Liquid crystal optical system

Abstract

The present invention provides an optical system (1000) consisting of an electrically controllable variable polarizer (100) having variable polarization through liquid crystal and dichroic dye.

Description

[0001] The present invention relates to a liquid crystal optical system including an electrically controllable device using liquid crystal.

[0002] There are liquid crystal systems in the form of first and second electro-active liquid crystal cells facing each other that allow light to pass or block light.

[0003] It is an object of the present invention to develop liquid crystal systems with alternating electro-optical properties or even to provide new functionalities.

[0004] To this end, the present invention proposes a liquid crystal optical system comprising an electrically switchable device with variable polarization (in transmission), called a variable polarizer, comprising:

[0005] a first transparent electrode, with an electric field E2 between the first and second electrodes, in particular in the form of a conductive layer on a common carrier element (coplanar arrangement), the first and second electrodes (preferably in the form of a layer) being coplanar (preferably on a common carrier element and not self-supporting), forming an alternation of first and second conductive strips (for example metal strips) having different electrical potentials, the conductive strips being in particular elongated strips (linear, preferably straight) along the direction r0,

[0006] - an electroactive layer having a submillimeter thickness and even up to 100 μm and at least 50 nm, in particular 50 nm to 50 μm and even 100 nm to 20 μm and better still at least 1 μm or 5 μm thickness, the electroactive layer - made of a thermotropic (preferably) material - comprising (or consisting of):

[0007] liquid crystals (preferably thermotropic), which are nematic, bent or non-bent, preferably twisted (under the action of an anchoring layer) and / or cholesteric in the voltage-free off state (preferably predominant by weight in the material (preferably at least 50%, 70%, 80%, 85%, 95% by weight of the liquid crystals), in particular liquid crystals containing mesogens, e.g. without polymer chains or groups incorporated into the main chain or side chains of a polymer (referred to in English as "LCP"), the liquid crystals in particular having a size of at most 50 nm, 20 nm or 10 nm (and less than Ep2), in particular mixtures of various liquid crystals (pure, in the sense of not being LCPs), and therefore of various mesogens,

[0008] a dichroic dye (particularly in solution, particularly dissolved in a liquid crystal), for example up to 30%, 20%, 10%, 5% by weight of a dichroic dye (one or more dichroic dyes), wherein the dichroic dye particularly has a size of at most 50 nm, 20 nm or 10 nm (and is smaller than Ep2); in particular, the liquid crystal and the dichroic dye have comparable sizes, for example each smaller than 20 or 10 nm,

[0009] - optional polymers (preferably non-crosslinked) or polymer precursors, preferably with at most 20%, 15%, 10%, 5% or 1% by weight of polymers (or polymers and polymer precursors), e.g. the electroactive layer is not of the (PDLC or PSLC) type,

[0010] - preferably, spacers, in particular having a height less than or equal to Ep2 (even a larger dimension), at the periphery (dielectric, transparent or opaque, optionally covered by a frame, for example made of polyester film, etc.) and / or dispersed in the electroactive layer (dielectric, transparent, in particular plastic, glass, silica, preferably sub-centimeter, in particular beads)

[0011] - Optional other additives (besides the dichroic dye), for example colored 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 molecules, preferably having a height less than or equal to Ep2 (and even having a larger dimension less than or equal to Ep2).

[0012] Preferably, the electrically switchable electroactive layer is sealed at the periphery (at the edge of the main surface) by a dielectric seal, in particular a polymer, in contact with said material (or separated by a perimeter spacer).

[0013] Designed in this way, the variable polarizer in its first functional state, the closed state, can transmit polarized light having polarization P1 (predominantly), and in its second functional state, the open state, can transmit polarized light having a second polarization P2 (preferably predominantly) different from P1.

[0014] The invention is applicable in various fields, in particular in buildings (windows, partitions, glass floors), in the outside world, in particular in urban spaces, or in road, sea, rail, air vehicles (windscreens, side windows, skylights, etc.).

[0015] When incorporated into a window pane of a building or vehicle, other devices may be indifferently facing outwards or inwards.

[0016] The variable polarizer itself does not require polarizers such as crossed polarizers and an analyzer to operate. In particular, the variable polarizer may be free of static polarizing films.

[0017] The switching time of the variable polarizer can be less than a few seconds. The switching state of the optical system is reversible and (quasi) instantaneous.

[0018] The variable polarizer requires only one liquid crystal layer (a monocell system) rather than multiple liquid crystal layers to form a variable polarizer.

[0019] The optical properties of the optical system are adjustable:

[0020] - by switching off or applying the electric field E2 (preferably alternating) and by selecting the voltage level U2

[0021] - by choosing an orientation of the output (main) polarization, called P1 , relative to a characteristic direction b of another polarization-sensitive device (as will be explained in detail later), in particular P1 being substantially parallel or substantially perpendicular to b.

[0022] Regarding the variable polarizer, the dichroic dye attached to the liquid crystal, preferably twisted in the off state, plays a key role in providing the variable polarization function. The variable polarizer with variable polarization is transparent, preferably with a haze of at most 10%, 1%, or 0.5% in the off state and the on state.

[0023] U2 can be less than 120V or even 80V.

[0024] It may be considered that U2 is applied (or even the level of U2 is selected) on command. Thus, means for controlling a variable polariser may be provided.

[0025] The optical system may have a thickness of at most 1 cm or 5 mm or 1 mm.

[0026] The variable polariser may have a thickness of at most 5 mm, or 1 mm, or 0.5 mm.

[0027] The first and second electrodes (preferably in layer form) are coplanar, resulting in in-plane switching.

[0028] The parameters that influence the optical properties are in particular:

[0029] - Selection of liquid crystals, in particular liquid crystals of mesogenic mixtures (in particular with regard to the operating temperature range and the reduction of the voltage level in the on state) and their dielectric anisotropy

[0030] - transparency level of electrodes with the lowest possible absorption (their possible substrate) and, in the case of stripe electrodes, the density of the stripes (in order to reduce the voltage by reducing the space between the stripes and in order to reduce the area without switching of the liquid crystal to increase the off / on contrast)

[0031] - Selection of dichroic dyes (their concentration, dichroic ratio, etc.), in particular in order to have the highest and most constant absorption spectrum in the visible range

[0032] -Thickness of the electroactive layer.

[0033] The optical characterization of the optical system according to the invention is performed on either side.

[0034] However, the output light on the side with the strip electrodes (along r0) is polarized more along P1 (perpendicular to r0 and preferably with a unidirectional anchor layer on the strip electrodes parallel to r0 along r1), and the output light on the side without the strip electrodes is polarized more along P2. This can be a plastic (drawn) film with a dichroic dye.

[0035] The first (respectively second) electrode may comprise (or even consist of) a conductive layer (single or multilayer, in particular a deposit), in particular a mineral conductive layer, in particular having a thickness of at most 200 nm (on a carrier element, preferably between the carrier element and the anchoring layer), in particular comprising at the edge means for supplying current (strips - busbars - in particular metallic, made of copper, silver, etc.).

[0036] Preferably, the density of the conductive strips is as high as possible (the width of the strips is as small as possible and the spaces between the strips are as small as possible).

[0037] Therefore, a potential difference is applied between two "terminals" that lie in the same plane and are electrically isolated from each other.

[0038] E2 is mostly planar (parallel to the first and second electrodes).

[0039] While maintaining conductivity, it is sought that the stripes are as narrow as possible to increase the "polarizer" power in ON mode. It is also sought to reduce the inter-strip width as much as possible (in other words, insulating strips without electrical conductors) to reduce the potential difference to be applied.

[0040] For example, the conductive strips and / or the inter-strip width (insulating strips) are at most 50 μm or 30 μm or 10 μm.

