JP5484504B2 - Eu-activated alkaline earth metal thioaluminate phosphor and method for producing the same - Google Patents

Description

  The present invention relates to an Eu-activated alkaline earth metal thioaluminate phosphor and a method for producing the same, and more specifically, for example, as a red phosphor that emits high-intensity fluorescence in the emission wavelength region of near-ultraviolet or blue light-emitting diodes. The present invention relates to an Eu-activated alkaline earth metal thioaluminate phosphor that can be used and a method for producing the same.

In recent years, with the development of blue LEDs and near-ultraviolet LEDs, development of white light-emitting elements that obtain white color by combining these LEDs and phosphors is progressing. When creating a white light emitting element using a blue LED, for example, as described in Patent Document 1, a technique for obtaining a white light emitting element by combining a blue LED and a yellow phosphor YAG: Ce ³⁺ Has been developed.

  However, white light obtained by combining this blue light and its complementary color yellow light has poor color reproducibility and low color rendering. Therefore, in order to solve this problem, a white light emitting element called a three-wavelength type has been developed.

  As the three-wavelength white light emitting element, a white light emitting element using 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 phosphor that emits red light is used. It has been proposed (see, for example, Patent Document 2).

Examples of red phosphors that can be excited by blue light include nitride phosphors such as CaAlSiN: Eu, (Sr, a) AlSiN, Ca ₂ Si ₅ N ₈ , and Sr ₂ Si ₅ N ₈ (for example, Patent Documents). 3 and 4, see Non-Patent Document 1) and sulfide phosphors such as CaS: Eu, SrS: Eu, (Ca, Sr) S: Eu (see, for example, Patent Document 5). Yes.

  However, although nitride phosphors have high performance as phosphors, they are specially manufactured by annealing at a high temperature of 1700 ° C. to 2000 ° C. and a nitrogen pressure of several atmospheres in order to synthesize nitrides. A process is required. Moreover, since it requires a special manufacturing process, it is very expensive. In addition, a simple manufacturing method has been proposed for sulfide phosphors in recent years, but it has a unique odor and may react with moisture in the atmosphere to generate corrosive gas. It becomes.

  The nitride phosphor and sulfide phosphor described above are known to absorb light having a wavelength of 500 nm to 600 nm. Since this wavelength band corresponds to a green to orange wavelength, when used in combination with a green or yellow phosphor, the emission of other phosphors is absorbed, and the emission color of the white LED tends to be uneven. There is a problem. Further, sulfide phosphors such as CaS: Eu, SrS: Eu, and (Ca, Sr) S: Eu also have a problem that they cannot be excited by light of 350 nm to 400 nm.

On the other hand, MS-Al ₂ S ₃ -based sulfide phosphors (M: alkaline earth metal element) are known as sulfide phosphors as high-intensity phosphors of blue and green (for example, non-patent literature). 2, 3, 4). In recent years, phosphors containing rare earth-added alkaline earth metal thioaluminate phosphors have been used as inorganic EL elements that are light-emitting materials for thin-film electroluminescence (EL) used in displays for displaying various information and images. Attention has been focused on application development such as a method for performing full-color display (see, for example, Patent Document 6).

  As rare earth-added alkaline earth metal thioaluminate phosphors, for example, EL materials having high luminance and blue light emission with excellent color purity, and thin film EL elements using the EL materials as light emitting layers are known ( For example, see Patent Document 7). This EL material uses an alkaline earth metal thioaluminate as a base material and a lanthanoid element such as cerium as an activator.

Furthermore, the alkaline earth metal thioaluminate phosphors represented by BaAl ₂ S ₄ and BaAl ₄ S ₇ can be excited by ultraviolet rays of 300 nm to 400 nm and emit blue fluorescence, and CaAl ₂ S ₄ and SrAl _2. alkaline earth metal thioaluminate phosphor represented by S ₄ emits blue-green fluorescence was excitable by ultraviolet light of 300 nm to 400 nm. The alkaline earth metal thioaluminate phosphor represented by Ba ₅ Al ₂ S ₈ is a phosphor material that emits green fluorescence when excited by light of 300 nm to 500 nm.

  Thus, the alkaline earth metal thioaluminate phosphor material can be excited by a near-ultraviolet LED (emission wavelength 380 to 410 nm) to obtain high-luminance visible fluorescence, or a blue LED (emission wavelength 440 to 470 nm). ) To obtain green fluorescence, which is useful as a monochromatic LED lamp or a white LED phosphor.

  However, in such alkaline earth metal thioaluminate phosphors, there is no known red phosphor that can emit fluorescence in the orange to red wavelength region.

Japanese Patent Laid-Open No. 10-242513 JP 2000-244021 A JP 2006-008721 A JP 2006-152296 A JP 56-82876 A Japanese Patent Laid-Open No. 07-122364 Japanese Patent Laid-Open No. 08-134440

Hiromu Watanabe and Naoto Kijima Journal of Alloys and Compounds 475 (2009) 434-439 b.Eisenmann, M.Jakowski, H.Schafer, Materials Research Bulletin, 1982, 17, 9, p.1169-1175 K.T.Le Thi, A.Garcia, F.Guillen, C.Foussaier, Material Science Engineering B, 1992, 14, 2, p.393 Ichiro Nakayo, Genichi Hata-Koshi, Hiroshi Kobayashi “Physics and Applications of Light Emitting and Receiving” Baifukan 2008

  Therefore, the present invention has been proposed in view of such circumstances, and can absorb and excite light having a wavelength in the range of 350 nm to 500 nm, and can be in the wavelength range of orange to red in the range of 588 nm to 610 nm. An object of the present invention is to provide an Eu-activated alkaline earth metal thioaluminate phosphor capable of emitting fluorescence and a method for producing the same.

As a result of intensive studies to solve the above-described problems, the inventors of the present invention added a rare earth element Eu represented by a general formula [(Ba _1-x Sr _x ) ₄ Al ₂ S ₇ : Eu]. In the Eu activated alkaline earth metal thioaluminate phosphor, by controlling the metal ratio of the alkaline earth metal Ba and Sr to a predetermined range, it absorbs light having a wavelength in the range of 350 nm to 500 nm and is excited. The present invention has been completed by finding that it emits fluorescence in the orange to red wavelength region of 588 nm to 610 nm.

That is, the Eu-activated alkaline earth metal thioaluminate phosphor according to the present invention is an Eu-activated alkaline earth metal thioaluminate phosphor to which Eu is added as an activator, and the composition thereof is represented by the general formula [(Ba _1-x Sr _x ) ₄ Al ₂ S ₇ : Eu], wherein x in the general formula is 0.1 ≦ x <0.9.

