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    • 专利摘要:
    The invention relates to a method of manufacturing a primary mold for producing a retroreflective screen, said method comprising the following steps: a) forming on the front face of a first substrate (501), a layer (503) a material such that the first substrate (501) is selectively etchable relative to said layer (503); and b) forming micro-recesses (311) from the rear face of the first substrate (501) by selective etching of the first substrate (501) with respect to said layer (503), each micro-recess (311) emerging on the back side of said layer (503) and having a bottom (312c) parallel to the front face of the first substrate (501) and first (312a) and second (312b) side walls orthogonal to each other and orthogonal to the bottom (312c), the first ( 312a) and second (312b) side walls and the bottom (312c) of the micro-recess joining at one point (S) and forming a trihedron.
    公开号:FR3046682A1
    申请号:FR1650226
    申请日:2016-01-12
    公开日:2017-07-14
    发明作者:Christophe Martinez；Bernard Aventurier
    申请人:Commissariat a lEnergie Atomique CEA；Commissariat a lEnergie Atomique et aux Energies Alternatives CEA；
    IPC主号:
    专利说明:

    METHOD FOR MANUFACTURING A SCREEN WITH MICROSTRUCTURES
    retroreflective
    Field
    The present application relates to the field of image display systems on transparent surfaces such as windshields of vehicles, especially motor vehicles. It is more particularly a screen provided with retroreflective microstructures adapted to such a system, a method of producing such a screen, and a mold for producing such a screen.
    Presentation of 11 prior art
    The applicant has recently proposed, in the French patent application FR3020149 filed on April 16, 2014 as well as in the corresponding international patent application WO2015158999 filed on April 9, 2015, a system for displaying an image on a windshield using a partially screen. transparent and partially retroreflective coating on the inner side of the windshield.
    Figure 1 is a schematic sectional view of such a system. This system comprises a screen 103 covering the inner face of a windshield 101, that is to say its face turned towards the inside of the vehicle, and a projector 105 adapted to be mounted on the head of a user 107, for example the driver of the vehicle. The projector 105 is adapted to project an image on all or part of the surface of the screen 103 facing the interior of the vehicle (that is to say opposite to the windshield 101). The screen 103 is partially transparent and partially retroreflective. More particularly, the screen 103 is adapted to retroreflect - that is to say, reflect towards its source - the light projected on its side facing the vehicle interior, and pass without significant alteration of the light from the windshield 101, that is to say from outside the vehicle. The screen 103 thus has a transparency function, allowing the user to see the external scene through the windshield 101 from inside the vehicle, and a retroreflection function, allowing the user - whose pupils are adjacent to the projector 105 - to see, in superposition of the external scene, an image produced by the projector 105.
    FIG. 2 is a sectional view showing in more detail the screen 103 of the system of FIG. 1. The screen 103 consists of a film made of a transparent material whose one face 201a is approximately smooth and whose opposite face 201b the face 201a has substantially identical protuberances 203 regularly distributed over the surface of the film. Each protuberance 203 has substantially the shape of a cube corner, that is to say a trihedron having three mutually perpendicular triangular lateral faces joining at the same point or vertex, and, opposite the vertex, a base, for example in the shape of an equilateral triangle. Each protuberance 203 has its top pointing to the outside of the film. The bases of the protuberances 203 are parallel to the smooth face 201a of the screen, and the central axis of each protrusion 203 (that is to say the axis passing through the top of the trihedron and the center of its base ) is orthogonal to the average plane of the film. Thus, the three faces of the trihedron are oblique with respect to the average plane of the film. The screen 103 differs from a traditional cube-corner retroreflective screen, in that, in the screen 103, the protuberances 203 are not adjacent but are separated from each other by substantially smooth zones 205 of the face 201b, parallel or approximately parallel to the face 201a of the screen. The screen 103 is intended to be illuminated by the projector 105 (Figure 1) by its face 201a, as schematically illustrates the arrow 207 of Figure 2. The screen portions located opposite the smooth zones 205 of the face 201a correspond to transparent portions of the screen 103, letting the light pass in both directions without significant defomation. The screen portions located opposite the protuberances 203 correspond to non-transparent retroreflective portions of the screen 103, adapted to send back towards its source the light coming from the projector 105. More particularly, when a light beam incident (not shown) reaches a retroreflective portion of the screen 103, this beam passes through a portion of the thickness of the screen until reaching the base of the corresponding cube corner 203, enters the cube corner, is reflected on each of the three lateral faces of the cube corner, and, after reflection on the third lateral face, starts towards its source. In the example shown, the reflections on the side faces of the cube corners are based on the principle of total internal reflection. Alternatively, the side faces of the cube corners may be covered with a reflective material on the side of the face 201b of the screen. The reflections on the side faces of the cube corners are then reflections of the mirror type. summary
    One embodiment provides a method of manufacturing a primary mold for producing a retro-reflective screen, the method comprising the following steps: a) forming on the front face of a first substrate having a front face and a rear face, a layer of a material such as the first substrate is selectively etchable relative to said layer; and b) forming microrevenements from the rear face of the first substrate by selective etching of the first substrate with respect to said layer, each microrenclosement opening on the rear face of said layer and having a bottom substantially parallel to the front face of the first substrate and first and second side walls substantially orthogonal to each other and substantially orthogonal to the bottom, the first and second side walls and the bottom of the micro-recess joining at one point and forming a trihedron.
    According to one embodiment, the method further comprises, before step a), a step of forming roughness on the front face of the first substrate.
    According to one embodiment, the step of forming the roughnesses on the front face of the first substrate comprises a grayscale lithography step.
