FR2950981A1 - Flexible cut film for use in e.g. advertisement field, has face provided with transparent self-sticking adhesive layer containing pressure sensitive adhesive, and light emitting element or distributor diffracts/diffuses light through guide - Google Patents

Abstract

The film (1) has a face provided with a transparent self-sticking adhesive layer (2) containing a pressure sensitive adhesive whose refractive index is less than, equal to or greater than that of a material constituting an optical guide illuminated by a light source e.g. LED. The adhesive contains elements, molecules or atoms i.e. organic refractive resistance atoms, that are chemically related to elastomer i.e. styrene-butadiene elastomer. A light emitting element, a reflector, a distributor or a divider diffracts/diffuses light through the optical guide. The organic refractive resistance atoms contain chlorine, bromine, iodine, sulfur and its derivatives, phosphor and its derivatives, carbonated aromatic ring, mononuclear or polynuclear heterocyclic ring, nitrogen dioxide, nitrile or isocyanate groups, saturated or unsaturated groups and ethylenic or acetylenic groups.

Description

2950981 Self-adhesive film applied to guided optics.

The present invention consists in the definition of a flexible, cuttable adhesive film applicable to the extraction of light guided by an optical guide and particularly by a flat optical guide of polymethyl methacrylate or PMMA is known in the state of the art of stickers consisting of a flexible film having an S-coated side of a glue film called PSA (acronym meaning English pressure sensitive adhesive or adhesive pressure sensitive) having the characteristic of adhering to a support under the action of a pressure. The other side of the flexible film generally comprises a drawing or a graphic or a message intended to be seen. According to another usual method of use of these stickers, the film is colored, and undergone a cut in the form of lt) letters for example which are glued on a support itself opaque or transparent, which can be backlit by a box a fluorescent tubes, letters which can in particular form a sign. Also known in the state of the art are guided optical lighting devices which consist of a plate or sheet of transparent material fed by one or more of their slices by a light source, such as a light source. fluorescent lamp or electroluminescent diodes. These devices comprise an extractor or decoupler pattern of the light flowing in the guide making it perceptible for an outside observer. This pattern can be a diffusing particle, a prism, a mirror, a frosted, elevations of the guide, etc ... The existing devices, although abundantly described, td received a limited scope in the general public because of their cumbersome implementation and the absence until a recent period of powerful, brilliant, inexpensive and efficient linear light source. Today a potential user of this device is forced to print, form, mold a shape itself, on the guide or on an object that it will stick on the final guide by its own means. The recent availability of energy-efficient white light-emitting diodes poses the problem of their use as point sources in large flat structures. The lighting by the slice is a natural solution. It therefore appears the need to propose a product similar to the existing stickers 30 today in the field of the sign operated by backlight, but used in guided optics or lighting by the edge. It also appears the need to have the full range of light extracting patterns described in the literature and potentially discoverable, in a form ready for use, flexible and universal in its implementation using inexpensive tools if not already available 3 S at the distributors of these products. According to the invention, this means is obtained by depositing the light-extracting pattern on a flexible and cut-off film and by providing a simple means of optically gluing one side of this film onto a reflective or propagating surface of a plane optical guide, ensuring a good transfer of the guided light to the film according to the invention provided with its extractor. According to an important aspect of the invention, the refractive index of this film must be greater than or equal to or slightly less than that of the guide material. Several types of bonding can be made in the state of the art. The most immediate for those skilled in the art would be to use optical glues, widely available in liquid form and polymerizable Ultra Violet and apply over the entire surface of the guide carrying the film. This operation is however delicate, dirty because handling liquids Z 2950981 susceptible of burrs, requires a tool and a very specific and expensive environment to be conducted (rolls, presses, ultraviolet polymerization installation, etc ...). Moreover these glues are expensive because intended for applications in advanced optics in general (telecommunications). Another type of bonding can be obtained by depositing between the plane guide and the re-emitter film a solid or pasty adhesive film. This film can mainly be a hot melt (common technical term meaning hot glue) or a PSA. The hot melt requires for its implementation high temperatures (130 ° C for example) which are incompatible with the strength of the usual thermoplastic films used in signage. On the other hand, most of the PSA-type glue films available for the graphic industries have a refractive index significantly lower than that of the cheapest usable optical guides, glass or PMMA. According to an essential characteristic of the invention , the adhesive film present between the re-emitting film and the optical guide has a particular optical role: it allows the refraction of the guided light to the re-emitting film. It must therefore have a refractive index close to that of the guide or greater than this one. This constraint does not exist at all with the pressure-sensitive adhesive films used today in the fields of the signboard and the graphic industries: in these existing products, the adhesive film has an exclusive role of bonding, without any optical role. and possibly makes it possible to ensure a passage of light but in transmission, that is to say in a regime where the refractive index Zd of the film does not intervene significantly. The