EP2883090A1

EP2883090A1 - Light guide plate comprising decoupling elements

Info

Publication number: EP2883090A1
Application number: EP13747406.0A
Authority: EP
Inventors: Thomas Fäcke; Friedrich-Karl Bruder; Rainer Hagen; Günther WALZE; Thomas RÖLLE; Horst Berneth; Dennis Hönel; Marc-Stephan Weiser; Werner Hoheisel
Original assignee: Bayer MaterialScience AG
Current assignee: Covestro Deutschland AG
Priority date: 2012-08-13
Filing date: 2013-08-09
Publication date: 2015-06-17
Also published as: KR20150043390A; IN2015DN01583A; WO2014026923A1; US20150192725A1; JP2015531886A; CN104704407A; RU2015108650A; JP6437435B2; TW201421085A; TWI617848B

Abstract

The invention relates to a planar light distribution module for a display, comprising a light guide plate, through which light that can be coupled via at least one lateral surface can propagate by means of total reflection, and comprising at least one planar decoupling system (2) which is mounted on one or both main surfaces of the light guide plate (1), is in optical contact with said plate and contains a plurality of holographic optical elements (13) which are designed in such a way that they can decouple light from the light guide plate (1). The light distribution module is characterised in that the holographic optical elements (13) are arranged in the decoupling system (2) without translation symmetry. The invention also relates to an optical display, in particular an electronic display which contains a light distribution module according to the invention.

Description

Light guide plate with decoupling elements

The invention relates to a planar light distribution module for a display, comprising a Lichtfüh- approximately plate which can propagate via at least one side surface einkoppelbares light by total reflection and at least one mounted on one or both of the main surfaces of the Lichtfüh- tion plate and standing in optical contact with this planar decoupling device in which a plurality of holographic optical elements configured to be able to extract light from the light guide plate (1) are arranged. The invention also relates to an optical display, in particular an electronic display, which includes a light distribution module according to the invention. Liquid crystal displays have become widely used. They are already available in many sizes. They range from small LCD displays in mobile phones, game computers, to mid-size displays for laptops, tablet PCs, desktop monitors, to large-scale applications such as TVs, billboards, and building installations.

Conventionally, cathode cathode light sources and light emitting diodes (LEDs) are used for light generation in the backlight unit (BLU). The radiation characteristic of these light sources is such; that these radiate comparatively undirected light. Basically, two types are used: direct lighting and edge lighting.

In direct lighting (direct BLU), the luminaires are mounted on the back of the display. This has the advantage that the light is distributed very homogeneously over the size of the display panel, which is particularly important in televisions meaning you also use LEDs in direct lighting, they can also be dimmed, which makes an increased contrast of the display possible A disadvantage are the high cost, since a variety of light sources is necessary For this reason, the edge lighting has more and more prevailed in the market Recently, the light sources are mounted only at the edges of a light guide plate In this, the light is coupled to the edge and is through Total reflection transported into the interior By on the surface side of the light guide plate mounted Lichtauskoppelelemente the light is thereby directed forward towards the LC panel Typical Lichtauskoppelelemente are printed patterns of white color, the roughening the surface of the light guide plate or embossed refractive structures. The number and density of these structures can be chosen freely and allows a fairly homogeneous illumination of the display.

In the further development of high-resolution LC displays, ways are being sought to make energy-saving displays with better presentation qualities possible. An important aspect is the enlargement of the color space (garnut) and the homogeneous illumination (luminance distribution).

Enlarging the color space is achieved by increasing the color fidelity of the individual pixels. This is accompanied by the use of increasingly narrow spectral distributions of the red, green and blue pixels. A narrowing of the spectral distribution of the color filters is conceivable, but at the expense of the luminous efficacy and increases the power consumption. Therefore, it is advantageous to use spectrally narrow emissive light sources, e.g. light emitting diodes or laser diodes.

The light output elements used in the current state of the art, such as e.g. white reflection color or surface roughness show the non-directional scattering behavior of a Lambertian radiator. This leads, on the one hand, to a multiplicity of light paths which have to be homogenized again by the diffuser and prism foils lying between the light guide plate and the LC panel and then have to be reoriented in order to provide a light distribution appropriate to the LC panel.

In addition to these reflective or refractive decoupling elements, diffractive surface structures on the light guide plate have been described:

US 2006/0285185 describes a light guide plate in which the depth of the molded-in diffractive surface structure matches the efficiency of decoupling. However, the effective efficiency is considered to be low due to only one frequency in the grating structure.

US 2006/0187677 teaches a light guide plate in which the molded diffractive surface structures should set a homogeneous intensity distribution by a different fill factor and different orientations. US 2010/0302798 discloses the use of two spatial frequencies by embossing superstructures into the diffractive surface structure. Similar adaptation by further _" cutaway" in the surface structure is taught by US 2011/0051035, in order to be able to separately optimize the decoupling properties of decoupling efficiencies. Park et al. (Optics Express 15 (6), 2888-2899 (2007)) reported dot-matrix diffractive point-like surface structures, but only achieved an intensity uniformity of 62%.

US 5,650,865 teaches the use of double holograms consisting of a reflection volume and a transmission volume hologram. The two holograms select light of narrow spectral width and deflect light from a certain angle from the light guide plate vertically. The double holograms for the three primary colors are geometrically assigned to the pixels of an LC panel. The orientation of two pixelated holograms to each other and their adjustment to the pixels of the LC panel is complicated and difficult. US 2010/0220261 describes lighting devices for liquid crystal displays containing a light guide plate containing volume holograms to redirect laser light. The volume holograms are at special distances from each other, obliquely positioned in the Lichtfuhrungsplatte. However, the production of volume holograms in light guide plates is very expensive. From GB 2260203 the use of volume holograms as color-selective grids on a light guide plate is known, wherein the individual volume holograms have Auskoppeleffizienzen, which increase along the irradiation direction. The color-selective grids are spatially adapted to the pixels of a translucent digital light modulator, which is complicated and thus expensive with increasingly high-resolution display panels. It is an object of the present invention to provide an improved display design with a particularly flat and compact light distribution module that efficiently and homogeneously illuminates light onto a translucent digital light modulator. The Lichtverteihusgsmodul should also allow a reduction in the number of light sources and thus make the production of optical displays cheaper. This object is achieved in a light distribution module of the type mentioned above in that the holographic optical elements are arranged in the decoupling device with respect to at least two spatial dimensions without translational symmetry and the holographic optical elements are designed as volume grids.

The invention is based on the finding that, in deviation from the information known from the prior art, in particular those from GB 2260203, no uniform arrangement tion of the holographic optical elements is required to allow a homogeneous light extraction from the light guide plate. In addition, in the solution according to the invention, no discrete allocation of the extraction points to individual pixels of a display is required.

Thus, in the light distribution module according to the invention, the light can be coupled out directionally from the light guide plate, and the homogeneous light extraction can be achieved by the distribution of the holographic optical elements on the light guide plate. In addition, for example, the shape, the size, the diffraction efficiency and / or the diffraction direction of the holographic optical elements can be varied or a wavelength selection can be carried out with the aid of the holographic optical elements. In other words, typically used light sources couple the light in a wide angular range in the Lichtfuhrungsplatte. In this case, the holographic optical elements select these rays and leave those rays that do not follow the Bragg condition in the Lichtfuhrungsplatte. By the skillful choice of the shape and size or the diffractive efficiency or the distribution of the holographic optical elements on the Lichtfuhrungsplatte or by the diffraction direction or by wavelength selection or by a combination of two or more of these properties, it is possible to uniformly adjust the light homogeneity on a Difiusor , The light guide plate thus serves as a light reservoir to which the holographic optical elements "pick" light and decouple this purposefully onto the diffuser other, eg, exciplex-containing plasma light sources; solid-state light sources, such as light-emitting diodes (LEDs) based on inorganic or organic materials, preferably so-called white LEDs, which contain an ultraviolet and / or blue emission and color-converting phosphors, the color-converting phosphors also containing half - can emit conductive nanoparticles (so-called quantum dots, Q-dots), which - as is known in the art - emit after excitation with blue or UV light in the appropriate red and green and possibly blue spectral range with high efficiency as narrow as possible Bandwidth of light emission are preferred. In addition, combinations of at least three monochromatic, ie red, green and blue LEDs are also suitable; Combinations of at least three monochromatic, eg red, green and blue laser diodes; or combinations of monochromatic LEDs and laser diodes, so that the basic colors can be produced by the combination. Alternatively, the base colors may also be generated in a blue-lit, track-like element that includes appropriate Q-dots to match the blue light of the LED Converted red and green light with narrow bandwidth with high efficiency to mix. The rail-shaped element, also available under the registered trade name "Quantum Rail", can be positioned in front of an array of blue LEDs or blue laser diodes.

