Functional element having electrically controllable optical properties

Abstract

A functional element having electrically controllable optical properties, includes a stack sequence of at least a first carrier film, an active layer, and a second carrier film, wherein at least one exit surface of the active layer on at least one lateral face of the stack sequence of the functional element is sealed at least in sections with a barrier material.

Claims

1. A functional element having electrically controllable optical properties, comprising a stack sequence of at least: a first carrier film, an active layer, and a second carrier film, wherein at least one exit surface of the active layer on at least one lateral face of the functional element is sealed at least in sections with a barrier material, and the barrier material is extruded onto the exit surface or is sprayed onto the exit surface, wherein the barrier material is arranged directly on the lateral face of the stack sequence of the functional element and directly on the exit surface of the active layer and lateral faces of the carrier films, wherein the barrier material is arranged bead-like on the lateral faceand is not implemented as a film, wherein the barrier material is formed such that it prevents the diffusion of plasticizer through the barrier material, wherein the barrier material is made of the same thermoplastic material as the carrier films, wherein the barrier material protrudes beyond all lateral faces of the functional element and covers an edge area of an upper side of the second outer carrier film and a lower side of the first outer carrier film, and wherein the barrier material and surfaces of the first outer carrier film and the second outer carrier film coming into contact with the barrier film have a fusion connection by localized melting.

2. The functional element according to claim 1, wherein the exit surfaces on all lateral faces are completely sealed with the barrier material or wherein at least one of the lateral faces are completely sealed with the barrier material.

3. The functional element according to claim 1, wherein the functional element is a polymer dispersed liquid crystal (PDLC) film.

4. The functional element according to claim 1, wherein the barrier material is plasticizer-poor or plasticizer-free.

5. The functional element according to claim 1, wherein the barrier material has, over the exit surface, a thickness d of at least 0.1 mm.

6. A composite pane having a functional element, comprising: a second stack sequence comprising an outer pane, a first intermediate layer, a second intermediate layer, and an inner pane, wherein the first and second intermediate layers contain at least one thermoplastic polymer film with at least one plasticizer, wherein, between the first intermediate layer and the second intermediate layer, a functional element having electrically controllable optical properties according to claim 1 is arranged at least in sections.

7. The composite pane according to claim 6, wherein the intermediate layer contains at least 3 wt.-% of a plasticizer and the plasticizer contains or is made of aliphatic diesters of tri- or tetraethylene glycol.

8. The composite pane according to claim 6, wherein the intermediate layer contains at least 60 wt.-% polyvinyl butyral (PVB).

9. A method for producing a functional element having electrically controllable optical properties according to claim 1, wherein at least a) a stack sequence of at least a first carrier film, an active layer, and a second carrier film is provided, and b) an exit surface of the active layer on at least one lateral face of the functional element is sealed at least in sections with a barrier material, wherein the barrier material is extruded in a heated state directly onto the exit surface or is sprayed directly onto the exit surface.

10. The method according to claim 9, wherein in a following step c) an outer pane, a first intermediate layer, the functional element having electrically controllable optical properties, a second intermediate layer, and an inner pane are arranged one over another in this order, and d) the outer pane and the inner pane are joined by lamination, wherein an intermediate layer with an embedded functional element is formed from the first intermediate layer and the second intermediate layer.

11. A method comprising utilizing a functional element according to claim 1 in a windshield or roof panel of a vehicle, wherein the functional element is used as a sun visor.

12. A method comprising utilizing a functional element according to claim 1 in an interior glazing or exterior glazing in a vehicle or a building, wherein the electrically controllable functional element is used as a sun screen or as a privacy screen.

13. The functional element according to claim 2, wherein all lateral faces are completely sealed with the barrier material.

14. The functional element according to claim 4, wherein the barrier material contains or is made of polyethylene terephthalate (PET) or polyvinyl fluoride (PVF).

Description

(1) The invention is explained in detail with reference to drawings and exemplary embodiments. The drawings are schematic representations and not to scale. The drawings in no way restrict the invention. They depict:

(2) FIG. 1A a plan view of a first embodiment of a composite pane according to the invention having a functional element according to the invention,

(3) FIG. 1B a cross-section through the composite pane of FIG. 1A along the section line X-X′,

(4) FIG. 1C an enlarged representation of the area Z of FIG. 1B,

(5) FIG. 2A an enlarged representation of a detail of a functional element according to the invention during the extrusion of the barrier material,

(6) FIG. 2B an enlarged representation of a detail of another example of a functional element according to the invention during the extrusion of the barrier material,

(7) FIG. 2C an enlarged representation of a detail of another example of a functional element according to the invention during the extrusion of the barrier material,

(8) FIG. 3 an enlarged representation of a detail of another exemplary embodiment of a functional element according to the invention during the spraying of the barrier material,

(9) FIG. 4A a plan view of another embodiment of a composite pane according to the invention using the example of a windshield with a sun visor,

(10) FIG. 4B a cross-section through the composite pane of FIG. 4A along the section line X-X′.