[0041] For example, the insulating strips form a serpentine arrangement and a first region of the conductive layer is separated from a second region of the layer by a first portion of a first insulating strip of the serpentine strip and a last portion of a last insulating strip of the serpentine strip.

[0042] It is conceivable to achieve such an insulating strip arrangement by removing the conductive solid layer (particularly 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 the strips is determined by the displacement of the laser beam.

[0043] Advantageously, the electric field E2 is alternating and the voltage U2 applied between the first and second electrodes is preferably at most 120 V.

[0044] E2 preferably alternates at a frequency starting from 50 Hz, for example 100 Hz, 1 kHz or 2 kHz. Voltage refers to the peak voltage (Vpeak).

[0045] The selection of U2 can be controlled, in particular it can be adjusted according to data (temperature, brightness, etc.) collected by sensors communicating with the device (control power supply).

[0046] Preferably, the variable polarizer is capable of transmitting as output (particularly on the side of the first and second electrodes) light having polarization P1 (predominant) in the closed functional state and a second polarization P2 (preferably predominant) perpendicular to P1 in the open state (the second functional state described in detail below).

[0047] More broadly, the variable polarizer may have first and second functional states such that:

[0048] - in a first functional state, which is an off state (no voltage), the variable polarizer is capable of transmitting (polarized) output light (particularly on the side of the first and second electrodes) with incident light (particularly on the side of the first and second electrodes) having a first component of the (polarization) electric field P1 along a first axis and a second component of the (polarization) electric field P2 along a second axis perpendicular to the first axis, with a first polarization ratio defined by:

[0049] [Mathematical formula 1]

[0050]

[0051] rp1 is at least 70%, better still at least 90%, even at least 95%, T1 is the total transmittance along the first axis at a wavelength of 380-800 nm, even at least the average total transmittance between 400 and 600 nm, even from 380 to 640 nm, and T2 is the total transmittance along the second axis at a wavelength of 380-800 nm, even at least the average total transmittance between 400 and 600 nm, even from 380 to 640 nm (for a first voltage of zero between the first and second electrodes);

[0052] - and in a second functional state (under voltage) being the on state:

[0053] Using unpolarized incident light (particularly on the side opposite to the first and second electrodes), the variable polarizer is capable of transmitting output light (particularly on the side of the first and second electrodes) having a second polarization ratio defined by:

[0054] [Mathematical formula 2]

[0055]

[0056] rp2 is at least 30%, even at least 50% or 60%.

[0057] T′1 is the total transmittance along the first axis at a wavelength of 380-800 nm, or even at least the average total transmittance in 400-600 nm or even from 380 to 640 nm, and T′2 is the total transmittance along the first axis at a wavelength of 380-800 nm, or even at least the average total transmittance in 400-600 nm or even from 380 to 640 nm (for a first voltage of zero between the first and second electrodes).

[0058] Naturally, the variable polarizer then has several functional states in the on state. In particular, there is a threshold voltage, starting from which the anchoring forces of the liquid crystal are overcome for a portion of the liquid crystal, and the more the voltage increases, the more the liquid crystal reorients, up to a saturation voltage, which is preferably at most 80 volts.

[0059] In this case, the polarization ratio can be changed according to the applied voltage U2.

[0060] The dielectric anisotropy of the electroactive layer is non-zero and can be negative or positive.

[0061] In one advantageous arrangement, the variable polariser comprises:

[0062] - a unidirectional planar anchoring layer along the direction r1 on the main face of the electroactive layer (in contact therewith) and on the first and second electrodes (in contact therewith), in particular P1 perpendicular to r1 and P2 parallel to r1

[0063] and a further unidirectional planar anchoring layer along direction r2 (preferably different from r1 ) on the other main face of the electroactive layer (in contact therewith).

[0064] In particular, r1 and r2 form an angle of 90°±15°, preferably 90°±5° (the nematic liquid crystal has a strong twist in the off state):

[0065] -r0 and r1 form an angle of up to 15° or even up to 5° and the liquid crystal has positive dielectric anisotropy

[0066] - or r0 forms an angle of 90°±15° with r1, more preferably 90°±5°, and the liquid crystal has negative dielectric anisotropy.

[0067] The optical system may comprise a static polarizer facing said variable polarizer, the static polarizer being defined by a polarization axis specifically arranged to absorb P1 (polarizer axis perpendicular to P1 ) or arranged to absorb P2 (polarizer axis perpendicular to P2 ).

[0068] As a static polarizer, there can be mentioned a plastic film with a dichroic dye stretched along a direction forming a polarization axis (which is orthogonal to the light absorption direction). In particular, a static polarizer can be designed to block a given polarization.

[0069] Several scenarios are possible:

[0070] - The output light of the variable polarizer is along P1 (off state) and the polarizer substantially blocks P1 , so that the optical system in the off state is obscuring / darkening.

[0071] - The output light of the variable polarizer is generally along P2 (on state) and the polarizer substantially blocks P1 , so that the optical system in the on state remains along P2 and non-blocking.

[0072] - The output light of the variable polarizer is along P1 (off state) and the polarizer substantially blocks P2, so that the optical system in the off state remains along P1 and non-blocking.

[0073] - The output light of the variable polarizer is generally along P2 (on state) and the polarizer substantially blocks P2, so that the optical system in the on state is obscuring / darkening.

[0074] The static polarizer, preferably having a similar shape to the variable polarizer, may extend over all or part of the variable polarizer as desired.

[0075] The optical system may be free of optical elements capable of depolarizing light between the variable polarizer and the static polarizer.

[0076] The optical system can be of any size, since polarizers can be easily implemented on surfaces of at least 1 m in length.

[0077] Between the polarizers, it may be desirable to avoid placing diffusers.

[0078] Of course, any opaque, blocking or reflective elements between the variable polarizer and the static polarizer may be avoided.

[0079] If one adds a switchable device that is particularly polarization (particularly characteristic direction b) sensitive (unidirectional anchoring layer along b of a PSLC liquid crystal device with focal conic domains), one can choose (for the off state of the device):

[0080] a) If P1 is perpendicular to b, then the clear off state is changed to the masked on state (masking becomes increasingly effective as a function of U2),

[0081] b) Or if P1 is parallel to b, then the masked off state is changed to a clear on state (with increasingly ineffective masking as a function of U2).

[0082] The device, in particular the polarization-sensitive electrically switchable device, preferably has a similar shape to the variable polarizer and may extend over the whole or part of the variable polarizer as required.

[0083] The optical system may be free of optical elements capable of depolarizing light between the variable polarizer and the polarization-sensitive device.

[0084] The optical system can be of any size, as these devices can be easily fabricated on surfaces of at least 1 m in length.

[0085] It may be desirable to avoid placing a diffuser between the variable polarizer and the polarization-sensitive device.

[0086] Of course, any opaque, blocking or reflective elements between the variable polarizer and the polarization-sensitive device may be avoided.

[0087] In one embodiment, the variable polarizer and the static polarizer (preferably a plastic film with a dichroic dye) and / or the polarization-sensitive electrically controllable device are separated and connected by a transparent adhesive layer, in particular an optical glue or a thermoplastic plastic layer, in particular a laminated intermediate layer, or the variable polarizer includes an element carrying a first and a second electrode forming said static polarizer.

[0088] The transparent adhesive layer may be colorless or colored.

[0089] The transparent bonding layer may have a thickness of at most 0.5 mm or even 0.1 mm.

[0090] The optical system may be flat or curved, being flexible to adapt to the curvature of, for example, a (single or laminated) glazing, in which case it is curved on the single glazing or, for example, in said laminated glazing.

[0091] The optical system according to the present invention may comprise a polarization-sensitive (electrically controllable) device facing the variable polarizer, in particular having an optical response that depends on the polarization state of the incident light on said device (in particular preferably comprising a focal cone domain of electrically controllable variable scattering by nematic liquid crystals, in particular as described in the application WO2020 / 065038 incorporated by reference).