The production of the holographic optical elements in the transparent layer is possible by various methods. It is possible to use a mask corresponding to the pattern to be generated, the mask containing openings (positive mask) corresponding to the pattern. In this case, the holographic exposure is constructed such that either the signal beam or the reference beam or both is locally modified by the mask in its intensity or polarization. This mask may be made of, inter alia, metal, plastic, strong cardboard or the like and thus contains apertures or areas in its place the beam is transmitted or its polarization is changed and a holographic optical interference by means of interference with the second beam in the holographic recording film Element generated In areas where only one beam strikes the recording material or where the polarization states of the two beams are orthogonal to one another, an exposure of the recording material takes place which does not feel like a holographically optic element

If locally different diffraction efficiencies are to be generated for the holographic optical elements, a gray filter can be used which locally adjusts the beam ratio of signal to reference beam and thus the amplitude of the interference field, which determines the diffraction efficiency of the holographic optical element from position varies to position The gray filter can eg be realized by a printed glass or transparent, largely free from birefringence present plastic film, which is placed on the mask. Ideally, the gray filter is realized by a digital printing technique such as ink-jet dmck or laser printing.

In addition to a gray filter, it is also possible to use an element which locally varies the polarization state of at least one of the two write beams since this can likewise influence the amplitude of the interference field. Suitable elements would be e.g. Linear polarizers, quarter-wave or half-wave plates. Linear polarizers can also act like gray filters.

If one not only wants to imprint a simple holographic grating but also a diffuser characteristic into the holographic optical element, then the signal beam can be modified by an optical diffuser. The mask can be placed on the diffuser, to enable the spatial allocation there. It is also possible to modify the reference beam analogously with the mask. In the latter case, the "signal" information is distributed to reference and signal beam, since the reference beam with the mask defines the range, the signal beam introduces the diffuser characteristic. It is also possible to first generate a master hologram of the diffuser, which in a second holographic exposure step is used to generate the actual holographic optical elements in the transparent layer If a master hologram is used, the positive mask is only needed for its production and may be dispensed with in the subsequent copy creation.

The output devices of the light distribution module, for example, by mask (positive mask), by varying the beam ratios by a gray filter, a polarizing filter, by using a diffuser, by incoherent pre-exposure through a gray filter (negative mask), by sequential optical pressure of individual holographic optical Elements take place, to name just a few examples. A modification of the coupling-out devices can be achieved, for example, by erasing holograms by radiation, chemical swelling or shrinkage; by mechanical post-processing or by a combination of two or more of these methods.

If one wishes to use several different layers with holographic optical elements, it may be advantageous to produce them separately and then to apply them to one another in a lamination step or in a bonding process. If different holographic optical elements with different diffraction angles are used, a separate mask is used for each of these groups and the beam geometry is modified accordingly. Here, the exposures are sensed sequentially.

If different holographic optical elements are used for different reconstruction frequencies, a separate mask and another laser are used correspondingly for each of these groups. Here, the exposures can be carried out sequentially. It is also possible to provide each mask aperture with a color filter which defines the color assignment. The exposure can then take place sequentially as well as simultaneously by means of a white laser consisting of a red, green and blue. If, in addition, the absorption of the color filter is also varied for the transmitted beam, the diffraction efficiency can also be adjusted at the same time If the holographic optical elements adjoin one another or overlap, the mask can be completely dispensed with and the glass plate / plastic film can be used alone for the exposure.

In addition to a positive mask, a negative mask can also be used. The areas that are exposed are desensitized by an incoherent pre-exposure. After this pre-exposure, the actual holographic exposure takes place in the remaining areas of the recording film. The incoherent preexposure can take place in different light intensity. Thus, it is possible to adjust each range from no to complete desensitization. The subsequent holographic exposure can now again be color-selective and / or direction-selective, so that in this way the diffraction efficiency is adjusted by the incoherent preexposure by means of a negative mask, the color selectivity and / or the direction is selectively effected by the positive mask in the second step. The desensitization of the recording material takes place a negative mask, so that the areas are defined without holographic optical element. Thereafter, the red, green and blue holographic optical elements with the respective lasers are sequentially written in the recording material with three positive masks. It is also possible to provide each positive mask opening with a color filter that defines the color assignment. The exposure may then be sequential as well as simultaneous with one of a red, green and blue white laser. In another method suitable for generating holographic optical elements in the outcoupler, each holographic optical element is optically printed sequentially either the recording material passed in front of an optical writing head via an xy shifting table, or the optical writing head is guided over the recording material by means of an xy positioning unit. Each position is approached one after the other and the holographic optical element is imprinted by means of interference exposure also for a slight adjustment of the reconstruction directions of the individual holographic optical elements, since an easy adaptation is possible by rotating the optical writing head or the recording material Of course, the write head may also include other functions such as color selectivity by using multiple lasers or by flexible grayscale filters or polarization elements that can adjust the signal reference beam ratio. It is also within the scope of the invention to apply first a holographic optical element covering the surface of the light guide plate and to structure in a subsequent step in isolated holographic optical elements by selectively deleting the hologram in areas or their diffraction properties for different wavelength ranges This can for example but not exclusively also be done by a mask, for example, by bleaching with UV radiation, the hologram or other used for the recording material extinguishing methods used

Furthermore, for example, the diffraction property of the holographic optical elements x-y can be adapted to be scanned by targeted local swelling or shrinkage to different spectral regions of the visible spectrum. Suitable agents would be, for example, actinic radiation crosslinkable monomers of suitable refractive index, which are locally diffused and then crosslinked. This procedure may be preferred when using photopolymers as recording material used.

Finally, it is possible to produce the holographic optical elements by means of a punchable and transferable film material. In this case, a uniform grid structure is exposed, the structure of the pattern mechanically punched and transferred to the waveguide, for example via a lamination step.

The output device preferably consists of a recording material for volume holograms. Suitable materials are, for example, silver halide emulsions, dichromate gelatin, photorefractive materials, photochromic materials or photopolymers. Of industrial relevance, these are essentially silver halide emulsions and photopolymers. Very bright and high-contrast holograms can be written in silver halide emulsion, however, an increased expenditure on the Schulz of the moisture-sensitive films is necessary in order to ensure sufficient long-term stability. There are several basic material concepts for photopolymers, common to all photopolymers is the photoinitiator system and polymerizable random monomers. In addition, these components may be embedded in support materials such as thermoplastic binders, crosslinked or non-crosslinked binders, liquid crystals, sol gels or nanosized glasses. In addition, further properties can be tailored to specific needs by means of special additives. In a particular embodiment, a photopolymer may also contain plasticizers, stabilizers and / or further additives. This is particularly advantageous in connection with photopolymers containing crosslinked matrix polymers, as described by way of example in EP2172505A1. The photopolymers described herein have as Photoinitiator a photoinitiator system modulatable to the necessary wavelength, writing monomers with active polymerizable groups and a high-crosslinked matrix polymer. If suitable additives, selected as described in WO 2011054796, are added, it is possible to prepare particularly advantageous materials which give an industrially interesting material in terms of their optical properties, manufacturability and processibility. Suitable additives according to this process are in particular urethanes, which are preferably substituted by at least one fluorine atom. With regard to their mechanical properties, these materials can be adjusted over a wide range and can thus be adapted to a wide variety of requirements both in the unexposed and the exposed state (WO 2011054749 A1). The photopolymers described can be prepared both in roll-to-roll processes (WO 2010091795) or in printing processes (EP 2218742).

