EP2883092A1

EP2883092A1 - Light guide plate comprising decoupling elements

Info

Publication number: EP2883092A1
Application number: EP13747843.4A
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: TWI617847B; IN2015DN01063A; JP2018195589A; KR20150043391A; US20150205034A1; JP2015525960A; CN104871051A; RU2015108651A; WO2014026918A1; TW201421084A

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) independently of one another extend by at least 300 μm along at least one spatial axis running parallel to the surface of the decoupling system (2). The invention also relates to an optical display, in particular an electronic display, the holographic optical elements (13) independently of one another having a surface that is 1.5 times greater than the pixels of the liquid crystal module.

Description

Light guide plate with decoupling elements

The invention relates to a planar light distribution module for a display, comprising a light guide plate can propagate through 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 Lichtfuh- rungsplatte and with this in optical contact planar coupling device with a Variety formed therein holographic optical elements which are designed so that they can decouple light from the light guide plate. The invention also relates to a visual display, in particular an electronic display with a light distribution module.

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

Typically, cold cathode light sources and light emitting diodes (LEDs) are used to generate light in the backlight unit (BLU). The off-radiation characteristic of these light sources is such that they emit relatively non-directional 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. If you also use LEDs in direct lighting, they can also be dimmed, which makes it possible to increase the contrast of the display. A disadvantage is the high cost, since a large number 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 in at the edge and is transported by total reflection into the interior. By on the surface side of the light guide plate mounted Lichtauskoppelelemente the light is thereby directed forward in the direction of the LC panel Typical light extraction elements are printed patterns of white color, the roughening of the surface of Lichtfüh- rungsplatt e 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, one is looking for ways to make energy-efficient displays with better presentation qualities possible. An important aspect is the enlargement of the color space (gamut) 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 large number of light paths, which must be homogenized again by the diffuser and prism foils lying between the light guide plate and the LC panel and then re-directed 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 diffractive surface structure is adapted to the efficiency of the coupling-out. However, the effective efficiency is considered low due to only one frequency in the lattice 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 impressing 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 coupling-out properties of coupling-out efficiencies. Park et al. (Optics Express 15 (6), 2888-2899 (2007)) report dot-matrix diffractive point-like surface structures, but only achieve 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 one another, positioned obliquely in the light guide plate. However, the production of volume holograms in light guide plates is very cost-intensive. 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 higher-resolution display panels Furthermore, the production costs increase significantly when using the aforementioned methods in the increasingly high-resolution displays. In particular, the exact alignment of the grid points on the smaller and smaller pixels of the display is extremely problematic.

The object of the present invention was therefore to provide an improved display design with a particularly flat and compact light distribution module that can efficiently and homogeneously project light onto a translucent digital light modulator. The light distribution module should also allow a reduction in the number of light sources and thus make the production of optical displays cheaper. The light distribution module should also be suitable for use in high-resolution displays. This object is achieved in a light distribution module of the type mentioned by a planar light distribution module for a display, comprising a Lichtführungsplatt e propagate through which at least one side surface einkoppelbares light by total reflection and at least one attached to one or both of the main surfaces of the light guide plate and with this in planar contact with a plurality formed therein holographic optical elements which are configured so that they can decouple light from the light guide plate, wherein the light distribution module is characterized in that the holographic optical elements independently an extension in at least one of the surface of the Extending device parallel spatial axis of at least 300 μιη and have at least 1, 5 times as large area as the pixels of the display.

In this case, the invention is based on the knowledge that, unlike the previously customary constructions, no discrete assignment of the holographic optical elements to a single pixel of a display is required, so that the individual holographic optical elements can have a significantly larger areal extent than the pixels of the display. Such a light distribution module can be made simpler and with lower overall height and yet, even with high-resolution displays - that is to say with correspondingly small pixels, it is possible to achieve a uniform illumination of the individual pixels. Thus, the holographic optical elements of a light distribution module according to the invention have, for example, an area at least 1.times as large as the pixels of the display, in particular an area at least twice or three times as large. In other words, when using a light distribution module according to the invention, it is therefore not necessary for the holographic optical elements to 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.

