Diffusing material, luminous glazing and manufacturing process

Abstract

The invention relates to a diffusing material (110), the material (110) comprising a transparent and diffusing layer (10) having two main faces (1, 2). According to the invention, the layer (10) comprises at least one zone comprising microcavities (5) having an elongated shape having a largest dimension in a longitudinal direction and a small transverse dimension, the largest dimension being greater than 50 micrometers, the small dimension being between 0.5 micrometers and 130 micrometers, the microcavities (5) having in a plane of incidence a spatial distribution determined by a separation distance between microcavities, in which a first ratio is defined equal to the ratio between the largest dimension and the separation distance, said first ratio is above a determined lower threshold, the layer (10) being capable of extracting and diffusing a percentage of an internal light beam (30) propagating between the two main faces (1, 2).

Description

Title of the invention: Diffusing material, luminous glazing and manufacturing method Technical field

[0001] The present invention relates to the technical field of light-extracting diffusing materials for light-emitting devices, in particular light-emitting diodes.

[0002] More particularly, the invention relates to a diffusing material, a glazing incorporating the diffusing material and a laser treatment method for transforming a transparent layer into a diffusing, light-extracting layer. Prior art

[0003] In the field of lighting devices, it is known to manufacture optical waveguides, for example optical fibers, comprising microcavities included in the waveguide, so as to diffuse light transversely to the axis of the waveguide. The microcavities are manufactured by trapping gas bubbles during the manufacture of the waveguide. These microcavities have a spherical shape and a random distribution in the material.

[0004] There are also lighting devices comprising light-emitting diodes and glazing, the diodes being arranged facing an edge of the glazing to couple radiation emitted by the diodes inside the glazing. To extract the radiation from the glazing, surface-diffusing microstructures are known. However, these diffusing microstructures exhibit residual diffusion when the diodes are off, which impairs vision in transmission.

[0005] There is a need for a material which has excellent transparency along the normal to its surface and which is capable of extracting and diffusing radiation propagating inside the material.

[0006] There is also a need for a manufacturing process for such materials, which is reproducible and industrializable. Statement of the invention

[0007] The invention relates to a diffusing material, in particular a diffuse light extractor, the material comprising a diffusing layer having two main faces, the layer in particular having an (optical) refractive index n2, the layer being transparent (in a visible spectral range).

[0008] According to the invention, the layer comprises at least one zone comprising microcavities included between the two main faces of the layer, the microcavities having an elongated shape having a larger dimension in one direction longitudinal and a small dimension transverse to the largest dimension, the largest dimension being greater than 50 micrometers, the small dimension being between 0.5 micrometers and 130 micrometers, the longitudinal direction of the microcavities being parallel or inclined relative to a normal (Z) to a main face of the layer at an angle of at most 15° and better still at most 10° or 5°, the microcavities having in a plane of incidence, including the normal, on said zone a spatial distribution determined by a separation distance between microcavities, in which a first ratio (RI) being defined equal to the ratio between the largest dimension and the first separation distance (Sx), the first ratio is above a determined lower threshold, the material being capable of extracting and diffusing a determined percentage of diffusion x M of an internal light beam propagating between the two main faces in said plane of incidence,in particular at an internal angle of incidence greater than or equal to an angle of total internal reflection Otir, to form at least one diffused external beam coming from at least one of the two main faces. The lower threshold is preferably equal to: .■■■*#...... ,

[0009] Advantageously, the diffusion percentage xM is greater than or equal to 0.01, preferably greater than or equal to 0.1.

[0010] Preferably in the case of a layer with free main faces, the lower threshold may be equal to: / z «, \ 2 ~ XM\ V «7 ) " 1

[0011] where neither the (optical) refractive index of air.

[0012] According to a particular aspect, the layer has an external cut-off angle (in air) 0c determined in said plane of incidence, and in which the first ratio is below an upper threshold which is equal to: ! J where xm represents a y sin"0c WT percentage of diffusion by transmission, where ni is the refractive index of air, the layer being capable of diffusing a percentage less than xm of an external light beam incident on one of the two main faces with a first angle of incidence less than the determined external cut-off angle and the layer being capable of diffusing a percentage greater than xm of an external light beam incident on one of the two main faces with a second angle of incidence greater than the determined external cut-off angle.

[0013] The lower threshold is preferably greater than or equal to 0.1, 0.2, 0.3, 0.4, 0.5, 0.8, 0.9, 1.0, 1.1, 1.2.

[0014] Advantageously, the upper threshold is less than or equal to 100.

[0015] Advantageously, the microcavities have an angular distribution (distribution of angles relative to the normal) with a standard angle deviation of less than 10 degrees, and even at most 5 degrees or 2 degrees and / or with an angle value at the peak of the angular distribution of at most 15° and even at most 10° or 5°.

[0016] The microcavities are empty or filled with a gas, with a refractive index close to 1, lower than the refractive index n2 of the layer (in the core in the case of an index cladding).

[0017] In this text the expression “between” two values ​​includes these two values ​​or limits.

[0018] The spatial distribution of microcavities can be regular and even periodic or pseudo-periodic.

[0019] According to a particular aspect, the spatial distribution of the microcavities is arranged according to a one-dimensional or two-dimensional microcavity network.

[0020] In an exemplary embodiment, the one-dimensional microcavity network comprises lines parallel to the main face of the layer and for example parallel to a lateral or longitudinal edge of the layer or even oblique relative to these edges.

[0021] In an exemplary embodiment, the two-dimensional microcavity network comprises lines of microcavities and columns of microcavities parallel to the main face, the columns being perpendicular to the lines, the columns of microcavities being arranged with a second separation distance Sy between adjacent columns of microcavities (in another direction parallel to one of the two main faces), and a second ratio R2 is defined equal to the ratio between the largest dimension and the second separation distance between Sy between columns: R2 = L / Sy, the second ratio is above the determined lower threshold.

[0022] Advantageously, the microcavities have a separation distance (Sx, Sy) of between 20 micrometers and 1 millimeter along at least one direction parallel to the main face of the layer and possibly a second separation distance (Sy) is between 20 micrometers and 1 millimeter along another direction parallel to the main face of the layer, in particular normal to said first direction.

[0023] According to another particular aspect, the microcavities have an aspect ratio between the largest dimension and the smallest dimension greater than 1.5 or 5 and even at least 20, 50 or 100.

[0024] Advantageously, the microcavities are closed or alternatively form openings on the surface of at least one of the main faces (in particular the face F3 of a glass sheet forming the layer in the case of laminated glazing or the main face of an interlayer sheet oriented towards the face F3, interlayer sheet forming the layer).

[0025] According to another particular and advantageous aspect, the transparent layer comprises or is a sheet, a mineral glass, in particular clear or extra-clear, based on glass (silico)soda-lime, aluminosilicate or borosilicate, in particular a thermally toughened glass, or comprises or is a transparent polymer sheet in particular based on polymethyl methacrylate, polycarbonate, polyurethane, polyesters, in particular a lamination interlayer sheet (thermoplastic or crosslinked), the interlayer sheet preferably being based on polyvinyl butyral, a vinyl acetate-ethylene copolymer or thermoplastic polyurethane.

[0026] Advantageously, the material is or forms part of a glazing, monolithic or laminated, in particular vehicle or building glazing, possibly multiple glazing (double or triple glazing) and in particular the layer is a sheet of glass or polymer.

[0027] According to another particular and advantageous aspect, the layer has a high visual transparency. The layer (sheet) may have a blur value H less than or equal to 30%, 25%, or 20%, preferably less than 18%, 16%, 14%, 12% or 10% and / or a clarity value greater than or equal to 85%, 90% or even 95%.

[0028] Advantageously, one or more of the following characteristics can be provided:

[0029] - the microcavities comprise a sheath (of index), in particular of thickness between 5 and 50 pm, for example about 10 pm

[0030] - the thickness of the layer is uniform or varies

[0031] - the first ratio (RI = L / Sx) is included in a range determined by a threshold lower and an upper threshold. For example, the first ratio is equal to 0.1; 0.2; 0.3; 0.4; 0.5; 0.8; 0.9; 1.0 or 1.1; 1.2, and preferably between 0.1 and 0.7 or even between 0.1 and 0.3

[0032] - the first ratio (RI = L / Sx) is included in a first determined range and the second ratio (R2 = L / Sy) is included in a second determined range; The first threshold and the second threshold can be equal (when the steps P and Q are identical, or different.

