JP2021059653A - Phosphor and light emitting device including the same - Google Patents

Abstract

To provide a phosphor that prevents emission intensity from decreasing due to a temperature rise even by irradiation with a high-power light source, and has emission properties in a long wavelength region.SOLUTION: A phosphor has a matrix crystal with a garnet structure, where the matrix crystal is activated with Ce3+ as an emission center ion and contains Li+. The phosphor may be represented by the following formula (1). M3-xAl2(AlO4)3: Ce3+xLi+y, (M=YαLu(1-α))(1), where the range of α value is 0.5≤α≤1, the range of x value is 0.01≤x≤0.1, the range of y value is 0.01≤y≤0.05.SELECTED DRAWING: None

Description

The present invention relates to a phosphor having a garnet structure as a parent crystal, and further, together with a solid-state light emitting source such as a light emitting diode (LED) or a laser diode (LD), an image of a display or a projector configured by using the phosphor Related to light emitting devices such as display devices and lighting devices.

In recent years, a light emitting device that combines a solid-state light source such as an LED or LD and a phosphor has become widespread. This light emitting device is used as a light source for video display devices such as displays and projectors and lighting devices. This light emitting device is composed of a combination of a solid-state light source having a blue region emission peak wavelength and a phosphor having a yellow region emission peak wavelength, and emits white light by combining the respective emission wavelengths. It is used according to each application.

Generally, a phosphor is composed of a parent crystal and a luminescence center ion. One of the well-known phosphors having a yellow region emission peak wavelength has Y ₃ Al ₂ (AlO ₄ ) ₃ , which is a compound having a garnet structure as a parent crystal, and activates ^{Ce 3+} as an emission center ion. There is a fluorescent substance (Y ₃ Al ₂ (AlO ₄ ) ₃ : Ce ^{3 +} fluorescent substance). Here, the garnet structure is one of the crystal structures, and is a crystal _{that can be represented as A 3} B ₂ (CO ₄ ) ₃ (coordinable elements are arranged in A, B, and C). .. Those in which Y atoms are arranged at the A site and Al atoms are arranged at the B and C sites are referred to as Y ₃ Al ₂ (AlO ₄ ) ₃ . However, the red region emission wavelength contained in the long wavelength side end of the _{Y 3} Al ₂ (AlO ₄ ) ₃ : Ce ^{3 +} phosphor having the yellow region emission peak wavelength is very small, and the color reproducibility can be improved. It is listed as an issue. One of the solutions to this problem is to lengthen the emission peak wavelength of the phosphor.

In Patent Document 1, Y ₃ Al ₂ (AlO ₄ ) ₃ : Ce ³⁺ phosphor in which a part of the Y site is replaced with Gd (Y, Gd) ₃ Al ₂ (AlO ₄ ) ₃ : Ce ³⁺ Fluorescent materials are disclosed. Y ₃ Al ₂ (AlO ₄ ) ₃ : Ce ³⁺ has an emission peak wavelength in the yellow region, whereas (Y, Gd) ₃ Al ₂ (AlO ₄ ) ₃ : Ce ³⁺ phosphor described in Patent Document 1 has an emission peak wavelength in the yellow region. , Has an orange region emission peak wavelength. Therefore, the emission peak wavelength is relatively shifted to the long wavelength side.

Japanese Patent No. 3503139

However, the luminous efficiency of the (Y, Gd) ₃ Al ₂ (AlO ₄ ) ₃ : Ce ³⁺ phosphor _{is higher than that of 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 maintenance rate decreases, is noticeable. The fact that temperature quenching is noticeable means that the output fluorescence wavelength changes significantly as the temperature of the phosphor changes, which greatly affects the chromaticity reproducibility of images and lighting with respect to the phosphor temperature. It is suggested that

The present invention has been made to solve the above problems, and the emission peak wavelength shifts to a relatively long wavelength side with respect _{to the Y 3} Al ₂ (AlO ₄ ) ₃ : Ce ^{3 + phosphor, and the temperature is increased.} It is an object of the present invention to provide a phosphor having suppressed quenching and a light emitting device using the same.

The fluorescent substance according to the present invention is a fluorescent substance having a garnet structure as a parent crystal and Ce ³⁺ being activated as a emission center ion in the ^{parent crystal, and is characterized in that Li +} is contained in the fluorescent substance. And.

