JP6512070B2 - Red phosphor - Google Patents

Description

The present invention relates to a red phosphor.

White light emitting elements are used for LEDs used for lighting, back lights of liquid crystal displays, and the like. As a 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 europium compound is added as an activator to a carbonate or sulfate of calcium or strontium, and the phosphor is fired in hydrogen sulfide. It is known to manufacture.
In addition, since the red phosphor has low visibility even if the emission intensity in physical observation is the same as that of the green phosphor, the luminance looks low as a result. Therefore, it has been desired to increase the luminance of the red phosphor.

In order to improve the luminance of a red phosphor, Patent Document 1 describes an aluminum group element (Al, Ga) as a sensitizer in a red phosphor having calcium sulfide and / or strontium sulfide as a matrix center and europium as a luminescence center. , In) and further contains a fluorine-containing red phosphor.

JP, 2005-146190, A

Even in the case of a red phosphor as disclosed in Patent Document 1, a red phosphor having high luminance and high color purity is desired because luminance and color purity are not sufficient in terms of color reproducibility. The

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 brightness and high color purity can be obtained by using a predetermined amount of Sr ₂ Ga ₂ S ₅ and an alkaline earth metal sulfide as a eutectic. The present invention was conceived.

That is, the red phosphor of the present invention is characterized in that a eutectic of an alkaline earth metal sulfide and Sr ₂ Ga ₂ S ₅ is a matrix, and the eutectic is activated by europium. I assume.

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.

In general, a europium-activated red phosphor containing strontium, gallium and sulfur often contains strontium, gallium and sulfur as SrGa ₂ S ₄ , Sr ₂ Ga as ₂ S ₅ hardly exist.
On the other hand, in the red phosphor of the present invention, Sr ₂ Ga ₂ S ₅ is present. Therefore, the red phosphor of the present invention can emit red fluorescence with high luminance and high color purity.
Although the principle by which the above-mentioned effect is obtained is not clear when Sr ₂ Ga ₂ S ₅ is present, it is considered to be due to some kind of interaction with the alkaline earth metal sulfide.

In the red phosphor of the present invention, it is preferable 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 the whole pattern fitting method is in the range of ₅ to 65 wt% .

The red phosphor of the present invention has a number of moles of the alkaline earth metal atom derived from the alkaline earth metal sulfide and a number of moles of the strontium atom derived from the Sr ₂ Ga ₂ S ₅ in total. It is desirable that 0.005 to 0.10 mol of the above-mentioned europium be included.

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

It is desirable that the red phosphor of the present invention further contains at least one metal selected from the group consisting of magnesium, calcium and barium in the above-mentioned 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 mole of strontium in the eutectic. .

The red phosphor of the present invention can emit red light with high luminance and high color purity by being 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 figure which shows the powder X-ray-diffraction pattern of the red fluorescent substance of Examples 1-5. 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 the mapping result of strontium in the cross section of the red phosphor of FIG. FIG. 5 is an analysis image showing the 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 a eutectic of an alkaline earth metal sulfide and Sr ₂ Ga ₂ S _5, and the eutectic is characterized by being 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), S is a sulfur element], Strontium sulfide or calcium sulfide is more desirable, and strontium sulfide is most desirable. The alkaline earth metal sulfides constitute a host that emits red fluorescence. In addition, when the alkaline earth metal sulfide is strontium sulfide, it becomes a bright red fluorescent substance having high fluorescence intensity.

The matrix of the red phosphor of the present invention is a eutectic of an 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, alkaline earth metals derived from raw materials, gallium, sulfur and the like and compounds thereof.

The mass concentration of Sr ₂ Ga ₂ S ₅ calculated from the powder X-ray diffraction pattern of the red phosphor of the present invention by the whole pattern fitting method 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 in this range, by being irradiated with blue light, it emits red fluorescence with high luminance and high color purity.

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 of containing Sr ₂ Ga ₂ S ₅ is suitably obtained, and the light emission of the red phosphor The intensity is likely to be sufficiently improved, 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 large amount of green to yellow fluorescence may be emitted, and thus a bright red may not be obtained. However, if 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 decrease in emission intensity due to the emission of green to yellow fluorescence is less likely to occur.

Here, a method of measuring a powder X-ray diffraction pattern and a method of measuring a mass concentration calculated from the whole pattern fitting method will be described.
The powder X-ray diffraction pattern can be measured by a powder X-ray diffractometer (apparatus name: manufactured by Rigaku Corporation, sample horizontal high-power 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 the whole pattern fitting method analyzes the powder X-ray-diffraction pattern obtained by the said measuring method by powder X-ray-diffraction pattern general analysis software (JADE Version 7.0, Materials Data. Inc. make). be able to.

In the red phosphor of the present invention, the number of moles of the alkaline earth metal atom derived from the alkaline earth metal sulfide and the number of moles of the strontium atom derived from the Sr ₂ Ga ₂ S ₅ are total It is further desirable that 0.005 to 0.10 mol of europium be included.
When the amount of europium is less than 0.005 mol, it is difficult to obtain sufficient luminescence intensity.
When the amount of europium exceeds 0.10 mol, while the emission intensity is saturated, it may affect other physical properties.

