Switchable optical filters and their applications

Abstract

The invention relates to an optical component (1) that can be used in different designs in different embodiments of a switchable filter (5), which additionally has a polarization filter (P) and / or other components for changing the polarization properties of light, such as a liquid crystal layer (3). The switchable filter (5) is combined with an image reproduction device to achieve a switchable privacy protection effect. The optical component (1) comprises a first layer (S1), or a first layer (S1) and a plurality of further layers (S2, ...), wherein each layer (S1, S2, ...) comprises a material with a plurality of light-absorbing transition dipole moments. Each transition dipole moment is oriented parallel to a selectable preferred direction or fluctuates around the preferred direction with a tolerance of up to 10°, at least in a first state, so that light incident on the optical component is transmitted or at least partially absorbed depending on its direction of incidence relative to the layer (S1, S2, ...) and its polarization state.

Description

Background Art

[0001] In recent years, significant progress has been made in widening the viewing angle of LCDs. However, in some cases, the visible range of very large screens can become a disadvantage. Mobile devices such as laptops and tablets are also increasingly providing information, such as banking details or other personal and sensitive data. Accordingly, there is a need to control who should see this sensitive data; it is necessary to be able to select within a wide viewing angle (public mode) to share the information on the display with others, for example when viewing holiday photos, or for advertising purposes. On the other hand, when it is desired to keep the image information confidential, a smaller viewing angle (private mode) is required.

[0002] Automotive engineering faces a similar challenge: the driver should not be distracted by visual content, such as digital entertainment, after the engine is started, while passengers also want to consume visual content while driving. Therefore, a screen that can switch between the corresponding presentation modes is required.

[0003] Microsheet-based additional films have been used in mobile displays to provide visual data protection. However, these films are not switchable or convertible; they must always be applied manually and then removed. They also must be transported separately from the display when not needed. Furthermore, the main disadvantage of using these sheet-based films is the resulting light loss.

[0004] US6765550B2 describes a privacy protection method using micro-lamellae. The major disadvantages are the mechanical removal or mechanical installation of the filter and the light loss in the protection mode.

[0005] US5993940A describes the use of a film having uniformly distributed, small, strip-shaped prisms on its surface to achieve a privacy mode, i.e., a restrictive viewing angle mode with a small viewing angle range. The technical difficulty of R&D and manufacturing is quite high.

[0006] In WO2012 / 033583A1, switching between free and restricted fields of view is achieved by controlling the liquid crystals between so-called "chromonisch" layers. This process results in light loss and is technically very difficult.

[0007] US2012 / 0235891A1 describes a very complex backlight in a screen. Figure 15, not only does it use multiple light guides, but it also employs other complex optical components, such as a microlens assembly 40 and a prism structure 50, to convert backlighting into frontlighting. This is costly to implement, technically complex, and also results in light loss. According to the modified example shown in FIG17 of US2012 / 0235891A1, both light sources 4R and 18 generate light with a narrow illumination angle, where the light from the rear light source 18 undergoes a complex process to be converted into light with a wide illumination angle. As previously mentioned, this complex conversion significantly reduces brightness.

[0008] JP2007-155783A uses an optical surface 19, which is complex to calculate and manufacture. It deflects light into narrower or wider areas depending on the angle of incidence. This structure is similar to a Fresnel lens. Furthermore, there are interfering side surfaces that deflect light in undesirable directions. This makes it unclear whether truly reasonable light distribution can be achieved.

[0009] US2013 / 0308185A1 describes a special light guide with steps, which transmits light to a large surface according to the direction in which the light guide is illuminated from a narrow surface. In combination with a transmissive image reproduction device, such as an LC display, this allows for the creation of a screen that can be switched between a free-viewing mode and a restricted-viewing mode. The main disadvantage is that the restricted-viewing effect can only be applied to the left / right or up / down, but not all at once, as is necessary for certain payment processes. Furthermore, even in restricted-viewing mode, residual light may still be visible from obstructed viewing angles.

[0010] WO 2015 / 121398 A1 of the present applicant describes a screen with two operating modes, wherein scattering particles are present in the volume of the corresponding light guide in order to achieve the switching of the operating modes. However, the polymer scattering particles selected in this case generally have the following disadvantages, namely, the light from the two large surfaces is decoupled (ausgekoppelt), so that about half of the useful light is reflected in the wrong direction, that is, emitted in the direction of the backlight, and cannot be recovered to a sufficient extent due to structural reasons. In addition, the polymer scattering particles distributed in the volume of the light guide can, in some cases, especially at higher concentrations, produce a scattering effect that reduces the anti-peeping effect in the protection mode.

[0011] Electric birefringence (EDB) technology is based on the concept of using the switchable liquid crystals of an additional LC panel to "filter" all light beams that do not exit the imaging layer at a specific emission angle. The disadvantages of this technology are the additional energy and cost expenditures, as well as the difficulty in changing the + / -40° sweet spot, the optimal viewing position. Because the light intensity drops off again at viewing angles exceeding the sweet spot, the LC structure's absorption is also insufficient, resulting in a maximum light intensity of 3% of the maximum intensity for viewing angles greater than + / -40°.

[0012] The above methods and configurations generally have the following disadvantages, namely, significantly reducing the brightness of the basic screen, and / or requiring complex and expensive optical components for mode conversion, and / or reducing the resolution in the free-viewing public mode, and / or having visual artifacts when the display resolution is very high. Summary of the Invention

[0013] Therefore, the present invention is directed to a switchable optical filter having an optical component, wherein light incident on the optical component is transmitted or partially or completely absorbed depending on its direction of incidence and polarization properties (but not its position). By using this switchable optical filter, the transmission of light is influenced in an angle-dependent manner (optionally perpendicular to a sitting or standing viewer), with the filter being switchable between at least two operating states. In particular, the transmission angle limitation in certain directions should be switchable.

[0014] The optical component or a system based on the optical component should be realizable at low cost and, in particular, should be universally applicable to different types of screens to enable switching between privacy protection (i.e., restricted field of view mode) and free field of view mode (at least in the horizontal direction relative to a standing or seated viewer), wherein the resolution of such a screen should not be substantially reduced.

[0015] In a first embodiment, this object is achieved by a switchable optical filter comprising a first optical component that is not inherently switchable. The optical component comprises a first layer, or the first layer and a plurality of other layers, preferably five or more. Each of the layers comprises a material having a plurality of light-absorbing transition dipole moments, wherein each transition dipole moment, at least in a first state, is oriented parallel to or fluctuates about a first preferred direction selectable for the first optical component with a tolerance of up to 10°, such that light incident on the first optical component is transmitted or at least partially absorbed depending on its direction of incidence relative to the layers and its polarization state.

[0016] A transition dipole moment (also called a transition matrix element) is a quantum mechanical vector that belongs to a specific transition between an initial state (usually the ground state) and a final state (usually an excited state) of a system, such as an atom, molecule, or solid. It corresponds to the electric dipole moment associated with this transition. The direction of the vector defines the polarization of the transition, which in turn determines how a system with electromagnetic waves interacts with a given polarization when transitioning from the ground state to an excited state that absorbs light of the corresponding polarization, for example. The absolute value of the vector corresponds to the strength of the interaction, or the transition probability.

[0017] For a given direction of light propagation, the first preferred direction corresponds to an orientation of the transition dipole moment such that absorption is the same for all polarizations of light. The preferred direction is the orientation of the transition dipole in the medium such that, in the privacy mode of operation described further below, absorption is minimized for propagation in this direction.

[0018] Materials containing an orientable transition dipole moment within the meaning of the present invention include, for example, dichroic dyes or dye mixtures in combination with a carrier material (e.g., liquid crystals or polymers) that does not impair the properties. For example, each of the layers may contain only one dye, with the dyes being pairwise different from one another for the different layers. However, it is also possible for a single layer to contain several dyes, i.e., a dye mixture.

[0019] The switchable optical filter further includes a polarization filter and means for selectively generating a first electric field or a second electric field. The polarization filter is positioned upstream or downstream of the first optical component, as viewed in the direction of incidence. A liquid crystal layer is disposed between the first optical component and the polarization filter. The first electric field or the second electric field acts on the liquid crystal layer, thereby affecting the polarization state of light passing through the liquid crystal layer. The switchable optical filter is operable in at least two operating modes. In a first operating mode B1, in which the first electric field is applied and which has a first sub-operating mode B1H and a second sub-operating mode B1V, at least 24% of unpolarized light incident on the switchable filter parallel to a first preferred direction is transmitted. At least 85% of unpolarized light incident on the switchable filter at an angle of 30° or greater to the first preferred direction is absorbed. This absorption occurs only in the first direction in the first sub-operating mode B1H, and only in a second direction perpendicular to the first direction in the second sub-operating mode B1V. In a second operating mode B2 in which a second electric field is applied and which has a first sub-operating mode B1H and a second sub-operating mode B1V, at least 24% of unpolarized light incident on the switchable filter parallel to the first preferred direction is transmitted, and at least 85% of unpolarized light incident on the switchable filter (5) at an angle of 30° or more to the first preferred direction is absorbed. The absorption occurs only in the second direction in the first sub-operating mode B1H and only in the second direction perpendicular to the first direction in the second sub-operating mode B1V, so that the absorption directions of the two sub-operating modes B1H and B1V differ by 90° for the first operating mode B1 and the second operating mode B2, and therefore for both operating modes B1 and B2. Absorption always occurs only in one direction, i.e., light is transmitted in the other direction.

[0020] In the first operating mode B1, in sub-operating mode B1H, absorption may occur, for example, in the horizontal direction, relative to a seated or standing viewer, or generally relative to the eye position. In sub-operating mode B1V, absorption may occur in the vertical direction, again relative to a seated or standing viewer, or generally relative to the eye position. In this case, the line connecting the eyes defines the horizontal direction and corresponds to the first direction, while the vertical direction is perpendicular to the horizontal direction and corresponds to the second direction. Accordingly, in the second operating mode B2, in sub-operating mode B1H, absorption occurs in the vertical direction, and in sub-operating mode B1V, absorption occurs in the horizontal direction.

[0021] The configuration of the first technical solution of the switchable optical filter can be switched between operating modes B1 and B2 or between B1H and B1V by rotating the polarization filter by 90°.

