Light module including a light guide with a guide sheet for homogeneous light intensity display

Abstract

The present invention relates to a light module comprising a light guide including a light-guiding mat and a light injection assembly, and a light source arranged to inject light rays into the entrance surface of at least one injection assembly. The light guide includes a film (111) comprising a light extraction zone with microstructures (113) adapted to redirect the light injected into the light guide to the outside of the light module. The film includes microstructures on a first face (701) and on a second face (702). For each portion among portions of the light extraction zone having different distances from a light injection slice (114), the sum of a microstructure density on the first face and on the second face is an increasing function of the distance between the portion and the injection slice. Fig. 7

Description

Title of the invention: Light module comprising a light guide with a guide sheet for displaying uniform light intensity

[0001] The present invention relates to the field of light guide light modules, in particular light modules with a flexible light guide.

[0002] It is now common to implement lighting functions in all types of equipment, particularly in equipment for motor vehicles, for lighting purposes, information signaling, for aesthetic purposes of personalization or creating an atmosphere.

[0003] It is known to use screens, such as LCD screens.

[0004] However, such technology is not only expensive but also sensitive to environmental conditions such as temperature, humidity or UV radiation. It is therefore inappropriate for many devices having uses that induce a variation in environmental conditions, as may be the case for devices used outdoors.

[0005] Furthermore, the aforementioned solution has the disadvantage of high energy consumption, which is all the more important as the surface area of ​​the equipment in which it is desired to integrate a light module is large.

[0006] It is known to use light modules with a light guide comprising a guide sheet incorporating a film, which may be flexible, in which light rays are guided, which are returned according to a given light pattern, depending on microstructures formed in the film. The light injection is carried out in an injection slice of the film.

[0007] Regardless of the technique used to form the microstructures in the light guide in order to produce the pattern, it is easier to produce the microstructures on the surface of the film, rather than in the volume of the film.

[0008] The areas in which microstructures are created are light extraction areas, while the areas not comprising the microstructures are so-called dark areas. The respective arrangements and shapes of the light extraction areas and the dark areas together form the light pattern of the light guide.

[0009] In order to allow light homogeneity between the light extraction zones, it may be provided to vary the density of the microstructures in the light extraction zones, as a function of a distance from a light injection slice of the film into which the light is injected.

[0010] However, the density of microstructures in a light extraction zone is limited by a maximum density. Such a maximum light density limits the size of the light guide for which homogeneity of the light extraction zones can be achieved. The size can be increased, but in this case, either the light intensity of the light guide must be limited or the light intensity homogeneity is affected.

[0011] There is thus a need to obtain a light module with a guide sheet for displaying a light pattern having good light homogeneity between the illuminated areas of the light pattern and having a large size.

[0012] The present invention improves the situation.

[0013] A first aspect of the invention relates to a light module comprising a light guide comprising a light guide sheet, the guide sheet being capable of receiving light rays through at least one light injection edge, and of returning the light rays in a direction substantially normal to the guide sheet, and at least one injection assembly capable of receiving light rays from an input surface and of guiding the light rays to inject them into the light injection edge of the guide sheet; a light source arranged to inject light rays into the input surface of the at least one injection assembly.

[0014] The guide sheet comprises a film, the film comprising at least one light extraction zone comprising microstructures capable of redirecting the light injected into the guide sheet at least in the substantially normal direction. The film comprises microstructures on a first face of the film and on a second face of the film. For each portion among portions of the light extraction zone having different respective distances from the light injection edge, a sum of a density of microstructures on a first face in said portion and a density of microstructures on the second face in said portion, is an increasing function of the distance between said portion and the light injection edge of the guide sheet.

[0015] Increasing the density of microstructures as a function of the distance from a light injection position makes it possible to produce a display on the light module with a homogeneous surface distribution of the light intensity. A light extraction dynamic is thus defined by the variation in microstructure densities as the distance from the light injection edge increases.

[0016] Forming microstructures on both sides of the guide sheet film makes it possible to extract light from the light guide over a longer distance. distance, while maintaining homogeneity in the surface distribution of light intensity in the light extraction zone. This makes it possible to produce larger light modules. Alternatively, for the same size, it is possible to extract more light from the light guide, thus increasing the brightness in the light extraction zone, while allowing homogeneity between the different parts of the light extraction zone.

[0017] According to embodiments, the parts of the light extraction zone may be opposite the same section of the light injection slice.

