WO2014104917A1 - Rare earth metal ion complex, luminescent composite material, light emitting device, and use - Google Patents

Rare earth metal ion complex, luminescent composite material, light emitting device, and use Download PDF

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Publication number
WO2014104917A1
WO2014104917A1 PCT/RU2012/001136 RU2012001136W WO2014104917A1 WO 2014104917 A1 WO2014104917 A1 WO 2014104917A1 RU 2012001136 W RU2012001136 W RU 2012001136W WO 2014104917 A1 WO2014104917 A1 WO 2014104917A1
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Prior art keywords
light emitting
rare earth
earth metal
metal ion
composite material
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PCT/RU2012/001136
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French (fr)
Inventor
Alexey Grigorjevich VITUKHNOVSKII
lljya Viktorovich TAIDAKOV
Sergey Aleksandrovich AMBROZEVICH
Denis Nikolaevich BYCHKOVSKII
Alexey Ruslanovich KOVSH
Vladislav Evgenjevich BOUGROV
Maxim Anatoljevich ODNOBLYUDOV
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Organic Lighting Solutions Ug
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Priority to PCT/RU2012/001136 priority Critical patent/WO2014104917A1/en
Publication of WO2014104917A1 publication Critical patent/WO2014104917A1/en

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D231/00—Heterocyclic compounds containing 1,2-diazole or hydrogenated 1,2-diazole rings
    • C07D231/02—Heterocyclic compounds containing 1,2-diazole or hydrogenated 1,2-diazole rings not condensed with other rings
    • C07D231/10—Heterocyclic compounds containing 1,2-diazole or hydrogenated 1,2-diazole rings not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members
    • C07D231/12—Heterocyclic compounds containing 1,2-diazole or hydrogenated 1,2-diazole rings not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members with only hydrogen atoms, hydrocarbon or substituted hydrocarbon radicals, directly attached to ring carbon atoms
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/06—Luminescent, e.g. electroluminescent, chemiluminescent materials containing organic luminescent materials
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B33/00—Electroluminescent light sources
    • H05B33/12—Light sources with substantially two-dimensional radiating surfaces
    • H05B33/14—Light sources with substantially two-dimensional radiating surfaces characterised by the chemical or physical composition or the arrangement of the electroluminescent material, or by the simultaneous addition of the electroluminescent material in or onto the light source
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K2211/00—Chemical nature of organic luminescent or tenebrescent compounds
    • C09K2211/18—Metal complexes
    • C09K2211/182—Metal complexes of the rare earth metals, i.e. Sc, Y or lanthanide

Definitions

  • the present invention relates to light emitting components, devices, and materials, in particular to light emitting devices wherein conversion of the primarily emitted light at a first wavelength range into another wavelength range is required, and to materials for performing said conversion.
  • a primary light emitting element wherein the color or wavelength of the light emitted by the primary light emitting element must be converted into one or more other colors or wavelengths.
  • a typical example is a white LED, where the initial wavelength range e.g. in the ultraviolet, blue, or green portion of the spectrum is converted into white light comprising several wavelength ranges. White light is required e.g. in illumination applications.
  • Other typical examples of electroluminescent components and devices where wavelength conversion is used are various displays for presenting alphanumerical and graphical information, backlight units, as well as fluorescent lamps.
  • the wavelength conversion is most typically made by means of a luminescent material receiving and absorbing the light of a first wavelength range emitted by the primary light emitting element, and emitting the absorbed energy at one or more other wavelength ranges.
  • a luminescent material receiving and absorbing the light of a first wavelength range emitted by the primary light emitting element, and emitting the absorbed energy at one or more other wavelength ranges.
  • luminescent materials often called "phosphors”, for this purpose known in the art.
  • phosphors for this purpose known in the art.
  • one of the most common wavelength conversion luminescent materials is cerium (III) doped yttrium aluminum garnet YAG.
  • a major challenge in the field of wavelength conversion in electroluminescent components and devices is to combine the need of high efficient luminescent materials, i.e. materials making the wavelength conversion with high quantum efficiency, to the requirement of low costs of the material and the manufacturing process.
  • other functional requirements for the luminescent materials are good photostability, i.e. resistance against photodegradation, high absorption coefficient at the wavelengths of the excitation light, i.e. the light emitted by the primary light emitting element, and low absorption of the wavelengths at which the luminescent material emits light in order to prevent re-absorption.
  • key requirements for the luminescent material are thermal stability, solubility in the monomers and polymers, as well as chemical compatibility with a suitable matrix without tendency to crystallize.
  • Yttrium mentioned above is an example of rare-earth elements, the use of which in luminescent materials opens up great possibilities to emit light in different regions of visible and IR spectrum.
  • Specific rare earth metal based materials in the form of complexes containing 4-trifluoroacetylpyrazolones as diketonate ligands have been proposed by Marchetti et al. in [F. Marchetti, C. Pettinari, R. Pettinari., Coord. Chem, Rev. (2005) , Volume 249, page 2909].
  • the second keto-group, or the side-chain is enclosed ill a conjugated pyrazolone system, thus limiting the possibilities to vary the structure of the complexes to adjust the technological and photophysical properties of the luminescent material .
  • US patent 2007/0085057 Al proposes to cap the LED chip with a transparent matrix doped with the rare earth metal complex, or to cover the chip with, the pure complex and to cap it with a transparent polymer afterwards.
  • This technique has its drawbacks in that the luminescence intensity tends to drift down due to the direct contact of the luminescent complex with the LED chip, and also due to the rare earth metal complex photodegradation processes stimulated by the short- wavelength light emitted by the LED.
  • the purpose of the invention is to provide a novel rare earth metal ion complex, a novel luminescent composite material comprising the same, use of the luminescent composite material for wavelength conversion, as well as a light emitting device comprising a primary light emitting device and the luminescent composite material.
  • the rare earth metal ion complex according to the present invention is defined by what is presented in claim 1.
  • the luminescent composite material according to the present invention is defined by what is presented in claim 7.
  • the light emitting device according to the present invention is defined by what is presented in claim 11.
  • Figure 1 is a schematic illustration of the basic principle of a light emitting device according to the present invention.
  • Figure 2 shows another embodiment of a light emitting device according to the present invention.
  • the present invention relates to a rare earth metal ion complex having the following formula (1) :
  • L n represents a trivalent rare earth metal ion
  • L 2 represents a bidentate ligand containing nitrogen
  • Li represents a diketonate ligand derivative having the following formula (2) :
  • Ri represents an alkyl group, a fluoroalkyl group, or a substituted or an unsubstituted aryl group
  • R 2 represents a hydrogen atom, an alkyl group, a fluoroalkyl group, a substituted or an unsubstituted aryl group, a halogen atom, or a N0 2 group;
  • R 3 represents an alkyl group, a substituted or unsubstituted aryl group, a halogen atom, or a N0 2 group;
  • R F represents an alkyl group substituted with at least one fluorine atom.
  • Ri, R 2 , R3 and R f are selected independently of each other.
