DE102019006022B3 - Optical element with variable transmission and screen with such an optical element - Google Patents

Abstract

The invention relates to an optical element comprising a substantially plate - shaped substrate (S) with a first large area designed as a light entry area (3) and a second large area designed as a light exit area (4), a plurality of lamellar embedded in the substrate (S) formed fluid chambers (R) with long and narrow sides, which extend between the first large area and the second large area, the narrow sides being arranged in the region of the large areas and connecting the long sides, a liquid (F) with which the fluid chambers (R ) are filled, the liquid (F) containing up to 20 percent by volume of electrophoretically or magnetophoretically movable particles (P), which absorb light of one or more wavelengths or wavelength ranges, flat on one or more sides of the fluid chambers (R) in the substrate (S) trained electromagnetic switching means (2), which in an on State generate an effective electromagnetic field in the fluid chambers (R), whereby the particles (P) are moved in the liquid (F), so that there is an angle-dependent transmission of the optical element for light of the wavelengths or wavelength ranges emitted by the particles (P ) are absorbed, which enters the substrate (S) at such angles via the light entry surface (3) that it meets the fluid chambers (R). The invention further relates to 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, comprising an optical element according to the invention and an image display unit arranged downstream of the optical element when viewed by a viewer.

Description

Field of the Invention

Much progress has been made in recent years to broaden the viewing angle of LCDs. However, there are often situations in which this very large viewing area of a screen can be disadvantageous. Information on mobile devices such as notebooks and tablet PCs is becoming increasingly available, such as bank data or other personal information, 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, for example when viewing vacation photos or for advertising purposes. On the other hand, they need a small viewing angle if they want to keep the image information confidential.
A similar problem arises in vehicle construction: There, the driver must not be distracted by image content, such as digital entertainment programs, when the engine is on, but the passenger also wants to consume the same while driving. A screen is therefore required which can switch between the corresponding display modes.

State of the art

Additional films based on micro-slats have already been used for mobile displays in order to achieve their visual data protection. However, these foils could not be (switched), 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 lamella films is also associated with the associated loss of light.

The US 6,765,550 A describes such a privacy screen with micro-slats. The main disadvantage here is the mechanical removal or mechanical attachment of the filter and the loss of light in protected mode.

In the US 5,993,940 A describes the use of a film that has 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 causes a loss of light and the effort is quite high.

The US 2012/0235891 A1 describes a very complex backlight in one screen. According to come there 1 and 15 not only several light guides are used, but also other complex optical elements such as microlens elements 40 and prism structures 50 that reshape the light from the rear lights on the way to the front lights. This is expensive and complex to implement and also involves loss of light. According to the variant 17th in the US 2012/0235891 A1 produce both light sources 4R and 18th Light with a narrow angle of illumination, the light from the rear light source 18th is only elaborately converted into light with a large lighting angle. As already noted above, this complex conversion greatly reduces brightness.

According to the JP 2007-155783 A become special, difficult to calculate and manufacture optical surfaces 19th used, which then deflect light into different 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. So it remains unclear whether really meaningful light distributions can be achieved.

US Pat. No. 2013/0308185 A1 describes a special light guide formed with steps, which emits light on 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, e.g. an LC display, a screen that can be switched between free and restricted viewing mode can be generated. One disadvantage of this is that the limited viewing effect can only be generated for left / right or for top / bottom, but not for left / right / top / bottom, as is necessary for certain payment transactions. In addition, even in restricted viewing mode, residual light is still visible from blocked viewing angles.

The font WO 2017/097975 A1 the applicant describes a screen with two operating modes, which uses scattering particles arranged in microlamellae to change the angle-dependent transmission. With this it is possible, depending on the direction, to blend a picture content in order to achieve a privacy screen. On the other hand, it is not possible with this screen to vary the transmission depending on the direction.

From the US 8,130,441 B2 and the US 9,740,075 B2 electrophoretic modulators are known. Electrophoretic particles in electrophoretic fluid chambers are used to change the direction of reflection. However, an angle-dependent transmission cannot be achieved with this.

The US 9,229,261 B2 describes optical means that influence the angle-dependent transmission. The switch between scattering and transmitting slats is particularly important. A real influence on the absolute transmission is therefore not possible. Rather, the strength of the scatter is regulated for certain directions.

Furthermore, the US 2007/0084549 A1 the production of a passive privacy film. This is not suitable for actively switching over several modes for the display; it therefore does not allow switching between a privacy screen and a free viewing mode.

In the DE 10 2015 012 271 A1 the applicant discloses a method for operating a screen in at least two operating modes B1 for a free viewing mode and B2 for a restricted viewing mode, the changeover taking place by changing the refractive index on defined areas. It is not possible to influence the absolute transmittance. Rather, the strength of the scatter is regulated for certain directions.

The WO2015 / 121398 A1 the applicant describes a screen of the type described in the introduction. There are scattering particles in the volume of the corresponding light guide which are essential for switching the operating modes. However, the scattering particles made of a polymer selected there generally have the disadvantage that light is coupled out from both large areas, as a result of which approximately half of the useful light is emitted in the wrong direction, namely towards the backlight, and there is not sufficient there due to the structure can be recycled. In addition, the scattering particles of polymer distributed in the volume of the light guide can, under certain circumstances, in particular at higher concentrations, lead to scattering effects which reduce the visual protection effect in the protected operating mode.

