SWITCHABLE DIFFUSION OR TRANSPARENCY ASSEMBLY, WITH VISIBLE AND NON-VISIBLE SEGMENTS

Abstract

The invention relates to an electrically switchable diffusion or transparency assembly (1) comprising an electrical control unit (ECU) and a laminated window (2) comprising an electrically switchable diffusion or transparency system (4) comprising a dispersed liquid crystal polymer layer having a series (S) of n, a positive integer greater than 1, juxtaposed and separately switchable segments (41, 41'), and in which at least one segment (41') is not visible from the exterior space and / or the interior space. Abstract figure: [Fig. 1]

Description

Title of the invention: SWITCHABLE DIFFUSION OR TRANSPARENCY ASSEMBLY, WITH VISIBLE AND NON-VISIBLE SEGMENTS Technical field

[0001] The invention relates to the field of glazing comprising an electrically switchable diffusion or transparency system.

[0002] The invention relates more broadly to an electrically switchable diffusion or transparency assembly comprising an electrical control unit and a laminated pane comprising an outer glass sheet, an inner glass sheet and an electrically switchable diffusion or transparency system located between said two glass sheets. In this assembly, the outer and inner glass sheets protect the electrically switchable diffusion or transparency system because it is fragile.

[0003] In this assembly, the glass generally has an outer face intended to be oriented towards an exterior space and an inner face intended to be oriented towards an interior space. The outer glass sheet then has an outer face which, thanks to the lamination operation, is merged with the outer face of said glass, an inner face which is oriented towards said electrically switchable diffusion or transparency system; the inner glass sheet thus has an inner face which is oriented towards said electrically switchable diffusion or transparency system, an inner face which is merged with the inner face of said glass.

[0004] Said electrically switchable diffusion or transparency system generally comprises a dispersed liquid crystal polymer layer having a series of n, positive integer greater than 1, juxtaposed segments which can be switched separately by the electrical control unit.

[0005] The invention is described with regard to an application of said assembly to a vehicle bay, and more precisely to a vehicle roof.

[0006] It is known that the roof glazing of vehicles is used in a part of the bodywork. These glazings can be designed as conventional glazings or as non-transparent glazings.

[0007] It is also known that functional glazings are used in buildings and / or vehicles. Windshields are also known in which a sun visor is integrated in the form of a functional element having electrically controllable optical properties, in particular a transmission or Electrically controlled diffusion. This allows the driver to control the transmission behavior of the windshield in the face of solar radiation, thus eliminating the need for a conventional mechanical sunshade. Electrically adjustable sunshades are also used in the glass roofs of motor vehicles.

[0008] Particularly in the case of large panoramic windows, it is necessary to variably control the transmission of the window. Depending on the position of the sun, it is sufficient to darken partial areas of the window or to make the entire area dark to protect the view into the parked vehicle.

[0009] Such an electrically switchable functional element is a functional element called "PDLC" (for "Polymer Dispersed Liquid Crystal" in English). The active layer contains liquid crystals embedded in a polymer matrix and this active layer is framed, on these two faces, by a thin conductor, generally based on oxide called "TCO" (for "Transparent Conductive Oxide" in English).

[0010] If no voltage is applied between the two TCO layers, the liquid crystals are aligned in a disordered manner, which results in strong scattering of the light passing through the active layer and a haze of around 97%, thus resulting in opacity through the glass; the light transmission can be around 10%.

[0011] When a voltage is applied to the surface electrodes, the liquid crystals align in a common direction and the haze disappears almost completely (there may remain a residual haze of the order of 5%); the transmission of light through the active layer (TL) is similar or may be slightly increased.

[0012] The electrical contacting of the electrically controlled functional elements is generally carried out via bus bars (also called "bus bars"), which are applied to the surface electrodes in the edge area of ​​the functional element and contact them in an electrically conductive manner. By connecting the bus bars to an external voltage source, for example via flat conductors attached to the bus bars, a voltage is applied to the surface electrodes and the active layer of the functional element is switched.

[0013] It is also known to provide several zones, or segments in the useful surface of the functional element and to allow these segments to operate independently of each other thanks to the electrical control unit otherwise called ECU (for “Electrical Command Unit” in English).

[0014] The development of the ECU is complex: many parameters must be taken into consideration so that the power supply produces the desired effect in the active layer and in particular, the nature of this layer, its thickness, the dimensions of the segments, etc.

