WO2014108392A1

WO2014108392A1 - Photoactive structure, process for manufacturing such a structure and illuminating system

Info

Publication number: WO2014108392A1
Application number: PCT/EP2014/050138
Authority: WO
Inventors: Amélie REVAUX
Original assignee: Commissariat à l'énergie atomique et aux énergies alternatives
Priority date: 2013-01-08
Filing date: 2014-01-07
Publication date: 2014-07-17
Also published as: FR3000783B1; FR3000783A1

Abstract

The invention relates to a photoactive structure (100) intended to receive light issued from a light source (200) and to emit light into a medium (300) of refractive index n₀. The structure (100) comprises a substrate (110) of refractive index n₁, the substrate (110) having at least one longitudinal first face (111) and a lateral side (113), and a photoactive layer (150) intended to react to the light emitted by the source by emitting light. The photoactive layer (150) has a refractive index n₂. The layer extends along the first face of the substrate (111), and the substrate comprises a receiving surface portion (115) intended to receive light issued from the light source in a direction substantially perpendicular to the surface portion (115), the surface portion (115) extending so as to make an acute angle α with the first face (111) respecting sin^-1(n₀/n₁) < α < sin^-1(n₂/n₁). The invention also relates to a process for manufacturing such a structure (100) and to an illuminating system.

Description

PHOTO-ACTIVE STRUCTURE, METHOD FOR MANUFACTURING SUCH STRUCTURE AND

LIGHTING SYSTEM

DESCRIPTION

TECHNICAL AREA

The invention relates to the field of lighting surfaces as used in urban advertising display and backlighting screens.

The development of lighting surfaces affects many areas including, for example, advertising displays in urban facilities, the backlighting of LCD screens, and decorative lighting panels.

Whatever the destination of such lighting surfaces, such surfaces must meet both constraints of compactness and homogeneity. It is to meet these two constraints that the photoactive structures have been developed.

The invention therefore relates more precisely to a photoactive structure, a method of manufacturing such a structure and a lighting system.

STATE OF THE PRIOR ART

The photoactive structures adapted to provide lighting surfaces are in particular known from the document US2011 / 0205727.

Such a structure is intended to receive light from at least one light source and to emit light in a medium such as air or a liquid crystal matrix. The photoactive structure comprises in particular:

a photoactive layer which is intended to emit light when subjected to light from the light source,

an at least partially transparent substrate, the substrate extending longitudinally with at least a first longitudinal face towards the middle and a lateral side by which it is intended to receive the light emitted by the a photo-active layer and a part of the light to which the photoactive layer is subjected, the substrate having a second face which is opposite to the first face of the substrate and which is adapted to reflect the light received by the lateral side,

a diffusion layer arranged on the first face of the substrate and which is adapted to diffuse the light in the medium when it is received on the first face of the substrate.

When such a structure is in place, the photoactive layer extends along the lateral side of the substrate. Thus, with a light source that is arranged so that the resulting light is transmitted in the substrate through the photoactive layer, the substrate receives both a portion of the light from the light source and that emitted by the photoactive layer in response to the light passing through it. This light which is both from the light source and the photoactive layer passes through the substrate and is reflected towards the first face by the second face. The diffusion layer then makes it possible to diffuse the light in the direction of the medium and to obtain a homogeneous radiation over the entire surface.

Nevertheless, if such a structure makes it possible to provide a homogeneous illumination surface, this with a reduced thickness, the light source or sources being offset on the lateral side, it has a number of disadvantages. Indeed, such a structure remains complex to manufacture with the need for a large number of elements, including a diffusion layer to obtain a uniform illumination. In addition, with such a structure, both the light from the light source and that emitted by the photoactive layer are transmitted into the medium. This can be problematic in the case where the light from the light source has a wavelength in the range of ultraviolet wavelengths, such light may be harmful to the people who would be subjected to it.

In addition, such a photoactive structure is necessarily opaque to the light emitted by the photoactive layer, the substrate necessarily having a first reflecting surface. Thus, it reduces the possibilities offered by such a structure when applied to lighting, the latter not providing a lighting surface at least partially transparent. STATEMENT OF THE INVENTION

The object of the invention is to remedy these drawbacks.

