EP4214051A1

EP4214051A1 - Laminated liquid crystal glazing and method for producing same

Info

Publication number: EP4214051A1
Application number: EP21785960.2A
Authority: EP
Inventors: Laurent Maillaud; Michael Labrot; Adil JAAFAR
Original assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Current assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Priority date: 2020-09-18
Filing date: 2021-09-15
Publication date: 2023-07-26
Also published as: FR3114267B1; CN114585507A; WO2022058685A1; US20240009970A1; FR3114267A1

Abstract

The invention relates to laminated glazing (1) with liquid crystal variable transmission, comprising a first glass substrate (10) and a second glass substrate (11), at least one liquid crystal cell (2), a first lamination interlayer (30) placed between the first glass substrate (10) and the liquid crystal cell (2), and a second lamination interlayer (40) placed between the second glass substrate (11) and the liquid crystal cell (2), the glazing being characterised in that said first interlayer (30) is a film made of a polymeric material and in that said second interlayer (40) is made of a transparent adhesive material (OCA) that, prior to the manufacture of the glazing, takes the form of a liquid and is crosslinkable.

Description

DESCRIPTION

TITLE: LAMINATED LIQUID CRYSTAL GLAZING AND METHOD OF MANUFACTURING IT

[001] The invention relates to the field of electrically controllable glazing with variable optical properties, and more particularly relates to laminated glazing with variable transmission by liquid crystals.

[002] The invention will apply to all uses, in particular for buildings, such as exterior walls or partitions or other interior glazed surfaces, or for vehicles of the motor vehicle, bus, train, aircraft type. .

[003] A laminated glazing with variable transmission by liquid crystals, comprises at least two main glass substrates, two intermediate films in plastic material for laminating the glass substrates, very often in polyvinyl butyral (PVB), and a liquid crystal cell placed between the two interlayer lamination films. The liquid crystal cell comprises liquid crystals encapsulated between two polymeric encapsulation films which are kept at a constant distance thanks to spacers such as glass beads. Each polymeric encapsulation film is provided with an electrode. When a voltage is applied to the electrodes, the liquid crystals associated with the dyes change orientation and modify the light transmission through the cell, the glazing changing from a clear state to a dark state, or vice versa. “Light state, dark state” means that the glazing has in its light state a light transmission in the visible greater than the light transmission that it has in its dark state. The liquid crystal cell may comprise in combination with the liquid crystals dichroic dyes, and/or polarizers on the outside of its faces. Depending on the intended application, the equilibrium orientation of the liquid crystals interacting with the dichroic dyes when present, the light and dark states will correspond to a power ON/OFF or OFF/ON state. electrodes. We will speak of a normally clear state of the glazing when the light transmission is highest in the absence of voltage between the electrodes (OFF state), therefore allowing vision through the glazing, while the dark state of said glazing will correspond when the electrodes are energized (ON state) causing a reorientation liquid crystals and a change in light transmission (light transmission becoming weaker). Conversely, the normally dark state of a glazing will be spoken of when the light transmission is lowest in the absence of voltage, while by applying a voltage, the glazing will become clear.

[004] The polymeric nature of the cell's encapsulation films, very often made of polyethylene terephthalate (PET) or polycarbonate (PC), makes it easy to laminate the cell with the PVB lamination inserts of the glass substrates.

[005] However, the process for manufacturing laminated glazing, due to the high pressure and temperature used during the laminating steps by using a vacuum bag and an autoclave, can cause local deformations polymeric films for encapsulating the liquid crystal cell, in particular an enlargement of the thickness of the cell, causing a local modification of the orientation of the liquid crystals. This results in an inhomogeneity in light transmission for the glazing, further manifesting itself visibly, by the presence of dark zones on a glazing which is normally light, or conversely the presence of light zones on a glazing which is normally dark. It is sought to avoid this inhomogeneity of light transmission.

[006] Furthermore, the cyclic deformation of the cell, due to the cycles of temperature variation in the use of the glazing, also affects the transparent electrodes with in particular the risk of propagation of cracks, which leads to a fall, or even a loss electrical conductivity and cell dysfunction.

[007] The object of the invention is therefore to overcome the aforementioned drawbacks by proposing a new laminated glazing composition and a new manufacturing process, so as to minimize the risk of deformation of the cell, and to avoid the presence of inhomogeneous zones in light transmission compared to the rest of the glazing, as well as avoiding damage to the electrodes.

[008] According to the invention, the laminated glazing with variable transmission by liquid crystals comprises a first glass substrate and a second glass substrate, at least one liquid crystal cell, as well as a first spacer placed between the first glass substrate and the liquid crystal cell, and a second spacer disposed between the second glass substrate and the liquid crystal cell, the laminated glazing being characterized in that said first spacer is a film of polymeric material and in that said second spacer is made of a transparent adhesive material (also called OCA for "Optical Clear Adhesive" in English) which is in liquid form before the manufacture of the glazing and is capable of being crosslinked.