[0022] For example, the field-free state can be described by a first electric field or a second electric field, with the other electric field having an absolute field strength greater than zero (e.g., 0.5 MV / m). Furthermore, depending on the design of the first optical component and the polarization filter, the field-free state may indicate the presence of operating modes B1 or B1H. However, operating modes B2 or B1V may also exist in the field-free state.

[0023] Thus, the switchable filter of the first technical solution, in conjunction with the image reproduction unit, allows, for example, switching between vertical privacy protection and horizontal privacy protection (e.g., up / down protection in sub-operating mode B1V and left / right protection in sub-operating mode B1H in operating mode B1). For example, using a laptop computer, this means that in operating mode B1, a user in sub-operating mode B1V can view content alongside others whose eyes are substantially at the same height as the user, while in sub-operating mode B1H, those nearby cannot see the image content.

[0024] In fact, in operating mode B1, the light emission angle range is vertically clipped (i.e., reduced) in sub-operating mode B1V, and horizontally clipped (i.e., reduced) in sub-operating mode B1H. In operating mode B2, the corresponding relationship is reversed. In both operating modes, the emission angle range is limited in one direction.

[0025] The switchable filter of the first technical solution can vary in its structure. Table 1 below lists some important structural variations. The first-mentioned element always faces the viewer, followed by the other components. In this context, the abbreviation "L / R" means that the optical effect is effective horizontally (the horizontal direction is defined above). For a polarizing filter, this means that the polarizing filter transmits horizontal linear polarization and (substantially) absorbs vertical linear polarization. Correspondingly, "O / U" for a polarizing filter means that the polarizing filter transmits vertical linear polarization and (substantially) absorbs horizontal linear polarization. For the effect produced by the switchable filter in conjunction with an image reproduction unit that can be positioned before or after the switchable filter, the abbreviation "L / R" means that the privacy effect acts horizontally, i.e., blocks left and right vision. This ultimately corresponds to operating mode B1 within sub-operating mode B1H of the switchable filter. Similarly, for the switchable filter in conjunction with an image reproduction unit, "O / U" means that the privacy effect acts vertically, i.e., blocks up and down vision. This corresponds to the operating mode B1 in the sub-operating mode B1V of the switchable optical filter.

[0026] Table 1:

[0027]

[0028] In the example given in Table 1, the liquid crystal layer is a nematic liquid crystal layer rotated 90°. That is, the preferred orientations of the liquid crystals on both surfaces, which induce and constrain the liquid crystal layer, are orthogonal to each other. In the case of the last row of the table, in state B1, incident light passes through the polarizer and is linearly polarized in the vertical direction (O / U). Subsequently, it passes through the liquid crystal layer, where the linear polarization is rotated 90° and then oriented horizontally (L / R). The smaller the angle between the horizontal direction and the incident direction, the lower the light transmittance. This is the basis for privacy protection along the horizontal direction (L / R). In state B2, a similar relationship applies, but the 90° polarization change is eliminated.

[0029] It should be pointed out again here that the “O / U” privacy effect in many practical cases allows normal viewing for multiple viewers when they observe from approximately the same height laterally of the image reproduction unit.

[0030] This object is also achieved by a second technical solution of a switchable optical filter. This switchable optical filter similarly comprises a first optical component, which is similar to the first optical component of the first technical solution, but is switchable and further characterized by the following characteristics: the transition dipole moment of each layer can change its orientation and / or its absolute value between a first state and at least one second state, so that each layer can be alternately placed in at least two different states. Here, a polarization filter is also provided upstream or downstream of the first optical component. The switchable optical filter according to the second technical solution also includes means for selectively generating a first electric field or a second electric field, wherein, for the first optical component, the first state is generated by applying the first electric field, and the second state is generated by applying the second electric field.

[0031] In the first operating mode B1, a first electric field is applied and the transition dipole moment of the first optical component layer is oriented along a first preferred direction. Typically, the electric field of this switchable filter and all other switchable filters described above or below is V RMS A square wave voltage <10V with a frequency of 1kHz is generated. The first operating mode B1 includes a first sub-operating mode B1H and a second sub-operating mode B1V. In the first operating mode B1, at least 24% of unpolarized light incident on the switchable filter parallel to the first preferred direction is transmitted. At least 85% of unpolarized light incident on the switchable filter according to the second technical solution at an angle of 30° or greater to the first preferred direction is absorbed. This absorption occurs only in the first direction in the first sub-operating mode B1H, and only in a second direction perpendicular to the first direction in the second sub-operating mode B1V.

[0032] In a second operating mode B3, a second electric field is applied and the transition dipole moments of the layers of the first optical component (1) are aligned parallel to the surface of the polarization filter and perpendicular to the transmission direction of the polarization filter. In this case, at least 24% of unpolarized light incident on the switchable filter at any angle to the first preferred direction is transmitted.

[0033] Here, the field-free state can also be described, for example, by a first electric field or a second electric field, with the other electric field having an absolute field strength greater than zero (e.g., 0.5 MV / m). Furthermore, depending on the design of the optical components and the polarization filter, the field-free state may indicate the presence of operating mode B3. However, the field-free state may also include operating mode B1 and one of sub-operating modes B1H or B1V.

[0034] Thus, similar to the first technical solution, when the first direction is equated with the horizontal direction and the second direction is equated with the vertical direction, the switchable filter of the second technical solution, in conjunction with the image reproduction unit, allows switching between vertical privacy protection (blocking up and down vision through a restricted emission angle range in sub-operating mode B1V) or horizontal privacy protection (blocking left and right vision through a restricted emission angle range in sub-operating mode B1H) and no privacy protection (in operating mode B3, the emission angle range is unrestricted and significantly greater than the emission angle range in operating mode B1 with its two sub-operating modes B1V and B1H). Unlike the first technical solution, operating mode B3 achieves an omnidirectional free-viewing mode.

[0035] In a third embodiment, the switchable filter comprises a first optical component and a second optical component, each of which is not inherently switchable. Each of the two optical components (whose structure and operating principle are described below) comprises a first layer, or the first layer and a plurality of other layers, preferably five or more. Each of the layers comprises a material having multiple light-absorbing transition dipole moments. Each transition dipole moment, at least in a first state, is oriented parallel to or fluctuates about a first preferred direction selectable for the first optical component and a second preferred direction selectable for the second optical component, with a tolerance of up to 10°. The first and second preferred directions differ from each other by less than 40°, preferably by less than 20°, and more preferably by less than 10°, including the case where they are identical, i.e., differ by 0°. Light incident on the first or second optical component is transmitted or at least partially absorbed depending on its incident direction relative to the layer and its polarization state.

[0036] A liquid crystal layer is disposed between the first and second optical components. The liquid crystal layer influences the polarization state of light passing through the liquid crystal layer based on a first electric field or a second electric field acting on the liquid crystal layer. The switchable optical filter of the third technical solution also includes components for selectively generating the first and second electric fields, such as transparent ITO (Indium Tin Oxide) electrodes. Furthermore, the switchable optical filter can selectively include a polarization filter disposed above or below the unit comprising the two optical components, or it can exclude a polarization filter.

[0037] In the case where a polarization filter is present, in the first operating mode B1 to which a first electric field is applied and which has a first sub-operating mode B1H and a second sub-operating mode B1V, on the one hand, at least 24% of the non-polarized light incident on the switchable filter parallel to the first preferred direction or the second preferred direction is transmitted, and on the other hand, at least 85% of the non-polarized light incident on the switchable filter at an angle of more than 30° to the corresponding preferred direction is absorbed, wherein this absorption occurs only in the first direction in the first sub-operating mode B1H and only in the second direction perpendicular to the first direction in the second sub-operating mode B1V, wherein the first direction or the second direction is perpendicular to the polarization direction of the polarization filter.

[0038] For another case where there is no polarization filter, in the first operating mode B1 with the first electric field applied, at least 24% of unpolarized light incident on the switchable filter at any angle is transmitted.

[0039] Regardless of whether a polarization filter is present, in a second operating mode B2 in which a second electric field is applied, on the one hand, at least 24% of unpolarized light incident on the switchable filter parallel to the first preferred direction or the second preferred direction is transmitted, and on the other hand, at least 85% of unpolarized light incident on the switchable filter at an angle of more than 30° to the corresponding preferred direction is absorbed.

[0040] As mentioned above, the two preferred directions of the two optical components can be identical or differ from each other by an angle of at most 40°, preferably 20° or only 10°. When the filter is tilted toward the surface normal of the filter, because transmittance is always maximized in the preferred direction, the range of emission angles corresponding to the viewing angle range is limited to the range around the surface normal. Therefore, by tilting one or both preferred directions, the angle at which transmittance is maximized is also tilted, and the restrictive viewing angle range is tilted accordingly.

[0041] When unpolarized light enters the first optical component and then undergoes a 90° polarization rotation through the liquid crystal layer in the absence of an electric field, the viewing angle is restricted to the left, right, and top. If the electromagnetic field is activated, the light's polarization is not rotated, and the viewing angle is not restricted, but the light is polarized perpendicularly to the projection of the incident light vector onto the plane of incidence. If the light entering the first optical component is linearly polarized by passing through the polarizer, the viewing angle is restricted upward, downward, right, and left in the absence of an electric field. If an electric field is applied, the viewing angle is restricted parallel to the linear polarization of the light entering the first optical component.

[0042] Thus, the switchable filter of the third technical solution, in cooperation with the image reproduction unit, allows switching between two-sided privacy protection (for example, privacy protection in the upper and lower directions in the sub-working mode B1V) and four-sided privacy protection (in the working mode B2, the viewing angle range is limited in the four directions of up / down / left / right) in the presence of a polarizing filter, or allows switching between omnidirectional free viewing with an unrestricted viewing angle range in the working mode B1 and four-sided privacy protection in the working mode B2 in the absence of a polarizing filter P. Additional delay plate It can be used to influence the polarization state. For example, if a λ / 4 plate is used, linearly polarized light is converted to circularly polarized light and can be switched between four-sided privacy protection and unrestricted viewing.

[0043] The field-free state can be described, for example, by a first electric field or a second electric field, with the other electric field having an absolute field strength greater than zero (e.g., 0.5 MV / m). Furthermore, depending on the design of the two optical components, the field-free state may indicate the presence of operating mode B2. However, the field-free state may also include operating mode B1 (without polarizer) or one of the sub-operating modes B1H and B1V (with polarizer).

