Switchable light filters, lighting devices and screens

Abstract

The present application relates to a switchable light filter (5), comprising a device for selectively influencing the angle-dependent transmittance of the switchable light filter (5) for at least incident light, wherein at least one time, for at least one direction in a hemisphere, said device generates at least three mutually different transmittance values, namely a minimum transmittance value, an intermediate transmittance value, and a maximum transmittance value, for selectable angles that are all the same at a plurality of different positions on the switchable light filter (5). The present invention also provides a switchable lighting device and a switchable screen.

Description

[Technical Field]

[0001] In recent years, great progress has been made in expanding the viewing angle of liquid crystal displays (LCDs). However, in some cases, a very wide viewing angle for a screen can often be a disadvantage. Mobile devices such as laptops and tablet PCs contain increasingly large amounts of information, including banking data and other personal and sensitive data. Therefore, there is a need to control who can view this sensitive data. Users need to be able to choose between a wide viewing angle (public mode) for sharing displayed information, such as travel photos or advertising content, with others, and a narrow viewing angle (private mode) for keeping the displayed information private.

[0002] A similar problem arises in automotive manufacturing: while the vehicle is moving, the driver must not be distracted by screen content such as digital entertainment programs, but passengers want to be able to view the screen content, so a screen that can switch between corresponding display modes is required.

[0003] To protect visual data, mobile displays use add-on films based on microlouver technology. However, these add-on films are either non-switchable or cannot be switched on / off, and must be manually attached and removed. Furthermore, when the add-on film is not needed, it must be carried separately from the display device. Furthermore, a major drawback of such louver films is the light loss that occurs during use. [Background technology]

[0004] US6765550B2 describes the anti-peeping effect of such micro louvers, but the biggest drawback of this technical solution is that the optical filter needs to be mechanically removed and attached, and there is a loss of light in the protection mode.

[0005] US5993940A discloses that a limited viewing mode with a narrow viewing angle range is realized by using a film with small strip-shaped prisms uniformly arranged on the film surface. However, the technical difficulty of developing and manufacturing such a film is extremely high.

[0006] In WO2012 / 033583A1, the switching between free and restricted modes is controlled by liquid crystals between the so-called "color" layers, which causes light losses and is technically very difficult.

[0007] US 2012 / 0235891 A1 describes a fairly complex screen backlight. As shown in Figures 1 and 15 of the document, not only are multiple light guides used, but complex optical elements such as microlens elements 40 and prism structures 50 are also used to convert rearward-illuminating light into forward-illuminating light. This is expensive, complex, and results in light loss. In a variation described in Figure 17 of US 2012 / 0235891 A1, both light sources 4R and 18 generate light with a narrow viewing angle, so the light from rearward-illuminating light source 18 must first be converted to light with a wide viewing angle through a complex conversion process. As previously mentioned, this complex conversion process significantly reduces brightness.

[0008] US 2013 / 0308185 A1 describes a special stepped light guide that emits light onto a large surface from different directions depending on which narrow side of the light guide is illuminated. It can be combined with a transmissive image display device (e.g., a liquid crystal display) to create a screen that can be switched between free-viewing mode and limited-viewing mode. Its drawback is that the limited-viewing effect can only be applied to the left / right or top / bottom sides, and cannot be applied to the left / right / top / bottom sides simultaneously, which is necessary for some payment transactions. Furthermore, even in limited-viewing mode, residual light can be seen from blocked angles.

[0009] The applicant's WO 2015 / 121398 A1 describes a screen with two operating modes, in which scattering particles present within the volume of the corresponding light guide plate are primarily used to switch between operating modes. However, polymeric scattering particles generally have the disadvantage of emitting light from two large surfaces, resulting in approximately half of the available light being emitted in the wrong direction, i.e., toward the backlight, and due to structural reasons, this light cannot be recycled to a sufficient extent. Furthermore, in some cases, especially at high concentrations, the polymeric scattering particles present within the volume of the light guide plate can cause scattering effects that reduce the anti-peeping effect in the protective mode.

[0010] The core idea of ​​"electric birefringence (EDB)" technology is to use switchable liquid crystals in an additional LCD panel to "filter" the light emitted from the image layer at a specific angle. However, this technology has several drawbacks, including additional energy consumption, high cost, and difficulty in adjusting the optimal viewing angle (i.e., the optimal observation position), which is usually fixed at around ±40°. Furthermore, the light absorption ability of the liquid crystal structure is insufficient, and the light intensity is not sufficiently attenuated at viewing angles greater than the optimal viewing angle. Even at viewing angles exceeding ±40°, the light intensity reaches 3% of the maximum light intensity.

[0011] The above methods and devices generally suffer from the following drawbacks: a significant reduction in the brightness of the base screen; and / or the need for complex and expensive optics for mode switching; and / or reduced resolution in free-view and public modes; and / or the occurrence of visual artifacts on very high resolution displays, particularly for partial switching between modes, which may result in objectionable edges in the areas between the different modes. Summary of the Invention

[0012] The object of the present invention is to provide a light filter in which light incident on the light filter is selectively transmitted or partially or (almost) completely absorbed at different positions on the light filter or on a screen equipped with the light filter. At least three operating modes are possible to prevent visible edges during partial switching and to allow for a change in transmittance, especially at specific angles or directions. Also provided are corresponding screens or lighting devices that allow for partial and local changes in the angle-dependent luminance distribution. Visible edges between regions in different modes can also be prevented.

[0013] The above objects are achieved by the switchable optical filter of the present invention.

[0014] The optical filter includes a device for selectively affecting the angle-dependent transmittance of the switchable optical filter for incident light, the device for affecting the angle-dependent transmittance generating, at least one time, at least three mutually distinct transmittance values, i.e., a minimum transmittance value, a median transmittance value, and a maximum transmittance value, for all the same selectable angles at a plurality of different positions on the switchable optical filter for at least one direction of the hemisphere. This does not necessarily apply to multiple or all possible angles, but to at least one all-the-same selectable angle. The term "median value" is merely a designation and may, but does not necessarily, refer precisely to the average of the minimum and maximum values. Preferably, in one embodiment, at least five, eight, or more mutually distinct transmittance values ​​are generated at the corresponding five, eight, or more positions.

