Composite element

Abstract

The invention relates to a composite element (10) having an outer support (20) and an inner component (30), which is held vertically in the outer support (20) under compressive stress, wherein the outer support (20) and the inner component (30) adjoin one another along a closed contour line (40), which comprises two opposite linearly extending linear sections (42) and two connecting sections (44), which connect the two linear sections (42) to form a closed contour line, wherein at least one of the two connecting sections (44) has an arcuately extending curved region (46).

Description

Technical Field

[0001] The present invention relates to a composite element having an outer support, particularly a metal frame, and an internal component, particularly a glass frame, wherein the internal component is housed in the outer support under compressive stress. Background Technology

[0002] Composite elements with an outer metal frame and an inner glass component, also known as glass-metal seals (GTMS), are used in a variety of applications, such as for tight-fitting housing components with viewing windows.

[0003] In principle, glass-metal composite components can be divided into two categories. One category consists of components where the thermal expansion behaviors of the metal housing and the glass component are matched, known as mated glass-metal seals. The other category consists of components where the metal housing applies compressive pressure to the glass component, known as compression glass-metal seals. Matted glass-metal seals are particularly suitable for situations where uniform expansion or contraction occurs under fluctuating temperature conditions, or where a thin metal housing is required to generate sufficient compressive pressure. If these factors are not critical, compression glass-metal seals are typically used. Compression glass-metal seals generally exhibit high corrosion resistance and pressure tolerance.

[0004] In a compression-type glass-metal seal, the inner glass body is held within an outer metal housing under pressure, for example, by contracting the outer metal housing onto the glass body. This results in the metal housing tightly enclosing the inner glass and forming a tight seal.

[0005] To date, compression glass-metal seals typically have a circular glass body that is then housed within a circular cutout in an outer metal frame. This creates a uniform, concentrated pressure on the inner glass component, thereby preventing stress or damage to the glass.

[0006] On the other hand, for some applications, non-circular geometries of the glass body are desirable. This includes, for example, housing components with viewing windows in which the largest possible viewing window is desired, but component size is limited, such as smartwatches. However, compression glass-metal seals with non-circular geometries present challenges in several aspects, particularly regarding stress in the glass component, deformation of the metal component, and the stability and sealing of the contact surfaces between the glass and metal. Summary of the Invention

[0007] Therefore, the object of the present invention is to provide a composite element having an outer support, particularly comprising metal, and an inner component, particularly comprising glass, housed under compressive stress, wherein a non-circular geometry is achieved, wherein stress in the glass component and / or deformation in the metal component is kept as low as possible and / or the stability and sealing of the contact surfaces between the glass and the metal are as high as possible.

[0008] This objective is achieved through the object of the independent claim. Advantageous improvements of the invention are defined in the dependent claims.

[0009] The present invention relates to a composite element having an external support and an internal component, the internal component being housed in the external support, particularly under compressive stress, wherein the external support and the internal component are adjacent to each other along a closed profile, wherein the profile is configured to be non-circular and at least partially curved, particularly configured to be oval or elliptical.

[0010] In a preferred embodiment, the present invention relates to a composite element having an external support and internal components housed within the external support under compressive stress.

[0011] In a preferred embodiment, the external support and internal components are adjacent to each other along a closed profile, wherein the profile includes two opposing linear segments extending in a straight line and two connecting segments that connect the two linear segments to form a closed profile, wherein at least one of the two connecting segments has a curved area extending in an arc.

[0012] The external support preferably comprises a material having a first coefficient of thermal expansion, particularly metal, or is made of a material having a first coefficient of thermal expansion, particularly metal, and the internal component preferably comprises a material having a second coefficient of thermal expansion, particularly glass, or is made of a material having a second coefficient of thermal expansion, particularly glass, wherein the first coefficient of thermal expansion of the material of the external support is preferably greater than the second coefficient of thermal expansion of the material of the internal component.

[0013] At least one of the two connecting segments may have a first arcuate bending region adjacent to one of the two linear segments and a second arcuate bending region adjacent to the other of the two linear segments.

[0014] Preferably, the other of the two connecting segments is formed in the same manner, such that the outline has four rounded corners, particularly formed as a rectangle with rounded corners.

[0015] The length of the curved area can be set to be at least 5% of the length of the connecting section (44), preferably at least 10% of the length of the connecting section (44), more preferably at least 15% of the length of the connecting section (44), more preferably at least 20% of the length of the connecting section (44), and particularly preferably at least 25% of the length of the connecting section (44).

[0016] Furthermore, at least one of the two connecting segments can be formed as a continuous arc-shaped curved region, especially such that the two linear segments are connected without a straight region between them.

[0017] Preferably, the other of the two connecting segments is formed in the same manner, such that the outline has two continuously rounded sides, particularly in the shape of a pill.

[0018] Preferably, the smallest possible envelope rectangle surrounding the contour line includes a first side length and a second side length extending orthogonally to the first side length, wherein the first side length is preferably parallel to at least one extension of two opposing straight line segments.

[0019] In this case, the length of the first side is preferably greater than the length of the second side, especially at least 1.1 times and at most 10 times, or at least 1.1 times and at most 6 times, or at least 1.1 times and at most 5 times, or at least 1.1 times and at most 4 times, or at least 1.1 times and at most 3 times, or at least 1.2 times and at most 5 times, or at least 1.2 times and at most 4 times, or at least 1.3 times and at most 5 times, or at least 1.3 times and at most 4 times, or at least 1.4 times and at most 5 times, or at least 1.4 times and at most 4 times, or at least 1.5 times and at most 5 times, or at least 1.5 times and at most 4 times, or at least 1.6 times and at most 5 times, or at least 1.6 times and at most 4 times, or at least 1.7 times and at most 5 times, or at least 1.7 times and at most 4 times, or at least 1.8 times and at most 5 times, or at least 1.8 times and at most 4 times, or at least 1.9 times and at most 5 times, or at least 1.9 times and at most 4 times, or at least 2 times and at most 5 times, or at least 2 times and at most 4 times, or at least 2.5 times and at most 5 times, or at least 2.5 times and at most 4 times, or at least 3 times and at most 5 times, or at least 3 times and at most 4 times.