[009] The expression "before the laminated glazing manufacturing process" means before assembly of all the constituent elements of the glazing.

[010] In the rest of the description, the term "film" means a monolithic element in the form of a manipulable sheet.

[011] The first interlayer is in the form of a polymeric film to be able to be laminated onto a glass substrate. The joining of this polymeric film with the first glass substrate is carried out during the process of laminating the glazing.

[012] The second interlayer is presented before constitution in the laminated glazing in the form of a liquid OCA to be deposited in liquid form between the liquid crystal cell and the second glass substrate, this liquid OCA being capable of being crosslinked for once hardened constitute said second spacer. The crosslinking of the OCA takes place after its deposition, for example by means of polymerization such as ultraviolet radiation. Unlike the first interlayer, the second interlayer is therefore not in the form of a film before it is attached to the second glass substrate.

[013] The liquid crystal cell is in the form of a film extending over all or part of the surface of the glazing. The liquid crystal cell has two opposite faces respectively facing the first and second inserts.

[014] Thus, the liquid crystal cell undergoes the lamination process on only one of its faces to ensure its attachment to the first glass substrate via the first spacer, while its other face is attached to the second glass substrate by an OCA liquid capable of cross-linking/hardening, involving a much less demanding implementation process for the cell. The mechanical stresses of the lamination operation (high temperature and high pressure) are exerted only on one side of the cell, and not on both sides, so that the risk of changing the thickness of the cell is lower , minimizing the risk of the presence of inhomogeneous zones in light transmission on the glazing after manufacture. In addition, the use of a crosslinkable transparent liquid adhesive (OCA) gives it dimensional stability and reduces its deformation under compression when the second glass substrate is added. [015] Advantageously, the liquid crystals can be in the form of a liquid volume of liquid crystals. The liquid volume is trapped in the cavity delimited by the cell encapsulation substrates and a peripheral sealing gasket.

[016] When the liquid crystal cell is without dyes, it comprises two polarizers. The polarizers are then associated with the external faces of the glass encapsulation substrates of the cell (faces opposite to the cavity containing the liquid volume).

[017] The liquid volume of liquid crystals may comprise one or more dichroic dyes. The liquid crystal cell comprising a liquid mixture of liquid crystals in which one or more dichroic dyes are dispersed, is called in the remainder of the description "host-guest" liquid crystal cell, or even "guest-host" liquid crystal cell. » using the English expression.

[018] The liquid crystal cell comprising a guest-host liquid mixture may further comprise one or more polarizers (on one or the outer faces of the cell).

[019] According to one characteristic, said first spacer is based on at least one polymer chosen from the following polymers: polyvinyl butyral (PVB), ethylene vinyl acetate (EVA), polyurethane (PU), polyethylene terephthalate (PET), polyethylene , polycarbonate, polymethylmethacrylate, polyacrylate, polyvinyl chloride, polyacetate resin, acrylate, fluorinated ethylene propylene, polyvinyl fluoride, ethylene tetrafluoroethylene, cyclic olefin copolymer (COC). Preferably, said first interlayer is a film of polyvinyl butyral (PVB), or of ethylene vinyl acetate (EVA), or of polyurethane (PU), or of polyethylene terephthalate (PET).

[020] By using a sheet or film of polymeric material such as PVB as the first spacer, the glazing retains its mechanical strength properties in order in particular to meet certain standards, for example in terms of road safety. In addition, this type of commercially common film is manufactured most often having one or more other functionalities, such as acoustic, anti-reflective, non-stick, anti-scratch, photocatalytic, anti-fingerprint, anti-fog, coloring properties. , etc., which at the same time confers additional properties on the glazing according to the intended use.

[021] The glazing can advantageously comprise one or more ultraviolet filters. In a preferred example, said first interlayer constitutes an ultraviolet filter, the first interlayer is for example PVB filtering ultraviolet rays. In addition to the known advantages of the UV cut-off of a glazing, such a filter extends the life of the liquid crystal glazing, in particular when the liquid crystal cell is a guest-host cell, because it prevents the degradation of dichroic dyes . When there is at least one ultraviolet filtering film placed between the liquid crystal cell and the first glass substrate, said first glass substrate will be intended to face the outside environment if the glazing is intended to be installed in an opening separating an interior from the exterior environment.

[022] If an ultraviolet filter was really needed for the liquid crystal cell on the side of the face associated with the OCA, the OCA will be selected to filter the ultraviolet, the liquid OCA containing for example additives absorbing ultraviolet rays and will be capable of cross-linking other than by ultraviolet radiation.

