Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
  • G03H1/22—Processes or apparatus for obtaining an optical image from holograms
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
  • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
  • G02F1/1333—Constructional arrangements; Manufacturing methods
  • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
  • G02F1/133553—Reflecting elements
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
  • G03H1/0005—Adaptation of holography to specific applications
  • G03H1/0011—Adaptation of holography to specific applications for security or authentication
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
  • G03H1/02—Details of features involved during the holographic process; Replication of holograms without interference recording
  • G03H1/0252—Laminate comprising a hologram layer
  • G03H1/0256—Laminate comprising a hologram layer having specific functional layer
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F2203/00—Function characteristic
  • G02F2203/07—Polarisation dependent
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
  • G03H1/02—Details of features involved during the holographic process; Replication of holograms without interference recording
  • G03H1/024—Hologram nature or properties
  • G03H1/0248—Volume holograms
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
  • G03H1/22—Processes or apparatus for obtaining an optical image from holograms
  • G03H1/2249—Holobject properties
  • G03H2001/2276—Polarisation dependent holobject
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H2250/00—Laminate comprising a hologram layer
  • G03H2250/38—Liquid crystal
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
  • G03H2250/00—Laminate comprising a hologram layer
  • G03H2250/41—Polarisation active layer

Definitions

• Security element with an electrically stimulable polarization-dependent volume hologram and method for its production
• the invention relates to security elements which comprise an electrically stimulatable hologram and to a method for the production thereof.
• the security elements serve to secure a security and / or value document against counterfeiting and / or copying.
• One type of security element comprises volume holograms Information is stored in a volume hologram. often also individualizing information, such as serial numbers, ID numbers, biometric data, geographic data, images (passport photos), etc, contain This information can be stored in plain text or image or optically encoded or machine-readable in the hologram
• hologram master which is designed as a hologram
• the hologram master is positioned behind a holographic recording material.
• a laser is irradiated to the hologram master side facing away from the holographic Aufzeichmation ⁇ , typically with a defined wavelength and a defined angle of incidence, optionally in accordance with the holographic master to be reconstructed holographic pattern It penetrates the holographic recording material and is diffracted by the hologram master, the hologram interfering with the incident light in the holographic Mauzeich ⁇ ungsmate ⁇ al maps and stores by photochemical or photophysical processes in the holographic recording Mate ⁇ al
• the hologram master can be designed so that it is sensitive to several wavelengths and this bends or reflected accordingly Other geometric arrangements than those described here are possible
• hologram masters which are not holograms.
• Such hologram masters can, for example, have a saw-tooth-like or imbricated structure, as are known from DE 2007 06796 U1
• An individualization of the hologram can take place via a modulation of the light used.
• Spatial light modulators in the form of liquid crystal displays (LCD) are known in practice. Its operation is similar to a projection of a slide, with the Spatial Light Modulator replacing the slide.
• digital projectors are known from practice which include, for example, a Digital Micro Mirror Device (DMD) or a Liquid Crystal on Silicon (LCoS) as Spatial Light Modulator.
• DMD Digital Micro Mirror Device
• LCDoS Liquid Crystal on Silicon
• an individualization can be made via individually printed foils, which are arranged similar to a transparency in the beam path of the coherent light, possibly also intimately connected to the holographic material
• An exposure of the hologram can be done with light of one wavelength (monochrome) or with different wavelengths (colored).
• different individualization patterns can be stored in the hologram in the different wavelengths.
• an interactive security element that comprises at least one volume hologram.
• the volume hologram responds to at least one external excitation and exhibits a defined optical effect in the form of an image, wherein the optical effect in the form of the image is preferably different for different viewing angles and the different images are observable at least when the external excitation has been applied.
• a method for the verification of the interactive security element as well as an application as a public feature for security products for example banknotes, passports, identification documents, tickets, etc. are described
• the light intensity modulator comprises an electrical circuit and a holographic optical element comprising a hologram.
• the holographic optical element is electrically connected to and receives a variable voltage generated by the electrical circuit.
• the holographic optical element receives incident light from a light source.
• the holographic optical element receives and diffracts the incident light to produce first and second output bits.
• An intensity of the first output light varies directly with a magnitude of the voltage.