The decoupling device can also have a layer structure, for example an optically transparent substrate and a layer of a photopolymer. It is particularly expedient to lamime ren the coupling device with the photopolymer directly on the light guide plate. It is also possible to carry out the coupling device such that the photopolymer is enclosed by two thermoplastic films In this case it is particularly advantageous; one of the two thermoplastic films adjacent to the photopolymer is attached to the light guide plate with an optically clear adhesive film.

The thermoplastic film layers of the coupling-out device preferably consist of transparent plastics. Particular preference is given to using polymethyl methacrylate, cellulose triacetate, amorphous polyamides, amorphous polyesters, amorphous polycarbonate, cycloolefmers (COC) or else blends of the abovementioned polymers. Also glass can be used for this.

The decoupling device may further contain silver halide emulsions, dichromated gelatin, photorefractive materials, photochromic materials and / or photopolymers, in particular photopolymers containing a photoinitiator system and polymerizable writing monomers, preferably photopolymers containing a photoinitiator system, polymerizable writing monomers and crosslinked matrix polymers.

An arrangement of the holographic optical elements without translational symmetry can be described, for example, by a physical model in which a regular point grid with a point spacing a is assumed as the starting configuration, each point being assigned a holo-dot scale. corresponds graphically optical element Each point of the grid is assigned a point mass; which is connected to each of its four nearest neighbors via a tension spring These tension springs are biased by a certain amount, that is; the rest length of the springs is smaller than the average distance between the grid points.

The spring constants of the springs are statistically distributed around an average value. Subsequently, the minimum of the energy of the entire system is determined. The resulting positions of the point masses form a grid with the sought-after properties:

The mean distance between two neighboring points is still a. The grid is aperiodic. No direction is excellent and the autocorrelation function decreases rapidly for values greater than a. The steepness of the waste can be controlled by the dispersion in the values of the spring constant.

In order to calculate the autocorrelation function of the grid, a function must first be assigned to this grid. This can be done by assigning the value 1 to all points (x, y) that lie on the lines of the grid and all other points by the value 0. For this function f (x, y) kamt is assigned to itself known manner (see, for example, E. Oran Brigham, FFT / Fast Fourier Transformation, R. Oldenbourg Verlag, Munich / Vienna 1982, p. 84 ff.), the autocorrelation function can be determined:

For a strictly periodic lattice, such as a quadratic lattice of edge length a, the function Z (x, y) has maxima of equal amplitude in all points where x = n * a or y = n * a with n as integer regardless of the value n. As soon as this lattice is deformed in such a way that the order of proximity is preserved, but the distance order is not, the height of the maxima decreases rapidly with increasing n.

An arrangement of the holographic optical elements made in this manner has the advantage that it is visually less conspicuous than a grating with translation symmetry. As a result, the average lattice spacing can be selected to be larger and the production costs can be reduced. Furthermore, will the greater average grid line spacing increases the light transmission of the decoupling device. In addition, the occurrence of a moiré effect is prevented.

In an advantageous embodiment of the light distribution module according to the invention, the holographic optical elements are arranged in such a way that the number of holographic optical elements per area increases from at least one edge to the center of the coupling-out device. This arrangement applies in particular to such edges of the coupling-out device as to a side surface of the light guide plate correspond, is eingekoppeh the light from a light source. As such, in the presence of two light sources disposed on opposite side surfaces of the light guide plate, the number of holographic optical elements per area may increase from these two opposite edges to the center of the outcoupler. If light sources are arranged on three or four side surfaces of the light guide plate, the aforementioned distribution applies accordingly. If the light sources are punctiform light sources, an increased number of outcoupling elements near the edge of the light guide plate is advantageous in each case between the punctiform light sources. Analogously, the configuration takes place when one or more light sources are positioned at the edges of the light guide plate. In the light distribution module according to the invention it is provided that a multiplicity of holographic optical elements are present in the outcoupling device. For the purposes of the present invention, a multiplicity means the presence of at least 10 holographic optical elements in the outcoupling device, preferably at least 30 holographic optical elements, preferably at least 50, more preferably at least 70, particularly preferably at least 100.

In a further embodiment of the light distribution module according to the invention, the holographic optical elements are formed in the outcoupling device and extend from one of the flat sides of the outcoupling device into this and / or penetrate them completely. In such an embodiment, it is particularly preferred that the outcoupling device with that flat side is in contact with the light guide plate on which the holographic optical elements are located. In this way, a particularly effective optical contact between the light guide plate and the output device can be generated, whereby the Auskopphmgseffizienz the holographic optical elements is improved.

In the context of the present invention, it may further be provided that the output device or the light guide plate is provided with a reflection layer which is arranged on the flat side opposite the output direction of the light. be realized by applying a metallic reflection layer via vapor deposition, splintering or other techniques. As a result, the coupling-out efficiency can be increased or a loss of intensity can be reduced.

According to a further preferred embodiment of the light distribution module according to the invention, the diffraction efficiency of the holographic optical elements is different, the diffraction efficiency of the holographic optical elements along a direction of incidence for light into the light guide plate starting from the edge of the outcoupling device increasing in particular If opposite light sources are provided, the diffraction efficiency decreases from the side edges starting at which the light sources einkoppem the light in the Lichtfuhrungsplatte up to the center in an advantageous manner too. If light sources are provided at three or four side edges of the light guide plate, the above arrangement for diffraction efficiency applies correspondingly. If the light sources are point-shaped light sources, then an increased diffraction efficiency near the edge of the light guide plate between the point-shaped light sources is additionally advantageous. In the context of the present invention, it is particularly advantageous if the holographic optical elements can decouple light from the light guide plate at least in the wavelength range from 400 to 800 .mu.m. Nevertheless, holographic optical elements covering a broader wavelength range can also be provided. Conversely, it is also possible to use holographic optical elements which only cover a section of the visible wavelength range, in particular, for example, only the area of red, blue or green light or alternatively additionally yellow light. In this way, a color selective decoupling of individual light colors from white light be realized from the light guide plate. Consequently, a particularly preferred embodiment of the present invention is in a light distribution module, in which the holographic optical elements can couple out wavelength-selective light, wherein in particular at least three groups of holographic optical elements are present, which are each wavelength-selective for red, green and blue light also a fourth group for yellow light can be optionally used.

In a further embodiment of the inventive light distribution module can be provided that the holographic optical elements are designed such that the ausgekop- pelted light passes through the coupling device completely transversely. In other words, therefore, transmissive coupling-out devices can be used. Alternatively or in addition to these transmissive coupling-out devices, the holographic optical elements can also be used. be equipped in such a way that the decoupled light is reflected and the light guide plate is traversed after decoupling Iransversal. In other words, such a reflective coupling-out device is arranged on the flat side of the light guide plate located opposite the emission direction of the light distribution module. A reflection layer can also be provided on the outer surface of such a reflective coupling-out device. This can, as stated above, consist in a vapor-deposited or fragmented metal layer.