(11) FIG. 1A, FIG. 1B, and FIG. 1C depict in each case a detail of a composite pane 100 according to the invention. The composite pane 100 comprises an outer pane 1 and an inner pane 2 that are joined to one another via a first intermediate layer 3a and a second intermediate layer 3b. The outer pane 1 has a thickness of 2.1 mm and is, for example, made of a clear soda lime glass. The inner pane 2 has a thickness of 1.6 mm and is, for example, also made of a clear soda lime glass. The composite pane 100 has a first edge designated as D, which is referred to in the following as the “upper edge”. The composite pane 100 has a second edge designated as M, which is arranged opposite the upper edge D and is referred to in the following as the “lower edge”. The composite pane 100 can be arranged, for example, as architectural glazing in the frame of a window with additional panes to form an insulating glazing unit.

(12) Arranged between the first intermediate layer 3a and the second intermediate layer 3b is a functional element 5 according to the invention, whose optical properties can be controlled by an electrical voltage. For the sake of simplicity, the electrical supply lines are not shown.

(13) The controllable functional element 5 is, for example, a PDLC multilayer film, comprising a stack sequence with an active layer 11 between two surface electrodes 12, 13 and two carrier films 14, 15. The active layer 11 contains a polymer matrix with liquid crystals dispersed therein, which align themselves as a function of the electrical voltage applied on the surface electrodes, by which means the optical properties can be controlled. The carrier films 14, 15 are made of polyethylene terephthalate (PET) and have a thickness of, for example, 0.125 mm. The carrier films 14, 15 are provided with a coating of ITO facing the active layer 11 and having a thickness of approx. 100 nm, forming the surface electrodes 12, 13. The surface electrodes 12, 13 can be connected to the vehicle's electrical system via bus bars (implemented, for example, by a silver-containing screen print) (not shown) and connecting cables (not shown).

(14) The intermediate layers 3a, 3b comprise in each case a thermoplastic film with a thickness of 0.38 mm. The intermediate layers 3a, 3b are made, for example, of 78 wt.-% polyvinyl butyral (PVB) and 20 wt.-% triethylene glycol bis(2-ethylhexanoate) as a plasticizer.

(15) The functional element 5 has on all lateral faces 5.1, 5.2, 5.3, 5.4 a barrier material 4, which, for example, covers the entire lateral face 5.1, 5.2, 5.3, 5.4. The barrier material 4 contains a plasticizer-poor PET and seals in particular the entire exit surface 8 of the active layer 11.

(16) The barrier material 4 is made, here, for example, substantially of PET, i.e., at least 97 wt.-%. The barrier film 4a, 4b contains less than 0.5 wt.-% plasticizer and is suitable for reducing or preventing the diffusion of plasticizer out of the intermediate layers 3a, 3b via the lateral faces 5.1, 5.2, 5.3, 5.4 into the functional layer 5.

(17) The barrier material 4 reduces or prevents diffusion of plasticizer into the active layer 11, thus increasing the service life of the functional element 5. The thickness (or, in other words, the material thickness) d of the barrier material 4 over (i.e., orthogonal to) the exit surface 8 is at least 0.3 mm.

(18) In aging tests, such composite panes 100 show significantly reduced brightening in the edge region of the functional element 5, since diffusion of the plasticizer out of the intermediate layers 3a, 3b into the functional element 5 and resultant degradation of the functional element 5 is avoided.

(19) FIGS. 2A, 2B, and 2C depict in each case enlarged representations of details of functional elements 5 according to the invention during the extrusion of the barrier material 4.

(20) At the time of the extrusions, the barrier material 24 is softened or liquefied by heating above the softening point, in the example of PET, by heating to 250° C. Then, the liquefied or softened barrier material 24 is pressed through an extrusion die 20 and the extrudate is brought into contact with the lateral face 5.1 of the functional element 5. There, the barrier material 4 cools and seals the lateral face 5.1 with the various layers of the functional element 5 and in particular the active layer 11.

