Switchable light filters, lighting fixtures, and displays.

Abstract

This invention relates to a switchable light filter (5) comprising a first optical element (1) which comprises several light-absorbing transition dipole moments, where the relative ratio p of all transition dipole moments, at which 0.6 ≤ p ≤ 1.0, is aligned parallel with a maximum tolerance of 15° with respect to the first preferred direction selectable for the first optical element (1); means for the selective generation of a first electric field (EF1) or a second electric field (EF2); and a liquid crystal layer (3) which is arranged behind or in front of the first optical element (1) in the line of sight, the first electric field (EF1) or the second electric field (EF2) acting on the liquid crystal layer to influence the polarization state of light passing through the liquid crystal layer.The absolute values ​​of the first electric field (EF1) and the second electric field (EF2) differ by at least 0.1 MV / m so that the transmission characteristics of the switchable light filter (5) differ between the first mode B1, in which the first electric field (EF1) is applied, and the second mode B2, in which the second electric field (EF2) is applied.

Description

title

[0001] Switchable light filter, lighting device and screen Technical field of the invention

[0002] In recent years, great strides have been made in widening the viewing angle of LCDs. However, there are often situations where the very large viewing area of ​​a screen can be a disadvantage. Information, such as banking details and other personal and sensitive data, is also becoming increasingly available on mobile devices such as notebooks and tablet PCs. Accordingly, people need control over who can see this sensitive data. They must be able to choose between a wide viewing angle – a public mode – in order to share information on their display with others, e.g., when looking at holiday photos or for advertising purposes. On the other hand, they need a narrow viewing angle – in a private mode – if they want to keep the image information confidential.

[0003] A similar problem arises in vehicle construction: The driver must not be distracted by image content, such as digital entertainment programs, when the engine is running, while the passenger also wants to consume these while driving. Therefore, a screen that can switch between the corresponding display modes is required.

[0004] Additional films based on micro-louvres have already been used for mobile displays to achieve visual privacy. However, these films were not switchable or reversible; they always had to be applied and removed manually. They also had to be transported separately from the display when not in use. A major disadvantage of using such louvre films is the associated light loss.

[0005] US Pat. No. 6,765,550 B2 describes such a privacy screen using micro-louvres. The biggest disadvantage here is the mechanical removal or installation of the filter, as well as the loss of light in protected mode.

[0006] US Pat. No. 5,993,940 A describes the use of a film with evenly spaced, small, strip-shaped prisms on its surface to achieve a private mode, i.e., a restricted viewing mode with a narrow viewing angle range. Development and production are technically quite complex.

[0007] US 2013 / 0308185 A1 describes a special light guide with steps that emits light across a large surface in different directions, depending on the direction from which it is illuminated from a narrow side. In conjunction with a transmissive image display device, e.g. an LC display, this makes it possible to create a screen that can be switched between free and restricted view modes. A disadvantage of this is that the restricted view effect can only be created for left / right or for top / bottom, but not for left / right / top / bottom simultaneously, as is necessary for certain payment transactions, for example. In addition, even in restricted view mode, residual light is still visible from blocked viewing angles.

[0008] The applicant's WO 2015 / 121398 A1 describes a screen with two operating modes, in which scattering particles are present in the volume of the corresponding light guide for switching between the operating modes. However, the polymer scattering particles selected there generally have the disadvantage that light is coupled out of both large surfaces, causing approximately half of the useful light to be emitted in the wrong direction, namely toward the backlight, where it cannot be adequately recycled due to their design. Furthermore, the polymer scattering particles distributed in the volume of the light guide can, under certain circumstances, particularly at higher concentrations, lead to scattering effects that reduce the privacy effect in the protected operating mode.

[0009] The aforementioned methods and arrangements generally have the disadvantage that they significantly reduce the brightness of the basic screen and / or require a complex and expensive optical element for mode switching and / or reduce the resolution in the freely viewable, public mode and / or visual exhibit artifacts on very high-resolution displays and / or are not suitable for self-luminous screen types such as OLED. Description of the invention

[0010] The object of the invention is therefore to describe light filters with an optical element in which light incident on the optical element is transmitted or partially or completely absorbed depending on its direction of incidence and its polarization properties – not primarily but depending on its position. Such light filters are intended to influence the transmission of light in an angle-dependent manner – optionally perpendicular to a seated or standing observer – with the possibility of switching between at least two operating modes. In particular, the angle-dependent relationship of the transmission behavior between the two operating modes is to be defined. Furthermore, the light filters are also intended to be usable with self-luminous display types such as OLEDs.

[0011] This object is achieved in a first embodiment according to the invention by a switchable light filter comprising a first optical element, in turn comprising • a plurality of light-absorbing transition dipole moments arranged in a layer with a thickness of at least 0.1 pm and a maximum of 40 pm, or in several separate layers with a total thickness of transition dipole moments (any adhesive layers between separate layers of transition dipole moments or substrate layers are not included here) of at most 40 pm, • wherein the transition dipole moments are preferably realized by means of at least two dichroic dyes, • where a relative proportion p of all transition dipole moments with 0.6 <p<1 ,0, mit typischerweise p<1 , permanent oder mindestens in einem ersten Zustand mit einer Toleranz von maximal 15° parallel zu einer für das erste optische Element wählbaren ersten Vorzugsrichtung ausgerichtet ist oder um diese herum variiert, wobei die erste Vorzugsrichtung in einem vorgegebenen Winkel a, z.B. mit a=0°, a=±2° oder Betrag(oc)> 2°, to the perpendicular bisector of the first optical element, wherein the angle a in a selectable first plane containing said bisector, and wherein preferably said first plane is parallel to an edge of the first optical element, such as the lower edge, • so that light which is incident on the first optical element with a direction of incidence and a polarization state is transmitted or at least partially absorbed depending on its direction of incidence relative to the first optical element and its polarization state, means for selectively generating a first electric field EF1 or a second electric field EF2, a liquid crystal layer arranged behind or in front of the first optical element in the viewing direction, on which the first electric field EF1 or the second electric field EF2 acts and which, depending thereon, influences the polarization state of light passing through it, wherein the absolute values ​​of the first electric field EF1 and the second electric field EF2 differ by at least 0.1 MV / m, a first linear polarization filter X arranged in front of the liquid crystal layer in the viewing direction,if the liquid crystal layer is arranged in front of the first optical element in the viewing direction, so that the transmission properties of the switchable light filter differ between a first operating mode B1, in which the first electric field EF1 is applied, and a second operating mode B2, in which the second electric field EF2 is applied, wherein the respective relative transmission in the two operating modes B1 and B2 at at least one point (preferably at least 5 points, particularly preferably at a plurality of points, distributed over the entire area of ​​the switchable light filter, or even over the entire surface of the light filter) on the switchable light filter up to a selectable tolerance (e.g. 5% or 10% or smaller or larger values) in each case by a first transmission Tßi(ß) for the first operating mode B1 or a second transmission T, B2(ß) for the second operating mode B2, which depends on an angle ß and is standardized in such a way that the values ​​of the transmission for the given angle ß=a are T B i(a)=1 and T B 2(a)=1 , so that if linearly polarized or elliptically polarized light, in which the ratio of major to minor semi-axis is at least 4:1, • at angles (ß) with a-5° < ß < a+5° into the switchable light filter, the ratio TBI (ß) / T B 2(ß) is greater than 0.9 + log (p) and less than 1.3 - log (p), • at angles (ß) with a-30° < ß < a-20° or a+20° < ß < a+30° into the switchable light filter, the ratio T B i(ß) / T B2 (ß) is greater than 2 ■ (1 + log (p)), and • at angles (ß) with a-45° < ß < a-35° or a+35° < ß < a+45° into the switchable light filter, the ratio T B i(ß) / T B2(ß) is greater than 9 ■ (1 + 2 ■ logio(p)).

