Permanent security film with high transparency and without predetermined breaking points
The present invention relates to peelproof security films made from a poly(meth)acrylate, more particularly from a polymethyl methacrylate, which comprises at most 10 wt % of or no impact modifiers. These films are highly transparent, have good printability qualities, and can be applied without intended break points. The peelproof security films can therefore find use in particular in documents, such as passports, for example, in security labels, such as road tax badges, for example, or for product theft prevention, or as price tags. These security labels are further distinguished by good weathering stability and in particular by especially good UV stability. The present invention relates more particularly to the use of these security labels, which have a thickness of not more than 2 mm, comprise at least 80 wt % of polymethyl methacrylate and contain no impact modification particles.
1. A security label, comprising an extruded polymethacrylate film,
wherein the extruded polymethacrylate film has a thickness of between 15 and 120 μm and an elongation at break of between 2.0% and 15%,
wherein the extruded polymethacrylate film comprises 55 to 100 wt % of a polymethacrylate which comprises 80 to 100 wt % of MMA and 0 to 20 wt % of styrene and/or other (meth)acrylates comprising an alkyl radical comprising, 1 to 4 carbon atoms,
wherein the extruded polymethacrylate film further comprises at most 10 wt % of an impact modifier or no impact modifier, and
wherein the weight-average molecular weight Mw of the polymethacrylate is from 80,000 to 300,000 g/mol.
2. The security label of claim 1 , wherein the extruded polymethacrylate film has a thickness of between 20 and 75 μm, and
wherein the extruded polymethacrylate film comprises 90 to 100 wt % of a polymethacrylate which comprises 90 to 100 wt % of MMA and 0 to 10 wt % of acrylates comprising an alkyl radical comprising 1 to 4 carbon atoms.
3. The security label of claim 1 , wherein the extruded polymethacrylate film is colored white and comprises between 5 and 40 wt % of titanium dioxide.
4. The security label of claim 1 , wherein a difference between a thinnest point and a thickest point of the extruded polymethacrylate film is at most 5 μm.
5. The security label of claim 1 , wherein the extruded polymethacrylate film comprises not more than 2 wt % of additives.
6. The security label of claim 1 , wherein the extruded polymethacrylate film comprises essentially no additives.
7. The security label of claim 1 , wherein the extruded polymethacrylate film comprises no impact modifier.
8. The security label of claim 1 , wherein the extruded polymethacrylate film is produced by an extrusion process wherein a production line used comprises:
an extruder,
a melt pump,
an optional melt filtration facility,
an optional static mixing element,
a flat film die,
a polishing stack or chill roll, and
a winder,
wherein the flat film die comprises a die lip comprising actuating elements for adjusting a die lip width, the actuating elements having a distance of 11 to 15 mm from one another, and a die body having an external geometry adapted to a shape of the polishing stack or chill roll, and
wherein a distance from a melt exit edge to a polishing nip is 80 mm or less.
9. The security label of claim 8 , wherein the flat film die is oriented relative to the polishing stack or chill roll with a laser, and
wherein a parallel deviation of the flat film die relative to the polishing stack or chill roll, measured at the two ends of one outer side of the flat film die, exhibits a maximum deviation of 3 mm.
10. The security label of claim 8 , wherein the flat film die and the polishing stack or chill roll have chrome surfaces which have a roughness Ra of less than 0.08 μm.
11. An application-capable security film, which has a thickness of between 15 and 120 μm and an elongation at break of between 2.0% and 15%, and, before application, comprises at least the following layers in the order stated:
a) the security label of claim 1 , with printing on at least one side,
b) a pressure-sensitive adhesive,
c) a release coating, and
d) a support layer.
12. The application-capable security film of claim 11 , wherein layer a) has a thickness without printing of between 20 and 75 μm,
the printing has a thickness of between 1.5 and 3 μm,
layer b) has a thickness of between 20 and 30 μm,
layer c) has a thickness of between 0.5 and 1.2 μm and
layer d) has a thickness of between 20 and 70 μm.
13. The application-capable security film of claim 11 , wherein the extruded polymethacrylate film is transparent and comprises 90 to 100 wt % of the polymethacrylate.
14. The application-capable security film of claim 11 , wherein the extruded polymethacrylate film is colored white and comprises 55 to 95 wt % of polymethacrylate and 5 to 40 wt % of titanium dioxide.
15. The application-capable security film of claim 11 , wherein the extruded polymethacrylate film comprises no impact modifier.
16. A chip card, document, security label, other label or price tag, comprising the application-capable security film of claim 11 .