[0015] To utilize a light filter according to the present invention, it is beneficial to have a device for generating linearly polarized light, such as a liquid crystal panel with a polarizer, or a polarizing filter if other image or light sources are present.

[0016] In a first aspect, an apparatus for selectively influencing the angle-dependent transmittance of a switchable light filter comprises at least one guest-host liquid crystal array or polymer-dispersed liquid crystal, each having a plurality of liquid crystal molecules, wherein the orientation of the plurality of liquid crystal molecules determines the angle-dependent transmittance of the switchable light filter, and the orientations of the plurality of liquid crystal molecules are different at the plurality of different positions on the switchable light filter.

[0017] In contrast, in a second aspect, the device for selectively influencing the angle-dependent transmittance of a switchable optical filter is integrated into a double-cell or multi-cell structure, in which the orientations of the liquid crystal molecules, each responsible for a variable angle-dependent transmittance, are different at the different positions on the switchable optical filter.

[0018] In a third aspect, a switchable optical filter includes a first optical element; the first optical element includes a plurality of absorption transition dipole moments; a device for selectively applying at least one of a first electric field EF1, a second electric field EF2, or a third electric field EF3; a liquid crystal layer; and a first linear polarizing filter; the plurality of absorption transition dipole moments are disposed in a layer having a thickness of at least 0.2 μm, wherein the plurality of transition dipole moments are, at least in a first state, disposed to be parallel to or vary about a selectable first preferred direction of the first optical element with a tolerance of up to 20°, the first preferred direction being disposed at a predetermined angle α with respect to a perpendicular bisector of the first optical element, the angle α being measured in a selectable first plane containing the perpendicular bisector; whereby a light ray having an incident direction and polarization state incident on the first optical element is transmitted or at least partially absorbed depending on the incident direction and polarization state of the light ray relative to the first optical element; with respect to the device for selectively applying the at least one first electric field EF1, second electric field EF2, or third electric field EF3, wherein the first electric field EF1, the second electric field EF2, and the third electric field EF3 can all be differently applied to a plurality of different locations on the switchable optical filter; the liquid crystal layer is disposed in front of or behind the first optical element along a viewing direction, and the first electric field EF1, the second electric field EF2, and the third electric field EF3 all act on the liquid crystal layer to affect the polarization state of the light beam passing through the liquid crystal layer by the electric fields; the first linear polarizing filter is disposed in front of the liquid crystal layer along the observation direction when the liquid crystal layer is disposed in front of the first optical element along the observation direction; This allows the transmission characteristics of the switchable optical filter 5 to be different among a first operation mode B1 in which the first electric field EF1 is applied, a second operation mode B2 in which the second electric field EF2 is applied, and at least one third operation mode B3 in which the third electric field EF3 is applied, and wherein the corresponding transmittances in the first operation mode B1, the second operation mode B2, and the third operation mode B3 are each different from the first transmittance T corresponding to the first operation mode B1 at any position within a selectable tolerance range. B1 (β), a second transmittance T corresponding to the second operating mode B2 B2 (β), and a third transmittance T corresponding to the third operating mode B3. B3 (β), and the first transmittance, the second transmittance, and the third transmittance are all normalized with respect to angle β so that the transmittance values ​​are normalized with respect to the predetermined angle α. B1 (α)=1, T B2 (α)=1, and T B3 (α)=1 is satisfied, Here, when a light ray is incident on the first optical element at the angle β that satisfies β=α−40° or β=α+40°, the s-polarized component of the light ray exhibits at least a first transmittance value T after normalization at a plurality of positions in a first operation mode B1 in which the first electric field EF1 is applied. B1(β)≧0.25 is transmitted, When a light ray is incident on the first optical element at an angle β that satisfies β=α−40° or β=α+40°, the p-polarized component of the light ray exhibits at least a second transmittance value T B2 (β)≧0.2 is transmitted, When a light ray is incident on the first optical element at the angle β that satisfies β=α−40° or β=α+40°, the light ray exhibits a third transmittance value T after normalization at a plurality of positions in a third operation mode B3 in which the third electric field EF3 is applied. B2 (β) <T B3 (β) <T B1 (β) is transmitted.

[0019] S-polarized light is light whose electric field direction is perpendicular to the plane of incidence of the medium, and P-polarized light is light whose electric field direction is parallel to the plane of incidence. The plane of incidence is determined by the normal to the medium interface and the direction of incidence.

[0020] In a fourth aspect, a switchable optical filter includes a first optical element; the first optical element includes a plurality of absorbing transition dipole moments; a liquid crystal layer having a plurality of liquid crystal molecules; and a first linear polarizing filter; the plurality of absorption transition dipole moments are disposed in a layer having a thickness of at least 0.2 μm, wherein the plurality of transition dipole moments are, at least in a first state, disposed to be parallel to or vary about a selectable first preferred direction of the first optical element with a tolerance of up to 20°, the first preferred direction being disposed at a predetermined angle α with respect to a perpendicular bisector of the first optical element, the angle α being measured in a selectable first plane containing the perpendicular bisector; whereby light rays incident on the first optical element are transmitted or at least partially absorbed depending on the incident direction and the polarization state relative to the first optical element; a liquid crystal layer having a plurality of liquid crystal molecules is arranged in front of or behind the first optical element along a viewing direction, and orientations of the plurality of liquid crystal molecules are influenced on a pixel-by-pixel basis by a locally controllable electric field, and the liquid crystal layer can influence the polarization state of the light beam passing through the liquid crystal layer according to the pixel-by-pixel selectable orientations of each of the plurality of liquid crystal molecules; wherein the locally controllable electric field is controlled by a control circuit, the control circuit is controlled by a plurality of digital signals, the plurality of digital signals are present for each pixel, and at least one maximum digital signal, one minimum digital signal, and a digital signal located between the maximum digital signal and the minimum digital signal are selected at at least one time point; the first linear polarizing filter is located in front of the liquid crystal layer along the observation direction when the liquid crystal layer is located in front of the first optical element along the observation direction; This allows, at a given time, when the control circuit performs control using the at least three digital signals, to generate at least three different transmittance values ​​of the transmittance, i.e., a minimum transmittance value, a middle transmittance value, and a maximum transmittance value, for the same selectable angle at multiple different positions on the switchable optical filter.