[0015] Furthermore, the dimensions of the windows themselves can vary from one model to another. vehicle to another and it can then be complicated to modify the parameters of an ECU tested for one series of glazing to adapt this ECU to another series of glazing.

[0016] The inventors discovered that, surprisingly, it was possible to adapt quite simply an ECU designed for one series of glazings so that it could operate for another series of glazings.

[0017] The present invention intends to propose a solution in which at least one segment is present in the glazing but is hidden.

[0018] Thus, for example, when the number of visible segments for the electrically switchable diffusion or transparency assembly is less than the number of segments available for the electrically switchable diffusion or transparency assembly, at least one segment is non-visible, without having to physically modify the ECU.

[0019] For this purpose, the invention relates to an electrically switchable diffusion or transparency assembly comprising an electrical control unit and a laminated pane comprising an outer glass sheet, an inner glass sheet and an electrically switchable diffusion or transparency system located between said two glass sheets, said pane having an outer face intended to be oriented towards an outer space and an inner face intended to be oriented towards an inner space, said outer glass sheet having an outer face which is the same as the outer face of said pane, an inner face which is oriented towards said electrically switchable diffusion or transparency system, said inner glass sheet having an inner face which is oriented towards said electrically switchable diffusion or transparency system, an inner face which is the same as the inner face of said pane,said electrically switchable diffusion or transparency system comprising a dispersed liquid crystal polymer layer having a series of n, positive integer greater than 1, juxtaposed and separately switchable segments, said assembly being remarkable in that at least one segment is not visible from said exterior space and / or said interior space.

[0020] Said electrically switchable diffusion or transparency system comprising a dispersed liquid crystal polymer layer may have a series of n, positive integer > 3, or even > 5, or even > 7 juxtaposed and separately switchable segments; it may have a series of n between 2 and 20, or even between 3 and 15, and in particular n = 9 juxtaposed and separately switchable segments.

[0021] Preferably, a fixed trim element is located further inward than the inner face of said window.

[0022] Preferably, the outer face or the inner face of said outer glass sheet comprises a covering means located opposite said at least one non-visible segment and / or in which the internal face or the inner face of said inner glass sheet comprises a covering means located opposite said at least one non-visible segment, said covering means having a length equal to or greater than a length of said at least one non-visible segment, this covering means preferably being a layer of enamel.

[0023] Preferably, said electrically switchable diffusion or transparency system comprises a covering means located opposite said at least one non-visible segment, this covering means preferably being an opaque film; this opaque film is for example positioned on the external internal face or the internal internal face of said electrically switchable diffusion or transparency system; it can also be located inside said electrically switchable diffusion or transparency system.

[0024] Preferably, said segments are juxtaposed along a length, n is an odd number, preferably n=9, and said at least one non-visible segment is located in the middle of said series along said length.

[0025] Preferably, said segments are juxtaposed along a length, n is an odd number, preferably n=9, and said at least one non-visible segment is located at one end of said series along said length, preferably at two ends of said series along said length.

[0026] Preferably, said segments are juxtaposed along two parallel lengths, n is an odd number, preferably n=9, and said at least one non-visible segment is located at one end of said series along the two lengths.

[0027] Preferably, a second laminated glass pane is positioned adjacent to said laminated glass pane, said second laminated glass pane comprising an outer glass sheet, an inner glass sheet and an electrically switchable diffusion or transparency system located between said two glass sheets and in which said electrical control unit is unique.

[0028] Preferably, said at least one non-visible segment is not powered by said electrical control unit, in order to save energy.

[0029] This (these) non-visible segment(s) is (are), each, physically connected to the electrical control unit ECU so that it has a behavior with all its segments (for example n = 9) but the non-visible segment(s) will never be switched; it (they) will not be electrically powered).

[0030] Preferably, said at least one non-visible segment has at least one curved edge.

[0031] The following figures illustrate the invention in a non-limiting manner: - [Fig.l] illustrates a schematic front view, from the inside, of an assembly according to the invention; - [Fig.2] illustrates a cross-sectional view along A-A' and partially exploded of the glass of [Fig.l]; - [Fig.3] illustrates a longitudinal sectional view along B-B' and partially exploded of the window of [Fig.l]; and - [Fig.4] to [Fig.9] each illustrate a schematic front view, from the inside, of a variant of a window for an assembly according to the invention.

