JPWO2009066452A1 - Blue phosphor - Google Patents

Abstract

In the blue phosphor represented by the general formula: Ba2SiS4: Ce, a part of the Si site is substituted with Al, and the general formula: Ba2 (Si1-xAlx) S4: Ce (where x is 0 <x <1). ), The emission intensity of the emission spectrum due to near-ultraviolet region excitation can be further increased, and the luminance can be further improved.

Description

  The present invention relates to a blue phosphor. More specifically, it is used as a phosphor for illumination using a near ultraviolet LED (light emitting diode) as an excitation source, or as a phosphor for a display such as FED (field emission display), PDP (plasma display), EL (electroluminescence), etc. The present invention relates to a blue phosphor that can be used.

  The current mainstream of light sources for illumination is fluorescent lamps and incandescent lamps, but those using LEDs (light-emitting diodes) as light sources consume less power and have longer lifespans than those of fluorescent lamps. In addition, it has safety that is not hot and does not contain harmful substances such as mercury, so it is excellent in terms of the environment. It is expected to become the mainstream of light sources for lighting in the near future.

  However, a conventional white LED that emits light by mixing blue and yellow light is inferior in color rendering that exhibits natural color development, and is unsuitable for indoor lighting such as merchandise lighting in a store or a dining table. As a method for improving the color rendering properties of white LEDs, a method of combining a near-ultraviolet LED with three types of phosphors of red, green, and blue is conceivable. However, existing phosphors have a luminous efficiency when excited by near-ultraviolet light. Since it is bad, development of the fluorescent substance which shows high light emission intensity in excitation of near ultraviolet light has been desired.

  On the other hand, in display technologies such as FED (field emission display), PDP (plasma display) and EL (electroluminescence), a blue phosphor, a red phosphor and a green phosphor are combined, or a blue phosphor and a color are combined. Color display is realized by combining with a conversion material, and there has been a demand for the development of phosphors that emit blue light with high purity, have high brightness, and are environmentally friendly.

Conventionally, as a blue phosphor for a display such as an inorganic EL, (1) SrS: Ce , (2) MGa 2 S 4: Ce (M = Sr, Ca), (3) BaAl 2 S 4: Eu, (4) Ba ₂ SiS ₄ : Ce and the like are known. Further, (5) (Ba, Mg) Al ₁₀ O ₁₇ : Eu, (6) Sr ₅ (PO ₄ ) ₃ Cl: Eu, and the like are known as blue phosphors for LED lamps.

The present applicants also disclosed a blue phosphor made of Ba ₂ SiS ₄ : Ce as a blue phosphor having good color purity, high luminance, good chemical stability and low crystallization temperature. (See Patent Document 1).

JP2007-2111265

The present invention, Patent Document 1 disclosed a Ba ₂ SiS _4: further studying the Ce, brightness further enhanced, in particular providing cents a new blue phosphor having excellent emission intensity by the excitation of near-ultraviolet region To do.

The present invention relates to a blue phosphor containing a crystal represented by the general formula: Ba ₂ (Si _1-x Al _x ) S ₄ : Ce (where x is 0 <x <1), that is, the general formula The present invention proposes a blue phosphor containing a crystal formed by substituting a part of the Si site of a crystal represented by: Ba ₂ SiS ₄ : Ce with Al.

By replacing a part of the Si site in the blue phosphor represented by the general formula: Ba ₂ SiS ₄ : Ce with Al, the emission intensity of the emission spectrum due to excitation in the near ultraviolet region (about 350 nm to 420 nm) is further increased. And the luminance can be further improved.
As a cause of this, first, by replacing a part of the Si site with Al, the influence of the charge compensation effect due to the introduction of trivalent Al into the divalent Si site can be considered. From the result that the improvement of the light emission intensity was not confirmed even when Ga or Y was added, it is considered that the effect was unique to Al.