For the holographic optical elements used in the present invention, a variety of possible Ausgestattungsformen be used, the configuration is particularly preferred as a volume grating In a further advantageous embodiment of erfmdungsge- light distribution module can each at least one coupling device on both flat sides of the Lichtfuhrungsplatte and / or at least two decoupling devices may be arranged on a flat side of the Lichtfuhrungsplatte. If a plurality of decoupling devices is provided on one of the flat sides of the light guide plate, it is further preferred that at least three decoupling devices are arranged on a flat side of the guide plate, wherein the three decoupling devices each contain wavelength-sensitive holographic optical elements for exactly one light color, in particular for red, green and blue Light In other words, in such an embodiment, each of the three outcouplers selectively decouples a light color, namely, for example, red, green, and blue light, respectively, from the light guide plate.

The coupling-out device can have any thickness required for the intended function. In particular, with photopolymer layer thicknesses ≥ 0.5 μm, preferably ≥ 5 μm and ≤ 100 μm, particularly preferred ≥ 10 μm and ≤ 40 μm, it is possible to achieve that only certain selected wavelengths are diffracted. For example, it is possible to laminate three photopolymer layer thicknesses of in each case ≥ 5 μm to one another and to describe them separately in advance in each case. Also, only a photopolymer layer ≥ 5 microns can be used if in this one photopolymer layer all at least three color-selective holograms are written simultaneously or successively or partially overlapping in time. As an alternative to the options described above, it is also possible to use photopolymer layers ≦ 5 μm, preferably ≦ 3 μm and particularly preferably ≦ 3 μμ and 0,5 0.5 μm. In this case, only a single hologram is written, preferably at a wavelength close to that in the spectral center of the visible electromagnetic spectral region or near the geometric mean of the two wavelengths of the longest wavelength of the shortest wavelength emission region of the illumination system In a further advantageous refinement of the light distribution module according to the invention, the holographic optical elements have, independently of one another, an extension in at least one spatial axis parallel to the surface of the coupling-out device of at least 300 μm, in particular at least 400 μm or even at least 500 μm. This embodiment is particularly advantageous, since it is not necessary in the context of the present invention that the holographic optical elements illuminate a discrete pixel of a display. Instead, the use of such larger holographic optical elements enables a diffused and uniform illumination of a display background

The holographic optical elements used for the light distribution module of the present invention may have any shape. Thus, the holographic optical elements independently of one another in the surface of the coupling-out device can have a circular, elliptical or polygonal, in particular three, four, five or hexagonal, trapezoidal or parallelogram-like cross section. This design also includes embodiments in which the holographic optical elements are arranged, for example, in the form of strips which extend from one side edge of the coupling-out device to the opposite one. These strips can be arranged parallel to the side edges of the coupling-out device or else at any other angle. In this case, the individual strip-shaped holographic optical elements can run parallel to one another or else at an angle.

According to a further embodiment possibility of the inventive light distribution module, the individual holographic optical elements of a coupling-out device partly overlap, wherein in particular the surface of the coupling-out device is largely completely occupied by holographic optical elements.

Depending on the production method of the decoupling device (eg by optical printing), discrete holographic optical elements can be generated which adjoin one another or overlap with adjacent holographic optical elements. Thus, more than two holographic optical elements can overlap with each other and on top of each other. Using other fabrication techniques (eg, grayscale masks), there may also be no discrete boundaries between the holographic optics. In this case, the imaging performance (eg, given by the resolution of the printhead, the ink dosage to represent a gray area) of the grayscale mask's printing process determines the underlying size, shape, diffraction efficiency, etc., of the holographic optical elements. The resolution of a printing process is typically expressed in dpi = dots per inch, assuming that at least 100 individual pressure droplets are needed to define a holographic optical element through a gray mask.

In the context of the present invention it can be provided that the light distribution module comprises a diffuser, which is arranged on the flat side of the combination of light distribution plate and outcoupling device, at which the light is radiated, wherein the diffuser preferably rests on the light guide plate and / or outcoupler without an optical contact is made. This is preferably achieved via a roughened surface or particle-shaped spacers on the surface of the light guide plate or the diffuser. The distance set by the surface finish is preferably less than or equal to 0.1 mm, in particular less than or equal to 0.05 mm. A Difiusor is a plate-shaped element that has or consists of a litter layer. In this way, a particularly uniform light distribution can be generated.

It is particularly advantageous if, in addition to the abovementioned first diffusor, a further diffuser is provided, which is positioned parallel to the diffuser behind the first diffusor in the radiation direction. For the further spacing, the above-mentioned preferred values apply with respect to the first diffuser. In other words, a light distribution module according to the invention optionally comprises one or more diffusers.

Alternatively or in addition to a diffuser, it may also be provided that the holographic optical elements inherently have a diffuser function. Such a function can be imparted to the holographic optical elements already during manufacture by appropriate illumination techniques.

It is also possible to use essentially only blue-emitting light sources and to design the light distribution module according to the invention in such a way that it directs light in the direction of the light modulator L only for blue wavelengths, with a color filter for the red and the green pixels in the color filter of the light modulator Color conversion is performed by Q-dots. The advantage of this design is the high light efficiency, since the color filter does not absorb light, but only converts and because the design of the light distribution module through its monochromatic (blue) outcoupler is simplified by the use of only one layer

Another object of the present invention relates to a visual display, in particular a display of a television, mobile phone, computer and the like, wherein the display is a light display. Distribution module according to the present invention includes The displays according to the invention comprises in addition to the light distribution module according to the invention usually a translucent digital spatial light modulator and a lighting unit Due to the low height of the Lichtverteirungsmoduls invention this is particularly suitable for compact thin designs and energy-efficient displays, as for televisions, Computei screens , Laptops, tablets, smartphones or other similar applications are needed.

In a preferred embodiment of the optical display according to the invention contains only essentially blue light emitting light sources, wherein a color conversion to green and red light by means of Q-dots in a Quantumrail in the light source, in the holographic optical elements of the coupling device, in a diffuser or in a Color filter is done

If you dispense with the usually rearward display housing and does not use rear mirroring, these lighting units are particularly suitable for transparent displays that find a variety of applications in point-of-sale displays, advertising applications in shop windows, in transparent information boards at airports, train stations and other public Places, in automotive applications in the headliner and as information displays in and on the dashboard and the windshield of an automobile, in window glass panes, in sales refrigerators with transparent doors or other household appliances. If desired, this can also be performed as a curved or flexible display.

The invention is explained in more detail below with reference to the drawings in the drawings

1 is a sectional view of a first embodiment of a display according to the invention rmt holographic optical elements in the transmission mode,

2 is a schematic side view of a second embodiment of a display according to the invention with holographic optical elements in the reflection mode,

3 is a schematic side view of a third embodiment of a display according to the invention with holographic optical elements in the transmission and reflection mode,

4 is a schematic side view of a fourth embodiment of a display according to the invention with three different types of holographic optical elements in the transmission mode for each primary color, 1 is a schematic detail view of FIG. 1 showing two beam paths and diffuse, directed diffraction of one of the beams through a holographic optical element in the direction of a diffuser containing a transparent layer (diffusion plate), FIG.

6 shows a schematic detail view of FIG. 1 showing three beam paths with different angles of incidence and diffuse, directed diffraction of one of the beams by a holographic optical element, FIG.

7 shows a schematic detail view of FIG. 6 with representation of three beam paths with different angles of incidence from an opposite direction to FIG. 6 without diffraction of the beams, FIG.

8 shows a schematic detail view of FIG. 2, showing a beam path and diffuse, directed diffraction by a holographic optical element and use of an additional diffuser (scatter plate) without a further transparent layer, FIG.

9 shows an alternative embodiment to FIG. 8 with a holographic optical element which has a reflective effect, FIG.

10 shows a schematic detail view of FIG. 2, showing a beam path and exclusively directed diffraction by a holographic optical element and use of two additional diffusers (scatter plates) separated by a transparent layer, FIG.

11 shows an alternative embodiment to FIG. 9 with a holographic optical element which has a reflective effect, FIG.

