DE102019009071A1 - Lighting device with at least two operating modes - Google Patents

Abstract

The invention relates to a lighting device (1a) which can be operated in at least two operating modes B1 and B2, comprising background lighting (2) which emits light with a first feature, a plate-shaped light guide (3) located in front of the background lighting (2) in the viewing direction ), which has decoupling elements (6) on at least one of the large surfaces and / or within its volume, the light guide (3) being at least 70% transparent for the light emanating from the background lighting (2), laterally on the narrow sides of the light guide (3 ) arranged illuminants (4), wherein a distribution of the decoupling elements (6) on at least one of the large areas and / or within the volume of the light guide (3) is predetermined so that the light sources (4) radiate into the light guide (3) and The light decoupled from the light guide (3) by the decoupling elements (6) has at least one second feature that differs from that first feature differentiates, and that such coupled-out light simultaneously has a first and a second type of polarization, an optical element (7) located in front of the plate-shaped light guide (3) in the viewing direction, which transmits light of the first type of polarization and reflects light of the second type of polarization, an in Viewing direction behind the plate-shaped light guide (3) located optical element (8) which optionally reflects and / or transmits light entirely or partially, with the background lighting (2) switched on and the illuminants (4) switched off in operating mode B2, and where in operating mode B1 at least the lamps (4) are switched on, so that in operating mode B2 only light from the background lighting (2) with the first feature is emitted from the lighting device (1a), and so that in operating mode B1 at least light from the Light guide (3) emitted from the lighting device (1a) w This light at least partially comprises light of the first type of polarization and has at least the second feature. The lighting device (1a) according to the invention, in conjunction with a transmissive imager (5), results in an advantageous screen (1) in which the aforementioned operating modes are enabled.

Description

Field of invention

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

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

State of the art

Additional films based on micro-lamellas have already been used for mobile displays in order to achieve their optical 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 U.S. 6,765,550 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 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 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 font US 2009/0067156 discloses a variety of ideas for designing a lighting system and a display device. The ones there in the 3A and 3B The variant shown uses in particular two backlights, so-called backlights, consisting of wedge-shaped light guides, and an LCD panel, the rear backlight 40 necessarily having to generate a wide illumination angle and the front backlight 38 a narrow illumination angle. However, it remains unclear how the backlight 38 is supposed to generate a narrow angle of illumination without the light with a wide angle of illumination, which originates from the backlight 40, being essentially converted into light with a narrow angle of illumination when passing through the backlight 38.

To design according to 5 the US 2009/0067156 it should be noted that both light guides 46 and 48 each produce “narrow light”, that is to say light with a narrow angle of illumination. The light of the light guide 48 is only converted into “wide light”, that is to say light with a wide angle of illumination, by a partial mirror 50, which is complex to produce with prismatic structures. This conversion cuts the light intensity extremely, as the light which is initially emitted in a narrow angle of illumination, which is the only light available, is then fanned out into a large angle of illumination, usually the half-space. As a result, depending on the parameters, the brightness is reduced by a factor of 5 or more (based on the luminance). So it is a practically irrelevant design.

In the design according to 7th the US 2009/0067156 a phosphor layer is absolutely necessary, this should convert UV light into visible light. This effort is great and if there is a desire for sufficient light from the backlight to illuminate an LCD panel in a legible manner, very high intensities of UV light are required. This is therefore expensive, time-consuming and impractical in terms of shielding the required UV radiation.

The US 2012/0235891 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 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.

According to the teaching of the GB 2428128 A Additional light sources that are clearly distant from the screen and illuminate a hologram attached to the screen are used to achieve a restricted view in order to superimpose the side view with special wavelengths. Disadvantages here are the required distance between the light sources and the screen and the effort involved in producing corresponding holograms.

In the US 2013/0308185 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 the applicant describes a screen of the type described at the outset. There, 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 polymer scattering particles distributed in the volume of the light guide can, under certain circumstances, especially at a higher concentration, lead to scattering effects which reduce the visual protection effect in the protected operating mode.

The aforementioned methods and arrangements generally have the disadvantage that they significantly reduce the brightness of the basic screen and / or require an active, but at least a special, optical element for mode switching and / or require complex and expensive production and / or reduce the resolution in freely viewable mode.

In many cases, an optical effect known as polarization recycling cannot be used.

Description of the invention

It is therefore the object of the invention to describe a lighting device which can switch and / or combine flatly distributed light of at least two different features, output it in a defined polarization and at least light present in the lighting device which does not have the defined polarization partially to be recycled in such a way that it is finally coupled out with the defined polarization.

• - eine flächenartig ausgedehnte Hintergrundbeleuchtung, die Licht mit einem ersten Merkmal abstrahlt (dieses Licht kann polarisiert oder unpolarisiert sein),
• - einen in Betrachtungsrichtung vor der Hintergrundbeleuchtung gelegenen, plattenförmigen Lichtleiter, welcher auf mindestens einer der Großflächen und / oder innerhalb seines Volumens Auskoppelelemente aufweist, wobei der Lichtleiter für das von der Hintergrundbeleuchtung ausgehende Licht zu mindestens 70% transparent ist,
• - seitlich an Schmalseiten des Lichtleiters angeordnete Leuchtmittel,
• - wobei eine Verteilung der Auskoppelelemente auf mindestens einer der Großflächen und / oder innerhalb des Volumens des Lichtleiters so vorgegeben ist, dass von den Leuchtmitteln in den Lichtleiter eingestrahltes und von den Auskoppelelementen aus dem Lichtleiter ausgekoppeltes Licht mindestens ein zweites Merkmal aufweist, das sich von dem ersten Merkmal unterscheidet, und das solches ausgekoppeltes Licht gleichzeitig eine erste und eine zweite Polarisationsart aufweist,
• - ein in Betrachtungsrichtung vor dem plattenförmigen Lichtleiter gelegenes erstes optisches Element, welches Licht der ersten Polarisationsart transmittiert und Licht der zweiten Polarisationsart reflektiert,
• - ein in Betrachtungsrichtung hinter dem plattenförmigen Lichtleiter gelegenes zweites optisches Element, welches in einer ersten Alternative als schaltbarer Spiegel ausgebildet ist und aus Richtung des Lichtleiters herrührendes Licht wahlweise reflektiert, welches in einer zweiten Alternative permanent Licht gleichzeitig teilweise reflektiert und transmittiert, oder welches in einer dritten Alternative Licht polarisationsabhängig reflektiert und/oder transmittiert,
• - wobei in der Betriebsart B2 die Hintergrundbeleuchtung ein- und die Leuchtmittel ausgeschaltet sind, und wobei in der Betriebsart B1 mindestens die Leuchtmittel eingeschaltet sind,
• - so dass in der Betriebsart B2 ausschließlich Licht der Hintergrundbeleuchtung mit dem ersten Merkmal aus der Beleuchtungseinrichtung abgegeben wird, und so dass in der Betriebsart B1 mindestens Licht aus dem Lichtleiter aus der Beleuchtungseinrichtung abgegeben wird, wobei dieses Licht mindestens teilweise Licht der ersten Polarisationsart umfasst und mindestens das zweite Merkmal aufweist.