    According to one embodiment, the method further comprises, after step a), a step of transferring the first substrate to a second support substrate, so that the front face of said layer is turned towards the second substrate.
    According to one embodiment, the first and second substrates are assembled by molecular bonding.
    According to one embodiment, the method further comprises, between step a) and step b), a step of thinning the first substrate by its rear face.
    According to one embodiment, in step b), the microburden is produced by deep reactive ion etching.
    According to one embodiment, the first substrate is silicon and said layer is silicon oxide.
    According to one embodiment, the method further comprises a step of forming, on the side of the rear face of the first substrate, trenches with oblique or curved sides, each microrenclosement opening into a trench.
    According to one embodiment, the method comprises the manufacture of a primary mold by a method as defined above, and the replication of the patterns of the rear face of the primary mold on one side of a film, by molding from of the primary mold.
    Another embodiment provides a primary mold for producing a retroreflective screen, comprising: a first substrate having a front face and a back face; a layer of a material such that the first substrate is selectively etchable with respect to said layer, coating the front face of the first substrate; and microrenfoncements extending from the rear face of the first substrate, each microrenfoncement opening on the rear face of said layer and having a bottom substantially parallel to the rear face of the first substrate and first and second side walls substantially orthogonal to each other and substantially orthogonal to the bottom, the first and second side walls and the bottom of the micro-recess meeting at one point and forming a trihedron.
    Another embodiment provides a retroreflective screen comprising a first film whose one face comprises a plurality of microrenfoncements, each microrenfoncement having a bottom substantially parallel to the mean plane of the screen and first and second side walls substantially orthogonal to each other and substantially orthogonal at the bottom, the first and second side walls and the bottom of the micro-recess meeting at one point and forming a trihedron.
    According to one embodiment, in each micro-recess, the first and second side walls and the bottom of the micro-recess are coated by a reflective metallization.
    According to one embodiment, the face of the first film further comprises trenches with oblique or curved sides, each microrenclosement opening into one of the trenches.
    According to one embodiment, the trenches are V trenches made by machining the face of the first film, several microrenfunctions opening into the same trench.
    According to one embodiment, the first film is made of a transparent material.
    According to one embodiment, the first film is made of a non-transparent material.
    According to one embodiment, the screen further comprises a transparent adhesive layer coating the face of the first film, and a second film of a transparent material coating the layer.
    According to one embodiment, the coverage rate of the screen by microrenfuncements is less than 50%.
    According to one embodiment, the screen comprises microrenfunctions of different dimensions and / or orientations in different areas of the screen.
    According to one embodiment, the microrenfoncements are distributed in a random or semi-random arrangement on the surface of the screen.
    Another embodiment provides a method for manufacturing a retroreflective screen as defined above, comprising the manufacture of a primary mold, one face of which has structures of the same shape as the structures of the face of the first film of the 'screen.
    According to one embodiment, the manufacture of the primary mold comprises a step of etching microrenfoncements on the side of a first face of a substrate, each microrenfunction having a bottom substantially parallel to the mean plane of the screen and the first and second walls lateral substantially orthogonal to each other and substantially orthogonal to the bottom, the first and second side walls and the bottom of the micro-recess joining at one point and forming a trihedron.
    According to one embodiment, the manufacture of the primary mold further comprises a step of forming, on the side of the face of the substrate, trenches with oblique or curved sides, each micro-recess opening into a trench.
    According to one embodiment, the method further comprises a step of replicating the patterns of said face of the primary mold on said face of the first film, by molding from the primary mold.
    According to one embodiment, the replication step comprises the production of a secondary mold of complementary shape to the primary mold, by molding from the primary mold.
    Another embodiment provides a primary mold for the manufacture of a retroreflective screen of the aforementioned type, a face of which has structurations of the same shape as the structure of the face of the first film.
    Brief description of the drawings
    These characteristics and their advantages, as well as others, will be described in detail in the following description of particular embodiments made without implied limitation in relation to the appended figures among which: FIG. 1, previously described, is a view in section showing schematically an example of a system for displaying an image on a windshield; Figure 2, previously described, is a sectional view showing in more detail a screen of the system of Figure 1; FIGS. 3A, 4A, 5A, 6A, 7A, 8A and 9A are perspective views schematically illustrating successive steps of an exemplary method of manufacturing an embodiment of a screen provided with retroreflective microstructures; FIGS. 3B, 4B, 5B, 6B, 7B, 8B and 9B are sectional views of the structures of FIGS. 3A, 4A, 5A, 6A, 7A, 8A and 9A respectively; FIGS. 10A, 10B, 10C and 10D are sectional views schematically illustrating an alternative embodiment of the method of FIGS. 3A, 3B, 4A, 4B, 5A, 5B, 6A, 6B, 7A, 7B, 8A, 8B and 9A, 9B; and FIGS. 11A, 11B, 11C, 11D, 11E, 11F and 11G are cross-sectional views schematically illustrating another alternative embodiment of the method of FIGS. 3A, 3B, 4A, 4B, 5A, 5B, 6A, 6B, 7A, 7B, 8A, 8B and 9A, 9B.
    detailed description
    The same elements have been designated with the same references in the various figures and, moreover, the various figures are not drawn to scale. In the description which follows, when reference is made to absolute position qualifiers, such as the terms "before", "backward", "up", "down", "left", "right", etc., or relative, such as the terms "above", "below", "upper", "lower", etc., or with qualifiers for orientation, such as the terms "horizontal", "vertical", etc., it Reference is made to the orientation of the corresponding sectional views, it being understood that, in practice, the described devices may be oriented differently. Unless otherwise specified, the expressions "approximately", "approximately", "substantially", and "of the order of" mean within 10%, preferably within 1%, or, in the case of angular values or assimilated (for example the qualifiers of orientation such as the terms parallel, orthogonal, vertical, horizontal, etc.) to 1 degree, preferably to 0.1 °.
