WO2006027304A1

WO2006027304A1 - Lighting device for evenly retroilluminating flat-panel monitors, comprising a fiber-optic light guide having diffractive surface elements

Info

Publication number: WO2006027304A1
Application number: PCT/EP2005/053939
Authority: WO
Inventors: Martin Klenke
Original assignee: Nanogate Advanced Materials Gmbh
Priority date: 2004-09-09
Filing date: 2005-08-10
Publication date: 2006-03-16
Also published as: JP2008512834A; KR100918243B1; JP4791474B2; KR20070041622A; TW200609623A

Abstract

The invention relates to a lighting device for retroilluminating flat-panel monitors, such as displays for mobile applications. Said lighting device comprises a light source (14) and a fiber-optic light guide (10). Light emitted by the light source is injected into the fiber-optic light guide (10). The light is ejected on an exits surface (28) of the fiber-optic light guide (10). According to the invention, a surface structure having diffractive surface elements (30) of constant amplitude is provided for the purpose of light propagation on the exit surface (28) of the fiber-optic light guide (10).

Description

ILLUMINATED EQUIPMENT FOR EVEN LIGHTING OF FLAT SCREENS, COMPRISING A LIGHT GUIDE WITH DIFFERENT SURFACE FINISHES

The invention relates to a Beleuchtungscinrϊchtung for backlighting Flachschulschϊrmcn, in particular displays for mobile applications.

Known illumination devices for displays for mobile applications have a light source, which is z. B. is a tubular light source (CCFL). The light emitted by the light source is coupled to an end face of a wedge-shaped in cross section light guide body in this. In particular, due to the wedge-shaped configuration of the light guide, a total reflection of the light rays at the phase boundary and by corresponding scattering centers, the light rays exit at the surface of the wedge-shaped light guide. The surface of the wedge-shaped Lichtieitkörpers is in this case arranged opposite to the screen to be screened. The surface of the light emitting element is structured in such a way that the light emerges from the optical waveguide by refraction. The light thus refracted is collimated by a plurality of foils which are arranged between the optical waveguide and the display and directed in such a way that a substantially white light is emitted to the display arrives. The construction of such lighting devices is complicated, especially since several slides, for example, in a frame or the like. Must be inserted and it must be ensured that slipping or the like. The -?

Foils is avoided. Due to the complicated structure, the manufacturing costs are high. Furthermore, there is a risk of malfunction.

From EP 1 194 915 a light guide body for mobile phone displays is known, in the light guide light of a light source, such as an LED is coupled. For decoupling the light, the light guide body has a diffractive structure on a surface. In this case, the entire surface is provided with different gratings, so that the grids adjoin one another directly. The grids are in this case designed such that they have a different diffraction efficiency to equalize the light outcoupling. Different diffraction efficiencies of individual gratings are achieved by varying the amplitude of the individual gratings or the height of the structure. The preparation of such a surface structure with different grating amplitudes is extremely difficult. Furthermore, by the immediate vicinity of the individual grids difficult to predict diffraction effects, such. B. unwanted interference due to the technically difficult to be guaranteed precision.

The object of the invention is to provide a lighting device for backlighting of flat screens, which ensures increased reliability with high efficiency and low cost.

The object is achieved according to the invention by the features of claim 1.

The lighting device according to the invention is particularly suitable for flat screens, such as displays for mobile phones, PDA displays, cameras, etc. Furthermore, the lighting device is also suitable for backlighting billboards, scoreboards, etc. The illumination device has a light source, wherein the light source may comprise one or more LEDs or CCFLs. That from the light source emitted light is eϊngckoppelt in a light guide. The light guide body is preferably made of transparent plastic, such as PPMA, PC, PET, PE, etc., and / or a mineral glass. The light coupled into the light-emitting body is coupled out at an exit surface of the light-guiding body. In this case, when the illumination device for a mobile telephone is used, the exit surface is arranged opposite the display, so that the light is emitted by the light guide body in the direction of the display. According to the invention, the exit surface has a surface structure with diffractive surface elements for the propagation of light. By providing preferably a multiplicity of surface elements of this kind, the foils provided according to the prior art between the light guide body and the display can be dispensed with, since sufficiently good illumination can be achieved on the basis of the diffractive surface elements according to the invention.

