Electrically controllable device having variable diffusion by liquid crystals, and method for same

Abstract

A device having scattering which can be varied by liquid crystals includes a stack with a first electrode, an electroactive layer with the liquid crystals being stabilized by the polymeric network, a second electrode. The material exhibits, starting from a temperature referred to as T1, a mesophase referred to as P. At a temperature T′ greater than or equal to T1, the stack is capable of exhibiting at least three variable scattering states, which are stable and reversible, in the visible region.

Claims

1. An electrically controllable device having scattering which is variable by liquid crystals comprising a stack of layers in this order: a first electrode with a first main surface forming a bonding surface and an opposite surface, a dielectric electroactive layer with a main face on the bonding surface side and a main opposite face, made of a material comprising: liquid crystals, polymers forming a polymeric network, the liquid crystals being stabilized by the polymeric network, a second electrode with, on the side of the opposite face of the dielectric electroactive layer, a main surface forming a second bonding surface and with an opposite surface, the electroactive layer being visible by transparency on the side of the first electrode or on the side of the second electrode, or both, wherein the material exhibits, starting from a temperature T1, a mesophase P in which the material comprises an assembly of subcentimetric domains, which comprise two-dimensional topological defects, and wherein, at a temperature T′ greater than or equal to T1, the stack is capable of exhibiting at least first, second and third scattering states for at least one wavelength in the visible region, the first state being scattering and the most scattering, the second state being scattering and less scattering than the first state, and the third state being transparent or scattering and less scattering than the second state, the first, second and third states being switchable, at least two of the first, second and third states being obtained by the application of an electric field between the first and second electrodes.

2. The electrically controllable device having scattering which is variable by liquid crystals as claimed in claim 1, wherein the first state is accessible in the absence of said applied electric field, the second and third states are accessible in the presence of said applied electric field, the second state being obtained for a voltage V1 and the third state being obtained for a voltage V2 which is greater than V1.

3. The electrically controllable device having scattering which is variable by liquid crystals as claimed in claim 1, wherein, under said electric field and at temperature T′, the stack exhibits a diffuse transmission or a haze, or both, which varies with the voltage in all or part between 5 and 120V.

4. The electrically controllable device having scattering which is variable by liquid crystals as claimed in claim 1, wherein the stack exhibits a total transmission TT of at least 5% at 550 nm, with a difference between a maximum total transmission and a minimum total transmission TTmax-TTmin of at most 5% from 400 to 600 nm and wherein the total transmission TT′ under said electric field is such that TT′-TT (in absolute value) is less than 2% at 550 nm.

5. The electrically controllable device having scattering which is variable by liquid crystals as claimed in claim 1, wherein the mesophase P is not smectic.

6. The electrically controllable device having scattering which is variable by liquid crystals as claimed in claim 1, wherein the mesophase P exhibits a lower positional order than a mesophase P′ of the material.

7. The electrically controllable device having scattering which is variable by liquid crystals as claimed in claim 1, wherein said domains of the mesophase P are domains remaining from another mesophase P′; and the mesophase P′ is not nematic, and wherein the mesophase P′ is smectic and defects of the mesophase P′ are smectic defects.

8. The electrically controllable device having scattering which is variable by liquid crystals as claimed in claim 1, wherein said domains of the mesophase P are domains remaining from another mesophase P′.

9. The electrically controllable device having scattering which is variable by liquid crystals as claimed in claim 1, wherein the domains are comparable to focal conic domains of smectic phases.

10. The electrically controllable device having scattering which is variable by liquid crystals as claimed in claim 1, wherein the defects are line defects chosen from a regular or irregular closed contour.

11. The electrically controllable device having scattering which is variable by liquid crystals as claimed in claim 1, comprising: in contact with the main face of the dielectric electroactive layer, a first surface anchoring layer for the liquid crystals, capable of anchoring at least a fraction of the liquid crystals in contact with this first surface anchoring layer according to a first orientation in the absence of said applied electric field, in contact with the main opposite face of the dielectric electroactive layer, a second surface anchoring layer capable of orientating a fraction of the liquid crystals in contact with the second surface anchoring layer according to a second orientation.

12. The electrically controllable device having scattering which is variable by liquid crystals as claimed in claim 11, wherein the first surface anchoring layer is a unidirectional or degenerate planar anchoring and the second surface anchoring layer is a normal or degenerate planar anchoring or the first surface anchoring layer is a dielectric layer.

