LAMINATED LIQUID CRYSTAL GLAZING AND METHOD FOR PRODUCING SAME

Abstract

A 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 interlayer (30) placed between the first glass substrate (10) and the liquid crystal cell (2), and a second interlayer (40) placed between the second glass substrate (11) and the liquid crystal cell (2), characterized 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 is in the form of a liquid, prior to the manufacture of the glazing, and is crosslinkable.

Claims

1. A laminated glazing with liquid crystal variable transmission, comprising a first glass substrate and a second glass substrate, at least one liquid crystal cell, a first interlayer placed between the first glass substrate and the liquid crystal cell, and a second interlayer placed between the second glass substrate and the liquid crystal cell, wherein said first interlayer is a film made of a polymeric material and in that said second interlayer is made of a transparent adhesive material (OCA) that is in the form of a liquid prior to the manufacture of the glazing and is crosslinkable.

2. The laminated glazing according to claim 1, wherein said first interlayer is based on at least one polymer selected from the following polymers: polyvinyl butyral (PVB), ethylene-vinyl acetate (EVA), polyurethane (PU), polyethylene terephthalate (PET), polyethylene, polycarbonate, polymethyl methacrylate, polyacrylate, polyvinyl chloride, polyacetate resin, acrylate, fluorinated ethylene propylene, polyvinyl fluoride, ethylene tetrafluoroethylene, and cyclic olefin copolymer (COC).

3. The laminated glazing according to claim 1, wherein said first interlayer constitutes an ultraviolet filter.

4. The laminated glazing according to claim 1, wherein it comprises a superposition of one or more other interlayer films made of polymeric material, placed between the first glass substrate and the liquid crystal cell, each of the interlayers constituting a film which may be provided with technical functionalities.

5. The laminated glazing according to claim 1, wherein it comprises a frame made of polymeric material which is arranged all around the liquid crystal cell and in contact with said first interlayer said frame preferably constituting an ultraviolet filter.

6. The laminated glazing according to claim 1, wherein said second interlayer made of an OCA is selected from the following materials: acrylic, polyvinyl acetate, polyurethane, silicone and epoxy.

7. The laminated glazing according to claim 1, wherein 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 other liquid crystal cell being a liquid crystal system wherein the volume of liquid crystals is not in liquid form.

8. The laminated glazing according to claim 1, wherein it comprises at least one functional infrared protection layer, the functional layer being arranged inside the laminated glazing.

9. The laminated glazing according to claim 1, wherein the liquid crystal cell comprises substrates for the encapsulation of the liquid crystal volume, said encapsulation substrates being polymeric or glass-based.

10. A process for the manufacture of a laminated glazing according to claim 1, comprising: positioning, on a support surface coated with a non-stick coating, the liquid crystal cell, and, optionally, arranging a frame surrounding the liquid crystal cell, then positioning the first interlayer made of polymeric material, optionally other elements to be laminated, and finally the first glass substrate; carrying out the lamination operation in order to form a laminated assembly; removing the support surface from the laminated assembly; arranging the liquid OCA between the second glass substrate and the laminated assembly on the side of the liquid crystal cell; crosslinking the liquid OCA to obtain the laminated glazing.

11. The manufacturing process according to claim 10, wherein the arranging the liquid OCA and crosslinking consist in depositing liquid OCA on the second glass substrate then in depositing the laminated assembly thereon, on the side of the liquid crystal cell, and finally in crosslinking the OCA in order to form the second interlayer.

12. The manufacturing process according to claim 10, wherein the arranging the liquid OCA and crosslinking consist in keeping the second glass substrate spaced apart from the laminated assembly in order to form a cavity intended to be filled with the liquid OCA, the liquid crystal cell facing said second glass substrate, the spacing and the leak-tightness being obtained by a peripheral seal comprising spacers, in making one or more openings in the seal in order to introduce the liquid OCA by injection through said openings until it fills the whole cavity between the second glass substrate and the liquid crystal cell, and finally in crosslinking the OCA in order thus to form the second interlayer.

Description

[0065] FIG. 1 depicts a schematic lateral sectional view of a first exemplary embodiment of a laminated glazing according to the invention.

[0066] FIG. 2 depicts a schematic plan view of the laminated glazing of FIG. 1.

[0067] FIG. 3 depicts a schematic lateral sectional view of a second exemplary embodiment of a laminated glazing according to the invention.

[0068] FIG. 4 is a schematic detail view of the guest-host cell of the exemplary embodiments of FIGS. 1 and 3.

[0069] FIG. 5 is a schematic view of the steps of the manufacturing process according to the invention for obtaining the laminated glazing of FIG. 1.

