JP2006324407A - Light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting device which is excellent in emission efficiency and color reproducibility as a backlight source. <P>SOLUTION: A yellow fluorescent body 7A which generates yellow light by the excitation of blue light emitted from an LED device 2, and a green fluorescent body 7B which generates an yellow color to a yellow-green spectrum by the excitation of blue light, are dispersedly mixed into a sealing resin 7 for the formation a light emitting body, so that the light emitting body is capable of expanding its color gamut in comparison with a white color obtained resting on a complementary relation between a blue color and an yellow color and improved in emission efficiency and color reproducibility. When the light emitting device 1 is used as a backlight source, an NTSC ratio can be improved, and when images of a television or a movie are reproduced, the images excellent and bright in image quality can be obtained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light-emitting device that emits white light by mixing a plurality of lights, and more particularly, to a light-emitting device that excels in luminous efficiency and color reproducibility as a backlight light source.

    Conventionally, a light emitting device using a light emitting diode (LED) element as a light source has been proposed. In such a light-emitting device, there is a light-emitting device that emits light of an emission color that cannot be originally realized by a single LED element by converting the wavelength of light emitted from the LED element (see, for example, Patent Document 1). ).

The light emitting device described in Patent Document 1 uses a GaN-based LED element having an emission wavelength peak of about 440 nm to about 470 nm, and YAG (Yttrium Aluminum Garnet) in which an appropriate amount of Ce (cerium) is added as an activator to a fluorescent binder layer. : When the single crystal of the chemical formula Y ₃ Al ₁₅ O ₁₂ , excitation wavelength peak of about 450 nm, emission wavelength peak of about 540 nm (yellowish green light) is used, the emission wavelength of the LED element and the excitation wavelength of the YAG phosphor are almost the same Therefore, the wavelength conversion is performed efficiently.

  In recent years, LEDs using LEDs as light sources have been proposed for uses such as lighting. Among them, particularly for white light, high luminous efficiency and excellent color rendering properties are required. In response to such demands, an LED element that emits blue light is used as a light source, blue light emitted from the LED element, green light obtained by exciting a green phosphor with blue light, and red fluorescence A light-emitting device that generates white light by mixing with red light obtained by exciting a body has been proposed (see, for example, Patent Document 2).

In addition, a light-emitting device using a phosphor that is excited by blue light and whose emission peak wavelength is provided from a green region to a yellow region has been proposed (see, for example, Patent Document 3).
Japanese Patent No. 2947344 ([0010], FIG. 1) JP 2003-133595 A ([0009] to [0011]) JP 2004-189997 A ([0018])

  However, in the conventional light emitting device, it is advantageous that the YAG phosphor is excited with blue light from the point of luminous efficiency, and white light is generated by mixing the resulting yellow light and blue light. Because the green component over yellow is insufficient, color reproducibility is not sufficient when trying to use it in backlight sources such as liquid crystals, and as a result, it cannot be expected to improve the NTSC (National TV Standards Committee) ratio. There's a problem.

  Accordingly, an object of the present invention is to provide a light emitting device that is excellent in luminous efficiency and color reproducibility as a backlight light source.

  In order to achieve the above object, the present invention provides a light emitting device that converts the wavelength of first light generated based on light emission of a light emitting element and externally emits second light having a wavelength region different from that of the first light. An LED element that emits a first light having an emission wavelength region of 480 nm to 530 nm based on the light emission, and a light emission of 550 to 570 nm that is excited based on the emission of the first light and is different from the first light A yellow phosphor emitting a second light having a wavelength region, and a third light having an emission wavelength region of 470 to 530 nm that is excited based on the emission of the first light and is different from the first light. Provided is a light emitting device having a wavelength conversion unit including a green phosphor to be emitted.

  According to the present invention, luminous efficiency and color reproducibility as a backlight light source can be improved.

(First embodiment)
FIG. 1 is a longitudinal sectional view showing a surface-mounted light emitting device according to a first embodiment of the present invention.

  The light emitting device 1 includes a flip chip type LED element 2 made of a GaN-based semiconductor, a substrate 4 having wiring layers 3A and 3B made of copper foil on the surface, and a case 5 formed integrally on the upper surface of the substrate 4. And an Au bump 6 that electrically connects the wiring layers 3A and 3B of the substrate 4 and the LED element 2, and a yellow phosphor 7A and a green phosphor 7B that are excited by light emitted from the LED element 2. And a sealing resin 7 for sealing the opening 5B provided in the case 5.