  • the diketonate fragment is not part of a conjugated pyrazole system as is the case in e.g. the above described complexes proposed by Marchetti et al.
  • the diketonate fragment can be attached to any position of the pyrazole ring.
  • the diketone fragment is at the C3, C4 or C5 position of the pyrazole ring. Being able to vary the position of the diketonate fragment withi the pyrazole ring enables the adjustment of electronic and steric properties of the ligand.
  • the trivalent rare earth metal ion is a lanthanide ion. In one embodiment of the present invention the trivalent rare earth metal ion is selected from a group consisting of Nd 3+ , Pr 3+ , Sm 3+ , Eu 3+ , Tb 3+ , Dy 3+ , Ho 3+ , Tm 3+ , Er 3+ , and Yb 3+ .
  • L 2 represents a bidentate ligand containing nitrogen.
  • a ligand is an ion or neutral molecule that bonds to a central metal atom or ion.
  • Ligands act as Lewis bases (electron donors), and the central metals they bond to act as Lewis acids (electron acceptors) .
  • Ligands have at least one donor atom with a pair of lone electrons used to form covalent bonds with the central metal ion or atom that they are attached to.
  • Bidentate ligands have two donor atoms which allow them to bond to a central metal atom or ion at two points.
  • the bidentate ligand containing nitrogen, i.e. N atoms is selected from a group consisting of 1.10-phenantroline, 2, 2' -bipyridyl, and 1-methyl- (2- pyridyl ) benzimidazole .
  • Li represents a diketonate ligand derivative according to formula (2) .
  • the diketonate ligand is a derivative of 1, 3-propanedione 3- ( (poly) fluoroalkyl) -1- (pyrazolyl) .
  • the alkyl group is Ci-12 alkyl, preferably Ci_ 6 alkyl, and more preferably C1-2 alkyl. In one embodiment of the present invention the alkyl group is methyl, ethyl, propyl, or butyl.
  • the fluoroalkyl group is an alkyl group containing one to twenty-five fluorine atoms, preferably one to ten fluorine atoms, more preferably one to three fluorine atoms. In one embodiment of the present invention the fluoroalkyl group is selected from a group consisting of CHF 2 , CF 3 , and C 3 F 7 .
  • the substituted aryl group is substituted phenyl or substituted naphthyl.
  • the unsubstituted aryl group is unsubstituted phenyl, or unsubstituted naphtyl.
  • the aryl group is substituted with at least one halogen atom, CN group, a N0 2 group, or a C1-C6 alkyl substituted with one to thirteen fluorine atoms .
  • the halogen atom is selected from a group consisting of fluorine, chlorine, and bromine.
  • R F represents an alkyl group substituted with at least one fluorine atom.
  • the alkyl group can be as above defined.
  • R F represents methyl substituted with one, two or three fluorine atoms.
  • the presence of the R F group affects the luminescence intensity of the rare earth metal ion complex.
  • the inventors of the present invention found out that the introduction of acceptor fluorinated groups (R F ) in the diketonate ligand according to formula (2) results in violation or distortion of the symmetry of electron density distribution both in the molecule of the parent ligand, i.e. the biketonate ligand, and in combination with rare earth metal ion.
  • the inventors of the present invention surprisingly found out that introducing the R3 group into C2 position of the 1.3-diketone fragment results in an increase of the efficiency and quantum yield of luminescence compared to similar kinds of rare earth metal ion complexes without this kind of R3 group present in the C2 position of the diketonate fragment.
  • the rare earth metal ion complexes according to the present invention are thermally stable. They can be sublimated without decomposition at high vacuum (10-6 torr) at 200-300 °C.
  • (1) can be synthesized in accordance with methods described for carboxylic analogs.
  • the ligands can be synthesized in accordance with the procedures described in e.g. C.J Sloop, C.L. Bumgardner et al., Journal of Fluorine Chemistry (2002), volume 118, page 135; D.V. Sevenard, G.V. Roeschenthaler, V.G. Nenajdenko et al., Tetrahedron. (2009) volume 65, page 7538; L. Barkley., Journal of the American Chemical Society (1953), volume 75, page 2059; or P.R Singh, R. Sahai. Austr., J. Chem. (1967), volume 20, page 649.
  • the bidentate ligand as defined in formula (1) can be purchased from commercial suppliers or be synthetized as it was described elsewere.
  • the rare earth metal ion complex according to the present invention is synthesized by reaction of the ligands and the rare earth metal ion.
  • the reaction is carried out in the presence of a base.
  • the reaction is carried out at a temperature of 50 - 60 °C for 1 - 24 hours .
  • a solution of a diketonate ligand, and a bidentate ligand containing nitrogen, which can be obtained e.g. as above described, in alcohol is formed and an aqueous solution of the base is added thereto in a dropwise manner at ambient temperature.
  • the alcohol is selected from a group consisting of methanol, ethanol, and 2-propanol.
  • the base is sodium hydroxide (NaOH) , potassium hydroxide (KOH) , or ammonia (NH3) .
  • the rare earth metal ion is introduced into the reaction mixture containing the ligands in the form of an aqueous solution of a rare earth metal salt.
  • the aqueous solution of the rare earth metal salt is added in a dropwise manner into the solution containing the diketonate ligand and the bidentate ligand containing nitrogen.
  • the rare earth metal salt is a chloride or a nitrate.
  • the reaction mixture after the reaction is completed, is cooled to ambient temperature and the formed rare earth metal ion complex is separated.
  • the formed rare earth metal ion complex is separated by filtration or by extraction from an appropriate solvent.
  • the solvent is CHCI3 or CH 2 C1 2 .
  • the present invention further relates to a luminescent composite material comprising a rare earth metal ion complex according to the present invention and polymer.
  • the polymer is selected from a group consisting of acrylate, styrene, epoxy resin, and optical polyurethane resin.
  • the rare earth metal ion complex may be mixed or dispersed within the selected polymer composition.
  • the luminescent composite material comprises 0,1 - 10 weight-% of the rare earth metal ion complex.
  • the advantage of the rare earth metal ion complex according to the present invention is that it does not crystallize from the polymers after polymerization or polycondensation of monomers.
  • the luminescent composite material is a fluorescent composite material.
  • an advantage of the present invention is that a new rare earth metal ion complex having an. increased efficiency and quantum yield can be formed.
  • an advantage of the present invention is that by the use of different rare earth metal ion complexes according to the present invention in the luminescent composite material it is possible to generate radiation in different ranges of visible and near-infrared spectrum.
  • the present invention is also focused on a light emitting device comprising a primary light emitting element configured to emit light at a first wavelength.
  • the light emitting device further comprises the luminescent composite material as described above for receiving at least part of the light emitted by the primary light emitting device and emitting at least part of the thereby received energy as light at a second wavelength which is longer than the first wavelength .
  • the light emitted by the primary light emitting element is at least partially absorbed by the luminescent composite material, and the energy thereby absorbed is at least partially emitted by the luminescent composite material so that the spectrum of the light emitted by the luminescent composite material differs from the spectrum of the light received by it.
