DISPLAY DEVICE, ELECTRONIC DEVICE COMPRISING THE SAME, AND METHOD OF SWITCHING A DISPLAY DEVICE BETWEEN A SHARING MODE AND A PRIVACY MODE TECHNICAL FIELD [0001] Embodiments of the present disclosure relate to display devices, particularly display devices being switchable between a privacy mode and a sharing mode. Further, embodiments of the present disclosure relate to electronic devices including such switchable display devices and methods of switching a display device between a sharing mode and a privacy mode. BACKGROUND [0002] Privacy and security are becoming increasingly relevant topics in the design of electronic devices. Displays are ubiquitous in many electronic devices, including mobile phones, tablets and laptop computers. There are various approaches for protecting users against unauthorized viewing of displays. [0003] For example, one approach is to employ a visual protection film for covering the display. In particular, the visual protection film is an additional hardware accessory for the display which is configured for decreasing the viewing angle of the display such that the display cannot be viewed from the side. [0004] Such visual protection films, also known as privacy screens, are of relatively low cost. However, such visual protection films are separate components which have to be mounted and demounted according to needs. Further, due to their thickness, such visual protection films are impractical to be used for smaller devices, e.g. mobile phones. [0005] Therefore, there exists a demand for improved display devices and methods which provide for a privacy mode and a sharing mode. SUMMARY [0006] In light of the above, a display device, an electronic device including a display device, and a method of switching a display device between a sharing mode and a privacy mode according to the independent claims are provided. Further aspects, benefits, and features of the present disclosure are apparent from the claims, the description, and the accompanying drawings. [0007] According to an aspect of the present disclosure, a display device is provided. The display device includes a liquid crystal cell, a backlight module configured for emitting collimated light, and a liquid crystal device provided between the backlight module and the liquid crystal cell. The liquid crystal device is switchable between a privacy mode and a sharing mode. The liquid crystal device includes a reverse prism structure facing the backlight module. [0008] According to another aspect of the present disclosure, an electronic device comprising a display device is provided. The display device includes a liquid crystal cell, a backlight module configured for emitting oblique light, and a liquid crystal device provided between the backlight module and the liquid crystal cell. The liquid crystal device is switchable between a privacy mode and a sharing mode. The liquid crystal device includes a reverse prism structure facing the backlight module. In particular, the display device is a display device according to any embodiments described herein. [0009] According to a further aspect of the present disclosure, a method of switching a display device between a sharing mode and a privacy mode is provided. The method includes applying a voltage between a transparent top electrode and a transparent bottom electrode. A polymer dispersed liquid crystal structure is provided between the transparent top electrode and the transparent bottom electrode. Applying the voltage results in an alignment of liquid crystal molecules provided in a plurality of droplets dispersed in a transparent polymer of the polymer dispersed liquid crystal structure such that a refractive index of the droplets substantially corresponds to a refractive index of the transparent polymer of the polymer dispersed liquid crystal structure. [0010] Embodiments are also directed at apparatuses for carrying out the disclosed method and include apparatus parts for performing each described method aspect. These method aspects may be performed by way of hardware components, a computer programmed by appropriate software, by any combination of the two or in any other manner. Furthermore, embodiments according to the disclosure are also directed at methods for operating the described apparatus. The methods for operating the described apparatus include method aspects for carrying out every function of the apparatus. BRIEF DESCRIPTION OF THE DRAWINGS [0011] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments. The accompanying drawings relate to embodiments of the disclosure and are described in the following: FIG.1 shows a schematic view of a display device according to embodiments described herein; FIG.2 shows a schematic view illustrating some further details of a display device according to further embodiments described herein; FIG.3 shows a schematic view of a display device according to embodiments described herein in a state upon voltage application; FIG.4 shows a schematic view of a display device according to embodiments described herein in a state without voltage application; FIG.5 shows a schematic view of a display device in a state upon voltage application for explaining privacy mode according to embodiments described; and FIG.6 shows a schematic view