JP2012144689A - Silicate phosphor and method for producing the same - Google Patents

Abstract

The present invention provides a blue phosphor that emits strong light when excited at around 400 nm, which is the emission wavelength of a near-ultraviolet LED, and has a small change in emission intensity due to a change in excitation wavelength, and a production method for easily obtaining the phosphor.
A silicate phosphor represented by a composition formula of Ba _1-x Eu _x ZrSi _y O _{3 + 2y} (where 0.001 ≦ x ≦ 0.5, 2.5 ≦ y ≦ 3), and powder The X-ray diffraction pattern has a BaZrSi ₃ O ₉ diffraction pattern, and the emission intensity at an excitation wavelength of 400 nm is 40% or more of the emission intensity at an excitation wavelength of 300 nm, and the excitation wavelength ranges from ^{380 nm to} 420 ^nm (I _ex ^{380 nm} −I _ex ^{420 nm} ) / I _ex ^{380 nm} × 100 The emission intensity change rate represented by the formula is 30% or less.
[Selection] Figure 3

Description

  The present invention relates to a silicate phosphor that exhibits high-luminance blue light emission when excited by light in the near ultraviolet to visible region, and a method for producing the same.

The white LED is manufactured by combining a blue or near ultraviolet LED (LD) and a phosphor. White LEDs have been developed mainly for backlight applications such as cellular phones because of their low luminous efficiency, but in recent years, they have attracted attention as next-generation lighting as the luminous efficiency increases.
As a method for configuring the white LED, a method of combining a blue LED and a yellow phosphor, a method of combining a near ultraviolet LED and a blue, green, and red phosphor have been proposed.
The near-ultraviolet LED excitation method requires a blue phosphor that is excited at around 400 nm, which is the emission wavelength of the LED, to emit light efficiently, and has been used in conventional fluorescent lamps (Ca, Sr) ₅ (PO ₄ ). ₃ Cl: Eu or _BaMgAl 10 _O 17: like Eu (BAM) is used is improved.
For example, Non-Patent Document 1 describes the excitation spectrum and emission spectrum of BAM improved for the near ultraviolet LED excitation system.

BaZrSi ₃ O ₉ : Eu is known as one of phosphors that emit blue light under near ultraviolet excitation. Non-Patent Document 1 describes Ba _0.99 ZrSi ₃ O ₉ : _0.01 Eu.
Patent Document 1 discloses (Ba, Sr) _0.99 ZrSi ₃ O ₉ : _0.01 Eu, and Patent Document 2 discloses (Ba ( _1-xy ) Sr _x Eu _y ) ( It is disclosed that by replacing the Ba site with Sr and the Zr site with Sn as a composition of Sn _1-z Zr _z ) Si ₃ O ₉ , the emission intensity is increased in near ultraviolet excitation.

Japanese Patent Publication No. 48-38550 JP 2008-63550 A JP 2010-7032 A

Taguchi Tsunemasa "All about white LED lighting technology", Industrial Research Committee, p. 110 G. Blasse, A.M. Brill, Journal of Solid State Chemistry, 1970, vol. 2, p105-108

However, looking at the excitation spectrum of BAM described in Non-Patent Document 1, the excitation intensity sharply decreases around 400 nm with a peak at about 380 nm, and the excitation intensity corresponds to the emission intensity at that wavelength. In order to cope with this, this indicates that the change in the emission intensity due to the change in the excitation wavelength is large (although by analogy, the change in the emission intensity at 380 nm to 420 nm is seen as about 60% from the graph).
In this way, when there is a sudden change in the emission intensity with respect to the excitation wavelength of the phosphor, the variation in the blue emission intensity due to the variation in the emission wavelength of the ultraviolet LED that is the excitation source also increases, resulting in variations in the color and emission intensity of the white LED. Since it connects, it is not preferable.

Ba _0.99 ZrSi ₃ O ₉ : _0.01 Eu described in Non-Patent Document 2 and Patent Document 1 has an excitation spectrum (FIG. 4 (b), Example 2; Patent Document 1, FIG. 3, curve). 6), it is clear that the excitation intensity rapidly decreases in the near-ultraviolet region and the emission intensity in the vicinity of the excitation wavelength of 400 nm is low (from the excitation spectrum of Patent Document 1) The change in emission intensity is around 35%, and the emission intensity at an excitation wavelength of 300 nm is estimated to be around 35% of the emission intensity at an excitation wavelength of 400 nm).
Further, it is formed by a solid phase reaction in which a mixture of BaCO ₃ , ZrO ₂ , SiO ₂ , Eu ₂ O ₃ is heat-treated in a nitrogen-hydrogen mixed gas. In such a solid phase reaction, Eu is uniform. It is difficult to obtain a phosphor having a high main phase purity dispersed in the material. Generally, high-temperature long-time heat treatment and repeated firing are performed to sufficiently advance the solid-phase reaction. The heat treatment performed in this manner is not industrially preferable. Moreover, since both require grinding | pulverization, it has the problem that a brightness | luminance falls by damage.

