EP2145216A1

EP2145216A1 - Lighting device and liquid crystal screen having such a lighting device

Info

Publication number: EP2145216A1
Application number: EP07802334A
Authority: EP
Inventors: Georg Diamantidis
Original assignee: NOCTRON SOPARFI SA
Current assignee: NOCTRON SOPARFI SA
Priority date: 2007-05-04
Filing date: 2007-09-15
Publication date: 2010-01-20
Also published as: CN101688943A; WO2008135072A1; TW200844589A

Abstract

The invention relates to a lighting device, particularly for background lighting of a liquid crystal panel (60), comprising a fiber optic element (12) delimited by a first main surface (14) and a second main surface (16) parallel to and spaced from said surface. Illuminants (28) are provided, which are located such that the light emitted by the illuminants (28) is coupled into the fiber optic element (12). A reflection device (53) is provided on the side of the second main surface (16) of the fiber optic element (12), reflecting light in a direction toward the interior of the fiber optic element (12). The invention further relates to a liquid crystal screen comprising a liquid crystal panel (60) and a lighting device (10, 10', 10'', 10'''), by means of which the liquid crystal panel (60) can have light applied to the side (64) thereof opposite a visible side (62). A lighting device (10, 10', 10'', 10''') according to any one of the claims 1 to 23 is provided for the liquid crystal screen.

Description

Lighting device and liquid crystal screen with such a lighting device

The invention relates to a lighting device according to the preamble of claim 1 and a liquid crystal screen according to the preamble of claim 24.

Liquid crystal displays, commonly known as LCD screens, are enjoying increasing popularity due to their low profile construction.

Such LCD screens comprise a liquid crystal panel, which is illuminated by means of a lighting device of the type mentioned. Frequently, the illuminants used require additional components, such as a hole reflector, a Fresnel lens and usually a plurality of diffusion filters, which are arranged between the liquid crystal panel and the lighting means.

However, this design often adversely affects the contrast and brightness of the image recognizable on the visible side of the LCD screen. The diffusion filters attenuate the intensity of the radiation emitted by the illumination device by about 10% before reaching the liquid crystal panel. The shadow mask has an even stronger effect. Through them, about 25% to 30% of the radiation emitted by the illumination device is absorbed, which is why only a correspondingly smaller proportion of light reaches the liquid crystal panel to be illuminated. In addition, it comes through the hole reflector to adverse interference effects.

To compensate for these interference effects and to improve the achievable contrast on the visible side of the LCD screen recognizable image, the Fresnel lens is provided. However, this also causes the angle at which the screen can be viewed to be reduced, so that an image produced by it is still clearly visible.

There is therefore a desire for a lighting device in which largely can be dispensed with above-mentioned correction components and which is still suitable as a backlight in a liquid crystal screen, has good luminosity and also builds flat.

The latter properties are also increasingly in lighting devices in the form of lamps for lighting rooms or outdoor environments in demand because the flat design an attractive appearance can be achieved. Frequently, however, a desired flat construction can not be reconciled with a required luminance of the lighting device.

The object of the invention is therefore to provide a lighting device of the type mentioned, which takes into account the above idea.

This object is achieved by a lighting device having the features specified in claim 1.

By the reflection device, the light output of the light emitted by the illumination device via its first main surface light is increased. This lighting device can be used in particular as a backlight for liquid crystal screens.

Advantageous developments are in the dependent claim 2 to 23 indicated.

The reflection effect of the reflection device is in each case increased by one or more of the measures according to one of the claims 2 to 4.

A strong reflection effect is achieved by the measure according to claim 5. For the paper sheet according to claim 5 basis weights have been found to be favorable, as indicated in claim 6.

By the measure according to claim 7 and a selection of the material of the reflection particles according to claims 8 or 9, the reflection effect of the reflection means and thus the luminosity of the illumination device can be further increased.

In this case, the measure according to claim 10 is particularly favorable, since such an advantageously homogeneous light reflection is ensured.

To further homogenize the light output, the second main surface of the light guide element is advantageously designed as specified in claim 11.

The light guide element preferably consists of one of the materials mentioned in claim 12.

If the light guide element is designed as specified in claim 13, it can be used in particular as a backlight for planar formed liquid crystal screens.

The measure according to claim 14 ensures that the thickness of the lighting device is less influenced by the arrangement. tion of the light source is affected.