[0012] In special applications, a second or even several additional states can be realized for the first optical element - for example by so-called guest-host liquid crystal cells.

[0013] The means for selectively generating a first electric field EF1 or a second electric field EF2 may, for example, be transparent electrodes, for example made of indium tin oxide, which are connected to control electronics.

[0014] In principle, it should apply that in angular ranges ß < a-5° or a+5° < ß the first transmission T B i(ß) for the first operating mode is usually larger than the second transmission T B2(ß) for the second operating mode B2. This is achieved, among other things, by the selection of the first and second electric fields EF1 and EF2, as explained below. For the following explanations, it should be assumed that linearly polarized or elliptically polarized light, with a ratio of major to minor semi-axis of at least 4:1, enters the switchable light filter, the polarization of which is predominantly parallel to the aforementioned first plane, within a tolerance of 5°.

[0015] Depending on the design of the liquid crystal layer as TN (Twisted Nematic), VA (Vertical Alignment), IPS (In Plane Switching), FFS (Fringe Field Switching) or possibly another type, if the liquid crystal layer is arranged behind the first optical element in the viewing direction, the first electric field EF1 is selected such that after transmission through the liquid crystal layer, the transmitted light has an electric field component of at least 40% perpendicular to the first plane, with its polarization being predominantly perpendicular to a tolerance of 5° (or in a selectable angle in a range of 45° to 135°) to the first plane, while the second electric field EF2 is selected such that after transmission through the liquid crystal layer, the transmitted light has an electric field component of at least 80% parallel to the first plane. Under the aforementioned condition that the polarization of the incident light is mostly parallel to said first plane up to a tolerance of 5°, the field strength of the second electric field EF2 could be 0 V / m, i.e. there is essentially no field. The field strength of the first electric field EF1 can be more than 0.1 MV / m, preferably it is an alternating field which changes polarity at a frequency of the order of magnitude of at least 50 Hz, preferably at least 0.8 kHz, in a rectangular or sinusoidal shape, e.g. at 1.0 kHz. Frequencies higher than 1.0 kHz are possible.In other words, in operating mode B2 with the second electric field EF2, the purest possible polarization state is created, since after transmission through the liquid crystal layer, the transmitted light has an electric field component of at least 80% parallel to the first plane. In contrast, in the first operating mode B1 with the first electric field EF1, a mixed or significantly rotated electric field component predominates, because after passing through the liquid crystal layer, the transmitted light has an electric field component of at least 40% perpendicular to the first plane. This is achieved, for example, in the case of a liquid crystal layer in the form of an IPS cell, or when circular polarization is used after the liquid crystal layer.

[0016] Alternatively, it is also possible that the first electric field EF1 represents field-free conditions and the second electric field EF2 has a field strength of more than 0.1 MV / m. Of course, it is also possible that both the first and second electric fields EF1 and EF2 are not field-free.

[0017] If the liquid crystal layer is arranged in front of the first optical element in the viewing direction, ie if a polarization filter is usually also located in front of the liquid crystal layer in the viewing direction, the above-mentioned values ​​for the first and second electric fields EF1 and EF2 can also be used to generate the operating modes B1 and B2. Such a structure is generally used in conjunction with a transparent image display device with a backlight, with the switchable light filter being located between them. In this embodiment, the first optical element transmits in the Essentially, at angles greater than 20°, the light is at least 90% s-polarized. Depending on the operating mode, this generates p- or s-polarized light with respect to the first plane (at least 95%), which is then largely either absorbed or transmitted at angles greater than 20°, depending on the orientation of the polarization filter, which may be part of the image display device.

[0018] What is particularly essential to the invention is that the selection of the relative proportion p of all transition dipole moments, in conjunction with the differently selected first and second electric fields EF1, EF2, and the associated polarization influence, leads to the fulfillment of the above-mentioned inequalities. These inequalities specify the angle-dependent contrast of the said transmissions. Furthermore, the use of thicker layers of transition dipole moments leads to more stringent inequalities, as explained below:

[0019] In a preferred embodiment, the first optical element comprises a plurality of light-absorbing transition dipole moments, which are arranged in a layer having a thickness of at least 1 pm and a maximum of 40 pm, or in several separate layers with a total thickness of transition dipole moments (any adhesive layers present between separate layers of transition dipole moments and substrates are not included here) of at least 1 pm and a maximum of 40 pm, whereby, when linearly polarized or elliptically polarized light, in which the ratio of major to minor semi-axis is at least 4:1, ■ at angles (ß) with a-5° < ß < a+5° into the switchable light filter, the ratio TBI (ß) / T B 2(ß) is greater than 1 ,0 + log (p) and less than 1 ,3 - log (p), ■ at angles (ß) with a-30° < ß < a-20° or a+20° < ß < a+30° into the switchable light filter, the ratio T B i(ß) / T B2(ß) is greater than 3 ■ (1 + logio(p)), and ■ at angles (ß) with a-45° < ß < a-35° or a+35° < ß < a+45° into the switchable light filter, the ratio T B i(ß) / T B2 (ß) is greater than 16 ■ (1 + 2 ■ logio(p)).

