FUNCTIONAL ELEMENT HAVING ELECTRICALLY CONTROLLABLE OPTICAL PROPERTIES

Abstract

A functional element having electrically controllable optical properties, includes a stack sequence formed of a first carrier film, a first surface electrode, an active layer, a second surface electrode, and a second carrier film, wherein the second carrier film has an overhanging region beyond the first carrier film and at least one barrier film is arranged on at least one edge region of the first carrier film and the overhanging region of the second carrier film.

Claims

1. A functional element having electrically controllable optical properties, comprising: a stack sequence formed of a first carrier film, a first surface electrode, an active layer, a second surface electrode, and a second carrier film, wherein the second carrier film has an overhanging region beyond the first carrier film and a barrier film is arranged on at least one edge region of the first carrier film and the overhanging region of the second carrier film.

2. The functional element according to claim 1, wherein the overhanging region defines an overhang u that is arranged at least at one side edge of the second carrier film.

3. The functional element according to claim 1, wherein the overhanging region defines an overhang u that is at least 4 mm.

4. The functional element according to claim 1, wherein an exit surface of the active layer between the first carrier film and the second carrier film is sealed by the barrier film.

5. The functional element according to claim 1, wherein the active layer contains or is made of liquid crystals.

6. The functional element according to claim 1, wherein, in the region of the overhang, the barrier film and the second carrier film are joined to one another at least in sections or over their entire surface.

7. The functional element according to claim 1, wherein, in the edge region, the barrier film and the first carrier film are joined to one another in sections or over their entire surface.

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

9. The composite pane according to claim 8, wherein the intermediate layer contains at least 3 wt. % of a plasticizer and the plasticizer preferably contains or is made of aliphatic diesters of tri- or tetraethylene glycol.

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

11. The composite pane according to claim 8, wherein the barrier film is implemented such that it the barrier film prevents the diffusion of plasticizer through the barrier film.

12. The composite pane according to claim 8, wherein the barrier film is low in plasticizer or free of plasticizer.

13. The composite pane according to claim 8, wherein the functional element is circumferentially surrounded by a third intermediate layer.

14. A method for producing a functional element having electrically controllable optical properties, comprising: a) providing a stack sequence formed of a first carrier film, a first surface electrode, an active layer, a second surface electrode, and a second carrier film, b) cutting back the first carrier film at at least one side edge by a region of the width u, by which means an overhanging region of the second carrier film is formed, and c) arranging a barrier film on the overhanging region, an exit surface of the active layer, and an adjacent edge region of the first carrier film.

15. A method according to claim 14, wherein at least in one region of another side edge, the second carrier film is cut back, by which means an overhanging region of the first carrier film is formed, and another barrier film is arranged on the overhanging region, the exit surface of the active layer, and an adjacent edge region of the second carrier film.

16. A method comprising utilizing a composite pane having an electrically controllable functional element according to claim 1 as interior glazing or exterior glazing in a vehicle or a building and the electrically controllable functional element as a sun screen or as a privacy screen.

17. The functional element according to claim 2, wherein the overhang u is arranged at least at three side edges of the second carrier film.

18. The functional element according to claim 3, wherein the overhang u is from 6 mm to 20 mm.

19. The functional element according to claim 5, wherein the active layer contains or is made of polymer dispersed liquid crystals (PDLC).

20. The functional element according to claim 6, wherein, in the region of the overhang, the barrier film and the second carrier film are glued to one another, or welded to one another.

Description

[0102] The invention is explained in detail with reference to drawings and exemplary embodiments. The drawings are schematic representations and not true to scale. The drawings in no way restrict the invention. They depict:

[0103] FIG. 1 an enlarged representation of a detail of a functional element according to the invention,

[0104] FIG. 2A a plan view of a composite pane according to the invention,

[0105] FIG. 2B a cross-section through the composite pane of FIG. 2A along the section line X-X′,

[0106] FIG. 3A, 3B, 3C representations of the individual steps for producing a functional element according to the invention, and

[0107] FIG. 4 an exemplary embodiment of the method according to the invention with reference to a flowchart.