[0092] Defect line domains are preferred because the haze (scattering power) is significant. As detailed in application WO 2020 / 065038, incorporated by reference, focal conic domains of smectic (meso) phase are preferred.

[0093] Defect domains usually contain two defect lines each, focal conics, and they occur in pairs, specifically an ellipse and another hyperbola with different eccentricities, so they are named "Elliptical-Hyperbolic Focal Conic Domains" or "EHFCD" in English.

[0094] Preferably, the nematic domains are focal conic domains, in particular smectic mesophases (mesophase P'), in particular having two defect lines, preferably one elliptical and the other hyperbolic (EHFCD).

[0095] The focal conic domains, in particular the EHFCDs, preferably form a linear network parallel to the direction b.

[0096] The liquid crystals of the polarization-sensitive device are preferably organized as a whole in a given direction b on the surface FA1 or the surface FA2 (called the planar orientation plane), with their director n - or major axis - being generally along this first direction b, b being in particular the (brush) axis of the unidirectional planar anchoring layer in contact with the planar orientation plane (creating the interaction between the liquid crystal and the solid layer).

[0097] The electrically controllable device with variable scattering of liquid crystal includes an electroactive layer with liquid crystal (nematic, preferably including a focal conic domain), and the direction b forms an angle of 0°±15° or 0°±5° with the polarization P1 of the output light in the closed state of the variable polarizer (on the first and second electrode sides) or an angle of 0°±15° or 0°±5 with r1 perpendicular to P1 or an angle of 90°±15 or 90°±5 with the polarization P11 (or an angle of 90°±15° with r1).

[0098] Thus, according to the present invention, the combination of the electrically controllable device with polarization-sensitive variable scattering and the variable polarizer makes it possible to have a wide range of usable optical properties, in particular a wide range of haze and light transmittance.

[0099] When incorporated into a window pane of a building or vehicle, the polarization-sensitive device can be oriented outward or inward.

[0100] The polarization-sensitive device preferably has a shape similar to that of the variable polarizer and can extend over the entire or part of the variable polarizer as required.

[0101] The optical system may be free of optical elements capable of depolarizing light between the polarization-sensitive device and the variable polarizer.

[0102] It may be desirable to avoid placing a diffuser between the polarization-sensitive device and the variable polarizer.

[0103] Of course, any opaque, blocking or reflective elements between the polarization-sensitive device and the variable polarizer may be avoided.

[0104] The optical system of the polarization-sensitive device plus the variable polarizer may have a thickness of at most 1 cm or 5 mm or 1 mm.

[0105] The polarization-sensitive device may have a thickness of at most 5 mm, or 1 mm, or 0.5 mm.

[0106] Parameters that influence the optical properties of the polarization-sensitive device are, in particular:

[0107] - Selection of the liquid crystal, in particular of the mesogenic mixture (in particular with respect to the operating temperature range and the voltage level U1 for "deanchoring" in the on state) and its dielectric anisotropy

[0108] - the thickness of the electroactive layer,

[0109] - Choice of anchor layer.

[0110] In particular, in the absence of an applied electric field (or for a given voltage), the haze value varies depending on the size or type of two-dimensional defects, their density, the thickness of the electroactive material, the choice of liquid crystal, the polymer network (degree of cross-linking, polymerization conditions), the monomers, and the difference in refractive index between the polymer and the liquid crystal.

[0111] In particular, the haze value in the absence of an applied electric field (or for a given voltage) will vary depending on the orientation of the liquid crystals, and in particular on the angle between the long (molecular) axis of the first liquid crystal and the polarization axis of polarized light along a plane parallel to the surface of the first electroactive layer.

[0112] The haze H is preferably defined as the ratio between the integral light transmittance associated with the diffuse transmittance TD and TL.

[0113] Advantageously, the electric field E1 of the polarization-sensitive device is alternating and the applied voltage U1 is preferably at most 120 V. Preferably, the electrodes are in different planes and the liquid crystal has a positive dielectric anisotropy (independent of the frequency of the electric field E1).

[0114] E2 and / or E1 are preferably alternating, with a frequency starting at 50 Hz, for example 100 Hz, 1 kHz or 2 kHz. Voltage refers to the peak voltage (Vpeak).

[0115] Electrically controllable devices with variable scattering have an optical response that depends on the polarization of the incident light. This differential response to light polarization is caused by the following factors:

[0116] - shape factor, internal structure of two-dimensional topological defects, in particular defect lines, in particular non-complex focal conic domains (non "TFCD" in English), defect lines of smectic mesophases, and / or the arrangement of different domains (in particular focal conic domains of smectic mesophases including "TFCD"), in particular their shape, their orientation, their symmetry, distribution such as random distribution, irregular distribution, etc., distribution conditions determined by anchoring (the two-dimensional anchoring layer can be adjusted, such as multi-directional anchoring).

[0117] Examples of various architectures of polarization-sensitive smectic focal conic domains (i.e., focal conic domains) are given in the publication by Ling Ling Ma et al., entitled “Smectic Layer Origami Preprogrammed Photoalignment” in Advances Materials, 2017, 1606671, pp. 1-7.

[0118] In a preferred embodiment, the variable polarizer is capable of transmitting light having polarization P1 in a first functional state which is a closed state, the polarization-sensitive device comprises a directional anchoring layer along a first direction b on the surface, and the variable polarizer 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).

[0119] In one embodiment, the variable polarizer is capable of transmitting light having polarization P1 in a first functional state which is a closed state, the polarization-sensitive device comprises a directional anchoring layer along a first direction b on a surface, and the variable polarizer is arranged so that P1 forms an angle of 90°±20° or better ±5° with b (in particular r1 forms an angle of 90°±20° or better ±5° with b).

[0120] As a unidirectional planar anchoring layer, a fluoropolymer film such as polytetrafluoroethylene (PTFE) or Teflon (wherein the polymer chains are aligned with the displacement direction of the polytetrafluoroethylene rods during deposition) can be used.

[0121] Unidirectional planar anchoring fixes the zenithal and azimuthal orientation of the liquid crystal director n), for example by texturing, brushing (also called rubbing) a planar anchoring layer, for example comprising nanogrooves or microgrooves.

[0122] A velvet fabric may be used for this brushing.

[0123] For normal anchoring, the most commonly used layers are based on octyltrichlorosilane (OTS) and N,N-dimethyl-N-octadecyl-3-aminopropyltrimethoxysilane chloride (DMOAP) or polyimide.

[0124] Layers based on sodium dodecyl sulfate (SDS) or even alkanethiolate mixtures may also produce normal anchoring.

[0125] The one or more anchoring layers are deposited, for example, by a liquid route.

[0126] Anchor layers are for example:

[0127] Preferably dielectric (especially amorphous, polymeric and / or mineral, glass) with surface functionalization; especially layers based on polyvinyl alcohol (PVA), polyimide, for example for planar anchoring.

[0128] The dichroic dye can be an anisotropic organic molecule with optical anisotropy that is elongated, particularly rod-shaped. It dissolves in the material, particularly the liquid crystal. The percentage of each dichroic dye is adjusted so as not to exceed the solubility limit. In particular, the dichroic dye(s) are selected to be compatible with the liquid crystal chemistry.

[0129] In particular, the (each) (elongated, rod-shaped) dichroic dye may have a long molecular axis and the absorption may vary along the long axis or the short axis.

[0130] The dichroic dye is controlled by the orientation of the liquid crystal in the electroactive layer. The movement (rotation) of the liquid crystal under the action of the applied electric field (E2) tends to align with the electric field, resulting in the movement (rotation) of the dichroic dye, and the long axis also tends to align with the electric field.