[0033] - the first ratio, respectively the second ratio, is for example equal to 0.1; 0.2; 0.3; 0.4; 0.5; 0.8; 0.9; 1.0; 1.1 or 1.2, and preferably between 0.1 and 0.7, or between 0.1 and 0.3.

[0034] - the first separation distance Sx, respectively the second separation distance separation Sy, is between 20 pm and 1 mm, preferably between 50 pm and 500 pm, for example 100 pm, 150 pm or 200 pm,

[0035] -the layer (sheet) is planar, that is to say that the two main faces are flat and parallel or the two main faces are flat and form an angle or the two main faces extend along non-flat but parallel surfaces.

[0036] For example, in a vehicle application, one of the main faces is concave and the other main face is convex, the two main faces being locally parallel to each other.

[0037] Alternatively, the two main faces extend along non-planar and non-parallel surfaces.

[0038] Preferably, the material of the layer (sheet) is clear and better extra-clear to limit absorption. By clear material, respectively extra-clear, is meant a material which has a light transmission TL, under normal incidence for visible radiation between 400 nm and 700 nm, of 90.0%, respectively 90.9% for a thickness of 6 mm and / or a light transmission TL of 88.8%, respectively 90.4% for a thickness of 10 mm. In the present document, the light transmission is calculated from the transmission spectrum between 380 nm and 780 nm taking into account illuminant A and the CIE 1964 reference observer (10°).

[0039] The layer (sheet) may have a thickness of between 0.1 mm and 19 millimeters, and preferably between 0.5 mm and 6 mm. In applications of diffusing material for (road) vehicles, the thickness of the layer is generally between 1.6 mm and 2.1 mm. In applications of diffusing material for buildings, the thickness of the layer may be between 2 mm and 10 or 12 mm for facades or 2 mm and 6 mm for windows and partitions.

[0040] Preferably, the microcavities have an elongated shape in a longitudinal direction. The microcavities have in particular a symmetrical shape of revolution around their longitudinal direction, for example ellipsoidal or cylindrical with a circular section. L denotes the largest dimension of a microcavity in its longitudinal direction and T the small dimension in a direction transverse to the longitudinal direction. The small dimension T is also called the diameter of the microcavity. The small dimension T is measured along a section of the microcavity, for example at mid-height of the largest dimension L. In other words, the largest dimension L is the length taken in a longitudinal section and the small dimension T is the width taken in a transverse section or the diameter of a circular section.

[0041] Advantageously, the small internal dimension T is less than 10 microns, and generally between 0.5 μm and 10 microns, generally greater than 1 μm, and preferably greater than 5 μm. The largest dimension L is generally between 50 μm and 12 mm. The microcavities 5 have an aspect ratio RA = L / T, defined as being the ratio between the largest dimension L and the small dimension T. According to one aspect of the present disclosure, the aspect ratio of a microcavity is above a lower threshold. According to one aspect of the invention, the aspect ratio of a microcavity (of the majority or even at least 80% or 90% or 100% of the microcavities) is preferably greater than 1.5, or 2, or 5, or 7 and in particular less than 20, or 15 or 10 (in particular by a Gaussian beam) and even at least 20, 50 or 100 (in particular by a Bessel beam which allows larger aspect ratios).

[0042] According to another aspect of the present disclosure, the aspect ratio of a microcavity is below an upper threshold. The aspect ratio of a microcavity may be within a range determined by the lower threshold and the upper threshold.

[0043] Advantageously, the microcavities are closed and have homogeneous dimensions, i.e. they preferably have the same largest dimension L ± 30% and the same small dimension T ± 30%.

[0044] In the case of microcavities comprising a cladding, the largest dimension of a microcavity is the largest external dimension of the cladding and the small dimension is the external dimension or diameter of the cladding perpendicular to the largest dimension. In this case, the small dimension may be between approximately 10 μm and 130 microns, preferably less than 50 microns, for example between 20 μm and 40 μm. And / or the largest dimension may be greater than or equal to 60 μm, and even between 60 μm and a few millimeters. The ranges of values ​​for the aspect ratio RA indicated above remain valid for microcavity structures 5 with an index cladding. An aspect ratio of, for example, 1.9; 2.2; 2.3; 2.7; 2.9 or even 3.0 is obtained. Alternatively, a thermal annealing process is applied after the laser treatment, so as to homogenize the properties of the layer around the microcavities.In this case, no sheath with a refractive index different from that of the layer around the core of the microcavities is detected. The presence of a sheath around the core of the microcavities can be measured, for example by optical microscope or by phase contrast imaging.

[0045] The area (treated by laser) covers at least 50%, 60%, 70%, 80%, and even at least 90%, 95%, 99% of the surface of the layer, in particular extending over the entire surface. In one embodiment, the area (treated by laser) extends over a limited part (and in particular of predetermined shape) of the surface of the layer. For example, the surface of the area extends over a surface of geometric shape or in the form of a pictogram, number, letter, logo or drawing or any other shape (adapted to the desired application). The surface of the area can range from 1 mm2 to 18 m2 depending on the applications, generally approximately 1.5 m2 for a window or automotive glazing, and approximately 3-5 m2 for a glazed partition.

[0046] The spatial distribution of the microcavities can have a variable density along a direction (parallel to one of the main faces) for example to allow homogeneous diffusion of light.

[0047] The material may be or form part of a glazing, monolithic or laminated, in particular vehicle or building glazing, possibly multiple glazing (double or triple glazing) and in particular the layer is a sheet of glass or polymer. The material may be a laminated glazing with a first sheet of clear glass, an interlayer of lamination (PVB or EVA), a second of clear and even extra-clear glass forming the diffusing layer.

[0048] The invention relates to a light extractor device. Also preferably a light source, in particular diodes (one or more diode strips), is arranged to generate and inject the internal light beam into the layer.

[0049] The light source can be removable, added, sold separately or in a kit. The light source is preferably a set of light-emitting diodes (on a printed circuit support such as a PCB for "printed circuit board" in English, for example flexible), in particular a straight or curved strip. Preferably, the diodes are surface-mounted components on the front face of a printed circuit board called a PCB board (with conductive tracks). The width (or length) of a diode with a single semiconductor chip, generally a square-shaped diode, is preferably at most 5mm. The width of the PCB board, in strip form, is preferably at most 5cm, better still at most 2cm, and even at most 1cm.

[0050] One or more light sources (peripheral, preferably offset by a window clear), several sets of diodes can be. The light source(s) can be mono- (emitting in blue, green, red, etc.) or polychromatic, or can be adapted or combined to produce for example white light, etc.; they can be continuous or discontinuous, etc. The light source can be extended linearly (rectangular strip like a bar of diodes) along one side of the glass or polymer sheet forming the layer (longitudinal edges) or split (with similar or distinct light for example other color intensity, controlled independently or simultaneously) along both sides.

[0051] The invention relates in particular to a luminous glazing comprising a light extracting device. Also the invention relates to said material forming a luminous glazing of a vehicle, in particular road (automobile, transport, truck, bus), rail (train, tram) or air, such as a side glazing, in particular laminated (including quarter window), a rear glazing (or window), a roof, in particular laminated, a windshield, in particular laminated, or a building glazing, in particular a facade glazing, in particular a window, a partition, a glass door.

[0052] The invention relates in particular to said material forming a luminous glazing (building, vehicle) comprising a first glass sheet, a lamination interlayer, a second transparent sheet of mineral or polymer glass, and the second glass sheet being said diffusing layer of refractive index n2, in particular a sheet facing the interior of a building or a (vehicle) passenger compartment.

[0053] The invention relates in particular to a luminous glazing material comprising a first sheet of glass (in particular tinted or clear with a solar control layer), in particular with main faces F1 and F2, an interlayer lamination which is said diffusing layer of refractive index n2, a second transparent sheet of mineral or polymer glass, in particular with main faces F3 and F4, and comprising an optical isolating element, between the first sheet and the interlayer lamination, of refractive index n3 less than n2. The interlayer lamination is preferably in contact with the internal face F3 of the second sheet of glass.

[0054] The invention relates in particular to said material forming luminous glazing for a road vehicle comprising a first sheet of glass (in particular tinted or clear with a solar control layer), one or more interlayer lamination layers, a second transparent sheet of mineral or polymer glass, in particular clear or extra-clear, and the diffusing layer is in particular the second sheet facing the passenger compartment when the glazing is a roof, or even side glazing or a windshield.

