WO2010022733A1

WO2010022733A1 - Uv-foil

Info

Publication number: WO2010022733A1
Application number: PCT/DK2009/050213
Authority: WO
Inventors: Jens Thorn; Per Jakobsen; Peter Egelund
Original assignee: Idéen ApS
Priority date: 2008-08-25
Filing date: 2009-08-25
Publication date: 2010-03-04

Abstract

The present invention concerns a transparent plastic film intended for solar screening of persons, where the film is made up of one, two or preferably three or more layers, where the layers e.g. are coextruded layers. The film layers contain or are coated with UV absorber which is adapted such that UV rays with different wavelengths are absorbed in predetermined quantities. By such a film, the UV protection can be tailored to precisely the UV protection desired for the intended purpose or application. It is thus possible it make a film which is particularly suited for sunshades and awnings, and which at the same time allows for a certain tanning effect on the skin by letting a modest part of UVB and UVA light pass through the film.

Description

UV-foil

Field of the Invention

The present invention concerns a transparent plastic film intended for solar screening of persons, where the film is made up of one, two or preferably three or more layers, where the layers e.g. are coextruded layers.

Background of the Invention

It is commonly known to use various kinds of plastic in connection with sunshades and other kinds of solar screening. Often a woven material is used, but various films are also known in use for the purpose. These films all have the property that shade is provided under the solar screening. However, there is a certain desire for being able to stay in the light surroundings outside, without having to stay in the shade. Therefore, there exist different solar screenings which allow a part of the sunlight (the visible light) to pass. For example, from US 6,131,591 it is known to make a parasol with openings in the parasol itself, implying a partial penetration of sunlight/visible light.

Other solutions are also known, where more or less transparent PVC film is used for umbrellas/parasols. However, these have the unfavourable property that the film is discoloured after some time and thus no longer appear with the desired expression.

At the same time, it is a fact that by the prior art solar screenings UVA, UVB and UVC light are excluded by the sunshade. UVB and in particular UVC light are harmful ultraviolet light waves with wavelengths of about 100 nanometres and 315 nanometres. Too much action by these may cause skin diseases, including skin cancer, while UVA which has wavelength in the range 315 - 380 nanometres is harmless to some extent.

People staying in the sun for sunbathing and thereby for achieving an attractive brown tan therefore use sunscreen with UV filter. Such a filter shuts off UVC, partly for UVB, which is required to achieve the brown tan, allowing some UVA to pass which also contributes to the tan. UVB radiation effects melamine to be formed in the skin which is oxidised by UVA radiation, thereby forming the attractive brown tan on the skin. Sunscreen is a good solution when one desires to stay in the sun, but when the skin is applied such creams it is often felt very hot and tight as the skin can no longer breathe freely due to the sunscreen.

In principle, humans can stand up to most UVA radiation, but not very much UVB and much less UVC. However, it is a fact that all three types of UV radiation may be harmful to humans. By the prior art types of solar screening it is, however, not possible simultaneously to be sufficiently protected against UVC and partly against UVB while the body is exposed to a limited quantity of UVB and to UVA to an appropriate extent.

Object of the Invention

It is the object of the invention to indicate a film which is transparent and yielding protection against the harmful UV light but which at the same time allows for a certain tanning effect on the skin by letting a modest part of UVB and UVA light pass through the film. Another object of the invention is that the film furthermore is to be strong, very transparent, and to be environment-friendly in making as well as by discarding. Such a film may according to the invention be used for sunshades, awnings and the like.

Description of the Invention As mentioned in the introduction, the invention concerns a transparent plastic film intended for solar screening of persons, where the film is made up of one or more layers which e.g. are coextruded layers. The film includes a UV absorber, where the said UV absorber is either applied to one or more film layers and/or contained in one or more film layers, where the contents of the UV absorber in or on the individual film layer or layers are adapted such that UV rays with different wavelengths are absorbed in predetermined quantities.

By such a film, the UV protection can be tailored to precisely the UV protection desired for the intended purpose or application. It is thus possible to make a film which is particularly suited for sunshades and awnings and which provide additional protection in geographical areas with a thin or perforated ozone layer, where care is to be taken regarding UVC rays which due to the said holes in the ozone layer are not filtered off in the atmosphere as usual.

