JP5331021B2 - Yellow phosphor and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a yellow fluorescent substance emitting a light to high luminance with higher efficiency when a required excitation wavelength is from a near-ultraviolet light to a visible light, i.e., in a range of the wavelength of 300-500 nm when further practical use of LED illumination from now is considered, and to provide a method for manufacturing the same. <P>SOLUTION: The yellow fluorescent substance has a crystal structure of the same monoclinic system as Eu<SB>2</SB>SiS<SB>4</SB>, is represented by the composition formula: (Ca<SB>1-y</SB>Sr<SB>y</SB>)<SB>2-x</SB>Eu<SB>x</SB>SiS<SB>4</SB>, has Eu concentration x in a range of 0&lt;x&le;0.2 and Sr concentration y of 0&lt;y&le;0.6, and is excited by a light from the near-ultraviolet ray to the visible area. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a novel yellow phosphor that emits yellow light with high luminance by photoexcitation in the ultraviolet to visible region, and a method for producing the same.

Phosphors that absorb light from the ultraviolet to the visible region and emit light with high brightness are used in various lighting and display devices. Recently, a light emitting diode that emits visible light from the near ultraviolet having a wavelength of 300 to 500 nm is used. Illumination that emits light with high efficiency as an excitation light source has attracted attention. In particular, attention is paid to illumination that produces white light by combining a high-efficiency blue light-emitting diode and a phosphor excited by the blue light, that is, development of a highly-efficient phosphor suitable for it.
A white LED using such a phosphor that can be excited by visible light has high energy conversion efficiency and is advantageous for energy saving. In addition, since it does not emit infrared or ultraviolet light, it has begun to be widely used for lighting for frozen food display.

So far, for example, the blue phosphor BaMgAl ₁₀ O ₁₇ : Eu ²⁺ (BAM), Sr ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu (SCA), and the green phosphor BaMgAl ₁₀ O ₁₇ : Eu, Mn (BAM: Mn), Ca ₃ Sc ₂ Si ₃ O ₁₂ : Ce, SrGa ₂ S ₄ : Eu were developed, and a part of Sr in a SrS thin film obtained by co-sputtering ZnS, SrS, and CeF ₃ was replaced with Zn. A thin film that exhibits EL emission has also been proposed.

Also, red phosphors Y ₂ O ₂ S: Eu ³⁺ , CaAlSiN ₃ : Eu, Ba ₂ ZnS ₃ : Eu have been developed, and yellow phosphors include Y ₃ Al ₅ O ₁₂ : Ce 3 ⁺ (YAG: Ce ), Eu-activated Ca-α sialon, Sr ₃ SiO ₅ : Eu, and the like have also been developed (see, for example, Non-Patent Documents 1 and 2 and Patent Document 1).
Furthermore, Ba ₂ SiS ₄ : Eu ²⁺ phosphor exhibits blue-green fluorescence (see Non-Patent Document 3), Ca ₂ SiS ₄ : Eu ²⁺ phosphor exhibits yellow and red, and Eu ₂ SiS ₄ exhibits red fluorescence. It is known (see Non-Patent Document 4).

  On the other hand, in a white LED in which a blue LED and a phosphor are combined, color bleeding occurs because the light distribution of the light emission of the blue LED and the phosphor is different. That is, it has been pointed out that it is difficult to see strong spot-like light emission because the light emission of the LED can be seen, and development of a white LED that combines a near-ultraviolet LED and a phosphor is also underway. However, there are few high-efficiency phosphors that can be excited by near-ultraviolet LEDs, and new phosphors are demanded (see Non-Patent Documents 5 and 6).

