JP5420015B2 - Sulfide phosphor and method for producing the same - Google Patents

Description

  The present invention relates to a sulfide phosphor and a method for producing the same, and more particularly, a sulfide that can be efficiently excited with visible light, emits green light with high luminance, and can be suitably used for a white light-emitting element. The present invention relates to a phosphor and a manufacturing method thereof.

  In recent years, with the development of blue LEDs and near-ultraviolet LEDs, development of white light-emitting elements that obtain white by combining LEDs and phosphors is progressing.

  When producing a white light emitting element using this blue LED, as described in Patent Documents 1, 2, and 3, for example, a white light emitting element combining a blue LED and a yellow phosphor has been developed. These white light-emitting elements are increasingly used for illumination and as backlight light sources for liquid crystal displays.

  However, white light composed of such blue and its complementary color has poor color reproducibility and low color rendering, so a white light-emitting element called a three-wavelength type has been developed.

As a three-wavelength type white light emitting element, for example,
(1) A light emitting element that emits blue light, a phosphor that emits green light by receiving blue light emitted from the light emitting element, and a white light emitting element that uses a phosphor that emits red light (see, for example, Patent Document 1). ),
(2) White light emission using a light emitting element that emits ultraviolet light, a phosphor that emits blue light upon receiving ultraviolet light emitted from the light emitting element, a phosphor that emits green light, and a phosphor that emits red light Development of devices is underway.

In general, as phosphors emitting green light, (Ba, Sr) ₂ SiO ₄ : Eu (for example, see Non-Patent Document 1), Eu-added β sialon (for example, see Patent Document 2), and the like are known. ing.

It is disclosed that (Ba, Sr) ₂ SiO ₄ : Eu can adjust the emission wavelength by changing the ratio of Ba and Sr. However, (Ba, Sr) ₂ SiO ₄ : Eu has strong emission intensity, but the half-value width in the shape of the emission spectrum is wide from 80 nm to 100 nm, whereas Eu-added β-sialon has a half-value width in the shape of the emission spectrum of 55 nm. It is sharp, but the emission intensity is weak.

  By the way, the backlight light source of the liquid crystal display separates white light into blue, green, and red with a color filter. At that time, the narrower the half-value width of the emission spectrum becomes sharper, the better the color separation and the color reproduction. It is said that the sex is improved.

Therefore, recently, Eu-added Ba ₃ Si ₆ O ₁₂ N ₂ (BSON, see, for example, Patent Document 3) has been developed. Although the half width of the emission spectrum is as narrow as 68 nm, the emission peak wavelength is 525 nm, which is slightly shorter than the green emission peak wavelength of 544 nm, which is ideal for RGB television.

On the other hand, thiogallate phosphors are known as green phosphors. As a typical thiogallate phosphor, the composition formula is (Sr, Ca, Ba) _1-x Eu _x Ga ₂ S ₄ , and the emission wavelength can be changed by changing the composition ratio of the alkaline earth metal. Thus, the characteristics that the emission peak wavelength is 544 nm and the half width of the emission spectrum is about 50 nm are obtained (for example, see Non-Patent Document 2).

Eu-added Ga ₂ S ₃ is also known to emit green light (see, for example, Non-Patent Document 3). However, in this phosphor, the divalent Eu substitutes for the trivalent Ga lattice position, and Ga lattice defects are generated to compensate for the charge. Therefore, it can be said that it is difficult to increase the light emission luminance.

  These phosphor materials can be excited with a blue LED (emission wavelength: 440 to 470 nm) to obtain green fluorescence, and are useful as a monochromatic LED lamp or a phosphor for a white LED. However, when used for a display, a phosphor having a narrower half-value width of an emission spectrum due to color separation by a color filter and a phosphor having a small luminance change with respect to a wavelength change of a blue LED is required. In particular, the blue-excited red phosphor has only a broad emission with a wide half-value width of the emission spectrum.

  From this, in order to suppress color mixing, it is conceivable to shift the red emission peak wavelength to the longer wavelength side. However, shifting to the long wavelength side causes a problem that the luminance of the screen cannot be maintained because the visibility is low.

  Therefore, in order to set the emission peak wavelength of other phosphors such as the red phosphor to an appropriate value, in the green phosphor, the half-value width of the emission spectrum is narrowed to enable good color separation, and further the emission luminance There has been a demand for a phosphor having an improved surface area.

JP 2000-244021 A JP 2005-255895 A JP 2008-138156 A

G. BLAST et. Al. , Philips Res. Report, 1968, Vol. 23, no. 2, p. 189 T.A. E. Peters J.M. A. Baglio, J .; Electrochem. Soc. 1972, vol. 119, p. 230 Askerov I. M.M. , Et. al. Sov. Phys. -Semicond. (Enggl. Transl.), 1991, Vol. 25, p. 1230

  The present invention has been proposed in view of such circumstances, has an emission wavelength peak in the green region of 530 nm to 550 nm efficiently excited with visible light, and has a half width of the emission spectrum of less than 50 nm. An object of the present invention is to provide a green phosphor that emits light with higher luminance.

The inventors of the present invention have made extensive studies to solve the above-described problems. As a result, the alkaline earth metal element Sr is added to Ga ₂ S ₃ to form a sulfide, and the Ga position is replaced with Eu ²⁺ to obtain a sulfide phosphor having a predetermined composition, thereby solving the above-described problems. The present inventors have found that the present invention can be accomplished and have completed the present invention.

