Liquid crystal optical system

Abstract

The present invention proposes an optical system (1000), which is composed of a first electrically controllable device (10) and a second electrically controllable device (100). The first electrically controllable device has variable scattering and color through a first liquid crystal and a first dichroic dye stabilized in a polymer network, and the second electrically controllable device has variable polarization through a second liquid crystal and a second dichroic dye.

Description

[0001] The present invention relates to a liquid crystal optical system, which includes an electrically controllable liquid crystal variable scattering device.

[0002] Such window glasses are known, and some of their characteristics can be modified under the action of a suitable power supply, particularly in terms of transmission, absorption, reflection, or light scattering in some electromagnetic radiation wavelengths, particularly in the visible light and / or infrared ranges.

[0003] Electrically controllable liquid crystal window glasses can be used anywhere in the construction and automotive fields, whenever the line of sight through the window glass must be blocked at a given moment.

[0004] Liquid crystal layers are known in terms such as "PDLC" (polymer dispersed liquid crystal), in the form of first liquid crystal droplets dispersed in a polymer matrix, or "PSLC" (polymer stabilized liquid crystal) in the form of a uniformly distributed liquid crystal.

[0005] Patent application WO2020 / 065038 proposes a liquid crystal electrically controllable device based on "PSLC", which includes two-dimensional topological defects, allowing many scattering states to be reversibly obtained.

[0006] One subject of the present invention is to develop an electrically controllable liquid crystal device having customized and more adjustable electro-optical properties.

[0007] To this end, the present invention proposes a liquid crystal optical system, which includes:

[0008] - An electrically controllable device with variable scattering (flat or curved device, particularly flexible), called the first device, which includes the following layer stack (optionally including an air gap, preferably forming a (solid) layer assembly including a liquid crystal layer):

[0009] - A first transparent electrode, particularly self-supporting (optionally a flexible film) or preferably on a dielectric substrate, the substrate preferably being transparent (and optionally flexible), particularly having a substrate with a thickness of at most 1 cm, 5 mm, 3 mm, or sub-millimeter, or particularly a plastic film or thin glass or ultra-thin glass ("UTG") substrate with a sub-millimeter thickness, even a film with a thickness of at most 200 nm, particularly the first electrode includes (or even consists of) a first conductive layer (single-layer or multi-layer, particularly a deposit), particularly an inorganic conductive layer, particularly a conductive layer with a thickness of at most 200 nm (on the first substrate), the first electrode having a first main surface called the first connection surface and a surface called the opposite surface Sb, particularly the first electrode includes first current supply means (strip - busbar - particularly metallic, made of copper, silver, etc.) at the edge of the first connection surface;

[0010] - A second transparent electrode, preferably facing the first electrode (the two electrodes form a "plane - plane" configuration), especially self - supporting (optionally flexible) or preferably on a dielectric support (preferably transparent) (preferably different from the substrate of the first electrode for the "plane - plane" configuration), in particular a support with a thickness of at most 1 cm, 5 mm, 3 mm or sub - millimeter, in particular a plastic film or thin glass or ultra - thin glass ("UTG") with a sub - millimeter thickness, even a film with a thickness of at most 200 nm. In particular, the second electrode includes a second conductive layer (single - layer or multi - layer, in particular a deposit) (or even consists of it), the second conductive layer is particularly inorganic, in particular at most 200 nm (on the support). The second electrode has a main surface called the second connection surface SA2 and an opposite outer surface SB2. In particular, the second electrode includes second power - supply means (bars - especially metal bars, busbars) at the edge of the second connection surface and is preferably opposite to the first power - supply means, and there is a first electric field E1 between the first and second electrodes.

[0011] - A first dielectric electro - active layer, which has a main face called face FA1 on one side of the first connection surface SA1 and a main face called the opposite face FA2, preferably on the side of the second connection surface SA2, preferably between the first and second connection surfaces with the second electrode (plane - plane configuration). The first electro - active layer has a sub - millimeter thickness Ep 1 , even at most 100 μm and at least 50 nm, especially 50 nm to 50 μm, even 100 nm to 20 μm, and preferably at least 1 μm or 5 μm in thickness. The first electro - active layer is made of a first material (preferably a thermotropic material), which contains (or even consists of):

[0012] - A first liquid crystal (preferably a thermotropic liquid crystal), preferably constituting a majority by weight in the material (preferably at least 50%, 70%, 80%, 85% by weight of the first liquid crystal). In particular, the first liquid crystal includes mesogens, such as those without polymer chains or groups incorporated in the main or side chains of a polymer (referred to as the "LCP" family). In particular, the size of the first liquid crystal is at most 50 nm, 20 nm or 10 nm (and less than Ep 1 ), in particular a plurality of first liquid crystals (pure, in the sense of not being LCP), thus a plurality of mesogens, in particular a mixture of first liquid crystals, which are oriented in the off - state (no voltage) along a first direction b on face FA1 or preferably on face FA2 by a unidirectional anchoring layer (preferably in contact with face FA1 or FA2) along the first direction b;

[0013] - A polymer that forms a (three-dimensional) polymer network, with the first liquid crystal being physically stabilized by the polymer network (i.e., belonging to the English "PSLC" family or the French "CLSPS" family), preferably having at most 20%, 15%, 10%, 5% by weight of the polymer (or polymer and polymer precursor),

[0014] - Optionally, a precursor of the (said) polymer or a non-crosslinked polymer (especially by adjusting the degree of polymerization),

[0015] - At least one first dichroic dye (especially in a dissolved state, particularly in the first liquid crystal), for example, at most 30%, 20%, 10%, 5% by weight of the first dichroic dye (one or more first dichroic dyes), the first dichroic dye having a size of at most 50 nm, 20 nm or 10 nm (and less than Ep 1 ); in particular, the first liquid crystal and the first dichroic dye have comparable sizes, for example, each less than 20 or 10 nm,

[0016] - Preferably, a (first) spacer, especially having a height less than or equal to Ep 1 (or even a larger size), at the periphery (dielectric, transparent or optionally masked by a frame made of, for example, a polyester film, etc.) and / or dispersed in the first electroactive layer (dielectric, transparent, especially plastic, glass, silica, preferably sub-centimeter, especially in the form of beads);

[0017] - Optionally, additives (different from the first dichroic dye), such as colored particles like metal nanoparticles (gold, silver, alloys of both, etc.) or metal oxide nanoparticles (tungsten oxide, tin oxide, etc.) or even any other non-dichroic dye or any other light-absorbing molecule, preferably having a height less than or equal to Ep1 (or even a larger size less than or equal to Ep1).

[0018] Preferably, for example, the first electroactive layer is sealed at the periphery by a dielectric sealant that is especially a polymer (at the edges of the first and second connection surfaces, in contact with the material based on the first crystal or separated by a peripheral spacer), with a width not exceeding 1 cm.

[0019] In addition, the first material has a mesophase called P, which starts from a temperature called Tl (and below a temperature called Tf, which can be the temperature of transition to the isotropic phase), wherein in particular the first material comprises (in volume, most usually in thickness) a set of domains (comprising a first liquid crystal stabilized by a polymer network, a first dichroic dye and optional additives), even being substantially divided into said domains or volume elements, - said domains preferably extending over at least a part of a thickness Ep1 and preferably over at least 90% of the thickness. And, said domains include two-dimensional topological defects, in particular line defects, with line defects having at least two shapes (e.g., one elliptical - including circular - and the other straight or curved, hyperbolic, etc.).

[0020] In particular, starting from a temperature T′ greater than or equal to T1 (and below a temperature called T f which can be the transition temperature in the isotropic phase), the electrocontrollable device can thus have a plurality of reversible scattering and / or colored states, in particular under a first electric field E1 (perpendicular or parallel to the first and second electrodes) between the first and second electrodes, in particular at a given voltage U1, preferably at most 120V or 100V.

[0021] In addition, the system according to the invention comprises, facing the first device, a device with variable polarization (in transmission), called the second device, which comprises:

[0022] - a third and a fourth transparent electrode, with a second electric field E2 between the third and fourth electrodes, in particular the third and fourth electrodes being coplanar or having a plane - plane configuration, self - supporting (optionally flexible) or in the form of a third and a fourth conductive layer on a common carrier element (coplanar configuration) or independent carrier elements facing each other (plane - plane configuration);

[0023] - a second electroactive layer, which has a main face FA3 on the side of the third electrode and a main face FA4 opposite to FA3, with a sub - millimeter thickness Ep 2 and even at most 100μm and at least 50nm, in particular 50nm to 50μm, even 100nm to 20μm, better still at least 1μm or 5μm in thickness Ep 2 wherein the second electroactive layer is made of a second (preferably) thermotropic material, comprising (or even consisting of):

[0024] - Second liquid crystal - (preferably thermotropic) - which is nematic (above T′), bent or non-bent, preferably twisted (under the action of the anchoring layer), without voltage in the off state and / or cholesteric - (preferably in the material, most (preferably at least 50%, 70%, 80%, 85%, 95% by weight) of the second liquid crystal, in particular the second liquid crystal includes mesogens, for example without polymer chains or it is a group incorporated into the main chain or side chain of a polymer (the family called "LCP"), in particular with a size of at most 50 nm, 20 nm or 10 nm (and less than Ep 2 ) of the second liquid crystal, in particular a mixture of various second liquid crystals (pure, in the sense of not being LCP), thus having various mesogens,

[0025] - Second dichroic dye (in particular in dissolved state, especially in the second liquid crystal), for example at most 30%, 20%, 10%, 5% by weight of the second dichroic dye (one or more second dichroic dyes), where the second dichroic dye in particular has a size of at most 50 nm, 20 nm or 10 nm (and less than Ep2); in particular, the second liquid crystal and the second dichroic dye have comparable sizes, for example each less than 20 or 10 nm, where the second dichroic dye preferably has an absorption wavelength within the absorption range of the first dichroic dye,

[0026] - Optional polymer (preferably non-crosslinked) or polymer precursor, preferably having at most 20%, 15%, 10%, 5% or 1% by weight of the polymer (or polymer and polymer precursor), for example the second electroactive layer is not of the type (PDLC or PSLC),

[0027] - Preferably, other spacers, in particular with a height (even larger size) less than or equal to Ep2, at the periphery (dielectric, transparent or opaque, optionally masked by a frame made of, for example, polyester film, etc.) and / or dispersed in the second electroactive layer (dielectric, transparent, especially plastic, glass, silica, preferably sub-centimeter, especially beads)

[0028] - Optional other additives (different from the second dichroic dye), such as coloring particles such as metal nanoparticles (gold, silver, alloys of both, etc.) or metal oxide nanoparticles (tungsten oxide, tin oxide, etc.) or even any other non-dichroic dye or any other light-absorbing molecule, preferably having a height less than or equal to Ep2 (and even having a larger size less than or equal to Ep2).

[0029] Preferably, the second electro-switchable electroactive layer is sealed at the periphery by a dielectric seal, in particular a polymer seal (at the edge of the main surface), in contact with a second material based on a second crystal or separated by a peripheral spacer).

[0030] The third electrode extends between the second electroactive layer and the first device (thus on the side of the first device), and is oriented towards the second surface SB2, for example if the first device has a planar-planar electrode configuration.

[0031] Furthermore, the fourth electrode can be coplanar with the third electrode (thus also between the second electroactive layer and the first device) or the active layer is between the third and fourth electrodes (planar-planar configuration).

[0032] Thus, according to the present invention, the combination of the first electrically controllable device having polarization-sensitive variable scattering and the second electrically switchable variable polarization device enables a wide range of available optical properties, in particular a wide range of haze, light transmittance, and coloring levels. In particular, the luminance L* can vary.

[0033] The measurement of the total transmittance TT or the diffuse transmittance TD, TL or the haze is the same as that described in the prior art WO2020 / 065038.

[0034] The CIE 1976 L*a*b* color space, generally abbreviated as CIELAB, is a color space specifically used to characterize the surface color. Three values L*, a*, and b* are used: the luminance L* is generated by the surface brightness; the two parameters a* and b* represent the color difference of the color relative to the gray surface with the same luminance. The presence of a gray, non-colored, achromatic surface means that it clearly indicates the composition of the light illuminating the colored surface. This light source is the standardized daylight D65 here.

