Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/382—Contact thermal transfer or sublimation processes
  • B41M5/38207—Contact thermal transfer or sublimation processes characterised by aspects not provided for in groups B41M5/385 - B41M5/395
• • 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
  • Y10S428/00—Stock material or miscellaneous articles
  • Y10S428/913—Material designed to be responsive to temperature, light, moisture
• • 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
  • Y10S428/00—Stock material or miscellaneous articles
  • Y10S428/914—Transfer or decalcomania
• • 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
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24802—Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]
  • Y10T428/24851—Intermediate layer is discontinuous or differential
  • Y10T428/24868—Translucent outer layer
  • Y10T428/24876—Intermediate layer contains particulate material [e.g., pigment, etc.]

Definitions

• the invention relates to a raster image which consists of at least two types of raster dots having different properties and is generated in a thermal transfer process. Furthermore, it is concerned with a thermal transfer film for producing such a raster image, the transfer layer of which can be transferred from a carrier film to the substrate and has a number corresponding to the number of different raster points and correspondingly differently designed areas for producing the different raster points.
• thermal transfer printing processes usually work with rasterization to produce halftone images, with raster dots of normally the same size being transferred from the thermal transfer foil to the substrate in accordance with the desired brightness of the raster image with different dot densities. If multicolored raster images are to be generated, thermal transfer foils, whose
• Transfer layer is divided into several areas, each color being assigned its own area of the transfer layer.
• the thermal transfer film is then over according to the desired color the substrate moves and colored halftone dots are generated by means of the printing tool, the dimensions of the differently colored areas of the transfer layer of the thermal transfer film generally corresponding to the substrate to be printed.
• the invention is therefore based on the object of opening up further design options for raster images without requiring a particularly large outlay on equipment.
• a raster image of the type mentioned at the outset in such a way that at least two types of raster points each have different dimensions.
• regions of the halftone image with a lower color density can be produced by halftone dots of smaller diameter are used, whereas if a rich color or good coverage is to be achieved, screen dots of larger diameter are provided.
• This variation of the halftone dot size is particularly favorable when the halftone dots have a special structure and are, for example, reflective, since in such a case the variation of the halftone dot size achieves a particularly uniform effect with respect to the respective structure.
• a raster image can be composed of dots with a matt surface and dots with a glossy surface, which not only enables the usual halftone or color resolution of a raster image, but also creates the possibility of designing the raster image with different gloss effects, etc. . In this way, one obtains very special ones, different from those previously known
• Raster images distinguishing raster images that are particularly difficult to imitate and e.g. are not reproducible by means of a color copier, which means that these raster images, for example, as security elements for documents of value, such as Banknotes, credit cards, ID cards or the like, which are tried again and again, especially with the help of modern color copiers, are particularly suitable.
• the optically effective structure of at least one type of raster point is a diffraction structure which generates diffraction or interference, preferably a lattice structure.
• diffraction or interference structures the Generate a wide variety of optical effects, the structure to be used depends on whether the raster image is observed in reflecting light or in transmitted light.
• a raster image By means of different structures, what is known per se is also possible, for example, to form a raster image as an optically variable image, in such a way that the raster image changes depending on the illumination or viewing angle or the wavelength of the light used for illumination, in the simplest form, only the color setting varies.
• two types of halftone dots with different diffraction structures by means of which e.g. alphanumeric characters are generated, can be achieved in such a case that the color of the characters on the one hand and the background on the other hand changes depending on the viewing angle or the light used for lighting.
• all the raster dots forming the raster image are reflective, but each to be provided with a different structure, for example certain types of raster dots with one Form lattice structure, while other grid points have a flat reflective layer.
• a thermal transfer film of the type mentioned at the outset for producing a raster image according to the invention is characterized in that the transfer layer has raster points of different dimensions in the different areas, in order, for example, to be able to always work with the same point density, but nevertheless have the possibility of being denser or less to produce densely printed areas of the raster image on the substrate.
• a thermal transfer film can also be expediently designed such that the different areas of the transfer layer each have an optically differently effective structure.
• the raster points are then transferred from the different areas of the transfer layer with the optically different structure to the substrate, for this purpose the thermal transfer film being moved relative to the substrate in the manner known per se from thermal color printers must in order to bring the area of the transfer layer, which has the desired surface structure, over the corresponding point on the substrate.
• the transfer layer has a reflective layer at least in one area
• the reflective layer Layer is expediently formed by a metallization, because then the raster image can be composed of reflecting and non-reflecting areas or, provided that all areas of the transfer layer are designed to be reflective, images of particular brightness can be achieved.