That is, the sulfide phosphor of the present invention have the general _formula: represented by _{Sr (Ga 1-x Eu x} ) y S 1.5y + 1, x in the formula, y is 0.008 <x <0.025 11.5 <y <12.5 is satisfied.

The production process of a sulfide phosphor according to the present invention have the general _formula: represented by _{Sr (Ga 1-x Eu x} ) y S 1.5y + 1, in wherein x is 0.008 <x <0.025 A method for producing a sulfide phosphor in which y is 11.5 <y <12.5, and a mixture obtained by mixing gallium nitrate and a europium compound so as to have a predetermined composition, A gel body preparation step of weighing and mixing strontium carbonate, adding oxycarboxylic acid and alcohol to obtain a gel body, heat-treating the gel body under a temperature condition of 400 ° C to 500 ° C, and then air atmosphere And an intermediate preparation step of obtaining an intermediate of an oxide precursor by oxidizing and baking at a temperature of 550 ° C. to 600 ° C., and pre-baking the intermediate at 700 ° C. to 1300 ° C. in an air atmosphere. Temporary firing step for obtaining an oxide precursor And a reduction firing step in which the oxide precursor obtained in the provisional firing step is subjected to reduction sulfidation treatment and firing under a temperature condition of 850 ° C. to 930 ° C.

  According to the sulfide phosphor according to the present invention, it is efficiently excited with visible light, has an emission wavelength peak in the green region of 530 nm to 550 nm, and has a half width of its emission spectrum of less than 50 nm and high luminance. Shows luminescence. According to such a sulfide phosphor, when producing a white light emitting device mixed with another phosphor, it becomes possible to perform good color separation while controlling the emission peak wavelength of the other phosphor to an appropriate value, Its industrial value is extremely large.

X-ray diffraction patterns of the phosphors prepared in Example 2 and Comparative Examples 3, 7, and 8, and X-ray diffraction of SrGa ₂ S ₄ , EuGa ₂ S ₄ and Ga ₂ S ₃ simulated using ICSD It is a figure which shows a pattern. It is a figure which shows the emission spectrum about Example 1, comparative example 3, 7, 8, and the fluorescent substance of a prior art example. It is a figure which shows the spectrum which normalized the emission spectrum of the fluorescent substance of Example 1, the comparative examples 3 and 8, and the prior art example with the peak wavelength. It is a figure which shows the result of the excitation characteristic about the fluorescent substance of Example 1, Comparative example 3, 7, 8, and a prior art example.

Hereinafter, a specific embodiment to which the present invention is applied (hereinafter referred to as “the present embodiment”) will be described in detail in the following order with reference to the drawings. In addition, this invention is not limited to the following embodiment, A various change is possible in the range which does not deviate from the summary.
1. 1. Sulfide phosphor 1-1. Composition and effect of sulfide phosphor 1-2. 1. Structural analysis of sulfide phosphors 2. Method for producing sulfide phosphor 2-1. Overview of manufacturing method 2-2. 2. A method for producing a sulfide phosphor via an oxide precursor by a liquid phase method. Example 3-1. Production of phosphor 3-2. Performance evaluation of phosphor 3-3. X-ray diffraction measurement of phosphor

<< 1. Sulfide phosphor >>
<1-1. Composition and effect of sulfide phosphor>
Sulfide phosphor according to the present embodiment, the general formula _(1): is represented by _{Sr (Ga 1-x Eu x} ) y S 1.5y + 1, x in the formula, y is, 0.008 <x < 0.025, 11.5 <y <12.5 is satisfied.

  The sulfide phosphor represented by the general formula (1) can be excited efficiently with visible light and has an emission peak in a green region of 530 nm to 550 nm. Further, in this sulfide phosphor, the half width of the emission spectrum is less than 50 nm. According to the sulfide phosphor having such light emission characteristics, for example, in the production of a white light emitting device mixed with another phosphor, color mixing can be effectively suppressed, and light emission of the other phosphor can be achieved. It can be suitably used as a green phosphor capable of good color separation while controlling the peak wavelength to an appropriate value.

  As described above, in this sulfide phosphor, the addition ratio of Eu satisfies 0.008 <x <0.025 as the ratio indicated by “x” in the general formula (1). . Further, the mixing ratio (Ga / Sr) of gallium (Ga) to strontium (Sr), which is an alkaline earth metal, is 11.5 <y <12 as a ratio indicated by “y” in the general formula (1). .5 is satisfied.

  In this way, by making the addition ratio of Eu and the ratio of Ga / Sr within the above-mentioned ranges, excitation is possible in a wide range of 400 nm to 500 nm, having a peak wavelength with high emission intensity, and enabling efficient excitation. To. Moreover, by setting it as such a composition, Eu can be substituted effectively and light emission extremely high compared with the past can be shown.

  Here, the improvement of the light emission luminance in the sulfide phosphor according to the present embodiment is a eutectic formed by a plurality of crystal phases, as can be seen from the result of structural analysis described later. It depends on some things.

<1-2. Structural analysis of sulfide phosphors>
FIG. 1 shows an X-ray diffraction pattern of phosphors produced in Examples described later, and SrGa ₂ S ₄ , EuGa ₂ S ₄ , and Ga ₂ S ₃ simulated using ICSD (inorganic crystal structure database). An X-ray diffraction pattern is shown. In FIG. 1, the phosphor represented by SrGa ₁₂ S ₁₉ : Eu 2% produced in Example 2 is an example of the phosphor represented by the general formula (1).

