JP2010053280A - Green-emitting phosphor and inorganic el element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a green phosphor which does not use rare earth elements and can be stably supplied. <P>SOLUTION: The green-emitting phosphor includes a parent material of a compound represented by general formula: M<SP>1</SP>M<SP>2</SP><SB>2</SB>S<SB>4</SB>(wherein, M<SP>1</SP>is Ca<SB>X</SB>Sr<SB>1-X</SB>(0≤X≤1), and M<SP>2</SP>is Ga<SB>Y</SB>Al<SB>1-Y</SB>(0≤Y≤1)) and bismuth contained in the parent material. The parent material preferably further contains manganese. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a green light emitting phosphor and an inorganic EL (electroluminescence) element.

Many types of fluorescent materials used for displays and light sources are known, and fluorescent materials using a thiogallate compound as a base material and added with metal ions for fluorescent emission are known. For example, Patent Document 1 discloses a fluorescent material obtained by adding tin or tin and cerium to a base material of a thiogallate compound (CaGa ₂ S ₄ ). This fluorescent material emits fluorescence over almost the entire visible light region from 500 nm to near 850 nm (half-value width 350 nm), and as the excitation light, ultraviolet light around 350 nm is effective, but excitation light of 400 nm or more does not emit light.

In Patent Document 2, a green phosphor can be produced by adding europium (Eu) that forms a light emission center to strontium gallium sulfide (SrGa ₂ S ₄ ), which is a thiogallate base material compound, as a green light-emitting phosphor. It is reported. This phosphor is supposed to be able to emit light when excited by radiation, electron beam, ultraviolet light and electric field. The peak wavelength of this green light emission is 535 nm, and the coordinates of the color point in the chromaticity diagram are x = 0.300 and y = 0.686. Then, it has been reported that a near-ultraviolet or blue LED can be used as a white light source by combining yellow to red cerium-activated carbide silicon nitride and this green phosphor with an excitation light source. Similarly, three phosphors, yellow to red cerium activated carbide silicon nitride, red phosphor Ca _1-X Sr _X S: Eu (0 ≦ X ≦ 1) and the like, and this green phosphor It has been reported that a white light source with higher color rendering can be obtained by combining them.
JP 2005-272624 A Special table 2007-526635

  In general, there are not many substances that emit fluorescence with a short wavelength. In particular, when a radiation such as near ultraviolet light or blue light is used as excitation light, it is difficult to obtain a green phosphor. In that respect, the green phosphor disclosed in Patent Document 2 is considered to be a useful fluorescent material because a blue light emitting diode is used as excitation light. On the other hand, the problem of securing resources has become important as the use of rare earth elements increases and the demand increases. Since rare earth elements are scarce and the production areas are biased, the difficulty of obtaining them will continue in the future. In the future, high-quality fluorescent materials used in displays and light sources, which will be increasingly demanded, do not need to use rare earth elements that are difficult to obtain and susceptible to price fluctuations even if the amount used is small. It is preferable. It is desirable that the fluorescent material that is the basic material of many electrical products and optical-related products is as stable as possible and can be manufactured from an inexpensive material. Moreover, it is desirable that various alternative materials can be provided. However, fluorescent materials often contain rare earth elements in the emission center, and in Patent Documents 1 and 2, cerium and europium are often required. In particular, fluorescent materials that emit green light require expensive rare earth elements.

  In view of such a current situation, an object of the present invention is to provide a green phosphor that can be stably supplied without using a rare earth element, and an inorganic EL (electroluminescence) element using the green phosphor.

In order to solve the above-mentioned problems, the present inventors searched for a phosphor that can replace a rare earth element such as cerium or europium as an element that forms a light emission center using a thiogallate compound as a base material. As a result, the base material M ¹ M ² ₂ S ₄ (where M ¹ = Ca _X Sr _1-X (0 ≦ X ≦ 1), M ² = Ga _Y Al _1-Y (0 ≦ Y ≦ 1)) Instead of the rare earth element, a phosphor emitting green light (green phosphor) to which bismuth was added, which was cheaper and easier to secure the supply stability, was obtained. The peak wavelength of emission of this green phosphor was about 533 nm, and the half width of the emission spectrum was 55 nm. According to the measurement by the present inventors, the emission intensity of this green phosphor was slightly lower than that of the green phosphor added with europium described in Patent Document 2, but the emission peak wavelength and emission spectrum The full width at half maximum was almost the same. In the case of the green phosphor to which bismuth is added, the excitation band is preferably near ultraviolet rays of about 300 nm, and has a characteristic that can be sufficiently excited even in the near ultraviolet region of about 400 nm.

