JP7266215B2 - Phosphor and light-emitting device using the same - Google Patents

Description

The present invention relates to a phosphor whose host crystal has a garnet structure, and furthermore, displays and projectors configured using the phosphor together with solid-state light sources such as light-emitting diodes (LEDs) and laser diodes (LDs). The present invention relates to light-emitting devices such as display devices and lighting devices.

2. Description of the Related Art In recent years, light-emitting devices that combine a solid-state light-emitting light source such as an LED or LD with a phosphor have been widely used. This light-emitting device is used as a light source for image display devices such as displays and projectors and lighting devices. This light-emitting device is composed of a combination of a solid-state light-emitting light source having an emission peak wavelength in the blue region and a phosphor having an emission peak wavelength in the yellow region. It is used according to each application.

A phosphor generally consists of a host crystal and a luminescent center ion. One of the well-known phosphors having an emission peak wavelength in the yellow region has Y ₃ Al ₂ (AlO ₄ ) ₃ , which is a compound having a garnet structure as a host crystal, and activates Ce ³⁺ as an emission center ion. (Y ₃ Al ₂ (AlO ₄ ) ₃ :Ce ³⁺ phosphor). Here, the garnet structure is one of crystal structures, and is a crystal that can be represented as A ₃ B ₂ (CO ₄ ) ₃ (A, B, and C are arranged with coordinating elements). . Y atoms arranged at the A site and Al atoms arranged at the B and C sites are represented as Y ₃ Al ₂ (AlO ₄ ) ₃ . However, the Y ₃ Al ₂ (AlO ₄ ) ₃ :Ce ³⁺ phosphor having the yellow region emission peak wavelength contains only a small amount of the red region emission wavelength at the long-wavelength side end, and the color reproducibility cannot be improved. mentioned as an issue. One solution to this problem is to lengthen the emission peak wavelength of the phosphor.

Patent Document 1 discloses (Y, Gd) ₃ Al ₂ (AlO ₄ ) ₃ :Ce ³⁺ in which a part of the Y site is substituted with Gd for a Y ₃ Al ₂ (AlO ₄ ) ₃ :Ce ³⁺ phosphor. Phosphors are disclosed. While Y ₃ Al ₂ (AlO ₄ ) ₃ :Ce ³⁺ has an emission peak wavelength in the yellow region, the (Y, Gd) ₃ Al ₂ (AlO ₄ ) ₃ :Ce ³⁺ phosphor described in Patent Document 1 has , has an orange region emission peak wavelength. Therefore, the emission peak wavelength has moved relatively to the longer wavelength side.

Japanese Patent No. 3503139

However, the (Y, Gd) ₃ Al ₂ (AlO ₄ ) ₃ :Ce ³⁺ phosphor has a higher luminous efficiency than the Y ₃ Al ₂ (AlO ₄ ) ₃ :Ce ³⁺ phosphor as the phosphor temperature rises. Temperature quenching, which is a phenomenon in which the retention rate decreases, is remarkably observed. The fact that temperature quenching is conspicuous means that the output fluorescence wavelength also changes greatly as the temperature of the phosphor changes. It suggests that

The present invention has been made in order to solve the above problems, and the emission peak wavelength of Y ₃ Al ₂ (AlO ₄ ) ₃ :Ce ³⁺ phosphor is relatively shifted to the long wavelength side, and the temperature An object of the present invention is to provide a phosphor whose quenching is suppressed and a light emitting device using the same.