[0018] Such a section may correspond to a set of injection positions of an injection element of the injection assembly, when such an injection assembly comprises several injection elements, capable of injecting light rays into distinct and consecutive sections of the light injection slice. A light extraction dynamic is thus defined for each section, which allows good homogeneity in the distribution of the light intensity between the different parts of said at least one light extraction zone.

[0019] According to embodiments, a shape of said at least one light extraction zone can form a light pattern of the light module.

[0020] It is thus made possible to display a large light pattern with good uniformity of light intensity.

[0021] According to embodiments, the film may further comprise at least one dark area not comprising a microstructure, and shapes of said at least one dark area and said at least one light extraction area may together form a light pattern of the light module.

[0022] It is thus made possible to produce a complex light pattern of large size and with good homogeneity of light intensity.

[0023] According to embodiments, the guide sheet may be transparent and, for each part of said at least one light extraction zone, the density of microstructures may be less than a maximum density, the maximum density of microstructures being determined so that the microstructures are invisible when no light ray is injected by the light source.

[0024] It is thus made possible to produce a large, transparent light module with good uniformity of light intensity.

[0025] According to embodiments, for the parts of said at least one light extraction zone having different respective distances from the light injection wafer, the density of microstructures on the first face may be a first increasing function of the distance between the part and the light injection wafer, the first increasing function may have a maximum density of microstructures in at least the part furthest from the light injection wafer, and the density of microstructures on the second face in the part furthest from the light injection slice may be equal to the maximum density of microstructures.

[0026] Thus, the maximum density of microstructures is doubled by using both faces, which makes it possible to increase the size of the light module, or, for equal size, to increase the quantity of light extracted.

[0027] In addition, the density of microstructures on the second face may be zero in the part furthest from the light injection slice.

[0028] Thus, the light extraction dynamics is defined mainly by the first face. Furthermore, the manufacture of such a light module is facilitated, since the part of the second face of the film on which microstructures are formed is minimized.

[0029] Additionally or alternatively, the first face may be oriented towards the outside of the light module and the second face may be oriented towards the inside of the light module.

[0030] Thus, the face that primarily defines the extraction dynamics is oriented toward the outside of the light module, which maximizes the amount of light rays emitted toward the outside of the light module. The efficiency associated with the light module is thus improved.

[0031] According to embodiments, the film may be made of polycarbonate, PC, polymethyl methacrylate, PMMA, thermoplastic polyurethane, TUP, polyethylene terephthalate, PET, or silicone, and may have a thickness of between 25 and 1000 micrometers, in particular between 50 and 1000 micrometers, for example between 200 and 500 micrometers.

[0032] It is thus made possible to produce a flexible guide sheet, which facilitates its integration into any type of equipment.

[0033] A second aspect of the invention relates to motor vehicle equipment comprising a light module according to the preceding claim.

[0034] Other characteristics and advantages of the invention will appear on examining the detailed description below, and the appended drawings in which:

[0035] [Fig. 1] illustrates a sectional view of elements of a light guide for a light module according to embodiments of the invention;

[0036] [Fig.2] illustrates a front view of the elements of a light guide for a light module according to embodiments of the invention;

[0037] [Fig.3] illustrates a front view of the elements of a light guide for a light module according to embodiments of the invention;

[0038] [Fig.4] illustrates a three-dimensional view of a light guide injection assembly for a light module according to embodiments of the invention;

[0039] [Fig.5] illustrates a light pattern displayed on a guide sheet of a module luminous according to embodiments of the invention;

[0040] [Fig.6] illustrates microstructure densities in portions of light extraction zones of a light module according to embodiments of the invention;

[0041] [Fig.7] illustrates several views of a light guide of a light module according to embodiments of the invention;

[0042] [Fig.8] illustrates several views of a light guide of a light module according to other embodiments of the invention.

[0043] The description focuses on the features that distinguish the exterior equipment and the light module from those known in the state of the art.

[0044] [Fig.l] shows elements of a light guide 105 of a light module according to embodiments of the invention.

[0045] The light guide 105 comprises a guide sheet 110 which may be flexible and capable of receiving light rays via at least one light injection edge 114 and of returning the light rays in a Z direction substantially normal to a surface of the guide sheet which thus extends in an XY plane in [Fig. 1]. A guide sheet is understood to mean an optical guide element one of whose dimensions is much smaller than the other two dimensions in space, for example smaller by one or more orders of magnitude. As illustrated in [Fig. 1], a guide sheet 110 is considered here whose thickness along the Z axis is at least two orders of magnitude smaller than its dimensions along the XY plane in which the guide sheet 110 extends.

