KR20070088848A - Light emitting device and display device having the same - Google Patents

Abstract

A light emitting device and an image display apparatus with the same are provided to enhance a color rendering index and a color reproducibility. A light emitting device includes a light emitting element and a molding portion. The light emitting element(400) is used for emitting light of a first wavelength. The molding portion contains a plurality of fluorescent substances. The plurality of fluorescent substances of the molding portion are capable of absorbing the light of a first wavelength emitted from the light emitting element and generating light having a different wavelength than the light.

Description

Light emitting device and image display device having the same {Light emitting device and display device having the same}

1 is a cross-sectional view schematically showing a light emitting device according to the present invention.

2 is a view showing an emission spectrum of each phosphor applied to the light emitting device according to the present invention.

3 is a sectional view schematically showing another example of a light emitting device according to the present invention;

Figure 4 is a view showing the color coordinates of the mixing ratio of each phosphor applied to the light emitting device according to the present invention.

5 is a view showing the color coordinates of the mixing ratio of the phosphor mixture to the molding resin in the light emitting device according to the present invention.

<Description of the symbols for the main parts of the drawings>

100, 100 '... heat sink 110, 110' ... hole space

200, 200 '... Reflector 300, 300' ... Lead frame

310, 310 '... Solder 400, 400' ... LED

410, 410 '... Submount 500, 500' ... PCB

600, 600 '... wire 700, 700' ... red molding

800, 800 '... green molding 900, 900' ... blue molding

The present invention relates to a light emitting device.

A light emitting diode (LED), which is one of light emitting devices, generates light when carriers injected into the active layer recombine, and its emission wavelength is determined in the band gap of the active layer. As a method for realizing a desired mixed color using such LED, there are the following methods. By combining a plurality of LEDs having different emission wavelengths and controlling the light output of each LED by controlling the current applied to each LED, the desired mixed color can be emitted. In addition, there is a method in which the phosphor absorbs the light emitted from the LED and converts the light into a wavelength.

The method of controlling the light output to emit light has a disadvantage in that the configuration is complicated and the control of the light output is not easy. On the contrary, the method of emitting light using the phosphor is advantageous in that it is possible to realize a desired mixed color by using only one LED and selecting an appropriate phosphor material and a combination thereof.

GaN-based materials can obtain most of the wavelength of the visible region from the ultraviolet region because the band gap energy is adjustable from 1.9 eV to 6.2 eV. In addition, GaN-based LED is a semiconductor light emitting device having a high luminous efficiency, low power consumption and good thermal stability than a conventional light source, has a long life and excellent response. A white light emitting device in which a YAG (Y ₃ Al ₅ O ₁₂ ) -based phosphor is combined with a GaN-based LED in the blue region has been developed.

However, when white light is emitted using the LED and the phosphor, the sensitivity is very sensitive to the method of applying the phosphor and operating conditions of the LED. Accordingly, the conventional YAG-based white light emitting device has many difficulties in reproducing the same white color.

In addition, although the conventional YAG-based phosphor has the advantage that the chemical stability is very high, it is a factor of the cost increase as the temperature of its manufacturing process is required to have a high temperature of 1600 ° C or more during solid phase production. In addition, a technique for replacing Y with Gd or Al with Ga for color control of a conventional YAG-based phosphor has been proposed, but there is a difficulty in color control.

The conventional YAG-based white light emitting device has a disadvantage in that color rendering is low due to lack of light emission in the green region. In addition, the conventional YAG-based white light emitting device has a disadvantage of emitting a cold white (cold white) due to the lack of light emission of the red region and the predominance of blue light emission.

Accordingly, researches on light emitting devices having high color rendering index and excellent color reproducibility have been conducted.

The present invention provides a light emitting device having a high color rendering index and excellent color reproducibility.

The present invention also provides an image display device including a light emitting device having a high color rendering index and excellent color reproducibility.