self-adhesive films developed to date have therefore never been developed taking into account the refractive index of the glue, and it turns out that the vast majority of available commercial PSA has a refractive index of 1.46 to 1.48 too low to be applied to the invention on a PMMA optical guide. It follows that there remains the need to offer bright designers and architects from all walks of life a simple, ready-to-use product that does not require research or development and allows the potential of the product to be used. Guided optics and LEDs for lighting and signage. The invention consists in selecting, among all the methods of bonding the re-emitter film on the optical guide, that of using a film of transparent PSA adhesive 3a or diffusive directly carried by the light-emitting film, and to confer a this PSA adhesive layer has a refractive index identical to or even greater than that of the material of the guide or in all cases less than this one. The present invention is therefore a flexible and cuttable film consisting of at least a first layer of one or more structural materials serving as a support for the other S elements, and at least a second layer of a transparent adhesive adhesive sensitive to the pressure or PSA deposited on one side of the film, characterized in that it is intended to be placed on the surface of an optical guide, in that the PSA has a refractive index of less than, equal to or greater than that of optical guide on which it must be placed, refractive index obtained by including in the molecule, macromolecule or formulation of PSA a 4 chemical ground said refractogenic, and in that the film contains contains, or supports on one of its faces , a reflector, reflector, distributor, divider, diffractive or diffusing element, or more generally a decoupler element, with respect to the light led by the optical guide. In particular, when the optical guide consists of PMMA, the PSA will preferably have a refractive index greater than 1.48. According to another aspect of the invention, this flexible and cutable film, characterized in that it is intended to be placed on the surface of an optical guide, will also be characterized in that it is applied to the field of signage, museography, signage and advertising. It should be noted that often the adhesive films intended for the sign and the signage have a layer of PSA that is alveolate or has withdrawals. These withdrawals are not in contact with the support and are therefore to be avoided for the application envisaged here because they prevent the guided light from penetrating to the reason of decoupling. Thus, according to one characteristic of the invention, the adhesive film must be designed to ensure controlled optical contact over the entire surface of the guide with which it is in contact. In particular the face of the adhesive layer intended to be in contact with the optical guide may be flat and smooth. The invention also consists in a particular film using this technique, and comprising in its structure a discontinuous refractive index layer for starting, dividing, attenuating and sieving the light flowing in the guide towards a structure to be illuminated. a more detailed description of this structure in the French patent FR2694069 of the same inventor, in particular, that film according to this latter variant is characterized in that it comprises a transparent structural film having a refractive index greater than 1.48, a first layer of transparent PSA and refractive index greater than 1.48 carried on the side of one side of the film, a second layer of transparent PSA and refractive index greater than 1.48 disposed on the side of the face of the film according to the invention opposite to the one carrying the first layer of q PSA, and a transparent film with a low refractive index, index lower than that of the material of structure of the film and that of the first and second PSA layers, low-index transparent film having discontinuities and interposed in the film according to the invention between the two layers of PSA first and second. On the other hand, this low refractive index layer may consist of a layer of air. Z. v In case the PSA layer can be discontinuous and constitute the discontinuities of the low refractive index layer. Without departing from the scope of the invention, this latter variant can also be produced in the form of a PSA adhesive film having a low refractive index, less than that of the guide, and having areas or discontinuities of higher refractive index or equal to that of the 2 S optical guide. It was noted in the previous discussion that the support films of the light extractor pattern and the PSA film should have a refractive index near or above that of the optical guide material. The most common material for making this guide is PMMA whose refractive index is close to 1.495. It is also possible to use glasses whose refractive index is higher (1.52 for example) but which are of a more confidential diffusion. According to a preferred embodiment of the invention, the optical waveguide will be considered to be made of PMMA. The invention also consists in selecting or synthesizing the materials of the self-adhesive film 3 S of PSA and that of the film carrying the light-repeater pattern. With regard to the film carrying the repeater pattern, commercially available films of PMMA, PVC (polyvinyl chloride), polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, teflon, etc ... According to the invention, the The film carrying the light repeater pattern will have a refractive index greater than 1.48, so as to be usable on a PMMA optical guide and will consist for example of PMMA, PVC, polyethylene terephthalate, or polycarbonate . According to the invention, the PSA film applied to the film carrying the light-repeater pattern will be transparent and have a refractive index greater than 1.48, and more preferably greater than 1.495. The known PSAs are based on a formulation comprising at least one elastomer, and optionally additives such as tack or contact agents, in addition to any pigments, plasticizers, waxes, oils, and other additives. The elastomer represents the majority proportion of the mixture, and will therefore be an important component for the final refractive index of PSA.

