JP3763719B2 - Phosphors based on oxynitride glass - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a phosphor useful as a phosphor of a white light emitting diode (white LED) using a blue light emitting diode (blue LED) as a light source.
[0002]
[Prior art]
Powders and thin film oxide emitters using rare earth elements have been widely known, but on the other hand, there are few research examples of emitters that activate rare earth elements in non-oxides. As for nitrides, Si—O—N-based oxynitride crystals such as β sialon structure (Japanese Patent Laid-Open No. 60-206889, JWHvan Krevel et al “Long wavelength Ce ³⁺ emission in Y-Si-0-N materials ", Journal of Alloys and Compounds 268 (1998) 272-277).
[0003]
In addition, a phosphorescent fluorescent glass containing a relatively large amount of Eu ₂ O ₃ or Tb ₂ O ₃ which is a luminescent center as a light-emitting body in a glass state rather than a crystalline powder or thin film (Japanese Patent Laid-Open No. 8-133780). And oxide fluorescent glass (Japanese Patent Laid-Open No. 10-167755) are known.
[0004]
Conventionally, in the lighting equipment and display industries, (1) Fields that require reliability, such as disaster prevention lighting, (2) Fields that prefer small and light weight, such as in-vehicle lighting and LCD backlights, (3) Station destination information boards, etc. White LEDs are used in fields that require visibility. The emission color of the white LED is obtained by the principle of light color mixing, and the blue light absorbed by the phosphor also acts as an excitation source and emits yellow fluorescence. This yellow light and blue light are mixed and appear as white to the human eye.
[0005]
As a phosphor suitable for a white LED, a phosphor in which Ce is doped in a YAG-based oxide matrix lattice represented by a composition formula of (Y, Gd) ₃ (Al, Ga) ₅ O ₁₂ is known. . This phosphor is conventionally used by being thinly coated on the surface of an InGaN blue LED chip as a light emitting source.
[0006]
However, the emission peak of the lnGaN blue LED used as the light source of the white LED is 465 to 520 nm, which is located on the longer wavelength side than the wavelength range in which the YAG phosphor can be excited.
[0007]
[Problems to be solved by the invention]
Conventional oxide phosphors generally have a significantly reduced excitation spectrum intensity when the wavelength exceeds 400 nm. For this reason, in a white LED (white light emitting diode) made by applying a YAG phosphor to an InGaN blue LED chip, the excitation peak of the phosphor does not efficiently overlap with the emission peak of the blue LED, and the shorter wavelength side Therefore, it was not necessarily a phosphor with good excitation efficiency for producing a high-intensity white LED.
[0008]
[Means for Solving the Problems]
Therefore, the inventor of the present invention has an idea that the excitation / emission wavelength can be freely changed if a part of oxygen (-2 valence) is replaced with nitrogen (-3 valence) and the ionicity or covalent ratio of the bond is changed. The present invention was completed by adding alkaline earth (+2) and luminescent center ions in a glass system in which the overall charge was neutrally balanced. Such an idea is novel, and there is no example of producing an oxynitride glass having an excitation spectrum in a wide wavelength range (≦ 550 nm) in the visible / ultraviolet light region.
That is, the phosphor of the present invention uses oxynitride glass as a base material, and Eu ²⁺ , Eu ³⁺ , Ce ³⁺ , Tb ^3+, etc. having a part of Ca ²⁺ ions of the base material as the emission center. The rare earth ions or transition metal ions such as Cr ³⁺ and Mn ²⁺ are substituted.
[0009]
The present invention is a phosphor made of glass using oxynitride glass as a base material of luminescent center ions, and the composition of the base material is expressed in mol% , and CaCO ₃ is converted to CaO: 20 to 50 mol. %, Al ₂ O _3: 0~30 mol%, SiO: 25 to 60 mol%, AlN: from 5 to 50 mol%, the content of rare earth oxides or transition metal oxides to be a luminescent center ion is 0. It is 1-20 mol%, and is a fluorescent substance characterized by the sum total of five components being 100 mol%.
[0010]
Further, the present invention is the above-described fluorescent bodies nitrogen content is equal to or less than 15 wt%.
[0011]
The present invention also provides the phosphor containing a rare earth oxide, wherein the rare earth oxide other than the rare earth oxide is used as a rare earth oxide in the fluorescent glass in an amount of 0.1 to 10 mol. % is above fluorescent body characterized in that in a content containing as a co-activator of.
