GB2624648A

GB2624648A - Protective film assembly

Info

Publication number: GB2624648A
Application number: GB2217515.2A
Authority: GB
Inventors: Nigrone Stefano
Original assignee: Spandex Ltd
Current assignee: Spandex Ltd
Priority date: 2022-11-23
Filing date: 2022-11-23
Publication date: 2024-05-29
Also published as: GB202217515D0

Abstract

A protective film assembly 100 for protecting a substrate (200, Fig. 2) comprises (i) a barrier film 110 having a rear surface 114 facing, in use, towards the substrate and an opposite front surface 112 and (ii) an adhesive 120 disposed on the rear surface for adhering the film assembly to the substrate. The substrate and/or printed matter 210 deposited thereon act as a source of outgassed vapour. The barrier film comprises perforations 116 for enabling the vapour to pass through the film from the rear surface to the front surface. Preferably, the perforations have an area of <1 mm2 and extend through the film, adhesive, and optionally a detachable liner 130 attached to the adhesive. The adhesive may be thermally cured or UV-curable. A kit of parts for a printed article comprises the film assembly and a printable substrate. A method for producing the film assembly is also disclosed.

Description

Protective film assembly

Field of the Invention

The present invention relates to protective films for use with a substrate, and more specifically to protective film assemblies for protecting the substrate wherein the substrate and/or printed matter deposited on the substrate is a source of outgassed vapour.

Background

In order to ensure long-term durability of composite material substrates such as glass-fibre or carbon-fibre composite substrates, foam board material such as polyvinyl chloride (PVC) foam board or Foamex, and/or substrates with printed matter printed thereupon (e.g. signage for outdoor use), it is known to apply a protective varnish coating or to use an overlaminate such as a protective film or a protective film assembly. These can protect the substrate and/or any printed graphics thereupon against damage from, for example, moisture, dirt, or UV degradation. The substrate and/or printing inks can comprise components (e.g. solvents) which can adversely interact with the protective coating and/or protective film. This can lead to failure of the coating and/or film, and/or shrinkage or distortion of the substrate, and therefore introduces challenges in applying the protective film.

The present invention has been devised in light of the above considerations

Summary of the Invention

In general, the present invention relates to a protective film assembly that can be applied to a substrate to protect the substrate itself, and/or any printed graphics on the substrate from environmental damage. For example, the substrate may be a composite material such as carbon-fibre composite or glass-fibre composite, a foam board such as a rigid foam board, a PVC foam board or Foamex, and/or may be a substrate on which printed matter ink may be printed.

A composite substrate such as carbon-fibre composite or glass-fibre composite comprises fibres embedded in a resin. The resin may comprise one or more volatile components which can outgas after the substrate is formed. Therefore, the substrate may be a source of outgassed 30 vapour.

Foam boards (e.g. rigid foam boards) such as PVC foam board or Foamex comprise a foam such as a polymer foam, which may be compressed to form a rigid or semi-rigid board. In some cases, the foam may form a core of the board and sheet of, for example, paper may be applied (e.g. adhered) to one or more faces of the board to form a surface that can be more readily printed upon than the foam itself (for example the foam core may be sandwiched between two printable surface sheets). Thus, the foam board may be a composite substrate. When the foam is formed, and/or the printable surface is applied to the foam, uncured resin or adhesive can remain as an outgassable substance within the substrate. Therefore, such substrates, which are commonly used in signage material, can be a substrate that is a source of outgassed vapour.

Meanwhile printed matter (e.g. an ink) may comprise volatile components such as photoinitiators and/or solvents. Once again, these can be outgassed from the printed matter, such that the printed matter is a source of outgassed vapour.

The protective film assembly includes a barrier layer or barrier film which has perforations to enable components of the substrate and/or printed matter (in particular volatile components such as solvents) to pass through the barrier film. This reduces the trapping of these components in the space between the protective film assembly and the substrate, which might otherwise cause damage to the substrate, any printed graphics, or the protective film assembly.

According to a first aspect of the invention, there is provided a protective film assembly for protecting a substrate, the substrate and/or a printed matter deposited on the substrate being a source of outgassed vapour. The protective film assembly comprises a barrier film having a rear surface facing, in use, towards the substrate, and a front surface opposite the rear surface; and an adhesive disposed on the rear surface of the barrier film, the adhesive being for adhering the protective film assembly to the substrate. The barrier film further comprises perforations through the barrier film for enabling vapour from the source of outgassed vapour to pass through the barrier film from the rear surface of the barrier film to the front surface of the barrier film Enabling outgassed vapour to pass through the barrier film means that volatile components of the substrate (such as solvents or resins) and/or components of inks printed onto the substrate (e.g. solvents, photoinitiators) are not trapped behind the protective film assembly, and rather are able to escape from a space between the protective film assembly and the substrate.