13. The electrically controllable device having scattering which is variable by liquid crystals as claimed in claim 1, comprising a laminated glazing comprising: a first glass sheet, which is optionally tinted, a thermoplastic lamination interlayer, a second glass sheet or a plastic sheet, wherein main internal faces of the first and second glass sheets face one another, the stack being between the main internal faces.

14. The electrically controllable device having scattering which is variable by liquid crystals as claimed in claim 13, wherein the glazing is laminated or is bent, or both, and is chosen from a glazing of an automobile or rail or nautical vehicle, or wherein the glazing is a glazed door, a shop window or display case, a partition, a glazed portion of street or household furniture or forms part of a double or triple glazing, or both, or wherein the electrically controllable device is used as projection or back projection screen.

15. The electrically controllable device having scattering which is variable by liquid crystals as claimed in claim 1, comprising laminated first and second glazings, and the stack is between the first and second glazings and forms a peripheral strip over an upper portion of the laminated first and second glazings, an external edge face of the stack being masked from the outside by a first opaque peripheral layer on an exterior glazing formed by one of the laminated first and second glazings, or an internal edge face of the stack being masked from the inside by a second opaque peripheral layer on the interior glazing formed by the other one of the laminated first and second glazings, or both.

16. A process for the manufacture of an electrically controllable device having scattering which is variable by liquid crystals, as claimed in claim 1, and comprising: providing a first electrode, providing a second electrode, providing a mixture comprising: at least one polymer precursor, liquid crystals including at least first liquid crystals exhibiting a mesophase P and optionally at least second liquid crystals, the mixture exhibiting a mesophase P and a mesophase P′, TA being the temperature for transition between the mesophase P and the mesophase P′ of the mixture, if necessary, a polymerization initiator, forming a stack of layers comprising, between the first and second electrodes, forming, starting from said mixture, an electroactive layer made of a material comprising said liquid crystals which are stabilized by a polymeric network, said forming comprising: at the temperature Ti which is less than TA, in mesophase P′, polymerizing said at least one precursor or precursors, resulting in said polymeric network.

17. The process for the manufacture of an electrically controllable device having scattering which is variable by liquid crystals as claimed in claim 16, wherein the first liquid crystals exhibit the mesophase P and the mesophase P′, the first liquid crystals having a temperature for transition Tp between the mesophase P and the mesophase P′, the polymerization is at the temperature Ti which is less than Tp or TA.

18. The process for the manufacture of the electrically controllable device having scattering which is variable by liquid crystals as claimed in claim 16, wherein the mesophase P is more distant from the crystalline phase than the mesophase P′.

19. The process for the manufacture of the electrically controllable device having scattering which is variable by liquid crystals as claimed in claim 16, comprising, in mesophase P′, forming domains with two-dimensional topological defects, remaining substantially in mesophase P.

20. The process for the manufacture of the electrically controllable device having scattering which is variable by liquid crystals as claimed in claim 16, comprising, in mesophase P′, forming domains: by bringing said mixture into contact with first and second layers for anchoring the liquid crystals, by application of stresses, by application of an electric field of at most 100 Hz, the mixture comprising charged particles.

21. The process for the manufacture of the electrically controllable device having scattering which is variable by liquid crystals as claimed in claim 16, wherein the first liquid crystals have a mesophase P′ which is smectic, and a nematic mesophase P and the second liquid crystals have a mesophase, and are devoid of smectic mesophase.

Description

(1) Other details and characteristics of the invention will become apparent from the detailed description which will follow, given with regard to the following appended drawings and in which:

(2) FIG. 1 represents a diagrammatic sectional view of a device having scattering which can be varied by liquid crystals 100 in a first embodiment of the invention

(3) FIGS. 2a and 2c represent a diagrammatic and detailed sectional view of an electroactive layer of the device having scattering which can be varied by liquid crystals of the type of FIG. 1, without electric field or under electric field, FIG. 2b illustrating the orientation of some liquid crystals under electric field

(4) FIGS. 3a to 7a show images (in black and white) of the electrically controllable device of FIG. 1 in a light booth with a backdrop 110 (paper with lines of writing) at 20 cm and under illuminant D65 in the absence of electric field (3a), for an electric field normal to the electroactive layer with a voltage of 25V (4a), of 50V (5a), of 70V (6a), and back to 0V (7a)

