JP2009293022A - Green phosphor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a green phosphor having a high internal quantum efficiency. <P>SOLUTION: The green phosphor comprises a host crystal comprising Sr, Ga and S, and a luminescence center. The molar ratio (Ga/Sr) of the Ga content to the Sr content is 2.02 to 3.02. Thus, the internal quantum efficiency can be enhanced as compared with that of a green phosphor having a host crystal comprising a stoichiometric composition represented by SrGa<SB>2</SB>S<SB>4</SB>. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a green phosphor. Specifically, it can be excited by a blue LED or a near-ultraviolet LED, used as an illumination phosphor, a liquid crystal backlight, FED (field emission display), PDP (plasma display), EL (electroluminescence), etc. The present invention relates to a green phosphor that can be used as a display phosphor.

  The current mainstream of light sources for illumination is fluorescent lamps and incandescent lamps, but those using LEDs (light-emitting diodes) as light sources consume less power and have longer lifespans than those of fluorescent lamps. It is not hot, so it is excellent in terms of safety and does not contain harmful substances such as mercury and is also excellent in terms of the environment. It is expected to become the mainstream of lighting light sources in the near future.

The current white LED is composed of a combination of a blue LED and YAG: Ce (yellow), but it is inferior in color rendering that exhibits a natural color development property. Even if it was illuminated with, it had a problem that it could not reproduce the color illuminated by natural light. Therefore, as a method for improving the color rendering properties of such current white LEDs, a combination of a near-ultraviolet LED and three types of phosphors of red, green and blue, or a blue LED and two types of phosphors of red and green, As a green phosphor used for this purpose, SrGa ₂ S ₄ : Eu is disclosed (see Patent Documents 1, 2, and 3).

JP 2002-060747 A JP 2007-056267 A JP 2007-214579 A

Conventionally disclosed green phosphors composed of SrGa ₂ S ₄ : Eu have had to further increase the luminous efficiency. In order to increase the luminous efficiency, it is said that it is important to use a phosphor having a high external quantum efficiency (= internal quantum efficiency × absorption rate). However, for example, as described above, when white light is obtained by combining a near-ultraviolet LED, a blue LED, and a phosphor including a green phosphor, the phosphor absorbs the light emitted from the LED and the light of this LED. In order to obtain white light in combination with the light emitted, it is necessary to appropriately transmit the light emitted by the LED. Therefore, in such an application, it is preferable to increase the external quantum efficiency by increasing the internal quantum efficiency of the phosphor or to increase the emission intensity of the phosphor.

  Therefore, the present invention mainly aims to provide a green phosphor capable of increasing the internal quantum efficiency.

  The present invention is a green phosphor containing a host crystal containing Sr, Ga and S and an emission center, and the molar ratio of Ga content to Ga content (Ga / Sr) is 2.02-3. A green phosphor characterized by 0.02 is proposed.

Green phosphor of the present invention, than stoichiometric composition represented by SrGa ₂ S ₄ is a green phosphor containing a large amount of Ga by a predetermined amount, having a host crystal comprising a stoichiometric composition represented by SrGa ₂ S ₄ Compared to green phosphors, it has a feature of high internal quantum efficiency. Thus, for example, when a near-ultraviolet LED or blue LED as an excitation source is combined with a phosphor containing the green phosphor of the present invention to form a white light-emitting element or device, the light from the LED is appropriately transmitted, and Light can be emitted efficiently and sufficient white light can be obtained. Further, since the internal quantum efficiency is high, the light emission efficiency is high. Therefore, even when a limited amount of green phosphor is combined with an LED having limited characteristics, a sufficient amount of light emission can be obtained.

It is the figure which showed the XRD pattern of Example 11 and Comparative Examples 4-6.

  Embodiments of the present invention will be described in detail below, but the scope of the present invention is not limited to the embodiments described below.

The green phosphor according to the present embodiment (hereinafter referred to as “the present green phosphor”) is a green phosphor obtained by doping a host crystal containing Sr, Ga, and S with Eu ²⁺ as the emission center.