Thus, in the light distribution module according to the invention, the light can be emitted out of the light guide plate in a directionally directed manner and the homogeneous light extraction can be achieved by distributing the holo-graphical 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 angle range in the light guide plate. The holographic optical elements select these rays and leave those rays that do not follow the Bragg requirement in the light guide plate. By the skillful choice of the shape and size or the diffractive efficiency or the distribution of the holographic optical elements 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 on a diffuser. The light guide plate thus serves as a light reservoir to which the holographic optical elements "pull" light and decouple this purposefully to the diffuser .These and other possibilities are discussed in more detail below

Suitable light sources for the inventive displays are plasma emission lamps, such as, for example, cold cathode fluorescent lamps or other, for example, 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, wherein the color-converting phosphors also such semi-conductive nanoparticles (so-called quantum dots, Q-dots), which - as is known to those skilled - emit after excitation with blue or UV light in the appropriate red and green and possibly blue spectral range with high efficiency. Q-dots with the narrowest possible bandwidth of light emission are also preferred. In addition, combinations of at least three monochromatic, that is to say 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, rail-form element that includes appropriate Q-dots to convert to the blue light of the LED, to mix red and green narrow bandwidth light with high efficiency. 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 into the transparent layer is possible by various methods The holographic exposure is constructed such that either the signal beam or the reference beam, or both, is spatially modified by the mask in its intensity or polarization The mask can be made of, among other things, metal, plastic, strong cardboard or the like, and thus contains openings or areas in which the beam is transmitted or its polarization is changed, and holographically by interference with the second beam in the holographic recording film generated optical element. In areas where only one beam is up If the etching material is incident 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 lead to a holographic optical 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 inkjet printing 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 also influence the amplitude of the interference field. Suitable elements would be e.g. Linear polarizers, Lambda quarter 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 allow the spatial assignment there. It is also possible to modify the reference beam analogously with the mask. In the latter case, the "signal" information is distributed to the reference and the signal beam, since the reference beam with the mask defines the range, the signal beam introduces the diffuser characteristic. It is also possible first to generate a master hologram of the diffuser, that in a second If a master hologram is used, the positive mask is needed only for its production and may be dispensed with in the subsequent copying.

The output devices of the light distribution module, for example, by masking (positive mask), 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 printing 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 performed sequentially.

If different holographic optical elements are used for different reconstruction frequencies, a separate mask and another laser are used accordingly for each of these groups. Here, the exposures can be performed sequentially. It is also possible to provide each mask aperture with a color filter defining the color mapping. The exposure can then be done sequentially as well as simultaneously by means of a white laser consisting of 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 are adjacent to each other or overlap, the mask can be completely dispensed with and the glass sheet plastic film can be used alone for the exposure.

In addition to a positive mask, a negative mask can also be used. In this case, the areas which are exposed are desensitized by an incoherent preexposure. After this pre-exposure, the actual holographic exposure takes place in the remaining areas of the recording film. The incoherent preexposure can be achieved in different light intensities. Thus, it is possible to set any 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 directional selection take place selectively through the positive mask in the second step. The desensitization of the recording material takes place Thereafter, the three green masks sequentially write the red, green and blue holographic optical elements with the respective lasers into the recording material. It is also possible to provide each Positivemaskenöfmung with a color filter that defines the color assignment The exposure can then be done sequentially and simultaneously by means of a consisting of a red, green and blue white laser.

In another method, which is suitable for generating holographic optical elements in the decoupling device, each holographic optical element is sequentially optically printed. In this case, either the recording material is passed in front of an optical writing head via an xy translation stage or the optical writing head is moved by means of a xy positioning unit passed over the recording material. Each position is approached one after the other and the holographic optical element is imprinted by means of interference exposure. The method is suitable in particular for easy adjustment of the reconstruction directions of the individual holographic optical elements, since the rotation of the optical writing head or the recording material easy adjustment is possible. Of course, the write head can also contain other functions, such as color selectivity by using multiple laser or through flexible grayscale filters or polarization elements that can adjust the signal reference beam ratio.