The main elastomers used in current products are butadiene styrene elastomers, butyl, silicones, nitriles, natural rubber and acrylic. About half of the market is based on natural rubber, the rest being essentially based on acrylics. However, these two materials in their current qualities have a refractive index too low of the order of 1.46 to 1.47 for the natural rubber and will constitute a reflective layer by total reflection of a significant fraction of the rays flowing in the guide, which n ' will not reach the reemitting layer. The PSAs that can be used for the product according to the invention will therefore have to be different from the films and qualities commonly used in their field of application and will require a choice, or a particular formulation or synthesis. According to one embodiment of the invention, the PSA comprises in its molecular structure or its formulation chemical units inducing an increase in its refractive index, or say refractogenic in this memory. These can be heavy halogens, Cl, Br, I, sulfur atoms, mono or polynuclear aromatic 1 S rings, nitro substituents (NO 2), compact ring structures such as norbornyl, and any other known and understood substituents. in the state of the art as having a positive effect on the refractive index of a molecule and causing its increase. In particular, PSA derived from styrene-butadiene rubbers which exist today can be used. Acrylic elastomers containing monomers with a high refractive index can be used, such as chloroalkyl, bromoalkyl, iodoalkyl acrylates or methacrylates, phenyl acrylates or methacrylates, alkyl phenyls, naphthyls, alkylnaphthyls, chloro, bromo, iodophenyl monosubstituted or polysubstituted, chloro, bromo, iodo naphthyl 2 S monosubstituted or polysubstituted, mono or polysubstituted nitro phenyl, mono- or polysubstituted nitro naphthyl. It is possible to use norbornyl acrylate or methacrylates. It is possible to use acrylic or methacrylic monomers containing sulfur or phosphorus atoms, such as sulfur contained in thiol substituents, thioethers, disulfides, polysulfides, thiocarboxylic acid or their esters or their salts, sulphonic acids and their esters and salts, etc. Monomers containing ethylenic or acetylenic unsaturations or more complex heteroatomic groups such as isocyanates may be used. The methyl methacrylate content of the acrylic elastomers can be increased. According to another embodiment of the invention, the content of oxygen and nitrogen atoms in the elastomers can be increased, for example by multiplying and increasing the number and the proportion in the elastomer of carboxylic functions, ester , ether, alcohol, or mono, di tri or tetrasubstituted amine functions, or amide, imide, nitrile functions. The atoms mentioned can be contained in aromatic heteroatomic rings or not. The elastomers used as PSA base may contain carboxylic functions salified by light or heavy metals (sodium, etc.). 4p It is possible to use vinyl elastomers comprising chlorine, bromine, iodine substituents, mono or polynuclear aromatic nuclei, nitro substituents (NO 2), compact cyclic structures such as norbornyl, etc. The polymerization can be carried out on acrylic, methacrylic, vinyl, styrenic, ethylenic monomers, or a mixture thereof, so as to obtain elastomeric copolymers at room temperature. The PSA elastomers according to the invention can be obtained by radical polymerization, ionic polymerization or polycondensation starting from monomers chosen so as to confer on the final molecule a sufficiently high refractive index. It goes without saying that this list is not As a guide, other monomers or S o structures with high refractive index can be created without departing from the scope of the invention. Alternatively or jointly, the refractive index of PSA can be doped using a high refractive index contact or tack additive or agent comprising in its molecules, for example aromatic rings, heavy halogens, or any group mentioned above, or an additive such as an oil of high refractive index, such as an aromatic oil for example.

