FR3150750A1 - Surface light guide for vehicle - Google Patents

Abstract

The invention relates to a surface light guide (1) for a vehicle comprising at least one group (10) of light injection elements (100) and a light guide sheet (11), said at least one group (10) being intended to be coupled to at least one light source (20) and said light injection elements (100) being folded so as to form a stack (103). According to the invention, the stack (103) comprises - a light mixing zone (103.0) configured to be arranged opposite said at least one light source (20), - an entry surface (103.1) configured to receive the light rays emitted by said at least one light source (20), and located at the end of said light mixing zone (103.0). Abstract: Figure 1

Description

Surface light guide for vehicle

The present invention relates to a surface light guide for a vehicle. It finds a particular but non-limiting application in motor vehicles.

A surface light guide known to those skilled in the art comprises a group of light injection elements and a light guide sheet, said group of light injection elements being configured to be coupled to at least one light source. The light injection elements are folded to form a stack. The stack has an entry surface configured to receive light rays emitted by the light source.

A disadvantage of this prior art is that when light enters a light injection element, it is coupled to this light injection element and does not exit. Consequently, there is an inhomogeneous distribution of light in the different light injection elements depending on their positioning in the stack relative to the light source. Indeed, since the light source arranged in front of the stack emits light in a cone, also called a light distribution cone, the light injection elements located at the upper and lower ends of the stack receive less light than those located in the middle of the stack. Consequently, the light that is injected by the light injection elements up to the light guide sheet (which is adjacent to the light injection elements) is injected inhomogeneously, and is thus transmitted to the outside by the light guide sheet inhomogeneously.

In this context, the present invention aims to provide a light guide which makes it possible to solve the mentioned drawback.

For this purpose, the invention proposes a surface light guide for a vehicle comprising at least one group of light injection elements and a light guide sheet, said at least one group being intended to be coupled to at least one light source and said light injection elements being folded so as to form a stack, characterized in that said stack comprises:
- a light mixing zone configured to be arranged opposite said at least one light source,
- an input surface configured to receive the light rays emitted by said at least one light source, and located at the end of said light mixing zone.

Thus, as we will see in detail later, the grouping of the ends of the injection elements allows the light to be reflected over the entire width of the stack so as to have at the exit of the light mixing zone a good homogeneity of light which is subsequently injected by the light injection elements up to the light guide sheet. All the light injection elements thus receive the same quantity of light.

According to non-limiting embodiments, said light guide may further comprise one or more additional characteristics taken alone or in all technically possible combinations, among the following.

According to a non-limiting embodiment, each light injection element comprises a main part and an end part separated by a fold. The fact that the light injection elements are folded makes it possible to reduce the size of the light guide. Furthermore, the fold makes it possible to redirect the light towards the light guide sheet.

According to a non-limiting embodiment, said end portions of said light injection elements are partially embedded in the resin to form said light mixing zone. This makes it possible to use different hot or UV polymerization processes for example. It should be noted that the temperatures used for hot polymerization are low, which prevents damage to the injection elements.

According to a non-limiting embodiment, said end portions of said light injection elements are partly grouped by fusion to form said light mixing zone. This makes it possible to reduce the material cost of the light guide.

According to a non-limiting embodiment, said light guide sheet is composed of a core and an envelope with a light refraction index lower than that of the core. This makes it possible to propagate the light rays in the core by total internal reflection.

According to a non-limiting embodiment, each light injection element is composed of only one core. This makes it possible to improve the mixing of the light rays at the entrance to the stack.

According to a non-limiting embodiment, said light guide sheet extends along a first direction and along a second direction and said light injection elements are adjacent to said light guide sheet by their main parts, their main parts extending along the first direction and their end parts extending along the second direction.

According to a non-limiting embodiment, said light guide sheet comprises at least one light emission zone comprising all or part of a light pattern.

According to a non-limiting embodiment, said at least one light source is a semiconductor light source.

According to a non-limiting embodiment, said semiconductor light source is a light-emitting diode or a laser diode.

According to a non-limiting embodiment, the end portions of the light injection elements are composed of first portions and second portions, one of which is part of the light mixing zone and the other of which is not part of the light mixing zone.

According to a non-limiting embodiment, the first parts are embedded in the resin.

According to a non-limiting embodiment, the first parts are grouped by merger.

According to a non-limiting embodiment, the resin has a light refraction index close to the light refraction index of the light injection elements. There is thus no reflection at the index jump.