Thus, the object of the invention is to provide a photoactive structure having a reduced number of elements with respect to a photoactive structure of the prior art without this having a significant effect on the homogeneity of lighting along the surface of the structure.

The object of the invention is also to provide a photoactive structure which, unlike the photoactive structures of the prior art, may be at least partially transparent to the emission wavelength of the photoactive layer or to that of the light source.

The object of the invention is also to provide a photoactive structure adapted so that the light coming from a light source arranged to excite the structure is not transmitted in the medium with that coming from the structure itself. .

For this purpose, the invention relates to a photoactive structure intended to receive light from at least one light source and to emit light in a medium of refractive index n ₀ , said structure comprising:

an at least partially transparent refractive index substrate ni, the substrate extending longitudinally with at least a first longitudinal face towards the middle and a lateral side through which the substrate is intended to receive the light emitted by the source,

a photoactive layer designed to react with the light emitted by the light source while emitting light, the photoactive layer having an index of refraction n ₂ ,

the layer extending along the first face of the substrate, and the substrate having a receiving surface portion for receiving light from the light source in a direction substantially perpendicular to the receiving surface portion, the portion receiving surface forming an acute angle with the surface of the first face which respects the following inequalities:

Above is meant by at least partially transparent substrate that the material in which the substrate is formed is adapted so that at least a portion of the radiation from the light source passes through the substrate.

The refractive indices n ₀ , n ₁ and n ₂ above are the refractive indices of respectively the medium, the substrate and the photoactive layer at the wavelength of the light emitted by the light source.

It may be noted that in a configuration in which the medium is air, the refractive index n ₀ is necessarily lower than that of the substrate and that of the photoactive layer ru, n ₂ .

Such a structure does not require the development of a diffusion layer since the light is directly emitted towards the medium by the active layer which extends on one of the faces of the substrate. This therefore results in a simplified design compared to a structure of the prior art requiring a diffusion layer.

In addition, such a structure allows, when illuminated by a light source in a direction substantially perpendicular to the receiving surface portion, to obtain an excitation of the optimized photoactive layer. Indeed, with such a configuration, part of the light from the excitatory source can penetrate into the photoactive layer without undergoing reflection at the interface between the substrate and the photoactive layer while being reflected at the interface between the photoactive layer and the medium. The part of the light of the source thus reflected by the photo-active layer / medium interface, which has not yet excited the photoactive layer, remaining in the structure, can excite the photoactive layer. This therefore results in an improvement of the efficiency of the structure, since a significant part of the light from the light source and which is injected into the structure is likely to excite the photoactive layer. In addition, the light from the light source being totally reflected at the interface between the photoactive layer and the medium, it does not enter the medium. Thus, such a structure does not present any nuisance of use regardless of the wavelength of the light from the light source. In addition, with such a configuration the substrate does not require a second reflecting surface and the structure can therefore be at least partially transparent to both the light from the at least one light source and the light emitted by the photo layer. -active. Thus, without being disturbed by diffusion phenomena, if the substrate is transparent, radiation is able to pass through the substrate perpendicularly to its longitudinal axis while being little or no diffusion. This allows the photoactive structure to maintain transparency for a user who can thus, for example, see through the structure.

Preferably, the substrate is at least partially transparent to the light coming from the at least one light source and to that emitted by the photoactive layer, and advantageously completely transparent.

The acute angle may be slightly greater than ^sin_1 (η ₀ / ηι), the acute angle α preferably having a difference with sin ^_1 (η ₀ / ηι) less than 1 ° and even more preferably less than 0 5 °

An optimized excitation of the photoactive layer is obtained with such an angle and thus a better light emission efficiency in the direction of the medium.

The value of the refractive index n ₂ of the photoactive layer has a difference with that of the refractive index n ₀ of the medium which is less than or equal to 0.2 and preferentially less than or equal to 0.1.

Such a refractive index value of the photoactive layer enables the photoactive layer to present a cone for extracting the light emitted by the photoactive layer which is larger than that of a structure exhibiting a light. greater difference in refractive index with the medium. It may be noted that the photoactive layer, by such a refractive index, can be described as "low-index layer".

