JP2016508174A - Terbium-containing aluminate-based yellow-green to yellow-emitting phosphor - Google Patents

Abstract

Disclosed herein are yellow-green to yellow-emitting lutetium aluminate-based terbium (Tb) -containing phosphors for use in white LEDs, general lighting, and LEDs and backlight displays. This phosphor may further contain gadolinium (Gd). The phosphor includes a cerium activated yellow-green to yellow light emitting lutetium aluminate phosphor having the formula (Lu1-xTbx) 3Al5O12: Ce, wherein A is at least one of Gd and Tb. 0.1 ≦ x <1.0, and the phosphor is configured to emit light having a peak emission wavelength in the range of about 550 nm to about 565 nm, and the phosphor contains at least some Tb. To do.

Description

  Embodiments of the present disclosure are directed to an aluminate-based yellow-green to yellow-emitting phosphor containing rare earth terbium (Tb). Such phosphors are used in various technical fields such as general illumination systems, white light illumination systems based on white LEDs, signal lights, indicator lights, and display applications including display backlights, plasma display panels, LED-based display panels, etc. It is possible to apply to.

  Embodiments of the present invention are directed to aluminate-based phosphors, which emit visible light in the yellow-green to yellow part of the electromagnetic spectrum when activated with cerium and doped with rare earth terbium (Tb). . The phosphor may also contain rare earth lutetium (Lu) and / or gadolinium (Gd). The term “visible light in the yellow-green to yellow part of the electromagnetic spectrum” is defined to mean light having a peak emission wavelength of about 550 nm to about 600 nm. Such phosphors can be used in the commercial market where white light is generated using so-called “white light LEDs”, but light emitting diodes emit specific monochrome light and are perceived as white by the naked eye. The term “white light LED” has some nuisance because it is not a combination of wavelengths to be used. Nevertheless, this term has taken root as a term in the lighting industry.

  Historically, YAG: Ce (cerium activated yttrium aluminate garnet) has been used to provide the yellow component of light in the lighting systems described above. Compared to those of other phosphor hosts, especially silicate, sulfate, nitridosilicate, and oxonitridosilicate, YAG: Ce has a relatively high absorption efficiency when excited by blue light. However, it is stable in a high temperature and high humidity environment and has a high quantum efficiency (QE> 95%) while still displaying a broad emission spectrum.

One disadvantage associated with the use of YAG: Ce-based phosphors is that, in addition to the disadvantage that color rendering is insufficient in some cases, the peak emission of the phosphor is too long, that is, for example, in backlight applications. For example, it is too deep orange or red for use as a light source. An alternative to YAG: Ce is the cerium-doped Lu ₃ Al ₅ O ₁₂ compound (LAG: Ce), which has the same crystal structure as YAG: Ce and is temperature and humidity stable similar to this yttrium compound As well as quantum efficiency. Despite such similarities, LAG: Ce exhibits a different peak emission wavelength than YAG: Ce, and in the case of lutetium, this peak wavelength is about 540 nm. However, this emission wavelength is not ideal for those applications because it is not short enough for certain applications such as, for example, suitable backlighting and general lighting applications.

  Accordingly, phosphors having a structure similar to garnet in terms of temperature and humidity stability and having a peak emission wavelength in the range of about 550 nm to about 600 nm are known in the art, particularly in the field of backlight technology and general lighting. is necessary. According to the present embodiment, these problems can be addressed by providing a lutetium (Lu) aluminate phosphor containing rare earth terbium (Tb). These phosphors may also contain rare earth gadolinium (Gd).

  Embodiments of the present disclosure are directed to yellow-green and yellow-emitting lutetium aluminate-based phosphors that contain terbium (Tb) (and in some embodiments also contain gadolinium (Gd) in addition to Tb). These phosphors can be used in white LEDs, general lighting applications, and LED displays and backlight displays.

In an embodiment of the present invention, the phosphor may include a cerium activated yellow-green to yellow light emitting lutetium aluminate-based phosphor including terbium (Tb), aluminum (Al), and oxygen (O). The phosphor is configured to absorb excitation radiation having a wavelength in the range of about 380 nm to about 480 nm and to emit light having a peak emission wavelength in the range of about 550 nm to about 600 nm. The yellow-green to yellow light emitting aluminate-based phosphor can be excited by radiation having a wavelength in the range of about 420 nm to about 480 nm. The phosphor has the formula _{(Lu 1-x Tb x)} 3 Al 5 O 12: may have a Ce, wherein x is in the range of less than about 0.1 to 1.0, the phosphor is about It is configured to absorb excitation radiation having a wavelength in the range of 380 nm to about 480 nm and emit light having a peak emission wavelength in the range of about 550 nm to about 565 nm. The phosphor may further include the rare earth element gadolinium (Gd), and may have the formula (Lu _1-xy Tb _x Gd _y ) ₃ Al ₅ O ₁₂ : Ce, where x is about The range is less than 0.1 to 1.0, y is greater than zero and x + y <1. Furthermore, this Tb-containing phosphor can shift less than 0.005 for both x and y coordinates over temperatures ranging from 20 ° C. to 220 ° C. in CIE coordinates, a specific example of such a phosphor. (Lu _0.61 Tb _0.3 Ce _0.09 ) ₃ Al ₅ O ₁₂ , (Lu _0.41 Tb _0.5 Ce _0.09 ) ₃ Al ₅ O ₁₂ , and (Lu _0.41 Gd _0.2 Tb _0.3 Ce _0.09 ) ₃ Al ₅ O ₁₂ .

In another embodiment of the present invention, the phosphor has the formula _{(Lu 1-x-y A} x Ce y) 3 B z Al 5 O 12 C 2z, wherein, A is Tb, B is Mg, At least one of Sr, Ca, and Ba, C is at least one of F, Cl, Br, and I, 0.001 ≦ x <1.0, and 0.001 ≦ A cerium activated yellow-green to yellow light emitting aluminate-based phosphor in which y <0.2 and 0 <z ≦ 0.5 is included.

In another embodiment of the present invention, the phosphor is a cerium activated yellow green to yellow light emitting aluminate-based fluorescence represented by the formula (Lu _0.91-x A _x Ce _0.09 ) ₃ Al ₅ O _12. Including the body. Here, A is Tb and may further contain Gd, and x is in the range of about 0.001 to about 1.0.

  According to a further embodiment of the present invention, the white light illumination system comprises an excitation source having an emission wavelength in the range of 200 nm to 480 nm, at least one of a red-emitting phosphor or a green-emitting phosphor, and cerium containing terbium. And an activated yellow-green to yellow-emitting lutetium aluminate-based phosphor, the phosphor being configured to emit light having a peak emission wavelength in the range of about 550 nm to about 565 nm. The cerium activated yellow-green to yellow light emitting lutetium aluminate-based phosphor can be configured to absorb excitation radiation having a wavelength in the range of about 380 nm to about 480 nm. This cerium activated yellow-green to yellow light emitting lutetium aluminate-based phosphor may further contain gadolinium.

