KR20110115716A - Light-emitting device with phosphor of strontium oxyosilicate type - Google Patents

Abstract

A light emitting device having phosphors of the strontium oxyosilicate type is disclosed. The light emitting device includes a light emitting diode for generating light in an ultraviolet or visible light region and a phosphor disposed around the light emitting diode to absorb at least a portion of the light emitted from the light emitting diode to emit light having a wavelength different from that of the absorbed light. . This phosphor is characterized in that a calcium mole fraction x having a value between 0 and 0.05 is added as a silicate phosphor having the general formula Sr _{3 -xy- z} Ca _x M ^II _y SiO ₅ : Eu _z . By adding a limited range of calcium to the strontium oxyosilicate mother phosphor, it is possible to improve stability to radiation loads and resistance to humidity, thereby increasing the lifespan of the light emitting device.

Description

LIGHT EMITTING DEVICE HAVING STRONTIUM OXYORTHOSILICATE TYPE PHOSPHORS}

The present invention provides a light emitting device having an efficient inorganic phosphor based on a silicate compound capable of converting higher energy excitation radiation, ie, UV beams or blue light, preferably with long wavelength radiation emitted in the visible spectral range. It is about.

Phosphors can be used in light sources in the form of LEDs that emit colored or white light, where such phosphors, optionally in combination with additional light emitters, can be used for long wavelength secondary radiation, In particular, it is used to effectively convert to white light.

For example, various phosphors with high luminous output, such as cerium-doped yttrium aluminum garnets, Eu-active alkaline earth metal orthosilicates, and other compositions of similarly doped nitrides, have already been disclosed for these applications, but for LED applications Further efforts are known to develop improved materials. The development trend is to find phosphors that have particularly better temperature characteristics and higher stability to the resulting radiation load and the influence of atmospheric humidity and other environmental factors. Such light emitters are required for the manufacture of light emitting devices such as LED lamps having relatively high power consumption and improved lifetime.

It is known that europium-activated alkaline earth metal oxyosilicates having the general form of Sr ₃ SiO ₅ : Eu are used in LEDs that emit colored or white light. Such phosphors are described, for example, in WO 2004 / 085570A1 and WO 2006 / 081803A1 and in, for example, Park, Joung-Kyu, et al., In Appl., Phys. Lett. 84 (2004), 1647-49, and Jee, Soon-Duc, et al., In J. Mater. Sci. 41 (2006), 3139-41.

Known emitters emit in the visible spectrum in the yellow to orange range and are distinguished by high luminous efficiency and extremely low thermal quenching up to temperatures of up to 250 ° C. In this respect, they are orange components in the phosphor mixture for warm white LEDs, which are likewise considerably superior to orthosilicates emitting between 580 and 610 nm and are increasingly preferred for these applications because of their beneficial properties and significantly lower manufacturing costs. It can compete with red emitting nitride phosphors.

On the other hand, it has been found that LEDs made from such phosphors can have a relatively short life under certain conditions of use. A possible cause of this detrimental behavior is presumed to be the relatively high humidity sensitivity of europium-doped alkaline earth metal oxyosilicates. As a result of this instability, the industrial availability of the disclosed light emitters may be limited or at least greatly complicated in certain areas.

International Publication WO 2004 / 085570A1 International Publication WO 2006 / 081803A1

Park, Joung-Kyu, et al., In Appl., Phys. Lett. 84 (2004), 1647-49 Jee, Soon-Duc, et al., In J. Mater. Sci. 41 (2006), 3139-41

It is therefore an object of the present invention to provide a light emitting device employing new and chemically modified oxyosilicate phosphors with significantly increased stability to atmospheric humidity, which are suitable as improved radiation converters, particularly for use in various technical applications. .

The light emitting device according to the embodiments of the present invention absorbs at least a portion of the light emitting diodes generating light in the ultraviolet or visible light region and the light emitted from the light emitting diodes disposed around the light emitting diodes so as to have light having a wavelength different from that of the absorbed light. It includes a phosphor that emits light. The object here is to provide a means for selectively replacing a small amount of strontium (Sr) with calcium (Ca) without altering the stoichiometry of the compound and its crystal structure in the parent phosphor lattice Sr ₃ SiO ₅ . Is achieved by use. This substitution results in a significant increase in stability to atmospheric humidity and other environmental factors of the corresponding europium-active oxyosilicate emitters and a marked improvement in the lifetime of the light emitting diodes (LEDs) produced therefrom.

