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WO2019068655A1 - Fenêtre à deux faces transparentes présentant des colorants dichroïques - Google Patents

Fenêtre à deux faces transparentes présentant des colorants dichroïques Download PDF

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Publication number
WO2019068655A1
WO2019068655A1 PCT/EP2018/076681 EP2018076681W WO2019068655A1 WO 2019068655 A1 WO2019068655 A1 WO 2019068655A1 EP 2018076681 W EP2018076681 W EP 2018076681W WO 2019068655 A1 WO2019068655 A1 WO 2019068655A1
Authority
WO
WIPO (PCT)
Prior art keywords
layer
liquid crystalline
crystalline mixture
embossing
foil
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/EP2018/076681
Other languages
English (en)
Inventor
Winfried HOFFMÜLLER
Manfred Heim
Mario Keller
Beatriz Cerrolaza
Carlos Carrasco
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Giesecke and Devrient Currency Technology GmbH
Alise Devices SL
Original Assignee
Giesecke and Devrient Currency Technology GmbH
Alise Devices SL
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Giesecke and Devrient Currency Technology GmbH, Alise Devices SL filed Critical Giesecke and Devrient Currency Technology GmbH
Priority to AU2018344427A priority Critical patent/AU2018344427B2/en
Publication of WO2019068655A1 publication Critical patent/WO2019068655A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
    • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
    • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
    • B42D25/30—Identification or security features, e.g. for preventing forgery
    • B42D25/324—Reliefs
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
    • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
    • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
    • B42D25/30—Identification or security features, e.g. for preventing forgery
    • B42D25/36—Identification or security features, e.g. for preventing forgery comprising special materials
    • B42D25/364—Liquid crystals

