable ink to the first side and / or the second side.

Preferably, the method further includes the step of: embossing the focusing elements in the embossable radiation curable ink in the first side. The method may further include the step of embossing the pixels in the embossable radiation-curable ink in the second side.

Embossable radiation-curable ink

As used herein, the term embossable radiation-curable ink comprises any inks, lacquers or coatings which can be applied to the substrate in a printing process and which can be embossed in the still unconsolidated state and cured by radiation to fix the embossed relief structure. The curing process does not occur before the radiation-curable ink is coined, but it is possible for the curing process to take place either after embossing or substantially simultaneously takes place with the step of embossing. The radiation-curable ink is preferably curable by ultraviolet (UV) radiation. Alternatively, the radiation-curable ink can be cured by other forms of radiation, such as electron beam or X-ray.

The radiation-curable ink is preferably a transparent or translucent ink formed from a transparent resin material. Such a transparent or translucent ink is particularly suitable for printing translucent security elements such as subwavelength gratings, diffractive transmission grids and lens structures.

In a particularly preferred embodiment, the transparent or translucent ink preferably comprises a UV-curable embossable acrylic-based lacquer or a UV-curable embossable acrylic-based coating.

Such UV-curable paints can be obtained from various manufacturers, including Kingfisher Ink Limited, product UVF-203, or the like. Alternatively, radiation curable embossable coatings based on other compounds, e.g. As nitrocellulose, are used.

The radiation-curable paints and coatings used here have proven to be particularly suitable for embossing microstructures, including diffractive structures such as diffraction gratings and holograms, as well as microlenses and lens arrays. However, they can also be embossed with larger relief structures such as non-diffractive optically variable devices.

Preferably, the ink is embossed substantially simultaneously and cured by ultraviolet (UV) radiation. In a particularly preferred embodiment, the application and embossing of the radiation-curable ink take place substantially simultaneously in a gravure printing process.

For gravure printing, the radiation-curable ink preferably has a viscosity that is substantially in the range of about 20 to about 175 centipoise, and more preferably about 30 to about 150 centipoise. The viscosity can be determined by measuring the run-out time of the varnish from a tooth-outflow cup # 2. A sample with 20 seconds flow time has a viscosity of 30 centipoise and a sample with 63 seconds flow time has a viscosity of 150 centipoise.

For some polymeric substrates, it may be necessary to apply an interlayer to the substrate prior to application of the radiation-curable ink to ensure improved adhesion of the imprint structure formed by the ink to the substrate. The intermediate layer preferably comprises a primer layer, and more preferably the primer layer comprises a polyethyleneimine. The primer layer may also include a crosslinking agent, for example a multifunctional isocyanate. Examples of other primers suitable for use in the invention include: hydroxyl-terminated polymers, polyester-terminated copolymers having hydroxyl end groups, crosslinked or uncrosslinked hydroxylated acrylates, polyurethanes, and UV-curing anionic or cationic acrylates. Examples of suitable crosslinkers include: isocyanates, polyaziridines, zirconium complexes, aluminum acetylacetone, melamines, and carbodiimides.

The type of primer may differ depending on the substrate and embossed ink structure. Preferably, a primer is selected which does not significantly affect the optical properties of the embossed ink structure.

The steps of forming the array of focusing elements and forming the array of picture elements are preferably carried out successively. However, in some embodiments, for example, when the focussing elements and picture elements are embossed, the steps may be performed simultaneously.

The method may further include the step of: curing the embossable radiation-curable ink. This is preferably done substantially simultaneously with the embossing step.

In a preferred embodiment, the picture elements comprise diffraction or subwavelength grating elements which are surrounded by a non-diffractive background area. The picture elements may alternatively be non-diffractive picture elements surrounded by a background area comprising diffraction or subwavelength grating elements.

The picture elements may be formed by printing or embossing the picture element form as a non-diffractive structure onto a background of diffraction or subwavelength grating elements. Alternatively, the pixels may be formed by embossing diffraction or subwavelength grating elements onto a non-diffractive background.

