JP2012188630A - Fluorescent substance, and light-emitting device made by combining the fluorescent substance and light-emitting element, and authenticity identification mark containing the fluorescent substance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluorescent substance which can be produced by an easy manufacturing method, is efficiently excited by ultraviolet light or visible light to show high luminous intensity, and is suitable for emitting red light, and to provide a red light-emitting fluorescent substance which can at least make either one of the followings possible: being able to be used, for example, for a light-emitting device for white light LED, being able to be used for an authenticity identification mark emitting light only by electromagnetic radiation at a specific wavelength, and the like.SOLUTION: The fluorescent substance includes a composition satisfying average composition formula (I): (LnCaEu)WO, wherein Ln is one kind selected from La, Gd and Y, x is any positive number satisfying 0<x≤0.05 and y is any positive number satisfying 0<y≤0.5.

Description

  The present invention relates to a phosphor that is efficiently excited by ultraviolet light or visible light and emits light, a light-emitting device that combines the phosphor and a light-emitting element, and an authenticity identification label that contains the phosphor.

  Conventionally, light-emitting diodes having various emission wavelengths by combining a light-emitting element such as a nitride compound semiconductor capable of efficiently emitting ultraviolet light or visible light and a phosphor that is efficiently excited by ultraviolet light or visible light to emit light (Hereinafter LED) has been developed. Especially, white light emitting LED is comprised from the blue light emitting diode element and the fluorescent substance which absorbs blue light and light-emits yellow, and is utilized for various illumination uses. However, since the conventional white LED has a small red component in the emission spectrum, the color rendering property of the emitted light is low, and the performance is insufficient in lighting applications.

  As means for solving this, for example, it has been proposed to add a phosphor containing an alkaline earth metal element and made of nitride or oxynitride to a conventional white LED (Patent Documents 1 to 4).

  However, since these phosphors are decomposed and oxidized in the atmosphere, the raw materials used for production need to be handled in an atmosphere such as nitrogen or argon. There is a problem that it requires a lot of equipment.

In order to solve the above problems, can be manufactured in a simple manufacturing process, and aims to provide a phosphor exhibiting red light emission by absorbing the blue light of a wavelength around 460 nm, the general formula Eu _2-x Ln A phosphor represented by _x M ₂ O ₉ (0 ≦ x ≦ 2, Ln = Y, La, Gd, at least one of M = W, Mo) has been proposed. However, such a phosphor has a problem that its emission intensity is lower than that of a nitride system (Patent Document 5).

  On the other hand, a fluorescent substance that emits visible light in response to irradiation with specific invisible electromagnetic waves is incorporated into a specific part of the product, and an authenticity identification mark for determining the authenticity of various objects such as brand products and industrial products. Has been proposed (Patent Documents 6 and 7).

  The phosphor used for the authenticity identification label is required to have a characteristic that it emits visible fluorescent light specifically in response to irradiation with a specific invisible electromagnetic wave and has a high emission intensity.

  However, the red phosphor described in the above-mentioned patent document shows a wide excitation spectrum, and therefore, a phosphor that selectively emits light with respect to an electromagnetic wave having a specific wavelength is desired.

International Publication No. 05 / 52087A1 Pamphlet Special table 2003-515655 gazette JP 2002-363554 A JP-T-2005-530917 JP 2005-264160 A International Publication No. 05 / 55154A1 Pamphlet JP 2008-96159 A

  In order to solve the above-mentioned problems, the present invention provides a phosphor that can be produced by a simple production method, is efficiently excited by ultraviolet rays or visible light, exhibits high emission intensity, and is suitable for red emission. Is an issue. In addition, the present invention enables at least one of, for example, that it can be used for a light-emitting device such as a white LED, that it can be used for an authenticity identification label that specifically emits light with an electromagnetic wave having a specific wavelength, and the like. It is an object to provide a red light emitting phosphor.

