Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M1/00—Inking and printing with a printer's forme
  • B41M1/06—Lithographic printing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M3/00—Printing processes to produce particular kinds of printed work, e.g. patterns
  • B41M3/14—Security printing
• • 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
  • B42D25/328—Diffraction gratings; Holograms
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S359/00—Optical: systems and elements
  • Y10S359/90—Methods

Definitions

• the invention relates to a method for generating a grid image by means of a writing device which has at least one grid field which can be seen with the naked eye and in which grid elements are arranged.
• the invention further relates to a device for the preparation and implementation of this method as well as a grid image and a security document with such a grid image.
• optically variable elements such as holograms or diffraction grating images
• holograms or diffraction grating images are often used as counterfeit or copy protection for documents of value, such as credit cards, banknotes or the like, but also for product security on any product packaging.
• master structures which have the respective phase information of the optically variable element in the form of a spatial relief structure.
• the master structure can reproduce the complete diffraction structure of a real hologram or a grating image composed of different diffraction gratings.
• the diffraction gratings differ with regard to the grating constant and / or the azimuth angle and / or the profile structure of the grating lines and the contour or the outline of the image area occupied by the respective diffraction grating.
• the lattice constant corresponds to the distance between the lattice lines and is essential for the color of the image area in the lattice image that is recognizable from a certain viewing angle.
• the azimuth angle describes the inclination of the grid lines with respect to a reference direction and is responsible for the visibility of these image fields in certain viewing directions.
• the line profile is generally responsible for the intensity and plays a special role in zero-order grid images.
• the basis of this technique can therefore be optically variable images, e.g. moving images or images that look plastic are generated.
• the individual diffraction gratings can be generated either holographically or by means of electron beam lithography.
• holographic recording of the diffraction gratings light beams from spatially extended, uniform wave fields are superimposed in a corresponding substrate. Laser radiation is usually used for this.
• electron steel lithography the diffractive grating lines are exposed directly into a corresponding substrate, the exposure process also often being referred to as a writing process.
• a glass plate is generally used as the substrate, which is coated with a layer (“photoresist”) that is sensitive to the corresponding particle or light radiation.
• the substrate and the electron beam can be moved relative to one another for exposure the possibility of holding the substrate still and electronically deflecting the electron beam.
• the deflection range of the electron beam is in the range of a few tenths of a millimeter. With larger deflections, the so-called "lens defects" of the electron optics, which also affect the finished lens, grid are recognizable.
• the substrate can be moved by means of an xy table while the electron beam is kept still. However, this requires a highly precise table guide.
• the entire grid image is broken down into a large number of small fields with an edge length of up to a few tenths of a millimeter.
• the grid image is thus broken down into individual "raster elements" regardless of the motif shown, which are labeled with grid lines by means of the electron beam.
• the grid lines are written in the individual small fields via the deflection of the electron beam, while the movement from field to field This allows large areas to be labeled.
• This type of electron beam exposure is generally referred to as "stitching mode".
• this procedure has the disadvantage that the image is composed of nothing but small areas that are visually recognizable on closer inspection, coarsen the image and lead to color errors.
• CPC mode Continuous Path Control, product of Leica Microsystems Ltd.
• the electron beam is stationary, while the table is moved according to the structures to be exposed.
• This mode is less suitable for the production of finely structured grids. Images, such as guilloche images, or images broken down into fine lines or micro-writing, since these finely structured images have a predominant number of short grid lines. For this reason, the table must be stopped and started up into the millions for each grid image. This puts a strain on the table mechanics and costs a lot of time.
• the invention is therefore based on the object of creating a method which makes it possible to generate finely structured grid images with the aid of electron beam lithography and thereby avoids the disadvantages mentioned above.
• the invention is based on the finding that, in order to avoid optical errors in grating images, the grating elements producing the optically variable effect, which are preferably designed as grating lines, must be generated continuously in one process step. Therefore, according to the method according to the invention, only the grating lines which lie over their entire length within the range of the electromagnetic deflection of the electron beam are exposed in this mode. In order to be able to compose grid images in this way, work areas are defined that can be accessed by moving the table. Within the individual working fields, the grid lines are exposed over their entire length by deflecting the electron beam into a corresponding substrate.
• the lattice elements, their start and end points (and if necessary also intermediate points) lie within the range of movement of the writing device.
• the working fields in which the writing device is moved relative to a carrier on which a substrate to be labeled is located are then defined.
