THERMOPLASTIC FILM FOR LAMINATED GLASS

Description

[0001] The invention relates to a thermoplastic plastic film suitable as an intermediate layer for a laminated glass pane, a method for its production, a laminated glass pane, as well as a method for its production and its use.

[0002] Laminated glass panes are used in many places today, especially in vehicle manufacturing. The term "vehicle" is broadly defined and includes, among other things, road vehicles, aircraft, ships, agricultural machinery, and construction equipment.

[0003] Laminated glass panes are also used in other areas. These include, for example, building glazing as well as information displays, e.g. in museums or as advertising displays.

[0004] A laminated glass pane generally consists of two glass surfaces laminated onto an interlayer. The glass surfaces themselves may be curved and are usually of a constant thickness. The interlayer typically consists of a thermoplastic material, usually polyvinyl butyral (PVB), of a predetermined thickness, e.g., 0.76 mm.

[0005] Since the laminated glass pane is generally tilted relative to the viewer, double images occur. These double images are caused by the fact that incident light usually does not pass completely through both glass surfaces, but that at least part of the light is first reflected and only then passes through the second glass surface.

[0006] These double images are particularly noticeable in darkness, especially with strong incoming light sources, such as the headlights of an oncoming vehicle.

[0007] These double images are extremely distracting. Particularly in the area of ​​camera windows, these double images lead to misinformation. Camera windows are areas of a window or pane of glass behind which a camera is mounted, recording images of the surroundings. Such camera windows are becoming increasingly important, for example, in the field of autonomous driving.

[0008] Laminated glass is often used as a head-up display (HUD) to show information. A projection device projects an image onto the laminated glass to display information in the viewer's field of vision. In vehicles, the projection device is typically mounted on the dashboard, so that the projected image is reflected onto the nearest glass surface of the laminated glass, which is angled towards the viewer.

[0009] However, some of the light enters the laminated glass pane and is then reflected, for example, at the inner boundary layer of the outermost glass surface (from the viewer's perspective) and the intermediate layer, and subsequently exits the laminated glass pane with a slight delay.

[0010] Here too, a similar effect occurs, the effect of ghost images, in relation to the image to be displayed.

[0011] A purely classical compensation for ghost images using a wedge-shaped film with a fixed wedge angle leads to overcompensation for double images in transmission. This causes the viewer to be confused or, in the worst case, receives incorrect information. Current attempts to solve this problem involve arranging the surfaces of the glass panes at a fixed angle instead of parallel. This is achieved, for example, by having the interlayer have a linearly increasing and / or decreasing thickness. In vehicle manufacturing, the thickness is typically varied so that the thinnest layer is used at the bottom of the laminated glass pane, near the engine compartment, while the thickness increases towards the roof; that is, the interlayer has a wedge shape.

[0012] Laminated glass panes of this type with a wedge-shaped interlayer and the optical laws on which they are based are known per se and are described, for example, in the international patent applications WO 2015 / 086234 A1, WO 2015 / 086233 A1 and WO 2009 / 071135 A1, the American patents US 8,451,541 B2, US 7,060,343 B2, US 6,881,472 B2, US 6,636,370 B2 and US 5,013,134 or the German patent applications DE 196 11 483 A1 and DE 195 35 053 A1.

[0013] The required wedge angle profile and the resulting thickness profile of the intermediate layer must be calculated separately for each disc shape. Up to now, the thickness profile according to the invention has been achieved by using a suitable slot die during film extrusion, or by selectively stretching the film after it has been heated with a corresponding temperature profile. These methods can also be combined, for example, by generating the thickness profile in one direction using a suitable slot die during extrusion and in the other direction by subsequently stretching the film.

[0014] However, problems arise with this type of manufacturing.

[0015] When the manufactured film webs are wound into rolls for storage and shipping, the rolls take on an increasingly conical shape, which causes difficulties in handling and transporting them. To avoid these difficulties, it is known from European patent EP 0 647 329 B1 to produce film webs that have a uniform thickness profile at both edges over a width of at least 20% of the web width, followed by a wedge-shaped thickness profile extending to the center of the film web.

[0016] European patent EP 1 063 205 B1 discloses a method for producing an interlayer film for laminated glass, in which the starting composition for the interlayer film is fed into a production plant comprising an extruder, an extrusion die, a first cooling roller, and a second cooling roller. The two cooling rollers each have a clear opening that is adjusted according to the desired cross-sectional profile of the interlayer film to be produced. However, this method carries the risk that the thermoplastic material cools down too much in the cooling rollers, leading to unsatisfactory results.

