# US 2023/0053738 A1 · Switchable light filter and use thereof > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2023/0053738 A1 - Document ID: US20230053738A1 - Status: Published application - Kind: A1 - Application number: 17/758,617 - Filed: 2021-09-27 - Published: 2023-02-23 - Earliest claimed: 2020-09-30 - Assignees: siOPTICA GmbH - Applicants: siOPTICA GmbH - Inventors: André HEBER; Andreas BREGULLA; Yannick BOURGIN; Markus KLIPPSTEIN - Web page: https://patentgrep.com/patent/US20230053738A1 ## CPC - G02F 1/1323: {Arrangements for providing a switchable viewing angle} - G02B 6/0056: {for producing polarisation effects, e.g. by a surface with polarizing properties or by an additional polarizing elements} - G02F 1/0136: {for the control of polarisation, e.g. state of polarisation [SOP] control, polarisation scrambling, TE-TM mode conversion or separation (G02F1/0353 takes precedence)} - G02F 1/133509: {Filters, e.g. light shielding masks} - G02F 1/133528: {Polarisers} - G02F 1/133606: {including a specially adapted diffusing, scattering or light controlling members} - G02F 1/133626: {providing two modes of illumination, e.g. day-night} - G02F 1/13475: {in which at least one liquid crystal cell or layer is doped with a pleochroic dye, e.g. GH-LC cell (G02F1/13476 takes precedence)} - G02F 1/137: characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering - G02F 1/13725: {based on guest-host interaction (G02F1/13762, G02F1/13737, take precedence)} - G02F 2202/04: dye - G02F 2203/01: transmissive - G02F 2203/48: Variable attenuator - G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract An optical element which can be utilized in various versions and implementations of switchable light filters having, in addition, polarization filters and/or other means for varying the polarization characteristics of light, for example, liquid crystal layers. A combination of switchable light filter and imaging display device makes possible a private viewing effect that can be switched on and off. The optical element comprises a first layer or a first layer and a plurality of further layers, each layer including a material with a plurality of light-absorbing transition dipole moments. At least in a first state, each transition dipole moment is oriented, with a tolerance of 10° at the maximum, parallel to a selectable preferential direction or fluctuates around it so that light which is incident in the optical element is transmitted or at least partially absorbed depending on its incident direction. ## Claims ### Claim 1 A switchable light filter comprising: a first optical element which comprises a first layer or a first layer and a plurality of further layers wherein each layer comprises a material with a plurality of light-absorbing transition dipole moments, wherein, at least in a first state, each transition dipole moment is oriented, with a tolerance of 10° at a maximum, parallel to a first preferential direction selectable for the first optical element or fluctuates around this, so that light which is incident in the first optical element is transmitted or at least partially absorbed depending on its incident direction relative to the layers and depending on its polarization state, a polarization filter which is arranged upstream or downstream of the first optical element considered in incident direction, an electric field generator configured to selectively generate a first electric field or a second electric field a liquid crystal layer arranged between the first optical element and the polarization filter, the liquid crystal layer being acted upon by the first electric field or the second electric field and, depending thereon, influencing the polarization state of light passing through it so that: in a first operating mode which the first electric field is applied and with a first sub-operating mode and a second sub-operating at least 24% of unpolarized light which is incident in the switchable light filter parallel to the first preferential direction is transmitted and, at least 85% of unpolarized light which is incident in the switchable light filter at an angle of greater than 30° to the first preferential direction is absorbed, wherein the absorption takes place exclusively in a first direction in the first sub-operating mode and exclusively in a second direction perpendicular to the first direction in the second sub-operating mode, in a second operating mode in which the second electric field is applied and with the first sub-operating mode and the second sub-operating mode, at least 24% of unpolarized light which is incident in the switchable light filter parallel to the first preferential direction is transmitted and, at least 85% of unpolarized light which is incident in the switchable light filter at an angle of greater than 30° to the first preferential direction is absorbed, wherein the absorption takes place exclusively in the second direction in the first sub-operating mode and exclusively in the second direction perpendicular to the first direction in the second sub-operating mode, so that the directions of absorption differ by 90°, respectively, for each of the two sub-operating modes for the first operating mode and the second operating mode. ### Claim 2 A switchable light filter comprising: a first