The positive effect of calcium substitution is limited to the narrow calcium concentration range chosen. If this is exceeded, preferred alkaline earth metal oxyosilicates, as a result of the continuous incorporation of calcium into the Sr ₃ SiO ₅ matrix, are no longer formed into the basic phosphor composite, but instead have a significantly increased calcium concentration, The corresponding orthosilicate composition (Sr, Ca) ₂ SiO ₄ is what is formed in nature.

WO ₃ SiO ₅ general formula _{(Sr 1 -x- y Ca x Ba} y) disclosed in 2006 / 081803A1: In the case of mixed silicates of Eu _2, x is may be considered to be a value up to 0.3, x- ray According to the structural inspection, preferred alkaline earth oxyosilicate phosphors can no longer be synthesized at a calcium fraction of x> 0.05 under known manufacturing conditions, and instead alkaline earth metal orthosilicate is formed in a predominant amount.

On the other hand, the inclusion of small amounts of calcium of x <0.05 that does not interfere with the formation of the Sr ₃ SiO ₅ lattice is a significant improvement in the humidity resistance of the corresponding europium-doped emitters and a significant increase in the lifetime of the LEDs produced therefrom. It was surprisingly found to cause.

(Means in Strontium Oxyosilicate Phosphor)

The strontium _oxyosilicate phosphors according to the invention with improved stability to the resulting radiation load and resistance to the effects of atmospheric humidity can be represented by the general formula Sr _{3 -xyz} Ca _x M ^II _y SiO ₅ : Eu _z As can be seen, the calcium mole fraction x can be a value between 0 and 0.05, while a value in the range of <0.25 is typical for the europium mole fraction z. The highest activator concentration depends on the specific conditions of use of the phosphor and can be easily determined experimentally.

In the general formula, M ^II represents divalent metal ions selected from the group consisting of magnesium (mg), barium (Ba), copper (Cu), zinc (Zn) and manganese (Mn) elements, and these ions are selectively It may be further contained into the phosphor lattice. In the case of barium, a complete replacement for strontium is possible; The fraction of other divalent metal ions contained in addition to strontium can be up to y = 0.5.

Europium (Eu) and additionally and optionally additionally, as principle, for example, samarium (Sm), or ytterbium (Yb) 2 has a rare-earth ion, or for example, cerium ions, such as (Ce ^{3 +)} in the doping element Certain trivalent rare earth ions are also suitable as activators.

For the purpose of optimizing luminescent properties and stability behavior, these phosphors also undergo further modifications in their compositions. Thus, for example, silicon (Si) may be replaced by germanium (Ge) and / or by aluminum (Al), gallium (Ga), boron (B) or phosphorus (P), but last mentioned Where appropriate, appropriate measures should be taken if necessary to maintain a charge balance that can be taken if necessary. It is also for example monovalent cations such as lithium (Li), sodium (Na) and potassium (K) or anions such as fluorine (F), chlorine (Cl), bromine (Br) or iodine (I) May be further contained into the parent lattice.

In a preferred embodiment, the phosphor having improved stability to the resulting radiation load and resistance to the effects of atmospheric humidity has the formula Sr _{3 -xy- z} Ca _x Ba _y SiO ₅ : Eu _z , according to the invention The molar fractions are 0 <x <0.05, 0 <y <0.5, and z <0.25.

When excited with high energy radiation, the phosphors emit within the visible portion of the spectrum, preferably between 560 and 620 nm, depending on their specific chemical composition. Eu ²⁺ excitation light emission ranges from 220 nm ultraviolet light to 550 nm visible light, which means that the light emitter of the present invention can also be excited by green excitation radiation to produce efficient yellow to orange or red light emission. In addition, a high intensity and technically usable luminescence process also occurs when irradiating phosphors with very low Ca fractions according to the invention with electron beams, X-ray beams or gamma radiation.

Because of the improved luminescence properties, the phosphors with very low Ca fractions according to the invention have long wavelengths which emit ionized gamma ray, X-ray or electron beam, ultraviolet, blue or green radiation, preferably in the yellow, orange and red spectral ranges. It can be used as a radiation converter to convert to visible light. This allows them to be used in various technical devices, such as cathode ray tubes and other image generation systems (scanning laser beam systems), X-ray image converters, fluorescent lamps, and LEDs, solar cells or emitting colored and white light. It can be used variously as a radiant convertor in greenhouse sheets and glasses, meaning that it can be used alone or in combination with other blue, green, yellow and / or red emitting phosphors.

Meanwhile, the light emitting device according to the present invention may implement white light or light of a desired color by a combination of the light emitting diode and the phosphor. For example, white light or light of a desired color may be realized by mixing light emitted from the light emitting diode with light emitted from the phosphor. In addition, in addition to the phosphor, another phosphor may be added to implement light of a desired color.

