Switchable filters, lighting, and screen

Abstract

The present invention relates to a switchable filter (5) comprising at least components for optionally influencing the angle-dependent transmittance of the switchable filter (5) for incident light, wherein the components for influencing the angle-dependent transmittance at least at one point in time at different positions on the switchable filter (5) for an optional angle, but correspondingly the same angle at the aforementioned different positions on the switchable filter (5), for at least one direction of the hemisphere, namely, minimum, medium and maximum transmittance values. The present invention also discloses a switchable lighting device and a switchable screen.

Description

Switchable Filter, Lighting Device and Screen In recent years, significant progress has been made in the aspect of viewing angle expansion of LCDs. However, there are often situations where the extremely large viewing area of the screen constitutes an adverse factor. More and more, information such as bank data or other personal information, as well as sensitive data, can also be provided on mobile devices such as laptops and tablets. Correspondingly, people need to control who can see such sensitive data; they need to be able to select a wide viewing angle - public mode, to share the information on the display with others, for example when viewing holiday photos or even for advertising purposes. On the other hand, if the confidentiality of the image information is to be maintained, a smaller viewing angle - private mode is required. There are similar problems in the field of automobile manufacturing: when the motor is turned on, the driver must be prevented from being distracted by the image content, such as digital entertainment programs, while the co-driver hopes to be entertained during the journey. Therefore, a screen that can switch between corresponding presentation modes is needed. Additional thin films based on micro-laminates have been applied to mobile displays to achieve data protection visually. However, these thin films cannot be switched or converted; they always have to be applied by hand first and then removed. They also have to be transported separately from the display when not in use. Another major disadvantage of using such laminate films is the light loss. US 6,765,550 B2 has described such anti-peeping achieved through micro-laminates. The biggest disadvantage of this solution lies in the mechanical removal and mechanical attachment of the filter, as well as the light loss in the protection mode. US 5,993,940 A describes the use of a thin film with small strip-shaped prisms evenly distributed on its surface to achieve a private mode, that is, a restricted viewing mode with a small viewing angle range. The technical difficulty in research and development and manufacturing is quite large. In WO 2012 / 033583 A1, the switching between a free viewing field and a restricted viewing field is achieved by controlling the liquid crystals between the so-called "chromogenic" layers. There will be light loss during this process, and the technical difficulty is quite high. US 2012 / 0235891 A1 describes an extremely complex screen backlight. According to FIGS. 1 and 15 of this case, not only several light guides are used, but also other complex optical elements such as micro-lens elements 40 and prism structures 50 are used, which shape the light from the rear illumination on the path to the front illumination. Its implementation cost is high, the technical difficulty is large, and it will also cause light loss. According to the variant shown in FIG. 17 of US 2012 / 0235891 A1, both light sources 4R and 18 generate light with a narrow illumination angle, and among them, the light from the rear light source 18 is converted into light with a large illumination angle after a complex process. As mentioned above, such a complex conversion significantly reduces the brightness. US 2013 / 0308185 A1 describes a special light guide body provided with steps, which emits light in different directions on a large surface, specifically depending on the direction from which the light guide body is illuminated from the narrow side. By cooperating with a transmissive image reproduction device such as an LC display, a screen that can switch between a free viewing mode and a restricted viewing mode can be produced. Its main disadvantage is that the restricted viewing effect can only be produced left / right or up / down, but not simultaneously left / right / up / down, which is necessary for certain payment processes, for example. Furthermore, even in the restricted viewing mode, residual light can still be seen from the blocked viewing angles. WO 2015 / 121398 A1 of the applicant describes a screen with two operating modes. In order to achieve the conversion of the operating modes, scattering particles exist in the volume of the corresponding light guide body. However, the polymer scattering particles selected in this case generally have the following disadvantages: light is output-coupled from two large surfaces, so approximately half of the useful light is emitted in the wrong direction, that is, towards the backlight direction, and due to structural reasons, it is impossible to recover it to a sufficient extent there. In addition, depending on the situation, especially at higher concentrations, the scattering particles composed of polymers distributed in the volume of the light guide body may cause a scattering effect, which weakens the anti-peeping effect in the protected operating mode. The basic idea of the "electro-optic birefringence (EDB)" technical method is to use the switchable liquid crystals of an additional coated LC panel to "filter" all light beams that do not exit from the imaging layer at a specific beam angle. The disadvantages of this technology are the additional energy consumption and higher costs, and it is difficult to change the optimal point of + / -40°, that is, the optimal viewing position. The absorbance of the LC structure is also insufficient because once the viewing angle exceeds the optimal point, the light intensity attenuation will rise again. Therefore, for viewing angles greater than + / -40°, the light intensity is at most 3% of the maximum light intensity. The above methods and configurations generally have the following disadvantages: significantly reducing the basic screen brightness and / or requiring complex and expensive optical components for mode conversion and / or reducing the resolution in the common mode of free viewing and / or having visual artifacts in the case of a display with extremely high resolution. Especially in the case of a partially switchable mode, there will be visible edges that are uncomfortable to the eye between the regions in different modes. In view of this, the object of the present invention is to describe a filter, in which the light incident on the filter is selectively transmitted or partially or (almost) completely absorbed by such a filter at different positions on the filter or on the screen. Among them, in order to prevent visible edges from appearing when at least three operating states are partially switched, the transmission behavior can be specifically converted for certain angles or directions. In addition, a corresponding screen and an illumination device are also described, the angle-dependent brightness distribution of which can be changed in some areas, and visible edges between regions in different modes can also be prevented. The solution of the present invention for achieving the above object is a switchable filter, including - members for optionally affecting the angle-dependent transmittance of the switchable filter for light incident thereon, wherein - these members for affecting the angle-dependent transmittance are at least at one point in time at different positions on the switchable filter, for an optional but correspondingly same angle at the aforementioned different positions on the switchable filter, generating at least three different transmittance values for at least one direction of the hemisphere, namely the minimum transmittance value, the medium transmittance value, and the maximum transmittance