Method for producing a vehicle composite pane having improved impact protection

Abstract

The invention relates to a method for producing a vehicle composite pane (10) having improved impact protection, in which method at least a) an outer pane (1) made of glass and an inner pane (2) made of glass are provided, b) defective points (4) are formed in the outer pane (1) and / or the inner pane (2) in at least one first portion (X), c) the outer pane (1) comprising defective points and / or the inner pane (2) comprising defective points are / is bent, d) a thermoplastic intermediate layer (3) is placed onto the outer pane (1) or the inner pane (2), e) the layer stack is completed with the inner pane (2) or the outer pane (1), and f) the layer stack composed of at least the outer pane (1), the thermoplastic intermediate layer (3) and the inner pane (2) is laminated to form a windshield (10), the defective points (4) being formed in the outer pane (1) and / or the inner pane (2) by means of indenting.

Description

[0001] Method for producing a vehicle composite window with improved impact protection

[0002] The invention relates to a method for producing a vehicle composite pane with improved impact protection, such a vehicle composite pane and its use.

[0003] Laminated glazing, which comprises at least two panes and at least one polymer film bonded between the panes, has been in widespread use for decades in various technical fields, particularly in building glazing and vehicle construction. The selection of materials and the dimensioning of components depend on the requirements of the specific application, particularly with regard to the desired mechanical strength of the finished glazing, taking into account the constraints imposed by the frame and any attachments.

[0004] US 3,437,552 A discloses laminated panes comprising two glass panes and an intermediate polyvinyl butyral (PVB) layer.

[0005] US 6,708,595 B1 discloses a bulletproof laminated glass pane for motor vehicles, which comprises a stacking sequence of several panes and several adhesive intermediate layers in between.

[0006] JP 2008133141 A discloses a composite pane comprising an intermediate layer, wherein the intermediate layer has a first region and a second region and the tensile stiffness of the intermediate layer is higher in the first region than in the second region.

[0007] Particularly in the automotive industry, there is a trend towards the use of thinner and therefore lighter glass in laminated glass panes as part of the efforts to reduce weight and thus achieve fuel and energy savings. Nevertheless, this glazing must meet defined mechanical requirements laid down in relevant industry standards. This increases the safety requirements not only with regard to vehicle occupants, but also with regard to other road users such as pedestrians. For example, in the event of a head-on collision between a pedestrian and a car, the pedestrian is highly likely to hit the hood of the car, with their head striking the windshield. This can result in serious or even fatal injuries to the pedestrian, particularly if their head penetrates the windshield and hits other objects such as the dashboard.With regard to other accident scenarios in which an object strikes the windshield, it is also desirable to specifically control the fracture characteristics of the windshield and thereby ensure improved impact protection in specific areas of the windshield. The areas of the windshield to be equipped with improved impact protection should be freely selectable depending on the customer's requirements, the windshield model, and the most likely accident scenario.

[0008] The invention is therefore based on the object of providing a method for producing a vehicle composite pane with controllable fracture characteristics and the associated improved impact protection, as well as a composite pane with these properties. In particular, the composite pane, when used as a windshield, should, on the one hand, offer greater accident safety for pedestrians and, on the other hand, ensure compliance with the relevant standards for windshields with regard to stone chip resistance and transparency.

[0009] This object is achieved according to the invention by a method according to claim 1. Advantageous embodiments of the invention emerge from the subclaims.

[0010] The method according to the invention for producing a windshield with improved impact protection comprises at least the steps a) providing an outer pane and an inner pane, b) introducing defects in at least a first partial area of ​​the outer pane and / or inner pane, c) bending the outer pane with defects and / or bending the inner pane with defects, d) applying a thermoplastic intermediate layer to the outer pane or the inner pane, e) completing the layer stack of at least the outer pane and the thermoplastic intermediate layer with the inner pane or

[0011] Completing the layer stack of at least outer pane and thermoplastic intermediate layer with the outer pane and f) laminating the layer stack of at least outer pane, thermoplastic intermediate layer and inner pane to form a windshield, wherein the defect locations in step b) are introduced into the outer pane and / or the inner pane by means of indentation and the inner pane and the outer pane are glass panes.

[0012] The inventors have determined that a composite vehicle window produced using the method according to the invention has improved fracture characteristics in the first partial region when an object strikes the windshield. The defects introduced by indentation lead to a targeted weakening of the outer pane and / or inner pane, which significantly influences the fracture characteristics of the composite vehicle window in the first partial region and reduces the deceleration rate of an impacting object. In the method according to the invention, the defects are first introduced by indentation and the panes are then bent. The inventors have determined that indentation of one or both panes of the composite vehicle window prior to bending leads to a composite window with the desired improved fracture characteristics while simultaneously maintaining the stone chip resistance of the vehicle window.In this context, improved fracture characteristics mean that the pane fractures prematurely in the first sub-area or sub-areas of the laminated pane. The location and size of the first sub-area(s) can be freely selected depending on the application. For example, the improved fracture characteristics are advantageous in areas of the windshield where the pedestrian's head is to be expected to impact in accidents involving pedestrians. Heating of the indented pane or panes during the bending process causes a partial healing of the defects created by indentation, which has a beneficial effect on the mechanical properties of the pane. Indentation of non-bent planar panes is also much easier to handle in practice than machining bent panes.