In another aspect, a security document is provided that includes or includes a security device according to the first, second, or third aspects of the invention The safety device according to the fourth or fifth aspect of the invention includes. The security device may be formed or applied in or on a window of the security document.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described with reference to the accompanying drawings, in which:

1 is a cross section through an embodiment of a security device according to the invention;

2 shows the safety device of 1 as part of a security document;

3 shows a series of picture elements for use with a security device according to an embodiment of the invention;

4 shows the picture elements of 3 when viewed through an array of focusing elements;

5 and 6 show a variation of the embodiment of the 3 and 4 ;

7 shows another embodiment of a security device in which the picture elements are printed;

8th shows an optically invariable image that becomes visible to a person following the security device 3 viewed from the side opposite to the array of focusing elements; and

9 shows an embodiment of a plant that is suitable for the production of security devices or security documents according to the above embodiments.

10 is a schematic sectional view of a safety device according to another embodiment of the invention;

11 is a schematic sectional view of a security document, in which the safety device of 10 is in a window of the document;

12 shows the security document of 11 with a first image that is visible from a first side when viewed in top light;

13 shows the security document of 11 with a second image that is visible from the second side when viewed in the top light;

14 shows an enlarged view of the window area and the security device of the security document of 12 ;

15 shows an enlarged view of the window area and the security device of the security document of 13 ; and

16 shows a modified embodiment of the security document of 12 and 15 with a third image visible by transmitted light observation.

DESCRIPTION OF PREFERRED EMBODIMENTS

1 shows a partial cross section through a safety device 10 with a transparent or translucent substrate 15 that's a first page 16 and a second page 17 having. On the first page 16 becomes an array of focusing elements in the form of part-spherical microlenses 20 trained and on the second page 17 becomes a corresponding array of repeating picture elements 30 educated.

The focusing elements 20 can be right in the surface of the first page 16 of the substrate 15 are formed, but are preferably formed in an embossable radiation-curable ink, which, preferably in gravure, on the first page 16 is applied.

The picture elements 30 can be printed picture elements, for example, in flexographic printing on the surface of the second page 17 be applied. Preferably, however, they are imprinted pixels that are formed by imparting an embossable radiation-curable ink to the second side 17 is applied, an array of relief structures is embossed in the embossable radiation-curable ink and the ink is cured.

2 is a partial cross section through a security document 100 that the security device 10 includes. The security document includes a transparent or translucent substrate 105 with a first page 106 and a second page 107 , On the first page 106 or second page 107 become layers of an opacifying ink 108 . 109 applied, except in a window area in which the security device 10 located. The opacifying ink 108 . 109 is preferably applied before the safety device 10 is formed in the window area to achieve the registration of safety device 10 and to facilitate window area.

Further details of the security device 10 are now referring to the 3 . 4 and 8th shown. That on the second page 17 of device 10 to be applied array of pixels 30 is achieved by making a dither or halftone version of an underlying input image 200 produced. In the example in 8th each pixel becomes the monochrome bitmap 200 is set to one of three brightness level values, each brightness value corresponding to a specific line thickness (line thickness) of the picture elements (amplitude modulation), as shown to the right in the enlarged views of the areas 211 . 212 . 213 of the picture element array 210 shown. In an alternative embodiment, the spatial distribution of the picture elements 30 on the second page 17 of the substrate corresponding to the brightness values of the underlying image 200 be modulated (frequency modulation), but preferred is the amplitude modulation.

Every picture area 211 . 212 . 213 includes pixels 25 , which are square surfaces, in their dimensions the dimensions of overlapping part-spherical lenses 20 correspond. The magnitude of the pixels 25 is generally in the range of 45 square microns to 65 square microns, but it can be seen that smaller or larger dimensions can be selected to suit the particular application. As will also be apparent, the pixels need not be square, but in many applications the selection of square pixels is favorable.

The picture area 211 corresponds to a part of the brightest area of the underlying image 200 and includes imaged pixels as such 30 that produce the largest amount of reflected or transmitted light, ie that have the largest line thickness. image area 212 lies within the second brightest part of image 200 and thus have the corresponding picture elements 31 one opposite the picture elements 30 slightly reduced line thickness. Equivalent has image area 213 that in the darkest areas of the underlying image 200 lies, picture elements 32 with the lowest line weight.

