WO2013144053A1 - Lighting device comprising luminophore body on heat sink - Google Patents

Description

Lighting device with phosphor body on heat sink

The invention relates to a lighting device which has a heat sink and at least one phosphor body, wherein the at least one phosphor body with its

Rear side is arranged on the heat sink and the

Irradiation is provided on its front. The

Lighting device is particularly applicable as a light-generating unit in a projector, e.g. For

Video projectors or as a vehicle light, e.g. For

Motor vehicles.

For efficient generation of long-wavelength (secondary) light (e.g., the colors green, yellow, red, infrared, etc.), phosphor is often used which emits blue (primary) light from

Light-emitting diodes (LEDs) or laser diodes wavelength converted or converted. The phosphor is usually in layer form with its back on a heat sink and is irradiated on the front side with the blue primary light.

Already in the first 10 to 30 micrometers, most of the blue primary light is converted and the resulting energy difference is converted into heat ('Stokes heat'). With typical layer thicknesses of the phosphor layer of 20 to 100 micrometers, this heat must first be transported through the phosphor layer to the heat sink. However, the phosphor layer usually has a poor thermal conductivity, so that the heat can be dissipated only insufficient. This affects one

Conversion efficiency and limits the achievable

Luminance.

So far, the insufficient heat dissipation is achieved by applying the phosphor to a rotating color wheel to reduce the thermal load of the phosphor by using a larger irradiated area. However, this is technically complex and prevents a compact design. If no color wheel is used, the power density of the irradiated blue primary light is kept so small that the accumulated heat can still be dissipated. This

However, this happens at the expense of the luminance.

Another possibility is the

 Phosphor layer should be designed so thin that the heat is still well dissipated. However, this happens at the expense of conversion efficiency.

It is the object of the present invention to overcome the disadvantages of the prior art, at least in part, and in particular to provide a lighting device which provides improved heat dissipation from a phosphor without a significant reduction in luminance and / or brightness

Conversion efficiency allows.

This object is achieved according to the characteristics of the independent

Claims solved. Preferred embodiments are

in particular the dependent claims.

The object is achieved by a lighting device, comprising a heat sink and at least one

Phosphor body, wherein the at least one

 Fluorescent body is arranged with its back to the heat sink and is occupied at its front to be irradiated with a transparent layer, which is a

at least the same high thermal conductivity as the phosphor body.

As a result, improved heat spreading and / or

Heat removal reaches the front of the phosphor body, at which most of the waste heat is generated. Even the larger-scale distribution of heat and thus heat dissipation surface (eg by convection) gives a considerable cooling effect. In addition, a thickness of the phosphor body does not need to be reduced so that the di Conversion efficiency does not suffer. Also needs one

Intensity of an incident light not to be reduced. In addition, the lighting device comes without

Movement mechanics and can therefore maintain a compact design.

It is a particularly preferred for effective heat dissipation development that the translucent layer has a higher thermal conductivity than that

Phosphor body. However, also like a translucent

Be sufficient location with the same or similar thermal conductivity as that of the phosphor body, since this position is not warmed up directly by the phosphor and so is available for a more effective heat dissipation.

In particular, the heat sink may be a metallic heat sink, e.g. made of aluminum and / or copper.

It is a development that the phosphor body is a layered or sheet-like phosphor body.

It is yet another development that the phosphor body has a light-permeable matrix material which has phosphor (particles) as filling material. The

In particular, matrix material is a transparent material, but may also be translucent or opaque. The translucent material may e.g. non-converting scattering particles

exhibit . The matrix material may be, for example, silicone, ABS or PC. It is particularly preferred that the matrix material is water glass, as this is higher temperature resistant.

For high temperature applications (especially greater about 150 ° C) is preferred as a phosphor body

 Ceramic converter used. The ceramic converter consists of highly concentrated phosphor, which is a ceramic

is trained. This luminescent ceramic is characterized by a particularly high thermal conductivity and temperature resistance.

The phosphor body may have one or more phosphors.