    A limitation of the screen 103 of FIG. 2 is that its efficiency in retroreflection is very good for angles of incidence of the projected beam that are close to normal on the screen, for example for angles of incidence between 0 and 20 degrees, drops sharply when the angle of incidence of the projected beam increases. By way of illustration, measurements of the intensity of the retroreflected beam were made on a screen of the type described in relation to FIG. 2 for different angles of the incident beam. These measurements show that the intensity of the retroreflected beam is maximal for a zero angle of incidence (normal incidence), falls to about 50% of its maximum value for an angle of incidence of 25 °, and falls to 10% of its maximum value for an angle of incidence of 50 °.
    This can be a problem for the application to the projection of an image on a vehicle windshield. Indeed, in many vehicles, the windshield is strongly inclined relative to the vertical. In addition, in a system of the type described in connection with FIG. 1, the headlamp 105 mounted on the head of the user may have its main axis of projection inclined downwards relative to the horizontal. Thus, the angle formed between the main axis of the projector 105 and the screen 103 lining the windshield can reach high values, for example of the order of 50 to 70 degrees. At such angles of incidence, the efficiency in retroreflection of the screen 103 of Figure 2 is relatively low.
    Another limitation of the screen 103 of FIG. 2 lies in its great manufacturing complexity, linked in particular to the fact that the retroreflective protuberances 203 have oblique faces (with respect to the mean plane of the screen) whose inclination angles must be very accurately controlled to achieve the desired retroreflective effect.
    FIGS. 3A, 3B, 4A, 4B, 5A, 5B, 6A, 6B, 7A, 7B, 8A, 8B, 9A and 9B schematically illustrate steps of a method of manufacturing an embodiment of a screen 400 provided with retroreflective microstructures, compatible with a system of the type described in connection with FIG. 1. FIGS. 3A, 4A, 5A, 6A, 7A, 8A and 9A are perspective views, and FIGS. 3B, 4B, 5B, 6B , 7B, 8B and 9B are sectional views along the BB plane of FIGS. 3A, 4A, 5A, 6A, 7A, 8A and 9A respectively.
    Figures 3A, 3B, 4A, 4B, 5A and 5B illustrate steps of manufacturing a primary mold 320 (Figures 5A and 5B) for use in the manufacture of the screen 400 itself.
    FIGS. 3A and 3B illustrate a step of placing a mask 303 on the upper face of a substrate 301 in which it is desired to form the primary mold 320. The substrate 301 is for example made of glass, of silicon, of a thermoplastic polymer such as poly (methyl methacrylate) or PMMA, or any other suitable material. The upper surface of the substrate 301 is preferably flat. The mask 303 comprises through openings 307 revealing portions of the upper surface of the substrate 301 to be etched in a subsequent step. The mask 303 is made of a material adapted to protect the unexposed portions of the substrate 301 during the subsequent etching step. By way of example, the mask 303 is made of metal or resin. Viewed from above, each opening 307 formed in the mask 303 comprises two side walls 308a and 308b substantially orthogonal to each other, joining to form an angle of approximately 90 degrees. Each opening 307 has, for example, seen from above, the shape of a convex pentagon. In the example shown, each opening 307 has, seen from above, the shape of a right isosceles triangle to which is juxtaposed a trapezium. The sides of the right triangle correspond to the side walls 308a and 308b, and the base of the right triangle is merged with a base (the large base in the example shown) of the trapezium. The openings 307 are for example all substantially identical and oriented substantially in the same manner. In the example shown, only two openings 307 have been shown for the sake of simplification. In practice, a large number of openings 307 may be provided. For example, the openings 307 are regularly distributed over the entire upper surface of the substrate 301. The openings 307 are for example arranged in a matrix according to rows and columns.
    FIGS. 4A and 4B illustrate a step of forming cavities or recesses 311 extending substantially vertically in the substrate 301, from its upper face, facing the openings 307 of the mask 303. Each cavity 311 comprises lateral walls that are substantially orthogonal to the upper face of the substrate 301, and a bottom substantially parallel to the upper face of the substrate. In particular, each cavity comprises two lateral walls 312a and 312b substantially orthogonal to one another, substantially coinciding, seen from above, with the side walls 308a and 308b of the openings 307. The side walls 312a and 312b and the bottom 312c of each cavity 311 are join at the same point S, and define a trirectangle trihedron or cube corner having the point S for vertex. In each cavity 311, the axis of symmetry or central axis of the vertex cube corner S forms, by construction, an angle of approximately 54.74 degrees with the upper face of the substrate 301.
    As will be explained in more detail below, in each cavity 311, the vertex cube corner S corresponds to a retroreflective microrefining of the future screen 400. The side wall 312d of each cavity 311 opposite the apex S (corresponding to the small base of the trapezium of the opening 307 in the example shown) is preferably relatively far from the vertex S, so as to define in the cavity 311 a clearance region facing the base of the cube corner. By way of example, seen from above, the cavity 311 has, in the direction of the bisector of the angle formed by the side walls 312a and 312b, a dimension of between 1 and 1.5 times at the depth of the cavity . The cavities 311 have, for example, a depth in the range of 20 to 500 μm and preferably in the range of 50 to 200 μm.