  • the second wavelength being longer than the first wavelength is meant that the peak wavelength of the spectrum of light emitted by the luminescent composite material is higher than the peak wavelength of the spectrum of the light absorbed by the luminescent composite material.
  • the light emitting device shares the advantages of high quantum yield, i.e. high wavelength conversion efficiency, and adjustable emission wavelength range.
  • the first wavelength i.e. the peak wavelength of the light emitted by the primary light emitting element lies in the range of 200 - 450 nm. At these wavelengths, the absorbance and also the quantum efficiency of wavelength conversion are at their highest.
  • the primary light emitting element can be any light emitting element preferably having the emission peak in the wavelength range specified above.
  • the primary light emitting device is a light emitting diode LED.
  • LEDs are highly efficient components typically having good stability . properties, so combining a LED and a luminescent composite material in accordance with the present invention provides a very efficient, stabile, and versatile light emitting device configuration.
  • Group III nitrides, such as gallium nitride GaN, and their derivatives form a class of semiconductor materials emitting at the preferred wavelength range of the first wavelength as specified above, thereby providing a good choice e.g. for high brightness white LEDs.
  • the primary light emitting device is a display element.
  • the actual configuration of the light emitting device according to the present invention can be based on principles as such known in the art.
  • the luminescent composite material can be arranged in direct physical contact with the primary light emitting element, as is the case e.g. in LED chips encapsulated within an encapsulant forming or comprising the luminescent composite material. Alternatively, it can be arranged as or in a separate wavelength conversion element or a coating at a distance from the primary light emitting element. In the field of white LEDs, this kind of wavelength conversion material is usually known as "remote phosphor" .
  • the present invention is also focused on use of the luminescent composite material as described above for receiving light at a first wavelength and emitting at least part of the thereby received energy as light at a second wavelength which is longer than the first wavelength.
  • the embodiments of this use are explained above in the context of the rare earth metal ion complex, the luminescent composite material, and the light emitting device aspects of the present invention.
  • the first wavelength range preferably lies in the range of 200 - 450 nm.
  • a rare earth metal ion complex may comprise one or more of the embodiments of the invention described as separate embodiments hereinbefore.
  • Tris- (4, 4, 4-trifluoro-1- ( 1-methyl-lH-pyrazol- 4-yl) -2-nitro-butane-l, 3-dionato) (1.10-phenantroline) Europium (III) was synthesized following the procedure described in Example 1. 0.795 g of 4, 4, 4-trifluoro-1- (l-methyl-lH-pyrazol-4-yl) -2-nitro-butane-l, 3-dione and 3 ml of a 1M aqueous solution of NaOH were used. Yield: 0.23 g (21%)
  • Tris- (1- [4-chloro-l- (4-nitro-phenyl) -1H- pyrazol-3-yl] -2- (3, 5-difluoro-phenyl) -4 , 4-difluoro- butane-1, S- ⁇ dionato) (1.10-phenantroline) Europium (III) was synthesized following the procedure described in Example - 1.
  • Tris- (4, , 4-trifluoro-l- (l-methyl-4-nitro-5- trifluoromethyl-lH-pyrazol-3-yl) -butane-1, 3- dionato) ( 1.10-phenantroline) Europium (III) was synthesized following the procedure described in Example 1. 1.00 g of 4 , 4 , 4-trifluoro-1- ( l-methyl-4- nitro-5-trifluoromethyl-lH-pyrazol-3-yl) -butane-1, 3- dione and 3 ml of a 1M aqueous solution of NaOH were used.
  • Tris- (4,4, 4-trifluoro-l- (1-methyl-lH-pyrazol- 4-yl) -butane-1, 3-dionato) ( 1.10-phenantroline) Europium (III) was synthesized following the procedure described in Example 1. 0.661 g of 4, 4, 4-trifluoro-1- (l-methyl-lH-pyrazol-4-yl) -1, 3-butanedione and 3 ml of a 1M aqueous solution of NaOH were used. Yield: 0.33 g (33 %)
  • Tris- (4, 4-difluoro-1- ( l-methyl-lH-pyrazol-4- yl) -1 , 3-butanedionato) (1.10-phenantroline) Europium (III) was synthesized following the procedure described in Example 1. 0.606 g of 4, 4-difluoro-1- ilmethyl-lH-pyrazol-4-yl) -1, 3-butanedione and 3 ml of a 1M aqueous solution of NaOH were used.
  • the supernatant was placed into a metal polished form, which was closed. Then the temperature was gradually increased up to 350 °C during 6 hours. The solution was kept at this temperature for 72 hours, after which it was cooled and disassembled from the form. The procedure resulted in a luminescent composite material in the form of a transparent block.
  • EXAMPLE 9 Preparation of luminescent composite material comprising epoxy resin and tris- (2, 4, 4, 4- tetrafluoro-1- (l-methyl-lH-pyrazol-4-yl) -butane-1, 3- dionato) ( 1.10-phenantroline) Europium (III)
  • EXAMPLE 10 Preparation of luminescent composite material comprising polyurethane resin and tris- (4,4, 4-trifluoro-1- (l-methyl-lH-pyrazol-4-yl) -2-nitro- butane-1, 3-dionato) (1.10-phenantroline) Europium (III)
  • Figure 1 illustrates schematically a light emitting device 1 comprising a primary light emitting element 2, e.g. a display element or a LED.
  • the primary light emitting element is configured to emit light 4 at a first wavelength ⁇
  • the emission spectrum of the primary light emitting element has a peak wavelength of ⁇ .
  • the light emitting device 1 further comprises a luminescent composite material 3 according to one embodiment of the present invention.
  • the luminescent composite material can be configured as a separate element at a distance from the primary light emitting element 2, as illustrated in Figure 1, or it can be in a direct contact with the primary light emitting element 2.
  • the luminescent composite material 3 can itself form a discrete component, or it can form e.g. a coating on another existing component, e.g. a lens.
  • the light 4 emitted by the primary light emitting element 2 is at least partially received and absorbed by the luminescent composite material 3. At least part of the energy thereby received by the luminescent composite material 3 is then released via emission of light 5 at a second wavelength ⁇ 2 , which is higher than the first wavelength ⁇ .
  • the luminescent composite material 3 is used to convert the wavelength of light emitted the primary light emitting device to a longer wavelength.
  • the first wavelength ⁇ can lie in the range of 200 to 450 nm.
  • the second wavelength ⁇ 2 depends on the accurate composition of the rare earth metal ion complex of the luminescent composite material. Examples of different compositions and the second wavelengths, i.e. emission wavelengths thereof, are given in the examples 1 to 9 above.
  • the emission wavelength of the luminescent composite material is adjustable over a broad wavelength range from about 500 nm to about 1500 nm.
  • FIG. 2 shows a cross-sectional view of a chip-on-board (COB) type light emitting module 1 as an example of a light emitting device according to the present invention.