Trapped components might otherwise affect the printed graphics and/or substrate, and may also cause a failure of the protective film assembly (e.g. clouding or buckling of the protective film assembly and/or localised or general delamination from the substrate). While such components could alternatively be allowed to escape before applying the protective film assembly, this process can take several hours or even days for some commonly used inks, even in the case of inks which are "touch" dry shortly after printing. Meanwhile, many substrates, including composite substrates and/or foam boards can continue to release volatile components even longer after the substrate is formed (as long as months or years), particularly if the substrate is later heated (as might be expected, for example, if the substrate is to be used in a location outdoors and in direct sunlight).

Use of the protective film assembly according to the present invention can therefore enable a protective film to be applied to a wider range of substrates and/or to be used with a wider range of inks, including those that are not compatible with conventional protective film assemblies due to vapour outgassing. Since outgassed vapour is able to escape from a space between the protective film assembly and the substrate by passing through the perforations in the barrier film, there is a reduced effect of any trapped outgassed vapour on the substrate, any printed matter thereupon, the adhesive of the protective film assembly and/or the barrier film of the protective film assembly. Additionally or alternatively, any wait time between either forming/manufacturing a substrate or printing a substrate with printed matter and applying the protective film assembly can be reduced, since residual outgassed vapour can escape through the perforations even with the protective film in situ.

A combined surface area of the perforations comprised in a unit area of barrier film (i.e. the proportion of the surface area of the barrier film which is perforated) may be selected or configured such that a flow rate of gas through the film is at or above a desired threshold level, depending on the differential pressure across the film. This can ensure that sufficient outgassed vapour can pass through the protective film assembly when in use. For example, a combined surface area of the perforations comprised in a unit area of barrier film may be such that at room temperature, with one side of the barrier film held at a pressure of 300 kPa, and the other at atmospheric pressure (approximately 100 kPa), or a pressure differential of approximately 200 kPa, the flow rate of gas (e.g. atmospheric air) through a 1 square metre area of film may be greater than 1 litre per minute, preferably greater than 2 litres per minute, more preferably greater than 3 litres per minute, or 4 litres per minute. Higher flow rates can enable any vapour to pass through the protective film more readily. The flow rate may be less than 8 litres per minute, preferably less than 6 litres per minute. While any differential pressure across the protective film assembly in use is likely to be minimal, a lower flow rate ensures that the protective properties of the protective film assembly are maintained, and that excessive contaminants cannot pass through the protective film assembly from a front surface to a rear surface thereof The perforations may be formed using a perforating tool held at an elevated temperature. For example, the perforating tool may be heated to more than 40°C, preferably more than 60°C, more preferably more than 70°C, or 100°C. An elevated temperature of the perforating tool may improve the durability of the perforations. For example, a heated perforating tool can cure or melt a region of the barrier film around the perforation, such that subsequent closure of the perforation is reduced. Meanwhile, the elevated temperature may be less than 160°C, preferably less than 140°C, more preferably less than 130°C. If the elevated temperature is too great, excessive damage may be caused to the barrier film (for example, the melted or cured area may extend further from the perforation than is required).

At least one perforation of the perforations may have an area of less than 1 square millimetres.

Furthermore, each perforation of the perforations may have an area of less than 1 square millimetres. At least one perforation or each perforation of the perforations may have an area of less than 0.8 square millimetres, more preferably an area of less than 0.65 square millimetres. Such perforations are large enough to enable vapour outgassed from printed matter to pass through, while reducing the passage of liquid moisture or dirt from through the film (for example from the front surface to the back surface). Perforations of this size are also less visible to the naked eye, thereby reducing the visual impact of the perforations on the protective film assembly. The surface area of the perforations may be constant along their length through the film, or may vary. For example, the perforations may taper and/or expand between the front surface and the rear surface of the barrier film.

The perforations may be microperforations in that they have a lateral extent (e.g. diameter) of, for example, less than 1000 pm. If the average size of the perforations or microperforations is too large, they can reduce the protective, optical and/or mechanical properties of the film. The perforations or microperforations may have a lateral extent or diameter of greater than 200 pm.

If the perforations or microperforations are too small, they cannot fulfil the function of enabling outgassed vapour to pass through the barrier film. The perforations or microperforations may have a range of lateral extents rather than each having the same lateral extent. The perforations may have an area density of more than 10000 perforations per square metre, preferably more than 200000 perforations per square metre, more preferably more than 300000 perforations per square metre, or 375000 perforations per square metre. A higher area density of perforations can enable vapour to pass more readily though the barrier film.

The perforations may be present at an area density of less than 500000 perforations per square metre, preferably less than 450000 perforations per square metre, more preferably less than 400000 perforations per square metre. A lower density of perforations may ensure that the perforations do not impact the mechanical or physical resistance and durability, or the optical properties and aesthetic appearance of the protective film assembly.

