OPTICAL LIQUID CRYSTAL SYSTEM

Description

[0001] The invention relates to a liquid crystal optical system comprising an electrically controllable liquid crystal variable scattering device.

[0002] We know of glazings whose certain characteristics can be modified under the effect of an appropriate electrical supply, in particular the transmission, absorption, reflection in certain wavelengths of electromagnetic radiation, notably in the visible and / or infrared, or even light diffusion.

[0003] Electrically controlled liquid crystal glazing can be used everywhere, both in the construction and automotive sectors, whenever the view through the glazing must be prevented at certain times.

[0004] The liquid crystal layers are known as “PDLC” (Polymer Dispersed Liquid Crystal) in the form of droplets of first liquid crystals dispersed in a polymer matrix or “PSLC” (Polymer Stabilized Liquid Crystal) liquid crystals distributed homogeneously.

[0005] Patent application WO2020 / 065038 proposes an electrically controllable liquid crystal device based on "PSLC" and comprising two-dimensional topological defects making it possible to obtain numerous diffusion states in a reversible manner. Documents WO 2021 / 115246 A1, WO 2015 / 177356 A1, US 2012 / 140133 A1 are also part of the state of the art useful for understanding the invention.

[0006] An object of the invention is to develop an electrocontrollable liquid crystal device with even more custom-tunable electro-optical properties. To this end, the present invention provides a liquid crystal optical system comprising: an electrically controllable device with variable diffusion (planar or curved device, in particular flexible), called the first device, comprising a stack of layers (air layer included, possibly preferably forming a set of (solid) layers including a liquid crystal layer) following: a first transparent electrode, in particular self-supporting (film, possibly flexible) or preferably on a dielectric substrate, preferably transparent (and possibly flexible), in particular a substrate with a thickness of at most 1 cm, 5 mm, 3 mm or submillimeter or in particular a substrate which is a plastic film or thin or ultrathin glass ('UTG' in English), a film with a thickness of submillimeter and even at most 200 nm, in particular a first electrode comprising (or even consisting of) a first electrically conductive layer (monolayer or multilayer, in particular deposit(s)) in particular mineral, in particular with a thickness of at most 200 nm (on the first substrate),first electrode with a first main surface called the first connecting surface and an opposite surface called the Sb surface, in particular a first electrode comprising a first current supply means (strip - bus bar - in particular metallic, copper, silver, etc.) at the edge of the first connecting surface a second transparent electrode, preferably facing the first electrode (two electrodes forming a "plane - plane" configuration), in particular self-supporting (possibly flexible) or preferably on a dielectric support, preferably transparent (preferably separate from said substrate for the first electrode in the "plane - plane" configuration), in particular a support with a thickness of at most 1 cm, 5 mm, 3 mm or submillimeter, in particular a plastic film or thin or ultrathin glass (UTG in English), a film with a thickness of submillimeter and even at most 200 nm,in particular second electrode comprising (or even consisting of) a second electroconductive layer (monolayer or multilayer in particular deposit(s)) in particular mineral in particular of at most 200nm (on the support), second electrode having a main surface called second bonding surface SA2 and with an opposite external surface SB2, in particular second electrode comprising a second current supply means (strip in particular metallic, bus bar) at the edge of the second bonding surface and better opposite the first current supply means, with a first electric field E1 between the first and second electrodes a first dielectric electroactive layer with a main face called face FA1 first bonding surface SA1 and a main face called face FA2 opposite preferably on the side of second bonding surface SA2, preferably between the first and second electrodes (plane-plane configuration),the first electroactive layer being of thickness Ep 1 submillimeter and even at most 100µm and at least 50nm, in particular from 50nm to 50µm and even from 100nm to 20µm and better at least 1µm or 5µm, first electroactive layer in a first material preferably thermotropic containing (or even consisting of): first liquid crystals (preferably thermotropic) preferably in the majority by weight in the material (preferably at least 50%, 70%, 80%, 85% by weight of said first liquid crystals), in particular first liquid crystals comprising mesogens, for example without polymer chain or which are groups incorporated in a main or side chain of a polymer (family called 'LCP' in English), in particular first liquid crystals of size at most 50nm, 20nm or 10nm (and less than Ep 1 ), in particular a mixture of several first liquid crystals (pure, in the non-LCP sense),therefore several mesogens, in particular first liquid crystals which on the FA1 face or preferably on the FA2 face are oriented in a first direction b in the off state (de-energized) via a unidirectional anchoring layer in the first direction b in contact with the FA1 or FA2 face, preferably polymers forming a (three-dimensional) polymer network, the first liquid crystals being stabilized (physically) by the polymer network - (i.e. of the PSLC family in English or CLSPS in French), preferably with at most 20%, 15%, 10%, 5% by weight of polymer (or polymers and polymer precursors), possibly precursors of said polymers or even non-crosslinked polymers (in particular by adjusting the polymerization rate), at least one first dichroic dye (in particular in the dissolved state, in particular in the first liquid crystals), for example at most 30%, 20%, 10%,5% by weight of first dichroic dye (one or more first dichroic dyes), first dichroic dye in particular of size of at most 50nm, 20nm or 10nm (and less than Ep 1 ) in particular first liquid crystals and first dichroic dye are of comparable sizes for example each of less than 20 or 10nm, preferably (first) spacers in particular of height (and even of greater dimension) less than or equal to Ep 1 , at the periphery (dielectric, transparent or not possibly masked by a frame, for example in mylar etc) and / or dispersed in the first electroactive layer (dielectric, transparent, in particular plastic, glass, silica, preferably subcentimetric, in particular beads) possibly additives (other than the first dichroic dye), for example coloring particles such as metallic nanoparticles (gold, silver, alloy of the two etc) or metal oxide (tungsten oxide,tin etc) or even any other non-dichroic dye or any other light-absorbing molecule, preferably of height less than or equal to Ep1 (and even of greater dimension less than or equal to Ep1).

[0007] Preferably, the first electroactive layer is sealed at the periphery by a dielectric seal, in particular a polymeric one (at the edge of the first and second bonding surfaces, in contact with the material based on the first crystals or separated by a peripheral spacer), for example at most 1 cm wide.

[0008] Furthermore, the first material has a mesophase called P, from a temperature called T1 (and below a temperature called Tf which can be the transition temperature in isotropic phase), in which in particular the first material comprises (in volume, in the thickness most often), a set of domains (containing the first liquid crystals stabilized by the polymer network and the first dichroic dye(s) and possibly additives), and is even essentially divided into said domains or volume elements, - the domains preferably extending at least over a fraction of the thickness Ep1 and preferably at least 90% of the thickness. And the domains comprise two-dimensional topological defects in particular line defects with at least two forms of line defects (for example one elliptical - circle included - the other straight line or curve, hyperbola etc).

[0009] In particular, from a temperature T' greater than or equal to T1 (and below a temperature called Tf which may be the isotropic phase transition temperature), the electrically controllable device is thus capable of exhibiting a plurality of reversible diffusing and / or colored states, in particular under a first electric field E1 between the first and second electrodes (normal or parallel to the first and second electrodes), in particular under a given electric voltage U1 preferably of at most 120V or 100V.

[0010] Furthermore, the system according to the invention comprises, face to face with the first device, a variable polarization device (in transmission), electroswitchable, called the second device, comprising: third and fourth transparent electrodes, with a second electric field E2 between the third and fourth electrodes, in particular the third and fourth electrodes being coplanar or of plane-plane configuration, self-supporting (possibly flexible) or in the form of third and fourth electroconductive layers on a common carrier element (coplanar configuration) or separate carrier elements facing each other (plane-plane configuration) a second electroactive layer, with a main face FA3 on the third electrode side and a main face FA4 opposite FA3, being of submillimeter thickness Ep 2 and even of at most 100µm and of at least 50nm, in particular from 50nm to 50µm and even from 100nm to 20µm and better still of at least 1µm or 5µm, second electroactive layer in a second material - thermotropic (preferably) - containing (or even consisting of): second thermotropic liquid crystals preferably which are (at T' and beyond) nematic, curved or not,preferably twisted (under the action of anchoring layers) in the off state without electrical voltage and / or cholesteric- (preferably majority by weight in the material (preferably at least 50%, 70%, 80%, 85% 95% by weight of said second liquid crystals), in particular second liquid crystals comprising mesogens, for example without polymer chain or which are groups incorporated in a main or side chain of a polymer (family called 'LCP' in English), in particular second liquid crystals of size of at most 50nm, 20nm or 10nm (and less than Ep 2 ), in particular a mixture of several second liquid crystals (pure, in the non-LCP sense), therefore several mesogens of the second dichroic dyes, (in particular in the dissolved state, in particular in the second liquid crystals), for example at most 30%, 20%, 10%, 5% by weight of second dichroic dyes (one or more second dichroic dyes),second dichroic dye in particular of size of at most 50nm, 20nm or 10nm (and less than Ep 2 ) in particular second liquid crystals and second dichroic dyes are of comparable sizes for example each of less than 20 or 10nm, second dichroic dyes preferably having an absorption wavelength included in the absorption range of the first dichroic dyes possibly polymers (preferably not crosslinked) or polymer precursor preferably with at most 20%, 15%, 10%, 5% or 1% by weight of polymer (or polymers and polymer precursors), for example the second electroactive layer not being of the type (PDLC or PSLC) preferably other spacers in particular of height (and even of larger dimension) less than or equal to Ep2, at the periphery (dielectric, transparent or not possibly masked by a frame, for example in mylar etc) and / or dispersed in the second layer electroactive (dielectric,transparent, in particular plastic, glass, silica, preferably subcentimetric, in particular beads) possibly other additives (other than the second dichroic dyes), for example coloring particles such as metallic nanoparticles (gold, silver, alloy of the two etc.) or metallic oxide (tungsten oxide, tin oxide etc.) or even any other non-dichroic dye or any other light-absorbing molecule, preferably of height less than or equal to Ep2 (and even of greater dimension less than or equal to Ep2).

[0011] Preferably, the second electroswitchable electroactive layer is sealed at the periphery by a dielectric seal, in particular a polymeric one (at the edge of the main surfaces), in contact with the second material based on second crystals or separated by a peripheral spacer).

[0012] The third electrode extends between the second electroactive layer and the first device (therefore on the side of the first device) for example oriented towards the second surface SB2 if the first device has a planar electrode configuration.

[0013] Furthermore, the fourth electrode may be coplanar with the third electrode (thus also between the second electroactive layer and the first device) or the active layer being between the third and fourth electrodes (plane-plane configuration). Thus according to the invention the combination of said first polarization-sensitive electrocontrollable variable diffusion device plus said second polarization-variable electroswitchable device makes it possible to have a wide range of optical properties available in particular a wide range of haze and light transmission and coloration level. In particular the clarity L* may vary.

[0014] The measurements of total transmission TT or diffuse transmission TD, TL or blur are identical to those described in the prior art WO2020 / 065038.

[0015] The CIE 1976 L*a*b* color space, generally called CIELAB, is a color space particularly used for the characterization of surface colors. Three quantities L*, a*, b* are used: the lightness L* derived from the luminance of the surface; the two parameters a* and b* express the deviation of the color from that of a gray surface of the same lightness. The existence of a gray, uncolored, achromatic surface implies explicitly indicating the composition of the light that illuminates the colored surface. This illuminant is here the standardized daylight D65.

[0016] The CIELAB color space is defined from the CIE XYZ space. Compared to the latter, it has the advantage of a color distribution more in line with the perception of color differences by the human visual system. It is also possible to define a colorimetric difference deltaE between two colors defined by the square root of the sum of the squared difference of the L*, the squared difference of the a*, and the squared difference of the b*. The deltaE between two colors (off state and on state of the second device with the first device off or between the off state of the first and second devices and the on state of the first device or even two colors under electric field E1 with the off state of the second device) in the present invention can be at least 1 or even at least 7.