These and other aspects and features of the invention will become apparent to those skilled in the art by reference to the following description of specific embodiments of the invention in conjunction with the accompanying figures.
FIG. ₅ shows the SEM morphology of Lu _2.91 Ce _0.09 Al ₅ O ₁₂ with different MgF ₂ additive concentrations, showing that the particle size becomes larger and more uniform with increasing amounts of MgF ₂ additive. FIG. 3 is a series of X-ray diffraction (XRD) patterns of an exemplary _Y2.91 Ce _0.09 Al ₅ O ₁₂ phosphor with different MgF ₂ additive concentrations. FIG. 4 is a series of X-ray diffraction (XRD) patterns of an exemplary Lu _2.91 Ce _0.09 Al ₅ O ₁₂ phosphor with different MgF ₂ additive concentrations. FIG. 4 is a series of X-ray diffraction (XRD) patterns of an exemplary Lu _2.91 Ce _0.09 Al ₅ O ₁₂ phosphor using 5 wt% MgF ₂ additive and 5 wt% SrF ₂ additive. FIG. 4 is a series of emission spectra of an exemplary _Y2.91 Ce _0.09 Al ₅ O ₁₂ phosphor with different concentrations of MgF ₂ additive, which is obtained by excitation of the phosphor with a blue LED. FIG. 4 is a series of normalized emission spectra of an exemplary Lu _2.91 Ce _0.09 Al ₅ O ₁₂ phosphor with different MgF ₂ additive concentrations under excitation with a blue LED. FIG. 4 is an emission spectrum of Lu _2.91 Ce _0.09 Al ₅ O ₁₂ phosphor with different MgF ₂ additive concentrations under excitation with a blue LED. Normalized emission spectrum of Lu _2.91 Ce _0.09 Al ₅ O ₁₂ phosphor with different concentrations of MgF ₂ additive under excitation with blue LED, the result is Lu _2.91 Ce The emission peak of _0.09 Al ₅ O ₁₂ is shifted to a shorter wavelength by a specific amount of MgF ₂ additive, and the emission peak wavelength is shortened as the amount of MgF ₂ additive is increased. . Normalized Lu _2.91 Ce _0.09 Al ₅ O ₁₂ phosphor with 5 wt% MgF ₂ additive and 5 wt% SrF ₂ additive when the phosphor is excited with a blue LED It is an emission spectrum, and shows the result compared with the control sample which does not contain a halide salt additive. These results show that the emission peak is higher when MgF ₂ synthetic compound is used than when SrF ₂ synthetic compound is used. The shift to shorter wavelengths is illustrated. FIG. 4 shows how the series of emission wavelengths of the exemplary Lu _2.91 Ce _0.09 Al ₅ O ₁₂ phosphor decreases with increasing concentration of SrF ₂ additive. FIG. 4 is a series of normalized excitation spectra of an exemplary Lu _2.91 Ce _0.09 Al ₅ O ₁₂ phosphor with different MgF ₂ additive concentrations, with the excitation spectrum narrowing with increasing MgF ₂ additive concentration. Showing. FIG. 5 shows the temperature dependence of an exemplary _Lu2.91 Ce _0.09 Al ₅ O ₁₂ phosphor with 5 wt% MgF ₂ additive compared to a commercially available Ce: YAG phosphor. 5 was used wt% of SrF ₂ additive, shows the spectrum of a white LED including a green light-emitting aluminate phosphor of example having the formula _{Lu 2.91 Ce 0.09 Al 5 O 12} , the white LED, Also included is a red phosphor having the formula (Ca _0.2 Sr _0.8 ) AlSiN ₃ : Eu ²⁺ , a white color obtained when both green and red phosphors are excited with InGaN LED-emitting blue light. The color characteristics of the light were CIE x = 0.24 and CIE y = 0.20. Blue InGaNLED, and (with either 3% by weight of MgF ₂ additives or 5 wt% of SrF ₂ additive) wherein _Lu 2.91 _Ce 0.09 _Al 5 _{O 12} green garnet having the formula (Ca _0.2 Sr _0.8 ) AlSiN ₃ : red nitride with Eu ²⁺ or silicate with formula (Sr _0.5 Ba _0.5 ) ₂ SiO ₄ : Eu ²⁺ The color coordinates of the white light are CIE (x = 0.3, y = 0.3). 15 is a spectrum of the white LED system of FIG. 14 measured at 2727 ° C. (3,000 K). This shows that the peak emission wavelengths of these halogenated aluminates with increasing Gd levels were generally in the range of about 550 nm to about 580 nm, with the Ba level being stoichiometrically 0. 15, the Sr level was stoichiometrically constant at 0.34. This shows that the peak emission wavelengths of these halogenated aluminates with increasing Gd levels were generally in the range of about 550 nm to about 580 nm, with the Ba level being stoichiometrically 0. 15, the Sr level was stoichiometrically constant at 0.34. It is an X-ray diffraction pattern of both the Ba series phosphor and the Sr series phosphor, and their luminous intensity data are shown in FIGS. It is an X-ray diffraction pattern of both the Ba series phosphor and the Sr series phosphor, and their luminous intensity data are shown in FIGS. It is a photoelectron emission spectrum of the typical Tb and / or Gd containing fluorescent substance excited with the blue light source by this embodiment, and this spectrum is a plot of the photoluminescence intensity according to a photoelectron emission wavelength. It is a photoelectron emission spectrum of the typical Tb and / or Gd containing fluorescent substance excited with the blue light source by this embodiment, and this spectrum is a plot of the photoluminescence intensity according to a photoelectron emission wavelength. It is a photoelectron emission spectrum of the typical Tb and / or Gd containing fluorescent substance excited with the blue light source by this embodiment, and this spectrum is a plot of the photoluminescence intensity according to a photoelectron emission wavelength. It is a plot of the peak emission wavelength versus the concentration of either Gd or Tb, thus showing the effect of the amount of Gd and / or Tb included on the peak emission wavelength. FIG. 22 is a plot of photoluminescence intensity versus peak emission wavelength for the same series of phosphors using the various Gd and Tb concentrations studied in FIG. FIG. 4 is a graph plotting CIE y coordinates versus CIE x coordinates for an exemplary series of phosphors as the temperature is increased; this data shows that increasing the temperature decreases the value of the CIE y coordinates and increases the CIE x coordinates. It shows that it leads to.

  Embodiments of the present invention will now be described in detail with reference to the figures provided as illustrative examples of the present invention to enable those skilled in the art to practice the present invention. The following figures and examples are not intended to limit the scope of the invention to one embodiment, but other embodiments may be obtained by exchanging some or all of the elements described or illustrated with one another. Note that it is possible. Further, in order to avoid obscuring the present invention, it is possible to understand the present invention in order to avoid obscuring the present invention when it is possible to implement the specific elements of the present invention partially or completely using known components. Only the parts necessary for the purpose are described, and detailed descriptions of other parts of such well-known ingredients are omitted. In the present specification, embodiments showing a single component should not be considered limiting, but rather, the invention is directed to other embodiments that include a plurality of the same component, unless expressly stated otherwise herein. Or vice versa, is intended to encompass other embodiments. Moreover, applicants do not intend to attribute any term in this specification or the claims to an uncommon or special meaning unless expressly stated otherwise. In addition, the present invention includes currently known equivalents and known future equivalents of known ingredients, which are illustratively referred to herein.

  Historically, the rare earth cerium-activated yttrium aluminum garnet compound (YAG: Ce) has been used in phosphor materials where the desired application is either high power LED lighting or cool white lighting with unspecified general properties. One of the most common options. Of course, for general illumination, in the case of LED chips that provide the blue light component of the resulting white light, and excitation of the phosphor that typically provides the yellow / green component of the resulting white light product. There is a need for highly efficient components in both cases of synchrotron radiation.

  As stated in the previous section of this disclosure, YAG: Ce with quantum efficiencies greater than about 95% has demonstrated this desirable high efficiency, and therefore it seems difficult to improve this number. Let's go. However, as is well known in the art, the efficiency of LED chips increases with decreasing emission wavelength, and therefore, at least in theory, phosphors combined with LED chips that emit at shorter wavelengths. Can be excited at those short wavelengths, the efficiency of the general lighting system seems to be improved. Unfortunately, the problem with this strategy is that the luminous efficiency of the YAG: Ce phosphor decreases when the wavelength of the blue excitation radiation is reduced to a level below about 460 nm.

  Of course, this means that YAG: Ce cannot actually be combined with an LED chip having an emission wavelength of about 450 to 460 nm or more. However, in the art, it is also important that the photon energy of the excitation radiation of the phosphor largely depends on the structure of the anionic polyhedron (including oxygen atoms in this case) surrounding the activator cation (cerium). It is well known. That is, the efficiency of this system can be improved if the excitation range of the garnet-based phosphor can be expanded toward shorter wavelengths relative to the YAG: Ce phosphor. Thus, one of the objectives of the present invention is to maintain (or even improve) the improved properties exhibited by many garnets, while maintaining the excitation range that the phosphor “wants” wants to see: Changing the structure and properties of this anionic polyhedron to shift to a shorter wavelength than that of Ce.

  The present disclosure is divided into sections, first describing the chemical description (using stoichiometric formulas) of the halogenated aluminates of the present invention, and then implementations that can be used to generate them. A possible synthesis method is briefly described. Next, the structure of the halogenated aluminate of the present invention will be described, and the relationship with experimental data including changes in wavelength and photoluminescence due to inclusion of a specific halogen dopant will be described. Finally, the role played by these yellow-green and yellow-emitting phosphors in white light illumination, general illumination, and backlight applications will be described using exemplary data.