JP-A-63-000995

“Trends in light-emitting devices”, Toray Research, 2006, p. 230-239 Hirosaki et al., “Development of Nitride Phosphors”, Material Integration, 2007, Vol. 20, No. 2, p. 17-22 Taikan, Ohashi, “Blue phosphor Ba2SiS4 for white LED: Improvement of light emission characteristics by adding Al in Ce”, Proceedings of the 321st Annual Meeting of the Phosphor Society of Japan, 2008 PF Smet, NAvci, B Loos, JE Van Haecke, D Poelman, Journal Physics Condensed: Matter, 2007, 19, 246223 Taguchi Tsunemasa, "All about white LED lighting technology", Industrial Research Committee, 2009 Ocho, Enomoto, Sasaki, and Shinomiya, “White LEDs Using New Phosphors Excited by Near Ultraviolet (nUV)”, Proc. Of the 330th Annual Meeting of the Phosphor Society of Japan, 2009

As described above, phosphors of various emission colors have been developed and proposed. When considering further practical use of LED lighting in the future, the excitation wavelength is changed from near ultraviolet light to visible light (wavelength 300 to 500 nm). ), A more efficient yellow phosphor is also desired.
Therefore, an object of the present invention is to provide a novel yellow phosphor that is excited by light in the visible region from near ultraviolet rays having a wavelength of 300 to 500 nm and emits light with high luminance, and a method for producing the same.

Under such circumstances, the present inventors have studied a composite sulfide of Ca ₂ SiS ₄ : Eu ²⁺ and Sr ₂ SiS ₄ : Eu ²⁺ , and can synthesize a compound of the chemical formula CaSrSiS ₄ , and this compound It was found that when Eu was added as an activator with yellow as a base, a novel yellow phosphor exhibiting yellow high-luminance emission having a peak near 560 nm with excitation light having a wavelength of 300 to 500 nm was obtained. Further, as a result of examining the composition of Ca and Sr, the composition contains the crystal phase of CaSrSiS ₄ as a main component, and is represented by a composition formula (Ca _1-y Sr _y ) _2−x Eu _x SiS ₄ , where 0 <x ≦ 0. It has been found that a high-luminance phosphor can be obtained if 2, 0 <y ≦ 0.6, and the present invention has been achieved.

The first invention of the present invention is a yellow phosphor excited by near ultraviolet to visible light, has the same monoclinic crystal structure as Eu ₂ SiS _4, and Eu concentration is x The composition formula (Ca _1-y Sr _y ) _2−x Eu _x SiS ₄ is characterized by being a yellow phosphor, and in this case, the Eu concentration x is 0 <x ≦ 0.2 The Sr concentration y is in the range of 0 <y ≦ 0.6 .

Second invention this is a method for producing a yellow phosphor, Eu Addition Eu are uniformly dispersed _{(Ca 1-y Sr y)} 2 S 2 powder, a Si powder and S powder, when the Eu concentration x The mixture of the composition formula (Ca _1-y Sr _y ) _2-x Eu _x SiS ₄ is vacuum-sealed in a quartz ampule, and the quartz ampule is fired at a temperature of 900 ° C. or higher and 1000 ° C. or lower. In the composition formula (Ca _1−y Sr _y ) _2−x Eu _x SiS ₄ where the Eu concentration x is in the range of 0 <x ≦ 0.2 and the Sr concentration y is in the range of 0 <y ≦ 0.6. A yellow phosphor is produced.

Furthermore, as a third invention, Eu-added (Ca _1-y Sr _y ) ₂ S ₂ powder in which Eu is uniformly dispersed is first dried as a first step by dissolving a solution obtained by dissolving Eu oxide with an acid. The resulting dried product is dissolved in water, and then a solution in which glycol, oxycarboxylic acid, carbonic acid Sr, and carbonic acid carbonate are sequentially added is prepared. The step of producing Eu-added Ca _1-y Sr _y CO _{3 in} which Eu is uniformly dispersed by pyrolyzing and firing in the atmosphere, and then, as a second step, Eu obtained in the first step is uniformly dispersed The Eu-added Ca _1-y Sr _y CO ₃ is produced by sulfidizing under a hydrogen sulfide atmosphere to produce Eu-added (Ca _1-y Sr _y ) ₂ S ₂ powder in which Eu is uniformly dispersed. The method of manufacturing the yellow phosphor Yellow phosphor according to Ming, distinguished by the use of the first step and the second Eu Addition Eu are uniformly dispersed to be produced from the process of step _{(Ca 1-y Sr y)} 2 S 2 powder Characteristics are obtained.