In general terms, this green phosphor is a phosphor containing a crystal represented by SrGa ₂ S ₄ : Eu ²⁺ . Therefore, in terms of the stoichiometric composition represented by SrGa ₂ S ₄ , it is common to manufacture by mixing Ga at a ratio of 2.00 mol with respect to 1 mol of Sr. ₂ Ga 4 is a mixture of Ga in excess of the stoichiometric composition indicated by S ₄ . That is, the molar ratio (Ga / Sr) of the Ga content to the Sr content is 2.02 to 3.02, preferably 2.02 to 2.72, particularly preferably 2.21 to 2.45. , Ga is excessively contained. Thus, if the molar ratio (Ga / Sr) of the Ga content to the Sr content is 2.02 to 3.02, the internal quantum efficiency can be increased. On the other hand, when Ga / Sr is larger than 2.72, although the light emission characteristics are improved, melting of the fired product starts, which is not preferable in production.

The emission center (luminescent ion) of the present green phosphor preferably contains divalent Eu ²⁺ , particularly only divalent Eu ²⁺ . The emission wavelength (color) of Eu ²⁺ strongly depends on the mother crystal and is known to exhibit various wavelengths depending on the mother crystal. A spectrum can be obtained.
The concentration of Eu ²⁺ is preferably 0.1 to 10 mol% of the concentration of Sr in the mother crystal, more preferably 0.5 to 7 mol%, and particularly preferably 1 to 5 mol%.
It should be noted that the same effect can be expected even if an ion other than Eu ²⁺ , for example, one or more ions selected from the group consisting of rare earth ions and transition metal ions is used as the luminescent center (luminescent ion). Can do. Examples of rare earth ions include ions such as Sc, Tb, and Er, and examples of transition metal ions include ions such as Mn, Cu, Ag, Cr, and Ti.

(Particle size distribution)
This green phosphor has a volume-based particle size distribution obtained by measurement by a laser diffraction / scattering particle size distribution measuring method, and a particle size (D10) of accumulated 10% from the small particle size side is 4.5 μm to 30 μm. It is preferable that the thickness is 5 μm to 30 μm, particularly 7 μm to 30 μm.
By regulating D10 to 4.5 μm or more, the external quantum efficiency (light extraction efficiency) of the phosphor particles can be further enhanced. However, if D10 exceeds 30 μm, the external quantum efficiency of the phosphor particles is not impaired, but depending on the application, the phosphor is dispersed in the resin and used. In that case, the filling rate per unit volume Is not preferable because of the possibility of lowering. Further, when a low-viscosity resin is used, dispersibility is deteriorated, so that it may be difficult to sufficiently obtain the performance of a light emitting element such as a white LED. Therefore, the upper limit value of D10 is preferably 30 μm or less.

In addition, this green phosphor has a volume-based particle size distribution obtained by measurement by a laser diffraction / scattering particle size distribution measuring method, and a particle diameter (D5) of 5% accumulated from the small particle diameter side is 3.5 μm. It is preferably ˜20 μm, particularly preferably 4.5 μm to 20 μm, and particularly preferably 5 μm to 20 μm.
In the green phosphor having the composition of the present green phosphor, the external quantum efficiency of the phosphor particles can be further enhanced by regulating D5 to 3.5 μm or more.
On the other hand, the upper limit of D5 is preferably 20 μm or less for the same reason as D10.

  Furthermore, in the volume-based particle size distribution obtained by measuring by the laser diffraction / scattering particle size distribution measuring method, the particle size (D90) of 90% of the accumulated portion from the small particle size side is 190 μm or less (particularly less than 190 μm) Of these, 100 μm or less (particularly less than 100 μm) is particularly preferable. It has been found that particle sizes greater than 100 μm, particularly those greater than 190 μm, do not contribute to increasing external quantum efficiency. Accordingly, D90 is preferably 190 μm or less (particularly less than 190 μm), and particularly preferably 100 μm or less (particularly less than 100 μm).

