DE102020002797B3 - Optical element with variable angle-dependent transmission and screen with such an optical element - Google Patents

Abstract

The invention relates to an optical element, comprising an essentially plate-shaped substrate (S) with a first large area designed as a light entry area and a second large area designed as a light exit area, a plurality of chambers embedded in the substrate (S) which, depending on their size either individually form a lamella or are combined in groups, each group forming a lamella, and each lamella having longitudinal and narrow sides which extend between the first large area and the second large area, the narrow sides of each lamella being arranged in the area of the large areas and the long sides connect them, a liquid or a framework matrix (F) with which the chambers (R) are filled, the liquid or the framework matrix (F) containing up to 95 percent by volume of electrophoretically or magnetophoretically movable particles (P), the particles (P) at least first particles (PA) of an ers The th type of particles which absorb light of one or more wavelengths or wavelength ranges in the range visible to a human eye, and second particles (PB) of a second type of particles which absorb light of one or more wavelengths or wavelength ranges in the range visible to a human eye Reflect and / or scatter the area, or in a second embodiment the liquid or the framework matrix (F) itself either fulfills the role of the first particle (PA) or the second particle (PB) and the particles (P) only the other particles ( PB) or (PA), and also comprehensively electromagnetic switching means which are embodied in planar fashion on one or more sides of the lamellae in the substrate (S) and which, when switched on, generate an electromagnetic field effective in the lamellae, whereby the particles (P) in the Liquid or the framework matrix (F) are moved so that an angle-dependent door Ansmission of the optical element for light of the wavelengths or wavelength ranges that are absorbed by the particles (P), which enters the substrate (S) at such angles that it hits the lamellae, changes, using the electromagnetic switching means and a control circuit at least two operating states B1 and B2 are defined as a function of the position of the particles (P), so that in the second operating state B2 more than 70% of the first particles (PA) are located on the longitudinal sides of the lamellas, and in which In the first operating state B1 more than 70% of the second particles (PB) are located on the longitudinal sides of the lamellas, so that the angle-dependent transmission in the first operating state B1 is more than 60% and in the second operating state B2 less than 5%, in an angular range of more than 30 ° based on a surface normal of the second large surface of the substrate and measured perpendicularly in one direction ht to a longitudinal extension of the lamellas. In addition, further design variants and a screen using the optical element are described.

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: With the engine 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 were not switchable, they always had 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 prismatic structures 50, which transform the light from the rear lighting on the way to the front lighting. This is expensive and time-consuming to implement and also associated with loss of light. According to the variant after 17th in the US 2012/0235891 Both light sources 4R and 18 produce light with a narrow angle of illumination, the light from the rear light source 18 only being 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 special optical surfaces 19, which are complex to calculate and manufacture, are used, which then deflect light into various narrow or wide areas depending on the angle of incidence of light. 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. The disadvantage here is, among other things, that the restricted visual effect can be generated either only for left / right or for up / down, but not for left / right / up / down at the same time, as is necessary for certain payment transactions, for example. 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, usually have the disadvantage that light is coupled out from both large surfaces, so that about half of the useful light is emitted in the wrong direction, namely towards the background lighting, and is not there to a sufficient extent due to the structure can be recycled. In addition, the im Scattering particles made of polymerizate distributed over the volume of the light guide may, in particular at higher concentrations, lead to scattering effects which reduce the visual protection effect in the protected operating mode.

In the DE 10 2019 006 022 B3 the applicant discloses an optical element with variable transmission. This allows the advantageous change in the angle-dependent transmission. However, only absorbing electro- or magnetophoretic particles are used there, and the advantages of particles or structures of the particles of different types in terms of optical properties remain unaffected.

US 2020/0050010 A1 describes a switchable light collimation layer. Possible advantages of particles of different types or structures of the particles with regard to the optical properties are not used here.

In addition, the US 2021/0223929 A1 an electrophoretic display based on colored particles. A function for varying the angle-dependent transmission of this display is not provided and cannot be implemented with the display features disclosed there.

Finally describes the EP 3066514 B1 an optically variable device that allows the visual impression of one and the same device to be varied. A function for varying the angle-dependent transmission of this device is not provided.

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.

Description of the invention

It is therefore the object of the invention to develop an optical element which can influence the transmission as a function of the angle (optionally perpendicular) and which can switch between at least two operating 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.

This object is achieved by the methods according to claims 1, 2, 7 and 8. Preferred embodiments are disclosed in the sub-claims and in detail in the description.

• - ein im Wesentlichen plattenförmiges Substrat mit einer als Lichteintrittsfläche ausgebildeten ersten Großfläche und einer als Lichtaustrittsfläche ausgebildeten zweiten Großfläche,
• - eine Vielzahl von in das Substrat eingebetteten Kammern, welche in Abhängigkeit von ihrer Größe entweder einzeln eine Lamelle formen oder gruppenweise zusammengefasst sind, wobei jede Gruppe eine Lamelle formt, und jede Lamelle Längs- und Schmalseiten aufweist, welche sich zwischen der ersten Großfläche und der zweiten Großfläche erstrecken, wobei die Schmalseiten jeder Lamelle im Bereich der Großflächen angeordnet sind und die Längsseiten diese verbinden,
• - eine Flüssigkeit oder eine Gerüstmatrix, mit der die Kammern gefüllt sind, wobei die Flüssigkeit oder die Gerüstmatrix bis zu 95 Volumenprozent elektrophoretisch oder magnetophoretisch bewegbarer Partikel P enthält, wobei die Partikel P
  1. i. entweder in einer ersten Ausgestaltung mindestens erste Partikel P_A einer ersten Art von Partikeln umfassen, welche Licht einer oder mehrerer Wellenlängen oder Wellenlängenbereiche im für ein menschliches Auge sichtbaren Bereich absorbieren, und zweite Partikel P_B einer zweiten Art von Partikeln umfassen, welche Licht einer oder mehrerer Wellenlängen oder Wellenlängenbereiche im für ein menschliches Auge sichtbaren Bereich reflektieren und/oder streuen, oder in einer zweiten Ausgestaltung die Flüssigkeit oder die Gerüstmatrix selbst entweder die Rolle der ersten Partikel P_A oder der zweiten Partikel P_B erfüllt und die Partikel P nur die jeweils anderen Partikel P_B oder P_A umfassen,
  2. ii. oder die Partikel P als Januspartikel ausgebildet sind und jeweils mindestens einen ersten Bereich mit einer ersten Struktur P₁ und einen davon verschiedenen zweiten Bereich mit einer zweiten Struktur P₂ aufweisen, wobei die ersten Strukturen P₁ Licht einer oder mehrerer Wellenlängen oder Wellenlängenbereiche absorbieren, und die zweiten Strukturen P₂ Licht einer oder mehrerer Wellenlängen oder Wellenlängenbereiche reflektieren und/oder streuen,

sowie außerdem umfassend flächenförmig an einer oder mehreren Seiten der Lamellen im Substrat ausgebildete elektromagnetische Schaltmittel, welche in einem eingeschalteten Zustand ein in den Lamellen wirksames elektromagnetisches Feld erzeugen, wodurch die Partikel P in der Flüssigkeit oder der Gerüstmatrix bewegt werden, so dass sich eine winkelabhängige Transmission des optischen Elements für Licht der Wellenlängen oder Wellenlängenbereiche, die von den Partikeln P absorbiert werden, welches in solchen Winkeln über die Lichteintrittsfläche in das Substrat eintritt, dass es auf die Lamellen trifft, ändert.The invention is as an optical element comprising,

