DE102020007974B3 - Optical element with variable transmission and screen with such an optical element - Google Patents

Abstract

The invention relates to an optical element, comprising a transparent light guide (1) with a light inlet surface (F1) and a light outlet surface (F2), with first areas (G1) alternating on the light inlet surface (F1) and corresponding thereto on the light outlet surface (F2). and second areas (G2) are formed, wherein at least the second areas (G2) lying on the side of the light exit surface (F2) each have a volume (V) which contains a transparent liquid (FL) or a framework matrix which light absorbing elements contains, which are designed either as liquid droplets (F) or as electrophoretic particles (P), and where by means of an electric field in the case of electrophoretic particles (P) their position and in the case of liquid droplets (F) their expansion, shape and / or position is adjustable, so that a) the light-absorbing elements (F, P) in a first state to more than 85% the second en electrodes (E2) cover, as a result of which the total internal reflection of light on the structured surfaces is disturbed, and b) the light-absorbing elements (F, P) in a second state cover less than 15% of the second electrodes (E2), see above that when light strikes the optical element, it leaves the optical element in a restricted angular range in the first state, or propagates in the light guide (1) in the second state until it leaves it at angles greater than those of said restricted angular range. The invention also relates to further alternatives of the optical element.

Description

Field of invention

In recent years, great advances have been made in widening the viewing angle in LCDs. However, there are often situations in which this very large viewing area of a screen can be a disadvantage. Information is also increasingly available on mobile devices such as notebooks and tablet PCs, such as bank details or other personal details and sensitive data. Accordingly, people need control over who can see this sensitive data; You have to be able to choose between a wide viewing angle in order to share information on your display with others, e.g. when looking at vacation photos or for advertising purposes. On the other hand, you need a small viewing angle if you want to treat the image information confidentially.

A similar problem arises in vehicle construction: When the engine is switched on, the driver must not be distracted by image content, such as digital entertainment programs, while the front passenger wants to consume it while driving. A screen is therefore required that can switch between the corresponding display modes.

State of the art

Additional films based on micro-lamellas have already been used for mobile displays in order to achieve their visual data protection. However, these foils cannot be switched over, they have to be put on by hand and then removed again. You also have to transport them separately to the display when you don't need them. A major disadvantage of using such lamellar foils is also associated with the associated loss of light.

the US 6,765,550 B2 describes such a privacy screen through micro-slats. The greatest disadvantage here is the mechanical removal or mechanical attachment of the filter as well as the loss of light in protected mode.

In the U.S. 5,993,940 A describes the use of a film with evenly arranged, small prism strips on its surface in order to achieve a privacy mode. Development and production are quite complex.

In the WO 2012/033583 A1 the switch between free and restricted view is generated by controlling liquid crystals between so-called "chromonic" layers. This results in a loss of light and the effort involved is quite high.

the US 2012/0235891 A1 describes a very complex backlight in a screen. There come according to 1 and 15th Not only several light guides are used, but also other complex optical elements such as microlens elements 40 and prism structures 50 that transform the light from the rear lights on its way to the front lights. This is expensive and time-consuming to implement and also associated with loss of light. According to the variant after 17th in US 2012/0 235 891 A1 both produce light sources 4R and 18th Light with a narrow angle of illumination, the light from the rear light source 18th is only converted into light with a large angle of illumination in a complex manner. This complex transformation is - as already noted above - strongly reducing the brightness.

According to the JP 2007-155783 A are special optical surfaces that are complex to calculate and manufacture 19th which then divert light into various narrow or wide areas depending on the angle of incidence. These structures are similar to Fresnel lenses. There are also interference edges that deflect light in undesired directions. It therefore remains unclear whether really sensible light distributions can be achieved.

In the US 2013/0308185 A1 describes a special, stepped light guide that emits light over a large area in different directions, depending on the direction from which it is illuminated from a narrow side. In interaction with a transmissive image display device, for example an LC display, a screen that can be switched between free and restricted viewing mode can thus be generated. One disadvantage here is that the restricted visual effect can only be created for the combination left / right, i.e. from the sides, or for the combination above / below, but not for all four options at the same time, as is necessary for certain payment transactions is where viewing from the side as well as from above or below should be restricted. In addition, residual light is still visible from blocked viewing angles in restricted viewing mode.

the WO 2015/121398 A1 the applicant describes a screen with two operating modes, in which scatter particles are essentially present in the volume of the corresponding light guide for switching the operating modes. The scattering particles selected there from a polymer, however, generally have the disadvantage that light is coupled out from both large areas, as a result of which about half of the useful light goes in the wrong direction, namely towards the backlight, radiated and there, due to the structure, cannot be recycled to a sufficient extent and is lost. In addition, the polymer scattering particles distributed in the volume of the light guide can, under certain circumstances, especially at a higher concentration, lead to scattering effects which reduce the visual protection effect in the protected operating mode.

Furthermore describes the WO 2021/032735 A1 the applicant an optical element with variable transmission and a screen with such an optical element. Depending on the design, different types of electro- or magnetophoretic particles are used, which are moved in chambers in order to vary the angle-dependent transmission. However, there is no provision there to disrupt the total reflection in the optical element in order to switch between different optical effects.

the US 2004/0136047 A1 discloses a display based on the disruption of total internal reflection. An angle-dependent transmission in several states cannot be generated with this, however.

Furthermore describes the US 2019/0107765 A1 a hybrid reflective display. Even with this teaching it is not possible to generate an angle-dependent transmission in several states.

In the US 2020/0050075 A1 a switchable light collimation layer is described. An inherent disadvantage of this solution is the long switching time which is necessary to cover the relatively long distances of the pigment particles in the chambers between the individual switching states.

the US 2017/0160620 A1 discloses a method and arrangement for a front-lit display which is constructed in a semi-retro-reflective manner. However, this does not make it possible to generate an angle-dependent transmission in several states.

Furthermore there is the WO 2007/082369 A1 a method for increasing brightness in reflective displays. Here, too, it is not possible to generate an angle-dependent transmission in several states.

Finally describes the EP 3327498 A1 a screen with a wide viewing angle based on the modulation of total internal reflection. With such a screen, no angle-dependent transmission can be achieved.

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 mode and / or a long time Have switching time.

Description of the invention

It is therefore the object of the invention to describe an optical element which can influence the transmission as a function of the angle and which can switch between at least two states. The optical element should be able to be implemented inexpensively and, in particular, be universally usable with different types of screen in order to enable a switchover between a privacy screen and a free viewing mode, the resolution of such a screen essentially not being reduced.

• ― einen transparenten, platten- oder schalenförmigen, als Lichtleiter aus einem Material mit einer Brechzahl n_L ausgestalteten Grundkörper mit einer als Lichteintrittsfläche ausgebildeten ersten Großfläche und einer als Lichtaustrittsfläche ausgebildeten zweiten Großfläche, wobei an der Lichteintrittsfläche und dazu korrespondierend an der Lichtaustrittsfläche einander abwechselnd erste Bereiche G1 und zweite Bereiche G2 ausgebildet, ausgespart oder angeordnet sind,
• ― wobei die ersten Bereiche G1 mit einem transparenten Material mit einer Brechzahl n_G1 ausgefüllt sind, wobei die Brechzahlen n_L und n_G1 höchstens bis zu einem Wert von 0,11 voneinander abweichen, und
• ― wobei mindestens die auf der Seite der Lichtaustrittsfläche liegenden zweiten Bereiche G2 jeweils ein Volumen aufweisen, welches eine transparente Flüssigkeit oder eine Gerüstmatrix mit einer Brechzahl n_G2, welche kleiner als die Brechzahl n_L ist, enthält, wobei die Flüssigkeit oder Gerüstmatrix Licht absorbierende Elemente enthält, welche in ihrer Gesamtheit entweder als Flüssigkeitstropfen oder als elektrophoretische Partikel ausgebildet sind, und wobei mittels eines wählbaren und veränderbaren elektrischen Feldes im Falle elektrophoretischer Partikel deren Position und im Falle von Flüssigkeitstropfen deren Ausdehnung, Form und/oder Position einstellbar ist, wobei die Brechzahlen n_L und n_G2 sich mindestens um einen Wert von 0,05 und höchstens um einen Wert von 0,35 unterscheiden,
• ― wobei der Lichtleiter an Grenzflächen zu den jeweils ein Volumen aufweisenden zweiten Bereichen G2 mindestens auf der Seite der Lichtaustrittsfläche strukturierte Oberflächen aufweist, welche Licht, dass über die Bereiche G1 in den Lichtleiter eintritt, überwiegend intern total reflektieren,
• ― elektrische Schaltmittel in den ein Volumen aufweisenden zweiten Bereichen G₂ auf der Seite der Lichtaustrittsfläche, mit planen ersten Elektroden an einer dem Lichtleiter abgewandten Fläche, welche zur Lichtaustrittsfläche des Lichtleiters parallel liegt oder dieser entspricht, und mit transparenten, an den strukturierten Oberflächen anliegenden zweiten Elektroden im Innern des zweiten Bereichs G₂ an einer Grenzfläche zum Lichtleiter, welche umgekehrt zu den ersten Elektroden gepolt sind und wobei die Polungen zwischen einem ersten und einem zweiten Zustand umschaltbar sind,
• ― sowie auf der Seite der Lichteintrittsfläche in den zweiten Bereichen G₂ analog strukturierte Oberflächen und/oder eine opake Reflexionsschicht, welche an der Lichteintrittsfläche angebracht ist, so dass
  1. a) die Licht absorbierenden Elemente im ersten Zustand zu mehr als 85% die zweiten Elektroden bedecken, wodurch die innere Totalreflexion von Licht an den strukturierten Oberflächen gestört und die Ausbreitung von Licht, welches über die ersten Bereiche G₁ in den Lichtleiter eintritt, mittels Absorption durch die Licht absorbierenden Elemente überwiegend unterbunden wird, und
  2. b) die Licht absorbierenden Elemente im zweiten Zustand zu weniger als 15% die zweiten Elektroden bedecken, so dass die Ausbreitung von Licht, welches über die ersten Bereiche G₁ in den Lichtleiter eintritt, zu weniger als 50% von den Licht absorbierenden Elementen absorbiert wird,
  • ― so dass, wenn Licht auf das optische Element einfällt, dieses mindestens durch an der Lichteintrittsfläche lokalisierte erste Bereiche G₁ in den Lichtleiter eintritt, und
    • ― im ersten Zustand das optische Element entweder in einem eingeschränkten Winkelbereich durch an der Lichtaustrittsfläche lokalisierte erste Bereiche G₁ verlässt oder aufgrund der Licht absorbierenden Elemente in den zweiten Bereichen G₂ überwiegend absorbiert wird, oder
    • ― im zweiten Zustand das optische Element entweder in einem eingeschränkten Winkelbereich durch an der Lichtaustrittsfläche lokalisierte erste Bereiche G₁ verlässt oder aufgrund innerer Totalreflexion an den strukturierten Oberflächen und ggf. Reflexion an einer reflektierenden Schicht an der Lichteintrittsfläche im Lichtleiter solange propagiert, bis es den Lichtleiter durch die an der Lichtaustrittsfläche lokalisierten ersten Bereiche G₁ in größeren Winkeln als die des besagten eingeschränkten Winkelbereichs verlässt.

This object is achieved in a first alternative by an optical element comprising

• - A transparent, plate-shaped or shell-shaped base body designed as a light guide made of a material with a refractive index n _L with a first large area designed as a light entry area and a second large area designed as a light exit area, with first areas alternating on the light entry area and correspondingly on the light exit area G1 and second areas G2 designed, recessed or arranged,
• - being the first areas G1 are filled with a transparent material with a refractive index n _G1 , the refractive indices n _L and n _G1 differing from one another by a maximum of 0.11, and
• - wherein at least the second areas lying on the side of the light exit surface G2 each have a volume which contains a transparent liquid or a framework matrix with a refractive index n _G2 , which is smaller than the refractive index n _L , wherein the liquid or framework matrix contains light-absorbing elements, which in their entirety either as liquid drops or as electrophoretic particles are formed, and by means of a selectable and changeable electrical field in the case of electrophoretic particles their position and in the case of liquid droplets their expansion, shape and / or position can be set, the refractive indices n _L and n _G2 at least by a value of 0, 05 and differ by a maximum of 0.35,
• - wherein the light guide at interfaces to the second areas each having a volume G2 at least on the side the light exit surface has structured surfaces, which light that over the areas G1 enters the light guide, mostly totally reflecting internally,
• - electrical switching means in the second areas G ₂ having a volume on the side of the light exit surface, with planar first electrodes on a surface facing away from the light guide, which is parallel to or corresponds to the light exit surface of the light guide, and with transparent second electrodes resting on the structured surfaces Electrodes in the interior of the second region G ₂ at an interface with the light guide, which are polarized in reverse to the first electrodes and wherein the polarity can be switched between a first and a second state,
• - As well as on the side of the light _{entry surface in the second regions G 2} similarly structured surfaces and / or an opaque reflective layer which is attached to the light entry surface, so that
  1. a) the light-absorbing elements in the first state cover more than 85% of the second electrodes, which disrupts the total internal reflection of light on the structured surfaces and the propagation of light which enters the light guide _{via the first areas G 1 by means of absorption} is predominantly prevented by the light-absorbing elements, and
  2. b) the light-absorbing elements in the second state cover less than 15% of the second electrodes, so that _{less than 50% of the propagation of light which enters the light guide via the first regions G 1 is} absorbed by the light-absorbing elements ,
  • - so that when light strikes the optical element, it _{enters the light guide at least through first regions G 1 located} on the light entry surface, and
    • - in the first state the optical element either _{leaves in a restricted angular range through first regions G 1} located on the light exit surface or is predominantly absorbed _{in the second regions G 2} due to the light-absorbing elements, or
    • - In the second state, the optical element either leaves the optical element in a restricted angular range through first areas G ₁ located on the light exit surface or due to total internal reflection on the structured surfaces and possibly reflection on a reflective layer on the light entry surface in the light guide until it propagates the light guide _{through the first regions G 1} located on the light exit surface at angles greater than those of said restricted angular region.