It is also within the scope of the invention to first apply a holographic optical element to the surface of the light guide plate in a covering manner and to structure it in a subsequent step into isolated holographic optical elements by deleting the hologram in targeted areas or their diffraction property 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 characteristic of the holographic optical elements xy can be adapted to be adapted to different spectral regions of the visible spectrum by targeted local swelling or shrinkage. Suitable agents would be, for example, actinic radiation crosslinkable monomers of suitable refractive index, which are locally diffused and then crosslinked. This procedure can preferably be used when using photopolymers as recording material. 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, but an increased effort is required to protect the moisture-sensitive films in order to ensure adequate 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 nanoporous glasses. In addition, further properties can be specifically tailored to suit specific additives. In a particular embodiment, a photopolymer may also contain plasticizers, stabilizers and / or other additives. This is particularly advantageous in connection with photopolymers containing crosslinked matrix polymers, as described by way of example in EP2172505 Al. The photopolymers described herein have, as a photoinitiator, a photoinitiator system modulatable to the necessary wavelength, writing monomers containing actinically polymerizable groups and a highly crosslinked matrix polymer. If suitable additives, selected as described in WO 2011054796, are added, it is possible to produce 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. These materials are to be adjusted in terms of their mechanical properties over a wide range and can be adapted to many requirements both in the unexposed and exposed state (WO 2011054749 AI). 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 laminate the decoupling device with the photopolymer directly onto the light guide plate. It is also possible to design the decoupling device in such a way that the photopolymer of two thermoplastic films is enclosed. In this case, it is particularly advantageous that one of the two thermoplastic films adjacent to the photopolymer be attached to the light guide plate with an optically clear adhesive film.

The thermoplastic film layers of the coupling-out device are preferably made of transparent plastics. In this case, preference is given to using polymethylmethacrylate, cellulose triacetate, amorphous polyamides, amorphous polyesters, amorphous polycarbonate and cycloolefms (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.

In a further embodiment of the light distribution module according to the invention, the holographic optical elements are arranged irregularly in the outcoupling device. This is particularly advantageous because in this way a uniform illumination can be achieved. This is important because, depending on the type, number and orientation of the light sources with which light is fed into the light distribution module, other radiation conditions prevail in the Lichtfuhrungsplatte. These differences can be compensated by the above measure. In other words, in this embodiment of the invention, no uniform arrangement of the holographic optical elements is required in order to enable homogeneous light extraction from the Lichtfuhrungsplatte.

An irregular arrangement of the holographic optical elements in the decoupling device is understood in particular to mean that no two-dimensional repetition sequence exists for the arrangement of the holographic optical elements in the decoupling device, in other words does not involve a regularly repeating, equidistant arrangement of the holographic optical elements An aperiodic arrangement of the holographic optical elements can be described, for example, by a physical model in which the output configuration is a regular point grid with a dot spacing a, where each dot corresponds to a holographic optical element. Each point of the grid is assigned a point mass, which is connected to each of its four nearest neighbors by 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 to the value 0. For this function, f (x, y) can be assigned to 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 periodic grating. As a result, the average grid spacing can be selected larger and the manufacturing costs can be reduced. Furthermore, the greater average grid line spacing increases the light transmission of the output device. In addition, the occurrence of a Moir6 effect is prevented.

In advantageous he embodiment of the light distribution module according to the invention, the holographic optical elements are arranged in such a manner that the number of holographic optical elements per area of at least one edge to the center of the coupling-out increases. This arrangement applies in particular to such edges of the coupling-out device, which correspond to a side surface of the light guide plate, is coupled to the light from a light source. Thus, in the presence of two light sources disposed on opposite side surfaces of the light guide plate, the number of holographic optical elements per surface may increase from these two opposite edges to the center of the output device. If light sources are arranged on three or four side surfaces of the light guide plate, the aforementioned distribution applies correspondingly. If the light sources are punctiform light sources, an increased number of outcoupling elements near the edge of the light guide plate, in each case between the punctiform light sources, is additionally advantageous. The embodiment is analogous 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 decoupling 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 formed the holographic optical elements in the output device and extend from one of the flat sides of the output device in this and / or penetrate them completely. In such an embodiment, it is particularly preferred that the outcoupling device with that flat side 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 Auskoplungsseffizienz the holographic optical elements is improved. In the context of the present invention may further be provided that the coupling-out device or the light guide plate is provided with a reflective layer which is mounted on the opposite side of the coupling-out direction of the light flat side. This can be realized, for example, 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, wherein the diffraction efficiency of the holographic optical elements along a direction of incidence of light in the light guide plate starting from the edge of the outcoupling device increases in particular If opposing light sources are provided, takes the diffraction efficiency of the side edges starting at which the light sources couple the light in the light guide plate up to the center in an advantageous manner. If light sources are provided on 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-guiding plate, at least in the wavelength range from 400 to 800 nm. Nevertheless, holographic optical elements covering a broader wavelength range can also be provided. Conversely, it is also possible to use holographic optical elements which cover only a section of the visible wavelength range, in particular, for example, only the range of red, blue or green light or optionally additionally yellow light. In this way, a color selective coupling of individual light colors of white light from the light guide plate e can be realized. Consequently, a particularly preferred embodiment of the present invention is 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, wherein a fourth group for yellow light can be optionally used.