In this case, it is favorable as far as the coupling of the light into the planar light guide element is concerned, if the luminous means according to claim 15 or according to claim 16 is arranged.

In order to increase the used proportion of the light emitted by the bulbs light, which is coupled into the planar light guide element, the measure is advantageous according to claim 17.

By the measures according to claims 18 and 19, a good light transmission is achieved by the bulbs on the planar light guide element. The silicone material may be, for example, silicone oil. An elastic silicone compound can also be used. For this purpose, the lighting means may e.g. are first coated with liquid silicone oil to which a hardener is added, so that the silicone oil solidifies after some time to an elastic mass.

If the wavelength of the light emitted by the lighting means does not coincide with a desired wavelength, this can be adjusted by the measure according to claim 20. Phosphor particles include phosphors and absorb incident radiation and emit radiation at least at a different (longer) wavelength. With a suitable choice of phosphor particles or phosphor particle mixtures, therefore, the radiation emitted by the lamps can be converted into radiation with a different spectrum.

The measure according to claim 21 ensures a homogeneous distribution of the light output. Energy efficient and efficient bulbs are specified in claim 22.

Alternatively, it is favorable if illuminants according to claim 23 are used.

It is also an object of the invention to provide a liquid crystal screen of the type mentioned, which combines a flat design with high brightness and high contrast.

This object is achieved by a liquid screen with the features of claim 24.

By the measure according to claim 25, a good light transmission between the lighting device and the liquid crystal panel is achieved.

It is advantageous if the optical coupling layer is formed from one of the materials specified in claim 26.

Embodiments of the invention are explained below with reference to the drawings. In these show:

Figure 1 is a partially broken plan view of a first embodiment of a plate-shaped lighting unit;

Figure 2 is a section through the lighting unit of Figure 1 along the section line II-II there;

Figure 3 is a partially broken plan view of a second embodiment of a plate-shaped lighting unit; Figure 4 is a section through the lighting unit of Figure 3 along the section line IV-IV there;

Figure 5 is a plan view of a third embodiment of a plate-shaped lighting unit;

6 shows a section through the lighting unit of Figure 5 along the section line VI-VI;

FIG. 7 shows a section corresponding to FIG. 6 through a fourth exemplary embodiment of a plate-shaped lighting unit;

FIG. 1 is a partially broken plan view of a liquid crystal panel of a liquid crystal panel having a lighting unit of FIG. 1 arranged thereunder; FIG. and

9 shows a section through the liquid crystal panel and the lighting unit of Figure 8 along the section line IX-IX.

In Figures 1 and 2, a lighting unit 10 is shown, which comprises a planar light guide plate 12 made of transparent acrylic glass. The light guide plate 12 may also be made of another homogeneous translucent material, such as a glass or an epoxy resin. The light guide plate 12 is preferably clear.

The light guide plate 12 has a first main surface 14, over which useful light generated by the illumination unit 10 is emitted. On the opposite side, the optical waveguide plate 12 has a second main surface 16 (see Fig. 2) which has an upper surface indicated by serrations 17. surface roughness, which will be discussed in more detail below.

On two opposite narrow surfaces of the light guide plate 12, which form the outer edges 18 and 20, the light guide plate 12 carries a respective housing 22 or 24 with ü-shaped cross-section and here not specifically provided with a reference numeral end walls. The respective open side of the housing 22 or 24 points in the direction of the correspondingly adjacent outer edge 18 or 20 of the light guide plate 12.

The housings 22 and 24 will be explained in more detail below using the example of the housing 22. The statements apply mutatis mutandis corresponding to the housing 24th

The housing 22 delimits with the outer edge 18 of the light guide plate 12 an interior space 26 in which light sources in the form of a plurality of semiconductor light-emitting chips 28a are arranged, of which only one is provided with a reference number in FIG.

The semiconductor light-emitting chip 28a comprises, for example, an n-conducting layer of n-GaN or n-InGaN and a p-conducting layer of a III-V semiconductor material such as p-GaN. Between such an n-type and such a p-type layer, an MQW layer may be disposed. MQW is the abbreviation for "Multiple Quantum Well". An MQW material includes a superlattice which has an electronic band structure altered according to the superlattice structure and accordingly emits light at other wavelengths. By selecting the MQW layer, the spectrum of the radiation emitted by the pn-semiconductor light-emitting chip can be influenced in a targeted manner. The interior 26 of the housing 22 is filled with a light-conducting liquid in the form of liquid silicone oil 30, which is indicated in the figures in the form of circles and light emitted from the semiconductor light-emitting chips 28 a light to the outer edge 18 of the light guide plate 12 passes. By the

Silicone oil 30 is at the same time dissipated by the semiconductor light-emitting chip 28 a generated heat to the outside, in particular to the walls of the housing 22.