The phosphor may be disposed on at least one side of the side, top and bottom of the light emitting diode. In addition, the phosphor may be mixed with an adhesive or a molding material and disposed around the light emitting diode.

On the other hand, the light emitting diode and the phosphor may be combined in one package. In addition, other light emitting diodes may be coupled within the package. The other light emitting diode may emit light having the same or different wavelength as that of the light emitting diode, and may emit light having a longer wavelength than the emission peak wavelength of the phosphor.

The package includes a substrate on which the light emitting diode is mounted, such as a printed circuit board or a lead frame. In addition, the package may further include a reflector reflecting light emitted from the light emitting diode. In this case, the light emitting diode is mounted in the reflector.

The light emitting device may further include a molding part encapsulating the light emitting diode on the substrate. The light emitting material may be distributed in the molding part, but is not limited thereto.

In addition, the package may include a heat sink, and the light emitting diode may be mounted on the heat sink.

Meanwhile, in embodiments of the present invention, the light emitting diode may be a light emitting diode formed of a compound semiconductor of (Al, Ga, In) N series.

The light emitting diode may be a light emitting diode having a single active region between an n-type semiconductor and a p-type semiconductor layer, for example, a double hetero structure, a single quantum well structure, and a multi-quantum well structure.

In addition, the light emitting diode may include a plurality of light emitting cells spaced apart from each other on a single substrate. Each of the light emitting cells has an active region, and the light emitting cells may be electrically connected in series and / or in parallel through a wire. Using these light emitting cells, an AC light emitting diode that can be driven directly under an AC power source can be provided. Such an AC LED has no external DC-AC converter by forming a series array of light emitting cells and bridge rectifiers connected to each other on a single substrate or by forming series arrays of light emitting cells connected in parallel to each other on a single substrate. It can be driven by being connected to an AC power source.

According to the present invention, a phosphor having improved stability to radiation load and resistance to atmospheric humidity can be manufactured, and the phosphor can be adopted to provide a long-life light emitting device.

1 is a cross-sectional view illustrating a light emitting device 100 according to an embodiment of the present invention.
2 is a cross-sectional view for describing a light emitting device 200 according to another exemplary embodiment of the present invention.
3 is a cross-sectional view for describing a light emitting device 300 according to still another embodiment of the present invention.
4 is a cross-sectional view for describing a light emitting device 400 according to still another embodiment of the present invention.
5 is a cross-sectional view for describing a light emitting device 500 according to still another embodiment of the present invention.
6 is an X-ray diffraction diagram of Sr ₃ Sio ₅ : Eu phosphors with different compositions.
7 is emission spectra of emitters and comparative emitters, optionally with very low Ca fractions.
FIG. 8 is Table 1 showing the lattice constants and fractions calculated from diffraction diagrams formed with different crystallographic phases.
9 is Table 2 showing the optical and performance parameters of typical phosphors and comparative materials with low Ca fractions.
Figure 10 is a table 3 showing the results of the moisture stability investigation of the oxyosilicate phosphor and silicate mixture according to the present invention having a low Ca fraction.

Hereinafter, a light emitting device according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(Light emitting device)

1 is a cross-sectional view illustrating a light emitting device 100 according to an embodiment of the present invention. 1 shows a chip-shaped package in which at least one light emitting diode and a phosphor are combined.

Referring to FIG. 1, electrode patterns 5 are formed at both ends of the substrate 1, and light emitting diodes 6 for generating primary light are mounted on one electrode pattern 5. The light emitting diode 6 is mounted on the electrode pattern 5 through a conductive adhesive 9 such as silver (Ag) epoxy, and is electrically connected to the other electrode pattern through the conductive wire 2.

The light emitting diode 6 emits light in the ultraviolet or visible light region and may be made of a gallium nitride-based compound semiconductor. In particular, the light emitting diode 6 may emit ultraviolet or blue light.

On the substrate 1 on which the light emitting diode 6 is mounted, a phosphor 3 is doped on the top and side surfaces of the light emitting diode 6, and a molding part 10 formed of a curable resin is used to connect the light emitting diode 6 to the light emitting diode 6. Encapsulate. Here, although the phosphor 3 is illustrated as being doped near the light emitting diode 6, the phosphor 3 may be evenly distributed throughout the molding part 10. A method of evenly distributing the phosphor 3 in the molding 10 is disclosed in US Pat. No. 6,482,664.

On the other hand, the phosphor 3 is disposed around the light emitting diode 6 to absorb at least a portion of the light emitted from the light emitting diode to emit light having a wavelength different from that of the absorbed light. The phosphor 3 is described in detail below.

