The invention relates to a device which is suitable for electromagnetic
Emit radiation, and a method for producing a
Component that is capable of electromagnetic radiation
A device which is suitable for emitting electromagnetic radiation is disclosed, for example, in the document DE 101 33 352 A1
described. In this case, at least one luminescence diode which emits a primary radiation in the range from 300 to 485 nm serves as the primary radiation source, the primary radiation being converted partially or completely into longer-wave radiation by luminescence conversion particles. As a rule, the luminescence conversion particles are embedded in a polymeric matrix mass which is applied to the primary radiation source or envelops it. The luminescence conversion particles and the polymeric matrix mass in this case form essential functional components of a luminescence conversion element. Components in which primary radiation from the UV or UV-near range is converted into visible light are particularly suitable for producing white or colored light with the aid of different luminescence conversion particles.
Disadvantage of such devices may be that they do not have to
Residual emission of primary radiation
have from the UV or UV near spectral range. This can be special
when using high power light emitting diodes as a primary radiation source
occur. However, one of the residual emissions is as far as possible
Avoid electromagnetic radiation from the UV or from
the visible UV-near wavelength range
can damage the human eye during intensive exposure.
The document US 2002/0180351 A1 is proposed in the polymeric
Matrix in which the luminescence conversion particles are embedded,
Particles to disperse, the unconverted primary radiation
to scatter. This is intended to unconverted primary radiation of the device
the luminescence conversion particles again made available
and reduce the percentage of unconverted radiation,
which is emitted by the device. Alternatively, it is suggested scattering
Particles in a separate layer on the luminescence conversion element
Document US 2002/0180351 A1 also discloses a light source,
which is based on a UV light-emitting diode and reflectors for ultraviolet
The publication DE 102 04 318 A1
relates to a class of photonic crystals having a bandgap or pseudo-bandgap between the 5th and 6th and / or the 8th and 9th bands.
Document WO 01/86038 A2 discloses germanium-based materials
with a photonic band gap.
The publication US 6,791,259 B1
discloses a lamp comprising a light source and a luminescence conversion substance. Between them there is a glass layer containing particles for scattering and absorption of radiation.
The object of the present invention is in particular a
Component with UV and / or UV-near-emitting primary radiation source
in which the device emitted during operation of the device
Proportion of unconverted UV and / or
UV-near radiation is reduced. Furthermore, it is the task of
Invention as possible
specify a simple method for producing such a device.
Tasks are achieved by a device according to claim 1 and a
Process according to claim
Further advantageous embodiments
of the component and the method are in the dependent claims 2 to
11 and 13 to 18 indicated.
A device according to the invention which is suitable for emitting electromagnetic radiation comprises in particular:
the photonic crystal ( 51 ) is designed such that it is as far as possible impermeable to emission unwanted radiation of the first wavelength range and this reflected, and at the same time is largely permeable to radiation of the second wavelength range
- At least one primary radiation source suitable for emitting primary electromagnetic radiation of a first wavelength range,
- At least one luminescence conversion element which converts at least part of the radiation originating from the primary radiation source into radiation of a second wavelength range which is at least partially different from the first wavelength range, and
- A filter element arranged downstream of the luminescence conversion element from the perspective of the primary radiation source, comprising a three-dimensional photonic crystal comprising structures which periodically continue in three spatial directions,
and wherein the photonic crystal is supported on a support which is at least partially transmissive is for the converted by the luminescence conversion element radiation, and the carrier is applied with the photonic crystal on the luminescence conversion element.
Crystals are materials that are equivalent
to the electronic band gap
of semiconductors a band gap
have, the so-called photonic band gap. Photons with energies
within the photonic band gap
do not spread in the photonic crystal and are from
this reflected. It should be noted at this point
that photonic crystals with partially formed photonic
according to the invention
can be used.
The photonic band gap
or partially, due to periodic structures of at least
two materials that comprise the crystal. Let photonic crystals
into one-dimensional, two-dimensional and three-dimensional photonic
Divide crystals. A three-dimensional photonic crystal
includes structures that periodically continue in three spatial directions.