[0055] In one embodiment, the material is a laminated luminous glazing (in particular a road vehicle roof) which comprises a light source, preferably a set of light-emitting diodes, which is optically coupled with the second sheet of preferably mineral glass, - thus forming an optical guide - being said diffusing layer:

[0056] - by a light redirection element, -local-, light redirection element reflector and third main face side F3 or transparent light redirection element fourth main face side F4, in particular facing an internal peripheral masking layer on the first sheet (enamel, black etc.).

[0057] - by all or part of the slice of the second sheet,

[0058] - or by a wall of a hole (through in thickness, closed) of the second sheet (or several walls of several holes), in particular a hole offset from a clear window, facing a peripheral internal masking layer on the first sheet (enamel, black etc.).

[0059] In the case of light injection through the second edge, the light source is coupled to the edge of the second sheet, possibly in a peripheral opening notch. The light source may be housed in a polymer encapsulation as described in application WO2010049638, in particular in FIG. 15 or in FIG. 16, and even having a recess for removal or replacement of the source.

[0060] In the case of light injection via an internal wall of a hole, the second sheet, in particular made of mineral glass, comprises at least one peripheral hole (through or even blind in thickness, open on the fourth face F4 side at least) under an internal masking layer (outside the clear glass) and the light source is coupled to the wall of the second sheet delimiting the hole, preferably housed in the hole. The light source, in particular the diodes, may be in the hole. Examples of embodiments described in patents WO2018 / 178591 or WO2013 / 110885 may be cited in particular.

[0061] In the case of light injection by moving the light source to the passenger compartment side, preferably the peripheral (prismatic) light redirection element is:

[0062] -reflector and third face side F3 or transparent fourth main face side F4.

[0063] The light source is then opposite or offset from the fourth main face, in particular direct optical coupling or via an optic, in particular light source and light redirection element offset by a window clear, facing an internal masking layer.

[0064] The laminated luminous glazing may incorporate one or more functional elements (non-adhesive) above the second sheet of glass forming the diffusing layer or the interlayer forming the diffusing layer in particular:

[0065] - electronic device (more or less extensive) chosen from at least one of the following devices: sensors; electrically controllable device with variable tint (electrochromic) and / or variable diffusion (liquid crystal based), a photovoltaic device, in particular with one or more connected photovoltaic cells (in one or more lines),

[0066] - functional polymer film, for example infrared reflective film (control solar, silver stacking, replacing a layer on the F2 face), and / or heating for example polymer substrate with an electroconductive coating (transparent), in particular with a thickness of at most 0.4 or 0.2 mm, in particular local or preferably extending over almost the entire glazing (and over the entire clear glass), with the electroconductive coating on the F2 face or F3 face

[0067] Examples of electrically controllable devices are PDLC functional elements (PDLC = Polymer Dispersed Liquid Crystal), known for example from DE102008026339A1 or SPD functional elements (SPD = Suspended Particle Device), known for example from EP0876608B1 and WO2011033313A1. There are also electrochromic functional elements, known for example from EP3702572A1 or EP2917159A1

[0068] The invention also relates to a method for manufacturing a diffusing material, in particular a diffuse light extractor, comprising a diffusing layer, comprising at least one of the following laser treatment steps: - applying a laser beam to a transparent layer having two main faces, in particular a glass or polymer sheet, the laser beam being incident on one of the two main faces, the laser beam being focused in the layer between the two main faces, the laser beam scanning at least one area of ​​the layer with a determined scanning speed, the laser beam comprising laser pulses of duration less than or equal to 100 picoseconds, the laser beam having an energy per pulse, a repetition frequency and a scanning speed adapted to generate an arrangement of microcavities between the two main faces of the layer in said at least one area, in particular the microcavities (5) being closed or forming openings on the surface of one of the main faces, the microcavities having an elongated shape having a larger dimension in a longitudinal direction and a small dimension transverse to the large dimension,the largest dimension being greater than 50 micrometers, the small dimension being between 0.5 micrometers and 130 micrometers, the longitudinal direction of the microcavities being parallel to a first alignment axis parallel or inclined relative to a normal to one of the two main faces in particular at an angle of at most 15° or even 10° or 5°, the arrangement of microcavities being arranged with a first separation distance between adjacent microcavities in at least one direction transverse to the longitudinal direction of the microcavities, in which a first ratio RI being defined equal to the ratio between the largest dimension and the first separation distance between microcavities, the first ratio is above a determined lower threshold. The lower threshold is preferably equal to: ....., where Qtir is the total reflection angle, internal and x M a determined diffusion percentage.

[0069] Advantageously, the energy per pulse is between 1 microjoule and 100 microjoules and the repetition frequency is less than or equal to 2 megahertz.

[0070] Advantageously, the laser beam operates in a laser-material interaction domain comprised between a refractive index modification domain of the transparent material and an ablation domain of the transparent material.

[0071] The method may comprise a step of spatially shaping the beam to adjust the shape of the laser beam, generally Gaussian, for example to form a Bessel beam (focused on a focal line) or to focus the beam (on a focal point), for example using a standard lens or an f-theta lens generally used in scanner systems.

[0072] According to a particular embodiment, the method comprises a heat treatment step following the laser treatment step, in particular of at least 500°C for a layer which is a sheet of glass, in particular monolithic glazing. The heat treatment may be thermal tempering of the glass.

[0073] According to a particular embodiment, the layer is an interlayer of lamination, the application of the laser beam is in said layer forming part of a laminated glazing.

[0074] In the present document, the term femtosecond pulse means a pulse with a duration less than or equal to 100 picoseconds, preferably less than or equal to 1 picosecond, generally between Ifs and 800 fs, for example approximately 300 fs. The laser pulses are emitted at an inter-pulse repetition frequency or repetition frequency, noted Frep. The repetition frequency Frep is generally between 1 kHz and several MHz, for example 1.5 MHz or 2 MHz. According to a variant, the femtosecond pulses are emitted in bursts, with a repetition frequency between pulse packets lower than the inter-pulse repetition frequency. Each pulse packet may comprise from 1 to 20 pulses, preferably between 1 and 5 pulses.

[0075] Adjusting the number of pulses, the repetition frequency Frep, the packet repetition frequency, the scanning speed and the focusing plane make it possible to control the regularity of the microcavities. It is thus possible to generate microcavities having in a plane parallel to one of the main faces of the layer a random spatial distribution, or in lines, in circles (to not favor any direction) or in points on a two-dimensional network, following a rectangular mesh grid for example.

[0076] Of course, the various features, variants and embodiments of the invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive. Brief description of the drawings

[0077] Furthermore, various other characteristics of the invention emerge from the appended description given with reference to the drawings which illustrate non-limiting forms of embodiment of the invention and where:

[0078] [Fig.l] is a schematic sectional view of a material according to the invention;

[0079] [Fig.2] is a schematic view of the manufacturing method according to the invention;

[0080] [Fig.3] is a diagram illustrating different laser-matter interaction domains between a femtosecond pulse laser and a layer as a function of the energy per pulse (on the abscissa) and the repetition frequency (on the ordinate);

[0081] [Fig.4] includes microscope images of examples of material comprising an arrangement of microcavities in top view (left) and in section (right);

[0082] [Fig.5] is a microscope image of a second example of a material comprising an arrangement of microcavities in top view;

[0083] [Fig.6] is a schematic cross-sectional representation of a material comprising a arrangement of microcavities modeled as cylinders, and illustrating the cut-off angle;

[0084] [Fig.7] is an example of a light-emitting diode module showing the extraction and the diffusion of the radiation emitted by the diodes, in lighting mode;

[0085] [Fig.8] is a view illustrating the transmission through the same diode module electroluminescent than in [Fig.7], the diodes being off.

[0086] It should be noted that in these figures the structural and / or functional elements common to the different variants may have the same references. Detailed description

[0087] In this document, the term "transparent or essentially transparent layer or material" means a layer or material capable of transmitting a light beam in a visible spectral range with little scattering. Such a transparent layer or material may nevertheless exhibit absorption in this visible spectral range or in another visible spectral range.

[0088] By diffusing material is meant a material capable of diffusing at least part of a light beam in the visible spectral range.

[0089] Preferably, the material of the layer is clear and better still extra-clear to limit absorption.