Possibly. Reflectors are provided on one or more side surfaces of the Lichtleitkörpcrs to increase the exiting at the exit surface amount of light. Likewise, the light source may be partially surrounded by reflectors in order to increase the amount of light coupled into the light guide body.

With the help of the illumination device according to the invention, it is possible between the exit surface c of the light guide and the display of the screen no further light-directing components such. As films to provide. Apart from the reflection elements described above, a transflective or transmissive backlight without further light-directing components is therefore provided according to the invention. Due to the provision of diffractive Oberflächenelcmente on the Austrϊttsoberfläche of the light guide body, the structure of the lighting device can be simplified. As a result, the quality of the illumination device and in particular the service life is improved. Preferably, the individual surface elements are designed such that they act as diffraction element, which preferably produce a collimated light bundle with spectral light splitting. For this purpose, the individual surface elements preferably have wave-shaped surface structures in cross-section, the wave spacing being selected as a function of the wavelength to be deflected. In this case, individual surface elements preferably have different diffraction gratings. It is particularly preferred that the Oberflächeneiemente are arranged such that predominantly monochromatic light and / or white light is formed by superposition of at least two adjacent light bundles. Here, monochromatic light is understood as meaning a wavelength range of J 100 nm, in particular ± 50 nm. As a result of the provision according to the invention of such surface elements, a largely monochromatic, in particular collimated light with high luminous flux density can thus be produced

By the design of the surface of the Oberflächeneiemente it is also possible to adjust the emission direction of the light from the exit surface. For this purpose, the diffraction grating provided on the surface elements is to be modified in accordance with the Fraunhoferschcn diffraction laws. The adjustability is preferably in the range of 0-90 ° to the exit surface.

Likewise, it is possible to adjust the color temperature of the radiated light due to the choice or design of the structure of the Oberflächcnelementc. Preferably, a setting of the color temperature in the range of 3000 K - 10, 000 K is possible.

The inventive design of the exit surface with diffractive surface elements in particular a spectral splitting is avoided or significantly reduced. Furthermore, a sufficient Lϊchtverstärkung is guaranteed with low energy consumption. Furthermore, due to the provision of the diffractive surface elements and in particular the arrangement of the Oberflächenelcmente a good Kollϊmatϊon the light can be achieved. It is particularly advantageous that these advantages without the provision of other Lichttenksysteme such. B. diffractive or refractive films, for light amplification or collimation can be achieved.

The diffractive surface elements according to the invention preferably have a size of 0.04 μm ^? up to 10,000 μm ² , in particular 0.04 μm ² to 500 μm ^? on. Due to the prospect of such small surfaces, it is possible to provide a variety of surface elements even for very small flat panel displays, such as displays for mobile applications. In this case, the distance of the individual surface elements from each other is preferably in the range of 0-100 μm, in particular 0-50 μm and particularly preferably 0-15 μm. It is particularly preferred that the Oberflächenelcmcnte have a distance> 0 to each other. The distance is preferably at least 1 μm, in particular at least 3 μm. This has the advantage that in areas of the light guide in which more light is to be coupled, the distance of the Oberflächenelcmente reduced and in areas in which a smaller amount of light is to be coupled out, a greater distance can be provided This allows a good Verglcichmäßigung the brightness distribution can be achieved. Furthermore, it is easier in the production to arrange the individual surface elements always at a distance from each other. If the surface elements are produced, for example, by a hardening lacquer in conjunction with a molding element or a negative, then falsification at the boundaries of the surface elements, for example due to the formation of paint webs, is avoided by the Bcabsteh of the surface elements. Furthermore, the spacing of the individual surface elements ensures that refractions or distortions of the diffraction by adjoining surface structures are avoided. Preferably, a plurality of surface elements having different surface structures are combined to form a surface element group. In this case, the different surface structures are selected such that substantially monochromatic and / or white light is emitted by a surface element group. The type of surface structure, in particular the wavelength change of the light caused by the surface structure, is determined as a function of the wavelength ranges emitted by the light source.