[0044] In a fourth technical solution, the switchable filter also includes a first optical component and a second optical component. Unlike the third technical solution, the first optical component and the second optical component are switchable. Each of the two optical components includes: a first layer, or a first layer and a plurality of other layers, preferably five or more. Each of the layers includes: a material having a plurality of light-absorbing transition dipole moments. Each transition dipole moment is oriented parallel to or fluctuates around a first preferred direction selectable for the first optical component (1) and a second preferred direction selectable for the second optical component (2) with a tolerance of up to 10°, at least in a first state. Light incident on the first or second optical component is transmitted or at least partially absorbed depending on its incident direction relative to the layer and its polarization state. Unlike the third technical solution, here, the transition dipole moment of each of the layers can change its orientation and / or its absolute value between a first state and at least one second state, so that each layer is alternately placed in at least two different states.

[0045] In a fourth embodiment of the switchable optical filter, the switchable optical filter further comprises a member for selectively generating a first electric field or a second electric field, wherein, for each of the two optical components, the first state is generated by applying the first electric field, and the second state is generated by applying the second electric field. Thus, two electric fields are applied to the two optical components simultaneously, but still one of the two electric fields can also mean a no-field state. An optically anisotropic layer is provided between the two optical components, which rotates the polarization direction of light passing through the alignment layer by 90°. The alignment layer is composed, for example, of a uniaxially twisted material (similar to a TN cell (TN = twisted dnematic, also known as a Schadt-Helfrich cell) and / or an optically active material.

[0046] Polarization filters can be optionally placed above or below the two optical components (understood as a unit), or not. Polarization filters are optional but can improve the performance of the switchable filter. The polarization of the polarization filter must be exactly the same as the polarization of the incident light.

[0047] In the fourth technical solution, in a first operating mode B1 in which a first electric field is applied, at least 24% of unpolarized light incident on the switchable filter at an arbitrary angle to the switchable filter is transmitted, wherein in the first operating mode B1, the transition dipole moments of the two optical components are oriented perpendicular to each other, and if a polarization filter is present, the polarization filter transition dipole component of the polarization filter The polarization filter is oriented parallel to the transition dipole moment of the switchable optical component closest to the polarization filter. In a second operating mode B2 with a second electric field applied, at least 24% of unpolarized light incident on the switchable filter parallel to the first preferred direction or the second preferred direction is transmitted, and at least 85% of unpolarized light incident on the switchable filter at an angle of 30° or more to the corresponding preferred direction is absorbed. In the operating mode B2, when a polarization filter is present, the transition dipole moment of the polarization filter and the transition dipole moment of the switchable optical component closest to the polarization filter are oriented perpendicular to each other, and the transition dipole moments of the two optical components are always oriented parallel to each other.

[0048] Thus, the switchable filter of the fourth technical solution, in conjunction with the image reproduction unit, allows switching between free omnidirectional viewing in the public or free operating mode B1 and privacy protection in the private or restricted operating mode B2, with a restricted viewing angle or emission angle range compared to operating mode B1, with four-sided privacy protection (up, down, right, and left relative to the preferred direction). When unpolarized light strikes the switchable filter in the private operating mode B2, light that is not approximately parallel to the preferred direction (preferably oriented parallel in operating mode B2) is absorbed. In the public operating mode B1, linearly polarized light is transmitted.

[0049] In a preferred embodiment of the first or third technical solution, at least one polarization compensation layer is provided upstream and / or downstream of the liquid crystal layer, thereby balancing the different polarization changes for light incident vertically on the one hand and light incident at an angle to the surface normal on the other hand.

[0050] Preferably, the preferred directions each make an angle between 0° and 45° with the surface normal of the first layer. Take for example a screen with such a switchable filter, which covers customary viewing angles.

[0051] For specific applications, regardless of which of the above technical solutions is used, the switchable filter can be divided into multiple individually switchable sections, thereby enabling localized conversion between various possible operating states. In conjunction with the image reproduction unit, this means that, for example, only a portion of the image area can be switched between a private mode for privacy protection and a public mode with no privacy protection effect (i.e., free viewing), while the complementary portion of the image area is always in the privacy mode or the non-privacy mode. There can even be multiple geometrically separate such sections that can be switched between operating modes individually or collectively.

[0052] Furthermore, preferably, individual layers of the first optical element and / or of any second optical element are constructed aperiodically. This reduces the occurrence of visual artifacts, such as Moiré patterns, which may be offensive to viewers of the respective screen.

[0053] The present invention achieves particular significance by combining the aforementioned switchable filter with an image reproduction unit to form a screen. In addition to the aforementioned switchable filter, such a screen further comprises an image reproduction unit positioned downstream or upstream of the switchable filter, as viewed from the viewer's perspective. The operating modes of the aforementioned switchable filter can be directly applied to the screen, allowing the screen to operate in the various operating modes described above, depending on the design of the switchable filter (e.g., at least in a first operating state for a free public viewing mode with an unrestricted horizontal emission angle range or viewing angle range, and in a horizontally restricted private viewing mode with a horizontally restricted emission angle range or viewing angle range compared to the free viewing mode). Viewers outside this restricted viewing angle range can only perceive the image content presented on the screen in the free viewing mode.

[0054] Advantageously, the image reproduction unit corresponds to an LCD panel, and one polarization filter of the LCD panel corresponds to the polarization filter of the switchable filter. Furthermore, this can be a front polarizer or a back polarizer in the LCD structure. Furthermore, advantageously, the switchable filter can be arranged between the LCD panel and its backlight to switch between a first operating state in a free field of view mode and a second operating state in a restricted field of view mode. This is because, due to the switchable filter, the light from the backlight is sometimes focused and sometimes unfocused in the horizontal direction, for example, when switched to a horizontal orientation. "Focusing" in this context does not mean focusing in the manner of a lens, but rather angularly reducing the emission range or transmission range.

[0055] The image reproduction unit can optionally be an OLED, a field emission display (SED), a field emission display (FED), a micro-LED display, or a vacuum fluorescent display (VFD) with a switchable filter in front of it. Since the switchable filter works independently of the type of image reproduction unit, any other type of screen is also conceivable.

[0056] Such a screen is advantageously used in mobile devices, cars, aircraft or ships, payment terminals or access systems, wherein it is possible to switch between the aforementioned operating modes to protect sensitive data, i.e., to present the image content perceptibly only to one viewer or to present the image content to multiple viewers simultaneously.

[0057] In the following, the optical component according to the invention will be explained in more detail and possible embodiments will be described, which optical component achieves the task and can be used in particular as the first and / or second optical component in the four aforementioned technical variants of the switchable filter.

[0058] Such an optical component comprises a first layer, or a first layer and a plurality of further layers, preferably more than five layers, wherein, within the scope of the present invention, each of the layers may correspond, for example, to a molecular layer, but may also be a mechanically separated layer of a suitable material. Each layer comprises a material having a plurality of light-absorbing transition dipole moments. Possible materials have already been mentioned above in the description of the optical component of the switchable filter. Each transition dipole moment, at least in a first state, is oriented parallel to a selectable preferred direction or fluctuates about this preferred direction with a tolerance of up to 10°, so that light incident on the optical component is transmitted or at least partially (to completely) absorbed, depending on its direction of incidence relative to the layer and its polarization state. Preferably, the preferred directions each make an angle of between 0° and 45° with the surface normal of the first layer.

[0059] The quenching (i.e., absorption) of light is related to the absolute number of transition dipole moments, and therefore, necessarily, the thickness of the layer (in which the transition dipole moments reside), as well as the orientation of the transition dipole moments and the polarization of the incident light. The density and strength of these transition dipole moments, or the refractive index of the layers of the optical component, can vary depending on the specific implementation. If a passive (i.e., non-switching) optical component is used, the volume density of transition dipoles can approach 100%.

[0060] For simplified transmission modeling, it is assumed that the transition dipole moment in the optical component is oriented parallel to the plane of incidence of the light on the optical component, with the preferred direction corresponding to the perpendicular bisector of the optical component. Furthermore, the plane of incidence is not the surface of the optical component, but rather the plane in which the light waves propagate, with the surface of the optical component at right angles to the plane of incidence. As transverse waves, light waves have a transverse magnetic oscillation component and a transverse electric oscillation component, which are perpendicular to each other and to the direction of propagation. When light incident on the optical component, all light waves are initially unpolarized, meaning that the oscillation directions of the transverse electric component and its corresponding transverse magnetic component are statistically distributed. Upon reaching the surface of the optical component, which has a transition dipole moment oriented perpendicular to the optical component surface, the light interacts with the transition dipole moment of the optical component or the material contained therein and becomes polarized. The oscillation component located in the plane of incidence is absorbed. Specifically, light polarized parallel to the plane of incidence (i.e., transverse magnetic polarization, or p-polarization) is absorbed, while light polarized perpendicular to the plane of incidence (i.e., parallel to the surface of the optical component) (i.e., transverse electric polarization, or s-polarization) is completely transmitted. Thus, unpolarized light that passes through an optical component not parallel to the transition dipole moment becomes at least partially s-polarized when passing through an optical component having a transition dipole moment oriented parallel to the plane of incidence of the light. If the preferred orientation does not correspond to the perpendicular bisector, o-polarization (ordinary polarization) is considered instead of s-polarization, and e-polarization (extraordinary polarization) is considered instead of p-polarization.

[0061] This characteristic is essential to all technical solutions of the present invention and constitutes the basic inventive means-effect relationship. Below, the transmission of p-polarized light with an incident intensity of I0(α) is modeled. The transmission of light by the absorbing layer is described by the Lambert-Beer law:

[0062]

[0063] Here, α is the propagation direction relative to the surface normal, d(α) is the optical path length relative to the propagation direction, N is the number of absorbing molecules, and σ abs (α) is the absorption cross section related to the angle of incidence. Using Snell's law of refraction, the propagation angle α in the medium can be calculated from the angle of incidence β. Then, using the equations for the transition dipole moment and the optical path length, we obtain:

[0064]

[0065] Depending on the application, individual layers are structurally periodic or aperiodic, wherein an aperiodic structure is advantageous with regard to avoiding visual artifacts.

[0066] In a preferred embodiment, each transition dipole moment is oriented along its own preferred direction within a tolerance of a maximum of 10° around the preferred direction. Consequently, the highest transmittance also occurs along this preferred direction. It is also preferred that at least two of these preferred directions in a selectable plane (typically within a layer) differ by more than 10°. This allows for the definition of multiple preferred directions in a single layer, all of which can be aligned with a point in space (e.g., the viewer). Different orientations can be achieved by appropriately adjusting the material properties within the layer, for example, through photo-alignment. For this purpose, liquid crystals are combined with photoreactive substances. Incident polarized light simultaneously aligns the molecules and triggers a photoreaction. By controlling the polarization, the molecular orientation can be influenced.