• the first and second output pitches include a non-zero angle between each other an alternating voltage changes a refractive index in a polymer-dispersed Flussigk ⁇ stall
• US Pat. No. 6,821,457 B1 discloses a photopolymerizable material which permits one-step recording of a volume hologram whose properties can be electrically controlled.
• a polymer-dispersed liquid nitrogen comprises a homogeneous mixture of a nematic liquid nitrogen and a multifunctional pentaacryl monomer in combination with a photoinitiator, co-initiator and a Crosslinking Agent
• the Proposed Material Can Store an Interference Pattern as a Hologram Providing Significantly Separate Flow Sigmas and Hardened Polymer Domes Bulk transmission gratings made with the new material can be electrically switched between nearly one hundred percent diffraction efficiency and nearly zero percent diffraction efficiency
• the invention is based on the technical problem of providing an improved security element or an improved method for producing a security element which can be stimulated via an applied voltage in order to trigger an optically perceptible effect, whereby volume holograms not adapted specifically to electrical stimulation can be used
• a security element is a structural unit which comprises at least one security feature.
• a security element can be an independent structural unit that is connected, for example glued, to a security and / or value document can, but it can also be an integral part of a security and / or document of value
• An example of the first is a stick on a security and / or value document visa Em example of the latter is an integrated into a bill or passport, for example laminated hologram
• a security feature is a structure that can only be produced or reproduced with (compared to simple copying) increased effort or not at all unauthorized
• a pattern typically consists of a plurality of juxtaposed pattern units or pixels.
• the pattern units or pixels of a pattern are assigned to one another and arranged laterally in a defined manner, typically in two spatial dimensions.
• the pattern units are generally the same, but they can also be different, for example of different sizes or irregularly arranged
• Such security and / or documents of value typically comprise at least one substrate, at least one print layer, and optionally a transparent cover layer.
• a substrate is a support structure to which the print layer is applied with information, images, patterns, and the like All professional materials on paper and / or plastic basis in question
• a Spatial Light Modulator allows two-dimensionally spatially resolved illumination or irradiation of a mostly planar object with modulated intensity and / or phase.
• This may be, for example, a DMD (Digital Micro Mirror Device) chip, an LCD (Liquid Crystal Display) transmission display or Common to all is that a multiplicity of SLM pixels is formed, wherein each SLM pixel can be activated or deactivated independently of other SLM pixels (also intermediate stages are possible), whereby by appropriate control SLM pixels can be used to project patterns or images Due to their free controllability, different images or patterns can be generated one after the other in chronological order, for example in the form of a passport photo
• a code or pattern is individualizing if it is unique to a person or an object or a group of persons or objects from a larger total of persons or objects.
• a code individualizing a group of persons within the total population of a country is City of Residence
• a code individualizing a person is, for example, the passport photo.
• a serial number of an identity card is an individualizing feature for the individual.
• Code customizing a group of banknotes within the total number of banknotes is valence. Individualizing for a banknote, the serial number is not an example individualizing codes or patterns are coats of arms, seals, insignia, etc for security or value documents of a territory.
• personalizing information those are considered which comprise information that can be assigned to a person D
• These may include, for example, image information, for example a passport photograph, a fingerprint, etc., or alphanumeric character strings, such as a name, an address, a place of residence, a date of birth, etc.
• a holographic Aufracesmate ⁇ al is p ine layer of e ⁇ em material which is photosensitive, and in what can be holograms save by irreversible, but also reversible photochemical and / or photophysikahsche processes by way of exposure All known materials can be used so that on The technical literature of the person of ordinary skill in the art can be referred to by way of example Only the photopolymers customary in holography may be mentioned
• color is understood as a wavelength or a narrow wavelength interval or a spectral line. Mixed colors have several different wavelengths or spectral lines. The term color therefore also includes UV and IR in addition to the visible range
• Fluigk ⁇ stalle are substances which are present in a phase which on the one hand has fluid properties such as a liquid, on the other hand, however, optical properties, such as a birefringence, as are typical for crystals
• Nematic Flussigknstalle are those that exist in a so-called nematic phase, in which the individual molecules (Flussigknstalle) along their molecular axis Alignment
• a subform of the nematic phase is the cholesten, which has a nematic order with continuously rotating preferential orientation. This means that a long-range helical superstructure results
• a functional unit which comprises Flussigk ⁇ staile arranged between alignment layers and associated electrodes, between which a voltage can be applied, so that the resulting electric field influencing the collective optical properties of Flussigknstalle results in particular alignment of the
• the liquid crystal cell does not have to be designed as a monolithic unit.