[023] According to another characteristic, the laminated glazing comprises a superposition of one or more other interlayer films of polymeric material (in addition to the first interlayer), placed between the first glass substrate and the liquid crystal cell, each of the interlayers constituting a film that can be provided with technical functionalities (ultraviolet filter properties or others). These other spacers are secured to the first glass substrate and to the liquid crystal cell by the lamination process.

[024] Advantageously, the laminated glazing comprises a frame made of polymeric material which is arranged all around the liquid crystal cell and in contact with said first spacer, said frame preferably constituting an ultraviolet filter. The frame is arranged between the two spacers of the glazing without protruding from the edge of the glazing. Indeed, it happens that the surface of the liquid crystal cell is only associated with a part of the surface of the glazing. The space existing between the two interlayer films and all around the cell is then compensated for, by arranging a frame (therefore running over the entire peripheral edge of the cell), this frame being in a polymeric material to ensure the lamination. The frame can be in one of the materials mentioned above for the constitution of the intermediate film.

[025] It is advantageously proposed to provide this polymer frame with an additional ultraviolet filter function. This additional UV filter configuration over the entire periphery of the edge of the liquid crystal cell, maximizes protection of the cell against ultraviolet rays, the liquid crystal cell being not only protected on its main face but also on its edge.

[026] This ultraviolet filtering frame configuration is particularly useful when the liquid crystal cell is a guest-host liquid crystal cell therefore containing dyes, so as to protect the dyes against ultraviolet rays. Indeed, the inventors have demonstrated that the degradation of dichroic dyes could take place via the edge of the guest-host cell. Although the edge of the liquid crystal cell represents a minimal surface compared to the main faces of the cell, surprisingly, the impact of ultraviolet rays through the edge of the cell is in fact not negligible. The guest-host liquid crystal cell may be affected during transport of the laminated glazing to its various storage locations before being permanently installed, and even after installation of the laminated glazing depending on the type of use.

[027] Consequently, the frame surrounding the liquid crystal cell, through its additional function of ultraviolet filter, will provide increased protection to the cell, from its integration into the glazing, until the final installation of said glazing, as well as during the use of glazing.

[028] The ultraviolet filter(s) (which may be the first lamination interlayer and/or the polymeric frame and/or the other superimposed interlayer film(s)) are designed so that each filter has a light transmission of at least between 280 nm and 400 nm, in particular has a light transmission at 400 nm which is less than 1%, preferably less than 0.1%, more preferably less than 0.01%. Light transmission is measured according to ISO 13887.

[029] While an ultraviolet filter is effective below 400 nm, ultraviolet absorption is not always effective at 400 nm, at the limit of the visible spectrum. Here, the filter(s) are designed to absorb ultraviolet at 400 nm. A filter absorbing ultraviolet rays at 400 nm will necessarily perform well for radiation below 400 nm.

[030] In addition, the selected ultraviolet filter will preferably be designed so that the ultraviolet absorption particles do not disturb the color of the filter too much, in particular, the filter will be adapted so that its color does not tend towards yellow .

[031] To achieve a light transmission of less than 0.01% for an ultraviolet filter in the form of at least one interlayer film, the laminated glazing may comprise a single interlayer film having this light transmission property of less than 0.01%, or may comprise the combination of a plurality of superimposed interlayer films, the combination making it possible to provide a light transmission of less than 0.01%.

[032] For example, by superimposing two commercial films of ultraviolet-filtering PVB, each of which has a light transmission at 400 nm of less than 1%, the first film constituting the first spacer and the second film constituting an additional spacer, the superposition of the two interlayer films provides a filter whose light transmission at 400 nm manages to be less than 0.01%. The ultraviolet filter therefore has a high performance at 400 nm, and even more so for the range below 400 nm for which the light transmission tends towards zero.

[033] According to another feature, said second insert made of a transparent adhesive material (OCA) is chosen from the following materials, acrylic, polyvinyl acetate (PVA), polyurethane (PU), silicone, and epoxy. The second spacer has in the laminated glazing (after manufacture) a thickness of less than 1 mm, or even less than 0.5 mm.

[034] According to a preferred characteristic, the liquid crystal cell is a liquid crystal cell comprising a liquid volume of liquid crystals. It turns out that during the autoclave lamination process of the cell, the cell undergoes less stress than if the matrix containing the liquid crystals were a solid polymer like the cells of the prior art. In addition, this contributes to minimizing the risk of variation in cell thickness during the lamination process when the cell is autoclaved, and makes it possible to greatly minimize visual defects once the glazing is finished and then during its use, especially when the glazing is curved.

[035]According to yet another feature, the laminated glazing may comprise two liquid crystal cells, optionally of different types. When the laminated glazing comprises two liquid crystal cells, at least one of them is a cell comprising a liquid volume of liquid crystals mixed with dichroic dyes, the other liquid crystal cell being a liquid crystal system in in which the volume of liquid crystals is not in liquid form, such as a polymer-dispersed liquid crystal system "PDLC" (for Polymer-Dispersed Liquid Crystal, in English where the liquid crystals are dispersed in a polymer matrix), or a crystal system cholesteric liquids “CLC” (for Cholesteric Liquid Crystal in English), or else a polymer network liquid crystal system “PNLC” (for Polymer Network Liquid Crystal in English).