Further, Ba _0.98 ZrSi ₃ O ₉ : _0.02 Eu disclosed as a comparative example of Patent Document 2 does not disclose an excitation spectrum around 400 nm, and the emission intensity is a relative value and is absolute. It is difficult to compare values. However, since the manufacturing method disclosed in Non-Patent Document 2 is almost the same (solid phase method), the emission intensity changes greatly around the excitation wavelength of 400 nm and the emission intensity is insufficient. . Moreover, in the Example of patent document 2, the relative luminance at the excitation of 365 nm, for example, is up to 1.9 times higher than that of Ba _0.98 ZrSi ₃ O ₉ : _0.02 Eu, which is a comparative example, by Sr substitution at the Ba site. Although it is rising, as described above, since Ba _0.98 ZrSi ₃ O ₉ : _0.02 Eu itself has a low strength, it cannot be said that it has a practically sufficient luminance.

  Under such circumstances, an object of the present invention is to provide a blue phosphor that emits strong light when excited at around 400 nm, which is the emission wavelength of a near-ultraviolet LED, and has little emission intensity change due to a change in excitation wavelength, and the phosphor. It is providing the manufacturing method which obtains easily.

As a result of repeated studies to solve the above problems, the present inventors have found that in the silicate phosphor represented by the composition formula of Ba _1-x Eu _x ZrSi _y O _{3 + 2y} , x and y are 0.001 ≦ x ≦ 0.5, 2.5 ≦ y ≦ 3, and a powder X-ray diffraction pattern having a BaZrSi ₃ O ₉ type diffraction pattern has a high emission intensity at an excitation wavelength near 400 nm, and the excitation wavelength It has been found that the rate of change of the emission intensity with respect to is small. Furthermore, in the composition formula of Ba _1-x Eu _x ZrSi _y O _{3 + 2y} , x and y are in the range of 0.001 ≦ x ≦ 0.5 and 3 <y ≦ 6. In the X-ray diffraction pattern, BaZrSi ₃ O ₉ It was found that those having a diffraction pattern of the type (ICDD29-0214) and having a peak derived from SiO ₂ cristobalite in the vicinity of 22 ° of the Bragg angle (2θ) have higher emission intensity.

In addition, the silicate phosphor having the above-described characteristics is obtained by mixing the constituent metal components Ba, Zr, Eu, and Si as an aqueous solution, and further heating the mixed liquid to which oxycarboxylic acid is added. In order to remove organic substances contained in the gel body, the gel body formed by gelling the mixed liquid and then dried is baked in the air to obtain a precursor in which constituent components are uniformly distributed, and then obtained. By heat-treating the obtained precursor in a reducing atmosphere, a BaZrSi ₃ O ₉ crystal phase is obtained, and at the same time, Eu is reduced doped into Ba sites to form silicate phosphor powder, which emits light with higher brightness. It has been found that a silicate phosphor can be easily obtained. Furthermore, the obtained phosphor powder was again heat-treated in a reducing atmosphere, whereby the emission intensity was further increased, and the present invention was completed.

That is, the first invention of the present invention is a silicate represented by a composition formula of Ba _1-x Eu _x ZrSi _y O _{3 + 2y} (where 0.001 ≦ x ≦ 0.5, 2.5 ≦ y ≦ 3). A phosphor having a diffraction pattern of BaZrSi ₃ O ₉ in a powder X-ray diffraction pattern, wherein the emission intensity at an excitation wavelength of 400 nm is 40% or more of the emission intensity at an excitation wavelength of 300 nm, and the excitation wavelength ranges from 380 nm to 420 nm. The emission intensity change rate represented by the following formula (1) is 30% or less,
It is characterized by being.

Further, the second invention of the present invention is a silicate phosphor represented by a composition formula of Ba _1-x Eu _x ZrSi _y O _{3 + 2y} (where 0.001 ≦ x ≦ 0.5, 3 <y ≦ 6). In the powder X-ray diffraction pattern, it has a diffraction pattern of BaZrSi ₃ O ₉ and has a peak derived from SiO ₂ (cristobalite) in the vicinity of 22 ° of the Bragg angle (2θ) at an excitation wavelength of 400 nm. The emission intensity is 40% or more of the emission intensity at an excitation wavelength of 300 nm, and the emission intensity change rate represented by the formula (1) is 30% or less in the excitation wavelength range of 380 nm to 420 nm. is there.

Furthermore, the third invention of the present invention is a silicate represented by a composition formula of Ba _1-x Eu _x ZrSi _y O _{3 + 2y} (where 0.001 ≦ x ≦ 0.5, 2.5 ≦ y ≦ 6). A method for manufacturing a phosphor, comprising the following steps 1 to 3.
Step 1: Ba, Zr, Eu, and Si elements, which are metal components in the constituent components, are mixed as an aqueous solution, and the mixed solution to which oxycarboxylic acid is added is heated to gel the mixed solution, and then dried. A step of forming a gel body.
Step 2: The step of producing a precursor in which constituent components are uniformly distributed by removing the organic matter contained in the gel by baking the gel produced in Step 1 in the air.
Step 3: A silicate phosphor powder that obtains a BaZrSi ₃ O ₉ crystal phase by heat-treating the precursor prepared in Step 2 in a reducing atmosphere, and simultaneously emits Eu at a Ba site by reduction doping. Forming.