Preferably, a surface clement group comprises at least two surface elements C with different surface structures. Preferably, the Oberflächenclcmente group comprises at least four, in particular at least six Oberflächenelemcnte, each having a different surface structure.

Since, according to a preferred embodiment of the invention, the individual surface elements have the same surface structure in terms of height or amplitude, the diffraction efficiency of the individual surface elements is identical. Only variations in the order of a few percent may occur, which, however, only slightly influence the diffraction efficiency.

It is particularly preferred to design the individual surface elements in such a way that the amplitude of the different surface structures is constant and only the frequency is changed. Depending on the type of surface structure, which does not necessarily have to be a sinusoidal surface structure, all elevations are generally the same, but have different distances. This leads to the fact that the light emitted by the light source is diffracted differently by the individual surface elements. It is advantageous in this case in particular that a variation of the distances is easier to produce than varying heights. The surface elements preferably arranged in surface element groups, which are, for example, six surface elements with a different surface structure, preferably have the same amplitude of 550 nm. In this case, the individual surface elements of a surface element group each have a frequency of, for example, 490 nm, 503 nm, 517 nm, 530 nm, 575 nm and 620 nm. In particular, the diffractive surface elements have a sinusoidal surface structure. The spacing between the individual surface elements is preferably in the range from 1 to 100 μm, in particular from 1 to 50 μm and particularly preferably from 1 to 15 μm.

The production of such small surface structures and surface elements is described for example in EP 05 003 358, to the contents of which reference is hereby made. A suitable material for producing the surface elements preferably has the following composition:

11 g of 1H, 1H, 2H, 2H-perfluorooctyl acrylate were diacrylate with 8 g of dipropylene glycol, 0.1 g of Irgacure ^® 819 and 0.2 g Irgacure ⁰⁰¹⁸⁴ from Ciba Spezialitätenchcmie Lampersheim mixed GmbH. 60 μl of this mixture was applied to a 2 × 2 cm nickel plate, on the surface of which a negative mold of a shaped body with scattering centers is formed. Subsequently, a 1 mm thick and 1 x 1 cm large plate of PMMA was applied to the surface of the mixture on the nickel plate. Thereafter, the resulting sandwich on the nickel plate with the intervening mixture was exposed for 2 seconds to UV radiation from a conventional UV mercury lamp. Subsequently, the substrate with the associated cured impression composition was removed from the negative mold.

The üchtleitkörper may be wedge-shaped in cross section. However, it is preferred to provide a cuboid light body, wherein the Lϊchteenttrittsfiäche is a side surface of the cuboid. The provision of a cuboid light guide body is possible due to the good light output achieved by the provision according to the invention of the diffractive surface elements. This achieves a significant simplification in production. The thickness of the cuboid light guide body is preferably in the range of 0.1 to 3 mm.

Preferably, a light source, which may be one or more LEDs and / or CCFLs, is disposed within and / or outside the light guide body. Depending on the position of the light source or the light sources, an arrangement of the surface elements takes place. By means of a corresponding arrangement of the surface elements, the different light intensity, etc. existing at different locations of the exit surface can be compensated for, so that at the exit surface of the surface elements a uniform, d. H. in particular collimated and monochromatic and / or white light is emitted.

In order to increase the amount of light directed in the direction of the exit surface, reflectors may be provided. For example, these partially surround the light source. An example rod-shaped light source is preferably arranged within the focal point of a parabolic reflector. Likewise, in addition to or instead of the parabolic reflector a plurality of planar reflectors may be provided. Further, the Lϊchtlcitkörpers, which is other than the exit surface of the light guide body, reflectors may be provided at outer surfaces in order to avoid an unwanted loss of light _* A corresponding Lϊchtlenkung can also be achieved by the provision of the inventive user interface elements, for example, on side surfaces of the light guide. A targeted light control and / or collimation and / or spectral influence can also be achieved by providing surface elements according to the invention on a surface of the light source In addition to or instead of the provision of surface elements on an exit surface of the light body, such surface elements can also be provided on the opposite side, ie on an underside of the light source. The light diffracted by the surface elements is thus directed through the light guide body in the direction of the display.

