WO1998002307A1

WO1998002307A1 - Cover foil

Info

Publication number: WO1998002307A1
Application number: PCT/NL1997/000421
Authority: WO
Inventors: Johannes Antonius Maria Reinders
Original assignee: Sallmetall B.V.
Priority date: 1996-07-16
Filing date: 1997-07-16
Publication date: 1998-01-22
Also published as: NL1003601C2; AU3465297A

Abstract

A light-transmitting cover foil (3, 17, 19) consists of a laminate, comprising: a first layer (13, 20) which is for instance only plastically deformable at a relatively high first temperature and is provided in advance with a structure, for instance a texture, a second layer (15) adhered thereto consisting of a dimensionally stable carrier layer, and adhered thereto either a third layer thermally-activated at a relatively low second temperature, or a pressure-sensitive glue layer (16), wherein the outer surface of the first layer is of the type which substantially does not adhere to the outer surface of the third layer such that in the rolled-up state of the cover foil these surfaces lying on one another substantially do not mutually adhere.

Description

COVER FOIL

The invention relates to a cover foil intended to be applied adheringly to a surface optionally carrying information such as letters, numbers, images or the like, for instance the surface of a carrier plate, which foil consists of a laminate, comprising: a first layer which is for instance only plastically deformable at a relatively high first temperature for instance in the range of 120"C - 200 "C, for instance comprising polycarbonate, PMMA, PVC, ABS, PP, PE, which first layer is provided before, during or after joining together with the other layers with a structure, for instance a texture and/or a pattern pressed out of its main surface by exerting pressure and increasing temperature to at least the said first temperature, for instance by using a heated profile roller; a second layer adhered thereto consisting of a dimensionally stable carrier layer, for instance comprising polycarbonate, PMMA, PVC, polyester/PET, ABS; and adhered thereto, either a third layer meltable and thus thermally-activated at a relatively low second temperature, for instance in the range of 50 ^*C - 90*C, and consisting of a hot-melt or glue layer, for instance comprising EVA, EEA, EBA, EMA, GBA or other low-melting plastics, including polyolefins, copolymer esters, polyacetate esters, softened PVCs, acrylates and acryl- based substances; or a pressure-sensitive glue layer, which said layers are mutually connected by adhesive agents, for instance by making use of co- extrusion. Such a cover foil is described in applicant's international patent application PCT/NL95/00318.

During use of a cover foil according to the said older patent application it has been found that, after winding of the foil into a roll, the outer surfaces of the foil then pressing onto each other with some force cannot always be entirely prevented from mutually adhering.

The third layer can be of the thermally- activated type, which for instance only melts at about 80^*. Under ideal and substantially tension-free and friction-free winding conditions the outer surfaces of the first and third layer can then in principle not adhere to each other. It has nevertheless been found that also at the said melting point this adhesion does in fact occur. It occurs because a thermally-activated glue also has a certain, albeit slight, pressure-sensitivity, but also because during winding up of the foil at a certain strip tension the layers lying on top of one another can slide over each other with friction, whereby a quite considerable temperature increase to above the said melting point can occur locally.

It will be apparent that when layers mutually adhere an easy, well-controlled and disturbance-free unwinding cannot always be guaranteed. The invention has for its object to embody a cover foil of the said type such that the described drawbacks do not occur.

In this respect the cover foil according to the invention has the special feature that the outer surface of the first layer is of the type which substantially does not adhere to the outer surface of the third layer such that in the rolled-up state of the cover foil these outer surfaces lying on one another substantially do not mutually adhere; and the second layer can also comprise PVF/Tedlar, acrylates and acryl-based substances or other relatively non-stretch materials. The foil can for instance be characterized by a non-adhesive layer arranged on the outer surface of the first layer.

This variant can be particularly embodied such that the non-adhesive layer consists of a film or layer of silicone material, PTFE, PE, PP and the like or combinations thereof.

Yet another embodiment has the special feature that the first layer consists of a light-transmitting material which substantially does not adhere to the outer surface of the third layer.

This latter embodiment can have the feature that the first layer consists of light-transmitting, for instance transparent, PTFE, PE, PP and the like or combinations thereof.