  The LED element 2 is formed by growing a GaN-based semiconductor layer 21 on a sapphire substrate 20 using a MOCVD (Metal Organic Chemical Vapor Deposition) apparatus. The GaN-based semiconductor layer 21 is formed by sequentially laminating an Si-doped n-GaN layer, a light emitting layer, and an Mg-doped p-GaN layer from the sapphire substrate 20 side, and rhodium is formed on the surface of the p-GaN layer. A p-side electrode 22 made of (Rh) is included. The n-side electrode 23 is provided on the n-GaN layer exposed by etching from the p-GaN layer to the n-GaN layer. In the present embodiment, the blue LED element 2 having a light emission wavelength region of 450 to 460 nm and a standard size (0.3 mm × 0.3 mm) is used, but a blue LED element 2 having a large size (1 mm × 1 mm) is used. It is also possible to use.

The substrate 4 is made of Al ₂ O ₃ , and wiring layers 3A and 3B having electrode patterns corresponding to the electrode arrangement of the LED elements 2 are provided on the surface thereof. The wiring layers 3 </ b> A and 3 </ b> B may be subjected to light reflection processing such as Ni plating on a portion exposed in the opening 5 </ b> B as a mounting surface of the LED element 2.

The case 5 is made of a resin material such as nylon, and the opening 5B is formed to have an inclined surface 50 whose diameter increases in the light extraction direction. The inclined surface 50 may have a light reflecting layer made of a metal material such as aluminum in order to improve light reflectivity. Further, the case 5 can be formed of Al ₂ O ₃ instead of nylon.

The sealing resin 7 is configured by containing a yellow fluorescent material 7A and a green fluorescent material 7B in a dispersed manner in a light-transmitting silicone. The yellow phosphor 7 </ b> A activates a YAG phosphor having a composition of Y ₃ Al ₁₅ O ₁₂ with Ce, and emits yellow light having an emission wavelength region of 550 to 570 nm by blue light emitted from the LED element 2. The yellow phosphor 7A may be a silicate phosphor that emits yellow light in addition to the YAG phosphor that is a garnet phosphor.

The green phosphor 7B is a phosphor represented by a general formula of M ′ _a M ″ _b M ′ ″ _c O _d , where M ′ is at least one of Mg, Ca, Zn, Sr, Cd, and Ba. A divalent metal element that is a seed, M ″ is a trivalent metal element that is at least one of Al, Sc, Ga, Y, In, La, Gd, and Lu, and M ′ ″ is Si, Ti, Ge , Zr, Sn, and Hf are each a tetravalent metal element that is a garnet structure phosphor having the compound as a base. The emission center ion contained in the compound matrix is divalent Mn, trivalent Ce, 2-3 trivalent Eu, trivalent Tb, or trivalent Ce, and is emitted from the LED element 2. Green light having an emission wavelength region of 480 nm to 530 nm is emitted by light.

The green phosphor 7B is a phosphor represented by a general formula of M ′ _a M ″ _b S ₄ in addition to the above, and M ′ is at least one of Mg, Ca, and Sr. A divalent element, M ″, is a trivalent element that is at least one of Al, Ga, and Y, and is a garnet structure phosphor based on a compound thereof. The luminescent center ion contained in the compound matrix may be divalent Mn, trivalent Ce, 2-3 trivalent Eu, trivalent Tb, or trivalent Ce. Such green phosphor 7B includes thiometallate and thiogallate.

  2A and 2B show emission characteristics of the light emitting device according to the first embodiment. FIG. 2A shows a light source spectrum, and FIG. 2B shows a color reproduction range. According to the light emitting device 1 of the present embodiment, as shown in (a), the light emission intensity in the wavelength region from yellow to yellow green of 480 nm to 530 nm is improved. Further, the color reproducibility of the light emitting device 1 of the present embodiment is superior to the color reproducibility C of the CRT.

(Effects of the first embodiment)
According to the first embodiment described above, the following effects are obtained.
Sealing resin 7 includes yellow phosphor 7A that generates yellow light based on excitation of blue light emitted from LED element 2 and green phosphor 7B that generates light of a yellow to yellow-green spectrum based on excitation of blue light. Therefore, the color gamut can be expanded as compared with the white color obtained based on the relationship between the complementary colors of blue and yellow, and the light emission efficiency and color reproducibility are improved. According to the backlight light source using the light emitting device 1, the NTSC ratio can be improved, and a bright and high-quality image can be obtained when reproducing a television or movie image.