In this first alternative, in the second state, the light-absorbing elements must not have any contact with the second electrode facing the light guide. This state corresponds to a so-called public mode in which the field of vision is not restricted.

In the first state, however, the absorbent elements are in contact with the interface. This state corresponds to a so-called private mode in which the field of vision is restricted. The minimum thickness of the layer made up of the light-absorbing elements on the electrode facing the light guide should be 100 nm on at least 85% of the surface. The maximum thickness of such a layer is typically five micrometers.

• ― einen transparenten, platten- oder schalenförmigen, als Lichtleiter aus einem Material mit einer Brechzahl n_L ausgestalteten Grundkörper mit einer als Lichteintrittsfläche ausgebildeten ersten Großfläche und einer als Lichtaustrittsfläche ausgebildeten zweiten Großfläche, wobei an der Lichteintrittsfläche und dazu korrespondierend an der Lichtaustrittsfläche einander abwechselnd erste Bereiche G1 und zweite Bereiche G2 ausgebildet, ausgespart oder angeordnet sind,
• ― wobei die ersten Bereiche G1 mit einem transparenten Material mit einer Brechzahl n_G1 ausgefüllt sind, wobei die Brechzahlen n_L und n_G1 höchstens bis zu einem Wert von 0,11 voneinander abweichen, und
• ― wobei mindestens die auf der Seite der Lichtaustrittsfläche liegenden zweiten Bereiche G2 jeweils ein Volumen aufweisen, welches eine transparente Flüssigkeit oder eine Gerüstmatrix enthält, wobei die Flüssigkeit oder Gerüstmatrix Licht reflektierende Elemente enthält, welche in ihrer Gesamtheit entweder als Flüssigkeitstropfen oder als elektrophoretische Partikel ausgebildet sind, und wobei mittels eines wählbaren und veränderbaren elektrischen Feldes im Falle elektrophoretischer Partikel deren Position und im Falle von Flüssigkeitstropfen deren Ausdehnung, Form und/oder Position einstellbar ist,
• ― wobei die ein Volumen aufweisenden zweiten Bereiche G2 an einer dem Lichtleiter abgewandten Seite jeweils eine opake Absorptionsschicht aufweisen,
• ― elektrische Schaltmittel in den ein Volumen aufweisenden zweiten Bereichen G2 auf der Seite der Lichtaustrittsfläche, mit ersten Elektroden an der dem Lichtleiter abgewandten Fläche, welche zur Lichtaustrittsfläche des Lichtleiters parallel liegt oder dieser entspricht, und mit transparenten, an einer planen Grenzfläche zum Lichtleiter anliegenden zweiten Elektroden im Innern des zweiten Bereichs G2, welche umgekehrt zu den ersten Elektroden gepolt sind und wobei die Polungen zwischen einem ersten und einem zweiten Zustand umschaltbar sind,
• ― sowie auf der Seite der Lichteintrittsfläche in den zweiten Bereichen G2 eine opake Reflexionsschicht, welche an der Lichteintrittsfläche angebracht ist, so dass
  1. a) die Licht reflektierenden Elemente im ersten Zustand zu weniger als 15% die zweite Elektrode bedecken, so dass Licht, welches über die ersten Bereiche G₁ in den Lichtleiter eintritt und in die zweiten Bereiche G2 übertritt, überwiegend an den opaken Schichten absorbiert wird, und
  2. b) die Licht reflektierenden Elemente im zweiten Zustand zu mehr als 85% die zweite Elektrode bedecken, so dass Licht, welches über die ersten Bereiche G1 in den Lichtleiter eintritt, an den Grenzflächen des Lichtleiters zu den zweiten Bereichen G2 reflektiert wird,
  • ― so dass, wenn Licht auf das optische Element einfällt, dieses mindestens durch an der Lichteintrittsfläche lokalisierte erste Bereiche G1 in den Lichtleiter eintritt, und
    • - im ersten Zustand das optische Element entweder in einem eingeschränkten Winkelbereich durch an der Lichtaustrittsfläche lokalisierte erste Bereiche G1 verlässt oder aufgrund der opaken Schichten in den zweiten Bereichen G2 absorbiert wird, oder
    • - im zweiten Zustand das optische Element entweder in einem eingeschränkten Winkelbereich durch an der Lichtaustrittsfläche lokalisierte erste Bereiche G1 verlässt oder aufgrund der Reflexion an einer reflektierenden Schicht an der Lichteintrittsfläche im Lichtleiter solange propagiert, bis es den Lichtleiter durch die an der Lichtaustrittsfläche lokalisierten ersten Bereiche G1 in größeren Winkeln als die des besagten eingeschränkten Winkelbereichs verlässt.

In a second alternative, the object of the invention is also achieved by an optical element comprising

• - A transparent, plate-shaped or shell-shaped base body designed as a light guide made of a material with a refractive index n _L with a first large area designed as a light entry area and a second large area designed as a light exit area, with first areas alternating on the light entry area and correspondingly on the light exit area G1 and second areas G2 designed, recessed or arranged,
• - being the first areas G1 are filled with a transparent material with a refractive index n _G1 , the refractive indices n _L and n _G1 differing from one another by a maximum of 0.11, and
• - wherein at least the second areas lying on the side of the light exit surface G2 each have a volume which contains a transparent liquid or a framework matrix, the liquid or framework matrix containing light-reflecting elements, which in their entirety are formed either as liquid droplets or as electrophoretic particles, and by means of a selectable and changeable electric field in the case of electrophoretic Particles whose position and, in the case of liquid droplets, their expansion, shape and / or position can be adjusted,
• - wherein the second areas having a volume G2 on one of the light guides facing away side each have an opaque absorption layer,
• - electrical switching means in the second areas having a volume G2 on the side of the light exit surface, with first electrodes on the surface facing away from the light guide, which is parallel to or corresponds to the light exit surface of the light guide, and with transparent second electrodes in the interior of the second area, resting on a flat interface with the light guide G2 , which are polarized opposite to the first electrodes and wherein the polarity can be switched between a first and a second state,
• - as well as on the side of the light entry surface in the second areas G2 an opaque reflective layer which is attached to the light entry surface so that
  1. a) the light-reflecting elements in the first state cover less than 15% of the second electrode, so that light which _{enters the light guide via the first regions G 1} and into the second regions G2 transfers, is mainly absorbed by the opaque layers, and
  2. b) the light-reflecting elements in the second state cover more than 85% of the second electrode, so that light which passes over the first areas G1 enters the light guide, at the interfaces of the light guide to the second areas G2 is reflected,
  • - so that when light is incident on the optical element, this is at least through first areas localized on the light entry surface G1 enters the light guide, and
    • - In the first state, the optical element either in a restricted angular range through first regions located on the light exit surface G1 leaves or due to the opaque layers in the second areas G2 is absorbed, or
    • - In the second state, the optical element either in a restricted angular range through first regions located on the light exit surface G1 leaves or propagates due to the reflection on a reflective layer on the light entry surface in the light guide until it passes the light guide through the first areas located on the light exit surface G1 leaves at angles greater than that of said restricted angular range.

For example, the second electrodes are formed over the entire area of the light guide, while the first electrodes can cover the entire area of the light guide or only parts thereof. In principle, it is also possible that the first and the second electrode are both applied to one and the same surface in a non-overlapping manner. Here, too, the first state corresponds to a private mode, while the second state corresponds to a public mode.

Optionally, an optical element according to the invention of the first or second alternative also comprises on the side of the light entry surface. in the second areas having a volume G2 electrical switching means with planar first electrodes on a surface facing away from the light guide, which is parallel to or corresponds to the light entry surface of the light guide, and with transparent second electrodes resting on the structured surfaces inside the second area G2 at an interface to the light guide, which are polarized in reverse to the first electrodes and wherein the polarity can be switched between a first and a second state. This configuration makes it possible to additionally, ie intensify, influence the two states on the side of the light entry surface of the light guide.

The light entry and light exit surfaces of the light guide can preferably be arranged parallel to one another. However, in special configurations, for example when special angle-dependent transmissions of the optical element are to be achieved, they can also be arranged non-parallel, e.g. in a wedge shape at a defined angle of up to 20 degrees to one another. A shell-shaped design of the light guide is also conceivable.

For the first alternative of the optical element, the structured surface of the light guide can be designed with wave-shaped, lens-shaped and / or prism-shaped structures.

For all embodiments of the invention - including those mentioned below - it applies that “predominantly” means at least 50% of the respective unit of measurement. However, this also includes in particular cases with more than 90% and more than 95% of the respective unit of measurement. The unit of measurement can be, for example, the intensity, the light intensity, the luminance, the transmittance, the degree of absorption and / or the degree of reflection.

An optical element of the first or second alternative can also be designed in such a way that the light-absorbing or light-reflecting elements are designed as electrophoretic particles which are designed as (nano) particles, quantum dots and / or dyes and have a spatial extent of at most 500 nm, a maximum of 200 nm, a maximum of 50 nm or a maximum of 20 nm. However, other configurations with larger or different maximum dimensions are explicit possible. “Spatial expansion” means the maximum expansion in three-dimensional space or the hydrodynamic radius, whichever is larger. In the case of spherical particles, this is the diameter. In the case of chain-shaped particles, this is the greatest possible distance that two points on the surface of the particle can have from one another.

For the second alternative, it is also possible that the light-reflecting elements are designed as electrophoretic particles, which are designed as reflecting spheres with diameters between 5 nm and 5000 nm.

As far as the light-absorbing elements, i.e. the light-absorbing electrophoretic particles or liquid drops, are concerned, one or more wavelengths or wavelength ranges in which they absorb light are preferably in the visible spectrum and particularly preferably completely cover it. For special purposes, however, they can also be outside the visible spectrum, e.g. if UV or IR light is to be influenced, e.g. for purposes of measurement technology.

Preferably, at least two operating states are defined by means of the electrical switching means and a control circuit, in the case that the light-absorbing or light-reflecting elements are designed as electrophoretic particles, depending on their position, and in the case that light-reflecting elements are designed as drops of liquid are, depending on their extension, shape and / or position, in a first operating state B1 the angle-dependent transmission is less than 50% and in a second operating state B2 at more than 50% in an angular range of more than 30 ° to 90 ° based on a surface normal of the light exit surface of the light guide, measured in a direction perpendicular to a longitudinal extension of the areas G1 . In the first operating state B1 the respective particles or droplets are predominantly in the first state and in the second operating state B2 they are in the second state.

It is particularly possible that the angle-dependent transmission in the second operating state B2 more than 20%, preferably more than 60%, and in the first operating state B1 is less than 5%, in an angular range of more than 30 ° based on a surface normal of the light exit surface of the light guide and measured in a direction perpendicular to a longitudinal extent of the areas G1 . Thus, in the interaction of the optical element with an image display device, a restricted viewing mode for the displayed image (operating state B1 corresponding to the first state of the optical element) and a free viewing mode for the displayed image (operating state B2 corresponding to the second state of the optical element). The angle-dependent transmission of the optical element in the first state in the said angular range is preferably even less than 2%, particularly preferably less than 1%.

In this sense, the angle range then includes angles from +/- 30 ° to +/- 90 ° (i.e. from -90 ° to -30 ° and at the same time from + 30 ° to + 90 °, but not between -30 ° and + 30 °) in this plane. The angular range can also be varied and instead of +/- 30 ° also the range from +/- 10 ° to +/- 90 °, +/- 20 ° to +/- 90 °, +/- 45 ° to + / -90 ° or +/- 25 ° to +/- 90 °. At 90 ° the angle is on the surface of the substrate.

Furthermore, it is possible for the first or second alternative that the light-absorbing or light-reflecting elements are designed as electrophoretic particles and at the same time several types of such particles are present which differ in their absorption properties and / or transport properties in the electromagnetic field. The term "transport properties" refers in particular to the behavior of the particles during (di-) electrophoresis, i.e. during transport in the field. This variant is particularly important in the case of (nano) particles: the difference between the types of particles is, for example, the particle size and / or the surface functionalization, i.e. the zeta potential. If quantum dots or dyes are used as particles and if these are fluorescent, a so-called “quencher” material is preferably used in order to avoid fluorescence.

For the optical element according to the invention of the first alternative, it is advantageous if the light-absorbing elements are designed as electrophoretic particles, which are BPQDs (Black Phosphorus Quantum Dots), lead sulfide (PbS), colloidal semiconductor quantum dots, azo dyes and / or metal oxide particles , are preferably formed from chromium (IV) oxide or Fe ₂ O ₃ , and have a size between 2 nm and 50 nm inclusive.