[0090] In [Fig. 1], a cross-sectional view of a material is schematically shown 110. The material 110 is formed from a transparent layer which is a sheet 10 having two main faces 1, 2 and side faces 3, 4. As described below, an arrangement of microcavities 5 is formed inside the transparent layer 10 between the two main faces 1, 2. The main faces extend over a suitable surface depending on the application, for example to form the roof of a road vehicle (automobile). The side faces 3, 4 extend along the thickness of the material. The side faces 3, 4 are also called slices of the material. In other words, the thickness of the material corresponds to the distance between the two main faces 1, 2. The thickness of the material can be uniform. The layer 10 is planar, that is to say that the two main faces 1, 2 are planar and parallel. Alternatively, the two main faces 1, 2 are planar and form an angle.Alternatively, the two main faces 1, 2 extend along non-planar but parallel surfaces. For example, in an application to a motor vehicle roof, one of the main faces 1, 2 is concave and the other main face is convex, the two main faces 1, 2 being locally parallel to each other. Alternatively, the two main faces 1, 2 extend along non-planar and non-parallel surfaces.

[0091] The layer 10 which is used in the manufacture of the material 110 may be a sheet of mineral glass or transparent polymer. The sheet is preferably made of mineral glass, soda-lime (silico)glass, aluminosilicate or borosilicate. The sheet may be thermally toughened glass. The sheet may be made of transparent polymer, in particular polymethyl methacrylate (PMMA), polycarbonate (PC), polyester or polyurethane (PU).

[0092] The material 110 comprises a layer 10 like a sheet and microcavities 5 (described below) formed within the layer 10. More specifically, the microcavities 5 are formed and arranged in the layer 10 during the manufacture of the material 110.

[0093] Alternatively, the material comprises several layers and even several sheets assembled to form a stack, one of the layers or sheets comprising microcavities. For example, the microcavities are formed in a layer such as a sheet usable in a laminated glazing comprising an interlayer sheet of polymer lamination, (for example polyvinyl butyral (PVB), EVA or PU), fixed between a glass sheet and a glass or polymer sheet. The microcavities are preferentially formed in one of the glass sheets in a laminated glazing. Alternatively, the microcavities are formed in an interlayer polymer sheet of lamination fixed between two glass sheets.

[0094] The material may comprise several layers attached to each other, the microcavities being arranged in one of the layers of the material.

[0095] The present disclosure also relates to a glazing comprising the material. The glazing may be single glazing, laminated glazing or multiple glazing, such as double glazing or triple glazing.

[0096] In [Fig. 1], an orthonormal XYZ reference frame is shown. For clarity of the description, without being in any way limiting, the two main faces 1, 2 of the layer 10 extend for example parallel to an XY plane.

[0097] The main face 1 has a normal 11 to its surface and, respectively, the main face 2 has a normal 12 to its surface.

[0098] The material 110 comprises microcavities 5 included in the transparent and diffusing layer 10 between the two main faces 1, 2, microcavities 5 being filled with a gas or vacuum, with a refractive index close to 1, less than n2. Advantageously, the microcavities 5 are entirely included in the layer 10 of the material 110. The microcavities 5 are located in the layer of the material 110 (or even over a fraction of the thickness, more or less equidistant from the main faces). For example, the microcavities 5 are at a distance of between 200 micrometers and several millimeters from each of the main faces 1, 2 of the layer 10. Advantageously, the microcavities 5 are closed. The manufacturing method of the microcavities 5 do not modify the surface of the main faces 1, 2 which remain flat. Alternatively, the microcavities 5 form openings on the surface of one of the main faces 1, 2.

[0099] The microcavities 5 have an elongated shape along a longitudinal direction. The microcavities 5 generally have a symmetrical shape of revolution around their longitudinal direction, for example ellipsoidal or cylindrical with a circular section. L denotes the largest dimension of a microcavity structure 5 along its longitudinal direction and T the small dimension along a direction transverse to the longitudinal direction.

[0100] In certain exemplary embodiments, each microcavity 5 comprises a solid sheath surrounding the empty core. The sheath has a refractive index different from the refractive index of the layer. The sheath has a thickness of between 5 and 50 μm, for example 100 μm. The presence of a sheath around the core of the microcavities can be measured, for example by optical microscope or by phase contrast imaging. The outer diameter or diameter of the sheath is, for example, of the order of 25 to 30 μm. In the case of microcavities comprising a sheath, the largest dimension of a microcavity structure is the largest dimension of the sheath and the small dimension is the dimension or diameter of the sheath perpendicular to the largest dimension.

[0101] In addition, the microcavities 5 are arranged in the layer according to a particular arrangement. The longitudinal direction of the microcavities 5 included in the layer 10 is parallel to a first alignment axis 6. The first alignment axis 6 is parallel or inclined relative to a normal 11, 12 to one of the two main faces 1, 2. According to one embodiment, illustrated in [Fig.4], the microcavities 5 are arranged in parallel lines separated by an average separation distance Sx. In other words, the lines of microcavities 5 are arranged with a periodic pitch noted P along an X axis. The pitch P from one line to the other along the X axis is equal to the sum of the separation distance Sx and the small dimension T of the microcavities 5. In a given incidence plane, we note a first ratio RI = L / (PT) = L / Sx, defined as being the ratio between the largest dimension and the separation distance Sx between lines of microcavities.According to the present disclosure, the first ratio (RI = L / Sx) is within a range determined by a lower threshold and an upper threshold. For example, the first ratio is equal to 0.1; 0.2; 0.3; 0.4; 0.5; 0.8; 0.9; 1.0 or 1.1; 1.2, and preferably between 0.1 and 0.7 or even between 0.1 and 0.3.

[0102] According to another embodiment, illustrated in [Fig.5], the microcavities 5 are arranged in parallel lines separated by a separation distance Sx and in parallel columns separated by a separation distance Sy. In other words, the lines of microcavities 5 are arranged with a periodic pitch noted P along an axis X and the columns of microcavities 5 are arranged with a periodic pitch noted Q along

[0103]

[0104]

[0105] a Y axis. The pitch P from one row to another along the X axis is equal to the sum of the separation distance Sx and the small dimension T of the microcavities 5 and the pitch Q from one column to another along the Y axis is equal to the sum of the separation distance Sy and the small dimension T of the microcavities 5. A second ratio R2 = L / Sy is noted, defined as being the ratio between the largest dimension and the separation distance Sy between columns of microcavities. According to the present disclosure, the first ratio (RI = L / Sx) is included in a first determined range and the second ratio (R2 = L / Sy) is included in a second determined range. The first threshold and the second threshold may be equal (when the steps P and Q are identical, or different. The first ratio, respectively the second ratio, is for example equal to 0.1; 0.2; 0.3; 0.4; 0.5; 0.8; 0.9; 1.0; 1.1 or 1.2, and preferably between 0.1 and 0.7, or between 0.1 and 0.3.The separation distance Sx, respectively Sy, is between 20 pm and 1 mm, preferably between 50 pm and 500 pm, for example 100 pm, 150 pm or 200 pm. According to the present disclosure, the material allows to extract diffuse light from guided light propagating by total internal reflection and which is scattered on the microcavities. In addition, the material is transparent for an incident external beam at normal incidence, weakly scattering up to an angle of incidence equal to a cut-off angle and more scattering above this cut-off angle 0c. Without being bound by a theory, the first ratio RI, respectively the second ratio R2, is above a lower threshold equal to: .....where xM represents a percentage of light diffusion propagating inside the layer perpendicular to the lines and, respectively, to the columns, of microcavities, with an internal angle of incidence greater than or equal to the angle of total internal reflection and which is diffused on the microcavities. For example, the first ratio (RI = L / Sx) is greater than or equal to 1.145 xM for a glass sheet having a refractive index of 1.5 arranged in air. In an exemplary embodiment, it is desired to obtain a percentage xM of at least 10% or 30% of light guided at the angle of total internal reflection diffused towards the outside for lines of microcavities having a pitch P of between 100 pm and 200 pm, a largest dimension L of approximately 55-60 pm, a small dimension D of approximately 7 pm and a cladding with a diameter of approximately 26 pm. Particularly advantageously, the first ratio RI, respectively the second ratio R2, is below an upper threshold equal to: xm 1”? , °where. 2Ü 77 ”1 sin bc »i xm represents a maximum percentage of light scattered on the microcavities from an external light refracted inside the layer in a plane of incidence perpendicular to the rows, respectively to the columns, of microcavities up to the cut-off angle 0c of the material, n2 represents the refractive index of the layer, nor the refractive index of air. For a given cut-off angle 0c, we want the percentage of scattered light to be less than xm when the angle of incidence of the external light beam is less than the cut-off angle 0c and the percentage of scattered light to be greater than xm when the angle of incidence of the external light beam is greater than the cut-off angle 0c.