[0035] The CIELAB color space is defined from the CIE XYZ space. Compared with the latter, its advantage is that the color distribution is more in line with the human eye visual system's perception of color deviation. It is also possible to define the color difference ΔE between two colors, which is defined as the square root of the sum of the square differences of L*, the square differences of a*, and the square differences of b*. In the present invention, the ΔE between two colors (the off state and the on state of the second device when the first device is in the off state, or between the off state of the first and second devices and the on state of the first device, or the two colors in the off state of the second device under the electric field E1) can be at least 1, or even at least 7.

[0036] The present invention is applicable in various fields, in particular in the construction field (windows, partition walls, glass floors), outdoors, especially in urban spaces, or in road, sea, rail, and air transportation vehicles (windshields, side windows, skylights, etc.).

[0037] When incorporated into building or vehicle window glasses, the first device can be oriented towards the outside or towards the inside.

[0038] The second device, preferably having a shape similar to that of the first device, can extend over all or part of the first device as needed.

[0039] The optical system may not have an optical element capable of depolarizing the light between the first device and the second device.

[0040] The optical system can be of any size because the first and second devices can be easily fabricated on a surface with a length of at least 1 m.

[0041] Between the first device and the second device, it is desirable to avoid placing a scatterer.

[0042] Of course, any opaque, obstructive, or reflective elements between the first device and the second device can be avoided.

[0043] However, a static polarizer, such as a plastic film (drawn) with a dichroic dye, can be added between the first device and the second device. In particular, the static polarizer can be designed to block a given polarization P1. In particular, the static polarizer can be designed to block a given polarization P2.

[0044] The second device itself does not require polarizers (such as cross polarizers and analyzers) for operation.

[0045] The switching time for each of the first and second devices can be less than a few seconds. The switching state of the optical system is reversible and (quasi) instantaneous.

[0046] The second device only requires one liquid crystal layer (single - cell system) and does not require multiple liquid crystal layers to form a variable polarizer.

[0047] The optical properties of the liquid crystal system can be adjusted:

[0048] - By turning off or applying a first electric field E1 (preferably alternating) and by selecting a voltage level U1

[0049] - And / or by turning off or applying a second electric field E2 (preferably alternating) and by selecting a voltage level U2

[0050] - By selecting an output (main) polarization direction P1 (for example, in the off - state of the second device) called, which is relative to the characteristic direction b of the first device described later. In particular, P1 is substantially parallel to or substantially perpendicular to b.

[0051] In particular, a non - masked state (easily observable through the optical system) can be selected for the "off" state of the optical system (both the first and second devices are off), in which P1 is perpendicular to b.

[0052] In particular, a masking state and a darker state can be selected for the "off" state of the optical system (the first and second devices are off), where P1 is parallel to b. The color mainly depends on the first dichroic dye and can also depend on the second dichroic dye.

[0053] The switching from one functional state to another can be achieved as follows:

[0054] - When the second device can provide sufficient polarization different from P1 (preferably perpendicular to P1), by applying a voltage to the second device,

[0055] - By applying a voltage to the first device, the second device remains off and P1 is parallel to b.

[0056] The optical system can have a thickness of at most 1 cm or 5 mm or 1 mm.

[0057] The second device can have a thickness of at most 5 mm or 1 mm or 0.5 mm.

[0058] The first device can have a thickness of at most 5 mm or 1 mm or 0.5 mm.

[0059] Regarding the first device, the domains cause a dependence of the scattering property as a function of the polarization state of light. The first dichroic dye causes a dependence of the absorption property as a function of the polarization state of light.

[0060] Regarding the second device, the second dichroic dye controlled by the second liquid crystal is preferably twisted in the off state and plays a key role in providing the variable polarization function. The second device with variable polarization is preferably transparent and has a haze of at most 10% or 1% or 0.5% in the off state and the illuminated (on) state.

[0061] The applied voltage can be lower than 120 V or even 80 V.

[0062] It is possible to consider applying U1 (even selecting the level of U1) and / or applying U2 (even selecting the level of U2) according to instructions. Thus, a device for controlling the first device and / or the second device can be provided.

[0063] The parameters affecting the optical properties are in particular:

[0064] - The selection of the first liquid crystal, in particular the selection of the mesogenic mixture (especially for the operating temperature range and the voltage U1 level for "de-anchoring" in the on state) and their dielectric anisotropy

[0065] - The transparency level of the electrodes (their possible carriers) with the lowest possible absorption, and in the case of strip electrodes, the density of the strips (to reduce the voltage by reducing the space between the strips and to increase the off / on contrast by reducing the area without switching the liquid crystal)

[0066] - The selection of the first and / or second dichroic dyes (dichroic ratio, their concentration, etc.), in particular with the highest and constant absorption spectrum in the visible light range

[0067] - The thickness of the first and / or second electroactive layer

[0068] - The selection of the anchoring layer of the first device (type or arrangement of defects) and the selection of the anchoring layer of the second device (inducing the polarization type in the off state, forcing the nematic to undergo a twisted deformation)

[0069] In particular, in the absence of an applied electric field (or for a given voltage), the haze value can vary as a function of the size or type of two-dimensional defects, their density, the thickness of the electroactive material, the selection of the first liquid crystal, the polymer network (degree of crosslinking, polymerization conditions), the monomer, and the refractive index difference between the polymer and the liquid crystal

[0070] In particular, the haze value in the absence of an applied electric field (or for a given voltage) will vary as a function of the orientation of the first liquid crystal, in particular as a function of the angle between the long (molecular) axis of the first liquid crystal and the polarization axis of the polarized light along the plane parallel to the surface of the first electroactive layer

[0071] The haze is defined, for example, as the ratio of the diffuse transmittance TD to the total transmittance TT. It is preferably expressed in %.

[0072] The haze H is preferably defined as the ratio between the integrated light transmittance related to the diffuse transmittance TD and TL

[0073] Each state of the optical system, scattering and / or more or less colored, can be defined by a given color, in particular by the luminance L* (also by a*, b*)

[0074] The entire system will function regardless of whether the unpolarized light is incident on the first device or the second device

[0075] The optical characterization of the optical system according to the invention is preferably carried out at the output of the first device on the side opposite to the second device. For simplicity, the explanation of the influence of the second device on the first device starts from the unpolarized incident light on the second device. However, by measuring the light at the output of the second device, substantially the same optical properties are obtained using the unpolarized incident light on the first device (opposite to the second device)

[0076] The level of scattering and / or coloring can be controlled, in particular adjusted according to data (temperature, brightness, etc.) collected by sensors communicating with an optical system (controlling one or more power supplies). Separate or shared power circuits can be provided, such as an alternating voltage generator (e.g., up to 120V).

[0077] Preferably, the second device in the off-state functional state is capable of transmitting light with polarization P1 (main) (first functional state detailed below) and light with a second polarization P2 in the on-state (second functional state detailed below), in particular P1 is perpendicular to r1 and P2 is parallel to r1.

[0078] More generally, the second device can have first and second functional states such that:

[0079] - In the first functional state, using unpolarized incident light on the side opposite to the first device, the second device is capable of transmitting output light (polarized) on the side of the first device, having a first component P1 of the (polarized) electric field along a first axis and a second component P2 of the (polarized) electric field along a second axis perpendicular to the first axis, where the first polarization ratio is defined by:

[0080] [Equation 1]

[0081]

[0082] rp1 is at least 70%, preferably at least 90%, and even at least 95%. T1 is the total transmittance at wavelengths of 380 - 800 nm along the first axis, or even the average total transmittance at least in the range of 400 - 600 nm, and even 380 - 640 nm. And T2 is the total transmittance at wavelengths of 380 - 800 nm along the second axis, or even the average total transmittance at least in the range of 400 - 600 nm, and even 380 - 640 nm for a given first voltage U2a (preferably zero) between the third and fourth electrodes;

[0083] - And in the second functional state:

[0084] i) Using unpolarized incident light on the side opposite to the first device, the second device is capable of transmitting (polarized) output light on the side of the first device, and the second polarization ratio is defined by:

[0085] [Equation 2]

[0086]

[0087] rp2 is at least 30%, and even at least 50% or 60%.

[0088] T′1 is the total transmittance along the first axis at wavelengths of 380 - 800 nm, even the average total transmittance at least at 400 - 600 nm or even 380 - 640 nm, and T′2 is the total transmittance along the second axis at wavelengths of 380 - 800 nm for a given second voltage U2b (preferably zero) between the third and fourth electrodes, even at least at 400 - 600 nm, even 380 - 640 nm, and U2b is different from U2a;

[0089] or j) unpolarized incident light from the side opposite to the first device, and the second device can provide unpolarized output light on the side of the first device,

[0090] One of the first and second functional states is in the off state (no voltage), and the other of the first and second functional states is in the on state (under voltage).

[0091] Preferably, the first functional state is the off state and the second functional state preferably follows i), or the first functional state is the on state and the second functional state preferably follows j).

[0092] In one configuration, the first functional state is the off state and the second functional state preferably follows i). Naturally, the second device then has multiple functional states in the on state. In particular, there is a threshold voltage from which, for a portion of the liquid crystal, the anchoring force of the second liquid crystal is overcome, and the more the voltage increases, the more the liquid crystal reorients until the saturation voltage, which is preferably at most 80 volts.

[0093] At this time, a polarization ratio that varies according to the applied voltage U2 can be obtained.

[0094] Advantageously, the first electric field E1 is alternating and preferably the first applied voltage U1 is at most 120 V, and the second electric field E2 is alternating and preferably the second applied voltage U2 is at most 120 V. Preferably, the first and second electrodes are in different planes, and the first liquid crystal has a positive dielectric anisotropy (independent of the frequency of the first electric field E1), and the first electric field E1 is perpendicular to the first and second electrodes.

[0095] Like E2, E1 is preferably alternating, having a frequency starting from 50 Hz, such as a frequency of 100 Hz, 1 kHz, or 2 kHz. The voltage means the peak voltage (referred to as Vpeak in English).

[0096] Therefore, the orientation change of the first liquid crystal is preferably caused by E1 perpendicular to the plane FA1 (if the stack is curved, such as flexible, and between curved substrates, particularly glass substrates, then in the mid - plane).

[0097] When the optical system according to the invention is in the closed state (the first and second devices are closed), it can be colored with a given color CO, which is defined in particular by a luminance L*0 (and also by a*0, b*0).

[0098] When the optical system according to the invention is in the open state of the second device (the first device is closed), it can be colored with a given color Ca, which is defined in particular by a luminance L* (and also by a*, b*).

[0099] When the optical system according to the invention is in the open state of the first and second devices, it can be colored with a given color Cb, which is defined in particular by a luminance L* (and also by a*, b*).

[0100] When the optical system according to the invention is in the open state of the first device (the second device is closed), it can be colored with a given color Cb, which is defined in particular by a luminance L* (and also by a*, b*).

[0101] Furthermore, the color can vary as a function of the voltage U1 and / or U2.

[0102] The selection of U1 and / or U2 can be controlled, in particular adjusted as a function of data (temperature, luminance, etc.) collected by sensors communicating with the device (control power supply).

[0103] The third (respectively fourth) electrode can comprise (or even consist of) a conductive layer (single or multi-layer, in particular a deposit), in particular an inorganic conductive layer, in particular with a thickness of at most 200 nm (the conductive layer is on a carrier element, preferably between the carrier element and an anchoring layer), and in particular includes a current-providing arrangement (bars - busbars - especially metallic, made of copper, silver, etc.) at the edges.

[0104] In a plane-plane configuration, the layered third and fourth electrodes extend over all or part of their respective carrier elements.

[0105] In a first preferred embodiment, for in-plane switching, the third and fourth electrodes (preferably layered) are coplanar (on a common carrier element rather than self-supporting), forming alternating first and second conductive bars (metal bars, for example) at different electric potentials, bars elongated along the direction r0 (linear, preferably straight) and preferably having the highest possible bar density (the bar width is as small as possible and the bar spacing is as small as possible).

[0106] Therefore, a potential difference is applied between two "terminals" that are in the same plane and electrically insulated from each other.

[0107] The second electric field E2 is interactive and mostly planar (parallel to the third and fourth electrodes) at this time.

