TWI428428B - Phosphors and light emitting device using the same - Google Patents

Description

Fluorescent material and illuminating device using same

The present invention relates to a novel fluorescent material and a light-emitting device using the same, and more particularly to a novel fluorescent material suitable for blue light excitation and a light-emitting device using the same.

Recently, the white LEDs actively developed have the advantages of high luminous efficiency, low power consumption, long life, environmental protection, small size, fast response, etc., which are considered to be the most potential alternative to incandescent lamps and fluorescent lamps. light source. At present, white LEDs are mainly divided into the following five systems: (1) white light emitting modules composed of red, blue and green three-color light emitting diodes; (2) blue light emitting diodes with yellow fluorescent powder; (3) blue light emitting two The polar body is matched with red and green fluorescent powder; (4) the ultraviolet light emitting diode is matched with the blue, green and red fluorescent powder uniformly mixed; (5) the ultraviolet light emitting diode is matched with the white fluorescent powder.

In the foregoing method, the use of three primary color LEDs for mixing light requires a complicated driving power source, and it is difficult to control the color rendering thereof, so that the fluorescent powder conversion type LED is the main white light LED on the market, and in 1996, Japan Nichia Chemical Co., Ltd. It is proposed to use YAG phosphor powder with yellow light to match blue LED, which is a common high efficiency white LED light source on the market. However, the use of YAG phosphor powder with blue LED has the disadvantages of low color rendering and high color temperature in general illumination; and the thermal stability of YAG phosphor powder is poor, and it is easy to produce color shift problem under high power long-term driving.

In addition, the green garnet structure phosphor powder Ca ₃ Sc ₂ Si ₃ O ₁₂ :Ce ³⁺ and CaAlSiN ₃ :Eu ²⁺ red phosphor powder are mixed at a ratio of 92:8, and then combined with gallium nitride GaN. The blue LED is packaged to obtain a white LED, and its color rendering index (Ra) can be as high as 92. Compared with the general blue LED with YAG yellow fluorescent powder white LED (color rendering index is only 60-80), it is more suitable as a General lighting source; in addition, the document also found that Ca ₃ Sc ₂ Si ₃ O ₁₂ :Ce ³⁺ has better thermal stability than YAG:Ce ³⁺ , which is suitable for high power white LED green Fluorescent powder. However, Ca ₃ Sc ₂ Si ₃ O ₁₂ :Ce ³⁺ fluorescent powder has the problem that the expensive elemental bismuth (Sc) is expensive and the preparation cost is high, so such green fluorescent powder has not been widely used.

SUMMARY OF THE INVENTION The main object of the present invention is to provide a novel fluorescent material which can improve the high cost of preparation of conventional tellurite fluorescent materials due to their high cost and at the same time enhance their luminescent properties.

In order to achieve the above object, the present invention provides a novel fluorescent material having the following chemical formula: Ca _x Sc _2-y Al _y Si ₃ O ₁₂ :Ce _z , wherein 2.97≦x+z≦3; 0<y≦0.4; And 0.003≦z≦0.3. Here, z=0.03 is preferable.

Accordingly, the present invention can replace the Sc ³⁺ by doping Al ³⁺ to improve the high cost of preparation due to the high cost of the crucible. In particular, the fluorescent material provided by the present invention not only has the advantages of high thermal stability of the conventional Ca ₃ Sc ₂ Si ₃ O ₁₂ :Ce ³⁺ fluorescent powder, but also has better crystallinity and can exhibit better than conventional knowledge. The luminescence properties of Ca ₃ Sc ₂ Si ₃ O ₁₂ :Ce ³⁺ fluorescent powder, such as preferred luminescence intensity, higher quantum efficiency, better color purity, and the like.

In addition, due to the difference in ionic charge between Ce ³⁺ and Ca ²⁺ , charge compensation is performed by trapping oxygen in the air to generate oxides, resulting in a decrease in luminescence intensity. Therefore, the present invention can further generate calcium vacancies. The way to achieve charge compensation is to increase the luminous intensity. Accordingly, it is preferably 2.97 ≦ x + z < 3, for example, in an embodiment of the present invention, x + z = 2.985.

As the amount of Al ³⁺ doping increases, it can be found that the emission wavelength of the fluorescent material exhibits a gradual red shift. Therefore, the present invention can control the emission wavelength of the fluorescent material by controlling the Al ³⁺ doping amount. It is preferably 0.05 ≦ y ≦ 0.4, more preferably 0.05 ≦ y ≦ 0.2.