In a further embodiment of the light distribution module according to the invention, provision can be made for the holographic optical elements to be designed in such a way that the light emitted by the latter light passes through the output device transversely completely. In other words, therefore, transmissive coupling-out devices can be used. As an alternative or in addition to these transmissive coupling-out devices, the holographic optical elements can also be designed in such a way that the coupled-out light is reflected and the light-guiding plate is traversed transversely after being coupled out. 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 sputtered-on metal layer.

For the holographic optical elements used in the present invention, a variety of possible embodiments can be used, wherein the configuration is particularly preferred as a volume grating. In a further advantageous embodiment of the light distribution module according to the invention, in each case at least one outcoupling device can be arranged on both flat sides of the light guide plate and / or at least two outcoupling devices on a flat side of the light guide plate. 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 .mu.m, preferably .gtoreq.5 .mu.m and .ltoreq.100 .mu.m, particularly preferred .gtoreq.10 .mu.m and.ltoreq.40 .mu.m, it can be achieved 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. It is also possible to use only one photopolymer layer ≥ 5 μm if in this one photopolymer layer all at least three color-selective holograms are inscribed simultaneously or in succession 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 μm and 0,5 0.5 μm. In this case, only a single hologram, preferably with a Written wavelength close to that in the spectral center of the visible electromagnetic spectral range or near the geometric mean of the two wavelengths of the longest wavelength of the shortest wavelength emission range of the illumination system

In a further advantageous embodiment of the light distribution module according to the invention, the holographic optical elements independently have an extension in at least one surface axis parallel to the surface of the extraction axis of at least 400 μιη, in particular at least 500 .mu.m, preferably at least 800 μιη or even at least 1000 μιη. The use of such larger holographic optical elements enables diffuse and uniform illumination of a display background. In addition, such light distribution modules can be manufactured more easily.

The holographic optical elements used for the light distribution module of the present invention may have any shape. Thus, the holographic optical elements can independently of one another have a circular, elliptical or polygonal, in particular three, four, five or hexagonal, trapezoidal or parallelogram-like cross section in the surface of the outcoupling device. The aforementioned extension of the holographic optical elements in at least one spatial axis running parallel to the surface of the coupling-out device means in each case the smallest extension in such forms.

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 light distribution module according to the invention, the individual holographic optical elements of a coupling device partially 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. So more than two holographic phisch optical elements 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, in which context it is assumed that at least 100 individual print 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 that flat side of the combination of light distribution plate and coupling device, at which the light is emitted, wherein the diffuser preferably rests on the light guide plate and / or coupling device without an optical contact is made. This is preferably achieved via a roughened surface or particulate spacers on the surface of the light guide plate or 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 diffuser 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 diffuser, a further diffuser is provided, which is positioned in the radiation direction behind the first diffuser and at a distance from it. 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. As an alternative or in addition to a diffuser, it may likewise 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 homogeneously only for blue wavelengths, wherein in the color filter of the light modulator for the light modulator red and the green pixels a color conversion is performed by Q-dots. 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 simplified by the use of only one layer Another object of the present invention relates to an optical display in particular a display of a television, mobile telephone, computer and the like, comprising a planar liquid crystal module having a plurality of pixels which can be switched by a control unit and a planar light distribution module in optical contact with the liquid crystal module, comprising a light guide plate through which at least a side surface can propagate einkoppelbares light by means of total reflection and at least one attached to one or both of the main surfaces of the light guide plate and standing in optical contact with this plana Recoupling device having a plurality of holographic optical elements formed therein which are adapted to couple out light from the light guide plate in the direction of the planar liquid crystal module, wherein the display is characterized in that the holographic optical elements independently of each other an extension in at least one of Have surface of the coupling-out parallel spatial axis, which exceeds the extent of the pixels in at least one of the surface of the liquid crystal module at least by a factor of 1.5, preferably at least by a factor of 1.8, more preferably at least by a factor of 2.0 more preferably at least a factor of 2.5, most preferably at least a factor of 3.0.

