Method for manufacturing a component for a backlighting device, and associated component for a backlighting device, backlighting device, image generation device, and head-up display

Abstract

The invention relates to a method for manufacturing a component (16) for a backlighting device, the method comprising the following steps: - depositing a cover layer on a reflective polariser, said reflective polariser (17) comprising a multilayer optical film (171); - printing patterns in the cover layer such that said printed cover layer forms an optical diffuser (18). The invention also relates to a component (16) for a backlighting device, to a backlighting device, to an image generation device, and to a head-up display.

Description

Description Title of the invention: Method for manufacturing a component for a backlighting device, component for a backlighting device, backlighting device, image generation device, associated head-up display

[0001] The present invention relates generally to the field of displays.

[0002] It relates more particularly to a method of manufacturing a component for a backlighting device, used for example in a head-up display for a motor vehicle, as well as such a component for a backlighting device, a backlighting device, an image generation device, and an associated head-up display.

[0003] Typically, a so-called "head-up" display forms a virtual image in the field of vision of a motor vehicle driver. The driver can thus view information relating to the operation of the vehicle, relating to a traffic lane facing the vehicle, or other information, without having to look away from this traffic lane. Indeed, the virtual image, containing the information to be displayed, is then visually superimposed on the environment facing the vehicle.

[0004] Generally, a so-called "head-up" display comprises, inside a housing, an image generation device from which a source light beam emerges and an optical projection system adapted to project an image generated by the image generation device towards the driver of the vehicle, via the windshield for example, so as to form the virtual image previously mentioned.

[0005] Automotive head-up displays using a liquid crystal display (LCD) in their image generation device are often exposed to two types of thermal stresses that produce screen heating: one of these stresses is linked to the light source of the head-up display, and the other to the concentration of solar rays on the screen.

[0006] Such image generating devices often include elements laminated on top of each other that are not very resistant to high temperatures.

[0007] In this context, the present invention provides a method of manufacturing a component for a backlighting device comprising the following steps: - depositing a coating layer on a reflective polarizer, said reflective polarizer comprising a multilayer optical film, - printing patterns in the coating layer so that said printed coating layer forms an optical diffuser.

[0008] Manufacturing the component by depositing the coating layer and then printing it makes it possible to avoid a lamination step and thus produce a component that is more resistant to high temperatures.

[0009] In one embodiment, the optical diffuser has an angular distribution whose width at half maximum is less than 45 degrees relative to a principal diffusion direction.

[0010] In one embodiment, the coating layer is formed from a material that polymerizes under ultraviolet radiation. It may then be provided, for example, to subject the coating layer to ultraviolet radiation during the step of printing the patterns (in order to harden the coating layer then having the patterns).

[0011] In one embodiment, the reflective polarizer further comprises at least one polycarbonate layer deposited on the multilayer optical film.

[0012] For example, the reflective polarizer comprises another polycarbonate layer, the at least one polycarbonate layer and the other layer being disposed on either side of the multilayer optical film.

[0013] In one embodiment, the at least one polycarbonate layer is diffusing.

[0014] For example, the at least one polycarbonate layer has a diffusion angle of 2 degrees.

[0015] In one embodiment, the at least one polycarbonate layer is bonded to the multilayer optical film using a layer of optical adhesive.

[0016] For example, the dimensions and shape of the patterns are defined based on the angular distribution of the optical diffuser.

[0017] One aspect of the invention also relates to a component for a backlighting device comprising: - a reflective polarizer on a first face, said reflective polarizer comprising a multilayer optical film, - an optical diffuser on a second face opposite the first face, wherein the optical diffuser is a coating layer comprising printed patterns.

[0018] In one embodiment, the reflective polarizer further comprises at least one polycarbonate layer deposited on the multilayer optical film.

[0019] For example, the at least one polycarbonate layer is bonded to the multi-layer optical film by means of a layer of optical glue.

[0020] For example, the reflective polarizer comprises another polycarbonate layer, the at least one polycarbonate layer and the other layer being disposed on either side of the multilayer optical film.

[0021] For example, at least one polycarbonate layer is diffusing.

[0022] For example, the optical diffuser has an angular distribution whose width at half maximum is less than 45 degrees relative to a principal scattering direction.

