Light-emitting module including a light guide with a light-guiding sheet for uniform luminous intensity display

Abstract

The present invention relates to a light emitting module including a light guide including a light guide sheet and a light incidence assembly, and a light source arranged to direct light rays into an incidence surface of at least one incidence assembly. The light guide sheet includes a film (111) including a light extraction region having microstructures (113) that can redirect light incident on the light guide sheet to the outside of the light emitting module. The film includes microstructures on a first surface (701) and a second surface (702). For each portion of the light extraction region that is at a different distance from the light incidence end surface (114), the sum of the densities of the microstructures on the first surface and the microstructures on the second surface is an increasing function of the distance between the portion and the incidence end surface.

Description

[Technical Field]

[0001] The present invention relates to the field of light emitting modules using light guides, and in particular to light emitting modules using flexible light guides. [Background technology]

[0002] 2. Description of the Related Art In recent years, it has become common for all kinds of devices, especially automotive devices, to implement light-emitting functions for purposes such as illumination, providing signal information, aesthetic customization, and creating an atmosphere.

[0003] It is known to use displays such as LCDs.

[0004] However, this technology is not only expensive but also susceptible to environmental conditions such as temperature, humidity, and UV rays, making it unsuitable for many devices that have applications that induce fluctuations in environmental conditions, such as devices used outdoors.

[0005] Furthermore, the aforementioned solutions have the drawback of high energy consumption, which increases the larger the surface area of ​​the device in which the light emitting module is integrated.

[0006] It is known to use light emitting modules with light guides, which include a light guiding sheet incorporating a film, which may be flexible, in which light rays are guided and directed into a given emission pattern by microstructures formed in the film. The light is incident on the entrance end of the film.

[0007] Whatever technique is used to microstructure the lightguide to create the pattern, it is easier to create the microstructure on the surface of the film rather than throughout the film.

[0008] The areas where the microstructures are formed are called light extraction areas, and the areas without the microstructures are called dark areas. The respective arrangements and shapes of the light extraction areas and dark areas together form the light emitting pattern of the light guide.

[0009] To achieve luminance uniformity between light extraction areas, the density of the microstructures in the light extraction areas may be specified to vary as a function of distance from the light incident end of the film onto which the light is incident.

[0010] However, the microstructure density in the light extraction area is limited by a maximum density, which limits the size of the light guide that can achieve uniformity in the light extraction area. Larger sizes are possible, but this limits the luminous intensity of the light guide or affects the uniformity of the luminous intensity.

[0011] Therefore, there is a need for a light guide sheet-based lighting module that displays a large lighting pattern with good lighting uniformity between the lighting areas of the lighting pattern. Summary of the Invention

[0012] The present invention aims to improve this situation.

[0013] A first aspect of the present invention is a light guide including: a sheet for guiding light, the light guide sheet configured to receive light rays through at least one light input end and to guide the light rays in a direction substantially perpendicular to the light guide sheet; and at least one input assembly configured to receive light rays from an input surface and to guide the light rays so that they are incident on the light input end of the light guide sheet; and a light source positioned to direct a light beam onto the entrance surface of the at least one entrance assembly; The present invention relates to a light emitting module including:

[0014] The light guide sheet includes a film, the film including at least one light extraction zone including microstructures that can redirect light incident on the light guide sheet in at least a substantially perpendicular direction. The film includes microstructures on a first surface and a second surface of the film. For each of the light extraction zone portions having different distances from the light incident end, the sum of the microstructure density on the first surface of the portion and the microstructure density on the second surface of the portion is an increasing function of the distance between the portion and the light incident end of the light guide sheet.

[0015] By increasing the microstructure density as a function of distance from the light input position, a display with a uniform luminous intensity distribution per unit area can be formed on the light emitting module. Thus, the dynamic light extraction range is defined by the change in microstructure density with increasing distance from the light input edge.

[0016] By forming microstructures on both sides of the light guide sheet film, it is possible to extract light from the light guide over a longer distance while maintaining a uniform distribution of luminous intensity per unit area in the light extraction area, thus enabling the production of larger light emitting modules, or for the same size, more light can be extracted from the light guide, thus increasing the brightness in the light extraction area while allowing uniformity between various parts of the light extraction area.

[0017] According to an embodiment, a portion of the light extraction area may face a given section of the light entrance end.

[0018] Such sections may correspond to a series of incidence positions of the incidence elements of the incidence assembly when the incidence assembly includes a plurality of incidence elements that can cause light rays to be incident on separate consecutive sections of the light incidence end. In this way, a dynamic light incidence range is defined for each section, thereby achieving good uniformity of the luminous intensity distribution among various parts of the at least one light extraction area.