[0017] The invention applies in various fields, particularly in buildings (windows, partitions, glazed floors), outdoors, particularly in urban areas, or in road, rail, maritime or aeronautical vehicles (windshields, side windows, glazed roofs, etc.). Integrated into the glazing of a building or vehicle, the first device can be oriented either outwards or inwards.

[0018] The second device, preferably similar in shape to the first device, may extend over all or part of the first device as required.

[0019] The optical system may be without an optical element capable of depolarizing light between the first device and the second device.

[0020] The optical system can be of any size because the first and second devices can be easily made without surfaces of length of at least 1m.

[0021] Between the first device and the second device, it may be desirable to avoid placing a diffuser.

[0022] Of course, any opaque, occulting or reflective element can be avoided between the first device and the second device.

[0023] However, a static polarizer can be added between the first device and the second device, such as a (stretched) plastic film with dichroic dyes. In particular, the static polarizer can be designed to block the given polarization P1. In particular, the static polarizer can be designed to block the given polarization P2.

[0024] The second device itself does not need polarizer(s) e.g. crossed polarizer and analyzer to operate.

[0025] The switching time of each of the first and second devices can be less than a few seconds. The switching states of the optical system are reversible and (quasi) immediate.

[0026] The second device only needs one layer of liquid crystals (single-cell system) and not several layers of liquid crystals to form a variable polarizer.

[0027] The optical properties of the liquid crystal system can be adjustable: by switching off or applying the first electric field E1 (preferably alternating) and choosing the voltage level U1 and / or by switching off or applying the second electric field E2 (preferably alternating) and choosing the voltage level U2 by choosing the orientation of the output (dominant) polarization called P1 (for example in the off state of the second device) relative to a characteristic direction b of the first device detailed later, in particular P1 substantially parallel or substantially perpendicular to b.

[0028] In particular, we can choose for the "off" state of the optical system (first and second devices switched off) a non-masking state (easy vision through the optical system), with P1 perpendicular to b.

[0029] In particular, one can choose for the "off" state of the optical system (first and second devices switched off) a masking and darker state with P1 parallel to b. The color depends essentially on the first dichroic dyes and can also depend on the second dichroic dyes.

[0030] You can switch from one functional state to another: by switching on the second device when it is capable of delivering a polarization sufficiently different from P1, preferably normal to P1. by switching on the first device, the second device remaining switched off, with P1 parallel to b.

[0031] The optical system can be at most 1cm or 5mm or 1mm thick.

[0032] The second device can be at most 5mm or 1mm or 0.5mm thick.

[0033] The first device may be at most 5mm or 1mm or 0.5mm thick.

[0034] Concerning the first device, the domains induce the dependence of the scattering properties on the polarization state of the light. The first dichroic dye induces the dependence of the absorption properties on the polarization state of the light.

[0035] Regarding the second device, the second dichroic dyes, slaved to the second liquid crystals, preferably twisted in the off state, play a key role in providing the variable polarization function. The second variable polarization device is transparent and preferably has a haze of at most 10% or 1% or 0.5% in the off state as in the on state.

[0036] Applied voltages can be lower than 120V or even 80V.

[0037] It is possible to provide for applying U1 (and even choosing the level of U1) and / or applying U2 (and even choosing the level of U2) depending on a setpoint. Thus, it is possible to provide means for controlling the first device and / or the second device.

[0038] Parameters influencing optical properties include: the choice of the first liquid crystals, in particular the mixture of mesogens (in particular for the working temperature range and the voltage level U1 for "unanchoring" in the on state) and their dielectric anisotropy the level of transparency of the electrodes with the lowest possible absorption (of their possible support) and in the case of strip electrodes the density of the strips (to lower the electrical voltage by reducing the space between strips and to reduce the areas without switching of the liquid crystals to increase the off / on contrast) the choice of the first and / or second dichroic dyes (the dichroic ratio their concentration, etc.) in particular to have the highest and constant absorption spectrum in the visible the thickness of the first and / or second electroactive layer.the choice of the anchoring layers of the first device (the type of defects or arrangement of defects) as of the second device (inducing the type of polarization in the off state, forcing the nematics to undergo a torsional deformation).

[0039] In particular, the value of the blur without an applied electric field (or for a given voltage) can vary depending on the size or type of two-dimensional defects, their density, the thickness of the electroactive material, the choice of the first liquid crystals, the polymer network (crosslinking rate, polymerization condition), the monomer, and the difference in refractive indices of the polymer with the liquid crystals.

[0040] In particular, the value of the blur without an applied electric field (or for a given voltage) will vary depending on the orientation of the first liquid crystal(s), in particular depending on the angle between the long (molecular) axis of the first liquid crystals and the polarization axis of a light polarized along the plane parallel to the surface of the first electroactive layer.

[0041] For example, blur is defined as the ratio of diffuse transmission TD to total transmission TT. It is preferred to express it as a %.

[0042] The haze H is preferably defined as the ratio between the integrated light transmission associated with diffuse transmission TD and the TL.

[0043] Each state of the optical system, diffusing and / or more or less colored, can be defined with a given color notably defined by a brightness L* (and in addition by a*, b*). The entire system works whether the unpolarized light is incident on the first or second device.

[0044] The optical characterization of the optical system according to the invention (and) is preferably carried out at the output of the first device on the side opposite the second device. For simplicity, the explanation of the influence of the second device on the first device is done from unpolarized light incident on the second device. However, substantially the same optical performances are obtained with unpolarized light incident on the first device (opposite the second device) by measuring the light at the output of the second device.

[0045] The level of diffusion and / or coloration can be controlled, in particular adjusted according to data collected by sensors (temperature, brightness, etc.) in communication with the optical system (controlling the power supply source(s). A separate or shared power supply circuit can be provided, for example an alternating voltage generator (and up to 120V for example).

[0046] Preferably the second device, in a functional state which is the off state, is capable of delivering light with a polarization P1 (dominant) (first functional state detailed later) and a second polarization P2 (preferably dominant) in the on state (second functional state detailed later) in particular P1 is normal to r1 and P2 parallel to r1.

[0047] More broadly, the second device may have first and second functional states such as: in the first functional state, from an incident light not polarized on the side opposite the first device, the second device is able to deliver an output light (polarized) on the first device side with a first component of the electric field (polarized) P1 along a first axis and a second component of the electric field (polarized) P2 along a second axis normal to the first axis, with a first polarization ratio defined by: rp 1 = T 1 T 1 + T 2 rp1 being at least 70% and better at least 90%, and even at least 95% T1 being the total transmission at a wavelength between 380 and 800nm along the first axis or even the total transmission averaged at least between 400 and 600nm and even from 380 to 640nm and T2 being the total transmission along the second axis at the wavelength between 380 and 800nm, or even the total transmission averaged at least between 400 and 600nm and even from 380 to 640nm for a first voltage U2a between the third and fourth electrodes, preferably zero, and in the second functional state: either i) from unpolarized incident light on the side opposite the first device, the second device being capable of delivering (polarized) output light on the first device side with a second polarization ratio defined by: rp 2 = T ′ 2 T ′ 1 + T ′ 2 rp2 being at least 30%, and even at least 50% or 60% T'1 being the total transmission at a wavelength between 380 and 800nm along the first axis or even the total transmission averaged at least between 400 and 600nm and even from 380 to 640nm and T'2 being the total transmission along the second axis at the wavelength between 380 and 800nm or even the total transmission averaged at least between 400 and 600nm and even from 380 to 640nm, for a second voltage U2b between the third and fourth electrodes given, possibly zero, U2b distinct from U2a i.e. j) from unpolarized incident light on the side opposite the first device, the second device being capable of providing unpolarized output light on the first device side, one of the first and second functional states being in the off state or off (power off electrical), the other of the first and second functional states being in an on state (electrically energized).

[0048] Preferably, the first functional state is the off state and the second functional state is preferably according to i) or the first functional state is an on state and the second functional state is according to j).

[0049] In one configuration, the first functional state is the off state and the second functional state is preferably according to i). Naturally, the second device then has a multitude of functional states in the on state. In particular, there is a threshold voltage from which the anchoring force of the second liquid crystals is overcome for a portion of the liquid crystals and the more the voltage is increased, the more the liquid crystals reorient themselves up to a saturation voltage which is preferably at most 80V. It is then possible to have a polarization ratio which varies according to the voltage U2 applied.

[0050] Advantageously, the first electric field E1 is alternating and preferably the first applied electric voltage U1 is at most 120V and the second electric field E2 is alternating and preferably the second applied voltage U2 is at most 120V. Preferably, the first and second electrodes are in separate planes, and the first liquid crystals have a positive dielectric anisotropy (independent of the frequency of the first electric field E1), the first electric field E1 being perpendicular to the first and second electrodes.

[0051] E1 as E2 is preferably alternating with a frequency from 50Hz, for example a frequency of 100Hz, 1kHz or 2kHz. By voltage we mean the peak voltage (Vpeak in English).

[0052] Thus the changes in orientation of the first liquid crystals are preferably induced by E1 normal to the face FA1 (in the mid-plane if the stack is curved, for example flexible, and between curved substrates, particularly glass).

[0053] The optical system according to the invention in the off state (first and second devices switched off) can be colored with a given color C0 notably defined by a brightness L*0 (and furthermore by a*0, b*0).

[0054] The optical system according to the invention in the on state of the second device (first device off) can be colored with a given color Ca notably defined by a clarity L* (and furthermore by a*, b*).

[0055] The optical system according to the invention in the on state of the first and second devices can be colored with a given color Cb notably defined by a clarity L* (and furthermore by a*, b*).

[0056] The optical system according to the invention in the on state of the first device (second device off) can be colored with a given color Cb notably defined by a clarity L* (and furthermore by a*, b*).

[0057] Furthermore, the color may vary depending on the voltage U1 and / or U2.

[0058] The choice of U1 and / or U2 can be controlled, in particular adjusted according to data collected by sensors (temperature, brightness, etc.) in communication with the device (controlling the power supply source).

[0059] The third (respectively the fourth) electrode may comprise (or even be made up of) an electroconductive layer (monolayer or multilayer, in particular deposit(s)) in particular mineral in particular with a thickness of at most 200nm (electroconductive layer on carrier element, preferably electroconductive layer between carrier element and anchoring layer), in particular comprising a current supply means (strip - bus bar - in particular metallic, copper, silver etc.) at the edge.

[0060] In a planar configuration, the third and fourth layered electrodes extend over all or part of their separate carrier element.

[0061] In a first preferred embodiment, for planar switching (in plane switching in English), the third and fourth electrodes (preferably in a layer) are coplanar (on a common carrier element preferably rather than self-supporting), forming an alternation of first and second electroconductive strips (metallic for example) at distinct potentials, elongated strips (linear, preferably rectilinear) in a direction r0 and preferably with the greatest possible strip density (strips of the smallest possible width and with the smallest possible inter-strip space).

[0062] Thus, a potential difference is applied between two “terminals” located in the same plane and electrically isolated 2 by 2.

[0063] The second field E2 is alternating and is then mainly planar (parallel to the third and fourth electrodes).

[0064] While preserving electrical conductivity, we seek to ensure that the bands are as thin as possible to improve the "polarizing" power in the ON mode. We also seek to reduce the interband width as much as possible (insulating bands without electrical conductor) to reduce the potential difference to be applied.

[0065] For example, the electrically conductive strips and / or the inter-strip width (insulating strips) are at most 50µm or 30µm or 10µm.