[0106] The microcavities 5 are generated in a layer 10, as described above, by a laser process. The laser process operates in a relatively narrow operating parameter range as illustrated in connection with FIGS. 2 and 3. For example, a solid-state laser, fiber laser or laser diode type laser is used. In one example, a Yb:YAG / Nd:YAG solid-state laser or a Yb:YVO4 laser is used.

[0107] In a first step 60, a femtosecond pulse laser beam is generated.

[0108] For example, a Yb:YAG solid-state laser type laser is used, emitting at a wavelength wavelength of about 1030 nm. The laser wavelength is chosen in the transparency range of the layer. In one example, the duration of a laser pulse is about 300 fs at a wavelength of 1030 nm. The repetition frequency Frep of the pulse packets is for example 2 MHz or a submultiple of 2 MHz. The inter-pulse frequency is for example 40 MHz. Each pulse packet may comprise from 1 to 20 pulses, preferably a number less than or equal to 5 pulses, for example 2 pulses.

[0109] The laser beam has an energy per pulse E. More particularly, as illustrated in [Fig.3], we are placed in a particular and narrow laser-matter interaction domain so as to generate microcavities 5 inside a material.

[0110] The method comprises an optional step of spatial shaping 61 of the beam to adjust the shape of the laser beam, for example to form a Bessel beam. The advantage of a Bessel beam is to have a small diameter over a large distance, which makes it possible to maintain focus over several tens, hundreds of microns, or even of the order of a millimeter along the propagation direction. A Bessel beam makes it possible to create microcavities having a larger aspect ratio RA or to better control the aspect ratio RA. On the contrary, for a Gaussian beam, there is a compromise between the diameter of the neck (waist in English) and the propagation distance over which this diameter is maintained.

[0111] In a step 62, the femtosecond pulsed laser beam is applied to a transparent layer to be treated. The laser beam is focused inside the layer 10, between the two main faces. The size of the focused laser beam is between 55 and 60 pm in diameter (defined by the “waist” or neck of a Gaussian beam). The laser beam is generally applied to a solid layer, for example through face 1 of layer 10. The laser beam is generally applied at an angle of incidence of less than 10 degrees and preferably at normal incidence to face 1 of layer 10.

[0112] In a step 63, a scan of the laser beam is carried out relative to an area of ​​the layer to be treated. Alternatively, in step 63, the layer is moved relative to the laser beam which is fixed to produce the scan of the laser beam over the area to be treated. The scanning can be carried out step by step, so as to apply the laser beam at determined points of the layer, the points being regularly spaced from one another, for example along lines or following a matrix of lines and columns. Alternatively, the scanning is carried out during the laser shots, for example to generate microcavities along lines regularly spaced from one another. Steps 60, (where appropriate 61), 62 and 63 are iterated until the entire area of ​​the layer to be treated is covered. A material 110 is thus obtained comprising microcavities 5 arranged inside the layer 10.

[0113] In certain exemplary embodiments, each microcavity structure 5 is surrounded by an envelope or sheath. For example, in [Fig. 4], viewed from above under an optical microscope, a microcavity structure appears as a black dot surrounded by a circle which corresponds to the boundary of the envelope. The solid envelope has a structure and / or an optical index of refraction different respectively from the structure and / or the refractive index of the transparent layer. This envelope is supposedly induced by compressive stresses in the layer during the laser process. These compressive stresses can be relaxed via a thermal annealing step which causes the envelope to disappear. Optionally, after having finished treating the material, the method comprises a heat treatment step 65 or thermal annealing. For example, the heat treatment is carried out at a temperature of 650°C for 3 minutes.This heat treatment makes it possible to increase the transmission of the material at an angle of incidence normal to the main faces 1,2.

[0114] Generally speaking, the application of a femtosecond pulsed laser beam to a transparent layer is likely to result in different laser-material interaction processes depending on the layer and the laser operating parameters. Laser operating parameters are understood here to mean all the laser parameters including in particular the energy per pulse, the duration of the laser pulses, the number of pulses, the inter-pulse repetition frequency and / or between pulse bursts, the wavelength of the laser beam, its spatial shape, the fixed-frequency or packet pulse regime, the scanning speed of the laser beam on the layer, the orientation of the laser beam.

[0115] In particular, the application of a femtosecond laser to a transparent layer is likely to produce different effects on the layer, as illustrated in the [Fig.3]. [Fig.3] shows different laser-matter interaction domains between a femtosecond laser beam focused inside a clear soda-lime glass sheet (here for example an SGG Planiclear glass from Saint-Gobain) as a function of two selected laser parameters: the energy E per pulse (on the abscissa) and the repetition frequency Frep (on the ordinate). In this example, the other laser parameters are assumed to be constant. In this example, a Yb:YAG laser is used, for example a Satsuma HP2 Laser from Amplitude Systèmes, which generates pulses with a duration of about 300 fs, at a wavelength of 1030 nm, the fixed-frequency pulse regime with a scanning speed of 5 mm / s. In [Fig.3], no effect is observed in the leaf in a 50 domain located below a first threshold of energy per pulse, here about 2 pj / pulse, this first threshold being almost independent of the repetition frequency Frep. Beyond the first threshold of energy per pulse and below a second threshold of energy per pulse, the creation of colored centers in the leaf in a 51 domain is observed, under the microscope or visually. For example, at Frep = 500 kHz, the second threshold of energy per pulse is about 4.5 pj / pulse. The second threshold of energy per pulse decreases progressively as a function of the increasing repetition frequency Frep up to 2 MHz, where second threshold of energy per pulse is very close to the first threshold of energy per pulse.In a 52 domain, located above the second pulse energy threshold and below a third pulse energy threshold, in a 52 domain, an evolution of the sheet is observed under the microscope, without modification of its color. According to the scientific literature, this evolution corresponds to a modification of refractive index in the sheet. The third pulse energy threshold decreases sharply as a function of the increasing Frep repetition frequency up to 2 MHz, where the third pulse energy threshold is very close to the second pulse energy threshold.This refractive index modification domain 52 covers a wide range of operating parameters, the energy per pulse being able to be between about 5 pJ / pulse and 20 pj / pulse at the Frep repetition frequency of 250 kHz, or between about 3 pj / pulse and 9 pj / pulse at the Frep repetition frequency of 666 kHz, or between about 2 pj / pulse and 6 pj / pulse at the Frep repetition frequency of 1 MHz and about 2.5 pJ / pulse at the Frep repetition frequency of 2 MHz. There is also a domain 54 with high energy per pulse and high Frep repetition frequency, in which ablation of the sheet, i.e. removal of material, is observed. However, the present disclosure highlights a narrow domain 53 of parameters, located between the domain 52 of modification of the refractive index of the layer and the domain 54 of ablation of the sheet, in which the creation of microcavities inside the sheet is observed, without removal of material.This domain 53 of microcavity generation is . located between the third pulse energy threshold and a fourth pulse energy threshold. The ablation domain 54 of the sheet lies beyond the fourth pulse energy threshold. The fourth pulse energy threshold decreases sharply with increasing Frep repetition frequency up to 2 MHz, where the fourth pulse energy threshold is about 4 pj / pulse. This domain 53 thus covers a narrow range of operating parameters, the energy per pulse being approximately 22 pj / pulse at the Frep repetition frequency of 250 kHz, or between approximately 13.5 pj / pulse and 14.5 pj / pulse at the Frep repetition frequency of 500 kHz, or between approximately 6 pj / pulse and 7.5 pj / pulse at the Frep repetition frequency of 1 MHz and between approximately 2.5 pj / pulse and 4 pj / pulse at the Frep repetition frequency of 2 MHz.However, it is observed that this domain 53 widens when the repetition frequency Frep increases, which makes it possible to define a domain sufficiently wide to ensure the stability of the process, for example for a repetition frequency Frep greater than or equal to 1 MHz.