[0017] Another disadvantage of the wedge-shaped thermoplastic films known to date is that the area of ​​the wedge profile in the HUD viewing windows is much larger than necessary for optimal ghost image suppression. Furthermore, manufacturing a film with two sections exhibiting different changes in the wedge angle, as required, for example, for use in a laminated glass pane with a HUD area and a camera window, is very difficult. European patent EP 2 883 693 A1 proposes cutting out the section intended for the HUD area from a film and then replacing it with a section featuring a wedge-shaped profile. However, no suggestions are made regarding the manufacturing process for the wedge-shaped profile. Additionally, the seams where the films are joined result in visually distracting transitions.

[0018] The object of the invention is to provide an improved thermoplastic film with at least one area having a changing wedge angle and to provide an improved method for its production.

[0019] The problem is solved according to the invention by a film according to independent claim 1. Preferred embodiments are described in the dependent claims.

[0020] The invention provides a thermoplastic film (F) suitable for a laminated glass pane, comprising at least one defined area intended for a camera window or a HUD (head-up display) area. This defined area has a non-zero wedge angle. The wedge angle can be constant within the defined area. This variant is particularly easy to manufacture.

[0021] Preferably, the defined region has a changing wedge angle. Thus, the thickness h2 of the thermoplastic film also changes within this region. The maximum thickness, h2max, is measured at the point where the thermoplastic film is thickest in the defined region. Adjacent to the defined region is the surrounding region, in which the thermoplastic film has a constant thickness h1. The maximum thickness h2max in the defined region is less than the thickness h1 of the thermoplastic film in the surrounding region. The film according to the invention therefore has a substantially constant thickness h1, except in the at least one defined region where the film is thinner everywhere than in the surrounding region. Preferably, the defined region is completely enclosed by the surrounding region, i.e., the defined region is surrounded on all sides by the surrounding region.In terms of the installation situation in the finished vehicle window, this means that the defined area directly borders the surrounding area at the top (roof edge), bottom, right and left.

[0022] Particularly good results are achieved when the film according to the invention is used as an interlayer in a laminated glass pane, since the thickness of the laminated glass pane varies only within a defined area and no increase in thickness occurs. Such increases in thickness can be problematic, especially in cases where the defined area in the laminated glass pane is intended for the edge region (10% distance from the pane edges relative to the total height of the finished pane). Optical advantages are particularly evident, as, for example, the transitions to the bodywork at the roof edge should appear as seamless as possible. With panes that are thicker at the upper edge than at the lower edge, complex measures are required to compensate for the differences.

[0023] The wedge angle is the angle measured at a specific point between the surfaces of the film. The fact that the wedge angle is not zero within the defined area means that, essentially, the wedge angle is not zero within that area. This does not preclude the existence of individual points within the defined area where the wedge angle is zero. With a variable wedge angle profile, after an increase in the wedge angle at the transition to the decreasing wedge angle, a point is reached at the corresponding inflection point where the wedge angle is zero.

[0024] The thickness of the thermoplastic film in the defined area is not constant, but variable. The wedge angle in the defined area is preferably variable and changes depending on the location. Preferably, the wedge angle changes in two directions perpendicular to each other (bidirectional wedge). When subsequently used in a windshield, these two directions correspond to the vertical direction (from the roof edge to the hood, i.e., from top to bottom) and the horizontal direction (from right to left).

[0025] The surrounding area is the area directly adjacent to the defined area. The defined area is enclosed by the surrounding area. Typically, the area of ​​the surrounding area is larger than the area of ​​the defined area.

[0026] In the surrounding area, the thermoplastic film has a substantially constant thickness. This does not preclude the possibility that the film may exhibit some roughness in the surrounding area due to the manufacturing process. However, manufacturing-related roughness differs from a planned decrease in thickness over a continuous area. The thickness h1 in the surrounding area is preferably from 50 µm to 2000 µm, particularly preferably from 300 µm to 850 µm, and typically from 380 µm to 760 µm. Films with these thicknesses produce particularly stable laminated glass panes.

[0027] The thermoplastic film according to the invention comprises one or more defined areas in which the wedge angle profiles are adapted as required.

[0028] When used in a laminated glass pane, the thermoplastic film according to the invention extends over the entire surface of the pane. The dimensions depend on the intended use and the size of the resulting laminated glass pane. Preferably, they have a length of 0.25 m to 5 m and a width of 0.25 m to 4 m.

[0029] The thermoplastic film can be formed by one or more flat thermoplastic films arranged on top of each other.

[0030] In a preferred embodiment, the thermoplastic film contains at least one material selected from the group consisting of polyvinyl butyral (PVB), ethylene vinyl acetate (EVA), polyethylene terephthalate (PET), polyurethane (PU), polypropylene (PP), polyacrylate, polyethylene (PE), polycarbonate (PC), polymethyl methacrylate, polyvinyl chloride, polyacetal resins, casting resins, polyacrylates, fluorinated ethylene-propylene copolymers, polyvinyl fluoride, ethylene tetrafluoroethylene copolymers, as well as copolymers and mixtures. Particularly preferably, the thermoplastic film consists essentially of PVB. This is especially suitable as an interlayer for laminated glass panes and yields good results.