A phosphor according to the present invention is a phosphor in which a garnet structure is used as a host crystal, Ce ³⁺ is activated as a luminescent center ion in the host crystal, and Li ⁺ is contained in the phosphor. and

According to the phosphor according to the present invention, the emission peak wavelength can be shifted to the longer wavelength side relative to the Y ₃ Al ₂ (AlO ₄ ) ₃ :Ce ³⁺ phosphor, and temperature quenching can be suppressed. It is possible to provide a phosphor and a light-emitting device with the

1 is a diagram showing the structure of a light-emitting device according to Embodiment 1; FIG. FIG. 2 shows fluorescence spectra of Example 2 and Comparative Example 2 in Embodiment 1; 1 is Table 1 showing compositions and various measurement results of Examples 1 to 4 and Comparative Examples 1 and 2;

In the phosphor according to the first aspect, the host crystal has a garnet structure, Ce ³⁺ is activated as an emission center ion in the host crystal, and Li ⁺ is included.

In the first aspect, the phosphor according to a second aspect may be represented by the following formula (1).
M _3−x Al ₂ (AlO ₄ ) ₃ : Ce ³⁺ _x Li ⁺ _y , (M=Y _α Lu _(1−α) ) (1)
In addition, the range of the value of α is 0.5 ≤ α ≤ 1,
the value range of x is 0.01≦x≦0.1,
The range of y values is 0.01 ≤ y ≤ 0.05

A light-emitting device according to a third aspect comprises the phosphor of the first or second aspect,
a light source;
Prepare.

Hereinafter, phosphors according to embodiments and light-emitting devices using the phosphors will be described in detail with reference to the accompanying drawings.

(Embodiment 1)
<Phosphor>
The phosphor according to Embodiment 1 has a garnet structure as a host crystal, is activated by Ce ³⁺ as a luminescence center ion, and contains Li ^{3 +} in this phosphor.

[Host crystal]
The garnet structure of the parent crystal refers to the crystal structure represented by the chemical formula A ₃ B ₂ (CO ₄ ) ₃ . In the chemical formula, elements that can be coordinated can be arranged in the parts A, B, and C, respectively, but the desired fluorescence peak wavelength can be realized, and the reliability against the external environment is high. The component of the host crystal is Y ₃ Al ₂ (AlO ₄ ) ₃ or (Y, Lu) ₃ Al ₂ (AlO ₄ ) ₃ in which a part of Y is substituted with Lu from the viewpoint of easily obtaining the emission peak wavelength. is desirable. If the ratios of Y and Lu are represented by α and (1−α), respectively, and (Y, Lu) in the above formula is represented by (Y _α Lu _{(1−α) )} , the range of values of α is 0.0. It is desirable that 5≦α≦1. If α is less than 0.5, the ratio of Lu ₃ Al ₂ (AlO ₄ ) ₃ in the host crystal increases, making it impossible to obtain the desired emission peak wavelength, which is not preferable.

[Emission center ion]
Emission center ions include, for example, Mn ²⁺ , Mn ⁴⁺ , Eu ²⁺ , and Eu ³⁺ , but Ce ³⁺ is preferably selected from the viewpoint of realizing a desired fluorescence peak wavelength. When the luminescence lifetime of the luminescence center ion is long, it takes time for the electrons that have transitioned from the ground state to the excited state by the excitation light to return to the ground state again. Therefore, as the excitation light intensity increases, the number of electrons that cannot return from the excited state to the ground state increases, resulting in a phenomenon of luminance saturation. Among luminescence center ions, Ce ³⁺ has a relatively short luminescence lifetime of several tens of nanoseconds. From this point of view as well, the emission center ion is preferably Ce ³⁺ .
Also, the atomic ratio x of Ce ³⁺ is preferably in the range of 0.01≦x≦0.1. If x is less than 0.01, the desired fluorescence intensity cannot be obtained, which is not preferred. Moreover, when x is larger than 0.1, a phenomenon called concentration quenching occurs, and fluorescence intensity decreases, which is not preferable.