（式中、ＬｎはＬａ，Ｇｄ及びＹから選ばれた少なくとも１種であり、ｘは０＜ｘ≦０．０５を満たす正の数、ｙは０＜ｙ≦０．５を満たす正の数である）を満たす組成を有することを特徴とする。
平均組成式（Ｉ）において、ｘの値は、好ましくは、０．０１以上０．０２以下であり、ｙの値は、好ましくは、０．４である。かかる蛍光体について、波長３９４ｎｍ及び波長４６４ｎｍ励起に対する波長６１２ｎｍの発光強度を、既存のＹ₂Ｏ₂Ｓ：Ｅｕ蛍光体の発光強度の強度を１００として相対的に求めた相対発光強度は、波長３９４ｎｍ励起では少なくとも１４５以上であり、波長４６４ｎｍ励起では少なくとも２８０以上であることが好ましい。 That is, the phosphor of the present invention has an average composition formula (I):

(In the formula, Ln is at least one selected from La, Gd and Y, x is a positive number satisfying 0 <x ≦ 0.05, and y is a positive number satisfying 0 <y ≦ 0.5. It is characterized by having a composition satisfying.
In the average composition formula (I), the value of x is preferably 0.01 or more and 0.02 or less, and the value of y is preferably 0.4. With respect to such a phosphor, the relative emission intensity obtained relative to the emission intensity of the wavelength 394 nm and the emission intensity of the wavelength 612 nm with respect to the excitation of the wavelength 464 nm and the intensity of the emission intensity of the existing Y ₂ O ₂ S: Eu phosphor as 100 is 394 nm. It is preferably at least 145 or more for excitation and at least 280 or more for excitation at a wavelength of 464 nm.

The light emitting device of the present invention is characterized in that the phosphor and a light emitting element are combined.
The authenticity identification label of the present invention is characterized by containing the phosphor.

The phosphor of the present invention can be produced in the atmosphere. That is, since it can be manufactured by mixing raw materials in the atmosphere and firing, it has an excellent effect that it is extremely easy to handle compared to conventional phosphors made of nitrides or oxynitrides.
In addition, the phosphor of the present invention emits light efficiently when excited by ultraviolet rays or visible light in the wavelength range of 220 to 550 nm, and particularly exhibits an excellent effect of exhibiting high emission intensity when excited at a wavelength of 394 nm and a wavelength of 464 nm. Have.
Furthermore, the phosphor of the present invention can be effectively used for light-emitting devices such as light-emitting diodes and / or can be used as a raw material for authentic identification labels that emit light specifically with electromagnetic waves of a specific wavelength. It has an excellent effect that it can be achieved.

The figure which shows the emission spectrum with respect to 394 nm excitation of fluorescent substance. In the figure, (A) and (B) show the results of Test Examples 1 to 4 and Test Examples 7 to 11, respectively. The figure which shows the emission spectrum with respect to 464 nm excitation of fluorescent substance. In the figure, (A) and (B) show the results of Test Examples 1 to 4 and Test Examples 7 to 11, respectively. The figure which shows the X-ray-diffraction pattern of fluorescent substance. In the figure, (A) and (B) show the results of Test Examples 1 to 6 and Test Examples 7 to 11, respectively. The figure which shows the excitation spectrum with respect to 612 nm emission of fluorescent substance. In the figure, (A) and (B) show the results of Test Examples 1 to 4 and Test Examples 7 to 11, respectively.

Hereinafter, embodiments of the phosphor of the present invention will be described.
As described above, the phosphor of the present embodiment has an average composition formula (I):

(In the formula, Ln is at least one selected from La, Gd and Y, x is an arbitrary positive number satisfying 0 <x ≦ 0.05, and y is an arbitrary satisfying 0 <y ≦ 0.5. Which is a positive number).

  In the present specification, the “phosphor” may be a solid solution composed of a single phase having a composition satisfying the average composition formula (I), and a plurality of compositions corresponding to a composition satisfying the average composition formula (I) as a whole. It may be a mixture of the oxide and / or a plurality of solid solutions.

Further, in this specification, the emission intensity is the emission intensity at a wavelength of 612 nm of an existing Y ₂ O ₂ S: Eu phosphor measured under the same conditions by measuring the emission for various excitation wavelengths with a fluorescence spectrophotometer. Can be evaluated based on the relative intensity (hereinafter referred to as relative emission intensity).