Chemical description of the halogenated aluminate phosphor of the present invention The yellow to green light emitting aluminate phosphor of the present invention contains both an alkaline earth component and a halogen component. Although these dopants are used to achieve the desired photoelectric emission intensity and spectral properties, the fact that simultaneous substitution of alkaline earths and halogens results in a self-contained charge balance is also coincidental. In addition, other advantageous corrections related to the overall variation across the unit cell size may also be possible, while replacing Sc, La, Gd, and / or Tb with Lu ( Either individually or in combination) may tend to increase or decrease the size of the lattice, and substituting oxygen with halogen may have the opposite effect.

There are several ways to describe the phosphor formulas of the present invention. In one embodiment, for emitting green light, aluminate-based phosphors cerium doped formula _{(Lu 1-a-b-} c Y a Tb b A c) 3 (Al 1-d B d) 5 (O 1 _-e C _{e) 12:} Ce, are those which may be described by Eu, wherein, A is selected from the group consisting of Mg, Sr, Ca and Ba, B is selected from the group consisting of Ga and an in, C Is selected from the group consisting of F, Cl and Br, 0 ≦ a ≦ 1, 0 ≦ b ≦ 1, 0 <c ≦ 0.5, 0 ≦ d ≦ 1, and 0 <e ≦ 0.2. Using the “A” element, which can be any of the alkaline earth elements Mg, Sr, Ca, and Ba, alone or in combination, is very effective for shifting the emission wavelength to a shorter value. These compounds are referred to in this disclosure as “halogenated LAG-based” aluminates or simply “halogenated aluminates”.

In an alternative embodiment, the yellow-green light emitting aluminate-based phosphor of the present invention can be described by the formula (Y, A) ₃ (Al, B) ₅ (O, C) ₁₂ : Ce ³⁺ , where , A is at least one of Tb, Gd, Sm, La, Lu, Sr, Ca, and Mg (including combinations of these elements), and the substitution amount of Y by these elements is stoichiometric. In the range of about 0.1 to about 100 percent. B is at least one of Si, Ge, B, P, and Ga (including combinations), and these elements stoichiometrically contain Al in amounts ranging from about 0.1 to about 100%. Replace. C is at least one of F, Cl, N, and S, including combinations, replacing oxygen in a stoichiometric amount ranging from about 0.1 to about 100%.

In an alternative embodiment, a yellow-green-emitting aluminate phosphor of the present invention, formula _{(Y 1-x Ba x)} 3 Al 5 (O 1-y C y) 12: are those which can be described by ^{Ce 3+} Wherein x and y each range from about 0.001 to about 0.2.

In an alternative embodiment, yellow-green to green-emitting aluminate-based phosphor has the formula ^{_{(A 1-x 3+ B x}} 2+) m Al 5 (O 1-y 2- C y 1-) n: is described by ^{Ce 3+} Wherein A is selected from the group consisting of Y, Sc, Gd, Tb, and Lu, B is selected from the group consisting of Mg, Sr, Ca, and Ba, C is F, Cl, and Selected from the group consisting of Br, 0 ≦ x ≦ 0.5, 0 <y ≦ 0.5, 2 ≦ m ≦ 4, and 10 ≦ n ≦ 14.

In an alternative embodiment, yellow-green to green-emitting aluminate-based phosphor has the formula ^{_{(A 1-x 3+ B x}} 2+) m Al 5 (O 1-y 2- C y 1-) n: is described by ^{Ce 3+} Wherein A is selected from the group consisting of Y, Sc, Gd, Tb, and Lu, B is selected from the group consisting of Mg, Sr, Ca, and Ba, C is F, Cl, and Selected from the group consisting of Br, 0 ≦ x ≦ 0.5, 0 ≦ y ≦ 0.5, 2 ≦ m ≦ 4, and 10 ≦ n ≦ 14, provided that m is not equal to 3. To do.

In an alternative embodiment, yellow-green to green-emitting aluminate-based phosphor has the formula ^{_{(A 1-x 3+ B x}} 2+) m Al 5 (O 1-y 2- C y 1-) n: is described by ^{Ce 3+} Wherein A is selected from the group consisting of Y, Sc, Gd, Tb, and Lu, B is selected from the group consisting of Mg, Sr, Ca, and Ba, C is F, Cl, and Selected from the group consisting of Br, 0 ≦ x ≦ 0.5, 0 ≦ y ≦ 0.5, 2 ≦ m ≦ 4, and 10 ≦ n ≦ 14, provided that n is not equal to 12. To do.

In an alternative embodiment, a yellow-green-emitting aluminate-based phosphor, which can be described by the formula _{(Lu 1-x-y A} x Ce y) 3 B z Al 5 O 12 C 2z, in the formula, A Is at least one of Sc, La, Gd, and Tb, B is at least one of the alkaline earth Mg, Sr, Ca, and Ba, and C is a halogen element F, C, Br, And I, and the values of the parameters x, y, and z are 0 ≦ x ≦ 0.5, 0.001 ≦ y ≦ 0.2, and 0.001 ≦ z ≦ 0.5 . “At least one” with respect to the formulas in this disclosure means that the elements of the group may be present in the phosphor individually or in combination, and the total amount of the group is given to it in terms of the stoichiometric total amount. This means that any combination of any of the elements in the group is possible, provided that

^Those skilled in the art will recognize that after processing steps such as sintering, C or halogen and B or alkali when the C and B components are added to the starting mixture in the form of an alkaline earth salt (eg B ²⁺ C ₂ ). It will be understood that the amount of earth is not always present in the phosphor product in the expected ratio of 2: 1 (in the stoichiometric sense). This is because the halogen component is volatile as is well known, and in some cases, a portion of C is lost relative to B, so the B: C ratio in the final phosphor product is 2: 1. Less than. Thus, in an alternative embodiment of the present invention, the amount of C is less than 2z in the clause [0045] equation and is numerically up to 5%. In various other embodiments, the amount of C is less than 2z and up to 10%, 25%, and 50% stoichiometrically.

Synthesis Any number of methods can be used to synthesize the yellow-green to yellow light emitting aluminate phosphors of the present invention, including methods that can involve both solid state reaction mechanisms and liquid mixing techniques. The liquid mixing step includes methods such as coprecipitation and sol-gel methods.

  One embodiment of the preparation includes a solid reaction mechanism that includes the following steps.

(A) the desired starting material _CeO 2 _amount, Y 2 _{O 3,} lutetium salts (nitrates lutetium, carbonate salts, halides, and / or oxides), Sc, La, other such Gd and Tb A rare earth salt, and M ²⁺ X ₂ , wherein M is a divalent alkaline earth metal selected from the group consisting of Mg, Sr, Ca, and Ba, and X is F, Cl, Br, and I A halogen selected from the group consisting of) to produce a starting material powder mixture.
(B) Mix the starting material powder mixture from step (a) in a dry state using any conventional method such as ball milling. Typical mixing times using ball milling are about 2 hours or longer (in one embodiment about 8 hours).
(C) mixing the mixed starting material powder from step (b) at about 1400 ° C. to about 1600 ° C. for about 6 under a reducing atmosphere (the purpose of this atmosphere is for the reduction of the ammonia-based compound); Mix for about 12 hours.
(D) The sintered product from step (c) is crushed and washed with water.
(E) Dry the washed product from step (d) under drying conditions of about 12 hours at a temperature of about 150 ° C.

The aluminate of the present invention can be synthesized by a liquid mixing method. An example of synthesizing a non-halogenated LAG compound having the formula Lu _2.985 Ce _0.015 Al ₅ O ₁₂ using coprecipitation is described in -L. Li et al., Described in “Fabrication of Transparent Cerium-Dopped Luthenium Aluminum Garnet Ceramics by Co-Precipitation Routes” (J. Am. Ceram. Soc. 89 [7] 2356-2358 (2006)). These non-halogenated LAG compounds do not contain alkaline earth components. The entire article is incorporated herein because it is believed that similar coprecipitation methods can be used to produce the halogenated LAGs of the present disclosure having an alkaline earth component.