A method of manufacturing a Eu-activated alkaline earth metal thioaluminate phosphor according to the present invention have the general formula _{[(Ba 1-x Sr x} ) 4 Al 2 S 7: Eu] in Eu-activated alkaline earth represented A method for producing a metal thioaluminate phosphor, wherein an alkaline earth metal carbonate is added to an aqueous solution obtained by mixing an Eu compound and water so that x in the above general formula is 0.1 ≦ x <0.9. Salt and aluminum nitrate are weighed and mixed, and a gel body production step for obtaining a gel body by adding oxycarboxylic acid and glycol or water to obtain a gel body, and heat-treating the gel body under a temperature condition of 400 ° C to 500 ° C. A carbonate precursor preparation step of preparing a carbonate precursor, and a preliminary firing step of heat-treating the precursor under a temperature condition of 700 ° C. to 1100 ° C. to obtain a precursor comprising carbonate and / or oxide; , Obtained in the pre-baking step A calcining step in which the precursor comprising the carbonate and / or oxide obtained is subjected to reduction sulfidation and calcining in an inert gas atmosphere containing carbon disulfide at a temperature of 800 ° C. to 1150 ° C. Features.

A method of manufacturing a Eu-activated alkaline earth metal thioaluminate phosphor according to the present invention have the general formula _{[(Ba 1-x Sr x} ) 4 Al 2 S 7: Eu] in Eu-activated alkaline earth represented A method for producing a metal thioaluminate phosphor, wherein an alkaline earth metal carbonate is added to an aqueous solution obtained by mixing an Eu compound and water so that x in the above general formula is 0.1 ≦ x <0.9. A gel body producing step of adding oxycarboxylic acid and glycol or water to obtain a gel body, and heat-treating the gel body under a temperature condition of 400 ° C. to 500 ° C. A carbonate precursor preparation step for producing a precursor, a pre-baking step for heat-treating the precursor under a temperature condition of 700 ° C. to 1100 ° C. to obtain a precursor composed of a carbonate and / or an oxide, and the pre-baking Carbonates obtained in the process and / or The precursor consisting of oxides, in an inert gas atmosphere containing hydrogen sulphide, calcined and reduced sulfide at a temperature of 800 ° C. to 1150 ° C., a first firing step to obtain a sulfide, the first With respect to the sulfide obtained in the firing step, Al ₂ S ₃ powder, or Al powder and sulfur, the total addition amount of which corresponds to the composition represented by the above general formula to the range of 30% excess amount And a second baking step in which the mixture is added and mixed so as to be inside, and is fired under a temperature condition of 800 ° C. to 1150 ° C.

  According to the Eu-activated alkaline earth metal thioaluminate phosphor according to the present invention, it is possible to absorb and excite light having a wavelength of 350 nm to 500 nm, and further to an orange to red wavelength region of 588 nm to 610 nm. Fluorescence can be emitted. Moreover, since it becomes the fluorescent substance which has the favorable crystallinity which consists of a single phase without a heterogeneous phase, it can absorb excitation light efficiently and can show high-intensity light emission in an orange-red wavelength range.

  In addition, according to the Eu-activated alkaline earth metal thioaluminate phosphor production method according to the present invention, a desired process can be efficiently performed without a complicated process and at a lower firing temperature condition as compared with the conventional method. It is possible to manufacture a phosphor that emits fluorescence.

It is a figure which shows the excitation and the emission spectrum which show the fluorescence characteristic of the sulfide fluorescent substance which light-emits the conventional orange to red light. It is a figure which shows the X-ray-diffraction result of Eu activation alkaline-earth metal thioaluminate fluorescent substance. Shows the results of crystal structure analysis of the phosphor represented _{by: [(Ba 1-x Sr} x) 4 Al 2 S 7 Eu]. It shows the resulting crystal structure by crystal structure analysis of _(Ba 0.625 _{Sr 0.375) 4} phosphor represented by Al ₂ S _7. An X-ray diffraction pattern simulated from a crystal structure of (Ba _0.625 Sr _0.375 ) ₄ Al ₂ S ₇ , Eu represented by [(Ba _0.6 Sr _0.4 ) ₄ Al ₄ S ₇ : Eu] X-ray diffraction pattern of activated alkaline earth metal thioaluminate phosphor, and - a diagram showing the X-ray diffraction pattern of the Ba ₄ Al ₂ S ₇ obtained from calculation It is a figure which shows the change of the Gibbs free energy of the reductive sulfidation reaction in a baking process. It is a figure which shows the excitation and the fluorescence spectrum of Eu activation alkaline-earth metal thioaluminate fluorescent substance produced in Example 1- Example 4. FIG. It is a figure which shows the excitation and the fluorescence spectrum of Eu activation alkaline-earth metal thioaluminate fluorescent substance produced in Example 5 and Example 6. FIG. 6 is a diagram showing an X-ray diffraction pattern of an Eu-activated alkaline earth metal thioaluminate phosphor produced in Example 7. FIG.

Hereinafter, the Eu-activated alkaline earth metal thioaluminate phosphor according to the present invention will be described in detail in the following order with reference to the drawings. Note that the present invention is not limited to the following embodiments, and various modifications can be made without departing from the gist of the present invention.
1. 1. Outline of the present invention 2. Eu activated alkaline earth metal thioaluminate phosphor. 3. Method for producing Eu-activated alkaline earth metal thioaluminate phosphor 3-1. First step 3-2. Second step 4. 4. Other manufacturing methods Example

<< 1. Outline of the present invention >>
The Eu-activated alkaline earth metal thioaluminate phosphor according to the present invention is an Eu-activated alkaline earth metal thioaluminate phosphor to which a rare earth element europium (Eu) is added as an activator, and its composition is generally It is represented by formula (1) [(Ba _1-x Sr _x ) ₄ Al ₂ S ₇ : Eu], and x in the general formula (1) is 0.1 ≦ x <0.9, To do.

As will be described in detail later, the Eu-activated alkaline earth metal thioaluminate phosphor having such a composition belongs to a monoclinic system and has a crystal structure of No14 in the space group. This crystal structure is the same crystal structure as (Ba _1-x Sr _x ) ₄ Al ₂ S ₇ (where 0.1 ≦ x <0.9).

  Here, FIG. 1 shows an excitation / emission spectrum showing the fluorescence characteristics of a conventional sulfide phosphor that emits red light from orange, represented by the general formula [(Sr, Ca) S: Eu]. The emission intensity in FIG. 1 is standardized with the maximum emission intensity of YAG: Ce as 1. As shown in FIG. 1, it can be seen that the conventional sulfide phosphor absorbs light having a wavelength of 500 nm to 600 nm and is excited. Since such a sulfide phosphor can be excited only in a wavelength band of 500 nm to 600 nm, when a white LED is produced by combining this sulfide phosphor with another phosphor, A problem arises in that light emitted from a phosphor (for example, a green phosphor or a yellow phosphor) is absorbed, and the emitted color is uneven.

  In contrast, the Eu-activated alkaline earth metal thioaluminate phosphor according to the present invention can be excited by absorbing light having a wavelength of 350 nm to 500 nm. For this reason, even when a white LED is manufactured in combination with another phosphor such as a conventional sulfide phosphor, the emission color of the phosphor does not absorb, and the emission color is uneven. Can be prevented, and light emission with high color purity can be exhibited.

  In addition, according to the Eu-activated alkaline earth metal thioaluminate phosphor having the above-described composition, it is possible to emit fluorescent light with high luminance in an orange to red wavelength region of 588 nm to 610 nm. Therefore, the Eu activated alkaline earth metal thioaluminate phosphor according to the present invention can be suitably used as a red phosphor.