The present invention is a novel yellow phosphor that emits light with high luminance by being excited by light in the visible region from the near ultraviolet region having a wavelength of 300 to 500 nm, and a method for producing the same.
The yellow phosphor according to the present invention is combined with a lamp that is excited by ultraviolet light or a light emitting diode that emits near ultraviolet light or visible light, and is combined with a high-luminance yellow light emitting / display element, or another phosphor to produce white or This facilitates the formation of light emitting / display elements of various colors.

Is a diagram showing an X-ray diffraction pattern of Eu added CaSrSiS ₄ phosphor of the present invention. Eu concentration x is a diagram comparing different _{(Ca 1-y Sr y)} 2-x Eu x X -ray diffraction pattern of SiS ₄ of Ca / Sr when 0.02. (Ca _1-y Sr _y ) _1.98 Eu _0.02 SiS ₄ luminescence when Eu concentration x is 0.02, (a) is y = 0, (b) is y = 0. 25, (c) is for y = 0.5, (d) is for y = 0.75, and (e) is for y = 1.0. ₄ is a diagram showing an X-ray diffraction pattern of the Eu-added CaSrSiS ₄ phosphor of Example 1. FIG. The X-ray diffraction patterns of (Ca _1−y Sr _y ) _2−x Eu _x SiS _{4 having} different Ca / Sr when the Eu concentration x produced in Examples 1 and 2 and Comparative Example 1 was 0.02 were compared. FIG. FIG. 3 is a graph showing the fluorescence intensity measurement results of the Eu-added CaSrSiS ₄ phosphor of Example 1. FIG. 3 is a diagram showing a correlation between fluorescence intensity and Eu concentration of Eu-added CaSrSiS ₄ phosphor of Example 1. The excitation and emission spectra of _Ca 1.98 _Eu 0.02 SiS ₄ prepared with the composition of y = 0 in Comparative Example 1 YAG: is a graph comparing the Ce. The excitation and emission spectra of Example 2 was prepared with the composition of _{y = 0.25 (Ca 0.75 Sr 0.25} ) 1.98 Eu 0.02 SiS 4 YAG: is a graph comparing the Ce. The excitation and emission spectra of Example 1 was prepared with the composition of _{y = 0.5 (Ca 0.5 Sr 0.5} ) 1.98 Eu 0.02 SiS 4 YAG: is a graph comparing the Ce. The excitation and emission spectra of the fabricated with the composition of the y = 0.75 Comparative Example _{1 (Ca 0.25 Sr 0.75) 1.98} Eu 0.02 SiS 4 YAG: is a graph comparing the Ce. The excitation and emission spectra of _Sr 1.98 _Eu 0.02 SiS ₄ prepared with the composition of y = 1 Comparative Example 1 YAG: is a graph comparing the Ce.

The yellow phosphor of the present invention is represented by a composition formula (Ca _1−y Sr _y ) _2−x Eu _x SiS ₄ (0 <x ≦ 0.2, 0 <y ≦ 0.6), and has an X-ray diffraction level. Is composed of a substantially single phase having the same monoclinic crystal structure as Eu ₂ SiS ₄ .
The variable x in this composition formula represents the Eu concentration. When Eu is not included, yellow fluorescence is not exhibited, and when x exceeds 0.2, the luminance decreases due to concentration quenching. The range of x needs to satisfy 0 <x ≦ 0.2, and a more preferable range of x is 0.001 <x ≦ 0.09. The variable y in the composition formula indicates the Sr concentration. In the present invention, it is necessary that the range is 0 <y ≦ 0.6, and more preferably 0.2 ≦ y ≦. The range is 0.6.

  Furthermore, from the X-ray diffraction pattern of the yellow phosphor of the present invention shown in FIG. 1, the yellow phosphor of the present invention is almost single phase at the X-ray diffraction level, and this yellow phosphor is a single phase crystal. It can be seen that it has a structure and a part of Ca or Sr is substituted with Eu as an activator.