As shown in X-ray diffraction pattern of Figure 1, Eu 1% added with _Ga 2 _S 3: In Eu1%, it is a phosphor consisting of a single phase coincides with the _Ga 2 _{S 3} was simulated by ICSD I understand. On the other hand, in SrGa ₁₂ S ₁₉ : Eu2%, which is the sulfide phosphor according to the present embodiment, there are a peak that matches Ga ₂ S ₃ and a peak that approximates SrGa ₂ S ₄ and EuGa ₂ S _4. I understand. From this, it can be estimated that the sulfide phosphor represented by the general formula (1) is formed of a plurality of crystal phases.

SrS—Ga ₂ S ₃ is known to be a eutectic system. Therefore, in the sulfide phosphor according to the present embodiment, a small amount of liquid phase appears due to the eutectic reaction of SrGa ₂ S ₄ and Ga ₂ S _{3 in} the production process, and the self-flux based on the liquid phase It is considered that due to the effect, the phosphor surface phase becomes a high-purity crystal, and as a result, emits light with extremely high brightness as compared with the conventional case.

≪2. Method for producing sulfide phosphor >>
Next, a method for manufacturing the above-described sulfide phosphor will be described.

<2-1. Overview of manufacturing method>
In general, it is difficult to replace an atomic position having a small ion radius such as gallium with an element having a large ion radius such as europium. In Ga ₂ O ₃ , it is said that Eu and Ga vacancies replacing Ga sites constitute a composite defect.

Accordingly, the present inventors have the general formula Eu is substituted with Ga _positions: represented by _{Sr (Ga 1-x Eu x} ) y S 1.5y + 1, in wherein x is 0.008 <x <0.025 In order to manufacture a sulfide phosphor in which y is 11.5 <y <12.5, alkaline earth metal Sr is added to Ga ₂ O ₃ once containing Eu and SrGa _y O _1. By producing an oxide precursor of _{5y + 1} and subjecting the oxide precursor to reduction sulfidation treatment with carbon disulfide or hydrogen sulfide, it is possible to efficiently form a sulfide phosphor in which Eu is substituted at the Ga position. It was found that a sulfide phosphor that is excited efficiently by visible light and emits green light with high luminance can be obtained.

Specifically, a complex oxide of an alkaline earth metal oxide and gallium oxide (Ga ₂ O ₃ ), which is the oxide precursor, can be manufactured by a solid phase method or a liquid phase method.

For example, in the solid phase method, alkaline earth metals strontium carbonate, gallium oxide, and europium oxide are mixed so as to have a predetermined composition ratio, and the mixture is heated at 700 ° C. to 1300 ° C. in an air atmosphere. It can be produced by firing. At the time of firing, if the firing temperature is lower than 700 ° C., the carbonate cannot be decomposed, making it difficult to form a composite oxide. On the other hand, when the firing temperature is higher than 1300 ° C., the volatilization of Ga ₂ O ₃ becomes intense, and the oxide precursor may melt and be unable to be subsequently reduced and sulfided.

  In the liquid phase method, for example, an oxide precursor can be produced using a complex polymerization method. Thus, by producing an oxide precursor by a liquid phase method, raw materials can be mixed uniformly, and this is a suitable production method for producing a phosphor with higher emission luminance. Below, the manufacturing method using the specific liquid phase method is mentioned as an example, and the manufacturing method of the sulfide phosphor according to the present embodiment will be described in more detail.

<2-2. Manufacturing Method of Sulfide Phosphor via Oxide Precursor by Liquid Phase Method>
Production process of a sulfide phosphor according to the present embodiment, the general _formula: represented by _{Sr (Ga 1-x Eu x} ) y S 1.5y + 1, in wherein x is 0.008 <x <0.025 And y is a method for producing a sulfide phosphor in which 11.5 <y <12.5.

  This manufacturing method includes a gel body preparation step in which an aqueous solution obtained by mixing raw materials is gelled to obtain a gel body, a heat treatment of the gel body to decompose organic matter, and an intermediate of the oxide precursor by an oxidation firing process. An intermediate preparation step for obtaining a body, a preliminary firing step for preliminarily firing an intermediate of an oxide precursor to obtain an oxide precursor, and a reduction firing step for performing a reduction sulfidation treatment on the oxide precursor .

(1) Gel body preparation process In a gel body preparation process, the liquid mixture obtained by mixing the raw material gallium nitrate (Ga) and a europium (Eu) compound so that it may become the predetermined composition shown by the said general formula. Then, strontium carbonate is weighed and mixed. And an oxycarboxylic acid and alcohol are added to the liquid mixture, and it heats at predetermined temperature and makes it gelatinize, and produces a gel body.

  Specifically, in the gel body preparation step, first, an aqueous solution of gallium nitrate and a europium compound is mixed to form a mixed solution, and strontium carbonate is mixed into the mixed solution.

  As the compound of the activation element Eu to be added, a water-soluble europium compound such as europium nitrate or oxide can be used. For example, as europium nitrate, the raw europium oxide is dissolved in a nitric acid solution having a concentration of 40 to 60% by mass and stirred for about 1 hour to completely dissolve the europium oxide, and then the europium solution is dried. Can be obtained.

  In addition, strontium carbonate as a strontium source is a relatively inexpensive material. By using this as a raw material, a phosphor with reduced cost can be manufactured.

The addition amounts of gallium nitrate, europium compound, and strontium carbonate are weighed and mixed so that the metal ratio of the desired phosphor composition is obtained. In this embodiment, the composition _formula: Sr is represented by _{(Ga 1-x Eu x)} y S 1.5y + 1, a wherein x is 0.008 <x <0.025, y is 11 The raw materials gallium nitrate, europium compound, and strontium carbonate are weighed and mixed so that .5 <y <12.5. Since the atomic ratio in the raw material to be supplied and the atomic composition ratio of the obtained phosphor are substantially the same, each raw material is weighed and mixed so that the desired composition ratio is obtained. It can be a range.