[0013] In a preferred embodiment of the method according to the invention, the defects are applied to the interior-side surface of the outer pane and / or to the interior-side surface of the inner pane. These pane surfaces are subject to the greatest deflection when an object impacts the exterior surface of the outer pane. In order to achieve premature breakage of the composite pane produced using the method according to the invention in at least a first partial area, for example when a human head impacts, it is advantageous to introduce the defects on the aforementioned pane surfaces. The defects introduced using the method according to the invention can be spherical, rectangular, rhombic, pyramid-shaped, or conical. The geometry of the defect is derived from the image of the indenter tip used.Methods for microindentation or nanoindentation are generally known to those skilled in the art and are generally used for testing the hardness of materials. In the method according to the invention, indentation is preferably carried out as microindentation or nanoindentation, with the indenter tip having a spherical, rectangular, rhombic, pyramidal, or conical geometry. Corresponding indenter tips are commercially available and known to those skilled in the art. Over time, a wide variety of methods for testing the hardness of materials have become established. These differ primarily in their area of ​​application within different material groups and in the geometry of the indenter tip.

[0014] The defect points are preferably introduced by indentation with an indenter tip for hardness testing according to Brinell (DIN EN ISO 6506-1 to EN ISO 6506-4), Vickers (DIN EN ISO 6507-1:2018 to -4:2018), Knoop (DIN EN ISO 4545-1 to -4), Rockwell (DIN EN ISO 6508-1) or with an indenter syringe with the basic shape of a triangular pyramid according to Berkovich. The Brinell hardness test uses a hard metal ball as the indenter tip, whereby the balls used can have a diameter of 1 mm, 2.5 mm, 5 mm or 10 mm. An indenter tip for the Vickers hardness test is designed as an equilateral diamond pyramid with an opening angle (measured between the side surfaces, not the edges of the pyramid) of 136°. The Knoop hardness test is based on the Vickers hardness test, but in contrast, a diamond tip with a rhombic shape is used with tip angles of 172.5° for the long side and 130° for the short side of the indenter tip.In the Rockwell hardness test, various indenter tip geometries are used, for example, steel balls or conical diamond tips are used as test specimens. A Berkovich indenter tip has the basic shape of a triangular pyramid and is described in detail in the publication "Determination of fracture toughness of brittle materials by indentation" (Acta Mechanica Solida Sinica, Vol. 28, No. 3, June, 2015). All mentioned indenter tips are commercially available and are further specified in the cited standards.

[0015] The defect locations are preferably introduced by identification using an indenter tip for hardness testing according to Vickers or Berkovich with an indentation load of 50 g to 700 g, particularly preferably 100 g to 600 g, in particular 200 g to 550 g. In a preferred embodiment of the method, the indenter tip is first positioned above the surface to be indented. The indenter tip is held in the air by a force sensor and then lowered onto the glass surface. When the indenter tip is no longer supported by the sensor, it indents the glass with a load corresponding to the mass of the components of the indenter tip plus an optionally applied additional load. An indenter tip with a mass of 250 g is preferably used, resulting in a corresponding indentation load that can be further increased if necessary, for example to 500 g.Tests by the inventors have shown that indentation using an indenter tip for Vickers hardness testing with an indentation load of 250 g or 500 g, or a weight between 250 g and 500 g, is particularly advantageous for achieving favorable fracture behavior with good stone chip resistance of the composite pane. The indentation load used can also vary depending on the position of the defect on the pane surface. Accordingly, it is possible to introduce larger defects into the glass surface in some places and smaller ones in others. By correlating the size of the defects with the indentation load, the fracture behavior of the pane can be controlled in general as well as specifically depending on the position of the defect on the pane.Areas where an earlier breakage of the disc is expected to occur are provided with larger defects created by means of a higher indentation load, while areas with smaller defects will break at a later time.

[0016] Laminated panes for vehicle glazing are typically manufactured by lamination of two curved flat glass panes. The float process is the most common and cost-effective method for producing flat glass, so panes for vehicle glazing are usually produced using this method. Depending on the defects inherent in the manufacturing process, indentation after the panes have been manufactured can be adjusted. The surface compressive stress of the panes after indentation is preferably between 50 MPa and 100 MPa.

[0017] In a preferred embodiment of the method according to the invention, the indentation in step b) is carried out by means of a plurality of indenter tips which contact the surface to be indented at least partially simultaneously. At least partially simultaneously means that at least two indenter tips contact the surface to be indented in the same time window or in two partially overlapping time windows. Particularly preferably, a plurality of indenter tips are mounted on a holder, for example a frame, and simultaneously lowered onto the surface to be indented. This results in simple handling and a time-efficient process duration. The number and position of the indenter tips mounted on a common holder preferably corresponds to the number and position of the defects to be introduced into a glass surface.The holder with indenter tips therefore only needs to be positioned once per workpiece, allowing all defects to be introduced simultaneously. The indentation load can be set differently for each indenter tip or the same for several or all indenter tips. A different indentation load is advantageous for adapting the size of the defects depending on the position of the defect on the disk. If defects of different sizes are required within a workpiece, different indentation loads can be applied between the respective indenter tip and the holder that supports the indenter tips. If the same indentation load is required for all indenter tips, one or more loads can also be applied to the holder itself.