In a further development of the inventive optical display, the display includes a light distribution module according to the present invention. The displays according to the invention generally comprise, in addition to the light distribution module according to the invention, a translucent digital spatial light modulator and a lighting unit. Due to the low height of the inventive light distribution module, this is particularly suitable for compact thin designs and energy-efficient displays, such as for televisions, computer screens, laptops, tablets , Smartphones or other similar applications are needed.

In a preferred embodiment of the inventive optical display this contains only essential 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 outcoupler, in a Difrusor or in a Color filter is done If you dispense with the usually backward display housing and does not use rearward mirroring, these lighting units are particularly suitable for transparent displays, the variety binden applications in point-of-sale displays, advertising in shop windows, in transparent information boards at airports, railway 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 werdea

The invention will be explained in more detail below with reference to the drawings. In the drawings show

1 is a sectional view of a first embodiment of a erfmdungsgernäßen display with 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 shows 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 a respective primary color,

5 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 is 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 (diffusion plate) without further transparent layer, FIG.

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

10 is 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 separated by a transparent layer, FIG.

FIG. 11 is an alternative embodiment to FIG. 9 with a holographically optic element which has a reflective effect, FIG.

12 shows a coupling device with holographic optical elements with along the direction of irradiation increasing diffraction efficiency in the plan view obliquely from above,

13 is a coupling-out device with holographic optical elements with distances decreasing 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;

15 is a coupling device with rectangular, holographic optical elements with decreasing distance in the transverse direction in plan view obliquely from above,

FIG. 16 shows an outcoupling device with holographic optical elements which bend light in planes orthogonal to one another in a plan 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 ° relative to one another in the plan view obliquely from above,

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

19 shows a decoupling device with holographic optical elements which successively diffract light of different frequency bands (wavelength bands), the planes in which they bend light, are successively twisted in 45 ° steps to each other in the top view obliquely from above,

FIG. 20 shows a coupling-out device with partially overlapping holographic optical elements grouped in element sets, which bend light of varying frequency bands (wavelength bands) in an oblique top view, FIG.

21 shows a decoupling 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 sides in the plan view obliquely from above,

22 shows a coupling-out device with adjoining and partially overlapping holographic optical elements which have 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 from obliquely above.

According to a first preferred embodiment, as shown schematically in Figure 1, the display 10 of 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 volume gratings have an extension of, for example, 300 μm, 400 μm or even 1000 μm in at least one spatial axis parallel to the surface of the coupling-out device. The light guide plate 1 and the decoupling device 2 are in optical contact with each other. Presently shown, the individual volume gratings are irregularly spaced from each other, and the invention is not limited to such an arrangement.

The light guide plate 1 consists of a transparent plastic, preferably a largely birefringence-free amorphous thermoplastics, more preferably of polymethylmethacrylate or polycarbonate. The light guide plate is between 50-3000 microns, preferably between 200-2000μιη and more preferably between 300-1500um thick.

The optical contact between the light guide plate 1 and the coupling-out device 2 can be achieved by direct lamination of the coupling-out device 2 onto the light guide plate 1. It is also possible to realize the optical contact by means of a liquid. If the refractive index of the light guide plate 1 and the output device 2 is different, the liquid should have a refractive index between those of the light guide plate 1 and the output device 2 Derar - Liquids should have a sufficiently low volatility for a permanent detention application. Also, the optical contact can be made possible by an optically clear (contact) adhesive, which is applied as a liquid. Also, by a transfer adhesive film, the optical contact can be realized. The refractive index of the optically clear adhesive and the transfer adhesive should also ideally be between that of the light guide plate 1 and the outcoupler 2. Preferably, the optical contact by means of liquid adhesive and transfer adhesive film.

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

It is likewise possible to improve the waveguide property 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 generally contain organic or inorganic layers whose layer thicknesses are of the same order of magnitude as the wavelengths to be reflected). The decoupler 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 photopolymer 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 that one of the two thermoplastic films adjacent to the photopolymer is attached to the light guide plate 1 with an optically clear adhesive film.

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 which are 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 wholly or partly by red or green fluorescent Q-Dots can be replaced and 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 light-transmitting digital light modulator L, which is constructed, for example, as a liquid crystal module consisting of color filters 4, polarizers 8 and 9 and of a liquid crystal panel 3. The liquid-crystal module can have various structures, in particular the liquid-crystal switching systems known to the person skilled in the art can be used which have certain, advantageously efficient shading of light at different beam angles. can achieve geometries. 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 fenoelectric pixelated light modulators.