  In the first embodiment, the configuration in which the yellow phosphor 7A and the green phosphor 7B are dispersedly mixed in the sealing resin 7 has been described. However, for example, yellow fluorescence is applied to the surface of the sealing resin 7. It is good also as a structure which laminated | stacked the body 7A, and also laminated | stacked the green fluorescent substance 7B on the surface.

  In the first embodiment, the configuration in which the yellow phosphor 7A and the green phosphor 7B described above are applied to the surface-mounted light-emitting device 1 has been described. However, the configuration of the light-emitting device is other than the surface-mounted type. For example, it can be contained in a sealing resin of a shell-type light emitting device in a dispersed state.

(Second Embodiment)
FIG. 3 is a longitudinal sectional view showing a surface-mounted light emitting device according to the second embodiment of the present invention.

  This light-emitting device 1 has a configuration in which a yellow phosphor layer 7C and a green phosphor layer 7D are provided so as to cover the surface of the flip chip type LED element 2 described in the first embodiment. It is different from the form. In the following description, the same reference numerals are given to the portions having the same configuration and function as those of the first embodiment.

  The yellow phosphor layer 7C is obtained by coating the surface of the LED element 2 after the LED element 2 is mounted by dispersing the yellow phosphor described in the first embodiment in a resin material such as translucent silicone. Is provided.

  Similarly to the yellow phosphor layer 7C, the green phosphor layer 7D is obtained by dispersing the green phosphor described in the first embodiment in a dispersed state in a resin material such as translucent silicone. It is applied and provided on the body layer 7C.

(Effect of the second embodiment)
According to the second embodiment described above, since the yellow phosphor layer 7C and the green phosphor layer 7D are provided on the surface of the LED element 2, in addition to the preferable effect of the first embodiment, the sedimentation of the phosphor. Therefore, the separation of the LED element light and the phosphor light can be suppressed. Moreover, the structure which provides a fluorescent substance layer in the surface of the LED element 2 can reduce the usage-amount of fluorescent substance, and is excellent in cost saving.

(Third embodiment)
FIG. 4 is a longitudinal sectional view showing a surface-mounted light-emitting device according to the third embodiment of the present invention.

  This light-emitting device 1 has a configuration in which a green organic material layer 7E is provided instead of the green phosphor layer 7D on the yellow phosphor layer 7C, which is an inorganic material described in the second embodiment, in the second embodiment. It is different from the form.

The green organic material layer 7E is formed by mixing tris (2-phenylpyridine) iridium (hereinafter referred to as “Ir (ppy) ₃ ”), which is a green-converting Ir metal complex, with silicone.

(Effect of the third embodiment)
According to the above-described third embodiment, in addition to the preferable effects of the second embodiment, the green organic material layer 7E is provided on the yellow phosphor layer 7C, which is an inorganic material, so that the LED element 2 emits light. Stable white light with little color change can be obtained over a long period of time without shortening the lifetime of the green organic material layer 7E by the blue light. Alternatively, the sealing resin 7 may be sealed by dispersing a green organic material in silicone.

(Fourth embodiment)
FIG. 5 is a longitudinal sectional view showing a surface-mounted light emitting device according to the fourth embodiment of the present invention.

  In this light emitting device 1, the sapphire substrate 20 side of the LED element 2 described in the first embodiment is mounted on the wiring layer 3B, and a yellow phosphor layer 7C is provided immediately below the sapphire substrate 20, The configuration in which the green phosphor layer 7D is laminated immediately below is different from the first embodiment. The p-side electrode 22 of the LED element 2 is connected to the wiring layer 3A via a wire 8 made of Au, and the n-side electrode 23 is connected to the wiring layer 3B via a wire 8 made of Au. In the fourth embodiment, it is preferable that the wiring layers 3A and 3B and the inclined surface 50 of the case 5 are subjected to reflection processing such as plating (not shown).

  The yellow phosphor layer 7 </ b> C and the green phosphor layer 7 </ b> D are provided in layers on the surface of the sapphire substrate 20 in the manufacturing process of the LED element 2. The green phosphor layer 7D is provided in a layered manner on the surface after the yellow phosphor layer 7C is formed. In this way, the wafer provided with the yellow phosphor layer 7C and the green phosphor layer 7D is cut into a predetermined element size.