  Next, in the gel body preparation step, the metal element is complexed by adding oxycarboxylic acid to the solution in which the raw material compounds are mixed in this manner, and alcohol is added to the solution in which the metal element is complexed. To gel the aqueous solution. Thus, by gelling the aqueous solution in which the raw materials are mixed into a gel body, the raw materials can be uniformly dispersed, and in particular, the rare earth element europium that becomes the luminescent center can be uniformly dispersed. A phosphor exhibiting high-luminance emission can be obtained.

  Here, as the oxycarboxylic acid, for example, citric acid, malic acid, tartaric acid, tartronic acid, glyceric acid, oxybutyric acid, hydroacrylic acid, lactic acid, glycolic acid and the like can be used, and among them, citric acid is used. More preferred.

  The amount of oxycarboxylic acid added is preferably about 3 to 5 times the molar ratio of all metal elements (Ga + Eu + Sr) composed of Ga, Eu, and Sr. If the amount of oxycarboxylic acid added is less than 3 times the moles of all metal elements, the raw material strontium carbonate cannot be completely dissolved, and the complexation of metal elements may not proceed sufficiently. is there. On the other hand, when the addition amount exceeds 5 times mole, the cost increases and the economic efficiency deteriorates, which is not preferable.

  There are no particular limitations on the metal element dissolution treatment and complexation treatment by adding oxycarboxylic acid, but for example, the aqueous solution is heated to about 50 ° C. to 160 ° C. and stirred for about 1 to 8 hours. By doing.

  Further, glycol is preferably used as the alcohol added to the solution in which the metal element is complexed. Specifically, it is preferable to use ethylene glycol or propylene glycol as the glycol.

  The amount of alcohol added is preferably about 8 to 12 times the molar ratio of all metal elements (Ga + Eu + Sr) composed of Ga, Eu and Sr. If the addition amount of the alcohol is less than 8 times moles with respect to all the metal group elements, the esterification reaction described later hardly occurs and gelation may not proceed efficiently. On the other hand, when the addition amount exceeds 12 times mol, the effect of alcohol addition does not increase any more, which is not preferable because the cost increases and the economic efficiency deteriorates.

  In the gelation reaction by addition of alcohol, for example, the temperature of the aqueous solution is heated to 120 ° C. to 250 ° C., more preferably 180 ° C. to 220 ° C., and the mixture is stirred. When the aqueous solution is heated and stirred in this manner, an esterification reaction occurs in the aqueous solution to polymerize to produce a polyester, whereby the aqueous solution gels.

  Regarding the above-described gelation temperature, if it is less than 120 ° C., the gelation time becomes long, and if it exceeds 250 ° C., uniform gelation becomes difficult. Further, the gelation time varies depending on the water content of the aqueous solution, but it is preferable to perform the gelation by stirring for 4 to 16 hours at the gelation temperature described above.

  In the gelation of the aqueous solution, when the esterification reaction proceeds, nitric acid in the aqueous solution is rapidly decomposed to generate a reddish gas, and bubbles may be formed in the polyester to expand rapidly. Since the bubbles are easily dissolved in water, it may be polyesterified by stirring and polymerizing by adding water as appropriate and preparing an aqueous solution again. In addition, if nitric acid remains in the aqueous solution, it should be noted that a rapid reaction may occur during the thermal decomposition of the organic matter.

(2) Intermediate production process In the intermediate production process, the gel body obtained in the gel body production process is subjected to heat treatment to thermally decompose the gel body, and then oxidized under a predetermined temperature condition in an air atmosphere. An intermediate of the oxide precursor is produced by firing treatment.

  The gel body obtained in the gel body preparation step contains organic substances derived from the added raw materials (carbonate, oxycarboxylic acid, alcohol, etc.). Therefore, first, in an intermediate body production process, the organic substance contained in a gel body is decomposed | disassembled by heat-processing with respect to a gel body. Thereby, the fall of the brightness | luminance by the undecomposed thing of the organic substance which remains can be suppressed, the emitted light intensity of the fluorescent substance obtained can be raised, and the fluorescent substance which shows high-intensity light emission can be produced.

  As heat processing temperature with respect to a gel body, it is preferable to set it as 400 to 500 degreeC, and it is more preferable to set it as 440 to 460 degreeC. Moreover, as heat processing time, it is preferable to set it as 1 hour-20 hours, and it is more preferable to set it as 4 hours-12 hours. In addition, by first performing heat treatment at 100 ° C. to 200 ° C. and then increasing the temperature to 400 ° C. to 500 ° C., the influence of rapid decomposition of organic substances contained in the gel can be avoided.

  Further, in the intermediate preparation step, following the heat treatment described above, the oxide precursor described later is subjected to an oxidation baking treatment in a temperature condition of 550 ° C. to 600 ° C. in the air atmosphere to the heat-treated product of the gel body. An intermediate of is prepared.

  In this oxidation firing treatment, heat treatment on the gel body alone often causes insufficient oxygen or agglomeration, resulting in insufficient thermal decomposition, so that organic substances can be burned and removed sufficiently to promote the oxidation reaction. Do. Therefore, it is desirable to lightly pulverize the heat-treated product of the gel body with a mortar or the like. Moreover, when oxygen or air is flowed, the intermediate preparation step and the pre-baking step, which is a subsequent step, can be performed continuously.