To operate the lighting device is front side

Primary light (e.g., blue light or UV light) on the

Fluorescent body blasted, by the

translucent layer through. This light is at least partially through the phosphor in secondary light

typically of larger wavelength and isotropically emitted. As a result, the secondary light and possibly an unconverted primary light component emerge again from the front side. To increase efficiency, at least one

Contact surface of the heat sink with the phosphor

be designed reflective, so that incident on the heat sink after re-passage through the light

Phosphor can also be emitted from the front.

It is an embodiment that the translucent layer is connected to the heat sink. This results in an even more effective heat dissipation from the front of the

Fluorescent body achieved.

It is a particularly simple embodiment of the fact that the translucent layer has an edge beyond the projecting at least one phosphor body

Has edge region and over the edge region with the

Heat sink is connected. This requires the

 Fluorescent body, for example, no recesses

show.

Also, such a production can be simplified

For example, by a mounted on the heat sink phosphor body in a step front and

potted on the edge with suitable material for a translucent layer, sprayed or otherwise can be occupied. Another advantage is, in particular in a fastening of the translucent layer by means of non-translucent means, for example, good thermal conductivity, mechanical

Fastening means, e.g. made of metal, that the attachment (s) of the phosphor body does not emit light

block or shadow. The at least one

Fastening means may comprise, for example, a snap means or a locking means.

It is still an embodiment that the phosphor body has water glass as a base material or matrix material and the translucent layer of glass material (glass, quartz, water glass or similar). The translucent layer thus has a similar refractive index as that

 Matrix material of the phosphor body, so that light losses due to reflection at the boundary layer between

Fluorescent body and translucent layer can be avoided.

It is generally preferred for reducing reflections at (internal) interfaces that a refractive index of the

translucent layer at least similar, in particular equal, a refractive index of a matrix material of the

Is phosphor body.

It is yet another embodiment that the

translucent layer is a diamond or sapphire plate. This is particularly heat-conducting and thus allows a particularly effective cooling.

It is also an embodiment that the translucent layer is a glass material plate (made of glass, quartz or the like), which is coated with a light-transmitting, electrically conductive material. The translucent, electrically conductive material is typically particularly highly thermally conductive, so that there is a further improved cooling of the phosphor body. It is a further development of that

translucent, electrically conductive material at least on a phosphor body facing side of the

is translucent layer and in particular is in contact with the phosphor body.

The translucent layer may in particular be made prior to application to the phosphor body, e.g. with the translucent, electrically conductive material

have been coated.

It is also an embodiment that the translucent, electrically conductive material is a TCO (Transparent

Conducting oxide) material is, that is, a transparent, electrically conductive oxide material. The TCO material may be e.g. Indium Tin Oxide (ITO), Fluorine Tin Oxide (FTO),

Aluminum-tin-oxide (AZO) and / or antimony-tin-oxide (ATO).

It is also an embodiment that the material is a material having an anisotropic thermal conductivity, e.g. with embedded graphene or carbon nanotubes. It is also an embodiment that the translucent layer has an antireflection coating. This can

in particular reflections on the front, at which the primary light is irradiated suppress, and thus increase a luminous efficacy and a precise color mixing

support.

A particularly preferred development consists in that the phosphor body comprises water glass as the matrix material, the translucent layer likewise consists of water glass and the light-permeable layer has an antireflection coating on the free surface facing away from the phosphor body. An advantage here is that the Application process of the antireflection coating does not or only slightly influences the phosphor particles.

In a variant which is particularly preferred for high-temperature applications, the phosphor body is designed as a phosphor ceramic.

It is also a training that on the

Phosphor body and / or on the translucent layer at least one optic is applied or integrated, e.g. by immersion. The optics may e.g. be a lens or a concentrator. The optics can be anti-reflective.

It is also a development that the heat sink is a stationary heat sink. This lighting device has the advantage that it allows a simple and compact design and yet the (at least one) phosphor is well cooled. Alternatively, the heat sink may be a movable heat sink, e.g. a rotatable disc of a light wheel or

Color wheel. The movable heat sink may provide even better cooling and / or distribution of the incident primary light.