    The cavities 311 are for example formed by a deep ionic reactive etching process, generally referred to in the art by the acronym DRIE ("Deep Reactive Ion Etching"). Such a method has the advantage of making it possible to easily make cavities having substantially vertical lateral faces over relatively high depths, and a substantially horizontal bottom. Any other suitable etching process may however be used, for example a laser etching or an X-ray etching.
    Once the etching is performed, the mask 303 (not shown in Figures 4A and 4B) is removed.
    FIGS. 5A and 5B illustrate a step of forming trenches or recesses 314 with oblique or curved sides in the substrate 301, from the upper face of the substrate. The trenches 314 have a depth less than the thickness of the substrate 301. The trenches 314 pass through the clearance regions of the cavities 311, avoiding the cube-corner regions corresponding to the retroreflective microrefinements of the screen 400. Preferably, the same trench 314 passes through several cavities 311. By way of example, seen from above, each trench 314 passes right through the substrate 301 in a direction of alignment of the cavities 311 not passing through the cube-corner portions of the cavities 311 Alternatively, a localized trench 314 is formed at each cavity 311, i.e. each trench 314 passes through a single cavity 311.
    The trenches 314 have a depth greater than or equal to that of the cavities 311, for example a depth of between 1 and 1.5 times the depth of the cavities 311. The trenches 314 preferably have a longitudinal plane of symmetry substantially orthogonal to the upper surface. of the substrate. The depth of the trenches 314, their width, and the inclination of their flanks, are chosen so as to eliminate all or part of the vertical walls of the cavities 311 which do not correspond to the cube-corner retroreflective regions of the screen 400. For example, the trenches 314 are V trenches. V-trenches can for example be obtained by machining the substrate by means of a saw, or by etching. V trenches have for example an angular aperture of between 20 and 60 degrees, and preferably of the order of 50 degrees. Alternatively, the trenches 314 are trenches with curved flanks, for example trenches C. Such trenches may for example be made by etching.
    The trench prediction 314 facilitates a subsequent demolding step of a screen element 400 made from the mold 320. Note however that the trenches 314 are optional, and may in particular be omitted if it does not arise. no particular difficulty of demolding in this subsequent step. It should further be noted that the angle of inclination of the flanks of the trenches 314 need not be precisely controlled, since the trenches 314 only serve to facilitate demolding of the screen, but have no optical function. in the final screen. The structure obtained after the steps 3A, 3B, 4A, 4B, 5A, 5B corresponds to the primary mold 320.
    FIGS. 6A and 6B illustrate a step during which the structures of the upper surface of the primary mold 320 are replicated, by molding, on one face (the upper face in the example represented) of a 351 film. For example, the film 351 is made of a plastic material, for example of the polymethylmethacrylate type. In this example, the film 351 is made of a transparent material. The replication of the patterns of the primary mold 320 on one side of the film 351 passes through the formation, from the primary mold 320, of a secondary mold (not shown) having a shape complementary to that of the primary mold 320. the upper face of the film 351 are then obtained from the secondary mold, by thermoforming or by any other suitable molding technique. For the sake of simplification, in the remainder of the description, the references 311, 312a, 312b, 312c, 312d, S and 314 used to designate elements of the structures of the upper face of the primary mold 320, will be used to designate the corresponding elements. structures of the upper face of the film 351. The unstructured face of the film 351, namely its underside in the example shown, is preferably substantially flat.
    FIGS. 7A and 7B illustrate a step of placing a mask 353 on the upper face of the film 351. The mask 353 comprises through openings 355 revealing portions of the upper face of the film 351. More particularly, the openings 355 are disposed substantially facing the cube corners of vertex S corresponding to the retroreflective microrefinements of the screen 400. The remainder of the upper surface of the film 351, and in particular the flat portions of the upper surface of the film 351 not occupied by the cavities 311 and the trenches 314, as well as the portions of the upper surface of the film 351 corresponding to the trenches 314 and cavity clearance regions 311, are covered by the mask 353.
    FIGS. 8A and 8B illustrate the result of a deposition step, through the apertures 355 of the mask 353, of reflective metallizations 357 coating the side walls and the bottom of the cube-corner micro-cavities of the upper face of the film 351. metallizations 357 are for example aluminum. The metallizations 357 may be spray deposited through the openings of the mask. In practice, the metallizations 357 may overflow on the upper face of the film 351 slightly beyond the limit of the cube corners S vertex. As an example, seen from above, each metallization 357 may have the shape of a substantially circular pastille in which is inscribed the corresponding right triangle, seen from above, to the cube-corner recess coated by the metallization 357.
    Once the metallizations 357 are deposited, the mask 353 is removed.
    FIGS. 9A and 9B illustrate a step of bonding a transparent coating film 359 to the upper face of the film 351. In this example, the faces of the film 359 are substantially planar. A layer of transparent glue 361 filling in particular the cavities 311 and the trenches 314 of the upper face of the film 351, interfaces between the upper face of the film 351 and the lower face of the film 359. Preferably, the coating film 359 and the transparent adhesive 361 have substantially the same refractive index as the film 351. The coating film 359 and the transparent adhesive layer 361 ensure a good transparency of the screen 400 outside the areas coated by the metallizations 357. The assembly thus obtained forms the screen 400. The screen 400 has retroreflective portions regularly distributed over its entire surface, corresponding to the metallized cube corner structures of the film 351. Each portion of the retroreflective screen is surrounded by a screen portion. transparent, so that the screen is partially retroreflective and partially transparent. The screen 400 is thus adapted to an operation of the type described in relation to FIG. 1 (the upper face of the screen being turned towards the projector 105). For a good transparency of the screen 400 for viewing an outdoor scene, the coverage rate of the screen 400 by the retro-reflective portions is for example less than 50%, and preferably less than 20%.