[0046] The guide sheet 110 may comprise a film 111 at its core, which may be flexible, comprising the light injection edge 114, being capable of guiding the light rays in a global direction X, and comprising a set of microstructures 113 capable of returning the light rays guided in the film 111 outside the flexible guide sheet 110, in particular in one or more directions substantially along the Z axis.

[0047] The film 111 may be a substrate film made of polycarbonate, PC, polymethyl methacrylate, PMMA, thermoplastic polyurethane, TUP, polyethylene terephthalate, PET, silicone, or even glass. The film 111 may have a thickness, i.e. a dimension along the Z axis, of between 12 and 1000 micrometers. More precisely, the thickness of the film 111 may be between 25 and 1000 micrometers, in particular between 50 and 1000 micrometers, for example between 200 and 500 micrometers. Alternatively, it is the guide sheet 110 which has a thickness of between 200 and 1000 micrometers.

[0048] The aforementioned materials, combined with a low thickness as described above, make it possible to obtain a flexible and transparent film 111. Other materials may be provided for the composition of the film 111. However, it is preferable according to the invention of providing deformable and transparent materials.

[0049] A thin coating of microstructures 113 can be created on one of the faces of the film 111, or in the film 111. According to the invention, microstructures 113 are formed on both faces of the film, as will be better understood upon reading the description of figures 5 and following.

[0050] The microstructures are formed on the surface of the film in a distribution that makes it possible to produce a light pattern. The light pattern is obtained from light extraction areas that are areas of the film 111 comprising microstructures 113. The light pattern may also comprise dark areas, which are areas of the film 111 that do not comprise microstructures 113. The respective arrangements and the shapes of the light extraction areas and the dark areas together form the light pattern. Alternatively, the light pattern comprises only one light extraction area of ​​a given shape.

[0051] Microstructures 113 are structures, or irregularities, of the flexible film, at least one of the dimensions of which is less than a few micrometers. For example, the microstructures 113 may be of the order of 50 micrometers in diameter and 1 or 2 micrometers in height. The microstructures thus also cover nanometric structures. Such sizes of microstructures 113 make it possible to ensure high transparency of the flexible film 111. In particular, a transparency of the order of 97% can be obtained in practice by the use of microstructures 113. Alternatively, the guide sheet may be semi-transparent.

[0052] The microstructures are capable of redirecting the light injected into the light guide in one or more directions different from the injection direction along the X axis. In particular, at least some of the redirected light rays are redirected in a direction substantially parallel to the Z axis, in particular in a direction directed towards the outside of the light module 100. In practice, such microstructures are capable of redirecting the guided light rays in all directions of space, in a Lambertian manner.

[0053] No restriction is attached to the manner in which the microstructures 113 are formed on the face of the film 111. The microstructures 113 can be obtained by adding or removing material from the flexible film.

[0054] For example, the microstructures can be obtained by embossing by applying a roller having irregularities to mechanically print microstructures on the surface of the film 111. Alternatively, the microstructures 113 can be obtained by irradiation, for example by UV rays, by baking a polymer in contact with a mold, a roller or any other surface comprising irregularities capable of forming the microstructures by shape complementarity.

[0055] As a further variant, the microstructures 113 are formed at locations where a re flexible film clothing made of a material having a low refractive index, is removed from the flexible film, so as to form microstructures by material removal. In this case, the micro structures are holes or gaps. Optionally and complementary, additional surface or volume elements, prismatic, reflective, diffracting or diffusing, can be added in the holes or gaps to form the micro structures 113.

[0056] The microstructures 113 can be obtained by treating the surface of the film 111, in which case they are of the same material as the film 111 or correspond to an absence of material from the film 111. Such treatment can be by mechanical or laser tracing, by laser ablation, by sandblasting, by exposure to radiation, by chemical treatment or by any other treatment making it possible to obtain irregularities in a controlled manner on the face of the film 111.

[0057] Alternatively or in a complementary manner, the microstructures 113 are elements exogenous to the film added to the face of the film 111.

[0058] The microstructure coating 113 may in particular have a thickness along the Z axis of less than 20 micrometers.