[0066] For example, the insulating strips form a serpentine arrangement and a first zone of the electrically conductive layer is insulated from a second zone of the layer by a first portion of the first insulating strip of the serpentine and by a last portion of the last insulating strip of the serpentine.

[0067] This arrangement of insulating strips can be achieved by removing a solid electrically conductive layer, particularly by laser beam. The limit in strip thickness is given by the size of the laser beam. The limit of the inter-strip distance is dictated by the displacement of the laser beam.

[0068] The dielectric anisotropy of the first electroactive layer (of the first liquid crystals) is non-zero and can be negative or positive. The dielectric anisotropy of the second electroactive layer (of the second liquid crystals) is non-zero and can be negative or positive.

[0069] The first device may include: a (first) directional anchoring layer along a first direction b on one of the faces FA1 or FA2, preferably on the face FA2, (first liquid crystals are generally oriented on this face FA2 or FA1 along this first direction b in the off state of the first device) in particular a (second) anchoring layer on the other of the faces FA1 or FA2, preferably on the face FA1, preferably distinct anchoring layer (antagonist) preferably normal anchoring, then inducing first liquid crystals generally oriented perpendicular to this other face FA1 or FA2 (homeotropic anchoring).

[0070] In a configuration with the third and fourth electrodes coplanar, the second device, preferably with second twisted nematic liquid crystals in the off state of the second device, comprises: a (third) unidirectional planar anchoring layer along a (second) direction r1 on (in contact with) the main face FA3 of the second electroactive layer and on the third and fourth electrodes in particular P1 is normal to r1 and P2 parallel to r1 and another (or fourth) unidirectional planar anchoring layer along a (third) direction r2 (preferably distinct from r1) on (in contact with) the main face FA4 of the second electroactive layer.

[0071] In particular, r1 forms an angle of 90°±15° and better of 90°±5° with r2 (the second nematic liquid crystals then having a twist in the off state): r0 forms an angle of at most 15° and even at most 5° with r1 and the second liquid crystals have a positive dielectric anisotropy (then the first functional state of the second device with the polarization P1 being the off state and second functional state being an on state and following i)) or r0 forms an angle of 90°±15° and better of 90°±5° with r1 and the second liquid crystals have a negative dielectric anisotropy (then the first functional state of the second device with the polarization P1 being the off state and second functional state being an on state and following i)).

[0072] Preferably, the second device, in a first functional state which is the off state, is capable of delivering light with a polarization P1 (dominant) and a second polarization P2 (dominant) in the functional state on (state i) in particular P1 is normal to r1 and P2 parallel to r1.

[0073] In one embodiment (in coplanar electrode mode of the second device) with j) unpolarized light the second nematic liquid crystals are at dual switching frequency (“dual frequency” in English) having a dielectric anisotropy changing from negative to positive depending on the frequency and the second electric field E2 which is alternating is at variable frequency.

[0074] Alternatively to the coplanar configuration, the second electroactive layer is between the third and fourth electrodes (surface SA1 on the face FA3 side, surface SA2 on the face FA4 side) and the second device comprises: a unidirectional planar anchoring layer along a direction r1 in contact with the face FA3 of the second electroactive layer and on the third electrode (in particular in contact with the third electrode) and another unidirectional planar anchoring layer along a direction r2 in contact with the face FA4 of the second electroactive layer and on the fourth electrode (in particular in contact with the fourth electrode) r1 forms an angle of at most 15° and even at most 5° with r2, the second liquid crystals have a positive dielectric anisotropy, (then the first functional state of the second device with the polarization P1 being the off state and second functional state of the second device being an on state (on, under electrical voltage) and following j) therefore unpolarized output light) or r1 forms an angle of 90°±15° and better of 90°±5 with r2,the second liquid crystals have a positive dielectric anisotropy (then the first functional state of the second device with the polarization P1 being the off state and the second functional state of the second device being an on state and following j) therefore unpolarized output light) or r1 forms an angle of at most 15° and even at most 5° with r2, the second liquid crystals have a negative dielectric anisotropy the orientation of the second liquid crystals in the thickness of the second electroactive layer in the off state of the second device is predominantly homeotropic. (then the first functional state of the second device with the polarization P1 being the on state and the second functional state of the second device being the off state and following j) therefore unpolarized output light).

[0075] In the latter case, the anchoring layers in the second device can each have an anchoring layer (polyimide etc.) generating a homeotropic anchoring, with brushing nevertheless to obtain a pretilt angle with the long axis of the mesogens of the second liquid crystals. Then an off state is quasi-hometropic and the on state (lit) where the electric field applied along the vertical will reorient the mesogens of negative dielectric anisotropy along the brushing direction. In this specific configuration, brushing an anchoring layer does not have a macroscopic unidirectional planar orientation effect in the OFF state thanks to the pretilt design on a layer generating, without brushing, a homeotropic anchoring.

[0076] This type of pre-tilt anchoring is described in the article by Li et al. entitled “Dye-doped dual-frequency nematic cells as fast-switching polarization-independent shutters” Vol 27 No. 4, February 2019 OPTICS EXPRESS 3861 pages concerning dual-cell liquid crystal systems for switching from linear polarization to full extinction.

[0077] Furthermore, the first electroactive layer (and therefore the variable scattering electrocontrollable device) has an optical response dependent on the polarization of the incident light.

[0078] This differentiated response to the polarization of light is induced: by the form factor, the internal structure of two-dimensional topological defects, in particular line defects, in particular line defects of non-toric focal conical domains (non-TFCD in English) of smectic mesophases and / or the arrangement of the different domains (in particular focal conical domains of smectic mesophases including "TFCD" in English), in particular their shape, their orientation, their degree of symmetry, distributed for example randomly, irregularly, etc., distribution dictated by the anchoring conditions (custom-adjustable 2D anchoring layer, for example multidirectional anchoring).

[0079] An example of various polarization-sensitive focal cone domain architectures of smectics (i.e., focal cone domain) is given in the publication “Smectic Layer Origami Preprogrammed Photoalignment” by Ling Ling Ma et al. Advances Materials 2017 1606671 pages 1-7.

[0080] In a preferred embodiment, the second device, in a first functional state which is the off state, is capable of delivering light with a polarization P1, the first device comprises a (first) directional anchoring layer along a first direction b on the face FA1 or preferably on the face FA2, the second device is arranged such that P1 forms an angle with b of 0°±20° or better of 0°±5° (in particular r2 forms an angle with b of 0°±20° or better of 0°±5°).

[0081] In one embodiment, the second device, in a first functional state which is the off state, is capable of delivering light with a polarization P1, the first device comprises a directional anchoring layer along a first direction b on the face FA1 (in contact with the face FA1) or preferably on the face FA2 (in contact with the face FA1), first liquid crystals are then generally oriented on the face FA1 or preferably on the face FA2 along this first direction b), the second device is arranged such that P1 forms an angle with b of 90°±20° or better 90°±5°, (in particular r1 forms an angle with b of 90°±20° or better 90°±5°).

[0082] Preferably, as already indicated, anchoring layers are used which serve to orient liquid crystals by surface interactions during manufacturing, in the absence of an applied electric field (E1 or E2).

[0083] Up to a certain distance from the surface with the anchoring layers the (first or second) liquid crystals can remain oriented to it up to a certain field level (voltage).

[0084] The thickness of the anchoring layers (of the second device and / or of the first device) is preferably at most 1 µm, better submicronic, for example less than 600nm.

[0085] There can also be several distinct anchoring zones on the same surface. These defects are generated by mechanical deformations of the material structure and are obtained by the boundary conditions imposed by the two anchoring layers forcing the liquid crystals in contact with these layers to specific and distinct orientations.

[0086] As a unidirectional planar anchoring layer (first or second device), a fluoropolymer film such as polytetrafluoroethylene PTFE or Teflon can be used (with the polymer chains aligned according to the direction of movement of the Teflon bar during deposition).

[0087] Unidirectional planar anchoring fixes the zenithal and azimuthal orientation of the n-director of the liquid crystal), for example by texturing, brushing the planar anchoring layer (rubbing in English), for example comprising nano or microgrooves.

[0088] A velvet cloth can be used for brushing.

[0089] For normal anchoring (preferably first device), the most commonly used layers are based on octyltrichlorosilane (OTS) and N,N-dimethyl-N-octadecyl-3-aminopropyltrimethoxysilane chloride (DMOAP) or polyimides as well.

[0090] A layer based on sodium dodecyl sulfate (SDS) or mixtures of alkanethiols can also generate normal anchoring.

[0091] One or more anchoring layers are, for example, deposited using liquid.

[0092] One or more anchoring layers may be a preferably thin (flexible) film, for example of at most 200 µm or 50 µm, which in particular carries the electrode (first and / or second) of the first device. One or more anchoring layers may be a preferably thin (flexible) film, for example of at most 200 µm or 50 µm, which in particular carries the electrode (third and / or fourth) of the second device.

[0093] An anchor layer (of the first or second device) is for example: preferably dielectric (in particular amorphous, polymeric and / or mineral, a glass), with a functionalization of the surface, in particular, a layer based on polyvinyl alcohol (PVA), polyimide for example for a planar anchoring (in particular for the first device) electrically conductive in particular which is a fraction of the thickness of the electrode of the first device (first or second full-surface electrode, planar-planar electrode configuration) or of the second device (third or fourth full-surface electrode, planar-plane electrode configuration) (for example for a planar anchoring).

[0094] An air gap provides normal anchoring but it is preferred to have a solid anchoring layer. It is also preferred that the anchoring layers be dielectric and separate from the electrodes.

[0095] There may even be more than two anchor layers (three or more), so there are multiple liquid crystal layers spaced apart by anchor layers. A single liquid crystal layer is preferred for simplicity for each of the first and second devices.

[0096] The second device, in a first functional state which is preferably the off state, is capable of delivering light with a polarization P1 in particular normal to r1 (preferably P1: forming an angle with the first direction b of 0° or 90°±20° or even of 0° or 90°±5°). And: in the first functional state, the blur H0 at the output of the first device is at least 10% (and even 20%) greater than the blur obtained with unpolarized incident light at the input of the second device and preferably in a second functional state, which is preferably the on state of the second device, the blur H1 at the output of the first device is at least 10% (and even 20%) less than the blur obtained with unpolarized incident light at the input of the second device.

[0097] The first liquid crystals preferably have a degree of organization overall in a given direction b on the FA1 face or on the FA2 face (called the planar orientation face).

[0098] Their director n - or long axis - is generally along this first direction b).

[0099] b is in particular the (brushing) axis of a unidirectional planar anchoring layer in contact with this planar orientation face (generating interactions between liquid crystals with this solid layer).

[0100] Line defect domains are preferred because the blurring (scattering power) is remarkable. Focal conical domains of smectic (meso)phase are preferred as detailed in application WO2020 / 065038 incorporated by reference.

[0101] Defect domains generally each comprise two defect lines (two defect lines), focal conics and which come in pairs, notably one elliptical with different degrees of eccentricities and the other hyperbolic, thus the name given is "Elliptic-Hyperbolic focal conic domain" or EHFCD in English.

[0102] Preferably, the P mesophase is nematic and the domains are focal conical domains, in particular of smectic mesophase (P' mesophase), in particular with two line defects, preferably one elliptical and the other hyperbolic (EHFCD). The focal conical domains, in particular EHFCD, preferably form a linear network parallel to the b direction.

[0103] The dichroic dye (first and / or second) can be an anisotropic organic molecule that exhibits optical anisotropy, is elongated, especially rod-shaped. It is dissolved in the material, especially dissolved in the first liquid crystals. The % of (each) dichroic dye is adjusted so as not to exceed the solubility limit. In particular, one (or more) dichroic dyes are chosen that are chemically compatible with the liquid crystals.