The photoactive layer may comprise a matrix in which photoluminescent charge molecules are distributed.

The charged molecules may comprise at least two types of charge molecules configured to emit each of the light at a wavelength different from that of the other type of charged molecules, said charged molecules being arranged on the surface so as to form a colored emission pattern.

Thus it is possible to form a photoactive structure with a predefined light emission pattern, such as that of an advertising poster.

The surface portion may extend the full width of the lateral side.

With such a surface portion it is possible to excite the photoactive layer over the entire width of the substrate and thus to obtain a light emission towards the medium which is improved.

The structure may comprise at least two receiving surface portions each extending on a different lateral side of the substrate.

The substrate may be glass or transparent polymer, such as polymethylmethacrylate or polyethylene terephthalate.

Polymethyl methacrylate and polyethylene terephthalate are better known by their respective acronym PMMA and PET.

The light source may include a light emitting diode and a light concentrator device adapted to redirect at least a portion of the radiation emitted by the diode in a direction substantially perpendicular to the receiving surface portion.

The invention also relates to a method of manufacturing a structure according to the invention comprising the steps of:

providing an at least partially transparent refractive index substrate ni, the substrate extending longitudinally with at least a first longitudinal face towards the middle and a lateral side by which it is intended to receive light emitted by the source ,

forming a photoactive layer designed to react with the light emitted by a light source, the photoactive layer having an index of refraction n ₂ ,

providing a receiving surface portion on the substrate for receiving the light from the light source in a direction substantially perpendicular to the receiving surface portion, the surface portion receiver receiving an acute angle a with the surface of the first face which respects the inequalities according to which ^sin_1 (η ₀ / ηι) <a <sin ¹ (n ₂ / ni).

Such a method allows the provision of a simplified structure vis-à-vis a structure of the prior art that requires a diffusion layer.

The step of forming the photoactive layer can be obtained by a printing method, for example of the inkjet type.

Such a method makes it possible to provide a photoactive layer having a light emission pattern, such as that of an advertising poster.

The invention also relates to a lighting system comprising at least one light source, and further comprising a structure according to the invention, the light source being adapted to emit radiation in a direction substantially perpendicular to the surface portion of the invention. reception towards this same portion of surface.

Such a lighting system makes it possible to provide a lighting surface that can be used in the field of advertising or screen backlighting which is simplified with respect to a lighting system of the prior art that includes a lighting system. photoactive structure ^'Moreover, the illumination system may also be transparent.

Such a light source allows the provision of a particularly compact lighting system while the light source has a high efficiency light emission. BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood on reading the description of exemplary embodiments, given purely by way of indication and in no way limiting, with reference to the appended drawings in which: FIG. 1 illustrates a side view of a structure according to the invention,

FIG. 2 illustrates a perspective view of the structure illustrated in FIG.

FIG. 3 illustrates the operating principle of a structure according to the invention,

FIG. 4 graphically illustrates a simulation of the variation of the emission of a structure according to the invention as a function of the index of the photoactive layer for different angles between a portion of the receiving surface and a face of the structure. these simulated variations are compared with a reference curve corresponding to a structure in which light injection occurs by the slice.

Identical, similar or equivalent parts of the different figures bear the same numerical references so as to facilitate the passage from one figure to another.

The different parts shown in the figures are not necessarily in a uniform scale, to make the figures more readable.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS FIGS. 1 and 2 illustrate, in side view and in perspective view, a lighting system 1 comprising a photo-active structure 100 according to the invention and a light source 200, said system being adapted to emit light, called the emitted light, into a medium 300 of refractive index n ₀ .

According to a particular application of the invention, the light source 200 is a light source that emits a so-called exciting light whose wavelength is comprised in the ultraviolet light and the structure 100 comprises a photoactive layer adapted to react with light whose wavelength is in the ultraviolet wavelength range. The refractive index values and the materials which are quoted below, when they concern the particular application, are given only as an indication and are therefore not limiting.

Such a structure 100 comprises:

an at least partially transparent substrate of refractive index r 1, the substrate 110 extending longitudinally with at least a first longitudinal face 111 in the direction of the medium 300 and a lateral side 113 through which it is intended to receive the emitted light by the light source 200,

a photo-active layer 150 intended to react with the exciting light, the photoactive layer has an index of refraction n ₂ .

