KR20070041622A - Lighting device for evenly retroilluminating flat-panel monitors, comprising a fiber optic light guide having diffractive surface elements - Google Patents

Abstract

The present invention relates to lighting devices for backlighting flat panel monitors such as displays for mobile applications. The lighting device includes a light source 14 and an optical fiber light guide 10. Light emitted from the light source is incident into the optical fiber light guide 10. Light is emitted from the exit face 28 of the optical fiber light guide 10. According to the present invention, a surface structure having diffractive surface elements 30 of constant amplitude is provided on the exit face 28 of the optical fiber light guide 10 for the purpose of light propagation.

Lighting device, flat panel display, backlighting flat panel display, light guide member

Description

LIGHTING DEVICE FOR EVENLY RETROILLUMINATING FLAT-PANEL MONITORS, COMPRISING A FIBER OPTIC LIGHT GUIDE HAVING DIFFRACTIVE SURFACE ELEMENTS}

The present invention relates to lighting devices for flat panel displays, in particular mobile application display backlights.

Known lighting devices for displays for mobile applications include light sources that can be, for example, tubular light sources (CCFLs). Light emitted from the light source is coupled into the light guide member of a wedge shaped cross section at its end face. In particular, because of the wedge-shaped configuration of the light guide member, total reflection of the light beam occurs at the boundary of the phase, and the light beam passes through the corresponding scattering center of the wedge-shaped light guide member. Appear on the surface. The surface of the wedge-shaped light guide member is arranged on the opposite side of the display and transmitted. The surface of the light guide member is configured such that light appears in the light guide by refraction. Thus, the refracted light is collimated and directed by a plurality of films arranged between the light guide member and the display such that white light substantially reaches the display. As the structure of such a lighting device becomes more complicated, for example, since a plurality of films must be placed in a frame or the like, it is necessary to secure prevention against slippage of the film or the like. Due to the complicated structure, the manufacturing cost is high. In addition, there is a risk of operation failure.

Light guide members for mobile phone displays are known from EP 1 194 915. Light from a light source, such as an LED, is coupled into the light source. To couple out light, the light guide member has a diffractive structure on the surface. Here, the entire surface is provided with different gratings adjacent to each other. The grating is configured to obtain uniformity of light coupling by having different diffraction efficiencies. Different diffraction efficiencies of the gratings are achieved by varying the amplitude of the grating structure or the amplitude of the individual gratings. It is very difficult to fabricate surface structures with different grating amplitudes. In addition, direct contact of individual gratings may result in diffracted effects that are difficult to predict, such as unwanted interference due to, for example, technically difficult to obtain.

SUMMARY OF THE INVENTION An object of the present invention is to provide a lighting device for a flat panel display backlight having high efficiency and low cost and guaranteeing improved operational reliability.

This object is solved according to the invention having the features of claim 1.

The lighting device is particularly suitable for flat panel displays, for example displays of mobile phones, PDA displays, cameras and the like. In addition, the lighting device is also suitable for backlighting billboards, display panels and the like. The lighting device has a light source that may include one or more LEDs or CCFLs. Light emitted from the light source is coupled into the light guide member. The light guide means is preferably made of transparent plastic material such as PPMA, PC, PET, PT and the like and / or mineral glass. Light coupled into the light guide member is coupled out at the exit face of the light guide member. If the lighting device is used for a mobile phone, the exit face is arranged on the opposite side of the display such that light is emitted from the light guide towards the display. According to the invention, the exit face comprises a surface structure having diffractive surface elements for light propagation. Preferably, by providing such a plurality of surface elements, since a sufficiently good illumination can be achieved by the diffractive surface element of the present invention, the film between the light guide member and the display installed in the prior art can be omitted.

At least one side of the light guide member may be provided with a reflector to improve the amount of light appearing at the exit surface. Similarly, the light source may be partially surrounded by the reflector to improve the amount of light coupled into the light guide member.

In using the present illumination device, it is possible to further omit any light guide component, such as a film, between the exit face of the light guide member and the display. Thus, in addition to the reflective elements described above, the present invention provides for semi-transmissive or transmissive background illumination in which any light guide component is further omitted. By equipping the exit surface of the light guide member with the diffractive surface element, the structure of the illumination device can be simplified. This improves the quality and in particular the service life of the lighting device.