The p-GaN / n-InGaN semiconductor light emitting chip 28a irradiates ultraviolet light and blue light in a wavelength range of 420 nm to 480 nm when voltage is applied. In order to produce white light with the semiconductor light-emitting chips 28a, in the silicone oil 30, fine phosphor particles 32 are homogeneously distributed, which are made of color-centered transparent solid-state materials. These phosphor particles 32 are indicated in the figures as circles, which are smaller than the silicone oil 30 characterizing circles. The phosphor particles 32 may also each be a mixture of several different types of phosphor particles. By suitable choice of phosphor particles or phosphor particle mixtures, therefore, the radiation emitted by the semiconductor light-emitting chips 28a radiation can be converted into a radiation having a spectrum which is adapted to a desired spectrum. When dispensing with phosphor particles 32, the illumination unit 10 radiates blue light.

The semiconductor light-emitting chips 28a are electrically connected in parallel and can be acted upon by voltage via two supply lines 34 and 36. For this purpose, the supply lines 34 and 36 terminate in externally accessible terminals 38 and 40, respectively. The supply lines 34 and 36 are not shown in FIG. 2 for the sake of clarity. The semiconductor light emitting chips 28a may also be connected in series when to work with a higher supply voltage.

The inner walls of the housing 22 are provided with a reflection layer 42, whereby light, which is first emitted by the semiconductor light-emitting chips 28a in a direction away from the light guide plate 12, is reflected onto the same or its outer edge 18.

As can be seen in particular in Figure 2, sits the

Light guide plate 12 with its second major surface 16 on a peripheral wall 43 of another housing 44 and as it forms a lid. The housing 44 and the second main surface 16 of the light guide plate 12 thus define an interior 46.

On the second main surface 16 of the light guide plate 12, a reflector substrate 48 in the form of a white paper sheet 48 is applied with a coupling layer 50 of a silicone material, which is also shown by circles.

Als silicone material comes, for example, a viscous silicone oil in question. The white paper sheet 48 is soaked with the viscous silicone oil of the coupling layer 50 prior to application to the light guide plate 12 and then pressed with a roller under pressure on the frosted second major surface 16 of the light guide plate 12. Care must be taken that all the bubbles possibly present in the silicone oil of the coupling layer 50 and between the paper sheet 48 and the light guide plate 12 are pressed out by the pressure of the roller. The white paper sheet 48 is fixed by the adhesion action of the silicone oil of the coupling layer 50 on the second main surface 16 of the light guide plate 12. Instead of thick silicone oil, the coupling layer 50 may also be made of a viscous elastic silicone compound. For this purpose, the paper sheet 48 can be soaked before application to the light guide plate 12 with thinner silicone oil, which was previously mixed with a hardener. As a result, the silicone oil can cure after application of the paper sheet 48 to the light guide plate 12 to an elastic silicone composition, wherein the light transmittance of the silicone material is maintained.

In a modification, the coupling layer 50 may be made of a translucent in the cured state resin, for example, an epoxy resin or a polyester resin, which is also shown by the circles.

To increase the reflection effect, reflection particles 51 are homogeneously distributed in the coupling layer 50 of silicone oil or of a resin. The reflection particles 51 are indicated as points within the circles representing the silicone oil or the resin of the coupling layer 50.

AlS-JXIaterial for the reflection particles 51 are in particular scandium oxide or zinc sulfide into consideration. Alternatively, oxides of lanthanum and the rare earth metals, e.g. Cerium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide or lutetium oxide serve as the material for the reflection particles 51.

Depending on the nature of the reflection particles 51 and their

Concentration in the coupling layer 50 of silicone oil or a resin, reflected light can be obtained in different intensities. Also different color effects or temperatures can be achieved by the targeted use of the above-mentioned reflection particles 51. If the coupling layer 50 is made of a resin in which reflection particles 51 are distributed, the reflection effect against the use of a coupling layer 50 made of silicone oil is increased and the proportion of the usable light, which leaves the light guide plate 12 on the first main surface 14.