The refractive indices n ₀ , n ₁ and n ₂ quoted above are at the wavelength of the exciting light. Thus, for the particular application, the refractive index values correspond to those for electromagnetic radiation whose wavelength is in the ultraviolet wavelength range. It may be noted that in the following, for the sake of simplification and the small difference in practice of the refractive indices in the ultraviolet wavelength range and in the visible wavelength range, it is not possible to no distinction will be made for the indexing of indices at the wavelength of the excitatory light and those at the wavelength at the emitted light.

The substrate 100 is in the form of a substantially flat panel. The substrate 100 comprises, in addition to the first face 111, a second face 112 which is opposite to the first face 111. The first and second faces are substantially rectangular, the substrate having a rectangular parallelepiped shape.

The substrate 100 extends longitudinally and has four lateral sides. The lateral side 113 through which the electromagnetic radiation is received, according to the possibility illustrated in FIG. 1, is a side along a width of the substrate 100.

The substrate 100 is made of a material at least partially, and preferably totally, transparent to the excitation light. For example, in the particular application, the substrate 100 may be made in a glass or in a polymethyl methacrylate, whose respective refractive indices are close to 1.5.

The lateral side 113 through which the substrate 100 receives the exciting light has a receiving surface portion 115. The surface portion 115 extends the entire length of the lateral side 113. The surface portion 115 defines a plane for receiving the exciting light which forms an acute angle with the first face of the substrate.

The acute angle a of the lateral portion respects the following inequalities:

^sin_1 (η ₀ / ηι) <a <sin ¹ (n ₂ / ni).

The photoactive layer 150 is a photoluminescent layer adapted to emit light by photoluminescence under excitation by the exciting light. The photoactive layer 150 can be, for example, a layer of a polymer, which is called a matrix, and at least one photoluminescent molecule or particle, which is said charged molecule.

According to this possibility of the invention, the matrix of the photoactive layer may be a polymer or a sol-gel such as, for example, silicon dioxide or titanium dioxide.

According to this same possibility, the charged molecules preferably have a maximum size which is less than the emission wavelength and even more preferably less than one-tenth of the emission wavelength, so as not to limit the transparency of the photoactive layer. Thus, the charged molecules may be, for example, phosphors selected from the group comprising quantum dots, organic dyes, lanthanide complexes, rare earth doped oxide or sulfide nanoparticles and metal particles. Thus, examples of such luminophores are described in the article by Penard et al. Published in 2012 in the scientific journal "Account on Chemical Research" No. 297 pages 680 to 688 and in the article by Dacanin et al. in 2012 in the journal Journal of Materials Engineering and Performance No. 21 on page 1511. According to an alternative possibility of the invention, the photoluminescent layer may itself be formed of a photoluminescent material such as a rare earth doped oxide or a luminescent polymer. Such materials have in particular been described by Rao et al. In an article published in 2011 in the scientific journal "Materials Chemistry and Physics" No. 129, pages 586 to 593.

According to the two possibilities explained above, it is possible to incorporate in the matrix elements making it possible to reduce the refractive index of the photoactive layer. Such elements may be nanoparticles of index different from the matrix or the photoluminescent material. For example, to obtain a low index, it is possible to introduce small porosity that does not disturb the transparency but that makes it possible to have a mean index of the intermediate layer between the substrate index and the index of the substrate. 'air. This possibility is particularly described in the work of Zhang et al. Published in 2011 in the scientific journal "Materials Chemistry and Physics" No. 129 pages 586 to 593, as well as in those of Gu and Al. Published in 2012 in the journal Journal of Solid State Chemistry, pages 36 to 44.

Thus, in the particular application, the matrix may be a transparent ultra-violet polymer with several charge molecules adapted to emit photoluminescence radiation covering the entire visible spectrum under the excitation of a light in the ultra-violet. . According to this possibility, with an adequate proportion and distribution of each of the charged molecules, the surface of the photoactive layer under illumination of the exciting light forms a lighting surface adapted to emit a white light. A structure 100, including such a surface, forms when it is in combination with a light source 200 the lighting system 1. According to this same possibility and with a suitable proportion and distribution of each of the molecules, the structure 100 can it may also emit a color other than that of white light, for example, that of a warm yellow light or a colder blue light.