[0019] According to an embodiment, the shape of the at least one light extraction area may form the light emitting pattern of the light emitting module.

[0020] This makes it possible to display a large light-emitting pattern with good uniformity of luminous intensity.

[0021] According to an embodiment, the film may further include at least one dark area that does not include a microstructure, and the shape of the at least one dark area and the at least one light extraction area may together form the light-emitting pattern of the light-emitting module.

[0022] Therefore, it is possible to produce large, complex light-emitting patterns with good uniformity of luminous intensity.

[0023] According to an embodiment, the light guide sheet may be transparent, and for each portion of the at least one light extraction area, the microstructure density may be less than a maximum density, and the maximum microstructure density is determined so that the microstructures are invisible when no light rays are incident from the light source. Here, the microstructure density may be the microstructure density on the first surface or the microstructure density on the second surface.

[0024] In other words, the maximum density is the threshold above which at least a portion of the microstructure becomes visible to the naked eye. Note that there is also a saturation density, which is related to technical feasibility, i.e., a limit that can be achieved with a given microstructure formation technology. Therefore, it is possible to manufacture large transparent light-emitting modules with good luminous intensity uniformity.

[0025] According to an embodiment, for portions of at least one light extraction area having different distances from the light incident end, the microstructure density on the first surface may be a first increasing function of the distance between the portion and the light incident end, the first increasing function may have a maximum microstructure density at least in the portion farthest from the light incident end, and the microstructure density on the second surface is a second increasing function of the distance between the portion and the light incident end, where the maximum microstructure density is determined so that the microstructures are invisible when no light is incident from the light source.

[0026] Furthermore, the first increasing function is different from the second increasing function. In other words, the microstructure density on the first surface varies according to a different mathematical function or calculation rule from the microstructure density on the second surface as a function of distance from the incident end, starting from the incident end to the portion furthest from the incident end. As an example, the microstructure density on the first surface increases linearly as a function of the distance between the portion and the light incident end of the light guide sheet. On the other surface, i.e., the second surface, the microstructure density may increase nonlinearly as a function of the distance between the portion and the light incident end of the light guide sheet, for example, hierarchically or according to a logarithmic or exponential law.

[0027] Therefore, it is possible to define the appropriate arrangement of the microstructures on each of the two sides of the light guide sheet to meet various requirements such as light guide uniformity, luminous intensity, etc. In this way, the proposed light guide can be tailored as needed.

[0028] Furthermore, the second increasing function may have a maximum microstructure density at least in the portion farthest from the light incident end, which may be equal to the maximum microstructure density of the first increasing function.

[0029] In this way, the maximum microstructure density is doubled by using both sides, which makes it possible to increase the size of the light emitting module or, for an equal size, increase the amount of light extracted.

[0030] Furthermore, the microstructure density on the second surface may be zero at the portion furthest from the light incident end.

[0031] In this way, the dynamic light extraction area is mainly defined by the first surface, and furthermore, the portion of the second surface of the film on which the microstructure is formed is minimized, facilitating the manufacture of such a light emitting module.

[0032] Additionally or alternatively, the first surface may face the outside of the light emitting module and the second surface may face the inside of the light emitting module.

[0033] In this way, the surface that primarily defines the dynamic extraction range faces the outside of the light emitting module, thereby maximizing the amount of light emitted towards the outside of the light emitting module, thus improving the efficiency associated with the light emitting module.

[0034] According to an embodiment, the film may be made of polycarbonate (PC), polymethyl methacrylate (PMMA), thermoplastic polyurethane (TPU), polyethylene terephthalate (PET), or silicone and may have a thickness of 25 to 1000 micrometers, in particular 50 to 1000 micrometers, for example 200 to 500 micrometers.

[0035] This allows flexible light guide sheets to be manufactured, facilitating their integration into any kind of device.

[0036] A second aspect of the invention relates to an automotive device comprising a light emitting module according to the preceding claims.