  An example of the synthesis of halogenated YAG compounds using the sol-gel technique is described in US Pat. McFarland et al., Symyx Technologies, the subject “Phosphor materials”. These halogenated (possibly) YAG compounds do not contain alkaline earth components. The entire contents of the above patents are incorporated herein as it is believed that it is possible to produce halogenated YAGs of the present disclosure having an alkaline earth component using similar sol-gel methods.

FIG. 1 shows the SEM morphology of an exemplary Lu _2.91 Ce _0.09 Al ₅ O ₁₂ phosphor using different MgF ₂ additive concentrations synthesized by the solid state mechanism described above. The morphology revealed by scanning electron microscopy (SEM) shows that the particle size becomes larger and more uniform as the amount of MgF ₂ additive increases. The diameter of the phosphor particles is approximately 10-15 microns.

Crystal structure of the yellow-green to yellow light emitting aluminate of the present invention The crystal structure of the yellow-green to yellow aluminate of the present invention is similar to the crystal structure of yttrium aluminum garnet (Y ₃ Al ₅ O ₁₂ ). Similar to the YAG compound formed, the aluminate of the present invention may belong to the Ia3d space group (No. 230). Since this space group is related to YAG, Y. Kuru et al. Described in an article entitled “Yttrium Aluminum Garnet as a Scavenger for Ca and Si” (J. Am. Ceram. Soc. 91 [11] 3663-3667 (2008)). Y. As described by Kuru et al., YAG has a complex crystal composed of 160 atoms (8 formula units) per lattice, Y ³⁺ is multiplicity 24, Wyckoff character “ c ”and a position of symmetry 2.22, and the O ²⁻ atom occupies a position of multiplicity 96, Wyckoff character“ h ”, and site symmetry 1. Two of the Al ³⁺ ions is placed in the position of the octahedral 16 (a), the remaining three ^{Al 3+} ions located tetrahedron 24 (d) sites.

  The lattice parameters of the YAG unit cell are a = b = c = 1.008 nm and α = β = γ = 90 °. Replacement of yttrium with lutetium is expected to increase the size of the unit cell, but the angle between the unit cell axes is expected not to change and the material will maintain its cubic properties.

FIG. 2 shows a series of X-ray diffraction (XRD) patterns of exemplary Y _2.91 Ce _0.09 Al ₅ O ₁₂ phosphors with different MgF ₂ additive concentrations, with alkaline earth and halogen ( It shows how the addition of the MgF ₂ ) component shifts the high angle diffraction peak to a higher value of 2θ. This means that the lattice constant is smaller than that of the YAG component having no alkaline earth / halogen, and further indicates that Mg ²⁺ is incorporated into the crystal lattice and occupies the Y ³⁺ position.

FIG. 3 shows a series of X-ray diffraction (XRD) patterns of an exemplary phosphor in a manner similar to FIG. 2, but the series of compounds is Lu _2.91 Ce ₀ with different MgF ₂ additive concentrations. _0.09 Al ₅ O ₁₂ phosphor, which was obtained by examining a lutetium compound, not an yttrium compound.

FIG. 4 shows a series of X-ray diffraction (XRD) of an exemplary Lu _2.91 Ce _0.09 Al ₅ O ₁₂ phosphor with either 5 wt% MgF ₂ additive or 5 wt% SrF ₂ additive. ) Pattern, this experiment shows a comparison of Mg and Sr components. This data shows that when the MgF ₂ additive is used in the Lu _2.91 Ce _0.09 Al ₅ O ₁₂ lattice, the high angle diffraction peak shifts to a larger 2θ value, which This means that the lattice constant has become smaller. Alternatively, with the SrF ₂ additive, the high angle diffraction peak moved to a smaller 2θ value, which means that its lattice constant increased. It will be apparent to those skilled in the art that both Mg ²⁺ and Sr ²⁺ are incorporated into the Lu _2.91 Ce _0.09 Al ₅ O ₁₂ lattice and occupy the Lu ³⁺ position. These peak positions shift because Mg ²⁺ (ionic radius 0.72０．７) is smaller than Lu ³⁺ (0.86Å), but Sr ²⁺ (1.18１．１) is larger than Lu ³⁺ .

Effect of Alkaline Earth and Halogen Mechanisms on Optical Properties In one embodiment of the present invention, Ce ³⁺ is an aluminate phosphor emission activator. The transition between the 4f and 5d energy levels of Ce ³⁺ ions corresponds to the excitation of the phosphor with blue light, and the emission of green light from the phosphor is the result of the same electron transfer. In the aluminate structure, Ce ³⁺ is located in the center of the octahedral site formed by a polyanionic structure of six oxygen ions. Those skilled in the art will understand that according to crystallographic theory, the surrounding anion (which may also be described as a ligand) induces an electrostatic potential on the 5d electron of the central cation. This 5d energy level split is 10 Dq, which is known to depend on the specific ligand species. From the spectrochemical series it can be seen that the Dq of the halide is less than that of oxygen, so it follows that the Dq decreases accordingly when the oxygen ion is replaced by the halide ion.

  This means that the band gap energy, that is, the difference in energy between the electronic levels of 4f and 5d, is increased by substitution of oxygen ions with halides in the polyanionic cage surrounding the activator ions. This is why the emission peak shifts to a shorter wavelength due to halogen substitution. Simultaneously with the introduction of halide ions within the polyanionic structure of oxygen forming the octahedral site, it is also possible to replace the moiety containing Lu (and / or Sc, La, Gd and Tb) with the corresponding cation. It is. If the cation replacing Lu (and / or other rare earths) is a smaller cation, the emission peak will shift towards the blue end of the spectrum. The luminescence emitted in this way will have a shorter wavelength than otherwise. In contrast, if the cation replacing Lu is a larger cation such as Sr or Ba, the emission peak will shift towards the red end of the spectrum. In this case, the wavelength of the emitted luminescence becomes longer.

  In combination with the influence of halides, if a blue shift is desired, the alkaline earth substitution is preferably done with Mg rather than Sr, which is shown experimentally in the following part of the disclosure. It is also known that the emission peak of LAG is a doublet due to spin orbit coupling. As the blue shift occurs, the emission with shorter wavelengths is biased and the intensity increases accordingly. This trend is not only useful for the blue shift of emission, but also improves photoluminescence.

FIG. 5 is a series of emission spectra of an exemplary Y _2.91 Ce _0.09 Al ₅ O ₁₂ phosphor with different concentrations of MgF ₂ additive, which emission spectrum is due to excitation of the phosphor by a blue LED. Obtained. This data shows that increasing the amount of MgF 2 increases the intensity of photoluminescence and shifts the peak emission wavelength to a shorter value. Although not shown in FIG. 5, the inventors of the present invention have data on the addition of 5 wt% BaF ₂ to the starting material powder, which phosphor is compared to three magnesium-containing phosphors. The photoluminescence intensity increased significantly and the peak emission wavelength was almost the same as that of the 1 wt% sample.

A normalized version of the data from FIG. 5 is shown in FIG. FIG. 6 is a normalized emission spectrum of the same series as an exemplary Lu _2.91 Ce _0.09 Al ₅ O ₁₂ phosphor with different MgF ₂ additive concentrations under blue LED excitation, the luminescence intensity is normalized to highlight a single _value, the emission peak of the Y _{2.91 Ce} 0.09 _Al 5 _{O 12} is shifted to shorter wavelengths as the increase of MgF ₂ additives. The greater the amount of MgF ₂ additive, the shorter the emission peak wavelength. As demonstrated below, this trend is the same as that exhibited by the Lu _2.91 Ce _0.09 Al ₅ O ₁₂ phosphor.

FIG. 7 is a series of emission spectra of an exemplary Lu _2.91 Ce _0.09 Al ₅ O ₁₂ phosphor using different concentrations of MgF ₂ additive, the emission spectrum of the phosphor using a blue LED. Obtained by excitation. This data is similar to the data of FIG. 5, but was examined for lutetium compounds rather than yttrium compounds. Like the yttrium data, this data for lutetium shows a trend similar to the shift in emission wavelength, but the trend in photoluminescence intensity seems not very similar.