of a display device in a state without voltage application for explaining sharing mode according to embodiments described herein. DETAILED DESCRIPTION OF EMBODIMENTS [0012] Reference will now be made in detail to the various embodiments of the disclosure, one or more examples of which are illustrated in the figures. Within the following description of the drawings, the same reference numbers refer to same components. Generally, only the differences with respect to individual embodiments are described. Each example is provided by way of explanation of the disclosure and is not meant as a limitation of the disclosure. [0013] Further, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the description includes such modifications and variations. [0014] With exemplary reference to FIG. 1, a display device 100 according to the present disclosure is described. According to embodiments which can be combined with other embodiments described herein, the display device 100 includes a liquid crystal cell 110, a backlight module 120 configured for emitting collimated light; and a liquid crystal device 130. The liquid crystal device 130 is provided between the backlight module 120 and the liquid crystal cell 110. Further, the liquid crystal device 130 is switchable between a privacy mode and a sharing mode. Additionally, the liquid crystal device 130 includes a reverse prism structure 140 facing the backlight module 120. [0015] Accordingly, compared to the state of the art, an improved display device with a privacy mode and a sharing mode can be provided. In particular, the display device as described herein has the advantage that an integrated switching function between a privacy mode and a sharing mode is provided. Further, compared to the state of the art, the display device of the present disclosure can be of smaller thickness, i.e. of slimmer design. [0016] Before further optional embodiments of the display device are described, some terms used in the present disclosure are briefly explained. [0017] In the present disclosure, a “liquid crystal cell” can be understood as a liquid crystal cell of a liquid-crystal display (LCD). In particular, each pixel of an LCD typically consists of a layer of molecules aligned between two transparent electrodes, and two polarizing filters (parallel and perpendicular), the axes of transmission of which are (in most cases) perpendicular to each other. Without the liquid crystal between the polarizing filters, light passing through the first filter would be blocked by the second (crossed) polarizer. Before an electric field is applied, the orientation of the liquid-crystal molecules is determined by the alignment at the surfaces of electrodes. For example, in a twisted nematic (TN) device, the surface alignment directions at the two electrodes are perpendicular to each other, and so the molecules arrange themselves in a helical structure, or twist. This induces the rotation of the polarization of the incident light, and the device appears gray. If the applied voltage is large enough, the liquid crystal molecules in the center of the layer are almost completely untwisted and the polarization of the incident light is not rotated as the light passes through the liquid crystal layer. This light will then be mainly polarized perpendicular to the second filter, and thus be blocked and the pixel will appear black. By controlling the voltage applied across the liquid crystal layer in each pixel, light can be allowed to pass through in varying amounts thus constituting different levels of gray. For color LCD systems the same technique can be used, with color filters used to generate red, green, and blue pixels. The color filters are made with a photolithography process. Red, green, blue and black resists are used. Typically, resists contain a finely ground powdered pigment, with small particles in the nanometer range. The black resist is the first to be applied; this will create a black grid that will separate red, green and blue subpixels from one another. After the black resist has been dried in an oven and exposed to UV light through a photomask, the unexposed areas are washed away. Then the same process is repeated with the remaining resists. This fills the holes in the black grid (or matrix) with their corresponding colored resists. [0018] In the present disclosure, a “backlight module” can be understood as module configured for providing backlight. In particular, a backlight module as described herein is configured for emitting collimated light, particularly collimated light with an acute light output angle D with respect to a surface of the backlight module. [0019] In the present disclosure, a “liquid crystal device” can be understood as a device having a polymer dispersed liquid crystal (PDLC) structure. The PDLC- structure typically includes a transparent polymer with a dispersion of a plurality of droplets containing liquid crystal molecules, as described herein. Accordingly, it is to be understood that in the embodiments of the present disclosure, the liquid crystal device is different from the liquid crystal cell. In particular, as described herein, the liquid crystal device is switchable between a privacy mode and a sharing mode. The privacy mode provides a limited