In addition, it is advantageous if all the electrophoretic particles present still have a surface functionalization, namely with a high zeta potential, on the one hand as stabilization in the liquid or framework matrix, and on the other hand for an improvement of the electrophoresis, ie a favoring of the electrophoresis, if it is electrophoretically movable particles. This can be implemented, for example, with PVP (polyvinylpyrrolidone) or PEG (polyethylene glycol) for aqueous systems.

For the second alternative, the light-reflecting elements can be configured as drops of liquid and contain metal microparticles or metal nanoparticles made of aluminum, chromium, silver or other metals, or metal or nanoparticle-coated polymer or silica microparticles to achieve reflection.

In preferred configurations of the first and the second alternative of the optical element, the regions G ₁ and G _{2 are} strip-shaped or rectangular when projected perpendicularly onto the light exit surface. In other words: The outer edges of the areas G ₁ and G ₂ represent strips or rectangles when projected from above in parallel. It is advantageous if the ratio of the area proportions of the surfaces of the areas G ₁ to the surfaces of the areas G _{2 during projection} perpendicular to the light exit surface is less than or equal to 1: 1, preferably 1: 2, particularly preferably 1: 4.

• - einen transparenten, platten- oder schalenförmigen Grundkörper mit einer als Lichteintrittsfläche ausgebildeten ersten Großfläche und einer als Lichtaustrittsfläche ausgebildeten zweiten Großfläche,
• - eine transparente Flüssigkeit oder Gerüstmatrix, welche zwischen der ersten Großfläche und der zweiten Großfläche angeordnet ist und Licht absorbierende Flüssigkeitstropfen enthält, deren Ausdehnung und Form und/oder Position im Grundkörper mittels eines wählbaren und veränderbaren elektrischen Feldes einstallbar ist, wobei die Ausdehnung in einer Ausdehnungsspanne zwischen einer Minimalausdehnung und einer Maximalausdehnung einstellbar ist,
• - elektrische Schaltmittel mit einer Vielzahl von ersten flächenförmigen Elektroden, welche transparent und zwischen den Großflächen angeordnet sind, und dazu korrespondierenden zweiten flächenförmigen Elektroden, welche an der Lichteintritts- (oder -austritts)-fläche angeordnet und umgekehrt zu den ersten flächenförmigen Elektroden gepolt sind, wobei die Polungen von ersten und zweiten flächenförmigen Elektroden umkehrbar sind,
• - wobei die Maximalausdehnung in der Größenordnung einer Längsausdehnung der ersten flächenförmigen Elektroden zwischen der ersten und zweiten Großfläche liegt,
• - bei einer Ausdehnung der absorbierenden Flüssigkeitstropfen von mindestens 85% der Maximalausdehnung ein Austrittswinkelbereich von Licht, welches aus der Lichtaustrittsfläche tritt, gegenüber einem Eintrittswinkelbereich des Lichts beim Eintritt über die Lichteintrittsfläche beschnitten ist, und
• - bei einer Ausdehnung der absorbierenden Flüssigkeitstropfen von weniger als 20% der Maximalausdehnung der Austrittswinkelbereich gegenüber dem Eintrittswinkelbereich nicht oder nur unwesentlich beschnitten ist.

Furthermore, the object is achieved in a third alternative, not according to the invention, by an optical element comprising

• - A transparent, plate-shaped or shell-shaped base body with a first large area designed as a light entry surface and a second large area designed as a light exit area,
• - A transparent liquid or framework matrix, which is arranged between the first large area and the second large area and contains light-absorbing liquid droplets, the extent and shape and / or position of which can be set in the base body by means of a selectable and changeable electrical field, the extent in an expansion range can be set between a minimum and a maximum expansion,
• - electrical switching means with a plurality of first sheet-like electrodes, which are transparent and arranged between the large areas, and corresponding second sheet-like electrodes, which are arranged on the light entry (or exit) surface and are polarized reversely to the first sheet-like electrodes, the polarity of the first and second sheet-like electrodes being reversible,
• - wherein the maximum extent is in the order of magnitude of a longitudinal extent of the first sheet-like electrodes between the first and second large areas,
• - With an expansion of the absorbing liquid droplets of at least 85% of the maximum expansion, an exit angle range of light which emerges from the light exit surface is trimmed compared to an entry angle range of the light when entering via the light entry surface, and
• - With an expansion of the absorbent liquid droplets of less than 20% of the maximum expansion, the exit angle area is not or only insignificantly cut off compared to the entry angle area.

Especially in the case of the third alternative, it is possible that the normals of the plurality of first sheet-like electrodes, which are transparent and are arranged between the large surfaces, have an angle of -25 degrees up to and including +25 degrees with the center perpendicular of the light exit surface of the light guide. This means that the cropped exit angle range can be tilted around an absolute value if the application requires this. However, the first electrodes can also all be aligned at the same angle to the second large area of the substrate, in particular in each case essentially parallel to the perpendicular to the substrate.

An advantage of this third alternative is that no chambers or the like are required for channeling the liquid or framework matrix and the liquid droplets located therein. The final localization of the liquid droplets after their movement basically eliminates the need for such chambers. The first electrodes can here, for example, be designed in the form of strips and are then arranged either parallel or in a grid-like manner, with areas that cross one another. The angle-dependent transmission properties of the optical element with respect to one or two perpendicular planes are then designed accordingly.

However, it is also possible to design as a single, two-dimensional second electrode, or to design the second electrode from honeycombs that cover the surface, whereby these can be controlled jointly, but also individually.

The electromagnetic switching means, mostly electrodes as described above, are advantageously at least 50% transparent in all three alternatives for light that enters the optical element via the light entry surface in the wavelength range visible to the human eye. This can be, for example, an indium tin oxide layer (ITO layer). In the case of electrodes on the side of the areas facing away from the light guide G2 however, under certain circumstances it can also be an opaque electrode.

For all alternatives it also applies that optionally the electrical switching means can be divided into several, separately switchable segments, whereby one segment by segment and thus locally restrictable switchability between the first operating state B1 and the second operating state B2 is made possible. Several first or second electrodes can be connected together in a segment: Local switchability here means that not in all areas G2 at the same time the operating status between B1 and B2 is changed, but that rather areas on the optical element at the same time G2 with both operating states B1 and B2 are present. This is advantageous, for example, when, when using the optical element in front of a screen, parts of the displayed image content are to be visible and others are not to be visible from a viewing angle of more than 30 degrees to the side.

In addition, it is optionally possible in all alternatives that the light-absorbing or light-reflecting elements are designed as liquid droplets and several types of such liquid droplets are present, which differ in their absorption properties and / or movement properties and / or deformation properties in the electromagnetic field.

The said framework matrix is designed, for example, as a polymer matrix, preferably as a gel matrix. Such a polymer matrix has a characteristic mesh size. Because of this mesh size, small particles feel less "resistance" than large particles and so small and large particles move at different speeds. On the one hand, this is advantageous in order to control the switching times and to accelerate the movement of the particles. On the other hand, such a polymer matrix has the advantage that it strongly inhibits diffusion and the particles therefore do not move by themselves, which can be advantageous.

The liquid can be polar or non-polar. It can also consist, for example, of water, oil, toluene or formaldehyde, also mixed with electrolytes or other organic substances in order to stabilize the particles in the liquid or to modify their electrophoretic properties.

In the case of the first or third alternative, the light-absorbing elements can be designed as drops of liquid and, to achieve absorption, organic dyes, soot, graphene, carbon, metal oxides such as chromium (IV) oxide, Fe ₂ O ₃ , Fe ₃ O ₄ or FeO or contain colloidal semiconductor quantum dots or are mixed with polymer or porous silica microparticles. A drop of liquid contains the aforementioned ingredients to a maximum of 70% by volume.

For all embodiments of the invention, it is advantageous that the light-absorbing or light-reflecting elements are configured as liquid droplets which each individually have a volume of 5 × 10 ⁻¹³ to 2 × 10 ⁻¹⁰ liters, inclusive. These values are obtained when the liquid droplets in the assumed cuboid shape occupy a minimum volume of 5 × 10 × 10 μm ³ and a maximum volume of 10 × 20 × 1000 μm ³ .

The light entry surface of the light guide or base body of a previously described optical element is usually located on the rear side of the optical element from the point of view of a viewer and, depending on its application, borders, for example, on an image display device, a light source or on a volume of air. Light then emerges from the last-mentioned objects through the said light entry surface or the areas G1 into the substrate.

• ― einen transparenten, platten- oder schalenförmigen, als Lichtleiter aus einem Material mit einer Brechzahl n_L ausgestalteten Grundkörper mit einer als Lichteintrittsfläche ausgebildeten ersten Großfläche und einer als Lichtaustrittsfläche ausgebildeten zweiten Großfläche, wobei an der Lichteintrittsfläche und dazu korrespondierend an der Lichtaustrittsfläche einander abwechselnd erste Bereiche G1 und zweite Bereiche G2 ausgebildet, ausgespart oder angeordnet sind,
• ― wobei die ersten Bereiche G1 mit einem transparenten Material mit einer Brechzahl n_G1 ausgefüllt sind, wobei die Brechzahlen n_L und n_G1 höchstens bis zu einem Wert von 0,11 voneinander abweichen, und
• ― wobei mindestens die auf der Seite der Lichtaustrittsfläche liegenden zweiten Bereiche G2 jeweils ein Volumen aufweisen, welches eine transparente Flüssigkeit oder eine Gerüstmatrix enthält, wobei die Flüssigkeit oder Gerüstmatrix Licht absorbierende Elemente enthält, welche in ihrer Gesamtheit entweder als Flüssigkeitstropfen oder als elektrophoretische Partikel ausgebildet sind, und wobei mittels eines wählbaren und veränderbaren elektrischen Feldes im Falle elektrophoretischer Partikel deren Position und im Falle von Flüssigkeitstropfen deren Ausdehnung, Form und/oder Position einstellbar ist,
• ― wobei die ein Volumen aufweisenden zweiten Bereiche G2 an einer dem Lichtleiter abgewandten Seite jeweils eine reflektierende Schicht aufweisen,
• ― elektrische Schaltmittel in den ein Volumen aufweisenden zweiten Bereichen G2 auf der Seite der Lichtaustrittsfläche, mit ersten Elektroden an der dem Lichtleiter abgewandten Fläche, welche zur Lichtaustrittsfläche des Lichtleiters parallel liegt oder dieser entspricht, und mit transparenten, an einer planen Grenzfläche zum Lichtleiter anliegenden zweiten Elektroden im Innern des zweiten Bereichs G2, welche umgekehrt zu den ersten Elektroden gepolt sind und wobei die Polungen zwischen einem ersten und einem zweiten Zustand umschaltbar sind,
• ― sowie auf der Seite der Lichteintrittsfläche in den zweiten Bereichen G2 eine (optional opake) Reflexionsschicht, welche an der Lichteintrittsfläche angebracht ist, so dass
  1. a) die Licht absorbierenden Elemente im ersten Zustand zu mehr als 85% die zweite Elektrode bedecken, so dass Licht, welches über die ersten Bereiche G1 in den Lichtleiter eintritt und in die zweiten Bereiche G2 übertritt, von den absorbierenden Elementen überwiegend absorbiert wird,
  2. b) die Licht absorbierenden Elemente im zweiten Zustand zu weniger als 15% die zweite Elektrode bedecken, so dass Licht, welches über die ersten Bereiche G1 in den Lichtleiter eintritt und in die zweiten Bereiche G2 übertritt, überwiegend an den reflektierenden Schichten reflektiert wird, und
  • ― so dass, wenn Licht auf das optische Element einfällt, dieses mindestens durch an der Lichteintrittsfläche lokalisierte erste Bereiche G1 in den Lichtleiter eintritt, und
    • - im ersten Zustand das optische Element entweder in einem eingeschränkten Winkelbereich durch an der Lichtaustrittsfläche lokalisierte erste Bereiche G1 verlässt oder aufgrund der absorbierenden Elemente in den zweiten Bereichen G2 absorbiert wird, oder
    • - im zweiten Zustand das optische Element entweder in einem eingeschränkten Winkelbereich durch an der Lichtaustrittsfläche lokalisierte erste Bereiche G1 verlässt oder aufgrund der Reflexion an einer reflektierenden Schicht an einer dem Lichtleiter abgewandten Seite jeweils eines zweiten Bereichs G2 und/oder an einer Reflexionsschicht an der Lichteintrittsfläche im Lichtleiter solange propagiert, bis es den Lichtleiter durch die an der Lichtaustrittsfläche lokalisierten ersten Bereiche G1 in größeren Winkeln als die des besagten eingeschränkten Winkelbereichs verlässt.