In addition, in the volume-based particle size distribution obtained by measuring by the laser diffraction / scattering particle size distribution measuring method, the particle size (D50) of 50% of the accumulated amount from the small particle size side is preferably 7 μm to 50 μm, particularly It is preferably 8 μm to 50 μm, particularly preferably 12 μm to 50 μm.
At this time, the ratio (p10 / p50) of the frequency (%, p10) of the accumulated part 10% from the small particle side to the frequency (%, p50) of the accumulated part 50% from the small particle side. ) Is preferably 0.20 to 0.65, more preferably 0.20 to 0.60, and particularly preferably 0.20 to 0.55.
Here, “frequency” means the frequency (%) of the particle size of the corresponding ch when the range of 0.1 μm to 1000 μm is divided into 128 ch.

(Specific surface area)
The specific surface area of the green phosphor is preferably from 0.2~1.2m ² / g, especially 0.2~0.9m ² / g, with among others 0.2~0.6m ² / g Preferably there is.

(Features of this green phosphor)
The green phosphor is excited by light having a wavelength in the near ultraviolet region to the blue region (about 300 nm to 510 nm) and emits green light.

With regard to the emission spectrum of the present green phosphor, it has an emission peak in the region of wavelengths of 502 nm ± 30 nm to 557 nm ± 30 nm by photoexcitation at a wavelength of about 300 nm to 510 nm.
In addition, if this green fluorescent substance is the same composition, even if it excites with any wavelength of the near ultraviolet region-blue region wavelength (about 300 nm-510 nm), the point that the width and position of the emission spectrum do not change. There is one feature.

  Speaking of CIE chromaticity coordinates, this green phosphor is expressed by x = 0.05 to 0.40 and y = 0.50 to 0.80 by substituting a part of Sr with Ca and Ba. Green light, especially x = 0.15 to 0.35, y = 0.60 to 0.75, especially x = 0.25 to 0.33, y = 0.65 to 0.73 The indicated green light can be emitted.

This green phosphor is observed in the XRD pattern using CuKα rays measured by an X-ray diffractometer (XRD) at a (400) plane observed near 2θ = 17.0 ° and 2θ = 34.4 °. The observed diffraction peak of the (800) plane is relatively strong, and the peak intensity ratio with respect to the (444) plane observed near 2θ = 38.4 ° is (400) / (444) or (800 ) / (444) is greater than 1.0, particularly greater than 2.0, and more preferably greater than 3.0.
The peak intensity ratios (400) / (444) and (800) / (444) are from 1.0 by blending the Ga amount so as to be excessive from the stoichiometric composition and firing at a high temperature of 1000 ° C. or higher. The crystal growth in the a-axis direction can be promoted, whereby the quantum efficiency can be increased.
From this viewpoint, the firing temperature is preferably 1000 ° C. or higher, particularly 1100 ° C. or higher, and particularly preferably 1150 ° C. or higher.

(Production method)
Next, an example of a preferable method for producing the green phosphor will be described. However, it is not limited to the manufacturing method demonstrated below.

In this green phosphor, raw materials such as Sr raw material, Ga raw material, S raw material and Eu raw material are weighed and mixed, fired at 900 to 1400 ° C. in a reducing atmosphere, and crushed with a stamp mill or a rough machine. It can be obtained by classification with a sieve or the like, and preferably by further sedimentation in a non-aqueous organic solvent such as ethanol or water, followed by drying after removing the supernatant.
At this time, it is important to weigh and mix Sr and Ga so that the molar ratio (Ga / Sr) of the Ga content (addition amount) to the Sr content is 2.02 to 3.02.

Examples of the Sr source include strontium salts such as double oxides and carbonates in addition to Sr oxides. Examples of the Ga source include gallium salts such as Ga ₂ O ₃ and Ga ₂ S _3. Can do.
Examples of the S raw material include SrS, Ga ₂ S ₃ , EuS, S, BaS, SiS ₂ , Ce ₂ S ₃ , and H ₂ S gas. Examples of the Eu raw material include europium compounds (Eu salts) such as EuS, EuF ₃ , Eu ₂ O ₃ and EuCl ₃ .