[0012]
Furthermore, the present invention is a white LED using the phosphor described above using an InGaN-based blue LED as a light source.
[0013]
CaCO _{3 which} is a component of the phosphor of the present invention is a raw material of CaO, and not only widens the vitrification range, but also contains a large amount and a stable amount of rare earth ions or transition metal ions serving as emission centers in the fluorescent glass. Can be made. The range of 20-30 mol% is more preferable. As described above, the content of the rare earth oxide or transition metal oxide that becomes the luminescence center ion by easily replacing the Ca ²⁺ ion at the Ca ²⁺ site with Sr ²⁺ or Ba ²⁺ ion is 0.1 as described above. It can be freely controlled within a range of ˜20 mol%.
[0014]
AlN and Al ₂ O ₃ are used to change the nitrogen content. AlN is 40 to 10 mol%, Al ₂ O ₃ is more preferably a range of 0 to 20 mol%.
SiO ₂ is one of the glass forming components, and CaO In combination, the melting temperature of the glass melt is lowered. The range of 30-40 mol% is more preferable.
[0015]
Rare earth oxides or transition metal oxides are raw materials for doping rare earth ions such as Eu ²⁺ , Eu ³⁺ , Ce ³⁺ and Tb ³⁺ or transition metal ions such as Cr ³⁺ and Mn ²⁺ into glass. Yes, it is activated in the range of 20 mol% or less, which is the glass composition limit, and has a strong emission intensity at an activation amount of 0.5 to 10 mol% in which concentration quenching of the emission center is not observed.
[0016]
Oxynitride glass is obtained by substituting part of oxygen with nitrogen. By introducing nitrogen, chemical bonds in the glass network structure are strengthened, and in addition to thermal properties such as glass transition temperature and softening temperature, mechanical properties are also observed. It is known that properties and chemical properties are remarkably improved (for example, Japanese Patent Publication No. 7-37333).
[0017]
In the phosphor of the present invention, the nitrogen content in the glass can move the peak position of the emission spectrum by controlling the nitrogen content in a glass composition range of 15 wt% or less. Further, the phosphor of the oxynitride glass phosphor The peak wavelength in the excitation spectrum can be adjusted in the range from ultraviolet to green. Since the shift of the emission peak wavelength gradually changes from yellow to red, the phosphor can be easily multicolored by changing the nitrogen content. A more preferable nitrogen content is 4 to 7 wt%.
[0018]
There are two typical methods for producing oxynitride glass, one is a method of melting using nitride as a nitrogen source, and the other method is a porous material produced by a sol-gel method or the like. There is a method of nitriding glass with ammonia gas.
[0019]
Since the former method decomposes nitrides at a high temperature at the time of melting, it is very difficult to increase the nitrogen content to 10 wt% or more. For example, by synthesizing these glasses under a nitrogen pressure of 10 atm, An oxynitride glass containing a relatively large amount of nitrogen is obtained. Such an oxynitride glass is further excellent in mechanical strength and chemical stability.
Fluorescent glass basically contains only one type of emission center. However, two kinds of rare earth elements may be included in the fluorescent glass. Two effects can be listed as the effect of simultaneously doping these two types into the fluorescent glass. One is a sensitizing action, and the other is to newly form a trap level of carriers to improve the expression and improvement of long afterglow and the thermoluminescence. As a combination sensitizing action is observed, in general, Tb ³⁺ ions with respect to Eu ³⁺ ions, Ce ³⁺ ions and the like with respect to Tb ³⁺ ions.
[0021]
In order to use other rare earth element ions (Gd ³⁺ , Tb ³⁺ , Dy ³⁺ or Sm ³⁺ ions) in addition to Eu ²⁺ (or Ce ³⁺ ) ions, these rare earth oxidations are used. The product can be included in the fluorescent glass as a co-activator at a content of 0.1 to 10 mol%.
[0022]
Examples of the oxynitride glass include Si—O—N, Mg—Si—O—N, Al—Si—O—N, Nd—Al—Si—O—N, Y—Al—Si—O—N, and Ca. -Al-Si-O-N, Mg-Al-Si-ON, Na--Si-ON, Na-Ca-Si-ON, Li-Ca-Al-Si-ON, Na—B—Si—O—N, Na—Ba—B—Al—Si—O—N, Ba—Al—Si—O—N, Na—B—O—N, Li—P—O—N, Systems such as Na—P—O—N are known. [0023]
Among these systems, the base material of the present invention is a Ca—Al—Si—O—N oxynitride glass (produced by Sakuhana et al. In 1983. “Journal of Non-Crystalline Solids 56 (1983) 147-152).