[0104] In particular, the (each) dichroic (elongated, rod-like) dye can have a molecular long axis and the absorption varies along the long axis or the short axis.

[0105] The (first or second) dichroic dyes are controlled by the orientation of the (first or second) liquid crystals of the electroactive layer in play (first or second), the movement (rotation) of the liquid crystals under the effect of the electric field (E1 or E2) in play, tending to align with the electric field in play, causing the movement (rotation) of the dichroic dyes, the long axis also tending to align it with the electric field in play.

[0106] The absorption of a dichroic dye therefore varies depending on its orientation relative to the polarization of the incident light. Conversely, a non-dichroic dye, which does not exhibit absorption anisotropy, is not or only slightly sensitive to the electric field and will not even change the absorption. Such dyes can be added to adjust the desired shade in the first device.

[0107] The first dichroic dye may have a first absorption band (in the visible) preferably of at least 200nm or 300nm, and even preferably of 380nm to 650nm or even to 700 or 780nm.

[0108] The second dichroic dye may have a second absorption band (in the visible) preferably of at least 200nm or 300nm, and even preferably from 380nm to 650nm or even to 700 or 780nm.

[0109] The first and second dichroic dyes preferably have a common absorption range (without necessarily having the same absorption maximum or the same absorption profile) preferably of at least 1 nm or 10 or 100 nm.

[0110] The first dichroic dye may have a maximum light absorption for light polarized along a direction r1.

[0111] The second dichroic dye can have a maximum light absorption for light polarized along this same direction r1.

[0112] There are several families of dichroic dyes, including those described in Mark T Sims' publication "dyes as guests in ordered systems: current understanding and future directions" Liquid Crystals, 2016, Vol 43, NOS. 13-15, page 2363-2374.

[0113] The dichroic dyes according to the invention may be azo dyes, with AZO (-N=N), in particular in rod form. Chemical modifications can be induced to the azo dyes, for example with incorporated ester groups (see p2366 of the aforementioned publication).

[0114] Other dyes are anthraquinones, usually fused rings or rods, with the addition of substituents. Examples of dichroic dyes (chromophores) are in Table 1 of this aforementioned publication.

[0115] Examples of dichroic dyes suitable for the invention are further cited in the book entitled "Electroopic effects in Liquid Crystal Materials" by LM Blinov et al., published by Springer in 1994 in particular in chapter 2.3 named Optical Anisotropy and Dichroism and pages 66 to 68 including table 2.2.

[0116] For example, for a blue dye, the maximum absorption wavelength can be 630nm±10nm and the wavelength outside the absorption band can be 430nm±50nm or ±10nm. For example, the M412 dye sold by Mitsui Chemicals can be cited.

[0117] For example, for a red dye, the maximum absorption wavelength can be 500nm±10nm and the wavelength outside the absorption band can be 650nm±50nm or ±10nm. For example, the dye SI-426 sold by Mitsui Chemicals can be cited.

[0118] For example, for a yellow dye, the maximum absorption wavelength can be 400nm±10nm and the wavelength outside the absorption band can be 600nm±50nm or ±10nm. For example, the dye SI-486 sold by Mitsui Chemicals can be cited.

[0119] For example, for a black dye, we can cite the SI-428 dye sold by the company Mitsui Chemicals.

[0120] Independently, one or more of the elements of the system (electrode, anchoring layer, substrate or support, lamination interlayer, counter glass, etc.) can be tinted (more or less strongly), for example with a maximum absorption distinct from the first dichroic dye.

[0121] The first device may include: a transparent dielectric substrate, carrying the first electrode (and an anchoring layer, in particular normal on the first electrode), substrate chosen from a glass sheet or a transparent polymeric sheet with a possible external anti-scratch layer a transparent dielectric support, carrying the second electrode (if plane-plane configuration) and at least one anchoring layer, in particular unidirectional according to b (preferably on the first electrode), substrate chosen from a glass sheet or a transparent polymeric sheet with a possible external anti-scratch layer.

[0122] The second device may include: a first transparent dielectric element, carrying the third electrode (and preferably the fourth electrode (coplanar configuration) and even the anchoring layer preferably unidirectional according to r1, first element chosen from a glass sheet or a transparent polymeric sheet distinct from or corresponding to said dielectric support a second transparent dielectric element, carrying the fourth electrode if plane-plane configuration and carrying at least one anchoring layer preferably unidirectional according to r2, second element chosen from a glass sheet or a transparent polymeric sheet (with a possible external anti-scratch layer)

[0123] The first device and the second device may be spaced apart, share a common support (on the same side or on opposite sides) or be bonded (dielectric support and first dielectric element bonded).

[0124] In one embodiment, the first device and the second device are linked: by a transparent bonding layer, in particular an optical adhesive (OCA in English) or a thermoplastic layer, in particular an EVA or PVB lamination interlayer or a transparent common support, preferably plastic glass, is supported: on a first main face of the second electrode (or even of the first electrode if coplanar) and in particular of the rest of the stack of layers and on the other side on a second main face opposite the third electrode (or even of the fourth electrode if coplanar) and in particular of the rest of the stack of layers.

[0125] The clear bonding layer can be colorless or tinted.

[0126] The transparent bonding layer can be as thick as 0.5mm or even 0.1mm.

[0127] The optical system can be flat or curved, flexible to adapt to the curvatures of, for example, a glazing (monolithic or laminated). It is then curved on the monolithic glazing or, for example, within said laminated glazing.

[0128] The invention also relates to laminated glazing, possibly curved, comprising: a first additional sheet of glass, in particular with a thickness of 0.7mm to 4mm, a thermoplastic lamination interlayer, in particular EVA or PVB, a second additional sheet of glass, in particular with a thickness of 0.7mm to 4mm or even less than 0.7mm, or a plastic sheet such as polycarbonate or PMMA (in particular with a PU lamination interlayer),

[0129] the main internal faces called F2 and F3 of the first and second additional glass sheets being opposite each other, the optical system as described previously being preferably between the faces F2 and F3 and preferably in the lamination interlayer.

[0130] Preferably, with respect to the first device, the substrate being polymeric and even the support being polymeric, occupying all or part of the surface of the first sheet. Preferably the first element being polymeric and even the second element being polymeric, occupying all or part of the surface of the first device.

[0131] Preferably the thermoplastic lamination interlayer surrounds the edge of the optical system (first and second device).

[0132] The edge of the optical system may be recessed relative to the outermost edge of the lamination interlayer (or first sheet).

[0133] Preferably, the possible carrier sheets of the layers (substrate, support, first and second elements) are preferably of a thickness of at most 0.7 mm and even at most 0.3 or 0.2 mm. For those made of glass, one can choose thin glass (less than 1 mm) and even ultra-thin ('UTG' in English).

[0134] One of the additional glass sheets can be tinted and the other clear or extra-clear. The thermoplastic lamination interlayer can be colorless (clear, extra-clear) or tinted. For the substrate and / or support or for an additional glass sheet or a glazing unit of a laminated and / or multiple glazing unit, clear or extra-clear glass can be chosen. Clear glass typically contains an iron oxide content by weight of around 0.05 to 0.2%, while extra-clear glass generally contains around 0.005 to 0.03% iron oxide.

[0135] The additional glass sheet or glazing of a laminated and / or multiple glazing can, however, be tinted, for example, in blue, green, gray or bronze.

[0136] An additional tinted glass sheet or tinted glazing of laminated and / or multiple glazing may preferably have a light transmission TL of less than or equal to 10%.

[0137] The glass is preferably of the soda-lime-silica type but it can also be of the borosilicate or alumino-borosilicate type. The thickness of the glass is generally in a range from 0.5 mm to 19 mm, preferably from 0.7 to 9 mm, in particular from 2 to 8 mm, or even from 4 to 6 mm. The glass is preferably of the float type.

[0138] The thermoplastic lamination interlayer provides a connection with a rigid or flexible element. This polymer lamination interlayer can be, in particular, a layer based on polyvinyl butyral (PVB), ethylene vinyl acetate (EVA), polyethylene (PE), polyvinyl chloride (PVC), thermoplastic urethane, polyurethane PU, ionomer, polyolefin-based adhesive, thermoplastic silicone or multi- or single-component resin, crosslinkable thermally (epoxy, PU) or ultraviolet (epoxy, acrylic resin).

[0139] The PVB interlayer may be wedge-shaped, therefore with a cross-section decreasing in a wedge shape from the top to the bottom of the laminated glazing to avoid a double image in the case of a head-up display (HUD), particularly for a windshield. The PVB interlayer is optionally acoustic and / or tinted. The acoustic PVB interlayer may comprise at least one so-called central layer made of viscoelastic plastic material with vibro-acoustic damping properties, in particular based on polyvinyl butyral (PVB) and plasticizer, and further comprising two external layers made of standard PVB, the central layer being between the two external layers.

[0140] The first and / or second glazing of the laminated glazing can (depending on the aesthetic rendering, the desired optical effect) be a clear glass (with a light transmission TL greater than or equal to 90% for a thickness of 4 mm), for example a standard soda-lime composition glass, Planilux ®< from the company Saint-Gobain Glass, or extra-clear (TL greater than or equal to 91.5% for a thickness of 4 mm), for example a soda-lime-silica glass with less than 0.05% Fe III or Fe 2 O 3, Diamant ®< glass from Saint-Gobain Glass, or Optiwhite ®< from Pilkington, or B270 ®< from Schott, or another composition described in document WO04 / 025334. Planiclear ®< glass from the company Saint-Gobain Glass can also be chosen.

[0141] The glass of the first and / or second glazing may be neutral (without coloring), or (lightly) tinted, in particular gray or green, such as the TSA glass from the Saint-Gobain Glass company. The glass of the first and / or second glazing may have undergone chemical or thermal treatment such as hardening, annealing or tempering (for better mechanical resistance in particular) or be semi-tempered.

[0142] The light transmission TL can be measured according to ISO 9050:2003 using illuminant D65, and is the total transmission (notably integrated in the visible range and weighted by the sensitivity curve of the human eye), taking into account both direct transmission and any diffuse transmission, the measurement being made for example using a spectrophotometer equipped with an integrating sphere, the measurement at a given thickness then being converted where appropriate to the reference thickness of 4mm according to ISO 9050:2003.

[0143] The optical system according to the invention can be integrated into a glazing, in particular monolithic or laminated (flat and / or curved), and the optical system forms a band, in particular peripheral, on a portion of a main face of the glazing.

[0144] The optical system according to the invention as defined above can be used in a vehicle or building.

[0145] It can be used in particular as: internal partition (between two rooms or in a space) in a building, in a land, rail, sea or air vehicle (between two compartments, in a taxi, bus, train etc.), in particular as a glass shower wall, bathtub, glass door (entrance or service), window (single, double, triple glazing), ceiling, paving (floor, ceiling), toilet door, a glazed part of urban or domestic furniture glazing of a motor vehicle (car, truck, bus, coach, etc.) therefore land, rail, sea (boat): windshield, side glazing, roof, projection or rear projection screen, store front, window, in particular of a ticket office.

[0146] Naturally, it can form all or part of a glazing (a partition and window type transom etc.).

[0147] Building glazing can therefore carry the optical system as described above, in particular monolithic, double or triple glazing (with or without laminated glazing), partition, window, etc.

[0148] Vehicle glazing, particularly road glazing, can therefore carry the optical system as described above, in particular windshields (the optical system forming peripheral strip(s)), glazed roofs, side glazing (monolithic or laminated), in particular quarter windows. The laminated glazing according to the invention, in particular for private cars (windshields, etc.) or trucks, can be curved (bent) in one or more directions, in particular for the first sheet, the second, and a radius of curvature of 10 cm to 40 cm. It can be flat for buses, trains, tractors.