According to the invention, this object is achieved by a lighting device which can be operated in at least two operating modes B1 and B2

• - an extensive backlight that emits light with a first characteristic (this light can be polarized or unpolarized),
• - A plate-shaped light guide located in front of the background lighting in the viewing direction, which has decoupling elements on at least one of the large areas and / or within its volume, the light guide being at least 70% transparent to the light emanating from the background lighting,
• - illuminants arranged laterally on the narrow sides of the light guide,
• - wherein a distribution of the decoupling elements on at least one of the large areas and / or within the volume of the light guide is specified so that the light emitted by the illuminants into the light guide and decoupled from the light guide by the decoupling elements has at least one second feature that differs from the distinguishes the first feature, and such coupled-out light simultaneously has a first and a second type of polarization,
• - a first optical element located in front of the plate-shaped light guide in the viewing direction, which transmits light of the first type of polarization and reflects light of the second type of polarization,
• - A second optical element located behind the plate-shaped light guide in the viewing direction, which is designed as a switchable mirror in a first alternative and optionally reflects light originating from the direction of the light guide, which in a second alternative permanently reflects and partially transmits light at the same time, or which in a third alternative light reflected and / or transmitted depending on polarization,
• - where in operating mode B2 the background lighting is switched on and the illuminants are switched off, and where in operating mode B1 at least the illuminants are switched on,
• - so that in the operating mode B2 only light of the background lighting with the first feature is emitted from the lighting device, and so that in the operating mode B1 at least light is emitted from the light guide from the lighting device, this light at least partially comprising light of the first type of polarization and has at least the second feature.

The two operating modes B1 and B2 differ in particular in that in operating mode B2 the background lighting is switched on and the light sources (on the narrow sides of the light guide) are switched off, and in operating mode B1 at least the light sources (on the narrow sides of the light guide) are switched on are. In this case, only light is taken into account that was originally radiated into the light guide by the lighting means and then emitted again from it via the decoupling elements, the emission taking place almost exclusively via the decoupling elements.

Two linear polarizations that are perpendicular to one another are particularly suitable for the first and second polarization. However, it is also possible to use other types of polarization, such as circular and / or elliptical.

It is essential for the invention that light of the second polarization is reflected back by the first optical element in the direction of the second optical element and thus initially remains in the lighting device. Since as a rule no polarized light is coupled out of a light guide in a lighting device as described above, this light of the second polarization would normally be lost for the useful balance. According to the invention, however, this is reflected, then passes through the light guide and is then partly or wholly reflected in the direction of the first optical element due to the second optical element.

Due to scattering and the associated destruction of polarization (e.g. through scattering on a surface in the structure, on the coupling-out elements and / or in the volume of the light guide) and / or, in embodiments described below, direct polarization change through one or more dedicated layers (such as Wave plates), the light then at least partially reflected back in the direction of the first optical element contains at least partially the first polarization property, so that the corresponding light component can penetrate through the first optical element and can be used as useful light with the first polarization.

In this way, at least part of the light that hits the first optical element with the second polarization is recycled.

Furthermore, due to the second optical element, some or all of the light is thrown back in the direction of the first optical element, which was unintentionally decoupled from the light guide in the direction of the second optical element from the start (without striking the first optical element immediately after its decoupling).

It must be emphasized that the aforementioned mechanisms of polarization recycling take place in the lighting device according to the invention, completely or almost completely without destroying the first feature of the light emitted by the backlight, which is unknown in the prior art.

A particularly great advantage that results from the polarization recycling according to the invention is that if the lighting device according to the invention is used in conjunction with an LCD panel, a higher brightness is achieved because more pre-polarized light of the first polarization in the direction of the LCD panel. Panels will be released than in systems without the features according to the invention.

• - die flächenartig ausgedehnte Hintergrundbeleuchtung Licht in einen eingeschränkten Winkelbereich abstrahlt, wobei dieser eingeschränkte Winkelbereich dem ersten Merkmal des Lichts entspricht,
• - wobei die Auskoppelelemente in ihrer Anzahl pro Fläche und in ihrer Ausdehnung derart gewählt sind, dass der Lichtleiter auf mindestens 50% seiner Fläche einen durchschnittlichen Haze-Wert kleiner als 7% aufweist, gemessen gemäß ASTM D1003, wodurch das von der Hintergrundbeleuchtung mindestens in der Betriebsart B2 in einen eingeschränkten Winkelbereich abgestrahlte Licht beim Durchgang durch den Lichtleiter höchstens geringfügig außerhalb des besagten Winkelbereichs gestreut wird,
• - wobei ferner eine Verteilung der Auskoppelelemente auf mindestens einer der Großflächen und / oder innerhalb des Volumens des Lichtleiters so vorgegeben ist, dass von den Leuchtmitteln in den Lichtleiter eingestrahltes und von den Auskoppelelementen aus dem Lichtleiter ausgekoppeltes Licht in einen Winkelbereich größer als 60° bezogen auf eine oder zwei vorgegebene, zueinander und zur Flächennormalen des Lichtleiters senkrechte Vorzugsrichtungen abgestrahlt wird, was dem zweiten Merkmal des Lichts entspricht.

In a preferred embodiment of the invention, the operating mode B1 is designed for a free viewing mode and the operating mode B2 for a restricted viewing mode by

• - the extensive backlighting emits light in a restricted angular range, this restricted angular range corresponding to the first feature of the light,
• - The number of decoupling elements per area and their extension are selected in such a way that the light guide has an average haze value of less than 7% on at least 50% of its area, measured in accordance with ASTM D1003, which means that the background lighting is at least in the operating mode B2 light emitted in a restricted angular range is scattered at most slightly outside of said angular range when passing through the light guide,
• - In addition, a distribution of the decoupling elements on at least one of the large areas and / or within the volume of the light guide is specified so that the light emitted by the lighting means into the light guide and decoupled from the light guide by the decoupling elements is based on an angular range greater than 60 ° one or two predetermined preferred directions perpendicular to each other and to the surface normal of the light guide are emitted, which corresponds to the second feature of the light.

In principle, any area that is smaller than the half-space in front of the background lighting can be considered as a restricted angular range; Preferably, however, an angular range of +/- 20 or 30 degrees horizontally and / or vertically or as a cone around the surface normal or a selectable direction vector on the background lighting is meant here; small amounts of light of less than 1% to 5% maximum brightness can be disregarded when defining the restricted angular range. The terms “vertical” and “horizontal” initially refer generally to two preferred directions perpendicular to one another on the surface of the background lighting or a large area of a light guide, which in operation, depending on the orientation of the screen used with the lighting device, usually fixed, is one actually correspond to the horizontal or vertical direction in relation to the position of an observer and thus the earth's surface.

Furthermore, the first and the second feature of the light can each include or exclusively form different colors or color temperatures of the respective light.

As an alternative or in addition, it is possible for the first and second features of the light to each include or exclusively form different light patterns.

• - mehr als 40% der auf einer der Großflächen zwischen einem Winkelbereich von -50° und +50° zur Flächennormalen der Großfläche ausgekoppelten Lichtmenge wird zwischen einem Winkelbereich von -20° und +20° bezogen auf eine oder zwei vorgegebene, zueinander und zur Flächennormalen senkrechte Vorzugsrichtungen abgestrahlt, und / oder mehr als 60% der auf einer der Großflächen zwischen einem Winkelbereich von -50° und +50° zur Flächennormalen der Großfläche ausgekoppelten Lichtmenge wird zwischen einem Winkelbereich von -30° und +30° bezogen auf die eine oder zwei Vorzugsrichtungen abgestrahlt.

Furthermore, it is possible that a distribution of the decoupling elements on at least one of the large areas and / or within the volume of the light guide is specified in such a way that light radiated into the light guide by the illuminants and decoupled from the light guide by the decoupling elements fulfills the following condition:

• - More than 40% of the amount of light coupled out on one of the large areas between an angle range of -50 ° and + 50 ° to the surface normal of the large area is between an angle range of -20 ° and + 20 ° related to one or two specified, to each other and to the surface normal perpendicular preferred directions, and / or more than 60% of the amount of light coupled out on one of the large areas between an angle range of -50 ° and + 50 ° to the surface normal of the large area is between an angle range of -30 ° and + 30 ° based on the one or emitted in two preferred directions.

The first optical element can be a reflective polarizer, preferably a wiregrid polarizer and / or a DBEF ™ film from 3M.

Furthermore, the second optical element can be a switchable mirror which reflects light originating from the direction of the light guide when the mirror function is switched on and otherwise predominantly transmits light, regardless of the direction of incidence.