[0059] As detailed later, the density of the microstructures 113 may vary in the light extraction zones depending on their distance from the light injection edge 114.

[0060] The term “pattern” means any predefined spatial distribution or distribution of the light intensity emitted by the light module. In particular, reference is made here to a two-dimensional or one-dimensional pattern. A pattern may thus comprise a homogeneous distribution of the light over the entire guide sheet, in which case a light extraction zone extends over the entire guide sheet. The pattern may also be a two-dimensional shape or symbol obtained by contrast between the light extraction zones and the dark zones of the guide sheet 110. The pattern may also comprise several shapes or symbols. Alternatively, a pattern covers a predefined spatial distribution of the light intensity not showing a general shape, such as a distribution inducing a cloud of light points.

[0061] The flexible guide sheet 110 may further comprise one or two optional protective layers 112.1 and 112.2, which make it possible to mechanically protect the film 111. In addition, at least one of the protective layers 112.1 and 112.2 may comprise an anti-UV treatment, preferably the protective layer 112.1 through which the light rays returned by the microstructures 113 are emitted, making it possible to protect the film against UV rays, once the microstructures 113 have been created. Without such UV protection, the pattern projected by the guide sheet 110 is likely to degrade over time, in particular when it is exposed to the sun's rays.

[0062] The film 111 and the protective layers 112.1 and 112.2 are shown spaced apart in [Fig.l], for illustrative purposes only. It will be understood, however, that the protective layers 112.1 and 112.2 may be attached to the film 111, in particular by lamination.

[0063] The propagation of the light rays in the film 111 is done by total internal reflection thanks to the difference between the refractive index of the film 111 and that of a layer of glue or adhesive applied to at least one face of the flexible film.

[0064] The assembly of the film 111 with the protective layers 112.1 and 112.2 can be done by gluing. Specifically, a layer of glue is located between the film 111 and each protective layer 112.1 and 112.2, and this on both sides of the film to adhere the protective layers to the film 111.

[0065] The chosen glue is transparent and has a refractive index different from, in particular lower than, that of the film so as to allow total internal reflection in the film 111. For example, the glue may comprise silicone or acrylic. In other words, due to the difference in refractive indices, the light rays propagating in the film 111 undergo total reflection when they encounter the interface between the film 111 and the glue layer with an angle of incidence lower than the normal incidence. Thus, the guide sheet is capable of guiding light by total internal reflection of this light, for example from an entry zone, here the injection edge 114, to an exit zone.

[0066] Since the guide sheet 110 can be flexible, it is not necessarily included in a plane but can be curved, depending on the position in which it is placed and the mechanical constraints applied to it.

[0067] The light guide 105 illustrated in [Fig.l] also comprises an injection assembly 120 comprising several light injection elements, described with reference to the following figures, the assembly 120 being capable of distributing the light in the guide sheet 110 at different positions along the Y axis, along the light injection edge 114. The light is injected, at each position along the Y axis, in a direction substantially parallel to the X axis.

[0068] The injection assembly 120 comprises an inlet surface 121 of rectangular or square section in [Fig.l]. However, the assembly 120 may have an inlet surface having a different shaped section.

[0069] In [Fig.l], the injection assembly 120 is shown with an outlet surface 122 extending in the Y direction and placed opposite the light injection edge 114. It will be understood from reading the description of the following figures that the outlet surface 122 and the light injection edge 114 are merged, the flexible film 111 and the injection assembly 120 forming a single piece.

[0070] The injection assembly 120 further comprises the input surface 121, at one end of the injection assembly 120, capable of receiving light rays from a light source external to the light guide 105 and not shown in [Fig.l], and the injection assembly 120 is capable of guiding the light longitudinally along the Y axis by distributing it on the output surface 122. The distribution of light by the output surface 122 will be better understood in the light of the description of the following figures.

[0071] [Fig.2] shows elements of a light module 100 comprising a light guide 105 with a set 120 of injection elements and a flexible guide sheet 110, and a light source 130.

[0072] Depending on the distribution of the microstructures 113, the guide sheet 110, or more precisely the film 111, may comprise a mixing zone 111.2 and a light emission zone 111.1, the light zone comprising at least one light extraction zone provided with the microstructures 113, and optionally one or more dark zones, so as to produce a light pattern in the light emission zone 111.1. The mixing zone 111.2 is arranged upstream of the light emission zone according to the direction of propagation of the light rays. The light emission zone 111.1 is integrated in a region 1110

[0073] The light injected into the light guide sheet 110 via the injection edge 114 is mixed in the mixing zone 111.2 in order to obtain better light homogeneity. The light then propagates into the light emission zone 111.1 through which the light emerges from the light guide sheet 110 in the Z direction.