[0149] The optical system according to the invention can be integrated within a laminated and in particular curved glazing, is between first and second glazings respectively called external and internal glazings and forms a peripheral band on an upper portion of the glazing, the so-called external edge of the stack being masked from the outside by a first opaque peripheral layer in particular an enamel on the external glazing (preferably on face F2), and / or the so-called internal edge of the stack being masked from the inside by a second opaque peripheral layer in particular an enamel on the internal glazing (on face F4 for example or even face F3).

[0150] The curved laminated glazing according to the invention, in particular windshield or side glazing, may have a TL - in the clear of the glass - which is preferably at least 70% and even at least 75% or even at least 80%.

[0151] The curved laminated glazing according to the invention, in particular a glazed roof, can have a light transmission TL of at most 10% and even 1 to 6%.

[0152] For an automotive roof, one or more of the following criteria are preferred: an energy transmission TE of at most 10% and even 4 to 6%, an energy reflection RE (preferably on the F1 side) of at most 10%, better 4 to 5% and a total transmission of solar energy TTS <30% and even <26%, even 20 to 23%.

[0153] The bending of the first and second glazings (windshields in particular) can be in one or more directions, for example described in document WO2010136702.

[0154] In order to limit heating in the passenger compartment or to limit the use of air conditioning, at least one of the glazings (preferably the exterior glass) is tinted, and the laminated glazing may also include a layer reflecting or absorbing solar radiation, preferably on face F4 or on face F2 or F3, in particular a layer of transparent electroconductive oxide called a TCO layer (on face F4) or even a stack of thin layers comprising at least one TCO layer, or stacks of thin layers comprising at least one silver layer (on face F2 or F3), where each silver layer is arranged between dielectric layers.

[0155] The optical system according to the invention can be used in combination with other electrically controllable devices such as those with electroluminescent systems (set of inorganic point diodes LED, organic diodes or OLED, TFEL (thin film). The two can be opposite or adjacent within a laminated glazing (of the lamination interlayer.

[0156] The optical system according to the invention can be used in particular in laminated glazing, in combination with another electrically controllable device such as an electroluminescent electrically controllable device, in particular LED, OLED, TFEL.

[0157] Other details and characteristics of the invention will appear from the detailed description which follows, given with reference to the following appended drawings and in which: There figure 1 represents a schematic sectional view of an optical system 1001 composed of a first electrically controllable device 10 which is diffusion and variable color by liquid crystals and dichroic dye and of a second electrically controllable device with variable polarization 100 by liquid crystals and dichroic dye 100 in a first embodiment of the invention. The figure 2 represents a schematic sectional view of an optical system 1002 composed of a first electrically controllable device 10 which is diffusion and variable color by liquid crystals and dichroic dye and of a second electrically controllable device with variable polarization 101 by liquid crystals and dichroic dye 100 in a second embodiment of the invention. The figure 3 represents a schematic sectional view of an optical system 1003 composed of a first electrically controllable device 10 which is diffusion and variable color by liquid crystals and dichroic dye and of a second electrically controllable device with variable polarization 102 by liquid crystals and dichroic dye 100 in a third embodiment of the invention. The figure 4 represents a schematic sectional view of an optical system 1000 composed of a first electrically controllable device 10 which is diffusion and variable color by liquid crystals and dichroic dye and of a second electrically controllable device with variable polarization 100 by liquid crystals and dichroic dye 100 in a fourth embodiment of the invention. figure 5 is a front view of strip and pair electrodes used in the second device of the figure 4 . There figure 6 is a partial schematic perspective view of the second device of the figure 4 in a first functional state which is the off state. The figure 7 is a partial schematic perspective view of the second device of the figure 4 in a second state which is an on state at a given voltage U2. The figure 8 represents a schematic and detailed sectional view of the electroactive layer between two plane-plane electrodes of the first device 10 outside the electric field, schematically illustrating the orientation of certain liquid crystals and of certain dichroic dyes without electric field E1. The figure 9 represents a schematic and detailed sectional view of the electroactive layer between two plane-plane electrodes of the first device 10 under the first electric field E1, schematically illustrating the orientation of certain liquid crystals and of certain dichroic dyes under said first electric field E1. figures 10, 11 , 12 show in front view images (in black and white) obtained by optical microscopy in polarized light (MOP) under polarizer under a magnification of x20 (with a white line scale of 50µm) of the first electroactive layer of the first electrocontrollable device 10 of the figure 4 (example 1) in the absence of said first electric field E1. The figure 13 shows a set of curves corresponding to the total transmission TT as a function of the wavelength between 380 and 630nm in a variant of the optical system of the figure 4 because P1 is perpendicular to b (second device rotated 90°). The figure 14 shows a set of curves corresponding to the diffuse transmission TD as a function of the wavelength between 380 and 630nm in a variant of the optical system of the figure 4 because P1 is perpendicular to b (second device rotated 90°). The figure 15 shows a set of three curves corresponding to the blur H (%) as a function of the first voltage U1 from 0 to 40V of the optical system of the figure 4 (with U2 equal to 0V). The figure 16 shows a set of three curves corresponding to the ratio of the diffuse transmission TD to the total transmission TT as a function of the wavelength between 380 and 630nm of the optical system of the figure 4 (in off + off mode of the optical system). The figure 17 shows a set of curves corresponding to the integrated light transmission TL as a function of the first voltage U1 from 0 to 40V of the optical system of the figure 4 (with U2 equal to 0V). The figure 18 shows a set of curves corresponding to the total transmission TT as a function of the wavelength between 380 and 630nm of the optical system of the figure 4 with P1 parallel to b. The figure 19 shows a set of three curves corresponding to the diffuse transmission TD as a function of the wavelength between 380 and 630nm of the optical system of the figure 4 with P1 parallel to b. The figure 20 represents a schematic sectional view of an optical system 1000' composed of a first electrically controllable device 10 which is diffusion and variable color by liquid crystals and dichroic dye and of a second electrically controllable device with variable polarization 100' by liquid crystals and dichroic dye in a variant of the fourth embodiment of the invention. figure 21 represents a schematic sectional view of an optical system 1000a composed of a first electrically controllable device 10a which is diffusion and variable color by liquid crystals and dichroic dye and of a second electrically controllable device with variable polarization 100a by liquid crystals and dichroic dye in a fifth embodiment of the invention. figure 22 represents a schematic sectional view of a glazing 2000 carrying an optical system 1000 according to the invention. The figure 23 represents a schematic sectional view of a laminated glazing 3000 carrying an optical system 1000 according to the invention. The figures 24 et 25 respectively represent a front view and a schematic sectional view of a laminated glazing 4000 carrying an optical system 1000 according to the invention.

[0158] The elements in the figures are not drawn to scale.

[0159] There figure 1 represents a schematic sectional view of an optical system 1001 composed of a first electrically controllable device 10 which is variable in diffusion and color by first liquid crystals and first dichroic dyes and of a second electrically controllable device with variable polarization 101 by second liquid crystals and second dichroic dyes in a first embodiment of the invention.

[0160] The first electrically controllable device 10 is here characterized by a first direction b of surface anchoring of the first liquid crystals (in the off state).

[0161] We define an orthonormal reference frame X, Y and Z. b is along the X axis.

[0162] The second electrically controllable device 101 is here characterized by a first direction r1 of anchoring of a surface of the second liquid crystals (in the off state) on the output side towards the first device 10 and even by a second direction r2 of anchoring of a surface of the second liquid crystals on the opposite side, therefore on the input side of the first device.

[0163] The second device 101 has first and second functional states and: in the first functional state which is the off state here, from an unpolarized incident light on the side opposite the first device (represented schematically by normal components Pa and Pb of the same intensity, with k the propagation vector of the light along Z), the second device 101 is able to deliver a polarized output light on the side of the first device 10 with a first component of the polarized electric field P1 along an X axis and a second component of the polarized electric field P2 along a Y axis normal to Y, with a first polarization ratio defined by rp 1 = T 1 T 1 + T 2 rp1 preferably being at least 70% or 90%, and even at least 95% T1 being the total transmission at a wavelength between 380 and 800nm along X and T2 being the total transmission along Y at the wavelength between 380 and 800nm for a first voltage U2a between the third and fourth electrodes given preferably zero, (P1 is therefore ultra dominant compared to P2) and in the second functional state which is here an on state, of powering up U2 (between two electrodes in preferably coplanar strips, two by two): i) from an incident light not polarized on the side opposite the first device, the second device 101 being able to deliver an output light polarized on the first device side with a second polarization ratio defined by rp 2 = T ′ 2 T ′ 1 + T ′ 2 rp2 being at least 30%, and even at least 50% or 60% T'1 being the total transmission at a wavelength between 380 and 800nm along the first axis and T'2 being the total transmission along the second axis at the wavelength between 380 and 800nm for a second voltage U2b between the third and fourth electrodes given, non-zero, U2b distinct from U2a.P2 is preferably in the majority compared to P1.

[0164] The polarization of the output light of the second device can be elliptical. Naturally, the second device then has a multitude of functional states in the switched-on state. In particular, there is a threshold voltage from which the anchoring force of the second liquid crystals is overcome for a portion of the liquid crystals and the more the voltage is increased, the more the liquid crystals reorient themselves up to a saturation voltage which is preferably at most 80V.

[0165] We can then have a polarization ratio r U 2 = T 2 T 1 + T 2 which varies depending on the applied voltage U2.

[0166] The first electrically controllable device 10 comprises a first electroactive layer which has an optical response depending on the polarization state of light incident on the first device; the optical response will vary depending on whether b is normal or parallel to P1.

[0167] There figure 2 represents a schematic sectional view of an optical system 1002 composed of a first electrically controllable device 10 which is variable in diffusion and color by first liquid crystals and first dichroic dyes and of a second electrically controllable device with variable polarization 101 by second liquid crystals and second dichroic dyes 102 in a second embodiment of the invention.

[0168] The system 1002 differs from the previous one in that the second device 102 (for example which has rotated 90°) has a direction r1 parallel to b, in other words P1 is normal to b.

[0169] There figure 3 represents a schematic sectional view of an optical system 1003 composed of a first electrically controllable device 10 which is variable in diffusion and color by first liquid crystals and first dichroic dyes and of a second electrically controllable device with variable polarization 103 by second liquid crystals and second dichroic dyes 103 in a third embodiment of the invention.

[0170] The system 1003 differs from the first system 1001 103 in that in the second state on, from unpolarized incident light on the side opposite the first device, the second device is capable of providing unpolarized output light on the first device side.

[0171] The following examples provide more details regarding the possible structure of the first and second devices and even their assembly.