In a particularly preferred embodiment of the invention, the distance of adjacent Oberfiächenelemente, which are provided in particular on the Austrϊttsoberfläche or the opposite surface, decreases with an increase in the distance to the light source. This takes into account the fact that the light intensity in the region of the light source is greater and decreases with increasing distance to the light source. For example, a light source arranged inside the light source may be surrounded by concentric circles of surface elements, wherein the distance between the circles decreases with increasing distance from the light source. Depending on the type of light source used, in particular the emission characteristic of the light source, different arrangements of the surface elements that are matched thereto can be advantageous.

It is thus a periodic, but also an aperiodic arrangement of the surface elements possible. Preferably, in this case, the arrangement of the Obcrflächenelemente depending on the nature and the position of the light source or the light sources.

A preferred embodiment of the invention relates to a flat screen with a liquid crystal element, such as an LCD element. The liquid crystal element is backlit according to the invention with a lighting device designed in accordance with the above description.

Known screen or Flußϊgkristall elements according to the prior art have a luminous element, such as a lightbox. By doing Lcuchtelement are a plurality of fluorescent tubes, in particular CCFLs, arranged as light sources. In order to compensate for the light emitted by the fluorescent tubes and thus to even out the illumination of the liquid-crystal element, foils are arranged between the fluorescent tubes and the liquid-crystal element. These are so-called BEF and DPEF foils. With the help of a BEF film, the brightness is to be improved. This is done by providing a plurality of prisms on the foil. With the aid of the DBEF-FoNe, the polarity of the light reflected from the back side of the liquid crystal element is changed and the light is redirected in the direction of the liquid crystal element. Furthermore, PRF films are used to change the polarity. However, the provision of such films has the disadvantage that a part of the light is absorbed by the films.

In the flat panel display according to the invention, the BEF film, and preferably also the DBEF film and the PDF film, are replaced by the light-emitting body formed according to the invention. As the light source, a plurality of light pipes, such as CCFLs, are preferably provided. A light guide body according to the invention is arranged in front of the light tubes and, as explained above, has a large number of surface elements or surface element groups. It is particularly preferred that the light-guiding body per light tube has a zone which is preferably arranged parallel to the light tube and has a plurality of surface elements or surface element groups. Here, the individual zones may be identical. As a result, the production costs can be reduced.

The individual surface elements or surface element groups are preferably arranged in rows and columns in the individual zones. It is particularly preferred in this case that the distance between the individual lines decreases with increasing distance from the light tube. As a result, a homogenization of the light emerging at the exit surface of the guide body, ie in particular a homogenization of the brightness distribution and / or a homogenization of the wavelength distribution can be achieved. This leads to the fact that the BEF film and possibly also the DBEF film and the PRF film can be omitted.

If necessary, the zones can be divided into individual subzones. The subzones are preferably rectangular zones, wherein the number of surface elements or surface element groups in subzones arranged on the lateral edge of the light guide body is greater than in subzones lying further inside. Furthermore, instead of providing zones and subzones, it is possible to provide an aperiodic arrangement of the surface elements or the surface element groups. In this case, the individual surface elements or surface element groups are arranged as a function of the luminous characteristic of the lightheads. The density of the surface elements or of the surface element groups is preferably higher, in particular in the corners and at the edges,

The invention will be explained in more detail with reference to a preferred embodiment with reference to the accompanying drawings.

Show it :

Fig. 1 is a schematic perspective view. one

Beleuchtungseinrϊchtung,

2 shows an example of a surface structure of a

Surface element,

Fig. 3 shows an example of a possible arrangement of

Interface elements, Fig. 4 shows an example of a division of a Austrittsoberfiäche one

Lichtlcitkörpers in different zones,

5 shows a first table which describes or defines the zones shown in FIG. 4,

6 is a second table describing or defining the zones shown in FIG. 4; FIG.

FIG. 7 is a third table describing the zones shown in FIG. 4. FIG.