value. This does not necessarily apply to multiple or all possible values, but at least applies to an optional and correspondingly same value. The concept of "medium value" is only a name and does not necessarily precisely represent the average of the minimum and maximum values, but this is not excluded. In a preferred technical solution, at least five or eight or more different transmittance values are generated at correspondingly five or eight or more positions. In order to use the filter of the present invention, preferably, there is also a member for generating linearly polarized light. For example, an LC panel with a polarizer, or - when there is another image source or light source - a polarizing filter. In a first technical solution, the members for affecting the angle-dependent transmittance of the switchable filter include at least one guest-host LC configuration or PDLC having LC molecules, wherein the orientation of the LC molecules respectively determines the angle-dependent transmittance of the switchable filter, and wherein the aforementioned orientation of the LC molecules is different at the aforementioned different positions on the switchable filter. In a second technical solution, the members for affecting the angle-dependent transmittance of the switchable filter are integrated in a bilayer or multilayer structure, wherein the orientation of the LC molecules responsible for the variable angle-dependent transmittance in the bilayer or multilayer structure is different at the aforementioned different positions on the switchable filter. Furthermore, in the third aspect, the switchable filter further includes - a first optical element, which includes • a plurality of photoabsorptive transition dipoles, which are arranged in a layer having a thickness of at least 0.2 microns, • wherein most of these transition dipoles are oriented at least parallel to a first preferred direction selectable for the first optical element or fluctuate around the first preferred direction in a first state, with a maximum tolerance of 20°, wherein the first preferred direction is arranged at a predetermined angle α with respect to the perpendicular bisector of the first optical element, and wherein the angle α is measured in an optional first plane containing the perpendicular bisector, • such that light incident on the first optical element with an incident direction and a polarization state is transmitted or at least partially absorbed according to its incident direction and polarization state with respect to the first optical element, - means for optionally generating at least one of a first, second, and third electric field EF1, EF2, EF3, wherein the corresponding electric fields EF1, EF2, EF3 can be selectively chosen in different ways for different positions on the switchable filter 5, - a liquid crystal layer arranged behind or in front of the first optical element along the viewing direction, and the corresponding electric fields EF1, EF2, EF3 act on the liquid crystal layer and thereby affect the polarization state of the light passing through the liquid crystal layer, - a first linear polarization filter X located in front of the liquid crystal layer along the viewing direction, if the liquid crystal layer is arranged in front of the first optical element along the viewing direction, - such that the transmission characteristics of the switchable filter 5 are different at each position between a first operating mode B1 (wherein a first electric field EF1 is applied), a second operating mode B2 (wherein a second electric field EF2 is applied), and at least one third operating mode B3 (wherein a third electric field EF3 is applied), wherein, in these three operating modes B1, B2, and B3, the corresponding relative transmittances are respectively described by a first transmittance T B1 (β) for the first operating mode B1, a second transmittance T B2 (β) for the second operating mode B2, or a third transmittance T B3 (β) for the third operating mode B3, and these transmittances are related to the angle β and are respectively normalized such that, for the transmittance values at the predetermined angle α, T B1 (α) = 1 and T B2 (α) = 1 and T B3When (α) = 1, specifically, when light is incident on the first optical element at an angle β that satisfies β = α - 40° or β = α + 40° at a position in the first operating mode B1 with the first electric field EF1 applied, the s-polarization component of the above light is transmitted with at least a first normalized transmittance value T B1 (β) ≥ 0.25. When light is incident on the first optical element at an angle β that satisfies β = α - 40° or β = α + 40° at a position in the second operating mode B2 with the second electric field EF2 applied, the p-polarization component of the above light is transmitted with at most a second normalized transmittance value T B2 (β) ≤ 0.2. And when light is incident on the first optical element at an angle β that satisfies β = α - 40° or β = α + 40° at a position in the third operating mode B3 with the third electric field EF3 applied, the above light is transmitted with a third normalized transmittance value T B2 (β) < T B3 (β) < T B1 (β). s-polarized light refers to light whose electric field is oriented perpendicular to the plane of incidence on the medium, and p-polarized light refers to light whose electric field is oriented parallel to the plane of incidence. The plane of incidence is formed by the normal to the medium interface and the direction of incidence. Furthermore, in the fourth aspect, the switchable filter further includes - a first optical element, which includes • a plurality of photoabsorptive transition dipole moments disposed in a layer having a thickness of at least 0.2 microns, • wherein most of these transition dipole moments are oriented at least in a first state parallel to a first preferred direction selectable for the first optical element or fluctuate around the first preferred direction with a maximum tolerance of 20°, wherein the first preferred direction is arranged at a predetermined angle α relative to the perpendicular of the first optical element, and wherein the angle α is measured in an optional first plane containing the perpendicular, • such that light incident on the first optical element is transmitted or at least partially absorbed according to its incident direction relative to the first optical element and its polarization state, - a liquid crystal layer having liquid crystal molecules arranged behind or in front of the first optical element along the observation direction, and these liquid crystal molecules can be affected in their orientation by a locally controllable electric field pixel by pixel, such that the electric field affects the polarization state of the light passing through the liquid crystal layer according to the corresponding pixel-by-pixel selectable orientation of the liquid crystal molecules, - wherein the locally controllable electric field is also controlled by a control electronic device, and the control electronic device can be controlled by a digital signal (which encodes at least one minimum, maximum, and intermediate transmittance), wherein there is a digital signal pixel by pixel, and at least at one time point at least one maximum, minimum, and digital signal therebetween is selected, - in the case where the liquid crystal layer is arranged in front of the first optical element along the observation direction, a first linear polarization filter X arranged in front of the liquid crystal layer along the observation direction, - such that at the time points when the control electronic device is controlled by the aforementioned at least three digital signals, at different positions on the switchable filter, at least three different transmittance values, namely a minimum transmittance value, an intermediate transmittance value, and a maximum transmittance value, are generated for an optional but corresponding same angle at the aforementioned different positions on the switchable filter. The corresponding digital signals can, for example, correspond to one of 256 gray levels stored in a bitmap file. Optionally, these digital signals can be dynamically adjusted. In all aspects, it is