Method for producing a composite pane

Abstract

The invention relates to a method for producing a composite pane (1), having the following steps: • a) forming a first stack sequence (2) which comprises, in the following order: • • - a first adhesive film (4) made of an optically transparent curable adhesive, • - an electro-optical functional film (9): and • - a second adhesive film (5) made of an optically transparent curable adhesive, • b) forming a layered frame (6) made of a thermoplastic material around the first stack sequence (2), • c) forming a second stack sequence (11) which comprises, in the following order: • - a first pane (3), • - at least one first thermoplastic film (12), • - the first stack sequence (2) with layered frames (6), • - at least one second thermoplastic film (13), and • - a second pane (10), • d) laminating the second stack sequence (11) under the effect of heat and pressure, and • e) curing the optically transparent adhesive.

Description

[0001] Process for producing a composite pane

[0002] The present invention lies in the technical field of pane production and relates to a method for producing a composite pane, a composite pane produced by the method according to the invention, and the use thereof.

[0003] Laminated panes generally consist of two individual panes, typically made of glass, which are firmly bonded together by at least one thermoplastic intermediate layer. Modern laminated panes, particularly windshields in motor vehicles, can exhibit complex curvatures in horizontal and / or vertical directions in order to meet aerodynamic requirements and design specifications of the automobile manufacturers. They increasingly also include electrically controllable functional elements that display information for the driver and / or front passenger, serve as lighting, and / or can change the optical transparency of the pane, for example, like a sun visor. In particular, the optical transparency of panes can be switched over large areas, for example in roof windows, rear side windows, or partitions. Electrically controllable functional elements in the form of electro-optical functional films are advantageously incorporated into the laminated pane.In particular, electro-optical functional films with a liquid crystal-based functional layer, which are based on the so-called "guest-host" effect, represent an interesting possibility for implementing an electro-optical switching function in a laminated pane in a simple, space-saving, cost-effective, and reliable manner. Here and below, electro-optical functional films with a liquid crystal-based functional layer, which are based on the "guest-host" effect, are referred to as "guest-host films" for the sake of simplicity.

[0004] Guest-host films typically comprise a nematic liquid crystal (host) provided with an additive (guest), wherein the additive can be, for example, dichroic dye molecules that absorb light anisotropically. Since the molecules of the additive are elongated, their orientation can be controlled by the orientation of the molecules of the liquid crystal, i.e. host, which in practice is achieved by applying an electric field to the liquid crystal. In this way, for example, the optical transparency of the guest-host film can be very precisely controlled by an external electric field. For example, windshields can be very advantageously provided with an electrically switchable transparency similar to a sun visor. To date, guest-host films have not been able to be incorporated into laminated windows using conventional, industrially used lamination processes.The reason for this is that guest-host films cannot yet be integrated into the usual production processes for manufacturing laminated glass. In fact, this poses a major challenge with regard to simple and cost-effective industrial series production of laminated glass with guest-host films. As practice has shown, guest-host films, due to their physical properties resembling a liquid, are very sensitive to mechanical stress caused by uneven contact pressure. Even the smallest local deviations in the contact pressure during lamination of the laminated glass and in the laminated composite glass lead to the occurrence of local optical defects in the guest-host films, which can render the composite glass unusable.

[0005] In the series production of curved laminated panes, however, it is unavoidable that the individual panes of the laminated pane do not fit perfectly. Rather, minor shape deviations within the usual dimensional tolerances always occur, leading to locally higher compressive loads during lamination. This is not critical for conventional laminated panes, as these locally higher compressive loads do not impair the optical quality of the laminated pane. However, these locally higher compressive loads are sufficient to create undesirable local optical defects (e.g., local discoloration, discoloration, or clouding) in guest-host films. Furthermore, local shape deviations or locally higher compressive loads can certainly be desired during the production of laminated panes.

[0006] To date, no method for laminating composite panes is known in the state of the art that enables the industrial series production of a composite pane with a guest-host foil integrated into the composite pane as an electro-optical functional element with usable optical quality.

[0007] WO 2021 / 069354 A1 discloses a composite pane with an integrated functional film, wherein an adhesive thin layer (not in combination with a thermoplastic film) is located on one side of the functional film and thermoplastic films (not in combination with an adhesive thin layer) are located on the other side of the functional film.

[0008] WO 2021 / 249801 A1 discloses a method for producing a composite pane with an integrated functional film, in which exclusively thermoplastic films are used to avoid mechanical compressive stress on the functional film. In contrast, the object of the present invention is to provide an improved method for producing a composite pane with an integrated guest-host film, by which the composite pane can be produced with high optical quality in industrial series production. In particular, the method should be usable in existing production facilities, thereby enabling composite panes with integrated guest-host films to be produced in large numbers simply, cost-effectively, and reliably.