(5) FIGS. 3b to 7b show images (in black and white) obtained by polarized light optical microscopy (PLM) under a magnification of 20 (with a scale in white line of 50 μm), images showing the domains having line defects of the electroactive layer of the electrically controllable device of FIG. 1 in the absence of electric field (3b), for an electric field normal to the electroactive layer with a voltage of 25V (4b), of 50V (5b), of 70V (6b), and back to 0V (7b)

(6) FIG. 8 shows an assembly A of curves corresponding to the total transmission TT as a function of the wavelength between 400 and 800 nm without electric field or under electric field normal to the electroactive layer with a voltage of 10V to 110V per step of 10V and an assembly of curves B corresponding to the diffuse transmission DT as a function of the wavelength between 400 and 800 nm without electric field or under electric field normal to the electroactive layer with a voltage of 10V to 110V per step of 10V for the device of FIG. 1

(7) FIG. 9 shows an assembly A of curves corresponding to the total transmission as a function of the wavelength between 400 and 2500 nm approximately without electric field or under electric field normal to the electroactive layer with a voltage of 10V to 120V per step of 10V for the device of FIG. 1 and an assembly of curves B corresponding to the diffuse transmission as a function of the wavelength between 400 and 2500 nm approximately without electric field or under electric field normal to the electroactive layer with a voltage of 10V to 120V per step of 10V for the device of FIG. 1

(8) FIG. 10 shows an assembly of curves corresponding to the haze H (expressed in %), which is the ratio of the diffuse transmission DT to the total transmission TT, as a function of the wavelength between 400 and 2500 nm approximately without electric field or under electric field normal to the electroactive layer with a voltage of 10V to 120V per step of 10V and an assembly of curves B corresponding to the diffuse transmission as a function of the wavelength between 400 and 2500 nm approximately without electric field or under electric field normal to the electroactive layer with a voltage of 10V to 120V per step of 10V for the device of FIG. 1

(9) FIG. 11 represents a diagrammatic sectional view of a device having scattering which can be varied by liquid crystals 200 in a second embodiment of the invention

(10) FIGS. 12a to 17a respectively show images, in black and white, of the electrically controllable device of FIG. 11 in a light booth with a backdrop 110 (paper with lines of writing) at 20 cm and under illuminant D65 in the absence of electric field (12a), for an electric field normal to the electroactive layer with a voltage of 20V (13a), of 40V (14a), of 70V (15a), of 120V (16a), and back to 0V (17a)

(11) FIGS. 12b to 17b respectively show images (in black and white) obtained by polarized light optical microscopy (PLM) under a magnification of 20 (with a scale in white line of 50 μm), images showing the domains having line defects of the electroactive layer of the electrically controllable device of FIG. 11 in the absence of electric field (12b), for an electric field normal to the electroactive layer with a voltage of 20V (13b), of 40V (14b), of 70V (15b), of 120V (16b), and back to 0V (17b)

(12) FIG. 18 shows an assembly A1 of curves corresponding to the total transmission as a function of the wavelength between 400 and 800 nm approximately without electric field or under electric field normal to the electroactive layer with a voltage of 10V to 120V per step of 10V for the device of FIG. 11 and an assembly of curves B1 corresponding to the diffuse transmission as a function of the wavelength between 400 and 2500 nm approximately without electric field or under electric field normal to the electroactive layer with a voltage of 10V to 120V per step of 10V for the device of FIG. 11

(13) FIG. 19 shows an assembly of curves corresponding to the haze H, which is the ratio of the diffuse transmission DT to the total transmission TT, as a function of the wavelength between 400 and 2500 nm approximately without electric field or under electric field normal to the electroactive layer with a voltage of 10V to 120V per step of 10V for the device of FIG. 11 and an assembly of curves B corresponding to the diffuse transmission as a function of the wavelength between 400 and 2500 nm approximately without electric field or under electric field normal to the electroactive layer with a voltage of 10V to 120V per step of 10V for the device of FIG. 11

(14) FIG. 20 represents a diagrammatic sectional view of a device having scattering which can be varied by liquid crystals 300 in a third embodiment of the invention

(15) FIG. 21 shows an image (in black and white) obtained by polarized light optical microscopy (PLM) under a magnification of 20 (with a scale in white line of 150 μm), image showing the domains having line defects of fan-shaped type of the electroactive layer of the electrically controllable device of FIG. 20 in the absence of electric field