[0018] In step c) of the method according to the invention, at least the pane or panes into which defects have been introduced are bent. The outer pane and / or the inner pane are preferably bent at a temperature of 500°C to 700°C.

[0019] The outer and inner panes can be bent individually. Preferably, the outer and inner panes are bent congruently together (i.e., simultaneously and using the same tool), as this ensures the shape of the panes is optimally matched for subsequent lamination.

[0020] In one possible embodiment of the invention, defects are simply introduced into the outer pane, and the inner pane is not pre-bent. A thin inner pane is used, which exhibits film-like flexibility and can thus be adapted to the pre-bent outer pane without the need for pre-bent itself. This simplifies the production of the laminated glass. In a preferred embodiment, the inner pane is also subjected to a bending process. This is particularly advantageous for strong bends in multiple spatial directions (so-called three-dimensional bends).

[0021] If coatings, such as solar control coatings or heatable coatings, are to be applied to the surfaces of the outer and inner panes facing the thermoplastic interlayer, the panes are preferably bonded to form a laminated glass after the coating has been applied. If the vehicle laminated pane includes coatings that are to be electrically contacted, the electrical contacting of the electrically conductive layers takes place via bus bars or other suitable electrical conductors before the laminated pane is laminated.

[0022] Any opaque masking prints applied to the edge area of ​​the composite pane are preferably applied using the screen printing process.

[0023] The bonding of the outer and inner panes via the thermoplastic intermediate layer to form the composite vehicle pane is preferably carried out by lamination under the influence of heat, vacuum, and / or pressure. Known processes for producing a composite pane can be used. During lamination, the heated, flowable thermoplastic material flows, creating a stable composite.

[0024] For example, so-called autoclave processes can be carried out at an elevated pressure of approximately 10 to 15 bar and temperatures of 130°C to 145°C for approximately 2 hours. Conventional vacuum bag or vacuum ring processes, for example, operate at approximately 200 mbar and temperatures of 80°C to 110°C. The outer pane, the thermoplastic intermediate layer, and the inner pane can also be pressed into a pane in a calender between at least one pair of rollers. Systems of this type are known for the production of panes and usually have at least one heating tunnel upstream of a pressing unit. The temperature during the pressing process can range, for example, from 40°C to 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 panes are laminated within, for example, about 60 minutes at reduced pressures of 0.01 mbar to 800 mbar and temperatures of 80°C to 170°C.

[0025] The invention further relates to a vehicle composite pane at least comprising an outer pane made of glass with an outer surface I and an interior surface II and an inner pane made of glass with an outer surface III and an interior surface IV, wherein the interior surface II of the outer pane and the outer surface III of the inner pane are connected to one another via a thermoplastic intermediate layer. The vehicle composite pane comprises, in at least a first partial region, defects introduced into the outer pane and / or inner pane, wherein the defects are introduced by indentation. The defects introduced by indentation reduce the strength of the glass. The inventors have exploited this generally undesirable effect to influence the fracture characteristics of the composite pane.In this way, early breakage of the pane can be induced in areas with defects, while in areas without defects the breakage may or may not occur at all. The areas in which early breakage is useful can vary depending on the accident scenario whose consequences are to be mitigated. The targeted weakening of the outer pane and / or inner pane of the laminated pane leads to early breakage in the event of an impact. After one or both of the glass panes break, a considerable amount of energy is absorbed by the stretching of the thermoplastic interlayer and the at least partial delamination in the area of ​​the broken glass panes. The thermoplastic interlayer is stretchable and therefore gives way, so that an impacting body is slowed down less abruptly and experiences a lower deceleration rate.The composite vehicle pane according to the invention is used, for example, to mitigate the impact of a human head on the windshield in accidents involving pedestrians. Abrupt deceleration of the head, as occurs in the case of late glass breakage, should be avoided. A composite pane not according to the invention without defects exhibits late glass breakage in the event of a head impact, with a large portion of the kinetic energy of the impact being dissipated by bending of the glass, resulting in a high deceleration rate of the head. To quantify this head impact, the Head Injury Criterion (HIC), for example, is used, which assesses the severity of an impact based on the deceleration rate of the head. High deceleration rates are generally associated with high HIC values, which are consistent with severe injuries to the pedestrian's head.A low HIC value is equivalent to a low risk of serious head injuries.

[0026] The areas of the deliberately introduced defects exhibit lower strength. Glass breakage usually always begins at a defect in the glass when tensile stress is applied in that area. Small, randomly distributed defects can be detected in glass panes due to manufacturing processes. However, their influence on fracture behavior is unpredictable due to the statistical distribution of such natural defects. Unlike random defects in the glass, the defects introduced according to the invention in the first sub-area of ​​the laminated pane can be deliberately placed in the first sub-area of ​​the windshield, the area where premature breakage is expected to occur.As a result, the composite pane according to the invention offers greater safety for pedestrians, for example, even in the event of a traffic accident involving pedestrians, since in the event of a frontal collision, the severity of the impact on the human head is mitigated by the early breakage of the composite pane.