[0108] FIG. 1 depicts an enlarged representation of a detail of a functional element 5 according to the invention in the region of a side edge 5.1 of the functional element.

[0109] The controllable functional element 5 is, for example, a PDLC multilayer film comprising an active layer 11 that is arranged between a first surface electrode 12 and a second surface electrode 13. The first surface electrode 12 has, on the surface facing away from the active layer 11, a first carrier film 14 that stabilizes the surface electrode 12. The second surface electrode 13 has, on the surface facing away from the active layer 11, a second carrier film 15 that stabilizes the second surface electrode 13. Here, 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 12, 13, by which means the optical properties can be controlled. The carrier films 14, 15 are made of PET and have a thickness of, for example, 0.14 mm. The carrier films 14, 15 are provided with a coating of ITO having a thickness of approx. 100 nm facing the active layer 11, forming the surface electrodes 12, 13.

[0110] The surface electrodes 12, 13 are, for example, applied in a known manner by means of a sputtering process. The surface electrodes 12, 13 can be connected to the vehicle's electrical system via busbars (not shown) (formed by a silver-containing screen print) and connection cables (not shown).

[0111] In the exemplary embodiment depicted, the second carrier film 15 is longer compared to the first carrier film 14; this is also referred to in the following as an overhang or overhanging region 15.1. In other words, the second carrier film 15 protrudes beyond the first carrier film 14 in the plane of the functional element 5.

[0112] A barrier film 4 is arranged in the overhanging region 15.1 at the side edge 5.1 on the second carrier film 15 and in an edge region of the width w of the first carrier film 14 and is bonded area-wise. As a result, the exit surface 20.1 of the active layer 11 is completely covered and sealed at the side edge 5.1. The barrier film 4 is arranged on the inward surface of the second carrier film 15 and on the edge region 14.1 of the outward surface of the first carrier film 14. The inward surface of the carrier films and the outward surfaces of the carrier films refers here to the surfaces relative to the functional element 5.

[0113] In this example, additional barrier films 4 are arranged on overhanging regions of the second carrier film at all side edges of the functional element (not shown in FIG. 1).

[0114] FIG. 2A and FIG. 2B 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 made, for example, of a clear soda lime glass. The inner pane 2 has a thickness of 1.6 mm and is also made, for example, of a clear soda lime glass. The composite pane 100 has a first edge referenced with D that is called the “upper edge” in the following. The composite pane 100 has a second edge referenced with M that is arranged opposite the upper edge D and is called the “lower edge” in the following. The composite pane 100 can be arranged, for example, as architectural glazing in the frame of a window with other panes to form an insulating glazing unit. Of course, the composite pane 100 can also be implemented and used as a roof panel of a vehicle or, with appropriate dimensioning, as a windshield or the like.

[0115] A functional element 5 according to the invention that is controllable in its optical properties via an electrical voltage is arranged between the first intermediate layer 3a and the second intermediate layer 3b. For the sake of simplicity, the electrical leads are not shown.

[0116] Here, the functional element according to the invention of FIG. 1 is, for example, the enlarged region Z, which is also reproduced in the following in FIG. 3C.

[0117] The intermediate layers 3a, 3b include 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-ethyl hexanoate) as plasticizer.

[0118] Here, the second carrier film 15 has, for example, an all-sided overhang u of, for example, 5 mm beyond the first carrier film 14. Here, “all-sided” means that there is an overhang u beyond each side edge 5.1, 5.2, 5.3, 5.4 of the functional element 5. A one-piece barrier film 4, implemented here in the shape of a frame, is, for example, arranged on the all-sided overhanging region 15.1 of the second carrier film 15 and on an edge region 14.1 of width w of the first carrier film 14 and bonded thereto. The exit surface 20.1 of the active layer 11 is sealed on all sides as a result of the all-sided, frame-shaped design of the barrier film 4.

[0119] Of course, the exit surfaces of the active layer between the second carrier film and the first carrier film at the individual side edges 5.1, 5.2, 5.3, 5.4 can also be covered and sealed with, in each case, one or a plurality of strip-shaped barrier films.