The emission spectrum of Lu _2.91 Ce _0.09 Al ₅ O _{12 in} FIG. 7 is normalized to emphasize the effect of the addition of the halogen salt on the peak emission wavelength, and FIG. 8 shows the normalized data. Show. As in the case of yttrium, the peak emission shifts to a shorter wavelength as the amount of the MgF ₂ additive is increased, that is, the larger the amount of the MgF ₂ additive, the shorter the emission peak wavelength. It was observed that increasing the MgF2 from zero (no additive) to about 5 wt% shifted the wavelength from about 550 nm to about 510 nm by about 40 nm.

Each of the graphs in FIGS. 5-8 plots the corresponding spectra of a series of phosphor compositions with increasing additive concentration from no additive to a maximum concentration of 5% by weight. In order to emphasize the comparison between SrF ₂ additive and MgF ₂ additive, ie, phosphors containing Sr alkaline earth and fluorine and phosphors containing Mg alkaline earth and fluorine, FIG. phosphor, namely, a phosphor without additives, phosphor having a SrF ₂ of 5 wt%, and were plotted phosphor together with 5% by weight of MgF _2. These phosphors are Lu _2.91 Ce _0.09 Al ₅ O ₁₂ sample-based phosphors.

The emission spectrum data of FIG. 9 has been normalized to emphasize the effect of the inclusion of halogen and alkaline earth on optical properties. The results when excited with a blue LED indicate that the emission peak shifts to a shorter wavelength with the addition of MgF ₂ and SrF ₂ . The Lu _2.91 Ce _0.09 Al ₅ O ₁₂ sample without additive shows a peak emission wavelength at about 550 nm, and when 5 wt% SrF ₂ additive is used, the peak emission wavelength is shifted to about 535 nm. With the weight percent MgF ₂ additive, the emission wavelength is further shifted to about 510 nm.

FIG. 10 shows how the series of emission wavelengths of the exemplary Lu _2.91 Ce _0.09 Al ₅ O ₁₂ phosphor decreases with increasing concentration of SrF ₂ additive. The peak emission wavelength is plotted according to the amount of SrF ₂ additive. SrF ₂ Additives 1, 2, 3, and 5 wt% with the samples were tested. The results show that the peak emission wavelength is about the same at about 535 nm for the 1 wt% and 2 wt% samples, and the peak emission wavelength decreases to about 533 nm as the SrF ₂ additive is increased to 3 wt%. As the SrF ₂ additive is further increased to 5% by weight, the peak wavelength rapidly decreases to about 524 nm.

Excitation Spectrum and Temperature Dependence FIG. 11 is a series of normalized excitation spectra of an exemplary Lu _2.91 Ce _0.09 Al ₅ O ₁₂ phosphor using different MgF ₂ additive concentrations, with MgF ₂ addition It shows that the excitation spectrum narrows with increasing agent concentration. The data show that the green light emitting aluminate phosphor of the present invention exhibits a broad wavelength band, and over that wavelength band the phosphor can be excited in the range from about 380 nm to about 480 nm.

The thermal stability of the garnet phosphor of the present invention is exemplified by a lutetium-containing compound (Lu _2.91 Ce _0.09 Al ₅ O ₁₂ ) having 5 wt% MgF ₂ , and the thermal stability is commercially available. FIG. 12 shows a comparison with the phosphor Ce ³⁺ : Y ₃ Al ₅ O ₁₂ . It can be observed that the thermal stability of this Lu _2.91 Ce _0.09 Al ₅ O ₁₂ compound is even better than YAG.

Backlight and Application to White Light Illumination System According to a further embodiment of the present invention, the green light emitting aluminate-based phosphor of the present invention is generally used for white light illumination systems and display applications known as “white LEDs”. Can be used for backlight configuration settings. Such a white light illumination system includes a radiation source configured to emit radiation having a wavelength greater than about 280 nm, and light having a peak wavelength in the range of 480 nm to about 650 nm, absorbing at least a portion of the radiation from the radiation source. And a halogenated anion-doped green aluminate phosphor.

Figure 13 shows the spectrum of a white LED including a green light-emitting aluminate phosphor of example having the formula _Lu 2.91 _Ce 0.09 _Al 5 _{O 12} with 5 wt% of SrF ₂ additives. The white LED further includes a red phosphor having the formula (Ca _0.2 Sr _0.8 ) AlSiN ₃ : Eu ²⁺ . When both the green aluminate and the red nitride phosphor were excited with an InGaN LED emitting blue light, the color coordinates of the obtained white light were CIE x = 0.24 and CIE y = 0.20. It was.

FIG. 14 shows a blue InGaN LED, a green garnet with formula Lu _2.91 Ce _0.09 Al ₅ O ₁₂ (with additive at either 3 wt% or 5 wt%) and formula (Ca _{0 .2} Sr _0.8 ) AlSiN ₃ : red nitride with Eu ²⁺ or silicate with formula (Sr _0.5 Ba _0.5 ) ₂ SiO ₄ : Eu ²⁺ and white LED spectrum The color coordinates of the white light are CIE (x = 0.3, y = 0.3). The sample having the most prominent double peak is a sample denoted as “EG3261 + R640”, and the notation EG3261 represents (Sr _0.5 Ba _0.5 ) ₂ SiO ₄ : Eu ²⁺ , which emits light at about 640 nm. Red R640 (Ca _0.2 Sr _0.8 ) AlSiN ₃ : Eu ²⁺ phosphor in combination. The _two peaks labeled LAG (3 wt% MgF ₂ ) + R640 and LAG (5 wt% SrF ₂ ) + R 640 show a much more uniform emission of white light perceived over the wavelength range 500-650 nm. This is a desirable attribute in the art.

  FIG. 15 is the spectrum of the white LED system of FIG. 14 measured at 2727 ° C. (3,000 K).

In embodiments of the present invention, the red nitride that can be used with the green aluminate can have the general formula (Ca, Sr) AlSiN ₃ : Eu ²⁺ , and the red nitride further comprises any halogen. In some cases, the oxygen impurity content of the red nitride phosphor may be about 2 wt% or less. The yellow-green silicate can have the general formula (Mg, Sr, Ca, Ba) ₂ SiO ₄ : Eu ²⁺ , the alkaline earth can be present in the compound individually or in any combination, and the phosphor Can be halogenated by F, Cl, Br, or I (also individually or in any combination).

Optical and Physical Data Tables A summary of exemplary data is listed in Tables 1 and 2. Table 1 shows test results of Lu _2.91 Ce _0.09 Al ₅ O ₁₂ based phosphors using three different concentrations of MgF ₂ additive. Table 2 shows test results of Lu _2.91 Ce _0.09 Al ₅ O ₁₂ based phosphors using four different concentrations of SrF ₂ additive. These results summarize and support that the MgF ₂ and SrF ₂ additives contained in Lu _2.91 Ce _0.09 Al ₅ O ₁₂ shift the emission peak wavelength to shorter wavelengths, The emission intensity increases with increasing concentrations of MgF ₂ and SrF ₂ . The particle size also increases with increasing concentrations of MgF ₂ and SrF ₂ additives.

Yellow Green to Yellow Luminescent Rare Earth Doped Aluminate Phosphor In a series of specific yellow green to yellow light emitting halogenated aluminate rare earth dopings that we have tested, the phosphor has the general formula (Lu _1-xy A _x Ce _y) had the _{3 B z Al 5 O 12 C} 2z. As described above, A is at least one of Sc, La, Gd, and Tb, B is at least one of alkaline earth Mg, Sr, Ca, and Ba, and C is a halogen element. At least one of F, C, Br, and I, and the values of the parameters x, y, z are 0 ≦ x ≦ 0.5, 0.001 ≦ y ≦ 0.2, and 0.001 ≦ z ≦ 0.5. In this series of phosphors, the rare earth dopant was Gd and the alkaline earth was either Ba or Sr. In all compounds tested in this series of experiments, the halogen was F. The formula for the specific aluminates tested is shown in Table 3.