Also provided is a lighting device for a vehicle, said lighting device comprising at least one light guide according to any one of the preceding characteristics and at least one light source arranged opposite said light mixing zone.

According to a non-limiting embodiment, said at least one light source has a light emission surface less than the thickness of said stack.

The invention and its various applications will be better understood by reading the description which follows and by examining the figures which accompany it:

is a schematic illustration of a surface light guide according to a first non-limiting embodiment of the invention, the light guide comprising a light guide sheet and a group of light injection elements, the light injection elements being folded so as to form a stack with a light mixing zone,

is a view of the light guide of the with the light injection elements that are unfolded,

is an enlarged view of a portion of light injection elements of the same group of light injection elements of the light guide according to the or the ,

is a view of one side of the stack formed by the light injection elements of the with the mixing zone,

is a side view of the light guide sheet of the light guide of the , the light guide sheet comprising, according to a non-limiting embodiment, a core and an envelope,

is a side view of the stack according to a first non-limiting embodiment, the stack being formed by the light injection elements of the which are partly embedded in resin to form the light mixing zone,

is a side view of the stack according to a second non-limiting embodiment, the stack being formed by the light injection elements of the which are partly grouped together by fusion to form the light mixing zone,

is a schematic illustration of a surface light guide according to a second non-limiting embodiment of the invention, the light guide comprising a light guide sheet and groups of light injection elements, the light injection elements being folded so as to form a stack with a light mixing zone.

Identical elements, by structure or function, appearing in different figures retain, unless otherwise specified, the same references.

The light guide 1 according to the invention is described with reference to FIGS. 1 to 8. In a non-limiting embodiment, the light guide 1 is a light guide for a vehicle. In a non-limiting embodiment, the vehicle (not illustrated) is a motor vehicle. By motor vehicle, we mean any type of motorized vehicle. This embodiment is taken as a non-limiting example in the remainder of the description. In the remainder of the description, the vehicle is thus otherwise called a motor vehicle. In a non-limiting variant embodiment, the vehicle is a thermal vehicle or an electric vehicle.

The light guide 1 is surface-based. Thus, it can be adapted to any type of flat or curved surface. A surface-based light guide is understood to mean an optical guiding element of which one of the dimensions is much smaller than the other two dimensions in space, for example smaller by one or more orders of magnitude. Here, the thickness of the light guide 1 is much smaller than its length and width. In a non-limiting embodiment, the light guide 1 has a thickness of between 10 and 1000 µm (micrometers). In a non-limiting variant embodiment, the thickness is between 50 and 1000 µm. In a non-limiting example, the thickness is 50 µm. The light guide 1 is thus very thin.

In a non-limiting embodiment, said light guide 1 is flexible. By flexible, it is understood that the light guide 1 is adapted to be curved without being damaged or breaking. It can thus be arranged in a lighting device 2 and follow curves linked to a particular style of said lighting device 2. The lighting device 2 may comprise a mask. In non-limiting embodiments, the lighting device 2 is a lighting and/or signaling device, or all or part of a front face or a rear face of the motor vehicle. A part of the front face may be the grille or the bumper in non-limiting examples. In non-limiting embodiments, the lighting and/or signaling device is a headlight or a rear light.

Due to the fact that it is surface-mounted and flexible, the light guide 1 is configured to be placed on the front face of the motor vehicle or in a headlight or rear light of the motor vehicle, for example behind an outlet window of the headlight or rear light or in front of a mask of the headlight or rear light.

In a non-limiting embodiment, the light guide 1 is made of polycarbonate (PC), polymethyl methacrylate (PMMA), thermoplastic polyurethane (TPU), or polyethylene terephthalate (PET). Such materials make it possible to produce a flexible light guide 1.

Light guide 1 includes:
- at least one group 10 of light injection elements 100, and
- a light guide sheet 11 comprising at least one light emission zone 110.

As illustrated in Figures 1 and 2, the light guide 1 comprises a group 10 of light injection elements 100 and the light guide sheet 11 comprises a single light emission zone 110 comprising all or part of a light pattern 111. In a non-limiting embodiment, the light guide sheet 11 comprises a plurality of light emission zones.

The light pattern 111 is formed by a plurality of microstructures for decoupling the light from the light guide 1. The light pattern 111 may extend over one or more light-emitting zones 110. In a non-limiting example, the light pattern 111 may be a logo. Thus, in this case, an illuminated logo can be obtained. In the non-limiting example illustrated in FIGS. 1 and 3, the light pattern 111 is arranged in the light-emitting zone 110 and has a rectangular shape.