[0023] Another aspect of the invention relates to a backlight device comprising: - a light source configured to emit a source beam, - a reflector configured to reflect at least part of the source beam into a reflected beam, - a component according to the invention, in which the first face of the component is placed on the side of the light source so as to intercept at least part of the reflected beam.

[0024] Another aspect of the invention relates to an image generation device comprising a backlighting device according to the invention, characterized in that it further comprises a liquid crystal screen placed downstream of the reflector on the light propagation path.

[0025] Finally, one aspect of the invention relates to a head-up display comprising an image generation device according to the invention, further comprising an optical projection system capable of returning a light beam generated by the image generation device towards a partially transparent blade.

[0026] Of course, the various features, variants and embodiments of the invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive.

[0027] In addition, various other characteristics of the invention emerge from the appended description given with reference to the drawings which illustrate non-limiting embodiments of the invention and where:

[0028] [Fig. 1] is a schematic view showing the integration of a head-up display according to the invention in a motor vehicle;

[0029] [Fig. 2] represents an embodiment of a backlighting device according to the invention;

[0030] [Fig. 3] represents a component for a backlighting device according to the invention;

[0031] [Fig. 4] schematically represents the arrangement of certain components of an image generating device according to the invention; and

[0032] [Fig. 5] represents the main steps of a method of manufacturing the component for a backlighting device according to the invention.

[0033] It should be noted that in these figures the structural and / or functional elements common to the different variants may have the same references.

[0034] In Figure 1, the main elements of a head-up display 1 are schematically represented, intended for example to equip a vehicle 2, in particular a motor vehicle.

[0035] The display 1 of Figure 1 is adapted to project a virtual image 3 into the field of vision of a driver 4 of the vehicle 2, so that the driver 4 can see this virtual image 3 and any information it contains without having to look away.

[0036] For this purpose, the display 1 comprises a partially transparent blade 5 placed in the field of vision of the driver 4, an image generation device 6 adapted to generate an image light beam 7 and an optical projection system 8 adapted to return, in the direction of said partially transparent blade 5, the image light beam 7 generated by the image generation device 6 after passing through a transparent window 9. The light beam returned in the direction of the partially transparent blade 5 is partly reflected by the partially transparent blade 5 in the direction of the driver 4 and thus produces the virtual image 3.

[0037] The partially transparent blade 5 is here merged with the windshield of the vehicle 2. In other words, it is the windshield of the vehicle 3 which has the function of partially transparent blade 5 for the head-up display 1.

[0038] As can be seen in Figure 1, the image generation device 6 and the optical projection system 8 are here placed in a housing 22, one opening of which is closed by the transparent window 9 already mentioned.

[0039] An embodiment of the image generating device 6 according to the invention is illustrated in FIG. 2. The image generating device 6 comprises a backlight device 10, a liquid crystal display 11 covering the backlight device 10, a first heat sink 12 and a second heat sink 13.

[0040] The backlighting device 10 comprises a light source 14 of the light-emitting diode matrix type, a reflector 15 and an optical component 16. The light source 14 is configured to emit a divergent source beam around a main direction D. The reflector 15 receives at least a portion of the source beam and reflects at least a portion thereof into a reflected beam in the direction of the optical component 16. The reflected beam is here collimated. The optical component 16 receives at least a portion of the reflected beam and transmits at least a portion thereof into a diffused beam towards the liquid crystal screen 11. The diffused beam illuminates the liquid crystal screen 11 so that the liquid crystal screen 11 lets at least a portion of the diffused beam pass through to form the image light beam 7.

[0041] Figure 3 represents an embodiment of the structure of the optical component 16. The optical component 16 comprises on a first face a reflective polarizer 17 and on a second face, opposite the first face, an optical diffuser 18. By reflective polarizer, it is meant a polarizer operating in reflection, that is to say reflecting a determined polarization component Pd. By optical diffuser, it is meant an optical element producing an angular spreading of an incident light.

[0042] The reflective polarizer 17 consists of a multilayer optical film 171 bonded to a first polycarbonate layer 172 on one side and to a second polycarbonate layer 173 on the opposite side by means of two layers of optical glue 174a and 174b. The multilayer optical film 171 consists of a stack of dielectric layers. For example, the multilayer optical film 171 comprises more than 100 atomic layers, for example between 100 atomic layers and 500 atomic layers, here 180 atomic layers, and / or has a thickness of between 20 microns and 200 microns, here 70 microns. Furthermore, the first polycarbonate layer 172 and the second polycarbonate layer 173 are here (slightly) diffusing. Typically, the first polycarbonate layer 172 and the second polycarbonate layer polycarbonate 173 each have an angular distribution whose width at half-height is equal to 2 degrees relative to a principal diffusion direction. For example, the principal diffusion direction is the direction normal to the plane of the first polycarbonate layer 172 and the second polycarbonate layer 173.