The perforations may be uniformly distributed in the barrier film. For example, the barrier film may have a length, width and depth (or thickness), with the depth (or thickness) being significantly smaller than both the length and width, and the perforations may be uniformly distributed with reference to the length and/or the width. This can enable consistent passage of vapour outgassed from the substrate and/or the printed matter through the film across an area of the protective film assembly. Therefore, there is a reduced chance of an area of the protective film assembly forming regions where vapour may still remain trapped.

The perforations may extend through (e.g. fully or completely through) the barrier film and the adhesive (e.g. their depths or thicknesses). For example, the perforations in the barrier film may be formed with the adhesive in situ. This can prevent, for example, adhesive blocking or flowing into perforations in the barrier film during application to the barrier film.

The adhesive may be an adhesive coating. It is not necessary for the adhesive to be a free-standing film (i.e. the adhesive may not have a solid structure independent to that of the barrier film), and thus it may instead be applied as a coating on the barrier film, reducing the number of component films or layers required to form the protective film assembly. Alternatively, the adhesive may be a layer or film 0.e. the layer may have a solid structure independent to that of the barrier film) comprising an adhesive that can be applied to the barrier film. The latter may be advantageous in having reduced movement or migration of the adhesive across the barrier film.

The protective film assembly may further comprise a detachable liner film adhered to the adhesive. The liner film can be used to apply the adhesive to the barrier film via a transfer process. The liner film may also protect the adhesive until the point of application of the protective film assembly to a substrate, at which point it may be peeled away or detached from the adhesive and barrier film and discarded.

The perforations may extend through (e.g. fully or completely through) the adhesive, the barrier film, and the liner film. As described above, this can enable the perforations to be formed after the films of the protective film assembly are assembled together.

The adhesive may be for adhering the protective film assembly to an impermeable substrate. For example, the adhesive may be chosen, formulated, or configured to be optimised for application to an impermeable substrate (i.e. a substrate through or into which the adhesive cannot flow or diffuse). Many substrates to which the protective film assembly may be applied or adhered are impermeable, and use of such an adhesive therefore ensures applicability to the relevant substrate types.

The adhesive may not be for adhering the protective film assembly to a porous or permeable substrate. In an embodiment, the adhesive may not be suitable for adhering to biological tissue (e.g. human skin), for example, the adhesive may not be biocompafible (e.g. the adhesive may be toxic or harmful to living biological tissue). In view of the likely application to impermeable substrates, an adhesive for adhering to a porous or permeable substrate may be unsuitable for use with such a substrate.

The adhesive may be configured to adhere the protective film assembly to a polymeric substrate, which may be, for example a PVC substrate. This can therefore ensure optimal compatibility with typical substrates with which the protective film assembly may be used.

The adhesive may additionally or alternatively be configured to adhere the protective film assembly to a foam board (e.g. a rigid foam board including a PVC foam board such as a Foamex board), or to an applied printable surface thereof This can therefore ensure optimal compatibility with typical substrates with which the protective film assembly may be used, and in particular with a class of substrates which can be a source of outgassed vapour.

The adhesive may be configured to adhere the protective film assembly to a composite substrate, such as a glass-fibre or carbon-fibre composite comprising fibres embedded in a resin matrix. Providing an adhesive which can adhere to such a substrate enables compatibility between the protective film assembly and a composite substrate with which the protective film assembly may be used.

The adhesive may be a thermally curable adhesive or an ultraviolet (UV)-curable adhesive. Such adhesives may be more readily applied, coated, or spread into a uniform layer, and can then be cured to fix the adhesive in place. The properties such as fluidic properties of the adhesive can thus be independently optimised for application and for usage.

The combined average optical transmittance of the barrier film and the adhesive may be greater than 70%, preferably greater than 80%, more preferably greater than 85%. The combined average haze of the barrier film and the adhesive may less than 15%. These averages may be calculated based on only a portion of the protective film assembly which is intended in normal use to be visible and/or which is intended in normal use to cover a portion of the substrate and/or any printed matter on the substrate. For example, the materials forming the barrier layer and/or adhesive may be selected to have particular optical properties. The thicknesses or depths of the layers forming the protective film assembly may be configured to achieve preferred optical properties. The refractive index mismatch between the layers may be selected to reduce, minimise, or substantially prevent any unwanted reflections at the interface between the layers. The size and area density of the perforations in the protective film assembly may be configured in view of an effect on the optical properties of the protective film assembly.

The protective film assembly is for use as a protective overlay for a substrate. Therefore, it may be necessary for the substrate to be visible through the protective film assembly. A film assembly with a suitable optical transparency and haze therefore can enable the substrate and any printed matter printed thereupon to be viewed through the protective film assembly. This can mean, for example, that where the substrate is printed with printed matter, the ink and colour saturation chosen to print the print matter does not need to be altered to compensate for the optical properties of the protective film assembly.