[0020] An important means-effect relationship is the following: By switching between the first operating mode B1 , in which the first electric field EF1 is applied, and the second operating mode B2 , in which the second electric field EF2 is applied, whereby the absolute values ​​of the first electric field field EF1 and the second electric field EF2 differ by at least 0.1 MV / m, p-polarized light incident on the liquid crystal layer is - depending on the design - only in one operating mode, e.g. the first operating mode B1, essentially converted into s-polarized light, which then impinges on the first optical element and is transmitted to a significant extent at angles greater than 20°. In contrast, depending on the design - only in the other operating mode, e.g. the first operating mode B2, essentially converted into p-polarized light incident on the liquid crystal layer is which then impinges on the first optical element and is absorbed to a significant extent at angles greater than 20°. The result is the ratios for the transmissions TBI (ß) / T B 2(ß) in the specified angular ranges.

[0021] Furthermore, if the absorbing transition dipole moments are formed by dichroic dyes, where the dye mass density is usually more than 1%, this helps to satisfy the given inequalities for reasonable transmission ratios.

[0022] Further operating modes B3, B4, etc. can be explicitly provided, with electric fields EF3, EF4, etc. that differ from the electric fields EF1 and EF2. Furthermore, the operating modes B1, B2, etc. can also differ locally on the switchable light filter. The latter means that the first optical element (and any further such optical element, if present) and / or the liquid crystal layer and / or the means for selectively generating a first or second electric field E1, E2 are divided into several separately switchable segments, thus enabling local switching between the respectively possible operating modes.

[0023] For standardization of the transmission T B i(a)=1 and T B2 (a)=1, the following should be noted: The angles ß and a are, of course, measured in the same plane described above. It is also possible that T B i(a)>1 and / or T B2 (oc)>1 applies to angle ß^a. In many cases, T B i(a)<1 and / or T B2 (OC)<1 applies to angle ß^a.

[0024] In case the transition dipole moments are variable, e.g. by their rotation in so-called guest-host liquid crystal cells, such guest-host Liquid crystal cells directly correspond to the aforementioned liquid crystal layer, but do not have to.

[0025] In a preferred embodiment, light penetrating the liquid crystal layer is transmitted essentially unchanged when the second electric field EF2 is applied, while when the first electric field EF1 is applied, the incident light is circularly or elliptically polarized, or the polarization of the light is rotated by 90°. Essentially, this means that at the interfaces, the orientation of the liquid crystal molecules is determined by electric fields and surface-induced forces. Thus, the liquid crystal molecules are not ideally aligned, leading to an undesirable, smaller change in polarization.

[0026] For designs with TN liquid crystals, the alignment of the liquid crystal molecules typically differs by 90° at the large surfaces that define the liquid crystal layer. This alignment is supported by PMI or PVA and additional mechanical or optical surface treatment. For TN liquid crystal layers, it is also generally true that when switching between the electric fields EF1 and EF2, the majority of the liquid crystals in the liquid crystal layer are rotated out of plane by 75 to 90 degrees. In the case of IPS and FFS liquid crystal layers, the rotations of the LC molecules are generally less than 45°, typically approximately 20° to 40°.

[0027] If the liquid crystal layer is arranged behind the first optical element in the viewing direction, the incident light is preferably linearly polarized or elliptically polarized light, in which the ratio of the major to minor semi-axis is at least 4:1 (preferably at least 5:1 or more). This can be achieved, for example, by linear polarization filters in the light path, or by λ / 4 layers in the case of circularly polarized light.

[0028] In a further embodiment, the switchable light filter comprises at least two first optical elements, with a birefringent retardation plate optionally arranged between at least two such first optical elements. Furthermore, the at least two first optical elements could, if appropriate, have different thicknesses of the layers containing the plurality of light-absorbing transition dipole moments, but this is not required.

[0029] The invention also comprises a lighting device in a first embodiment for a screen which can be operated in at least two operating modes B1 for a free view mode and B2 for a restricted view mode, in which light is emitted into a viewing angle range which is restricted for a viewer compared to the free view mode, comprising - a surface-like extended backlight that radiates light and is optionally directly luminous (e.g. with a locally dimmable LED matrix), as well as - a switchable light filter according to the invention arranged in front of the background lighting in the viewing direction as described above.

[0030] In addition to this, the invention also comprises a screen in a first embodiment, which can be operated in at least two operating modes B1 for a free view mode and B2 for a restricted view mode, in which light is emitted into a viewing angle range that is restricted for a viewer compared to the free view mode, comprising - a lighting device as described above, - and, if no first linear polarization filter is arranged in the switchable light filter of the illumination device, a second linear polarization filter P arranged in front of the background illumination in the viewing direction, whereby light emanating from the background illumination and penetrating the second linear polarization filter P is restricted in its propagation directions, and - a transmissive image display device which is arranged in front of the switchable light filter in the viewing direction, - wherein in operating mode B2 the second electric field EF2 is applied and in operating mode B1 the first electric field EF1 is applied.

[0031] It is preferred that the first or second linear polarization filter P is arranged in the transmissive image display device or is a part of it.

[0032] Furthermore, the invention comprises a screen in a second embodiment, which can be operated in at least two operating modes B1 for a free view mode and B2 for a restricted view mode, in which light is emitted into a viewing angle range that is restricted for a viewer compared to the free view mode, comprising - an image display device, whereby in principle any type of image display device is possible, for example LC panel, OLED, microLED and others, - in the viewing direction in front of the image display device, a switchable light filter according to the invention as described above, - wherein in operating mode B2 the second electric field EF2 is applied and in operating mode B1 the first electric field EF1 is applied.

[0033] Optionally, the switchable light filter can be retrofitted by a user and / or reversibly attached to the image display device. In this case, a light filter can be sold as a so-called "after-market product."