[0043] In a first variant, the reflective polarizer 17 consists of a multilayer optical film 171 bonded to a first polycarbonate layer 172 on one side and to a second polycarbonate layer 173 on the opposite side, but only one of the first polycarbonate layer 172 and the second polycarbonate layer 173 is (slightly) diffusing, the other not being diffusing.

[0044] In a second variant, the reflective polarizer 17 consists of a multilayer optical film 171 bonded to a first polycarbonate layer 172 on one side and to a second polycarbonate layer 173 on the opposite side, and the first polycarbonate layer 172 and the second polycarbonate layer 173 are not diffusing.

[0045] In a third variant, the reflective polarizer 17 consists of a multilayer optical film 171 bonded to a single polycarbonate layer. The single polycarbonate layer may be (slightly) diffusing or non-diffusing.

[0046] The optical diffuser 18 comprises a coating layer of a material sensitive to ultraviolet radiation and capable of adhering to the reflective polarizer 17. The optical diffuser 18 comprises patterns printed in the coating layer. The shape of the printed patterns is defined on the basis of the angular distribution of the optical diffuser 18. For example, the angular distribution of the optical diffuser 18 has a Gaussian profile, the width at half-maximum of which is equal to 30 degrees and 15 degrees respectively in two perpendicular directions, and with respect to a principal direction of diffusion. For example, the principal direction of diffusion is the direction normal to the plane of the optical diffuser 18.

[0047] In other words, a light beam illuminating the optical component 16 and incident on the first polycarbonate layer 172, passes (in part) through the reflective polarizer 17, then the optical diffuser 18 and emerges therefrom in an angularly spread beam, with an angular distribution whose width at mid-height is equal, in the example mentioned above, to respectively 30 degrees and 15 degrees in two perpendicular directions. The shape of the patterns printed in the coating layer thus takes into account the diffusion introduced by the first polycarbonate layer 172 and the second layer of polycarbonate 173 in order to obtain the angularly spread beam of standard deviation 30 degrees and 15 degrees in two perpendicular directions.

[0048] Generally, the angular distribution of the optical diffuser 18 has a width at mid-height less than 45° relative to the main diffusion direction.

[0049] The first face of the optical component 16 is positioned on the side of the reflector 15, which corresponds to the side of the light source 14. This configuration makes it possible to improve the recycling of the light inside the backlighting device 10. Indeed, if a portion of the source beam does not have the polarization transmitted by the reflective polarizer, it is reflected by the reflective polarizer 17 and can be reintercepted by the reflector 15, then reflected again in the direction of the optical component 16.

[0050] The liquid crystal screen 11 comprises a liquid crystal matrix interposed between an upstream polarizer 19 and a downstream polarizer 20, the upstream polarizer 19 being located on the side of the optical component 16. The upstream polarizer 19 is configured to selectively transmit a light component having an upstream polarization Pa into the liquid crystal matrix. A suitable activation of certain elements of the liquid crystal matrix selectively allows the passage of the light received from the upstream polarizer 19 by modifying the polarization thereof through the elements of the liquid crystal matrix and transmission or not through the downstream polarizer 20.

[0051] The determined polarization Pd reflected by the reflective polarizer 17 is adjusted orthogonally to the upstream polarization Pa. In other words, the polarization of the light Pt transmitted by the reflective polarizer 17 is aligned with the polarization direction transmitted by the upstream polarizer 19 of the liquid crystal screen 11. Figure 4 schematically illustrates this adjustment.

[0052] The beam emerging from the liquid crystal screen 11 corresponds to the image light beam 7, shown in FIG. 1, generated by the image generation device 6.

[0053] A method of manufacturing the optical component 16 according to the invention is now described, the main steps of which are shown in Figure 5.

[0054] In a step E0, a coating layer of a material sensitive to ultraviolet radiation is deposited on a substrate provided with a reflective polarizer comprising a multilayer film (formed of layers of dielectric material). This reflective polarizer here further comprises two polycarbonate layers (optionally diffusing) arranged on either side of the multilayer optical film.