[0020] Preferably, the curved regions of the connecting segments transition into the linear segments without steps, preferably without bends, and particularly preferably without abrupt changes in curvature. It can also be configured such that the contour lines extend without steps at each location, preferably without bends, and particularly preferably without abrupt changes in curvature.

[0021] Preferably, the contact pressure at any location along the contour line is positive, and the contact pressure is preferably greater than 1 MPa, more preferably greater than 2 MPa, more preferably greater than 3 MPa, more preferably greater than 4 MPa, more preferably greater than 10 MPa, more preferably greater than 20 MPa, particularly preferably greater than 30 MPa, and / or the contact pressure at at least one location along the contour line is greater than 100 MPa, preferably greater than 200 MPa, more preferably greater than 500 MPa, particularly preferably greater than 1000 MPa.

[0022] Preferably, the load along the contour line on the external support is less than 300 MPa, preferably less than 250 MPa, more preferably less than 240 MPa, more preferably less than 230 MPa, more preferably less than 225 MPa, more preferably less than 220 MPa, more preferably less than 215 MPa, and more preferably less than 210 MPa.

[0023] Preferably, the load on the internal component along the contour line is less than 300 MPa, preferably less than 200 MPa, more preferably less than 100 MPa, more preferably less than 150 MPa, more preferably less than 95 MPa, more preferably less than 90 MPa, more preferably less than 85 MPa, and more preferably less than 80 MPa.

[0024] Preferably, the deformation of the external support is less than 0.03 mm / mm, more preferably less than 0.029 mm / mm, more preferably less than 0.028 mm / mm, and especially preferably less than 0.027 mm / mm.

[0025] Composite elements are preferably used as enclosure elements of the housing, particularly in the rear of wearable electronic devices such as heart rate monitors, smartwatches, fitness trackers, etc. These elements are also referred to as back covers and are included herein. In this document, viewing windows are particularly used for heart rate measurement, where optical transmitters and sensors can measure the wearer's heart rate. Therefore, primarily for the purpose of separating light signals, the back cover of such electronic devices advantageously has more than one viewing window.

[0026] The inventors have discovered that the present invention allows viewing windows to be arranged closer together than originally intended without adversely reducing compressive stress on the viewing windows. This is particularly advantageous for wearable electronic devices, as it provides more viewing windows and / or more viewing window area per back cover for a given area.

[0027] In the improved embodiment, the composite element may include an outer support, an inner component, and an electrical conductor extending through the inner component, wherein the outer support and the inner component are adjacent to each other along a closed profile, and wherein the inner component and the electrical conductor are also adjacent to each other along a closed second profile.

[0028] For example, an electrical conductor extending through an electrically insulated internal component can be provided, which can be used, for example, as an electrode.

[0029] The external support may include a material having a first coefficient of thermal expansion, particularly metal, or be made of a material having a first coefficient of thermal expansion, particularly metal; the internal components may include a material having a second coefficient of thermal expansion, particularly glass, or be made of a material having a second coefficient of thermal expansion, particularly glass; and the electrical conductor may include a material having a third coefficient of thermal expansion, particularly metal, or preferably be made of a material having a third coefficient of thermal expansion, particularly metal.

[0030] It can be set such that the third coefficient of thermal expansion is 3 times smaller than the second coefficient of thermal expansion, preferably 2 times smaller, particularly preferably 1.5 times smaller, and more preferably 1.25 times smaller.

[0031] It can be set such that the third coefficient of thermal expansion is 3 times smaller than the first coefficient of thermal expansion, preferably 2 times smaller, particularly preferably 1.5 times smaller, and more preferably 1.25 times smaller.

[0032] refer to Figure 28 The outline along which the external support and internal components are adjacent to each other can define a minimum possible first envelope rectangle that surrounds the outline, and the second outline along which the internal components and electrical conductors are adjacent to each other can define a minimum possible second envelope rectangle that surrounds the second outline, wherein the first envelope rectangle and the second envelope rectangle have a longer side length and a shorter side length, respectively, and wherein the longer side lengths of the two envelope rectangles extend parallel to each other or at an angle to each other, the angle being less than 20 degrees, preferably less than 10 degrees, and particularly preferably less than 5 degrees.

[0033] The longer side length of the first enclosing rectangle can be greater than the shorter side length of the first enclosing rectangle by a first factor, and the longer side length of the second enclosing rectangle can be greater than the shorter side length of the second enclosing rectangle by a second factor. The difference between the second factor and the first factor is less than 400%, preferably less than 200%, particularly preferably less than 100%, or less than 50%, or less than 25%, or less than 20%, or less than 15%, or less than 10%, or less than 5%.

[0034] The second profile along which the internal components and electrical conductors are adjacent to each other may include two opposing linear segments extending in a straight line and two connecting segments that connect the two linear segments to form a closed profile, wherein at least one of the two connecting segments may have an arcuate curved area.

[0035] Regarding the second contour line along which the internal components and electrical conductors are adjacent to each other, at least one of the two connecting sections may have a first curved region and a second curved region. The first curved region extends in an arc shape adjacent to one of the two linear sections, and the second curved region extends in an arc shape adjacent to the other of the two linear sections. Preferably, the other of the two connecting sections is formed in the same manner, such that the second contour line has four rounded corners, particularly formed as a rectangle with rounded corners.

[0036] Regarding the second contour line along which the internal components and electrical conductors are adjacent to each other, the length of the arc-shaped curved region is at least 5% of the length of the connecting section, preferably at least 10% of the length of the connecting section, more preferably at least 15% of the length of the connecting section, even more preferably at least 20% of the length of the connecting section, and particularly preferably at least 25% of the length of the connecting section.

[0037] Regarding the second contour line along which the internal components and electrical conductors are adjacent to each other, at least one of the two connecting sections can be formed as a curved region extending in a continuous arc, particularly formed such that the two linear sections are connected without a region of straight extension between them. Preferably, the other of the two connecting sections is formed in the same manner, such that the second contour line has two continuously rounded sides, particularly formed in a pill shape.

