JP2008208202A - Phosphor, wavelength converter and light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phosphor emitting a yellowish green color having a high light-emitting efficiency, a wavelength converter and a light-emitting device. <P>SOLUTION: This phosphor containing Sr, Ba, Si, Eu and O is equipped with a Sr<SB>2-x-y</SB>Ba<SB>x</SB>Eu<SB>y</SB>SiO<SB>4</SB>crystal (0≤x≤1, 0.01≤y≤0.10) as a main crystal, the molar ratio of the Eu<SP>2+</SP>to Eu<SP>3+</SP>in the Eu satisfies (Eu<SP>2+</SP>)/(Eu<SP>2+</SP>+Eu<SP>3+</SP>)<0.9, and also (Sr+Ba+Eu)/Si=2.02 to 2.07 by the molar ratio is satisfied. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wavelength converter including a phosphor that absorbs ultraviolet light or visible light and emits visible light and a phosphor that converts light emitted from a light emitting element such as an LED (Light Emitting Diode) and extracts the light to the outside. And a light emitting device equipped with a wavelength converter.

  A light-emitting element made of a semiconductor material (hereinafter also referred to as “LED chip”) is small in size, has high power efficiency, and vividly colors. LED chips have excellent characteristics such as long product life, strong on / off lighting repeatability, and low power consumption, so they are expected to be applied to backlight sources such as liquid crystals and lighting sources such as fluorescent lamps. Has been.

  The application of the LED chip to the light emitting device is that the wavelength of part of the light of the LED chip is converted with a phosphor, and the wavelength-converted light and the light of the LED that is not wavelength-converted are mixed and emitted, thereby It has already been manufactured as a light emitting device that emits a color different from that of light.

In this light emitting device, a yellow component phosphor such as a YAG phosphor represented by a composition formula of (Y, Gd) ₃ (Al, Ga) ₅ O ₁₂ is formed on a blue LED chip.

  In this light-emitting device, when the light emitted from the light-emitting element is irradiated onto the yellow component phosphor, the yellow component phosphor is excited to emit visible light, and this visible light is used as an output.

  However, when the brightness of the light emitting element is changed, the light quantity ratio between blue and yellow changes, so that there is a problem that the color tone of white changes and the color rendering property is inferior.

  Therefore, in order to solve such problems, a purple LED chip having a peak of 400 nm or less is used as a light emitting element, and the wavelength converter employs a structure in which three types of phosphors are mixed in a polymer resin. In addition, it has been proposed to emit white light by converting purple light into red, yellow-green, and blue wavelengths (see Patent Document 1). Thereby, a color rendering property can be improved. As a yellowish green phosphor that can be used in combination with an LED chip having a peak wavelength of 400 nm or less of a light emitting element, phosphors containing Eu have been actively developed (see Patent Document 2).

Then, phosphor comprising been _{Sr 2-x-y Ba x} Eu y SiO 4 crystal described in Patent Document 2 is manufactured such that 2 (Sr + Ba + Eu) / Si.
JP 2002-314142 A JP 2004-115633 A

However, a phosphor containing Sr2 _-xy Ba _x Eu _y SiO ₄ crystal in which (Sr + Ba + Eu) / Si is 2 emits light with high color rendering by combining with a LED chip having a peak wavelength of 400 nm or less. Although the device can be manufactured, there has been a demand for further improving the luminous efficiency.

  An object of the present invention is to provide a phosphor that emits yellowish green with high luminous efficiency, a wavelength converter, and a light emitting device.

The phosphor of the present invention is a phosphor containing Sr, Ba, Si, Eu, and O, and has Sr _2-xy Ba _x Eu _y SiO ₄ crystal (0 ≦ x ≦ 1, 0.01 ≦ y ≦ 0.10), and Eu ²⁺ and Eu ³⁺ in Eu satisfy Eu ²⁺ / (Eu ²⁺ + Eu ³⁺ ) <0.9 in molar ratio and (Sr + Ba + Eu) / Si = in molar ratio 2.02 to 2.07 are satisfied.

  The wavelength converter of the present invention is characterized in that the phosphor described above is dispersed in a transparent matrix.