[0032] The elements shown are not to scale with each other in each figure; background elements are generally not shown.

[0033] The present invention relates to an electrically switchable diffusion or transparency assembly 1, as seen in [Fig.1] and in partially exploded views in [Fig.2], and [Fig.3], comprising an electrical control unit ECU and a laminated window 2. This window 2 comprises an outer glass sheet 3, an inner glass sheet 5 and an electrically switchable diffusion or transparency system 4 located between said two glass sheets.

[0034] The present invention is described by way of example in the context of an application as vehicle glazing, and in particular for a motor vehicle, this glazing providing a separation between an exterior space E which is exterior to the vehicle and an interior space I which is interior to the vehicle. The concepts of “exterior face” and “interior face” are therefore considered in relation respectively to this exterior space E and this interior space I.

[0035] The present invention is described in particular as applied to a vehicle roof glazing; [Fig.l] being a front view, of the interior space I, of the assembly before its installation in a vehicle.

[0036] In the context of the present document, the notion of verticality is introduced with reference to the vertical axis Z of a vehicle; the central horizontal longitudinal axis of advance of the vehicle equipped with the glazing according to the invention as side glazing, being the axis generally called the X axis of the vehicle, as visible in [Fig.l] and the horizontal lateral axis being the Y axis.

[0037] The window 2 has an outer face 20 intended to be oriented towards the outer space E and an inner face 22 intended to be oriented towards the inner space I. The outer glass sheet 3 thus has an outer face 30 which is merged with the outer face 20 of the window 2, an inner face 32 which is oriented towards the electrically switchable diffusion or transparency system 4; the inner glass sheet 5 thus having an inner face 52 which is merged with the inner face 22 of the window 2 and an inner face 50 which is oriented towards the electrically switchable diffusion or transparency system 4.

[0038] The window 2 can be curved.

[0039] As seen in more detail in [Fig.2] and [Fig.3], the diffusion system or electrically switchable transparency 4 includes an electrically switchable functional element 49 (seen unbroken in these figures).

[0040] The electrically switchable diffusion or transparency system has a series S of n, a positive integer greater than 1, segments 41, 41' juxtaposed and separately switchable.

[0041] The electrically switchable diffusion or transparency system comprising a dispersed liquid crystal polymer layer may have a series of n, positive integer > 3, or even > 5, or even > 7 juxtaposed and separately switchable segments; it may have a series of n between 2 and 20, or even between 3 and 15. Here, the electrically switchable diffusion or transparency system comprising a dispersed liquid crystal polymer layer has a series of n = 9 juxtaposed segments and all separately switchable via the single electrical control unit (ECU).

[0042] The electrically switchable diffusion or transparency system 4 has an outer intermediate face 40 which is oriented towards the inner face 32 and which is here in contact with this inner face 32 in the laminated glass 2, an inner intermediate face 42 which is oriented towards the outer face 50 and which is here in contact with this outer face 50 in the laminated glass 2 and an edge which is located between these two intermediate faces.

[0043] The electrically switchable diffusion or transparency system 4 comprises, depending on its thickness, for example a total of three thermoplastic films 6, 6', 6” with a thickness of for example 0.38 mm in PVB. A first thermoplastic film 6, external, is bonded to the outer glass sheet 3 during the lamination operation of the window 2. A second thermoplastic film 6', internal, is also bonded to the outer glass sheet 3 during the lamination operation of the window 2. A third thermoplastic film 6”, central, is located between the first film and the second and is sandwiched between them during the operation of integrating the functional element 49 into the electrically switchable diffusion or transparency system 4, prior to the lamination operation of the window 2.The third 6” thermoplastic film follows the periphery of the electrically switchable diffusion or transparency system 4 and is perforated in its center to accommodate the functional element 49.

[0044] The third thermoplastic film thus forms a sort of master key for the functional element 49, which is thus encapsulated all around in thermoplastic material and is therefore protected. The functional element 49 is inserted with a precise fit into the central hole of the third thermoplastic film 6” just before the lamination operation of the glass 2.

[0045] At the center, along the X and Y axes, of the functional element 49, the latter comprises, along its thickness (Z axis), in this order from the external space E, the first film thermoplastic 6, the functional element 49 and second thermoplastic film 6' while at the periphery it comprises, according to its thickness, in this order from the external space E, the first thermoplastic film 6, third thermoplastic film 6” and second thermoplastic film 6'.

