JP2017088719A - Red phosphor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a red phosphor having high luminance and high chromatic purity by irradiating blue color.SOLUTION: There is provided a red phosphor having an eutectic crystal of alkali earth metal sulfide (containing at least one kind of metal selected from magnesium, calcium and barium) and SrGaS(mass concentration calculated by all pattern fitting method from a powder X ray diffraction pattern is in a range of 5 to 60% in the red phosphor) as a base material, which is activated by europium contained at 0.005 to 0.1 mol per mole number 1 mol by summing mole number of the alkali earth metal atom and mole number of strontium atom.SELECTED DRAWING: Figure 1

Description

The present invention relates to a red phosphor.

White light emitting elements are used for LEDs used for illumination, backlights of liquid crystal displays, and the like. As the white light emitting element, a blue light emitting element, a green light emitting element, and a red light emitting element are used. A sulfide phosphor is known as such a red light-emitting element, and a phosphor is obtained by adding a europium compound as an activator to calcium or strontium carbonate or sulfate and firing it in hydrogen sulfide. It is known to produce
Further, even if the red phosphor has the same luminous intensity as that of the green phosphor in physical observation, the luminance appears low because of low visibility. Therefore, it has been desired to increase the brightness of the red phosphor.

In order to improve the luminance of the red phosphor, Patent Document 1 discloses that a red phosphor having calcium sulfide and / or strontium sulfide as a base and europium as a luminescent center, and an aluminum group element (Al, Ga) as a sensitizer. , In), and further, a red phosphor containing fluorine is disclosed.

JP 2005-146190 A

Even the red phosphor disclosed in Patent Document 1 cannot be said to have sufficient luminance and color purity from the viewpoint of color reproducibility, and a red phosphor having high luminance and high color purity is desired. It was.

In view of the above problems, an object of the present invention is to provide a red phosphor having high luminance and high color purity.

The present inventors have found that a red phosphor having high luminance and high color purity can be obtained by using a eutectic of a predetermined amount of Sr ₂ Ga ₂ S ₅ and an alkaline earth metal sulfide. The present invention has been conceived.

That is, the red phosphor of the present invention is based on an eutectic of alkaline earth metal sulfide and Sr ₂ Ga ₂ S _5, and the eutectic is activated by europium. And

The eutectic in this specification _refers to a crystal phase of Sr 2 _Ga 2 _{S 5,} those crystal phase and / or amorphous phase of Sr 2 _Ga 2 _{S 5} other than the alkaline earth metal-containing compound are both.

It includes a generally strontium, gallium, and sulfur, red phosphor activated with europium, and strontium, and gallium, and sulfur, often present as SrGa ₂ S _4, Sr ₂ Ga Almost no ₂ S ₅ exists.
On the other hand, Sr ₂ Ga ₂ S ₅ exists in the red phosphor of the present invention. Therefore, the red phosphor of the present invention can emit red fluorescence with high luminance and high color purity.
The principle that the above effect can be obtained when Sr ₂ Ga ₂ S ₅ is present is not clear, but is thought to be due to some interaction with the alkaline earth metal sulfide.

In the red phosphor of the present invention, it is desirable that the mass concentration of the Sr ₂ Ga ₂ S _{5 in} the red phosphor calculated from the powder X-ray diffraction pattern by a total pattern fitting method is in the range of ₅ to 65 wt%. .

The red phosphor of the present invention has a number of moles per mole of the total number of moles of alkaline earth metal atoms derived from the alkaline earth metal sulfide and the number of moles of strontium atoms derived from the Sr ₂ Ga ₂ S ₅ . It is desirable to contain 0.005-0.10 mol of the above europium.

In the red phosphor of the present invention, the alkaline earth metal sulfide is preferably strontium sulfide.

The red phosphor of the present invention preferably further contains at least one metal selected from the group consisting of magnesium, calcium and barium in the eutectic.

The red phosphor of the present invention preferably contains 0.001 to 0.95 mol of at least one metal atom selected from the group consisting of magnesium, calcium and barium per mol of strontium in the eutectic. .

The red phosphor of the present invention can emit red fluorescence with high luminance and high color purity when irradiated with blue light.

FIG. 1 is a diagram showing emission spectra of red phosphors of Examples 1 to 5 and Comparative Example 1. FIG. 2 is a diagram showing powder X-ray diffraction patterns of the red phosphors of Examples 1 to 5. FIG. 3 is a scanning electron micrograph of the cross section of the red phosphor of Example 3. FIG. 4 is an analysis image showing a mapping result of strontium in the cross section of the red phosphor of FIG. FIG. 5 is an analysis image showing a mapping result of gallium in the cross section of the red phosphor of FIG.