[0031] In a further preferred embodiment of the invention, the thermoplastic film exhibits a noise-reducing effect. This advantageously reduces the transmission of noise through a composite pane provided with the thermoplastic film, thereby mitigating disturbance from ambient and road noise. Such an effect can be achieved by a multilayered, for example, three-layered thermoplastic film, wherein the inner layer (acoustic core) has a higher plasticity or elasticity than the surrounding outer layers, for example, due to a higher proportion of plasticizers. The thermoplastic film preferably has a multilayered structure, particularly a three-layered structure.

[0032] In a preferred embodiment, the thickness difference Δh2 min between the thickness of the thermoplastic film in the surrounding region h1 and the thickness at its thinnest point in the defined range is between 0.10 mm and 0.30 mm, preferably between 0.15 mm and 0.25 mm. Due to this minimal thickness difference, laminated glass panes can be laminated very effectively without causing critical stresses.

[0033] The defined area for a HUD preferably extends over an area of ​​10,000 mm² to 200,000 mm². Preferably, the HUD area is located on the driver's side of a vehicle's windshield.

[0034] The HUD area is typically located on the driver's side within the viewing area of ​​the laminated glass pane. The viewing area refers to the portion of the pane designed and suitable for viewing. This viewing area is, in particular, transparent and does not contain any opaque, printed areas, such as the usual perimeter screen printing. For the purposes of this invention, a pane is considered transparent if it exhibits a transmission of >70% in the visible spectral range.

[0035] Preferably, the wedge angle in the defined area of ​​the finished laminated glass pane increases gradually from bottom to top to avoid image distortion caused by an abrupt rise. Subsequently, the wedge angle increases in a central area according to a previously optimized profile to optimally suppress ghosting. This is followed by an area where the wedge angle gradually decreases to make the transition to the first thermoplastic film as inconspicuous as possible. Such a wedge angle profile is suitable for camera windows and HUD areas.

[0036] The defined area for a camera window preferably extends over an area of ​​2,000 mm² to 10,000 mm². On a vehicle windshield, the camera window is preferably located near the roof edge. This area is generally no longer part of the field of view.

[0037] The thermoplastic film has a first surface and an opposing second surface. In the surrounding region of constant thickness h1, the planes of the first surface and the second surface are arranged parallel to each other. In a preferred embodiment, the plane of the second surface is continuously parallel to the plane of the first surface in the surrounding region within the defined area (see embodiment in Figure 4 This means that material was removed from the first surface only within the defined area, compared to the surrounding area. Therefore, within the defined area, the first surface is not continuously parallel to the plane of the second surface in the surrounding area. This film is to be produced in a single step.

[0038] In a further preferred embodiment, the first and second surfaces are not parallel to the planes of the first and second surfaces in the surrounding area within the defined region. In this case, material has been removed from both the side of the first surface and the side of the second surface. Particularly preferably, this material removal is symmetrical, meaning that at each point, exactly the same amount of material has been removed from the side of the first surface as from the side of the second surface (see embodiment in Figure 10This results in the thermoplastic film having a mirror plane / plane of symmetry in the defined area. The plane of symmetry is parallel to the planes of the first and second surfaces in the surrounding area and is located centrally between these planes. This symmetrical design leads to particularly good results. This embodiment is especially advantageous in combination with multilayer thermoplastic films, since only the outer layers are affected by a smaller amount of material removal than if material were removed from only one side of the film.

[0039] In a further preferred embodiment, the thermoplastic film comprises more than one defined area, preferably two defined areas. A first defined area is particularly preferably provided as a HUD area and is located in the viewing area of ​​the pane, and a second defined area is provided as a camera window and is located in the upper third of the pane. Since the wedge angle profiles in the defined areas of the thermoplastic film according to the invention are achieved by a decrease in thickness, several defined areas can be provided without causing increased stresses in the finished laminated glass pane.

[0040] In one embodiment of the invention, the thermoplastic film can have at least one tinted area. Such a tinted area at the upper edge of the window is known to those skilled in the art, for example, as a "shaded band" – this can reduce the driver's glare from sunlight.

[0041] In one embodiment of the invention, the thermoplastic film can have a sun or heat protection function. For example, the thermoplastic film can contain a reflective coating in the infrared range or IR-absorbing additives.