• the individual components need not all adjoin one another directly Flussigkristallzelle belong, be arranged
• An alignment layer is a entity that affects alignment of liquid crystals adjacent to that alignment layer.
• the alignment layer may be a specially treated surface of another structural unit, such as a substrate or electrode
• the invention provides a security element, comprising at least one liquid crystal cell, which comprises Flussigknstalle arranged between two oppositely arranged alignment layers, wherein the Flussigkristallen facing surfaces of the alignment layers are such that the Flussigknstalle, ie the molecules of Flussigk ⁇ stallmediums, helically in a field-free ground state the at least one Flusstechnikskristallzelle are associated with two electrodes between which an electric field can be applied, in whose existence a switching state occurs, in which the Flussigknstalle reorient, and on a Lichtemfallseite the Flussigknstalle the at least one Flussigkristallzelle a polarizing filter is disposed is provided, on one of the Lichtemfallseite opposite Lichtausfallseite the Flussigknstalle the at least one Flusstechnikskristallzelle at least one holo
• a liquid cell is designed to be polarized through the cell
• the flux rods usually molecules
• the light can pass through the liquid cell without changing its polarization state.
• This is on a light failure side of the liquid junction cell of the liquid cell arranged at least one hologram designed so that its diffraction efficiency of the Pola ⁇ sationswinkel of the incident reconstruction light is dependent, it can be influenced by an influencing g the polarization of the incident light by an electrically induced switching between the ground state and the switching state, a reconstruction of the hologram are electrically switching influenced
• a Flusstechniksknstallzelle is advantageously designed so that linearly polarized light incident on the light incident side in the Flussigknstalle the Flusstechniksknstallzelle in Pola ⁇ sationsSullivan is changed so that a Polansationscardi measured transversely to the propagation direction by an angle of 90 ° or 270 ° is rotated
• the electric field vector of the light in the Flusstechniksknstallzelle is rotated by 90 ° or 270 °
• an additional rotation of the electric field vector by a multiple of 180 ° in each case substantially the same causes da as a result of holograms dependent polarization a cos 2 ⁇ - Abhang ⁇ gke ⁇ t of Pola ⁇ sationswinkel measured in a plane perpendicular to the propagation direction of the light relative to the diffraction plane, is, by a change in the Polansationsplatz by 90 °, 270 ° with a suitable orientation of the
• twisted nematic Flussigk ⁇ stallzellen twisted nematic, TN
• STN-Flussigk ⁇ stallzellen Super Twisted Nematic, STN
• DSTN-Flussigkristallzellen Double Super Twist Nematic, DSTN
• PDLC Flussigk ⁇ stallzellen Polymer-Dispersed-Liquid-C ⁇ stall, PDLC
• a polarization filter can be saved on a light failure side
• a method for producing a security element provides that at least one Flussigknstallzelle comprising between two oppositely arranged alignment layers Flussigknstalle, wherein the Flussigknstallen facing surfaces of the alignment layers are such that the Flussigknstalle align helically in a field-free ground state, and reorient the Flussigknstalle in a switching field having an electric field, between two of the at least one Flussigknstallzelle associated electrodes is arranged between which the electric field for generating the switching state can be applied, and in front of a Lichtemfallseite the Flussigknstalle the Flussigknstallzelle a polarizing filter is arranged, is provided in that, on the side of the light drop side opposite the light exit side, the flow balls of the at least one flow control cell arrange at least one hologram t, whose reconstruction is dependent on a polarization state of the light.
• a security feature produced in this way can be integrated, for example, in a security and / or value document in order to protect it against counterfeiting. This can be achieved, for example, by laminating and / or sticking on or any other way.
• phrases such as "in front of the light incident side” or "on the side of a light incident side” take place
• Light emission side of the liquid crystals of the at least one liquid crystal cell should each denote an area in front of and behind the light incident side or light failure side of the liquid crystal
• one or more elements, such as an electrode may be disposed between the liquid crystals and the corresponding unit.
• the described embodiment of the invention has a different reconstruction behavior of the hologram in the ground state and in the switching state of the liquid crystal cell, even without a polarization filter is disposed between the light failure side of the liquid crystals of the liquid crystal cell and the at least one hologram, as is usual in conventional liquid crystal displays.