[0131] Thus, the absorption of dichroic dyes varies as a function of their orientation relative to the polarization of the incident light. In contrast, non-dichroic dyes, which lack absorption anisotropy, are insensitive to electric fields, or are only slightly sensitive, or even exhibit no change in absorption. Such dyes can be added to adjust the desired hue.

[0132] There are several families of dichroic dyes, in particular those described in the publication by Mark T Sims entitled “dyes as guests inordered systems: current understanding and future directions”, Liquid Crystals, 2016, Vol. 43, NOS. 13-15, pp. 2363-2374.

[0133] The dichroic dye according to the invention may be an azo dye with AZO (-N=N), in particular in rod form. Azo dyes can be induced to undergo chemical changes, for example using introduced ester groups (see page 2366 of the above publication).

[0134] Other dyes are anthraquinones, which are generally fused rings or, by adding substituents, rod-shaped. Examples of dichroic dyes (chromophores) are given in Table 1 of the above publication.

[0135] Examples of dichroic dyes suitable for the present invention are further mentioned in the book by LM Blinov et al. entitled "Electrooptic effect in Liquid Crystal Materials", published by Springer in 1994, in particular in Chapter 2.3 entitled "Optical Anisotropy and Dichroism" and on pages 66 to 68, including Table 2.2.

[0136] For example, for a blue dye, 630 nm ± 10 nm may be selected as the maximum absorption wavelength, and 430 nm ± 50 nm or ± 10 nm may be selected as the wavelength outside the absorption band. For example, the dye M412 sold by Mitsui Chemicals may be mentioned.

[0137] For example, for a red dye, 500 nm ± 10 nm may be selected as the maximum absorption wavelength, and 650 nm ± 50 nm or ± 10 nm may be selected as the wavelength outside the absorption band. For example, mention may be made of the dye SI-426 sold by the company Mitsui Chemicals.

[0138] For example, for a yellow dye, 400 nm ± 10 nm may be selected as the maximum absorption wavelength, and 600 nm ± 50 nm or ± 10 nm may be selected as the wavelength outside the absorption band. For example, mention may be made of the dye SI-486 sold by the company Mitsui Chemicals.

[0139] For example, as a black dye, mention may be made of the dye SI-428 sold by the company Mitsui Chemicals. The variable polarizer may comprise:

[0140] a first transparent dielectric element carrying the first and second electrodes in the form of strips (coplanar configuration) and even an anchoring layer, preferably a unidirectional anchoring layer according to r1, the first element being chosen from a glass sheet or a transparent polymer sheet (different from or corresponding to said dielectric support),

[0141] - a second transparent dielectric element carrying at least one unidirectional anchoring layer preferably along r2, the second element being chosen from a glass sheet or a transparent polymer sheet (with an optional external scratch resistant layer)

[0142] The optical system may be flat or curved, flexible to adapt to the curvature of, for example, a (single or laminated) glazing, in which case it is curved on the single glazing or, for example, in said laminated glazing.

[0143] The invention also relates to an optionally curved laminated glazing comprising:

[0144] - a first additional glass sheet, in particular having a thickness of 0.7 mm to 4 mm

[0145] - a thermoplastic laminating intermediate layer, in particular EVA or PVB,

[0146] a second additional glass sheet, in particular a glass sheet having a thickness of 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 lamination interlayer),

[0147] the main inner faces of the first and second additional glass sheets facing each other, called F2 and F3, the optical system as previously described preferably being between the faces F2 and F3 and preferably in the laminating interlayer,

[0148] The main internal faces, called F2 and F3, of the first and second additional glass sheets are opposite the optical system as described previously, preferably between the surfaces F2 and F3 and preferably in the lamination interlayer; preferably, the first element with the first and second electrodes is a polymer, and even the second element (on the side of the anchoring layer with r2) is a polymer.

[0149] Preferably, the thermoplastic laminate interlayer surrounds the edge faces of the optical system (variable polarizer, etc.).

[0150] The edge face of the optical system may be set back relative to the outermost edge face of the laminating interlayer (or first sheet).

[0151] Preferably, the optional sheet material carrying the layers (substrate, support, first and second elements) preferably has a thickness of at most 0.7 mm and even at most 0.3 or 0.2 mm. As glass sheets, thin glass (less than 1 mm) or even ultra-thin glass ("UTG" in English) can be chosen.

[0152] One of the additional glass sheets may be tinted and the other may be clear or extra clear.The thermoplastic laminating interlayer may be colorless (clear, extra clear) or tinted.

[0153] For the carrier element or for the additional glass sheet or the glass of the laminated and / or multiple glazing, clear or extra clear glass can be chosen. Clear glass generally has an iron oxide content of approximately 0.05 to 0.2% by weight, while extra clear glass generally contains approximately 0.005 to 0.03% by weight of iron oxide.

[0154] The additional glass sheets or the glass panes of the laminated and / or multiple glazing units may still be tinted, for example blue, green, grey or bronze.

[0155] The tinted additional glass sheet or the tinted glass pane of the laminated and / or multiple glazing may preferably have a light transmission T less than or equal to 10%. L .

[0156] The glass is preferably of the soda-lime-silica type, but it may also be of the borosilicate or aluminoborosilicate type. The thickness of the glass is generally in the range of 0.5 to 19 mm, preferably 0.7 to 9 mm, in particular 2 to 8 mm, or even 4 to 6 mm.

[0157] The thermoplastic laminating interlayer provides the bond to the rigid or flexible element. The polymer laminating interlayer can be based on polyvinyl butyral (PVB), ethylene vinyl acetate (EVA), polyethylene (PE), polyvinyl chloride (PVC), thermoplastic polyurethane, polyurethane (PU), ionomer, polyolefin-based adhesive, thermoplastic silicone or multi-component or single-component, heat-crosslinkable (epoxy resin, PU) or UV-crosslinkable (epoxy resin, acrylic resin) resins.

[0158] 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 glazing, in order to avoid ghosting in the case of head-up displays (HUDs), particularly for windshields. The PVB interlayer is optionally sound-insulating and / or tinted. The acoustic PVB interlayer can comprise at least one "center" layer made of a viscoelastic plastic with acoustic damping properties, in particular based on polyvinyl butyral (PVB) and a plasticizer, and two outer layers made of standard PVB, with the center layer being located between the two outer layers.

[0159] Optionally, one or both outer layers have a cross section that decreases in a wedge shape from the top to the bottom of the laminated glazing, and the layer made of viscoelastic plastic with acoustic damping properties has a cross section that is constant from the top to the bottom of the laminated glazing. As an example of an acoustic sheet, patent EP0844075 may be mentioned.

[0160] The first and / or second pane of glass of the laminated glazing may (depending on the aesthetic effect or the desired optical effect) be clear glass (light transmission T for a thickness of 4 mm). L greater than or equal to 90%), such as standard soda-lime composition glass, such as that from Saint-Gobain Glass Or ultra-clear glass (thickness 4 mm T L greater than or equal to 91.5%), such as soda-lime silicate glass - with less than 0.05% FeIII or Fe2O3, such as from Saint-Gobain Glass Glass, or from Pilkington Glass or from Schott glass, or another composition described in document WO04 / 025334. Alternatively, glass from Saint-Gobain Glass Glass.

[0161] The glass of the first and / or second glass panes may be neutral (not tinted) or (slightly) tinted, in particular grey or green, such as TSA glass from Saint-Gobain Glass. The glass of the first and / or second glass panes may have undergone a chemical or thermal treatment of the hardening or annealing type or may have been tempered (in particular to obtain better mechanical strength) or semi-tempered.

[0162] Light transmittance T L , which can be measured using illuminant D65 in accordance with standard ISO 9050:2003 and is the total transmittance (integrated in particular in the visible region and weighted by the sensitivity curve of the human eye), taking into account direct transmission and possible diffuse transmission, for example using a spectrophotometer equipped with an integrating sphere, with the measured value at a given thickness subsequently being appropriately converted to a reference thickness of 4 mm in accordance with standard ISO 9050:2003.