12 is a Auskopplungseinrichturig with holographic optical elements with increasing along the direction of irradiation diffraction efficiency in the plan view obliquely from above

13 is a Auskopplungseinrichturig with holographic optical elements with decreasing distances along the irradiation direction in the plan view obliquely from above

FIG. 14 shows an outcoupling device with holographic optical elements having an increasing size along the direction of irradiation in a top view obliquely from above, FIG.

15 is a coupling device with rectangular, holographic optical elements with decreasing distance in the transverse direction in plan view obliquely from above, 16 is a coupling-out device with holographic optical elements which bend in orthogonal planes to each other light in the top view obliquely from above,

FIG. 17 shows a coupling-out device with holographic optical elements which bend light in planes which are successively rotated in steps of 45 ° in a plan view obliquely from above, FIG.

18 a coupling-out device with holographic optical elements, which diffract light of different frequency bands (wavelength bands) in the drainage obliquely from above,

19 a coupling device with holographic optical elements which successively diffract light of different frequency bands (wavelength bands), wherein the planes in which they bend light are successively rotated in 45 ° steps relative to one another in the top view obliquely from above,

FIG. 20 shows an outcoupling device with partially overlapping holographic optical elements grouped into element sets, which bend light of varying frequency bands (wavelength bands) obliquely from above in the plan view, FIG.

21 a coupling device with a distribution of holographic optical elements of the same shape, diffraction direction, diffraction plane and diffraction efficiency, wherein the distribution of the holographic optical elements ensures a uniform light distribution of two light sources, which are positioned on one or more end faces in the plan view obliquely from above,

22 shows a coupling-out device with adjoining and partially overlapping holographic optical elements having the same shape and diffraction direction and diffraction plane and a varying diffraction efficiency, which ensures a uniform light distribution of two light sources, which are positioned at one or more end faces in the plan view of oblique above.

According to a first preferred embodiment, as shown schematically in Figure 1, the display 10 according to the invention consists of a light guide plate 1 and a coupling device 2 containing holographic optical elements 13 in the form of volume gratings in the transmission mode. The light guide plate 1 and the decoupling device 2 are in optical contact with each other. The light guide plate 1 consists of a transparent plastic preferably a largely birefringence-free amorphous thermoplastics, more preferably of polymethylmethacrylate or polycarbonate The Lichtfuhrungsplatte is between 50-3000 microns, preferably between 200-2000um and more preferably between 300-1500um thick. The optical contact between the light guide plate 1 and the decoupling device 2 can be achieved by direct lamination of the decoupling device 2 on the Lichtfuhrungsplatte 1. It is also possible to realize the optical contact by means of a liquid, ideally a liquid which corresponds to the refractive index of the light guide plate 1 and the coupling-out device 2. If the refractive index of the light guide plate 1 and the coupling-out device 2 differs, the liquid should have a refractive index. The liquid lying between those of the light guide plate 1 and the decoupling device 2 Such liquids should have a sufficiently low volatility for a permanent adhesive application. Also, the optical contact can be made possible by an optically clear (contact) adhesive, which is applied as a liquid. Likewise, the optical contact can be realized by means of a transfer adhesive membrane. Also, the refractive index of the optically clear adhesive and the transfer adhesive should ideally be between that of the light guide plate 1 and the outcoupler 2. Preferably, the optical contact is by means of liquid adhesive and transfer adhesive.

It is also possible to optionally mirror the light guide plate 1 on one side, preferably on the side adjacent to air, as by metallization (eg Auflamination of metal foils, metal deposition in vacuo, applying a dispersion of metal-containing colloids with subsequent sintering or through Applying a metal-ion-containing solution followed by a reduction step) can be achieved. Here, a reflection layer 7 is generated, which is also in optical contact with the light guide plate 1

It is likewise possible to improve the waveguide properties by means of a coating with a specifically lower refractive index, preferably at interfaces of the light guide plate 1 which are in direct optical contact with further transparent components and are not covered by holographic optical elements 13. Furthermore, it is possible to use multi-layer structures having alternating refractive indices and layer thicknesses. Such multilayer structures with reflection properties usually contain organic or inorganic layers whose layer thicknesses are of the same order of magnitude as the wavelength (s) to be reflected.

The decoupling device 2 consists of a recording material for volume holograms 13. Typical materials are holographic silver halide emulsions, dichromated gelatin or Photopolymers. The photopolymer consists at least of a photoinitiator system and polymerizable writing monomers. Special photopolymers may additionally contain plasticizers, thermoplastic binders and / or crosslinked matrix polymers. Preference is given to photopolymers containing crosslinked matrix polymers. It is particularly preferred that the photopolymers consist of a photoinitiator system, one or more random monomers, plasticizers, and crosslinked matrix polymers.

The decoupling device 2 can also have a layer structure, for example an optically transparent substrate and a layer of a photopolymer. In this case, it is particularly expedient to laminate the decoupling device 2 with the photopyristor directly onto the light guide plate 1.

It is also possible to carry out the coupling-out device 2 in such a way that the photopolymer is enclosed by two thermoplastic films. In this case, it is particularly advantageous for one of the two thermoplastic films which adjoin the photopolymer to be provided with an optically clear adhesive film on the light guide plate 1 is attached. The thermoplastic film layers of the decoupling device 2 are made of transparent plastics. Preference is given to using largely birefringence-free materials such as amorphous thermoplastics. Polymethyl methacrylate, cellulose triacetate, amorphous polyamides, polycarbonate and cycloolefins (COC) or else blends of the abovementioned polymers are suitable. Also glass can be used for this. In a preferred embodiment, the light distribution module comprises a diffuser 5, which consists of a transparent substrate 6 and a diffusely scattering layer 6 '. The diffuser is a volume spreader. The diffusely scattering layer can consist of organic or inorganic scattering particles which are non-absorbing in the visible region and embedded in a lacquer layer and which are preferably shaped like spheres. The scattering particles and the lacquer layer have different refractive indices.

In a further preferred embodiment, the light distribution module comprises a diffuser 5 which consists of a transparent substrate 6 and a diffusely scattering and / or fluorescent layer 6 '. The diffusely scattering or fluorescent layer may consist of visibly non-absorbing organic or inorganic scattering particles which in whole or in part can be replaced by red or green fluorescent Q-dots and which are embedded in a lacquer layer The scattering particles and the lacquer layer have different refractive indices.

The display 10 according to the invention further comprises a translucent digital light modulator L, e.g. The liquid crystal module can have various configurations, in particular the liquid crystal switching systems known to the person skilled in the art can be used which achieve certain advantageous efficient shading of light with different beam geometries can. Special mention should be made of twisted nematic (TN), super twisted nematic (STN), double super twisted nematic (DSTN), triple super twisted nematic (TSTN, film TN), vertical alignment (PVA, MVA), in-plane switching (IPS), S-IPS (Super IPS), AS-IPS (Advanced Super IPS), A-TW-IPS (Advanced True White IPS), H-IPS (Horizontal IPS), E-IPS (Enhanced IPS), AH -IPS (Advanced High Performance IPS) and ferroelectric pixelated light modulators.

Figure 2 shows a second embodiment of a display 10 according to the invention, which differs from the first embodiment of Figure 1 in that the outcoupling device 2 containing the holographic optical elements 13 is now arranged on the opposite side surface of the light guide plate 1 and diffracts light in the reflection mode.

FIG. 3 shows a third embodiment of a display 10 according to the invention, which differs from the first embodiment of FIG. 1 in that two outcoupling devices 2 are arranged with holographic optical elements 13 on both flat sides of the light guide plate 1, wherein the first outcoupling device 2 in the transmission and the other output device 2 diffracts light in the reflection mode

FIG. 4 shows a fourth embodiment of a display 10 according to the invention, which differs from the first embodiment of FIG. 1 in that three outcoupling devices 2 a, 2 b, 2 c are arranged one above the other on a flat side of the light guide plate 1, wherein each of these outcoupling devices 2 a, 2 b 2c contains holographic optical elements 13 which diffract light in the transmission mode. In this case, it is possible for each of the coupling-out devices 2a, 2b, 2c to diffract only one of the primary colors "red", "green" and "blue" or else to diffract all of the wavelength components of the visible light.The wavelengths of the primary colors red, green and blue are determined by the emission wavelength of the light sources used. It is also possible more than the three primary colors "red", "green" and "blue" to use, for example, "yellow" and the like.