[Activating ion]
As the activating ion, for example, various elements can be used from the viewpoint of crystal engineering, but it is desirable to select Li ⁺ from the viewpoint that a desired fluorescence peak wavelength can be realized. It is considered that Li ⁺ does not satisfy the conditions for substitution at the site of the host crystal, which is preferable this time, and is present between the sites of the host crystal. It is thought that this changed the inter-crystal distance between each site and affected the optical characteristics.
The Li ⁺ atomic ratio y is preferably in the range of 0.01≤y≤0.05. If y is less than 0.01, it is not possible to obtain a phosphor exhibiting a desired fluorescence peak wavelength, which is not preferable. Moreover, when y is larger than 0.05, it is difficult to fabricate, which is not preferable.

[Phosphor]
Summarizing the above, the chemical formula for the structure of the phosphor is:
M _3−x Al ₂ (AlO ₄ ) ₃ : Ce ³⁺ _x Li ⁺ _y , (M=(Y _α Lu _(1−α) ))
where the value range of α is 0.5 ≤ α ≤ 1, the value range of x is 0.01 ≤ x ≤ 0.1, and the value range of y is 0.01 ≤ y ≤ 0.05. Preferably.

[Light emitting device]
FIG. 1 is a diagram showing the structure of a light-emitting device 10 according to Embodiment 1. FIG. This light emitting device 10 includes an excitation light source 1 that emits excitation light 2 and a phosphor 3 that receives the excitation light 2 and emits fluorescence 4 . , 4 indicate fluorescence, respectively. The excitation light source 1 generally has an excitation wavelength of 365 nm or 450 nm, but it is preferable to select 450 nm from the viewpoint that the phosphor 3 in Embodiment 1 can be efficiently excited. . The excitation light source 1 is installed directly below the phosphor 3 and irradiates the phosphor 3 with excitation light 2 . The phosphor 3 emits fluorescence 4 upon receiving the excitation light 2 .

A more specific description will be given below based on examples and comparative examples.
Although various synthesis methods are known for synthesizing phosphors, phosphors shown in Examples and Comparative Examples were synthesized using a solid-phase reaction method, and their optical properties were evaluated.

(Example 1)
<Synthesis of Phosphor>
(material)
Raw material powders used in this synthesis method are shown below.
・ Yttrium oxide (Y ₂ O ₃ Shin-Etsu Chemical Co., Ltd. purity: >99.99%)
・ Lutetium oxide (Lu ₂ O ₃ manufactured by Wako Pure Chemical Industries, Ltd. Purity: >99.5%)
・ Aluminum oxide (Al ₂ O ₃ manufactured by Sumitomo Chemical Co., Ltd. Purity: ≥ 99.99%)
・ Cerium oxide (CeO ₂ Shin-Etsu Chemical Co., Ltd. Purity: >99.99%)
・ Gadolinium oxide (Gd ₂ O ₃ manufactured by Kojundo Chemical Laboratory, purity: >99.9%)
・ Lithium oxide (Li ₂ O manufactured by Kojundo Chemical Laboratory Co., Ltd. Purity: > 99.0%)

(i) First, raw material powders other than lithium oxide serving as a Li ⁺ source were weighed at a predetermined ratio and placed in an agate mortar, and sufficiently pulverized and mixed using an agate pestle to obtain a mixed powder. . In order to sufficiently mix the raw material powders, volatile ethanol was added to the mixed powders and mixed in a wet process.
(ii) After that, the obtained mixed powder was put into an alumina boat. Lithium oxide serving as a Li ⁺ source was weighed so as to be the same amount as the mixed powder, and put into an alumina boat separate from the mixed powder.
(iii) The two prepared alumina boards were placed in a tubular furnace (manufactured by YAMADA DENKI Co., LTD, model number: TSR-630) and fired at 1300° C. for 3 hours. At this time, nitrogen gas was flowed at a rate of 100 ml/min in order to create an inert gas atmosphere in the tubular furnace. After sintering, the lithium oxide serving as the Li ⁺ source did not retain its original shape in the alumina board, but the mixed powder changed from white to orange-yellow phosphor powder.
(iv) The removed phosphor powder was placed in the agate mortar again, pulverized and mixed with an agate pestle, and the phosphor powder to be evaluated was obtained.

