KR20160081091A - Phosphor blend and white light emitting device comprising the same - Google Patents

Abstract

The present invention relates to a phosphor blend having improved color reproducibility and latent light characteristics, and a white light emitting device comprising the same. In a blue light emitting diode having a main light emission peak in a wavelength range of 420-500 nm, a green phosphor having a main light emission peak in a wavelength range of 500-570 nm is used in combination with a red phosphor having a main light emission peak in a wavelength range of 610-670 nm to emit white light. Herein, the red phosphor is a blend of a first red phosphor based on Mn^4+-activated fluoride with a second red phosphor based on a nitride different from the first red phosphor. According to the present invention, the use of the second red phosphor blended in an small amount provides substantially the same color reproducibility and significantly improved latent light characteristics, as compared to the use of the first red phosphor based on Mn^4+-activated fluoride alone.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a phosphorescent material,

The present invention relates to a phosphor mixture and a white light emitting device including the same.

A light emitting diode (LED) is a device that emits light while recombining electrons and holes in the active layer. A p-type semiconductor layer and an n-type semiconductor layer are provided on both sides of the active layer. When a voltage is applied between the p-type semiconductor layer and the n-type semiconductor layer, electrons and holes are injected into the active layer and recombined to emit light.

The light emitting diodes include blue light emitting diodes, green light emitting diodes, and red light emitting diodes depending on the color of the light emitting diodes. Recently, the demand for white light emitting devices using light emitting diodes for lighting and display backlighting has greatly increased. The white light emitting device may be manufactured by combining blue, green, and red light emitting diodes, or may be manufactured by combining a light emitting diode and a phosphor that emit short wavelength light. Examples of the white light emitting device using a phosphor include a light emitting diode that emits light of a UV (ultraviolet) wavelength, a light emitting device that combines a phosphor that emits blue, green, and red light by absorbing ultraviolet light, There is a light emitting device in which blue light is absorbed by a light emitting diode that emits blue light and a phosphor that emits light in a complementary relationship with blue light. Among them, a white light emitting device in which a phosphor is combined with a blue light emitting diode is mainly used.

As a phosphor used for a white light emitting device using a blue light emitting diode, yttrium aluminum garnet activated with cerium of the general formula (Y, Gd) ₃ (Al, Ga) ₅ O ₁₂ : Ce ³⁺ , Based phosphor. YAG fluorescent material is a phosphor that emits yellow light by absorbing blue light and has a merit of being able to produce white light even if only one phosphor is used. However, since the white light thus produced has a characteristic of blue due to insufficient red component The color reproducibility is not excellent. In particular, these characteristics are considered to be unsuitable for display backlights requiring high color reproduction characteristics.

To solve this problem, a method of using a green phosphor and a red phosphor together with a blue light emitting diode instead of a yellow phosphor has been proposed. For example, a blue light emitting diode having a main emission peak in a wavelength range of 420 to 500 nm is used as an excitation source, and a green phosphor having a main emission peak in a wavelength range of 500 to 570 nm and a green phosphor having a main emission peak in a wavelength range of 570 to 700 nm It is possible to obtain a white light emitting device having excellent color reproducibility because the red component is supplemented as compared with the case where the yellow phosphor is used.

Typical green phosphors used for this purpose are Si _6-z Al _z O _z N _{8 -z} : Eu ²⁺ (β-SiAlON) having a main emission peak at a wavelength of about 540 nm, Lu ₃ Al ₅ O ₁₂ : Ce ³⁺ phosphor, and the red phosphor is a nitride-based phosphor such as Ca (Sr) AlSiN ₃ : Eu ²⁺ .