The picture elements 30 . 31 . 32 all have essentially the same shape and differ only in their line width. The line weight may be modulated to the extent permitted by the resolution of the process used to apply the pixels. In flexographic printing, the smallest resolution is about 7 microns. In an embossing process, the smallest resolution is limited by the resolution of the electron beam or other process used to make the embossing master, and may be on the order of nanometers. Embossing processes are therefore preferred because they allow a finer gradation between line widths and thus brightness values and thus create the impression of a smooth transition between areas of different coloration or brightness.

The array of lenses 20 and the array of pixels 30 . 31 . 32 can be made to produce a moiré magnified image if the two arrays have slightly different pitches or a different rotational orientation. The magnification degree for a lens array having period a and a pixel array having period b is given as a ² / Δ, where Δ = a-b is the pitch distance difference. If the lens array and the image array have identical periods a but their axes are at an angle θ to each other, the magnification is about 1 / (1-cos θ).

The 3 × 3 grid of pixels 25 in 3 each contains three picture elements 30 . 31 and 32 , Every picture element 30 . 31 respectively. 32 is an embossed or printed non-diffractive element made from a surface 35 . 36 respectively. 37 surrounded, which comprises an embossed surface relief structure. The surface relief structures in the background areas 35 . 36 and 37 may have the same parameters (embossing depth, spatial frequency, curvature, azimuth angle) to each other, or the surface relief parameters may be different from area to area, if desired.

As can also be seen, the picture elements 30 - 32 through unembossed areas of pixels 25 that is, it becomes the entirety of a pixel 25 shaped with the omission of an area whose edge is the shape of the picture element 30 . 31 or 32 having.

The surface relief structure may be a diffractive structure to produce a light colored background area that varies with the viewing angle. Alternatively, the surface relief structure may be a zero wavelength sub-wavelength grating having a particular color at all viewing angles. Advantageously, subwavelength structures typically also produce strong polarization effects, and thus the change (for example) in the azimuthal angle of the relief structure between pixels can give rise to another authenticity feature that can be considered among polarizing filters.

The device 10 of the 1 . 3 . 4 and 8th achieves the following optical effects.

Will the device 10 from the first page 16 of the substrate 15 is considered from as a result of the lenses 20 Moiré magnification effect produced at least one enlarged and rotated version 130 the individual picture elements 30 . 31 . 32 seen. Although the picture elements 30 . 31 . 32 are not exactly identical, they can be made so that their respective line strengths deviate sufficiently from each other so that the collective effect obtained by scanning individual picture elements through the lenses 20 is an "average" of the individual scanned images. The image can also be above or below the plane of the device 10 appear floating and / or show an orthoparallactic displacement when the device 10 is tilted forwards and backwards by the observer or from one side to the other. When using diffractive (diffractive) background surfaces 35 . 36 and 37 can the enlarged pictures 130 also have a light-colored and optically variable background.

Will the device 10 from the second page 17 of the substrate 15 From considered, no enlargement of the individual picture elements takes place 30 . 31 . 32 which are too small to be perceived by the naked eye (preferably of the order of 150 microns or less, more preferably less than 70 microns so as not to be seen at a viewing distance of 20 cm), and together give the impression of monochrome or colored picture 200 result.

The device 10 thus creates an optically variable, magnified floating or moving image, regardless of intuition, when viewed from the first side 16 from an optically invariable, tonal monochrome or full-color image, when viewed from the second side 17 the transparent or translucent substrate 15 out of view.

The 5 and 6 show an alternative embodiment in which embossed picture elements 40 . 41 and 42 within the pixels 25 of non-diffracting surfaces 45 are surrounded. The picture elements 40 . 41 and 42 have different thicknesses and, in this embodiment, also include diffraction or subwavelength surface relief structures. The surface relief structures may have identical parameters (embossing depth, spatial frequency, curvature, azimuth angle) in each pixel, or the parameters may differ from pixel to pixel or between different pixel thicknesses. The embodiment of the 5 and 6 generated when through lenses 20 considered, at least one enlarged and rotated version 140 the individual picture elements 40 . 41 . 42 whose color also corresponds to the color of the scanned individual picture elements. As with the 3 and 4 shows the device of 5 and 6 if from the second page 17 the transparent or translucent substrate 15 from an optically invariable, tonal monochrome or full color image, as in 8th shown.