Further, in the composition formula (Ca _1-y Sr _y ) _2-x Eu _x SiS ₄ when the Eu concentration x is 0.02, y is set to 0.0, 0.25, 0.5, 0.75, 1 FIG. 2 shows the X-ray diffraction pattern when changed to 0.0, and FIG. 3 shows the state of light emission. The X-ray diffraction patterns (FIGS. 2B and 2C) of the yellow phosphor of the present invention are as follows. 2A is different from Ca ₂ SiS _{4 in} FIG. 2A or Sr ₂ SiS ₄ in FIG.

Next, the manufacturing method of the yellow fluorescent substance of this invention is demonstrated.
The production of the yellow phosphor represented by the composition formula (Ca _1-y Sr _y ) _2-x Eu _x SiS ₄ (0 <x ≦ 0.2, 0 <y ≦ 0.6) according to the present invention Uni-dispersed Eu-added (Ca _1-y Sr _y ) ₂ S ₂ powder, Si powder and S powder have a predetermined Eu concentration (x ₀ ) (Ca _1-y Sr _y ) _2-x0 Eu _x0 SiS _A predetermined amount is mixed so as to be _4, and then sealed in a quartz ampoule and baked at a temperature of 900 ° C. or higher and 1000 ° C. or lower and synthesized. In addition, since S powder turns into vapor | steam at high temperature, you may add more than predetermined amount.

The synthesis of the powder represented by this composition formula (Ca _1-y Sr _y ) _2−x Eu _x SiS ₄ (0 <x ≦ 0.2, 0 <y ≦ 0.6) is possible even in an inert gas. However, when oxygen or moisture is mixed into the gas, sulfates and oxides are formed, so that the fluorescent properties of the obtained phosphor are unstable due to lack of reproducibility. It is necessary to perform the firing while preventing the mixing of moisture as much as possible, and it is desirable to perform the firing by enclosing the mixed powder raw material in a vacuum.
Moreover, as a method other than this vacuum sealing and firing, for example, it is possible to use a method of synthesizing by hot pressing after Ar gas replacement after evacuation, but when Ar gas replacement, dry Ar gas or high purity Ar gas or the like may be used to prevent oxygen and water from entering.

As another production method for producing the composition formula (Ca _1-y Sr _y ) _2-x Eu _x SiS ₄ (0 <x ≦ 0.2, 0 <y ≦ 0.6), first, Ca _2-x Eu _x SiS ₄ and Sr _2-x Eu _x SiS ₄ are synthesized, mixed, and the mixture is vacuum-sealed in a quartz ampoule and fired at a temperature of 900 ° C. or higher and 1000 ° C. or lower, or SrS as a raw material. At least one selected from EuS, EuF ₃ and Eu ₂ O ₃ as CaS, Si and Eu sources are mixed in a predetermined amount, and the mixture is fired at a temperature of 850 ° C. or higher and 1000 ° C. or lower in a hydrogen sulfide flow. It can also be synthesized by a solid phase reaction method.

However, when synthesized by the method of the previous paragraph, it does not become a single phase of (Ca _1-y Sr _y ) _2−x Eu _x SiS ₄ . In addition, there is a problem that Eu is not uniform in the solid phase reaction method, so that the yellow phosphor showing yellow light emission with high luminance of the present invention cannot be obtained.

Furthermore, if Si is contained excessively, since SiS ₂ has a melting point of 1090 ° C. and a high vapor pressure, it is considered that SiS is generated as a high-temperature phase at a high temperature, and this SiS has a lower melting point than SiS _2. When SiS is formed, a liquid phase may appear at about 1000 ° C., which may hinder the production of the phosphor. Therefore, the composition formula (Ca _1-y Sr _y ) _2-x Eu _x SiS _{In order} to synthesize ₄ , it is necessary to synthesize in a sulfur atmosphere so that SiS is not generated.