  According to the blue phosphor of the present invention, since the emission intensity of the emission spectrum by excitation in the near ultraviolet region (about 350 nm to 420 nm) can be increased, for example, for an illumination device using a near ultraviolet LED (for example, 405 nm) as an excitation source. It can be used as a phosphor, or as a phosphor for a light emitting element or a device of a display such as FED (field emission display), PDP (plasma display), EL (electroluminescence).

  In addition, by combining the blue phosphor of the present invention, the yellow phosphor, and the excitation source, a white light emitting element or device having a high luminance that does not contain harmful substances such as mercury, Se, and Cd can be formed. it can.

FIG. 3 is a diagram showing the X-ray diffraction (XRD) charts of the phosphors obtained in Test Example 1 side by side. FIG. 3 is a diagram showing a photoluminescence (PL) emission spectrum of each phosphor obtained in Test Example 1. 4 is a diagram showing a photoluminescence (PL) excitation spectrum of each phosphor obtained in Test Example 1. FIG. 6 is a diagram showing a photoluminescence (PL) emission spectrum of each phosphor obtained in Test Example 2. FIG. It is the figure which showed the relationship between Ce density | concentration and a peak wavelength, and the relationship between Ce density | concentration and peak intensity | strength about the fluorescent substance obtained in Test Example 2. It is a manufacturing-process figure of a pellet-shaped blue fluorescent substance. It is another manufacturing process figure of pellet-shaped blue fluorescent substance. It is another manufacturing-process figure of a pellet-shaped blue fluorescent substance. It is a manufacturing process figure which shows the example of manufacture of a blue phosphor of a target shape, a process, and bonding.

BEST MODE FOR CARRYING OUT THE INVENTION

  Embodiments of the present invention will be described in detail below, but the scope of the present invention is not limited to the embodiments described below.

The blue phosphor according to the present embodiment (hereinafter referred to as “the present blue phosphor”) has a general formula: Ba ₂ (Si _1-x Al _x ) S ₄ : Ce (where x in the formula is 0 <x <1 ), And a phosphor composed of a single phase composed of the crystal.

It is important that the emission center (luminescent ion) of the blue phosphor is trivalent Ce ³⁺ .

The concentration of Ce ³⁺ is preferably from 0.1 to 5 mol%, particularly preferably from 1 to ₂ mol%, relative to Ba ₂ SiS ₄ . As the amount of Ce added increases, the emission color shifts in the green direction and appears brighter. Therefore, when emphasis is placed on luminance improvement, the concentration of Ce ³⁺ is 0.5 to ₄ mol with respect to Ba ₂ SiS ₄ . %, Preferably 1-2 mol%.

The general formula: Ba ₂ (Si _1-x Al _x ) S ₄ : Ce has a structure in which a part of the Si site in the compound represented by the general formula: Ba ₂ SiS ₄ : Ce is substituted with Al. In the general formula: Ba ₂ (Si _1-x Al _x ) S ₄ : Ce, the value of x indicating the Al substitution ratio may be 0 <x <0.1, preferably 0.05 or more. Yes, particularly preferably 0.1 or more. The upper limit value is preferably 0.4 or less, particularly 0.3 or less, and particularly preferably 0.2 or less.

When compared with a compound represented by the general formula: Ba ₂ SiS ₄ : Ce, it has been confirmed that luminance is improved by substituting a part of the Si site of the compound with Al. If it is above, the luminance can be further improved, and if it is 0.1 or more, the luminance can be improved by about 30%. On the other hand, when Al is added too much, for example, when x = 0.5 or more, a heterogeneous phase such as BaAl ₂ S ₄ is precipitated, and the luminance of emitted light is lowered.

(Features of this blue phosphor)
When the blue phosphor is subjected to X-ray diffraction (XRD) using CuKα rays, the half width of the main peak appearing at the diffraction angle 2θ = 21 to 23.5 ° in the XRD pattern is represented by the general formula: Ba ₂ SiS ₄ : It can be smaller than the full width at half maximum of the peak of Ce, and is less than 90-100%, even 90-98%, or even 90% of the full width at half maximum of the peak of the general formula: Ba ₂ SiS ₄ : Ce. It can be -95%. From this point of view, the value of x indicating the Al substitution ratio in the general formula: Ba ₂ (Si _1-x Al _x ) S ₄ : Ce is 0.05 to 0.3 (particularly less than 0.3). It is preferable that it is 0.1-0.2.