[0021] The corresponding digital signals may correspond to one of 256 grayscales stored in a bitmap file, for example. Optionally, these digital signals may be dynamically adjusted.

[0022] Particularly preferably, in all embodiments, for the same selectable angle, at least three mutually different transmittance values ​​are generated at a plurality of positions of the switchable optical filter (5), preferably the positions being directly adjacent to each other. That is, for a fixed angle, the transmittance decreases from a maximum value to a minimum value or vice versa along a selectable straight line on the surface of the switchable optical filter. At least intermediate transmittance values ​​are spatially located between them, so that a smoother transition from the minimum transmittance value to the maximum transmittance value (or vice versa) can be achieved.

[0023] As mentioned above, to make the transition more continuous and visually pleasing, it may be necessary to arrange more than two transmittance values ​​(e.g., five, eight, or more).

[0024] The same transmission property relationship applies to all the above embodiments: at a certain angle (e.g., when the observer's horizontal angle is 45°, i.e., when the switchable light filter is in privacy mode at this position), instead of a minimum transmission at a local position being followed immediately by a maximum transmission position, there is either at least one intermediate position reflecting the average transmission at this angle, or there are multiple intermediate transmission positions as described above.

[0025] The third and fourth embodiment variants can be rephrased as follows for specific embodiments:

[0026] Preferably, polarized light is incident on the liquid crystal layer and the first optical element, and the dichroic dye is arranged parallel or perpendicular to the substrate surface. The electrodes E1 and E2 can apply locally different first and second electric fields EF1 and EF2 to select transmission characteristics. By statically and / or dynamically superimposing the first and second electric fields EF1 and EF2, specific intermediate values ​​of transmittance can be generated, thereby minimizing the perceptibility of edges between the locations with the first and second electric fields, respectively.

[0027] Generally, the term "position" (if present) refers to a two-dimensional coordinate position that indicates the same X and Y coordinates on the surface of the first optical element 1 and the switchable optical filter 5, respectively. Therefore, "position" can be used synonymously for both (i.e., optical element and optical filter).

[0028] If present, the first optical element and / or the liquid crystal layer may be divided into a plurality of independently switchable segments, thereby allowing localized switching between various possible operating states.

[0029] In certain embodiments, the switchable optical filter may include at least two first optical elements, optionally with a retardation plate disposed between the at least two first optical elements.

[0030] The present invention further includes an illumination device for a screen, the illumination device being operable in at least a first operating mode B1 for a free-viewing mode and a second operating mode B2 for a limited-viewing mode, in which a viewing angle from which light rays are emitted for a viewer is limited relative to the free-viewing mode, the illumination device comprising: a flat extended backlight for emitting light, optionally arranged to emit light directly; and a switchable light filter disposed in front of the backlight along a viewing direction;

[0031] The present invention further includes a screen, the screen being operable in at least a first operating mode B1 for a free-viewing mode and a second operating mode B2 for a limited-viewing mode, and in the limited-viewing mode, a viewing angle at which light rays are emitted for a viewer is limited relative to the free-viewing mode, and the screen is a lighting device as described above; a second linear polarization filter arranged in front of the backlight along the viewing direction when the first linear polarization filter is not arranged in the switchable optical filter of the illumination device, so that light rays emitted from the backlight and transmitted through the second linear polarization filter are restricted in their propagation direction; and a transmissive image display device disposed in front of a switchable optical filter along a viewing direction; Here, in the second operation mode B2, the second electric field EF2 is applied, and in the first operation mode B1, the first electric field EF1 is applied. The first linear deflection filter or the second linear deflection filter may be disposed in the transmissible image display device or may be a part of the transmissible image display device.

[0032] The object of the present invention can also be achieved by a screen, the screen comprising: Image display device; and The switchable optical filter (5) is arranged in front of or behind the image display device along the viewing direction. Here, the switchable optical filter 5 can be installed later by the user and / or can be pre-installed in the image display device.

[0033] The present invention further includes a screen, the screen being operable in at least a first operation mode B1 for a free-viewing mode and a second operation mode B2 for a limited-viewing mode, and in the limited-viewing mode, a viewing angle at which light rays are emitted for a viewer is limited compared to the free-viewing mode, and the screen is a transmissive image display device, preferably an LC panel; a backlight arranged behind the transmissible image display device along a viewing direction and having an asymmetric light density distribution, preferably the asymmetry being with respect to the horizontal direction of the viewer (i.e. parallel to the direction of an imaginary line connecting the viewer's eyes); a switchable optical filter disposed in front of or behind the transmissive image display device along a viewing direction;

[0034] The present invention can also be realized by a lighting device for a screen, which is operable in at least a first operating mode B1 for a free-viewing mode and a second operating mode B2 for a limited-viewing mode, and in the limited-viewing mode, a viewing angle from which light rays are emitted for a viewer is limited compared to the free-viewing mode, and the lighting device for the screen is a planar extended backlight emitting light rays within a limited angular range, preferably arranged to emit light directly; a light guide arranged in front of the backlight along the viewing direction, the light guide having at least one large surface and / or a plurality of output elements within its volume; and a light source disposed laterally adjacent at least one short side of the light guide; Preferably, a linear polarizing filter; and a switchable optical filter disposed in front of the backlight along a viewing direction; Here, in the second operation mode B2, the backlight is turned on and the light source is turned off, and in the first operation mode B1, at least the light source is turned on.

[0035] Alternatively, the lighting device for the screen is operable in at least a first operating mode B1 for a free-viewing mode and a second operating mode B2 for a limited-viewing mode, in which a viewing angle from which light rays are emitted for a viewer is limited relative to the free-viewing mode, and the lighting device for the screen is a planar extended backlight emitting light rays within an unrestricted angular range, preferably arranged to emit light directly; a light guide located in front of the backlight along the viewing direction, the light guide having at least one large surface and / or a plurality of exit elements within its volume, the exit elements coupling out a majority of the light that couples in from at least one short side of the light guide within a limited angular range; and a light source disposed laterally adjacent at least one short side of the light guide; Preferably, a linear polarizing filter; and a switchable optical filter disposed in front of the backlight along a viewing direction; Here, in the second operation mode B2, the backlight is turned on and the light source is turned off, and in the first operation mode B1, at least the light source is turned on.