7 FIG. 12 shows part of another embodiment of a flexographic printing apparatus employing a 3x3 grid of pixels 25 pixels 50 . 51 . 52 that includes flexographic points 60 composed and of corresponding diffractive background areas 55 . 56 . 57 are surrounded. The picture elements 50 . 51 . 52 have essentially the same shape (letter 'A'), but differ in the number of flexographic points, from which they are each composed.

As with the embodiments of 3 and 5 shows the device when viewed from the second page 17 the transparent or translucent substrate 15 from an optically invariable, tonal monochrome or full color image as shown in FIG 8th ,

With reference to 9 Now, an embodiment of a plant for producing security documents, which include devices of the above type, is shown.

In the 9 schematically illustrated printing and embossing plant 500 includes a feeder unit 502 for feeding a flat substrate 501 to various printing and embossing stations, which is an opacification station 504 , a first printing station 506 , an embossing station 510 , a second printing station 606 , a second embossing station 610 and a third printing station 514 include.

The substrate 501 is preferably made from a substantially transparent or translucent polymeric material, such as biaxially oriented polypropylene (BOPP), and may be from a roll of material 503 at the feeder unit 502 continuously to the opacification station 504 be guided. The Opacification Station 504 includes opacifying agents for applying at least one opacifying layer to at least one side of the substrate 501 , The opacifying agent is preferably in the form of a printing unit, e.g. B. with one or more gravure cylinders 505 for applying one or more opacifying ink coatings to one or both sides of the substrate. It is possible, however, that the opacification station 504 Opacifying means in the form of a laminating unit to apply one or more sheet layers of at least a partially-opaque material, such as paper or other fibrous material, to at least one side of the transparent substrate.

Preferably, the opacifying agent 505 at the Opacification Station 504 so arranged to omit at least one opacifying layer on one side or on both sides of the substrate in at least one area to form a window or half-window area.

The first printing station 506 includes pressure medium 507 . 508 for applying an embossable radiation-curable ink to the substrate 501 , The pressure medium can at least one pressure cylinder 507 , z. A gravure cylinder, the opacified transparent substrate between the impression cylinder 507 and a corresponding cylinder (or roller) located on the opposite side of the substrate 508 is introduced.

The pressure medium 507 . 508 is arranged so that it is the radiation-curable ink on the first page 16 of the substrate 501 apply where at the embossing station 510 the lenses 20 are to be applied. The lenses may be applied in a window area by omitting the area at the opacification station 504 applied opacifying ink was formed.

The embossing station 510 comprises embossing means preferably in the form of a plate cylinder 511 and a counter-pressure cylinder 512 , The embossing agent 511 . 512 includes embossing sections which are arranged so that they emboss different areas of the substrate, while this the press nip between plate and impression cylinder 511 . 512 passes.

The embossing station 510 can also be radiation curing agent 513 to emboss the embossable, radiation-curable ink substantially simultaneously with, or immediately after, embossing the ink to form the lenses 20 to harden. Alternatively, a separate curing station may be provided. The radiation curing agent preferably comprises an ultraviolet (UV) curing unit for curing a UV curable ink, but for X-ray or electron beam curable inks, x-ray or electron beam (EB) curing units can be used.

The second printing station 606 includes pressure medium 607 . 608 for applying an embossable radiation-curable ink to the second side 17 of the substrate 501 , The pressure medium can at least one pressure cylinder 607 , z. A gravure cylinder, the opacified transparent substrate between the impression cylinder 607 and one on the opposite side 16 of the substrate 501 located corresponding cylinder (or roller) 608 is introduced. The pressure medium 607 . 608 is arranged so that there is radiation-curable ink in an area directly opposite and in register with the lenses 20 on the second page 17 of the substrate 501 applying. If the lenses 20 in a window region, the radiation-curable ink in the window region becomes on the opposite side of the substrate 501 applied.