Hereinafter, the red phosphor of the present invention will be specifically described. However, the present invention is not limited to the following description, and can be appropriately modified and applied without departing from the scope of the present invention.

The red phosphor of the present invention is based on an eutectic of alkaline earth metal sulfide and Sr ₂ Ga ₂ S _5, and the eutectic is activated by europium. .

In the red phosphor of the present invention, the alkaline earth metal sulfide is preferably a substance represented by the general formula AS [A is an alkaline earth metal (Ca, Sr, or Ba), and S is a sulfur element]. More preferred is strontium sulfide or calcium sulfide, and most preferred is strontium sulfide. The alkaline earth metal sulfide constitutes a matrix that emits red fluorescence. Further, when the alkaline earth metal sulfide is strontium sulfide, a red phosphor having a bright and strong fluorescence intensity is obtained.

The base material of the red phosphor of the present invention is a eutectic of alkaline earth metal sulfide and Sr ₂ Ga ₂ S ₅ . The eutectic is obtained, for example, by firing an alkaline earth metal source, a gallium source, and a sulfur source. Furthermore, the alkaline earth metal atom derived from the alkaline earth metal sulfide or the strontium atom derived from Sr ₂ Ga ₂ S ₅ in the matrix is partially substituted with europium. That is, the red phosphor of the present invention is activated with europium.
The red phosphor of the present invention may contain, in addition to the eutectic and europium, an alkaline earth metal derived from the raw material, gallium, sulfur, and the like and these compounds.

The mass concentration of Sr ₂ Ga ₂ S ₅ calculated by the total pattern fitting method from the powder X-ray diffraction pattern of the red phosphor of the present invention is preferably 5 to 65 wt%, more preferably 5 to 25 wt%. desirable.
When the mass concentration of Sr ₂ Ga ₂ S ₅ is within this range, it emits red fluorescence with high luminance and high color purity when irradiated with blue light.

This is because, when the mass concentration of Sr ₂ Ga ₂ S _{5 in} the red phosphor is 5 wt% or more, the effect that Sr ₂ Ga ₂ S ₅ is contained is preferably obtained, and the light emission of the red phosphor The intensity can be improved sufficiently, but on the other hand, when Sr ₂ Ga ₂ S ₅ is irradiated with blue light, it emits green to yellow (500 to 570 nm) fluorescence. At this time, when the mass concentration of Sr ₂ Ga ₂ S ₅ exceeds 65 wt%, a lot of green to yellow fluorescence may be emitted, so that bright red may not be obtained. However, when the mass concentration of Sr ₂ Ga ₂ S ₅ is 65 wt% or less, green to yellow fluorescence is suppressed, and a bright red color is easily obtained. Furthermore, it is estimated that the emission intensity is less likely to decrease due to the emission of green to yellow fluorescence.

Here, a measurement method for the mass concentration calculated from the measurement method of the powder X-ray diffraction pattern and the total pattern fitting method will be described.
The powder X-ray diffraction pattern can be measured under the following conditions using a powder X-ray diffractometer (device name: Rigaku Corporation, sample horizontal strong X-ray diffractometer RINT-TTRIII).
Optical system: Parallel beam optical system (long slit: PSA200 / aperture angle: 0.057 °)
・ Target: Direct drive type rotor target (DPTA-II Cu)
Measurement range (2θ): 60 ° to 90 °
・ Step width: 0.02 °
-Counting time: 1.0 sec.
For the quantification by the total pattern fitting method, the powder X-ray diffraction pattern obtained by the above measurement method is analyzed by a powder X-ray diffraction pattern comprehensive analysis software (JADE Version 7.0, manufactured by Materials Data. Inc.). be able to.

In the red phosphor of the present invention, the number of moles of the alkaline earth metal atoms derived from the alkaline earth metal sulfide and the number of moles of strontium atoms derived from the Sr ₂ Ga ₂ S ₅ are combined per mole of 1 mol. It is further desirable to contain 0.005 to 0.10 mol of europium.
When the amount of this europium is less than 0.005 mol, it becomes difficult to obtain sufficient emission intensity.
If the amount of europium exceeds 0.10 mol, the emission intensity is saturated, but other physical properties may be affected.

The red phosphor of the present invention may further contain a coactivator other than europium. Although it does not specifically limit as a co-activator, The compound or ion of rare earth elements other than europium is mentioned. Examples of rare earth elements other than the above europium are selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, etc. Examples include at least one element. Examples of the rare earth element compounds include carbonates, oxides, chlorides, sulfates, nitrates, and acetates of the above elements.