[0163] The optical system according to the invention can be integrated into a glazing, in particular a one-piece (flat and / or curved) glazing, and form a strip, in particular a peripheral strip, on a portion of a main face of the glazing.

[0164] The optical system according to the invention as defined above may be used in a vehicle or a building.

[0165] It can be used in particular as:

[0166] - interior partitions (between two rooms or within a space) in buildings, road, rail, sea or air vehicles (between two carriages, in taxis, buses, trains, etc.), in particular as glass shower walls or bathtubs,

[0167] - Glass doors (entrance doors or service doors), windows (single, double, triple glazed), ceilings, tiles (floor or ceiling), toilet doors, glass parts of domestic or street furniture

[0168] - Window glass of motor vehicles (cars, trucks, buses, cars, etc.), thus road vehicles, rail vehicles, marine vehicles (ships), windshields, side windows, roofs, etc.

[0169] - projection or rear projection screen,

[0170] - Shop facades, display windows, especially exhibition stand windows.

[0171] Naturally, it may form all or part of the glazing (transom partitions, windows etc).

[0172] Thus, architectural glazing may carry an optical system as described above, in particular single-, double- or triple-glazed (with or without laminated glazing) partitions, windows or the like.

[0173] Thus, vehicle glazings, in particular for road vehicles, may carry an optical system as described above, in particular windscreens (optical system forming one or more peripheral bands), sunroofs, (monolithic or laminated) side windows, in particular rear quarter panels.

[0174] The laminated glazing according to the invention, in particular for cars (windshields, etc.) or trucks, can be curved (bent) in one or more directions, in particular with respect to the first and second sheets, and with a radius of curvature of 10 to 40 cm. It can also be flat (for buses, trains, tractors).

[0175] The optical system according to the invention can be integrated in a laminated, in particular curved, glazing, between a first and a second glass pane (referred to respectively as the outer and inner glass pane) and forming a peripheral strip in the upper part of the glazing, the "outer" edge face of the stack being masked from the outside by a first opaque peripheral layer, in particular an enamel on the outer glass pane (preferably on face F2), and / or the "inner" edge face of the stack being masked from the inside by an opaque peripheral layer, in particular an enamel on the inner glass pane (for example on face F4 or even face F3).

[0176] The curved laminated glazing according to the invention, in particular a windscreen or side glazing, may have a T L - in the pane light - preferably at least 70% and even at least 75% or even at least 80%.

[0177] The curved laminated glazing according to the invention, in particular the glass skylight, may have a light transmission T of up to 10% or even 1% to 6%. L .

[0178] For motor vehicle roofs, at least one or all of the following criteria are preferred:

[0179] -Energy transfer rate T E Up to 10%, even 4 to 6%,

[0180] - Energy reflectivity R of up to 10%, preferably 4-5% E (preferably on the side of surface F1),

[0181] - Total transmittance of solar energy TTS <30% or even <26%, or even 20%-23%.

[0182] The curvature of the first and second glass panes (in particular a windshield) can be in one or more directions, as described, for example, in document WO2010136702.

[0183] In order to limit heating or to limit the use of air conditioning in the passenger compartment, at least one pane of glass (preferably the outer pane) is tinted, and the laminated glazing may also include a layer that reflects or absorbs solar radiation, preferably on face F4 or on faces F2 or F3, in particular a transparent conductive oxide layer, called "TCO layer", (on face F4) or even a thin-film multilayer comprising at least one TCO layer, or a thin-film multilayer comprising at least one silver layer (on F2 or F3), the or each silver layer being situated between dielectric layers.

[0184] The optical system according to the invention can be used in combination with other electrically controllable devices, such as those with electroluminescent systems (inorganic point source LED arrays, organic diodes or OLEDs, TFELs (with thin films)). The two can be facing or adjacent in a laminated glazing (laminated interlayer).

[0185] The optical system according to the invention can be used in particular in laminated glazings in combination with another electrically controllable device, such as an electroluminescent electrically controllable device, in particular an LED, OLED, TFEL. Further details and features of the invention will become apparent from the following detailed description given in conjunction with the following drawings, in which:

[0186] Figure 1 A schematic cross-sectional view of an optical system 1000 is shown in a first embodiment of the present invention, the optical system 1000 including an electrically controllable variable polarizer 100 using liquid crystal and dichroic dye associated with a static polarizer 10.

[0187] Figure 2 is Figure 1 Front view of the strip electrodes used in the variable polarizer and powered two by two.

[0188] Figure 3 A schematic cross-sectional view of an optical system 1000' in a second embodiment of the present invention is shown, the optical system 1000' consisting of an electrically controllable variable polarizer 100 using liquid crystals and dichroic dyes associated with a static polarizer 10'.

[0189] Figure 4 A schematic cross-sectional view of an optical system 1001 consisting of an electrically controllable variable polarizer 100 using liquid crystal and dichroic dye associated with a polarization-sensitive electrically controllable device 20 in a third embodiment of the present invention is shown.

[0190] Figure 5 It is in the first functional state of the closed state Figure 1 Schematic partial perspective view of a variable polarizer.

[0191] Figure 6 The second state is the open state at a given voltage U2 Figure 1 Schematic partial perspective view of a variable polarizer.

[0192] Figure 7 is a schematic partial perspective illustration of a system 1002 including a variable polarizer and an alternative static polarizer having a structure similar to the variable polarizer but without electrodes, in a first functional state of the variable polarizer, which is a closed state.

[0193] Figure 8 The variable polarizer is in the second functional state of the open state. Figure 7 Schematic partial perspective view of a variable polarizer and an alternative static polarizer.

[0194] Figure 9 is in the first functional state of the variable polarizer which is the closed state. Figure 7 A variant of the Figure 1 Schematic partial perspective view of a variable polarizer and an alternative static polarizer, the alternative static polarizer having a structure similar to the variable polarizer but without the electrodes, and the alternative static polarizer having been rotated 90°.

[0195] Figure 10 It is in the second function state of the open state Figure 9 Schematic partial perspective view of a variable polarizer and an alternative static polarizer.

[0196] Figure 11 A set of five curves is shown corresponding to the total transmission TT as a function of wavelength λ between 380 and 630 nm of a variable polarizer illuminated with light polarized along r2 (parallel to ).

[0197] Figure 12 A set of five curves is shown corresponding to the total transmission TT as a function of the wavelength λ between 380 and 630 nm of the variable polarizer illuminated with light polarized perpendicular to r2.

[0198] Figure 13 A schematic cross-sectional view of a window pane with an optical system 2000 according to the invention is shown.

[0199] Figure 14 A schematic cross-sectional view of a laminated glazing with an optical system 3000 according to the invention is shown.

[0200] Figure 15 Shown in Figure 14 Schematic cross-section of a laminated glazing carrying an optical system 3000 according to the invention, in a variant in which, in addition to the variable polariser 100 and the static polariser 10, a polarisation-sensitive electrically controllable device 20 is added.

[0201] Figure 16 and 17 Shown are a front view and a schematic cross-sectional view, respectively, of a laminated glazing with an optical system 4000 according to the invention.

[0202] Elements shown in the figures are not drawn to scale.

[0203] Figure 1 A schematic cross-sectional view of an optical system 1000 is shown in a first embodiment of the present invention, the optical system 1000 comprising an electrically controllable variable polarizer 100 using liquid crystal and a dichroic dye associated with a static polarizer 10 (a stretched plastic film with a dichroic dye). Figure 2 is Figure 1 A front view of strip-shaped electrodes used in the variable polarizer 100 and powered in pairs.

[0204] An orthogonal coordinate system X, Y and Z is defined.