• - an essentially plate-shaped substrate with a first large area designed as a light entry surface and a second large area designed as a light exit area,
• - A multiplicity of chambers embedded in the substrate, which, depending on their size, either individually form a lamella or are combined in groups, each group forming a lamella, and each lamella having longitudinal and narrow sides, which are located between the first large area and the extend the second large area, the narrow sides of each lamella being arranged in the area of the large areas and the long sides connecting them,
• a liquid or a framework matrix with which the chambers are filled, the liquid or the framework matrix containing up to 95 percent by volume of electrophoretically or magnetophoretically movable particles P, the particles P
  1. i. either in a first embodiment _{comprise at least first particles P A of} a first type of particles which absorb light of one or more wavelengths or wavelength ranges in the range visible to a human eye, and second particles P _{B of} a second type of particles which absorb light from one or more wavelengths or wavelength ranges reflect and / or scatter several wavelengths or wavelength ranges in the range visible to a human eye, or in a second embodiment the liquid or the framework matrix itself either _{fulfills the role of the first particle P A} or the second particle P _B and the particles P only each include other particles P _B or P _A,
  2. ii. or the particles P are designed as Janus particles and each have at least one first region with a first structure P ₁ and a second region different therefrom with a second structure P ₂ , the first structures P ₁ absorbing light of one or more wavelengths or wavelength ranges, and the second structures P ₂ reflect and / or scatter light of one or more wavelengths or wavelength ranges,

and also comprising electromagnetic switching means which are embodied in planar fashion on one or more sides of the lamellae in the substrate and which are shown in FIG an activated state generate an effective electromagnetic field in the lamellae, whereby the particles P are moved in the liquid or the framework matrix, so that an angle-dependent transmission of the optical element for light of the wavelengths or wavelength ranges that are absorbed by the particles P, which enters the substrate at such angles across the light entry surface that it hits the lamellae changes.

The one or more wavelengths or wavelength ranges in which the electrophoretically or magnetophoretically movable particles P 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.

The first and second large areas of the plate-shaped substrate are preferably arranged parallel to one another. However, in special configurations, for example if 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.

The first large surface of the plate-shaped substrate, designed as a light entry surface, is generally located on the back of the substrate from the perspective of an observer and, depending on the application of the optical element, is adjacent to an image display device, a light source or a volume of air, for example. From the last-mentioned objects, light then enters the substrate through the said light-entry surface.

The invention is advantageously implemented in such a way that the particles P _{comprise first particles P A} and / or second particles P _B , which are embedded in stationary capsules that are located on edge surfaces of the chambers or form the chambers, or in which the particles P as Janus particles are formed, which are fixedly located on the edge surfaces of the chambers R, but can rotate freely.

The term “Janus particles” is understood to mean microparticles or nanoparticles whose surfaces have at least two different physical properties in separate areas. For example, a spherical particle can be divided into two hemispheres, each of the hemispheres having different properties, which can be achieved, for example, through appropriate coatings / functionalizations, or through an intrinsic structural difference.

The lamella-like chambers with longitudinal and narrow sides, which extend between the first large area and the second large area, can for example be aligned parallel to the large areas and have a cuboid shape. However, it is also possible that it is a trapezoidal or curved - such as arcuate - narrow sides. A lamellar design is understood to mean that the dimension along the long sides is significantly longer than along the narrow sides, such as in the case of the prongs of a comb or the slats of a blind. Usually, several lamellae are also arranged parallel to one another along their longitudinal directions; a grid-like arrangement is also conceivable.

In the case of the (non-cube-shaped) cuboid shape, the narrow sides are then the elongated sides which have a smaller surface area, i.e. the long sides which in turn usually have the largest surface area of all six surfaces of a fluid chamber. Typically, the narrow sides are parallel or - apart from a tilt angle described below - parallel to the large surfaces of the substrate, while the long sides are perpendicular or - except for the tilt angle - perpendicular to the large surfaces of the substrate.

In contrast, the remaining end faces are those two surfaces which do not embody any narrow sides or long sides.

It is also explicitly possible for the chambers to protrude at least partially on one or both large surfaces of the substrate.

The chambers are advantageously filled with a framework matrix which is designed as a polymer matrix, for example as a gel matrix. Such a polymer matrix has a characteristic mesh size. Because of this mesh size, small particles P feel less “resistance” than large particles P and thus small and large particles P each move at different speeds. On the one hand, this is advantageous in order to control the switching times and to accelerate the uniform distribution of the particles P if they are designed as first particles of the first type P _A and second particles of the second type P _B ; for capsules and Janus particles, however, this is irrelevant. On the other hand, such a polymer matrix has the advantage that it strongly inhibits diffusion and the particles P therefore do not move by themselves, which is advantageous for the capsules.

If the chambers are filled with a liquid, a refractive index contrast to the liquid is necessary in the case of scattering particles P. The liquid in the chambers can be polar or be non-polar. It can also consist predominantly of water, oil, toluene or formaldehyde, possibly also mixed with electrolytes.

In the event that the particles P _{comprise first particles P A of} a first type and / or second particles P _{B of} a second type, the first particles P _{A are,} for example, nanoparticles, quantum dots and / or dyes with a spatial extension of a maximum of 200 nm , preferably of a maximum of 50 nm, particularly preferably of a maximum of 20 nm. The second particles P _B are designed as transparent or reflective spheres with diameters between 5 nm and 5000 nm.

Here it is conceivable, for example, that the first particles P _A as BPQDs (Black Phosphorus Quantum Dots), lead sulfide (PbS), CdTeSeS type II quantum dots, azo dyes and / or as metal oxide particles, preferably made of CrO (in particular chromium ( IV) oxide), Fe ₂ O ₃ , Fe ₃ O ₄ or FeO are formed and have a size between 2 nm and 50 nm inclusive.

“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-like particles, this is the greatest possible distance between two points on the surface of the particle.

In the other variant, the particles P are designed as Janus particles with a spherical surface, in which the first and the second area are each formed by hemispheres of the spherical surface. The particles P are designed as micro-particles and have a spatial extension of a maximum of 200 μm, preferably a maximum of 50 μm, particularly preferably a maximum of 20 μm. In particular, it is conceivable that the Janus particles are formed from a transparent material, preferably polystyrene, melamine resin or silica and one of the hemispheres is coated with a metal layer or a metallic nanoparticle layer in order to achieve electrophoretic properties.

It is also possible that the Janus particles are made of a transparent material, preferably latex, PMMA, polystyrene, melamine resin or silica and one of the hemispheres for realizing magnetophoretic properties with a ferromagnetic and absorbing metal or metal oxide layer or a ferromagnetic nanoparticle layer, preferably with Fe ₂ O ₃ -, FesO ₄ - or FeO nanoparticles is coated, and the other half is coated with a reflective layer, preferably a silver or aluminum layer, or a white layer.

As already explained above, the essential characteristic of a spherical Janus particle is that it has two hemispheres that realize different physical properties from one another. The first hemisphere is said to scatter or reflect light incident on it and the other to absorb incident light. Thus, the light-absorbing first hemisphere fulfills the properties of the first particles of the first type P _A and the light-scattering / reflecting second hemisphere fulfills the properties of the second particles of the second type P _B.

1. a) wie vorstehend genannt: transparente Kugel (Polystyrol, Melaminharz oder Silica) oder streuende Kugel mit absorbierender Hemisphäre,
2. b) Farbige oder schwarze Kugel mit reflektierender Hemisphäre, sowie
3. c) Kugel mit je einer reflektierenden und je einer absorbierenden Hemisphäre.

For example, Janus particles suitable for use in the optical element according to the invention can be configured in the following way:

1. a) as mentioned above: transparent ball (polystyrene, melamine resin or silica) or scattering ball with absorbing hemisphere,
2. b) Colored or black sphere with reflective hemisphere, as well
3. c) Sphere with one reflecting and one absorbing hemisphere.

A scattering sphere can be realized, for example, by means of TiO ₂ nanoparticles or silica nanoparticles in a polystyrene sphere. In general, all suitable materials are conceivable that are white-scattering or reflective. A refractive index contrast between the nanoparticles used and the spherical material of the Janus particles makes the transparent sphere more scattering.

Alternatively, a colored or black sphere is also possible as a realization of the Janus particles, for example made of polystyrene and filled with absorbent nanoparticles, quantum dots or dyes. The examples are the same as for the particles P _A. A chrome (IV) oxide ball with ferromagnetic properties can also be used.