According to a second aspect of the invention, there is provided a kit of parts for a printed article, comprising a protective film assembly according to the first aspect of the invention and a substrate for printing with printed matter. Such a kit of parts can ensure optimal compatibility between the protective film assembly and the substrate.

According to a third aspect of the present invention, there is provided a printed article comprising a substrate having printed matter deposited on a first surface thereof and a protective film assembly according to the first aspect of the invention adhered to the first surface of the substrate.

According to a fourth aspect of the present invention, there is provided a kit of parts for a protected substrate, comprising a protective film assembly according to the first aspect of the invention, and substrate which can be a source of outgassed vapour. As with the second aspect of the invention, providing a kit of parts for a protected substrate can ensure optimal compatibility between the components.

According to a fifth aspect of the present invention, there is provided a substrate being a source of outgassed vapour, and a protective film assembly according to the first aspect of the invention.

According to a sixth aspect of the present invention, there is provided a method for producing a protective film assembly for protecting a substrate, the substrate and/or printed matter deposited on the substrate being a source of outgassed vapour. The method comprises the steps of providing a barrier film having a rear surface facing, in use, towards the substrate and a front surface opposite the rear surface; applying an adhesive to the rear surface of the barrier film, and perforating the barrier film to produce perforations through the barrier film. The produced perforations through the barrier film are for enabling vapour from the source of outgassed vapour to pass through the barrier film from the rear surface of the barrier film to the front surface of the barrier film. The order of the steps of this process may be changed such that, for example, the barrier film is perforated prior to the adhesive being applied.

The step of perforating the barrier film may comprise perforating the barrier film with a perforating tool. Use of a perforating tool, which may comprise needles, pins, or blades to pierce and perforate the barrier film, can ensure that perforations are efficiently produced (e.g. multiple perforations can be produced at once) at a suitable area density and correctly arrayed or distributed across the substrate.

The step of perforating the barrier film to produce perforations may be a hot-perforating process. In a hot perforating process, the perforations may be formed using a perforating tool held at an elevated temperature. For example, the perforating tool may be heated to more than 40°C, preferably more than 60°C, more preferably more than 70°C, or 100°C. An elevated temperature of the perforating tool may improve the durability of the perforations. For example, a heated perforating tool can cure or melt a region of the barrier film around the perforation, such that subsequent closure of the perforation is reduced. Meanwhile, the elevated temperature may be less than 160°C, preferably less than 140°C, more preferably less than 130°C.

A combined surface area of the perforations comprised in a unit area of barrier film (i.e. the proportion of the surface area of the barrier film which is perforated) may be selected or configured such that a flow rate of gas through the film is at or above a threshold level, depending on the differential pressure across the film. For example, a combined surface area of the perforations comprised in a unit area of barrier film may be such that with one side of the barrier film held at a pressure of 300 kPa, and the other at atmospheric pressure (approximately 100 kPa), the flow rate of gas through a 1 square metre area of film may be greater than 1 litre per minute, preferably greater than 2 litres per minute, more preferably greater than 3 litres per minute, or 4 litres per minute. The flow rate may be less than 8 litres per minute, preferably less than 6 litres per minute.

The perforations may be produced at an area density of more than 10000 perforations per square metre, preferably more than 200000 perforations per square metre, more preferably more than 300000 perforations per square metre, or 375000 perforations per square metre. The perforations may be produced at an area density of less than 500000 perforations per square metre, preferably less than 450000 perforations per square metre, more preferably less than 400000 perforations per square metre.

The step of perforating the barrier film may comprise perforating the adhesive, for example where the adhesive is applied to the barrier film prior to perforation. The step of perforating the barrier film may further comprise perforating the adhesive and the liner film, for example where the adhesive and a liner film are applied to the barrier film prior to perforation.

The step of applying the adhesive to the barrier film may be via a transfer coating process, comprising the steps of coating a liner film with adhesive, applying the adhesive-coated liner film to the barrier film. A transfer coating method for the adhesive can enable separation of forming the adhesive coating and application to the barrier film. Therefore, should the adhesive require, for example, curing via heating or ultraviolet light exposure, any effect of the curing process on the barrier film can be avoided. Where a barrier film is used, the step of perforating the barrier film may further comprise perforating the adhesive and the liner film.

The adhesive-coated liner film may applied to the barrier film via application of heat and/or pressure. The adhesive-coated liner film may applied to the barrier film via a calendering process. This can enable reliable and effective application of the adhesive to the barrier film.

The adhesive may be cured in a curing process prior to application to the barrier film. As discussed above, curable adhesives may be advantageous by enabling differing properties for application and subsequent usage.