The above-mentioned 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 switching modes and / or reduce the resolution in the freely viewable mode.

Description of the invention

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

• - ein im Wesentlichen plattenförmiges Substrat mit einer als Lichteintrittsfläche ausgebildeten ersten Großfläche und einer als Lichtaustrittsfläche zweiten ausgebildeten Großfläche,
• - eine Vielzahl von in das Substrat eingebetteten, lamellenartig ausgebildeten Fluidkammern mit Längs- und Schmalseiten, welche sich zwischen der ersten Großfläche und der zweiten Großfläche erstrecken, wobei die Schmalseiten im Bereich der Großflächen angeordnet sind und die Längsseiten diese verbinden,
• - eine Flüssigkeit F, mit der die Fluidkammern gefüllt sind, wobei die Flüssigkeit bis zu 20 Volumenprozent elektrophoretisch oder magnetophoretisch bewegbarer Partikel enthält, welche Licht einer oder mehrerer Wellenlängen oder Wellenlängenbereiche absorbieren,
• - flächenförmig an einer oder mehreren Seiten der Fluidkammern im Substrat ausgebildete elektromagnetische Schaltmittel, welche in einem eingeschalteten Zustand ein in den Fluidkammern wirksames elektromagnetisches Feld erzeugen, wodurch die Partikel in der Flüssigkeit bewegt werden, so dass sich eine winkelabhängige Transmission des optischen Elements für Licht der Wellenlängen oder Wellenlängenbereiche, die von den Partikeln absorbiert werden, welches in solchen Winkeln über die Lichteintrittsfläche in das Substrat eintritt, dass es auf die Fluidkammern trifft, ändert.

According to the invention, this object is achieved by an optical element comprising

• an essentially plate-shaped substrate 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 lamellar-shaped fluid chambers embedded in the substrate and having longitudinal and narrow sides, which extend between the first large area and the second large area, the narrow sides being arranged in the region of the large areas and connecting the long sides,
• a liquid F with which the fluid chambers are filled, the liquid containing up to 20 percent by volume of electrophoretically or magnetophoretically movable particles which absorb light of one or more wavelengths or wavelength ranges,
• - Flat-shaped on one or more sides of the fluid chambers in the substrate formed electromagnetic switching means, which generate an effective electromagnetic field in the fluid chambers in an activated state, whereby the particles are moved in the liquid, so that an angle-dependent transmission of the optical element for light Wavelengths or wavelength ranges which are absorbed by the particles and which enter the substrate at such angles via the light entry surface that they strike the fluid chambers changes.

The first and the second large area of the plate-shaped substrate are preferably arranged parallel to one another. However, in special configurations, for example if particular angle-dependent transmissions of the optical element are to be achieved, they can also be non-parallel, e.g. be arranged in a wedge shape at a defined angle of up to 20 degrees to one another.

The first large area of the plate-shaped substrate, which is designed as a light entry surface, is generally located on the back of the substrate from the viewer's perspective and, depending on the application of the optical element, borders, for example, an image display device, a light source or an air volume. From the latter objects, light then enters the substrate through said light entry surface.

The lamellar fluid 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 for the sides to be trapezoidal or curved, such as curved, to be narrow.
In the case of the (non-cube-shaped) cuboid shape, the narrow sides are then the elongated sides which have a smaller area, that is to say the long sides, which in turn generally have the largest area of all six surfaces of a fluid chamber. Typically, the narrow sides are arranged parallel or — up to a tilt angle described further below — parallel to the large areas of the substrate, while the long sides are arranged perpendicularly — or up to a tilt angle described below — perpendicular to the large areas of the substrate.
In contrast, the remaining end faces are those two surfaces that do not embody any narrow sides and no long sides.

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

The one or more wavelengths or wavelength ranges in which the electrophoretically or magnetophoretically movable particles absorb light are preferably in the visible spectrum and particularly preferably cover them completely. However, they can also lie outside the visible spectrum for special purposes, e.g. if UV or IR light is to be influenced, e.g. for purposes of measurement technology.

The electromagnetic switching means embodied in the form of a surface on one or more sides of the fluid chambers in the substrate are arranged, for example, on the narrow sides of the respective fluid chambers.

The particles are, for example, nano-particles, quantum dots and / or dyes. These have a spatial extent of at most 100 nm, preferably of at most 50 nm, particularly preferably of at most 20 nm.
Spatial expansion here 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 cord-shaped particles, this is the largest possible distance that two points on the surface of the particle can have from each other.

The liquid can be polar or non-polar. It can also consist, for example, of water, oil, toluene or formaldehyde, also mixed with a 10% by volume ferrofluid and / or electrolyte.