The reflective hemisphere can be implemented, for example, by means of a film or nanoparticles made of aluminum, chromium, silver or other metals, as described for the second particles of the second type P _B. For the absorbing hemisphere, for example, carbon, chromium (IV) oxide, Fe ₂ O ₃ , Fe ₃ O ₄ or FeO as a film or even nanoparticles as described for P _{B come} into question.

The electrophoretic properties are determined by the properties of the surfaces. These can be improved or controlled by surface functionalization. In order for the Janus particles to be magnetophoretic, either the sphere itself, ie the material of the sphere, must be magnetophoretic, or one of the hemispheres, ie the surface coating in this hemisphere. Magnetic materials are for example nickel, iron or chromium (IV) oxide. When choosing the material, it must be ensured that the magnetic dipoles of the spheres are permanent so that the Janus particles can be rotated in a targeted manner. This can be achieved, for example, with ferromagnetic Janus particles.

The diameter of the Janus particles is normally more than 200 nm and the thickness of the applied layers is more than 10 nm, but these values can also be exceeded or not reached.

In addition, all particles P present should also 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 to promote electrophoresis, provided that the particles are electrophoretically movable. This can be implemented, for example, with PVP (polyvinylpyrrolidone) or PEG (polyethylene glycol) for aqueous systems.

The electromagnetic switching means, which are flat on one or more sides of the chambers in the substrate, are arranged, for example, on the narrow sides of the respective chambers.

For all of the aforementioned configurations, it is preferred that either the particles P are electrically charged and the electromagnetic switching means are designed as electrodes for generating a static or dynamic electric field or the particles P are magnetic and the electromagnetic switching means are electromagnetic layers for generating a static or dynamic one Magnetic field are formed, so that the electromagnetic particles P perform a movement in the electric or magnetic field in the liquid. When a homogeneous electric field is applied, for example, the corresponding electric field lines are then formed in parallel in the middle of a fluid chamber and tend to show deviations from parallelism at the edge. However, other configurations are also possible.

Dominant physical effects for the movement of the particles when an electromagnetic field is applied, in particular a static field, are (di-) electrophoresis or magnetophoresis. In the event that no electrical or no magnetic field is applied, the particles move in the chambers, in particular due to diffusion, and are thus distributed homogeneously over time. In the case of particles that are no larger than 50 nm, gravity is also irrelevant; they do not sediment or change their vertical position in the chamber.

Said electrodes can be arranged parallel, perpendicular or at another defined angle to the first large area of the substrate S.

If the particles P _{comprise first particles P A} and / or second particles P _B , then the first particles P _A and the second particles P _{B can} execute a translational movement along the electric or magnetic field. Alternatively, if the particles P are designed as Janus particles, the movement is preferably a rotary movement about a predetermined axis which is parallel to a longitudinal or narrow side of the lamella.

At least two operating states are defined by means of the electromagnetic switching means and a control circuit, the angle-dependent transmission being more than 50% in a first operating state B1 and less than 50% in a second operating state B2. This applies in an angle range of preferably +/- 30 ° to +/- 90 ° (i.e. in each case from -90 ° to -30 ° and at the same time from + 30 ° to + 90 °, but not between -30 ° and + 30 ° ) based on a surface normal of the second large surface of the substrate and measured in a direction perpendicular to a longitudinal extension of the lamellar (fluid) chambers. 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 °. The longitudinal extent is defined here with the straight line connecting the surface centers of the two end faces of each fluid chamber.

For the application in which the particles P _{comprise first particles P A} and second particles P _B , more than 70% of the first particles P _A in the second operating state B2 and for the case that the particles P are designed as Janus particles are, for example, the first structures P _{1 of} the particles P each localized on the longitudinal sides of the lamellae, in the case of the first structures P ₁ these facing the longitudinal sides and the second structures P ₂ facing away from the longitudinal sides, and in the first operating state B1 more than 70% of the second particles P _B or the second structures P _{2 of} the particles P are each located on the longitudinal sides of the lamellae, in the case of the second structures P ₂ these facing the longitudinal sides and the first structures P ₁ facing away from the longitudinal sides, so that the Angle-dependent transmission in the first operating state B1 is more than 60% and in the second operating state B2 less than 5%, in an angle range of more than 30 °, respectively ogen to a surface normal of the second large surface of the substrate and measured in a direction perpendicular to a longitudinal extension of the lamellae.

In contrast, it is also possible that in the first operating state B1 more than 70% of the first particles P _A or the first structures P _{1 of} the particles P are each located on the narrow sides of the lamellae, with the narrow sides in the case of the first structures P ₁ facing and the second structures P ₂ facing away from the narrow sides, and in the second operating state B2 more than 70% of the second particles P _B or the second structures P _{2 of} the particles P are each located on the narrow sides of the lamellae, in the case of second structures P ₁ facing the narrow sides and the first structures P ₂ facing away from the narrow sides, so that the angle-dependent transmission in the first operating state B1 is more than 60% and in the second operating state B2 less than 5%, in an angular range of more than 30 ° based on a surface normal of the second large surface of the substrate and measured in a direction perpendicular to a longitudinal extension of the lamella le.

In other words: the various operating states B1, B2 differ in particular in that the respective local concentration and localization of the particles in the chambers is changed in order to change the transmission properties due to the absorption by the particles.

It is also within the scope of the invention that more than two operating states B1, B2, B3 etc. can be set. For example, compared to the variants described above for operating states B1 and B2, a different type of electromagnetic field would be applied in a third (fourth, fifth, ...) operating state, which means that the level of particle or particle type is differently strong between the operating 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 angle-dependent dimming applications. Ultimately, the other operating states are only differently designed configurations of the operating state B2.

In addition, it should be noted that if electromagnetic switching means are only formed in planar form on one surface of the chambers in the substrate, they can then generate an effective electromagnetic field within the chambers in a switched-on state, which is similar to an electromagnetic field, as is the case in so-called IPS ("In Plane Switching") LCD panels are used.

Advantageously, the electromagnetic switching means are at least 50% transparent for light that falls perpendicularly through the light entry surface into the substrate S in the wavelength range that is visible to the human eye.

The electromagnetic switching means (as well as the fluid chambers) can furthermore be divided into several, separately switchable segments, so that local switchability between the first operating state B1 and the second operating state B2 is made possible. Local switchability means that the operating state is not changed between B1 and B2 in all chambers at the same time, but rather that areas with both operating states B1 and B2 are present on the optical element at the same time. This is advantageous, for example, when, when using the optical element in front of a screen, parts of the displayed image content should be visible and others should not be visible from a viewing angle of over 30 degrees to the side.

Several types of particles which differ in their transport properties in the electromagnetic field are advantageously present in the liquid or in the framework matrix.

In a further advantageous embodiment, several types of particles are present in the liquid which differ in their absorption properties and / or their transport properties in the electromagnetic field. “Transport properties” particularly mean the behavior of the particles during (di) electro- or magnetophoresis (transport in the field). This variant is particularly important in the case of nanoparticles: the difference between the types of particles is, for example, the particle size and / or the surface function, 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.

The lamellae or chambers can either be aligned parallel to one another or in a grid-like manner with areas crossing one another. The angle-dependent transmission properties of the optical element with respect to one or two planes perpendicular to one another are then designed accordingly. In the preferred application, the chambers (in particular their long sides) are each aligned parallel to the perpendicular to the substrate S.

In contrast, it is also possible for the chambers to be inclined with respect to the perpendicular to the substrate S in an angular range (“tilt angle”) of -30 ° to + 30 °, possibly even between -30 ° and + 30 °. This configuration also influences the angular dependence of the transmission of the optical element, in particular in the operating state B2. Due to the mentioned angle of inclination, the angle-dependent due to the particle absorption and the particle positions within the chambers Absorption tilted by a fixed offset angle, for example when low transmission at a particularly steep angle is desired.