According to the phosphor according to the present invention, the emission peak wavelength can be moved to a relatively long wavelength side with respect _{to the Y 3} Al ₂ (AlO ₄ ) ₃ : Ce ^{3 + phosphor, and temperature quenching is also suppressed.} It becomes possible to provide a fluorescent substance and a light emitting device.

It is a figure which showed the structure of the light emitting device which concerns on Embodiment 1. FIG. It is a figure which showed the fluorescence spectrum of Example 2 and Comparative Example 2 in Embodiment 1. FIG. Table 1 shows the compositions of Examples 1 to 4 and Comparative Examples 1 and 2 and various measurement results.

In the phosphor according to the first aspect, the parent crystal has a garnet structure, Ce ³⁺ is activated as a luminescence center ion in the ^{mother crystal, and Li +} is contained in the mother crystal.

As for the fluorescent substance according to the second aspect, the fluorescent substance may be represented by the following formula (1) in the first aspect.
M _3-x Al ₂ (AlO ₄ ) ₃ : Ce ^{3 +} _x Li ⁺ _y , (M = Y _α Lu _(1-α) ) (1)
The range of α values is 0.5 ≤ α ≤ 1,
The range of x values is 0.01 ≤ x ≤ 0.1,
The range of y values is 0.01 ≤ y ≤ 0.05

The light emitting device according to the third aspect includes the phosphor of the first or second aspect and the phosphor.
Light source and
To be equipped.

Hereinafter, the phosphor according to the embodiment and the light emitting device using the same will be described in detail with reference to the accompanying drawings.

(Embodiment 1)
<Fluorescent material>
The phosphor according to the first embodiment is a phosphor in which a garnet structure is used as a parent crystal and Ce ³⁺ is activated as a emission center ion, and Li ⁺ is contained in the phosphor.

[Maternal crystal]
The garnet structure, which is the parent crystal, refers to the crystal structure represented by the chemical formula of _{A 3} B ₂ (CO ₄ ) _3. Although coordinable elements can be arranged in the parts A, B, and C in the chemical formula, the desired fluorescence peak wavelength can be realized and the reliability with respect to the external environment is high. From the viewpoint of easily obtaining the emission peak wavelength, the components of the parent crystal are Y ₃ Al ₂ (AlO ₄ ) _{3 or (Y, Lu) 3} Al ₂ (AlO ₄ ) _{3 in} which a part of Y is replaced with Lu. Is desirable. When the ratio of Y and Lu is expressed by α and (1-α), respectively, and (Y, Lu) in the above equation is expressed as (Y _α Lu _(1-α) ), the range of the value of α is 0. It is desirable that 5 ≦ α ≦ 1. When α becomes smaller than 0.5, _{the ratio of Lu 3} Al ₂ (AlO ₄ ) _{3 in} the mother crystal increases, and the target emission peak wavelength cannot be obtained, which is not preferable.

[Luminescent center ion]
Examples of the emission center ion include Mn ²⁺ , Mn ⁴⁺ , Eu ²⁺ , Eu ^{3+, and the} like, but it is desirable to select ^{Ce 3+} from the viewpoint of realizing a desired fluorescence peak wavelength. When the emission lifetime of the emission 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, and as a result, a phenomenon called luminance saturation occurs. Ce ³⁺ has a relatively short emission lifetime of several tens of nsec among the emission center ions. From this point of view, the emission center ion is preferably ^{Ce 3+.}
Further, ^{the atomic ratio x of Ce 3+} preferably exists 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 preferable. Further, when x is larger than 0.1, a phenomenon called concentration quenching occurs and the fluorescence intensity decreases, which is not preferable.

[Activated ion]
Examples of the activating ion include various elements from the viewpoint of crystal engineering, and it is desirable to select ^{Li + from the viewpoint of achieving a desired fluorescence peak wavelength.} It is considered that Li ⁺ does not satisfy the condition of being replaced with the preferred matrix crystal sites this time, and exists between the matrix crystal sites. It is considered that this changed the inter-crystal distance between each site and affected the optical characteristics.
The atomic ratio y of Li ⁺ preferably exists in the range of 0.01 ≦ y ≦ 0.05. When y is less than 0.01, it is not preferable because a phosphor exhibiting a desired fluorescence peak wavelength cannot be obtained. Further, when y is larger than 0.05, it is difficult to produce it, which is not preferable.