An external power source is connected to the light emitting diode 6 through the electrode pattern 5, whereby primary light is generated in the light emitting diode 6. The phosphor 3 absorbs at least some of the primary light emitted from the light emitting diode 6 and emits secondary light having a longer wavelength than the primary light. Accordingly, mixed light, in which the primary light emitted from the light emitting diode 6 and the secondary light emitted by the phosphor 3 are mixed, is emitted to the outside of the light emitting device 100. Light of the color required by eg white light is realized.

The light emitting device 100 may include two or more light emitting diodes. These light emitting diodes may emit light of the same or different wavelengths. For example, the light emitting device 100 may include the same or different light emitting diodes that emit ultraviolet light or blue light. In addition, the light emitting device 100 may include a light emitting diode that emits light having a longer wavelength than the emission peak wavelength of the phosphor. Such a long wavelength light emitting diode may be adopted to improve the color rendering of the light emitting device 100. In addition, the light emitting device 100 may further include other phosphors in addition to the phosphors 3. The other phosphor is not particularly limited, and includes an orthosilicate phosphor, a YAG-based phosphor or a thiogallate phosphor. Accordingly, the light of the color required by the user can be easily realized by appropriate selection of the light emitting diode 6 and the phosphor.

2 is a cross-sectional view for describing a light emitting device 200 according to another exemplary embodiment of the present invention. 2 shows a typical tower package with a reflector 21.

Referring to FIG. 2, the light emitting device 200 has a structure similar to the light emitting device 100 described above, except that a reflector 21 is added to the substrate 1. The light emitting diode 6 is mounted in the reflector 21. The reflector 21 reflects the light emitted from the light emitting diode 6 to increase the brightness within a particular direction angle.

On the other hand, the phosphor 3 is disposed around the light emitting diode 6 and absorbs at least a part of the light emitted from the light emitting diode as described with reference to FIG. 1 to emit light having a wavelength different from that of the absorbed light. The phosphor 3 may be doped on the light emitting diode 6 in the reflector 21 or uniformly distributed in the curable resin molding 10. The phosphor 3 is described in detail below.

The light emitting device 200 may also include two or more light emitting diodes having the same or different emission wavelengths as described with reference to FIG. 1, and may further include various phosphors in addition to the phosphor 3. .

Meanwhile, the light emitting devices 100 and 200 illustrated in FIGS. 1 and 2 may use a substrate 1 made of a metallic material having excellent thermal conductivity, such as a metal PCB. Such a substrate easily dissipates heat generated in the light emitting diode 6. In addition, a lead frame including lead terminals may be directly used as the substrate 1. The lead frame may be supported by being surrounded by the molding part 10 encapsulating the light emitting diode.

Meanwhile, in FIG. 2, the substrate 1 and the reflector 21 may be formed of different materials, but are not limited thereto and may be formed of the same material. For example, the lead frame on which the lead terminals are formed may be inserted and molded in plastic such as PPA to form the substrate 1 and the reflector 21 together. Thereafter, the lead patterns 5 are formed by bending the lead terminals.

3 is a cross-sectional view for describing a light emitting device 300 according to still another embodiment of the present invention. The light emitting device 300 is generally known as a light emitting diode lamp.

Referring to FIG. 3, the light emitting device 300 includes a pair of lead electrodes 31 and 32, and a cup part 33 having a cup shape is formed at an upper end of one lead electrode 31. At least one light emitting diode 6 is mounted in the cup 33 through the conductive adhesive 9, and is electrically connected to the other lead electrode 32 through the conductive wire 2. When a plurality of light emitting diodes are mounted in the cup part 33, the light emitting diodes may emit light having the same or different wavelengths.

On the other hand, the phosphor 3 is arranged around the light emitting diode 6. As described with reference to FIG. 1, the phosphor 3 is disposed around the light emitting diode 6 to absorb at least a portion of the light emitted from the light emitting diode to emit light having a wavelength different from that of the absorbed light. The phosphor 3 may be doped on the light emitting diode 6 in the cup part 33 or uniformly distributed in the curable resin molding part 34 formed in the cup part 33. The phosphor 3 will be described in detail below.

Meanwhile, the molding part 10 encapsulates the light emitting diode 6 and the phosphor 3 and also seals portions of the pair of lead electrodes 31 and 32. The molding part 10 may be formed of epoxy or silicon.

Although the lamp type light emitting device 300 having a pair of lead electrodes 31 and 32 has been shown and described, more lead electrodes may be included in the light emitting device 300.

4 is a cross-sectional view for describing a light emitting device 400 according to still another embodiment of the present invention. 4 shows a high power light emitting diode package.