In order to improve color rendering properties, rare earth elements such as Pr and Sm may be added to the raw material as a color adjusting agent.
In order to improve excitation efficiency, one or more elements selected from rare earth elements such as Sc, La, Gd, and Lu may be added to the raw material as a sensitizer.
However, these addition amounts are preferably 5 mol% or less with respect to Sr. When the content of these elements exceeds 5 mol%, a large amount of heterogeneous phases are precipitated, and the luminance may be remarkably lowered.
Further, alkali metal elements, monovalent cation metals such as Ag ⁺ , and halogen ions such as Cl ⁻ , F ⁻ and I ⁻ may be added to the raw material as charge compensators. The amount added is preferably about the same as the content of aluminum group or rare earth group in terms of charge compensation effect and luminance.

Mixing of the raw materials may be performed either dry or wet.
In the case of dry mixing, the mixing method is not particularly limited. For example, zirconia balls may be used as a medium, mixed with a paint shaker or a ball mill, and dried as necessary to obtain a raw material mixture. .
In the case of wet mixing, the raw material is in a suspension state, and after mixing with a paint shaker or a ball mill using zirconia balls as the medium, the medium is separated with a sieve, and dried under reduced pressure, vacuum dried, or sprayed. Water may be removed from the suspension by an appropriate drying method such as drying to obtain a dry raw material mixture.

  Before firing, the raw material mixture obtained as described above may be pulverized, classified and dried as necessary. However, crushing, classification, and drying are not necessarily performed.

Firing is preferably performed at 1000 ° C. or higher.
As the firing atmosphere at this time, a nitrogen gas atmosphere containing a small amount of hydrogen gas, a carbon dioxide atmosphere containing carbon monoxide, an atmosphere of hydrogen sulfide, carbon disulfide, other inert gas or reducing gas, etc. are adopted. However, firing in a hydrogen sulfide atmosphere is preferable. If the firing temperature is 1000 ° C. or higher, sufficient and uniform firing can be performed.
The upper limit of the firing temperature is determined by the durability temperature of the firing furnace, the decomposition temperature of the product, etc., but in the method for producing the green phosphor, firing at 1000 to 1200 ° C. is particularly preferable. Moreover, although baking time is related with baking temperature, it is about 2 to 24 hours.

In the above firing, when the raw material mixture does not contain a sulfur raw material, it is preferably fired in an atmosphere of hydrogen sulfide or carbon disulfide. However, when the raw material mixture contains a sulfur raw material, it can be fired in an atmosphere of hydrogen sulfide, carbon disulfide, or an inert gas. In this case, hydrogen sulfide and carbon disulfide may become a sulfur compound, and also have a function of suppressing decomposition of the product.
On the other hand, when hydrogen sulfide or carbon disulfide is used in the firing atmosphere, these compounds are also sulfur compounds. For example, when BaS is used as a raw material component, a barium compound and a sulfur compound are used. .

In the production of the present green phosphor, it is preferable that after firing, it is crushed with a stamp mill, a rough machine, a paint shaker or the like, and then classified with a sieve or the like. When crushing, it is preferable to adjust the crushing time so that the particle size does not become too fine.
In the classification using a sieve or the like, it is preferable to classify so as to cut a particle size larger than 150 μm, particularly a particle size larger than 130 μm, especially a particle size larger than 110 μm. Further, it is preferable to classify so as to cut a particle size smaller than 2 μm, particularly smaller than 3 μm, especially smaller than 4 μm.

  Furthermore, it is preferable to put in a non-aqueous organic solvent such as ethanol or water, stir while applying ultrasonic vibration, and let stand, collect the precipitate except for the supernatant, and then dry. By this last solvent sedimentation classification treatment, the internal quantum efficiency and the external quantum efficiency can be remarkably increased (see Example 6 described later).

(Use)
The green phosphor can be combined with an excitation source to form a green light emitting element or device, and can be used for various applications. For example, in addition to general illumination, it can be used for special light sources, liquid crystal backlights, display devices such as EL, FED, and CRT display devices.