The alkaline earth metal sulfide contained in the eutectic of alkaline earth metal sulfide and Sr ₂ Ga ₂ S ₅ is preferably strontium sulfide, and the eutectic further contains magnesium, calcium and barium. It is more desirable to include at least one metal selected from the group consisting of:
The metal source is preferably magnesium, calcium or barium oxide, carbonate, hydroxide, halide, sulfate, nitrate, phosphate, hydrogen phosphate, and the like. When these metals are contained in the eutectic, the maximum wavelength of the red phosphor shifts. Therefore, a red phosphor having a maximum wavelength according to the application can be selected.

The red phosphor may contain 0.001 to 0.95 mol of at least one metal atom selected from the group consisting of magnesium, calcium and barium per mol of strontium in the eutectic. .
When the content of magnesium, calcium, and barium is within this range, the maximum wavelength of the red phosphor can be shifted without lowering the emission intensity of the red phosphor, and the desired maximum wavelength can be obtained.

Next, an example of the method for producing the red phosphor of the present invention will be described.

(1) Raw material mixing step First, in this step, a strontium compound, a gallium compound, and a europium compound are mixed. In addition, a magnesium compound, a calcium compound, a barium compound, or the like may be added.

Examples of the strontium compound include, but are not limited to, strontium carbonate, strontium oxide, strontium hydroxide, strontium halide (such as strontium chloride), strontium sulfate, strontium nitrate, strontium hydrogen phosphate, strontium sulfide, and the like.
Examples of the magnesium compound include, but are not limited to, magnesium carbonate, magnesium oxide, magnesium hydroxide, magnesium halide (magnesium chloride, etc.), magnesium sulfate, magnesium nitrate, magnesium hydrogen phosphate, magnesium sulfide, and the like.
Examples of the calcium compound include, but are not limited to, calcium carbonate, calcium oxide, calcium hydroxide, calcium halide (calcium chloride and the like), calcium sulfate, calcium nitrate, calcium hydrogen phosphate, calcium sulfide and the like.
Examples of the barium compound include, but are not limited to, barium carbonate, barium oxide, barium hydroxide, barium halide (such as barium chloride), barium sulfate, barium nitrate, barium hydrogen phosphate, and barium sulfide.

When at least one compound selected from the group consisting of magnesium compounds, calcium compounds and barium compounds is used, it is selected from the group consisting of magnesium compounds, calcium compounds and barium compounds per mol of strontium in the strontium compounds. It is desirable to use 0.001 to 0.95 mol of at least one metal atom.

The gallium compound is not particularly limited, and examples thereof include gallium oxide, gallium sulfate, gallium sulfide, gallium nitrate, gallium bromide, gallium chloride, and gallium iodide.

The europium compound is not particularly limited, and examples thereof include europium carbonate, europium oxide, europium chloride, europium sulfate, europium nitrate, and europium acetate.

In the raw material mixing step, the strontium compound, the gallium compound, and the europium compound are mixed at a predetermined molar ratio. In this step, a co-activator other than europium, a dispersant, a flux component, and the like may be further added.
More preferably, the mixing ratio of the strontium compound and the europium compound is such that the molar ratio is strontium atom: europium atom = 1: 0.005-0.05.
The mixing ratio of the strontium compound and the gallium compound is more preferably such that the molar ratio is strontium atom: gallium atom = 1: 0.001-1.0.
Furthermore, the mixing ratio of the gallium compound and the europium compound is more preferably such that the molar ratio is gallium atom: europium atom = 1: 0.02-0.10. When the gallium compound and the europium compound are mixed at this ratio, the red phosphor obtained through the subsequent steps contains Sr ₂ Ga ₂ S ₅ .
Furthermore, the mass concentration of Sr ₂ Ga ₂ S ₅ calculated from the powder X-ray diffraction pattern by the total pattern fitting method can be in the range of ₅ to 65 wt%.

The mixing in the raw material mixing step is preferably performed by adding water to these raw materials to form a slurry, and further mixing a grinding medium such as alumina balls to perform wet grinding.
The type of the grinding medium is not particularly limited, and examples thereof include alumina balls, zirconia balls, silicon nitride balls, carbon nitride balls, glass beads, nylon-coated iron core balls, and the like. Mainly used. Of these, alumina balls are preferable.