  The light-emitting device of the present invention comprises the above-described wavelength converter and a light-emitting element that emits excitation light, and irradiates the phosphor of the wavelength converter with the excitation light.

According to the phosphor of the present invention, it is a phosphor containing Sr, Ba, Si, Eu, and O, and a Sr _2-xy Ba _x Eu _y SiO ₄ crystal (0 ≦ x ≦) as a main crystal. 1, 0.01 ≦ y ≦ 0.10), Eu Eu ²⁺ and Eu ³⁺ satisfy Eu ²⁺ / (Eu ²⁺ + Eu ³⁺ ) <0.9, and (Sr + Ba + Eu) /Si=2.02 By satisfying 2.07, Eu ²⁺ / (Eu ²⁺ + Eu ³⁺ ) <0.9, which has been conventionally used, becomes a phosphor with higher luminous efficiency than the phosphor of (Sr + Ba + Eu) / Si = 2.

  And according to the wavelength converter of this invention which disperse | distributed the fluorescent substance of this invention mentioned above in the transparent matrix, the light emission efficiency of the light of a yellow-green component can be improved.

  In addition, according to the light emitting device of the present invention, the light emitting device includes a wavelength converter and a light emitting element that emits excitation light, and the excitation light is emitted to the phosphor of the wavelength converter. A light-emitting device with excellent efficiency can be provided.

The phosphor of the present invention is a phosphor containing Sr, Ba, Si, Eu, and O, and this phosphor is composed of Sr _2-xy Ba _x Eu _y SiO ₄ crystal (0 ≦ 0) as a main crystal. x <1, 0.01 ≦ y ≦ 0.10), and Eu ²⁺ and Eu ³⁺ contained in the phosphor have a molar ratio of Eu ²⁺ / (Eu ²⁺ + Eu ³⁺ ) <0.9. It is important to satisfy (Sr + Ba + Eu) /Si=2.02 to 2.07 in terms of molar ratio.

That is, in the phosphor having the main crystal of the Sr2 _-xy Ba _x Eu _y SiO ₄ crystal disclosed in Patent Document 2, (Sr + Ba + Eu) / Si = 2, but Eu ²⁺ / ( In a region satisfying (Eu ²⁺ + Eu ³⁺ ) <0.9, (Sr + Ba + Eu) / Si is made larger than 2 and set to 2.02 or more, which is disclosed in Patent Document 2 (Sr + Ba + Eu) / Si = 2. Luminous efficiency superior to that of the phosphor can be realized.

Here, the value of (Sr + Ba + Eu) / Si is not a value obtained from the constituent element composition of the Sr _2-xy Ba _x Eu _y SiO ₄ crystal in the phosphor, but a value obtained from the constituent element composition of the entire phosphor. Point to.

In an ideal Sr2 _-xy Ba _x Eu _y SiO ₄ crystal that emits fluorescence, the stoichiometric ratio is (Sr + Ba + Eu) / Si = 2 in terms of molar ratio, so the phosphor composition is also (Sr + Ba + Eu) / Although it seems desirable to set Si = 2, the reason is currently unknown, but the Eu ²⁺ and Eu ³⁺ of Eu is a region where Eu ²⁺ / (Eu ²⁺ + Eu ³⁺ ) <0.9. Then, it is clear that a phosphor with high luminous efficiency can be obtained in the range of (Sr + Ba + Eu) /Si=2.02 to 2.07 which is not (Sr + Ba + Eu) / Si = 2 but rather deviated from the stoichiometric ratio. It was.

In the case of (Sr + Ba + Eu) /Si≧2.02, the presence of Sr _3−xy Ba _x Eu _y SiO ₅ crystals in the phosphor is confirmed. The presence of Sr3 _-xy Ba _x Eu _y SiO ₅ crystals in the phosphor is considered to increase the luminous efficiency of the phosphor. The reason for this is currently unknown, but the presence of Sr _3-xy Ba _x Eu _y SiO ₅ compensates for Sr, Ba, Eu defects in the phosphor, so Sr _3-xy It is thought that the presence of Ba _x Eu _y SiO ₅ has the effect of suppressing the formation of Sr _1-xy Ba _x Eu _y SiO ₃ crystals that are by-produced in the phosphor and do not exhibit the desired light emission characteristics. .