Definitions

  • the present invention is directed towards a method for producing a foil security element for securing a document of value by means of a liquid crystalline mixture containing dichroic dyes and is furthermore directed towards the foil security element as such. Furthermore / a document of value is suggested comprising the foil security element along with an apparatus for providing such a security element and a computer program product.
  • EP 2 508 358 Al teaches a procedure for manufacturing sheets having several latent images, fabricated from a polymerizable liquid crystal.
  • EP 1 894 736 A2 describes a model based on a liquid crystal featuring chiral behavior (liquid crystal molecules show orientational order and optical activity, generating a rotation of the light as it travels through). Two liquid crystal layers are placed on a support substrate, the second one being chiral. Interaction between the chiral layer and the first layer, whose molecules are partially oriented, generates a variable interlacing between layers that produces a color variation by the tilt/ twist of the liquid crystal molecules.
  • EP 1 894 736 Al teaches a security element using liquid crystals and furthermore providing a color-shift effect.
  • a polymerized liquid crystalline layer contains at least one substance, whose orientation depends on the orientation of the molecules of the liquid crystals surrounding it.
  • This substance may be a dye, whose absorption of light depends on its orientation in relation to the orientation of the polarization of the incident light.
  • Liquid crystals in their liquid crystalline state may be oriented by outside forces.
  • the orientation may be induced by electric fields, magnetic fields, electrostatic, chemical composition of surfaces and their topography.
  • the desired two-sided image window feature requires a special orientation of the liquid crystals.
  • the two major faces of the liquid crystal layer have to be oriented independently of each other, yet the orienting force has to be applied until (or almost until) the orientation is finally fixed by crosslinking of the liquid crystals.
  • Crosslinking can take place by UV curing.
  • One way is applying an electrical field with electrodes. These may be planar. They may contain a structured layer of ITO on glass. Structuring is done according to an aspect of the present invention in such a way that the ITO on each glass plate (or other carrier) forms both poles for the electric field. This means that it is neither necessary nor desired to have an electric field crossing the whole thickness of the liquid crystal layer.
  • the field is used to orient the liquid crys- tal molecules near the respective surface.
  • Another way to orient the liquid crystals is using rubbed and/ or embossed foils which may carry an embossing lacquer. While several security elements are already known, there is a need for combining such security elements and furthermore produce such security elements in a large scale. For the production of foils for banknote application, a much higher productivity is necessary on the one hand, and on the other hand the combination with further security features is required.
  • a method for producing a foil security element for securing a document of value by means of a liquid crystalline mixture containing dichroic dyes providing latent images comprising: arranging (100) a lacquer layer on a carrier substrate layer; performing an embossing (101) of the lacquer layer to provide a first alignment structure; at least partly covering (102) the lacquer layer by the uncured liquid crystalline mixture containing dichroic dyes; and - performing an embossing (103) of the uncured liquid crystalline mixture to provide a second alignment structure, wherein the first and the second alignment structure cause the liquid crystalline mixture to show different images from respectively opposite sides in a cured state.
  • the embossing is performed by the use of a circular molding tool (or rather a circular embossing tool) having a structured surface for providing the embossing of the first or the second alignment structure.
  • the circular molding tool is preferably selected from a roll, a cylinder, a belt, a film or a metal plate.
  • the circular molding tool comprises a structured surface consisting of a plurality of identical, repeatedly arranged embossing patterns for manufacturing several embossed items.
  • the circular molding tool may comprise a plurality of stamping dies, wherein said stamping dies are mounted on a cylinder.
  • a foil security element for securing a document of value by means of a liquid crystalline mixture containing di- chroic dyes providing latent images comprising: a lacquer layer being arranged on a carrier substrate layer; - the lacquer layer is embossed to provide a first alignment structure of the liquid crystalline mixture; the lacquer layer being at least partly covered by the uncured liquid crystalline mixture containing dichroic dyes; and the uncured liquid crystalline mixture is embossed to provide a second alignment structure, wherein the first and the second alignment structure cause the liquid crystalline mixture to show different images from respectively opposite sides in a cured state.
  • a document of value in particular a banknote or an identity document, comprising the foil security element according to clause 11. 13.
  • An apparatus for producing a foil security element for securing a document of value by means of a liquid crystalline mixture containing dichroic dyes providing latent images comprising: an arrangement unit for arranging (100) a lacquer layer on a carrier substrate layer; a covering unit for at least partly covering (102) the lacquer layer by the uncured liquid crystalline mixture containing dichroic dyes, characterized in that a first embossing unit for embossing (101) of the lacquer layer is provided to provide a first alignment structure of the liquid crystalline mixture; and a second embossing unit for embossing (103) of the uncured liquid crystalline mixture to provide a second alignment structure, wherein the first and the second alignment structure cause the liquid crystalline mixture to show different images from respectively opposite sides in a cured state.
  • the first and/ or the second embossing unit is based on a circular molding tool (or rather a circular embossing tool) having a structured surface for providing the embossing of the first and/ or the second alignment structure.
  • the circular molding tool is preferably selected from a roll, a cylinder, a belt, a film or a metal plate.
  • the circular molding tool comprises a structured surface consisting of a plurality of identical, repeatedly arranged embossing patterns for manufacturing several embossed items.
  • the circular molding tool may comprise a plurality of stamping dies, wherein said stamping dies are mounted on a cylinder.