[0116] [Fig.4] illustrates a top view (left) and a sectional view (right) of materials obtained following femtosecond laser processing according to the present disclosure. The material 10 is here formed from a sheet of soda-lime glass with main faces 1, 2 that are planar and parallel. The thickness of the sheet 10 between the main faces 1, 2 is approximately 4 mm. In this example, a Yb:YAG laser is used which generates pulses having a duration of approximately 300 fs, at a wavelength of 1030 nm, the pulse regime at a burst repetition frequency of 2 MHz, with an energy per pulse burst of 21% of 10 pJ distributed between the different pulses of the burst. A scanner device allows scanning along lines parallel to the Y axis spaced at a pitch P of approximately 50 pm to 300 pm with a scanning speed of, for example, 5 mm / s.Advantageously, the lines are arranged regularly, that is to say that the pitch P from one line to the next along the X axis is constant on the treated surface. This produces a material 110 comprising lines forming a one-dimensional periodic structure. The scanner device comprises an f-theta lens which focuses the laser beam through the main face 1 at mid-distance between the main faces of the sheet. In the top view, microcavities 5 are observed aligned along the scanning lines of the laser beam. In the sectional view, it is observed that the microcavities 5 are elongated parallel to a first alignment axis 6. The microcavities 5 with their sheath 15 have here, on average, a large dimension L of between approximately 300 pm and 600 pm and a small dimension D of approximately 25 pm to 50 pm. Sx denotes the average separation distance, here along the X axis, between two adjacent lines of microcavities 5.The step P from one line to another along the X axis is equal to the sum of the average separation distance Sx and the small dimension D of the microcavities 5. .

[0117] The longitudinal end of the microcavities 5 is at a distance of approximately 200 pm to 300 pm from the main surface 1. The other longitudinal end of the microcavities 5 is at a distance of approximately 1 mm from the main surface 2. The microcavities 5 here form neither hollow nor bump on the main faces 1 and 2 of the material 110 which are flat.

[0118] The parameters of the scanner device are adjusted so that the distance Sx between two adjacent lines of microcavities is less than or equal to the product of the large dimension L and a factor depending on the refractive index of the sheet and the target scattering level. The ratio L / Sx determines a cut-off angle in an incidence plane parallel to the XZ plane, as detailed below.

[0119] In [Fig.4] we observe a very high regularity of the microcavities 5 concerning not only their dimensions L and D, but also their position in the material between the two main faces 1, 2 and also the orientation of their longitudinal axis. This high regularity is allowed by the laser process. The adjustment of the laser scanning parameters makes it possible to adjust the spatial distribution of the microcavities 5. The adjustment of the number of pulses, the repetition frequency Frep, the repetition frequency of the packets, the scanning speed and the focusing plane make it possible to control the regularity of the microcavities 5. It is thus possible to generate microcavities 5 having in an XY plane a random spatial distribution, or in lines, in circles (to not favor any direction) or in points on a two-dimensional network, following a rectangular mesh grid for example.

[0120] As indicated previously, the scanning direction and speed also make it possible to adjust the orientation and inclination of the first alignment axis 6 of the microcavities 5. It is thus possible to adjust a determined inclination angle of the first alignment axis 6 of the microcavities 5 relative to the normal 11, 12 to the main face 1, 2 of the material 110.

[0121] [Fig.5] illustrates another example of spatial distribution of microcavities 5 in a material 110 following a two-dimensional network. In this example, the layer 10 is a 4 mm thick sheet of soda-lime glass (SGG Planiclear), the femtosecond laser applies pulses having a duration of approximately 300 fs, at a wavelength of 1030 nm. The laser beam is focused in the middle of the layer in the direction of the thickness.

[0122] In [Fig.5], the scanning of the laser beam is carried out point by point in rows and columns, the laser beam being interrupted between each point. The laser beam is here static during each irradiation. The laser operates here with a burst energy of 21% of 10 pJ, two pulses per burst, with a burst repetition frequency of 2 MHz. The microcavities 5 appear spontaneously according to the points arranged in a regular mesh in rows and columns, here with a pitch P of 100 pm and a pitch Q of 100 pm. This gives a distribution of the microcavities 5 according to a periodic lattice of square mesh of 100 pm on each side. In this example, the lines are spaced by a distance Si of approximately 90 pm and the columns are spaced by a distance S2 of approximately 90 pm. In addition, a very high regularity of the transverse dimensions of the microcavities 5 is observed over the entire laser-treated area. In this example, the laser beam being static during the irradiation of each point, the microcavities 5 are aligned in a direction perpendicular to the surface of the main faces 1, 2. Alternatively, the lines are arranged periodically with a pitch P greater than or equal to 30 pm, for example 50 pm or 200 pm, and the columns are arranged periodically with a pitch Q greater than or equal to 30 pm, for example 50 pm or 200 pm.Preferably, the pitch P is equal to the pitch Q, so as to allow homogeneous diffusion of light in both X and Y directions. However, in certain applications, the pitch P is different from the pitch Q.

[0123] Sy denotes the average separation distance between two adjacent microcavities in the same column. The pitch Q between microcavities of a column along the Y axis is equal to the sum of the average distance Sy and the small dimension T of the microcavities 5. Advantageously, the average distance Sy, here along the Y axis, between two adjacent microcavities of the same column is less than or equal to the product of the large dimension L and a factor depending on the refractive index of the layer and the targeted diffusion level. This second ratio L / Sy determines the cut-off angle in another plane of incidence parallel to the YZ plane, as detailed below. By choosing a pitch Q different from the pitch P, a different cut-off angle can be obtained depending on the plane of incidence.

[0124] The laser-treated area advantageously extends over the entire surface of the material. In other embodiments, the treated area extends over a limited part of the surface of the material. For example, the surface of the treated area extends over a surface of geometric shape or in the shape of a number, letter, logo or design or any other shape suitable for the desired application. The surface of the treated area can range from 1 mm2 to 18 m2 depending on the applications, generally approximately 1.5 m2 for a window or automotive glazing.

[0125] We will now describe the optical properties and operation of the material 110 in connection with figures 1, 6 and the different examples of spatial distribution of the microcavities 5. The material 110 has both angularly selective diffusion and transmission properties, and allows extraction of diffused light.

[0126] In the example of figures 1 and 6, the first alignment axis 6 of the microcavities 5 is parallel to the normal 11 to the main face 1. The microcavities 5 are arranged in lines parallel to a second alignment direction oriented along the Y axis. The XZ incidence plane of [Fig.l] includes the first main axis 6 and the X axis transverse to the second alignment direction.

[0127] The material 110 is adapted to receive an internal light beam 30 propagating between the two main faces 1, 2. The light beam 30 is emitted by a light source, for example a light-emitting diode 7 arranged opposite a lateral face 3 of the material. The light beam 30 forms an angle, denoted ALPHA, with the normal 11 to the main face 1. The angle ALPHA is greater than or equal to a total internal reflection angle determined by the refractive index n2 of the material of the layer and the refractive index ni of air. For example, for a glass in air and a light beam 30 in the visible, the total internal reflection angle is approximately 41 degrees. In the absence of microcavities 5, the internal light beam 30 propagates for example by multiple internal reflection between the two main faces 1, 2. The internal light beam 30 then propagates in the layer 10 without absorption and without diffusion along the direction of the X axis.Alternatively or complementary, another light source is arranged to inject another light beam propagating between the two main faces 1, 2 in the direction Y.

[0128] As illustrated in [Fig.l], the microcavities 5 are configured and arranged to receive a portion of the internal light beam 30 propagating in the layer 10 between the two main faces 1, 2 in the propagation direction X. The light beam incident on the microcavities 5 is diffused in different directions and forms a diffused internal beam 35. A portion of the diffused internal beam which forms an angle smaller than the total internal reflection angle with the normal to the main face 1 is extracted from the material 110 and forms a diffused external beam 41 coming from the main face 1. Similarly, another portion of the diffused internal beam which forms an angle smaller than the total internal reflection angle with the normal to the main face 2 is extracted from the material 110 and forms a diffused external beam 42 coming from the main face 2.On the other hand, the parts of the scattered internal beam which form an angle greater than the total internal reflection angle with the normal to the main face 1, respectively 2, remain trapped and can again be scattered onto other microcavities 5. This gives an external scattered beam 41, respectively 42, extracted from the material 110 through the main face 1, respectively the main face 2. The properties of the external scattered beam 41, respectively 42, in particular the intensity distribution in the XZ incidence plane are a function of the material of the layer, the spatial distribution (in particular the average separation distance Sx between lines of microcavities along the X axis) of the microcavities 5, the first ratio RI = L / (PT) = L / Sx, between the largest dimension and the average distance. of separation Sx between lines of microcavities. It follows that the external beam diffused 41, respectively 42 outside the material 110 forms an angle less than an angle corresponding to the angle of total internal reflection with the normal 11, respectively 12 to the main face 1, respectively the main face 2. The external beam diffused 41, respectively 42 is therefore diffused essentially around the axis Z, that is to say transversely to the direction of propagation, along the axis X, of the internal light beam 30 injected into the layer 10.

