KR100735287B1 - Red light emitting phosphor and light emitting device - Google Patents

Abstract

The present invention relates to a new red phosphor which can be excited with high efficiency at near ultraviolet or blue wavelength, and is represented by the composition formula M _{2 -xy} Eu _x Sm _y WO ₆ , wherein M is yttrium (Y), aluminum ( Al), gallium (Ga) and at least one element selected from the group consisting of lanthanum-based elements, x is 0.2 ≤ x ≤ 1.2, and y is 0 ≤ y ≤ 0.7 to provide a red light-emitting phosphor . In addition, the present invention also provides a white light emitting device having a wavelength conversion portion formed in the form of a mixture of the above-described red phosphor with a light emitting phosphor of a different color.

Red light emitting phosphor, tungstate, yittrium

Description

RED LIGHT EMITTING PHOSPHOR AND LIGHT EMITTING DEVICE}

1 shows an excitation spectrum having a parent which is a conventional Y ₂ WO ₆ .

Figure 2a shows the excitation spectrum according to the amount of europium (Eu) added in the red light-emitting phosphor according to the present invention.

Figure 2b shows the emission spectrum according to the excitation wavelength in the red light-emitting phosphor according to the present invention.

3 shows an excitation spectrum according to the amount of samarium (Sm) added in the red light-emitting phosphor according to the present invention.

4A and 4B are side cross-sectional views showing an example of a white light emitting device according to the present invention.

<Code Description of Main Parts of Drawing>

20,30: White light emitting device 22a, 22b, 32a, 32b: Lead frame

25,35; Near UV LED 26a, 26b, 36a, 36b: wire

28: appearance molding part 29, 39: wavelength conversion part

31: package substrate

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a red light emitting phosphor, and more particularly, to a new red light emitting phosphor and a light emitting device including the same.

In general, the phosphor material for wavelength conversion is used as a material for converting specific wavelength light of various light sources into the desired wavelength light. In particular, since light emitting diodes among various light sources can be advantageously applied as LCD backlights, automobile lights, and home lighting devices due to low power driving and excellent light efficiency, phosphor materials have recently been spotlighted as a core technology for manufacturing white LEDs.

Conventional white light emitting devices are generally manufactured by applying YAG (Y ₃ Al ₅ O ₁₂ ) -based or TAG-based yellow phosphors to blue LEDs, but have low color rendering and increase the operating temperature due to prolonged use. There is a problem that yellowing occurs. In order to solve this problem, the applicant is using a method of combining a mixture of near-ultraviolet LED and red, green, blue phosphor powder in Korean Patent Application No. 2004-0076300 (filed September 23, 2004). Such a white light emitting device can alleviate yellowing and have a good color rendering index (CRI), and can realize a wide color distribution.

However, in such a light emitting device, since the red light emitting phosphor is less efficient than the green or blue phosphor, it should be mixed in a relatively large proportion (more than 60wt%). This increases the total amount of the phosphor powder, there may be a disadvantageous effect by the phosphor particles in terms of optical properties.

The low efficiency of such a red light-emitting phosphor is because the red phosphor has a relatively low excitation spectrum in the desired near ultraviolet band or blue band as compared with other phosphors.

1 shows an excitation spectrum for a conventional red phosphor of Y ₂ WO ₆ doped with a small amount of Eu (0.005 mol%).

Referring to FIG. 1, the yttrium tungstate-based red light-emitting phosphor exhibits a strong absorption peak near 320 nm, while relatively very low excitation in the near ultraviolet region (390 to 410 nm) and the blue region (450 to 480 nm). Has a spectrum.

However, considering that a general LED has a near ultraviolet ray or a blue band, it is difficult to expect high efficiency with a red phosphor having an excitation spectrum as shown in FIG. Therefore, there is a need in the art to develop a new red light-emitting phosphor composition so that the strong absorption peak region appears in the near ultraviolet or blue wavelength band. The development of the red light-emitting phosphor may contribute to the improvement of the light efficiency of the white light emitting diode using the commercially available near ultraviolet light or the blue light emitting diode.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and its object is to increase the appropriate range of europium to a tungstate matrix such as Y ₂ WO ₆ and, at the same time, selectively add samarium in the near ultraviolet or blue wavelength. It is to provide a new red light emitting phosphor composition with more improved efficiency.

In addition, the present invention is to provide a white light emitting device including the high-efficiency red light-emitting phosphor.