For example, the lamellar fluid chambers in a first plane parallel to the main direction of propagation of the substrate can be between 2 µm and 30 µm wide (distance from long side to long side of a fluid chamber) and a minimum of 10 µm and a maximum of 150 µm from one another (distance from the long side to the next adjacent long side of the next adjacent fluid chamber ) being. Finally, the lamellar shaped chambers R can have a height (distance narrow side to narrow side) of a minimum of 10 μm and a maximum of 300 μm, measured in a plane perpendicular to the first plane. However, deviations from these typical dimensions are possible and are also within the scope of the invention.

• - ein erfindungsgemäßes optisches Element, wie vorstehend beschrieben, und
• - eine dem optischen Element von einem Betrachter aus gesehen nach- oder vorgeordnete Bildwiedergabeeinheit.

The invention is particularly important in that the optical element is used in a screen which can be operated in a first operating state B1 for a free viewing mode and in a second operating state B2 for a restricted viewing mode

• an optical element according to the invention, as described above, and
• - An image reproduction unit arranged downstream or upstream of the optical element as seen by a viewer.

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

Furthermore, it is also possible to use the optical element according to the invention in an image display unit which has a backlight, for example in an LCD screen. Here, the optical element is then advantageously arranged between the image display panel (i.e. the LCD panel) and the background lighting in order to switch between a first operating state B1 for a free viewing mode and a second operating state B2 for a restricted viewing mode, because the light from the background lighting due to the optical element it is focused once (in operating state B2) and once not focused (in operating state B1).

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.

• 1 eine Prinzipskizze zu zwei verschiedenen Partikelarten innerhalb einer Kapsel,
• 2 eine Prinzipskizze zur bevorzugten Ausgestaltung von Januspartikeln,
• 3 eine Prinzipskizze zu einer zweiten Ausgestaltung von Januspartikeln,
• 4 eine Prinzipskizze zu einer dritten Ausgestaltung von Januspartikeln,
• 5 die Prinzipskizze einer ersten Ausgestaltung des erfindungsgemäßen optischen Elements im Betriebszustand B1 in Schnittdarstellung,
• 6 die Prinzipskizze einer ersten Ausgestaltung des erfindungsgemäßen optischen Elements im Betriebszustand B2 in Schnittdarstellung,
• 7 die Prinzipskizze einer zweiten Ausgestaltung des erfindungsgemäßen optischen Elements im Betriebszustand B1 in Schnittdarstellung,
• 8 die Prinzipskizze einer zweiten Ausgestaltung des erfindungsgemäßen optischen Elements im Betriebszustand B2 in Schnittdarstellung,
• 9 die Prinzipskizze eines erfindungsgemäßen optischen Elements in Draufsicht, wobei lokal verschieden beide Betriebszustände B1 und B2 eingeschaltet sind, und wobei die Kammern parallel zueinander angeordnet sind,
• 10 die Prinzipskizze eines erfindungsgemäßen optischen Elements in Draufsicht, wobei lokal verschieden beide Betriebszustände B1 und B2 eingeschaltet sind, und wobei die Kammern gekreuzt zueinander angeordnet sind, sowie
• 11 eine Prinzipskizze zur Wirkung eines erfindungsgemäßen optischen Elements in beiden Betriebszuständen B1 und B2.

The invention is explained in more detail below with reference to drawings, which also show features essential to the invention. It shows

• 1 a schematic diagram of two different types of particles within a capsule,
• 2 a schematic diagram of the preferred design of Janus particles,
• 3 a basic sketch of a second embodiment of Janus particles,
• 4th a schematic diagram of a third embodiment of Janus particles,
• 5 the schematic diagram of a first embodiment of the optical element according to the invention in the operating state B1 in a sectional view,
• 6th the schematic diagram of a first embodiment of the optical element according to the invention in the operating state B2 in a sectional view,
• 7th the schematic diagram of a second embodiment of the optical element according to the invention in the operating state B1 in a sectional view,
• 8th the schematic diagram of a second embodiment of the optical element according to the invention in the operating state B2 in a sectional view,
• 9 the schematic diagram of an optical element according to the invention in plan view, both operating states B1 and B2 being switched on locally differently, and the chambers being arranged parallel to one another,
• 10 the schematic diagram of an optical element according to the invention in plan view, both operating states B1 and B2 being switched on locally differently, and the chambers being arranged crossed to one another, and
• 11 a schematic diagram of the effect of an optical element according to the invention in both operating states B1 and B2.

The drawings are not true to scale and only represent basic representations. First shows the 1 a schematic diagram of two different types of particles, which _{comprise first particles P A of} a first type of particles which absorb light of one or more wavelengths or wavelength ranges in the range visible to a human eye, and second particles P _B comprise a second type of particles which reflect and / or scatter light of one or more wavelengths or wavelength ranges in the range visible to a human eye, with several particles of both types preferably located within a capsule (indicated here by a circle).

Furthermore shows 2 a schematic diagram for the preferred configuration of Janus particles, each having at least one first area with a first structure P ₁ and a different second area with a second structure P ₂ , the first structures P ₁ absorbing light of one or more wavelengths or wavelength ranges, and the second structures P ₂ reflect and / or scatter light of one or more wavelengths or wavelength ranges.

Also shows 3 a schematic diagram of a second embodiment of Janus particles, in which the second area is significantly larger than the first area, and 4th a schematic diagram of a third embodiment of Janus particles, in which there are, strictly speaking, three areas, two identical first areas with the first structure P _{1 being} separated by a second area with the second structure P ₂ . Further design options, for example also with a third area with a third structure P ₃ , which in turn has other optical properties (for example _{less scattering or reflection than P 2} ), are conceivable.

In 5 the schematic diagram of an optical element in operating state B1 is shown. The circles represent capsules filled with particles of the first and second types or Janus particles.

• - ein im Wesentlichen plattenförmiges Substrat S mit einer als Lichteintrittsfläche ausgebildeten ersten Großfläche und einer als Lichtaustrittsfläche ausgebildeten zweiten Großfläche,
• - eine Vielzahl von in das Substrat S eingebetteten Kammern R, welche in Abhängigkeit von ihrer Größe entweder einzeln eine Lamelle formen oder gruppenweise zusammengefasst sind, wobei jede Gruppe eine Lamelle formt, und jede Lamelle Längs- und Schmalseiten aufweist, welche sich zwischen der ersten Großfläche und der zweiten Großfläche erstrecken, wobei die Schmalseiten jeder Lamelle im Bereich der Großflächen angeordnet sind und die Längsseiten diese verbinden,
• - eine Flüssigkeit oder eine Gerüstmatrix F, mit der die Kammern R gefüllt sind, wobei die Flüssigkeit oder die Gerüstmatrix F bis zu 95 Volumenprozent elektrophoretisch oder magnetophoretisch bewegbarer Partikel P enthält, wobei die Partikel P
  1. i. entweder in einer ersten Ausgestaltung mindestens erste Partikel P_A einer ersten Art von Partikeln umfassen, welche Licht einer oder mehrerer Wellenlängen oder Wellenlängenbereiche im für ein menschliches Auge sichtbaren Bereich absorbieren, und zweite Partikel P_B einer zweiten Art von Partikeln umfassen, welche Licht einer oder mehrerer Wellenlängen oder Wellenlängenbereiche im für ein menschliches Auge sichtbaren Bereich reflektieren und/oder streuen, oder in einer zweiten Ausgestaltung die Flüssigkeit oder die Gerüstmatrix F selbst entweder die Rolle der ersten Partikel P_A oder der zweiten Partikel P_B erfüllt und die Partikel P nur die jeweils anderen Partikel P_B oder P_A umfassen,
  2. ii. oder die Partikel P als Januspartikel ausgebildet sind und jeweils mindestens einen ersten Bereich mit einer ersten Struktur P₁ und einen davon verschiedenen zweiten Bereich mit einer zweiten Struktur P₂ aufweisen, wobei die ersten Strukturen P₁ Licht einer oder mehrerer Wellenlängen oder Wellenlängenbereiche absorbieren, und die zweiten Strukturen P₂ Licht einer oder mehrerer Wellenlängen oder Wellenlängenbereiche reflektieren und/oder streuen.