[0129] In a plane transverse YZ to the plane of [Fig. 1], the response of the material for the extraction and diffusion of light depends on the spatial distribution of the microcavities 5. Let us first consider a first example where the microcavities 5 are arranged in lines parallel to the Y axis, the distribution of the microcavities 5 along the Y axis not being ordered.

[0130] In another example, the microcavities 5 are arranged in columns parallel to the X axis and Sy denotes the average separation distance between two columns. In this case, in a manner analogous to the description of diffusion in the XZ plane of incidence, the internal light beam propagating by total internal reflection undergoes diffusion under certain conditions. The external beam diffused in the transverse plane YZ to the plane of [Fig.l] is extracted from the material 110 through the main face 1, respectively 2. Similarly, in the YZ plane of incidence, the properties of the external diffused beam 41, respectively 42, are a function of the material of the layer, of the spatial distribution (in particular the average separation distance Sy between points or between columns of microcavities along the Y axis), and in particular of the second ratio R2 = L / (QT) = L / Sy, between the largest dimension and the average separation distance Sy between microcavities along the Y axis.

[0131] The material 110 comprising elongated and ordered microcavities has advantages for the extraction and diffusion of light compared to a material comprising randomly dispersed bubbles. It makes it possible to extract and diffuse a portion of the light propagating inside the layer by total internal reflection, and thus obtain a diffusion of light in a direction transverse to the main faces of the material 110, which thus makes it possible to obtain more efficient lighting.

[0132] The material also has particular transmission properties. Generally, the transmission depends on the density of the microcavities and their small dimension T. Advantageously, the material has low diffusion by transmission, through the material, of an external beam incident on one of the main faces at an angle of incidence less than a determined external cut-off angle.

[0133] Consider an external light beam 20 incident on the main face 1 in the XZ incidence plane of [Fig.l]. The external light beam 20 transmitted through the main face 1 forms a light beam 21 refracted in the material 10, then exits through the opposite main face 2, in the form of a transmitted light beam 22. When the external light beam 20 is parallel to the normal 11 to the main face 1, the refracted light beam 21 is also parallel to the normal IL. In the example of [Fig.l], the refracted light beam 21 is then parallel to the first alignment axis 6 of the microcavities 5. If the first alignment axis 6 is inclined, the direction in which the glazing is transparent corresponds to the direction aligned with the first alignment axis 6, taking into account the refraction. The transverse dimension T of the microcavities 5 is between 0.5 micrometers and 130 micrometers and preferably greater than or equal to 10 μm.It follows that the transmitted light beam 22 through the material 110 parallel to the first alignment axis 6 undergoes practically no diffusion on the microcavities 5. More generally, as long as the angle between the refracted light beam 21 and the first alignment axis 6 of the microcavities remains less than an internal cut-off angle 0r, the transmitted light beam 22 is not or only slightly diffused by the microcavities 5. This remains valid when the first alignment axis 6 is inclined relative to the normal 11 to the main face 1. On the other hand, when the angle between the refracted light beam 21 and the first alignment axis 6 is greater than or equal to the internal cut-off angle, the refracted light beam 21 is likely to be diffused by the microcavities 5. The internal cut-off angle 0r corresponds to an external cut-off angle 0c (see [Fig.6]).

[0134] The presence of the microcavities of small transverse dimension aligned in a direction normal to the surface has the effect that the material 110 has a high visual transparency under normal incidence or when the angle of incidence of an external light beam incident on one of the main faces of the layer is less than a cut-off angle 0c determined in the plane of incidence. The visual transparency can be evaluated by means of a haze meter, which measures the intensity in transmission TL, the haze value, noted H (or "haze" in English) and the clarity value, noted C (or "clarity" in English) of the material. For example, a HazeGard Plus haze meter from the company BYK-Gardner is used to carry out measurements according to the ASTM D1003 standard.The haze meter measurements in the table below were carried out under normal incidence for different samples, in which microcavity lines are formed, at a scanning speed of 5 mm / s and with a separation distance between microcavity lines of 100 pm, 150 pm and 200 pm respectively. The microcavities have a largest dimension L of about 60 pm ± 5 pm, a small dimension T of about 7 pm ± 5 pm and a cladding diameter of index . of about 27 ± Ipm. The microcavities are here fabricated in a layer having an optical index of refraction of about 1.5. [Tables 1] P (pr^i W) 100 90.8 ± 1 23.1 ± 1-8 88.8 *1 15Q 91.8 ±1 15.4 ± 1 93.811 200 88.6 ±1 4'1 wire S 95.6 ± 1

[0135] The more the separation distance between microcavity lines increases, the more the blur decreases and the more the clarity increases.

[0136] Furthermore, the presence of the microcavities elongated in a direction normal to the surface has the effect of observing an external cut-off angle 0 „ beyond which the material 110 has a lower visual transparency. By modeling the microcavities in the form of cylinders of circular section, having a height equal to the largest dimension L and a diameter equal to the transverse dimension T, the separation distance between microcavities being noted Sx = P - T, where P is the pitch between lines of microcavities, and % m the percentage of light diffused on the microcavities, the external cut-off angle 0 c is calculated according to the following formula:

[0137] \"'r+^A /

[0138] The percentage % of diffused light considered here is understood in relation to the external light incident on one of the main incident faces, transmitted directly through the material without diffusion.

[0139] For a given L and an xm of 30%, the cut-off angle is chosen to be 34 degrees for a step P of 100 pm, respectively 49 degrees for a step of 150 pm, or 75 degrees for a step of 200 pm.

[0140] To have the highest transparency at all observation angles, we seek to have the highest possible cut-off angle for a given xm (the lowest possible acceptable).

[0141] The material has a high visual transparency for an external light beam 20 incident on one of the main faces 1, 2 with an angle of incidence less than the external cut-off angle in the plane of incidence and the material 110 has a strong diffusion towards the outside of the material for an internal light beam 30 forming an angle ALPHA greater than an internal cut-off angle with the longitudinal direction 6 of the microcavities in the plane of incidence.

[0142] The internal cut-off angle is determined by the ratio between the large dimension L and the distance Sx between lines along the X direction. The internal cut-off angle corresponds to an external cut-off angle of the external light beam 20 incident on the main face 1. The relationship between the internal cut-off angle and the external cut-off angle is determined by the Snell-Descartes laws as a function of the refractive index of the material of the layer. Consequently, the external light beam 20 is transmitted without diffusion when it forms an angle less than this external cut-off angle in a plane determined by the first alignment axis 6 and a direction X transverse to the microcavity lines 5.

[0143] The higher the average separation distance Sx, respectively Sy, between microcavities, the higher the transmission, particularly in off mode for a lighting module.

[0144] The material 110 of the present disclosure finds applications in particular in the manufacture of a lighting device such as luminous glazing (of a building, of a vehicle) in particular monolithic or laminated or multiple, for example comprising a module with light-emitting diodes (or LEDs), as illustrated in transmission in the lit state in [Fig.7] and in the unlit state in [Fig.8].

[0145] The lighting device 100 here comprises a material 110 which is a glazing combined with a plurality of light-emitting diodes 7, 17 here arranged on a lateral face or edge of the material. An area of ​​the material comprises microcavities 5 arranged in lines as described above. This area of ​​the material appears brighter when the LEDs 7 are lit due to the extraction and diffusion of light through one of the faces of the material. The diffused light beam 4L is thus observed. Another area 8 of the material is devoid of microcavities. This other zone 8 appears dark due to the absence of light diffusion although the LED 17 illuminates the interior of this zone 8 between the main faces 1, 2 of the material in a manner similar to the LEDs 7 illuminating the microcavity zone 5. However, the light from the LED 17 remains inside this zone 8 and is not extracted or diffused outside the material 110 in this zone without microcavities.

[0146] In [Fig.8], all LEDs 7, 17 are off. In this case, no scattered beam is observed. On the contrary, a background image 9 can be clearly observed by transmission through the material. The transmission transversely to the main faces is excellent and free of scattering, in other words with little blurring and high transmission and clarity.