[0205] The electrically variable polarizer 100 here features a surface first anchoring direction r1 of the liquid crystal (in the off state) on the output side (on the side co-located with the strip electrodes 21, 22) and even a surface second anchoring direction r2 of the liquid crystal on the side opposite to the output.

[0206] The variable polarizer 100 has first and second functional states, and:

[0207] - In a first functional state, here the closed state, with unpolarized incident light (on the side of which it is coplanar with the strip electrodes 21, 22) (schematically represented by normal components Pa and Pb of equal intensity, where k is the propagation vector of the light along Z), the variable polarizer is able to transmit polarized output light with a first component of the polarization electric field P1 along the axis X (perpendicular to r1) and a second component of the polarization electric field P2 along the axis Y perpendicular to Y, with a first polarization ratio defined as

[0208] [Mathematical formula 3]

[0209]

[0210] rp1 is preferably at least 70% or 90%, or even at least 95%, T1 is the total transmittance along X at a wavelength of 380-800 nm and T2 is the total transmittance along Y at a wavelength of 380-800 nm (thus, P1 has a strong advantage over P2),

[0211] In the second functional state, which is the on state, at voltage U2 (between two coplanar strip electrodes):

[0212] Using unpolarized incident light, the variable polarizer is able to transmit polarized output light with a second polarization ratio defined by:

[0213] [Formula 4]

[0214]

[0215] rp2 is at least 30%, or even at least 50% or 60%, T'1 is the total transmittance along the first axis at a wavelength of 380-800 nm, and T'2 is the total transmittance along the second axis at a wavelength of 380-800 nm, for a voltage U2b between the third and fourth electrodes,

[0216] P2 preferably predominates over P1.

[0217] The polarization of the output light of the variable polarizer can be elliptical.

[0218] Naturally, the variable polarizer now has several functional states in the switched-on state. In particular, there is a threshold voltage at which the anchoring forces of the liquid crystal are overcome for a portion of the liquid crystal, and the more the voltage increases, the more the liquid crystal reorients, up to a saturation voltage, which is preferably at most 80 volts.

[0219] At this time, the polarization ratio can be It varies as a function of the applied voltage U2.

[0220] Optionally, a static polarizer 10 is added as needed so that in the off state there is no longer any light (or almost no light) - in Figure 1 Indicated by a cross symbol and in the on state (at U2), a little light remains along the P2 axis.

[0221] More precisely, the variable polarizer 100 comprises a stack of layers (physical, solid) in the following order:

[0222] - a first transparent dielectric element 1 ′ having main faces 11 ′ and 12 ′, here 1.1 mm thick glass - or as a variant, a plastic such as PET

[0223] - Separate strip-shaped first and second transparent electrodes 2, comprising a first strip 21 and a second / first strip 22 between insulating strips 23 - ITO indium tin oxide layer with a sheet resistance of 100 ohms / square, more generally between 5-300 ohms / square

[0224] - a first transparent dielectric element 1 ′ (face 11 ′) and a first unidirectional planar anchoring layer 4 ′ transparent in the direction r1 along Y on the strips 21 , 22

[0225] a colored dielectric electroactive layer 3 in contact with this first anchoring layer 4 ′, having a main face, called face F3, on the other device side, and a main face, called opposite face FA4, here with a thickness Ep1 (less than 20 μm) made of a material comprising:

[0226] -liquid crystal

[0227] - one or more dichroic dyes (in dissolved state)

[0228] - Spacers are distributed in the material, here glass beads

[0229] - The layer 3 is sealed at the periphery by a polymer seal 5 , for example made of epoxy acrylate, in this case cyanoacrylate

[0230] - a second transparent anchoring layer 4, here unidirectionally anchored in a direction r2 perpendicular to r1 and parallel to X

[0231] - a second transparent dielectric element 1 (layer 4) with main faces 11 and 12, here 1.1 mm thick glass - or in a variant, a plastic such as PET

[0232] For power supply via a power source, conductive strips (not shown), in particular metallic conductive strips, for example made of copper, are fixed along and on the peripheral edges, for example by adhesive bonding, and are in contact with the electrodes 21, 22 (one conductive strip per electrode, preferably on opposite edges). These conductive strips are then connected to the power source. The edge faces of the electrodes 21, 22 and the edges of the electroactive layer are preferably set back relative to the edges of the rectangular or any other shaped (glass) element 1, 1′. The thickness of the (glass) element 1, 1′ can be, for example, 0.7 mm to 4 mm. They can have a thickness preferably greater than 100 μm and up to 300 μm to achieve better mechanical strength of the assembly and / or ease of use and handling, but can be reduced, for example, to 50 microns if greater flexibility is desired.

[0233] The preparation method is described in more detail below.

[0234] Thus, the first anchoring layer 4 ′ is a layer that induces unidirectional planar anchoring of the liquid crystals (in the absence of an electric field) along the direction r1 at the surface in contact with this layer 4 .

[0235] A first anchoring layer 4 ′ is deposited on the ITO stripes 21 and 22 and on the first element 1 ′ between the stripes 23 by spin coating an approximately 500 nm thick polyvinyl alcohol (PVA; Sigma-Aldrich; molecular weight 27 kDa) solution.

[0236] The first anchoring layer 4' is now brushed in the direction r1 parallel to the strips extending in the direction r0 / / r1)

[0237] Therefore, the second anchoring layer 4 is a layer that induces unidirectional planar anchoring of the second liquid crystal at the surface in contact with the layer 4 (in the absence of an electric field) along the direction r2.

[0238] The second anchoring layer 4 is deposited on the second element 1 by spin coating a polyvinyl alcohol (PVA; Sigma-Aldrich; molecular weight 27 kDa) solution with a thickness of about 300 nm. The second anchoring layer 4 is then brushed in a direction r2 perpendicular to r1.

[0239] The electroactive layer 3 of liquid crystals consisted of nematic liquid crystals E7 (98% by weight) and a black dichroic dye sold by Mitsui Chemicals called S428 (2% by weight). The thickness of the second electroactive layer was 10 μm.

[0240] like Figure 2 As shown, for example, insulating strips 23 form a serpentine arrangement, and a first region of the conductive layer is isolated from a second region of the layer by a first portion 23a of the first insulating strip of the serpentine strip and by a last portion 23b of the last insulating strip of the serpentine strip.

[0241] Conductive strips 21 and 22 are parallel to r0 and r1.

[0242] It is conceivable to achieve such an arrangement of insulating strips by hollowing out a solid conductive layer, in particular by means of a femtosecond laser beam (e.g., with a diameter of 30 μm) and the strips being 15 μm. The thickness of the strips is limited by the laser beam size. The distance between the strips is limited by the movement of the laser beam.

[0243] The liquid crystal has positive dielectric anisotropy.

[0244] Figure 3A schematic cross-sectional view of an optical system 1000′ consisting of an electrically controllable variable polarizer 100 using liquid crystal and a dichroic dye in association with a static polarizer 10′ (a stretched plastic film with a dichroic dye) in a second embodiment of the present invention is shown, which differs from the first embodiment in that the static polarizer 10′ is rotated 90° so that it cuts the polarization along P2.

[0245] Figure 4 A schematic cross-sectional view of an optical system 1001 is shown, which consists of an electrically controllable variable polarizer 100 using liquid crystal and dichroic dye associated with a polarization-sensitive electrically controllable device 20 in a third embodiment of the present invention.

[0246] The device 100 is similar to Figure 1 The device described in .

[0247] Device 20 may have a similar layer stack as device 10, with the following modifications:

[0248] - Anchor layer along the direction of b

[0249] - Planar anchoring layer

[0250] - Planar-type electrodes (on either side of the electroactive layer), so normal electric field (along Z)

[0251] - Nematic liquid crystals with focal conic domains, in particular EFHCD

[0252] - Optional colored electroactive layer, PSCL type (with cross-linked polymers).

[0253] Figure 5 It is in the first functional state of the closed state Figure 1 Schematic partial perspective view of a variable polarizer.