[0036] A switchable lighting device is operable in at least a first operating mode B1 for a free viewing mode and a second operating mode B2 for a limited viewing mode, in which the viewing angle from which light rays are emitted for a viewer is restricted relative to the free viewing mode, and the switchable lighting device achieves the same technical effect as described above. a planar extended backlight emitting light rays within a first alternative, a limited angular range, and a second alternative, an unlimited angular range; a light guide arranged in front of the backlight along the viewing direction, the light guide having at least one large surface and / or a plurality of output elements within its volume; and a light source disposed laterally adjacent at least one short side of the light guide; wherein in the first alternative, the backlight is turned on and the light source is turned off in the second operating mode B2, and at least the light source is turned on in the first operating mode B1; and in the second alternative, the backlight is turned off and the light source is turned on in the second operating mode B2, and at least the backlight is turned on in the first operating mode B1; For the backlight and / or the light guide, when one or both of the backlight and the light guide emit light rays, at least three different brightness values, namely a minimum brightness value, a middle brightness value, and a maximum brightness value, are generated at a plurality of different positions on the backlight and / or the light guide at at least one time for selectable angles that are all the same at the plurality of different positions.

[0037] Likewise, the explanations of the above embodiments also apply here. Particularly preferably, at least three different transmittance values ​​are generated at a plurality of adjacent (preferably directly adjacent) positions of the backlight and / or light guide, all at the same angle.

[0038] Finally, the present invention also includes a switchable screen having the same technical effect when applied, said switchable screen comprising: at least an image display device; and a device for influencing the angle-dependent brightness of said switchable screen; The device for influencing the angle-dependent brightness of the switchable screen generates, at at least one point in time, at a plurality of different positions on the switchable screen, at least three mutually different brightness values, namely a minimum brightness value, a middle brightness value and a maximum brightness value, for selectable angles that are all the same at the plurality of different positions.

[0039] To realize a device for influencing said angle-dependent brightness, controllable angle-dependent absorption, reflection, or contrast and scattering techniques can be used.

[0040] The optical filter, lighting device, or such screen can be advantageously applied to mobile devices, vehicles, aircraft, ships, payment terminals, or access control systems. By switching between the above operating modes, sensitive data can be protected (i.e., visual content is only displayed to a single observer), and multiple observers can simultaneously observe the image content.

[0041] Essentially, the performance of the present invention can be maintained when the above parameters are varied within certain ranges.

[0042] It is understood that the features mentioned above and those to be described below may be used not only in the corresponding combinations shown, but also in other combinations or alone, without departing from the scope of the invention. [Brief explanation of the drawings]

[0043] The present invention will be described in detail below using embodiments in conjunction with the accompanying drawings. These embodiments also disclose essential technical features of the present invention. These embodiments are for illustrative purposes only, and their contents should not be construed as limiting the scope of protection. For example, a description of an embodiment including multiple elements or components should not be construed as meaning that all of these elements or components are essential for implementation. More specifically, other embodiments can be implemented by using alternative elements or components, reducing the number of elements, or adding additional elements. Unless otherwise specified, elements or components of different embodiments can be combined with each other. Changes and modifications described in one embodiment may also be applied to other embodiments. To avoid redundancy, identical or corresponding elements in different drawings will be given the same figure numbers and will not be described separately. These elements will be described below respectively. [Figure 1a] FIG. 1a is a schematic diagram of the working principle of an exemplary switchable optical filter with locally different transmittance. [Figure 1b] FIG. 1b is a schematic diagram illustrating the operation principle of an exemplary switchable optical filter in locally different operation modes B1, B2 and B3. [Figure 2] FIG. 2 is a schematic diagram illustrating an exemplary structure of the switchable optical filter in the first embodiment. [Figure 3]FIG. 3 is an exemplary normalized transmittance graph (schematic diagram simulated by actual measurement data) over a range of horizontal angles for maximum transmittance T1 in a first (local) operation mode B1 of a switchable optical filter. [Figure 4] FIG. 4 is an exemplary normalized transmittance graph (schematic diagram simulated by actual measurement data) over a range of horizontal angles for the minimum transmittance T2 in the second (local) operation mode B2 of the switchable optical filter. [Figure 5] FIG. 5 is an exemplary normalized transmittance graph (schematic diagram simulated by actual measurement data) over a range of horizontal angles for the first intermediate transmittance T3 in the third (local) operation mode B3 of the switchable optical filter. [Figure 6] FIG. 6 is an exemplary normalized transmittance graph (schematic diagram simulated by actual measurement data) over a range of horizontal angles for the second intermediate transmittance T3 in the third (local) operation mode B3 of the switchable optical filter. [Figure 7] FIG. 7 is an exemplary normalized transmittance graph (schematic diagram simulated by actual measurement data) over a range of horizontal angles for a third intermediate transmittance T3 in a third (local) operation mode B3 of the switchable optical filter. [Figure 8] FIG. 8 is a schematic diagram of a digital signal corresponding to one gray scale among 256 gray scales in the prior art. [Figure 9a] FIG. 9a is another schematic diagram of a digital signal corresponding to one of 256 grayscales, where the visibility of vertical edges between regions of different operating modes is reduced. [Figure 9b] FIG. 9b is another schematic diagram of a digital signal corresponding to one of 256 grayscales, where the visibility of horizontal edges between regions of different operating modes is reduced. [Figure 10] FIG. 10 is another schematic diagram of a digital signal corresponding to one of 256 gray scales, where the radial visibility of the transitions between regions of different operating modes is reduced. DETAILED DESCRIPTION OF THE INVENTION

[0044] The drawings are for illustrative purposes only and are not drawn to scale.