As an example of a green light emitting element or device that combines the green phosphor and an excitation source that can excite the green phosphor, for example, in the vicinity of a light emitter that generates light having a wavelength of 300 nm to 510 nm (that is, purple light to blue light), that is, The green phosphor can be configured at a position where the light emitted from the light emitter can be received. Specifically, a phosphor layer made of the green phosphor may be laminated on a light emitter layer made of a light emitter.
At this time, the phosphor layer is prepared by, for example, adding the powdery green phosphor together with a binder to an appropriate solvent, thoroughly mixing and dispersing uniformly, and applying the obtained coating liquid to the surface of the light emitting layer. What is necessary is just to make it apply | coat and dry and form a coating film (phosphor layer).
Alternatively, the phosphor layer can be formed by kneading the green phosphor into a glass composition or a resin composition and dispersing the green phosphor in the glass layer or the resin layer.
Furthermore, the green phosphor may be formed into a sheet shape, and this sheet may be laminated on the phosphor layer, or the green phosphor may be directly sputtered onto the phosphor layer to form a film. You may do it.

  Further, a white light emitting element or device can be configured by combining the green phosphor, the red phosphor, the blue phosphor as necessary, and an excitation source that can excite them, for example, for general illumination. In addition, it can be used for special light sources, liquid crystal backlights, display devices such as EL, FED, and CRT display devices.

As an example of a white light emitting element or device configured by combining the green phosphor, the red phosphor, the blue phosphor as necessary, and an excitation source capable of exciting these, for example, light having a wavelength of 300 nm to 510 nm The green phosphor is disposed in the vicinity of a light emitter that generates (i.e., purple light to blue light), i.e., a position where the light emitted from the light emitter can be received, and a red phosphor and, if necessary, a blue phosphor It can comprise by arrange | positioning.
Specifically, a phosphor layer made of the green phosphor, a phosphor layer made of a red phosphor, and a phosphor layer made of a blue phosphor if necessary. What is necessary is just to laminate | stack.
In addition, the powdery green phosphor, red phosphor and, if necessary, the blue phosphor are added to a suitable solvent together with a binder, mixed thoroughly and dispersed uniformly, and the resulting coating solution is What is necessary is just to make it apply | coat and dry on the surface of a light emitting layer, and to form a coating film (phosphor layer).
Further, the green phosphor, the red phosphor and, if necessary, the blue phosphor are kneaded into a glass composition or a resin composition so that the phosphor is dispersed in the glass layer or the resin layer. Layers can also be formed.
In addition, a phosphor layer formed by kneading the green phosphor and the red phosphor in a resin may be formed on an excitation source composed of a blue LED or a near ultraviolet LED.
Furthermore, the green phosphor, the red phosphor and, if necessary, the blue phosphor may be formed into a sheet shape, and this sheet may be laminated on the phosphor layer. The phosphor and the red phosphor may be directly sputtered onto the phosphor layer to form a film.

(Glossary of terms)
In the present invention, the “light emitting element” in the “green light emitting element or apparatus” or “white light emitting element or apparatus” is a light emitting element that emits a relatively small light and includes at least a phosphor and a light emitting source as its excitation source. A device is intended, and a “light-emitting device” is intended to mean a light-emitting device that emits a relatively large amount of light and includes at least a phosphor and a light-emitting source as its excitation source.
In the present invention, when “X to Y” (X and Y are arbitrary numbers) is described, it means “preferably greater than X” or “preferably greater than Y” with the meaning of “X to Y” unless otherwise specified. The meaning of “small” is also included.
Further, when “X or more” (X is an arbitrary number) or “Y or less” (Y is an arbitrary number), an intention of “preferably larger than X” or “preferably smaller than Y” Is included.

  Hereinafter, the present invention will be described based on examples. However, the present invention is not construed as being limited to these.

<Composition analysis of phosphor>
The phosphor powders obtained in Example 1-11 and Comparative Example 1-6 were completely dissolved with hydrofluoric acid or the like, and an ICP (inductively coupled plasma) emission analyzer (SPS3000, manufactured by SII Nanotechnology Inc.) was used. The composition analysis was conducted. Tables 1 and 2 show the contents (wt%) of Ga, Sr, and Eu when the total amount of elements of the phosphor (Ga + Sr + Eu + S + unavoidable impurities) is 100 wt%.

<Measurement of PL emission spectrum>
About the phosphor powder obtained in Example 1-11 and Comparative Example 1-6, a PL (photoluminescence) spectrum was measured using a spectrofluorometer (manufactured by Hitachi, F-4500), and PL emission intensity was measured. The results are shown in Tables 1 and 2.