(21) The barrier material 4 can be extruded on such that it protrudes beyond the lateral face 5.1 and covers an edge area of the upper side of the second carrier film 14 and the under side of the first carrier film 15, as shown, for example, in FIG. 2B.

(22) As shown in detail in FIG. 2C, the functional element 5 is arranged completely on a working surface 25 during the extrusion, in other words, the functional element 5 rests, for example, on the working surface 25 via the first carrier film 15.

(23) Alternatively, the functional element 5 can protrude beyond the working surface on one or all sides (see, for example, FIG. 2A or 2B) such that the barrier material 4 can be extruded particularly evenly onto the lateral faces.

(24) During the extrusion, the functional element 5 is moved relative to the extrusion die 20. This can be achieved by a stationary extrusion die 20 and a moving functional element 5, by a stationary functional element 5 and a moving extrusion die 20, or a combination of both.

(25) FIG. 3 depicts an enlarged representation of a detail of a functional element 5 according to the invention during the spraying of the barrier material 4. For this purpose, the heated and liquefied barrier material 4 is atomized by a stream of compressed air 32 in a spray head 30. The resultant spray mist 31 precipitates as a re-solidified barrier material 4 on the lateral face 5.1 of the functional element 5 and, in the example depicted here, seals the lateral face 5.1 completely.

(26) During the spraying, the functional element 5 can be arranged completely on a working surface, in other words, the functional element 5 rests on the working surface via the first carrier film 15. Alternatively, the functional element 5 can protrude beyond the working surface on all sides such that the barrier material 4 can be sprayed particularly evenly onto the lateral faces. During the spraying, the functional element 5 is moved relative to the spray head 30. This can be achieved by a stationary spray head 30 and a moving functional element 5, by a stationary functional element 5 and a moving spray head 30, or a combination of both.

(27) The stream of compressed air 32 preferably contains or is air, nitrogen, or another protective gas. The barrier material 34 is softened by heating above the softening point, in the example of PET, by heating to 250° C.

(28) FIG. 4A and FIG. 4B depict in each case a detail of an exemplary composite pane 100 according to the invention as a windshield with an electrically controllable sun visor. The composite pane 100 of FIGS. 4A and 4B corresponds substantially to the composite pane 100 of FIG. 1A-C such that only the differences will be discussed in the following.

(29) The windshield comprises a trapezoidal composite pane 100 with an outer pane 1 and an inner pane 2 that are joined to one another via two intermediate layers 3a,3b. The outer pane 1 has a thickness of 2.1 mm and is made of green-colored soda lime glass. The inner pane 2 has a thickness of 1.6 mm and is made of clear soda lime glass. The windshield has has an upper edge D facing the roof in the installed position and a lower edge M facing the engine compartment in the installed position.

(30) The windshield is equipped with an electrically controllable functional element 5 according to the invention as a sun visor that is arranged in a region above the central field of vision B (as defined in ECE-R 43). The sun visor is formed by a commercially available PDLC multilayer film as the functional element 5 that is embedded in the intermediate layers 3a,3b. The height of the sun visor is, for example, 21 cm. The first intermediate layer 3a is bonded to the outer pane 1; the second intermediate layer 3b is bonded to the inner pane 2. A third intermediate layer 3c position therebetween has a cutout, into which the cut-to-size PDLC multilayer film is inserted precisely, i.e., flush on all sides. The third intermediate layer 3c thus forms, so to speak, a sort of passe-partout for the functional element 5, which is thus encapsulated all around in a thermoplastic material and is protected thereby.

(31) The first intermediate layer 3a has a tinted region 6 that is arranged between the functional element 5 and the outer pane 1. The light transmittance of the windshield is thus additionally reduced in the region of the functional element and the milky appearance of the PDLC functional element 5 in the diffuse state is mitigated. The aesthetics of the windshield are thus significantly more attractive. The first intermediate layer 3a has, in the region 6, for example, average light transmittance of 30%, with which good results are achieved.

(32) The region 6 can be homogeneously tinted. However, it is often visually more appealing if the tinting decreases in the direction of the lower edge of the functional element 5 such that the tinted and the non-tinted regions merge smoothly.