Common sense is that if an impurity is added, the crystallinity is lowered and the half-value width is usually increased. However, in the case of the present blue phosphor, even if a part of the Si site is replaced with Al, the substitution takes place. Compared with those not, the half-value width of the crystal peak can be the same or smaller.
The main peak appearing at the diffraction angle 2θ = 21 to 23.5 ° is presumed to be the peak of the (012) plane.

  The blue phosphor is characterized by being excited by light having a wavelength of 250 nm to 480 nm, particularly light in the near ultraviolet region (about 350 nm to 420 nm) to emit blue light.

  In terms of the emission spectrum, the present blue phosphor is characterized by having an emission peak in a region of at least 435 nm ± 30 nm by photoexcitation at a wavelength of 405 nm.

(Production method)
Next, an example of a preferable method for producing the blue phosphor will be described. However, it is not limited to the manufacturing method demonstrated below.

  In this blue phosphor, barium raw material, silicon raw material, aluminum raw material and cerium raw material, and if necessary, further sulfur raw materials are weighed and mixed, fired at 1000 to 1400 ° C. in a reducing atmosphere, and classified as necessary. Can be obtained.

Examples of the barium raw material include BaS and BaCO ₃ .

Examples of the silicon raw material include Si and SiS ₂ .

Examples of the aluminum raw material include Al and Al ₂ S ₃ .

Examples of the sulfur raw material include S, BaS, SiS ₂ and Ce ₂ S ₃ .

Examples of the cerium raw material include Ce ₂ S ₃ and Ce ₂ (CO ₃ ) ₃ .

  In order to improve color rendering properties, rare earth elements such as Pr and Sm may be added to the raw material as a color adjusting agent.

  In order to improve excitation efficiency, one or more elements selected from rare earth elements such as Sc, La, Gd, and Lu may be added to the raw material as a sensitizer.

  However, the addition amount is preferably 5 mol% or less. When the content of these elements exceeds 5 mol%, a large amount of heterogeneous phases are precipitated, and the luminance may be remarkably lowered.

Further, alkali metal elements, monovalent cation metals such as Ag ⁺ , and halogen ions such as Cl ⁻ , F ⁻ and I ⁻ may be added to the raw material as charge compensators. The amount added is preferably about the same as the content of aluminum group or rare earth group in terms of charge compensation effect and luminance.

  Mixing of the raw materials may be performed either dry or wet.

  In the case of dry mixing, the mixing method is not particularly limited. For example, zirconia balls may be used as a medium, mixed with a paint shaker or a ball mill, and dried as necessary to obtain a raw material mixture. .

  In the case of wet mixing, the raw material is in a suspension state, and after mixing with a paint shaker or a ball mill using zirconia balls as a medium in the same manner as described above, the medium is separated with a sieve or the like, and dried under reduced pressure or vacuum. What is necessary is just to remove a water | moisture content from suspension by a drying method suitably, and to obtain a dry raw material mixture.

  Before firing, the raw material mixture obtained as described above may be pulverized, classified, and dried as necessary. However, crushing, classification, and drying are not necessarily performed.

  Firing is preferably performed at 800 ° C. or higher.

  As the firing atmosphere at this time, a nitrogen gas atmosphere containing a small amount of hydrogen gas, a carbon dioxide atmosphere containing carbon monoxide, an atmosphere of hydrogen sulfide, carbon disulfide, an inert gas, or a reducing gas should be adopted. Can do.

  When the firing temperature is less than 800 ° C., the firing tends to take a long time or the firing is insufficient. On the other hand, the upper limit of the firing temperature is determined by the durability temperature of the firing furnace, the decomposition temperature of the product, etc., but in the method for producing the blue phosphor, firing at 1000 to 1200 ° C. is particularly preferable. Moreover, although baking time is related with baking temperature, it is about 2 to 24 hours.