The fourth invention of the present invention is characterized by further comprising a step of heat-treating the silicate fluorescent powder produced in the step 3 in a reducing atmosphere.
The fifth invention of the present invention is characterized in that it further includes a step of heat-treating the silicate fluorescent powder produced in the step 3 at a temperature of 500 to 1500 ° C. in an air atmosphere.

  According to the present invention, it is possible to provide a silicate phosphor that is efficiently excited at around 400 nm, which is the emission wavelength of a near-ultraviolet LED, and has a small change in emission intensity with respect to the excitation wavelength. Can be manufactured by a simple method.

It is the schematic explaining the double crucible method used at the time of the heat processing for forming fluorescent substance. A diagram showing an X-ray diffraction pattern of the phosphor powder produced in Example, the diffraction pattern of the "BaZrSi ₃ O _9" described in 2-0 ICDD (29-0214), the fluorescence of Example 1 2-1 The body powder, 2-2 is the phosphor powder of Example 2, 2-3 is the phosphor powder of Example 3, and 2-4 is the diffraction pattern of the phosphor powder of Example 4. It is PL spectrum figure of the fluorescent substance powder produced in Examples 1-6 and the comparative example 1. FIG. It is a figure which compares the excitation spectrum shape of the fluorescent substance powder of Example 1, 6 and the fluorescent substance powder disclosed by patent document 1, (a) is the excitation spectrum of Example 1, 6 and (b) is patent document 1. It is an excitation spectrum of (Example 2). 2 is a PL spectrum diagram of the phosphor powder produced in Examples 1 and 7 to 10 and Comparative Example 1. FIG.

Hereinafter, embodiments for carrying out the present invention will be described in detail.
The present invention is a phosphor represented by a composition formula of Ba _1-x Eu _x ZrSi _y O _{3 + 2y} , wherein x and y are in a composition range of 0.001 ≦ x ≦ 0.5 and 2.5 ≦ y ≦ 6. This is the first feature.
x is more preferably in the range of 0.005 ≦ x ≦ 0.2. The optimum Eu concentration varies depending on the value of y. However, when x <0.005, the concentration of Eu as an activator is too low, and the emission intensity decreases. In addition, when x> 0.2, the emission intensity decreases due to concentration quenching.

If y <2.5, it becomes too SiO ₂ poor and a different phase (Ba ₂ Zr ₂ Si ₃ O ₁₂ ) is generated, resulting in a decrease in emission intensity.
By setting y> 3, the emission intensity increases. This is considered to be because Eu ₂ O ₃ is easily reduced and doped by making SiO ₂ excessive from the theoretical amount.
Moreover, it is considered that the crystal growth is facilitated during the heat treatment by making SiO ₂ excessive from the theoretical amount. When SiO ₂ is further excessive, BaZrSi ₃ O ₉ and SiO ₂ (cristobalite) are detected in the XRD pattern as will be described later.

Since the SiO ₂ present in the finally obtained silicate phosphor does not contribute to light emission, the optimum amount of SiO _2, the effect of the emission intensity in the course of heat treatment due to the SiO ₂ excess is increased, excessive It is determined by the balance between the decrease in the emission intensity due to the decrease in the ratio of the phase contributing to the emission due to the remaining SiO ₂ and the influence on the emission intensity.
When y> 6, there is almost no effect on the increase in emission intensity. However, when the purpose is to leave more SiO ₂ in the phosphor, the composition can satisfy y> 6, but it is difficult to avoid a decrease in emission intensity.

For the purpose of improving the emission intensity, the excitation wavelength, and the emission wavelength, part of Ba in the composition formula of Ba _1-x Eu _x ZrSi _y O _{3 + 2y} is Sr, Ca, Mg, etc., and part of Zr is Ti, Hf. , Sn, etc., a part of Si can be replaced with Ge.

In the silicate phosphor of the present invention, the powder X-ray diffraction pattern shows a diffraction pattern attributed to BaZrSi ₃ O ₉ described in powder diffraction data: ICDD (29-0214) issued by “International Diffraction Data Center”. It is also a feature.
If it is a trace amount that does not affect the light emission characteristics, ZrO ₂ , Ba silicate, Zr silicate, and the like can be included as heterogeneous components. Further, when the composition is SiO ₂ rich, there is a feature that a peak derived from SiO ₂ (cristobalite) appears at the same time around 22 ° of the Bragg angle (2θ).

The silicate phosphor of the present invention has an emission intensity at an excitation wavelength of 400 nm of 40% or more of an emission intensity at an excitation wavelength of 300 nm, and a change rate of the emission intensity in an excitation wavelength range of 380 nm to 420 nm is 30% or less. It also has features.
Therefore, it is excited as a near-ultraviolet LED emission wavelength around 400 nm and emits strong light, and the rate of change in emission intensity due to the change in excitation wavelength is small, so it is suitably used as a near-ultraviolet LED excitation-type blue phosphor. be able to.

Next, a method for producing the silicate phosphor of the present invention will be described.
Since it is important for the silicate phosphor of the present invention that the constituent components Ba, Zr, Eu, and Si are contained uniformly, by using a manufacturing method including the following steps, the emission intensity can be increased. A high phosphor can be produced more easily.