≪2. Eu-activated alkaline earth metal thioaluminate phosphor >>
More specific description will be given below. As described above, the composition of the Eu-activated alkaline earth metal thioaluminate phosphor according to the present invention is represented by the general formula (1) [(Ba _1-x Sr _x ) ₄ Al ₂ S ₇ : Eu]. In the general formula, x satisfies 0.1 ≦ x <0.9.

  The Eu-activated alkaline earth metal thioaluminate phosphor according to the present invention belongs to the monoclinic system and has a crystal structure with a space group of No14.

In the above general formula (1), when x is less than 0.1, heterogeneous Ba ₅ Al ₂ S ₈ : Eu is generated, the crystallinity is deteriorated, and excitation light cannot be efficiently absorbed, The fluorescence intensity also decreases. For example, in the case of x = 0, that is, in the case of a phosphor whose composition formula is represented by Ba ₄ Al ₂ S ₇ : Eu, an emission peak is at 534 nm, the maximum excitation wavelength is 350 nm, and orange to red emission Not shown. Moreover, about the fluorescent substance represented by this composition formula, although the XRD pattern is known, the detailed crystal structure is not known.

On the other hand, in the general formula (1), even when x is 0.9 or more, a heterogeneous phase is generated, the crystallinity is deteriorated, and a phosphor composed of a single-phase crystal is not obtained. Further, for example, when x = 1, that is, a phosphor whose composition formula is represented by Sr ₄ Al ₂ S ₇ : Eu, it is difficult to manufacture the phosphor. Regarding a phosphor having an emission wavelength comparable to the emission wavelength of 534 nm, although the phosphor represented by SrGa ₂ S ₄ : Eu (538 nm emission) exhibits very strong emission, Sr ₄ Al ₂ S ₇ : Eu Since it is difficult to produce sulfides, they cannot be produced efficiently without causing heterogeneous phases.

Here, the present inventors have studied to dissolve Sr in a phosphor represented by the composition formula Ba ₄ Al ₂ S ₇ : Eu. That is, the examination which changes the ratio of Ba and Sr was performed. As a result, in the general formula (1) [(Ba _1-x Sr _x ) ₄ Al ₂ S ₇ : Eu], by setting x in the general formula to 0.1 ≦ x <0.9, 588 nm to The inventor found that it shows light emission in the orange to red region of 610 nm. Further, the light emission intensity at this time was as strong as 0.28 to 0.91 in terms of YAG: Ce (P46 manufactured by Kasei Optonics Co., Ltd.), indicating that the light emission intensity was practical.

Thus, it is represented by the general formula (1) [(Ba _1−x Sr _x ) ₄ Al ₂ S ₇ : Eu], and x in the general formula (1) is 0.1 ≦ x <0.9. By doing so, light can be emitted in the orange to red region of 588 nm to 610 nm, and it can be suitably used as a red phosphor.

In addition, the present inventors are represented by the general formula (1) [((Ba _1-x Sr _x ) ₄ Al ₂ S ₇ : Eu)], and x in the general formula is 0.1 ≦ x <0. .9, it was found that a crystal phase different from the composition was not included, and a phosphor composed of a single phase was obtained. According to such Eu-activated alkaline earth metal thioaluminate phosphor, it is possible to efficiently excite not only near-ultraviolet light but also light in the wavelength region of 350 nm to 500 nm, and the emission wavelength is from 588 nm to 610 nm. Red fluorescence can be emitted with high luminance. In particular, by exciting with light having a wavelength exceeding 400 nm, light can be emitted with higher luminance.

  Specifically, this is because the Eu-activated alkaline earth metal thioaluminate phosphor having the above-described composition belongs to the monoclinic system and the space group has a No14 crystal structure.

Here, first, in FIG. 2, Eu-activated alkaline earth represented by the general formula (1) [(Ba _1-x Sr _x ) ₄ Al ₂ S ₇ : Eu] (0.1 ≦ x <0.9) The X-ray-diffraction result of metal thioaluminate fluorescent substance is shown. As shown in FIG. 2 (A), even when x is changed in the range of 0.1 ≦ x <0.9 and the metal ratio of Ba and Sr is changed, the X-ray diffraction patterns are all the same. I understand that there is. Incidentally, the phosphor X-ray diffraction pattern of also seen that as compared with the conventional SrS and BaAl ₂ S phosphors such as ₄ a peak in a different position.

Also, diffraction angle (2θ) 20-22 deg. As is clear from FIG. 2B showing the peak at, the diffraction peak moves to the higher angle side as the Sr solid solution amount increases. This is considered to be due to the fact that the crystal lattice contracts because the ionic radius of Sr atoms is smaller than Ba. Specifically, in FIG. 3 and Table 1, a phosphor represented by the general formula (1) [(Ba _1-x Sr _x ) ₄ Al ₂ S ₇ : Eu] (0.1 ≦ x <0.9) Shows the change of the lattice constant according to the Ba and Sr ratio when the crystal structure analysis is performed on.

  As shown in FIG. 3 and Table 1, it can be seen that as the solid solution amount of Sr increases, the lengths of the a-axis, b-axis, and c-axis of the crystal lattice decrease and the crystal lattice contracts.

Here, FIG. 4 shows a crystal structure (crystal lattice) obtained by crystal structure analysis of the phosphor represented by (Ba _0.625 Sr _0.375 ) ₄ Al ₂ S ₇ . As shown in FIG. 4, the crystal structure of (Ba _1-x Sr _x ) ₄ Al ₂ S ₇ (0.1 ≦ x <0.9) belongs to the monoclinic system, and the space group is No14 (Herman Morgan). Symbol P2 ₁ / m). In addition, there are four types of positions of Ba and Sr atoms in the crystal structure. These four types have different occupancy rates of Ba and Sr. This crystal structure is the same as that of Ba ₄ Al ₂ S ₇ (monoclinic system, space group No. 11) in that it belongs to the monoclinic system, but the space group is different.

Then, as shown in FIG. 5, an X-ray diffraction pattern simulated by calculation from the crystal structure of the phosphor represented by (Ba _0.625 Sr _0.375 ) ₄ Al ₂ S ₇ and the above general formula ( 1) Eu-activated alkaline earth metal thioaluminate phosphor represented by [(Ba _0.6 Sr _0.4 ) ₄ Al ₄ S ₇ : Eu] in which x = 0.4 (Examples below) 2) and X-ray diffraction patterns. Note that the X-ray diffraction pattern of Ba ₄ Al ₂ S ₇ shown as a reference was simulated by the lattice constant and the angle β based on the description in Non-Patent Document 3 above. Non-patent document _3, the crystal structure of Ba 4 _Al 2 _{S 7 have} been described to be the same structure as Ba 4 _Ga 2 _{S 7.}

As shown in FIG. 5, Eu-activated alkaline earth metal represented by the general formula (1) [(Ba _1-x Sr _x ) ₄ Al ₂ S ₇ : Eu] (0.1 ≦ x <0.9) X-ray diffraction pattern of (Ba _0.6 Sr _0.4 ) ₄ Al ₂ S ₇ : Eu, which is an example of a thioaluminate phosphor, and the above-mentioned (Ba _0.625 Sr _0.375 ) ₄ Al ₂ S ₇ It can be seen that the X-ray diffraction pattern of FIG. 1 is almost identical in peak position, although there is a slight difference in diffraction peak intensity. Therefore, it can be seen that the crystal structure of the Eu-activated alkaline earth metal thioaluminate phosphor belongs to the monoclinic system and the space group is No14.