Preferably, each surface element is preferably configured to act as a diffractive element that produces a collimated light bundle with spectral light splitting. For this purpose, each surface element preferably comprises a surface structure of a wavy cross section, and the pitch between waves is selected by the wavelength to be deflected. Preferably, the individual surface elements comprise different diffractive gratings. In particular, the surface element is preferably arranged to produce at least two adjacent light bundles, mainly monochromatic light and / or white light. The monochromatic light here is in the wavelength range of ± 100 nm, in particular ± 50 nm. Thus, by providing such a surface element according to the present invention, it is possible to generate light collimated mainly at a single color, in particular at a high light flux density.

The surface configuration of the surface element can also adjust the radiation direction of light at the exit surface. For this purpose, the diffraction grating installed in the surface element must be changed in accordance with the Fraunhofer diffraction rule. It is preferable to adjust in the range of 0-90 degrees with respect to an exit surface.

Likewise, it is possible to adjust the color temperature of the emitted light by the selection of the structure of the surface element or the construction of the surface element. Preferably, the color temperature can be adjusted within the range of 3000K to 10000K.

The present configuration of the exit face with diffractive surface elements avoids or significantly reduces spectral segmentation in particular. In addition, sufficient amplification of light and low energy consumption are achieved simultaneously. In addition, by providing the diffractive surface elements, and in particular by the arrangement of the surface elements, good collimation of light is achieved. Here, these advantages are particularly advantageous that optical amplification or collimation can be obtained without further installing a light guide system such as a diffractive or reflective action film.

The diffractive surface element preferably has a size of 0.04 to ² ㎛ 10000 ㎛ ^2, in particular 0.04 to ² ㎛ 500㎛ ^2. With such small surface installations it is possible to install a plurality of surface elements even in very small flat displays such as displays for mobile applications. Here, the mutual spacing between the individual surface elements is preferably in the range of 0-100 μm, in particular 0-50 μm, particularly preferably 0-15 μm. It is particularly preferable that the surface element has a mutual distance of greater than zero. The distance is preferably at least 1 μm, in particular at least 3 μm. This means that in the area of the light guide member where a greater amount of light is coupled out, the distance between the surface elements can be reduced, but in a region where a small amount of light is coupled out, a greater distance may be provided. It is advantageous in that it can. Thereby, good uniformity of the luminance distribution can be obtained. In addition, it is easy to manufacture so as to arrange individual surface elements with always equal intervals. For example, when a surface element is produced in a hardened lacquer in combination with a forming element or a negative electrode, the spacing of the surface element is for example the surface element by the formation of a lacquer web. Avoid corruption at the boundary of In addition, the spacing of individual surface elements avoids the refraction or curvature of diffraction caused by adjoining the surface structure.

It is preferable that a plurality of surface elements having different surface structures be included in a group of surface elements. To do so, another surface structure is selected such that the group of surface elements emit substantially monochromatic and / or white light. The shape of the surface structure, in particular the change in wavelength of light caused by the surface structure, is determined by the wavelength range emitted by the light source.

The group of surface elements preferably comprises at least two surface elements having different surface structures. The group of surface elements preferably comprises at least four, in particular at least six surface elements, each having a different surface structure.

According to a preferred embodiment of the present invention, since each surface element has the same surface structure with respect to height or amplitude, the diffraction efficiency of each surface element is the same. Only a few percent production related changes can occur that only slightly affect the diffraction efficiency.

It is particularly desirable to configure the individual surface elements such that the amplitudes of the other surface structures are constant and only the frequency changes. By the type of surface structure that does not have to be a sinusoidal surface structure, all the relief portions generally have the same height but different mutual distances. This is due to the fact that the light emitted from the light source is diffracted differently by the individual surface elements. In this regard, it is particularly advantageous that changing the distance is simpler to produce than changing the height.

Surface elements preferably arranged in groups of surface elements, which can be surface elements of six different surface structures, preferably have the same amplitude, for example of 550 nm. Individual surface elements of the group of surface elements have, for example, frequencies of 490 nm, 503 nm, 517 nm, 530 nm, 575 nm, and 620 nm, respectively. In particular, the diffractive surface element has a sinusoidal surface structure. The distance between the individual surface elements is preferably in the range of 1 to 100 μm, in particular 1 to 50 μm, and most preferably 1 to 15 μm.