[0172] There figure 4 represents a schematic sectional view of an optical system 1000 composed of a first electrically controllable device 10 which is variable in diffusion and color by first liquid crystals and first dichroic dyes and of a second electrically controllable device 100 with variable polarization by liquid crystals and dichroic dye 100 in a fourth embodiment of the invention. FIRST DEVICE

[0173] The first device 10 comprises a stack of layers (physical, solid) in this order: a transparent dielectric substrate 1'a with a slice and main faces 11'a and 12'a, here a 1.1mm glass - or in a plastic variant such as PET a first transparent electrode 2'a with a first main surface called the SA1 bonding surface and an opposite surface called the SB surface and a slice, transparent electrode which is a layer of indium tin oxide ITO with a square resistance of 100ohm / square, more broadly between 5 and 300ohm / square and for color neutrality, this electrode or each electrode may also comprise at least two thin dielectric sub-layers under the ITO layer and even one or two (dielectric) over-layers a first normal planar anchoring layer 4'a transparent (on the first electrode 2'a) in contact with the first anchoring layer 4'a a first colored dielectric electroactive layer 3a with a main face called the FA1 face on the SB bonding surface side and a main face called opposite side FA2,here of thickness Ep0 (less than 20µm) in a first material comprising: first liquid crystals polymers forming a polymer network, the liquid crystals being stabilized by the polymer network, one or more first dichroic dyes (in the dissolved state) the first material having from a temperature called T1, a mesophase called P in which the material comprises a set of domains here submillimetric which comprise two-dimensional topological defects such as line defects and under T1 a mesophase P' spacers being distributed in the material here glass beads the layer 3a being sealed at the periphery by a polymer seal 5a for example in epoxy in acrylate here in cyanoacrylate a second transparent anchoring layer 4a,here unidirectional anchoring along a direction b parallel to X a second transparent electrode 2a with face side A2 a main surface called second bonding surface SA2 and with an opposite surface called surface SB2, in particular second electrode 2a which is an ITO layer with square resistance 100ohm / square, more broadly between 5 and 300ohm / square and for color neutrality, this or each electrode can also include at least two thin dielectric sub-layers under the ITO layer and even one or two over-layers a transparent dielectric support 1a of the second electrode 2a with a slice and main faces 11a and 12a, here a 1.1mm glass -or in a plastic variant such as PET-,

[0174] For the power supply via an electrical source, conductive strips (not shown), in particular metallic, for example copper, are fixed for example by gluing along and on peripheral edges and are in contact with the electrodes 2'a, 2a (one strip per electrode, the strips preferably being on opposite edges). These strips are then connected to a power supply. The edges of the electrodes 2'a, 2a and the edge of the electroactive layer are preferably set back from the edges of the substrate, support (glasses) 1a, 1'a, rectangular or of any other shape. The thicknesses of the substrate, support (glasses) 1a, 1'a can be for example 0.7 mm to 4 mm. They can be preferably thicker than 100µm and at most 300µm for better mechanical strength of the assembly and / or ease of implementation and handling, but if more flexibility is desired, it can be reduced to, for example, 50µm.

[0175] The manufacturing process is described in more detail below.

[0176] The first anchoring layer 4'a is an octyltrichlorosilane (OTS) layer. It is obtained by immersing the glass with the second ITO 2' in a 10nM OTS solution in n-heptane for 30 minutes, rinsing with deionized water and drying under nitrogen. The first anchoring layer 4'a induces a normal (homeotropic) anchoring of the liquid crystals on the surface (outside the electric field), in contact with this first anchoring layer 4'a.

[0177] Under said electric field E1, the first device 10 can exhibit alone a diffuse transmission, a blur and a color which vary with the voltage.

[0178] The second anchoring layer 4a is deposited on the second ITO layer 2a by spin coating a solution of polyvinyl alcohol (PVA; Sigma-Aldrich; molecular weight 27 kDa) of approximately 1 µm in deionized water (9.1% by weight of PVA). Before deposition, the ITO is preferably cleaned (surfactant) rinsed in deionized water and dried under nitrogen.

[0179] The second anchoring layer 4a is then brushed along the first direction b for unidirectional planar anchoring along this first direction b of the first liquid crystals on the surface (out of field) in contact with this layer 4a.

[0180] The first electroactive layer 3a is composed of a mixture comprising a blue dichroic dye called M412 sold by the company Mitsui Chemicals having a maximum absorption wavelength of 630nm±10nm.

[0181] The first electroactive layer 3a is polymerized using a monomer here mesogenic forming the stabilizing polymer network such as 1,4-bis[4-(3-acryloyloxyexyloxy)benzoyloxy]-2-methylbenzene ST03021 (sold by Synthon Chemicals) of formula C 33 H 32 O 10 .

[0182] A liquid crystal mixture of 4-octyl-4-cyanobiphenyl (8CB from Tokyo Chemicals) and 4-cyano-4'-pentylbiphenyl (5CB sold by Tokyo Chemicals) (which does not have a smectic phase) is used.

[0183] More precisely, to produce the colored electroactive layer 3a, a mixture is formed with these two types of liquid crystals 5CB and 8CB, the monomer, the dichroic dye, and a photoinitiator 2,2-dimethoxy-2-phenylacetophenone called DPMA.

[0184] The mixture contains: 95.4% by weight of 5CB and 8CB liquid crystals in the ratio 1g of 5CB to 4g of 8CB 2% by weight of monomer ST03021, 2% by weight of dichroic dye M412, 0.6% by weight of photoinitiator DPMA.

[0185] The initial mixture before polymerization above has a smectic P' mesophase A at a temperature of about 12±2°C and a nematic P mesophase between about 12±2°C and about 43±2°C (and an isotropic phase above about 43±2°C).

[0186] The final mixture (after polymerization) exhibits a smectic P' mesophase A under a modified temperature T1 of approximately 16±2°C with nematic P mesophase between 16±2°C and 41±2°C (and an isotropic phase beyond approximately 41±2°C).

[0187] A layer of this colored mixture with a thickness of approximately 10 µm is formed between the anchor layers 4a and 4'a.

[0188] Then, the whole is illuminated under UV (λ = 365 nm) for polymerization at 3°C (or at least below 12°C), therefore in smectic phase A.

[0189] The colored electroactive layer 3a then comprises in the nematic phase domains which are similar to the focal conical domains of the smectic A phases, in particular here not TFCD. These defect domains each comprise two defect lines (two line defects), the focal conical ones and which come in pairs, the first elliptical with different degrees of eccentricity and the second hyperbolic. The name given is EHFCD (in English). SECOND DEVICE

[0190] The second device 100 comprises a stack of layers (solids) in this order: a first transparent dielectric element 1' with main faces 11' and 12' here a 1.1mm glass - or in a plastic variant such as PET third and fourth transparent electrodes in disjoint strips 2 comprising first strips 21 and second strips 22 between insulating strips 23, - ITO strips with a square resistance of 100ohm / square, more broadly between 5 and 300ohm / square a third unidirectional planar anchoring layer 4' along a direction r1 perpendicular to b and to X, on the first transparent dielectric element 1' (face 11') and on the ITO strips 21, 22 in contact with this third anchoring layer 4', a second dielectric electroactive layer 3 with a main face called face FA3 on the first device side and a main face called face FA4 opposite,here of thickness (less than 20µm) in a second material comprising: second liquid crystals one or more second dichroic dyes (in the dissolved state) spacers being distributed in the material here glass beads layer 3 being sealed at the periphery by a polymeric seal 5 for example in epoxy in acrylate here in cyanoacrylate a fourth transparent anchoring layer 4, here unidirectional anchoring in a direction r2 perpendicular to r1 and parallel to X a second transparent dielectric element 1 (of layer 4) with main faces 11 and 12, here a glass of 1.1mm - or in a plastic variant such as PET.

[0191] For the power supply via an electrical source, conductive strips (not shown), in particular metallic, for example copper, are fixed for example by gluing along and on peripheral edges and are in contact with the electrodes 21, 22 (one strip per electrode, the strips preferably being on opposite edges). These strips are then connected to a power supply. The edges of the electrodes 21, 22 and the edge of the second electroactive layer are preferably set back relative to the edges of the rectangular or any other shaped elements (glasses) 1, 1'. The thicknesses of the elements (glasses) 1, 1' may be for example 0.7mm to 4mm. They may preferably be thicker than 100µm and at most 300µm for better mechanical strength of the assembly and / or ease of implementation and handling, but if more flexibility is desired, it may be reduced to 50µm for example.

[0192] The manufacturing process is described in more detail below.

[0193] The third anchoring layer 4' is therefore a layer inducing unidirectional planar anchoring along a direction r1 of the second liquid crystals on the surface (out of field) in contact with this layer 4'.

[0194] The third anchoring layer 4' is deposited on the ITO strips 21 and 22 and between the strips, called insulating strips 23, on the first element 1' by 'spin coating' of a solution of polyvinyl alcohol (PVA; Sigma-Aldrich; molecular weight 27 kDa) of approximately 500 nm.

[0195] The third anchor layer 4' is then brushed along the direction r1 parallel to the strips 21,22 extending along a direction r0 / / to r1.

[0196] The fourth anchoring layer 4 is therefore a layer inducing unidirectional planar anchoring along a direction r2 of the second liquid crystals on the surface (out of field) in contact with this layer 4.

[0197] The fourth anchoring layer 4 is deposited on the second element 1 by spin coating a solution of polyvinyl alcohol (PVA; Sigma-Aldrich; molecular weight M w ~ 27 kDa) of approximately 300 nm. The fourth anchoring layer 4 is then brushed along the direction r2 normal to r1.

[0198] The second electroactive liquid crystal layer 3 is composed of E7 nematic liquid crystals (98% by weight) with a black dichroic dye called S428 sold by Mitsui Chemicals (2% by weight). The thickness of the second electroactive layer is 10µm.

[0199] There figure 5 is a front view of strip electrodes 21, 22 and two by two used in the second device of the figure 4 .

[0200] For example, the insulating strips 23 form a serpentine arrangement and a first zone of the electrically conductive layer is insulated from a second zone of the layer by a first portion 23a of the first insulating strip of the serpentine and by a last portion 23b of the last insulating strip of the serpentine.

[0201] The electrically conductive strips 21 and 22 are parallel to ro and r1.

[0202] This arrangement of insulating strips can be achieved by removing a solid electroconductive layer, in particular by a femtosecond laser beam, for example with a diameter of 30µm and the strips being 15µm. The limit in strip thickness is given by the size of the laser beam. The limit of the inter-strip distance is dictated by the displacement of the laser beam.

[0203] The first and second liquid crystals exhibit positive dielectric anisotropy here.

[0204] As explained in relation to the principle figure 1, the second device 100 which receives polarized light as input, delivers either in the first off state a light polarized mainly along P1 normal to r1 (parallel to b) or in a second on state a light polarized mainly along P2 normal to P1 (normal to b).

[0205] There figure 6 is a partial schematic perspective view of the second device of the figure 4 in the first state which is the off state.

[0206] On the surface of the fourth anchoring layer 4, the second liquid crystals 312 (defined by the director n2) and dichroic dyes 322 are (generally) parallel to r2.

[0207] On the surface of the third antagonistic anchoring layer 4', the second liquid crystals 310 (defined by the director n1) and dichroic dyes 320 are (generally) parallel to r1.

[0208] This antagonism forces the second nematic liquid crystals to undergo torsional deformation and the second dichroic dyes are enslaved to the nematics.

[0209] In the thickness of the second electroactive layer 3 the second liquid crystals 311 (defined by the director n3) and second dichroic dyes 321 form an angle (globally) with r1 and r2.

[0210] There figure 7 is a partial schematic perspective view of the second device of the figure 4 in the second state which is an on state at a given voltage U2.

[0211] On the surface of the fourth anchoring layer 4, the second liquid crystals 312 (defined by the director n2) and dichroic dyes 322 remain (generally) parallel to r2.

[0212] In the thickness of the second electroactive layer 3 the second liquid crystals 311 (defined by the director n3) and second dichroic dyes 321 tend overall to align along r2.

[0213] At the output, the polarization P1 perpendicular to r1 decreases and can be almost extinguished.

[0214] There figure 8 represents a schematic and detailed sectional view of the electroactive layer 3 between two plane-plane electrodes of the first device outside the electric field, schematically illustrating the orientation of certain first liquid crystals 34, 34' and of certain of the first dichroic dyes 35, 35' without electric field E1.