In general, the optical element comprises

• - a substantially plate-shaped substrate S with a first large area designed as a light entry area and a second large area designed as a light exit area,
• - A plurality of chambers R embedded in the substrate S, which, depending on their size, either individually form a lamella or are combined in groups, each group forming a lamella, and each lamella having longitudinal and narrow sides, which are located between the first large area and the second large area, the narrow sides of each lamella being arranged in the area of the large areas and the long sides connecting them,
• a liquid or a framework matrix F with which the chambers R are filled, the liquid or the framework matrix F containing up to 95 percent by volume of electrophoretically or magnetophoretically movable particles P, the particles P
  1. i. either in a first embodiment _{comprise at least first particles P A of} a first type of particles which absorb light of one or more wavelengths or wavelength ranges in the range visible to a human eye, and second particles P _{B of} a second type of particles which absorb light from one or more wavelengths or wavelength ranges reflect and / or scatter several wavelengths or wavelength ranges in the range visible to a human eye, or in a second embodiment the liquid or the framework matrix F itself either _{fulfills the role of the first particles P A} or the second particles P _B and the particles P only the each comprise other particles P _B or P _A ,
  2. ii. or the particles P are designed as Janus particles and each have at least one first region with a first structure P ₁ and a second region different therefrom with a second structure P ₂ , the first structures P ₁ absorbing light of one or more wavelengths or wavelength ranges, and the second structures P ₂ reflect and / or scatter light of one or more wavelengths or wavelength ranges.

The optical element also comprises electromagnetic switching means, which are embodied in planar fashion on one or more sides of the lamellae in the substrate S and which, when switched on, generate an electromagnetic field effective in the lamellae, whereby the particles P are moved in the liquid or the framework matrix F so that an angle-dependent transmission of the optical element for light of the wavelengths or wavelength ranges that are absorbed by the particles P, which enters the substrate S at angles such that it hits the lamellae, changes.

For all subsequent considerations regarding the drawings 5 until 8th is for the sake of simplicity of the variant Janus particles according to 2 assumed, although the same agent-effect relationships according to the invention can also be implemented for configurations with particles P _A and particles P _B.

5 shows the schematic diagram of a first embodiment of the above-described optical element in the operating state B1 in a sectional illustration, and 6th the same optical element in the operating state B2, also in a sectional view.

In the second operating state B2 ( 6th ) are more than 70% of the first structures P _{1 of} the particles P each localized on the longitudinal sides of the lamellae and facing the longitudinal sides and the second structures P ₂ facing away from the longitudinal sides. In the first operating state B1 ( 5 ), on the other hand, more than 70% of the second structures P _{2 of} the particles P are located on the long sides of the lamellae and face the long sides and the first structures P ₁ face away from the long sides, so that the angle-dependent transmission due to the effect of the second structures P ₂ in the first operating state B1 is more than 60% and due to the effect of the first structures P ₁ in the second operating state B2 is less than 5%, in an angular range of more than 30 ° based on a surface normal of the second large area of the substrate S and measured in one direction perpendicular to a longitudinal extension of the lamellas.

Suitable electrodes E ₁ , E ₂ , E ₃ , E ₄ , ... (of which only a part is drawn and marked) are also present as electromagnetic switching means. It can be seen that the aforementioned electrodes are switched on correspondingly differently in the different operating states in order to enable the movement (rotation) of the Janus particles.

Also shows 7th the schematic diagram of a second embodiment of the optical element according to the invention in the operating state B1 in a sectional illustration, and 8th same in operating state B2. In the first operating state B1 in accordance with 7th more than 70% of the first structures P _{1 of} the particles P each localized on the narrow sides of the lamellae and facing the narrow sides, and the second structures P ₂ face away from the narrow sides. In the second operating state B2 according to 8th more than 70% of the second structures P _{2 of} the particles P are located on the narrow sides of the lamellas and face the narrow sides, while the first structures P ₂ face away from the narrow sides, so that the angle-dependent transmission in the first operating state B1 is more than 60% and in the second operating state B2 is less than 5%, in an angular range of more than 30 ° based on a surface normal of the second large surface of the substrate and measured in a direction perpendicular to a longitudinal extension of the lamella. Here, too, electrodes E are present as electromagnetic switching means.

Finally poses 11 a schematic diagram of the effect of an optical element according to the invention in both operating states B1 and B2. The ordinate here is the relative brightness and the abscissa shows the measurement angle (horizontal, ie perpendicular to the longitudinal extension of the lamellas). The measurement angle covers the above-mentioned angle range, that is, it relates to the surface normal of the second large surface of the substrate S and is measured in a direction perpendicular to the longitudinal extent of the lamella. In the case of a screen built into a car, this can be, for example, the angle in the horizontal plane.

The one or more wavelengths or wavelength ranges in which the electrophoretically or magnetophoretically movable particles P _A or the structures P _{1 of} the Janus particles 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.

The first and second large areas of the plate-shaped substrate S are preferably arranged parallel to one another. However, in special configurations, for example if 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.

The first large surface of the plate-shaped substrate S, designed as a light entry surface, is generally located on the rear side of the substrate S from the perspective of a viewer and, depending on the application of the optical element, is adjacent to an image display device, a light source or a volume of air, for example. From the last-mentioned objects, light then enters the substrate through the said light-entry surface.

The particles P advantageously include first particles P _A and / or second particles P _B , which are embedded in stationary capsules that are located on the edge surfaces of the chambers R or form the chambers R, or in which the particles P are designed as Janus particles are located stationary on the edge surfaces of the chambers R, but can rotate freely.

The lamellar chambers with longitudinal and narrow sides, which extend between the first large area and the second large area, can for example be aligned parallel to the large areas and, in the simplest case, have a cuboid shape. However, it is also possible that it is a trapezoidal or curved - such as arcuate - narrow sides. In the case of the (non-cube-shaped) cuboid shape, the narrow sides are then the elongated sides, which have a smaller area than the long sides, which in turn usually have the largest area of all six surfaces of a fluid chamber. Typically, the narrow sides are parallel or - apart from one further Tilt angles described below - arranged parallel to the large areas of the substrate, while the long sides are perpendicular or - except for the tilt angle - perpendicular to the large areas of the substrate.

In contrast, the remaining end faces are those two surfaces which do not embody any narrow sides or long sides.

It is explicitly also possible for the chambers to protrude at least partially on one or both large surfaces of the substrate.

The chambers are advantageously filled with a framework matrix F, which is designed as a polymer matrix and in particular as a gel matrix. Such a polymer matrix has a characteristic mesh size. Because of this mesh size, small particles P feel less "resistance" to movement than large particles P and thus small and large particles P each move at different speeds. On the one hand, this is advantageous in order to control the switching times and to accelerate the uniform distribution of the particles P if they are designed as first particles of the first type P _A and second particles of the second type P _B ; for capsules and Janus particles, however, this is irrelevant. On the other hand, such a polymer matrix has the advantage that it strongly inhibits diffusion and the particles P therefore do not move by themselves, which is advantageous for the capsules.

If the chambers are filled with a liquid, a refractive index contrast to the liquid F is necessary in the case of scattering particles P. The liquid F in the chambers can be polar or non-polar. It can also consist predominantly of water, oil, toluene or formaldehyde, possibly mixed with electrolytes.

In the event that the particles P _{comprise first particles P A} and / or second particles P _B , the first particles P _{A are} preferred, for example, as nano-particles, quantum dots and / or dyes with a spatial extension of a maximum of 200 nm of a maximum of 50 nm, particularly preferably a maximum of 20 nm. The second particles P _B are designed as transparent or reflective spheres with diameters between 5 nm and 5000 nm.