particularly preferred that at least three different transmittance values are generated at preferably adjacent positions on the switchable filter for the same angle. That is, the transmittance values for a fixed angle decrease or increase from the maximum value to the minimum value or vice versa along an optional straight line on the surface of the switchable filter 5. Thus, a smooth transition of the transmittance value from the minimum value to the maximum value or from the maximum value to the minimum value is achieved because at least the average value of the transmittance still lies between the two. As mentioned above, it is preferably to use more than three transmittance values (such as five, eight, or more than eight) to make the aforementioned transition more continuous and visually more comfortable. The same means-effect relationship applies to all of the foregoing technical solutions. At an optional angle that is usually equivalent to the angle α but can also be selected otherwise (for example, 45° in the horizontal direction of the observer's viewing angle, i.e., in the privacy mode at that location on the switchable filter), the local location with the minimum transmittance is not immediately adjacent to the location with the maximum transmittance, but rather represents the average transmittance at a given angle or at least one location among the foregoing multiple transmittance values therebetween. The third and fourth technical solutions can be rewritten for some embodiments as: Light with a preferred polarization is incident on the liquid crystal layer and the second optical element, where the dichroic dye is parallel or perpendicular to the substrate surface. Electrodes E1 and E2 achieve the application of locally different first electric field EF1 and second electric field EF2, so that the transmission characteristics can be selected. In this case, the static and / or dynamic superposition of the first and second electric fields EF1 and EF2 can generate a defined average transmittance, which minimizes the perceptibility of the edge between the locations with the first and second electric fields. Overall, "position" refers to a two-dimensional position, which (if present) indicates the same X and Y coordinates on the surface of the first optical element and the switchable filter, respectively. Thus, "position" can be applied to both, i.e., the optical element and the switchable filter, with the same meaning. If present, the first optical element and / or the liquid crystal layer can be divided into multiple individually switchable segments for local conversion between the corresponding possible operating states. In a special technical solution, the switchable filter includes at least two first optical elements, and optionally, a retarder is arranged between at least two such first optical elements. The present invention also includes an illumination device for a screen, which can be operated in at least two operating modes B1 for a free viewing mode and B2 for a restricted viewing mode. In the restricted viewing mode, light is emitted within a viewing angle range that is more limited for the observer compared to the free viewing mode. The illumination device includes - a planar extended backlight that emits light and is optionally constructed in a direct light-emitting manner, and - the foregoing switchable filter arranged in front of the backlight along the viewing direction. The invention also includes a screen which can be operated in at least two operating modes: B1 for a free viewing mode and B2 for a restricted viewing mode. In the restricted viewing mode, light is emitted within a viewing angle range that is more limited for an observer compared to the free viewing mode. The screen includes - the aforementioned lighting device, - if a first linear polarizing filter is not arranged in the switchable filter of the lighting device, a second linear polarizing filter arranged in front of the backlight lamp along the viewing direction, thereby restricting the propagation direction of the light emitted from the backlight lamp and passing through the second linear polarizing filter, and - a transmissive image reproduction device, which is arranged in front of the switchable filter along the viewing direction, - wherein, a second electric field EF2 is applied in the operating mode B2, and a first electric field EF1 is applied in the operating mode B1. Wherein, the first or second linear polarizing filter can be arranged in or be part of the transmissive image reproduction device. Another solution of the invention to achieve the above object is a screen, including - an image reproduction device, - the aforementioned switchable filter located in front of or behind the image reproduction device along the viewing direction. Wherein, the switchable filter 5 is subsequently installed on the image reproduction device by the user and / or reversibly. In addition, the invention also includes a screen which can be operated in at least two operating modes: B1 for a free viewing mode and B2 for a restricted viewing mode. In the restricted viewing mode, light is emitted within a viewing angle range that is more limited for an observer compared to the free viewing mode. It includes - a transmissive image reproduction device, preferably an LC panel, - a backlight lamp arranged downstream of the transmissive image reproduction device along the viewing direction, wherein the backlight lamp has an asymmetric light emission density distribution, and preferably, the asymmetry is with respect to the horizontal direction as viewed from the angle of the observer, i.e., parallel to the imaginary connection line between the observer's two eyes, - the aforementioned switchable filter located in front of or behind the image reproduction device along the viewing direction. The invention can also be realized by means of an illumination device for a screen, which can be operated in at least two operating modes B1 for a free viewing mode and B2 for a restricted viewing mode. In the restricted viewing mode, light is emitted within a more limited angular range compared to the free viewing mode. The illumination device comprises - a planar extended backlight that emits light within a limited angular range and is optionally constructed in a direct emission manner, and - a plate-shaped light guide located in front of the backlight in the viewing direction, which has output coupling elements on at least one of the large surfaces and / or within its volume, - lighting means arranged laterally on at least one narrow side of the light guide, and - an optional linear polarization filter, - the aforementioned switchable filter arranged in front of the backlight in the viewing direction, - wherein, in the operating mode B2, the backlight is turned on and the light-emitting elements are turned off, while in the operating mode B1, at least the light-emitting elements are turned on. Alternatively, the illumination device for a screen, wherein the screen can be operated in at least two operating modes B1 for a free viewing mode and B2 for a restricted viewing mode. In the restricted viewing mode, light is emitted within a more limited angular range compared to the free viewing mode. The illumination device may comprise the following - a planar extended backlight that emits light within a non-limited angular range and is optionally constructed in a direct emission manner, and - a plate-shaped light guide located in front of the backlight in the viewing direction, which has output coupling elements on at least one of the large surfaces and / or within its volume, wherein the above output coupling elements output-couple most of the light that is laterally input-coupled into at least one narrow side of the light guide within a limited angular range, - lighting means arranged laterally on at least one narrow side of the light guide, and - an optional linear polarization filter, - the aforementioned switchable filter arranged in front of the backlight in the viewing direction, - wherein, in the operating mode B2, the backlight is turned off and the light-emitting elements are turned on, while in the operating mode B1, at least the backlights are turned on. The