On the other hand, the X-ray diffraction pattern of the above Eu-activated alkaline earth metal thioaluminate phosphor is clearly different from the X-ray diffraction pattern of Ba ₄ Al ₂ S ₇ , and the general formula (1) [ The Eu activated alkaline earth metal thioaluminate phosphor represented by (Ba _1-x Sr _x ) ₄ Al ₂ S ₇ : Eu] (0.1 ≦ x <0.9) is Ba ₄ Al ₂ S _7. It can be seen that it is a solid solution single phase rather than a mixture of and other impurities.

As described above, the Eu-activated alkaline earth metal thioaluminum represented by the general formula (1) [(Ba _1-x Sr _x ) ₄ Al ₂ S ₇ : Eu] (0.1 ≦ x <0.9) Nate phosphors belong to the monoclinic system and have a crystal structure in which the space group is No14. Such an Eu-activated alkaline earth metal thioaluminate phosphor can absorb and excite light having a wavelength in the near-ultraviolet light region of 350 nm to 500 nm, and further, orange to red of 588 nm to 610 nm. It is possible to emit fluorescence in the wavelength region.

In addition, the Eu-activated alkaline earth metal thioaluminate phosphor according to the present invention forms a solid solution, and as described above, unlike Ba ₄ Al ₂ S ₇ , the crystal does not include a different phase and is a single phase. Thus, a phosphor having good crystallinity is obtained. In such a phosphor, light having a wavelength in the range of 350 nm to 500 nm can be more efficiently absorbed and excited, and high-luminance emission can be obtained in the orange to red wavelength range of 588 nm to 610 nm. it can.

  In addition, regarding the amount of sulfur in the general formula (1), even if the sulfur is reduced due to slight oxidation or loss, there is no significant effect on the fluorescence luminance.

≪3. Method for producing Eu-activated alkaline earth metal thioaluminate >>
Next, a method for producing an Eu-activated alkaline earth metal thioaluminate phosphor having the above-described characteristic composition will be described.

The manufacturing method of the phosphor according to the present invention is represented by the general formula (1) [(Ba _1-x Sr _x ) ₄ Al ₂ S ₇ : Eu], and x in the general formula (1) is 0.1. This is a method for producing an Eu-activated alkaline earth metal thioaluminate phosphor in which ≦ x <0.9. In this production method, an aqueous solution in which raw materials are mixed is polymerized to form a gel body, and a first step of obtaining a precursor comprising a carbonate or an oxide, or a mixture thereof, and the precursor is reduced and sulfided. And a second step of obtaining an Eu activated alkaline earth metal thioaluminate phosphor.

<3-1. First step>
In the first step, raw material compounds weighed so as to have a desired composition are mixed to form an aqueous solution, the aqueous solution is polymerized to form a gel body, and the gel body is subjected to heat treatment to produce MO- A precursor made of Al ₂ O ₃ carbonate, MO-Al ₂ O ₃ oxide, or a mixture thereof is obtained. Here, M in the MO-Al ₂ O ₃ -based carbonate and MO-Al ₂ O ₃ -based oxide represents Ba and Sr.

More specifically, in this first step, an alkaline earth metal carbonate and aluminum nitrate weighed to obtain a desired composition are mixed with an aqueous solution obtained by mixing an Eu compound and water, and an oxycarboxylic acid and a glycol are mixed. Alternatively, by adding water and heating at a predetermined temperature, the gel body producing step is performed, and the obtained gel body is heat-treated at a temperature condition of 400 ° C. to 500 ° C. to prepare a carbonate precursor. A precursor comprising a carbonate precursor preparation step and a MO-Al ₂ O ₃ carbonate or MO-Al ₂ O ₃ oxide, or a mixture thereof by heat-treating the precursor under a temperature condition of 700 ° C. to 1100 ° C. A preliminary firing step for obtaining a body.

(Gel body production process)
In the gel body production step, alkaline earth metal carbonate and aluminum nitrate are weighed in an aqueous solution obtained by mixing Eu compound as an activation element and water so that the composition represented by the general formula (1) is obtained. Then, oxycarboxylic acid and glycol or water are added, and heated at a predetermined temperature to cause gelation, thereby producing a gel body.

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

  In the gel body generation step, the above-described Eu compound such as Eu nitrate and water are mixed and redissolved to form an aqueous solution, and the alkaline earth metal carbonate and aluminum nitrate as raw materials are mixed with the aqueous solution (dissolved solution). .

  As the alkaline earth metal carbonate, barium carbonate and strontium carbonate are used. Such alkaline earth metal carbonate is a relatively inexpensive material, and by using it as a raw material, a phosphor with reduced cost can be produced.

The addition amounts of the Eu compound, alkaline earth metal carbonate, and aluminum nitrate are weighed so as to have a desired metal ratio of the phosphor composition and added to the aqueous solution. In the present embodiment, the composition is represented by the general formula (1) [(Ba _1-x Sr _x ) ₄ Al ₂ S ₇ : Eu], and x in the general formula (1) is 0.1 ≦ x The raw alkaline earth metal carbonate, Eu compound, and aluminum nitrate are weighed and mixed so that <0.9. Since the atomic ratio in the raw material to be supplied and the atomic composition ratio of the obtained phosphor are substantially the same, the respective raw materials are weighed and mixed so as to have the desired composition ratio, whereby the respective atoms are in the above-mentioned range. It can be.

  In the gel body generation step, the aqueous solution is gelled by adding oxycarboxylic acid and adding glycol or water to the solution in which the raw material compounds are mixed in this way.

  The order of adding each compound is not limited to the order described above. For example, an oxycarboxylic acid and glycol or water are completely dissolved in an aqueous solution in which an Eu compound is dissolved, and then the temperature of the aqueous solution is increased to about 65 ° C. to 85 ° C. to obtain an alkaline earth metal carbonate. After adding alkaline earth metal carbonate, aluminum nitrate may be added.

  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. As glycol, ethylene glycol or propylene glycol is preferably used, and polyethylene glycol can also be used.

  In addition, as the addition amount of oxycarboxylic acid and glycol, the molar ratio of the oxycarboxylic acid is about 4 to 5 times moles with respect to the total number of moles of the metal element composed of alkaline earth metal, Eu and Al, The glycol is preferably about 11 to 12 moles.

  In addition, when the addition amount of glycol is less than 11 times mole with respect to the total number of moles of metal elements, the polymerization reaction described later hardly occurs and gelation may not proceed efficiently. On the other hand, when it exceeds 12 times mole with respect to the total number of moles of a metallic element, since the effect of glycol addition does not increase any more and cost increases, it is not preferable.