  • the module comprises a substrate plate 6 on which LED chips 2 have been mounted as primary light emitting elements. Patterned metal plating 7 forms the electrical interface of the module as well as the electrical connections between the LED chips.
  • the chips are encapsulated within an encapsulant 8 comprising a luminescent composite material 3 according to the present invention.
  • the luminescent composite material is in direct contact with the LED chips.
  • the encapsulant 8 surrounds the LED chips, thereby ensuring that practically all the light from the LED chips - is received by the encapsulant 8 and the luminescent composite material 3 therein.
  • the general operation principle of the COB type light emitting module is the same as that the schematically illustrated light emitting device of Figure 1.

Abstract

The invention relates to a rare earth metal ion complex for luminescent composite (3) material for wavelength conversion. The complex has the following formula (1): [Ln(L1)3L2], wherein Ln represents a trivalent rare earth metal ion; L2 represents a bidentate ligand containing nitro-gen; and L1 represents a diketonate ligand derivative having the following formula (2) wherein R1 represents an alkyl group, a fluoroalkyl group, or a substituted or an unsubstituted aryl group; R2 represents a hydrogen atom, an alkyl group, a fluoroalkyl group, a substituted or an unsubstituted aryl group, a halogen atom, or a NO2 group; R3 represents an alkyl group, a substituted or unsubstituted aryl group, a halogen atom, or a NO2 group; and RF represents an alkyl group substituted with at least one fluorine atom.

Description

RARE EARTH METAL ION COMPLEX, LUMINESCENT COMPOSITE MATERIAL, LIGHT EMITTING DEVICE, AND USE
FIELD OF THE INVENTION
The present invention relates to light emitting components, devices, and materials, in particular to light emitting devices wherein conversion of the primarily emitted light at a first wavelength range into another wavelength range is required, and to materials for performing said conversion.
BACKGROUND OF THE INVENTION
There are various light emitting components and devices based on a primary light emitting element, wherein the color or wavelength of the light emitted by the primary light emitting element must be converted into one or more other colors or wavelengths. A typical example is a white LED, where the initial wavelength range e.g. in the ultraviolet, blue, or green portion of the spectrum is converted into white light comprising several wavelength ranges. White light is required e.g. in illumination applications. Other typical examples of electroluminescent components and devices where wavelength conversion is used are various displays for presenting alphanumerical and graphical information, backlight units, as well as fluorescent lamps.
The wavelength conversion is most typically made by means of a luminescent material receiving and absorbing the light of a first wavelength range emitted by the primary light emitting element, and emitting the absorbed energy at one or more other wavelength ranges. There is a great variety of different luminescent materials, often called "phosphors", for this purpose known in the art. Just as an example, in the field of white LEDs based on blue-emitting gallium nitride diodes as the primary light emitting elements, one of the most common wavelength conversion luminescent materials is cerium (III) doped yttrium aluminum garnet YAG.
In general, a major challenge in the field of wavelength conversion in electroluminescent components and devices is to combine the need of high efficient luminescent materials, i.e. materials making the wavelength conversion with high quantum efficiency, to the requirement of low costs of the material and the manufacturing process. In addition to the high quantum efficiency, other functional requirements for the luminescent materials are good photostability, i.e. resistance against photodegradation, high absorption coefficient at the wavelengths of the excitation light, i.e. the light emitted by the primary light emitting element, and low absorption of the wavelengths at which the luminescent material emits light in order to prevent re-absorption. From the manufacturing technology point of view, key requirements for the luminescent material are thermal stability, solubility in the monomers and polymers, as well as chemical compatibility with a suitable matrix without tendency to crystallize.
Yttrium mentioned above is an example of rare-earth elements, the use of which in luminescent materials opens up great possibilities to emit light in different regions of visible and IR spectrum. Specific rare earth metal based materials in the form of complexes containing 4-trifluoroacetylpyrazolones as diketonate ligands have been proposed by Marchetti et al. in [F. Marchetti, C. Pettinari, R. Pettinari., Coord. Chem, Rev. (2005) , Volume 249, page 2909]. In the proposed compounds, the second keto-group, or the side-chain, is enclosed ill a conjugated pyrazolone system, thus limiting the possibilities to vary the structure of the complexes to adjust the technological and photophysical properties of the luminescent material .
In order to employ certain rare earth metal complexes in the light sources with an inorganic semiconductor LED chip as the primary light emitting element, US patent 2007/0085057 Al proposes to cap the LED chip with a transparent matrix doped with the rare earth metal complex, or to cover the chip with, the pure complex and to cap it with a transparent polymer afterwards. This technique has its drawbacks in that the luminescence intensity tends to drift down due to the direct contact of the luminescent complex with the LED chip, and also due to the rare earth metal complex photodegradation processes stimulated by the short- wavelength light emitted by the LED.
To summarize, despite the variety of existing solutions there is still a need for further enhanced and adjustable solutions for wavelength conversion with high efficiency, low re-absorption of the emitted light, high long-term stability of the luminescent material, and good compatibility of the luminescent material with the manufacturing processes of light emitting devices and components.
PURPOSE OF THE INVENTION
The purpose of the invention is to provide a novel rare earth metal ion complex, a novel luminescent composite material comprising the same, use of the luminescent composite material for wavelength conversion, as well as a light emitting device comprising a primary light emitting device and the luminescent composite material.
SUMMARY
The rare earth metal ion complex according to the present invention is defined by what is presented in claim 1.
The luminescent composite material according to the present invention is defined by what is presented in claim 7.
The light emitting device according to the present invention is defined by what is presented in claim 11.
The use according to the present invention is defined by what is present in claim 15.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are included to provide a further understanding of the invention and constitute a part of this specification, illustrate embodiments of the invention and together with the description help to explain the principles of the invention. In the drawings:
Figure 1 is a schematic illustration of the basic principle of a light emitting device according to the present invention, and
Figure 2 shows another embodiment of a light emitting device according to the present invention.
In the figures, for reasons of simplicity, same reference numbers are used for the corresponding elements of different drawings.
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rare earth metal ion complex having the following formula (1) :
[L„(Li.) 3L2] formula (1) wherein
Ln represents a trivalent rare earth metal ion;
L2 represents a bidentate ligand containing nitrogen; and
Li represents a diketonate ligand derivative having the following formula (2) :
Figure imgf000006_0001
formula (2) wherein
Ri represents an alkyl group, a fluoroalkyl group, or a substituted or an unsubstituted aryl group;
R2 represents a hydrogen atom, an alkyl group, a fluoroalkyl group, a substituted or an unsubstituted aryl group, a halogen atom, or a N02 group;
R3 represents an alkyl group, a substituted or unsubstituted aryl group, a halogen atom, or a N02 group; and
RF represents an alkyl group substituted with at least one fluorine atom. '
Ri, R2, R3 and Rf are selected independently of each other. In the present invention the diketonate fragment is not part of a conjugated pyrazole system as is the case in e.g. the above described complexes proposed by Marchetti et al. In the rare earth metal ion complex according to the present invention the diketonate fragment can be attached to any position of the pyrazole ring. In one embodiment of the present invention the diketone fragment is at the C3, C4 or C5 position of the pyrazole ring. Being able to vary the position of the diketonate fragment withi the pyrazole ring enables the adjustment of electronic and steric properties of the ligand.