Here it is conceivable, for example, that the first particles P _A as BPQDs (Black Phosphorus Quantum Dots), lead sulfide (PbS), CdTeSeS type II quantum dots, azo dyes and / or as metal oxide particles, preferably made of CrO (in particular chromium ( IV) oxide) or Fe2O3, and have a size between 2 nm and 50 nm inclusive.

“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 string-shaped particles, this is the greatest possible distance that two points on the surface of the particle can have from one another.

In the other variant, the particles P are designed as Janus particles with a spherical surface, in which the first and the second area are each formed by hemispheres of the spherical surface. The particles P are designed as micro-particles and have a spatial extension of a maximum of 200 μm, preferably a maximum of 50 μm, particularly preferably a maximum of 20 μm. In particular, it is conceivable that the Janus particles are formed from a transparent material, preferably polystyrene, melamine resin or silica and one of the hemispheres is coated with a metal layer or a metallic nanoparticle layer in order to achieve electrophoretic properties.

It is also possible that the Janus particles are formed from a transparent material, preferably polystyrene, melamine resin or silica and one of the hemispheres for realizing magnetophoretic properties with a ferromagnetic and absorbing metal or metal oxide layer or a ferromagnetic nanoparticle layer, preferably with Fe ₂ O ₃ - Nanoparticles is coated, and the other half is coated with a reflective layer, preferably a silver or aluminum layer, or a white layer.

As already explained above, the essential characteristic of a spherical Janus particle is that it has two hemispheres which have different physical properties from one another. The first hemisphere is said to scatter or reflect light incident on it and the other to absorb incident light. The light-absorbing first hemisphere thus quasi fulfills the properties of the first particles P _{A of} the first type and the light-scattering / reflecting hemisphere the properties of the second particles P _{B of} the second type.

• d) wie vorstehend genannt: transparente Kugel (Polystyrol, Melaminharz oder Silica) oder streuende Kugel mit absorbierender Hemisphäre,
• e) Farbige oder schwarze Kugel mit reflektierender Hemisphäre, sowie
• f) Kugel mit je einer reflektierenden und je einer absorbierenden Hemisphäre.

For example, Janus particles suitable for use in the optical element according to the invention can be configured in the following way:

• d) as mentioned above: transparent ball (polystyrene, melamine resin or silica) or scattering ball with absorbing hemisphere,
• e) Colored or black sphere with reflective hemisphere, as well
• f) Sphere with one reflecting and one absorbing hemisphere.

A scattering sphere can be realized, for example, by means of TiO nanoparticles in a polystyrene sphere or silica nanoparticles in a polystyrene sphere. In general, all suitable materials are conceivable that are white-scattering or reflective. A refractive index contrast between the nanoparticles used and the spherical material of the particles makes the transparent sphere more scattering. Alternatively, a colored or black ball is also possible for the particles P, for example filled with polystyrene with absorbent nanoparticles, QD or dyes. The examples are the same as for the particles P _a . A chrome (IV) oxide ball with ferromagnetic properties can also be used.

The reflective hemisphere can be implemented, for example, by means of a film or nanoparticles made of aluminum, chromium, silver or other metals, as described for the second particles of the second type P _B. For the absorbing hemisphere, for example, carbon, chromium (IV) oxide, Fe ₂ O ₃ as a film or even nanoparticles as described for P _{B are possible} .

The electrophoretic properties are determined by the properties of the surfaces. These can be improved or controlled by surface functionalization. In order for the Janus particles to be magnetophoretic, either the sphere itself, i.e. the material of the sphere, must be magnetophoretic, or one of the hemispheres, i.e. more precisely a surface coating in this hemisphere. Magnetic materials are, for example, nickel, iron or chromium (IV) oxide. When choosing the material, it must be ensured that the magnetic dipoles of the spheres are permanent so that the Janus particles can be rotated in a targeted manner. This can be achieved, for example, with ferromagnetic Janus particles.

The diameter of the Janus particles is normally more than 200 nm and the thickness of the applied layers is more than 10 nm, but these values can also be exceeded or not reached.

In addition, as far as possible, all existing particles P should have a surface functionalization, namely with a high zeta potential - on the one hand as stabilization in the liquid or framework matrix F and on the other hand to promote electrophoresis, provided that the particles are electrophoretically movable. This can be implemented with PVP (polyvinylpyrrolidone) or PEG (polyethylene glycol) for aqueous systems.

The electromagnetic switching means, which are flat on one or more sides of the chambers in the substrate, are arranged, for example, on the narrow sides of the respective chambers.

For all of the aforementioned configurations, it is preferred that either the particles P are electrically charged and the electromagnetic switching means are designed as electrodes for generating a static or dynamic electric field or the particles P are magnetic and the electromagnetic switching means are electromagnetic layers for generating a static or dynamic one Magnetic field are formed, so that the electromagnetic particles P perform a movement in the electric or magnetic field in the liquid. When a homogeneous electric field is applied, for example, the corresponding electric field lines are then formed in parallel in the middle of a fluid chamber and tend to show deviations from parallelism at the edge. However, other configurations are also possible.

Dominant physical effects for the movement of the particles when an electromagnetic field is applied, in particular a static field, are (di-) electrophoresis or magnetophoresis. In the event that no electrical or no magnetic field is applied, the particles move in the chambers, in particular due to diffusion, and are thus distributed homogeneously over time. In the case of particles that are no larger than 50 nm, gravity is also irrelevant; they do not sediment or change their vertical position in the chamber.

Said electrodes E, E ₁ , E ₂ ,... Can be arranged parallel, perpendicular or at another defined angle to the first large area of the substrate S.

If the particles P _{comprise first particles P A} and / or second particles P _B , then the first particles P _A and the second particles P _{B can} execute a translational movement along the electric or magnetic field.

Alternatively, if the particles (P) are designed as Janus particles, the movement is preferably a rotary movement about a predetermined axis which is parallel to a longitudinal or narrow side of the lamella.

At least two operating states are defined by means of the electromagnetic switching means and a control circuit, the angle-dependent transmission being more than 50% in a first operating state B1 and less than 50% in a second operating state B2. This applies in an angle range of preferably +/- 30 ° to +/- 90 ° (i.e. in each case from -90 ° to -30 ° and at the same time from + 30 ° to + 90 °, but not between -30 ° and + 30 ° ) based on a surface normal of the second large surface of the substrate and measured in a direction perpendicular to a longitudinal extension of the lamellar (fluid) chambers. 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 °. The longitudinal extent is defined here with the straight line connecting the surface centers of the two end faces of each fluid chamber.

In other words: the various operating states B1, B2 differ in particular in that the respective local concentration and localization of the particles in the chambers is changed in order to change the transmission properties due to the absorption by the particles.

It is also within the scope of the invention that more than two operating states B1, B2, B3 etc. can be set. For example, compared to the variants described above for operating states B1 and B2, a different type of electromagnetic field would be applied in a third (fourth, fifth, ...) operating state, which means that the level of particle or particle type is differently strong between the operating 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 angle-dependent dimming applications. Ultimately, the other operating states are only differently designed configurations of the operating state B2.

In addition, it should be noted that if electromagnetic switching means are only formed in planar form on one surface of the chambers in the substrate, they can then generate an effective electromagnetic field within the chambers in a switched-on state, which is similar to an electromagnetic field, as is the case in so-called IPS ("In Plane Switching") LCD panels are used.

Advantageously, the electromagnetic switching means are at least 50% transparent for light that falls perpendicularly through the light entry surface into the substrate S in the wavelength range that is visible to the human eye.

The electromagnetic switching means E, E ₁ , E ₂ , ... (as well as the fluid chambers) can furthermore be divided into several, separately switchable segments, so that local switchability between the first operating state B1 and the second operating state B2 is made possible. Local switchability means that the operating state is not changed between B1 and B2 in all chambers at the same time, but rather that areas with both operating states B1 and B2 are present on the optical element at the same time. This is advantageous, for example, when, when using the optical element in front of a screen, 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.

This is shown in 9 . This drawing shows the basic sketch of an optical element in plan view, both operating states B1 and B2 being switched on locally differently, and the chambers R being arranged parallel to one another.