[036] When the laminated glazing comprises two liquid crystal cells, the two liquid crystal cells are coupled together by an adhesive material. If the two cells are coupled together before lamination, it is the combination of the two which will be laminated with the first glass substrate via the first polymeric interlayer. If the second cell is coupled after the lamination of the first cell, the second cell will be attached by bonding to the first cell, for example by an OCA which may be of the same nature as the bonding OCA used to make the second substrate integral glassmaker. The combination of two cells will notably make it possible to provide a more intense dark state.

[037] When the laminated glazing additionally comprises a liquid crystal system other than a liquid crystal cell, the volume of liquid crystals of which is in liquid form, in particular a PDLC film, said system will be made integral by the process of lamination or will be attached by gluing. Thus, said other liquid crystal system will be arranged and secured by lamination between the liquid crystal cell and the first spacer, or else will be secured to the liquid crystal cell by an adhesive layer on the side opposite the first spacer.

[038] When said other liquid crystal system is laminated between the first interlayer and an additional interlayer, the first interlayer and the additional interlayer will be ultraviolet filters, which will further protect the guest-host liquid crystal cell comprising dyes .

[039] Said other liquid crystal system, in particular the PDLC film, can advantageously provide a function of variation of the light diffusion to the glazing. When the glazing is notably dark, the dark aspect will be more intense, associated with a greater variation in light transmission.

[040] Said other liquid crystal system, in particular the PDLC film, may be powered up concomitantly or not with the powering up of the liquid crystal cell. The control of said other liquid crystal system may be independent of that of the liquid crystal cell. [041] Furthermore, the laminated glazing may comprise at least one functional infrared protection layer, the functional layer being arranged inside the laminated glazing, for example applied to the internal face of the first glass substrate and/or of the second substrate glass, and/or the first spacer, or consists of the first spacer, and/or consists of another spacer integral with the first spacer. This infrared protection layer will be particularly useful for reflecting infrared so as not to heat the liquid crystal cell. Indeed, too high a temperature would affect the proper functioning of the liquid crystals with the risk of phase transition. In addition, the risk of propagation of cracks (linked to cycles of deformation due to cycles of temperature variation in the position of use of the glazing) at the level of the electrodes of the liquid crystal cell is also minimized.

[042] In a particular example of application, the laminated glazing comprises an infrared protection layer on the internal face of the first glass substrate (face 2 of the glazing, in the installed position of the glazing in contact with the external environment - face 1 of the glazing being by convention the face in contact with the external environment) to protect the cell from infrared radiation coming from the outside, an ultraviolet filter consisting of the first lamination insert with the first glass substrate, preferably the insert being a PVB film and which can be tinted, and a low emissive layer on the external face of the second glass substrate (face 4 of the glazing) which is intended to reflect the long wavelength infrared coming from the interior of a passenger compartment or an interior room.

[043] The laminated glazing may include other functionalities, which are added via coatings in direct contact with the glass substrates and/or the first interlayer and/an additional interlayer associated with the first interlayer or with one of the first and second glass substrates, and/or consisting of the first spacer and/or consisting of an additional spacer associated with the first spacer or with one of the first and second glass substrates. These various functionalities are, for example, acoustic, anti-reflective, non-adhesive, anti-scratch, photocatalytic, anti-fingerprint, anti-fog, coloring, etc. properties.

[044] When an additional spacer is added to the laminated glazing, this spacer can be made integral during lamination when it is between the first glass substrate and liquid crystal cell; when the additional spacer is arranged between the liquid crystal cell and the second glass substrate, it will be attached by gluing or will have been pre-laminated with the second glass substrate.

[045] As regards the liquid crystal cell, the latter comprises substrates for encapsulating the volume of liquid crystals, said encapsulating substrates being polymeric or glass. If usually, the encapsulation substrates are made of polymeric material, the inventors propose a new form of encapsulation by ultra-thin glass substrates, in particular when the liquid crystal cell presents its volume of liquid crystals in liquid form, in optionally comprising one or more dichroic dyes.

[046] In the case of glass encapsulation substrates, these are ultra-thin making the cell flexible like a film to easily handle it and laminate it, in particular with the main glass substrates of the glazing when these are curved . The inventors have unexpectedly demonstrated that the liquid crystal cell made from glass encapsulation substrates rather than plastic encapsulation films is much less subject to a local variation in thickness during the process. of lamination, all the more so when the volume of liquid crystals is liquid. The glazing remains uniform in color, no colored spots appearing.