FIG. 2 shows a second embodiment of a display 10 according to the invention, which differs from the first embodiment of FIG. 1 in that the output 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.

Figure 3 shows a third embodiment of a display 10 according to the invention, which differs from the first embodiment of Figure 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 coupling device 2 diffracts light in the reflection mode

Figure 4 shows a fourth embodiment of a display 10 according to the invention, which differs from the first embodiment of Figure 1 differs in that on a flat side of the light guide plate 1, three coupling devices 2a, 2b, 2c are arranged one above the other, each of these outcouplers 2a, 2b, 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 to use more than the three primary colors "red", "green" and "blue", for example "yellow" and the like.

The use of a plurality of holographic optical elements 13, which only diffract light for certain selected light sources (eg red, green and blue), succeeds in particular with photopolymer layer thicknesses 5 5 μm. It is possible to laminate three respective photopolymer layer thicknesses of ≥ 5 μm on each other and in each case previously described separately. It is also possible to use only one photopolymer layer SSum, but to inscribe all three color-selective holographic optical elements 13 at the same time or in succession. Furthermore, it is possible to use photopolymer layers≤5μm, preferably≤3μm and more preferably≤3μm and ≥0.5μm. In this case, only one holographic optical element 13, preferably having a wavelength which lies in the spectral middle of the visible electromagnetic spectral range, is also written. This wavelength, with which the holographic optical element 13 is written, can also be expressed as a geometric mean lie two wavelengths of the long-wave light source and the short-wave light source. It is also important to consider that inexpensive and sufficiently powerful lasers are available. Nd: YV04 crystal lasers with 532 nm and argon ion lasers with 514 nm are preferred.

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 embossed holograms in that the diffraction efficiency can be significantly higher and up to theoretically 100% , the frequency and angle selectivity with the active layer thickness is set and that by the geometries of the holographic exposure is largely freedom to adjust the corresponding diffraction angle (Bragg condition).

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

Methods for bulk replication of reflection volume holograms are described in US Pat. No. 6,824,929 wherein a photosensitive material is positioned on a master hologram and subsequently copied by means of coherent light. The production of transmission holograms is likewise known. For example, US Pat. No. 4,973,113 describes a method by means of 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 Imaging", John Wiley & Sons, 2008, Chapter 18) and a review of classical two- and three-stage manufacturing processes (see Q. Huang, H. Caulfield, SPIE Vol 182), reference is also made to WO 94/18603 which describes edge flattening and waveguiding holograms. Furthermore, special production methods based on a special optical adapter block are disclosed in WO 2006/111384. The holographic optical elements 13 containing directed laser light in the illumination unit according to the invention are preferably edged with holograms. These are particularly preferred volume gratings because they work with steep incident light that couples in with total reflection

FIG. 5 shows a section of the structure of FIG. 1. 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 between the light guide plate 1 and air serves as an interface for the total reflection or the optional reflection layer 7 on the one side and the interface of the coupling 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 outcoupler 2, no light is diffracted as it passes through no diffractive diffractive optical element 13 (see position 15). The beam is also not diffracted in the other holographic optical element 13, since there the Bragg condition is not met, while upon passage of the light beam 12 through the Auskopplungsemrichtung 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 5 made up of transparent layer 6 and diffuser layer 6 'and is further widened. This diffuse widening is advantageous in order 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 5. The thickness of the transparent layer 6, the divergence angle 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.