The embossing station 610 comprises embossing means preferably in the form of a plate cylinder 611 and a counter-pressure cylinder 612 , The plate cylinder 611 carries the structures of the picture elements 30 - 32 and or 40 - 42 as well as, if embossed background areas 35 - 37 . 45 or 55 - 57 also the structures of these background areas. After passing through the embossing station 610 carries the substrate 501 an array of lens structures 20 on its first surface 16 and a corresponding array of picture elements 30 - 32 respectively. 40 - 42 that with the Arraylinsen 20 is essentially in register.

The embossing station 610 can also be radiation curing agent 613 to emboss the embossable, radiation-curable ink substantially simultaneously with, or immediately after, embossing the ink to form the cured embossed image elements 30 - 32 respectively. 40 - 42 to harden.

It will also be apparent that the second printing station 606 and the second embossing station 610 be replaced by a printing station, such as a flexographic printing station, if printed picture elements 50 - 52 should be used.

The third printing station 514 includes pressure means for applying printed features to the substrate. The pressure means preferably includes a pressure cylinder 516 such as a gravure, offset or intaglio cylinder, and can be used to apply a variety of different printing features to the substrate. For example, the impression cylinder 516 at the second printing station 514 be used for applying printed security features that are in register with the embossed security element, adjacent to this or surround this.

When operating the system becomes the transparent substrate 501 from the feeder unit 502 through the opacification station 504 where at least one opacifying layer is on at least one side of the substrate 501 is applied. The at least partially opacified substrate 501 is then passed through the first printing station 506 where the embossable radiation-curable ink is applied in an area (for example, a window area) used to form the lenses 20 should be marked.

The substrate 501 is then passed through the embossing station 510 where the previously applied ink surface is stamped on the first page 16 of the substrate 501 the microlenses 20 train. The radiation-curable ink is then used to fix the embossed lenses 20 hardened, preferably at the embossing station 510 ,

The substrate 501 is through the second printing station 606 and second embossing station 610 led to the second page 17 of the substrate 501 embossed picture elements 30 - 32 respectively. 40 - 42 in substantial register with the embossed lenses 20 train.

The attachment 500 may also include other printing stations or embossing stations (not shown) around the substrate 501 with other printed or embossed features.

It is also possible to have an opacification station after the embossing station 510 this opacification station having at least one opacifying layer on at least one side of the substrate 501 while applying the area of embossed lenses 20 and embossed picture elements 30 - 32 respectively. 40 - 42 leaves out to form a window.

In some embodiments, simultaneous embossing of both sides of the substrate may be possible, so that the lenses 20 and picture elements 30 - 32 or 40 - 42 be formed at the same time on opposite sides of the substrate in substantial register.

The 10 to 16 Figure 11 illustrates further embodiments of security devices and security documents of the present invention that produce different images when viewed from opposite sides of the device in top light and when viewed in transmitted light.

10 shows a partial cross section through a safety device 700 with a transparent or translucent substrate 705 that's a first page 706 and a second page 707 having. On the first page 706 becomes a first array 712 repetitive elements in the form of picture elements 720 trained, and on the second page 707 becomes a second array 713 repetitive elements in the form of picture elements 730 trained with the picture elements 730 of the first array 713 are essentially in register.

The picture elements 720 . 730 of the first and second arrays 712 . 713 are preferably formed as fine lines or dots, with spaces 721 . 722 between the points allow the passage of light through the transparent or translucent substrate. When lines are used, they may be straight, curved, wavy, or otherwise shaped. When points are used, they are preferably round, but may take other regular or irregular shapes. In any case, the picture elements have 730 of the second array 713 preferably substantially the same shape as the picture elements 720 of the first array 712 and are essentially in register.

The picture elements 720 . 730 of the first and second arrays 712 . 713 may be colored or gray-scale pixels that are modulated in regions according to the color or brightness values of corresponding regions of an underlying color or gray value image.

11 is a partial cross section through a security document 800 that the security device 700 includes. The security document includes a transparent or translucent substrate 805 with a first page 806 and a second page 807 , On the first page 806 or second page 807 become layers of an opacifying ink 808 . 809 applied, except in a window area 810 in which is the security device 700 located. The opacifying ink 808 . 809 is preferably applied before the safety device 700 in the window 710 is trained to achieve the registration of security device 700 and to facilitate windows.