A film according to the invention with UV protection is thus a very suitable film for use in connection with sunshades, awnings and other kinds of coverings of areas where people can stay without being in shade and while achieving the tanning effect simultaneously being protected against harmful quantities of UV light.

hi a preferred variant, the film is mainly made up of polyethylene (PE) and by making the film of PE, several advantages are achieved. Among other things, PE is a suitable material for sunshades and awnings etc. since it has a suitable toughness and tear strength. Moreover, PE is easy to discard as it may readily be processed in common waste plants without risk of harmful substances being discharged to the atmosphere. A further advantage of PE before other plastic types is that with the proper UV absorbers, it may appear clear as glass, thereby allowing a person staying under the film experience the full light impression from the surroundings.

In a variant of a transparent plastic film intended for solar screening according to the invention, the film may be with a structure having a first film layer and a first UV absorber, a second film layer and a second UV absorber and possibly additional film layers with one or more UV absorbers, respectively. The different types of UV absorbers may be with different other properties. For example, there are some types that cause the film not to appear clear as glass, but with a milky white tinge. Similarly, the various UV absorbers may have special properties regarding UV rays with different wavelengths. Thus it is e.g. possible to design each single film layer in a coextruded film for precisely a definite range of wavelengths.

A transparent plastic film intended for solar screening according to the invention may provided with a triple-layered film structured with first layer constituting 10 to 40% of the thickness of a triple-layered film, a second layer constituting 20 to 80% of the thickness of a triple-layered film, and a third layer constituting 10 to 40% of thickness of a triple-layered film. By adapting the thickness of respective layers which either have the same, different or overlapping UV-protective properties, there may be achieved exactly the protection against UV rays which is desired. In other words, it is possible with properties adapted to different needs.

In a preferred embodiment, the transparent plastic film according to the invention is provided with a total thickness of 100 to 250 μm. Within this thickness range, many different variants can be made without becoming too weak or too heavy.

A film according to the invention may, as mentioned, be made up of at least two film layers and maybe of more layers. The thickness of such a film may vary between 100 μm and 250 μm, or even be thicker. The thickness and the number of layers is adapted to the actual need, but by making the film with more layers there is achieved the clear advantage that the film appears with higher quality, since by a plurality of layers there is less risk that possible defects in the film become arranged over each other. There is, so to speak, achieved a higher quality with reduced risk of defects.

In the example 1 below, there is indicated a film which is with three layers, and where first and third layers have the same thickness, while the second layer is with double thickness. This structure is just one example, and respective layers in a triple layer film may advantageously be provided with thicknesses in the ranges indicated above.

A transparent plastic film intended for solar screening which is made as a multi- layered film, may advantageously be with a structure wherein each layer contains between 85 % and 97 % PE and between 3 % and 15 % UV absorber. By such a composition, the desired protection may be achieved simultaneously with achieving the desired attractive transparent properties as well. In the individual layers in a film according to the invention, there may also be contained various auxiliary substances, such as release agents. These substances are added in very small amounts and are therefore not explained in detail. However, it is very clear for a skilled in the art in the area that such substances may advantageously be added to particularly the outermost layers in the finished film.

Example 1: Film thickness 140 μm

In the

shown example, in the first layer there may e.g. be absorbed 50 % UVC, 22 % UVB and 20 % UVA. In the second layer is absorbed the rest of UVC, 44% UVB due to the double layer thickness and 40% UVA also due to the double layer thickness. In the third layer is absorbed 22% UVB and 20% UVA as the layer thickness corresponds to the first layer. In this variant, 12% UVB and 20% UVA therefore pass through the film. However, there are innumerable possibilities of varying the individual layers in the film, and this example is based on the fact that the layers have the same composition of PE and UV absorber.

By structuring the film as a triple-layered film there is achieved the advantage that each single layer can be designed with regard to the thickness and the content and type of UV absorber such that the desired absorption of respective UV rays is achieved.

Example 2:

Film thickness 200 μm In

example 2 is indicated a film according to the invention which may be designed such that respective layers only constitute a UV filter for a specific UV wavelength interval. The first layer may thus e.g. be designed as a filter for UVC, whereas the second layer may be designed to be a filter for UVB, and the third layer for UVA. By such a solution, each single layer in a coextruded film may have its own function independently of the other layers in the film, where each single layer absorbs its own type of UV rays. Such a solution may be achieved by carefully selecting respective UV absorbers and adapting the added amount.