The present invention also provides a liquid crystal display device including a light emitting device having a high color rendering index and excellent color reproducibility as a backlight unit.

A light emitting device according to the present invention includes a light emitting device for emitting light of a first wavelength; A molding part having a plurality of phosphors configured to absorb light emitted from the light emitting device and emit light having a wavelength longer than that of the first wavelength; It includes.

An image display device according to the present invention includes a light emitting device that emits light of a first wavelength, and a plurality of phosphors that absorb light emitted from the light emitting device and emit light having a wavelength longer than that of the first wavelength. A light emitting device having a molding unit formed with; A controller for controlling the light emitting device to display an image; It includes.

According to an exemplary embodiment of the present invention, a liquid crystal display device includes a light emitting device that emits light of a first wavelength, and a plurality of phosphors that absorb light emitted from the light emitting device and emit light having a wavelength longer than that of the first wavelength. A backlight unit having a light emitting device having a molded part formed thereon; A liquid crystal panel configured to display an image by receiving the light provided from the backlight unit; It includes.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention;

The light emitting device according to the present invention includes a light emitting device for emitting light of a first wavelength and a plurality of phosphors for absorbing light emitted from the light emitting device to emit light having a relatively longer wavelength than the first wavelength. It includes a molding part.

1 is a cross-sectional view schematically showing a light emitting device according to the present invention.

For example, the light emitting device according to the present invention uses the LED 400 for emitting ultraviolet light of 250 ~ 420nm. In addition, the light emitting device according to the present invention includes a metal heat sink 100, and the PCB 500 is formed on the heat sink 100. The sub mount 410 is provided on the hole space 110 formed in the heat sink 100 and the PCB 500. The LED 400 is mounted on the sub mount 410, and the LED 400 and the lead frame 300 are connected by a wire 600.

In the light emitting device according to the present invention, a reflective member 200 is formed on the heat sink 100. The lead frame 300 may be formed on the reflective member 200. The red molding part 700, the green molding part 800, and the blue molding part 900 may be stacked in the reflective member 200.

The red molding part 700 may protect the LED 400 and may be formed by mixing a red phosphor for red light emission and a molding resin such as transparent epoxy or silicon. The green molding part 800 may be formed on the red molding part 700 by mixing a green phosphor and a molding resin for green light emission. A blue molding part 900 may be formed on the green molding part 800 by mixing a blue phosphor and a molding resin for blue light emission.

The heat sink 100 is a cooling means made of a metallic material that absorbs heat from the LED 400 and emits heat absorbed to the outside, and may be formed to a predetermined thickness of 200 to 400 μm.

The reflective member 200 may be formed by injection molding of a plastic material, for example, PC, PCABS, PPA, nylon, PET, and PBT. The reflective member 200 may be bonded to the heat dissipation plate 100 and the PCB 500 by using a paste in the hole space 110 formed by milling, drilling, or chemical etching. A lead frame 300 connected to the wire 600 may be formed inside the reflective member 200. Here, the lead frame 300 is connected to the wire 600 is used to electrically connect the LED 400 to an external power source, and protrudes out of the reflective member 200 so as to be suitable for engaging and bonding to the PCB 500. It is.

In addition, when the reflective member 200 is bonded to the hole space 110 by using a paste, the reflective member 200 is formed in a stepped structure having one or more locking jaws for stable bonding and is engaged with the hole space 110. On the surface of the reflective member 200, for example, phthalocyanine may be coated on a metal film (not shown) such as Sn and Ag to improve reflection efficiency. Constant luminance amplification can be expected only by forming the reflective member 200 into a cylindrical shape and inserting the reflective member 200 into the mounting area. The shape of the reflective member 200, by having a lower diameter than the upper diameter to adjust the difference in diameter can be increased the luminous efficiency emitted to the top.