Finally, the object of the invention is achieved in a fourth alternative by an optical element comprising

• - A transparent, plate-shaped or shell-shaped base body designed as a light guide made of a material with a refractive index n _L with a first large area designed as a light entry area and a second large area designed as a light exit area, with first areas alternating on the light entry area and correspondingly on the light exit area G1 and second areas G2 designed, recessed or arranged,
• - being the first areas G1 are filled with a transparent material with a refractive index n _G1 , the refractive indices n _L and n _G1 differing from one another by a maximum of 0.11, and
• - wherein at least the second areas lying on the side of the light exit surface G2 each have a volume which contains a transparent liquid or a framework matrix, the liquid or framework matrix containing light-absorbing elements, which in their entirety are formed either as liquid droplets or as electrophoretic particles, and by means of a selectable and changeable electric field in the case of electrophoretic Particles whose position and, in the case of liquid droplets, their expansion, shape and / or position can be adjusted,
• - wherein the second areas having a volume G2 each have a reflective layer on a side facing away from the light guide,
• - electrical switching means in the second areas having a volume G2 on the side of the light exit surface, with first electrodes on the surface facing away from the light guide, which face the light exit surface of the The light guide lies parallel or corresponds to this, and with transparent second electrodes in the interior of the second region, which lie against a planar interface with the light guide G2 , which are polarized opposite to the first electrodes and wherein the polarity can be switched between a first and a second state,
• - as well as on the side of the light entry surface in the second areas G2 an (optionally opaque) reflective layer which is attached to the light entry surface, so that
  1. a) the light-absorbing elements in the first state cover the second electrode to more than 85%, so that light which passes over the first areas G1 enters the light guide and into the second areas G2 passes over, is predominantly absorbed by the absorbent elements,
  2. b) the light-absorbing elements in the second state cover less than 15% of the second electrode, so that light which passes over the first areas G1 enters the light guide and into the second areas G2 transgresses, is mainly reflected on the reflective layers, and
  • - so that when light is incident on the optical element, this is at least through first areas localized on the light entry surface G1 enters the light guide, and
    • - In the first state, the optical element either in a restricted angular range through first regions located on the light exit surface G1 leaves or due to the absorbent elements in the second areas G2 is absorbed, or
    • - In the second state, the optical element either in a restricted angular range through first regions located on the light exit surface G1 leaves or due to the reflection on a reflective layer on a side facing away from the light guide in each case of a second area G2 and / or propagates on a reflective layer on the light entry surface in the light guide until it passes the light guide through the first regions located on the light exit surface G1 leaves at angles greater than that of said restricted angular range.

The design variants given above apply analogously to the fourth alternative; they can be applied analogously and are not repeated at this point for reasons of redundancy.

The invention is particularly important in that the optical element according to the first, second, third or fourth alternative, including modifications thereof, is used in a screen which is in a first operating state B1 for a restricted viewing mode and in a second operating state B2 can be operated for a free viewing mode. Such a screen comprises at least one optical element as described above and an image display unit which is arranged downstream or upstream of the at least one optical element as seen by a viewer. The use of two optical elements, preferably of identical design, stacked one on top of the other improves perception in the operating state B2 . It is particularly advantageous if the optical elements are of the same type, but the areas G ₂ on the two optical elements are each arranged rotated relative to one another by a predetermined angle in the plane of one of the exit surfaces or in the plan view of the screen. The specified angle can be up to 25 ° and is preferably 16 °. The image display unit is, for example, an OLED display, an LCD panel, an SED, a FED, a micro-LED display or a VFD. Since the optical element is effective regardless of the type of image display unit, any other types of screen are also possible.

It is also possible, for example, to use the optical element according to the invention in an image display unit which has a backlight, such as, for example, in an LCD screen. Here, the optical element is then advantageously arranged between the image display panel (that is to say the LCD panel) and the background lighting in order to switch between a first operating state B1 for a restricted viewing mode and a second operating state B2 to switch for a free viewing mode because the light of the backlight focuses once due to the optical element ( B1 ) and once out of focus ( B2 ) will. “Focusing” does not mean focusing in the manner of lenses, but a spatial narrowing of the emission area according to the respective transmission properties of the optical element according to the invention, ie a limitation of the solid angle area in which light is emitted.

It is also within the scope of the invention that more than two states of an optical element according to the invention can be set. For this purpose, a different electromagnetic field is applied in a third (fourth, fifth, ...) state compared to the variants described above for the first and second states, which leads to the fact that in the case of electrophoretic particles P. their position and in the case of liquid drops F. the extent, shape and / or position of which is configured differently between all adjustable states, so that a total of three or more different angle-dependent degrees of transmission can be achieved. This can be of interest, for example, for an angle-dependent darkening. Ultimately, the other operating states are just differently designed configurations of the second state.

The invention also includes the use of an optical element of one of the four alternatives or of a screen as described above in a car, a mobile device, a desktop screen, in an ATM or in a payment terminal.

In principle, the performance of the invention is retained if the parameters described above are varied within certain limits.

It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the specified combinations, but also in other combinations or on their own, without departing from the scope of the present invention.

Figure list

• 1 die Prinzipskizze eines optischen Elements gemäß einer ersten Alternative in einem ersten Zustand,
• 2 die Prinzipskizze eines optischen Elements gemäß der ersten Alternative in einem zweiten Zustand,
• 3 die Prinzipskizze eines optischen Elements gemäß einer zweiten Alternative in einem ersten Zustand,
• 4 die Prinzipskizze eines optischen Elements gemäß der zweiten Alternative in einer ersten Ausgestaltung in einem zweiten Zustand,
• 5 die Prinzipskizze eines optischen Elements gemäß der zweiten Alternative in einer zweiten Ausgestaltung in einem zweiten Zustand,
• 6 eine schematische Draufsicht auf die Bereiche G1 und G2 in einer ersten Ausgestaltung,
• 7 eine schematische Draufsicht auf die Bereiche G1 und G2 in einer zweiten Ausgestaltung,
• 8 die Prinzipskizze eines optischen Elements gemäß einer dritten Alternative in einem ersten Zustand, bei der ein Austrittswinkelbereich von Licht, welches aus der Lichtaustrittsfläche tritt, gegenüber einem Eintrittswinkelbereich des Lichts beim Eintritt über die Lichteintrittsfläche beschnitten ist,
• 9 die Prinzipskizze eines optischen Elements gemäß der dritten Alternative in einem zweiten Zustand, bei der ein Austrittswinkelbereich von Licht gegenüber dessen Eintrittswinkelbereich nicht oder nur unwesentlich beschnitten ist,
• 10 die Prinzipskizze eines optischen Elements gemäß einer vierten Alternative in einer ersten Ausgestaltung in einem ersten Zustand,
• 11 die Prinzipskizze eines optischen Elements gemäß der vierten Alternative in einer zweiten Ausgestaltung in einem ersten Zustand,
• 12 die Prinzipskizze eines optischen Elements gemäß der vierten Alternative in einer dritten Ausgestaltung in einem zweiten Zustand,
• 13 die Prinzipskizze eines optischen Elements gemäß der vierten Alternative in einer vierten Ausgestaltung in einem zweiten Zustand,
• 14 die Prinzipskizze zur Anlagerung eines opaken Flüssigkeitstropfens oder einer Vielzahl an opaken elektrophoretischen Partikeln an einer negativ geladenen ersten Elektrode,
• 15 die Prinzipskizze zur Anlagerung eines opaken Flüssigkeitstropfens oder einer Vielzahl an opaken elektrophoretischen Partikeln an einer negativ geladenen zweiten Elektrode,
• 16 die Prinzipskizze einer Draufsicht auf Bereiche G1 und G2 eines optischen Elements gemäß der ersten bis vierten Alternative, wobei unterschiedliche Teilbereiche der Bereiche G2 in unterschiedlichen Zuständen befindlich sind, sowie
• 17 die Prinzipskizze einer Draufsicht auf Bereiche G1 und G2 eines optischen Elements gemäß der ersten bis vierten Alternative, wobei unterschiedliche Teilbereiche der Bereiche G2 in unterschiedlichen Zuständen befindlich sind, und wobei ferner sich kreuzende Bereiche G2 vorgesehen sind.

The invention is explained in more detail below on the basis of exemplary embodiments with reference to the accompanying drawings, which likewise disclose features that are essential to the invention. These exemplary embodiments are used for illustration purposes only and are not to be construed as restrictive. For example, a description of an exemplary embodiment with a large number of elements or components should not be interpreted to the effect that all of these elements or components are necessary for implementation. Rather, other exemplary embodiments can also contain alternative elements and components, fewer elements or components, or additional elements or components. Elements or components of different exemplary embodiments can be combined with one another, unless otherwise stated. Modifications and variations which are described for one of the exemplary embodiments can also be applied to other exemplary embodiments. To avoid repetition, elements that are the same or that correspond to one another are denoted by the same reference symbols in different figures and are not explained more than once. Show it:

• 1 the schematic diagram of an optical element according to a first alternative in a first state,
• 2 the schematic diagram of an optical element according to the first alternative in a second state,
• 3 the schematic diagram of an optical element according to a second alternative in a first state,
• 4th the schematic diagram of an optical element according to the second alternative in a first embodiment in a second state,
• 5 the schematic diagram of an optical element according to the second alternative in a second embodiment in a second state,
• 6th a schematic plan view of the areas G1 and G2 in a first embodiment,
• 7th a schematic plan view of the areas G1 and G2 in a second embodiment,
• 8th the schematic diagram of an optical element according to a third alternative in a first state in which an exit angle range of light which emerges from the light exit surface is trimmed in relation to an entry angle range of the light when entering via the light entry surface,
• 9 the schematic diagram of an optical element according to the third alternative in a second state, in which an exit angle range of light is not or only insignificantly cropped compared to its entrance angle range,
• 10 the schematic diagram of an optical element according to a fourth alternative in a first embodiment in a first state,
• 11 the schematic diagram of an optical element according to the fourth alternative in a second embodiment in a first state,
• 12th the schematic diagram of an optical element according to the fourth alternative in a third embodiment in a second state,
• 13th the schematic diagram of an optical element according to the fourth alternative in a fourth embodiment in a second state,
• 14th the schematic diagram for the accumulation of an opaque liquid drop or a large number of opaque electrophoretic particles on a negatively charged first electrode,
• 15th the schematic diagram for the accumulation of an opaque liquid drop or a large number of opaque electrophoretic particles on a negatively charged second electrode,
• 16 the schematic diagram of a plan view of areas G1 and G2 of an optical element according to the first to fourth alternative, with different subregions of the regions G2 are in different states, as well as
• 17th the schematic diagram of a plan view of areas G1 and G2 of an optical element according to the first to fourth alternative, with different subregions of the regions G2 are in different states, and also intersecting areas G2 are provided.

Detailed description of the drawings

The drawings are not true to scale and only represent basic representations. In addition, for the sake of clarity, only a small selection of electrodes, light beams, particles, liquid droplets or the like are usually shown, although in reality there can or is a real multitude of these. In the following, four different alternatives are described which, in particular with regard to the nature of the substrate per se and the nature of the particles, have similarities that are not explicitly repeated for each alternative.

In 1 FIG. 14 is the schematic diagram of a first optical element in cross section according to a first alternative in a first state, and FIG 2 shown in a second state.

• ― einen transparenten, plattenförmigen, als Lichtleiter 1 aus einem Material mit einer Brechzahl n_L ausgestalteten Grundkörper mit einer als Lichteintrittsfläche F1 ausgebildeten ersten Großfläche und einer als Lichtaustrittsfläche F2 ausgebildeten zweiten Großfläche, wobei an der Lichteintrittsfläche F1 und dazu korrespondierend an der Lichtaustrittsfläche F2 einander abwechselnd erste Bereiche G1 und zweite Bereiche G2 ausgebildet sind,
• ― wobei die ersten Bereiche G1 mit einem transparenten Material mit einer Brechzahl n_G1ausgefüllt sind, wobei die Brechzahlen n_L und n_G1 höchstens bis zu einem Wert von 0,11 voneinander abweichen, und
• ― wobei mindestens die auf der Seite der Lichtaustrittsfläche F2 liegenden zweiten Bereiche G2 jeweils ein Volumen V aufweisen, welches eine transparente Flüssigkeit mit einer Brechzahl n_G2 welche kleiner als die Brechzahl n_L ist, enthält, wobei die Flüssigkeit FL Licht absorbierende Elemente enthält, welche in ihrer Gesamtheit als elektrophoretische Partikel P ausgebildet sind, und wobei mittels eines wählbaren und veränderbaren elektrischen Feldes deren Position einstellbar ist, wobei die Brechzahlen n_L und n_G2 sich mindestens um einen Wert von 0,05 und höchstens um einen Wert von 0,35 unterscheiden,
• ― wobei der Lichtleiter 1 an Grenzflächen zu den jeweils ein Volumen V aufweisenden zweiten Bereichen G2 mindestens auf der Seite der Lichtaustrittsfläche F2 strukturierte Oberflächen aufweist, welche Licht, dass über die Bereiche G1 in den Lichtleiter 1 eintritt, überwiegend intern total reflektieren,
• ― elektrische Schaltmittel in den ein Volumen V aufweisenden zweiten Bereichen G₂ auf der Seite der Lichtaustrittsfläche F2, mit planen ersten Elektroden E1 an einer dem Lichtleiter 1 abgewandten Fläche, welche zur Lichtaustrittsfläche F2 des Lichtleiters 1 parallel, und mit transparenten, an den strukturierten Oberflächen anliegenden zweiten Elektroden E2 im Innern des zweiten Bereichs G2 an einer Grenzfläche F2 zum Lichtleiter 1, welche umgekehrt zu den ersten Elektroden E1 gepolt sind und wobei die Polungen zwischen einem ersten und einem zweiten Zustand umschaltbar sind,
• ― sowie auf der Seite der Lichteintrittsfläche F1 in den zweiten Bereichen G2 eine opake Reflexionsschicht 2, welche an der Lichteintrittsfläche F1 angebracht ist, so dass
  1. a) die Licht absorbierenden Elemente P im ersten Zustand zu mehr als 85% die zweiten Elektroden E2 bedecken, wodurch die innere Totalreflexion von Licht an den strukturierten Oberflächen gestört und die Ausbreitung von Licht, welches über die ersten Bereiche G1 in den Lichtleiter 1 eintritt, mittels Absorption durch die Licht absorbierenden Elemente P überwiegend unterbunden wird, und
  2. b) die Licht absorbierenden Elemente P im zweiten Zustand zu weniger als 15% die zweiten Elektroden E2 bedecken, so dass die Ausbreitung von Licht, welches über die ersten Bereiche G1 in den Lichtleiter 1 eintritt, zu weniger als 50% von den Licht absorbierenden Elementen P absorbiert wird,
• ― so dass, wenn Licht auf das optische Element einfällt, dieses mindestens durch an der Lichteintrittsfläche F1 lokalisierte erste Bereiche G1 in den Lichtleiter 1 eintritt, und
  • ― im ersten Zustand das optische Element entweder in einem eingeschränkten Winkelbereich durch an der Lichtaustrittsfläche F2 lokalisierte erste Bereiche G1 verlässt oder aufgrund der Licht absorbierenden Elemente P in den zweiten Bereichen G2 überwiegend absorbiert wird, oder
  • ― im zweiten Zustand das optische Element entweder in einem eingeschränkten Winkelbereich durch an der Lichtaustrittsfläche F2 lokalisierte erste Bereiche G1 verlässt oder aufgrund innerer Totalreflexion an den strukturierten Oberflächen und Reflexion an einer reflektierenden Schicht 2 an der Lichteintrittsfläche F1 im Lichtleiter solange propagiert, bis es den Lichtleiter 1 durch die an der Lichtaustrittsfläche F2 lokalisierten ersten Bereiche G1 in größeren Winkeln als die des besagten eingeschränkten Winkelbereichs verlässt.