[0037] Other features and advantages of the present invention will become apparent from consideration of the following detailed description and accompanying drawings. [Brief explanation of the drawings]

[0038] [Figure 1]FIG. 1 shows a cross-sectional view of a light guide component of a light emitting module according to an embodiment of the present invention. [Figure 2] FIG. 2 shows a front view of the light guide components of a light emitting module according to an embodiment of the present invention. [Figure 3] FIG. 3 shows a front view of components of a light guide of a light emitting module according to an embodiment of the present invention. [Figure 4] FIG. 4 shows a three-dimensional view of a light guide entrance assembly of a light emitting module according to an embodiment of the present invention. [Figure 5] FIG. 5 shows a light emitting pattern displayed on a light guide sheet of a light emitting module according to an embodiment of the present invention. [Figure 6] FIG. 6 shows the microstructure density in a portion of the light extraction area of ​​a light emitting module according to an embodiment of the present invention. [Figure 7] FIG. 7 shows multiple views of a light guide of a lighting module according to an embodiment of the present invention. [Figure 8] FIG. 8 shows multiple views of a light guide of a lighting module according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0039] This specification focuses on features that differentiate the external device and light emitting module from those known in the prior art.

[0040] FIG. 1 shows components of a light guide 105 of a lighting module according to an embodiment of the present invention.

[0041] The light guide 105 includes a light guide sheet 110, which may be flexible. The light guide sheet 110 can receive light rays through at least one light incident edge 114 and can guide the light rays in a Z direction, which is substantially perpendicular to the surface of the light guide sheet, which extends in the XY plane in FIG. 1 . A light guide sheet refers to a wave-guiding optical element in which one of its spatial dimensions is much smaller, for example, by an order of magnitude or more, than the other two spatial dimensions. As shown in FIG. 1 , the light guide sheet 110 considered herein has a thickness along the Z axis that is at least two orders of magnitude smaller than the dimensions in the XY plane in which the light guide sheet 110 extends.

[0042] The light guiding sheet 110 may include at its core a film 111. The film 111 may be flexible, include a light input edge 114, and include a series of microstructures 113 that are capable of directing light rays generally in the X direction, and that are capable of directing light rays guided within the film 111 out of the flexible guiding sheet 110, particularly in one or more directions substantially along the Z axis.

[0043] The film 111 may be a substrate film made of polycarbonate (PC), polymethyl methacrylate (PMMA), thermoplastic polyurethane (TPU), polyethylene terephthalate (PET), silicone, or glass. The film 111 may have a thickness of 12 to 1000 micrometers, i.e., a dimension along the Z axis. More precisely, the thickness of the film 111 may be 25 to 1000 micrometers, in particular 50 to 1000 micrometers, for example 200 to 500 micrometers. In a variant, the light guide sheet 110 has a thickness of 200 to 1000 micrometers.

[0044] The aforementioned materials, combined with the low thicknesses mentioned above, make it possible to obtain a flexible and transparent film 111. Other materials are also conceivable for the components of the film 111. However, according to the invention, it is preferred to provide a deformable and transparent material.

[0045] A thin coating of microstructures 113 may be created on either side of film 111 or within film 111. In accordance with the present invention, microstructures 113 are formed on both sides of the film, as will be better understood from the description of Figure 5 and the like.

[0046] The microstructures are formed on the surface of the film and distributed to produce a light-emitting pattern. The light-emitting pattern is achieved by light-extraction areas, i.e., areas of the film 111 that include the microstructures 113. The light-emitting pattern may also include dark areas, i.e., areas of the film 111 that do not include the microstructures 113. The shapes and respective arrangements of the light-extraction and dark areas together form the light-emitting pattern. Alternatively, the light-emitting pattern includes only one light-extraction area of ​​a given shape.

[0047] By microstructures 113 is meant structures or irregularities present in the flexible film, at least one dimension of which is smaller than a few micrometers. For example, the microstructures 113 may have a diameter of the order of 50 micrometers and a height of 1 or 2 micrometers. Thus, the term microstructures also covers nanoscale structures. Microstructures 113 of such size make it possible to ensure high transparency of the flexible film 111. In particular, the use of microstructures 113 may actually result in a transparency of the order of 97%. Alternatively, the light guide sheet may be translucent.

[0048] The microstructures can redirect light incident on the light guide in one or more directions different from the direction of incidence along the X-axis. In particular, at least a portion of the redirected light rays are redirected in a direction substantially parallel to the Z-axis, particularly in a direction directed outward from the light emitting module 100. In practice, such microstructures can redirect guided light rays in a Lambertian manner in any direction in space.

[0049] There is no limitation on the method for forming the microstructure 113 on the surface of the film 111. The microstructure 113 can be obtained by adding or removing material from the flexible film.

[0050] For example, the microstructure may be obtained by embossing by applying a roller with indentations to mechanically print the microstructure on the surface of the film 111. Alternatively, the microstructure 113 can be obtained, for example, by irradiating with ultraviolet light or by baking a polymer in contact with a mold, roller, or other surface containing indentations that can form a microstructure of complementary shape.