In one embodiment of the present invention the trivalent rare earth metal ion is a lanthanide ion. In one embodiment of the present invention the trivalent rare earth metal ion is selected from a group consisting of Nd3+, Pr3+, Sm3+, Eu3+, Tb3+, Dy3+, Ho3+, Tm3+, Er3+, and Yb3+.
In formula (1) L2 represents a bidentate ligand containing nitrogen. A ligand is an ion or neutral molecule that bonds to a central metal atom or ion. Ligands act as Lewis bases (electron donors), and the central metals they bond to act as Lewis acids (electron acceptors) . Ligands have at least one donor atom with a pair of lone electrons used to form covalent bonds with the central metal ion or atom that they are attached to. Bidentate ligands have two donor atoms which allow them to bond to a central metal atom or ion at two points. In one embodiment of the present invention the bidentate ligand containing nitrogen, i.e. N atoms, is selected from a group consisting of 1.10-phenantroline, 2, 2' -bipyridyl, and 1-methyl- (2- pyridyl ) benzimidazole .
In formula (1) Li represents a diketonate ligand derivative according to formula (2) . In one embodiment of the present invention the diketonate ligand is a derivative of 1, 3-propanedione 3- ( (poly) fluoroalkyl) -1- (pyrazolyl) .
In one embodiment of the present invention the alkyl group is Ci-12 alkyl, preferably Ci_6 alkyl, and more preferably C1-2 alkyl. In one embodiment of the present invention the alkyl group is methyl, ethyl, propyl, or butyl.
In one embodiment of the present invention the fluoroalkyl group is an alkyl group containing one to twenty-five fluorine atoms, preferably one to ten fluorine atoms, more preferably one to three fluorine atoms. In one embodiment of the present invention the fluoroalkyl group is selected from a group consisting of CHF2, CF3, and C3F7.
In one embodiment of the present invention the substituted aryl group is substituted phenyl or substituted naphthyl. In one embodiment of the present invention the unsubstituted aryl group is unsubstituted phenyl, or unsubstituted naphtyl. In one embodiment of the present invention the aryl group is substituted with at least one halogen atom, CN group, a N02 group, or a C1-C6 alkyl substituted with one to thirteen fluorine atoms .
In one embodiment of the present invention the halogen atom is selected from a group consisting of fluorine, chlorine, and bromine.
As above presented RF represents an alkyl group substituted with at least one fluorine atom. The alkyl group can be as above defined. In one embodiment of the present invention RF represents methyl substituted with one, two or three fluorine atoms. The presence of the RF group affects the luminescence intensity of the rare earth metal ion complex. The inventors of the present invention found out that the introduction of acceptor fluorinated groups (RF) in the diketonate ligand according to formula (2) results in violation or distortion of the symmetry of electron density distribution both in the molecule of the parent ligand, i.e. the biketonate ligand, and in combination with rare earth metal ion. The distortion of the symmetry of electron density distribution in the diketonate ligand results in more intensive light absorption. I.e. increased amount of energy is brought to the molecule resulting in a more intense luminescence. This has the advantage effect of improving energy transfer within the complex, and as a result, increases the efficiency and quantum yield of luminescence .
The inventors of the present invention surprisingly found out that introducing the R3 group into C2 position of the 1.3-diketone fragment results in an increase of the efficiency and quantum yield of luminescence compared to similar kinds of rare earth metal ion complexes without this kind of R3 group present in the C2 position of the diketonate fragment.
The rare earth metal ion complexes according to the present invention are thermally stable. They can be sublimated without decomposition at high vacuum (10-6 torr) at 200-300 °C.
The diketonate ligands as defined in formula
(1) can be synthesized in accordance with methods described for carboxylic analogs. The ligands can be synthesized in accordance with the procedures described in e.g. C.J Sloop, C.L. Bumgardner et al., Journal of Fluorine Chemistry (2002), volume 118, page 135; D.V. Sevenard, G.V. Roeschenthaler, V.G. Nenajdenko et al., Tetrahedron. (2009) volume 65, page 7538; L. Barkley., Journal of the American Chemical Society (1953), volume 75, page 2059; or P.R Singh, R. Sahai. Austr., J. Chem. (1967), volume 20, page 649. The bidentate ligand as defined in formula (1) can be purchased from commercial suppliers or be synthetized as it was described elsewere.
In one embodiment of the present invention the rare earth metal ion complex according to the present invention is synthesized by reaction of the ligands and the rare earth metal ion. The reaction is carried out in the presence of a base. In one embodiment of the present invention the reaction is carried out at a temperature of 50 - 60 °C for 1 - 24 hours .
In one embodiment of the present invention a solution of a diketonate ligand, and a bidentate ligand containing nitrogen, which can be obtained e.g. as above described, in alcohol is formed and an aqueous solution of the base is added thereto in a dropwise manner at ambient temperature. In one embodiment of the present invention the alcohol is selected from a group consisting of methanol, ethanol, and 2-propanol. In one embodiment of the present invention the base is sodium hydroxide (NaOH) , potassium hydroxide (KOH) , or ammonia (NH3) . In one embodiment of the present invention the rare earth metal ion is introduced into the reaction mixture containing the ligands in the form of an aqueous solution of a rare earth metal salt. In one embodiment of the present invention the aqueous solution of the rare earth metal salt is added in a dropwise manner into the solution containing the diketonate ligand and the bidentate ligand containing nitrogen. In one embodiment of the present invention the rare earth metal salt is a chloride or a nitrate.
In one embodiment of the present invention the reaction mixture, after the reaction is completed, is cooled to ambient temperature and the formed rare earth metal ion complex is separated. In one embodiment of the present invention the formed rare earth metal ion complex is separated by filtration or by extraction from an appropriate solvent. In one embodiment of the present invention the solvent is CHCI3 or CH2C12.
The present invention further relates to a luminescent composite material comprising a rare earth metal ion complex according to the present invention and polymer.
In one embodiment of the present invention the polymer is selected from a group consisting of acrylate, styrene, epoxy resin, and optical polyurethane resin. The rare earth metal ion complex may be mixed or dispersed within the selected polymer composition.
In one embodiment of the present invention the luminescent composite material comprises 0,1 - 10 weight-% of the rare earth metal ion complex. The advantage of the rare earth metal ion complex according to the present invention is that it does not crystallize from the polymers after polymerization or polycondensation of monomers.
In one embodiment of ,the present invention the luminescent composite material is a fluorescent composite material.