[0009] These and other objects are achieved according to the invention by a method for producing a composite pane with an electro-optical functional film according to the independent patent claim. Advantageous embodiments of the invention are set out in the subclaims.

[0010] According to the invention, a method for producing a composite pane, in particular a laminated glass pane, with an integrated electro-optical functional film is shown. The electro-optical functional film is integrated into the composite pane, i.e., it is located between the two individual panes of the composite pane.

[0011] The process for manufacturing a composite pane comprises the following steps, which are carried out, for example but not necessarily, in the order given according to alphabetical designation:

[0012] Step a)

[0013] Forming a first stacking sequence comprising in this order: a first adhesive film made of an optically transparent, curable adhesive, an electro-optical functional film, a second adhesive film made of an optically transparent, curable adhesive.

[0014] Step b)

[0015] Forming a layered frame made of a thermoplastic material around the first stacking sequence.

[0016] Step c)

[0017] Forming a second stacking sequence comprising in this order: a first pane, at least one first thermoplastic film, the previously produced first stacking sequence with layered frame, at least one second thermoplastic film, a second pane.

[0018] Step d)

[0019] Laminating the second stack sequence under the influence of heat and pressure.

[0020] Step e)

[0021] Curing of the optically transparent adhesive.

[0022] During lamination of the second stacking sequence in step d), the thermoplastic films soften due to the increase in temperature, meaning the viscosity decreases or the flowability of the thermoplastic increases. This allows the thermoplastic to melt and, after cooling, i.e., solidify, form a strong bond with the adjacent components. However, the composite pane is not yet firmly bonded. A strong bond between the composite pane only occurs after the curable adhesive has hardened.

[0023] The term "lamination" in the context of the present invention describes the heating and pressure application of the second stacking sequence, as well as the cooling of the second stacking sequence until the thermoplastic layer solidifies.

[0024] The adhesive films made of an optically transparent, curable adhesive melt during lamination in step d) due to the increase in temperature, wherein the curable adhesive is designed in such a way that the effect of heat during lamination in step d) results in a reduction in the viscosity or an increase in the flowability of the adhesive.

[0025] Preferably, the optically transparent, curable adhesive is designed such that the (absolute) viscosity of the curable adhesive (of the first adhesive film and the second adhesive film) decreases more than the (absolute) viscosity of the thermoplastic material (of the first thermoplastic film, the second thermoplastic film, and the layered frame). In other words, the curable adhesive becomes more fluid than the thermoplastic material due to the temperature increase during lamination.Thus, during lamination in step d), with increasing temperature increase, a reduction in the viscosity of the thermoplastic and a reduction in the viscosity of the optically transparent, curable adhesive occur, wherein particularly preferably, at least above a (minimum) temperature dependent on the materials used, the viscosity of the optically transparent, curable adhesive is lower than the viscosity of the thermoplastic, i.e., the flowability of the optically transparent, curable adhesive is greater than the flowability of the thermoplastic. During the increase in temperature during lamination in step d), the viscosity of the optically transparent, curable adhesive can always be lower than the viscosity of the thermoplastic.However, it is also possible that, as the temperature increases during lamination in step d), the viscosity of the optically transparent, curable adhesive is only lower than the viscosity of the thermoplastic above a (minimum) temperature that depends on the materials used. If the optically transparent, curable adhesive is thermally curable, the viscosity increases again with further temperature increases as soon as crosslinking begins. In any case, there is also a temperature range in which the viscosity of the optically transparent, curable adhesive is lower than the viscosity of the thermoplastic.

[0026] For the purposes of this invention, the term "viscosity" always refers to the absolute viscosity, so that a reduction in viscosity refers to a reduction in the absolute viscosity. In accordance with common understanding, viscosity describes the viscosity or flowability of a substance, with the lower the viscosity, the greater the flowability, and vice versa. For the purposes of this invention, viscosity can be considered to be the dynamic viscosity, typically measured in millipascal seconds (mPas). Viscosity can be measured using methods familiar to those skilled in the art, for example, using a rotational rheometer. It is important that the same measurement method is used when measuring the viscosities of the thermoplastic and the optically transparent, curable adhesive.A comparison of the viscosities of the thermoplastic and the optically transparent, curable adhesive therefore refers to the same temperature (and the same pressure) and the same measuring method for measuring the viscosity, for example and preferably using a rotational rheometer, the structure and mode of operation of which are familiar to those skilled in the art and therefore need not be discussed here. In the process according to the invention, it is particularly preferred if, at least above a (minimum) temperature which depends on the materials used, the viscosity of the optically transparent, curable adhesive is lower than the viscosity of the thermoplastic, i.e. the flowability of the optically transparent, curable adhesive is greater than the flowability of the thermoplastic. The viscosities can each be determined separately, i.e. outside the second stacking sequence.