[0108] While maintaining conductivity, the strip is sought to be as narrow as possible to increase the "polarizer" power in the ON mode. Also, the width between strips (insulating strips without electrical conductors) is sought to be minimized to reduce the potential difference to be applied.

[0109] For example, the conductive strip and / or the width between strips (insulating strip) is at most 50 μm or 30 μm or 10 μm.

[0110] For example, the insulating strip forms a serpentine arrangement and the first region of the conductive layer is isolated from the second region of the layer by the first part of the first insulating strip of the serpentine strip and the last part of the last insulating strip of the serpentine strip.

[0111] It is possible to consider implementing such an insulating strip arrangement by removing the conductive solid layer (in particular by a laser beam). The limit of the strip thickness is determined by the size of the laser beam. The limit of the distance between strips is determined by the displacement of the laser beam.

[0112] The dielectric anisotropy of the first electroactive layer (of the first liquid crystal) is non-zero and can be negative or positive. The dielectric anisotropy of the second electroactive layer (of the second liquid crystal) is non-zero and can be negative or positive.

[0113] The first device may include:

[0114] - A (first) alignment anchoring layer on one of the faces FA1 or FA2, preferably on face FA2 along the first direction b, (in the off state of the first device, the first liquid crystal is generally oriented along this first direction b in the face FA2 or FA1)

[0115] - In particular, a (second) anchoring layer on the other of the faces FA1 or FA2, preferably on face FA1, preferably a separate anchoring layer (anti-alignment layer), preferably normal anchoring, which then induces the first liquid crystal to be generally oriented perpendicular to the other face FA1 or FA2 (vertical anchoring).

[0116] In a configuration with coplanar third and fourth electrodes, a second device, which preferably has a second nematic liquid crystal that is twisted in the off state of the second device, includes:

[0117] - A (third) unidirectional planar alignment anchoring layer along the (second) direction r1 on the main face FA3 of the second electroactive layer and on the third and fourth electrodes, in particular with P1 perpendicular to r1 and P2 parallel to r1,

[0118] - And another (or fourth) unidirectional planar alignment anchoring layer along the (third) direction r2 (preferably different from r1) on the main face FA4 of the second electroactive layer (in contact therewith).

[0119] In particular, r1 and r2 form an angle of 90° ± 15°, preferably 90° ± 5° (the second nematic liquid crystal has a twist in the off state):

[0120] - r0 and r1 form an angle of at most 15°, even at most 5°, and the second liquid crystal has a positive dielectric anisotropy (in this case, the first functional state of the second device with polarization P1 is the off state and the second functional state is the on state and follows i)),

[0121] - or r0 and r1 form an angle of 90° ± 15°, even at most 90° ± 5°, and the second liquid crystal has a negative dielectric anisotropy (in this case, the first functional state of the second device with polarization P1 is the off state and the second functional state is the on state and follows i)).

[0122] Preferably, the second device, in its first functional state, i.e., the off state, is capable of transmitting light with polarization P1 (mainly) and in the functional on state (state i) has a second polarization P2 (mainly), in particular, P1 is perpendicular to r1 and P2 is parallel to r1.

[0123] In an embodiment with j) unpolarized light (in the coplanar electrode mode of the second device), the second nematic liquid crystal is at a dual frequency, has a dielectric anisotropy that varies from negative to positive as a function of the frequency and the second alternating electric field, and the alternating second electric field E2 is at a variable frequency.

[0124] As an alternative to the coplanar configuration, the second electroactive layer is located between the third and fourth electrodes (surface SA1 on the side of FA3, surface SA2 on the side of FA4) and the second device includes:

[0125] - A unidirectional planar anchoring layer in the direction of r1 that contacts the face FA3 of the second electroactive layer and is on the third electrode (in particular, in contact with the third electrode);

[0126] - And another unidirectional planar anchoring layer in the direction of r2 that contacts the face FA4 of the second electroactive layer and is on the fourth electrode (in particular, in contact with the fourth electrode);

[0127] - r1 and r2 form an angle of at most 15°, even at most 5°, the second liquid crystal has a positive dielectric anisotropy, (in this case, the first functional state of the second device with polarization P1 is the off state and the second functional state of the second device is the on state (on, under voltage) and follows j), so the output light is unpolarized);

[0128] - Or r1 and r2 form an angle of 90° ± 15°, and preferably 90° ± 5°. The second liquid crystal has positive dielectric anisotropy. (In this case, the first functional state of the second device with polarization P1 is the off state and the second functional state of the second device is the on state, and it follows j), so the output light is unpolarized).

[0129] - Or r1 and r2 form an angle of at most 15°, and even at most 5°. The second liquid crystal has negative dielectric anisotropy. The orientation of the second liquid crystal in the thickness of the second electroactive layer is mainly vertical (homeotrope) in the off state of the second device. (In this case, the first functional state of the second device with polarization P1 is the on state and the second functional state of the second device is the off state, and it follows j), so the output light is unpolarized).

[0130] In the latter case, the anchoring layers (such as polyimide) in the second device can each produce vertical anchoring, but still need to be rubbed to obtain a pretilt angle with respect to the long axis of the mesogen of the second liquid. The off state is almost vertical, and the on state, where an electric field applied along the vertical direction will reorient the negative dielectric anisotropy mesogens in the rubbing direction. In this specific configuration, the rubbing of the anchoring layer does not have a macroscopic unidirectional planar orientation effect in the OFF state because the pretilt design on the layer produces vertical anchoring without rubbing.

[0131] This type of anchoring with pretilt is involved in the article by Li et al. titled "Dye-doped dual-frequency nematic cells as fast-switching polarization-independent shutters" (Vol 27 no. 4 February 2019, page 3861 of OPTICS EXPRESS), which concerns a dual liquid crystal cell system for changing from linear polarization to total extinction.

[0132] In addition, the first electroactive layer (and thus the electrocontrollable device with variable scattering) has an optical response that depends on the polarization of the incident light.

[0133] This different response to light polarization is caused by the following factors:

[0134] - The shape factor and internal structure of two-dimensional topological defects, especially line defects, particularly the line defects of the non-complex surface focal conic domains (abbreviated as non-TFCD) of the smectic mesophase.

[0135] - and / or arrangements of different domains (in particular the focal conic domains of the smectic mesophase, including "TFCD"), in particular their shape, their orientation, their degree of symmetry, such as random distribution, irregular distribution, etc., the distribution being determined by the anchoring conditions (the 2D anchoring layer can be adjusted as required, for example multi-directional anchoring).

[0136] Examples of various architectures of polarization-sensitive smectic focal conic domains (i.e., focal cone domains) are given in the publication by Ling Ling Ma et al. entitled "Smectic Layer Origami Preprogrammed Photoalignement" on pages 1 - 7 of 《Advances Materials》20171606671.

[0137] In a preferred embodiment, the second device, in a first functional state which is a closed state, is capable of transmitting light having polarization P1, the first device includes a (first) directional anchoring layer on surface FA1 or preferably on surface FA2 along a first direction b, and the second device is arranged such that P1 forms an angle of 0° ± 20°, or better 0° ± 5°, with b (in particular r2 forms an angle of 0° ± 20°, or better 0° ± 5°, with b).

[0138] In one embodiment, the second device, in a first functional state which is a closed state, is capable of transmitting light having polarization P1, the first device includes a directional anchoring layer on surface FA1 (in contact with surface FA1) or preferably on surface FA2 (in contact with surface FA1) along a first direction b, at this time the first liquid crystal as a whole is oriented along this first direction b on surface FA1 or preferably on surface FA2, and the second device is arranged such that P1 forms an angle of 90° ± 20°, or better 90° ± 5°, with b (in particular r1 forms an angle of 90° ± 20°, or better 90° ± 5°, with b).

[0139] Preferably, as already pointed out, an anchoring layer is used which is used to orient the liquid crystal by surface interaction during preparation in the absence of an applied electric field (E1 or E2).

[0140] Up to a certain distance from the surface having the anchoring layer, the (first or second) liquid crystal can maintain its orientation in this direction until a certain field strength (voltage).

[0141] The thickness of the anchoring layer (of the second device and / or the first device) is preferably at most 1 μm, more preferably sub-micron, for example less than 600 nm.

[0142] There can also be multiple different anchoring regions on the same surface. These defects are generated by mechanical deformation of the material structure and are obtained by the constraint conditions applied by the two anchoring layers (forcing the liquid crystal to contact these layers in specific and separate orientations).

[0143] As a unidirectional planar anchor (first or second device), a fluoropolymer film such as polytetrafluoroethylene PTFE or Teflon can be used, where the polymer chains are aligned with the displacement direction of the polytetrafluoroethylene rod during deposition.

[0144] The unidirectional planar anchor fixes the zenith angle and azimuthal orientation of the liquid crystal director n, for example, by texturing, brushing (also called rubbing) the planar anchor layer, for example, including nano-grooves or micro-grooves.

[0145] A velvet fabric can be used for this brushing.

[0146] For normal anchoring (preferably the first device), the most commonly used layers are based on octyltrichlorosilane (OTS) and N,N-dimethyl-N-octadecyl-3-aminopropyltrimethoxysilane chloride (DMOAP) or polyimide.

[0147] Layers based on sodium dodecyl sulfate (SDS) or even mixtures of alkanethiols can also produce normal anchoring.

[0148] One or more anchor layers are deposited, for example, by a liquid route.

[0149] One or more anchor layers can be preferably thin (flexible) films, for example, up to 200 μm or 50 μm, which particularly carry the (first and / or second) electrodes of the first device. One or more anchor layers can be preferably thin (flexible) films, for example, up to 200 μm or 50 μm, which are particularly the carriers of the electrodes (third and / or fourth electrodes) of the second device.

[0150] The anchor layer (of the first or second device) is, for example:

[0151] - Preferably dielectric (especially amorphous, polymeric and / or inorganic, glass), with surface functionalization, in particular, layers based on polyimide, polyvinyl alcohol (PVA), for example, for planar anchoring (especially for the first device)

[0152] - Conductive, especially it is part of the electrode thickness of the first device (first or second whole-surface electrode, planar-plane electrode configuration) or the second device (third or fourth whole-surface electrode, planar-plane electrode configuration) (for example, for planar anchoring).

[0153] The air gap provides normal anchoring, but preferably has a strong anchor layer. It is also preferred that the anchor layer, especially the dielectric anchor layer, is different from the electrode.

[0154] There can even be more than two anchoring layers (three or more), in which case there are multiple liquid crystal layers separated by the anchored layers. For simplicity, for each of the first and second devices, a single liquid crystal layer is preferred.

[0155] In a first functional state, which is preferably a closed state, the second device is capable of transmitting light with polarization P1, particularly perpendicular to r1 (preferably P1: forming an angle of 0° or 90° ± 20°, or even 0° or 90° ± 5° with the first direction b). And:

[0156] - In the first functional state, the haze H0 at the output of the first device is at least 10% (even 20%) higher than the haze obtained using unpolarized incident light at the input of the second device.

[0157] - And preferably in a second functional state, which is preferably an open state of the second device, the haze H1 at the output of the first device is at least 10% (even 20%) lower than the haze obtained using unpolarized incident light at the input of the second device.

[0158] The first liquid crystal preferably has an overall texture in a given direction b on the surface FA1 or surface FA2 (referred to as the planar alignment surface).

[0159] Their director n - or major axis - generally follows this first direction b).

[0160] b is in particular the (brushing) axis of a unidirectional planar anchoring layer in contact with this planar alignment surface (creating an interaction between the liquid crystal and the solid layer).

[0161] Defect line domains are preferred because the haze (scattering ability) is significant. As detailed in the application WO2020 / 065038 incorporated by reference, the focal conic domains of the smectic (intermediate) phase are preferred.

[0162] The defect domains generally each contain two defect lines, are focal conic domains and occur in pairs, in particular one is an ellipse with a different eccentricity and the other is a hyperbola, hence the name "elliptical - hyperbolic focal conic domain" or in English EHFCD.

[0163] Preferably, the intermediate phase P is nematic and the domains are focal conic domains, especially the smectic intermediate phase (intermediate phase P′), in particular having two defect lines, preferably one ellipse and the other hyperbola (EHFCD).

[0164] The focal conic domains, especially EHFCD, preferably form a linear network parallel to the direction b.