same means-effect relationship also applies to a switchable lighting device that can be operated in at least two operating modes B1 for a free viewing mode and B2 for a restricted viewing mode. In the restricted viewing mode, light is emitted within a more limited angular range compared to the free viewing mode. The lighting device includes - a planar backlight that emits light within a limited angular range in a first alternative and within a non-limited angular range in a second alternative, and is optionally configured to emit light directly, and - a plate-shaped light guide located in front of the backlight along the viewing direction, which has output coupling elements on at least one of the large surfaces and / or within its volume, - lighting elements arranged laterally on at least one narrow surface of the light guide, and - wherein, in the first alternative in operating mode B2, the backlight is turned on and the light-emitting elements are turned off, while in operating mode B1, at least the light-emitting elements are turned on, and in the second alternative in operating mode B2, the backlight is turned off and the light-emitting elements are turned on, while in operating mode B1, at least the backlight is turned on, - wherein in particular the backlight and / or the light guide, i.e., in the case of light emission from one or both of them, at least at one point in time at different positions on the backlight and / or the light guide, for an optional but correspondingly the same angle at the aforementioned different positions, at least three different brightness values are generated, namely minimum, medium, and maximum brightness values. The indications in the technical solutions given previously also apply here. Particularly preferably here, at least three different brightness values are generated for the same angle at preferably adjacent positions on the backlight and / or the light guide. Finally, the invention also includes a switchable screen to which the same means-effect relationship also applies, wherein the screen at least includes - an image reproduction device, - elements for influencing the angle-dependent brightness of the switchable screen, wherein - the elements for influencing the angle-dependent brightness at least at one point in time at different positions on the switchable screen, for an optional but correspondingly the same angle at different positions on the switchable screen, generate at least three different brightness values, namely minimum, medium, and maximum brightness values. To achieve this, controllable angle-dependent absorption, reflection, or contrast and scattering can be employed. The above-mentioned filters, lighting devices, or such screens are advantageously used in mobile devices, motor vehicles, airplanes or ships, payment terminals, or access control systems. In this case, it is possible to switch between the above-mentioned operating modes in order to protect sensitive data, i.e., to display it in a way that is only perceivable by one observer, or as an alternative, to display image content for multiple observers simultaneously. In principle, if the above parameters are changed within certain limits, the performance of the invention can be maintained. Of course, within the scope of the present invention, the features described above and below can not only be combined in the manner given in this application, but also be combined and applied in other ways or applied alone. The drawings are not drawn to scale and are schematic only. Figure 1a is a schematic diagram of the principle of the mode of operation of an exemplary switchable filter 5 with locally different transmittances T1, T2, T3. The region with the minimum transmittance T2 is completely surrounded by the region with the medium transmittance T3, which in turn is completely surrounded by the region with the maximum transmittance T1. Other technical solutions can also be adopted. Such an exemplary switchable filter 5 at least comprises - means for optionally influencing the angle-dependent transmittance of the switchable filter 5 for light incident thereon, wherein - these means for influencing the angle-dependent transmittance are at least at one point in time at different positions on the switchable filter 5, for an optional, but correspondingly identical angle at the aforementioned different positions on the switchable filter 5, generating at least three different transmittance values for at least one direction of the hemisphere, namely the minimum transmittance value (T2), the medium transmittance value (T3) and the maximum transmittance value (T1). This does not necessarily apply to multiple or all possible values, but at least to an optional, correspondingly identical value. The concept of "medium value" is only a name and does not necessarily precisely represent the average of the minimum and maximum values, but this is not excluded. In a preferred technical solution, at least five or eight or more different transmittance values are generated at the corresponding five or eight or more positions. In order to use the filter of the present invention, it is preferably also provided with means for generating linearly polarized light. For example, an LC panel with a polarizer, or - when there is another image source or light source - a polarizing filter. Figure 1b is a schematic diagram of the operating principle of the exemplary switchable filter 5 in three different local operating modes B1, B2, and B3. The exemplary filter 5 includes a. a first optical element 1, which includes i. a plurality of optical absorption transition dipoles, which are arranged in a layer at least 0.2 micrometers thick, ii. wherein most of these transition dipoles are oriented at least in a first state parallel to a first preferred direction selectable for the first optical element 1 or fluctuate around the first preferred direction, with a maximum tolerance of 20°, wherein the first preferred direction is arranged at a predetermined angle α with respect to the perpendicular bisector of the first optical element 1, and wherein the angle α is measured in an optional first plane containing the perpendicular bisector, iii. such that light incident on the first optical element 1 in a certain incident direction and polarization state is transmitted or at least partially absorbed according to its incident direction and polarization state with respect to the first optical element 1, b. means for optionally generating at least one first, second, and third electric field EF1, EF2, EF3, wherein the corresponding electric fields EF1, EF2, EF3 can be selectively chosen in different ways for different positions on the switchable filter 5, c. a liquid crystal layer 3 arranged behind or in front of the first optical element 1 along the observation direction, and the corresponding electric fields EF1, EF2, EF3 act on the liquid crystal layer and thereby affect the polarization state of the light passing through the liquid crystal layer, d. in the case where the liquid crystal layer 3 is arranged in front of the first optical element 1 along the observation direction, a first linear polarization filter X located in front of the liquid crystal layer 3 along the observation direction, e. such that the transmission characteristics of the switchable filter 5 are different at each position between a first operating mode B1 (wherein the first electric field EF1 is applied), a second operating mode B2 (wherein the second electric field EF2 is applied), and at least one third operating mode B3 (wherein the third electric field EF3 is applied), wherein, in these three operating modes B1, B2, and B3, the corresponding relative transmittances are described at each of the aforementioned positions, except for an optional tolerance, respectively, by a first transmittance T B1 (β) for the second operating mode B2, a second transmittance T B2 (β) or a third transmittance T B3 (β) for the third operating mode B3, and these transmittances are related to the angle β and are respectively normalized such that for the transmittance values at a predetermined angle α, T B1 (α) = 1 and T B2 (α) = 1 and T B3(α) = 1, f. Specifically, when light i. is incident on the first optical