The perforation step can be combined with a step of cutting the protective film assembly into lengths of film assembly for storage and later application to the printed substrate. Combining the perforation and cutting steps into a single process provides a more efficient means for producing a protective film assembly.

The invention includes the combination of the aspects and preferred features described except where such a combination is clearly impermissible or expressly avoided.

Summary of the Figures

Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which: Figure 1 illustrates a schematic view of the protective film assembly as manufactured; Figure 2 illustrates a schematic view of the protective film assembly as applied to a substrate; Figure 3 illustrates a transfer process for applying an adhesive to the protective film assembly; and Figure 4 illustrates a manufacturing process for the protective film assembly.

Detailed Description of the Invention

Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art.

A protective film assembly 100 according to an embodiment of the present invention is as illustrated in Figure 1. The protective film assembly 100 comprises a barrier film 110, an adhesive 120, and a liner film 130. In some embodiments, the liner film 130 may be omitted, as described in greater detail below. The protective film 100 can be applied to a substrate 200 as illustrated in Figure 2. The substrate 200 may be a composite material such as carbon-fibre composite or glass-fibre composite. The substrate 200 may be a foam board such as a rigid foam board, for example PVC foam board or Foamex. Additionally or alternatively, the substrate 200 may be a substrate comprising printed matter 210 printed on the substrate. While Figure 2 illustrates that printed matter 210 (being a source of outgassed vapour) is printed on the substrate 200, this is not essential, as the substrate 200 may itself be a source of outgassed vapour (whether or not it is printed with printed matter 210).

To apply the protective film 100 to the substrate 200, the liner film 130 (if present) is peeled away and discarded, exposing the adhesive 120. The protective film 100 is then adhered to the substrate 200, covering the substrate 200 and providing protection against environmental degradation or damage for the substrate and/or for any printed matter 210 such as printed text or printed graphics which may be printed on the substrate 200. Examples of environmental damage include damage from moisture or contaminants such as dirt or dust, as well as UV damage.

The protective film assembly 100, as applied, is preferably optically transparent or substantially optically transparent, such that the substrate 200 and any printed matter 210 remain visible through the protective film assembly. For example, the barrier film 110 or preferably the protective film assembly 100 (i.e. the barrier film 110 and the adhesive 120) may have an optical transmittance (i.e. the proportion of light that is transmitted by the film or film assembly) of greater than 70%, preferably greater than 80%, more preferably greater than 90%. The transmittance may be uniform across the visible spectrum On other words, the barrier film 110 is colourless or has a neutral density tint) or may vary (such that the barrier film 110 is tinted or coloured). In embodiments where the protective film assembly 100 and/or the barrier film is tinted or coloured, or has a neutral density tint, the preferred transmittance may be less than 70%, more preferably less than 50%. In this context, the transmittance may be understood to refer to the average transmittance across an area of the protective film assembly 100 or barrier film 110. Furthermore, the protective film assembly 100 also preferably has a low level of haze (i.e. the proportion of light that is scattered by the film assembly). For example, the total haze of the barrier film 110 and the adhesive 120 (i.e. of the protective film assembly 100 as applied to a substrate 200) may be less than 15%, preferably less than 10%, more preferably less than 5%. Again, the haze in this context may be understood to refer to the average transmittance across an area of the protective film assembly 100 or barrier film 110. The optical transmittance and/or haze may be influenced, for example, by the choice of materials forming the barrier film 110 and the adhesive 120, the thickness of the barrier film 110 and the adhesive 120 and/or the presence or absence of refractive index mismatch between the barrier film 110 and the adhesive 120.

The barrier film 110 has a front surface 112 and a rear surface 114. The barrier film 110 is an optically transparent film, and the front surface 112 may be gloss or matt as required. The barrier film 110 is formed from an impermeable polymeric material. The barrier film 110 may be formed, for example, from PVC, such as monomeric PVC, polymeric PVC, or cast PVC, polypropylene (PP), polyethylene terephthalate (PET), polyethylene (PE), polyvinyl fluoride (PVF) or polyvinylidene fluoride (PVDF).

The barrier film 110 further comprises perforations 116 extending through the barrier film 110 from the rear surface 114 to the front surface 112. The perforations 116 are to enable outgassed vapour to pass through the barrier film 110. Vapour may arise, for example, from the substrate 200 and/or from the printed ink forming the printed features 210, either of which may be a source of outgassed vapour. The perforations 116 are illustrated as extending perpendicularly to the front surface 112 and rear surface 114 of the barrier film 110, but in some embodiments may have a uniform non-perpendicular orientation (i.e. each perforation 116 has the same non-perpendicular orientation within the barrier film 110), or may be randomly oriented through the barrier film 110 (i.e. each perforation 116 has a different orientation within the barrier film 110).