[047] In addition, the inventors have unexpectedly demonstrated that the use of a liquid crystal cell made from encapsulating glass substrates (in particular when the encapsulated volume of liquid crystals is liquid), is particularly effective in the manufacture of curved laminated glazing; no inhomogeneous zone in terms of light transmission is detected in the curved laminated glazing.

[048] Even more particularly, the inventors have unexpectedly demonstrated that the use of chemically tempered glass encapsulation substrates even better avoids the risk of cell thickness variation during the lamination process. Thus, preferably, each of the glass encapsulation substrates of the liquid crystal cell is made of chemically tempered glass.

[049] According to one characteristic, each of the glass encapsulation substrates of the liquid crystal cell has a thickness such that the liquid crystal cell constitutes a flexible film, that is to say which conforms at room temperature to the shape of the surface on which said flexible film/said cell is deposited.

[050] In particular, each of the glass encapsulation substrates of the liquid crystal cell has a minimum radius of curvature which is of the order of 600 mm and can even reach 200 mm.

[051] Each of the glass encapsulation substrates of the liquid crystal cell has a thickness of less than 1000 μm, in particular between 25 μm and 700 μm, preferably a thickness of less than 300 μm, or even less than 100 μm.

[052] The laminated glazing of the invention can constitute a building or vehicle glazing, in particular a vehicle chosen from among an automobile, a train, a truck, an aircraft, a bus, a military vehicle.

[053] In the case of vehicle glazing, the laminated glazing is in particular chosen from a roof glazing, a rear window, a side window, a windshield, and a gradient strip of the part top of the windshield.

[054] The laminated glazing can be flat or curved.

[055] Laminated glazing can be used in double glazing or in triple glazing.

[056] The invention also relates to a method of manufacturing the aforementioned laminated glazing of the invention, the steps of which are as follows: positioning on a support surface such as a counter-glass, which is covered with a non-stick coating such as PTFE, the liquid crystal cell, preferably the liquid crystal cell consisting of a liquid mixture (volume) of liquid crystals and optionally at least one dichroic dye, and arranging if necessary a frame surrounding the liquid crystal cell, then position the first spacer in the form of a film of polymeric material, possibly other elements to be laminated (such as a PDLC system and an additional spacer film), and lastly the first substrate glassmaker, so as to form a stack; carry out the operation of laminating the stack to form a laminated assembly; the operation is well known per se, preferably with the placement of the entire stack in a vacuum bag (instead of implementing a stack calendering operation to expel the air) and autoclaving; removing the support surface (the back glass) from the laminated assembly which is composed of the first glass substrate, the first spacer, the liquid crystal cell and possibly the frame; arranging the liquid OCA between the second glass substrate and the laminated assembly on the side of the liquid crystal cell; cross-link the liquid OCA to obtain the laminated glazing.

[057] Consequently, the method only implements the laminating operation on one side of the cell, minimizing the risk of variation in its thickness. Once the counter glass has been removed, the liquid crystal cell relaxes and any spots of inhomogeneous light transmission disappear. In addition, the deposition on the other face of the cell of a liquid material will avoid deformation in thickness on the side of this face and will confer surface flatness at the interface between this other face of the cell and the second glass substrate . Laminated glazing (in the sense of a stack of material) will present less risk of inhomogeneity in light transmission.

[058] The frame made of polymeric material can be attached around the liquid crystal cell once the latter has been deposited on the first spacer. As a variant, the frame may already be integral with the contour of the liquid crystal cell, the cell and the frame forming a one-piece assembly which is deposited on the first spacer.

[059] The present invention is now described using only illustrative examples and in no way limiting the scope of the invention, and from the accompanying illustrations, in which:

[060] [Fig. 1] or FIG. 1 represents a schematic view in side section of a first embodiment of a laminated glazing according to the invention.

[061] [Fig.2] or Figure 2 shows a schematic top view of the laminated glazing of Figure 1.

[062] [Fig. 3] or FIG. 3 represents a schematic view in side section of a second embodiment of a laminated glazing according to the invention.

[063] [Fig. 4] or figure 4 is a schematic detail view of the guest-host cell of the example embodiments of figures 1 and 3.

[064] [Fig. 5] or Figure 5 is a schematic view of the steps of the manufacturing process according to the invention for obtaining the laminated glazing of Figure 1. [065] For the sake of clarity, the various elements shown in the figures are not necessarily reproduced to scale.

[066] The laminated glazing 1 of the invention illustrated in Figure 1 is a laminated glazing with variable transmission by liquid crystals comprising a liquid crystal cell 2.