[0165] (The first and / or second) dichroic dye may be an anisotropic organic molecule having optical anisotropy, which is elongated, especially rod-shaped. It is in a dissolved state in the material, especially dissolved in the first liquid crystal. The percentage of (each) dichroic dye is adjusted so as not to exceed the solubility limit. In particular, one (or more) dichroic dyes compatible with the liquid crystal chemistry are selected.

[0166] In particular, each (elongated, rod-shaped) dichroic dye may have a long molecular axis and the absorption varies along the long axis or the short axis.

[0167] (The first or second) dichroic dye is controlled by the orientation of the (first or second) liquid crystal of the (first or second) electroactive layer in operation. The movement (rotation) of the liquid crystal under the action of the electric field (E1 or E2) tends to align with the electric field in operation, resulting in the movement (rotation) of the dichroic dye, and the long axis also tends to align it with the electric field in operation.

[0168] Therefore, the absorption of the dichroic dye varies as a function of its orientation with respect to the polarization of the incident light. On the contrary, a non-dichroic dye without absorption anisotropy is not sensitive to the electric field, or is not very sensitive, and even does not change the absorption. Such dyes can be added to adjust the desired hue in the first device.

[0169] The first dichroic dye may have a first absorption band (in visible light) preferably of at least 200 nm or 300 nm, even preferably 380 nm to 650 nm or even up to 700 or 780 nm.

[0170] The second dichroic dye may have a second absorption band (in visible light) preferably of at least 200 nm or 300 nm, even preferably 380 nm to 650 nm or even up to 700 or 780 nm.

[0171] The first and second dichroic dyes preferably have a common absorption range preferably of at least 1 nm or 10 or 100 nm (not necessarily having the same absorption maximum or the same absorption curve).

[0172] The first dichroic dye may have maximum light absorption for light polarized along the direction r1.

[0173] The second dichroic dye may have maximum light absorption for light polarized along the same direction r1.

[0174] There are multiple families of dichroic dyes, particularly those described in the publication by Mark T Sims titled "dyes as guests in ordered systems: current understanding and future directions", Liquid Crystals, 2016, Volume 43, NOS. 13 - 15, pages 2363 - 2374.

[0175] The dichroic dye according to the present invention can be an azo dye having AZO (-N=N), particularly rod-shaped. Chemical changes can be induced in the azo dye, for example, using an introduced ester group (see page 2366 of the above-mentioned publication).

[0176] Other dyes are anthraquinone-based, generally having a condensed ring structure, or rod-shaped by adding substituents. Examples of dichroic dyes (chromophores) are in Table 1 of the above-mentioned publication.

[0177] Examples of dichroic dyes suitable for the present invention are additionally mentioned in the book by L.M Blinov et al. titled Electrooptic effect in Liquid Crystal Materials, published by Springer in 1994, particularly in Chapter 2.3 titled "Optical Anisotropy and Dichroism" and on pages 66 to 68, including Table 2.2.

[0178] For example, for a blue dye, 630 nm ± 10 nm can be selected as the maximum absorption wavelength, and 430 nm ± 50 nm or ± 10 nm can be selected as the wavelength outside the absorption band. For example, the dye M412 sold by Mitsui Chemicals can be mentioned.

[0179] For example, for a red dye, 500 nm ± 10 nm can be selected as the maximum absorption wavelength, and 650 nm ± 50 nm or ± 10 nm can be selected as the wavelength outside the absorption band. For example, the dye SI-426 sold by Mitsui Chemicals can be mentioned.

[0180] For example, for a yellow dye, 400 nm ± 10 nm can be selected as the maximum absorption wavelength, and 600 nm ± 50 nm or ± 10 nm can be selected as the wavelength outside the absorption band. For example, the dye SI-486 sold by Mitsui Chemicals can be mentioned.

[0181] For example, for a black dye, the dye SI-428 sold by Mitsui Chemicals can be mentioned.

[0182] Independently, one or more elements of the system (electrodes, anchoring layers, substrates or supports, laminated interlayers, glass backings, etc.) can be colored (more or less strongly), for example having a maximum absorption different from that of the first dichroic dye.

[0183] The first device can include:

[0184] - A transparent dielectric substrate carrying a first electrode (and an anchoring layer, particularly normal to the first electrode), the substrate being selected from glass sheets or transparent polymer sheets and having an optional external scratch-resistant layer,

[0185] - A transparent dielectric support carrying a second electrode (if in a planar-planar configuration) and at least one anchoring layer, particularly unidirectional along b (preferably on the first electrode), the substrate being selected from glass sheets or transparent polymer sheets (with an optional external scratch-resistant layer).

[0186] The second device can include:

[0187] - A first transparent dielectric element carrying a third electrode (and preferably a fourth electrode) (coplanar configuration) and even an anchoring layer, preferably a unidirectional anchoring layer along r1, the first element being selected from glass sheets or transparent polymer sheets corresponding to or different from the dielectric support,

[0188] - A second transparent dielectric element, if in a planar-planar configuration, carrying a fourth electrode and carrying at least one anchoring layer, preferably a unidirectional anchoring layer along r2, the second element being selected from glass sheets or transparent polymer sheets (with an optional external scratch-resistant layer).

[0189] The first device and the second device can be spaced apart, share a common support (on the same side or on both sides) or be connected (dielectric support and connected first dielectric element).

[0190] In one embodiment, the first device and the second device are connected:

[0191] - By a transparent adhesive layer, in particular an optical adhesive (OCA) or a thermoplastic layer, in particular an EVA or PVB laminated interlayer,

[0192] - Or a transparent common support, preferably plastic glass, carrying on:

[0193] - On the first main surface of the second electrode (even on the first main surface of the first electrode if coplanar) and in particular the rest of the layer stack

[0194] - And on the other side, on the second main surface opposite the third electrode (even the fourth electrode if coplanar), in particular the rest of the layer stack.

[0195] The transparent adhesive layer can be colorless or colored.

[0196] The transparent adhesive layer can have a thickness of at most 0.5 mm or even 0.1 mm.

[0197] The optical system can be flat or curved, flexible to adapt to the curvature of, for example, (monolithic or laminated) window glass. In this case, it is curved on the monolithic window glass or, for example, within the laminated window glass.

[0198] The invention also relates to an optionally curved laminated window glass, comprising:

[0199] - A first additional glass sheet, in particular having a thickness of 0.7 mm - 4 mm

[0200] - A thermoplastic laminated interlayer, in particular EVA or PVB,

[0201] - A second additional glass sheet, in particular a glass sheet having a thickness ranging from 0.7 mm to 4 mm or even less than 0.7 mm, or a plastic sheet, such as polycarbonate or PMMA (in particular with a PU laminated interlayer),

[0202] - The mutually facing main inner surfaces of the first and second additional glass sheets, designated as F2 and F3, and the optical system as described above is preferably between the surfaces F2 and F3 and preferably within the laminated interlayer.

[0203] Preferably, with respect to the first device, the substrate is polymeric and even the carrier is polymeric, occupying all or part of the surface of the first sheet.

[0204] Preferably, the first element is polymeric and even the second element is polymeric, occupying all or part of the surface of the first device.

[0205] Preferably, the thermoplastic laminated interlayer surrounds the edges of the optical system (the first and second devices).

[0206] The edge surface of the optical system can be retracted relative to the outermost edge surface of the laminated interlayer (or the first sheet).

[0207] Preferably, the sheets of the optional carrier layer (substrate, support, first and second elements) preferably have a thickness of at most 0.7 mm and even at most 0.3 or 0.2 mm. For glass sheets, thin glass (less than 1 mm) or even ultra - thin glass (UTG) can be selected.

[0208] One of the additional glass sheets can be colored, and the other can be translucent or super - translucent. The thermoplastic laminated interlayer can be colorless (translucent, super - translucent) or colored.

[0209] For the substrate and / or support or for additional glass sheets or laminated and / or multi-pane window glass panes, clear or extra-clear glass can be selected. Clear glass typically contains an iron oxide content of about 0.05 to 0.2% by weight, while extra-clear glass generally contains about 0.005 to 0.03% of iron oxide.

[0210] The additional glass sheets or the glass panes of laminated and / or multi-pane window glass can still be tinted, for example blue, green, grey or bronze.

[0211] The tinted glass panes of the additional tinted glass sheets or of the laminated and / or multi-pane window glass preferably have a light transmittance T less than or equal to 10%. L .

[0212] The glass is preferably of the soda-lime-silica type, but it can also be of the borosilicate or aluminoborosilicate type. The thickness of the glass is generally in the range of 0.5 mm to 19 mm, preferably 0.7 mm to 9 mm, particularly 2 mm to 8 mm and even 4 mm to 6 mm. The glass is preferably of the float glass type.

[0213] The thermoplastic laminated interlayer provides adhesion to rigid or flexible elements. The polymeric laminated interlayer can in particular be based on polyvinyl butyral (PVB), ethylene vinyl acetate (EVA), polyethylene (PE), polyvinyl chloride (PVC), thermoplastic polyurethane, polyurethane (PU), ionomer, polyolefin-based adhesives, thermoplastic silicone resins or multi-component or single-component, thermally crosslinkable (epoxy resin, PU) or UV crosslinkable (epoxy resin, acrylic resin) resins.

[0214] The PVB interlayer can be wedge-shaped, so that the cross-section decreases in a wedge shape from the top to the bottom of the laminated window glass, in order to avoid double images in the case of a head-up display (HUD), very particularly for windshields. The PVB interlayer is optionally sound-insulating and / or tinted. The acoustic PVB interlayer can comprise at least one "central" layer made of a viscoelastic plastic having sound vibration damping properties, particularly based on polyvinyl butyral (PVB) and a plasticizer, and also two outer layers made of standard PVB, the central layer being between the two outer layers.

[0215] The first and / or second glass panes of the laminated window glass can (depending on the aesthetic effect or the desired optical effect) be clear glass (for a thickness of 4 mm, the light transmittance T L higher than or equal to 90%), for example standard soda-lime composition glass, such as that from Saint-Gobain Glass or extra-clear glass (T for a thickness of 4 mm LHigher than or equal to 91.5%), e.g. sodium calcium silicate glass - having less than 0.05% Fe III or Fe 2 O 3 , e.g. glass from Saint - Gobain Glass, or from Pilkington or from Schott or glass of another composition described in document WO04 / 025334. Glass from Saint - Gobain Glass company can also be selected glass.

[0216] The glass of the first and / or second glass plate can be neutral (uncolored) or (slightly) colored, especially gray or green, e.g. TSA glass from Saint - Gobain Glass. The glass of the first and / or second glass plate can have been subjected to chemical or heat treatment or quenching of the hardening or annealing type (especially to obtain better mechanical strength) or semi - quenching.

[0217] The light transmittance T L can be measured using light source D65 according to standard ISO 9050:2003, and it is the total transmittance (especially integrated in the visible light region and weighted by the sensitivity curve of the human eye), taking into account direct transmission and possible diffuse transmission, e.g. measured using a spectrophotometer equipped with an integrating sphere, and subsequently converting the measured value at a given thickness to a reference thickness of 4 mm appropriately according to standard ISO 9050:2003.

[0218] The optical system according to the invention can be integrated into window glass, especially single - pane or laminated (flat and / or curved) window glass, and the optical system forms a strip, especially a peripheral strip, on a part of the main face of the window glass.

[0219] The optical system according to the invention as defined above can be used in vehicles or buildings.

[0220] It can be used especially as:

[0221] - Interior partition walls (between two rooms or within a space) of buildings, roads, railways, sea or air vehicles (between two carriages, in taxis, buses, trains, etc.), especially as glass shower walls or bathtubs,

[0222] - Glass doors (entrance doors or service doors), windows (single - pane, double - pane, triple - pane window glass), ceilings, tiles (floor or ceiling), toilet doors, glass parts of household or street furniture

[0223] ​- Window glass for motor vehicles (cars, trucks, buses, passenger cars, etc.), thus for road, rail vehicles, sea transport (ships), windshields, side windows, roofs, etc.

[0224] - Projection or rear projection screens

[0225] - Shop front walls, display windows, in particular display windows of exhibition stands.

[0226] Naturally, it can form all or part of the window glass (ventilation partitions and windows, etc.).