On the other hand, in the case of (Sr + Ba + Eu) / Si <2.02, since the Sr _1-x Ba _x SiO ₄ crystal mainly containing Eu is generated, the luminous efficiency of the phosphor is lowered.

  The value of x in the phosphor of the present invention can be arbitrarily selected within the range of 0 to 1. When x = 0, the phosphor can be yellow, and when x = 1, the phosphor can be green. Here, x ≦ 1 is set because x> 1 is possible, but in this case, the water resistance of the phosphor is lowered.

In the phosphor of the present invention, in order to set Eu ²⁺ and Eu ³⁺ of Eu to Eu ²⁺ / (Eu ²⁺ + Eu ³⁺ ) <0.9, halogens such as SrCl ₂ , BaCl ₂ , NH ₄ Cl, and SrF ₂ are used. The raw material powder may be heat-treated without using a so-called flux such as a chemical compound or an alkali compound such as NaOH or KOH.

Thus, when heat treatment is performed without using a flux, Eu ²⁺ / (Eu ²⁺ + Eu ³⁺ ) tends to be smaller and luminous efficiency tends to be lower than when flux is used, but it is not necessary to remove the flux. . For this reason, a phosphor manufactured without using a flux is suitably used in applications where the presence of alkali elements or halogen elements is a problem.

  The phosphor of the present invention may be in the form of particles, or the phosphor particles may be formed and further baked into an arbitrary shape.

  For example, by dispersing the phosphor of the present invention in a matrix made of a transparent resin or the like, the wavelength converter of the present invention having excellent luminous efficiency can be obtained. In the wavelength converter of the present invention, in addition to the phosphor of the present invention, a conventionally known fluorescent material such as red or blue may be added, and in that case, wavelength conversion with excellent color rendering properties may be added. Can be provided.

  Further, by combining the wavelength converter of the present invention with a light emitting element such as an LED, the light emitting device of the present invention is obtained, and this light emitting device has excellent luminous efficiency.

  Hereinafter, the method for producing the phosphor of the present invention will be described. The phosphor of the present invention comprises a compound containing elements of Sr, Ba, Eu and Si, for example, powders of strontium carbonate, barium carbonate, europium oxide and silica, and the molar ratio of each element is Eu / Si = 0.01 to 0.00. 1, (Sr + Ba + Eu) /Si=2.02 to 2.07, Ba / (Sr + Eu) = 0 to 1, each mixed powder was weighed and mixed powder of the following (A) or (B) After adjusting by, it can manufacture by heat-processing. At this time, since disappearance due to volatilization of each element by heating is small, each powder may be weighed in advance at the above ratio.

  (A): Dry pulverizer such as hammer mill, roll mill, ball mill, jet mill, etc., pulverization using mortar and pestle and mixer such as ribbon blender, V-type blender, Henschel mixer, or mixing using mortar and pestle And dry mixing method.

  (B): Using a pulverizer or a mortar and pestle or the like, add water or the like in a slurry state or a solution state, mix with a pulverizer, mortar and pestle, or evaporating dish and stirring rod, A wet mixing method in which drying is performed by heat drying or natural drying.

  Among these mixing methods, it is preferable to use a liquid medium because each raw material powder needs to be mixed and dispersed uniformly throughout.

  The phosphor of the present invention can be produced by heat-treating the raw material powder thus adjusted.

  As a heat treatment method, in a heat-resistant container such as a crucible or tray made of alumina or quartz, 1000 ° C to 1300 ° C, and a gas such as oxygen, nitrogen, hydrogen, argon, etc. alone or in a mixed atmosphere for 1 to 24 hours, Heat.

In addition, in order to suppress evaporation of the constituent components during the heating process, heat treatment may be performed using filling baking, microwave baking, or a co-agent.