element 1 at an angle β that satisfies β = α - 40° or β = α + 40° at a position in the first operating mode B1 where the first electric field EF1 is applied, the s-polarized component of the above light is transmitted with at least a first normalized transmittance value T B1 (β) ≥ 0.25, ii. when incident on the first optical element 1 at an angle β that satisfies β = α - 40° or β = α + 40° at a position in the second operating mode B2 where the second electric field EF2 is applied, the p-polarized component of the above light is transmitted with at most a second normalized transmittance value T B2 (β) ≤ 0.2, and iii. when incident on the first optical element 1 at an angle β that satisfies β = α - 40° or β = α + 40° at a position in the third operating mode B3 where the third electric field EF3 is applied, the above light is transmitted with a third normalized transmittance value T B2 (β) < T B3 (β) < T B1 (β). The letters s and p indicate whether it is s-polarized light or p-polarized light involved. In the local operating mode B3 with a medium transmittance T3, if |β - α| > 30°, then only part of the light (i.e., s-polarized light) is transmitted to the side, while most of the p-polarized light is absorbed by the first optical element 1. T B2 (β) or T B3 (β) or T B1 (β) can be related to or equal to the transmittance T2 or T3 or T1 respectively for one (or more) selected but fixed angles β. Normalization T of the transmittance B1 (α) = 1 and T B2 (α) = 1, the following should be noted: Of course, the angles β and α are measured in the same plane as above. In principle, T B1 (α) > 1 and / or T B2 (α) > 1 can also be applicable to the case where β ≠ α. In many cases, T B1 (α) < 1 and / or T B2(α) < 1 and is also applicable to an angle β ≠ α. For clarity, the value of the angle α shown in FIG. 1 is greater than 0°. However, for all subsequent considerations, α = 0° should be applicable in principle. A value of α ≠ 0° allows for an inclination that enables switching of the preferred transmission direction (i.e., maximum transmittance) of the switchable filter 5. Advantageously, the transition dipole moment is constructed as one or more dichroic dyes, which are mixed with the liquid crystal in a guest-host layout. For the permanent transition dipole moment, the liquid crystal can be fixed through a curing process. The dichroic dye molecules are usually oriented parallel to the liquid crystal molecules. The first preferred direction can, for example, form an angle of 0° to 45° with the surface normal of the first optical element 1. In addition, the first preferred direction can also vary within the range of the surface of the first optical element 1. For the present invention, the average weighted preferred direction is applicable. In addition, FIG. 2 is a schematic diagram of the principle of an exemplary structure of the switchable filter 5 in the first technical solution. Here, the liquid crystal layer 3 is arranged in front of the first optical element 1 along the observation direction (from top to bottom). In addition, this first technical solution also includes a first linear polarization filter (X) located in front of the liquid crystal layer 3 along the observation direction, and its preferred polarization transmission direction is preferably parallel to the edge of the optical element 1, preferably the lower edge. In addition, FIG. 3 is an exemplary normalized transmittance diagram (based on the schematic diagram of the measurement principle) of the switchable filter 5 in the first (partial) operating mode B1 for the maximum transmittance T1 within the horizontal angle range. For selectable angles, the (normalized) maximum transmittance T1 can be selected here. In addition, FIG. 4 is an exemplary normalized transmittance diagram (based on the schematic diagram of the measurement principle) of the switchable filter in the second (partial) operating mode B2 for the minimum transmittance T2 within the horizontal angle range. For selectable angles, the (normalized) minimum transmittance T2 can be selected here. FIG. 5 is an exemplary normalized transmittance diagram (based on the schematic diagram of the measurement principle) of the switchable filter in the third (partial) operating mode B3 for the first intermediate transmittance T3 within the horizontal angle range. For selectable angles, the (normalized) first intermediate transmittance T3 can be selected here. In addition, FIG. 6 is an exemplary normalized transmittance diagram (based on the schematic diagram of the measurement principle) of the switchable filter in the third (partial) operating mode B3 for the second intermediate transmittance T3 within the horizontal angle range. For selectable angles, the (normalized) second intermediate transmittance T3 can be selected here. FIG. 7 is an exemplary normalized transmittance diagram (based on the schematic diagram of the measurement principle) of the switchable filter in the third (partial) operating mode B3 for the third intermediate transmittance T3 within the horizontal angle range. For selectable angles, the (normalized) third intermediate transmittance T3 can be selected here. The aforementioned diagrams in FIGS. 3 to 7 can generally be generated, for example, in the third technical solution described above with reference to FIGS. 1b and 2. In addition, the switchable filter 5 in the fourth technical solution with reference to FIG. 1b or FIG. 2 includes - a first optical element 1, which includes • a plurality of light absorption transition dipole moments arranged in a layer with a thickness of at least 0.2 micrometers, • wherein most of these transition dipole moments are oriented at least parallel to a first preferred direction selectable for the first optical element 1 or fluctuate around the first preferred direction in a first state, with a maximum tolerance of 20°, wherein the first preferred direction is arranged at a predetermined angle α with respect to the perpendicular bisector of the first optical element 1, and the angle α is measured in an optional first plane containing the perpendicular bisector, • such that the light incident on the first optical element 1 is transmitted or at least partially absorbed according to its incident direction with respect to the first optical element 1 and its polarization state, - a liquid crystal layer 3 with liquid crystal molecules arranged behind or in front of the first optical element 1 along the observation direction, and these liquid crystal molecules can be affected in terms of orientation by a locally controllable electric field pixel by pixel, such that the electric field affects the polarization state of the light passing through the liquid crystal layer according to the corresponding pixel-by-pixel selectable orientation of the liquid crystal molecules, - wherein the locally controllable electric field is also controlled by a control electronic device (not shown), and the control electronic device can be controlled by a digital signal, and there are digital signals pixel by pixel, and at least one maximum, minimum, and digital signal in between are selected at least at one time point, - in the case where the liquid crystal layer 3 is arranged in front of the first optical element 1 along the observation direction, a first linear polarization filter X located in front of the liquid crystal layer 3 along the observation direction, - such that at the time point of controlling the control electronic device with the aforementioned at least three digital signals, at different positions on the switchable filter 5, at least three different transmittance values, namely a minimum transmittance value (T2), a medium transmittance value (T3), and a maximum transmittance value (T1), are generated for an optional but corresponding same angle at the aforementioned different positions on the switchable filter 5. The corresponding digital signals can, for example, correspond to one of 256 gray levels stored in a bitmap file, for example. Optionally, these digital signals can be dynamically adjusted. Such digital signals can also be applied to electronic control to generate the first, second, and third electric fields EF1, EF2, EF3 in the third technical solution, but can