It is still an embodiment that the lighting device at least one light source, in particular

 Semiconductor light source, for irradiating a front side of the phosphor body. Thus, advantageously, a high-energy, efficient on the (at least one)

Fluorescent tuned primary light beam with a

be provided relatively little effort.

The at least one light source has, in particular, at least one ultraviolet and / or blue light radiating light

Light source on. However, this spectral range is not meant to be limiting. It is also a development that the at least one light source has at least one laser. Such a laser can be made particularly bright and narrow and may be particularly efficiently matched to a phosphor. The laser may be formed, for example in the form of a laser diode as a semiconductor light source. Such a development is particularly suitable as a light-generating unit in a projector, such as video projector.

It is also a development that the at least one light source at least one light-emitting diode as a

Semiconductor light source has. However, the lighting device is not limited thereto and may, for example, also have a different type of light source, e.g. a fluorescent tube. The light source may be followed by a spectral filter. It is also a continuing education that the

 Lighting device is a vehicle lighting device or a part thereof. The vehicle light device can

in particular be a headlight. For example, land vehicles (eg cars, trucks,

Motorcycles, e-bikes, bicycles, etc.), but also aircraft or ships, etc.

The above-described characteristics, features and advantages of this invention as well as the manner in which they are achieved will become clearer and more clearly understood

 In connection with the following schematic description of exemplary embodiments that are associated with the

Drawings are explained in more detail. It can to

Clarity identical or equivalent elements must be provided with the same reference numerals. Fig.l shows a sectional view in side view a

Lighting device according to a first

 Embodiment;

2 shows a sectional side view of a

 Lighting device according to a second

 Embodiment; and

3 shows a sectional view in side view of a

 Lighting device according to a third

 Embodiment.

Fig.l shows a lighting device 11 according to a first embodiment with a heat sink 12 and a

layer-like phosphor body 13. A typical layer thickness of the phosphor body 13 is about 20 to 100 microns, especially 50 to 100 microns.

The phosphor body 13 is arranged with its rear side 14 on the heat sink 12 and to be irradiated at its

Front 15 with a translucent layer 16 occupied. The light-permeable layer 16 has at least the same high thermal conductivity as the phosphor body 13.

The heat sink 12 is for example made of aluminum, while the phosphor body 13 as water glass

Matrix material 17, are embedded in the phosphor particles 18 as filler.

In a variant which is particularly preferred for high-temperature applications (not shown), the phosphor body is formed as a phosphor ceramic. For example, the phosphor ceramic is mounted on the heat sink with a high thermal conductivity adhesive.

Front side of the phosphor body 13 is a

Semiconductor light source in the form of a blue primary light P emitting (blue ^λ ) laser 19, in particular laser diode mounted. The blue primary light P passes through the

translucent layer 16, then hits the ply-like Phosphor body 13 and is there at least partially converted into secondary light S lesser wavelength, eg in yellow secondary light S. In the first 10 to 30 micrometers, a large part of the blue primary light P is converted and the resulting energy difference is converted into heat ('Stokes heat '). However, the phosphor body 13 has one with respect to the thickness of the

Phosphor body 13 only comparatively bad

Thermal conductivity, so that the heat without the

translucent layer 16 is insufficient due to the

Heat sink 12 would be dissipated.

However, by means of the transparent sheet 16, the Stokes heat generated in a region of the phosphor body 13 in the vicinity of the front surface 15 can be spread (e.g., at a comparatively small focal spot) and also dissipated more intensely via the transparent sheet 16, e.g. by heat convection in the environment. This improves cooling of this near-side area.

The translucent layer 16 is like the matrix material 17 of the phosphor body 13 made of water glass. So can

Advantageously, a refraction of light and reflection at the interface between the phosphor body 13 and the translucent layer 16 are prevented. In addition, a precisely fitting, firm connection without mechanical or thermal mismatch results.