The 12 and 13 show the security document 800 when viewed from the first or second side 806 . 807 out. The 14 and 15 show enlarged views of the window area 810 and the security device 700 in the 12 respectively. 13 illustrated security document.

The picture elements 720 . 730 are at least partially opaque. So is the security device 700 in the overhead light from a direction substantially perpendicular to the plane of the substrate extending from the first side 806 From the perspective, only the picture elements are 720 of the first array 712 visible, allowing one out of the picture elements 720 formed first color or gray value image 725 is visible, as in the 12 and 14 shown. Equally the safety device 700 in the overhead light from a direction substantially perpendicular to the plane of the substrate extending from the second side 807 From the perspective, only the picture elements are 730 of the first array 713 visible, allowing one out of the picture elements 730 formed first color or gray value image 735 is visible, as in the 13 and 15 shown.

The 12 and 14 show as a mere example a simple black and white picture 725 in the form of a four-pointed star. Such an image may be formed by opaque black pixels forming the star shape and opaque white pixels forming the star background. The 13 and 15 show a simple gray picture 735 in the form of an eight-pointed star formed by opaque gray lines or dots forming the star shape and opaque white lines or dots forming the star background. However, more complex gray level images can be formed by modulating the brightness values of gray pixels area by area according to the brightness values of corresponding regions of the underlying gray level image in a more complex manner.

It is also possible to form colored or multicolor images by using colored picture elements and by modulating the color or brightness values of the colored lines or dots by the color or brightness values of corresponding areas of an underlying color image.

If substantially vollopaque picture elements are used on both sides, only the first picture is visible from the first page in top light and transmitted light and only the second picture from the second side in top light and transmitted light. In other embodiments, such as 16 As shown, it is possible to form one or more images that are visible in transmitted light by using on the first and / or second side picture elements that are partially opaque and partially transparent or translucent, thus permitting the passage of light. If, for example, the four-pointed constellation 725 forming picture elements 720 of the first array are completely opaque and the eight-pointed star 735 forming picture elements 730 of the second array are partially opaque and partially transparent, when the transmitted light is viewed from the second side, the device becomes a combined third image 740 visible from the four-pointed star 725 and the eight-pointed star 735 exists, as in 16 shown.

The picture elements 720 . 730 The first or second or both arrays may be printed pixels applied to one or both surfaces of the substrate by, for example, flexographic printing or simultaneous printing. Alternatively, the picture elements 720 . 730 be imprinted picture elements of the first or second or both arrays. Embossed picture elements can be formed by applying an embossable radiation curable ink to the substrate, embossing an array of relief structures into the embossable radiation curable ink, and curing the ink. For example, a translucent colored radiation-curable ink can be used to form embossed picture elements that are partially transparent such that when combined with transmitted light from at least one side, a combined image is visible.

In a further modification, the picture elements on at least one side of the substrate are diffractive picture elements. Diffractive image elements can be used to form optically variable images, while printed image elements generally form optically invariable images. In one embodiment, the pixels of the first array may be printed images forming an optically invariant image and the pixels of the second array may be diffractive pixels to form an optically variable image.

In another embodiment, the pixels on at least one side of the substrate are non-diffractive pixels surrounded by a diffraction or sub-wavelength grating structure, such that a background region of the resulting image that is visible from that side of the substrate is an optically variable one Color effect shows.

Diffractive picture elements, or a diffractive or sub-wavelength structure, may be formed by applying an embossable radiation-curable ink to a surface of the substrate, embossing the required diffractive or sub-wavelength structure into the radiation-curable ink, and curing the ink.

For producing security documents including embossed or diffractive picture elements or structures, an apparatus for producing security documents similar to that described with reference to FIG 9 described plant can be used. If the picture elements in the first and second arrays are printed elements, a simpler layout can be used where the first and second printing and embossing stations 506 . 510 . 606 and 610 from 9 replaced by a simultaneous pressure station.