[0027] The vehicle composite pane according to the invention is preferably produced by means of the method according to the invention.

[0028] The vehicle composite window is intended for separating a vehicle interior from the outside environment. The vehicle composite window is therefore a window pane that is inserted into a window opening in the vehicle body or is intended for this purpose. A first pane of the vehicle composite window represents the outer pane of the vehicle composite window, which faces the outside environment of the vehicle, while the second pane of the vehicle composite window forms the inner pane, which is oriented towards the vehicle interior. It is understood that the first pane, the second pane, and the thermoplastic intermediate layer have essentially the same external dimensions. The surface of the respective pane which, in the installed position, faces the outside environment of the vehicle is referred to as the outside surface.The surface of the respective pane that faces the interior of the vehicle in the installed position is referred to as the interior surface. The interior surface of the outer pane is bonded to the exterior surface of the inner pane via the thermoplastic interlayer. Typically, the exterior surface of the outer pane is referred to as "Side I," the interior surface of the outer pane as "Side II," the exterior surface of the inner pane as "Side III," and the interior surface of the inner pane as "Side IV."

[0029] The vehicle composite pane according to the invention has a first surface area, referred to as the first sub-area. This first sub-area comprises at least a portion of the surface area of ​​the vehicle composite pane, but can also comprise the entire pane surface of the vehicle composite pane. If the first sub-area comprises less than the entire pane surface of the vehicle composite pane, the surface area not encompassed by the first sub-area is referred to as the second sub-area of ​​the vehicle composite pane. The second sub-area comprises areas in which no defects caused by indentation are present. There can also be a plurality of first sub-areas and / or second sub-areas, wherein the first sub-areas comprise defects while the second sub-areas are free of defects.In a preferred embodiment, the vehicle composite pane has only a first partial area and a second partial area, which together cover the entire surface of the vehicle composite pane.

[0030] The thermoplastic intermediate layer can comprise one or more additional films. These can be films with electrically switchable functions or colored areas, for example. The thermoplastic intermediate layer can be single-layer or multi-layered. In one possible embodiment, the thermoplastic intermediate layer is designed as a film laminate, for example, a film laminate with three layers.

[0031] The defect points created by indentation are applied to the outer pane and / or the inner pane. This deliberately weakens one or both panes of the vehicle's composite window to cause early breakage. The severity of the impact is reduced by the early breakage of the vehicle's composite window. After the glass breaks, a significant amount of energy is absorbed by the stretching of the thermoplastic interlayer and the partial delamination of the broken glass fragments. Due to the stretching of the thermoplastic interlayer, the human head is subjected to a relatively low deceleration rate. Very abrupt head decelerations, such as those that occur in the case of late glass breakage, are thereby avoided. The defect points are preferably applied to the interior surface of the outer pane and / or the interior surface of the inner pane.A laminated pane does not break directly as a result of an object striking the outside of the laminated pane, but rather as a result of the tensile stress created in the glass, particularly on the interior surfaces of the outer pane and the inner pane. This is particularly the case with semi-rigid objects such as a human head. The laminated pane breaks first at the points where the tensile stress is greatest. If an impact occurs on the outside surface of the outer pane, the greatest tensile stresses arise on the interior surface of the outer pane and on the interior surface of the inner pane. If the defects are located on one of these surfaces, the desired early breakage occurs there. Defects are particularly preferably located on at least the interior surface of the inner pane. The highest tensile stresses occur on this surface.The diameter of the defect sites is preferably 10 pm to 500 pm, particularly preferably 15 pm to 250 pm. The diameter of a defect site is determined as the maximum diameter of the defect site, i.e. as the maximum measurable extent of the defect site. This makes it possible to achieve reliable breakage of the pane, while at the same time the indentation area can be kept small in order to save costs and avoid visual impairment. The diameter of the defect sites is measured as the total diameter of the visible defect caused by indentation. This is made up of the imprint of the indenter tip visible in the glass surface and any other adjacent damage, such as cracks originating from the imprint of the indenter tip.

[0032] If the defects are created using a Vickers tip as an indenter tip, the length of the diagonal of the tip imprint is preferably between 10 pm and 500 pm. Tip imprints with a diameter of 15 pm to 250 pm, especially 20 pm to 40 pm, have proven particularly preferred. Defects with tip imprints of this size are visually very inconspicuous to the driver and, in the inventors' tests, lead to the desired early breakage of the windshield while simultaneously providing sufficient stone chip resistance.

[0033] Preferably, the defect sites form a regular or irregular pattern within the first partial region of the composite pane, with adjacent defect sites within a plane having an average distance of 1 cm to 50 cm, preferably 2 cm to 30 cm, particularly preferably 3 cm to 15 cm, for example 5 cm to 10 cm. This has proven advantageous so that a head impacting the composite pane always lands near a defect site in the first partial region.

[0034] The first partial area in which defects are introduced preferably occupies between 10% and 100%, preferably 20% to 90%, particularly preferably 30% to 70% of the total area of ​​the composite pane. Tests have shown that the aforementioned preferred surface areas of the first partial area are sufficient to achieve a high level of safety.