For example, a coupling layer 50 made of a hardened liquid resin in which the reflection particles 51 are homogeneously distributed is applied to the second main surface 16 of the light guide plate 12. Before the coupling layer 50 hardens out of resin, the paper sheet 48 is placed, which is then fixed after the curing of the resin.

Alternatively, first, a homogeneous mixture of resin, a hardener, and reflective particles 51 dispersed therein may be distributed on the white paper sheet 48. The thus coated paper sheet 48 is then pressed with the coating of resin, hardener and reflection particles 51 onto the second main surface _-X6- of the light guide plate 12. When the light guide plate 12 is made of acrylic glass, the resin / hardener mixture dissolves the acrylic glass during the curing of the coupling layer 50. As a result, a surface roughness is generated on the second main surface 16 of the light guide plate 12. Therefore, a light guide plate 12 can be used without surface roughness already generated in advance, as it is more advantageous when the coupling layer 50 is formed of silicone oil.

It is also possible, in the casting liquid acrylic glass on a coated with hardened resin, in which the reflection particles 51 are homogeneously distributed, coated white paper 48, which in one of the light guide plate 12th appropriate form is applied to apply. A light guide plate 12 thus obtained, which already carries the white paper sheet 48 and the coupling layer 50 with reflection particles 51, may for example be between 1 mm and 10 mm thick.

Also by an extrusion process, a light guide plate 12 can be obtained, which carries the white paper sheet 48 and the coupling layer 50 with reflection particles 51. Extrusion methods can be used to obtain light guide plates 12 which are between 2 m and 3 m wide and between 3 m and 10 m long.

The coupling layer 50 of resin between the white paper sheet 48 and the second major surface 16 of the light guide plate 12 is between 1 μm and 1000 μm, preferably between 50 μm and 250 μm, and more preferably between 100 μm and 200 μm thick. The above-mentioned effect of the coupling layer 50 of silicone oil or of a resin with the reflection particle 51 also depends on the thickness of this layer, so that the desired properties can also be adapted by choosing a specific thickness thereof. _

The white paper sheet 48 has a basis weight of from 50 g / m ² to 200 g / m ² , preferably from 80 g / m ² to 170 g / m ² , more preferably from 100 g / m ² to 150 g / m ^2, and most preferably from 120 g / m ² .

As a reflector substrate 48, instead of the white paper sheet, it is also possible to provide, for example, a white plastic film or a mirror film, which can be compatible with the coupling layer 50 made of silicone oil or a resin.

In a modification, phosphor particles, in particular, are in the coupling layer 50 made of silicone oil or from a resin luminescent particles, and in particular phosphorescent particles, homogeneously distributed, which are not specifically shown. In this case, the illumination unit 10 can emit light even without active lighting means whose spectrum can be adjusted by an appropriate choice of the luminescent particles or a mixture of such luminescent particles.

An additional reflection layer 52 is provided on the side of the paper sheet 48 remote from the coupling layer 50 made of silicone oil or from a resin, which may be provided, for example, in the form of a self-adhesive mirror film or also of a white plastic film.

This sandwich arrangement of the reflective layer 52, the reflector substrate 48 and the coupling layer 50 made of silicone oil or a resin is covered by the housing 44, wherein the bottom 54 abuts against the reflective layer 52. The housing 44, the reflector substrate 48, the coupling layer 50 with or without reflection particles 51 and the reflection layer 52 together form a reflection device 53 for the light, which leaves the light guide plate 12 on its second major surface 16.

So that no light is emitted via those outer edges of the light guide plate 12, which carry no bulbs 28, the light guide plate 12 is covered there by opaque films 55. These foils 55 may support a reflective layer as described above so that light incident on them via the corresponding outer edge of the light guide plate 12 is reflected towards the inside of the light guide plate 12. On the other hand, if a light exit via the outer edges of the light guide plate 12 is desired, eg as a lateral reading or working light, it is possible to apply one or both foils 55 accordingly be waived.

FIGS. 3 and 4 show a further exemplary embodiment of a lighting unit 10 '. Components already explained with reference to FIGS. 1 and 2 bear the same reference numerals in FIGS. 3 and 4.

The lighting unit 10 'differs from the lighting unit 10 according to FIGS. 1 and 2 in that the light-emitting means 28 are not semiconductor light-emitting chips 28a but light-emitting tubes 28b. The fluorescent tubes 28b may be formed as compact fluorescent lamps, which are also known under the terms energy-saving lamps or CFL tubes. Fluorescent lamps or cold cathode tubes are also suitable as fluorescent tubes 28b. Cold cathode tubes are also known by the term CCFL tubes.

