DE102007026795A1 - Illuminating device for e.g. liquid crystal display, has reflection device provided on side of main surface, where device reflects light in direction to interior of guiding unit, and includes reflection substrate arranged on surface side - Google Patents

Abstract

The device (10) has a light guiding unit (12), which is limited by parallel main surfaces (14), where one of the main surfaces is arranged at a distance to the other surface. Illuminants (28) are arranged in such a manner that light emitted from the illuminants are coupled into the guiding unit. A reflection device (53) is provided on a side of the former main surface, and reflects the light in the direction to the interior of the guiding unit, where the reflection device has a reflector substrate (48) arranged on the side of the former surface, and a coupling layer and a reflection particle.

Description

The The invention relates to a lighting device according to the preamble of claim 1 and a liquid crystal screen according to the generic term of claim 21.

Liquid crystal screens, which generally as LCD screens are known, enjoy due to their flat construction increasing popularity.

such LCD screens comprise a liquid crystal panel, which by means of illuminated a lighting device of the type mentioned becomes. In known such lighting devices are as lighting neon lights used. These need for a relatively large amount Energy and on the other hand require additional components, such as one Hole reflector, a Fresnel lens and mostly several diffusion filters, the between the liquid crystal panel and the neon tubes are arranged.

By However, this structure is often the Contrast and brightness of the visible side of the LCD screen recognizable image adversely affected. Through the diffusion filters becomes the intensity the radiation emitted by the illumination device by about 10% weakened, before putting the liquid crystal panel reached. Even stronger the shadow mask turns off. They account for about 25% to 30% of the radiation emitted radiation device, which is why only a correspondingly lower proportion of light to be illuminated Liquid crystal panel reached. In addition, it comes through the hole reflector to disadvantageous Interference effects.

To the Compensate for these interference effects and improve the possible Contrast of the visible on the visible side of the LCD screen image the Fresnel lens is provided. However, this also causes that the angle at which the screen is viewed decreases can be so that an image produced by him still recognizable is.

It There is therefore a desire for a lighting device, at which largely dispenses with the above-mentioned correction components which can still be used as a backlight in one Liquid crystal screen suitable is, has a good luminosity and is also very flat construction.

The The latter properties are also increasingly included Lighting devices in the form of lamps for lighting rooms or outdoor environments asked, because the flat design an attractive look can be achieved can. Often but can be a desired flat Construction not with a required luminosity of the lighting device be reconciled.

task The invention is therefore an illumination device of the above to create type mentioned, which takes into account the above idea.

These Task is solved by a lighting device with the specified in claim 1 Features.

Thereby, in that semiconductor lighting chips are used as the lighting means, are components for correcting the usable light largely unnecessary, which is why the lighting device as a whole flat construction than conventional Lighting devices of the type mentioned who designed the can.

advantageous Trainings are dependent claims specified.

By the measure according to claim 2 it is achieved that the thickness of the lighting device not is influenced by the arrangement of the semiconductor light-emitting chips.

there it is what the coupling of the light into the plate-shaped light guide element concerns, favorably, when the semiconductor light-emitting chip according to claim 3 or claim 4 is arranged.

Around the proportion of light emitted by the semiconductor light-emitting chip to increase, in the plate-shaped Light guide element is coupled, the measure is advantageous according to claim 5.

By the measures according to the claims 6 and 7 will be a good light transmission achieved by the semiconductor light chip on the plate-shaped light guide element. The silicone material may be, for example, silicone oil. Also an elastic silicone compound can be used. This can be the Semiconductor light chip z. B. first with liquid silicone oil wrapped become a hardener is added, so that the silicone oil after some time to a viscous elastic mass solidifies.

If the wavelength of the light emitted from the semiconductor light-emitting chip does not coincide with a desired wavelength, it can be adjusted by the measure according to claim 8. Phosphor particles absorb radiation impinging on them and emit radiation at least at a different wavelength. In a suitable Thus, the choice of phosphor particles or phosphor particle mixtures can convert the radiation emitted by the semiconductor light-emitting chip into radiation with a different spectrum.

The measure guaranteed according to claim 9 an advantageous homogeneous distribution of the phosphor particles.

Around the luminous efficacy of the of the lighting device on their first main area increase the emitted light, is the measure according to claim 10 favorable. It is advantageous if the reflection device according to a the claims 11 to 14 is formed. A strong reflection effect becomes in particular by the measures Claim 12 reached. The reflection effect is reflected by the measure Claim 13 advantageously further increased.

For the paper sheet according to claim 14 have basis weights as cheap proved, as indicated in claim 15.