In the present invention, the fluorescent material can be obtained by a solid state reaction method, for example, a calcium precursor, a ruthenium precursor, a ruthenium precursor, a ruthenium precursor, and an aluminum precursor can be used as a starting material at a predetermined temperature. The calcination was carried out to obtain a Ca _x Sc _2-y Al _y Si ₃ O ₁₂ :Ce _z fluorescent material. More specifically, an embodiment of the present invention uses CaCO ₃ , Sc ₂ O ₃ , SiO ₂ , Ce ₂ (C ₂ O ₄ ) ₃ ‧9H ₂ O, and Al ₂ O ₃ as a starting material. The calcination is carried out at 1450 ° C for about 3 hours to obtain a garnet structure of Ca _x Sc _2-y Al _y Si ₃ O ₁₂ :Ce _z fluorescent material, wherein the doping element Al ³⁺ can be substituted for Sc ³⁺ eight The position of the face.

In the present invention, the fluorescent material can be excited by blue light having a wavelength of about 350 nm to 500 nm to emit green light having a wavelength of about 430 nm to 650 nm, so the fluorescent powder can be applied to a blue-emitting light-emitting device. .

Accordingly, the present invention further applies the above-mentioned fluorescent material to a light-emitting device, comprising: an excitation unit for providing an excitation light; and a phosphor layer capable of emitting after being irradiated by the excitation light Visible light, the fluorescent material layer comprises a fluorescent material represented by the following chemical formula: Ca _x Sc _2-y Al _y Si ₃ O ₁₂ :Ce _z , wherein 2.97≦x+z≦3, 0<y≦0.4, and 0.003≦z≦0.3.

One aspect of the present invention provides a blue excitation unit as an excitation unit having a wavelength in the range of about 350 nm to 500 nm. Here, the blue light excitation unit may be any device that can emit blue light. For example, the blue light excitation unit may include: a carrier member provided with a cathode electrode and an anode electrode; and a blue light emitting device. And electrically connected to the cathode electrode and the anode electrode, and the phosphor material layer covers the blue light emitting element.

In the present invention, the carrier member is not particularly limited, and may be, for example, a package base or a circuit substrate. Further, the blue light emitting element is not particularly limited, and may be, for example, a blue LED wafer (for example, a gallium nitride blue LED wafer).

In the present invention, the phosphor layer may further include a red fluorescent material (such as CaAlSiN ₃ :Eu ²⁺ ) to obtain a white LED. Accordingly, the white LED provided by the present invention can exhibit a higher color rendering index than a white LED with a YAG yellow fluorescent powder, and is more suitable as a general illumination source.

In summary, the novel fluorescent material provided by the present invention can improve the high cost of preparation of the conventional tellurite fluorescent material, which not only has the conventional Ca ₃ Sc ₂ Si ₃ O ₁₂ :Ce ³⁺ fluorescent powder. The advantages of high thermal stability show better luminescence characteristics. In particular, when the fluorescent material of the present invention is applied to a white LED, a higher color rendering index can be exhibited, and since the thermal stability of the fluorescent material is good, the problem of easy color shift under high-power long-term driving can be avoided. Accordingly, the white light LED using the fluorescent material of the present invention is more suitable as a light source for general illumination than the conventional white LED with YAG yellow fluorescent powder white light LED, and has the potential to replace the conventional white light LED.

The embodiments of the present invention are described by way of specific examples, and those skilled in the art can readily appreciate the other advantages and advantages of the present invention. It should be noted that the following drawings are simplified schematic diagrams. The number, shape and size of components in the drawings can be changed arbitrarily according to actual implementation conditions, and the component layout state can be more complicated. The present invention may be embodied or applied in various other specific embodiments, and various modifications and changes can be made without departing from the spirit and scope of the invention.

Preparation examples 1 to 6

According to the stoichiometric scale shown in Table 1 below, CaCO ₃ , Sc ₂ O ₃ , SiO ₂ , Ce ₂ (C ₂ O ₄ ) ₃ ‧9H ₂ O and Al ₂ O _{3 were} uniformly mixed and placed in a polyethylene ball mill jar. Using a 5 mm zirconia grinding ball, shake the ball for 15 minutes. Next, the ball-milled mixture powder was placed in an alumina crucible, and heated at a heating rate of 5 ° C/min to 1450 ° C for 3 hours to carry out calcination to obtain a green fluorescent material of the garnet structure of the present invention: Ca _2.955 Sc _2-y Al _y Si ₃ O ₁₂ :Ce _0.03 .