In order to solve the above technical problem, one aspect of the present invention,

Formula M _2-xy Eu _x Sm _y WO ₆ , wherein M is at least one element selected from the group consisting of yttrium (Y), aluminum (Al), gallium (Ga), and lanthanide-based elements. , x is 0.2 ≦ x ≦ 1.2, and y is 0 ≦ y ≦ 0.7 to provide a red light-emitting phosphor.

Preferably, the phosphor has a relatively strong absorption peak in the 390 ~ 400nm wavelength band and 450 ~ 480nm wavelength band. A red light-emitting phosphor more suitable for this has x in the range of 0.4 < x &lt; 1.0.

Preferably, the phosphor may have an additional absorption peak in the 400 ~ 410nm wavelength band. This effect can be realized with an appropriate addition of samarium (Sm). In consideration of this, the composition formula of the phosphor has a y range of 0.3 <y ≦ 0.5.

The red phosphor according to the present invention can be expected to have a higher efficiency in the light emission wavelength of the commercially available near-ultraviolet or blue light emitting diodes, and can be mixed with other green and blue phosphors to form a wavelength conversion portion of the excellent white light emitting device.

Another aspect of the invention includes a white light emitting device using the red light emitting phosphor described above. The white light emitting device includes a light emitting diode and a wavelength converting portion formed on the light emitting side of the light emitting diode, the mixture comprising a red light emitting phosphor, a green phosphor, and a blue phosphor, and a curable resin, wherein the red light emitting phosphor is of formula M. _2-xy Eu _x Sm _y WO ₆ , wherein M is at least one element selected from the group consisting of yttrium (Y), aluminum (Al), gallium (Ga) and lanthanide-based elements, x Is 0.2 ≦ x ≦ 1.2, and y is 0 ≦ y ≦ 0.7.

As described above, the red light-emitting phosphor according to the present invention is a mixture of wavelength conversion phosphors in a white light-emitting device using a light emitting diode which emits near-ultraviolet light (390-400 nm or 400-410 nm) or blue (450-480 nm) wavelength light. It can be advantageously employed as.

Hereinafter, with reference to the accompanying drawings, the present invention will be described in more detail.

Figure 2a shows the excitation spectrum according to the amount of europium (Eu) added in the red light-emitting phosphor according to the present invention.

As an example of the red light-emitting phosphor according to the present invention, a red light-emitting phosphor in which yttrium tungstate (YWO ₆ ) is used as a parent and a different amount of europium (Eu) was added was prepared. Here, each of the prepared red light-emitting phosphors has a value of 0.2 in composition Y _2-x Eu _x WO ₆ , unlike the conventional yttrium tungstate phosphor doped with a low level of Eu (x is from 10 ⁻³ to 10 ⁻² ). Relatively more europium was added so as to be 0.4, 0.9. Thus, a red light emitting phosphor having a compositional formula of Y _1.8 Eu _0.2 WO ₆ , Y _1.6 Eu _0.4 WO ₆ , Y _1.1 Eu _0.9 WO ₆ , respectively, was prepared as the first to third samples, and 200 to 550 nm for each sample. The excitation spectrum was measured over the wavelength of. The results are shown as ⓐ, ⓑ and ⓒ in the graph of FIG. 2A, respectively.

Referring to Fig. 2A, like the first sample, Y ₂ WO ₆ having an excitation wavelength of 320 nm has a strong absorption peak at a wavelength of near ultraviolet (390 to 400 nm) when Y is substituted so that the europium becomes 0.2. Was formed. In the second and third samples in which the addition amount of europium was increased to 0.4 and 0.9, an absorption peak stronger than that of the parent excitation wavelength was formed in the near ultraviolet wavelength band.

In addition, referring to Figure 2a, the absorption peak also increased in the blue band of 450 ~ 480nm according to the addition amount of europium.

Thus, it can be confirmed that by increasing the amount of europium added to the yttrium tungstate matrix, the excitation efficiency due to absorption in near ultraviolet or blue light can be greatly improved.

Next, in order to confirm the emission efficiency with respect to the excitation wavelength, the emission spectrum of Y _1.1 Eu _0.9 WO ₆ as a third sample was measured. The results are shown in Figure 2b. At this time, the excitation wavelengths were 395 nm and 466 nm. Referring to FIG. 2B, it was confirmed that Y _1.1 Eu _0.9 WO ₆ converts 395 nm wavelength and 466 nm wavelength into wavelength light around 610 nm.