[Fluorescent material]
To summarize the above, the chemical formula of the composition of the phosphor is
M _3-x Al ₂ (AlO ₄ ) ₃ : Ce ^{3 +} _x Li ⁺ _y , (M = (Y _α Lu _(1-α) ))
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. It is preferable to have.

[Light emitting device]
FIG. 1 is a diagram showing the structure of the light emitting device 10 according to the first embodiment. The light emitting device 10 includes an excitation light source 1 that irradiates the excitation light 2, and a phosphor 3 that receives the excitation light 2 and emits fluorescence 4. 4 indicates 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 of efficiently exciting the phosphor 3 in the first embodiment. .. The excitation light source 1 is installed directly under the phosphor 3 and irradiates the phosphor 3 with the excitation light 2. The phosphor 3 emits fluorescence 4 by receiving the excitation light 2.

Hereinafter, more specific description will be given based on Examples and Comparative Examples.
Although various synthetic methods are known for synthesizing fluorescent substances, the fluorescent substances shown in Examples and Comparative Examples were synthesized by using the solid-phase reaction method, and the optical characteristics were evaluated.

(Example 1)
<Synthesis of phosphor>
(material)
The raw material powder used in this synthesis method is 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 manufactured by Shin-Etsu Chemical Co., Ltd. Purity:> 99.99%)
-Gadolinium oxide (Gd ₂ O ₃ manufactured by High Purity Chemical Laboratory Co., Ltd. Purity:> 99.9%)
-Lithium oxide (Li ₂ O, manufactured by High Purity Chemical Laboratory Co., Ltd. Purity:> 99.0%)

(I) First, with ^{respect to lithium oxide as a Li +} source, each raw material powder weighed at a predetermined ratio was placed in an agate mortar and sufficiently pulverized and mixed using an agate pestle to obtain a mixed powder. .. In order to sufficiently mix each raw material powder, volatile ethanol was added into the mixed powder and mixed in a wet state.
(Ii) Then, the obtained mixed powder was put into an alumina boat. Lithium oxide as a Li ⁺ source was weighed so as to have the same amount as the mixed powder, and was put into an alumina boat separate from the mixed powder.
(Iii) The two prepared alumina boards were placed in a tube furnace (YAMADA DENKI Co., manufactured by LTD, model number: TSR-630) and fired at 1300 ° C. for 3 hours. At this time, nitrogen gas was flowed under the condition of 100 ml / min in order to create an inert gas atmosphere in the tubular furnace. After firing, the Li ⁺ source lithium oxide did not retain its original shape in the alumina board, but the mixed powder changed from white to orange-yellow phosphor powder.
(Iv) The taken-out fluorescent powder was placed in the agate mortar again, pulverized and mixed using an agate pestle to obtain a fluorescent powder to be evaluated.

(Example 2 and Example 4)
Except that the ratio of each raw material powder was changed as shown in Table 1, the Li ⁺ source lithium oxide was weighed to double the amount of the mixed powder, and was 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 fluorescent 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 as a Li + source was removed.}

<Evaluation of optical characteristics>
The prepared fluorescent powder was evaluated for optical characteristics at the following three points.

(Photoluminescence (PL) measurement)
PL measurement was performed using a spectrofluorometer (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 spectrofluorometer.
(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, photomal 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) The samples listed in each Example and Comparative Example were measured, and the fluorescence peak wavelength was recorded.
(4) When applied to products intended for mounting, the required fluorescence peak wavelength range is 580 nm or more and 630 nm or less, so the judgment was 〇 for samples within this range and × for samples outside this range. ..

(Quantum efficiency (QE) measurement)
The QE measurement was performed using a spectrofluorometer (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 spectrofluorometer.
(2) Next, the following measurement conditions were set on the software. Measurement mode: Emission, excitation bandwidth: 5.0 nm, fluorescence bandwidth: 5.0 nm, photomal 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 the quantum efficiency was recorded.
(4) Since the required quantum efficiency is 80% or more when applied to products that are intended to be installed, the judgment is 0 for samples within this range, and × for samples outside this range.