Around the loss of light emitted by the reflection device in Direction to the second main area of the plate-shaped Reflected light guide element, due to a reflection on this second main surface of the plate-shaped Optic element itself possible is low, the second major surface of the plate-shaped light guide element advantageously formed as specified in claim 16.

The disc-shaped Optical fiber element is preferably one of the 17 materials mentioned.

Around to obtain a high luminosity of the lighting device is this formed as specified in claim 18. The can activities according to claim 19 and 20 for white balance of be used by the lighting device radiated light. In this case, if necessary, on the the semiconductor luminescent chips surrounding phosphor particles are dispensed with.

It is also Object of the invention, a liquid crystal screen of the type mentioned above, which in this context accounted for the difficulties encountered.

These Task is solved through a liquid screen with the features of claim 21.

By the measure According to claim 22, a good light transmission between the lighting device and the liquid crystal panel reached.

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

1 a partially broken plan view of a first embodiment of a lighting device;

2 a section through the lighting device of 1 along the section line II-II;

3 a plan view of a second embodiment of a lighting device;

4 a section through the lighting device of 3 along the section line IV-IV;

5 one of the 4 corresponding section through a third embodiment of a lighting device;

6 a partially broken plan view of a liquid crystal panel of a liquid crystal screen with the lighting device arranged underneath 1 ; and

7 a section through the liquid crystal panel and the lighting device of 6 along the section line VII-VII.

In the 1 and 2 is a lighting device 10 shown which a 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 major surface 14 on, through which through the lighting device 10 generated useful light is emitted. On the opposite side has the light guide plate 12 a second main surface 16 (see. 2 ), which has a surface roughness indicated by teeth, which will be discussed in more detail below.

On two opposite outer edges 18 and 20 carries the light guide plate 12 one housing each 22 respectively. 24 with U-shaped cross section and not specifically provided with a reference numeral end walls. The open side of the housing 22 respectively. 24 points in the direction of the corresponding adjacent outer edge 18 , respectively. 20 the light guide plate 12 ,

The housing 22 respectively. 24 will be described below only using the example of the housing 22 explained in more detail. The explanations apply mutatis mutandis accordingly for the housing 24 ,

The housing 22 limited to the outer edge 18 the light guide plate 12 an interior 26 in which a plurality of semiconductor light-emitting chips 28 are arranged, of which in 1 only one is provided with a reference numeral.

The semiconductor light chip 28 For example, it may comprise an n-type layer of n-type GaN or n-type InGaN and a p-type layer of a III-V type semiconductor material such as p-type GaN, as it is known per se. 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 is a superlattice which has an electronic band structure altered according to the superlattice structure and correspondingly 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 with a photoconductive liquid in the form of liquid silicone oil 30 filled, which is indicated in the figures in the form of circles and of the semiconductor light-emitting chips 28 emitted light to the outer edge 18 the light guide plate 12 passes. Through the silicone oil 30 in addition, the semiconductor light-emitting chip 28 generated heat to the outside, in particular to the walls of the housing 22 , dissipated.

The semiconductor light chip 28 p-GaN / n-InGaN emits ultraviolet light and blue light in a wavelength range of 420 nm to 480 nm when a voltage is applied. To deal with the semiconductor light-emitting chips 28 To produce white light are in silicone oil 30 phosphor particles 32 homogeneously distributed, which are made of color centers having transparent solid state materials. These phosphor particles 32 are indicated in the figures as circles, which are smaller than the silicone oil 30 distinctive circles. For the phosphor particles 32 it may also be a mixture of several different phosphor particles. By the appropriate choice of phosphor particles or phosphor particle mixtures so that of the semiconductor luminescent chips 28 emitted radiation can be converted into a radiation having a spectrum which is adapted to a desired spectrum. It is understandable that if on phosphor particles 32 is omitted, the lighting device 10 a blue light emits.

The semiconductor light-emitting chips 28 are connected in parallel and via two supply lines 34 and 36 energized. The supply lines end for this purpose 34 and 36 in externally accessible connections 38 respectively. 40 , The supply lines 34 and 36 are in 2 for the sake of clarity not shown. The semiconductor light-emitting chips 28 can also be connected in series.

The inner walls of the housing 22 are with a reflective layer 42 provided, which also light, which from the semiconductor light-emitting chips 28 in one of the light guide plate 12 weglaufende direction is radiated to the same or its outer edge 18 is reflected.

As in particular in 2 can be seen, sits the light guide plate 12 with its second major surface 16 on here not specifically provided with a reference numeral walls of another housing 44 and, as it were, forms its lid. The housing 44 and the second major surface 16 the light guide plate 12 thus limit an interior 46 ,

On the second main surface 16 the light guide plate 12 is a white paper sheet 48 with a layer 50 applied from a silicone material, which is also represented by circles.