The first optical element in the first alternative comprises in an exemplary embodiment

• - a transparent, plate-shaped, as a light guide 1 made of a material with a refractive index n _L and designed as a light entry surface F1 trained first large area and one as a light exit area F2 formed second large area, with the light entry surface F1 and correspondingly on the light exit surface F2 alternating first areas G1 and second areas G2 are trained
• - being the first areas G1 are filled with a transparent material with a refractive index n _G1 , the refractive indices n _L and n _G1 differing from one another by a maximum of 0.11, and
• - at least the one on the side of the light exit surface F2 lying second areas G2 one volume each V which contains a transparent liquid with a refractive index n _G2 which is smaller than the refractive index n _L , the liquid FL Contains light absorbing elements, which in their entirety are called electrophoretic particles P. are formed, and the position of which can be adjusted by means of a selectable and changeable electric field, the refractive indices n _L and n _G2 differing by at least a value of 0.05 and at most a value of 0.35,
• - being the light guide 1 at interfaces to each of the volumes V having second areas G2 at least on the side of the light-emitting surface F2 Has structured surfaces, which light that over the areas G1 into the light guide 1 Entering, mostly reflecting totally internally,
• - electrical switching means in the one volume V having second regions G ₂ on the side of the light exit surface F2 , with flat first electrodes E1 on one of the light guides 1 facing away from the surface facing the light exit surface F2 of the light guide 1 parallel, and with transparent second electrodes resting on the structured surfaces E2 inside the second area G2 at an interface F2 to the light guide 1 which is the reverse of the first electrodes E1 are polarized and the polarities can be switched between a first and a second state,
• - as well as on the side of the light entry surface F1 in the second areas G2 an opaque reflective layer 2 , which at the light entry surface F1 is appropriate so that
  1. a) the light absorbing elements P. in the first state, more than 85% of the second electrodes E2 cover, as a result of which the internal total reflection of light on the structured surfaces is disturbed and the propagation of light which over the first areas G1 into the light guide 1 occurs, by means of absorption by the light absorbing elements P. is predominantly prevented, and
  2. b) the light absorbing elements P. in the second state, less than 15% of the second electrodes E2 cover so that the propagation of light falling over the first areas G1 into the light guide 1 occurs, less than 50% of the light absorbing elements P. is absorbed,
• - so that when light strikes the optical element, this at least through to the light entry surface F1 localized first areas G1 into the light guide 1 occurs, and
  • - In the first state, the optical element either in a restricted angular range through to the light exit surface F2 localized first areas G1 leaves or due to the light absorbing elements P. in the second areas G2 is mostly absorbed, or
  • - In the second state, the optical element either in a restricted angular range through to the light exit surface F2 localized first areas G1 leaves or due to total internal reflection on the structured surfaces and reflection on a reflective layer 2 at the light entry surface F1 propagated in the light guide until it hits the light guide 1 due to the light emitting surface F2 localized first areas G1 leaves at angles greater than that of said restricted angular range.

In the in 1 and 2 The embodiment shown is used as the material for the light guide 1 and the first areas G1 PMMA (polymethyl acrylate or acrylic glass) with a refractive index of 1.48 is used, so the refractive indices n _L and n _G1 are the same. Water with a refractive index of 1.33 is used here as the transparent liquid. Light coming through the first areas G1 into the light guide 1 enters and in the first and second state the optical element in a restricted angular range through to the light exit surface F2 localized first areas G1 is symbolized by the ray of light, which is the central area G1 in 1 and 2 leaves. Light coming from the areas G1 into the light guide 1 below the areas G2 passes over, is absorbed there in the first state, like 1 shows for the ray entering from the right. In the second state, however, this beam is reflected several times and leaves the light guide 1 also through to the light exit surface F2 localized areas G1 , how 2 shows. The areas G1 The areas extend here over the entire depth (corresponding to the vertical direction in the plane of the drawing) G2 however, they are only localized in the area of the light exit surface.

In reality there are a multitude of first and second areas G1 and G2 available, even if only a few are shown here in the drawings and, for the sake of clarity, are only primarily labeled in detail on the left-hand side.

Alternatively, instead of electrophoretic particles P. also drops of liquid F. be used. The extent, shape and / or position of the electric field can be adjusted by means of a selectable and changeable electric field. Otherwise, the above-described statements in conjunction with the operation of the optical element apply 1 and 2 .

In this first alternative, the light-absorbing elements are allowed in the second state F. , P no contact with the light guide 1 facing second electrode E2 to have. In the first state, however, the light-absorbing elements are F. , P. in contact with the interface F2 . The minimum thickness of the absorbent elements F. , P. on the second electrode facing the light guide E2 piled layer should be 100 nm on at least 85% of the area F2 in the fields of G2 be. The maximum thickness of such a layer is typically five micrometers. In the case of electrophoretic particles P. the said layer is formed by the accumulation of a large number of particles, in the case of liquid droplets F. by superimposing and / or moving a large number of drops of liquid F. .

• ― einen transparenten, plattenförmigen, als Lichtleiter 1 mit einer Brechzahl n_L ausgestalteten Grundkörper mit einer als Lichteintrittsfläche F1 ausgebildeten ersten Großfläche und einer als Lichtaustrittsfläche F2 ausgebildeten zweiten Großfläche, wobei an der Lichteintrittsfläche F1 und dazu korrespondierend an der Lichtaustrittsfläche F2 einander abwechselnd erste Bereiche G1 und zweite Bereiche G2 ausgebildet sind,
• ― wobei die ersten Bereiche G1 mit einem transparenten Material mit einer Brechzahl n_G1 ausgefüllt sind, wobei die Brechzahlen n_L und n_G1 höchstens bis zu einem Wert von 0,11 voneinander abweichen, und
• ― wobei mindestens die auf der Seite der Lichtaustrittsfläche F2 liegenden zweiten Bereiche G2 jeweils ein Volumen V aufweisen, welches eine transparente Flüssigkeit FL enthält, wobei die Flüssigkeit FL Licht reflektierende Elemente enthält, welche in ihrer Gesamtheit als Flüssigkeitstropfen F ausgebildet sind, und wobei mittels eines wählbaren und veränderbaren elektrischen Feldes deren Position einstellbar ist,
• ― wobei die ein Volumen V aufweisenden zweiten Bereiche G2 an einer dem Lichtleiter 1 abgewandten Seite jeweils eine opake Absorptionsschicht 3 aufweisen,
• ― elektrische Schaltmittel in den ein Volumen V aufweisenden zweiten Bereichen G2 auf der Seite der Lichtaustrittsfläche F2, mit ersten Elektroden E1 an der dem Lichtleiter 1 abgewandten Fläche, welche zur Lichtaustrittsfläche F2 des Lichtleiters parallel liegt, und mit transparenten, an einer planen Grenzfläche F2 zum Lichtleiter 1 anliegenden zweiten Elektroden E2 im Innern des zweiten Bereichs G2, welche umgekehrt zu den ersten Elektroden E1 gepolt sind und wobei die Polungen zwischen einem ersten und einem zweiten Zustand umschaltbar sind,
• ― sowie auf der Seite der Lichteintrittsfläche F1 in den zweiten Bereichen G2 eine opake Reflexionsschicht 2, welche an der Lichteintrittsfläche F1 angebracht ist, so dass
  1. a) die Licht reflektierenden Elemente P im ersten Zustand zu weniger als 15% die zweite Elektrode E2 bedecken, so dass Licht, welches über die ersten Bereiche G1 in den Lichtleiter 1 eintritt und in die zweiten Bereiche G2 übertritt, überwiegend an den opaken Schichten 3 absorbiert wird, und
  2. b) die Licht reflektierenden Elemente P im zweiten Zustand zu mehr als 85% die zweite Elektrode E2 bedecken, so dass Licht, welches über die ersten Bereiche G1 in den Lichtleiter 1 eintritt, - je nach Ausgestaltung, z.B. gemäß einer Umsetzung nach 4 an den Grenzflächen F2 des Lichtleiters 1- zu den zweiten Bereichen G2 reflektiert wird,
  • ― so dass, wenn Licht auf das optische Element einfällt, dieses mindestens durch an der Lichteintrittsfläche F1 lokalisierte erste Bereiche G1 in den Lichtleiter 1 eintritt, und
    • ― im ersten Zustand das optische Element entweder in einem eingeschränkten Winkelbereich durch an der Lichtaustrittsfläche F2 lokalisierte erste Bereiche G1 verlässt oder aufgrund der opaken Schichten 3 in den zweiten Bereichen G2 absorbiert wird, oder
    • ― im zweiten Zustand das optische Element entweder in einem eingeschränkten Winkelbereich durch an der Lichtaustrittsfläche F2 lokalisierte erste Bereiche G1 verlässt oder aufgrund der Reflexion an einer reflektierenden Schicht 2 an der Lichteintrittsfläche F1 im Lichtleiter 1 solange propagiert, bis es den Lichtleiter 1 durch die an der Lichtaustrittsfläche F2 lokalisierten ersten Bereiche G1 in größeren Winkeln als die des besagten eingeschränkten Winkelbereichs verlässt.

3 represents the schematic diagram of an exemplary optical element according to a second alternative in a first state, 4th the schematic diagram of an optical element according to the second alternative in a first embodiment in a second state, and 5 the schematic diagram of an optical element according to the second alternative in a second embodiment in the second state. This optical element according to the second alternative comprises

• - a transparent, plate-shaped, as a light guide 1 with a refractive index n _L designed base body with a light entry surface F1 trained first large area and one as a light exit area F2 formed second large area, with the light entry surface F1 and correspondingly on the light exit surface F2 alternating first areas G1 and second areas G2 are trained
• - being the first areas G1 are filled with a transparent material with a refractive index n _G1 , the refractive indices n _L and n _G1 differing from one another by a maximum of 0.11, and
• - at least the one on the side of the light exit surface F2 lying second areas G2 one volume each V have, which is a transparent liquid FL contains, the liquid FL Contains light reflecting elements, which in their entirety as liquid droplets F. are formed, and the position of which is adjustable by means of a selectable and changeable electric field,
• - being the one volume V having second areas G2 on one of the light guides 1 facing away from each other an opaque absorption layer 3 exhibit,
• - electrical switching means in the one volume V having second areas G2 on the side of the light emitting surface F2 , with first electrodes E1 at the light guide 1 facing away from the surface facing the light exit surface F2 of the light guide is parallel, and with transparent, on a flat interface F2 to the light guide 1 adjacent second electrodes E2 inside the second area G2 which is the reverse of the first electrodes E1 are polarized and the polarities can be switched between a first and a second state,
• - as well as on the side of the light entry surface F1 in the second areas G2 an opaque reflective layer 2 , which at the light entry surface F1 is appropriate so that
  1. a) the light reflecting elements P. in the first state less than 15% use the second electrode E2 cover so that light is pouring over the first areas G1 into the light guide 1 enters and into the second areas G2 crosses over, predominantly on the opaque layers 3 is absorbed, and
  2. b) the light reflecting elements P. in the second state, more than 85% of the second electrode E2 cover so that light is pouring over the first areas G1 into the light guide 1 occurs, - depending on the design, e.g. according to an implementation after 4th at the interfaces F2 of the light guide 1- to the second areas G2 is reflected,
  • - so that when light strikes the optical element, this at least through to the light entry surface F1 localized first areas G1 into the light guide 1 occurs, and
    • - In the first state, the optical element either in a restricted angular range through to the light exit surface F2 localized first areas G1 leaves or due to the opaque layers 3 in the second areas G2 is absorbed, or
    • - In the second state, the optical element either in a restricted angular range through to the light exit surface F2 localized first areas G1 leaves or due to the reflection on a reflective layer 2 at the light entry surface F1 in the light guide 1 until it propagates the light guide 1 through the light emitting surface F2 localized first areas G1 at angles greater than that of said restricted angular range.