[0051] In another variation, the microstructures 113 are formed where a coating of the flexible film made from a material with a low refractive index has been removed from the flexible film, such that the microstructures are formed by removing material. In this case, the microstructures are holes or gaps. Optionally and supplementarily, additional (prismatic, reflective, diffractive or diffusive) surface or bulk elements may be added to the holes or gaps to form the microstructures 113.

[0052] 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 material-free areas of the film 111. Such treatment can be achieved by mechanical or laser scribing, laser ablation, sandblasting, exposure to radiation, chemical treatment, or any other treatment that makes it possible to obtain irregularities in a controlled manner on the surface of the film 111.

[0053] Alternatively or additionally, the microstructures 113 are exogenous elements of the film, added to the surface of the film 111 .

[0054] The coating of the microstructure 113 may in particular have a thickness along the Z axis of less than 20 micrometers.

[0055] As described in more detail below, the density of the microstructures 113 may vary in the light extraction area as a function of distance from the light input end 114 .

[0056] By "pattern" is meant any predefined spatial distribution of luminous intensity emitted by a light-emitting module. In particular, reference is made here to two-dimensional or one-dimensional patterns. Thus, a pattern may include a uniform distribution of light across the light guide sheet, where the light extraction areas extend across the entire light guide sheet. A pattern may also include two-dimensional shapes or symbols resulting from the contrast between the light extraction areas and dark areas of the light guide sheet 110. A pattern may also include multiple shapes or symbols. Alternatively, a pattern may also refer to a predefined spatial distribution of luminous intensity that does not form a general shape, such as a cloud of luminous dots.

[0057] The flexible light guiding sheet 110 may further include one or two optional protective layers 112.1 and 112.2 that provide mechanical protection for the film 111. Furthermore, at least one of the protective layers 112.1 and 112.2 may include an anti-UV treatment, preferably including protective layer 112.1 through which light guided by the microstructures 113 passes and is emitted, providing UV protection for the film after the microstructures 113 are formed. Without such UV protection, the pattern projected by the light guiding sheet 110 is likely to deteriorate over time, especially when exposed to sunlight.

[0058] The film 111 and the protective layers 112.1 and 112.2 are shown spaced apart in Figure 1 purely for purposes of illustration, however, it will be understood that the protective layers 112.1 and 112.2 may also be adhered to the film 111, in particular by lamination.

[0059] Light rays propagate within film 111 by total internal reflection due to the difference between the refractive index of film 111 and that of an adhesive or pressure sensitive adhesive layer applied to at least one side of the flexible film.

[0060] The film 111 may be bonded to the protective layers 112.1 and 112.2 by adhesive bonding. Specifically, a layer of adhesive is disposed between the film 111 and each of the protective layers 112.1 and 112.2 on both sides of the film to adhere the protective layers to the film 111.

[0061] The selected adhesive is transparent and has a refractive index different from, and particularly smaller than, that of the film 111 so as to enable total internal reflection in the film 111. For example, the adhesive may include silicone or acrylic. In other words, due to the different refractive indices, light propagating through the film 111 undergoes total internal reflection when it encounters the interface between the film 111 and the adhesive layer at an angle of incidence smaller than normal incidence. Therefore, the light guiding sheet can guide light by total internal reflection of light, for example, from the input area at the input end 114 to the output area.

[0062] The light guide sheet 110 may be flexible, so that it does not necessarily lie flat, but may be curved depending on where it is placed and any mechanical constraints that may be applied.

[0063] 1 also includes an incidence assembly 120 including a plurality of light incidence elements, as described with reference to subsequent figures, that can distribute light along light incidence edge 114 to light guide sheet 110 at various positions along the Y axis. At each position along the Y axis, light is incident in a direction substantially parallel to the X axis.

[0064] The input assembly 120 includes an input surface 121 that is rectangular or square in cross section in Figure 1. However, the assembly 120 may have an input surface with a cross section of a different shape.

[0065] 1, the illustrated input assembly 120 has an output surface 122 that extends in the Y direction and is positioned facing the light input end 114. It will be understood from reading the following description of the drawings that the output surface 122 and the light input end 114 are integral, and that the flexible film 111 and the input assembly 120 form a single component.

[0066] Incident assembly 120 further includes an incident surface 121 at one end thereof that can receive light rays from a light source external to light guide 105 (light source not shown in FIG. 1 ), and incident assembly 120 can direct the light longitudinally along the Y axis while distributing the light to exit surface 122. The distribution of light by exit surface 122 will be better understood in view of the following description of the figures.