As illustrated in the , the light guide 1 comprises a plurality of groups 10 of light injection elements 100 and the light guide sheet 11 comprises a light emitting area 110. In the non-limiting example illustrated in the , it includes three groups 10.

The light guide sheet 11 extends in its width La in a first direction y and in its length Lg in a second direction z substantially perpendicular to the first direction y and to a third direction x. It will be noted that this can be the reverse. It will be noted that the width La and the length Lg can be equal. It will be noted that the third direction x is substantially perpendicular to the front face or the rear face of the vehicle when the light guide 1 is mounted on the front face or the rear face of the vehicle. Specifically, the third direction x is perpendicular to the surface on which the light guide 1 is mounted. In a non-limiting embodiment, said surface is part of the front face or the rear face of the vehicle. In a configuration where this surface is curved, the third direction x is perpendicular to the tangent of the curvature of this surface.

As illustrated in the , in a non-limiting embodiment, the light guide sheet 11 is composed of a core 11.5 and a shell 11.6 with a light refractive index lower than that of the core 11.5. The core 11.5 is a flexible film. In a non-limiting embodiment, the core 11.5 has a thickness of between 25 µm (micrometers) and 150 µm. In a non-limiting variant embodiment, the thickness is approximately 50 µm. The thickness is defined such that it is necessary to be able to handle the film during its manufacture and to resolve the integration problem (forming, molding). In a non-limiting embodiment, the shell 11.6 has a thickness of between 10 µm and 40 µm. In a non-limiting variant embodiment, the thickness is between 25 µm and 40 µm.

The envelope 11.6 is arranged on either side of the core 11.5. In a non-limiting embodiment, the envelope 11.6 is a glue, namely it is made of an optical adhesive material, which allows it to adhere to the core 11.5. In another non-limiting embodiment, the envelope 11.6 is made from polymerizable resin, which allows it to naturally adhere to the core 11.5. The resin is polymerized by UV or heat in non-limiting examples. In other non-limiting embodiments:
- the envelope 11.6 is overmolded on the core 11.5, or
- the core 11.5 is dipped in a resin bath which serves as an envelope 11.6 by an immersion process called in English “Deep Coating”, or
- the core 11.5 and the envelope 11.6 are two films that are laminated to each other with an adhesive to assemble them. In this case, the adhesive has the same light refraction index as the core 11.5 or the envelope 11.6.

As illustrated in the , in the unfolded state, the light injection elements 100 extend mainly along the first direction y in a non-limiting embodiment. The dimension measured along this first direction y is thus considered to be the length Lg' of the light injection element 100.

It will be noted that during the manufacturing process of the light guide 11, the light injection elements 100 and the light guide sheet 11 are manufactured from a large sheet which is sheared on one end to separate the different light injection elements 100 along the y axis illustrated in the (in the non-limiting example illustrated) and thus form the different light injection elements 100 and the light guide sheet 11. Thus, the light injection elements 100 remain attached to the light guide sheet 11 on one of their ends.

The groups 10 and the light injection elements 100 are described in detail below.

A group 10 comprises several light injection elements 100. In a non-limiting embodiment, it comprises between three and ten light injection elements 100. In a non-limiting alternative embodiment, it comprises ten light injection elements 100. In the non-limiting example of the , the light guide 1 comprises three groups 10 and each group comprises ten light injection elements 100.

A group 10 is coupled with at least one light source 20. Said at least one light source 20 is configured to emit light rays R (illustrated in FIGS. 4, 6 and 7) which will propagate by total reflection in the light injection elements 100 of the group 10 (including the light mixing zone 103.0 described later) so as to bring light to the light guide sheet 11 which is adjacent to the light injection elements 100 and which will thus illuminate the light emission zone(s) 110 of the light guide sheet 11. In a non-limiting embodiment, each group 10 is coupled with a plurality of light sources 20. In another non-limiting embodiment, each group 10 is coupled with a single light source 20. This latter non-limiting embodiment is taken as a non-limiting example in the remainder of the description. Said light source 20 is part of the lighting device 2. It is arranged opposite the light mixing zone 103.0 described later.