Alternatively, it is possible that the second optical element is a beam splitter which permanently reflects light partially and partially at the same time.

Finally, further variants are conceivable, for example if, in a third alternative, light is reflected and / or transmitted as a function of polarization. These are, for example, chiral-selective mirrors.

The efficiency of the invention with regard to polarization recycling can furthermore be increased if at least one wave plate and / or one scattering layer is furthermore present in the lighting device. This can be designed to be permanent or switchable.

In this regard, it is conceivable that in the viewing direction there is at least one lambda / 4 or a lambda 3/4 wave plate and / or an anamorphic or other scattering layer, which differs from the first optical layer, below - but not necessarily directly below - the light guide Element through the light guide back reflected light of the second polarization changes in its polarization properties, both before and after this hits the second optical element for back reflection in the direction of the light guide.

Such a wave plate can, however, also be located above the light guide.

• - eine erfindungsgemäße Beleuchtungsanordnung, wie vorstehend beschrieben, sowie
• - einen in Betrachtungsrichtung vor dem Lichtleiter angeordneten transmissiven Bildgeber, in welchen optional das erste optische Element direkt integriert ist.

A screen is particularly advantageously generated by means of the lighting arrangement according to the invention, which screen can be operated in at least two operating modes B1 for a free viewing mode and B2 for a restricted viewing mode. This includes:

• - A lighting arrangement according to the invention, as described above, as well as
• - A transmissive imager arranged in front of the light guide in the viewing direction, in which the first optical element is optionally directly integrated.

Such an image generator is, for example, an LCD panel in which a wire-grid polarizer, for example, is installed as the first optical element on the lighting side. Such LCD panels are available on the market.

It is also advantageous for the invention if an image generator is used which is composed of pixels, which in turn consist of subpixels, and each dimension of the said decoupling elements in height, depth and width is smaller than the minimum of width and height of the subpixels of an imager used, ie smaller than the minimum of these two values. Each dimension of the said decoupling elements in height, depth and width is preferably even by a factor of 1.3; 1.5 or 2.0 smaller than the minimum of the width and height of the subpixels of an imager used. In this way, the image becomes more homogeneous and, under certain circumstances, superimposition of structural patterns and subpixel patterns can be avoided.

The light guide can consist of a transparent, thermoplastic, thermosetting or thermoelastic plastic or of glass. For example, the light guide or its substrate can comprise at least 40 percent by weight of polymethyl methacrylate, preferably at least 60 percent by weight of polymethyl methacrylate, based on its weight. Alternatively, it can be, for example, polycarbonate (e.g. PC, COP or PMMI).

• - einem flächigen Strahler, vorzugsweise einem Lichtleiter mit seitlich oder auf der Rückseite angeordneten Leuchtmitteln,
• - mindestens einem in den flächigen Strahler integrierten und / oder davor angeordneten Lichtkollimator, wie etwa einem Licht-Control-Filter und/oder einem oder mehreren Prismenfolien;
• - optional kann weiterhin mindestens eine Wellenplatte (lambda/4 oder lambda-3/4) enthalten sein.

The backlight consists of, for example

• - a flat spotlight, preferably a light guide with lamps arranged on the side or on the back,
• - At least one light collimator integrated into the flat radiator and / or arranged in front of it, such as a light control filter and / or one or more prismatic foils;
• - Optionally, at least one wave plate (lambda / 4 or lambda-3/4) can also be included.

Accordingly, the background lighting can basically be constructed like an LED backlight, for example as a so-called side light, edge light, direct LED backlight, edge LED backlight, OLED or as another surface emitter, on which, for example, at least one permanent privacy filter (with micro-slats ) is applied. Other variants provide for the use of so-called "Directed Backlights", that is, directional background lighting.

A further advantageous embodiment of the invention provides that for the operating mode B1, depending on predetermined critical angles σ, γ, the decoupled light, which exits the light guide at an angle β, at every point on the surface of the light guide in angle ranges that meet the conditions 80 °> β> γ and / or -80 ° <β <-σ, with 10 ° <γ <80 ° and 10 ° <σ <80 ° are sufficient, preferably γ = σ = 40 °, measured perpendicular to the surface of the light guide and in at least one of the two preferred directions has a maximum of 80%, preferably 60%, particularly preferably a maximum of 50% of the light intensity that the light has which emerges from such a point on the surface of the light guide along the normal of the surface. The preferred direction is often the vertical orientation. A negative angle is used without any reason. (without loss of generality) assigned to the side on which the light is coupled in, so an angle of -90 ° corresponds to a direction from which it is coupled in. The critical angles σ, γ are fixedly specified, based on the optical performance desired for the respective application. In the case of the particularly preferred critical angle γ = σ = 40 °, the light intensity condition then only applies to angles between -40 ° and -80 ° and 40 ° and 80 °. The smaller the critical angles σ, γ in each case, the more the light is concentrated in the respective preferred direction or directions to the perpendicular. For example, in a car where the driver and front passenger look at a screen with the lighting device according to the invention at relatively well-defined viewing angles in operating mode B1, the critical angles σ, γ can be selected to be smaller than 40 °. In contrast, in a laptop, due to the foldability of the screen and the universal application scenario, values of 40 ° or more can be useful with regard to the viewing angles of different people. Under certain circumstances, the 80 ° limit can also be 70 ° and possibly also assume other values.

As a result, for example, a reduction in disruptive reflections in the windshield, especially when driving at night, is achieved if the lighting device according to the invention is installed with a screen in a vehicle. Furthermore, if the aforementioned condition is met, good power efficiency is achieved from the light guide.

In operating mode B1, as described above, at least the lighting means on the narrow sides of the light guide are switched on. It is possible that the background lighting is switched on or off.

The required properties, which are essential for the invention, for the decoupling elements with regard to their number per unit area, their shape and extent in three dimensions and their distribution over at least one of the large areas and / or within the volume of the light guide can be achieved, for example, with optical simulation software such as " LightTools ”from Synopsis or other providers and then physically implemented accordingly.

It is possible that decoupling elements are attached to both large areas and, optionally, in the volume.

Furthermore, it is advantageous if the distribution of the decoupling elements on at least one of the large areas and / or within the volume of the light guide is specified in such a way that the decoupled light achieves a luminance homogeneity of at least 70% on at least 70% of the area of the light guide.

The outcoupling elements have maximum dimensions of 100 μm, but preferably between 1 μm and 30 μm.

The coupling-out elements are generally microlenses and / or microprisms and / or diffractive structures and / or three-dimensional structural elements and / or scattering elements. In the case of diffractive structures, it can be a hologram or a grating / diffraction grating, for example.

The number of decoupling elements per area and their extension are selected such that the light guide has an average haze value of less than 7%, preferably less than 2%, particularly preferably less, on at least 50%, preferably 80% of its area than 1%, measured according to ASTM D1003 - whereby the measurement according to the more common procedure A with a hazemeter is used as a reference - whereby the light emitted by the backlight in at least operating mode B2 in a limited angular range when passing through the light guide is at most is scattered slightly outside of said angular range. “Slightly” means, for example, that - due to the low haze - at an angle of, for example, 40 ° horizontally from the surface normal, a maximum of 1% of the luminance is added due to scattering, which the lighting device emits at an angle of 0 °.

During the production of the light guide, the decoupling elements can in principle be distributed in or on the light guide in different ways in accordance with adaptable and predeterminable conditions for the decoupling of the light. The decoupling elements are locally limited structural changes in the volume and / or on the surfaces of the light guide. The term decoupling element therefore explicitly does not include additional optical layers that are applied to the surfaces of the light guide, i.e. e.g. diffusion layers, reflective layers or (dual) brightness enhancement or polarization recycling layers ((dual) brightness enhancement film - (D) BEF). These additional layers, which do not fall under the term “decoupling element”, are only connected to the light guide at the edges, but are only loosely in the area of the large areas and do not form a physical unit with the light guide. On the other hand, paints applied to the large surfaces, which connect to the light guide through chemical reactions, form a physical unit and can no longer be separated from one another; such lacquers therefore do not count as an additional layer in the above sense.