Referring to FIG. 4, the light emitting device 400 includes a heat-sink 41 accommodated in the housing 43. The bottom surface of the heat sink 41 is exposed to the outside. Meanwhile, the lead terminals 44 are exposed in the housing 43 and extend outside through the housing. At least one light emitting diode 6 is mounted on the top surface of the heat sink 41 via the conductive adhesive 9 and electrically connected to one of the lead terminals 44 via the conductive wire. In addition, another conductive wire connects the other of the lead terminals 44 to the heat sink 41, as a result of which the light emitting diode 6 is electrically connected to the two lead terminals 44, respectively.

On the other hand, the phosphor 3 is disposed around the light emitting diode 6 on the heat sink 41. As described with reference to FIG. 1, the phosphor 3 is disposed around the light emitting diode 6 to absorb at least a portion of the light emitted from the light emitting diode to emit light having a wavelength different from that of the absorbed light. The phosphor 3 may be doped on the light emitting diode 6 on the heat sink 41 or evenly distributed in a molding part (not shown) covering the light emitting diode. The phosphor 3 will be described in detail below.

5 is a cross-sectional view for describing a light emitting device 500 according to still another embodiment of the present invention.

Referring to FIG. 5, the light emitting device 500 includes a housing 53 and a plurality of heat sinks 51 and 52 coupled to the housing and insulated from each other. Light emitting diodes 6, 7 are respectively mounted on the heat sinks 51, 52 via a conductive adhesive 9 and electrically connected to lead terminals 54 through conductive wires (not shown). . The lead terminals 54 extend outwardly in the housing. Although two lead terminals 54 are shown in the figure, a larger number of lead terminals may be provided.

On the other hand, the phosphor 3 is disposed around at least one of the light emitting diodes 6, 7 as described with reference to FIG. 4. The phosphor 3 will be described in detail below.

In the embodiments of the present invention, the light emitting diode 6 is described as being mounted on the substrate 1 or the heat sink via the conductive adhesive 9 and electrically connected to the electrode pattern or the lead terminal through one conductive wire. However, this example is limited to the case where the light emitting diode 6 has "one bond die", that is, electrodes on the upper side and the lower side, respectively. For example, when the light emitting diode 6 is a "two bond die" having two electrodes on the upper side, the light emitting diode 6 is electrically connected to the electrode patterns or lead terminals by two conductive wires, respectively. Can be. In this case, the adhesive need not be conductive.

In the embodiments of the present invention, the light emitting diode 6 may be a light emitting diode formed of a compound semiconductor of (Al, Ga, In) N series.

The light emitting diode 6 may be a light emitting diode having a single active region between the n-type semiconductor and the p-type semiconductor layer, for example, a double hetero structure, a single quantum well structure, and a multi-quantum well structure.

In addition, the light emitting diode 6 may include a plurality of light emitting cells spaced apart from each other on a single substrate. Each of the light emitting cells has an active region, and the light emitting cells may be electrically connected in series and / or in parallel through a wire. In particular, a light emitting diode that can be driven directly under an AC power supply using these light emitting cells can be provided. Such an AC LED has no external DC-AC converter by forming a series array of light emitting cells and bridge rectifiers connected to each other on a single substrate or by forming series arrays of light emitting cells connected in parallel to each other on a single substrate. It can be driven by being connected to an AC power source. Since the AC LED connects a plurality of light emitting cells in series through wiring, the operating voltage can be increased to a voltage of a home power supply, for example, a voltage of 110V or 220V. Thus, a light emitting device that can be operated by a home power supply is Can be provided.

In addition, the phosphor 3 may be disposed between the light emitting diode 6 and the substrate 1 or heat sink on which the light emitting diode is mounted, or may be distributed in the adhesive 9. This phosphor 3 absorbs at least some of the light emitted down from the light emitting diode 6 and emits light of different wavelengths.

Although some structures of the light emitting device have been described above, the present invention is not limited to these structures, and the structures vary depending on the type of light emitting diode, the electrical connection method, the required angle of light, and the purpose of use of the light emitting device. Can be modified.

(Phosphor)

Hereinafter, the phosphor 3 used in the embodiments of the present invention will be described.

The strontium _oxyosilicate phosphors according to the invention with improved stability to the resulting radiation load and resistance to the effects of atmospheric humidity can be represented by the general formula Sr _{3 -xyz} Ca _x M ^II _y SiO ₅ : Eu _z As can be seen, the calcium mole fraction x can be a value between 0 and 0.05, while a value in the range of <0.25 is typical for the europium mole fraction z. The highest activator concentration depends on the specific conditions of use of the phosphor and can be easily determined experimentally.