[0035] In a preferred embodiment, the composite vehicle pane according to the invention is a windshield. The peripheral edge of the composite pane has four sections, which, with reference to the installation situation of the windshield in a motor vehicle, are referred to as the engine edge, roof edge, and side edges, with two opposing side edges connecting the engine edge and the roof edge. The windshield has at least a first partial region that extends adjacent to the engine edge of the windshield in the direction of the roof edge. The windshield has a transmission of at least 70% in the visible range of the light spectrum. In particular, in the main field of vision of the windshield, also referred to as the A-field, a transmission of at least 70% in the visible range is required in order to comply with the legal regulations for windshields (ECE-R 43, Annex 3, Section 9).1 Method for testing the light transmittance of motor vehicle windows.) If the first partial area extends into the main field of vision of the windshield, a transmission of 70% should be achieved; in other areas, a lower transmission is sufficient.

[0036] Preferably, the first partial area of ​​the composite pane in which the defect areas are located is an area adjacent to the engine edge in which the head of a pedestrian is more likely to hit in the event of an accident.

[0037] Preferably, the first sub-region extends at least in sections, starting from the motor edge of the windshield, by an amount in the direction of the roof edge of the windshield that corresponds to 10% to 90%, preferably 20% to 70% of the height of the windshield. The height of the windshield is determined by measuring the shortest distance to the roof edge at the relevant position of the motor edge. Subsequently, the amount by which the first sub-region extends in the direction of the roof edge is determined at the same position of the motor edge as the shortest distance between the motor edge and the upper edge of the first sub-region offset in the direction of the roof edge, thereby yielding the height of the first sub-region at this position along the motor edge.This height of the first sub-area is set in relation to the height of the windshield, in each case measured at the same position along the windshield, thereby determining the relative amount by which the first sub-area extends from the edge of the engine towards the edge of the roof. The height to which the first sub-area extends is determined as a function of the vehicle geometry, with the area in which a pedestrian's head would most likely hit in the event of an accident preferably being located in the first sub-area. The first sub-area is mounted adjacent to the edge of the engine and extends from there, at least in sections, up to the aforementioned height of the windshield."Sectionally" means that the first partial area extends into the windshield in at least one section along the motor edge of the windshield up to the specified height in the direction of the roof edge, but can also have a lower height in other sections. The upper edge of the first partial area, i.e., the edge section of the first partial area that is the greatest distance from the motor edge of the windshield, preferably runs in a straight line or in a curved manner between the side edges of the windshield.

[0038] In one possible embodiment, the density of defects, i.e., the number of defects per unit area, decreases within the first sub-region from the motor edge toward the roof edge. Adjacent to the upper edge of the first sub-region, the density of defects is thus lower than the density of defects adjacent to the motor edge. In this way, a gradual transition can be created between the first sub-region and an adjacent second sub-region without defects.

[0039] In a particularly preferred embodiment, the size of the first partial region is selected such that, when the windshield is installed in a motor vehicle, the size of the first partial region corresponds to at least 90% of the area of ​​the projection of the vehicle's dashboard onto the windshield. Particularly preferably, the size of the first partial region corresponds at least to the area of ​​the projection of the dashboard onto the windshield. A common accident scenario involving pedestrians is that the pedestrian's head hits the windshield in the area of ​​the dashboard. If the windshield is penetrated in this area, the pedestrian's head hits the dashboard behind it directly, increasing the likelihood of serious injuries.In this respect, it is advantageous to design the area of ​​the windshield that is covered by a projection of the dashboard onto the windshield when installed as the first partial area, which causes the windshield to break at an early stage.

[0040] The upper edge of the first sub-region is the edge section of the first sub-region that is the greatest distance from the engine edge along the engine edge. The edge of the first sub-region is a line enclosing the first sub-region with defect areas. The upper edge of the first sub-region preferably extends between the side edges of the windshield, whereby the upper edge can end at the side edges of the windshield, but does not have to. This means that the upper edge can meet the respective side edge on one or both side edges of the windshield. The first sub-region can in principle have any desired shape and is preferably in the form of a rectangle or a rounded rectangle or a semicircle or a semi-ellipse, in each case adjacent to the engine edge of the windshield. Depending on the geometry of the windshield, other shapes are also useful.

[0041] In a preferred embodiment, the upper edge of the first partial region runs in a straight line between the side edges and ends at the side edges of the windshield. For a straight upper edge, a horizontal line when the windshield is installed in the vehicle has proven advantageous in order to achieve the desired strength reduction in the first partial region uniformly in all areas along the engine edge. In a further preferred embodiment, the upper edge of the first partial region has a curved line. The upper edge can end in the area of ​​the side edges or taper towards the corner regions and end directly in the corner region or at the sections of the engine edge adjacent to the corner region. This results in a semicircular or semi-elliptical geometry of the first partial region.

[0042] The thermoplastic intermediate layer preferably comprises polyvinyl butyral (PVB), polyurethane (PU), ionomers, and / or ethylene vinyl acetate (EVA), particularly preferably PVB. These materials have proven particularly suitable for securely bonding the panes to one another.