[0027] Pressure is applied to the second stacking sequence during lamination in step d) only when the viscosity of the optically transparent, curable adhesive of the two adhesive films has been reduced sufficiently by increasing the temperature that any local irregularities in the pressure load can be absorbed by the optically transparent, curable adhesive, so that the electro-optical functional film is subjected to uniform pressure. It is understood that the curable adhesive has not yet cured when pressure is applied to the second stacking sequence in step d).

[0028] For the purposes of the present invention, "pressurization" generally refers to a pressure applied to the second stacking sequence that is higher than ambient pressure. It is understood that a very low pressure application, which is not effective for lamination, also does not lead to any local optical effect in the electro-optical functional film. The term "pressurization" can therefore reasonably also be understood to mean the application of a pressure effective for lamination to the second stacking sequence. In any case, when applying pressure to the second stacking sequence, the viscosity of the optically transparent, curable adhesive must be so low that local irregularities in the pressure can be absorbed by the curable adhesive.

[0029] Advantageously, the second stacking sequence is pressurized during lamination in step d), in particular with a pressure effective for lamination, in particular with a maximum pressure used during lamination, only if a viscosity of the optically transparent, curable adhesive reduced by heating during lamination in step d) is lower than a viscosity of the thermoplastic material reduced by heating during lamination in step d).

[0030] The present invention thus advantageously demonstrates a new way of minimizing or even completely avoiding uneven contact pressure on the electro-optical functional film, particularly due to local deviations in the shape of the two sheets during lamination. For this purpose, the electro-optical functional film is not simply laminated between two thermoplastic intermediate films, which generally cannot adequately absorb local load peaks due to an insufficient reduction in viscosity. Rather, the electro-optical functional film is embedded between two layers of an optically transparent, curable adhesive, which, due to the temperature increase during lamination, experience such a reduction in viscosity (increased flowability) that they can absorb uneven load pressure on both sides of the electro-optical functional film.Local stress peaks during the pressing of the electro-optical functional film between the two panes during lamination can thus be effectively avoided, or at least reduced to such an extent that the occurrence of optical defects in the electro-optical functional film is prevented. Therefore, during lamination of the second stacking sequence, uneven compressive forces do not act on the electro-optical functional film, meaning that the compressive load is evened out by the curable adhesive.

[0031] During lamination in step d), the second stacking sequence is heated and subjected to pressure, with the lamination generally being carried out within a specific (selectable) temperature and pressure range, with a maximum temperature and maximum pressure always being specifiable depending on the particular process conditions selected. As already explained, pressure is applied, in particular with a pressure effective for lamination, in particular with the maximum pressure of the second stacking sequence, only when the optically transparent, curable adhesive has such a greatly reduced viscosity (which is particularly preferably lower than the viscosity of the thermoplastic) that local pressure irregularities acting on the electro-optical functional film can be absorbed.

[0032] The optically transparent, curable adhesive is preferably cured under pressure applied to the second stacking sequence. This means that step d) for laminating the second stacking sequence under heat and pressure and step e) for curing the optically transparent adhesive are preferably carried out simultaneously rather than sequentially. This has the advantage that, due to the highly fluid state of the adhesive layers, irregularities can be compensated particularly well, and this state is then essentially "preserved" by curing (still under pressure).

[0033] In contrast to the lamination processes known in the prior art, the process according to the invention avoids uneven contact pressure on the electro-optical functional film and minimizes the risk of local defects in the electro-optical functional film. This is a major advantage of the present invention.

[0034] The composite pane produced (or obtained) in particular by the method according to the invention is usually used to separate an interior space from an external environment. The composite pane comprises a first pane with an outer side and an inner side, and a second pane with an inner side and an outer side, which are firmly connected to one another. The first pane can also be referred to as the outer pane, and the second pane as the inner pane. The surfaces or sides of the two individual panes are referred to from outside to inside as Side I, Side II, Side III and Side IV. For example, the first pane is the outer pane of the composite pane, and the second pane is therefore its inner pane. When installed, the outer pane faces the external environment. An electro-optical functional film is located between the two individual panes, i.e. it is integrated into the composite pane.

[0035] The films made of thermoplastic material soften during lamination due to the increase in temperature, whereby in the composite pane, a first intermediate layer made of thermoplastic material is formed from the at least one first thermoplastic film and a second intermediate layer made of thermoplastic material is formed from the at least one second thermoplastic film. The same applies to the frame made of thermoplastic material, which fuses with the intermediate layers of thermoplastic material during lamination. After lamination, the two layers of thermoplastic material and the frame made of thermoplastic material are fused together. In this case, too, a layered frame can be defined (at least conceptually) around the electro-optical functional film. The layered frame surrounds the electro-optical functional film completely all the way around without interruption, i.e.Completely, like a passe-partout. The frame is layered, i.e., it is a layer of thermoplastic material that surrounds the electro-optical functional film.