The use of different rare earth metal ion complexes according to the present invention in the luminescent composite material allows generating radiation in different ranges of visible and near- infrared spectrum. In other words, one advantageous feature of the .present invention is that it allows adjustment of the emission wavelength of the luminescent composite material. As examples only, it can be ' mentioned that europium based complexes can obtain radiation in the red range (620 nm) , terbium based complexes in the green (520 nm) , and ytterbium based complexes in the infrared (1550 nm) spectrum. To summarize, an advantage of the present invention is that a new rare earth metal ion complex having an. increased efficiency and quantum yield can be formed. Moreover, an advantage of the present invention is that by the use of different rare earth metal ion complexes according to the present invention in the luminescent composite material it is possible to generate radiation in different ranges of visible and near-infrared spectrum.
The present invention is also focused on a light emitting device comprising a primary light emitting element configured to emit light at a first wavelength. According to the present invention, the light emitting device further comprises the luminescent composite material as described above for receiving at least part of the light emitted by the primary light emitting device and emitting at least part of the thereby received energy as light at a second wavelength which is longer than the first wavelength .
In other words, the light emitted by the primary light emitting element is at least partially absorbed by the luminescent composite material, and the energy thereby absorbed is at least partially emitted by the luminescent composite material so that the spectrum of the light emitted by the luminescent composite material differs from the spectrum of the light received by it. By the second wavelength being longer than the first wavelength is meant that the peak wavelength of the spectrum of light emitted by the luminescent composite material is higher than the peak wavelength of the spectrum of the light absorbed by the luminescent composite material.
The light emitting device according to the present invention shares the advantages of high quantum yield, i.e. high wavelength conversion efficiency, and adjustable emission wavelength range. Preferably, the first wavelength, i.e. the peak wavelength of the light emitted by the primary light emitting element lies in the range of 200 - 450 nm. At these wavelengths, the absorbance and also the quantum efficiency of wavelength conversion are at their highest.
The primary light emitting element can be any light emitting element preferably having the emission peak in the wavelength range specified above.
In one embodiment of the present invention the primary light emitting device is a light emitting diode LED. LEDs are highly efficient components typically having good stability . properties, so combining a LED and a luminescent composite material in accordance with the present invention provides a very efficient, stabile, and versatile light emitting device configuration. Group III nitrides, such as gallium nitride GaN, and their derivatives form a class of semiconductor materials emitting at the preferred wavelength range of the first wavelength as specified above, thereby providing a good choice e.g. for high brightness white LEDs.
In another embodiment of the present invention the primary light emitting device is a display element.
The actual configuration of the light emitting device according to the present invention can be based on principles as such known in the art. The luminescent composite material can be arranged in direct physical contact with the primary light emitting element, as is the case e.g. in LED chips encapsulated within an encapsulant forming or comprising the luminescent composite material. Alternatively, it can be arranged as or in a separate wavelength conversion element or a coating at a distance from the primary light emitting element. In the field of white LEDs, this kind of wavelength conversion material is usually known as "remote phosphor" .
The present invention is also focused on use of the luminescent composite material as described above for receiving light at a first wavelength and emitting at least part of the thereby received energy as light at a second wavelength which is longer than the first wavelength. The embodiments of this use are explained above in the context of the rare earth metal ion complex, the luminescent composite material, and the light emitting device aspects of the present invention. For example, the first wavelength range preferably lies in the range of 200 - 450 nm.
The embodiments and features of the invention described hereinbefore may be used in any combination with each other. Several of the embodiments may be combined together to form a further embodiment of the invention. Thus, a rare earth metal ion complex, a luminescent composite material, a light emitting device, and a use to which the invention is related, may comprise one or more of the embodiments of the invention described as separate embodiments hereinbefore. EXAMPLES
Reference will now be made to the embodiments of the present invention, an example of which is illustrated in the accompanying drawings.
The description below discloses some embodiments of the invention such that a person skilled in the art is able to utilize the invention based on the disclosure. Not all steps of the embodiments are discussed in detail, as many of the steps will be obvious for the person skilled in the art based on this specification and the common general knowledge in the art. EXAMPLE 1. Synthesis of tris- (2 , 4 , 4 , 4-tetrafluoro-1- ( l-methyl-lH-pyrazol-4-yl) -butane-1, 3-dionato) (1.10- phenantroline) Europium (III) To a solution of 2, 4, , 4-tetrafluoro-1- (1- methyl-lH-pyrazol-4-yl) -butane-1, 3-dione (0.714 g, 3 mmol) and of 1.10-phenantroline (0.18 g, 1 mmol) in 15 ml of ethanol at 25 °C, 3 ml of 1M aqueous solution of NH3 was added under constant, stirring, followed by dropwise addition of 5 ml of an aqueous 0.2 M EuCl3 solution. The resulting reaction mixture was stirred for 5 hours at 60 °C, after which the reaction mixture was cooled. The resulting solid complex was separated by filtration, washed by ethanol and cold water, and finally dried in vacuum to a constant weight.
Yield: 0.39 g (37 %)
Found, %: C(41.51), N(10.90), H (2.29), Eu (14,63) Calculated, %: C(41.39), N(10.73), H (2.32), Eu (14.55)
max. em. (the wavelength of the maximum intensity of the emitted light) = 617 nm, max . ex. (the wavelength of the maximum intensity of the excitation light used) = 390 nm, Φ (the quantum efficiency of the wavelength conversion) - 68±5 %
EXAMPLE 2. Synthesis of tris- ( 4 , 4 , 4-trifluoro-1- ( 1- methyl-lH-pyrazol-4-yl) -2-nitro-butane-l, 3- dionato) (1.10-phenantroline) Europium (III)
Tris- (4, 4, 4-trifluoro-1- ( 1-methyl-lH-pyrazol- 4-yl) -2-nitro-butane-l, 3-dionato) (1.10-phenantroline) Europium (III) was synthesized following the procedure described in Example 1. 0.795 g of 4, 4, 4-trifluoro-1- (l-methyl-lH-pyrazol-4-yl) -2-nitro-butane-l, 3-dione and 3 ml of a 1M aqueous solution of NaOH were used. Yield: 0.23 g (21%)
Found, %: C(38.61), N(13.83), H (2.33), Eu (13.53) Calculated, %: 0(38.42), N(13.69), H (2.15), Eu (13.50)
Xmax. em. = 621 ran, max. ex^ = 405 ran, Φ = 62±5 %
EXAMPLE 3. Synthesis of tris- (4, 4, 5, 5, 5-pentafluoro-2- methyl-1- [2- (2, 2, 2-trifluoro-ethyl) -2H-pyrazol-3-yl] - pentane-1, 3-dionato) (2.2-bipyridyl) Ytterbium (III)
Tris- (4,4,5,5, 5-pentafluoro-2-methyl-l- [2- (2,2, 2-trifluoro-ethyl) -2H-pyrazol-3-yl] -pentane-1, 3- dionato) (2.2-bipyridyl) Ytterbium (III) was synthesized following the procedure described in Example 1. 1.056 g of 4, 4, 5, 5, 5-pentafluoro-2-methyl- 1- [2- (2, 2, 2-trifluoro-ethyl) -2H-pyrazol-3-yl] -pentane- 1,3-dione, 0.156 g of 2.2-bipyridyl, 3 ml of a 1M aqueous solution of NH3 and 1 ml of a 1M aqueous solution of YbCl3 were used.