A photonic crystal in two dimensions equals equivalent
Structures that are periodically formed in two spatial directions
and a one-dimensional photonic crystal comprises structures,
which are periodically formed in a spatial direction. It will
each reflects such photons from the photonic crystal,
their energy lies within the photonic band gap and their propagation direction
essentially coincides with the direction of the periodic material change.
It should be noted at this point that it is also conceivable
two-dimensional photonic crystals with appropriate photonic
Band gap in
insert the filter element.
three-dimensional photonic crystal with a suitable band gap as
Part of the filter element has the advantage that this
unconverted radiation from all directions partially or
selectively reflected. This can depend on the severity of the
photonic band gap
Percentage of unconverted primary radiation
of the first wavelength range
be filtered out while
converted radiation of the second wavelength range, the filter element largely
can happen and is emitted by the device.
unconverted primary radiation
is reflected by the photonic crystal, this is advantageously
after reflection by the filter element, at least in part,
furthermore the luminescence conversion element available. This proportion
the primary radiation
is therefore not lost, such as during use
absorbent materials for filtering primary radiation before exit
from the component. As a result, the radiation yield of the component
the filter element reflects at least part of the primary radiation
back to the luminescence conversion element. Particularly preferably reflected
the filter element as much as possible
the primary radiation
back to the luminescence conversion element. This can cause primary radiation
after reflection on the photonic crystal by the luminescence conversion element in FIG
Radiation of the second wavelength range
be converted and leave the device. So the radiation yield
of the component further increased
a preferred embodiment
The photonic crystal comprises three-dimensional periodic inverse
Opal structures. Three-dimensional inverse opal structures provide the
Advantage radiation with energies within the photonic band gap substantially
partially or completely reflected by the direction of incidence. Furthermore
they are made relatively easy. The radiation becomes partial
reflected when the ratio
from the refractive index of the material in the interstices and
to the refractive index of the material in the spherical areas
is less than or equal to 2.9 and completely reflected if that
is equal to 2.9.
For example, inverse opal structures can be used
can be generated by placing balls in a cubic or hexagonal closest to one another
Ball packing are arranged and subsequently the spaces between
the balls are filled with a suitable material. After refilling the
the balls are removed. The diameter of the balls is here
in the range of wavelength
the radiation to be reflected.
Balls in cubic structures or in hexagonal densest sphere packages
to arrange, self-organizing processes are preferably used.
These processes provide, in particular over serial methods for
Pattern generation, the advantage usually expire quickly and inexpensively.
Preferably, the photonic crystal comprises periodic structures with air inclusions. Furthermore, the photonic crystal preferably comprises materials having a refractive index greater than or equal to 1.4, such as TiO 2 , SiO 2 , Si and Ge.
In order to reflect the largest possible proportion of primary radiation with the aid of the filter element, a photonic crystal with a possible required complete photonic band gap. Such arises in particular when the refractive indices of the materials of which the periodic structures of the crystal are composed have the largest possible difference in refractive index. For example, an inverse opal structure has a complete photonic band gap if the ratio of the refractive index of the material in the interstices and the refractive index of the material in the spherical regions is greater than or equal to 2.9. Therefore, the periodic structures of the photonic crystal preferably comprise at least two materials, one of which has a relatively small and a relatively large refractive index. Since air has a relatively low refractive index (n (air) ≈1) with respect to many materials, periodic air inclusions are particularly suitable as part of the periodic structures of a photonic crystal with as complete a photonic bandgap as possible. Furthermore, the materials TiO 2 , Si and Ge each have a relatively large refractive index (n (rutile) ≈2.71, n (Si) ≈3.4, n (Ge) ≈4.0). For this reason, they are particularly suitable for filling the spaces between the spherical regions of a photonic crystal having an inverse opal structure with as complete a photonic band gap as possible.