[0036] In the second stacking sequence, the at least one first thermoplastic plastic film, the first stacking sequence with layered frame and the at least one second thermoplastic plastic film preferably have the same dimensions, ie are of the same area.

[0037] The layers of a thermoplastic material and the layered frame of a thermoplastic material are each provided by at least one thermoplastic film. The first stacking sequence is preferably inserted into a cutout of at least one thermoplastic film for the layered frame. Preferably, the layered frame of a thermoplastic material and the first stacking sequence have the same thickness, so that the first stacking sequence neither protrudes nor is recessed relative to the layered frame (in the direction perpendicular to the electro-optical functional film).

[0038] The second stacking sequence is created from the first stacking sequence, i.e. the first stacking sequence is a component of the second stacking sequence. The second stacking sequence is produced by embedding the first stacking sequence in thermoplastic films, with at least one thermoplastic film being arranged on each side of the first stacking sequence. A first pane and a second pane are arranged on the thermoplastic films on either side of the first stacking sequence. The second stacking sequence is laminated by the action of heat and pressure, i.e. increasing the temperature and applying pressure, with the optically transparent, curable adhesive liquefying more than the thermoplastic, so that at least above a certain (minimum) temperature the viscosity of the optically transparent, curable plastic is lower than the viscosity of the thermoplastic.

[0039] The optically transparent, curable adhesive of the two adhesive films is curable, meaning it can be irreversibly cured. Typically, it is a plastic that is cured into a polymer-crosslinked state through curing. This distinguishes the curable adhesive significantly from a thermoplastic, which, while also optically transparent, can be reversibly softened by the application of heat. In contrast, the curable adhesive can no longer be made flowable once it has cured. The optically transparent, curable adhesive is therefore not a thermoplastic. For the purposes of the present invention, the terms "curable adhesive" and "thermoplastic" are to be understood in this sense.

[0040] The curable, optically transparent adhesive can be cured by heat, exposure to electromagnetic radiation, preferably UV radiation, and / or chemically. Curing preferably occurs by applying heat or increasing the temperature and / or UV radiation. Particularly preferably, the optically transparent, curable adhesive is cured by applying heat, wherein curing of the curable adhesive can occur at or below a maximum temperature used during lamination of the second stacking sequence in step d). However, it is also possible for the curable adhesive to cure above a maximum temperature used during lamination of the second stacking sequence in step d).In any case, during lamination, the curable adhesive is first liquefied by heating (transition from the solid state to the liquid state) and cured upon further heating (irreversible transition from the liquid state to the solid state). This very advantageously represents a particularly efficient process. The second stacking sequence is only pressurized if the curable adhesive has a sufficiently low viscosity, which is particularly preferably lower than the viscosity of the thermoplastic, so that local pressure differences can be absorbed during lamination. As already explained, there is particularly preferably at least one temperature range in which the viscosity of the optically transparent, curable adhesive is lower than the viscosity of the thermoplastic.If the curing of the curable adhesive occurs above the maximum temperature used during lamination, the temperature of the second stacking sequence is further increased accordingly.

[0041] In the method according to the invention, the first stacking sequence is first formed, which is then arranged within the second stacking sequence. According to an advantageous embodiment of the method according to the invention, the first stacking sequence is formed as an adhesive pre-composite, which can facilitate its embedding in the second stacking sequence. This can be achieved easily, for example, due to the adhesive nature of the two adhesive films. However, it is also possible for the first stacking sequence to be non-adhesively bonded.

[0042] According to one embodiment of the method according to the invention, the second stacking sequence is evacuated before or during lamination, which has the advantage that air bubbles and other gaseous inclusions can be removed from the second stacking sequence.

[0043] The electro-optical functional film can, in principle, be designed in any desired manner. Examples of electrically switchable or controllable functional films are SPD (suspended particle device), PDLC (polymer dispersed liquid crystal), electrochromic, or electroluminescent functional films, and are known per se to those skilled in the art. The functional film can also be a polymeric, electrically conductive layer, for example, containing at least one conjugated polymer or a polymer provided with conductive particles. The functional film generally contains at least one carrier film with a functional layer. The carrier film preferably contains a polymer, in particular polyvinyl butyral (PVB), ethylene-vinyl acetate (EVA), polyurethane (PU), polyethylene terephthalate (PET), or combinations thereof.

[0044] The method according to the invention is particularly advantageous for guest-host films with a functional layer made of a liquid-crystalline material with an incorporated additive. Reference is made to the above statements regarding guest-host films. Guest-host films are well known as such to those skilled in the art, so they need not be discussed in detail here. Guest-host films are commercially available, for example, under the term "light control film," for example from Dai Nippon Printing Co., Ltd., Japan, under the product name LCF005(EU). The electro-optical functional film is preferably a guest-host film.