[Step 1]
In this process, Ba, Zr, Eu, and Si, which are metal components among the constituent components, are mixed as an aqueous solution, further added with oxycarboxylic acid, heated to gel, and then dried to form a gel body.

[Step 2]
In this step, thermal decomposition and atmospheric firing are performed to remove the organic matter in the gel body produced in step 1, and a precursor in which constituent components are uniformly distributed is formed.

[Step 3]
In this process, the formed precursor is heat-treated in a reducing atmosphere to obtain a BaZrSi ₃ O ₉ crystal phase, and at the same time, Eu is reduced-doped to the Ba site to produce a silicate phosphor powder that emits light with high brightness. .

Hereafter, the manufacturing method by this invention is demonstrated in detail for every process.
[Step 1]
In this step, Ba, Zr, Eu, and Si, which are metal components in the constituent components, are mixed as an aqueous solution, further added with oxycarboxylic acid, heated to gel, and then dried to form a gel body. is there.
First, an aqueous solution of Ba, Zr, Eu, and Si, which are metal components among the constituent components, is prepared.
As the Ba source, water-soluble Ba salts such as barium chloride BaCl ₂ and barium acetate Ba (CH ₃ COO) ₂ can be used. Carbonic acid Ba may be dissolved in a suitable acid.

As the Zr source, ZrOCl ₂ .8H ₂ O or ZrO (NO ₃ ) ₂ .2H ₂ O can be used. It is preferable to use ZrOCl ₂ · 8H ₂ O because of its high water solubility.

As the Eu source, europium nitrate Eu (NO ₃ ) ₃ .6H ₂ O or europium chloride EuCl ₂ can be used. Europium oxide Eu ₂ O ₃ can also be used by dissolving in a suitable acid.

  As the Si source, a known water-soluble silicon compound disclosed in Patent Document 3 can be used.

  The method disclosed in Patent Document 3 can be used to produce the water-soluble silicon compound. For example, 22.8 g (0.1 mol) of tetraethoxysilane is added to 22.8 g (0.3 mol) of 1,2-propanediol, and a hot stirrer is used so that the liquid temperature becomes 54 ° C. Then, 2 g (0.02 mol) of lactic acid is added, and the mixture is further mixed for 1 hour at a liquid temperature of 54 ° C. to prepare a water-soluble silicon compound.

Next, each metal source is weighed so that each metal component has a predetermined molar ratio, dissolved in an aqueous solution, and mixed. In the case of a small amount, an aqueous solution having a predetermined concentration may be prepared in advance, and a predetermined amount may be weighed and mixed with a pipette or a graduated cylinder. Further, oxycarboxylic acid is added and heated and mixed at 80 ° C.
The purpose of this oxycarboxylic acid addition is to complex metal ions other than silicon.
It is preferable to use citric acid as the oxycarboxylic acid. The amount of oxycarboxylic acid is preferably 1 to 6 times the number of moles of all metal elements. An aqueous oxycarboxylic acid solution having a predetermined concentration may be prepared in advance, and a predetermined amount may be weighed and mixed with a pipette or a graduated cylinder.

Then, it heat-mixes at 120 degreeC and dries. In the process of heating and mixing, SiO ₂ forms a network by hydrolysis and dehydration condensation, and a gel body in which constituent components are uniformly distributed is formed by drying. In addition, before heating and mixing at 120 ° C., glycol (ethylene glycol, propylene glycol, etc.) can be added to the raw material aqueous solution. In this case, a dehydrating ester reaction occurs between the carboxyl group of oxycarboxylic acid and the hydroxyl group of glycol during heat drying, and a polyester polymer gel in which metal ions are uniformly dispersed is obtained.

[Step 2]
This step is a step of forming a precursor in which constituent components are uniformly distributed by subjecting the gel body to thermal decomposition and atmospheric firing for the purpose of removing organic substances contained in the formed gel body.

The heat treatment in the atmosphere is performed in order to decompose an organic substance contained in the gel body and obtain a precursor in which fine oxides of constituent components are uniformly distributed.
The organic substance contained in the gel body refers to polyhydric alcohols such as 1,2-propanediol contained in the water-soluble silicon compound, and those derived from oxycarboxylic acids such as citric acid added for complexation. These removals are preferably performed at 400 to 600 ° C. in the atmosphere.

  Thereafter, a heat treatment in the atmosphere is performed at a higher temperature to completely remove residual carbon. Removal of residual carbon is preferably performed at 600 to 1000 ° C. in the atmosphere. These atmospheric heat treatments may be performed a plurality of times at different temperatures as necessary. Crushing at each heat treatment step is effective in promoting the decomposition and removal of organic matter.

Through such steps, a precursor in which oxides derived from raw material components are finely and uniformly distributed can be obtained. The change to the oxide can be estimated by the weight reduction with respect to the charged weight. The uniformity can be confirmed by X-ray diffraction. When non-uniform precipitation of constituent components occurs, diffraction patterns derived from oxides and raw material salts are confirmed.
The precursor obtained by such a method is preferably amorphous although it depends on the heat treatment temperature condition for carbon removal.