Furthermore, either the particles are electrically charged and the electromagnetic switching means are designed as electrodes for generating a static or dynamic electrical field, or the particles are magnetic and the electromagnetic switching means are designed as electromagnetic layers for generating a static or dynamic magnetic field, so that the electromagnetic Move particles in the electrical or magnetic field in the liquid. The corresponding electric field lines would then be formed in parallel in the middle of a fluid chamber, for example, and would rather show deviations from parallelism at the edge. However, other configurations are also possible.
Leading physical effects for the movement of the particles when an electromagnetic field is applied, in particular a static field, are accordingly (di) electrophoresis or magnetophoresis.
In the event that there is no electrical or magnetic field, the particles move in particular due to diffusion in the fluid chambers and thus spread homogeneously over time. For particles that are no larger than 50 nm, gravity does not matter; they do not sediment.

At least two operating states are defined by means of the electromagnetic switching means and a control circuit, in a first operating state B1 the angle-dependent transmission at more than 50% and in a second operating state B2 is less than 50%. This applies in an angular range of more than 30 ° (this angle can also be varied, for example 10 °, 20 ° or 25 °) in relation to 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 longitudinal extent is defined here with the connecting straight line Center points of the two faces of each fluid chamber.
In a preferred development of this embodiment, it applies that in the first operating state B1 more than 70% of the particles are each located in areas on the sides of the fluid chambers on which the electromagnetic switching means are formed and in the second operating state B2 , in which the switching means are configured so that there is no static electromagnetic field or a changing electromagnetic field, more than 50% of the particles (primarily due to diffusion and / or the changing electromagnetic field) are predominantly evenly distributed in the fluid chambers, so that the angle-dependent transmission in the first operating state B1 more than 60% and in the second operating state B2 is less than 5%. This again applies in an angular range of more than 30 ° (this angle can also be varied, for example 10 °, 20 ° or 25 °) 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 lamellar fluid chambers .
In other words: the different operating states B1 , B2 , .. differ in particular in that the respective local concentration and localization of the particles in the fluid chambers is changed in order to change the transmission properties due to the absorption by the particles.

The electromagnetic switching means are advantageously at least 50% transparent for light incident in the substrate in the visible wavelength range perpendicularly via the light entry surface into the substrate.

The electromagnetic switching means (as well as the fluid chambers) can further 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 here means that the operating state between is not simultaneously in all fluid chambers B1 and B2 is changed, but rather that areas with both operating states are simultaneously on the optical element B1 and B2 are available. This is advantageous if, for example, when using the optical element in front of a screen from a viewing angle of over 30 degrees to the side, parts of the displayed image content are to be visible and others are not to be visible.

In a further advantageous embodiment, the liquid contains several types of particles which differ in their absorption properties and / or their transport properties in the electromagnetic field. “Transport properties” means in particular the behavior of the particles during the respective phoresis (transport in the field).
This variant is particularly important in the case of nanoparticles: the difference between the particle types is, for example, the particle size and / or the surface function, ie 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 fluid chambers can be aligned either parallel or lattice-like 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.

As a rule, the fluid chambers (in particular their longitudinal sides) are each aligned essentially parallel to the perpendicular to the substrate S. In contrast, however, it is also possible for the fluid chambers to be inclined relative to the perpendicular to the substrate in an angular range (“tilt angle”) of -10 ° to + 10 °, 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 angle of inclination mentioned, the angle-dependent absorption based on the particle absorption and the particle positions within the fluid chambers is tilted by a fixed offset angle, for example if a low transmission at a particularly steep angle is desired.

As an example, the lamellar fluid chambers, in a plane PL1 parallel to the main direction of propagation of the substrate, can be between 2µm and 30µm wide (distance from long side to long side of a fluid chamber) and in each case a minimum of 10µm and a maximum of 150µm from each other (distance from long side to the next adjacent long side of the next neighboring fluid chamber).

Finally, the lamellar-shaped fluid chambers can have a height (distance narrow side to narrow side) of at least 10 µm and maximum 300 µm, measured in one plane PL2 perpendicular to the plane PL1 .
However, deviations from these typical dimensions are possible and are also within the scope of the invention.

• - ein erfindungsgemäßes optisches Element, und
• - eine dem optischen Element von einem Betrachter aus gesehen nachgeordnete Bildwiedergabeeinheit.

Bei der Bildwiedergabeeinheit handelt es sich beispielsweise um ein OLED, ein LCD-Display, ein SED-Display, ein FED-Display, in micro-LED-Display oder ein VFD Display. Da das optische Element unabhängig von der Art der Bildwiedergabeeinheit wirksam ist, kommen jedwede andere Bildschirmtypen ebenso in Frage.Furthermore, the invention also includes a screen that is in a first operating state B1 for a free viewing mode and in a second operating state B2 can be operated for a restricted viewing mode, comprehensively

• - an optical element according to the invention, and
• an image display unit arranged downstream of the optical element when viewed 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 type of screen can also be used.

Furthermore, it is possible, for example, to use the optical element according to the invention in an image display unit which has backlighting, for example in an LCD screen. In this case, the optical element would then advantageously be arranged between the image display panel (ie the LCD panel) and the backlight, in order to switch between a first operating state B1 for a free viewing mode and a second operating state B2 switch for a restricted viewing mode because the light of the backlight focuses once due to the optical element ( B2 ) and not focused at all ( B1 ) becomes.