<Measurement of absorption rate, internal quantum efficiency, external quantum efficiency>
For the phosphor powders obtained in Example 1-11 and Comparative Example 1-6, the absorptance, internal quantum efficiency, and external quantum efficiency were measured as follows.
A spectrofluorophotometer FP-6500 and an integrating sphere unit ISF-513 (manufactured by JASCO Corporation) were used and the calculation was performed according to a solid quantum efficiency calculation program. The spectrofluorometer was corrected using a sub-standard light source and rhodamine B.
A calculation formula (Formula 1) of the absorptivity, internal quantum efficiency, and external quantum efficiency of the SrGa ₂ S ₄ : Eu phosphor when the excitation light is 466 nm is shown below.
The obtained results are shown in Tables 1 and 2.

Formula 1

<XRD measurement>
The phosphor powder obtained in Example 11 and Comparative Example 4-6 was used as a sample for X-ray diffraction, this sample was mounted on a holder, and MXP18 (Bruker AXS Co., Ltd.) was used. The angle and intensity of the diffraction line were measured under the following conditions and are shown in FIG.

(Tube) CuKα ray (Tube voltage) 40 kV
(Tube current) 150 mA
(Sampling interval) 0.02 °
(Scanning speed) 4.0 ° / min
(Starting angle) 5.02 °
(End angle) 80 °

(Example 1-5, Example 7-10, and Comparative Example 1-3)
Using SrS, Ga ₂ S ₃ and EuS as starting materials, each starting material was weighed and blended, and mixed with a paint shaker for 100 minutes using φ3 mm zirconia balls as media, and the resulting mixture was hydrogen sulfide Firing was performed at 1000 ° C. to 1150 ° C. for 6 hours in an atmosphere (see Table 1 for the firing temperature). Next, it is pulverized for 1 minute with a rakai machine (“ALM-360T” manufactured by Nippon Ceramic Science Co., Ltd.), using a 140 mesh mesh and a 440 mesh sieve, and under a 140 mesh mesh and 440 mesh openings. The mesh screen was collected to obtain phosphor powder composed of crystals represented by the general formula SrGa ₂ S ₄ : Eu ²⁺ .

(Example 6)
For the phosphor powder obtained in Example 3, ultrasonic waves (“W-113” manufactured by Honda Electronics Co., Ltd.) were applied at 28 Hz, 45 Hz, while stirring in a 99.5% ethanol solution (25 ° C.). After dispersing for 100 seconds in order and allowing to stand for 30 seconds, only the sediment that had been removed except for the supernatant was recovered, dried in a dryer (100 ° C.) for 10 minutes, and expressed by the general formula SrGa ₂ S ₄ : Eu ²⁺ A phosphor powder composed of the crystals shown was obtained.

(Discussion)
About the phosphor powder obtained in Comparative Example 1-3 and Example 1-10, when the excitation spectrum and the emission spectrum were measured, it was sufficiently excited by light having a wavelength of 300 nm to 510 nm (namely, purple light to blue light). Since two peaks were observed, it was confirmed that excitation was more sufficiently performed by near-ultraviolet light and blue light.
In addition, the emission peak position within a wavelength range of 502 nm ± 30 nm to 557 nm ± 30 nm is shown, and green light is emitted in a range of CIE chromaticity coordinates x = 0.05 to 0.40 and y = 0.50 to 0.80. Confirmed that it can.

Example 1-10 in which the molar ratio (Ga / Sr) of the Ga content to the Sr content is in the range of 2.02 to 3.02 is the molar ratio (Ga / Sr) of the stoichiometric composition Comparative Example 1 It was found that the internal quantum efficiency and the PL emission intensity were higher than those in FIG. Also, the molar ratio (Ga / Sr) is higher than that of Comparative Example 2 in which the molar ratio (Ga / Sr) is 1.70 or less and Comparative Example 2 in which the molar ratio (Ga / Sr) is 3.50 or more. Was found to be significantly higher in internal quantum efficiency and PL emission intensity.
In particular, Example 2-6 in which the molar ratio of Ga content (Ga / Sr) is in the range of 2.21 to 3.02 was found to have significantly higher internal quantum efficiency and PL emission intensity.