• a polarizing filter is disposed in front of the light incident side of the liquid crystals of the liquid crystal cell and "behind" the light emission side of the liquid crystals of the liquid crystal cell. These are oriented to one another in a selected manner.
• the polarizing filters are aligned parallel to one another, light is transmitted through the arrangement only in the switching state. In the ground state, on the other hand, no light emerges from the second polarization filter.
• this also means that the light, which does not impinge upon the at least one hologram at an optimal reconstruction angle, passes through it, so that information possibly arranged behind the at least one hologram, for example, characters printed on an underlying layer , Texts, etc., are visible to a viewer.
• the at least one hologram is oriented relative to the polarization filter and at least one liquid crystal cell is configured so that the at least one hologram has a maximum diffraction efficiency in the field-free ground state of the liquid crystal cell and a minimum diffraction efficiency in the switching state of the liquid crystal cell.
• Another embodiment sees exactly the opposite, that the at least one hologram in the field-free ground state of Flussigk ⁇ stallzelle a minimum diffraction efficiency and in the switching state of Flussigkristallzelle maximum diffraction efficiency having The configuration of the Flussigkristallzelle sets, for example, by what amount the Pola ⁇ sationscardi the light passing through is rotated
• both a reflection hologram structure and a transmission hologram structure can be stored in the at least one hologram, which have maximum or minimum diffraction efficiency for the same and / or different polarization directions
• one or more flow cell cells are additionally arranged next to the at least one liquid crystal cell are each associated with electrodes or are to achieve upon application of an electric field, a reorientation of Flussigkristalle, and before the incidence side of the polarization filter or further polarization filters are arranged in one execution is thus between a polarizing filter and at least one hologram a plurality of individually trained Liquid crystal cells formed, each having two electrodes are assigned to the cells between the ground state and the switching state by an investment In this case, two individual electrodes can be individually assigned in the individual flow cell cells.
• Embodiments in which the liquid crystal cells each have a common electrode and additionally have an individually assigned electrode for switching over the individual liquid crystal cells are also possible.
• An arrangement of the individual liquid crystal cells can thus likewise be used to realize an individualization pattern. This is most easily possible if the at least one liquid crystal cell and the further liquid crystal cells are generated in a matrix-like grid or any other arrangement and then their electrodes are combined selectively into one or more groups. This can be done in a simple manner by first all the liquid crystal cells individually associated electrodes are electrically connected to each other. It is then possible, for individualization, to selectively interrupt the electrically conductive connections between individual ones of the liquid crystal cells and / or at a common electrical contact point, via which the voltage can be applied.
• the display matrix is advantageously made up of rows and columns, this form forms a passive matrix.
• the display can also be constructed as an active matrix, in which each pixel (pixel, pattern unit) is assigned an active Druck ⁇ l ⁇ m ⁇ nt, z. B. a diode or a transistor.
• the electrodes are preferably made transparent.
• an embodiment of the electrodes by means of transparent metal oxides, such as indium tin oxide (SnO 2 ) ITO, indium zinc oxide, ZnO, antimony tin oxide (ATO), or organic materials, such as PEDOT / PSS, Pani®, Orgacon® offers.
• Individualization can be achieved in the production or subsequently, for example, by targeted laser irradiation and an ablation of individual electrodes or compounds caused thereby.
• Alternative methods include etching and photolithographic patterning, but also printing, sputtering, spincoating.
• a reflective element in particular a reflecting element, is or is arranged on a side of the hologram facing away from the liquid crystal cell and / or the plurality of liquid crystal cells ,
• a reflective element is or is arranged on a side of the hologram facing away from the liquid crystal cell and / or the plurality of liquid crystal cells .
• Such may, for example, be a metallic layer.
• Such a layer may be on a substrate support, for example by printing by means of different printing processes be applied. Alternatively, such a layer may be applied by sputtering, evaporation, or the like.
• the at least one hologram and the liquid crystal cell or cells as well as electrodes and the polarization filter or the polarization filters can be attached thereto.
• the generated security element can assume different characteristics.
• a first individualizing and / or personalizing information for example a facial image of a person, can be stored above or with the security element. In one embodiment, this is done by one or more individualizing and / or personalizing first information is or are stored in the at least one hologram.