Another example of a film according to the invention is that the film may be made of five coextruded layers where the two outermost layers have a thickness of only 10 μm. These outermost layers may have the advantage that they act as additional wearing layers, thereby imparting the film a longer service life and greater stability.

In order to meet different wishes from the consumers, a transparent plastic film according to the invention may be provided with at least one of the layers in the film being tinted with a colour. For example, brown, black or other colour by which the look through the film will correspond to using sunglasses. This action may be desired in areas with very strong sunlight where a greater contrast in colours is desired.

In a variant of a transparent plastic film according to the invention, the film may be coated with a UV absorbing coating on one or two sides and preferably made up of several film layers, where at least one or more film layers are coated with a UV absorbing coating on one or two sides. By applying the UV absorbing coating on the sides of the film, there is achieved the advantage that the strength properties of the film are not influenced by the UV absorber as it does not form part of the film layer itself. Moreover, there is achieved the advantage that the finished film can be made up as a sandwich structure where one or more single film layers are joined by a UV absorbing adhesive, e.g. by extrusion coating. It is thus the UV absorber that acts a adhesive between respective film layers which may be with uniform or different properties with regard to strength and transparency.

Coating a plastic film with one or more layers of UV absorber may be performed in different known ways, e.g. by flexo-printing.

hi the same way can be designed a sandwich structure with a layer that only has a loadbearing purpose. For example, a reinforcing net layer or other element providing improved stretch stability may be advantageous in connection with large items as awnings and the like.

A transparent plastic film for a solar screening according to the invention may be adapted to a given shape by welding the film, by sewing, gluing or combinations of these, or by other joining methods whereby a film may readily be adapted to a specific purpose.

Claims

1. A transparent plastic film intended as solar screening for persons, wherein the film is made up of one, two or preferably three or more layers, where the layers e.g. are coextruded layers, where the film includes a UV absorber, where the UV absorber is either applied on one or more film layers and/or contained in one or more film layers, where the contents of the UV absorber in or on the individual film layer or layers is adapted such that UV rays with different wavelengths are absorbed in predetermined quantities, characterised in that the film is with a structure having a first film layer and a first UV absorber, a second film layer and a second UV absorber and possibly additional film layers with one or more UV absorbers, respectively.

2. Transparent plastic film intended as solar screening according to claim 1, characterised in that the film is substantially made up of polyethylene (PE).

3. Transparent plastic film intended for solar screening according to any of claims 1-2, characterised in that the film is a triple-layered film with a structure in which the first layer constitutes 10 to 40% of the thickness of a triple-layered film, the second layer constitutes 20 to 80% of the thickness of a triple-layered film, and the third layer constitutes 10 to 40% of thickness of a triple-layered film.

4. Transparent plastic film intended for solar screening according to any of claims 1-3, characterised in that the film has a total thickness of 100 to 250 μm.

5. Transparent plastic film intended for solar screening according to any of claims 1-4, characterised in that the film is a multi-layered film with a structure wherein each layer contains between 85 and 97 % PE and between 3 and 15 % UV absorber.

6. Transparent plastic film intended for solar screening according to any of claims 1-5, characterised in that at least one of the layers in the film is tinted with a colour.

7. Transparent plastic film intended for solar screening according to any of claims 1-6, characterised in that the film is coated with a UV absorbing coating on one or two sides and preferably made up of several film layers, where at least one or more film layers are coated with a UV absorbing coating on one or two sides.

8. Transparent plastic film intended for solar screening according to any of claims 1-7, characterised in that the film is made up as a sandwich structure where one or more single film layers are joined by a UV absorbing adhesive, e.g. by extrusion coating.

9. Transparent plastic film intended for solar screening according to any of claims 1-8, characterised in that the film is formed into a given shape by welding the film.

10. Transparent plastic film intended for solar screening according to any of claims 1-8, characterised in that the film is formed into a given shape by sewing the film.

11. Transparent plastic film intended for solar screening according to any of claims 1-8, characterised in that the film is formed into a given shape by gluing the film.