  In the oxidation firing treatment, if the firing temperature is less than 550 ° C., the remaining organic matter and nitric acid are not easily decomposed by combustion, which is not preferable. On the other hand, when the temperature exceeds 600 ° C., the intermediate is partially crystallized and the oxide precursor is hardly uniform, which is not preferable. The firing time is preferably 1 hour to 4 hours.

  Moreover, this oxidation baking treatment is performed in an air atmosphere or an oxygen atmosphere as described above. By performing the heat treatment in an atmosphere containing oxygen, the organic matter remaining in the gel body can be effectively decomposed, and it is possible to suppress the carbon from remaining on the surface and reducing the luminance of the phosphor.

(3) Pre-baking step In the pre-baking step, the oxide precursor obtained in the intermediate preparation step is pre-baked in the atmosphere to completely convert it into an oxide, which is an alkaline earth metal Sr. An oxide precursor made of a composite oxide (SrGa _y O _1.5y-1 ) of gallium oxide (Ga ₂ O ₃ ) containing Eu oxide and Eu is prepared.

The firing temperature in the temporary firing step is preferably 700 ° C to 1300 ° C. If the firing temperature is lower than 700 ° C., the remaining raw material carbonate cannot be efficiently decomposed, and therefore it becomes difficult to form a composite oxide. On the other hand, when the firing temperature exceeds 1300 ° C., the volatilization of Ga ₂ O ₃ may become intense, or the composite oxide may melt and the reduction sulfurization reaction in the subsequent reduction firing process may not proceed easily. Therefore, it is not preferable.

  Moreover, as processing time of temporary baking, it is preferable to set it as 3 hours-8 hours, and it is more preferable to set it as 4 hours-6 hours.

Here, generally, sublimation of Ga ₂ O ₃ becomes remarkable at a temperature higher than 800 ° C. Therefore, in this preliminary firing step, the intermediate of the oxide precursor is once fired at a temperature of 700 ° C. to 800 ° C. or less to form an oxide (first preliminary firing step), and the oxide is again 1000 It is also possible to perform a two-stage baking process of baking at a temperature of 1C to 1300C (second temporary baking process).

In this way, the oxide precursor intermediate obtained in the intermediate preparation step is subjected to a two-step baking treatment and pre-baked to reduce Ga ₂ O ₃ volatilization loss and efficiently oxidize. The precursor of a product can be obtained, and a phosphor having a desired composition can be efficiently produced.

  Further, when the intermediate of the oxide precursor is baked at 800 ° C. or lower, it may be an oxide precursor that does not crystallize and has no peak in X-ray diffraction. In general, when an amorphous and uniform oxide precursor is reduced and sulfided, it is not necessary to change the structure of the crystal or to diffuse, so that the target substance can be synthesized at a low temperature. In addition, what is necessary is just to crystallize at high temperature, when obtaining a target composition using a specific crystal structure.

(4) Reduction firing step In the reduction firing step, the oxide precursor obtained in the provisional firing step is subjected to a reduction sulfidation treatment and firing under a predetermined temperature condition. By this reductive sulfidation treatment, an oxide precursor is reductively sulfidized to form a host crystal, and a Sr site of the host crystal is doped with Eu, thereby obtaining a sulfide phosphor in which Eu is uniformly dispersed. .

  Specifically, the reduction sulfidation treatment can be performed using an inert gas containing hydrogen sulfide gas or carbon disulfide. Among these, it is particularly preferable to carry out in an inert gas atmosphere containing carbon disulfide. When reductive sulfidation treatment is performed for a long time under high temperature conditions, sulfur that tends to volatilize tends to escape from the reductive sulfurized base crystal, and a phosphor having high luminance and a desired emission wavelength is manufactured. It becomes difficult. In this respect, since carbon disulfide has a strong reducing power, the oxide can be sulfided at a low temperature and can be fired under a low temperature condition. Suppressing the escape of sulfur and phosphor having a desired composition Can be produced effectively. Further, it is possible to reduce labor and cost at the time of raising the temperature, which is preferable from an economical viewpoint.

  In the manufacturing method according to the present embodiment, it is important to control the firing temperature condition in the reduction sulfurization treatment in the reduction firing step. Specifically, the reduction sulfur treatment is performed by controlling the temperature in the range of 850 ° C. to 930 ° C.

Here, as described above, the sulfide phosphor represented by the general formula (1): Sr (Ga _1-x Eu _x ) _y S _{1.5y + 1} is an eutectic formed from a plurality of crystal phases. It has become. In producing this sulfide phosphor by reducing and sulfurating, by setting the firing temperature to 850 ° C. or higher, a small amount of liquid phase appears due to the eutectic reaction by a plurality of crystal phases. Then, a self-flux effect is generated by the appearing liquid phase, and the obtained phosphor surface phase can be made into a high-purity crystal, and the fluorescence characteristics can be improved. Specifically, it becomes a sharp emission spectrum whose half width is less than 50 nm, and the emission intensity can be remarkably improved. On the other hand, if the firing temperature exceeds 930 ° C., the liquid phase produced by the eutectic reaction increases, coarse particles are generated, and the fluorescence characteristics deteriorate.

  Therefore, in the reductive sulfidation treatment, by setting the baking temperature condition in the range of 850 ° C. to 930 ° C., a phosphor having a half width of the emission spectrum of less than 50 nm and a high emission luminance can be produced.

  Although it does not specifically limit as processing time of a reductive sulfidation process, It is preferable to hold | maintain for 1 to 12 hours on the temperature conditions mentioned above.