• the one or more further liquid crystal cells are individually controllable and form a display device.
• it can be achieved via a targeted control that, for example, only certain areas of the at least one hologram are reconstructed or not reconstructed.
• one or more Schaitense are connected to the at least one liquid crystal cell and / or the plurality of further liquid crystal cells, so that these individually and / or in groups on the one or more switching elements can be acted upon with a voltage.
• this provides a further possibility for storing and selectively retrieving individualizing or personalizing information in the security feature.
• an embodiment alternatively or additionally provides that some liquid-crystal cells of the at least one and several further liquid-crystal cells and / or some of the further polarization filters assigned to these some liquid-crystal cells are designed such that they have a polarization property deviating from the other liquid-crystal cells in a de-energized state for some liquid-crystal cells and a second individualizing and / or personalizing information is stored via a relative arrangement of these some liquid crystal cells to one another and / or with respect to the alignment layers of the remaining liquid crystal cells.
• This can be achieved, for example, in which the alignment layers are configured relative to a common polarization filter and be aligned so that they are rotated by 90 ° relative to the other liquid crystal cells.
• a plurality of further polarizing filters individually associated with the liquid crystal cells they may or may not be oriented for the some liquid crystal cells which are of the same construction and orientation as the remaining liquid crystal cells, unlike the other liquid crystal cells.
• an individualizing and / or personalizing information may be stored in which the electrodes associated with the at least one liquid crystal cell and the plurality of further liquid crystal cells are structured such that a selection thereof can be switched jointly between their ground state and their switching state by applying a single voltage , This enables the selection of the liquid crystal cells to be switched while the remaining remaining liquid crystal cells are not changed.
• FIG. 1 shows a schematic sectional view through a security element
• FIG. 2 shows a schematic illustration for explaining the polarization dependence of the diffraction efficiency of a hologram
• 3a shows a schematic sectional representation through a security element, in which no voltage is applied between the electrodes and a high diffraction efficiency of the hologram is present;
• Fig. 3b a schematic representation of the security element according to Fig. 3a, in which a voltage is applied between the electrodes, and a diffraction efficiency is minimal;
• FIG. 4 is a schematic representation of a plan view of a security element comprising a plurality of liquid crystal cells and associated electrodes; and 5 shows a schematic sectional view along the line AA according to FIG. 4
• FIG. 1 schematically shows a sectional view through a security element 1.
• the security element comprises a hologram 2 which is usually an optically thick lattice and can be produced in any manner known to the person skilled in the art.
• the hologram can be exposed in a recording medium via a contact copy Embodiments in which the hologram 2 is individualized for a person and / or an object are particularly preferred. This means that, for example, an individualization pattern is stored in the hologram 2.
• the hologram 2 can be single or multi-colored.
• the security element comprises a hologram 2 which is usually an optically thick lattice and can be produced in any manner known to the person skilled in the art.
• the hologram can be exposed
• the security element 1 further comprises a Flussigknstallzelle 3, the liquid crystals 4 between opposite alignment layers 5 of the Flussigknstallzelle 3 including the alignment layers 5 are formed so that a nematic phase de r F'us ⁇ igk ⁇ tal'e 4 forms in a choi ⁇ sterischcn Formation
• the spacing of the alignment layers 5 and a surface texture of the alignment layers 5 are selected so that a helical connection of the nematic Flussigkristalle 4zw ⁇ schen the aligning layers 5 adjacent Flussigk ⁇ stallen the Flussigknstallzelle 3 further includes Electrodes 6 and 7, which are arranged relative to the Flussigk ⁇ stallen 4 so that, via an application of a voltage, ie a charging with a charge, between the electrodes 6 and 7 an e In the illustrated embodiment, the electrodes are arranged above and below the liquid crystal billet 4. A voltage can be applied between the electrodes 6 and 7
• the security element further comprises a polarizing filter 8.
• the polarizing filter 8 is able to linearly polarize incident light, for example.
• a polarization dependence of a diffraction efficiency of an optically thick grating, ie a volume hologram, will be explained with reference to FIG.
• two differently polarized reconstruction light beams 9, 10, which are polarized differently One reconstruction light beam 9 is polarized perpendicular to the diffraction plane, ie, the electric field vectors 11 are perpendicular to the diffraction plane defined by the one incident reconstruction light beam 9 and the diffracted reconstruction light beam 9 1 . In this case, the maximum diffraction.