[0046] This embedding of the functional element 49 in the electrically switchable diffusion or transparency system 4, itself integrated in a laminated window 2, is well known to the person skilled in the art, so that a precise representation is unnecessary. As is also known to the person skilled in the art, the functional element 49 generally comprises a dispersed liquid crystal polymer layer 400, which is the active layer and which is located between two surface electrodes 46, 46' and two carrier films '47, 47'. The active layer contains a polymer matrix in which liquid crystals are dispersed, which align themselves according to the electrical voltage applied to the surface electrodes 46, 46' by the ECU, whereby the optical properties of the window 2 can be controlled.

[0047] The functional element 49 is here divided for example into nine segments by insulation lines 44.

[0048] The segments are designed as strips, which can be straight or with curved contours. The insulation lines 44 between the segments have, for example, a width of 40 μm (micrometers) to 50 μm. It can, for example, be introduced into the prefabricated multilayer film using a laser.

[0049] In particular, the insulation lines 44 separate both the functional element 49 and the upper surface electrode 46' into strips insulated from each other and connected, each to each other by an electrically conductive track 48' to a separate electrical connection C1, C2 ... up to C9 of the electrical control unit ECU; the lower surface electrode 46 is connected to the common return m by a common track 48. The supply voltage here is 48V alternating current.

[0050] The nine segments can thus be switched independently of one another.

[0051] The respective surface electrodes of the segments 49 are brought into contact individually on one side via bus bar sections 45' (shown on the left in [Fig.l]) and on the opposite side via a common bus bar 45 (shown on the right in [Fig.l]).

[0052] In order to apply voltage to the individual busbar sections of the nine segments and to the common busbar 45, ten independent power line connections are required here, for example.

[0053] A connection arrangement as known from international patent application No. WO 2023 / 052099 may be used.

[0054] The driver or another occupant of the vehicle can, for example, operate the PDLC functional element depending on the position of the sun, for example via a touch control element (not shown here).

[0055] According to the invention, a series S of n, positive integer greater than 1, segments 41, 41' juxtaposed and separately switchable is provided in the electrically switchable diffusion or transparency system 4 and at least one segment 41' of this series S is not visible from the exterior space E and / or from the interior space I; Thus, regardless of the state of this non-visible segment 41' (operation or not via the ECU), the entirety of this segment is not visible respectively to a person in the exterior space E and / or to an occupant of the vehicle in the interior space I.

[0056] As visible in [Fig.3], the means for making the segment 41' invisible from the interior space I may be a fixed trim element 15 which is located further into the interior space I than the inner face 22 of the window 2.

[0057] Alternatively or cumulatively, the means for making the segment 41' non-visible from the interior space I may be a covering means 53 which is located on the internal face 50 or on the internal face 52 of the interior glass sheet 5, opposite the at least one non-visible segment 41', the covering means 53 having a length L3, along the axis X, equal to or greater than a length L4' of the at least one non-visible segment 41', hidden by this covering means 53.

[0058] Alternatively or cumulatively, the means for making the segment 41' non-visible from the interior space I may be a covering means 43 located on the interior intermediate face 42 of the electrically switchable diffusion or transparency system 4, opposite the at least one non-visible segment 41', the covering means 43 having a length L3, along the axis X, equal to or greater than a length L4' of the at least one non-visible segment 41', hidden by this covering means 43.

[0059] Alternatively or cumulatively, the means for making the segment 41' invisible from the external space E may be a covering means 33 located on the external face 30 or on the internal face 32 of the external glass sheet 3 opposite the at least one invisible segment 41', the covering means 33 having a length L3, along the axis X, equal to or greater than a length L4' of the at least one invisible segment 41', hidden by this covering means 33.

[0060] Alternatively or cumulatively, the means for making the segment 41' non-visible from the interior space I may be a covering means 43 located on the outer intermediate face 40 of the electrically switchable diffusion or transparency system 4, opposite the at least one non-visible segment 41', the covering means 43 having a length L3, along the axis X, equal to or greater than a length L4' of the at least one non-visible segment 41', hidden by this covering means 43.

