Method and device for transferring a decorating segment of an embossing film

Abstract

A method for transferring a decorative section of a stamping foil onto a substrate by means of an embossing die, wherein the stamping foil includes a carrier film and a transfer ply arranged on the carrier film. The method includes: a) Provision of the stamping foil; b) Embossing or pressing of at least one compression section spaced apart from the edge of the decorative section, into the transfer ply; c) Stamping of the decorative section onto the substrate; d) Detachment of the residual stamping film from the substrate embossed with the decorative section.

Claims

1. A method for transferring a decorative section of a stamping foil onto a substrate by means of an embossing die, wherein the stamping foil comprises a carrier film and a transfer ply arranged on the carrier film, the method comprising: a) Provision of the stamping foil; b) Forming a predetermined mechanically loaded breaking point at a defined position in the transfer ply of the stamping foil by embossing or pressing of at least one compression section, spaced apart from an edge of the decorative section, into the transfer ply, the predefined mechanically loaded breaking point facilitating breaking of the transfer ply when subjected to bending stress; c) Stamping of the decorative section from the stamping foil onto the substrate, wherein the decorative section is embossed and transferred to the substrate such that remaining portions of the stamping foil not transferred form a residual stamping film; d) Detachment of the residual stamping film from the substrate embossed with the decorative section by exerting a bending stress at the predefined mechanically loaded breaking point, wherein, during said embossing or pressing, a pressing pressure p.sub.k is applied, which is greater than a stamping pressure p.sub.p applied during said stamping.

2. The method according to claim 1, wherein the ratio of the pressing pressure p.sub.k to the stamping pressure p.sub.p lies in a range of over 1:1 to 10,000:1.

3. The method according to claim 1, wherein the pressing pressure p.sub.k is applied in a linear section or at least piecewise linear section, wherein the linear or at least piecewise linear section is straight, jagged or wavy or has a closed contour, in the form of a circle, ellipse, triangle, rectangle or star.

4. The method according to claim 3, wherein the width of the linear section lies in a range of from 0.02 mm to 0.2 mm.

5. The method according to claim 1, wherein the spacing of the at least one compression section from the edge of the decorative section lies in a range of from 0 mm to 2 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is now explained in more detail with reference to embodiment examples. There are shown in

(2) FIG. 1 a first embodiment example of the stamping device in a first operating position in a schematic representation;

(3) FIG. 2 the stamping device in FIG. 1 in a second operating position;

(4) FIG. 3 a detail III in FIG. 2 in an enlarged schematic representation;

(5) FIG. 4 an embossing die of a second embodiment example of the stamping device in a schematic sectional representation;

(6) FIG. 5 an embossing die of a third embodiment example of the stamping device in a schematic sectional representation;

(7) FIG. 6 an embossing die of a fourth embodiment example of the stamping device in a schematic sectional representation;

(8) FIG. 7 a side view VII in FIG. 6;

(9) FIG. 8 an embossing die of a fifth embodiment example of the stamping device in a schematic sectional representation;

(10) FIG. 9 an embodiment example for the structure of a stamping foil in a schematic representation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(11) FIGS. 1 and 2 show a first embodiment example of the stamping device 1 according to the invention in a schematic representation;

(12) In the embodiment shown, the stamping device 1 is formed as a lifting stamping device and for the roll-to-roll method, in which both a substrate 2 to be embossed and a stamping foil 3 are provided on supply rolls 4.

(13) The stamping foil 3 comprises a carrier film 31, a detachment layer 32, a transfer ply 33 and an adhesive layer 34 (see FIG. 3). The structure of the stamping foil 3 is described in more detail in FIG. 9 below.

(14) The stamping foil 3 and the substrate 2 are fed to a stamping station 5 with a vertically movable embossing die 6, wherein the substrate 2 lies with its underside on a stamping support 7 in the stamping station 5. The stamping foil 3 lies with its adhesive layer 34 on the top of the substrate 2. Alternatively (not shown), the embossing die can also be formed as a rolling stamping wheel or as a curved embossing die rolling over its curvature.

(15) The embossing die 6 has a heated stamping surface 6p on its end face facing the stamping support 7, wherein the dimensions of the stamping surface 6p defines the dimensions of a decorative section 3d to be transferred from the stamping foil 3 onto the substrate. On the stamping surface 6p, at least in one section, a folding element 8 is arranged, with a linear pressing surface 8p spaced apart from the edge of the stamping surface 6p (see FIG. 3). The pressing surface 8p is formed as a convex surface. The spacing a of the pressing surface 8p from the edge of the stamping surface 6p is approximately 0.1 mm to 0.2 mm. The pressing surface 8p is preferably aligned with the stamping surface 6p in a plane parallel to the stamping foil and to the substrate, i.e. it does not project in the direction towards the stamping foil with respect to the stamping surface 6p. However, it is also possible that the pressing surface 8p projects downwards (in the direction towards the stamping foil) up to a maximum of 50% of the thickness of the carrier film 31 with respect to the stamping surface 6p.