(16) FIG. 22 represents a diagrammatic sectional view of a device having scattering which can be varied by liquid crystals 400 in a fourth embodiment of the invention

(17) FIG. 22 represents a diagrammatic sectional view of a device having scattering which can be varied by liquid crystals 400 in a fourth embodiment of the invention

(18) FIG. 23 represents a diagrammatic sectional view of a device having scattering which can be varied by liquid crystals 500 in a fifth embodiment of the invention

(19) FIGS. 24a and 24b respectively represent a diagrammatic front and sectional view of a device having scattering which can be varied by liquid crystals 600 in a sixth embodiment of the invention

(20) FIG. 25 represents a diagrammatic sectional view of a device having scattering which can be varied by liquid crystals 700 in a seventh embodiment of the invention.

(21) The elements in the figures are not represented to scale.

EXAMPLE 1

(22) Exemplary embodiment No. 1 represented in FIG. 1 shows an electrically controllable device having scattering which can be varied by liquid crystals 100 according to the invention which comprises a stack of layers in this order: a transparent dielectric substrate 1 with an edge face 10 and main faces 11 and 12 and comprising a first transparent electrode 2 with a first main surface referred to as bonding surface and a surface referred to as opposite surface Sb and an edge face 10, in this instance a glass of 1.1 mm—or, in an alternate form, plastic, such as PET—with an ITO layer with a sheet resistance of 10 ohm/square, more broadly between 5 and 300 ohm/square, and for a neutrality in colors; this electrode or each electrode can also comprise at least two thin dielectric underlayers under the ITO layer and even one or two (dielectric) overlayers a transparent (in this instance degenerate) planar first anchoring layer 4 on the first electrode 2 in contact with the first anchoring layer 4, a dielectric electroactive layer 3 with a main face referred to as face on the bonding surface side and a main face referred to as opposite face A2, in this instance with a thickness of 6 μm, made of a material comprising: liquid crystals polymers forming a polymeric network, the liquid crystals being stabilized by the polymeric network the material exhibiting, starting from a temperature referred to as T1, a mesophase referred to as P in which the material comprises an assembly of domains, in this instance submillimetric, which comprise two-dimensional topological defects, such as line defects spacers being distributed in the material, in this instance glass beads the layer being sealed at the periphery by a polymeric seal 5, for example made of epoxy, of acrylate, in this instance of cyanoacrylate a transparent second anchoring layer 4′, in this instance a normal anchoring layer a second transparent electrode 2′ with on the side of face A2 a main surface referred to as second bonding surface and with a surface referred to as opposite surface Sc, in particular second electrode which is an ITO layer with a sheet resistance of 10 ohm/square, more broadly between 5 and 300 ohm/square, and for a neutrality in colors; this or each electrode can also comprise at least two thin dielectric underlayers under the ITO layer and even one or two overlayers a transparent dielectric support 1′ of the second electrode 2′ with an edge face 10′ and main faces 11′ and 12′, in this instance a glass of 1.1 mm—or, in an alternative form, plastic, such as PET.

(23) In order to supply electricity via a source 110, conductive bands (not shown), in particular metallic conductive bands, for example made of copper, are fixed, for example by adhesive bonding, along and on peripheral edges and are in contact with the electrodes 2,2′ (one band per electrode, the bands preferably being on opposite edges). These bands are subsequently connected to an electrical supply.

(24) The edge faces 20,20′ of the electrodes 2,2′ and the edge of the electroactive layer are preferably set back with respect to the edges 10,10′ of the glasses 1,1′.

(25) The glasses 1,1′ are rectangular but can be of any shape, for example round or square, and of any size, for example with a length of at least 1 m and even with a width of at least 10 cm (strip, and the like). The thicknesses can, for example, be from 0.7 mm to 4 mm. They can have a thickness preferably of greater than 100 μm and of at most 300 μm for better mechanical strength of the assembly and/or for ease of processing or of handling but, if greater flexibility is desired, it is possible to go down, for example, to 50 μm.

(26) In the “OFF” state, that is to say before the application of an electric voltage, this glazing having liquid crystals 100 is scattering, that is to say that it transmits optically but is not transparent. As soon as a voltage is applied between the two electrodes, the layer 3 changes to the less scattering state with a variable level of scattering which depends on the voltage.

(27) Under said electric field, the stack exhibits a diffuse transmission and a haze which varies with the voltage, in this instance between 5V and 120V.