Claims (46)

An optical safety device comprising: a transparent or translucent substrate, at least a first array of repeating elements in or on a first side of the substrate, at least a second array of repeating elements on a second side of the substrate, the at least one second array of repeating elements in the substrate Is substantially in register with the at least one first array of elements, and wherein, when the device is viewed from the first side, a first image is visible and when the device is viewed from the second side, a second image is visible. An optical safety device according to claim 1, wherein the repetitive elements on at least one side of the substrate are modulated in regions according to the brightness or color values of corresponding areas of an underlying gray scale or color image. The optical safety device of claim 2, wherein the repeating elements are amplitude modulated on at least one side of the substrate. An optical safety device according to claim 3, wherein the thickness or area of the repeating elements is modulated. An optical safety device according to any one of the preceding claims, wherein the first image is an optically variable image and the second image is an optically invariant image. An optical safety device according to any preceding claim, wherein the first and second images are optically invariant images. An optical safety device according to any one of the preceding claims including two or more arrays of repeating elements on or in at least one side of the substrate. An optical safety device according to any one of the preceding claims, wherein the repetitive elements are imaged pixels on at least one side of the substrate. The optical safety device of claim 8, wherein each imprinted pixel has a depth and the depth is modulated in regions. An optical safety device according to any one of the preceding claims, wherein the repetitive elements are picture elements printed on at least one side of the substrate. An optical safety device according to any one of the preceding claims, wherein the repeating elements are diffractive pixels on at least one side of the substrate. An optical safety apparatus according to any one of the preceding claims, wherein the repetitive elements on at least one side of the substrate are non-diffractive pixels surrounded by a background region comprising a diffraction or subwavelength grating structure and a background region of the image on that side of the substrate shows a visually variable color effect. An optical safety device according to any one of the preceding claims, wherein the at least one first array of repeating elements in or on a first side of the substrate is an array of focussing elements; and the at least one second array of repeating elements in or on the second side of the substrate is an array of picture elements having a substantially identical shape to each other, and wherein the picture elements of the at least one second array are modulated in regions according to the brightness values of corresponding areas of an underlying gray value or color image, such that upon viewing the device from the first side, an enlarged image is visible that includes at least one enlarged version of the pixel shape, and when the device is viewed from the second side, the gray scale or color image is visible. Optical security device comprising: a transparent or translucent substrate, an array of focusing elements in or on a first side of the substrate and at least one array of repeating picture elements having a substantially identical shape to one another and arranged in or on a second side of the substrate, the array of repeating pixels being substantially in register with the array of focusing elements, and wherein the picture elements are modulated in regions according to the brightness values of corresponding areas of an underlying gray scale or color image, such that upon viewing the device from the first side, an enlarged image is visible that includes at least one enlarged version of the pixel shape, and when the device is viewed from the second side, the gray scale or color image is visible. An optical safety device according to claim 13 or claim 14, wherein the focal length of the focusing elements in an object plane located on the second side of the device is about equal to, or in the region of 20%, the width of the pixels. An optical safety apparatus according to claim 14, wherein the picture elements are non-diffractive picture elements surrounded by a background area including a diffraction or subwavelength grating structure, and a background area of the magnified image exhibits an optically variable color effect. An optical safety apparatus according to claim 14, wherein said picture elements comprise diffraction or subwavelength grating structures surrounded by a non-diffractive background region, and said enlarged image exhibits an optically variable color effect. An optical safety device according to any one of claims 13 to 17, wherein the focusing elements are refractive microlenses. Optical safety device according to one of claims 13 to 17, wherein the focusing elements are Fresnel lenses, diffractive zone plates or photon sieves. The optical safety device of claim 1, wherein the at least one first array of repeating elements in or on the first side are picture elements forming a first image, the at least one second array in or on the second side are picture elements comprising a forming second images that are at least partially opaque to pixels of at least one of the first and second array of repeating pixels, the first image being visible from the first side when the device is topped, and the second image being viewed from the second side upon viewing the device is visible. Optical security device comprising: a transparent or translucent substrate, at least a first array of repeating pixels forming a first image in or on a first side of the substrate, at least a second array of repeating pixels forming a second image on a second side of the substrate, wherein the at least one second