[0061] The covering means 33, 53 applied to one face of a glass sheet may be, for example, a layer of enamel, in particular black enamel, present locally in the form of a strip.

[0062] The covering means 43 applied to one face of the electrically switchable diffusion or transparency system 4 may be, for example, an opaque film, present locally in the form of a strip.

[0063] Seven main variants of the production of laminated glass 2 with electrically switchable diffusion or transparency are presented here. In these variants, only the position of the non-visible segment(s) 41' vary.

[0064] The means for making the exterior space E and / or the interior space I invisible may be those presented in [Fig.2] and [Fig.3].

[0065] In a first variant, illustrated in [Fig.l], [Fig.2] and [Fig.3], the segments 41, 41' of the series S are juxtaposed along the length L, n= 9, and two non-visible segments (41') are each located at one end of the series S along the length L.

[0066] In a second variant, illustrated in [Fig.4], the segments 41, 41' of the series S are juxtaposed along the length L, n= 9, and the non-visible segment 41' is unique and is located in the middle of the series S along the length L; thus, starting from the top in this figure, only the four segments 41 at the top and the four segments at the bottom are visible from the exterior space E and / or from the interior space I.

[0067] In a third variant, illustrated in [Fig.5], the segments 41, 41' of the series S are juxtaposed along the length L, n= 9, and two non-visible segments 41' are located at the bottom of the series S along said length L; thus, starting from the top in this figure, only the seven segments 41 at the top are visible from the exterior space E and / or from the interior space I.

[0068] In a fourth variant, illustrated in [Fig.6], the segments 41, 41' of the series S are juxtaposed along two parallel lengths L, L', both extending along the X axis, n=9, and only one segment 41' is not visible, at the top; it is located at one end of the series S along the two lengths L, L'. Starting from the top in this figure, only the eight segments 41 located lower than the first segment, at the top, are visible from the exterior space E and / or the interior space I. The non-visible segment 41' could of course be at the bottom.

[0069] In a fifth variant, illustrated in [Fig.7], the segments 41, 41' of the series S are juxtaposed along the length L, n= 9 and only one segment 41' is not visible; it is located at the upper end of the series S along the length L; it could be located at the lower end of the series S along the length L.

[0070] In a sixth variant, illustrated in [Fig.8], the assembly 1 comprises two laminated panes: a second laminated pane 2' is positioned adjacent to the laminated pane 2, here in the direction X. This second laminated pane 2' also comprises, like the other laminated glass 2: an outer glass sheet 3, an inner glass sheet 5 and an electrically switchable diffusion or transparency system 4 located between said two glass sheets, similar or identical. In this assembly 1 of [Fig.8], the electrical control unit ECU (not shown) is unique.

[0071] In this sixth variant, as for the second variant, the segments 41, 41' of the series S are juxtaposed along the length L, n= 9, and the non-visible segment 41' is unique and is located in the middle of the series S along the length L; thus, starting from the top in this [Fig.8], only the four segments 41 at the top of the laminated glass 2 at the top and the four segments of the second laminated glass 2' at the bottom are visible from the exterior space E and / or from the interior space I.

[0072] In variants 1 to 6, the non-visible segment(s) 41' are in the form of straight transverse strip(s) (elongated in the Y direction); that is to say in the form of straight parallelepiped(s).

[0073] In a seventh variant, illustrated in [Fig.9], the segments 41, 41' of the series S are juxtaposed along the length L, n= 9 and a single segment 41' is not visible; it is located at the upper end of the series S along the length L, as for the fifth variant; here, the non-visible segment 41' is in the form of a strip with a curved edge, here in the direction of the center of the laminated glass 2.

[0074] The non-visible segment 41' with a curved edge could be located at the lower end of the series S along the length L or the set 1 could comprise two non-visible segments 41' each having a curved edge.

[0075] When a non-visible segment 41' has at least one curved edge, preferably the edge of the covering means 33, 43, 53 follows the curvature of this curved edge.

[0076] Whatever the shape of the edges of a non-visible segment 41', preferably, the edge of the covering means 33, 43, 53 which hides this non-visible segment 41' follows the edge of this non-visible segment 41', preferably extending a little more than the edge of this non-visible segment 41' in order to guarantee that this non-visible segment 41' is well hidden from the exterior space E and / or from the interior space I.

[0077] The seven variants above do not constitute an exhaustive presentation. They can be combined with each other.