Yield: 0.54 g (39%)
Found, %: C(37.45), N(8.37), H (2.28), Yb(12.64)
Calculated, %: 0(37.32), N(8.10), H (2.19), Yb (12.50) λπ^χ. em. = 1552nm, max. ex. = 390 nm, Φ = 6±2 %
EXAMPLE 4. Synthesis of tris- ( 1- [ 4-chloro-l- ( 4-nitro- phenyl) -lH-pyrazol-3-yl] -2- (3, 5-difluoro-phenyl ) -4, - difluoro-butane-1, 3-dionato) (1.10-phenantroline)
Europium (III)
Tris- (1- [4-chloro-l- (4-nitro-phenyl) -1H- pyrazol-3-yl] -2- (3, 5-difluoro-phenyl) -4 , 4-difluoro- butane-1, S-^dionato) (1.10-phenantroline) Europium (III) was synthesized following the procedure described in Example - 1. 1.37 g of 1- [4-chloro-l- (4-nitro-phenyl) - lH-pyrazol-3-yl] -2- (3, 5-difluoro-phenyl) -4, 4 -difluo.ro- butane-1, 3-dione and 3 ml of a 1M aqueous solution of NaOH were used.
Yield: 0.65 g (43%)
Found, %: C(48.99), N(9.14), H (2.29), Eu (9.12)
Calculated, %: C(48.85), N(9.08), H (2.08), Eu (8.96) max. em. = 620 nm, max. ex. = 395 nm, Φ = 1±4 %
EXAMPLE 5. Synthesis of tris- ( 4 , 4 , 4-trifluoro-1- ( 1- methyl-4-nitro-5-trifluoromethyl-lH-pyrazol-3-yl) - butane-1, 3-dionato) (1.10-phenantroline) Europium (III)
Tris- (4, , 4-trifluoro-l- (l-methyl-4-nitro-5- trifluoromethyl-lH-pyrazol-3-yl) -butane-1, 3- dionato) ( 1.10-phenantroline) Europium (III) was synthesized following the procedure described in Example 1. 1.00 g of 4 , 4 , 4-trifluoro-1- ( l-methyl-4- nitro-5-trifluoromethyl-lH-pyrazol-3-yl) -butane-1, 3- dione and 3 ml of a 1M aqueous solution of NaOH were used.
Yield: 0.49 g (37%)
Found, %: C(35.36), N(11.65), H (1.68), Eu (11.52) Calculated, %: 0(35.23), N(11.59), H (1.59), Eu .(11.43)
max. em. = 620 nm, max. ex. = 390 nm, Φ = 49±5 %
Comparative example 6. Synthesis of tris-" (4, 4, 4- trifluoro-1- ( l-methyl-lH-pyrazol-4-yl ) -butane-1, 3- dionato) ( 1.10-phenantroline) Europium (III)
Tris- (4,4, 4-trifluoro-l- (1-methyl-lH-pyrazol- 4-yl) -butane-1, 3-dionato) ( 1.10-phenantroline) Europium (III) was synthesized following the procedure described in Example 1. 0.661 g of 4, 4, 4-trifluoro-1- (l-methyl-lH-pyrazol-4-yl) -1, 3-butanedione and 3 ml of a 1M aqueous solution of NaOH were used. Yield: 0.33 g (33 %)
Found, %: C(43.77), N(11.19), H(2.69),
Eu (15. 0) Calculated, %: C(43.69), N(11.32), H(2.65), Eu(15.36)
max. em. = 617 nm, max. ex. = 390 nm, Φ = 36±3 %
Comparative example 7. Synthesis of tris-(4,4- difluoro-1- (l-methyl-lH-pyrazol-4-yl) -1, 3- butanedionato) ( 1.10-phenantroline) Europium (III)
Tris- (4, 4-difluoro-1- ( l-methyl-lH-pyrazol-4- yl) -1 , 3-butanedionato) (1.10-phenantroline) Europium (III) was synthesized following the procedure described in Example 1. 0.606 g of 4, 4-difluoro-1- ilmethyl-lH-pyrazol-4-yl) -1, 3-butanedione and 3 ml of a 1M aqueous solution of NaOH were used.
Yield: 0.38 g (41 %)
Found, %: C(46.33), N(12.06), H(3.16), Eu(16.37)
Calculated, %: C(46.21), N(11.98), H(3.12), Eu(16.24) Xmax. em. = 618 nm, Xmax. ex. = 390 nm, Φ = 11+5 %
The inventors found out that the absolute quantum yield of the rare earth metal ion complexes according to the present invention was markedly higher when comparing the values with values received with corresponding comparative complexes, e.g. with complexes having the same central ion. EXAMPLE 8. Preparation of luminescent composite material comprising polyacrylate resin and tris- (2, 4, 4, 4-tetrafluoro-1- (l-methyl-lH-pyrazol-4-yl) - butane-1, 3-dionato) (1.10-phenantroline) Europium (III) 250 mg of the rare earth metal ion complex from Example 1 was dissolved in 10 g of dissolved methyl methacrylate (manufacturer - Aldrich, USA) (phosphor concentration 2,5 %). 100 mg of dry dibenzoyl peroxide was added to the formed solution after which the solution was centri uged at 15,000 rev/min for 10 minutes. The formed supernatant was poured off, after which gaseous helium was purged through the capillary for 5 minutes to remove dissolved gases.
The supernatant was placed into a metal polished form, which was closed. Then the temperature was gradually increased up to 350 °C during 6 hours. The solution was kept at this temperature for 72 hours, after which it was cooled and disassembled from the form. The procedure resulted in a luminescent composite material in the form of a transparent block.
Emission spectrum was characterized by the following values: Xmax exc. = 390 nm, the wavelength at the maximum of luminescence spectrum: 619 nm.
EXAMPLE 9. Preparation of luminescent composite material comprising epoxy resin and tris- (2, 4, 4, 4- tetrafluoro-1- (l-methyl-lH-pyrazol-4-yl) -butane-1, 3- dionato) ( 1.10-phenantroline) Europium (III)
100 mg of the rare earth metal ion complex from Example 1 was dissolved in 8 g of optical epoxy PEO-10K (component A, the production of Polymers Laboratory of St. Petersburg Technical University) (phosphor concentration 1 %) and 2 g of a hardener (part B, an aliphatic polyamine) was added. The formed mixture was stirred and centrifuged at 15,000 rev/min for 10 minutes. Then the supernatant was placed into a metal polished form, which was placed in a vacuum chamber for 20 minutes at 10 Torr, where after it was removed, closed and maintained at 250 °C for 24 hours. The procedure resulted in a luminescent composite material being formed in the form of a transparent block. Emission spectrum was characterized by the following values: Amah exc. = 390 nm, the wavelength at the maximum of luminescence spectrum: 618 nm.
