KR20100074474A - Red phospor based on nitride - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitride-based red fluorescent material which is applicable to a white LED and which is reliable and has excellent color rendering properties.

The red phosphor according to the present invention not only realized red light emission by doping Mn ²⁺ to a reliable MgSiN ₂ host, but also significantly improved the light emission intensity through co-doping of Mn ²⁺ and Ce ³⁺ . There is a characteristic.

Description

Nitride-based red phosphors {RED PHOSPOR BASED ON NITRIDE}

The present invention, more specifically, co-doping of dopant (doping) or Mn ^2+, and Ce ³⁺ Mn ²⁺ as the active component in the nitride of MgSiN ₂ hosts (host) on the fluorescent substance which can be applied to the LED for Through co-doping, red light can be emitted from an excitation source of 460 nm, and particularly relates to a nitride-based red fluorescent material suitable for LEDs.

A light emitting diode (LED) is a semiconductor solid light emitting device formed by joining a p-type semiconductor and an n-type semiconductor. The light emitting diode (LED) is light and short in size with excellent characteristics such as long life, excellent impact resistance, low power consumption, and high reliability. It has been spotlighted as a light source of various devices.

In particular, white LEDs emitting white light are expected to be applied to indoor lighting in general homes in order to save energy, as well as fields such as LCD backlights and halogen replacement lights that are currently applied.

There are three ways to implement this white LED.

First, the white LED is realized by combining three LEDs that emit three primary colors of light, red, green, and blue. However, since this method requires three LEDs to make one white light source, a special circuit for controlling each LED is required, thus increasing the manufacturing cost of the LEDs.

Second, a method of realizing white color by exciting a yellow phosphor by using a blue LED as a light source is excellent in luminous efficiency, but is not good in color rendering and has a characteristic of changing chromaticity according to current density. Not only is it difficult to obtain white light close to the light, but also has poor color reproducibility, and thus there is a limit to application in fields such as an LCD backlight where chromaticity and color reproducibility are important. Therefore, attempts have been made to improve color rendering by reinforcing red phosphors, and development of red phosphors for this purpose has become a very important issue.

Finally, the ultraviolet light emitting LED is used as a light source to excite the three primary phosphors to make white. This method can be used under high current and is actively studied because it has excellent color and no special circuit. In this case, it is technically important to secure a phosphor having excellent optical characteristics.

On the other hand, among the three primary phosphors, particularly red phosphors, in the early stage of development, sulfide phosphors and nitride phosphors are known as a material capable of emitting red light. However, since the sulfide-based phosphor has excellent chromaticity and luminance characteristics, but it is not practical due to its low durability in the LED environment, interest in nitride-based phosphors is increasing as a red phosphor for LEDs. As such nitride-based red phosphors, only a small portion of phosphors such as CaSiN ₂ : Eu ²⁺ and Sr (Ba) Si ₅ N ₈ : Eu ²⁺ have been applied until now, and thus red light having excellent optical characteristics The development of fluorescent materials is required.

An object of the present invention is to provide a novel red phosphor that can be used to implement a white LED.

Red phosphor according to the present invention for achieving the above object of the present invention is characterized by having a composition represented by the following formula (1).

[Equation 1]

Mg _1-x SiN ₂ : xMn ²⁺

(x = 0.001 to 0.05)

As shown in Equation 1, the present invention has a technical feature in that red light emission with excellent chromaticity is realized by using manganese as an active material without using europium, which is mainly used in a nitride-based red phosphor.

The emission spectrum of the phosphor doped with Mn ²⁺ using MgSiN ₂ as a host may be separated into two Gaussian peaks, a long wavelength component and a short wavelength component, as shown in green in FIG. 1A. As the Mn ²⁺ concentration is added, the relative distribution of the two peaks constituting the emission spectrum changes, and as the Mn ²⁺ concentration increases, the longer wavelength component becomes more superior, thereby shifting the entire emission spectrum toward red ( shift), red light emission can be realized.