In the average composition formula (I) of the phosphor, Ln is not particularly limited as long as it is selected from at least one of La, Gd, and Y, and can be set according to desired emission intensity.
For example, in the luminescence measurement, high luminescence is exhibited such that the relative luminescence intensity of the 612 nm emission with respect to the wavelength 394 nm excitation is 145 or more, and the relative luminescence intensity of the 612 nm emission with respect to the wavelength 464 nm excitation is 280 or more. In the case of producing a phosphor, the composition of the phosphor preferably includes Gd as Ln in the average composition formula (I).
In addition, for example, in the emission measurement, a phosphor that emits light having a relative light emission intensity of a wavelength of 612 nm with respect to excitation of a wavelength of 394 nm is less than 145 and a light emission of a relative emission intensity of light with a wavelength of 612 nm with respect to excitation of a wavelength of 464 nm In the case of production, the composition of the phosphor may be other than Gd in the average composition formula (I).

Moreover, the composition of the phosphor is not particularly limited as long as it satisfies the average composition formula (I), and can be set according to a desired light emission intensity.
For example, in the luminescence measurement, for example, a fluorescence showing a high luminescence in which the relative luminescence intensity of the 612 nm emission with respect to the excitation of the wavelength 394 nm is 145 or more and the relative luminescence intensity of the 612 nm emission with respect to the 464 nm excitation is 280 or more. When the body is manufactured, the composition of the phosphor is preferably such that the value of x is 0.01 to 0.02 and the value of y is 0.4 in the average composition formula (I).
Also, for example, in the case of producing a phosphor having a relative emission intensity of less than 145 at a wavelength of 612 nm with respect to excitation at a wavelength of 394 nm or less than 280 at an emission wavelength of 612 nm with respect to excitation at a wavelength of 464 nm. The composition of the phosphor may be such that, in the average composition formula (I), the value of x is outside the range of 0.01 to 0.02, and the value of y is other than 0.4.

The phosphor is a composite oxide which is shown to have a monoclinic phase having high crystallinity as a main component in an X-ray diffraction pattern. In the phosphor, calcium tungstate (CaWO ₄ ) or the like may be observed as an impurity depending on the composition. However, when obtaining a phosphor exhibiting high emission intensity, the phosphor is preferably a complex oxide composed of a single phase having a monoclinic structure having high crystallinity in an X-ray diffraction pattern.

  Further, in the fluorescence spectrum, when the phosphor is excited by light having a wavelength of 394 nm corresponding to near-ultraviolet light and light having a wavelength of 464 nm corresponding to blue light, the emission intensity of wavelength 612 nm is specifically increased. That is, it is a phosphor that emits light by an electromagnetic wave having a specific wavelength. The characteristics of the emission spectrum can be recognized regardless of the type of Ln, the value of x, and the value of y in the average composition formula (I) of the phosphor, for example. Such a fluorescence spectrum can be measured with a fluorescence spectrophotometer.

Next, a method for manufacturing the phosphor will be described.
The method for producing the phosphor is not particularly limited, and as the production method, for example, a method using a solid phase reaction or the like can be adopted. The present invention also includes a method for producing such a phosphor.

  Examples of the method by the solid phase reaction include a solid phase reaction method in which a mixture of predetermined compounds (lanthanum compound, gadolinium compound, yttrium compound, europium compound, calcium compound, and tungsten compound) is baked. The mixture of compounds is a mixture that can become a phosphor having a composition represented by the average composition formula (I) by firing.

Examples of the lanthanum compound, gadolinium compound, yttrium compound, europium compound, calcium compound, and tungsten compound used in the solid phase reaction method include oxides (for example, lanthanum oxide, gadolinium oxide, yttrium oxide, oxide) Europium, calcium oxide, tungsten oxide, etc.). In addition, compounds that can be decomposed at high temperatures to become oxides (for example, lanthanum, gadolinium, yttrium, europium, calcium, and tungsten compounds that can become oxides) can be used.
The lanthanum, gadolinium, yttrium, and europium compounds that can be decomposed into oxides at high temperatures are not particularly limited. Specifically, for example, these hydroxides, carbonates, nitrates, ammonium nitrates, chlorides, Examples thereof include sulfates, acetates, citrates, and hydrates thereof. Of these, carbonates are preferred from the viewpoint of easy availability and low cost.
Although it does not specifically limit as said calcium compound which can decompose | disassemble at the said high temperature and becomes an oxide, For example, a calcium hydroxide, a calcium carbonate, a calcium oxalate, a calcium nitrate, a calcium chloride, a calcium sulfate etc. are mentioned, for example. . Of these, calcium carbonate is preferred from the viewpoint of easy availability and low cost.
The tungsten compound that can be decomposed into an oxide at a high temperature is not particularly limited, and specific examples include ammonium paratungstate, tungsten sulfide, and the like. In view of the above, the tungsten oxide is preferably used.
It is desirable that the lanthanum compound, gadolinium compound, yttrium compound, europium compound, calcium compound, and tungsten compound have high purity (for example, 99.9% or more).