[0045] The curable, optically transparent (clear) adhesive can, in principle, be chosen arbitrarily, as long as it is flowable or liquid in the uncured state or can be made liquid (e.g., by increasing the temperature) and is irreversibly curable. Transparent adhesives are based on silicone, for example. Optically transparent adhesives are known by the acronym OCA (Optically Clear Adhesive), while the acronym LOCA (liquid optically clear adhesive) is particularly used for liquid optically transparent adhesives. Optically transparent adhesives are characterized by their high optical quality and are particularly common where a virtually invisible adhesive layer is required, for example, in displays or touch panels.Optically transparent adhesives are widely used in touch-sensitive displays, for example, to firmly bond them to an LCD or to firmly bond plastic covers to touch-sensitive displays. After application, the optically transparent adhesive is often cured using UV radiation. Optically transparent adhesives are freely available from a variety of suppliers.

[0046] The optically transparent (clear), curable adhesive can, for example, contain or consist of polyurethane (PU), polyacrylate, polyacetate resin, casting resin, silicone or a copolymer or mixture thereof. Advantageously, the optically transparent adhesive contains or consists of a casting resin, in particular based on polyurethane or silicone. Depending on the adhesive used, the optically transparent adhesive can be cured by thermal curing (i.e. application of heat), by electromagnetic radiation, in particular UV radiation, IR radiation or microwave radiation, by ultrasound, by application of moisture or by a chemical reaction between different components (in particular two-component adhesives). The time required for the optically transparent adhesive to cure can be influenced by the temperature in many curing processes. In particular, curing can be accelerated by the application of heat.Conversely, curing can be slowed by cooling. The curing time can be controlled, for example, by heating or cooling the optically transparent adhesive.

[0047] Each individual pane of the composite pane (i.e., first pane and second pane) preferably contains or consists of glass, particularly preferably flat glass, float glass, quartz glass, borosilicate glass, soda-lime glass, aluminosilicate glass, or clear plastics, preferably rigid clear plastics, in particular polyethylene, polypropylene, polycarbonate, polymethyl methacrylate, polystyrene, polyamide, polyester, polyvinyl chloride, and / or mixtures thereof. Particularly preferably, each pane contains or consists of glass, in particular soda-lime glass. Suitable glasses are known, for example, from EP 0847965 B1.

[0048] The thickness of each individual pane of the composite pane can vary widely and be adapted to the requirements of the individual case. Standard thicknesses of panes ranging from 1.0 mm to 25 mm are preferred, and preferably from 1.4 mm to 2.1 mm. The size of the panes can vary widely and depends on the application.

[0049] The composite pane can have any three-dimensional shape and be planar or slightly or strongly curved in one or more directions of space. The composite pane preferably has a curvature, since the method according to the invention is particularly advantageous for curved composite panes. It goes without saying that the two individual panes of the composite pane are curved accordingly for a precise fit. As is usual, however, the two individual panes do not usually have an exact (matching) fit before lamination, but rather are subject to dimensional inaccuracies within the scope of dimensional or production tolerances.

[0050] The layers and the layered frame made of a thermoplastic material preferably contain or consist of polyvinyl butyral (PVB), ethylene vinyl acetate (EVA), thermoplastic polyurethane (TPU), and / or polyethylene terephthalate (PET). The thermoplastic material is formed by one or more superimposed thermoplastic films, with the thickness of a thermoplastic film preferably being between 0.25 mm and 1 mm, typically 0.38 mm or 0.76 mm.

[0051] The layers and the layered frame can be made of the same thermoplastic or of different thermoplastics. In the case of different thermoplastics, the information regarding viscosity or flowability provided in this description of the invention refers to each thermoplastic.

[0052] For the purposes of this invention, "transparent" means that the total transmission of the laminated pane complies with the legal requirements of the European Union for windshields and front side windows and preferably has a visible light transmittance of more than 70%, and in particular more than 75%. For rear side windows, roof windows, and rear windows, "transparent" can also mean 10% to 70% light transmission. Accordingly, "opaque" means a light transmission of less than 15%, preferably less than 5%, and in particular 0%.

[0053] Known processes for producing a composite pane can be used for lamination. For example, so-called autoclave processes can be carried out at an elevated pressure of approximately 1 bar to 15 bar and temperatures of 100°C to 145°C for approximately 2 hours. Known vacuum bag or vacuum ring processes, for example, operate at approximately 200 mbar and 130°C to 145°C. The two panes can also be pressed into a composite pane in a calender between at least one pair of rollers. Systems of this type are known for producing composite panes and normally have at least one heating tunnel upstream of a pressing unit. The temperature during the pressing process is, for example, between 40°C and 150°C. Combinations of calender and autoclave processes have proven particularly successful in practice. Alternatively, vacuum laminators can be used.These consist of one or more heatable and evacuatable chambers in which the first pane and the second pane can be laminated within, for example, approximately 60 minutes at reduced pressures of 0.01 mbar to 800 mbar and temperatures of 80°C to 170°C. The invention further extends to a composite pane produced in particular by the method according to the invention.The composite pane comprises, in this order, a first pane, at least one first intermediate layer made of a thermoplastic, a first adhesive layer made of an optically transparent, cured adhesive, an electro-optical functional film, a second adhesive layer made of an optically transparent, cured adhesive, wherein the first adhesive layer, the electro-optical functional film and the second adhesive layer are surrounded by a layered frame made of a thermoplastic, at least one second intermediate layer made of a thermoplastic and a second pane.