    When they enter the screen 400 from the upper face of the film 359, the incident rays are deflected by an angle which depends on the optical index of the film 359. The maximum efficiency in retroreflection of the cube corner the screen 400 is in principle obtained when the rays projected on these structures are parallel to the central axis of the corner cube corners S, that is to say when the rays propagating inside the screen are tilted about 54.74 degrees from the mid-plane of the screen. Such an inclination of the rays inside the screen can not generally be obtained in practice, this inclination being greater than the limit angle of refraction of the upper diopter of the screen. By way of example, for a film 359 of optical index of the order of 1.5, the refractive limit angle is about 42 degrees. Note further that the higher the angle of incidence of the light rays on the screen 400, the higher the reflection losses on the upper face of the screen 400 are important. Depending on the chosen materials, it will be easy to find, by measurement and / or simulation, the angle of incidence of the light rays for which the efficiency in retroreflection of the screen is maximum. By way of example, analyzes have shown that, when the films 359 and 351 and the adhesive layer 361 have a refractive index of the order of 1.5, the maximum efficiency in retroreflection of the screen 400 is obtained for an angle of incidence (outside the screen) of the order of 60 degrees. More generally, the studies carried out show that the proposed structure provides good retroreflection efficiency for angles of incidence in the range of 30 to 80 degrees, and preferably in the range of 50 to 70 degrees. Thus, the screen 400 is well suited to the application to the projection of an image on a vehicle windshield.
    Another advantage of the screen 400 is that it is relatively simple to implement, because the cube-corner microbreaks forming the retroreflective portions of the screen do not have oblique faces relative to the mean plane of the screen. 'screen. The faces of the cube-corner microbreaks of the screen 400 are substantially orthogonal or parallel to the mean plane of the screen. Thus, the cube-corner micro-cavities can be obtained by simple vertical-side etching from the upper surface of the substrate 301. Alternatively, at the step of FIGS. 6A and 6B, instead of replicating by molding the structure of the upper surface of the primary mold 320 on the upper face of the film 351, it can be provided to form by molding on the upper face of the film 351, structures complementary to those of the upper face of the primary mold 320. For this it is possible, for example, to produce from the secondary mold (not shown) a tertiary mold (not shown) having identical or similar structures to those of the primary mold 320. This tertiary mold can then be used to mold the structure of the mold. the upper face of the film 351. The subsequent manufacturing process of the screen 400 is then substantially identical to what has been described above, a few adjustments close to the reach of the skilled person. The resulting screen 400 then no longer includes retroreflective recesses in cube corners, but retroreflective protuberances in cube corners. In this variant, the screen 400 is intended to be illuminated by its lower face.
    Particular embodiments have been described. Various variations and modifications will be apparent to those skilled in the art. In particular, the described embodiments are not limited to the above-mentioned example in which the cube-corner micro-cavities forming the retroreflective portions of the screen 400 are substantially identical and oriented in the same manner. In practice, depending on the needs of the application, cube corner micro-cavities may have different dimensions and / or different orientations (seen from above) in different areas of the screen.
    In addition, the cube corner microrangements forming the retroreflective portions of the screen 400 are not necessarily aligned in rows and columns, but may have a random or semi-random arrangement on the surface of the screen, in particular to avoid possible diffractive phenomena that may occur at certain angles of incidence when the microbreaks have a regular disposition.
    In addition, the embodiments described are not limited to the exemplary method of producing the reflective metallizations 357 described in relation with FIGS. 7A, 7B, 8A, 8B. As a variant, the step of producing the mask 353 described with reference to FIGS. 7A and 7B may be omitted. Instead, a conformal metal layer coating the entire upper surface of the structure of Figs. 6A and 6B can be realized. The deposited metal can then be removed at the level of the upper planar regions of the structure (corresponding to the transparent areas of the screen), for example by mechanical-chemical polishing. During this step, only the portions of the metal layer coating the walls of the cavities 311, and, where appropriate, the trenches 314, are preserved, forming the reflective metallizations 357.
    Furthermore, it will be noted that in an application of the type described with reference to FIG. 1, the light source 105 is generally not placed exactly in the axis of the user's gaze. Thus, the screen 400 should preferably be adapted to diffuse the retroreflected light in a diffusion cone encompassing the pupils of the user, so that the user can see the image displayed by the projector. In practice, the inventors have found that the diffraction effects on the edges of microrenfoncements and / or the inevitable surface imperfections of the screen, may be sufficient to obtain the required diffusion effect. To amplify and / or control this diffusion, one can for example play on the roughness of the flanks and the bottom of the cavities 311 of the primary mold 320.
    In addition, the described embodiments are not limited to the application to the projection of an image on a transparent surface. In particular, the embodiments described may have applications in various fields using retroreflective surfaces, not necessarily transparent, for example for signaling purposes. In some cases, it may indeed be desirable to have a surface with good retroreflection efficiency for high angles of incidence. By way of example, such a surface may have utility for ground signaling applications in the field of motor vehicle routes. In the case where the transparency is not sought, it will preferably seek to maximize the coverage rate of the screen by the retroreflective portions of cube corners. In addition, the material of the film 351 may be non-transparent. The coating film 359 and the intermediate glue layer 361, on the other hand, must be transparent to allow the incident light to reach the cube-corner metallizations 357 and then to emerge from the screen after reflection on the faces of the metallizations. Alternatively, the coating film 359 and the intermediate glue layer 361 may be omitted. On the other hand, if the transparency of the screen is not required, the reflective metallizations 357 are not necessarily localized on the cube-corner portions of the substrate 351, but can form a continuous layer made by conformal deposition, coating the entire upper surface of the substrate 351.