  In the solid phase reaction method, the lanthanum compound, gadolinium compound, yttrium compound, europium compound, calcium compound, and tungsten compound are mixed manually by an agate mortar or the like, usually a ball mill that is used industrially, V-type It can be performed by mechanical mixing using a mixer, a stirring device or the like.

  In the method using the solid phase reaction method, the mixing ratio (molar ratio) of the lanthanum compound, gadolinium compound, yttrium compound, europium compound, calcium compound, and tungsten compound can be appropriately set within a range that satisfies the average composition formula (I). . In particular, from the viewpoint of further improving the emission intensity, it is desirable to mix so that the value of x is 0.01 or more and 0.02 or less and the value of y is 0.4 in the average composition formula (I).

  In the method using the solid phase reaction method, the phosphor can be obtained by firing the obtained mixture after mixing.

In the method using the solid phase reaction method, the firing temperature is not particularly limited, but can be appropriately set according to the type of each of the lanthanum compound, gadolinium compound, yttrium compound, europium compound, calcium compound, and tungsten compound used. . For example, the firing temperature is preferably 1000 ° C. or higher, and more preferably 1100 ° C. or higher, from the viewpoint of allowing the reaction to proceed easily. Moreover, it is preferable that it is 1500 degrees C or less from a viewpoint of suppressing energy cost, and it is more preferable that it is 1300 degrees C or less.
When the compound that can be decomposed into an oxide at the high temperature is used as the lanthanum compound, the gadolinium compound, the yttrium compound, the europium compound, the calcium compound, and / or the tungsten compound, in order to convert the compound into an oxide in advance and / or In order to remove moisture from the compound in advance, it can be calcined, for example, in a temperature range of 500 ° C. or higher and lower than 1000 ° C. before firing.

  In the method using the solid phase reaction method, the firing time may be appropriately set according to the firing temperature, the lanthanum compound, the gadolinium compound, the yttrium compound, the europium compound, the calcium compound, and the tungsten compound used. it can. Specifically, for example, when the firing temperature is 1000 ° C. to 1100 ° C., the firing time is preferably 15 hours or more and more preferably 30 hours or more from the viewpoint of completing the solid phase reaction. . Further, from the viewpoint of suppressing grain growth and sintering and shortening the production time, it is preferably 100 hours or shorter, more preferably 80 hours or shorter.

  In the method using the solid phase reaction method, the firing atmosphere includes air, oxygen gas, a mixed gas of oxygen and argon, oxygen and nitrogen from the viewpoint of suppressing the reduction of europium and / or tungsten and further improving the emission intensity. An oxidizing atmosphere such as a mixed gas is desirable. Further, from the viewpoint of promoting the reaction, water vapor may coexist in the firing atmosphere.

  The phosphor obtained as described above may be further washed and / or classified, for example. Further, from the viewpoint of enhancing the crystallinity of the obtained phosphor, re-baking may be performed.

  The manufactured phosphor is usually in a powder form, and from the viewpoint of improving dispersibility and further improving luminous efficiency, the average particle diameter is preferably 10 nm or more, and more preferably 100 nm or more. . Further, from the viewpoint of further improving dispersibility when the phosphor powder is dispersed in a resin or the like, it is preferably 50 μm or less, and more preferably 10 μm or less.

  In the present specification, the average particle diameter is directly observed and measured by a scanning electron microscope, and is calculated by biaxial arithmetic average diameter (average value of the sum of the maximum diameter and the minimum diameter of the composite oxide particles). Value.

