KR100966373B1 - Phosphor for converting wavelength and light emitting device using the same - Google Patents

Abstract

The phosphor for wavelength conversion includes a phosphor powder that absorbs excitation light and converts the wavelength of the excitation light, and is attached to a surface of the phosphor powder to selectively resonate and absorb light of a specific wavelength band of the excitation light to induce surface plasmon vibration. It includes a plurality of nano metal particles. The wavelength conversion phosphor may be advantageously used as a phosphor in a wavelength conversion light emitting device such as a white light emitting device.

Phosphor, nanoparticle, surface plasmon vibration, light emitting diode

Description

Phosphor for conversion and light emitting device using the same

The present invention relates to a wavelength conversion phosphor, and more particularly, to a wavelength conversion phosphor with improved wavelength conversion efficiency and a light emitting device using the same.

Recently, many researches and developments have been conducted to apply white light emitting devices using LEDs to general lighting devices as well as backlights of display devices.

Representatively, a method of implementing an LED white light emitting device is known by a simple combination of blue, red, and green LEDs manufactured by individual LEDs and a method of using phosphors. In general, a method of combining individual LEDs of multiple colors on the same printed circuit board requires a complex driving circuit for this purpose, and accordingly has a disadvantage of miniaturization, and thus, a method of manufacturing a white light emitting device using phosphors has recently been widely used.

Conventionally, a method of manufacturing a white light emitting device using phosphors may include a method of using a blue light emitting diode and a method of using an ultraviolet or near ultraviolet light emitting diode.

For example, when a blue light emitting diode is used, blue light is converted into white light using a YAG phosphor. That is, the blue wavelength generated from the blue LED excites the YAG (Yittrium Aluminum Garnet) phosphor to emit yellow light, and the yellow light and the remaining blue wavelength light of the LED may be mixed to finally emit white light.

As described above, in the case of providing white light by exciting a fluorescent material with specific light emission wavelength of the LED chip, since the internal quantum efficiency of the phosphor itself, that is, the light conversion efficiency due to the phosphor is low, much loss of the final light amount is caused.

In addition, in the white light emitting device of this type, in particular, the white light emitting device using a high brightness blue light emitting diode chip, there is a disadvantage that the optical properties of the phosphor due to high heat is lowered, and in the phosphor placed in the epoxy resin or silicone resin Light emission also has a problem in that the external quantum efficiency is greatly reduced due to the total reflection caused by the refractive index mismatch between the resin and the phosphor.

The present invention is to solve the above problems of the prior art, an object of the present invention is to provide a phosphor for wavelength conversion to improve its internal quantum efficiency using nano-sized metal particles.

Another object of the present invention is to provide a light emitting device using a phosphor for wavelength conversion to improve its internal quantum efficiency using nano-sized metal particles.

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

A phosphor powder for absorbing excitation light and converting the wavelength of the excitation light, and a plurality of nano metal particles attached to a surface of the phosphor powder and selectively resonating and absorbing light in a specific wavelength band of the wavelength band of the excitation light to induce surface plasmon vibration It provides a wavelength conversion phosphor comprising a.

Preferably, the nano metal particles may be a metal selected from the group consisting of Al, Au, Ag, Pt and Pd.

Preferably, the nano-metal particles may be a polyhedral structure having a plurality of vertices to facilitate electric field concentration.

Preferably, the size of the nano metal particles may be 150 ~ 350nm.

According to another aspect of the present invention, there is provided a package structure having first and second wiring structures and having a chip mounting portion, and a light emitting diode mounted on a chip mounting portion of the package structure to be electrically connected to the first and second wiring structures. And a resin package formed to surround the light emitting diodes and containing a wavelength converting phosphor, wherein the wavelength converting phosphor includes phosphor powder for absorbing light emitted from the light emitting diode and converting the wavelength thereof; Provided is a wavelength conversion light emitting device comprising a plurality of nano-metal particles attached to the surface of each phosphor powder to selectively resonant absorption of light of a specific wavelength band of the emitted light to induce surface plasmon vibration. .

Preferably, the phosphor powder may include at least two kinds of phosphor powders for converting light of different wavelengths.

 According to the present invention, by using a phosphor structure coated with metal nanoparticles, the internal quantum efficiency of the phosphor can be greatly improved to provide light having a desired wavelength with high efficiency. The high thermal conductivity of the metal particles can be expected to mitigate the thermal problems that can occur in high-brightness LED chips. Since the wavelength conversion part composed of the phosphor according to the present invention has high thermal stability and conversion efficiency, it can be advantageously applied to a wavelength conversion light emitting device such as a white light emitting device.

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

1 is a schematic diagram for explaining a light conversion process in a wavelength conversion phosphor according to an aspect of the present invention.

Referring to FIG. 1, a phosphor powder P having a plurality of nano metal particles N attached to a surface thereof is illustrated.