[0074] More generally, the mixing zone 111.2 is an area of ​​the flexible guide sheet not comprising the light pattern emitted by the flexible guide sheet 110, the mixing function of the zone 111.2 being optional.

[0075] The set 120 of injection elements 120.1 is capable of injecting light rays from the source 130 into the injection slice 114 towards the mixing zone 111.2. In [Fig.2], a single injection set 120 is shown, for illustrative purposes.

[0076] Note that the light guide 105 may comprise several injection assemblies 120 per injection slice 114, each injection assembly 120 being arranged at a given set of Y positions of the injection slice 114. Each injection assembly 120 is thus configured to illuminate a different region 1110 in the light guide sheet. In the following, a single injection assembly 120 per injection slice 114 is considered, for illustrative purposes.

[0077] The assembly 120 comprises several light injection elements 120.1. The assembly 120 may in particular comprise between three and ten injection elements 120.1. In the non-limiting example of [Fig.2], the light guide 105 comprises a set 120 with ten injection elements. For reasons of clarity, only two light injection elements 120.1 have been referenced.

[0078] The assembly 120 is coupled with at least one light source 130 so as to receive the light rays R emitted by said light source in each of the light injection elements 121.

[0079] Given that the light injection elements 121 are obtained by cutting from the same material as the flexible film 111, the light rays R will propagate by total internal reflection in the light injection elements 120.1 so as to bring light to the light guide sheet which is adjacent and integral with the light injection elements 120.1, and the light will thus illuminate the light extraction zone(s) of the light guide sheet 110.

[0080] The superposition of the light injection elements 120.1 forming the assembly 120 can thus be a coupling bar, or light bar, configured to receive the light rays coming from the light source 130 and propagate them in the light guide sheet 110. The assembly 120 can be of square or rectangular section.

[0081] No restriction is attached to the light source 130, which may be any light source technology. For example, the light source 130 may be an electroluminescent element, such as an LED for example, mounted on a substrate 131. A heat dissipation element 132 may furthermore be arranged below the substrate 131.

[0082] The light source 130 may be capable of generating light in a range of wavelengths. Such an interval may be centered around a visible color, in order to generate colored light, for example blue, red or green. Alternatively, the light source 130 may emit light rays over the entire range of wavelengths visible to the human eye, so as to generate white light. The light source 130 may be controlled by a control element not shown. Alternatively, the light source 130 is not arranged directly opposite an input surface 121 of the injection element 120, but the light module 100 further comprises an optical fiber placed between the source 130 and the injection assembly 120, which makes it possible to offset the source 130 relative to the light guide 105.

[0083] It is thus made possible to inject light at different longitudinal positions along the Y axis of the injection slice 114.

[0084] The guide sheet 110 may have a width La along the Y axis and a length Lg along the X axis. The light guide 105 may be cut from a roll of the same material as the film 111 and the injection elements 120, the roll extending along the X axis and having the same width La as the light guide 105.

[0085] The references (pj) refer to injection positions of index j, each injection position of index j corresponding to an interval of positions along the injection Y axis in the injection slice 114, j varying between 1 and N, N being the number of injection elements 120.1 in the injection assembly 120 (i.e. N=10 in the example considered so far).

[0086] The light module 100 thus comprises the light guide 105, comprising the flexible guide sheet 110 and the injection assembly 120, and the light source 130.

[0087] A non-visible part 13 of the light module 100 may comprise the assembly 120 and the light source 130. Such a part may be hidden while the light emission zone 111.1 is on the contrary visible from the outside of equipment comprising the light guide 105.

[0088] [Fig. 3] illustrates the light guide of [Fig. 2] with the light injection elements 120.1 of the injection assembly 120 being unfolded. In [Fig. 3], each injection element 120.1 has a respective length Lh and has a width W.

[0089] For the sake of clarity in [Fig. 3], only the length Lh and the width W of the longest injection element 120 have been referenced. The lengths Lh of the other injection elements 120 are less than the length Lh of the longest injection element. On the other hand, the widths W of all the injection elements 120.1 may be equal.