  In the gel body production step, alkaline earth metal carbonate, aluminum nitrate, oxycarboxylic acid, glycol or water is added to the aqueous solution in which the Eu compound is dissolved as described above, and then the liquid temperature of the aqueous solution is 120 ° C. to The aqueous solution is heated to 250 ° C., more preferably 180 ° C. to 220 ° C., and stirred. By heating and stirring the aqueous solution in this manner, a polymerization reaction occurs and the aqueous solution gels. This polymerization reaction occurs when an esterification reaction occurs by adding glycol to a solution of a metal complex formed with oxycarboxylic acid and stirring and heating.

  As for 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 hours to 16 hours at the gelation temperature described above.

  In this way, in the gel body generation step, the aqueous solution mixed with the raw materials is gelled to form a gel body, whereby the raw materials can be uniformly dispersed, and in particular, the rare earth element Eu that becomes the emission center is uniformly distributed. A phosphor with high brightness can be obtained.

(Carbonate precursor preparation process)
Next, in the carbonate precursor preparation step, the obtained gel body is subjected to heat treatment to thermally decompose the gel body to prepare a carbonate precursor.

  The gel body obtained as described above contains an organic substance derived from the material added in the gel body generation step. Therefore, the organic substance is decomposed by performing a heat treatment in the carbonate precursor preparation step to obtain a carbonate precursor. Thereby, the fluorescence intensity of the obtained phosphor can be increased, and a phosphor with high brightness can be produced.

  As heat processing temperature in thermal decomposition, it is preferable to heat to 400 to 500 degreeC, and it is more preferable to heat to 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.

(Preliminary firing process)
Next, in the heat treatment product preparation step, MO-Al ₂ in which Eu as an activation element is uniformly dispersed by subjecting the precursor powder obtained in the carbonate precursor preparation step to heat treatment and provisional firing. A precursor composed of an O ₃ carbonate or MO-Al ₂ O ₃ oxide or a mixture thereof is obtained.

In this pre-baking step, the remaining organic matter is further decomposed and the carbonate of [(Ba _1-x Sr _x ) ₄ Al ₂ CO _z : Eu] or [(Ba _1-x Sr _x ) ₄ Al ₂ O _z : Eu], or a precursor composed of a mixture thereof.

  After the heat treatment in the carbonate precursor preparation step described above, the gel body is a gray carbonaceous powder. Therefore, in the preliminary firing step, the carbonaceous powder is pulverized. The pulverization method is not particularly limited, and for example, a method in which powder is put in a mortar and lightly pulverized can be used.

  Moreover, as heat processing temperature (temporary baking temperature), it is preferable to heat on 700 degreeC-1100 degreeC conditions, and it is more preferable to heat on 750 degreeC-890 degreeC conditions. When the heat treatment temperature is less than 700 ° C., the decomposition of the remaining organic matter may not proceed effectively. On the other hand, when the heat treatment temperature is higher than 1100 ° C., the carbonate is decomposed to become an oxide, but a complete oxide It can not be. Moreover, when complete oxide crystals are generated by this heat treatment, it is difficult to reduce and sulfidize in the next step.

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

<3-2. Second step (firing step)>
In the second step, the precursor made of the MO-Al ₂ O ₃ carbonate or MO-Al ₂ O ₃ oxide obtained in the first step, or a mixture thereof is reduced and sulfurized and fired. , A firing step for obtaining an Eu-activated alkaline earth metal thioaluminate phosphor.

In this firing step, reduction sulfidation firing is performed in an atmosphere of a mixed gas in which a predetermined amount of carbon disulfide (CS ₂ ) and an inert gas such as argon gas are mixed. By this reduction sulfidation firing, the above-mentioned precursor is reduced and sulfided to form a base crystal, and Eu is doped by reducing Eu at the Ba site and Sr site of the base crystal, and Eu is uniformly dispersed. A fired body of the activated alkaline earth metal thioaluminate phosphor is obtained.

  In the firing process, when it is performed for a long time under high temperature conditions, sulfur that tends to volatilize tends to escape from the reduced-sulfurized host crystal, producing a phosphor having high luminance and a desired emission wavelength. It becomes difficult to do. Therefore, in this reduction and sulfidation step, the precursor is calcined by reduction and sulfidation in an atmosphere of a mixed gas of carbon disulfide and an inert gas. Since carbon disulfide makes it possible to sulfidize oxides at a low temperature, this reduction sulfidation treatment allows firing at a low temperature condition, and prevents sulfur from escaping. This phosphor 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.

  Specifically, in the firing step, heating is performed in an inert gas containing carbon disulfide, and the temperature is preferably kept at 800 ° C. to 1150 ° C., more preferably 900 ° C. to 1100 ° C. for 1 hour to 12 hours. Reductive sulfidation firing is performed by heat treatment.

  If the temperature of the calcination treatment is less than 800 ° C., the reduction sulfidation becomes insufficient, which is not preferable. On the other hand, if the temperature of the baking treatment exceeds 1150 ° C., the temperature exceeds the melting point of aluminum sulfide, which may cause partial melting, which is not preferable because the fired product becomes non-uniform. Further, if the treatment is performed at a temperature exceeding 1150 ° C., the sulfur vapor pressure becomes high and sulfur is volatilized, which is not preferable.

Here, the Gibbs free energy change is shown when it is assumed that the reductive sulfidation reaction in this firing step occurs according to the following reaction formula. In the high temperature is preferable to carbonyl sulfide (COS) is decomposed into CO and S ₂ calculated in consideration to become stable.
Al ₂ O ₃ + 3CS ₂ (g) = Al ₂ S ₃ + 3CO (g) + 3 / 2S ₂ (g)
Al ₂ O ₃ + 4SrCO ₃ + 11CS ₂ (g)
= Al ₂ S ₃ + 4SrS + 15CO (g) + 15 / 2S ₂ (g)
Al ₂ O ₃ + 4BaCO ₃ + 11CS ₂ (g)
= Al ₂ S ₃ + 4BaS + 15CO (g) + 15 / 2S ₂ (g)

FIG. 6 shows the calculation result. As shown in FIG. 6, when Al ₂ O _{3 is used} alone, it is sulfided at a high temperature of about 1300 ° C., but when Ba or Sr is contained, the sulfurization temperature is lowered. However, since it is an equilibrium calculation that does not take into account the sulfidation rate, it is presumed that at 800 ° C., the decomposition of carbonate is difficult to proceed and it takes time.

  Thus, in the manufacturing method of the Eu activation alkaline earth metal thioaluminate phosphor according to the present invention, since it is manufactured to contain Ba and Sr at a predetermined metal ratio, the temperature is lower than that of the prior art. Reduction sulfidation firing can be efficiently performed under temperature conditions.

  Argon gas is preferably used as the inert gas used in the reduction sulfurization treatment. 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.

  Further, the temperature of carbon disulfide or Ar gas is preferably 15 ° C. or higher and lower than 46 ° C., more preferably 20 ° C. to 25 ° C. 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. Although it is conceivable to use nitrogen gas as the inert gas, it is not preferable because aluminum nitride may be formed.