• the path of movement of the carrier is determined, so that the working fields can be approached one after the other by moving the carrier and the grid elements lying in the respective working field can be generated.
• the grid elements are preferably determined on the basis of a data record which contains information about start and end points and, if appropriate, also intermediate points of the grid elements forming the grid field in the form of location coordinates.
• grid image preferably means an image motif that can be recognized with the naked eye or an alphanumeric information with light diffractive or reflective effects. Alphanumeric information is also to be understood as micro-writing.
• the grid image has at least one grid field of any outline contour which can be seen with the naked eye and in which a grid pattern of grid elements of any shape is arranged. These lattice elements preferably consist of lattice lines which can be straight, curved or in any other shape.
• the light diffractive grating images are preferably composed of different diffraction gratings. With the method according to the invention, however, any complicated diffraction structures up to computer-generated holograms can be produced.
• the method according to the invention is preferably suitable for the production of finely structured grid images or grid images which have grid fields, the length and / or width of which is in the range from 5 ⁇ m to 500 ⁇ m and is preferably 20 ⁇ m to 100 ⁇ m.
• the grating fields in turn are provided with grating elements, preferably grating lines, with a grating constant of approximately 0.1 to 10 ⁇ m, preferably 0.5 to 2 ⁇ m.
• a particle beam in particular an electron beam, is preferably used as the writing device in the method according to the invention, since it enables resolutions down to the nanometer range.
• grid images are to be generated that do not require this high resolution, for example grid images based purely on reflective effects, other lithography instruments can also be used to generate the grid elements in a corresponding substrate. This can be, for example, a focusing UV laser or a precision milling device.
• Metal plates are preferably used as the substrate for the milling process.
• photoresist in the context of the invention therefore encompasses any substrates into which information in the form of a relief structure can be introduced.
• the principle according to the invention of dividing the writing process into a high-precision, pure transport process and a high-precision movement and writing process, which is optimized with regard to the writing device used, can also be used advantageously here.
• the working areas can be approached via a table which is operated using a high-precision Mechanism of how a high-precision spindle can be controlled.
• a table which is operated using a high-precision Mechanism of how a high-precision spindle can be controlled.
• a further smaller table can be arranged on the table, which is moved, for example, piezoelectrically.
• the small table can also be moved in a different way, for example using magnetostriction. This means that short distances in the micrometer range can be covered quickly and precisely. That is, during the writing process, the substrate to be labeled is moved by means of the piezoelectric table relative to the stationary writing device until all elements of the overall motif that can be reached with the piezoelectric table have been written.
• both the substrate and the piezoelectric table are transported to the next work area with the aid of the mechanically movable table, in the area of which the substrate is labeled again.
• This procedure is preferably suitable for milling devices, but can also be used for all other writing devices mentioned.
• an electron beam as already mentioned, it is alternatively possible to approach the working fields by moving the table, while the grid elements lying in the working field are generated by electromagnetic deflection of the electron beam.
• a grid image which consists only of a straight, linear grid field with a width in the above-mentioned range of 0.02 and 0.2 mm.
• the length of the line is arbitrary.
• This line-shaped lattice field has straight lattice lines as lattice elements which run across the width of the lattice field and thus have a length which corresponds to the width of the lattice field.
• This grid image is to be exposed in an appropriate photoresist using an electron beam.
• the photoresist is located here on a substrate, preferably a glass plate, which is arranged on a movably mounted xy table.
• a data record is provided for the generation of this grid image, which contains information about the start and end points of the grid lines.
• This data record can originate, for example, from the drafting phase of the grid image, in particular if the design of the grid image was created with the aid of special programs using computer programs.
• This data is used to determine which of the grid lines lie in the electromagnetic deflection area of the electron beam. Since the start and end points of all grid lines lie in the range that can be achieved by electromagnetic deflection of the electron beam, all grid lines can be written continuously without interruption over their entire length. Finally, a path of movement is determined for the table on which the photoresist is located. After all the data required for the control of the respective devices has been determined, the first working area is moved to by moving the table.
• the grid lines are generated by deflecting the electron beam.
• the individual grid lines are generated by continuous deflection of the electron beam and have no interruptions or unwanted kinks.
• the method according to the invention has the advantage that the individual lattice elements are uniform in the largest possible areas and are not composed of several partial segments within these areas are. In addition, by dividing the grid area into work areas, the number of time-consuming stops and starts of the table is reduced to a minimum.