  Prior to the firing, temporary firing may be performed.

  At this time, the pre-baking is performed at 800 ° C. in an atmosphere of nitrogen gas containing a small amount of hydrogen gas, carbon dioxide containing carbon monoxide, hydrogen sulfide, carbon disulfide, inert gas or reducing gas. You may calcine at the above temperature for 2 hours-24 hours. In the case of this calcination, unlike the case of calcination, it can also be carried out in a reducing gas atmosphere.

  When the calcination temperature is less than 800 ° C., when carbonate is used as a raw material, the decomposition of carbon dioxide gas is insufficient, and when a halide is used, a sufficient flux effect cannot be obtained. On the other hand, at a high temperature exceeding 1100 ° C., abnormal grain growth occurs and it becomes difficult to obtain uniform fine particles. Moreover, if the calcining time is less than 1 hour, it is difficult to obtain reproducibility of the material characteristics, and if it exceeds 12 hours, there arises a problem of composition variation due to increase in material scattering.

  After calcination, the mixed powder may be further pulverized and mixed and fired so that the entire mixed powder becomes uniform.

  In the calcination and preliminary calcination, when a sulfur raw material is not included in the raw material mixture, it is necessary to perform calcination in an atmosphere of hydrogen sulfide or carbon disulfide. However, when the raw material mixture contains a sulfur raw material, it can be fired in an atmosphere of hydrogen sulfide, carbon disulfide, or an inert gas. In this case, hydrogen sulfide and carbon disulfide may become a sulfur compound, and also have a function of suppressing decomposition of the product.

On the other hand, when hydrogen sulfide or carbon disulfide is used in the firing atmosphere or calcining atmosphere, these compounds are also sulfur compounds. For example, when BaS is used as a raw material component, barium compounds and sulfur compounds are used. In other words, when SiS ₂ is used, a silicon compound and a sulfur compound are used.

  Further, a mixture containing two components of barium raw material, silicon raw material, sulfur raw material, aluminum raw material and cerium raw material is heated at a temperature of 800 ° C. or higher in an atmosphere of hydrogen sulfide, carbon disulfide, inert gas or reducing gas. It is also possible to use a mixture obtained by calcining for 24 hours, classification, and then mixing the remaining raw materials.

  In the manufacturing method of this blue fluorescent substance, it can bake with the shape of the pellet for vapor deposition. Manufacturing examples of the pellet-shaped blue phosphor are shown in the manufacturing process diagrams of FIGS.

  6 to 8, the description of “(S compound)” means that a sulfur compound may be added or not added, but hydrogen sulfide or two in both the calcining atmosphere and the firing atmosphere. When carbon sulfide is not used, addition of a sulfur compound is essential.

  Moreover, in the manufacturing method of this blue fluorescent substance, it can bake with the shape of the target for sputtering. An example of manufacturing, processing, and bonding of the target-shaped blue phosphor is shown in the manufacturing process diagram of FIG.

  6 to 9, there is no particular limitation on the mixing conditions as long as they can be mixed uniformly. For example, it can be mixed for 100 minutes with a paint shaker.

The conditions for calcination and firing are as described above. The classification is not particularly limited as long as subsequent mixing and molding are easy. For example, classification is performed to 150 mesh or less. In order to obtain a pellet-shaped blue phosphor for vapor deposition, it can be molded at about 200 kg / cm ² .

(Use)
The blue phosphor constitutes a blue light emitting element or device in combination with an excitation source, and can be used for various applications. For example, in addition to general illumination, it can be used for special light sources, liquid crystal backlights, display devices such as EL, FED, and CRT display devices.