Then, Eu is Eu added _{(Ca 1-y Sr y)} 2 S 2 powder production method will be described to uniformly disperse for use in the production of the yellow phosphor of the present invention, but it is an aspect of the present invention, Eu-added CaSrS ₂ is produced through an intermediate product in which Ca, Ba, and Eu are uniformly diffused using a solution method.
In the present invention, as a first step, a dried product obtained by drying a solution obtained by dissolving Eu oxide with an acid is dissolved in water, and glycol and oxycarboxylic acid, Sr carbonate and Ca carbonate are sequentially added and dissolved. The dissolved solution is heated to be gelled, and the gel is thermally decomposed and fired in the air to produce Eu addition (Ca _1-y Sr _y ) CO ₃ (the above intermediate product) in which Eu is uniformly dispersed, Subsequently, as a second step, Eu-added Ca _1-y Sr _y CO ₃ in which Eu produced in the first step is uniformly dispersed is sulfided in a hydrogen sulfide atmosphere and Eu-added CaSrS in which Eu is uniformly dispersed. _Two powders are produced.

A more detailed manufacturing method of the present invention will be described below using a case where the concentration y is 0.5.
As a first step, in order to obtain a solution by first dissolving raw material Eu oxide (Eu ₂ 0 ₃ ) with an acid, it is preferably dissolved in nitric acid or acetic acid having a concentration of 40 to 60% by mass. Although sulfuric acid and hydrochloric acid can be used for dissolving Eu oxide, if sulfuric acid traces or chlorine remain, it is not preferable because it is difficult to completely dissolve Sr and Ca. In order to completely dissolve this raw material Eu oxide (Eu ₂ 0 ₃ ), stirring is preferably performed for about 1 hour.

Next, by drying the solution of Eu oxide, excess nitric acid is evaporated to obtain a dried product. The dried product thus obtained is dissolved in pure water, and then oxycarboxylic acid and glycol are added.
As the oxycarboxylic acid to be added, citric acid, malic acid, tartaric acid and the like can be used, and citric acid is particularly preferable. As glycol, propylene glycol, ethylene glycol, polyvinyl alcohol, or the like can be used. In particular, propylene glycol is preferable.

Next, in the case of adding citric acid as oxycarboxylic acid and propylene glycol as glycol, after the citric acid is completely dissolved, the liquid temperature is increased to 35 to 45 ° C., and the same molar amounts of strontium carbonate and calcium carbonate are added. In addition, the mixture is kept at 40 to 85 ° C. and stirred until it is completely dissolved. In that case, it is preferable to stir for 8 hours or more in order to completely dissolve the hardly soluble carbonate. It is desirable to add citric acid 4 to 6 times the number of moles of metal element and propylene glycol 8 to 12 times.
In addition, an aqueous solution in which metal elements such as strontium such as acetate and barium and calcium are dissolved, rather than poorly soluble carbonates and oxides, is mixed into a solution containing a complexing material such as a citric acid solution and complexed. Also good.

After this carbonate is completely dissolved, the liquid temperature is set to 120 to 250 ° C., more preferably 180 to 220 ° C., for polymerization, and the mixture is stirred until a viscous gel is formed. Thereby, a gel containing Eu uniformly is obtained.
Subsequently, the obtained gel is heated to 400 to 500 ° C., more preferably 440 to 460 ° C., and the gel is thermally decomposed to produce a precursor powder. When the thermal decomposition of the precursor powder is insufficient, a heat treatment may be further performed at 500 to 550 ° C. for 2 to 4 hours. Thereafter, the obtained precursor powder is lightly pulverized and annealed for carbonation. As annealing conditions, the annealing temperature is 650 to 1000 ° C., more preferably 750 to 900 ° C., and the annealing time is 1 to 24 hours, more preferably 2 to 10 hours. Thus, Eu-added Ca _0.5 Sr _0.5 CO _{3 in} which Eu is uniformly dispersed by the first step is obtained. Calcium carbonate decomposes at a relatively low temperature and becomes calcium oxide. Calcium oxide may react with moisture in the atmosphere to form calcium hydroxide. Therefore, depending on the firing conditions, it becomes a carbonate mixed with calcium oxide or calcium hydroxide, but Eu is uniformly dispersed, and even calcium oxide or calcium hydroxide can be sulfided without any problem.