On the other hand, a red phosphor material for producing white light together with a blue light emitting diode and a green phosphor is important in terms of luminous efficiency (luminescent efficiency) for absorbing blue light and emitting red light, and its main emission peak wavelength, but also the form of emission spectrum is important. That is, even if a red phosphor having the same main luminescence peak wavelength does not have a sharp emission peak but has a relatively large half-width, it includes light emission in a wavelength range outside the visible range, so that Luminous Efficacy of Radiation (LER) Or Luminosity of the main emission peak is lower than that of the main emission peak, the use of the red phosphor exhibiting the emission spectrum with a relatively small half width of the main emission peak makes a white light emitting device having excellent visibility. This point is taken into consideration, while the 610-state emission peaks at 650nm range appear relatively K ₂ SiF the red phosphor having small half size width in _6: Mn ^4+, etc. ^{_{A 2 MF 6: Mn 4+ (}} A = Li, Na, K, Rb, Cs, M = Ge, Si, Sn, Ti, Zr). However, the A ₂ MF ₆ : Mn ⁴⁺ red phosphor has an advantage of obtaining excellent color reproducibility, but has a long afterglow time, which limits its application to displays, in particular, to three-dimensional (3D) displays.

Accordingly, there is a continuing need for a red phosphor that satisfies both color reproducibility and short afterglow characteristics suitable for application to a display backlight.

Korean Patent No. 10-0816693

It is an object of the present invention to provide a phosphor mixture and a white light emitting device including the same that can satisfy both the color reproducibility and the short afterglow characteristics of a white light emitting device .

According to one aspect of the present invention, there is provided a white light emitting device comprising a blue light emitting diode having a main emission peak in a wavelength range of 420 to 500 nm, a green phosphor having a main emission peak in a wavelength range of 500 to 570 nm, And a red phosphor having a main emission peak in a wavelength range of 610 to 670 nm, wherein the red phosphor comprises a first red phosphor of the fluoride series activated by Mn ⁴⁺ , and a second red phosphor of a second nitride series different from the first red phosphor And is a mixture of red phosphors.

In this case, the first red phosphor may be A ₂ MF ₆ : Mn ⁴⁺ (A = Li, Na, K, Rb, Cs, M = Ge, Si, Sn, Ti, Zr) Ca (Sr) AlSiN: Eu ²⁺ .

In addition, the weight ratio of the second red phosphor may be 10% or less of the total red phosphor, and more specifically, 1.8 to 7.4%.

In addition, the white light emitting device according to the present invention may have a color reproduction ratio of 85% or more as compared with NTSC, and a second red phosphor having a main emission peak in a wavelength range of 650 nm or more may be used and the color reproduction rate may be 90% or more of NTSC.

A phosphor mixture according to another aspect of the present invention is a phosphor mixture for producing a white light emitting device by absorbing light emitted from a blue light emitting diode and emitting light having a different wavelength and has a main emission peak in a wavelength range of 500 to 570 nm And a red phosphor having a main luminescence peak in a wavelength range of 610 to 670 nm, wherein the red phosphor comprises a fluorophore-based first red phosphor activated with Mn < ^{4 +} > and a red phosphor different from the first red phosphor A second red phosphor of the second red phosphor type.

A red phosphor according to another aspect of the present invention is a red phosphor for fabricating a white light emitting device together with a blue light emitting diode and a green phosphor, wherein the red phosphor comprises K ₂ SiF ₆ : Mn ⁴⁺ and a nitride- And the like.

The phosphor mixture according to the present invention and the white light emitting device including the same can improve afterglow characteristics as compared with a white light emitting device using a conventional red phosphor and can provide color reproducibility and light quantity characteristics suitable for display backlight .

1 is a schematic structural view of a white light emitting device according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited to or limited by the embodiments. In describing the various embodiments of the present invention, corresponding elements are denoted by the same names and the same reference numerals.

In the process of looking for the inventors of the present invention a solution for the above problem, according to a white light-emitting device combining a blue light emitting diode and a green phosphor and a red phosphor, a red phosphor K ₂ SiF _6: Mn ^4+, such as Mn ⁴⁺ In the case of using a phosphor mixture obtained by mixing a red phosphor of the fluoride series activated with a nitride based red phosphor such as Ca (Sr) AlSiN ₃ : Eu ²⁺ in an appropriate ratio, the afterglow characteristics are improved, It has been found that properties suitable for use as a backlight are obtained, leading to the present invention.