As such, the yttrium tungstate to which Eu is added in a considerable amount may have a high absorption peak at 390 to 400 nm in near ultraviolet light and 450 to 480 nm in blue band. Therefore, high efficiency can be expected in normal near ultraviolet and blue LEDs.

The effects described in FIGS. 2A and 2B can be applied to other tungstates similar to yttrium tungstate (Y ₂ WO ₆ ). For example, when the red light-emitting phosphor according to the present invention is represented by the composition formula Y _2-x Eu _x WO ₆ , in the composition formula, M is aluminum (Al), gallium (Ga) and lanthanum-based elements in addition to yttrium (Y). It may be at least one element selected from the group consisting of. In addition, the amount x of europium may exhibit absorption peaks in near ultraviolet or blue when at least 0.2 is added, and if it exceeds 1.2, the absorption peak may be reduced in the band beyond the threshold. Therefore, x may be defined as 0.2 ≦ x ≦ 1.2. In addition, in the preferred Eu addition amount range (x), an amount larger than 0.4 may be added and set to 1.0 or less for a sufficient effect that can be put to practical use. Most preferably, x may be set to 0.9 as in the third sample of FIG. 2A.

In addition, the red light emitting phosphor according to the present invention may additionally add samarium. Samarium can form additional absorption peaks at 400-410 nm, for example 405 nm, as added.

3 shows an excitation spectrum according to the amount of samarium (Sm) added in the red light-emitting phosphor according to the present invention.

As another example of the red light-emitting phosphor according to the present invention, a red light-emitting phosphor in which yttrium is substituted with a different amount of samarium (Sm) in Y _1.1 Eu _0.9 WO ₆ , which is the third sample of FIG. 2A, was prepared. That is, the red light-emitting phosphors of the first to the fourth samples to have a composition formula of Y _1.1 Eu _0.9 WO ₆ , Y _0.8 Eu _0.9 Sm _0.3 WO ₆ , Y _0.6 Eu _0.9 Sm _0.5 WO ₆ , Y _0.4 Eu _0.9 Sm _0.7 WO ₆ , respectively. Prepared. The excitation spectrum was measured over a wavelength of 350 to 500 nm for these first to fourth samples, and the results are shown as ①, ②, ③, and ④ in the graph of FIG.

Referring to FIG. 3, unlike the first sample, an absorption peak was formed at 400 to 410 nm in the second sample to which Sm was added. In addition, as Sm increased to 0.3, 0.5, 0.7, additional absorption peaks increased from 400 to 410 nm. This indicates that the addition of Sm extends the excitation wavelength to a wider near ultraviolet band (390 to 410 nm).

Thus, according to the result of FIG. 3, by adding the amount of samarium, the additional absorption peak in 400-410 nm can be formed, and the near ultraviolet wavelength band which can be excited can be widened. When the amount of samarium added for such an effect exceeds 0.7, the luminance may be decreased in the emission wavelength, so it is required to be defined as 0.7 or less.

Furthermore, as can be seen from the graph of Fig. 3, since the absorption peak at 405 nm is insufficient when the amount of samarium is 0.3, it is preferable to add at least more than 0.3, and when it exceeds 0.5, Y _{2 Since} the intrinsic absorption peak wavelength in the excitation spectrum of _-x Eu _x WO ₆ (0.2 <x <1.2) is reduced, it is preferred to add it below 0.5.

Based on the above experimental results, the composition formula of the red light-emitting phosphor according to the present invention can be represented by M _2-xy Eu _x Sm _y WO ₆ , wherein M is yttrium (Y), aluminum (Al), gallium At least one element selected from the group consisting of (Ga) and lanthanum-based elements, the amount of europium added (x) is 0.2 ≦ x ≦ 1.2, and the amount of samarium (y) is defined as 0 ≦ y ≦ 0.7 Can be done. In addition, in consideration of further improved efficiency, the amount of addition of the preferred europium may be set to 0.4 <x ≦ 1.0 and the amount of samarium added y may be set to 0.3 <y ≦ 0.7.

4A and 4B are side cross-sectional views showing an example of a white light emitting device according to the present invention.

The white light emitting device 20 illustrated in FIG. 4A may include an outer molding part 28 and two lead frames 22a and 22b. One lead frame 22a has one end having a cup structure, and the near-ultraviolet LED 25 is mounted on the cup structure portion. Two electrodes (not shown) of the near ultraviolet or blue light emitting diodes 25 are connected to the lead frames 22a and 22b through wires 26a and 26b, respectively. In addition, the wavelength conversion unit 29 including the white phosphor mixture and the curable resin is provided on the cup structure in which the LED 25 is mounted. As the curable transparent resin, an epoxy resin, a silicone resin or a silicone epoxy mixed resin may be used.