[0227] Thus, architectural window glass can carry the optical system as described above, in particular single, double or triple glazing (with or without laminated glazing) partitions, windows, etc.

[0228] Thus, vehicle window glass, especially for road vehicles, can carry the optical system as described above, in particular windshields (forming an optical system with one or more peripheral bands), skylights, (single or laminated) side windows, in particular rear quarter panels.

[0229] The laminated window glass according to the invention, in particular for private cars (windshields, etc.) or trucks, can be bent (curved) along one or more directions, in particular for the first sheet, the second sheet and with a radius of curvature of 10 cm to 40 cm. It can be flat (for buses, trains, tractors).

[0230] The optical system according to the invention can be integrated within the laminated, in particular curved, window glass, between the first and second glass plates (respectively called the outer and inner glass plates), and form a peripheral strip at the upper part of the window glass, the "outer" edge surface of the stack being covered from the outside by a first opaque peripheral layer (in particular enamel on the outer glass plate (preferably on face F2)), and / or the "inner" edge surface of the stack being covered from the inside by a second opaque peripheral layer (in particular enamel on the inner glass plate (for example on face F4, even F3)).

[0231] The curved laminated window glass according to the invention, in particular a windshield or a side window, can have a T L - In the light of the pane glass - preferably at least 70% and even at least 75% or even at least 80%.

[0232] The curved laminated window glass according to the invention, in particular a glass skylight, can have a light transmittance T of at most 10% and even 1 - 6% L .

[0233] For a motor vehicle roof, preferably at least one or all of the following criteria:

[0234] - Energy transfer rate T Eis at most 10%, even 4 - 6%,

[0235] - an energy reflectance R of at most 10%, more particularly 4 - 5%, E (preferably on the side of face F1),

[0236] - a total transmittance of solar energy TTS < 30% and even < 26%, even being 20% - 23%.

[0237] The bending of the first and second glass plates (in particular the windshield) can be in one or more directions, for example as described in document WO2010136702.

[0238] To limit heating in the passenger compartment or limit the use of air conditioning, at least one glass plate (preferably the outer glass) is colored, and the laminated window glass can also include a layer that reflects or absorbs solar radiation, preferably on face F4 or face F2 or F3, in particular a transparent conductive oxide layer, called a "TCO layer", (on face F4) or even a thin - layer stack including at least one TCO layer, or a thin - layer stack including at least one silver layer (on face F2 or F3), with the silver layer or each silver layer being located between dielectric layers.

[0239] The optical system according to the invention can be used in combination with other electro - controllable devices, such as those having an electroluminescent system (inorganic point - source LED sets, organic diodes or OLEDs, TFELs (with thin layers)). The two can be facing or adjacent within the laminated window glass (laminated intermediate layer).

[0240] The optical system according to the invention can be used in particular in a laminated window glass, in combination with another electro - controllable device, such as an electroluminescent electro - controllable device, in particular an LED, an OLED, a TFEL.

[0241] Other details and features of the invention will become apparent from the following detailed description taken in conjunction with the following drawings, and in which:

[0242] Figure 1 A schematic cross - sectional view of an optical system 1001 in a first embodiment of the invention is shown, the optical system being composed of a first electro - controllable device 10 and a second electro - controllable device 100. The first electro - controllable device 10 has variable scattering and color through liquid crystals and dichroic dyes, and the second electro - controllable device 100 has variable polarization through liquid crystals and dichroic dyes 100.

[0243] Figure 2Shows a schematic cross-sectional view of the optical system 1002 in the second embodiment of the present invention. The optical system is composed of a first electro-controllable device 10 and a second electro-controllable device 101. The first electro-controllable device 10 has variable scattering and color through liquid crystal and dichroic dyes, and the second electro-controllable device 101 has variable polarization through liquid crystal and dichroic dye 100.

[0244] Figure 3 Shows a schematic cross-sectional view of the optical system 1003 in the third embodiment of the present invention. The optical system is composed of a first electro-controllable device 10 and a second electro-controllable device 102. The first electro-controllable device 100 has variable scattering and color through liquid crystal and dichroic dyes, and the second electro-controllable device 102 has variable polarization through liquid crystal and dichroic dyes.

[0245] Figure 4 Shows a schematic cross-sectional view of the optical system 1000 in the fourth embodiment of the present invention. The optical system 1000 is composed of a first electro-controllable device 10 and a second electro-controllable device 100. The first electro-controllable device 10 has variable scattering and color through liquid crystal and dichroic dyes, and the second electro-controllable device 100 has variable polarization through liquid crystal and dichroic dye 100.

[0246] Figure 5 Is the front view of the strip electrodes placed pairwise in the second device of Figure 4

[0247] Figure 6 Is the schematic partial perspective view of the second device of Figure 4 in the first functional state of the closed state.

[0248] Figure 7 Is the schematic partial perspective view of the second device of Figure 4 in the second state, which is the on state at a given voltage U2.

[0249] Figure 8 Shows a schematic detailed cross-sectional view of the electro-active layer between the two planar-plane electrodes of the first device 10 in electricity (without an electric field), which schematically illustrates the orientation of some liquid crystals and some dichroic dyes in the absence of an electric field E1.

[0250] Figure 9 Shows a schematic detailed cross-sectional view of the electro-active layer between the two planar-plane electrodes of the first device 10 in an electric field E1, which schematically illustrates the orientation of some liquid crystals and some dichroic dyes in the electric field E1.

[0251] Figure 10 、 11Figures 11 and 12 show, in the absence of the first electric field E1, Figure 4 a front view, at 20x magnification (with a 50 μm white line segment scale bar), of an image (black and white) obtained by polarized light optical microscopy (MOP) of the first electroactive layer of the first electrocontrollable device 10 of

[0252] Figure 13 Figure 13 shows a set of curves corresponding to Figure 4 the total transmittance TT as a function of the wavelength in the range 380 - 630 nm in a variant of the optical system of

[0253] Figure 14 Figure 14 shows a set of curves corresponding to Figure 4 the diffuse transmittance TD as a function of the wavelength in the range 380 - 630 nm in a variant of the optical system of

[0254] Figure 15 Figure 15 shows a set of three curves corresponding to Figure 4 the haze H (%) as a function of the first voltage U1 in the range 0 to 40 V in the optical system of

[0255] Figure 16 Figure 16 shows a set of curves corresponding to Figure 4 the ratio of the diffuse transmittance TD to the total transmittance TT as a function of the wavelength in the range 380 - 630 nm in the optical system of

[0256] Figure 17 Figure 17 shows a set of curves corresponding to Figure 4 the integrated light transmission TL as a function of the first voltage U1 in the range 0 - 40 V in the optical system of

[0257] Figure 18 Figure 18 shows a set of curves corresponding to Figure 4 the total transmittance TT as a function of the wavelength in the range 380 - 630 nm in the optical system of

[0258] Figure 19 Figure 19 shows a set of three curves corresponding to Figure 4 the diffuse transmittance TD as a function of the wavelength in the range 380 - 630 nm in the optical system of

[0259] Figure 20Shows a schematic cross-sectional view of an optical system 1000' in a variant of the fourth embodiment of the present invention, the optical system 1000' being composed of a first electro-controllable device 10 and a second electro-controllable device 100', the first electro-controllable device 10 having variable scattering and color through liquid crystal and dichroic dye and the second electro-controllable device 100' having variable polarization through liquid crystal and dichroic dye.

[0260] Figure 21 Shows a schematic cross-sectional view of an optical system 1000a in the fifth embodiment of the present invention, the optical system being composed of a first electro-controllable device 10a having variable scattering and color through liquid crystal and dichroic dye and a second electro-controllable device 100a having variable polarization through liquid crystal and dichroic dye.

[0261] Figure 22 Shows a schematic cross-sectional view of a window glass 2000 carrying an optical system 1000 according to the present invention.

[0262] Figure 23 Shows a schematic cross-sectional view of a laminated window glass 3000 carrying an optical system 1000 according to the present invention.

[0263] Figure 24 and 25 Respectively show a front view and a schematic cross-sectional view of a laminated window glass 4000 carrying an optical system 1000 according to the present invention.

[0264] The elements shown in the figures are not drawn to scale.

[0265] Figure 1 Shows a schematic cross-sectional view of an optical system 1001 in the first embodiment of the present invention, the optical system 1001 being composed of a first electro-controllable device 10 having variable scattering and color through a first liquid crystal and a first dichroic dye and a second electro-controllable device 101 having variable polarization through a second liquid crystal and a second dichroic dye.

[0266] Here, the first electro-controllable device 10 is characterized by a first surface anchoring direction b (in the off state) of the first liquid crystal.

[0267] Defines an orthogonal reference system X, Y, and Z. b is along the X-axis.

[0268] The second electro-controllable device 101 is characterized here by: a first anchoring direction r1 on the surface of the second liquid crystal (in the off state) on the output side facing the first device 10, and even a second anchoring direction r2 on the surface of the second liquid crystal on the opposite side (thus on the input side of the first device).

[0269] The second device 101 has first and second functional states and:

[0270] - In the first functional state, which is in the closed state here, using unpolarized incident light on the side opposite to the first device (schematically represented by normal components Pa and Pb of the same intensity, where k is the propagation vector of the light along Z), the second device 101 can transmit polarized output light on the side of the first device 10, where the first component of the polarized electric field P1 is along the axis X and the second component of the polarized electric field P2 is along the Y-axis normal to Y, where the first polarization ratio is defined as

[0271] [Equation 3]

[0272]

[0273] rp1 is preferably at least 70% or 90%, even at least 95%, T1 is the total transmittance along X at wavelengths from 380 - 800 nm, T2 is the total transmittance along Y at wavelengths from 380 - 800 nm, and for the first voltage U2a between the third and fourth given electrodes, it is preferably zero.

[0274] (Therefore, P1 has a super advantage over P2)

[0275] - And in the second functional state, which is the on state here, at voltage U2 (between two strip electrodes, preferably in a coplanar, pairwise manner):

[0276] i) Using unpolarized incident light on the side opposite to the first device, the second device 101 can transmit polarized output light on the side of the first device, and the second polarization ratio is defined as

[0277] [Equation 4]

[0278]

[0279] rp2 is at least 30%, even at least 50% or 60%, T′1 is the total transmittance along the first axis at wavelengths from 380 - 800 nm, and T′2 is the total transmittance along the second axis at wavelengths from 380 - 800 nm, for the non-zero second voltage U2b between the third and fourth electrodes, where U2b is different from U2a. P2 is preferably dominant over P1.

[0280] The polarization of the output light of the second device can be elliptical.

[0281] Naturally, the second device then has multiple functional states in the on state. In particular, there is a threshold voltage. For a part of the liquid crystal, the anchoring force of the second liquid crystal is overcome starting from this threshold voltage, and the more the voltage increases, the more the liquid crystal reorients until the saturation voltage, which is preferably at most 80 volts.

[0282] At this time, it is possible to have a polarization ratio r(U2) = T2 / (T1 + T2), which varies according to the applied voltage U2.

[0283] The first electrocontrollable device 10 includes a first electroactive layer having an optical response depending on the polarization state of the incident light on the first device, and the optical response varies according to whether b is perpendicular or parallel to P1.

[0284] Figure 2 A schematic cross-sectional view of an optical system 1002 in the second embodiment of the present invention is shown. The optical system consists of a first electrocontrollable device 10 having variable scattering and color through a first liquid crystal and a first dichroic dye, and a second electrocontrollable device 101 having variable polarization through a second liquid crystal and a second dichroic dye.

[0285] The system 1002 differs from the previous system in that the second device 102 (e.g., rotated 90°) has a direction r1 parallel to b, in other words, P1 is perpendicular to b.

[0286] Figure 3 A schematic cross-sectional view of an optical system 1003 in the third embodiment of the present invention is shown. The optical system 1003 consists of a first electrocontrollable device 10 having variable scattering and color through a first liquid crystal and a first dichroic dye, and a second electrocontrollable device 103 having variable polarization through a second liquid crystal and a second dichroic dye 103.

[0287] The system 1003 differs from the first system 1001103 in that, in the second on state, using unpolarized incident light on the opposite side of the first device, the second device can provide unpolarized output light on the side of the first device.