In the general formula, M ^II represents divalent metal ions selected from the group consisting of magnesium (mg), barium (Ba), copper (Cu), zinc (Zn) and manganese (Mn) elements, and these ions are selectively It may be further contained into the phosphor lattice. In the case of barium, a complete replacement for strontium is possible; The fraction of other divalent metal ions contained in addition to strontium can be up to y = 0.5.

Europium (Eu) and additionally and optionally additionally, as principle, for example, samarium (Sm), or ytterbium (Yb) 2 has a rare-earth ion, or for example, cerium ions, such as (Ce ^{3 +)} in the doping element Certain trivalent rare earth ions are also suitable as activators.

For the purpose of optimizing luminescent properties and stability behavior, these phosphors also undergo further modifications in their compositions. Thus, for example, silicon (Si) may be replaced by germanium (Ge) and / or by aluminum (Al), gallium (Ga), boron (B) or phosphorus (P), but last mentioned Where appropriate, appropriate measures should be taken if necessary to maintain a charge balance that can be taken if necessary. It is also for example monovalent cations such as lithium (Li), sodium (Na) and potassium (K) or anions such as fluorine (F), chlorine (Cl), bromine (Br) or iodine (I) May be further contained into the parent lattice.

In a preferred embodiment, the phosphor having improved stability to the resulting radiation load and resistance to the effects of atmospheric humidity has the formula Sr _{3 -xy- z} Ca _x Ba _y SiO ₅ : Eu _z , according to the invention The molar fractions are 0 <x <0.05, 0 <y <0.5, and z <0.25.

When excited with high energy radiation, the phosphors emit within the visible portion of the spectrum, preferably between 560 and 620 nm, depending on their specific chemical composition. Eu ²⁺ excitation light emission ranges from 220 nm ultraviolet light to 550 nm visible light, which means that the light emitter of the present invention can also be excited by green excitation radiation to produce efficient yellow to orange or red light emission. In addition, a high intensity and technically usable luminescence process also occurs when irradiating phosphors with very low Ca fractions according to the invention with electron beams, X-ray beams or gamma radiation.

Because of the improved luminescent properties, the phosphors having a very low Ca fraction according to the invention can be used as radiation converters which convert ultraviolet, blue or green radiation into long wavelength visible light which is preferably emitted in the yellow, orange and red spectral ranges. . The phosphor may be used alone or in combination with other blue, green, yellow and / or red emitting phosphors.

These phosphors are preferably formed on the basis of an optional multistage high temperature solid state reaction between alkaline earth metal carbonates or corresponding oxides and finely divided SiO ₂ used as starting materials, which facilitate the reaction and control the particle size distribution of the resulting light emitters. To this end an amount of flux or a mineralization additive such as NH ₄ Cl, NH ₄ F or certain alkali or alkaline earth metal fluorides can also be added to the reaction mixture. These starting materials are thoroughly mixed and then fired for 1 to 48 hours at a temperature of 1300 to 1700 ° C. in an inert or reducing atmosphere. This main firing phase for the purpose of optimizing the properties of the phosphor can optionally also have a plurality of firing steps in different temperature ranges. After the firing process is finished, the sample is cooled to room temperature and subjected to a suitable post-treatment process, for example, for the purpose of removing flux residues, minimizing surface defects or precisely adjusting the particle size distribution. Instead of finely divided silica, silicon nitride (Si ₃ N ₄ ) may also be used alternatively as a reactant for reacting with the alkaline earth metal compound used.

In this context, the synthesis of the phosphor according to the invention is not limited to the above-described manufacturing processes.

Detailed information on the composition of phosphors with low Ca fraction is disclosed below.

Experimental Example  One

Composition _{Sr 2 .9285 Ca 0 .03 Cu 0} .0015 SiO 5: Eu to the fluorescent substance manufactured having a low fraction of the Ca _{0 .04,} 432.4g of SrCO _3, CaCO _3, 0.12g of 3.0g CuO, 7.04 g of Eu ₂ O ₃ and 60.94 g of SiO ₂ are used as starting materials, to which 1.5 g of NH ₄ F is added as flux. After complete homogenization, the batch mixture is transferred to a corundum crucible placed in a hot furnace. There, the solid mixture is carried out in a fired form with a first step of holding at 1200 ° C. for 3 hours and a second step of holding at 1550 ° C. for 5 hours. Firing is carried out in pure oxygen until a 1550 ° C. ramp is reached and in a N ₂ / H ₂ mixed gas containing 20% hydrogen during the 1550 ° C. step. Post-treatment of the cooled calcined material includes milling, performing the washing process and drying and sieving the final product.