which at least partially for
the radiation converted by the conversion element is permeable,
such as polymers
be used advantageously, the spaces between
to fill the balls,
if the photonic crystal is not as possible
should be optimized, but to the highest possible degree of transparency for the
Luminescence conversion particles emitted secondary radiation
of the second wavelength range.
a preferred embodiment
of the device is the photonic crystal in a layer with
a thickness greater or
equal to 2 microns
and less than or equal to 50 microns
educated. A thin layer thickness
offers the advantage of being for
Part of the converted radiation of the second wavelength range
Furthermore, the component preferably has as primary radiation source at least one light-emitting diode chip which is suitable for emitting electromagnetic radiation with wavelengths in the ultraviolet range and / or short-wave blue range. Together with suitable Lumineszenzkonversionsstoffen so advantageously a device can be created that emits white light during operation. If the light-emitting diode chip emits UV radiation, a portion of the primary UV radiation can be converted into yellow light and a further portion of the primary UV radiation into blue light with the aid of corresponding luminescence conversion particles. The yellow light and the blue light mix, leaving the viewer with a white color impression. Wavelength conversion materials can also be used to produce any other colors. Correspondingly suitable light-emitting diode chips and luminescence conversion materials are known to the person skilled in the art and are therefore not explained in more detail here. For example, it is possible to use conventional UV-emitting and / or short-wave blue-emitting light-emitting diode chips and conventional phosphors which are suitable for this purpose. A corresponding LED chip is for example in the document EP 599 224 A1
described. Lumineszenzkonversionsstoffe are further, for example, in the document DE 101 33 352 A1
A method for producing a component which is suitable for emitting electromagnetic radiation comprises in particular the steps:
- Providing at least one primary radiation source suitable for emitting electromagnetic radiation having at least one radiation-emitting side,
- Applying a luminescence conversion element at least to the radiation-emitting side of the primary radiation source, and
- - Applying a three-dimensional photonic crystal on the luminescence conversion element.
Radiation source and the luminescence conversion element and / or
between the luminescence conversion element and the photonic
if appropriate, additional
Layers, such as tie layers, be arranged.
Photonic crystal is applied to a support and the support with
the photonic crystal is on the luminescence conversion element
applied. The carrier
is hereby preferably at least partially permeable to that of
the luminescence conversion element converted radiation. These
of the method offers the advantage that the photonic crystal is separated
can be made from the rest of the device. So in particular
Technologies for producing the photonic crystal applied
which would damage the rest of the device. The carrier with
Optionally, the photonic crystal may be exposed to the luminescence conversion element
be applied that the photonic crystal to the luminescence conversion element
turned away or gone.
In a further preferred embodiment of the method, the application comprises photonic crystal self-assembly of colloidal particles. Self-organizing processes include, for example, evaporation processes, electrophoresis and / or sedimentation steps. The colloidal particles may, for example, be polystyrene or SiO 2 spheres. Colloidal particles are known to the person skilled in the art and are therefore not explained in more detail here. On the one hand, self-organizing processes usually have the advantage of being comparatively easy to carry out. On the other hand, self-organizing processes can be used to generate periodic structures with a variety of geometries.
Preferably, the deposition of the photonic crystal comprises at least
an electrophoretic step for applying colloidal
using the colloidal particles in a periodic structure
applied an electrophoretic process step may also
that the spaces between
to fill between the colloidal particles, advantageously
either simultaneously or with the aid of a subsequent electrophoretic
Step be applied. This usually offers the advantage
a simplified procedure.
Furthermore, electrophoretic processes offer the advantage, clearly
to be able to
as, for example, sedimentation or evaporation processes. You can also use
Electrophoretic processes usually realized thicker layers
be considered with alternative methods.
are preferred as colloidal particles balls with a diameter
greater or equal
100 nm and less than or equal to 250 nm used. Become these particles
arranged in a cubic or hexagonal closest packing,
they form the basic grid for
an inverse opal structure whose photonic band gap in the UV
or UV-near range of visible light.