1 is a schematic structural view of a white light emitting device according to the present invention. 1, the white light emitting device 100 according to the present invention includes a blue light emitting diode 200, a molding unit 300, and a phosphor mixture 400.

The blue light emitting diode 200 is a light emitting diode having a main emission peak in a wavelength range of 420 to 500 nm and includes a substrate 210, an n-type semiconductor layer 220 sequentially stacked on the substrate 210, an active layer 230, a p-type semiconductor layer 240, a p-type electrode 250 formed on the p-type semiconductor layer 240, and an n-type electrode 260 formed on the n-type semiconductor layer 220.

The substrate 210 has a structure that supports the blue light emitting diode 200 as a whole. The material of the substrate 210 is not particularly limited. However, the light generated from the active layer 230 must be emitted through the substrate 210, The substrate 210 may include at least one selected from the group consisting of Al ₂ O ₃ , SiC, GaN, GaAs, Si, Ge, ZnO, MgO), aluminum nitride (AlN), boron nitride (BN), gallium phosphide (GaP), indium phosphide (InP), and lithium-aluminum oxide (LiAlO ₃ ).

The n-type semiconductor layer 220 may be an n-type AlxInyGazN (0 = x, y, z = 1, x + y + z = 1) doped with an n-type impurity, , Ge, Sn, Se, and Te. The p-type semiconductor layer 240 may be p-type AlxInyGazN (0 = x, y, z = 1, x + y + z = 1) or p-type GaN doped with a p-type impurity, , Zn, Ca, Sr, Be, and Ba. The active layer 230 may include a group III-V compound material as a layer for recombining holes and electrons injected from the n-type semiconductor layer 220 and the p-type semiconductor layer 240 to generate light, For example, AlxInyGazN (0 = x, y, z = 1, x + y + z = 1), InGaN or AlGaN. The active layer 230 may be a single quantum well (SQW) or a multi quantum well (MQW). For example, the active layer 230 may include a GaN / InGaN / GaN MQW structure, a GaN / AlGaN / GaN MQW structure Lt; / RTI > The description of the n-type semiconductor layer 220, the active layer 230, and the p-type semiconductor layer 240 is exemplary and may vary depending on the design of the blue light emitting diode.

The p-type electrode 250 is formed on the p-type semiconductor layer 240 and the n-type electrode 260 is formed on the n-type semiconductor layer 220, A material such as lead (Pb), gold (Au), titanium (Ti), copper (Cu), nickel (Ni), tin (Sn), chromium (Cr), tungsten Or an alloy layer or a lamination layer. At this time, the active layer 230 and the p-type semiconductor layer 240 stacked on the n-type semiconductor layer 220 are removed to expose the n-type semiconductor layer 220, A reflective layer (not shown) for reflecting light toward the substrate 210 may be further provided on the electrodes 250 and 260, or the electrodes 250 and 260 may serve as a reflective layer.

Although the blue light emitting diode 200 of FIG. 1 is a flip-chip device for emitting light generated in the active layer 230 and utilizing the light transmitted through the substrate 210, the white light emitting device 100 does not limit the blue light emitting diode 200 to a flip-type structure, but a lateral device for utilizing light transmitted in the direction of electrode formation surface, or an n-type electrode and a p- Or may be a vertical device provided. That is, the type and the specific structure of the blue light emitting diode 200 of the present invention are not limited.

The molding part 300 surrounds the blue light emitting diode 200 and disperses the phosphor mixture 400 therein to convert blue light emitted from the blue light emitting diode 200 into white light. The molding part 300 may be made of a transparent resin such as a silicone resin, and although not shown in FIG. 1, other particles such as a diffusion agent may be dispersed in the fluorescent material mixture 400. The molding part 300 may be formed to surround all the parts of the blue light emitting diode 200 excluding the electrodes 250 and 260 as shown in FIG. 1, but the present invention is not limited thereto.