[0038] The smallest possible envelope rectangle surrounding the second contour line may include a first side length and a second side length extending orthogonally to the first side length. The first side length is preferably parallel to at least one of the two opposing linear segments, wherein the first side length is preferably greater than the second side length, particularly at least 1.1 times and at most 10 times, or at least 1.1 times and at most 6 times, or at least 1.1 times and at most 5 times, or at least 1.1 times and at most 4 times, or at least 1.1 times and at most 3 times, or at least 1.2 times and at most 5 times, or at least 1.2 times and at most 4 times, or at least 1.3 times and at most 5 times, or at least 1.3 times and at most 4 times, or at least 1.4 times and at most 5 times. Or at least 1.4 times and at most 4 times, or at least 1.5 times and at most 5 times, or at least 1.5 times and at most 4 times, or at least 1.6 times and at most 5 times, or at least 1.6 times and at most 4 times, or at least 1.7 times and at most 5 times, or at least 1.7 times and at most 4 times, or at least 1.8 times and at most 5 times, or at least 1.8 times and at most 4 times, or at least 1.9 times and at most 5 times, or at least 1.9 times and at most 4 times, or at least 2 times and at most 5 times, or at least 2 times and at most 4 times, or at least 2.5 times and at most 5 times, or at least 2.5 times and at most 4 times, or at least 3 times and at most 5 times, or at least 3 times and at most 4 times.

[0039] It can be configured such that, with respect to the second contour line along which the internal components and electrical conductors are adjacent to each other, the curved regions of the connecting segments extending in an arc manner transition into the linear segments without steps, preferably without bends, and particularly preferably without abrupt changes in curvature, and / or the second contour line extends without steps, preferably without bends, and particularly preferably without abrupt changes in curvature at each location.

[0040] According to one embodiment, at least one of the contour lines along which the external support and internal components are adjacent to each other, particularly at least one of the connecting sections, particularly at least one of the curved regions, can define a first curved section, and at least one of the second contour lines along which the internal components and electrical conductors are adjacent to each other, particularly at least one of the connecting sections, particularly at least one of the curved regions, can define a second curved section, the second curved section being directly opposite the first curved section, and wherein the distance between the contour lines and the second contour lines is greater in the region of the first and second curved sections than in the region of the smaller curved section or the region of the no-curve section, particularly greater in the region of the linear section.

[0041] According to one embodiment, the contour lines along which the external support and internal components are adjacent to each other, particularly at least one of the connecting sections, particularly at least one of the curved regions, can define a first radius, and the second contour lines along which the internal components and electrical conductors are adjacent to each other, particularly at least one of the connecting sections, particularly at least one of the curved regions, can define a second radius, the second radius being directly opposite the first radius, and wherein the ratio of the first radius to the second radius is less than 10, preferably less than 5, particularly preferably less than 3, more preferably less than 2 or less than 1.5 or less than 1.25 or less than 1, particularly such that the distance between the contour lines and the second contour lines is greater in the region of the first and second radii than in the region of the linear section.

[0042] According to one embodiment, the outline along which the outer support and the inner component are adjacent to each other, and the second outline along which the inner component and the electrical conductor are adjacent to each other, are spaced at a constant distance along the entire outline except for the curved areas of the outline, and wherein the distance between the outlines is larger in the curved areas of the outline.

[0043] The composite element may have a first side and a second side, such that an electrical conductor extends from the first side of the composite element through an internal component to the second side of the composite element.

[0044] The outlines along which the external support and internal components meet are preferably equal on both sides of the composite element. Similarly, the outlines along which the internal components and electrical conductors meet are preferably equal on both sides of the composite element.

[0045] The electrical conductor may be flush with or offset from the internal components on one or both sides of the composite element, with the offset being less than 500 μm, preferably less than 150 μm, and particularly preferably less than 100 μm.

[0046] On the other hand, the electrical conductor may extend a protrusion from the internal components on one or both sides of the composite element, wherein the protrusion is particularly larger than 500 μm, and is particularly capable of making electrical contact. Attached Figure Description