It should be noted at this point that the periodic structures
of the photonic crystal in the invention not only with
Help self-organizing processes, such as electrophoresis, evaporation
or sedimentation can be generated, but also with each
other suitable process, such as with the help of lasers (interference lithography)
and vapor deposition. It should also be noted that
according to the invention
not only inverse opal structures as photonic crystals for use
but all the periodic structures that make up a photonic crystal
form with a suitable photonic band gap.
Other features, advantages and advantages of the invention will become apparent from the following in connection with the 1 to 3 and 4a to 4d described embodiments.
1 a schematic sectional view of a component,
2 a further schematic sectional view of an embodiment of the component,
3 , Another schematic sectional view of another embodiment of the device, and
4a to 4d , Schematic cross-sectional views of process stages for applying a photonic crystal on a support.
and the figures are the same or equivalent components respectively
provided with the same reference numerals. The illustrated elements
The figures, in particular the layer thicknesses, are not to be regarded as true to scale.
Rather, you can
for a better understanding
At the in 1 The example shown, the embodiment of which does not correspond to the presently claimed invention, is a light-emitting diode chip 1 on a chip carrier 2 applied and with a bonding wire 3 electrically contacted. The LED chip 1 is from a luminescence conversion element 4 envelops. The luminescence conversion element 4 comprises a polymeric matrix 41 in the luminescence conversion particles 42 are embedded. On the luminescence conversion element 4 is in direct contact a layer of a photonic crystal 51 applied, the band gap is formed so that in terms of the emission of the device unwanted primary radiation of the LED chip 1 is largely reflected and converted radiation is transmitted as far as possible. The photonic crystal 51 is applied so that it covers the entire surface of the luminescence conversion element 4 covered. Furthermore, the thickness of the layer is between 2 and 50 microns. The photonic crystal forms an essential functional component of a filter element 5 , which has the task of primary radiation of the LED chip 1 weeding out before leaving the device.
During operation, the LED chip sends 1 electromagnetic radiation emitted by the conversion particles 42 in the enveloping matrix 41 is converted into radiation of a desired wavelength. The LED chip 1 can for example Send UV radiation, from within the luminescence zenzkonversionselementes 4 a certain part is transformed into yellow light and another part into blue light. The yellow light and the blue light mix and leave a white color impression on the viewer.
The conversion of UV radiation to light of another wavelength occurs when a photon encounters a luminescence conversion particle 42 therefore meets and takes place according to statistical laws. In this process, there is a likelihood that photons will be the luminescence conversion element 4 can pass unhindered and so unconverted primary radiation from the LED chip 1 on the photonic crystal 51 meets. There she is usually from the photonic crystal 51 back into the luminescence conversion element 4 reflects and is the luminescence conversion particles 42 again available.
For depositing a layer of photonic crystal 51 on the luminescence conversion element 4 is, for example, by immersing the device in a suspension with SiO 2 balls 6 and subsequent evaporation, a layer of balls 6 in a cubic or hexagonal close packing on the luminescence conversion element 4 generated. In a subsequent step, the spaces become 7 filled with TiO 2 , which is mixed with a binder for stabilization. Subsequently, the SiO 2 spheres 6 dissolved out by chemical means, for example by etching with hydrofluoric acid. The diameter of the SiO 2 balls used 6 lies in the range between 100 and 250 nm.
UV-emitting and / or entertaining blue light-emitting
LED chips and for that
suitable luminescence conversion materials are known to the person skilled in the art
and are therefore not explained in detail at this point. It can, for example, conventional
UV-emitting and / or short-wave blue emitting LED chips
suitable for it
Phosphors are used.
In the embodiments according to the 2 and 3 is in contrast to the embodiment according to 1 a chip carrier 2 used, which has a recess into which the LED chip 1 is mounted. To increase the radiation yield of the component, the sides of the chip carrier recess may have reflective elements 8th contain. The chip carrier recess is still complete with a polymeric mass 41 with embedded luminescence conversion particles 42 filled out, so this together with the chip carrier 2 forms a substantially planar surface. On this essentially plane surface is a carrier 9 attached, on which a layer of photonic crystal 51 is applied. The carrier 9 In this case, for example, be attached by gluing.