[0288] The following examples provide more details regarding the possible structures of the first and second devices and even their assembly.

[0289] Figure 4 A schematic cross-sectional view of an optical system 1000 in the fourth embodiment of the present invention is shown. The optical system 1000 consists of a first electrocontrollable device 10 having variable scattering and color through a first liquid crystal and a first dichroic dye, and a second electrocontrollable device 100 having variable polarization through a liquid crystal and a dichroic dye 100.

[0290] The first device

[0291] The first device 10 includes a stack of layers (physical layers, solid layers) in the following order:

[0292] - A transparent dielectric substrate 1′a having edge faces and main faces 11′a and 12′a, here 1.1 mm thick glass - or as a variant, plastic, such as PET

[0293] - A first transparent electrode 2′a, having a first main surface called a connection surface SA1 and a surface and edge surface called an opposite surface SB, the transparent electrode being an indium tin oxide ITO layer with a sheet resistance of 100 Ω / square, more broadly between 5 - 300 Ω / square, and for color neutrality, the electrode or each electrode may further include at least two dielectric thin bottom layers under the ITO layer, and even one or two (dielectric) cover layers

[0294] - A first transparent normal plane anchoring layer 4′a (on the first electrode 2′a)

[0295] - A first colored dielectric electroactive layer 3a in contact with the first anchoring layer 4′a, having a main surface called a face FA1 on the side of the connection surface SB and a main surface called an opposite face FA2, here with a thickness of Ep0 (less than 20 μm) made of a first material, the first material comprising:

[0296] - A first liquid crystal

[0297] - A polymer forming a polymer network, and the liquid crystal is stabilized by the polymer network

[0298] - One or more first dichroic dyes (in dissolved state)

[0299] - The first material has a mesophase called P starting from a temperature called T1, in which the material contains a set of domains, here submillimeter domains, which contain two-dimensional topological defects such as line defects, and is a mesophase P′ at T1

[0300] - Spacers are distributed in the material, here glass beads

[0301] - The layer 3a is sealed at the periphery by a polymer seal 5a, the seal being made of, for example, epoxy acrylate, here made of cyanoacrylate

[0302] - A second transparent anchoring layer 4a, here unidirectionally anchoring in a direction b parallel to X

[0303] - A second transparent electrode 2a, having a main surface called a second connection surface SA2 on the side of the face A2 and a surface called an opposite surface SB2, in particular the second electrode 2a is an ITO layer with a sheet resistance of 100 ohms / square, more broadly between 5 - 300 ohms / square, and for color neutrality, the electrode or each electrode may further include at least two dielectric thin bottom layers under the ITO layer, and even include one or two cover layers

[0304] - The transparent dielectric support 1a of the second electrode 2a, having an edge face and main faces 11a and 12a, is here 1.1 mm glass - or as a variant plastic, for example PET.

[0305] For power supply via a power source, conductive bars (not shown), especially metal conductive bars, for example made of copper, are fixed, for example along the peripheral edge and on the peripheral edge, by an adhesive and are in contact with the electrodes 2′a, 2a (one conductive bar for each electrode, the conductive bars preferably on opposite edges). These conductive bars are then connected to the power source. The edge faces of the electrodes 2′a, 2a and the edge faces of the electroactive layer are preferably recessed with respect to the edge faces of the rectangular (glass) or any other shaped substrate and support 1a, 1′a. The thickness of the (glass) substrate and support 1a, 1′a can be, for example, from 0.7 mm to 4 mm. They can have a thickness preferably greater than 100 μm and at most 300 μm to increase the mechanical strength of the assembly and / or ease of use and handling, but can be reduced down to, for example, 50 μm if greater flexibility is desired.

[0306] The preparation method is described in more detail below.

[0307] 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 10 nM OTS solution in n - heptane for 30 minutes, rinsing with deionized water and drying under nitrogen. The first anchoring layer 4′a causes normal (vertical) anchoring of the liquid crystal in contact with this first anchoring layer 4′a on the surface (in the absence of an electric field).

[0308] Under the said electric field E1, the first device 10 can have a diffused transmittance, haze and color that vary with voltage.

[0309] The second anchoring layer 4a is deposited on the second ITO layer 2a by spin - coating a solution of approximately 1 μm of polyvinyl alcohol (PVA; Sigma - Aldrich; molecular weight 27 kDa) in deionized water (9.1 wt% PVA). Before deposition, the ITO is preferably cleaned (with a surfactant), rinsed in deionized water and dried under nitrogen.

[0310] Then the second anchoring layer 4a is brushed along the first direction b to cause unidirectional planar anchoring of the first liquid crystal in contact with this layer 4a along the first direction b at the surface (in the absence of an electric field).

[0311] The first electroactive layer 3a consists of a mixture that contains a blue dichroic dye called M412 sold by Mitsui Chemicals, having a maximum absorption wavelength of 630 n ± 10 nm.

[0312] The first electroactive layer 3a is polymerized using a monomer, here a mesogen, to form a stable polymer network, such as 1,4-bis[4-(3-acryloyloxyhexyloxy)benzoyloxy]-2-methylbenzene ST03021 of the formula C 33 H 32 O 10 , sold by Synthon Chemicals.

[0313] A liquid crystal mixture consisting of 4-octyl-4-cyanobiphenyl (8CB produced by Tokyo Chemicals) and 4-cyano-4'-pentylbiphenyl (5CB sold by Tokyo Chemicals) (which does not have a smectic phase) is used.

[0314] More precisely, in order to obtain the colored electroactive layer 3a, a mixture is formed from these two types of liquid crystals 5CB and 8CB, a monomer, a dichroic dye, and a photoinitiator 2,2-dimethoxy-2-phenylacetophenone (referred to as DPMA).

[0315] This mixture contains:

[0316] - 95.4 wt% of the liquid crystals 5CB and 8CB, in a ratio of 1 g of 5CB to 4 g of 8CB

[0317] - 2 wt% of the monomer ST03021,

[0318] - 2 wt% of the dichroic dye M412,

[0319] - 0.6 wt% of the photoinitiator DPMA,

[0320] The initial mixture before polymerization above has a smectic A mesophase P' at a temperature of about 12 ± 2 °C, and a nematic mesophase P (and an isotropic phase above about 43 ± 2 °C) between about 12 ± 2 °C and about 43 ± 2 °C.

[0321] The final mixture (after polymerization) has a smectic A mesophase P' at a modified temperature T1 of about 16 ± 2 °C, and a nematic mesophase P between 16 ± 2 °C and 41 ± 2 °C (and an isotropic phase above about 41 ± 2 °C).

[0322] A layer of this colored mixture is formed in a thickness of about 10 μm between the anchoring layers 4a and 4'a.

[0323] Next, the assembly is irradiated with UV (λ = 365 nm) at 3 °C (or at least below 12 °C) for polymerization, thus being in the smectic A phase.

[0324] The colored electroactive layer 3a then contains, in the nematic phase, domains similar to the focal conic domains of the smectic A phase, and in particular here non-TFCD domains. These defect domains each contain two defect lines (double line defects), pairs of focal conic domains, a first ellipse and a second hyperbola with different eccentricities. The given name is EHFCD (English).

[0325] Second device

[0326] The second device 100 includes a stack of layers (solid) in the following order:

[0327] - A first transparent dielectric element 1' with main faces 11' and 12', here glass 1.1 mm thick - or in a variant plastic such as PET

[0328] - Third and fourth transparent electrodes in the form of independent strips, including a first strip 21 and a second strip 22 between insulating strips 23, - ITO strips with a sheet resistance of 100 ohms per square, more generally between 5 - 300 ohms per square

[0329] - A third unidirectional planar anchoring layer 4' along the direction r1 perpendicular to b and X, on the first transparent dielectric element 1' (face 11') and on the ITO strips 21, 22

[0330] - A second dielectric electroactive layer 3 in contact with this third anchoring layer 4', having a main face called face FA3 on the side of the first device and a main face called the opposite face FA4, here having a thickness (less than 20 μm), made of a second material containing:

[0331] - A second liquid crystal

[0332] - One or more second dichroic dyes (in dissolved state)

[0333] - Spacers distributed in the material, here glass beads

[0334] - The layer 3 is sealed at the periphery by a polymer seal 5, the seal being made for example of epoxy acrylate and here made of cyanoacrylate

[0335] - A fourth transparent anchoring layer 4, here unidirectionally anchored along the direction r2 perpendicular to r1 and parallel to X

[0336] - A second transparent dielectric element 1 (layer 4) with main faces 11 and 12, here glass 1.1 mm thick - or in a variant, plastic such as PET

[0337] For power supply via a power source, conductive strips (not shown), in particular metallic conductive strips, such as made of copper, are fixed along and on the peripheral edge, for example by means of an adhesive, and are in contact with electrodes 21, 22 (one conductive strip per electrode, the conductive strips preferably being on opposite edges). These conductive strips are then connected to the power source. The edge faces of electrodes 21, 22 and the edge of the second electroactive layer are preferably recessed with respect to the edge of the (glass) element 1, 1′ of rectangular or any other shape. The thickness of the (glass) element 1, 1′ can be, for example, from 0.7 mm to 4 mm. They can have a thickness preferably greater than 100 μm and at most 300 μm in order to obtain better mechanical strength of the assembly and / or ease of use and handling, but can be reduced, for example, down to 50 μm if greater flexibility is desired.

[0338] The preparation method is described in more detail below.

[0339] Thus, the third anchoring layer 4′ is a layer that induces a unidirectional planar anchoring of the second liquid crystal (without an electric field) along the direction r1 on the surface in contact with layer 4.

[0340] The third anchoring layer 4′ is deposited by “spin-coating” a solution of polyvinyl alcohol (PVA; Sigma-Aldrich; molecular weight 27 kDa) about 500 nm thick on the ITO strips 21 and 22 and between the strips called insulating strips 23 on the first element 1′.

[0341] The third anchoring layer 4′ is then wiped in the direction r1 parallel to the strips 21, 22 (extending / / perpendicular to r1 in the direction r0).

[0342] Thus, the fourth anchoring layer 4″ is a layer that induces a unidirectional planar anchoring of the second liquid crystal (without an electric field) along the direction r2 on the surface in contact with this layer 4.

[0343] The fourth anchoring layer 4 is deposited by “spin-coating” a solution of polyvinyl alcohol (PVA; Sigma-Aldrich; Mw ∼27 kDa) on the first element 1′, being about 300 nm thick. The fourth anchoring layer 4″ is then wiped along the direction r2 perpendicular to r1.

[0344] The second liquid crystal electroactive layer 3 consists of nematic liquid crystal E7 (98 wt%) and a black dichroic dye called S428 sold by Mitsui Chemicals (2 wt%). The thickness of the second electroactive layer is 10 μm.

[0345] Figure 5 is in Figure 4 a front view of the strip electrodes 21, 22 used in pairs in the second device.

[0346] For example, the insulating strip 23 forms a serpentine arrangement, and the first zone of the conductive layer is isolated from the second zone of this layer by the first part 23a of the first insulating strip of the serpentine strip and by the last part 23b of the last insulating strip of the serpentine strip.

[0347] The conductive strips 21 and 22 are parallel to r0 and r1.

[0348] This arrangement of the insulating strips can be considered to be achieved by hollowing out (retrait) a solid conductive layer, in particular by means of a femtosecond laser beam (for example having a diameter of 30 μm) and the strips being 15 μm. The thickness limit of the strips is provided by the laser beam size. The limit of the distance between the strips is determined by the movement of the laser beam.

[0349] The first and second liquid crystals have a positive dielectric anisotropy here.

[0350] As explained with regard to the principle Figure 1 The second device 100 which receives polarized light as input transmits light which is mainly polarized in P1 perpendicular to r1 (parallel to b) in a first off state or light which is mainly polarized in P2 (perpendicular to b) perpendicular to P1 in a second on state.

[0351] Figure 6 is in a first state which is the off state Figure 4 Schematic partial perspective view of the principle of the second device.

[0352] On the surface of the fourth anchoring layer 4, the second liquid crystal 312 (defined by the director n2) and the dichroic dye 322 are (generally) parallel to r2.

[0353] On the surface of the third counter-anchoring layer 4, the second liquid crystal 310 (defined by the director n1) and the dichroic dye 320 are (generally) parallel to r1.