[067] The laminated glazing 1 is intended for a building application or a vehicle application. The laminated glazing 1 sees its light transmission modified when an electric voltage is applied to the electrodes of the liquid crystal cell 2. The glazing 1 can be normally clear (of high light transmission, such as of the order of 70%) in l absence of voltage, and it becomes dark (of low light transmission, such as of the order of 25%), by applying a voltage. Conversely, the glazing can be designed as normally dark, off; it then becomes clear by applying a voltage. The normally light or normally dark state depends on the use of the glazing. In its clear state, the glazing may or may not have a colored appearance depending on the intended application (glass substrate(s) and/or interlayer film(s), or even the liquid crystal cell, which can be tinted ).

[068] The laminated glazing 1 of the first example illustrated in FIG. 1 comprises: a first glass substrate 10; a second glass substrate 11 arranged at a distance and opposite the first substrate 10; the liquid crystal cell 2, arranged at the heart of the glazing and having two opposite main faces 20 and 21; a first interlayer 30 for lamination between the first substrate 10 and one of the main faces 20 of the cell 2; a second spacer 40 which makes it possible to make the second substrate 11 integral with the opposite main face 21 of the cell 2, by a process other than the lamination process.

[069] The liquid crystal cell 2 is surrounded by a frame 5. The frame 5 is for example made of PVB or epoxy resin. As visible in Figure 2, when the liquid crystal cell 2 does not extend over the entire surface of the glazing, the frame 5 serves as a spacer of the same thickness as that of the liquid crystal cell 2, to fill the empty space which would otherwise exist between the two spacers 30 and 40. [070] Depending on the uses made of the laminated glazing 1 described below with reference to the figures or in envisaged variants not shown, the laminated glazing will be used in a single piece as is, or will be combined with one or other glass substrates in laminated with the first substrate, or to one or more glass substrates spaced from the first substrate and/or from the second substrate.

[071] In the second embodiment illustrated in Figure 3, the laminated glazing 1 comprises between the liquid crystal cell 2 and the first glass substrate 10, another liquid crystal system 6, such as a PDLC, laminated between the first spacer 30 and an additional spacer 31, the latter being laminated with the first substrate 10. On the opposite face 21 of the liquid crystal cell 2, as for FIG. 1, the second spacer 40 makes it possible to make the second substrate glass 11 of said opposite face 21 of cell 2, without a lamination process.

[072] The glass substrates 10 and 11 have a thickness suitable for the use of laminated glazing. The thickness may be between 0.3 mm and 15 mm, preferably between 1 to 5 mm; it is for example 1.6 mm, 1.8 mm or 2.1 mm.

[073] The lamination inserts 30 and 31 are films made of polymeric material such as PVB. They have in particular a thickness of between 0.07 mm and 2 mm, in particular is 0.38 mm or 0.76 mm.

[074] The lamination inserts 30 and 31 and/or the glass substrates 10 and 11 may have technical features such as ultraviolet cut-off, infrared protection, acoustic properties, anti-reflective, anti-adhesive, anti-scratch, photocatalytic, anti -fingerprints, anti-fog, staining.

[075] The liquid crystal cell 2 is preferably a liquid crystal cell comprising a liquid volume of liquid crystals. In the present example, the liquid crystal cell is a guest-host liquid crystal cell comprising a liquid volume 22 of liquid crystals mixed with at least one dichroic dye. As illustrated in Figure 4, the liquid crystal cell 2 comprises the liquid mixture 22, two alignment layers 23 and 24, two electrodes 25 and 26, two glass encapsulation substrates T1 and 28, and a sealing gasket 29. The two glass encapsulation substrates T1 and 28 are kept spaced apart by glass spacers, not shown, and form with the seal 29 a cavity accommodating the liquid volume 22 with liquid crystals. The tightness of the edge of the cell is made by the peripheral sealing joint 29, for example in epoxy resin or silicone. The spacers are arranged throughout the cavity and preferably also the sealing joint. The inner surface facing the cavity of each of the two encapsulation substrates T1 and 28 is covered with electrode 25, 26 respectively, for example made of ITO, itself covered with alignment layer 23, 24 respectively. , the alignment layers 23 and 24 being in contact with the liquid volume 22. The liquid crystal cell 2 has a total thickness of between 250 and 350 μm. The height of the cavity corresponds to the height of the spacers, the cavity having a height in particular of the order of 10 μm.

[076] The two encapsulation substrates T1 and 28 of the liquid crystal cell 2 are made of thin glass. Preferably, they are made of chemically tempered glass. Each of the glass encapsulation substrates T1, 28 has a thickness of less than 1000 μm, in particular between 25 μm and 700 μm, preferably a thickness of less than 300 μm, or even less than 100 μm. The glass thickness of each encapsulation substrate is sufficiently thin to provide the liquid crystal cell with film-like flexibility when it comes to associating the cell with the glass substrates 10 and 11, especially when they are curved. In particular, the glass thickness of each glass encapsulation substrate T1, 28 is such that each glass encapsulation substrate has a minimum radius of curvature which is at least of the order of 600 mm and can even reach 200mm.

