WO2019068478A1

WO2019068478A1 - Conversion material and radiation-emitting component

Info

Publication number: WO2019068478A1
Application number: PCT/EP2018/075498
Authority: WO
Inventors: Rebecca RÖMER; Ivar TÅNGRING
Original assignee: Osram Opto Semiconductors Gmbh
Priority date: 2017-10-05
Filing date: 2018-09-20
Publication date: 2019-04-11
Also published as: DE102017123097B4; DE102017123097A1

Abstract

The invention relates to a conversion material comprising: a matrix material (30); particles of a first phosphor (10), which are embedded in the matrix material (30); and particles of a second phosphor (20), which are embedded in the matrix material (30), the particles of the second phosphor (20) being smaller than the particles of the first phosphor (10) and/or having a lower density, and the particles of the second phosphor (20) having a coating (25). The invention further relates to a radiation-emitting component containing the conversion material.

Description

description

KONVERS IONSMATERIAL AND RADIATION EMITTING COMPONENT A conversion material is specified as well as a radiation-emitting component that contains the conversion material

contains.

Typical conversion materials for radiation emitting devices, such as white LEDs, contain two, three or more different phosphors. These

Phosphors can be selected from a wide variety of phosphors available. The selected phosphors have different densities among each other and

Crystal morphologies and different grain or

Particle sizes in which they can be produced. A

Phosphor mixture with desired spectral properties, can thus consist of phosphors, the very

have different densities and grain sizes. This leads to large differences in the sedimentation rates of the individual phosphors in the phosphor mixture.

Differences in sedimentation rates can cause various problems. For example, in the processing of the phosphors these usually with

Mixed silicones and optionally solvents stored in a large cartridge and applied from there to an LED package. This can be done for example by means of dispensing or spraying. During storage of the phosphors in the cartridge, the different phosphors sediment at different rates so that the phosphor mixture that is applied from the cartridge to an LED does not evenly mixed, which is in an unwanted

Color drift of the manufactured LED results.

A sedimentation of the phosphors in one

On the other hand, phosphor mixture, which is arranged, for example, in a cavity above an LED, is desirable since it can lead to a certain stability of the component compared to a phosphor mixture which is uniformly distributed over the entire volume of the cavity. If, however, phosphors with different

Sedimentation rates are mixed and

sediment, an unwanted phosphor separation may occur when z. B. phosphors that have a high

Have heat development, seen from the LED on phosphors with a lower heat development

be deposited. The phosphors with the higher

Heat development is then located farther away from the heat sink (the LED chip), which leads to a reduced stability of the device.

Another disadvantage caused by sedimentation occurs when relatively few phosphor materials are present and by sedimentation

incomplete coverage of the LED chip occurs. A

However, complete coverage is desirable, especially with volume emitters, to provide good and good angles at any angle

to produce uniform color quality.

The object of at least one embodiment is to

Conversion material with improved properties

provide. Another object is to provide a radiation-emitting device with improved properties. These tasks are through Conversion material and a radiation-emitting

Component solved according to the independent claims.

Further developments and further embodiments are

Subject-matter of dependent claims.

A conversion material is specified. According to one

Embodiment comprises the conversion material

Matrix material, particles of a first phosphor embedded in the matrix material, and particles of a second phosphor embedded in the matrix material.

Conversion material is to be understood as meaning a material which can at least partially convert electromagnetic radiation of a first wavelength into electromagnetic radiation of a second wavelength. Out of such

Conversion material can, for example, a

Conversion layer may be formed for an LED. Under particles of a first or second

Phosphor are particles of a certain size to be understood, which are formed from the respective phosphor. Such particles can also be referred to as grains, their size also as grain size. In the following, the term particles of the first phosphor or particles of the second

Phosphorus synonymous with first phosphor particles and second phosphor particles used.

The fact that the particles are embedded in the matrix material means that they are surrounded by matrix material, but can at least partly also touch one another. According to one embodiment, the particles of the second phosphor are smaller than the particles of the first phosphor and / or have a lower density than the particles of the first phosphor. In other words, the

Particles of the second phosphor have a smaller particle size than the particles of the first phosphor and / or a lower density.

According to a further embodiment, the particles of the second phosphor have a coating. Under

Coating in this context should not be understood to mean exclusively a homogeneous layer on the surface of the particle, but this term also includes a

uneven distribution of coating material on the surface of the particle. This means that areas of the surface of the particle can also be free of coating and that the thickness of the coating does not have to be the same everywhere. The coating thus serves solely to increase the volume of the particles and optionally to

Increase their density.

The coating can thus provide larger particles of the second phosphor than can be produced by ordinary syntheses. As a result, a scattering in the LED can be avoided and the brightness of the radiation-emitting component can be increased.

It is specified a conversion material, the one

Matrix material, particles of a first phosphor embedded in the matrix material, and particles of a second phosphor embedded in the matrix material. The particles of the second phosphor are smaller than the particles of the first phosphor and / or have a lower density. The particles of the second phosphor furthermore have a coating.

Adding an optionally thick and dense

Coating to the smaller and / or less dense

Particles of the second phosphor can their

Increase sedimentation rate to a desired value. For such small and / or less dense

Particles of the second phosphor may be

for example, to red emitting phosphors

(Ca, Sr) AlSiN ₃ : Eu ²⁺ (SCASN), Sr (Ca, Sr) Al ₂ Si ₂ N ₆ : Eu ²⁺ and

M ₂ S1 _{5 8} : Eu ²⁺ with M = Ca, Ba or Sr act. The coating can also be applied to other phosphor particles.

If a certain coating thickness and density is selected, the sedimentation rate of the smaller and / or less dense particles of the second phosphor can be adjusted to the sedimentation velocity of the particles of the first phosphor such that either one of the two

Mixture of the particles of the first phosphor and the second phosphor is achieved in the matrix material or a desired layer formation or desired

Concentration gradient of the particles of the phosphors by sedimentation in the matrix material occurs without the

To reduce grain size of the larger and / or denser particles of the first phosphor.