• optically effective structure of the transfer layer is a diffraction structure, in particular a lattice structure, which produces diffraction or interference.
• the transfer layer has a transparent protective lacquer layer in at least one area adjacent to the carrier film, because the abrasion resistance of the raster image generated on the substrate can then be increased.
• a transparent protective lacquer layer is present, it can advantageously have a different color in at least two areas of the transfer layer, which opens up the possibility of producing multicolored raster images.
• the optically effective structure of the transfer layer is advantageously produced by being embossed in a lacquer layer of the transfer layer.
• Corresponding embossing processes are known from the production of hot stamping foils with diffraction structures etc.
• the structures are embossed into a thermoplastic or not fully cured lacquer by means of a matrix.
• these methods can be used in the same way on thermal transfer foils or their Transfer layers are transferred, at most it may be necessary to adapt the structure depth to the field of application, because the thickness of the transfer layer of thermal transfer foils is limited in order to ensure a perfect transfer of the transfer layer to the substrate with the known devices.
• the protective lacquer layer covers the optically active structure when the transfer layer is applied to a substrate, because then an impression and thus a forgery is made difficult, if not impossible.
• the durability of the raster image is increased because the surface structure is protected against direct mechanical attacks.
• the transfer layer of the thermal transfer foil With regard to the basic structure of the transfer layer of the thermal transfer foil, reference can be made to known foils and hot stamping foils, the only difference of the thermal transfer foil according to the invention compared to known thermal transfer foils being emphasized that in the thermal transfer foil according to the invention, the surface of the surface on the surface is structured in at least one area The substrate to be transferred must be transferred, which is why a correspondingly deformable layer must be provided. Further details on the composition of the layers and their thickness are explained below.
• Figure 1 is a schematic example of a raster image, which is composed of four different types of raster points.
• Fig. 2 is a schematic view of a portion of a thermal transfer film for generating the raster image of Fig. 1 with four different areas and
• Fig. 3 schematically shows a longitudinal section through the film of Fig. 2, but only short
• the raster image shown in Fig. 1 consists of four different types of raster points. Accordingly, the thermal transfer film shown in FIGS. 2 and 3 each have four different areas A, B, C and D in succession, by means of which the screen dots of types a, b, c and d are generated.
• the raster dots of type a are relatively large raster dots, which correspond closely to one another in accordance with the dimensions of the tool used for the transfer process, with a surface which is smooth in the present example and is reflectively formed by a metallic coating.
• the screen dots of type b are also relatively large and have an overall surface provided with a reflective layer.
• the raster points of type b are clearly structured, the raster points of type b preferably being provided with a lattice structure or generally with a diffraction structure which generates diffraction or interference.
• the halftone dots of type a and b only depend on the dimensions of the tool, for example dots, used for the corresponding transfer of the transfer layer to a substrate (in the illustrated embodiment, a dot is used which is so large that dense rows of halftone dots are lined up type a and b a full coverage of the substrate is possible), the halftone dots of type c and d are independent of the diameter of the tool used to transfer the transfer layer.
• the halftone dots of type c and d differ on the one hand in terms of their diameter.
• the dots of type d have a much larger diameter than the dots of type c.
• all types of halftone dots a, b, c and d are each provided with a reflective layer, so that the halftone image according to FIG. 1 appears to be metallically reflective overall, so that it is particularly useful as a security element for a document of value or the like. can be used.
• a thermal transfer film for producing a raster image usually comprises a carrier film 1 which, on its upper side facing the thermal bar in FIG. 3, carries a sliding layer 2 known per se.
• a transfer layer consisting of several layers, designated overall by 3, which is detached from the carrier film 1 in the thermal transfer process and placed on the substrate, which is not shown in the drawing, for example a paper sheet or the like . Like., is determined.
• the transfer layer 3 comprises, starting from the carrier film 1, in any case a lacquer layer and one for
• the structure of the transfer layer 3 is somewhat more complicated. It is assumed that the grid points each comprise a reflective layer 5 or 5 'formed by a metallization.
• the carrier film 1 is provided with a release layer 6, usually a wax layer, before the remaining layers of the transfer layer 3 are applied.
• a layer 7 of a transparent protective lacquer then generally adjoins the wax layer 6.
• an adhesion promoter layer 8 is normally provided between the adhesive layer 4 and the metallization 5 or 5 '.
• the transfer layer 3 of the thermal transfer film according to FIGS. 2 and 3 corresponds in the different areas A, B, C and D to the extent that there is always a release layer 6, a transparent protective lacquer layer 7, a metallization 5 or 5 ', the adhesion promoter layer 8 and the adhesive layer 4 are provided.
• a full-area, smooth metallization 5 is provided directly on the protective lacquer layer 7.