[0047] Figure 1 The glass-metal composite element is shown in top view (a) and sectional view (b), including the internal glass component having a circular geometry. It also shows two partial schematic diagrams (c) and (d) of the load on the external support including the metal, two partial schematic diagrams (e) and (f) of the deformation of the external support including the metal, two partial schematic diagrams (g) and (h) of the load on the internal glass component, and a partial schematic diagram (i) of the contact pressure. Figure 2Glass-metal composite components are shown, including internal glass components with square geometries (a) and (b), as shown. Figure 1 As shown, and with Figure 1 The corresponding diagrams (c) to (i) Figure 3 The diagram shows a glass-metal composite element, including an internal glass component having a square geometry including rounded corners (a) and (b), as shown. Figure 1 As shown, and with Figure 1 The corresponding diagrams (c) to (i); Figure 4 The diagram illustrates a glass-metal composite element, including an internal glass component with a rectangular geometry having an aspect ratio of 1:1.4 (a) and (b), as shown. Figure 1 As shown, and with Figure 1 The corresponding diagrams (c) to (i); Figures 5 to 12 Both show glass-metal composite components, including internal glass components with different aspect ratios ( Figure 5 1:1.2 up to Figure 12 (1:4) and the rectangular geometric structures with rounded corners (a) and (b), as shown in Figure 1 As shown, and with Figure 1 The corresponding diagrams (c) to (i); Figures 13 to 19 Both show glass-metal composite components, including internal glass components with different aspect ratios ( Figure 13 The ratio of 1:1.4 in the middle Figure 14 1:1.2 up to Figure 19 The pill-shaped geometric structure (a) and (b) of 1:4 in the text, as shown in the figures. Figure 1 As shown, and with Figure 1 The corresponding diagrams (c) to (i); Figure 20 The images show glass-metal composite elements, including internal glass components with pill-shaped geometries having different aspect ratios of 1:1.6 (a) and (b), as shown. Figure 1 As shown, and with Figure 1 The corresponding diagrams (c) to (i); Figure 21 , 22 All show glass-metal composite elements, including internal glass components with aspect ratios of 1:1.6 and varying corner radii. Figure 21 The middle is 0.25mm and Figure 22 The rectangular geometric structure with rounded corners (a) and (b) with a thickness of 0.5mm in the middle, as shown in the figures. Figure 1 As shown, and with Figure 1The corresponding diagrams (c) to (i); Figure 23 A larger view of the two composite elements is shown, wherein the outlines of the inner component 30 and the outer support 20 adjacent to each other include two opposing linear segments 42 extending in a straight line and two connecting segments 44 that connect the two linear segments 42 to form a closed outline, wherein the connecting segments 44 have two curved regions (a) extending in an arc and separated from each other by a linear segment or curved regions (b) extending in a continuous arc. Figure 24 A side view of a glass-metal composite element having an electrical conductor 50 extending through an inner component 30 is shown, wherein the electrical conductor 50 is adjacent to the inner component 30 at a second profile line 60, wherein the electrical conductor is capable of terminating flush with the inner component on one or both sides (a) or is capable of extending from the inner component on one or both sides (b). Figure 25 A top view of a glass-metal composite element having an electrical conductor 50 extending through an inner component 30 is shown, wherein the outlines of the inner component 30 and the outer support 20 adjacent to each other are configured as a rectangular geometry (a) or a pill-shaped geometry (b) with rounded corners, and the electrical conductor 50 has a rounded shape, thus defining a rounded outline 60 of the electrical conductor 50 adjacent to the inner component 30. Figure 26 Similar to Figure 25 A top view of a glass-metal composite element with an electrical conductor 50 extending through an internal component 30 is shown, wherein the electrical conductor 50 has an elongated shape, here elliptical, along a second profile 60 adjacent to the internal component 30, wherein the principal axis of the second profile 60 coincides with the principal axis of the profile 40, i.e., the longitudinal extension extends in the same direction. Figure 27 Similar to Figure 25 A top view of a glass-metal composite element having an electrical conductor 50 extending through an internal component 30 is shown, wherein the electrical conductor 50 includes two opposing linear segments 42 extending in a straight line and two connecting segments 64 along a second profile 60 adjacent to the internal component 30, the two connecting segments 64 connecting the two linear segments 42 to form a closed profile, such that the second profile 60 has the same characteristics as the profile 40. Figure 28 A top view of a glass-metal composite element having an electrical conductor 50 is shown, wherein contour line 40 and second contour line 60 have a rectangular geometry including rounded corners, wherein the distance between contour lines 40 and 60 remains constant along the entire contour line (a) or remains constant along the entire contour line except for the area of ​​the rounded corners where the distance increases (b). Figure 29A top view of a glass-metal composite element having an electrical conductor 50 is shown, wherein a contour line 40 defines a first envelope rectangle 41 that is as small as possible and a second contour line 60 defines a second envelope rectangle 61 that is as small as possible, wherein the two envelope rectangles are oriented toward each other such that the longer sides (and the shorter sides) of the envelope rectangles extend parallel to each other, in other words, such that the principal axes of the contour lines 40, 60, which are elliptical in shape here, extend in the same direction. Figure 30 A glass-metal composite element with an external support is shown, in which a plurality of internal components are housed, each having an electrical conductor 50 extending through it, wherein the internal components serve in particular as insulators for electrical conductors, such as electrodes. Detailed Implementation

[0048] As Figures 1 to 22 To supplement the computer-generated schematic diagram shown, the following table contains additional data, in particular stress on the external metal support (metal stress) in MPa, deformation of the external metal support (metal deformation) in mm / mm, load on the internal glass components (glass stress) in MPa, and maximum and minimum contact pressures in MPa (maximum contact pressure, minimum contact pressure). The following observations can generally be determined: • Stress and metal deformation in all components increase by several orders of magnitude from circular to square / rectangular (see...) Figure 1 , 2 4).

[0049] • Squares and rectangles with sharp edges have similar levels of stress (see Figure 2 , 3 4).

[0050] • The transition from sharp corners to rounded corners reduces load (see...) Figure 8 , 21 ,twenty two).

[0051] • As the aspect ratio of the rectangle increases, the tensile stress on the glass surface increases in area. Other aspects remain relatively similar (see [reference needed]). Figures 4 to 12 ).

[0052] • Rectangular glass with rounded corner radii has several regions that include negative contact pressure until a specific radius value is reached (see...). Figure 21 ,22 ).

[0053] • Compared to rectangular shapes with rounded corners, the stress in the glass is reduced by several orders of magnitude for pill-shaped glass (see [link]). Figure 9 , 16 ).

[0054] • If the aspect ratio of pill-shaped glass is increased to 1:3, the tensile stress on the glass surface increases significantly (see...). Figure 18 ).

[0055] • At an aspect ratio of 1:4, the tensile stress on the glass becomes very large (the entire surface is red) (see [reference]). Figure 19 ).

[0056] • Even with an aspect ratio of 1:4, positive contact pressure still unexpectedly exists for the minimum value (see Figure 19 ).

[0057] • The risk of metal deformation is in the same range in pill-shaped glass as in round glass (see configurations 13 to 22).

[0058] In a particularly advantageous embodiment, the back cover has more than one viewing window. The aspect ratio is advantageously from 1.6:1 to 2.0:1 or from 1.7:1 to 1.9:1. In a back cover made of steel, especially stainless steel, advantageously austenitic stainless steel, the minimum spacing between two viewing windows is advantageously 1.0 to 1.2 times the shorter linear segment of each.

[0059] A particularly advantageous embodiment is a back cover made of austenitic stainless steel, having one or more viewing windows, wherein the aspect ratio is 1.8:1 and the minimum spacing between two viewing windows is 2.0 mm. The material thickness of this back cover is advantageously from 0.7 mm to 1 mm, at least at the edges of the viewing windows.

[0060] Minimum spacing is the minimum distance between two viewing windows.

[0061] In the case of a glass-metal composite element having an electrical conductor extending through an internal component, the contour line 40 between the outer support 20 and the internal component 30 and the second contour line 60 between the internal component 30 and the electrical conductor 50 are each defined by a plurality of linear segments connected to each other by radii 40R, 60R, which can be configured to form equal spacing between contour lines 40, 60 along the entire contour lines, i.e., the width of the internal components is the same. Figure 28 a).

[0062] This specifically means that the radius 60R of the second profile 60 (and therefore the electrical conductor) is smaller than the radius 40R of the profile 40 (and therefore the internal component). In this case, it is actually desirable to generate less tensile stress in the region between the electrical conductor and the internal component due to the smaller radius of the electrical conductor 50, and / or to apply higher compressive stress to the internal component and the electrical conductor due to the larger radius of the internal component. Therefore, it is particularly desirable that the radius 40R of the profile 40 is smaller than the radius 60R of the second profile 60.