In a non-limiting embodiment, the light source 20 is a semiconductor light source. In a non-limiting embodiment, the semiconductor light source is part of a light-emitting diode or a laser diode. By light-emitting diode, we mean any type of light-emitting diode, whether in non-limiting examples LEDs ("Light Emitting Diode" in English), OLEDs ("Organic LED" in English), AMOLEDs ("Active-Matrix-Organic LED" in English), or FOLEDs ("Flexible OLED" in English). In a non-limiting embodiment, the light source 20 is composed of several distinct emitters. In a non-limiting example, the light-emitting diode is an RGB diode. The RGB light source is said to be multi-source with three RG and B emitters which have different sizes and with different geometric arrangements. In a non-limiting embodiment, the light source 20 is arranged on an electronic support 21 (illustrated in the ). In a non-limiting embodiment, the electronic support 20 is a printed circuit board otherwise called in English “Printed Circuit Board Assembly”.

As illustrated in the , a light injection element 100, otherwise called a coupling bar 100, or light bar 100, or simply bar 100, is configured to receive the light rays R emitted by the light source 20. The light injection element 100 is of rectangular or square section. The light injection element 100 comprises a length Lg' (illustrated in the ), a width La' (illustrated in figures 3 and 4) and a thickness e (illustrated in the ). Its thickness e is that of the thickness of the light guide 1. The light injection element 100 comprises two ends 100.1, one of which is directly adjacent and attached to the light guide sheet 11 and the other is configured to face said light source 20. The light rays R emitted by the light source 20 enter through one end 100.1 and are transmitted to the other end 100.1 then to the light guide sheet 11.

As illustrated in the , the light injection elements 100 are composed of:
- a main part 100.2 which extends along the y axis, namely in the first direction of the light guide sheet 11, and
- an end portion 100.3 which extends along the z axis, namely in the second direction of the light guide sheet 11.

The main part 100.2 is connected to the light guide sheet 11. The two parts 100.2 and 100.3 are separated by a fold 100.4. The end part 100.3 extends after the fold 100.4. In a non-limiting embodiment, the fold 100.4 is a right-angled fold. The length Lg’ of a light injection element 100 is the sum of the dimension of the main part 100.2 and the end part 100.3.

There illustrates the end portions 100.3, the main portions 100.2 of light injection elements 100 of a group 10 and the fold 100.4 which separates them. illustrates the terminal portions 100.3 of ten light injection elements 100 of a group 10 and a light source 20 coupled to said group 10.

As illustrated in the , each light injection element 100 thus comprises a fold 100.4.

Thus, in each group 10, the light injection elements 100 are folded so that their end portions 100.3 form a stack 103 (illustrated in the ) with a thickness E adapted to an emission surface of the light source 20. The thickness E is the sum of the thicknesses e of each light injection element 100 whose end parts 100.3 form the stack 103.

Stack 103 presents:
- a light mixing zone 103.0 (illustrated in FIGS. 3, 6 and 7) configured to be arranged facing the light source 20,
- an entry surface 103.1 (illustrated on the ) formed by the ends of the terminal portions 100.3 of each of the light injection elements 100 of the group 10, and configured to receive the light emitted by the light source 20. This input surface 103.1 is located at the end 103.01 (illustrated in FIGS. 6 and 7) of the light mixing zone 103.0.

As illustrated in the , in a non-limiting embodiment, the end portions 100.3 of the light injection elements 100 are composed of first portions 100.30 and second portions 100.31, one of which 100.30 is part of the light mixing zone 103.0 and the other 100.31 is not part of the light mixing zone 103.0. In other words, the light mixing zone 103.0 groups together the first portions 100.30 of the end portions 100.3 of the light injection elements 100, while the second portions 100.31 of the end portions 100.3 of the light injection elements 100 remain distinct from the light mixing zone 103.0.

As illustrated in the , in a non-limiting embodiment, the light source 20 coupled to the group 10 is arranged opposite the entry surface 103.1 of the stack 103. The light rays R from the light source 20 enter via this entry surface 103.1 and thus propagate in the light mixing zone 100.3.

As illustrated in Figures 6 and 7, the light rays R are completely reflected within this light mixing zone 103.0. Each light ray R is reflected with a different angle depending on its angle of incidence. After a certain propagation length (approximately 20 to 30 millimeters), the light rays R are completely mixed, which allows a homogeneous light distribution in the mixing zone 103.0 and thus makes the beam homogeneous at the exit of the mixing zone 103.0 and arrives in the second parts 100.31 (illustrated in Figures 6 and 7) of the end parts 100.3 of the light injection elements 100 which are not grouped in the light mixing zone 103.0. They are then redirected via the folds 100.4 of the light injection elements 100 to the light guide sheet 11. The second parts 100.31 thus receive light distributed homogeneously in the light injection elements 100, and consequently, the light guide sheet 11 also receives homogeneous light. Thanks to this light mixing zone 103.0, the light is reflected over the entire width of the light guide 1. At the exit of the light mixing zone 103.0, there is good homogeneity of light.