[0024]
The nitrogen content of this Ca—Al—Si—O—N-based oxynitride glass is reported to be about 5.5 wt%, and the composition of this oxynitride glass is used as the base glass of the phosphor of the present invention. Can be used.
[0025]
As the method for producing the Ca—Al—Si—O—N-based oxynitride glass phosphor of the present invention, the above-described conventionally known methods can be used. In that case, rare earth oxide is used as a raw material, and other raw materials are used. And is heated and melted in a nitrogen atmosphere as a starting material to synthesize fluorescent glass.
[0026]
For example, it can be synthesized by adding AlN to rare earth oxide or metal oxide CaO (← CaCO ₃ , Al ₂ O ₃ , SiO ₂ ) and melting at high temperature, for example, about 1700 ° C. At this time, the nitrogen content in the glass can be changed by changing the ratio of Al ₂ O ₃ and AlN.
[0027]
Hereinafter, the relationship between the nitrogen content and the excitation / fluorescence spectrum in the Ca—Al—Si—O—N-based oxynitride glass doped with Eu ²⁺ ions will be described in detail. The sample was prepared using the following raw material composition. The raw material powder was mixed with each composition of the following samples A, B, and C, this mixed sample powder was wrapped in molybdenum foil to avoid reaction with the furnace material, and using a high frequency furnace at 1700 ° C. in a nitrogen atmosphere. It was heated and melted for 2 hours, and further rapidly cooled to obtain fluorescent glass.
[0028]
(Sample A)
CaCO ₃ : Al ₂ O ₃ : SiO ₂ : AlN: Eu ₂ O ₃ = 24.0: 3.3: 33.4: 33.3: 6.0 (N: 5 wt%)
(Sample B)
CaCO ₃ : Al ₂ O ₃ : SiO ₂ : AlN: Eu ₂ O ₃ = 26.2: 9.1: 36.4: 21.8: 6.5 (N: 3 wt%)
(Sample C)
CaCO ₃ : Al ₂ O ₃ : SiO ₂ : AlN: Eu ₂ O ₃ = 27.7: 15.4: 38.5: 11.5: 6.9 (N: 2 wt%)
[0029]
FIG. 1 shows excitation / fluorescence spectra of Ca—Al—Si—O—N-based oxynitride glass doped with Eu ²⁺ ions. The nitrogen content of the fluorescent glass decreases as sample A changes to sample C. The excitation spectrum intensity of these phosphors suddenly increases from 400 nm and has a maximum value around 500 nm. On the other hand, the peak of the emission spectrum was around 600 nm (red). The position of the emission spectrum shifted to the short wavelength side as the nitrogen content in the glass decreased. As described above, the phosphor can be multicolored by controlling the nitrogen content. Sample A has a nitrogen content of about 5 wt%, Sample B has a nitrogen content of about 3 wt%, and Sample C has a nitrogen content of about 2 wt%.
[0030]
The excitation spectrum of FIG. 1 has two peaks. The 250-350 nm peak is attributed to the Eu-O charge transfer absorption band, while the 450-550 nm peak is attributed to the Eu-N charge transfer absorption band. Therefore, if the nitrogen content in the fluorescent glass decreases, the charge transfer absorption band peak of Eu-O at 450 to 550 nm decreases.
[0031]
The oxynitride glass phosphor of the present invention can be said to have a better nitrogen content when an InGaN blue LED is used as excitation light (450 to 550 nm).
Comparing sample A and sample B, it can be seen that the peak of the Eu-N charge transfer absorption band shifts to the longer wavelength side as the nitrogen content increases. Therefore, it is possible to match the wavelength of the excitation light of various blue LEDs by slightly changing the nitrogen content.
[0032]
When the nitrogen content is decreased from sample A to sample C, the emission peak moves continuously from 680 nm to 580 nm. If the peak position of the excitation spectrum is not taken into the material design, a fluorescent glass having an emission of 580 to 680 nm can be obtained by controlling the nitrogen content.
[0033]
From the above results, the nitrogen content is preferably 4 to 7 wt%, and by changing the nitrogen content in this range, a fluorescent glass having excitation and emission spectra as required can be synthesized.