It is noted that the stated, undesired mutual adhesion of the two outer surfaces of the foil could also be prevented by arranging a protective foil against the outer surface of the third layer. The drawback thereof is that this protective foil must be removed during unwinding and separately rolled up or discarded. This makes machine processing of the foil needlessly complicated and also has the drawback of resulting in additional waste. Attention is drawn to the fact that when a pressure-sensitive third layer is used the melting temperature of the first layer can be relatively low, in particular considerably lower than the range of 120°- 200*C mentioned in the preamble. Arranging of a silicone film can take place by making use of a solvent evaporating after application such as toluene, by spraying on an emulsion or by applying a pure silicone material without using a solvent. Use can for instance be made of a squeegee or the like. The thickness of a silicone film can be very small and lie for instance in the order of a few micrometers. When a relatively porous outer surface is used it can be recommended to treat this surface such that it is sealed, for instance by a treatment at increased temperature and a certain pressure.

It has been found that a cover foil of the above described type with a smooth and therefore glossy outer surface of the first layer has a quite considerable scratch-sensitivity. This can be determined experimentally in simple manner by scratching over the surface with a nail. After this experimental treatment the surface will often display a distinct scratch, this of course depending on the test conditions and the applied materials. Such scratches can also occur when the finished cover foil is manufactured in the factory or is rolled up in the finished state and for instance transported along stationary guides. There is also the possibility of said scratch damage occurring due to a somewhat careless handling of the finished cover foil in order to adhere this to a surface for covering.

Said drawback can be obviated with a cover foil of the stated type which has the feature that the outer surface of the first layer has a certain surface roughness and that a film of cured silicone material is present on this outer surface.

This embodiment has a number of great technical advantages. The reflectivity or the glossy character of the outer surface can be precisely controlled by a well- considered choice of the surface roughness and the film of silicone material. Because the generally very thin layer of silicone material will to some degree at least have the effect of effectively concealing the surface roughness to a certain extent, the glossy character of the rough outer surface is concealed and a glossier surface is obtained. A high-gloss surface can even be realized subject to the roughness and thickness of the silicone material. The considerably reduced scratch- resistance cannot be the result of the hardness of the silicone material which is anyway not a specifically hard material and which is moreover very thin. The low scratch-resistance probably results from the fact that due to the presence of the film of silicone material a caused scratch does not manifest itself optically, or hardly so. In the strict sense therefore there is perhaps no "real" increased scratch-resistance but the effect is that possible scratches hardly manifest themselves optically, or at least do so to a considerably lesser extent.

The best effect in the above-stated sense is obtained with a cover foil having the feature that the cover foil is transparent and the cured silicone material has an optical refractive index which is at least roughly the same as the refractive index of the first layer. The cover foil with a rough outer surface having cured silicone material thereon can be manufactured in simple manner if the cover foil has the feature that the first layer is manufactured by carrying a foil strip of the relevant material through the pinch of heated pressure rollers urged toward each other, wherein the outer surface of one of these pressure rollers has a profile corresponding with the desired roughness of the outer surface of the first layer.

This cover foil can further have the special feature that the silicone material is cured by polymerization, for instance by a thermal treatment or radiating with ultraviolet radiation. The layer of silicone material is applied, for instance sprayed on, in the form of a solution of a polymer, a catalyst and an inhibitor. The inhibitor is removed in a drying tunnel where an increased temperature prevails. By removing the inhibitor the catalyst becomes active to cure the polymer.

As stated above, use can alternatively be made of a polymer which cures under the influence of ultraviolet radiation. The invention will now be elucidated with reference to the annexed drawing. Herein: figure 1 shows a schematic view of a device which is adapted for processing a cover foil, wherein the outer surface of the third layer is covered by a protective foil which must be removed before use; figure 2 shows a cross section through a first embodiment of a cover foil according to the invention; figure 3 is a cross section through a variant.