[0067] The micro-thin-layer filters described in the prior art (also called "ViewControlFilter-VCF" or "LightControlFilter-LCF") utilize geometric optics. Due to the periodic alternation of transparent and absorbing layers, incident light propagating at large angles relative to a defined direction is almost completely absorbed. Here, the position of the absorber is controlled. In contrast, since the absorption cross section of the molecules changes with the propagation direction, the transmittance of light with different propagation directions changes in the optical component according to the invention. Therefore, in the present invention, the position of the absorber is not controlled, but rather the orientation (orientation) of the absorber is controlled. In other words, the present invention is based on the direction-dependent absorption of the light beam when it passes through the optical component according to the invention and is essentially independent of the beam position, with the exception of the preferred direction specified for the transition dipole moment. This applies both to the non-switchable optical component according to the invention described above and to the switchable design described below.

[0068] To ensure the switchability of the optical effect of the optical component according to the present invention, i.e., to achieve a switchable optical component, the transition dipole moment in each layer can change its orientation and / or absolute value between a first state and at least one second state, so that the layers can be alternately placed in at least two different states. Possible designs for the switchable optical component or each layer thereof are, for example, based on liquid crystals and / or dyes or dye mixtures, which can be arranged in a so-called "vertical alignment cell" or a liquid crystal cell with uniform surface orientation and in which the transition dipole moment can be rotated between at least two states. Furthermore, the absorption transition dipole moment is also rotated, thereby assuming at least two active states. In particular, in this embodiment, it is conceivable to obtain two or more states (for example, three or eight) each with a different optical effect. Other liquid crystal cell designs are also conceivable. For this purpose, in particular, an electric field is used to rotate the liquid crystal. For example, the field-free state can be described by the first or second electric field, while the other electric field has an absolute field strength greater than zero (for example, 0.5 MV / m).

[0069] Therein, the first state corresponds to the above-mentioned condition, and at least one second state differs in having at least one other preferred direction.

[0070] In such active, i.e., switchable, optical components, it is possible to envision a volume density of the liquid crystal-based transition dipole moment between 0.1% and 90%. Alternatively, the switchable optical component, or each layer thereof, can be configured such that the transition dipole moment is embedded in a liquid subjected to an electrowetting process. This allows, in particular, but not exclusively, the density of the transition dipole moment to be varied.

[0071] Furthermore, the optical component can also be divided into a plurality of individually switchable parts in order to achieve a local switchability between at least two different states. In this way, within the scope of the switchability with at least two states, it can be achieved in particular that the local transmission maxima between the at least two states lie in respective different directions.

[0072] Furthermore, preferably, the respective preferred direction of the transition dipole moment can be selected according to the position of the transition dipole moment in the respective layer.

[0073] In another preferred embodiment of the optical component, each layer is divided into zones along a selectable reference line for each layer. Each zone has a selectable zone preferred direction that applies to all transition dipole moments of the corresponding layer within the zone. All zone preferred directions differ from one another in pairs and point in the direction of the viewer within a tolerance of a maximum of + / -10°. Thus, within a layer and within each applicable zone, all transition dipole moments are parallel to the preferred direction applicable therein within a tolerance of a maximum of + / -10°. Advantageously, each of the layers is constructed non-periodically, thereby reducing or avoiding the occurrence of disruptive visual artifacts. This arrangement has the advantage that, in restricted viewing mode, the viewer perceives the screen as uniformly illuminated. Since the luminous intensity is viewing angle-dependent, the viewer perceives the screen as non-uniform if the orientation of the transition dipole moments is constant across the entire surface of the filter.

[0074] A simple method for producing the optical component of the present invention as described above is to laminate multiple polymer thin-film polarizers. In this case, the optical component comprises a laminate of multiple polymer thin-film polarizers. Alternatively or in combination, the optical component can also be produced by photo-aligning molecules or particles.

[0075] Preferably, the material of the optical component comprises at least one dye, preferably a dichroic dye mixture. The at least one dye consists of dye molecules, wherein advantageously, a transition dipole or transition dipole moment is associated with each dye molecule, i.e., each dye molecule corresponds to a transition dipole or transition dipole moment. Typically, in an LC dye mixture, the dye accounts for, for example, 0.01% to 10% by weight, preferably 0.1% to 5% by weight, of the material of each layer. The layer thickness preferably ranges from 0.2 μm to 50 μm, preferably from 0.5 μm to 20 μm, all limit values ​​being inclusive. The dyes or dye mixtures of different layers can be different.

[0076] Furthermore, the material of the optical component may contain liquid crystals and / or be mixed with liquid crystals. In the case of multiple layers, it may also vary from layer to layer.

[0077] As a preferred embodiment, for each layer, a mixture of liquid crystals with at least one dye, in particular with at least one dichroic dye mixture is suitable. Suitable dichroic dyes or dye mixtures include, for example, azomethine dyes, indigo and thioindigo dyes, merocyanine, azulene, quinolinone dyes, perylene dyes, phthalopyrine dyes, dichloromethane dyes, phthalocyanine ... Dioxazinfarbstoffe, Triphenylmethane Triphenodioxazinfarbstoffe, quinine Phenophthalate dyes, triazine dyes, tartrazine, azo dyes, and anthraquinone dyes. The production of liquid crystal dye mixtures is described, for example, in US Pat. No. 4,695,131 A. Furthermore, the surface of the outer blocking layer is preferably treated, for example, by drawing, in order to achieve a uniform surface orientation of the transition dipole moment or any liquid crystals present.

[0078] In particular, when used in switchable optical filters, a polarization filter can generally be advantageously positioned before or after the optical component in the viewing direction. The polarization filter facilitates the determination or analysis of the polarization properties of light passing through the optical component and should preferably always be present. In this case, the maximum transmission of the optical component is generally always parallel to the polarization direction of the polarization filter. Alternatively, two such polarization filters, one before and one after the optical component in the viewing direction, can be positioned, with their linear polarization directions oriented substantially parallel to one another, thereby improving the protection provided in the restricted field of view mode.

[0079] Therefore, the present invention also includes a lighting device having the above-mentioned optical component. This lighting device can operate in at least two operating modes: an operating mode B1 for free field of view mode, and an operating mode B2 for restricted field of view mode. The restricted field of view mode differs from the free field of view mode in that the light is emitted in the direction of the viewer within a restricted angle range compared to the free field of view mode. A viewer outside the restricted angle range cannot see the light emitted by the lighting device. The same applies to the screen, as will be explained below. In the free field of view mode, the viewer can perceive the light emitted by the lighting device or screen as long as the viewer is within the emission angle range that is essentially naturally restricted by the lighting device or screen in the free field of view mode, and this emission angle range is significantly larger than the emission angle range in the restricted field of view mode. The restriction can occur in multiple spatial directions, such as upward, downward, right and / or left, depending on the specific application.

[0080] The lighting device comprises a planar backlight that includes the optical components described in detail above and emits light. The lighting device comprises a plate-shaped light guide disposed in front of the backlight in the viewing direction and having a decoupling component on at least one of its large surfaces and / or within its volume, wherein the light guide is transparent for at least 40%, preferably at least 70%, of the light emitted from the backlight. A light-emitting element is disposed laterally on at least one narrow side of the light guide. Furthermore, a linear polarization filter is disposed in front of the backlight or the light guide in the viewing direction, thereby limiting the propagation direction of light emitted from the backlight and passing through the polarization filter. In operating mode B2, the backlight is on and the light-emitting element is off. In operating mode B1, at least the light-emitting element is on, i.e., in operating mode B1, it is not important whether the backlight is on or off.

[0081] Finally, as previously mentioned, the optical assembly described above can also be used in a screen capable of operating in at least two of the operating modes mentioned above in conjunction with the lighting device: operating mode B1 for free field of view and operating mode B2 for restricted field of view. Such a screen comprises a planar backlight that contains the optical assembly and emits light. The screen also comprises a plate-shaped light guide disposed in front of the backlight in the viewing direction and having a decoupling component on at least one of its large surfaces and / or within its volume. The light guide is transparent for at least 40%, preferably at least 70%, of the light emitted from the backlight. A light-emitting element is laterally arranged on at least one narrow side of the light guide. Furthermore, a linear polarization filter is disposed in front of the backlight or in front of the light guide in the viewing direction, thereby limiting the propagation direction of light emitted from the backlight and passing through the polarization filter. Furthermore, a transmissive image reproduction device is disposed in front of the light guide in the viewing direction. The polarization filter can be arranged in the image reproduction device and, in particular, can be part of the image reproduction device (for example, this is the case in an LC display). In operating mode B2, the backlight is on and the luminous means are off. In operating mode B1, at least the luminous means are on, i.e., in operating mode B1, it is not important whether the backlight is on or off.

[0082] More generally, the present invention also encompasses a screen comprising at least one optical component or configuration as described above, and an image reproduction unit arranged downstream or upstream of the optical component, as viewed from a viewer. Advantageously, the image reproduction unit corresponds to an LCD panel, and one of the polarization filters of the LCD panel corresponds to the aforementioned polarization filter. Furthermore, it can be the front polarizer or the back polarizer in the LCD structure. The image reproduction unit can optionally be an OLED, a field emission display (SED), a field emission display (FED), a micro-LED display, or a vacuum fluorescent display (VFD), with the optical component positioned in front of it. Because the optical component functions independently of the type of image reproduction unit, any other type of screen is also contemplated. Such a screen is advantageously used in mobile devices, automobiles, aircraft or ships, payment terminals, or access systems. In the case of a switchable optical component, switching between the aforementioned operating modes is possible to protect sensitive data, i.e., to present the image content perceptibly only to one viewer or simultaneously to multiple viewers. In addition, the switchable optical component or non-switchable optical component using the above technical solution can be used with static images or dynamic image reproduction units such as LCD panels to, for example, allow advertising content to be viewed only within a restricted visual range.

[0083] If the above parameters are changed within certain limits, the performance of the present invention can be maintained in principle.