Fig. 8 u. 9 schematic plan views of further embodiments of illumination devices,

10 is a schematic representation of a flat screen in a

Explosion sketch

11 is a schematic plan view of a LleitchtleitkÖrpers which erfϊndungsgemäß in a flat screen is used and

Fig. 12 is an enlargement of a portion of the Lichtleitkörpcrs.

The illumination device according to the invention has a guide body 10, which is parallelepipedal in the illustrated embodiment and consists, for example, of a transparent resin or a plastic, such as PPMA or the like. In the exemplary embodiment shown, a rod-shaped light source 14 is arranged along a side face 12 of the light guide body 10, wherein the longitudinal axis of the light source 14 is arranged parallel to the side face 12. The light source 14 is surrounded by a parabclförmϊgen reflector 16, the open side facing in the direction of the side surface 12, This increases the coupled into the side surface 12 amount of light. - 1 ] -

The light source 14, which may also be a plurality of LEDs instead of the illustrated light tube, preferably has a luminance in the range of 20,000 - 50,000 cd / m ² . When providing a tubular light source 14, this is preferably arranged in the focal axis of the parabolic reflector 16.

On a lower side 18 of the light guide body 10 is a reflector 20, which may be a reflector sheet or the like., Arranged. Possibly. For example, further reflectors can be arranged on the side surfaces 22 and / or 24 and / or 26. Instead of providing reflectors, the corresponding surfaces can also be polished. Possibly. is a vapor deposition of a reflective layer advantageous.

On the exit surface 28 of the light guide body 10 is a plurality of diffractive surface element cn 30, so that a surface structure according to the invention is formed.

The individual surface elements 30 act as diffraction gratings. In this case, different Oberflächenelementc may be provided, which are formed as linear diffraction gratings with different lattice constants. In this case, the surface 32 (FIG. 2) of individual surface elements 30 is designed, for example, as a phase sine grid. In this case, each surface element 30 preferably has two sine half-waves.

The production of the individual Oberflächcnelemente 30 and in particular the surface structure 32 of the surface elements 30 according to the invention, for example, by photo-lithographic process. Furthermore, the surface elements 30 can be produced in a particularly preferred embodiment as described in EP 05 003 358.

In a particularly preferred embodiment of the invention, the individual surface elements 30 are surface element group groups 33 (FIG. 3). summarized. In the exemplary embodiment shown, a surface element group 33 has six surface elements 30, which are preferably arranged on a gap and at a constant distance from each other. Each one of the surface elements 30 has a different surface structure such that a surface element group 33 emits substantially monochromatic or white light.

For coupling out light with different wavelength, preferably different surface elements 30, d. H. Surface elements 30 with different surface structure arranged. For example, as shown in the exemplary embodiment illustrated in FIG. 3, these are six different surface elements 30, which are designated by 1 to 6 in FIG. 3. As is apparent from Fig. 3, in the illustrated embodiment, the different surface elements 1 to 6, each serving for coupling out light of a specific wavelength, arranged in a repeating structure.

The surface elements 30 are square in the illustrated embodiment and have an edge length of about 15 microns.

In a particularly preferred embodiment (FIG. 4), the individual surface elements 30 are arranged in zones. The zones are designated 1 to 10 and 1_1 to 1 4 in FIG. 4. The dimensions of the zones as well as the distance of the surface elements inside the zones can be seen from the table shown in FIG.

In the exemplary embodiment illustrated in FIGS. 4 and 5, the light source in FIG. 4 is arranged on the left side, ie next to the zone denoted by 1. Starting from the light source, the spacing of the individual surface elements 30 decreases stepwise with increasing distance from the light source - J

Light source from each other. Innet has the same zones or areas, the surface elements have a constant distance. However, it is also possible that the Oberflächenelementc have different distances within a zone. In particular, the distance in the longitudinal direction, i. in Fig. 4 from left to right, vary with respect to the distance perpendicular to the longitudinal direction.

With the help of the simulator software "Light Tools" from the company ORA, a lighting device was created as shown in Figs. 1 to 5 described with the zones defined in Fig. 4 and 5 and measurements carried out in terms of homogeneity, color, luminance, illuminance and collimation. The corresponding measurements were made at nine points, which are located in the corners, the edge mats with an edge distance of approx. 2 mm and in the center of the light guide.