According to a further embodiment, the matrix material has a first refractive index, the particles of the second phosphor a second refractive index and the

Coating a third refractive index, the third Refractive index is equal to the first refractive index or lies between the first and the second refractive index. This means that the material of the coating is selected such that its refractive index at the

Refractive index of the second phosphor particles is adjusted or has a value which is between the value of the refractive index of the second phosphor particles and the matrix material. Thus, Fresnel reflections of the radiation emitted by the particles of the second phosphor can be avoided or at least minimized. Preferably, the refractive index of the coating is equal to the root of the product of the refractive indices of the second phosphor particles and the matrix. According to another embodiment, the coating has a density which is greater than or equal to the density of

Particle of the second phosphor is. This can be the

Total density of the particles of the second phosphor, which have the coating, are increased, and thus the sedimentation of the particles of the second

Fluorescent.

According to another embodiment, the

Sedimentation velocity of the particles of the second

Phosphor comprising the coating greater than or equal to the sedimentation of the particles of the first phosphor. By "equal" in this context is a high or an exact match of

Understand sedimentation rates, with minor deviations in both directions should be included. Thus, under "equal" is also a sedimentation of the particles of the second phosphor, which is slightly smaller than that of the particles of the first phosphor, too understand. When the sedimentation rates of

Particles of the first and the second phosphor are the same size, a mixture of the first and second

Phosphor particles are achieved in the matrix material. If the sedimentation velocity of the particles of the second phosphor is greater than that of the first phosphor, a layer formation of the phosphors in the matrix material can be produced, wherein the particles of the second phosphor are arranged under the particles of the first phosphor.

Under "layering of the phosphors" is here and in the

Not following the training of completely separate

To understand layers. Rather, this is to be understood as the formation of concentration gradients in the conversion material, which results in a predominantly first range

Phosphor particles (a first layer) and in another area predominantly second phosphor particles (a second layer) are to be found. Thus, here and below, a "first layer" formed by the first phosphor particles is to be understood as a region in which the first phosphor particles have a significantly larger area

Concentration as the second phosphor particles, and under a "second layer" formed by the second phosphor particles, a region in which the second phosphor particles have a significantly greater concentration than the first phosphor particles.

The sedimentation rates may thus be adjusted by adjusting or changing the size of the particles of the second phosphor and / or the total density of the particles of the second phosphor to or against the size and / or density of the particles of the first phosphor Requirements are adjusted. Thus, a mixture of the first and second phosphor particles in the matrix material can be achieved and thus an undesired separation of the first of the second phosphor particles, if

Conversion material, for example in a cartridge

is prevented.

Furthermore, by targeted sedimentation and a

desired layer formation of the first and second

Be achieved phosphor particles. If the second

Phosphor is chosen so that it has a larger Stokes shift than the first phosphor, for example, the coating on the particles of the second phosphor can cause the second phosphor particles due to their higher sedimentation rate predominantly arrange under the first phosphor particles. That can happen when the conversion material is emitting in a radiation

Component is used to increase the

Brightness and improved life expectancy. Also, a quenching of the phosphor emission due to high

Radiation densities of the exciting radiation can be reduced and thus the brightness can be increased when the

Phosphor particles are stored with a high intensity quenching by targeted sedimentation over phosphor particles with lower intensity quenching and thus are exposed only to a lower radiation density of the exciting radiation.

According to another embodiment, each one

Particles of the second phosphor on a coating and / or more particles of the second phosphor together have a coating. This means that not only the sedimentation rate of a second This objective can also be achieved if two or more smaller and / or less dense second phosphor particles in the conversion material are glued together in the conversion material by means of a coating to form a large particle compared to the first phosphor particles become .

According to a further embodiment, the coating has a thermal conductivity that is greater than a thermal conductivity of the matrix material. On

typical matrix material such as silicone has a thermal conductivity of 0.1 to 0.2 W / mK. Thus, choosing a material for the coating which has a higher thermal conductivity may help to reduce the temperature in the particles of the second phosphor. Heat generated in the luminescent centers of the second phosphor particles can thus be very effectively derived from the centers and over a large area

Grain volume are distributed. In addition, by the

Coating the surface of the particles of the second

Phosphor through the non-converting coating increases and thus also the surface through which heat can be dissipated to the matrix material.

When the peak temperature of the coated second

Phosphor particle is reduced, also the scattering on the particle of the second phosphor is reduced, since the refractive index of a typical polymeric matrix material is temperature dependent and falls with increasing temperature. Thus, the refractive index contrast between the second phosphor particles and the matrix material is increased. By lowering the temperature and thus reducing the Refractive index contrast between phosphor particles and matrix will increase the brightness of the radiation

Component due to less scattering in a

Conversion material containing conversion layer or

Conversion element and associated lower

Backscatter losses increased. In addition, the lifetime of the conversion material is increased when the peak temperatures are reduced on the particles of the second phosphor, since the lifetime is limited by temperature-induced matrix, for example, silicone degradation.

If the conversion material for the conversion layer of a radiation-emitting component, such as an LED,

used, the life of the LED is increased the most when the coating of the second phosphor particles, the highest heat generation under the

Have phosphor particles. In addition, a reduced average temperature in the conversion material leads to an increased quantum efficiency of all phosphor particles, since all phosphors have a thermal quenching of the quantum efficiency. Due to the reduced quantum efficiency losses, the brightness is also increased and the lifetime

extended. According to a further embodiment, the coating has a thermal conductivity which is greater than a thermal conductivity of the particles of the second

Phosphor. Thus, the total thermal conductivity of the conversion material is increased and the temperature of the

Particles of the second phosphor reduces because heat generated by the conversion in the second phosphor is transferred faster from the converting material to the second phosphor

Coating is discharged. According to a further embodiment, the coating has, at least in places, a thickness which is> 100 nm,

preferably> 500 nm. Such a thickness of the coating is particularly advantageous when the thermal

Conductivity of the coating greater than that of the

Matrix material and / or the second phosphor is because the thermal conductivity of thin films is usually lower than in the bulk material, while the thermal conductivity of thick layers is similar to or equal to in the bulk material. A high thickness of

Coating can also protect the particles of the second phosphor from mechanical stresses. In particular

Particles of phosphors which have a protective layer, for example to make them moisture-stable (for example SCASN), can be protected from mechanical stress during processing by means of a thick, and in particular soft, coating and thus destruction of the protective layer can be avoided. According to a further embodiment is between the

Particles of the second phosphor and the coating arranged a protective layer. Such a protective layer may, for example, precede the particles of the second phosphor

Protect moisture and / or prevent a reaction of the material of the coating with the material of the particles of the second phosphor.