array of repeating pixels is substantially in register with the at least one first array of repeating pixels, and the at least one first array and / or the at least one second array of repeating pixels are at least partially opaque, wherein the first image is visible from the first side when the device is viewed from the first side, and the second image is visible when the device is viewed from the second side. The optical safety device of claim 20 or claim 21, wherein the pixels of at least one of the first and second arrays are completely opaque. The optical safety device of any one of claims 20 to 22, wherein the pixels of at least one of the first and second arrays are repetitive, partially opaque, and partially transparent such that the first image and the second image combine to form a third image that is visible when the safety device is viewed in transmitted light. An optical safety apparatus according to any one of claims 20 to 23, wherein the picture elements of at least one of the first and second arrays are color picture elements modulated in regions according to the color or brightness values of respective areas of an underlying color picture. An optical safety apparatus according to any one of claims 20 to 24, wherein the picture elements of at least one of the first and / or second arrays are gray-scale picture elements modulated in regions according to the brightness values of corresponding areas of an underlying gray scale picture. An optical safety device according to any one of claims 20 to 25, wherein the picture elements are picture elements printed on at least one side of the substrate. An optical safety device according to any one of claims 20 to 26, wherein the pixels are imaged pixels on at least one side of the substrate. The optical safety device of any of claims 20 to 27, wherein the pixels on at least one side of the substrate are diffractive structures or sub-wavelength structures. An optical safety apparatus according to any one of claims 20 to 27, wherein the repeating picture elements on at least one side of the substrate are non-diffractive picture elements surrounded by a background area comprising a diffraction or subwavelength grating structure and a background area of the image included in Viewing the device is visible from this side, shows a visually variable color effect. A method of manufacturing a security device, comprising the steps of: forming at least a first array of repeating elements in or on a first side of a transparent or translucent substrate; and forming at least one second array of repeating elements in or on a second side of the substrate, wherein the at least one second array of repeating elements is substantially in register with the at least one first array of repeating elements, such that when viewed from the first Page from a first picture is visible and at Viewing the device from the second page from a second image is visible. The method of claim 30, including the step of: modulating the repeating elements on at least one side of the substrate by the brightness or color values of an underlying gray scale or color image. The method of claim 30 or claim 31, including the step of: printing the repetitive elements on at least one side of the substrate to form repeating pixels. The method of claim 32, including the step of: printing the repetitive elements on both sides of the substrate to form repeating pixels. The method of claim 33, wherein the simultaneous printing is used to form the repeating picture elements. The method of any one of claims 30 to 32, including the step of: forming the repeating elements on at least one side of the substrate as diffractive pixels. The method of any one of claims 30 to 32 or claim 35, including the step of embossing the repeating elements on at least one side of the substrate. The method of any one of claims 30 to 35, wherein the step of forming the at least one first array of repeating elements and the step of forming the at least one second array of pels are performed substantially simultaneously. Method for producing a safety device comprising the following steps: Forming an array of focusing elements in or on a first side of a transparent or translucent substrate; and Forming at least one array of repeating picture elements having a substantially identical shape to each other in or on a second side of the substrate, the array of repeating pixels being substantially in register with the array of focusing elements, and wherein the picture elements are modulated in regions according to the brightness or color values of corresponding areas of an underlying gray scale or color image, such that upon viewing the device from the first side, an enlarged image is visible that includes at least one enlarged version of the pixel shape, and when the device is viewed from the second side, the gray scale or color image is visible. The method of claim 38 further including the step of applying an embossable radiation-curable ink to the first side and / or the second side. The method of claim 39 further including the step of embossing the focusing elements into the embossable radiation-curable ink on the first side. The method of claim 39 or claim 40 further including the step of embossing the focusing elements into the embossable radiation-curable ink on the second side. The method of any one of claims 39 to 41, further including the step of: curing the embossable radiation-curable ink. The method of claim 42, wherein the step of curing is performed substantially simultaneously with the step of embossing. A security document including a security device according to any one of claims 1 to 29 or a security device made according to any one of claims 30 to 43. The security document of claim 44, wherein the security device is formed or applied in or on a window of the security document. The security document of claim 45, comprising a transparent or translucent substrate, wherein the window is formed by applying an opacifying layer to at least one side of the substrate, except in the region of the window.

Images