In a non-limiting embodiment, the mixing zone 100.3 has a length (measured along the Z axis) of between 20 mm and 40 mm to ensure good mixing of the light rays R. If the light source is single-color, then the mixing zone 100.3 can be shorter. If the light source is an RGB LED for example, the mixing zone 100.3 must be longer. In a non-limiting variant embodiment, the mixing zone 100.3 has a length of approximately 30 mm. This allows good mixing of R, G and B colors.

In a non-limiting embodiment, the light source 20 is disposed approximately 0.5 mm millimeters from the entrance surface of the mixing zone 103.0.

In a first non-limiting embodiment illustrated in the , the light injection elements 100 are composed of a core 100.5 and an envelope 100.6 arranged partially on either side of said core 100.5. In particular, the core 100.5 is surrounded by an envelope 100.6 in the second part 100.31 of the end parts 100.3 of the light injection elements 100, while the core 100.5 is devoid of an envelope 100.6 in the first part 100.30 of the end parts 100.3. It will be noted that in a non-limiting embodiment the core 100.5 is a flexible film.

In a non-limiting embodiment illustrated in the , the light injection elements 100 are composed of only a core 100.5. They are devoid of an envelope unlike the light guide sheet 11. The cores 100.5 are thus stacked on top of each other to form the stack 103. A stack 103 with envelope layers could result in a loss of light. Seen from the side, the second parts 100.31 of the end parts 100.3 of the light injection elements 100 which are therefore composed of a core 100.5 resemble layers or lamellae. Thus, having only layers of cores 100.5 makes it possible to have a better light coupling efficiency. This makes it possible to improve the mixing of the light rays R at the entrance to the stack 103. It will be noted that in a non-limiting embodiment the core 100.5 is a flexible film.

In a first non-limiting embodiment illustrated in the , the light mixing zone 103.0 is obtained by partially embedding the end portions 100.3 of the light injection elements 100 in the resin. Thus, a portion of the stack 103 is embedded in the resin C, namely the first portions 100.30 of the end portions 100.3. This eliminates the air between the different layers of the stack 103. The resin C has a light refractive index close to the light refractive index of the light injection elements 100, here of the core 100.5. The cores 100.5 are thus bonded with the resin C. Bonding the cores 100.5 with the resin C improves the mixing of the light rays R at the entrance to the stack 103. Since the difference in the refractive index of light is small, a homogeneous material is obtained in the light mixing zone 103.0. There is no reflection at the index jump. At the exit of the light mixing zone 103.0, there is thus good homogeneity of light. At the exit of the light mixing zone 103.0, this homogeneous light is propagated to the light guide sheet 11 by the part of the end parts 100.3 of the light injection elements 100 which has not been embedded in the resin, namely by the second parts 100.31.

In a second non-limiting embodiment illustrated in the , the light mixing zone 103.0 is obtained by partly merging the end portions 100.3 of the light injection elements 100. Thus, a portion of the stack 103 is merged, namely the first portions 100.30 of the end portions 100.3 and in particular the cores 100.5 of the light injection elements 100. Thus, the cores 100.2 are merged. Merging the cores 100.5 improves the mixing of the light rays R at the entrance to the stack 103. Merging removes the layers of the stack 103 to have only one layer, here the light mixing zone 103.0 in which the light can be reflected homogeneously. At the exit of the light mixing zone 103.0, this homogeneous light is propagated to the light guide sheet 11 by the part of the end parts 100.3 of the light injection elements 100 which has not been merged, namely by the second parts 100.31. The merging makes it possible to have a fill factor (called in English "fill factor") of 100% of the light mixing zone 103.0 because by merging the cores 100.5 in particular, the material (air) with a low light refractive index between the cores 100.5 is removed. The fill factor is a filling rate of the useful surface on the total surface. The light received by the light injection elements 100 at the exit of the light mixing zone 103.0 will thus be very homogeneous from one light injection element 100 to another light injection element 100. In non-limiting embodiments, the fusion is carried out by welding the first parts 100.30 by heating or by ultrasound.

Of course, the description of the invention is not limited to the embodiments described above and to the field described above.

Thus, in the vehicle field, in another non-limiting embodiment, it can be applied to an interior element of the vehicle such as a door trim panel, dashboard or any other light decoration element or even a dashboard with one or more illuminated patterns. This pattern is then seen by an observer who is located inside the vehicle in this case.