  Moreover, when performing reductive sulfidation in an inert gas atmosphere containing carbon disulfide, it is preferable to use argon (Ar) gas as the inert gas. Moreover, as a method of including carbon disulfide in the argon gas, a method of circulating the argon gas in liquid carbon disulfide can be used.

  Moreover, as temperature of carbon disulfide or argon gas, it is preferable to set it as 15 to 46 degreeC, and it is more preferable to set it as 20 to 25 degreeC. If the temperature is less than 15 ° C., the concentration of carbon disulfide contained in the argon gas is low, and the reduction sulfidation may not proceed effectively. On the other hand, if the temperature is 46 ° C. or higher, it becomes higher than the boiling point of carbon disulfide, and it becomes difficult to control the evaporation amount, and it is difficult to perform uniform reduction sulfurization.

  The firing furnace for performing the reduction sulfidation treatment is not particularly limited, and for example, a tubular furnace in which the furnace core tube is quartz can be used. Moreover, as temperature rising conditions, a temperature rising rate can be performed, for example as 10-30 degree-C / min.

  When firing in a tubular furnace, it is preferable to flow a gas such as an inert gas containing hydrogen sulfide gas or carbon disulfide immediately after the start of heating so that the gas in the quartz tube can be expelled. In particular, in a period of about 10 to 20 minutes from the start of heating, it is preferable to flow a gas that is twice to three times the volume of the entire quartz tube. Further, it is preferable to adjust the flow rate of the supply gas so that the amount of gas serving as the reduction medium becomes a sufficient amount at the temperature at which the reduction sulfurization starts. Even during firing, a sufficient amount of gas is required as described above. Therefore, it is preferable to keep the gas flowing until cooling is completed and the temperature reaches room temperature.

  By performing the reduction sulfidation treatment as described above, a baked powder of the sulfide phosphor represented by the general formula (1) can be obtained, and carbon is attached to the surface of the baked powder. Sometimes. In such a phosphor with carbon attached to the surface, the light emission luminance may decrease. Therefore, it is preferable to form a new surface on the surface by pulverizing the obtained fired powder after the above-described reduction sulfurization treatment. Thereby, the fall of the brightness | luminance of fluorescent substance can be prevented and a high-intensity fluorescent substance can be obtained.

By the manufacturing method described above in detail, the general _formula: Sr is represented by _{(Ga 1-x Eu x)} y S 1.5y + 1, a wherein x is 0.008 <x <0.025, y 11.5 A sulfide phosphor satisfying <y <12.5 can be produced.

As described above, in this manufacturing method, an oxide precursor of a composite oxide of Eu-containing Ga ₂ O ₃ and an alkaline earth metal Sr is prepared. For this reason, Eu having a large ionic radius can be effectively substituted at the Ga position, and an oxide precursor that suppresses the generation of complex defects of Eu and Ga vacancies can be obtained.

  In this manufacturing method, the obtained oxide precursor is subjected to reduction sulfidation treatment while being controlled within a temperature range of 850 ° C. to 930 ° C., so that it has a sharp emission spectrum and emits light. A strong phosphor can be obtained.

≪3. Examples >>
Hereinafter, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited to the following Example.

<3-1. Production of phosphor>
[Example 1]
(Gel body production process)
Metal gallium (Ga) was put in a nitric acid solution 7 times the number of moles of Ga, and the vessel was covered and dissolved on a hot plate at 80 ° C. for 1 day so that the nitric acid would not volatilize. Since NO _x is generated in the reaction, an opening is provided in the lid. After dissolving metal gallium, excess nitric acid was removed by evaporation on a hot plate at 130 ° C., and water was added to make a constant solution at 1 M / L.

  Next, gallium nitrate (1 M / L) and europium nitrate (Eu) (0.1 M / L) are mixed in a beaker so that the metal molar ratio is 99: 1. Strontium carbonate (Sr) was added so that Ga + Eu: Sr was 12: 1, and 3 times moles of citric acid of all metal elements (Ga + Eu + Sr) was added to prepare an aqueous solution. Subsequently, this aqueous solution is stirred on an 80 ° C. hot plate for 1 hour to completely dissolve strontium, and propylene glycol is added to this aqueous solution in an amount 10 times the number of moles of all metal elements, and the temperature of the hot plate is set to 120. In order to evaporate nitric acid at 1 ° C. for 1 hour, the mixture was stirred at 140 ° C. for 1 hour for a total of 2 hours to prepare a gel body.

(Intermediate production process)
Next, the obtained gel was heated with a mantle heater set at 180 ° C. for 1 hour, the temperature was raised to 450 ° C., and heat treatment was performed for 2 hours to decompose the organic matter in the gel. Further, the heat-treated product after the heat treatment was put into a box furnace and subjected to an oxidation baking treatment in an air atmosphere at a temperature condition of 550 ° C. for 2 hours to produce an oxide precursor intermediate.

(Preliminary firing process)
Subsequently, the oxide precursor intermediate obtained in the box furnace was baked for 2 hours at 750 ° C. in an air atmosphere to produce an oxide precursor.

(Reduction firing process)
Next, the obtained oxide precursor was placed in a graphite vessel and placed in a tubular furnace, and in a mixed gas atmosphere in which 35% by volume of carbon disulfide was mixed with 65% by volume of argon (Ar) gas, A sulfide phosphor (thiogallate phosphor) having a composition formula of Sr (Ga _0.99 Eu _0.01 ) ₁₂ S ₁₉ was produced by reducing and sulfiding at 900 ° C. for 1 hour.