(Example 2 and Example 4)
Except that the ratio of each raw material powder was changed as shown in Table 1, and that the lithium oxide serving as the Li ⁺ source was weighed so as to be double the amount of the mixed powder and put into an alumina boat separate from the mixed powder. obtained a phosphor powder in the same manner as in Example 1.

(Example 3)
A phosphor powder was obtained in the same manner as in Example 1 except that the ratio of each raw material powder was changed as shown in Table 1.

(Comparative Example 1 to Comparative Example 2)
A phosphor powder was obtained in the same manner as in Example 1, except that the ratio of each raw material powder was changed as shown in Table 1, and in particular, lithium oxide serving as a Li ⁺ source was removed.

<Evaluation of optical properties>
Optical properties of the produced phosphor powder were evaluated for the following three points.

(Photoluminescence (PL) measurement)
PL measurement was performed using a spectrofluorophotometer (manufactured by Hitachi High-Technologies, model number: F-7100).
(1) First, the obtained sample was placed in a sample cell specified by the manufacturer, and set in a sample holder in a spectrofluorophotometer.
(2) Next, the following measurement conditions were set on the software. Excitation side slit width: 5.0 nm, fluorescence side slit width: 1.0 nm, photomultiplier voltage: 600 V, excitation wavelength: 450 nm, fluorescence wavelength measurement range: 470 nm to 800 nm.
FIG. 2 is a diagram showing fluorescence spectra of Example 2 and Comparative Example 2 measured under set conditions.
(3) Each of the samples listed in Examples and Comparative Examples was measured, and the fluorescence peak wavelength was recorded.
(4) When applied to products that are planned to be installed, the necessary range of fluorescence peak wavelength is 580 nm or more and 630 nm or less. .

(Quantum efficiency (QE) measurement)
QE measurement was performed using a spectrofluorophotometer (manufactured by JASCO Corporation, model number: FP-6500).
(1) First, the obtained sample was placed in a sample cell specified by the manufacturer, and set in a sample holder in a spectrofluorophotometer.
(2) Next, the following measurement conditions were set on the software. Measurement mode: Emission, excitation bandwidth: 5.0 nm, fluorescence bandwidth: 5.0 nm, photomultiplier voltage: 205 V, excitation wavelength: 450 nm, fluorescence wavelength measurement range: 430 nm to 800 nm.
(3) The samples listed in each example and comparative example were measured and their quantum efficiencies were recorded.
(4) Since the required quantum efficiency is 80% or higher when applying to products that are planned to be installed, samples within this range were evaluated as ◯, and samples outside this range were evaluated as x.

(Measurement of fluorescence intensity maintenance rate)
The fluorescence intensity maintenance rate was measured using a spectrofluorophotometer (manufactured by JASCO Corporation, model number: FP-6500).
(1) First, a temperature-adjustable sample holder was set in the spectrofluorophotometer. The obtained sample was placed in a sample cell specified by the manufacturer, and set in a temperature-adjustable sample holder set in a spectrofluorophotometer.
(2) Next, the following measurement conditions were set on the software. Measurement mode: Emission, excitation bandwidth: 5.0 nm, fluorescence bandwidth: 5.0 nm, photomultiplier voltage: 205 V, excitation wavelength: 450 nm, fluorescence wavelength measurement range: 430 nm to 800 nm, sample holder temperature: 25°C and 150°C.
(3) Fluorescence intensities of the samples listed in Examples and Comparative Examples were recorded at sample holder temperatures of 25° C. and 150° C., respectively. After that, the ratio of the fluorescence intensity measured when the sample holder was set at 150° C. to the fluorescence intensity measured when the sample holder was set at 25° C. was calculated as the fluorescence intensity maintenance rate.
(4) When applied to products that are planned to be installed, the required fluorescence intensity maintenance rate is 80% or more.