According to a further embodiment, an anti-reflection layer is arranged on the coating. This may be, for example, a layer which has a thickness of λ / 4η, "λ" designates the peak wavelength of the coated phosphor particles and "n" the refractive index of the coating. This is an anti-reflection layer on the coating of the particles of the second phosphor present, which allows light to enter the second

Phosphor particles is produced without coupling loss of reflection in the matrix material, such as silicone.

According to a further embodiment, the particles of the first phosphor form a first layer and the particles of the second phosphor form a second layer in the

Matrix material, wherein the first layer on the second

Layer is arranged. For this purpose, the particles of the second phosphor have a greater sedimentation rate than the particles of the first phosphor, which is due to the

Presence of the coating is conditional. Due to the greater sedimentation speed, the particles of the second phosphor sink down faster, so that a layer of the particles of the second phosphor forms below the first layer. Will the conversion material

For example, applied to an LED, the second layer is positioned closer to the LED than the first layer.

According to a further embodiment, the particles of the first phosphor and the particles of the second phosphor are mixedly distributed in the matrix material. In this case, the particles of the first phosphor and the particles of the second phosphor have the same or at least similar sedimentation rates

Presence of the coating on the particles of the second phosphor is conditional. According to a further embodiment, the

Conversion material continues to particles of a third

Phosphor which have a coating. Thus, the size and / or density and thus the Sedimentationgeschwindigkeit the third phosphor particles are adapted to the size, density and sedimentation of the first and / or second phosphor particles. All above with respect to the coating or on the second phosphor particles on which the coating

is present, said characteristics also apply to the third phosphor particles or for the coating of the third phosphor particles. According to another embodiment, the coating comprises a material selected from the group consisting of KCl, LiCl, hB (graphite structure), NaCl, a-Si _{3 4} / b-Si ₃ 4,

LiB ₃ O ₅ , LiF, CaCO ₃ , MgF ₂ , CaF ₂ , AlN (wurtzite type), c-BN

(Diamond structure), MgO, diamond, BaB ₂ 0 ₄ , Sc ₂ 0 ₃ , SrF ₂ , TiO ₂ (rutile), YAG (undoped), Nb ₂ 0 ₅ , BaF ₂ , ZrO ₂ , Y ₂ 0 ₃ , SrTiO ₃ , ZnO (wurtzite), TeO ₂ , BaTiO ₃ , LuAG (undoped), LiTaO ₃ , Ta ₂ 0 ₅ , Yb ₂ 0 ₃ , Lu ₂ O ₃ , HfO ₂ , M ₂ SiF ₆ (M = Li, Na , K, Rb, Cs alone or in mixture), silicones, polysilazanes, siloxanes, and with

Nanoparticles comprising filled silicones.

In addition, a radiation-emitting component is specified, which comprises an active layer sequence, the electromagnetic radiation of a first

Wavelength range emitted. The component further contains a conversion layer, which in the beam path of

Radiation of the first wavelength range is arranged and a conversion material according to one of the above

Features contains. All in relation to that

Conversion material mentioned features thus also apply to the radiation-emitting device and vice versa. The radiation emitting device may be

for example, an LED, especially a white

emitting LEDs act. According to another embodiment, the converts

Conversion layer the radiation of the first

Wavelength range at least partially in radiation

at least a second and third wavelength range. Contains the conversion material more than two

Phosphor species, the conversion layer, the radiation of the first wavelength range at least partially in radiation of a fourth, fifth, etc. wavelength range to convert. For an external observer, the emitted radiation of the component appears as a mixture of the radiation of the first, second, third and possibly further wavelength ranges.

According to a further embodiment, the particles of the second phosphor form a second layer and are on the side facing the active layer sequence

Conversion layer arranged. The particles of the first

Phosphor form a first layer and are arranged on the side facing away from the active layer sequence side of the second layer in the conversion layer. In this case, the particles of the second phosphor can be red-emitting phosphors which have a high luminosity

Have heat generation. The particles of the first

Phosphors, on the other hand, have lower heat generation.

With reference to the figures and embodiments, the invention will be explained in more detail. Figure 1 shows an image of a radiation emitting

Component, FIG. 2 shows the typical thermal quenching of the quantum efficiency of some phosphors,

Figure 3 shows a schematic side view of the

Sedimentation behavior of a conversion material,

Figure 4 shows a schematic side view of the

Sedimentation behavior of a conversion material, Figure 5 shows a schematic side view of the

Sedimentation behavior of a conversion material according to an embodiment,

Figure 6 shows a schematic side view of the

Sedimentation behavior of a conversion material according to another embodiment,

Figure 7 shows a schematic side view of the

Sedimentation behavior of a conversion material according to another embodiment.

In the exemplary embodiments and figures, identical, identical or equivalent elements can each be provided with the same reference numerals. The illustrated elements and their proportions with each other are not to be regarded as true to scale, but individual elements, such as layers, components, components and areas, for better presentation and / or better understanding may be exaggerated.

Be two or more different phosphors for one

Conversion material mixed and embedded in a matrix material such as silicone, they usually have different grain sizes, densities and crystal morphologies. This can be different

Lead sedimentation of the phosphor particles and lead to an unwanted separation of the phosphors in the conversion material. Such an unwanted separation is shown in FIG. Here, an image of an LED is shown, wherein on the chip a conversion material is applied. It can be seen that a phosphor is on the bottom, adjacent to the LED chip,

has collected, the other is arranged over it. In this case, the lower phosphor is a green garnet phosphor arranged above it

Fluorescent around a red SCASN phosphor. Due to the higher heat generation of the red SCASN phosphor, it would be desirable to have this below the green

Phosphor material would be arranged.

Typical phosphors which can be used in conversion materials and their sizes and / or densities with each other by means of one as described above

Coating can be adjusted, together with their typical densities p, typical average grain sizes ds o and typical grain morphologies in Table 1 are given.