The white light emitting device 30 shown in FIG. 4B includes a substrate 31 on which two lead frames 32a and 32b are formed. Near-ultraviolet or blue light emitting diodes 35 are disposed on the substrate 31. Two electrodes (not shown) of the near-ultraviolet light emitting diodes 35 are connected to the lead frame 32a through wires 36a and 36b, respectively. , 32b). In addition, the wavelength conversion unit 39 is formed to surround the light emitting diodes 35 by using the white light-emitting phosphor mixture. The wavelength converter 39 is used by appropriately mixing not only the white phosphor mixture but also a curable transparent resin such as an epoxy resin, a silicone resin, or a silicon epoxy mixed resin. In addition, the forming process of the wavelength conversion unit 39 can be easily implemented through a molding process such as transfer molding, as will be apparent to those skilled in the art.

In general, the light emitting diodes 25 and 35 used in the white light emitting devices 20 and 30 are near-ultraviolet light emitting diodes emitting wavelength light of 390 to 410 nm or blue light emitting diodes emitting wavelength light of 450 to 480 nm. Can be. Since the wavelength converters 29 and 39 use the red light emitting phosphor having high efficiency in the emission wavelength band, the white light having excellent luminous efficiency can be provided with only a relatively small amount of red phosphor powder as compared with the prior art. .

It is intended that the invention not be limited by the foregoing embodiments and the accompanying drawings, but rather by the claims appended hereto. Accordingly, various forms of substitution, modification, and alteration may be made by those skilled in the art without departing from the technical spirit of the present invention described in the claims, which are also within the scope of the present invention. something to do.

As described above, according to the present invention, a new red light emission with improved efficiency at near-ultraviolet or blue wavelengths by increasing the appropriate range of europium to a tungstate matrix such as Y ₂ WO ₆ and optionally adding samarium. It is possible to provide a phosphor composition. In particular, the red light-emitting phosphor according to the present invention is used as a wavelength conversion phosphor mixture in a white light-emitting device using a light emitting diode that emits wavelength light of near ultraviolet (390-400 nm or 400-410 nm) or blue (450-480 nm). Can be advantageously employed.

Claims (11)

Formula M _2-xy Eu _x Sm _y WO ₆ , wherein M is at least one element selected from the group consisting of yttrium (Y), aluminum (Al), gallium (Ga), and lanthanide-based elements. and x is 0.2 ≦ x ≦ 1.2 and y is 0 ≦ y ≦ 0.7. The method of claim 1, The phosphor has a relatively strong absorption peak in the 390 ~ 400nm wavelength band and 450 ~ 480nm wavelength band characterized in that the red light-emitting phosphor. The method according to claim 1 or 2, In the composition formula, x is 0.4 <x ≤ 1.0, characterized in that the red light-emitting phosphor The method of claim 2, The phosphor has an additional absorption peak in the 400 ~ 410nm wavelength band red light emitting phosphor. The method of claim 4, wherein The phosphor is a red light emitting phosphor, characterized in that y is 0.3 <y ≤ 0.5 in the composition formula. Light emitting diodes; And, It is formed on the light emitting side of the light emitting diode, and includes a wavelength conversion unit made of a mixture of a red light emitting phosphor, a green phosphor and a blue phosphor and a curable transparent resin, The red light-emitting phosphor is represented by the composition formula M _{2 -xy} Eu _x Sm _y WO ₆ , wherein M is at least selected from the group consisting of yttrium (Y), aluminum (Al), gallium (Ga), and lanthanum-based elements. 1 element, wherein x is 0.2 ≦ x ≦ 1.2 and y is 0 ≦ y ≦ 0.7. The method of claim 6, The light emitting diode is a white light emitting device, characterized in that the light emitting diode emitting light of 390 ~ 400nm wavelength. The method of claim 6, The light emitting diode is a white light emitting device, characterized in that for emitting light of 450 ~ 480nm wavelength. The method according to claim 7 or 8, In the composition formula, x is 0.4 <x ≤ 1.0, characterized in that the white light emitting device. The method of claim 6, The red light emitting phosphor has an absorption peak in a wavelength band of 400 to 410 nm. The method of claim 10, The red light-emitting phosphor of the white light emitting device, characterized in that y is 0.3 <y ≤ 0.5 in the composition formula.

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