[077] The inventors have demonstrated that when the method of laminating the cell 2, and the first glass substrate 10 by the intermediate film of polymeric material 30 or 31, is implemented using a liquid crystal cell whose encapsulation substrates T1 and 28 are made of thin glass (and not of plastic material), this minimizes the risk of deformation as the cell increases in thickness, avoiding damage to the electrodes and an inhomogeneous appearance of light transmission once the glazing totally finished assembling.

[078] If the first spacer 30 is a polymeric film making it possible to make the liquid crystal cell 2 integral with the first substrate by lamination, the second spacer 40 is made of a transparent adhesive material to avoid subjecting the steps of the method of lamination to the other face 21 of the liquid crystal cell to be secured to the second glass substrate 11. The second interlayer is a liquid OCA which is capable of being crosslinked once deposited by a liquid route and covered with the second substrate. OCA becomes hard by means of polymerization such as ultraviolet radiation. The OCA is for example an acrylic resin.

[079] Furthermore, the laminated glazing 1 with liquid crystals of the invention is preferably designed to protect the liquid crystal cell 2 from ultraviolet radiation, thanks to one or more ultraviolet filters. The protection will be provided at least on one of the main faces of the cell, face which will correspond to that facing the outside environment when the laminated glazing 1 is used in an opening giving onto the outside. Preferably, protection against ultraviolet radiation will be established in a complementary manner on the other main face of cell 2 and/or at the edge of cell 2.

[080] In the examples of Figures 1 and 2, at least the lamination inserts 30 and 31 are films of polymeric material filtering ultraviolet rays, and this not only below 400 nm but also at 400 nm. The ultraviolet cutoff property is provided for example by particles embedded in the film, which are capable of blocking ultraviolet rays and which do not diffuse in visible radiation. Advantageously, an ultraviolet film has a light transmission at least between 280 nm and 400 nm, in particular a light transmission at 400 nm, which is less than 1%, preferably less than 0.1%, even more preferably less than 0, 01%.

[081] In addition, to ensure protection of the liquid crystal cell 2 against ultraviolet at its edge, the frame 5 also constitutes an ultraviolet filter. Frame 5 also has a light transmission at least between 280 nm and 400 nm, in particular a light transmission at 400 nm, which is less than 1%, preferably less than 0.1%, even more preferably less than 0, 01%.

[082] The method of manufacturing the laminated glazing 1 of Figure 1 is now described with reference to Figure 5:

The first step (Step 1) consists in positioning on a support surface 7, such as counter-glass, which is covered with a non-stick coating 70 such as PTFE, for example, the liquid crystal cell 2 and possibly arranging the frame 5 around the liquid crystal cell, then the first spacer 30 made of polymer material such as a PVB film, possibly other elements to laminate (such as the PDLC system 6 and the additional interlayer film 31 of the example of FIG. 3), and finally the first glass substrate 10 so as to form a stack. The stack having been placed in a vacuum bag, it then undergoes the lamination operation to form a laminated assembly 1'.

The second step (Step 2) consists in removing the back glass 7 from the laminated assembly which is composed of the first glass substrate 10, the first spacer 30, the liquid crystal cell 2 and possibly the frame 5.

The third step (Step 3) consists in arranging the liquid OCA between the second glass substrate 11 and the laminated assembly 1′ on the side of the liquid crystal cell 2, then in cross-linking the liquid OCA to obtain the second interlayer 40 and laminated glazing 1.

[083] The way in which the liquid OCA hardens depends on its nature, certain OCAs crosslinking in particular by means of polymerization such as ultraviolet radiation or another input of energy, for example by heating, and others crosslinking with room temperature with the addition of a hardener.

[084] The support surface 7 could be an inflatable membrane.

[085] When a frame 5 is necessary, the frame 5 is for example made of PVB and arranged all around the liquid crystal cell 2. As a variant, the frame 5 can be obtained by depositing a sealing barrier such as a adhesive on and at the edge of the back glass, and by depositing a liquid OCA between the cell and the barrier, then by curing the OCA. Still as a variant, the frame 5 can already be integral with the liquid crystal cell 2 when it is supplied.

[086] In a first non-limiting example of step 3, this step consists of depositing liquid OCA on the second glass substrate 11, then depositing the laminated assembly 1′ on the side of the crystal cell liquids 2, and finally cross-linking the OCA to thus form the second spacer 40, and obtain the laminated glazing 1 of the invention.

[087] In a second non-limiting example of step 3, the second glass substrate 11 is kept spaced apart from the laminated assembly 1′ to provide a cavity intended to be filled with the liquid OCA, the crystal cell liquids 2 facing said second glass substrate 11. The spacing and sealing are obtained by a peripheral seal comprising spacers whose height corresponds to the height of liquid OCA to be injected. One or more openings are made in the sealing joint in order to introduce the liquid OCA through them by injection until it occupies the entire cavity between the second glass substrate 11 and the liquid crystal cell 2. To accelerate the filling process, it is possible to provide vacuum extraction through an opening opposite the injection opening(s). Then, the OCA is hardened to obtain the laminated glazing 1 of the invention.