In order to make the efficient excitation near-ultraviolet region even longer, a green phosphor having an excitation band in the near-ultraviolet region near 400 nm was obtained by simultaneously adding bismuth and manganese. Thus, it has been found that the green phosphor of the present invention can be replaced with a green phosphor (SrGa ₂ S ₄ : Eu) to which a rare earth element (such as europium) is added without using a rare earth element.

That is, the present invention has a general formula M ¹ M ² ₂ S ₄ (where M ¹ is Ca _X Sr _1-X (0 ≦ X ≦ 1) and M ² is Ga _Y Al _1-Y (0 ≦ Y ≦ 1). )) Is a phosphor emitting green light, characterized in that it contains bismuth in the compound represented by Moreover, a preferable present invention is a phosphor emitting green light, wherein the phosphor further contains manganese.

  Another aspect of the present invention is an inorganic EL (electroluminescence) element characterized in that a thin film made of the phosphor emitting green light is sandwiched from both sides by a pair of electrodes.

  According to the present invention, it is possible to provide a phosphor that emits green light that can be stably supplied without using a rare earth element, and an inorganic EL element using the phosphor.

The phosphor emitting green light of the present invention (sometimes abbreviated as green phosphor) has a general formula M ¹ M ² ₂ S ₄ (where M ¹ is Ca _X Sr _1-X (0 ≦ X ≦ 1)). , M ² contains a bismuth ion serving as a luminescent center ion in a base material compound represented by Ga _Y Al _1-Y (0 ≦ Y ≦ 1). As the bismuth ion source, metal bismuth may be used, and in some cases, an oxide, sulfide, hydroxide, or bismuth salt may be used. The bismuth salt may be any salt, but includes inorganic salts such as halides, sulfates and nitrates. Examples of the halide include bismuth fluoride, bismuth chloride, bismuth bromide, bismuth iodide, and the like.

  The content of bismuth is preferably about 0.1 to 10 mol%, preferably about 0.5 to 5 mol%, based on the base material. The bismuth content may be 10 mol% or more, but the fluorescence emission intensity does not increase, so there is no need to add more. If the bismuth content is less than 0.1 mol%, the emission intensity may decrease, or if the mixing with the base material is not sufficient, uneven emission of fluorescence may occur.

  FIG. 1 shows the emission characteristics of this green phosphor. Spectrum (1) is a chart of fluorescence emission by excitation light of 300 nm, the peak wavelength of emission was about 534 nm, and the half width of the emission spectrum was 55 nm. The spectrum (2) is a chart of fluorescence emission by excitation light in the emission region of a blue light emitting diode of 400 nm. The emission peak wavelength is the same 534 nm green monochromatic light, but the emission spectrum intensity is 300 nm excitation light. It was about 60 to 70% of the fluorescence emission due to. The spectrum (3) represents the emission intensity of the fluorescence with respect to the wavelength of the excitation light of the green phosphor. As can be seen from this spectrum chart, this green phosphor exhibits a light emission peak due to excitation by excitation light having a wavelength of about 320 nm, and excitation light up to a wavelength of about 450 nm emits considerable light. And this green fluorescent substance can be light-emitted by the excitation by the excitation light to wavelength 500nm. This green phosphor does not deny that other substances are included in addition to the base material and bismuth.

  In the phosphor of the present invention, when manganese is further contained in addition to bismuth, manganese may be used as the manganese source, and in some cases, oxide, sulfide, hydroxide, or manganese salt is used. May be. Further, the manganese salt may be any salt, but includes inorganic salts such as halides, sulfates and nitrates. Examples of the halide include manganese fluoride, manganese chloride, manganese bromide, and manganese iodide.

  The manganese content is preferably about 0.1 to 15 mol%, particularly about 0.5 to 5 mol% in total of bismuth and manganese with respect to the base material. In addition, when it contains manganese, bismuth content may be less than 0.1 mol%. The total content of bismuth and manganese can be 15 mol% or more, but the fluorescence emission intensity does not increase, so it is not necessary to contain more. If the total content of bismuth and manganese is less than 0.1 mol%, the emission intensity may decrease, or if the mixing with the host material is not sufficient, uneven emission of fluorescence may occur.

The green phosphor of the present invention can have an excitation band peak in the blue light or near-ultraviolet region near 420 nm by containing bismuth and manganese simultaneously with the base material. Therefore, the green phosphor doped with a rare earth element (europium, etc.) without the use of (SrGa ₂ S ₄ Eu), can be excited by the blue light emitting diode having an emission peak around 420 nm.