Note that an atmosphere necessary for obtaining an ion state (valence) in which the Eu element contributes to light emission is selected as the heating atmosphere. In order to obtain Eu ²⁺ / (Eu ²⁺ + Eu ³⁺ ) <0.9 in the molar ratio as in the phosphor of the present invention, heat treatment is performed in a reducing atmosphere containing hydrogen or carbon monoxide, such as nitrogen or argon. It is preferable to do. The composition ratio of the constituent elements of the phosphor of the present invention can be measured by a technique such as ICP analysis, and the ratio of Eu ²⁺ and Eu ³⁺ can be obtained by XANES analysis or the like.

  Next, the wavelength converter of the present invention comprising the phosphor of the present invention and a light emitting device equipped with the wavelength converter will be described with reference to the drawings. FIG. 1 is a schematic sectional view showing an embodiment of a light emitting device 1 of the present invention. According to FIG. 1, the light emitting device 1 of the present invention is formed so as to cover the light emitting element 7 on the substrate 5, the light emitting element 7 provided on the substrate 5, and the substrate 5. In addition, a single-layer wavelength converter 9 and a reflecting member 11 that reflects light are provided.

  The wavelength converter 9 includes, for example, a blue phosphor (not shown) emitting fluorescence of 430 nm to 490 nm, a yellow green phosphor (not shown) emitting fluorescence of 520 nm to 570 nm, and a yellow green fluorescence in a transparent matrix. A phosphor (not shown) that emits light is provided. These phosphors convert the wavelength of light emitted from the light emitting element 7 that is a light source, and output output light including the light whose wavelength has been converted.

  The wavelength converter 9 of the present invention is characterized by using the phosphor of the present invention as a yellow-green phosphor, and the light-emitting device 1 of the present invention includes the wavelength converter 9 of the present invention. It is characterized by being used.

The blue phosphor is not particularly limited as long as it is excited by light of around 400 nm and emits fluorescence of 430 nm to 490 nm, but (Sr, Ca, Ba, Mg) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu _{, BaMgAl 10 O 17: Eu,} Mn, BaMgAl 10 O 17: Eu, (Ba, Eu) MgAl 10 O 17, (Sr, Ca, Ba, Mg) 10 (PO 4) 6 Cl 17: Eu, Sr 10 ( _{PO 4) 6 Cl 12: Eu} , (Ba, Sr, Eu) (Mg, Mn) Al 10 O 17, 10 (Sr, Ca, Ba, Eu) · 6PO 4 · Cl 2, BaMg 2 Al 16 O 25: Eu, etc. are used. The blue phosphor is preferably [(M, Mg) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu] (M is at least one of Ca, Sr, Ba) or [BaMgAl ₁₀ O ₁₇ : Eu]. Used for.

The red phosphor is not particularly limited as long as it is excited by light of around 400 to 550 nm and emits fluorescence of 600 to 750 nm, but WO ₃ : Eu, M ₃ MgSi ₂ O ₈ : Eu, Mn (M Is at least one selected from Ca, Sr, and Ba).

  The average particle diameter of the phosphor is preferably 0.1 to 50 μm, particularly preferably 0.1 to 20 μm, and more preferably 1 to 20 μm. When the average particle diameter is larger than 50 μm, the light transmittance of the wavelength converter 9 is remarkably lowered, so that the light emitted by the phosphor does not exit from the wavelength converter 9, and as a result, the light emission of the light emitting device 1. Efficiency is significantly reduced.

  Further, the thickness of the wavelength converter 9 is 0.1 to 5.0 mm, preferably 0.2 to 1 mm, from the viewpoint of conversion efficiency. If the thickness is within this range, the wavelength conversion efficiency of the phosphor can be improved, and the converted light can be suppressed from being absorbed by other phosphors. As a result, light emitted from the light emitting element 7 can be converted into visible light with high efficiency, and the converted visible light can be transmitted to the outside with high efficiency.

  The peak wavelength of the output light converted in the wavelength converter 9 is preferably 400 to 750 nm, particularly 450 to 650 nm. Thereby, the emission wavelength can be covered in a wide range, and the color rendering can be improved. Thus, in order to improve color rendering, a plurality of phosphors having different emission wavelengths may be used in combination.