In the next second step, Eu Addition Eu and Eu added _Ca 0.5 _Sr 0.5 CO ₃ which Eu was prepared in the first step is to uniformly disperse the sulfide under an atmosphere of hydrogen sulfide are uniformly dispersed CaSrS ₂ powder is prepared.

Specifically, the Eu-added Ca _0.5 Sr _0.5 CO ₃ powder produced in the first step is heated in nitrogen containing 10% hydrogen sulfide or argon gas containing 10% hydrogen sulfide. An Eu-added CaSrS ₂ powder in which Eu is uniformly dispersed can be obtained by annealing at a temperature of 850 to 1100 ° C., more preferably 900 to 1000 ° C. for 7 to 12 hours.
In the present invention, the concentration ratio of Ca and Sr can be changed, that is, the Sr concentration y in the case of (Ca _1−y Sr _y ) ₂ S ₂ can be changed in the range of 0 <y ≦ 0.6. By using a predetermined amount of Ca carbonate and Sr carbonate, (Ca _1-y Sr _y ) ₂ S ₂ powder having a desired concentration ratio of Ca and Sr can be obtained.

The powder obtained in this way exhibits an XRD pattern consistent with SrS and CaS according to X-ray diffraction. During annealing, a gas containing hydrogen sulfide is required, and during the cooling after the completion of the reaction, if there is no hydrogen sulfide in the gas, a sulfate may be generated. It is preferable to allow hydrogen sulfide to flow in.
Moreover, when sulfate is included, the powder may show a yellow color. In such a case, it can be reduced to sulfide by annealing in vacuum. As the conditions, when the degree of vacuum is about 0.1 to 5 Pa and the annealing temperature is 920 to 1000 ° C. for 7 to 12 hours, sulfate can be reduced to sulfide.
Hereinafter, the present invention will be described in detail using examples.

1. Production of Eu-added (Ca _1-y Sr _y ) ₂ S ₂ powder: y = 0.5
[First step]
First, 0.143 g of europium oxide (3N manufactured by Furuuchi Chemical Co., Ltd.) was added to nitric acid (60 manufactured by Kanto Chemical Co., Ltd.) 60% so that the Eu concentration x of the carbonate prepared in the first step was 0.02. %) Was dissolved in 1 ml, and 5 minutes later, 5 ml of pure water was added, and the mixture was further stirred for 1 hour for complete dissolution. After stirring, 50 ml of pure water, 30.75 ml of propylene glycol (99% manufactured by Kanto Chemical Co., Inc.) and 31.09 g of citric acid (98% manufactured by Wako Pure Chemical Industries, Ltd.) were added to this solution, and the citric acid was completely dissolved. Thereafter, the liquid temperature was set to 40 ° C., and 2.95 g of strontium carbonate (SrCO ₃ ) and 2.00 g of calcium carbonate (CaCO ₃ ) were further added, followed by stirring for 8 hours to completely dissolve the carbonate. Subsequently, the temperature of the dissolved mixture was increased to 200 ° C. and stirred until it became a viscous gel. After stirring, the obtained gel is heated to 450 ° C. with a mantle heater, the gel is pyrolyzed to produce a precursor powder, this precursor powder is lightly pulverized with an agate mortar, and then placed in an alumina crucible and a tubular furnace The carbonic acid salt was produced by annealing at 800 ° C. for 2 hours.

When X-ray diffraction of the obtained powder was performed, only an XRD pattern corresponding to strontium carbonate (SrCO ₃ ) and calcium carbonate (CaCO ₃ ) was obtained, and Eu-added Ca _0.5 Sr ₀ in which Eu was uniformly dispersed was obtained. It was confirmed that _0.5 CO ₃ powder was obtained.