[0084] It is understood that the above-mentioned features and the features yet to be explained below can be used not only in the combination specified but also in other combinations or alone without departing from the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Below, the present invention will be explained in more detail by way of examples and with reference to the accompanying drawings, which also disclose important features of the present invention. The examples are for illustrative purposes only and should not be construed as restrictive. For example, the description of an embodiment with multiple components or assemblies should not be construed as meaning that all components or assemblies are necessary for implementation. On the contrary, other embodiments may also include alternative components and elements, fewer components and elements, or additional components and elements. Unless otherwise stated, the components and elements of different embodiments may be combined with each other. Modifications and variations described for one of the embodiments may also be applied to other embodiments. To avoid repetition, identical or corresponding components in different figures are identified with the same symbols and are not explained multiple times. Among them:

[0086] Figure 1a This is a schematic diagram of the principle of a non-switching optical component.

[0087] Figure 1b is a schematic diagram of the principle of a switchable optical component in a first state,

[0088] Figure 1c For the second state, Figure 1b Schematic diagram of the switchable optical components in

[0089] Figure 2a This is a schematic diagram of the principles of other optical components.

[0090] Figure 2b is a schematic diagram of a section of another switchable optical component in a first position,

[0091] Figure 2c is a schematic diagram of a section of the other switchable optical component in a second position,

[0092] Figure 3 To have a basis Figure 1b and Figure 1c as well as Figure 2b and Figure 2c Schematic diagram of the structure of the switchable optical component,

[0093] Figure 4 To be based on Figures 2a-2c illustrative diagram comparing the transmission behavior of an optical component measured at different angles with the transmission behavior of a thin-film filter in the prior art measured at different angles,

[0094] Figure 5This is a schematic diagram of the principle of a switchable filter with a polarization filter in the third technical solution.

[0095] Figure 6 This is a schematic diagram of the principle of a switchable filter without a polarization filter in the third technical solution.

[0096] Figure 7a-7c Based on Figure 6 A simplified diagram of the light affected by the switchable filter,

[0097] Figure 8 This is a schematic diagram of the principle of the switchable filter in the fourth technical solution.

[0098] Figure 9 This is a schematic diagram of the principle of the switchable filter in the first technical solution.

[0099] Figure 10 is a schematic diagram of the principle of the switchable filter in the second technical solution, and

[0100] Figures 11 to 15 An optical simulation used to illustrate the optical effects of optical components. DETAILED DESCRIPTION

[0101] The drawings are not drawn to scale and are schematic only.

[0102] Figure 1a A simplified schematic diagram of an exemplary non-switchable optical component 1 is shown. The optical component comprises at least one layer S1, wherein the layer S1 comprises a material having a plurality of photo-absorbing electro-optical transition dipole moments (illustrated here simply as small vertical lines), wherein the photo-absorbing electro-optical transition dipole moments are, at least in a first state, oriented parallel to a selectable preferred direction (here, perpendicular to the surface of the layer S1) or fluctuate about the preferred direction, whereby the preferred direction comprises an angle between 0° and 45° with respect to the surface normal of the layer S1, such that light incident on the optical component is transmitted or partially or completely absorbed depending on its incident direction relative to the layer S1 and its polarization properties.

[0103] The optical component 1 can be made, for example, by laminating multiple polymer thin-film polarizers and / or by photo-aligning molecules or particles. The density of the aforementioned electric transition dipoles in layer S1 can vary depending on the implementation. If a passive polarizer is used, the volume density can be close to 100%.

[0104] The material of the optical component 1 containing the transition dipole moment may also contain at least one dye, in particular a dye molecule, preferably at least one dichroic dye or a mixture of dichroic dyes. Advantageously, the dye molecule may correspond to the transition dipole moment. Typically, the dye comprises 0.01% to 30% by weight of the material of each layer S1, S2, ..., preferably 0.1% to 15% or 5%, or 0.01% to 10%. The layer thickness preferably ranges from 0.2 μm to 50 μm, preferably from 0.5 μm to 20 μm. The dye or dye mixture may be different in different layers.

[0105] The layers S1, S2, ... comprising transition dipole moments may also comprise liquid crystals or polymers and / or may be mixed with liquid crystals. Preferably, the layers S1, S2, ... comprise a mixture of liquid crystals or polymers with at least one dye, in particular with at least one dichroic dye.

[0106] Optical component 1 acts as a privacy filter for linearly polarized light. Therefore, a polarization filter P is provided here, which polarizes light incident from below linearly parallel to the drawing surface. However, polarization filter P does not change the propagation direction of the light. The two thick arrows represent two possible light propagation directions. Due to the effect of the transition dipole moment, light with an (inclined) direction of, for example, approximately more than 30° relative to the preferred direction (here, the perpendicular to the midline of layer S1) is absorbed by optical component 1. Finally, as indicated by the single arrow in the upper portion of the figure, essentially only light incident along the preferred direction, or in this case, perpendicular to optical component 1, remains after passing through the optical component. Depending on the application, each of layers S1, S2, ..., can be structurally periodic or aperiodic.

[0107] The quenching (i.e., absorption) of light is related to the absolute amount of transition dipole moments and, therefore, necessarily to the thickness of the layer of material having transition dipole moments. The density and strength of these transition dipole moments, or the refractive index in layers S1, S2, ..., can vary depending on the implementation. If a passive (i.e., non-switching) optical component 1 is used, the volume density of transition dipoles can approach 100%.

[0108] to this end, Figures 11 to 15 An optical simulation is shown for explaining the optical effect of the optical component 1 . Figure 11 A diagram showing the normalized transmission of light through the optical component 1 according to FIG. 1 is plotted here over a horizontal measurement angle of -90° to +90°. Strong absorption effects are clearly visible for angles above + / - 25°. The simulation is based on the assumption that the optical component 1 has a layer thickness of d = 0.5 mm, a material refractive index n = 1.5, and a molar concentration M = 0.01 mol m -3 and an exemplary molar extinction ratio ε = 12700 m 2 mol -1The thickness and the concentration can be varied in proportion to each other, so that, for example, the same transmittance can be obtained with a thickness ten times smaller and a concentration ten times higher. Figure 12 In the example, for the value range that is important for use, the Figure 11 The relationship between the transmittance and the transmittance is plotted in logarithmic form on the vertical axis. It can be seen that under these parameters, at + / -25°, the transmittance has dropped to about 1%, and at + / -40°, the transmittance has decreased to only about 0.001%. Figure 13 In terms of refractive index n, Figure 11 The assumed conditions were calculated for the values ​​n=1.0; 1.3; 1.5 and n=1.7. It can be seen that the lower the refractive index of the material of layer S1, the more limited the transmittance (Transmission in Winkel) at the angle. In addition, Figure 14 The thickness of the optical component 1 is shown in FIG. Figure 11 The change in the normalized transmittance of the optical component 1 with respect to . The calculations were performed for layer thicknesses of d = 0.1 mm; 0.2 mm; 0.3 mm; 0.4 mm and 0.5 mm. As expected, a greater layer thickness results in a stronger restriction of the transmittance at the above angles. Finally, Figure 15 The angle-dependent, normalized transmittance is shown for three selected parameter sets (1. n = 1.0 and d = 0.2 mm; 2. n = 1.5 and d = 0.5 mm; 3. n = 1.7 and d = 0.65 mm). These three parameter sets produce very similar optical effects.

[0109] In contrast, the micro-thin-layer filters known from the prior art (also called "View Control Filter - VCF" or "Light Control Filter - LCF") make use of geometrical optics. Due to the periodic alternation of transparent and absorbing layers, light propagating at large angles relative to a defined direction is (almost) completely absorbed. The position of the absorber is controlled. In contrast, since the absorption cross section of the molecules varies with the propagation direction, the transmittance of light with different propagation directions in the optical component 1 varies. Therefore, it is not the position of the absorber that is controlled, but rather, in particular, its orientation. In other words, the effect of the optical component 1 is based on the direction-dependent absorption of the light beam as it passes through the optical component and is essentially independent of the beam position. This applies both to the non-switchable optical components described above and to the switchable designs described below.

[0110] In order to make the optical effect of the optical component 1 switchable, that is, to make the optical component 1 switchable, the photo-absorbing photo-transition dipole moment in each layer S1, S2, ... can change its orientation and / or its absolute value, so that each layer S1, S2, ... can be placed in at least two different states. A possible design of the switchable optical component 1 or each layer S1, S2, ... therein is based, for example, on liquid crystals or phosphors, which can be arranged in a so-called "vertical alignment cell" or in a liquid crystal cell with uniform surface orientation, and wherein rotation between at least two states is possible. As a result, the photo-absorbing photo-transition dipole moment also rotates and can assume at least two active states. In particular, in this technical solution, it is conceivable to obtain two or more states (for example, three or eight states), each having a different optical effect. Other liquid crystal cell designs are also conceivable.

[0111] to this end, Figure 1b a simplified schematic diagram showing a switchable optical component in a first state, Figure 1c Schematic diagram showing a switchable optical component in a second state.

[0112] For this example it is assumed that the incident light is p-polarized, i.e. polarized parallel to the plane of incidence (see Figure 1b ). If the transparent electrodes E1 and E2 are uncharged, that is, they generate an electric field EF1 of 0 V / m (no electric field), then the liquid crystal molecules and dye molecules (here, for example, constructed as layers S1, S2, and S3), shown here as dots, are oriented along the surfaces of the electrodes E1 and E2. This can be achieved by appropriately combining surface functionalization with liquid crystals and is known in the art. For light propagating in the drawing plane and having s-polarization, the polarization of the light and the transition dipole moment of the liquid crystal are always oriented perpendicular to each other. Therefore, no absorption occurs, and therefore the propagation direction of the light having s-polarization shown above and below the substrate S will pass through the switchable optical component 1 unimpeded.

[0113] like Figure 1c As shown, if the electrodes E1 and E2 are charged, that is, they generate an electric field with EF2>0V / m, the liquid crystal rotates in the layers S1, S2 and S3. When the voltage and field strength EF2 exceed a certain threshold, the liquid crystal molecules and (if present) the dye molecules are oriented almost parallel to the field lines of the electric field EF2. As a result, the light is absorbed according to the angle α (the angle between the propagation direction of the light and the normal to the surface of the layer S1). The absorption rate increases with increasing angle α. The blanking of the electric field of the light is proportional to sin(α). In principle, it is advantageous to control the orientation of the dye molecules in order to thereby control the anti-peeping axis or to exert a defined light influence. In accordance with Figure 1b In the state, the transition dipole moment is perpendicular to the polarization of the incident light, according to Figure 1cIn the state of the switchable optical component, the volume density of the liquid crystal-based dye is between 0.1% and 20%, and if necessary up to 90%.