• the grid fields have complicated outline contours, e.g. Guilloche lines, it can happen that the grid elements have start and end points that lie outside the deflection area of the writing device. These grid elements which are too large can be produced either simply by moving the substrate with a fixed writing device or by breaking the grid elements down into smaller pieces which can be reached by the writing device and are placed next to one another.
• the device according to the invention for carrying out the method according to the invention has a transport device with which the writing device and the substrate can be moved relative to one another over a relatively large distance, a moving device with which the writing device and the substrate are moved relative to one another during the actual writing process can, as well as facilities for controlling the aforementioned.
• the movement device can be, for example, the already mentioned piezoelectric table or a device for deflecting a particle or light beam. The movement device enables rapid and precise relative movement of the substrate and writing device in the micrometer range.
• the device preferably has a movably mounted table for the pure transport process and an electromagnetic deflection device for the electron beam during the writing process.
• the device according to the invention can also contain a computing unit in which the described Movements of the writing device and the carrier can be calculated.
• the preparation and the decision as to how the grid image is put together in detail, or the calculation of the control data for the writing device and the carrier is preferably carried out in a computer simulation before the actual one Writing process instead. It is decided here which grating elements lie within the deflection area of the writing device, how the working fields have to be designed, which grating elements lie in which working field, how the carrier has to be moved in order to be able to approach all working fields in an economical manner, whether, and if so, which lattice elements are to be generated by another method.
• the method according to the invention can of course also be used for grid images which have both finely structured and larger-area grid image components.
• it is determined which parts of the grid image are to be generated using the method according to the invention and which parts are to be generated using another method.
• the writing paths within the work areas can be carried out in different ways.
• the writing device can be guided in a meandering or zigzag fashion.
• the meandering guide When using an electron beam or a laser, the meandering guide has the advantage that the beam on the short connecting pieces does not have to be switched off. In the case of a zigzag-shaped writing path, the beam switched off when driving back or the way back is traveled so quickly that no significant exposure occurs.
• only one line or one grid element is written in each work field.
• the writing device generates a grid element that lies in its working area.
• the carrier is moved step by step or continuously from lattice element to lattice element.
• the individual lattice elements can be straight or curved as desired.
• the successive grid elements have the identical shape.
• any grid elements can also be generated if the writing device is programmed accordingly.
• the substrate produced by the method according to the invention forms a master structure which can be implemented in any embossing tools.
• embossing tools for example, the relief structure of the grid image, e.g. by spraying on a metal layer, made electrically conductive and then galvanically molded into a nickel foil.
• a metal layer made electrically conductive and then galvanically molded into a nickel foil.
• nickel foils are molded, which are used, for example, to emboss a large number of benefits in a thermoplastic plastic plate, e.g. Plexiglass.
• This plastic plate is also galvanically molded and the molded metal foil is used as an embossing mold for a large number of uses of the original grid image.
• the metal foil is preferably welded into a cylindrical embossing mold and drawn onto a clamping cylinder.
• any layers such as a thermoplastic layer or a lacquer layer, in particular a UV hardenable lacquer layer.
• the embossable layer is preferably on a carrier material, such as a plastic film.
• the plastic film can have additional layers or security features.
• the plastic film can be used as a security thread or security label.
• the plastic film can be designed as a transfer material, for example in the form of a hot stamping film, which is used to transfer individual security elements to objects to be secured.
• the grid images are preferably used to secure documents of value, such as banknotes, identity cards, passports and the like. Of course, they can also be used for other goods to be secured, such as CDs, books, bottles, etc.
• Fig. 1 design that according to the inventive method in one
• FIG. 2 shows a detail of the grid image according to the invention shown in FIG. 1 in a large magnification, 3a-3c production of a grid field by the method according to the invention,
• Fig. 9 further variant of the method according to the invention.
• FIG. 1 shows a grid image 1 according to the invention.
• the example shown is a finely structured grid image 1, which is composed of guilloche lines 2.
• the individual guilloche lines 2 are represented by different diffraction structures, in particular diffraction gratings.
• the diffraction gratings can differ with regard to their grating constants and / or the azimuth angle, so that only a part of the guilloche lines 2 can be seen from a certain viewing angle and the visible guillocheline lines 2 show different colors.
• other guilloche lines 2 become visible and the colors of the individual guilloche lines 2 change.
• the diffraction gratings can also be designed in such a way that all guilloche lines 2 can be seen from any viewing angle and differ only in their color. In this case, only a color change occurs when changing the viewing angle. 2 shows the detail a in a large magnification, so that the individual diffraction grating lines 5, 7 can be seen.