[0063] Surprisingly, it was found that, even more advantageously, the radii 40R and 60R differed by less than 5 times, especially less than 3 times, especially less than 2 times, especially less than 1.5 times, especially less than 1.25 times, or even equal. Figure 28 b).

[0064] Surprisingly, in this case, the tensile stress of the electrical conductor can be compensated for or offset by the compressive stress applied by the external component to the system consisting of the internal component and the electrical conductor (and, in the case of identical geometry, these stresses can even be eliminated directly). Thus, higher compressive stress and / or lower minimum contact stress can be achieved in a particularly advantageous manner.

Claims

1. A composite element (10) having an outer support (20) and an internal component (30), the internal component being housed within the outer support (20) under compressive stress. in, The external support (20) and the internal component (30) are adjacent to each other along a closed contour line (40). The contour line (40) includes two linear segments (42) extending in a straight line and two connecting segments (44) that connect the two linear segments (42) to form a closed contour line, wherein at least one of the two connecting segments (44) has a curved area (46) extending in an arc. The external support (20) comprises or is made of a material having a first coefficient of thermal expansion, and The internal component (30) comprises or is made of a material having a second coefficient of thermal expansion, and Wherein, the first coefficient of thermal expansion of the material of the external support (20) is greater than the second coefficient of thermal expansion of the material of the internal component (30). Wherein, the contact pressure at any point along the contour line (40) is positive, and wherein, the load along the contour line (40) on the internal component (30) is less than 300 MPa, and The outline (40) is formed as a rectangle with four rounded corners, wherein the outline has a corner radius of at least 0.5 mm, or... The two connecting segments (44) are formed as a continuous arc-shaped curved region (46) such that the two linear segments (42) are connected without a straight region between them. The smallest possible envelope rectangle surrounding the contour line (40) includes a first side length and a second side length extending orthogonally to the first side length. The first side length extends parallel to at least one of the two opposing linear segments (42), wherein the first side length is at least 1.1 times and at most 4 times greater than the second side length.

2. The composite element (10) according to claim 1. in, The external support (20) comprises or is made of a metal having a first coefficient of thermal expansion. The internal component (30) includes glass having a second coefficient of thermal expansion or is made of glass having a second coefficient of thermal expansion.

3. The composite element (10) according to claim 1 or 2, wherein, The length of the curved region (46) is at least 5% of the length of the connecting section (44).

4. The composite element (10) according to claim 1 or 2. in, The length of the curved region (46) is at least 10% of the length of the connecting section (44).

5. The composite element (10) according to claim 1 or 2, wherein the length of the arc-shaped bending region (46) is at least 15% of the length of the connecting segment (44).

6. The composite element (10) according to claim 1 or 2, wherein the length of the arc-shaped bending region (46) is at least 20% of the length of the connecting section (44).

7. The composite element (10) according to claim 1 or 2, wherein the length of the arc-shaped bending region (46) is at least 25% of the length of the connecting section (44).

8. The composite element (10) according to claim 1 or 2. in, At least one of the two connecting segments (44) is formed as a continuous arc-shaped curved region (46) such that the two linear segments (42) are connected without a straight region between them, and wherein the other of the two connecting segments (44) is formed in the same manner such that the contour line (40) has two continuously rounded sides.

9. The composite element (10) according to claim 1 or 2, wherein the contour line (40) is formed in the shape of a pill.

10. The composite element (10) according to claim 1 or 2, wherein the length of the first side is at least 1.1 times and at most 3 times greater than the length of the second side.

11. The composite element (10) according to claim 1 or 2, wherein the length of the first side is at least 1.2 times and at most 4 times greater than the length of the second side.

12. The composite element (10) according to claim 1 or 2, wherein the length of the first side is at least 1.3 times and at most 4 times greater than the length of the second side.

13. The composite element (10) according to claim 1 or 2, wherein the length of the first side is at least 1.4 times and at most 4 times greater than the length of the second side.

14. The composite element (10) according to claim 1 or 2, wherein the length of the first side is at least 1.5 times and at most 4 times greater than the length of the second side.

15. The composite element (10) according to claim 1 or 2, wherein the length of the first side is at least 1.6 times and at most 4 times greater than the length of the second side.

16. The composite element (10) according to claim 1 or 2, wherein the length of the first side is at least 1.7 times and at most 4 times greater than the length of the second side.

17. The composite element (10) according to claim 1 or 2, wherein the length of the first side is at least 1.8 times and at most 4 times greater than the length of the second side.

18. The composite element (10) according to claim 1 or 2, wherein the length of the first side is at least 1.9 times and at most 4 times greater than the length of the second side.

19. The composite element (10) according to claim 1 or 2, wherein the length of the first side is at least twice and at most four times greater than the length of the second side.

20. The composite element (10) according to claim 1 or 2, wherein the length of the first side is at least 2.5 times and at most 4 times greater than the length of the second side.

21. The composite element (10) according to claim 1 or 2, wherein the length of the first side is at least 3 times and at most 4 times greater than the length of the second side.

22. The composite element (10) according to claim 1 or 2. in, The curved region (46) of the connecting section (44) transitions seamlessly into the linear section (42), and / or The outline (40) extends without steps at each location.

23. The composite element (10) according to claim 1 or 2. in, The curved region (46) of the connecting section (44) transitions seamlessly into the linear section (42), and / or The outline (40) extends without bending at each location.

24. The composite element (10) according to claim 1 or 2. in, The curvature of the curved region (46) of the connecting segment (44) transitions seamlessly into the linear segment (42), and / or The contour line (40) extends at each location with a curvature that does not change abruptly.

25. The composite element (10) according to claim 1 or 2. in, The contact pressure at any point along the contour line (40) is greater than 1 MPa, and / or Wherein, the contact pressure at at least one location along the contour line (40) is greater than 100 MPa.

26. The composite element (10) according to claim 1 or 2. in, The contact pressure at any point along the contour line (40) is greater than 2 MPa, and / or Wherein, the contact pressure at at least one location along the contour line (40) is greater than 200 MPa.

27. The composite element (10) according to claim 1 or 2. in, The contact pressure at any point along the contour line (40) is greater than 3 MPa, and / or Wherein, the contact pressure at at least one location along the contour line (40) is greater than 500 MPa.