(Measurement of fluorescence intensity maintenance rate)
The fluorescence intensity maintenance rate was measured using a spectroscopic fluorometer (manufactured by JASCO Corporation, model number: FP-6500).
(1) First, a sample holder whose temperature can be adjusted was set in the spectrofluorometer. The obtained sample was placed in a sample cell specified by the manufacturer and set in a temperature-adjustable sample holder set in a spectrofluorometer.
(2) Next, the following measurement conditions were set on the software. Measurement mode: Emission, excitation bandwidth: 5.0 nm, fluorescence bandwidth: 5.0 nm, photomal 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) The samples listed in each Example and Comparative Example were sampled, and the fluorescence intensity was recorded at the sample holder temperatures of 25 ° C. and 150 ° C., respectively. Then, the ratio of the fluorescence intensity measured by the sample holder at 150 ° C. was determined as compared with the fluorescence intensity measured by the sample holder at 25 ° C., and used as the fluorescence intensity maintenance rate.
(4) Since the required fluorescence intensity maintenance rate is 80% or more when applied to a product to be mounted, the judgment is 0 for samples within this range and x for samples outside this range.

(Comprehensive judgment)
As a comprehensive judgment, in each Example and Comparative Example, if the judgments of PL measurement, quantum efficiency, and fluorescence intensity maintenance rate are all 〇, the comprehensive judgment is 〇 (good), and even one of the judgment results has ×. The overall judgment was x (impossible).

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

In Example 1 and Example 3, the ratio of the M part of the mother crystal was changed, respectively. When the M part coexists with Y and Lu as in Example 1 (α = 0.5), as 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 the increase in the _{so-called Lu 3} Al ₅ O ₁₂ component due to the increase in Lu to be replaced with the M part. ^{However, since Li +} is added to both of them, the emission peak wavelength clears 580 nm or more and 630 nm or less, which is a necessary condition when mounting an optical product. In Comparative Example 1, Li ⁺ was not added as compared with Example 1, but the emission peak wavelength was 546.4 nm, and the ^{presence or absence of the addition of Li +} greatly affected the shift of the emission peak wavelength. You can see that it is doing. It is considered that this is because ^{the effect of the addition of Li +} causes distortion in the parent crystal and changes the coordination environment of the crystal containing the emission center ion.

In Example 2 and Example 4, each x value of Example 1 and Example 3 was increased, and the ratio of the M part of the mother crystal was changed. Similar to Examples 1 and 3, the fluorescence peak wavelength is shifted to the shorter wavelength side by about 10 nm as compared with the case where the M part is only Y (α = 1.0), but for the same reason as described above. I believe that. In Comparative Example 2, Li ⁺ was not added as compared with Example 4, but the emission peak wavelength was 553.0 nm, and from this result, the presence or absence of addition of ^{Li + was the emission peak wavelength.} It can be seen that it has a great influence on the shift.

Summarizing these, the emission peak wavelength, the quantum efficiency, and the fluorescence intensity retention rate are good in Examples 1 to 4. Therefore, the overall judgment is 〇. However, in ^{Comparative Example 1 and Comparative Example 2 in which Li +} is not added, although the quantum efficiency and the fluorescence intensity retention rate are good, the emission peak wavelength cannot clear the determination conditions. Therefore, the overall evaluation of Comparative Example 1 and Comparative Example 2 is x.

As shown in the above embodiment, according to this embodiment, an excellent orange phosphor capable of suppressing a decrease in emission intensity due to a temperature rise and having emission characteristics in a long wavelength region even when irradiated with a high-power light source. Can be provided.

It should be noted that the present disclosure includes appropriately combining any of the various embodiments and / or examples described above, and the respective embodiments and / or embodiments. The effects of the examples can be achieved.

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 long wavelength side and temperature quenching is suppressed, and the brightness is high. It can be deployed in lighting and projectors.

1 Excitation light source 2 Excitation light 3 Fluorescence 4 Fluorescence 10 Luminous device

Claims (3)

A phosphor having a garnet structure in the parent crystal, in which Ce ³⁺ is activated as a luminescent center ion and Li ⁺ is contained in the mother crystal. The fluorescent substance according to claim 1, which is 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) ,
The range of α values is 0.5 ≤ α ≤ 1,
The range of x values is 0.01 ≤ x ≤ 0.1,
The range of y values is 0.01 ≤ y ≤ 0.05 The fluorescent substance according to claim 1 or 2,
Light source and
A light emitting device equipped with.

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