light emission angle distribution, as exemplarily shown in FIG.5. The sharing mode provides a broader light emission angle distribution than the privacy mode. In particular, the sharing mode provides a substantially even light emission angle distribution, as exemplarily shown in FIG.6. [0020] In the present disclosure, a “reverse prism structure” can be understood as a structure including a plurality of prisms, wherein the plurality of prisms are reversely oriented. In particular, as exemplarily shown in FIG. 3, the plurality of prisms are arranged such that the tips 140 of the prisms face the backlight module 120. [0021] With exemplary reference to FIG. 2, according to embodiments which can be combined with other any embodiments described herein, the liquid crystal device includes a polymer dispersed liquid crystal (PDLC) structure 131 provided between a transparent top electrode 132 and a transparent bottom electrode 133 opposite the transparent top electrode 132. In particular, the PDLC-structure 131 is in contact with the transparent top electrode 132 and the transparent bottom electrode 133. As exemplarily shown in FIG.2, the transparent top electrode 132 is provided adjacent to the liquid crystal cell 110. More specifically, the transparent top electrode 132 is provided between the PDLC-structure 131 and the liquid crystal cell 110. The transparent bottom electrode 133 is provided adjacent to the backlight module 120. More specifically, transparent bottom electrode 133 is provided between the backlight module 120 and the PDLC-structure 131. [0022] In the present disclosure, the term “transparent” may be understood in that a total transmission of, for example, 70% to 100%, typically 80% to 100%, and more typically 90% to 100% is provided. Accordingly, a transparent electrode, e.g. the transparent top electrode 132 and/or the transparent bottom electrode 133 as described herein, may provide for a total transmission of 70% to 100%, particularly 80% to 100%, and more particularly 90% to 100%. The term “total transmission” (T) is to be understood as the amount of incident light that passes through a material. [0023] According to embodiments which can be combined with other embodiments described herein, the transparent top electrode 132 is made of a transparent polymer. Additionally, the transparent top electrode 132 may include a first transparent conductive coating 134 facing the PDLC-structure 131, as exemplarily shown in FIG.2. In particular, the first transparent conductive coating 134 may be provided between the PDLC-structure 131 and the transparent top electrode 132. More specifically, the first transparent conductive coating 134 may be in direct contact with the transparent top electrode 132 and/or the PDLC- structure 131, particularly the transparent polymer 150 of the PDLC-structure 131, as exemplarily shown in FIG.3. [0024] According to embodiments which can be combined with other embodiments described herein, the transparent bottom electrode 133 is made of a transparent polymer. Additionally, the transparent bottom electrode 133 may include a second transparent conductive coating 135 facing the polymer dispersed liquid crystal structure 131, as exemplarily shown in FIG. 2. In particular, the second transparent conductive coating 135 may be provided between the transparent bottom electrode 133 and the PDLC-structure. More specifically, the second transparent conductive coating 135 may be in direct contact with the transparent bottom electrode 133 and/or the PDLC-structure 131, particularly the transparent polymer 150 of the PDLC-structure 131, as exemplarily shown in FIG.3. [0025] As exemplarily shown in FIG. 2, according to embodiments which can be combined with other embodiments described herein, the transparent bottom electrode 133 includes the reverse prism structure 140. In particular, the reverse prism structure can be an integral part of the transparent bottom electrode 133. [0026] According to embodiments which can be combined with other embodiments described herein, the reverse prism structure 140 is made of a polymeric material having a refractive index matched to the transparent polymer of the bottom electrode 133. In particular, the reverse prism structure 140 and the bottom electrode 133 may be made of the same transparent polymer. [0027] As exemplarily indicated in FIG.2, according to embodiments which can be combined with other embodiments described herein, typically the reverse prism structure is arranged such that tips 141 of the reverse prism structure 140 face the backlight module 120. [0028] According to embodiments which can be combined with other embodiments described herein, the reverse prism structure 140 can be made by thermal forming or UV-forming. [0029] With exemplary reference to FIGS. 3 and 4, according to embodiments which can be combined with other embodiments described herein, the PDLC- structure 131 includes a transparent polymer 150 with a dispersion of a plurality of droplets 151. The droplets include one or more liquid crystal molecules 152. In particular, the one or more liquid crystal molecules are nematic with positive dielectric anisotropy. [0030] The term “nematic” relates to a type of liquid crystal phase. In a nematic phase, the calamitic