[0043] The thickness of the thermoplastic intermediate layer is preferably between 300 pm and 1000 pm, particularly preferably between 500 pm and 900 pm, in particular between 650 pm and 850 pm.

[0044] The outer and inner panes are made of glass, preferably soda-lime glass, as is common for window panes. However, the panes can also be made of other types of glass, such as quartz glass, borosilicate glass, or aluminosilicate glass.

[0045] The outer pane and the inner pane can be made of non-tempered, semi-tempered, or toughened glass, independently of each other. If the outer pane and / or the inner pane are to be tempered, this can be thermally or chemically toughened.

[0046] The outer pane and the inner pane preferably have a thickness of 0.8 mm to

[0047] 2.5 mm, particularly preferably from 1.2 mm to 2.2 mm. The thickness of the outer pane is typically from 1.0 mm to 2.5 mm. The thickness of the inner pane is preferably between 0.8 mm and 2.1 mm. The thickness of the outer pane is preferably greater than the thickness of the inner pane. For example, the outer pane can be 2.1 mm and the inner pane 1.1 mm thick, or the outer pane can be 1.8 mm and the inner pane 1.4 mm thick, or the outer pane can be 1.6 mm and the inner pane 1.1 mm thick, or the outer pane can be 1.6 mm and the inner pane 0.7 mm thick, or the outer pane can be 1.4 mm and the inner pane 1.1 mm thick.

[0048] The inner pane, the outer pane, and the thermoplastic interlayer can be clear and colorless, but also tinted or colored. The tint of the outer pane, inner pane, and the thermoplastic interlayer is selected depending on the intended application of the laminated pane. For windshields, high transmission in the visible range of the light spectrum is desired, and dark tints of the components are avoided. The total transmission through the windshield, when used as a windshield of a motor vehicle, is greater than 70%, based on illuminant A. The term "total transmission" refers to the procedure for testing the light transmittance of motor vehicle windows specified in ECE-R 43, Annex 3, Section 9.1.

[0049] The composite vehicle pane according to the invention is curved in one or preferably in several directions of space, as is usual for panes of motor vehicles, with typical radii of curvature being in the range of about 10 cm to about 40 m.

[0050] The inner pane, the outer pane and / or the thermoplastic intermediate layer may have further suitable coatings known per se, for example anti-reflective coatings, non-stick coatings, anti-scratch coatings, photocatalytic coatings or sun protection coatings or low-E coatings.

[0051] Automotive glazing, in particular windshields, rear windows, and roof windows, usually has a circumferential peripheral masking print made of opaque enamel, which serves in particular to protect the adhesive used to install the window from UV radiation and to visually conceal it. Preferably, at least the outer pane has such an opaque peripheral masking print; particularly preferably, both the outer pane and the inner pane are printed, so that visibility is prevented from both sides. The opaque masking print is applied, for example, in the form of a screen print, so that this screen print circumscribes the field of vision of the window or forms its outer edge. Any electrical conductors arranged in the edge region of the window, as well as any coating-free edge region provided in the case of coated panes, are preferably covered by this masking print and are thus visually concealed.The opaque screen printing can be applied to any level of the windshield.

[0052] The invention further comprises a vehicle comprising the composite pane according to the invention, wherein the size of the first partial region with defects is selected such that the size of the first partial region corresponds to at least 90% of the area of ​​the projection of the dashboard of the motor vehicle onto the vehicle composite pane. The vehicle composite pane is the windshield of the motor vehicle. Particularly preferably, the size of the first partial region corresponds at least to the area of ​​the projection of the dashboard onto the windshield. A common accident scenario involving pedestrians is that the pedestrian's head hits the windshield in the area of ​​the dashboard. If the windshield is penetrated in this area, the pedestrian's head strikes the dashboard behind it directly, increasing the likelihood of serious injuries.In this respect, it is advantageous to design the area of ​​the windshield that is covered by a projection of the dashboard onto the windshield when installed as the first partial area, which causes the windshield to break at an early stage.

[0053] All standards mentioned refer to the version valid on the date of filing.

[0054] The various embodiments of the invention can be implemented individually or in any combination. In particular, the features mentioned above and those to be 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 invention. This applies unless exemplary embodiments and / or their features are explicitly mentioned only as alternatives or are mutually exclusive. In particular, the features described in the context of the method according to the invention also apply to the composite pane, and vice versa.

[0055] The invention is described in more detail below with reference to the figures. It should be noted that various aspects are described, each of which can be used individually or in combination. This means that any aspect can be used with different embodiments of the invention, unless explicitly presented as a mere alternative.

[0056] The drawings are simplified, schematic representations and not to scale. The drawings do not limit the invention in any way.

[0057] They show:

[0058] Fig. 1a, b a plan view of an embodiment of a vehicle composite pane according to the invention as a windshield,

[0059] Fig. 2 shows a section of a cross-section through the embodiment of a vehicle composite pane according to the invention as a windshield shown in Fig. 1,

[0060] Fig. 3a, b Samples with defects after indentation with Vickers tip at different indentation loads,

[0061] Fig. 4 Diagram for the investigation of the bending strength of glasses with defects as a function of the indentation load and

[0062] Fig. 5 Device for indentation of the samples according to figures 3a, b.