The production of such small surface structures and surface elements is described, for example, in European Patent 05 003 358, the disclosure of which is hereby incorporated by reference. It is preferable that the suitable material for making a surface element has the following structures.

11g of 1H, 1H, 2H, 2H-perfluoro octyle acrylate is 0.1g of Irgacure® 819 and 0.2 sold by 8g of dipropylene glycol diacrylate and Ciba Spezialitaetenchemie Lampersheim GmbH It was mixed with gram of Irgacure® 184. 60 μl of this mixture was applied onto a 2 × 2 cm nickel plate patterned in the negative form of a mold body with scattering centers. Subsequently, a plate of PMMA, 1 mm thick and 1 × 1 size, was applied to the surface of the mixture on the nickel plate. The mixture obtained on the nickel plate sandwiched between the nickel plate and the small plate of PPMA is then subjected to 2 seconds of UV radiation from a conventional quicksilver lamp. Next, the substrate with the cured forming composite bonded thereto is removed from the negative mold.

The light guide member may have a wedge shape in cross section. However, it is preferable that a parallelepiped light guide member is provided, and the light entry surface is the side of the parallelepiped. It is preferable that the parallelepiped light guide member is cubic. The installation of the parallelepiped light guide member is possible by the good light efficiency obtained due to the diffractive surface element installed according to the present invention. Thus, substantial simplification of production is achieved. It is preferable that the thickness of the parallelepiped light guide member is in the range of 0.1-3 mm.

Preferably, the light source, which is one or a plurality of LEDs or CCFLs, is arranged inside and / or outside of the light guide member. The surface element is arranged by the light source or the position of the light sources. By arranging the surface elements correspondingly, the intensity of other light, etc., present at different locations on the exit surface, can be compensated such that uniform, ie, collimated monochromatic and / or white light is emitted at the exit surface by the surface element. .

The reflector may be installed to improve the amount of light directed toward the exit surface. This reflector partially surrounds the light source, for example. For example, a rod-shaped light source is preferably arranged at the focal point of the parabolic reflector. Similarly, a plurality of planar reflectors may be installed in addition to or in place of the parabolic reflectors. Also, the outer surface of the light guide member, which is not the exit surface of the light guide member, can be installed to avoid inadvertent loss of light. The corresponding light guide can also be obtained from the side of the light guide member, for example by installing a surface element according to the invention. Guides for the purpose of light and / or collimation and / or spectral influence can also be further achieved by installing the present surface element on the surface of the light source.

In addition to installing the surface element on the exit surface of the light guide member or instead of installing the surface element, such a surface element may also be provided on the opposite side of the light guide member, that is, on the bottom side. Thus, the light diffracted by the surface element is guided through the light guide member facing the display.

In particular, in a preferred embodiment of the present invention, the distance between adjacent surface elements which are particularly installed on the exit surface or the opposite surface decreases with increasing distance to the light source. This allows the fact that the light intensity is high in the vicinity of the light source and decreases with increasing distance to the light source. For example, the light source arranged in the light guide member may be surrounded by concentric circles of the surface element, and the mutual distance of the circles decreases as the distance to the light source increases. Depending on the type of light source, in particular the radiation characteristics of the light source, it may be advantageous to arrange the surface elements differently for that type.

Thus, aperiodic as well as periodic arrangement of the surface elements is possible. The surface element is preferably arranged by the type and position of the light source or light sources.

According to a preferred embodiment of the present invention, the flat panel display has a liquid crystal element such as an LCD element. According to the invention, the liquid crystal element is backlit by an illumination device configured to correspond to the above specification.

Known displays or liquid crystal elements according to the prior art include optical elements such as light boxes. A plurality of fluorescent tubes, in particular CCFLs, are arranged as light sources in the optical device. In order to make the light emitted by the fluorescent tube more uniform and to make the illumination of the liquid crystal element more uniform, the foil is arranged between the fluorescent light tube and the liquid crystal element. These foils are called so-called BEF and DBEF foils respectively. BEF foils enhance luminosity. This is accomplished by installing a plurality of prisms on the foil. The DBEF foil is used to change the polarity of the light reflected from the back side of the liquid crystal element and to return the light toward the liquid crystal element. Also, PRF foils are used to change the polarity. However, the installation of such foils has the drawback that the foil absorbs some of the light.