[0054] Furthermore, the invention extends to the use of the composite pane according to the invention on buildings or in means of transport for land, air, or water traffic, in particular in motor vehicles, for example as a windshield, rear window, side windows, and / or roof window. According to the invention, the use of the composite pane in motor vehicles is preferred, particularly preferably as a windshield or roof window.

[0055] The various embodiments of the invention can be implemented individually or in any combination. In particular, the features mentioned above and further explained below can be used not only in the specified combinations, but also in other combinations or on their own, without departing from the scope of the present invention.

[0056] The invention is explained in more detail below using exemplary embodiments, with reference to the accompanying figures. They show, in simplified form and not to scale:

[0057] Fig. 1 is a cross-sectional view of an intermediate product for producing a first stacking sequence with electro-optical functional film,

[0058] Fig. 2 is a cross-sectional view of a first stacking sequence with electro-optical functional foil,

[0059] Fig. 3 is a plan view of the first stacking sequence of Fig. 2 with a layered frame,

[0060] Fig. 4 is a cross-sectional view of the first stacking sequence of Fig. 3 with a layered frame, Fig. 5 is a cross-sectional view of a second stacking sequence with the first stacking sequence of Figs. 3 and 4,

[0061] Fig. 6 is a cross-sectional view of an embodiment of the composite pane according to the invention,

[0062] Fig. 7 is a flow chart illustrating the method according to the invention.

[0063] The method according to the invention for producing a composite pane and the composite pane according to the invention, designated overall by the reference number 1, are explained by way of example with reference to Figures 1 to 6.

[0064] Let us first consider Figures 1 and 2. Figure 1 shows a simplified schematic representation of a cross-sectional view of an intermediate product for forming a first stacking sequence 2 for use in producing the composite pane 1 according to the invention. A first adhesive film 4 made of an optically transparent, curable adhesive is arranged on one side or surface of an electro-optical functional film 9. Figure 2 shows the first stacking sequence 2, in which, in addition to the first adhesive film 4, a second adhesive film 5 made of an optically transparent, curable adhesive is arranged on the other or opposite side or surface of the electro-optical functional film 9. The curable adhesive of the first adhesive film 4 and the curable adhesive of the second adhesive film 5 can be the same or different from one another; they are preferably the same.The first stacking sequence 2 is produced as an adhesive pre-bond, which is easily possible because the two adhesive films 4, 5, for example, have adhesive properties. This facilitates further processing of the first stacking sequence 2.

[0065] The two adhesive films 4, 5 are each provided with cover films on both sides, for example. To produce the first stacking sequence 2, for example, a cover film is first peeled off the first adhesive film 4 and this is glued with its sticky side to the electro-optical functional film 9. The composite of the electro-optical functional film 9 and the first adhesive film 4 is then turned 180°, a cover film is peeled off the second adhesive film 5, and the second adhesive film 5 is glued with its sticky side to the electro-optical functional film 9. The first stacking sequence 2, produced as an adhesive pre-composite, then has a cover film on both surfaces, which enables easy storage of the first stacking sequence 2. The cover films are removed for further processing of the first stacking sequence 2.

[0066] In the first stacking sequence 2 shown in Figure 2, the electro-optical functional film 5 is embedded between the two adhesive films 4, 5, so that the electro-optical functional film 5 is protected by the two adhesive films 4, 5 during lamination. The electro-optical functional film 5 and the two adhesive films 4, 5 have the same dimensions, ie, they have the same surface area.

[0067] Reference is now made to Figures 3 and 4, which illustrate a layered frame 6 for the first stacking sequence of Figure 2. Figure 3 shows a plan view of the first stacking sequence 2, and Figure 4 shows a cross-sectional view along section line AA in Figure 3.

[0068] As can be clearly seen in Figure 3, the first stacking sequence 2 is inserted into a cutout 7 of a thermoplastic frame film 8, which forms the layered frame 6 made of thermoplastic material for the first stacking sequence 2. The electro-optical functional film 9 is inserted into the cutout 7 so that the remaining part of the frame film 8 completely surrounds the electro-optical functional film 9. The cutout 7 is here, for example, made centrally in the frame film 8. The thickness (i.e. dimension perpendicular to the first stacking sequence 2) of the frame 6 or the frame film 8 made of thermoplastic material and the thickness of the first stacking sequence 2 are the same, so that the first stacking sequence 2 does not protrude or is set back with respect to the frame 6 made of thermoplastic material.Although only a single frame foil 8 is illustrated in Figure 4, it would be equally possible for two or more frame foils with a common cutout for the electro-optical functional foil 9 to be used.