[0042] The invention further provides a method for producing a thermoplastic film according to the invention, which is suitable as an interlayer for a laminated glass pane. In a first step of the method according to the invention, a thermoplastic film with a substantially constant thickness h1 is provided. Such films, which are suitable as interlayers for laminated glass panes, are known. In a previously defined area, thermoplastic polymer is ablated in a second step using a laser. This creates a previously defined wedge angle profile. By using the laser, it is possible to precisely transfer a wedge angle profile previously calculated using simulation tools onto the thermoplastic film with constant thickness. This is particularly advantageous for more complex wedge angle profiles that cannot be produced with such precision using conventional methods.

[0043] The method according to the invention is particularly flexible because the position of the defined area is freely selectable. For example, a suitable film with a HUD area for right-hand drive or left-hand drive vehicles can be produced by removing thermoplastic polymer at the corresponding location. Since the wedge angle is generated by ablation, no material incompatibilities occur. Furthermore, visual impairments at cut edges are reduced if, for example, defined areas are manufactured separately and inserted into a recess in a film. The method according to the invention is particularly suitable for processing films consisting of several layers with different compositions. One example is an intermediate layer with a noise-reducing effect.Since only small amounts of material need to be removed, even films with wedge angle profiles can be produced without causing disturbing optical defects. Preferably, such an intermediate layer with noise-reducing properties consists of three layers. Preferably, the inventive method removes only enough material so that the inner layer is not touched. The inner layer may have a different refractive index, so removing material from this layer could lead to disturbing optical aberrations.

[0044] The method according to the invention is particularly suitable for producing thermoplastic films with at least one defined area that is completely enclosed by the surrounding area. Such a thermoplastic film cannot be produced using conventional methods, such as that disclosed in EP 0 647 329 B1. The method described therein only yields thermoplastic films whose area, with varying wedge angles, extends to the edge of the thermoplastic film. However, when used in a laminated glass pane, this has the disadvantage already described: the thickness of the pane varies from the top to the bottom edge.

[0045] Using a wedge angle that varies in two directions, double images and ghost images can be particularly effectively avoided or reduced. The relationship between wedge angle profiles and the avoidance and reduction of ghost images and double images is known in the prior art and is described, for example, in WO2015086234A1 and WO2015086233A1. Preferably, the optimal wedge angle profile has been previously optimized using simulation tools to avoid double images and ghost images.

[0046] In a preferred embodiment of the inventive method, the first surface of the untreated thermoplastic film is first treated with the laser in a defined area, and polymer is removed there. Subsequently, the second surface of the thermoplastic film is treated with the laser in the same defined area. Preferably, the same amount of polymer is removed from both sides (mirror symmetrical). In this way, the removal on one side can be reduced so that only the surface of the polymer needs to be removed. In the case of multilayer films, this avoids removing material from several layers. Thus, any optical impairment caused by the removal process is kept to a minimum.

[0047] In a preferred embodiment of the method according to the invention, the ablation depth is between 0.10 mm and 0.30 mm, preferably between 0.15 mm and 0.25 mm. The ablation depth is the depth to which material is removed, caused by the interaction between the laser and the material. At the described ablation depths, only a very superficial layer of material is removed. Therefore, thickness variations across the entire film are very small, making the film particularly well-suited as an interlayer for laminated glass. Furthermore, multilayer films, especially noise-reducing films, can also be modified at these ablation depths without causing any disturbing optical distortions at the edge of the defined area.

[0048] Furthermore, the invention proposes a laminated glass pane with a thermoplastic film according to the invention.

[0049] The laminated glass pane according to the invention comprises at least a first glass pane, a second glass pane, and a thermoplastic polymer film according to the invention, wherein the thermoplastic polymer film is arranged between the first glass pane and the second glass pane. The laminated glass pane according to the invention, with a locally defined area of ​​variable wedge angle, is particularly stable because the thickness variation of the film is limited to a comparatively small area. In conventional films with a constant wedge angle, the thickness varies in the vertical and / or horizontal direction across the entire pane height and / or width, leading to the development of stresses. The thickness of such a conventional laminated glass pane is greater at the top than at the bottom. This thickness difference also leads to optical disadvantages in an installed pane, as a thicker edge of the pane may protrude at the transition to the roof edge.When using a thermoplastic film according to the invention, the thickness of the laminated glass pane according to the invention is the same at the upper and lower edges.

[0050] In an advantageous embodiment, the total thickness of the laminated glass pane is 3.5 mm to 6.0 mm, preferably 4.0 mm to 6.0 mm, and particularly preferably 4.4 mm to 5.6 mm. Laminated panes with these thicknesses exhibit sufficient mechanical stability and strength, as well as advantageous acoustic properties with regard to the shielding of ambient noise. At the same time, they are not too thick or heavy to be used as windshields in typical vehicles, especially motor vehicles.

[0051] The outer pane and the inner pane preferably have a constant thickness with essentially plane-parallel main surfaces and a circumferential side edge connecting them.