[Example 2]
In the gel body preparation step, the composition was the same as in Example 1 except that the Ga: Eu ratio in preparing the mixed solution of the raw material gallium nitrate and europium nitrate was 98: 2 in terms of the metal molar ratio. A sulfide phosphor having the formula Sr (Ga _0.98 Eu _0.02 ) ₁₂ S ₁₉ was produced.

[Example 3]
A sulfide phosphor was produced in the same manner as in Example 2 except that the temperature condition in the reduction sulfurization treatment in the reduction firing step was 915 ° C.

[Example 4]
A sulfide phosphor was produced in the same manner as in Example 2 except that the temperature condition in the reduction sulfurization treatment in the reduction firing step was 880 ° C.

[Comparative Example 1]
In the gel body preparation step, the same as Example 1 except that the ratio of Ga: Eu at the time of preparing the mixed liquid of the raw material gallium nitrate and europium nitrate was 99.5: 0.5 in terms of the metal molar ratio. By the method, a sulfide phosphor having a composition formula of Sr (Ga _0.995 Eu _0.005 ) ₁₂ S ₁₉ was produced.

[Comparative Example 2]
In the gel body preparation step, the composition was the same as in Example 1, except that the Ga: Eu ratio in preparing the mixed liquid of the raw material gallium nitrate and europium nitrate was 97: 3 in terms of the metal molar ratio. A sulfide phosphor having the formula Sr (Ga _0.97 Eu _0.03 ) ₁₂ S ₁₉ was prepared.

[Comparative Example 3]
In the gel body preparation step, the composition was the same as in Example 1 except that the Ga: Eu ratio in preparing the mixed solution of the raw material gallium nitrate and europium nitrate was 90:10 in terms of the metal molar ratio. A sulfide phosphor having the formula Sr (Ga _0.90 Eu _0.10 ) ₁₂ S ₁₉ was produced.

[Comparative Examples 4 to 6]
In the gel body preparation step, the ratio of Sr: Ga when adding strontium carbonate to the mixed solution of the raw material gallium nitrate and europium nitrate is 1:10 (Comparative Example 4), 1:11 (Comparative Example 5) 1:13 (Comparative Example 6), except that the composition formula is Sr (Ga _0.99 Eu _0.01 ) ₁₀ S ₁₉ (Comparative Example 4), in the same manner as in Example 1. Sulfide phosphors of Sr (Ga _0.99 Eu _0.01 ) ₁₁ S ₁₉ (Comparative Example 5) and Sr (Ga _0.99 Eu _0.01 ) ₁₃ S ₁₉ (Comparative Example 6) were produced.

[Comparative Example 7]
The composition formula is Ga ₂ S ₃ : Eu in the same manner as in Example 1 except that, in the gel body preparation step, the mixture was prepared without adding strontium carbonate to the raw material mixture of gallium nitrate and europium nitrate. A sulfide phosphor was prepared.

[Comparative Example 8]
In the gel body preparation step, the composition was the same as that in Comparative Example 7 except that the Ga: Eu ratio in preparing the mixed liquid of the raw material gallium nitrate and europium nitrate was 90:10 in terms of the metal molar ratio. A sulfide phosphor having the formula Ga ₂ S ₃ : Eu was produced.

[Comparative Example 9]
A sulfide phosphor was produced in the same manner as in Example 2 except that the temperature condition of the reduction sulfurization treatment in the reduction firing step was set to 800 ° C.

[Comparative Example 10]
A sulfide phosphor was produced in the same manner as in Example 2 except that the temperature condition of the reduction sulfurization treatment in the reduction firing step was 950 ° C.

  Note that the phosphor obtained in Comparative Example 10 was partially melted to become coarse particles. Therefore, in the following fluorescence measurement, the coarse particles were measured by pulverizing them with a mortar.

[Conventional example]
The following fluorescence characteristics were measured using SrGa ₂ S ₄ : Eu manufactured by Phosphor technology as a conventional example as a commercially available green sulfide phosphor.

<3-2. Evaluation of phosphor performance>
(Measurement of fluorescence characteristics and measurement results)
About the fluorescent substance produced in each Example and comparative example mentioned above, excitation and the emission spectrum were measured using the fluorescence spectrophotometer (FP-6500, JASCO Corporation make), and the fluorescence characteristic was measured. The spectra obtained by fluorescence measurement were compared by standardizing the peak intensity of commercially available Y ₃ Al ₅ O ₁₂ : Ce ³⁺ (YAG: Ce, P46 manufactured by Kasei Optonics Co., Ltd.) as 1.

  Tables 1 to 3 below show the fluorescence characteristics of the phosphors produced in the examples and comparative examples. FIG. 2 shows emission spectra of the phosphors of Example 1, Comparative Examples 3, 7, 8 and the conventional example. FIG. 3 shows spectra obtained by normalizing the emission spectra of the phosphors of Example 1, Comparative Examples 3 and 8, and the conventional example with the peak wavelength, thereby comparing the half widths. FIG. 4 shows the results of excitation characteristics for the phosphors of Example 1, Comparative Examples 3, 7, 8 and the conventional example.

(Evaluation)
As can be seen from the results shown in Tables 1 to 3 and FIGS. 2 and 3, the phosphors of Example 1 and Example 2 are in the green emission wavelength region having a peak wavelength of 530 nm to 550 nm, and emit green light. It can be seen that Further, the half-value width of the emission spectrum is 46 nm, which indicates that the emission spectrum is very narrow and sharp compared to the half-value width of 53 nm of the conventional green sulfide phosphor (commercially available product).

  Furthermore, it can be seen that the phosphors of Example 1 and Example 2 are phosphors having extremely high emission intensity and exhibiting high-luminance emission.