As an example of a blue light-emitting element or device that combines the blue phosphor and an excitation source that can excite the blue phosphor, it receives light in the vicinity of the light-emitting body that generates light having a wavelength of 250 nm to 480 nm, that is, light emitted from the light-emitting body. It can be configured by arranging the present blue phosphor at a position where it is possible.
Specifically, a phosphor layer made of the present blue phosphor may be laminated on a light emitter layer made of a light emitter.

  At this time, the phosphor layer is prepared by, for example, adding the powdery blue phosphor together with a binder to an appropriate solvent, thoroughly mixing and uniformly dispersing the resulting coating solution on the surface of the light emitting layer. What is necessary is just to make it apply | coat and dry and form a coating film (phosphor layer).

  Alternatively, the phosphor layer can be formed by kneading the blue phosphor in a glass composition and dispersing the blue phosphor in the glass layer.

  Furthermore, the blue phosphor may be formed into a sheet shape, and this sheet may be laminated on the phosphor layer, or the blue phosphor may be directly sputtered onto the phosphor layer to form a film. You may do it.

(Glossary of terms)
The blue phosphor may be in the form of a powder or a molded body.

  In the present invention, the “light emitting element” in the “blue light emitting element or device” or “white light emitting element or device” means a relatively small light having at least a phosphor and a light emitting source as its excitation source. A light-emitting device that emits light, and a “light-emitting device” is intended to mean a light-emitting device that emits a relatively large amount of light and includes at least a phosphor and a light-emitting source as an excitation source thereof.

  In the present specification, when “X to Y” (X and Y are arbitrary numbers) is described, it means “preferably greater than X” or “preferably Y” with the meaning of “X to Y” unless otherwise specified. It also includes the meaning of “smaller”.

  Hereinafter, the present invention will be described based on examples. However, the present invention is not construed as being limited to these.

<Measurement of PL emission spectrum>
A PL (photoluminescence) spectrum was measured using a spectrofluorometer (manufactured by Hitachi, F-4500).

<XRD measurement>
A sample for X-ray diffraction was filled in a glass holder with bioden mesh cement, and an RRD-2200V (manufactured by Rigaku Corporation) was used to obtain an XRD pattern using CuKα rays, and a diffraction angle 2θ = 21-23. The full width at half maximum (FWHM) of the main peak appearing at 5 ° (the maximum peak in this range) was determined.
The refinement at this time was performed using the application software (software name: refinement of lattice constant) attached to the RINT-2200V.

(Test Example 1)
BaS, Si, Ce ₂ S ₃ and Al ₂ S ₃ are used as starting materials and are blended so that the atomic ratio of Al / Si is 0/1 to 0.5 / 0.5, and a zirconia ball having a diameter of 3 mm Was mixed for 100 minutes with a paint shaker.

Next, after calcining at 1150 ° C. for 4 hours in a hydrogen sulfide atmosphere, the obtained calcined product is formed into a columnar shape and calcined at 1150 ° C. for 4 hours in a hydrogen sulfide atmosphere. The general formula: Ba ₂ (Si _{1-x Al x) S 4} : Ce ( here, x in the formula to obtain a phosphor represented by shown in Table 1).

  As a result of analyzing the obtained phosphor by ICP (Inductively Coupled Plasma), as shown in Table 1, it was confirmed that the compounded Al / Si atomic ratio and the analysis value by ICP were substantially the same. did.

  Further, X-ray diffraction (XRD) of the obtained phosphor was performed, and the XRD chart was summarized and shown in FIG. 1, and the photoluminescence (PL) intensity (au) was measured, and the emission spectrum was shown. The excitation spectrum is shown in FIG.

When this blue phosphor is subjected to X-ray diffraction (XRD), as shown in FIG. 1, the obtained phosphor is composed of a single phase represented by Ba ₂ (Si _1-x Al _x ) S ₄ : Ce. I was able to confirm that.
Furthermore, the half width of the main peak appearing at the diffraction angle 2θ = 21 to 23.5 ° determined from the XRD pattern using the CuKα ray is smaller than the half width of the peak of the general formula: Ba ₂ SiS ₄ : Ce, It turned out that it becomes 90 to 95% of the half width of the peak of the general formula: Ba ₂ SiS ₄ : Ce.