In the present flat panel display, the BEF foil and preferably also the DBEF foil and the PDF foil are replaced with a light guide member constructed in accordance with the present invention. Preferably, a plurality of optical tubes such as CCFLs are provided. As described above, the light guide member according to the present invention arranged on the front surface of the light tube includes a plurality of surface elements or groups of surface elements. The light guide member has one zone per light tube, which zone is preferably arranged parallel to the light tube and has a plurality of surface elements or groups of surface elements. Here, the individual zones may be identical in configuration. Therefore, the production cost can be reduced.

It is preferable that individual surface elements or groups of surface elements are arranged in lines and columns in individual zones. It is particularly preferable here that the distance between single lines decreases with increasing distance from the light tube. Therefore, the light exiting from the exit surface of the light guide member can be made uniform, that is, in particular the brightness distribution and / or the wavelength distribution can be more uniform. As a result, BEF foils and possibly also DBEF foils and PRF foils can be omitted.

It is possible for the zone to be divided into individual subzones. The lower zone is preferably a rectangular zone, and the number of surface elements or surface element groups in the lower zone located at the side edges of the light guide member is preferably larger than the lower zone located further. It is also possible to provide an aperiodic arrangement of surface elements or groups of surface elements instead of the provision of zones and subzones.

Here, individual surface elements or groups of surface elements are arranged by the light intensity characteristic of the light tube. The density of the surface element or group of surface elements is preferably high at the corners and corners.

The fullest possible disclosure of the present invention, including the best mode for those skilled in the art, will be more particularly described in the remainder of the specification, which includes references to the accompanying drawings.

1 is a schematic perspective view of a lighting device.

2 shows an example of a surface structure of a surface element.

3 shows an example of a possible arrangement of surface elements.

4 shows an example of dividing the exit face of the light guide member in another zone;

FIG. 5 shows a first table describing or defining the zone shown in FIG. 4; FIG.

FIG. 6 shows a second table describing or defining the zone shown in FIG. 4; FIG.

FIG. 7 shows a third table describing or defining the zone shown in FIG. 4; FIG.

8 and 9 are schematic top views of further embodiments of the lighting device.

10 is a schematic representation of a flat panel display in exploded view;

11 is a schematic top view of a suitable light guide member according to the invention for use in a flat panel display.

12 is a partially enlarged view of the light guide member.

The lighting device of the present invention is in the illustrated embodiment and includes a light guiding member 10 which is cubic in shape and can be made of a transparent resin or plastic material, for example PPMA or the like. In the embodiment shown, a rod-shaped light source is arranged along one side 12 of the light guide member 10, and the longitudinal axis of the light source 14 is arranged parallel to the side 12. . The light source 14 is surrounded by a parabolic reflector 16, with the open side of the parabolic reflector being directed towards the side 12. Thus, the amount of light coupled into the side 12 is increased. It is preferable that the light source 14 which is a plurality of LEDs instead of the light tube shown has a light density in the range of 20,000 to 50,000 mW / m 2. In the case of providing a tubular light source 14, it is preferable that the tubular light source 14 be arranged equally in the focal axis of the parabolic reflector 16.

The bottom 18 of the light guide member 10 is provided with a reflector 20 such as a reflector film. It is also possible for the reflectors to be arranged on the sides 22 and / or 24 and / or 26. Instead of installing the reflector, its corresponding surface may also be polished. Alternatively, it may be advantageous to vapor depositing the reflection layer.

A plurality of diffractive surface elements 30 are located on an exit surface 28 of the light guide member 10 such that the surface structure according to the invention is formed.

Each surface element 30 acts as a diffraction grating. Here, different surface elements are designed and installed as linear diffraction gratings having different grating constants. The surface 32 (FIG. 2) of the individual surface elements 30 is designed, for example, in a sine lattice phase. Here, each surface element 30 preferably comprises two sinusoidal half waves.

The production of the individual surface elements 30, and in particular the surface structure 32 of the surface element 30, is made by a photolithographic process according to the invention. In addition, in a particularly preferred embodiment, the surface element 30 can be manufactured as described in EP 05 003 358.