[0069] Figure 5 shows a second stacking sequence 11 in a schematic cross-sectional view. In this example, it comprises the first stacking sequence 2 with the frame 6 made of thermoplastic material in the central position. On one side of the first stacking sequence 2, a first pane 3 is arranged with a first thermoplastic film 12 interposed. On the other side of the first stacking sequence 2, a second pane 10 is arranged with a second thermoplastic film 13 interposed.

[0070] The second stacking sequence 11 is laminated under increased temperature and pressure. First, the temperature of the second stacking sequence 11 is increased without pressure being applied, which causes the two adhesive films 4, 5 made of an optically transparent, curable adhesive to melt and liquefy. In addition, the two thermoplastic films 12, 13 soften due to the increase in temperature. After the two adhesive films 4, 5 have been liquefied, the second stacking sequence 11 is subjected to pressure with further heating in order to laminate the two panes 3, 10, whereby the thermoplastic melts. The liquefied, optically transparent, curable adhesive protects the electro-optical functional film 9 from uneven pressure during lamination.The second stacking sequence 11 is only pressurized when the viscosity of the optically transparent, curable adhesive of the two adhesive films 4, 5 is lower than the viscosity of the thermoplastic of the two thermoplastic films 12, 13. In other words, the second stacking sequence 11 is only pressurized when the flowability of the optically transparent, curable adhesive of the two adhesive films 4, 5 is greater than the flowability of the thermoplastic of the two thermoplastic films 12, 13.

[0071] While the pressure is applied during lamination, the two adhesive films 4, 5 are cured. This occurs thermally, for example, here. For this purpose, the second stacking sequence 11 is further heated beyond the maximum temperature used during lamination. However, it is also possible for curing to occur even at the maximum temperature used during lamination. As is known to those skilled in the art, the second stacking sequence 11 can be evacuated during lamination. After the curable adhesive has cured, the composite pane 1 is firmly bonded.

[0072] Figure 6 shows an example of the composite pane 1 according to the invention, which results after laminating the second stacking sequence 11 from Figure 5 and curing of the adhesive. It comprises, in this order, the first pane 3, a first intermediate layer 14 made of thermoplastic material, the electro-optical functional film 9, which is surrounded by the layered frame 6 made of thermoplastic material, a second intermediate layer 15 made of thermoplastic material, and the second pane 10. Adjacent to the electro-optical functional film 9 are a first adhesive layer 16 made of cured adhesive and a second adhesive layer 17 made of cured adhesive. The first intermediate layer 14 made of thermoplastic material, the frame 6 made of thermoplastic material, and the second intermediate layer 15 made of thermoplastic material are fused together.

[0073] The laminated pane 1 can be installed in a building or motor vehicle and separates an interior space from an external environment. For example, the laminated pane 1 is the windshield of a motor vehicle. The first pane 3 and the second pane 10 are each made of glass, preferably soda-lime glass, and are transparent to visible light. The thermoplastic used in the laminated pane 1 preferably consists of polyvinyl butyral (PVB), ethylene-vinyl acetate (EVA), thermoplastic polyurethane (TPU), and / or polyethylene terephthalate (PET).

[0074] The outer surface of the first pane 3 faces the outside environment and is simultaneously the outer surface of the composite pane 1. The inner surface of the second pane 10 faces the building or vehicle interior and is simultaneously the inner surface of the composite pane 1. It is understood that the composite pane 1 can have any suitable geometric shape and / or curvature. As a windshield, the composite pane 1 typically has a convex curvature. The electro-optical functional film 9 integrated into the composite pane 1 is preferably a guest-host film, as described above.

[0075] In the process for producing the composite pane 1 illustrated above, the first stacking sequence 2 was produced as an adhesive pre-composite. It would also be conceivable for the first stacking sequence 2 not to be produced as an adhesive pre-composite.

[0076] In Figure 7, the method according to the invention is illustrated again using a flow diagram. It comprises the following steps in this order: a) Forming a first stacking sequence 2, which comprises in this order: a first adhesive film 4 made of an optically transparent, curable adhesive, an electro-optical functional film 9, a second adhesive film 5 made of an optically transparent, curable adhesive, b) Forming a layered frame 6 made of a thermoplastic material around the first stacking sequence 2, c) Forming a second stacking sequence 11, which comprises in this order: a first pane 3, at least one first thermoplastic film 12, the first stacking sequence 2 with layered frame 6, at least one second thermoplastic film 13, a second pane 10, d) Laminating the second stacking sequence 11 by the action of heat and pressure, e) Curing the optically transparent adhesive.The optically transparent, curable adhesive is designed such that a reduction in viscosity occurs upon heating during lamination in step d), wherein particularly preferably the viscosity of the curable adhesive is reduced more than the viscosity of the thermoplastic material, wherein at least above a certain (minimum) temperature the viscosity of the optically transparent, curable adhesive is lower than the viscosity of the thermoplastic material.