  The firing furnace for performing the reduction sulfidation firing is not particularly limited, and for example, a tubular furnace in which the furnace core tube is quartz can be used. Further, as the temperature raising condition, for example, the temperature raising rate is 10 to 30 ° C./min, and the temperature can be set at a relatively low temperature condition of 800 ° C. to 1150 ° C. as described above.

  Further, when firing in a tubular furnace, it is preferable to flow a gas containing carbon disulfide immediately after the start of heating so that the gas in the quartz tube can be expelled. In particular, it is preferable to flow a gas that is twice to three times the volume of the entire quartz tube during the period from about 10 minutes to 20 minutes from the start of heating. Further, it is preferable to adjust the gas flow rate so that the amount of carbon disulfide becomes a sufficient amount at the temperature at which the reduction sulfurization is started. During firing, a sufficient amount of carbon disulfide-containing gas is required as described above. Therefore, it is preferable to continue flowing the gas containing carbon disulfide until cooling is completed and the temperature reaches room temperature.

  As described above, a fired body of Eu-activated alkaline earth metal thioaluminate phosphor can be obtained by performing reduced sulfur firing, but carbon may adhere to the surface of the fired product. In such a phosphor with carbon attached to the surface, the fluorescence brightness may be lowered. Therefore, it is preferable to form a new surface on the surface by pulverizing the obtained fired body after the above-described reduction sulfurization firing. Thereby, the fall of the brightness | luminance of fluorescent substance can be prevented and a high-intensity fluorescent substance can be obtained.

<< 4. Other manufacturing methods >>
Eu represented by the general formula (1) [(Ba _1-x Sr _x ) ₄ Al ₂ S ₇ : Eu], wherein x in the general formula (1) is 0.1 ≦ x <0.9. The activated alkaline earth metal thioaluminate phosphor is not limited to the production method described above, and can also be produced by the method described below.

  That is, first, similarly to the above-described manufacturing method, a solution obtained by mixing a raw material Eu compound and alkaline earth metal carbonate is gelled to form a gel body, and the gel body is subjected to heat treatment to obtain a precursor. Make it. Next, the precursor is subjected to reductive sulfidation treatment and fired at a temperature of 800 ° C. to 1150 ° C. to obtain (Ba, Sr, Eu) S powder.

  In addition, when preparing the gel body, the addition amount of the oxycarboxylic acid can be about 4 to 5 times the sum of the moles of metal of Ba, Sr and Eu, and the addition amount of glycol is , Ba, Sr, and Eu can be about 11 to 12 times the sum of the number of metal moles.

Next, in this manufacturing method, the obtained (Ba, Sr, Eu) S powder and Al ₂ S ₃ powder, or Al powder and sulfur are mixed to obtain a mixture. Then, the mixture is sealed in a vacuum ampule and is baked at a temperature of, for example, 800 ° C. to 1150 ° C., more preferably 900 ° C. to 1100 ° C. for about 12 hours to 36 hours, thereby obtaining a phosphor.

The vacuum ampule used for firing is not particularly limited, but when a quartz ampule is used, it may react with Al ₂ S ₃ , so that the sample can be placed in a carbon coating on a quartz tube or a carbon cylindrical container. preferable.

In this production method, it is important to appropriately control the addition amount of Al ₂ S ₃ powder or Al powder and sulfur. Specifically, it is added so as to be within the range of theoretical equivalent to 30% excess with respect to the amount corresponding to the desired composition. Considering the viewpoints such as the evaporation of Al ₂ S ₃ and the self-flux effect, the addition amount of Al ₂ S ₃ powder or Al powder and sulfur should be added within the range of theoretical equivalent to 30% excess. Thus, a phosphor having a desired composition can be produced with good crystallinity. On the other hand, when the excess amount exceeds 30%, a heterogeneous phase is generated, which is not preferable.

≪5. Examples >>
Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

In this example, the phosphors produced in each example were measured using a fluorescence spectrophotometer (FP6500, manufactured by JASCO Corporation), and the wavelengths of the excitation spectrum and emission spectrum were examined. . In addition, the emission intensity is compared and evaluated by standardizing the maximum luminance of Y ₃ Al ₅ O ₁₂ : Ce ³⁺ (YAG: Ce, P46 manufactured by Kasei Optonics Co., Ltd.), which is a conventional yellow phosphor, as 1. did.

[Example 1]
(Production of phosphor)
(First step)
Europium oxide (3N: Eu ₂ O ₃ manufactured by Furuuchi Chemical Co., Ltd.) was completely dissolved in nitric acid (60% manufactured by Kanto Chemical Co., Ltd.) having a concentration of 15 mol / L to prepare an aqueous solution of Eu nitrate. This aqueous solution of Eu nitrate was placed in a beaker and mixed with distilled water, and the resulting aqueous solution was mixed with barium carbonate (manufactured by Kanto Chemical Co., Ltd.) and strontium carbonate (manufactured by Kanto Chemical Co., Ltd.) with a metal ratio of 8: 2. Weighed and added so that an aluminum nitrate solution was further added. The amount of Eu was 1% of the number of metal moles of Ba and Sr. Subsequently, citric acid was added to this mixed solution, and the solution temperature was kept at 80 ° C. to completely dissolve citric acid and carbonate. The amount of citric acid added was four times the sum of the moles of metal of Ba, Sr, Eu and Al. Then, after stirring until carbonate melt | dissolves and a complex is formed, propylene glycol was added to the liquid mixture. The amount of propylene glycol added was 12 times the sum of the number of metal moles of Ba, Sr, Eu and Al.

  Subsequently, the solution was heated to 130 ° C. to cause an esterification reaction between citric acid and propylene glycol in the solution to gel the solution.

  Next, the obtained gel-like substance (gel body) was placed in a mantle heater together with a beaker and heated to 450 ° C. to thermally decompose the gel body to prepare a carbonate precursor.

  Next, the obtained carbonate precursor was pulverized using a mortar to obtain a precursor powder, which was heat-treated (pre-baked) at a temperature of 800 ° C. to obtain a heat-treated powder.

(Second step)
Next, the heat-treated powder obtained by pre-baking is put in an alumina crucible and reduced by applying a heat treatment for 2 hours under a temperature condition of 950 ° C. under a flow of argon gas through liquid carbon disulfide. A calcination treatment for sulfuration was performed. Thus, a phosphor represented by the composition formula [(Ba _0.8 Sr _0.2 ) ₄ Al ₂ S ₇ : Eu] was produced. The Ar flow rate was 50 ml / min, and the gas was allowed to flow until the furnace reached room temperature. The gas flow rate was measured using a digital flow meter (manufactured by Kofloc, Model 8300).

(Fluorescence measurement evaluation of phosphors)
Excitation / emission spectra were measured for the obtained phosphor. FIG. 7 shows the result of fluorescence measurement. In addition, the emission spectrum in FIG. 7 is a spectrum at an excitation wavelength of 450 nm. FIG. 2 shows an X-ray diffraction pattern of the produced phosphor.