[Second step]
In the second step, 1.0 g of Eu-added Ca _0.5 Sr _0.5 CO ₃ powder in which Eu produced in the first step is uniformly dispersed is mixed with an argon-hydrogen sulfide mixed gas having a hydrogen sulfide concentration of 10%. It was heated in, and annealed at 950 ° C. for 5 hours to obtain Eu-added CaSrS ₂ powder. When X-ray diffraction of the powder was performed, only XRD patterns corresponding to CaS and SrS were observed.

2. Production of (Ca _1-y Sr _y ) _2-x Eu _x SiS ₄ (x = 0.02, y = 0.5) Next, a composition formula (Ca _0.5 Sr _0.5 ) _1.98 Eu _{0 .02 SiS 4 (x = 0.02,} y = 0.5) and so that, the Eu added CaSrS ₂ powder 0.195 g, fumed Si (Wako Ltd. 98%) 0.028 g and S powder (manufactured by Kanto Chemical Co. 99.5%) 0.065 g was weighed and mixed in an agate mortar for 20 minutes, and this mixture was pressed to 2 MPa with a hand press, and a molded body (pellet) was vacuum-sealed in a quartz ampule. The ampule was heated to 950 ° C. and heat-treated for 24 hours.

The X-ray diffraction pattern of the obtained sample is shown in FIG. 4 and FIG.
As is apparent from FIG. 4 and FIG. 5C, the obtained Eu-added CaSrSiS ₄ powder represented by the composition formula (Ca _0.5 Sr _0.5 ) _1.98 Eu _0.02 SiS ₄ is CaSrSiS. It can be seen that this is almost a single phase of ₄ .

Weigh strontium carbonate, calcium carbonate and europium oxide so that the composition formula (Ca _0.75 Sr _0.25 ) _1.98 Eu _0.02 SiS ₄ (x = 0.02, y = 0.25) A phosphor was synthesized in the same manner as in Example 1 except for the addition.
The X-ray diffraction pattern of the obtained sample is shown in FIG.

Composition formula (Ca _0.5 Sr _0.5 ) _2-x Eu _x SiS _{4 so} that x is 0.01, 0.02, 0.04, 0.06, 0.10, 0.20 A phosphor was synthesized in the same manner as in Example 1 except that strontium carbonate, calcium carbonate and europium oxide were weighed and added. x = 0.06 and 0.10 produced two samples. The measurement result of the fluorescence intensity is shown in FIG. In FIG. 7, the horizontal axis represents Eu concentration (× 1/100), the vertical axis represents fluorescence intensity, and the relative intensity when the fluorescence intensity of YAG: Ce is set to 1.
FIG. 6 shows that the Eu concentration has a fluorescence intensity of about 30% of YAG: Ce even when a small amount of 0.01 is added, and the fluorescence intensity has a peak value of about 50% from the Eu concentration of 0.02 to around 0.06. You can see that it has.

(Comparative Example 1)
As Comparative Example 1, in a compound represented by the chemical formula (Ca _1-y Sr _y ) _1.98 Eu _0.02 SiS _{4 in} which the Eu content x is 0.02, y = 0, 0.75, 1. A phosphor was synthesized in the same manner as in Example 1 except that strontium carbonate, calcium carbonate, and europium oxide were weighed and added so as to be 0.
The X-ray diffraction pattern of the obtained sample is shown in FIG. In FIG. 5, y = 0 indicates (a), y = 0.75 indicates (d), and y = 1.0 indicates (e).

[Crystal phase evaluation]
Table 1 summarizes the results of evaluating the crystal phase from the XRD patterns obtained from the samples of Examples 1 and 2 and Comparative Example 1 described above.