[0354] This counter-action forces the second nematic liquid crystal to undergo a distorted deformation, and the second dichroic dye is controlled by the nematic.

[0355] In the thickness of the second electroactive layer 3, the second liquid crystal 311 (defined by the director n3) and the second dichroic dye 321 form an angle with r1 and r2 (generally).

[0356] Figure 7 is in a second state which is the on state at a given voltage U2 Figure 4 Schematic partial perspective view of the principle of the second device.

[0357] On the surface of the fourth anchoring layer 4, the second liquid crystal 312 (defined by the director n2) and the dichroic dye 322 remain (generally) parallel to r2.

[0358] In the thickness of the second electroactive layer 3, the second liquid crystal 311 (defined by the director n3) and the second dichroic dye 321 generally tend to align along r2.

[0359] At the output, the polarization P1 perpendicular to r1 is attenuated and can be quasi - turned off.

[0360] Figure 8 A schematic detailed cross - sectional view of the electroactive layer 3 between the two planar - planar electrodes of the first device (without an electric field) is shown, schematically illustrating the orientation of some first liquid crystals 34, 34' and some first dichroic dyes 35, 35' in the absence of the electric field E1.

[0361] Figure 8 A layered structure 36 of a liquid crystal with a dichroic dye is shown, a structure fixed by a polymer network not shown.

[0362] The liquid crystal layers are curved towards the planar anchoring layer (degraded here) in the central region 34, and these layers are planar and parallel to each other in two more or less unfolded lateral regions (which may be absent).

[0363] In the first electroactive layer 3a, there are defect domains, each defect domain containing two defect lines (two line defects), which are focal conic domains and occur in pairs, especially an elliptical one (in the plane X, Y) and another hyperbolic one (thick line 36), thus named "elliptical - hyperbolic focal conic domain" or in English "EHFCD".

[0364] The first series of first liquid crystals (rods) 34 are perpendicular to the anchoring layers 4a, 4'a, and thus along Z. This also applies to some first dichroic dyes 35 present in this region.

[0365] The second series of first liquid crystals 34' form an angle with respect to the anchoring layer 4a. This also applies to some other dichroic dyes 35'.

[0366] Figure 9 A schematic detailed cross - sectional view of the electroactive layer between the two planar - planar electrodes of the first device under the first electric field E1 is shown, schematically illustrating the orientation of some first liquid crystals 34, 34' and some first dichroic dyes 35, 35' under the said first electric field E1.

[0367] Under the electric field, the second series of first liquid crystals 34' tend to also be perpendicular to the anchoring layers 4a, 4'a, and thus along Z. This also applies to some other dichroic dyes 35'.

[0368] Figure 10 、 11 and 12 shows in the absence of the said electric field E1 Figure 4Front view of the image (black and white) of the first electroactive layer of the first electrocontrollable device 10 of (Example 1) obtained by polarized light optical microscopy (MOP) under a polarizer, magnification 20x (scale bar using 50 μm white line).

[0369] Figure 10 is polarized light incident on the first device, and the first device has a linear polarization Pi along a direction parallel to b.

[0370] Figure 11 is polarized light incident on the first device, and the first device has a linear polarization Pi along a direction perpendicular to b.

[0371] Figure 12 is polarized light incident on the first device, and the first device has a linear polarization Pi along a direction perpendicular to b, and by adding an analyzer perpendicular to this polarization Pi.

[0372] It is observed that the EHFCD focal conic domains form a linear network parallel to the direction b.

[0373] Figure 13 Shows a set of curves corresponding to the total transmittance TT as a function of the wavelength between 380 - 630 nm in a variant of the optical system of Figure 4 since P1 is perpendicular to b (the second device is rotated 90°)

[0374] Curve 1 is the off + off mode (the first voltage U1 is 0 V, the second voltage U2 is 0 V).

[0375] Curve 2 is the on + off mode (the first voltage U1 is 40 V, the second voltage U2 is 0 V).

[0376] Curve 3 is the off + on mode (the first voltage U1 is 0 V, the second voltage U2 is 40 V).

[0377] Curve 4 is the on + on mode (the first voltage U1 is 40 V, the second voltage U2 is 40 V).

[0378] Figure 14 Shows a set of curves corresponding to the diffuse transmittance TD as a function of the wavelength between 380 and 630 nm in a variant of the optical system of Figure 4 since P1 is perpendicular to b (the second device is rotated 90°).

[0379] Curve 1 is the off + off mode of the optical system (the first voltage U1 is 0 V, the second voltage U2 is 0 V).

[0380] Curve 2 is the on + off mode of the optical system (the first voltage U1 is 40 V, the second voltage U2 is 0 V).

[0381] Curve 3 is the off + on mode of the optical system (the first voltage U1 is 0 V and the second voltage U2 is 40 V).

[0382] Curve 4 is the on + on mode of the optical system (the first voltage U1 is 40 V and the second voltage U2 is 40 V).

[0383] Figure 15 Shows a set of three curves corresponding to Figure 4 the haze H (%) of the optical system (U2 equal to 0 V) as a function of the first voltage U1 from 0 to 40 V.

[0384] The haze H is the ratio of the integrated light transmittance to the diffuse transmittance TD.

[0385] Curve 1 is the haze measured when P1 is / / b.

[0386] Curve 2 is the haze measured when the incident light is not polarized.

[0387] Curve 3 is the haze measured when P1 is perpendicular to b.

[0388] Figure 16 Shows a set of three curves corresponding to Figure 4 the ratio of the diffuse transmittance TD to the total transmittance TT of the optical system as a function of the wavelength between 380 and 630 nm (in the off + off mode of the optical system).

[0389] Figure 17 Shows a set of curves corresponding to Figure 4 the integrated light transmittance TL of the optical system as a function of the first voltage U1 from 0 to 40 V (where U2 is equal to 0 V).

[0390] Curve 1 is the TL measured when P1 / / b.

[0391] Curve 2 is the TL measured when the incident light is not polarized.

[0392] Curve 3 is the TL measured when P1 is perpendicular to b.

[0393] Figure 18 Shows a set of curves corresponding to Figure 4 the total transmittance TT of the optical system as a function of the wavelength between 380 - 630 nm, where P1 is parallel to b.

[0394] Curve 1 is the off + off mode (the first voltage U1 is 0 V and the second voltage U2 is 0 V).

[0395] Curve 2 is in the turn-on + turn-off mode (the first voltage U1 is 40 V and the second voltage U2 is 0 V).

[0396] Curve 3 is in the turn-off + turn-on mode (the first voltage U1 is 0 V and the second voltage U2 is 40 V).

[0397] Curve 4 is in the turn-on + turn-on mode (the first voltage U1 is 40 V and the second voltage U2 is 40 V).

[0398] The total transmittance change from one curve to another is very small.

[0399] Figure 19 A set of three curves is shown, corresponding to Figure 4 the diffuse transmittance TD of the optical system as a function of the wavelength between 380 and 630 nm, where P1 is parallel to b

[0400] Curve 1 is in the turn-off + turn-off mode (the first voltage U1 is 0 V and the second voltage U2 is 0 V).

[0401] Curve 2 is in the turn-on + turn-off mode (the first voltage U1 is 40 V and the second voltage U2 is 0 V).

[0402] Curve 3 is in the turn-off + turn-on mode (the first voltage U1 is 0 V and the second voltage U2 is 40 V).

[0403] Regarding Example 1 described (r1 is perpendicular to b), for measuring the color change, the measured luminance L* and parameters a* and b* are calculated from the total transmittance, and the integral TL is calculated from the total transmittance (TL1) or the diffuse transmittance (TL2), and the haze H is TL2 / TL1. A Perkin Elmer Lambda 950 spectrometer is used. Figure 4 The measured and calculated values are listed in Table 1.

[0404] The measured and calculated values are listed in Table 1.

[0405] [Table 1]

[0406] 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

[0407] The colorimetric deviation ΔE (between the 0 V / 0 V and 0 V / 40 V cases) is 11.9.

[0408] Regarding a variant (r1 is parallel to b), for measuring the color change, the luminance L* and parameters a* and b* are calculated from the total transmittance, and the integral TL is calculated from the total transmittance (TL1) or the diffuse transmittance (TL2), and the haze H is the ratio of TL2 / TL1. A Perkin Elmer Lambda 950 spectrometer is used.

[0409] The measured and calculated values are listed in Table 2.

[0410] [Table 2]

[0411] 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

[0412] The colorimetric deviation ΔE (between the cases of 0 V / 0 V and 0 V / 40 V) is 3.6.

[0413] For polarization P1 (perpendicular to r1), the first polarization ratio has been defined as follows:

[0414]

[0415] For polarization P2 (parallel to r1 and perpendicular to P1), the second polarization ratio has been defined as follows:

[0416]

[0417] T1 is the average total transmittance between 380 and 640 nm along the P1 axis, and T2 is the average total transmittance between 380 and 640 nm along the P2 axis. A Perkin Elmer Lambda 950 spectrometer is used.

[0418] The variations of the ratios r1 and r2 as a function of the applied voltage U2 are shown in Table 3.

[0419] [Table 3]

[0420] U2 (V) <![CDATA[r 1 (%)]]> <![CDATA[r 2 (%)]]> 0 99 1 20 49 51 40 32 68 60 26 74 80 22 78

[0421] At zero voltage, the polarization is basically along P1.

[0422] As the voltage increases, the component P2 increases.

[0423] Figure 20 A schematic cross-sectional view of the optical system 1000' in a variant of the fourth embodiment of the present invention is shown. The optical system 1000' consists of a first electrocontrollable device 10 and a second electrocontrollable device 100'. The first electrocontrollable device 10 has variable scattering and color through liquid crystal and dichroic dyes, and the second electrocontrollable device 100' has variable polarization through liquid crystal and dichroic dyes.

[0424] The optical system is Figure 4 different from the system in that the support 1'a is a common support form for the first and second devices (carrying all electrodes on its two main surfaces).

[0425] Figure 21Fig. shows a schematic cross-sectional view of the optical system 1000a in the fifth embodiment of the present invention, which is composed of a first electrically controllable device 10a with variable scattering and color through liquid crystal and dichroic dyes, and a second electrically controllable device 100a with variable polarization through liquid crystal and dichroic dyes.

[0426] The optical system 1000a is different from the system 1000 of Figure 4 in that:

[0427] - The third and fourth electrodes 2 and 2' are planar-planar (non-coplanar)

[0428] - r1 and r2 form an angle of 0°.

[0429] As a result, in the on state, the output light of the second device is not polarized.

[0430] Assembly example

[0431] Figure 22 Fig. shows a schematic cross-sectional view of the glass assembly 2000, which includes a transparent sheet 7 (any possible thickness) carrying the optical system 1000 according to the present invention.

[0432] The first device 10 is bonded to the transparent glass or plastic (e.g., rigid) sheet 7 by an optical adhesive 60 and is also bonded to the second device 100 by an optical adhesive 61.

[0433] For example, it is a partition wall (vertical position).

[0434] This assembly can form part of a multi-layer window glass (double or triple glazing). For double glazing, the system 1000 can be on one side of the faces F1 (conventionally the outer face), F2, F3; F4 (conventionally the inner face). For triple glazing, the stack can be on one side of the faces F1 (outer face), F2, F3; F4, F5, F6 (outer surface). The sheet 7 can be the same size as or larger than the system 1000.

[0435] The glass assembly 2000 can be:

[0436] - On the preferred outer face of a shower wall or the element 7 is a shower wall

[0437] - Or on the preferred inner face (face 'F4') of a curved window glass of a vehicle, especially a motor vehicle: roof, side window glass, windshield, rear window, or the element 7 is a curved window glass

[0438] In particular, the glass assembly 2000 can be used as a projection screen.

[0439] Figure 23Shows a schematic cross - section of a laminated window glass 3000 carrying an optical system 1000 according to the present invention, including a first device 10 bonded to a second device 100 by an optical adhesive 60.

[0440] The laminated window glass 3000 comprises:

[0441] - a transparent first additional glass sheet 8

[0442] - a thermoplastic laminated interlayer 70, in particular EVA or PVB,

[0443] - a transparent second additional glass or plastic sheet 8'

[0444] The main inner faces, designated F2 and F3, of the first and second additional sheets face each other, and the optical system 1000 is between the faces F2 and F3 and within a laminated interlayer of sub - millimeter or at most 2 mm thickness.