[Step 3]
In this step, the precursor formed in step 2 is heat-treated and baked in a reducing atmosphere to obtain a BaZrSi ₃ O ₉ crystal phase, and at the same time, Eu is reduced-doped to a Ba site to produce a silicate phosphor powder. It is a manufacturing process.
A BaZrSi ₃ O ₉ crystal phase is obtained by heat-treating the precursor, and at the same time, Eu ₂ O ₃ (Eu ³⁺ ) is reduced to Eu ²⁺ and doped into the Ba site. The heat treatment (firing) temperature varies depending on the final firing conditions of the precursor, but is preferably in the range of 1100 ° C. to 1500 ° C. If it is less than 1100 ° C., the heat treatment temperature is low and the target crystal phase cannot be formed, or the crystal growth is insufficient and the emission intensity is lowered. When the temperature exceeds 1500 ° C., it completely melts, and after that, strong pulverization is required. This causes a decrease in emission intensity due to crystal damage due to pulverization.

Moreover, crystal growth and grain growth can be promoted by adding chloride, fluoride or the like as a flux. Examples of the flux include LiF, NaF, KF, LiCl, NaCl, KCl, Li ₂ CO ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , NaHCO ₃ , NH ₄ Cl, NH ₄ I ₂ , MgF ₂ , CaF ₂ , _{SrF 2, BaF 2, MgCl 2} , CaCl 2, SrCl 2, BaCl 2, MgI 2, CaI 2, SrI 2, etc. BaI ₂ can be used.

This heat treatment is divided into calcination in the atmosphere for completely forming a BaZrSi ₃ O ₉ crystal phase and main calcination in a reduction atmosphere for reducing and doping Eu contributing to light emission to the Ba site. The heat treatment may be performed once. You can also crush at each step.
The heat treatment time is 1 to 24 hours, preferably 2 to 4 hours.
If the heat treatment time is short, crystal growth becomes insufficient and the light emission intensity decreases. If the heat treatment time is too long, it may melt, and if it is melted / sintered, strong pulverization is required, and crystals are damaged by pulverization, resulting in a decrease in emission intensity.

The reducing atmosphere is preferably a CO—CO ₂ atmosphere.
Heating in a CO—CO ₂ atmosphere can be facilitated by placing in a crucible or the like together with a carbon source such as graphite or activated carbon, capping and firing in the atmosphere. An inert atmosphere such as Ar or N ₂ may be used. A highly reducing gas such as H ₂ or NH ₃ can also be used. The stronger the reducing atmosphere, the more advantageous it is for reducing Eu ₂ O ₃ , but oxygen deficiency is likely to occur in the mother crystal, which adversely affects the phosphor properties, and thus the degree of reduction must be controlled.

Since the phosphor powder obtained by this reduction firing proceeds efficiently, a pulverization or pulverization step is required depending on the degree of sintering in order to obtain a desired particle size.
That is, the phosphor powder obtained in this manner contains surface defects, which may adversely affect the light emission characteristics. Further, a part of Eu ₂ O ₃ may remain unreduced. Therefore, for the purpose of recovering surface defects and promoting reduction of the remaining Eu ₂ O ₃ , it is more preferable to pulverize after reductive firing to adjust the particle size, and then repeatedly refire in a reducing atmosphere.
The recovery of the surface defect can be confirmed by directly observing the particle surface with SEM or the like. The progress of the reduction of Eu ₂ O ₃ can be confirmed by comparing the intensity of a spike-like weak emission spectrum that appears in the vicinity of 620 nm when the obtained phosphor powder is excited at a wavelength of about 250 to 300 nm. . The light emission intensity is further improved by this repeated heat treatment.

It is more effective for crystal growth and grain growth to add the flux at the time of re-reduction firing.
The optimum temperature for refiring varies depending on the particle size and the presence or absence of flux addition, but is preferably 1100 ° C to 1500 ° C. If the temperature is lower than 1100 ° C., the effect cannot be sufficiently obtained. If the temperature exceeds 1500 ° C., the sintering proceeds and strong pulverization is required. As a result, surface defects are regenerated, and a sufficient effect is obtained. Absent.

Furthermore, in order to repair the oxygen defect produced | generated here, fluorescence brightness | luminance can be improved by heat-processing in air | atmosphere after the said reduction | restoration baking process.
Since ZrO ₂ contained as a component easily causes oxygen defects in a reducing atmosphere, oxygen defects are also generated in BaZrSi ₃ O ₉ : Eu obtained by reduction firing. This oxygen defect in the mother crystal becomes a recombination center in the excitation / light emission process, and the non-radiative transition that does not contribute to light emission increases to cause a decrease in luminance.
Therefore, by heat-treating the obtained phosphor powder in an oxygen atmosphere such as in the atmosphere (air), oxygen defects on the powder surface due to the reduction treatment in the previous stage can be recovered and the luminance can be significantly increased. In particular, when the reduction treatment of the previous stage is performed using highly reducing hydrogen, the amount of oxygen defects introduced may increase, so heat treatment in the atmosphere containing this oxygen Is effective for brightness recovery.