Phosphorus emission p [g / cm ³ ] d ₅ o [ym] Typical color grain morphology

A ₃ B ₅ 0i ₂ : Ce ³⁺ green to 4.6 - 7.0 5 - 25 spherical (A = Lu, Y, Tb, yellow

B = Al, Ga)

(Ca, Sr) red 3.2 - 3.8 9 - 15 platelets AlSiN ₃ : Eu ²⁺

(SCASN) Sr (Ca, Sr) Si ₂ Al ₂ red 4.2 9 - 20 platelets N ₆ : Eu ²⁺

(Ca, Ba, Sr) ₂ Si ₅ N ₈ orange 3,5 - 4,6 8 - 17 cuboid,: Eu ²⁺ to red platelets

Sr ₄ Al ₁₄ O ₂ 5: Eu ²⁺ cyan 3.7 10 - 15

ß-SiAlON, green 3.2 12 - 20 sticks,

Eu _x Si ₆ - _z Al _z O _z N ₈ - _z cuboid

-SiA10N yellow to 3.21 (for 6 - 15 sticks

M _x Sii2- _m - _n orange Cao, 8S19, ₂ A1 ₂

Al _{m + n} O _n N _n _ _16: Eu ^2+, SOI, ₂ Ni4, g)

M ₂ Si0 ₄ : Eu ²⁺ green to 3.0 - 5.5 10 - 20 cuboid (M = Ba, Sr, Ca, Mg) orange

K ₂ SiF ₆ : Mn ⁴⁺ red 2.6 - 2.7 27 - 28 large (KSF) polygons

MSi ₂ N ₂ 0 ₂ : Eu ²⁺ cyan to 3.7 - 4.5 6 - 15 platelets, (M = Ba, Sr, Ca) yellow cuboid

Table 1

In a combination of particles of different of these phosphors, the sizes and / or densities of the

individual phosphor particles are adapted to each other to either achieve a mixture of the phosphor particles in a matrix material or a specific

Layering of the phosphor particles in the matrix material to produce.

However, adjusting the sedimentation rate only over the grain size of the phosphor particles is difficult. For example, a green emitting LuYAG phosphor having a density of 6.4 g / cm ³ and a grain size of 22 ym and a red emitting M ₂ SisN ₈ phosphor having a density of 4.3 g / cm ³ and a grain size of 15 ym in one

Conversion material combined, this leads to big problems during processing, since, among other things, the red-emitting and green-emitting phosphor particles in the reservoir for spray or dispensing process separate over the duration of the process and thus over the duration of the process at the outlet of the reservoir different

Mixing ratios of the phosphors and the

Matrix material present. If the grain size of the LuYAG phosphor particles is reduced to 12 ym to the

Adjusting the sedimentation rate to that of the M ₂ S ₅ N ₈ phosphor particles also reduces the brightness of an LED to which such a conversion material is applied by about 3% due to increased scattering losses. When a layer formation of the red-emitting

Phosphor particles among the green emitting

Phosphor particles is desired, the

Sedimentation rate of green emitting

Phosphor particles are reduced by two to three times, so the particle size of LuYAG be reduced to 8.5 ym or 6 ym. Such small grain sizes would be the

Scatter losses continue to increase and another

Loss of brightness. On the other hand, an increase in the grain size of the M ₂ SisN ₈ particles to 27 ym

Synthetically no longer feasible, since this phosphor according to the synthesis methods described in the prior art only with a mean particle size of about 15-17 ym

can be produced. A comparison of the densities p, particle sizes dso and the product r ² p as a measure of the sedimentation rate of the two phosphors is shown in Table 2. Phosphor density p [g / cm ³ ] d ₅₀ [ym] r ² p

LuYAG 6, 4 22 0,774

LuYAG 6, 4 12 0.230

LuYAG 6, 4 8 0, 102

LuYAG 6, 4 6 0.058

M ₂ Si ₅ N ₈ 4.3 15 0.242

M ₂ Si ₅ N ₈ 4.3 27 0.784

Table 2

So that an adaptation of the sedimentation of the first 10 and second phosphor particles 20 in one

Conversion material is one of the two

Phosphors, namely those whose particles are smaller and / or less dense (second phosphor particles 20), provided with a coating 25. The coating 25 may have a higher density than the second phosphor particles 20 and a refractive index which corresponds to the refractive index of the matrix material 30 surrounding the phosphor particles 10, 20 or lies between that of the matrix material 30 and the second phosphor particles 20. Possible ways of providing particles of the second phosphor 20 with a coating 25 are shown below.

Particles of the second phosphor 20 are mixed with a ceramic precursor and a binder or solvent and particles of the desired size by

Spray drying or spray freeze drying, followed by annealing or heating to room temperature to remove the binder or solvent and subsequent annealing to make the ceramic coating 25.

This method is suitable, for example, for garnets which are provided with undoped grenades, Al ₂ O ₃ , LU ₂ O ₃ or Y ₂ O ₃ . Furthermore, this method is suitable for nitride phosphors, which are coated for example with undoped nitride phosphors, S1 ₃ N ₄ , A1N or BN. Furthermore, particles of the second phosphor 20 can be coated with a precursor and subsequently a reaction of the precursor can be brought about to produce a

To obtain coating. This can for example

Tetraethylortosilicate (TEOS) as a precursor for S1O ₂ or barium (II) hydro-tri (1-pyrazolyl) borate as a precursor for

BaB ₂ C> 4 are used. Also conceivable is one

Material mixture of precursors, for example, Y ₂ O ₃ + Al ₂ O ₃ for YAG or Ba (OH) ₂ + B (OH) ₃ for BaB ₂ 0 ₄ , which then react to form the coating 25.

On the particles of the second phosphor 20 may also first a thin protective layer, for example by means of ALD (Atomic Layer Deposition), CVD (Chemical Vapor Deposition) or PVD (Physical Vapor Deposition) are applied and then a coating material 25 are applied, which without protective layer would react with the phosphor material. For example, nitrides are only with a nitridic protective layer of S1 ₃ N ₄ , A1N or the

coated undoped phosphor material and then provided with a coating 25 of an oxide material. During annealing of the oxide material, the oxide then reacts with the protective layer to form a Si-O-N or Al-O-N phase without attacking the material of the underlying second phosphor particles 20.

The second phosphor particles 20 can also be synthesized with a reagent additive which serves as an adhesive for the second phosphor particles 20 or supports the formation of an adhesive layer between a plurality of phosphor particles 20. For example, M ₂ SisN8 phosphor particles can be prepared and combined with a combination of LiF and L1 ₂ B ₄ O ₇ larger, multiple particle units are glued.