The structure of the decoupling elements can be specified so that the effect of each decoupling element is known at least approximately and properties of the light guide or the light emerging from the light guide can be specifically determined by a predeterminable distribution of the decoupling elements.

In special configurations, it is also possible for coupling-out elements formed within the volume of the light guide to be present, these coupling-out elements being formed as cavities which preferably have the outer shape of microlenses, microprisms or diffractive structures.

The cavities can be filled with a gaseous, liquid or solid material, the material having a refractive index which differs from that of the material used for the light guide, is preferably lower, or the cavities are evacuated.

It is also conceivable that the cavities are filled with a gaseous, liquid or solid material, the material having a haze value which differs from that of the material used for the light guide, is preferably higher.

In this context, there is also the possibility that the light guide is formed from two preferably similar substrate layers connected to one another at interfaces and the cavities as material cutouts at at least one of the interfaces, preferably having the outer shape of microlenses, microprisms, three-dimensional structural elements or diffractive structures, are trained.

If the decoupling elements are attached to at least one of the large areas of the light guide, they are advantageously formed from a plastic or glass structured with a tool, the structure of which has been thermally impressed by means of a tool. This is possible, for example, in mass production by applying a UV-curing material - e.g. a lacquer, a monomer, etc. - to a light guide substrate, which is structured by means of a tool and cured by UV radiation, e.g. polymerized. Other radiation curing materials can also be used. The formation of the recesses for realizing the decoupling elements can be realized, for example, mechanically, lithographically or by printing technology, or else by applying, converting, removing or dissolving material.

For example, lattice structures, microprisms - either convex with plastic on the surface pointing outwards, and / or concave as an embossing or recess within the surface layer of the structured plastic -, other three-dimensional structural elements with other shapes, or even microlenses can be implemented inexpensively and with mass production capability become. Concave and convex structures can be used in the same way.

The distribution of the decoupling elements on at least one of the large areas and / or within the volume of the light guide is advantageously specified in such a way that the decoupled light achieves a luminance homogeneity of 70% on at least 70% of the area of the light guide. For this purpose, the luminance homogeneity can be defined as L _v ^min / L _v ^max , that is to say as the ratio of the smallest value of the luminance to the largest value per unit area. Another applicable regulation for the definition of luminance homogeneity is defined in the "Uniformity Measurement Standard for Displays V1.3" by the German Flat Display Forum.

Means for reducing or controlling reflections, for example an anti-glare and / or an anti-reflective coating, can be arranged on the top of the imager and / or on at least one of the large areas of the light guide as well as on at least one of the privacy filters, if present.

In all of the aforementioned configurations, said lighting means can be LEDs or LED rows or laser diodes. Other variants are conceivable and are within the scope of the invention.

A screen with a lighting device according to the invention is particularly advantageously used in a vehicle for the optional display of image content only for the passenger in operating mode B2 or simultaneously for the driver and the passenger in operating mode B1. The former is helpful, for example, when the passenger is watching entertainment that could distract the driver.

Furthermore, it is advantageous for some applications if the said restricted angular range is designed asymmetrically around the surface normal of the background lighting. The asymmetrical design is preferably carried out in one of the preferred directions. This is particularly helpful for applications in the vehicle, for example when a screen to be combined with the lighting device according to the invention is arranged as a so-called center information display in the dashboard approximately in the middle between the driver and front passenger. In this case, the restricted angular range released exclusively for the front passenger in operating mode B2 must be designed asymmetrically for the view, i.e. directed towards the front passenger. The preferred direction in which the asymmetry is formed corresponds here to the horizontal.

A screen with a lighting device according to the invention can also be used to input or display confidential data, for example PIN codes, emails, SMS or passwords, at ATMs, payment terminals or mobile devices.

Furthermore, the desired restricted angle ranges for mode B2 for a restricted view can be defined and implemented independently of one another for the horizontal and vertical directions. For example, a larger angle (or possibly no restriction at all) could be useful in the vertical direction than in the horizontal direction, for example if people of different sizes should see a picture at ATMs, while the side view should remain strongly or completely restricted. For POS Payment terminals, on the other hand, are often required to have visual restrictions in mode B2 both in the horizontal and in the vertical direction due to security regulations.

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

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

Figure list

• 1 eine Prinzipskizze zur erfindungsgemäßen Beleuchtungseinrichtung,
• 1a eine Prinzipskizze zur erfindungsgemäßen Beleuchtungseinrichtung in Verbindung mit einem Bildgeber in einer ersten Ausgestaltungsvariante,
• 2 eine Prinzipskizze zur erfindungsgemäßen Beleuchtungseinrichtung in Verbindung mit einem Bildgeber in einer zweiten Ausgestaltungsvariante,
• 3 eine Prinzipskizze zur erfindungsgemäßen Beleuchtungseinrichtung in Verbindung mit einem Bildgeber in einer dritten Ausgestaltungsvariante,
• 4 eine Prinzipskizze zur erfindungsgemäßen Beleuchtungseinrichtung in Verbindung mit einem Bildgeber in einer vierten Ausgestaltungsvariante,
• 5 eine Prinzipskizze zur erfindungsgemäßen Beleuchtungseinrichtung in Verbindung mit einem Bildgeber in einer fünften Ausgestaltungsvariante,
• 6 eine Prinzipskizze zur erfindungsgemäßen Beleuchtungseinrichtung in Verbindung mit einem Bildgeber in einer sechsten Ausgestaltungsvariante,
• 7 eine Prinzipskizze zur erfindungsgemäßen Beleuchtungseinrichtung in Verbindung mit einem Bildgeber in einer siebten Ausgestaltungsvariante,
• 8 eine Prinzipskizze zur erfindungsgemäßen Beleuchtungseinrichtung in Verbindung mit einem Bildgeber in einer achten Ausgestaltungsvariante,
• 9 eine Prinzipskizze zur erfindungsgemäßen Beleuchtungseinrichtung in Verbindung mit einem Bildgeber in einer neunten Ausgestaltungsvariante, sowie
• 10 eine schematische Darstellung zur Definition der vertikalen Richtung des zu messenden Winkels β.

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 the lighting device according to the invention,
• 1a a schematic diagram of the lighting device according to the invention in connection with an image generator in a first embodiment variant,
• 2 a schematic diagram of the lighting device according to the invention in connection with an image generator in a second embodiment variant,
• 3 a schematic diagram of the lighting device according to the invention in connection with an image generator in a third embodiment variant,
• 4th a schematic diagram of the lighting device according to the invention in connection with an image generator in a fourth embodiment variant,
• 5 a schematic diagram of the lighting device according to the invention in connection with an image generator in a fifth embodiment variant,
• 6th a schematic diagram of the lighting device according to the invention in connection with an image generator in a sixth embodiment variant,
• 7th a schematic diagram of the lighting device according to the invention in connection with an image generator in a seventh embodiment variant,
• 8th a schematic diagram of the lighting device according to the invention in connection with an image generator in an eighth embodiment variant,
• 9 a schematic diagram of the lighting device according to the invention in connection with an image generator in a ninth embodiment variant, and
• 10 a schematic representation for the definition of the vertical direction of the angle to be measured β.