  Moreover, physical damage exists on the powder surface that has undergone the pulverization step, and it is said that such damage also adversely affects the luminance. Such physical defects can be expected to be recovered by heat treatment, which is considered to contribute to the improvement of luminance.

Since the above heat treatment atmosphere may be in the presence of oxygen, an oxygen gas having an arbitrary concentration can be used.
The optimal oxygen concentration is not uniquely determined because it varies depending on the calcination conditions and reduction firing conditions (the degree of oxygen defects) of the precursor in the sample, but heat treatment in the atmosphere provides a significant brightness enhancement effect, Since the apparatus is also simple, it is an industrially effective treatment method. However, this does not limit the recovery annealing of oxygen defects using an arbitrary concentration of oxygen gas.

  The heat treatment temperature is not uniquely determined because it varies depending on the degree of oxygen defects and the oxygen concentration in the phosphor, but in the case of heat treatment in the air, it is preferably 500 ° C. or higher and 1500 ° C. or lower. If the temperature is lower than 500 ° C., a sufficient brightness enhancement effect (oxygen defect recovery) cannot be obtained, and if the temperature exceeds 1500 ° C., the reduction-doped divalent Eu is oxidized to become trivalent Eu. Since it melts, the luminance decreases. Moreover, it is more preferable that it is 800 degreeC or more and 1300 degrees C or less.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.
X-ray diffraction of the obtained phosphor was measured by “Fully automatic multipurpose X-ray diffractometer X′pert Pro MPD” manufactured by Spectris.
Fluorescence measurement was performed using an “F-4500 spectrofluorometer” manufactured by Hitachi, Ltd., and the excitation spectrum at an emission wavelength of 480 nm and the emission intensity at excitation wavelengths of 300, 380, 400, and 420 nm were measured. The PL spectrum in FIG. 3 is a comparison between the excitation spectrum and the emission spectrum at an excitation wavelength of 300 nm at which the maximum emission intensity is obtained.

[Preparation of aqueous solutions of metal components]
Ba source: barium acetate Ba (CH ₃ COO) ₂ , Zr source: ZrCl ₂ O · 8H ₂ O, Eu source: Eu (NO ₃ ) ₃ · 6H ₂ O with distilled water as a metal element concentration of 1 mol / L The volume was constant.
The water-soluble silicon compound of the Si source was prepared by adding 1,2-propanediol: 22.8 g (0.3 mol) to tetraethoxysilane: 20.8 g (0.1 mol) and having a liquid temperature of 54 A hot stirrer was used so that the temperature became 0 ° C., and the mixture was mixed for 24 hours with stirring. . Then, the volume was adjusted to 1 mol / L as the silicon concentration with distilled water.

Citric acid was made up to a volume of 2 mol / L with distilled water.
These metal raw material aqueous solutions are poured into a beaker with a pipette so that Ba: Zr: Si: Eu is 0.98: 1.0: 3.0: 0.02, and the total amount of all metal elements is further increased. An aqueous citric acid solution was poured into a beaker so as to have a molar ratio of 4 times. Next, the gelation treatment was performed with a hot stirrer under the conditions of 80 ° C. × 2 hours, and then the mixture was placed in an oven and dried at 120 ° C. for 12 hours. After this drying, a brownish gel was obtained. Thereafter, a heat treatment was performed under conditions of 550 ° C. × 6 hours to decompose the organic matter and form a precursor. The obtained precursor was crushed in a mortar and subjected to heat treatment in the atmosphere at 800 ° C. for 12 hours to remove carbon and obtain a calcined powder.

Next, the obtained calcined powder 11 was charged into a double crucible 10 as shown in FIG. 1 and heat-treated in a reducing atmosphere. In this heat treatment, first, the calcined powder 11 was placed on an alumina dish 4 with a carbon sheet 3 and placed in an alumina crucible 1 with graphite powder 5 on the bottom, and the lid 1a was formed. Thereafter, graphite powder 5 was laid on the bottom of alumina crucible 2 that was slightly larger than alumina crucible 1, alumina crucible 1 was placed on graphite powder 5, and lid 2a of alumina crucible 2 was closed. This was placed in a small box furnace (KBF314N1 type) furnace and heat-treated at 1400 ° C. for 2 hours in a reducing atmosphere.
The internal structure of the crucible used for this heat treatment is shown in FIG. By using such a double crucible method, heat treatment can be easily performed in a CO—CO ₂ reducing atmosphere.

Since the sintered sample was slightly sintered, it was crushed to obtain a phosphor powder. The obtained phosphor showed the diffraction pattern of BaZrSi ₃ O ₉ described in ICDD (29-0214) as shown in FIG. FIG. 3 shows the PL spectrum, and Table 1 shows the relative emission intensity at each excitation wavelength (300 nm, 380 nm, 400 nm, 420 nm).

A phosphor was obtained by performing the same operation as in Example 1 except that the aqueous raw material solution was pipetted into a beaker so that Ba: Zr: Si: Eu was 0.98: 1.0: 3.3: 0.02. A powder was prepared.
The XRD pattern is shown in FIG.
The obtained phosphor shows a diffraction pattern of BaZrSi ₃ O ₉ (see 2-0 in FIG. 2) described in ICDD (29-0214). Further, in the vicinity of 2θ = 22 degrees, weak SiO ₂ (cristobalite) is obtained. ) Phase confirmed.
FIG. 3 shows the PL spectrum, and Table 1 shows the relative emission intensity at each excitation wavelength.