Second phosphor particles 20 containing or consisting of K ₂ SiF ₆ : Mn ⁴⁺ (KSF: Mn) can be labeled with undoped K ₂ S 1 F ₆ or M ₂ SiF ₆ (M = Li, Na, K, Rb, Cs alone or in mixture). This can be done, for example, by growing the undoped compounds M ₂ S 1 F ₆ (M = Li, Na, K, Rb, Cs alone or in a mixture) onto K ₂ SiF ₆ : Mn ⁴⁺ phosphor particles (seed crystals) in a saturated solution containing M ₂ S 1 F ₆ (M = Li, Na, K, Rb, Cs alone or in a mixture). The coating steps may be repeated several times to adjust the size of the second phosphor particles 20 to the desired value.

Second phosphor particles 20 can also be used

Glass materials are coated. This is the

corresponding phosphor mixed with a very fine glass powder and a binder or solvent, particles of the desired size by spray drying or

Spray freeze drying, then annealed or heated to room temperature to remove the binder or solvent and then annealed to produce a coating 25 of glass.

Second phosphor particles 20 can also be coated with silicones, polysilazanes or siloxanes and nanoparticle-filled silicones. Production methods for these coated particles, one or more second

Containing phosphor particles 20 may, for example, be based on spray-drying, freeze-spray drying, spray pyrolysis or production of particles in emulsions.

Possible coating materials for the coating 25 are mentioned in Table 3. The material for the coating is selected according to the requirements of density p, refractive index RI and thermal conductivity. The Coating materials can be used as coating 25 for all phosphors listed in Table 1 according to their chemical compatibility and together with another phosphor from Table 1, the no

Coating 25 has to be combined in a conversion material. The phosphor for the second

Phosphor particle 20 is suitably chosen to have smaller and / or less dense particles than the particles of the first phosphor 10 combined with the particles of the second phosphor 20.

Coating material p [g / cm ³ ] RI Thermal

conductivity

[W / mK]

KCl 1, 98 1.48 6.5 - 7.2

LiCl 2, 07 1, 66 6 - 7

h-B (graphite structure) 2, 1 1,8 approx. 30

Fused silica 2, 1 1.45 1.4

NaCl 2, 17 1.54 7.2

a-Si ₃ ₄ / b-Si ₃ 4 2,3- 3,5 1,9 - 2,4 10 - 43

LiB ₃ 0 ₅ 2.47 1.57 - 1.61 3.5

LiF 2, 64 1.38 11.3 - 16, 1

Si0 ₂ (a-quartz) 2, 65 1.54 6.8 - 12

CaC0 ₃ 2.75 1, 65 4.6-5.5

MgF ₂ 3, 15 1.38 21 - 34

CaF ₂ 3, 18 1.43 9.71

A1N (wurtzite type) 3.26 1.9 - 2.2 285

c-BN (diamond 3,45 2, 1 about 30

Structure)

MgO 3.56 1.72 30-60

Diamond 3, 52 2.42 1,000

BaB ₂ 0 ₄ 3, 85 1, 66 1.24 - 1.65

SC2O3 3.86 1, 99 16, 5

Al 2 O 3 (sapphire) 3, 95 1.72 - 1.75 30

SrF ₂ 4.24 1.48 1.42

TiO ₂ (rutile) 4,26 2,58 8 - 13

YAG (undoped) 4, 6 1, 82 7 - 8, 11 Nb ₂ 0 ₅ 4, 6 2, 34

BaF ₂ 4.89 1.47 11.72

Zr0 ₂ 5.0 - 6, 15 2, 14 1.7 - 2.7

Y2O3 5, 01 1, 92 13, 6

SrTi0 ₃ 5, 12 2.38 11 - 12

ZnO (wurtzite) 5, 6 1, 96 37-147

Te0 ₂ 6 2, 61 30

BaTi0 ₃ 6, 02 2, 34 6

LuAG (undoped) 6.71 1.84 8.3

LiTa0 ₃ 7.45 2.17 - 2.18 46

Ta ₂ 0 ₅ 8,2 2,15 2 - 3

Yb ₂ 0 ₃ 9, 17 1, 94

Lu ₂ 0 ₃ 9, 42 1, 93 12, 5

Hf0 ₂ 9, 68 2.09 1.1

Table 3

Such a coating 25 on the particles of the second phosphor 20, for example, results in that the average temperature of the conversion material is reduced if the thermal conductivity of the coating 25 is greater than that of the matrix material 30 in the conversion material. A reduced average temperature of the conversion material increases the quantum efficiency of the first and second

Phosphor particles 10, 20, since all phosphors

have thermal quenching of the quantum efficiency. FIG. 2 shows the thermal quenching behavior of some exemplary phosphors. The x-axis shows the temperature T in ° C and the y-axis the quantum efficiency at a certain temperature T in relation to the quantum efficiency at 25 ° C (QE (T) / QE (25 ° C)).

Figure 3 shows a schematic side view of the

Sedimentation behavior of a conversion material. On the left in the picture is the conversion material with the matrix material 30, the first phosphor particles 10 and the second phosphor particles 20 before the sedimentation

shown. After the sedimentation, which is indicated by an arrow, the result is shown on the right in the picture

Conversion material. For better clarity, only a first 10 and a second phosphor particles 20 are provided with a reference numeral. This general

Description applies analogously to the following FIGS. 4 to 7.

Here are the first phosphor particles 10 and second

Phosphor particles 20 in a matrix material 30

embedded. The first phosphor 10 is a green-emitting LuYAG: Ce having a size ds o of 13 ym and a density p of 6.4 g / cm ³ . The second

Phosphor particles 20 are formed of M ₂ Si ₅ N ₈ : Eu (M = Ca, Sr, Ba) having a size ds o of 15 ym and a density p of 4.3 g / cm ³ . Both phosphor particles 10, 20 have similar sedimentation rates, since the first

Phosphor particles 10 having the higher density have a relatively small size, resulting in a sedimented layer of the first and second phosphor particles 10, 20 which are similarly mixed as the first and second

Phosphor particles 10, 20 before the sedimentation

(indicated by an arrow) begins. The first and second phosphor particles 10, 20 are then more compact, without changing their relative order to each other. Due to the relatively small size of the first phosphor particles 10 containing LuYAG: Ce, the conversion material, however, has a large dispersion, which when using the

Conversion material in a radiation-emitting

Component to a light loss of about 3% compared to a device with a conversion material with first Phosphor particles 10 containing LuYAG: Ce with a ds o of 22 ym leads.