In particular, in a preferred embodiment of the present invention, individual surface elements 30 are included in a group 33 of surface elements (FIG. 3). In the illustrated embodiment, the group 33 of surface elements preferably comprises six surface elements 30 arranged at a constant mutual distance and the spacing between the groups. Each individual surface element 30 has a different surface structure such that the group of surface elements 33 emits substantially monochromatic or white light.

It is preferable to provide another surface element 30, that is, a surface element 30 of another surface structure, so as to couple out light of different wavelengths. For example, as shown in the embodiment of FIG. 3, these elements may be six different surface elements 30, labeled 1 through 6 in FIG. 3. As is apparent from FIG. 3, the other surface elements 1 to 6 of the illustrated embodiment used to couple out specific wavelengths are each arranged in a repeating structure.

In the embodiment shown, the surface element 30 is square and has a length of an edge of about 15 μm.

In particular, in a preferred embodiment (FIG. 4), the individual surface elements 30 are arranged in zones. In FIG. 4, the zones are designed from 1 to 10 and 1_1 to 1_4. The dimensions of the zone and the distance of the surface elements in the zone are evident from the table shown in FIG. 5.

In the embodiment shown in FIGS. 4 and 5, the light source is located on the left side, ie next to the zone indicated by 1 in FIG. 4. Starting from the light source, the mutual distance of the individual surface elements 30 gradually decreases as the distance to the light source increases. Within individual zones or regions, the surface elements have a constant distance. However, it is also possible for the surface element to have different distances in one zone. In particular, the distance from the longitudinal direction, ie from left to right in FIG. 4, can be changed from the distance perpendicular to the longitudinal direction.

Using ORA's simulation software “Light Tool”, an illumination device as described with reference to FIGS. 1 to 5 consists of the zones defined in FIGS. 4 and 5 and is homogeneous, color, and light density. , Collimation as well as illuminating power was measured. Corresponding measurements were taken at the corner, at the center of the corner about 2 mm from the corner, and at nine points located at the center of the light guide.

In the arrangement of the surface elements as defined in FIGS. 4 and 5, the simulations performed showed the following results.

Homogeneity: 91%

Color: white

Average dimming power: 1600 lux

Average Light Density: 2950 nit

Collimation direction: 17 °

In another simulation, the distance between the surface elements 30 in the individual zones (FIG. 4) was clearly defined from FIG. 6.

Here, the following results are obtained.

Homogeneity: 86%

Color: gray (slightly blue)

Average dimming power: 1000 lux

Average light density: 1900 nit

Collimation direction: 17 °

In another simulation, the distance between the surface elements 30 in the individual zones (FIG. 6) was clearly defined from FIG. 7.

Here, the following results are obtained.

Homogeneity: about 78%

Color: white

Average dimming power: 1050 lux

Average light density: 1850 nit

Collimation direction: 17 °

In other tests, zones 8, 9 and 10 were omitted to examine the shorter light guide member 10 which light was also coupled from the left side corresponding to the light member shown in FIG. Thus, the light guide member tested had dimensions of about 36 mm (length) and 44 mm (width) and the length was measured from the left to the right in the direction of the zone, ie in FIG. 4. The distance between the individual surface elements in the zone corresponds to the distance defined in FIG. 5 for zones 1 to 6 and zones 1_1, 1_2, 1_3 and 1_4. Here, the following results were measured.

Homogeneity: about 88%

Color: white

Average dimming power: 1100 lux

Average light density: 2150 nit

Collimation direction: 17 °

In a further test, the surface of the light guide member 10 was not divided into zones, and a constant distance between the individual surface elements was selected. Here, the following results were obtained.

Distance: 4 μm

Homogeneity: about 75%

Color: white

Average dimming power: 1850 lux

Average light density: 3350 nit

Collimation direction: 17 °

Distance: 6 ㎛

Homogeneity: about 78%

Color: white

Average dimming power: 1600 lux

Average light density: 2400 nit

Collimation direction: 17 °

Distance: 8 ㎛

Homogeneity: about 82%

Color: white

Average dimming power: 1400 lux

Average light density: 2500 nit

Collimation direction: 17 °

Distance: 10 ㎛

Homogeneity: about 84%

Color: white

Average dimming power: 1200 lux

Average light density: 2200 nit

Collimation direction: 17 °

Distance: 11 μm

Homogeneity: about 87%

Color: white

Average dimming power: 1200 lux

Average light density: 2150 nit

Collimation direction: 17 °

From the test results, the following conclusion is drawn.