The phosphor was obtained by performing the same operation as in Example 1 except that Ba: Zr: Si: Eu was 0.98: 1.0: 4.5: 0.02 and the raw material aqueous solution was pipetted into the beaker. A powder was prepared.
The XRD pattern is shown in FIG. The obtained phosphor showed a diffraction pattern of BaZrSi ₃ O ₉ described in ICDD (29-0214), and a SiO ₂ (cristobalite) phase was confirmed around 2θ = 22 °.
FIG. 3 shows the PL spectrum, and Table 1 shows the relative emission intensity at each excitation wavelength.

The phosphor was obtained by performing the same operation as in Example 1 except that Ba: Zr: Si: Eu was 0.98: 1.0: 6.0: 0.02 and the aqueous raw material solution was pipetted into the beaker. A powder was prepared.
The XRD pattern is shown in 2-4 of FIG. The obtained phosphor showed a diffraction pattern of BaZrSi ₃ O ₉ described in ICDD (29-0214), and a SiO ₂ (cristobalite) phase was confirmed around 2θ = 22 °.
FIG. 3 shows the PL spectrum, and Table 1 shows the relative emission intensity at each excitation wavelength.

The phosphor powder produced in Example 2 was again heat-treated in a reducing atmosphere at 1400 ° C. for 2 hours with a graphite double crucible.
FIG. 3 shows the PL spectrum, and Table 1 shows the relative emission intensity at each excitation wavelength.

A phosphor powder was produced in the same manner as in Example 5 except that the charged Ba: Zr: Si: Eu was changed to 0.96: 1.0: 3.3: 0.04.
FIG. 3 shows the PL spectrum, and Table 1 shows the relative emission intensity at each excitation wavelength.

  The phosphor powder obtained in Example 1 is placed in an alumina crucible, placed in a small box furnace (KBF314N1 type) furnace, and subjected to heat treatment at 500 ° C. for 1 hour in an air atmosphere to obtain the phosphor powder. Obtained. The fluorescent characteristics of the obtained phosphor powder were evaluated and are shown in FIG.

  The phosphor powder obtained in Example 1 is put in an alumina crucible, placed in a small box furnace (KBF314N1 type) furnace, and heat-treated at 1000 ° C. for 1 hour in an air atmosphere to obtain the phosphor powder. Obtained. The fluorescent characteristics of the obtained phosphor powder were evaluated and are shown in FIG.

  The phosphor powder obtained in Example 1 is placed in an alumina crucible, placed in a small box furnace (KBF314N1 type) furnace, and subjected to heat treatment at 1200 ° C. for 1 hour in an air atmosphere to obtain the phosphor powder. Obtained. The fluorescent characteristics of the obtained phosphor powder were evaluated and are shown in FIG.

  A calcined powder was prepared under the same conditions as in Example 1, and this was placed in a tabletop high-temperature tubular furnace (manufactured by Yamada Denki, TSR-630), and argon gas containing 4% of hydrogen gas was allowed to flow at a flow rate of 100 ml / min. Heat treatment was performed in a reducing atmosphere at 1400 ° C. for 2 hours to obtain phosphor powder. Thereafter, the obtained phosphor powder was put in an alumina crucible, placed in a small box furnace (KBF314N1 type) furnace, and subjected to heat treatment at 1200 ° C. for 1 hour in an air atmosphere to obtain a phosphor powder. . The fluorescent characteristics of the obtained phosphor powder were evaluated and are shown in FIG.

(Comparative Example 1)
BaCO ₃ (manufactured by Kanto Chemical Co., Inc., purity 3N), ZrO ₂ (manufactured by Wako Pure Chemical Industries, Ltd.), SiO ₂ (manufactured by Wako Pure Chemical Industries, Ltd.), Eu ₂ O ₃ (manufactured by Furuuchi Chemical Co., Ltd.) The raw materials were weighed so that the molar ratio of Ba: Zr: Si: Eu was 0.98: 1.0: 3.0: 0.02, and mixed in an agate mortar for 20 minutes.
This was heat-treated at 1400 ° C. for 2 hours using the same graphite double crucible as in Example 1. The obtained phosphor showed the diffraction pattern of BaZrSi ₃ O ₉ described in ICDD (29-0214) as in Example 1. The PL spectrum is shown in FIG. 3, and the relative emission intensity at each excitation wavelength is shown. Are shown together in Table 1, and the emission intensity was extremely low.

(Comparative Example 2)
Except that the heat treatment temperature was 450 ° C., heat treatment was performed in the air under the same conditions as in Example 7 to obtain a phosphor powder. It was the same as the fluorescence characteristic of Example 1 and showed similar light emission characteristics, and no improvement in characteristics due to heat treatment in the atmosphere was observed.