[0034] For some of the screens described above, it may be advantageous when used in cars if a second optical element is arranged in front of the transmissive image display device in the viewing direction, which second optical element comprises: • a large number of light-absorbing transition dipole moments; the dye mass density is greater than 1% or even greater than 10%. • wherein the majority of the transition dipole moments are aligned, at least in a first state, with a tolerance of a maximum of 20° (alternatively 10°) parallel to a second preferred direction that can be selected for the second optical element or vary around this, wherein the second preferred direction is arranged at an angle oci to the perpendicular bisector of the second optical element (for example, ai = 0°, ai = ±2° or amount (oci)>2° can apply), wherein the angle oci is measured in a selectable second plane that contains said perpendicular bisector; the second plane is preferably perpendicular to the first plane of the first optical element, • so that light which is incident on the second optical element is transmitted or at least partially absorbed depending on its direction of incidence relative to the second optical element and its polarization state.

[0035] This latter design advantageously ensures reduced transmission in the vertical direction and can thus reduce or completely avoid reflections of image content displayed on the said screen on the windshield in the vehicle.

[0036] By “limited angular range” is meant in the context of the invention, and in particular with regard to operating mode B2, that the corresponding luminance is concentrated to at least 80% or 90% in a defined angular range, while there may still be residual light outside the defined limited angular range, which is generally due to technical reasons. Ideally, such residual light is minimal and decreases at larger angles. In order to achieve particularly strong minimization, a corresponding light filter is used in addition to a backlight that emits light in a limited angular range. This also applies to the variant described below with a light guide that emits or decouples light predominantly in a limited angular range. In contrast to this embodiment of the invention, luminance curves of backlights over horizontal (if applicable) angles aretypically bell-shaped over angular ranges (including vertical ones), although there need not be a real concentration of luminance around a smaller angular range.

[0037] Advantageously, the transition dipole moments of a first optical element (or, if present, also of a second or further optical element) are formed as one or more dichroic dyes mixed with the liquid crystals in a guest-host arrangement, with the dye mass density generally being more than 1% or more than 10%. For permanent transition dipole moments, the liquid crystals can preferably be fixed via a curing process.

[0038] In contrast, the transition dipole moments can also be embedded in a liquid crystal layer in a non-fixed manner as a guest-host arrangement, so that the transition dipole moments can be varied in their orientation and / or their magnitude between the first and at least one second state depending on the influence of this liquid crystal layer.

[0039] The dichroic dye molecules generally align parallel to the liquid crystal molecules.

[0040] Alternatively, the first optical element may be formed as a laminate of layers of polymer film polarizers.

[0041] The aforementioned configurations also ensure that the first optical element is non-periodic in its structure. This is advantageous because, in interaction with the pixel structures of screens, there is no risk of artifacts such as moiré effects.

[0042] The first preferred direction can, for example, enclose an angle between 0° and 45° with a surface normal of the first optical element. Furthermore, it is possible for the first preferred direction to vary across the surface of the first optical element. For the purposes of the invention, the average, weighted preferred direction then applies.

[0043] The transition dipole moment—also known as the transition matrix element—is a quantum-mechanical vector quantity associated with a specific transition between an initial state—usually the ground state—and a final state—usually an excited state—of a system, i.e., an atom, molecule, or solid. It corresponds to the electric dipole moment associated with this transition. The direction of the vector defines the polarization of the transition, which in turn determines how the system interacts with an electromagnetic wave of a given polarization. For example, during the transition from the ground state to the excited state, light of the corresponding polarization is absorbed. The magnitude of the vector corresponds to the strength of the interaction or the transition probability.

[0044] The first (second) preferred direction corresponds to the orientation of the transition dipole moments of the first (second) optical element for a given propagation direction of light, in which the absorption is the same for any polarization of the light.

[0045] The first and second preferred directions can also be identical or differ in their orientation by only a few degrees (maximum 10°), and both are particularly perpendicular to the respective optical element. This is a preferred case. However, depending on the application, it is also possible for the first and second preferred directions to differ by more than 10°.

[0046] The light filter may further comprise a polarization filter, which is arranged upstream or downstream of the first or second optical element in the direction of incidence. Alternatively or additionally, a 4X layer is also conceivable, for example in the case of Incident of circularly polarized light, which is converted into (essentially) linearly polarized light due to this layer.

[0047] A first exemplary manufacturing variant for a first or second optical element using the guest-host principle is based on mixtures of dichroic dyes or dichroic dye mixtures with liquid crystal mixtures or compounds, and comprises the following manufacturing steps (with reference to US 9,481,658 B2 or WO2021 / 177308A1 paragraph 37ff.) A low- or non-birefringent substrate is coated with a film that determines the orientation of the molecules relative to the surface, usually parallel or perpendicular to the surface. Polymers, preferably polyvinyl alcohol or polyimides, are used for this purpose. - Optional: Optical or mechanical treatment of the surfaces to improve the subsequent quality of molecular alignment. - Applying the mixture of dichroic dye and thermotropic liquid crystalline compounds or polymers. By irradiating with light, the side chains are locally condensed so that the dyes are permanently aligned perpendicular to the surface.

[0048] An alternative, second manufacturing variant uses thermotropic, liquid crystalline dichroic dyes (reference to JP201 1 -237513A), and includes the following steps: Preparation of the corresponding dyes and addition of a polar group. - Application of the dye mixture as well as photo-alignment and curing of the dye mixture using polarized light.

[0049] The following materials, for example, are suitable for various manufacturing variants, although this list is not exhaustive: - As polymer substrate with low or no birefringence: preferably TAC, - As dichroic substances or mixtures: Dichroic dyes (preferably azo dyes) or dichroic metal nanoparticles (preferably gold, silver, copper, and aluminum); these are usually single dyes of one or mixtures of typically up to three different dyes to enable absorption across the entire spectrum, - For surface treatment by aligning dyes or liquid crystalline substances: polymers, preferably polyvinyl alcohol or polyimides, For thermotropic liquid crystalline compounds or polymers, reference is made to JP 201 1 -237513A as an example. - As chemical groups for crosslinking, which are bound to the thermotropic liquid crystalline compounds or polymers (crosslinking): metaacrylic groups, epoxy groups, oxetanyl groups, and styrene groups, preferably methacrylic groups. Alternatively, these can be polymerizable liquid crystal compounds, such as those described in JP 6268730B2. Polymerizable liquid crystalline dichroic dyes, for example azo dyes.

[0050] The at least one dye consists of dye molecules, each dye molecule advantageously associated with a transition dipole or transition dipole moment, i.e., each dye molecule corresponds to a transition dipole or transition dipole moment. Typically, a dye has a mass fraction of at least 0.01%, preferably from 1% to 15%, of the material of the respective layers of the respective optical element. In special cases, the concentration can even reach 95% in the case of liquid-crystalline dichroic dyes. The dyes or dye mixtures for different layers within an optical element can be different, but do not have to be.