[0070] For the sake of clarity, the various elements depicted in the figures are not necessarily reproduced to scale.

[0071] The laminated glazing 1 of the invention illustrated in FIG. 1 is a liquid crystal variable transmission laminated glazing comprising a liquid crystal cell 2.

[0072] The laminated glazing 1 is intended for an application in construction or an application in vehicles. The light transmission of the laminated glazing 1 is modified when an electric voltage is applied to the electrodes of the liquid crystal cell 2. The glazing 1 may be normally light (high light transmission, such as approximately 70%) in the absence of voltage, and become dark (low light transmission, such as approximately 25%) by applying a voltage. Conversely, the glazing can be designed to be normally dark when not powered; it then becomes light by applying a voltage. The normally light or normally dark state is based on the use of the glazing. In the light state thereof, the glazing may have a colored or colorless appearance depending on the targeted application (glass substrate(s) and/or interlayer film(s), or even the liquid crystal cell, possibly being tinted).

[0073] The laminated glazing 1 of the first example illustrated in FIG. 1 comprises: [0074] a first glass substrate 10; [0075] a second glass substrate 11 arranged at a distance from, and opposite, the first substrate 10; [0076] the liquid crystal cell 2, arranged at the core of the glazing and having two main opposing faces 20 and 21; [0077] a first lamination interlayer 30 between the first substrate 10 and one of the main faces 20 of the cell 2; [0078] a second interlayer 40 which makes it possible to secure the second substrate 11 and the opposite main face 21 of the cell 2, by a process other than the lamination process.

[0079] The liquid crystal cell 2 is surrounded by a frame 5. The frame 5 is for example made of PVB or epoxy resin. As can be seen in FIG. 2, when the liquid crystal cell 2 does not extend over the whole surface of the glazing, the frame 5 serves as a spacer of the same thickness as that of the liquid crystal cell 2, in order to fill the empty space which would otherwise exist between the two interlayers 30 and 40.

[0080] Depending on the uses made of the laminated glazing 1 described below with regard to the figures or in envisioned variants (not shown), the laminated glazing will be employed as is in a one-piece manner, or will be combined with one or other glass substrates in a laminate with the first substrate, or with one or other glass substrates spaced apart from the first substrate and/or from the second substrate.

[0081] In the second exemplary embodiment illustrated in FIG. 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 interlayer 30 and an additional interlayer 31, the latter being laminated with the first substrate 10. On the opposite face 21 of the liquid crystal cell 2, like for FIG. 1, the second interlayer 40 makes it possible to secure the second glass substrate 11 of said opposite face 21 of the cell 2, without a lamination process.

[0082] The glass substrates 10 and 11 have a thickness which is suited to the use of the 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.

[0083] The lamination interlayers 30 and 31 are films made of polymeric material such as PVB. In particular, they have a thickness of between 0.07 mm and 2 mm, in particular is 0.38 mm or 0.76 mm.

[0084] The lamination interlayers 30 and 31 and/or the glass substrates 10 and 11 may have technical functionalities, such as ultraviolet blocking, infrared protection, acoustic, anti-reflective, non-stick, scratch-proof, photocatalytic, anti-fingerprint, anti-fog, coloring properties.

[0085] 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 shown in FIG. 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 27 and 28, and a seal 29. The two glass encapsulation substrates 27 and 28 are kept spaced apart by glass spacers (not shown) and form, with the seal 29, a cavity which accommodates the liquid crystal liquid volume 22. The leak-tightness of the edge face of the cell is produced by the peripheral seal 29, for example made of epoxy resin or silicone. The spacers are arranged throughout the cavity and preferentially also the seal. The inner surface facing the cavity of each of the two encapsulation substrates 27 and 28 is coated by the electrode 25, respectively 26, made of ITO, itself coated by the alignment layer 23, respectively 24, 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 m. The height of the cavity corresponds to the height of the spacers, the cavity having a height in particular of approximately 10 m.

[0086] The two encapsulation substrates 27 and 28 of the liquid crystal cell 2 are made of thin glass. They are preferably made of chemically tempered glass. Each of the glass encapsulation substrates 27, 28 has a thickness of less than 1000 m, in particular of between 25 m and 700 m, preferably a thickness of less than 300 m, or even of less than 100 m. The glass thickness of each encapsulation substrate is thin enough to afford the liquid crystal cell flexibility in the manner of a film when it is required to associate the cell to the glass substrates 10 and 11, all the more so when the latter are curved. In particular, the glass thickness of each glass encapsulation substrate 27, 28 is such that each glass encapsulation substrate has a minimal radius of curvature which is at least approximately 600 mm and may even reach 200 mm.