As silicone material, for example, a viscous silicone oil in question. The white paper sheet 48 is applied to the light guide plate before application 12 with the thick silicone oil of the layer 50 soaked and then with a roller under pressure on the second major surface 16 the light guide plate 12 pressed. Care must be taken to ensure that the pressure of the roller all possibly in the silicone oil of the layer 50 and between the paper sheet 48 and the light guide plate 12 existing bubbles are pressed out. The white paper sheet 48 is due to the adhesion effect of the silicone oil of the layer 50 on the second main surface 16 the light guide plate 12 fixed.

Instead of thick silicone oil, the layer 50 also be made of a viscous elastic silicone compound. This may be the paper sheet 48 before application to the light guide plate 12 be soaked in less viscous silicone oil, which was previously mixed with a hardener. This allows the silicone oil after applying the paper sheet 48 on the light guide plate 12 cure to an elastic silicone composition, wherein the light transmission of the silicone material does not suffer.

In a modification, the layer 50 be in the cured state translucent resin, for example, an epoxy resin or a polyester resin, which should also be indicated by the circles.

For example, on the second main surface 16 the light guide plate 12 a layer 50 applied from a provided with a hardening liquid resin. Before the shift 50 hardened from resin, the paper sheet becomes 48 placed on top, which is then fixed after curing of the resin.

To increase the reflection effect are in the layer 50 made of silicone oil or a resin reflector particles 51 homogeneously distributed in the form of, for example, scandium oxide or zinc sulfide. The reflector particles 51 are as points within the silicone oil or the resin of the layer 50 suggesting circles.

If the layer 50 is made of a resin in which reflector particles 51 are distributed, the reflection effect over the use of a layer 50 increased from silicone oil and the proportion of usable light larger, which is the light guide plate 12 on their first main surface 14 leaves.

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 especially preferably from 120 g / m ² .

On the of the silicone oil 50 lying side of the paper sheet 48 is an additional reflection layer 52 provided, which may be provided for example in the form of a self-adhesive mirror film or a white plastic film.

This sandwich arrangement of the reflection layer 52 , the paper sheet 48 as well as the layer 50 made of silicone oil or a resin is through the case 44 covered, with its bottom 54 at the reflection layer 52 is applied. The housing 44 , the paper sheet 48 , the layer 50 and the reflective layer 52 Together form a Reflexionsein direction for the light, which is the light guide plate 12 on the second outer side 16 leaves.

In the 3 and 4 is another embodiment of a lighting device 10 ' shown. Already to the 1 and 2 explained components carry in the 3 and 4 the same reference numerals.

As in particular in 4 can be seen, the lighting device is different 10 ' from the lighting device 10 after the 1 and 2 in that the semiconductor light-emitting chips 28 not laterally outside next to the outer edges 18 respectively. 20 the light guide plate 12 but within one of the first major surface 14 the light guide plate 12 recessed groove 56 are arranged. Inside the groove 56 are the semiconductor light-emitting chips 28 also of silicone material 30 and homogeneously distributed phosphor particles therein 32 surround. If the silicone material is relatively fluid silicone oil 30 can act a cover 58 for the groove 56 be provided, which in 4 indicated by a dotted line. Is it the silicone material 30 To ensure a sufficiently viscous and elastic mass, so can on this cover 58 be waived.

In a not specifically shown modification of the lighting device 10 ' is the groove 56 on the second outside 16 the light guide plate 12 Action.

In 5 is another embodiment in the form of a lighting device 10 '' shown. Already to the 1 to 4 explained components carry in 5 the same reference numerals.

In contrast to the lighting devices 10 and 10 ' are in the lighting device 10 '' two light guide plates 12a and 12b provided, which, while maintaining a distance between the outer edge 20a the light guide plate 12a and the outer edge 20b the light guide plate 12b are arranged parallel to each other and in a plane.

The semiconductor light-emitting chips 28 are provided in the remaining gap and of silicone oil 30 , which contains phosphor particles 32 is surrounded.

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

For the three illustrated lighting devices 10 . 10 ' . 10 '' are the semiconductor light-emitting chips 28 each arranged so that they relative to the light guide plate 12 between through the first major surface 14 given level and the second main surface 16 predetermined level are arranged.

As mentioned above, the second major surface is 16 the light guide plate 12 roughened. This surface roughness is of the order of the wavelength of the light emitted by the reflection means 44 . 48 . 50 . 52 is reflected on it. 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.