FIG. 6 describes in detail the angular selection of the holographic optical element 13. Only the beam 20 is deflected while the light beams 21 are not diffracted with slightly different angles of incidence which do not follow the Bragg condition. The holographic optical element 13 consists of several frequency-selective ones Partial holograms (eg for red, green and blue light), is the layer thickness≥ 5μηι to choose. The angle selection is chosen so that it lasts between 1-6 °. The advantage of this approach is the ability to adjust chromatic aberrations and general color matching by customizing the diffraction efficiency for each color. If one chooses a layer thickness of the outcoupling device 2 in the range from .gtoreq.5 .mu.m to 5 .mu.m, an angle selection of approximately 30.degree.-30.degree. 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-incident 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 at 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 reflected again at the other edge of the light guide 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 light guide plate 1. After propagation under total reflection, it passes the holographic optical element 13 in the decoupling device 2 and is diffracted at position 14 under the Bragg condition. The holographic optical element 13 diffracts the beam into a divergent diffuse beam, which now exits directly from the light guide plate 1 meets the Diffüsor 5, which then again generates an angular dispersion, so that in the illumination of the light-transmitting digital spatial light modulator L, a homogeneous, divergent surface light is present advantage of this structure is the more compact design, as can be dispensed with an additional spacer layer. 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 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 divergent diffuse beam which now, after leaving the light guide plate 1, strikes the diffuser S directly, which then again generates an angular dispersion, so that when the light-transmitting digital spatial light modulator L, not shown, illuminates homogeneous, divergent surface light is present. The advantage of this design is the more compact design, as it can be dispensed with an additional spacer layer. Furthermore, it is possible to dispense with the embodiments shown in Figure 5, Figure 8 and Figure 9 on the diffuser S, 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, if smaller holographic optical elements 13 and / or overlapping holographic optical elements 13 are used, this is advantageous since 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 position 14 under the Bragg condition. The holographic optical element 13 diffracts the beam into a directed beam, which now, after exiting the light guide plate 1, first encounters a diffuser 5, where the light is divergently diffused. At position 16, this light then hits a second diffuser S, which diffuses again diffusely. The first diffuser S is used to homogenize the light intensity, the second is used 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.

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 irradiated into the light guide plate 1. The light passes through 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. the now after leaving the light guide plate 1 strikes a first diffuser layer 6 'in the diffuser 5, where the light is divergently diffused. At position 16, this light then strikes a second diffuser layer 6 ', which diffuses again diffusely. The first diffuser layer 6 'is used to homogenize the light intensity, the second is used to disperse the emission angle 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.

Various 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 reflection 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 lighting. 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. It may be advantageous, not only linear or geometric changes in diffraction efficiency, but also irregular variable diffraction efficiencies. This is particularly advantageous in lighting effects at corners of the optical waveguide or by the coupling characteristic of the light sources.

FIG. 13 shows a further possible arrangement for compensating different luminance distributions in the light guide plate 1. At this time, the distance between the holographic optical elements 40 to 46 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. 14 shows a further possible arrangement for compensating different luminance distributions in the light guide plate 1. The size of the holographic optical elements SO to 56 is thereby 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, different shape patterns of the holographic optical elements 60-61 are selected. 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. 16 shows a further possible arrangement for compensating different luminance distributions in the light guide plate 1. 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. The direction of the diffraction planes of the holographic optical elements 70 to 77 is changed in 45 ° steps. Advantage of this arrangement is that the light rays present in the light guide plate under total reflection can be coupled out more directly and therefore 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 should be noted 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

FIG. 18 shows a further possible arrangement for compensating 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 narrow-emitting light-emitting diodes (LEDs), which have between 5-lOOnm, preferably 10-50nm and more 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, a respective primary color can be operated by a respective decoupling device 2 a, 2 b and 2 c. Of course, it is also possible in a layer 2, as shown in Figure 1, the holographic optical elements 80-82. However, it is important that the layer thickness is 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 also possible as a coating. FIG. 19 shows a further possible arrangement for compensating different luminance distributions in the light guide plate 1. The spectral region (color) in which the holographic optical elements 90-96 (eg blue for all marked 90, all for red with 91 and all for green with 92 marked holographic optical elements) diffracts light with the diffraction planes of the holographic optical Elements (marked with 93-96) combined and varied in 45 ° steps Advantage is a further adaptation and optimization of light homogeneity.

FIG. 20 shows a further possible arrangement for compensating 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 positioned one above another or by building in one 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 can take place separately, the second possibility shows a simplified structure which makes it possible to produce thinner layer structures to realize.

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 increases from those edges at which light sources 110 are located toward 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.

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

(26) Where no flexion occurs

(30) - (36) Holographic optical elements of equal 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 having diffraction efficiency in the green wavelength region (81) Holographic optical element having diffraction efficiency in the red wavelength region

(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 having diffraction efficiency in the red wavelength region (93), (95) Holographic optical elements having 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

claims:

1. Planar light distribution module for a display, comprising a light guide plate through which at least one side surface einkoppelbares light can propagate by total reflection and at least one on one or both of the main surfaces of the Lichtfuhrungsplatte (1) attached and with this in optical contact planar coupling device ( 2) having a multiplicity of holographic optical elements (13) formed therein, which are designed so that they can decouple light from the light guide plate (1), characterized in that the holographic optical elements (13) independently extend in at least one to the surface of the coupling-out device (2) parallel spatial axis of at least 300 μιη and have at least 1.5 times as large area as the pixels of the display.