[0052] In an advantageous embodiment, the thickness of the inner disc is from 0.3 mm to 3.5 mm, preferably from 0.7 mm to 2.6 mm.

[0053] In an advantageous embodiment, the thickness of the outer pane is at least 1.8 mm, preferably at least 2.1 mm. The thickness of the outer pane is preferably at most 4.5 mm, more preferably at most 3.5 mm. In a particularly advantageous embodiment, the thickness of the outer pane is from 2.1 mm to 4.5 mm, for example from 2.1 mm to 3.5 mm or from 2.5 mm to 4.5 mm, preferably from 2.5 mm to 3.5 mm. In this range, the laminated pane exhibits advantageous mechanical stability and noise-insulating properties, while still being sufficiently thin and light to be used as a windshield.

[0054] The outer and inner panes are preferably made of glass, especially soda-lime glass, which is common for window panes. However, the panes can also be made of other types of glass (for example, borosilicate glass, quartz glass, aluminosilicate glass) or transparent plastics (for example, polymethyl methacrylate or polycarbonate).

[0055] The outer disc and the inner discs can be independently unstressed, partially stressed, or stressed. If at least one of the discs is to have a prestress, this can be a thermal or chemical prestress.

[0056] Furthermore, the invention proposes a manufacturing process for the laminated glass pane. Two glass panes are provided. The thermoplastic film according to the invention is placed between these glass panes, and the resulting assembly of two glass panes and thermoplastic film is bonded together. Preferably, the bonding is carried out using a lamination process. Suitable lamination methods, such as the autoclave process or the vacuum bag process, are known to those skilled in the art.

[0057] Furthermore, the invention proposes a head-up display arrangement, an arrangement with a camera, and the use of laminated glass panes. Brief description of the drawings

[0058] Embodiments of the present invention are described by way of example with reference to the attached drawings, which show: Fig. 1the fundamental connection of the formation of double images in transmission, Fig. 2 the fundamental connection between the emergence of ghost images in reflection, Fig. 3 an exemplary structure of a laminated glass pane with a wedge-shaped intermediate layer, Fig. 4 a cross-section through an area of ​​a thermoplastic film according to the invention, Fig. 5 a top view of a laminated glass pane according to the invention with a camera window, Fig. 6 the basic structure of a camera setup, Fig. 7 a top view of a laminated glass pane according to the invention with HUD area, Fig. 8 a schematic representation of a method according to the invention, Fig. 9 a schematic top view of a defined area during the process, Fig. 10 a cross-section through an area of ​​a thermoplastic film according to the invention and Fig. 11a cross-section through an area of ​​a thermoplastic film according to the invention.

[0059] In Figure 1The fundamental relationship for the formation of double images in transmission is illustrated using a ray diagram. A curved disk 1 is assumed. The curved disk has a radius of curvature (R+D) at the point where a ray enters the curved glass disk 1. Light is emitted from a light source 3. This light strikes the disk and, according to the known laws of refraction, is refracted at the first interface between air and glass, and at the second interface between glass and air, entering the eye 2 of an observer. This ray is represented as a solid line P. From the observer's perspective, the light source 3 appears to be located at 3'. This is represented as ray P'.Besides this ray P, which is called the primary ray, the ray is only partially refracted at the second glass / air interface in the manner described above; a smaller portion is reflected at the second interface and reflected once more at the first interface before the ray passes through the second interface and enters the observer's eye 2. This ray, the so-called secondary ray, is represented as a dashed line S. From the observer's perspective, the light source 3 also appears to be located at position 3". The angle η enclosed by the primary ray P' and the secondary ray S is the so-called double image angle.

[0060] To counteract this double image, it can now be provided that a wedge angle is placed between the two in Figure 1 Essentially parallel boundary layers are assumed to be provided.

[0061] According to JP Aclocque, "Double images as a disturbing optical defect of the windshield" in Z. Glastechn. Ber. 193 (1970) pp. 193-198, the double image angle can be calculated as a function of the bending radius of the glass pane and the angle of incidence of the light ray according to the following relationship: η = 2 d R ⋅ sin φ n 2 − sin 2 φ , where η denotes the double image angle, n the refractive index of the glass, d the thickness of the glass pane, R the bending radius of the glass pane at the location of the incident light ray, and ϕ the angle of incidence of the light ray to the normal to the tangent to the pane.

[0062] For flat glass panes, the double image angle η is given by η = 2 ⋅ δ ⋅ n 2 − sin 2 φ cos φ depending on the wedge angle δ formed by the glass surfaces.

[0063] Thus, by equating the aforementioned formulas, the necessary wedge angle for eliminating the double image can be calculated: δ = d R ⋅ cos φ ⋅ sin φ n 2 − sin 2 φ .