In an arrangement of the surface elements as shown in FIGS. 4 and 5, the simulation performed led to the following results:

Homogeneity: 91%

Color white

average illuminance: 1600 lux

Average luminance: 2950 Nits. Collimation direction: 17 °

In a further simulation, the distances between the surface elements 30 in the individual zones (FIG. 4), as shown in FIG. 6, were defined.

The following results were determined: - 1 G

Homogeneity: 86%

Color: neutral (slightly blue)

average illuminance: 1000 lux

average luminance: 1900 nits

Collation direction: 17 °

In a weather simulation, the distances between the surface elements 30 in the individual zones (Figure 6), as shown in Figure 7, were defined.

The following results were determined:

Homogeneity: approx. 78%

Color white

average illuminance: 1050 lux

average luminance: 1850 Nits

Collation direction: 17 °

In a further investigation, the zones 8, 9 and 10 were omitted, and thus a shorter light guide body 10 was examined, in which the light was also coupled according to the Lϊchtkörper shown in Fig. 4 from the left. The tested Lϊchtleitkörper thus had dimensions of about 36 mm (length) and 44 mm (width), the length in the direction of the zones, 7 -

d. H. in Fig. 4 is measured from left to right. The distances of the individual surface elements within the zones corresponded to those defined in FIG. 5 for zones 1 to 6, zones 1. The following results were measured:

Homogeneity: approx. 88%

Color white

average illuminance: 1100 lux

average luminance: 2150 nits

Collimation direction: 17 °

In further investigations, the surface of the light guide 10 was not divided into zones, but a constant distance of the individual surface elements selected. The following results could be determined:

Distance: 4 μm

Homogeneity: approx. 75%

Color white

average illuminance: 1850 lux

average luminance: 3350 Nits

Collimation: 17 ° Distance: 6 μm

Homogeneity: approx. 78%

Color white

Illuminance: 1600 lux

Luminance: 2400 Nits

Collimation: 17 °

Distance: 8 μm

Homogeneity: approx. 82%

Color white

average illuminance: 1400 lux

average luminance: 2500 nits

Collation direction: 17 °

Distance: 10 μm

Homogeneity: approx. 84% Color white

average illuminance: 1200 lux

average luminance: 2200 nits

Koüimationsrichtung: 17 °

Distance: 11 μm

Homogeneity: approx. 87%

Color white

average illuminance: 1200 lux

average luminance: 2150 nits

Collision direction: 17 °

From the above findings, the following conclusions can be drawn:

1. The arrangement and distribution of the diffractive surface elements, it is possible to set high homogeneities with respect to the Lichtverteϊlung

2. Even with relatively poorer arranged Oberfiächenanordnungen with less homogeneity, the color mixture is always given to white.

3. The collimation direction can be set independently of the distribution of the surface elements

4. The light intensity is a function of the distance between the dots - <. O -

In particular, when using the illumination device according to the invention as a backlight for mobile phones, in which a homogeneity of 75% or more is acceptable, a pleasant and high-quality lighting of a display is made possible for the user. In particular, targeted collimation directions in conjunction with preset color temperature can be produced without the aid of light-guiding films. This enables a further miniaturization of the overall system with simultaneously lower number of components and high flexibility of the layout.

FIGS. 8 and 9 show two further embodiments of illumination devices which are particularly suitable as backlight for mobile phones.

The light guide 10 are basically formed as described with reference to the preceding figures. The light sources are LEDs. In the exemplary embodiment illustrated in FIG. 8, a single LED 34 is arranged in a corner of the light-guiding body 10. Here, the corresponding corner 36 is preferably beveled so that the exit side of the LED 34 is disposed within the corner or within the rectangular Lichtleitkörpers 10 is provided _™ the light is coupled via a beveled surface 48 in the light guide 10. Since the light guide 10 is not square, but is usually rectangular, the bevel is not in a 45 ° angle, but preferably made such that an angle α between the narrow side 40 and the inclined surface 38 is less than 45 °.