In contrast, shows 10 the schematic diagram of an optical element in plan view, both operating states B1 and B2 being switched on locally differently, and the chambers R being arranged crossed to one another.

Several types of particles are advantageously present in the liquid or in the framework matrix F which differ in their transport properties in the electromagnetic field.

The lamellae or chambers R can, as in 9 and 10 shown, be aligned either parallel or in a grid shape with intersecting areas. The angle-dependent transmission properties of the optical element with respect to one or two planes perpendicular to one another are then designed accordingly. In the preferred application, the chambers (in particular their long sides) are each aligned parallel to the perpendicular to the substrate S.

In contrast, it is also possible for the chambers to be inclined with respect to the perpendicular to the substrate S in an angular range (“tilt angle”) of -30 ° to + 30 °, possibly even between -30 ° and + 30 °. This configuration also influences the angular dependence of the transmission of the optical element, in particular in the operating state B2. As a result of the aforementioned angle of inclination, the angle-dependent absorption established by the particle absorption and the particle positions within the chambers is tilted by a fixed offset angle, for example when a low transmission at a particularly steep angle is desired.

For example, the lamellar fluid chambers, in a first plane parallel to the main direction of propagation of the substrate, between 2 µm and 30 µm wide (distance from long side to long side of a fluid chamber) and at least 10 µm and a maximum of 150 µm apart (distance from long side to next adjacent long side of the next one) Fluid chamber). Finally, the lamellar shaped chambers R can have a height (distance narrow side to narrow side) of a minimum of 10 μm and a maximum of 300 μm, measured in a plane perpendicular to the first plane. However, deviations from these typical dimensions are possible and are also within the scope of the invention.

• - ein optisches Element, wie vorstehend beschrieben, und
• - eine dem optischen Element von einem Betrachter aus gesehen nach- oder vorgeordnete Bildwiedergabeeinheit.

The optical element described above is particularly suitable for use in a screen which can be operated in a first operating state B1 for a free viewing mode and in a second operating state B2 for a restricted viewing mode

• - an optical element as described above, and
• - An image reproduction unit arranged downstream or upstream of the optical element as seen by a viewer.

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

Furthermore, it is also possible to use the optical element according to the invention in an image display unit which has a backlight, for example in an LCD screen. Here, the optical element is then advantageously arranged between the image display panel (i.e. the LCD panel) and the background lighting in order to switch between a first operating state B1 for a free viewing mode and a second operating state B2 for a restricted viewing mode, because the light from the background lighting due to the optical element it is focused once (in operating state B2) and once not focused (in operating state B1).

The above-described optical element according to the invention solves the problem: An optical element was described which can influence the transmission as a function of the angle (and optionally perpendicular) and which can switch between at least two operating states. The optical element 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.

The invention described above can 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 on mobile phones Devices. As described above, the invention can also be used in vehicles, in particular in passenger cars.

Claims (22)