also be applied to the first and second technical solutions described above, the corresponding variants for double-layer panels, or other technical solutions. For this purpose, FIG. 8 is a schematic diagram of the principle of an exemplary digital signal corresponding to one of 256 gray levels in a bitmap in the prior art. Using the bitmap shown in FIG. 8 in the fourth technical solution makes the edge between the left region in working mode B1 and the right region in working mode B2 much clearer as long as the observer moves the head slightly (such as a few centimeters). FIG. 9a is another schematic diagram of an exemplary digital signal corresponding to one of 256 gray levels in the dot matrix diagram, wherein in the case of using such a dot matrix diagram in the fourth technical solution, the visibility of the vertical edges between regions of different working modes is reduced. In addition, FIG. 9b is another schematic diagram of an exemplary digital signal corresponding to one of 256 gray levels in the dot matrix diagram, wherein in the case of using such a dot matrix diagram in the fourth technical solution, the visibility of the horizontal edges between regions of different working modes is reduced. Finally, FIG. 10 is another schematic diagram of an exemplary digital signal corresponding to one of 256 gray levels in the dot matrix diagram, wherein in the case of using such a dot matrix diagram in the fourth technical solution, the radial visibility of the transition between regions of different working modes is reduced. More technical solutions of such dot matrix diagrams or digital signals are also possible. In all technical solutions, preferably, at least three different transmittance values are generated at positions preferably adjacent to the switchable filter 5 for the same angle. That is, the transmittance values for a fixed angle decrease or increase from a maximum value to a minimum value or vice versa along an optional straight line on the surface of the switchable filter 5. Thus, a smooth transition of the transmittance value from a minimum value to a maximum value or from a maximum value to a minimum value is achieved because at least the average value of the transmittance still lies between the two. As described above, it is preferably to use more than three transmittance values (such as five, eight or more than eight) to make the aforementioned transition more continuous and visually more comfortable. The same means-effect relationship applies to all the aforementioned technical solutions. The local location of the minimum transmittance T2 at the optional angle (the angle is, for example, 45° along the horizontal direction of the observer's viewing angle, that is, in the privacy mode at that location on the switchable filter 5) does not immediately follow the location of the maximum transmittance T1, but reflects the average value of the transmittance T3 or at least one of the aforementioned multiple transmittance values T3 between them at a given angle. Overall, "position" refers to a two-dimensional position, which (if any) indicates the same X coordinate and Y coordinate on the surfaces of the first optical element 1 and the switchable filter 5 respectively. Thus, "position" can be applied to both of them, namely the optical element 1 and the switchable filter 5, with the same meaning. The solution of the present invention to achieve the above object lies in: describing a filter, wherein the light incident on the filter is selectively transmitted by such a filter at different positions on the filter or on the screen, or partially or (almost) completely absorbed. Among them, in order to prevent visible edges from appearing when switching at least three working states B1, B2, B3 partially, the transmission behavior can be locally converted specifically for certain angles or directions. In addition, a corresponding screen and an illumination device are also described, the angle-dependent brightness distribution of which can be changed in partial areas, and wherein the visible edges between areas in different modes can also be prevented. The above invention can be advantageously combined with an image reproduction device and is generally used in places where it is necessary to display and / or input confidential data, such as entering a PIN or displaying data on an ATM or a payment terminal, or entering a password, or reading an email on a mobile device. As further described above, the present invention can also be applied to passenger vehicles to avoid disturbing the image content of the driver or passengers. 1: First optical element 3: Liquid crystal layer 5: Switchable filter p: p-polarized light s: s-polarized light T1: Maximum transmittance T2: Minimum transmittance T3: Medium transmittance X: Polarization filter The present invention will now be described in detail with reference to the accompanying drawings that also disclose the essential features of the present invention, in conjunction with embodiments. These embodiments are for illustrative purposes only and do not constitute a limitation. For example, the description of an embodiment containing several elements or components does not mean that all such elements or components are indispensable. Specifically, other embodiments may also include alternative elements and components, reduced elements or components, or additional elements or components. In the absence of other instructions, the elements or components of different embodiments may be combined with each other. The changes and variations described for one of the embodiments may also be applied to other embodiments. To avoid repetition, the same or corresponding elements in different drawings are denoted by the same reference signs and will not be described again. Among them: FIG. 1a is a schematic diagram of the principle of the operation mode of an exemplary switchable filter with locally different transmittances; FIG. 1b is a schematic diagram of the principle of the operation mode of an exemplary switchable filter in three different local operating modes B1, B2, and B3; FIG. 2 is a schematic diagram of the principle of an exemplary structure of the switchable filter in the first technical solution; FIG. 3 is an exemplary normalized transmittance diagram (based on the principle of measurement) of the switchable filter in the horizontal angle range for the maximum transmittance T1 in the first (local) operating mode B1; FIG. 4 is an exemplary normalized transmittance diagram (based on the principle of measurement) of the switchable filter in the horizontal angle range for the minimum transmittance T2 in the second (local) operating mode B2; FIG. 5 is an exemplary normalized transmittance diagram (based on the principle of measurement) of the switchable filter in the horizontal angle range for the first medium transmittance T3 in the third (local) operating mode B3; FIG. 6 is an exemplary normalized transmittance diagram (based on the principle of measurement) of the switchable filter in the horizontal angle range for the second medium transmittance T3 in the third (local) operating mode B3; FIG. 7 is an exemplary normalized transmittance diagram (based on the principle of measurement) of the switchable filter in the horizontal angle range for the third medium transmittance T3 in the third (local) operating mode B3; FIG. 8 is a schematic diagram of the principle of a digital signal corresponding to one of 256 gray levels in the prior art; FIG. 9a is another schematic diagram of the principle of a digital signal corresponding to one of 256 gray levels, in which the visibility of the vertical edges between regions of different operating modes is reduced; FIG. 9b is another schematic diagram of the principle of a digital signal corresponding to one of 256 gray levels, in which the visibility of the horizontal edges between regions of different operating modes is reduced; and FIG. 10 is another schematic diagram of the principle of a digital signal corresponding to one of 256 gray levels, in which the radial visibility of the transition between regions of different operating modes is reduced. 5: Switchable filter T1: Maximum transmittance T2: Minimum transmittance T3: Medium transmittance