The nature and the field of application of the invention will emerge more clearly from the following diagrams.

FIG. 1 represents a sectional view of a device resulting from the application of a film according to the invention to an optical guide 3 illuminated on its edge by a light source 10. This light source can be for example a fluorescent tube, a light-emitting diode, an arc lamp, an incandescent lamp, etc ... The light flowing in the guide by total reflection at its walls meets the high index PSA film 2 deposited against one of the faces delimiting the plane guide, substantially extended face and parallel to the guided light rays, totally reflective face vis-à-vis the guided light in the absence of superficial deposit and so-called reflective or propagative, and allowing optical contact with a transparent carrier film index high 1. The guided light is refracted and transmitted through the PSA layer 2, and enters the film 1 support of the light emitter or decoupler pattern 11. In this case the film 1 is transparent and the decoupler pattern 11 comprises a surface substantially perpendicular to the rays flowing in the guide, and reached by them, surface which allows their decoupling to the medium 5 'surrounding the guide, for example air and which allows to illuminate a surface 5 so as to make it more visible for an observer O located in this case on the other side of the guide. Note that the device described in Figure 1 is part of so-called front lighting devices that allow to illuminate any object on its front so as to avoid loss of lights due to a backlight. The decoupler 2. S 11 may be for example a transverse strip of material substantially perpendicular to the direction of propagation of the light in the guide, or a pad of transparent material, of high refractive index, preferably higher than the refractive index of the guide 3.

FIG. 2 represents a sectional view of a device having the same function as the device described in FIG. 1, but different in that the decoupler units 12 consist of inclined prisms made of transparent material whose refractive index is greater than the material of the guide 3 These prisms may be contiguous at their base, or spaced apart by non-decoupling flat portions vis-à-vis the guided light.

FIG. 3 represents a device resulting from the application of a film according to the invention to an illuminated optical guide 3 on its wafer, characterized in that the decoupler pattern 13 is this time made up of reflecting mirrors allowing the reflection of light. guided towards the opposite face of the light guide 3 to that carrying the pattern 13, to an object 5 and an observer O or to an observer O ', etc. .... The reflection may be metallic or total. In this way it is possible to colimate the beam circulating in the guide in the form of a plane wave normal to 40 and large in size. It is possible to impose on the mirror 13 a shape making it possible to obtain a large beam having defined characteristics of emission in spatial directions and in intensity so as to increase its visibility in a given direction (emission in a restricted solid angle) or to improve the energy performance of a lighting module (applications in the flat screen, road signs, etc ...). FIG. 4 represents a device resulting from the application of a film according to the invention to an illuminated optical guide 3 on its wafer, characterized in that the decoupler unit 14 consists of a thickness of diffusing material allowing the extraction of the light flow guided by the guide 3 to an object 5 and an observer O. It is thus possible to obtain homogeneous and economic planar sources for transforming the point light of a light-emitting diode into a flat source with good performance.The applications are located in the sign, signage, lighting (inexpensive light wall and original lights), etc ....

FIG. 5 represents a device resulting from the application of a film according to the invention to an illuminated optical guide 3 on its wafer, characterized in that the decoupler pattern 15 consists of a thickness of a diffusing element enabling an illumination on both sides of the device.