In order to reduce the scattering and to obtain 3% in brightness, the size of the first phosphor particles 10 containing LuYAG: Ce may be increased to 22 μm. The effect of this change is more schematic in Figure 4

Side view shown. The particles of the first and second phosphors 10, 20 then have different

Sedimentation speeds, the first

Phosphor particles 10 sediment three times faster than the second phosphor particles 20. Due to the increased volume of the first phosphor particles 10, the number of first phosphor particles 10 also changes by about one third for the same volume of conversion material. The result of the higher sedimentation rate of the first

Phosphor particle 10 is a layer formation of the first phosphor particles predominantly among the particles of the second phosphor 20. Thus, the green emitting phosphor in this example is placed under the red emitting phosphor which generates the higher thermal energy. Thus, placing this conversion material on an LED places the most thermal energy producing phosphor furthest away from the heat sink. This also causes a loss of efficiency, with most of the red-emitting photons being generated by double conversion. If the conversion material is arranged on a blue-emitting LED, blue light is converted first into green and then into red light, whereby first the conversion losses of the first phosphor particle 10 and subsequently the conversion losses of the second

Phosphor particles 20 (QE (first

Phosphor particles 10) * QE (second phosphor particle 20)). The second red emitting phosphor particles 20 disposed over the first green emitting phosphor particles 10 then absorb the light emitted from the first phosphor particles 10. As a result of the enlargement of the particles of the first phosphor 10, an undesired layer formation is thus produced.

If a coating 25 is added to the second phosphor particles 20, in this case M ₂ Si 5 s: Eu, their

Sedimentation be increased until they are either equal or even greater than that

Sedimentationgeschwindigkeit of the first phosphor particles 10 is. Examples of suitable coating materials, coating thicknesses r _B, and coating densities p _B to obtain the same sedimentation rate described by the product r ² p of the first and second phosphor particles 10, 20 are shown in Table 4 together with FIGS

Phosphors whose densities p and particle sizes dso indicated. With these coatings 25, a separation of the first 10 and second phosphor particles 20 in the

Conversion material prevented and achieved a mixture of the first and second phosphor particles 10, 20 after sedimentation when applied in a conversion layer on an LED. Thicker coatings 25 would result in a higher sedimentation rate of the second

Phosphor particles 20 compared to the first

Led phosphor particles 10, which then the red

emitting second phosphor particles 20 would be placed under the green emitting first phosphor particles 10. Luminous P d ₅₀ [ym] coating PB r _B [ym] r ² p substance [g / cm ³ ] mat [g / cm ³ ] [g / cm] erial

LuYAG: 6, 4 22 7,744

Ce * 10 ^"6

M ₂ Si ₅ N ₈ 4.3 15 2.419: Eu * 10 ^"6

M ₂ Si ₅ N ₈ 4,3 15 Si ₃ N ₄ 2, 9 8,446 7,744: Eu * 10 ^"6

M ₂ Si ₅ N ₈ 4.3 15 Zr0 ₂ 5.58 4, 615 7.744: Eu * 10 ^"6

M ₂ Si ₅ N ₈ 4.3 15 LiTa0 ₃ 7.45 3, 464 7.744: Eu * 10 ^"6

Table 4

In this example, all three coating materials for the second phosphor particles 20 containing M ₂ SisN ₈ : Eu are chosen such that their refractive index RI between the typical refractive indices of silicone matrix materials (1.4-1.56) and the refractive index of the second phosphor particles ( 2.4-2.5): S1 ₃ N ₄ has a refractive index RI of 1.9-2.4, Zr0 ₂ has a refractive index RI of 2.14 and LiTaO 3 has a refractive index RI of 2.2. Furthermore, all three coating materials have a thermal conductivity greater than that of typical silicone materials (0.1-0.2 W / mK): S1 ₃ N ₄ has a thermal conductivity of 10-43 W / mK, Zr0 ₂ has one thermal conductivity of 1.7 - 2.7 W / mK and LiTa03 has a thermal conductivity of approximately 46 W / mK.

The example with the coating 25 made of LiTaO 3 is also shown in FIG. 5 in a schematic side view. In the mixed conversion material after sedimentation (indicated by the arrow) are the first

Phosphor particles 10 of LuYAG: Ce with a particle size dso of 22 ym and a density p of 6.4 g / cm ³ and the second phosphor particles 20 of ^ SisNsiEu with a particle size dso of 15 ym, a density p of 4.3 g / cm ³ and one

Coating of Li a0 ₃ in the same mixture as before sedimentation before. The coating has an average thickness of 3.5 ym and a density p of 7.45 g / cm ³ . By the coating 25 and the scattering behavior of

Particles of the second phosphor 20 improves, resulting in an increase in brightness in a device. Furthermore, the thermal conductivity of the conversion layer containing the conversion material can be increased because the thermal conductivity of Li.sub.oO.sub.3 is about three to four times higher than that of the second phosphor particles 20. Further, the coating 25 helps heat generated in the conversion from the second phosphor particles 20 over an area which is two times larger than without coating to dissipate, resulting in a reduction of the temperature in both

Itself as well as in the surrounding, for example, polymeric matrix material. The overall conversion layer of the conversion material becomes larger by the increase in the size of the second phosphor particles 20 through the coating 25, but the peak temperature, which is critical to the aging behavior of the matrix material, for example silicone, is reduced. Due to a reduced temperature in the phosphor, increased efficiency is also achieved by lower thermal quenching.

Should the sedimentation rate of the second

Phosphor particles 20 larger than the first

Phosphor particles 10 can, in this example, the Size of the second phosphor particles 2 0 are further increased to 2 9 ym by the coating 25 of Li aÜ3 has a thickness of 7 ym. Such an example is shown in Figure 6 in a schematic side view. Due to the increased sedimentation speed of the second phosphor particles 20, a layer of the red-emitting, second phosphor particles 20 forms on the ground and thus closer to the

Heat sink in an LED when the conversion material is used for the conversion layer of an LED. This also prevents the second phosphor particles 20 from absorbing too much of the emitted radiation of the first phosphor particles 10. In this example, the total thickness of a conversion layer increases significantly as the second

Phosphor particles 2 0 with coating 25 are now about seven times larger than without coating 25.