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

Detailed description of the drawings

• - eine flächenartig ausgedehnte Hintergrundbeleuchtung 2, die Licht mit einem ersten Merkmal abstrahlt,
• - einen in Betrachtungsrichtung (hier in der Zeichenebene von oben) vor der Hintergrundbeleuchtung 2 gelegenen, plattenförmigen Lichtleiter 3, welcher auf mindestens einer der Großflächen und / oder innerhalb seines Volumens Auskoppelelemente 6 aufweist, wobei der Lichtleiter 3 für das von der Hintergrundbeleuchtung 2 ausgehende Licht zu mindestens 70% transparent ist,
• - seitlich an Schmalseiten des Lichtleiters 3 angeordnete Leuchtmittel 4,
• - wobei eine Verteilung der Auskoppelelemente 6 auf mindestens einer der Großflächen und / oder innerhalb des Volumens des Lichtleiters 3 so vorgegeben ist, dass von den Leuchtmitteln 4 in den Lichtleiter 3 eingestrahltes und von den Auskoppelelementen 6 aus dem Lichtleiter 3 ausgekoppeltes Licht mindestens ein zweites Merkmal aufweist, das sich von dem ersten Merkmal unterscheidet, und das solches ausgekoppeltes Licht gleichzeitig eine erste und eine zweite Polarisationsart aufweist,
• - ein in Betrachtungsrichtung vor dem plattenförmigen Lichtleiter 3 gelegenes erstes optisches Element 7, welches Licht der ersten Polarisationsart transmittiert und Licht der zweiten Polarisationsart reflektiert,
• - ein in Betrachtungsrichtung hinter dem plattenförmigen Lichtleiter 3 gelegenes zweites optisches Element 8, welches in einer ersten Alternative als schaltbarer Spiegel ausgebildet ist und aus Richtung des Lichtleiters 3 herrührendes Licht wahlweise reflektiert, welches in einer zweiten Alternative permanent Licht gleichzeitig teilweise reflektiert und transmittiert, oder welches in einer dritten Alternative Licht polarisationsabhängig reflektiert und/oder transmittiert,
• - wobei in der Betriebsart B2 die Hintergrundbeleuchtung 2 ein- und die Leuchtmittel 4 ausgeschaltet sind, und wobei in der Betriebsart B1 mindestens die Leuchtmittel 4 eingeschaltet sind,
• - so dass in der Betriebsart B2 ausschließlich Licht der Hintergrundbeleuchtung 2 mit dem ersten Merkmal aus der Beleuchtungseinrichtung 1a abgegeben wird, und so dass in der Betriebsart B1 mindestens Licht aus dem Lichtleiter 3 aus der Beleuchtungseinrichtung 1a abgegeben wird, wobei dieses Licht mindestens teilweise Licht der ersten Polarisationsart umfasst und mindestens das zweite Merkmal aufweist.

The 1 shows a schematic diagram of the lighting device according to the invention 1a which can be operated in at least two operating modes B1 and B2 and comprises the following components:

• - an extensive backlight 2 that emits light with a first characteristic,
• - One in the viewing direction (here in the plane of the drawing from above) in front of the background lighting 2 located, plate-shaped light guide 3 , which decoupling elements on at least one of the large areas and / or within its volume 6th having, wherein the light guide 3 for that from the backlight 2 outgoing light is at least 70% transparent,
• - laterally on the narrow sides of the light guide 3 arranged illuminants 4th ,
• - With a distribution of the decoupling elements 6th on at least one of the large areas and / or within the volume of the light guide 3 is specified so that from the illuminants 4th into the light guide 3 irradiated and from the decoupling elements 6th from the light guide 3 outcoupled light has at least one second feature that differs from the first feature, and the such outcoupled light has a first and a second type of polarization at the same time,
• - One in the viewing direction in front of the plate-shaped light guide 3 located first optical element 7th , which transmits light of the first type of polarization and reflects light of the second type of polarization,
• - One behind the plate-shaped light guide in the viewing direction 3 located second optical element 8th , which is designed as a switchable mirror in a first alternative and from the direction of the light guide 3 Originating light optionally reflected, which in a second alternative permanently reflects and partially transmits light at the same time, or which in a third alternative reflects and / or transmits light depending on polarization,
• - where in operating mode B2 the background lighting 2 one and the bulbs 4th are switched off, and in operating mode B1 at least the lighting means 4th are switched on,
• - so that in operating mode B2 only light from the background lighting 2 with the first feature from the lighting device 1a is emitted, and so that in the operating mode B1 at least light from the light guide 3 from the lighting device 1a is emitted, this light at least partially comprising light of the first polarization type and having at least the second feature.

The two operating modes B1 and B2 differ in that in operating mode B2 the background lighting 2 one and the bulbs 4th (on one or more narrow sides of the light guide 4th ) are switched off, and in operating mode B1 at least the lamps 4th (on the narrow side (s) of the light guide 4th ) are switched on. Only light is taken into account, which originally came from the light sources 4th into the light guide 3 irradiated and from this then again via the decoupling elements 6th was emitted, the radiation almost exclusively via the decoupling elements 6th he follows.

For the first and second polarization, two mutually perpendicular, linear polarization planes are particularly suitable. However, it is also possible to use other types of polarization, such as circular and / or elliptical.

It is essential for the invention that light of the second polarization passes through the first optical element 7th in the direction of the second optical element 8th is thrown back and thus initially in the lighting device 1a remains. Since from a light guide 3 in lighting device 1a Normally unpolarized light is coupled out, this light of the second polarization would normally be lost for the useful balance. According to the invention, however, this is achieved by the first optical element 7th reflected, then goes through the light guide 3 through and then becomes due to the optical element 8th partially or entirely in the direction of the first optical element 7th thrown back.

Light of the first polarization passes through the first optical element unimpeded 7th through. Due to scattering and the associated destruction of polarization (e.g. through scattering on a surface in the structure of the lighting device 1a , Scattering at the decoupling elements 6th and / or in the volume of the light guide 3 ) and / or - in embodiments described below - direct or defined polarization change through one or more dedicated layers (such as waveplates) then contains this again at least partially in the direction of the first optical element 7th light reflected back at least partially the first polarization property, so that the corresponding light component through the first optical element 7th can penetrate and be used as useful light of the first polarization.

In this way, according to the invention, at least part of the light is recycled, which with the second polarization on the first optical element 7th hits without the ability to turn on the backlight 2 to make a first feature impossible with light.

Furthermore, due to the optical element 8th Light partially or entirely in the direction of the first optical element 7th thrown back, which from the start unintentionally from the light guide 3 in the direction of the second optical element 8th was decoupled (without directly after its decoupling on the first optical element 7th hold true). This is a further advantage for the usage balance of the light.

It must be emphasized that the aforementioned mechanisms of polarization recycling in the lighting device according to the invention 1a take place completely or almost completely without the first characteristic of the backlight 2 to destroy emitted light, which is unknown in the prior art.

A particularly great advantage that results from the polarization recycling according to the invention is that if the lighting device according to the invention 1a in conjunction with an LCD panel as an image generator 5 (as will be described further below) is used, so that a higher brightness is achieved because more pre-polarized light of the first polarization is emitted in the direction of the LCD panel than in systems without the features according to the invention.

• - die flächenartig ausgedehnte Hintergrundbeleuchtung 2 Licht in einen eingeschränkten Winkelbereich abstrahlt, wobei dieser eingeschränkte Winkelbereich dem ersten Merkmal des Lichts entspricht,
• - wobei die Auskoppelelemente 6 in ihrer Anzahl pro Fläche und in ihrer Ausdehnung derart gewählt sind, dass der Lichtleiter 3 auf mindestens 50% seiner Fläche einen durchschnittlichen Haze-Wert kleiner als 7% aufweist, gemessen gemäß ASTM D1003, wodurch das von der Hintergrundbeleuchtung 2 mindestens in der Betriebsart B2 in einen eingeschränkten Winkelbereich abgestrahlte Licht beim Durchgang durch den Lichtleiter 3 höchstens geringfügig außerhalb des besagten Winkelbereichs gestreut wird,
• - wobei ferner eine Verteilung der Auskoppelelemente 6 auf mindestens einer der Großflächen und / oder innerhalb des Volumens des Lichtleiters 3 so vorgegeben ist, dass von den Leuchtmitteln 4 in den Lichtleiter 3 eingestrahltes und von den Auskoppelelementen 6 aus dem Lichtleiter 3 ausgekoppeltes Licht in einen Winkelbereich größer als 60° bezogen auf eine oder zwei vorgegebene, zueinander und zur Flächennormalen des Lichtleiters 3 senkrechte Vorzugsrichtungen abgestrahlt wird, was dem zweiten Merkmal des Lichts entspricht.