[0067] FIG. 2 shows the components of a light emitting module 100 including a light guide 105 having an assembly of incident elements 120 and a flexible light guiding sheet 110 , and a light source 130 .

[0068] Depending on the distribution of the microstructures 113, the light guide sheet 110, or more precisely the film 111, may comprise a mixed area 111.2 and a light emitting area 111.1, the light emitting area comprising at least one light extraction area with microstructures 113 and optionally one or more dark areas, so as to generate a light emitting pattern in the light emitting area 111.1. The mixed area 111.2 is located upstream of the light emitting area in the propagation direction of the light rays. The light emitting area 111.1 is integrated into the region 1110.

[0069] Light incident on the light guide sheet 110 through the input end 114 is mixed in the mixing area 111.2 to achieve better light emission uniformity, and then the light propagates to the light emission area 111.1, where it exits the light guide sheet 110 in the Z direction.

[0070] More generally, mixing area 111.2 is an area of ​​the flexible light guide sheet that does not contain the luminous pattern emitted by flexible light guide sheet 110, and the mixing function of area 111.2 is optional.

[0071] The assembly 120 of input elements 120.1 can direct light rays generated by the light source 130 into the input end 114 and towards the mixing region 111.2. Figure 2 shows a single input assembly 120 for illustrative purposes.

[0072] It should be noted that the light guide 105 may include multiple input assemblies 120 per input end 114, with each input assembly 120 positioned at a given set of Y positions on the input end 114. Thus, each input assembly 120 is configured to illuminate a different region 1110 within the light guide sheet. In the following, for purposes of illustration, a single input assembly 120 per input end 114 will be considered.

[0073] The assembly 120 includes a plurality of light entrance elements 120.1. The assembly 120 may include, in particular, between 3 and 10 entrance elements 120.1. In the non-limiting example of Figure 2, the light guide 105 includes an assembly 120 having 10 entrance elements. For clarity, only two light entrance elements 120.1 are designated by reference.

[0074] The assembly 120 is coupled to at least one light source 130 such that a light ray R emitted by the light source is received by each light entrance element 121 .

[0075] Considering that the light incident element 121 is obtained by cutting from the same material as the flexible film 111, the light ray R propagates through the light incident element 120.1 by total internal reflection and supplies light to a light guide sheet adjacent to and integrated with the light incident element 120.1, whereby the light illuminates one or more light extraction areas of the light guide sheet 110.

[0076] The superposition of light entrance elements 120.1 forming assembly 120 may thus form a coupling bar (light bar) configured to receive light rays generated by light source 130 and propagate them into light guide sheet 110. Assembly 120 may be of square or rectangular cross section.

[0077] The light source 130 is not particularly limited and may be any light source technology. For example, the light source 130 may be an electroluminescent element, such as an LED, mounted on a substrate 131. Furthermore, a heat dissipation element 132 may be disposed below the substrate 131.

[0078] The light source 130 may generate light in a certain wavelength range. Such wavelength range may be centered around a visible color to generate colored light, such as blue, red, or green light. Alternatively, the light source 130 may emit light rays across the entire wavelength range visible to the human eye to generate white light. The light source 130 may be controlled by a control element (not shown). Alternatively, the light source 130 is not positioned directly facing the incident surface 121 of the incident element 120, but the light emitting module 100 further includes an optical fiber positioned between the light source 130 and the incident assembly 120, thereby allowing the light source 130 to be positioned away from the light guide 105.

[0079] Therefore, light can be incident on the incident end 114 at various longitudinal positions along the Y axis.

[0080] The light 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 incident element 120, the roll extending along the X axis and having the same width La as the light guide 105.

[0081] The reference symbol (pj) designates the incident position of index j, where each incident position of index j corresponds to one interval between positions along the Y axis of incidence at the incident end 114, and j varies from 1 to N, where N is the number of incident elements 120.1 in the incident assembly 120 (i.e., in the example considered so far, N=10).

[0082] Thus, the light emitting module 100 includes a light guide 105 that includes a flexible light guiding sheet 110 and an input assembly 120 , and a light source 130 .

[0083] The assembly 120 and light source 130 may be included in a non-visible portion 13 of the light emitting module 100. Such portion may be hidden, whereas the light emitting area 111.1, in contrast, is visible from outside the device, including the light guide 105.

[0084] Figure 3 shows the light guide of Figure 2 with the light entrance elements 120.1 of the entrance assembly 120 expanded. In Figure 3, each entrance element 120.1 has a respective length Lh and width W.