• corresponding areas are separated from the transfer layer 3 (according to the size of the dot used for the transfer) and transferred from the carrier film 1 to the substrate.
• the areas B of the thermal transfer film which are used to generate the raster dots of type b are likewise provided with a metallization 5 'over the entire surface.
• the transfer layer 3 has a further lacquer layer 9 in the areas B between the transparent protective lacquer layer 7 and the metallization 5, which layer can be structured accordingly.
• the lacquer layer 9 can be formed, for example, by a thermoplastic lacquer or also by a lacquer that can still be deformed in a certain time, so that in a replication process the corresponding structure for the metallization 5 'into the Paint layer 9 can be impressed.
• the raster dots of type b are also generated in accordance with the dots of type a by separating a part corresponding to the size of the dot from the transfer layer 3 and transferring it to the substrate by means of the dot.
• the size of the halftone dots thus generated depends only on the resolution of the thermal printer or other tool used to generate the halftone dots.
• the areas C and D of the thermal transfer film are designed such that the size of the resulting raster dots of type c and d is independent of the size of the corresponding transfer tool.
• the size of the grid points that appear is predetermined by the area of the existing metallization 5 or 5 ′. This means that in areas C and D, which basically correspond to areas A and B, the metallization 5, 5 'is only provided in some areas.
• the metallization is provided in the form of corresponding raster points, the metallization being smooth in the areas C and structured in accordance with the area B in the areas D.
• a dot is used whose diameter is larger (or is also smaller) than the diameter of the metallized sections of the metallization 5 or 5 'which represent the raster points of type c or b.
• dots will be used that allow full coverage of the substrate by means of halftone dots in accordance with the halftone dots of types a and b.
• screen dots c and d After transferring the transfer layer 3 from the areas C and D to the substrate, screen dots c and d nevertheless arise, the dimensions of which can be significantly smaller than the dimensions of the screen dots a and b, the screen dots of type c additionally appearing glossy while the D-type screen dots are able to produce special optical effects due to the corresponding structure, for example a lattice structure.
• the screen dots of type d appear to be larger than those of type c, because the metallization sections 5 ′ are larger than the metallization sections 5.
• the grid points of types a, b, c and d thus differ, as explained above, on the one hand by the structure.
• the halftone dots of type a and c have a smooth surface, while the halftone dots of type b and d are provided with an optically effective structure, this structure preferably being a diffraction or
• Diffraction structure generating interference expediently a lattice structure.
• the screen dots of the different types also differ, at least apparently, in terms of their size.
• the halftone dots of types a and b are large in the exemplary embodiment shown, so that when halftone dots are transferred point to point using the thermal transfer printer, the entire surface of the substrate is covered.
• the halftone dots of types c and d are apparently smaller, so that even if a halftone dot is transferred to each location on the substrate provided for this purpose, there is still no full coverage of the substrate with halftone dots c and d.
• this effect is only achieved in the present case in that the optically appearing surface of the halftone dots, for example the metallization 5,5 ', has different dimensions.
• Transfer process are filled, is provided over the entire area.
• screen dots of different diameters in a different way than by correspondingly partial-area metallization 5, 5 '.
• colored dots of different diameters could be formed in the transfer layer 3, which moreover would not have to be embedded in a protective lacquer layer or the like.
• halftone dots of different colors a different structure would also be achievable, for example by processing matt lacquers and glossy lacquers.
• the procedure according to the invention can also be used in principle if metallization is only provided in one or a few areas, whereas other areas of the thermal transfer film have no metallization.
• Raster images according to the invention can thus be realized in the most varied of embodiments, with a variety of possibilities being opened up to the design wishes by appropriate variation of the halftone dot diameter, the halftone dot structure and color.
• the thermal transfer film can basically be constructed as follows:
• Sliding layer (2) layer thickness 0.1 to 1.0 ⁇ carrier film (1): polyethylene terephthalate with a layer thickness of 3.5 to 12 ⁇ m
• Peeling layer (6) wax layer (ester wax with dropping point 90 ° C)
• Protective lacquer layer (7) layer thickness 0.4 to 2.0 ⁇ m
• Structurable lacquer layer (9) layer thickness 0.2 to 1.2 ⁇ m
• the different layers can be composed as follows:
• Methyl methacrylate 245 (daily approx. 105 ° C)
• Various detachable dyes or pigments can optionally be added to produce colored raster images.
• Structurable lacquer layer (9) parts by weight
• Areas C and D are generated in a generally known manner.