The perforations 116 are perforations in the barrier film 110, and are arranged across the substrate. The perforations 116 may be arranged randomly or in an irregular pattern, or arranged in a regular array such as a grid. The perforations 116 are formed by perforating the barrier film 110. The perforations 116 may be, for example, linear cuts extending along a width and/or length of the barrier film 110 or circular or square holes in the barrier film 110.

The perforations 116 can be formed using a perforating tool (not illustrated) which comprises an array of pins or blades for perforating the substrate. When perforating the barrier film 110, the perforating tool may be held at an elevated temperature, since this can assist in forming the perforations 116, and ensuring that the perforations 116 do not close after the perforating process is complete. The elevated temperature may be more than 40°C, preferably more than 60°C, more preferably more than 70°C, or 100°C. The elevated temperature may be less than 160°C, preferably less than 140°C, more preferably less than 130°C.

The perforations can be defined in terms of the area density (i.e. the average number of perforations per square metre of barrier film 110). For example, the perforations may be present at an area density of between 10000 and 500000 perforations per square metre, preferably between 300000 and 400000 perforations per square metre. A higher area density of perforations can enable vapour to pass more readily though the barrier film 110. Meanwhile, a lower density of perforations ensures that the perforations 116 do not impact the mechanical or physical resistance and durability, or the optical properties and aesthetic appearance of the protective film assembly 100. The area density or area density range of the perforations 116 may thus be selected to provide a desired characteristic in the protective film assembly 100.

For example, the area density of the perforations may be selected to maintain a sufficiently high transmittance and sufficiently low haze.

The perforations 116 may alternatively be defined in terms of the percentage surface area encompassed by the perforations. For example, each perforation may have an area of between 0.1 square millimetres and 1.2 square millimetres. Thus, at an area density of between 300000 and 400000 per square metre, the percentage of barrier film 110 that is perforated may be between around 4% and around 50%.

The perforations 116 may be defined in terms of the permeability of the resultant protective film assembly 100. In other words, the protective film assembly 100 may allow gas to pass through at a defined rate according to the differential pressure and the configuration of the perforations 116. For example, with one side of the barrier film held at a pressure of 300 kPa, and the other at atmospheric pressure (approximately 100 kPa), the flow rate of gas through a 1 square metre area of film is greater than 1 litre per minute, preferably greater than 2 litres per minute, more preferably 4 litres per minute. Higher flow rates can enable any vapour to pass through the protective film more readily.

The adhesive 120 is a layer of adhesive which can either be applied directly to the barrier film 110, or transferred to the barrier film 110 via a transfer process using the liner film 130. The adhesive 120 may be an adhesive coating (i.e. a coating of adhesive on the barrier film 110 or liner film 130), or may be a free-standing layer or film comprising an adhesive, such as a polymer film infused with adhesive. The adhesive 120 is used to adhere the barrier film 110 and protective film assembly 100 to the substrate 200. Providing the adhesive 120 on the protective film assembly 100 (i.e. making the protective film assembly 100 self-adhesive) allows the protective film assembly 100 to be more readily applied, since it is not necessary to apply adhesive to either the barrier film 110 or the substrate 200 at the point of application. The adhesive 120 may be, for example, an acrylic solvent-based adhesive, an acrylic water-based adhesive, a hot-melt adhesive, or an ultraviolet (UV) curable adhesive. The adhesive 120 may require curing after application to either the liner film 130 or the barrier film 110, and this may be, for example via heating or via UV exposure. An adhesive that is curable in this way may have different fluidic properties before and after curing, enabling, for example, simpler coating without sacrificing adhesive effectiveness.

The adhesive may be chosen, formulated, or configured to be chemically compatible with a particular substrate 200 material. For example, the adhesive may be formulated or configured for optimal adhesion to an impermeable substrate 200.

Additionally or alternatively, the adhesive may be formulated or configured for optimal adhesion to polymeric materials such as those commonly used as substrates for printing with printed matter, for example PVC.

Additionally or alternatively, the adhesive may be formulated or configured for optimal adhesion to a foam board, or to an applied printable surface thereof Additionally or alternatively, the adhesive may be formulated or configured for optimal adhesion to composite materials, including fibre composite materials such as glass-fibre or carbon-fibre.

The adhesive may be optimised for applying the protective film 100 to the substrate 200 at a particular temperature range. For example, the adhesive 120 may require a minimum surface temperature of the substrate 200 for application of greater than 5°C, preferably greater than 8°C. This can ensure the adhesive is sufficiently tacky or fluid to conform to and adhere to the substrate 200. Meanwhile, the adhesive 120 may require the substrate 200 to have a surface temperature of less than 35°C, preferably less than 30°C. This can avoid the adhesive 120 melting or detaching, as well as avoiding distortion arising from different thermal expansion properties between the barrier film 110, adhesive 120 and substrate 200.