[0051] A light filter, lighting device, or screen as described above is advantageously used in a mobile device, a motor vehicle, aircraft, or watercraft, in a payment terminal, or in an access system. Switching between the aforementioned operating modes is possible to protect sensitive data, i.e., to display it in a way that is perceptible to only one viewer, or alternatively, to display image content simultaneously for multiple viewers.

[0052] In principle, the performance of the invention is maintained if the parameters described above are varied within certain limits.

[0053] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations indicated, but also in other combinations or on their own, without departing from the scope of the present invention. Short description of the drawings

[0054] The invention is explained in more detail below using exemplary embodiments with reference to the accompanying drawings, which also disclose features essential to the invention. These exemplary embodiments are for illustrative purposes only and are not to be interpreted as restrictive. For example, a description of an embodiment with a large number of elements or components should not be interpreted to mean that all of these elements or components are necessary for implementation. Rather, other embodiments may also contain alternative elements and components, fewer elements or components, or additional elements or components. Elements or components of different exemplary embodiments may be combined with one another unless otherwise stated. Modifications and variations described for one of the exemplary embodiments may also be applicable to other exemplary embodiments.To avoid repetition, identical or corresponding elements in different figures are designated by the same reference numerals and are not explained more than once. They show: Fig. 1 shows a schematic diagram of a switchable light filter. Fig. 2 exemplary ratios of transmissions for two parameter sets ID1 and ID2, Fig. 3 exemplary ratios of transmissions for two parameter sets ID3 and ID4, Fig. 4 exemplary ratios of transmissions for two parameter sets ID5 and ID6, Fig. 5 a schematic diagram of another switchable light filter, Fig. 6 a schematic diagram of a lighting device with a switchable light filter, Fig. 7 a schematic diagram of a first screen with a switchable light filter, as well as Fig. 8 shows a schematic diagram of a second screen with a switchable light filter. Detailed description of the drawings

[0055] The drawings are not to scale and only represent schematic diagrams.

[0056] Fig.1 shows a schematic diagram of a switchable light filter 5, comprising a first optical element 1, in turn comprising • a plurality of light-absorbing transition dipole moments arranged in a layer of at least 0.1 pm and at most 40 pm thickness, or in several separate layers with a total thickness of transition dipole moments (any adhesive layers between separate layers of transition dipole moments or substrate layers are not included here) of at most 40 pm; a few dipole moments are schematically shown in Fig. 1 in the first optical element with the arrows, while in reality a large number of them are present, • wherein said transition dipole moments are realized by means of at least two (different) dichroic dyes, • where a relative proportion p of all transition dipole moments is 0.6 <p<1 ,0, mit typischerweise p<1 , (in diesem Beispiel) permanent mit einer Toleranz von maximal 15° parallel zu einer für das erste optische Element 1 wählbaren ersten Vorzugsrichtung ausgerichtet ist oder um diese herum variiert (in Fig.1 sind beispielhaft und stellvertretend drei Pfeile, also drei Dipolmomente, als zu dem relativen Anteil p zugehörig eingezeichnet, von den insgesamt 14 eingezeichneten Dipolmomenten erfüllen 12 das vorgenannte Kriterium für die Ausrichtung, hier ist also auch die Ungleichung 0,6<p<1 ,0 erfüllt), wobei die erste Vorzugsrichtung in einem vorgegebenen Winkel a, z.B.with oc=0°, a=±2° or amount (a)>2°, to the perpendicular bisector (see dash-dot line) of the first optical element 1, wherein the angle a is measured in a selectable first plane containing said perpendicular bisector, and wherein preferably said first plane lies parallel to an edge of the first optical element 1, for example the lower edge. • so that light which is incident on the first optical element 1 with a direction of incidence and a polarization state is transmitted or at least partially absorbed depending on its direction of incidence relative to the first optical element 1 and its polarization state, means (not shown in the drawing) for selectively generating a first electric field EF1 or a second electric field EF2, a liquid crystal layer 3 arranged behind or in front of the first optical element 1 in the viewing direction, on which the first electric field EF1 or the second electric field EF2 acts and which, depending thereon, influences the polarization state of light passing through it, wherein the absolute values ​​of the first electric field EF1 and the second electric field EF2 differ by at least 0.1 MV / m,so that the transmission properties of the switchable light filter 5 differ between a first operating mode B1, in which the first electric field EF1 is applied, and a second operating mode B2, in which the second electric field EF2 is applied, wherein the respective relative transmission in the two operating modes B1 and B2 at at least one point (preferably at least 5 points, particularly preferably at a plurality of points, distributed over the entire surface of the switchable light filter 5) on the switchable light filter 5 up to a selectable tolerance in each case by a first transmission T, B i(ß) for the first operating mode B1 or a second transmission T B 2(ß) for the second operating mode B2, which depend on an angle ß and are standardized in such a way that the values ​​of the transmission for the given angle ß=a are T B i(a)=1 and T B2(a)=1 , so that if linearly polarized or elliptically polarized light, in which the ratio of major to minor semi-axis is at least 4:1, • at angles (ß) with a-5°< ß < a+5° into the switchable light filter 5, the ratio TBI (ß) / T B2 (ß) is greater than 0.9 + log (p) and less than 1.3 - log (p), • at angles (ß) with a-30°< ß < a-20° or a+20° < ß < a+30° into the switchable light filter 5, the ratio T B i(ß) / T B2 (ß) is greater than 2 (1 + log (p)), and • at angles (ß) with a-45°< ß < a-35° or a+35° < ß < a+45° into the switchable light filter 5, the ratio T B i(ß) / T B 2(ß) is greater than 9 ■ (1 + 2 ■ log (p)).

[0057] In principle, it should apply that in angular ranges ß < a-5° or a+5°< ß the first transmission T B i(ß) for the first operating mode is usually larger than the second transmission TB 2(ß) for the second operating mode B2. This is achieved, among other things, by the choice of the first and second electric fields EF1 and EF2, as explained below. For the following explanations, it should apply that linearly polarized or elliptically polarized light, in which the ratio of major to minor semi-axis is at least 4:1, is incident on the switchable light filter 5, the polarization of which is predominantly parallel to the said first plane, up to a tolerance of 5°. For the sake of simplicity, oM)° should apply to all following considerations.