CFL tubes preferably used herein may have a diameter of 5 mm to 25 mm, preferably 5 mm to 8 mm, and a length of 5 cm to 150 cm, preferably 8 cm to 40 cm.

CCFL tubes to be used in the illumination unit 10 'may have a diameter of 2 mm to 6 mm, preferably 3 mm to 4 mm, and a length of 4 cm to 120 cm, preferably 8 cm to 55 cm, to have.

The fluorescent tubes 28b may be filled with various gases, such as neon, helium, nitrogen, carbon dioxide, krypton, argon, optionally argon with mercury, and the like, with aging resistant filler gases being preferred.

The tubular body of the fluorescent tubes 28b may be made of glass or plastic and be flexible in the latter case. In FIGS. 3 and 4, a fluorescent tube 28b is shown in each housing 22 and 24, respectively, which can be acted upon by voltage via the supply lines 34 and 36. Alternatively, two or more fluorescent tubes 28b may be disposed in each housing 22 and 24, for example, three CCFL tubes 28b, the first of which generate red light, the second green light, and the third blue light. For this purpose, the glass or the plastic of the fluorescent tubes 28b may be colored accordingly, or the color of the light generated is adjusted via the corresponding choice of the gas filling of the fluorescent tubes 28b.

As can be seen in FIGS. 3 and 4, in contrast to the lighting unit 10 shown in FIGS. 1 and 2, no silicone oil and no phosphor particles are provided in the housings 22 and 24 of the lighting unit 10 '. In a modification, however, this is also provided when a color transformation of the light generated by the arc tube 28b is desired.

In a modification of the lighting unit 10 'which is not shown specifically, lighting tubes 28b may also be formed by extending in the outer edges 20 and 22 of the light guide plate 12 elongated cavities, for example krypton, e.g. Grooves, are provided, which are gas-tight to the outside by means of a mirror film, wherein for the operation of such a fluorescent tube 28b necessary electrodes protrude into these grooves. Also, a single groove is possible, which extends around the circumference of the light guide plate 12 around.

FIGS. 5 and 6 show a further exemplary embodiment of a lighting unit 10 ". Components already explained with reference to FIGS. 1 to 4 bear in FIGS and 6 the same reference numerals.

As can be seen in particular in FIG. 6, the illumination unit 10 '' differs from the illumination unit 10 according to FIGS. 1 and 2 in that the semiconductor light-emitting chips 28a do not laterally outwardly adjacent to the outer edges 18 and 20 of the light guide plate 12, but are arranged within a recessed from the first main surface 14 of the light guide plate 12 groove 56. Within the groove 56, the semiconductor light-emitting chips 28a are also surrounded by silicone material 30 and homogeneously distributed phosphor particles 32 therein. If the silicone material is relatively liquid silicone oil 30, a cover 58 may be provided for the groove 56, which is indicated in FIG. 4 by a dotted line. If the silicone material 30 is a sufficiently viscous and elastic compound, then this cover 58 can be dispensed with.

In a not specifically shown modification of the lighting unit 10 ', the groove 56 on the second main surface 16 of the light guide plate 12 proceed.

FIG. 7 shows a further exemplary embodiment in the form of a lighting unit 10 '' '. Components already explained with reference to FIGS. 1 to 6 bear the same reference numerals in FIG.

In contrast to the illumination units 10 and 10 ", two light guide plates 12a and 12b are provided in the illumination unit 10 '", which maintain a distance between the outer edge 20a of the light guide plate 12a and the outer edge 20b of the light guide plate 12b parallel to each other and in a plane are arranged. The semiconductor light emitting chips 28a are provided in the space thus left and surrounded by silicone oil 30 which is added with phosphor particles 32.

As can be seen in FIG. 5, phosphor particles 32 are also distributed in the silicone oil 50 between the light guide plates 12a, 12b and the paper sheet 48 here.

In the case of the three illustrated lighting units 10, 10 ', 10 ", the semiconductor light-emitting chips 28a are each arranged such that they are arranged relative to the light guide plate 12 between the plane predetermined by the first main surface 14 and the plane predetermined by the second main surface 16 thereof ,

As mentioned above, the second major surface 16 of the light guide plate 12 is roughened. This surface roughness is in or below the order of the wavelength of the light reflected from the reflecting means 44, 48, 50, 52. Preferably, the roughness is of the order of 100 μm to 500 μm, preferably from 200 μm to 400 μm, and more preferably from 300 μm to 500 μm.