The light guide 1 and the first areas G1 are also in this example made of PMMA with a refractive index of 1.48. Here, too, water can be used as the liquid. Light coming through the first areas G1 into the light guide 1 enters and in the first and second state the optical element in a restricted angular range through to the light exit surface F2 localized first areas G1 is symbolized by the ray of light, which is the central area G1 in 3 until 5 leaves. Light coming from the areas G1 below the areas G2 into the light guide 1 occurs, but in the first state it is in the opaque areas G2 absorbed how 3 shows. In the second state, however, such light is generated in both configurations by multiple reflection after refraction at the reflection layer 2 as well as the interfaces F2 the light guide again in areas G1 - in the 4th and 5 on the left - leaves.

There are the second electrodes E2 over the entire surface of the light guide 1 trained, at least in the areas G2 while the first electrodes E1 the entire area of the light guide 1 or only cover parts of it. In principle, it is also possible that the first and the second electrode E1 , E2 both are applied to one and the same surface without overlapping.

In the 4th and 5 The embodiments shown differ in that according to 4th the second electrodes E2 in close proximity to directly on the interfaces F2 in the fields of G2 are arranged while according to 5 the first electrodes E1 and the second electrodes E2 spatially close to one another, possibly even in the same plane. Here, for example, the first electrodes would be E1 and the second electrodes E2 alternating and in stripes immediately in front of the opaque layer 3 are located. The exemplary collections of electrophoretic particles P. in the first state according to 3 would then be achieved by the first electrodes E1 and the second electrodes E2 are accordingly polarized in a complementary manner, so that no particle accumulation on the second electrodes E2 , but on the first electrodes E1 takes place.
In the case of such a configuration according to 5 would for example the light reflecting elements P. in the second state, more than 85% of the second electrodes E2 and optionally at the same time the first electrodes E1 (Here, as an exception, both electrodes have the same polarity E1 and E2 ) cover so that light shines over the first areas G1 into the light guide 1 enters, to the second areas G2 is reflected.

Alternatively, instead of electrophoretic particles P. also drops of liquid F. be used. The extent, shape and / or position of the electric field can be adjusted by means of a selectable and changeable electric field. Otherwise, the above-described statements in conjunction with the operation of the optical element apply 3 until 5 .

The light entry and the light exit area F1 , F2 of the light guide 1 are arranged parallel to each other here.

For the first alternative of the optical element, the structured surface F2 of the light guide 1 be formed with wave-shaped, lens-shaped and / or prism-shaped structures.

An optical element of the first or second alternative can also be designed in such a way that the light-absorbing or light-reflecting elements are electrophoretic particles P. are designed, which are designed as (nano) particles, quantum dots and / or dyes and have a spatial extent of a maximum of 500 nm. “Spatial expansion” means the maximum expansion in three-dimensional space or the hydrodynamic radius, whichever is larger. In the case of spherical particles, this is the diameter. With chain-shaped particles P. this is the greatest possible distance that two points on the surface of the particle can have from one another.

For the optical element according to the invention of the first alternative, it is advantageous if the light-absorbing elements are electrophoretic particles P. are designed, which are designed as BPQDs (Black Phosphorus Quantum Dots), and have a size between 2 nm and 50 nm inclusive.
In addition, it is advantageous if all electrophoretic particles are present P. still have a surface functionalization, namely with a high zeta potential, on the one hand as a stabilization in the liquid FL and, on the other hand, to improve electrophoresis, ie to favor electrophoresis, provided that the particles are electrophoretically movable P. acts. This can be implemented, for example, with PVP (polyvinylpyrrolidone) or PEG (polyethylene glycol) for aqueous systems.

For the second alternative, it is also possible that the light-reflecting elements are used as electrophoretic particles P. are designed, which are designed as reflective spheres with diameters between 5 nm and 5000 nm.
One or more wavelengths or wavelength ranges in which the light-absorbing particles P. or drops of liquid F. Absorb light, are preferably in the visible spectrum and particularly preferably completely cover it. For special purposes, however, they can also be outside the visible spectrum, for example if UV or IR light is to be influenced, for example for purposes of measurement technology.

Both alternatives of the optical element shown here are designed in such a way that by means of the electrical switching means E1 , E2 and a control circuit at least two operating states are defined, wherein in the case that the light absorbing or light reflecting elements as electrophoretic particles P. are designed, depending on their position and where in the case that light-reflecting elements as drops of liquid F. are designed, depending on their extension, shape and / or position, in a first operating state B1 the angle-dependent transmission is less than 50% and in a second operating state B2 at more than 50% in an angular range of more than 30 ° to 90 ° based on a surface normal of the light exit surface F2 of the light guide 1 , measured in a direction perpendicular to a longitudinal extent of the areas G1 .

It is particularly possible that the angle-dependent transmission in the second operating state B2 more than 60% and in the first operating state B1 is less than 5%, in an angular range of more than 30 ° based on a surface normal of the light exit surface F2 of the light guide 1 and measured in a direction perpendicular to a longitudinal extent of the regions G1 . If the optical element, as explained in more detail below, is used in connection with an image display unit, the aforementioned direction in which measurement is carried out can preferably correspond to the horizontal direction of extent of the image display device.

In this sense, the angle range in the example shown then includes the angles from +/- 30 ° to +/- 90 ° (i.e. from -90 ° to -30 ° and at the same time from + 30 ° to + 90 °, but not between -30 ° and + 30 °) in this plane. At 90 ° the angle is on the surface of the optical element.

Furthermore, it is possible for the first or second alternative to use the light-absorbing or light-reflecting elements as electrophoretic particles P. are designed and at the same time several types of such particles P. are present that differ in their absorption properties and / or transport properties in the electromagnetic field. The term “transport properties” is particularly the behavior of the particles P. in the case of (di-) electrophoresis, ie during transport in the field. This variant comes especially in the case of (nano) particles P. to bear: the difference in the types of particles P1 , P2 , P3 , ... consists in the particle size and / or the surface functionalization, ie in the zeta potential. In the case of using quantum dots or dyes as particles P. and if these are fluorescent, a so-called “quencher” material is preferably used to avoid the fluorescence.

6th shows a schematic plan view of a first possible arrangement of the first and second areas G1 respectively. G2 . The first areas G1 are light, the second areas G2 are shown dark. The first and second areas are for preferred configurations of the first and the second alternative of the optical element G1 respectively. G2 when projecting perpendicularly onto the light exit surface strip or rectangular, as in 6th shown. In other words: the outer edges of the first areas G1 and the second areas G2 represent stripes or rectangles with parallel projection from above. This creates the angle influence for the light emerging from the optical element in exactly one plane. It is advantageous if the ratio of the area proportions of the surfaces of the first areas G1 to the surfaces of the second areas G2 is less than or equal to 1: 1 for projection perpendicular to the light exit surface, as shown here.

Alternatively there 7th a schematic plan view of the first and second areas G1 respectively. G2 in a second possible arrangement again. There are rectangular second areas G2 into a first region that essentially covers the entire surface of the optical element G1 embedded. In contrast to the variant after 6th it is possible here to influence the angle for the light emerging from the optical element in two planes.

Furthermore shows 8th the schematic diagram of an optical element according to a third alternative in cross section in a first state in which an exit angle range of light emerging from the light exit surface is trimmed compared to an entry angle range of the light when entering via the light entry surface, and 9 the schematic diagram of the optical element according to the third alternative in a second state in which an exit angle range of light is not or only insignificantly cropped compared to its entrance angle range.

• - einen transparenten, plattenförmigen Grundkörper S mit einer als Lichteintrittsfläche F1 ausgebildeten ersten Großfläche und einer als Lichtaustrittsfläche F2 ausgebildeten zweiten Großfläche,
• - eine transparente Flüssigkeit FL, welche zwischen der ersten Großfläche F1 und der zweiten Großfläche F2 angeordnet ist und Licht absorbierende Flüssigkeitstropfen F enthält, deren Ausdehnung und Form und/oder Position im Grundkörper mittels eines wählbaren und veränderbaren elektrischen Feldes einstallbar ist, wobei die Ausdehnung in einer Ausdehnungsspanne zwischen einer Minimalausdehnung und einer Maximalausdehnung einstellbar ist,
• - elektrische Schaltmittel mit einer Vielzahl von ersten flächenförmigen Elektroden E1, welche transparent und zwischen den Großflächen F1, F2 angeordnet sind, und dazu korrespondierenden zweiten flächenförmigen Elektroden E2, welche an der Lichteintrittsfläche F1 angeordnet und umgekehrt zu den ersten flächenförmigen Elektroden E1 gepolt sind, wobei die Polungen von ersten und zweiten flächenförmigen Elektroden E1, E2 umkehrbar sind,
• - wobei die Maximalausdehnung in der Größenordnung einer Längsausdehnung der ersten flächenförmigen Elektroden E1 zwischen der ersten und zweiten Großfläche F1, F2 liegt,
• - bei einer Ausdehnung der absorbierenden Flüssigkeitstropfen F von mindestens 85% der Maximalausdehnung ein Austrittswinkelbereich von Licht, welches aus der Lichtaustrittsfläche F2 tritt, gegenüber einem Eintrittswinkelbereich des Lichts beim Eintritt über die Lichteintrittsfläche F1 beschnitten ist (siehe 8), und
• - bei einer Ausdehnung der absorbierenden Flüssigkeitstropfen F von weniger als 20% der Maximalausdehnung der Austrittswinkelbereich gegenüber dem Eintrittswinkelbereich nicht oder nur unwesentlich beschnitten ist (siehe 9).

Such an optical element according to the third alternative includes by way of example

• - A transparent, plate-shaped base body S with a light entry surface F1 trained first large area and one as a light exit area F2 trained second large area,
• - a transparent liquid FL , which between the first large area F1 and the second large area F2 is arranged and light-absorbing liquid drops F. contains whose expansion and shape and / or position in the base body can be adjusted by means of a selectable and changeable electrical field, the expansion being adjustable in an expansion range between a minimum expansion and a maximum expansion,
• - electrical switching means with a plurality of first sheet-like electrodes E1 which are transparent and between the large areas F1 , F2 are arranged, and corresponding second sheet-like electrodes E2 , which at the light entry surface F1 arranged and vice versa to the first sheet-like electrodes E1 are polarized, the polarities of the first and second sheet-like electrodes E1 , E2 are reversible,
• - wherein the maximum dimension is of the order of magnitude of a longitudinal dimension of the first sheet-like electrodes E1 between the first and second large area F1 , F2 lies,
• - when the absorbing liquid drops expand F. at least 85% of the maximum extent an exit angle range of light, which from the light exit surface F2 occurs, compared to an entry angle range of the light when entering via the light entry surface F1 is circumcised (see 8th ), and
• - when the absorbing liquid drops expand F. of less than 20% of the maximum extent, the exit angle range is not or only insignificantly cut off compared to the entry angle range (see 9 ).

Especially in the case of the third alternative, it is possible that the normals of the plurality of first sheet-like electrodes E1 which are transparent and between the large areas F1 , F2 are arranged at an angle of -25 degrees up to and including +25 degrees with the center perpendicular of the light exit surface F2 of the optical element. This means that the cropped exit angle range can be tilted around an absolute value if the application requires this.

An advantage of this third alternative is that there are no chambers or the like for channeling the liquid FL or framework matrix and the liquid droplets contained therein F. are necessary. The final localization of the liquid droplets after they have moved on the electrodes basically eliminates the need for such chambers. The first electrodes E1 are here, for example, strip-shaped and either parallel or lattice-shaped, with intersecting areas. The angle-dependent transmission properties of the optical element with respect to one or two perpendicular planes are then designed accordingly.

The first electrodes E1 are all aligned here at the same angle to the second large surface of the substrate, each essentially parallel to the perpendicular to the substrate.

The electromagnetic switching means, ie the electrodes as described above E1 , E2 , are advantageous in all alternatives for light that comes through the light entry surface F1 falls into the optical element is at least 50% transparent in the wavelength range visible to the human eye. This can be, for example, an indium tin oxide layer (ITO layer). In the case of electrodes E1 on the side of the areas facing away from the light guide G2 however, under certain circumstances it can also be an opaque electrode.

The liquid FL can be polar or non-polar. It can also consist, for example, of water, oil, toluene or formaldehyde, also mixed with electrolytes or other organic substances, around the particles P. in the liquid FL to stabilize or modify their electrophoretic properties.

Are the light-absorbing elements as drops of liquid F. designed, they can contain organic dyes, soot, graphene, carbon, metal oxides such as chromium (IV) oxide, Fe ₂ O ₃ , Fe ₃ O ₄ or FeO or colloidal semiconductor quantum dots or be mixed with polymer or porous silica microparticles to achieve absorption . It contains a single drop of liquid F. the aforementioned ingredients to a maximum of 70% by volume and has a volume of 5 × 10 ^-13 to 2 × 10 ^-10 liters inclusive.

The light entry surface F1 of the light guide 1 of a previously described optical element is usually located on the rear side of the optical element from the point of view of a viewer and, depending on its application, is adjacent, for example, to an image display device, a light source or to a volume of air. Light then emerges from the latter objects through the said light entry surface F1 or the areas G1 into the optical element.