In the embodiment according to 2 is the carrier 9 so attached to the plane surface that the photonic crystal 51 the luminescence conversion element 4 is facing. In contrast, in the embodiment according to 3 the carrier 9 applied the other way round, leaving the photonic crystal 51 from the luminescence conversion element 4 turned away. The carrier 9 can also be removed in a subsequent step.
Becomes the photonic crystal 51 on a carrier 9 applied, may be used as a support material, for example, quartz, glass, a transparent ceramic or a high-temperature polymer. The support material must be substantially transparent to that of the luminescence conversion element 4 be converted radiation.
On this carrier 9 become colloidal particles such as polystyrene beads 6 or SiO 2 spheres 6 with the aid of a self-organizing process, such as an electrophoretic step applied (see 4b ).
Another self-organizing process for applying balls 6 in a cubic or hexagonal closest packing (cf. 4b ) comprises, for example, the drying of a suspension with balls 6 on the carrier 9 , For the production of thick layers several evaporation processes may be necessary.
Shall the balls 6 by means of an electrophoretic step on the support 9 be applied, the carrier must 9 be electrically conductive. For this purpose, for example, an electrically conductive layer can be applied, which is also substantially transparent to the luminescence conversion element 4 converted radiation is. Such a layer includes, for example, indium tin oxide (ITO).
In a further step, the interspaces are subsequently 7 between the balls 6 filled with another material, such as TiO 2 or SiO 2 (cf. 4 ). This can be done for example by means of a sol-gel method. In this case, an organometallic starting material, for example titanium isopropoxide or tetraethyl orthosilicate in an alcoholic solution to the structure of polystyrene or SiO 2 spheres 6 applied. This is the carrier 9 with the balls 6 either dipped in the solution or the solution is made on the structure of balls 6 applied. Depending on Composition of the solution is such a step several times required, the carrier 9 with the balls 6 between the steps each dried. It is also conceivable that between the steps, a calcination at lower temperatures, such as 300 ° C takes place.
Finally, a calcination takes place at the one between the balls 6 gels formed by cleavage of the organic radicals are converted into oxides and sintered. The other is the bullets 6 Burned out during calcination, provided that it is polystyrene beads 6 is.
The gaps 7 between balls 6 can also be filled with material by means of an electrophoretic step. This is particularly useful if already the balls 6 were deposited by means of an electrophoretic step. The carrier 9 For this purpose, it is placed in a suspension containing a nanoscale oxide such as TiO 2 or SiO 2 . The particles of the oxide must be less than 10 nm and protected against agglomeration.
Alternatively, the spaces between 7 between the balls 6 also be filled with the aid of a chemical vapor deposition method (CVD method).
Be the spaces 7 between polystyrene beads 6 not filled with material by a sol-gel process; but for example electrophoretically or by means of a CVD method, the polystyrene beads 6 baked in an oven at 450 ° C to 600 ° C for two to ten hours in air. At the same time a sintering of the material takes place in the interstices 7 ,
Alternatively, it is also conceivable, the polystyrene beads 6 by chemical means, for example, if it is not possible to use elevated temperatures in the production of the photonic crystal.
Will the periodic structure using SiO 2 spheres 6 generated, the material is in the spaces 7 first sintered in an oven, although higher temperatures can be used here than with the use of polystyrene beads 6 , In a subsequent step, SiO 2 spheres 6 with a hydrofluoric acid solution of the material in the interstices 7 etched, provided that the spaces are not filled with SiO 2 or Si.
In addition to the materials already mentioned TiO 2 , SiO 2 , Si and Ge, it is also conceivable, the spaces 7 between the balls 6 with polymeric materials or with hybrid materials of polymers and a nanoscale powder, such as SiO 2 or TiO 2 to fill.