According to another possibility of the particular application, the photoactive layer 150 may comprise at least three charged molecules emitting respectively in red, green and blue and whose distribution and proportion are varied along of the photoactive layer 150 to form a predefined color emission pattern, such as that of an advertising poster. In this way, when the photoactive layer 150 receives the exciting light, the photoactive layer returns, via the emitted light, the pattern. Such a possibility is compatible with a formation of the photoactive layer 150 by coating the substrate by a printing method such as, for example, ink jet printing.

The photoactive layer 150 has a refractive index n ₂ at the emission length, the difference in absolute value with the refractive index n ₀ of the medium is less than 0.2 and preferably less than 0.1.

Depending on the particular application, the medium being air, the photoactive layer has a refractive index of less than 1.2 and preferably less than 1.1.

Such a structure can be manufactured by means of a manufacturing method comprising the steps of:

- providing an at least partially transparent refractive index substrate ni, the substrate extending longitudinally with at least a first longitudinal face towards the middle and a lateral side by which it is intended to receive the light emitted by the source,

forming a photoactive layer for reacting with the light emitted by a light source, the photoactive layer having an index of refraction n ₂ ,

providing a receiving surface portion on the substrate for receiving the light from the light source in a direction substantially perpendicular to the receiving surface portion, the receiving surface portion extending to form a acute angle a with the surface of the first face which respects the inequalities according to which ^sin_1 (η ₀ / ηι) <a <sin ^_1 (n ₂ / ni).

The step of arranging the surface portion 115 may also, without departing from the scope of the invention, be carried out prior to the step of forming the photoactive layer 150. Thus, it is even envisaged that this development of the surface portion 115 will be carried out simultaneously with the supply of the substrate, the latter may be, for example, molded with a preformed surface portion 115.

The structure 100 is adapted to be illuminated at the side side 113 by the light source 200 with an exciting light which is substantially unidirectional. The exciter light illuminates the structure in a direction, called the excitation direction, which is substantially perpendicular to the surface portion 115.

Such a source 200 may be provided, for example, by a substantially punctual light emitter with respect to the structure, such as a light emitting diode, and a converging lens. According to this possibility, the diode is placed at the lens focal point so that the light emitted by the diode forms, after passing through the lens, a unidirectional radiation along the axis of the lens. Thus, with a placement of the lens facing the surface portion 115 so that its focal plane is substantially parallel to the surface portion 115, the emitted radiation is directed towards the receiving surface substantially perpendicular to the surface portion 115 According to this possibility, the lens forms a light concentrator device adapted to redirect at least a portion of the radiation emitted by the diode in a direction substantially perpendicular to the surface portion 115.

Of course, for a practical application of the invention, it is advantageous to provide a plurality of sources 200 distributed along the surface portion 115. According to a possible development of this practical application of the invention, with a surface portion 115 arranged on each side of the substrate, a plurality of sources 200 may be envisaged on the periphery of susbtrat 100.

Figure 3 illustrates the operating principle of a structure according to the invention. Thus, FIG. 3 schematically illustrates the trajectory of a luminous ray 50 of the exciting light after it has been emitted by the source 200.

The ray 50 being emitted in a direction substantially perpendicular to the surface portion 115 when it enters the substrate 110, is not deflected and therefore penetrates with a direction forming an angle ii with the first face 111 which is equal to 1 acute angle a. When the ray meets the interface between the substrate 110 and the photo-active layer 150, at least a portion of the ray 50 is transmitted in the photoactive layer 150 at an angle i ₂ relative to the face of the photoactive layer which is opposite to the first face 111.

Indeed, the beam forms with the substrate interface 110 / photocurrent layer 150 an angle ii equal to the acute angle a. ii is therefore smaller than sin ¹ (n ₂ / ni) and is therefore, according to the Snell-Descartes laws, at least partially transmitted in the photoactive layer in a direction forming an angle i ₂ equal to sin ¹ (n n ₂ xsin (ii)), that is, sin ^-1 (ηι / η ₂ χ5ΐη (α)). Thus according to this principle, for an angle α less than sin ¹ (n ₂ / nl), a portion of the exciting light, when it reaches the substrate interface 110 / photoactive layer 150, is transmitted in the photo layer. -active 110 and allows to excite the latter.