On the other hand, the concentration of the activator Mn ²⁺ is preferably 0.001 to 0.05, as shown in Equation 1, when less than 0.001 is not effective enough red light emission, when it exceeds 0.05, luminous efficiency is greatly reduced. For losing.

In addition, the present invention provides a fluorescent material having a composition represented by the following formula (2).

Mg _1-xy SiN ₂ : xMn ²⁺ , yCe ³⁺

(x = 0.001 to 0.05, y = 0.005 to 0.05)

As shown in FIG. 1C, the activator Ce ³⁺ shows a very wide light emission peak around 500 nm when doped with MgSiN ₂ host alone, which is suitable for white light emission.

However, as shown in FIG. 1B, when co-doping with Mn ²⁺ in MgSiN ₂ host, Ce ³⁺ eliminates light emission by itself and instead enhances Mn ²⁺ light emission. Done. Through this, the emission intensity of 460nm excitation source of MgSiN ₂ : Ce ³⁺ and Mn ²⁺ is improved up to 270% compared to MgSiN ₂ : Mn ²⁺ .

That is, when the Ce ³⁺ to the co-doped Mn ^2+, Mn ²⁺ is the absorption efficiency of ultraviolet and blue greatly improved when compared to the sole doping and consequently higher red light emission efficiency, which is a red fluorescent material according to the invention Increase the practicality of.

On the other hand, the concentration of Ce ³⁺ is preferably maintained in the range of 0.005 to 0.05, because the effect of improving the ultraviolet absorption efficiency is not sufficient if it is out of the above range.

In addition, the concentration of Mn ²⁺ is more preferably 0.004 to 0.06 in consideration of chromaticity and luminous efficiency when co-doping Mn ²⁺ and Ce ³⁺ .

The red fluorescent substance according to the present invention has the following effects.

First, by using Mn ²⁺ as an activator not previously considered based on nitride, it is possible to provide a novel red fluorescent material applicable to white LEDs, thereby producing a white LED having excellent color and color reproducibility. It becomes possible.

Second, the red phosphor according to the present invention can improve the luminous efficiency by improving the absorption efficiency of the ultraviolet light through the co-doping of Mn ²⁺ and Ce ³⁺ to the MgSiN ₂ host.

Hereinafter, a red fluorescent substance according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited by the following examples. Therefore, it will be apparent to those skilled in the art that the present invention may be variously modified without departing from the technical spirit of the present invention.

Example 1

The concentrations of Mn ²⁺ in MgSiN ₂ : xMn ²⁺ to be synthesized from Aldrich α-Si ₃ N ₄ powder and Mg ₃ N ₂ powder and high-junction MnO powder were respectively 0.001, 0.005, 0.01, Weighed to 0.03, 0.05.

The powders were then ground completely and mixed uniformly with ethanol in a glove box filled with nitrogen gas.

The mixed powder synthesized MgSiN ₂ : Mn ²⁺ phosphor through a conventional solid phase reaction under a nitrogen gas pressure of 5 Mpa for 6 hours at 1500 ° C.

The fluorescent material prepared as described above was analyzed by using a PL instrument spectrometer equipped with a D2 lamp and a 460nm-LED lamp to analyze emission and excitation spectra and investigate emission characteristics.

1A to 1C are emission spectra of MgSiN ₂ : 0.005Mn ²⁺ , MgSiN ₂ : 0.02Ce ³⁺ , 0.005Mn ²⁺ and MgSiN ₂ : 0.02Ce ³⁺ phosphors, respectively. The emission spectrum of the fluorescent material according to the embodiment of the present invention was measured using a 460nm LED excitation source, MgSiN ₂ : Ce ³⁺ phosphor was measured by a 254nm continuous light excitation source.