The phosphor emits light when efficiently excited by ultraviolet rays or visible light in a wavelength range of 350 to 500 nm, and exhibits an excellent effect of exhibiting high emission intensity particularly when excited at a wavelength of 394 nm and a wavelength of 464 nm.
In addition, the phosphor can be manufactured from an inexpensive raw material and exhibits an excellent effect that it can be manufactured at a low cost.
Furthermore, since the phosphor has a strong light emission intensity even in a small amount, it exhibits an excellent effect that a light-emitting device such as a light-emitting diode and an authenticity identification label that specifically emits light with an electromagnetic wave of a specific wavelength can be manufactured at low cost. .

  The phosphor is essentially composed of a complex oxide having a composition represented by the average composition formula (I), as long as it does not impair the object of the present invention. (Also referred to as “trace substances”). The trace substance is not particularly limited as long as it does not inhibit the object of the present invention, and examples thereof include magnesium, strontium, molybdenum and the like.

  Since the phosphor is preferably manufactured at an extremely high temperature of 1000 ° C. or higher, for example, even when used in a temperature range of 50 ° C. or higher and 200 ° C. or lower, the emission intensity hardly changes and is chemically It is stable and has excellent heat resistance. Therefore, it can be used as a phosphor requiring temperature characteristics such as a light emitting diode. In addition, since the phosphor is excellent in heat resistance, it can be used as a phosphor in a wide range of fields such as a high-temperature molding material such as a resin.

The light emitting device of the present invention is a combination of the phosphor and a light emitting element.
The light emitting element emits visible light having a wavelength of at least 220 to 550 nm.

  In the present specification, the “light-emitting diode (LED)” as the light-emitting device is not particularly limited, and the “light-emitting diode (LED)” is, for example, a wavelength of the phosphor of the present invention and an emission spectrum of 220 nm to 550 nm. By combining with light emitting diodes in the range, it can be applied to LEDs of various emission colors. For example, by combining the phosphor of the present invention with a light emitting diode that emits ultraviolet light or near ultraviolet light having an emission spectrum within 220 to 400 nm, an LED having a red emission color can be obtained. Further, for example, a combination of a red light-emitting phosphor as the phosphor of the present invention and a light-emitting diode that emits visible light having an emission spectrum within 400 to 550 nm, that is, the red light-emitting phosphor by this visible light. LEDs having various emission colors in which the light emitted by excitation of the light and the visible light of the light emitting diode are mixed can be mentioned. Furthermore, LEDs having various emission colors can be produced by combining the phosphor of the present invention, a plurality of other types of phosphors, and the light emitting diode (emission spectrum is 220 to 550 nm). In particular, in a white LED, color rendering properties and luminance can be improved by using the phosphor of the present invention.

  The authenticity identification label of the present invention contains the phosphor.

In the present specification, the “authentication identification label” is not particularly limited. For example, when the phosphor of the present invention is contained in a molding material of a component made of a synthetic resin and irradiated with an electromagnetic wave having a specific wavelength. And those incorporating a specific part configured to emit red light only.
By incorporating this specific part into various objects such as brand products and industrial products, an authenticity determination mark can be obtained. Further, since it is difficult to extract and analyze the phosphor from this specific part manufactured by kneading, a high forgery prevention effect can be obtained.

  Examples The present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Gd ₂ O ₃ , Eu ₂ O ₃ , CaO, and WO ₃ were weighed in the proportions shown in Table 1, mixed with a ball mill, and then calcined at 800 ° C. for 15 hours in air. Furthermore, after baking twice in air at 1000 ° C. for 15 hours, baking was carried out at 1100 ° C. for 15 hours to produce a phosphor.

The emission intensity of each phosphor obtained was emitted under excitation with a wavelength of 394 nm and a wavelength of 464 nm using a fluorescence spectrophotometer (trade name: RF-5300PC, manufactured by Shimadzu Corporation). As shown in 2 representative examples, red light emission having a wavelength of 612 nm was observed. The relative emission intensity was determined by setting the emission intensity at a wavelength of 612 nm to 100 as the intensity of the emission intensity of an existing Y ₂ O ₂ S: Eu phosphor measured under the same conditions.