[0078] For the manufacture of the glazing 1 according to the invention, the outer 3 and inner 5 glass sheets are cut to the desired size, and these glass sheets are then curved and thermally toughened, or even semi-thermally toughened; one of these sheets may optionally be chemically toughened rather than thermally toughened.

[0079] For the lamination operation as such, the electrically switchable diffusion or transparency system 4 is prepared to the desired dimension. Then, the electrically switchable diffusion or transparency system 4 is interposed between the outer glass sheet 3 and the inner glass sheet 5. Finally, the lamination is implemented: the temperature and pressure will cause the electrically switchable diffusion or transparency system 4 (and more precisely the first thermoplastic film 6 and the second thermoplastic film 6') to adhere to the outer 3 and inner 5 glass sheets on the one hand and the third thermoplastic film 6' on the other hand.

[0080] The present invention constitutes in particular a reliable and practical solution for managing different configurations of assemblies 1 with electrically switchable diffusion or transparency.

Claims

Claims

1.

2.

3.

4. Electrically switchable diffusion or transparency assembly (1) comprising an electrical control unit (ECU) and a laminated window (2) comprising an outer glass sheet (3), an inner glass sheet (5) and an electrically switchable diffusion or transparency system (4) located between said two glass sheets, said window (2) having an outer face (20) intended to be oriented towards an exterior space (E) and an inner face (22) intended to be oriented towards an interior space (I), said outer glass sheet (3) having an outer face (30) which is merged with the outer face (20) of said window (2), an inner face (32) which is oriented towards said electrically switchable diffusion or transparency system (4), said inner glass sheet (5) having an inner face (50) which is oriented towards said electrically switchable diffusion or transparency system (4),an inner face (52) which is merged with the inner face (22) of said window (2), said electrically switchable diffusion or transparency system (4) comprising a dispersed liquid crystal polymer layer (400) having a series (S) of n, positive integer greater than 1, segments (41, 41') juxtaposed and separately switchable, characterized in that at least one segment (41') is not visible from said outer space (E) and / or from said inner space (I)., Assembly (1) according to claim 1, wherein a fixed trim element (15) is located further inward than the inner face (22) of said window (2). Assembly (1) according to claim 1 or 2, wherein the outer face (30) or the inner face (32) of said outer glass sheet (3) comprises a covering means (33) located opposite said at least one non-visible segment (41') and / or wherein the inner face (50) or the inner face (52) of said inner glass sheet (5) comprises a covering means (53) located opposite said at least one non-visible segment (41'), said covering means (33, 53) having a length (L3) equal to or greater than a length (L4') of said at least one non-visible segment (41'), this covering means (33, 53) preferably being a layer of enamel. Assembly (1) according to any one of claims 1 to 3, in wherein said electrically switchable diffusion or transparency system (4) comprises a covering means (43) located opposite said at least one non-visible segment (41'), this covering means (43) preferably being an opaque film.

5. Assembly (1) according to any one of claims 1 to 4, in which said segments (41, 41') are juxtaposed along a length (L), n is an odd number, preferably n= 9, and said at least one non-visible segment (41') is located in the middle of said series (S) along said length (L).

6. Assembly (1) according to any one of claims 1 to 5, in which said segments (41, 41') are juxtaposed along a length (L), n is an odd number, preferably n= 9, and said at least one non-visible segment (41') is located at one end of said series (S) along said length (L), preferably at two ends of said series (S) along said length (L).

7. Assembly (1) according to any one of claims 1 to 5, in which said segments (41, 41') are juxtaposed along two parallel lengths (L, L'), n is an odd number, preferably n= 9, and said at least one non-visible segment (41') is located at one end of said series (S) along the two lengths (L, L').

8. An assembly (1) according to any one of claims 1 to 7, wherein a second laminated pane (2') is positioned adjacent to said laminated pane (2), said second laminated pane (2') comprising an outer glass sheet (3), an inner glass sheet (5) and an electrically switchable diffusion or transparency system (4) located between said two glass sheets and wherein said electrical control unit (ECU) is unique.

9. Assembly (1) according to any one of claims 1 to 8, wherein said at least one non-visible segment (41') is not powered by said electrical control unit (ECU).

10. Assembly (1) according to any one of claims 1 to 9, in which said at least one non-visible segment (41') has at least one curved edge.

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