28. The composite element (10) according to claim 1 or 2. in, The contact pressure at any point along the contour line (40) is greater than 4 MPa, and / or Wherein, the contact pressure at at least one location along the contour line (40) is greater than 1000 MPa.

29. The composite element (10) according to claim 1 or 2, wherein, The contact pressure at any point along the contour line (40) is greater than 10 MPa.

30. The composite element (10) according to claim 1 or 2, wherein, The contact pressure at any point along the contour line (40) is greater than 20 MPa.

31. The composite element (10) according to claim 1 or 2, wherein, The contact pressure at any point along the contour line (40) is greater than 30 MPa.

32. The composite element (10) according to claim 1 or 2. in, The load on the external support (20) along the outline (40) is less than 300 MPa.

33. The composite element (10) according to claim 1 or 2, wherein, The load along the outline (40) on the outer support (20) is less than 250 MPa.

34. The composite element (10) according to claim 1 or 2, wherein, The load along the outline (40) on the outer support (20) is less than 240 MPa.

35. The composite element (10) according to claim 1 or 2, wherein, The load along the outline (40) on the outer support (20) is less than 230 MPa.

36. The composite element (10) according to claim 1 or 2, wherein, The load along the outline (40) on the outer support (20) is less than 225 MPa.

37. The composite element (10) according to claim 1 or 2, wherein, The load along the outline (40) on the external support (20) is less than 220 MPa.

38. The composite element (10) according to claim 1 or 2, wherein, The load along the outline (40) on the outer support (20) is less than 215 MPa.

39. The composite element (10) according to claim 1 or 2, wherein, The load along the outline (40) on the outer support (20) is less than 210 MPa.

40. The composite element (10) according to claim 1 or 2. in, The load along the outline (40) on the internal component (30) is less than 200 MPa.

41. The composite element (10) according to claim 1 or 2, wherein, The load along the outline (40) on the internal component (30) is less than 100 MPa.

42. The composite element (10) according to claim 1 or 2, wherein, The load along the outline (40) on the internal component (30) is less than 150 MPa.

43. The composite element (10) according to claim 1 or 2, wherein, The load along the outline (40) on the internal component (30) is less than 95 MPa.

44. The composite element (10) according to claim 1 or 2, wherein, The load along the outline (40) on the internal component (30) is less than 90 MPa.

45. The composite element (10) according to claim 1 or 2, wherein, The load along the outline (40) on the internal component (30) is less than 85 MPa.

46. ​​The composite element (10) according to claim 1 or 2, wherein, The load along the outline (40) on the internal component (30) is less than 80 MPa.

47. The composite element (10) according to claim 1 or 2. in, The deformation of the external support (20) is less than 0.03 mm / mm.

48. The composite element (10) according to claim 1 or 2, wherein, The deformation of the external support (20) is less than 0.029 mm / mm.

49. The composite element (10) according to claim 1 or 2, wherein, The deformation of the external support (20) is less than 0.028 mm / mm.

50. The composite element (10) according to claim 1 or 2, wherein, The deformation of the external support (20) is less than 0.027 mm / mm.

51. The composite element (10) according to claim 1 or 2. The composite element includes an outer support (20), an inner component (30), and an electrical conductor (50) extending through the inner component (30). in, The external support (20) and the internal component (30) are adjacent to each other along a closed contour line (40), and The internal component (30) and the electrical conductor (50) are adjacent to each other along a closed second contour line (60).

52. The composite element (10) according to claim 51. in, The external support (20) comprises or is made of a material having a first coefficient of thermal expansion, and wherein the internal component (30) comprises or is made of a material having a second coefficient of thermal expansion, and wherein the electrical conductor (50) comprises or is made of a material having a third coefficient of thermal expansion. Wherein, the third coefficient of thermal expansion is 3 times smaller than the second coefficient of thermal expansion, and / or The third coefficient of thermal expansion is three times smaller than the first coefficient of thermal expansion.

53. The composite element (10) according to claim 51. in, The external support (20) comprises or is made of a metal having a first coefficient of thermal expansion, the internal component (30) comprises or is made of glass having a second coefficient of thermal expansion, and the electrical conductor (50) comprises or is made of a metal having a third coefficient of thermal expansion. Wherein, the third coefficient of thermal expansion is 2 times smaller than the second coefficient of thermal expansion, and / or The third coefficient of thermal expansion is twice as small as the first coefficient of thermal expansion.

54. The composite element (10) according to claim 51. in, The third coefficient of thermal expansion is 1.5 times smaller than the second coefficient of thermal expansion, and / or The third coefficient of thermal expansion is 1.5 times smaller than the first coefficient of thermal expansion.

55. The composite element (10) according to claim 51. in, The third coefficient of thermal expansion is 1.25 times smaller than the second coefficient of thermal expansion, and / or The third coefficient of thermal expansion is 1.25 times smaller than the first coefficient of thermal expansion.

56. The composite element (10) according to claim 51. in, The outline (40) along which the outer support (20) and the inner component (30) are adjacent to each other defines a minimum possible first envelope rectangle (41) that surrounds the outline (40). Wherein, the second contour line (60) along which the internal component (30) and the electrical conductor (50) are adjacent to each other defines the smallest possible second envelope rectangle (61), the second envelope rectangle surrounding the second contour line (60), and The first envelope rectangle (41) and the second envelope rectangle (61) have a longer side length and a shorter side length, respectively, and the longer side lengths of the first envelope rectangle (41) and the second envelope rectangle (61) extend parallel to each other or at an angle to each other, wherein the angle is less than 20 degrees.

57. The composite element (10) according to claim 56, wherein, The angle is less than 10 degrees.

58. The composite element (10) according to claim 56, wherein, The angle is less than 5 degrees.

59. The composite element (10) according to claim 51. in, The second contour line (60) along which the internal component (30) and the electrical conductor (50) are adjacent to each other includes two opposing second linear segments (62) and two second connecting segments (64) extending in a straight line, the two second connecting segments (64) connecting the two second linear segments (62) to form a closed contour line, wherein at least one of the two second connecting segments (64) has an arcuate curved region (66).