(16) In a first operating position, the embossing die 6 is arranged spaced apart from the stamping foil 3 and the substrate 2 (FIG. 1).

(17) In a second operating position (FIG. 2), the embossing die 6 is lowered onto the stamping foil 3 and the substrate 2 and applies the stamping foil 3 to the substrate 2, forming a stamping pressure p.sub.p. The heated stamping surface 6p of the embossing die 6 activates the adhesive layer 34 of the stamping foil 3 in the region of the stamping surface 6p and there connects the stamping foil 3 to the substrate 2 in the region of the decorative section 3d. At the same time, the stamping foil 3 is pressed together in the region of the pressing surface 8p, forming a pressing pressure p.sub.k, wherein material of the stamping foil 3 is displaced to the side of the pressing surface 8p. As a result of the pressing pressure p.sub.k, the layers of the stamping foil 3 arranged under the carrier film 31 are mechanically loaded in a ribbon-shaped compression section 8v. These layers are predominantly lacquer layers.

(18) In the case of a pressing surface 8p aligned with the stamping surface 6p and spaced apart from the stamping surface 6p, the lacquer layers are differently deformed within the smallest space by the mechanical loading acting on the region of the pressing surface 8p and the simultaneous unloading in the region of the spacing between stamping surface 6p and pressing surface 8p, such that in the region of the compression section 8v, a predetermined breaking point forms, which breaks under the bending stress caused by the removal of the carrier film.

(19) In the case of a pressing surface 8p projecting relative to the stamping surface 6p, during the application of the embossing die 6 to the stamping foil 3 and the substrate 2 in the region of the pressing surface 8p, a comparatively high pressing pressure p.sub.k is exerted on the stamping foil 3 and the substrate 2, with the result that, due to this strong local mechanical loading, the compression section 8v is produced or pressed/embossed in the lacquer layers as a predetermined breaking point, which breaks under the bending stress caused by the removal of the carrier film 31. Seen over time, the pressing surface 8p first of all touches the stamping foil 3 and dips comparatively deep into the stamping foil 3 without damaging it. Subsequently, the embossing die 6 then contacts the stamping foil 3 and secures or stamps the decorative section 3d on the substrate 2.

(20) After the stamping, the embossing die 6 is raised and returned to the first operating position (FIG. 1). The carrier film 31 is guided downstream via a deflection roller 10 behind the stamping station 5. The carrier film 31 is removed from the transfer ply 33 behind the deflection roller 10, and a residual stamping film 3r, comprising the carrier film 31, remaining residues of the transfer ply 33 and of the adhesive layer 34, is fed to a first take-up reel 9. The detachment of the carrier film 31 is supported by the detachment layer 32. The embossed substrate 2 is fed to a second take-up reel 9.

(21) Pairs of transport rollers 11 are provided for the transport of the substrate 2 and of the stamping foil 3.

(22) In the first embodiment example represented in FIGS. 1 to 3, the folding element 8 is formed in one piece with the embossing die 6. A trough-shaped recess is provided to form a spacing a between the pressing surface 8p and the edge of the stamping surface 6p. In a top view not shown here, the recess shown in cross section in FIGS. 1 to 3 can be formed, for example, elongated in a straight line, but also jagged or wavy. In top view, the recess can have an open form, in particular as the named line forms, or alternatively also have a closed contour, for example in the form of a circle, ellipse, triangle or rectangle, in particular in the form of a star.

(23) In the second embodiment example shown in FIG. 4, the embossing die 6 has a rectangular stamping surface 6p, wherein on two opposite sides of the embossing die 6, in each case a folding element 8 is arranged, the pressing surface 8p of which runs parallel to the adjacent edge of the stamping surface 6p. The pressing surface 8p of the folding element 8 is aligned with the stamping surface 6p of the embossing die 6.

(24) The folding elements 8 and the embossing die 6 are connected to each other by fastening screws 12, which engage in threaded holes in the embossing die 6.

(25) The spacing a of the pressing edge 8k from the edge of the stamping surface 6p is determined by the thickness of a spacer plate 13 which is arranged between the folding element 8 and the embossing die 6. It is also possible, instead of a spacer plate, to provide a stack of several thin spacer plates, in order to be able to sensitively adjust the spacing a.

(26) The third embodiment example represented in FIG. 5 is designed like that described above, with the difference that in the folding element 8, elongated holes are provided which are penetrated by the fastening screws 12, and that the spacing a of the pressing edge 6k from the edge of the stamping surface 6p is defined by spacer disks 14 instead of a spacer plate.

(27) The elongated holes allow a depth adjustment of the pressing surface 8p of the folding element 8 relative to the stamping surface 6p. For the depth adjustment, for example, a spacer plate can be arranged between a straightening plate and the stamping surface 6p, and then the folding elements 8 can be lowered such that the pressing surfaces 8p lie flush against the straightening plate. The flush positioning can, for example, be checked with the light-gap method. After tightening of the fastening screws 12, the spacer plate can be removed and the embossing die 6 can be introduced into the stamping station 5.