As seen in FIG. 1A, the MgSiN ₂ : Mn ²⁺ phosphor shows a characteristic peak following a typical ⁴ T ₁ ( ⁴ G) → ⁶ A ₁ ( ⁶ S) transfer. In addition, the emission spectrum from Mn ²⁺ of the MgSiN ₂ host shows a broad distribution of peaks around 640 nm, which means that red light can be emitted with excellent chromaticity.

In addition, as shown in green in FIG. 1A, the emission spectra of MgSiN ₂ : Mn ²⁺ are separated into Gaussian peaks of two long-wavelength components and short-wavelength components, and the relative distribution of the two peaks is shown in FIG. 3. As can be seen, as the Mn ²⁺ concentration increases, the longer wavelength component becomes more superior, resulting in shifting the entire spectrum towards the red.

In addition, the results of measuring the color purity of the fluorescent material according to Example 1 of the present invention were as Table 1 below.

Furtherance
(Mg _1-x SiN ₂ : xMn ²⁺ ) Color coordinates x X Y 0.001 0.595614 0.398906 0.005 0.636054 0.362684 0.01 0.589583 0.404882 0.03 0.623625 0.374208 0.05 0.638347 0.360196

As confirmed in Table 1, it can be seen that the fluorescent material according to Example 1 of the present invention can emit red light having a sufficient chromaticity enough to be applied to a white LED.

On the other hand, looking at the luminous efficiency according to the doping amount of Mn ²⁺ , as can be seen in Figure 3, since the luminous efficiency drops sharply to the peak of 0.005, the doping amount of Mn ²⁺ ranges from 0.004 to 0.006 It is more preferable to keep as.

[Example 2]

Same as Example 1, but Mg _1-xy SiN ₂ : _x Mn ^{2 +} yCe ^{3 +} phosphor was synthesized by adding CeO powder of Kojundo Co., Ltd. to the mixture. At this time, the concentration of Ce ^{3+ in} the synthesized fluorescent material was adjusted so that the concentration of Mn ²⁺ in the synthesized phosphor was fixed at 0.005 and the concentration of Ce ³⁺ was 0.005, 0.02, 0.05.

The luminescent material and the excitation spectrum were analyzed by using a PL instrument spectrometer equipped with a D2 lamp and a 460nm-LED lamp in the same manner as in Example 1, and the luminescence properties were evaluated.

First, in order to confirm the co-doping effect of Mn ²⁺ and Ce ³⁺ , MgSiN ₂ : Ce ³⁺ was synthesized, and its emission and excitation spectra were analyzed. As shown in FIG. 1C, according to the 4f-5d transition, In contrast to MgSiN ₂ : Mn ²⁺ , the emission peak of MgSiN ₂ : C ^{e3 +} is located very broadly around 500 nm, which is meaningful for white light emission but in terms of color rendering improvement in red light emission. It is not meaningful.

However, as in Example 2 of the present invention, in the case of MgSiN ₂ co-doped with Ce ³⁺ and Mn ²⁺ , as shown in FIG. 1B, light emission due to Ce ³⁺ disappears, but due to Mn ²⁺ Luminescence was enhanced, and it was confirmed that luminescence intensity at 460 nm excitation source of MgSiN ₂ : 0.02Ce ³⁺ and 0.005Mn ²⁺ phosphors was improved by about 270% compared to MgSiN ₂ : 0.005Mn ²⁺ phosphor.

2 shows excitation spectra of MgSiN ₂ : 0.005Mn ²⁺ , MgSiN ₂ : 0.02Ce ³⁺ , 0.005Mn ²⁺ and MgSiN ₂ : 0.02Ce ³⁺ phosphors synthesized according to Examples 1 and 2 of the present invention. .

Here, the excitation spectra of MgSiN ₂ : Mn ²⁺ and MgSiN ₂ : Ce ³⁺ , Mn ^{2+ show} relatively strong lattice absorption around 270 nm and show no significant effect by co-doping of Ce ³⁺ .