In a preferred embodiment of the invention, the operating mode B1 is designed for a free viewing mode and the operating mode B2 for a restricted viewing mode by

• - the extensive backlighting 2 Emits light in a restricted angular range, this restricted angular range corresponding to the first characteristic of the light,
• - The decoupling elements 6th are chosen in their number per area and in their extension such that the light guide 3 has an average haze value of less than 7% on at least 50% of its area, measured in accordance with ASTM D1003, whereby that of the Backlight 2 Light emitted at least in operating mode B2 in a restricted angular range when passing through the light guide 3 is scattered at most slightly outside the said angular range,
• - In addition, a distribution of the decoupling elements 6th on at least one of the large areas and / or within the volume of the light guide 3 is specified so that from the illuminants 4th into the light guide 3 irradiated and from the decoupling elements 6th from the light guide 3 outcoupled light in an angular range greater than 60 ° based on one or two specified, to each other and to the surface normal of the light guide 3 perpendicular preferred directions is emitted, which corresponds to the second characteristic of light.

In principle, any area that is smaller than the half-space in front of the background lighting can be considered as a restricted angular range; Preferably, however, an angular range of +/- 20 or +/- 30 degrees or +/- 45 degrees horizontally and / or vertically or as a cone around the surface normal or a selectable direction vector on the background lighting is meant here; small amounts of light of less than 1% to 5% maximum brightness can be disregarded when defining the restricted angular range. The terms “vertical” and “horizontal” initially relate generally to two preferred directions that are perpendicular to one another on the surface of the background lighting 2 or a large area of a light guide 3 in operation depending on the orientation of the lighting device 1a used, usually fixed screen 5 , one actually corresponding to the position of an observer and thus the earth's surface horizontal or vertical direction.

It is true that the first and second features of the light can each include or exclusively form different colors or color temperatures of the respective light. As an alternative or in addition, it is also possible for the first and second features of the light to each include or exclusively form different light patterns. In the following, however, only cases are to be considered in which a restricted angular range corresponds to the first feature of light and the coupling of light in an angular range greater than 60 ° in relation to one or two specified, to one another and to the surface normal of the light guide 3 preferred perpendicular directions corresponds to the second characteristic of light.

• - mehr als 40% der auf einer der Großflächen zwischen einem Winkelbereich
• - von -50° und +50° zur Flächennormalen der Großfläche ausgekoppelten Lichtmenge wird zwischen einem Winkelbereich von -20° und +20° bezogen auf eine oder zwei vorgegebene, zueinander und zur Flächennormalen senkrechte Vorzugsrichtungen abgestrahlt, und / oder mehr als 60% der auf einer der Großflächen zwischen einem Winkelbereich von -60° und +50° zur Flächennormalen der Großfläche ausgekoppelten Lichtmenge wird zwischen einem Winkelbereich von -30° und +30° bezogen auf die eine oder zwei Vorzugsrichtungen abgestrahlt.

It is also possible for the decoupling elements to be distributed 6th on at least one of the large areas and / or within the volume of the light guide 3 is specified so that from the illuminants 4th into the light guide 3 irradiated and from the decoupling elements 6th from the light guide 3 outcoupled light fulfills the following condition:

• - more than 40% of the on one of the large areas between an angular range
• - The amount of light coupled out from -50 ° and + 50 ° to the surface normal of the large area is emitted between an angle range of -20 ° and + 20 ° in relation to one or two specified preferred directions perpendicular to each other and to the surface normal, and / or more than 60% of the on one of the large areas between an angle range of -60 ° and + 50 ° to the surface normal of the large area, the amount of light decoupled is emitted between an angle range of -30 ° and + 30 ° in relation to one or two preferred directions.

In all drawings except 1 are the bulbs 4th and the decoupling elements 6th not shown for the sake of clarity. Of course, they are always there.

• - eine erfindungsgemäße Beleuchtungsanordnung 1a, wie vorstehend beschrieben, sowie
• - einen in Betrachtungsrichtung vor dem Lichtleiter 3 angeordneten transmissiven Bildgeber 5, in welchen optional das erste optische Element 7 direkt integriert ist.

As in 1a shown by means of the lighting arrangement according to the invention 1a a screen 1 generated, which can be operated in at least two operating modes B1 for a free viewing mode and B2 for a restricted viewing mode. This includes:

• - A lighting arrangement according to the invention 1a as described above, as well as
• - One in the viewing direction in front of the light guide 3 arranged transmissive imager 5 , in which optionally the first optical element 7th is directly integrated.

All of the following design variants, shown in the drawings 2-9 , are based on the use of such an imager 5 .

With such an imager 5 it is, for example, an LCD panel in which a wire-grid polarizer, for example, is installed on the lighting side. Such LCD panels are available on the market. Instead of the wire-grid polarizer, however, a DBEF film, for example, can also be used, which is then not directly integrated into the LCD panel.

Furthermore, it is advantageous for some applications that the said restricted angular range is the first feature of the light to be asymmetrical about the surface normal of the background lighting 2 is trained. The asymmetrical design is preferably carried out in one of the preferred directions. This is particularly helpful for applications in the vehicle, for example when using the lighting device according to the invention 1a screen to be created 1 as a so-called center information display in the The dashboard is located approximately in the middle between the driver and front passenger. In this case, the restricted angular range released exclusively for the front passenger in operating mode B2 must be designed asymmetrically for the view, i.e. directed towards the front passenger. The preferred direction in which the asymmetry is formed corresponds here to the horizontal.

With the first optical element 7th it can be a reflective polarizer, preferably a wiregrid polarizer and / or a DBEF ™ film from 3M.

Furthermore, the second optical element 8th be a switchable mirror, which from the direction of the light guide 3 When the mirror function is switched on, light is reflected and otherwise light, regardless of the direction of incidence, is predominantly transmitted.

This is in 2 , 3 and 4th shown schematically.

There are also lambda-4 wave plates 9 / 9a, one or two lamellar filters in various variations in the beam path 10 , DBEF layers 11 and / or weakly scattering layers 12th present (the elements 10 and 11 correspond as parts of the background lighting, which is not completely shown in the drawing 2 ).

With the weakly scattering layers 12th it can be, for example, an anamorphic or homogeneous diffuser.

In the drawings 3-9 is the backlight 2 not shown. Rather, this is in each case below the second optical element due to some of its components 8th indicated, for example by the lamellar filter 10 and / or the DBEF 11 and / or the wave plate 9a . In any case, the backlight closes 2 always in the viewing direction of the second optical element 8th at.

The efficiency of the invention with regard to polarization recycling can be increased by the fact that, as described above, at least one wave plate 9 / 9a and / or a diffusion layer 12th in the lighting device 1a is available. This can be designed to be permanent or switchable.

In the variations mentioned, it is possible that in the viewing direction below - but not necessarily directly below - the light guide 3 at least one lambda / 4 or one lambda 3/4 wave plate 9 and / or an anamorphic or other scattering layer is present, which is from the first optical element 7th through the light guide 3 light of the second polarization reflected back changes in its polarization properties both before and after it hits the optical element 8th for back reflection in the direction of the light guide 3 meets.

Alternatively, it is possible that the second optical element 8th is a beam splitter, which permanently reflects and partially transmits light at the same time. The beam splitting ratio can expediently be selected here, for example 40/60, 50/50 or 60/40. Other variants are possible.

Such configurations are in the 5 , 6th and 7th shown.

Here, too, there are again lambda-4 wave plates 9 / 9a, one or two lamellar filters in various variations in the beam path 10 and / or DBEF layers 11 (the Elements 10 and 11 correspond as parts of the background lighting, which is not completely shown in the drawing 2 ) available.