  • a method for producing a foil security element for securing a document of value by means of a liquid crystalline mixture containing dichroic dyes providing latent images comprising arranging a lacquer layer on a carrier substrate layer, performing an embossing of the lacquer layer to provide a first alignment structure, at least partly covering the lacquer layer by the uncured liquid crystalline mixture containing dichroic dyes, performing an embossing of the uncured liquid crystalline mixture to provide a second alignment structure, wherein the first and the second alignment structure cause the liquid crystalline mixture to show different images from respectively opposite sides in a cured state.
  • respectively opposite sides refer to both sides of the foil security element containing the crystalline mixture containing dichroic dyes.
  • the method proposed here achieves a polymerized liquid crystal sheet with several latent images on each side.
  • the manufacturing procedure employs confinement plates that induce an alignment pattern onto a polymerizable liquid crystal doped with a dichroic dye.
  • the resulting sheet will show two or more latent images when shined on with polarized light from either side, or when the sheet is observed through a polarizer.
  • a foil security element is a security element, which is arranged to form a foil comprising several layers, which can be joined together. Joining layers is preferably accomplished using laminating processes.
  • the respective foil security element as such forms a foil, which can be used in combination with further security elements and can, for instance, be introduced in a banknote.
  • a document of value is not restricted to a banknote but may also be present in the form of a passport. The respective document of value is secured such that security personnel or any user may verify the respective document of value.
  • the main advantage of the present invention is that several images can be formed using liquid crystalline mixture materials such that the user can see a different appearance of a single image or even several images when viewing the foil security element from opposite sides. It may be the case that the images can be seen with the unarmed eye or, more preferably, using additional tools such as a polarizer. Accordingly, such images serving as security fea- tures are named latent images.
  • Arranging a lacquer layer on a carrier substrate is first accomplished, wherein the carrier substrate may be formed by PET.
  • the arranging of the lacquer layer can be performed using any known techniques comprising for instance printing techniques.
  • the lacquer layer may be sensitive to ultraviolet radiation such that curing is performed using such irradiation.
  • the lacquer layer is at least partly covered by uncured liquid crystalline mixture, which means that the liquid crystal is not crosslinked yet. Accordingly, it is possible to emboss both the lacquer layer on its top side and the liquid crystalline mix- ture on its top side.
  • the notion of top side refers to an arrangement as, for instance, being depicted throughout the figures.
  • the liquid crystalline mixture is arranged above the lacquer layer and two different alignment structures are caused, one being created on top of the lacquer layer and one being created on top of the liquid crystalline mixture.
  • the liquid crystalline mixture is at least partly covering the lacquer layer, which means that the liquid crystalline mixture may be formed by an additional layer completely covering the lacquer layer or by means of specific areas, which merely partly cover the lacquer layer.
  • the liquid crystalline mixture comprises a first and a second alignment structure being arranged on both sides of the liquid crystalline mixture. Accordingly, each alignment structure causes the liquid crystalline mixture to arrange in a specific fashion, thereby providing respec- tively different images. Due to this arrangement, it is possible that the liquid crystalline mixture provides two different images, which are observable from respectively one side. An optical effect is established such that when viewing the foil security element from one side, a first image is visible and when viewing the foil security element from the opposite side, a second, different image is visible. This is due to the fact that the liquid crystalline structure can be created differently and especially separately from each other using both alignment structures. Accordingly, each alignment structure causes a specific behavior of the crystalline mixture to show a specific image.
  • the present invention is directed towards a document of value, especially a banknote, with a window portion, in which the security element is arranged, the security element comprising dichroic dyes being inserted into a liquid crystalline layer or material.
  • the liquid crystal feature can be seen in transparent light using the front side or the back side.
  • the security feature is not visibly recognizable, according to an aspect of the present invention.
  • a polarizer may be used to identify the latent images. Accordingly, linear polarized light may be used to identify respectively different security information on the front side or respectively the rear side of the banknote.
  • the foil security element comprises an embossing being applied on a so-called UV-lacquer.
  • a UV-lacquer is a lacquer layer being sensitive to ultravi- olet light.
  • the crystalline layer may be printed along with the dichroic dyes. This is performed in a not yet crosslinked state.
  • the arrangement may comprise a metallized layer comprising a cavity (herein also referred to as a gap) or a relief.
  • Such features may form patterns, characters, numbers and suchlike.
  • a metallized layer forming a positive text or a negative text is obtainable.
  • the metallizing can be performed using evaporating techniques.
  • a demetallizing ink can be applied.
  • a print receptive layer can be applied such that additional security elements can be printed on the security feature.
  • Such print recep- tive layers typically are based on binders, optionally containing fillers such as AI 2 O3 or S1O2, wherein additional leveling agents or stabilizer materials can be used.
  • the procedure of producing a metallized layer containing cavities by means of a demetallizing ink is known, for example, from EP 972462 A2.
  • spacer materials can be used to make sure that at least the liquid crystalline layer is of a constant thickness. Moreover, a tilt effect can be implemented. Furthermore, it is possible to print a so-called metallic mask as a further security feature. Furthermore, a reflective coating can be arranged comprising metal flakes and/ or metal pigments. Such a metallized layer may form a reflective layer.
  • the step of covering the lacquer layer by the uncured liquid crystalline mixture is performed after embossing of the lacquer layer, wherein the uncured liquid crystalline mixture at least in part covers the embossed first alignment structure.