  As shown in FIG. 7, it can be seen that the emission spectrum shows a single emission having a peak at 588 nm. Further, it can be seen from the excitation spectrum that there are two broad excitations of 250 nm to 300 nm and 380 nm to 500 nm.

[Example 2]
A phosphor was prepared in the same manner as in Example 1 except that the gel was prepared by weighing the raw materials so that the metal ratio of Ba and Sr was 6: 4 and that the reduced sulfurization temperature was 1050 ° C. .

  FIG. 7 shows the result of fluorescence measurement of the produced phosphor. FIG. 2 shows an X-ray diffraction pattern of the produced phosphor. As shown in FIG. 7, it can be seen that the emission spectrum shows a single emission having a peak at 590 nm. In addition, it can be seen from the excitation spectrum that it has a wide bimodal excitation of 300 nm and 500 nm.

[Example 3]
A phosphor was prepared in the same manner as in Example 1 except that the gel was prepared by weighing the raw materials so that the metal ratio of Ba and Sr was 4: 6, and that the reduced sulfurization temperature was 1050 ° C. .

  FIG. 7 shows the result of fluorescence measurement of the produced phosphor. FIG. 2 shows an X-ray diffraction pattern of the produced phosphor. As shown in FIG. 7, it can be seen that the emission spectrum shows a single emission having a peak at 596 nm. In addition, it can be seen from the excitation spectrum that it has a wide bimodal excitation of 300 nm and 500 nm.

[Example 4]
A phosphor was prepared in the same manner as in Example 1 except that the gel was prepared by weighing the raw materials so that the metal ratio of Ba and Sr was 2: 8.

  FIG. 7 shows the result of fluorescence measurement of the produced phosphor. FIG. 2 shows an X-ray diffraction pattern of the produced phosphor. As shown in FIG. 1, it can be seen that the emission spectrum shows a single emission having a peak at 610 nm, and that the excitation spectrum has a wide bimodal excitation of 300 nm and 500 nm. I understand.

<About other manufacturing methods>
[Example 5]
Europium oxide (3N: Eu ₂ O ₃ manufactured by Furuuchi Chemical Co., Ltd.) was completely dissolved in nitric acid (60% manufactured by Kanto Chemical Co., Ltd.) having a concentration of 15 mol / L to prepare an aqueous solution of Eu nitrate. This aqueous solution of Eu nitrate was placed in a beaker and mixed with distilled water, and the resulting aqueous solution was mixed with barium carbonate (manufactured by Kanto Chemical Co., Ltd.) and strontium carbonate (manufactured by Kanto Chemical Co., Ltd.) with a metal ratio of 6: 4. Weighed so as to be added. The amount of Eu was 1% of the number of metal moles of Ba and Sr. Subsequently, citric acid was added to this mixed solution, and the solution temperature was kept at 80 ° C. to completely dissolve citric acid and carbonate. The amount of citric acid added was 4 times the sum of the moles of metal of Ba, Sr, and Eu. Then, after stirring until carbonate melt | dissolves and a complex is formed, propylene glycol was added to the liquid mixture. The amount of propylene glycol added was 12 times the sum of the number of metal moles of Ba, Sr, and Eu.

  Next, this solution was heated to 130 ° C. to cause an esterification reaction between citric acid and propylene glycol in the solution to gel the solution.

  The obtained gel-like substance (gel body) was placed in a mantle heater together with a beaker and heated to 450 ° C. to thermally decompose the gel body to prepare a carbonate precursor.

  Next, the obtained carbonate precursor was pulverized using a mortar to obtain a precursor powder, which was heat-treated (pre-baked) at a temperature of 800 ° C. to obtain a heat-treated powder.

Next, the heat-treated powder calcined at 800 ° C. was put in an alumina crucible and subjected to heat treatment for 5 hours in Ar at 10% hydrogen sulfide under a temperature condition of 950 ° C. to perform reduction sulfidation. Thereby, a sulfide having a composition formula [(Ba _0.6 Sr _0.4 ) S: Eu] was produced. The Ar flow rate of 10% hydrogen sulfide was 20 ml / min, and the gas was allowed to flow until the furnace reached room temperature. The gas flow rate was measured using a digital flow meter (manufactured by Kofloc, Model 8300).

Subsequently, the sulfide of [(Ba _0.6 Sr _0.4 ) S: Eu], Al powder, and sulfur (S) in a molar ratio of 4: 2.2: 3.75 (Al: 10 % Excess, S: 11% excess (Al and S: 21% excess)), and molded into a 10 mm plate by hand press. The molded product was put in a quartz ampoule in which a carbon sheet (thickness 0.2 mm, manufactured by Toyo Tanso Co., Ltd.) was rolled and sealed in a vacuum. Al powder and sulfur were increased considering Al oxidation. The ampule was placed in an electric furnace and baked for 24 hours at a temperature of 950 ° C.

  FIG. 8 shows the result of fluorescence measurement of the phosphor. The emission spectrum in FIG. 8 is a spectrum at an excitation wavelength of 450 nm. As shown in FIG. 8, the fluorescence characteristic is an emission spectrum showing a single emission having a peak at 590 nm as in Example 2 above, and an excitation spectrum having a wide bimodal excitation at 300 nm and 500 nm. there were. The emission intensity was 1.06 times in terms of YAG ratio.

  Thus, also in the manufacturing method carried out in Example 5, light having a wavelength in the region of 350 nm to 500 nm can be efficiently absorbed and excited, and light is emitted in the orange to red wavelength region of 588 nm to 610 nm. It has been found that a phosphor that emits light with high brightness can be obtained.

[Example 6]
The gel material was prepared by weighing the raw materials so that the metal ratio of Ba and Sr was 4: 6, and the mixture (sulfide, Al powder and sulfur) was vacuum sealed in a vacuum sample, and then the temperature was 1050 ° C. A phosphor was produced in the same manner as in Example 5 except that firing was performed under the conditions.

  FIG. 8 shows the result of fluorescence measurement of the produced phosphor. As shown in FIG. 8, the fluorescence characteristic is an emission spectrum showing a single emission having a peak at 590 nm as in Example 5 above, and an excitation spectrum having a wide bimodal excitation at 300 nm and 500 nm. there were. The emission intensity is 1.56 times in terms of the YAG ratio, and it can be seen that the emission intensity is high.

[Example 7]
(Examination of addition amount of Al powder and sulfur)
In the same manner as in Example 5, a sulfide represented by the composition formula [(Ba _0.6 Sr _0.4 ) S: Eu] was prepared, and then this [(Ba _0.6 Sr _0.4 ) S : Eu] sulfide, Al powder and sulfur (S) in a molar ratio of 4: 2.4: 3.6 (Al and sulfur (S): 20% excess), 4: 2.6: 3.9 (Al and S: 30% excess), 4: 2.8: 4.2 (Al and S: 40% excess), 4: 3: 4.5 (Al and S sulfur: 50% excess) Amount), 4: 3.2: 4.8 (Al and S: 60% excess amount) were weighed so as to satisfy each of the five conditions, and molded into a 10 mm plate shape by a hand press. The molded product was put into a quartz ampoule in which a carbon sheet (thickness 0.2 mm, manufactured by Toyo Tanso Co., Ltd.) was rolled and sealed in vacuum one by one. Al and sulfur were increased considering Al oxidation. Then, 5 ampoules were put in an electric furnace and baked for 24 hours at a temperature of 950 ° C.