[0254] At the surface of the anchor layer 4, the liquid crystal 312 (defined by the director n2) and the dichroic dye 322 are (generally) parallel to r2.

[0255] At the surface of the counter-anchoring layer 4', the liquid crystal 310 (defined by the director n1) and the dichroic dye 320 are (generally) parallel to r1.

[0256] This opposing force forces the nematic liquid crystal to twist and deform, and the dichroic dye is controlled by the nematics.

[0257] In the thickness of the electroactive layer 3, the liquid crystal 311 (defined by the director n3) and the dichroic dye 321 form angles with r1 and r2 (as a whole).

[0258] Figure 6 yes Figure 1Schematic partial perspective view of a variable polarizer in a second state of the open state at a given voltage U2.

[0259] At the surface of the anchor layer 4, the liquid crystal 312 (defined by the director n2) and the dichroic dye 322 remain (generally) parallel to r2.

[0260] Throughout the thickness of the electroactive layer 3, the liquid crystal 311 (defined by the director n3) and the dichroic dye 321 generally tend to align along r2.

[0261] At the output, the polarization state P1 perpendicular to r1 is weakened and can be quasi-turned off.

[0262] For polarization P1 (perpendicular to r1), the first polarization ratio is defined as follows:

[0263]

[0264] For polarization P2 (parallel to r1 and perpendicular to P1), the second polarization ratio is defined as follows:

[0265]

[0266] 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 900 spectrometer was used.

[0267] The variation of the ratios r1 and r2 as a function of the applied voltage U2 is shown in Table 1.

[0268] [Table 1]

[0269] U2(V) <![CDATA[r1(%)]]> <![CDATA[r2(%)]]> 0 99 1 20 49 51 40 32 68 60 26 74 80 22 78

[0270] At zero voltage, the polarization along P1 is almost perfect.

[0271] As the voltage increases, the component P2 increases.

[0272] Figure 7 is a schematic partial perspective view of a system 1002 including a variable polarizer and an alternative static polarizer 3′ (the alternative static polarizer structure is similar to the variable polarizer but without the electrodes) in a first functional state of the variable polarizer, which is the closed state (as described in Figure 5 middle).

[0273] The alternative static polarizer 3′ comprises the same unidirectional anchoring layers 40, 40′ along r4 and r5 (reproducing r1 and r2), a twisted nematic liquid crystal (nematic 315 and dye 325) between the surface 40, the core of the passive liquid crystal layer 3′ (nematic 314 and dye 324) and the surface 40′ (nematic 313 and dye 323).

[0274] Figure 8 The second functional state of the variable polarizer is in the open state (eg Figure 6 described in Figure 7 Schematic partial perspective view of a variable polarizer and an alternative static polarizer.

[0275] Figure 9 is a schematic partial perspective view of system 1002 in a first functional state of the variable polarizer, which is a closed state, including Figure 1 The variable polarizer and the alternative static polarizer 3' (the alternative static polarizer structure is similar to the variable polarizer but without electrodes), which Figure 7 In a variant of , the alternative static polarizer 3" has been rotated by 90°.

[0276] Figure 10 It is in the second function state of the open state Figure 9 Schematic partial perspective view of a variable polarizer and an alternative static polarizer 3".

[0277] Figure 11 A set of five curves is shown, corresponding to the total transmission TT of the variable polarizer illuminated with light polarized along r2 (parallel) as a function of wavelength λ between 380 and 630 nm.

[0278] Curve 1 is the on-mode (using a voltage U2 equal to 80V).

[0279] Curve 2 is the on-mode (using a voltage U2 equal to 60V).

[0280] Curve 3 is the on-mode (using a voltage U2 equal to 40V).

[0281] Curve 4 is the on-mode (using a voltage U2 equal to 20V).

[0282] Curve 5 is the off-mode (using a voltage U2 equal to 0V).

[0283] In the off state of the variable polarizer, the total transmission TT is almost zero. The total transmission TT increases with the applied voltage.

[0284] Figure 12A set of five curves is shown, corresponding to the total transmission TT of the variable polarizer illuminated with polarized light perpendicular to r2 as a function of wavelength λ in the range 380-630 nm.

[0285] Curve 1 is the off-mode (using a voltage U2 equal to 0V).

[0286] Curve 2 is the on-mode (using a voltage U2 equal to 20V).

[0287] Curve 3 is the on-mode (using a voltage U2 equal to 40V).

[0288] Curve 4 is the on-mode (using a voltage U2 equal to 60V).

[0289] Curve 5 is the on-mode (using a voltage U2 equal to 80V).

[0290] The total transmission TT increases with the applied voltage.

[0291] Assembly Example

[0292] Figure 13 A schematic cross-sectional view of a glass assembly 2000 is shown, comprising a transparent sheet 7 (of any possible thickness) carrying an optical system 1000 according to the invention.

[0293] Static polarizer 10 is bonded to a transparent glass or plastic (eg, rigid) sheet 7 by optical glue 60 , and is also bonded to variable polarizer 100 by optical glue 61 .

[0294] For example, it is a partition wall (vertical position).

[0295] This assembly may form part of a multiple glazing unit (double or triple glazing). For a double glazing unit, the system 1000 may be on the sides of faces F1 (conventionally the exterior face), F2, F3, and F4 (conventionally the interior face). For a triple glazing unit, the stack may be on the sides of faces F1 (exterior face), F2, F3, and F4 (exterior face). Sheet 7 may be the same size as system 1000 or larger.

[0296] The glass assembly 2000 may be:

[0297] - On the preferably outer face of the shower wall or element 7 is the shower wall

[0298] - or on the preferably inner face (face 'F4') of a curved glazing of a vehicle, in particular a motor vehicle: roof, side windows, windshield, rear window, or element 7 is a curved glazing

[0299] In particular, the glass assembly 2000 may be used as a projection screen.

[0300] Figure 14 A schematic cross-sectional view of a laminated glazing 3000 is shown with an optical system 1000 according to the invention comprising a static polariser 10 connected to a variable polariser 100 by means of an optical glue 60 .

[0301] Laminated glazing 3000 includes:

[0302] - a transparent first additional glass sheet 8

[0303] - a thermoplastic laminating intermediate layer 70, in particular EVA or PVB,

[0304] - A transparent second additional glass or plastic sheet 8'

[0305] The main inner faces, called F2 and F3, of the first and second additional sheets face each other, with the optical system 1000 between faces F2 and F3 and within a sub-millimeter or at most 2 mm lamination interlayer.

[0306] During production, three intermediate sheets can be used: two complete sheets 72, 73 resting against the inner surfaces of the sheets 8, 8', and an intermediate sheet 71 with an opening for accommodating the system 1000. After lamination, the interface between the sheets (indicated by the dotted line) is not necessarily recognizable. It is preferred that the opening be closed rather than completely open on one side. Thus, the entire edge face of the system 1000 is surrounded by the laminated intermediate layer 70. Naturally, for the power supply, connections can extend from the system 1000 and even protrude beyond one or more side edges of the window pane.

[0307] Alternatively, two middle sheets may be used, without the need for a hollowed-out middle sheet if the system 1000 is thin enough, eg, at most 0.2 mm thick.

[0308] One of the sheets 8 or 8' can be colorless or colored (gray, green, bronze, etc.), while the other 8' or 8' of the window pane can be clear or super clear. One of the first intermediate sheets can be colored (gray, green, bronze, etc.) and the other one or more can be clear or super clear. One of the sheets 8 or 8' can be replaced by a plastic sheet such as polycarbonate or PMMA (particularly with a PU laminated intermediate layer).

[0309] The edge faces of the laminating interlayer 70 may be set back (eg, by at most 5 mm) from the edge faces of the sheets 8, 8'.