It is also within the scope of the invention that more than two operating states B1 , B2 , B3 etc. can be set. This would, for example, compared to the variants for the operating states described above B1 and B2 in a third (fourth, fifth, ..) operating state, a different type of electromagnetic field is applied, which means that the degree of application of the particles or particle types is different between the operating modes, so that a total of three or more different angle-dependent degrees of transmission are achieved. This can be of interest, for example, for angle-dependent dimming applications.

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

• - ein im Wesentlichen plattenförmiges Substrat mit einer als Lichteintrittsfläche ausgebildeten ersten Großfläche und einer als Lichtaustrittsfläche zweiten ausgebildeten Großfläche,
• - eine Vielzahl von in das Substrat eingebetteten, Fluidkammern mit jeweils einer oder mehreren Oberflächen,
• - eine Flüssigkeit, mit der die Fluidkammern gefüllt sind, wobei die Flüssigkeit bis zu 20 Volumenprozent elektrophoretisch oder magnetophoretisch bewegbarer Partikel enthält, welche Licht einer oder mehrerer Wellenlängen oder Wellenlängenbereiche absorbieren,
• - flächenförmig an einer oder mehreren Oberflächen der Fluidkammern im Substrat ausgebildete elektromagnetische Schaltmittel, welche in den Fluidkammern in einem eingeschalteten Zustand ein innerhalb der Fluidkammern wirksames elektromagnetisches Feld erzeugen, wodurch die Partikel in der Flüssigkeit bewegt werden, so dass sich die Transmission des optischen Elements für Licht der Wellenlängen oder Wellenlängenbereiche, die von den Partikeln absorbiert werden, ändert, wobei in einem ersten Betriebszustand B1 die Transmission bei mehr als 50% und in einem zweiten Betriebszustand B2 bei weniger als 50% liegt, bezogen auf die Richtung der Flächennormale der zweiten Großfläche des Substrats.

The following explanations relate to an exemplary embodiment not belonging to the invention. It is another optical element, comprising

• an essentially plate-shaped substrate 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 fluid chambers embedded in the substrate, each with one or more surfaces,
• a liquid with which the fluid chambers are filled, the liquid containing up to 20 percent by volume of electrophoretically or magnetophoretically movable particles which absorb light of one or more wavelengths or wavelength ranges,
• - Electromagnetic switching means which are formed in a planar manner on one or more surfaces of the fluid chambers in the substrate and which generate an electromagnetic field which is effective within the fluid chambers in the switched-on state, as a result of which the particles are moved in the liquid, so that the transmission of the optical element for Light of the wavelengths or wavelength ranges that are absorbed by the particles changes, being in a first operating state B1 the transmission at more than 50% and in a second operating state B2 is less than 50%, based on the direction of the surface normal of the second large area of the substrate.

In this case, the fluid chambers can be, for example, honeycomb, cylindrical or rectangular and fill part or essentially all of the substrate. This further optical element according to the invention can be used in particular to control the vertical (but in combination with it at the same time the non-vertical) passage of light with respect to the transmission. An application would be e.g. the complete or partial dimming of windows in a car in order to prevent the driver from being dazzled. Switchable mirrors can also be implemented with the additional optical element.

The design variants and means-effect relationships given above apply mutatis mutandis, which should not be repeated here for reasons of redundancy.

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 die Prinzipskizze eines erfindungsgemäßen optischen Elements im Betriebszustand B1,
• 2 die Prinzipskizze eines erfindungsgemäßen optischen Elements im Betriebszustand B2,
• 3 die Prinzipskizze eines erfindungsgemäßen optischen Elements in Draufsicht, wobei lokal verschieden bei Betriebszustände B1 und B2 eingeschaltet sind, und wobei die Fluidkammern parallel zueinander angeordnet sind,
• 4 die Prinzipskizze eines erfindungsgemäßen optischen Elements in Draufsicht, wobei lokal verschieden bei Betriebszustände B1 und B2 eingeschaltet sind, und wobei die Fluidkammern gekreuzt zueinander angeordnet sind, sowie
• 5 eine Prinzipskizze zur Wirkung eines erfindungsgemäßen optischen Elements in beiden Betriebszuständen B1 und B2. Die folgenden Zeichnungen beziehen sich auf ein Ausführungsbeispiel, das nicht zur Erfindung gehört. Dazu zeigt
• 6 die Prinzipskizze eines zweiten erfindungsgemäßen optischen Elements in Schnittansicht,
• 7 die Prinzipskizze eines zweiten erfindungsgemäßen optischen Elements in Draufsicht, wobei sich dieses im Betriebszustand B1 befindet, sowie
• 8 die Prinzipskizze eines zweiten erfindungsgemäßen optischen Elements in Draufsicht, wobei sich dieses im Betriebszustand B2 befindet.