Finally, further variants are conceivable, for example if, in a third alternative, light is reflected and / or transmitted as a function of polarization. These are, for example, chiral-selective mirrors (switchable or not switchable). No separate drawing was attached for this.

In 8th a special case is shown: the mirror 8a the second optical element cannot be switched here. This can be the case with the mirror 8a For example an ESR reflector from 3M, a metallic mirror or a white reflector.

A wave plate 9 can also be located above the light guide 3 as in 9 shown.

It is also advantageous for the invention if an image generator 5 is used, which is composed of pixels, which in turn consist of sub-pixels, and each dimension of the said decoupling elements 6th is smaller in height, depth and width than the minimum of the width and height of the subpixels of an imager used, ie smaller than the minimum of these two values. Any dimension of the said decoupling elements is preferred 6th in height, depth and width even by a factor of 1.3; 1.5 or 2.0 smaller than the minimum of the width and height of the subpixels of an imager used 5 . In this way, the image becomes more homogeneous and, under certain circumstances, superimposition of structural patterns and subpixel patterns can be avoided.

• - einem flächigen Strahler, vorzugsweise einem Lichtleiter mit seitlich oder auf der Rückseite angeordneten Leuchtmitteln (zeichnerisch nicht dargestellt),
• - mindestens einem in den flächigen Strahler integrierten und / oder davor angeordneten Lichtkollimator 10, wie etwa einem Licht-Control-Filter (Lamellenfilter oder vergleichbares Element) und/oder einem oder mehreren Prismenfolien, wie etwa einer DBEF,
• - optional kann auch hier weiterhin mindestens eine Wellenplatte 9a (lambda/4 oder lambda-3/4) enthalten sein.

The backlight 2 consists for example of

• - a flat spotlight, preferably a light guide with lamps arranged on the side or on the back (not shown in the drawing),
• - At least one light collimator integrated into the flat spotlight and / or arranged in front of it 10 such as a light control filter (lamella filter or comparable element) and / or one or more prismatic foils, such as a DBEF,
• - Optionally, at least one wave plate can also be used here 9a (lambda / 4 or lambda-3/4).

The background lighting can be accordingly 2 basically be constructed like an LED backlight, for example as a so-called side light, edge light, direct LED backlight, edge LED backlight, OLED or as another surface emitter, on which, for example, at least one permanent privacy filter 10 (with micro lamellas) is applied. Other variants provide for the use of so-called "Directed Backlights", that is, directional background lighting.

A further advantageous embodiment of the invention provides that for the operating mode B1, depending on predetermined critical angles σ, γ, the decoupled light, which exits the light guide at an angle β, at each point on the surface of the light guide 3 in angular ranges that meet the conditions 80 °>β> γ and / or -80 ° <β <-σ, with 10 ° <γ <80 ° and 10 ° <σ <80 °, preferably γ = σ = 40 °, measured perpendicular to the surface of the light guide 3 and in at least one of the two preferred directions has a maximum of 80%, preferably 60%, particularly preferably a maximum of 50% of the light intensity that the light has, which comes from such a point on the surface of the light guide 3 emerges along the normal of the surface. The preferred direction is often the vertical orientation. A negative angle is assigned (without loss of generality) to the side on which the light is coupled in, so an angle of -90 ° corresponds to a direction from which the coupling is made. The critical angles σ, γ are fixedly specified, based on the optical performance desired for the respective application. In the case of the particularly preferred critical angle γ = σ = 40 °, the light intensity condition then only applies to angles between -40 ° and -80 ° and 40 ° and 80 °. The smaller the critical angles σ, γ in each case, the more the light is concentrated in the respective preferred direction or directions to the perpendicular. For example, in a car, where the driver and front passenger are in operating mode B1, viewing angles that can be defined relatively well can be viewed on a screen 1 with the lighting device according to the invention 1a look, the critical angles σ, γ are chosen to be smaller than 40 °. In contrast, in a laptop, due to the foldability of the screen 1 and the universal application scenario with regard to the viewing angles of different people, values of 40 ° or greater make sense. Under certain circumstances, the 80 ° limit can also be 70 °. In this regard shows 10 a schematic representation for the definition of the vertical direction of the angle to be measured β, wherein the light guide 3 (as well as the imager, not shown 5 ) is arranged in landscape mode, ie the long sides are at the top and bottom. The dash-dotted line stylizes a line perpendicular to the surface of the light guide 3 standing direction to which the angle β is measured in vertical alignment or plane, here marked by the double arrow labeled "V".

In this way, for example, a reduction in disruptive reflections in the windshield, especially when driving at night, is achieved when the lighting device according to the invention is used 1a in one screen 1 is installed in a vehicle.

The required properties for the decoupling elements that are essential for the invention 6th in terms of their number per unit area, their shape and extent in three dimensions and their distribution over at least one of the large areas and / or within the volume of the light guide 3 can, for example, be determined with optical simulation software such as "LightTools" from Synopsis or other providers and then physically implemented accordingly.

It is possible that decoupling elements 6th on both large areas and optionally in the volume.

The light guide 3 can consist of a transparent, thermoplastic or thermoelastic plastic or of glass.

It is also advantageous if the distribution of the decoupling elements 6th on at least one of the large areas and / or within the volume of the light guide 3 is specified so that the decoupled light on at least 70% of the area of the light guide 3 a luminance homogeneity of at least 70% is achieved.

The decoupling elements 6th have maximum dimensions of 100 μm, but preferably between 1 μm and 30 μm.

With the decoupling elements 6th it is usually microlenses and / or microprisms and / or diffractive structures and / or three-dimensional structural elements and / or scattering elements. In the case of diffractive structures can it is, for example, a hologram or a grating / diffraction grating.

The decoupling elements 6th are selected in their number per area and in their extension in such a way that the light guide has an average haze value of less than 7%, preferably less than 2%, particularly preferably less than 1, on at least 50%, preferably 80% of its area %, measured according to ASTM D1003 - the measurement according to the more common procedure A with a hazemeter being used as a reference - which means that from the backlight 2 At least in the operating mode B2 light emitted in a restricted angular range is scattered at most slightly outside of said angular range when passing through the light guide. “Slightly” is to be understood as meaning, for example, that - due to the low haze - at an angle of, for example, 40 ° horizontally from the surface normal, a maximum of 1% of the luminance due to scattering is added by the lighting device 1a emits at an angle of 0 °.

The decoupling elements 6th can be used in the manufacture of the light guide 3 correspondingly adaptable and predeterminable conditions for the coupling out of the light basically in different ways in or on the light guide 3 be distributed. With the decoupling elements 6th it concerns locally limited structural changes in the volume and / or on the surfaces of the light guide. Expressly not included in the term decoupling element 6th therefore additional optical layers fall on the surfaces of the light guide 3 be applied, ie for example diffusion layers, reflective layers or (dual) brightness-enhancing or polarization-recycling layers ((dual) brightness enhancement film - (D) BEF). These additional layers, which do not fall under the concept of the “decoupling element”, are only connected to the light guide at the edges, but only lie loosely in the area of the large areas and form with the light guide 3 no physical unit. On the other hand, paints applied to the large areas form, which are combined with the light guide 3 connect by chemical reactions, a physical unit, can no longer be separated from each other; such lacquers therefore do not count as an additional layer in the above sense.

The structure of the decoupling elements 6th can be specified so that the effect of each decoupling element 6th is at least approximately known and properties of the light guide 3 or from the light guide 3 emerging light in a targeted manner through a predeterminable distribution of the decoupling elements 6th can be set.