[0063] Figures 1a, b show a plan view of an embodiment of a composite vehicle pane 10 according to the invention as a windshield, while Figure 2 shows a section of a cross section through the embodiment shown in Figure 1 along the section line C'-C according to Figure 1. Figure 1b shows an enlarged view of the area Z of the windshield from Figure 1a.

[0064] The windshield 10 shown in Figures 1a, b and 2 comprises an outer pane 1 and an inner pane 2, which are connected to one another via a thermoplastic intermediate layer 3. The outer pane 1 has an outer surface I and an interior surface II. The inner pane 2 has an outer surface III and an interior surface IV. In the installed state of the windshield 10, the outer surfaces I, III point towards the surroundings, while the interior surfaces II, IV are oriented towards the vehicle interior in the installed state. The interior surface II of the outer pane 1 is connected to the outer surface III of the inner pane 2 via the thermoplastic intermediate layer 3.The windshield 10 has a roof edge D, an engine edge M opposite the roof edge, and two opposite side edges S that connect the engine edge M and the roof edge D. The windshield 10 has a first partial region X and a second partial region Y, wherein the first partial region X is arranged adjacent to the engine edge M.

[0065] As can be seen from Figures 1b and 2, defects 4 are arranged in the first partial area X of the windshield 10. The remaining surface area of ​​the windshield 10 is referred to as the second partial area Y and is completely free of such defects 4. The outer pane 1 is, for example, a glass pane made of soda-lime glass with a thickness of 2.1 mm. The inner pane 2 is, for example, made of soda-lime glass and has a thickness of 1.6 mm.

[0066] The first partial region X has an upper edge 5 which, starting from the engine edge M, is offset in the direction of the roof edge D. The upper edge 5 of the first partial region X runs between the side edges K, with the defect points 4 being introduced between the upper edge 5 of the first partial region X and the engine edge M. Defect points 4 are arranged in the present case on the interior-side surface IV of the inner pane 2. This has proven particularly advantageous for achieving premature breakage of the windshield 10 in the head impact test. Further improved results can be achieved if, as shown in Figure 2, defect points 4 are additionally arranged on the interior-side surface II of the outer pane 1.

[0067] The inventors have carried out tests which experimentally confirm the targeted weakening of a glass pane in the area of ​​a defect 4 introduced by indentation. The inventors carried out tests for this purpose using float glass panes with a thickness of 1.6 mm and 2.1 mm. A series of such samples were provided with defects 4, whereby the indentation load was varied. Glass produced using the float glass process has different surface characteristics and stresses on the opposite surfaces of the float glass pane. A distinction is made between the so-called tin side, also called the bath side, the float glass pane, which refers to the glass surface that was in contact with the tin bath, and the so-called air side (also called the fire side or atmosphere side), which refers to the remaining opposite glass surface.Figures 3a and 3b show defect areas 4 introduced by indentation on the fire side of two samples. The sample shown in Figure 3a is a glass pane 6 consisting of float glass with a thickness of 2.1 mm, whereby the indentation was carried out using a Vickers tip in accordance with DIN EN ISO 6507-1:2018 to -4:2018 with an indentation load of 250 g on the air side of the sample. The same applies to the sample in Figure 3b, with the difference that the indentation was carried out with an indentation load of 500 g. A schematic representation of the device used to indent the samples is shown in Figure 5. A force sensor 11 is attached to a holding device 15. The force sensor 11 holds a system 12 for adjusting the height of the indenter tip and the indenter tip 14. The indenter tip 14 is first positioned over the area of ​​the sample 6 to be indented, with the indenter tip 14 being held in the air by the force sensor 11.The height adjustment system 12 comprises a plate 13, by whose weight the indentation load can be adjusted.

[0068] The samples in Figures 3a and 3b, as well as other samples indented using the same method with different indentation loads, were subjected to a flexural strength test in accordance with DIN EN 1288-5. The diagram in Figure 4 shows the flexural strength of a series of samples as a function of the indentation load when indented using a Vickers tip in accordance with DIN EN ISO 6507-1:2018 to -4:2018. With an indentation load of 100 g, no systematic fracture occurred in the area of ​​the indentation imprint. Therefore, when using a Vickers tip, indentation loads greater than 100 g are preferred. As can be seen in the diagram, a significant reduction in flexural strength is observed with increasing indentation load. This is also to be expected in the event of a pedestrian impact in the first partial area X of a vehicle composite pane 10 with defects 4.Defect areas introduced with an indentation load of 250 g to 500 g have proven particularly advantageous in order to make them as visually inconspicuous as possible and to ensure good stone chip resistance of the windscreen.