[0310] The system 1000 covers, for example, almost the entire main face of the sheet 8 and even here in the middle. The PVB width is the same on both sides of the system 1000.

[0311] The sheets 8, 8' are planar or curved, the system 1000 being able to adapt to the curvature of the glass sheets 8, 8' which are curved in this case.

[0312] The optical system 1000 can be a partition wall or a roof. For example, for a motor vehicle roof:

[0313] - Sheet 8 is outermost and curved, optionally colored, e.g. 3 mm thick

[0314] - Sheet 8' is the innermost, curved, preferably clear or extra clear, e.g. 3 mm thick or less

[0315] The laminating intermediate layer 70 is made of PVB, which may be acoustic, in particular double or triple layer (sheet 71 or 72 or 73).

[0316] The vehicle roof can thus also have a changeable color, for example from dark blue to light blue using voltage U1 or U2 .

[0317] Figure 15 Shows the load Figure 14 Schematic cross-sectional view of a laminated glazing according to an embodiment of the invention in a variant of an optical system 3000 in which, in addition to the variable polarizer 100 and the static polarizer 10, a polarization-sensitive electrically controllable device 20 is added and the electrically controllable device is bonded to the static polarizer 10 by optical glue 60'.

[0318] As a variant, the static polarizer 10 is eliminated.

[0319] Figure 16 and 17 Shown are a front view and a schematic cross-sectional view, respectively, of a laminated glazing carrying an optical system 4000 according to the invention.

[0320] Laminated Window Glass 4000 with Figure 14 The laminated glazing of is different in that the optical system 1000 covers part of the surface of the sheet 8 , in particular a peripheral strip, for example along the upper longitudinal edge H over almost the entire length of the laminated glazing.

[0321] This is, for example, a motor vehicle windshield.

[0322] Such an optical system 1000 is in the edge region, where the TL and the criterion of absence of haze are freer than in the central region ZB.

[0323] Therefore, the color of the optical system 1000 can also be changed with voltage, for example, from dark blue to light blue.

[0324] like Figure 17As shown in FIG. 1 (sectional view), 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.

[0325] As a variant or alternative, it may be present along the lower longitudinal edge B of the windshield, over the entire length or over a portion of the length.

[0326] like Figure 16 As shown (front view from the inside of the vehicle), the windshield comprises first opaque frames 91′ to 94′, for example made of enamel (black or other), on the lateral and longitudinal edges of the free face (F4) 82′ of the inner sheet 8′, and second opaque frames 91 to 94, for example made of enamel (black or other), on the lateral and longitudinal edges of the free face (F1) 82 of the outer sheet 8.

[0327] The edge faces of the optical system 1000 located on the side of the lower longitudinal edge, and even those located on the side of the transverse edge, can be located between (on the surface of) the layers 92, 92', 93, 93', 94, 94' of the enamel frame. For example, the connections and other power supply lines (for U1 and U2) can also be masked by these layers 92, 92', 93, 93', 94, 94'.

[0328] In a variant, it is a motor vehicle roof, for example with tinted outer glass 8 and / or tinted PVB 71 and an optical system 1000 which even covers substantially the entire main surface of the glass 8 , 8 ′.

Claims

1. A liquid crystal optical system (1000, 1000', 1001, 1002, 1003) comprising a variable polarization electrically switchable device (100, 100', 101, 102) called a variable polarizer, the variable polarizer comprising: - first and second transparent electrodes, with an electric field E2 between the first and second electrodes, the first and second electrodes being coplanar and forming alternating first and second conductive strips at different potentials, - an electroactive layer (3) made of a material comprising liquid crystals and a dichroic dye, the liquid crystals being nematic, wherein the first and second conductive strips are elongated along the r0 direction, and the variable polarizer comprises: - a unidirectional planar anchoring layer (4') on the main face of the electroactive layer and on the first and second electrodes in the direction r1, and another unidirectional planar anchoring layer along direction r2 on the other main face of the electroactive layer (3), and direction r1 is different from direction r2 and r1 and r2 form an angle of 90°±15°.

2. The liquid crystal optical system (1000, 1000', 1001, 1002, 1003) according to claim 1, characterized in that The liquid crystal is twisted nematic in the off state of the variable polarizer.

3. The liquid crystal optical system (1000, 1000', 1001, 1002, 1003) according to any one of the preceding claims 1-2, characterized in that Variable polarizers do not have static polarizing films.

4. The liquid crystal optical system (1000, 1000', 1001, 1002, 1003) according to any one of the preceding claims 1-2, characterized in that The electric field E2 is alternating.

5. The liquid crystal optical system (1000, 1000', 1001, 1002, 1003) according to any one of the preceding claims 1-2, characterized in that The variable polarizer has first and second functional states, and In a first functional state, which is an off state, the variable polarizer is capable of transmitting output light having a first component of an electric field P1 along a first axis and a second component of an electric field P2 along a second axis perpendicular to the first axis, with a first polarization ratio defined by the following equation: [Formula 5] rp1 is at least 70%, T1 is the total transmittance along the first axis at a wavelength of 380-800 nm, T2 is the total transmittance along the second axis at a wavelength of 380-800 nm, - and in the second functional state of the on state: Using unpolarized incident light, the variable polarizer is able to transmit output light with a second polarization ratio defined by: [Formula 6] rp2 is at least 30%, For a non-zero voltage between the first and second electrodes, T'1 is the total transmittance along the first axis at a wavelength of 380-800 nm, and T'2 is the total transmittance along the second axis at a wavelength of 380-800 nm.

6. The liquid crystal system according to claim 1, wherein: r1 and r2 form an angle of 90°±15°: -r0 forms an angle of up to 15° with r1, and the liquid crystal has positive dielectric anisotropy, - or r0 and r1 form an angle of 90°±15°, and the liquid crystal has negative dielectric anisotropy.

7. The liquid crystal optical system according to any one of claims 1 to 2, characterized in that It comprises a static polarizer facing the variable polarizer.

8. The liquid crystal optical system according to any one of claims 1 to 2, characterized in that: The variable polariser and the static polariser or polarisation-sensitive electrically controllable device are separate or connected by a transparent adhesive layer or are characterized in that the variable polariser comprises an element carrying first and second electrodes forming the static polariser.

9. The liquid crystal optical system according to any one of claims 1 to 2, characterized in that: It comprises a polarization-sensitive electrically controllable device facing the variable polarizer.

10. The liquid crystal optical system according to claim 9, wherein: The polarization-sensitive electrically controllable device is a variable-scattering electrically controllable device using nematic liquid crystals containing focal conic domains.

11. The liquid crystal optical system according to claim 10, wherein: The domain is a focal conic domain.

12. The liquid crystal optical system according to claim 11, wherein: The domain is a focal conic domain with two defect lines, one elliptical and the other hyperbolic.

13. The liquid crystal optical system according to claim 11, wherein: The domains are focal conic domains forming a linear network parallel to the direction b.

14. The liquid crystal optical system according to claim 11, wherein: The variable scattering electrically controllable device using liquid crystal comprises an electroactive layer having liquid crystal and a direction b which forms an angle of 0°±15° or 90°±15° with the polarization P1 of the output light in the off state of the variable polarizer.

15. A laminated glazing comprising: - a transparent first additional glass sheet (8), - Thermoplastic laminated middle layer, - a second additional glass or transparent plastic sheet (8'), The main inner faces, called F2 and F3, of the first and second additional sheets are facing, with the liquid crystal optical system according to any of the preceding claims 1 to 14 being between faces F2 and F3.

16. The laminated glazing according to claim 15, wherein A liquid crystal optical system according to any of the preceding claims 1 to 14 in a lamination interlayer.

17. A vehicle glazing carrying a liquid crystal optical system according to any one of the preceding claims 1 to 14.

18. A building window pane carrying a liquid crystal optical system according to any one of claims 1 to 14.

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