Due to this surface roughness of the second major surface 16 the light guide plate 12 an antireflection effect is achieved, whereby by the reflection means 44 . 48 . 50 . 52 again in the direction of the light guide plate 12 reflected light not partially through the light guide plate 12 itself reflects and is not used anymore can be. So the overall yield of the light guide plate becomes 12 finally over the first main area 14 leaving light increases.

In all embodiments of the lighting device 10 . 10 ' . 10 '' is the silicone oil 30 which the semiconductor light-emitting chips 28 surrounds, in direct contact with the corresponding outer edge 18 respectively. 20 the light guide plate 12 , This ensures that that of the semiconductor light-emitting chips 28 emitted light reliably into the light guide plate 12 is coupled. Without the silicone oil 30 There is a risk that a larger share of the semiconductor luminescent chip 28 emitted light from the respective outer edge 18 respectively. 20 the light guide plate 12 would be reflected and not usable.

Another way, that of the lighting device 10 . 10 ' . 10 '' To set emitted light, there is a variety of semiconductor light-emitting chips 28 to use. For example, predominantly semiconductor luminescent chips 28 installed, which emit blue light. In addition, however, there are still semiconductor light-emitting chips 28 used, which emit in the red and green. By an appropriate vote, also as regards the respective light output, so a white balance can be achieved.

Also, semiconductor light-emitting chips can 28 can be used, which emit UV light. Then should be on the first main surface 14 However, a UV filter can be applied.

The lighting devices explained above 10 . 10 ' and 10 '' can be used as separate bulbs, for example for the illumination of interiors. Through the lighting devices 10 . 10 ' and 10 '' However, in addition, a good backlight for a liquid crystal screen is provided. This is based on the 6 and 7 explains in which example the lighting device 10 is shown.

As in particular in 7 shown section is in front of the first main surface 14 the light guide plate 12 the lighting device 10 a liquid crystal panel 60 with a flat visible side 62 and one of these opposite sides 64 appropriate. A liquid crystal panel 60 is known in and of itself, which is why at this point to a further explanation is omitted.

On the website 64 of the liquid crystal panel 60 is the lighting device 10 arranged so that the first major surface 14 the light guide plate parallel to the liquid crystal panel 60 runs. Between the first main surface 14 the light guide plate 12 and the page 64 of the liquid crystal panel 60 is a layer 66 made of a thick silicone oil or an elastic silicone compound. The silicone material is also indicated here by circles. The layer 66 From the elastic silicone compound can be obtained by adding a hardener to a fluid silicone oil. The layer 66 is immediately adjacent to the first main surface 14 the light guide plate 12 and with the surface of the liquid crystal panel 60 on its side 62 in contact.

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

Through the lighting device 10 is about the first major surface 14 the light guide plate 12 emitted a uniform high intensity light, which over the layer 66 of silicone oil or a viscous silicone composition to the liquid crystal panel 60 is transmitted and this from its side 64 lit up.

The lighting devices 10 . 10 ' and 10 '' have a good luminosity while ensuring a relatively large viewing angle of the liquid crystal panel, as compared with the prior art backlighting for liquid crystal panel using additional components such as hole reflector masks, Fresnel lenses and diffusion filters 60 in which the image created with it is still clearly visible.

In addition, the semiconductor light-emitting chips 28 compared to other light sources such as the neon tubes mentioned above energy-saving.

It is usually sufficient if at an edge length of the outer edges 18 respectively. 20 the light guide plate 12 of approximately 50 cm each four semiconductor light-emitting chips 28 along the corresponding outer edge 18 . 20 or within the groove 56 are provided.

The lighting devices 10 . 10 ' . 10 '' can, what their dimensions and the number of semiconductor chips 28 To be manufactured in many different forms.

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

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

The recording power of the lighting devices 10 . 10 ' . 10 '' is due to the semiconductor light-emitting chips 28 low.

Claims (22)