The use of a plurality of photographic optical elements 13, which diffract light only for certain selected light sources (for example red, green and blue), is possible in particular with photopolymer layer thicknesses> 5 μm. It is possible to laminate three photopolymer layer thicknesses of> 5 .mu.m in each case and to describe them separately beforehand in each case. It is also possible to use only one photopolymer layer> 5 μm, but to inscribe all three color-selective photographic optical elements 13 simultaneously or in succession. Furthermore, it is possible to use photopolymer layers <5 μm, preferably <3 μm and particularly preferably <3 μm and> 0.5 μm. In this case, only a photographic optical element 13, preferably having a wavelength lying in the spectral center of the visible electromagnetic spectral range, is also written. Also, this one wavelength at which the photographic optical element 13 is written may also be in the geometric mean of the two wavelengths the long-wave light source and the short-wave light source are. It should also be considered that inexpensive and sufficiently powerful lasers are available. Preference is given to Nd: YV04 crystal lasers with 532 nm and argon ion lasers with 514 nm

The simplest holographic optical elements 13 consist of diffractive gratings which diffract light by a refractive index modulation corresponding to the grating. The lattice structure is generated photonically in the entire layer thickness of the recording material by exposure by means of two interfering, collimated and mutually coherent laser beams. It differs from so-called surface holograms (embossed folograms) in that the diffraction efficiency is significantly higher and theoretically 100 %, the frequency and angle selectivity is set with the active layer thickness and that due to the geometries of the holographic exposure, there is freedom to set the corresponding diffraction angle (Bragg condition).

The production of volume photograms is known (H.M. Smith in "Principles of Holography" Wiley-Interscience 1969) and can be done, for example, by two-beam interference (S. Benton, "Holography Imaging", John Wiley & Sons, 2008).

Methods for bulk duplication of reflltered volume photograms are described in US Pat. No. 6,824,929 wherein a photosensitive material is positioned on a master photogram and subsequently copied by means of coherent light. The production of transmission holograms is also known. For example, US 4,973,113 describes a method by means of a role replication.

In particular, attention should also be drawn to the production of edgelit holograms which require special exposure geometries. In addition to the introduction by S. Benton (S. Benton, "Holography Tmaging", John Wiley & Sons, 2008, Chapter 18) and a review of classical two- and three-stage manufacturing processes (see Q. Huang, H. Caulfield, SPIE VoL 1600, International Symposium on Display Holography (1991), p. 182), reference is also made to WO 94/18603 which describes edge modulation and waveguide holograms. Furthermore, special production methods based on a special optical adapter block are disclosed in WO 20067111384 Holographic optical elements 13 containing directed laser light are preferably edged with holograms, which are particularly preferred volume gratings since they work with steeply incident light which couples in with total reflection

FIG. 5 shows a detail of the structure from FIG. The light beams 11 and 12 coupled in by the light source follow the total reflection and propagate in the light guide plate 1. The interface of the total reflection is the interface between the light guide plate 1 and air or the optional reflection layer 7 on the one side and the interface from the output device 2 containing the holographic optical elements 13 and air. If the decoupler 2 contains other thermoplastic layers (e.g., as a protection or substrate foil), then the total reflection will take place on the layer that is in direct contact with the air

Upon passage of the light beam 11 through the output device 2, no light is diffracted; since it passes through no diffractive directive optical element 13 (see position IS). The beam is also not diffracted in the other holographic optical element 13; because there the Bragg condition is not fulfilled; while in the passage of the light beam 12 through the Auskopplungsein- device 2 in the holographic optical element 13, the light is diffracted in the direction of the translucent digital spatial light modulator. At this time, the holographic optical element 13 simultaneously exhibits a diffuser characteristic which was imprinted in the production of the holographic optical element 13.

The slightly expanded diffuse light beam impinges on the diffuser S constructed of transparent layer 6 and diffuser layer 6 'and is further widened. This diffuse expansion is advantageous; to enable a largely angle-independent viewing of the display. Important for the position of the holographic optical elements 13 is now the homogeneous light intensity at the location of the diffuser S. The thickness of the transparent layer 6, the angle of divergence of the diffraction of all holographic optical elements 13 and the position of the light sources play a role. A person skilled in the art can determine the optimal distribution for a specific design by means of iterative simulation and experiments.

Figure 6 describes in detail the angular selection of the holographic optical element 13. Only the beam 20 is thereby deflected, while the light beams 21 are not diffracted with slightly different angles of incidence, which do not follow the Bragg condition. If the holographic optical element 13 consists of a plurality of frequency-selective sub-holograms (that is to say, for example, red, green and blue light), the layer thickness> 5 μm must be selected. The angle selection is chosen in this case; The advantage of this approach is the ability to adjust chromatic aberrations and general color matching by individually adjusting the diffraction efficiency for each color.

If one selects a layer thickness of the output device 2 in the range of> 0.5 μm to 5 μm, an angle selection of approximately 5-30 ° is generated and has a good diffraction efficiency for all wavelength ranges of the visible light.

Since light sources couple the light into the light guide plate 1 in a wide angular range, the holographic optical elements 13 select these rays and leave those non-Bragg rays in the light guide plate 1. By judicious choice of shape and size or diffractive efficiency or the distribution of the holographic optical elements 13 on the light guide plate or by the diffraction direction or by wavelength selection or by a combination of two or more of these properties, it is possible to uniformly adjust the light homogeneity of the diffuser 5. The light guide plate 1 thus serves as a light reservoir to which the holographic optical elements 13 "extract" light and decouple this purposefully onto the diffuser 5.

Figure 7 shows the analog light beams 25, all of which are not diffracted, since the holographic optical elements 13 diffract the light directionally selective. Thus, light rays reflected at the edge of the light guide plate 1 can not be diffracted by the holographic optical element 13 (at the position 26). Only when these are again reflected on the other edge of the Lichtfuhrungs- plate 1, a new bending of the light is possible. Figure 8 shows a further inventive embodiment in which a transmissive holographic optical element 13, which is read in reflection, is used. The light beam 12 is irradiated into the Lichtfuhrungsplatte 1 After propagation under total reflection, it passes through the holographic optical element 13 in the decoupler 2 and is bent at the position 14 under the Bragg condition The holographic optical element 13 diffracts the beam into a divergent diffuse beam now after exiting the Lichtfuhrungsplatte 1 directly to the diffuser S meets, which then again generates an angular dispersion; so that in the illumination of the light-transmitting digital spatial light modulator L, not shown, a homogeneous, divergent surface light is present advantage of this structure is the more compact design, as can be dispensed with an additional Abslandschicht.

FIG. 9 shows a further inventive embodiment in which a holographic optical element 13 having a reflective effect is used. The light beam 12 is irradiated in the light guide plate 1. The light passes the holographic optical element 13 in the outcoupler 2 in the rearward direction and is diffracted at the position 14 under the Bragg condition. The holographic optical element 13 diffracts the beam into a divergent diffused beam now After exiting the Lichtfuhrungsplatte 1 directly to the diffuser 5, which then again generates an angular dispersion, so that in the illumination of the light-transmitting digital spatial light modulator L, not shown, a homogeneous, divergent surface light is present advantage of this structure is the more compact design, as a additional spacer layer can be dispensed with. Furthermore, it is possible to dispense with the embodiments shown in Figure 5, Figure 8 and Figure 9 on the diffuser 5, when the density and distribution of the holographic optical elements 13 in the transparent layer 2 is such that already by the diffuser property of the elements 13 a sufficiently homogeneous light distribution on the translucent digital spatial light modulator L is achieved. In particular, when smaller holographic optical elements 13 and / or overlapping holographic optical elements 13 are used, this is advantageous; because the entire layer structure can be constructed thinner.