  FIG. 2 shows the light emission characteristics of the green phosphor of the present invention containing bismuth and manganese at the same time. Spectrum (4) is a chart of fluorescence emission by excitation light of 400 nm, the peak wavelength of emission was about 533 nm, and the half width of the emission spectrum was 60 nm. Spectrum (5) represents the emission intensity of fluorescence having a wavelength of 533 nm with respect to the excitation wavelength of the excitation light of this green phosphor. As can be seen from the spectrum chart, the green phosphor exhibits a light emission peak due to excitation by excitation light having a wavelength of around 420 nm, and excitation light up to a wavelength of around 450 nm prompts considerable emission. In addition, the fluorescence by excitation light with a wavelength of around 320 nm is much weaker than that of the green phosphor not containing manganese.

  Any of the green phosphors of the present invention is a solid fluorescent material characterized by near ultraviolet radiation excitation, green emission, and fluorescence in a relatively narrow wavelength range. These green phosphors are excellent in monochromaticity, and can be combined with a red phosphor or a yellow phosphor that can be obtained relatively easily to provide a white light source with excellent color rendering properties. In particular, when a blue light emitting diode is used as an excitation light source, color rendering can be performed by a combination of four light emitting sources, which is suitable for generating a desired white light source.

It is represented by the general formula M ¹ M ² ₂ S ₄ (where M ¹ is Ca _X Sr _1-X (0 ≦ X ≦ 1) and M ² is Ga _Y Al _1-Y (0 ≦ Y ≦ 1)). When the compound is used as a base material, the general formula M ¹ M ² ₂ S ₄ (provided that M ¹ is Ca is based on the X-ray diffraction measurement of the green phosphor of the present invention itself or a powder obtained by pulverizing the green phosphor) A diffraction line identified as a compound represented by _X Sr _1-X (0 ≦ X ≦ 1) and M ² is Ga _Y Al _1-Y (0 ≦ Y ≦ 1)) is observed, It means that it can be judged that a crystalline solid of a compound represented by the formula M ¹ M ² ₂ S ₄ is formed. In general formula ^M 1 ^M ₂ 2 _{S 4} described above, as an extreme _{example, CaGa 2 S 4, CaAl 2} S 4, SrGa 2 S 4, SrAl 2 that S may be a _four course.

  The crystalline solid means a single crystal body, a polycrystalline sintered body, a polycrystalline or single crystal film, a thin layer body, or a bulk body. In addition, fine particles of a polycrystalline sintered body, a thin piece of a polycrystalline or single crystalline film, a polycrystalline or single crystalline microcrystal dispersed in a liquid or an organic polymer, etc. Even if it is in a liquid form or an amorphous form, the basic element exhibiting fluorescence is a crystalline solid, and thus corresponds to the crystalline solid mentioned here.

The green phosphor of the present invention has a general formula M ¹ M ² ₂ S ₄ (where M ¹ is Ca _X Sr _1-X (0 ≦ X ≦ 1) and M ² is Ga _Y Al _1-Y (0 ≦ Y). Since there is novelity in combining bismuth or bismuth and manganese with the compound represented by ≦ 1)) as an additive element in the base material, any production method may be used. For example, like the conventional phosphor manufacturing method, a dry method in which each raw material powder is mixed and sintered, or a compound containing an element serving as each raw material is reacted in an aqueous solution, and the reaction product is precipitated. What is necessary is just to utilize the wet method etc. which dry and sinter depending on the case. Any method may be used for producing a polycrystalline or single crystal having a special form such as a green phosphor film or a laminate of the present invention. Membrane methods can be used.

For example, an example of a method for producing the green phosphor of the present invention by a dry method will be described. As raw materials for the base material, calcium sulfide powder (CaS), strontium sulfide powder (SrS), gallium sulfide powder (Ga ₂ S ₃ ), aluminum sulfide powder _(Al 2 _{S 3)} are mixed in a desired ratio. However, the total amount of the calcium sulfide powder and the strontium sulfide powder and the total amount of the gallium sulfide powder and the aluminum sulfide powder are set to 1: 1 as a molar ratio. Bismuth powder and, if necessary, manganese powder are added to the mixed raw material of the base material and mixed uniformly. What is necessary is just to enclose the pellet obtained by press-molding these mixed powders in a vacuum ampule, and to sinter at the temperature of about 800-1300 degreeC for about 1 to 10 hours. Instead of bismuth powder, bismuth sulfide powder, oxide powder, hydroxide powder, or manganese powder may be used instead of manganese sulfide powder, oxide powder, or hydroxide powder. Further, this sintered body can be used as it is, even if it is pulverized and thinned, or it can be thinned using an MBE apparatus (molecular beam epitaxy apparatus) or the like.