  For purposes of this disclosure, green emission is defined as having a peak emission wavelength of about 500 nm to about 550 nm. Emission extending from about 550 nm to about 600 nm can be described as including wavelengths that change from yellow-green to yellow. In the experiment described, the addition of Gd doping converts the phosphor from a substantially green emitting sample to a substantially yellow sample. Although not shown, when the Gd concentration is further increased (from about 0.33 for the Ba sample and from about 0.13 for the Sr sample), the emission further shifts towards the yellow region of the electromagnetic spectrum, and the yellow Enter the area. The peak emission wavelength depends not only on the selection and concentration of the rare earth dopant present as an additive to lutetium (eg, Gd added to Lu), but also on the selection and amount of alkaline earth and halogen contained. So it may be difficult to generalize. The halogenated aluminates of the present disclosure are defined as emitting in the yellow-green to yellow region of the electromagnetic spectrum at a wavelength of about 550 nm to about 600 nm. Green light emitting halogenated aluminates emit substantially at peak wavelengths in the range of about 500 nm to about 550 nm. For green light emitting aluminate, see U.S. Patent No. 13 / 181,226 (filed July 12, 2011), assigned to the same assignee as this patent application, which is incorporated herein in its entirety. I want to be.

  The data in Table 3 and FIGS. 16A-B show that the peak emission wavelengths of these halogenated aluminates ranged from about 550 nm to about 580 nm overall with increasing Gd levels, where the Ba level is Stoichiometrically fixed to 0.15 for the Ba series and Sr levels fixed to 0.34 stoichiometrically for the Sr series (this concentration is stoichiometric and the concentration is by weight It means by numbers, not things). The Ce activator level was also stoichiometrically fixed at 0.03 for all samples. Specifically, for the Ba sample, as the amount of Gd is stoichiometrically increased from 0.07 to 0.17 to 0.33, the peak emission wavelength is increased from 554 nm to 565 nm and further to 576 nm. Increased. For the Sr sample, the peak emission wavelength increased from 551 nm to 555 nm and further to 558 nm as the amount of Gd stoichiometrically increased from 0.03 to 0.07 and further to 0.13.

The actual compounds in the Ba series are (Lu _0.90 Gd _0.07 Ce _0.03 ) ₃ Ba _0.15 Al ₅ O ₁₂ F _0.30 , (Lu _0.80 Gd _0.17 Ce _{0, respectively. .03) 3 Ba 0.15 Al 5 O} 12 F 0.30, and _{(was Lu 0.64 Gd 0.33 Ce 0.03) 3} Ba 0.15 Al 5 O 12 F 0.30. The actual compounds tested in the Sr series were (Lu _0.94 Gd _0.03 Ce _0.03 ) ₃ Sr _0.34 Al ₅ O ₁₂ F _0.68 , (Lu _0.90 Gd _0.07 Ce, respectively. _{0.03) 3 Sr 0.34 Al 5 O} 12 F 0.68, and _{(was Lu 0.84 Gd 0.13 Ce 0.03) 3} Sr 0.34 Al 5 O 12 F 0.68.

  It can be seen that the Sr series emitted light with a relatively high photoluminescence intensity compared to the Ba series, but at the same time several other variables (eg Gd content, alkaline earth content and halogen concentration) were also changed. Thus, those skilled in the art will understand that the conclusions must be carefully deduced.

  17A-B are X-ray diffraction patterns of both the Ba series phosphor and the Sr series phosphor, and the luminosity data thereof are shown in FIGS.

Yellow light emitting aluminate-based phosphors characterized by terbium (Tb) and / or gadolinium (Gd) In certain compositions, the yellow-green to yellow light emitting halogenated aluminate is a rare earth element terbium (in accordance with embodiments of the present invention). Tb). The inventors of the present invention have described the composition (Lu _0.91-x A _x Ce _0.09 ) ₃ Al ₅ O ₁₂ (wherein A represents at least one of Gd and Tb individually or in combination) Experiments were conducted to compare the relative effects of terbium and gadolinium in Terbium is next to gadolinium in the periodic table, the former (Tb) has the atomic number 65 and the electronic structural formula [Xe] 4f ⁹ 6s ² , while the latter (Gd) has the atomic number 64 and the electronic structural formula [Xe] 4f. ⁷ 5d6s ² The formula (Lu _0.91-x A _x Ce _0.09 ) ₃ Al ₅ O ₁₂ is a rare earth lutetium (Lu) in which both terbium and gadolinium have the atomic number 71 and the electronic structural formula [Xe] 4f ¹⁴ 5d6s ² Indicates a replacement.

  With respect to the method described above for the production of aluminate-based phosphors, it is also possible to use further the following method. The production method of the novel aluminate-based phosphor disclosed in the present specification is not limited to any one production method. For example, 1) mixing of starting materials, 2) sintering of starting material mixture, 3) firing It can be synthesized in a three-step process including a variety of processes including grinding and drying performed on the combined material. In some embodiments, the starting material may include various types of powders such as alkaline earth metal compounds, aluminum compounds, lutetium compounds, and the like. Examples of alkaline earth metal compounds include carbonates, nitrates, hydroxides, oxides, oxalates and halides of alkaline earth metals. Examples of aluminum-containing compounds include nitrates, fluorides and oxides. Examples of the lutetium compound include lutetium oxide, fluorinated lutetium, and lutetium chloride. The starting materials are formulated so that the desired final composition is obtained. In some embodiments, the alkaline earth aluminum-containing compound and the lutetium compound are blended in the appropriate ratio and then sintered to obtain the desired composition. The compounded starting material can be sintered in a second step and the flux can be used (at any stage or various stages of the sintering process) to increase the reactivity of the compounded material. The flux can include various types of halides and boron compounds, examples of which include strontium fluoride, barium fluoride, strontium chloride, barium chloride, and combinations thereof. Examples of boron-containing flux compounds include boric acid, boron oxide, strontium borate, barium borate, and calcium borate.

  In some embodiments, the fluxing compound is used in an amount ranging from about 0.01 to 0.2 mole percent, with a value typically ranging from about 0.01 mole percent to 0.1 mole percent. The range is as follows.

Various techniques for mixing the starting materials (with or without flux) include the use of a mortar, mixing with a ball mill, mixing with a V-shaped mixer, mixing with a cross rotary mixer, jet mill Mixing, and mixing using a stirrer, but is not limited thereto. The starting materials can be mixed either by dry mixing or wet mixing, which means mixing without using a solvent. Solvents that can be used in the wet mixing process include water or organic solvents, which can be either methanol or ethanol. The mixture of starting materials can be fired by a number of techniques well known in the art. It can be fired using a heater such as an electric furnace or a gas furnace. The type of the heater is not limited to a specific type as long as the starting material mixture is fired at a desired temperature for a desired time. In some embodiments, the firing temperature may be in the range of about 800-1600 ° C. In other embodiments, the firing time can range from about 10 minutes to 1000 hours. The firing atmosphere can be selected from air, low pressure atmosphere, vacuum, inert gas atmosphere, nitrogen atmosphere, oxygen atmosphere, and oxidizing atmosphere. In some embodiments, the composition may be fired in a reducing atmosphere at about 100 ° C. to about 1600 ° C. for about 2 to about 10 hours. The phosphor disclosed in the present specification can be prepared using a sol-gel method or a solid reaction method. In some embodiments, metal nitrate is used to provide the divalent metal component of the phosphor as well as the aluminum component of the aluminate-based phosphor. In some embodiments, the metal nitrate that provides the divalent metal component may be Ba (NO ₃ ) ₂ , Mg (NO ₃ ) _2, or Sr (NO ₃ ) ₂ , and the metal nitrate that provides aluminum is Al (NO ₃ ) ₃ may be used.

The method may further include using a metal oxide to provide the oxygen component of the aluminate-based phosphor. Examples of this method include the following steps. a) Raw material selected from the group consisting of Ba (NO ₃ ) ₂ , Mg (NO ₃ ) ₂ , Ca (NO ₃ ) ₂ , Sr (N 0 ₃ ) ₂ , Al (NO ₃ ) ₃ , and Lu ₂ O ₃ B) dissolving Lu ₂ O ₃ in a nitric acid solution, then mixing the desired amount of metal nitrate to produce an aqueous nitrate solution, c) heating the solution from step b) D) heating the gel of step c) to about 500 ° C. to about 1000 ° C. to decompose the nitrate mixture into an oxide mixture, and e) reducing the powder of step d) to a reducing atmosphere. Sintering at a temperature of about 1000 ° C to about 1500 ° C.