"Table 1"

Test example 1

The phosphor powder prepared in Preparation Examples 1-6 was subjected to phase identification using an X-ray diffractometer (Rigaku D/max IIIV). The target is copper (K _α =1.54056 ), the operating voltage is 30kV, the operating current is 20mA, the scanning range is 20°~80°, and the scanning speed is 4°/min. The tantalum powder was selected as the standard, mixed with the fluorescent powder for XRD measurement, and the 2θ of the diffraction peak was corrected. See Figure 1 for the X-ray diffraction pattern of the fluorescent material prepared in Preparation Examples 1-6.

As shown in Figure 1, a small amount of Sc ₂ O ₃ impurity remains in the undoped Al ³⁺ (y = 0), however, Sc ₂ O can be observed after doping Al ³⁺ (y = 0.05 ~ 0.4) ₃ disappearance of the _heterophase , so it is known that doping Al ³⁺ can help eliminate the Sc ₂ O ₃ impurity phase, which is beneficial to improve the purity and crystallinity of Ca _2.955 Sc _2-y Al _y Si ₃ O ₁₂ :Ce _0.03 phosphor powder. .

In addition, the surface morphology and particle size of the phosphor powder were observed and analyzed using a variable pressure scanning electron microscope (EVO-SEM). It was found that the phosphor powder appeared granular when Al ³⁺ was not added, and with Al ^{3 When the} amount of doping increases, the sintering phenomenon becomes more and more obvious. When the doping amount of Al ³⁺ increases to y=0.4, the particle size becomes significantly larger, and it has an irregular block shape with a particle diameter of about 1 to 10 μm. .

According to the results of XRD and SEM, it is known that the addition of Al ³⁺ contributes to the formation of liquid phase sintering, helps to eliminate the Sc ₂ O ₃ heterophase, and increases the purity and crystallinity of the phosphor powder.

Test example 2

The fluorimetric materials prepared in Preparation Examples 1-6 were subjected to FTIR spectroscopy using a Jasco model-460 Fourier transform infrared spectroscopy, and the scanning range was 400 to 4000 cm ^-1 . The results are shown in Fig. 2 .

As shown in Fig. 2, a new vibration signal can be found at 682 cm ^{-1 by} doping Al ³⁺ (y=0.05~0.4). The new vibration signal is the vibration induced by Al ³⁺ doping, Al ³⁺ The new phonon vibration energy level induced by doping accelerates the multi-phonon transmission speed and reduces the energy loss during energy transfer. This effect is also reflected in the luminescence properties of the phosphor powder, which is doped by Al ^3+. Miscellaneous can increase luminous intensity and quantum efficiency. In addition, as the amount of Al ³⁺ doping increases, it can be observed that the Sc-O-based vibration signal has a tendency to shift toward high frequency, which means that Al ³⁺ does replace the position of Sc ³⁺ octahedron, causing bond vibration. Faster, the Sc-O base signal is gradually shifted to the high frequency.

In addition, Raman spectroscopy was performed using a micro-Raman spectrometer (Micro-Raman), and a He-Ne laser (wavelength: 633 nm) was used as an excitation source. The scanning range was 200 to 1000 cm ^-1 . See Figure 3.

As shown in Fig. 3, as the Al ³⁺ doping amount increases, the surrounding tetrahedral SiO ₄ rotates faster, causing the Raman peak at 350 to 400 cm ^-1 to move to a high frequency.

According to the results of FTIR and Raman spectroscopy, Al ³⁺ does replace the position of Sc ³⁺ octahedron, and the new phonon vibration level induced by Al ³⁺ doping accelerates the multi-phonon transmission speed. Reduce the loss of energy during energy transfer.

Test Example 3

The luminescent properties of the fluorescent materials prepared in Preparation Examples 1-6 were measured using a Hitachi F-7000 fluorescence spectrometer. The results are shown in Figures 4A and 4B. Here, both the excitation light grating and the emission light grating are set to 2.5 nm and the scanning rate is 240 nm/min.

4A is a fluorescence excitation (PLE) spectrum of Ca _2.955 Sc ₂ Si ₃ O ₁₂ :Ce _0.03 doped with different concentrations of Al ³⁺ , the spectrum of which consists of two peaks at _{280-350 nm and 365-500} nm, respectively. with the increase of the doping amount of Al ^3+, with the highest peak at 450 nm excitation spectrum when y = 0.05.