[0064] As a rule, this wedge angle is achieved by inserting a wedge-shaped intermediate layer F between a first glass layer GS 1 and a second glass layer GS 2 in laminated glass panes 1, see Figure 3 In general, it can be assumed for simplification that the refractive index n is constant, since the difference in the refractive index of the intermediate layer F and the glass layers GS 1 , GS 2 is rather small, so that the small difference has hardly any effect.

[0065] This idea can also be applied to curved windshields. As a rule, for simplicity, the angle of incidence and the bending radius are assumed for a reference viewing point, and the resulting wedge angle is then applied to the entire windshield.

[0066] However, for large laminated glass panes 1, so-called panoramic panes, and / or more strongly curved laminated glass panes 1, this approach is no longer sufficient, so that as a rule a wedge angle profile that changes in the vertical direction must be determined.

[0067] Then, for example, a compensation wedge angle profile δ can be determined by point-by-point calculation along an imaginary vertical centerline of a laminated glass pane and possible interpolation. After determining the compensation wedge angle profile, a corresponding intermediate layer F can be produced.

[0068] With regard to head-up displays, a problem arises similar to the phenomenon of double images, which is called ghosting.

[0069] In Figure 2The fundamental relationship of the formation of ghost images in reflection is illustrated using a ray diagram. A curved glass pane 1 is assumed. The curved glass pane 1 has a radius of curvature R at the point where a ray enters it. Light is emitted from a light source 3, which represents a head-up display (HUD). This light travels along the ray Ri from the inside of the glass pane 1 at an angle Θ and is reflected there at the same angle Θ. The reflected ray Rr enters the eye 2 of an observer. This ray path is represented as a solid line. From the observer's perspective, the light source 3 appears to be virtually located at position 3', i.e., in front of the glass pane 1. This is represented as ray Rv. In addition to this first ray, another ray enters the eye 2 of the observer.This ray R' i also originates from light source 3. However, according to the known laws of refraction, this ray R' i enters the glass pane 1 at the inner air / glass interface and is reflected at the outer glass / air interface before passing through the inner interface and reaching the observer's eye 2 as ray R' r. The inner interface is thus the interface closer to the observer, while the outer interface is the interface farther away. This ray path is represented by a dashed line. From the observer's perspective, light source 3 also appears to be virtually located at position 3", i.e., also in front of glass pane 1. This is represented as ray R' v.

[0070] To address this problem, the wedge angle can now be changed so that the ray R' r reflected at the outer interface and the ray R r reflected at the inner interface overlap with respect to the observer's eye 2, i.e., the ray reflected at the outer interface emerges at the point of reflection of the ray incident at the inner interface.

[0071] If this is only performed for a single eye position, the resulting wedge angle may not yield optimal results. This can be explained, among other things, by the fact that both the height of drivers, for whom head-up displays are primarily intended, and their seating positions vary considerably, resulting in a multitude of possible eye positions. Consequently, the virtual display is located in different positions depending on the eye position, and therefore, a different value for an optimized wedge angle may be obtained for each of these eye positions.Furthermore, a wedge angle optimized exclusively for ghost images generally leads to an overcompensation of double images, so that the resulting double images are problematic in terms of the viewer's perception and / or compliance with legal testing regulations and / or compliance with customer specifications regarding double images.

[0072] Wedge angle profiles, which take into account both the different eye positions and the compensation of double images in the HUD area, are not constant in either the horizontal or vertical direction. The resulting thickness profiles for the intermediate layer F cannot be produced using simple extrusion processes.

[0073] In Figure 4Figure 1 shows a cross-sectional area of ​​a thermoplastic film F according to the invention. In this example, the film F is made of PVB. In the surrounding area A, the thickness h1 is 0.76 mm and is essentially constant. In the defined area K, the thickness decreases. At its thinnest point, the thermoplastic film F is 0.56 mm thick. This means that the thickness difference Δh2 min between the thicknesses in the surrounding area and at the thinnest point in the defined area is 0.76 mm - 0.56 mm = 0.20 mm = Δh2 min. The film F is thinner in the defined area than in the surrounding area; that is, even at its thickest point, the thickness h2 max is less than the thickness h1. In the defined area K, the wedge angle in the first boundary region g1 initially increases slowly and then increases in a central region according to a previously optimized profile.Subsequently, the wedge angle gradually decreases again in a second boundary region g2 to make the transition to the surrounding region A as inconspicuous as possible. Accordingly, the film thickness initially decreases gradually in the first boundary region g1, then changes in a central region according to a previously optimized profile, and then gradually increases again in the second boundary region g2. This arrangement with two boundary regions featuring gradually increasing and decreasing wedge angles at the top and bottom, and to the right and left, respectively, relative to an installed windshield, is particularly advantageous for minimizing the visual impairment at the transition between the surrounding region A and the defined region K. The cross-section shows that no material removal has occurred along the second surface 10.2; that is, the second surface continues in the defined region in the same plane as in the surrounding region A, parallel to the first surface 10.1 in the surrounding area. Thus, in the defined area, material was only removed from the side of the first surface 10.1.