    Note that in the present description, the term film has been used to designate the elements 351 and 359 of the screen 400. However, this term must be understood broadly, and includes in particular elements similar to films such as leaves, plates, etc.
    FIGS. 10A, 10B, 10C and 10D are cross-sectional views schematically illustrating an alternative embodiment of the method of FIGS. 3A, 3B, 4A, 4B, 5A, 5B, 6A, 6B, 7A, 7B, 8A, 8B and 9A, 9B. The method of FIGS. 10A, 10B, 10C and 10D differs from the method of FIGS. 3A, 3B, 4A, 4B, 5A, 5B, 6A, 6B, 7A, 7B, 8A, 8B and 9A, 9B essentially in the manufacturing steps of FIG. primary mold used to make the retroreflective screen.
    FIG. 10A illustrates an initial step during which, on and in contact with the front face of a first substrate 501 having a front face (the upper face in the orientation of FIG. 10A) and a rear face (FIG. the lower face in the orientation of Figure 10A), a layer 503 of a material such as the substrate 501 is selectively etchable with respect to the layer 503. The front face of the substrate 501 is preferably flat. For example, the substrate 501 is made of silicon and the layer 503 is made of silicon oxide. The layer 503 is for example formed by oxidation of the upper surface of the substrate 501.
    FIG. 10B illustrates a step subsequent to the formation of the layer 503, during which the first substrate 501 is transferred to a second substrate or support substrate 505, so that the front face of the layer 503, that is, that is, the face of the layer 503 opposite the substrate 501 is facing towards the substrate 505. By way of example, the substrate 505 is a silicon substrate identical or similar to the substrate 501, and the substrate 505 is coated with side of its front face (the upper face in the orientation of Figure 10B), a silicon oxide layer 507 identical or similar to the layer 503. In the transfer step of Figure 10B, the The front face of the layer 503 is brought into contact with the front face of the layer 507. In this example, the respective front faces of the silicon oxide layers 503 and 507 are surface-treated beforehand to obtain a molecular bonding of the two layers. when they are put in contact. The described embodiments are however not limited to this particular case. Alternatively, the support substrate 505 may not be of the same nature as the substrate 501. In addition, the support substrate 505 is not necessarily coated with a layer of the same nature as the layer 503. , the bonding of the substrates 501 and 505 can be achieved by a technique other than molecular bonding.
    FIG. 10C illustrates a step subsequent to the step of transferring the substrate 501 to the substrate 505, during which the substrate 501 is thinned from its rear face (that is to say its upper face in the orientation of Figure 10C). The thinning comprises for example a step of grinding the rear face of the substrate 501, followed by a planarization step, for example a mechanochemical polishing. More generally, any other known thinning process may be used. Alternatively, the thinning may comprise a cleavage step, followed by a planarization step. In this case, a prior ion implantation step may be provided to define the cleavage zone. If the thickness of the substrate 501 remaining above the layer 503 at the end of the cleavage step is insufficient, a step of depositing or growing a layer of the substrate material on the rear face of the substrate 501 may be provided after the cleavage step. At the end of the thinning step, the rear face of the substrate 501 is preferably substantially flat and parallel to the front face of the substrate 501. The thickness of the substrate 501 remaining above the layer 503 to the resulting from the thinning step is equal to the depth of the cavities or recesses in cube corners 311 of the primary mold that one seeks to achieve. By way of example, the thickness of substrate 501 remaining above layer 503 is in the range of 20 to 500 μm and preferably in the range of 50 to 200 μm.
    The process of FIGS. 3A, 3B, 4A, 4B, 5A, 5B, 6A, 6B, 7A, 7B, 8A, 8B and 9A, 9B is then carried out identically or similarly to what has been described above. , replacing the substrate 301 by the assembly formed by the thinned substrate 501, the layer 503, the support substrate 505 and the layer 507. For the implementation of this method, the rear face of the thinned substrate 501 is substituted for the upper face of the substrate 301.
    Figure 10D illustrates the step of fomation cavities or recesses 311 of the primary mold, extending substantially vertically in the substrate 501 from its rear face. This step corresponds to the step described above in relation to FIGS. 4A and 4B. In the process of FIGS. 10A to 10D, the etching process used to form the cavities 311 is chosen to etch the substrate selectively with respect to the material of the layer 503. By way of example, the cavities 311 are made by etching Deep ionic reactive (DRIE). The layer 503 forms an etch stop layer, that is to say that the etching of the cavities 311 is interrupted on the rear face of the layer 503. Thus, the bottom 312c of each cavity 311 is formed by the back side of layer 503.
    The other steps of the manufacturing process of the primary mold 320 and the method of manufacturing the retroreflective screen 400 from the primary mold 320, are identical or similar to what has been described with reference to FIGS. 3A, 3B, 4A, 4B, 5A, 5B, 6A, 6B, 7A, 7B, 8A, 8B and 9A, 9B.
    An advantage of the method of FIGS. 10A to 10D lies in the fact that the presence of the etch stop layer 503 ensures a good flatness of the bottom 312c of the cavities 311. In particular, the bottom 312c of each cavity 311 remains plane to the top S of the cube corner, so that the right angle obtained between the bottom 312c and the side faces 312a, 312b of each cavity 311 is clean (without rounding). This makes it possible to improve the retroreflection performance of the final screen with respect to the method of FIGS. 3A, 3B, 4A, 4B, 5A, 5B, 6A, 6B, 7A, 7B, 8A, 8B and 9A, 9B, in which the angle between the bottom 312c and the side walls 312a, 312b of each cavity 311 is likely to have a slight rounding.