Experimental Example  2

The composition of the present invention, _{Sr 2 .91 Ca 0 .04 Ba 0} .01 SiO 5: Eu 0. _For the preparation of ₀₄ alkaline earth metal oxyosilicate phosphors, 429.6 g SrCO ₃ , 1.97 g BaCO ₃ , 4.01 g CaCO ₃ , 7.04 g Eu ₂ O ₃ , 60.9 g SiO ₂ and 0.54 g NH ₄ Cl is thoroughly mixed and then calcined for 6 hours at a temperature of 1380 ° C. in an N ₂ / H ₂ atmosphere with 20% hydrogen. After the firing process is finished, the fired material is homogenized by milling and then subjected to heat treatment again at 1350 ° C. in a reduced N ₂ / H ₂ atmosphere having a hydrogen concentration of at least 5%. Final workup of the synthesized phosphor sample is performed in the manner described in Experimental Example 1.

FIG. 6 shows an X-ray diffraction diagram of europium-active strontium oxyosilicate phosphors with different fractions of added calcium. Diffraction Diagram 1 relates to a comparison material _{Sr 2 .95 Ba 0 .01 Eu 0} .04 SiO 5. Diffraction diagram 2 applies to the Sr ₃ SiO ₅ phosphor Sr _2.95 Ba _0.01 Ca _0.02 Eu _0.04 SiO ₅ . Diffraction diagram 3 shows the Sr ₃ SiO ₅ phosphor Sr _2.8 Ba _0.01 Ca _0.15 Eu _0.04 SiO ₅ , with arrows in the diagram indicating the reflective properties of the foreign phase structure of Sr ₂ SiO ₄ .

7 shows emission spectra of emitters and comparative materials, optionally with very low calcium ratios. Comparative material _{Sr 2 .95 Ba 0 .01 Eu 0} .04 SiO 5 has a first spectrum. Sr ₃ SiO ₅ fluorescent spectrum of _{Sr 2 .95 Ba 0 .01 Ca 0} .02 Eu 0 .04 SiO 5 is characterized by 2 Sr ₃ SiO ₅ phosphor _{Sr 2.8 Ba 0.01 Ca 0.15 Eu 0.04} SiO 5 is characterized by a 3 do.

Pure Sr ₃ SiO ₅ and in the case x = ₃ having a Sr 0.05 Ca mole fraction of _{-xy- z Ca x Ba 0 .01 SiO} 5 the base in both the case of a grating, known from the literature Sr ₃ SiO ₅ structural type of reflection Is found exclusively in the diffractogram, and the diffraction angle of the calcium substituted material shifts slightly relative to the diffraction angle of the pure Sr ₃ SiO ₅ phase as expected. In _{contrast, x = Sr 3 -xy- z Ca} x Ba 0 .01 SiO 5 with a calcium fraction of 0.1: in the preparation of Eu _z phosphor, a diffraction pattern of the material is with respect to the orthosilicate compound of Sr ₂ SiO ₄ form Characteristic reflections were obtained with high intensity in addition to reflections on the Sr ₃ SiO ₅ phase.

Table 1 of FIG. 8 shows the fractions of the different crystal phases, synthesized similarly to the series of preparation methods described in Experimental Example 1, and calculated from the fractional diagrams of the series of compounds with an increased amount of calcium contained in the Sr ₃ SiO ₅ medium. And lattice constants. As shown in Table 1, the increase in the added calcium initially leads to a reduction in the lattice constant of the Sr ₃ SiO ₅ phase in principle, with corresponding values for the phosphors having a calcium mole fraction of x <0.05 according to the invention being very different from each other. Slightly different Larger deviations from the values of known literature and the lattice constants of the reference material occur only in the case of calcium containing x> 0.05.

However, the effect of increased calcium concentration is not limited to further reductions of lattice constants. As shown by the data listed in Table 1 for the percentage phase composition of the materials resulting in increased calcium addition, the mixture of Sr ₃ SiO ₅ and Sr ₂ SiO ₄ phases increased with increasing calcium fraction. Formed, the fraction of the onosilicate phase instead of the oxyosilicate of the Sr ₃ SiO ₅ structure type is already 42% for the calcium fraction of x = 0.1 based on the total mixture.

From Table 1 it is also clear that the calcium free reference material as well as the low calcium content oxyosilicate phosphors according to the invention have trace amounts of the corresponding osilicate external phases. This phenomenon is known and can be attributed to the partial phase change upon cooling of the corresponding plastic materials, which can only be excluded from the high temperature synthesis of the phosphor with very large effort. However, it can be considered proven that the efficiency of the oxyosilicate emitter is not affected by this extremely small fraction of the external phase.