4B is a fluorescence emission (PL) spectrum of Ca _2.955 Sc ₂ Si ₃ O ₁₂ :Ce _0.03 doped with different concentrations of Al ³⁺ , excited by blue light with a wavelength of 450 nm, and its luminescence spectrum is a broad peak with a wavelength of 430-650 nm. . As the Al ³⁺ doping increases, it is observed that the luminescence wavelength exhibits a tendency to gradually red-shift.

Test Example 4

Quantum efficiency measurements were performed on the phosphor materials prepared in Preparation Examples 1-6 using a Hitachi F-7000 fluorescence spectrometer with an integrating sphere. The quantum efficiency and absorption rate of doping different concentrations of Al ^{3+ were} calculated by excitation with blue light at 450 nm. As shown in Table 2 below, the quantum efficiency increased from 41.2% without addition of Al ³⁺ (y=0) to 46.8% with y=0.05, and, in addition, the highest absorption rate 79.1 when Al ^{3+ was} added to y=0.15. %. It can be seen that the doping of Al ³⁺ can increase the quantum efficiency and absorption rate of Ca _2.955 Sc ₂ Si ₃ O ₁₂ :Ce0 _.03 phosphor powder.

"Table 2"

Test Example 5

The fluorescent material prepared in Preparation Example 1-6 was measured by PL spectroscopy, and the software was calculated by CIE, and the chromaticity coordinates (0.3101, 0.3162) of the 1931 CIE standard white light source C were used as the origin coordinates to calculate each fluorescent material. The chromaticity coordinates (x, y) and color purity are shown in Table 3 below.

"table 3"

Al ³⁺ is a dominant wavelength between about 503 ~ 506 nm, as the added amount of Al ³⁺ may be found in the color purity increased from 61.2 to 64.8%, and the chromaticity coordinate displacement to red.

Example 1

5 is a cross-sectional view of a light emitting device according to a preferred embodiment of the present invention.

As shown in FIG. 5, the light-emitting device of the present embodiment includes: a carrier member 11; a blue light-emitting device 12 disposed on the carrier member 11 and electrically connected to the carrier member 11; and a phosphor layer 13 The blue light emitting element 12 is covered. In detail, the light-emitting device of the present embodiment is a white light-emitting diode, which uses a package foot as the carrier element 11, and the carrier element 11 is provided with a cathode electrode 11A and an anode electrode 11B, and the blue light-emitting element 12 is The cathode electrode 11A and the anode electrode 11B of the carrier element 11 are electrically connected to each other through the wire 14. In addition, in this embodiment, a gallium nitride (GaN) light-emitting diode wafer (light-emitting wavelength of about 450 nm) is used as the blue light-emitting element 12, and the fluorescent material layer 13 is doped with a green light-emitting material (Ca _2.955). A transparent sealant of Sc _2-y Al _y Si ₃ O ₁₂ :Ce _0.03 ) and a red fluorescent material (CaAlSiN ₃ :Eu ²⁺ ). Accordingly, when a voltage is applied to the cathode electrode 11A and the anode electrode 11B of the carrier member 11, the blue light-emitting element 12 is driven to emit blue light; then, the blue light emitted from the blue light-emitting element 12 excites the phosphor in the phosphor layer 13. The light material is mixed with the light emitted by the fluorescent material to be released into white light.

Example 2

6 is a cross-sectional view of a light emitting device according to another preferred embodiment of the present invention.

As shown in FIG. 6, the light-emitting device of the present embodiment includes: a carrier member 11; a blue light-emitting device 12 disposed on the carrier member 11 and electrically connected to the carrier member 11; and a phosphor layer 13 The blue light emitting element 12 is covered. In detail, the light-emitting device of the present embodiment is a white light-emitting diode, which uses a circuit substrate as the carrier member 11, and the carrier member 11 is provided with a cathode electrode 11A and an anode electrode 11B, and the blue light-emitting device 12 is The cathode electrode 11A and the anode electrode 11B of the carrier element 11 are electrically connected through the wire 14. In addition, in this embodiment, a gallium nitride (GaN) light-emitting diode wafer (light-emitting wavelength of about 450 nm) is used as the blue light-emitting element 12, and the fluorescent material layer 13 is doped with a green light-emitting material (Ca _2.955). A transparent sealant of Sc _2-y Al _y Si ₃ O ₁₂ :Ce _0.03 ) and a red fluorescent material (CaAlSiN ₃ :Eu ²⁺ ). Accordingly, as described in Embodiment 1, the blue light emitted from the blue light-emitting element 12 is mixed with the light emitted from the phosphor material layer 13 to be white light-released.