By this surface roughness of the second main surface 16 of the light guide plate 12, scattering is achieved, whereby the light leaving the light guide plate 12 via the first main surface 14 becomes more uniform.

Also in the lighting units 10 '' and 10 '' 'may be provided 28b instead of the light chips 28a fluorescent tubes. It then applies the above to the figures 3 and 4 said mutatis mutandis accordingly.

In the exemplary embodiments of the illumination unit 10, 10 '' and 10 '''stands the silicone oil 30, which contains the semiconducting In this way, it is ensured that the light emitted by the semiconductor luminescent chips 28a is reliably coupled into the optical waveguide plate 12.

Another way to adjust the color of the light emitted by the illumination unit 10, 10 ', 10' 'is to use different types of semiconductor light emitting chips 28a. For example, predominantly semiconductor light-emitting chips 28a are installed, which emit blue light. In addition, however, semiconductor light-emitting chips 28a are used, which emit in red and green. By appropriate tuning, also with regard to the respective light output, a color adjustment, in particular a largely white balance, can be achieved.

It is also possible to use semiconductor luminescent chips 28a which emit UV light. Then, however, a UV filter should be applied to the first main surface 14 when the generated light is intended for the human eye.

The lighting units 10, 10 ', 10' 'and 10' '' explained above can be used as lighting means, for example for illuminating interior spaces. Not only interiors of buildings, but also interiors of ships, aircraft, motor vehicles and the like come into consideration. The lighting units 10, 10 ', 10' 'and 10' 'can be used, inter alia, as luminous wall paneling or clothing. The latter is also conceivable for the outer lining of buildings.

The lighting units 10, 10 ', 10''and10''' can be accommodated in a sealed housing in a simple manner. Therefore, also comes a use in medicine, eg in medical devices, instruments or microscopes, but also as a lighting unit for operating theaters, into consideration.

With the appropriate light intensity, the lighting units 10, 10 ', 1O ^1' and 10 '' further 'in the medial region may as movies, television and the like can be used.

Especially in connection with solar cells as an energy source is also to think of the street and guard rail lighting.

In addition, applications in the field of photography come as a flash in question. A stroboscope can also be equipped with the illumination units 10, 10 ', 10 "or 10"' '.

In particular, when the light guide plate 12 is made of acrylic glass, it can be brought into a certain shape in a manner known per se, i. this is then no longer flat, but an arbitrarily shaped, in particular curved, light guide element. In this case, the corresponding lighting unit itself can form a utility object, which can have an additional function to that of the lighting. It is conceivable, for example, to form the light guide element and thus the entire lighting unit in the form of a bathtub or shower cubicle. But also other furnishings, e.g. Chairs, tables and the like come into question.

The lighting units 10, 10 ', 1O ^1' and 10 ''', however, are primarily intended as a backlight for a liquid crystal screen. This will be explained with reference to FIGS. 8 and 9, in which the lighting unit 10 is shown by way of example. As can be seen, in particular, in the section shown in FIG. 9, a liquid-crystal panel 60 having a flat viewing side 62 and a side 64 opposite thereto is provided in front of the first main surface 14 of the light guide plate 12 of the illumination unit 10. A liquid crystal panel 60 is known per se, and therefore a detailed explanation thereof will be omitted here.

On the side 64 of the liquid crystal panel 60 is the

Lighting unit 10 arranged so that the first main surface 14 of the light guide plate is parallel to the liquid crystal panel 60. Between the first main surface 14 of the light guide plate 12 and the side 64 of the liquid crystal panel 60, an optical coupling layer 66 made of a thick silicone oil or of an elastic silicone compound is provided. The silicone material is also indicated here by circles. The optical coupling layer 66 made of the elastic silicone composition can be obtained by adding a hardener to a more fluid silicone oil. The optical coupling layer 66 is in direct contact with the first major surface 14 of the light guide plate 12 and with the surface of the liquid crystal panel 60 on its side 62.

In a modification, the optical coupling layer 66 may also be made of a resin, for example of an epoxy resin or a polyester resin. In this case, the optical coupling layer 66 can be obtained by curing a liquid applied resin, to which a hardener was added, as it is known per se.