Thus, the invention can be applied to any application other than the vehicle application, such as an application in the field of aviation, railway, for example for lighting a pattern in a cockpit of an airplane or a cabin of a train. It can also be applied to applications in the field of advertising on billboards or on storefronts or in buildings. It can also be applied to applications in the field of toys, decoration, or multimedia.

Thus, the light device 2 may comprise more than one light source 20. It may comprise three light sources R G and B which are each arranged facing the light mixing zone 103.0, so as to form white light when the light rays R emitted by the three light sources R G and B mix in the light mixing zone 103.0.

Thus, the invention described presents in particular the following advantages:
- it allows for a homogeneous distribution of light in all the light injection elements 100 of the light guide 1: it thus allows the light injection elements 100 located at the upper and lower ends of the stack 103 to receive the same quantity of light as those located in the middle of the stack 103,
- it makes it possible to resolve problems of homogeneity of the light because it avoids having thin air blades between the cores 11.5, or 100.5 of the light guide sheet 11 (when the latter has them, which result in total reflection guidance of the light individually in each core 11.5, or 100.5 of the light guide 1,
- it allows to use a so-called multi-source RGB light source with three RG and B emitters which have different sizes and with different geometric arrangements. Any geometry of light sources 20 can be used. It is not necessary to have the same size of R, G and B emitters and to find the right geometric arrangement as in the case of the prior art to avoid observing in the light guide sheet inhomogeneous color mixtures located anywhere in the light guide sheet; thanks to the invention, on the contrary, a homogeneous light mixture is obtained which thus makes it possible to obtain white light,
- it thus makes it possible to decorrelate the choice of the light source 20 from the light guide 1,
- it is not necessary to have a size of the light source 20 as large as the thickness of the stack 103 for the light injection elements 100 to all receive the same amount of light. It is possible to have a smaller light source 20,

- the light mixing zone 100.3 makes it possible to avoid having separate layers for the light input surface 103.1 which result in inhomogeneity of light, the light coupling with a layer and not emerging from this layer,
- by gluing or merging the cores 100.5 of the light injection elements 100, it allows the light to pass from one core 100.5 to the other 100.5 and no longer to be guided only independently in each core 100.5 through which it entered. This gives homogeneous light, unlike a prior art where the cores 100.5 are stacked on top of each other without merging or gluing and where the propagation of the light is done independently in the different cores 100.5 and therefore not homogeneously.

Claims (10)

Surface light guide (1) for a vehicle (3) comprising at least one group (10) of light injection elements (100) and a light guide sheet (11), said at least one group (10) being intended to be coupled to at least one light source (20) and said light injection elements (100) being folded so as to form a stack (103), characterized in that said stack (103) comprises:
- a light mixing zone (103.0) configured to be arranged opposite said at least one light source (20),
- an input surface (103.1) configured to receive the light rays (R) emitted by said at least one light source (20), and located at the end (103.01) of said light mixing zone (103.0). Light guide (1) according to claim 1, wherein each light injection element (100) comprises a main portion (100.2) and an end portion (100.3) separated by a fold (100.4). Light guide (1) according to claim 2, wherein said end portions (100.3) of said light injection elements (100) are partly embedded in the resin (C) to form said light mixing zone (103.0). Light guide (1) according to claim 2, wherein said end portions (100.3) of said light injection elements (100) are partly merged to form said light mixing zone (103.0). Light guide (1) according to any one of the preceding claims, wherein said light guide sheet (11) is composed of a core (11.5) and a shell (11.6) with a light refractive index lower than that of the core (11.5). Light guide (1) according to any one of the preceding claims, wherein each light injection element (100) is composed of a core (100.5) only. Light guide (1) according to any one of claims 2 to 6, wherein said light guide sheet (11) extends along a first direction (y) and along a second direction (z) and said light injection elements (100) are adjacent to said light guide sheet (11) by their main parts (100.2), their main parts (100.2) extending along the first direction (y) and their end parts (100.3) extending along the second direction (z). A lighting device (2) for a vehicle, said lighting device (2) comprising at least one light guide (1) according to any one of the preceding claims and at least one light source (20) arranged opposite said light mixing zone (103.0). Luminous device (2) according to the preceding claim, according to which said at least one light source (20) has a light emission surface less than the thickness (E) of said stack (103). Luminous device (2) according to claim 8 or claim 9 according to which said at least one light source (20) is composed of several distinct emitters.