[0045] 1a is a schematic diagram of the operating principle of an exemplary switchable optical filter with locally different transmittances. A region of minimum transmittance T2 is completely surrounded by a region of intermediate transmittance T3, which is in turn completely surrounded by a region of maximum transmittance T1. However, other embodiments may be employed.

[0046] Such an exemplary switchable optical filter 5 includes: The switchable optical filter (5) includes a device for selectively influencing the angle-dependent transmittance of at least incident light, wherein the device for influencing the angle-dependent transmittance generates, at least one time, for at least one direction of the hemisphere, at least three mutually distinct transmittance values ​​for all the same selectable angles at different positions on the switchable optical filter (5): a minimum transmittance value, a median transmittance value, and a maximum transmittance value. This does not necessarily apply to multiple or all possible angles, but to at least one all-the-same selectable angle. The term "median value" is merely a designation and may, but does not necessarily, refer precisely to the average of the minimum and maximum values. Preferably, in one embodiment, at least five, eight, or more mutually distinct transmittance values ​​are generated at corresponding five, eight, or more positions.

[0047] To utilize a light filter according to the present invention, it is beneficial to have a device for generating linearly polarized light, such as a liquid crystal panel with a polarizer, or a polarizing filter if other image or light sources are present.

[0048] 1b is a schematic diagram illustrating the operation principle of an exemplary switchable optical filter 5 in locally different operating modes B1, B2 and B3. a. A first optical element 1, wherein the first optical element 1 comprises: i. an absorbing transition dipole moment disposed in a layer having a thickness of at least 0.2 μm; ii. wherein the plurality of transition dipole moments are, at least in a first state, arranged to be parallel to or fluctuating around a selectable first preferred direction of the first optical element 1 with a tolerance of up to 20°, the first preferred direction being arranged at a predetermined angle α with respect to a perpendicular bisector of the first optical element 1, the angle α being measured in a selectable first plane containing the perpendicular bisector; iii. whereby light rays incident on the first optical element (1) are transmitted or at least partially absorbed depending on the direction and polarization of incidence on the first optical element (1); b. a device for selectively applying at least one of a first electric field EF1, a second electric field EF2, or a third electric field EF3, each of which can be differently applied to a plurality of different locations on the switchable optical filter 5; c. a liquid crystal layer 3 disposed in front of or behind the first optical element 1 along the observation direction, the first electric field EF1, the second electric field EF2, and the third electric field EF3 all acting on the liquid crystal layer 3 to affect the polarization state of the light passing through the liquid crystal layer 3; d. a first linear polarizing filter X located in front of the liquid crystal layer 3 along the viewing direction when the liquid crystal layer 3 is located in front of the first optical element 1 along the viewing direction; e. This allows the transmission characteristics of the switchable optical filter (5) to be different among a first operating mode B1 in which a first electric field (EF1) is applied, a second operating mode B2 in which a second electric field (EF2) is applied, and at least one third operating mode B3 in which a third electric field (EF3) is applied, wherein the corresponding transmittances in the first operating mode B1, the second operating mode B2, and the third operating mode B3 are each different from the first transmittance T corresponding to the first operating mode B1 at any position within a selectable tolerance range. B1 (β), a second transmittance T corresponding to the second operating mode B2 B2 (β), and a third transmittance T corresponding to the third operating mode B3. B3 (β), and the first transmittance, second transmittance, and third transmittance are all normalized with respect to angle β so that the transmittance values ​​are normalized to T for a given angle α. B1 (α)=1, T B2 (α)=1, and T B3 Ensure that (α)=1 is satisfied; f. Specifically, i. When a light ray is incident on the first optical element (1) at an angle β that satisfies β=α−40° or β=α+40°, the s-polarized component of the light ray exhibits at least a first transmittance value T after normalization at a plurality of positions in a first operating mode B1 where the first electric field EF1 is applied. B1 (β) ≥ 0.25 is transmitted; ii. At a plurality of positions in a second operating mode B2 where the second electric field (EF2) is applied, the p-polarized component of the light beam exhibits at least a second normalized transmittance value T B2 (β) ≥ 0.2 and transmitted; and iii. At a plurality of positions in a third operating mode B3 where the third electric field EF3 is applied, the light beam exhibits a third normalized transmittance value T B2 (β) <T B3 (β) <T B1 (β) is transmitted.

[0049] The letters "S" and "P" refer to S-polarized or P-polarized light, respectively. In a local operating mode B3 with an intermediate transmittance T3, when |β-a|>30°, only some light rays (i.e., S-polarized light) are transmitted to the side, and most of the P-polarized light is absorbed by the first optical element 1. The values ​​of TB2(β), TB3(β), or TB1(β) can be correlated or equivalent to the transmittances T2, T3, or T1, respectively, at one (or more) selected fixed angles β.

[0050] Regarding the normalization of the transmittances TB1(α) = 1 and TB2(α) = 1, the following should be noted: Obviously, the angles β and α must be measured in the same plane as mentioned above. In principle, it is also possible that TB1(α) > 1 and / or TB2(α) > 1 applies when the angle β ≠ α, but in most cases TB1(α) < 1 and / or TB2(α) < 1 applies when the angle β ≠ α.

[0051] For clarity, in Fig. 1, the value of the angle α is greater than 0°. In all subsequent discussions, α = 0° applies as a rule. A value of α ≠ 0° may result in a tilt of the preferential transmission direction (i.e., the direction of maximum transmission) of the switchable optical filter 5.

[0052] Advantageously, the multiple transition dipole moments are constituted by one or more dichroic dyes mixed with the liquid crystal in a guest-host configuration. For permanent transition dipole moments, the liquid crystal can be fixed by a curing process. The dichroic dye molecules are usually aligned parallel to the liquid crystal molecules.

[0053] For example, the first preferred direction may form an angle of 0° to 45° with respect to the surface normal of the first optical element 1. The first preferred direction may also vary on the surface of the first optical element 1. In the present invention, an average weighted preferred direction is applied.