Claims

1. A switchable filter (5), comprising: The components for optionally influencing the angle-dependent transmittance of the switchable filter (5) for incident light are characterized in that: the components for influencing the angle-dependent transmittance at least at one point in time at different and adjacent positions on the switchable filter (5) for an optional angle that is correspondingly the same at the aforementioned different and adjacent positions on the switchable filter (5), such that the transmittance values ​​for the fixed angle decrease from a maximum value to a minimum value or increase from a minimum value to a maximum value along an optional straight line on the surface of the switchable filter (5).

2. As in request item 1, the switchable filter (5), wherein, The components used to influence the angle-dependent transmittance of the switchable filter (5) include at least one guest-host LC configuration or PDLC having LC molecules, wherein the orientation of the LC molecules determines the angle-dependent transmittance of the switchable filter (5), and wherein the aforementioned orientation of the LC molecules is different at the aforementioned different positions on the switchable filter (5).

3. As in request item 1, the switchable filter (5), wherein, The components used to affect the angle-dependent transmittance of the switchable filter (5) are integrated in a two- or multi-layer structure, wherein the orientation of the LC molecules responsible for the variable angle-dependent transmittance in the two- or multi-layer structure is different at the aforementioned different positions on the switchable filter (5).

4. The switchable filter (5) of claim 1, comprising a first optical element (1) including a plurality of light absorption transition dipole moments arranged in a layer at least 0.2 micrometers thick, wherein, Most of these transition dipole moments are oriented or fluctuate around a first preferred direction selectable for the first optical element (1), at least in the first state, with a maximum tolerance of 20°. The first preferred direction is arranged at a predetermined angle α relative to the perpendicular bisector of the first optical element (1), wherein the angle α is measured in a selectable first plane including the perpendicular bisector, such that light incident on the first optical element (1) with an incident direction and a polarization state is transmitted or at least partially absorbed according to its incident direction and polarization state relative to the first optical element (1). A component for optionally generating at least one first, second, and third electric field (EF1, EF2, EF3) is provided, wherein the corresponding electric fields (EF1, EF2, EF3) can be selected in different ways for different positions on the switchable filter (5). A liquid crystal layer (3) is arranged behind or in front of the first optical element (1) along the observation direction. The corresponding electric fields (EF1, EF2, EF3) act on the liquid crystal layer and thereby affect the polarization state of the light passing through the liquid crystal layer. A first linear polarizing filter (X) is located in front of the liquid crystal layer (3) along the observation direction. If the liquid crystal layer (3) is arranged in front of the first optical element (1) along the observation direction, The transmittance characteristics of the switchable filter (5) are such that they differ at each position between a first operating mode B1 (where a first electric field (EF1) is applied), a second operating mode B2 (where a second electric field (EF2) is applied), and at least one third operating mode B3 (where a third electric field (EF3) is applied). In each of the three operating modes B1, B2, and B3, the corresponding relative transmittance at each of the aforementioned positions is described, except for optional tolerances, by a first transmittance TB1(β) for the first operating mode B1, a second transmittance TB2(β) for the second operating mode B2, or a third transmittance TB3(β) for the third operating mode B3. These transmittances are related to angle β and are respectively normalized such that, for a transmittance value at a predetermined angle α, TB1(α) = 1, TB2(α) = 1, and TB3(α) = 1. Specifically, when light is at a position in the first operating mode B1 where the first electric field (EF1) is applied, β = α - 40° or β = When the light is incident on the first optical element (1) at an angle (β) of α+40°, the s-polarized component of the light is transmitted at least with a first normalized transmittance value TB1(β) ≥ 0.