[0085] 3, only the length Lh and width W of the longest entrance element 120 are designated as references. The lengths Lh of the other entrance elements 120 are shorter than the length Lh of the longest entrance element. In contrast, the widths W of all entrance elements 120.1 may be equal.

[0086] As a non-limiting example, the length Lh of the longest entrance element 120.1 may be between 100 and 500 millimeters. Similarly, the width W may be between 1 and 20 mm.

[0087] 3 shows a folding position 300 in which each incident element 120.1 can be folded so that the incident elements 120.1 overlap to form the assembly 120. The length Lh of each of the incident elements is determined based on the folding position and the Y position of each of the incident elements such that their ends together form the incident surface 121.

[0088] FIG. 4 shows a three-dimensional view of the assembly 120 and light source 130 of the lighting module 100 according to an embodiment of the present invention.

[0089] As shown in Figure 4, each light entrance element 120.1 has a thickness e, which corresponds to the thickness of the light guide 105, i.e., the film 111. The light entrance element 120.1 has two ends 120.10, one of which is integral with the light guide sheet 110 as shown in Figure 2, and the other of which can be positioned facing the light source 130 as shown in Figure 4. Light rays emitted from the light source 130 enter from one end 120.10, called the first end, and are transmitted to the other end 120.10, called the second end, and then transmitted to the light guide sheet 110 via the light entrance end 114, which coincides with the second end 120.10 of the entrance element 120.1.

[0090] It should be noted that during the manufacturing process of the light guide 105, the incident elements 120.1 and light guide sheet 110 may be manufactured from a roll of material, engraved with a given pattern, and then cut with a blade or cutter to separate the light guide 105 from the rest of the roll and separate the various incident elements 120.1 along the X axis, thereby forming the various incident elements 120.1 before being folded at the folding position 300.

[0091] Thus, the light entrance elements 120.1 remain attached to the light guide sheet 110 at their second ends 120.10.

[0092] The length Lh of each of the entrance elements 120.1 is such that their first ends 120.10 facing the light source 130 come together to form the entrance face 121 of the assembly.

[0093] The entrance surface 121 therefore has a thickness E equal to the sum of the thicknesses e of the entrance elements 120.1.

[0094] FIG. 5 shows a light guide sheet 110 of the light guide of the light emitting module 100 according to an embodiment of the present invention.

[0095] The input assembly 120 is not shown in FIG. 5 for simplicity.

[0096] The light-emitting pattern is formed by four light-extraction areas 502.1, 502.2, 502.3, and 502.4, which contain microstructures (not shown in FIG. 5), and a dark area 504, which does not contain microstructures. The dark area 504 and the light-extraction areas 502.1, 502.2, 502.3, and 502.4 are complementary and together form the light-emitting pattern of the light-emitting area 111.1.

[0097] One of the incident positions 501 at the light incident end 114 is shown in Figure 5. The incident position 501 along the Y axis corresponds to where a portion 503.1 of the first light extraction area 502.1, a portion 503.2 of the second light extraction area 502.2, a portion 503.3 of the third light extraction area 502.3, and a portion 503.4 of the fourth light extraction area 502.4 are located. Preferably, the incident position 501 is a section 501 that includes an interval of Y positions. This may be, for example, a series of Y positions corresponding to one incident element 120.1 of the assembly 120 of incident elements 120.1.

[0098] Each of portions 503.1-503.4 is not limited and may be any region of a size greater than the dimensions of the microstructures, preferably at least 10 times greater than the dimensions of the microstructures, such that the microstructure density therein can be determined.

[0099] Light rays incident at incident position 501, and possibly light rays incident close to incident position 501, i.e. at two nearby Y positions, are guided through light guiding sheet 110, and the light rays are gradually extracted from light guiding sheet 110 by portion 503.1, then by portion 503.2, then by portion 503.3, and then by portion 503.4.

[0100] To maintain the luminous intensity in each of the portions 503.1-503.4 similarly, and thereby achieve a light-emitting pattern with uniform luminous intensity, the microstructure density within each of the portions 503.1-503.4 may vary as shown in FIG. 6.

[0101] In particular, the microstructure density in a given portion of the light extraction area depends on the distance between that portion and the light input end 114 .

[0102] FIG. 6 shows the microstructure density in the portion of the light extraction area shown in FIG.

[0103] 6, the density of microstructures 113 in a given portion varies directly with (or is an increasing function of) the distance between that portion and the light entrance end 114. Specifically, the amount of light reaching portion 503.4 is less than the amount reaching portion 503.1. To compensate for this, the microstructure density in portion 503.4 is greater than in portion 503.1.