or rod-shaped organic molecules have no positional order, but they self-align to have long-range directional order with their long axes roughly parallel. Thus, the molecules are free to flow and their center of mass positions are randomly distributed as in a liquid, but still maintain their long-range directional order. According to an example, the liquid crystal molecules are uniaxial nematics, i.e. having one axis (called directrix) that is longer and preferred, with the other two being equivalent (can be approximated as cylinders or rods). According to an alternative example, the liquid crystal molecules are biaxial nematics, meaning that in addition to orienting their long axis, they also orient along a secondary axis. Nematics have fluidity similar to that of ordinary (isotropic) liquids but can be easily aligned by an external magnetic or electric field. Aligned nematics have the optical properties of uniaxial crystals. [0031] According to embodiments which can be combined with other embodiments described herein, the one or more liquid crystal molecules 152 are selected such that upon voltage application, the liquid crystal molecules 152 are aligned, as exemplarily shown in FIG. 3. In particular, upon voltage application, the liquid crystal molecules 152 can be aligned such that a refractive index of the droplets substantially corresponds to a refractive index of the transparent polymer 150 of the polymer dispersed liquid crystal structure 131. Accordingly, as exemplarily shown in FIG.5 in which rays of light are indicated with dotted lines, light, particularly collimated light, emitted from the backlight module 120 can pass the PDLC-structure 131 without scattering and the light passing the liquid crystal device 130 is substantially unidirectional. As a result thereof, the rays of light arriving at the liquid crystal cell 110 are substantially parallel such that a privacy mode can be provided. [0032] According to embodiments which can be combined with other embodiments described herein, the one or more liquid crystal molecules 152 are selected such that without voltage application, the liquid crystal molecules 152 are randomly distributed, as exemplarily shown in FIG. 4. In particular, without voltage application, the liquid crystal molecules 152 are randomly distributed such that the refractive index of the droplets is different from the refractive index of the transparent polymer of the polymer dispersed liquid crystal structure 131. [0033] Accordingly, as exemplarily shown in FIG. 6, in which rays of light are indicated with dotted lines, light emitted from the backlight module 120 cannot pass the PDLC-structure 131 without scattering and the light scattered in the liquid crystal device 130 is multidirectional. As a result thereof, the rays of light arriving at the liquid crystal cell 110 have different and randomly distributed angles such that a sharing mode can be provided. [0034] With exemplary reference to FIGS. 5 and 6, according to embodiments which can be combined with other embodiments described herein, the backlight module 120 is configured for providing collimated light. Accordingly, the backlight module 120 may also be referred to as collimated backlight module. For example, the backlight module 120 may include a light guide plate configured for providing an acute light output angle D with respect to a surface 121 of the backlight module 120 facing the reverse prism structure 140. For instance, the light guide plate may include a wedge-like pattern for providing an acute light output angle D with respect to a surface 121 of the backlight module 120. Additionally or alternatively, the light guide plate may include microprisms configured for providing an acute light output angle D with respect to a surface 121 of the backlight module 120. Typically, the light output angle D is 10°I D I 60°. [0035] With exemplary reference to FIGS. 5 and 6, it is to be understood that according to embodiments which can be combined with other embodiments described herein, the reverse prism structure 140 is configured for providing a light input angle J at the interface between the transparent bottom electrode 133 and the PDLC-structure 131. Typically, the light input angle J is larger than the light output angle D, i.e. J > D, as exemplarily shown in FIGS. 5 and 6. In particular, the light input angle J can be J=90°±20°, particularly J=90°±10°. [0036] According to embodiments which can be combined with other embodiments described herein, the PDLC-structure 131 includes a scattering haze selected from a range of 80% to 97%. Further, the PDLC-structure 131 may include a full width at half maximum (FWHM) intensity distribution selected from a range of 31.5 degrees to 56 degrees. In this regard, it is to be noted that the scattering haze is measured according to the standard test method for haze and luminous transmittance of transparent plastics as specified in ASTM-D1003. Further, it is to be noted that FWHM is calculated from the luminance curve f(x), where x is the viewing angle. The luminance is measured as specified in the standard ISO/CIE 19476 “Characterization of the performance of illuminance meters and luminance meters”. Exemplary experimental results for FWHM and PDLC scattering haze are