It can be advantageously mentioned that the luminous efficiencies of the phosphors of the invention and their temperature dependence are not inferior to commercially available Sr ₃ SiO ₅ : Eu phosphors.

As shown by the results listed in Table 2 of FIG. 9 for the corresponding measurements, phosphors having a relatively or high luminous output can be prepared based on the manufacturing methods described in Experimental Examples 1 and 2. FIG.

In the case of the phosphor, some shift from the emission maximum to a larger wavelength is initially found with increasing calcium content. This may be due to the increasing crystal field due to the reduction of the lattice constant. In conjunction with crystallographic findings, this shift in the optical parameters of the illuminant is also a reliable indicator that the amount of calcium added according to the invention was also actually contained in the Sr ₃ SiO ₅ lattice within the concentration ranges described.

On the other hand, addition of calcium above the region of x = 0.05 results in a silicate mixed phase whose luminescent properties are characterized by reduced efficiency, broader emission spectrum and reduced temperature stability. It is also apparent from FIG. 7 in which the emission spectrum of the phosphor having a low Ca fraction according to the invention is compared with the reference material and the calcium-rich phase.

To assess the humidity stability of the materials, the corresponding phosphor sample is stored for 7 days at a temperature of 85 ° C. and a relative humidity of 85% in a conditioned chamber. Thereafter, the luminous bodies are dried at 150 ° C., and then a comparative measurement of the luminous yield is performed. Typical results of such a test are listed in Table 3 of FIG. The data in Table 3 are commercially available Sr ₃ SiO _5: Eu, and the description made of the reference object ₍₂ Sr _.95 Ba _{.01 0 .04 0} Eu) phosphor SiO ₅ are all included in the storage humidity atmosphere After about 70% of the original luminous efficiency.

Surprisingly, however, the Sr ₃ SiO ₅ : Europium-doped oxyososilicate phosphor of the selectively small fraction of strontium replaced by calcium according to the invention does not adversely affect the formation of the Sr ₃ SiO ₅ structure. , Has significantly improved humidity resistance. After 7 days of storage in an 85 ° C./85% relative humidity atmosphere, luminous yields greater than 90%, luminous efficiency greater than 95% are still found for optimized samples.

Claims (16)

Light emitting diodes; And
A phosphor disposed around the light emitting diode to absorb at least a portion of the light emitted from the light emitting diode to emit light having a wavelength different from that of the absorbed light;
The phosphor is a light emitting device, characterized in that the calcium mole fraction x having a value between 0 and 0.05 is added as a silicate phosphor having the general formula Sr _{3 -xyz} Ca _x M ^II _y SiO ₅ : Eu _z . The method according to claim 1, wherein the europium mole fraction z in the general formula is a value in the range of ≤ 0.25, M ^II is a group consisting of magnesium (Mg), barium (Ba), copper (Cu), zinc (Zn) and manganese (Mn). A divalent metal ion selected from wherein these ions are optionally further contained into the parent phosphor lattice. The light emitting device according to claim 2, wherein the fraction of said other divalent metal ions contained in addition to strontium is at most 0.5. The light emitting device according to claim 1, wherein in the general formula, the europium mole fraction z is a value ranging from ≤ 0.25, M ^II is barium, and barium completely replaces strontium. The light emitting device of claim 1, wherein the phosphor further comprises divalent rare earth metal ions or trivalent rare earth metal ions in addition to europium as an activator. The light emitting device according to claim 5, wherein the divalent rare earth metal ion activator is samarium or ytterbium ions. The method according to claim 5, wherein the trivalent rare earth metal ion activator is a light-emitting device characterized in that the cerium ions (Ce ^{+ 3).} The light emitting device of claim 1, wherein white light or light of a desired color is realized by mixing light emitted from the light emitting diode with light emitted from the phosphor. The light emitting device of claim 1, wherein the phosphor emits light having an emission peak wavelength between 560 and 620 nm. The light emitting device of claim 1, wherein the light emitting diode and the phosphor are combined in one package. The light emitting device of claim 10, further comprising another light emitting diode coupled in the package, wherein the other light emitting diode emits light having a longer wavelength than the peak emission wavelength of the phosphor. The method of claim 10, wherein the package comprises a substrate,
The light emitting diode is mounted on the substrate. The light emitting device of claim 12, wherein the substrate comprises a printed circuit board or a lead frame. The method of claim 13, further comprising a molding unit encapsulating the light emitting diode on the substrate,
The phosphor is distributed in the molding portion. The device of claim 10, wherein the package includes a heat sink,
The light emitting diode is mounted on the heat sink. The light emitting device of claim 1, wherein the light emitting diode is a light emitting diode having a plurality of light emitting cells.

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