  • first an embossing is performed on the lacquer layer such that the respective structure arises, as such a structure is covered in further steps with the liquid crystalline mixture. Accordingly, it is possible to provide a first alignment structure under the liquid crystalline mixture.
  • the lacquer layer is curable by means of ultraviolet irradiation. This provides the advantage that the lacquer layer can be cured and therefore hardened at any state of the production process using known curing processes.
  • the first alignment structure and the second alignment structure are arranged on different sides of the liquid crystalline mixture.
  • This provides the advantage that different images as security features can be applied on a single liquid crystalline mixture layer. Accordingly, both sides of the liquid crystalline mixture layer can be created differently and apart from each other such that it is possible to implement different optical informations on both sides.
  • At least one primer layer is provided for providing a homogeneous thickness of the foil security element.
  • a heat sealing layer a print-receptive layer, a coating layer, a lamination-adhesive layer, a metal layer, a color-shift effect layer and/ or a protective layer are provided.
  • a color-shift effect layer provides an optical effect such that different colors are provided as a function of a viewing angle.
  • the foil security ele- ment is arranged to form a patch or a stripe. This provides the advantage that several application domains are possible for the suggested foil security element.
  • a metal layer is pro- vided being partly demetallized to provide patterns, characters, numbers and suchlike.
  • a metal layer forming a positive text or a negative text is obtainable.
  • the carrier substrate layer is provided by means of polyethyleneterephthalat, PET for short. This provides the advantage that PET provides an easy-to-use carrier layer which can be easily inserted, for instance into a banknote.
  • arranging the lacquer layer on the carrier substrate layer is performed using printing techniques. This provides the advantage that the lacquer layer can be applied with little technical effort. According to the present invention, any known printing technique is suitable for applying the lacquer layer.
  • a foil security element for securing a document of value by means of a liquid crystalline mixture containing dichroic dyes providing latent images, comprising a lacquer layer being arranged on a carrier substrate layer, the lacquer layer being at least partly covered by the uncured liquid crystalline mixture containing dichroic dyes, wherein the lacquer layer is embossed to provide a first alignment structure of the liquid crystalline mixture, and the uncured liquid crystalline mixture is embossed to provide a second alignment structure, wherein the first and the second alignment structure cause the liquid crystalline mixture to show different images from respectively opposite sides in a cured state.
  • the object is also solved by a document of value comprising the foil security element according to the suggested features.
  • the foil security element is inserted into a window portion of the document of value. This provides the advantage that the foil security element can be made part of any document of value, especially banknotes, and furthermore that the security feature is visible through the window. ⁇
  • an apparatus being arranged in accordance with the suggested method. Accordingly, an arrangement unit, a covering unit as well as a first embossing unit and a second embossing unit are suggested.
  • the respectively suggested units provide features for accomplishing the suggested method. Accordingly, the method is arranged to operate the suggested apparatus. By performing the suggested method and operating the sug- gested apparatus, the foil security element as currently suggested can be established.
  • the object is also solved by a computer program product implementing the respective method steps and furthermore being able to operate the suggested apparatus.
  • Fig. 1 a product after a first step on an embossing machine with two embossing stations according to an aspect of the present invention
  • Fig. 2 the product after a metallizing and demetallizing procedure according to a further aspect of the present invention
  • Fig. 3 the product wherein a primer, heat sealing, and a print receptive layer is applied according to an aspect of the present invention
  • Fig. 4 the product after a preliminary step on an embossing machine with two embossing stations and making use of a spacer according to an aspect of the present invention
  • Fig. 5 the respective product without demetallizing ink according to an aspect of the present invention
  • Fig. 6 the product comprising a heat-sealing layer according to an aspect of the present invention
  • Fig. 7 a transfer foil with color-shift effect according to a further aspect of the present invention.
  • Fig 8 a foil being arranged as a patch according to an aspect of the pre- sent invention
  • Fig. 9 a foil with additional masking of the LC element according to a further aspect of the present invention
  • Fig. 10 a flowchart illustrating the method for producing the foil security element according to an aspect of the present invention.
  • Figures 1-8 show respective intermediate steps of the suggested method, where a layer arrangement is provided for producing the foil security element.
  • FIG. 1 to 3 demonstrate example V. Production of a foil to be used as a foil stripe applied to a security paper with a window (hole).
  • a polyester foil (according to an aspect of the present invention, 6 ⁇ to 36 ⁇ , preferably 12 ⁇ , pretreated for ink adhesion) is coated with an embossing lacquer (any coating/ printing process, e. g. flexo, gravure, slot die ...), embossed and UV cured. If there is the need for registration of one of the motives to the position of the liquid crystals (later to be applied), it is preferably this.
  • the mixture to be used according to an aspect of the present invention as the liquid crystal component is used in a printable state. This may be achieved by thinning with a suitable solvent (physical drying is necessary) or pref era- bly by heating. Most preferable is a temperature between 50°C and 80°C (of course depending on the mixture). Besides the pressure, the temperature of the mixture in the deposition step, and the foil and roller temperatures are key factors to control the thickness of the layer.
  • the application of the mixture is done in register to the embossing structure applied in the first step. Horizontal movement of the liquid crystal mixture during further processing is taken into account.
  • Printing processes/ coating processes which can be easily used in register are preferred. This can be use of a piezo system (like inkjet), application with other nozzles, silk screen, gravure or flexo.
  • nozzles/ inkjet and silk screen as the excess volume of liquid crystal material needed is small.
  • a chamber blade system should be used to minimize the volume of material needed. Reducing wasting material as much as possible should also be key to select the printing process.