FIG. 9 shows the X-ray diffraction results of the obtained phosphor. As shown in FIG. 9, when the excess amounts of Al and sulfur were 20% and 30%, the same diffraction pattern as that of the CS ₂ composite was shown. On the other hand, when the excess amount was 40% to 60%, an impurity peak that appeared to be Ba ₂ AlS ₅ appeared. In particular, the diffraction angle 2θ is 10 to 20 deg. It can be seen that the peak appearing in the range (Y part in FIG. 9) corresponds to the impurity Ba ₂ AlS ₅ .

[Conventional Examples 1 to 3]
Calcium carbonate (manufactured by Kanto Chemical Co., Inc.) and strontium carbonate (manufactured by Kanto Chemical Co., Ltd.) are weighed in molar ratios as Ca: Sr = 1: 0, 0.75: 0.25, 0.85: 0.15. Each was placed in distilled water. To this was added an aqueous solution of Eu nitrate so that Eu would be 0.2% with respect to the sum of the molar amounts of Sr and Ca. To this aqueous solution, citric acid having a mole number of 6 times the number of moles of all metal elements was added and stirred at 80 ° C. for 1 hour to dissolve the carbonate. Further, after dissolution, the solution was heated to 120 ° C. to gel the solution.

  The obtained gel body was put into a mantle heater and heated to 450 ° C. to thermally decompose the gel body. Next, the pyrolyzed powder was put in an alumina crucible and fired at 750 ° C. for 2 hours to prepare a precursor.

  Then, the precursor was put in a carbon container and reduced and sulfided in carbon disulfide to prepare a sulfide phosphor. The reducing sulfidation was carried out for 1 hour under a temperature condition of 900 ° C. under Ar flowing through liquid carbon disulfide. The Ar flow rate was 30 cc / min.

FIG. 1 shows the obtained sulfide phosphors CaS: Eu 0.2% (conventional example 1), Sr _0.75 Ca _0.25 S: Eu 0.2% (conventional example 2), Sr _0.85 Ca. Each fluorescence characteristic of _0.15 S: Eu0.2% (conventional example 3) is shown. As shown in FIG. 1, these conventional sulfide phosphors emit fluorescence in the wavelength region of 600 nm or more, but have an excitation spectrum peak at 500 nm or more, and excitation in the wavelength region of 500 nm or more. It turns out that it absorbs light.

  The Eu-activated alkaline earth metal thioaluminate phosphor according to the present invention can be excited by light in a wavelength region of 350 nm to 500 nm and exhibits practical luminance emission in an orange to red region of 588 nm to 610 nm. . According to such Eu activated alkaline earth metal thioaluminate phosphor, it can be suitably used as a red phosphor.

  In addition, since this Eu-activated alkaline earth metal thioaluminate phosphor does not absorb green to yellow fluorescence, which has been a problem in conventional phosphors, near-ultraviolet LEDs and blue light in the vicinity of wavelengths of 350 nm, 400 nm, and 450 nm. It can be effectively used as a phosphor for a three-wavelength white light-emitting element formed in combination with an LED and a phosphor emitting green to yellow light. Moreover, it can use suitably also as fluorescent substance used for display displays, such as FED (electrolytic emission type display) and inorganic EL.

Claims (7)

An Eu-activated alkaline earth metal thioaluminate phosphor to which Eu is added as an activator,
The composition is represented by the general formula [(Ba _1-x Sr _x ) ₄ Al ₂ S ₇ : Eu], and x in the general formula is 0.1 ≦ x <0.9. Activated alkaline earth metal thioaluminate phosphor.   The Eu-activated alkaline earth metal thioaluminate phosphor according to claim 1, which belongs to a monoclinic system and has a crystal structure of No14 as a space group.   The Eu-activated alkaline earth metal thioaluminate fluorescence according to claim 1 or 2, which can be excited by excitation light having a wavelength of 350 nm to 500 nm and emits orange to red fluorescence having a wavelength of 588 nm to 610 nm. body. A method for producing an Eu-activated alkaline earth metal thioaluminate phosphor represented by a general formula [(Ba _1-x Sr _x ) ₄ Al ₂ S ₇ : Eu],
An alkaline earth metal carbonate and aluminum nitrate are weighed and mixed in an aqueous solution obtained by mixing an Eu compound and water so that x in the above general formula is 0.1 ≦ x <0.9. A gel body generating step of adding an acid and glycol or water to obtain a gel body by gelation;
A carbonate precursor preparation step of heat-treating the gel body under a temperature condition of 400 ° C. to 500 ° C. to prepare a carbonate precursor;
A pre-baking step of heat-treating the precursor at a temperature of 700 ° C. to 1100 ° C. to obtain a precursor composed of carbonate and / or oxide;
Firing in which the precursor made of carbonate and / or oxide obtained in the pre-firing step is subjected to reduction sulfidation and firing in an inert gas atmosphere containing carbon disulfide at a temperature of 800 ° C. to 1150 ° C. And a process for producing an Eu-activated alkaline earth metal thioaluminate phosphor.   The method for producing an Eu-activated alkaline earth metal thioaluminate phosphor according to claim 4, wherein the oxycarboxylic acid is citric acid.   The method for producing an Eu-activated alkaline earth metal thioaluminate phosphor according to claim 4 or 5, wherein the glycol is ethylene glycol or propylene glycol. A method for producing an Eu-activated alkaline earth metal thioaluminate phosphor represented by a general formula [(Ba _1-x Sr _x ) ₄ Al ₂ S ₇ : Eu],
An alkaline earth metal carbonate is weighed and mixed in an aqueous solution obtained by mixing an Eu compound and water so that x in the above general formula is 0.1 ≦ x <0.9, and oxycarboxylic acid and glycol or A gel body producing step of adding water to gel to obtain a gel body;
A carbonate precursor preparation step of heat-treating the gel body under a temperature condition of 400 ° C. to 500 ° C. to prepare a carbonate precursor;
A pre-baking step of heat-treating the precursor at a temperature of 700 ° C. to 1100 ° C. to obtain a precursor composed of carbonate and / or oxide;
The precursor comprising the carbonate and / or oxide obtained in the pre-baking step is reduced and sulfidized under a temperature condition of 800 ° C. to 1150 ° C. under an inert gas atmosphere containing hydrogen sulfide, and then sulfide. a first firing step of obtaining a
With respect to the sulfide obtained in the first firing step, Al ₂ S ₃ powder, or Al powder and sulfur, the theoretical addition corresponding to the composition represented by the above general formula to 30% excess An Eu-activated alkaline earth metal thioaluminate phosphor comprising: a second baking step of adding and mixing so as to be within the amount range, and baking at a temperature of 800 ° C. to 1150 ° C. Production method.

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