The same effect can be achieved if, instead of a higher layer thickness of the coating 25, a smaller size of the particles of the first phosphor 10 would be selected.

Such an example is shown in Figure 7, again in schematic side view. Here are the first ones

Phosphor particles 1 0 have a diameter dso of 12 ym and the second phosphor particles 2 0 in turn a coating 25 of Li a03 with a thickness of 3, 5 ym. Again, after sedimentation, a layer of second phosphor particles 2 0 again forms on the bottom and a layer of first phosphor particles 10 above the second phosphor particles 20. Due to the reduced size of the first

Although phosphor particles 10 become the scattering of this

Fluorescent increases again, but because the blue light emitted by one LED, first to the second

Phosphor particles 2 0 must pass and a big part of it is not left much blue light that could be scattered on the first phosphor particles 10. In the case of scattering, it at least partially re-passes the second phosphor particles 20 and thus receives a second opportunity to be converted. The

3% brightness loss, as shown in Figure 3, is thus significantly reduced in this example, since most scatter-based loss mechanisms involve blue light.

In a further exemplary embodiment, a LuAGaG: Ce phosphor is used for the first phosphor particles 10 and a SCAS: Eu phosphor for the second phosphor particles 20. Without an additional coating 25 of the second phosphor particles 20, these phosphor particles 10, 20 would separate, with the first phosphor particles 10 due to their higher sedimentation rate

Sediment faster and thus accumulate on the ground. With an additional coating 25 of the second phosphor particles 20 can their

Sedimentation be increased to obtain either a same or even greater sedimentation rate than that of the first phosphor particles 10. Examples of coating materials and their densities p _B and thicknesses r _B in order to obtain the same sedimentation rates, ie to avoid a separation of the phosphor particles 10, 20, are given in Table 5. Furthermore, the product r ² p of the phosphor particles are given as a measure of the sedimentation rates. Thicker coatings 25 would lead to a higher sedimentation rate of the second phosphor particles 20 and thus to a layer formation with the second phosphor particles 20 under the first phosphor particles 10. Luminous P d ₅₀ [ym] coating PB r _B [ym] r ² p substance [g / cm ³ ] mat [g / cm ³ ] [g / cm] erial

LAGAG 7,0 17 5, 058: Ce * 10 ^"6

SCASN: 4.2 13 1.775

Eu * 10 ^"6

SCASN: 4.2 13 Si ₃ N ₄ 2, 9 6, 339 5, 058

Eu * 10 ^"6

SCASN: 4,2 13 A1N 3,2 5, 791 5, 058

Eu * 10 ^"6

SCASN: 4,2 13 Lu ₂ 0 ₃ 9, 42 1, 966 5, 058

Eu * 10 ^"6

Table 5

All three coating materials are chosen so that their refractive index RI lies between the typical refractive index for silicone matrix materials (1.4-1.56) and the refractive index of the second phosphor particles 20 (2.1): S1 ₃ N ₄ has a refractive index RI from 1.9 - 2.4, A1N has one

Refractive index RI of 1.9 - 2.2 and LU2O ₃ has one

Refractive index of 1.93. Furthermore, all three have

Coating materials have a thermal conductivity greater than that of typical silicone materials (0.1 - 0.2 W / mK). S1 ₃ N ₄ has a thermal conductivity of 10 - 42 W / mK, A1N has a thermal conductivity of 285 W / mK and LU2O ₃ has a thermal conductivity of 12 - 13 W / mK.

In a further embodiment, a mixture of a LuAGaG: Ce phosphor (first phosphor particles 10) and a YAG: Ce phosphor with a RI of 1.82 and with the same particle size ds o of 17 ym (second phosphor particles 20) is to be achieved and a Stratification of this mixture of first and second phosphor particles 10, 20 above a SACSN phosphor having an RI of 2.1 and a ds o of 13 ym (third phosphor particles). In order to achieve the mixture of the first 10 and second phosphor particles 20, the second phosphor particles 20 can either with a 2.4 ym thick coating 25 of Al 2O ₃ (RI = 1.73, 30 W / mK), a 2.0 ym thick coating 25 of undoped YAG (RI = 1.82, 7 - 11 W / mK) or a 1.8 ym thick

Coating 25 of Y ₂ 0 ₃ (RI = 1.92, 13 - 14 W / mK)

be coated. In order to achieve a sedimentation rate for the third phosphor particles which is greater than that of the first 10 and second phosphor particles 20, the third phosphor particles can be coated either with a more than 6.4 μm thick coating 25 of S1 ₃ N ₄ (RI = 1.9 - 2.4, 10 - 43 W / mK), a more than 5.8 ym thick coating 25 of A1N (RI = 1.9-2.2, 285 W / mK) or more than 3.4 ym thick Coating 25 made of BN (RI = 2.1, 30 W / mK)

be coated. The phosphors, their densities p

and thicknesses ds o and the associated coatings with their densities p _B and thicknesses r _B are shown in Table 6. Furthermore, as a measure of the sedimentation rates the

Product r ² p of the phosphor particles indicated.

Luminous P d ₅ o [ym] coating PB r _B [ym] r ² p substance [g / cm ³ ] mat [g / cm ³ ] [g / cm] erial

LAGAG 7,0 17 5, 058: Ce * 10 ^"6

YAG: Ce 4, 6 17 3, 302

* 10 ^"6

YAG: Ce 4, 6 17 Al 2 O 3 3, 95 2,419 5, 058

* 10 ^"6 YAG: Ce 4, 6 17 YAG 4, 6 2.004 5, 058

* 10 ^"6

YAG: Ce 4, 6 17 Y ₂ 0 ₃ 5, Ol 1,805 5, 058

* 10 ^"6

SCASN: 4.2 13 1.775

Eu * 10 ^"6

SCASN: 4,2 13 S13N4 2, 9 6, 339 5, 058

Eu * 10 ^"6

SCASN: 4,2 13 A1N 3,2 5, 791 5, 058

Eu * 10 ^"6

SCASN: 4,2 13 BN 3,45 5,399 5, 058

Eu * 10 ^"6

Table 6

In another embodiment, a

Stratification can be achieved, with a bottom

Sr ₄ Ali ₄ 0 ₂ 5: Eu (d ₅ o = 15 ym) phosphor layer (third

Phosphor particles) and above a mixture of the phosphors KSF with a dso of 27 ym (first phosphor particles 10) and β-SiAlON with a dso of 15 ym (second phosphor particles 20). In order to achieve a layer formation, the third phosphor particles are provided with a coating 25 which contains more than 2.8 μm thick SrTiO ₂ . In order to obtain the same sedimentation rates r ² p for the particles of the first 10 and second phosphor particles 20, the second phosphor particles 20 can be coated with a 3, 9 ym thick coating 25 of Al 2 O ₃ . This phosphor mix and the respective ones