[0215] There figure 8 shows a 36-layer structure of liquid crystals with dichroic dyes, a structure frozen by the polymer network not shown.

[0216] The liquid crystal layers are curved towards the planar anchoring layer (here degenerate) in a central zone 34 and the layers are flat and parallel to each other over two more or less extensive lateral zones which may be non-existent.

[0217] In the first electroactive layer 3a there are defect domains each comprising two defect lines (two defect lines), the focal conics and which go in pairs, notably one elliptical (in the X, Y plane) and the other hyperbolic (line 36 in bold), thus the name given is "Elliptic-Hyperbolic focal conic domain" or EHFCD in English.

[0218] A first series of first liquid crystals (rods) 34 are perpendicular to the anchoring layers 4a 4'a, therefore along Z. The same is true for certain first dichroic dyes 35 present in this zone.

[0219] A second series of first liquid crystals 34' form an angle with respect to this anchoring layer 4a. The same is true for certain other first dichroic dyes 35'.

[0220] There figure 9 represents a schematic and detailed sectional view of the electroactive layer between two plane-plane electrodes of the first device under the first electric field E1, schematically illustrating the orientation of certain first liquid crystals 34, 34' and of certain of the first dichroic dyes 35, 35' under said first electric field E1.

[0221] Under field, the second series of first liquid crystals 34' tend to be also perpendicular to the anchoring layers 4a 4'a, therefore along Z. The same is true for certain other first dichroic dyes 35'.

[0222] THE figures 10,11 , 12show in front view images (in black and white) obtained by optical microscopy in polarized light (MOP) under polarizer under a magnification of x20 (with a white line scale of 50µm) of the first electroactive layer of the first electrocontrollable device 10 of the figure 4 (example 1) in the absence of said first electric field E1.

[0223] There figure 10 is for polarized light incident on the first device which has a linear polarization Pi along a direction parallel to b.

[0224] There figure 11 is for polarized light incident on the first device which has a linear polarization Pi along a direction perpendicular to b.

[0225] There figure 12 is for polarized light incident on the first device which has a linear polarization Pi following a direction perpendicular to b and by adding an analyzer perpendicular to this polarization Pi.

[0226] It is observed that the EHFCD focal cone domains form a linear array parallel to the b direction.

[0227] There figure 13 shows a set of curves corresponding to the total transmission TT as a function of the wavelength between 380 and 630nm in a variant of the optical system of the figure 4 because P1 is perpendicular to b (second device rotated 90°) Curve 1 is the off+off mode (with a first voltage U1 at 0V and a second voltage U2 at 0V).

[0228] Curve 2 is the on +off mode (with a first voltage U1 at 40V and a second voltage U2 at 0V).

[0229] Curve 3 is the off +on mode (with a first voltage U1 at 0V and a second voltage U2 at 40V).

[0230] Curve 4 is the on+on mode (with a first voltage U1 at 40V and a second voltage U2 at 40V).

[0231] There figure 14 shows a set of curves corresponding to the diffuse transmission TD as a function of the wavelength between 380 and 630nm in a variant of the optical system of the figure 4 because P1 is perpendicular to b (second device rotated 90°). Curve 1 is the off+off mode of the optical system (with a first voltage U1 at 0V and a second voltage U2 at 0V).

[0232] Curve 2 is the on + off mode of the optical system (with a first voltage U1 at 40V and a second voltage U2 at 0V).

[0233] Curve 3 is the off + on mode of the optical system (with a first voltage U1 at 0V and a second voltage U2 at 40V).

[0234] Curve 4 is the on+on mode of the optical system (with a first voltage U1 at 40V and a second voltage U2 at 40V)

[0235] There figure 15 shows a set of three curves corresponding to the blur H (%) as a function of the first voltage U1 from 0 to 40V of the optical system of the figure 4 (with U2 equal to 0V).

[0236] The blur H which is the ratio between the integrated light transmission on the diffuse transmission TD.

[0237] Curve 1 is the blur measured when P1 is / / at b.

[0238] Curve 2 is the blur measured when the incident light is unpolarized.

[0239] Curve 3 is the blur measured when P1 is normal to b.

[0240] There figure 16 shows a set of three curves corresponding to the ratio of the diffuse transmission TD to the total transmission TT as a function of the wavelength between 380 and 630nm of the optical system of the figure 4 (in off + off mode of the optical system).

[0241] There figure 17 shows a set of curves corresponding to the integrated light transmission TL as a function of the first voltage U1 from 0 to 40V of the optical system of the figure 4 (with U2 equal to 0V).

[0242] Curve 1 is the TL measured when P1 is / / at b.

[0243] Curve 2 is the TL measured when the incident light is unpolarized.

[0244] Curve 3 is the TL measured when P1 is normal to b.

[0245] There figure 18 shows a set of curves corresponding to the total transmission TT as a function of the wavelength between 380 and 630nm of the optical system of the figure 4 with P1 parallel to b.

[0246] Curve 1 is the off+off mode (with a first voltage U1 at 0V and a second voltage U2 at 0V).

[0247] Curve 2 is the on +off mode (with a first voltage U1 at 40V and a second voltage U2 at 0V).

[0248] Curve 3 is the off +on mode (with a first voltage U1 at 0V and a second voltage U2 at 40V).

[0249] Curve 4 is the on+on mode (with a first voltage U1 at 40V and a second voltage U2 at 40V).

[0250] The total transmission varies little from one curve to another.

[0251] There figure 19 shows a set of three curves corresponding to the diffuse transmission TD as a function of the wavelength between 380 and 630nm of the optical system of the figure 4 with P1 parallel to b

[0252] Curve 1 is the off+off mode (with a first voltage U1 at 0V and a second voltage U2 at 0V).

[0253] Curve 2 is the on +off mode (with a first voltage U1 at 40V and a second voltage U2 at 0V).

[0254] Curve 3 is the off +on mode (with a first voltage U1 at 0V and a second voltage U2 at 40V).

[0255] Regarding Example 1 described in relation to the figure 4 (r1 perpendicular to b), to measure the color variation we calculate the lightness L* and the parameters a* and b* measured from the total transmission as well as the integrated TL calculated from the total transmission (TL1) or the diffuse transmission (TL2), and the blur H which is the ratio TL2 / TL1. We use a Perkin Elmer Lambda 950 type spectrometer. The measurements and calculations are recorded in table 1 [Table 1] U2 / U1 (V) TL1(%) TL2 ((%) H (%) L a b 0 / 0 9,7 7,1 73,7 37,3 -4,2 -21,3 0 / 40 13,7 4,5 32,8 43,8 -3,8 -11,3 40 / 0 14,3 7,8 54,4 44,7 -4,4 -16,5 40 / 40 16,6 5,2 31,1 47,7 -4,1 -12,1

[0256] The deltaE color difference (between the 0V / 0V and 0V / 40V cases) is 11.9.

[0257] Concerning a variant (r1 parallel to b), to measure the color variation we calculate the lightness L* and the parameters a* and b* from the total transmission as well as the integrated TL calculated from the total transmission (TL1) or the diffuse transmission (TL2), and the blur H which is the ratio TL2 / TL1. We use a Perkin Elmer Lambda 950 type spectrometer.

[0258] The measurements and calculations are recorded in Table 2 [Table 2] U2 / U1 (V) TL1(%) TL2 (%) H (%) L a b 0 / 0 13,5 5,8 43,0 43,4 -5,0 -13,2 0 / 40 14,4 2,1 14,6 44,9 -1,9 -12,1 40 / 0 12,2 8,7 71,3 41,5 -1,2 -22,3 40 / 40 16 6,6 41,3 46,9 -1,4 -14,4

[0259] The color difference deltaE (between the 0V / 0V and 0V / 40V cases) is 3.6.

[0260] We defined a first polarization ratio for the P1 polarization (normal to r1) as: r 1 U 2 = T 1 T 1 + T 2

[0261] A second polarization ratio for P2 polarization (parallel to r1 and normal to P1) was defined as: r 2 U 2 = T 2 T 1 + T 2

[0262] T1 being the total transmission averaged between 380 and 640nm along the P1 axis and T2 being the total transmission along the P2 axis averaged between 380 and 640nm. A Perkin Elmer Lambda 950 spectrometer was used.

[0263] The evolution of the ratios r1 and r2 as a function of the applied voltage U2 is indicated in table 3. [Table 3] U2 (V) r 1 (%) r 2 (%) 0 99 1 20 49 51 40 32 68 60 26 74 80 22 78

[0264] At zero voltage, the polarization is essentially along P1.

[0265] As the voltage increases the P2 component increases.

[0266] There figure 20 represents a schematic sectional view of an optical system 1000' composed of a first electrically controllable device 10 which is diffusion and variable color by liquid crystals and dichroic dye and of a second electrically controllable device with variable polarization 100' by liquid crystals and dichroic dye in a variant of the fourth embodiment of the invention.

[0267] The optical system differs from the system of the figure 4 in that the support 1'a forms a common support for the first and second devices (carrying all the electrodes on its two main faces).

[0268] There figure 21 represents a schematic sectional view of an optical system 1000a composed of a first electrically controllable device 10a which is diffusion and variable color by liquid crystals and dichroic dye and of a second electrically controllable device with variable polarization 100a by liquid crystals and dichroic dye in a fifth embodiment of the invention.

[0269] The 1000a optical system differs from the 1000 system of the figure 4 in that: the third and fourth electrodes 2 and 2' are plane-planar (not coplanar) r1 forms an angle of 0° with r2.

[0270] As a result, in the on state, the output light from the second device is unpolarized. ASSEMBLY EXAMPLES

[0271] There figure 22 represents a schematic sectional view of a glazed assembly 2000 comprising a transparent sheet 7 (any possible thickness) carrying an optical system 1000 according to the invention.

[0272] The first device 10 is glued by an optical glue 60 to the transparent sheet 7, of glass or plastic (rigid for example), and is also glued by an optical glue 61 to the second device 100.

[0273] For example, it is a partition (vertical position).

[0274] The assembly can be part of a multiple glazing unit (double or triple glazing). For double glazing, the system 1000 can be rated face F1 (external face by convention), F2, F3; F4 (internal face by convention). For triple glazing, the stack can be rated face F1 (external face), F2, F3; F4, F5, F6 (external face). The sheet 7 can be the same size or larger than the system 1000.

[0275] The 2000 glass unit can be: on the preferably external face of a shower screen or element 7 is a shower screen or on the preferably internal face (face 'F4') of curved glazing of a vehicle, in particular an automobile: roof, side glazing, windshield, rear window or element 7 is the curved glazing

[0276] In particular, the 2000 glass unit can be used as a projection screen.

[0277] There figure 23 represents a schematic sectional view of a laminated glazing 3000 carrying an optical system 1000 according to the invention comprising the first device 10 linked to the second device 100 by an optical glue 60.

[0278] The 3000 laminated glazing includes: a first additional sheet of glass 8, transparent a thermoplastic lamination interlayer 70 in particular EVA or PVB a second additional sheet of glass 8' or transparent plastic the main internal faces called F2 and F3 of the first and second additional sheets being opposite, the optical system 1000 being between the faces F2 and F3 and within the submillimetric lamination interlayer or at most 2mm

[0279] During manufacturing, three interlayer sheets can be used: two solid sheets 72, 73 against the internal faces of the sheets 8, 8' and a central sheet 71 with an opening to house the system 1000. After lamination, the interface between sheets (symbolized by dotted lines) is not necessarily discernible. It is preferable for the opening to be closed rather than completely open on one side. Thus, the entire edge of the system 1000 is surrounded by lamination interlayer 70. Naturally, for the power supply, connections can come out of the system 1000 and even protrude on one or more sides of the edges of the glazing.