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

• 1 the schematic diagram of an optical element according to the invention in the operating state B1 ,
• 2nd the schematic diagram of an optical element according to the invention in the operating state B2 ,
• 3rd the schematic diagram of an optical element according to the invention in plan view, locally different in operating conditions B1 and B2 are switched on, and the fluid chambers are arranged parallel to one another,
• 4th the schematic diagram of an optical element according to the invention in plan view, locally different in operating conditions B1 and B2 are switched on, and wherein the fluid chambers are arranged crossed to one another, and
• 5 a schematic diagram of the effect of an optical element according to the invention in both operating states B1 and B2 . The following drawings relate to an exemplary embodiment which is not part of the invention. This shows
• 6 the schematic diagram of a second optical element according to the invention in a sectional view,
• 7 the schematic diagram of a second optical element according to the invention in plan view, this being in the operating state B1 located, as well
• 8th the schematic diagram of a second optical element according to the invention in plan view, this being in the operating state B2 located.

The drawings are not to scale and only represent basic representations.

In 1 is therefore the schematic diagram of an optical element according to the invention in the operating state B1 reproduced.

• - ein im Wesentlichen plattenförmiges Substrat S mit einer als Lichteintrittsfläche ausgebildeten ersten Großfläche 3 und einer als Lichtaustrittsfläche zweiten ausgebildeten Großfläche 4,
• - eine Vielzahl von in das Substrat S eingebetteten, lamellenartig ausgebildeten Fluidkammern mit Längs- und Schmalseiten, welche sich zwischen der ersten Großfläche 3 und der zweiten Großfläche 4 erstrecken, wobei die Schmalseiten im Bereich der Großflächen 3, 4 angeordnet sind und die Längsseiten diese verbinden,
• - eine Flüssigkeit F, mit der die Fluidkammern R gefüllt sind, wobei die Flüssigkeit bis zu 20 Volumenprozent elektrophoretisch oder magnetophoretisch bewegbarer Partikel P enthält, welche Licht einer oder mehrerer Wellenlängen oder Wellenlängenbereiche absorbieren,
• - flächenförmig an einer oder mehreren Seiten der Fluidkammern R im Substrat S ausgebildete elektromagnetische Schaltmittel 2, welche in einem eingeschalteten Zustand ein in den Fluidkammern R wirksames elektromagnetisches Feld erzeugen, wodurch die Partikel P in der Flüssigkeit F bewegt werden, so dass sich eine winkelabhängige Transmission des optischen Elements für Licht der Wellenlängen oder Wellenlängenbereiche, die von den

The optical element according to the invention shown here comprises

• an essentially plate-shaped substrate S with a first large area designed as a light entry area 3rd and a second large area designed as a light exit area 4th ,
• - A plurality of embedded in the substrate S, lamellar-shaped fluid chambers with long and narrow sides, which are between the first large area 3rd and the second large area 4th extend, the narrow sides in the area of large areas 3rd , 4th are arranged and the long sides connect them,
• - A liquid F with which the fluid chambers R are filled, the liquid up to 20 percent by volume of electrophoretically or magnetophoretically movable particles P contains which absorb light of one or more wavelengths or wavelength ranges,
• - Flat on one or more sides of the fluid chambers R electromagnetic switching means formed in the substrate S. 2nd which, in an on state, in the fluid chambers R generate effective electromagnetic field, causing the particles P be moved in the liquid F, so that there is an angle-dependent transmission of the optical element for light of the wavelengths or wavelength ranges which are different from the

Particles P are absorbed, which at such angles over the light entry surface 3rd enters the substrate S that it is on the fluid chambers R hits, changes.

The first and the second large area 3rd , 4th of the plate-shaped substrate S are preferably arranged parallel to one another. However, in special configurations, for example if particular angle-dependent transmissions of the optical element are to be achieved, they can also be arranged non-parallel, for example wedge-shaped, at a defined angle of up to 20 degrees to one another.

The first large area designed as a light entry area 3rd of the plate-shaped substrate S is usually located from the viewer's perspective on the back of the substrate S and, depending on the application of the optical element, borders, for example, on an image display device (in the drawing with the identifier 1 indicated), a light source or an air volume. Light then emerges from the latter objects through said light entry surface 3rd into the substrate.

The lamellar fluid chambers R with long and narrow sides, which are between the first large area 3rd and the second large area 4th extend, have a cuboid shape in this example and are parallel to the large areas 3rd , 4th aligned. In contrast, the remaining end faces are those two surfaces that do not embody any narrow sides and no long sides.

It is also explicitly possible for the fluid chambers R at least partially on one or both large areas 3rd and or 4th of the substrate S protrude as in the drawings 1 and 2nd shown.

The one or more wavelengths or wavelength ranges in which the particles that can be moved electrophoretically or magnetophoretically P Absorb light here are in the visible spectrum and essentially cover it completely.

The areal on one or more sides of the fluid chambers R electromagnetic switching means formed in the substrate S. 2nd are for example on the narrow sides of the respective fluid chambers R arranged as in 1 and 2nd shown.

With the particles P it is, for example, as nano-particles, quantum dots and / or dyes. These have a maximum spatial extension of 20 nm.
Spatial expansion here means the maximum expansion in three-dimensional space. In the case of spherical particles, this is the diameter.