25. When the light is incident on the first optical element (1) at an angle (β) of β = α-40° or β = α+40° under the second operating mode B2 where the second electric field (EF2) is applied, the p-polarized component of the light is at most with a second normalized transmittance value TB2(β) ≤ 0.When light is transmitted into the first optical element (1) at a position under the third operating mode B3 where the third electric field (EF3) is applied, at an angle (β) satisfying β = α - 40° or β = α + 40°, the light is transmitted with a third normalized transmittance value TB2(β) < TB3(β) < TB1(β).

5. The switchable filter (5) of claim 1, comprising a first optical element (1) including a plurality of light absorption transition dipole moments arranged in a layer at least 0.2 micrometers thick, wherein, Most of these transition dipole moments are, at least in the first state, oriented parallel to or fluctuating around a first preferred direction selectable for the first optical element (1), with a maximum tolerance of 20°. This first preferred direction is arranged at a predetermined angle α relative to the perpendicular bisector of the first optical element (1), wherein the angle α is measured in a selectable first plane containing the perpendicular bisector, such that light incident on the first optical element (1) is transmitted or at least partially absorbed according to its incident direction and polarization state relative to the first optical element (1). A liquid crystal layer (3) containing liquid crystal molecules is arranged behind or in front of the first optical element (1) along the observation direction. These liquid crystal molecules can be influenced pixel-by-pixel by a locally controllable electric field, such that the electric field influences the polarization state of light penetrating the liquid crystal layer according to the corresponding pixel-by-pixel selectable orientation of the liquid crystal molecules. The locally controllable electric fields are also controlled by a control electronic device, which can be controlled by digital signals, wherein digital signals exist pixel by pixel, and at least one maximum, minimum and intermediate digital signals are selected at at least one time point. When the liquid crystal layer (3) is arranged in front of the first optical element (1) along the viewing direction, the first linear polarizing filter (X) located in front of the liquid crystal layer (3) along the viewing direction produces at least three different transmittance values, namely minimum, medium and maximum transmittance values, at different positions on the switchable filter (5) for an optional angle that is correspondingly the same at the aforementioned different positions on the switchable filter (5), at the time point when the control electronic device is controlled by the aforementioned at least three digital signals.

6. An illumination device for a screen that can operate in at least two operating modes, B1 for a free viewing mode and B2 for a restricted viewing mode, wherein light is emitted to a viewing angle that is more limited for the observer than in the free viewing mode, the illumination device comprising a planar extended backlight that emits light, and a switchable filter (5) of any one of claims 1 to 5 arranged in front of the backlight along the viewing direction.

7. A screen, including an image reproduction device, and a switchable filter (5) of any one of claims 1 to 5 located in front of or behind the image reproduction device along the viewing direction.

8. A screen operable in at least two operating modes, B1 for a free viewing mode and B2 for a restricted viewing mode, wherein light is emitted into a viewing angle that is more limited for the observer compared to the free viewing mode, the screen comprising a transmissive image reproduction device and a backlight disposed downstream of the transmissive image reproduction device along the viewing direction, wherein... The backlight has an asymmetrical luminous density distribution, and the switchable filter (5) of any one of the requests 1 to 5 is located in front of or behind the image reproduction device along the observation direction, wherein the second electric field (EF2) is applied in the operating mode B2, and wherein the first electric field (EF1) is applied in the operating mode B1.

9. A switchable lighting device operable in at least two operating modes, B1 for a free viewing mode and B2 for a restricted viewing mode, wherein light is emitted to a more limited angular range compared to the free viewing mode, the lighting device comprising a planar extended backlight that emits light to a limited angular range in a first alternative and to a non-limited angular range in a second alternative, and a plate-shaped light guide located in front of the backlight along the viewing direction, the light guide having an output coupling element on at least one of the large surfaces and / or within its volume, and lighting equipment laterally arranged on at least one narrow surface of the light guide, wherein... In the first alternative under operating mode B2, the backlight is on and the light-emitting components are off; in operating mode B1, at least the light-emitting components are on; and in the second alternative under operating mode B2, the backlight is off and the light-emitting components are on, wherein in operating mode B1, at least the backlight is on. The backlight and / or the light guide, i.e., in the case of one or two of them emitting light, at least at one point in time, at different and adjacent positions on the backlight and / or the light guide, for a selectable angle that is correspondingly the same at the aforementioned different and adjacent positions, generate more than three different brightness values, such that the brightness values ​​for the fixed angle decrease from a maximum value to a minimum value, or increase from a minimum value to a maximum value, along a selectable straight line on the surface of the lighting device.

10. A switchable screen, comprising at least an image reproduction device, and components for influencing the angle-dependent brightness of the switchable screen, characterized in that: the components for influencing the angle-dependent brightness generate more than three different brightness values ​​at at least one point in time at different and adjacent positions on the switchable screen for an optional angle that is correspondingly the same at the aforementioned different and adjacent positions on the switchable screen, such that the brightness values ​​for the fixed angle decrease from a maximum value to a minimum value or increase from a minimum value to a maximum value along an optional straight line on the surface of the switchable screen.

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