(28) FIGS. 6 and 7 show a fourth embodiment example in which the spacing a of the pressing edge 8k from the edge of the stamping surface 6p is not formed adjustable due to the formation of the folding element 8 with a recessed pressing surface 8p.

(29) As in the embodiment example described in FIG. 5, a depth adjustment of the pressing surface 8p of the folding element 8 relative to the stamping surface 6p is provided. The depth adjustment is realized by means of a worm gear 15 which comprises an adjustment screw 15s and an adjustment wheel 15e. The adjustment screw 15s is formed with a fine thread. The adjustment screw 15s is rigidly connected to the upper end section of the folding element 8 and engages in a threaded hole of the adjustment wheel 15e. The adjustment wheel 15e can have a scale, in order to be able to reproduce the adjustment path of the worm gear 15.

(30) The embossing die 6 has a projecting upper end section in which the worm gear 15 is arranged. The adjustment screw 15s is mounted in a through-hole vertically penetrating the upper end section. The adjustment wheel 15e is arranged in a horizontal slot-shaped receiver of the upper end section of the embossing die 6 and is thus not axially displaceable.

(31) As described in FIG. 5, fastening screws 12 which penetrate the elongated holes of the folding element 8 are provided for fixing the folding element 8 to the embossing die 6.

(32) The fifth embodiment example represented in FIG. 8 differs from the embodiment example represented in FIG. 7 in that, for the depth adjustment of the pressing surface 8p, a double worm gear 16 is provided, which comprises a first adjustment screw 16s and a second adjustment screw 26t which are formed with different thread pitches, wherein the first adjustment screw 16s is adjustable from outside and engages in a perpendicular threaded hole of a projecting upper end section of the embossing die 6, and the second adjustment screw 16t engages in a central threaded hole of the first adjustment screw 16s and is rigidly connected to the upper end section of the folding element 8. The smaller the difference between the thread pitches of the two adjustment screws 16s and 16t, the more sensitive the adjustment of the vertical adjustment path of the pressing surface 8p.

(33) FIG. 9 shows the layered structure of a stamping foil 3 used in the stamping device 1 according to the invention, wherein the schematic representation approximately reproduces the thickness ratios of the stamping foil 3.

(34) In this embodiment example the carrier film 31 is formed as a PET film with a layer thickness of 19 m.

(35) The detachment layer arranged between the carrier film 31 and the transfer ply 33 is a lacquer layer with a thickness of from 0.5 m to 1 m.

(36) The transfer ply 33 has the following layers which are in each case formed by a lacquer a protective layer 331 made of an acrylate crosslinked with UV radiation, with a thickness of from 1 m to 10 m, a decorative layer 332 made of an acrylate, of PVC or a mixture thereof with dyes and/or color pigments, with a thickness of from 0.5 m to 50 m, in particular 0.5 m to 30 m, a stabilization layer 333 made of an acrylate crosslinked with UV radiation, with a thickness of from 1 m to 10 m.

(37) The thickness of the transfer ply 33 is thus between 5.5 m and 70 m.

(38) In the embodiment examples described above, the adhesive layer 34 is a hot adhesive layer which is heat-activatable. The adhesive layer 34 is made of PVC with a layer thickness of from 1 m to 10 m. However, it is also possible to use a cold adhesive layer, which can be activated by means of high-energy radiation.

(39) During testing of the proposed stamping device 1, the following parameters proved useful.

(40) The stamping temperature lies in a range of from 80 C. to 250 C., preferably in a range from 100 C. to 200 C., depending on the stamping station 5 and the substrate 2.

(41) The stamping pressure lies in a range of from 1 kN/cm.sup.2 to from 10 kN/cm.sup.2.

(42) The stamping time lies in a range of from 1 ms to 1000 ms, in particular in a range of from 1 ms and 500 ms.

LIST OF REFERENCE NUMBERS

(43) 1 stamping device 2 substrate 3 stamping foil 3d decorative section 3r residual stamping film 4 supply roll 5 stamping station 6 embossing die 6p stamping surface 7 stamping support 8 folding element 8k pressing edge 8p pressing surface 8v compression section 9 first and second take-up reel 10 deflection roller 11 pair of transport rollers 12 fastening screw 13 spacer plate 14 spacer disk 15 worm gear 15e adjustment wheel 15s adjustment screw 16 double worm gear 16s first adjustment screw 16t second adjustment screw 31 carrier film 32 detachment layer 33 transfer ply 34 adhesive layer 331 protective layer 332 decorative layer 333 stabilization layer a spacing of the pressing edge 8k from the edge of the stamping surface 6p p.sub.p stamping pressure p.sub.k pressing pressure