[0445] During preparation, three intermediate thin sheets can be used: two complete thin sheets 72, 73 resting on the inner surfaces of the sheets 8, 8' and an intermediate thin sheet 71 having an opening for receiving the system 1000. After lamination, the interfaces between the thin sheets (represented by dotted lines) are not necessarily distinguishable. Preferably, the opening is closed rather than completely open on one side. Thus, the entire edge face of the system 1000 is surrounded by the laminated interlayer 70. Naturally, for power supply, connections can extend from the system 1000 and even protrude beyond one or more side edges of the window glass.

[0446] Alternatively, two intermediate thin sheets can be used. If the system 1000 is thin enough, for example with a thickness of at most 0.2 mm, there is no need for a hollowed - out intermediate thin sheet.

[0447] One of the sheets 8 or 8' can be colorless or colored (grey, green, bronze, etc.), while the other 8' or 8 in the window glass can be translucent or super - translucent. One of the first intermediate thin sheets can be colored (grey, green, bronze, etc.) and the other one or more are translucent or super - translucent. One of the sheets 8 or 8' can be replaced by a plastic sheet such as polycarbonate or PMMA (especially with a PU laminated interlayer).

[0448] The edge face of the laminated interlayer 70 can be recessed (e.g., by up to 5 mm) from the edge faces of the sheets 8, 8'.

[0449] The system 1000, for example, almost covers the entire main face of the sheet 8 and is even in the middle here. The width of the PVB on both sides of the system 1000 is the same.

[0450] The sheets 8, 8' are planar or curved, and the system 1000 is capable of adapting to the curvature of the then - curved glass sheets 8, 8'.

[0451] The optical system 1000 can be a partition wall or a vehicle roof. For example, for a motor vehicle roof:

[0452] - The sheet 8 is the outermost and is curved, optionally colored, for example 3 mm thick

[0453] - The sheet 8' is the innermost, curved, preferably translucent or super-translucent, for example 3 mm thick or thinner

[0454] - The laminated intermediate layer 70 is made of PVB and can be acoustic, in particular double or triple (sheets 71 or 72 or 73).

[0455] The roof can thus also have a variable color, for example from dark blue to light blue using voltages U1 or U2.

[0456] Figure 24 And 25 respectively show a front view and a schematic cross-sectional view of a laminated window glass carrying the optical system 1000 according to the invention.

[0457] The laminated window glass 4000 differs from the previous window glass 3000 in that the optical system 1000 covers a partial surface of the sheet 8, in particular the peripheral strip, for example along the upper longitudinal edge H over almost the entire length of the laminated window glass.

[0458] It is, for example, a motor vehicle windshield.

[0459] This strip-shaped optical system 1000 is in the edge region where the TL and the standard ratio without haze are more liberal than in the central region ZB.

[0460] Therefore, this strip-shaped optical system 1000 can also be a color that can vary with voltage, for example from dark blue to light blue.

[0461] As Figure 25 (Cross-sectional view) shows that the width 7a of the central intermediate layer 73 between the optical system 1000 and the lower longitudinal edge B is greater than the width 7b of the central intermediate layer 73 between the optical system 1000 and the upper longitudinal edge H.

[0462] As a variant or alternatively, it can be present along the lower longitudinal edge B of the windshield, over the entire length or a part of the length.

[0463] As Figure 24As shown in the front view of the inner side of the vehicle, the windshield includes first opaque frames 91' to 94' on the transverse and longitudinal edges of the free surface (F4) 82' of the inner sheet 8', made of enamel (black or other), for example, and second opaque frames 91 to 94 on the transverse and longitudinal edges of the free surface (F1) 82 of the outer sheet 8, made of enamel (black or other), for example.

[0464] The edge surfaces of the optical system 1000 located on one side of the lower longitudinal edge, and even those on one side of the transverse edge, can be between (on the surfaces of) the layers 92, 92', 93, 93', 94, 94' of the enamel frames. For example, the connection and other power supply bands (for U1 and U2) can also be masked through these layers 92, 92', 93, 93', 94, 94'.

[0465] In a variant, it is the roof of a motor vehicle, for example, having an outer glass 8 that is colored and / or a PVB 71 that is colored and even an optical system 1000 that substantially covers the entire main surface of the glasses 8, 8'.

Claims

1. A liquid crystal optical system (1000, 1000', 1001, 1002, 1003, 1000a), which comprises: - An electrically controllable device (10) with variable scattering, called the first device, comprising the following layer stack: - A transparent first electrode (2'a) having a main surface called the first connection surface SA1 and a surface called the opposite outer surface SB, - A transparent second electrode (2a) having a main surface called the second connection surface SA2 and an opposite outer surface SB2, with a first electric field E1 between the first electrode and the second electrode, - A first dielectric electroactive layer (3a) having a main face called face FA1 on the side of the first connection surface SA1 and a main face called face FA2, made of a first material, the first material comprising: - A first liquid crystal, - A polymer forming a polymer network, the first liquid crystal being stabilized by the polymer network, The first material has a mesophase called P starting from a temperature called T1, wherein the first material comprises a set of domains that contain two-dimensional topological defects, characterized in that the first material contains at least one first dichroic dye, characterized in that the first dielectric electroactive layer (3a) has an optical response depending on the polarization state of the incident light on the first device, and characterized in that the optical system comprises, facing the first device, a variable polarization electrically switchable device (100, 100', 100a, 101, 102) called the second device, the second device comprising: - Third and fourth transparent electrodes (2, 2'), with a second electric field E2 between the third and fourth transparent electrodes, - A second electroactive layer (3) made of a second material, having a main face FA3 on the side of the third transparent electrode (2) and an opposite main face FA4, which contains: - A second nematic liquid crystal, - A second dichroic dye, and characterized in that the third transparent 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 has no electrostatic polarization film.

3. The liquid crystal optical system (1000, 1000', 1001, 1002, 1003, 1000a) according to any one of the preceding claims, characterized in that, the first electric field E1 is alternating and the second electric field E2 is alternating, and the first liquid crystal has a positive dielectric anisotropy.

4. The liquid crystal optical system (1000, 1000', 1001, 1002, 1003, 1000a) according to one of claims 1 to 2 of the preceding claims, characterized in that, the second device (100) has first and second functional states, and: - In a first functional state, using unpolarized incident light on the side opposite to the first device (10), the second device is capable of transmitting output light on the side of the first device, the output light having 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 perpendicular to the first axis, having a first polarization ratio defined by the following formula: [Mathematical formula 5] rp1 is at least 70%, T1 is the total transmittance at a wavelength of 380 - 800 nm along the first axis, and T2 is the total transmittance at a wavelength of 380 - 800 nm along the second axis, for a given first voltage U2a between the third and fourth transparent electrodes; - And in a second state: i) Using unpolarized incident light on the side opposite to the first device, the second device is capable of transmitting output light on the side of the first device, the output light having a second polarization ratio defined by the following formula: [Mathematical formula 6] rp2 is at least 30%, for a given second voltage U2b between the third and fourth transparent electrodes, T'1 is the total transmittance at a wavelength of 380 - 800 nm along the first axis, and T'2 is the total transmittance at a wavelength of 380 - 800 nm along the second axis, U2b being different from U2a, or j) Using unpolarized incident light on the side opposite to the first device, the second device is capable of providing unpolarized output light on the side of the first device, One of the first and second states is in the off state and the other of the first and second states is in the on state.

5. The liquid crystal optical system (1000, 1000', 1001, 1002, 1003) according to any one of the preceding claims 1 to 2, characterized in that the third and fourth transparent electrodes are coplanar, forming first and second conductive strips (21, 22) with different electric potentials in an alternating manner, the first and second conductive strips extending along a direction r0, and characterized in that the second device has first and second functional states, and in the first functional state which is the off state, the second device comprises: - A unidirectional planar anchoring layer (4') along a direction r1 in contact with the surface FA3 of the second electroactive layer (3) and on the third and fourth transparent electrodes, and - Another unidirectional planar anchoring layer (4) along a direction r2 in contact with the surface 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 and r2 form an angle of 90° ± 15°: - r0 and r1 form an angle of at most 15° and the second liquid crystal has a positive dielectric anisotropy, - Or r0 and r1 form an angle of 90° ± 15° and the second liquid crystal has a negative dielectric anisotropy.

7. The liquid crystal optical system (1000, 1000', 1001, 1002) according to any one of the preceding claims 1 to 2, characterized in that The second device has first and second functional states. The second device (100, 100', 101, 102) can transmit polarized light with polarization P1 in the first functional state which is a closed state, and can transmit polarized light with second polarization P2 in the second functional state which is an open state.

8. The liquid crystal optical system according to any one of claims 1 to 2, wherein the second device has first and second functional states. In the first functional state which is a closed state, the second device can transmit light with polarization P1. The first device includes an alignment anchoring layer (2a) along the first direction b on the surface FA1 or on the surface FA2. The second device is arranged such that P1 forms an angle of 0° ± 20° with b.

9. The liquid crystal optical system according to any one of claims 1 to 2, wherein, the second device has first and second functional states. In the first functional state which is a closed state, the second device can transmit polarized light with polarization P1. The first device includes an alignment anchoring layer (2a) along the first direction b on the surface FA1 or on the surface FA2. The second device (100) is arranged such that P1 forms an angle of 90° ± 20° with b.

10. The liquid crystal optical system according to any one of claims 1 to 2, wherein, the second electroactive layer is between the third electrode and the fourth transparent electrode, and the second device includes: - a unidirectional planar anchoring layer along the direction r1 on the main surface FA3 of the second electroactive layer and on the third transparent electrode, - and another unidirectional planar anchoring layer on the main surface FA4 of the second electroactive layer and on the fourth transparent electrode, characterized in that: - r1 forms an angle of at most 15° with r2. The second liquid crystal has negative dielectric anisotropy. In the closed state of the second device, the orientation of the second liquid crystal in the thickness of the second electroactive layer is mainly vertically aligned, - or r1 forms an angle of at most 15° with r2, and the second liquid crystal has positive dielectric anisotropy, - or r1 forms an angle of 90° ± 15° with r2, and the second liquid crystal has positive dielectric anisotropy.

11. The liquid crystal optical system (1000, 1000', 1001, 1002) according to any one of the preceding claims 1 to 2, wherein, the second device has first and second functional states. The second device can transmit light with polarization P1, - in the first functional state, the haze at the output end of the first device is at least 10% higher than the haze obtained using unpolarized incident light at the input end of the first device - and the haze at the output end of the first device is at least 10% smaller than the haze obtained using unpolarized incident light at the input end of the first device.

12. The liquid crystal optical system according to any one of the preceding claims 1 to 2, wherein the mesophase P is nematic and the domains are focal conic domains.

13. The liquid crystal optical system according to claim 4, wherein the second voltage U2b is zero.

14. The liquid crystal optical system (2000, 3000, 4000) according to any one of the preceding claims 1 to 2, characterized in that, the first and second devices are separate or bonded by a transparent adhesive layer, or characterized by a transparent common carrier that carries the second electrode on one main surface and, on the other side, the third transparent electrode on the opposite second main surface.

15. A laminated window glass (3000, 4000) comprising the liquid crystal optical system according to any one of the preceding claims 1 to 2, further comprising: - a transparent first additional glass sheet (8), - a thermoplastic laminated intermediate layer, - a transparent second additional glass sheet or plastic sheet (8'), the main inner faces, called F2 and F3, of the first and second additional sheets face each other, and the optical system according to any one of the preceding claims 1 to 2 is between the faces F2 and F3.

16. A vehicle or building window glass (2000, 3000, 4000) carrying the liquid crystal optical system according to any one of the preceding claims 1 to 13.

17. The vehicle or building window glass (2000, 3000, 4000) according to the preceding claim 16, further comprising: - a transparent first additional glass sheet (8), - a thermoplastic laminated intermediate layer, - a transparent second additional glass sheet or plastic sheet (8'), the main inner faces, called F2 and F3, of the first and second additional sheets face each other, and the optical system according to any one of the preceding claims 1 to 2 is between the faces F2 and F3.

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