[0114] Figure 2a The schematic diagram of another non-switching optical component 1 is shown. The optical component comprises (here for example only one) layer S1, wherein the layer S1 comprises: a plurality of light-absorbing transition dipole moments (composed of Figure 2a The optical component 1 is made of a material (represented by a short line in the middle layer S1). Each transition dipole moment, at least in a first state, is oriented parallel to or fluctuates about a respective preferred direction (represented here by a thick arrow) with a tolerance of up to 10°. The preferred direction of each transition dipole can be selected based on its position within layer S1, with at least two of these preferred directions differing by more than 10° in a selectable plane (here, the drawing plane). This allows light incident on the optical component 1 to be transmitted or partially or completely absorbed, depending on its direction of incidence relative to layer S1 and its polarization properties. The highest transmittance for each transition dipole lies in the preferred direction selected for its position within layer S1, with a tolerance of up to 10° being permitted.

[0115] Compared to FIG1 , the optical component 1 shown in FIG2 is designed such that layer S1 is divided along a selectable reference line (here, the bottom edge of the layer) into different areas A1, A2, A3, A4, and A5. Each area A1, A2, ... has its own selected area-preferred direction (see thick arrow), which applies to all transition dipole moments of layer S1 within a particular area A1, A2, ... . Furthermore, all area-preferred directions differ from one another in pairs and point toward the viewer 6 with a maximum tolerance of + / -10°. Consequently, within layer S1 and within each applicable area A1, A2, ..., all transition dipole moments are parallel to the applicable area-preferred direction with a maximum tolerance of + / -10°. Due to the definable transmittance of the optical component 1, it can be particularly advantageously used to create privacy protection solutions.

[0116] In order to ensure the switchability of the optical effect of the optical component 1, that is, in order to ensure a switchable optical component 1, the absorption transition dipole moment in each layer S1, S2, ... can change its orientation (orientation) and / or its absolute value and / or its density, so that the individual layers S1, S2, ... can be placed in at least two different states.

[0117] to this end, Figure 2b The first section of the switchable optical component is shown in the first state (corresponding to Figure 2a A1) schematic diagram, Figure 2c The second section of the switchable optical component in the first state (corresponding to Figure 2a A schematic diagram of the principle of A5 in FIG. Here, three layers S1, S2, and S3 are exemplarily present. The liquid crystal mixed with the dichroic dye mixture is represented by the elliptical elements in layers S1, S2, and S3. The black elliptical elements represent dye molecules in a highly simplified manner, while the white elliptical elements represent liquid crystals in a highly simplified manner. The tilt of the ellipse further indicates spatial orientation. The substrate S can be glass, a polymer, or other transparent material.

[0118] Each transparent electrode E1, E2, such as an indium tin oxide layer (ITO layer), is used to control the orientation of the liquid crystal mixed with the dye mixture. However, different orientations of the liquid crystal molecules and the dye are preferably achieved through different surface functionalizations. Mechanical and optical methods are conceivable here. Figure 2b The orientation of the liquid crystal together with the dye mixture shown is approximately equivalent to that according to Figure 2a Orientation of the preferred direction of the middle segment A1. Figure 2c The orientation of the liquid crystal together with the dye mixture shown is approximately equivalent to that according to Figure 2a The preferred direction of the middle segment A5 is oriented. Figure 2b In the case of , light incident on the optical component 1 from below is transmitted to the greatest extent in the corresponding preferred direction of the transition dipole; in other directions it is partially or completely absorbed. This also applies in a similar manner to the Figure 2c situation.

[0119] Regarding the behavior of p-polarized light and s-polarized light incident on an optical component when electric fields EF1 and EF2 are applied, refer to Figure 1b and Figure 1c The detailed description of , which applies analogously here, except that the transition dipole moment is oriented differently and that in the medium predominantly o-polarization instead of s-polarization and e-polarization instead of p-polarization.

[0120] Figure 3 Show that there is a basis Figure 1b and Figure 1c as well as Figure 2b and Figure 2cSchematic diagram of the structure of a switchable optical component 1 according to an embodiment of the present invention. Two linear polarization filters P are present on the outer surface, one of which is optional, wherein the polarization directions of the linear polarization filters are substantially parallel to one another (i.e., without taking into account a tolerance of a few degrees). A transparent substrate S is provided on the inner side of each (i.e., on the side opposite the polarization filter P), on the inner side of which electrodes E1 and E2 are provided. An orientation layer 4 facing inward serves to orient the liquid crystals, which are mixed with at least one dichroic dye to form the inner layers S1, S2, ... . The transition dipole moment is formed by the at least one dichroic dye. In principle, in all described variations of the structure of the optical component 1, additional retardation films can also be used to further adjust the polarization state.

[0121] The square wave voltage applied between electrodes E1 and E2 preferably has an effective value between 0 V and 20 V. The alignment layer 4 is, for example, a treated surface (e.g. brushed glass or polymer) to achieve a uniform surface orientation of the transition dipole moment or liquid crystal. Figure 2b and Figure 2c The status shown.

[0122] at last, Figure 4 According to Figure 2 and Figure 3 Schematic diagram showing the normalized transmission behavior of the optical component 1 (solid line) measured at different angles compared with the normalized transmission behavior of the thin-film filter in the prior art (dashed line) measured at different angles. The horizontal axis is the respective measurement angle and the vertical axis is the normalized transmittance. For the transmission behavior of the exemplary optical component 1, a so-called "top-hat" distribution can be observed in the continuous curve, that is, the transmittance remains stable at at least 80% within a wide angle range of about -17° to +17°. Here, the half-value width is about 40° in total. Therefore, a viewing angle change of ±15° provides a good transmission uniformity perceived by the viewer 6, which in turn achieves a good uniformity during illumination or image reproduction in cooperation with the image reproduction unit). In comparison, the exemplary thin-film filter in the prior art (whose normalized transmission behavior is shown in dashed form) Figure 4 ), in contrast, has a reduced half-value width of only about 35°, and furthermore does not have a distribution that is approximately "top hat" and also has poorer anti-peeping protection in the angular ranges of -30° to -25° and +25° to +30°, because the transmittance in this angular range is greater than that of optical component 1.

[0123] The optical component is particularly applicable to a switchable optical filter 5 . Figure 5A third embodiment of such a switchable optical filter 5 is shown. To maintain consistency with the general description of the present invention, the designation "third" is used before "first" and "second." It comprises a first optical component 1 and a second optical component 2. Both optical components 1 and 2 are inherently non-switchable, i.e., static. The preferred directions of the transition dipole moments of the two optical components differ from each other by less than 40°, preferably by less than 20°, and particularly preferably by less than 10°. The first preferred direction of the first optical component 1 and the second preferred direction of the second optical component 2 are selectable. In this example, the two preferred directions are illustratively parallel to each other and correspond to the perpendicular bisector of the switchable optical filter 5, located in the drawing plane. A switchable liquid crystal layer 3 is disposed between the optical components 1 and 2. This switchable liquid crystal layer influences or does not influence the polarization properties of light passing through it, depending on which of the electric fields EF1 and EF2 act on it. In the figure, from the perspective of viewer 6, polarization filters P are disposed below optical components 1 and 2; such polarization filters may also be disposed above optical components 1 and 2. Not shown are the components for selectively generating first and second electric fields EF1 and EF2, such as electrodes disposed above and below liquid crystal layer 3.

[0124] In a first operating mode B1, in which a first electric field EF1 is applied and which has a first sub-operating mode B1H and a second sub-operating mode B1V, at least 24% of unpolarized light incident on the switchable filter 5 parallel to the first preferred direction or the second preferred direction is transmitted, while at least 85% of unpolarized light incident on the switchable filter 5 at an angle of at least 30° to the respective preferred direction is absorbed. This absorption occurs only in the first direction in the first sub-operating mode B1H, and only in a second direction perpendicular to the first direction in the second sub-operating mode B1V. The first direction or the second direction is perpendicular to the polarization direction of the polarization filter P. When applied to a screen, the first direction may correspond to the horizontal direction, and the second direction may correspond to the vertical direction. "Horizontal" refers to a line parallel to the distance line between the viewer's eyes. In this case, the horizontal line is, for example, parallel to the bottom edge of layer S1 or the screen, and the vertical line is parallel to the left or right edge.

[0125] In the second operating mode B2 to which the second electric field EF2 is applied, on the one hand, at least 24% of the unpolarized light incident on the switchable filter 5 parallel to the first preferred direction or the second preferred direction is transmitted, and on the other hand, at least 85% of the unpolarized light incident on the switchable filter 5 at an angle of more than 30° to the corresponding preferred direction is absorbed.

[0126] Figure 6 A variant of the third embodiment of the switchable filter 5 is shown in FIG. 1 , in which no polarization filter P is provided. The behavior of this variant in operating mode B2 is similar to that of the reference embodiment. Figure 5The described switchable filter 5 behaves identically, but in the first operating mode B1 with the first electric field EF1 applied, at least 24% of unpolarized light incident on the switchable filter (5) at any angle is transmitted.

[0127] Therefore, the switchable filter 5 of the third technical solution, in cooperation with the image reproduction unit, allows switching between two-sided privacy protection and four-sided privacy protection (for example, up / down protection B1V and up / down / left / right protection B2) when a polarization filter P is present, or, when the polarization filter P is not present, allows switching between omnidirectional free viewing and four-sided privacy protection (for example, free viewing B1 and up / down / left / right protection B2).

[0128] For example, the no-field state can be described by either an electric field EF1 or an electric field EF2, with the other electric field EF2 or EF1 having an absolute field strength greater than zero (e.g., 0.5 MV / m). Therefore, depending on the design of optical components 1 and 2, the no-field state may indicate the presence of operating mode B2. However, operating mode B1 may also exist in the no-field state, including one of sub-operating modes B1H and B1V if a polarization filter P is present.