  When the wiring layers 3A and 3B are connected to a power supply unit (not shown) and a voltage is applied, light emission based on the recombination of carriers and holes occurs in the light emitting layer provided in the GaN-based semiconductor layer 21, and blue light is emitted. Of this blue light, the light emitted in the direction of the substrate 4 passes through the sapphire substrate 20 and enters the yellow phosphor layer 7C. In the yellow phosphor layer 7C, the yellow phosphor is excited by blue light to generate yellow light. The blue light transmitted through the yellow phosphor layer 7C is incident on the green phosphor layer 7D. In the green phosphor layer 7D, the green phosphor is excited by blue light to generate green light. As a result, white light based on a mixture of blue light, yellow light, and green light is generated between the sapphire substrate 20 and the wiring layer 3 </ b> B, and is reflected by the inclined surface 50 of the case 5 and radiated outside.

  Further, the blue light emitted from the light emitting layer toward the electrode formation surface is reflected by the p-side electrode 22, passes through the sapphire substrate 20, and enters the yellow phosphor layer 7 </ b> C.

(Effect of the fourth embodiment)
According to the above-described fourth embodiment, the yellow phosphor layer 7C and the green phosphor layer 7D are laminated at the wafer stage and divided into LED elements 2, so that the white color change is small. The mass productivity of the element 2 is excellent. In addition, since the LED element 2 is mounted face-up and the yellow phosphor layer 7C and the green phosphor layer 7D are laminated on the substrate 4 side, the LED element 2 is not required to be highly positioned by a flip chip bonder. Thus, a white light emitting device with little white color change can be obtained.

In the fourth embodiment, the green organic material layer 7E made of Ir (ppy) ₃ described in the third embodiment may be used instead of the green phosphor layer 7D. Alternatively, the sealing resin 7 may be sealed by dispersing a green organic material in silicone.

(Fifth embodiment)
6A and 6B show a reflective light-emitting device according to a fifth embodiment of the present invention, where FIG. 6A is a plan view seen from the light emitting side, and FIG. FIG. The light emitting device 1 includes a cylindrical case 5 provided on the light emitting side, a hemispherical reflecting mirror unit 10 provided below the case 5, and an end face of a heat sink 5 A provided on the case 5. A circuit board 9 attached by bonding; an LED element 2 mounted on the circuit board 9; a reflecting mirror surface 10A that is provided on the inner surface of the reflecting mirror part 10 and reflects blue light emitted from the LED element 2; It has a green phosphor layer 7D formed on the surface of the reflecting mirror surface 10A and a yellow phosphor layer 7C laminated on the green phosphor layer 7D, and the LED element 2 is coated with a silicone coating material 2A. . Further, the yellow phosphor layer 7C and the green phosphor layer 7D are formed so as to have a constant thickness.

  The case 5 is made of aluminum having excellent heat dissipation, and as shown in FIG. 8A, a heat radiating plate 5A is provided so as to divide the hollow interior into two in the length direction. The heat radiating plate 5A is configured such that an end surface serving as an element mounting portion protrudes into the reflecting mirror unit 10, and is formed from the opening 5B of the case 5 based on the distance between the light emitting surface of the LED element 2 and the reflecting mirror surface 10A. Emits parallel light.

  The circuit board 9 is made of an insulating substrate such as polyimide, and has copper foil layers 9A and 9B in the cross section. Copper foil layers 9 </ b> A and 9 </ b> B have a configuration in which part is exposed so that electrical connection with LED element 2 is possible in the element mounting portion.

  The light emitted from the LED element 2 passes through the yellow phosphor layer 7C and the green phosphor layer 7D and is reflected by the reflecting mirror surface 10A. At this time, in the yellow phosphor layer 7C, the yellow phosphor is excited by blue light to generate yellow light. In the green phosphor layer 7D, the green phosphor is excited by blue light to generate green light. As a result, the light reflected by the reflecting mirror surface 10A becomes white light based on a mixture of blue, yellow, and green, and is radiated from the opening 5B as parallel light.

(Effect of 5th Embodiment)
According to the fifth embodiment described above, the blue light emitted from the LED element 2 enters the reflecting mirror surface 10A, and the yellow light and the green light generated by exciting the yellow phosphor layer 7C and the green phosphor layer 7D. The light-emitting device 1 is excellent in radioactivity without causing light absorption due to the transmission of the sealing resin or the like.