(Comprehensive judgment)
As a comprehensive judgment, in each example and comparative example, if the PL measurement, quantum efficiency, and fluorescence intensity maintenance rate are all 〇, the overall judgment is 〇 (good), and even one of each judgment result is ×. Regarding, the overall judgment was x (impossible).

Table 1 in FIG. 3 shows the compositions and various measurement results of Examples 1 to 4 and Comparative Examples 1 and 2.

In Examples 1 and 3, the ratio of the M portion of the host crystal was changed. When the M part coexists with Y and Lu (α = 0.5) as in Example 1, compared with the case where the M part is only Y (α = 1.0) as in Example 3 The fluorescence peak wavelength is shifted to the short wavelength side by about 10 nm. It is suggested that this is due to an increase in the so-called Lu ₃ Al ₅ O ₁₂ component due to an increase in the amount of Lu substituting in the M portion. However, since Li ⁺ is added to both of them, the emission peak wavelength satisfies the condition of 580 nm or more and 630 nm or less, which is a necessary condition when mounting optical products. Compared to Example 1, Comparative Example 1 does not have Li ⁺ added, but the emission peak wavelength is 546.4 nm, and the presence or absence of Li ⁺ addition greatly affects the shift of the emission peak wavelength. I know you are. It is considered that this is because the effect of adding Li ^{2 +} causes strain in the host crystal and changes the coordination environment of the crystal containing the luminescent center ion.

Examples 2 and 4 are obtained by increasing each x value of Examples 1 and 3 and changing the ratio of the M portion of the base crystal. As in Examples 1 and 3, the fluorescence peak wavelength is shifted to the short wavelength side by about 10 nm compared to the case where the M portion is Y (α = 1.0) only, for the same reason as described above. I believe that. Compared to Example 4 ^, Comparative Example 2 does not contain Li ⁺ but has an emission peak wavelength of 553.0 nm. It can be seen that the shift is greatly affected.

In summary, Examples 1 to 4 are excellent in emission peak wavelength, quantum efficiency, and fluorescence intensity maintenance rate. Therefore, the overall judgment is 0. However, in Comparative Examples 1 and 2, in which Li 2 ⁺ was not added, the quantum efficiency and the fluorescence intensity maintenance rate were good, but the emission peak wavelength could not satisfy the judgment conditions. Therefore, the overall evaluation of Comparative Examples 1 and 2 is x.

As shown in the above examples, according to this example, an excellent orange phosphor that can suppress the decrease in emission intensity due to temperature rise even when irradiated with a high-output light source and has emission characteristics in the long wavelength region. can be provided.

It should be noted that the present disclosure includes appropriate combinations of any of the various embodiments and / or examples described above, and each embodiment and / or The effects of the embodiment can be obtained.

As described above, according to the phosphor according to the present invention, it is possible to provide a phosphor and a light-emitting device in which the emission peak wavelength is relatively shifted to the longer wavelength side and temperature quenching is suppressed, resulting in high luminance. It can be applied to lighting, projectors, and so on.

1 excitation light source 2 excitation light 3 phosphor 4 fluorescence 10 light emitting device

Claims (3)

A phosphor, wherein a host crystal has a garnet structure, Ce ³⁺ is activated as an emission center ion in the host crystal, and Li ^{3 +} is contained in the host crystal. 2. The phosphor according to claim 1, characterized by being represented by the following formula (1).
M _3-x Al ₂ (AlO ₄ ) ₃ : Ce ³⁺ _x Li ⁺ _y (1)
M=Y _α Lu _(1−α) ,
In addition, the range of the value of α is 0.5 ≤ α ≤ 1,
the value range of x is 0.01≦x≦0.1,
The range of y values is 0.01 ≤ y ≤ 0.05 The phosphor according to claim 1 or 2,
a light source;
A light emitting device.

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