Example 1
Calcium sulfide powder (CaS) 0.1 mol, strontium sulfide powder (SrS) 0.1 mol, gallium sulfide powder _{(Ga 2} S 3) 0.1 mol of aluminum sulfide powder _{(Al 2} S 3) 0.1 moles Mix. To this mixed material, 0.005 mol of bismuth sulfide sulfide powder (Bi ₂ S ₃ ) was added and mixed uniformly, then pressed into a pellet and sintered in a vacuum heating furnace at 1000 ° C. for 3 hours. The sintered body was cooled and then pulverized to produce a green phosphor A. The fluorescence emission characteristics of this green phosphor A are shown in FIG. Although FIG. 1 has already been described, it can be seen that the green phosphor A is a suitable green phosphor. Although the green phosphor was produced by changing the mixing ratio of the raw material of the base material and bismuth and the fluorescence emission characteristics were measured, there was almost no change from FIG.

(Example 2)
Calcium sulfide powder (CaS) 0.1 mol, strontium sulfide powder (SrS) 0.1 mol, gallium sulfide powder (Ga ₂ S ₃ ) 0.1 mol, aluminum sulfide powder (Al ₂ S ₃ ) 0.1 mol Mix. To this mixed raw material, 0.003 mol of bismuth sulfide powder (Bi ₂ S ₃ ) and 0.002 mol of manganese sulfide powder (MnS ₂ ) are added and mixed uniformly, and then pressure-formed into a pellet and vacuum-heated Sintered at 1000 ° C. for 3 hours. The sintered body was cooled and pulverized to produce a green phosphor B. The fluorescence emission characteristics of this green phosphor B are shown in FIG. Although FIG. 2 has already been described, it can be seen that this green phosphor B is a suitable green phosphor particularly for excitation light in the blue wavelength region. The green phosphor was produced by changing the raw material of the base material and the mixing ratio of bismuth and manganese, and the fluorescence emission characteristics were measured. However, there was no significant change from FIG.

  The green phosphors A and B emitted the same green light as the photoluminescence spectrum even when irradiated with an electron beam of 1 kV to 10 kV. Moreover, the same green light emission as a photoluminescence spectrum was obtained by exciting by an electric field.

(Example 3)
A light emitting layer of an inorganic thin film EL element using the green phosphor of the present invention as a light source was produced. Using a MBE apparatus (molecular beam epitaxy apparatus), the raw material constituting the above-described Example 2 green phosphor B was heated and evaporated to form a thin film on a substrate at 500 to 800 ° C. The metal raw material constituting the phosphor became a green phosphor thin film having a thickness of about 0.5 microns while chemically reacting on the substrate. This thin film was sandwiched from both sides by a tantalum pentoxide thin film having a thickness of about 0.5 microns produced by sputtering, and further sandwiched from the outside by a transparent electrode and an aluminum electrode to form a light emitting layer of an inorganic thin film EL element. This inorganic thin film EL element has a structure as shown in FIG. 3, and emitted green light when an AC voltage of 300 V was applied between the electrodes of the light emitting layer.

  The green phosphor according to the present invention uses bismuth and manganese, which are cheaper than the conventional rare earth elements such as europium and cerium, and thereby has a green emission characteristic in the same wavelength region. It emits fluorescence with a narrow value range. Such a green phosphor can be suitably applied as a phosphor for illumination and display and as one of white light sources having excellent color rendering properties.

Photoluminescence (PL) spectrum and PL excitation spectrum of the green phosphor of the present invention (Bi system) Photoluminescence (PL) spectrum and PL excitation spectrum of the green phosphor (Bi, Mn system) of the present invention Sectional drawing which shows the structure of the inorganic thin film EL element of the green fluorescent substance (Bi, Mn type) of this invention

Explanation of symbols

(1): Photoluminescence (PL) for excitation wavelength of 300 nm of green phosphor (Bi system)
(2): Photoluminescence (PL) for green phosphor (Bi system) with an excitation wavelength of 400 nm
(3): Excitation spectrum of green phosphor (Bi system) with respect to fluorescence wavelength of 534 nm (4): Photoluminescence (PL) with respect to excitation wavelength of 400 nm of green phosphor (Bi, Mn system)
(5): Excitation spectrum of green phosphor (Bi, Mn-based) with respect to fluorescence wavelength of 533 nm 1: Inorganic thin film EL element 2: Glass substrate 3: Transparent electrode 4: Green phosphor layer 5: Insulating layer 6: Metal electrode 7: Power supply

Claims (3)

It is represented by the general formula M ¹ M ² ₂ S ₄ (where M ¹ is Ca _X Sr _1-X (0 ≦ X ≦ 1) and M ² is Ga _Y Al _1-Y (0 ≦ Y ≦ 1)). A phosphor emitting green light, wherein the compound contains bismuth.   The phosphor according to claim 1, further comprising manganese.   An inorganic EL element, wherein the thin film made of the phosphor according to claim 1 or 2 is sandwiched from both sides by a pair of electrodes.

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