Optical element, comprising, - a substantially plate-shaped substrate (S) with a first large area designed as a light entry surface and a second large area designed as a light exit area, - a multiplicity of chambers embedded in the substrate (S), which depending on their size either individually Form a lamella or are combined in groups, each group forming a lamella, and each lamella having long and narrow sides which extend between the first large area and the second large area, the narrow sides of each lamella being arranged in the area of the large areas and the long sides connect these, - a liquid or a framework matrix (F) with which the chambers (R) are filled, the liquid or the framework matrix (F) containing up to 95 percent by volume of electrophoretically or magnetophoretically movable particles (P), the particles ( P) either in a first embodiment at least the first part kel (P _A ) of a first type of particles which absorb light of one or more wavelengths or wavelength ranges in the range visible to a human eye, and second particles (P _B ) of a second type of particles which include light of one or more wavelengths or Reflect and / or scatter wavelength ranges in the range visible to a human eye, or in a second embodiment the liquid or the framework matrix (F) itself either _{fulfills the role of the first particles (P A} ) or the second particles (P _B ) and the particles (P) only _{encompass the other particles (P B} ) or (P _A ), - as well as electromagnetic switching means which are embodied in a planar manner on one or more sides of the lamellae in the substrate (S) and which are active in the lamellae when switched on Generate electromagnetic field, whereby the particles (P) are moved in the liquid or the framework matrix (F), so d ate himself an angle-dependent transmission of the optical element for light of the wavelengths or wavelength ranges that are absorbed by the particles (P), which enters the substrate (S) at such angles that it hits the lamellae, - with means the electromagnetic switching means and a control circuit at least two operating states B1 and B2 are defined depending on the position of the particles (P), so that in the second operating state B2 more than 70% of the first particles (P _A ) are located on the longitudinal sides of the slats , and in the first operating state B1 more than 70% of the second particles (P _B ) are located on the longitudinal sides of the lamellas, so that the angle-dependent transmission in the first operating state B1 is more than 60% and in the second operating state B2 less than 5% , in an angular range of more than 30 ° based on a surface normal of the second large area of the substrate and geme ssen in a direction perpendicular to a longitudinal extension of the lamellas. Optical element, comprising, - a substantially plate-shaped substrate (S) with a first large area designed as a light entry surface and a second large area designed as a light exit area, - a multiplicity of chambers embedded in the substrate (S), which depending on their size either individually Form a lamella or are combined in groups, each group forming a lamella, and each lamella having long and narrow sides which extend between the first large area and the second large area, the narrow sides of each lamella being arranged in the area of the large areas and the long sides connect these, - a liquid or a framework matrix (F) with which the chambers (R) are filled, the liquid or the framework matrix (F) containing up to 95 percent by volume of electrophoretically or magnetophoretically movable particles (P), the particles ( P) in a first embodiment, at least first particles (P _A ) comprise a first type of particles which absorb light of one or more wavelengths or wavelength ranges in the range visible to a human eye, and second particles (P _B ) comprise a second type of particles which light one or more wavelengths or wavelength ranges for a Reflect and / or scatter the area visible to the human eye, or in a second embodiment the liquid or the framework matrix (F) itself either _{fulfills the role of the first particle (P A} ) or the second particle (P _B ) and the particles (P) only which comprise the other particles (P _B ) or (P _A ), - as well as electromagnetic switching means which are formed in a flat manner on one or more sides of the lamellae in the substrate (S) and which, when switched on, generate an electromagnetic field effective in the lamellae, whereby the particles (P) in the liquid or the framework matrix (F) are moved so that an angle-dependent transmission of the optical element for light of the wavelengths or wavelength ranges that are absorbed by the particles (P), which enters the substrate (S) at such angles that it hits the lamellae, - with means the electromagnetic switching means and a control circuit at least two operating states B1 and B2 are defined depending on the position of the particles (P), so that in the first operating state B1 more than 70% of the first particles (P _A ) are located on the narrow sides of the slats , and in the second operating state B2 more than 70% of the second particles (P _B ) are located on the narrow sides of the lamellas, so that the angle-dependent transmission in the first operating state B1 is more than 60% and in the second operating state B2 less than 5% , in an angular range of more than 30 ° based on a surface normal of the second large area of the substrate and ge measure in a direction perpendicular to a longitudinal extension of the lamellas. Optical element according to Claim 1 or 2 , in which the particles (P) are embedded in stationary capsules which are located on edge surfaces of the chambers or which form the chambers. Optical element according to one of the Claims 1 until 3 , characterized in that the first particles (P _A ) are designed as nanoparticles, quantum dots and / or dyes with a spatial extension of a maximum of 200 nm, preferably a maximum of 50 nm, particularly preferably a maximum of 20 nm, and the second particles (P _B ) are designed as transparent or reflective spheres with diameters between 5 nm and 5000 nm. Optical element according to Claim 4 , characterized in that the first particles (P _A ) as BPQDs (Black Phosphorus Quantum Dots), lead sulfide (PbS), CdTeSeS quantum dots, azo dyes and / or as metal oxide particles, preferably made of chromium (IV) oxide or Fe ₂ O ₃ and have a size between 2 nm and 50 nm inclusive. Optical element according to one of the preceding claims, characterized in that either the particles (P) are electrically charged and the electromagnetic switching means are designed as electrodes for generating a static or dynamic electric field or the particles (P) are magnetic and the electromagnetic switching means as electromagnetic layers are designed to generate a static or dynamic magnetic field, so that the electromagnetic particles (P) in the electric or magnetic field in the liquid move. Optical element, comprising, - a substantially plate-shaped substrate (S) with a first large area designed as a light entry surface and a second large area designed as a light exit area, - a multiplicity of chambers embedded in the substrate (S), which depending on their size either individually Form a lamella or are combined in groups, each group forming a lamella, and each lamella having long and narrow sides which extend between the first large area and the second large area, the narrow sides of each lamella being arranged in the area of the large areas and the long sides connect these, - a liquid or a framework matrix (F) with which the chambers (R) are filled, the liquid or the framework matrix (F) containing up to 95 percent by volume of electrophoretically or magnetophoretically movable particles (P), the particles ( P) are designed as Janus particles and each have at least one en first area with a first structure (P ₁ ) and a different second area with a second structure (P ₂ ), wherein the first structures (P ₁ ) absorb light of one or more wavelengths or wavelength ranges, and the second structures (P ₂ ) Reflecting and / or scattering light of one or more wavelengths or wavelength ranges, - as well as electromagnetic switching means which are formed comprehensively on one or more sides of the lamellae in the substrate (S) and which, when switched on, generate an electromagnetic field effective in the lamellae, whereby the particles (P) in the liquid or the framework matrix (F) are moved, so that an angle-dependent transmission of the optical element for light of the wavelengths or wavelength ranges that are absorbed by the particles (P), which at such angles over the Light entry surface in the substrate (S) that it enters the lamella n hits, changes, - whereby at least two operating states B1 and B2 are defined depending on the position of the particles (P) by means of the electromagnetic switching means and a control circuit, so that in the second operating state B2 more than 70% of the first structures (P ₁ ) of the particles (P) are located on the longitudinal sides of the lamellae, the first structures (P ₁ ) facing the longitudinal sides and the second structures (P ₂ ) facing away from the longitudinal sides, and in the first operating state B1 more than 70% of the second structures (P ₂ ) of the particles (P) are each located on the longitudinal sides of the lamellae, the second structures (P ₂ ) facing the longitudinal sides and the first structures (P ₁ ) facing away from the longitudinal sides, so that the angle-dependent transmission in the first operating state B1 is more than 60% and in the second operating state B2 is less than 5%, in an angular range of more than 30 ° based on a surface normal of the second Large area of the substrate and measured in a direction perpendicular to a longitudinal extension of the lamellae. Optical element, comprising, - a substantially plate-shaped substrate (S) with a first large area designed as a light entry surface and a second large area designed as a light exit area, - a multiplicity of chambers embedded in the substrate (S), which depending on their size either individually Form a lamella or are combined in groups, each group forming a lamella, and each lamella having long and narrow sides which extend between the first large area and the second large area, the narrow sides of each lamella being arranged in the area of the large areas and the long sides connect these, - a liquid or a framework matrix (F) with which the chambers (R) are filled, the liquid or the framework matrix (F) containing up to 95 percent by volume of electrophoretically or magnetophoretically movable particles (P), the particles ( P) are designed as Janus particles and each have at least one en first area with a first structure (P ₁ ) and a different second area with a second structure (P ₂ ), wherein the first structures (P ₁ ) absorb light of one or more wavelengths or wavelength ranges, and the second structures (P ₂ ) Reflecting and / or scattering light of one or more wavelengths or wavelength ranges, - as well as electromagnetic switching means which are formed comprehensively on one or more sides of the lamellae in the substrate (S) and which, when switched on, generate an electromagnetic field effective in the lamellae, whereby the particles (P) in the liquid or the framework matrix (F) are moved, so that an angle-dependent transmission of the optical element for light of the wavelengths or wavelength ranges that are absorbed by the particles (P), which at such angles over the Light entry surface in the substrate (S) that it enters the lamella n hits, changes, - at least two operating states B1 and B2 are defined by means of the electromagnetic switching means and a control circuit depending on the position of the particles (P), so that in the first operating state B1 more than 70% of the first structures (P ₁ ) of the particles (P) are each located on the narrow sides of the lamellae, the first structures (P ₁ ) facing the narrow sides and the second structures (P ₂ ) facing the narrow sides are turned away, and in the second operating state B2 more than 70% of the second structures (P ₂ ) of the particles (P) are each located on the narrow sides of the lamellae, the second structures (P ₂ ) facing the narrow sides and the first structures ( P ₁ ) facing away from the narrow sides, so that the angle-dependent transmission in the first operating state B1 is more than 60% and in the second operating state B2 less than 5%, in an angular range of more than 30 ° based on a surface normal of the second large surface of the substrate and measured in a direction perpendicular to a longitudinal extension of the lamella Optical element according to Claim 7 or 8th , in which the particles (P) are located in a stationary manner on the edge surfaces of the chambers. Optical element according to one of the Claims 7 until 9 , in which the particles (P) are designed as Janus particles with a spherical surface, in which the first and the second area are each formed by hemispheres of the spherical surface. Optical element according to Claim 10 , characterized in that the particles (P) are designed as microparticles and have a spatial extent of a maximum of 200 µm, preferably a maximum of 50 µm, particularly preferably a maximum of 20 µm. Optical element according to Claim 10 or 11 , characterized in that the Janus particles are formed from a transparent material, preferably latex, PMMA, polystyrene, melamine resin or silica and one of the hemispheres is coated with a metal layer or a metallic nanoparticle layer to achieve electrophoretic properties. Optical element according to Claim 10 or 11 , characterized in that the Janus particles are formed from a transparent material, preferably polystyrene, melamine resin or silica and one of the hemispheres for realizing magnetophoretic properties with a ferromagnetic and absorbing metal or metal oxide layer or a ferromagnetic nanoparticle layer, preferably with Fe ₂ O ₃ nanoparticles is coated, and the other half is coated with a reflective layer, preferably a silver or aluminum layer, or a white layer. Optical element according to one of the Claims 12 or 13th , characterized in that the diameter of the Janus particles is more than 200 nm and the thickness of the applied layers is more than 10 nm. Optical element according to one of the Claims 7 until 14th , characterized in that either the particles (P) are electrically charged and the electromagnetic switching means are designed as electrodes for generating a static or dynamic electric field or the particles (P) are magnetic and the electromagnetic switching means as electromagnetic layers for generating a static or dynamic magnetic field are formed, so that the electromagnetic particles (P) perform a movement in the electric or magnetic field in the liquid. Optical element according to Claim 15 , characterized in that the movement is a rotary movement about a predetermined axis which is parallel to a longitudinal or narrow side of the lamella. Optical element according to one of the preceding claims, characterized in that the electromagnetic switching means are at least 50% transparent in the wavelength range visible to the human eye for light that falls perpendicularly into the substrate (S) via the light entry surface. Optical element according to one of the preceding claims, characterized in that the electromagnetic switching means are divided into several, separately switchable segments, so that local switchability between the first operating state B1 and the second operating state B2 is made possible. Optical element according to one of the preceding claims, characterized in that several types of particles are present in the liquid or in the framework matrix (F) which differ in their transport properties in the electromagnetic field. Optical element according to one of the preceding claims, characterized in that the lamellae are aligned with one another either parallel or in a grid-like manner with areas crossing one another. Optical element according to one of the preceding claims, characterized in that the lamellae are inclined in an angular range of -30 ° to + 30 ° with respect to the perpendicular perpendicular to the substrate (S). Screen that can be operated in a first operating state B1 for a free viewing mode and in a second operating state B2 for a restricted viewing mode, comprising - an optical element according to one of the Claims 1 until 21 , and - an image display unit arranged downstream or upstream of the optical element as seen by a viewer.

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