[0280] Alternatively, only two sheets of interleaf sheets can be used, the hollowed-out central sheet not being necessary if the system 1000 is sufficiently thin, for example with a thickness of at most 0.2 mm.

[0281] One of the 8 or 8' sheets can be colorless or tinted (gray, green, bronze etc.) and the other clear or extra-clear 8' or 8 glazing. One of the first interlayer sheets can be tinted (gray, green, bronze etc.) and the other(s) clear or extra-clear. One of the 8 or 8' sheets can be replaced by a plastic sheet such as polycarbonate or PMMA (in particular with a PU lamination interlayer).

[0282] The edge of the lamination interlayer 70 may be set back (by at most 5 mm for example) from the edge of the sheets 8.8'.

[0283] The 1000 system, for example, covers almost all of the main faces of the 8 sheets and even here is centered. There is the same width of PVB on both sides of the 1000 system.

[0284] The 8, 8' sheets are flat or curved, the 1000 system being able to adapt to the curvature(s) of the then curved 8, 8' glass sheets.

[0285] The optical system 1000 can be a partition or even a vehicle roof. For example, for an automobile roof: sheet 8 is the outermost and curved, which is possibly tinted, for example 3mm sheet 8' is the innermost, curved, preferably clear or extra-clear, for example 3mm or thinner the lamination interlayer 70 is made of PVB which can be acoustic, in particular two-layer or three-layer (sheet 71 or 72 or 73).

[0286] The roof can therefore also be of variable color, for example from dark blue to light blue with voltage U1 or U2.

[0287] THE figures 24 et 25 respectively represent a front view and a schematic sectional view of a laminated glazing unit carrying an optical system 1000 according to the invention. The laminated glazing unit 4000 differs from the previous 3000 in that the optical system 1000 covers a portion of the surface of the sheet 8, in particular a peripheral strip for example along an upper longitudinal edge H over almost the entire length of the laminated glazing unit.

[0288] For example, this is a motor vehicle windshield.

[0289] This 1000 band optical system is in a marginal zone in which the TL and blur-free criteria are freer than in the central ZB zone.

[0290] This 1000 band optical system can therefore also be of variable color, for example from dark blue to light blue with the voltage.

[0291] As shown in figure 25 (sectional view), the width 7a of central spacer 73 between the optical system 1000 and the lower longitudinal edge B is greater than the width 7b of central spacer 73 between the optical system 1000 and the upper longitudinal edge H.

[0292] Alternatively or cumulatively, it may be present along a lower longitudinal edge B of the windshield, over the entire length or a portion of the length.

[0293] As shown in figure 24 (front view from the inside of the vehicle), the windshield comprises a first opaque frame, for example made of enamel (black or other) 91' to 94' on the lateral and longitudinal edges of the free face (F4) 82' of the internal sheet 8' and a second opaque frame, for example made of enamel (black or other) 91 to 94 on the lateral and longitudinal edges of the free face (F1) 82 of the external sheet 8.

[0294] The edge of the optical system 1000 which is on the lower longitudinal edge side, and even those on the lateral edges side can be (facing) between the layers 92, 92', 93, 93', 94, 94' of the enamel frames. For example, the connectors and other current supply strips (for U1 and U2) can also be masked by these layers 92, 92', 93, 93', 94, 94'.

[0295] Alternatively, it is an automobile roof for example with the external glass 8 which is tinted and / or the PVB 71 which is tinted and the optical system 1000 which even covers substantially the entire main face of the glasses 8, 8'.

Claims

1. A liquid crystal optical system (1000, 1000', 1001, 1002, 1003, 1000a) including: - a variable-scattering electrically controllable device (10), referred to as a first device, including a following stack of layers: - a transparent first electrode (2'a) with a main surface referred to as a first connecting surface SA1 and an opposite surface called an opposite external surface SB - a transparent second electrode (2a) with a main surface referred to as a second connecting surface SA2 and with an opposite external surface SB2, with a first electric field E1 between the first and second electrodes - a first dielectric electroactive layer (3a) with a main face referred to as face FA1 on the side of the connecting surface SA1 and a main face referred to as face FA2, made of a first material including: - first liquid crystals, - polymers forming a polymeric network, the first liquid crystals being stabilized by the polymeric network, the first material exhibits, from a temperature referred to as T1, a mesophase referred to as P, wherein the first material includes a set of domains, which include two-dimensional topological defects, that the optical system is such that the first material includes at least a first dichroic dye, and that the first electroactive layer (3a) has an optical response depending on the state of polarization of an incident light on the first device, and that the optical system includes, facing the first device, an electroswitchable device with variable polarization, referred to as a second device (100, 100', 100a, 101, 102), the second device including: - third and fourth transparent electrodes (2, 2') with a second electric field E2 between the third and fourth electrodes - a second electroactive layer (3) made of a second material with a main face FA3 on the side of the third electrode (2) and an opposite main face FA4 including: - second liquid crystals which are nematic - second dichroic dyes, and that the third electrode (2, 21) extends between the second electroactive layer (3) and the first device (10).

2. The liquid crystal optical system (1000, 1000', 1001, 1002, 1003, 1000a) according to the preceding claim, characterized in that the second device is devoid of static polarizing films.

3. The liquid crystal optical system (1000, 1000', 1001, 1002, 1003, 1000a) according to one of the preceding claims, characterized in that the first electric field E1 is alternating and the second electric field E2 is alternating, and preferably the first and second electrodes (4'a, 4a) are in distinct planes, and the first liquid crystals have positive dielectric anisotropy.

4. The liquid crystal optical system (1000, 1000', 1001, 1002, 1003, 1000a) according to one of the preceding claims, characterized in that the second device (100) has first and second functional states and: - in the first functional state, from an unpolarized incident light on the side opposite to the first device (10), the second device is able to deliver an output light on the side of the first device with a first component of the electric field P1 along a first axis and a second component of the electric field P2 along a second axis normal to the first axis, with a first polarization ratio defined by: rp 1 = T 1 T 1 + T 2 rp1 being at least 70%, and even at least 90%, T1 being the total transmission at a wavelength between 380 and 800 nm along the first axis and T2 being the total transmission along the second axis at the wavelength between 380 and 800 nm for a first voltage U2a between the third and fourth electrodes a value that is preferably zero - and in the second state: either i) from an unpolarized incident light on the side opposite to the first device, the second device being able to deliver an output light on the side of the first device with a second polarization ratio defined by: rp 2 = T ′ 2 T ′ 1 + T ′ 2 rp2 being at least 30%, and even at least 50% T'1 being the total transmission at a wavelength between 380 and 800 nm along the first axis and T'2 being the total transmission along the second axis at the wavelength between 380 and 800 nm for a second given voltage U2b between the third and fourth electrodes, a value potentially zero, U2b being distinct from U2a or j) from an unpolarized incident light on the side opposite to the first device, the second device being able to provide an unpolarized output light on the side of the first device, one of the first and second states being in the off state, the other of the first and second states being in an on state.

5. The liquid crystal optical system (1000, 1000', 1001, 1002, 1003) according to one of the preceding claims, characterized in that the third and fourth electrodes are coplanar, forming an alternation of first and second electrically conductive strips (21, 22) at distinct potentials, first and second electrically conductive strips elongated in a direction r0, and in that the second device preferably with second twisted nematic liquid crystals in the off state of the second device, includes: - a unidirectional planar anchoring layer in a direction r1 (4') in contact with face FA3 of the second electroactive layer (3) and on the third and fourth electrodes - and another unidirectional planar anchoring layer in a direction r2 (4) preferably distinct from r1 in contact with face FA4 of the second electroactive layer (3).

6. The liquid crystal system (1000, 1000', 1001, 1002, 1003) according to claim 5, characterized in that r1 forms an angle of 90°±15° and better still of 90°±5° with r2: - r0 forms an angle of at most 15° and even at most 5° with r1 and the second liquid crystals have positive dielectric anisotropy - or r0 forms an angle of 90°±15° and better still of 90°±5° with r1 and the second liquid crystals have negative dielectric anisotropy.

7. The liquid crystal optical system (1000, 1000', 1001, 1002) according to one of the preceding claims, characterized in that the second device (100, 100', 101, 102) in a first functional state which is the off state is able to deliver a polarized light with a polarization P1 and in a second functional state which is the on state is able to deliver a polarized light with a second polarization P2, in particular P1 is normal to r1 and P2 parallel to r1.

8. The liquid crystal optical system according to one of claims 1 to 7, characterized in that the second device, in a first functional state which is the off state, is able to deliver a light with a polarization P1 in particular normal to r1, the first device includes a directional anchoring layer (2a) along a first direction b on face FA1 or preferably on face FA2, the second device is arranged such that P1 forms an angle with b of 0°±20° or even 0±5°.

9. The liquid crystal optical system according to one of claims 1 to 7, characterized in that the second device, in a first functional state which is the off state, is able to deliver a polarized light with a polarization P1 in particular normal to r1, the first device includes a directional anchoring layer (2a) along a first direction b on face FA1 or preferably on face FA2, the second device (100) is arranged such that P1 forms an angle with b of 90°±20° or even 90±5°.

10. The liquid crystal optical system according to one of claims 1 to 4, characterized in that the second electroactive layer is between the third and fourth electrodes and in that the second device includes: - a unidirectional planar anchoring layer in a direction r1 on the main face FA3 of the second electroactive layer and on the third electrode - and another unidirectional planar anchoring layer, on the main face FA4 of the second electroactive layer and on the fourth electrode in that: - r1 forms an angle of at most 15° and even of at most 5° with r2, the second liquid crystals have negative dielectric anisotropy, the orientation of the second liquid crystals in the thickness of the second electroactive layer in the off state of the second device is predominantly homeotropic - or r1 forms an angle of at most 15° and even at most 5° with r2, the second liquid crystals have positive dielectric anisotropy - or r1 forms an angle of 90°±15° and better still of 90°±5° with r2, the second liquid crystals have positive dielectric anisotropy.

11. The liquid crystal optical system (1000, 1000', 1001, 1002) according to one of the preceding claims, characterized in that the second device, in a first functional state which is preferably the off state, is capable of delivering a light with a polarization P1 in particular normal to r1 - in the first functional state, the haze at the output of the first device is at least 10% greater than the haze obtained with an unpolarized incident light at the input of the first device - and preferably in a second functional state, which is preferably the on state of the second device, the haze at the output of the first device is at least 10% less than the haze obtained with an unpolarized incident light at the input of the first device.

12. The liquid crystal optical system according to one of the preceding claims, characterized in that the mesophase P is preferably nematic and the domains are focal conic domains, in particular with two defect lines, especially one elliptical and the other hyperbolic, preferably the focal conic domains form a linear network parallel to a direction b.

13. The optical liquid crystal system (2000, 3000, 4000) according to one of the preceding claims, characterized in that the first device and the second device are disjoined or linked by a transparent bonding layer, especially an optical glue or a thermoplastic layer, especially a lamination interlayer or in that a transparent common support, preferably plastic glass, bears on a first main face the second electrode and on the other side, on an opposite second main face, the third electrode.

14. A laminated glazed unit (3000, 4000) including the optical system according to one of the preceding claims and: - a first additional glass sheet (8) that is transparent - a thermoplastic, especially EVA or PVB, lamination interlayer - a second transparent additional glass (8') or plastic sheet the main internal faces, referred to as F2 and F3, of the first and second additional sheets facing one another, the optical system according to one of the preceding claims preferably being faces F2 and F3 and preferably in the lamination interlayer.

15. A vehicle or building glazed unit (2000, 3000, 4000) bearing the optical system according to one of the preceding claims.