  • Parts of the machinery in direct contact with the liquid crystals should be kept at a controlled temperature to prevent the liquid crystals from solidifying/ crystallizing and also to guarantee the LC phase in which the molecules will be oriented in right direction (overheating the mixture will be also adequate).
  • a heating of the foil may be necessary for higher process speeds as the speed of alignment depends on the temperature.
  • additives may have to be added to the liquid crystalline mixture.
  • the pulling of threads is of disadvantage for coating with nozzles. This has to be taken into account when deciding on the pressure distribution in the nozzle area during and after dosing.
  • the threads may have to be removed mechanically or by the use of additives to the formulation like defoamers.
  • Irradiation with light of the right wavelength and intensity (e. g. laser) in the area between nozzle and substrate may break the thread in the right moment.
  • the liquid crystal mixture is directly applied to the embossed surface of the foil.
  • an application on the embossing roll described hereafter is also possible, it can be done in an area shielded from light before the foil touches the cylinder.
  • a step of thickness/ leveling control may be done by introducing the film with the mixture between two pressure rollers at a given temperature.
  • the roll or the foil in the material's side may include pillars (spacers grown) to ensure a controlled material's thickness. By carefully controlling the temperature, i. e. the material's viscosity, a well-established and uniform material thickness can be obtained prior to subsequent processing.
  • the foil containing the liquid crystalline mixture locally is brought into contact with the embossing roll which is being kept, according to an aspect of the present invention, at a suitable temperature.
  • the foil may either just enter the nip between embossing roll and impression roller, or it may be led to the embossing roll by the impression roller.
  • the impression roller is pressed against the embossing roll with a pressure suitable for preventing the incorporation of larger amounts of air bubbles into the liquid crystal mixture in the nip between the rolls. Besides this requirement for the minimum pressure, the pressure must be suitable for achieving the ideal thickness of the liquid crystal material if the thickness is not exactly defined by the coating/ printing process. E. g. the application of one or more drops from a nozzle may lead to a very high thickness at the points of application and zero thickness in the other areas.
  • the leveling can take place between embossing roll and impres- sion roller.
  • the coating will be hazy in the areas not reaching the ideal temperature in time.
  • Spacers are hard particles with a defined diameter (e. g. 8 ⁇ ). However, they can be used advantageously only in combination with a hard impression roller. Growing spacers, pillars or columns in the lacquer structure is also suggested as an alternative way to fix the final thickness.
  • the embossing roll may be made from different materials. It may be made from nickel, diverse plastics, silicones, or quartz. In contrast to the established UV embossing process, where the positioning of the lamps is only of limited importance, it is here preferred for the alignment process and the thermal conditioning to perform curing only after some time on the embossing roll. The respective area in the embossing station is shielded from UV light to avoid disturbing the alignment early.
  • the thickness of the liquid crystals after this process according to an aspect of the present invention is 2 ⁇ to 30 ⁇ , preferably 3 ⁇ to 14 ⁇ , most preferably 4 ⁇ to 8 ⁇ .
  • the embossing rolls (1 st step and 2 nd step) should contain structures suitable for alignment covering the areas which either directly (second roll) or indirectly (first roll; structure transferred to embossing lacquer) come into contact with the liquid crystal mixture.
  • Theses structures should be de- signed in a way that each of the embossing rolls induces alignment in the form of a motive/ background containing alignment structures inducing alignment in at least two directions, giving a good contrast in polarized light, and containing various alignment areas preferably covering the whole surface with at least two alignment directions (different orientations could be used to generate more than one latent image and also to generate grey levels).
  • Orienting structures may have very small depth and still be efficient as shown in rubbing processes. For the use of established embossing processes, alignment structures with a line distance of 50 nm to 1500 nm and a depth of 50 nm to 1500 nm may be used. The structures do not have to be periodic to be effective. The chosen structures may be adapted to the other requirements of the production process of the other security features as a wide range of structures is effective for alignment. E.
  • UV-crosslinking of liquid crystals can be done either in one step or in several steps.
  • An iron-doped medium pressure mercury lamp is especially effective for curing on the embossing roll.
  • the UV source it has to be considered that at least a substantial part of the emitted light should be transmitted by the carrier substrate (in the case of PET, 300 nm and longer wavelength) and be able to crosslink the liquid crystals. This condition is also met by gallium-doped lamps and especially in recent years by LED sources. Sources emitting at 365 nm are preferred.
  • any medium-pressure mercury lamp can be used for this step.
  • Most liquid crystal mixtures are cured under inert conditions (nitrogen or CO2 inerting). After this step, the new optical feature is functional already (apart from the open structures on the surface which should be closed to render them optically inactive).
  • liquid crystalline material may cover a larger area than necessary for the optical effect, possibly even larger than the optical window in the substrate. The amount of excess material has to be minimized as it would also fill embossed structures needed for other optical effects.
  • the embossing structure outside the window of the second embossing step may be chosen in a way that it matches or harmonizes with the first embossing.
  • Another solution is to mask this area e. g. by later coatings or an opaque layer (e. g. very thin/ small metal pigments useful for holograms) in this area before applying the liquid crystals.
  • Optical features on security foils often contain structured PVD layers and/ or further liquid crystal layers. PVD layers can easily be structured in a washing process.
  • the foil is coated with a spe- cial coating.
  • the application is usually done by gravure or flexo printing.