EXAMPLE 10. Preparation of luminescent composite material comprising polyurethane resin and tris- (4,4, 4-trifluoro-1- (l-methyl-lH-pyrazol-4-yl) -2-nitro- butane-1, 3-dionato) (1.10-phenantroline) Europium (III)
100 mg of rare earth metal ion complex from Example 2 was dissolved in 5 g of optical polyurethane resin Crystal Clear (component A, the production of Smooth-On, USA) (phosphor concentration 1 %) . 5 g of hardener (part B, an aromatic or aliphatic diamine) was added thereto, after which the formed mixture was stirred and centrifuged at 15,000 rev/min for 10 minutes. The supernatant was placed into a metal polished form, which was placed into a vacuum chamber for 20 minutes at 10 Torr, where after it was removed, closed and maintained at 250 °C for 24 hours. The procedure resulted in a luminescent composite material being formed in a form of a transparent block.
Emission . spectrum was characterized by the following values: Amah exc. = 405 nm, the wavelength at the maximum of luminescence spectrum: 621 nm.
EXAMPLE 11. Light emitting devices
Figure 1 illustrates schematically a light emitting device 1 comprising a primary light emitting element 2, e.g. a display element or a LED. The primary light emitting element is configured to emit light 4 at a first wavelength λι· In other words, the emission spectrum of the primary light emitting element has a peak wavelength of λι.
The light emitting device 1 further comprises a luminescent composite material 3 according to one embodiment of the present invention. The luminescent composite material can be configured as a separate element at a distance from the primary light emitting element 2, as illustrated in Figure 1, or it can be in a direct contact with the primary light emitting element 2. The luminescent composite material 3 can itself form a discrete component, or it can form e.g. a coating on another existing component, e.g. a lens.
The light 4 emitted by the primary light emitting element 2 is at least partially received and absorbed by the luminescent composite material 3. At least part of the energy thereby received by the luminescent composite material 3 is then released via emission of light 5 at a second wavelength λ2, which is higher than the first wavelength λι. Thus, in the light emitting device, the luminescent composite material 3 is used to convert the wavelength of light emitted the primary light emitting device to a longer wavelength.
The first wavelength λχ can lie in the range of 200 to 450 nm. The second wavelength λ2 depends on the accurate composition of the rare earth metal ion complex of the luminescent composite material. Examples of different compositions and the second wavelengths, i.e. emission wavelengths thereof, are given in the examples 1 to 9 above. As an advantageous feature of the present invention, the emission wavelength of the luminescent composite material is adjustable over a broad wavelength range from about 500 nm to about 1500 nm.
Figure 2 shows a cross-sectional view of a chip-on-board (COB) type light emitting module 1 as an example of a light emitting device according to the present invention. The module comprises a substrate plate 6 on which LED chips 2 have been mounted as primary light emitting elements. Patterned metal plating 7 forms the electrical interface of the module as well as the electrical connections between the LED chips. The chips are encapsulated within an encapsulant 8 comprising a luminescent composite material 3 according to the present invention. Thus, in this example, the luminescent composite material is in direct contact with the LED chips. The encapsulant 8 surrounds the LED chips, thereby ensuring that practically all the light from the LED chips - is received by the encapsulant 8 and the luminescent composite material 3 therein. The general operation principle of the COB type light emitting module is the same as that the schematically illustrated light emitting device of Figure 1.
As is obvious to a person skilled in the art, with the advancement of technology, the basic idea of the invention may be implemented in various ways. The invention and its embodiments are thus not limited to the examples described above; instead they may vary within the scope of the claims.

Claims

1. A rare earth metal ion complex having the following formula (1) :
[L„(Li)3L2] formula (1) wherein
Ln represents a trivalent rare earth metal ion;
L2 represents a bidentate ligand containing nitrogen; and
Li represents a diketonate ligand derivative having the following formula (2) :
Figure imgf000023_0001
formula (2) wherein
Ri represents an alkyl group, a fluoroalkyl group, or a substituted or an unsubstituted aryl group;
R2 represents a hydrogen atom, an alkyl group, a fluoroalkyl group, a substituted or an unsubstituted aryl group, a halogen atom, or a N02 group;
R3 represents an alkyl group, a substituted or unsubstituted aryl group, a halogen atom, or a N02 group; and RF represents an alkyl group substituted with at least one fluorine atom.
2. The rare earth metal ion complex as defined in claim 1, wherein the trivalent rare earth metal ion is a lanthanide ion.
3. The rare earth metal ion complex as defined in any one of claims 1 - 2, wherein the substituted aryl group is substituted phenyl, or substituted naphthyl.
4. The rare earth metal ion complex as defined in any one of claims 1 - 2, wherein the unsubstituted aryl group is unsubstituted phenyl, or unsubstituted naphthyl.
5. The rare earth metal ion complex as defined any one of claims 1 - 4, wherein the halogen atom is selected from a group consisting of fluorine, chlorine, and bromine.
6. The rare earth metal ion complex as defined in any one of claims 1 - 5, wherein RF represents methyl substituted with one, two or three fluorine atoms.
7. A luminescent composite material comprising a rare earth metal ion complex according to any one of claims 1 - 6 and polymer.
8. The luminescent composite material as defined in claim 7, wherein the polymer is selected from a group consisting of acrylate, styrene, epoxy resin, and optical polyurethane resin.
9. The luminescent composite material as defined in any one of claims 7 - 8, wherein the luminescent composite material comprises 0,1 - 10 weight-% of the rare earth metal ion complex.
10. The luminescent composite material as defined in any one of claims 7 - 9, wherein the luminescent composite material is a fluorescent composite material.
11. A light emitting device (1) comprising a primary light emitting element (2) configured to emit light (4) at a first wavelength lf wherein the light emitting device further comprises luminescent composite material (3) according to any one of claims 7 - 10 for receiving at least part of the light (4) emitted by the primary light emitting device (2) and emitting at least part of the thereby received energy as light (5) at a second wavelength λ2 which is longer than the first wavelength λχ.
12. A light emitting device (1) as defined in claim 11, wherein the first wavelength χ lies in the range of 200 - 450 nm.
13. A light emitting device (1) as defined in claim 11 or 12, wherein the primary light emitting device (2) is a light emitting diode.
14. A light emitting device (1) as defined in claim 11 or 129, wherein the primary light emitting device (2) is a display element.
15. Use of luminescent composite material (3) as defined in any of claims 7 - 10 for receiving light (4) at a first wavelength λι and emitting at least part of the thereby received energy as light (5) at a second wavelength λ2 which is longer than the first wavelength λι .
16. Use as defined in claim 15, wherein the first wavelength λι lies in the range of 200 - 450 nm.
PCT/RU2012/001136 2012-12-28 2012-12-28 Rare earth metal ion complex, luminescent composite material, light emitting device, and use WO2014104917A1 (en)

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WO2022023260A1 (en) * 2020-07-27 2022-02-03 Novaled Gmbh Metal complexes of 3-(2,3,5-trifluoro-6-(trifluoromethyl)pyridin-4-yl)pentane-2,4-dione and similar ligands as semiconductor materials for use in electronic devices
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