Figure 6 shows a structure constituting a second aspect of the invention. The figure represents a device resulting from the application of a film according to the invention to an illuminated optical guide 3 on its edge, characterized in that a transparent film is interposed between the object or structure to be illuminated and the guide. The light penetrating into the film 1 at grazing incidence is reflected by total reflection on the layer 16 and returns to the guide 3, while the light penetrating into the film 1 grazing incidence. is refracted and transmitted by discontinuities 16 'of the low index layer. These discontinuities provide optical contact with, in this example, a second upper adhesive layer 2 'of sufficiently high refractive index. This light transmitted in 2 'through 16' can thus fulfill its function which is to illuminate any decoupling pattern 6, which may be of the type described above for example, or a drawing, image, pasted photograph. on the layer 2 '. It will be noted that the low refractive index layer 16, and its discontinuities 16 'are totally invisible for an observer O, and that the object 6 is absolutely visible through this layer (16). It will be noted that the discontinuities 16 'can be filled by the PSA adhesive film 2, 2'.

FIG. 7 shows in plan the same device as that represented for example in FIGS. 1 and 6. Parallelepipedic decoupler units or discontinuities of a layer with a low fraction index are represented distributed on the surface of the film 1 on a regular basis and uniform. These patterns 8 are preferably made of very small size, from 1 to 500 μm in length, for example, and brought together so as to obtain a continuous illumination effect for a human observer. Coverage ranges of the film 1 by these patterns are possible to extend the versatility of these devices on the basis of several film qualities working on different guide length ranges 3.

FIG. 8 represents an exemplary self-adhesive film according to the invention, derived from the application example presented in FIG. 6. The film comprises successively: a layer 2 of PSA according to the invention deposited on one of the faces of a discontinuous refractive index layer 16, 16 ', the layer 16/16' itself deposited on one side of a film 6 of sufficiently high refractive index fulfilling the structural role of film 1 of the previous examples and the film 6 which may contain or support or be intended to support any repeater, reflector, splitter, divider, diffracting or (as shown in the figure) diffusing pattern. The outer face of the PSA film 2 is protected by a tear-off protective sheet 9 without damage to the underlying structure. The film 6 may be a tinted film containing a diffusing pigment (17) illuminated in the areas 16 'by the incident light guided at 16', and visible from day to night. It can be easily cut exactly like the well-known teacher films in this field of the art, and made uniformly illuminated wafer-lit signs by the sieving of discontinuities 16 'vis-à-vis the guided light . It can also be transparent, so as to give the user complete freedom to deposit what he wants, such as a painting that will appear naturally bright without a visible source of light, thus creating a new graphic support for artists.

FIG. 9 illustrates one of the possibilities described in FIG. 8. A film carrying a layer 6 made of a tinted and pigmented material is cut into the form of letters 4 bonded by the PSA film on one side of a PMMA plate 3 illuminated on its slice by electroluminescent diodes 7. The lettering is illuminated uniformly and visible day and night.

FIG. 10 represents an exemplary self-adhesive film according to the invention, derived from the application example presented in FIG. 6. The film comprises successively: a layer 2 of PSA according to the invention deposited on one of the faces of a transparent film 1 of sufficiently high refractive index, this film 1, a discontinuous low refractive index layer 16, 16 ', deposited on the other side of the film 1, then another layer of PSA 2' according to the invention deposited on the layer 16. The outer faces of the PSA films 2 and 2 'are protected by two protective sheets 9 and 9' removable without damage to the underlying structures for releasing the adhesive film 2 or 2 'that just before application while allowing easy transport, storage and prior manipulation of the product .This set is flexible, transparent and easily cut to any size to be applied to an optical guide for the desired application.

FIG. 11 represents another example of a self-adhesive film according to the invention, derived from the application example presented in FIG. 1. The film comprises successively: a layer 2 of PSA according to the invention deposited on one of the faces of a transparent film 1 with a sufficiently high refractive index 2, this film 1, light extracting patterns 11 deposited on this film 1 and forming a body with it consisting of transverse strips substantially perpendicular to the direction of propagation of the light in the guide 1 or parallelepipedic studs of refractive index transparent material at least equal to the refractive index of the film 1. In addition two protective layers 9 and 9 'without damage to the underlying structures can store , transport and handle the film easily before use.This set is flexible, transparent and easily cut to any size to be applied to an optical guide. ue in view the desired application.