The red phosphor of the present invention may further contain coactivators other than europium. The coactivator is not particularly limited, but includes compounds or ions of rare earth elements other than europium. Examples of the rare earth elements other than europium are selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and the like. At least one or more elements can be mentioned. Moreover, as a compound of the said rare earth elements, carbonate of the said element, an oxide, a chloride, a sulfate, nitrate, acetate, etc. are mentioned.

Strontium sulfide is desirable as the alkaline earth metal sulfide contained in the eutectic of alkaline earth metal sulfide and Sr ₂ Ga ₂ S _5, and magnesium, calcium and barium are further contained in the eutectic. It is more desirable to include at least one metal selected from the group consisting of
The metal source is preferably an oxide of magnesium, calcium or barium, a carbonate, a hydroxide, a halide, a sulfate, a nitrate, a phosphate, a hydrogen phosphate and the like. When these metals are contained in the eutectic, the maximum wavelength of the red phosphor shifts. Therefore, it is possible to select a red phosphor having a maximum wavelength according to the application.

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 mole of strontium in the eutectic. .
When the content of magnesium, calcium and barium is in this range, the maximum wavelength of the red phosphor can be shifted without reducing the emission intensity of the red phosphor, and a desired maximum wavelength can be obtained.

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

(1) Raw material mixing process First, at this process, a strontium compound, a gallium compound, and a europium compound are mixed. In addition to these, magnesium compounds, calcium compounds, barium compounds and the like may be added.

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

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 mole of the number of moles 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, gallium iodide and the like.

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

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 coactivator other than the above-described europium, a dispersant, a flux component and the like may be further added.
It is more desirable that the mixing ratio of the strontium compound to the europium compound be such that the molar ratio is strontium atom: europium atom 1: 0.005 to 0.05.
Further, as for the mixing ratio of the strontium compound and the gallium compound, it is more preferable that the molar ratio be strontium atom: gallium atom = 1: 0.001 to 1.0.
Furthermore, as for the mixture ratio of a gallium compound and a europium compound, it is more desirable to make it a molar ratio be 1: 0.02-0.10 of a gallium atom: europium atom. When the gallium compound and the europium compound are mixed in this proportion, the red phosphor obtained through the subsequent steps will contain 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 whole pattern fitting method can be in the range of ₅ to 65 wt%.

In the mixing in the raw material mixing step, it is desirable to add water to these raw materials to form a slurry, and further mix grinding media such as alumina balls to perform wet grinding.
The type of grinding media 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, and those having a diameter of 10 mm or less Mainly used. Among them, alumina balls are preferable.

Pulverization can be performed by a known pulverizer, and the type of pulverizer is not particularly limited, but in order to efficiently pulverize, it is preferable to use a reaction vessel equipped with a pulverizing medium agitation type pulverizer. preferable. Here, with the grinding medium stirring type grinding machine, the grinding medium is put into the grinding container, and the grinding container is shaken or rotated (rotation or revolution) with the object to be ground, or the grinding medium is stirred. In the above, it is a crusher that carries out direct crush and crush. An example of the grinding medium agitation 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 vibrating mill. Among them, a planetary mill with rotation and revolution is particularly preferable.

(2) Drying Step After the pulverization, it is desirable to separate the pulverizing medium and carry out the drying step.
Desirably, drying is preferably carried out at 110 to 150 ° C. for about 1 to 48 hours using any commonly used dryer.

The solid obtained by drying is preferably pulverized and classified to a powder having an average particle diameter of 60 μm or less.
The grinding can be carried out by the above-mentioned grinding medium stirring type grinder.

(3) Firing Step Subsequently, firing is performed in a sulfur-containing gas atmosphere to form a eutectic of an alkaline earth metal sulfide and Sr ₂ Ga ₂ S ₅ . As a 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 a sulfur compound such as hydrogen sulfide gas or carbon disulfide is preferably 10% by volume or more.
The firing conditions are preferably 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 pulverized or classified into a powder having an average particle diameter of about 10 to 60 μm to form a red phosphor as a final product. At this time, particles of 50 μm or more may be removed by using a sieve or the like.

According to the above process, a red phosphor having an eutectic of alkaline earth metal sulfide and Sr ₂ Ga ₂ S ₅ as a base, wherein the eutectic is activated by europium can be produced. .
The red phosphor emits red light with high luminance and high color purity by being irradiated with blue light, and thus is suitable for use as a material for a white light emitting element or the like.

The following examples are provided to further illustrate the present invention. However, the present invention is not limited by these examples.

Example 1
The red phosphor according to Example 1 was manufactured by the following method.
(1) Mixing Step Strontium carbonate, gallium oxide and europium oxide were prepared as raw materials.
Next, water was added to the mixture obtained by mixing the above raw materials to form a slurry, and mixing was carried out for 30 minutes by a wet method using a planetary ball mill, using alumina balls of φ 1.5 mm as grinding media.
At this time, the molar ratio of the strontium atom, the gallium atom, and the europium atom contained in the above mixture was adjusted to be strontium atom: gallium atom: europium atom = 0.982: 0.05: 0.018 .