[0090] By way of non-limiting example, the length Lh of the longest injection element 120.1 is between 100 and 500 millimeters. Similarly, the width W can be between 1 and 20 mm.

[0091] A folding position 300 is further indicated in [Fig. 3], each injection element 120.1 being capable of being folded into the folding position 300 so that the injection elements 120.1 are superimposed to form the assembly 120. The respective lengths Lh of the injection elements are determined from the folding position and the respective Y positions of the injection elements, so that their ends together form the injection surface 121.

[0092] [Fig.4] illustrates a three-dimensional view of the assembly 120 and the light source 130, of a light module 100 according to embodiments of the invention.

[0093] As illustrated in [Fig. 4], each light injection element 120.1 has a thickness e. The thickness e corresponds to the thickness of the light guide 105, i.e. the film 111. The light injection element 120.1 comprises two ends 120.10, one of which, illustrated in [Fig. 2], is secured to the guide sheet 110 and the other, illustrated in [Fig. 4], is able to face the light source 130. The light rays emitted by the light source 130 enter through one end 120.10, called the first end, and are transmitted to the other end 120.10, called the second end, then to the light guide sheet 110 via the light injection edge 114, which coincides with the second ends 120.10 injection elements 120.1.

[0094] It should be noted that during the manufacturing process of the light guide 105, the injection elements 120.1 and the light guide sheet 110 can be manufactured from a roll of material, engraved according to a given pattern, then cut or sheared, to separate the light guide 105 from the rest of the roll, and to separate the different injection elements 120.1 along the X axis and thus form the different injection elements 120.1 before folding according to the folding position 300.

[0095] Thus, the light injection elements 120.1 remain attached to the guide sheet 110 on their second ends 120.10.

[0096] The respective lengths Lh of the injection elements 120.1 are such that the first ends 120.10 facing the light source 130 coincide to form the injection surface 121 of the assembly.

[0097] The injection surface 121 thus has a thickness E equal to the sum of the thicknesses e of the injection elements 120.1.

[0098] [Fig.5] shows a guide sheet 110 of a light guide of a light module 100 according to embodiments of the invention.

[0099] The injection assembly 120 is not shown in [Fig.5], for the sake of simplification.

[0100] A light pattern is formed from four light extraction zones 502.1, 502.2, 502.3 and 502.4 comprising microstructures not shown in [Fig.5], as well as a dark zone 504 not comprising microstructures. The dark zone 504 and the light extraction zones 502.1, 502.2, 502.3 and 502.4 are complementary and together form the light pattern in the light emission zone 111.1.

[0101] An injection position 501 in the light injection slice 114 is shown in [Fig. 5]. The injection position 501 corresponds to a position along the Y axis opposite which there is a portion 503.1 of the first light extraction zone 502.1, a portion 503.2 of the second light extraction zone 502.2, a portion 503.3 of the third light extraction zone 502.3 and a portion 503.4 of the fourth light extraction zone 502.4. Preferably, the injection position 501 is a section 501 comprising an interval of Y positions. It may for example be a set of Y positions corresponding to an injection element 120.1 among the set 120 of injection elements 120.1.

[0102] No restriction is attached to each of the parts 503.1 to 503.4 which is any surface of size greater than the dimensions of the microstructures, preferably at least ten times greater than the dimensions of the microstructures, so as to be able to determine a density of microstructures there.

[0103] The light rays injected into the injection position 501, and possibly light rays injected near the injection position 501, i.e. in two close Y positions, are guided in the guide sheet 110, and the light rays are progressively extracted from the guide sheet 110 by the part 503.1, then by the part 503.2, then by the part 503.3, then by the part 503.4.

[0104] In order to allow the light intensity in each of the portions 503.1 to 503.4 to be close, and consequently in order to allow having a light pattern with a homogeneous light intensity, the respective densities of microstructures within the portions 503.1 to 503.4 may vary as illustrated in [Fig.6].

[0105] In particular, the density of microstructures in a portion of a light extraction zone depends on a distance between the portion and the light injection slice 114.

[0106] [Fig.6] illustrates the microstructure densities in portions of light extraction zones illustrated in [Fig.5].

[0107] As shown in [Fig.6], the density of microstructures 113 in a given portion varies positively with (or is an increasing function of) the distance between the portion and the light injection slice 114. Indeed, the quantity of light rays reaching the portion 503.4 is less than that reaching the portion 503.1. In order to compensate for this, the density of microstructures in the portion 503.4 is greater than in the portion 503.1.