[0054] 2 is a schematic diagram illustrating an exemplary structure of the switchable optical filter 5 in the first embodiment. Here, the liquid crystal layer 3 is arranged in front of the first optical element 1 along the viewing direction (from top to bottom). This first embodiment also includes a first linear polarizing filter X arranged in front of the liquid crystal layer 3 along the viewing direction, and preferably, the polarized light transmission direction is parallel to the edge (preferably the lower edge) of the first optical element 1.

[0055] 3 is an exemplary normalized transmittance graph (schematic diagram simulated by actual measurement data) of the maximum transmittance T1 over a range of horizontal angles in the first (local) operation mode B1 of the switchable optical filter 5. For selectable angles, the (normalized) maximum transmittance T1 can be selected here.

[0056] 4 is an exemplary normalized transmittance graph (schematic diagram simulated by actual measurement data) of the minimum transmittance T2 in the second (local) operation mode B2 of the switchable optical filter over a range of horizontal angles. For selectable angles, the (normalized) minimum transmittance T2 can be selected here.

[0057] 5 is a diagram showing an example of a normalized transmittance graph (simulated by actual measurement data) of the first intermediate transmittance T3 in the third (local) operating mode B3 of the switchable optical filter over a range of horizontal angles. For selectable angles, the (normalized) first intermediate transmittance T3 can be selected here.

[0058] 6 is an exemplary normalized transmittance graph (schematic diagram simulated by actual measurement data) of the second intermediate transmittance T3 in the third (local) operation mode B3 of the switchable optical filter over a range of horizontal angles. For selectable angles, the (normalized) second intermediate transmittance T3 can be selected.

[0059] 7 is a diagram showing an example of a normalized transmittance graph (simulated by actual measurement data) of the third intermediate transmittance T3 in the third (local) operation mode B3 of the switchable optical filter over a range of horizontal angles. For selectable angles, the (normalized) third intermediate transmittance T3 can be selected here.

[0060] For example, based on the graphs shown in FIGS. 3 to 7, they can be actually generated based on the third embodiment described above with reference to FIGS. 1b and 2. FIG.

[0061] In addition, in the fourth embodiment, the switchable optical filter 5 further includes a first optical element 1 as shown in FIG. 1 and FIG. 2, the first optical element 1 including: a plurality of absorption transition dipole moments; a liquid crystal layer 3 having a plurality of liquid crystal molecules; and a first linear polarizing filter X; a plurality of absorption transition dipole moments disposed in a layer having a thickness of at least 0.2 μm, wherein the plurality of transition dipole moments are, at least in a first state, arranged to be parallel to a selectable first preferred direction of the first optical element 1 with a tolerance of up to 20° or to vary about the first preferred direction, the first preferred direction being arranged at a predetermined angle α with respect to a perpendicular bisector of the first optical element 1, the angle α being measured in a selectable first plane containing the perpendicular bisector; Thereby, a light ray incident on the first optical element 1 is transmitted or at least partially absorbed depending on the incident direction and polarization state with respect to the first optical element 1, a liquid crystal layer (3) having a plurality of liquid crystal molecules is arranged in front of or behind the first optical element (1) along the observation direction, the orientation of the plurality of liquid crystal molecules is influenced for each pixel by a locally controllable electric field, and the liquid crystal layer (3) can influence the polarization state of light passing through the liquid crystal layer (3) according to the pixel-selectable orientation of each of the plurality of liquid crystal molecules, wherein the locally controllable electric field is controlled by a control circuit, and the control circuit is controlled by a plurality of digital signals, the plurality of digital signals exist for each pixel, and at least one maximum digital signal, one minimum digital signal, and a digital signal located between the maximum digital signal and the minimum digital signal are selected at at least one time point; the first linear polarizing filter X is located in front of the liquid crystal layer 3 along the observation direction when the liquid crystal layer 3 is located in front of the first optical element 1 along the observation direction; This allows the control circuit to generate at least three different transmittance values, namely a minimum transmittance value T2, a middle transmittance value T3, and a maximum transmittance value T1, for the same selectable angle at multiple different positions on the switchable optical filter 5 when the control circuit uses at least three digital signals for control at a time.

[0062] For example, the corresponding digital signal can correspond to one of 256 gray scales stored in a bitmap file, for example. Optionally, these digital signals can be dynamically adjusted. Such digital signals can also be used to generate electronic control of the first electric field EF1, the second electric field EF2, and the third electric field EF3 in the third embodiment, but can also be used in the first and second embodiments described above, the corresponding variations of the dual-cell panel structure, or other embodiments. Figure 8 is a schematic diagram of a digital signal corresponding to one of 256 gray scales in the prior art. When applied to the variation of the fourth embodiment according to the bitmap in Figure 8, a viewer can see a clear edge between the left region of the first operating mode B1 and the right region of the second operating mode B2 by simply moving their head slightly (e.g., a few centimeters).

[0063] FIG. 9a is another schematic diagram of a digital signal corresponding to one grayscale out of 256 grayscales, where the use of such a bitmap in the fourth embodiment reduces the visibility of vertical edges between regions of different operating modes.

[0064] FIG. 9b is another schematic diagram of an exemplary digital signal corresponding to one grayscale out of 256 grayscales in a bitmap, where the use of such a bitmap in the fourth embodiment reduces the visibility of horizontal edges between regions of different operating modes.

[0065] FIG. 10 is another schematic diagram of an exemplary digital signal corresponding to one of 256 grayscales in a bitmap, where the use of such a bitmap in the fourth embodiment reduces the radial visibility of the transitions between regions of different operating modes.

[0066] There are several other embodiments of such bitmaps and digital signals.

[0067] Particularly preferably, in all embodiments, for the same selectable angle, at least three mutually different transmittance values ​​are generated at a plurality of positions of the switchable optical filter (5), preferably the positions being directly adjacent to each other. That is, for a fixed angle, the transmittance decreases from a maximum value to a minimum value or vice versa along a selectable straight line on the surface of the switchable optical filter. At least intermediate transmittance values ​​are spatially located between them, so that a smoother transition from the minimum transmittance value to the maximum transmittance value (or vice versa) can be achieved.

[0068] As mentioned above, to make the transition more continuous and visually pleasing, it may be necessary to arrange more than two transmittance values ​​(e.g., five, eight, or more).