[0104] There is no limit to the increasing function relating the distance from the light entrance edge 114 to the density of the microstructures 113. Such a function depends on the desired brightness of the light emission pattern, the inherent properties of the light guide 110, and the light source 130.

[0105] In the example shown in Figure 5, the X positions of the portions 503.1 to 503.4 are not contiguous, in particular the portions 503.1 to 503.4 are separated by dark areas 504 of the luminous pattern.

[0106] However, particularly when the light emission pattern includes only a single light extraction area (and therefore no dark areas), portions of a single light extraction area having successive positions can be considered when describing the variation in density of the microstructure 113. Such an example will be used to explain Figure 7 below.

[0107] As explained at the beginning, there is a limit to the density of the microstructures 113, that is, it is not possible to infinitely increase the density of the microstructures 113 as a function of the distance from the light incident end 113. As a result, If it is desired to maintain a uniform pattern, the size of the light guide sheet is limited or Alternatively, although the size of the light guide sheet is not limited, the density of the microstructures may saturate, causing the light emission pattern to appear non-uniform. Specifically, the luminous intensity of the light extraction area beyond the X position where the density saturates will be lower than the luminous intensity before saturation.

[0108] FIG. 7 is a side view, a top view, and a bottom view of a film 111 of a light guide sheet of a light emitting module according to an embodiment of the present invention.

[0109] According to the present invention, the microstructures 113 are formed on both the upper surface 701 and the lower surface 702 of the light guiding sheet 110 .

[0110] Regardless of whether the microstructures 113 are formed on the upper surface 701 or the lower surface 702, they are capable of directing light outward from the upper surface 701 in a direction at least substantially along the Z axis, the upper surface facing outward from the light-emitting module 100.

[0111] Therefore, the amount of light extracted in each X position section of the light guide sheet depends on the sum of the density of the microstructures on the upper surface 701 and the density of the microstructures on the lower surface 113 in that X position section. Therefore, if the maximum density of the microstructures 113 on a given surface is dmax, the sum of the densities in each X position section can vary from 0 to 2×dmax, rather than from 0 to dmax as in the prior art.

[0112] The sum of the densities of the microstructures 113 on the upper surface 701 and the lower surface 702 for a given portion of the light extraction area is an increasing function of the distance between that portion and the light incident edge 114. In other words, for any pair of opposing portions of a given section of the incident edge, the sum of the densities of the microstructures on both sides of the portion closest to the incident edge is less than the same sum of the portion furthest away.

[0113] therefore, Increasing the amount of light extracted for a given size of light guide sheet 110 while displaying an illumination pattern with a uniform luminous intensity distribution; and It is possible to increase the size of the light guide sheet 110 while still displaying a light emitting pattern with uniform brightness.

[0114] The maximum density dmax may correspond to the maximum density at which the microstructures 113 are not visible when no light rays are incident on the light guiding sheet 110. Such a maximum density is advantageous when a transparent light guiding sheet 110 is used.

[0115] Alternatively, the maximum density may correspond to the maximum density at which the microstructures 113 do not touch each other. The maximum density may be set by the manufacturing process of the lightguide 105.

[0116] In the example of Figure 7, the density of the microstructures 113 on the upper surface increases with distance from the light incident end until it saturates at a certain value X (denoted as X1). Beyond the saturation value X1, the microstructures 113 are formed on the lower surface 702. This causes the sum of the densities on both surfaces to continue to increase with distance from the light incident end. As a variant, as shown in Figure 7, the microstructures are formed on the lower surface from a value X2 that is greater than X1.

[0117] The light extraction area may be divided into sections, as shown in Figure 5. Regardless of the division into sections used, the sum of the microstructure densities on the top and bottom surfaces of a section is an increasing function of the section's distance from the light incidence end 114. In other words, the farther a section is from the light incidence end 114, the greater the sum of the densities on its bottom and top surfaces.

[0118] 7, the lower surface 701 includes only the microstructures in the portion farthest from the incident end, i.e., the portion beyond X2. The portion from X1 to X2 is the portion of the upper surface 701 where the microstructure density is greatest, but in this portion, the lower surface still does not include microstructures.

[0119] Note that in Figure 7, a single extraction area is shown that is uninterrupted by one or more dark areas, so that the total microstructure density increases continuously. However, the invention also applies to light-emitting patterns that include dark areas, and the increase in microstructure density as a function of distance from the light-entrance edge applies only to portions of the light extraction area, not to dark areas that do not include microstructures.