The liner film 130 is a film used in transferring the adhesive to the barrier film 110, and in protecting the adhesive 120 prior to application to the substrate 200. The liner film 130 may be, for example a Glassline liner, clay coated Kraft (CCK) liner, PE coated liner (either single sided or double-sided coating), a PET liner, or a PE liner. The liner film 130 may have, for example, a surface coating on a face of the liner film 130 facing the adhesive, the surface coating being to ensure that the liner film 130 can be readily detached or peeled from the adhesive 120.

The transfer process for transferring the adhesive 120 to the barrier film 110 using the liner film is as follows, and as set out in Figure 3. First, a coating of adhesive, is applied to the liner film 130, for example by flood coating or bar coating (S301). Alternatively, a film comprising the adhesive may be applied to the liner film 130. If the adhesive is one which requires curing, the adhesive coated liner film 130 is next cured, for example by heating in an oven, using an infra-red (IR) curing lamp, or using a UV lamp (S302). Applying a curable adhesive to a liner film 130 rather than directly to the barrier film 110 may be advantageous, since it avoids any impact from the curing process on the barrier film 110. Finally, the adhesive coated liner film 130 is laminated via a calendering process onto the barrier film 110 (S303). A calendering process involves passing the adhesive coated liner film 130 and the barrier film 110 through one or more pairs of heated rollers to apply heat and/or pressure and to press the respective layers together, thus forming the protective film assembly 100.

The manufacturing process for producing the protective film assembly 100 is as outlined in Figure 4. The barrier film 110 is provided (S401). An adhesive 120 is applied to the barrier film (S402). This may be via the transfer process outlined in Figure 3, and thus step S402 may correspond to step 5303 of Figure 3. The protective film assembly 100 is next perforated to produce perforations in the barrier film 110 (S403). Finally, the protective film assembly 100, which may initially be manufactured as a long sheet, is cut into lengths of, for example 50 metres (S404). Other lengths may be used, as required by the end application of the protective film assembly. Steps S403 and S404 may be completed simultaneously, such that the protective film assembly 100 is both perforated and cut to size in a single process.

Steps S402 and S403 may be interchanged, such that the barrier film 110 is perforated before the adhesive 120 is applied. If a liner film 130 is used, it is removed and discarded prior to application to the substrate, and therefore it is not necessary to perforate the liner film 130.

Furthermore, unlike the barrier film 110, the adhesive 120 can be permeable to vapour, and therefore the adhesive may not need to be perforated. In addition, when the protective film assembly 100 is applied to the substrate 200, the adhesive 120 may be deformed such that any perforations present in the adhesive 120 are lost. Therefore, while the perforations 116 may extend through the barrier film 110, adhesive 120 and liner film 130, this is not necessary to realise the invention.

The perforations 116 can be formed in step 5403 using a perforating tool held at an elevated temperature. The elevated temperature may be more than 40°C, preferably more than 60°C, more preferably more than 80°C, or 100°C. The elevated temperature may be less than 160°C, preferably less than 140°C, more preferably less than 120°C. Perforations formed at an elevated temperature in this way are less liable to closure, and can therefore ensure more consistent performance of the protective film assembly 100 in enabling outgassing through the perforations 116.

To apply the protective film assembly 100 to a substrate, the liner film 130 (if present) is removed and the protective film assembly is placed or laminated onto the substrate 200, with the adhesive 120 facing the substrate 200. This can be a manual or an automated process.

Where the substrate is a substrate comprising printed matter, the protective film assembly 100 may be applied as part of a roll-to-roll printing process, such that the substrate 200 is both printed and has the protective film assembly 100 applied in a single process. Alternatively, the protective film assembly 100 may be applied to the substrate 200 immediately or shortly (e.g. less than 24, 12, 6, 3, or 1 hours) following printing. In either case, the perforations 116 enable residual solvent and ink vapour outgassed from the printed features 210 to pass through the protective film assembly, reducing or removing the need for a drying period. The substrate 200 may be an impermeable substrate, such as a polymeric substrate, for example, PVC film. The printed features or graphics 210 may be printed using water-based inks, solvent-based inks, or UV-curable inks. The substrate 200 may itself be a self-adhesive film, for application to a surface. For example, the substrate 200 may be used for indoor or outdoor signage on flat or slightly curved substrates.

Where the substrate 200 is a composite material substrate (e.g. a fibre composite material comprising fibres embedded in a resin matrix), the protective film assembly 100 may be applied during or shortly after the curing process of the resin component of the composite substrate. Where the substrate 200 is a foam board such as a rigid foam board including PVC foam board or Foamex, the protective film assembly 100 may be applied during or shortly after the forming or manufacturing of the foam board substrate. Alternatively, the protective film assembly 100 may be applied in an entirely separate process to the manufacturing process of the substrate 200.