(28) In an alternative to the choice of ITO, alone or in a multilayer, a silver-containing stack is chosen for one or both electrodes. It is even possible to choose, for one of the electrodes, a layer with a lower T.sub.L or even a reflecting layer.

(29) One or the external faces of the first and second carrier substrates 1,1′ can comprise one or more functional layers (antireflective, and the like) already known.

(30) One of the first and second carrier substrates 1,1′, and even the associated electrode, can be greater in size than the remainder of the stack. For example, the electrically conductive layer 2 or 2′, such as ITO (or other), can act as solar control layer. The ITO region acting as electrode can then be isolated by laser etching, for example, in order to form an ITO strip.

(31) One and/or other of the glasses 1,1′ can be replaced by a polymeric sheet, for example PET, of at most 500 μm or 200 μm, with or without a layer on its external face, or else by a plastic sheet—with or without a layer on its external face—for example thicker (such as from 1 to 10 mm), a polycarbonate or else a PMMA.

(32) The manufacturing process of example No. 1 is described more precisely below.

(33) The first anchoring layer 4 is a layer of poly(vinyl alcohol) (PVOH; Sigma-Aldrich; molecular weight M.sub.w˜27 kDa) of approximately 300 nm, bringing about a (degenerate) planar anchoring of the liquid crystals at the surface (without field),

(34) The PVOH layer is deposited on the first ITO layer 2 by spin coating with a solution of PVOH in deionized water (9.1% by weight). Before the deposition, the ITO is cleaned with ethanol and dried under nitrogen.

(35) The second anchoring layer 4′ is a layer of octyltrichlorosilane (OTS), bringing about a normal (homeotropic) anchoring of the liquid crystals at the surface (without field). It is obtained by immersion of the glass with the second ITO 2′ in a solution of OTS in n-heptane for 30 minutes, rinsing with deionized water and drying under nitrogen.

(36) In order to produce the electroactive layer 3, a mixture with two types of liquid crystals 5CB and 8CB, a monomer and a photoinitiator is formed.

(37) The mixture contains: 98% by weight of the liquid crystals 5CB and 8CB in a ratio 1:4 2% by weight of the combination formed by the monomer bisphenol A dimethacrylate with a photoinitiator 2,2-dimethoxy-2-phenylacetophenone.

(38) The mixture exhibits a smectic A mesophase under 17.5° C. and a nematic mesophase between 17.5° C. and 38° C. (and an isotropic phase above).

(39) A layer of this mixture is formed between the anchoring layers 4 and 4′.

(40) Subsequently, the combination is illuminated under UV radiation (λ, =365 nm) for polymerization at 5° C. (or at least under 17.5° C.), thus in smectic A phase.

(41) The electroactive layer 3 then comprises, in nematic phase, domains which are comparable to the focal conic domains of the smectic A phases, in particular in this instance toric focal conic domains or TFCDs.

(42) FIGS. 2a and 2c represent a diagrammatic and detailed sectional view of an electroactive layer of the device having scattering which can be varied by liquid crystals of the type of FIG. 1, without electric field or under electric field, FIG. 2b illustrating simply the orientation of some liquid crystals under electric field.

(43) The layer 3 in nematic phase exhibits smectic defects of TFCD type.

(44) It is considered that FIG. 2a represents a single focal conic domain of TFCD type.

(45) FIGS. 2a and 2c show a structure as layers 33 of liquid crystals 31, 31a, 31b, 310 imposed by the polymeric network (not represented).

(46) The layers are curved in the direction of the (in this instance degenerate) planar anchoring layer in a central zone 34 and the layers are flat and parallel with one another over two lateral zones 35, 35′ which are more or less extensive and which may be nonexistent.

(47) The domain exhibits a line defect in the plane of the glass 1, such as a surface with a closed contour of circular type (more or less irregular), and another line defect which has a linear geometry 36.

(48) On the side of the planar anchoring layer (lower part), some liquid crystals (short rods) 31a are parallel to this layer along all the directions of the plane.

(49) On the side of the normal anchoring layer (upper part), some liquid crystals 31b are perpendicular to this layer.

(50) Outside the contact zone with the planar anchoring layer 4, without electric field, for example at the middle of the thickness of the layer 3, the liquid crystals 310 have an orientation normal to the layers 4 and 4′.

(51) For example, the liquid crystals have a first orientation along an oblique angle with respect to the axis Z (in the vertical field E) without electric field in the curved zone and then become closer to the axis Z (of the field) when the field is applied (cf FIG. 2b), for example 25V.