Here, the LED 400 and the lead frame 300 are electrically connected by bonding using the wire 600. In addition, a solder 310 is provided for electrical bonding between the lead frame 300 and the PCB 500. The submount 410 may be formed of a silicon optical bench (SiOB), and the LED 400 may be flip bonded.

In such a structure, the reflective member 200 may be simply pressed using a paste in the hole space 110 of the heat sink 100 and the PCB 500 in the form of a module including the lead frame 300.

The red molding part 700 may be formed on the connected LED 400 and the sub mount 410. The red molding part 700 may be formed of a molding resin made of a material such as a red phosphor and transparent epoxy or silicon. The red phosphor may be formed of a silicate-based phosphor that absorbs 250 to 420 nm ultraviolet light emitted from the LED 400 and emits red light having a wavelength of 570 to 630 nm as shown in FIG. 2. For example, the red molding part 700 may be formed by mixing a silicate-based phosphor composed of Sr _{3 - X} SiO ₅ : Eu ^{2 +} _X with a molding resin made of a material such as transparent epoxy or silicon at a predetermined ratio. .

The green molding part 800 may be formed on the red molding part 700. The green molding part 800 may be formed of a green phosphor and a molding resin made of a material such as transparent epoxy or silicon. The green phosphor may be formed of a silicate-based phosphor that absorbs 250-420 nm ultraviolet rays emitted from the LED 400 and emits green of 500-550 nm wavelength as shown in FIG. 2. For example, the green molding part 800 may be formed of Zn _{2 - X} SiO ₄ : Eu ^{2 +} _X (0 <X <1), Sr _{2 - X} SiO ₄ : Eu ^{2 +} _X (0 <X <1), Sr _{4 - X} Mg _Y Ba _Z Si ₂ O ₈ : Eu ²⁺ (0 <X <1, 0 ≤ Y ≤ 1, 0 ≤ Z ≤ 1) of at least one silicate-based phosphor material such as transparent epoxy or silicon It can be formed by mixing with a molding resin of a predetermined ratio.

The blue molding part 900 may be formed on the green molding part 800. The blue molding part 800 may be formed of a molding resin made of a material such as a blue phosphor and transparent epoxy or silicon. The blue phosphor may be formed of a silicate-based phosphor that absorbs 250-420 nm ultraviolet light emitted from the LED 400 and emits blue light having a wavelength of 450-500 nm as shown in FIG. 2. For example, the blue molding part 900 is a transparent epoxy silicate-based phosphor composed of M _{3 - X} MgSi ₂ O ₈ : Eu ^{2 +} _X (M = Sr, Ba, Ca, 0 <X <1) Or it may be formed by mixing with a molding resin of a material such as silicon in a predetermined ratio.

Of course, the red molding part 700, the green molding part 800, and the blue molding part 900 may be stacked by changing their stacking positions. In addition, the molding unit may be formed by only molding resin under the red molding unit 700, that is, on the LED 400 and the sub-mount 410.

The red molding part 700, the green molding part 800, and the blue molding part 900 absorb ultraviolet rays emitted from the LED 400, respectively, to emit red light, green light, and blue light, respectively, and finally white light is emitted. It becomes possible.

3 is a cross-sectional view schematically showing another example of a light emitting device according to the present invention.

For example, the light emitting device according to the present invention uses an LED 400 'emitting 250-420 nm ultraviolet rays. In addition, the light emitting device according to the present invention includes a metal heat sink 100 ′, and a PCB 500 ′ is formed on the heat sink 100 ′. The sub mount 410 ′ is provided on the hole space 110 ′ formed in the heat sink 100 ′ and the PCB 500 ′. The LED 400 'is mounted on the sub-mount 410', and the LED 400 'and the lead frame 300' are connected by a wire 600 '.

In the light emitting device according to the present invention, a reflective member 200 ′ is formed on the heat sink 100 ′. The lead frame 300 ′ may be formed in the reflective member 200 ′. In the reflective member 200 ′, a red molding part 700 ′, a green molding part 800 ′, and a blue molding part 900 ′ may be stacked to have a lens shape.