Referring to Table 4, those skilled in the art will recognize that all compositions listed in the table emitted light at peak emission wavelengths in the range of about 550 nm to about 560 nm. Each of the first two entries, labeled T1 and T2, does not contain Gd and has Tb concentrations of x = 0.3 and 0.5, respectively. Accordingly, their compositions are (Lu _0.61 Tb _0.3 Ce _0.09 ) ₃ Al ₅ O ₁₂ and (Lu _0.41 Tb _0.5 Ce _0.09 ) ₃ Al ₅ O ₁₂ , respectively. They emit at the highest relative photoluminescence intensity of the compounds in Table 4 with the exception of YAG1 and YAG2.

The third composition from the top of Table 4 contains Gd and Tb at concentrations of 0.2 and 0.3, respectively, and therefore its stoichiometry is (Lu _0.41 Gd _0.2 Tb _{0. 3} Ce _0.09 ) ₃ Al ₅ O ₁₂ . This compound, designated TG1, emitted light at a peak emission wavelength almost as high as (Lu _0.41 Tb _0.5 Ce _0.09 ) ₃ Al ₅ O ₁₂ (555.4 nm vs. 555.8 nm, respectively). The photoluminescence intensity was lower than either of the two compounds containing only Tb and no Gd. The latter two compounds, (Lu _0.61 Tb _0.3 Ce _0.09 ) ₃ Al ₅ O ₁₂ and (Lu _0.41 Tb _0.5 Ce _0.09 ) ₃ Al ₅ O ₁₂ are (Lu ₀ showed _{.41 Gd 0.2 Tb 0.3 Ce 0.09)} 3 Al 5 O 12 low chromaticity coordinates CIE x than it, CIE y chromaticity coordinates were higher.

The data in the fourth row of Table 4 is data of a compound (Lu _0.71 Gd _0.2 Ce _0.09 ) ₃ Al ₅ O ₁₂ designated as G1. This compound emits light having a peak wavelength at about 550 nm, which is the shortest wavelength among the compounds listed in Table 4 except YAG1. It also shows the lowest chromaticity coordinate CIE x in the group. The CIE y coordinate of this compound was the highest in this group. A similar compound, designated G3, containing Gd at a higher level but not Tb, emitted at the highest peak wavelength in this group. This compound has the formula (Lu _0.41 Gd _0.5 Ce _0.09 ) ₃ Al ₅ O ₁₂ . When comparing (Lu _0.41 Gd _0.5 Ce _0.09 ) ₃ Al ₅ O ₁₂ with the previously described (Lu _0.41 Tb _0.5 Ce _0.09 ) ₃ Al ₅ O ₁₂ compound, Gd Although the containing compound emits light at a longer wavelength than the Tb-containing compound, it can be seen that the Tb-containing compound emits light with a higher photoluminescence intensity.

The two compositions labeled “YAG1” and “YAG2” in Table 4 are yttrium (Y) rather than lutetium (Lu), and these Y-based compositions are included for comparison. They each have an approximate calculation formula (Y _0.91 Ce _0.09 ) ₃ Al ₅ O ₁₂ . These compounds also emit light in the range of 550 nm to 560 nm.

The data in Table 4 can be represented by graphs as shown in FIGS. 18-20, which also show a blue light source (such as a GaN LED) used to excite the phosphor composition of the present invention. As shown, a blue light source and a yellow phosphor provide a “white” light source. FIG. 18 is a plot of the photoluminescence intensity of two compounds labeled “G1” and “T1”. The former has a composition with a Gd concentration of x = 0.2, so the formula is (Lu _0.71 Gd _0.2 Ce _0.09 ) ₃ Al ₅ O ₁₂ . The peak emission wavelength is about 550 nm. Here, the Gd-containing compound (x = 0.2, upper curve) has almost the same photoluminescence intensity and peak emission wavelength as “T1” (lower curve).

The two compounds of FIG. 19 have approximately the same photoluminescence intensity as the compound of FIG. 18, but the peak emission wavelength of FIG. 19 is slightly shifted to longer wavelengths. Since the upper graph of FIG. 19 is “T2” and the Tb concentration is x = 0.5, the composition is (Lu _0.41 Tb _0.5 Ce _0.09 ) ₃ Al ₅ O ₁₂ . . The lower curve in FIG. 19 is sample “G2”, and its Gd concentration is x = 0.3, so the composition is (Lu _0.61 Gd _0.3 Ce _0.09 ) ₃ Al ₅ O ₁₂ It is. Comparing these two compounds, it can be seen that the Tb-containing compound (x = 0.5) has a slightly higher photoluminescence intensity and a slightly shorter peak emission wavelength than the “G2” compound.

A compound having a slightly longer emission wavelength compared to FIGS. 19 and 18 is shown in FIG. Referring to FIG. 20, the upper curve of the graph is for a sample labeled “TG1”, the Gd concentration is 0.2, and the Tb concentration is 0.3. _0.41 Gd _0.2 Tb _0.3 Ce _0.09) a ₃ Al ₅ O _12. The curve below the graph is for a sample with a Gd concentration of 0.5, labeled “G3”. Since this compound does not contain Tb, its formula is (Lu _0.41 Gd _0.5 Ce _0.09 ) ₃ Al ₅ O ₁₂ . Here, a compound containing both Gd and Tb exhibits higher photoluminescence intensity than a compound containing the same amount of rare earth (x = 0.5) in a Gd-only manner, and a compound containing Tb and Gd is Gd. It emits at a slightly shorter wavelength than the only compound.

FIG. 21 shows the effect of changing either the Gd concentration or the Tb concentration in the compound having the general formula (Lu _0.91-x A _x Ce _0.09 ) ₃ Al ₅ O ₁₂ . (In this experiment, it is emphasized that A is either Gd or Tb, but according to an embodiment of the invention, Gd and Tb may be present individually or in combination. ). Referring to FIG. 21, when the Gd concentration is increased from x = 0 to x = 0.5, the peak emission is more than the peak emission wavelength of a series of compounds in which the Tb concentration is increased from x = about 0 to x = about 1.0. One skilled in the art can recognize that the wavelength increases more rapidly. In other words, in order to increase the emission wavelength from about 542 nm (the phosphor contains Lu only x = 0) to about 562 nm, it was necessary to completely replace all Lu with Tb (Tb x = 1). However, this increase in wavelength was achieved with a Gd concentration of half that value (x = 0.5, thus replacing only half Lu with the Gd series).

  FIG. 22 shows the relationship between the photoluminescence intensity and the peak emission wavelength of the Gd-containing series compound and the Tb-containing series compound. In this graph, the relative photoluminescence intensity on the ordinate (y axis) is plotted against the peak emission wavelength (unit: nm, on the x axis). For both compound series, the relative photoluminescence intensity decreases with increasing Gd or Tb concentration (and also with increasing peak emission wavelength), and the photoluminescence intensity is greater in the Gd containing series of samples than in the Tb containing samples. Is falling faster.

  The specific data used to create the plots of FIGS. 21 and 22 are listed in Tables 5 and 6 above.

  The thermal stability of exemplary Tb-containing compounds and Tb and Gd-containing compounds is shown in FIG. For comparison, a Gd-containing phosphor compound containing Gd but not Tb is also shown. Referring to FIG. 23, this plots CIE y chromaticity coordinates on the y-axis and CIE x chromaticity coordinates on the x-axis. Data points are collected at 20 ° C intervals at temperatures from 20 ° C to 220 ° C. This temperature range includes the handling temperature of the phosphor material in most applications. The data is shown in Tables 7 (i) and 7 (ii). It is preferred that the shift in CIE coordinates is less than 0.005 over the temperature range of this test, and it can be seen that only the Tb-containing material shows a shift in CIE coordinates within this range on both x and y coordinates. Specifically, only T1, T2 and TG1 show preferred temperature stability. The result that the terbium-containing phosphor material has better temperature stability than the phosphor material containing gadolinium and not containing terbium was unexpected.

Note that the principles, embodiments and concepts described in this disclosure may also apply to this section dealing with terbium (Tb) and gadolinium (Gd). For example, in one embodiment of the present invention, the phosphor has the formula _{(Lu 1-x-y A} x Ce y) 3 B z Al 5 O 12 yellow green-yellow-emitting aluminate which is cerium-activated with a _{C 2z} A phosphor, wherein A is at least one of Sc, La, Gd, and Tb, B is at least one of Mg, Sr, Ca, and Ba; Is at least one of F, Cl, Br, and I, 0.001 ≦ x ≦ 1.0, 0.001 ≦ y ≦ 0.2, and 0 ≦ z ≦ 0.5. Embodiment phosphors contain at least some Tb.