[0108] No restriction is attached to the increasing function that relates the distance to the light injection slice 114 to the microstructure density 113. Such a function depends on the desired brightness for the light pattern, the intrinsic characteristics of the light guide 110 and the light source 130.

[0109] In the example described in [Fig.5], the X positions of the parts 503.1 to 503.4 are non-consecutive. The parts 503.1 to 503.4 are notably separated by the dark zone 504 of the light pattern.

[0110] However, particularly when the light pattern comprises only a single light extraction zone (hence no dark zone), parts of the single light extraction zone having consecutive positions can be considered to describe the variation of the microstructure densities 113. Such an example is used to describe [Fig.7] below.

[0111] As explained in the introductory part, the density of the microstructures 113 is limited, that is to say that it is not possible to indefinitely increase the density of the microstructures 113 as a function of the distance from the light injection slice 113. This results in: - either the size of the guide sheet is limited if we wish to maintain a homogeneous pattern; - either the guide sheet is not limited by its size, but the density of the microstructures saturates and the light pattern is not homogeneous. Indeed, the intensities luminous intensities of the light extraction zone parts beyond the X position at which the density saturates are lower than the luminous intensities before saturation.

[0112] [Fig.7] shows a side view, a top view and a bottom view of a film 111 of a light module guide sheet according to embodiments of the invention.

[0113] According to the invention, micro structures 113 are formed both on an upper face 701 but also on a lower face 702 of the guide sheet 110.

[0114] The microstructures 113, whether formed on the upper face 701 or on the upper face 702, are capable of returning the light at least in one direction substantially along the Z axis, towards the outside of the upper face 701, the upper face being oriented towards the outside of the light module 100.

[0115] Thus, the quantity of light extracted at each interval of positions in X of the guide sheet depends on the sum of the density of the microstructures on the upper face 701 and the density of the microstructures 113 on the lower face, in the interval of positions in X. Thus, by noting dmax as the maximum density of microstructures 113 on a given surface, the sum of the densities for each interval of positions in X can vary between 0 and 2*dmax, instead of a variation between 0 and dmax in the prior art.

[0116] The sum of the microstructure densities 113 on the upper face 701 and on the lower face 702, for a given part of the light extraction zone, is an increasing function of the distance between the light injection slice 114 and said part. In other words, for any pair of parts facing the same section of the injection slice, the part closest to the injection slice has a sum of microstructure densities on its two faces which is less than the same sum for the most distant part.

[0117] It is thus made possible: - to increase the quantity of light extracted at equal guide sheet size 110, while displaying a light pattern with homogeneous distribution of light intensity; - to increase the size of the guide sheet 110 while displaying a light pattern with uniform brightness.

[0118] The maximum density dmax may correspond to the density below which the microstructures 113 are invisible when no light ray is injected into the guide sheet 110. Such a maximum density is advantageous when a transparent guide sheet 110 is used.

[0119] Alternatively, the maximum density may correspond to a density from which the microstructures 113 are in contact with each other. The maximum density can also be fixed by the manufacturing method of the light guide 105.

[0120] In the example of [Fig.7], the density of the microstructures 111 on the upper face increases with the distance from the light injection edge, up to saturation for a certain value of X, denoted XL. Beyond the saturation value of XI, microstructures 113 can be formed on the lower face 702, so that the sum of the densities on the two faces continues to increase with the distance from the light injection edge. Alternatively, as shown in [Fig.7], the microstructures are formed on the lower face from a value X2, greater than XL.

[0121] As for [Fig.5], the light extraction zone can be decomposed into parts. Regardless of the part decomposition used, the sum of the microstructure densities on the upper and lower faces of a part is an increasing function of the distance of the part from the light injection edge 114. In other words, the further a part is from the light injection edge 114, the greater the sum of the densities on its lower and upper faces.

[0122] As shown in [Fig.7], the lower face 701 only comprises microstructures in the part furthest from the injection slice, i.e. the part beyond X2. The part between X1 and X2 is a part of the upper face 701, for which the density of microstructures is maximum, but the lower face does not comprise any microstructures in this part.

[0123] Note that, in [Fig. 7], the sum of the microstructure densities increases continuously because a single extraction zone is represented, not interrupted by one or more dark zones. However, the invention applies indifferently to light patterns having dark zones, and the growth of the density of the microstructures as a function of the distance from the light injection edge only applies to parts of light extraction zones, and not to dark zones, which do not include any microstructure.