The phosphor mixture 400 includes a first red phosphor 410, a second red phosphor 420, and a green phosphor 430. The first red phosphor 410 is a fluorophore-based red phosphor activated by Mn ⁴⁺ . A ₂ MF ₆ : Mn ⁴⁺ (A = Li, Na, K, Rb, Cs, M = Ge, Ti, Zr), and more specifically may be a phosphor represented by the general formula: K ₂ SiF ₆ : Mn ⁴⁺ . Further, the second red phosphor 420 may be a red phosphor of a different kind from the first red phosphor 410, and may be a nitride red phosphor. In particular, the second red phosphor 420 may be a nitride red phosphor activated by Eu ²⁺ , and more specifically, a Ca (Sr) AlSiN ₃ : Eu ²⁺ phosphor.

The first red phosphor 410 may be a phosphor that emits red light having a main emission peak in a wavelength range of 610 to 650 nm by absorbing blue light emitted from the blue light emitting diode 200, And may be a phosphor that absorbs blue light emitted from the light emitting diode 200 and emits red light having a main emission peak in a wavelength range of 610 to 670 nm. At this time, the main emission peak from the first red phosphor 410 may be a sharp peak whose half width is smaller than the main emission peak from the second red phosphor 420.

The mixing ratio of the second red phosphor 420 among the entire red phosphors may be 10% or less, specifically, 1.8 to 7.4%.

The green phosphor 430 is a phosphor that absorbs blue light emitted from the blue light emitting diode 200 and emits green light having a main emission peak in a wavelength range of 500 to 570 nm, and Si _6-z Al _z O _z N _8-z : Eu ²⁺ (? -SiAlON).

Although the first and second red phosphors 410 and 420 and the green phosphor 430 are shown only in a part of the molding part 300 in FIG. 1, it is preferable that the above phosphors are uniformly dispersed throughout the molding part 300 Do.

When a voltage is applied between the p-type electrode 250 and the n-type electrode 260 in the white light emitting device 100 according to the present invention having such a structure, electrons and holes recombine in the active layer 230 to generate blue light, And is incident on the molding unit 300 through the substrate 210. The first and second red phosphors 410 and 420 dispersed in the molding part 300 absorb a part of the blue light incident on the molding part 300 to emit red light while the green phosphor 430 absorbs a part of blue light. Thereby emitting green light. Accordingly, the white light emitting device 100 according to the present invention includes blue light emitted from the blue light emitting diode 200, red light emitted from the first and second red phosphors 410 and 420, Are combined to emit white light.

At this time, the white light emitting device 100 according to the present invention is suitable for application to a display backlight by using a fluorophore-based red phosphor activated by Mn ⁴⁺ having a narrow half width of the main emission peak as the first red phosphor 410 Color reproducibility characteristics can be obtained. On the other hand, if only the first red phosphor 410 is used, there is a problem that the afterglow time is very long and is not suitable for application to the display backlight despite excellent visibility characteristics. However, the second red phosphor 420 is mixed The afterglow characteristics can be greatly improved without deteriorating the color reproducibility. In particular, according to the present invention, it is possible to obtain such characteristics by merely mixing a relatively small amount of the second red phosphor 420.

Hereinafter, the present invention will be described more specifically by way of Comparative Examples and Examples.

1. Fabrication of white light emitting device

Using a blue light emitting diode having a main emission peak at a wavelength of about 450 nm, a white light emitting device having the structure as shown in FIG. 1 was fabricated. Silicone resin was used as the molding part and β-SiAlON phosphor was used as the green phosphor dispersed in the molding part.

K ₂ SiF ₆ : Mn ⁴⁺ was used as the first red phosphor, and (Ca, Sr) AlSiN ₃ : Eu ²⁺ phosphor in which the main emission peak appeared at 615 nm as the second red phosphor, the main light emission at 650 nm or 660 nm CaAlSiN ₃ : Eu ²⁺ phosphor in which a peak appears is used. The mixing ratio of the second red phosphor was 1.8 ~ 7.4% of the total red phosphor, and a device without the second red phosphor was also prepared for comparison.