When the decoupling elements 6th on at least one of the large areas of the light guide 3 are attached, these are advantageously formed from a plastic or glass structured with a tool, the structure of which was embossed by means of a tool. This is possible, for example, in mass production by applying a UV-curing material - eg a lacquer, a monomer, etc. - to a light guide substrate, which is structured by means of a tool and cured by UV radiation, eg polymerized. Other radiation curing materials can also be used. The formation of the recesses for realizing the decoupling elements 6th can be realized mechanically, lithographically or by printing technology, for example, or also by applying, converting, removing or dissolving material.

For example, lattice structures, microprisms - either convex with plastic on the surface pointing outwards, and / or concave as an embossing or recess within the surface layer of the structured plastic -, other three-dimensional structural elements with other shapes, or even microlenses can be implemented inexpensively and with mass production capability become. Concave and convex structures can be used in the same way.

The distribution of the decoupling elements is advantageous 6th on at least one of the large areas and / or within the volume of the light guide 3 specified so that the decoupled light on at least 70% of the area of the light guide 3 a luminance homogeneity of 70% is achieved. The luminance homogeneity can be ^{defined as Lv min} / Lv ^max , i.e. as the ratio of the smallest value of the luminance to the largest value per unit area. Another applicable regulation for the definition of luminance homogeneity is defined in the "Uniformity Measurement Standard for Displays V1.3" by the German Flat Display Forum. Alternatively, it is also possible to define the luminance homogeneity, for example as a 9-point test according to ICDM.

On top of the imager 5 and / or on at least one of the large areas of the light guide 3 as well as on at least one of the privacy filters (lamella filters) 10 If present, means for reducing or controlling reflection, for example an antiglare and / or an antireflection coating, can be arranged.

• Es wurde eine Beleuchtungseinrichtung beschrieben, durch welche flächig verteiltes Licht mindestens zweier verschiedener Merkmale wahlweise umgeschaltet und/oder kombiniert werden kann, wobei dieses Licht in einer definierten Polarisation ausgeben wird. Gleichzeitig wird in der Beleuchtungseinrichtung vorhandenes Licht, welches nicht die definierte Polarisation aufweist, mindestens teilweise derart recycelt, dass es schließlich mit der definierten Position ausgekoppelt wird.

The lighting device according to the invention described above 1a solves the given task:

• A lighting device has been described by means of which light distributed over a large area of at least two different features can be switched over and / or combined as desired can be, whereby this light is output in a defined polarization. At the same time, light present in the lighting device which does not have the defined polarization is at least partially recycled in such a way that it is finally coupled out with the defined position.

The invention described above can advantageously be used in combination with an image generator 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 cars.

List of reference symbols

1

screen

1a

Lighting device

2

Backlight

3

Light guide

4th

Bulbs

5

transmissive imager

6th

Decoupling elements

7th

Optical element that transmits light of the first type of polarization and reflects light of the second type of polarization (e.g. reflective polarizer)

8th

optical element (selective or switchable mirror or beam splitter)

8a

Permanent mirror

9

Wave plate

9a

Wave plate

10

Lamellar filter

11

DBEF

12th

Litter layer

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• US 6765550 [0004]
• US 5993940 [0005]
• WO 2012/033583 [0006]
• US 2009/0067156 [0007, 0008, 0009]
• US 2012/0235891 [0010]
• JP 2007155783 [0011]
• GB 2428128 A [0012]
• US 2013/0308185 [0013]
• WO 2015/121398 [0014]

Claims (10)

Lighting device (1a) which can be operated in at least two operating modes B1 and B2, comprising - an extensive backlight (2) that emits light with a first feature, - A plate-shaped light guide (3) located in front of the backlight (2) in the viewing direction, which has decoupling elements (6) on at least one of the large areas and / or within its volume, the light guide (3) for the backlight (2) outgoing light is at least 70% transparent, - Illuminants (4) arranged laterally on the narrow sides of the light guide (3), - wherein a distribution of the decoupling elements (6) on at least one of the large areas and / or within the volume of the light guide (3) is specified so that the light emitted by the illuminants (4) into the light guide (3) and from the decoupling elements (6) light coupled out from the light guide (3) has at least one second characteristic which differs from the first characteristic, and the such coupled out light has a first and a second type of polarization at the same time, - An optical element (7) located in front of the plate-shaped light guide (3) in the viewing direction, which transmits light of the first type of polarization and reflects light of the second type of polarization, - An optical element (8) located behind the plate-shaped light guide (3) in the viewing direction, which in a first alternative is designed as a switchable mirror and optionally reflects light originating from the direction of the light guide (3), which in a second alternative permanently partially reflects light at the same time reflects and transmits, or which, in a third alternative, reflects and / or transmits light depending on polarization, - the background lighting (2) being switched on and the lighting means (4) switched off in operating mode B2, and at least the lighting means (4) being switched on in operating mode B1, - so that in operating mode B2 only light from the backlight (2) with the first feature is emitted from the lighting device (1a), and so that in operating mode B1 at least light is emitted from the light guide (3) from the lighting device (1a) wherein this light at least partially comprises light of the first polarization type and has at least the second feature. Lighting device (1a) according to Claim 1 characterized in that - the operating mode B1 is designed for a free viewing mode and the operating mode B2 for a restricted viewing mode in that - the extensive backlighting (2) emits light in a restricted angular range, this restricted angular range corresponding to the first feature of the light, - The decoupling elements (6) are selected in their number per area and in their extension such that the light guide (3) has an average haze value of less than 7% on at least 50% of its area, measured in accordance with ASTM D1003, whereby the light emitted by the backlight (2) at least in operating mode B2 in a restricted angular range is scattered at most slightly outside of said angular range when passing through the light guide (3), - furthermore a distribution of the decoupling elements (6) on at least one of the large areas and / or within the volume of light conductor (3) is specified so that the light emitted by the illuminants (4) into the light guide (3) and the decoupling elements (6) decoupled from the light guide (3) in an angular range greater than 60 ° based on one or two specified , preferred directions perpendicular to each other and to the surface normal of the light guide (3) are emitted, which corresponds to the second feature of the light. Lighting device (1a) according to Claim 1 or 2 characterized in that the first and second features of the light each include different color temperatures of the respective light. Lighting device (1a) according to one of the Claims 1 to 3 , characterized in that the first and second features of the light each include different light patterns. Lighting device (1a) according to one of the Claims 1 to 4th , characterized in that a distribution of the decoupling elements (6) on at least one of the large areas and / or within the volume of the light guide (3) is specified in such a way that the light emitted by the lighting means (4) into the light guide (3) and by the decoupling elements (6) the light decoupled from the light guide (3) fulfills the following condition: - more than 40% of the amount of light decoupled on one of the large areas between an angle range of -50 ° and + 50 ° to the surface normal of the large area is between an angle range of -20 ° and + 20 ° based on one or two specified preferred directions perpendicular to each other and to the surface normal, and / or more than 60% of the amount of light coupled out on one of the large surfaces between an angle range of -50 ° and + 50 ° to the surface normal of the large surface between an angle range of -30 ° and + 30 ° based on one or two preferred directions. Lighting device (1a) according to one of the preceding claims, characterized in that the optical element (7) is a reflective polarizer, preferably a wiregrid polarizer and / or a DBEF ™ film from 3M. Lighting device (1a) according to one of the preceding claims, characterized in that the optical element (8) is a switchable mirror which reflects light coming from the direction of the light guide (3) when the mirror function is switched on and otherwise predominantly transmits light, regardless of the direction of incidence . Lighting device (1a) according to one of the Claims 1 to 6th , characterized in that the optical element (8) is a beam splitter which permanently reflects and partially transmits light at the same time. Lighting device (1a) according to one of the preceding claims, characterized in that at least one wave plate (9, 9a) and / or one scattering layer (12) is also present. Screen (1) which can be operated in at least two operating modes B1 for a free viewing mode and B2 for a restricted viewing mode, comprising - A lighting arrangement (1a) according to one of the preceding claims, as well as - A transmissive image generator (5) arranged in front of the light guide (3) in the viewing direction, in which the optical element (7) is optionally integrated.

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