• the other reconstruction light beam 10 has a polarization direction in which the electric field vectors 11 are aligned parallel to the diffraction plane. In this case, diffraction efficiency is minimal.
• the diffraction efficiency for a reconstruction light beam 9 polarized perpendicular to the diffraction plane is more than 90% and the diffraction efficiency for an incident reconstruction light beam 10 polarized in the diffraction plane is 0%.
• ⁇ denotes the angle of the electric field vector relative to the diffraction plane
• a dependence on cos 2 ⁇ applies to the diffraction efficiency.
• the angle dependence is not so pronounced in all holograms, as described here by way of example.
• a strong dependence on the direction of polarization is usually obtained when the angle between the incident reconstruction beam and the emergent reconstructed, ie, diffracted, beam is 90 °.
• a Pola ⁇ sationstechnischsabhangmaschine is often observed but also in other reconstruction geometry
• FIG. 3 the security element according to FIG. 1 is shown again schematically, with the individual components being shown separated by intermediate spaces
• the security element 1 is not the same as the security element according to FIG.
• the alignment layers 5 are each formed on the sides of the electrodes 6, 7 facing the liquid crystals 4 Be
• polarized reconstruction light 12 ' whose electric field vector 11 in the drawing plane is The polarized Recon ⁇ tmtechniksiicht 12 "then t ⁇ tt through the electrode 6, the a
• the electrode 6 and the electrode 7, which faces a light failure side 14, are transparent to the reconstruction light 12 or the polarized reconstruction light 12 '.
• the hologram can be arranged between the light exit side 14 Flussigk ⁇ stalle 4 of Flussigknstallzelle 3 and the electrode 7
• the electr or 7 may not necessarily be transparent
• the flow cell 3 is in the ground state, ie no voltage is applied between the electrodes 6, 7, as indicated by an open switch 15 interrupting a connection to a voltage source 16.
• the liquid crystals 4 in the flow cell 3 thus have a nematic one This means that the electric field vector 11 of the polarized reconstruction bulb 12 'is rotated as it passes through the liquid nodule cell 3, more precisely the liquid crystal 4 of the liquid nodule cell 3.
• the liquid nodule cell 3 is now advantageously designed so that the electric field vector 11 in the ground state by 90 °, 270 °, is rotated
• the emerging from the Flussigknstallzelle 3 reconstruction light 12 " is thus polarized perpendicular to entering the Flussigknstallzelle 3 reconstruction light 12"
• After passing the electrode 7 hits the reconstruction light 12 "on the Hologram 2
• This is designed to maximally diffract polarized reconstruction light perpendicular to the plane of the drawing.
• Diffracted reconstruction light 12 '' again passes through the electrode 7 and flow cell 3.
• the electric field vector 11 is rotated again just like that from the liquid crystal cell 3 diffracted reconstructive light 12 IV has a parallel polarization direction to the polarized reconstruction light 12 'entering the liquid state cell 3.
• the diffracted reconstruction light 12 IV can pass unhindered through the polarization filter s and a reconstruction of the hologram 2 are observed
• FIG. 3 b the same security element 1 is again shown schematically, but the switch 15 is closed, so that a voltage is applied across the voltage source 16 between the electrodes 6, 7.
• a voltage is applied across the voltage source 16 between the electrodes 6, 7.
• an electric field is formed between the electrodes 6, 7
• the direction of the field vector 11 of the polarized reconstruction light 12 "wirH in this case not changed in the Flussigknstallzelle 3
• the emerging from the Flussigkristallzelle 3 reconstruction light 12" in this case is always Since the hologram 2 is designed such that it optimally diffracts reconstruction light polarized perpendicular to the plane of the drawing, it accordingly bends light polarized in the plane of the drawing with minimal diffraction efficiency, ideally not at all. In this case, the reconstruction light 12 occurs through the hologram 2
• the hologram 2 can, of course, be oriented differently with respect to the polarization filter 8, only in such a way that in the ground state, ie without an adjacent field between the electrodes, the light 12 "emerging from the liquid state cell 3 is polarized. that no reconstruction of the hologram 2 takes place, whereas a reconstruction takes place in the switching state
• FIG. 4 shows a schematic plan view of a security element 1 comprising a multiplicity of flow control cells 3 to which electrodes 6 are respectively assigned.