The red molding part 700 ′ may protect the LED 400 ′ and may be formed by mixing a red phosphor for red light emission and a molding resin such as transparent epoxy or silicon. A green molding part 800 'may be formed on the red molding part 700' in which a green phosphor and a molding resin are mixed to emit green light. A blue molding part 900 'may be formed on the green molding part 800' in which a blue phosphor for molding blue light and a molding resin are mixed.

The heat sink 100 ′ is a cooling means made of a metallic material that absorbs heat from the LED 400 ′ and emits heat absorbed to the outside. The heat sink 100 ′ may be formed to have a predetermined thickness of 200 μm to 400 μm.

Then, the bonding between the wire 400 'is electrically connected between the LED 400' and the lead frame 300 '. In addition, a solder 310 'is provided for electrical bonding between the lead frame 300' and the PCB 500 '. The submount 410 ′ may be formed of a silicon optical bench (SiOB), and the LED 400 ′ may be flip bonded.

Here, since the red molding part 700 ', the green molding part 800', and the blue molding part 900 'are each formed in the shape of a hemispherical lens, the light collecting efficiency can be improved to emit light.

On the other hand, the above description has been described based on a structure in which phosphors emitting different colors are stacked in different layers. However, phosphors emitting different colors may be formed by mixing them in the same layer. In addition, one layer may be formed by mixing phosphors emitting a plurality of colors, and a phosphor emitting a single color may be formed as a separate layer.

In the light emitting device according to the present invention, the emission characteristics are controlled by adjusting the content ratio of the phosphors constituting the red molding parts 700 and 700 ', the green molding parts 800 and 800', and the blue molding parts 900 and 900 '. To change.

For example, as shown in FIG. 4, when the content ratio of the blue phosphor (B), the green phosphor (G), and the red phosphor (R) is 4: 1.5: 1.5 (■), the color coordinates are X = 0.274, It is located at Y = 0.28. In addition, when the content ratio of the blue phosphor (B), the green phosphor (G), and the red phosphor (R) is 4: 1.8: 1.2 (●), the color coordinates are located at X = 0.292, Y = 0.29, When the content ratio of the blue phosphor (B), the green phosphor (G), and the red phosphor (R) is 4: 1.6: 1.4 (▲), the color coordinates are located at X = 0.31 and Y = 0.31.

Therefore, as can be seen from the color coordinates illustrated in FIG. 4, it can be seen that all three cases (■, ●, ▲) described above are located in the white region, and among them, 4: 4: 1.6: 1.4 (▲) It can be seen that is located on the white side with relatively lower color temperature and higher color rendering index. Here, the content ratio of the blue phosphor B, the green phosphor G, and the red phosphor R may of course vary depending on the setting conditions of the light emitting device.

When considering the white light emission luminance of the light emitting device according to the present invention, as the main other factor, the content ratio of each phosphor to the molding resin can be considered.

For example, in the case where the content ratio of blue phosphor (B), green phosphor (G), and red phosphor (R) is 4: 1.6: 1.4 in the light emitting device with LEDs emitting 405 nm ultraviolet rays, 5 is shown in FIG. 5 according to the change in the content of the phosphor to the molding resin.

For example, when the mixture of the blue phosphor (B), the green phosphor (G) and the red phosphor (R) is mixed at 9w% with respect to the molding resin, the color coordinates are located at X = 0.265 and Y = 0.3. In addition, when the mixture of the blue phosphor (B), the green phosphor (G) and the red phosphor (R) is mixed at 13w% with respect to the molding resin, the color coordinates are located at X = 0.281 and Y = 0.325. When the mixture of the blue phosphor (B), the green phosphor (G) and the red phosphor (R) is mixed at 18w% with respect to the molding resin, the color coordinates are located at X = 0.309 and Y = 0.351. As such, the color coordinates change according to the phosphor content, and a change in emission luminance may occur.