[0069] List of reference symbols

[0070] 10 Windshield

[0071] 1 outer pane

[0072] 2 inner pane

[0073] 3 thermoplastic intermediate layer

[0074] 4 defect areas

[0075] 5 Top edge of the first section X

[0076] 6 Glass pane, sample

[0077] 11 Force sensor

[0078] 12 System for height adjustment of the indenter tip

[0079] 13 Plate for adjusting the indentation load

[0080] 14 Indenterspitze

[0081] 15 Holding device

[0082] X first sub-area

[0083] Y second sub-area

[0084] D roof edge

[0085] M engine edge

[0086] S side edges

[0087] Z enlarged section

[0088] CC' cutting line

[0089] I outside surface of the outer pane 1

[0090] II Interior surface of the outer pane 1

[0091] III outer surface of the inner pane 2

[0092] IV Interior surface of the inner pane 2

Claims

Patent claims 1. A method for producing a vehicle composite pane (10) with improved impact protection, wherein at least a) an outer pane (1) made of glass and an inner pane (2) made of glass are provided, b) defect locations (4) are introduced into the outer pane (1) and / or the inner pane (2) in at least a first partial region (X), c) the outer pane (1) with defect locations (4) and / or the inner pane (2) with defect locations (4) are bent, d) a thermoplastic intermediate layer (3) is placed on the outer pane (1) or the inner pane (2), a) the layer stack is closed off with the inner pane (2) or the outer pane (1), and b) the layer stack comprising at least the outer pane (1), the thermoplastic intermediate layer (3), and the inner pane (2) is laminated to form a windshield (10), wherein the defect locations (4) are introduced into the outer pane (1) and / or the inner pane (2) by indentation.

2. Method according to claim 1, wherein the defect locations (4) are provided on the interior-side surface (II) of the outer pane (1) and / or on the interior-side surface (IV) of the inner pane (2).

3. Method according to claim 1 or 2, wherein the defect sites (4) are spherical, rectangular, rhombic, pyramidal or conical and are introduced by means of microindentation or nanoindentation.

4. Method according to one of claims 1 to 3, wherein the defect locations (4) are introduced by indentation with an indenter tip for hardness testing according to Brinell according to DIN EN ISO 6506-1 to EN ISO 6506-4, Vickers according to DIN EN ISO 6507-1:2018 to -4:2018, Knoop according to DIN EN ISO 4545-1 to -4, Rockwell according to DIN EN ISO 6508-1 or an indenter syringe with the basic shape of a triangular pyramid according to Berkovich.

5. The method according to claim 4, wherein the defect locations are introduced by identification with an indenter tip for hardness testing according to Vickers with an indentation load of 50 g to 700 g, preferably 100 g to 600 g, in particular 200 g to 550 g.

6. Method according to one of claims 1 to 5, wherein the indentation in step b) is carried out by means of several indenter tips which contact the surface to be indented at least partially simultaneously.

7. Method according to one of claims 1 to 6, wherein the outer pane (1) and / or the inner pane (2) are bent in step c) at a temperature of 500 °C to 700 °C.

8. Vehicle composite pane (10) comprising an outer pane (1) made of glass with an outer surface (I) and an interior surface (II) and an inner pane (2) made of glass with an outer surface (III) and an interior surface (IV), wherein the interior surface (II) of the outer pane (1) and the outer surface (III) of the inner pane (2) are connected to one another via a thermoplastic intermediate layer (3), and wherein - the vehicle composite pane (10) comprises, in at least a first partial area (X), defect areas (4) which are incorporated into the outer pane (1) and / or inner pane (2) and - the defect areas (4) are introduced into the outer pane (1) and / or inner pane (2) by indentation.

9. Vehicle composite pane (10) according to claim 8, wherein the defect locations (4) are introduced on the interior-side surface (II) of the outer pane (1) or the interior-side surface (IV) of the inner pane (2).

10. Vehicle composite pane (10) according to claim 8 or 9, wherein the defect locations (4) form a regular or irregular pattern and adjacent defect locations (4) have an average distance of 1 cm to 50 cm, preferably of 2 cm to 30 cm, from one another.

11. Vehicle composite pane (10) according to one of claims 8 to 10, wherein the first partial region (X) occupies a proportion of 10% to 100%, preferably a proportion of 20% to 90%, particularly preferably 30% to 70% of the total area of ​​the vehicle composite pane (10).

12. Vehicle composite window (10) according to one of claims 8 to 11, wherein the vehicle window (10) is a windshield comprising an engine edge (M), a roof edge (D) and two side edges (S) running between them and the first partial region (X) extends at least in sections starting from the engine edge (M) by an amount in the direction of the roof edge (D) which corresponds to 10% to 90%, preferably 20% to 70%, of the height of the windshield (10).

13. Vehicle composite window (10) according to one of claims 8 to 12, wherein the thermoplastic intermediate layer (3) comprises polyvinyl butyral (PVB), polyurethane (PU), ionomers and / or ethylene vinyl acetate (EVA).

14. Vehicle composite pane (10) according to one of claims 8 to 13, wherein the outer pane (1) and the inner pane (2) comprise glass and each have a thickness of 0.8 mm to 2.5 mm, preferably of 1.2 mm to 2.2 mm.

15. A vehicle comprising a vehicle composite pane (10) according to one of claims 8 to 14, wherein the size of the first partial region (X) is selected such that the size of the first partial region (X) corresponds to at least 90% of the area of ​​the projection of the dashboard of the motor vehicle onto the windshield (10).

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