[0077] From the above, it can be seen that the invention provides an improved method for producing a laminated pane with an integrated electro-optical functional film. Uneven pressure application to the electro-optical functional film between the two panes during lamination is avoided because the low-viscosity or liquefied adhesive on both sides of the electro-optical functional film compensates for uneven mechanical stress. The method according to the invention can be easily implemented in the industrial series production of laminated panes. The laminated panes with integrated electro-optical functional films can be produced simply, cost-effectively, and with high optical quality.

[0078] List of reference symbols

[0079] 1 composite pane

[0080] 2 first stacking sequence 3 first slice

[0081] 4 first adhesive film

[0082] 5 second adhesive film

[0083] 6 frames

[0084] 7 Cutout 8 Frame foil

[0085] 9 electro-optical functional film

[0086] 10 second slice

[0087] 11 second stacking sequence

[0088] 12 first thermoplastic film 13 second thermoplastic film

[0089] 14 first intermediate layer

[0090] 15 second intermediate layer

[0091] 16 first adhesive layer

[0092] 17 second adhesive layer

Claims

Patent claims 1 . Method for producing a composite pane (1), which comprises the following steps: a) forming a first stacking sequence (2) which comprises in this order: a first adhesive film (4) made of an optically transparent, curable adhesive, an electro-optical functional film (9), a second adhesive film (5) made of an optically transparent, curable adhesive, b) forming a layered frame (6) made of a thermoplastic material around the first stacking sequence (2), c) forming a second stacking sequence (11) which comprises in this order: a first pane (3), at least one first thermoplastic film (12), the first stacking sequence (2) with layered frame (6), at least one second thermoplastic film (13), a second pane (10), d) laminating the second stacking sequence (11) by the action of heat and pressure, e) curing the optically transparent adhesive.

2. The method according to claim 1, wherein the curable adhesive is designed such that a reduction in viscosity occurs upon heating during lamination in step d), the viscosity of the curable adhesive being reduced to a greater extent than the viscosity of the thermoplastic material.

3. Method according to claim 1 or 2, in which pressure is applied to the second stacking sequence (11) in step d), in particular with a pressure effective for the lamination, only when a viscosity of the curable adhesive reduced by heating during lamination in step d) is lower than a viscosity of the thermoplastic material reduced by heating during lamination in step d).

4. A method according to any one of claims 1 to 3, wherein the curable adhesive is cured by the action of heat.

5. The method according to claim 4, wherein the curable adhesive is cured at or below a maximum temperature used in laminating the second stack sequence (11) in step d).

6. The method according to claim 4, wherein the curable adhesive is cured above a maximum temperature used in laminating the second stack sequence (11) in step d).

7. The method according to any one of claims 1 to 3, wherein in step e) the curable adhesive is cured by exposure to electromagnetic radiation and / or chemically.

8. The method according to any one of claims 1 to 7, wherein the optically transparent adhesive is cured during pressure application in step d) during lamination of the second stack sequence (11).

9. Method according to one of claims 1 to 8, wherein the first stacking sequence (2) is formed as an adhesive pre-composite.

10. Method according to one of claims 1 to 9, in which, in order to form the layered frame (6), the first stacking sequence (2) is inserted into a cutout (7) of at least one thermoplastic film (8).

11. Method according to one of claims 1 to 10, wherein in step d) the second stack sequence (11) is evacuated during lamination.

12. The method according to claim 1, wherein the electro-optical functional film (9) comprises a guest-host film with a functional layer made of a liquid-crystalline material with an incorporated additive.

13. Method according to one of claims 1 to 12, wherein the first pane (3) and / or the second pane (10) consist of glass, in particular of soda-lime glass.

14. Composite pane (1), in particular obtained by the method according to one of claims 1 to 13, which comprises in this order: a first pane (3), at least one first intermediate layer (14) made of a thermoplastic material, a first adhesive layer (16) made of an optically transparent, cured adhesive, an electro-optical functional film (9), a second adhesive layer (17) made of an optically transparent, cured adhesive, wherein the first adhesive layer (16), the electro- optical functional film (9) and the second adhesive layer (17) are surrounded by a layered frame (6) made of a thermoplastic material, at least one second intermediate layer (15) made of a thermoplastic material, a second pane (10).

15. Use of the composite pane (1) according to claim 14 on buildings or in means of transport for traffic on land, in the air or on water, in particular in motor vehicles, for example as a windscreen, rear window, side windows and / or roof window.

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