[0129] Figures 7a to 7c Shown due to Figure 6 Schematic diagram of the polarization states of light generated by a switchable optical filter. Figure 7a The polarization states of the common modes are shown, corresponding to operating mode B1 with an unrestricted viewing angle range, in which light with a viewing angle greater than 30° is tangentially polarized and light with normal incidence is linearly polarized. The preferred directions correspond to the respective perpendicular midlines. Figure 7c The polarization state in the restricted field of view mode is shown. Here, light with an incident angle of, for example, greater than 30° is strongly attenuated, while light incident at right angles is transmitted without changing the polarization state.

[0130] The orientation or alignment of the transition dipole moment results in the light being polarized at the angle of incidence, i.e. the linear polarization of the light is always perpendicular to the origin in the viewing space, which in this case is the perpendicular bisector. This state is shown in Figure 7a The polarization state of light is not absorbed, and is applicable to light after it passes through the non-switching optical component 1. Light with a small angle is only weakly polarized. Ideally, light incident vertically is not absorbed, that is, the polarization state remains unchanged.

[0131] At this point, when light enters the liquid crystal layer 3 from the optical component 2, whether and how the polarization state of the light changes, or remains unchanged, depends on the state of the liquid crystal layer 3. For example, if polarization rotation in the liquid crystal layer 3 is disabled, such as in the no-electric-field state EF1, the aforementioned state remains unchanged. After passing through the liquid crystal layer 3 and further through the non-switching optical component 1, the transmittance remains substantially unchanged. If a polarization filter P is present above the optical component 1 or below the optical component 2, one of the sub-operating modes B1H or B1V is implemented, depending on the design. If such a polarizer is absent, operating mode B1 is implemented.

[0132] In contrast, if the polarization rotation in the liquid crystal layer 3 is turned on, for example by applying an electric field EF2>0 V / m, the polarization is rotated by 90° everywhere. Figure 7b Middle: This shows the polarization state after passing through the optical component 2 and the polarization-rotated liquid crystal layer 3. Therefore, in the case of further light propagation, all light propagating at an angle greater than 25° or approximately 30° is blanked by the optical component 1. This corresponds to operating mode B2 and is shown in FIG. Figure 4 c.

[0133] Figure 8 A simplified schematic diagram of the principle of a switchable optical filter 5 in a fourth embodiment is shown. The switchable optical filter 5 includes two switchable optical components 1 and 2, wherein each of the two optical components includes a first layer S1, or a first layer S1 and a plurality of other layers S2, ... . Similar to the optical components of the third embodiment, each of the layers S1, S2, ... comprises a material having a plurality of light-absorbing transition dipole moments, wherein each transition dipole moment is, at least in a first state, oriented parallel to a first preferred direction selectable for the first optical component 1 and a second preferred direction selectable for the second optical component 2, or fluctuates about the preferred direction, with a tolerance of up to 10°. As a result, light incident on the first or second optical component 1, 2 is transmitted or at least partially absorbed depending on its direction of incidence relative to the layers S1, S2, ... and its polarization state.

[0134] However, unlike the third solution, the optical components 1 and 2 are switchable here. That is, the transition dipole moment of each of the layers S1, S2, ... can change its orientation and / or value between a first state and at least one second state, so that each layer S1, S2, ... can alternate between at least two different states. In this solution, the switchable filter 5 includes means for selectively generating a first electric field EF1 or a second electric field EF2. For each of the two optical components 1 and 2, the first state is generated by applying the first electric field EF1, and the second state is generated by applying the second electric field. In an embodiment according to the fourth solution, the first electric field EF1 is applied to the first optical component 1, and the second electric field EF2 is applied to the second optical component 2.

[0135] Optionally, a polarization filter can be placed above or below the combined optical component 1. This is optional, but can improve the performance of the switchable filter 5. The polarization of the polarization filter P must be identical to that of the incident light. An optically anisotropic layer 7 is positioned between the two optical components 1 and 2 to rotate the polarization direction of light passing through the layer 7 by 90°. The optically anisotropic layer 7 can be, for example, a layer containing liquid crystals or a half-wave plate. The components for generating the two electric fields EF1 and EF2 are not shown.

[0136] When a first electric field EF1 is applied in the first operating mode B1 for the free field mode, at least 24% of the unpolarized light incident on the switchable filter 5 at any angle is transmitted, wherein, in the first operating mode B1, the transition dipole moments of the two optical components 1 and 2 are oriented perpendicular to each other, and if a polarization filter P is present, the polarization filter transition dipole component of the polarization filter P is oriented parallel to the transition dipole moment of the switchable optical component 1 and 2 closest to the polarization filter P.

[0137] When a second electric field EF2 is applied in a second operating mode B2 for a restricted field of view mode, on the one hand, at least 24% of the unpolarized light incident on the switchable filter 5 parallel to the first preferred direction or the second preferred direction is transmitted, and on the other hand, at least 85% of the unpolarized light incident on the switchable filter 5 at an angle of more than 30° to the corresponding preferred direction is absorbed, wherein, in operating mode B2, the transition dipole moment of the polarization filter P (if present) and the transition dipole moments of the switchable optical components 1 and 2 closest to the polarization filter P are oriented perpendicular to each other, and the transition dipole moments of the two optical components 1 and 2 are oriented parallel to each other. Here, preferably, the preferred direction also corresponds to the transition dipole moment in Figure 8 The perpendicular bisector of the switchable filter 5, which is located in the drawing plane, is centered. As described above in conjunction with the third technical solution, this applies to the corresponding orientation of the switchable filter 5, in particular, when the horizontal direction is parallel to the bottom edge of the layer S1 and the vertical direction is parallel to the left or right edge of the layer, and applies to both the horizontal and vertical directions.

[0138] Therefore, the switchable filter 5 of the fourth technical solution, in cooperation with the image reproduction unit, allows switching between omnidirectional free viewing and four-sided privacy protection (free viewing B1 and up / down / left / right protection B2).

[0139] Figure 9A first embodiment of a switchable optical filter 5 is shown as a schematic diagram. This embodiment comprises a non-switchable first optical component 1, similarly comprising a first layer S1, or a first layer S1 and a plurality of further layers S2, etc., wherein each layer S1, S2, etc. comprises a material having a plurality of light-absorbing transition dipole moments. Each transition dipole moment, at least in a first state, is oriented parallel to or fluctuates about a first preferred direction selectable for the first optical component 1, with a tolerance of up to 10°. As a result, light incident on the first optical component 1 is transmitted or at least partially absorbed depending on its direction of incidence relative to the layers S1, S2, etc. and its polarization state.

[0140] A polarization filter P is provided upstream or downstream of the first optical component 1. The figure also does not show the components for selectively generating the first electric field EF1 or the second electric field EF2. A liquid crystal layer 3 is provided between the first optical component 1 and the polarization filter P. The first electric field EF1 or the second electric field EF2 acts on the liquid crystal layer, and the liquid crystal layer influences the polarization state of light passing through the liquid crystal layer according to the first electric field EF1 or the second electric field EF2.

[0141] In this first technical solution, in the first operating mode B1, in which a first electric field EF1 is applied and which has a first sub-operating mode B1H and a second sub-operating mode B1V, at least 24% of unpolarized light incident on the switchable filter 5 parallel to the first preferred direction is transmitted, while at least 85% of unpolarized light incident on the switchable filter 5 at an angle of 30° or greater to the first preferred direction is absorbed. This absorption occurs only in the first direction in the first sub-operating mode B1H, and only in a second direction perpendicular to the first direction in the second sub-operating mode B1V. Furthermore, the first preferred direction is preferably still parallel to the perpendicular bisector of the switchable filter 5 within the drawing plane. Regarding the positions of the first and second directions, the same principles as those described in connection with the third technical solution apply.

[0142] In the second working mode B2 applied with the second electric field EF2 and having the first sub-working mode B1H and the second sub-working mode B1V, on the one hand, at least 24% of the non-polarized light incident on the switchable filter 5 parallel to the first preferred direction is transmitted, and on the other hand, at least 85% of the non-polarized light incident on the switchable filter 5 at an angle of more than 30° to the first preferred direction is absorbed, wherein this absorption occurs only in the second direction in the first sub-working mode B1H and only in the second direction perpendicular to the first direction in the second sub-working mode B1V. Therefore, the absorption directions of each of the two sub-working modes B1H and B1V differ by 90° for the first working mode B1 and the second working mode B2.

[0143] Unlike before, both operating modes here are restricted field of view modes, in which privacy protection can be switched between two mutually perpendicular directions (e.g., horizontal and vertical). The first technical solution of the switchable filter 5 can be switched between sub-operating modes B1V and B1H by rotating the polarization filter P 90°.

[0144] Here, the no-field state can also be described, for example, by the first electric field EF1 or the second electric field EF2, with the other electric field EF2 or EF1 having an absolute field strength greater than zero (e.g., 0.5 MV / m). Therefore, depending on the design of the optical component 1 and the polarization filter P, the no-field state may indicate the presence of the sub-operating mode B1H. However, the sub-operating mode B1V may also exist in the no-field state.

[0145] Thus, the switchable filter 5 of the first technical solution, in conjunction with the image reproduction unit, allows switching between vertical privacy protection and horizontal privacy protection (up / down protection B1V and left / right protection B1H). For example, using a laptop computer, this means that in sub-operating mode B1V, the user can view content alongside others whose eyes are substantially at the same height, while in sub-operating mode B1H, those nearby cannot see the image content. As previously mentioned, the switchable filter 5 of the third technical solution can vary in structure.

[0146] at last, Figure 10 A second technical solution for a switchable optical filter 5 is shown as a simplified schematic diagram. The structure of the first optical component 1 is similar to that of the optical component 1 of the first technical solution, except that it is switchable. That is, the transition dipole moment of each of the layers S1 and S2 can change its orientation and / or absolute value between a first state and at least one second state, allowing each layer S1, S2, ... to be alternately placed in at least two different states. A polarization filter P is provided upstream or downstream of the first optical component 1. The figure also does not show the means for selectively generating the first electric field EF1 or the second electric field EF2. For the first optical component 1, the first state is generated by applying the first electric field EF1, and the second state is generated by applying the second electric field.

[0147] In a first operating mode B1, in which a first electric field EF1 is applied and the transition dipole moments of the layers S1, S2, ... of the first optical component 1 are oriented along a first preferred direction, and in which a first sub-operating mode B1H and a second sub-operating mode B1V are provided, at least 24% of unpolarized light incident on the switchable filter 5 parallel to the first preferred direction is transmitted, while at least 85% of unpolarized light incident on the switchable filter 5 at an angle of 30° or greater to the first preferred direction is absorbed. This absorption occurs only in the first direction in the first sub-operating mode B1H, and only in a second direction perpendicular to the first direction in the second sub-operating mode B1V. Furthermore, the first preferred direction is preferably still parallel to the perpendicular bisector of the switchable filter 5 within the drawing plane. Regarding the positions of the first and second directions, the same principles as those described in connection with the third technical solution apply.