• This arrangement forms a display device or a display.
• FIG. 5 shows a schematic sectional view along the line AA the single ones Components of the security element 1 are again shown separated from each other by interspaces for the sake of illustration.
• a common polarizing filter 8 is provided for the plurality of liquid crystal cells 3.
• Each of the liquid crystal cells 3 is associated with exactly one electrode 6.
• each liquid crystal cell 3 is assigned another electrode 7.
• these electrodes 7 may be replaced by a common electrode, as indicated by a dashed line 17.
• the hologram 2 is reconstructed in the ground state of the liquid crystal cells 3, ie, the reflection light having the maximum diffraction efficiency is diffracted.
• the liquid crystal cells 3, from which diffracted reconstruction light emerges, are shown in gray in FIG.
• the electrodes 6 associated with the other liquid crystal cells 3 are coupled to a voltage source (not shown), so that an electric field is present in the corresponding liquid crystal cells 3, so that they are in the switching state and, accordingly, the hologram is not reconstructed at these locations, ie the reconstruction light does not bow.
• the electrodes can be electrically connected to one another in such a way that an individualization pattern becomes visible through the application of a single voltage.
• the security element can be configured such that the individual electrodes 6, 7 can be selectively activated.
• the liquid crystal cells can also be designed as segments of any desired shape and realize an individualization pattern over this.
• embodiments are provided in which the individual electrodes can be controlled via integrated semiconductor switches.
• the large number of electrodes makes it possible to "display" random patterns or images by means of a specific control, which means that a reconstruction of the hologram can be influenced locally.
• the individual reconstructing and non-reconstructing pattern units or at least modified reconstructing pattern units are controlled by targeted activation
• the regions in which the hologram reconstructs for example, form a contour of a face or the like
• it is also possible to read out, observe and / or evaluate information which codes in the hologram is the control of the individual Electrodes may be effected by an external control device. Alternatively, however, active switching elements, for example transistors or the like, may also be integrated into the security element
• a hologram is first exposed. This can be carried out according to any method in the prior art. In particular, it is possible to store different interference structures or hologram-like structures in the hologram. These can be designed to have a different polarization dependence For example, in the basic state of one or more liquid crystal cells, one hologram-like structure and, in the switching state, the other hologram-like structure can be reconstructed.
• Reflection hologram-like structures are particularly preferred Structures
• other embodiments may provide transmission holograms as security element is applied to a security document which is not transparent, it is possible to provide a reflective layer on a side facing away from the light exit side of the Flussigk ⁇ stalle the Flussigk ⁇ stallzelle side de '; Hologram vo r 2u Eye to zuruckzureflekt Schl the reconstructed in transmission hologram through the hologram
• the liquid crystal cell or the liquid crystal cells with the corresponding electrodes are arranged above the hologram. If several liquid nitrogen cells are arranged above the hologram, then a common electrode can be formed for these liquid crystal cells. In order to enable an individual controllability of the liquid nitrogen cells, they additionally have In addition, the polarization filter and optionally a plurality of polarization filters are arranged. These are preferably connected to one another. It should be noted that each liquid crystal cell can have its own polarization filter assigned to it , wherein the individual liquid crystal cells polarizing filter can be assigned, which is a Also, an individualization pattern can be stored in the security element via an arrangement of the polarization filters
• Personalizing and / or individualizing information may also be stored by arranging the alignment layers of a selection of the plurality of liquid crystal cells with respect to their preferred directions in which they affect alignment of the liquid crystals differently relative to each other and / or the alignment layers of the remaining liquid crystal cells
• the invention is described in the exemplary embodiments by way of example using nematic twist flow cells (TN flow cell cells).
• TN flow cell cells nematic twist flow cells
• the electrodes can be laterally related to a light incidence and / or light drop side of the flow cells of the flow cell or cells Its only requirement is that a polarization of the light passing through be changed as a function of the electric field generated by applying a voltage to the electrodes
• security elements are preferably integrated into a security document and / or value document.
• a security element can be glued onto a card body, preferably made of plastic. to label a security element in such a card body

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• 2008
  • 2008-04-21 DE DE102008020770A patent/DE102008020770B3/de not_active Expired - Fee Related
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  • 2009-04-20 EP EP09735466A patent/EP2279459B1/de active Active
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