The phosphor P absorbs excitation light of a specific wavelength and converts it into light of another wavelength. The nano metal particles (N) has a size capable of selectively resonant absorption of light of a specific wavelength band of the wavelength band of the excitation light. The nano metal particles (N) may induce surface plasmon vibration through resonance absorption of a specific wavelength. The nano metal particles N may be designed to have a resonant frequency that is a specific wavelength light belonging to an excitation wavelength light of the phosphor P, that is, a wavelength band of a light source such as a light emitting diode. Such a design may be implemented in an appropriate size (S) and shape according to each material. The material constituting the nano metal particles (N) may be a metal selected from the group consisting of Al, Au, Ag, Pt, and Pd, but is not limited thereto.

Surface plasmon vibration caused by the nano-metal particles (N) may increase the electric field (F) strength. The internal quantum efficiency in the vicinity of the surface of the phosphor (P) in contact with the nano-metal particles (N) can be improved. Therefore, as shown in FIG. 1, the phosphor P increases the electric field F intensity by attaching a large number of nano metal particles (N) that can be resonantly absorbed by a specific wavelength band belonging to the excitation wavelength band. (P) The conversion efficiency in the vicinity of the surface can be greatly improved.

For example, when the phosphor P shown in FIG. 1 absorbs the wavelength light of the blue LED chip like the YAG-based phosphor, part of the phosphor P is not converted into the blue light B 'as it is and is partially converted to yellow Y. For example, the efficiency of changing to yellow light (Y) may be increased due to an increase in quantum efficiency inside the phosphor due to an increase in electric field intensity on the surface of the phosphor.

In addition, since the nanoparticles on the surface of the phosphor is a metal material having high thermal conductivity, it can act as a medium for effectively conducting heat generated in the device, such as a blue LED.

Figure 2 shows the electrical distribution around the spherical metal nanoparticles for explaining the principle of the present invention.

In general, when light waves are applied to a metal, surface plasmon oscillations, which correspond to the collective vibration of surface electrons, occur, and oscillating dipole fields due to the wavelength of metal nanoparticles that are much smaller than the wavelength. Is formed as shown in FIG.

The vibrating dipole field is characterized by a strong increase in electric field strength at close range, and when the size of the particle becomes larger than the wavelength, multipolar oscillations occur and the increase in electric field strength may decrease drastically, but the light source used (excited light source) When the frequency of Δ is close to the resonance frequency of the metal particles, the effect of the extreme electrical field intensity due to the surface plasmon vibration can be obtained.

The present invention can increase the electric field strength in the vicinity of the surface of the phosphor by using a nano-metal particles having a condition that can induce surface plasmon vibration by the excitation light source. As a result, this strong increase in electric field strength can improve the internal quantum efficiency near the phosphor surface.

It is generally known that the excitation rate of (single) molecules adjacent to a strong field of electric field can be greatly increased.

Therefore, as shown in FIG. 3, the nano metal particles N may be disposed near the phosphor P to form a locally strong electric field space by the blue light emitted from the blue LED chip. The internal quantum efficiency of the phosphor can be improved as a whole by greatly improving the excitation rate of the phosphor adjacent thereto.

Of course, the nano metal particles (N) employed in the present invention are designed to resonate only with light emitted from the LED chip (for example, blue light), and react with light (for example, yellow light) of the wavelength converted by the phosphor. It needs to be designed so as not to.

The nano metal particles may be manufactured to have a size that can have a resonance frequency in the wavelength band of the light source used. This size may vary slightly depending on the material and shape of the nano metal particles. In particular, the nano-metal particles employed in the present invention may be a polyhedral structure having a plurality of vertices such as, for example, a pyramid.

In the polyhedral structure, unlike the sphere, a strong electric field may be induced by the presence of regions such as corners or vertices where surface charge density due to structural characteristics may be concentrated. As such, the nano metal particles are preferably a polyhedral structure having a plurality of vertices to facilitate electric field concentration.

For example, it is assumed that nanoparticles, which are aluminum, are provided in a pyramidal shape having a triangular cross section, and the FDTD method is used to increase the electric field strength near a vertex according to the height of the triangle, which is a nanoparticle cross section. The calculations are similar to those of Fig. 4 for the 405 nm and 633 nm wavelengths.

Referring to FIG. 4, it was shown that the difference in electric field strength at two wavelengths under the above-described conditions was the largest in the nano metal particle size (based on triangle cross-sectional height) in the range of 220 to 320 nm. As shown in the present example, the nanoparticles of the pyramidal structure Al may have the largest difference in resonant electric field strength according to two wavelengths when the triangular height of the cross section is about 270 nm.

The size of the nanoparticles according to the resonant frequency may vary depending on the shape and material of the particles, and may vary depending on the wavelength of the light source used. Therefore, it is possible to determine nano metal particles having an optimal structure by comprehensively considering these matters.

In general, considering the ultraviolet, near-ultraviolet and blue LED chip used in the white light emitting device as the excitation wavelength light source, the size of the nano-metal particles may be preferably selected in the range of 150 ~ 350nm.