The liquid F is e.g. Example water, mixed with a 10 vol .-% ferrofluid and electrolyte.

Furthermore, the particles P electrically charged and the electromagnetic switching means 2nd formed as electrodes for generating a static or dynamic electrical field, so that the electromagnetic particles P move in the electric field in the liquid F. The corresponding electric field lines would then, for example, be in the middle of a fluid chamber R be parallel and tend to show deviations from parallelism. However, other configurations are also possible.
Leading physical effects for the movement of the particles P when an electromagnetic field, in particular a static field, is present, the (di) electrophoresis is in this case.
In the event that there is no electrical field, the particles move P especially due to diffusion in the fluid chambers R and thus spread homogeneously over time. With the particles chosen here, which are not larger than 50 nm, gravity does not matter; these do not sediment.

By means of the electromagnetic switching means 2nd At least two operating states are defined, for example as transparent electrodes, and a control circuit, in a first operating state B1 the angle-dependent transmission at more than 50% and in a second operating state B2 is less than 50%. This applies in an angular range of more than 30 ° (this angle can also be varied, for example 10 °, 20 ° or 25 °) in relation to a surface normal of the second large area 4th of the substrate and measured in a direction perpendicular to a longitudinal extension of the lamellar fluid chambers R . The longitudinal extent is defined here with the connecting straight line of the surface center points of the two end faces of each fluid chamber R . For the operating state B1 is about the switching means 2nd a static electric field is generated around the particles P to move while for operating status B2 no electric field is applied to the particles P by diffusion within the fluid chambers R to distribute.
In a preferred development of this embodiment, it applies that in the first operating state B1 due to a static electric field more than 70% of the particles P each in areas on the sides of the fluid chambers R1 , R2 , ... are located on which the electromagnetic switching means 2nd are formed, and in the second operating state B2 , in which the switching means 2nd are configured so that there is no static electromagnetic field or an alternating electromagnetic field, more than 50% of the particles P (primarily due to diffusion and / or the changing electromagnetic field) predominantly evenly in the fluid chambers R are distributed so that the angle-dependent transmission in the first operating state B1 more than 60% and in the second operating state B2 is less than 5%. This in turn applies in an angular range of more than 30 ° (this angle can also be varied, for example 10 °, 20 ° or 25 °) based on a surface normal of the second large surface of the substrate S and measured in a direction perpendicular to a longitudinal extension of the lamellar Fluid chambers R .
In other words: the different operating states B1 , B2 , .. differ in particular in that the respective local concentration and localization of the particles P in the fluid chambers R is changed to change the transmission properties due to absorption by the particles.

The electromagnetic switching means are advantageous 2nd for at least 50%, preferably more than 80%, transparent to the incident light in the visible wavelength range perpendicular to the light entry surface into the substrate S.

The electromagnetic switching means 2nd (like the fluid chambers R ) can also 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 not in all fluid chambers R at the same time the operating state between B1 and B2 is changed, but rather that areas with both operating states are simultaneously on the optical element B1 and B2 are available. This is advantageous, for example, when using the optical element in front of a screen 1 From an angle of more than 30 degrees to the side, parts of the depicted Image content should be visible and others should not be visible.
Such a configuration is in 3rd shown. This schematic diagram shows the top view of an optical element according to the invention, with local differences in operating states B1 and B2 are turned on, and being the fluid chambers R are arranged parallel to each other. The brightly drawn fluid chambers R are in the operating state B1 and the dark ones in the operating state B2 .

The fluid chambers R can, as in 3rd shown, either in parallel or as in 4th shown, aligned with each other in a lattice 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. The outline sketch 4th shows the top view of an optical element according to the invention, locally different in operating states B1 and B2 are turned on, and being the fluid chambers R are arranged in a grid-like cross pattern. The brightly drawn fluid chambers R are in the operating state B1 and the dark ones in the operating state B2 .

In a further advantageous embodiment, there are several types of particles in the liquid F. P1 , P2 , ... which differ in their absorption properties and / or their transport properties in the electromagnetic field. The "transport properties" is particularly the behavior of the particles P in the respective phoresis (transport in the field).
This variant is particularly important in the case of nanoparticles: the difference between the particle types P1 , P2 , ... consists, for example, in the particle size and / or the surface function, ie in 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.

As a rule, the fluid chambers R (in particular their long sides) are each aligned essentially parallel to the perpendicular to the substrate S.
In contrast, it is also possible that the fluid chambers R are inclined relative to the perpendicular to the substrate S in an angular range (“tilt angle”) of -10 ° to + 10 °, possibly even between -30 ° and + 30 °. This configuration also influences the angular dependence of the transmission of the optical element, in particular — but not exclusively — in the operating state B2 . The angle of inclination or tilting mentioned means that due to the particle absorption and the particle positions within the fluid chambers R justified angle-dependent 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 R in a plane PL1 parallel to the main direction of propagation of the substrate S about 10 µm wide (distance long side to long side of a fluid chamber R ) and 50µm apart from each other (distance on the long side to the next adjacent long side of the next neighboring fluid chamber R ) be.