[0034]
【Example】
Example 1
Example raw material powder doped with Eu ²⁺ ions was mixed with the following composition, this mixed sample powder was wrapped in molybdenum foil, and heated and melted at 1700 ° C. for 2 hours in a nitrogen atmosphere using a high-frequency heating furnace. Further, it was rapidly cooled to obtain fluorescent glass.
[0035]
(Sample A)
CaCO ₃ : Al ₂ O ₃ : SiO ₂ : AlN: Eu ₂ O ₃ = 28.2: 3.1: 31.4: 31.3: 6.0 (N: 5 wt%) (Eu: 12.0% )
(Sample B)
CaCO ₃ : Al ₂ O ₃ : SiO ₂ : AlN: Eu ₂ O ₃ = 28.6: 3.1: 31.9: 31.8: 4.6 (N: 5 wt%) (Eu: 9.2% )
(Sample C)
CaCO ₃ : Al ₂ O ₃ : SiO ₂ : AlN: Eu ₂ O ₃ = 29.1: 3.2: 32.3: 32.3: 3.1 (N: 5 wt%) (Eu: 6.2% )
(Sample D)
CaCO ₃ : Al ₂ O ₃ : SiO ₂ : AlN: Eu ₂ O _{3 2} = 29.4: 3.2: 32.7: 32.6: 2.1 (N: 5 wt%) (Eu: 4.2 %)
[0036]
FIG. 2 shows excitation / emission spectra of Ca—Al—Si—O—N-based oxynitride glasses having different doping amounts of Eu ²⁺ ions. The shape of the excitation / emission spectrum is the same regardless of the doping amount of Eu ²⁺ ions. However, the excitation / emission peak moves from D to A toward the longer wavelength side as the amount of Eu ²⁺ ions in the fluorescent glass increases.
[0037]
Example 2
Example raw material powder doped with Ce ³⁺ ions was mixed in the following composition, this mixed sample powder was wrapped in molybdenum foil, heated and melted at 1700 ° C. for 2 hours in a nitrogen atmosphere using a high frequency furnace, Quenching was performed to obtain fluorescent glass.
[0038]
(Sample A)
CaCO ₃ : Al ₂ O ₃ : SiO ₂ : AlN: CeO ₂ = 28.3: 3.3: 33.8: 33.6: 1.0 (N: 5 wt%) (Ce: 1.0%)
(Sample B)
CaCO ₃ : Al ₂ O ₃ : SiO ₂ : AlN: CeO ₂ = 29.5: 3.3: 33.4: 33.3: 0.5 (N: 5 wt%) (Ce: 0.5%)
[0039]
FIG. 3 shows an excitation / emission spectrum of a Ca—Al—Si—O—N-based oxynitride doped with Ce ³⁺ ions. The shape of the excitation spectrum changed greatly with the change of the doping amount of Ce ³⁺ ions, but the emission spectrum did not change so much and showed a broad peak having a maximum value in the range of 400 to 450 nm. The excitation spectrum of sample B with a small doping amount of Ce ³⁺ ions has two peaks, and the peak at 200 to 330 nm is Ce ³⁺ −. O and a peak at 330 to 400 nm are attributed to the charge transfer absorption band of Ce ³⁺ —N, respectively. Each of these fluorescent glasses has a long persistence that continues to emit light even after irradiation with ultraviolet light, which is excitation light, is stopped.
[0040]
Example 3
Example raw material powder doped with Cr ³⁺ was mixed with the following composition, this mixed sample powder was wrapped in molybdenum foil, heated and melted at 1700 ° C. for 2 hours in a nitrogen atmosphere using a high frequency furnace, and further rapidly cooled. As a result, fluorescent glass was obtained. Two types of fluorescent glasses activated with Cr ³⁺ were prepared in order to examine the uniformity of the obtained samples.
[0041]
(Sample A)
CaCO ₃ : Al ₂ O ₃ : SiO ₂ : AlN: Cr ₂ O ₃ = 28.3: 3.3: 33.8: 33.6: 1.0 (N: 5 wt%) (Cr: 2.0% )
(Sample B)
CaCO ₃ : Al ₂ O ₃ : SiO ₂ : AlN: Cr ₂ O ₃ = 28.3: 3.3: 33.8: 33.6: 1.0 (N: 5 wt%) (Cr: 2.0% )
[0042]
FIG. 4 shows excitation / emission spectra of Ca—Al—Si—O—N-based oxynitride glass doped with Cr ³⁺ ions. In FIG. 4, two types of samples (A and B) were confirmed for the oxynitride glass doped with Cr ³⁺ taken from the same batch. The excitation spectrum of sample A is the result of measurement while monitoring the emission at 470 nm. The emission spectrum is measured using 270 nm as excitation light.