2. Color reproducibility and afterglow characteristics

The color reproducibility and afterglow characteristics of the white light emitting devices according to Examples and Comparative Examples were measured and are shown in Table 1 below. In Table 1, the color reproduction ratio is a% value as compared with NTSC, and the afterglow characteristic represents the time taken to decrease the afterglow to 1/10 after the voltage applied to the light emitting device is reduced in msec.

division Second red phosphor primary emission peak wavelength Second red phosphor ratio (%) Color Repeatability (% of NTSC) Afterglow characteristics
(Decay time, 1/10) (msec) Example 615 nm 1.8-3.3 86 ~ 89 5.5 to 8.2 650 nm 3.8 to 7.4 90 ~ 92 660 nm 1.8-3.3 91 ~ 93 Comparative Example - 0 92.7 12

As can be seen from the results in Table 1, it was confirmed that the afterglow characteristics were greatly improved by mixing a small amount of the second red phosphor of less than 10%. That is, when only the first red phosphor, K ₂ SiF ₆ : Mn ^4+, is used, the decay time of 1/10 afterglow is 12 msec. When a small amount of the second red phosphor is mixed, the main luminescence peak wavelength of the second red phosphor Regardless of the mixing amount, the afterglow characteristics were improved by more than 50% at less than 8.2 msec.

Particularly, when the second red phosphor in which the main emission peak appears in a wavelength range of 650 nm or more is mixed, the case of using only the first red phosphor and the case of actually using the red color phosphor There was no difference in characteristics. Considering that the second red phosphor having a main emission peak at a relatively short wavelength of 615 nm is mixed, the color reproduction rate is relatively decreased. However, considering that the color reproduction rate of a white light emitting device using only a nitride based red phosphor is usually 85% It was possible to apply it to backlight.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. Accordingly, the scope of protection of the present invention should be determined by the description of the claims and their equivalents.

100: white light emitting element
200: blue light emitting diode
210: substrate
220: an n-type semiconductor layer
230:
240: a p-type semiconductor layer
250: p-type electrode
260: n-type electrode
300: Molding part
400: phosphor mixture
410: first red phosphor
420: second red phosphor
430: green phosphor

Claims (9)

A blue light emitting diode having a main emission peak in a wavelength range of 420 to 500 nm;
A green phosphor having a main emission peak in a wavelength range of 500 to 570 nm; And
A red phosphor having a main emission peak in a wavelength range of 610 to 670 nm,
^Wherein the red phosphor is a mixture of a first red phosphor of a fluoride series activated by Mn ⁴⁺ and a second red phosphor of a nitride series different from the first red phosphor. The method according to claim 1,
Wherein the first red phosphor is A ₂ MF ₆ : Mn ⁴⁺ (A = Li, Na, K, Rb, Cs, M = Ge, Si, Sn, Ti, Zr). The method according to claim 1,
And the second red phosphor is Ca (Sr) AlSiN: Eu ²⁺ . The method according to claim 1,
Wherein the weight ratio of the second red phosphor to the total red phosphor is 10% or less. 5. The method of claim 4,
Wherein the weight ratio of the second red phosphor to the total red phosphor is in the range of 1.8 to 7.4%. The method according to claim 1,
And a color reproduction ratio of 85% or more with respect to NTSC. The method according to claim 6,
Wherein the second red phosphor has a main emission peak in a wavelength range of 650 nm or more,
Wherein the color reproduction ratio is 90% or more of NTSC. A phosphor mixture for producing a white light emitting device by absorbing light emitted from a blue light emitting diode and emitting light having a different wavelength,
A green phosphor having a main emission peak in a wavelength range of 500 to 570 nm; And
A red phosphor having a main emission peak in a wavelength range of 610 to 670 nm,
^Wherein the red phosphor comprises a fluorophore-based first red phosphor activated by Mn ⁴⁺ and a second red phosphor of a nitride type different from the first red phosphor. As a red phosphor for producing a white light emitting device together with a blue light emitting diode and a green phosphor,
Wherein the red phosphor is a mixture of K ₂ SiF ₆ : Mn ⁴⁺ and a nitride-based red phosphor.

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