The light emitting device having such a configuration can be applied to a variety of image display devices. In one solution, the light emitting device may be applied to an electronic display. Such an image display apparatus includes a control unit for displaying an image by controlling the light emitting device and the light emitting device.

In addition, such a light emitting device may be applied as a backlight unit of a liquid crystal display device. In this case, the liquid crystal display includes the light emitting device as a backlight unit and includes a liquid crystal panel which displays an image by receiving the light provided from the backlight unit.

As described above, the present invention can provide a light emitting device, an image display device, and a liquid crystal display device having a high color rendering index and excellent color reproducibility.

Claims (19)

A light emitting device emitting light of a first wavelength; A molding part having a plurality of phosphors configured to absorb light emitted from the light emitting device and emit light having a wavelength longer than that of the first wavelength; Light emitting device comprising a. The method of claim 1, At least one of the plurality of phosphors is a silicate-based phosphor composed of Sr _{3 - x} SiO ₅ : Eu ^{2 +} _x (0 <x <1) for absorbing the light emitted from the light emitting element to emit red light. The method of claim 1, At least one of the plurality of phosphors is Zn _{2 - X} SiO ₄ : Eu ^{2 +} _X (0 <X <1), Sr _{2 - X} SiO ₄ : Eu ² to absorb the light emitted from the light emitting device to emit green light At least one silicate of ⁺ _X (0 <X <1), Sr _{4 - X} Mg _Y Ba _Z Si ₂ O ₈ : Eu ^{2 +} (0 <X <1, 0 ≤ Y ≤ 1, 0 ≤ Z ≤ 1) A light emitting device which is a phosphor. The method of claim 1, At least one of the plurality of phosphors is M _{3 - X} MgSi ₂ O ₈ : Eu ^{2 +} _X (M = Sr, Ba, Cr one of the absorbing light emitted from the light emitting device to emit blue light, 0 <x < A light emitting device which is a silicate-based phosphor composed of 1). The method of claim 1, The light emitting device is a light emitting device for emitting light in the ultraviolet region. The method of claim 1, The molding unit is a light emitting device formed of a laminated structure of a plurality of layers. The method of claim 1, The molding unit comprises a silicon or a resin. The method of claim 1, The phosphor includes a red phosphor emitting light in a wavelength region of 570 to 630 nm, a green phosphor emitting light in a wavelength range of 500 to 550 nm, and a blue phosphor emitting light in a wavelength range of 450 to 500 nm. The method of claim 8, The blue phosphor has a higher content ratio than the green phosphor and the red phosphor. The method of claim 8, The green phosphor has a higher content ratio than the blue phosphor and the red phosphor. The method of claim 8, The red phosphor has a higher content ratio than the green phosphor and the blue phosphor. The method of claim 8, A light emitting device in which the content ratio of the blue phosphor, the green phosphor, and the red phosphor is 4: 1.5: 1.5. The method of claim 8, And a content ratio of the blue phosphor, the green phosphor, and the red phosphor is 4: 1.8: 1.2. The method of claim 8, A light emitting device in which the content ratio of the blue phosphor, the green phosphor, and the red phosphor is 4: 1.6: 1.4. The method of claim 1, And the molding part includes the phosphor mixture and a molding resin, and the phosphor mixture is formed at 9w% of the molding resin. The method of claim 1, And the molding part includes the phosphor mixture and a molding resin, and the phosphor mixture is formed at 13w% of the molding resin. The method of claim 1, Wherein the molding part includes the phosphor mixture and a molding resin, and the phosphor mixture is formed at 18w% of the molding resin. 18. A light emitting device according to any one of claims 1 to 17; A controller for controlling the light emitting device to display an image; Image display device comprising a. A backlight unit having a light emitting device according to any one of claims 1 to 17; A liquid crystal panel configured to display an image by receiving the light provided from the backlight unit; Liquid crystal display comprising a.

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