    FIGS. 11A, 11B, 11C, 11D, 11E, 11F and 11G are cross-sectional views schematically illustrating another alternative embodiment of the method of FIGS. 3A, 3B, 4A, 4B, 5A, 5B, 6A, 6B, 7A, 7B. , 8A, 8B and 9A, 9B.
    The method of FIGS. 11A-11G has similarities with the method of FIGS. 10A-10D, and takes advantage of the presence of the etch stop layer 503 to form roughness on the bottom 312c of the cavities 311 of the primary mold, way to introduce a function of controlled diffusion of the light retroreflected by the screen, so that the user can see the image displayed by the projector even when the light source 105 is not placed exactly in the axis of the gaze of the user. This controlled diffusion is particularly interesting in systems in which the projector is dissociated from the user, for example when the projector is secured to the vehicle and not the user himself.
    FIGS. 11A and 11B illustrate an initial stage of formation of roughnesses on the front face of the substrate 501, before the deposition of the layer 503. For this, in the example represented, it is expected to deposit on the front face of the substrate 501 a photosensitive resin layer 601 (FIG. 11A), in which the desired roughness pattern is formed by a grayscale lithography step. The structures (not visible in FIG. 11A) of the resin layer 601 are then transferred by etching to the upper face of the substrate 501 (FIG. 11B). More generally, any other method for structuring the upper surface of the substrate 501 to obtain the desired diffusion function can be used. Examples of roughness patterns for obtaining a controlled diffusion of light are for example described in US8114248. Preferably, the roughnesses formed on the front face of the substrate 501 have dimensions greater than the longest wavelength of the light that one seeks to retroreflect.
    FIG. 11C illustrates a step of forming the layer 503 on and in contact with the structured front face of the substrate 501. This step is, for example, identical or similar to what has been described with reference to FIG. 10A. Once the layer 503 has been formed, the latter has on its rear face (ie its lower face in the orientation of FIG. 11C) structures complementary to those of the front face of the substrate 501. It will be noted that in the case where the layer 503 is formed by oxidation of the front face of the substrate 501, the roughnesses previously formed on the front face of the substrate 501 may be deformed by oxidation. The dimensioning of the roughnesses formed on the front face of the substrate 501 in the steps of FIGS. 11A and 11B can be achieved taking into account these deflations. In addition, although the subsequent etching step of the cavities 311 of the primary mold is carried out by a method of selective etching of the substrate 501 with respect to the layer 503, this etching step may nevertheless result in deformation of the structures of the rear face of the layer 503. This deformation can be taken into account in the dimensioning of the roughnesses formed on the front face of the substrate 501 in the steps of FIGS. 11A and 11B.
    Fig. 11D illustrates a planarization step of the front face (i.e., the upper face in the orientation of Fig. 11D) of the layer 503.
    FIG. 11E illustrates a step subsequent to the deposition of the layer 503, during which the substrate 501 is transferred to a second substrate or support substrate 505, so that the front face of the layer 503, that is to say say the face of the layer 503 opposite the substrate 501, is turned towards the substrate 505.
    This step is for example identical or similar to what has been described in connection with FIG. 10B.
    FIG. 11F illustrates a step subsequent to the step of placing the substrate 501 on the substrate 505, during which the substrate 501 is thinned from its rear face. This step is for example identical or similar to what has been described in relation to FIG. 10C.
    The process of FIGS. 3A, 3B, 4A, 4B, 5A, 5B, 6A, 6B, 7A, 7B, 8A, 8B and 9A, 9B is then carried out identically or similarly to what has been described above. , replacing the substrate 301 by the assembly obtained at the end of the step of FIG. 11F. For the implementation of this method, the rear face of the thinned substrate 501 is substituted for the upper face of the substrate 301.
    FIG. 11G illustrates the step of forming the cavities or recesses 311 of the primary mold, extending substantially vertically in the substrate 501, from its rear face. This step is for example identical or similar to what has been described in relation to FIG. 10D.
    The other steps of the manufacturing process of the primary mold 320 and the method of manufacturing the retroreflective screen 400 from the primary mold 320, are identical or similar to what has been described above and will not be detailed again.
    An advantage of the method of FIGS. 11A to 11G is that it makes it possible, in a relatively simple manner, to produce, in the cube corner regions of the cavities 311 of the primary mold 320, corresponding to the retroreflective portions of the screen 400, structuring adapted to increase the opening of the diffusion cone of the retroreflected light.
    It will be noted that in the examples of the manufacturing process of the primary mold of FIGS. 10A to 10D and 11A to 11G, the step of thinning the substrate 501 by its rear face can be omitted if the thickness of the substrate 501 is already equal to the depth of the cavities or recesses cube corners 311 that one seeks to achieve.
    In the examples of FIGS. 10A to 10D and 11A to 11G, the support substrate 505 on which the substrate 501 and the etch stop layer 503 are transferred serves to ensure the mechanical strength of the assembly from which is formed the primary mold. In particular, the support substrate 505 is necessary when the primary mold comprises demolding trenches 314 passing right through the substrate as has been described in connection with FIGS. 5A and 5B. Indeed, the trenches 314 being deeper than the cavities 311, the fomation of the trenches 314 amounts to cutting the substrate 501 into disjoint strips. In the absence of the support substrate 505, these substrate strips 501 would disengage from one another.