[0147] A lighting device such as luminous glazing (of a building, of a vehicle) may be based on a distribution of microcavities 5 along lines or in lines and columns. Alternatively, the distribution of the microcavities has a variable density along a direction, for example to allow homogeneous diffusion of light.

[0148] Of course, various other modifications may be made to the invention within the scope of the appended claims.

Claims

Claims

1. Diffusing material, the material (110) comprising a diffusing layer (10) having two main faces (1, 2), the layer (10) being transparent, in particular having a refractive index n2,, characterized in that: the layer (10) comprises at least one zone comprising microcavities (5) included between the two main faces (1, 2) of the layer (10), the microcavities (5) having an elongated shape having a largest dimension in a longitudinal direction and a small dimension transverse to the largest dimension, the largest dimension being greater than 50 micrometers, the small dimension being between 0.5 micrometers and 130 micrometers, the longitudinal direction of the microcavities (5) being parallel or inclined relative to a normal (11, 12) to a main face (1, 2) of the layer at an angle of at most 15°, the microcavities (5) having in a plane of incidence, including the normal,on said area a spatial distribution determined by a first separation distance (Sx) between microcavities, in which being defined a first ratio (RI) equal to the ratio between the largest dimension and the first separation distance, the first ratio is above a determined lower threshold, the layer (10) being capable of extracting and diffusing a determined diffusion percentage x M of an internal light beam (30) propagating between the two main faces (1, 2) in said plane of incidence, in particular under an internal angle of incidence greater than or equal to a total internal reflection angle dy / j^ to form at least one diffused external beam (41, 42) coming from at least one of the two main faces (1, 2), the lower threshold being preferably equal to: XM,

2. Material (110) according to claim 1, wherein the diffusion percentage xM is greater than or equal to 0.01, preferably greater than or equal to 0.

1.

3. Material (110) according to one of claims 1 or 2, the lower threshold is equal to: / / 'ht2 , where ni is the refractive index of XM\ \ «T 1 -1 the air.

4. Material (110) according to one of claims 1 to 3, the layer (10) having an external cut-off angle 0c determined in said plane of incidence, and in which the first ratio is below an upper threshold which is equal to: xm I ] where xm represents V sin% «î ' 1 a percentage of diffusion by transmission, where ni is the refractive index of air, the layer (10) being capable of diffusing a percentage less than xm of an external light beam (20) incident on one of the two main faces (1, 2) with a first angle of incidence less than the determined external cut-off angle and the layer (10) being capable of diffusing a percentage greater than xm of an external light beam (20) incident on one of the two main faces (1, 2) with a second angle of incidence greater than the determined external cut-off angle.

5. Material (110) according to one of claims 1 to 4 in which the lower threshold is greater than or equal to 0.

1.

6. Material (110) according to one of claims 1 to 5 in which the upper threshold is less than or equal to 100.

7. Material (110) according to one of the preceding claims in which the microcavities have an angular distribution with an angle standard deviation of less than 10 degrees, and even 5 degrees or 2 degrees and / or with an angle value at the peak of the distribution of at most 15° and even at most 10° or 5°.

8. Material according to one of the preceding claims in which the spatial distribution of the microcavities (5) is according to a one-dimensional or two-dimensional network of microcavities, in particular the one-dimensional network comprises lines of microcavities parallel to the main face (1, 2) of the layer.

9. Material (110) according to claim 8 wherein the two-dimensional network comprises lines of microcavities and columns of microcavities parallel to the main face (1, 2), the columns being perpendicular to the lines, the columns of microcavities being arranged with a second separation distance Sy between adjacent columns of microcavities (5), in which a second ratio R2 is defined equal to the ratio between the largest dimension and the second separation distance between Sy between columns: R2 = L / Sy, the second ratio is above the determined lower threshold.

10. Material according to one of the preceding claims in which the first separation distance (Sx) is between 20 micrometers and 1 millimeter in a first direction parallel to the main face (1, 2) of the layer and optionally a second separation distance (Sy) is between 20 micrometers and 1 millimeter in another direction parallel to the main face (1, 2) of the layer, in particular normal to said first direction.

11. Material according to one of the preceding claims in which the microcavities (5) have an aspect ratio between the largest dimension and the smallest dimension of at least 1.5 or 5 and even of at least 20, 50 or 100.

12. Material (110) according to one of the preceding claims in which the microcavities (5) are closed.

13. Material (110) according to one of claims 1 to 11 in which the microcavities form openings on the surface of at least one of the main faces (1, 2).

14. Material (110) according to one of the preceding claims in which the transparent layer comprises a sheet of mineral glass, preferably clear or extra-clear, in particular based on soda-lime glass, aluminosilicate or borosilicate, in particular thermally toughened glass, or the transparent layer comprises a sheet of transparent polymer in particular based on polymethyl methacrylate, polycarbonate, polyurethane, polyesters, in particular an interlayer lamination sheet preferably based on polyvinyl butyral, an ethylene / vinyl acetate copolymer, thermoplastic polyurethane.

15. Material (110) according to one of the preceding claims in which the material is a glazing, monolithic or laminated, in particular vehicle or building glazing, possibly multiple glazing and in particular the layer is a sheet of glass or polymer.

16. Material (110) according to one of the preceding claims in which a light source (7) is arranged to generate and inject the internal light beam (30) into the layer (10).

17. Material according to one of the preceding claims, forming a luminous glazing of a vehicle, in particular a road, rail or air vehicle, such as a side glazing, a rear glazing, a roof in particular. laminated, a windshield in particular laminated, or building glazing in particular facade glazing, in particular window, a partition, a glass door.

18. Material according to one of claims 1 to 17 forming luminous glazing comprising a first glass sheet, a lamination interlayer, a second transparent sheet of mineral or polymer glass, and the second glass sheet being said diffusing layer of refractive index n2, in particular a sheet oriented towards the interior of a building or a passenger compartment.

19. Material according to one of claims 1 to 17 forming luminous glazing comprising a first sheet of glass, an interlayer of lamination which is said material with said diffusing layer of refractive index n2, a second transparent sheet of mineral or polymer glass, and comprising an optical isolating element between the first sheet and the interlayer of lamination of refractive index n3 less than n2.

20. A method of manufacturing a diffusing material comprising a diffusing layer comprising at least one of the following laser treatment steps: - applying a laser beam to a transparent layer (10) having two main faces (1, 2), in particular a glass or polymer sheet, the laser beam being incident on one of the two main faces (1, 2), the laser beam being focused in the layer between the two main faces (1, 2), the laser beam scanning at least one area of the layer (10) with a determined scanning speed, the laser beam comprising laser pulses of duration less than or equal to 100 picoseconds, the laser beam having an energy per pulse, a repetition frequency and a scanning speed adapted to generate an arrangement of microcavities (5) included between the two main faces of the layer (10) in said at least one area,in particular the microcavities (5) being closed or forming openings on the surface of one of the main faces (1, 2), the microcavities (5) having an elongated shape having a larger dimension in a longitudinal direction and a small dimension transverse to the large dimension, the larger dimension being greater than 50 micrometers, the small dimension being between 0.5 micrometers and 130 micrometers, the longitudinal direction of the microcavities (5) being parallel to a first alignment axis (6), parallel or inclined relative to a normal (11, 12) to one of the two main faces (1, 2), the arrangement of microcavities being arranged with a first separation distance between adjacent microcavities (5) in at least one direction transverse to the longitudinal direction of the microcavities (5), in which a first ratio RI is defined equal to the ratio between the largest dimension and the first separation distance between microcavities, the first ratio is above a determined lower threshold, the lower threshold preferably being equal to: _i*L_, where ®tir represents the angle of total internal reflection and x M a determined percentage of diffusion.

21. Method according to the preceding claim in which the energy per pulse is between 1 microjoule and 100 microjoules and the repetition frequency is less than or equal to 2 megahertz.

22. Method according to one of claims 20 to 21 in which the laser beam operates in a laser-material interaction domain comprised between a refractive index modification domain of the transparent layer and an ablation domain of the transparent layer.

23. Method according to one of claims 20 to 22 comprising a step of spatially shaping the beam to adjust the shape of the laser beam, in particular to form a Bessel beam or to focus the beam.

24. Method according to one of claims 20 to 23 comprising a heat treatment step (65) following the laser treatment step, in particular of at least 500°C for a layer which is a sheet of mineral glass, in particular monolithic glazing.

25. Method according to one of claims 20 to 23 characterized in that the layer is an interlayer of lamination, the application of the laser beam is in said layer forming part of a laminated glazing.

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