(52) FIG. 2c shows the case where (virtually) all the liquid crystals are aligned vertically, for example starting from 120V, indeed even 150V.

(53) FIGS. 3a to 7a show images (in black and white) of the electrically controllable device of FIG. 1 in a light booth with a backdrop 110 (paper with lines of writing) at 20 cm and under illuminant D65 in the absence of electric field (3a), for an electric field normal to the electroactive layer 3 with a voltage of 25V (4a), of 50V (5a), of 70V (6a), and back to 0V (7a). The temperature is 21° C., thus in the nematic phase with smectic A defects.

(54) FIGS. 3b to 7b show images (in black and white) obtained by polarized light optical microscopy (PLM) under a magnification of 20 (with a scale in white line of 50 μm), images showing the domains having line defects of the electroactive layer 3 of the electrically controllable device of FIG. 1 in the absence of electric field (3b), for an electric field normal to the electroactive layer 3 with a voltage of 25V (4b), of 50V (5b), of 70V (6b), and back to 0V (7b). The temperature is 21° C.

(55) The domains are characterized by polarized light optical microscopy, referred to as PLM, on the image of said PLM, each domain being defined by a surface referred to as apparent surface SD.

(56) The domains are of polydisperse surface SD (contours more visible under a low-voltage field, for example at 25V).

(57) 1104 defects are counted in a rectangle with a length of 324 μm and with a width of 167 μm, i.e. 1922 domains.Math.mm.sup.2.

(58) FIGS. 7a and 7b testify to the reversibility from the most transparent state to the most scattering state (without electric field).

(59) The more the voltage is increased, the better the writing is distinguished from the backdrop 110.

(60) FIG. 8 shows: an assembly A of curves corresponding to the total transmission TT as a function of the wavelength between 400 and 800 nm without electric field or under electric field normal to the electroactive layer with a voltage of 10V to 110V per step of 10V for the device of FIG. 1 and an assembly of curves B corresponding to the diffuse transmission DT as a function of the wavelength between 400 and 800 nm without electric field or under electric field normal to the electroactive layer with a voltage of 10V to 110V per step of 10V for the device of FIG. 1.

(61) The stack exhibits, in this instance, a total transmission TT of at least 70% from 450 to 800 nm (and even at 75% from 450 nm to 600 nm), with a difference between the maximum total transmission and the minimum total transmission TTmax-TTmin of at most 5% from 450 to 600 nm.

(62) The total transmission TT remains fairly constant even with an electric field (and for any voltage level).

(63) The total transmission TT over the wavelength range 400-2500 nm is (virtually) independent of the switching voltage.

(64) It is possible to reduce the absorption in particular caused by the ITO layers.

(65) On the other hand, its is well and truly observed that the diffuse transmission DT (curves B) varies and gradually decreases as the voltage increases for each wavelength. Thus, it is shown very quantitatively that the diffuse transmission is adjustable with the voltage. For example, DT passes from approximately 10% to 55% at 600 nm on passing from 120V to 0V.

(66) FIG. 9 shows the same curves as FIG. 8 but up to 2500 nm.

(67) The total transmission TT remains fairly constant even with an electric field (every voltage level) between 800 nm and 1500 nm.

(68) The total transmission TT over the wavelength range 400-2500 nm is (virtually) independent of the switching voltage.

(69) On the other hand, it is also observed that the diffuse transmission DT (curves B) varies and gradually decreases as the voltage increases.

(70) FIG. 10 shows an assembly of curves corresponding to the haze H (expressed in %), which is the ratio of the diffuse transmission DT to the total transmission TT, as a function of the wavelength between 400 and 2500 nm approximately without electric field or under electric field normal to the electroactive layer with a voltage of 10V to 120V per step of 10V and an assembly of curves B corresponding to the diffuse transmission as a function of the wavelength between 400 and 2500 nm approximately without electric field or under electric field normal to the electroactive layer with a voltage of 10V to 120V per step of 10V for the device of FIG. 1.

EXAMPLE 2

(71) FIG. 11 represents a diagrammatic sectional view of a device having scattering which can be varied by liquid crystals 200 in a second embodiment of the invention which differs from the first embodiment 100 in that the planar first anchoring layer PVOH 4 is rubbed with velvet for a directional planar anchoring.