The pulverization can be performed by a known pulverizer, and the type of the pulverizer is not particularly limited. However, in order to efficiently perform the pulverization, a reaction vessel equipped with a pulverization medium stirring type pulverizer is used. preferable. Here, the pulverization medium stirring type pulverizer refers to the pulverization medium that is put into the pulverization container and stirred together with the object to be pulverized by rotating and rotating (rotating or revolving) the pulverization container. This is a pulverizer that performs pulverization with direct stirring. An example of the pulverization medium stirring type pulverizer is not particularly limited, but is preferably any one selected from the group consisting of a planetary mill, a bead mill, and a vibration mill. Among these, a planetary mill with rotation and revolution is particularly preferable.

(2) Drying process After grinding, it is desirable to separate the grinding media and perform the drying process.
The drying is desirably performed at 110 to 150 ° C. for about 1 to 48 hours using any commonly used dryer.

The solid obtained by drying is preferably made into a powder having an average particle diameter of 60 μm or less by pulverization and classification.
The pulverization can be performed by the above-described pulverization medium stirring type pulverizer.

(3) Firing step Subsequently, firing is performed in a sulfur-containing gas atmosphere to generate an eutectic of alkaline earth metal sulfide and Sr ₂ Ga ₂ S ₅ . As the sulfur source, hydrogen sulfide gas, hydrogen sulfide gas, a mixed gas of carbon disulfide and an inert gas, or the like can be used. When a mixed gas is used, the concentration of sulfur compounds such as hydrogen sulfide gas and carbon disulfide is preferably 10% by volume or more.
The firing conditions are desirably 700 to 900 ° C. and about 2 to 12 hours.
As a baking apparatus, it can carry out using arbitrary baking furnaces, such as a muffle furnace and a tubular furnace.

The solid obtained by firing is desirably made into a red phosphor as a final product as a powder having an average particle size of about 10 to 60 μm by pulverization and classification. At this time, particles of 50 μm or more may be removed by using a sieve.

According to the above process, a red phosphor that is based on a eutectic of alkaline earth metal sulfide and Sr ₂ Ga ₂ S ₅ and in which the eutectic is activated by europium can be produced. .
Since this red phosphor emits red fluorescence with high luminance and high color purity when irradiated with blue light, it is suitable for use as a material for a white light emitting element or the like.

In order to illustrate the present invention in detail, the following examples are given. However, the present invention is not limited to these examples.

Example 1
The red phosphor according to Example 1 was manufactured by the following method.
(1) Strontium carbonate, gallium oxide, and europium oxide were prepared as raw materials for the mixing process.
Next, water was added to the mixture in which the above raw materials were mixed to form a slurry, and the mixture was mixed for 30 minutes by a wet method using a planetary ball mill using φ1.5 mm alumina balls as grinding media.
Under the present circumstances, it prepared so that the molar ratio of the strontium atom, gallium atom, and europium atom contained in the said mixture might be set to strontium atom: gallium atom: europium atom = 0.982: 0.05: 0.018. .

(2) Drying step Next, the slurry of the alumina balls and the raw material mixture was separated, and the resulting slurry was put in a drier at a preset temperature of 130 ° C. and dried overnight.

(3) Firing step After the obtained solid was pulverized with a mortar and pestle and classified, the mixture exceeding 150 μm was removed. Further, these mixtures were placed in a quartz boat, and a synthetic quartz tubular furnace at 900 ° C. for 4 hours. Firing was performed in an atmosphere containing hydrogen sulfide gas. Hydrogen sulfide gas having a purity of 99.9% was injected into the tubular furnace at 200 mL / min.

Next, the obtained solid was pulverized with a mortar and pestle and classified to produce a red phosphor according to Example 1, except for those exceeding 50 μm.

(Example 2) to (Example 5) and (Comparative Example 1)
Except that the molar ratio of strontium atoms, gallium atoms and europium atoms contained in a mixture of strontium carbonate, gallium oxide and europium oxide was adjusted as shown in Table 1, it was the same as in Example 1. Red phosphors according to Examples 2 to 5 and Comparative Example 1 were produced.

(Maximum wavelength and photoluminescence relative intensity evaluation)
About the manufactured red fluorescent substance of Examples 1-5 and the comparative example 1, the excitation wavelength was 450 nm and the emission spectrum was measured using the spectrofluorimeter (the JASCO make, FP-6500).
In FIG. 1, the emission spectrum of the red fluorescent substance of Examples 1-5 and the comparative example 1 is shown.
Table 1 shows the photoluminescence (Photo Luminescence) relative intensity of the red phosphors of Examples 1 to 5 and Comparative Example 1 based on FIG. 1 and the maximum wavelength that is the wavelength when the emission intensity shows the maximum value. .
The photoluminescence relative intensity is a relative intensity when the emission intensity in Comparative Example 1 is 100%.