1. The arrangement and distribution of diffractive surface elements have great homogeneity with respect to light distribution.

2. Even a relatively less excellent surface arrangement with almost no homogeneity, the color is always white when mixed.

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

4. The intensity of light is a function of the distance between the points.

In particular, when the present lighting device is used as a backlight for a mobile phone where at least 75% homogeneity is accepted, illumination of a high quality display suitable for the user is achieved. In particular, the target direction of collimation can be achieved in combination with a predetermined color temperature without the aid of a light guide foil. Thus, the number of components is reduced, the design is much more flexible, and the whole system can be further miniaturized.

8 and 9 show two different embodiments of lighting devices which are particularly suitable as backlights for mobile phones.

The light guide member 10 is basically configured as described with respect to the previous figures. The light source is LED. In the embodiment of FIG. 8, a single LED 34 is arranged at the corner of the light guide member 10. The corresponding corner 36 preferably shaves off the corners such that the exit side of the LED 34 is arranged in the corner or in the rectangular light guide member 18. As a result, the light is coupled into the light guide member 10 through the chamfered surface 48. Since the light guide member 10 is typically rectangular rather than square, the cutout edge is not made at an angle of 45 ° and the angle α between the short side 40 and the inclined surface 38 is greater than 45 °. It is desirable to be made small.

In the illustrated embodiment, the individual surface elements or the arrangement of individual groups of surface elements allow the light to be evenly coupled out. Here, the distance between individual surface elements or groups of surface elements in the direction of dash line 42 changes so that the distance between individual elements or groups decreases as the distance from the LED increases.

The embodiment of the lighting device shown in FIG. 9 also includes an LED 44 as a light source, in which the three LEDs 44 are arranged on the short side 40 of the light guide member 10. . Here, it is preferable that the light guide member 10 includes the recessed part 46 in the short side 40. Preferably, the recess 46 is semicircular. In the embodiment shown, the recess 46 extends over the entire thickness of the light guide member 10. It is also possible to provide a recess of the hemisphere, and the diameter of the sphere is smaller than the thickness of the light guide member 10.

In this embodiment, the surface elements or groups of surface elements are rearranged to obtain uniformity of the luminance distribution at the exit surface 20.

Of course, other embodiments described may be combined. For example, LEDs can be installed on different sides. In particular, a plurality of LEDs are arranged around the entire periphery of the light guide member 10. Similarly, a combination of the embodiments shown in FIGS. 8 and 9 is possible. In particular, it may be appropriate for the LED to couple with one or several CCFL tubes. For example, the lighting device shown in FIG. 1 can be modified such that each LED is installed at two corners opposite the CCFL tube 14, as shown in particular in FIG. 8. Thus, good illumination of these two corners at a considerable distance from the CCFL tube 14 can be ensured in a simple manner.

In a preferred embodiment of the present lighting device, the same is provided for a flat panel display. An essential element of a flat panel display is liquid crystal 50 (FIG. 10). The liquid crystal element is usually an LCD element. In addition, a light box or the like is provided as a light source 52 including a plurality of mutually parallel light tubes 54. The light tube 54 is preferably CCFL.

According to the prior art, several foils are provided between the light box 52 and the liquid crystal element 50. These are called BEF, DBEF and PRF foils.

According to the invention, at least the BEF foil is replaced with a light guide member 56. The light guide member 56 is basically configured as described above with respect to FIGS.

The light guide member 56 includes a plurality of zones 58 in horizontal or parallel orientation with the light tube 54. Each zone 58 is associated with a light tube 54, with the light tube 54 preferably located at the center behind the zone 58. Zones 58 are identically structured, ie each zone preferably has the same arrangement of surface elements or groups of surface elements.

A preferred arrangement of the group of surface elements 33 is shown in FIG. Here, the individual groups 33 of surface elements are arranged symmetrically with respect to the centerline 60. Starting from the centerline 60, the distance between the individual groups 33 of surface elements decreases in the direction of the arrow 62, ie outwardly.