In another embodiment of the present invention, the phosphor comprises a cerium activated yellow-green to yellow light emitting aluminate-based phosphor, wherein the phosphor is of the formula (Lu _1-x A _x ) ₃ Al ₅ O ₁₂ : Ce Wherein A is at least one rare earth selected individually or in combination from the group consisting of Gd and Tb, x is in the range of about 0.001 to about 1.0, and the phosphor is at least some Of Tb.

In another embodiment of the present invention, the phosphor is a cerium activated yellow green to yellow light emitting aluminate-based fluorescence represented by the formula (Lu _0.91-x A _x Ce _0.09 ) ₃ Al ₅ O _12. Including the body. Here, A is at least one rare earth selected from the group consisting of Gd and Tb, and x ranges from about 0.001 to about 1.0. Similar to the embodiments disclosed in the previous section, this phosphor also contains at least some Tb.

  Although the present invention has been specifically described with reference to yellow-green to yellow-emitting aluminate-based phosphors, the teachings and principles of the present invention are that some or all of Al is replaced with Ga, Si, or Ge. This also applies to phosphors such as silicate-based, gallate-based, and germanate-based phosphors.

  Embodiments of phosphor materials containing halogen include (1) halogens contained in the crystal in a substitutional manner, (2) halogens contained between crystal lattices, and / or (3) grains, regions and / or It can have halogens contained within the grain boundaries that separate the phases.

In accordance with a further embodiment of the present invention, the Lu aluminate material of Table 8 was made and tested as described above. An example of a representative procedure for making a compound having the formula (Lu _1-y Ce _y ) ₃ Al ₅ O ₁₂ is given. Lu ₂ O ₃ (272.664 g), CeO ₂ (7.295 g), Al ₂ O ₃ (120.041 g) and flux (20.000 g) were mixed in a mixer for 4-20 hours and then added to the crucible. . The crucible was placed in a continuous furnace and sintered at 1500 ° C. to 1700 ° C. for 2 to 10 hours in a reducing atmosphere. The sintered material was powdered with a crusher. The powder was washed with acid and deionized water and then dried in an oven at 120 ° C. to 180 ° C. for 12-24 hours. Finally, the powder was sieved through a 20 μm mesh to obtain Lu _2.945 Ce _0.055 Al ₅ O ₁₂ and the characteristics (ie emission wavelength, intensity, CIE value, particle size distribution, etc.) were examined. .

According to a further aspect of the present invention, the white light illumination system comprises an excitation source having an emission wavelength in the range of 200 nm to 480 nm, at least one of a red-emitting phosphor or a green-emitting phosphor, and cerium-activated containing terbium. A yellow-green to yellow-emitting lutetium aluminate-based phosphor, wherein the phosphor is configured to emit light having a peak emission wavelength in the range of about 550 nm to about 565 nm. (See above for examples of specific compounds that meet this requirement and examples that also meet the following requirements): Further, the cerium-activated yellow-green to yellow-emitting lutetium aluminate-based phosphor can be configured to absorb excitation radiation having a wavelength in the range of about 380 nm to about 480 nm. Still further, the red light emitting phosphor may have an emission wavelength in the range of 600 nm to 660 nm. Further, the green light emitting phosphor may have an emission wavelength in the range of 500 nm to 545 nm. Still further, the red light emitting phosphor may be a nitride. Further, the nitride is at least one of (Ca, Sr) AlSiN ₃ : Eu ²⁺ , (Ca, Sr) ₂ N ₅ N ₈ : Eu ²⁺ , and (Ca, Sr) AlSi ₄ N ₇ : Eu ^2+. possible. Still further, the green-emitting phosphor can be a silicate. Furthermore, the silicate may have the formula (Sr, Ba, Mg) ₂ SiO ₄ : Eu ²⁺ .

  Although the present invention has been specifically described with reference to specific embodiments, those skilled in the art will recognize that the form and details can be changed and modified without departing from the spirit and scope of the invention. Easy to understand.

Claims (22)

A cerium-activated yellow-green to yellow-emitting lutetium aluminate-based phosphor having the formula (Lu _1-x Tb _x ) ₃ Al ₅ O ₁₂ : Ce, wherein x is about 0.1 to 1. Less than 0, and the phosphor is configured to absorb excitation radiation having a wavelength in the range of about 380 nm to about 480 nm and emit light having a peak emission wavelength in the range of about 550 nm to about 565 nm. A yellow-green to yellow-emitting lutetium aluminate phosphor.   The yellow-green to yellow-emitting lutetium aluminate phosphor according to claim 1, wherein x is in the range of about 0.3 to 1.0.   The yellow-green to yellow light emitting lutetium aluminate phosphor according to claim 1, wherein the excitation radiation has a wavelength in the range of about 420 nm to about 480 nm. The formula is _{(Lu 0.91-x Tb x Ce} 0.09) 3 Al 5 O 12, yellow-green-yellow light lutetium aluminate phosphor according to claim 1.   The yellow-green to yellow-emitting lutetium aluminate phosphor according to claim 3, wherein x is in the range of 0.3 to 0.5.   The yellow-green to yellow-emitting lutetium aluminate-based phosphor according to claim 1, further comprising a rare earth element gadolinium (Gd). The formula is (Lu _1-xy Tb _x Gd _y ) ₃ Al ₅ O ₁₂ : Ce, where x is in the range of about 0.1 to 1.0, y is greater than zero, and x + y < The yellow-green to yellow-emitting lutetium aluminate phosphor according to claim 6, which is 1. The equation _{(Lu 0.91-x-y Tb} x Gd y Ce 0.09) a ₃ Al _{5 O 12,} y is greater than zero, it is x + y <1, yellow-green-according to claim 6 Yellow light emitting aluminate phosphor.   The yellow-green to yellow light emitting aluminate phosphor according to claim 8, wherein x = 0.3 and y = 0.2.   The yellowish green to yellow light emitting aluminate phosphor according to claim 1, further comprising a halogen.   The yellowish green to yellow light emitting aluminate phosphor according to claim 10, wherein the halogen is substituted and contained in the crystal.   The yellow-green to yellow light-emitting aluminate phosphor according to claim 10, wherein the halogen is contained between crystal lattices. Formula _{(Lu 1-x Tb x)} 3 A z Al 5 O 12 C 2z: has a Ce, wherein
A is at least one of Mg, Sr, Ca, and Ba;
B is at least one of F, Cl, Br, and I;
0.001 ≦ x <1.0 and 0 <z ≦ 0.5.
A cerium-activated yellow-green to yellow-emitting lutetium aluminate phosphor.   The yellow-green to yellow light-emitting aluminate phosphor according to claim 13, further comprising rare earth element gadolinium (Gd). A white light illumination system,
An excitation source having an emission wavelength in the range of 200 nm to 480 nm;
At least one of a red light emitting phosphor and a green light emitting phosphor,
A white-light illumination system comprising: a cerium-activated yellow-green to yellow-emitting lutetium aluminate-based phosphor containing terbium configured to emit light having a peak emission wavelength in the range of about 550 nm to about 565 nm. .   16. The white light of claim 15, wherein the cerium activated yellow green to yellow light emitting lutetium aluminate-based phosphor is configured to absorb excitation radiation having a wavelength in the range of about 380 nm to about 480 nm. Lighting system.   The white light illumination system of claim 15, wherein the red light emitting phosphor has an emission wavelength in a range of 600 nm to 660 nm.   The white light illumination system of claim 15, wherein the green-emitting phosphor has an emission wavelength in a range of 500 nm to 545 nm.   The white light illumination system of claim 15, wherein the red light emitting phosphor is a nitride. The nitride is at least one of (Ca, Sr) AlSiN ₃ : Eu ²⁺ , (Ca, Sr) ₂ N ₅ N ₈ : Eu ²⁺ , and (Ca, Sr) AlSi ₄ N ₇ : Eu ²⁺ 20. The white light illumination system of claim 19, wherein:   The white light illumination system of claim 15, wherein the green-emitting phosphor is a silicate. The white light illumination system of claim 21, wherein the silicate has the formula (Sr, Ba, Mg) ₂ SiO ₄ : Eu ²⁺ .

Images