Through the illumination unit 10, a uniform light of high intensity is emitted via the first main surface 14 of the light guide plate 12, which is transmitted via the coupling layer 66 is transferred from silicone oil or a viscous silicone composition to the liquid crystal panel 60 and this lit from its side 64 ago.

The illumination units 10, 10 ', 10' 'and 10' '', in comparison to known backlighting for liquid crystal panels, in which additional components, such as Lochreflektormasken, Fresnel lenses and diffusion filters are used, a good luminosity while ensuring a relatively large viewing angle of the liquid crystal panel 60, in which the image produced therewith is still clearly visible.

When the illumination devices 10, 10 ', 10' 'and 10' 'are used as backlight for a liquid crystal screen, it can also be borne in that the reflection particles 51 can have, in addition to their reflective effect, also the phosphor particles 32 corresponding properties and radiation incident on them in part absorb and radiation of a different wavelength can emit.

If, for example, particles of scandium oxide or of zinc sulfide are used as the reflection particles 51 and semiconductor light-emitting chips 28a are used which emit light in the wavelength range between 160 nm and 380 nm, the phosphor particles 32 in the silicone oil 30 can be dispensed with. Even the reflection particles 51 of scandium oxide or zinc sulfide convert this light in the wavelength range between see 160 nm and 380 nm of the semiconductor light-emitting chips 28a in white light. In this is emitted from the reflection particles 51 in all spatial directions and at least largely reflected by the reflection layer 52 in the direction of the light guide plate 12. If semiconductor light emitting chips 28a which emit blue light in the wavelength range of 450 nm to 475 nm are used, it is converted into light blue light when the reflection particles 51 are made of scandium oxide.

The apparent spectrum of the light exiting on the visible side 62 of the liquid crystal panel 60 can also be influenced by targeted control of the permeability of the liquid crystal cells of the liquid crystal panel 60.

Even with conventional liquid crystal screens, which work with color filters, this effect can be used. The more energetic radiation is transmitted not only by the blue filter, but also by the red and green filters of a per se known color mask of a corresponding liquid crystal screen. A compensation of the color intensities can be achieved by an appropriate electronics.

The light blue light is more energetic than red or green light, but more difficult to perceive by the human eye. This enhances the visual impression for the viewer without sacrificing the color impression.

The individual pixels of the liquid crystal screen appearing in red, green and blue appear clearer than a pure white backlight.

It is generally sufficient if, with an edge length of the outer edges 18 or 20 of the optical waveguide plate 12 of approximately 50 cm, four semiconductor luminescent chips 28a are respectively provided along the corresponding outer edge 18, 20 or within the groove 56. The illumination units 10, 10 ', 10''can be manufactured in many different configurations in terms of their dimensions and the number of semiconductor chips 28a or the fluorescent tubes 28b.

The lighting units 10, 10 ', 10' ', for example, each with seven interconnected semiconductor lighting chips 28a, an edge length of the outer edges 18, 20 of the light guide plate 12 of about 100 cm and a width of the light guide plate 12 of about 20 cm to be made.

The edge length of the outer edges 18, 20 of the light guide plate 12 may, for example, from 10 cm to 200 cm, and the width of the light guide plate 12 may vary, for example, from 1 cm to 20 cm.

The recording power of the lighting units 10, 10 ', 10 "is low when semiconductor light-emitting chips 28a are used.

Claims

claims

1. Lighting device, in particular for the backlight of a liquid crystal panel (60), with

a) a light guide element (12) which is delimited by a first main surface (14) and a second main surface (16) spaced apart parallel thereto;

b) light-emitting means (28) which are arranged such that light emitted by the light-emitting means (28) is coupled into the light-conducting element (12),

characterized in that

c) on the side of the second main surface (16) of the light guide element (12) a reflection means (53) is provided, which reflects light in the direction of the interior of the light guide element (12).

2. Beleuchtungsvorr-ichtung according to claim 1, characterized in that the reflection means (53) comprises a reflection layer (52), in particular a mirror foil or a white plastic film.

3. Lighting device according to claim 1 or 2, characterized in that the reflection means (53) a

Reflector substrate (48), which is on the side of the second main surface (16) of the light guide element (12) is arranged ^¬ .

4. Lighting device according to claim 3, characterized in that the reflection device (53) has a coupling layer (50) of silicone material, in particular from thick silicone oil or from an elastic silicone compound, or from a resin, in particular from an epoxy resin or from a polyester resin, which directly contacts the second main surface (16) of the light conductor element (12).