In the embodiment shown, the groups of surface elements 33 are arranged in lines and columns and the distance between the columns is constant. In the development of the present invention, the zone 58 is preferably divided into rectangular lower zones. In Fig. 2 these lower zones are arranged side by side. Here, it is possible to install different spacing distances within the individual lower zones, and it is desirable to have smaller spacing distances in the lower zone at the corners, ie left or right in FIG. 12.

Instead of or in addition to the light box 52 (FIG. 10), the four or more light tubes 54 may, for example, allow the light guide member to be irradiated laterally to the light guide member 56. It may be arranged along the periphery of 56. Further, the surface elements or groups of surface elements are arranged such that the luminous intensity is distributed as uniformly as possible from the light guide member facing the LCD element. The distance between individual surface elements or groups of surface elements is preferably reduced toward the center of the light guide member. It is also possible to divide the surface of the light guide member into four zones or segments, preferably four identical rectangular segments which are preferably composed of respective points symmetrical about the center of the light guide member.

Although the present invention has been described and described with reference to detailed exemplary embodiments, the present invention is not limited to these exemplary embodiments. Those skilled in the art will recognize that changes and modifications can be made without departing from the essential scope of the invention as defined by the following claims. Accordingly, all such changes and modifications that fall within the scope of the appended claims and their equivalents are included within the invention.

Claims (23)

Lighting devices for flat panel displays, in particular mobile application display backlights Light source, A light guide member coupled to the light emitted from the light source and coupled out at an exit surface, The exit surface has a surface structure comprising a diffractive surface element for light propagation, And wherein all surface elements have a surface structure with a constant amplitude. The method of claim 1, Said individual surface elements acting as diffractive elements generating a collimated bundle of light with spectral light splitting. The method according to claim 1 or 2, And the surface element is arranged such that monochromatic and / or white light is generated by superposition of bundles of two or more adjacent lights. The method of claim 1, Said surface element having a size of 0.04 to 10000 μm ² , in particular 0.04 to 500 μm ² . The method of claim 1, The individual surface elements have a mutual distance of 0 to 100 μm, in particular 0 to 50 μm, particularly preferably 0 to 15 μm. The method of claim 1, And the distance of the adjacent surface element decreases as the distance from the light source increases. The method of claim 6, And the distance between the adjacent surface elements decreases step by step. The method of claim 1, And the surface elements are arranged aperiodically. The method of claim 1, And the exit surface comprises an area in which the surface elements have the same distance. The method of claim 1, And the light source is arranged in and / or without the light guide member. The method of claim 1, And the light source is partially enclosed by a reflector to enhance the coupling in of the light. The method of claim 11, A parabolic reflector is provided and the light source designed as a fluorescent tube is arranged at a focal point. The method of claim 1, At least one side of the light guide member other than the exit surface is provided with a reflector and / or has a reflecting surface. The method of claim 1, And the light source comprises one or a plurality of LEDs. The method of claim 1, And the light guide member has a parallel pipe shape. The method of claim 1, And the light guide member is wedge-shape and the light source is arranged on the small side of the wedge. The method of claim 1, A plurality, preferably at least two, in particular at least four, most preferably at least six surface elements are included in the group of surface elements, the group of surface elements emitting monochromatic and / or white light Lighting device. A flat panel display comprising the liquid crystal element and the illuminating device according to any one of claims 1 to 17 for backlighting the liquid crystal element. The method of claim 18, As said light source there are in particular provided a plurality of mutually parallel light tubes, said light guide member comprising one zone per light tube, said zone being preferably arranged parallel to said light tube and having surface elements and And / or group of surface elements. The method of claim 19, The surface elements and / or groups of surface elements are arranged in lines and columns in the zone, preferably the distance between the lines decreases as the distance from the light tube increases. Flat display. The method of claim 19 or 20, And the arrangement of the surface elements or groups of surface elements is symmetrical to the center line in each zone and the center line is preferably installed at the shortest distance from the light tube. The method of claim 19, Wherein said zone is divided into a lower zone, said lower zone being preferably rectangular in shape. The method of claim 22, And the lower section laterally installed at the corner further comprises a surface element or a group of surface elements than the other lower region.

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