Coatings 25 are shown in Table 7. Luminous P d ₅₀ [ym] coating PB r _B [ym] r ² p substance [g / cm ³ ] mat [g / cm ³ ] [g / cm] erial

KSF: Mn 2, 65 27 4,830

* 10 ^"6 ß ^" 3.2 15 1.800

SiAlON * 10 ^"6 : Eu

ß ^" 3.2 15 A1 ₂ 0 ₃ 3, 95 3, 872 4,830

SiAlON * 10 ^"6 : Eu

Sr ₄ Al ₁₄ 3.7 15 2.081 0 ₂₅ : Eu * 10 ^"6

Sr ₄ Al ₁₄ 3,7 15 SrTi0 ₃ 5, 12 2,782 4,830 0 ₂₅ : Eu * 10 ^"6

Table 7

The invention is not limited by the description with reference to the embodiments. Rather, the includes

Invention every new feature as well as every combination of

Features, which includes in particular any combination of features in the claims, even if this feature or this combination itself is not explicitly in the

Claims or embodiments is given.

This patent application claims the priority of German Patent Application 10 2017 123 097.1, the disclosure of which is hereby incorporated by reference. Reference sign list

10 particles of the first phosphor

20 particles of the second phosphor

25 coating

30 matrix material

T temperature

QE (T) / QE (25 ° C) thermal quenching of the quantum yield

QE normalizes to the quantum yield at 25 ° C

Claims

claims

1. Conversion material comprising

a matrix material (30),

- Particles of a first phosphor (10), in the

Embedded matrix material (30), and

- Particles of a second phosphor (20), in the

Embedded matrix material (30), wherein

the particles of the second phosphor (20) are smaller than the particles of the first phosphor (10) and / or have a lower density and wherein the particles of the second phosphor (20) have a coating (25),

wherein the sedimentation velocity of the particles of the second phosphor (20) comprising the coating (25) is greater than or equal to the sedimentation velocity of the particles of the first phosphor (10).

2. Conversion material according to the preceding claim, wherein the matrix material (30) has a first refractive index, the particles of the second phosphor (20) have a second refractive index and the coating (25) has a third refractive index, the third

Refractive index is equal to the first refractive index or lies between the first and the second refractive index.

3. Conversion material according to one of the preceding

Claims, wherein the coating (25) has a density which is greater than or equal to the density of the particles of the second phosphor (20).

4. Conversion material according to one of the preceding

Claims, wherein in each case a particle of the second

Phosphor (20) has a coating (25) and / or a plurality of particles of the second phosphor (20) together have a coating (25).

5. Conversion material according to one of the preceding

Claims, wherein the coating (25) is a thermal

Conductivity greater than a thermal

Conductivity of the matrix material (30).

6. Conversion material according to one of the preceding

Claims, wherein the coating (25) is a thermal

Having conductivity that is greater than a thermal conductivity of the particles of the second phosphor (20).

7. Conversion material according to one of the preceding

Claims, wherein the coating (25) at least in places has a thickness which is greater than 100 nm, preferably greater than 500 nm.

8. Conversion material according to one of the preceding

Claims, wherein between the particles of the second

Phosphor (20) and the coating (25) a

Protective layer is arranged.

9. Conversion material according to one of the preceding

Claims, wherein on the coating (25) a

Antireflection layer is arranged.

10. Conversion material according to one of the preceding

Claims, wherein the particles of the first phosphor (10) a first layer and the particles of the second phosphor (20) form a second layer in the matrix material (30) and the first layer is disposed on the second layer.

11. Conversion material according to one of claims 1 to 9, wherein the particles of the first phosphor (10) and the

Particles of the second phosphor (20) mixed in the

Matrix material (30) are distributed.

12. Conversion material according to one of claims 1 to 9, further comprising particles of a third phosphor, which have a coating (25).

13. Conversion material according to one of the preceding

Claims, wherein the coating (25) is a material

which is selected from a group including KCl, LiCl, h-BN (graphite structure), NaCl, a-Si _{3 4} / b-Si ₃ 4, LiB ₃ O ₅ , LiF, CaCO ₃ , MgF ₂ , CaF ₂ , AlN (wurtzite type), c-BN (diamond structure), MgO, diamond, BaB ₂ O ₄ , Sc ₂ O ₃ , SrF ₂ , TiO ₂ (rutile), YAG

(undoped), Nb ₂ 0 ₅ , BaF ₂ , ZrO ₂ , Y ₂ O ₃ , SrTiO ₃ , ZnO (wurtzite), TeO ₂ , BaTiO ₃ , LuAG (undoped), LiTaO ₃ , Ta ₂ 0 ₅ , Yb ₂ 0 ₃ , Lu ₂ 0 ₃ ,

HfO ₂ , M ₂ SiF ₆ (M = Li, Na, K, Rb, Cs alone or in mixture), silicones, polysilazanes, siloxanes, and nanoparticle-filled silicones.

14. A radiation-emitting component comprising an active layer sequence, which emits electromagnetic radiation of a first wavelength range, and a conversion layer, which in the beam path of the radiation of the first

Wavelength range is arranged and a

Conversion material according to one of the preceding claims.

15. The component according to the preceding claim, wherein the conversion layer, the radiation of the first

Wavelength range at least partially in radiation

at least a second and third wavelength range converted.

16. Component according to one of claims 14 and 15, wherein the particles of the second phosphor (20) form a second layer and are arranged on the active layer sequence facing side of the conversion layer, and the

Particles of the first phosphor (10) form a first layer and on the side facing away from the active layer sequence side of the second layer in the conversion layer

are arranged.