The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

Throughout this specification, including the claims which follow, unless the context requires otherwise, the word "comprise" and "include", and variations such as "comprises", "comprising", and "including" will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

It must be noted that, as used in the specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent "about," it will be understood that the particular value forms another embodiment. The term "about" in relation to a numerical value is optional and means for example +/-10%.

Where the above description includes discussion of layers, coatings or films and their relative positions, this is understood to encompass both arrangements where the layers are directly adjacent to one another with no intervening or intermediate layer or element, and arrangements wherein there is at least one intermediate or intervening layer or element, coating or film is interposed between the described layers. Where the layers, coatings or films are described as being directly adjacent to one another this is understood to mean that there are no intermediate or intervening layers, elements, coatings or films interposed between the layers, coatings or films.

Claims

Claims: 1 A protective film assembly for protecting a substrate, the substrate and/or a printed matter deposited on the substrate being a source of outgassed vapour, the protective film assembly comprising: a barrier film having a rear surface facing, in use, towards the substrate, and a front surface opposite the rear surface; and an adhesive disposed on the rear surface of the barrier film, the adhesive being for adhering the protective film assembly to the substrate; wherein the barrier film comprises perforations through the barrier film for enabling vapour from the source of outgassed vapour to pass through the barrier film from the rear surface of the barrier film to the front surface of the barrier film.
2 A protective film assembly according to claim 1, wherein: a combined surface area of the perforations comprised in a unit area of barrier film is such that a flow rate of gas through a 1 metre square of protective film assembly at a differential pressure of 200 kPa across the assembly is greater than 2 litres per minute, preferably greater than 3 litres per minute.
3 A protective film assembly according to any preceding claim, wherein: the perforations are formed using a perforating tool heated to an temperature of greater than 70°C and, optionally, less than 130°C.
4 A protective film assembly according to any preceding claim, wherein: at least one perforation has an area of less than 1 square millimetre, preferably an area of less than 0.8 square millimetres, and more preferably an area of less than 0.65 square millimetres.
5. A protective film assembly according to any preceding claim, wherein: the perforations have an area density of between 50000 and 500000 perforations per square metre, preferably between 300000 and 400000 perforations per square metre.
6. A protective film assembly according to any preceding claim, wherein: the perforations are uniformly distributed in the barrier film.
7. A protective film assembly according to any preceding claim, wherein: the perforations extend through the barrier film and the adhesive.
8. A protective film assembly according to any preceding claim, further comprising: a detachable liner film adhered to the adhesive.
9. A protective film assembly according to claim 10, wherein: the perforations extend through the adhesive, the barrier film, and the liner film.
10. A protective film assembly according to any preceding claim, wherein: the adhesive is for adhering the protective film assembly to an impermeable substrate.
11. A protective film assembly according to any preceding claim, wherein: the adhesive is not suitable for adhering the protective film assembly to a permeable substrate.
12. A protective film assembly according to any preceding claim, wherein: the adhesive is a thermally curable adhesive or a UV-curable adhesive.
13. A kit of parts for a printed article, comprising: a protective film assembly according to any preceding claim, and a substrate for printing with printed matter.
14. A method for producing a protective film assembly for protecting a substrate, the substrate and/or printed matter deposited on the substrate being a source of outgassed vapour, the method comprising: providing a barrier film having a rear surface facing, in use, towards the substrate and a front surface opposite the rear surface; applying an adhesive to the rear surface of the barrier film, and perforating the barrier film to produce perforations through the barrier film, the perforations through the barrier film being for enabling vapour from the source of outgassed vapour to pass through the barrier film from the rear surface of the barrier film to the front surface of the barrier film.
15. A method for producing a protective film assembly according to claim 14, wherein: the step of perforating the barrier film comprises perforating the barrier film with a perforating tool heated to a temperature of greater than 70°C and, optionally, less than 130°C.
16. A method for producing a protective film assembly according to any of claims 14 to 15, wherein: the perforations are produced with a combined surface area comprised in a unit area of barrier film such that a flow rate of gas through a 1 metre square of protective film assembly at a differential pressure of 200 kPa across the assembly is greater than 2 litres per minute, preferably greater than 3 litres per minute.
17. A method for producing a protective film assembly according to any of claims 14 to 16, wherein: the perforations are produced at an area density of between 50000 and 500000 perforations per square metre, preferably between 300000 and 400000 perforations per square metre.
18. A method for producing a protective film assembly according to any one of claims 14 to 17, wherein: the step of perforating the barrier film further comprises perforating the adhesive.
19. A method for producing a protective film assembly according to any one of claims 14 to 18, wherein the step of applying the adhesive to the barrier film is via a transfer coating process, comprising the steps of: coating a liner film with adhesive, applying the adhesive-coated liner film to the barrier film.
20. A method for producing a protective film assembly according to claim 19, wherein: the step of perforating the barrier film further comprises perforating the adhesive and the liner film.