  Furthermore, comparing Example 3 and Example 6, it was also found that the internal quantum efficiency, the PL emission intensity, and the external quantum efficiency can be significantly improved by washing and sedimentation with ethanol.

  Further, from the viewpoint of light emission characteristics, the molar ratio (Ga / Sr) is preferably in the range of 2.10 to 3.10 (internal quantum efficiency of 72% or more), and more preferably in the range of 2.30 to 2.80. It was found to be more preferable (internal quantum efficiency of 77% or more).

(Example 11 and Comparative Example 4-6)
Using SrS, Ga ₂ S ₃ and EuS as starting materials, each starting material was weighed and blended, and mixed with a paint shaker for 100 minutes using φ3 mm zirconia balls as media, and the resulting mixture was hydrogen sulfide Firing was performed at 900 to 1150 ° C. for 6 hours in an atmosphere (see Table 2 for the firing temperature). Next, it is pulverized for 1 minute with a rakai machine (“ALM-360T” manufactured by Nippon Ceramic Science Co., Ltd.), using a 140 mesh mesh and a 440 mesh sieve, and under a 140 mesh mesh and 440 mesh openings. The mesh screen was collected to obtain a phosphor powder composed of crystals represented by the general formula SrGa ₂ S ₄ : Eu ²⁺ .
The obtained phosphor powder was measured for PL emission intensity, absorption rate, internal quantum efficiency, and external quantum efficiency, and are shown in Table 2.

A phosphor composed of a crystal represented by the general formula SrGa ₂ S ₄ : Eu ²⁺ having a Ga-rich composition and obtained by high-temperature firing at 1000 ° C. or higher has an X-ray diffraction pattern in the vicinity of 2θ = 17.0 °. The diffraction peaks of the (400) plane observed and the (800) plane observed in the vicinity of 2θ = 34.4 ° are relatively strong. The peak intensity ratio with the (444) plane observed near 2θ = 38.4 ° is (400) / (444) = 3.08, (800) /
(444) = 3.26. This suggests that the crystal plane in the a-axis direction of the SrGa ₂ S ₄ crystal that is the base material is preferentially developed.
Accordingly, the peak intensity ratios (400) / (444) and (800) / (800) / (800) / (800) / (800) / (800) / (800) / (800) / (800) / (800) / (800) /
(444) can be larger than 1, preferably larger than 3, that is, crystal growth in the a-axis direction can be promoted, whereby a phosphor having higher quantum efficiency than conventional can be obtained. Was found (see Example 11).

Even when fired at a high temperature of 1100 ° C., the phosphor adjusted in stoichiometric composition has a peak intensity ratio of (400) / (444) and (800) / (444) of 1 as shown in Comparative Example 4. The crystal growth in the a-axis direction is not promoted. Therefore, the internal quantum efficiency remains low, and the effect as in Example 11 is not obtained.
Moreover, even if it is Ga excess composition, in the fluorescent substance baked at 900 degreeC below 1000 degreeC, the peak intensity ratio of (400) / (444) and (800) / (444) like the comparative example 5 Is less than 1, and the crystal growth in the a-axis direction is not promoted. Therefore, the internal quantum efficiency remains low, and the effect of Example 11 is not obtained.

Note that the diffraction peak observed near 2θ = 34.4 ° of the X-ray diffraction pattern is shown as the (642) plane in the ICDD card or the like, but when actually calculated, it is observed near this 2θ. The peak to be detected was found to be the (800) plane. Therefore, in the present invention, the peak is treated as the (800) plane.
Experimentally, if the peak on the (400) plane increases, the peak tends to increase along with this, so it is more appropriate to consider the (800) plane.

Claims (4)

  A green phosphor containing a host crystal containing Sr, Ga and S and an emission center, and the molar ratio of Ga content to Ga content (Ga / Sr) is 2.02 to 3.02. A green phosphor characterized by that. The green phosphor according to claim 1, wherein Eu ²⁺ is contained as an emission center.   A green light emitting device or apparatus comprising an excitation source and the green phosphor according to claim 1. The white light emitting element thru | or apparatus provided with the excitation source, the green fluorescent substance of Claim 1 or 2, and the red fluorescent substance.

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