For the production of the product described in FIG. 11, the following method may for example be used. A tear-off or delaminable film 9 'bears, on its inner face facing the film 1, recessed patterns constituting the preforms of the morphology of the final growths. of the film. These preforms are filled with a precursor liquid of the material constituting the protrusions 11 such as a molten polymer or an oligomer to be crosslinked. This film 9 'is applied to the face of the film 1 to carry the growths 11 by pressing without trapping air bubbles, such as by means of a roller exerting a sufficient pressure 4 to expel any excess liquid. In a next step the liquid is frozen under a solid state, either by cooling or by UV or thermal polymerization. During this step, the material of the protrusions 11 strongly adheres to the substrate film 1. The film 9 'can be torn off before use without compromising the integrity of the substrate 1 and the protuberances 11 to release the optical function of the device. The film 9 'may for example consist of a polyolefin.

1S v 2.

Claims (9)

Claims1- Flexible and cutable film consisting of at least a first layer (1), (6) of one or more structural materials for supporting the other elements, and at least a second layer (2) of an adhesive pressure-sensitive transparent sticker or t PSA deposited on one side of the flexible film, characterized in that it is intended to be placed on the surface of an optical guide, in that the PSA is transparent and has a refractive index less than, equal to or greater than that of the material constituting the optical guide, in that the PSA contains in its molecule, macromolecule, or formulation one or more elements, molecules or atoms said to be refractogenic, and in that the film 0 contains, or supports on one of its faces, a reflector element, reflector, splitter, divider, diffractant or diffusing vis-à-vis the light driven by the optical guide. 2-film according to claim 1 characterized in that the PSA film (2) contains in its molecule, macromolecule or formulation one or more elements, molecules or 1 S refractogenic atoms in an amount sufficient for its refractive index is not less than 1.495, refractive index of a PMMA guide, minus 1.48, desirable minimum refractive index of the PSA joining the decoupler pattern with a PMMA guide, to the refractive index of the guide on which it is to be in other words, such that the refractive index of the PSA film (2) is not more than 0.015 units less than the refractive index of the guide on which it is to be laid. 3- Film according to claim 1 characterized in that the PSA film (2) contains in its molecule, macromolecule, or formulation one or more elements, molecules or refractogenic atoms in an amount sufficient to cause the increase in its `LS index of refraction above 1.48. 4. Film according to claim 1 characterized in that the adhesive film has a means, which may be sufficient flatness, to ensure perfect optical contact with the entire surface of the guide with which it must be in contact 5. Film according to any one of claims 1 to 4 characterized in that it is 3 d applied to the field of the sign, the signage, museography or non-animated advertising. 6. Film according to any one of claims 1 to 5 characterized in that a refractogenic organic molecule causing the increase in the refractive index of PSA contains one or more functional groups selected from chlorine, bromine S, iodine, sulfur and its derivatives, phosphorus and its derivatives, mononuclear or polynuclear carbon or heterocyclic aromatic rings, NO2 groups, nitrile, isocyanate, compact saturated or unsaturated cyclic groups, ethylenic or acetylenic unsaturations. 7. Film according to claim 3 characterized in that a refractive index greater than 40 1.48 PSA is obtained by increasing the content of oxygen or nitrogen atoms of the elastomer constituting the PSA, so that the molecular ratio atoms of N + atoms of O) / atoms of C is greater than 3/4. 8. Film according to any one of claims 1 to 7 characterized in that the elements, molecules or atoms causing the increase in the refractive index of PS PSA are chemically related to the elastomer constituting the main component of the PSA, additives added thereto, or to the elastomer and to one or more of these additives. 9- Film according to claim 8 characterized in that the elastomer is a styrene-butadiene elastomer.- Film according to claim 1 characterized in that it is interposed between the retransmitter element, reflector, splitter, divider, diffracting or diffusing and guiding a transparent film (16) with a low refractive index, index lower than that of the guide (1) and the PSA layer (2), film (16) having discontinuities (16 ').