(72) The line defects are then referred to as non-TFCD or square TFCD.

(73) FIGS. 12a to 17a show images, in black and white, of the electrically controllable device of FIG. 11 in a light booth with a backdrop 110 (paper with lines of writing) at 20 cm and under illuminant D65 in the absence of electric field (12a), for an electric field normal to the electroactive layer with a voltage of 20V (13a), of 40V (14a), of 70V (15a), of 120V (16a), and back to 0V (17a).

(74) FIGS. 12b to 17b show the images (in black and white) obtained by polarized light optical microscopy (PLM) under a magnification of 20 (with a scale in white line of 50 μm), images showing the domains having line defects of the electroactive layer of the electrically controllable device of FIG. 11 in the absence of electric field (12b), for an electric field normal to the electroactive layer with a voltage of 20V (13b), of 40V (14b), of 70V (15b), of 120V (16b), and back to 0V (17b).

(75) The domains are arranged more regularly than for example 1 and are less polydisperse. The analyses on the influence of the applied field on the scattering, the diffuse transmission, and the total transmission are analogous to those of example 1.

(76) 2400 domains per mm.sup.2 are counted.

(77) FIG. 18 shows: an assembly A1 of curves corresponding to the total transmission as a function of the wavelength between 400 and 800 nm approximately without electric field or under electric field normal to the electroactive layer with a voltage of 10V to 120V per step of 10V for the device of FIG. 11, and an assembly of curves B1 corresponding to the diffuse transmission as a function of the wavelength between 400 and 800 nm approximately without electric field or under electric field normal to the electroactive layer with a voltage of 10V to 120V per step of 10V for the device of FIG. 11.

(78) The look of the curves is similar to those of FIG. 18.

(79) FIG. 19 shows: an assembly of curves corresponding to the haze H, which is the ratio of the diffuse transmission DT to the total transmission TT as a function of the wavelength between 400 and 2500 nm approximately without electric field or under electric field normal to the electroactive layer with a voltage of 10V to 120V per step of 10V for the device of FIG. 11 and an assembly of curves B corresponding to the diffuse transmission as a function of the wavelength between 400 and 2500 nm approximately without electric field or under electric field normal to the electroactive layer with a voltage of 10V to 120V per step of 10V for the device of FIG. 11.

(80) The analyses on the influence of the applied field on the scattering, the diffuse transmission, the total transmission and are analogous to those of example 1.

EXAMPLE 3

(81) FIG. 20 represents a diagrammatic sectional view of a device having scattering which can be varied by liquid crystals 300 in a third embodiment of the invention which differs from the first embodiment 100 in that the second anchoring layer becomes a (degenerate) planar anchoring layer 4′ and in this instance is identical to the planar first anchoring layer PVOH.

(82) FIG. 21 shows an image (in black and white) obtained by polarized light optical microscopy (PLM) under a magnification of 20 (with a scale in white line of 150 μm), image showing the domains having line defects of fan-shaped type of the electroactive layer of the electrically controllable device of FIG. 20 in the absence of electric field. The line defects are of fan-shaped FCD type.

(83) Assemblage Examples

(84) FIG. 22 represents a diagrammatic sectional view of a device having scattering which can be varied by liquid crystals 400 in a fourth embodiment of the invention which differs from the first embodiment 100 in that: the glasses 1 and 1′ are replaced by PETs 1,1′ and the stack is adhesively bonded by an optical adhesive 60 to an element 7, such as a glass 7 or rigid plastic, for example.

(85) For example, a partition is concerned (vertical position).

(86) The assembly can form part of a multiple glazing (double or triple glazing).

(87) For a double glazing, the stack can be side face 1 (exterior face), 2, 3; 4 (interior face). The stack of the device 400 can be flexible, can fit the curvatures of the added element 7.

(88) For a triple glazing, the stack can be side face 1 (exterior face), 2, 3; 4, 5, 6 (exterior face).

(89) The element 7 can be of the same size as or greater in size than the stack.

(90) The stack can be: on the preferably external face of a shower wall, on the preferably internal face (face “F4”) of a bent glazing of a vehicle, in particular an automobile: roof, side window, windshield, rear window.

(91) In particular, the device 400 can act as projection screen.