[0069] The same transmission property relationship applies to all the above embodiments: at a certain angle (e.g., when the observer's horizontal angle is 45°, i.e., when the switchable light filter is in privacy mode at this position), the local location of minimum transmittance T2 is not immediately adjacent to the location of maximum transmittance T1, but is at least one location exhibiting an intermediate value of transmittance T3 at the given angle, or at least one location of several transmittance values ​​therebetween, as described above.

[0070] Generally, the term "position" (if present) refers to a two-dimensional coordinate position that indicates the same X and Y coordinates on the surface of the first optical element 1 and the switchable optical filter 5, respectively. Therefore, "position" can be used synonymously for both (i.e., optical element and optical filter).

[0071] The present invention has been made to solve the above-mentioned problems, and its object is to provide an optical filter in which light incident on the optical filter is selectively transmitted or partially or (almost) completely absorbed at different positions on the optical filter or on a screen equipped with the optical filter, whereby the light can be locally transformed, particularly for specific angles or directions, to prevent the appearance of visible edges when partially switching between at least three operating modes B1, B2, and B3. Also described are corresponding screens and lighting devices, whose angle-related luminance distribution can be partially and regionally modified, but also to prevent the appearance of visible edges between regions of different operating modes.

[0072] The present invention can be used in combination with an image display device and is applicable to situations where private data needs to be displayed and / or entered. For example, entering a PIN code or display data at an ATM or payment terminal, entering a password, or viewing email on a mobile device. Thus, the present invention can also be applied to passenger vehicles, where image content can be selectively prevented from interfering with the driver or passenger in the front seat. [Explanation of symbols]

[0073] 1. First Optical Element 3 Liquid crystal layer 5 Switchable Optical Filters PP Polarized SS Polarized T1 maximum transmittance T2 minimum transmittance T3 intermediate transmittance X polarizing filter

Claims

1. A switchable optical filter (5), a device for selectively influencing the angle-dependent transmittance of the switchable optical filter (5) for incident light, A switchable optical filter (5), characterized in that the device for influencing angle-dependent transmittance generates, at at least one time point, for at least one direction of the hemisphere, at least three mutually different transmittance values, namely a minimum transmittance value, an intermediate transmittance value and a maximum transmittance value, for selectable angles that are all the same at different positions on the switchable optical filter (5).

2. The device for selectively influencing the angle-dependent transmittance of a switchable optical filter (5) comprises at least one guest-host liquid crystal arrangement or a polymer dispersed liquid crystal, each having a plurality of liquid crystal molecules; The switchable optical filter (5) of claim 1, characterized in that the orientations of the liquid crystal molecules respectively determine the angle-dependent transmittance of the switchable optical filter (5), and the orientations of the liquid crystal molecules are different at the different positions on the switchable optical filter (5).

3. a device for selectively influencing the angle-dependent transmittance of a switchable optical filter (5) integrated into a double-cell or multi-cell structure, 2. The switchable optical filter (5) of claim 1, wherein in the double cell structure or the multi-cell structure, the orientations of the liquid crystal molecules, each responsible for a variable angle-dependent transmittance, are different at the different positions on the switchable optical filter (5).

4. A switchable optical filter (5) comprising a first optical element (1), The first optical element (1) comprises a plurality of absorption transition dipole moments; a device for selectively applying at least one of a first electric field (EF1), a second electric field (EF2), or a third electric field (EF3); a liquid crystal layer (3); and a first linear polarizing filter (X); the plurality of absorption transition dipole moments are arranged in a layer having a thickness of at least 0.2 μm, wherein the plurality of transition dipole moments are arranged, at least in a first state, to be parallel to a selectable first preferred direction of the first optical element (1) with a tolerance of at most 20° or to vary around the first preferred direction, the first preferred direction being arranged at a predetermined angle α with respect to a perpendicular bisector of the first optical element (1), the angle α being measured in a selectable first plane containing the perpendicular bisector; whereby a light ray having an incident direction and polarization state incident on the first optical element (1) is transmitted or at least partially absorbed depending on the incident direction and polarization state of the light ray relative to the first optical element (1), with respect to the device for selectively applying the at least one first electric field (EF1), second electric field (EF2) or third electric field (EF3), wherein the first electric field (EF1), the second electric field (EF2) and the third electric field (EF3) can all be applied differently at a plurality of different positions on the switchable optical filter (5); the liquid crystal layer (3) is disposed in front of or behind the first optical element (1) along a viewing direction, and the first electric field (EF1), the second electric field (EF2), and the third electric field (EF3) all act on the liquid crystal layer (3), and the electric fields affect the polarization state of the light passing through the liquid crystal layer (3); the first linear polarizing filter (X) is disposed in front of the liquid crystal layer (3) along the observation direction when the liquid crystal layer (3) is disposed in front of the first optical element (1) along the observation direction; This allows the transmission characteristics of the switchable optical filter (5) to be different among a first operation mode B1 in which the first electric field (EF1) is applied, a second operation mode B2 in which the second electric field (EF2) is applied, and at least one third operation mode B3 in which the third electric field (EF3) is applied, wherein the corresponding transmittances in the first operation mode B1, the second operation mode B2, and the third operation mode B3 are each within a selectable tolerance range at any of the positions, and the first transmittance T corresponding to the first operation mode B1 is Ｂ１ (β), the second transmittance T corresponding to the second operation mode B2 Ｂ２ (β), and a third transmittance T corresponding to the third operation mode B3 Ｂ３ (β), and the first transmittance, the second transmittance, and the third transmittance are all normalized with respect to the angle β so that the transmittance values ​​are normalized with respect to the predetermined angle α. Ｂ１ (α)=1, T Ｂ２ (α)=1, and T Ｂ３ (α)=1, where When a light ray is incident on the first optical element (1) at an angle β that satisfies β=α−40° or β=α+40°, the s-polarized component of the light ray exhibits at least a first transmittance value T after normalization at a plurality of positions in a first operating mode B1 where the first electric field (EF1) is applied. Ｂ１ (β)≧0.25 and is transmitted; When a light ray is incident on the first optical element (1) at an angle β that satisfies β=α−40° or β=α+40°, the p-polarized component of the light ray exhibits at least a second transmittance value T Ｂ２ (β)≧0.2 and is transmitted. When a light ray is incident on the first optical element (1) at an angle β that satisfies β=α−40° or β=α+40°, the light ray exhibits a third transmittance value T after normalization at a plurality of positions in a third operation mode B3 in which the third electric field (EF3) is applied. Ｂ２ (β) < T Ｂ３ (β) < T Ｂ１ 2. A switchable optical filter (5) according to claim 1, characterized in that it is transmitted at (β).