Claims

CLAIMS Laminated glazing (1) with variable transmission by liquid crystals comprising a first glass substrate (10) and a second glass substrate (11), at least one liquid crystal cell (2), as well as a first spacer (30) arranged between the first glass substrate (10) and the liquid crystal cell (2), and a second insert (40) placed between the second glass substrate (11) and the liquid crystal cell (2), characterized in that the said first spacer (30) is a film of polymeric material and in that said second spacer (40) is made of a transparent adhesive material (OCA) which is in liquid form before the manufacture of the glazing and which is capable of being crosslinked. Laminated glazing according to Claim 1, characterized in that the said first insert (30) is based on at least one polymer chosen from the following polymers: polyvinyl butyral (PVB), ethylene vinyl acetate (EVA), polyurethane (PU), polyethylene terephthalate (PET), polyethylene, polycarbonate, polymethylmethacrylate, polyacrylate, polyvinyl chloride, polyacetate resin, acrylate, fluorinated ethylene propylene, polyvinyl fluoride, ethylene tetrafluoroethylene, cyclic olefin copolymer (COC), preferably said first spacer is a film of polyvinyl butyral (PVB), or ethylene vinyl acetate (EVA), or polyurethane (PU), or polyethylene terephthalate (PET). Laminated glazing according to Claim 1 or 2, characterized in that the said first interlayer (30) constitutes an ultraviolet filter. Laminated glazing according to Claim 1 or 2, characterized in that it comprises a superposition of one or more other interlayer films of polymeric material, placed between the first glass substrate and the liquid-crystal cell, each of the interlayers constituting a film that can be equipped with technical features. Laminated glazing according to any one of the preceding claims, characterized in that it comprises a frame (5) of polymeric material which is arranged all around the liquid crystal cell (2) and in contact with the said first spacer (30) , said frame (5) preferably constituting an ultraviolet filter. Laminated glazing according to any one of the preceding claims, characterized in that the said second interlayer (40) made of an OCA is chosen from the following materials, acrylic, polyvinyl acetate, polyurethane, silicone, and epoxy. Laminated glazing according to any one of the preceding claims, characterized in that it comprises two liquid crystal cells, at least one of them being a cell comprising a liquid volume of liquid crystals mixed with dichroic dyes, the the other liquid crystal cell being a liquid crystal system in which the volume of liquid crystals is not in liquid form, such as a polymeric dispersed liquid crystal "PDLC" system or a cholesteric liquid crystal "CLC" system or even a polymer network liquid crystal system “PNLC”. Laminated glazing according to any one of the preceding claims, characterized in that it comprises at least one functional infrared protection layer, the functional layer being arranged inside the laminated glazing. Laminated glazing according to any one of the preceding claims, characterized in that the liquid crystal cell (2) comprises encapsulation substrates (27, 28) of the volume of liquid crystals, said encapsulation substrates (27, 28) being polymeric or glass. Process for manufacturing laminated glazing according to any one of the preceding claims, characterized in that it comprises the following steps: positioning on a support surface (7) covered with a non-stick coating (70), the cell to liquid crystals (2) and arranging if necessary a frame (5) surrounding the liquid crystal cell (2), then positioning the first spacer (30) made of polymeric material, possibly other elements to be laminated, and finally the first substrate glassmaker (10); carry out the laminating operation to form a laminated assembly (1'); removing the support surface (7) from the laminated assembly (1'); arranging the liquid OCA between the second glass substrate (11) and the laminated assembly (1') on the side of the liquid crystal cell (2); to cross-link the liquid OCA to obtain the laminated glazing (1). Manufacturing process according to the preceding claim, characterized in that the steps of arranging the liquid OCA and cross-linking, consist in depositing liquid OCA on the second glass substrate (11), then in depositing the laminated assembly (1') on the side of the liquid crystal cell (2), and finally cross-linking the OCA to thus form the second spacer (40). Manufacturing process according to Claim 10, characterized in that the steps of arranging the liquid OCA and of crosslinking consist in keeping the second glass substrate (11) spaced with respect to the laminated assembly (1') in order to a cavity intended to be filled with the liquid OCA, the liquid crystal cell (2) facing said second glass substrate (11), the spacing and sealing being obtained by a peripheral seal comprising spacers, arranging one or more openings in the sealing joint in order to introduce the liquid OCA therethrough by injection until it occupies the entire cavity between the second glass substrate (11) and the crystal cell liquids (2), and finally to cross-link the OCA to thus form the second spacer (40).