(Comparative Example 3)
The phosphor powder obtained in Example 1 was heat-treated in the atmosphere under the same conditions as in Example 7 except that the heat treatment temperature in the atmosphere was changed to 1550 ° C. to obtain a phosphor powder. The phosphor melted and decomposed and did not emit light.

[Evaluation results of phosphor powder]
As is apparent from FIG. 3 and Table 1, it can be seen that the phosphors according to the present invention all exhibit a flat excitation spectrum around 400 nm, which is the emission wavelength of the near-ultraviolet LED. In particular, Examples 1 to 6 using the production method of the present invention show significantly higher emission intensity than Comparative Example 1 by the solid phase method which is a conventional method. In Examples 2, 3, and 4 in which SiO ₂ is made richer than the stoichiometry, the emission intensity is higher than that in Example 1. In addition, the phosphors of Examples 5 and 6 that have been subjected to re-reduction firing have particularly improved emission intensity. From comparison of the excitation spectrum shapes shown in FIG. 4, it is apparent that the BaZrSi ₃ O ₉ : Eu phosphor according to the present invention has a shape different from that of the known excitation spectrum (Example 2 of Patent Document 1).

As apparent from FIG. 5 and Table 1, as shown in Examples 7 to 10 and Comparative Examples 2 and 3, the effects of the heat treatment in the oxygen atmosphere performed after the reduction treatment are within the scope of the present invention, that is, In Example 7 to Example 10 in which heat treatment was performed in an oxygen atmosphere such as air (air) in a temperature range of 500 to 1500 ° C., excitation characteristics and light emission were compared with Example 1 in which this heat treatment was not performed. It can be seen that both characteristics are improved. In particular, in Examples 8, 9, and 10 treated at a heat treatment temperature of 1000 ° C. to 1200 ° C., significant improvement is observed.
On the other hand, in Comparative Example 2 in which the temperature of this heat treatment was as low as 450 ° C., neither the excitation characteristics nor the light emission characteristics were improved as compared with Example 1, and the effect of the heat treatment was not seen. In Comparative Example 3 where the temperature was too high, a sample could not be produced.

As described above, the BaZrSi ₃ O ₉ : Eu phosphor according to the present invention has a large emission intensity around 400 nm, which is the emission wavelength of a near-ultraviolet LED, and a small change in emission intensity with respect to a change in excitation wavelength. Therefore, the silicate phosphor of the present invention is very suitable as a blue phosphor for near-ultraviolet LED excitation.

1 Alumina crucible (inside)
1a Alumina crucible 1 lid 2 Alumina crucible (outside)
2a Alumina crucible 2 lid 3 Carbon sheet 4 Alumina dish 5 Graphite powder 10 Double crucible 11 Calcined powder

Claims (5)

A silicate phosphor represented by a composition formula of Ba _1-x Eu _x ZrSi _y O _{3 + 2y} (where 0.001 ≦ x ≦ 0.5, 2.5 ≦ y ≦ 3),
In the powder X-ray diffraction pattern, it has a diffraction pattern of BaZrSi ₃ O ₉
The emission intensity at an excitation wavelength of 400 nm is 40% or more of the emission intensity at an excitation wavelength of 300 nm,
In the excitation wavelength range of 380 nm to 420 nm, the emission intensity change rate represented by the following formula (1) is 30% or less,
It is characterized by being.

A silicate phosphor represented by a composition formula of Ba _1-x Eu _x ZrSi _y O _{3 + 2y} (where 0.001 ≦ x ≦ 0.5, 3 <y ≦ 6),
In the powder X-ray diffraction pattern, it has a diffraction pattern of BaZrSi ₃ O ₉ and has a peak derived from SiO ₂ (cristobalite) around 22 ° of the Bragg angle (2θ),
The emission intensity at an excitation wavelength of 400 nm is 40% or more of the emission intensity at an excitation wavelength of 300 nm,
In the excitation wavelength range of 380 nm to 420 nm, the emission intensity change rate represented by the formula (1) is 30% or less. A method for producing a silicate phosphor represented by a composition formula of Ba _1-x Eu _x ZrSi _y O _{3 + 2y} (where 0.001 ≦ x ≦ 0.5, 2.5 ≦ y ≦ 6),
The following steps 1 to 3 are included.
Step 1: Ba, Zr, Eu, and Si elements, which are metal components in the constituent components, are mixed as an aqueous solution, and the mixed solution to which oxycarboxylic acid is added is heated to gel the mixed solution, and then dried. A step of forming a gel body.
Step 2: The step of producing a precursor in which constituent components are uniformly distributed by removing the organic matter contained in the gel by baking the gel produced in Step 1 in the air.
Step 3: A silicate phosphor powder that obtains a BaZrSi ₃ O ₉ crystal phase by heat-treating the precursor prepared in Step 2 in a reducing atmosphere, and simultaneously emits Eu at a Ba site by reduction doping. Forming.   4. The method for producing a silicate phosphor according to claim 3, further comprising a step of heat-treating the silicate phosphor powder produced in the step 3 in a reducing atmosphere.   The method for producing a silicate phosphor according to claim 3, further comprising a step of heat-treating the silicate fluorescent powder produced in the step 3 at a temperature of 500 to 1500 ° C in an air atmosphere.

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