5 shows an example of a wavelength conversion light emitting device according to another aspect of the present invention.

Referring to FIG. 5, the wavelength conversion type light emitting device 20 includes a package substrate 21 on which a light emitting diode chip 25 is mounted. The light emitting diode chip 25 may be a blue LED chip or an ultraviolet / near ultraviolet LED chip.

The package substrate 21 may be implemented in various forms, but as shown in the present embodiment, the lower substrate 21a on which the first and second wiring structures 23a and 23b are provided and the upper substrate 21b on which the cavity is provided are provided. It may include.

In addition, the first and second wiring structures 23a and 23b are shown only on the upper surface of the lower substrate, but as will be apparent to those skilled in the art, the first and second wiring structures 23a and 23b may be structures connected through electrode pads and via holes on the lower surface for external connection of the package. have. Two electrodes (not shown) of the light emitting diode chip 25 may be connected to the first and second wiring structures 23a and 23b by wires, respectively.

In the cavity provided in the upper substrate 21b, a resin packing part 27 may be formed to surround the LED chip 25. The resin packaging part 27 may be made of a transparent resin such as a silicone resin, an epoxy resin, or a mixture thereof. The phosphor powder 29 to which a plurality of metal nanoparticles are attached is dispersed in the resin packaging portion 27 employed in the present embodiment. The phosphor 28 functions to convert the light of the wavelength of the light emitting diode into another wavelength of light, and may be mainly used to obtain white light.

The phosphor 29 employed in the present invention is phosphor powder P having a plurality of nano metal particles N attached to the surface thereof. As described above, the nano-metal particles (N) may induce surface plasmon vibration by absorbing light of a specific wavelength band of the wavelength band of the excitation light for the phosphor (P). The induced surface plasmon vibration increases the electric field (F) strength, and as a result, it is possible to improve the internal quantum efficiency near the surface of the phosphor (P) in contact with the nano-metal particles (N).

In addition, the nano metal particles (N) may be a metal selected from the group consisting of Al, Au, Ag, Pt and Pd. As such, since the nano metal particles N are made of a metal material having high thermal conductivity, the nano metal particles N may help to release heat generated from the LED chip to the outside.

The present invention is not limited by the above-described embodiments and the accompanying drawings, but is defined by the appended claims. Therefore, it will be apparent to those skilled in the art that various forms of substitution, modification, and alteration are possible without departing from the technical spirit of the present invention described in the claims, and the appended claims. Will belong to the technical spirit described in.

1 is a schematic diagram for explaining a light conversion process in a wavelength conversion phosphor according to an aspect of the present invention.

Figure 2 shows the electrical distribution around the spherical metal nanoparticles for explaining the principle of the present invention.

Figure 3 is a schematic diagram showing the effect of the spherical metal nanoparticles on the phosphor for explaining the principle of the present invention.

Figure 4 is a graph showing the increase in the electric field strength according to the length and wavelength of the pyramidal aluminum nanoparticles.

5 shows an example of a wavelength conversion light emitting device according to another aspect of the present invention.

Claims (9)

A phosphor powder for absorbing excitation light and converting the wavelength of the excitation light, Wavelength conversion to increase the internal quantum efficiency of the phosphor powder including a plurality of nano-metal particles attached to the surface of the phosphor powder to selectively resonant absorption of light of the wavelength band of the excitation light to induce surface plasmon vibration Phosphor for use. The method of claim 1, The nano metal particle is a wavelength conversion phosphor, characterized in that the metal selected from the group consisting of Al, Au, Ag, Pt and Pd. The method of claim 1, The nano metal particles are a wavelength conversion phosphor, characterized in that the polyhedral structure having a plurality of vertices. The method of claim 1, The nano-metal particles have a size of 150 ~ 350nm, the wavelength conversion phosphor. A package structure having first and second wiring structures and having a chip mounting portion; A light emitting diode mounted on a chip mounting portion of the package structure to be electrically connected to the first and second wiring structures; And It is formed to surround the light emitting diode, and includes a resin packaging containing a phosphor for converting wavelengths, The wavelength converting phosphor includes a phosphor powder which absorbs light emitted from the light emitting diode and converts the wavelength thereof, and a resonance powder that is attached to a surface of each phosphor powder to selectively absorb light of a specific wavelength band among the wavelength bands of the emitted light. And a plurality of nano metal particles that induce surface plasmon vibrations to increase the internal quantum efficiency of the phosphor powder. The method of claim 5, The nano-metal particle is a wavelength conversion light emitting device, characterized in that the metal selected from the group consisting of Al, Au, Ag, Pt and Pd. The method of claim 5, The nano-metal particle is a wavelength conversion type light emitting device, characterized in that the polyhedral structure having a plurality of vertices. The method of claim 5, The nano metal particles have a size of 150 ~ 350nm wavelength conversion type light emitting device. The method of claim 5, The phosphor powder comprises at least two kinds of phosphor powder for converting the light of different wavelengths.

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