Finally, the lamellar fluid chambers R have a height (distance from narrow side to narrow side) of approximately 40 μm, measured in a plane PL2 perpendicular to plane PL1.
However, deviations from these typical dimensions are possible and are also within the scope of the invention.

• - ein erfindungsgemäßes optisches Element, und
• - eine dem optischen Element von einem Betrachter aus gesehen nachgeordnete Bildwiedergabeeinheit 1.

Bei der Bildwiedergabeeinheit 1 handelt es sich beispielsweise um ein OLED-Display. Da das optische Element unabhängig von der Art der Bildwiedergabeeinheit 1 wirksam ist, kommen jedwede andere Bildschirmtypen ebenso in Frage.
Das von der Bildwiedergabeeinheit 1 ausgesandte Licht dringt über die Lichteintrittsfläche, d.h. die Großfläche 3, in das optische Element ein und wird dann im optischen Element je nach Betriebszustand in seiner Ausbreitung beeinflusst, um hernach durch die Großfläche 4 wieder aus dem optischen Element zu einem oder mehreren Betrachtern hin weiter zu propagieren.Furthermore, the invention also includes a screen that is in a first operating state B1 for a free viewing mode and in a second operating state B2 can be operated for a restricted viewing mode, comprehensively

• - An optical element according to the invention, and
• an image display unit arranged downstream of the optical element when viewed by a viewer 1 .

With the image display unit 1 it is for example an OLED display. Because the optical element regardless of the type of image display unit 1 any other type of screen is also effective.
That from the image display unit 1 emitted light penetrates the light entry surface, ie the large surface 3rd , into the optical element and is then influenced in the optical element in its spread depending on the operating state, and subsequently by the large area 4th to propagate again from the optical element to one or more viewers.

The schematic shows this 5 to the effect of an optical element according to the invention in front of an image display device in both operating states B1 ("Public Mode") and B2 ("Privacy mode") the relative brightness ("relative luminance") over the viewing angle ("View angle"). The in the two operating states B1 and B2 different angle-dependent transmission of the optical element for light of the wavelengths or wavelength ranges by the particles P absorbed, ensures that the image display device 1 in the operating state B1 is visible from all horizontal viewing angles while in the operating state B2 a view is only possible from a clearly restricted angular range, as in 5 illustrated.

Furthermore, it should be noted that if only on one surface of the fluid chambers R in the substrate S electromagnetic switching means 2nd are formed, these are then in the fluid chambers R can generate an effective electromagnetic field within the fluid chambers, which is similar to an electromagnetic field, as it is used in so-called IPS ("In Plane Switching") LCD panels.

• - ein im Wesentlichen plattenförmiges Substrat S mit einer als Lichteintrittsfläche ausgebildeten ersten Großfläche 3 und einer als Lichtaustrittsfläche zweiten ausgebildeten Großfläche 4,
• - eine Vielzahl von in das Substrat S eingebetteten, Fluidkammern R mit jeweils einer oder mehreren Oberflächen,
• - eine Flüssigkeit F, mit der die Fluidkammern R gefüllt sind, wobei die Flüssigkeit bis zu 20 Volumenprozent elektrophoretisch oder magnetophoretisch bewegbarer Partikel P enthält, welche Licht einer oder mehrerer Wellenlängen oder Wellenlängenbereiche absorbieren,
• - flächenförmig an einer oder mehreren Oberflächen der Fluidkammern R im Substrat S ausgebildete elektromagnetische Schaltmittel 2, welche in den Fluidkammern R in einem eingeschalteten Zustand ein innerhalb der Fluidkammern R wirksames elektromagnetisches Feld erzeugen, wodurch die Partikel P in der Flüssigkeit F bewegt werden, so dass sich die Transmission des optischen Elements für Licht der Wellenlängen oder Wellenlängenbereiche, die von den Partikeln P absorbiert werden, ändert, wobei in einem ersten Betriebszustand B1 die Transmission bei mehr als 50% und in einem zweiten Betriebszustand B2 bei weniger als 50% liegt, bezogen auf die Richtung der Flächennormale der zweiten Großfläche 4 des Substrats S.

The following explanations relate to an exemplary embodiment not belonging to the invention.
It is an optical element, which is initially based on 6 which a schematic diagram of such a second optical element in a sectional view in the operating state B1 reproduces, should be explained. This includes

• an essentially plate-shaped substrate S with a first large area designed as a light entry area 3rd and a second large area designed as a light exit area 4th ,
• a plurality of fluid chambers embedded in the substrate S. R each with one or more surfaces,
• - A liquid F with which the fluid chambers R are filled, the liquid up to 20 percent by volume of electrophoretically or magnetophoretically movable particles P contains which absorb light of one or more wavelengths or wavelength ranges,
• - Flat on one or more surfaces of the fluid chambers R electromagnetic switching means formed in the substrate S. 2nd which in the fluid chambers R in an on state within the fluid chambers R generate effective electromagnetic field, causing the particles P can be moved in the liquid F so that the transmission of the optical element for light of the wavelengths or wavelength ranges emitted by the particles P are absorbed, changes, in a first operating state B1 the transmission at more than 50% and in a second operating state B2 is less than 50%, based on the direction of the surface normal of the second large area 4th of the substrate S.