Light distribution module according to claim 1, characterized in that the holographic optical elements (13) independently of one another have an extension in at least one to the surface of the coupling device (2) parallel spatial axis of at least 400 .mu.m, in particular at least 500 .mu.m, preferably at least 800 μιη or even at least 1000 μm.

Light distribution module according to claim 1 or 2, characterized in that in the decoupling device (2) at least 30 holographic optical elements (13) are arranged, in particular at least 50. 4. Lichtvert hurry module according to one of the preceding claims, characterized in that the holographic optical elements (13) independently of each other in the surface of the coupling-out device (2) have a circular, elliptical or polygonal, in particular three, four, five or hexagonal, trapezoidal or parallelogram cross-section and / or that the individual holographic optical elements (13) of a Outconding device (2) partially overlap, in particular, the surface of the coupling device (2) is largely completely occupied with holographic optical elements. Light distribution module according to one of the preceding claims, characterized in that the holographic optical elements (13) are arranged irregularly in the outcoupling device (2). Light distribution module according to claim S, characterized in that for the arrangement of the holographic optical elements (13) in the decoupling device (2) no two-dimensional repetitive sequence exists and / or that the number of holographic optical elements (13) per area of at least one edge to the center the decoupling device (2) increases.

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

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

Light distribution module according to one of the preceding claims, characterized in that the diffraction efficiency of the holographic optical elements (13) is different, wherein the diffraction efficiency of the holographic optical elements (13) along a direction of incidence of light in the light guide plate (1) increases in particular light distribution module according to one of preceding claims, characterized in that the holographic optical elements (13) at least in the wavelength range of 400 to 800 nm light from the light guide plate (1) can decouple and / or that the holographic optical elements (13) can decouple light wavelength selective, in particular at least there are three groups of holographic optical elements (13) which are wavelength selective for red, green and blue light, respectively.

11. Light distribution module according to one of the preceding claims, characterized in that the holographic optical elements (13) are designed such that the decoupled light passes through the outcoupling device (2) completely transversely. 12. Light distribution module according to one of the preceding claims, characterized in that the holographic optical elements (13) are designed such that the decoupled light is reflected and the light guide plate (1) passes transversely after coupling out. 13. Light distribution module according to one of the preceding claims, characterized in that the holographic optical elements (13) are designed as volume gratings.

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

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

16. Light distribution module according to one of the preceding claims, characterized in that the coupling-out device (2) has a thickness of 0.5 .mu.m to 100 .mu.m, in particular from 0.5 .mu.m to 40 .mu.m, preferably a thickness of at least 5 .mu.m

17. Light distribution module according to one of the preceding claims, characterized in that the output device (2) contains 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. Light distribution module according to one of the preceding claims, characterized in that on the flat side of the light guide plate (1) and / or coupling device (2) on which the light is emitted at least one Difiusor (5) is arranged, which is preferably from the Lichtiuhrungsplatte (1) and / or the outcoupling device (2) is spaced, preferably less than or equal to 0, 1 mm, in particular by less than or equal to 0.05 mm light distribution module according to one of the preceding claims, characterized in that the holographic optical elements (13) have a Diffüsorfunktion.

Optical display, in particular display of a television, mobile telephone, computer and the like, having a planar liquid crystal module which has a plurality of pixels which can be switched by means of a control unit and a planar light distribution module comprising a light guide plate by means of total light einkoppelbares at least one side surface by means of total reflection can propagate and at least one mounted on one or both of the main surfaces of the light guide plate (1) and with this in optical contact planar decoupling means (2) having a plurality of holographic optical elements formed therein (13) which are configured so that they light from the Light guide plate (1) can decouple in the direction of the planar liquid crystal module, characterized in that the holographic optical elements (13) independently of one another at least 1.5, preferably a 2 and more preferably a third have as large an area as the pixels of the liquid crystal module.

An optical display according to claim 20, characterized in that only essential blue light emitting light sources (110) are used, wherein a color conversion to green and red light by means of Q-dots in a Quantumrail in the light source (110), in the holographic optical elements ( 13) of the decoupling device (2), in a Difiusor (5) or in a color filter (4). Optical display according to claim 20 or 21, characterized in that the light distribution module is one according to one of claims 1 to 19.