Moreover, the acute angle a being greater than ^sin_1 (η ₀ / ηι), the angle i _{2 itself} respects the inequality according to which i ₂ is greater than sin ¹ (n ₀ / n ₂ ). The ray 50 is thus totally reflected at the interface between the photoactive layer 150 and the medium 300. Thus, according to this principle, the part of the light transmitted in the photoactive layer 150 is reflected towards the substrate 110, without leaving the structure 100, and can excite the photoactive layer 150. Exciting light transmission towards the medium 300 is thus avoided and the excitation of the photoactive layer 150 is optimized.

It can also be noted, with regard to the light emitted by the photoactive layer 150, that the surface portion 115 allows effective light injection into the photoactive layer 150 by the lateral side 113 of the substrate 110 without constraint. vis-à-vis the refractive index n ₂ of the photoactive layer 150. It is therefore possible to use a photoactive layer 150 having an index of refraction n ₂ close to that of the medium. This makes it possible to increase the proportion of the radiation emitted by the photoactive layer 150 which is emitted towards the medium and does not remain trapped in the photoactive layer. Indeed, the extractive cone of the light emitted by the photoactive layer 150 is directly related to the difference in refractive index between the medium 300 and the photoactive layer 150. Thus, for example, in the particular application in which the medium 300 is air, the passage of a refractive index n ₂ of the photoactive layer 150 equal to 1.5 at an index of refraction n ₂ of 1.2 causes an increase of more than 80% of the extraction cone.

FIG. 4 graphically illustrates simulations that demonstrate the effect of the application of the principle of the invention on a structure 100. Thus, FIG. 4 illustrates the simulation of the variation of the emission of a structure 100 according to FIG. according to the refractive index n ₂ of the photoactive layer 150 for angles of 41 °, 42 ° and 45 ° between the surface portion 115 and the first face 111 of the substrate 110, these simulated variations being compared with a reference curve 401 corresponding to a structure 100 not having a receiving surface portion according to the invention and wherein the light injection takes place by the wafer by means of a light emitting diode. In these simulations, the refractive indices n ₀ and n ₁ are respectively fixed at 1 and 1.5, and the photoactive layer 150 has a thickness of 100 μιη.

For the reference curve 401, the emission increases significantly with the increase in the refractive index n ₂ of the photoactive layer. This increase can be mainly attributed to an improvement of the transmission of the excitatory light towards the photoactive layer, the exciter light remaining for the low refractive index layers trapped in the substrate. Thus, with the increase of the refractive index n ₂ of the photoactive layer, the excitation of the latter is improved and the light emission towards the medium increases.

Regarding the curve 402, this corresponds to an angle between the receiving surface portion and the first face 111 of the substrate 110 equal to 41 °, the structure 100 has no significant emission. Indeed, such an angle a does not respect the inequality according to which a> ^sin_1 (η ₀ / ηι) and therefore the excitation light is totally reflected at the interface between the photoactive layer 150 and the substrate 110 without excitation significant of the photoactive layer 150. There is therefore no light emission by the photoactive layer 150 towards the medium 300.

The curve 403 corresponds to an angle between the receiving surface portion and the first face 111 of the substrate 110 equal to 42 ° which therefore respects the two inequalities according to which ^sin_1 (η ₀ / ηι) <α <sin ¹ (n ₂ / ni). It is thus observed that with such an injection portion the structure emits significantly more light than the structure having no receiving surface portion, regardless of the refractive index of the photoactive layer 150. Indeed, according to the principle of the invention, the majority of the exciting light injected by the surface portion 115 is transmitted in the photoactive layer 150 and thus makes it possible to excite the photoactive layer 150. It is also noted that the emission is more important for the low refractive indices n ₂ of the photoactive layer 150 which is related to an increase of the extraction cone towards the medium 300 of the light emitted by the photoactive layer 150.