[0058] Depending on the design of the liquid crystal layer 3 as TN (Twisted Nematic), VA (Vertical Alignment), IPS (In Plane Switching), FFS (Fringe Field Switching) or possibly another type, if the liquid crystal layer 3 is arranged behind the first optical element 1 in the viewing direction, the first electric field EF1 is selected such that after transmission through the liquid crystal layer 3 the transmitted light has an electric field component of at least 40% perpendicular to the first plane, wherein its polarization is mostly aligned perpendicular (or at a selectable angle in a range from 45° to 135°) to the first plane up to a tolerance of 5°, while the second electric field EF2 is selected such that the transmitted light after passing through the liquid crystal layer 3 has an electric field component of at least 80%, preferably more than 85%, parallel to the first plane.Under the aforementioned condition that the polarization of the incident light is mostly parallel to the said first plane up to a tolerance of 5°, the field strength of the second electric field EF2 would be 0 V / m, i.e. there is essentially no field. The field strength of the first electric field EF1 can be more than 0.1 MV / m, preferably it is an alternating field which changes polarity at a frequency of the order of magnitude of at least 50, preferably at least 0.8 kHz, in a rectangular or sinusoidal form, e.g. at least 1.0 kHz. Frequencies higher than 1.0 kHz are possible. In other words, in operating mode B2 with the. The second electric field EF2 creates the purest possible polarization state, since after transmission through the liquid crystal layer 3, the transmitted light has an electric field component of at least 80% parallel to the first plane. In contrast, in the first operating mode B1 with the first electric field EF1, a mixed or significantly rotated electric field component predominates, because after passing through the liquid crystal layer 3, the transmitted light has an electric field component of at least 40% perpendicular to the first plane. This is implemented, for example, in the case of a liquid crystal layer 3 in the form of an IPS cell, or when circular polarization is used after the liquid crystal layer 3.

[0059] What is particularly essential to the invention is that the selection of the relative proportion p of all transition dipole moments, in conjunction with the differently selected first and second electric fields EF1, EF2, of the absolute values ​​differ by at least 0.1 MV / m, and the associated polarization influence leads to the fulfillment of the above-mentioned inequalities. The inequalities specify the angle-dependent contrast or the ratios of the said transmissions. Fig. 2 shows exemplary ratios of transmissions for two parameter sets ID1 and ID2. These are simulations based on measurements.The parameters used here for light with a wavelength of 500 nm and a real part of the refractive index of 1.5 are: for ID1, the layer thickness of the dichroic dye is 6 pm with an imaginary part of the refractive index of 0.15 for p-polarized light and 0.0025 for s-polarized light, and for ID2, the layer thickness is 6 pm with an imaginary part of the refractive index of 0.15 for p-polarized light and 0.005 for s-polarized light. Furthermore, the second electric field EF2 is field-free, while the first electric field EF1 has an absolute value of 0.1 MV / m. It can be seen that the ratio T. B i(ß) / T B2(ß) in the case of ID2, especially at angles ß<-40° or ß>40°, differs significantly from the ratio mentioned for ID1, which is due to the reduced absorption of s-polarized light for ID1 compared to ID2. Nevertheless, both parameter sets ID1 and ID2 satisfy the inequalities resulting from the invention. The parameter sets ID1 and ID2 even satisfy the circumstance that, when linearly polarized or elliptically polarized light, for which the ratio of the major to the minor semi-axis is at least 4:1, ■ at angles (ß) with a-5°< ß < a+5° into the switchable light filter (5), the ratio TBI (ß) / T B 2(ß) is greater than 1 ,0 + log (p) and less than 1 ,3 - log (p), ■ at angles (ß) with a-30°< ß < a-20° or a+20° < ß < a+30° into the switchable light filter (5), the ratio T B i(ß) / T B 2(ß) is greater than 3 (1 + log (p)), and ■ at angles (ß) with a-45°< ß < a-35° or a+35° < ß < a+45° into the switchable light filter (5), the ratio T B i(ß) / T B2 (ß) is greater than 16 ■ (1 + 2 ■ log (p)).

[0060] An important means-effect relationship lies in the following fact: By switching between the first operating mode B1, in which the first electric field EF1 is applied, and the second operating mode B2, in which the second electric field EF2 is applied, wherein the absolute values ​​of the first electric field EF1 and the second electric field EF2 differ by at least 0.1 MV / m, p-polarized light incident on the liquid crystal layer is - depending on the design - only in one operating mode, e.g. the first operating mode B1, essentially converted into s-polarized light, which then incident on the first optical element 1 and is transmitted to a significant extent even at angles greater than 20°. In contrast, depending on the design, only in the other operating mode, e.g.In the first operating mode B2, s-polarized light incident on the liquid crystal layer 3 is essentially converted into p-polarized light, which then impinges on the first optical element 1 and is absorbed to a significant extent at angles greater than 20°. As a result, the ratios for the transmissions T described above are obtained. B I (ß) / T B2 (ß) in the specified angular ranges.

[0061] If the absorbing transition dipole moments are further formed by at least two dichroic dyes, where the dye mass density is usually more than 1%, this helps to satisfy the given inequalities for reasonable transmission ratios.

[0062] For standardization of the transmission T B i(a)=1 and T B2(a)=1, the following should be noted: The angles ß and a are, of course, measured in the same plane described above. It is also possible that T B i(a)>1 and / or T B 2(oc)>1 applies to angle ß^a. In many cases, T B i(a)<1 and / or T B 2(OC)<1 applies to angle ß^a.

[0063] Furthermore, Fig. 3 shows exemplary transmission ratios for two parameter sets ID3 and ID4 and Fig. 4 shows exemplary transmission ratios for two parameter sets ID5 and ID6. In the case of ID3 - ID6, light with a wavelength of 500 nm is irradiated and the dye layer has a thickness of 6 pm with a refractive index of 1.5 + 0.15i for p-polarized light and 1.5 + 0.0025i for p-polarized light. For positive complex refractive indices, absorption occurs. In the case of ID3, the linear polarization of the light differs by 45° between B1 and B2 and by 60° for ID4. For ID5, the light is linearly polarized in state B2 and circularly polarized in B2. For ID6, the light is linearly polarized in state B2 and elliptically polarized in B2 when it strikes the optical element 1.