(92) FIG. 23 represents a diagrammatic sectional view of a device having scattering which can be varied by liquid crystals 500 in a fifth embodiment of the invention which comprises the first device 100 (glasses 1,1′ optionally replaced by PET films, for example) in a laminated glazing, that is to say in a lamination interlayer 7, for example PVB or EVA, which is submillimetric or of at most 2 mm, between a first and a second glazing 8,8′, for example of rectangular (or more broadly quadrilateral, polygonal) general shape with identical or similar dimensions, for example with a thickness of at most 5 mm or 3 mm, with internal main faces 81,81′ on the interlayer side and external main faces 82,82′.

(93) During manufacture, it is possible to use three interlayer sheets: two full sheets 71,72 against the internal faces 81, 81′ of the glazings 8,8′ and a central sheet with an opening for housing the stack of FIG. 1. After lamination, the interface between sheets (symbolized in dotted lines) is not necessarily discernible. It is preferable for the opening to be closed rather than completely emerging on one side. Thus, the entire edge of the stack is surrounded with lamination interlayer 7. Naturally, for the electrical supply, connections can exit from the device 500 and even protrude over one or more sides of the edges of the glazings.

(94) Alternatively, it is possible to use two interlayer sheets 71,72, the central hollowed-out sheet not being necessary if the stack is sufficiently thin, for example with a thickness of at most 0.2 mm.

(95) The first glazing 8 or 8′ can be tinted (gray, green, bronze, and the like) and the other glazing 8′ or 8 clear or extra-clear. A first interlayer sheet can be tinted (gray, green, bronze, and the like) and the other(s) clear or extra-clear. One of the first glazings 8 or 8′ can be replaced by a plastic sheet, such as a polycarbonate or a PMMA (in particular with a lamination interlayer made of PU).

(96) The edge 70 of the lamination interlayer can be set back (by at most 5 mm, for example) from the edge 80, 80′ of the glazings 8,8′.

(97) The device 500 covers virtually the whole of the main faces of the glasses 8 and even in this instance is centered. There is the same width of PVB 7a,7b on either side of the device 500.

(98) The glazings 8,8′ are flat or bent, it being possible for the device 500 to fit the curvature or curvatures of the glazings.

(99) The device 500 can be a partition or else a vehicle roof. For example, for an automobile roof: the glazing 8 is the bent exterior glazing, which is a tinted glazing of 3 mm the glazing 8′ is the bent interior glazing, which is a clear glazing of 3 mm or thinner the lamination interlayer 7 is made of PVB, which can be acoustic, in particular bilayer or trilayer (sheet 71 or 72).

(100) FIGS. 24a and 24b respectively represent a diagrammatic front and sectional view of a device having scattering which can be varied by liquid crystals 600 in a sixth embodiment of the invention.

(101) The device 600 differs from the device 100 in that the stack of FIG. 1 100 covers a surface portion, in particular a peripheral strip, for example along an upper longitudinal edge H of an automobile vehicle windshield (bent laminated glazing with the device 100), over virtually the whole length of the windshield.

(102) This strip 100 is in a marginal zone in which the criteria of T.sub.L and of absence of haze are looser than in the central zone ZB.

(103) As shown in FIG. 24b (sectional view), the width 7a of central interlayer 73 between the device 200 and the lower longitudinal edge B is greater than the width 7b of central interlayer 73 between the device 600 and the upper longitudinal edge H.

(104) In an alternative form or simultaneously, it can be present along a lower longitudinal edge B of the windshield, over the entire length or a portion of length.

(105) As shown in FIG. 24a (front view, interior side of the vehicle), the windshield comprises a first opaque frame, for example made of enamel (black or other), 91′ to 94′ over the lateral and longitudinal edges of the free face (F4) 82′ of the internal glazing 8′ and a second opaque frame, for example made of enamel (black or other), 91 to 94 over the lateral and longitudinal edges of the free face (F1) 82 of the external glazing 8.

(106) The edge face of the device 600, which is on the side of the lower longitudinal edge, and even those on the side of the lateral edges, can be (opposite) between the layers 92, 92′, 93, 93′, 94, 94′ of the enamel frames. For example, the connections and other strips for conveying current can also be masked by these layers 92, 92′, 93, 93′, 94, 94′.

(107) FIG. 25 represents a diagrammatic sectional view of a device having scattering which can be varied by liquid crystals 700 in a seventh embodiment of the invention which differs from the last embodiment 600 in that it concerns an automobile roof, for example with the external glass 8 is tinted and/or the PVB 71 is tinted and the device 100 covers substantially the entire main face of the glasses 8,8′.