• ― einen transparenten, plattenförmigen, als Lichtleiter 1 aus einem PMMA mit einer Brechzahl n_L =1,48 ausgestalteten Grundkörper mit einer als Lichteintrittsfläche F1 ausgebildeten ersten Großfläche und einer als Lichtaustrittsfläche F2 ausgebildeten zweiten Großfläche, wobei an der Lichteintrittsfläche F1 und dazu korrespondierend an der Lichtaustrittsfläche F2 einander abwechselnd erste Bereiche G1 und zweite Bereiche G2 ausgebildet, ausgespart oder angeordnet sind,
• ― wobei die ersten Bereiche G1 mit einem transparenten Material - hier ebenfalls PMMA - mit der Brechzahl n_G1 =1,48 ausgefüllt sind, und
• ― wobei mindestens die auf der Seite der Lichtaustrittsfläche F2 liegenden zweiten Bereiche G2 jeweils ein Volumen V aufweisen, welches eine transparente Flüssigkeit FL enthält, wobei die Flüssigkeit FL Licht absorbierende Elemente enthält, welche in ihrer Gesamtheit entweder als Flüssigkeitstropfen F oder als elektrophoretische Partikel P ausgebildet sind, und wobei mittels eines wählbaren und veränderbaren elektrischen Feldes im Falle elektrophoretischer Partikel P deren Position und im Falle von Flüssigkeitstropfen F deren Ausdehnung, Form und/oder Position einstellbar ist,
• ― wobei die ein Volumen V aufweisenden zweiten Bereiche G2 an einer dem Lichtleiter 1 abgewandten Seite jeweils eine reflektierende Schicht 4 aufweisen,
• ― elektrische Schaltmittel in den ein Volumen V aufweisenden zweiten Bereichen G2 auf der Seite der Lichtaustrittsfläche F2, mit ersten Elektroden E1 an der dem Lichtleiter 1 abgewandten Fläche, welche zur Lichtaustrittsfläche F2 des Lichtleiters 1 parallel liegt, und mit transparenten, an einer planen Grenzfläche F2 zum Lichtleiter 1 anliegenden zweiten Elektroden E2 im Innern des zweiten Bereichs G2, welche umgekehrt zu den ersten Elektroden E1 gepolt sind und wobei die Polungen zwischen einem ersten und einem zweiten Zustand umschaltbar sind,
• ― sowie auf der Seite der Lichteintrittsfläche F1 in den zweiten Bereichen G2 eine (optional opake) Reflexionsschicht 2, welche an der Lichteintrittsfläche F1 angebracht ist, so dass
  1. a) die Licht absorbierenden Elemente F, P im ersten Zustand zu mehr als 85% die zweite Elektrode E2 bedecken, so dass Licht, welches über die ersten Bereiche G1 in den Lichtleiter eintritt und in die zweiten Bereiche G2 übertritt, von den absorbierenden Elementen überwiegend absorbiert wird,
  2. b) die Licht absorbierenden Elemente F,P im zweiten Zustand zu weniger als 15% die zweite Elektrode bedecken, so dass Licht, welches über die ersten Bereiche G1 in den Lichtleiter eintritt und in die zweiten Bereiche G2 übertritt, überwiegend an den reflektierenden Schichten 2, 4 reflektiert wird, und
  • ― so dass, wenn Licht auf das optische Element einfällt, dieses mindestens durch an der Lichteintrittsfläche F1 lokalisierte erste Bereiche G1 in den Lichtleiter 1 eintritt, und
    • ― im ersten Zustand das optische Element entweder in einem eingeschränkten Winkelbereich durch an der Lichtaustrittsfläche F2 lokalisierte erste Bereiche G1 verlässt (siehe Strahl, der den zentralen Bereich G1 in 10 und 11 verlässt) oder aufgrund der absorbierenden Elemente F, P in den zweiten Bereichen G2 absorbiert wird (siehe den Strahl, der im Bereich G2 in 10 und 11 absorbiert wird), oder
    • ― im zweiten Zustand das optische Element entweder in einem eingeschränkten Winkelbereich durch an der Lichtaustrittsfläche F2 lokalisierte erste Bereiche G1 verlässt (siehe den Strahl, der den zentralen Bereich G1 in 12 und 13 verlässt) oder aufgrund der Reflexion an einer reflektierenden Schicht 4 an einer dem Lichtleiter 1 abgewandten Seite jeweils eines zweiten Bereichs G2 und/oder an einer Reflexionsschicht 2 an der Lichteintrittsfläche F1 im Lichtleiter 1 solange propagiert, bis es den Lichtleiter 1 durch die an der Lichtaustrittsfläche lokalisierten ersten Bereiche G1 in größeren Winkeln als die des besagten eingeschränkten Winkelbereichs verlässt (siehe den Strahl, der den links eingezeichneten Bereich G1 in 12+13 verlässt).

Finally shows 10 the schematic diagram of an optical element according to a fourth alternative in a first embodiment in a first state, 11 the schematic diagram of an optical element according to the fourth alternative in a second embodiment in the first state, 12th the schematic diagram of an optical element according to the fourth alternative in the third embodiment in a second state, and 13th the schematic diagram of an optical element according to the fourth alternative in the fourth embodiment in the second state. Such an exemplary optical element according to the fourth alternative comprises

• - a transparent, plate-shaped, as a light guide 1 from a PMMA with a refractive index n _L = 1.48 designed base body with a light entry surface F1 trained first large area and one as a light exit area F2 formed second large area, with the light entry surface F1 and correspondingly on the light exit surface F2 alternating first areas G1 and second areas G2 designed, recessed or arranged,
• - being the first areas G1 with a transparent material - here also PMMA - _{are filled with the refractive index n G1} = 1.48, and
• - at least the one on the side of the light exit surface F2 lying second areas G2 one volume each V have, which is a transparent liquid FL contains, the liquid FL Contains light-absorbing elements, which in their entirety are either liquid droplets F. or as electrophoretic particles P. are formed, and by means of a selectable and changeable electrical field in the case of electrophoretic particles P. their position and in the case of liquid drops F. whose expansion, shape and / or position can be adjusted,
• - being the one volume V having second areas G2 on one of the light guides 1 facing away from each side a reflective layer 4th exhibit,
• - electrical switching means in the one volume V having second areas G2 on the side of the light emitting surface F2 , with first electrodes E1 at the light guide 1 facing away from the surface facing the light exit surface F2 of the light guide 1 lies parallel, and with transparent, on a flat interface F2 to the light guide 1 adjacent second electrodes E2 inside the second area G2 which is the reverse of the first electrodes E1 are polarized and the polarities can be switched between a first and a second state,
• - as well as on the side of the light entry surface F1 in the second areas G2 an (optionally opaque) reflective layer 2 , which at the light entry surface F1 is appropriate so that
  1. a) the light absorbing elements F. , P. in the first state more than 85% the second electrode E2 cover so that light is pouring over the first areas G1 enters the light guide and into the second areas G2 passes over, is predominantly absorbed by the absorbent elements,
  2. b) the light absorbing elements F. , P in the second state to less than 15% cover the second electrode, so that light which passes over the first areas G1 enters the light guide and into the second areas G2 crosses over, mainly on the reflective layers 2 , 4th is reflected, and
  • - so that when light strikes the optical element, this at least through to the light entry surface F1 localized first areas G1 into the light guide 1 occurs, and
    • - In the first state, the optical element either in a restricted angular range through to the light exit surface F2 localized first areas G1 leaves (see ray, which the central area G1 in 10 and 11 leaves) or due to the absorbent elements F. , P. in the second areas G2 is absorbed (see the ray coming in the area G2 in 10 and 11 is absorbed), or
    • - In the second state, the optical element either in a restricted angular range through to the light exit surface F2 localized first areas G1 leaves (see the ray that the central area G1 in 12th and 13th leaves) or due to the reflection on a reflective layer 4th on one of the light guides 1 facing away from each side of a second area G2 and / or on a reflective layer 2 at the light entry surface F1 in the light guide 1 until it propagates the light guide 1 by the first areas located on the light exit surface G1 at angles greater than those of the said restricted angular range (see the ray that marks the area on the left G1 in 12th +13 leaves).

As a material for the light guide 1 and for the first areas G1 PMMA was taken here in each case. In general, however, it is possible to use different materials whose refractive indices can differ from one another by up to an absolute value of 0.11. For example, another polymer, polycarbonate, PET or even glass could be used.

The difference between the configurations of the fourth alternative of the optical element according to the drawings 10 11 (first embodiment) and 11 (second embodiment) consists in that the electrodes are arranged differently. According to the first embodiment of the fourth alternative in 10 are the second electrodes E2 directly at the light exit surface F2 of the light guide 1 arranged so that the absorbent elements F. , P. arrange and distribute themselves there with the appropriate polarity for the first state. In contrast, according to the second embodiment 11 the first and second electrodes E1 and E2 structured in such a way that they have a flat distribution of the absorbing elements through corresponding flat polarity F. , P. achieve in the first state, and another time for the second state according to 12th or 13th the absorbent elements F. , P. only selectively in the area G2 to distribute.

The third and fourth embodiments according to the drawings 12th and 13th again differ in that here too the first electrodes E1 each structured differently to accommodate different distributions of the absorbent element F. , P. achieve in the second state, in particular by each different distribution of the first electrodes E1 , as can be seen from the drawings mentioned.
It is thus possible to use the first ( 10 ) or second ( 11 ) Design of the first electrodes E1 to maintain the first state with the third ( 12th ) and fourth embodiments ( 13th ) of the second electrodes E2 to combine.

For the fourth alternative, the design variants given above apply analogously, in particular for the first design. For reasons of redundancy, these are not repeated at this point.

Moreover shows 14th generally the schematic diagram for the deposition of an opaque drop of liquid F. or a variety of opaque electrophoretic particles P. on negatively charged first electrodes E1 and 15th the schematic diagram for the deposition of an opaque drop of liquid F. or a variety of opaque electrophoretic particles P. on a flat, negatively charged second electrode E2 .

Furthermore there 16 the schematic diagram of a plan view of the first areas G1 and second areas G2 of an optical element according to the first, second or fourth alternative, with different subregions of the second regions G2 are in different states, which is highlighted by the portion framed by dashed lines.

Continues to provide 17th the schematic diagram of a plan view of the first areas G1 and second areas G2 of an optical element according to the first, second or fourth alternative, with different subregions of the second regions G2 are in different states (see framed part), and furthermore here crossing first areas G1 are provided.

For all alternatives of the optical element, in this context, the electrical switching means are optional E1 , E2 can be subdivided into several separately switchable segments, thereby enabling a segment-wise and thus locally restrictable switchability between the first state and the second state. Local switchability here means that not in all of the second areas G2 at the same time that is changed between the first and the second state, but rather that, rather, two areas on the optical element at the same time G2 with both the first and second states. This is advantageous, for example when, when using the optical element in front of or behind an image display device, parts of the displayed image content should be visible and others should not be visible from a viewing angle of more than 30 degrees to the side.

The invention is particularly important in that the optical element according to the first, second or fourth alternative, including modifications thereof, is used in a screen which is in a first operating state B1 for a restricted viewing mode and in a second operating state B2 can be operated for a free viewing mode. Such a screen comprises at least one optical element - as described above - and an image display unit which is arranged downstream or upstream of the at least one optical element as seen by a viewer. The use of two optical elements, preferably of identical design, stacked one on top of the other improves perception in the operating state B2 . It is particularly advantageous if the optical elements are of the same type, but the second areas G2 are arranged on the two optical elements rotated relative to each other by a predetermined angle in the plane of one of the exit surfaces or in the plan view of the screen. Said predetermined angle can be up to 25 ° and is preferably 16 °.

The image display unit is, for example, an OLED display, an LCD panel, an SED, a FED, a micro-LED display or a VFD. Since the optical element is effective regardless of the type of image display unit, any other types of screen are also possible.

It is also possible, for example, to use the optical element according to the invention in an image display unit which has a backlight, such as, for example, in an LCD screen. In this case, the optical element would then advantageously be arranged between the image display panel (that is to say the LCD panel) and the background lighting in order to switch between a first operating state B1 for a restricted viewing mode and a second operating state B2 to switch for a free viewing mode because the light of the backlight focuses once due to the optical element ( B1 ) and once out of focus ( B2 ) will. In this context, “focusing” does not mean focusing in the manner of lenses, but rather a spatial narrowing of the emission area in accordance with the respective angle-dependent transmission properties of the optical element according to the invention.

The invention also includes the use of an optical element of one of the four alternatives or of a screen as described above in a car, a mobile device, a desktop screen, in an ATM or in a payment terminal.

The optical element described above can advantageously be used in conjunction with an image display device wherever confidential data is displayed and / or entered, such as when entering a PIN or for displaying data at ATMs or payment terminals or for entering passwords or when reading emails mobile devices. As described above, the optical element can also be used in a car. It is also possible to use the optical element in connection with an image display device for advertising purposes, for example when certain advertisements are only to be seen with a certain body size and other advertisements may be visible to all persons.

With the above-described embodiments of an optical element according to the invention, it is possible to achieve what was desired, namely to influence the transmission as a function of the angle, with the optical element being able to switch between at least two operating states. It can be implemented inexpensively and, in particular, can be used universally with different types of screen in order to enable switching between a privacy screen and a free viewing mode, the resolution of such a screen being essentially not reduced.