optical element which comprises a first layer or a first layer and a plurality of further layers wherein each layer comprises a material with a plurality of light-absorbing transition dipole moments, wherein, at least in a first state, each transition dipole moment is oriented, with a tolerance of 10° at a maximum, parallel to a first preferential direction selectable for the first optical element or fluctuates around this, so that light which is incident in the first optical element is transmitted or at least partially absorbed depending on its incident direction relative to the layers and depending on its polarization state, wherein the transition dipole moments in each of the layers can be varied with respect to their orientation and/or their amount between the first state and at least a second state in order to alternatively put the respective layer in at least two different states, a polarization filter which is arranged upstream or downstream of the first optical element, an electric field generator configured to selectively generate a first electric field or a second electric field, wherein the first state is generated for the first optical elementby applying the first electric field and the second state is generated for the second optical element by applying the second electric field so that in a first operating mode in which the first electric field is applied and the transition dipole moments of the layers of the first optical element are oriented along the first preferential direction and which has a first sub-operating mode and a second sub-operating mode, at least 24% of unpolarized light which is incident in the switchable light filter parallel to the first preferential direction is transmitted and at least 85% of unpolarized light which is incident in the switchable light filter at an angle of greater than 30° to the first preferential direction is absorbed wherein the absorption takes place exclusively in a first direction in the first sub-operating mode and exclusively in a second direction perpendicular to the first direction in the second sub-operating mode, and in a second operating modein which the second electric field is applied and the transition dipole moments of the layers of the first optical element are oriented parallel to a surface of the polarization filter and perpendicular to a transmission direction of the polarization filter, at least 24% of unpolarized light which is incident in the switchable light filter at any angle to the first preferential direction is transmitted. ### Claim 3 A switchable light filter comprising: a first optical element and a second optical element, wherein each of the two optical elements comprises: a first layer or a first layer and a plurality of further layers wherein each layer comprises a material with a plurality of light-absorbing transition dipole moments, wherein, at least in a first state, each transition dipole moment is oriented, with a tolerance of 10° at a maximum, parallel to a first preferential direction selectable for the first optical element and to a second preferential direction selectable for the second optical element or fluctuates around these, so that light which is incident in the first optical element or second optical element is transmitted or at least partially absorbed depending on its incident direction relative to the layers and depending on its polarization state, wherein the first preferential direction and the second preferential direction of the transition dipole moments differ from one another by less than 40°, a liquid crystal layerarranged between the first optical element and the second optical element, which liquid crystal layer influences the polarization state of light passing through it depending on a first electric field or second electric field acting on the liquid crystal layer, an electric field generator configured to selectively generate the first electric field or second electric field, electively, a polarization filter arranged above or below one of the two optical elements, or no polarization filter so that either, in a case where a polarization filter present, in a first operating mode in which the first electric field is applied and with a first sub-operating mode, at least 24% of unpolarized light which is incident in the switchable light filter parallel to the first preferential direction or second preferential direction is transmitted and, at least 85% of unpolarized light which is incident in the switchable light filter an angle of greater than 30° to the corresponding preferential direction is absorbed, wherein the absorption takes place exclusively in a first direction in the first sub-operating mode and exclusively in a second direction perpendicular to the first direction in the second sub-operating mode, wherein either the first direction or the second direction is perpendicular to a polarization direction of the polarization filter, or, in a case where there is no polarization filter, in a first operating mode in which the first electric field is applied, at least 24% of unpolarized light which is incident in the switchable light filter at any angle is transmitted, and regardless of whether or not there is a polarization filter, in a second operating modein which the second electric field is