As a result, as shown in Table 2, it can be seen that the relative emission intensity varies depending on the composition of the phosphor. Specifically, in the average composition formula (I), x is an arbitrary positive number satisfying 0 <x ≦ 0.05, and y is an arbitrary positive number satisfying 0 <y ≦ 0.5. if any, emission intensity of the existing Y ₂ O ₂ S: Eu phosphor becomes it is found greater than (relative light intensity 100). In addition, in the average composition formula (I), the phosphor having a composition in which the value of x is 0.01 to 0.02 and the value of y is 0.4 has a relative emission intensity of 145 or more with respect to excitation at a wavelength of 394 nm, It can be seen that the relative light emission intensity with respect to excitation with a wavelength of 464 nm is 280 or more, indicating a higher light emission intensity.

<Powder X-ray diffraction>
About the fluorescent substance of Test Examples 1-11, the X-ray-diffraction pattern was analyzed using the powder X-ray-diffraction apparatus (Rigaku Corporation make, brand name: Multiflex). The result is shown in FIG.

  As a result, as shown in FIG. 3, single-phase diffraction peaks having a monoclinic structure were observed in the phosphors of Test Examples 1 to 4 and 7, and Test Examples 5, 6 and 8 to 11 were used. In addition to the diffraction peak of the monoclinic structure, a peak of calcium tungstate, which is an impurity phase, was observed in the phosphors of No. 1 and No. 2.

<Excitation spectrum>
About the fluorescent substance of Test Examples 1-11, the excitation spectrum with respect to light emission with a wavelength of 612 nm was measured using the fluorescence spectrophotometer (brand name: RF-5300PC, Shimadzu Corporation make). A representative example of the result is shown in FIG.

  As a result, as shown in the representative example of FIG. 4, it can be seen that there are strong excitation peaks at the wavelength of 394 nm and the wavelength of 464 nm. That is, it can be seen that a phosphor having a composition satisfying the average composition formula (I) emits strong light with respect to an electromagnetic wave having a specific wavelength.

の組成を満たす蛍光体に対して、室温、２００℃、４００℃で１時間、５時間又は２４時間加熱処理を施した。対照として、同じ組成を有する未処理の蛍光体を用いた。その後、得られた蛍光体の発光スペクトルを、蛍光分光光度計（商品名：ＲＦ−５３００ＰＣ、島津製作所製）により測定し、既存のＹ₂Ｏ₂Ｓ：Ｅｕ蛍光体の発光強度の強度を１００として相対発光強度を求めることによって定量化を行なうことにより、前記蛍光体を評価した。 <Heat resistance evaluation>
Average composition formula (II):

The phosphor satisfying the composition was subjected to heat treatment at room temperature, 200 ° C., and 400 ° C. for 1 hour, 5 hours, or 24 hours. As a control, an untreated phosphor having the same composition was used. Thereafter, the emission spectrum of the obtained phosphor was measured with a fluorescence spectrophotometer (trade name: RF-5300PC, manufactured by Shimadzu Corporation), and the intensity of the emission intensity of the existing Y ₂ O ₂ S: Eu phosphor was set to 100. The phosphor was evaluated by performing quantification by determining the relative emission intensity as follows.

  As a result, it was found that when the heat treatment was performed for 1 hour, the emission intensity did not change from room temperature to 200 ° C., and therefore the phosphor was stably present at least in the range from room temperature to 200 ° C. Moreover, since the same result was obtained even if it changed the time of heat processing, it turns out that the heat resistance of fluorescent substance is largely dependent on heating temperature rather than heating time.

  The phosphor of the present invention can be used in a wide range of fields such as light-emitting devices such as light-emitting diodes and authenticity identification labels that emit light specifically with respect to electromagnetic waves of a specific wavelength.

Claims (5)

Average composition formula (I):
(Ln _1-xy Ca _x Eu _y ) ₂ W ₂ O ₉ (I)
(In the formula, Ln is at least one selected from La, Gd and Y, x is a positive number satisfying 0 <x ≦ 0.1, and y is a positive number satisfying 0 <y ≦ 0.5. A phosphor that has a composition satisfying   The phosphor according to claim 1, wherein x and y in the formula (I) are 0.01 ≦ x ≦ 0.02 and y = 0.4.   The phosphor according to claim 1 or 2, wherein Ln in the formula (I) is Gd.   A light emitting device comprising a combination of the phosphor according to claim 1 and a light emitting element.   An authenticity identification label comprising the phosphor according to any one of claims 1 to 3.

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