The above-mentioned embodiments are merely examples for convenience of description, and the scope of the claims is intended to be limited to the above embodiments.

11. . . Carrier element

11A. . . Cathode electrode

11B. . . Anode electrode

12. . . Blue light emitting element

13. . . Fluorescent material layer

14. . . wire

1 is an X-ray diffraction pattern of Ca _2.955 Sc ₂ Si ₃ O ₁₂ :Ce _0.03 and Ca _2.955 Sc _2-y Al _y Si ₃ O ₁₂ :Ce _0.03 fluorescent material prepared in Preparation Examples 1 to 6 of the present invention. .

2 is an FTIR spectrum of Ca _2.955 Sc ₂ Si ₃ O ₁₂ :Ce _0.03 and Ca _2.955 Sc _2-y Al _y Si ₃ O ₁₂ :Ce _0.03 fluorescent material prepared in Preparation Examples 1 to 6 of the present invention.

3 is a Raman spectrum of Ca _2.955 Sc ₂ Si ₃ O ₁₂ :Ce _0.03 and Ca _2.955 Sc _2-y Al _y Si ₃ O ₁₂ :Ce _0.03 fluorescent material prepared in Preparation Examples 1 to 6 of the present invention.

4A is a fluorescence excitation spectrum of Ca _2.955 Sc ₂ Si ₃ O ₁₂ :Ce _0.03 and Ca _2.955 Sc _2-y Al _y Si ₃ O ₁₂ :Ce _0.03 fluorescent material prepared in Preparation Examples 1 to 6 of the present invention. , where -■- is y = 0 (light emission wavelength is 503 nm), -○- is y = 0.05 (light emission wavelength is 505 nm), -△- is y = 0.1 (light emission wavelength is 505 nm) , -▽- is y = 0.15 (light emission wavelength is 507 nm), -◇- is y=0.2 (light emission wavelength is 506 nm), -×- is y=0.4 (light emission wavelength is 505 nm).

4B is a fluorescence emission spectrum of Ca _2.955 Sc ₂ Si ₃ O ₁₂ :Ce _0.03 and Ca _2.955 Sc _2-y Al _y Si ₃ O ₁₂ :Ce _0.03 fluorescent material prepared in Preparation Examples 1 to 6 of the present invention. Wherein, -■- is y=0, -○- is y=0.05, -△- is y=0.1, -▽- is y=0.15, -◇- is y=0.2, -×- is y=0.4 .

Figure 5 is a cross-sectional view showing a light-emitting device of Embodiment 1 of the present invention.

Figure 6 is a cross-sectional view showing a light-emitting device according to a second embodiment of the present invention.

Claims (12)

A fluorescent material having the chemical formula: Ca _x Sc _2-y Al _y Si ₃ O ₁₂ :Ce _z , wherein 2.97≦x+z≦3; 0<y≦0.4; and 0.003≦z≦0.3. The fluorescent material according to claim 1, wherein z=0.03. The fluorescent material according to claim 1 or 2, wherein x+z=2.985. For example, the fluorescent material described in claim 1 or 2, wherein 0.05 ≦ y ≦ 0.4. For example, the fluorescent material described in claim 1 or 2, wherein 0.05 ≦ y ≦ 0.2. A light-emitting device comprising: an excitation unit for providing an excitation light; and a phosphor material layer capable of emitting visible light after being irradiated by the excitation light, the fluorescent material layer comprising fluorescent light represented by the following chemical formula Material: Ca _x Sc _2-y Al _y Si ₃ O ₁₂ : Ce _z , where 2.97 ≦ x + z ≦ 3, 0 < y ≦ 0.4, and 0.003 ≦ z ≦ 0.3. The illuminating device of claim 6, wherein z=0.03. The illuminating device of claim 6 or 7, wherein x+z=2.985. The illuminating device of claim 6 or 7, wherein 0.05 ≦ y ≦ 0.4. The illuminating device of claim 6 or 7, wherein 0.05 ≦ y ≦ 0.2. The illuminating device of claim 6, wherein the excitation light has a wavelength in the range of 350 nm to 500 nm. The illuminating device of claim 6, wherein the excitation unit comprises: a carrier member provided with a cathode electrode and an anode electrode; a light-emitting element disposed on the carrier member and coupled to the cathode The electrode and the anode electrode are electrically connected, and the fluorescent material layer covers the light emitting element.