In the illustrated embodiment, the arrangement of the individual surface elements or .. the individual surface element groups is arranged such that the most uniform possible coupling of the light takes place. In this case, the spacing of the individual surface elements or surface element groups in the direction of the dashed lines 42 changes in such a way, - 2y -

that the distance of the individual elements or groups decreases with an increase in the distance from the LED 34.

The embodiment of the illumination device illustrated in FIG. 9 also has LEDs 44 as light sources, with three LEDs 44 being arranged on a narrow side 40 of the light-conducting body 10 in the exemplary embodiment shown. In this case, the light guide 10 on the narrow side 40 preferably indentations 46 ,. The recesses 46 are preferably formed semicircular. In the illustrated embodiment, the bumps 46 extend over the entire thickness of the light guide 10. It is also possible to provide, for example, hemispherical bulges, wherein the ball diameter is less than the thickness of the light guide 10.

In this exemplary embodiment, the surface elements or the surface element groups are in turn arranged such that an equalization of the brightness distribution at the exit surface 28 is given.

Of course, the different embodiments described may be combined. For example, LEDs can be provided on several sides. In particular, a plurality of LEDs are arranged around the entire circumference of the Lichtleitkörpcrs 10. Likewise, a combination of the embodiment described in FIGS. 8 and 9 is possible. In particular, it may also be convenient to combine LEDs together with one or more CCFL tubes. For example, the illumination device illustrated in FIG. 1 can be modified in such a way that an LED, in particular as shown in FIG. 8, is provided in the two CCFL tubes 14 opposite corners. In this way, a good illumination of these two corners, which have a large distance from the CCFL tube 14, can be ensured in a simple manner. In a preferred application of the illumination device according to the invention, this is arranged in a flat screen. The essential element of a flat screen is a liquid crystal element 50 (FIG. 10). The liquid crystal element is usually an LCD element. Furthermore, a light box or dg! .. is provided as the light source 52, wherein the latter has a plurality of light tubes 54 arranged parallel to one another. The light tubes 54 are preferably CCFLs.

According to the prior art, a plurality of films are arranged between the light box 52 and the liquid crystal element 50. These are so-called BEF, DBEF and PRF foiia.

According to the invention, at least the BEF film is replaced by a light guide body 56. The light guide body 56 is in principle constructed as described above in particular with reference to FIGS. 1-3.

The light guide 56 preferably has a plurality of horizontally or parallel to the light tubes 54 aligned zones 58. In this case, each zone 58 is preferably associated with a light tube 54, wherein the Lϊchtröhre 54 is arranged centrally behind the zone 58. Preferably, the zones 58 are identically constructed, i. H. each zone has an identical arrangement of surface elements or groups of surface elements.

A preferred arrangement of surface element groups 33 is shown in FIG. Here, the individual surface element groups 33 are arranged symmetrically to a center line 60. Starting from the center line 60, the distance of the individual surface element groups 33 from each other increases in the direction of an arrow 62, d. H. to the outside, from.

In the illustrated Ausfuhrungsbeispie! For example, the surface element groups 33 are arranged in rows and columns, with the spacing of the columns being constant - I \ -

is. In a further development of the invention, the zones 58 can be divided into preferably rectangular subzones. These are then arranged side by side in FIG. In this case, it is possible to provide, for example, different column spacings within the individual subzones, with those at one edge, i. H. in Fig. 12 left or right at the zone 58 provided sub-zones preferably have smaller gaps distances.

Instead of or in addition to a light box 52 (FIG. 10), it is also possible, for example, to provide four or more light tubes 54 which are arranged on the circumference of the light emitting body 56, so that the light is irradiated laterally into the light guide body 56. The arrangement of the surface elements or the surface element groups is in turn made in such a way that a uniform distribution of brightness is given by the light guide in the direction of the LCD element. In this case, the spacing of the individual surface element groups or surface element groups preferably decreases in the direction of the center of the light guide body. It is also possible that the surface of the Lichtieitkörpers is divided into four zones or segments, preferably four identical rectangular segments, which are preferably each point-symmetrically constructed to the center of the Lichtieitkörpers.