[0120] Here, the barrier film 4 is made, for example, substantially of PET, in other words, up to 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 over the side edges 5.1, 5.2, 5.3, 5.4 into the active layer 11 of the functional element 5 according to the invention.

[0121] In aging tests, such composite panes 100 present a 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 a resulting degradation of the functional element 5 is avoided.

[0122] In an advantageous development of the functional element 5 according to the invention, an adhesive means, for example, an acrylate-based adhesive, that fixedly glues the barrier film 4 to the carrier films 14, 15, is arranged between the barrier film 4 and the touching sections of the second carrier film 15 and the edge region 14.1 of the first carrier film 14. The adhesive connection prevents slippage of the barrier film 4 during assembly. At the same time, inclusions of air bubbles and resultant visual distractions or impairments are avoided since the barrier film 4 rests fixedly on the second carrier film 15 and the first carrier film 14.

[0123] Of course, the composite pane according to the invention is not limited to the exemplary embodiment presented here. Further exemplary embodiments not presented here include, for example, windshields or roof panels of vehicles and the use of electrically controllable functional elements 5 as sun visors.

[0124] FIGS. 3A, 3B, and 3C depict exemplary embodiments of a functional element 5 according to the invention during production.

[0125] FIG. 4 depicts an exemplary embodiment of the production method according to the invention with reference to a flowchart with the steps S1 through S3.

[0126] Initially, in a first step S1, a stack sequence formed of a first carrier film 14, a first surface electrode 12, an active layer 11, a second surface electrode 13, and a second carrier film 15 is provided.

[0127] Such stack sequences are, for example, are commercially available by the meter as multilayer film material. Then, the product is customized and trimmed to the dimensions of the later use, for example, by laser cutting.

[0128] FIG. 3A depicts an enlarged representation of the side edge 5.1 of such a stack sequence. The various elements of the stack sequence, i.e., the first carrier film 14, the first surface electrode 12, the active layer 11, the second surface electrode 13, and the second carrier film 15 have the same dimensions and are stacked congruently atop one another.

[0129] In a second step S2, for example, the first carrier film 14 is cut back at at least one side edge (here, 5.1) by a region of width u, by means of which an overhanging region 15.1 of the second carrier film 15 is formed. The result is accordingly shown in FIG. 3B.

[0130] In a third step S3, a barrier film 4 is arranged on the overhanging region 15.1 of the second carrier film 15, the exit surface 20.1 of the active layer 11, and an adjacent edge region (14.1) of width w of the first carrier film (14). The result is accordingly shown in FIG. 3C.

[0131] The barrier film 4 can optionally be joined to the first carrier film 14, for example, by gluing, melting, or welding in sections or over the entire surface.

[0132] Independently of this, by lamination of the functional element 5 according to the invention in a composite pane 100 and by the internal pressure in the finished laminated composite pane 100, the barrier film 4 is firmly pressed onto the first carrier film 14 and the second carrier film 15 and fixed, resulting in a hermetic seal.

LIST OF REFERENCE CHARACTERS

[0133] 1 outer pane [0134] 2 inner pane [0135] 3a first intermediate layer [0136] 3b second intermediate layer [0137] 4 barrier film [0138] 5 functional element having electrically controllable optical properties [0139] 5.1,5.2,5.3,5.4 side edge of the functional element 5 [0140] 11 active layer of the functional element 5 [0141] 12 first surface electrode of the functional element 5 [0142] 13 second surface electrode of the functional element 5 [0143] 14 first carrier film [0144] 14.1 edge region of the first carrier film 14 [0145] 15 second carrier film [0146] 15.1 overhanging region of the second carrier film 15 [0147] 16 isolation lines [0148] 20.1 exit surface [0149] 100 composite pane [0150] B central field of vision of the windshield [0151] D upper edge of the windshield, roof edge [0152] M lower edge of the windshield, engine edge [0153] u overhang, width of the overhanging region 15.1 [0154] w width of the edge region 14.1 [0155] S1, S2, S3 steps [0156] X-X′ section line [0157] Z enlarged region