60. The composite element (10) according to claim 59. in, Regarding the second contour line (60) along which the internal component (30) and the electrical conductor (50) are adjacent to each other, at least one of the two second connecting sections (64) has a first curved region (66) and a second curved region (66), the first curved region (66) extending in an arc adjacent to one of the two second linear sections (62), and the second curved region (66) extending in an arc adjacent to the other of the two second linear sections (62).

61. The composite element (10) according to claim 60, wherein, The other of the two second connecting sections (64) is formed in the same manner, such that the second contour line (60) has four rounded corners.

62. The composite element (10) according to claim 61, wherein the second contour line (60) is formed as a rectangle with rounded corners.

63. The composite element (10) according to claim 59. in, Regarding the second contour line (60) along which the internal component (30) and the electrical conductor (50) are adjacent to each other, the length of the arc-shaped curved region (66) is at least 5% of the length of the second connecting section (64).

64. The composite element (10) according to claim 63, wherein, The length of the curved extension (66) is at least 10% of the length of the second connecting segment (64).

65. The composite element (10) according to claim 63, wherein, The length of the curved extension (66) is at least 15% of the length of the second connecting segment (64).

66. The composite element (10) according to claim 63, wherein, The length of the curved extension (66) is at least 20% of the length of the second connecting segment (64).

67. The composite element (10) according to claim 63, wherein, The length of the curved extension (66) is at least 25% of the length of the second connecting segment (64).

68. The composite element (10) according to claim 59. in, Regarding the second contour line (60) along which the internal component (30) and the electrical conductor (50) are adjacent to each other, at least one of the two second connecting sections (64) is formed as a continuously arcuate curved region (66), such that the two second linear sections (62) are connected without any straight-line extending region between them.

69. The composite element (10) according to claim 68, wherein, The other of the two second connecting sections (64) is formed in the same manner, such that the second contour line (60) has two continuously rounded sides.

70. The composite element (10) according to claim 69, wherein, The second outline (60) is formed into a pill shape.

71. The composite element (10) according to claim 59. in, The smallest possible envelope rectangle surrounding the second contour line (60) includes a first side length and a second side length extending orthogonally to the first side length, wherein the first side length of the second contour line (60) is parallel to at least one of two opposing second linear segments (62).

72. The composite element (10) according to claim 71, wherein, The length of the first side of the second contour line (60) is greater than the length of the second side of the second contour line (60).

73. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 1.1 times and at most 10 times greater than the length of the second side of the second profile (60).

74. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 1.1 times and at most 6 times greater than the length of the second side of the second profile (60).

75. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 1.1 times and at most 5 times greater than the length of the second side of the second profile (60).

76. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 1.1 times and at most 4 times greater than the length of the second side of the second profile (60).

77. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 1.1 times and at most 3 times greater than the length of the second side of the second profile (60).

78. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 1.2 times and at most 5 times greater than the length of the second side of the second profile (60).

79. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 1.2 times and at most 4 times greater than the length of the second side of the second profile (60).

80. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 1.3 times and at most 5 times greater than the length of the second side of the second profile (60).

81. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 1.3 times and at most 4 times greater than the length of the second side of the second profile (60).

82. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 1.4 times and at most 5 times greater than the length of the second side of the second profile (60).

83. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 1.4 times and at most 4 times greater than the length of the second side of the second profile (60).

84. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 1.5 times and at most 5 times greater than the length of the second side of the second profile (60).

85. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 1.5 times and at most 4 times greater than the length of the second side of the second profile (60).

86. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 1.6 times and at most 5 times greater than the length of the second side of the second profile (60).

87. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 1.6 times and at most 4 times greater than the length of the second side of the second profile (60).

88. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 1.7 times and at most 5 times greater than the length of the second side of the second profile (60).

89. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 1.7 times and at most 4 times greater than the length of the second side of the second profile (60).

90. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 1.8 times and at most 5 times greater than the length of the second side of the second profile (60).

91. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 1.8 times and at most 4 times greater than the length of the second side of the second profile (60).

92. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 1.9 times and at most 5 times greater than the length of the second side of the second profile (60).

93. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 1.9 times and at most 4 times greater than the length of the second side of the second profile (60).

94. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least twice and at most five times greater than the length of the second side of the second profile (60).

95. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least twice and at most four times greater than the length of the second side of the second profile (60).

96. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 2.5 times and at most 5 times greater than the length of the second side of the second profile (60).

97. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 2.5 times and at most 4 times greater than the length of the second side of the second profile (60).

98. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 3 times and at most 5 times greater than the length of the second side of the second profile (60).

99. The composite element (10) according to claim 72, wherein, The length of the first side of the second profile (60) is at least 3 times and at most 4 times greater than the length of the second side of the second profile (60).

100. The composite element (10) according to claim 59. in, Regarding the second contour line (60) along which the internal component (30) and the electrical conductor (50) are adjacent to each other, the curved region (66) of the second connecting section (64) extending in an arc shape transitions seamlessly into the second linear section (62), and / or The second contour line (60) extends without steps at each location.

101. The composite element (10) according to claim 59. in, Regarding the second contour line (60) along which the internal component (30) and the electrical conductor (50) are adjacent to each other, the curved region (66) of the second connecting section (64) extending in an arc transitions seamlessly into the second linear section (62), and / or The second contour line (60) extends without bending at each location.

102. The composite element (10) according to claim 59. in, Regarding the second contour line (60) along which the internal component (30) and the electrical conductor (50) are adjacent to each other, the curvature of the curved region (66) of the second connecting section (64) extending in an arc transitions smoothly into the second linear section (62), and / or The second contour line (60) extends with a curvature that is constant at each location.

103. The composite element (10) according to claim 59. in, The outer support (20) and the inner component (30) are adjacent to each other along the contour line (40) that defines a first curved section, and Wherein, the second contour line (60) along which the internal component (30) and the electrical conductor (50) are adjacent to each other defines a second curved section, the second curved section being directly opposite the first curved section, and The distance between the contour line (40) and the second contour line (60) is greater in the region of the first curved section and the second curved section than in the region of the smaller curved section or the region without a curved section.

104. The composite element (10) according to claim 103. in, The outer support (20) and the inner component (30) are adjacent to each other along at least one of the connecting sections (44) defining a first bending section, and Wherein, at least one of the second connection sections (64) along which the internal component (30) and the electrical conductor (50) are adjacent to each other defines a second bending section, the second bending section being directly opposite the first bending section, and The distance between the contour line (40) and the second contour line (60) is greater in the region of the first curved section and the second curved section than in the region of the linear section (42) and the second linear section (62).