As shown in Table 1 and FIG. 1, the red phosphors of Examples 1 to 5 had a photoluminescence relative intensity of 140% or more as compared with Comparative Example 1. In particular, the red phosphors of Examples 3 to 5 had a photoluminescence relative intensity of about 380 to 590% with respect to Comparative Example 1.

(Powder X-ray diffraction evaluation)
The red phosphors according to Examples 1 to 5 were analyzed by powder X-ray diffraction.
The powder X-ray diffraction pattern was measured with a powder X-ray diffractometer (device name: Rigaku Corporation, sample horizontal strong X-ray diffractometer RINT-TTRIII) under the following conditions.
Optical system: Parallel beam optical system (long slit: PSA200 / aperture angle: 0.057 °)
・ Target: Direct drive type rotor target (DPTA-II Cu)
Measurement range (2θ): 60 ° to 90 °
・ Step width: 0.02 °
-Counting time: 1.0 sec.
And the quantification by all pattern fitting methods analyzed the powder X-ray-diffraction pattern obtained by the said measuring method with the powder X-ray-diffraction pattern comprehensive analysis software (JADE Version 7.0, Materials Data. Inc. product). .
The results are shown in FIG. FIG. 2 is a diagram showing powder X-ray diffraction patterns of the red phosphors of Examples 1 to 5.

In the powder X-ray diffraction pattern, SrS has strong peaks at 25-26 °, 29-30 °, 42-43 °, 50-51 °, 52-53 ° (indicated by black circles in FIG. 2), and Sr ₂ Ga ₂ S ₅ has a large number of peaks (indicated by black triangles in FIG. 2), particularly a strong peak at 22 to 35 ° and a maximum peak at 25 to 26 °.
As shown in FIG. 2, in the prepared red phosphors according to Examples 1 to ₅ , the crystal phase of strontium and gallium composite sulfide Sr ₂ Ga ₂ S _{5 and} the crystal phase of SrS are formed. understood. In addition, Ga compounds other than Sr ₂ Ga ₂ S ₅ could not be confirmed.

Next, the mass concentration of the Sr ₂ Ga ₂ S ₅ crystal phase and the SrS crystal phase was determined from the powder X-ray diffraction pattern by a total pattern fitting method. The results are shown in Table 2.

As shown in Table 2, it was found that the mass concentration of the crystal phase of Sr ₂ Ga ₂ S ₅ increased in proportion to the amount of gallium mixed during production.

(Distribution evaluation of strontium and gallium)
The cross section of the red phosphor according to Example 3 was subjected to elemental analysis of strontium and gallium by mapping analysis using an energy dispersive X-ray analyzer (manufactured by Oxford Instruments). The results are shown in FIG. FIG. 3 is a scanning electron micrograph of the cross section of the red phosphor of Example 3. Further, strontium mapping and gallium mapping in the cross section of the red phosphor in FIG. 3 were performed. The results are shown in FIGS. FIG. 4 is an analysis image showing a mapping result of strontium in the cross section of the red phosphor of FIG. FIG. 5 is an analysis image showing a mapping result of gallium in the cross section of the red phosphor of FIG.
As shown in FIGS. 4 and 5, it was found that strontium and gallium are uniformly distributed in the red phosphor particles. The distribution of these strontium and gallium hardly changed even when the observation place was changed.

As described above, the red phosphor of the present invention exhibits a sensitizing effect by eutecticizing alkaline earth metal sulfide and Sr ₂ Ga ₂ S _5, and exhibits high luminance light emission.

Claims (6)

A red phosphor having a base of an eutectic of alkaline earth metal sulfide and Sr ₂ Ga ₂ S ₅ , wherein the eutectic is activated by europium. _2. The red phosphor according to claim 1, wherein a mass concentration of the Sr ₂ Ga ₂ S _{5 in} the red phosphor calculated by a total pattern fitting method from a powder X-ray diffraction pattern is in a range of ₅ to 65 wt%. 0.005 to 0 of the europium per mole of the total number of moles of alkaline earth metal atoms derived from the alkaline earth metal sulfide and the moles of strontium atoms derived from the Sr ₂ Ga ₂ S ₅ The red phosphor according to claim 1 or 2, comprising .10 mol. The red phosphor according to claim 1, wherein the alkaline earth metal sulfide is strontium sulfide. The red phosphor according to claim 4, wherein the eutectic further contains at least one metal selected from the group consisting of magnesium, calcium, and barium. 6. The red phosphor according to claim 5, comprising 0.001 to 0.95 mol of at least one metal atom selected from the group consisting of magnesium, calcium and barium per mol of strontium in the eutectic.