shown in Table 1. Table 1: FWHM measurement with different haze PDLC [0037] According to another aspect of the present disclosure, a method of switching a display device between a sharing mode and a privacy mode is provided. In particular, the display device can be a display device 100 according to embodiments described herein. The method includes applying a voltage between a transparent top electrode 132 and a transparent bottom electrode 133. A polymer dispersed liquid crystal structure 131 is provided between the transparent top electrode 132 and the transparent bottom electrode 133. Applying the voltage results in an alignment of liquid crystal molecules 152 provided in a plurality of droplets 151 dispersed in a transparent polymer 150 of the polymer dispersed liquid crystal structure 131, such that a refractive index of the droplets substantially corresponds to a refractive index of the transparent polymer of the polymer dispersed liquid crystal structure. [0038] In view of the above, it is to be understood that a display device, particularly an information display device, with an angular distribution of light output brightness switchable between two modes, namely a sharing mode of even distribution, and a privacy mode of narrow distribution, can be provided. The display device includes, particularly consists of, a light emitting backlight module, one or more liquid crystal cells, and a switchable liquid crystal device inserted between light emitting backlight module and the one or more liquid crystal cells. [0039] Typically, the backlight module is configured for providing collimated light. In particular, the light emitting backlight module can be an oblique emitting collimated backlight module, for example configured for providing an acute light output angle D as exemplarily described with reference to FIGS.5 and 6. The said oblique emitting backlight module features a light output direction of an acute angle D vs. the output surface. This can be achieved by design strategies such as wedge-like patterns in the light guide plate, or a light guide with microprisms. [0040] The switchable liquid crystal device typically includes an integrated reverse-prism structure. Further, the switchable liquid crystal device typically includes two transparent electrodes which can be arranged parallel to each other, e.g. the transparent top electrode and the transparent bottom electrode as described herein. For instance, the transparent top electrode may consist of a transparent polymer film. [0041] Additionally, a transparent conductive coating may be provided on the surface of the transparent top electrode, as exemplarily described herein. The transparent bottom electrode may consist of a transparent polymer film. On one surface of the transparent bottom electrode, a transparent conductive coating may be provided and on the other surface of the transparent bottom electrode a reverse prism structure as described herein can be provided. The reverse prism structure is typically composed of a refractive index aligned polymer, with tips of the prisms facing the direction of the light emitting backlight module. For example, the reverse prism structure can be thermal formed or UV-formed onto the transparent polymer film of the transparent bottom electrode. [0042] The transparent conductive coated sides of the said two transparent electrodes, i.e. the first transparent conductive coating and the second transparent conductive coating as described herein, are typically arranged to face each other. The space between said two transparent electrodes can be filled with at least one transparent polymer having multiple cavities (i.e. a dispersion of a plurality of droplets as described herein). In particular, those cavities include at least one kind of nematic liquid crystal (LC) molecule with positive dielectric anisotropy. [0043] When a voltage is applied, the said liquid crystal molecules within the said cavities are aligned such that the refractive index of those LC-filled cavities along the normal direction of the display surface is very close to the said transparent polymer provided in the space between said two transparent electrodes. The light scattering by those cavities are thus minimized, and the light emitting from the backlight module having a narrow angular distribution is duplicated, enabling the privacy mode, as exemplarily described with reference to FIG.5. [0044] When no voltage is applied, the said liquid crystal molecules within the said cavities are randomly distributed, and the refractive index of those LC-filled cavities is different from the said transparent polymer provided in the space between said two transparent electrodes. The light emitting from the backlight module having narrow angular distribution is thus scattered by those cavities, resulting in an even angular distribution, providing a sharing mode, as exemplarily described with reference to FIG.6. [0045] Accordingly, in view of the embodiments described herein, it is to be understood that beneficially an electronic device including a display device as described herein can be provided, which is improved compared to the state of the art. [0046] While the foregoing is directed to embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.