[0043]
On the other hand, excitation spectrum 1 of sample B is measured while monitoring 440 nm emission. The emission spectrum 1 of B is measured using 255 nm as excitation light, and the emission spectrum 2 of B is measured using 335 nm as excitation light.
[0044]
The excitation / emission spectrum of sample A is different from both spectra of sample B, but if observed carefully, each excitation spectrum has two peaks. Moreover, both samples are similar considering that the broad peak of the emission spectrum is similarly present at 350 to 600 nm. Note that the 255 nm peak of the excitation spectrum is attributed to the absorption of the base material of the fluorescent glass, and the 335 nm peak is attributed to the absorption of Cr ³⁺ ions themselves.
[0045]
Example 4
Example raw material powder doped with Mn ²⁺ was mixed with the following composition, this mixed sample powder was wrapped in molybdenum foil, and heated and melted at 1700 ° C. for 2 hours in a nitrogen atmosphere using a high-frequency heating furnace. Quenching was performed to obtain fluorescent glass. Two types of fluorescent glasses activated with Mn ²⁺ were prepared in order to examine the uniformity of the obtained samples.
[0046]
(Sample A)
CaCO ₃ : Al ₂ O ₃ : SiO ₂ : AlN: MnCO ₃ = 29.9: 2.8: 33.2: 33.1: 1.0 (N: 5 wt%) (Mn: 1.0%)
(Sample B)
CaCO ₃ : Al ₂ O ₃ : SiO ₂ : AlN: MnCO ₃ = 29.9: 2.8: 33.2: 33.1: 1.0 (N: 5 wt%) (Mn: 1.0%)
[0047]
FIG. 5 shows an excitation / emission spectrum of Ca 1 Al—Si—O—N oxynitride glass doped with Mn ²⁺ ions. From the comparison of the excitation and emission spectra of Sample A and Sample B in FIG. 5, the oxynitride glass doped with Mn ²⁺ is uniform.
[0048]
【The invention's effect】
In the phosphor of the present invention, the position of the excitation spectrum moves significantly to the longer wavelength side compared to the oxide glass, the absorption peak becomes the maximum near the emission peak of the blue LED (450 to 520 nm), and the peak width also increases. Therefore, when an lnGaN blue LED is used as an excitation light source, it is excited efficiently when combined with this phosphor, and a brighter white LED can be realized. Also, unlike crystals such as oxynitride, glass can freely change the ratio of O and N in the oxynitride glass as long as the reaction conditions can be satisfied due to its loose structure. It is possible to easily increase the number of colors of the phosphor by changing the amount.
[Brief description of the drawings]
FIG. 1 is a graph of excitation / fluorescence spectra showing the N content dependency of Eu-doped oxynitride glass of the present invention.
FIG. 2 is a graph of excitation / fluorescence spectra showing the Eu amount dependence of the Eu-doped oxynitride glass of the present invention.
FIG. 3 is a graph of excitation and fluorescence spectra of Ce-doped oxynitride glass of the present invention.
FIG. 4 is a graph of excitation / fluorescence spectra of Cr-doped oxynitride glass of the present invention.
FIG. 5 is a graph of excitation / fluorescence spectra of Mn-doped oxynitride glass of the present invention.

Claims (4)

A phosphor made of glass using oxynitride glass as a base material of luminescent center ions, and the composition of the base material in terms of mol%, when CaCO ₃ is converted to CaO: 20 to 50 mol%, Al ₂ O ₃ : 0 to 30 mol%, SiO: 25 to 60 mol%, AlN: 5 to 50 mol% , and the content of rare earth oxide or transition metal oxide to be the emission center ion is 0.1 to 20 mol % and is, phosphor total 5 component is characterized in that 100 mol%.  The phosphor according to claim 1, wherein the nitrogen content is 15 wt% or less. The phosphor according to claim 1 , which contains a rare earth oxide, and contains other rare earth element ions serving as a sensitizer in addition to the rare earth oxide in the fluorescent glass in an amount of 0.1 to 10 mol%. The phosphor according to claim 1, wherein the phosphor is contained as a co-activator in an amount.  A white light-emitting diode using an InGaN-based blue light-emitting diode as a light source and using the phosphor according to any one of claims 1 to 3.

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