The curve 404 corresponds to an angle between the receiving surface portion and the first face 111 of the substrate 110 equal to 45 ° which also respects the two inequalities according to the invention. Note that for such an angle, the emission of the structure remains significantly greater than that of the structure having no portion of the receiving surface. It can also be noted that the intensity is reduced with respect to the curve 403. Such a difference in intensity can be attributed to the fact that for the curve 403, the angle between the receiving surface portion and the first face 111 of the substrate 110 is slightly greater than sin ^_1 (η ₀ / ηι) and therefore a light injection in the photoactive layer 150 optimized.

Of course, if in the embodiment described above the substrate has a substantially flat shape, the substrate can extend in a curvilinear plane that does not significantly affect its waveguide function, this without sort of the scope of the invention.

Claims

A photo-active structure (100) for receiving light from at least one source (200) of light and emitting light in medium (300) of refractive index n ₀ , said structure ( 100) comprising:

an at least partially transparent refractive index substrate (110) ni, the substrate (110) extending longitudinally with at least a first longitudinal face (111) towards the middle (300) and a lateral side (113) whereby the substrate (110) is for receiving the light emitted by the source (200),

a photoactive layer (150) intended to react with the light emitted by the light source (200) while emitting light, the photoactive layer (150) having a refractive index n ₂ ,

The structure (100) being characterized in that the layer extends along the first face of the substrate (110),

and in that the substrate comprises a receiving surface portion (115) for receiving light from the light source (200) in a direction substantially perpendicular to the receiving surface portion (115), the surface portion Receiving (115) at an acute angle α with the surface of the first face (111) which respects the following inequalities:

2. Structure (100) according to claim 1, wherein the acute angle a is slightly greater than sin ^_1 (η ₀ / ηι), the acute angle a preferably having a difference with sin ^-1 (n ₀ / nl) less than 1 ° and even more preferably less than 0.5 °.

3. Structure (100) according to claim 1 or 2, wherein the value of the refractive index n ₂ of the photoactive layer (150) has a difference with that of the refractive index n ₀ of the medium ( 300) which is less than or equal to 0.2 and preferably less than or equal to 0.1.

4. Structure (100) according to any one of the preceding claims, wherein the photoactive layer (115) comprises a matrix in which are distributed photoluminescent charge molecules.

5. Structure (100) according to the preceding claim, wherein the charged molecules comprise at least two types of charged molecules configured to emit each of the light at a wavelength different from that of the other type of charged molecules, said charge molecules being arranged on the surface to form a colored emission pattern.

The structure (100) of any preceding claim, wherein the surface portion (115) extends the full width of the lateral side (113).

7. Structure (100) according to any one of the preceding claims, wherein the substrate (110) is glass or transparent polymer, such as polymethyl methacrylate or polyethylene terephthalate.

A method of manufacturing a structure (100) according to any one of the preceding claims comprising the steps of:

providing an at least partially transparent refractive index substrate (110) and the longitudinally extending substrate (110) having at least one longitudinal first face (111) toward the middle (300) and a lateral side ( 113) by which it is intended to receive the light emitted by the source (200),

forming a photoactive layer (150) for reacting with the light emitted by a source (200) of light, the photoactive layer (150) having an index of refraction n ₂ ,

providing a receiving surface portion (115) on the substrate (111) for receiving light from the light source (200) in a direction substantially perpendicular to the surface portion (115) of receiving, the receiving surface portion (115) forming an acute angle α with the surface of the first face (111) which respects the inequalities according to which ^sin_1 (η ₀ / ηι) ≤ a≤ sin ¹ (n ₂ / ni ).

9. The manufacturing method according to the preceding claim wherein the step of forming the photoactive layer (150) is obtained by a printing method, for example of the ink jet type.

10. Lighting system (1) comprising at least one source (200) of light characterized in that it further comprises a structure (100) according to any one of the preceding claims and in that the source (200) ) light is adapted to emit radiation in a direction substantially perpendicular to the receiving surface portion (115) towards the same surface portion (115).

11. Lighting system (1) according to the preceding claim wherein the source (200) of light comprises a light emitting diode and a light concentrator device adapted to redirect at least a portion of the radiation emitted by the diode in a substantially perpendicular direction to the receiving surface portion (115).