Figure 1 shows a device 1 for arranging a light-transmitting cover foil 3 on a carrier 2. The cover foil 3 comprises a third layer acting as glue layer. The glue is of the pressure-sensitive type and is covered in the rolled-up state on roll 4 by a silicone protective foil 5 which must be removed prior to the application process in application station 6. For this purpose the protective foil is deflected by a deflecting roller 7 and guided therefrom to a waste roll 8 in order to be wound thereon. In order to arrange onto the carrier 2 the foil 3 from which the protective foil 5 is removed, this foil 3 is deflected by deflecting roller 9 and subsequently introduced into the pinch between two rollers 10, 11 for pressing onto carrier 2 while being transported according to arrow 12.

It will be apparent that this device 1 operates impractically insofar that special provisions are necessary to remove the protective foil 5.

Figure 2 shows a light-transmitting cover foil according to the invention. This foil comprises a first layer which is only plastically deformable at a relatively high first temperature, for instance in the range of 120 °C - 200°C, for instance consisting of polycarbonate, PMMA, PVC, ABS, PP, PE or combinations thereof, which first layer 13 is provided before, during or after joining together with the other layers mentioned hereinbelow with a structure, for instance a texture of outer surface 14.

Adhered to the first layer 13 by means of adhesive agents (such as an adhesive layer or co- extrusion) is a second layer 15, consisting of a dimensionally stable carrier layer, for instance

instance will therefore not adhere to this foil, which can be regarded as a very welcome additional feature of the invention.

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Claims

1. Cover foil intended to be applied adheringly to a surface optionally carrying information such as letters, numbers, images or the like, for instance the surface of a carrier plate, which foil consists of a laminate, comprising: a first layer which is for instance only plastically deformable at a relatively high first temperature for instance in the range of 120^*C - 200*C, for instance comprising polycarbonate, PMMA, PVC, ABS, PP, PE, which first layer is provided before, during or after joining together with the other layers with a structure, for instance a texture and/or a pattern pressed out of its main surface by exerting pressure and increasing temperature to at least the said first temperature, for instance by using a heated profile roller; a second layer adhered thereto consisting of a dimensionally stable carrier layer, for instance comprising polycarbonate, PMMA, PVC, polyester/PET, ABS; and adhered thereto, either a third layer meltable and thus thermally-activated at a relatively low second temperature, for instance in the range of 50"C - 90^*C, and consisting of a hot-melt or glue layer, for instance comprising EVA, EEA, EBA, EMA, GBA or other low-melting plastics, including polyolefins, copoly er esters, polyacetate esters, softened PVCs, acrylates and acryl- based substances; or a pressure-sensitive glue layer, which said layers are mutually connected by adhesive agents, for instance by making use of co- extrusion, characterized in that the outer surface of the first layer is of the type which substantially does not adhere to the outer surface of the third layer such that in the rolled-up state of the cover foil these outer surfaces lying on one another substantially do not mutually adhere; and the second layer can also comprise PVF/Tedlar, acrylates and acryl-based substances or other relatively non-stretch materials.

2. Cover foil as claimed in claim 1, characterized by a non-adhesive layer arranged on the outer surface of the first layer.

3. Cover foil as claimed in claim 2, characterized in that the non-adhesive layer consists of a film or layer of silicone material, PTFE, PE, PP and the like or combinations thereof.

4. Cover foil as claimed in claim 1, characterized in that the first layer consists of a light-transmitting material which substantially does not adhere to the outer surface of the third layer.

5. Cover foil as claimed in claim 4, characterized in that the first layer consists of light- transmitting, for instance transparent, PTFE, PE, PP and the like or combinations thereof.

6. Cover foil as claimed in claim 1, characterized in that the outer surface of the first layer has a certain surface roughness and that a film of cured silicone material is present on this outer surface.

7. Cover foil as claimed in claim 6, characterized in that the cover foil is transparent and the cured silicone material has an optical refractive index which is at least roughly the same as the refractive index of the first layer.

8. Cover foil as claimed in claim 6, characterized in that the first layer is manufactured by carrying a foil strip of the relevant material through the pinch of heated pressure rollers urged toward each other, wherein the outer surface of one of these pressure rollers has a profile corresponding with the desired roughness of the outer surface of the first layer.

9. Cover foil as claimed in claim 6, characterized in that the silicone material is cured by polymerization, for instance by a thermal treatment or radiating with ultraviolet radiation.

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