  • This coating is a mixture that is applied to a substrate and usually physically dried before a further coating process, usually PVD metallizing. After this, a washing process takes place, in which this coating is removed together with the coatings which have been applied on top of it. This washing can be done using solvents, water and mechanical tools like brushes or felts. This removable coating is used to cover substantial parts of the newly produced optical security feature.
  • One or more PVD layers may be applied which may be structured individually or altogether by washing processes (special removable coating before PVD) or etching processes (resistive coating after PVD, before etching). E. g.
  • aluminium-metallizing may be used as a mirror for holograms (adhesion of aluminum may be achieved by using a small amount of chromium as a first "layer” or other adhesion promoting measures (corona and/ or plasma treatment). After the metallizing and demetallizing/ washing processes further layers may be applied:
  • the embossed structures of the liquid crystals can be kept visible by applying a coating that does not match the refractive index of the liquid crystals. It may be a HRI coating.
  • the coating with primers and heat, sealing layers may cover either the whole element or only part of it.
  • the liquid crystal element should be coated with coatings with good transparency.
  • the top of the foil may be coated using primers and ink receptive coatings.
  • decorative coatings are also possible. They may be used to cover areas covered with liquid crystals due to technical reasons. These decorative layers may also contain metallic pigments Squashings of the liquid crystals may be minimized by achieving a good uniformity of the layer, e. g. by silk screen printing.
  • the grammage of the liquid crystalline mixture near the borders may be lowered so much that during embossing it is not squashed beyond the predefined area.
  • An attractively look with well-defined edges can be achieved using careful deposition of the material, such as silk-screen printing, potentially in combination with features limiting the extension of the materials in the layer.
  • any less well-defined edges can be masked by additional, opaque, or semi-opaque, layers deposited on top and/ or below the area with material. If the masking is done prior to curing, and if UV curing is employed, care has to be taken to ensure that the material is exposed adequately to the curing light.
  • Another way of getting an attractive feature is, according to an aspect of the present invention, applying a metallizing/ demetallizing process to the embossed foil before applying the liquid crystal or producing a kind of mask by a printing process.
  • an optically attractive frame can be generated through which the liquid crystals can be seen.
  • imperfections likely to be concentrated near the borders of the liquid crystal area can be masked.
  • the liquid crystals can be seen only through transparent areas of the substrate whose borders are structured separately.
  • the applied mask has to be produced in a way that the covered areas transmit at least enough light of the wavelength needed for crosslinking the liquid crystals.
  • the first masking layer which is not completely opaque
  • the liquid crystal layer may be added some more layers after the first masking layer (which is not completely opaque) and the liquid crystal layer.
  • another curing station for completely curing the liquid crystals possibly under inert atmosphere, e. g nitrogen
  • ebeam curing can be used if curing by UV is not possible.
  • the end user of the banknote may not know what kind of motive he is supposed to see when verifying the banknote.
  • the motives shown in the see- through situation may be repeated elsewhere on the side of the banknote facing the viewer or on other parts of the foil.
  • the see-through feature may also be completed by other design elements on the respective side on the banknote.
  • a windowed security thread such as a so-called
  • the first embossing is just done in the established way.
  • a removable coating is applied.
  • a metallizing/ demetallizing process is done (separate machines).
  • the embossing structures may contain holograms, microlenses, micro- mirrors, microcavities, moth eyes, in principle any structure which can be embossed.
  • the embossed structures may be rendered visible by applying coatings with a different refractive index (e.g. high refractive index (HRI)), metals (e. g. aluminium, chromium, copper), multilayer PVD coatings show- ing color shift or defined colors, multilayer PVD coatings giving other see- through features like a first color (e.g. gold) in reflection andsa second color (e.g. blue) in transmission, which may advantageously be used in the case of banknotes with at least two windows or one window covering both areas (liquid crystals area and PVD area).
  • HRI high refractive index
  • metals e. g. aluminium, chromium, copper
  • multilayer PVD coatings show- ing color shift or defined colors
  • multilayer PVD coatings giving other see- through features like a first
  • Figure 7 demonstrates example 2 as follows:
  • An untreated polyester foil may be used as a temporary carrier. This may be (not necessarily) coated with an additional release layer that makes removal of the foil possible later on under more defined conditions.
  • This foil is coated with an embossing lacquer.
  • the embossing lacquer is embossed with the desired structure. If a one-layered UV curing system is used, a precuring step (UV) can be used before embossing. The UV intensity is so low that complete cure is not effected. In a multilayer system, the first layer is cured at least to a degree that contamination of rolls within the machine is avoided. As long as good adhesion by the following embossing layer is achieved, any degree of cure is possible. In this process embossing can usually take place in a casting process (that means without precuring), which is an advantage for the replication of the structures.
  • the embossing lacquer has to be chosen in a way that the liquid , crystalline substance does not attack the layer too severely as this would be detrimental to the aligning effect of the structures. Further processing may take place similarly to example 1. In this case, an extra print receptive layer is not always necessary as the top layer (after removal of the carrier foil) is already print-receptive enough.
  • Figure 8 demonstrates example 3 as follows, namely the production of a foil to be applied as a patch on a banknote or to be laminated in a card.
  • any additional foil is laminated to the carrier foil already there.
  • any additional layers may be introduced (e.g. metallizing, demetallizing, high refractive index(HRI)-layers, any pigmented layers) under the precondition that the layers do not permanently cover the area important for alignment of the liquid crystals (example: special coating for demetallizing process later on in the window), or at least do not disturb the alignment of the liquid crystals.
  • the liquid crystals are deposited and brought into contact with the embossing roll (a suitable temperature has to be chosen) and crosslinked.