• the guilloche lines shown here form the grid fields 4, 6 according to the invention, in each of which grid elements 5, 7 are arranged.
• the grid elements 5, 7 in the present example are straight and run over the entire width b of the grid fields 4, 6.
• the shape of the grid fields 4, 6 is determined solely by the image motif 1.
• the width and length of the grid fields 4, 6 is determined by the motif. In the present example of a guilloche line, the width is preferably in the range from 0.02 to 0.2 mm.
• the grid fields 4, 6 are produced by the method according to the invention. The method according to the invention is explained below using grid field 4.
• a data set is provided for generating the grid field 4, which contains information about the shape and position of the grid elements 5, which are preferably present as coordinates in a specific coordinate system. If the grid lines are straight, the coordinates of the start and end points of the individual grid elements 5 are sufficient. This is outlined schematically in FIG. 3a.
• Each of the grid lines 5 has a starting point A and an end point B, the coordinates of which are stored in a defined xy plane in the data set.
• the length L of each grid line 5 and the distance of the individual grid lines 5 from one another indirectly result from the start and end points. In the example shown, the distance d is constant for all grid lines 5 of the grid field 4.
• the data set contains the coordinates of many closely spaced intermediate points, which describe the shape of the grid elements as a polygon.
• the shape of the grid elements can also be described as a Bezier curve, in which only the coordinates of a few intermediate points and additionally a tangential direction with respect to the further course of the curve are stored.
• the coordinates of a grid element can therefore only consist of the coordinates of the start and end point of the grid element or else include the coordinates of a certain number of intermediate points and possibly direction information.
• the coordinates of the individual grid elements 5 to be generated determine which of the grid elements can be written continuously by deflecting an electron beam.
• a window is defined in the size of the work area. Starting from a defined starting point, this coordinate window is placed over the coordinates of the grid elements and it is determined which successive grid elements lie completely in the area of this coordinate window.
• the coordinates of the grid lines 5 which lie within a coordinate window are now sorted and arranged in such a way that polygons AiBi, A 2 B2 and A3B 3 are created. This process step is shown in Fig. 3b.
• the work fields 8, 9, 10 are shown in FIG. 3c.
• the y coordinate of the coordinate window is set to the y value of the starting point Ai and the coordinate window is shifted in the x direction until the end point D of the first grid element lies completely within the defined coordinate window.
• the coordinates The following grid elements are compared with the coordinates of the window and checked whether they are completely in the area of the coordinate window. The position of the coordinate window can still be optimized. From this comparison of the coordinates of the window and the grid elements, it finally emerges that the grid element 100 is the last grid element that completely fits into the coordinate window beginning with AI.
• the working field 8 ends with the end point Bi of the grid element 100.
• the coordinate window is set due to the inclination of the grid field 4 in the y direction to the end point B 2 of the following grid element 101 and again shifted until the maximum possible complete number of grid elements lies in the coordinate window.
• This process is carried out with the aid of a computer and is repeated until all the grid elements are assigned to a work area.
• the work fields 8, 9, 10 can definitely overlap.
• the size of the working fields 8, 9, 10 corresponds to the size of the electromagnetic deflection area of the electron beam.
• the table is first brought into a position in which the working field 8 comes to rest under the electron beam.
• the electron beam is deflected electromagnetically and is moved along the polyline AiBi, and the corresponding grid lines 5 are written.
• the short connecting pieces 11 between the grid lines 5 within a polyline AiBi, A 2 B 2 , A 3 B 3 can also be exposed or not.
• the table is moved so that the working field 9 comes to lie under the electron beam.
• the electron beam drives the polygon A 2 B 2 by means of electromagnetic deflection and exposes the corresponding grid lines 5 in the substrate.
• FIG. 4 shows the grid field 4, in the event that it is produced according to the known stitching mode.
• the “grid elements” 30, independent of the motif depicted, in which sections of the grid lines are arranged, can be clearly seen. Since the grid elements cannot be placed exactly against one another, most grid lines running across the width of the grid field have gaps and / or Click on, as can be seen in the marked area c.
• FIG. 5 shows a variant of the method according to the invention, in which a grid field 20 is to be written, which likewise has a linear outline contour.
• the grid lines representing the grid field 20 partly consist of grid lines 12, the coordinates of which lie in the deflection area of the electron beam.