[0064] In a preferred embodiment, light penetrating the liquid crystal layer 3 is transmitted essentially unchanged when the second electric field EF2 is applied, while when the first electric field EF1 is applied, the incident light is circularly or elliptically polarized, or the polarization of the light is rotated by 90°. In this context, this essentially means that the orientation of the liquid crystal molecules at the interfaces is determined by electric fields and surface-induced forces, thus the liquid crystal molecules are not ideally aligned, which leads to an undesirable, smaller change in polarization.

[0065] If the liquid crystal layer 3 is arranged behind the first optical element 1 in the viewing direction, the incident light is preferably linearly polarized or elliptically polarized light, in which the ratio of the major to the minor semi-axis is at least 4:1 (preferably at least 5:1 or more). This can be achieved, for example, by linear polarization filters in the light path, or by λ / 4 layers in the case of circularly polarized light.

[0066] Furthermore, Fig.5 shows a schematic diagram of a further switchable light filter 5. The liquid crystal layer 3 is arranged in front of the first optical element 1 in the viewing direction, ie even if there is usually a polarization filter X in front of the liquid crystal layer 3 in the viewing direction, the values ​​for the first and second electric fields EF1 and EF2 are used to generate the operating modes B1 and B2. Such a structure is generally used in conjunction with a transparent image display device with a backlight, with the switchable light filter 5 located between them. In this embodiment, the light transmitted by the first optical element 1 is essentially at least 75% or even 90% s-polarized light at angles greater than 20°. Depending on the applicable operating mode, this produces p- or s-polarized light (at least 95%) with respect to the first plane, which is then either largely absorbed or transmitted at angles greater than 20° depending on the orientation of the polarization filter X, which can be part of the said image display device.

[0067] In a further embodiment, the switchable light filter 5 comprises at least two first optical elements, with a birefringent retardation plate optionally arranged between at least two such first optical elements. Furthermore, the at least two first optical elements could, if appropriate, have different thicknesses of the layers containing the plurality of light-absorbing transition dipole moments, but this is not required.

[0068] Fig. 6 shows a schematic diagram of a lighting device with a switchable light filter 5 in a first embodiment for a screen, which can be operated in at least two operating modes B1 for a free view mode and B2 for a restricted view mode, in which light is emitted into a viewing angle range that is restricted for a viewer compared to the free view mode, comprising - a surface-like extended backlight 8, which radiates light and which is optionally constructed to be directly luminous (e.g. with a locally dimmable LED matrix), as well as - a switchable light filter 5 according to the invention arranged in front of the background lighting 8 in the viewing direction as described above.

[0069] Furthermore, Fig. 7 shows a schematic diagram of a first screen which can be operated in at least two operating modes B1 for a free view mode and B2 for a restricted view mode, in which light is emitted into a viewing angle range which is restricted for a viewer compared to the free view mode, in a first embodiment with a switchable light filter. This comprises - a lighting device as described above, - and, if no first linear polarization filter is arranged in the switchable light filter 5 of the illumination device, a second linear polarization filter P arranged in front of the background illumination 8 in the viewing direction, whereby light emanating from the background illumination 8 and penetrating the second linear polarization filter P is restricted in its propagation directions, and - a transmissive image display device 11, which is arranged in front of the switchable light filter 5 in the viewing direction, - wherein in operating mode B2 the second electric field EF2 is applied and in operating mode B1 the first electric field EF1 is applied.

[0070] It is preferred that the first or second linear polarization filter P is arranged in the transmissive image display device 11 or is a part of it.

[0071] Furthermore, Fig. 8 shows a schematic diagram of a second screen in a second embodiment, which can be operated in at least two operating modes B1 for a free view mode and B2 for a restricted view mode, in which light is emitted into a viewing angle range that is restricted for a viewer compared to the free view mode, with a switchable light filter 5, comprising - an image display device 12, whereby in principle any type of image display device 12 is possible, for example LC panel, OLED, microLED and others, - in the viewing direction in front of the image display device 12, a switchable light filter 5 according to the invention as described above, - wherein in operating mode B2 the second electric field EF2 is applied and in operating mode B1 the first electric field EF1 is applied.

[0072] Optionally, the switchable light filter 5 can be subsequently attached by a user and / or reversibly to the image display device 12. In this case, a light filter 5 can be sold as a so-called "after-market product."

[0073] By “limited angular range” is meant within the scope of the invention, and in particular with regard to operating mode B2, that the corresponding Luminance is concentrated to at least 80% or 90% within a defined angular range, while residual light may still be present outside the defined, restricted angular range, which is usually due to technical reasons. Ideally, such residual light is minimal and decreases with increasing angles.

[0074] The switchable light filter 5 can further comprise a polarization filter, which is arranged upstream or downstream of the first optical element 1 in the direction of incidence. Alternatively or additionally, a 4-fold polarization layer is also conceivable, for example, in the case of incident circularly polarized light, which is converted into (essentially) linearly polarized light due to this layer.

[0075] The invention solves the stated problem: A light filter with an optical element has been described, in which light incident on the optical element is transmitted or partially or completely absorbed depending on its direction of incidence and its polarization properties – not primarily but depending on its position. Such light filters influence the transmission of light in an angle-dependent manner – optionally perpendicular to a seated or standing observer – with the possibility of switching between at least two operating modes. In particular, the angle-dependent ratio of the transmission behavior between the two operating modes is defined. Furthermore, the light filters can also be used with self-luminous display types such as OLEDs.