FIG. 10 shows a further inventive embodiment in which a transmissively acting holographic optical element 13 which is read in reflection is used. Light beam 12 is irradiated into the light guide plate 1 After propagation under total reflection, it passes through the holographic optical element 13 in the decoupling device 2 and is diffracted at the position 14 under the Bragg condition. The holographic optical element 13 diffracts the beam into a directed beam which Now after exiting the Lichtfühnmgsplatte 1 first on a diffuser. 5 meets where the love divergent is scattered diffusely. At position 16, this light then impinges on a second diffuser 5, which diffuses again diffusely. The first diffuser S is used to homogenize the light intensity, the second serves to disperse the emission angle in order to allow a wide angle view of the display 10. The advantage of this structure is the high diffraction efficiency that can be achieved with such a holographic optical element 13. One or both pushers 6 'may contain scattering or fluorescent particles.

FIG. 11 shows an alternative embodiment to FIG. 10, in which a holographically optical element having a reflective effect is used. The light beam 12 is radiated into the light guide plate 1. The light passes the holographic optical element 13 in the output device 2 in the rearward direction and is diffracted at the position 14 under the Bragg condition. The holographic optical element 13 diffracts the beam into a directed beam now after exiting the Lichtfuhrungsplatte 1 on a first diffuser layer 6 'in the diffuser 5 meets, where the light is divergently diffused scattered. At position 16, this light then impinges on a second diffuser layer 6 ', which diffuses again diffusely. The first diffuser layer 6' is used to homogenize the light intensity, the second serves to disperse the emission angles in order to allow a wide angle view of the display. The advantage of this structure is the high diffraction efficiency that can be achieved with such a holographic optical element 13.

Different embodiments with respect to the arrangement of the holographic optical elements in the coupling-out device 2 are shown in FIGS. 12-19. This is an oblique perspective view from the user side of the display. In FIG. 12, the light beam 12 propagating under a total depth is symbolized by an arrow. The outgoing light beam 17 points in perspective at the observer. In this simplest embodiment, the holographic optical elements 13 are shown as a circle However, there is no limit to the choice of shapes. It is thus possible to choose not only circular shapes but also ellipses, squares, triangles, polygons, trapezoids, parallelograms or any other shapes. The illustrated circles are selected as such only from the point of view of the simplified graphical representation

As a rule, the luminance distribution is not homogeneously distributed during edge illumination. FIG. 12 shows an example where such a horizontal luminance distribution is compensated for by increasing the diffraction efficiency of the holographic optical elements 30 to 36. not only using linear or geometric changes in diffraction efficiency, but also irregular variable diffraction efficiencies. This is special in lighting effects at corners of the optical waveguide or by the coupling characteristic of the light sources of advantage

FIG. 13 shows a further possible arrangement; compensate for different luminance distributions in the light guide plate 1. At this time, the distance between the holographic optical elements 40 to 46 is changed. The advantage of this arrangement is that the holographic exposure conditions in the production of all holographic optical elements 13 can be chosen to be the same.

FIG. 14 shows a further possible arrangement for compensating different luminance distributions in the light guide plate 1. At this time, the size of the holographic optical elements 50 to 56 is changed. Advantage of this arrangement is that the holographic exposure conditions in the production of all holographic optical elements 13 can be chosen the same.

FIG. 15 shows a further possible arrangement for compensating different luminance distributions in the light guide plate 1. In this case, as in FIG. 14, the size of the holographic optical elements 13 is changed. In contrast to this, other shape patterns of the holographic optical elements 60-61 are selected. The advantage of this arrangement is that the holographic exposure conditions can be selected to be the same in the production of all holographic optical elements 13.

FIG. 16 shows a further possible arrangement for compensating different luminance distributions in the light guide plate 1. In this case, the direction of the diffraction planes of the holographic optical elements 70 to 73 is changed in 90 ° steps. The advantage of this arrangement is that the light beams present in the light guide plate under total reflection can be coupled out more directly and thus more efficiently. Also, such a design is advantageous when the light sources are positioned at more than one edge of the light guide plate. FIG. 17 shows a further possible arrangement for compensating different luminance distributions in the light guide plate 1. At this time, the direction of the diffraction planes of the holographic optical elements 70 to 77 is changed to 45 °. The advantage of this arrangement is that the light beams present in the light guide plate under total reflection can be coupled out more directly and thus more efficiently. Also, such a design is advantageous when the light sources are positioned at more than one edge of the light guide plate 1. It is important It is pointed out that in principle any form of directional dependence of the holographic optical elements 13 can be used and that there is no restriction to certain angles

In Figure 18, another possible arrangement is shown; compensate for different luminance distributions in the light guide plate 1. At this time, the spectral range (color) in which the holographic optical elements 80 to 82 diffract light is changed. It makes sense to use chromatically narrow emitting light sources, such as e.g. narrow emissive light emitting diodes (LEDs), which have between 5-100nm, preferably 10-50nm and most preferably 10-35nm bandwidth. Advantage of this arrangement is to compensate for the primary colors specific luminance distributions in the light guide plate 1. As already shown in FIG. 4; can be operated by a respective decoupling device 2 a, 2 b and 2 c per one primary color. Of course, it is also possible in a layer 2, as shown in Figure 1; to engrave the hobgobical optical elements 80-82. However, it is important that the layer thickness be at least 5 μm in order to set a sufficiently narrow spectral Bragg condition.

In a related embodiment of FIG. 18, when only blue LEDs or laser diodes are used as the light source, only such holographic optical elements can be used that are tuned to the wavelength of the blue light source. Red and green spectral components are then obtained by applying suitable Q-dots to a part of the holographic optical elements. The elements 80 to 82 then represent holographic optical elements to which either no Q-dots have been applied or red or green emitting Q-dots. Mixtures of red and green emitting Q-dots are possible as a coating.

In Figure 19, another possible arrangement is shown; compensate for different luminance distributions in the light guide plate 1. In this case, the spectral range (color) in which the holographic optical elements 90-96 (eg for blue all marked 90, all for green with 91 and all for red with 92 marked holographic optical elements) diffracts light with the diffraction planes of holographic optical elements (marked 93-96) combined and varied in 45 ° increments. The advantage is a further adaptation and optimization of the light homogeneity

In Figure 20, another possible arrangement is shown; compensate for different luminance distributions in the light guide plate 1. This is related to that in Fig. 18, where spectrally diffracting holographic optical elements 101-103 are used. In Figure 20, the holographic optical elements 101-103 are positioned partially overlapping each other and have a high diffraction efficiency for a specific visible light spectral range. This is possible by using three separate layers placed one above the other or by building them in a layer. The former has the advantage that the requirement for the dynamic range of the recording medium (ie the ability to generate holographic gratings) is lower and the production of the layers takes place separately The second possibility shows a simplified structure, which makes it possible to realize thinner layer structures.

Fig. 20 shows a case which can be manufactured by means of negative and positive mask. The desensitization of the recording material is carried out by a negative mask, so that the areas without holographic optical element are defined thereby. Thereafter, the red, green and blue holographic optical elements with the respective lasers are sequentially written in the recording material with three positive masks.

FIG. 21 shows a particularly preferred arrangement of the holographic optical elements 13 in order to compensate for different luminance distributions in the light guide plate 1 which is illuminated by two light sources 110. The holographic optical elements 13 are of the same size, diffraction efficiency and diffraction direction, whereby the homogeneous light distribution in the transparent layer 2 is made possible by different density distribution and arrangement of the holographic optical elements 13 to the two light sources 110. In this case, the number per area of the holographic optical elements 13 of the edges at which there are light sources 110 is added to the center of the light guide plate 1.