  Moreover, from FIG.2 and FIG.3, it confirmed that this blue fluorescent substance was excited by the light of wavelength 250nm -480nm, and light-emitted blue light.

  Regarding the emission spectrum, it was also confirmed that the present blue phosphor has an emission peak in a region of at least 435 nm ± 30 nm by photoexcitation at a wavelength of 405 nm.

  Further, from the viewpoint of further increasing the intensity of the emission spectrum, the amount x of Al is preferably 0.05 or more, more preferably 0.05 to 0.30 (particularly less than 0.30), It was found that it was preferably 0.10 or more, and it was found that it was particularly preferably 0.10 to 0.20.

(Test Example 2)
Al ₂ S ₃ is blended so that the atomic ratio of Al / Si is 0.1 / 0.9, or Ga ₂ S ₃ and Y ₂ S ₃ are used instead of Al ₂ S ₃ Then, the phosphor was obtained in the same manner as in Test Example 1 except that it was blended so that the atomic ratio of M / Si (M = Ga or Y) was 0.1 / 0.9.

  The photoluminescence (PL) intensity (au) of the obtained phosphor was measured, and the results are shown in FIG.

As a result of FIG. 4, by replacing a part of the Si site in the blue phosphor represented by the general formula: Ba ₂ SiS ₄ : Ce with Al, the emission intensity of the emission spectrum by excitation in the near ultraviolet region is further increased. It was confirmed that the luminance was further improved.

  On the other hand, it was found that even when trivalent Ga and Y were added, the emission intensity of the emission spectrum could not be increased. Accordingly, it is expected that such an improvement effect of luminance is an effect peculiar to Al.

(Test Example 3)
In the case where Al ₂ S ₃ was blended so that the atomic ratio of Al / Si was 0.1 / 0.9, the Ce concentration was changed between 0.5 to 4 mol%, otherwise the test example As in Example 1, a phosphor was obtained.

  The photoluminescence (PL) intensity (au) of the obtained phosphor was measured, and the relationship between Ce concentration and peak wavelength and the relationship between Ce concentration and peak intensity are shown in FIG.

From FIG. 5, it can be seen that the concentration of Ce ³⁺ is 0.5 mol% or more with respect to Ba ₂ SiS ₄ , and it is particularly preferably 1-2 mol% when focusing on the peak intensity. However, as the amount of Ce added increases, the emission color shifts in the green direction and appears brighter. Therefore, when emphasis is placed on luminance improvement, the concentration of Ce ³⁺ is 0.5 to ₄ mol with respect to Ba ₂ SiS ₄ . % Is preferable, and it is considered that 1 to 2 mol% is particularly preferable.

Claims (6)

Blue phosphor containing a crystal represented by the general formula: Ba ₂ (Si _1-x Al _x ) S ₄ : Ce (where x is 0 <x <1). A blue phosphor containing a crystal represented by the general formula: Ba ₂ (Si _1-x Al _x ) S ₄ : Ce, wherein x is 0.05 to 0.30. Blue phosphor. In XRD pattern using CuKα ray, the half-value width of the main peak appearing at diffraction angle 2 [Theta] = 21-23.5 ° has the general formula: Ba ₂ SiS _4: and being smaller than the half width of the peak of Ce The blue phosphor according to claim 1 or 2. In the XRD pattern using CuKα rays, the half width of the main peak appearing at the diffraction angle 2θ = 21 to 23.5 ° is less than 90 to 100% of the half width of the peak of the general formula: Ba ₂ SiS ₄ : Ce. The blue phosphor according to claim 3, wherein the blue phosphor is present.   The blue light emitting element thru | or apparatus provided with the excitation source and the blue fluorescent substance in any one of Claims 1-4. The white light emitting element thru | or apparatus provided with the excitation source, the blue fluorescent substance in any one of Claims 1-4, and a yellow fluorescent substance.

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