In the fifth embodiment, the green organic material layer 7E made of Ir (ppy) ₃ described in the third embodiment may be used instead of the green phosphor layer 7D. The yellow phosphor layer 7C and the green phosphor layer 7D are not provided on the reflecting mirror surface 10A, and a light transmissive member such as glass is provided on the upper surface of the case 5 which is the light emitting end of the opening 5B. It is good also as a structure which provides in a laminated form and permeate | transmits reflected light. In the configuration of the fifth embodiment, since the intensity of the reflected light at the opening 5B is uniform, white light based on a good mixing property of light can be obtained.

1 is a longitudinal sectional view showing a surface-mounted light emitting device according to a first embodiment of the present invention. The light emission characteristic view of the light-emitting device of 1st Embodiment is shown, (a) is a light source spectrum, (b) is a figure which shows a color reproduction range. It is a longitudinal cross-sectional view which shows the surface mounted light-emitting device based on the 2nd Embodiment of this invention. It is a longitudinal cross-sectional view which shows the surface mount type light-emitting device based on the 3rd Embodiment of this invention. It is a longitudinal cross-sectional view which shows the surface mount type light-emitting device based on the 4th Embodiment of this invention. The reflective light-emitting device which concerns on the 5th Embodiment of this invention is shown, (a) is the top view seen from the light-projection side, (b) is sectional drawing in the AA part of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Light-emitting device, 2 ... LED element, 2A ... Coating material, 3A, 3B ... Wiring layer, 4 ... Board | substrate, 5 ... Case, 5A ... Heat sink, 5B ... Opening part, 6 ... Bump, 7 ... Sealing resin, 7A ... Yellow phosphor, 7B ... Green phosphor, 7C ... Yellow phosphor layer, 7D ... Green phosphor layer, 7E ... Green organic material layer, 8 ... Wire, 9 ... Circuit board, 9A, 9B ... Copper foil layer, DESCRIPTION OF SYMBOLS 10 ... Reflector part, 10A ... Reflector mirror surface, 20 ... Sapphire substrate, 21 ... GaN-based semiconductor layer, 22 ... P-side electrode, 23 ... N-side electrode, 50 ... Inclined surface

Claims (9)

In the light emitting device for converting the wavelength of the first light generated based on the light emission of the light emitting element and emitting the second light in a wavelength region different from the first light to the outside,
An LED element that emits first light having an emission wavelength region of 480 nm to 530 nm based on emission;
A yellow phosphor that emits second light having an emission wavelength region of 550 to 570 nm different from that of the first light by being excited based on the radiation of the first light; and based on the radiation of the first light. And a wavelength conversion unit including a green phosphor that emits third light having a light emission wavelength region of 470 to 530 nm different from that of the first light.   The light emitting device according to claim 1, wherein the yellow phosphor is a YAG phosphor of a garnet structure phosphor. The green phosphor is represented by a general formula of M ′ _a M ″ _b M ′ ″ _c O _d , where M ′ is at least one of Mg, Ca, Zn, Sr, Cd and Ba. M ″ is selected from trivalent metal elements that are at least one of Al, Sc, Ga, Y, In, La, Gd, and Lu, and M ′ ″ is Si, Ti, Ge 2. The light emitting device according to claim 1, wherein the light emitting device is a garnet structure phosphor based on a compound selected from a tetravalent metal element which is at least one of Zr, Sn, and Hf. The green phosphor is represented by a general formula of M ′ _a M ″ _b S ₄ , where M ′ is selected from divalent elements that are at least one of Mg, Ca, and Sr, and M ″ is Al, The light-emitting device according to claim 1, wherein the light-emitting device is a garnet structure phosphor having a compound selected from trivalent elements as at least one of Ga and Y as a base.   The light emitting device according to claim 1, wherein the LED element is sealed with a sealing material as the wavelength conversion unit including the green phosphor and the yellow phosphor.   The light emitting device according to claim 1, wherein the wavelength conversion unit includes a yellow phosphor layer provided to cover a surface of the LED element, and a green phosphor layer laminated on the yellow phosphor layer.   The wavelength converter includes a first phosphor layer containing the yellow phosphor on the substrate side of the flip-chip type LED element, and a second phosphor containing the green phosphor laminated on the first phosphor layer. The light emitting device according to claim 1, wherein the second phosphor layer is mounted on a mounting surface.   The light emitting device according to claim 1, wherein the wavelength conversion unit is provided on a reflecting mirror surface that reflects light emitted from the light emitting element, and wavelength-converts light incident on the reflecting mirror surface. 2. The light emitting device according to claim 1, wherein the wavelength conversion unit is provided in a state where the reflected light emitted from a reflecting mirror surface that reflects the light emitted from the light emitting element is laminated on a portion having uniform intensity.

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