[0087] The inventors have demonstrated that, when the process for lamination of the cell 2 and of the first glass substrate 10 by the interlayer film made of polymeric material 30 or 31 is implemented using a liquid crystal cell, the encapsulation substrates 27 and 28 of which are made of thin glass (and not plastic material), this minimizes the risk of deformation when increasing the thickness of the cell, preventing damage to the electrodes and an inhomogeneous light transmission appearance once the glazing has finished being entirely assembled.

[0088] If the first interlayer 30 is a polymeric film, making it possible to secure the liquid crystal cell 2 to the first substrate by lamination, the second interlayer 40 is made of a transparent adhesive material in order to avoid having to subject the other face 21 of the liquid crystal cell, which has to be secured to the second glass substrate 11, to the steps of the lamination process. The second interlayer is a liquid OCA which is able to be crosslinked once deposited by a liquid route and coated with the second substrate. The OCA cures by polymerization means such as ultraviolet radiation. The OCA is for example an acrylic resin.

[0089] Furthermore, the laminated glazing 1 containing liquid crystals of the invention is preferably designed to protect the liquid crystal cell 2 from ultraviolet radiation, by virtue of one or more ultraviolet filters. The protection will be provided at least on one of the main faces of the cell, which face will correspond to that facing the exterior environment when the laminated glazing 1 is used in an opening which opens out to the outside. Preferably, the protection against ultraviolet radiation will be provided complementarily on the other main face of the cell 2 and/or at the edge face of the cell 2.

[0090] In the examples of FIGS. 1 and 2, at least the lamination interlayers 30 and 31 are films made of polymeric material which filters ultraviolet rays, not only below 400 nm but also at 400 nm. The ultraviolet blocking property is provided for example by particles embedded in the film which are able to block ultraviolet rays and which do not scatter in the visible radiation range. 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%, more preferably still less than 0.01%.

[0091] Moreover, in order to ensure protection of the liquid crystal cell 2 against ultraviolet rays at its edge face, the frame 5 also constitutes an ultraviolet filter. The 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%, more preferably still less than 0.01%.

[0092] The process for manufacturing the laminated glazing 1 of FIG. 1 is now described with regard to FIG. 5: [0093] The first step (Step 1) consists in positioning, on a support surface 7 such as a counter-glass, which is coated with a non-stick coating 70, for example made of PTFE, the liquid crystal cell 2 and optionally arranging the frame 5 around the liquid crystal cell, then the first interlayer 30 made of polymeric material, such as a PVB film, optionally other elements to be laminated (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. With the stack having been placed in a vacuum bag, it then undergoes the lamination operation to form a laminated assembly 1. [0094] The second step (Step 2) consists in removing the counter-glass 7 from the laminated assembly which is composed of the first glass substrate 10, the first interlayer 30, the liquid crystal cell 2 and optionally the frame 5. [0095] 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 crosslinking the liquid OCA to obtain the second interlayer 40 and the laminated glazing 1.

[0096] The way in which the liquid OCA cures depends on its nature, with some OCAs crosslinking in particular by polymerization means such as ultraviolet radiation or some other energy supply, for example by heating, and others crosslinking at ambient temperature with the addition of a curing agent.

[0097] The support surface 7 may be an inflatable membrane.

[0098] 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 leak-tight barrier such as an adhesive on and at the edge of the counter-glass, and by depositing a liquid OCA between the cell and the barrier, then by curing the OCA. As yet another variant, the frame 5 may already be secured to the liquid crystal cell 2 when it is supplied.

[0099] In a first nonlimiting example of step 3, this step consists in depositing liquid OCA on the second glass substrate 11, then in depositing the laminated assembly 1 thereon, on the side of the liquid crystal cell 2, and finally in crosslinking the OCA in order thus to form the second interlayer 40 and to obtain the laminated glazing 1 according to the invention.

[0100] In a second nonlimiting example of step 3, the second glass substrate 11 is kept spaced apart from the laminated assembly 1 in order to form a cavity intended to be filled with the liquid OCA, the liquid crystal cell 2 facing said second glass substrate 11. The spacing and the leak-tightness are obtained by a peripheral seal comprising spacers, the height of which corresponds to the height of liquid OCA to be injected. One or more openings are made in the seal in order to introduce the liquid OCA by injection through said openings until it fills the whole cavity between the second glass substrate 11 and the liquid crystal cell 2. In order to accelerate the filling process, it is possible to provide vacuum suction through an opening opposite the injection opening(s). The OCA is then cured to obtain the laminated glazing 1 of the invention.