  On the other hand, in the phosphors produced in each comparative example, the peak wavelength of any phosphor is in the range of 530 nm to 550 nm, which is the green emission wavelength region, and the half-value width of the emission spectrum is the same as the conventional example. It was narrower than that. However, the phosphors obtained in the respective comparative examples had very inferior emission intensity compared to the examples.

  As can be seen from the results of the excitation characteristics shown in FIG. 4, the phosphor of Example 1 has a flat peak wavelength in a wide range of 400 nm to 500 nm, and the emission intensity is very high by excitation in that range. It can be seen that it can be excited efficiently. On the other hand, although the phosphors of Comparative Examples 3, 7, and 8 have a flat peak wavelength in a wide range of 400 nm to 500 nm, it can be seen that the emission intensity is very weak.

  From the results of the excitation characteristics shown in FIG. 4, the phosphor of Example 1 is flat in a wide range from 400 nm to 500 nm as described above, and the intensity is reduced by excitation from 400 nm to the short wavelength side. I understand. It can be seen that this excitation characteristic is significantly different from that of a commercially available green phosphor as a conventional example.

  Further, as shown in Table 2, in Example 1, the temperature conditions during the reductive sulfidation treatment in the phosphor manufacturing process were set to 900 ° C., Example 3 set to 925 ° C., and Example 4 set to 880 ° C. The wavelength was in the green light emission wavelength region, and the half-value width of the emission spectrum was very narrow, less than 50 nm, and the emission intensity was extremely strong, resulting in a phosphor exhibiting high luminance emission. On the other hand, in Comparative Example 7 in which the temperature condition of the reductive sulfiding treatment was 800 ° C. and Comparative Example 8 in which the temperature condition of 950 ° C. was used, although the wavelength region and the half-value width of the emission spectrum were good, the emission luminance was similar to that of conventional YAG. It was only the same level and showed very weak light emission.

  From this, it was found that in the reduction sulfurization treatment in the production of the phosphor, by controlling the firing temperature condition in the range of about 850 ° C. to 930 ° C., it becomes a phosphor exhibiting high luminance.

<3-3. X-ray diffraction measurement of phosphor>
Next, X-ray diffraction measurement was performed on the phosphors produced in Example 2 and Comparative Examples 3, 7, and 8 to obtain X-ray diffraction patterns. Further, by using the ICSD (Inorganic Structural Database) was simulated X-ray diffraction pattern for the _{SrGa 2 S 4, EuGa 2 S} 4, and _Ga 2 _{S 3.} FIG. 1 shows the respective X-ray diffraction patterns.

As shown in FIG. 1, it can be seen that Ga ₂ S ₃ : Eu 1% added with 1% Eu matches the X-ray diffraction pattern of Ga ₂ S ₃ simulated by ICSD, and consists of a single phase. I understand that. On the other hand, in SrGa ₁₂ S ₁₉ produced in Example 2, there are a peak that matches Ga ₂ S ₃ and a peak that approximates SrGa ₂ S ₄ and EuGa ₂ S ₄ , and a Ga ₂ S ₃ phase, SrGa. ₂ S _4-phase, and EuGa ₂ was found to be formed from S ₄ phase multiple crystalline phases.

In such a phosphor formed of a plurality of crystal phases, a small amount of liquid phase appears due to the eutectic reaction of SrGa ₂ S ₄ and Ga ₂ S _{3 in} the production process, and the self-flux effect based on the liquid phase As a result, it is considered that the phosphor surface phase has become a high-purity crystal. As a result, it is considered that the phosphor surface phase emits light with higher brightness than the conventional case.

Claims (5)

General formula: Sr (Ga _1-x Eu _x ) _y S _{1.5y + 1,} where x and y satisfy 0.008 <x <0.025, 11.5 <y <12.5 A sulfide phosphor characterized by that.   The sulfide phosphor according to claim 1, wherein the sulfide phosphor is formed of a plurality of crystal phases. _Formula: Sr is represented by _{(Ga 1-x Eu x)} y S 1.5y + 1, a wherein x is 0.008 <x <0.025, y is a 11.5 <y <12.5 A method for producing a sulfide phosphor, comprising:
Gel that obtains a gel body by weighing and mixing strontium carbonate to a mixture obtained by mixing gallium nitrate and europium compound so as to have a predetermined composition, and adding oxycarboxylic acid and alcohol to gel. Body production process;
An intermediate preparation step in which the gel body is heat-treated at a temperature condition of 400 ° C. to 500 ° C., and then oxidized and fired in an air atmosphere at a temperature condition of 550 ° C. to 600 ° C. to obtain an oxide precursor intermediate;
A pre-baking step of pre-baking the intermediate in an air atmosphere at a temperature condition of 700 ° C. to 1300 ° C. to obtain an oxide precursor;
And a reduction firing step in which the oxide precursor obtained in the preliminary firing step is subjected to a reduction sulfidation treatment under a temperature condition of 850 ° C. to 930 ° C., and a firing method.   4. The method for producing a sulfide phosphor according to claim 3, wherein, in the firing step, a reduction sulfur treatment is performed in an inert gas atmosphere containing carbon disulfide. The pre-baking step is
A first pre-baking step of baking the intermediate in an air atmosphere at a temperature condition of 700 ° C. to 800 ° C .;
The second pre-baking step of baking the oxide obtained through the first pre-baking step under a temperature condition of 1000 ° C to 1300 ° C in an air atmosphere. The manufacturing method of the sulfide fluorescent substance of description.

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