FIG. 22 shows a further possible arrangement for compensating different luminance distributions in the light guide plate 1, which is illuminated by two light sources 110. The holographic optical elements 30-35 are of different diffraction efficiency at the same diffraction direction. Furthermore, the holographic optical elements 30-35 overlap each other.

LIST OF REFERENCE NUMBERS

(1) light guide plate

(2) decoupling device

(2a) - (2c) decoupling device

(3) transmissive pixelated light modulator

(4) color filter

(5) Difiusor

(6) Transparent layer

(6 ') Diflusor layer

(7) reflection layer

(8), (9) polarizing filter (crossed)

(10) Display

(10 ') lighting unit

(11) Light beam that does not conform to the Bragg condition (12) Light beam that corresponds to the Bragg condition

(13) Holographic optical element, volume grating

(14) Place the diffraction of the light beam

(15) Point at which no diffraction occurs

(16) Place the scatter in a Difiusor

(17) Divergent light beam

(20) Beam corresponding to the Bragg condition

(21) Light rays that do not conform to the Bragg condition (25) Light rays that do not conform to the Bragg condition

(26) Where no flexion occurs

(30) - (36) Holographic optical elements of the same size and different diffraction efficiency

(40) - (46) Holographic optical elements of equal diffraction efficiency with different close spatial position to each other

(50) - (56) Holographic optical elements of different sizes

(60), (61) Holographic optical elements in a rectangular shape

(70), (71) Holographic optical elements with diffraction efficiency in vertical alignment

(72), (73) Holographic optical elements with diffraction efficiency in horizontal alignment

(74) - (77) Holographic optical elements with diffractive efficiency in diagonal orientation

(80) Holographic optical element with diffraction efficiency in the green wavelength region

(81) Holographic optical element with diffraction efficiency in the red wavelength range

(82) Holographic optical element with diffraction efficiency in the blue wavelength range

(90) Holographic optical element with diffraction efficiency in the blue wavelength range

(91) Holographic optical element with diffraction efficiency in the green wavelength range

(92) Holographic optical element with diffraction efficiency in the red wavelength range

(93), (95) Holographic optical elements with diagonal diffraction efficiency

(94) Holographic optical elements with horizontal diffraction efficiency (96) Holographic optical elements with vertical diffraction efficiency

(101) Overlapping holographic optical element with diffraction efficiency in the green

Wavelength range

(102) Overlapping holographic optical element with diffraction efficiency in the red

Wavelength range

(103) Overlapping holographic optical element with diffraction efficiency in blue

Wavelength range

(110) light source

L light modulator

Claims

Patent claims:

1. Planer light distribution module for a display, comprising a light guide plate through which light that can be coupled in via at least one side surface can propagate by means of total reflection and at least one planar decoupling device (2) attached to one or both of the main surfaces of the light guide plate (1) and in optical contact with it. , in which a plurality of holographic optical elements (13), which are designed so that they can couple out light from the light guide plate (1), are arranged, characterized in that the holographic optical elements (13) in the decoupling device (2) with respect to at least two spatial dimensions are arranged without translational symmetry and the holographic optical elements (13) are designed as a volume grid.

2. Light distribution module according to claim 1, characterized in that there is no two-dimensional repeat sequence for the arrangement of the holographic optical elements (13) in the decoupling device (2) and / or that the number of holographic optical elements (13) per area of at least one edge increases towards the center of the decoupling device (2).

3. Light distribution module according to claim 1 or 2, characterized in that at least 30 holographic optical elements (13) are arranged in the decoupling device (2), in particular at least 50.

4. Light distribution module according to one of the preceding claims, characterized in that the holographic optical elements (13) are formed in the decoupling device (2) and extend from one of the flat sides of the decoupling device (2) into it and / or completely penetrate it, wherein the decoupling device (2) is in contact with the light guide plate (1) in particular with that flat side on which the holographic optical elements (13) are located.

5. Light distribution module according to one of the preceding claims, characterized in that the decoupling device (2) or the light guide plate (1) with a reflection layer 7 is provided, which is attached to the flat side opposite the output direction of the light

6. Light distribution module according to one of the preceding claims, characterized; that the diffraction efficiency of the holographic optical elements (13) is different, the diffraction efficiency of the holographic optical elements (13) increasing in particular along an irradiation direction for light into the light guide plate (1).

7. Light distribution module according to one of the preceding claims, characterized in that the holographic optical elements (13) can couple out light from the light guide plate (1) at least in the wavelength range from 400 to 800 μm and/or that the holographic optical elements (13) emit light wavelength-selective can be coupled out, in particular at least three groups of holographic optical elements (13) being present, each of which is wavelength-selective for red, green and blue light.

8. Light distribution module according to one of the preceding claims, characterized in that the holographic optical elements (13) are designed such that the light coupled out by them passes completely through the decoupling device (2) transversely.

9. Light distribution module according to one of the preceding claims, characterized in that the holographic optical elements (13) are designed such that the coupled-out light is reflected and passes transversely through the light guide plate (1) after coupling-out,

10. Light distribution module according to one of the preceding claims, characterized in that at least one decoupling device (2) is arranged on both flat sides of the light guide plate (1) and / or at least two decoupling devices (2) on a flat side of the light guide plate (1).

11. Light distribution module according to one of the preceding claims, characterized in that at least three outcoupling devices (2a, 2b, 2c) are arranged on a flat side of the light guide plate (1), the three outcoupling devices (2a, 2b, 2c) each being for contain exactly one color of light wavelength-selective holographic optical elements (13), in particular for red, green and blue light

12. Light distribution module according to one of the preceding claims, characterized; that the decoupling device (2) has a thickness of 0.5 μm to 100 μm, in particular of

0.5 μm to 40 μm, preferably a thickness of at least 5 μm.

13. Light distribution module according to one of the preceding claims, characterized in that the decoupling device (2) contains silver halogen emulsions, dichromate gelatin, photorefractive materials, photochromic materials and / or photopolymers, in particular photopolymers containing a photoinitiator system and polymerizable writing monomers, preferably containing photopolymers Photoinitiator system, polymerizable writing monomers and cross-linked matrix polymers.

14. Light distribution module according to one of the preceding claims, characterized in that the holographic optical elements (13) independently of one another have an extension of at least 300 μm in at least one spatial axis running parallel to the surface of the output device (2), in particular at least 400 μm or even at least 500 μm

15. Light distribution module according to one of the preceding claims, characterized in that the holographic optical elements (13) independently of one another in the surface of the decoupling device (2) have a circular, elliptical or polygonal, in particular triangular, quadrilateral, five or hexagonal, trapezoidal or have a parallelogram-like cross-section and/or that the individual holographic optical elements (13) of a decoupling device (2) partially overlap, in particular the surface of the decoupling device (2) being largely completely covered with holographic optical belts

16. Light distribution module according to one of the preceding claims, characterized in that on that flat side of the light guide plate (1) and / or decoupling device

(2) on which the light is emitted at least one diffuser (5) is arranged, which is preferably spaced from the light guide plate (1) and/or the decoupling device (2), preferably less than or equal to 0.1 mm, in particular less than or equal to 0.05mm.

17. Light distribution module according to one of the preceding claims, characterized in that the holographic optical elements (13) have a diffuser function.

18. Optical display, in particular the display of a television, mobile phone, computer and the like, characterized; that the display includes a light distribution module according to one of claims 1 to 17

19. Optical display according to claim 18, characterized in that only light sources (110) emitting essentially blue light are used, with a color conversion to green and red light using Q-dots in a quantum rail in the light source (110), in the holographic optical Elements (13) of the decoupling device (2), in a diffuser (5) or color filter (4).