  • the geometry is chosen in such a way that curing is effected only after the liquid crystals have had some time for alignment according to the structure on the embossing roll and the structure on the carrier film (alignment).
  • Printing of additional decorative layers may take place, however, the essential areas of the area covered with liquid crystals and placed on a transparent window to be seen from both sides are not covered by opaque layers.
  • another foil is laminated to the side of the element the liquid crystals are on. This foil is to remain in the final product.
  • This foil is coated with primer(s) and heat-seal coatings.
  • the foil is punched from the side of the heat-seal coating. Punching takes place in a way that at least the embossing coating is punched and at most the temporary carrier foil and the laminating adhesive between the temporary carrier foils is punched.
  • the matrix containing the parts not needed is stripped away, the patches needed for the final product and the patches needed for technical reasons stay on the temporary carrier foil.
  • the patches may be applied to a suitable foil, e. g. polycarbonate.
  • This foil can be laminated together with the patches.
  • Either a primer and heat-seal coating is applied in the next step and then punching a matrix stripping is done, or punching and matrix stripping is done directly as polycarbonate may be used as heat-seal coating to polycarbonate. Then the original temporary carrier foil is removed. Then one major surface contains polycarbonate and the other major surface (of the patches) contains a release coating, or more likely a UV lacquer.
  • the embossing structure according to an aspect of the present invention has to contain structures inducing alignment just in the area to be covered with liquid crystals. In addition to these structures in this area, and especially in all the other areas, other structures are possible. Examples are micro mirrors, holographic structures, micro cavities, micro lenses, Fresnel structures and the like.
  • PVD physical vapor deposition
  • a layer system (obtainable for example by PVD) comprising several layers, e.g. (i) a color shifting layer system showing an angle dependent color change, particularly comprising a reflecting layer, a dielectric layer and an absorbing layer, e.g. Al/ Si0 2 /Cr; or (ii) a semi-transparent layer system showing a first color in reflection (e.g. gold) and a second color in transmission (e.g. blue), described, for example, in WO 2011/082761 Al;
  • a color shifting layer system showing an angle dependent color change, particularly comprising a reflecting layer, a dielectric layer and an absorbing layer, e.g. Al/ Si0 2 /Cr
  • a semi-transparent layer system showing a first color in reflection (e.g. gold) and a second color in transmission (e.g. blue), described, for example, in WO 2011/082761 Al;
  • a surface relief e.g. a surface relief containing micro- structures
  • a conventional printing system such as flexography, rotogravure, offset printing, silkscreen printing, digital printing, and ink jet printing;
  • platelet-shaped metal pigments e.g. thin aluminium or silver pigments, enable angle-dependent color shifting effects or reflec- tion/ transmission-depending color change effects and are known in the art, e.g. WO 2013/186167 A2, WO 2010/069823 Al and WO 2005/051675 A2.
  • the alignment of the liquid crystals is described only on the second embossing roll. This was tested at the pilot line. In this way only limited line speeds are possible, as the distance between first contact with the cylinder and removal of the foil from the cylinder is limited by the circumference of the cylinder and the wrap angle possible, and alignment of the liquid crystals needs a certain amount of time.
  • This limitation may be avoided by using an embossing foil as an endless belt taking over the function of the embossing roll. The contact time possible depends on the length of the belt. In this way, this step is not limiting for the line speed anymore.
  • One of the most common foils is polyester foil.
  • Using the kind of foil for opti- cal features involving polarizing effects has several shortcomings. The major one is that the foil is optically anisotropic and even has a certain dispersion. This may reduce the contrast of this kind of feature.
  • One solution is using a foil that has been produced without a stretching step, e. g. cast foils. If the mechanical stability of these foils is insufficient, they might be used only in the final step.
  • the security feature is transferred to an isotropic foil.
  • Another way to cope with this problem is using PET foils which have been stretched in a way to minimize optical anisotropy or even more important dispersion. Also several thinner layers may be used if these layers are selected for minimal optical interference with the feature or to compensate each other.
  • the inventive process is not limited to PET. Any transparent foil may be used. However, the machine parameters and the necessary primers have to be chosen accordingly. Especially polycarbonate should be mentioned.
  • UV curing coatings may show good adhesion to it if a certain temperature is reached before and/ or during curing and/ or certain reactive diluents (like HDD A) are used to induce some swelling.
  • polycarbonate is subjected to high temperatures which may have an influence on the optical properties (e. g. on birefringence).
  • a step of thickness/ leveling control Prior to any posterior procedure, it may be necessary to introduce a step of thickness/ leveling control. This may be done by introducing the film with the mixture between two pressure rollers at a given temperature. Potentially the roll or the foil in the material's side may include pillars (spacers grown) to ensure a controlled material's thickness. By carefully controlling the temperature, i. e. the material's viscosity, a well-established and uniform materi- al thickness can be obtained prior to subsequent processing.
  • Fig. 9 shows a further aspect of the present invention, namely masking of the LC element.
  • Fig. 10 shows a flowchart depicting a method for producing a foil security element for securing a document of value by means of a liquid crystalline mixture containing dichroic dyes providing latent images, comprising arranging 100 a lacquer layer on a carrier substrate layer, at least partly covering 102 the lacquer layer by the uncured liquid crystalline mixture containing dichroic dyes, wherein embossing 101 of the lacquer layer is performed to provide a first alignment structure of the liquid crystalline mixture and embossing 103 of the uncured liquid crystalline mixture to provide a second alignment structure, where the first and the second alignment structure cause the liquid crystalline mixture to show different images from respectively opposite sides in a cured state of the liquid crystalline mixture.
  • embossing 101 of the lacquer layer is performed to provide a first alignment structure of the liquid crystalline mixture and embossing 103 of the uncured liquid