[0120] Distributions of microstructures 113 other than those shown in FIG. 7 are also contemplated within the scope of the present invention.

[0121] For example, FIG. 8 shows a side view, a top view, and a bottom view of a film 111 of a light guiding sheet of a light emitting module according to an embodiment of the present invention, which has a different distribution of microstructures 113 than the distribution shown in FIG.

[0122] 8, the microstructure density increases with distance from the light incident end 114 on each of the upper and lower surfaces 701, 702. Therefore, the total density also increases with distance from the light incident end 114.

[0123] In the example of Figure 8, whatever the portion of the at least one light extraction zone, the microstructure density on the upper surface 701 in that portion is a first increasing function of the distance of that portion from the light incident edge 114. Similarly, the microstructure density on the lower surface 702 in a portion is a second increasing function of the distance of that portion from the light incident edge. As shown in Figure 8, the first function and the second function may be different. Thus, the function corresponding to the sum of the microstructure densities on the upper and lower surfaces 701, 702 is the sum of the first function and a second function that also increases.

[0124] The invention is not limited to the embodiments described above by way of example, but extends to other variants.

Claims

1. a light guide (105) comprising a sheet (110) for guiding light, said light guide sheet being configured to receive light rays through at least one light entrance edge (114) and to reflect said light rays in a direction substantially perpendicular to said light guide sheet, and at least one entrance assembly (120) configured to receive light rays from an entrance surface (121) and to guide said light rays so as to be incident on said light entrance edge of said light guide sheet; a light source (130) arranged to direct a light beam at the entrance face of the at least one entrance assembly; A light emitting module (100) comprising: the light guide sheet comprises a film (111), the film comprising at least one light extraction area (502.1; 502.4) comprising microstructures (113) capable of redirecting the light incident on the flexible light guide sheet at least in the substantially perpendicular direction; the film comprises microstructures on a first side (701) of the film and on a second side (702) of the film; A light-emitting module (100) in which, for each of the light extraction area portions (503.1; 503.4) having different distances from the light incident end, the sum of the microstructure density on the first surface of the portion and the microstructure density on the second surface of the portion is an increasing function of the distance between the portion and the light incident end of the light guiding sheet.

2. 2. The light emitting module according to claim 1, wherein the light extraction area portions (503.1; 503.4) face the same given section (501) of the light entrance end (114).

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

4. 4. The light emitting module according to claim 1, wherein the film (111) further comprises at least one dark area (504) that does not include a microstructure (113), and the shapes of the at least one dark area and the at least one light extraction area (502.1; 502.4) together form a light emitting pattern of the light emitting module.

5. 5. The light-emitting module according to claim 1, wherein the light-guiding sheet (110) is transparent and, for each portion (503.1; 503.4) of the at least one light extraction area (502.1; 502.4), the microstructure density (113) on the first surface (701) or the microstructure density on the second surface (702) is less than or equal to a maximum density, the maximum microstructure density being determined such that the microstructures are not visible when no light rays are incident from the light source.

6. 6. The light-emitting module according to claim 1, wherein for the portions (503.1; 503.4) of the at least one light extraction zone (502.1; 502.4) having different distances from the light incident end (114), the microstructure density (113) on the first surface (701) is a first increasing function of the distance between the portion and the light incident end, the first increasing function having a maximum microstructure density at least in the portion farthest from the light incident end, and the microstructure density (113) on the second surface (702) is a second increasing function of the distance between the portion and the light incident end, the maximum microstructure density being determined such that the microstructures are invisible when no light beam is incident from the light source.

7. The light emitting module of claim 6 , wherein the first increasing function is different from the second increasing function.

8. 8. The light-emitting module according to claim 6, wherein the second increasing function has a maximum microstructure density at least in a portion farthest from the light-incident end.

9. 9. The light emitting module according to claim 8, wherein the microstructure density (113) of the second surface (702) is zero in portions (503.1; 503.4) of the light extraction area (111.1) other than the portion furthest from the light entrance end.

10. The light emitting module according to any one of claims 5 to 9, wherein the first surface (701) faces the outside of the light emitting module (100) and the second surface (702) faces the inside of the light emitting module.

11. 11. The light emitting module according to claim 1, wherein the film (111) is made of polycarbonate (PC), polymethyl methacrylate (PMMA), thermoplastic polyurethane (TPU), polyethylene terephthalate (PET), or silicone and has a thickness of 50 to 1000 micrometers, for example 200 to 500 micrometers.

12. An automotive device comprising a light emitting module (100) according to any one of claims 1 to 11.

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