applied, at least 24% of unpolarized light which is incident in the switchable light filter parallel to the first preferential direction or to the second preferential direction is transmitted and at least 85% of unpolarized light which is incident in the switchable light filter at an angle of greater than 30° to the corresponding preferential direction is absorbed. ### Claim 4 A switchable light filter comprising a first optical element and a second optical element, wherein each of the two optical elements comprises a first layer or a first layer and a plurality of further layers wherein each layer comprises a material with a plurality of light-absorbing transition dipole moments, wherein, at least in a first state, each transition dipole moment is oriented, with a tolerance of 10° at a maximum, parallel to a first preferential direction selectable for the first optical element and to a second preferential direction selectable for the second optical element or fluctuates around these, so that light which is incident in the first optical element or second optical element is transmitted or at least partially absorbed depending on its incident direction relative to the layers and depending on its polarization state, wherein the transition dipole moments in each of the layers may be varied with respect to their orientation and/or their amount between the first state and at least a second state in order to alternatively put the respective layer in at least two different states, an electric field generator configured to selectively generate a first electric field or a second electric field wherein for each of the two optical elements the first state is generated by applying the first electric field and the second state is generated by applying the second electric field an optically anisotropic layer for rotating a polarization direction of light passing through the optically anisotropic by 90° arranged between the two optical elements electively, a polarization filter arranged above or below one of the two optical elements, or no polarization filter so that: in a first operating mode in which the first electric field is applied, at least 24% of unpolarized light which is incident in the switchable light filter at any angle relative to the switchable light filter is transmitted, wherein in the first operating mode, the transition dipole moments of the two optical elements are aligned perpendicular to one another and, in a case where a polarization filteris present, polarization filter transition dipole elements of the polarization filter aligned parallel to the transition dipole moments of the switchable optical element located closest to the polarization filter, and in a second operating mode in which the second electric field is applied, at least 24% of unpolarized light which is incident in the switchable light guide parallel to the first preferential direction or second preferential direction is transmitted and, at least 85% of unpolarized light which is incident in the switchable light guide at an angle of greater than 30° to the corresponding preferential direction is absorbed, wherein in the second operating mode, the transition dipole moments of the polarization filter, if present, and the transition dipole moments of the switchable optical element located closest to the polarization filter are oriented perpendicular to one another, and the transition dipole moments of the two optical elements are oriented parallel to one another. ### Claim 5 (depends on 1) The switchable light filter according claim 1 wherein at least one polarization compensation layer is arranged upstream and/or downstream of the liquid crystal layer. ### Claim 6 (depends on 1) The switchable light filter according to claim 1 wherein the preferential directions form an angle of between 0° and 45° to a surface normal of the first layer. ### Claim 7 (depends on 1) The switchable light filter according to claim 1 wherein the switchable light filter is divided into a plurality of separately switchable segments so that localized switching between the respective possible operating states is made possible. ### Claim 8 (depends on 1) The switchable light filter according claim 1 wherein each of the layers of the first optical element and/or of the second optical element, if any, is constructed non-periodically. ### Claim 9 (depends on 1) A display screen comprising a switchable light filter according to claim 1 and an imaging display unit arranged downstream or upstream of the switchable light filter from a perspective of an observer. ### Claim 10 An optical element comprising: a first layer, or a first layer and a plurality of further layers wherein each layer comprises a material with a plurality of light-absorbing transition dipole moments, wherein, at least in a first state, each transition dipole moment is oriented, with a tolerance of 10° at a maximum, parallel to a selectable preferential direction or fluctuates around this, so that light which is incident in the optical element is transmitted or at least partially absorbed depending on its incident direction relative to the layers. ### Claim 11 (depends on 10) The optical element according to claim 10, wherein the preferential directions form an angle between 0° and 45° to a surface normal of the first