Claims

-? A -patent claims

1. Lighting device for backlighting flat screens, especially displays for mobile applications, with

a light source (14) and

a light guide body (10) in which light emitted by the light source (14) is coupled in and is coupled out at an exit surface (28),

wherein the light propagating exit surface (28) has diffractive surface elements (30),

characterized in that

all surface elements (30) have a surface structure with constant amplitude.

2. Lighting device according to claim 1, characterized in that the individual surface elements (30) act as diffraction elements which generate a collimated light beam with spectral light splitting.

3. Lighting device according to claim 1 or 2, characterized in that the surface elements (30) are arranged such that monochromatic light and / or white light is produced by superposition of at least two adjacent light bundles. - 2 '3 -

4. Lighting device according to one of claims 1 - 3, characterized in that the surface elements (30) have a size of 0.04 - 10.000 μtn ² , in particular 0.04 - have 500 microns ² .

5. Lighting device according to one of claims 1 - 4, characterized in that the individual surface elements (30) with each other a distance of 1 - .1.00 microns, in particular 1-50 microns and more preferably 1 - have 15 microns.

6. Lighting device according to one of claims 1-5, characterized in that the distance between adjacent Obcrflächcnelemente (30) decreases with an increase in the distance to the light source (14).

7. Belcuchtungseinrichtung according to claim 6, characterized in that the distance between adjacent surface elements (30) gradually decreases,

8. Lighting device according to one of claims 1-7, characterized in that the surface elements (30) are arranged aperiodically "

9. Lighting device according to one of claims 1-8, characterized in that the exit surface (28) has areas within which the surface elements (30) have the same distance.

10. Lighting device according to one of claims 1-9, characterized in that the light source (14) within and / or outside of the Lichtleϊtkörpers (10) is arranged. -?. β -

11. Lighting device according to one of claims 1 - 10, characterized in that to improve the coupling of the light, the light source (14) is partially surrounded by reflectors.

12. Lighting device according to claim 11, characterized in that a parabolic reflector is provided and in particular designed as a fluorescent tube light source (14) is arranged in the focal point.

13. Beleuchtungseϊnrichtung according to any one of claims 1-12, characterized in that at least one side surface of the light guide body (10) which is not the exit surface is provided with a reflector and / or has a reflective surface.

14. Beieuchtungscinrichtung according to any one of claims 1-11, characterized in that the light source comprises one or more LEDs.

15. Lighting device according to one of claims 1-14, characterized in that the light guide body (10) is cuboidal.

16. Lighting device according to one of claims 1-15, characterized in that the light guide body (10) is wedge-shaped, wherein the light source (14) is arranged on a narrow side of the wedge.

17. Lighting device according to one of claims 1 - 16, characterized in that a plurality, preferably at least two, in particular at least four and particularly preferably at least six surface elements (30) are combined to form a surface element group (33), wherein the surface element group ( 33) emits monochromatic and / or white light. -? 1 -

18. flat screen, with a Flussigkristall-element (50) and a liquid keitskristall- the element backlit Beleuchtungseϊnrichtung according to any one of claims 1-17.

19. Flat screen according to claim 18, characterized in that a plurality of light tubes (54) arranged in particular parallel to one another are provided, and the light guide body (56) per light tube (54) has a zone (58) arranged preferably parallel to the light tube (54) Surface element (30) and / or surface element groups (33).

20. Flat screen according to claim 19, characterized in that the surface elements (30) and / or the surface element groups (33) in a zone (58) are arranged in rows and columns, wherein the spacing of the lines preferably with increasing distance to Light tube (54) reduced.

21. Flachhiidschirm according to claim 19 or 20, characterized in that the arrangement of the surface elements (30) and the surface element groups (33) per zone (58) to a center line (60) is symmetrical, wherein the center line (60) is preferably is arranged at the shortest distance to the Lϊchtröhre (54).

22. Flat screen according to one of claims 19 - 21, characterized in that the zones (58) are divided into sub-zones, wherein the sub-zones are preferably formed rectangular.

23. Flat screen according to claim 22, characterized in that laterally arranged at the edge of sub-zones have more surface elements (30) or Oberflächeneiemente groups {33) than the other sub-zones,