(33) In the case depicted, the lower edges of the tinted region 6 and the lower edge of the PDLC functional element 5 (here, its lateral face 5.1) are arranged flush with the barrier material 4. This is, however, not necessarily the case. It is also possible for the tinted region 6 to protrude beyond the functional element 5 or, vice versa, for the functional element 5 to protrude beyond the tinted region 6. In the latter case, it would not be the entire functional element 5 that would be bonded to the outer pane 1 via the tinted region 6.

(34) The windshield has, as is customary, a surrounding peripheral masking print 9 that is formed by an opaque enamel on the interior side surfaces (facing the interior of the vehicle in the installed position) of the outer pane 1 and of the inner pane 2. The distance of the functional element 5 from the upper edge D and the side edges of the windshield is less than the width of the masking print 9 such that the lateral faces of the functional element 5—with the exception of the side edge facing the central field of vision B—are concealed by the masking print 9. The electrical connections (not shown) are also reasonably mounted in the region of the masking print 9 and thus hidden.

(35) The controllable functional element 5 is a multilayer film, consisting of an active layer 11 between two surface electrodes 12, 13 and two carrier films 14, 15. The active layer 11 contains a polymer matrix with liquid crystals dispersed therein, which align themselves as a function of the electrical voltage applied to the surface electrodes, as a result of which the optical properties can be controlled. The carrier films 14, 15 are made of PET and have a thickness of, for example, 0.125 mm. The carrier films 14, 15 are provided with coating of ITO facing the active layer 11 and having a thickness of approx. 100 nm, forming the electrodes 12, 13. The electrodes 12, 13 can be connected to the vehicle's electrical system, via a bus bar (not shown) (formed, for example, by a silver-containing screen print) and via connecting cables (not shown).

(36) A barrier material 4 is extruded, for example, onto the lateral faces 5.1, 5.2, 5.3, and 5.4 of the functional element 5, analogously to FIG. 2C. In the example depicted, all lateral faces 5.1, 5.2, 5.3, and 5.4 are completely sealed with a barrier material 4 made of plasticizer-poor PET. Thus, the functional element 5 is particularly well protected against aging.

(37) A so-called “high flow PVB”, which has stronger flow behavior compared to standard PVB films, can preferably be used for the intermediate layers 3a, 3b, 3c. The layers thus flow around the barrier film 4 and the functional element 5 more strongly, creating a more homogeneous visual impression, and the transition from the functional element 5 to the intermediate layer 3c is less conspicuous. The “high flow PVB” can be used for all or even for only one or more of the intermediate layers 3a, 3b, 3c.

(38) In another example, not illustrated here, the windshield and the functional element 5 with the barrier material 4 substantially correspond to the embodiment of FIGS. 4A and 4 B. The PDLC functional element 5 is, however, divided by horizontal isolation lines into, for example, six strip-like segments. The isolation lines have, for example, a width of 40 μm to 50 μm and are spaced 3.5 cm apart. They were introduced into the prefabricated multilayer film by laser. The isolation lines separate, in particular, the surface electrodes into strips isolated from one another, which have in each case a separate electrical connection. The segments can thus be switched independently of one another. The thinner the isolation lines, the less conspicuous they are. Even thinner isolation lines can be realized by etching.

(39) The height of the darkened functional element 5 can be adjusted by the segmentation. Thus, depending on the position of the sun, the driver can darken the entire sun visor or even only part of it.

(40) In a particularly convenient embodiment, the functional element 5 is controlled by a capacitive switch area arranged in the region of the functional element, wherein the driver determines the degree of darkening by the location at which he touches the pane. Alternatively, the functional element 5 can also be controlled by contactless methods, for example, by gesture recognition, or as a function of the state of the pupil or eyelid determined by a camera and suitable evaluation electronics.

LIST OF REFERENCE CHARACTERS

(41) 1 outer pane 2 inner pane 3a first intermediate layer 3b second intermediate layer 3c third intermediate layer 4 barrier material 5 functional element having electrically controllable optical properties 5.1,5.2,5.3,5.4 lateral face of the functional element 5 6 tinted region of the first intermediate layer 3a 8 exit surface of the active layer 11 9 masking print 11 active layer of the functional element 5 12 surface electrode of the functional element 5 13 surface electrode of the functional element 5 14 carrier film 15 carrier film 20 extrusion die 24,34 heated barrier material 30 spray nozzle 31 spray jet, spray mist 32 compressed air 100 composite pane B central field of vision of the windshield D upper edge of the windshield, roof edge M lower edge of the windshield, engine edge d thickness, material thickness X-X′ section line Z enlarged region