[0074] In Figure 5A top view of a laminated glass pane 1 according to the invention is shown. The laminated glass pane is intended as a windshield for a passenger car. In the drawing, the upper edge borders the roof edge of the car, and the lower edge borders the engine compartment edge. A camera window K is arranged in the upper third of the laminated glass pane, outside the viewing area. The windshield preferably has a cover print 9 in the upper edge region. Cover prints are common for vehicle windows outside the central viewing area to conceal add-on parts or to protect the adhesive bonding the vehicle window to the body from UV radiation. The cover print typically consists of a black or dark enamel applied and baked on using a screen printing process. In this example, the cover print 9 surrounds the camera window K of the vehicle window to conceal the camera behind it.The laminated glass pane consists of two glass layers, GS1 and GS2, and a thermoplastic film F sandwiched between them. The glass layers GS1 and GS2 are made of soda-lime glass and are 2.1 mm thick. The thermoplastic film F is configured as shown in [reference]. Figure 4 described. The defined area K forms the camera window.

[0075] In Figure 6Figure 6 shows a possible camera arrangement consisting of the described laminated glass pane 1 and a camera 7. The glass layer GS1 of the laminated glass pane 1 faces the outside of the vehicle, and the glass layer GS2 faces the inside. The camera 7 is located inside the vehicle and captures the light rays entering from the outside through the laminated glass pane 1. The camera is directed at the specified area; that is, it is mounted so that the light rays enter through the area with the optimized wedge angle profile. This allows double images in transmission to be efficiently reduced. This can be successfully used, for example, in lane departure warning systems.

[0076] In Figure 7Figure 1 shows a top view of a laminated glass pane 1 according to the invention, with a HUD area that is surrounded on all sides by the surrounding area A. The HUD area is located in the defined area K, in which an optimized wedge angle profile is arranged to prevent ghosting and double images. In the example shown, the HUD area is located on the left side of the windshield in the viewing area.

[0077] When manufacturing the laminated glass pane 1 from glass layer GS1, glass layer GS2 and thermoplastic polymer film F according to the invention, this design can easily be adapted for a right-hand drive vehicle by removing thermoplastic polymer in the defined area K on the right side according to a previously optimized wedge angle profile.

[0078] In Figure 8An exemplary process sequence according to the invention is shown. In step I, a thermoplastic film with a substantially constant thickness 4 is provided. In step II, the laser 8 is positioned at a distance a of approximately 1700 mm from the surface 10 of the thermoplastic film with constant thickness 4 in the defined area K. A CO₂ laser with a wavelength of 10.6 µm and a power of 250 W is suitable, for example. The defined area was scanned in lines 11 with this laser (see Figure 9 ). In Figure 9Figure 1 shows a top view of a defined area K being treated with a laser in lines. The laser was initially used at low power, which was then gradually increased. At a speed v of 10 m / s, polymer was ablated in lines within the defined area. After each line, the laser was moved 0.1 mm away and then the polymer was ablated along the next line. After approximately 50 lines (5 mm), the laser power P was increased to increase the rate of polymer ablation. This also increased the ablation depth. This process was repeated until the desired profile was achieved. This gradual increase in power allowed for the precise determination of the desired wedge angle.

[0079] In Figure 10A thermoplastic film F is shown, which was treated with a laser in the defined area on its first surface 10.1 and on its second surface 10.2. A mirror-symmetrical ablation of thermoplastic polymer was performed there. This allows larger wedge angles to be achieved, with the absolute ablation depths on the surfaces being smaller than if ablation were performed on only one surface.

[0080] In Figure 11 A thermoplastic film F is shown, which is in the specified area as in Figure 10The first surface 10.1 and the second surface 10.2 were treated with a laser. Only the wedge angle profile differs within the defined area K. The same amount of material was removed from each surface 10.1 and 10.2. This results in a mirror-symmetric arrangement of the two surfaces 10.1 and 10.2 within the defined area K. The mirror plane / plane of symmetry S is the plane that runs parallel to the planes of the first surface 10.1 and the second surface 10.2 in the surrounding area, centered between them. The mirror plane S therefore runs parallel to the plane of the first surface 10.1 and parallel to the plane of the second surface 10.2 in the surrounding area A, at a distance of ½ h1. Reference symbol list