[0076] The invention described above, in conjunction with an image display device, can be advantageously used wherever confidential data is displayed and / or entered, such as when entering a PIN or displaying data at ATMs or payment terminals, entering a password, or reading emails on mobile devices. As described above, the invention can also be used in cars to selectively withhold distracting image content from the driver or passenger. List of reference symbols first optical element 2 second optical element 3 Liquid crystal layer 5 switchable light filters 8 Backlight 11 Transmissive image display device 12 Image display device P, X polarizing filters

Claims

Patent claims 1 . Switchable light filter (5), comprising a first optical element (1 ), in turn comprising • a plurality of light-absorbing transition dipole moments arranged in a layer with a thickness of at least 0.1 pm and a maximum of 40 pm, or in several separate layers with a total thickness of transition dipole moments of a maximum of 40 pm, • where a relative proportion p of all transition dipole moments is 0.6 <p<1 ,0 permanent oder mindestens in einem ersten Zustand mit einer Toleranz von maximal 15° parallel zu einer für das erste optische Element (1 ) wählbaren ersten Vorzugsrichtung ausgerichtet ist oder um diese herum variiert, wobei die erste Vorzugsrichtung in einem vorgegebenen Winkel a zur Mittelsenkrechten des ersten optischen Elements (1 ) angeordnet ist, wobei der Winkel a in einer wählbaren ersten Ebene, welche die besagte Mittelsenkrechte enthält, gemessen wird, • so that light which is incident on the first optical element (1) with a direction of incidence and a state of polarization is transmitted or at least partially absorbed depending on its direction of incidence relative to the first optical element (1) and its state of polarization, Means for selectively generating a first electric field (EF1) or a second electric field (EF2), a liquid crystal layer (3) arranged behind or in front of the first optical element (1) in the viewing direction, on which the first electric field (EF1) or the second electric field (EF2) acts and which, depending thereon, influences the polarization state of light passing through it, wherein the absolute values ​​of the first electric field (EF1) and the second electric field (EF2) differ by at least 0.1 MV / m, a first linear polarization filter (X) arranged in front of the liquid crystal layer (3) in the viewing direction, if the liquid crystal layer (3) is arranged in front of the first optical element (1) in the viewing direction, so that the transmission properties of the switchable light filter (5) can be switched between a first operating mode B1, in which the first electric field (EF1) is applied,and a second operating mode B2, in which the second electric field, (EF2), whereby the respective relative transmission in the two operating modes B1 and B2 at least at one point on the switchable light filter (5) is determined up to a selectable tolerance by a first transmission T B i(ß) for the first operating mode B1 or a second transmission T B 2(ß) for the second operating mode B2, which depend on an angle ß and are standardized in such a way that the values ​​of the transmission for the given angle ß=a are T B i(a)=1 and T B2 (a)=1 , so that if linearly polarized or elliptically polarized light, in which the ratio of major to minor semi-axis is at least 4:1, • at angles (ß) with a-5° < ß < a+5° into the switchable light filter (5), the ratio TBI (ß) / T B2(ß) is greater than 0.9 + log (p) and less than 1.3 - log (p), • at angles (ß) with a-30 °< ​​ß < a-20° or a+20° < ß < a+30° into the switchable light filter (5), the ratio T B i(ß) / T B2 (ß) is greater than 2 (1 + log (p)), and • at angles (ß) with a-45° < ß < a-35° or a+35° < ß < a+45° into the switchable light filter (5), the ratio T B i(ß) / T B2 (ß) is greater than 9 ■ (1 + 2 ■ log (p)).

2. Switchable light filter (5) according to claim 1, characterized in that its first optical element (1) comprises a plurality of light-absorbing transition dipole moments arranged in a layer having a thickness of at least 1 pm and at most 40 pm, or in several separate layers with a total thickness of transition dipole moments of at most 40 pm, - so that when linearly polarized or elliptically polarized light, in which the ratio of major to minor semi-axis is at least 4:1, ■ at angles (ß) with a-5° < ß < a+5° into the switchable light filter (5), the ratio T B I (ß) / T B2 (ß) is greater than 1 .0 + log (p) and less than 1 .3 - log (p), ■ at angles (ß) with a-30°< ß < a-20° or a+20° < ß < a+30° into the switchable light filter (5), the ratio T B i(ß) / T B2 (ß) is greater than 3 (1 + log (p)), and ■ at angles (ß) with a-45°< ß < a-35° or a+35° < ß < a+45° into the switchable light filter (5), the ratio T B i(ß) / T B 2(ß) is greater than 16 ■ (1 + 2 ■ log (p)).

3. Switchable light filter (5) according to claim 1 or 2, characterized in that the first optical element (1) and / or the liquid crystal layer (3) and / or the means for selectively generating a first or second electric field E1, E2 is divided into several separately switchable segments, so that local switchability between the respectively possible operating modes is enabled.

4. Lighting device for a screen which can be operated in at least a first operating mode B1 for a free view mode and a second operating mode B2 for a restricted view mode, in which light is emitted into a viewing angle range which is restricted for a viewer compared to the free view mode, comprising - a surface-like backlight (8) which emits light and - a switchable light filter (5) according to one of claims 1 to 3, arranged in front of the background lighting (8) in the viewing direction.

5. A screen which can be operated in at least a first operating mode B1 for a free view mode and a second operating mode B2 for a restricted view mode, in which light is emitted into a viewing angle range which is restricted for a viewer compared to the free view mode, comprising - a lighting device according to claim 4, - if no first linear polarization filter (X) is arranged in the switchable light filter (5) of the illumination device, a second linear polarization filter (P) arranged in front of the background illumination (8) in the viewing direction, whereby light emanating from the background illumination and penetrating the second linear polarization filter (P) is restricted in its propagation directions, and - a transmissive image display device (11) which is arranged in front of the switchable light filter (5) in the viewing direction, - wherein 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.

6. Screen according to claim 5, characterized in that - if present - the first linear polarization filter (X) and otherwise the second linear polarization filter (P) are arranged in the transmissive image display device (11) or are part of it.

7. A screen which can be operated in at least a first operating mode B1 for a free view mode and a second operating mode B2 for a restricted view mode, in which light is emitted into a viewing angle range which is restricted for a viewer compared to the free view mode, comprising - an image display device (12), - in the viewing direction in front of the image display device (12) a switchable light filter (5) according to one of claims 1 to 3, - wherein 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.

8. Screen according to claim 7, characterized in that the switchable light filter (5) can be subsequently attached by a user and / or reversibly to the image display device (12).

9. Screen according to one of claims 7 to 8, characterized in that a second optical element (2) is arranged in front of the image display device (12) in the viewing direction, which second optical element comprises: • a multitude of light-absorbing transition dipole moments, • wherein the majority of the transition dipole moments are permanently or at least in a first state with a tolerance of maximum 20° parallel to a second preferred direction selectable for the second optical element (2) or fluctuate around this, wherein the second preferred direction is arranged at an angle oci to the perpendicular bisector of the second optical element (1), wherein the angle oci is measured in a selectable second plane containing said perpendicular bisector, • so that light which is incident on the second optical element (2) is transmitted or at least partially absorbed depending on its direction of incidence relative to the second optical element (2) and its polarization state.

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