Claims (20)

An optical element, comprising - a transparent, plate-shaped or shell-shaped base body designed as a light guide (1) made of a material with a refractive index nL with a first large area designed as a light entry area (F1) and a second large area designed as a light exit area (F2), with an first areas (G1) and second areas (G2) are alternately formed, recessed or arranged on the light entry surface (F1) and corresponding thereto on the light exit surface (F2), - the first areas (G1) with a transparent material with a refractive index nG1 are filled, the refractive indices nL and nG1 differ from each other by a maximum of 0.11, and - at least the second areas (G2) lying on the side of the light exit surface (F2) each have a volume (V) which is a transparent liquid (FL) or a framework matrix with a refractive index nG2, which is smaller than the refractive index nL holds, whereby the liquid (FL) or framework matrix contains light-absorbing elements, which in their entirety are designed either as liquid droplets (F) or as electrophoretic particles (P), and where, by means of a selectable and changeable electrical field, in the case of electrophoretic particles (P) their position and in the case of liquid droplets (F) their expansion, shape and / or position is adjustable, whereby the refractive indices n _L and n _G2 differ by at least a value of 0.05 and at most a value of 0.35, - the light guide (1) at interfaces to each of the volumes ( V) having second areas (G2) at least on the side of the light exit surface (F2) has structured surfaces which predominantly totally internally reflect light that enters the light guide (1) via the first areas (G1), - electrical switching means in the a volume (V) having second regions (G2) on the side of the light exit surface (F2), with planar first electrodes (E1) on one of the light guides (1) ndth surface which lies parallel to or corresponds to the light exit surface (F2) of the light guide (1), and with transparent second electrodes (E2) resting on the structured surfaces in the interior of the second area (G2) at an interface with the light guide (1) , which are polarized in reverse to the first electrodes (E1) and the polarities can be switched between a first and a second state, - as well as on the side of the light entry surface (F1) in the second areas (G2) similarly structured surfaces and / or opaque Reflective layer (2) which is attached to the light entry surface (F1) so that a) the light absorbing elements (F, P) in the first state cover more than 85% of the second electrodes (E2), whereby the total internal reflection of light disturbed on the structured surfaces and the propagation of light which enters the light guide (1) via the first areas (G1) is mainly prevented by absorption by the light absorbing elements (F, P), and b) the light absorbing elements (F, P) in the second state cover the second electrodes (E2) by less than 15%, so that the propagation of light which enters the light guide (1) via the first regions (G1) is less than 50% of the light-absorbing elements (F, P) is absorbed, - so that when light strikes the optical element, it enters the light guide (1) at least through first areas (G1) located on the light entry surface (F1), and - im first state nd leaves the optical element either in a restricted angular range through first areas (G1) located on the light exit surface (F2) or is predominantly absorbed in the second areas (G2) due to the light-absorbing elements (F, P), or - in the second state leaves the optical element either in a restricted angular range through first areas (G1) located on the light exit surface (F2) or due to total internal reflection on the structured surfaces and possibly reflection on a reflective layer (2) on the light entry surface (F1) in the light guide ( 1) propagates until it leaves the light guide (1) through the first areas (G1) located on the light exit surface (F2) at angles greater than those of the said restricted angular area. Optical element, comprising - A transparent, plate-shaped or shell-shaped base body designed as a light guide (1) made of a material with a refractive index nL with a first large area designed as a light entry surface (F1) and a second large area designed as a light exit area (F2), with the light entry area (F1 ) and first areas (G1) and second areas (G2) are formed, cut out or arranged corresponding to one another on the light exit surface (F2), - the first regions (G1) being filled with a transparent material with a refractive index nG1, the refractive indices nL and nG1 differing from one another by a maximum of 0.11, and - wherein at least the second areas (G2) lying on the side of the light exit surface (F2) each have a volume (V) which contains a transparent liquid (FL) or a framework matrix, the liquid (FL) or framework matrix containing light-reflecting elements which in their entirety are designed either as liquid droplets (F) or as electrophoretic particles (P), and where, by means of a selectable and changeable electric field, their position in the case of electrophoretic particles (P) and their expansion in the case of liquid droplets (F), Shape and / or position is adjustable, - the second regions (G2) having a volume (V) each having an opaque absorption layer (3) on a side facing away from the light guide (1), - electrical switching means in the second areas (G2) having a volume (V) on the side of the light exit surface (F2), with first electrodes (E1) on the surface facing away from the light guide (1) which faces the light exit surface (F2) of the light guide ( 1) is parallel or corresponds to this, and with transparent second electrodes (E2) in the interior of the second area (G2), which are adjacent to a planar interface with the light guide (1) and which are polarized in reverse to the first electrodes (E1) and where the Polarity can be switched between a first and a second state, - As well as on the side of the light entry surface (F1) in the second areas (G2) an opaque reflective layer (2) which is attached to the light entry surface (F1) so that a) the light-reflecting elements (F, P) in the first state cover less than 15% of the second electrode (E2), so that light which enters the light guide (1) via the first areas (G1) and into the second Areas (G2) crosses over, is predominantly absorbed by the opaque layers (3), and b) the light-reflecting elements (F, P) in the second state cover more than 85% of the second electrode (E2), so that light which enters the light guide (1) via the first areas (G2) at the interfaces of the light guide (1) is reflected to the second areas (G2), - so that when light strikes the optical element, it enters the light guide (1) at least through first regions (G1) located on the light entry surface (F1), and - In the first state, the optical element either leaves in a restricted angular range through first regions (G1) located on the light exit surface (F2) or is absorbed in the second regions (G2) due to the opaque layers (3), or - In the second state, the optical element either leaves in a restricted angular range through first areas (G1) located on the light exit surface (F2) or propagates in the light guide (1) due to the reflection on a reflective layer (2) on the light entry surface (F1) until it leaves the light guide (1) through the first areas (G1) located on the light exit surface (F2) at angles greater than those of said restricted angular area. Optical element according to Claim 1 or 2 , also comprising on the side of the light entry surface (F1) in the second areas (G2) having a volume (V) electrical switching means with planar first electrodes (E1) on a surface facing away from the light guide (1) which faces the light entry surface (F1) of the Light guide (1) is parallel or corresponds to this, and with transparent second electrodes (E2) resting on the structured surfaces in the interior of the second area (G2) at an interface with the light guide (1), which is opposite to the first electrodes (E1) are polarized and wherein the polarities can be switched between a first and a second state. Optical element according to Claim 1 , characterized in that the structured surface of the light guide (1) is formed with wave-shaped, lens-shaped and / or prism-shaped structures. Optical element according to Claim 1 or 2 , characterized in that the light-absorbing or light-reflecting elements are designed as electrophoretic particles (P), which are designed as nano-particles, quantum dots and / or dyes and have a spatial extension of a maximum of 500 nm, a maximum of 200 nm, have a maximum of 50 nm or a maximum of 20 nm. Optical element according to Claim 2 , characterized in that the light-reflecting elements are designed as electrophoretic particles (P) which are designed as reflecting spheres with diameters between 5 nm and 5000 nm. Optical element according to Claim 1 , characterized in that the light-absorbing elements are designed as electrophoretic particles (P), which are made as BPQDs (Black Phosphorus Quantum Dots), lead sulfide (PbS), colloidal semiconductor quantum dots, azo dyes and / or as metal oxide particles, preferably made of chromium (IV ) Oxide or Fe ₂ O _{3 are} formed, and have a size between 2 nm and 50 nm, each inclusive. Optical element according to one of the Claims 1 or 2 , characterized in that at least two operating states are defined by means of the electrical switching means (E1, E2) and a control circuit, in the event that the light-absorbing or light-reflecting elements are designed as electrophoretic particles (P), depending on their position and in the event that light-reflecting elements are designed as liquid droplets (F), depending on their expansion, shape and / or position, the angle-dependent transmission is less than 50% in a first operating state B1 and is less than 50% in a second operating state B2 more than 50% in an angular range of more than 30 ° to 90 ° based on a surface normal of the light exit surface of the light guide (1), measured in a direction perpendicular to a longitudinal extension of the first areas (G1). Optical element according to Claim 8 , characterized in that the angle-dependent transmission in the second operating state B2 is more than 60% and in the first operating state B1 less than 5%, in an angular range of more than 30 ° based on a surface normal of the light exit surface (F2) of the light guide (1) and measured in a direction perpendicular to a longitudinal extension of the first areas (G1). Optical element according to one of the preceding claims, characterized in that the electrical switching means (E1, E2) are subdivided into several separately switchable segments, whereby a segment-wise and thus locally restrictable switchability is made possible between the first and the second state. Optical element according to one of the Claims 1 or 2 , characterized in that the light-absorbing or light-reflecting elements are designed as electrophoretic particles (P) and there are several types of such particles (P) which differ in their absorption properties and / or transport properties in the electromagnetic field. Optical element according to one of the Claims 1 or 2 , characterized in that the light-absorbing or light-reflecting elements are designed as liquid droplets (F) and several types of such liquid droplets (F) are present, which differ in their absorption properties and / or movement properties and / or deformation properties in the electromagnetic field. Optical element according to Claim 1 , characterized in that the light-absorbing elements are designed as liquid droplets (F) and contain organic dyes, carbon black, graphene, metal oxides or semiconductor quantum dots or are mixed with polymer or porous silica microparticles to achieve absorption. Optical element according to Claim 2 , characterized in that the light-reflecting elements are designed as liquid droplets (F) and contain metal microparticles, metal nanoparticles, or metal- or nanoparticle-coated polymer or silica microparticles to achieve a reflection. Optical element according to one of the Claims 1 or 2 , characterized in that the light-absorbing or light-reflecting elements are designed as liquid droplets (F), which each individually have a volume of 5 × 10 ^-13 to 2 × 10 ^-10 liters, inclusive. Optical element according to one of the Claims 1 or 2 , characterized in that the first areas (G1) and the second areas (G2) are strip-shaped or rectangular when projected perpendicularly onto the light exit surface (F2). Optical element according to one of the Claims 1 or 2 , characterized in that the ratio of the area proportions of the surfaces of the first areas (G1) to the surfaces of the second areas (G2) when projected perpendicular to the light exit surface (F2) is less than or equal to 1: 1, preferably 1: 2, particularly preferably 1 : 4 is. Screen that can be operated in a first operating state B1 for a restricted viewing mode and in a second operating state B2 for a free viewing mode, comprising at least one optical element according to one of the Claims 1 until 17th and an image display unit which is arranged downstream or upstream of the at least one optical element as seen by a viewer. Use of an optical element or a screen according to one of the preceding claims in a car, a mobile device, a desktop screen, in an ATM or in a payment terminal. An optical element, comprising - a transparent, plate-shaped or shell-shaped base body designed as a light guide (1) made of a material with a refractive index nL with a first large area designed as a light entry area (F1) and a second large area designed as a light exit area (F2), with an first areas (G1) and second areas (G2) are alternately formed, recessed or arranged on the light entry surface (F1) and corresponding thereto on the light exit surface (F2), - the first areas (G1) with a transparent material with a refractive index nG1 are filled, the refractive indices nL and nG1 differ from each other by a maximum of 0.11, and - at least the second areas (G2) lying on the side of the light exit surface (F2) each have a volume (V) which is a contains transparent liquid (FL) or a framework matrix, the liquid (FL) or framework matrix absorbing light containing elements, which in their entirety are formed either as liquid droplets (F) or as electrophoretic particles (P), and where, by means of a selectable and changeable electric field, in the case of electrophoretic particles (P) their position and in the case of liquid droplets (F) the extent, shape and / or position of which is adjustable, - the second regions (G2) having a volume each having a reflective layer (4) on a side facing away from the light guide (1), - electrical switching means in which a volume (V) having second areas (G2) on the side of the light exit surface (F2), with first electrodes (E1) on the surface facing away from the light guide (1), which is parallel to or corresponds to the light exit surface (F2) of the light guide (1), and with transparent second electrodes (E2) in the interior of the second region (G2), which are in contact with the light guide (1) and are opposite to de n first electrodes (E1) are polarized and the polarity can be switched between a first and a second state, - as well as on the side of the light entry surface (F1) in the second areas (G2) a reflective layer (2) which is applied to the light entry surface ( F1) is attached so that a) the light-absorbing elements (F, P) in the first state cover more than 85% of the second electrode (E2), so that light which enters the light guide (1) via the first areas (G1) and into the second Areas (G2), is predominantly absorbed by the absorbing elements (F, P), b) the light absorbing elements (F, P) in the second state cover less than 15% of the second electrode (E2), so that light, which enters the light guide (1) via the first areas (G1) and passes into the second areas (G2), is mainly reflected on the reflective layers (4), and - so that when light strikes the optical element, this enters the light guide (1) at least through first areas (G1) localized on the light entry surface (F1), and - in the first state either leaves or leaves the optical element in a restricted angular range through first areas (G1) localized on the light exit surface (F2) due to the absorbing elements (F, P) is absorbed in the second areas (G2), or - in the second state, the optical element either leaves in a restricted angular range through first areas (G1) located on the light exit surface (F2) or due to the reflection at a reflective layer (4) on a side facing away from the light guide (1) in each case of a second area (G2) and / or on a reflective layer (2) on the light entry surface (F1) in the light guide (1) propagates until the light guide (1 ) leaves through the first areas (G1) located on the light exit surface (F2) at angles greater than those of said restricted angular area.

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