In order to improve the luminous efficacy and to suppress a color deviation by reflection on a free (front) surface 20 of the transparent layer 16, this may be provided with an antireflection coating 21. One

An additional advantage of the translucent layer 16 made of water glass is that the application process of the antireflection coating 21 does not or only slightly influences the phosphor particles 18 and thus can, for example, prevent them from thermal decomposition or chemical destruction. 2 shows a sectional side view of a lighting device 31 according to a second embodiment. In the lighting device 31, the transparent layer 32 is a self-supporting layer, for example of sapphire or diamond, which is placed flat on the phosphor body 13.

For mechanical attachment to the and thus also

thermal connection with the heat sink 12 protrudes the

translucent layer 32 laterally beyond the phosphor body 13 out. The translucent layer 32 thus has an edge beyond the phosphor body 13 protruding

Edge region 33, by means of which it is connected to the heat sink 12. The fastening takes place, for example, via thermally conductive clamps 34 or latching elements, e.g. made of aluminum or copper, or else via thermally conductive interface material (TIM material), e.g. via thermally conductive adhesive or thermal paste, etc. Fig. 3 shows a sectional side view of a

Lighting device 41 according to a third embodiment. The lighting device 41 differs from the

Luminous device 31 characterized in that the translucent layer 42 to further increase the heat dissipation of the thermally loaded front side of the phosphor body 13 on its phosphor body 13 side facing a coating 43 of a transparent, electrically conductive material, in particular a TCO material such as indium Tin oxide (ITO). The coating 43

thus contacts the phosphor body 13 directly over a large area. The third embodiment is particularly advantageous if the light-transmissive layer 42 itself has too low a thermal conductivity, e.g. at a

translucent layer 42 of glass or another

Glass material like quartz may appear.

Although the invention is shown in detail by the

Exemplary embodiments has been illustrated and described in more detail, thus, the invention is not limited thereto and other variations can be deduced therefrom by those skilled in the art without departing from the scope of the invention. Thus features of the embodiments shown can be interchanged or combined.

For example, a light-transmissive layer may have both a coating of a transparent, electrically conductive material and an anti-reflection coating.

Claims

claims Lighting device (11; 31; 41) comprising a  Heat sink (12) and at least one phosphor body (13), wherein the at least one phosphor body (13) - With its rear side (14) on the heat sink (12)  is arranged and  - At its front to be irradiated (15) with a translucent layer (16; 32; 42) is occupied, which has at least the same high thermal conductivity as the phosphor body (13). The light emitting device (31; 41) according to claim 1, wherein the light transmitting layer (32; 42) is connected to the heat sink (12). A light-emitting device (31; 41) according to claim 2, wherein the translucent layer (32; 42) has an edge over the at least one phosphor body (13).  has protruding edge region (33) and is connected via the edge region (33) with the heat sink (12) Lighting device according to one of claims 1 to 3, wherein the phosphor body is formed as a phosphor ceramic. 5. lighting device (11) according to any one of claims 1 to 3, wherein the phosphor body (13) water glass as  Matrix material and the translucent layer (16) consists of glass material. A light emitting device (31) according to any one of claims 1 to 4, wherein the translucent sheet (32) is a diamond or sapphire chip. Lighting device (41) according to one of claims 1 to 4 wherein the translucent layer (42) a Glass material plate is that with a translucent, electrically conductive material (43) is coated. 8. lighting device (41) according to claim 7, wherein the  Material (43) is a TCO material. 9. lighting device (41) according to claim 7, wherein the  Material (43) a material with an anisotropic  Thermal conductivity is. 10. lighting device (11) according to one of the preceding  Claims wherein the translucent sheet (16) comprises an antireflective coating (21). 11. lighting device (11; 31; 41) according to one of  previous claims, wherein the lighting device (11; 31; 41) comprises at least one semiconductor light source for irradiating a front side (15) of the  Having phosphor body (13). 12. lighting device (11; 31; 41) according to one of  preceding claims, wherein the lighting device (11; 31; 41) is a vehicle lighting device.