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  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Credit Cards Or The Like (AREA)
  • Laminated Bodies (AREA)
  • Liquid Crystal (AREA)
  • Polarising Elements (AREA)
  • Printing Methods (AREA)

Abstract

La présente invention porte sur un procédé de production d'un élément de protection en feuille destiné à protéger un document de valeur au moyen d'un mélange cristallin liquide contenant des colorants dichroïques, et porte en outre sur l'élément de protection en feuille en tant que tel. En outre, l'invention concerne un document de valeur donné à titre d'exemple et comprenant l'élément de protection en feuille, ainsi qu'un appareil destiné à la fourniture d'un tel élément de protection et un produit-programme informatique.
PCT/EP2018/076681 2017-10-05 2018-10-01 Fenêtre à deux faces transparentes présentant des colorants dichroïques Ceased WO2019068655A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2018344427A AU2018344427B2 (en) 2017-10-05 2018-10-01 Two-sided transparent window feature with dichroic dyes

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP17194937.3A EP3466711B1 (fr) 2017-10-05 2017-10-05 Caractéristique de fenêtre transparente à deux faces comportant des colorants dichroïques
EP17194937.3 2017-10-05

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WO2019068655A1 true WO2019068655A1 (fr) 2019-04-11

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AU (1) AU2018344427B2 (fr)
ES (1) ES2814449T3 (fr)
WO (1) WO2019068655A1 (fr)

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US20230038961A1 (en) * 2021-08-04 2023-02-09 Alise Devices S.L. Semi-finished product, security element, methods of producing them and document of value
EP4461555A1 (fr) 2023-05-08 2024-11-13 Giesecke+Devrient Currency Technology GmbH Élément de sécurité comprenant une couche de cristaux liquides formant un motif

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BR112020003100A2 (pt) 2017-10-05 2020-09-01 Wavefront Technology, Inc. estruturas ópticas que fornecem efeitos dicroicos
EP3938218A4 (fr) 2019-04-04 2022-11-30 Wavefront Technology, Inc. Structures optiques fournissant des effets dichroïques
DE102019003947A1 (de) * 2019-06-06 2020-12-10 Giesecke+Devrient Currency Technology Gmbh Verfahren zum Herstellen eines optisch variablen Sicherheitselements
DE102020005522A1 (de) * 2020-09-09 2022-03-10 Giesecke+Devrient Currency Technology Gmbh Optisch variables Sicherheitselement
WO2022077012A1 (fr) 2020-10-07 2022-04-14 Wavefront Technology, Inc. Produits optiques, maîtres de fabrication de produits optiques, et procédés de fabrication de maîtres et de produits optiques
EP4217773A4 (fr) 2020-10-07 2024-10-23 Wavefront Technology, Inc. Produits optiques, gabarits pour la fabrication de produits optiques et procédés de fabrication de gabarits et de produits optiques
DE102020007028A1 (de) 2020-11-17 2022-05-19 Giesecke+Devrient Currency Technology Gmbh Sicherheitselement, mit demselben ausgestattetes Wertdokument und Herstellungsverfahren
DE102021001588A1 (de) * 2021-03-25 2022-09-29 Giesecke+Devrient Currency Technology Gmbh Herstellungsverfahren für ein optisch variables Sicherheitselement
DE102021001589A1 (de) * 2021-03-25 2022-09-29 Giesecke+Devrient Currency Technology Gmbh Herstellungsverfahren für ein optisch variables Sicherheitselement

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EP1894736A2 (fr) 2006-08-28 2008-03-05 Giesecke & Devrient GmbH Elément de sécurité à effet chatoyant et procédé de fabrication dudit élément
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EP1972462A2 (fr) 2007-01-05 2008-09-24 Giesecke & Devrient GmbH Procédé de fabrication de feuilles de sécurité
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EP2508358A1 (fr) 2009-12-01 2012-10-10 Universidad Politécnica De Madrid Procédé et dispositif de sécurité pour des documents reposant sur la génération d'images multiples
WO2013186167A2 (fr) 2012-06-14 2013-12-19 Basf Se Procédé destiné à fabriquer des éléments de sécurité et des hologrammes

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WO2005051675A2 (fr) 2003-11-14 2005-06-09 Printetch Limited Impression
EP1894736A2 (fr) 2006-08-28 2008-03-05 Giesecke & Devrient GmbH Elément de sécurité à effet chatoyant et procédé de fabrication dudit élément
WO2008031170A1 (fr) * 2006-09-15 2008-03-20 Securency International Pty Ltd Dispositifs de sécurité à encre en relief séchable par rayonnement destinés à des documents sécurisés
EP1972462A2 (fr) 2007-01-05 2008-09-24 Giesecke & Devrient GmbH Procédé de fabrication de feuilles de sécurité
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EP2508358A1 (fr) 2009-12-01 2012-10-10 Universidad Politécnica De Madrid Procédé et dispositif de sécurité pour des documents reposant sur la génération d'images multiples
WO2011082761A1 (fr) 2009-12-14 2011-07-14 Giesecke & Devrient Gmbh Elément à couche mince de couleur dorée présentant une structure multicouche
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US20230038961A1 (en) * 2021-08-04 2023-02-09 Alise Devices S.L. Semi-finished product, security element, methods of producing them and document of value
US12189157B2 (en) * 2021-08-04 2025-01-07 Giesecke+Devrient Currency Technology Gmbh Semi-finished product, security element, methods of producing them and document of value
EP4461555A1 (fr) 2023-05-08 2024-11-13 Giesecke+Devrient Currency Technology GmbH Élément de sécurité comprenant une couche de cristaux liquides formant un motif
DE102023111992A1 (de) 2023-05-08 2024-11-14 Giesecke+Devrient Currency Technology Gmbh Sicherheitselement mit motivbildender Flüssigkristallschicht

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EP3466711A1 (fr) 2019-04-10
AU2018344427A1 (en) 2020-05-07
EP3466711B1 (fr) 2020-06-03
ES2814449T3 (es) 2021-03-29
AU2018344427B2 (en) 2022-10-13

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