[0081] GS1 Glass layer 1, Glass pane 1 GS2 Glass layer 2, Glass pane 2 F Thermoplastic sheet K Fixed area A Surrounding area g1 First boundary area g2 Second boundary area h1 Thickness of raw thermoplastic sheet, Thickness of thermoplastic sheet in surrounding area A h2 Thickness of thermoplastic sheet in fixed area h2 max Maximum thickness of thermoplastic sheet in fixed area S Plane of symmetry, Mirror plane 1 Glass pane 2 Eye 3 Light source, HUD projector 4 Thermoplastic sheet with constant thickness, raw thermoplastic sheet 5 HUD array 6 Camera array 7 Camera 8 Laser 9 Cover print 10 Surface of thermoplastic sheet 10.1 First surface of thermoplastic sheet 10.2 Second surface of thermoplastic sheet 11 Line

Claims

1. Thermoplastic film (F) suitable as an intermediate layer for a laminated glass pane (1), wherein the thermoplastic film (F) comprises at least - a defined region (K), which is provided for a camera window or an HUD (head-up display) region that has a non-zero wedge angle, and - a region (A) surrounding the defined region (K) on all sides, in which the thermoplastic film has a substantially constant thickness (h1), wherein the maximum thickness (h2max) in the defined region (K) of the thermoplastic film is less than the thickness (h1) in the surrounding region (A).

2. Thermoplastic film (F) according to claim 1, wherein the defined region (K) has a variable wedge angle.

3. Thermoplastic film (F) according to claim 1 or 2, wherein the thickness (h1) of the thermoplastic film in the surrounding region (A) is between 50 µm and 2000 µm, preferably between 300 µm and 850 µm, and particularly preferably between 380 µm and 760 µm.

4. Thermoplastic film (F) according to one of claims 1 through 3, wherein the thermoplastic film (F) is made substantially of PVB.

5. Thermoplastic film (F) according to one of claims 1 through 4, wherein the thermoplastic film (F) has a noise-reducing effect.

6. Thermoplastic film (F) according to one of claims 1 through 5, wherein the defined region (K) extends over an area of 2000 mm2 to 200,000 mm2, preferably over an area of 10,000 mm2 to 200,000 mm2 for an HUD region and over an area of 2000 mm2 - 10,000 mm2 for a camera window.

7. Thermoplastic film (F) according to one of claims 1 through 6, wherein the thermoplastic film (F) has a first surface (10.1) and an opposite second surface (10.2), whose planes are arranged parallel to one another in the surrounding region (A), and wherein the thermoplastic film has, in the defined region (K), a mirror plane / plane of symmetry (S), which is arranged parallel to the planes of the first surface (10.1) and the second surface (10.2) in the surrounding region centrally between these planes.

8. Method for producing a thermoplastic film (F) suitable as an intermediate layer for a laminated glass pane, wherein the thermoplastic film (F) comprises at least a defined region (K) that has a non-zero wedge angle, and comprises a surrounding region (A), in which the thermoplastic film (F) has a substantially constant thickness (h1), wherein the maximum thickness (h2max) in the defined region (K) of the thermoplastic film is less than the thickness (h1) in the surrounding region (A), the method comprising at least the steps: - Providing a thermoplastic film having a constant thickness (4), - Ablating thermoplastic polymer using a laser (8) in at least one defined region (K).

9. Method according to claim 8, wherein the wedge angle in the defined region (K) changes.

10. Method according to claim 8 or 9, wherein first, a first surface (10.1) of the thermoplastic film having a constant thickness (4) is treated with the laser (8) in the defined region (K) and then, the second surface (10.2) of the thermoplastic film is treated with the laser (8) in the same defined region (K).

11. Method according to one of claims 8 through 10, wherein the ablation depth is between 0.10 mm and 0.30 mm, preferably between 0.15 mm and 0.25 mm.

12. Laminated glass pane (1), at least comprising a first glass layer (GS1), a second glass layer (GS2), and a thermoplastic film (F) according to one of claims 1 through 7, wherein the thermoplastic film (F) is arranged between the first glass layer (GS1) and the second glass layer (GS2).

13. Method for producing a laminated glass pane (1), comprising the steps - Providing a first glass pane (GS1) - Providing a second glass pane (GS2) - Placing a thermoplastic film (F) according to one of claims 1 through 7 on the first glass pane (GS1), - Placing a second glass pane (GS2) on the thermoplastic film (F), and - Joining the second glass pane (GS2) to the thermoplastic film (F).

14. Head-up display arrangement (5), comprising a projector (3) for illuminating a head-up display area of a laminated glass pane (1) and a laminated glass pane (1) according to claim 12, wherein, during operation, the projector (3) substantially illuminates the defined region (K).

15. Camera arrangement (6), comprising a camera (7) and a laminated glass pane (1) according to claim 12, wherein the camera (7) is directed at the defined region (K) and records light beams that pass through the laminated glass pane (1).

16. Use of the laminated glass pane (1) according to claim 12 as a front pane with a head-up display and / or camera window in means of transportation on water, on land, and in the air.