[Evaluation of fluorescence intensity]
Next, the phosphors prepared in Examples 1 and 2 and Comparative Example 1 were subjected to fluorescence measurement, and their luminance was compared.
The result of the fluorescence measurement is compared with a conventional yellow phosphor Y ₃ Al ₅ O ₁₂ : Ce ³⁺ (YAG: Ce, manufactured by Kasei Optonics Co., Ltd.). FIG. 6 shows the fluorescence measurement results and the state of light emission of the Eu-added CaSrSiS ₄ powder represented by the composition formula (Ca _0.5 Sr _0.5 ) _1.98 Eu _0.02 SiS ₄ produced in Example 1. 8 to 12 show fluorescence characteristics and excitation characteristics of Examples 1 and 2 and Comparative Example 1. FIG. The dotted lines in FIGS. 8 to 12 are the results of comparison YAG: Ce.

  FIG. 6 shows that excitation is possible even in the near ultraviolet region from 400 nm to 500 nm, and the intensity of the peak wavelength is larger than that of the YAG: Ce phosphor. It can also be seen that when excited at a wavelength of around 400 nm, the YAG: Ce phosphor does not emit light, but the phosphor of Example 1 emits light at the same level as the peak luminance.

Further, from FIG. 9 (Example 2) and FIG. 10 (Example 1), it can be seen that the change in luminance is small at the excitation wavelength of 300 nm to 450 nm and exceeds the luminance of YAG: Ce. The emission characteristics are also yellow with a peak at 590 nm. On the other hand, in FIGS. 8, 11, and 12 corresponding to Comparative Example 1, the change in excitation characteristics is small in the near ultraviolet, but the luminance is comparable or small compared to the excitation of YAG: Ce at 340 nm, and the emission peak is as shown in FIG. (Ca ₂ SiS ₄ ) is 660 nm, and the ratio of Sr is greater than 0.6. In FIGS.

  As is clear from FIGS. 9 and 10 and Table 1, the yellow phosphor according to the present invention is a yellow phosphor that emits high-intensity light by photoexcitation in the ultraviolet to visible region. In combination with a light emitting diode that emits visible light or in combination with a high-luminance amber light emitting / display element or in combination with other phosphors, it can be used for light emitting / display elements of various colors including white.

Claims (3)

A yellow phosphor that is excited by light from the near ultraviolet to the visible region,
Has a crystal structure of the same monoclinic system as Eu ₂ SiS _4, expressed by a composition formula _{(Ca 1-y Sr y)} 2-x Eu x SiS 4,
Eu concentration x is in the range of 0 <x ≦ 0.2,
A yellow phosphor, wherein the Sr concentration y is in the range of 0 <y ≦ 0.6. Composition formula (Ca _1-y Sr _y ) _2−x Eu when Eu is added to uniformly disperse Eu (Ca _1−y Sr _y ) ₂ S ₂ powder, Si powder and S powder, and Eu concentration is x _x SiS ₄ is mixed in a vacuum in a quartz ampule, and the quartz ampule is fired at a temperature of 900 ° C. or higher and 1000 ° C. or lower, whereby a composition formula (Ca _1-y Sr _y ) _2−x Eu _A method for producing a yellow phosphor, characterized by producing a yellow phosphor represented by _x SiS ₄ (Eu concentration x is 0 <x ≦ 0.2, Sr concentration y is 0 <y ≦ 0.6). The Eu addition (Ca _1-y Sr _y ) ₂ S ₂ powder in which the Eu is uniformly dispersed is dried in a solution obtained by dissolving the oxidized Eu in the first step with an acid. Dissolve, and then prepare a solution in which glycol, oxycarboxylic acid, Sr carbonate, and Ca carbonate are sequentially added. The prepared solution is heated to gel, and the gel is pyrolyzed and baked in the atmosphere. A step of producing Eu-added Ca _1-y Sr _y CO _{3 in} which Eu is uniformly dispersed, and then the second step, Eu-added Ca _1-y Sr _y CO _{3 in} which Eu is uniformly dispersed, in a hydrogen sulfide atmosphere The method for producing a yellow phosphor according to claim 2 , wherein the yellow phosphor is produced by a step of producing Eu-added (Ca _1-y Sr _y ) ₂ S ₂ powder that is sulfurized and uniformly dispersed.