• the grid field 20 has large grid elements, the coordinates of which lie outside the deflection area of the electron beam. In the example shown, these grid elements are also grid lines 13.
• work fields 14, 15, 16, 17, 18 according to the invention are also defined, in which the respective polygon lines A 1, B 1, A2B2, AB, A5B5 and A 6 B ⁇ which are writable by the method already described are arranged.
• the polygon A 3 B 3 is also continuously written purely by moving the table. That is, the electron beam is not deflected and is mounted in a fixed position, while the table and the substrate to be exposed thereon are moved relative to the electron beam in accordance with the polygon AsB 3 .
• the polygons lying in a working area can be exposed in exactly this form in the substrate.
• the various options for guiding the writing device are described on the basis of a polygon that is processed within a work area.
• 6a shows the variant in which only the grating lines without the connecting pieces 11 of the polygon are to be exposed in the substrate. That is, after the electron beam has written the grid line 21 from the starting point Ai to the end point Bi in the substrate, the electron beam must travel an "empty path" to the starting point A 2 of the next grid line 22. The empty paths on the connecting pieces 11 are therefore in 6a, the electron beam can be switched off or otherwise prevented from exposing the substrate.
• the connecting pieces 11 do not have to be straight, but rather can be rounded, as a result of which the writing speed of the electron beam can be increased even further.
• This embodiment is shown in Fig. 6c.
• the meandering writing paths shown in Figures 6a to 6c are very useful because they shorten the writing paths, but they are not absolutely necessary according to the invention.
• 6d shows another possibility of guiding the writing device, in particular the electron beam, between the individual exposure processes.
• the electron beam is guided from the starting point Ai of the grid line 21 to the end point Bi of the grid line 21 and the grid line 21 is exposed in the substrate.
• the electron beam on the connecting piece 23 is guided diagonally back to the starting point A 2 of the grid line 22. No exposure of the substrate takes place on this diagonal connecting path 23.
• the grating line 22 is then exposed to the end point B 2 in the substrate. This process is repeated in a kind of zigzag course until all grid lines of the work area have been written.
• the electron beam is either switched off or moved so quickly that no exposure takes place.
• FIG. 7a to 7c show a special embodiment of the method according to the invention, in which only one line is written in the working area, ie in the deflection area of an electron beam.
• 7a is a corresponding line 301 with the start point Ai and the end point Bi shown.
• the electron beam moves in its deflection region along this line 301.
• the carrier moves either step-by-step or at a suitable speed continuously along the movement path 31.
• the superimposition of the carrier movement 31 with the electron beam movement is shown in FIG. 7b.
• the electron beam has already written the grid lines 301 to 309, the electron beam being switched off on the way back between the end point of the respective written line and the start point of the next line. This is indicated by the dashed connecting lines 32.
• FIG. 7 c shows the completely written grid image 33, which consists of nothing but grid lines of the same length, which are arranged along the movement path 31.
• FIG. 8a to 8c show a similar variant of the method according to the invention, in which, however, the electron beam in its deflection area writes a more complicated grid line 401 with the starting points Ai and Bi.
• the electron beam is switched off on the return path 42.
• the straight return path 42 is not shown in FIG. 8b. Only the grid lines 401 to 420 written along the movement path 41 are shown here.
• the finished grid line image 43 again shows FIG. 8c.
• any lattice structures can also be written along a movement path of the carrier.
• FIG. 9 the shape of the grid lines varies along the movement path 51.
• the grid line 501 is strongly curved.
• the grating lines gradually become longer and their shape always approaches more like a straight line.
• the grid line 519 is practically straight and has a much greater length than the grid line 501.
• the grid lines are not completely in the deflection area of the electron beam, they can either be divided into smaller pieces or a different writing mode (e.g. CPC) is used.
• CPC writing mode

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• Diffracting Gratings Or Hologram Optical Elements (AREA)
• Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)

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• 2003
  • 2003-06-10 US US10/517,483 patent/US7746558B2/en not_active Expired - Fee Related
  • 2003-06-10 RU RU2005100756/28A patent/RU2339981C2/ru not_active IP Right Cessation
  • 2003-06-10 WO PCT/EP2003/006082 patent/WO2003107047A1/de not_active Application Discontinuation
  • 2003-06-10 AU AU2003240749A patent/AU2003240749A1/en not_active Abandoned
  • 2003-06-10 EP EP03730159A patent/EP1516210A1/de not_active Withdrawn

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