[0055] It is assumed that the angular distribution of the optical scatterer that is desired to be formed on the substrate is predefined, so that the shape of the patterns to be printed in the coating layer can be determined and a stamp has been shaped from these patterns.

[0056] In step E2, the stamp is pressed into the coating layer to define the desired patterns.

[0057] In a step E4, with the stamp still attached to the coating layer, annealing is carried out in order to freeze the structure of the patterns in the coating layer. More precisely, the coating layer is illuminated with a beam of ultraviolet rays so as to produce a polymerization (i.e. a hardening) of the coating layer.

[0058] Once the buffer is detached, the resulting stack is cut to the desired size in order to obtain the optical component 16.

Claims

Demands

1. A method for manufacturing a component (16) for a backlighting device comprising the following steps: - deposition on a reflective polarizer (17) of a coating layer, said reflective polarizer (17) comprising a multilayer optical film (171), - printing patterns into the coating layer so that said printed coating layer forms an optical diffuser (18).

2. A manufacturing method according to claim 1, characterized in that the optical diffuser (18) has an angular distribution whose full width at half maximum is less than 45 degrees with respect to a principal diffusion direction.

3. A manufacturing method according to any one of claims 1 or 2, characterized in that the coating layer is formed into a material which polymerizes under ultraviolet radiation.

4. A manufacturing method according to any one of claims 1 to 3, characterized in that the reflective polarizer (17) further comprises at least one polycarbonate layer (172; 173) deposited on the multilayer optical film (171).

5. A manufacturing method according to claim 4, characterized in that the reflective polarizer (17) comprises another polycarbonate layer, the at least one polycarbonate layer (172,173) and the other layer being arranged on either side of the multilayer optical film (171).

6. A manufacturing method according to any one of claims 4 or 5, wherein at least one polycarbonate layer (172, 173) is diffusing.

7. A manufacturing method according to claim 6, characterized in that at least one polycarbonate layer (172, 173) has a diffusion angle of 2 degrees.

8. A manufacturing method according to any one of claims 4 to 7, characterized in that at least one polycarbonate layer (172, 173) is bonded to the multilayer optical film (171) by means of an optical adhesive layer (174a, 174b).

9. A manufacturing method according to any one of claims 1 to 8, characterized in that the dimensions and shape of the patterns are defined on the basis of the angular distribution of the optical diffuser (18).

10. Component (16) for a backlighting device comprising: - a reflective polarizer (17) on a first face, said reflective polarizer (17) comprising a multilayer optical film (171), - an optical diffuser (18) on a second face opposite the first face, in which the optical diffuser (18) is a coating layer comprising printed patterns.

11. Component (16) for backlighting device according to claim 10, characterized in that the reflective polarizer (17) further comprises at least one polycarbonate layer (172; 173) deposited on the multilayer optical film (171).

12. Component (16) for backlighting device according to claim 11, characterized in that at least one polycarbonate layer (172, 173) is bonded to the multilayer optical film (171) by means of an optical adhesive layer (174a, 174b).

13. Component (16) for a backlighting device according to any one of claims 11 or 12, characterized in that the reflective polarizer comprises another polycarbonate layer, at least one polycarbonate layer (172,173) and the other layer being arranged on either side of the multilayer optical film (171).

14. Component (16) for a backlighting device according to any one of claims 11 to 13, characterized in that at least one polycarbonate layer (172, 173) is diffusing.

15. Component (16) for a backlighting device according to any one of claims 10 to 14, characterized in that the optical diffuser (18) has an angular distribution whose full width at half maximum is less than 45 degrees with respect to a principal diffusion direction.

16. Backlighting device (10) comprising: - a light source (14) configured to emit a source beam, - a reflector (15) configured to reflect at least a part of the source beam into a reflected beam, - a component (16) according to any one of claims 10 to 15, characterized in that the first face of the component (16) is placed on the side of the light source (14) so ​​as to intercept at least part of the reflected beam.

17. Image generation device (6) comprising a backlighting device (10) according to claim 16, characterized in that it further comprises a liquid crystal display (11) placed downstream of the reflector (15) on the path of propagation of the light.

18. Head-up display (1) comprising an image generation device (6) according to claim 17, further comprising an optical projection system (8) capable of reflecting a light beam generated by the image generation device (6) towards a partially transparent blade (5).

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