    权利要求:
    Claims (11)
    [1" id="c-fr-0001]
    1. A method of manufacturing a primary mold (320) for producing a retroreflective screen (400), said method comprising the following steps: a) forming on the front face of a first substrate (501) having a face before and a backside, a layer (503) of a material such as the first substrate (501) is selectively etchable relative to said layer (503); and b) forming microrevenements (311) from the rear face of the first substrate (501) by selective etching of the first substrate (501) with respect to said layer (503), each micro-recess (311) opening on the back side of said layer (503) and having a bottom (312c) substantially parallel to the front face of the first substrate (501) and first (312a) and second (312b) side walls substantially orthogonal to each other and substantially orthogonal to the bottom (312c), the first (312a) and second (312b) side walls and the bottom (312c) of the micro-recess joining at one point (S) and forming a trihedron.
    [2" id="c-fr-0002]
    2. The method of claim 1, further comprising, prior to step a), a step of forming roughness on the front face of the first substrate (501).
    [3" id="c-fr-0003]
    The method of claim 2, wherein the step of forming roughness on the front face of the first substrate (501) comprises a grayscale lithography step.
    [4" id="c-fr-0004]
    4. Method according to any one of claims 1 to 3, further comprising, after step a), a step of transfer of the first substrate (501) on a second substrate (505) support, so that the face before said layer (503) is facing the second substrate (505).
    [5" id="c-fr-0005]
    The method of claim 4, wherein the first (501) and second (505) substrates are joined by molecular bonding.
    [6" id="c-fr-0006]
    6. Method according to any one of claims 1 to 5, further comprising, between step a) and step b), a step of thinning the first substrate (501) by its rear face.
    [7" id="c-fr-0007]
    7. Method according to any one of claims 1 to 6, wherein, in step b), the microrenfoncements (311) are made by deep reactive ion etching.
    [8" id="c-fr-0008]
    The method of any one of claims 1 to 7, wherein the first substrate (501) is silicon and wherein said layer (503) is silicon oxide.
    [9" id="c-fr-0009]
    The method according to any one of claims 1 to 8, further comprising a step of forming, on the back side of the first substrate (501), trenches (314) with oblique or curved sides, each microdefinement (311). ) opening into a trench (314).
    [10" id="c-fr-0010]
    A method of manufacturing a retroreflective screen (400), comprising manufacturing a primary mold (320) by a method according to any one of claims 1 to 9, and replicating the patterns of the back side of the mold primary (320) on one side of a film (351) by molding from the primary mold (320).
    [11" id="c-fr-0011]
    A primary mold for making a retroreflective screen (400), comprising: a first substrate (501) having a front face and a back face; a layer (503) of a material such that the first substrate (501) is selectively etchable with respect to said layer (503), coating the front face of the first substrate (501); and microbreaks (311) extending from the rear face of the first substrate (501), each micro-recess (311) opening on the rear face of said layer (503) and having a bottom (312c) substantially parallel to the rear face of the first substrate (501) and first (312a) and second (312b) side walls substantially orthogonal to each other and substantially orthogonal to the bottom (312c), the first (312a) and second (312b) sidewalls and the bottom (312c) of the microrenfoncement (311) joining at one point (S) and forming a trihedron.
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    同族专利:
    公开号 | 公开日
    US20170197338A1|2017-07-13|
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    EP3192645A1|2017-07-19|
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    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US20040004765A1|2002-06-27|2004-01-08|Ichiro Ihara|Corner cube array and method of making the corner cube array|
    JP2011191404A|2010-03-12|2011-09-29|Stanley Electric Co Ltd|Two-face corner reflector array optical element and display device using the same|
    US6406638B1|2000-01-06|2002-06-18|The Regents Of The University Of California|Method of forming vertical, hollow needles within a semiconductor substrate, and needles formed thereby|
    US8114248B2|2007-01-03|2012-02-14|Asahi Kasei Kabushiki Kaisha|Roll-to-roll method and system for micro-replication of a pattern of large relief three-dimensional microstructures|
    FR3020149B1|2014-04-16|2017-09-15|Commissariat Energie Atomique|SYSTEM FOR DISPLAYING AN IMAGE ON A WINDSHIELD|
    FR3040502B1|2015-08-28|2018-02-16|Commissariat A L'energie Atomique Et Aux Energies Alternatives|SCREEN WITH RETROREFLECTIVE MICROSTRUCTURES|EP2499191A4|2009-11-12|2016-12-28|3M Innovative Properties Co|Irradiation marking of retroreflective sheeting|
    EP3764169A1|2019-07-10|2021-01-13|Patek Philippe SA Genève|Method for frosting some parts of a silicon timepiece component|
    FR3103575B1|2019-11-27|2021-12-03|Commissariat Energie Atomique|Screen with retro-reflective microstructures|
    法律状态:
    2017-01-31| PLFP| Fee payment|Year of fee payment: 2 |
    2017-07-14| PLSC| Publication of the preliminary search report|Effective date: 20170714 |
    2018-01-31| PLFP| Fee payment|Year of fee payment: 3 |
    2019-01-30| PLFP| Fee payment|Year of fee payment: 4 |
    2020-10-16| ST| Notification of lapse|Effective date: 20200906 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1650226|2016-01-12|
    FR1650226A|FR3046682B1|2016-01-12|2016-01-12|METHOD FOR MANUFACTURING A SCREEN WITH RETROREFLECTIVE MICROSTRUCTURES|FR1650226A| FR3046682B1|2016-01-12|2016-01-12|METHOD FOR MANUFACTURING A SCREEN WITH RETROREFLECTIVE MICROSTRUCTURES|
    EP17150779.1A| EP3192645B1|2016-01-12|2017-01-10|Method for manufacturing a screen provided with retroreflective microstructures|
    US15/404,684| US10583585B2|2016-01-12|2017-01-12|Method of manufacturing a screen provided with retroreflective microstructures|
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