(2) Drying Step Subsequently, the slurry of alumina balls and the raw material mixture was separated, and the obtained slurry was placed in a dryer at a set temperature of 130 ° C. and dried overnight.

(3) Firing step The obtained solid is crushed and classified with a mortar and pestle and classified to remove those exceeding 150 μm, and further, these mixtures are put in a quartz boat, and 900 ° C. for 4 hours in a synthetic quartz tube furnace It baked in the atmosphere containing hydrogen sulfide gas. Hydrogen sulfide gas with a purity of 99.9% was injected into the tubular furnace at 200 mL / min.

Subsequently, the obtained solid was crushed and classified with a mortar and a pestle, and classified to remove the one exceeding 50 μm, thereby producing a red phosphor according to Example 1.

(Example 2) to (Example 5) and (Comparative Example 1)
Similar to Example 1 except that the molar ratio of strontium atom, gallium atom and europium atom contained in the mixture of strontium carbonate, gallium oxide and europium oxide is prepared as shown in Table 1. The red fluorescent substance concerning Example 2-5 and the comparative example 1 was manufactured.

(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 made into 450 nm and the measurement of the emission spectrum was performed using the spectrofluorophotometer (The Nippon Bunko Co., Ltd. make, FP-6500).
The emission spectrum of the red fluorescent substance of Examples 1-5 and the comparative example 1 is shown in FIG.
The photoluminescence (Photo Luminescence) relative intensity of the red fluorescent substance of Examples 1-5 based on FIG. 1 and Comparative example 1 and the maximum wavelength which is a wavelength when luminescence intensity shows the maximum in Table 1 are shown. .
The photoluminescence relative intensity is a relative intensity when the light emission intensity in Comparative Example 1 is 100%.

As shown in Table 1 and FIG. 1, the red phosphors of Examples 1 to 5 have a photoluminescence relative intensity of 140% or more as compared with Comparative Example 1. In particular, the red phosphors of Examples 3 to 5 have a relative photoluminescence intensity of about 380 to 590% relative 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 by a powder X-ray diffractometer (apparatus name: manufactured by Rigaku Corporation, sample horizontal high-power 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 the whole pattern fitting method analyzed the powder X-ray-diffraction pattern obtained by the said measuring method by powder X-ray-diffraction pattern general analysis software (JADE Version 7.0, Materials Data. Inc. make). .
The results are shown in FIG. FIG. 2: is a figure which shows the powder X-ray-diffraction pattern of the red fluorescent substance of Examples 1-5.

In the powder X-ray diffraction pattern, SrS has strong peaks at 25 to 26 °, 29 to 30 °, 42 to 43 °, 50 to 51 °, and 52 to 53 ° (shown by black circles in FIG. 2), Sr ₂ Ga ₂ S ₅ has a large number of peaks (indicated by black triangles in FIG. 2), in particular, a strong peak at 22 to 35 ° and a maximum peak at 25 to 26 °.
As shown in FIG. 2, in the red phosphors according to Examples 1 to 5 produced, the crystal phase of the composite sulfide Sr ₂ Ga ₂ S ₅ of strontium and gallium and the crystal phase of SrS are formed. understood. _{Incidentally,} Sr 2 _Ga 2 _{S 5 Ga} compound in addition 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 the full 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 at the time of production.

(Evaluation of distribution of strontium and gallium)
With respect to the cross section of the red phosphor according to Example 3, elemental analysis of strontium and gallium was performed by mapping analysis of 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. Moreover, mapping of strontium in the cross section of the red fluorescent substance of FIG. 3 and mapping of gallium were performed. The results are shown in FIGS. 4 and 5. FIG. 4 is an analysis image showing the mapping result of strontium in the cross section of the red phosphor of FIG. FIG. 5 is an analysis image showing the 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 were uniformly distributed in the particles of the red phosphor. There was almost no change in the distribution of these strontium and gallium even if the observation place was changed.

From the above, the red phosphor of the present invention exhibits a sensitizing effect by eutectically forming an alkaline earth metal sulfide and Sr ₂ Ga ₂ S ₅ and exhibits high-intensity light emission.

Claims (6)

A red phosphor comprising a eutectic of an alkaline earth metal sulfide and Sr ₂ Ga ₂ S ₅ as a base, wherein the eutectic is activated by europium. The red phosphor according to claim 1, wherein the mass concentration of the Sr ₂ Ga ₂ S _{5 in} the red phosphor calculated from the powder X-ray diffraction pattern by the whole pattern fitting method is in the range of ₅ to 65 wt%. The 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 per mol is 0.005 to 0 per mol of the total number of moles The red phosphor according to claim 1 or 2, containing .10 mol. The red phosphor according to any one of claims 1 to 3, wherein the alkaline earth metal sulfide is strontium sulfide. 5. The red phosphor according to claim 4, further comprising at least one metal selected from the group consisting of magnesium, calcium and barium in the eutectic. 6. The red phosphor according to claim 5, containing 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.