The transmission mentioned preferably changes in the operating state B1 from over 80% to less than 10% in the operating state B2 , which is easily possible by appropriate selection of the parameters within the scope of the invention.

The fluid chambers R are, for example, honeycomb-shaped in this case and they essentially fill the entire substrate S. In in 6 shown operating state B1 are the particles P due to an applied static electrical field on an electrode of the switching means 2nd each concentrated so that the transmission of the optical element in the vertical direction reaches a maximum.
7 shows the schematic diagram of such an optical element in plan view, this being in the operating state B1 located, and 8th gives the operating status B2 as a schematic diagram again.

This further optical element can be used in particular to control the vertical (in combination with it, however, at the same time also the non-vertical) light transmission with respect to the transmission. An application for this are e.g. the complete or partial dimming of windows in a car in order to prevent the driver from being dazzled.

The design variants and means-effect relationships given above apply mutatis mutandis, which should not be repeated here for reasons of redundancy.

The above-described optical element according to the invention achieves the object: An optical element has been described which can influence the transmission as a function of the angle (and optionally perpendicularly) 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 screens, in order to enable a switchover between a privacy screen and a free viewing mode, the resolution of such a screen not being substantially reduced.

The invention 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 reading emails on mobile devices Devices. As described above, the invention can also be used in cars.

Claims (11)

Optical element, comprehensive, an essentially plate-shaped substrate (S) with a first large area designed as a light entry area (3) and a second large area designed as a light exit area (4), - a multiplicity of fluid chambers (R) with longitudinal and narrow sides, which extend between the first large area and the second large area, the narrow sides being arranged in the region of the large areas and the long sides connecting them, a liquid (F) with which the fluid chambers (R) are filled, the liquid Contains up to 20 volume percent of electrophoretically or magnetophoretically movable particles (P) which absorb light of one or more wavelengths or wavelength ranges, - electromagnetic switching means (2) formed in the form of a surface on one or more sides of the fluid chambers (R) in the substrate (S), which in in an activated state, an electroma effective in the fluid chambers (R) generate a magnetic field, whereby the particles (P) are moved in the liquid, so that there is an angle-dependent transmission of the optical element for light of the wavelengths or wavelength ranges which are absorbed by the particles (P), which at such angles over the light entry surface ( 3) enters the substrate (S) to meet the fluid chambers (R). Optical element after Claim 1 , characterized in that the particles (P) are designed as nano-particles, quantum dots and / or dyes and have a spatial extent of at most 100 nm, preferably at most 50 nm, particularly preferably at most 20 nm. Optical element according to one of the preceding claims, characterized in that either the particles (P) are electrically charged and the electromagnetic switching means (2) are designed as electrodes for generating a static or dynamic electrical field or the particles (P) are magnetic and the electromagnetic switching means (2) are designed as electromagnetic layers for generating a static or dynamic magnetic field, so that the electromagnetic particles (P) move in the electrical or magnetic field in the liquid (F). Optical element according to one of the preceding claims, characterized in that at least two operating states are defined by means of the electromagnetic switching means (2) and a control circuit, the angle-dependent transmission being more than 50% in a first operating state B1 and B2 in a second operating state less than 50% in an angular range of more than 30 ° based on an area normal of the second large area of the substrate and measured in a direction perpendicular to a longitudinal extension of the lamellar fluid chambers (R). Optical element after Claim 4 , characterized in that in the first operating state B1 more than 70% of the particles (P) are each located in areas on the sides of the fluid chambers (R) on which the electromagnetic switching means (2) are formed, and in the second operating state B2, in which the switching means (2) are configured so that there is no static electromagnetic or alternating electronic magnetic field, more than 50% of the particles (P) are predominantly evenly distributed in the fluid chambers (R), 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 ° in relation to a surface normal of the second large area of the substrate and measured in a direction perpendicular to a longitudinal extension of the lamellar fluid chambers (2). Optical element according to one of the preceding claims, characterized in that the electromagnetic switching means (2) are at least 50% transparent to light incident on the substrate (S) in the visible wavelength range perpendicularly via the light entry surface (3). Optical element according to one of the preceding claims, characterized in that the electromagnetic switching means (2) are subdivided 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 in the liquid (F) there are several types of particles (P1, P2, ...) which differ in their absorption properties and / or their transport properties in the electromagnetic field. Optical element according to one of the preceding claims, characterized in that the fluid chambers (R) are aligned either parallel or lattice-shaped with intersecting areas. Optical element according to one of the preceding claims, characterized in that the fluid chambers (R) are inclined relative to the perpendicular to the substrate (S) in an angular range from -10 ° to + 10 °. Screen that is in a first operating state B1 for a free viewing mode and in a second operating state B2 can be operated for a restricted viewing mode, comprising - an optical element according to one of the Claims 1 to 10th , and - an image display unit (1) arranged downstream of the optical element as viewed by a viewer.

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