However, the peak intensities of several direct absorption peaks of Mn ²⁺ ions in the 390-550 nm range show a significant improvement, due to the crystalline field splitting at 4D and 4G levels.

In addition, as indicated by the arrows in FIG. 2, Ce ³⁺ co-doping results in a significant improvement in absorption strength in the range between host absorption and Mn ²⁺ direct absorption, which is dependent on the excitation spectrum of MgSiN ₂ : Ce ³⁺ . Matches. Such a Mn ²⁺ Ce directly improve the absorption due to the above-described ³⁺ MgSiN _2: 460nm indicating the difference in light emission intensity at an excitation source of Ce ^3+, Mn ²⁺ phosphor: Mn ²⁺ phosphor and a MgSiN ₂ It seems to be the cause.

FIG. 5 is a graph showing changes in emission spectra according to the amount of Ce ³⁺ co-doped phosphor in a phosphor doped with 0.005Mn ²⁺ using MgSiN ₂ as a host. As shown in FIG. 5, there is almost no change in the emission spectrum according to the doping amount of Ce ³⁺ . That is, co-doping of Ce ³⁺ is MgSiN _2: emission wavelength of Mn ^2+, Ce ³⁺ phosphor without affecting the can just know which affects only the light-emitting efficiency.

On the other hand, as a result of evaluating the color purity of the fluorescent material according to Example 2 of the present invention was as Table 2 below.

Furtherance
(Mg _1-0.005-y SiN ₂ : 0.005Mn ²⁺ yCe ³⁺ ) Color coordinates y X Y 0.005 0.615543 0.360227 0.02 0.626087 0.362491 0.05 0.622332 0.360439

As confirmed in Table 2, the fluorescent material according to Example 2 of the present invention exhibits a constant color coordinate, regardless of the amount of Ce ³⁺ co-doping, and the color purity can be sufficiently applied to implement a white LED It is enough.

On the other hand, as shown in Figure 6, when the co-doping amount of Ce ³⁺ is out of the range of 0.005 ~ 0.05, since the effect on the luminous efficiency is greatly reduced, it is preferable to be doped within the above range.

1A to 1C are emission spectra of MgSiN ₂ : 0.005Mn ²⁺ , MgSiN ₂ : 0.02Ce ³⁺ , 0.005Mn ²⁺ and MgSiN ₂ : 0.02Ce ³⁺ phosphors, respectively.

2 is an excitation spectrum of MgSiN ₂ : 0.005Mn ²⁺ , MgSiN ₂ : 0.02Ce ³⁺ , 0.005Mn ²⁺ and MgSiN ₂ : 0.02Ce ³⁺ phosphors.

3 is a graph showing the change in the emission spectrum according to the doping amount of Mn ²⁺ when Mn ²⁺ is doped with MgSiN ₂ as a host.

4 is a graph measuring the change in emission intensity according to the doping amount of Mn ²⁺ when Mn ²⁺ is doped with MgSiN ₂ as a host.

FIG. 5 is a graph showing changes in emission spectra according to the amount of Ce ³⁺ co-doped phosphor in a phosphor doped with 0.005Mn ²⁺ using MgSiN ₂ as a host.

FIG. 6 is a graph measuring the change in luminescence intensity according to the amount of Ce ³⁺ co-doped phosphor in a phosphor doped with 0.005Mn ²⁺ using MgSiN ₂ as a host.

Claims (4)

Red fluorescent substance characterized by the following formula 1. [Equation 1] Mg _1-x SiN ₂ : xMn ²⁺ (x = 0.001 to 0.05) Red fluorescent substance characterized by the following formula 2. [Equation 2] Mg _1-xy SiN ₂ : xMn ²⁺ , yCe ³⁺ (x = 0.001 to 0.05, y = 0.005 to 0.05) 3. The red phosphor of claim 2, wherein x is in the range of 0.004 to 0.006. The white LED using the red fluorescent substance in any one of Claims 1-3.

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