5. Lighting device according to claim 3 or 4, characterized in that the reflector substrate (48) is a white paper sheet (48).

6. Lighting device according to claim 5, characterized in that the paper sheet (48) has a basis weight of 50 g / m ² to 200 g / m ² , preferably from 80 g / m ² to 170 g / m ² , more preferably 100 g / m ² to 150 g / m ² and particularly preferably of 120 g / m ² has.

7. Lighting device according to one of claims 1 to 6, characterized in that the reflection means (53) reflection particles (51).

8. The illumination device according to claim 7, characterized in that the reflection particles (51) comprise one or more of the following compounds: zinc sulfide, scandium oxide, lanthanum oxide, cerium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide.

9. Lighting device according to claim 8, characterized in that the reflection particles (51) of scandium oxide or zinc sulfide are.

10. Lighting device according to one of claims 7 to 9 with reference to one of claims 4 to 6, characterized in that the reflection particles (51) in the coupling layer (50) of silicone material or of a resin are largely homogeneously distributed.

11. Lighting device according to one of claims 1 to 10, characterized in that the second main surface (16) of the light guide element (12) at least partially a surface roughness in the order of 100 .mu.m to 500 .mu.m, preferably from 200 .mu.m to 500 .mu.m, more preferably 300 microns to 500 microns, and more preferably in the order of magnitude of the wavelength of the light, which is reflected by the reflecting means (53) has on it.

12. Lighting device according to one of claims 1 to

11, characterized in that the light guide element (12) made of glass or acrylic glass or epoxy resin is made.

13. Lighting device according to one of claims 1 to

12, characterized in that the light guide element (12) is planar.

14. Lighting device according to claim 13, characterized in that the lighting means (28) relative to the planar light guide element (12) between the plane defined by the first main surface (14) and the plane defined by the second main surface (16) is arranged.

15. Lighting device according to claim 14, characterized in that at least part of the lighting means (28) is arranged laterally next to an outer edge (18, 20) of the planar light guide element (12).

16. Lighting device according to one of claims 1 to 15, characterized in that at least a part of

Illuminant (28) is arranged in a groove (56) which in one of the main surfaces (14, 16) of the light guide element (12) is provided.

17. Lighting device according to one of claims 1 to

16, characterized in that at least one side of the lighting means (28) at least partially opposite a reflection layer (52) which reflects light emitted by the light sources (28) toward the interior of the light guide element (12).

18. Lighting device according to one of claims 1 to

17, characterized in that the lighting means (28) are at least partially coupled via a light-conducting material (30) with the light guide element (12).

19. Lighting device according to claim 18, characterized in that the light-conducting material (30) is a silicone material, in particular a silicone oil or an elastic silicone compound.

20. Lighting device according to one of claims 1 to 19, characterized in that the lighting means (28) at least partially surrounded by phosphor particles (32), preferably homogeneously distributed Phorporpartikeln, which absorb light emitted by the light emitting means (28) and in turn Emit light of a different wavelength.

21. Lighting device according to claim 20 with reference to claim 19 or 18, characterized in that the phosphor particles (32) in the light-conducting material (30) are distributed, preferably distributed homogeneously.

22. Lighting device according to one of claims 1 to 21, characterized in that the lighting means (28) comprise at least one semiconductor light-emitting chip (28a), which emits light when voltage is applied.

23. Lighting device according to one of claims 1 to 22, characterized in that the lighting means (28) comprise at least one arc tube (28b).

24. Liquid crystal screen comprising:

a) a liquid crystal panel (60) having a flat viewing side (62);

b) a lighting device (10, 10 ', 10'',10' ¹ '), by means of which the liquid crystal panel (60) can be exposed to light on the side (64) remote from the visible side (62),

characterized in that

c) the lighting device (10, 10 ', 10'',10' ¹ ') according to one of claims 1 to 23 is formed.

25. Liquid crystal screen according to claim 24, characterized in that between the first main surface

(14) of the light guide element (12) and the liquid crystal panel (60) an optical coupling layer (66) is provided.

26. Liquid crystal screen according to claim 25, characterized in that the optical coupling layer (66) made of silicone material, in particular of viscous silicone oil or of an elastic silicone composition, or of a resin, in particular of an epoxy resin or of a polyester resin is formed ,