[0124] Other distributions of the microstructures 113 than those shown in [Fig.7] are conceivable within the framework of the invention.

[0125] For example, [Fig.8] shows a side view, a top view and a bottom view of a film 111 of a light module guide sheet according to embodiments of the invention, with a distribution of microstructures 113 different from that of [Fig.7].

[0126] According to the distribution of [Fig.8], the microstructure densities increase with the distance from the light injection edge 114 for each of the upper 701 and lower 702 faces. The sum of the densities therefore also increases with the distance from the light injection edge 114.

[0127] According to the example of [Fig. 8], regardless of the parts of said at least one light extraction zone, the density of microstructures on the upper face 701 in a part is a first increasing function of the distance of the part from the light injection edge 114. Similarly, the density of microstructures on the lower face 702 in a part is a second increasing function of the distance of the part from the light injection edge. As shown in [Fig. 8], the first and second functions may be different. The function corresponding to the sum of the densities of the microstructures on the upper 701 and lower 702 faces is thus a sum of the first function and the second function, which is also increasing.

[0128] The present invention is not limited to the embodiments described above as examples; it extends to other variants.

Claims

1. Claims Light module (100) comprising • a light guide (105) comprising a light guide sheet (110), the guide sheet being capable of receiving light rays via at least one light injection edge (114), and of returning the light rays in a direction substantially normal to the guide sheet, and at least one injection assembly (120) capable of receiving light rays from an entry surface (121) and of guiding the light rays to inject them into the light injection edge of the guide sheet; • a light source (130) arranged to inject light rays into the input surface of the at least one injection assembly; wherein the guide sheet comprises a film (111), the film comprising at least one light extraction zone (502.1; 502.4) comprising microstructures (113) capable of redirecting the light injected into the flexible guide sheet at least in the substantially normal direction; wherein the film comprises microstructures on a first face (701) of the film and on a second face (702) of the film; wherein, for each of portions (503.1; 503.4) of the light extraction area having different respective distances from the light injection edge, a sum of a density of microstructures on the first face in said portion and a density of microstructures on the second face in said portion is an increasing function of the distance between said portion and the light injection edge of the guide sheet, and wherein said guide sheet (110) is transparent and wherein, for each portion (503.1; 503.4) of said at least one light extraction zone (502.1; 502.4), the density of microstructures (113) is less than a maximum density, the maximum density of microstructures being determined so that the microstructures are invisible when no light ray is injected by the light source.

2. Light module according to claim 1, in which the parts (503.1; 503.4) of the light extraction zone are opposite the same section (501) of the light injection edge (114).

3. A light module according to claim 1 or 2, wherein a shape of said at least one light extraction area (502.1; 502.4) forms a light pattern of the light module (100).

4. A light module according to one of the preceding claims, wherein the film (111) further comprises at least one dark area (504) not comprising a microstructure (113), and wherein shapes of said at least one dark area and said at least one light extraction area (502.1; 502.4) together form a light pattern of the light module.

5. A light module according to one of the preceding claims, wherein for the portions (503.1; 503.4) of said at least one light extraction zone (502.1; 502.4) having different respective distances from the light injection wafer (114), the density of microstructures (113) on the first face (701) is a first increasing function of the distance between the portion and the light injection wafer, wherein the first increasing function has a maximum density of microstructures in at least the portion furthest from the light injection wafer, and wherein the density of microstructures on the second face in the portion furthest from the light injection wafer is equal to the maximum density of microstructures.

6. A light module according to claim 5, wherein the density of microstructures (113) on the second face (702) is zero in the parts (503.1; 503.4) of the light extraction zone (111.1) other than said part furthest from the light injection edge.

7. A light module according to claim 5 or 6, wherein the first face (701) is oriented towards the outside of the light module (100) and the second face (702) is oriented towards the inside of the light module.

8. A light module according to any preceding claim, wherein the film (111) is made of polycarbonate, PC, polymethyl methacrylate, PMMA, thermoplastic polyurethane, TUP, polyethylene terephthalate, PET, or silicone, and has a thickness of between 50 and 1000 micrometers, for example between 200 and 500 micrometers.

9. Motor vehicle equipment comprising a light module (100) according to one of the preceding claims.

Images