  The wavelength converter 9 is preferably formed by being dispersed in a transparent matrix such as a polymer resin or a glass material because the wavelength converter 9 can uniformly disperse and carry the phosphor and suppress light deterioration of the phosphor. . As a glass material such as a polymer resin film or a sol-gel glass thin film, a material having high transparency and durability that is not easily discolored by heating or light is desirable.

  The material of the polymer resin film is not particularly limited. For example, epoxy resin, silicone resin, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polystyrene, polycarbonate, polyethersulfone, cellulose acetate, polyarylate, Derivatives of these materials are used. In particular, it is preferable to have excellent light transmittance in a wavelength region of 350 nm or more. In addition to such transparency, a silicone resin is more preferably used from the viewpoint of heat resistance.

  Examples of the glass material include silica, titania, zirconia, and composite materials thereof. Each of the phosphors is formed in the glass material by dispersing it alone. Compared to a polymer resin film, it has a high durability against light, particularly ultraviolet light, and further has a high durability against heat, so that the product life can be extended. In addition, since the glass material can improve stability, a light-emitting device with excellent reliability can be realized.

  The wavelength converter 9 can be formed by a coating method using a glass material such as a sol-gel glass film or a polymer resin film. Although it will not be limited if it is a general coating method, the application | coating by a dispenser is preferable. For example, it can be produced by mixing a phosphor with a liquid uncured resin, a glass material, or a resin and a glass material plasticized with a solvent. As the uncured resin, for example, a silicone resin can be used. These resins may be of a type that is cured by mixing two liquids, or a type that is cured by one liquid. The body may be kneaded, or the phosphor may be kneaded in either one of the liquids. In addition, as a resin made plastic with a solvent, for example, an acrylic resin can be used.

  The cured wavelength converter 9 can be obtained by forming it into a film shape by using a coating method such as a dispenser in an uncured state, or pouring it into a predetermined mold and hardening it. As a method of curing the resin and the glass material, there are a method of using heat energy and light energy, and a method of volatilizing the solvent.

  The electrode 3 has a function as a conductive path for electrically connecting the light emitting element 7 and is connected to the light emitting element 7 with a conductive bonding material. As the electrode 3, for example, a metallized layer containing a metal powder such as W, Mo, Cu, or Ag can be used. When the substrate 5 is made of ceramics, the electrode 3 is formed by firing a metal paste made of tungsten (W), molybdenum (Mo) -manganese (Mn) or the like on the upper surface of the substrate 5 at a high temperature. , Lead terminals made of copper (Cu), iron (Fe) -nickel (Ni) alloy, etc. are molded and fixed inside the substrate 5.

  Since the substrate 5 is required to have excellent thermal conductivity and a high total reflectance, for example, a polymer resin in which metal oxide fine particles are dispersed is suitably used in addition to a ceramic material such as alumina or nitrogen aluminum. It is done.

  The light-emitting element 7 uses a light-emitting element including a semiconductor material that emits light having a center wavelength of 370 to 420 nm because phosphors can be excited efficiently. As a result, it is possible to increase the intensity of the output light and obtain a light emitting device with higher emission intensity.

The light emitting element 7 preferably emits the above-mentioned center wavelength, but having a structure (not shown) having a light emitting layer made of a semiconductor material on the surface of the light emitting element substrate has a high external quantum efficiency. preferable. Examples of such semiconductor materials include various semiconductors such as ZnSe and nitride semiconductors (GaN, etc.), but the type of the semiconductor material is not particularly limited as long as the emission wavelength is in the above wavelength range. A stacked structure including a light-emitting layer made of a semiconductor material may be formed over a light-emitting element substrate using a crystal growth method such as a metal organic chemical vapor deposition method (MOCVD method) or a molecular beam epitaxial growth method. In order to form a nitride semiconductor with good crystallinity with high productivity, for example, when a light emitting layer made of a nitride semiconductor is formed on the surface of the light emitting element substrate, sapphire, spinel, SiC, Si, ZnO, ZrB ₂ , GaN And materials such as quartz are preferably used.