5. A switchable optical filter (5) comprising a first optical element (1), The first optical element (1) includes a plurality of absorption transition dipole moments; a liquid crystal layer (3) having a plurality of liquid crystal molecules; and a first linear polarizing filter (X); the plurality of absorption transition dipole moments are arranged in a layer having a thickness of at least 0.2 μm, wherein the plurality of transition dipole moments are arranged, at least in a first state, to be parallel to a selectable first preferred direction of the first optical element (1) with a tolerance of at most 20° or to vary around the first preferred direction, the first preferred direction being arranged at a predetermined angle α with respect to a perpendicular bisector of the first optical element (1), the angle α being measured in a selectable first plane containing the perpendicular bisector; whereby a light ray incident on the first optical element (1) is transmitted or at least partially absorbed depending on the incident direction and the polarization state relative to the first optical element (1), a liquid crystal layer (3) having a plurality of liquid crystal molecules is arranged in front of or behind the first optical element (1) along a viewing direction, the orientation of the plurality of liquid crystal molecules being influenced pixel by pixel by a locally controllable electric field, and the liquid crystal layer (3) can influence the polarization state of the light beam passing through the liquid crystal layer (3) according to the pixel by pixel selectable orientation of each of the plurality of liquid crystal molecules; wherein the locally controllable electric field is controlled by a control circuit, the control circuit being controlled by a plurality of digital signals, the plurality of digital signals being present for each pixel, and at least one maximum digital signal, one minimum digital signal, and a digital signal located between the maximum digital signal and the minimum digital signal are selected at at least one time point; 2. The switchable optical filter (5) of claim 1, wherein the first linear polarizing filter (X) is located in front of the liquid crystal layer (3) along the observation direction when the liquid crystal layer (3) is arranged in front of the first optical element (1) along the observation direction, and wherein, at the time when the control circuit performs control using the at least three digital signals, the switchable optical filter (5) generates at least three mutually different transmittance values ​​of the transmittance, namely a minimum transmittance value, a middle transmittance value and a maximum transmittance value, for the same selectable angle at a plurality of different positions on the switchable optical filter (5).

6. A switchable optical filter (5) according to any one of claims 1 to 5, characterized in that for all the same selectable angles at least three mutually different transmittance values ​​are generated at a plurality of positions of the switchable optical filter (5), preferably the plurality of positions being immediately adjacent.

7. 1. An illumination device for a screen, comprising: be operable in at least a first operating mode B1 for a free-viewing mode and a second operating mode B2 for a limited-viewing mode; In the restricted viewing mode, the viewing angle from which the light beam is emitted for the viewer is restricted compared to the free viewing mode, The lighting device includes: a planar extended backlight for emitting light; and 7. An illumination device for a screen, characterized in that it comprises a switchable light filter (5) according to any one of claims 1 to 6, arranged in front of the backlight along the viewing direction.

8. A screen, an image display device; and A screen, characterized in that it comprises a switchable light filter (5) according to any one of claims 1 to 6, arranged in front of or behind the image display device along a viewing direction.

9. A screen, be operable in at least a first operating mode B1 for a free-viewing mode and a second operating mode B2 for a limited-viewing mode; In the restricted viewing mode, the viewing angle from which the light beam is emitted for the viewer is restricted compared to the free viewing mode, The screen is Transmissive image display devices; a backlight disposed behind the transmissive image display device along a viewing direction and having an asymmetric light density distribution; a switchable optical filter (5) according to any one of claims 1 to 6, which is arranged in front of or behind the transmissive image display device along a viewing direction; Here, in the second operating mode B2, the second electric field (EF2) is applied, and in the first operating mode B1, the first electric field (EF1) is applied.

10. 1. A switchable lighting device, comprising: be operable in at least a first operating mode B1 for a free-viewing mode and a second operating mode B2 for a limited-viewing mode; In the restricted viewing mode, the viewing angle through which the light beam is emitted for the viewer is restricted relative to the free viewing mode, and the switchable lighting device a planar extended backlight emitting light rays in a first alternative within a limited angular range and in a second alternative within an unlimited angular range; a light guide arranged in front of the backlight along the viewing direction, the light guide having at least one large surface and / or a plurality of output elements within its volume; and a light source disposed laterally adjacent at least one short side of the light guide; wherein in the first alternative, the backlight is turned on and the light source is turned off in the second operating mode B2, and at least the light source is turned on in the first operating mode B1; and in the second alternative, the backlight is turned off and the light source is turned on in the second operating mode B2, and at least the backlight is turned on in the first operating mode B1; 1. A switchable lighting device, characterized in that for the backlight and / or the light guide, when one or both of the backlight and the light guide emit light rays, at least three different brightness values, namely a minimum brightness value, a middle brightness value and a maximum brightness value, are generated at a plurality of different positions on the backlight and / or the light guide at at least one time for selectable angles that are all the same for the plurality of different positions.

11. 11. A switchable lighting device according to claim 10, characterized in that for all the same selectable angles at least three mutually different transmittance values ​​are produced at a plurality of positions on the backlight and / or the light guide, respectively, preferably the plurality of positions being immediately adjacent.

12. A switchable screen, at least an image display device; and a device for influencing the angle-dependent brightness of said switchable screen; A switchable screen, characterized in that the device for influencing the angle-dependent brightness of the switchable screen generates, at least at one time, at a plurality of different positions on the switchable screen at least three mutually different brightness values, namely a minimum brightness value, a middle brightness value and a maximum brightness value, for selectable angles that are all the same at the plurality of different positions.

Images