[0148] In a second operating mode B2, in which a second electric field EF2 is applied, the transition dipole moments of the layers S1, S2, ... of the first optical component (1) are oriented parallel to the surface of the polarization filter P (also referred to as substrate in this case) and perpendicular to the transmission direction of the polarization filter P. Consequently, at least 24% of unpolarized light incident on the switchable filter (5) at any angle to the first preferred direction is transmitted.

[0149] Here, the field-free state can also be described, for example, by either the electric field EF1 or the electric field EF2, with the other electric field EF2 or EF1 having an absolute field strength greater than zero (e.g., 0.5 MV / m). Therefore, depending on the design of the optical component 1 and the polarization filter P, the field-free state may indicate the presence of the operating mode B2. However, the field-free state may also include the presence of the operating mode B1 with one of the sub-operating modes B1H or B1V.

[0150] Therefore, the switchable filter 5 of the second technical solution, in cooperation with the image reproduction unit, allows switching between anti-peeping protection and no anti-peeping effect in the vertical or horizontal direction (up / down protection B1V or left / right protection B1H and no anti-peeping protection B3).

[0151] For specific applications, regardless of which of the above technical solutions is used, the switchable filter 5 can be divided into multiple, individually switchable sections, thereby enabling localized switching between possible operating states. In conjunction with the image reproduction unit, this means that, for example, only a portion of the image area can be switched between privacy protection and free viewing without privacy protection, while the complementary image area remains in either privacy mode or non-privacy mode. There can even be multiple geometrically separate sections that can be switched between operating modes individually or collectively.

[0152] As previously described, the switchable filter 5 can be combined with an image reproduction unit to form a screen. This screen can operate in at least a first operating state B1V and / or B3 to achieve a horizontally free field of view mode, and can operate in at least a second operating state B1H and / or B2 to achieve a horizontally restricted field of view mode. This screen comprises: a switchable filter 5 as described above, according to one of the four technical solutions described above, and an image reproduction unit arranged downstream or upstream of the switchable filter 5 from the perspective of a viewer 6.

[0153] Advantageously, the image reproduction unit corresponds to an LCD panel, and one of the polarization filters of the LCD panel corresponds to polarization filter P. This can thus be either a front polarizer or a back polarizer in the LCD structure. Furthermore, advantageously, a switchable filter is arranged between the LCD panel and its backlight to switch between a first operating state B3 (or B1V) in free field of view mode and a second operating state B1H or B2 in restricted field of view mode. This is because the switchable filter allows the backlight light to be sometimes focused (B2 or B1H) and sometimes unfocused (B3 or B1V) in the horizontal direction. Furthermore, "focusing" does not refer to focusing in the manner of a lens, but rather to narrowing the emission range or transmittance depending on the angle of incidence.

[0154] Such a screen is advantageously used in mobile devices, cars, aircraft or ships, payment terminals or access systems, wherein it is possible to switch between the aforementioned operating modes to protect sensitive data, i.e., to present the image content perceptibly only to one viewer or to selectively present the image content to multiple viewers simultaneously.

[0155] In the above-described optical component, light entering and passing through the optical component is transmitted or partially or completely absorbed depending on its incident direction and polarization properties. A switchable filter using such an optical component influences the transmission of light depending on the angle (optionally vertical), wherein the optical component can be switched between at least two operating states: a free view mode (with respect to the viewing angle of the viewer) and a restricted view mode. Furthermore, in particular, the angular restriction of transmission in certain directions is switchable. The optical component or a system based on the optical component is cost-effective to implement and can be universally used with various screen types to switch between privacy protection (at least in the horizontal direction) and a free view mode, wherein the resolution of the screen is not reduced in principle.

[0156] The above invention, in conjunction with an image reproduction device, can be advantageously used in any location where confidential data is displayed and / or entered, such as when entering a PIN code or displaying data at an ATM or payment terminal, entering a password, or reading email on a mobile device. As mentioned above, the present invention can also be used in passenger vehicles to selectively block disruptive image content from the driver or passengers.

[0157] Reference Signs List

[0158] 1. First optical component

[0159] 2 Second optical component

[0160] 3 Liquid crystal layer

[0161] 4 Orientation Layer

[0162] 5 Switchable filters

[0163] 6 viewers

[0164] 7 Optically anisotropic layer

[0165] Areas A1…A5

[0166] E1, E2 electrodes

[0167] E2 Second electric field

[0168] P polarizing filter

[0169] S Transparent Substrate

[0170] S1…S3 layers

Claims

1. A switchable optical filter (5), capable of switching between a first operating mode and a second operating mode, the switchable optical filter comprising: A first optical component (1) comprising: a first layer (S1) of a material having multiple light-absorbing transition dipole moments, wherein each of the transition dipole moments is oriented, at least in a first state, with a tolerance of at most 10° parallel to a first preferred direction selectable for the first optical component (1), wherein the first preferred direction corresponds to the following orientation of the transition dipole moment: In this orientation, the absorption is the same for all polarization directions of light. So that light incident on the first optical component (1) is transmitted or at least partially absorbed depending on its incident direction relative to the first layer (S1) and its polarization state, the polarization filter (P) is arranged upstream or downstream of the first optical component (1) along the incident direction of the light, an electric field generator configured to selectively generate a first electric field (EF1) in the first operating mode or a second electric field (EF2) in the second operating mode, a liquid crystal layer (3) arranged between the first optical component (1) and the polarization filter (P), with no other polarization filter between the liquid crystal layer and the first optical component, the liquid crystal layer being arranged and configured to receive the first electric field (EF1) in the first operating mode and the second electric field (EF2) in the second operating mode, and the liquid crystal layer thereby affecting the polarization state of light passing through the liquid crystal layer, so that the switchable filter is configured to: In a first operating mode (B1) in which the first electric field (EF1) is applied and which has a first sub-operating mode (B1H) and a second sub-operating mode (B1V), on the one hand, at least 24% of unpolarized light incident on the switchable filter (5) parallel to the first preferred direction is transmitted, and on the other hand, at least 85% of unpolarized light incident on the switchable filter (5) at an angle of 30° or more to the first preferred direction is absorbed, wherein the absorption occurs only in a first direction in the first sub-operating mode (B1H) and only in a second direction perpendicular to the first direction in the second sub-operating mode (B1V). When the second electric field (EF2) is applied and the first sub-operation mode is In the second working mode (B2) of the first sub-working mode (B1H) and the second sub-working mode (B1V), on the one hand, at least 24% of the non-polarized light incident on the switchable filter (5) parallel to the first preferred direction is transmitted, and on the other hand, at least 85% of the non-polarized light incident on the switchable filter (5) at an angle of more than 30° to the first preferred direction is absorbed, wherein the absorption occurs only in the second direction in the first sub-working mode (B1H) and only in the first direction perpendicular to the second direction in the second sub-working mode (B1V), so that the absorption directions of each of the two sub-working modes (B1H, B1V) differ by 90° for the first working mode (B1) and the second working mode (B2).

2. The switchable optical filter (5) according to claim 1, characterized in that At least one polarization compensation layer is provided upstream and / or downstream of the liquid crystal layer (3).

3. The switchable optical filter (5) according to claim 1, characterized in that The first preferred directions each make an angle between 0° and 45° with the surface normal of the first layer (S1).

4. The switchable optical filter (5) according to claim 1, characterized in that The switchable filter (5) is divided into a plurality of individually switchable parts, thereby achieving local switchability.

5. The switchable optical filter (5) according to claim 1, characterized in that The first layer (S1) is constructed aperiodically.

6. A screen comprising: The switchable optical filter (5) according to claim 1; and an image reproduction unit arranged downstream or upstream of the switchable filter (5) as seen by a viewer.

7. A switchable optical filter (5), capable of switching between a first operating mode and a second operating mode, the switchable optical filter comprising: A first optical component (1) and a second optical component (2), wherein each of the first optical component (1) and the second optical component (2) comprises: a first layer (S1) of a material having multiple light-absorbing transition dipole moments, and wherein each transition dipole moment is oriented, at least in a first state, parallel to a first preferred direction selectable for the first optical component (1) and a second preferred direction selectable for the second optical component (2) with a tolerance of at most 10°, wherein the first preferred direction corresponds to an orientation of the transition dipole moment in which the absorption is the same for any polarization direction of the light, and wherein the first preferred direction and the second preferred direction differ from each other by less than 40°, Thus, light incident on the first optical component (1) or the second optical component (2) is transmitted or at least partially absorbed according to its incident direction relative to the first layer (S1) and its polarization state, an electric field generator configured to generate a first electric field (EF1) in the first operating mode or a second electric field (EF2) in the second operating mode, an optically anisotropic layer (7) disposed between the first optical component and the second optical component, the optically anisotropic layer being configured to rotate the polarization direction of light passing through the optically anisotropic layer (7) by 90°, a polarization filter (P) arranged above or below the first optical component (1) or the second optical component (2), so that the switchable filter is further configured such that: in a first operating mode (B1) in which the first electric field (EF1) is applied, a polarization filter transition dipole component of the polarization filter (P) is oriented parallel to a transition dipole moment of the switchable optical component closest to the polarization filter (P); in a second operating mode (B2) in which the second electric field (EF2) is applied, a transition dipole moment of the polarization filter (P) is oriented perpendicular to a transition dipole moment of the switchable optical component closest to the polarization filter (P); and Such that the switchable optical filter is configured as: in a first operating mode (B1) with the first electric field (EF1) applied, aligning the transition dipole moment components of the two optical components perpendicular to each other and transmitting at least 24% of unpolarized light incident on the switchable filter (5) at any angle to the switchable filter, and In a second operating mode (B2) in which the second electric field (EF2) is applied, at least 24% of unpolarized light incident on the switchable filter (5) parallel to the first preferred direction or the second preferred direction is transmitted, and at least 85% of unpolarized light incident on the switchable filter (5) at an angle of more than 30° to the corresponding preferred direction is absorbed, and the transition dipole moments of the first optical component (1) and the second optical component (2) are respectively oriented parallel to each other.

Images