105. The composite element (10) according to claim 103. in, The outer support (20) and the inner component (30) are adjacent to each other along at least one of the bending regions (46) defining a first bending segment, and Wherein, at least one of the bending regions (66) along which the internal component (30) and the electrical conductor (50) are adjacent to each other defines a second bending section, the second bending section being directly opposite the first bending section.

106. The composite element (10) according to claim 59. in, The outer support (20) and the inner component (30) are adjacent to each other along the contour line (40) that defines a first radius, and Wherein, the second contour line (60) along which the internal component (30) and the electrical conductor (50) are adjacent to each other defines a second radius, which is directly opposite to the first radius, and Wherein, the ratio of the first radius to the second radius is less than 10. The distance between the contour line (40) and the second contour line (60) is greater in the region of the first radius and the second radius than in the region of the linear segment (42) and the second linear segment (62).

107. The composite element (10) according to claim 106. in, The outer support (20) and the inner component (30) are adjacent to each other along at least one of the connecting sections (44) that define a first radius, and Wherein, at least one of the second connection segments (64) along which the internal component (30) and the electrical conductor (50) are adjacent to each other defines a second radius, the second radius being directly opposite the first radius, and Wherein, the ratio of the first radius to the second radius is less than 5.

108. The composite element (10) according to claim 106. in, The outer support (20) and the inner component (30) are adjacent to each other along at least one of the curved regions (46) defining a first radius, and Wherein, at least one of the curved regions (66) along which the internal component (30) and the electrical conductor (50) are adjacent to each other defines a second radius, the second radius being directly opposite the first radius, and Wherein, the ratio of the first radius to the second radius is less than 3.

109. The composite element (10) according to claim 106, wherein, The ratio of the first radius to the second radius is less than 2.

110. The composite element (10) according to claim 106, wherein, The ratio of the first radius to the second radius is less than 1.

5.

111. The composite element (10) according to claim 106, wherein, The ratio of the first radius to the second radius is less than 1.

25.

112. The composite element (10) according to claim 106, wherein, The ratio of the first radius to the second radius is less than 1.

113. The composite element (10) according to claim 60. in, The outer support (20) and the inner component (30) are adjacent to each other along the outline (40), and the inner component (30) and the electrical conductor (50) are adjacent to each other along the second outline (60). Except at the curved areas of the outline (40) and the second outline (60), they are spaced apart from each other at a constant distance along the entire outline (40) and the second outline (60). In particular, the distance between the contour line (40) and the second contour line (60) is relatively large in the curved areas of the contour line (40) and the curved areas of the second contour line (60).

114. The composite element (10) according to claim 59. in, The composite element has a first side (12) and a second side (14), wherein the electrical conductor (50) extends from the first side (12) of the composite element through the internal component (30) to the second side (14) of the composite element.

115. The composite element (10) according to claim 114, wherein, The outline (40) along which the outer support (20) and the inner component (30) are adjacent to each other is equal on both sides (12, 14) of the composite element, and The second contour line (60) along which the internal component (30) and the electrical conductor (50) are adjacent to each other is equal on the two sides (12, 14) of the composite element.

116. The composite element (10) according to claim 59. in, The electrical conductor (50) is flush with or offset from the internal component (30) on one or both sides of the composite element, the offset being less than 500 μm, and / or The electrical conductor (50) extends a protrusion from the internal component (30) on one or both sides of the composite element.

117. The composite element (10) according to claim 116. in, The offset is less than 150 μm, and / or Wherein, the protrusion is greater than 500 μm.

118. The composite element (10) according to claim 116, wherein the offset is less than 100 μm.

119. A composite element (10) having an outer support (20) and an internal component (30), the internal component being housed within the outer support (20) under compressive stress. in, The external support (20) and the internal component (30) are adjacent to each other along a closed contour line (40). Wherein, the outline (40) is non-circular and at least partially curved. The external support (20) comprises or is made of a material having a first coefficient of thermal expansion, and The internal component (30) comprises or is made of a material having a second coefficient of thermal expansion, and Wherein, the first coefficient of thermal expansion of the material of the external support (20) is greater than the second coefficient of thermal expansion of the material of the internal component (30). Wherein, the contact pressure at any point along the contour line (40) is positive, and wherein, the load along the contour line (40) on the internal component (30) is less than 300 MPa, and The outline (40) is formed as a rectangle with four rounded corners, wherein the outline has a corner radius of at least 0.5 mm, or... The contour line (40) comprises two linear segments (42) and two connecting segments (44) that connect the two linear segments (42) to form a closed contour line. The two connecting segments (44) are formed as a continuous arc-shaped curved region (46) such that the two linear segments (42) are connected without a straight region between them. The smallest possible envelope rectangle surrounding the contour line (40) comprises a first side length and a second side length extending orthogonally to the first side length. The first side length is parallel to the extension of at least one of the two opposing linear segments (42). The first side length is at least 1.1 times and at most 4 times greater than the second side length.

120. The composite element (10) according to claim 119, wherein, The outline (40) is oval or elliptical.

121. A back cover for a wearable electronic device, the back cover comprising a composite element (10) according to any one of claims 1 to 118.

122. The rear cover according to claim 121, wherein, The wearable electronic device is a heart rate monitor, smartwatch, or fitness tracker.

123. The rear cover according to claim 121 or 122, wherein the rear cover is made of steel and has one or more viewing windows, wherein, The aspect ratio of the observation window is 1.4:1 to 2.0:

1.

124. The rear cover according to claim 123, wherein, The back cover is made of stainless steel.

125. The rear cover according to claim 123, wherein, The aspect ratio of the observation window is 1.7:1 to 1.9:

1.

126. The back cover according to claim 123, wherein the back cover is made of austenitic stainless steel, wherein, The aspect ratio of the observation window is 1.8:1, and the minimum spacing between the observation windows is 2.0 mm.

127. The rear cover according to claim 123, wherein, The back cover has a thickness of at least 0.7 mm to 1 mm in the area surrounding the viewing window.

128. The rear cover according to claim 123, wherein, The back cover has a thickness of at least 0.8 mm in the area surrounding the viewing window.

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