  If necessary, a reflection member 11 that reflects light is provided on the side surfaces of the light emitting element 7 and the wavelength converter 9, and the light escaping to the side surface can be reflected forward to increase the intensity of the output light. Examples of the material of the reflecting member 11 include aluminum (Al), nickel (Ni), silver (Ag), chromium (Cr), titanium (Ti), copper (Cu), gold (Au), iron (Fe), and these. These laminated structures and alloys, ceramics such as alumina ceramics, or resins such as epoxy resins can be used.

  The light emitting device of the present invention can be obtained by installing a wavelength converter 9 on a light emitting element 7 as shown in FIG. As a method of installing the wavelength converter 9 on the light emitting element 7, it is possible to install the cured sheet-like wavelength converter 9 on the light emitting element 7, and a liquid uncured material is applied on the light emitting element 7. It is also possible to harden and install after installation.

  Hereinafter, the phosphor, the wavelength converter, and the light emitting device of the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited only to the following Examples.

  First, powders of strontium carbonate, barium carbonate, silica, and europium oxide were prepared so that the molar ratios of Sr, Ba, Eu, and Si were as shown in Table 1. Furthermore, 150% by mass of 2-propyl alcohol and 1000 parts by mass of zirconia media balls were put in a polypot with respect to the total amount of these powders, and the mixture was stirred and mixed for 48 hours.

  The resulting mixed solution was discharged using a nylon mesh having an opening of 190 μm while removing the media balls, and then heated at 110 ° C. for 8 hours to remove 2-propyl alcohol.

Next, the raw material mixed powder from which 2-propyl alcohol was removed was placed in an alumina crucible and heated at 1200 ° C. for 3 hours in an air atmosphere. Thereafter, the phosphor was synthesized by heating at 1350 ° C. for 9 hours in a nitrogen gas flow containing 12% hydrogen to synthesize a phosphor having Sr _2-xy Ba _x Eu _y SiO ₄ crystal as a main crystal.

In addition, as a comparative example, a phosphor (strontium chloride) was added to produce a phosphor having a molar ratio of Eu ²⁺ / (Eu ²⁺ + Eu ³⁺ ) of 0.9 or more. Then, these phosphors were washed with water.

Subjecting the phosphor and the the washing process and XANES analysis, ^Eu 2+ a peak near 6975EV, determined the value of ^{Eu 2+ / (Eu 2+ + Eu} 3+) from the area ratio of the peak in the vicinity of 6985eV as ^{Eu 3+.}

Further, the phosphor subjected to the water washing treatment was subjected to ICP analysis to determine the composition ratio of the phosphor, and from the result, (Sr + Ba + Eu) / Si (molar ratio) was obtained. The composition was omitted.

As shown in Table 1, Sample No. which is outside the scope of the present invention. The phosphors 1 and 2 had a low luminous efficiency of 29% or less. In addition, the sample No. 2 having a Eu ²⁺ / (Eu ²⁺ + Eu ³⁺ ) value of 0.9 or more, which is outside the scope of the present invention. With the phosphors of 8 and 9, the luminous efficiency was a low value of 24 to 28%.

  On the other hand, sample No. which is a sample within the scope of the present invention. The phosphors 3 to 6 showed high luminous efficiency of 35 to 36%.

It is sectional drawing which shows an example of the light-emitting device which comprised the wavelength converter provided with the fluorescent substance of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Light-emitting device 3 ... Electrode 5 ... Substrate 7 ... Light-emitting element 9 ... Wavelength converter

Claims (3)

A phosphor containing Sr, Ba, Si, Eu, and O, and a Sr _2-xy Ba _x Eu _y SiO ₄ crystal (0 ≦ x ≦ 1, 0.01 ≦ y ≦ 0) as a main crystal. 10), and Eu ²⁺ and Eu ³⁺ of Eu satisfy Eu ²⁺ / (Eu ²⁺ + Eu ³⁺ ) <0.9 in molar ratio, and (Sr + Ba + Eu) /Si=2.02 to 2.07 in molar ratio A phosphor characterized by satisfying A wavelength converter, wherein the phosphor according to claim 1 is dispersed in a transparent matrix. A light-emitting device comprising the wavelength converter according to claim 2 and a light-emitting element that emits excitation light, wherein the phosphor of the wavelength converter is irradiated with the excitation light.

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