layer. ### Claim 12 (depends on 10) The optical element according to claim 10 wherein each of the layers is constructed aperiodically with respect to its structure. ### Claim 13 (depends on 10) The optical element according to claim 10, wherein every transition dipole moment is oriented in the respective preferential direction within a tolerance of 10° at the maximum around the latter. ### Claim 14 (depends on 10) The optical element according to claim 10 wherein at least two such preferential directions in a selectable plane differ by more than 10°. ### Claim 15 (depends on 10) The optical element according to claim 10 whereint the transition dipole moments in every layer can be varied with respect to their orientation and/or their amount between the first state and at least a second state so that the respective layer can be brought alternatively into at least two different states. ### Claim 16 (depends on 15) The optical element according to claim 15, wherein the optical element is divided into a plurality of segments separately switchable between the first state and at least the second state. ### Claim 17 (depends on 10) The optical element according to claim 10 whereint the respective preferential direction of a transition dipole moment is selectable depending on its position in the respective layer. ### Claim 18 (depends on 10) The optical element according to claim 10 wherein every layer is divided along a selectable reference line on the respective layer into different regions, wherein every region can have its own selected regional preferential direction which applies to all of the transition dipole moments of the corresponding layer located within a region and wherein all of the regional preferential directions differ pairwise and face in a direction of an observer to within a tolerance of ±10° at the maximum. ### Claim 19 (depends on 10) The optical element according to claim 10 wherein the material contains at least one dye, preferably a dichroic dye mixture. ### Claim 20 (depends on 10) The optical element according to claim 10 wehrein the material contains liquid crystals. ### Claim 21 (depends on 10) The optical element according to claim 10 wherein the optical element is formed as a laminate of layers of polymer film polarizers. ### Claim 22 (depends on 11) An illumination device for a display screen, which illumination device can be operated in at least two operating modes: a first operating mode for a free viewing mode and a second operating mode for a limited viewing mode, comprising: a two-dimensionally extensive backlight which contains the optical element according to claim 11, a plate-shaped light guide which is located in front of the backlight in a viewing direction and which has out-coupling elements on at least one of the large surfaces and/or within its volume, wherein the light guide is at least 40% transparent to light emanating from the backlight, illuminants arranged laterally on at least one narrow side of the light guide, a linear polarization filter arranged in front of the backlight or in front of the light guide in the viewing direction so that light emanating from the backlight and passing through the polarization filter is limited with respect to its propagation directions, wherein the backlight is switched on and the illuminants are switched off in the second operating mode, and wherein at least the illuminants are switched on in the first operating mode. ### Claim 23 (depends on 22) The illumination device according to claim 22, wherein the light guide is at least 70% transparent to the light emanating from the backlight. ### Claim 24 (depends on 11) A display screen which can be operated in at least two operating modes, a first operating mode for a free viewing mode and a second operating mode for a limited viewing mode, comprising: a two-dimensionally extensive backlight which contains an optical element according to claim 11 and which emits light, a plate-shaped light guide which is located in front of the backlight in a viewing direction and which has out-coupling elements on at least one oflarge surface of the light guide and/or within a volume of the light guide, wherein the light guide is at least 40% transparent to light emanating from the backlight, illuminants arranged laterally on at least one narrow side of the light guide, a linear polarization filter arranged in front of the backlight or in front of the light guide in the viewing direction so that light emanating from the backlight and passing through the polarization filter is limited with respect to its propagation directions, a transmissive imaging display device which is arranged upstream of the light guide in the viewing direction and in which the linear polarization filter is arranged, wherein the backlight is switched on and the illuminants are switched off in the operating mode, and wherein at least the illuminants are switched on in the first operating mode. ### Claim 25 (depends on 24) The display screen according to claim 24, wherein the light guide is at least 70% transparent to the light emanating from the backlight. ### Claim 26 (depends on 24) The display screen according to claim 24, wherein the linear polarization filter is arranged in the imaging display device or is a part of the imaging display device.