Lighting device, in particular for backlighting a liquid crystal panel ( 60 ), with a) a plate-shaped light guide element ( 12 ), which is defined by a first main surface ( 14 ) and a second major surface spaced parallel thereto ( 16 ) is limited; b) bulbs ( 28 ), which are arranged such that of the lighting means ( 28 ) emitted light in the plate-shaped light guide element ( 12 ) is coupled, characterized in that c) the lighting means ( 28 ) at least one semiconductor light chip ( 28 ) which emits light when exposed to voltage. Lighting device according to claim 1, characterized in that the semiconductor light chip ( 28 ) relative to the plate-shaped light guide element ( 12 ) between the first main surface ( 14 ) and the second main surface ( 16 ) predetermined level is arranged. Lighting device according to claim 2, characterized in that the semiconductor light chip ( 28 ) laterally next to an outer edge ( 18 . 20 ) of the plate-shaped light guide element ( 12 ) is arranged. Lighting device according to claim 2 or 3, characterized in that the semiconductor light-emitting chip ( 28 ) in a groove ( 56 ) arranged in one of the main surfaces ( 14 . 16 ) of the plate-shaped light guide element ( 12 ) is provided. Lighting device according to one of claims 1 to 4, characterized in that at least one side of the semiconductor luminescent chip ( 28 ) at least partially a reflection layer ( 42 ) facing away from the semiconductor light-emitting chip ( 28 ) emitted light toward the interior of the plate-shaped light guide element ( 12 ) reflected. Lighting device according to one of claims 1 to 5, characterized in that the semiconductor light-emitting chip ( 28 ) of a photoconductive material ( 30 ), which surrounds the plate-shaped light guide element ( 12 ) contacted directly. Lighting device according to claim 6, characterized in that the light-conducting material ( 30 ) is a silicone material, in particular a silicone oil or an elastic silicone composition. Lighting device according to one of claims 1 to 7, characterized in that the semiconductor light chip ( 28 ) at least in regions of substantially homogeneously distributed phosphor particles ( 32 ) surrounded by the semiconductor light chip ( 28 ) absorb light emitted and in turn emit light of a different wavelength. Lighting device according to claim 8 and claim 6 or 7, characterized in that the phosphor particles ( 32 ) in the photoconductive material ( 30 ) are distributed. Lighting device according to one of claims 1 to 9, characterized in that on the side of the second main surface ( 16 ) of the plate-shaped light guide element ( 12 ) a reflection device ( 44 . 48 . 50 . 52 ) is provided, which of the second main surface ( 16 ) of the plate-shaped light guide element ( 12 ) radiated light toward the interior of the plate-shaped light guide element ( 12 ) reflected. Lighting device according to claim 10, characterized in that the reflection device ( 44 . 48 . 50 . 52 ) a reflection layer ( 52 ), in particular a mirror foil or a white mirror foil. Lighting device according to claim 10 or 11, characterized in that the reflection device ( 44 . 48 . 50 . 52 ) a layer ( 50 ) 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, which has the second main surface ( 16 ) of the plate-shaped light guide element ( 12 ) contacted directly. Liquid crystal display panel according to claim 12, characterized in that in the layer ( 50 ) of silicone material or of a resin a reflector material ( 51 ), in particular scandium oxide or zinc sulfide, is largely homogeneously distributed. Lighting device according to claim 12 or 13 and claim 11, characterized in that the reflection device ( 44 . 48 . 50 . 52 ) a white paper sheet ( 48 ), which between the reflective layer ( 52 ) and the layer ( 50 ) is arranged from silicone material or a resin. Lighting device according to claim 14, characterized in that the 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 particularly preferably from 120 g / m ² has. Lighting device according to one of claims 10 to 15, characterized in that the second main surface ( 16 ) of the plate-shaped 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 from 300 .mu.m to 500 .mu.m and particularly preferably in the order of the wavelength of the light which is emitted by the reflection device ( 44 . 48 . 50 . 52 ) is reflected on it. Lighting device according to one of claims 1 to 16, characterized in that the plate-shaped light guide element ( 12 ) is made of glass or acrylic glass or epoxy resin. Lighting device according to one of claims 1 to 17, characterized in that the lighting means ( 28 ) a plurality of semiconductor light-emitting chips ( 28 ). Lighting device according to claim 18, characterized in that at least two of the semiconductor luminescent chips ( 28 ) emit a different spectrum of light. Lighting device according to claim 19, characterized in that at least one semiconductor light chip ( 28 ) Light in the blue, at least one semiconductor light chip ( 28 ) Light in the red and at least one semiconductor light chip ( 28 ) Emits light in the green, so that substantially white mixed light is generated. Liquid crystal screen, comprising: a) a liquid crystal panel ( 60 ) with a flat visible side ( 62 ); b) a lighting device ( 10 . 10 ' . 10 '' ), by means of which the liquid crystal panel ( 60 ) on the visible side ( 62 ) far side ( 64 ) can be acted upon with light, characterized in that, c) the lighting device ( 10 . 10 ' . 10 '' ) is designed according to one of claims 1 to 20. Liquid crystal screen according to claim 21, characterized in that between the first main surface ( 14 ) of the light guide plate ( 12 ) and the liquid crystal panel ( 60 ) a layer ( 66 ) 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 provided.