• the metal layer 5, 5 'applied in a conventional vapor deposition process can be overprinted in a dot-shaped raster print by means of an etching resist lacquer, the etching resist lacquer being able to be composed as follows:
• the etch resist is advantageously applied with an electronically engraved anilox roller, which usually prints at least two halftone fields with different halftone dot sizes or halftone dot densities.
• the following dimensions can be used:
• Cell diagonal 125 ⁇ m + 5 ⁇ m web width: 60 ⁇ m ⁇ 5 ⁇ m or cell diagonal: 170 ⁇ m ⁇ 5 ⁇ m web width: 15 ⁇ m ⁇ 5 ⁇ m
• the areas of the metallization 5,5 'which are not covered can be etched off after application of the etching resist lacquer and its corresponding hardening, for example with an aqueous, alkaline solution (pH> 10) at room temperature.
• the partial metallization can also be carried out according to other methods known from the literature, e.g. using water / alcohol-soluble blocking funds, in other etching technology or also by laser ablation, for example with an Nd-YAG laser.
• the various layers of the transfer layer 3 are applied to the carrier film 1 in the manner known per se from hot stamping foils, which is why no further explanation in this regard seems necessary. There are various ways of generating the raster image according to FIG. 1.
• One possibility is to grid a full-surface metallized thermal transfer film (see areas A, B of the exemplary embodiment), which preferably has several differently designed, optically effective structures, onto the substrate, e.g. to transfer a plastic card.
• the thermal transfer is expediently controlled via a control computer and a suitably modular software system.
• a thermal printer with a resolution of 16 dots / mm can be used.
• the grids can have a wide variety of shapes, e.g. Have a circular shape, a rectangular shape, with rounded corners, etc.
• the other possibility (corresponding to working with the areas C and D of the thermal transfer film of the exemplary embodiment) is that a partially metallized thermal transfer film is used which, for example, has several different, optically effective structures in accordance with the areas C and D. Partial metallization grid fields of different point sizes are generated. In this case too, the raster image is generated by full-area transmission of image areas which, however, have different raster dot sizes or raster dot densities.
• optically effective surface structures such as are provided, for example, in areas B and D of the exemplary embodiment, variations can be caused by differences in the number of grating lines (500-2000 lines / mm), the grating line depth (0.2-2.0 ⁇ m) and the grid shape (line, rectangular or sinusoidal grid structure) are, the corresponding structures can be freely selected or combined in accordance with the desired effect.
• the different image areas of the raster image or the raster point types thus differ in terms of their different size, different optically effective structure and possibly different color, which means that a raster image according to the invention can be designed and composed in an extremely versatile manner.
• a raster image according to the invention can be designed and composed in an extremely versatile manner.
• the raster image offers high security against counterfeiting, in particular by means of color copying.
• the different coloring of the halftone dots is achieved by different coloring of the protective lacquer layer.

Landscapes

• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Thermal Transfer Or Thermal Recording In General (AREA)
• Decoration By Transfer Pictures (AREA)
• Laminated Bodies (AREA)
• Inks, Pencil-Leads, Or Crayons (AREA)
• Adhesives Or Adhesive Processes (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 1994
  • 1994-09-03 DE DE4431532A patent/DE4431532A1/de not_active Withdrawn
• 1995
  • 1995-08-30 WO PCT/DE1995/001179 patent/WO1996007543A1/fr active IP Right Grant
  • 1995-08-30 JP JP8509108A patent/JPH10505296A/ja active Pending
  • 1995-08-30 CA CA002198904A patent/CA2198904C/fr not_active Expired - Fee Related
  • 1995-08-30 US US08/793,826 patent/US6428877B1/en not_active Expired - Fee Related
  • 1995-08-30 ES ES95930373T patent/ES2116106T3/es not_active Expired - Lifetime
  • 1995-08-30 BR BR9508695A patent/BR9508695A/pt not_active IP Right Cessation
  • 1995-08-30 EP EP95930373A patent/EP0778800B1/fr not_active Expired - Lifetime
  • 1995-08-30 DE DE59501661T patent/DE59501661D1/de not_active Expired - Lifetime
  • 1995-08-30 CN CN95194871A patent/CN1080650C/zh not_active Expired - Fee Related
  • 1995-08-30 DE DE19580964T patent/DE19580964D2/de not_active Expired - Fee Related
  • 1995-08-30 AT AT95930373T patent/ATE164122T1/de not_active IP Right Cessation
  • 1995-08-30 RU RU97105029A patent/RU2144473C1/ru not_active IP Right Cessation
  • 1995-08-30 AU AU33790/95A patent/AU691963B2/en not_active Ceased
• 1998
  • 1998-05-13 HK HK98104130A patent/HK1005060A1/xx not_active IP Right Cessation

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